Abstract:
A loading dock including a dock surface and a supporting structure positioned within a pit in the dock surface. The loading dock also includes a ramp, an inflatable assembly, and a support. The ramp is pivotally coupled to the supporting structure, and the inflatable assembly is positioned under the ramp and adapted to move the ramp between a lowered position and a raised position. The support is positioned under and supports the inflatable assembly. The support is supported by a pit floor and is unsecured to the pit floor.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 10/222,444 filed Aug. 16, 2002, which is a continuation of U.S. patent application Ser. No. 10/005,395 filed Dec. 3, 2001, now U.S. Pat. No. 6,460,212, which is a continuation of U.S. patent application Ser. No. 09/613,224 filed Jul. 10, 2000, now abandoned, which is a continuation of U.S. patent application Ser. No. 09/456,207 filed Dec. 7, 1999 now abandoned, which is a continuation of U.S. patent application Ser. No. 09/093,234 filed Jun. 8, 1998, now U.S. Pat. No. 5,996,156, which is a continuation-in-part of U.S. patent application Ser. No. 08/531,011 filed Sep. 20, 1995, now U.S. Pat. No. 5,802,650, which is a continuation-in-part of U.S. patent application Ser. No. 08/131,983 filed Oct. 4, 1993, now U.S. Pat. No. 5,471,693, all of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to dock levelers, and more particularly to dock levelers having inflatable members. 
     BACKGROUND OF THE INVENTION 
     Dock levelers or dock boards are mounted on loading docks and are adapted to bridge the gap between the dock and the bed of a truck or carrier parked in front of the dock to enable material handling equipment, such as a forklift truck to move between the dock and the truck bed. 
     The typical dock leveler includes a frame or supporting structure which is mounted in a pit or depression in the loading dock and the rear end of a ramp or deck plate is pivoted to the supporting structure so that the ramp is movable between a horizontal cross traffic position and an upwardly inclined position. 
     Hinged to the forward end of the ramp is an extension lip that is movable between a downwardly hanging pendant position and an extended position where the lip forms an extension to the ramp. 
     After a truck has parked in front of the loading dock in preparation for a loading operation, the ramp of the conventional dock leveler is pivoted upwardly and as the ramp approaches its upwardly inclined position, the lip is pivoted outwardly to the extended position. As the ramp is subsequently lowered, the extended lip will engage the bed of the truck. After the loading operation has been completed, the lip will fall by gravity to the pendent position as the truck pulls away from the loading dock. 
     Traditionally, the ramp of the dock leveler has been operated either by a mechanical or hydraulic mechanism. With a typical mechanical operation, an extension spring is mounted in the pit beneath the ramp and is connected through a lever arm to the rear edge of the ramp. When a ramp holddown mechanism is released, the force of the spring will pivot the ramp to the upwardly inclined position. 
     With a hydraulically-operated dock leveler, a hydraulic cylinder unit is connected between the supporting frame and the ramp and through extension of the cylinder unit, the ramp will be pivoted to the upwardly inclined position. 
     U.S. patent application Ser. No.  07 / 814 , 002 , filed Dec. 26, 1991, now abandoned, describes an inflatable bag mechanism that is utilized to pivot the ramp to the upwardly inclined position. As described in that patent application, a pleated bag is interposed between the bottom of the pit in the loading dock and the undersurface of the ramp. By inflating the bag with low pressure air, the ramp will be pivoted to the upwardly inclined position. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention includes a loading dock including a dock surface and a supporting structure positioned within a pit in the dock surface. The loading dock also includes a ramp, an inflatable assembly, and a support. The ramp is pivotally coupled to the supporting structure, and the inflatable assembly is positioned under the ramp and adapted to move the ramp between a lowered position and a raised position. The support is positioned under and supports the inflatable assembly. The support is supported by a pit floor and is unsecured to the pit floor. 
     An additional embodiment of the invention includes a loading dock including a dock surface and a supporting structure positioned within a pit in the dock surface. The loading dock also includes a ramp, an inflatable assembly, and a support. The ramp is pivotally coupled to the supporting structure for movement between a generally horizontal lowered position and an upwardly-inclined raised position. The inflatable assembly is positioned under the ramp, and the support is positioned under and supports the inflatable assembly. The support is supported by a pit floor and can be manually lifted completely out of engagement with the pit floor when the ramp is in the raised position. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical section of a dock leveler incorporating the invention with the ramp being shown in the horizontal position; 
     FIG. 2 is a view similar to FIG. 1 showing the ramp in the upwardly inclined position; 
     FIG. 3 is an enlarged fragmentary vertical section showing the attachment of the bag support member to the ramp; 
     FIG. 4 is a section taken along line  4 — 4  of FIG. 2; 
     FIG. 5 is a section taken along line  5 — 5  of FIG. 1; and 
     FIG. 6 is a section taken along line  6 — 6  of FIG.  1 . 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order. 
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a dock leveler I which is mounted in a pit or depression  2  in a loading dock  3 . The lower surface or floor  4  of pit  2  slopes downwardly and forwardly as seen in FIGS. 1 and 2. Dock leveler  1  is adapted to bridge the gap between the upper surface of the loading dock  3  and the bed of a truck or carrier parked in front of the loading dock. 
     Dock leveler  1  includes a frame or supporting structure  5 , which is mounted in the rear of pit  2 , and the rear end of a ramp or deck plate  6  is pivoted to the frame  5 , so that the ramp is movable between a generally horizontal cross traffic position, where the ramp is flush with the upper surface of dock  3 , and an upwardly-inclined position, as shown in FIG.  2 . 
     To pivot the ramp  6  to frame  5 , a series of lugs  7  are mounted on vertical legs  8  of frame  5  and are pivoted through a hinge pin  9  to the rear end of ramp  6 . 
     Hinged to the forward end of ramp  6  is an extension lip  10  which is adapted to be pivoted from a downwardly hanging pendant position, as shown in FIG. 1 to an outwardly extending position, as shown in FIG. 2, where the lip forms an extension to ramp  6 . Lip  10  can be moved from the pendant to the extension position and held in that position by various mechanical hydraulic or pneumatic mechanisms, and the lip lifting and latching mechanism is not, in itself, a part of the present invention. 
     When the ramp is in the horizontal position, as shown in FIG. 1, and the lip  10  is pendant, the lower end of the lip is retained within keepers  10   a , which are mounted on the front face of dock  3 . Engagement of lip  10  with keepers  10   a  maintains the ramp in the horizontal position. 
     An inflatable bag assembly  11  is located in pit  2  beneath the ramp  6 , and by inflating the bag assembly ramp  6  can be pivoted from the horizontal to the upwardly inclined position. Bag assembly  11  is composed of a pair of vertically superimposed bags  12  and  13 . While the drawings show a pair of bags  12  and  13 , it is contemplated that any number of stacked bags can be utilized in the bag assembly. 
     The construction of the bag assembly  11  can be similar to that described in U.S. Pat. No. 5,446,938. 
     Bags  12  and  13  are preferably formed of fabric, such as nylon or polyester, impregnated with a thermoplastic resin and have contiguous horizontal surfaces which are joined together along an annular sealed area  14  that borders an unsealed central area. One or more holes  15  extend through the central area to provide communication between the interiors of the bags  12  and  13 . 
     The upper surface of bag assembly  11  bears against an upper plate  17  which is mounted to the underside of ramp  6 , while the lower surface of the bag assembly is supported on a bag support member or frame  18 . 
     To inflate bag assembly  11 , a low pressure fan  19 , similar to that described in pending U.S. patent application Ser. No. 07/814,002, filed Dec. 26, 1991, now abandoned, is mounted to the undersurface of ramp  5  between the parallel beams  22  of the ramp  6 . The outlet of fan  19  is connected through an air line  20  to a fitting  21  in bag  12 . With this construction operation of fan  19  will inflate bags  12  and  13 . When operation of fan  19  is terminated, the weight of the ramp  6  will deflate the bags  12  and  13 , exhausting the air through the fan  19 . 
     The bag support member  18 , as best shown in FIGS. 4 and 5 is composed of a plurality of parallel, spaced, channel-shaped sections  23 . Rollers  24  are located between adjacent sections  23  and similar rollers  24  are located outboard of the outer sections  23 . Rollers  24  are journaled on a shaft  25  that extends through the flanges of the channel-shaped sections  23 . 
     As shown in FIGS. 1 and 2, rollers  24 , which are located at the forward end of the bag support member  18 , are adapted to ride on the sloping floor  4  of pit  2 , as the ramp is raised and lowered. 
     As a feature of the invention, the rear end of the bag support member  18  is pivoted to the rear end of ramp  6 . In this regard, a cross bar  26  is mounted to the underside of the ramp and extends transversely of the ramp, and a series of lugs  27  extend downwardly from cross bar  26 . A pivot shaft  28  extends through aligned holes in lugs  27 , as well as in the flanges of the channel-shaped sections  23 , and serves to pivotally connect the bag support member  18  to the ramp. 
     Each of the bags  12  and  13  is provided with a rearwardly extending strip or tether  29  and the tethers are secured to the rear end of bag support member  18 , as best illustrated in FIG. 3. A cross bar  30  extends transversely across the upper surfaces of the sections  23 , and the tethers  29  are secured to the cross bar through a clamping bar  31  and bolts  32 . The tethers  29  prevent the bags  12  and  13  from squeezing forwardly as the bags are inflated to elevate the ramp  6 . 
     As the bag support member  18  is connected directly to the ramp  6 , the bag support member will move forwardly with the ramp as the ramp is pivoted upwardly and the rollers  24  permit the bag support member to ride on the pit floor  4 , as the ramp is raised and lowered. As the ramp  6  and bag support member  18  move together, relative movement between the bag assembly  11  and ramp plate  17  and bag support member  18  is minimized. 
     If bag support member  18  was not tied to ramp  6  and instead was connected to frame  5 , the ramp would tend to move forwardly to a greater extent than the bag support member as the bag was inflated and the ramp was elevated. Initially, friction would tend to hold the bag in engagement with the ramp plate and the bag supporting plate, but as the bag was further inflated, the frictional forces are overcome causing the bag to snap forwardly. This action would put a strain on the tethers. Further, the relative movement between the upper and lower surfaces of the bag against the ramp plate and the bag support member could cause undue wear on the bag surfaces. 
     As a feature of the invention, the upper surface face of bag  12  is connected to the plate  17 , preferably by a removable connection. As shown in the drawings, the releasable connection can take the form of a pair of loops  34  secured to the forward end of upper bag  12 , and the loops are each connected through a strap or cord  35  to the underside of ramp  6 . Engagement of straps  35  and loops  34  will prevent the bag assembly  11  from collapsing downwardly against the bag supporting member  18  when operation of fan  19  is discontinued and will maintain the bag volume. For example, when the ramp  6  descends from the upwardly inclined position shown in FIG. 2, due to discontinuation of operation of fan  19 , the extended lip  10  will engage the truck bed, but the bag assembly  11  will maintain its volume and will not collapse against the bag support member  18 , due to the connections  34 , 35 . If the truck bed is above the level of dock  3  and the truck subsequently pulls away from the dock, the ramp will further descend, compressing the air within the bag assembly  11 , and exhausting the air through the restriction of fan  19 . Thus, the ramp will descend slowly, enabling the lip  10  to fall to its pendant position where it can engage the keepers  10   a  on the dock face. 
     The connection between the bag assembly  11  and the ramp plate  17  is also important in situations where the ramp may be at a downwardly inclined position during the loading operation. When the truck subsequently pulls away from the dock with the ramp  6  in this downwardly inclined position, the lip  10  will not be in position to engage the keepers  10   a , with the result that the ramp will descend and bottom out in the pit  2 . With the connection between the plate  17  and the bag assembly  11 , which retains the bag volume, the descent of the ramp will be slowed, so it will not slam into the pit floor. 
     While the drawings show the releasable connection to be straps  35  and loops  34 , it is contemplated that various types of connections can be employed to connect the upper end of bag assembly  11  to the ramp plate  17  or the ramp  6 , to thereby prevent the deflated bag assembly from collapsing downwardly against the bag support member  18 . 
     The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain best modes known for practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.