Abstract:
A vehicle restraint at a loading dock includes a vertically moving barrier that engages a truck&#39;s rear ICC bar to help prevent the truck from accidentally moving too far away from the face of the dock. The restraint includes an inclined barrier actuator with minimal linkage that provides a low-profile stored position. The barrier actuator powers the barrier up to engage the ICC bar and powers the barrier down to a stored position. A compliant coupling provides the barrier with vertical float to allow for incidental vertical movement of the ICC bar, as the truck is being loaded or unloaded of its cargo. The restraint also includes a novel switch actuator that senses whether the ICC bar is properly positioned relative to the barrier.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     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 to a vehicle restraint that responds to vertical movements of the truck, as the truck is being loaded or unloaded of its freight. 
     2. Description of Related Art 
     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 often 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. However, an ICC bar 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. To release the truck, many restraints lower to a stored position below the bar, which then allows the next truck to back into the dock. Other hook-style restraints store in a normally raised position and include an inclined lead-in that an ICC bar uses to help push the restraint underneath the bar as the truck backs into the dock, as disclosed in U. S. Pat. Nos. 5,702,223; 4,443,150; and 4,938,647. Once underneath the bar, usually a barrier rises in front of the bar (e.g., rotates to such a position) to restrain the truck. 
     Current hook-style vehicle restraints provide a wide variety of advantages and features. Some restraints have a sensor or switch intended for determining whether the hook or barrier is properly positioned to obstruct the ICC bar, as disclosed in U.S. Pat. No. 4,759,678. However, in the &#39;678 device, an ICC bar catching the very distal end of the restraint carriage (i.e., just in front of the hook) would appear to allow the hook to rise and trip the switch to indicate that the ICC bar was restrained, when actually the bar would be in front of the hook. This problem is avoided by the restraints of U. S. Pat. Nos. 4,488,325 and 5,297,921, which include switches that more directly sense the position of an ICC bar. However, these restraints, as well as the &#39;678 restraint, have a significantly high vertical profile in their lowered, stored positions. The high profile may prevent some especially low ICC bars from passing over the top of the restraint, even when the restraint is lowered to its stored position. 
     Further, to move a restraint barrier or hook, often a complicated linkage (for various reasons) is employed to raise or lower the barrier under the power of an actuator, as disclosed in U. S. Pat. Nos. 4,861,217; 4,674,941; and 4,830,563. Although the linkages may provide some benefit, their relative complexity can add to their maintenance and cost. 
     It is usually desirable for a restraint to allow for some vertical movement of the ICC bar, which is often caused by weight being added or removed from the truck (and thus the suspension) while at the loading dock. The changes in weight can be due to cargo being added or removed, and/or can be due to a forklift driving on and off the truck bed. For truck beds with rear air suspension, an ICC bar may move up and down several inches. If the barrier does not rise with the bar, the bar may rise up and over the barrier, thus limiting the truck&#39;s resistance to movement away from the dock face. If the barrier does not descend when the weight of the truck forces the ICC bar down, the immoveable barrier might bend the bar under the truck&#39;s added weight. 
     To allow for incidental vertical movement of a truck&#39;s ICC bar, many vehicle restraints employ pneumatic cylinders for moving the barrier. The compressibility of the air within the cylinder provides a gas spring effect that allows some movement of the barrier even when control valves of the pneumatic system trap the air within the cylinder. In some cases, however, there may be an advantage to using a motor-driven actuator or hydraulics, rather than pneumatics, for moving the barrier. For example, a hydraulically actuated vehicle restraint and a nearby hydraulically actuated dock leveler could perhaps share the same hydraulic pump, tank, and other hydraulic components. Sometimes, hydraulics is preferred over pneumatics to provide a more controlled rate of movement or to positively maintain the position of certain parts after the parts have stopped moving. Moreover, for a pneumatic system, a source of compressed air must be present. 
     Unfortunately, in applications where a motor-driven actuator or hydraulics is preferred, it can be difficult to provide a vehicle restraint that can allow for vertical movement of the ICC bar once the restraint&#39;s actuator has moved the barrier into position. Further, it can be difficult to provide a restraint that allows for vertical movement of an ICC bar without sacrificing other features of the restraint, such as a low vertical profile when in a lowered, stored position; minimal mechanical complexity; and a switch that ensures that an ICC bar is in position. 
     SUMMARY OF THE INVENTION 
     In order to provide a low-profile vehicle restraint, the restraint disclosed herein includes a vertically moveable barrier that is moved by an angled actuator from a lowered, stored position to a raised, operative position to obstruct an ICC bar, wherein the restraint allows for incidental vertical movement of the ICC bar after the barrier is at its raised, operative position. 
     In some embodiments of the restraint, the use of linkages is minimized to perhaps minimize maintenance and improve the reliability of the restraint. 
     In some embodiments, the restraint includes a compliant coupling that allows for incidental vertical movement of an ICC bar even when the length of a barrier actuator remains substantially constant. 
     In some embodiments, the compliant coupling can be disposed at either an upper or lower end of the barrier actuator. 
     In some embodiments, a piston/cylinder or a motor-driven actuator can move the barrier. 
     In some embodiments of the restraint, the force to vertically move the barrier is transmitted along a generally straight line between the barrier and a frame of the restraint to help provide a strong, reliable barrier/frame connection, and the line of force is inclined to reduce the vertical profile of the restraint when in its lowered, stored position. 
     In some embodiments, to reduce the vertical profile of the restraint when in its lowered, stored position, the actuator pivots as the barrier moves vertically. 
     In some embodiments, a pressure relief valve is used to allow for incidental vertical movement of an ICC bar. 
     In some embodiments, an accumulator is used to allow for incidental vertical movement of an ICC bar. 
     In some embodiments, the barrier is powered both up and down, rather than relying on spring force, horizontal movement of the truck, the weight of the barrier, or the weight of a trolley that carries the barrier to cause vertical movement. 
     In some embodiments, a vehicle restraint is provided with an ICC bar sensor that includes a switch actuator captured within the geometry of the restraint&#39;s hook to help protect the switch actuator from damage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a vehicle restraint with one frame plate of the restraint omitted for clarity, and with a barrier of the restraint shown in a first operative position. 
     FIG. 2 is a top view of FIG.  1 . 
     FIG. 3 is the same as FIG. 1, but with the barrier is a stored position. 
     FIG. 4 is the same as FIG. 1, but with an ICC bar having moved upward. 
     FIG. 5 is the same as FIG. 1, but with the ICC bar having moved the barrier down to a second operative position. 
     FIG. 6 is similar to FIG. 1, but of another embodiment of a vehicle restraint. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A vehicle restraint  10  that can help prevent a truck from separating from a face  13  of a loading dock  12  is shown with a barrier  14  in a raised, operative position in FIGS. 1 and 2, and is shown with barrier  14  in a lowered, stored position in FIG.  3 . In the operative position, a shank  16  of barrier  14  presses up against the underside of a truck&#39;s ICC bar  18 , while a distal end  20  of barrier  14  helps limit the extent to which bar  18  can move away from dock face  13 . In the stored position, of FIG. 3, distal end  20  of barrier  14  is below bar  18  to allow the truck to move away from dock  12  without being inhibited by restraint  10 . 
     To fix restraint  10  against movement away from dock  12  and to help protect some of the restraint&#39;s components, restraint  10  includes a frame  22  that in a preferred embodiment includes two frame plates  24  and  26 . Both frame plates  24  and  26  are shown in FIG. 2, but plate  24  is omitted in the rest of the drawing figures to more clearly show other features of the restraint. 
     To move barrier  14  between its operative and stored positions, an elongated member, such as a barrier actuator  28 , moves barrier  14  along a generally vertical track  30  that is fixed relative to frame  22 , a driveway  15 , and dock face  13 . The relative movement between barrier  14  and track  30  can be provided by any conventional track system that employs rollers, slides, or some other moving connection. In some embodiments, rollers  32  are attached to two shafts  34 , which in turn are attached to a proximal end  36  of two hook-shaped side plates  38  of barrier  14 . Rollers  32  can then roll within the confines of two channels  40  that face each other to comprise track  30 . The flanges of channels  40  provide a bearing surface at each vertical position of barrier  14 . That is, pull-out forces exerted on barrier  14  by a vehicle attempting to leave the dock while the restraint is engaged are reacted into dock face  13  through the rollers engaging track  30  which is in turn coupled to frame  22 . In addition, track  30  forms a bearing surface to facilitate the barrier  14  moving vertically between its operative and stored positions. As will be clear from the discussion below, the actuator for raising the barrier  14  will exert forces thereon that have both horizontal and vertical components. Bearing engagement between rollers  31  and channels  40  (particularly the rear walls thereof) will restrict the barrier  14  from moving horizontally toward and away from the dock face  13 , even when the applied forces have a horizontal component. The inner end of barrier  14  is thus guided vertically by this bearing arrangement. This vertical movement could also be characterized as “substantially linear” in the sense that the rollers at the inner end of the barrier move within an envelope having a width defined by the width of the track (its distance away from the dock face). Since the distance of the inner end of the barrier from the dock face does not vary significantly because of the engagement with the track, the movement is substantially vertical. 
     To provide the motive force for lifting barrier  14 , a linear member (e.g., actuator  28 ) is coupled between barrier  14  and frame  22 . The linear member includes a first end movably coupled to frame  22  and a second end movably coupled to barrier  14 , such that the linear member can lean relative to a vertical reference line and assume a range of acute angles facing toward dock face  13  as barrier moves up and down. In some embodiments, the linear member may have a variable length, and itself be an actuator for providing the motive force to move barrier  14 . In other embodiments, the linear member has a fixed length and is operatively coupled to an actuator for providing the motive force, which is then transferred by the linear member. In either case, the linear member includes a centerline that remains parallel to a line segment connecting the points where the two ends of the linear member are coupled to frame  22  and barrier  14 , respectively. The presence of the linear member further provides that the load path along which the motive force for lifting barrier  14  is applied is a linear path, again extending between the coupling points of the linear member to frame  22  and barrier  14 . The parallelism of the centerline of the linear member to the coupling points, and the presence of a linear load path distinguishes the embodiments shown herein from restraints in which a multi-component mechanical linkage transmits a barrier motive force between frame  22  and barrier  14 . There, the load path necessarily follows the non-linear path established by the orientation of the components forming the linkage. The coupling of the linear member to the frame and barrier in such a way as to allow the member to assume a range of acute angles toward dock face  13  also distinguishes the restraint disclosed herein from those in which a vertically disposed linear actuator is used to raise the restraint barrier. 
     Returning to the restraint of FIGS. 1-5, the linear member is illustrated in the form of a variable-length actuator  28 . Actuator  28  is schematically illustrated to represent any of a variety of actuators including, but not limited to, a hydraulic cylinder (i.e., a piston moveable within a cylinder to move a piston rod, wherein the term, “rod” encompasses any elongated member), a pneumatic cylinder, and an electromechanical actuator (e.g., a gear-motor driving a linearly extendible rod or elongated member). Here, actuator  28  includes a cylinder  42  having a first point  44  coupled to frame  22  and includes a piston rod  46  having a second point  48  coupled to barrier  14 . In this embodiment, the coupling of first point  44  to frame  22  provides both pivotal and translational movement of the linear member or actuator relative to frame  22 . Thus, the extension and retraction of rod  46  along its centerline  50  respectively raises and lowers barrier  14 . As barrier  14  moves up and down, centerline  50  remains collinear with or parallel to a line  52  extending from point  44  to  48 . Actuator  28  also provides a load path  54  along which a barrier-moving force is transmitted from  44  to  48 , wherein centerline  50 , line segment  52 , and the center of load path  54  remain collinear as the barrier moves up and down. 
     To indicate when barrier  14  is in its stored position or at an operative position that effectively blocks the movement of bar  18 , restraint  10  is provided with two limit switches  56  and  58 . Switches  56  and  58  are schematically illustrated to encompass switches of a variety of styles including, but not limited to, lever-actuated switches, hall-effect proximity switches, photoelectric eyes, motor current sensors (sensing current to a motor-driven barrier actuator), resolver or encoder (sensing rotation of a motor-driven barrier actuator), piston sensor (sensing the position of a piston within a cylinder), pressure sensor (sensing the fluid pressure within a cylinder that moves barrier  14 ), and various combinations thereof. In some embodiments, switch  56  is a hall-effect proximity switch that attaches to frame  22  at a location where barrier  14  can trip switch  56  by lowering to its stored position, adjacent to switch  56 . 
     Switch  58  can be attached to one side plate  38  of barrier  14  and can operate similar to switch  56 , but work in conjunction with a switch actuator  60 . In some embodiments, for example, switch actuator  60  comprises a rod  62  attached to an inverted U-shaped bracket  64 . Rod  62  and bracket  64  pivot about a pin  66  that extends through the two side plates  38  of barrier  14  and through two downwardly extending tabs  68  of bracket  64 . Pin  66 , incidentally, also provides a convenient location for coupling piston rod  46  to barrier  14  at point  48 . In the absence of an ICC bar, a spring  70  acting between bracket  64  and a fixed point  72  on barrier  14  pivots rod  62  clockwise (as viewed in FIG.  3 ). The pivotal motion extends rod  62  above shank  16  and moves at least one tab  68  or some other portion of switch actuator  60  away from switch  58 , as shown in FIG.  3 . 
     When barrier  14  rises against the underside of ICC bar  18 , as shown in FIG. 1, the relative movement between barrier  14  and ICC bar  18  pivots rod  62  counterclockwise about pin  66 . This causes rod  62  to pivot or retract below an upper surface of shank  16  and into a cavity  72  between side plates  38 , which helps protect rod  62  from damage. The downward pivotal motion also causes one tab  68 , or some other portion of switch actuator  60 , to move to a position that trips switch  58 , thus indicating that barrier  14  is in a position to block the movement of bar  18 . 
     Feedback from switches  56  and  58  can be used in conjunction with conventional control circuitry (e.g., control relays, programmable logic controls, etc.) to simply operate one or more lights that indicate the position of barrier  14  relative to frame  22  and/or indicate the position of barrier  14  relative to ICC bar  18 . Feedback from the switches can further be used in controlling the movement of barrier  14 . For example, feedback from switch  56  can be used for automatically discontinuing the retraction of barrier actuator  28  upon barrier  14  reaching its lowered, stored position. 
     If barrier  14  and ICC bar  18  were in the positions shown in FIG. 1, and bar  18  then rose to the position of FIG. 4 (e.g., due to weight being removed from the truck), feedback from switch  58  could serve as a signal that automatically causes actuator  28  to lift barrier  14  until switch actuator  60  trips switch  58  once again. Tripping switch  58  could stop the extension of barrier actuator  28  to keep distal end  20  above the underside of bar  18  without shank  16  exerting excessive force up against bar  18 . 
     If weight is added to the truck, which forces ICC bar  18  down to a second operative position of FIG. 5, but barrier actuator  28  neither extends nor retracts (i.e., the length of line segment  52  defined by points  44  and  48  remains substantially constant), restraint  10  can still allow barrier  14  to descend with bar  18  by virtue of a compliant coupling  74 . Such a coupling can be disposed at almost any location between barrier  14  and frame  22 , including, but not limited to, being disposed somewhere along the length of actuator  28  or at either end of actuator  28 , at point  44  or  48 . 
     In a currently preferred embodiment, compliant coupling  74  is disposed at point  44 . In this example, coupling  74  includes one or more springs  76  stretched between one pin  78  at point  44  and a second pin or anchor  80 , which is fixed at a third point  82  relative to frame  22 . Pin  78  also extends through a trunnion  84  at the lower end of cylinder  42 , and preferably extends through one or more guide blocks  86 . A lower track  88  includes a slot  90  along which pin  78  travels and includes a side flange  92  and a top flange  94  that help guide the movement of block  86 . Thus, as ICC bar  18  forces barrier  14  down (from the first operative position of FIG. 1 to a second operative position of FIG.  5 ), the length of actuator  28  (i.e., the length of line segment  52 ) remains generally constant; point  48  moves down; and point  44 , pin  78 , and block  86  move horizontally to the left, as viewed in FIG.  5 . Both points  44  and  48  move relative to point  82 . The horizontal movement of pin  78  stretches spring  76  to maintain some upward pressure against ICC bar  18 . If bar  18  later returns to its position of FIG. 1, spring  76  pulling on pin  78  causes actuator  28  to keep barrier  14  pressed up against bar  18 . 
     In an alternate vehicle restraint  96 , barrier  14  is moved by an elongated member, such as a fixed-length linear member  98  that is pinned between pins  66  and  78  and is tilted or leaning at an angle from vertical, in order to assume a range of acute angles facing toward dock face  13  as barrier  14  moves up and down, as shown in FIG.  6 . An actuator  28 ′ is pinned between a fixed pin  98  and pin  78  and lies generally horizontally. To raise barrier  14 , actuator  28 ′ retracts to move pin  78  to the right (as viewed in FIG. 6) and pin  66  upward. To lower barrier  14 , actuator  28  extends to move pin  78  to the left (again, as viewed in FIG. 6) and pin  66  downward. Member  98  provides a generally linear load path  100  and a fixed length connection between points  44  and  48  that remains collinear with a line connecting points  44  and  48  as barrier  14  moves up and down. 
     Once in the position of FIG. 6, additional incidental upward movement of ICC bar  18  may release switch actuator  60 , which causes barrier  14  to rise in a manner similar to that of restraint  10 . 
     To allow for some forced downward movement of ICC bar  18 , a pressure relief valve  101  and/or a gas-charged accumulator  106  can be hydraulically coupled to cylinder  42 , as shown in FIG.  6 . Relief valve  101  connects a line  102  leading to the rod end of cylinder  28  to a second line  104  leading to the cylinder end or opposite side of the piston. A hydraulic system (one dedicated to restraint  96  or one associated with a nearby dock leveler) selectively pressurizes lines  102  and  104  to extend and retract rod  46 , thereby respectively lowering and raising barrier  14 . When the weight of a truck forces its ICC bar  18  down, link  98  urges cylinder rod  46  to extend, which builds pressure in line  102 . If the pressure exceeds a predetermined limit, relief valve  101  opens, which allows rod  46  to extend, which in turn allows barrier  14  to descend. As an alternative, or in addition to valve  101 , accumulator  106  can be connected to line  102 . Now, if ICC bar  18  exerts excessive downward force against barrier  14 , the resulting buildup of pressure in line  102  can compress the gas in accumulator  106 . Accumulator  106  taking on hydraulic fluid from line  102  allows piston rod  46  to extend a limited distance to lower barrier  14 . 
     It should be noted that the hydraulic circuit comprising lines  102  and  104 , valve  101 , and accumulator  106  is schematically illustrated in FIG.  6 . The schematic is not intended to show the physical locations of each component, as the components can be positioned almost anywhere. Likewise, cylinder  42  does not necessarily have to be mounted horizontally with rod  46  pointing away from dock face  13 . Cylinder  42  could be mounted in various other positions and still act between point  44  and another point fixed relative to frame  22 . 
     Although the actual structure of barrier  14  can vary, in preferred embodiments barrier  14  includes several features that provide restraints  10  and  96  with strength and durability. For example, a curved member  108  welded between side plates  38  not only strengthens barrier  14 , but an upper tip  110  of member  108  prevents rod  60  from extending above distal end  20  of barrier  14  (see FIG.  4 ). Keeping switch actuator  60  contained within the envelope of barrier  14  helps protect rod  62  from damage. When a truck attempts to pull away from dock  22  while barrier  14  is restraining the truck&#39;s ICC bar, an upper bar  112  welded across the tops of side plates  38  is adapted to engage track channels  40 . Bar  112  engaging channels  40  helps counteract the trucks excessive pullout force, thus reducing the load on rollers  32 . 
     Although the invention is described with reference to a preferred embodiment, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. Therefore, the scope of the invention is to be determined by reference to the claims that follow.