Abstract:
A vehicle restraint includes a restraining member that rises to an operative position and lowers to a stored position to respectively engage and release an ICC bar of a truck parked at a loading dock. In moving to the lowered stored position, the restraining member also rotates off to its side, so as not to obstruct snow removal equipment or incoming vehicles having an especially low ICC bar or low ground clearance. In some embodiments, rotation of the restraining member is achieved by various actuators that apply a generally uniform torque. A resilient member, moves the restraining member upward to engage the ICC bar, and allows for vertical movement of the truck as it is being loaded or unloaded. Opposing the upward urging of the resilient member, a drive unit forcibly moves the restraining member downward when the truck is ready to be released.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention generally pertains to a vehicle restraint and more specifically to one that moves to a low-profile stored position. 
     2. Description of Related Art 
     When a truck backs up against a dock for loading or unloading the truck, a generally safe practice is to restrain the truck to prevent it from accidentally pulling away from the dock. This is often accomplished by a hook-style vehicle restraint that engages what is known as an ICC bar or a Rear Impact Guard (RIG). An ICC bar or RIG is basically a bumper in the form of a horizontal bar or beam that runs along the rear of a truck, below the truck bed. Its primary purpose is to prevent an automobile from under-riding the truck in a rear-end collision. A conventional hook-style restraint includes a hook that moves between a lowered stored position and a raised operative position. The lowered stored position allows the ICC bar to pass over the hook as the truck backs up against the dock. The hook then rises to its operative position where the hook engages the bar to restrain the vehicle. 
     With many hook-style vehicle restraints, a hook&#39;s stored position can create several problems. First, a stored hook protruding out from the face of the dock can be an obstacle that prevents smaller vehicles or those with low ground clearance from getting close enough to the dock for effective loading and unloading. For example, when a protruding hook forces a pick-up truck or van to park a short distance away from the dock, the protruding hook can be a tripping hazard for anyone on the driveway trying to load or unload the vehicle. Second, in some cases, a truck or trailer&#39;s ICC bar is too low to clear the top of a stored hook. This problem is becoming more prevalent, as newer vehicles are being built with lower beds. And third, a stored hook protruding from the face of a dock can obstruct snow removal equipment. 
     To address some of these problems, U.S. Pat. No. 4,664,582 discloses a truck restraint with a hook that not only moves vertically between a raised operative position and a lowered stored position, but also rotates about a vertical axis. The rotation allows the hook to alternately swing between being perpendicular to the dock face or generally flat up against it. The &#39;582 restraint, however, has a stored height that may still interfere with some vehicles with a relatively low ICC bar. Although the hook, in its stored position, might be below the bar initially, the hook has to raise some in order for the hook to rotate outward away from the dock face. The initial ascent of the hook to effect the rotation may place the hook above the bar before the hook is able to swing underneath it. The initial lift can be minimized by reducing the steepness of the inclined edge that causes the hook to rotate, but that increases the upward force required to lift the hook. And increasing the upward force can lead to a situation that can damage the ICC bar. For example, once the hook rotates outward and off the inclined edge, the sustained high upward force is free to simply accelerate the hook upward at an speed until the hook strikes the ICC bar. A sufficiently high impact could damage the bar. Moreover, a sufficiently high upward force on the hook may limit the vehicle from normal vertical float. Vertical float of a couple of inches or more is common and is caused by varying cargo weight and the weight of a forklift driving onto the bed of the vehicle as it is being loaded or unloaded. If the hook provides no give to slightly descend as the truck is loaded, the added weight could crush the ICC bar between the bed of the vehicle and the hook, as ICC bars are not normally intended to support the weight of the truck&#39;s cargo. 
     Some vehicle restraints have a rotational hook, as disclosed in U.S. Pat. Nos. 4,553,895; 4,605,353; and Re33,154. With these restraints, however, the hook is rotated manually. Also, the hooks of the patented restraints are lowered onto an ICC bar, which means the vehicle must have clearance above its ICC bar in order for the hook to swing into position. Not all vehicles provide such clearance. 
     Another vehicle restraint, disclosed in U.S. Pat. No. 4,634,334, includes a hook that is power-rotated between a stored position and an operative position. However, except for hook&#39;s rotation, the restraint does not move vertically to accommodate ICC bars of various heights. 
     SUMMARY OF THE INVENTION 
     In order to provide a low-impact vehicle restraint with a low-profile stored position, a restraint is provided with a hook that moves both vertically and rotationally between a lowered stored position and a raised operative position. In the raised operative position the hook is adapted to engage an ICC bar of a vehicle to limit the vehicle&#39;s movement away from a loading dock. In the lowered stored position, the hook&#39;s position allows the vehicle to back up against the dock. The hook&#39;s rotation is such that it has a minimal affect on the restraint&#39;s effective range, wherein the range is defined by those elevations at which an ICC bar can be effectively restrained by the hook. The restraint includes a resilient member that provides upward movement of the hook while allowing some downward movement of the vehicle being restrained. 
     In some embodiments, the hook rotates about an axis that is generally perpendicular to the dock face so that the hook in its lowered stored position lies rather low to the ground to accommodate especially low ICC bars or vehicles with relatively low ground clearance. 
     In some embodiments, the rotation of the hook is completed before the hook begins rising, thus being able to accommodate relatively low ICC bars. 
     In some embodiments, the force that rotates the hook is applied at a generally uniform distance from the hook&#39;s rotational axis to avoid a peak force or peak torque that might slam the hook into position. 
     In some embodiments, the force that rotates the hook is applied at a generally uniform distance from the hook&#39;s rotational axis so that when the force is brought on by vertical movement of the hook, peak vertical forces that may tend to slam the hook up against the underside of the ICC bar are avoided. 
     In some embodiments, the force that rotates the hook is applied in a direction generally perpendicular to the hook&#39;s rotational axis to keep the total force less than what would otherwise be required if the force were just a component of a greater force applied at an angle other than ninety degrees to the rotational axis. 
     In some embodiments, a resilient member, such as a spring, provides upward movement of the hook to engage an ICC bar of a vehicle while allowing some downward movement of the vehicle once it is restrained. 
     In some embodiments, a resilient member, such as a spring, avoids damaging an ICC bar of a vehicle by limiting the upward thrust that a restraining member can exert against the bar. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a vehicle backing into a loading dock that includes a vehicle restraint in its lowered stored position. 
     FIG. 2 is a front view of a vehicle restraint in its lowered stored position. 
     FIG. 3 is a top cross-sectional view taken along line  3 — 3  of FIG.  2 . 
     FIG. 4 is the same as FIG. 1, but with the vehicle restraint in its raised operative position. 
     FIG. 5 is a top cross-sectional view taken along line  5 — 5  of FIG.  6 . 
     FIG. 6 is the same as FIG. 2, but with the vehicle restraint in its raised operative position. 
     FIG. 7 is a front view of another vehicle restraint in its lowered stored position. 
     FIG. 8 is a top cross-sectional view taken along line  8 — 8  of FIG.  7 . 
     FIG. 9 is the same as FIG. 7, but with the restraint&#39;s restraining member rotated outward away from the dock face. 
     FIG. 10 is a top cross-sectional view taken along line  10 — 10  of FIG.  9 . 
     FIG. 11 is the same as FIG. 9, but with the restraint&#39;s restraining member in its raised operative position. 
     FIG. 12 is a top cross-sectional view taken along line  12 — 12  of FIG.  11 . 
     FIG. 13 is a front view of another vehicle restraint in its lowered stored position. 
     FIG. 14 is a top cross-sectional view taken along line  14 — 14  of FIG.  13 . 
     FIG. 15 is the same as FIG. 13, but with the restraint&#39;s restraining member rotated outward away from the dock face. 
     FIG. 16 is a top cross-sectional view taken along line  16 — 16  of FIG.  15 . 
     FIG. 17 is a front view of another vehicle restraint in its lowered stored position. 
     FIG. 18 is a top cross-sectional view taken along line  18 — 18  of FIG.  17 . 
     FIG. 19 is the same as FIG. 17, but with the restraint&#39;s restraining member rotated partially away from its stored position. 
     FIG. 20 is a top cross-sectional view taken along line  20 — 20  of FIG.  19 . 
     FIG. 21 is the same as FIG. 17, but with the restraint&#39;s restraining member rotated to an upright position. 
     FIG. 22 is a top cross-sectional view taken along line  22 — 22  of FIG.  21 . 
     FIG. 23 is the same as FIG. 21, but with the restraint&#39;s restraining member in its raised operative position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A vehicle restraint  10  adapted to engage a vehicle&#39;s ICC bar  12  to prevent a vehicle  14  from accidentally pulling away from a loading dock  16  is shown in FIGS. 1-6. To alternately restrain and release vehicle  14 , restraint  10  includes a restraining member  18  that moves between a lowered stored position (FIGS. 1-3) and a raised operative position (FIGS.  4 - 6 ). In moving to the stored position, restraining member  18  not only descends but also rotates out of the way to allow vehicle  14 , such as a track or trailer, to back up against dock  16  or drive away without interference from member  18 . When vehicle  14  parks up against the generally vertical dock face  20  or against dock bumpers  22 , restraining member  18  rotates and rises to its operative position to engage a portion of bar  12 , which prevents vehicle  14  from pulling away. 
     The vertical movement of restraining member  18  is accomplished by coupling member  18  to a generally vertical track  24 , which in turn is attached to dock face  20  by way of fasteners  26 . In some embodiments, track  24  includes an outer housing  28  and a central guide rod  30  along which restraining member  18  is free to move. Restraining member  18  is vertically supported, in this exemplary embodiment, by a C-shaped sleeve  32  that slides along rod  30 . Sleeve  32  includes upper and lower flanges that slidingly fit around rod  30  and are vertically spaced-apart from each other to inhibit sleeve  32  from cocking or binding on rod  30 . A drive unit  34  raises and lowers restraining member  18  by vertically sliding sleeve  32  along rod  30 . 
     To limit the upward thrust that restraining member  18  can exert against an ICC bar, drive unit  34  lifts member  18  by way of a spring  36  or some other resilient member, such as a gas piston/cylinder or a conventional coiled-spring counterbalancer often used for supporting heavy tools. In some embodiments, for example, spring  36  coupled to a roller chain  38  (or a link chain, cable, rope, etc.) is held in tension between a stationary anchor point  40  at one end and another anchor point  42  on sleeve  32 . A sprocket  44  at the upper end of track  24  supports chain  38  so that the tension of chain  38  urges sleeve  32  and restraining member  18  upward. An upper notch  46  in housing  28  accommodates sprocket  44  and chain  38 . 
     To control the height to which spring  36  can lift restraining member  18  or to forcibly move restraining member  18  back down to disengage ICC bar  12 , drive unit  34  includes another roller chain  48  (or a link chain, cable, rope, etc.) connecting sleeve  32  to a powered take-up device  50 . Device  50  is schematically illustrated to represent any device for forcing member  18  downward (either acting directly on member  18  or coupled to it) against the force of spring  36 . Examples of device  50  include, but are not limited to a cable or chain winch (possibly similar to those used on a conventional electric or pneumatic jib hoist); a gearmotor driven or otherwise powered roller chain sprocket; or a linear actuator, such as a piston/cylinder. In some embodiments, drive unit  34  includes a lower idler sprocket  52  that changes the direction of pull of chain  48  from vertical to horizontal so that drive unit  34  fits conveniently within the physical constraints of the loading dock area. A lower notch in housing  28  accommodates sprocket  52  and chain  48 . 
     To prevent an ICC bar from accidentally lifting off restraining member  18  as vehicle  14  rises while being unloaded (e.g., a forklift driving off the bed of the truck and onto the dock), drive unit  34  includes a tensioner  54  that keeps chain  48  taut. In some embodiments, tensioner  54  includes a spring-loaded idler sprocket  56  that is able to offset a section of chain  48  when much of the tension of spring  36  is countered by restraining member  18  abutting the underside of bar  12 , as best shown in FIG.  6 . If bar  12  rises slightly (e.g., up to a couple of inches or more) while take-up device  50  is inactive, there is enough tension in spring  36  to overcome the pull of tensioner  54  and lift restraining member  18  up to maintain contact with bar  12 . Tensioner  54  yielding to spring  36  allows sprocket  56  to move to reduce some of the offset of chain  48 , which in turn releases some of chain  48  to follow the upward movement of sleeve  32  and restraining member  18 . 
     After completing the loading or unloading of vehicle  14 , drive unit  34  pulls sleeve  32  back down, so restraining member  18  descends to release ICC bar  12 . To ensure that restraining member  18  is out of the way as much as possible when in its lowered stored position, restraint  10  includes a rotational actuator  59  comprising two interactive guide elements  58  and  60 . In some embodiments, one guide element  58  associated with restraining member  18  engages the other guide element  60  which is associated with rod  30 . Together, guide elements  58  and  60  rotate member  18  between an outwardly extended position and a position where it lies about parallel to dock face  20 . A notched-out section  62  of housing  28  minimizes the extent to which restraining member  18 , when in its stored position, extends out from dock face  20 . As for the guide elements, some examples of guide elements  58  and  60  include, but are not limited to, a rigid protruding pin; a spring-loaded plunger (also known as a ball plunger); a groove that is inclined, helical or otherwise curved; or an elongated key or edge that is inclined, helical or otherwise curved. 
     In the embodiment of FIGS. 1-6, for example, guide element  58  is a spring-loaded plunger  64  attached to restraining member  18 . And a helical groove  66  or flute on rod  30  serves as guide element  60 . A tip  68  of plunger  64  protrudes into groove  66 , so that as drive unit  34  allows spring  36  to pull restraining member  18  upward from its stored position, plunger  64  travels along groove  66  to rotate restraining member  18  about a generally vertical axis  70  (longitudinal centerline of rod  30 ). When rising, restraining member  18  rotates in a counterclockwise direction (as viewed in FIGS. 3 and 6) and rotates clockwise when descending. It should be appreciated by those skilled in the art, that the locations of plunger  64  and groove  66  can be interchanged with plunger  64  being attached to rod  30  with groove  66  being disposed along an inner bore of restraining member  18 . 
     To avoid peak rotational torques that may require excessive vertical thrust to rotate restraining member  18  in a controlled, even motion, the radial distance between axis  70  and tip  68  (when protruding into groove  66 ) is kept substantially constant. 
     To avoid having to machine groove  66  along the full vertical length that restraining member  18  or tip  68  travels, tip  68  is able to retract against the urging of a spring within plunger  64 . As restraining member  18  continues rising and tip  68  begins moving above an upper end  72  of groove  66 , tip  68  is able to retract and ride along the outer diameter of rod  30 . In other embodiments where guide element  58  is a rigid protruding pin, groove  66  may need to extend further up along rod  30 . Rather than continuing up along a helical path; however, groove  66  would preferably extend in a straight upward direction from end  72 . A rigid pin protruding into the straight vertical section of the groove could also serve to keep restraining member  18  extended generally perpendicular to dock face  20  once member  18  rotates out from its lowered stored position. 
     Once restraining member  18  rotates to its outwardly extended position, another way to keep it generally perpendicular to dock face  20  is to provide restraint  18  with a crossbar  74 . In one embodiment, crossbar  74  includes a bore  76  for sliding vertically along rod  30  and includes two edges  78  that slidingly engage two front flanges  80  of outer housing  28 . The engagement of edges  78  with flanges  80  prevents crossbar  74  from rotating about rod  30 . When restraining member  18  is in its lowered stored position, crossbar  74  rests upon a stationary stop  82  just above member  18 . Crossbar  74  also includes a vertical slot  84  into which a shank  86  of restraining member  18  can rise. 
     Thus, as restraining member  18  rises and rotates out from its stored position, shank  86  slips up into slot  84  to limit member  18  from further rotation relative to rod  30 . Continued upward movement of restraining member  18  causes shank  86  to lift crossbar  74  off stop  82 . In other words, above stop  82 , restraining member  18  and crossbar  74  move as a unit up and down along track  24 , while shank  86  protruding through slot  84  keeps member  18  generally perpendicular to dock face  20 . When restraining member  18  moves downward toward its stored position, shank  86  deposits crossbar  74  on stop  82  and then slips out from within slot  84  to allow member  18  to rotate back to where it is generally parallel to dock face  20 . 
     To prevent a pullout force (i.e., the force a restrained vehicle exerts on restraining member  18  in an attempt to pull away from dock  16 ) from permanently bending rod  30 , restraining member  18  includes two shoulders  88  and  90  that abut an inside face  92  of crossbar  74 . With such an arrangement, a pullout force on restraining member  18  is transmitted though shoulders  88  and  90 , crossbar  74  and onto front flanges  80 . Thus housing  28  anchored to dock  16  counters the pullout force to protect rod  30 , which for mechanical reasons is significantly weaker than housing  80 . 
     To eliminate crossbar  74 , if desired, sleeve  32  can be modified so that a front face  96  of sleeve  32  slidingly engages front flanges  80 , as opposed to edges  78  engaging flanges  80 . Then a rigid pin, as opposed to plunger  64 , engages a straight vertical section of a groove in rod  30  to keep restraining member  18  in an extended outright position, as described earlier. In this way, a pullout force on restraining member  18  is transmitted through shank  86 , only across a short section of rod  30  (between the upper and lower flanges of modified sleeve  32 ), through modified sleeve  32 , and onto front flanges  80  of housing  28 . 
     In another embodiment, shown in FIGS. 7-12, a vehicle restraint  94  is able to engage a relatively low ICC bar  12 , as restraining member  18  requires no vertical lift to rotate from its stored position of FIGS. 7 and 8 to its extended position of FIGS. 9 and 10. This is accomplished by an actuator  98  that rotates member  18  before member  18  ascends to its raised operative position. Actuator  98 , in this example, includes a toothed element, such as a full or partial gear  100 , meshing with another toothed element, such as a gear rack  102 . A cylinder  105 , or some other actuator (e.g., a linear actuator, solenoid, etc.), drives gear rack  102  to rotate gear  100  about vertical axis  70 . Gear  100  includes one or two upwardly protruding pins  104  that engage, in this example, the sides of restraining member  18 . So rack  102  rotating gear  100  causes pins  104  to rotate restraining member  18 . After restraining member  18  rotates to its extended position of FIGS. 9 and 10, drive unit  34  lifts sleeve  32  off gear  100  and continues to control the vertical movement of member  18  in a manner similar to that of vehicle restraint  10 . However, shank  86  slides between lateral plates  106  and  108  to help keep restraining member  18  generally perpendicular to dock face  20  when member  18  is not in its lowered stored position. 
     To ensure smooth rotational operation of restraining member  18 , rack  102  exerts a force  110  substantially perpendicular to axis  70  and at a generally uniform offset distance from the axis. Further, it should be appreciated by those skilled in the art, that pins  104  engaging the sides of shank  86  is just one exemplary disconnectable coupling that allows restraining member  18  to lift and separate from rotational actuator  98 . Other examples of a disconnectable coupling include, but are not limited to a single pin on gear  100  protruding upward into a hole in the bottom of shank  86  (or protruding into a ring attached thereto), or a single pin on shank  86  protruding downward into a hole in gear  100 . 
     FIGS. 13-16 shows a vehicle restraint  112  similar to restraint  94 ; however, a rotational actuator  114  includes a linkage assembly comprising a rotational link  116  pinned to an actuator link  118 . Links  116  and  118  replace gear  100  and rack  102  respectively. Similar to restraint  94 , cylinder  105  moving link  118  provides a force that rotates link  116  about vertical axis  70 . Link  116  exerts a force  120  substantially perpendicular to axis  70  and at a generally uniform offset distance from the axis to ensure smooth, even rotation of restraining member  18 . With upwardly protruding pins  104  engaging the sides of shank  86 , the rotation of link  116  rotates restraining member  18  from its stored position of FIGS. 13 and 14 to its outwardly extended position of FIGS. 15 and 16. Once restraining member  18  is in its extended position of FIGS. 15 and 16, vertical movement of member  18  is controlled in the same manner as in restraints  10  and  94 . 
     In order to engage an especially low ICC bar or clear vehicles with low ground clearance, a vehicle restraint  122 , of FIGS. 17-23, includes a restraining member  124  that rotates about an axis  126  that is preferably perpendicular to dock face  20  or at least traverses it. A line or axis traversing a plane or a dock face means that the line or axis intersects the plane rather than lying along the plane or being parallel to it. Axis  126  traversing dock face  20  provides restraining member  124  with a lowered stored position (FIGS. 17 and 18) that is appreciable lower than that of the other embodiments. To provide the rotation, restraining member  124  includes an integral shaft  128  that is rotatably disposed within a carriage  130  and restrained axially by way of a pin  132  or some other type of fastener. 
     Vertical movement of restraining member  124  is provided by carriage  130  being able to move vertically along a track  134 . Bearing pads  136  or rollers minimize the friction between carriage  130  and track  134 . For upward movement, spring  36  is fixed relative to track  134  at point  138  (FIG.  23 ), sprocket  44  is rotatably mounted at the upper portion of track  134 , and one end of chain  38  is connected to spring  36  while an opposite end is connected to a lug  140  extending from carriage  130 . In such a configuration, chain  38 , sprocket  44  and spring  36  operate to urge carriage  130  upward (and restraining member  124  with it) in nearly the same manner as in the other embodiments already described. For downward movement or to limit the extent to which carriage  130  may rise, one end of chain  48  connects to lug  140  while the rest of chain  48  extends around sprocket  52  (FIG. 23) to connect to the remainder of drive unit  34 , as already described with reference to other embodiments. In other words, spring  36  urges carriage  130  up, and powered take-up device  50  (FIG. 2) of drive unit  34  pulls it down. 
     Just as with vehicle restraint  10 , the vertical movement of restraining member  124  also causes its rotation. Carriage  130  lifting restraining member  124  causes member  124  to rotate from its stored position of FIGS. 17 and 18, through a partially turned rotation of FIGS. 19 and 20, and onto its upright position of FIGS. 21 and 22. Carriage  130  lowering restraining member  124  back down causes member  124  to rotate back to its stored position. This is accomplished by a stationary protrusion  142  interacting with restraining member  124 . 
     In one embodiment, for example, protrusion  142  is fixed relative to track  134  (e.g., protrusion  142  is fastened to or is an integral feature of track  134 ) and alternately engages a heel  144  and a pin  146  of restraining member  124 . As carriage  130  starts lifting restraining member  124  from its stored position, heel  144  abutting protrusion  142  creates a force  147  that rotates member  124  clockwise as viewed in FIG.  19 . To ensure smooth operation, the force  147  that protrusion  142  exerts on heel  144  is perpendicular to axis  126  and is applied at a generally constant offset distance from it. 
     Once restraining member  124  rotates to its upright position of FIG. 21, drive unit  34  can lift it further to restrain ICC bar  12 , as shown in FIG.  23 . Lowering carriage  130  and restraining member  124  releases bar  12 . Further lowering of member  124  below its position of FIG. 21 causes pin  146  to abut protrusion  142 . This creates a contact force (generally opposite to force  147 ) that protrusion  142  exerts against pin  146  to rotate restraining member  124  counterclockwise until member  124  returns to its stored position of FIGS. 17 and 18. 
     When restraining member  124  rotates to its upright position of FIG. 21, it tends to stay upright by way of a detent mechanism. In some embodiments, the detent is provided by a ball plunger  148  screwed into carriage  130 . As shaft  128  rotates within carriage  130 , spring-loaded tip  150  of ball plunger  148  alternately protrudes into a recess  152  on shaft  128  or presses against the outer diameter of shaft  128 . When restraining member  124  rotates to its upright position (FIGS.  21 - 23 ), its integral shaft  128  rotates with it. This moves recess  152  around (with relative sliding or rolling of tip  150  along the outer diameter of shaft  128 ) until spring-loaded tip  150  protrudes into recess  152 . Tip  150  pressing into recess  152  provides a holding force sufficient to hold member  124  upright as member  124  moves vertically between its positions of FIGS. 21 and 23. However, the forces that protrusion  142  exerts on heel  144  and pin  146  are able to overcome the holding force of plunger  148 , so that restraining member  124  can still rotate between its stored and upright positions. 
     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.