Scrubbing machine
United States Patent Kasper Apr. 29, 1975 [5 SCRUBBING MACHINE 2.683.885 7/1954 Johnson 15/83 x 3O54.l30 9/l962 Ferrari 15/340 [75] Inventor: 3 Kasper 3.436.788 4/1969 Tamny .4 15/340 inn. 73 A T C M I I, FOREIGN PATENTS OR APPLICATIONS 1 ga ompany 678.194 [/1964 Canada 15/320 [22] Flledi 1972 Primary ExuminerEdward L. Roberts [211 App] No 299 824 Altar/1e Agent or Firm-Dugger, Johnson &amp;  
 &#39; Westman Related U.S. Application Data [62] Division of Scr. No, 72.275, Sept 15. W70. Pat. No, [57] ABSTRACT 7 A scrubbing machine having a drive unit on which an [52] U 8 Cl 15/50 5/320 [5/340 operator can sit, and a separate scrubbing unit [5 H 11/18 mounted for movement independently of the frame of [58] Fie&#39;ld C 5| 52 the drive unit. The scrubber uses double brushes &#34;ls/79 98 5 6 driven under power which will pick up debris from and scrub surfaces on which the unit is operating. The [56] Reterences Cited drive unit as shown operates on a dry surface because the scrubbing unit is trailing UNITED STATES PATENTS 913,460 2/1909 Bishop 3 15/340 Clams 22 Drawmg figures 7/ X I 1 I l &#39;1&#39; 1 111 11 1 1&#39; ll&#39; .1.  
 n... 1 1.. HM- P 1 \L PATENYECAPRZBIHYS 3 879 789 SHKU 1 0F 9 F. B i  
 WENTEE APR 2 9 ms SHEET 2 UP 9 SCRUBBING MACHINE CROSS-REFERENCE TO RELATED APPLICATIONS This application is a divisional application of US. Ser. No. 72,275, filed Sept. I5, I970, now U.S. Pat. No. 3,702,488.  
 BACKGROUND OF THE INVENTION l. Field of the Invention The present invention has relation to self-propelled power driven scrubbing machines.  
 2. Prior Art Various types of powered scrubbing machines have been advanced in the prior art, and some of them have utilized double brush scrubbing. A typical prior art machine having a double brush hand operated unit is shown in US. Pat. No. 3,061,859. U.S. Pat. No. 1,694,937 shows another type of hand propelled floor scrubbing machine utilizing two scrub brushes.  
  Counterrotating double brushes have been used in street sweeping machines, for example in US. Pat. No. 574,580. In US. Pat. No. 2,683,885 a double brush floor cleaning machine having an operator seat thereon is shown. This machine is used for picking up liquids or other debris from floors and is not utilized with a scrubbing brushv A further floor cleaner is shown in US. Pat. No. 1,938,068 and this has double brushes, but the brushes are divided with an axially extending baffle which limits their effectiveness.  
  Many of these prior art devices are very difficult to manufacture, and operate. For example, there is difficulty in steering or maneuvering the devices, and when turning the squeegee or drying means utilized will tend to leave streaks or puddles. The devices are not quickly and easily transported and do not adequately pick up debris. This means that the surface usually has to be swept before scrubbing in the prior art machines. Further, the scrubbing job has been incomplete, scrubbing liquid re-use poor, and the ability to get close to walls has been poor.  
 SUMMARY OF THE INVENTION The present invention relates to a self-propelled scrubbing machine that increases speed of operation, conserves scrubbing liquid and does not require sweeping of the floor before scrubbing because of the ability to pick up debris. The drive and steering wheels are on a power unit of the vehicle, and a double brush wet scrubbing assembly forms a separate unit. The two units are connected together with links to permit the unit carrying the scrubbing brushes to be raised and lowered with respect to the power unit. A controlled floating action on the scrubbing unit is provided to control down pressure on the scrubbing brushes.  
  The entire assembly is constructed so that the components utilized are arranged for balance, and the double brushes used with the scrubbing unit are properly positioned and of proper construction and size, and operated at proper speed to pick up debris as well as scrub. The unit may be thus used as a dry sweeper. The water or scrubbing liquid is reused by carrying it over the leading one of the brushes, and any excess water or scrubbing liquid carried by the trailing brush is squeegeed up and carried to a tank with a vacuum. A debris hopper or receptacle is provided to receive debris and water or scrubbing liquid swept up by the scrubbing brushes. The debris hoppper may be mounted ahead of the double brush unit, or to the rear of the double brush unit, as desired.  
  As shown, the two brushes are mounted so that they will scrub close to the side edges of the machine, and the brushes are made so that they can be removed for service by removing a bracket at one end of the brushes, and being pulled in this direction.  
  The frame member for the trailing unit includes a divider and guide between the brushes so that scrubbing liquid will be recirculated and reused, and debris will be guided into the debris receptacle.  
  Additional features include optional short turn devices for the drive unit and a sensing device to automatically remove some of the downward load on the brushes when the power required to drive the brushes increases, thereby providing automatic compensation so that the engine used with the unit is not overloaded.  
  If desired, the trailing unit can be mounted to move sideways so that sharper turns may be made when the unit is adjacent the wall, and positioning of the hydraulic reservoir used for supplying fluid to the fluid actuated drive components at the forward end of the drive and power unit to counterbalance the trailing unit.  
  Two different size brushes may be used in the double brush scrubber for obtaining the desired control of the scrubbing operation.  
  A feature of the invention is that the power unit operates on a surface that has not been wetted by the sc rubber. In instances where the entire surface has been flooded or is wet from external sources prior to scrubbing, the device may include means to deliver a drying air blast to the wet surface immediately ahead of the drive and steering wheels.  
  The side squeegees used are mounted with leaf springs to permit them to float and still prevent escape of wash water and debris, even when turning. The side squeegee leaf springs also automatically adjust for wear of the cylindrical brushes, so they dont have to be manually reset or adjusted. The rear squeegee cooperates with the side squeegees to prevent streaking in turning. A hydraulic cylinder controls up and down movement of the rear squeegee so that it can be lifted upwardly when desired to prevent damage, or forced downwardly with the desired amount of force.  
  The scrubber has variable speeds, is easy to steer and control, and is highly versatile.  
  Objects of the invention are to provide a versatile scrubbing machine which has long life, good reuse of the scrubbing liquid, picks up debris as it scrubs, variable speed, has ability to lift and lower the scrubbing unit, and provides the features described above and in the following specification.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a scrubbing machine made according to the present invention;  
  FIG. 2 is an enlarged side elevational view of the device of FIG. 1 with parts in section and parts broken away;  
  FIG. 3 is a fragmentary enlarged top plan view of a scrubbing unit of the present invention taken as on line 33 in FIG. 2;  
  FIG. 3A is a fragmentary perspective view showing a debris hopper being removed from the scrubbing unit of the present invention;  
  FIG. 3B is a fragmentary sectional view taken as on line 3B3B in FIG. 3&#39;,  
  FIG. 4 is a side elevational view of the scrubbing unit with parts in section, and controls for a rear squeegee used shown partly schematically;  
  FIG. 5 is a fragmentary side view of a side squeegee showing the leaf spring mounting thereof;  
  FIG. 5A is a fragmentary sectional view taken as on line 5ASA in FIG. 5.  
  FIG. 6 is a schematic representation of the hydraulic circuit for the device of the present invention;  
  FIG. 6A is a schematic representation of a modification of the drive circuit to aid in making sharper turns;  
  FIG. 7 is a part schematic side view of the trailing unit of the present invention showing a control for relieving the downward pressure on the scrubbing brushes in response to the torque required to drive the brushes,  
  FIG. 8 is a fragmentary side sectional view showing a hopper dump mechanism made according to the present invention;  
 FIG. 9 is a top plan view of the device of FIG. 8;  
  FIGS. 9A and 9B are a side and top view, respectively of a manual actuator for the hopper dump mechanism;  
  FIG. 10 is a schematic top plan view of a modified form of the invention showing a traversing trailer scrubber unit which permits sharper turns when the scrubber is adjacent to a wall;  
  FIG. 10A is a fragmentary rear view taken on line l0Al0A in FIG. 10;  
  FIG. 11 is a side view of a modified scrubber showing means for drying a surface that was wet prior to scrubbing;  
  FIG. 12 is a detailed view of a selector valve used when exhaust gases are used for the drying air blast;  
 FIG. 13 is a view taken as on line l313 in FIG. 11;  
  FIG. 14 is a side view of a scrubbing unit modified to mount the main debris hopper ahead of the brushes and also showing a second rear mounted hopper; and  
  FIG. 15 is a side view of a scrubbing unit showing brushes of different sizes used for scrubbing.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS A scrubbing machine illustrated generally at 10 made up of a power and driving unit 11, and a scrubbing unit 12, which are independently constructed, and are connected together so that the power unit 11 will, as shown, pull the scrubbing unit 12 over the surface to be scrubbed through a plurality of connecting links illustrated generally at 13. The power unit comprises a main frame 14, powered drive wheels 15 at the rear thereof, and a front central steering wheel 16. This perhaps can be best seen in FIG. 6A. Each of the drive wheels 15 is driven through a separate hydarulic motor 17 and 18, respectively, which are powered in a suitable manner through a variable volume pump, as desired. The hydraulic motors are thus variable speed controlled, and a foot pedal 21 is used for controlling the speed of the vehicle by adjusting the variable volume pump.  
  The scrubbing drive unit can have brakes operated from a pedal 22 by an operator sitting on the operator seat 23. The hydraulic motors l7 and 18 can be mounted to the frame of the power unit independently, and the drive wheels 15 are then drivably mounted on the respective output shafts of the drive motors. Any  
 other suitable arrangement can be utilized for driving the vehicle in well known manner.  
  The steering wheel 16 is mounted about an upright axis with a suitable frame 24, and is controlled from the operator steering wheel 25 through a drag link 26 and steering arm 27 shown in FIG. 6A. An automotive type steering gear is used at the base end of the steering column.  
  The drive unit is powered with an air cooled engine illustrated generally at 30 located at the forward end of the power unit 11 and mounted onto the frame 14. The air cooled engine as shown is used for the components, such as a main drive variable volume pump 29 (shown only schematically) and a hydraulic pump 31 for accessories, driven through a belt arrangement 32 from the engine output shaft. The pump 31 is used for powering the hydraulically driven components of the unit. As can be seen, a main hydraulic fluid reservoir 33 is at the front part of the frame 14.  
  The frame for the power unit also supports a clean scrubbing liquid tank 34 on which the operator seat 23 is mounted, and as can be seen the clean liquid tank is hingedly attached to the frame so that it can be tilted rearwardly as shown in dotted lines in FIG. 2 to permit access to components positioned under the clean liquid tank. The battery, filter and other components can be housed under the clean liquid tank. The clean scrubbing liquid tank is used for supplying water or other scrubbing liquid, such as detergent or solvent solutions, to the surface 35 over which the vehicle is moving and which will be scrubbed. This means that there will be wet scrubbing. As shown, a hose 36 extends from the clean liquid tank downwardly to a transverse scrub liquid spreader pipe 37 which extends across the width of the machine and is spaced slightly above the surface, and permits the scrubbing liquid indicated at 38 to run out onto the floor and wet the surface ahead of the scrubbing unit 12. The pipe 37 of course may be of suitable type of applicator pipe, and these per se are well known in the art. The pipe 37 comprises a liquid distribution header. The tube 36 includes a manually operated on-off valve to control liquid flow. Clean liquid can be supplied to the liquid spreader pipe or nozzles under pressure or gravity feed.  
  The scrubbing unit 12, as shown, has a frame indicated generally at 41 surrounding the scrubbing unit. This frame 41 is in turn reinforced with a cover frame plate 42 fixed thereto, and a transverse support and divider baffle member 43 fixed to the plate to reinforce in plate (FIG. 4). The frame 41, as shown, has a removable brace member 44 on one side thereof removably joining front and rear cross members, and this brace member may be removed (see FIGS. 3 and 4) to permit installation and removal of a pair of scrubbing brushes 45 and 46. The forward or leading scrubbing brush 45 is driven so that it rotates in direction as indicated by the arrow 47, and the rear or trailing scrubbing brush 46 is driven as indicated by the arrow 48. The brushes are selected to have good debris pick up characteristics. Thus the rows of bristles are spaced to permit the brushes to walk over debris. The brushes are not full fill brushes. Further, the bristle rows are preferably of a herring bone pattern.  
  On the opposite end of the brushes from the removable brace, the drive motors for the brushes are shown. These motors are fixed displacement hydraulic motors 51 and 52, respectively. The hydraulic motors are fastened through brackets 53 to the side of the frame 41 and the motors extend inwardly so that the output shafts of each of the motors, for example the drive shaft 52A shown for motor 52 is coaxial with the rotational axis of its respective brush. As shown, the brushes are constructed with an open tubular core member, as shown at SIB and 52B, and the bristles extend outwardly. The hydraulic motors fit within the respective tubular members. The shafts for the hydraulic motors have suitable connections for connecting to mating adapter plugs shown at 56, in each of the respective brushes. The drive connections from the hydraulic motors are through the adapter plugs to the interior of the tubular members 518 and 528. The brushes are both supported by their respective motor shafts 52A and 51A, and also are driven by these shafts.  
  The opposite end of the brushes are mounted on idler bearing plug assemblies attached to the brace member 44 which, as shown, fixedly mounts a pair of shafts 57 and 58, respectively. The shafts may be welded to the brace member, if desired. These shafts 57 and 58 in turn have suitably mounted bearings thereon which are merely idler bearings, and brush end adapter plugs 59 and 60, respectively, are mounted onto the bearings so that the plugs will rotate freely with respect to these shafts. The adapter plugs fit inside the tubular cores for the brushes and in turn have flanges which abut against the end surfaces of the tubular cores for the respective brushes 45 and 46. The plugs fit snugly within the interior cores. Thus when the brace member 44 is bolted in place the frame 41 is held together, and the plugs 59 and 60 fit inside the brushes to hold them in proper position relative to the frame and to the drive motors. The brushes will rotate under power when their respective hydraulic motors 51 and 52 are powered. The brushes 46 and 45 may be rotated at the same speed, or at different speeds. The higher speed brush, if different speeds are used, is theone adjacent the hopper. Different speeds on the brushes may help in debris pick up (sweeping action) as well as liquid pick up. As an example of preferred operation, brushes have an outer diameter of l 1% inches are operated at between 450 and 550 rpm. with both brushes at the same speed.  
  A door 61 is provided to cover the opening through which the brushes are removed and serviced. A suitable hinge 62 is provided for this door.  
  The divider baffle 43 is a transverse member, as shown, and is positioned above the two brushes 45 and 46.  
  In this form of the invention, as shown, a debris hopper illustrated generally at 65 is mounted. As shown, in FIGS. 3A and 3B, the debris hopper 65 is removably supported on provided ledges 41A formed by the frame 41, and has a lip portion 67 which is closely adjacent the bristles of the rear brush 46. The lip also is substantially along or slightly below a horizontal plane passing through the rotational axis of this brush. The frame plate member 42, as shown, ends along a rearward edge that overlies the debris hopper, so any liquid thrown up by the brushes and carried along the underside of the panel will drop off into the debris hopper.  
  The debris hopper has a pair of handles 68 that can be used for manually removing the hopper from the frame member for emptying when the hopper is full of debris.  
  Then, at the rear of the frame 14, and inside the frame, there is a rear squeegee assembly illustrated generally at 70 which is controlled in up and down direction with a hydraulic cylinder 71, (FIG. 4) operated through a valve of suitable design, as explained in connection with FIG. 6. This squeegee assembly 70 is mounted on pivoting parallel arms 72, 72 on opposite ends thereof so that when the unit is raised and lowered with the hydraulic cylinder 71, it will raise parallel. Also as it wears and is lowered, the squeegee will move straight down against the surface rather than cock at an angle thereto. The squeegee has a top frame 73 with upright members 73A to which the links 72 are pivotally mounted. The opposite ends of the links 72 are pivoted to the frame member 41.  
  The hydraulic cylinder 71 can be used to provide a down force on the squeegee, and when the down force is overcome (a relief valve in valve HA is used for relieving this force) the squeegee will raise guided by the parallel arms 72 against the down force of the relief valve.  
  As shown, the rear squeegee top frame member 73 has resilient, downwardly extending, spaced apart flaps 74 attached to frame 73. The flaps can be made of a suitable elastomeric or other flexible material that will give slightly and provide a good drying seal against the surface 35 to trap any liquid that gets past the scrubbing brushes and collect it. The forward flap has a rib 74A that will engage the rear flap when the flaps are under vacuum to prevent the vacuum from being closed off from the ends of the squeegee. The flap has slots so liquid can go between the flaps. The double brush assembly actually picks up most of the scrubbing liquid in the hopper, and the rear squeegee in some instances can be lifted off the surface,  
  A vacuum fan illustrated schematically at 75 is mounted on the vehicle frame in a suitable location, and is driven with a hydraulic motor 75A. The suction line, shown schematically, is connected to a dirty liquid tank illustrated schematically at Z6 also mounted on the frame below the operator&#39;s platform. This tank is closed and sealed with a plenum chamber at the top. The plenum chamber has a vacuum line 77 leading therefrom on the output side. Line 77 is above the liquid livel. The vacuum hose 77 extends from the power and drive unit where the dirty liquid tank is mounted, back to the scrubbing unit, underneath the frame plate member 42. The end of vacuum hose 77 has a Y connected pipe assembly 78 thereon. The Y pipe coming from the vacuum hose 77 is split and has two vertical sections 78A and 788. Section 78A fits down inside the debris receptacle or hopper 65. The vacuum pipe 78A just clears the floor of the receptacle by a short distance and is surrounded by a screen 79 (large size) that keeps out large pieces of debris, as shown in FIG. 38.  
  Pipe 78B extends downwardly through a provided recess in the debris receptacle or hopper 65, and is removably coupled with a slip coupling 78D to a fixed pipe 78C which has a tapered end portion. The lower end of fixed pipe 78C fits between the rear flaps 74 to create a vacuum or suction on the channel formed between the squeegee blade members. The squeegee flaps extend around the rear of the machine and then extend forwardly adjacent the sides of the machine to guide liquid toward the center of the machine. Thus the rear squeegee members collect the liquid from surface 35 that is left over from scrubbing. The liquid moves toward the rear center of the squeegee, enters the chamber between the front and rear squeegee members, and then is vacuumed up through the pipe 78C, 78B and into the Y portion 78, tube 77 and back to the dirty liquid tank. The liquid is collected in the dirty liquid tank. Likewise, any liquid that is carried into the receptacle or hopper 65 by the brush 46 will be vacuumed up or sucked up through pipe 78A. A screen or grille protecting member is provided adjacent pipe 78A if desired to prevent debris from being picked up by the vacuum pipe 78A. The rib 74A prevents the front flap 74 from collapsing and cutting off vacuum from the ends of the squeegee.  
  In addition to the rear squeegee assembly, there are squeegees provided along the sides of the scrubbing unit. As shown in FIG. 3, there is a squeegee assembly 80 along the right hand side of the unit which is fastened to the frame member 41, and a squeegee 81 which is along the left hand side of the unit and this squeegee is fastened to the cover member 61 so that it moves with the cover member. Both the squeegee 80 and 81 are provided with end portions 80A and 81A, as shown in FIG. 3, that go on the inside or forward edge of the forwardly extending end portions of the rear squeegee 70. The scrubbing liquid collected along the side squeegees is thus guided to the rear squeegee and further guided toward the center thereof for pick up.  
  The squeegees are mounted in a unique manner, as shown in FIG. 5. The side squeegees each comprise upper frames 82 and they are mounted on leaf springs 83 which are attached to the frames 82, and to some portion of the main frame 41. In the case of squeegee 81, it is attached to the door 61. The leaf springs permit the flexible skirt portion 84 of the squeegee which is attached to the frames 82 to move laterally over the floor and to give slightly sideways, and also move up and down in a linear direction without causing the squeegee to twist, rub extensively and wear out.  
  The leaf springs further provide some give&#34; when the unit swings sideways during turning, as a trailing unit will, and provide for automatic adjustment for wear of the brushes. The leaf or blade springs give to compensate for this wear without manual adjustment.  
  Small brushes 85 are attached to the frames 82 and are positioned along side the main brushes and are row brushes. The side squeegee members are formed so that the flexible sections 84 extend outwardly at an angle with respect to the support 82. The flexible sec tions extend outwardly, as shown in FIG. A, and the brushes 85, which are attached to the upper frames 82, extend inwardly toward the main rotary brushes 45 and 46. The small brushes 85 are positioned to engage the surface being swept, as well as being very close to the end bristles of the main rotary brushes 45 and 46. This action keeps the debris from being spilled out around the ends of the main brushes and also prevents the debris from being lost from between the brushes 45 and 46 underneath the squeegees when the corners are being turned and the rotary brushes slide sideways.  
  The outwardly extending flexible sections on the squeegee will insure that the side portions are kept free of debris and also the scrubbing liquid is kept inside the unit. The outward extension of the flexible section makes it easier for the flexible sections 84 to be in contact with the surface 35 where the flexible members on the side squeegees angle inwardly to be inside the rear squeegee as shown in 80A and 81A. This outwardly extending slant of the flexible section also permits them to follow the surface 35 when corners are being turned without turning under and getting out of position. When the vehicle is turned the squeegees have to slide sideways a substantial amount. The straight flexible members tend to fold in or out and when this happens, the squeegees would fold out of position and no longer give a good seal. The outward slant of flexible members prevents this.  
  The scrubbing unit is attached to the power unit in an independent manner. While rear mounting is shown, the unit may be front mounted and pushed rather than pulled. The improvements described in the scrubbing unit are very beneficial whether the unit is front or rear mounted, but rear mounting permits the power unit 11 to operate on a dry surface. The links shown generally at 13 are shown in greater detail in FIGS. 2, 3 and 4. As can be seen, a pair of spaced apart channel members 87 are fixed to the top plate member 42 of the frame 41 and extend upwardly therefrom to form a control mast assembly. It should be noted that these channel members are positioned substantially directly above the cross frame member 43 that extends transversely across the frame.  
  The channel members 87 in turn have a channel shaped main tow and lift link 88 pivotally between them with a pin 89. The pin 89 extends along a transverse axis. The link 88 as shown, is not straight, but has a bend in it for clearance purposes, and the opposite end of the link 88 is pivotally attached with a pin 90 to a provided mounting portion of the frame 14 of the power unit. In addition, the scrubbing unit is connected to the power unit with a pair of spaced apart outboard drag links 91 and 92, respectively, which have suitable part spherical seat pivoting rod ends thereon. First ends of the drag links are attached to suitable ears 93 on the main frame of the power unit 11, and the opposite ends of links 91 and 92 are attached to suitable ears 94 on the frame plate member 42 of the scrubbing unit. These drag links keep the scrubbing unit properly positioned as it is being towed through the main pull link 88, and also control the angle of the scrubbing unit with respect to the surface 35 as the scrubbing unit is raised.  
  The support for the scrubbing unit comes through link 88, and this link can twist and give to permit one end of the scrubbing unit to raise relative to the other as it moves over irregularities. The links 91 and 92 permit this movement.  
  Raising and lowering of the scrubbing unit is controlled with a hydraulic cylinder 95, which can be single acting because it only has to lift the scrubbing unit, and the weight of the scrubbing unit will cause it to retract, and this hydraulic cylinder 95 is attached as at 96 to the main frame of the power unit. The cylinder 95 has an extendable and retractable rod 97 pivotally attached as at 98 to the link 88.  
  Thus, when the power unit is powered and moving over the surface, the link 88 will pull the scrubbing unit along, and the links 91 and 92 will also keep the scrubbing unit properly positioned and exert a pull on it, while permitting the unit to float over objects, if necessary.  
  As can be seen in FIG. 2 in dotted lines, the trailing unit can be raised. The drag links 91 and 92 control the angle of the scrubbing unit with respect to the surface when the scrubbing unit is lifted. When the pull link 88 is raised to its dotted line position, it can be seen that the rear portions of the scrubbing unit raise much higher than the forward portions to provide for clearance at the rear if the vehicle is driven up an inclined surface.  
  A safety lock member 100 is pivotally mounted about the same pin 98 as the rod of the hydraulic cylinder, between the legs of the link 88, and is controlled through a push pull control wire 101 which is similar to an ordinary choke control. The control wire can be moved to its solid line position as shown in FIG. 2, and then the cylinder 95 will be operable and can be retracted when the control valve for the cylinder is operated. However, when the cylinder 95 is extended, the control 101 can be pushed to its dotted line position by an operator and this will move the safety lock member 100 into position as shown in dotted lines where the end of the member 100 will abut against the end surface of the cylinder itself around the rod, and prevent the rod from retracting. This will hold the scrubber unit raised even if hydraulic pressure should fail, as a safety measure. The scrubbing unit is raised and may be locked in raised position for rapid transport without having the brushes and squeegees wearing against the surface 35.  
  The control line leading to the cylinder 95 can have a suitable valve assembly shown schematically at 102, which can be adjusted so that only a desired amount of lift pressure will be exerted on the cylinder 95. This will mean that the operator can vary the load supported by the cylinder 95 so that the downward bearing pressure of the scrubbing unit on the brushes 45 and 46 can be changed by adjusting the valve to change the size of a bypass orifice and thus change the pressure in the line 104 and cause the cylinder 95 to bear more of the weight of the scrubbing unit. It should also be noted that a flow divider 105, which is shown schematically, divides the flow from the pump 31 so that a low flow, for exmaple 1 gallon a minute, will be flowing through the valve 102. Then, even if the engine 30 drops in r.p.m. so the output of the pump drops, this small flow will be maintained, and the cylinder 95 will not suddenly drop because of a reduction flow through the control valve 102.  
  A feature of the unit is that the forward housing 108 over the engine has a center opening 109, that has a sealing member 110 that mates against the outer periphery of the inlet opening to the provided engine cooling fan so that there is no possibility for air to be drawn from around the interior of the housing 108 into the engine and fresh clean air will always be blown across the engine. The engine is a conventional air cooled engine. The warm air can be disbursed out through suitable ducts.  
  Additionally, the carburetor for the engine can be mounted so that it has its intake open directly to the air cooling housing for the engine fan so that there is a fresh flow of air coming through opening 109 into the carburetor which slightly super charges the engine. The engine cover having opening 109 of course can be removed for servicing.  
  A sheet metal housing 107 can be used over the scrubbing unit. The housing 107 may also be plastic if desired, and has a movable cover member 107A that is hinged to the main part of the housing 107 and can be raised and lowered to get into the debris hopper, and remove it for cleaning or to service components in the scrubbing unit. This cover is shown in its dotted position in FIG. 1. The cover 107A when fastened down with suitable clamp means, holds the debris hopper in proper position.  
  FIG. 6 is a hydraulic schematic representation of the drive components of the present invention. It was previously mentioned that the unit used two different hydraulic pumps, and these pumps are shown schematically. The engine 30 drives the hydraulic pump 31 which is the hydraulic pump for auxiliary components, and the engine also drives a variable displacement piston type pump 29 which is used for driving the wheel motors l7 and 18 in a closed circuit. The variable displacement pump is a commercially available pump that has a lever control operated by foot pedal 21 that regulates the amount of oil that is pumped, and the amount of oil being pumped through the motors 17 and 18, which, as shown, are in parallel, determines the speed of movement of the vehicle. A suitable hydraulic makeup circuit 28 can be installed in this circuit to take care of any leakage losses and the like. The makeup circuit is a common circuit furnished with the pump, which is made and sold by Vickers Mobile Division of Sperry Rand Corporation. The pump has a swash plate control to regulate the amount of fluid under pressure being pumped out into the motors 17 and 18. The pump is an over-center pump that may provide reverse flow to the motors and thereby reverse rotation of the motors as well as provide a neutral or stopped position. The pump 31 has the flow divider 105 built into the pump and this delivers a set low volume, for example gallon a minute, at 1,000 pounds per square inch pressure to the hydraulic cylinder for the control of lifting and lowering the trailing unit. The valve assembly 102 includes a manually controllable spool shown at 102A that can be shifted from a central position wherein flow from the flow divider will merely pass through the valve and out into a return line 103 but do this through a variable orifice valve 102B that controls the amount of back pressure in the lines leading from the flow divider 105. A relief valve 102C is also provided across the line to relieve overpressures.  
  When the valve 102A is shifted to position wherein the side indicated at 102D is aligned with line 104, it can be seen that fluid under pressure will be applied to the hydraulic cylinder 95, but only the amount of pressure that the adjustable valve 1028 provides as a back pressure. This then actuates the rod 97 of the cylinder at a selected manually variable pressure so that the downward load on the brushes in the scrubbing unit can be regulated by adjusting the valve 10213. When the spool is moved in the opposite direction so that the section 102E aligns with the line 104, the full pressure of the relief valve setting of valve 102 can be applied to the cylinder 95, and positively raise the scrubbing unit. This means that the scrubbing unit can thus be held in an upright position, and when the valve spool 102A is again returned to its centered position as shown in solid lines, the line 104 is blocked in the central portion of the valve and the flow from the flow divider 105 is directed through the spool into the series circuit through line 103.  
  The cylinder 71 for the rear squeegee assembly 70 is connected through a valve 71A to the line 103. This valve or cylinder 71 is a double acting cylinder and the spool valve 71A is a normal fourway valve which will block both lines leading to the cylinder 71 in its central position, and will in one position force the rod of cylinder 71 out and in the other position force the rod of cylinder 71 in. The unit is normally operated with the valve set to force the rod outwardly. A suitable relief valve is also supplied in valve 71A and is set to open when the pressure urging the rod of cylinder 71 out exceeds a preselected amount. The relief valve setting in valve 71A thus determines the force applied to the rear squeegee and is usually set very low, for example 50 p.s.1.  
  The various valves are connected to drain or reservoir through lines shown schematically to the reservoir 33 which is also shown schematically.  
  The balance of the output of the auxiliary pump 31 comprises a higher volume of flow, for example a flow of 7 gallons per minute at rated speed for the pump 31. This secondary flow is in a circuit driving the brushes and the vacuum fan. The flow divider 105 has priority, so even when the motor 31 is running at low speeds, the 1 gallon per minute will be delivered to make the adjustable valve 1028 effective to hold the trailing unit at the desired force level. This l gallon per minute is a constant flow even though the engine 30 may be idling, so that the setting of adjustable orifice valve 1028 can be held constant.  
  The pump 31 in a normal situation is used for driving the brush motors and the fan motor in a series hydraulic circuit. A control valve 113 is used, and in its centered position it will merely return the flow from the pump 31 on the secondary side indicated at line 114 to the reservoir 33. However, when it is shifted to position so that the section 113A is aligned with the center connecting pipes, it can be seen that the branch line 114A will be directed toward a blocked port 1148. The output of the pump 31 on the secondary side is then directed to the motor 51, then to motor 52, and then to the motor 75A for the vacuum fan in series. The other side of the motor 75A then returns to the reservoir. This is the normal operation where all of the motors are operating at once, including the scrubbing brushes, and the vacuum fan motor.  
  When the valve 113 is shifted so the portion 1138 is aligned with the center section, it provides a means for stopping the brush motors 51 and 52 and operating the vacuum fan motor 75A alone. This may be a situation where scrubbing is not desired, but vacuum is wanted, for example, for picking up of liquid in a stationary position or even picking up liquid with the squeegees as the unit moves over a surface. In this instance, the branch line 114 directs the fluid under pressure through a check valve 115 into a line 116 that intercepts the series connected line between motor 52 and motor 75A, and supplies fluid under pressure to this point. Because this pressure will be equal to that on the line 114 through the motors 51 and 52, the motors 51 and 52 will not rotate but will maybe stand still, and the entire output of the pump 31 on the secondary side will be directed through line 116 to motor 75A and drive this vacuum fan motor. The valve 113 can again be returned to neutral when the unit is merely idling and not being used at all.  
  A low pressure bypass valve is used in the return line coming from the valves 102 and 71A to bypass a filter shown in the return line when the filter back pressure exceeds this setting.  
  Thus, the wheel drive circuit is separate from the accessory circuit and the variable volume pump takes care of just the wheel motors, and the setting of the pump determines the speed at which the motors operate. The setting of the pump can be actuated through the pedal 21 to operate a swash plate. The pump 29 also drives the unit in reverse.  
  The accessory pump 31 has a priority circuit through flow divider 105 that goes to a cylinder first so that the float on the rear unit can be adjusted accurately by adjusting the variable valve 1028. The unit is thus all hydraulically driven in its accessory and ground drive circuits.  
  In operation, the unit is steered through the use of the front steering wheel. The unit can be moved to scrub within one and a half inches of a vertical side wall and will turn corners in a usual manner.  
  The scrubbing liquid tank has a valve that can be opened so that the scrubbing liquid carries out through openings in the spreader pipe or header 37, and the hydraulic motors for the scrubbing brushes 45 and 46 are activated to rotate the scrubbing brushes 45 and 46 in the directions as indicated by the arrows for the respecitve brushes. The power unit will then be driven forwardly and debris on the surface 35 will be picked up by the leading brush, carried up by the second brush between the two brushes together with the scrubbing liquid that has contacted the surface and a scrubbing action will take place. Scrub liquid is reused by diverting some of the liquid over the front brush and back onto the floor. The frame divider member 43 will divide the flow of liquid and direct the debris backward into the debris hopper. It should be noted that the divider frame member 43 is positioned so that it is closer to the leading brush adjacent the top parts thereof and this causes debris to be deflected along the trailing surfaces of this frame member and over the trailing brush back into the rear debris hopper. Liquid will be carried forwardly over the bristles of the front brush 46 and will be reused or applied to the surface 35 as the scrub bing action takes place. Liquid collecting on the divider frame member 43 and along the underside of the plate 42 will drip off the edge of the frame member back into the forward brush and be carried over this brush. Some of the liquid will be carried back by the rear brush 46 into the debris hopper, which is very close to the brush bristles, and this liquid will be sucked into the dirty liquid tank through hose connection 78A.  
  Liquid that remains on the surface 35 will be gathered in by the squeegees as the scrubbing unit moves forwardly and will be trapped between the flexible members 74, 74 and sucked by the pipe 78C through pipe 788 and into the dirty liquid tank as well.  
  Thus the surface is swept and scrubbed clean and left dry. The scrubbing unit also may be used as a double brush mobile sweeper, merely by turning off the flow of liquid in spreader pipe 37. With the brushes running they will pick up dust and debris and deposit it in the debris hopper as the unit moves over the surface. The rear squeegee can be raised and the vacuum can be used for dust control, if desired.  
  The speed of the scrubbing brushes, the relative size of the two scrubbing brushes, the spacing between the brushes, and the travel speed of the unit are all interrelated in doing a good scrubbing or sweeping job. Brush peripheral speeds should be above l feet per min- Hi6.  
  The use of two brushes traveling at the same speed tends to throw the liquid and debris almost straight up. The deflectors or guides used then determine the direction of movement of the liquid and debris. If one brush rotates faster than the other and both are the same size, the debris will be deflected at an angle toward the slower brush. If two different size brushes are used, the larger brush deflects the debris at an angle over the smaller brush. Thus, speed and size of the brushes can be selected to obtain the desired trajectory of liquid and debris while scrubbing. The brushes are preferably close together, but can be spaced for debris pick up. The close spacing is helpful for liquid and fine dust pick Driving 1 1% inch diameter brushes between 450 and 550 rpm. gives a good balance between ability to pick up dust, dirt, liquid and debris and prevents atomizing or misting of liquid because of too high a speed, which mainly consumes horsepower. In other words, if the brushes are traveling at a very high rate of speed, the scrub liquid tends to mist, and the consumption of horsepower goes way up in relation to the ability to scrub and sweep.  
  A further point in recirculation of scrubbing liquid is that the divider baffle member 43 is positioned so that the tip of it is above the forward brush in the first form of the invention so that the scrubbing liquid is recirculated. The liquid will drip off the tip of the edge down on the brush and be recirculated. This is a desirable feature, and of course the positioning of the center baffle therefore is important so that the tip or edge that extends parallel to the axis of rotation of the brush is above the brush bristles and scrub liquid dripping off this tip or edge will be dropped back onto the recirculating brush, which in this instance is the forward brush 45. If a forwardly mounted unit is utilized, recirculation of liquid can be achieved by having suitable means in the debris hopper for recirculating some of the liquid.  
  In FIG. 7 a modified automatic arrangement for controlling the down pressure on the scrubbing brushes is shown. In this device, the brushes 45 and 46 are mounted in the frame as before, and the hydraulic motors 51 and 52 are shown mounted to the frame structure 41. In this instance, the hydraulic pump is shown schematically and supplies pressure to the cylinder 95 acting on the link. In this instance, the input line to the cylinder is line 150 connected to a suitable control valve shown schematically at 151, which also controls the flow to the brush drive motors 51 and 52 through a line 152. As shown, the motors 51 and 52 are hydraulically coupled in series. A cylinder tap off line 153 is connected to the line between the two motors 51 and 52, and operates through a check valve 154 to connect to the line 150. A small fixed restriction orifice 154A limits flow into line 150 through the check valve. The adjustable flow restriction valve 155 (a variable flow valve which is manually operable) is utilized. In normal operation the valve 151 is moved to position wherein flow goes from the pump to line 152 through motor 51, driving it, and then to motor 52, and then back to the reservoir. The pressure of the motor 52 acts through bleed off line 153 causing the flow through check valve 154 and restruction orifice 154A. Flow back to the reservoir through line 150 is restricted to a set amount because of the adjustment of the variable restriction valve 155. The back pressure thus acts on cylinder 95 and acts to exert a lifting force on the trailing unit.  
  If the load on the motor 52 increases because of heavier brushing, the increased pressure in line 153 will act through the check valve 154 to increase the pressure in line 150 on the base end of the cylinder 95 and thus tend to increase the force bearing on link 88. This will tend to lift the scrubbing unit 12, and will in turn reduce the downward load on the brushes and consequently reduce the power necessary to drive the brush motors. A balanced condition will be reached to maintain the load on the motors 51 and 52 below a maximum. There is therefore an automatic reduction of the load on the brushes when the pressures that operate the motor 52 increases to a point beyond that which the normal pressure in line 150 would be. The check valve 154, of course, prevents flow from the line 150 into the motor circuit. In this instance, if the scrubbing unit is to be lifted for transport, the valve 151 can be moved to position wherein the pump is coupled to line 150. The pressure will then act to extend the cylinder rod for cylinder and raise the scrubbing unit.  
  Automatic compensation to prevent killing of the engine 30 is provided because the load on the pump shown schematically will be regulated in accordance with the load on the scrubbing brushes.  
  Referring to FIGS. 8 and 9, a modified form of the debris hopper is shown. In FIG. 8, the trailing unit 12 is modified so that the frame 41 mounts a transverse rear baffle panel that is fixed to the frame adjacent the upper rear parts thereof, and extends downwardly and forwardly and is attached between the side members of the frame. The baffle forms a rear wall of the debris hopper indicated generally at 126 positioned behind the rear brush 46. The debris hopper includes a transversely extending front panel 127 that is attached between the side member of frame 41 and is positioned just immediately to the rear of the rear brush 46. Al though the vacuum hose is not shown, the vacuum hose will be used with this hopper as well.  
  A movable bottom panel 128 is utilized for the hopper, and this is dust sealed along the front and rear edges with respect to the rear panel 125 and the front panel 127. The bottom panel 128 is mounted on a centrally mounted rod 129 which is pivotally mounted to a suitable ear 130 on the bottom panel, and also is pivotally mounted to a projecting support 131 fixed to the rear panel 125. The link or rod 129 holds the bottom panel in the proper position when the panel is in its solid line position as shown in FIG. 8. The position of the false bottom panel 128 is controlled through a pair of spaced apart links 134 that are pivotally mounted to space support ears 135 fixed adjacent the front edge of the bottom panel 128 and is also mounted onto the outwardly extending end spaced levers 136 of a bell crank assembly. The levers are fixed to a rock shaft 137 that is pivotally mounted to frame members on the rear frame portions of the trailing unit 12. The rock shaft also includes a central control lever 137A fixed to the rock shaft. The lever 137A is attached as at 138 to the outer end of the rod 139 on a hydraulic piston-cylinder assembly 140. The base end of the cylinder of this assembly 140 is mounted as at 141 to the frame for the trailing unit 12.  
  The cylinder assembly 140 can be extended and retracted through a suitable control valve 144 that actuates the cylinder from a source of pressure. When the cylinder is extended, as shown in solid lines in FIG. 8, the levers are in their solid line position and the links 134 force the false bottom 128 downwardly to close the opening between the front panel 127 and rear panel 125. This means that any debris coming from the brush 46 will be trapped and held in the hopper, and also the scrubbing liquid will be collected and removed with the vacuum line as previously explained.  
  When the debris hopper fills, however, the false bottom panel 128 provides a means for emptying the dcbris hopper without manually lifting it out as previously shown in FIG. 3A. In order to do this, the valve 144 is actuated to retract the cylinder 140 to its retracted position shown in dotted lines, which will in turn lift the levers as shown in dotted lines, and this will cause the bottom panel to pivot about the connection between the links 129 and brackets 130 and also then will pull up the forward edge of the panel 128 so that the panel 128 will tilt upwardly as shown in dotted lines in FIG. 8. The link 129 will also pivot about its connection to the supports 131 and will hold the rear edge of the bottom panel downwardly so that the bottom panel 128 extends almost substantially perpendicular to the surface being traversed causing complete dumping of any debris in the hopper, without removing the hopper itself. The use of the raisable rear squeegee assemblies thus is very important here because the squeegee can be lifted up over the debris when the scrubbing unit is driven forwardly. This device for dumping also can be used where the main debris receptacle is ahead of the brushes, as shown in FIG. 14.  
  As an alternative, shown in FIGS. 9A and 9B, in place of the hydraulic cylinder 140, a manual lever 145 can be pivotally mounted as at 146 to a position of the frame for the trailing unit 12 and a link 147 extends backward to the trailing unit and is attached to point 138 to the rock shaft lever. Movement of the manual lever by the operator will cause the same action as the hydraulic cylinder retracting. This will cause the movable bottom 128 to dump and it can be done manually. This is just an alternate method of manual operation as opposed to power actuated operation which occurs with the cylinder 140.  
  FIGS. 10 and 10A are schematic showings of a mounting for the scrubbing unit 12 with respect to the power unit 11 so that the scrubbing unit can be moved laterally from side to side if desired to give more side clearance when sharp turns are made in either direction with the power unit 11. This is shown schematically for purposes of illustration, and it is to be understood that the steering and drive mechanism for the power unit 11 will be the same as previously disclosed. The mounting for the scrubbing unit is modified so that the link 88 is replaced with a link 160 that is similar to the link 88 except it has an outwardly extending end tab 161. In place of the pin and upright channels 87, the trailing unit has a pair of upright posts 162, 162 mounted thereon which are spaced apart a substantial distance and are wider than the link 160. The upright posts are fixed to the cross frame plate 42 and are sufficiently sturdy and reinforced so that they will support the entire weight of the scrubbing unit 12. A cross shaft 163 is fixedly mounted (it can be removable if desired) between the posts 162, 162 and extends through the downwardly depending legs of the bracket 160 as the pin 89 extends through the legs of the bracket 88. However. the shaft 163 is slidably mounted in suitable hubs along the legs of the bracket 160.  
  The position of the scrubbing unit along the longitudinal axis of the shaft 163 is controlled with a double acting hydraulic cylinder 164 that is attached as at 165 to the outer end 161 of the link 160, and the cylinder 164 has an extendable and retractable rod 166 that is attached at 167 to a bracket that extends upwardly from the base of unit 12 so that the cylinder is in proper alignment. The cylinder 164 may be controlled through a suitable valve 168 from a pump and reservoir is the usual manner, and it is a double acting cylinder. The links 91 and 92 as previously explained, have rod ends at their outer ends where they attach to the frame work of the trailing unit 12 and these rod ends have part spherical seats of conventional design in the present form of the invention shown in FIGS. 10 and 10A. The entire scrubbing unit 12 can be moved axially along shaft 163 by either extending or retracting the cylinder 164. In normal operation the side edge of the trailing unit indicated at 171 is offset from the main part of the vehicle so that it will travel next to a wall while the power unit is spaced from the wall. In turning away from the wall the cylinder 164 is operated so the edge 17] is moved away from the wall so both side edges 170 and 171 of the scrubbing unit are flush with the edges of the power and drive unit. A sharp turn can be made because the scrubbing unit will not immediately engage the wall but will give some room for starting the turn before it gets close to the wall. Also, the offset keeps the power unit away from the wall for easier maneuver By properly controlling the cylinder 164, the scrubbing unit can be slid axially along the shaft 163 to accomplish the desired positioning. The offsettable features are desirable whether the scrubber is from or rear mounted. The unit may be operated with the scrubbing unit in its dotted line position with edges 170 and 171 aligned with the edges of the power unit.  
  The cylinder 164 may also be automatically actuated by a solenoid valve 156 operated by switches 1S7 actuated by the vehicle steering arm 27 after the arm has been moved a preselected amount in either direction.  
  Switches 158 along the sides of the trailing unit also could be used to control a solenoid valve 159 so that if the trailing unit rubbed against a side wall surface, the cylinder 164 would be actuated to move the trailing unit in proper direction away from the wall.  
  Referring now to FIG. 6A, a further modification of the device of the present invention, which is used for making sharp turns is disclosed. Here the power unit 11 has wheels, and drive motors l7 and 18, as well as the steering assembly arm 27. The motors l7 and 18 are normally in parallel, and both operate in the same direction. A reversing valve 175 is connected to permit normal parallel operation with both motors turning in the same direction or with one rotating in reverse from the other. The reversing valve is shown in reverse position. The valve 175 is controlled by a solenoid 176 to its reverse position so motors 17 and 18 rotate in opposite directions. When the scrubbing machine is to be turned in direction as indicated by the arrow 177, a switch 178 is contacted by the outer end of the steering arm 27 when the arm reaches its full turn position which will energize the solenoid 176 to move the valve 175 to its reverse position as shown, thus making the machine turn much sharper because of the reverse driving action of the two wheels. Opposite direction reversal is possible by having another switch (not shown) that is engaged by the steering arm 27 when the wheel for steering is turned in the opposite direction. By reversing the flow to the wheel motors l7 and 18, these sharper turns can easily be accomplished. Normally.  
  17 the motors operate from the straight through position of valve 175.  
  in FIGS. 11, 12 and 13, there is a device shown which is used to direct a blast of drying air or gaseous medium onto the surface 35 as shown. In one form, the engine 30 is an internal combustion engine and the drive shaft is connected through an engageable-disengageable (clutched) belt drive shown schematically at 190 to a centrifugal fan 19] which has a pressure outlet 192. This pressure outlet is connected through a pipe 193 to a cross pipe 194. The cross pipe 194 has downwardly extending pipe sections 195 and 196 that are positioned in front of each of the drive wheels 15 of the power unit. The downwardly extending pipes 195 and 196 end in flat broad nozzles 195A and 196A, respec tively, that are positioned closely adjacent surface 35 and immediately ahead of the respective wheel 15 to direct a jet of air down onto the surface and blow any liquid on the surface 35 out of the way, as well as create a surface drying action because of the moving air.  
  At the forward end of the power unit 12, on the steering member, the pipe 192 is connected to a flexible hose 197. A downwardly extending pipe 198 then is attached to the mounting frame for the wheel 16, which steers and of course moves, so that this downwardly extending pipe 198 moves with the wheel. Pipe 198 has a nozzle 198A that is also flattened out slightly and is directed immediately in front of the steering wheel. The steering wheel 16 is thus also provided with a dry path immediately ahead of the wheel, even though it may be turned from its straight ahead position as shown in dotted lines in FIG. 13.  
  As an alternative and/or supplement, a selector can be used for directing heated exhaust gas from the exhaust system of the engine 30 into the pipe 192. This is shown schematically. and it is to be understood that the blower can be disengaged, or left off entirely, and only the exhaust system unit utilized for heated dry air if desired. Likewise, the exhaust system can be left out of the pipe circuit entirely if desired and only the blower 191 utilized.  
  The exhaust pipe 202 of the engine 30 is made so that it normally has an outwardly extending portion 203 that connects to a suitable muffler if desired, or is merely discharged to atmosphere. Between the engine and the outwardly extending end of the exhaust pipe a selector valve assembly illustrated generally at 204 is provided. The selector valve assembly, as shown perhaps best in FIG. 12, has a flapper valve 205 operated by a lever 206 which can pivot about an axis and is movable between two positions. A drying gas pipe 207 is connected to pipe 202 and also to pipe 192. The flapper valve will move between two positions, one wherein it blocks off exhaust pipe 203 and leaves pipe 207 open, and a second position wherein it blocks off pipe 207 and leaves pipe 203 open.  
  When the use of exhaust gas as a drying medium is desired, for example if the heated gas from the exhaust is necessary to provide a dry surface, the belt drive 190 may be disengaged so that the blower is not operating and the blower blades of course will substantially block the outlet to the blower 191. This then will permit the moving of the valve lever 206 to its solid line position wherein the flapper 205 blockes off the pipe 203 and the exhaust gases are forced into the pipe 207 and then through the pipe system 192, 193, 194, 195, I97 and 198. This means that hot air will be blown down onto the surface 35 ahead of the wheels through the nozzles 195A and 196A and 198A if additional air is desired, or a mixing of the air is desired, the belt drive can be engaged and the blower also utilized. This will create some back pressure on the valves of the engine, but the blower pressure 191 will not have to be high because of the open pipe system leading to the nozzles that direct the blasts of air down onto the surface.  
  In the usual instance, either the exhaust air or the blower air will be utilized, but in some instances they can be intermixed.  
  This permits the drying of the surface 35 if it has been previously wetted by being flooded, or if it is wet prior to the scrubbing operation.  
  A feature, of course, is that the scrubber unit, including the spreader pipe for the scrubbing liquid, whether it be detergent solution or water, is trailing the drive and steering wheels of the power unit so that they will normally operate on a dry surface unless the surface 35 has previously been flooded or wetted. With the attach ments of the present invention, namely the nozzles directing air blasts ahead of the drive and steering wheels, the unit can still operate on a dry surface even though it has previously been flooded, and the surface will subsequently be scrubbed to remove any streaks caused by the drying air and the power unit wheels.  
  Referring to FIG. 14, a modification of the present invention is shown wherein the scrubber unit can be made with a debris hopper positioned ahead of the forward brush in relation to the direction of travel. The scrubber unit can be made substantially similar as in the previous form of the invention, and the frame 215 is the same as frame 41 in construction extending transversely with respect to the direction of travel, and the frame mounts brushes 216 and 217 for rotation in direction as indicated by the arrows 218 and 219. [n this instance, however, the unit is moving in direction as indicated by the arrow 220 so that a dirt receptacle or hopper 221 is mounted ahead of the brush 217, which in this case would be the leading brush.  
  The scrubbing unit can either be a trailing unit or a forward pushed unit (which is the form shown) in this instance, and as shown, a mast 222 has a link 223 that is a push link attached to a power drive and steering unit such as unit 12. The push link is pivotally mounted on the power drive and steering unit and lifted and lowered with a cylinder such as cylinder 95. Control links 224 to keep the scrubbing unit in proper position are also included. The hopper 221 is constructed with the dump bottom as described in connection with FIGS. 9 and 8. The bottom and links are numbered as explained in connection with FIGS. 8 and 9. Other types of dumping could be used if desired, or a manually removable receptacle could also be used.  
  The brushes 216 and 217 are driven by hydraulic motors, and mounted with a removable frame member 225 which corresponds to the frame member 44 in the previous forms of the invention. The brush mountings would be the same as before. The brushes would be rotated so that the deflector in this instance 226 would deflect large debris forwardly into the hopper 221, and a vacuum tube 227 would be used for removing any liquid that went into the debris hopper 221.  
  A secondary debris receptacle 230 is removably mounted just behind the rear brush 216 as well, if desired, and as an opeional feature this also would have a vacuum tube 231 connected to a source of vacuum as previously explained to remove any dirty liquid that would get into the debris receptacle. This receptacle 230 can be smaller than the main receptacle which in this instance is positioned ahead of the brushes.  
  A squeegee assembly 232 corresponding to the rear squeegee assembly 70 is also mounted at the rear of the scrubber unit to wipe up any of the excess liquid, and to remove it with a suitable vacuum hose in the usual manner.  
  Thus, it can be seen that the debris receptacle 221 can be positioned ahead of or to the rear of the double brush scrubbing unit, and the baffle 226 can be positioned to give the desired direction of debris throw. Further, the brushes 216 and 217 can be run at different speeds, as can the brushes 46 and 45. This will change the trajectory of the swept material.  
  A scrubbing liquid spreader pipe 233 is mounted on the frame 215 adjacent the leading portions ahead of the forward brush 217 when looked at in relation to the direction of travel, and this liquid spreader pipe will take scrubbing liquid from a scrubbing liquid solution tank on the power unit used and distribute the liquid onto the surface 234 that is being scrubbed.  
  In FIG. IS, a simplified showing of a scrubbing unit illustrated generally at 240 is shown, to show that scrub brushes of different sizes can be used. Here, the frame 241 has a removable debris hopper 242 that is mounted at the trailing end of the scrubbing unit, and suitable means can be used for removing it. As shown, the hopper will lift out of the frame. In this particular instance, the frame 241 mounts a pair of brushes, namely a large diameter brush 243, and a smaller diameter brush 244 about parallel axes for rotation as indicated by the direction of arrows 245 and 246. The brushes are driven with hydraulic motors mounted as previously described, and at the idler end of the brushes they are mounted on removable frame member 247 which corresponds to the removable member previously mentioned. In this instance, a divider guide and baffle 248 is mounted to direct debris into the debris hopper 242, and a portion of the scrubbing liquid will be carried over the forward brush and reused. A squeegee assembly is utilized on the trailing end of the scrubber, and on the sides thereof as shown in previous forms of the invention. In this particular instance, the debris will go over the small brush, and the trajectory from the large brush will help to guide the debris over as will the deflector or guide member 248. The unit can either be a trailing or a push unit if desired, using suitable mounting members which are not shown to the separate power unit 11.  
  These brushes also usually will be rotating at different speeds. The optimum relationship between brush sizes has been found to be :4 which means that a inch diameter brush 243 would use an 8 inch diameter brush 244, and speed ratios is about 2:3 in rpm. is found to be satisfactory. For example, if the brush 243, the larger diameter brush, is traveling at 600 r.p.m., the small diameter brush 244 would traveling at 900 r.p.m. This would make the peripheral speed of the small brush greater than the peripheral speed of the large brush, and this aids in carrying debris over into the hopper. The large brush tends to throw material upwardly and over the small brush.  
  The different diameter brushes can be used in the double brush scrubbing unit, and different brush speeds can also be used. The positioning of the hopper, whether it be ahead ofor trailing the brushes in relation to the direction of movement, is not of critical importance, but in the instance where a small brush and a large brush are used, the small brush should be adjacent the hopper lip, as shown at 250. Here again, the hopper 242 can be removable manually with suitable handles right out of the frame 241 and the frame, of course, is constructed as previously explained. The brushes extend transversely across the frame to get the desired brush width, and the movement of the scrubbing unit can be in either direction. As described, the hopper is trailing. The scrubbing unit will be supported by the power unit I1 and the power unit would hold the spreader pipe for applying a scrubbing liquid.  
  The separate scrubbing unit and power, drive and steering unit are easily made into a front mounted scrubber. The pull link 88 would become a push link and the drag links also could be used in compression. The scrubbing unit could be raised or lowered with a hydraulic cylinder as desired.  
  The present device has the ability to operate on smooth or rough surfaces, as the double brush will clean rough surfaces well.  
  The solenoid valves used for operating the cylinder 164 for automatic positioning of the scrubbing unit operate with suitable power sources such as the vehicle battery. Also, the valves are four-way valves and are shown only schematically with pressure sources shown schematically.  
  The fourway valves have neutral positions that block off the ports to cylinder 164 so other valves can actuate the cylinder 164 in parallel.  
 what is claimed is:  
  l. A scrubbing machine for scrubbing a surface comprising a frame, a pair of surface engaging rotary tools mounted on the frame for rotation about parallel, transversely extending axes, means on the frame for applying a scrubbing liquid to the surface in the path of movement of the rotary tools over the surface, and means mounted on the frame for collecting scrubbing liquid, the last mentioned means including squeegee means along the lateral sides of the frame laterally aligned with said rotary tools, said squeegee means ineluding surface engaging row brushes on each side of the frame adjacent the ends of the rotary tools and aligned with the gaps between the rotary tools, said squeegee means further including a squeegee frame ex tending along one lateral side of the frame, one of the row brushes being mounted on the squeegee frame, and a flexible surface engaging member mounted on the squeegee frame laterally outwardly of said one row brush from the rotary tools and extending fore and aft of the rotary tools.  
  2. The apparatus of claim 1 further characterized in that the rotary tools are rotary brushes, that the one row brush is attached to the squeegee frame to extend inwardly toward the rotary brushes and engage the surface close to the ends of the rotary brushes, and that the flexible members are slanted outwardly with reference to the squeegee frame.  
  3. A scrubbing machine for scrubbing a surface comprising a frame, a pair of surface engaging rotary tools mounted on the frame for rotation about parallel, transversely extending axes, means on the frame for applying a scrubbing liquid to the surface in the path of movement of the rotary tools over the surface, and