Double-wall inflatable column assembly for a dock leveler

Abstract

A dock leveler for a truck loading dock includes a pivotal deck that is actuated by an inflatable column assembly. The inflatable column assembly includes an outer pliable tube that contains a more airtight inflatable bladder. The pliable tube is made of a tough fabric to protect the inner bladder. In some embodiments, the pliable tube has a generally vertical cylindrical shape that can provide a heavy deck with ample columnar support.

We claim:  
     
         1 . A dock leveler for a vehicle at a loading dock, comprising: 
 a deck having a rear edge and a forward edge, wherein the rear edge is adapted to be pivotally coupled to the loading dock to enable vertical movement of the forward edge relative to the loading dock;    a lip extension adjacent the forward edge of the deck and being moveable relative thereto, the lip extension being adapted to engage the vehicle;    a pliable tube disposed underneath the deck;    a bladder disposed inside the pliable tube and defining an air gap therebetween, the bladder being inflated when the deck is raised, and deflated when the deck is lowered; and    a source of pressurized air coupled to the bladder such that air discharged from the source of pressurized air pressurizes air inside the bladder to create greater air pressure inside the bladder than inside the air gap, whereby the source of pressurized air inflates the bladder, which in turn expands the pliable tube to push the deck upward.    
     
     
         2 . The dock leveler of  claim 1 , wherein the pliable tube has a first unrestrained maximum air capacity, and the bladder has a second unrestrained maximum air capacity that is greater than the first maximum unrestrained air capacity of the pliable tube.  
     
     
         3 . The dock leveler of  claim 1 , wherein the air gap gets smaller upon inflating the bladder.  
     
     
         4 . The dock leveler of  claim 1 , wherein the pliable tube is substantially cylindrical when expanded.  
     
     
         5 . The dock leveler of  claim 1 , wherein the bladder deviates from a cylindrical shape when inflated and unrestrained.  
     
     
         6 . The dock leveler of  claim 1 , wherein the bladder is generally pillow-shaped when inflated and unrestrained.  
     
     
         7 . The dock leveler of  claim 1 , wherein the bladder is more airtight than the pliable tube.  
     
     
         8 . The dock leveler of  claim 1 , wherein the pliable tube is stronger than the bladder.  
     
     
         9 . The dock leveler of  claim 1 , wherein the bladder comprises two pliable sheets integrally joined to each other by a peripheral joint, whereby the two pliable sheets and the peripheral joint are of the same material.  
     
     
         10 . The dock leveler of  claim 1 , wherein the bladder comprises a tubular sheet having two sealed joints at opposite ends thereof.  
     
     
         11 . The dock leveler of  claim 1 , wherein the bladder comprises a pliable sheet having a peripheral edge, wherein a crease exists along a first portion of the peripheral edge and a sealed joint exists along a second portion of the peripheral edge.  
     
     
         12 . The dock leveler of  claim 1 , further comprising a nozzle that couples the source of pressurized air to the bladder, wherein the nozzle defines an air passageway that provides a diverging flow pattern of air discharged from the source of pressurized air.  
     
     
         13 . The dock leveler of  claim 12 , wherein the air passageway extends along a curved centerline that defines an obtuse angle.  
     
     
         14 . The dock leveler of  claim 1 , wherein the lip extension is linearly moveable relative to the deck.  
     
     
         15 . The dock leveler of  claim 1 , wherein the source of pressurized air remains at a substantially fixed location.  
     
     
         16 . The dock leveler of  claim 1 , further comprising a flexible tube that couples the source of pressurized air to the bladder.  
     
     
         17 . A dock leveler for a vehicle at a loading dock, comprising: 
 a deck having a rear edge and a forward edge, wherein the rear edge is adapted to be pivotally coupled to the loading dock to enable vertical movement of the forward edge relative to the loading dock;    a lip extension adjacent the forward edge of the deck and being moveable relative thereto, the lip extension being adapted to engage the vehicle;    a pliable tube disposed underneath the deck, wherein the pliable tube has a first unrestrained maximum air capacity;    a bladder disposed inside the pliable tube, wherein the bladder has a second unrestrained maximum air capacity that is greater than the first unrestrained maximum air capacity, the bladder being inflated when the deck is raised and deflated when the deck is lowered; and    a source of pressurized air coupled to the bladder such that air discharged from the source of pressurized air inflates the bladder, which in turn expands the pliable tube to push the deck upward.    
     
     
         18 . The dock leveler of  claim 17 , wherein an air gap between the bladder and the pliable tube gets smaller upon inflating the bladder.  
     
     
         19 . The dock leveler of  claim 17 , wherein the pliable tube is substantially cylindrical when expanded.  
     
     
         20 . The dock leveler of  claim 17 , wherein the bladder deviates from a cylindrical shape when inflated and unrestrained.  
     
     
         21 . The dock leveler of  claim 17 , wherein the bladder is generally pillow-shaped when inflated and unrestrained.  
     
     
         22 . The dock leveler of  claim 17 , wherein the bladder is more airtight than the pliable tube.  
     
     
         23 . The dock leveler of  claim 17 , wherein the pliable tube is stronger than the bladder.  
     
     
         24 . The dock leveler of  claim 17 , wherein the bladder comprises two pliable sheets integrally joined to each other by a peripheral joint, whereby the two pliable sheets and the peripheral joint are of the same material.  
     
     
         25 . The dock leveler of  claim 17 , further comprising a nozzle that couples the source of pressurized air to the bladder, wherein the nozzle defines an air passageway that provides a diverging flow pattern of air discharged from the source of pressurized air.  
     
     
         26 . The dock leveler of  claim 25 , wherein the air passageway extends along a curved centerline that defines an obtuse angle.  
     
     
         27 . The dock leveler of  claim 17 , wherein the lip extension is linearly moveable relative to the deck.  
     
     
         28 . The dock leveler of  claim 17 , wherein the source of pressurized air is at a substantially fixed location.  
     
     
         29 . The dock leveler of  claim 17 , further comprising a flexible tube that couples the source of pressurized air to the bladder.  
     
     
         30 . A method of operating a dock leveler that includes a deck and a lip extension, wherein the deck is lifted by a bladder disposed inside of a pliable tube, and an air gap exists between the bladder and the pliable tube, the method comprising: 
 inflating the bladder to raise the deck;    while raising the deck, exhausting air from within the air gap;    moving the lip extension relative to the deck; and    deflating the bladder when the deck is lowered.    
     
     
         31 . The method of  claim 30 , further comprising: in the event of a bladder failure, using the pliable tube to lower the deck at a controlled rate of descent.  
     
     
         32 . The method of  claim 30 , further comprising pivoting a lip extension relative to the deck.  
     
     
         33 . The method of  claim 30 , further comprising sliding a lip extension relative to the deck.  
     
     
         34 . A method of using a bladder disposed inside of a pliable tube to raise a deck of a dock leveler that includes a lip extension, comprising: 
 inflating the bladder;    while inflating the bladder, exhausting air out from within a gap between the bladder and the pliable tube;    expanding the pliable tube by continuing to inflate the bladder;    pushing the deck upward by expanding the pliable tube;    moving the lip extension relative to the deck; and    deflating the bladder when the deck is lowered.    
     
     
         35 . The method of  claim 34 , further comprising: in the event of a bladder failure, using the pliable tube to lower the deck at a controlled rate of descent.  
     
     
         36 . The method of  claim 34 , further comprising pivoting a lip extension relative to the deck.  
     
     
         37 . The method of  claim 34 , further comprising sliding a lip extension relative to the deck.