Abstract:
A method of securing a vehicle at a desired location using a wheel chocking device ( 30 ) having a chock ( 38 ) movable between a lowered position and a raised position. The method comprises the steps of positioning the vehicle at the desired location with the chock ( 38 ) in the lowered position, raising the chock to the raised position, moving the raised chock toward a wheel of the vehicle, sensing the presence of an obstruction on the vehicle, lowering the raised chock to an intermediate position to allow the chock to pass under the obstruction, and contacting the chock with the wheel. The wheel chocking device ( 30 ) includes a drive mechanism ( 40 ) that is positioned underneath the chock so that the vehicle actually drives over the drive mechanism. The drive mechanism is simplified with the use of a drive screw ( 152 ) and a partial drive nut ( 148, 154 ) that facilitates the use of support members ( 156 ) for supporting the drive screw at spaced locations along the length of the drive screw. A multi-link chock facilitates use of the device on wheels of varying sizes.

Description:
This application is a 371 of PCT/US97/11081 filed Jun. 25, 1997 and also claims benefit of Provisional No. 60/020,686 filed Jun. 27, 1996. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of vehicle restraining devices that prevent movement of a vehicle away from a desired location. More specifically, the present invention relates to powered wheel chocking devices. 
     BACKGROUND OF THE INVENTION 
     Powered wheel chocking devices have been developed to allow a vehicle (e.g., a straight truck, a trailer with or without a tractor, etc.) to be secured at a desired location (e.g., a loading dock) so that loading, unloading or other operations can be performed without risk that the vehicle will unexpectedly move away. Such wheel chocking devices typically include a chock that can be selectively moved by a drive mechanism between a chocked position and an unchocked position. These devices are commonly provided with visual and audible signals that indicate when the chock is in the chocked position and when the chock is in a unchecked position. 
     One type of powered wheel chocking device has been designed by Michel Roux, and is disclosed in European Patent Publication No. 537,075. The Roux device includes a chock that is movable between an unchecked lowered position and chocked raised position. The Roux device is designed to maintain the chock in a lowered position until the chock has been moved longitudinally into contact with the vehicle wheel. After contact with the vehicle wheel, further movement of the drive mechanism causes the chock to pivot to the raised position to secure the vehicle wheel. 
     A similar device is disclosed in U.S. Pat. No. 5,375,965 to Springer et al. The Springer device also includes a chock that is movable between lowered and raised positions, and the chock is designed to be moved longitudinally into contact with the vehicle wheel while the chock is in the lowered position. After contact with the wheel, the drive mechanism will continue to drive a portion of the chock until the chock moves to the raised position. 
     SUMMARY OF THE INVENTION 
     One problem with the above noted powered wheel chocking devices is that the chock can prematurely move to the raised position before the chock is positioned in contact with the vehicle wheel. This can be caused by an impediment (e.g., ice, debris, damage or other discontinuity) in the path of the chock. Such an impediment can restrict movement of the chock to such a degree that the device acts as if the vehicle wheel has been engaged, when in fact it has not been engaged. The result is that the chock can prematurely move to the raised position. After the chock is raised, the drive mechanism can overcome the impediment and continue moving the raised chock toward the vehicle wheel. If the vehicle includes depending obstructions (e.g., tool boxes, spare tires, etc.) hanging down from the vehicle in the chock&#39;s path, the raised chock could engage the obstruction and give a false indication that the vehicle wheel has been properly engaged. 
     Another problem with some of the prior art devices is that the drive mechanisms are unnecessarily complex, requiring sliding support blocks and collapsing chock wheels. Some of these devices also position the drive mechanism offset from the wheel path, thereby requiring the use of two chocks and a centered drive mechanism to compensate for the misaligned forces involved in securing the vehicle. 
     The present invention alleviates the above noted problem by providing a wheel chocking device that is designed to deflect around any obstructions that could be depending from a vehicle in the chock&#39;s path. In this regard, the invention is embodied in a method of securing a vehicle at a desired location- using a wheel chocking device having a chock movable between a lowered position and a raised position. The method comprises the steps of positioning the vehicle at the desired location with the chock in the lowered position, raising the chock to the raised position, moving the raised chock toward a wheel of the vehicle, sensing the presence of an obstruction on the vehicle, lowering the raised chock to an intermediate position to allow the chock to pass under the obstruction, and contacting the chock with the wheel. 
     The present invention also provides a wheel chocking device having a drive mechanism that is positioned underneath the chock so that the vehicle actually drives over the drive mechanism. The drive mechanism of the present invention is simplified with the use of a drive screw and a partial drive nut that facilitates the use of support members for supporting the drive screw at spaced locations along the length of the drive screw. A multi-link chock facilitates use of the device on wheels of varying sizes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a wheel chocking device embodying the present invention and positioned at a loading dock. 
     FIG. 2 is a partial top view of the wheel chocking device of FIG.  1 . 
     FIG. 3 a section view taken along line  3 — 3  in FIG.  2 . 
     FIG. 4 is a schematic section view taken along line  4 — 4  in FIG. 2 with the chock in a lowered position. 
     FIG. 5 is the section view of FIG. 4 with the chock in a raised position. 
     FIG. 6 is the section view of FIG. 4 with the chock in an intermediate position deflecting around an obstruction. 
     FIG. 7 is the section view of FIG. 4 with the chock in a raised and supported position at a vehicle wheel. 
     FIG. 8 is the section view of FIG. 4 illustrating the action of the chock when the vehicle wheel is driven. 
     FIG. 9 is a perspective view of the interior components of the chock when the chock is in the lowered position. 
     FIG. 10 is the perspective view of FIG. 9 with the chock in a raised position. 
     FIG. 11 is the perspective view of FIG. 9 with the chock in a raised and supported position. 
     FIG. 12 is a section view taken along line  12 — 12  in FIG.  2 . 
     FIG. 13 is a section view taken along line  13 — 13  in FIG.  2 . 
     FIG. 14 is a section view taken along line  14 — 14  in FIG.  2 . 
     FIG. 15 is a section view taken along line  15 — 15  in FIG.  2 . 
     FIG. 16 is a side section view taken along line  16 — 16  in FIG.  1 . 
     FIG. 17 is a top section view taken along line  17 — 17  in FIG.  16 . 
    
    
     DETAILED DESCRIPTION 
     The illustrated wheel chocking device  30  generally includes a base frame  32  adapted to be secured to an underlying surface  34 , a cover plate  36  covering the base frame  32 , a chock  38  positioned over the cover plate  36  and adapted to slide relative to the base frame  32 , and a drive mechanism  40  positioned substantially within the base frame  32  and under the cover plate  36 . The wheel chocking device  30  is specifically designed to be positioned adjacent to a loading dock  42  so that a vehicle that is backed against the loading dock  42  can be secured in position adjacent to the loading dock  42 . As used herein, the rearward direction denotes movement toward the loading dock  42  as resented by the arrow  46 , and the frontward direction is opposite to the rearward direction as represented by the arrow  48 . 
     Referring to FIGS. 1,  2  and  12 , the base frame  32  includes a base plate  50  that is designed to be secured to the surface  34  by a series of fasteners  52 . For example, the illustrated base plate  50  is secured to a concrete or asphalt driveway in front of the loading dock  42 . Referring specifically to FIG. 12, inner side walls  54  are secured to the base plate  50  and define a recess  56  therebetween for housing a portion of the drive mechanism  40 , as described below in more detail. Outer side walls in the form of guide members  58  and support members  60  define side slots  62  for guiding the drive mechanism  40 , as described below in more detail. The inner side walls  54  and guide members  58  cooperatively provide a non-securing support for the cover plate  36 . That is, the cover plate  36  rests upon but is not secured to the inner side walls  54  and guide members  58 . Side angles  64  are secured to the longitudinal edges of the base plate  50  to protect the wheel chocking device  30  from potential damage from snow plows. The side angles  64  could be made detachable (e.g., by attaching with bolts) from the base plate  50 . The base plate  50  is further provided with stop blocks  66  (FIGS. 2 and 15) that stop movement of the drive mechanism  40  in the frontward direction, as described below in more detail. 
     The cover plate  36  extends along substantially the entire length of the base frame  32  to provide a protective cover for the drive mechanism  40 . The cover plate  36  allows a vehicle  44  to drive on top of the wheel chocking device  30  without damaging any of the components of the drive mechanism  40 . The cover plate  36  is secured to the base frame  32  only at its ends, and thus the middle portion of the cover plate  36  is allowed to move vertically away from the base frame  32  or “float” to allow portions of the drive mechanism  40  to pass between the base frame  32  and the cover plate  36 . This allows the drive mechanism  40  to be interconnected with the chock  38 . 
     Referring to FIGS. 2-8, the chock  38  generally includes a rear portion  68  adapted to engage a vehicle wheel  108 , and a front portion  70  that is movably interconnected with and provides support to the rear portion  68 . Referring specifically to FIGS. 2 and 3, the rear portion  68  comprises a series of three links: a lower link  72 , a middle link  74  and an upper link  76 . The lower link  72  includes a lower plate  78  and a lower side member  80  secured near each side of the lower plate  78  (see FIGS.  3  and  15 ). The middle link  74  includes a middle plate  82  and a middle side member  84  secured near each side of the middle plate  82  (FIG.  3 ). The middle side members  84  are pivotally connected to the lower side members  80 . The upper link  76  comprises an upper plate  86  and an upper side member  88  secured near each side of the upper plate  86 . The upper side members  88  are pivotally secured to the middle side members  84 . Upper tube members  90  (FIGS. 2 and 4) are secured to the upper plate  86  to provide a location for securing the upper link  76  to the front portion  70  of the chock  38 . 
     The front portion  70  of the chock  38  includes a single large link  91  comprising a large plate  92  and a large side member  94  secured near each side of the large plate  92  (FIG.  3 ). A front tube member  96  (FIG. 2) is secured to the large plate  92  in alignment with the upper tube members  90 . The front tube member  96  and upper tube members  90  are designed to receive a pin member  98  for pivotally securing the large link  91  with the upper link  76 . 
     A support link  100  is pivotally connected to the pin member  98  (FIGS.  2  and  4 - 8 ). The support link  100  includes a support plate  102  and two hinge members  104  secured to each side of the support plate  102 . The hinge members  104  are positioned between the upper tube members  90  and the front tube member  96  and are designed to receive the pin member  98  so that the support link  100  is pivotally attached to the pin member  98 . A cross member  106  is secured to the other end of the support plate  102  to provided a more stable footing for the support link  100  when it engages the cover plate  36 , as described below in more detail. The cross member  106  also provides an attachment point for two link members  107 . In the illustrated embodiment, the link member  107  are made from a flexible material, such as chain, and their function is described below in more detail. 
     The above-described chock  38  is designed to slide longitudinally (i.e., in the frontward and rearward directions) relative to the base frame  32  and cover plate  36 . Such sliding motion allows the chock  38  to be moved into contact with a vehicle wheel  108  positioned on the cover plate  36 . More specifically, the chock  38  can be moved from a stored position (FIGS. 3 and 4) to a raised and unsupported position (FIG.  5 ). When the chock is in the unsupported position, the support link  100  does not support the chock  38 . In this unsupported position, the chock  38  is designed to have the ability to deflect around an obstruction  109  hanging down from the vehicle  44  (FIG.  6 ). Once the raised chock  38  is brought into contact with the vehicle wheel  108 , the support link  100  will move to a supporting position in a manner described below in more detail. In the supporting position, the support link  100  will prevent the chock  38  from deflecting downward in the event that the vehicle attempts to drive away from the loading dock (FIG.  8 ). 
     The chock  38  is moved and raised by the drive mechanism  40 . The drive mechanism  40  is best shown in FIGS. 9-15, and includes, inter alia, a front slider  110 , a rear slider  112 , and a drive member  114 . 
     The front slider  110  comprises a front plate  116  slidably positioned between the base frame  32  and the cover plate  36  (FIGS.  9  and  13 ). A front block  118  is secured to each side edge of the front plate  116 . Each front block  118  includes a front slot  120  and a front hole  122  for facilitating pivotal engagement with the large side members  94  of the link (see FIGS. 2,  3  and  13 ). The front slider  110  further includes two front tubes  124  secured to the bottom surface of the front plate  116 , and a front spring bracket  126  secured to each front tube  124 . Because of the pivotal engagement between the front slider  110  and the large link  91 , it can be seen that movement of the front slider  110  will result in movement of the front end of the large link  91 . 
     The rear slider  112  includes a rear plate  128  slidably positioned between the base frame  32  and the cover plate  36  (FIGS.  9  and  15 ). A rear block  130  is secured to each side edge of the rear plate  128 . Each rear block  130  includes a rear slot  132  and a rear hole  134  for facilitating pivotal engagement with the lower side members  80  of the lower link. Each rear block  130  is provided with a bar member  136  positioned within the side slots  62  formed by the guide members  58  of the base frame  32  (FIGS.  2  and  15 ). The bar members  136  provide guidance to the rear slider  112  and prevent the rear slider  112  from moving upwardly away from the base frame  32 . The bar members  136  further provide a means for stopping movement of the rear slider  112  in the frontward direction. More specifically, the bar members  136  will contact the stop blocks  66  of the base frame  32  to stop the rear slider  112  in the stored position (see FIG.  2 ). The rear slider  112  further includes two spring tubes  138  secured to the bottom surface  34  of the rear plate  128 , and a rear spring bracket  140  secured to each spring tube. 
     The front slider  110  and rear slider  112  are interconnected by two coil springs  142  secured on one end to the front spring brackets  126  and on the other end to the rear spring brackets  140  (FIG.  9 ). The coil springs  142  provide a biasing force tending to pull the front slider  110  and rear slider  112  toward each other. Such movement of the front slider  110  and rear slider  112  toward each other will result in the chock  38  moving to the raised position. Thus, the chock  38  is biased to the raised position. 
     The drive member  114  is operatively positioned between the front slider  110  and the rear slider  112 . The drive member  114  is designed to drive the rear slider  112  when the chock  38  is being moved in the rearward direction, and is designed to drive the front slider  110  when the chock  38  is being moved in the frontward direction. The drive member  114  comprises a drive plate  146  slidably positioned between the base frame  32  and the cover plate  36 , and a drive block  148  secured to the bottom surface of the drive plate  146  (FIGS.  9  and  14 ). The drive block  148  includes internal threads  150  for threadedly engaging a screw member  152 . The drive block  148  includes an open portion  154  such that the internal threads  150  do not engage the entire outer circumference of the screw member  152 . 
     The open portion  154  of the drive block  148  allows an arcuate segment of the screw member  152  to be supported by a series of lower screw supports  156  spaced along the longitudinal length of the screw member  152 . In a preferred embodiment, the longitudinal position of the lower screw supports  156  is limited by a plurality of spaced weld beads  155  (FIGS. 12-15) between the base frame  32  and the side walls  54 . Upper screw supports  157  are secured to each of the front plate  116  and the rear plate  128  (FIGS.  9 - 15 ). The upper and lower screw supports  156 , 157  are preferably made from a low friction material (e.g., brass, plastic, etc.) to provide low friction engagement between the screw member  152  and the lower screw supports  156 . In the illustrated embodiment, the upper and lower screw supports are made from a polymer material, such as ultra high molecular weight polyethylene. 
     The drive member  114  further includes two drive tubes  158  (FIGS. 10 and 14) secured to the bottom surface of the drive plate  146 . The drive tubes  158  are positioned in alignment with the front tubes  124  on the front slider  110 . The drive tubes  158  and front tubes  124  slidably receive a rod  160  having collars  162  that prevent the rod  160  from sliding out of the tubes. A gas spring  164  is operatively positioned between each rod  160  and the corresponding spring tube  138  of the rear slider  112 . Each gas spring  164  includes a cylinder  166  (FIG. 9) slidably positioned within the corresponding spring tube, and a piston rod  168  secured to the corresponding rod  160  by a coupling  170  and set screw  171 . In the illustrated embodiment, the piston rod  168  is biased away from the cylinder  166  at a force of about 100 lbs. The link members  107  are secured to opposing sides of the drive member  114 , and are designed to control the position of the support link  100  in relation to the position of the drive member  114 . 
     The above-described components of the drive mechanism  40  operate in the following manner to provide movement to the chock  38 . In the stored position, the drive member  114  pushes the front slider  110  all the way to the front end of the base frame  32  (FIGS.  4  and  9 ). In this position, the rear slider  112  is held in spaced relation to the front slider  110  by the stop blocks  66  interacting with the bar members  136  (FIG.  2 ). In the stored position, the coil springs  142  are stretched, and the cylinder  166  of the gas spring  164  is partially pulled out of the spring tubes  138 . The support link  100  is held in a non-supporting position by the link members  107 . 
     Movement of the device is initiated by rotating the screw member  152 , which results in movement of the drive member  114  in the rearward direction. Due to the biasing force of the coil springs  142 , the front slider  110  will follow the rearward movement of the drive member  114 , thereby resulting in raising of the chock to a raised position (FIGS.  5  and  10 ). At this point, the drive member  114  contacts the couplings  170 , and the cylinders  166  are bottomed out within the spring tubes  138 . Further movement of the drive member  114  therefore results in driving of the rear slider  112  in the rearward direction. The support link  100  is held in a non-supporting position by the link members  107 . 
     If the raised chock encounters an obstruction  109  while moving rearwardly toward the wheel, the chock will deflect around the obstruction  109  and will subsequently return to the raised position after the obstruction  109  has been passed (FIG.  6 ). Such downward deflection of the chock is facilitated by the compliant biasing of the front slider  110  toward the rear slider  112 , and further by the fact that the rear slider  112  is being driven. More specifically, if an obstruction  109  is encountered, the rear slider  112  will continue to be driven rearwardly, and the front slider  110  is allowed to slide forwardly, if necessary, to allow the chock to deflect downwardly to an intermediate position. Because the support link  100  is in a non-supporting position, the support link  100  does not interfere with the downward deflection of the chock. Furthermore, the flexible nature of the illustrated link members  107  allows the drive member  114  to move relative to the support link  100 . Rather than have the wheel chock contact the obstruction, the wheel chock could be provided with a proximity sensor that senses the presence of an obstruction. If an obstruction is sensed, then the chock could be automatically lowered to a height lower than the obstruction (e.g., using a powered lowering means, such as an electric motor) until the obstruction is passed. 
     Once the vehicle wheel  108  has been engaged by the chock, the rear slider  112  will stop, but the drive member  114  will continue rearward movement until the collars  162  of the rods  160  engage the front tubes  138  and couplings  170  engage the spring tubes  138  (FIGS.  7  and  11 ). Such movement of the drive member  114  results in the support link  100  moving to the supporting position, thereby placing the chock  38  in the raised and supported position. 
     Movement of the chock  38  back to the stored position is accomplished in substantially the reverse order. It is noted, however, that movement of the chock  38  in the frontward direction is accomplished by driving the front slider  110 . In this manner, the chock  38  will be allowed to deflect downwardly to an intermediate position to avoid any obstructions that may be encountered when moving the chock  38  back to the stored position. 
     The illustrated screw member  152  is driven by a power mechanism in the form of an electric motor  172  interconnected with the screw member  152  by a drive shaft  174  (FIGS.  16  and  17 ). The drive shaft  174  includes flexible couplings  176  for accommodating misalignment of the motor shaft with the screw member  152  (only one end is shown). The screw member  152  is slidably mounted within screw bushings  178  positioned on either end of the screw member  152 . That is, the screw member  152  is supported by, but is not axially restrained by the screw bushings  178 . Each end of the screw member  152  is provided with a screw collar  180  secured to the screw member  152 , and a biasing spring  182  positioned between the screw bushing and the screw collar  180 . In this manner, the screw member  152  is biased to a neutral position (FIG. 17) relative to the screw bushings  178 . 
     A sensing mechanism is provided for sensing the axial position of the screw member  152 . In the illustrated embodiment, the sensing mechanism includes a first sensor  184  positioned in alignment with the screw collar  180  when the screw member  152  is in a neutral position, and a second sensor  186  positioned to detect movement of the screw member  152  in the rearward direction. When the screw member  152  is being used to move the chock in either direction, the screw member  152  is positioned in the neutral position. When the chock has engaged a vehicle wheel, the screw member  152  will move frontwardly due to the resistance encountered by the drive member  114 . Such frontward movement of the screw member  152  will be detected by the first sensor  184 . Conversely, when the chock is in the stored position, the screw member  152  will move rearwardly due to the resistance encountered by the bar members  136  on the stop blocks  66 . Such rearward movement of the screw member  152  will be detected by the second sensor  186 . Information regarding the axial position of the screw member  152  can be provided to a control mechanism  188  (shown schematically in FIG. 17) and used to selectively disengage the power drive mechanism. More specifically, when the screw member  152  moves rearwardly, it is an indication that the stored position has been reached and the motor can be deactivated. Conversely, frontward movement of the screw member  152  indicates that a wheel has been engaged and the motor can be deactivated. 
     Alternatively, the power mechanism can be provided with a torque-limiting device, such as a torque or current sensor, to deactivate the power mechanism. As another alternative, a proximity sensor can be used to sense when the drive member  114  is in the stored position (FIGS. 3,  4  and  9 ). The use of a proximity sensor is advantageous in that it is a positional sensor that directly measures the position of the drive member  114 , as opposed to a conditional sensor that measures a certain condition of the chock and infers the position of the chock. 
     The above-noted mechanisms for sensing the position of the wheel chock can be used to provide signals to a communication system. For example, the loading dock can be provided with a dock lighting system for communicating with the dock workers and a driver lighting system for communicating with the driver of the vehicle. Each lighting system can include a red light and a green light. When the chock is in the stored position, the driver lighting system will show a green light, indicating that the driver can enter or exit the loading dock, and the dock lighting system will show a red light, indicating that no loading or unloading operations should be performed. After the vehicle is positioned at the dock and the chock is activated to move toward the wheel of the vehicle, both lighting systems will show a red light and an audible warning can be provided to indicate that the chock is being moved. After the chock is secured at the vehicle wheel, the dock lighting system will show a green light indicating that loading and unloading operations can be performed, and the driver lighting system will remain red, indicating that the vehicle is secured and that the driver should not attempt to pull away from the dock. After loading and unloading operations are complete, the chock is moved back toward the stored position, during which time both lighting systems will show a red light and an audible warning will indicate that the chock is being moved. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain best modes known for practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.