Abstract:
An invention ( 58 ) for attachment to a near frictionless fluid levitated transporter includes a guide wheel ( 18 ) integrated with a ground rubbing brake ( 20 ). Invention ( 58 ) both guides and stops transporter movement.

Description:
BACKGROUND-FIELD OF INVENTION 
     This invention applies to the industry concerned with guidance and propulsion of heavy loads from place to place about a floor. This is a fluid bearing industry where loads levitate upon a near frictionless pressurized fluid plenum during transport. More particularly, this invention relates to the integration of a guide wheel function with the ground rubbing brake function within one assembly. Prior inventions include guide wheels that have connected a braking function that does not include ground contact. Examples of prior art include a wheel with disc brakes and a wheel with shoe brakes. A specific example of a similar guide wheel with a non ground contacting braking function used in the fluid levitated load industry includes that disclosed in U.S. Pat. No. 4,427,086 by Coiselet Jan. 24, 1984. 
     The wheel with integrated brake assembly of my invention includes a braking pad that does rub on the ground to slow the levitated load. 
     BACKGROUND-DESCRIPTION OF PRIOR ART 
     Since loads levitate upon a nearly frictionless fluid cushion, it takes surprisingly low forces to move load. On level floors, relatively smaller loads move by a human operator pushing or pulling on load. Heavier loads often move with a motorized transporter. A problem is not so much in getting load to move, but to stop its inertia safely once it gets moving, especially down a slight grade. Prior art inventions have solved the stopping problem by attaching a ground rubbing brake assembly to the bottom of the load. Representative prior art ground rubbing brake invention includes that disclosed in U.S. Pat. No. 3,752,331 by Colburn Aug. 14, 1973. 
     Sometimes it is most difficult to guide load in the direction of motion desired by the operator. Even the slightest uneven floor condition and cause the load to drift laterally. Prior art inventions have solved the guiding problem by attaching a guide wheel assembly under the load. Both the brake assembly and the guide wheel assembly are expensive. Both assemblies take significant effort to attach to load and to plumb to the pressurized fluid supply. Both assemblies together are difficult to attach to load. Usually there is minimal available space under load that is unoccupied either by the fluid bearing devices or by some other load structure feature. It is often difficult enough to find the space to attach either a brake assembly or a guide wheel assembly, without having to find space to attach both assemblies. 
     Some inventions in this industry disclose a guide wheel that is brakeable with conventional type structures such as disc brake or shoe brake. The fluid bearing industry rarely uses these structures. One reason for their limited use is that fluid bearings levitating the load are relatively thin. The bearing&#39;s thickness is approximately two and one half inches. This same thickness usually dictates the distance from the floor to the bottom of load. The wheel with conventional brake shoe or disc would be most difficult and expensive to manufacture with a two and one half inch overall thickness. The solution is not practical to place the wheel outbound of the load. The load area footprint is usually quite large, and adding inches would make transport around doorways and aisles unduly difficult. An example of an outbound wheel disclosed invention is U.S. Pat. No. 3,586,118 by Bertin Jun. 22, 1971. Finally, the wheel with disc brake to be effective has be quite robust in design. The wheel assembly is very thick and made of heavy components. This is necessary to absorb the energies involved in stopping the inertia of say a typical moving 15,000 pound load. Such wheel and brake combinations would be very expensive and large and would appear similar to those used on an automobile. Typical brakes used in the fluid caster industry use a pressure actuated ground rubbing pad for purposes of thin profile to fit beneath load and for low manufacturing cost. 
     My invention has the object of integrating the rubbing brake function with the guide wheel function within one assembly while maintaining the thinness necessary to fit beneath the load. Additional unexpected advantages resulted: The cost of the integrated assembly is much less than the cost of the separate assemblies. The attachment footprint of the integrated assembly is much less than the footprint of the separate assemblies. Plumbing the integrated assembly to a pressurized fluid supply is easier. Attachment of the integrated assembly to the load is easier. The weight of the integrated assembly is less. 
     SUMMARY OF THE INVENTION 
     My invention integrates a ground rubbing brake assembly with a guide wheel assembly. The combined assembly results in a unique device that both stops a moving load levitated with fluid cushions and guides the load in a direction desired by the operator. The integrated brake and wheel assembly retains the thinness necessary to fit beneath load. 
     Many unexpected advantages result from the combination invention. My invention is about half size of the prior art brake assembly, plus guide wheel assembly. My invention is about half the weight of the prior art brake assembly, plus guide wheel assembly. My invention has almost half the parts of the prior art brake assembly, plus guide wheel assembly. My invention is much lower in cost than the prior art brake assembly, plus guide wheel assembly. My invention requires one less hose to interconnect to the pressure supply. For about the same price of either a brake assembly alone or a guide wheel assembly alone, a user can purchase my invention with both functions. Setup of my invention is easier as it has one less hose to connect. My invention requires about half the size footprint area under the load. My invention requires about half the holes and bolt connections of the brake assembly, plus guide wheel assembly. 
    
    
     By way of example, my invention is illustrated herein by the accompanying drawing, wherein: 
     DRAWING FIGURES 
     FIG. 1 is perspective view of a guide wheel integrated with ground rubbing brake shown interconnected a load levitated upon fluid casters including symbolically represented fluid controls. 
     FIG. 2 is a perspective exploded view of the preferred cylinder and piston actuated embodiment of guide integrated with ground rubbing brake showing construction details. 
     FIG. 3 is a perspective view of an alternative air bag actuated embodiment of guide wheel integrated with ground rubbing brake. 
     FIG. 4 is a bottom plan view with a partial broken away section of a similar guide wheel integrated with ground rubbing brake assembly of FIG. 2 including a power motor castering steering feature. 
     FIG. 5 is a plan elevation view of the assembly of FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     1. The Invention in General 
     My invention ‘guide wheel integrated with ground rubbing brake’ is shown in the view of FIG.  1  and is referred to as numeral  58 . Invention  58  is shown attached to a heavy load  60  that is to be moved upon a load base  54  structure. Load base  54  levitates off a floor on fluid plenums created under floatation caster  56  devices. Compressed fluid pressurizes the plenum areas of casters  56 , as is well known in this art. My invention  58  can bolt to the bottom of load base  54  via bolts extending through mounting holes  42 . 
     The view of FIG. 1 shows at the underside of invention  58  a brake  20  and a wheel  18 . Invention  58  has affixed a tube  36  that conveys pressurized fluid during actuation of either the brake function or the guide wheel function. 
     2. Pressurized Modes of Operation 
     Invention  58  has three pressurized modes of operation. Operator uses a depressurized mode when they desire to use neither the brake nor the guide wheel functions. This mode is useful when load base  54  rests without levitation or is being steered to a new direction. Operator chooses the two remaining pressurized modes as they manipulate a wheel valve  50  or a brake valve  52 . Details of these modes are presented next. 
     3. Fluid Controls 
     Fluid controls of FIG. 1 are not part of invention  58 . However, a description of their functioning could help in understanding invention  58  operation. A facility pressurized fluid supply  44  plumbs to a wheel regulator  48  and to a brake regulator  46 . Regulator  48  adjusts to a pressure corresponding to downward force desirable on wheel  18 . Regulator  46  adjusts to a pressure corresponding to desirable downward force on brake  20 . Practical operation dictates that wheel regulator  48  pressure always be set less than the pressure of brake regulator  46  as will become apparent later. The output fluid pressures from wheel regulator  48  and from brake regulator  46  plumb to wheel valve  50  and brake valve  52  respectively. A check valve  64  plumbs to exit port of valve  50 . Check valve  64  prevents higher brake regulator  46  pressure from ever bleeding off through the self relieving feature of regulator  48 . The fluid exiting valves  64  and  52  plumb together and connect with a flexible hose to tube  36 . When wheel valve  50  opens, a low pressure preset by regulator  48  conveys to invention  58 , and wheel  18  forces against the floor guiding load base  54 . When brake valve  52  opens, a high pressure preset by regulator  46  conveys to invention  58 , and brake  20  forces to the floor stopping load base  54 . 
     4. Invention Construction Detail 
     The view of FIG. 2 shows detail about invention  58  operation. A hollow piston  10  slides axially within a cylinder  12 . A seal  16  such as an o-ring affixed in a gland at the end of piston  10  contains pressurized fluid within cylinder  12  cavity. Multiple dog point set screws  29  thread through one end of cylinder  12 , and slide within corresponding piston  10  wall slots  28  extending only partially through piston  10  wall. Multiple slot  28  and screw  29  combinations around the periphery prevents piston  10  from rotating, as is important in keeping drive wheel  18  always point in in one direction. Additionally, slot  28  and screw  29  combinations limit piston  10  travel so seal  16  never contacts set screws  29 . A disc shaped flange  14  attaches without leakage to cylinder  12  defining a contained cavity for pressurizing fluid. Flange  14  includes perforating mounting holes  42  for bolting attachment to load base  54  of FIG.  1 . 
     Flange  14  includes a radial fluid passage  38  within its thickness extending from the periphery of flange  14  to the center point. At this center point, a corresponding aperture  40  conveys one end of passage  38  with cylinder  12  pressurized cavity. The outer end of passage  38  has attached without leakage tube  36 . Pressurized fluid front either valve  64  or  52 , shown in FIG. 1 view, plumb to tube  36 , through passage  38 , though aperture  40 , and into cylinder  12  cavity forcing against piston  10  surface. One end of piston  10  joins without leakage to a flat plate  62 . Plate  62  seals piston  10 , and serves as a mounting base for welding brackets  22 . Brackets  22  have slots near one end to slideable accept a shaft  24 . Shaft  24  is able to move in the same direction as piston  10  travel within the slots of brackets  22 . Shaft  24  serves as the axle for guide wheel  18 . Wheel  18  is free to revolve on shaft  24 . Wheel  18  includes a center bore with appropriate annular clearance for rotation. Wheel  18  can be made from a medium hardness polyurethane material. Polyurethane assures judicious combination of floor traction, appropriate stiffness to stand downward forces, abrasion durability, with zero to limited need for lubrication at its shaft  24  interface. Under shaft  24 , and adjacent to brackets  22  nest preloaded compressive springs  26  of the flexible rubber pad type. Springs  26  keep a nearly constant force applied to shaft  24 . Springs  26  normally force shaft  24  to the limit of slot travel within brackets  22 . Spring  26  force magnitude is that necessary to accommodate traction of wheel  18  against the floor, and is in the order of one or two hundred pounds. Springs  26  are made from a medium hardness latex rubber thus assuring appropriate compliance and strength without age setting. An annular disc shaped flange  30  attaches with welding to the other end of piston  10 . Attached to flange  30  is similar shaped brake  20 . Brake  20  is made from medium to hard polyurethane material so as to possess appropriate friction properties and durability. Brake  20  rigidly attaches to flange  30  with bolts. The surface of brake  20  offsets from cylindrical wheel  18  outer most surface that is to touch the floor. In this way, wheel  18  can guide load base  54  while brake  20  is off the floor. However, if piston  10  applies enough force, floor reaction force against wheel  18  will push shaft  24  against springs  26  and along bracket  22  slots retracting wheel  18  within piston  10 . When wheel  18  retracts, brake  20  will push onto the floor and stop load base  54 . When there is no pressurization, the subassembly  116  including piston  10  retracts within cylinder  12 . Several, one only shown, extension springs  32  perform the retractive force. Springs  32  are secure to flanges  14  and  30  using anchors  31 . Each anchor  31  joins to flanges  14  and  30  with bolts  34 . In this manner, guide wheel  18  will not touch the floor until cylinder  12  cavity pressurizes. 
     Referring to FIG. 2, preferred materials for cylinder  12 , piston  10 , flanges  14  and  30 , brackets  22 , plate  62 , and tube  36  are strong rigid materials such as metal, plastic, composite fiber, and the like. Shaft  24  is made from stainless steel pre-ground rod stock. Standard welding, casting, brazing, silver soldering, adhesives, and bolts can join permanently attached parts. 
     5. Alternate Embodiment with Air Bag Actuator 
     The view of FIG. 3 shows an alternative embodiment of ‘guide wheel integrated with ground rubbing brake’ referred to as assembly  58   a . As shown, a flat upper plate  72  attaches pivotally to a subassembly that includes arms  82 . Assembly  58   a  forms a hinged clamshell type arrangement. A shaft serves as a pivot  80 . Upper plate  72  includes mounting holes  70  for bolt attachment to load base  54  of FIG.  1 . Positioned between upper plate  72  subassembly and arm  82  subassembly is an air bag  66 . When air bag  66  pressurizes, it forces plate  72  to separate radially from arm  82  subassembly about pivot  80 . A spring  94  connects between arm  82  subassembly and plate  72  to close the clamshell whenever pressure vacates air bag  66 . In this manner, guide wheel  92  will not touch the floor until air bag  66  pressurizes. 
     Plate  72  includes a radial fluid passage  74  within its thickness extending from one edge to the center point of air bag  66 . At this center point, a corresponding aperture  78  conveys one end of passage  74  to a bag  66  interior. The outer end of passage  74  has attached without leakage a tube  76 . A gasket, not shown, sandwiches between air bag  66  and plate  72 . As shown in the view of FIG. 1, pressurized fluid from valves  64  or  52  convey to tube  36 . Fluid then flows, as shown in FIG. 3, through passage  74 , through aperture  78 , and into air bag  66 . Pressurized air bag  66  forces arm  82  subassembly down away from plate  72 , and toward the floor. Arms  82  include slots  84  near one end to slideable accept a shaft  88 . Thus shaft  88  is able to move in the direction of the arrow shown in the view of FIG.  3 . Shaft  88  is the axle for a guide wheel  92 . Wheel  92  is free to revolve on shaft  88 . Wheel  92  includes a center bore with appropriate annular clearance for rotation. Under shaft  88 , and adjacent to arms  82  nest preloaded compressive springs  90 . Springs  90  are flexible rubber pad type. Springs  90  keep a nearly constant force applied to shaft  88 , and forces shaft  88  to the limit of slot  84  travel. Spring  90  force magnitude is that necessary to supply traction of wheel  92  with the floor. A brake pad  89  fastens to arm  82  subassembly in such a position that brake  89  is above the floor, about a minimum of 0.1 inch, when guide wheel  92  touches the floor. With this arrangement, wheel  92  can guide load base  54  while brake  89  is off the floor. However, if arm  82  subassembly forces further radially, by air bag  66 , wheel  92  retracts within its slots  84 , and brake  89  forces against the floor, stopping load base  54 . Brake  89  is made from medium to hard polyurethane so as to have appropriate friction properties and durability. Brake  89  attaches to arm  82  subassembly using adhesives or bolts. 
     6. Alternate Embodiment—Including Power Steering 
     A bottom planar view of an alternative powered embodiment of my invention, referred to as assembly  46   a , is shown in FIG. 4 view. This embodiment adds to invention  58  of FIGS. 1 and 2, a gear motor  106  power feature that can rotate a center subassembly that includes guide wheel  69  and brake  70 . Gear motor  106  is a reversible miniature air motor and gearbox type as described in the industrial catalog McMaster Carr of Los Angeles. A mounting plate  14   a  is similar to flange  14  described in FIG. 2 above with two more radial fluid passages  94  added. Passages  94  are similar to previously described passage  22 . The length of both of these passages  94  are chosen so as to end in perpendicular attached leakproof tubes  114  shown best in side plan view of assembly  46   a  of FIG.  5 . The opposite ends of passages  94  have fixed two more tubes  96 . Two flexible air hoses  108  complete the plumbing of tubes  96  to gear motor  106 . Pressurized fluid entering one of tubes  96  will drive gear motor  106  in one direction. Fluid entering other tube  96  will reverse gear motor  106  rotation. The view of FIG. 4 shows brake  70  surface partially broken away near gear motor  106  to reveal a large annular shaped worm ring gear  98 . Ring gear  98  rigidly attaches to the bottom of brake  70  via a bolt attached cylinder. Ring gear  98  moves vertically with brake  70  stroke during movement of assembly  46   a . Ring gear  98  is made from a brass component selected from commercial Boston Gear catalog. Ring gear  98  has its center bore enlarged to match assembly  46   a  outside diameter. A gear motor mounting block  100  positions gear motor  106  in a positive radial and central position with respect to ring gear  98 . Shaft of gear motor  106  has attached a mating worm gear  102 . Worm gear  102  is made from a steel material component also selected from the Boston Gear catalog. As gear motor  106  shaft rotates, ring gear  98  also rotates with respect to mounting plate  14   a . Since ring gear  98  moves vertically with assembly  46   a  stroke, mounting block  100  attaches slidably, in the vertical direction, to plate  14   a  via long pins  104 . The ends of pins  104  near brake  70  include heads that limit brake  70 , ring gear  98 , and mounting block  100  travel. Pins  104  are made from ground steel and are attached to plate  14   a  with threads or roll pins, not shown in the view. Block  100  includes a slot a few one thousands of an inch thicker than ring gear  98 . Ring gear  98  slides in the slot during rotation. When ring gear  98  moves vertically, mounting block  100  and attached gear motor  106  move with it. The mounting block  100 , ring gear  98 , and gear motor  106  all return to their inactivated position via brake retraction spring  112 . Block  100  is made from delrin material so as to resist friction, wear, and include strength characteristics necessary while contacting pins  104  and ring gear  98 . 
     When a human operator desires to alter load base  54  direction, they apply pressurized fluid to one of tubes  96 . Simple valves, not shown, but similar to the valves of the fluid controls previously described, work well for this purpose. This action causes gear motor  106  to rotate ring gear  98 . Ring gear  98  rotation causes rotation of central subassembly. Since guide wheel  69  is part of the subassembly, it rotates also. With this embodiment, an invention  46   a  can power steer in infinite directions. Once operator sets desired guide wheel  69  direction, worm gear  102  automatically locks in that position. Worm gear  102  inherent mating characteristics with ring gear  98  refuses to allow unpowered rotation. 
     Gear motor  106  would not necessarily have to be fluid powered, and another embodiment could substitute an electric motor for example. 
     7. Alternate Embodiments—Additional 
     The particular invention shown in the view of FIG. 2 is not the only structure or shape that can include the motor powered rotation feature. For example, the air bag actuated embodiment of 
     FIG. 3 can be easily adapted for steering with similar worm gears and gear motor drive. For purposes of exemplification, particular embodiments of the invention have been shown and described to the best understanding thereof. However, other embodiments can include other guide wheel integrated with ground rubbing brake assemblies, irrespective of their particular structure, materials, fluidic plumbing, without departing from the spirit and scope of the claimed invention. 
     The embodiments and descriptions above have been by way of illustration, rather than limitation. The scope and content of this invention being determined by the following claims.