Patent Publication Number: US-6705332-B2

Title: Hard floor surface cleaner utilizing an aerated cleaning liquid

Description:
RELATED APPLICATION 
     This is a Continuation of U.S. patent application Ser. No. 10/026,411, filed Dec. 21, 2001, now U.S. Pat. No. 6,585,827 issued Jul. 1, 2003, which claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 60/308,773 filed Jul. 30, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to surface maintenance or conditioning machines, and more particularly to those machines employing one or more surface maintenance or conditioning appliances or tools to perform a hard floor surface wet scrubbing task. 
     BACKGROUND OF THE INVENTION 
     Hard floor surface scrubbing machines are widely used to clean the floors of industrial and commercial buildings. They range in size from a small model which may clean a path ranging from 15 inches up to 36 inches wide controlled by an operator walking behind it, to a large model cleaning a path as wide as five feet controlled by an operator riding on the machine. Such machines in general are wheeled vehicles with suitable operator controls. Their bodies contain power and drive means, a solution tank to hold a cleaning liquid and a recovery tank to hold soiled solution recovered from the floor being scrubbed. The cleaning liquid may be water and a chemical detergent. The detergent typically includes a solvent, builder, and surfactant. Builders and surfactants provide for foam generation and foam stability. A scrub head which contains one or more scrubbing brushes and associated drive means are attached to the vehicle and may be located in front of, under or behind it. A solution distribution system dispenses cleaning liquid from the solution tank to the floor in the vicinity of the scrubbing brush or brushes. For a typical scrubber with a 32 inch wide scrub swath, the solution distribution rate varies between 0.5 gallons per minute (GPM) to 1.0 GPM. 
     Hard floor surface scrubbing machines typically further include a system to recover soiled scrubbing solution from the floor after it has been scrubbed. A solution recovery system may be a vacuum system including, for example, a double lipped vacuumized squeegee that wipes the floor behind the scrub head and collects the soiled scrubbing solution of water, detergent and soilage that has been loosened from the floor. The soiled scrubbing solution may include foam or froth generated by mechanical action of the brushes against the cleaning solution and the hard floor surface. Additional amounts of foam may be generated through the vacuum recovery process. Foam (air expanded cleaning solution) has heretofore been a shortcoming of prior art scrubbers as foam occupies a significantly greater volume as compared to the volume of unexpanded cleaning solution. Excessive foam within the recovery tank can necessitate shutting down the machine and emptying the recovery tank before the solution tank is empty, which reduces the productivity of the machine. As a result, foam elimination or reduction techniques have included specifically adapted enlarged solution recovery tanks and the addition of defoaming chemicals to the recovered solution tank. 
     Other limitations of vacuum systems for soiled solution recovery include power requirements, noise generation, and reliability. An alternative to vacuum-based soiled solution recovery systems for use upon a hard floor surface scrubbing machine would be desired. 
     One limitation of prior art scrubbers has been a relatively limited operational run time. For a typical scrubber with a 32 inch wide scrub swath and 30 gallon solution tank, the solution distribution rate varies between 0.5 GPM to 1.0 GPM. Run time based on solution capacity is between approximately 30 to 40 minutes. Merely increasing the size of the cleaning solution tanks is not a viable solution to achieving increased machine run times. An increase in cleaning solution capacity typically necessitates modifications to the frame and motive components, all of which result in additional weight and energy requirements for such a device. To the contrary, a need exists for a device having an increased run time achieved by reducing the amount of water required for the scrubbing process. 
     Another aspect of prior art scrubbers is the inefficient use of cleaning liquid in the scrub process. A relatively large amount of cleaning liquid is utilized to ensure wetting of the floor surface. The scrub process generates a relatively large amount of soiled cleaning liquid, most of which is recovered by the scrubber. Disposal of soiled solution in some applications remains an issue, especially where the cleaning process removes harmful or hazardous chemicals. Special handling or additional costs may be incurred to properly dispose a particularly soiled solution. By reducing the amount of water needed to perform a scrubbing process, a concomitant reduction in the amount of soiled solution is achieved. A need exists for a cleaning process providing efficient usage of cleaning solution. 
     The prior art discloses devices for cleaning surfaces, namely carpets, utilizing foam generation systems and mechanical brushes. These devices have utilized a variety of foam generation systems and recovery systems. Examples of such foam cleaning devices include U.S. Pat. Nos. 3,761,987; 3,931,662; and 5,813,086. 
     Nayfa et al (U.S. Pat. Nos. 3,761,987 and 3,931,662) discloses a machine for scrubbing or shampooing rugs or carpeted floor surfaces, for scrubbing hard floor surfaces, or for waxing and polishing hard floor surfaces. Stated objects of the invention of Nayfa et al. include: 
     an improved floor surface cleaning machine having the capability to shampoo and remove surface dirt from a carpet surface in one operation, to scrub and remove surface dirt from a hard floor surface in one operation, or to apply wax to and polish a floor surface in one operation, 
     a floor surface cleaning machine having a cleaning solution foaming system within the machine and a pressurized foam dispensing system, 
     a rug cleaning machine having means for scrubbing the pile, removing the dirt from the pile, and lifting the pile to original position in one operation, 
     a rug cleaning machine wherein the machine support and drive rollers function as squeegies to direct the cleaning foam and entrapped dirt toward the vacuum pickup nozzles, and 
     a floor surface cleaning machine having an improved solution dispensing mechanism including means for forming a foam, means for effecting flow of the foam under pressure, and means for controlling the rate of flow of foam to the floor surface. 
     These devices have not addressed limitations of prior art floor scrubbers, such as efficient cleaning solution usage in a hard floor surface scrubbing process. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     Briefly stated, an improved hard floor surface scrubbing machine according to the present invention includes an aerator for generating a foam-like aerated cleaning liquid, one or more scrub brushes for engaging aerated cleaning liquid and the hard floor surface, and a soiled solution recovery system for removing soiled solution from the hard floor surface. A variety of liquid aerators may be utilized to practice the present invention. A particularly preferred aerator includes a pressurized air source, a pressurized cleaning liquid source, and a plurality of mixing elements for generating the aerated cleaning liquid. Alternative soiled solution recovery systems may be utilized in embodiments of the present invention. 
     An object of the present invention is to overcome the drawbacks of the conventional technology and to provide an efficient hard floor surface scrubbing machine. 
     Another object of the present invention is to provide a hard floor surface scrubbing machine which utilizes a foamed cleaning liquid in an efficient scrubbing process. The cleaning liquid may be water and a chemical surfactant. The aerated cleaning liquid may be generated via a variety of known aeration devices or systems. The aerated cleaning liquid permits a substantial reduction in the amount of cleaning solution liquid required in a scrub cleaning process. The reduction of cleaning liquid requirements may translate into decreased machine size and/or increased machine run times. Additionally, the amount of soiled cleaning solution which may require special disposal or additional handling may be reduced. 
     An aspect of the present invention is the provision of a cleaning liquid which can be efficiently aerated via known aeration devices, applied to a surface during a scrubbing process, and be rapidly dearated prior to a soiled solution recovery process. 
     Another aspect of the present invention is the provision of a cleaning liquid which may be efficiently aerated to a foam-like consistency, applied to the floor surface, and quickly dearated by engagement with a scrub brush. In a preferred embodiment of the present invention, the foam-like aerated cleaning liquid is substantially dearated by the scrub brush prior to soiled solution recovery. 
     Another aspect of the present invention is the provision of a defoaming device for de-aerated foamed soiled solution recovered during machine operation. The defoaming device may include a chemical-based defoamant, or may include a radiant heating element to thermally de-aerate the recovered foam. 
     Another aspect of the present invention is to provide a chemical dosing or metering system for combining a chemical with water to create a cleaning liquid during operation of the machine. In one embodiment of the invention, a machine may have a clean water tank and a chemical dosing system for combining water and a chemical prior to aeration. The chemical dosing system may include a configured removable chemical cartridge adapted to engage a correspondingly configured portion of the cleaning machine. The chemical dosing system may include active or passive elements for combining a chemical with water to create the cleaning liquid. 
     Yet another aspect of the present invention is a process for cleaning hard floor surfaces including the steps of aerating a cleaning liquid to form an aerated cleaning liquid, selectively conveying the aerated cleaning liquid to the hard floor surface and a rotating scrub brush, engaging the hard floor surface and the aerated cleaning liquid with the rotating scrub brush to loosen soil from the hard floor surface and to create a soiled solution of cleaning liquid and soil, and removing at least a portion of the soiled solution from the hard floor surface through the fluid recovery system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of the scrubber of the present invention. 
     FIG. 2 is a front elevation view of the scrubber of FIG.  1 . 
     FIG. 3 is a detailed front elevation view of a cleaning liquid aeration system according to the present invention. 
     FIG. 4 is a detailed front elevation view of a portion of a scrubber according to the present invention. 
     FIG. 5 is a side elevation view of another embodiment of a scrubber of the present invention. 
     FIG. 6 is a cross sectional view of yet another embodiment of a scrubber similar to that of FIGS. 1-4. 
     FIG. 7 is a detailed front elevation view of another embodiment of a cleaning liquid aeration system according to the present invention. 
     FIG. 8 is a detailed front elevation view of another embodiment of a cleaning liquid aeration system according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates an embodiment of a surface maintenance vehicle according to the present invention. The illustrated surface maintenance vehicle is a walk-behind scrubber machine  10  utilized to clean hard floor surfaces, such as concrete, tile, vinyl, terrazzo, etc. In alternative embodiments, the surface maintenance vehicle may be a ride-on or towed-behind vehicle performing a scrubbing operation as described herein. The surface maintenance vehicle may be powered through an on-board power source, such as batteries or an IC engine, or though an electrical cord. In the embodiment of FIG. 1, the scrubber  10  includes a recovery tank  12 , a lid  14  and a front cover  16 . The lid  14  is attached along one side of the recovery tank by hinges (not shown) so the lid  14  can be pivoted up to provide access to the interior of the tank  12 . The lid  14  defines a cleaning solution tank  18  for containing a cleaning liquid, such as a mixture of water and a cleaning chemical to be conditioned, applied to the hard floor surface, and recovered from the floor surface as further described herein. 
     A scrub head  20  includes a scrubbing medium  22 , shrouds  24 , and a scrubbing medium drive  26 . The scrubbing medium  22  may be one or more brushes. In the illustrated embodiment, a pair of brushes  22  define the scrubbing medium. The brushes  22  may include bristle brushes, pad scrubbers, or other hard floor surface engaging devices for scrubbing. The term “brush” as used herein is not limited to bristle devices, but is intended to cover a variety of known hard floor surface scrubbing elements. One or more electric motor brush drives  26  may be utilized to rotate the brushes  22 . The scrubbing medium may be a disk-type scrub brush rotating about a generally vertical axis of rotation relative to the hard floor surface. The scrubbing medium may also be a cylindrical-type scrub brush rotating about a generally horizontal axis of rotation relative to the hard floor surface. Alternative embodiments of the present invention may include scrub brushes  22  being oscillated rather than rotated into contact with the hard floor surface. A variety of brush rotation and/or oscillation devices would be appreciated by those skilled in the relevant arts. In the illustrated embodiment, a pair of rotating disk brushes  22  are utilized. The scrub head  20  is attached to the machine  10  such that the scrub head  20  can be moved between a lowered working position and a raised traveling position. 
     A machine frame supports the recovery tank  18  on wheels  24  and casters  26 . Further details of the frame are shown and described in U.S. Pat. No. 5,611,105 the disclosure of which is incorporated herein by reference. Wheels  24  are preferably driven by a motor and transaxle assembly shown schematically at  28 . The rear of the frame carries a linkage  30  to which a fluid recovery device  32  is attached. In the embodiment of FIG. 1, the fluid recovery device  32  includes a vacuum squeegee  34  in vacuum communication with an inlet chamber in the recovery tank  12  through a hose  36 . The bottom of the inlet chamber is provided with a drain  40  with a drain hose  42  connected to it. An alternative non-vacuumized fluid recovery device  32  is described in more detail herein with particular reference to FIG.  5 . 
     The vehicle body incorporates a battery compartment  44  in which batteries  46  reside, as shown in FIG.  1 . The batteries  46  provide power to the drive motors  26 , scrub head  20 , and a vacuum fan  48 . The vacuum fan  48  is mounted in the lid  14 . A control unit  50  mounted on the rear of the body includes steering control handles  52  and the necessary operating controls and gauges for the scrubber. Additional aspects of automatic scrubber machines are disclosed in U.S. Pat. Nos. 5,483,718; 5,515,568; and 5,566,422, each incorporated by reference herein. Alternative motive systems such as an IC engine system may be utilized in another embodiment of the present invention. 
     In a preferred embodiment of the present invention the cleaning liquid includes water and a chemical surfactant. Alternative cleaning liquids may also be utilized in other embodiments of the present invention. Alternative cleaning liquids may be water or chemical based. Alternative cleaning liquids may include one or more surfactants, builders, solvents, or other components. A particularly preferred surfactant is DeTERIC CP-Na-38 manufactured by DeForest Enterprises, Inc. of Boca Raton, Fla. A particularly preferred surfactant concentration of the cleaning liquid is approximately 0.1%. In a preferred embodiment, no additional solvents or builders are utilized. As described in more detail hereinafter, the cleaning liquid is aerated to create a foam/water mix which is delivered to the hard floor surface and utilized in a scrubbing process. The foam-like aerated cleaning liquid facilitates an efficient wetting of the floor surface. As described in more detail herein, one benefit of the preferred surfactant is the ability to efficiently aerate the cleaning liquid into a foam, apply the foamed cleaning liquid to the hard floor surface, work the foamed cleaning liquid with the scrub brushes, and substantially deaerate the foamed cleaning liquid prior to soiled solution recover. In operation, dearation of the aerated cleaning liquid is rapidly achieved via brush  22  contact. As a result, relatively little foam is transferred into the recovery tank  12 . One skilled in the relevant arts will appreciate that alternative surfactants may also be practicable. As a result, the identification of a particular surfactant herein is not intended to be limiting. Additionally, detergents including a surfactant along with other solvents, builders, or other components may be practicable for an application of the present invention. 
     The cleaning liquid may be contained within solution tank  18  as a mixture of water and the surfactant. The surfactant may be added to water within the solution tank  18  to achieve a predetermined concentration within the solution tank  18 . For example, a predetermined amount of surfactant may be added to a predetermined amount of water, such as during a refilling operation. Alternatively, the mixture of water and surfactant may be achieved during machine operation through a chemical dispenser. Additional aspects of such dispensers are described hereinafter with reference to FIG.  7  and FIG.  8 . 
     Referring to FIGS. 1-4, a cleaning liquid aerator for generating a foam-like aerated cleaning liquid for application to the hard floor surface during a scrubbing process according to the present invention is generally indicated at  60 . The aerator  60  may include a variety of known foam generation devices, including but not limited to pressurized air and/or pressurized liquid systems, agitation systems, etc. A particularly preferred aerator  60  is disposed on the housing above the scrubbing head  20  and includes an air system  62  for pressurizing air, a liquid cleaning solution system  64  for pressurizing cleaning liquid, a first mixing element  66  for receiving pressurized air and pressurized liquid cleaning solution, a second mixing element  68  for further mixing in fluid communication with the first mixing element  66 . A foam dispensing system  70  distributes foam generated by the mixing elements  66 ,  68 . An electric solenoid valve  72  is provided to control the flow of foam from the aerator  60 . 
     Referring particularly to FIG. 3, additional aspects of the cleaning liquid aerator  60  will be described. The air system  62  for generating and conveying pressurized air includes an air pump  74 , a check valve  76 , and associated fluid conduits  78 ,  80 . In a particularly preferred embodiment of the machine, the air pump is a piston pump model number 22D1180-206-1002 manufactured by Gast Manufacturing, Inc., of Benton Harbor, Mich. Other types of air pumps may also be practicable in alternative foam systems, including but not limited to different piston, diaphragm or rotary vane pumps. Check valve  76  is provided for back flow prevention of cleaning solution into the air pump  74 . A measured pressure at the air pump output during operation is approximately 40 pounds per square inch (psi). 
     The system for generating and conveying pressurized cleaning liquid includes a diaphragm pump  82 , a metering orifice  84 , and associated fluid conduits  86 ,  88 ,  90 . The diaphragm pump  82  receives cleaning liquid from tank  18  via conduit  86 . In a particularly preferred embodiment of the machine, the diaphragm pump is model number 8006-543-250 manufactured by Shur Flo, of Garden Grove, Calif. Pump  82  output is conducted via conduit  88  to metering orifice  84 . In one preferred embodiment, metering orifice  84  size is 0.0030 inch. Flow rate through the metering orifice  84  during operation is approximately 0.2 gallons per minute. Output from metering orifice  84  is conducted to the first mixing element  66  via conduit  90 . 
     The first mixing element  66  receives pressurized air from the air pump  74  via conduit  80  and pressurized cleaning solution from the solution pump  82  via conduit  90  and discharges a mixture of pressurized air and cleaning liquid through an outlet port  98 . The first mixing element  66 , in this embodiment a Y coupling, has a pair of inlet ports  94 ,  96  and an outlet port  98  through which the mixture is discharged. First mixing element  66  may be alternatively configured, though defining at least a pair of inlet ports for pressurized air and pressurized cleaning liquid and an outlet port for the mixture. First mixing element  66  may be defined as a passive mixing element. An alternative first mixing element may include active mixing devices, such as energized impeller. 
     The outlet port  98  of the first mixing element  66  is coupled to the electric solenoid valve  72  via conduit  92 . Valve  72  controls the flow of mixture to the second mixing element  68  via conduit  100 . Valve  72  is operable between an open position in which solution is permitted to flow out of the first mixing element  66  and a closed position in which solution flow is blocked. Alternative valves may be used to control the flow of mixture within the system, including but not limited to variable output valves, etc. 
     The second mixing element  68  receives and further mixes the pressurized air and cleaning liquid from the first mixing element  66 . Second mixing element  68  is a passive element including a relatively rigid receiver  102  having an inlet port  104  and an outlet port  106 . A diffusion medium  108  is contained within the receiver  102 . The diffusion medium  108  is capable of producing foam by shearing action, air entrainment or a combination of both. In a preferred embodiment, the diffusion medium  108  includes a plurality of SCOTCH-BRITE brand copper pads, manufactured by Minnesota Mining and Manufacturing Company of St. Paul, Minn. Alternative diffusion medium may also be practicable, including but not limited to glass beads, foams, and other porous substrates. 
     The length and diameter of the receiver  102  as well as structure of the diffusion medium  108 , are sized so as to maintain the operating pressure of the foaming system  60  at a desired level. For the embodiment of FIGS. 2-4, the operating pressure within air conduit  78  is about 40 psi. The diffusion medium  108  and receiver  102  size affect the quality of the foam generated in the second mixing element  68 . More particularly, using coarser diffusion medium  108  allows for easier passage of the foam through the receiver  102  since there are fewer contact, or blocking, points between medium  108  in the receiver  102 . However, the coarser diffusion medium also results in larger foam bubbles. By using a sufficiently long receiver  102  with an appropriate diffusion medium  108 , large foam bubbles formed near the upstream end of the receiver  102  will break down into more desirable smaller bubbles prior to reaching the downstream end of the receiver  102 . As an example, the receiver  102  of the illustrated embodiment is about 9 inches long and has an inner diameter of approximately 2 inches. The receiver  102  may be provided at an incline relative to the ground surface so that inlet port  104  is at a slightly lower elevation than outlet port  106 . By so providing the inlet port  104  above the outlet port, the amount of aerated cleaning liquid delivered to the scrub brushes  22  after the solenoid valve  72  has closed may be minimized. Various modifications and adaptations to the aerator  60  may be practicable. 
     A foamed solution of aerated cleaning liquid is discharged from the second mixing element  68  and directed toward the scrub head  20  via conduit  110 . Flow within conduit  110  is separated by a T coupling  112  into conduits  114  and  116 . The outlet of conduits  114 ,  116  are provided above associated disk brushes  22 . As illustrated in FIG. 4, flow from conduit  114  can exit near the center of the scrub brushes  22  to deliver cleaning fluid into an annular trough  122  in the pad driver hub  124 . The outlet of conduit  116  (FIG. 2) is also preferably similarly positioned near the center of scrub brushes  22 . A series of holes  126  in the bottom of trough  122  pass the aerated cleaning liquid down to the central region of the cleaning brush  22 . During operation, the cleaning liquid is centrifuged cut under the brush  22  in contact with the hard floor surface. Alternative approaches to aerated cleaning liquid delivery would be appreciated by those skilled in the relevant arts. 
     A foam control switch  130  is electrically connected to the air compressor  62 , cleaning liquid pump  82 , and solenoid valve  72  for controlling operation of the foam aerator system  60 . The foam control switch  130  may include a manual switch mounted on the control panel. 
     In operation, electrical current flows to the air compressor  62 , fluid pump  82 , and electric solenoid valve  72 . Pressurized air is directed through conduit  78 , check valve  76 , and conduit  80 . Pressurized cleaning solution is directed through conduit  88 , metering orifice  84 , and conduit  90 . Pressurized air and cleaning solution is received into the first mixing element  66  and directed via conduit  92  through the control valve  72 , and then through conduit  100  and into the second mixing element  68 . As the mixture of air and cleaning solution flows through the diffusion medium  108  of the second mixing element  68 , foam bubbles are generated. Foam output from the second mixing element  68  is discharged via conduits  110 ,  114 ,  116  to the scrub brushes  22 . In a particular embodiment, the ratio of volumes between the unaerated cleaning liquid and foamed cleaning liquid is approximately 1:8, e.g., 0.15 gallons of cleaning liquid is aerated to occupy 1.25 gallons. Other volume ratios would yield acceptable scrubbing results. A foams “dryness” may be defined in relation to this volumetric expansion ratio. A “dry” foam having a higher expansion ratio as compared to a “wet” foam. High-expansion foams used in presently available types of carpet cleaning machines are actually relatively “dry” as the ratio of air to water is particularly high. Dry foams are used in carpet cleaning to facilitate quick drying of the cleaned carpet. A “wet” foam is not typically used in carpet cleaning devices as these foams can cause excessive wetting of the carpet which may lead long drying times and mold development. 
     The cleaning machine  10  is then moved forward, with the foam-like aerated cleaning liquid being dispensed from the conduits  114 ,  116  at the front of the chassis. As the cleaning machine  10  moves forward, the brushes  22  engage the aerated cleaning liquid and hard floor surface. The foamed cleaning liquid permits an efficient wetting of the hard floor surface, even at dramatically reduced cleaning solution usage. For example, cleaning liquid rates of 0.2 gallons per minute have yielded acceptable results. In comparison, prior art scrubbing machines of similar size often utilize approximately 1 gallon per minute. The process of mechanically working the foam with the brushes  22  results in substantial defoaming or de-aeration (up to 95% reduction in volume) of the foamed cleaning solution prior to soiled solution recovery. In contrast, prior art devices using known chemical detergents may create additional foam by the brush action, necessitating defoaming devices as mentioned herein. 
     In operation, a soiled solution of cleaning liquid and soil is developed by the interaction of the scrubbing medium in contact with the foamed cleaning liquid and the hard floor surface. The soiled solution includes partially deaerated cleaning liquid and soil released from the hard floor surface. The soiled solution is recovered from the hard floor surface through vacuum squeegee  34  and conveyed to the recovery tank  12  through hose  36 . Alternative soiled solution recovery devices may also be practicable. The recovered soiled solution may be treated to reduce foam via known defoaming techniques, including an addition of defoaming chemical to the recovery tank  12 . In the embodiment described herein, the soiled solution is substantially defoamed during the scrubbing process. The above referenced particular surfactant beneficially yields a foamed cleaning solution which rapidly de-aerates after contact with the rotating scrub brushes  22 . As a result, in a preferred embodiment no additional defoaming devices or chemicals are required. 
     FIG. 5 illustrates a scrubber utilizing an alternative soiled solution recovery device  32 . The soiled solution recovery device  32  may include a non-vacuumized mechanical device for lifting the soiled solution away from the floor surface and conveying the soiled solution toward a collection tank or receptacle  142 . In the embodiment of FIG. 5 the soiled solution recovery device includes a plurality of wiping medium such as pliable material elements  140  which are rotated into contact with the floor surface to engage and lift the soiled solution from the floor surface. The pliable material elements  140  may be of an absorbent material. The pliable material elements  140  convey the solution to the collection receptacle  142 . Solution captured on the pliable elements  140  may be removed via a mechanical action, such as through a shearing device or a squeezing device. In the embodiment of FIG. 5, the mechanical action used to remove soiled solution from the pliable material elements  140  is a scraper bar  144  which engages the pliable material elements  140  to release the soiled solution. Alternative mechanical devices, structures, or systems may be used to convey the soiled solution from the floor surface toward a collection receptacle. 
     The scrubber  10  may include a defoaming device or system to reduce the volume of the collected soiled solution. The defoaming device or system may be part of the soiled solution collection and handling device  32  or may be disposed in relation to the soiled solution tank  12 . The defoaming device or system may include a chemical defoaming system for applying a defoaming chemical to collected foam. The defoaming device may include an acoustic and/or mechanical defoaming device. FIG. 6 illustrates one particular defoaming device  146  for use with the scrubber of FIGS. 1-4. FIG. 6 is a cross sectional view taken through the recovery tank  12 , vacuum conduit  36 , and vacuum squeegee  34 . The defoaming device  146  may be an selective device finding applicability in high foam situations. Foam lifted from the squeegee  34  through vacuum conduit  36  is passed by the defoaming device  146  containing a defoaming chemical  148 . The defoaming device  146  is a passive device allowing the chemical  148  to passively interact with the recovered foam. The defoaming device  146  may have a porous or apertured element for promoting contact between the defoaming chemical or defoamant  148  and the recovered foam. One particular defoamant which may be used is FOAM-OUT™ manufactured by LaPorte Water Technologies, Inc., of Alpharetta, Ga. Alternative defoaming devices or defoamants may also be practicable. 
     Another defoaming device is illustrated in FIG.  5  and FIG. 6 as numeral  130 . Defoaming device  130  is a radiant heating element disposed above the soiled solution in the recovery tank  12 . Radiant heating element  130  may be an electric heating element powered by the batteries  46  (FIG.  1 ), or may be powered by another heat source, such as propane or recovered heat from an IC engine. Radiant heating element  130  functions to de-aerate foam within the solution tank  12  via a thermal process. One or more radiant heating elements  130  may be utilized in embodiments of the present invention. 
     Additional aspects of the present invention will be addressed. Regarding the foam system, alternative foam generation systems may be practicable. In the above described embodiment, a compressed air and pressurized cleaning liquid process is utilized. Other means for generating the foam-like aerated cleaning liquid may utilize known foam generating devices. One or more known foam generating devices may be used to generate the foam-like aerated cleaning liquid for use in a scrubbing operation as described herein. 
     Foam generation devices utilizing an agitation process are known. An agitation process uses a mechanical device, such as a rotating impeller, to engage and entrain air within a solution. U.S. Pat. Nos. 3,761,987 and 3,931,662 each disclose an agitation-type foam generator, the disclosures of which are incorporated by reference herein. 
     Foam generation devices utilizing a pressurized liquid process are also known. These devices include foam generating nozzles such as for use in fire fighting equipment. Ambient air may be aspirated into a solution at the nozzle end of a hose by an air-aspirating nozzle. Aspirated foam systems do not use compressed gases to create the foam. A mixture of foam concentrate and water is pumped through a special aspirating nozzle located at the end of the delivery hose. This special nozzle is designed to draw in atmospheric air and mix it with the foam concentrate-water mix to create foam. 
     Foam generation devices utilizing a pressurized gas process are also known. A method of expanding the volume of a solution into foam is to introduce compressed air into the solution prior to the solution reaching a nozzle. Compressed gas, usually air, is introduced into the foam concentrate-water mixture at high pressure, usually in the range of 60-100 psi. The air is mixed with the foam concentrate-water mixture either with an active mixing device or a passive mixing device which can be as simple as a long length of conduit. 
     Referring to FIGS. 7 and 8, an additional chemical dispenser aspect of the present invention is disclosed. Illustrated as numeral  150 , a chemical dispenser may be utilized to combine water and the surfactant to form the cleaning liquid. The term “dispenser” as used herein is broadly meant to include devices or systems for providing, distributing, releasing, injecting, conveying, and/or dosing a chemical or chemicals into a solution to create the cleaning liquid. A variety of chemical dispensers would be appreciated by those skilled in the relevant arts. A chemical dispenser is particularly well suited for a scrubber according to the present invention given the relatively small amount of surfactant needed to form an aerated cleaning liquid. The chemical dispenser  150  may include active and/or passive elements. A passive element chemical dispenser is illustrated in FIG. 7, wherein the surfactant  152  is permitted to diffuse through a porous medium  154  and into conduit  100 . An active element chemical dispenser is illustrated in FIG. 8, wherein the surfactant  152  is pumped through one or more conduits  156 ,  158 ,  160  for mixing with water. In one embodiment, chemical dispenser  150  may dispense the chemical to a water tank  162  via conduit  156  for mixing with a predetermined volume of water, such as during refilling. In another embodiment, chemical dispenser  150  may dispense the chemical via lines  158  and/or  160  for mixing within the associated conduits to generate the cleaning liquid. 
     Yet another aspect of the chemical dispenser  150  is the provision of a removable cartridge  164  containing the surfactant  152  and/or other chemicals. The term “cartridge” as used herein is broadly meant to include structures for holding a chemical, including but not limited to sealed or unsealed tanks, bottles, vessels, and other containers. The cartridge  164  may be specifically adapted to engage a retaining structure  166  on the machine  10 . A variety of cartridges  164  and retaining structures  166  would be appreciated by those skilled in the relevant arts. The chemical dispenser  150  may include one or more disposable chemical cartridges  164 . A family of chemical cartridges  164  may be provided, each member of the family having a different predetermined surfactant and/or chemical contained therein. For example, a first chemical cartridge  164  may include a surfactant and other chemicals (such as disinfectants, solvents, alkaline builders, etc.) specifically adapted for a heavily soiled surface, with a second chemical cartridge  164  being adapted for lightly soiled surface. 
     Distribution of the aerated cleaning liquid may include alternative structures. For example, the aerated solution may be sprayed on the hard floor surface or brushes  22  or both. The aerated solution may be delivered through the brushes  22 , such as via apertures in the brush  22 , and/or applied directly to the floor surface in front of the brushes  22 . Distribution of aerated cleaning liquid may include a selective application to the hard floor surface, the brushes, or both. Alternative distribution systems may be appreciated by those skilled in the relevant art. 
     As various changes could be made in the above methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.