Please see the [Transcriber’s Notes] at the end of this text.

Vacuum Cleaning Systems

A Treatise on the Principles and
Practice of Mechanical Cleaning

BY

M. S. COOLEY, M. E.

Mechanical Engineer in Office of the Supervising
Architect, Treasury Department, Washington, D. C.

FIRST EDITION

New York:
Heating and Ventilating Magazine Company,
1123 Broadway

Copyright, 1913,
BY
Heating and Ventilating Magazine Co.

CONTENTS.

TABLES.

ILLUSTRATIONS.

PREFACE.

The contents of this work are compiled from the observations of the author through the seven years during which he has been engaged in the preparation of specifications for, and the testing of, complete plants installed in the buildings under the control of the Treasury Department.

During this time it has become necessary to alter no less than five times the stock form of specifications for stationary vacuum cleaning plants which were adopted by the Government, with the intent of obtaining the widest competition possible with efficient and economical operation, in order to keep pace with the variation and improvement in the apparatus manufactured. As each new type of system has come on the market a personal investigation at the factory, together with tests, has been made. An exhaustive test of carpet renovators was also conducted, using one of the Government plants. In addition the vacometers recommended for use in capacity tests were carefully calibrated, using the machine at the Department of Agriculture.

The writer wishes to acknowledge the aid received from the various manufacturers in furnishing illustrations and data on their machines, to Messrs. Ewing & Ewing and Prof. Sidney A. Reeve for data on tests made by Prof. Reeve and used in defending the Kenney basic patent.

In analyzing the results of his tests and observations, the writer has endeavored to put his own conclusions into concrete form for the use of the consulting engineer and has not entered into the problems to be encountered in the design and manufacture of the various forms of apparatus.

CHAPTER I.
History of Mechanical Cleaning.

Early Attempts.

—Whenever machinery has been introduced to assist or replace manual labor, the earlier attempts have been in imitating the tools formerly used by man. As the earliest mechanically-propelled carriages were mechanical walking machines, the earliest steamboats mechanical rowing machines, and the earliest flying machines mechanical birds, so were the earliest mechanical cleaners in the form of mechanical brooms.

These mechanical brooms were introduced about 1880 and took the form of the well-known street sweeper, with a large circular brush mounted on a four-wheeled cart and rotated by means of gearing driven from the wheels, the propelling power being the horses which drew the machine.

This machine at once made itself unpopular with the residents of the streets cleaned on account of its great activity in stirring up dust, because the streets were swept dry. This trouble was later overcome to a considerable extent by sprinkling the streets before sweeping, but only at a sacrifice in efficiency of cleaning, especially where such uneven surfaces as cobble or medina stone blocks formed the surface of the roadway. Various attachments were added to reduce this dust nuisance, but none has apparently been successful, as we see these machines in their original form in use today.

Almost simultaneously with the introduction of the street sweeper came its counterpart, the carpet sweeper, with a similar but smaller brush, enclosed in a wood and metal case, the brush being driven by friction from the wheels supporting the box and the power for operation being derived from the person who pushed the machine along the floor.

This machine has not been modified to any great extent during the thirty odd years of its existence. It is today in practically its original form, and is doing no better work than when first introduced. This form of mechanical cleaner occupied the field of household cleaning for nearly twenty years without a rival, during which time it won its way into the hearts and hands of many housekeepers in this and other countries.

Limitations of the Carpet Sweeper.

—This device, with its light brush and equally light pressure on the surface cleaned and its limited capacity for carrying the material picked up, has never been a thorough cleaner in any sense of the word, and has been and is now used only to take up that portion of the usual litter and light dust which is located directly on the surface, and is, therefore, most annoying to the housekeeper, owing to its being visible to the eye. Because of its generous proportions, made necessary to accommodate the material picked up, and its centrally-pivoted handle, made necessary by its mechanical construction, it is impossible to operate it under low furniture. Like the lawn mower, it must be in motion in order to operate its revolving brush, on which its cleaning action is dependent. It is impossible to make use of same in corners, along walls, or close to heavy furniture, its use being limited to a literal slicking up of those portions of the carpet in the most conspicuous portions of the apartment. In spite of these serious defects it came into, and is still in, nearly universal use, even in households equipped with the latest approved types of mechanical cleaners. Its use on bare floors has never been even a moderate success and in no case has it superseded the broom and dust pan of our grandmothers.

Compressed Air Cleaners.

—Compressed air has been in use for many years in foundries and machine shops, for cleaning castings and producing certain finishes on metal. With the introduction of modern electrical machinery it was rapidly adapted to the cleaning of windings and other inaccessible parts of this machinery. Its first use in cleaning buildings was undoubtedly in the form of an open jet for dislodging dust from carvings and relief work, for which purpose it is very efficient as a remover of the dust from the parts to be cleaned and also as a distributor of this same dust over the widest possible area for subsequent removal by other means. It has a draw-back in that the expansion of air both cools the same and reduces its ability to retain moisture, resulting in the deposit of moisture on the surfaces cleaned.

About 1898, attempts to overcome the objections to the open air jet and to produce a commercially successful compressed air carpet cleaner were undertaken almost simultaneously by two companies, the American Air Cleaning Company, of Milwaukee, operating under the Christensen patents, and the General Compressed Air Cleaning Company, of St. Louis, operating under the Thurman patents.

The renovator used by the American Air Cleaning Company consisted of a heavy metal frame, about 18 in. long and 12 in. wide, having mounted on its longer axis a wedge-like nozzle extending the entire length of the frame, with a very narrow slit, ¹⁄₆₄ in. wide, extending the entire length of its lower edge. This nozzle was pivoted and so connected to the operating handle, by which the renovator was moved over the floor, that when the renovator was alternately pushed and pulled over the surface to be cleaned, the slot was always inclined in the direction in which the renovator was being moved. The top of the renovator was closed by a canvas bag, smaller at the neck than in its center, which was supported by a wire hook.

Air was introduced into the nozzle, at a pressure of from 45 to 55 lbs. per square inch, and issued from the slot in a thin sheet which impinged on the carpet at an angle. The frame was held close to the carpet by its weight, preventing the escape of the air under its lower edge. The air striking the carpet at an angle was deflected up into the bag, inflating same like a miniature balloon. The dust loosened from the carpet by the impact of the air was carried up into the bag where it lodged, the air escaping through the fabric of the canvas into the apartment.

The renovator used by the General Compressed Air Cleaning Company differed from the above-described renovator in that it contained two nozzles, with slots inclined at fixed angles to the carpet. A pair of hand-operated valves were provided in the handle to introduce air into the nozzle which was inclined in the direction in which the renovator was moving; otherwise the renovator was identical with that used by the Milwaukee company.

These renovators were generally supplied with air from a portable unit, consisting of an air compressor, driven by a gasoline engine mounted with the necessary gasoline and air storage tanks on a small truck. One of these machines was in use in Washington last year, but its use at that time was very limited and it is not to be seen this year.

These trucks were drawn up in front of the building to be cleaned and a large-size hose, usually 1¹⁄₄ in. in diameter, was carried into the house and attached to an auxiliary tank from which ¹⁄₂-in. diameter hose lines were carried to two or more renovators.

A few buildings were equipped with air compressors and pipe lines, with outlets throughout the building for use with this type of renovator, among which was the Hotel Astor in New York City.

These renovators, the construction of which is shown diagrammatically in [Fig. 1], required approximately 35 cu. ft. of free air per minute at a pressure of from 45 to 55 lbs. per square inch and were usually driven by a 15 H. P. engine.

FIG. 1. EARLY TYPE OF MECHANICAL CLEANING NOZZLE USING COMPRESSED AIR.

The renovators were very heavy to carry about, although their operation with the air pressure under them was not difficult. However, their operation was complicated, requiring skilled operators. Owing to their generous proportions it was impossible to clean around furniture, making its removal from the apartment necessary, and limiting their use to the cleaning of carpets at the time of general house cleaning. The cooling effect of the expansion of the air in the nozzle often caused condensation of moisture on the carpets when the relative humidity was high. They were also at a disadvantage in that all the heavy dust collected in the canvas bag had to be carried from the apartment by hand. Owing to the constant agitation of the dust in the bag by the entering air currents, much of the finer particles of dust and all the disease germs liberated by the renovator were blown through the bag back into the apartment. They were not, therefore, by any means sanitary devices.

Vacuum Produced by Compressed Air.

—The General Compressed Air Cleaning Company also introduced another form of renovator for use with their compressed air plants. This was composed of an ejector operated by compressed air, with a short hose attached to a carpet renovator of the straight narrow-slot type, such as was used later in vacuum cleaning systems. The outlet from this ejector was connected by another short hose to a metal box containing a canvas bag, woven backwards and forwards over metal frames to give a large surface for the passage of air. The dust picked up by the suction of the ejector was carried with the air into the box and there separated from the air, which escaped through the canvas into the apartment.

This form of renovator overcame some of the objections to the former type in that there was no condensation of moisture on the carpets, and it was possible to operate the renovator under and around furniture, and even on portieres and other hangings. However, the apparatus was rendered inefficient by the resistance of the bag, causing a back pressure on the injector which greatly reduced its air-drawing capacity.

Compressed Air Supplemented by Vacuum.

—Shortly after these two companies began operation, the Sanitary Devices Manufacturing Company, of San Francisco, introduced a new system of mechanical cleaning under the Lotz patents. This system used a renovator having a compressed air nozzle terminating in a narrow slot, similar to the nozzles of the American and Thurman systems, but differing from them in that the slot was fixed vertically, pointing downward. This nozzle was surrounded by an annular chamber having an opening at the bottom of considerable width. The whole formed a renovator about 14 in. long and not over 2 in. wide at its base. In addition to the compressed air connection to its nozzle, a second hose, 1 in. in diameter, was connected to the annular space surrounding the nozzle and led to a vacuum pump by which the air liberated through the nozzle, together with the dust which was liberated from the carpet, was carried from the apartment. The construction of this renovator is shown diagrammatically in [Fig. 2].

FIG. 2. ANOTHER TYPE OF COMPRESSED AIR CLEANING NOZZLE, SUPPLEMENTED WITH VACUUM PIPE.

As dust-laden air was not suitable to be carried through the pump used as a vacuum producer, separators had to be provided to remove the dust from this air before it reached the pump. The separators used consisted of two cylindrical tanks. The air was introduced into the first tank in such a way that a whirling motion was imparted to it, thus separating the heavier particles of dust by centrifugal force. The second tank contained water which was brought into intimate contact with the air by means of an atomizer located in the pipe connection between the two tanks, thus washing the air in a manner somewhat similar to the familiar air washers used in connection with mechanical ventilating systems. The air and spray then entered the second tank, above the water line, where the entrained water separated on the reduction of velocity and fell back into the water below, to be recirculated through the atomizer. The air passed on out of the top of the tank to the pump. An illustration of these separators is shown in [Fig. 3].

FIG. 3. SEPARATORS USED WITH COMBINED COMPRESSED AIR AND VACUUM MACHINES.

FIG. 4. PISTON TYPE OF VACUUM PUMP, MOUNTED TANDEM WITH AIR COMPRESSOR.

Piston Pump the First Satisfactory Vacuum Producer.

—Various types of apparatus were tried as vacuum producers, including an air ejector, such as was used with the Thurman renovator, and found to be ineffective due to its inability to overcome the back-pressure necessary to discharge the air through the hose, which was placed on its outlet. A rotary pump was next tried, but, owing to the selection of an inefficient type, this was abandoned and, finally, a piston-type vacuum pump, with very light poppet valves and mounted tandem with the air compressor, was adapted and remained in use with this system until straight vacuum was adopted, when the air compression cylinder was omitted. This pump is illustrated in [Fig. 4].

FIG. 5. MR. KENNEY’S FIRST RENOVATOR, VACUUM ALONE BEING USED AS CLEANING AGENT.

In this system we see the first sanitary device to be introduced into the field of mechanical cleaning, as the dust and germ-laden air were removed entirely from the apartment and purified before being discharged into the outside atmosphere. The foulness of the water in the separators clearly showed the amount of impurities removed from the air.

These machines were mounted on wagons, similar to their forerunners, and were also installed in many buildings as stationary plants, among which were the old Palace Hotel and the branch Mint, in San Francisco, and the old Fifth Avenue Hotel, in New York City.

Systems Using Vacuum Only.

—In 1902 David T. Kenney, of New York, installed the first mechanical cleaning system in which vacuum alone was used as the cleaning agent. Mr. Kenney used a renovator with a slot about 12 in. long and ³⁄₁₆ in. wide, attached to a metal tube which served as a handle, and to a ³⁄₄-in. diameter hose and larger pipe line leading to separators and vacuum pump. Mr. Kenney’s first renovator is illustrated in [Fig. 5].

FIG. 6. AIR COMPRESSORS ARRANGED FOR OPERATION AS VACUUM PUMPS.

Mr. Kenney used as vacuum pumps commercial air compressors, the first of which was installed in the Frick Building in 1902 and is illustrated in [Fig. 6]. Later he adapted the Clayton air compressor, with mechanically-operated induction and poppet eduction valves on larger sizes, and single mechanically-operated induction and eduction valves on the smaller sizes.

The separators used by Mr. Kenney differed from those used by the Sanitary Devices Manufacturing Company in that they contained several interior partitions, screens, and baffles, and the air was drawn directly through the body of water in the wet separator. The relative merits of these types of separators will be discussed in a later chapter.

FIG. 7. SEPARATORS INSTALLED BY MR. KENNEY IN FRICK BUILDING.

The separators installed by Mr. Kenney in the Frick Building, and which are practically the same as were used by him as long as he manufactured vacuum cleaning apparatus, are illustrated in [Fig. 7].

After his application had been in the patent office for about six years he was granted a fundamental patent on a vacuum cleaning system.

Renovator with Inrush Slot.

—The Sanitary Devices Manufacturing Company then produced a carpet renovator using vacuum only as a cleaning agent. This cleaner has a wider cleaning slot than the cleaners usually furnished by Mr. Kenney, about ⁵⁄₁₆ in. wide, with a supplemental slot or vacuum breaker opening out of the top of the renovator and separated from the cleaning slot by a narrow partition extending nearly to the carpet, as illustrated in [Fig. 8]. The relative merits of these types of renovators will be discussed in a later chapter.

FIG. 8. VACUUM RENOVATOR WITH INRUSH SLOT, INTRODUCED BY THE SANITARY DEVICES MANUFACTURING CO.

Shortly after the introduction of vacuum cleaning by Mr. Kenney and the Sanitary Devices Manufacturing Company, the American Air Cleaning Company published an interesting little booklet entitled, “Compressed Air Versus Vacuum,” which set forth in great detail the so-called advantages of compressed air over vacuum as a medium of mechanical carpet cleaning, and, apparently, proved that vacuum cleaners were much less efficient than cleaners operated by compressed air. A year or two later the American Air Cleaning Company evidently had a change of heart and began to manufacture these same “inefficient” vacuum cleaners. Their previous treatise on vacuum cleaning, which apparently was not copyrighted, was republished by both the Sanitary Devices Manufacturing Company and by the Vacuum Cleaner Company, which had acquired Mr. Kenney’s patents, and freely distributed. Thus this little work of the Milwaukee company, instead of injuring their competitors, was turned into good advertising for them and required a lot of explanation from the Milwaukee company.

Steam Aspirators Used as Vacuum Producers.

—The American Air Cleaning Company used a steam aspirator as its vacuum producer and, unlike its predecessor, the air-operated ejector, it made good and has also been used to a limited extent by the Sanitary Devices Manufacturing Company. It is now marketed by the Richmond Radiator Company, and its merits will be discussed in a later chapter. The American Air Cleaner Company also used as a vacuum producer the single-impeller type of rotary pump, made by the Garden City Engineering Company, which was also later adopted, to a limited extent, by the Vacuum Cleaner Company. This will be discussed further on.

The renovator used by this company was a single-slot type, with ¹⁄₈-in. by 10-in. cleaning slot. These systems at once became notable on account of the small size of the vacuum producers used, the low degree of vacuum carried, and the vigorous campaign of advertising which was conducted.

Several firms soon began to market vacuum cleaning systems almost identical with that of Mr. Kenney, among which were the Blaisdell Machinery Company, The Baldwin Engineering Company, and The General Compressed Air and Vacuum Machinery Company, the latter being the original Thurman company.

The Vacuum Cleaner Company then began a series of infringement suits against nearly every manufacturer of vacuum cleaning systems. In nearly every case the suit has resulted in the offending company paying license fees to the Vacuum Cleaner Company, and this concern has now abandoned the manufacture of vacuum cleaners and has become a licensing company. At this writing nearly twenty firms are paying license fees to the Vacuum Cleaner Company and there is one suit now in the courts.

Piston Pump Used Without Separators.

—A vacuum cleaning system of somewhat different design was produced by two former employees of the Vacuum Cleaner Company, Mr. Dunn, the once well-known “Farmer Dunn” of the weather bureau, afterward salesman for the Vacuum Cleaner Company, and Mr. Locke, at one time this firm’s engineer. This company was first known as the Vacuum Cleaning Company, and, shortly afterward, as the Dunn-Locke Vacuum Cleaning Company. No separators were used with this system, but the dust-laden air was led from the pipe lines directly into a chamber on the pump, known as the “saturation chamber,” and there mingled with a stream of water converting the dust into a thin mud. The air, water and mud then passed through the pump, the muddy water was discharged into the sewer, and the air into the atmosphere. The vacuum producer used was a piston pump without suction valves. With this system it was possible to handle water in almost unlimited quantities and with this feature a system of mechanical scrubbing was attempted for which great claims were made, none of which, however, were realized in a commercial way.

These gentlemen sold their patents to the E. H. Wheeler Company, which attempted to market the system in its original form. It was found, however, that the piston pump was not adapted to the handling of grit which was picked up by the renovators, and a rotary pump, with single impeller and a follower was substituted. This system is now marketed by the Vacuum Engineering Company, of New York, and is known as the Rotrex system.

Mr. Dunn again entered the field of vacuum cleaning and began marketing his machine a short time ago with a new form of automatic separator discharging to sewer.

First Portable Vacuum Cleaner.

—About 1905, Dr. William Noe, of San Francisco, constructed the first portable vacuum cleaner. This machine contained a mechanically-driven rotary brush, similar to the brushes used in the familiar carpet sweeper, for loosening the dust from the carpet. This dust was sucked up by a two-stage turbine fan and discharged into a dust bag, mounted on the handle, similar to the bags on the compressed air cleaners. The whole machine was mounted on wheels and provided with a small direct-connected motor. This machine is illustrated in [Fig. 9] and is the original form of the well-known Invincible renovator manufactured by the Electric Renovator Company, of Pittsburgh. This company now produces a complete line of stationary and portable vacuum cleaners, all of which use multi-stage turbines. The sale of the product of this company, until recently, was controlled by the United States Radiator Corporation.

FIG. 9. FIRST PORTABLE VACUUM CLEANER, CONSTRUCTED BY DR. WILLIAM NOE, OF SAN FRANCISCO, IN 1905.

First Use of Stationary Multi-Stage Turbine Blowers.

—About 1905 Mr. Ira Spencer, president and engineer of the Organ Power Company, which manufactured a multi-stage turbine blower for organs, known as the “Orgoblow,” organized the Spencer Turbine Cleaner Company and marketed a vacuum cleaning system, using a modification of the “Orgoblow” as a vacuum producer. These machines were first constructed with sheet metal casings and had sheet steel fans, with wings riveted on and mounted on horizontal shafts. The separators were sheet metal receptacles with screens for catching litter. Light-weight hose, 2 in. in diameter, was used to connect the renovators to 4-in. sheet metal pipe lines. A variety of renovators was produced for use with this system. Carpet renovators having cleaning slots varying from 10 in. by ³⁄₄ in. to 20 in. by ¹⁄₄ in. were used, and a very complete line of swivel joints for connecting the renovators and the hose to the handles was developed. This system was operated at 5 in. vacuum, which was much lower than that used by any other system, 15 in. being standard at that time, and a much larger volume of air was exhausted under certain conditions than was possible with any of the then existing systems. Owing to the large volume of air exhausted and to the large size of the renovators, hose and pipe lines, larger articles could be picked up than was possible with any of the existing systems. A great deal of weight was attached to this condition by the manufacturers, a favorite stunt being to pick up nails, washers, waste, small pieces of paper and even pea coal from a floor and finally to pick up a quantity of flour which had first been carefully arranged for the demonstration.

FIG. 10. LATE TYPE OF SPENCER VACUUM CLEANING MACHINE, OPERATED BY MULTI-STAGE TURBINE BLOWER.

This invasion of the vacuum cleaning field was considered by the established manufacturers as a freak and the apparatus was christened “the tin machine.” Whenever it was installed in competition with other forms of cleaning systems, the daily question asked by its competitors was, “Has the tin machine fallen apart?” However, the tin machine did not fall apart, but held its own with the other systems, even in its crude and inefficient state. Finding that the construction he had adopted was too flimsy and subject to abnormal leakage, Mr. Spencer developed a new form of machine, using cast-iron casing and welded fan wheels and adopted standard pipe and fittings. He also brought out a line of sheet metal tools and on the whole perfected a satisfactory cleaning system. One of his machines of a later type is illustrated in [Fig. 10].

Separators Emptying to Sewer by Air Pressure.

—A new form of vacuum cleaning system was introduced by Mr. Moorhead, of San Francisco, who used an inrush type of renovator having an inlet for air on each side of the cleaning slot.

The separator used with this system was a wet separator and contained a screen cleaned by a rotary brush into which all the dust contained in the air lodged. The pump used with this system was generally of the piston type, fitted with a single rotary valve, so connected to the valve stem that it could be rotated thereon and the machine changed from a vacuum pump to an air compressor in order that the contents of the separators might be discharged into the sewer by air pressure when it was desired to empty same.

This system was marketed by the Sanitary Dust Removal Company, of San Francisco, and, later, was taken over by the American Rotary Valve Company, of Chicago, which is now marketing same. It eliminates the manual handling of the dust at any stage of its removal, a feature which is made much of by its manufacturers, but one which is likely to cause some trouble for the sewerage system if care is not exercised.

Machines Using Root Blowers as Vacuum Producers.

—The use of a Root type of rotary pump as a vacuum producer was first undertaken by the Foster and Glidden Engineering Company, of Buffalo, which marketed the Acme system about 1907, the same company having previously built a similar system for the removal of grain from steam barges. The other features of this system did not differ materially from those already on the market.

Being familiar with the various uses to which this type of vacuum pump had been adapted, the principal one being the operation of pneumatic tube systems, the author suggested the use of this type of vacuum producer about two years previous to its introduction and was advised by one manufacturer that such a type of pump was not suitable for vacuum cleaning. The fallacy of this statement will be brought out in detail in a later chapter.

The type of vacuum producer just described has been adopted in many makes of vacuum cleaners, including the Hope, Connellsville, Arco, and, lately, in the American Rotary Valve Company’s smaller systems.

During the past four years a score or more of new stationary vacuum cleaning systems have been introduced, among which are the Palm, a modification of the Dunn-Locke system; the Tuec, a turbine cleaner; the Water Witch, which uses a water-operated turbine as a vacuum producer, and the Hydraulic, with water-operated ejector. At the same time a hundred or more portable vacuum cleaners have been marketed. These are of almost every conceivable type and form and are operated by hand, electricity, and water power. Among them will be found machines which are good, bad and indifferent, the efficiency and economy of which will be discussed in a later chapter.

This nearly universal invasion of the vacuum cleaner field by anybody and everybody looking for a good selling article, establishes the fact that the vacuum cleaner is not a fad or fancy, but has become almost a household necessity and has led large corporations to take it up as a branch of their business. First, the Sanitary Devices Manufacturing Company and the Vacuum Cleaner Company, the pioneers in the field, after a legal battle of years, consolidated with a view of driving their competitors from the field as infringers of the patents controlled by the two organizations. The result of this was the licensing of other companies. In an attempt to control the sale of their type of apparatus notice was served on all users of other types of vacuum cleaners that they were liable to prosecution for using infringing apparatus.

Later, the McCrum-Howell Company, a manufacturer of heating boilers and radiators, secured control of the products of the American Air Cleaning Company and the Vacuum Cleaner Company and sold these machines to the trade for installation by the plumbers and steam fitters. The McCrum-Howell Company has been succeeded by the Richmond Radiator Company, which is handling these vacuum cleaning machines.

Shortly afterwards, the United States Radiator Corporation secured control of the Invincible and the Connellsville systems, and, lastly, the American Radiator Company secured the Wand system.

Thus we see that vacuum cleaning seems to be virtually in the control of the manufacturers of heating apparatus, who are also among the largest corporations in this country and well able to control the future of this business to their liking.

As to the future of vacuum cleaning the author considers that it is at present, like the automobile, at the height of its career, and also, like the automobile, that it is a useful appliance to mankind and that it has its proper place as a part of the mechanical equipment of our modern buildings.

As to the type of vacuum cleaner of the future, the author believes that these appliances will become standardized, just as all other useful appliances have been, and that the form that it will then take will be a survival of the fittest. What that form may resemble the reader may more readily judge when he has completed the reading of this book.

CHAPTER II.
Requirements of an Ideal Vacuum Cleaning System.

Before a comparison of the relative merits of any line of appliances, used for any one purpose, can be intelligently made, one must have either some form of that apparatus which we consider as a standard for comparison that we may rate all others as inferior or superior thereto, or else an ideal of a perfect system must be assumed, and the measures with which each of the various appliances approaches the requirements of the ideal will establish their relative merits.

The author has elected to use the latter method in comparing the various systems of vacuum cleaning, and it is necessary, therefore, to first determine what are the requirements we shall impose on the ideal system.

An ideal vacuum cleaning system would be one which, when installed in any building, will displace all appliances used for dry cleaning in the semi-annual renovating or house cleaning, the weekly cleaning or Friday sweeping and the daily supplemental cleaning. If our system be truly an ideal one, the premises should never become so dirty as to require any semi-annual cleaning at all, and, if the daily cleaning be anyway thorough, there need be no weekly cleaning. This latter condition may be governed by the will of the housekeeper or janitor.

The compressed air cleaners first introduced were intended for use only at the semi-annual cleaning and they were in reality carpet renovators, which were assumed as imparting to the carpets all the beneficial results that could be obtained by taking them up and sending them to a carpet-cleaning establishment, with the advantage over this latter method, that the labor of removal and replacement of the carpets was rendered unnecessary, but with the disadvantage that all the germ-laden air, used as a means of cleaning the carpets, was blown back into the apartment, leaving the germs in their former abode.

This disadvantage, however, is partly offset by the fact that while the majority of the germs in one’s own carpet are blown out at the carpet cleaners, a mixed company of germs from your neighbors’ and others’ carpets, which may be in the tumbling barrel at the same time with your own, are returned to you with your carpet.

Neither of these conditions is ideal and we will expect our ideal cleaner to completely remove from the premises, not only the dust and dirt, but also the germ-laden air which is used as a means of conveying this dirt.

For replacing the weekly and the daily cleaning, these earlier renovators were not suitable, as in order to use same the furniture must all be removed from the apartment.

To accomplish this daily and weekly cleaning, the ideal vacuum cleaner must replace the broom and dust pan, and their inseparable companion, the duster, and must also supersede that time-honored mechanical cleaner, the carpet sweeper.

The reader will doubtless consider that in making this statement the author is asking the vacuum cleaner to perform much more than it is usually called on to do. However, we are now discussing an ideal system, and the above requirements are not absolutely beyond what can be accomplished by some of the cleaning systems now on the market.

To accomplish this requirement the ideal cleaner must pick up everything likely to be found on the floor which cannot be readily picked up by hand. The character of this material will vary greatly according to the uses of the apartment cleaned. In residences and offices, where carpets or rugs are in use, cigar stumps and matches are usually deposited in cuspidors and small pieces of paper in waste baskets, consequently there should be nothing but dust to be removed from a residence and, perhaps, mud and sand from the shoes of the many visitors, in addition to the dust in an office.

However, there are special conditions likely to be met in many cases; sewing rooms will be littered with basting threads and scraps of cloth; department stores, with a great quantity of pins; banking rooms with bands and large-sized bank pins; all of which increase the requirements of the ideal system. A cleaner which is perfectly adapted to one sort of apartment will be entirely unsuited for another, and the ideal cleaner will be one which can be readily adapted to all conditions likely to be met in the building in which it is installed.

The ideal cleaner must be able to accomplish the above stated requirements without the necessity of moving heavy pieces of furniture out of or about the apartment; that is, it must be capable of being efficiently operated under beds, tables and chairs, around the legs of other heavy furniture, behind bookcases, pianos, cabinets, etc., over curtains, draperies and hangings, over walls, behind pictures and over mouldings and carved ornaments, all without injury to any of the furniture or fittings of the apartment, and with the least expenditure of energy by the operator.

These conditions should be met with the fewest possible number of cleaning appliances, none of which should be provided with small attachments liable to be lost or misplaced, and all parts of the system, which must necessarily be moved about, either before, after or during the cleaning operation, should be of minimum weight and bulk, but of rugged and lasting construction.

The ideal vacuum cleaner should be of such proportions and provided with ample motive power to clean rapidly and effectively.

For use in an office building the cleaner should be able to thoroughly clean an average-sized office, including floor, walls, furniture and fittings in from 10 to 15 minutes, and for residence work, should be of sufficient capacity to clean an apartment, including floor, walls, curtains, draperies, pictures and furniture in not exceeding 30 minutes.

The ideal system should be so arranged that any apartment in the building can be cleaned with the least possible disturbance and without affecting the use of any other apartment, excepting perhaps, the corridors or hallways.

In large offices, drafting rooms and similar apartments, it may become necessary to clean same while they are occupied; therefore, our ideal system must be practically noiseless in operation and must offer the least possible obstruction to the proper use of the room by its regular occupants.

Necessity and Proper Location of Stationary Parts.

—To be of sufficient power to do rapid cleaning and in order to remove from the building all dust and germ-laden air, the cleaning system must necessarily contain some stationary parts. The motive power can generally be confined to these stationary parts, and must, in such cases, be located within the building to be cleaned. Therefore, it should operate with the minimum of noise and vibration.

Machines located in office or other large buildings, containing elevators or other complicated apparatus requiring skilled attendance, which are provided with complicated control and with other attachments, are not objectionable, and in such cases simplicity should give way to efficiency, but unnecessary complications should be avoided.

In residences and other small buildings, where the vacuum cleaner is likely to be the only machinery installed, the system must be one which requires the minimum attention and must be capable of being started and stopped by any person of average ability, without the necessity of going to the point where the machine is located.

The power consumption of the ideal system should be a minimum to accomplish satisfactory results and should be, as nearly as possible, directly proportioned to the amount of cleaning being done. This requirement is most important in hotels, where some cleaning is likely to be done at all hours, day and night. In other words, vacuum must be “on tap” and as readily attainable at any point in the building as your water or electric light. In office buildings, where a schedule of cleaning hours is fixed, and in residences where cleaning hours are few and the capacity of the plant is rarely more than could be attended to by one operator, this requirement is not of as great importance.

Lastly, our ideal system, from the standpoint of the purchaser, must be of such rugged construction, as will enable it to operate efficiently for, at least, ten years and its mechanical details such that it will operate continuously, without expert attention, and that the annual expense for repairs during the life of the machine will not exceed 5% of the first cost of the system.

CHAPTER III.
The Carpet Renovator.

In undertaking the comparison of a number of different makes of any appliance, in order to determine the good and bad points in each, where the apparatus is composed of a number of separate and distinct parts, each having its proper function, which they must perform in order to make the whole apparatus effective, as in a vacuum cleaning system, it becomes necessary to isolate temporarily each part and consider its action, first, as a unit working under the most favorable conditions, and, second, as a component part of the whole apparatus in order to determine where the weak points in any system occur and what modifications are necessary in the various parts of the apparatus to make some vital part of the whole more effective. It is further necessary to determine what are the vital parts of the system in order that the other parts may be accommodated to the effective action of that part.

Four Important Parts of Vacuum Cleaning System.

—In analyzing a vacuum cleaning system it naturally divides itself into four parts, viz.: the cleaning tool or renovator, the air-conveying system or hose and pipe lines, the separators or other means of disposal of the material picked up, and the vacuum producer.

The author considers that the renovator is the most important part of the system and that the other parts should be made of such proportions and with such physical characteristics as will produce the proper conditions at the renovator to permit it to perform its functions in the most effective manner.

As the vacuum cleaning system must be capable of cleaning surfaces of a widely variable character many forms of renovators are necessary. Of the various surfaces cleaned the author considers that carpets and rugs comprise the most important, as well as the most difficult to clean effectively, so that the carpet renovator will be considered first.

The Straight Vacuum Tool.

—Various forms of carpet renovators have been and are in use by manufacturers of vacuum cleaning systems. The first type of renovator to be considered is that having a cleaning slot not over 12 in. long, with its edges parallel throughout its length, and not over ³⁄₈ in. wide, with a face in contact with the carpet not over ³⁄₈ in. wide on each side of the slot. This form of renovator is illustrated in [Fig. 11] and is designated by the writer as Type A. The first of these renovators was introduced by Mr. Kenney and, as finally adopted by him, was 12¹⁄₂ in. long, with ⁷⁄₈-in. face and with a cleaning slot 11¹⁄₂ in. long and ⁵⁄₃₂ in. wide. This form of cleaner was termed the “straight vacuum tool” and is used today by many manufacturers. Slight modifications in its form and dimensions were made in some cases, as in the one manufactured by the American Air Cleaning Company. In the one used in all tests by the writer on type A renovators, the slot was reduced to 10 in. long and ¹⁄₈ in. wide and the face of the renovator was slightly rounded at the outer edges, leaving very little surface in contact with the carpet.

FIG. 11. TYPE A, THE STRAIGHT VACUUM TOOL.

FIG. 12. TYPE B, WITH WIDE SLOT AND WIDE BEARING SURFACE.

A renovator of this type is easily operated over any carpet even when a considerable degree of vacuum exists within the renovator itself. It has met with favor when used with the piston type of vacuum pump without vacuum control, as was the case with the earlier systems. However, when a very high degree of vacuum occurs within the renovator it has a tendency to pull the nap from the pile of the carpet.

Soon after the introduction of this form of renovator, some users of same, particularly in San Francisco, complained that while the renovator effectively removed the dust from carpets it failed to pick up matches and other small articles and preliminary or subsequent cleaning was necessary in order to remove such litter.

To overcome this difficulty Mr. Kenney increased the width of the cleaning slot to nearly ¹⁄₂ in., with the result that when a high degree of vacuum existed within the renovator, which often occurred where no vacuum control was used, it stuck to the carpet, rendering its operation difficult and, at the same time, doing great damage to the carpet. Hence, its use with the piston type of vacuum pumps was abandoned.

Mr. Kenney then modified this wide slot renovator by making the face of same much wider, thus having more surface in contact with the carpet on each side of the slot, preventing the renovator from sinking into the nap of the carpet. This type of renovator is illustrated in [Fig. 12] and has been designated as Type B. While not as destructive to the carpets, when a high degree of vacuum existed under the same, it still pushed hard and was not as rapid a cleaner as the narrow-lipped Type A renovator.

Renovator with Auxiliary Slot Open to Atmosphere.

—The renovator introduced by the Sanitary Devices Manufacturing Company differed widely from the former types in that it was provided with an auxiliary slot, open to the atmosphere through the top of the renovator, which communicated with the slot open to the vacuum by a space of ¹⁄₃₂-in. under the partition separating the slots. The cleaning slot was made ⁵⁄₁₆-in. wide and the face of the renovator was made 2-in. wide, which gave a contact of ¹³⁄₃₂-in. in front of the inrush slot and ²¹⁄₃₂-in. in the rear of the cleaning slot. This form of renovator is illustrated in [Fig. 13] and is designated as Type C.

The auxiliary slot or vacuum breaker permitted air to enter the cleaning slot even when the renovator was placed on a surface plate, and, owing to this feature, a high degree of vacuum never existed within the renovator. It was always easy to operate and did not damage the carpet. Owing to the wide slot, articles of considerable size could be picked up, and there was always an abundance of air passing through the renovator to produce a velocity in the hose and pipe lines sufficient to carry any heavy articles picked up.

The vacuum producer, control apparatus and the proportions of the hose and piping used at that time made the degree of vacuum in the renovator a function of the quantity of air passing, with wide limits of variation under existing conditions, and this form of renovator is practically the only one which will do effective cleaning, including the picking up of litter, without undue wear on carpets, when used with a system having the above-stated characteristics. This renovator, however is not without its faults. Owing to the wide surface in contact with the carpet, a considerable degree of vacuum is necessary in order that any air shall enter the renovator under the faces of same and, as the air entering the inrush slot prevents the formation of such vacuum within the renovator, very little air enters the renovator between its face and the carpet. When the renovator is operated on a carpet having a glue-sized back, no air enters through the carpet, therefore all air entering the renovator must come through the inrush slot and under the partition separating same from the cleaning slot. Under these conditions only one side of the vacuum slot is effective and this effective side is raised above the surface of the carpet.

FIG. 13. TYPE C, WITH AUXILIARY SLOT, OPEN TO ATMOSPHERE.

FIG. 14. TYPE D, WITH TWO CLEANING SLOTS.

When operated on an ingrain or other loose-fabric carpet, much air enters through the fabric of the carpet, due to the wide cleaning and inrush slots, in addition to the quantity of air entering through the inrush slot, making this renovator, when operating under these conditions, use an unnecessary amount of air. Apparently, this renovator has been designed to prevent the formation of any great degree of vacuum under same and such a design has resulted in a greater volume of air at a lower vacuum passing through than through renovators of other types.

This property of the renovator raises the question whether the quantity of air or the degree of vacuum in the renovator is most essential for the removal of dirt from carpets. Tests made by Mr. S. A. Reeve, consulting engineer for the Vacuum Cleaner Company, with this type of renovator, with the inrush open and repeated with the inrush closed, disclose the fact that it does more effective cleaning with its inrush closed, while the volume of air passing is considerably less with the inrush closed. The degree of vacuum was greater, which tends to indicate that the vacuum within the renovator is the most important factor.

An extract from the affidavits of Mr. Reeve in one of the numerous patent suits will show his explanation of this phenomenon: “If we examine more closely into the actual process whereby such a sweeper succeeds in extracting dust from carpets, etc., it will appear that the actual cleaning is effected at the periphery of the slot in the lower surface of the sweeper. It is accomplished chiefly by the development of local changes of air pressure at the lips defining this slot, incidentally to the movement of the tool over the carpet. These changes cause the air occupying the interstices between the dust particles to expand suddenly, thus ‘raising the dust.’ To a lesser degree, the scouring is effected by highly localized air currents of considerable velocity, engendered where the tool comes in contact with the carpet. These air currents pick up the dust which has already been expanded or raised by pressure change. They will be of higher velocity, and therefore more effective, the better the contact of the tool with the carpet. The same is true of the pressure changes.

“All this action depends for its intensity, speed and effectiveness, not on the vacuum existing at the pump or in the separators, but upon the vacuum prevailing within the sweeper head itself.”

Renovator with Two Cleaning Slots.

—Another form of renovator was introduced by the Blaisdell Machinery Company which contained two cleaning slots each ³⁄₁₆-in. wide and 12-in. long, separated by a partition ¹⁄₄-in. wide in contact with the surface of the carpet, as indicated in [Fig. 14] (Type D). While this form of renovator has a greater area of cleaning slot than Type A, its individual cleaning slots are no wider; therefore, it cannot pick up anything larger than can be picked up by Type A. As no air can enter under the partition it can do no more effective work as a dust remover when operated on a carpet with a glue-sized back and its only advantage over a cleaner of Type A is that when operated on a loose-fabric carpet more air can pass through the fabric into the cleaning slot, thus giving a greater variation in the quantity of air exhausted when operated on carpets of different texture, a condition which is undesirable when used with a system having characteristics previously described.

Tests of this type of renovator, made by Mr. Reeve, are given later in this chapter.

Renovator with Inrush Slots on Each Side.

—Another form of renovator, introduced by Mr. Moorhead, is illustrated in [Fig. 15] (Type E). This is a modification of Type A in that an inrush slot is provided on each side of the vacuum slot, these inrushes being hinged members which form the sides of the cleaning slot. This cleaner has the advantage over Type C renovator in that it can take air from either side, but in action it takes air from but one side at any time. Its inrush will not become entirely clogged, but its mechanically-moving parts in contact with the dust and lint picked up will easily become inoperative and are as like as not to become caught wide open when the air entering the cleaner will not come into intimate contact with the carpet. In that event, its cleaning efficiency will be greatly reduced. The author has not had an opportunity to make any comparative tests of this form of renovator.

When Mr. Spencer introduced the centrifugal fan as a vacuum producer, he also brought out a series of carpet renovators of various forms and sizes. One had a cleaning slot ³⁄₄-in. wide and 10-in. long, another a slot 15-in. long, ¹⁄₄-in. wide at its end, increasing to ³⁄₄-in. at the center. Another had a slot 20-in. long and ³⁄₈-in. wide, and finally he adopted a tool with a cleaning slot 15-in. long and ¹⁄₂-in. wide throughout its length. This is merely the re-entrance into the field of the wide-slot tool first used by Mr. Kenney and its successful operation depends on its use with a vacuum producer of such characteristics and a hose and pipe line of such proportions that practically a constant vacuum is maintained within the renovator, regardless of the quantity of air passing through the tool. The latest form of this renovator, as used by Mr. Spencer, is illustrated in [Fig. 16]. At the time that the writer made tests on renovators of this make, the majority of the tests were made with a renovator having a cleaning slot 10-in. long and ³⁄₄-in. wide. This renovator is designated as Type F, while the 15-in. × ¹⁄₄-in. to ³⁄₄-in. slot is designated as Type F¹.

FIG. 15. TYPE E, WITH INRUSH SLOT ON EACH SIDE OF VACUUM SLOT.

FIG. 16. TYPE F, AN EXAGGERATED FORM OF TYPE B.

About seven years ago the Supervising Architect of the United States Treasury Department gave consideration to the use of a carpet cleaning test to determine the acceptability of any vacuum cleaning system which might be installed in any of the buildings under his control. The author was instructed to make a series of tests of carpet renovators, with a view of determining: (1) the feasibility of using a carpet cleaning test to determine the merits of a vacuum cleaning system; (2) to fix the requirements to be incorporated in a specification where the acceptance of the system was dependent on a satisfactory carpet cleaning test, to be made at the building after the completion of the installation; (3) to determine what requirements, other than a cleaning test, would be necessary to obtain a first-class cleaning system.

The record of many such tests was shown to the author, shortly before he began making tests. These purported to have been made by Prof. Miller at the Massachusetts Institute of Technology, with a pump furnished by the Sanitary Devices Manufacturing Company, in which the efficiency of the inrush type of renovator (Type C) and the straight vacuum renovator (Type A) was compared. The results of these tests, as given in a brief resumé, which was distributed by the Sanitary Devices Manufacturing Co., indicated that the Type C renovator was the more rapid and efficient cleaner.

The author learned that these tests were made by the undergraduate students as a part of the regular laboratory work, and that later a series of tests was made as the basis of a thesis by Messrs. Paterson and Phelps in 1906, using the above-described apparatus. The following year another series of tests was made by Mr. Stewart R. Miller, as the basis of an undergraduate thesis, in which the efficiencies of the piston pump and inrush sweeper of the Sanitary Devices Manufacturing Co. were compared with those of the steam aspirator and straight vacuum renovator of the American Air Cleaner Company. A copy of this thesis was furnished the author by the Sanitary Devices Manufacturing Company shortly after the completion of the tests made by the author.

The relative efficiency of the two types of renovators reported by these tests differed widely in each case, an occurrence which is liable to happen where undergraduate students are engaged in such work. They were, therefore, considered as of doubtful reliability.

The author could find no record of any tests made by anyone of longer experience and, indeed, these were the only tests of which he could find any record.

As the author desired to specify a cleaning test which could be readily repeated at the building in which the cleaning system was installed, which building was likely to be located in any part of the United States, no exhaustive laboratory methods were desired or attempted. As the building was likely to be located in a city where no other vacuum cleaning systems were then installed and in a new building in which no dirty carpets were available, and as it was not desirable to have the contractor furnish the material for the test, it was considered necessary to use some material in soiling carpets which would be readily obtainable anywhere, which could be readily brought to a standard, and which, when worked into the carpets in a reasonable length of time, would be as difficult to remove as the dirt found in the average dirty carpet.

Tests on Dirty Carpets.

—As no tests of cleaning an actually dirty carpet were on record, quicksand having been used in the Institute of Technology tests, it was necessary to first clean some carpets that had been soiled in actual daily service in order to obtain a standard with which to compare the results in removing various substances, which it was intended to try as a substitute for dirt. A carpet which had been in actual use for a number of years on the floors of the old United States Mint building, in Philadelphia, and receiving the ordinary amount of cleaning, was procured. This was a Brussels carpet with a glue-sized back, containing about 20 sq. yds. It was divided into three approximately equal parts.

An indicator was attached to the vacuum pump for taking air measurements, and it was found that there was considerable leakage of air into the system through the connections to the separators and at other points, therefore the pump was operated with 22 in. of vacuum in the separator and a card taken with all outlets closed and the amount of leakage noted. During the tests this degree of vacuum was always maintained in the separators and pipe lines and the vacuum in the renovator was varied throughout the tests by throttling the hose cock. This manner of making tests gave a practically constant leakage which was deducted from the quantities shown by the indicator cards taken with the renovators in operation.

As the writer had already made many tests of the efficiency of various types of vacuum pumps as air movers under various degrees of vacuum, and as the capacity of the pump available was far in excess of that required to operate one renovator, no attempt to obtain the efficiency of the plant as a unit was made. Instead, the vacuum at the hose cock was adjusted until the degree obtained was what the writer had found to be within the limit obtained in practice. The resulting vacuum at the renovator was then noted.

Each piece of carpet was cleaned during six periods of one minute each, using a different vacuum at the tool for each piece of carpet. The carpets were weighed at the beginning of the test and after each one-minute period. At the conclusion of these tests each carpet was cleaned until no change of weight occurred after two minutes’ cleaning. They were then considered as being 100% clean and this standard was made a basis for computing the percentage of dirt removal. A renovator of Type C was used in these tests.

Shortly afterward a similar test was made on a dirty carpet of 4.6 sq. yds. area, using a renovator of Type F. This carpet was also a Brussels, with glue-sized back, which had been in use in the shoe department of a large department store in Hartford. These carpets contained approximately 2 oz. of dust per square yard, none of which was visible on the surface, and they were probably as clean as the average carpet after being gone over with a carpet sweeper or after a light application of a broom.

TABLE 1.
Cleaning Tests of Dirty Carpets.

As the sizes of the carpets used in making the tests were not always the same, allowance has been made for this variation by using, in the case of Type F renovator, instead of the true time, a calculated time which allows each renovator the same time for cleaning 1 sq. yd. of carpet. For instance, in the case of the small carpet cleaned with Type F renovator, an interval of 60 × 4.6 ÷ 6, or 46 seconds, was taken as equal to one minute’s cleaning of the carpet with types A and C renovators. Such interval is stated and plotted as one minute in the [table] opposite, which gives the results of cleaning dirty carpets with the three types of renovators.

Type A Renovator Most Efficient on Dirty Carpets.

—The results of the tests of the three types of renovators, each when it was operated with the highest vacuum under the renovator, are plotted in [Fig. 17] in order that a ready comparison may be made. This curve indicates that Type A renovator does more effective cleaning in less time than either of the other two types tested.

FIG. 17. TESTS OF THREE RENOVATORS ON DIRTY CARPETS.

Referring to the second line of the table, which gives the degree of vacuum obtained in the renovator during the tests, it will be noted that the highest vacuum attained with each type of renovator is practically the same. This degree of vacuum was obtained with the average vacuum at the hose cock, using 100 ft. of hose in each case, and corresponds to that obtained in the commercial operation of each of the renovators with the vacuum producers ordinarily used, which was 15 in. in the case of Type C, 10 in. in case of Type A, and 5 in. in case of Type F, the hose being the size used by each of the systems as marketed.

The third line, which shows the cubic feet of free air per minute passing the renovator, indicates that Type A renovator requires much less air at the same degree of vacuum than either of the other types to do better work.

From the readings in these two lines the horse power required at the renovator, to move the air that passes same is obtained with 100% efficiency adiabatic compression. The results are tabulated in the ninth line of the table.

This indicates that Type A renovator does more effective work with about 50% of the power required by either of the other types of renovators.

The tenth line gives the rate of cleaning and again shows Type A renovator to be the most rapid cleaner.

The eleventh line gives the horse power required at the renovator when in operation, from which it will be seen that effective cleaning cannot be accomplished with less than ¹⁄₄ H. P. at the renovator.

Attention is called to the great reduction in power in case of Type A renovator when the vacuum at the tool is reduced from 4¹⁄₂ in. to 2 in. and to the small reduction in the efficiency which results from this great reduction in power. This is not the case with the Type C renovator, where there is a considerable reduction in the already low efficiency with each reduction in the vacuum. This characteristic of Type A renovator is discussed further on in the chapter on [hose].

Tests of Carpets “Artificially” Soiled.

—Having determined the efficiency of the various types of renovators when operated on dirty carpets, the author then attempted to find some substance easily obtained anywhere which could be used as a substitute for actual dirt, and which would give approximately equal results with these obtained on dirty carpets.

A test of this character was made by the author some time previous to the tests of dirty carpets and was made on a Wilton velvet rug of about 12 sq. yds. area. The material spread on same was ordinary wheat flour, as used in demonstrations, 3 lbs. of which were placed on the rug and rubbed in with sticks of wood as well as possible and the rug cleaned for three minutes, using a Type A renovator attached to the separator with 50 ft. of 1-in. diameter hose. The results were as follows:

The vacuum at the renovator was not measured at the time of making this test and its amount is not exactly known, but further tests with this type of renovator under nearly the same conditions gave the following results:

and it is probable that the vacuum at the renovator during these tests was approximately the same.

Comparison of the results of this test, in which 4 sq. yds. of carpet were cleaned per minute, with those of the tests of dirty carpets, in which only 1 sq. yd. was cleaned per minute, indicates that wheat flour is not a suitable substitute for dirt in making a carpet cleaning test.

The author, believing that flour is of sufficient fineness, but not of sufficient weight, tried Portland cement, which is very heavy and at the same time exceedingly fine, as a substitute for dirt in soiling carpets. The same carpet that had been cleaned in Philadelphia was used and 6¹⁄₂ oz. of cement was worked into the same. It was then cleaned with a Type C renovator, with a vacuum of 2¹⁄₂ in. hg. at the renovator and 95% of the cement was removed in two minutes’ cleaning, as against 59% of the dirt in the carpet when received.

Ordinary dirt, taken from some flower pots which had been left dry for some time, was then tried with the same carpet, using a Type C renovator and 1 in. hg. With this arrangement, 71¹⁄₂% of the dirt was removed in two minutes as against 52% of the dirt in the carpet as received.

This dirt was then mixed with water to a thin mud and spread over the carpet and the carpet dried before cleaning. Then 11¹⁄₄ oz. of this material was worked into 6 sq. yds. of carpet and a Type C renovator removed 100% of this in four minutes’ cleaning, with a vacuum of 2¹⁄₂ in. hg. at the tool as against 72% of the dirt in the carpet as received.

The author’s ingenuity being about exhausted, he referred to the test of Mr. Stewart R. Miller in which quicksand which would pass a 50-mesh to the inch screen was used, a long-napped Brussels carpet being filled with 5¹⁄₂ oz. per square yard and cleaned with Types A and C renovators.

This test indicated that a nearer approach to the results in cleaning dirty carpets was possible with this substance than with any which the author had tried. The author repeated Mr. Miller’s test, using a Type F renovator, 10-in. × ³⁄₄-in. cleaning slot, and also a Type F¹ renovator, 15-in. × ¹⁄₄-in. to ³⁄₄-in. cleaning slot. In duplicating these tests the author was associated with Mr. E. L. Wilson, a graduate of the Institute, who was familiar with the methods used by Mr. Miller. With his assistance, the conditions of Mr. Miller’s tests were almost exactly duplicated. The results of Mr. Miller’s and the author’s tests are given in the [table] opposite, correction being made in the time of cleaning proportional to the size of carpets used, to allow the same time for cleaning 1 sq. yd. of carpet by each renovator.

TABLE 2.
Cleaning Tests of Carpets Filled with 5¹⁄₂ Oz. of Quicksand
per Square Yard of Carpet.

The results of these tests are shown graphically in [Fig. 18]. Comparison of these curves with the curves of cleaning dirty carpets ([Fig. 17]), shows a falling off in the efficiency of cleaning by Type A renovator while there is a gain in the efficiency in cleaning by all of the other types of renovators, Type C being now nearly as efficient as Type A, while Types F and F¹ renovators are now more efficient than Type A. This result must be due either to the increased quantity of material to be removed, 5¹⁄₂ oz. per square yard in case of the sand as against 2 oz. per square yard in case of the dirt, or else to the change in the character of the material removed, the sand having much sharper surfaces than would be encountered in case of dirt which must necessarily be ground under the feet before it reaches the carpet, or to the longer nap of the carpet.

FIG. 18. CLEANING TESTS OF CARPETS FILLED WITH QUICKSAND.

In order to determine the effect of the increase in the quantity of material on the results, the tests were repeated using 1 oz. of sand per square yard of carpet in each case, omitting the test on Type F¹ renovator.

These tests were made on a glue-sized back, short napped Brussels carpet, using as much sand as could readily be worked out of sight in this carpet. The results of tests are given in the following table:

TABLE 3.
Cleaning Tests Using 1 Ounce of Sand per Square Yard of Carpet.

The results of these tests at the higher vacua are shown graphically in [Fig. 19]. Comparison of these curves with those obtained when removing sand from a long napped carpet ([Fig. 18]), shows:

First, a marked increase in the efficiency of Type A renovator, this being slightly better than obtained when cleaning a dirty carpet.

Second, practically no change in the efficiency of Type C renovator.

Third, a small decrease in the efficiency of Type F renovator, which still shows a much higher efficiency than when cleaning dirty carpets.

In order to determine how much, if any, of these changes in the behavior of the renovators was due to the increase in the quantity of material to be removed, the horizontal line, representing 1 oz. of sand remaining in the long-napped carpet, was drawn on [Fig. 18] and, using this as a base line, it will be seen that Type A renovator removes this remaining material in three minutes, the same time as was required to remove the same amount from the short-napped carpet. However, the first 4¹⁄₂ oz. of sand have been removed from the long-napped carpet in three minutes, or at a rate 4¹⁄₂ times as fast as the last 1 oz. was removed. This indicates that the narrow slot renovator is capable of handling more material than is likely to be encountered in any dirty carpet and that the apparent decrease in the efficiency of this renovator is not due to the increased quantity of material to be removed.

FIG. 19. CLEANING TESTS USING 1 OZ. OF SAND PER SQUARE YARD OF CARPET.

It will be noted that the Type C renovator removed the last 1 oz. per square yard from the long-napped carpet in the same time that was required by Type A renovator, while it needed nearly twice as long to remove this amount of material from the short-napped carpet ([Fig. 19]). This renovator, however, was slower in removing the first 4¹⁄₂ oz. per square yard.

Type F renovator removed the last 1 oz. per square yard from the long-napped carpet in two minutes, while it required twice this time to remove the same amount from the short-napped carpet. This renovator also removed the first 4¹⁄₂ oz. per square yard from the long-napped carpet in two minutes, while it required three minutes for Type A and 3-³⁄₄ minutes for Type C renovators to remove the same quantity. It is, therefore, evident that sand is removed more rapidly from a long than from a short-napped carpet when a wide slot renovator is used. The same time is required to remove small quantities of sand from a long or short-napped carpet with a narrow slot.

This phenomenon is probably due to the sand being held in the carpets by the adhesion of its sharp edges to the sides of the nap, this being more pronounced in the case of the long-napped carpet where it is easier to work the material out of sight without grinding it into intimate contact with the pile of the carpet. When the wide-slot renovator passes over the carpet, the carpet is arched up into the slot and the upper ends of the nap separated. The longer the nap or the wider the slot, the greater will be this separation. With the long-napped carpet this separation will at once release the sand, while, in case of the short nap, there is less separation and also more adhesion of the sand to the pile of the carpet, due to the harder grinding necessary to work the material out of sight. Therefore, the wider the cleaning slot used, the faster the sand will be removed, as is evident by comparison of the tests of Types F and F¹ renovators on the long-napped carpet.

With the narrow slot renovator the arching of the carpet under the cleaning slot is negligible and no advantage is gained when using this type of renovator to remove sand from a long-napped carpet. It is also possible that the nap of the carpet may be longer than the width of the cleaning slot, in which case the nap will not snap back to a vertical position when it is under the cleaning slot, but will be pressed down and will impair the action of the renovator. The author considers that the width of the slot should always be greater than the length of the nap of the carpet in order to do effective cleaning.

Shortly after making the above-described tests, the author had occasion to make somewhat similar tests, using a sand-filled carpet, in an attempt to try out a proposed carpet cleaning test intended to be used as a standard for use in specifications for a vacuum cleaning system. When a Wilton carpet was used, it was found that neither Type A or C renovator would fulfill the test requirements, which were within the results obtained in tests already described. Unfortunately a Type F renovator was not available, but the author is of the opinion that it would have done better.

The test was then repeated, using a Brussels carpet and the test requirement was easily met. This discovery led the author to make further tests of carpets of different makes, filled with sand and cleaned under the same conditions which yielded far from uniform or satisfactory results, and the use of a cleaning test, where artificially-soiled carpets are used, was abandoned.

The author is of the opinion that no substance artificially applied to a carpet, other than regular sweepings, will give anything like the same results as will be obtained in actual cleaning. Sand seems to be the only substance which can be worked into the carpet that is nearly as difficult to remove as the actual dirt found in carpets, and, in many cases, this material gives results that are misleading and unfair to some types of renovators. No test which uses a carpet artificially soiled with artificially prepared dirt is considered to be of any value in determining the relative efficiency of various types of carpet renovators.

A series of tests was made by Mr. Sidney A. Reeve consulting engineer, of New York City, in October, 1910, at the works of the Vacuum Cleaner Company, Plainfield, N. J., in which the conditions were such as would give much more uniform results than were possible in the tests made by the author.

In making these tests the renovator was held firmly clamped in any desired position in a wooden carriage rolling upon a straight wooden track. The portion of the carriage supporting the sweeper is attached to the remainder of the carriage by hinges, so that the sweeper is free to seek its own contact with the carpet. The carriage was given a reciprocating motion by its attachment to a large bell crank, which in turn received its motion from the factory shafting. The construction of the bell crank was such that the driving power could be readily thrown in and out of gear at any time.

The carpet was stretched tightly upon a platen which was fitted for movement across the line of motion of the sweeper, along straight guides suitably attached to the floor. The ends of the carpet were first wedged tightly in clamps and the clamps wedged apart so as to stretch the carpet.

The tests consisted in first weighing the carpet, then stretching it upon the platen, then sprinkling thereon a suitable and known weight of dirt taken from the separators of the company’s machines, from which the lint and coarse, fibrous material had been sifted and which was thoroughly trodden into the fibres of the carpet, whereupon the sweeper was set in motion for a given number of strokes.

In nearly all cases the tests were repeated upon the same piece of carpet, with the same charge of dirt, by repeatedly placing the carpet in the frame and giving it a further and more extended cleaning.

All tests were corroborated by repetition before being admitted to the records. Every effort was made to have the tests approach the conditions occurring in actual practice, as nearly as possible, and still keep them definite and measurable.

The carpet used was a Wilton, of the standard width of 27 in. and something over a yard long, and the sweeper was given a stroke of 34 in. at the rate of 40 strokes per minute. The sweepers were attached to a 6-ft. tubular handle, ¹⁵⁄₁₆-in. inside diameter, and connected to the separator by 50 ft. of 1-in. diameter hose.

Before making any tests, the piston pump used in the experiments was calibrated by pumping through a rotary meter and the amount of air moved per revolution for each degree of vacuum from open inlet to closed system was carefully determined. In making the tests of various renovators, each renovator was allowed to pass the same amount of air as the others tested in comparison therewith and the vacuum at the renovator and at the separator was allowed to be what was necessary to pass this known amount of air through the renovators. This method is widely different from that used by the author where the degree of vacuum at the renovator head was determined and used as a limiting factor, the quantity of air being allowed to vary as necessary to produce this vacuum.

The results of three series of tests are given in [Fig. 20], which shows those obtained with Kenney Type A renovators, having a face 12¹⁄₂ in. × ⁷⁄₈ in. and a cleaning slot 11¹⁄₂ in. × ⁵⁄₃₂ in. Curve A was made with the angle of the handle such as would give as near as possible a perfect contact of the sweeper with the carpet. Curve B was made with the sweeper handle canted 5° below the proper angle. Curve C was made with the sweeper handle raised approximately 15° above the proper angle. The ordinates represented the amount of dust in the carpet in 40ths of a pound, also reduced by the author to ounces, and the abscissae the number of strokes made by the sweeper.

FIG. 20. THREE SERIES OF TESTS WITH KENNEY TYPE A RENOVATORS.

Curves B and C show the loss in efficiency which occurs when the renovator is canted from its proper position on the carpet. This falling off in efficiency will necessarily be greater the wider the face of the renovator, as is shown in further tests by Mr. Reeve, using a Type C renovator, which tests also show that this renovator gives a slightly higher efficiency when operated with the inrush slot stopped, as is shown in [Fig. 21].

In this curve the ordinates represent the per cent. of normal dirt, i. e., the amount likely to be found in a dirty carpet, remaining in the carpet at any stage of the cleaning, and the abscissae the number of strokes that have been made by the sweeper. Heavy solid lines represent the results with the inrush open and dotted lines the results with the inrush stopped. The figures on the curve represent the degree to which the handle has been varied from the position giving the best results in cleaning.

FIG. 21. TESTS BY MR. REEVE, USING TYPE C RENOVATOR.

[Fig. 22] shows the results of tests by Mr. Reeve using a renovator of Type D, having a double cleaning slot, and indicate that this type of cleaner is not as efficient as Type A and is affected more by the canting of the handle from the best angle for cleaning.

The above mentioned tests are published through the courtesy of Messrs. Ewing and Ewing, attorneys for the Vacuum Clean Cleaner Company.

Since the method of making these tests is entirely different from that used by the author, a comparison of the results, with any assurance that the same conditions existed in both cases, is impossible. It occurred to the author that a comparison of the results of the tests by Mr. Reeve, using a carpet artificially filled with actual dirt taken from carpets, with the tests made by the author on carpets naturally soiled, would tend to show if equal results could be obtained by a vacuum cleaner by artificially soiling a carpet with dirt taken from another carpet, and in cleaning a carpet naturally soiled.

FIG. 22. TESTS BY MR. REEVE, USING TYPE D RENOVATOR.

The author has reduced these results to the same units of time per square yard of carpet cleaned as in the test on the Philadelphia carpet with the small-sized Type A renovator (11-in. × ¹⁄₂-in. face and 10-in. × ³⁄₁₆-in. cleaning slot). The carpet used by the author contained 6 sq. yds. and was held in cleaning by a weight at each corner, while the carpet used by Mr. Reeve was ³⁄₄ yd. wide and cleaned for approximately one yard of its length, the relative size being 1 to 8. The time of cleaning was 6 min. in the author’s test which would correspond to ³⁄₄-min. cleaning in Mr. Reeve’s test, or 30 strokes of the sweeper. The total dust in the carpet in Mr. Reeve’s test was ⁵⁄₄₀ lbs., or 2.66 oz. per square yard, and his test is compared with the author’s test with the carpet containing 2 oz. per square yard. Calculation of the per cent. of total dirt removed in each 5 strokes of the sweeper in Mr. Reeve’s test, and a comparison of the per cent. of dirt removed in each one minute’s test by the author are given below:

TABLE 4.
Comparison of Tests Made by Mr. Reeve and by the Author.

The above comparison was made using curve A, [Fig. 20], with the sweeper at its best angle with the floor. The close agreement of the two tests indicates that a carpet artificially soiled with dirt actually removed from another carpet by a vacuum cleaner is as difficult to remove as dirt which has been worked into a carpet by ordinary daily use. This condition does not result when any other substance is used to artificially soil the carpet, as will readily be seen by reference to the tests of carpets filled with sand and other substances which have been described in this chapter.

A comparative test of three different renovators was recently made by the author. Renovator No. 1 had a cleaning slot 14 in. long by ³⁄₄ in. wide, the edges of the slot being a segment of a circle having a ¹⁄₈-in. radius. This form of cleaning surface allows very small area of contact with the surface cleaned and permits the admission of large air volumes, about 56 cu. ft., with 2-in. vacuum. It is practically a Type F renovator, similar to that used in the tests at Hartford.

Renovator No. 2 had a cleaning slot 9¹⁄₂ in. long and ¹⁄₄ in. wide, the face of the renovator being approximately ⁷⁄₈ in. wide and practically a plain surface, a typical Type B renovator.

Renovator No. 3 had a cleaning slot 7¹⁄₄ in. long and ¹⁄₈ in. wide, the face of the renovator being ³⁄₈ in. wide and the edges slightly rounded, a typical Type A renovator.

The carpet used was a Colonial velvet rug with ¹⁄₈-in. nap, closely woven, containing 6 sq. yds. This rug was filled with 12 oz. of dirt taken from separators of cleaning machines, from which the lint and litter had been screened. This was rubbed into the carpet until no dirt was visible on the surface, the surface being then lightly swept with a brush and weighed.

In cleaning this carpet the renovator was passed once over the entire surface at the rate of about 70 ft. per minute. This required six strokes and 50 seconds for No. 1 cleaner, nine strokes and 77 seconds for No. 2 cleaner, and 12 strokes and 100 seconds for No. 3 cleaner.

The carpet was then weighed, spread down and gone over three times, weighed, spread down and gone over four times. This operation was repeated until the carpet came within ¹⁄₂ oz. of its weight when received.

Each of the three renovators was operated with a vacuum of 2 in. at the renovator.

The results of these tests are illustrated by curves 1A, 2A and 3A in [Fig. 23]. This shows that to remove 95% of the dirt the renovator had to be passed over the carpet 20 times for No. 1 renovator, 15 times for No. 2 renovator and 8 times for No. 3 renovator.

Similar tests were then made with each of the renovators, with a vacuum of 4.5 in. of mercury at the renovator. The results are shown by curves 1B, 2B and 3B ([Fig. 23]) These show that to remove 95% of the dirt the renovator had to be passed over the carpet 11 times with No. 1 renovator, 6¹⁄₂ times with No. 2, and 4¹⁄₂ times with No. 3.

These tests are all on the same carpet, with the same quantity of the same dirt and with the renovators moved at the same speed in each case. The comparison of the results should give a fair indication of the efficiency of the different types of renovators at different degrees of vacuum within the renovator and, therefore, form the most conclusive proof of the statements relative to the efficiency of renovators as given in this chapter.

All cleaning tests that the author has observed indicate that the higher the vacuum within the renovator the more rapid and effective the cleaning, and that the efficiency of the renovator is fully as high with a small as with a large volume of air passing through the renovator and with the same degree of vacuum within same. Therefore, the most effective and economical renovator should be that which gives the highest vacuum with the least air passing.

FIG. 23. TESTS SHOWING EFFICIENCY OF DIFFERENT TYPES OF RENOVATORS AT DIFFERENT DEGREES OF VACUUM.

If the degree of vacuum within the renovator be carried to an abnormally high degree, there will be a tendency for the renovator to cling so close to the carpet that its operation will be difficult and the wear on the carpet rapid. The production of this high vacuum, with a larger quantity of air exhausted, will result in the expenditure of power at the renovator in excess of the gain in efficiency and speed of cleaning.

It is evident that the wider the cleaning slot, the greater will be the tendency of the renovator to stick to the carpet with a high vacuum within the same. The author has experienced no difficulty in operating the 10-in. renovator, with ³⁄₁₆-in. cleaning slot, with a vacuum as high as 9 in. of mercury, but wider-slot renovators always push hard when any high degree of vacuum exists within them.

Effort Necessary to Operate Various Types of Renovators.

—The author made a series of tests to determine the effort necessary to operate the various types of renovators under different conditions. In making these tests the renovator was attached to a spring balance and pulled along the floor, the pull required to move the renovator being observed by the reading of the balance. Three types of renovators were used in this test: Type A, having a cleaning slot ⁵⁄₁₆ in. wide and 12 in. long; Type C, having a cleaning slot ⁵⁄₁₆ in. wide and 12 in. long, with an auxiliary inrush slot ¹⁄₄ in-wide and 12 in. long; Type F, having a cleaning slot ³⁄₄ in. wide and 10 in. long. The results were as follows:

TABLE 5.
Effort Necessary to Operate Cleaning Tools.

It may be noted that, when operating on the Brussels and the glue-sized velvet, the pull required to move all types of renovators bears a direct ratio to the degree of vacuum under the renovator, and that the quantity of air exhausted is the same for each renovator on either carpet, but different for each type of renovator. It is evident that, in this case, very little air enters the renovator by passing up through the carpet, and hence the action of the inrush slot on Type C renovator is noticeable only to a slight degree. When operating on velvet carpet, without glue-sized back, the inrush slot, in conjunction with the greater quantity of air coming through the carpet, has caused the passage of a large quantity of air, while the vacuum maintained at the renovator is greatly reduced over that which was maintained under Type A renovator when the same quantity of air was passing. In this case, nearly all of the air entering Type A renovator came from the under side of the carpet. The effect on the efficiency of cleaning with Type C renovator under these conditions can readily be imagined, by reference to former tests, as being greatly reduced over that of Type A when passing the same quantity of air. With linoleum, the action of the inrush slot of the Type C renovator has again greatly reduced the vacuum under the renovator, although the quantity of air is much in excess of that passing Type A renovator. The difference in the behavior of the renovators on different makes of carpet is seen to be due largely to the difference in the quantity of air which passes up through the carpet into the renovator.

It is evident that, with the same degree of vacuum within the renovator, all types are equally easy to push and that, if the vacuum within the renovator becomes higher than is necessary to produce good cleaning results, unnecessary effort will be required to operate the renovator.

Relative Damage to Carpets with Various Types of Renovators.

—A few tests have been made by the author to determine the relative damage to carpets with the various types of renovators in use and it is found that, when the edges of the renovators are made exceedingly sharp, considerable nap is pulled out. However, if the edges are made slightly rounding and not too narrow, no undue wear will occur with any of the types of renovators described, provided the vacuum in the renovator is not permitted to become greater than 5 in. of mercury.

The author considers that for best results the vacuum should not be less than 3¹⁄₂ in. of mercury at the renovator and that at least 2 in. is necessary to do even fair work, while, to permit easy operation and prevent undue wear on the carpets, it should not be higher than 5 in.

Before deciding which type of renovator will be most economical to use in any case the character of the cleaning to be done must be considered.

Of the various types of renovators considered in this chapter, Type C can be dismissed at once, as it is neither as effective a dust remover as Types A or F nor will it remove litter any more effectively than Type F. Tests of Type D renovator do not show as good results as a dust remover as Type A, nor will it remove litter any more effectively. Type E renovator is a modification of Type C and is not likely to be any better.

The selection, therefore, lies between Type A and Type F renovators, the former being by far the best dust remover, while the latter will pick up a limited amount of small litter, such as matches, cigar and cigarette stumps, and small bits of paper. Where large quantities of these articles are likely to be encountered, it is more important that the renovator should be capable of picking them up, but, unfortunately, when these articles are met with, there are also likely to be much larger articles present that cannot be picked up by any but a specially-designed renovator, and other means must be employed to remove them.

In residences, private offices and nearly every place where carpets or rugs are likely to be used, waste baskets and cuspidors are provided and the articles mentioned are deposited in them rather than on the floor. Thus, the renovator will be required to remove dust, cigar ashes and sand or mud only, all of which can be readily removed with a Type A renovator with less expenditure of power than with a Type F renovator.

Public places, such as ante-rooms, reception rooms and other offices to which the general public is admitted in great numbers and which are sometimes carpeted, are likely to contain articles which can be picked up by Type F renovator and not by Type A. For cleaning such places, a Type F renovator is necessary, although it requires considerably more power, but the author sees no reason why this type of renovator should be used to the exclusion of Type A, even in buildings containing rooms of this character. If the building also contains several rooms where litter will not be encountered, the author would recommend that both types of renovators be used, each in its proper place, and thereby cause a considerable saving of power in cleaning rooms where no litter is encountered.

For residence work there is little need of providing carpet renovators capable of picking up litter and, also, there will be very little bare floor cleaning to be done, which requires larger volumes of air. A smaller capacity exhausting plant, therefore, can be installed, if the Type A renovator is adopted.

In large office buildings where all cleaning is done after office hours, where the building is provided with its own power plant, and where speed of cleaning and ability to clean all apartments with the fewest tools to be carried by the cleaners is desired, it appears to be better to use only Type F renovators for all carpet work, as the extra power required will not be of vital importance.

Summing up the matter, the author believes that both Type A and F renovators have their uses in their proper places but that Type A has the widest field of usefulness, yet it need not invade the field of the other. He also believes that this fact will be realized by manufacturers in the near future, when the two types of renovators will work together side by side for the general good of the manufacturers and the users.

CHAPTER IV.
Other Renovators.

The renovator which is next in importance to the carpet renovator is that used for cleaning bare floors. The earliest form of this renovator was the oscillating floor type introduced by Mr. Kenney. This was a modification of the narrow-slot carpet renovator introduced by him. The body of same was curved and supported on two small wheels or rollers, with the intention of bringing the cleaning slot close to the surface cleaned without its touching same, as indicated in [Fig. 24].

FIG. 24. EARLY TYPE OF BARE FLOOR RENOVATOR.

FIG. 25. LATER TYPE OF BARE FLOOR RENOVATOR.

This form of renovator was found to be impracticable for the reason that any change in the angle with which the stem or tube connecting the body of the renovator with the handle in relation to the surface cleaned tended to make its action ineffective. If the angle were made less the distance between the cleaning slot and the floor was increased, allowing the air to enter the cleaning slot without coming in contact with the surface to be cleaned, or, if the angle were made greater, it would cause the face of the renovator to strike and damage the surface of the floor.

The wheels or rollers on which this renovator was mounted, being so small, were subject to rapid wear both on their faces and in their bearings, and when these wheels were slightly worn the renovator was practically useless. On account of the above defects this form of renovator was abandoned shortly after its introduction.

The next form of renovator to be tried was a modification of the ordinary soft bristle brush, such as had been in general use for cleaning hard wood floors. The bristles were arranged around the edges of the cleaning slot, in the body, which was shaped similar to the slot in the carpet renovator. Rubber or leather curtains or skirting, extending nearly to the ends of the bristles, was placed inside of these bristles in order to cause the air in entering the body of the renovator to come into intimate contact with the surface to be cleaned. The general form of this type is shown in [Fig. 25].