Abstract:
An assembly “( 42 )” including a fluid levitated caster and a debris scraper “( 31 )” device positioned external to a levitation membrane “( 11 )”. Assembly “( 42 )” levitates heavy loads upon a near frictionless pressurized fluid, and also sweeps aside potentially membrane destructive debris “( 25 )” from a floor “( 27 )” in the path of movement. The external debris scraper “( 31 )” function does not noticeably increase movement friction, and does not require increased power air flow or consumption.

Description:
BACKGROUND 
     1. Field of the Invention 
     This invention applies to the industry concerned with guidance and propulsion of heavy loads from place to place about a floor in an industry where loads levitate upon a pressurized fluid caster during transport. More particularly, this invention integrates a fluid levitated caster with an external debris scraper. 
     2. Description of Prior Art 
     In the fluid caster industry of my invention, a load levitates near frictionless upon multiple fluid casters attached beneath the load. It often takes surprisingly low forces to move the levitated load. On flat floors, relatively smaller loads move by an operator pushing or pulling the load by hand. The low force required to move the levitated load is a major advantage for utilizing fluid caster methodology to move heavy loads. 
     Fluid caster movement upon floors covered with debris such as nails, sand, screws, nuts, metal chips can be problematic. While inflated, the fluid caster levitation membrane is in near physical contact with the floor surface (usually a couple of thousands of an inch above the floor surface). A debris object squeezed between the floor surface and the levitation membrane surface (if large enough) can cause sufficient air leakage out of the membrane to cause enough friction between the membrane floor to halt movement. Additionally, if the debris particle is large and sharp, it can cut through the levitation membrane rendering it useless. For these reasons, operators of fluid levitated casters take came to carefully sweep the floor clean of debris before use. Sometimes debris particles can be overlooked. It is advantageous for the fluid levitated caster to be able to sweep aside floor debris, keeping it away from the levitation membrane. It is an object of my invention to integrate the fluid levitated caster with an external debris scraper. 
     Numerous inventors have patented various configurations of fluid levitated casters from about the 1960&#39;s and on. However, none of these patents mention the inclusion of a scraper ring which sweeps aside potentially caster damaging floor surface debris. U.S. Pat. No. 3390736 by Thomas, Jun. 28, 1966 shows a very representative fluid caster patent. This levitation caster shows a levitation membrane  22  in contact (or near contact) with the floor surface  30 . Note there exists controlled air (fluid) leakage flowing between the levitation membrane  22  and the floor surface  30  creating near-frictionless load transport. The same view also shows the fluid caster frame  34  raised or levitated off floor surface  30  by an amount equal to the levitation membrane  22  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 sweep away any debris from the floor surface  30 . It is also clear from this patent, that any debris on the floor surface  30  could end up under the floor contact portion of the levitation membrane  22  as the fluid caster translates or moves laterally. Such floor debris as sharp metal chips can cut through levitation membranes rendering them useless. Larger floor debris such as screws, nuts, and the like can produce a gap between the flexible levitation membrane  22  and floor surface  30  causing lubrication fluid to escape, creating friction between floor surface  30  and levitation membrane  22 , therefore halting load movement. 
     A cited unpatented fluid levitated caster product is marketed which includes an internal debris scraper ring. The product utilizes the scraper ring both as a debris sweeper and as the levitation membrane. The scraper ring sweeps aside debris objects well, but is not very effective as a levitation membrane. For effective and practical levitation, the levitation membrane should be very compliant to conform to floor imperfections such as pits, cracks, flatness undulations etc. Lack of compliance of the levitation membrane results in poor air sealing with the local floor surface. Poor air sealing can lose the advantage of near frictionless movement force. It&#39;s use is like moving levitated loads across the floor with “brakes on”! Even more importantly, the poor air sealing between the floor and the scraper ring necessitates larger air flows and consumption in order that the load stay levitated. With identical air supply flow rates and levitated loads, this fluid caster with internal scraper ring as compared to typical fluid casters without a scraper ring requires a near perfect floor to perform similarly. With real life floor conditions and imperfections, fluid casters without scraper ring can move loads with far less friction, and with far less air consumption. 
     My invention has the advantage over conventional fluid casters in that it includes an external scraper to sweep aside floor debris so it won&#39;t cut levitation membrane or cause friction between levitation membrane and floor surface. My invention has the advantage over the above cited fluid caster with internal scraper ring in that it retains the near-frictionless fluid caster advantage, and requires far less air consumption and flow rate. 
     SUMMARY OF THE INVENTION 
     My invention integrates a fluid caster with an external scraper ring into a single assembly. This invention results in a unique device that not only efficiently levitates with near-frictionless a heavy load for transporting, but can also sweep aside floor debris such as nails, sand, screws, nuts, metal chips. This added function prevents debris from causing friction between floor surface and levitation membrane or from cutting the levitation membrane. The scraper ring is external to the levitation membrane, thereby being able to sweep away debris before the debris reaches the levitation membrane area The external scraper ring can be slideably attached to the fluid caster subassembly frame so the scraper ring can move vertically in unison with the levitation membrane vertical lift movement. A separation force between the fluid caster subassembly frame and the scraper ring can insure that the scraper ring is always in forced floor contact sweeping away debris. This downward force on scraper ring can be created in many ways including: gravity pull on heavy weight, spring, fluid pressure/air bag, fluid pressure/piston and cylinder, etc. 
     The scraper ring design can also assume many embodiments including, but not limited to: ring with brush fibers attached, ring with flexible strip attached, ring with replaceable wear surface attached, ring scrape surface shaped in one of many advantageous configurations conforming to particular floor debris conditions, ring material constructed of one of many materials conforming to particular floor/debris conditions, ring with motorized sweeping rotation, and ring made from several ring segments. 
     Operators of prior art fluid caster transport systems typically inspect and sweep every square inch of the floor surface over which the load is to be moved to insure all debris is removed. Operators using the fluid casters of my invention need not be concerned that typical unremoved debris will cut through the levitation membrane. 
     My invention is not appreciably larger in physical size, in weight, nor in cost than that of prior art fluid casters alone. Therefore cost advantages can be realized considering minimizing or eliminating operator floor sweeping and floor inspection labor costs. 
     An unexpected advantage of my invention is that operator oversight of not finding or not cleaning some floor debris does not result in levitation cut failure. 
    
    
     By way of example, my invention is illustrated herein by the accompanying drawing, wherein: 
     DRAWING FIGURES 
     FIG. 1 is a perspective view of a fluid caster integrated with external scraper ring beneath a levitated load shown sweeping debris across a floor. 
     FIG. 2 is a perspective exploded view of fluid caster integrated with external scraper ring showing more detail. 
     FIG. 3 shows a fragmentary sectional elevation view taken as suggested by lines  3 — 3  of FIG. 2 shown sweeping debris across a floor. 
     FIG. 4 shows a fragmentary sectional elevation view taken as suggested by lines  4 — 4  of FIG. 2 with more detail shown of the scraper ring cross section. 
     FIG. 5 shows a scraper brush alternative embodiment of the scraper ring of FIG.  4 . 
     FIG. 6 shows a replaceable base alternative embodiment of the scraper ring of FIG.  4 . 
     FIG. 7 shows a flexible strip alternative embodiment of the scraper ring of FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     1. The Invention Embodiment in General with Preferred Scraper Ring Configuration 
     The view of FIG. 1 shows my invention “fluid levitated caster integrating external debris scraper” referred to as assembly  42 . Assembly  42  is shown positioned beneath a heavy load  29  that is to be moved across a floor  27 . Shown on floor  27  is debris  25 . Assembly  42  includes a frame  35 , a levitation membrane  11 , and a scraper ring  31 . Frame  35  has on it&#39;s periphery a series of tapped holes  15  shown in the view of FIG.  2 . Returning to the view of FIG. 1, scraper ring  31  includes through it&#39;s wall a series of slots  21 , the quantity and position of which matches tapped holes  15 . A series of attachment screws  17  position within slots  21  and secure into tapped holes  15 . Via this preferred design configuration, scraper ring  31  is free to move vertically within the limits of slot  21  and attachment screw  17  travel. Vertical scraper ring  31  travel is necessary as levitation membrane  11  inflates, deflates, and moves vertically during normal operation. One of a series of spring holes  44  placed into the top surface of scraper ring  31  is shown in the view of FIG.  2 . FIG. 1 shows a spring  13  inserted within each spring hole  44 . Springs  13  insure that scraper ring  31  is in continual force contact with floor  27  as frame  35  moves vertically with respect to floor  27 . 
     2. Invention Construction Detail 
     More details of invention  42  operation and construction show in the view of FIG.  3 . As shown in the view of FIG. 3, frame  35  is lifted off floor  27  a distance equal to the inflatable lift of levitation membrane  11 . As levitation membrane  11  deflates, frame  35  lowers so that it&#39;s bottom most surface eventually touches floor  27 . This vertical travel range is slightly exceeded by the range of travel of attachment screws  17  within slots  21 . Springs  13  are positioned between frame  35  and scraper ring  31 . This combination of scraper ring  31  vertical travel and spring  13  downward force insures that scraper ring is always in contact with floor  27  as assembly  42  is moved laterally during transport. As assembly  42  in general and scraper ring  31  in particular move across floor  27 , debris  25  in it&#39;s path is swept aside as is portrayed in the view of FIG.  3 . Scraper ring  31  inside diameter is slightly larger than frame  35  outside diameter so that there exists a gap between the two components. This gap allows scraper ring  31  to be able to bias slightly or position with a slightly different plane than the plane of frame  35 . Such biasing is important for example as scraper ring  31  lifts over a transition sheet metal plate laid on floor  27  while levitation membrane  11  has yet to reach the plate. A reasonable gap magnitude for medium sized assembly  42  is about {fraction (1/16)} inch. Attachment screw  17  is preferably of the common shoulder screw hardware variety so there is a gap between attachment screw  17  head and the outside surface of scraper ring  31 . This attachment screw  17  gap is comparable to the former mentioned gap between frame  35  and scraper ring  31 . 
     One preferred cross sectional shape of scraper ring  31  is shown in the view of FIG.  4 . Scraper ring  31  is made of a single piece of homogeneous material including a bottom surface taper and a radiused leading edge. Scraper ring  31  width can be about ⅜ inch minimum to allow for spring hole  44  bore and to retain necessary operating strength. Total spring  13  forces against scraper ring  31  depends on the floor conditions, debris encountered, and size of assembly  42 ; but 24 pounds of force is a practical value. Scraper ring  31  primary construction material could be any strong rigid material such as aluminum, steel, plastics (including PVC, polypropylene, dense polyethylene, resin fiber) or composites. 
     3. Alternate Embodiment—Downward Scraper Ring  31  Force 
     Alternate embodiments of assembly  42  can include other spring  13  configurations such as leaf springs or torsion springs. Even downward force of gravity resultant from a heavy scraper ring  31  design can insure adequate floor  27  contact. Since fluid pressure is readily available at assembly  42 , it is practical to include air bags or pistons/cylinders as the forcing elements adding the advantage of zero downward force while installing unpowered assembly  42  on the transport system. 
     4. Alternate Embodiment—Scraper Ring  31  Configuration 
     An alternative embodiment can include the design shown in the view of FIG. 5 where a scraper ring  31 a includes a scraper brush  38  element capable of sweeping aside smaller sized debris  25  particles. 
     5. Alternate Embodiment—Scraper Ring  31  Configuration 
     An alternative embodiment can include the design shown in the view of FIG. 6 where a scraper ring  31 b includes a replaceable base  39  element capable of low cost replacement following wear out. 
     6. Alternate Embodiment—Scraper Ring  31  Configuration 
     An alternative embodiment can include the design shown in the view of FIG. 7 where a scraper ring  31 c includes a flexible strip  40  element capable of sweeping aside more sticky debris  25  particles. 
     7. Alternate Embodiment—Powered Scraper Ring  31  Configuration 
     An alternative embodiment (not shown) of assembly  42  can include an added motor powered feature that can rotate scraper ring  31 . This configuration can be useful to remove debris  25  that is both plentiful and sticky. 
     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 external scraper ring assembly integrations with a fluid caster, irrespective of particular structure configuration and materials without departing from the spirit and scope of the claimed invention.