the present invention provides an apparatus and methods for cleaning surfaces and particularly for better controlling the high velocity airflow applied to those surfaces to entrain and remove spent cleaning fluid and dislodged debris . the improved results achieved using the apparatus and methods of the present invention are obtained by applying a vacuum only to a relatively small area about the periphery of the housing above the surface being cleaned to entrain and remove cleaning fluid and dislodged debris from the surface . accordingly , a higher velocity is developed across this smaller surface area without increasing the tendency of the slab cleaning device to suck down and become stuck on the surface being cleaned . a slab cleaner 10 in accord with the present invention is illustrated in fig1 - 5 . in general , the slab cleaner 10 of the present invention is similar in appearance to a rotary powered lawnmower . in the preferred embodiment , slab cleaner 10 includes a double - walled housing . within outer housing 12 is disposed inner housing 14 which provides the shield to define the opening for positioning adjacent a hard surface 100 to be cleaned . in the illustrated embodiment , inner housing 14 is generally concentric with but not coextensive with outer housing 12 . inner housing 14 does not extend upwardly to the top centermost portion of outer housing 12 . welded to the upper portion of inner housing 14 are a plurality of bolts 16 extending upwardly for cooperation with holes in outer housing 12 . with bolts 16 extending through the holes in outer housing 12 , nuts 18 are employed to securely fasten inner housing 14 to outer housing 12 . formed between the inner and outer housings is peripheral chamber 20 through which a vacuum may be applied to a small area of hard surface 100 about the periphery of inner housing 14 . slab cleaner 10 includes means for delivering any conventional cleaning fluid at a high velocity against surface 100 in the area to be cleaned under inner housing 14 . in the preferred embodiment illustrated in fig3 the cleaning fluid is delivered through line 30 to a rotary joint 32 bolted to the top of housing 12 . rotary joint 32 passes through housing 12 . disposed on the underside of rotary joint 32 is rotatable hub 34 having fluid passageway 36 therein . connected into a plurality of bores in hub 34 and in fluid communication with passageway 36 are a plurality of distribution arms 38 . arms 38 may be connected to hub 34 by any conventional method , e . g ., arms 38 may be welded or threaded to hub 34 . while a single arm 38 would be sufficient , a plurality of symmetrically disposed arms 38 provide better balance and more uniform and consistent operation . distribution arms 38 are preferably comprised of hollow tubes plugged at the ends thereof distal to hub 34 . alternatively , arms 38 may be comprised of hollow tubing bent to provide the desired direction of fluid flow against the hard surface . disposed near the distal end of each of arms 38 is at least one nozzle 40 for directing the flow of exiting fluid onto hard surface 100 . additional nozzles 40 may be disposed along the length of arms 38 . in the preferred embodiment , the nozzles direct the cleaning fluid against surface 100 at an angle which is neither normal to the surface nor in the plane of rotation of nozzles 40 . by disposing nozzles 40 at an angle so that the exiting fluid does not strike the surface perpendicularly , rotary motion will be imparted to arms 38 and hub 34 by the reactionary force of the exiting fluid . such an arrangement eliminates the need for a motor or other means to rotate fluid distribution arms 38 , and is , therefore , preferred . however , for some applications , it may be desirable to include a separate power source , e . g ., an air or electric motor , to independently rotate arms 38 . when using an independent motor to rotate arms 38 , nozzles 40 may be positioned to direct the exiting fluid perpendicularly against surface 100 . nozzles 40 may be of any conventional type connected to a plurality of bores disposed near the end and , optionally , along the length of arms 38 . alternatively , nozzles 40 may simply be comprised of holes drilled in arms 38 and disposed at the appropriate angle . while the cleaning fluid often merely comprises water , any conventional liquid or gaseous cleaning fluid may be employed . the cleaning fluid may also include an additive that will reduce the cohesive bond between the contaminants and the surface being cleaned . the cleaning fluid may include one or more conventional cleaning agents , e . g ., surfactants , soft abrasives , hard abrasives and mixtures thereof . in fact , the cleaning fluid may also include anti - foaming agents and the like as desired . the cleaning fluid may be drawn from a continuous source , e . g ., a fire hydrant , or a storage tank , e . g ., a conventional tank 94 , in which it is readily prepared and stored . alternatively , the fluid may be recirculated and the dislodged debris removed by conventional filters or other means . the fluid is pumped from the source , e . g ., storage tank 94 , using a high pressure pump 96 capable of developing as much as 60 , 000 psi . in operation , it has been found desirable to deliver the fluid at a pressure between about 1 , 000 psi and about 40 , 000 psi . at these pressures , water used as the cleaning fluid will exit the nozzles at about 400 ft / sec and about 2 , 400 ftusec , respectively . most preferably , the slab cleaner 10 of the present invention is operated with water at a pressure of about 10 , 000 psi . at this pressure , the water exits the nozzles at a velocity of about 1200 ft / sec . however , in some applications where the cleaning fluid comprises air with entrained particulate abrasives , it may be desirable to operate at a pump pressure as low as about 80 psi . those skilled in the art will be able to select an appropriate pump pressure to develop the ext velocity required to dislodge the contaminating materials from the surface . the fluid is delivered from tank 94 to slab cleaner 10 through conventional high pressure lines to cleaning fluid inlet 42 conveniently disposed on handle 50 of slab cleaner 10 . handle 50 is rigidly connected with housing 12 at a pair of diametrically disposed handle mounts 90 . inlet port 42 comprises one port of a three - way connector 44 disposed in handle 50 of slab cleaner 10 . fluid entering handle 50 at connector 44 is directed to nozzles 40 or returned to tank 94 depending upon the position of dump valve 54 . with dump valve 54 in the operating position , fluid entering connector 44 is directed through fluid conduit 46 , comprising a portion of one arm of handle 50 to elbow 48 connected with cleaning fluid line 30 . the presently most preferred embodiment of slab cleaner 10 includes dump valve 54 for diverting the cleaning fluid from hard surface 100 without requiring that pump 96 be shut down . by releasing handle 56 , a less restrictive flow path is created to return cleaning fluid to tank 94 . with dump valve 52 in the standby or dump position , fluid entering connector 44 is diverted through hollow hand grip 52 , dump valve 54 , line 58 and outlet 60 to a hose ( not shown ) for return to tank 94 . because this flow path will be less restrictive than the path through nozzles 40 , most of the fluid entering inlet 42 will be diverted through outlet 60 away from hard surface 100 in the standby position . this convenient feature permits the operator to temporarily halt the cleaning operation without requiring that pump 96 be shut down . spent cleaning fluid and dislodged debris are removed from under slab cleaner 10 by entrainment within a high velocity airflow created by applying a vacuum to peripheral chamber 20 . chamber 20 defines at its lower extremity an annular vacuum port 22 disposed about the periphery of inner housing 14 . annular port 22 has a relatively small cross - section through which fluid and debris are withdrawn . the cross - sectional area of annular opening 22 is substantially less than the area subtended by inner housing 14 . in fact , to provide the best results , the cross - sectional area of opening 22 should be less than about 10 percent , preferably less than about 5 percent , of the area being cleaned as defined by housing 14 . the vacuum applied to chamber 20 draws airflow through port 22 both through the interior of housing 14 and from the exterior of housing 12 as illustrated by the arrows in fig3 and 5 . near the top of chamber 20 are disposed one or more exit ports 24 to which one or more conduits 26 are affixed . attached to conduits 26 are a flexible suction line 28 in fluid communication with a conventional vacuum source 98 for applying a vacuum to chamber 20 . because the vacuum is applied to a smaller chamber and because the cross - sectional area of port 22 is significantly smaller than that subtended by inner housing 14 , high air velocity is developed across hard surface 100 adjacent annular port 22 without fear that slab cleaner 10 will suck down and become temporarily stuck on surface 100 . air velocity at annular port 22 must be sufficient to entrain and remove the spent cleaning fluid and dislodged debris . while air velocity of at least about 75 ft / sec are acceptable for many applications , it is preferred that the velocities be in the range of about 75 - 200 ftusec . most preferably the air velocity at port 22 should be about 125 - 150 ftusec . the high air velocity developed over this smaller surface area also provides improved entrainment and removal of spent cleaning fluid and dislodged debris from under slab cleaner 10 . slab cleaner 10 also includes one or more vent openings 80 through outer housing 12 directly into the cleaning chamber defined by inner housing 14 . vents 80 permit air to enter the cleaning chamber , thus minimizing the chance that the cleaner 10 will suck down on the surface being cleaned . in a simple embodiment , vent openings 80 are unadjustable . in an alternative , vent openings 80 are covered by an appropriate filter ( not shown ). in another alternative , slab cleaner 10 of the present invention may include a vent system to permit more precise adjustment of the airflow through inner housing 14 . this feature is readily seen in slab cleaner 10 illustrated in fig2 - 4 . this feature is most easily understood with reference to fig2 and 4 . a pair of fan - shaped diametrically opposed vent openings 80 are placed through outer housing 12 directly into the cleaning chamber defined by inner housing 14 . carried on the exterior surface of outer housing 12 is rotatable adjustment plate 82 characterized by a pair of similarly fan - shaped slots 84 for cooperation with openings 80 . by simple rotation of plate 82 , slots 84 cooperate with openings 80 to close , open and adjust the size of the air vent through housing 12 . rotatable plate 82 is disposed below tabs 86 which carry adjustment and locking screws 88 . when plate 82 has been adjusted to provide the desired vent opening , it may be fixed in place by tightening of screws 88 to frictionally lock it in place . a flexible skirt 70 is subtended from the lower side of exterior housing 12 to assist in retaining under slab cleaner 10 the cleaning fluid expelled from nozzles 40 and dislodged debris and to reduce the intake of air from outside the housing . flexible skirt 70 generally extends from the lower side of housing 12 to a plane defined by the lower surface of wheels 62 and 72 in order to be substantially in contact with hard surface 100 . however , skirt 70 need not form a seal with hard surface 100 but should be flexible to generally conform therewith in order to reduce the intake of air from outside of housing 12 and to contain the fluid and debris within housing 12 . those skilled in the art will be aware of convenient methods for maintaining slab cleaner 10 at a substantially fixed distance above surface 100 and providing means for moving slab cleaner 10 across that surface . the simplest means and the one illustrated in the preferred embodiment employs a plurality of wheels disposed on appropriate supports . in the illustrated embodiment , two large rear wheels 62 are disposed at opposite ends of axle 64 carried through a pair of rear axle mounts 66 projecting rearwardly from outer housing 12 . fig1 also illustrates handle support strut 68 extending upwardly from the axle mounts 66 . disposed at the front of slab cleaner 10 are one or more front wheels . in the illustrated embodiment , a pair of front wheels 72 are caster mounted from swivel yokes 74 connected to front wheel mounting platforms 76 braced with supporting struts 78 . swivel mounted front wheels 72 permit slab cleaner 10 to be both easily steered and sharply turned . the foregoing description of the invention has been directed in primary part to a particular preferred embodiment in accordance with the requirements of the patent statutes and for purposes of explanation and illustration . it will be apparent , however , to those skilled in the art that many modifications and changes in the specifically described apparatus and methods may be made without departing from the true scope and spirit of the invention . for example , while the manifold , hub , arm and nozzle assembly described provides the preferred means for directing cleaning fluid to the surface to be cleaned , any conventional arrangement which accomplishes this goal may be used . while it is presently preferred to employ the previously described system where the force of the exiting fluid provides the means for rotating the hub , there may be circumstances where it will be desirable to employ a motor to drive the hub , or even to employ a plurality of fixed nozzles in some applications . therefore , the invention is not restricted to the preferred embodiment described and illustrated but covers all modifications which may fall within the scope of the following claims .
the present invention is directed to methods and apparatus for cleaning industrial and commercial operations hard surfaces , e . g ., concrete and asphalt slabs , walls , tanks , grates , and ship hulls , contaminated by oil and chemical spills or barnacles . the methods and apparatus of the present invention produce a high velocity airflow about only the periphery of the area being cleaned by the device to provide improved entrainment and removal of cleaning fluid and dislodged debris . high velocity streams of cleaning fluid are directed against the surface from nozzles disposed on rotating arms of a hub suspended within the portable housing of the slab cleaner . the spent cleaning fluid and dislodged debris are removed by the application of a vacuum to a chamber extending about the periphery of the housing to create the high velocity airflow . thus , high velocity airflow is developed without fear that the slab cleaner will be sucked down and become temporarily stuck on the surface being cleaned . control of the airflow through the central housing also may be achieved through adjustment of an air vent therein , together with the action of a flexible skirt or seal about the exterior of the peripheral chamber .