Abstract:
A vehicle restraint for a loading dock employs spring force to urge the restraint&#39;s barrier up and back against a truck&#39;s rear ICC bar, whereby the spring loaded barrier accommodates both horizontal and vertical float of the bar as the truck is loaded or unloaded of its cargo. While spring force urges the barrier up and back, hydraulic force can move the barrier selectively down and forward. The restraint includes a positive mechanical stop that limits the distance that the truck can move away from the face of the dock. The restraint is particularly suited for mounting within a pit underneath a dock leveler.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The subject invention generally pertains to a vehicle restraint that engages a truck&#39;s rear ICC bar to help prevent the truck from accidentally pulling away from a loading dock and more specifically pertains to a pit-mounted vehicle restraint that includes hydraulic extension, spring return, and a positive mechanical stop that limits the vehicle restraint&#39;s extension.  
         [0003]     2. Description of Related Art  
         [0004]     When loading or unloading a truck parked at a loading dock, it is generally a safe practice to help restrain the truck from accidentally moving too far away from the dock. This is typically accomplished by a hook-style vehicle restraint that engages what is often referred to in the industry as an ICC bar or a Rear Impact Guard (RIG). An ICC bar or RIG is a bar or beam that extends horizontally across the rear of a truck, below the truck bed. Its primary purpose is to help prevent an automobile from under-riding the truck in a rear-end collision.  
         [0005]     An ICC bar, however, also provides a convenient structure for a hook-style restraint to reach up in front of the bar to obstruct the bar&#39;s movement away from the dock. A typical example of such a vehicle restraint is disclosed in U.S. Patent Application Publication 2004/0042882. The restraint described in that application extends and retracts hydraulically to firmly capture an ICC bar within a hook. Hydraulic pressure of the hook cylinder resists any longitudinal movement of the hook. Using hydraulics to arrest the horizontal movement of an ICC bar, however, may create a couple of problems.  
         [0006]     First, a hook-restrained truck (i.e., the hook is hydraulically moved and held in contact with the ICC bar) forcibly pulling away from a dock can pull on the hook with several tons of force. If it is the hydraulic pressure in the hook&#39;s cylinder that arrests the pulling force of the truck, extreme pressure may develop within the cylinder (pulling force of the truck divided by the effective area of the piston). This is particularly true when the pressure is at the rod end of the cylinder, as the cross-sectional area of the piston rod reduces the effective area of the piston. Moreover, when the pressure is at the rod end, highly pressurized hydraulic fluid may not only force itself past the piston seal but may also blow past the rod seal.  
         [0007]     Secondly, although some vehicle restraints yield in response to incidental vertical movement of a truck&#39;s ICC bar, often vehicle restraints do not accommodate horizontal movement of the bar. A vehicle restraint unyielding to at least some horizontal movement can be a problem particularly with trucks whose trailers have pneumatic suspension. As the trailer is being loaded or unloaded of its cargo, the trailer&#39;s suspension may allow the trailer bed to rise and descend in response to the change in weight carried by the trailer. With an active pneumatic suspension, the vertical movement may be several inches and is typically accompanied by an equivalent horizontal movement (also known as trailer walk) due to the mechanism of today&#39;s pneumatic suspension systems.  
         [0008]     In some cases, a truck driver may deactivate the trailer&#39;s pneumatic suspension at the loading dock, whereby the trailer descends to a lowered position so that the trailer bed stays at a generally constant, bottomed-out elevation as the trailer is being loaded or unloaded. If the vehicle restraint engages the ICC bar prior to deactivating the pneumatic suspension, the tremendous weight of the rear end of the trailer plus about half its cargo weight (e.g., 34,000 pounds in all) suddenly forces itself down upon the hook, thus attempting to push the hook downward and forward several inches. Attempting to hydraulically arrest such movement may damage the ICC bar and blow the seals of the restraint&#39;s hydraulic cylinder and/or cause damage to other hydraulic components.  
       SUMMARY OF THE INVENTION  
       [0009]     In some embodiments, a vehicle restraint employs spring force to urge the restraint&#39;s barrier up and back against a vehicle&#39;s ICC bar, whereby the spring force accommodates both horizontal and vertical float of the bar.  
         [0010]     In some embodiments, spring force moves the barrier up and back, and hydraulic force moves the barrier down and forward.  
         [0011]     In some embodiments, the vehicle restraint employs the combined effort from both a hydraulic system and a spring system to move the barrier to a stored position.  
         [0012]     In some embodiments, the vehicle restraint employs the combined effort from both a hydraulic system and a spring system to move the barrier to an operative position.  
         [0013]     In some embodiments, the vehicle restraint relies on a hydraulic cylinder&#39;s mechanical travel limit, rather than its hydraulic pressure, to limit the extent to which the vehicle&#39;s ICC bar can move away from the front face of a loading dock.  
         [0014]     In some embodiments, the return spring of a hydraulic cylinder is mounted outside of the cylinder to reduce the overall length of the cylinder/spring assembly and to achieve a greater spring force than what could otherwise be achieved by mounting a smaller spring within the cylinder.  
         [0015]     In some embodiments, a hydraulic cylinder of the vehicle restraint is operated as a single-acting cylinder so that the hydraulic power system only affects the forward movement of the barrier until the cylinder reaches its mechanical travel limit.  
         [0016]     In some embodiments, a hydraulic cylinder of the vehicle restraint is operated as a single-acting cylinder so that the hydraulic power system only affects the downward movement of the barrier until the barrier or the cylinder bottoms out.  
         [0017]     In some embodiments, the barrier of the vehicle restraint stores underneath a dock leveler.  
         [0018]     In some embodiments, the vehicle restraint is powered by the hydraulic system of the dock leveler.  
         [0019]     In some embodiments, the barrier of a vehicle restraint can not only rotate vertically to engage or disengage a vehicle&#39;s ICC bar, but the barrier can also rotate horizontally to minimize the overall length of the restraint when in its stored position, whereby the restraint may be more readily stored underneath a dock leveler. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a perspective view of a vehicle restraint.  
         [0021]      FIG. 2  is a perspective view of the vehicle restraint of  FIG. 1  installed in a sub-pit underneath a dock leveler.  
         [0022]      FIG. 3  is a schematic side view showing the restraint in a stored position.  
         [0023]      FIG. 4  is a schematic side view showing the restraint in a lowered, fully extended position.  
         [0024]      FIG. 5  is a schematic side view showing the restraint in a raised, fully extended position.  
         [0025]      FIG. 6  is a schematic side view showing the restraint within its range of resilient operative positions.  
         [0026]      FIG. 7  is a schematic side view showing the restraint raised and fully extended to its mechanically limited position.  
         [0027]      FIG. 8  is a perspective view of the restraint in a shipping box.  
         [0028]      FIG. 9  is a top view of a barrier/cylinder mechanism in a retracted position.  
         [0029]      FIG. 10  is a side view of the mechanism of  FIG. 9 .  
         [0030]      FIG. 11  is a top view of the mechanism of  FIG. 9  but with the barrier fully extended.  
         [0031]      FIG. 12  is a side view of the mechanism of  FIG. 11 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]     A vehicle restraint  10  includes a barrier  12  for engaging an ICC bar  14  of a truck  16  to help prevent the truck from accidentally pulling forward and away from a face  18  of a loading dock  20  as the truck is being loaded or unloaded of its cargo. To facilitate the loading and unloading operations, dock  20  may have a pit  22  that contains a conventional dock leveler  24 . Dock leveler  24  includes a pivotal deck  26  and a lip  28  for providing a bridge between a dock platform  30  and a rear edge of truck  16 . In this particular example, dock leveler  24  happens to be hydraulically actuated; however, vehicle restraint  10  can be used with other types of dock levelers, or it can be used alone without any dock leveler.  FIG. 1  shows restraint  10  alone,  FIG. 2  shows the restraint installed in a sub-pit  32  underneath dock leveler  24 , and  FIGS. 3-7  schematically illustrate restraint  10  in its various operating positions.  
         [0033]     In typical operation, truck  16  backs into dock  20  while vehicle restraint  10  is in its stored position, wherein barrier  12  is retracted and lowered as shown in  FIG. 3 . Next, a barrier actuator, preferably in the form of a main cylinder  34  (preferably but not necessarily hydraulic) extends barrier  12  to reach underneath ICC bar  14 , as shown in  FIG. 4 . While barrier  12  is fully extended, a positioning actuator, preferably in the form of a position cylinder  36  (preferably but not necessarily hydraulic) releases its fluid pressure to allow the tension in one or more position springs  38  to raise barrier  12  up against the underside of bar  14  to an operative position, as shown in  FIG. 5 . Once barrier  12  engages bar  14  at an operative position, main cylinder  34  can release its hydraulic pressure to enable the tension in one or more retract springs  40  to draw barrier  12  back against a front edge of bar  14  to a retracted operative position. The retracted operative position is beneficial in that barrier  12  is pulled into contact with bar  14  meaning that any movement of bar  14  away from the dock face will be inhibited by the presence of barrier  12 . Compare the position of barrier  12  in the retracted operative position of  FIG. 6  to the operative position of  FIG. 5  in which movement of bar  14  away from the dock face would initially be unimpeded by barrier  12  because of the separation between the two. The current design thus has the advantage of automatically retracting barrier  12  to the retracted operative position—to inhibit any movement of bar  14  away from the dock face at this point in the operational sequence, dock leveler  24  can position its deck  26  and lip  28  as shown in  FIG. 6 .  
         [0034]     With the barrier  12  in the retracted operative position, springs  38  and  40  provide barrier  12  with a range of resilient operative positions where barrier  12  remains in snug contact with bar  14 . The term, “spring,” broadly encompasses any device that can store energy for providing a resilient or restorative force. Examples of a spring include, but are not limited to, a coiled tension spring, a coiled compression spring, leaf spring, gas spring (e.g., pneumatic cylinder or bladder), counterweight, rubber or polyurethane cylinder, etc.  
         [0035]     To prevent undue strain of the ICC bar structure during its incidental movement, upward spring force  85  and rearward spring force  87  are used to maintain barrier  12  in contact with the ICC bar, as shown in  FIG. 6 . Spring forces  85  and  87  enable barrier  12  to responsively float, both vertically and horizontally, within a certain range of allowable movement to follow the incidental movement of bar  14  as truck  16  is loaded and unloaded of its cargo. Forces  85  and  87 , however, are yieldable; meaning that barrier  12  will yield for substantial applied forces rather than remaining rigid and potentially damaging the ICC bar/RIG.  
         [0036]     If truck  16  attempts to pull forward away from dock face  18 , barrier  12  could follow that motion up to a mechanically limited position, as shown in  FIG. 7 . In this example, the mechanically limited position is provided by a piston  42  reaching the end of its travel within cylinder  34 ; however, other mechanical stops could provide such a mechanically limited position. The mechanically limited position should be such that the ICC bar&#39;s forward movement is arrested at a position where lip  28  still safely overlaps the rear edge of truck  16 .  
         [0037]     To release the truck, the piston side of cylinders  34  and  36  are pressurized to extend and lower barrier  12  to the position of  FIG. 4 . Subsequently, main cylinder  34  is depressurized to allow spring  40  to retract barrier  12  to its stored position of  FIGS. 1 and 3 .  
         [0038]     Although the aforementioned operation can conceivably be achieved by a broad range of mechanisms, in a currently preferred embodiment, vehicle restraint  10  comprises the basic elements of a frame  44 , barrier  12 , a powered system (e.g., main cylinder  34  and position cylinder  36 ), a spring system (e.g., position spring  38  and retract spring  40 ), and a lever arm  46 . The term, “powered system” refers to any apparatus that receives energy and converts it to work.  
         [0039]     Frame  44  provides a foundation and an anchor for installing restraint  10  within sub-pit  32 . Referring to  FIG. 8 , restraint  10  may initially be housed within a shipping box  48  that also serves as a mold about which concrete can be poured to create sub-pit  32 . Once the concrete sets, the walls of box  48  can be broken away and removed, while tabs  50  and  52  remain embedded within the concrete to help anchor frame  44  within sub-pit  32 .  
         [0040]     To render barrier  12  horizontally movable, one or more fasteners  54  rigidly attach barrier  12  to an extendable piston rod  56  of main cylinder  34 . Pressurizing the piston side of cylinder  34  via a first main port  58  extends rod  56  and barrier  12 . To retract barrier  12 , port  58  is de-pressurized, so spring  40  can draw piston rod  56  back into cylinder  34 . The spring return action can be achieved by stretching spring  40  between one anchor point  60  coupled to barrier  12  and another, more stationary, anchor point  62  attached to cylinder  34  or some other suitable location.  
         [0041]     Selectively pressurizing and depressurizing port  58  can be achieved with a conventional hydraulic power supply  64  ( FIG. 2 ) with appropriate control valves. Such hydraulic power supplies are well known to those of ordinary skill in the art. In some cases, hydraulic supply  64  is the same supply that serves dock leveler  24 , whereby vehicle restraint  10  and dock leveler  24  share the same hydraulic power supply  64 . While port  58  is selectively pressurized and depressurized, the rod side of cylinder  34  can be left depressurized by venting a port  66  to a tank of hydraulic power supply  64  or venting it to atmosphere through a suitable breather.  
         [0042]     Vertical movement of barrier  12  is achieved by having a pin  68  (e.g., a bolt) pivotally couple main cylinder  34  to a bracket assembly  70  affixed to frame  44 . Lever arm  46  is rigidly attached to the base of main cylinder  34  so that position cylinder  36  and position spring  38  can act upon lever arm  46  to rotate main cylinder  34  about pin  68 , whereby cylinder  34  pivots to selectively raise and lower barrier  12 .  
         [0043]     To lower barrier  12 , a port  72  on the rod side of cylinder  36  is pressurized to extend the cylinder&#39;s piston rod  74 . Cylinder  36  is mounted between one point  76  on lever arm  46  and another point  78  coupled to frame  44 . So, as cylinder  36  extends, it pushes on lever arm  46  to rotate main cylinder  34  counterclockwise (as viewed from the perspective of  FIGS. 3-7 ), which lowers barrier  12 .  
         [0044]     To raise barrier  12 , port  72  is de-pressurized, so spring  38  can draw piston rod  74  back into cylinder  36 , which rotates lever arm  46  and main cylinder  34  clockwise. The spring return action can be achieved by stretching spring  38  between one point  80  on lever arm  46  and another point  82  at a generally fixed location. While hydraulic power supply  64  (with its appropriate control valves) selectively pressurizes and depressurizes port  72  to respectively lower and raise barrier  12 , the rod side of cylinder  36  can be left depressurized by venting a rod-side port  84  of cylinder  36  to the tank of supply  64  or venting it to atmosphere through a suitable breather. Even though cylinders  34  and  36  are shown with rod side ports  66  and  84 , they can be readily interchanged with ram style (or direct acting) cylinders that only have pressure ports  58  and  72 .  
         [0045]     Consequently, moving barrier  12  from its stored position where barrier  12  is down and back ( FIG. 3 ) to an operative position where barrier  12  is up and forward ( FIG. 5 ), involves the combined effort (sequentially or simultaneously) of electrically powering barrier  12  forward and spring  38  moving barrier  12  upward via spring force  85 . Subsequently, spring force  87  moves barrier  12  to a retracted operative position against bar  14  ( FIG. 6 ). The term, “electrically powering,” refers to any method or mechanism driven by or involving electricity. Electrically powering, for example, may include hydraulic system  64  whose hydraulic pump is driven by an electric motor. It should be noted that spring force  85  is also the force that enables barrier  12  to follow the incidental vertical movement of ICC bar  14  as vehicle  16  is being serviced.  
         [0046]     After loading or unloading vehicle  16 , moving barrier  12  from its operative position to its stored position involves the combined effort (sequentially or simultaneously) of electrically powering barrier  12  downward and spring  40  moving barrier  12  backward via spring force  87 .  
         [0047]     Vehicle restraint  10  may include several additional features that enhance its operation or value. Barrier  12 , for instance, has a raised edge  86  ( FIG. 6 ) that leans back to help prevent the barrier from slipping off the truck&#39;s ICC bar.  
         [0048]     Point  78 , which couples the base of position cylinder  36  to frame  44 , can be a pin and slot connection  88  that provides the base of cylinder  36  with limited sliding motion. The freedom to slide allows barrier  12  to respond more quickly to vertical movement of ICC bar  14  without always being dampened by the repeated extension and retraction of cylinder  36 .  
         [0049]     Referring to  FIG. 1 , vehicle restraint  10  may also include features that make the restraint easier to repair. Pin  68 , for instance, fits within a slot  90  in bracket  70  where retaining bars  92  hold pin  68  in place. Similarly, at point  78 , a pin  94  (e.g., a bolt) also fits within a slot  96 . Thus, the working mechanism of restraint  10  can be easily lifted out from within frame  44  by unbolting pin  94  and removing retaining bars  92 , which allows pins  68  and  94  to slide out from within their slots  90  and  96 .  
         [0050]     Restraint  10  can also be provided with a bar sensing device  98  that detects when barrier  12  is fully engaged with ICC bar  14 . Such a sensing device can assume various forms, such as an upwardly biased lever  100  that a pin  102  pivotally connects to barrier  12 . When barrier  12  engages the underside of ICC bar  14 , the bar forces lever  100  downward relative to the upward moving barrier  12 . A limit switch, proximity switch, magnet actuated sensor, etc., can be associated with lever  100  to generate a signal that indicates barrier-to-bar engagement. The signal can be used for various purposes including, but not limited to, triggering a light that tells operators in the area that the truck is restrained, initiating the depressurizing of main cylinder  34  so that barrier  12  retracts back against the forward facing surface of bar  14 , and/or enabling dock leveler  24  to place its deck  26  and lip  28  upon the bed of truck  16 .  
         [0051]     Additional sensors, such as a limit switch, proximity switch, magnet actuated sensor, etc. can be installed at appropriate locations to sense other operating conditions or positions of vehicle restraint  10 . A sensor, for example, could be used to indicate when barrier  12  is at its stored position of  FIG. 3 .  
         [0052]     In some cases, it may be desirable to minimize the overall length of the restraint when in its stored position, thereby reducing the required size of sub-pit  32 . To do this, barrier  12  and main cylinder  34  can be replaced by a mechanism  104  shown in  FIGS. 9-12 .  FIGS. 9 and 10  respectively show a top and side view of mechanism  104  in its retracted, stored position, and  FIGS. 11 and 12  respectively show a top and side view of mechanism  104  in its extended, operative position. As mechanism  104  retracts, a barrier  12 ′ flips back toward the face of the loading dock, assuming a generally right-angle position relative to its main cylinder  34 ′.  
         [0053]     This is accomplished by having a pin  106  pivotally couple barrier  12 ′ to a piston rod  56 ′ of main cylinder  34 ′. A link  108  has one end  110  pivotally connected to a lug  112  extending from barrier  12 ′ and an opposite end terminating at a knob  114 . Link  108  is free to slide within a guide member  116 , but its sliding motion is limited by the distance that knob  114  can travel between guide member  116  and an end stop  118 . When cylinder  34 ′ retracts to its stored position of  FIGS. 9 and 10 , knob  114  abuts end stop  118 , which causes link  108  to push barrier  12 ′ around to its flipped back position. When cylinder  34 ′ extends to its operative position of  FIGS. 11 and 12 , knob  114  abuts guide member  116  so that link  108  pulls barrier  12 ′ around to its outreached position.  
         [0054]     Although the invention is described with reference to a preferred embodiment, it should be appreciated by those of ordinary skill in the art that various modifications are well within the scope of the invention. For example, brush seals and/or other types of seals can be used to help cover the front opening of sub-pit  32 . Uprights  120  of frame  44  may provide a suitable mounting surface to which such seals can be attached. Therefore, the scope of the invention is to be determined by reference to the following claims: