text: the present invention is directed both to a method of cleaning surfaces and an apparatus for performing the method . in a broad sense as will subsequently be described , the cleaning process in accordance with the present invention includes dual modes of operation . fig1 illustrates an embodiment of a transportable floor surface cleaning machine 10 according to the present invention . more particularly , machine 10 , for illustrative purposes , is illustrated as a battery - powered walk - behind machine similar to those known in the art , including a cleaning solution tank 12 for containing a cleaning liquid 14 , such as a mixture of water and a cleaning chemical , a recovery tank 16 , a cleaning head 18 , a cleaning liquid dispensing system , and a soiled solution extraction system as further described herein . in operation , machine 10 is supported upon the ground surface 20 by drive wheels 22 and caster wheels 24 . representative examples of battery - powered walk - behind carpet machines having a cleaning solution tank 12 , recovery tank 16 , cleaning liquid dispensing means , and a soiled solution vacuum extraction system include models 1510 and 1550 extractors manufactured by tennant company , minneapolis , minn . cleaning head 18 is attached at a forward portion of the machine 10 via a positioning actuator ( not shown ). in alternative embodiments of the invention , cleaning head 18 may be attached at other portions of a machine . in an illustrated embodiment , cleaning head 18 in accordance with the present invention may be used in conjunction with one of such known walk - behind extractor machines and the like . referring to fig2 and 3 , cleaning head 18 in one embodiment of the present invention , includes a cleaning medium 26 and associated drive assembly as is more particularly shown in detail in fig2 and 3 . drive assembly includes drive motors 28 and belts 30 to rotate cleaning medium 26 relative to cleaning head 18 and surface 20 . in the illustrated embodiment , cleaning medium 26 includes a pair brushes 32 for use in an extraction mode of operation ( as depicted in fig2 ) and a pair of soil transfer rolls 34 for use in a soil transfer roll mode of operation ( as depicted in fig3 ). as described in more detail hereinafter , cleaning medium 26 may alternatively include a combination brush / soil transfer roll suitable for use in both modes of operation . brushes 32 and soil transfer rolls 34 of cleaning medium 26 are rotatably driven by cleaning medium drive assembly including drive belts 30 and electric motors 28 . cleaning head 18 further includes two sets of spray nozzles 36 , 38 for spraying cleaning solution 14 on the brushes 32 , soil transfer rolls 34 and / or floor surface 20 . the discharge of solution through roll spray nozzles 36 and floor spray nozzles 38 is controlled by activation of valves 40 , 42 . a fluid pump 46 is provided to pressurize cleaning solution 14 . in an exemplary embodiment of the invention , cleaning solution dispensing system includes pump 46 for selectively pumping cleaning liquid 14 through conduits 48 , 50 , 52 and nozzles 36 , 38 thereby delivering cleaning liquid 14 to floor surface 20 , soil transfer rolls 34 , and / or brushes 32 . appropriate fluid controls , such as valves 40 , 42 switches ( not shown ), etc . are provided to control the application of cleaning fluid 14 . as depicted in fig2 floor spray nozzle 38 discharges cleaning solution 14 to floor surface 20 and front extractor brush 32 . as depicted in fig3 roll spray nozzle 36 discharges cleaning solution 14 to soil transfer rolls 34 during a soil transfer roll mode of operation . alternative dispensing means may include drip bars or gravity feed techniques , transfer rolls , etc . cleaning head 18 further includes a plurality of vacuum extraction tools 54 , 56 , 58 for removing soil solution from either the floor surface 20 , the soil transfer rolls 34 , or both . extractors 54 , 56 , 58 each include an elongated slot and an outlet aperture . extractors 56 , 58 share a common outlet aperture 60 . as depicted in fig2 floor surface engaging extractor 54 is coupled to the vacuum system during an extraction mode of operation . extractor 54 is configured to remove soiled solution from floor surface 20 . as depicted in fig3 extractors 56 , 58 are configured to remove soiled solution from soil transfer rolls 34 . extractors 56 , 58 are sized in relation to soil transfer rolls 34 to remove soiled solution across substantially the entire transverse length of the rolls 34 . an alternative vacuum extractor system may include two separate outlets each having a separate conduit to recovery tank 16 . in operation , extractors 54 , 56 , 58 are selectively coupled to a vacuum - based solution recovery system including recovery tank 16 for soiled solution and vacuum fan 62 . a vacuum conduit 64 may be selectively connected to either the floor surface engaging extractor 54 ( fig2 ) or the pair of roll extractors 56 , 58 ( fig3 ). vacuum conduit 64 may be connected between the different extractors 54 , 56 , 58 by manually switching conduit 64 . other manual valving may be practicable to make the connections in the vacuum recovery system . in another embodiment , vacuum connections of the soiled solution recovery system may be automatically performed , such as via a controlled valve , etc . referring again to fig2 extractor brushes 32 may be bristle - type cylindrical brushes as known in the art . referring to fig3 soil transfer rolls 34 may of a variety of different materials . a combination of pad - like or bristle - like or foam - like materials , and the like , may be used . in a preferred embodiment a material such as a woven synthetic fabric , having pile fibers tufted thereunto is utilized . in one embodiment of the invention , the substrate has an appearance and feel that is similar to the surface fabric used on a common paint roller . in some instances , it may be desirable to intersperse stiffer fibers , i . e ., brush - like bristles , into the substrate to enhance the agitation action of soil transfer rolls 34 . it is further envisioned that a single “ hybrid ” roll design may be utilized during both modes of operation . a hybrid roll / brush design may contain aspects of a bristle brush and soil transfer roll material ( fabric , pile structures , etc .). a hybrid roll design would eliminate the requirement of switching rolls 34 with brushes 32 during operational mode changes . operation of machine 10 will now be described . in operation , machine 10 is propelled across surface 20 . to initiate a cleaning operation , appropriate controls 65 , such as switches , are used to activate vacuum fan 62 , motors 28 , valves 40 , 42 , cleaning liquid pump 46 , etc . at least two modes of operation are available , an extraction mode and a soil transfer roll mode . switching between the two modes may entail a change of vacuum connections between extractors 54 , 56 , 58 and recovery tank 16 , activation of valves 40 , 42 , and switching brushes 32 with soil transfer rolls 34 . in the extraction mode of operation ( as depicted in fig2 ), machine 10 functions similarly to known carpet extractors . machine 10 operates in a direction as indicated by arrow 66 . cleaning solution 14 is pressurized by pump 46 and directed through valve 40 and conduit 52 to floor spray nozzle ( s ) 38 . cleaning solution discharged through nozzle ( s ) 38 is directed primarily onto the floor surface 20 . nozzle ( s ) 38 may also direct some cleaning solution onto front extractor brush 32 . extractor brushes 32 are driven via motors 28 to engage the floor surface and transfer soil into a soiled cleaning solution . brushes 32 may include bristles to facilitate soil transfer . the direction of brush rotation is indicated by arrows 68 , 70 . as cleaning machine progresses across the floor surface 20 , floor extractor 54 engages the wetted portion of the floor to remove soiled solution from the surface . soiled solution is moved through vacuum conduit 64 and into recovery tank 16 by operation of vacuum fan 62 . a description of a second mode of operation , a soil transfer roll mode , may be made with reference to fig3 . one or more transfers between the two modes of operation may occur during a machine usage , e . g ., an operator may perform the extraction process on a portion of a floor surface and perform the soil transfer roll process on another portion of the floor surface . in the second mode of operation , soil transfer rolls 34 are wetted with cleaning liquid 14 by cleaning solution nozzle 36 , then extracted by operation of roll extractors 56 , 58 to remove soiled cleaning liquid , and then wiped against floor surface 20 so as to transfer soil from surface 20 onto soil transfer rolls 34 . soil transfer rolls 34 revolve by operation of motors 28 in directions as indicated by arrows 68 , 70 so that different portions of the soil transfer rolls 34 are being wetted with cleaning liquid 14 , extracted by roll extractors 56 , 58 , or wiped against surface 20 . in this second mode of operation , cleaning solution is pressurized via pump 46 and flows through valve 42 and conduit 50 toward roll nozzle ( s ) 36 . cleaning solution usage ( solution volume / area of floor surface ) during the second mode of operation ( soil transfer roll cleaning ) may be substantially less than during the first mode of operation ( hot water extraction ). floor spray nozzle 38 may be optionally activated during the second mode of operation to increase the amount of solution 14 applied to floor 20 . in the soil transfer roll mode of operation , wetted portions of rolls 34 may be defined as those roll portions which receive cleaning liquid from the spray nozzle 36 . vacuum extractors 56 , 58 each engage a roll 34 to remove some of the just deposited cleaning liquid 14 and soil previously transferred from the carpet surface 20 . each roll 34 is engaged by its associated vacuum extractor 56 , 58 to reduce the local wetness of the roll 34 . as a result , rotating rolls 34 have a wetted portion as defined above , and a reduced wetness portion which engages the carpet surface 20 . as rolls 34 are revolved , reduced wetness portions engage the carpet fibers and cause soil to be transferred from the carpet fibers to rolls 34 . as rolls 34 are further rotated , the reduced wetness portions ( having received soil from the carpet ) are sprayed with cleaning liquid 14 by nozzle 36 and subsequently vacuum extracted by extractors 56 , 58 to convey soiled cleaning liquid from rolls 34 into soiled solution recovery tank 16 . the soil transfer roll cleaning process thus includes the steps of wetting a portion of rolls 34 with cleaning liquid 14 , reducing the relative wetness of the wetted portion of the rolls 34 by extraction , and wiping the surface with the rolls 34 so as to transfer soil from the surface to the rolls 34 . soil upon the rolls 34 is subsequently removed as the revolving rolls 34 are rewetted and extracted . in turn , the soil transfer roll cleaning process repeats as a cycle with rolls 34 revolving so that cleaning liquid 14 is applied to one portion , extractors 56 , 58 reduce the relative wetness of another portion of rolls 34 ( and removing soiled solution therefrom ), and yet another portion of rolls 34 wipe the surface 20 to transfer soil from the surface to the rolls 34 . additional aspects of the present invention will be addressed . it is envisioned that the cleaning processes according to the present invention may be performed on a variety of different machines , ranging from small manually operated devices , to large operator driven vehicles . the illustrated device is a walk - behind type cleaning machine , more particularly a battery powered self - propelled machine . in alternative embodiments , machine 10 may be propelled by an operator or may include a vehicle , such as a ride - on or towed - behind vehicle . machine 10 may be powered through battery power , as shown , through alternating current supplied through a cord , or through another type of on - board power source , such as an ic engine . embodiments of the present invention may be utilized for cleaning a variety of floor surfaces , including but not limited to carpets , rugs , tile , vinyl , terrazzo , wood floors , and concrete surfaces . additional surfaces which may be cleaning through a process as described herein include walls , stairways , upholstered furniture or fabric , such as curtains and the like . in a particularly preferred embodiment and as described herein with reference to machine 10 operation , the present invention is utilized for cleaning floor coverings . in another embodiment soil transfer rolls 34 may be cylindrical shaped elements having a combination of foam and bristle surfaces ( not shown ). rolls 34 may include a variety of different materials including fabrics , synthetic scouring pads , foam elements , monofilament fibers for enhancing agitation of the carpet , and the like which serve the intended function of transferring soil from a surface being wiped onto the soil transfer roll 34 . extractors 54 , 56 , 58 may be provided by a wide array of structures and techniques as may be appreciated by those skilled in the relevant arts . one particular extractor technology is disclosed in u . s . application ser . no . 10 / 236 , 746 , entitled “ fluid recovery device ”, assigned to tennant company , and incorporated in its entirety herein by reference . further , although a preferred cleaning solution dispensing means includes a pump 46 , other arrangements are of course possible so as to achieve the intended function of conveying cleaning solution 14 during the cleaning processes . additionally , the cleaning liquid may comprise any cleaning solution which assists the transfer of the soil on the surface onto the cleaning medium . for example , cleaning liquid 14 could also be in the form of a foam , vapor , liquid with suspended solids , a granular cleaning material , plain water , and the like . other modifications to the described embodiment may also be practicable . one or more cleaning liquid dispensing devices may be utilized in alternative embodiments of the invention . additionally , vacuum extractor tools 56 , 58 may be alternatively configured . for example , a plurality of vacuum extracting locations may be practicable , i . e ., a first vacuum extraction location for reducing the relative dampness of the rotating cleaning medium prior to contact with the floor surface , and a second vacuum extraction location for removing soiled solution from the cleaning medium . other embodiments of the present invention may position vacuum extractor tools 56 , 58 at different locations as compared to fig1 - 3 . for example , it may be desirable to extract a portion of cleaning implement 34 after that portion is wiped against the carpet . in this manner , the steps of operation would include wetting a portion of cleaning implement 34 , wiping that portion of cleaning implement 34 against the carpet surface , and then extracting that portion to removed soiled cleaning solution . a modification to the illustrated embodiment of fig1 - 3 could entail positioning extractors 56 , 58 between motors 28 . other positions of extractors 56 , 58 may also be practicable . extractors 54 , 56 , 58 may each be independently movable between an operational position and a nonoperational position . for example , extractor 54 may engage carpet surface 20 as indicated in fig2 during a first mode of machine operation and be moved away from carpet surface 20 as indicated in fig3 during a second mode of operation . in another example , extractors 56 , 58 may be selectively moved relative to rolls 34 and / or brushes 32 to increase or decrease the distance between the elements . the positioning of extractors 54 , 56 , 58 may be electro - mechanically or manually controlled . other embodiments of the present invention may utilize a different drive system to power rolls 34 and / or brushes 32 . a single electric motor may be one option . mounting and support structures for the rolls 34 and / or brushes 32 may also vary . rolls 34 may be held upon a wire frame , similar to a paint roller , and allow for removal from one side of the machine . other roll 34 / brush 32 connections would be appreciated by those of ordinary skill in the arts . the direction of rotation of rolls 34 / brushes 32 may be altered from that illustrated in the preferred embodiment . three or more rolls 34 and / or brushes 32 may be practicable . roll 34 and brush 32 rotational speed may be selectively controlled so that speeds differ between differ modes of operation . down pressure of rolls 34 and brushes 32 may be selectively controlled so that the down pressures differ between modes of operation . additional spray nozzles may be desirable to convey cleaning solution 14 to rolls 34 , brushes 32 , or surface 20 . a system may be provided to momentarily increase the application of cleaning solution 14 to the various components or surface 20 . such a system may include a button or other switch to activate additional nozzles , etc . for a predetermined period of time . in the preferred embodiment of the invention as illustrated in fig1 the revolving cleaning implement is roll 34 . roll 34 may be constructed of nylon fibers secured to a polypropylene core . other materials or material combinations would be appreciated by those of ordinary skill in the arts . in alternative embodiments , the revolving cleaning medium may be a belt ( not shown ). a belt comprised of a substrate , such as a woven synthetic fabric , having pile fibers tufted thereinto may be practicable . in some instances it may be desirable to tuft stiffer monofilament fibers into the fabric substrate to enhance the agitating action of the belt . the softer pile fibers tufted into the fabric serve to carry cleaning liquid , while the stiffer monofilament fibers serve to scrub the carpet . the belt may be supported between rollers and driven via a variety of known approaches . u . s . pat . no . 6 , 145 , 145 , incorporated by reference herein , discloses a belt technology which may be applicable to the present invention . definitions are provided herein with reference to terms used in the specification and appended claims : “ cleaning medium ”: a part , component , assembly , or structure capable of engaging a carpet or other surface in a wiping manner and accepting soil from the carpet or other surface . a cleaning medium may assume a variety of shapes , including but not limited to roll - like brushes , belts , disk - shaped elements , etc . a cleaning medium may consist of a variety of different materials of construction , such as absorbent and nonabsorbent materials , bristle - type materials , abrasive elements , fabric , etc . “ revolving ”: tending to revolve or happen repeatedly , available at regular intervals . as used herein , the term broadly describes a cyclical movement of the cleaning medium relative to surface 20 . a cylindrical shaped “ revolving ” cleaning medium may be rotate about an axis of rotation . a belt shaped “ revolving ” cleaning medium may be supported for movement about a pair of rollers , etc . “ extracting ”: drawing or pulling out , using force or effort , to remove or obtain from a substrate by mechanical action , as by mechanical pressure or vacuum . as used herein , the term broadly describes the step of removing cleaning liquid and / or soil from the rolls 34 or surface 20 . the step of extracting may be achieved through a mechanical shearing type operation , or a vacuum removal operation , or both . “ wipe ”: to rub against or otherwise engage a surface in a moving manner . as used herein , the term broadly describes physical engagement between the cleaning medium and surface 20 . in one mode of machine operation , rolls 34 engage surface 20 in a “ wiping ” manner to transfer soil from surface 20 to roll 34 . wiping does not necessarily imply or suggest removing liquid from surface 20 . cleaning rolls 34 when wiped against the carpet surface may transfer some cleaning liquid to the carpet surface . as various changes could be made in the above methods and devices 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 .