FIELD OF THE DISCLOSURE 
     This patent generally pertains to vehicle restraints and, more specifically, to vehicle restraints with anti-rotation features. 
     BACKGROUND 
     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. Some known restraints include a hook-style vehicle restraint that engages what is often referred to in the industry as a truck&#39;s ICC bar (Interstate Commerce Commission bar) or RIG (Rear Impact Guard). An ICC bar or RIG comprises 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. 
     A RIG, 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. To release the truck and prepare for the next truck to enter the dock, many restraints descend below the bar to a preparatory position. Although the horizontal bar of a RIG is fairly standardized, the bar&#39;s supporting structure can vary significantly. In some cases, the supporting structure can interfere with the operation of the restraint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an example vehicle restraint constructed in accordance with the teachings disclosed herein, wherein an example vehicle is shown approaching the example vehicle restraint. 
         FIG. 2  is a side view similar to  FIG. 1 , but showing the example vehicle restraint being engaged by the example vehicle. 
         FIG. 3  is a side view similar to  FIG. 1 , but showing an example barrier of the vehicle restraint of  FIGS. 1 and 2  in an example blocking position. 
         FIG. 4  is a side view similar to  FIG. 3 , but showing the example vehicle having pushed the example barrier of  FIGS. 1-3  to an example intermediate blocking position. 
         FIG. 5  is a side view similar to  FIG. 4 , but showing the example vehicle restraint moving to an example release position. 
         FIG. 6  is a side view similar to  FIGS. 1-5 , but showing the example vehicle restraint in the release position. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-6  show an example vehicle restraint  10  that helps prevent a vehicle  12  (e.g., truck, trailer, etc.) from accidentally moving too far forward away from a dock face  14  of a loading dock  16  while cargo is being added or removed from the vehicle. To limit such forward movement, restraint  10  includes a barrier  18  moveable to a range of blocking positions for capturing or restraining the vehicle&#39;s RIG  20  (Rear Impact Guard), also known as an ICC bar (Interstate Commerce Commission bar). The term, “RIG” encompasses the horizontal impact bar and/or the framework or structure that connects the bar to the vehicle. 
     In the illustrated example, the range of blocking positions of barrier  18  includes an upper blocking position ( FIG. 3 ) and an intermediate blocking position ( FIG. 4 ). Barrier  18  is also movable to a stored position ( FIGS. 1 ,  2  and  6 ) to release vehicle  12 . In the illustrated example, the intermediate blocking position is between the blocking position and the stored position. With barrier  18  in a blocking position, securing vehicle  12 , a dock leveler  22  can be deployed to provide a bridge across which forklifts and other material handling equipment can travel to transfer cargo between vehicle  12  and an elevated platform  24  of dock  16 . 
     To ensure that barrier  18  can positively restrain RIG  20 , some examples of vehicle restraint  10  include a brace  26  movable between a supporting position ( FIGS. 3 and 4 ) to support or engage barrier  18  and a release position ( FIGS. 1 ,  2  and  6 ) to release or disengage barrier  18 . With brace  26  in the supporting position, as shown in  FIGS. 3 and 4 , brace  26  restricts or limits the downward movement of barrier  18  in a direction away from the dock face  14 . If vehicle  12  attempts separating or moving away from elevated platform  24  prematurely (e.g., in a direction away from dock face  14 ), RIG  20  urges barrier  18  to move or rotate toward the stored position. Barrier  18  may be configured to be yieldable in the rotational direction in order to protect the actuator  42  and its related components from, for example, damage. However, brace  26  holds or engages barrier  18  at a position or height sufficient to enable barrier  18  to restrain or engage RIG  20  as shown in  FIG. 4 . 
     The vehicle restraint  10  of the illustrated example includes a track  28  attached to dock face  14 . The vehicle restraint  10  also includes a main body  30  mounted to travel (e.g., substantially vertically) along track  28  and one or more springs  32  to urge main body  30  toward the dock leveler  22  or the RIG  20  (e.g., an upward direction in the orientation of  FIG. 1 ). A shaft  34  connects or couples barrier  18  to main body  30  such that barrier  18  can rotate about a first axis  36  relative to main body  30  and a shaft  38  connects or couples brace  26  to main body  30  such that brace  26  can rotate about a second axis  40  relative to main body  30 . An actuator  42  moves or positions barrier  18  between the stored position and the blocking position and moves brace  26  between the supporting position and the release position. In the illustrated example, actuator  42  is shown as a single cylinder (i.e., one piston/cylinder apparatus) coupled to barrier  18  at a first connection point  44  and coupled to brace  26  at a second connection point  46 . Other examples of actuator  42  include, but are not limited to, multiple cylinders, a solenoid, a linear motor, an electric motor, a hydraulic motor, a spring, and/or various combinations thereof. 
     One operation example of vehicle restraint  10  follows the sequence of  FIGS. 1-6 .  FIG. 1  shows vehicle  12  backing into dock  16  and approaching vehicle restraint  10 . At this point in the operation, spring  32  holds main body  30  at an elevated preparatory elevation or position to receive or be engaged by RIG  20 . To allow vehicle  12  to move RIG  20  over the top of barrier  18 , actuator  42  retracts to rotate brace  26  to its release position and to rotate barrier  18  to its stored position. In some examples, brace  26  rotates or travels between the release position and the supporting position at least partially simultaneously with barrier  18  as barrier  18  rotates or travels between the stored position and the blocking position. The barrier&#39;s center of gravity relative to first axis  36  assists in rotating barrier  18  to its stored position.  FIG. 1  shows barrier  18  resting upon a stop  48  that prevents barrier  18  from rotating below its stored position. Another stop  50  prevents brace  26  from rotating past its release position. 
     Next,  FIG. 2  shows vehicle  12  continuing to move back toward dock face  14 . Upon doing so, RIG  20  forces the vehicle restraint&#39;s main body  30  downward by RIG  20  sliding along a ramp portion  52  of main body  30 . In cases where RIG  20  is exceptionally low, an articulated lead-in ramp extension  54  is used in some examples to guide RIG  20  onto ramp  52 . In this example, a set of rollers  56  on main body  30  and extending into track  28  reduces (e.g., minimizes) friction as main body  30  travels vertically along track  28 . As RIG  20  pushes main body  30  down, as shown in  FIG. 2 , barrier  18  remains in its stored position, and brace  26  is in its release position. 
     Referring to  FIG. 3 , after RIG  20  pushes main body  30  down to a lowered operative elevation or position ( FIGS. 3-6 ) and after the vehicle  12  moves the RIG  20  sufficiently close to dock face  14 , actuator  42  is energized and/or moves from a restored state ( FIGS. 1 ,  2 ,  5  and  6 ) to an activated state ( FIGS. 3 and 4 ). The activated state is defined as the condition in which actuator  42  urges barrier  18  toward its upper blocking position or at least attempts to hold barrier  18  at a blocking position. The restored state is defined as the condition in which actuator  42  urges or at least allows barrier  18  to return to its stored position. 
     In some examples of the activated state, hydraulic pressure  58  at a cylinder-end port  60  of actuator  42  extends actuator  42  to rotate barrier  18  about first axis  36  toward the barrier&#39;s upper blocking position and rotate brace  26  (e.g., simultaneously) about second axis  40  to the brace&#39;s supporting position. Specifically, the extension of actuator  42  rotates first connection point  44  about first axis  36  from a first position shown in  FIG. 2  to a second position shown in  FIG. 3 . The extension of actuator  42  also rotates (e.g., simultaneously) second connection point  46  about second axis  40  from a first location shown in  FIG. 2  to a second location shown in  FIG. 3 . As viewed from the perspective of  FIGS. 2 and 3 , barrier  18  and brace  26  rotate in the same direction (e.g., a clockwise direction in the orientation of  FIG. 3 ) as actuator  42  extends between the restored state and the activated state. A stop  62  prevents brace  26  from rotating past its supporting position shown in  FIG. 3 . With brace  26  in its supporting position and barrier  18  in its upper blocking position, vehicle restraint  10  restrains vehicle  12  at dock  16 , so dock leveler  22  can be deployed as shown in  FIG. 3 . 
     If, while still being restrained, vehicle  12  moves forward away from dock face  14 , RIG  20  might exert sufficient force to push barrier  18  away from the blocking position and toward the stored position (e.g., in a downward or counterclockwise direction about axis  36 ). However, rotation of the barrier  18  away from the dock face  14  is limited to the intermediate blocking position because barrier  18  encounters or engages brace  26 , which provides a solid mechanical engagement that restricts or limits further rotational movement of barrier  18  (e.g., in a downward or counterclockwise direction) as shown in  FIG. 4 . In some examples, barrier  18  supported by brace  26  provides a much greater resistive force  64  to the forward push of vehicle  12  than the force barrier  18  could otherwise exert under the urging of actuator  42  alone (without excessive pressure building within the hydraulic cylinder or excessive force being applied to first connection point  44 ). 
     In examples where barrier  18  exerts less holding force  66  ( FIG. 3 ) in the upper blocking position than in the intermediate blocking position, the reduced holding force can be particularly beneficial when the supporting structure of RIG  20  includes a relatively lightweight plate  68 . When barrier  18  is at the upper blocking position, as shown in  FIG. 3 , a tip of barrier  18  might engage a relatively weak portion of plate  68 . Barrier  18  exerting significant pressure or force (e.g., a maximum force) at this point or position may cause damage to plate  68 . Thus, it might be beneficial to limit the barrier&#39;s holding force at the barrier&#39;s upper blocking position. However, if the barrier&#39;s holding force is too light throughout its full range of blocking positions, vehicle  12  might forcibly release itself completely from vehicle restraint  10 . To prevent forcible release of the vehicle, brace  26  enables barrier  18  to exert substantial resistive force  64  at the barrier&#39;s intermediate blocking position, as shown in  FIG. 4 . Moreover, barrier  18  at the intermediate blocking position, in some cases, engages lower areas of plate  68  and/or other areas of RIG  20  where RIG  20  can withstand relatively greater amounts of force. 
     Referring to  FIG. 5 , to release vehicle  12  from the condition shown in  FIGS. 3 and 4 , actuator  42  is switched to the restored state. To retract or switch actuator  42  to the restored state, hydraulic pressure is released at cylinder-end port  60 . In some cases, hydraulic pressure  70  is provided at a rod-end port  72  of actuator  42 . When actuator  42  retracts, brace  26  rotates about axis  40  to the release position and barrier  18  rotates about axis  36  to the stored position.  FIG. 5  shows actuator  42  rotating barrier  18  and brace  26  in the same direction (e.g., in a counterclockwise direction). Additionally, actuator  42  may rotate barrier  18  and brace  26  simultaneously. 
     The rotation continues until brace  26  reaches its release position at stop  50  and barrier  18  reaches its stored position at stop  48  as shown in  FIG. 6 . With barrier  18  in its stored position as shown in  FIG. 6 , vehicle  12  is free to depart dock  16  without interference from the barrier  18 . As vehicle  12  travels in a forward direction  75 , RIG  20  moves or slides along the upper edge and ramp portion  52  of main body  30 . As RIG  20  slides along ramp portion  52 , spring  32  forces main body  30  back to its elevated preparatory position of  FIG. 1  so that restraint  10  is ready for the next vehicle that approaches loading dock  16 . 
     In some cases, as brace  26  and barrier  18  rotate, the upper end of brace  26  might travel across the lower edge of barrier  18 . To reduce friction in this area, in some examples, brace  26  includes a roller  74  for engaging barrier  18 . 
     In the illustrated example, brace  26  has a main arm  26   a  with an integral lever arm  26   b . However, in some examples, arms  26   a  and  26   b  are separate structures that are keyed to shaft  38  such that arms  26   a  and  26   b  rotate as a unitary unit. 
     Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of the coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.
Example vehicle restraints having example anti-rotation features are disclosed herein. In some examples, an actuator in the form of a hydraulic cylinder moves both a vehicle barrier and its brace between stored and activated positions. If the vehicle pushes the barrier from an upper blocking position to an intermediate blocking position, the brace helps support the barrier at the intermediate blocking position to prevent the vehicle from further pushing the barrier to its stored position. To avoid damaging a cover plate or other relatively weak areas of a vehicle's RIG (rear impact guard), some example barriers disclosed herein exert a holding force that is less at the upper blocking position than at the intermediate blocking position.