Abstract:
A bumper assembly for use at a loading dock comprises a resiliently compressible pad protected by a readily replaceable metal faceplate. The bumper assembly has certain metal components that move relative to each other as the bumper assembly is compressed by a vehicle backing into the dock. Those metal components are spaced apart from each other to avoid metal-to-metal frictional wear. In some cases, the compressible pad has internal cavities that help reduce the extent to which the core bulges under compression.

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure generally pertains to loading dock bumpers, and more specifically to a dock bumper with a protective metal faceplate. 
     DESCRIPTION OF RELATED ART 
     A typical loading dock of a building includes an exterior doorway with an elevated platform for loading and unloading vehicles, such as trucks and trailers. In some cases, a loading dock may include a dock leveler to compensate for a height difference that may exist between the loading dock platform and an adjacent bed of a truck or trailer. Dock levelers typically include a deck whose front edge can be raised or lowered to the approximate height of the truck bed. An extension plate or lip may extend outward from the deck&#39;s front edge to span the gap between the rear of the truck bed and the front edge of the deck, thereby providing a path that allows personnel and material handling equipment to readily move on and off the truck bed during loading and unloading operations. 
     Dock bumpers are often installed near the doorway for several reasons. They can protect the face the building from vehicle impact; they can protect the rear end of the truck from damage; they can prevent a dock seal from being over compressed by a vehicle backing into the dock, and/or in cases where the dock includes a dock leveler, they can establish a predetermined minimum distance between the rear of the vehicle and the dock leveler so that the dock leveler has clearance to operate. Bumpers are typically made of a molded polymer such as rubber or a stack of rubber pads stamped out of old tires, conveyor belt material, or the like. The stack of rubber pads can be clamped between two steel plates. The plates hold the pads together and provide a way for installing the bumper to the loading dock. Bumpers are usually installed near the bottom of the doorway, adjacent either side of the dock leveler lip and protrude a few inches out from the face of the dock where they can be abutted by the rear of the vehicle. 
     Dock bumpers not only have to absorb the impact of trucks backing into the dock, but they must also endure tremendous vertical friction caused by weight being added and removed from the truck bed as the truck is being loaded or unloaded at the dock. Whenever a forklift, for instance, drives onto or off the truck bed, the truck&#39;s suspension allows the bed to rise and fall accordingly. The resulting friction between the face of the bumper and the back of the truck can quickly wear out the bumper. 
     Replacing a worn bumper can be surprisingly difficult and time consuming. Corroded anchor bolts and mounting plates that have been welded in place and may need to be cut off. 
     To prolong the life of bumpers and thus reduce their frequency of replacement, some bumpers have their impact absorbing material encased within a telescoping steel housing. The exterior steel plates of such a housing not only provide more wear resistance, but the steel plates also reduce the sliding friction between the bumper and the truck, as the coefficient of friction of metal-to-metal is generally much lower than that of rubber-to-metal. 
     Steel encased bumpers, unfortunately, have some drawbacks. First, a metal-to-metal sliding connection typically couples the bumper&#39;s front metal plate (which protects the underlying polymeric core) to a metal mounting bracket. As a truck is loaded or unloaded of its cargo, the truck&#39;s suspension reacts by allowing the truck to move up and down, and back and forth repeatedly. This repeated movement transfers to the bumper and can quickly wear out the metal-to-metal connection. Second, steel encased bumpers are usually very heavy, which makes them more difficult to install and replace than rubber ones. Often a hoist of some sort is needed to assist in replacing a steel encased bumper. In addition, there is typically metal to metal contact between the steel facing of such bumpers and their housing—inhibiting their range of free movement. 
     Consequently, a need exists for a dock bumper that is more durable than conventional rubber bumpers yet is easier to service or replace than today&#39;s steel encased bumpers. 
     SUMMARY OF THE DISCLOSURE 
     In some embodiments, a bumper assembly includes a tie rod that secures both a polymeric bumper and a metal faceplate to a metal bracket; however, the bracket is spaced apart from the faceplate. 
     In some embodiments, metal mounting tabs extend from the faceplate into the bumper. 
     In some embodiments, to restrict the faceplate&#39;s movement, the mounting tabs extend into a socket defined by the bumper. 
     In some embodiments, the bumper includes multiple compression cavities whose volumes decrease upon compression of the bumper, thereby reducing the bumper&#39;s outward expansion. 
     In some embodiments, the faceplate includes a peripheral flange that helps maintain the position of the faceplate relative to the bumper. 
     In some embodiments, the bumper is molded as a unitary piece. 
     In some embodiments, the bumper comprises a laminated stack of polymeric pads. 
     In some embodiments, the tie rod avoids the compressive force of a vehicle pressing against the bumper due to ample clearance between the tie rod and the bumper. 
     In some embodiments, sliding metal contact between relative moving parts is avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vehicle backing into loading dock to which two bumper assemblies are mounted. 
         FIG. 2  is a side view of a bumper assembly shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the bumper assembly of  FIG. 2 . 
         FIG. 4  is a top view of the bumper assembly of  FIG. 2 . 
         FIG. 5  is a front view of the bumper used in the bumper assembly of  FIG. 2 . 
         FIG. 6  is a side view of the bumper of  FIG. 5 . 
         FIG. 7  is a front view of another embodiment of a bumper used in the bumper assembly of  FIG. 2 . 
         FIG. 8  is a side view of the bumper of  FIG. 7 . 
         FIG. 9  is a cross-sectional view of another embodiment of a bumper assembly. 
         FIG. 10  is a cross-sectional view of another embodiment of a bumper assembly. 
         FIG. 11  is a side view of another embodiment of a bumper assembly. 
     
    
    
     DESCRIPTION 
       FIG. 1  shows a loading dock  10  with a dock leveler  12 . To absorb the impact from a vehicle  14  backing into the dock, to ensure adequate operating clearance between a lip  16  of dock leveler  12  and the back of vehicle  14 , and/or to protect a dock seal (not shown) from being over compressed by the back end of vehicle  14 , one or more bumper assemblies  18  can be attached to a dock wall  20 , dock leveler  12 , or some other suitable mounting surface of the loading dock. 
     In one embodiment, shown in  FIGS. 1-6 , bumper assembly  18  includes a compressible pad  22  interposed between two metal brackets  24 . Pad  22  is resiliently compressible in response to the impact of vehicle  14  backing against it. In this context, “compressible” indicates that the pad will be compressed by the backing vehicle as it transmits the force of that vehicle to the dock wall, and then return to a relaxed shape when the force is removed. While all material have some degree of compressibility, the compressible pad of the embodiments herein is intended to compress substantially more that the relatively rigid/incompressible metal faceplate that overlays the compressible pad. With the addition of an anchor bolt  26 , a base plate  28 , weld seam  30 , or some other suitable mounting hardware, brackets  24  help fasten bumper  22  to dock  10 . A metal faceplate  32  overlays a front surface  34  of bumper  22  to protect the relatively soft bumper material from wear. 
     To hold bumper assembly  18  together, a tie rod  36  can extend through brackets  24 , bumper  22 , and metal mounting tabs  38 . Tabs  38  can be welded to faceplate  32 , and each tab can extend into a socket  40  of bumper  22 . Tie rod  36  extending through an opening  42  of tab  38  is what couples faceplate  32  to pad  22 . Opening  42  is preferably oversized or elongated to create sufficient clearance between tab  38  and tie rod  36  so that when vehicle  14  compresses pad  22 , the compressive forces are not transferred to tie rod  36 . As a result pad  22  receives the brunt of the impact, so tie rod  36  can be made relatively light. 
     It should be noted that tabs  38  and faceplate  32  are intentionally spaced apart from brackets  24  to avoid sliding frictional wear between those components as vehicles repeatedly compress bumper assembly  18 . Also, in some cases, the vertical clearance between tie rod  36  and tab  38  is greater than the vertical clearance between tab  38  and a sidewall  44  of socket  40  to help avoid metal-to-metal contact between tie rod  36  and tab  38 . To ensure that tie rod  36  is not completely loose and unsupported, the clearance between tie rod  36  and the corresponding hole in brackets  38  is less than the clearance between tie rod  36  and pad  22 . 
     As vehicle  14  compresses pad  22 , the bumper tends to bulge outward and press against an inner surface  46  of bracket  24 . To minimize this pressure against bracket  24  and thus minimize the wear of pad  22  in this area, pad  22  can be provided with one or more compression cavities, such as cavities  48  and  50  of  FIG. 5 . With cavities  48  and  50 , bumper  22  can bulge into these cavities, thereby reducing their volume and reducing the expansion or pressure against bracket  24 . Cavities  48  and  50  can be blind-holes that extend only partway through pad  22 , or cavities  48  and  50  can be thru-holes that extend completely through pad  22 . 
       FIGS. 7 and 8  show a variation of pad  22 , wherein a bumper  52  includes a slot  54  for receiving tie rod  36 . Slot  54  replaces a hole  56  through which tie rod  36  extends in bumper assembly  22 . Slot  54  facilitates the manufacturability of bumper  52  in cases where pad  52  is molded of a unitary piece. With slot  54 , pad  52  can be released from its injection mold without having to provide the mold with retractable draw pins for producing holes running perpendicular to each other such is the case with, for example, hole  56  and cavity  54 . 
       FIG. 9  shows a variation where a faceplate  58  replaces faceplate  32 . In this example, faceplate  58  includes one or more peripheral flanges  60  and  62  that overlie an upper bumper surface  64  and a lower bumper surface  66  respectively. Engagement between flange  60  and surface  64  or engagement between flange  62  and surface  66  limits the relative vertical movement between faceplate  58  and pad  22 . This engagement can perhaps endure greater vertical loads than what could otherwise be endured by vertical engagement between tie rod  36  and tab  38  or vertical engagement between a narrow edge of tab  38  and socket  40  of bumper  22 . Moreover, flanges  60  and  62  can inhibit pad  22  from spreading apart in the area of slot  54  ( FIG. 7 ). 
       FIG. 10  shows a bumper assembly  68  where a tab  70  replaces tab  38 . In this example, an opening  72  to receive tie rod  36  is created by having tab  70  be L-shaped. Thus, the “opening” defined by the metal mounting tab does necessarily have to be a hole, but rather can be a recess, detent, concavity, or the like. 
       FIG. 11  shows a bumper assembly  72  where unitary compressible pad  22  is replaced by a compressible pad  74  comprising a plurality of laminations  76 . The plurality of laminations can be a stack of pads made of a variety of materials including, but not limited to, rubber tires or belting material. 
     Although the invention is described with respect to various embodiments, modifications thereto will be apparent to those skilled in the art. Various features described with respect to one embodiment may be readily applied to other embodiments. Therefore, the scope of the invention is to be determined by reference to the following claims.