Abstract:
A wheel-activated vehicle restraint for use at a loading dock includes a wheel-blocking barrier that is selectively locked to a frame by a latching mechanism that engages an inverted gear rack. Components of the latching mechanism are arranged to prevent spreading apart upper and lower members of the frame members. The latching mechanism includes an alignment device that helps ensure that the teeth of a latching member positively engages the teeth of the gear rack, thus preventing the teeth from coming together peak-to-peak. An upper rail of the wheel restraint&#39;s frame includes a contoured leading edge that smoothly guides the lift of the wheel-blocking barrier from its stored position to its wheel-chocking position. A wheel support is used to prevent a vehicle&#39;s mud flap from getting pinched between the vehicle&#39;s wheel and a trigger assembly of the wheel restraint.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The subject invention generally pertains to a system for restraining a vehicle at a loading dock, and more specifically to a vehicle restraint that is wheel-actuated.  
           [0003]    2. Description of Related Art  
           [0004]    In the loading and unloading of vehicles at a loading dock, heavy equipment such as forklifts pass into and out of the vehicle to facilitate and expedite the unloading and/or loading of the vehicle. Accordingly, it is important that the vehicle remain generally fixed relative to the loading dock to avoid accidents and to protect the safety of dock personnel. Otherwise, there is a potential hazard for the vehicle to inadvertently move away from the loading dock during the loading/unloading operation. If this were to occur without the knowledge of the dock personnel, they could continue to attempt to move cargo into or out of the vehicle while assuming the vehicle is secured at the dock. Thus, injury to personnel or damage to dock equipment could occur.  
           [0005]    A common method of restraining a vehicle at a loading dock involves manually wedging wheel chocks in front of a vehicle&#39;s wheels. The use of wheel chocks, however, have several drawbacks: 1) the blocks are easily lost or damaged; 2) the blocks may not operate effectively due to a slippery road surface from oil, grit, rain, ice, or snow; 3) wheel chocks are awkward to handle and sometimes difficult to remove from the wedged position; 4) vehicles have been known to drive over wheel chocks; and 5) manually reaching underneath a vehicle (to insert or remove chocks) is inherently hazardous.  
           [0006]    Given the potential hazards of such manual placement of wheel chocks, automated chocking systems have been employed. While such systems are safer and more convenient than manual positioning of chocks, they may have their own disadvantages. For example, such systems may not be suitable for some vehicles, because the vehicle&#39;s undercarriage, tailgate lifts, mud flaps or adjacent tires, may interfere with the movement of the chock as the chock attempts to engage the wheel. In addition, automated chocking systems may not be adjustable to accommodate the large range of tire sizes on cargo vehicles. Such systems may also be awkward, difficult and time consuming to engage and disengage from the vehicle parked at the dock.  
           [0007]    To overcome the disadvantages of these earlier automated chocking devices, improved automated chocking systems are disclosed in U. S. Pat. Nos. 5,762,459 and 5,582,498 and in co-pending application Ser. No. 09/477,264; all of which are expressly incorporated by reference herein. The disclosure of the present invention provides further improvements and enhancements to the designs of the incorporated references.  
         SUMMARY OF THE INVENTION  
         [0008]    In some embodiments, a vehicle restraint includes a latching member that engages an inverted gear rack whose gear teeth point downward to prevent dirt and ice from accumulating between the gear teeth.  
           [0009]    In some embodiments, a vehicle restraint includes an upper rail with a contoured leading edge for smoothly guiding a wheel-blocking barrier from a stored position to an elevated wheel-chocking position.  
           [0010]    In some embodiments, a wheel support helps prevent a low hanging mud flap from getting pinched between a trigger assembly of the vehicle restraint and the vehicle&#39;s wheel.  
           [0011]    In some embodiments, a tooth alignment device helps align the teeth of a latching member to that of a gear rack.  
           [0012]    In some embodiments, the tooth alignment device includes a movable alignment tooth that is offset relative to the pitch spacing of other teeth.  
           [0013]    In some embodiments, the alignment tooth is spring loaded to protrude beyond adjacent teeth.  
           [0014]    In some embodiments, the components of a vehicle restraint are arranged to avoid developing on the vehicle restraint&#39;s frame a bending moment that may otherwise exist as a latching member engages a gear rack. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a side view of a vehicle parked at a loading dock and restrained by a vehicle restraint in a wheel-chocking position according to one embodiment.  
         [0016]    [0016]FIG. 2 is an opposite side view of the vehicle restraint of FIG. 1, however, with the vehicle removed and the restraint in a stored position.  
         [0017]    [0017]FIG. 3 is a top view of the vehicle restraint of FIG. 2, but with a lock assembly of the restraint moved to a chocking position.  
         [0018]    [0018]FIG. 4 is a partial side view of the vehicle restraint of FIG. 1, but with the restraint in its stored position and a wheel near the start of its dockward movement.  
         [0019]    [0019]FIG. 5 is similar to FIG. 4, but with the wheel closer to the dock.  
         [0020]    [0020]FIG. 6 is similar to FIG. 5, but with the restraint in the chocking position and the wheel even closer to the dock.  
         [0021]    [0021]FIG. 7 is similar to FIG. 6 with the restraint in the chocking position but with the restraint&#39;s lock assembly not yet latched in place.  
         [0022]    [0022]FIG. 8 is similar to FIG. 7, but with the lock assembly locked in place.  
         [0023]    [0023]FIG. 9 is a cross-sectional view taken along line  9 - 9  of FIG. 7.  
         [0024]    [0024]FIG. 10 is a cross-sectional view taken along line  10 - 10  of FIG. 8.  
         [0025]    [0025]FIG. 11 a  is a cross-sectional view taken along line  11 - 11  of FIG. 9 showing a latch member properly aligned but disengaged from a gear rack.  
         [0026]    [0026]FIG. 11 b  is similar to FIG. 11 a,  but with an alignment tooth of the latch member just making contact with the gear rack.  
         [0027]    [0027]FIG. 11 c  is similar to FIG. 11 a,  but showing the alignment tooth retracting into a pocket in the latch member.  
         [0028]    [0028]FIG. 11 d  is similar to FIG. 11 a,  but with the latching member fully engaging the gear rack.  
         [0029]    [0029]FIG. 12 a  is similar to FIG. 11 a,  but with the teeth of the latching member and the gear rack in peak-to-peak alignment with each other.  
         [0030]    [0030]FIG. 12 b  is similar to FIG. 12 a,  but showing an alignment tooth of the latching member engaging the gear rack.  
         [0031]    [0031]FIG. 12 c  is similar to FIG. 12 b,  but showing how the engagement of the alignment tooth in the gear rack and the tooth&#39;s retraction into an angled pocket corrects the alignment of the latching member to the gear rack.  
         [0032]    [0032]FIG. 12 d  is the same as FIG. 11 d  to illustrate how an initially misaligned latching member can end up fully engaged with the gear rack just as in the case of the properly aligned latching member of FIG. 11 a.    
         [0033]    [0033]FIG. 13 is similar to FIGS. 11 d  and  12   d,  but with the cross-sectional lines omitted to clearly show forces associated with the latching mechanism in the latched position.  
         [0034]    [0034]FIG. 14 is a first of three drawings showing the sequence of a wheel entering the actuation assembly of the vehicle restraint of FIG. 1.  
         [0035]    [0035]FIG. 15 is a second of three drawings showing the sequence of a wheel entering the actuation assembly of the vehicle restraint of FIG. 1.  
         [0036]    [0036]FIG. 16 is a third of three drawings showing the sequence of a wheel entering the actuation assembly of the vehicle restraint of FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0037]    A tire-actuated vehicle restraint  10  according to the present invention is shown in an illustrative operating environment in FIG. 1. The restraint device  10  engages a leading tire  12  of a vehicle  14  to maintain vehicle  14  in a loading/unloading position adjacent a loading dock  16 . Throughout the specification and claims, the terms “wheel” and “tire” are used interchangeably and refer to the combination of a wheel and a tire rotatably mounted to a vehicle. Thus, an action performed on a tire is also performed on a wheel, and vice versa. Tire  12  is referred to as the “leading” tire as it is the first to approach dock  16  as vehicle  14  backs into position over a roadway  18 . The term, “roadway” is meant to broadly encompass vehicle support surfaces of every kind including roads, driveways, ramps, bridges, pits, truck leveler surfaces, and the like.  
         [0038]    As is conventional, dock  16  shown in FIG. 1 includes a dock leveler  20 , which spans the gap between the rear of a truck and an elevated floor  22  of loading dock  16  to allow forklifts and other dock equipment and personnel to pass into and out of the bed of the vehicle. As leveler  20  is pivoted relative to dock  16 , it also serves to compensate for height differentials between the bed of the truck and floor  22  as may arise during loading and unloading of the vehicle  14 . As is also conventional, dock  16  may include a bumper  25  that a rear end of vehicle  14  may abut when vehicle  14  is in the loading/unloading position of FIG. 1.  
         [0039]    In FIG. 1, vehicle restraint  10  is shown in a chocking and latched position in which restraint  10  helps prevent vehicle  14  from moving away from dock  16  while it is being loaded or unloaded. As will be described in greater detail below, restraint  10  is moved into the chocking position, in which a lock assembly  24  (see FIG. 2) engages the leading and trailing surfaces of wheel  12  by means of the dockward movement of wheel  12  itself. Accordingly, restraint  10  is referred to as being “wheel-activated.” In addition, vehicle restraint  10  includes the feature of being variable to automatically accommodate and successfully chock wheels having a wide range of sizes. Once restraint  10  is in the chocking position, in which lock assembly  24  engages wheel  12 , lock assembly  24  can be latched into position relative to dock  16  by an operator controlled latching mechanism  26 . Once the operator controlled latching mechanism is activated, restraint  10  actively prevents vehicle  14  from moving away from the dock face. Conversely, de-activation of operator controlled latching mechanism  26  allows the vehicle to move away from dock  16  after the loading/unloading operation is completed, thereby re-positioning lock assembly  24  back in the stored position for activation by the wheel of the next vehicle.  
         [0040]    The elevation view of vehicle restraint  10  in FIG. 2 shows the various components comprising the restraint. Lock assembly  24  is shown in a stored position at the distal end of a frame  28 . The end of frame  24  furthest from the dock  16  will be referred to as a distal end  30 , while the end adjacent the dock face will be referred to as the dock end. According to the invention, the lock assembly is activated by wheel  12  as it travels in a dockward direction over roadway  18 . In response, lock assembly  24  moves along frame  28  from the distal, stored position of FIG. 2 to a plurality of chocking positions, such as that shown in FIGS. 1, 3, and  6 - 10 . The position shown in FIG. 6 is a chocking position, since wheel  12  is engaged on both its leading edge (as at  32 ) and at its trailing edge (as at  34 ). Once lock assembly  24  moves to a chocking position, further dockward movement of wheel  12  simply causes lock assembly  24  to move dockward along with the wheel. Once wheel  12  and vehicle  14  are adjacent the dock in the loading/unloading position, the operator controlled latching mechanism  26  may be actuated to latch lock assembly  24  in place along frame  28 , thus blocking movement of vehicle  14  away from the dock.  
         [0041]    Returning to FIG. 2, frame  28  includes a stationary member, illustratively in the form of a guide member  36  disposed adjacent roadway  18 . In the present embodiment, and as seen in the cross-sectional of FIG. 9, guide member  36  is shown in the shape of an I-beam including an upper flange, a lower flange and a vertical web portion, the space between the flanges forming a track on each side of the web. The I-beam is fixed to roadway  18  in the present embodiment, although it could also be simply disposed along roadway  18  or spaced therefrom, depending on the nature of the installation. Frame  28  also includes an upper rail  38 , which, in the present embodiment, is disposed above and separated from guide member  36 . In some embodiments, rail  38  can be separate or connected to guide member  36 . At its distal end, rail  38  includes a ramp portion  40 , which is angled toward roadway  18 . An upper surface  42  of ramp portion  40  serves as a camming surface to assist movement of lock assembly  24  from the stored position of FIG. 4 through an intermediated position of FIG. 5 and to the chocking position of FIG. 6, as described in greater detail below. Latching mechanism  26  includes a latching bar  44 , shown depending from upper rail  38  and a latching member  46 . In all, latching mechanism  26  comprises latching bar  44 , latching member  46 , a support bar  107 , a bracket  118 , pins  122 , a gear rack  106 , a gear rack segment  110 , spacers  126 , all of which will be explained later in greater detail. Latching mechanism  26  is actuated by an actuator  48  shown mounted to frame  28 . Examples of actuator  48  include but are not limited to a hydraulic cylinder, pneumatic cylinder, motor-driven linear actuator, and various combinations thereof.  
         [0042]    Lock assembly  24  includes an actuation assembly  50  and a locking arm  52  (also referred to as a locking arm or chock assembly). Actuation assembly  50  moves relative to and along frame  28 , and serves to actuate locking arm  52  between the stored position of FIGS. 2 and 4 and the chocking position of FIG. 6 in response to the dockward movement of wheel  12  as vehicle  14  backs into the loading/unloading position adjacent the dock. At the same time, the structure of actuation assembly  50  serves to properly size the wheel and capture the leading edge at an engagement point  54  in FIG. 6, while moving locking arm  52  to capture the trailing edge of the wheel as at point  56  in FIG. 6.  
         [0043]    To achieve the automatic positioning function and the wheel sizing function, actuation assembly  50  includes a trigger assembly  58 , and a trolley assembly  60 . Both trigger assembly  58  and trolley assembly  60  move linearly along guide member  36  between the stored position of FIG. 2 and a plurality of chocking positions, such as that shown in FIG. 6. Trigger assembly  58  also engages and moves along roadway surface  18  in response to movement of wheel  12 . Toward that end, trigger assembly  58  comprises a guiding portion  62  and a tire-engaging portion  64 . To allow trigger assembly  58  to move along guide member  36 , the guiding portion, according to the present embodiment, includes rollers  66 . Rollers  66  are received within the tracks formed in I-beam  36  between the top flange and bottom flange to guide the movement of trigger assembly  58 . In a like manner, trolley assembly  60  includes rollers  68 , which are also disposed within tracks in I-beam  36  to guide the movement of trolley assembly  60  along the I-beam guide member  36 .  
         [0044]    The tire-engaging portion  64  of trigger assembly  58 , according to the present embodiment, includes roadway-engaging rollers  70  to provide a smooth rolling action as the tire-engaging portion  64  travels over roadway surface  18 . Tire-engaging portion  64  also includes tire-engaging roller  72 . Since the dockward traveling wheel  12  will engage roller  72  at an engagement point  54 , the ability of this roller to rotate ensures that wheel  12  will not roll up and over the tire-engaging portion  64 . Rather, the wheel will roll against roller  72 , and the tire-engaging portion  64  will be pushed dockward under the influence of wheel  12 .  
         [0045]    Resilient members, such as springs  74 , provide a coupling that couples trigger assembly  58  to trolley assembly  60 , while allowing some relative movement between the two. Trolley assembly  60  and trigger assembly  58 , according to the present embodiment, each include spring tabs for receiving the respective ends of the springs  74 . Springs  74  allow trigger assembly  58  to move relative to trolley assembly  60  until the springs reach a predetermined amount of tension to facilitate movement of the trolley assembly in a dockward direction. As will be described in greater detail below, this action allows the actuation assembly  50  to adjust to properly size and engage tire  12  of vehicle  14  as it backs toward the loading/unloading position. According to some embodiments, a limiting assembly comprising a stop bar  76  (FIG. 3) is provided between trolley assembly  60  and the trigger assembly  58 . Stop bar  76  limits the maximum separation between the trigger assembly  58  and the trolley assembly  60  to prevent springs  74  from being stretched beyond their limit. Stop bar  76  extends through holes in blocks  78  and  80  fixed to trigger assembly  58  and trolley assembly  60 , respectively. The maximum separation distance is defined by the location of lock nuts  82 . If the maximum separation is reached, stop bar  76  causes trolley assembly  60  to be pulled by trigger assembly  58  without further stretching of springs  74 .  
         [0046]    As can be seen in FIG. 6, locking arm  52  is disposed distally of the trigger assembly  58  and is operatively connected to trolley assembly  60 . In the present embodiment, this operative connection is at a connection point, designated  84  in FIG. 6 and, which in the present embodiment comprises a pivotal connection. Connection point  84  and trigger assembly  58  are selectively positionable relative to each other, since trigger assembly  58  can move in a dockward direction without movement of trolley assembly  60  or locking arm  52 .  
         [0047]    Locking arm  52  includes a proximal end (relative to frame  28 ) adjacent connection point  84  of trolley assembly  60 . Locking arm  52  also includes a first roller  86  (FIGS. 3, 9 and  10 ) disposed at its proximal end. As seen in the top view of FIG. 3, locking arm  52  also includes a wheel-blocking barrier  88  having a second roller  90  disposed at the distal end of the locking arm and projecting away from frame  28  into the path of wheel  12  along roadway  18 . Preferably, rollers  86  and  90  are on a common shaft  92 . As is also clear from FIG. 3, locking arm  52 , according to the present embodiment includes sideplates  94  and  96  and a top plate  98 . A hole  100  in top plate  98  provides a convenient place to temporarily insert a pipe or rod, which can then serve as a handle for manually manipulating actuation assembly  50  along upper rail  38 .  
         [0048]    Locking arm  52  is intended to move from the stored position of FIG. 4 to the chocking position of FIG. 6 as actuation assembly  50  (comprising trigger assembly  58  and trolley assembly  60 ) moves in a dockward direction as activated by wheel  12 . Referring to FIG. 5, as trolley assembly  60  moves in a dockward direction, connection point  84 , between trolley  60  and locking arm  52  also moves dockward. This in turn causes roller  86  to begin moving along top camming surface  42  of ramp portion  40 . Surface  42  is preferably curved to provide locking arm  52  with a smooth transition from its stored position of FIG. 4 to its elevated position of FIG. 6. In some cases, a lower section  102  of camming surface  42  is concave and an upper section  104  is convex to reduce the vertical acceleration and deceleration of roller  86  when locking arm  52  is near its stored position or near its fully elevated position. This enhances the tracing capability of roller  90  along the periphery of the tire. As roller  86  continues upward along camming surface  42 , locking arm  52  rotates about pivotal connection point  84 . As trolley assembly  60  continues dockward, roller  86  reaches the top of camming surface  42 , and engages the generally horizontal top surface of upper rail  38 . The locking arm is now in the chocking position where wheel-blocking barrier is elevated as shown in FIG. 6. Further dockward movement of trolley assembly  60  does not change the orientation of locking arm  52  and barrier  88  relative to the trolley assembly  60 . Rather, locking arm  52  and barrier  88  simply stay in an elevated chocking position, and continue to move along with vehicle  14 .  
         [0049]    As locking arm  52  was moving from the stored position to the chocking position as just described, the attached second roller  90  was moving along with it. As will now be described in greater detail with reference to FIGS.  4 - 6 . Such movement, as effected by movement of trigger assembly  58  and trolley assembly  60  as activated by wheel  12 , properly sizes and chocks wheel  12  and allows roller  90  of barrier  88  to initially engage a bottom portion of wheel  12  and move along the peripheral surface of the tire to the chocking position shown in FIG. 6. FIG. 4 shows wheel  12  as it first engages trigger assembly  58  by contact at an engagement point  54  with the tire-engaging roller  72 . Since locking arm  52  and roller  90  are disposed distally (to the right in the sense of FIG. 6) relative to trolley assembly  60 , wheel  12  is now disposed between roller  90  and roller  72  of trigger assembly  58 , thereby automatically adjusting itself to the size of wheel  12  shown in FIG. 6. Continued dockward movement of wheel  12  moves trigger assembly  58  in a dockward direction.  
         [0050]    As the wheel  12  continues dockward, the tension within springs  74  allows trolley assembly  60  to be pulled in a dockward direction. As described in detail above, such dockward movement of trolley assembly  60  causes locking arm  52  and wheel-blocking barrier  88  to begin moving from their stored position (FIG. 4) toward the chocking position, such initial movement being shown in FIG. 5. The locking arm is thus resiliently biased from the stored position to a chocking position and moves to the chocking position by the engagement between the wheel and trigger mechanism  58 . As locking arm  52  moves toward the chocking position, roller  90  of locking arm  88  moves along and maintains contact with the peripheral surface of wheel  12 . During this operation, the separation between connection point  84  and trigger assembly  58  may increase as more of the wheel is positioned therebetween. This is a further example of selective positioning between trigger  58  and connection point  84 . As the wheel continues toward the dock, trigger assembly  58  continues dockward and, because of springs  74 , pulls trolley assembly  60  such that the trigger and trolley move together and effect the continued movement of locking arm  52  to the chocking position, as shown in FIG. 6.  
         [0051]    Once locking arm  52  is in the chocking position, further dockward movement of wheel  12  simply translates lock assembly  24  further dockward, as it is maintained in the chocking position. When vehicle  14  is backed all the way up to the dock in the loading/unloading position, the latching mechanism  26  is actuated to hold locking arm  52  and barrier  88  in place along frame  28 . Barrier  88  being elevated and held stationary can now prevent excessive movement of vehicle  14  away from the dock.  
         [0052]    Latching mechanism  26  is actuated to latch lock assembly  24  into position along frame  28  when lock assembly  24  is in a chocking position as shown in FIG. 1, and once vehicle  14  has backed into the loading/unloading position adjacent dock  16 . Latching mechanism  26 , according to the present embodiment, latches lock assembly  24  in position along frame  28  by selectively securing trolley assembly  60  to a gear rack  106 , which is fixed relative to frame  28 . The term, “gear rack” is meant to encompass any elongated member having a series of spaced features such as teeth, holes, or indentations. Since locking arm  52  is operatively connected to trolley assembly  60 , the securement of trolley assembly  60  to gear rack  106  (and thus securement to frame  28 ) also prevents movement of locking arm  52  in a direction away from the dock. Movement of vehicle  14  away from the dock is thus restrained.  
         [0053]    To selectively secure trolley assembly  60  to gear rack  106 , latching mechanism  26  includes latching member  46 , which is carried by trolley  60  and selectively engageable with gear rack  106 . In a preferred embodiment, gear rack  106  is attached to the underside of upper rail  38  by way of a support bar  107 . In the present embodiment, gear rack  106  has a series of gear teeth  108  (FIG. 11 a ) that point downward to inhibit dirt and ice from plugging the space between the teeth. Latching member  46  includes a similar but much shorter segment  110  of gear rack  106  that can move vertically relative to trolley assembly  60 ; however, horizontal movement between latching member  46  and trolley assembly  60  is very limited. The gear teeth  112  of latching member  46  point upward so latching member  46  can be lifted up against gear rack  106  to engage teeth  112  with teeth  108 .  
         [0054]    To provide vertical movement between latching member  46  and trolley assembly  60 , latching member  46  includes a shank  114  that slides vertically within a hole in a top plate  116  (FIG. 9) of trolley assembly  60 . Latching member  46  also includes a bracket  118  with upper flanges  120  (FIG. 10). Bracket  118  helps shelter gear segment  110  from dirt and ice and allows latching bar  44  to raise and lower latching member  46 . In a preferred embodiment, two latching bars  44  slide along either side of gear rack  106  and support bar  107 . Latching bars  44  extend through bracket  118  to engage its upper flanges  120 , which enables the vertical movement of latching bars  44  to raise and lower latching member  46  in and out of engagement with gear rack  106 .  
         [0055]    Coupling each latching bar  44  to support bar  107  provides vertical movement of latching bar  44 . A series of pins  122  interconnecting latching bars  44  also extends through a corresponding series of sloped slots  124  in bar  107  (FIG. 13). Because pins  122  are free to slide within slots  124 , linear movement of latching bar  44  in a direction parallel to upper rail  38  translates into vertical movement of latching bar  44 . Spacers  126  allow gear rack  110  to fit between latching bars  44  and minimizes wear between support bar  107  and latching bars  44 . In addition, various other wear pads can be installed to protect other surfaces subject to sliding motion and wear. In reference to FIGS. 7 and 8, as actuator  48  extends to move latching bar  44  to the right, pins  122  engage the sidewalls of slots  124  such that the sidewalls urge latching bar  44  upward, which in turn forces latching member  46  to engage gear rack  106 . Actuator  48  retracting moves latching bar  44  to the left, which lowers and disengages latching member  46  from gear rack  106 . Thus, selectively extending and retracting actuator  48  respectively locks (FIG. 8) and releases (FIG. 7) locking arm  52  relative to frame  28 . Initiating the actuation of actuator  48  can be done in any conventional manner, such as in response to the action of a dockworker (e.g., operating a push button, switch, lever, etc.) or in response to an automatic sensor that determines that vehicle  14  is properly parked at the dock and is ready to be loaded or unloaded.  
         [0056]    The physical relationship of upper rail  38 , support bar  107 , gear rack  106 , pin  122 , slot  124 , and latching member  46  are such that the latching force does not tend to spread upper rail  38  and lower guide member  36  apart. Rather, the latching force is isolated to certain components of latch mechanism  26 , such as latching member  46 , gear rack  106 , support bar  107  and pin  122 . With latching member  46  being interposed between rail  38  and guide member  36  in the configuration shown in FIGS. 9 and 13, an upward latching force  128  exerted by latching member  46  against gear rack  106  is countered by a corresponding reaction force  130  that pin  122  exerts against a side wall of slot  124  in support bar  107 . Since forces  128  and  130  are not transmitted through rail  38  and guide member  36 , those structures do not need to be designed to withstand such forces.  
         [0057]    When lifting bar  44  lifts latching member  46  against gear rack  106 , the gear teeth of both members may initially meet peak-to-peak, rather than meshing into full engagement. When this occurs, only slight incidental movement of lock assembly  24  is needed to jog the members from peak engagement to full engagement. Such incidental movement can occur naturally or can be deliberately forced by providing latch member  46  with an alignment member that guides latching member  46  and gear rack  106  together. In some embodiments, the alignment member is a spring-loaded alignment tooth  132 , as shown in FIGS. 11 a - 11   d  and  12   a - 12   d.  In this example, alignment tooth  132  slides along an angle within a pocket  134  in gear segment  110 . A spring  136  (e.g., resilient polymeric spring, coil spring, leaf spring, etc.) biases alignment tooth  132  to protrude above teeth  112 . When extended, alignment tooth  132  is displaced or offset relative to whatever certain pitch that teeth  112  are distributed, wherein the pitch is the peak-to-peak or center-to-center spacing of teeth  112 . When alignment tooth  132  retracts within pocket  134 , alignment tooth  132  becomes aligned with the same pitch as teeth  112 . Such a tooth alignment system ensures solid engagement between the teeth of latching member  46  and gear rack  106  regardless of how the two are aligned as they initially come together.  
         [0058]    If the teeth of gear rack  106  and latching member  46  are properly aligned as they start coming together, the operating sequence generally follows that of FIGS. 11 a - 11   d.  FIG. 11 a  shows latching member  46  properly aligned directly underneath gear rack  106 . As latching member  46  rises, alignment tooth  132  touches one tooth  108 ′ of gear rack  106 , as shown in FIG. 11 b.  As latching member  46  continues rising, alignment tooth  132  slides along the back of tooth  108 ′, while spring  136  compresses, as shown in FIG. 11 c.  Finally, in FIG. 11 d,  alignment tooth  132  retracts completely as teeth  112  of latching member  46  fully engage teeth  108  of gear rack  106 .  
         [0059]    If members  46  and  106  are aligned so the peaks of their teeth will meet, as shown in FIG. 12 a,  then the operating sequence generally follows that of FIGS. 12 a - 12   d.  In FIG. 12 b,  latching member  46  inserts alignment tooth  132  between teeth  108 ′ and  108 ″ of gear rack  106 . In FIG. 12 c,  continued upward movement of latching member  46  forces latching member  46  to shift slightly over to the left as the upward movement forces alignment tooth  132  to retract. The shifting motion of latching member  46  is provided by clearance or anticipated give between or within restraint  4  and vehicle  14 . As alignment tooth  132  shifts over, teeth  112  of latching member  46  are able to fully engage teeth  108  of gear rack  106 , as shown in FIG. 12 d  (which is the same end result as shown in FIG. 11 d ).  
         [0060]    In some embodiments, as vehicle  14  begins backing into dock  16 , a first wheel support  140  helps prevent a mud flap  142  of vehicle  14  from getting pinched at engagement point  54  between wheel  12  and tire-engaging roller  72  of trigger assembly  58 . Wheel support  140  includes an upper surface  141  that protrudes above roadway  18  at a location between tire-engaging roller  72  and barrier  88  when locking arm  52  is at its stored position of FIG. 14. In this way, wheel support  140  forces vehicle  14  to lift the lower edge of mud flap  142  up and over tire-engaging roller  72 . The process is shown sequentially in FIGS. 14, 15 and  16 .  
         [0061]    The size and location of wheel support  140  can affect its function significantly. If upper surface  141  is too high, it tends to cut into the tire. If upper surface  141  is too low or too close to roller  90  of barrier  88 , wheel support  140  becomes ineffective in lifting mud flap  142  over tire-engaging roller  72 . Upper surface  141  of wheel support  140  should be a predetermined distance  143  away from roller  90 , with distance  143  being greater than a diameter  145  of roller  90 . Distance  143  is preferably about 6.75 to 7.75 inches when roller diameter  145  is 3.5 inches. Also, good results have been achieved when the uppermost point or apex of surface  141  is no higher than roller  90 , and no more than one-inch lower than the upper surface of roller  90 . Wheel support  140  preferably includes an inclined surface  144 , so barrier  88  does not catch on wheel support  140 , which might prevent locking arm  52  from traveling along camming surface  42 . In some embodiments, trigger assembly  58  includes an upper inclined surface  147  facing away from wheel support  140 . Inclined surface  147  helps guide a lower edge of mud flap  142  away from tire-engaging roller  72  as wheel  12  start descending upon driving back off of wheel support  140 .  
         [0062]    In some cases, another wheel support  146  can be installed on the other side of barrier  38 . Here, wheel support  146  includes an inclined surface  148  that smoothly leads wheel  12  over barrier  88 . Wheel supports  140  and  146  can each be provided with a second inclined surface. Having a pair of inclined surfaces provides a relatively strong wheel support structure with a minimal amount of material. Moreover, the second inclined surface of wheel support  140  provides wheel  12  with a ramp for traveling over barrier  88  upon departing the loading dock.  
         [0063]    In some embodiments, the vehicle restraint may include signaling components to enhance the safety of vehicle loading and unloading. As one example of such safety enhancements, the restraint according to the invention may be provided with a switch that is responsive to movement of latching bar  44  to the latching position for illuminating a visual signal. For this purpose, a switch  150  is disposed at a position such that it will sense movement of latching bar  44  to the latching position. In the present embodiment, this is achieved by switch  150  being disposed adjacent one end of latching bar  44  when latching bar is in the unlatched position of FIG. 7. As latching bar  44  moves to the latching position of FIG. 8, latching bar  44  interacts with switch  150 ; causing it to emit a signal that latching bar  44  is in the latching position. Switch  150  may be any of a variety of sensors, including (by way of example) electromechanical, magnetic and electro-optic sensors. Accordingly, the “interaction” of latching bar  44  with switch  150  may be a mechanical interaction, or it may simply be bar  44  passing in front of an electric eye or the like. In any event, latching bar  44  is shown interacting with switch  150  in the position of FIG. 8. Switch  150  is further connected to electronics (not shown), which illuminate a visual signal, such as a green light  152  (FIG. 1) upon movement of latching bar  44  to the latching position. Since the activation of switch  150  serves as an indication that a vehicle is safely restrained at loading dock  16 , an inside green light  152  serves as an indication to the dock personnel that vehicle  14  is restrained and may be safely loaded or unloaded. In addition, the switch  150  may also serve to illuminate a corresponding outside red signal (not shown). An inside red light  154  responsive to switch  150  serves as an indication to the dock personnel that the vehicle is not restrained in a loading/unloading position.  
         [0064]    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.