Abstract:
Abstract: A fluid levitating caster lifts a heavy load “( 17 )” off a floor “( 18 )” with near friction-less-ness for transport has integrated a load lifting device. This extra rise height “(ER)” lifting feature accommodates moving loads “( 17 )” which have flexible-sagging frames, over uneven floors “( 18 )”, and which have frames that are not parallel to floor “( 18 )”. An inflatable bellows “( 22 )” design of the load lifting device receives its pressurization from fluid levitating caster, and additionally serves as a dampening reservoir to reduce hopping-pressure surges inherent in fluid levitating casters.

Description:
BACKGROUND—FIELD OF THE INVENTION  
       [0001]     This invention “fluid levitating caster integrating load lifting device” applies to the industry concerned with transporting heavy loads from place to place about a floor in an industry where loads levitate upon pressurized fluid casters during transport. More particularly, this invention integrates a fluid levitating caster with a load lifting device to extend fluid caster usefulness to transporting loads with flexible-sagging frames over un-flat floors.  
       BACKGROUND—DESCRIPTION OF PRIOR ART  
       [0002]     In the fluid caster industry of my invention, a load is levitated upon multiple fluid casters attached beneath the load. Fluid casters accomplish the levitation or load lift from fluid pressure confined within a plenum volume beneath the casters. Plenum volume is constrained by the floor upon which the load is moving and the wall of a hollow flexible membrane of the fluid caster.  
         [0003]     Most fluid casters used today utilize membranes of such design shape that the footprint area near floor contact is a circle. With these designs, each caster will then lift or levitate a weight equal to the circular area (in square inches for example) multiplied by the plenum fluid pressure (in pounds per square inch for this example).  
         [0004]     The levitation or rise height of the load is determined by the designed shape of the caster and particularly the caster membrane. Manufacturers try to design casters with the maximum lift possible for reasons which will soon become apparent. Typically, this lift height is about ⅜ inch for smaller casters 8 inches in diameter and increases to about ¾ inch for larger casters 24 inches in diameter.  
         [0005]     This relatively low rise height of ⅜ inch to ¾ inch can be problematic. Several conditions can occur in air bearing transport applications where these low rise heights are insufficient:  
       Difficulty Flexible-Sagging Load  
       [0006]     One example of insufficient caster rise height would be an application where the machine to be moved is large and is flexible. Consider a 6,000 pound machine 10 foot square in size, constructed on a frame fabricated from thin gauge square tubes, normally resting on four legs. If one were to place four air bearings with a rise height of ⅜ inch at four places strategically placed under this machine frame, the casters when inflated will all rise ⅜ inch, but the machine frame may be so compliant (bendable) as to only allow the frame tubing in close proximity above the casters to lift the ⅜ inch. However, the machine frame at locations further away from the casters may not lift at all or very little. One or more machine legs may remain resting on the floor when the casters inflate. If the operator tried to move the machine as described, the dragging leg or legs could damage the machine or floor, or cause enough friction as to not allow the machine to move at all! 
       Difficulty Un-flat Floor  
       [0007]     Another example of insufficient caster rise height would be where the floor is undulated (un-flat) and includes pockets of recessed areas or raised areas that exceed the caster rise heights within an area about the same size as the caster. Visualize another machine again with a very rigid frame resting normally on four legs. Assume four air bearings with a rise height of ⅜ inch are placed strategically under the machine frame. Consider that the floor over which the machine is to be moved has a depression or pocket of size about equal to the caster size and about ½ inch deep. If the operator were to try to move the machine over this depression, one of the casters would lower into the ½ inch depression, the machine over that caster would also lower ½ inch, and one or more machine legs would drag on the floor and cause damage or stop the move!  
       Difficulty Caster Tilting  
       [0008]     A third example of insufficient caster rise height would be combination of the previous two scenarios and involves caster tilting. Conditions of floor flatness and machine frame bending can combine to cause non-parallel-ness between the local floor area (where the caster traverses) and the sagging frame structure to which the caster is attached. If this condition occurs, the caster membrane can be tilted or tipped from one side to the other exceeding the rise height capability of the caster. If this occurs, the membrane can not seal with the floor and the caster will not levitate. It happens, that manufacturers design caster lift heights relative to membrane diameters such that casters must be positioned parallel to the local floor within 2½ degrees for the caster to be able to seal with the floor. This 2½ degree limit can be exceeded by combinations of local machine frame bending and local floor undulation.  
         [0009]     It is an object of my invention to integrate the fluid levitating caster with a high rise load lifting device so that the caster functionality problems described above are solved. This high rise caster integration of my invention can have a machine or load lifting capability of several times the ⅜ and ¾ inch membrane lifting heights described. With my invention, practical machine lifting heights exceeding 3 inches for the caster diameters of 8″ to 24″ are quite practical. With my invention “fluid levitating caster integrating load lifting device”, the common operational problems associated with machine frame flexure/bending, undulating floors, and non parallel caster mounting between the floor and load disappear! 
         [0010]     Numerous inventors have patented various configurations of fluid levitating casters from about the 1960&#39;s and on. However, none of these patents mention the inclusion of a high lift device to add lift beyond the membrane lift height. U.S. Pat. No. 3,756,342 by Burdick, Sep. 15, 1971 shows a very representative fluid caster patent.  FIG. 3  shows a (levitation membrane) diaphragm  15  in contact (or near contact) with a floor  12 . The same view also shows a fluid caster platform  10  raised or levitated off floor  12  by an amount equal to diaphragm  15  lift (as caused by automobile inner tube like air inflation). In this patent (as all others in this industry), it is clear that no structure element exists to raise caster platform  10  an amount exceeding diaphragm  15  lift.  
       Prior Art Method to Achieve High Load Lift  
       [0011]     Prior to my invention, if an air caster operator wanted to lift a load higher than the caster membrane lift height (to compensate for load frame flexure, uneven floors, etc.); they would attach an independent load lifting device between each caster mounting plate and the load frame. A typical example of such a device would be an independent air bag.  
         [0012]     Air bags used are smaller in diameter than the caster and so must operate at a greater fluid pressure to lift the same load as the caster beneath. A typical application might use an 8 inch diameter caster operating at 25 pounds per square inch, and an air bag above the caster of 4 inches in diameter. The air bag would have to operate at 100 pounds per square inch pressure to lift the same load as the caster. The dual pressure requirements increases the system complexity significantly.  
         [0013]     For one thing, each caster/air bag unit must include two supply hoses.  
         [0014]     For another complexity, the air bag can&#39;t just rest on top of the caster. Instead, it must be secured to either the load frame above or the caster frame below. The securing design or method will be complex as it must allow flexible vertical motion between the load and the caster, yet constrain the caster center to the center of the load area above. Additionally, the air bag securing method must not add appreciable collapsed height to the caster as it may no longer fit under the load space.  
         [0015]     As a final complexity, the caster control console with pressure gauges, valves, regulators, quick connects, etc. (needed to operate the caster/air bag system) is nearly double in complexity over that required for my invention. The system operators have to contend with a larger control console to move around and to manipulate. The purchaser of the relatively awkward caster/air bag system will have to pay significantly extra for the transport system over that of my invention.  
       SUMMARY OF THE INVENTION  
     General  
       [0016]     My invention integrates a fluid caster with a load lifting device into a single assembly. This invention results in a unique device that not only efficiently levitates with near-friction-less-ness a heavy load for transporting, but can also lift the load a height off the floor far exceeding the rise height of prior art fluid casters alone. The word “caster” will be used to mean “fluid caster” to simplify hereafter discussions.  
         [0017]     Loads to be levitated for moving usually rest on four legs contacting the floor—legs cumulatively support the load weight. Four casters are usually placed under the load somewhere near the legs, so as they inflate, the load legs lift off the floor for transport on casters. It is advantageous for casters to lift the load above the floor as far as is possible as some flexible loads can have at least one load leg remaining or dragging on the floor even after prior art casters are inflated. Multiple conditions can occur when a load leg is not lifted off the floor when prior art casters inflate: 
        One condition is when the load frame is so compliant as to sag an amount more than the prior art caster rise height.     Another condition is when the local floor area over which a prior art caster is moving includes a concave or convex area (about the same size as the caster area) and of a depth or height exceeding the prior art caster rise height.     Another condition is when prior art casters are mounted between local load attachment areas and local floor traverse areas at a bias angle exceeding that possible by prior art caster rise heights (about 2½ degrees for commercially available prior art casters).        
 
         [0021]     The high rise feature of my invention “fluid levitating caster integrating load lifting device” can transport loads normally experiencing the above problematic conditions.  
         [0022]     A load can have four of my inventions positioned beneath it so as they are pressurized (levitated) the load rises a greater height above the floor then possible with prior art casters. The load lifts all four resting legs off the floor and assumes a position to be transported.  
         [0023]     With my invention, a smaller contribution to the load rise height is the rise of the caster membranes. The larger contribution to the load rise height is the rise of the load lifting device on top of the fluid caster. The load lifting device of my invention pushes upward against the bottom of the load, and so raises the load an additional amount.  
       Bellows Load Lifting Device  
       [0024]     One practical design shape of the load lifting device of my invention is a round pie pan shaped flexible bellows held in place on top of the fluid caster frame plate by a clamping ring sealing the bellows lip so as to form a fluid leak proof bellows type chamber. As the bellows load lifting device inflates, it pushes up on the base of the load, and lifts it an amount that is far greater than possible with caster membrane lift alone. The word “bellows” will be used to mean “bellows load lifting device” to simplify hereafter discussions.  
         [0025]     The bellows designed lifting area should be made only slightly larger than the caster membrane area so that it can operate at the identical pressure of the caster membrane and still lift the same load as the caster. With this design, the bellows does not require a separate hose, controls, or pressure supply. The bellows can simply be inflated via a conduit or pressure port from the caster membrane plenum. A port passageway through the caster frame plate conveying pressure from the caster membrane plenum to the inside of the bellows will insure that the bellows inflates whenever the caster membrane inflates. Note, if the bellows area were smaller than the membrane footprint area, than the load would rise only the amount of caster membrane lift, but not receive the added rise from the bellows; as the bellows could not exert enough force to lift the load.  
         [0026]     Of course, my invention design must include some vertical limit constraining hardware between the bottom load surface and the caster frame plate to keep the load lift operating in the proper range. This vertical constraining hardware must also act as a lateral positioner of the caster frame plate with respect to the load. With proper constraining hardware, my invention will allow the rise height of the load to vary from a rest zero position to a full rise extent possible by the constrained bellows.  
         [0027]     This constraining hardware can simply comprise four shoulder screws thread anchored into the bottom of the load, but slideable with regard to the caster frame plate. The bottom of the load can then move vertically with respect to the caster frame plate if the corresponding caster frame plate holes are larger than the screw shoulder diameters. This shoulder screw design also constrains the caster frame plate laterally to the load, as the shoulder screws are guiding within the caster frame plate holes. With properly selected shoulder screw lengths/diameters and corresponding caster frame plate hole diameters: 
        My invention can allow the load to move up and down freely as it is inflated and uninflated to a maximum design height that is far greater than the prior art caster membrane lifting capability.     My invention can allow the load to tilt an angle far exceeding 2½ degrees with respect to the floor—2½ degrees being the design limit of commercial prior art casters.        
 
       Constraining Hardware—Mounting Plate and Brackets  
       [0030]     Another constraining hardware configuration is to add an additional mounting plate above the caster frame plate so that the bellows is sandwiched between the two plates. Brackets can be securely attached to the new mounting plate, but vertically slideable relative to the caster frame plate to the design limits of the bracket. These brackets can slide along the caster frame plate so the caster frame plate is confined laterally. With properly selected bracket design shape/positioning on the mounting plate: 
        My invention can allow the load to move up and down freely as it is inflated and uninflated to a maximum design height that is far greater than the prior art caster membrane lifting capability.     My invention can allow the load to tilt an angle far exceeding 2½ degrees with respect to the floor.        
 
         [0033]     The bellows was discussed only as one example of many possible load lifting devices that maybe integrated with the caster. A second example would be a pressure fluid bag such as that used by emergency rescue teams. The fluid bag can be mounted between the caster body/frame/plate and the load (or another mounting plate which in turn can attach to the load).  
         [0034]     My invention vertical motion limit and horizontal constraining hardware discussed above as shoulder screws in one example and formed brackets in another example are not the only hardware devices possible. These were discussed to provide two design methods to provide understanding of achieving free vertical motion of the load above the caster to a limit, while preventing lateral motion of the caster body. Many other design hardware methods can accomplish same: including telescoping tubes, pins siding within slots, and flexible webbing straps to name but only three more.  
         [0035]     The important invention objective is to integrate with a prior art fluid caster a practical vertical load lifting device that can lift the load to a far greater height than prior art fluid caster membranes can alone.  
         [0036]     My invention “fluid levitating caster integrating load liffing device” is not appreciably larger in physical size, nor in weight, nor in cost than that of prior art fluid casters alone. Therefore cost and space advantages can be realized over alternative methods required when high load lifting is required over non flat floors, with loads having bendable frames, or when casters are mounted non-parallel to the load.  
         [0037]     The original problem my invention was attempting to solve was to add increased load lift to prior art casters with low cost, and low uninflated thickness so it can be positioned under loads resting only a nominal distance above the floor.  
       Unexpected Angular Operational Benefit  
       [0038]     However during my invention development, two unexpected advantages were realized: First, it was learned the invention became useful in situations where the caster is angled relative to the load (or where the floor slopes are at an angle relative to the load). In these situations, if this angle exceeded about 2½ degrees, prior art casters would not operate/inflate. However, my invention hardware designs between the load and the caster frame plate allow the caster to tilt relative to the load at an angle far exceeding the here-to-fore 2½ degree practical limit. This angular operating feature/benefit of my invention opens to the industry the fluid levitated transport of loads using casters in situations not possible with prior art casters.  
       Unexpected Dampening Benefit  
       [0039]     The second unexpected advantage of my invention is that the bellows chamber in direct pressure communication with the caster levitation chamber provides a most effective vibration or hopping damping correction to the caster. This unstable hopping characteristic of fluid casters is well understood by caster designers, and so, is the solution of adding the largest possible fluid reservoir in pressure communication with the caster levitation chamber. The high lift device of my invention “fluid levitating caster integrating load lifting device” includes just such a bellows chamber reservoir and unexpectedly solves the hopping problem inherent in fluid casters without having to add an external costly, and space consuming reservoir.  
         [0040]     The prior art U.S. Pat. No. 3,756,342 by Burdick, Sep. 15, 1971 identifies this prior art solution to the inherent caster hopping problem. This Burdick U.S. Pat. No. 3,756,342 patent at about line 48 of column 2 of the specification refers to a dampening chamber 32 in pressure connection with the caster annular zone 25 through a damping opening 36. Damping chamber 32 purpose is described as serving to dampen or smooth out surges in air pressure within caster annular zone 25.  
         [0041]     The bellows or similar pressure chambered high rise device of my invention “fluid levitating caster integrating load lifting device” serves the exact same damping function of the Burdick U.S. Pat. No. 3,756,342 damping chamber 32.  
         [0042]     By way of example, my invention is illustrated herein by the accompanying drawings, wherein: 
     
    
     DRAWING FIGURES  
       [0043]     In the drawings, closely related components from different figure assemblies have the same number but different alphabetic suffixes.  
         [0044]      FIG. 1  is a perspective view of a prior art fluid caster  
         [0045]      FIG. 2  shows a fragmentary sectional elevation view of  FIG. 1  taken as suggested by lines  2 - 2  shown placed between a floor and load to be levitated and moved.  
         [0046]      FIG. 3  is a perspective view of a fluid levitating caster integrated with a load lifting device—where lift device vertical motion is constrained by shoulder screws.  
         [0047]      FIG. 4  shows a sectional elevation view taken as suggested by lines  4 - 4  of  FIG. 3  shown placed between floor and load to be levitated and moved—where caster is shown inflated.  
         [0048]      FIG. 5  shows a sectional elevation view of the assembly of  FIG. 4 —where caster is shown uninflated.  
         [0049]      FIG. 6  shows a sectional elevation view of the assembly of  FIG. 4 —where caster is shown inflated and floor is not parallel to the load.  
         [0050]      FIG. 7  shows another embodiment of a fluid levitating caster integrated with a load lifting device—where lift device vertical motion is constrained by slideable brackets.  
         [0051]      FIG. 8  shows a sectional elevation view taken as suggested by lines  8 - 8  of  FIG. 7  shown placed between floor and load to be levitated and moved 
     
    
     REFERENCE NUMERALS IN DRAWINGS  
       [0000]    
       
           11  &amp;  11  a membrane  
           12  &amp;  12   a  caster body  
           13  &amp;  13   a  conduit  
           14  &amp;  14   a  caster plate  
           15  &amp;  15   a  plenum  
           16  mounting plate  
           17  load  
           18  floor  
           19  clamp ring  
           20  ring screw  
           21  bellows port  
           22  bellows  
           23  &amp;  23   a  mounting shoulder screws  
           24  positioning brackets  
           25  bracket screws  
           26  mounting holes  
           27  &amp;  27   a  levitation chamber  
           30  assembly  
           31  invention A  
           32  invention B  
          MR membrane rise height  
          ER extra rise height  
          AR angular tilt  
       
     
       DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0075]     1. Description of a Prior Art Embodiment  
         [0076]     The view of  FIG. 1  shows a prior art fluid caster construction referred to as an assembly  30 . Components of assembly  30  will be referred to as the same numbers with an “a” suffix as components later used in my invention descriptions to help comparative understanding. Assembly  30  includes a caster body  12   a , a levitation membrane  11   a , a mounting caster plate  14   a , and a pressure inlet conduit  13   a . Referring now to the view of  FIG. 2 , assembly  30  is shown resting on the surface of a floor  18 . Positioned above assembly  30  is a load  17  to be levitated and moved. Load  17  is shown fastened to caster plate  14   a  with mounting shoulder screws  23   a . Assembly  30  is shown inflated in that load  17  rises a height above floor  18  an amount referred to as a membrane rise height MR. Levitation is accomplished whenever pressurized fluid is conveyed into conduit  13   a , which pressurizes a sealed levitation chamber  27   a  above membrane  11   a  and within a membrane plenum  15   a . Note the total load  17  lift is only that distance provided by membrane  11   a  inflation—membrane rise height MR.  
         [0077]     2. The Invention A Embodiment With Bellows High Lift And Shoulder Screw Attachment To Load  
         [0078]     The view of  FIG. 3  shows an embodiment of my invention “fluid levitating caster integrating load lifting device” referred to as an invention A  31 . Invention A  31  includes a caster body  12 , a levitation membrane  11 , a mounting caster plate  14 , and a pressure inlet conduit  13 . Referring now to the view of  FIG. 4 , invention A  31  is shown resting on surface of floor  18 . Positioned above invention A  31  is load  17  to be levitated and moved. Load  17  is shown fastened to caster plate  14  with a series of long mounting shoulder screws  23 . Invention A  31  is shown inflated in that caster body  12  rises a height above floor  18  an amount equal to membrane rise height MR. Levitation is accomplished whenever pressurized fluid is conveyed into conduit  13 , which pressurizes a levitation chamber  27  above membrane  11  and within plenum  15 . So far invention A  31  is nearly identical in design and function to prior art caster assembly  30  of  FIG. 1 .  
         [0079]     Mounting plate  16  thickness found to work well to attach with high rise lifting bellows  22  is ¼ inch and made from a stiffer aluminum alloy such as 6061 T6. However, thicker plates should work as well as or better to the limit of fitting under the load space available. However, attached to the top of invention A  31  are additional extra lifting components: These include a pie plate shaped bellows  22 , with a clamp ring  19  and an annular series of ring screws  20 . Ring screws  20  and clamp ring  19  seal bellows  22  with the top surface of caster plate  14  so bellows  22  confines an inflatable chamber within. Included in invention A  31  is a bellows port  21  which conveys pressurized fluid from a caster levitation chamber  27  to bellows  22 . In this manner, whenever caster membrane  11  is pressurized, bellows  22  is also pressurized.  
         [0080]     The area of bellows  22  in contact with load  17  is designed to be slightly larger than the contact area of membrane  11  with floor  18 . This area selection insures that when enough pressure is applied within membrane  11  to levitate load  17 , bellows  22  will also lift load an extra height referred as an extra rise height ER.  
         [0081]     A flexible thin material that has been found to work well for fabricating bellows  22  is polyurethane reinforced with cotton cloth weave. An effective hardness for the polyurethane can be 65 shore A, as it is flexible enough to seal well under clamp ring  19  and ring screws  20 . A good material thickness is 0.05 inches. Bellows  22  lip width to affect a leak proof seal is around ⅝ inch. The molding can be easily performed by most commercial rubber molding houses such as Advanced Urethane Solutions, 3912 Tryon Courthouse Road, Cherryville, N.C. 28021.  
         [0082]     Mounting shoulder screws  23  slip within caster plate  14 , and thread within the bottom of load  17 . In this way, mounting shoulder screws  23  allow bellows  22  to lift load  17  vertically while constraining laterally to extra rise height ER limit as determined by the shoulder length of mounting shoulder screws  23 .  
         [0083]     Shoulder screws  23  used in the first constraining mount configuration are well known fasteners by machinists and machine designers. It has been found that 5/16 inch shoulder diameter provides good strength for lateral caster plate  14  guidance. They can be purchased from catalog sales from McMaster Carr Supply Company of Dayton, N.J. 08810.  
         [0084]     Note the total load  17  lift is the sum of membrane rise height MR plus extra rise height ER. Load  17 , with invention A  31 , can be lifted to far greater heights above floor  18  (easily several times membrane rise height MR of prior art caster assembly  30  of  FIG. 1 ).  
         [0085]     Invention A  31  is shown in  FIG. 5  uninflated. Membrane  11  is collapsed against floor  18  and there is no membrane rise height MR. High lift bellows  22  is collapsed between load  17  and caster plate  14 , with load  17  resting upon clamp ring  19 . Mounting shoulder screws  23  are shown slipped to their fullest extent toward floor  18 .  
         [0086]     Invention A  31  is shown in  FIG. 6  with an angular tilt AR separation shown between load  17  and caster body  12 . The angularity is possible simply by using enlarged holes through caster plate  14  through which slide mounting shoulder screws  23 . Note angular tilt AR magnitude is greater than maximum possible membrane rise height MR With invention A  31 , load  17  can be tilted with respect to local floor  18  area to a far greater amount than is possible with prior art caster assembly  30  of  FIG. 1 .  
         [0087]     3. The invention B Embodiment With Bellows High Lift And Bracket With Mounting Plate Attachment To Load  
         [0088]     The view of  FIG. 7  shows an embodiment of my invention “fluid levitating caster integrating load liffing device” referred to as an invention B  32 . Invention B  32  includes caster body  12 , levitation membrane  11 , caster plate  14 , and pressure inlet conduit  13 . Invention B  32  includes an extra mounting plate  16  above bellows  22 . Mounting plate  16  has attached to its periphery a series of positioning brackets  24  secured with a series of bracket screws  25  rigidly securing positioning brackets  24  and threaded into mounting plate  16 . Positioning brackets  24  are positioned and shaped so that they allow vertical travel between caster plate  14  and mounting plate  16  as bellows  22  lifts and contracts. Yet positioning brackets  24  constrain lateral motion between mounting plate  16  and caster plate  14 . Note further that the design and location of positioning brackets  24  with respect to caster plate  14  will allow angular tilt AR similar to that shown in  FIG. 6 .  
         [0089]     Brackets  24  used in the second constraining mount configuration can be made of a formed steel alloys, with a thickness exceeding about 0.10 inch, and a width exceeding about 1 inch. These approximate minimum sizes provide good lateral caster plate  14  guidance.  
         [0090]     Referring to the view of  FIG. 8 , caster invention B  32  is shown resting on surface of floor  18 . Positioned above invention B  32  attached to mounting plate  16  with screws (not shown) through a series of mounting holes  26  (shown in  FIG. 7 ) is load  17  to be levitated and moved. As with invention A  31  of  FIGS. 3-6 , attached to the top of invention B  32  are the extra lifting components: bellows  22 , clamp ring  19  ring screws  20 . Invention B  32  is shown levitated in that load  17  rises a height above floor  18  an amount equal to membrane rise height MR plus extra rise height ER.  
         [0091]     The embodiments and descriptions above have been by way of illustration, rather than limitation. The scope and content of this invention “fluid levitating caster integrating load lifting device” being determined by the following claims: