Patent Publication Number: US-2005118004-A1

Title: Removable load bed for a vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      The present application is a division of U.S. patent application Ser. No. 09/493,478, filed Jan. 28, 2000, which is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to devices for loading and unloading containers and more particularly, to a chain locking mechanism for safely loading a movable frame onto a stationary vehicle.  
      2. Description of Related Art  
      A conventional cab and chassis vehicle when used to transport loads usually comprises a frame and a device for pulling a movable frame from the ground up and over onto the vehicles&#39; stationary frame, and guiding the frame into the loaded position. During normal usage, the movable frame supports a load which is transferred from the ground to the vehicle chassis via an arrangement of elevating booms and guide systems that are controlled by an operator. This simple approach has many limitations and there are many patents disclosing devices that simplify the procedure and/or improve the safety aspects of such a maneuver.  
      U.S. Pat. No. 1,794,318 (Perkins et al.) discloses a dumping body frame truck that is driven by a chain drive. The body is formed by telescopic sections that are collapsed to dump a load. While the sections are designed to slide along the chassis body, there is no bed that is removable from the chassis.  
      U.S. Pat. No. 2,811,269 (Anderson) discloses a removable bed that relies on a winch assembly to draw the truck body onto the chassis.  
      U.S. Pat. No. 5,203,788 (Marmur) discloses an apparatus for loading a container onto a truck body or trailer. This arrangement discloses the use of a pivoting arm and a cable to move the trailer.  
      U.S. Pat. No. 5,269,746 (Zoromski) discloses a container loading and unloading system that is particularly suited for loading campers and cargo boxes onto a truck bed. The system appears to be independent of the vehicle except for a yoke and pivot bar structure that is attached to the rear bumper.  
      U.S. Pat. No. 5,856,869 (Slokum et al.) discloses a removable load bed that includes a tiltable bed that is operated by a piston to control loading and unloading of the container. The system relies on a cable and bracket system to move the container. While the tiltable bed and interlocking bracket and cavity aspect of this patent appear to address deficiencies that are present in the previously described patents, it still suffers from the potential that the cable may come off the bracket, and therefore, could potentially be a safety hazard.  
      The frames of common conventional loading devices are generally similar in size and construction, and thus many of the loads that are to be used with such a frame arrangement tend to rely on a smooth and easy transfer from the ground to the truck bed. It is often difficult to maintain adequate control of this maneuver, and thus inadvertent lateral movement and slippage of the pulling mechanism can occur, especially during the initial lifting procedure.  
      Thus, there is a need for a removable load bed assembly for use with a conventional cab and chassis vehicle that provides a safe method of transferring a load from the ground onto the chassis of the vehicle. This patent should not be limited to this only. Other examples are military track and rubber tired vehicles that could have the bodies changed from a gun carrier to personal carrier to an ambulance body. This system will lift any load from one level to another.  
     SUMMARY OF THE INVENTION  
      The invention reduces the difficulties and disadvantages of the prior art by providing a guide system, a simple chain locking assembly and a device to control tilting action which can be retrofitted to most conventional truck chassis at relatively low cost. The device provides a secure and simple means for loading a load onto a truck, thus reducing relative movement therebetween.  
      The invention provides a loading apparatus for a vehicle, the apparatus comprising: 
      a first frame;     a second frame having a chain mounted thereupon; and     a locking system mounted on the first frame, the system having a drive wheel, a first arm member and a second arm member, the system being configured such that:     in a generally closed position, the chain engages the drive wheel in a first position, the drive wheel being connected to the arms; the arms being urged into the closed position; and in a generally open position, the chain engages the drive wheel in a second position, the arms being urged into the open position by the second frame.    

      In another aspect, the invention provides: 
      a third arm member;     a stationary support member fixably mounted on the drive wheel, the support member having a first end portion and a second end portion; and     a compressing member mounted on the support, the compressing member being attached to the arms, the arms being urged towards each other in the closed position     wherein the first arm member and the second arm member interlock with each other in the closed position.    

      In another aspect the invention provides the first arm member having a projection extending outwardly therefrom, the arm member having a first end portion and a second end portion, the first end portion being urged towards the chain, the second end portion being pivotally attached to the first end portion of the support; the second arm member having a first end portion and a second end portion, the first end portion being urged towards the chain, the second end portion being pivotally attached to the second end portion of the support member; and the third arm member having a first end portion and a second end portion, the first end portion, the second end portion being pivotally attached to the second end portion of the support member. The third arm member has a groove disposed therein, the groove being shaped to cooperate with the projection on the first arm member.  
      In yet another aspect, the invention provides the first frame further comprising: a front end portion and a rear end portion, the frame being mounted on a vehicle chassis, a prime mover mounted on the chassis; and an axle connected to the drive wheel to alternatively move the drive wheel in a first and a second direction.  
      In another aspect the invention provides a loading frame comprising: the first frame as claimed as described above; an actuator; and an elevatable support to receive a load from the second frame and connected to the actuator. The loading frame further including: a guide system having a central rail shaped to cooperate with the second frame. The rail has a slidably resilient material fixably mounted thereupon.  
      In another aspect, the invention provides the second frame further having: a plurality of wheels such that the second frame is movable relative to the first frame; a first rail, a second rail and a central rail, the central rail being shaped so as to cooperate with the central rail on the first frame.  
      In yet another aspect, the invention provides the second frame having a front end portion and a rear end portion, the front end portion being disposed towards the rear end portion of first frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In drawings which illustrate embodiments of the invention,  
       FIG. 1  is a side view of a first embodiment of the invention showing a movable frame engaging a stationary frame on a vehicle via a chain;  
       FIG. 2  is a top view of the vehicle showing the stationary frame attached to the vehicle;  
       FIG. 3  is a rear end view of the rear block assemblies mounted on the rear of the vehicle;  
       FIG. 4  is a simplified side view of the first embodiment showing the relationship between a rear block assembly and a frame rail;  
       FIG. 5  is a simplified view of the locking pin assembly;  
       FIG. 6  is a side view of the moveable frame;  
       FIG. 7  is a top view of the movable frame;  
       FIG. 8  is a simplified side view of the chain detail attached to the movable frame;  
       FIG. 9  is a simplified side view of the first embodiment in a locked position engaging the chain;  
       FIG. 10  is a simplified view of the first embodiment in a partially open position showing the frame engaging the locking system;  
       FIG. 11  is a simplified side view of the first embodiment in a fully open position;  
       FIG. 12  is a simplified end-on view of the moveable frame loaded on the stationary frame showing the interlocking of the rail systems;  
       FIG. 13  is a schematic rear view of the first embodiment;  
       FIG. 14  is a front end view of the moveable frame;  
       FIG. 15  is a simplified view of the internal ramp and lift tab;  
       FIG. 16  is a schematic view of the stationary shoe showing shape;  
       FIG. 17  is a side view of the front end of the moveable frame;  
       FIG. 18  is a detailed side view of the stationary frame;  
       FIG. 19  is a detailed view of the elevatable support;  
       FIG. 20  is a detailed top view of the front of the moveable frame rail; and  
       FIG. 21  is a cut away side view of the movable frame shown in  FIG. 7 , balanced on the stationary frame shown in  FIG. 2 . 
    
    
     DETAILED DESCRIPTION  
      Referring to  FIGS. 1 and 2 , an apparatus according to a first embodiment of the invention is shown generally at  10  and connects a movable frame  11  to a conventional cab and chassis vehicle  13  via a chain  66 , the frame  11  having a load  100  securely mounted thereupon. The vehicle  13  has a chassis  9  and a stationary frame  19  securely mounted thereupon. The stationary frame  19  is a “skeleton body” and is secured to the chassis  9  by conventional means, and is arranged such that a front end of the frame is disposed towards the rear of the cab of the vehicle  13  and a rear end portion is disposed towards a rear end portion of the chassis  9 .  
      The stationary frame  19  has a guide system mounted on the chassis  9  of the vehicle  13  and comprises a “skeleton-type” arrangement of rails  16 . The rails  16  are positioned parallel to each other along the side of the chassis  9  and are shaped so as to allow efficient sliding and seating of the moveable frame  11  during loading and are coated with an ultra-high molecular weight (UHMW) polymer  20 . One skilled in the art will understand that polymers of this type act as a lubricant to assist the moveable frame  11  as it slides over the stationary frame  19 , as will be described below. It will be understood that there are many different types of polymeric coatings used in this type of operation.  
      Referring to  FIGS. 1, 2 ,  3 ,  12  and  18 , an elevatable support  17  is centrally and rotatably attached to an axle  14  and includes a “skeleton framework”  61  having a separate guide system  59  consisting of a forwardly disposed end and a rearwardly disposed end. The guide system  59  consists of a C-shaped channel  54  with an internal ramp  33 , and a slide rail  44 . The slide rail  44  is covered with UHMW  50  on upper and lower faces. The skeleton framework  61  has two ends and a center that is parallel to the axle  14 . The skeleton framework  61  ends are rotatably attached to the axle  14  by a pair of bushings  106 . The position of skeleton framework  61  on the axle  14  is maintained by a pair of cylindrical spacers  107 . Each spacer  107  is positioned on the axle  14  between the elevatable support bushings  106  and a pair of outer axle bearings  108 . Those skilled in the art will recognize that bearings of different types may be used in place of the bushings  106  and spacers  107 . The axle  14  is rotatably mounted to the chassis  9  by the bearings  108  and a bearing  122 . Each bearing  108  is fixably attached to and located on the axle  14  adjacent the two end portions  21  and  55 . The bearings  108  are fixably attached to each of the chassis  9  frame rails. The bearing  122  is fixably attached and located in the center of the axle  14  and is supported by the stationary frame  19 . The axle  14  is driven by an electric motor  94 . Those skilled in the art will recognize that other types of motors may be used to implement aspects of the invention. The axle  14  has two end portions  21  and  55  that covers the first embodiment  10 . The motor  94  is attached to the axle  14  by a keyed sprocket and an endless roller chain  104 . The turning motion of the axle  14  is transferred to a pair of keyed sprockets  12  that are mounted on the ends of the axle  14 .  
      The guide system  59  is aligned parallel to and between the frame rails  16 , and is fixably attached to the framework  61  such that a movable frame receiver  72  aligns and interlocks with the slide rail  44  when the frame  11  is mounted on stationary frame  19 , as will be described. The bottom edge of the rearwardly disposed section of the guide system  59  is fixably attached to the top edge of the center portion of the skeleton framework  61 . A pair of support frame members,  111  and  112 , are attached to the guide system  59 , and each having first and second ends. The first end top edges of the support members,  111  and  112 , are fixably attached to the bottom edge of the forwardly disposed end of guide system  59 , whereas the second ends are fixably attached to the corresponding ends of the skeleton framework  61 . The support members,  111  and  112 , support the forwardly disposed end of guide system  59 , thereby ensuring the guide system  59  remains parallel with the frame rails  58  on the moveable frame  11 . The top and bottom surfaces of the rail  44  are covered with UHMW  50 .  
      As best seen in  FIGS. 1, 2 ,  3  and  19 , a hydraulic cylinder  46  is attached to the stationary frame  19  and is moved by a pair of arms,  15  and  37 , that are pivotally attached to the frame  19 , a cross member  53  and the forwardly disposed end of the guide system  59 . The hydraulic cylinder  46  acts as a shock absorber during on-loading and off-loading and also allows an operator to stop the tilting motion of the moveable frame  11  at any time thereby giving the system a greater degree of control during operation. It will be understood that other “damping” systems may be used with the elevatable support  17 .  
      Also, those skilled in the art will recognize that the elevatable support  17  does not require arms  15  and  37  for the hydraulic cylinder  46 . Another possible method would be to use a longer cylinder thereby avoiding the use of the arms,  15  and  37 .  
      As best seen in  FIG. 21 , the elevatable support  17  is pivotally attached to the axle  14  that is positioned at the rear end of the vehicle  13 . The movable frame rail  58  pivots when loading or offloading on the surface of a slide  8  with the center of the circumference of the axle  14  being the center of the arc of the slide  8  (see  FIG. 4 ). This creates a common pivot point for both the receiver  72  on the movable frame  11  and the elevatable support  17  thereby ensuring both alignment and non-binding movement between the elevatable support  17  and the receiver  72  (see  FIG. 6 ) prior to interlocking and when interlocked. As best illustrated in  FIGS. 2 and 19 , a pair of springs  43  assist in lifting and holding the elevatable support  17  up by exerting a twisting force on a hinge pin  47  that is fixably attached to the arm  15 . The outer coils of the springs  43  are attached to a bar  64  that is attached to the arm  37 . This twisting action assists in opening the arms,  15  and  37 , with the hinge pin  47  as the center axis. The lifting and maintaining of the elevatable support  17  vertical position may be accomplished by placing the springs in other areas, for example, over the cylinder  46  or to the frame  19  and lifting under the arms,  15  and  37 , below the hinge pin  47 . Those skilled in the art will recognize other means of assisting the lift and holding the elevatable support.  
      Also, those skilled in the art will recognize that the elevatable support  17  does not require arms  15  and  37  for the hydraulic cylinder  46 . Another possible method would be to use a longer cylinder thereby avoiding the use of the arms,  15  and  37 .  
      As seen in  FIGS. 2, 3  and  4 , the frame  19  has a pair of rear block assemblies  80  generally located at the rear end of the frame rails  16  of the vehicle  13  and fixably attached to the chassis  9 . Each rear block assembly  80  consists of a slide arrangement  8  that is designed to evenly distribute the load of the movable frame  11  during loading and unloading, and to distribute the overall weight of the loaded moving frame away from the sprockets  12  during the loading and unloading process. As best seen in  FIGS. 3 and 4 , the axle  14 , the sprocket  12 , the elevatable support  17  and the slide arrangement  8  are co-axially arranged, ensuring the vertical alignment of the elevatable support rail  44  with the receiver  72  ( FIG. 12 ) while the slides  8 , rails  16  and the frame rails  58  assume lateral alignment.  
      At the front end of the stationary frame is a locking pin assembly  82 . As best seen in  FIG. 5 , the assembly  82  provides a manual positive lock system when the movable frame  11  is fully loaded on the stationary frame  19  and is a safety feature that prevents movement of the movable frame  11  into the cab of the vehicle during an accident. A rod  74 , is attached to a first locking pin  71  and second locking pin  78 , adjacent a handle  89 . The first pin  71  is moveable in the same direction as the rod  74 . The second pin  78  is positioned away from the handle  89  and is attached to a fulcrum plate  76  which reverses the direction of the rod  74  during operation. As the rod moves in a first direction, the first pin  71  moves in the same direction, whereas the pin  78  moves in a second direction.  
      As best seen in  FIGS. 3, 4  and  6 , a pair of stop plates  81  in the rear block assembly  80 , act as collision impact buffers to prevent the movable frame  11  from damaging the vehicle body when a movable frame stop plate  67  abuts the stop plate  81 . Furthermore, the stop plates  81  and  67  allow precise location of the movable frame  11  on the frame  19  and also allows for precise alignment of the locking pin assembly  82  (see  FIGS. 4, 5  and  12 ) on the frame  19  with a plurality of lock pin holes (not shown) on the movable frame  11 . Slide  8  on the rear block assembly  80  are coated with the UHMW  45  that acts as a lubricant to assist the movable frame as it slides over the rear block  80 .  
      The rear block assembly stop plates  81  are positioned rearward of the axle  14  yet forward of the most rearward teeth of the sprocket  12 . As seen in  FIGS. 1, 7 ,  8  and  17 , this allows a cross member  65  and a front portion  25  of the rail  58  to be unobstructed by the stop plate  81  when lifting or lowering moveable frame  11  when tag chains  66  and or links  62  are engaged on teeth of the sprockets  12 .  
      With the moveable frame  11  tilting backward, the front of the receiver  72  tilts up, and with the receiver  72  and the slide rail  44  interlocked, the elevatable support  17  also moves up. The elevatable support  17  in turn pulls on the arms  15  by an arm pin  48 . In turn, the arm  15  pulls on the hinge pin  47  in turn pulling the lower arm  37  up with the lower end of the arms  37  connected to the sub frame cross member  1  with a hinge pin  49 . The arms  15  and  37  hinge open with hinging taking place on the hinge pin  47 . This action extends the hydraulic cylinder  46  as the ram  41  is connected to the arm  15  through the upper cylinder pin  39  and the barrel of the cylinder  42  is connected to lower arm  37  by a lower cylinder pin  51 . An operator can allow the moveable frame  11  to tilt without further forward and rearward movement if frame  11  is in an unbalanced condition.  
      Referring now to  FIGS. 1, 6 ,  7 ,  12  and  14 , the movable frame  11  comprises a “skeleton body” type frame with a pair of longitudinal rails  58  which act as slides so as to guide the rails  16  on the frame  19 . Disposed between, and parallel to, the rails  58  is the receiver  72  which is positioned across the under side of a plurality of cross members  77  and along a portion of the frame  11  length. Mounted to the frame is the load  100  and a set of removable wheels  56  to allow movement. Those skilled in the art will recognize that other means for moving the frame  11  are available to implement aspects of the invention, for example, skid plates. The movable frame  11  has a front end portion  25  and a rear end portion  27 . The front end portion  25  is disposed toward the rear of the stationary frame  19  during initial maneuvering. The load  100  is attached to the frame  11  with the front portion  25  of the box  100  positioned rearward of the front portion  25  of the frame  11 . This positioning allows the movable frame  11 , when on or off-loading, to be lifted or lowered without the box  100  contacting the tag chains  66  or the sprockets  12 .  
      As best illustrated in  FIGS. 1, 6 ,  8 ,  17 ,  20  and  21 , the frame  11  has a tag chain  66  that is attached to a roller chain  83 . The roller chain  83  is fixably attached to a roller chain frame  60 , which in turn is fixably mounted to the frame  11 . With the movable frame resting on level ground, the vertical distance between the bottom face of the portion of rail  58  that slides on the top of slide  8  and the bottom of the roller on the roller chain  83  is equivalent to the distance between the radiuses of the slide  8  and bottom of valleys, between the teeth, of sprocket  12 . These equivalent measurements allow the frame rail to slide over the slide  8  and the rail  58  support the heavier loads. The curved nose  123  of the front portion of the rail  58  that slides over slide  8  is curved to allow the rail  58  to slide over slide  8  when initially loading a heavily loaded frame  11 . A first link  62  of the chain  83  is positioned adjacent lips  52  that are supported on the frame  11 . The lips  52  forwardly protrude from the roller chain frame  60  and over the top of the side plates of the link  62  and prevent the over stressing of the side plates. This reduces the possibility that the side plates may break during the lifting or lowering of the front portion  25  of the frame  11 . One skilled in the art will recognize that the side plates are not designed for excessive force 90 degrees to the chain side plate. The tag chain  66  has an unattached end portion  63  that enables an operator to guide the tag chain  66  onto the sprockets  12  of the frame  19 . The sprockets  12  are positioned such that the unattached end portion  63  of the chain  66  can be engaged on the sprockets without hindrance from other components. When the sprockets  12  are turned by the axle  14 , the tag chain  66  is pulled tight in the direction of the wheels&#39; rotation and serves to pull the loaded frame  11  toward and up onto the first frame  19 . When not in use, the tag chains  66  are pivoted up and back on to the top of roller chain frame  60 . This advantageously protects the chain from damage. There is a corresponding storage track  84  on the frame  19  which also acts as a housing for the tag chain  66  when the frame  19  is fully loaded with the movable frame  11 .  
      Referring now to  FIGS. 2, 3 ,  7 ,  14  and  17 , a plurality of disposed tie-down brackets  85  on the frame  19  permit locking of the movable frame  11  to the frame  19  in the final loaded position. Disposed towards each of the four corners of the movable frame  11 , the tie-down brackets  85  lock the movable frame  11  to the frame  19  to prevent vertical movement of the movable frame during motion of the vehicle over uneven ground. The movable frame  11  has a plurality of tie-down brackets  86  that cooperate with the tie-down brackets  85  on the frame  19 . The forwardly disposed frame brackets,  85  and  86 , are positioned lower than the rearwardly disposed frame brackets,  85  and  86 , to allow the forwardly disposed frame brackets  86  on the movable frame  11  to slide under the rearwardly disposed brackets  85  of the frame  19  during the initial loading. In the final loaded stage, the brackets  86  are positioned directly under the corresponding stationary frame brackets  85 . Advantageously, the brackets eliminate excessive noise between frame  11  and frame  19  when the vehicle is operating and also has the safety advantage of preventing a roll over of the movable frame  11  when loaded on the frame  19 .  
      The movable frame  11  has wheels  56  on the frame  11  so that frame  11  can be moved relative to the stationary frame  19  prior to engagement. The wheels  56  are removable when the wheels are off the ground. The wheels  56  are removed by removing the hitch pin  113  from pin hole (not shown) in the wheel support tubing  114  and allowing the shaft of front wheel frame  57  to drop down out of the movable frame wheel support tubing  114 , then replacing hitch pin  113  in pin hole. The vehicle  13  may be maneuvered to align to the moveable frame, such that if the wheels  56  are used on the rear of the movable frame  11 , they are aligned such that they track straight and parallel to the lines of the movable frame rails  58 . This wheel alignment encourages the movable frame  11  to remain in alignment with the frame  19  when loading and off-loading.  
      Referring now to  FIGS. 1, 9 ,  10 ,  11  and  13 , a pair of chain locking systems  10  are rearwardly mounted on the frame  19  and adjacent the rear wheel of the vehicle as each of the chain locking systems  10  comprises a sprocket  12 , a movable shoe arm  22 , a movable shoe  26 , a sensing plate  32 , a locking arm  28 , a support member  88  and a pair of main springs  36  and  38 , attachment bracket  93 , slot  120 , bolt  110 , spring tensioning plate  35  and pin  119 . The support member  88  has a first end portion  101  and a second end portion  102  and is fixably attached by attachment bracket  93  to the chassis frame  9 . The first end portion has a slot  120  best seen on  FIG. 13 . Fixably attached to the first end portion  101  by a bolt  110  is the adjustable spring tensioning plate  35  and fixably attached to the spring tensioning plate is a pin  119 . The pin  119  has two ends and each end projects from the side spring tensioning plate  35 . The first end has a slot in the pin that the spring  36  is fixably attached to and the second end is positioned as a pivot for the arm  22  with arm  22  positioned in slot  120 . The center portion of the support member  88  is a bushing  109  that encases the circumference of the axle  14  adjacent the outer end. The support member  88  allows axle  14  to rotate inside the bushing  109  additionally supporting the axle  14  by the chassis  9  when the front end portion  25  of the movable frame is being lifted during initial loading.  
      The support member  88  allows the axle  14  to rigidly support a stationary shoe  23 . Should the movable frame  11  rise, the roller chain frame  60  will rise up to the stationary shoe  23  thereby keeping the chain  83  engaged with the sprocket teeth  12 . The stationary shoe  23  is advantageously placed and shaped so that it maintains the tag chain  66  or the roller chain  83  on the sprocket. Referring to  FIG. 16 , the stationary shoe  23  is positioned at an imaginary intersection point that is defined by the tangential angle of contact between the movable frame and the sprocket. This exact placement allows the movable frame  11  to maintain a maximum angle during loading, as shown by a pair of tangent lines  117  and  116 . The stationary shoe  23  is also shaped so that it follows these tangent lines and this allows the movable frame  11  to rotate through all desired angles on the sprocket. In all cases, the stationary shoe  23  prevents the tag chain  66  and the roller chain  83  from skipping off of the teeth on the sprocket  12  by allowing minimum clearance between the stationary shoe  23  and the sprocket  12 . The stationary shoe  23 , with the combined strength of the axle  14  and the support  88 , the frame  11  and a frame attachment bracket  93 , prevents the movable frame  11  from rolling sideways off the vehicle should the other safeties fail.  
      Referring now to  FIG. 13 , the sensing/locking arm shaft  40  is rotatably mounted on the second end portion  102  of the support member  88 . The locking arm  28 , the sensing plate  32  and the main spring  38  are co-axially and fixably attached to the shaft  40 . Those skilled in the art will recognize that the sensing plate  32  and locking arm  28  could be manufactured from a single plate. The outer coil end of spring  38  is fixably attached to an attachment bracket  93 . The movable shoe arm  22  has a first end portion and a second end portion. The first end portion of the shoe arm  22  is urged towards the chain and the second end portion is pivotally attached to the first end portion in slot  120  of the support  88  by the pin  119 .  
      Referring now to  FIGS. 9, 10  and  11 , the moveable shoe arm  22  has a projection  103  that extends outwardly therefrom. The movable shoe  22  has a second projection  118  and fixably attached to this projection is the outer coil of the spring  36 . The locking arm  28  has a first end portion and a second end portion, the second end portion being fixably attached to the first end portion of the shaft  40  ( FIG. 13 ). Furthermore, the locking arm  28  has a groove  31  that is machined into the body. The groove  31  is shaped so that when the shoe  22  and the arm  28  are sprung into a closed position, the groove  31  co-operates closely with the projection  103  on the shoe arm  22 . The arm  28  also has a tab  30  that is shaped such that it pushes chain  66  off of the sprocket  12 . The tab  30  also redirects the chain  66  back onto the teeth of the sprocket  12 . The sensing plate  32  has a first end portion and second end portion. The first end portion of the plate  32  has a bearing  34  attached thereto and is urged upwards against the bottom side  92  ( FIG. 11 ) of the movable frame rails  58 . The second end portion of the plate  32  is fixably attached to the center portion of the sensing/locking plate shaft  40 .  
      The movable shoe  22  spring tensioning can be adjusted by turning the bolt  110  to loosen the spring tensioning plate  35  and then swiveling the plate which in turn turns the center of the main spring  36 . A front release fork  24  prevents the tag chain  66  from wrapping around the sprocket  12  during the initial chain engagement. A rear chain release fork  18  prevents the tag chain  66  from wrapping around the sprocket  12  after the movable frame  11  is lowered to the ground but before the sprockets  12  allow the tag chain ends to drop to the ground.  
      Referring to  FIGS. 3, 4  and  7 , during final engagement of the movable frame  11  with the frame  19 , a pair of stop plates  68  at the rear end portion  27  of the moveable frame  11  abuts a pair of stop plates  81  in the rear block assembly  80 . Advantageously, the stop plate face  68  is also covered with UHMW  67  to prevent the rubbing noise of metal on metal when the vehicle is moving.  
      Operation  
      With reference to  FIGS. 1, 8  and  9 , the operation of the first embodiment will now be described. With the movable frame  11  positioned on the ground the operator may back the vehicle  13  up to the movable frame  11 . The tag chain  66  is placed onto the sprocket  12 . The tag chains  66  are aligned to the rear of the stationary shoe  23  so as to line the end portion  63  of the chains in the same clock position on the sprockets  12 . The operator activates the motor  94  from an electrical control box (not shown) which releases an integral motor brake and begins rotation of the axle  14 .  
      As the sprockets turn, the tag chain  66  tightens and the front-end portion  25  of the movable frame  11  begins lifting off of the ground. At this point, the weight of the movable frame  11  is distributed between both of the rear wheel assemblies  56 , the ground, the two tag chains  66  and the sprockets  12 . The tag chain lifting force is transferred 90 degrees to the first link  62  of the roller chain  83 . Each sprocket  12  has about 180° of contact with the tag chain  66 . This is sufficient contact to allow safe lifting or lowering of the movable frame  11 . At this stage, the front release fork  24  prevents the tag chain  66  from wrapping around the sprocket  12 .  
      The chain  66  begins lifting the weight of the movable frame  11 . The tag chain/locking process remains in place until the weight of the loaded movable frame  11  is supported by the rear block assembly slide  8 . This advantageously eliminates the opportunity of the tag chain  66  slipping off the sprocket  12  and dropping the loaded movable frame  11 . The tag chains  66  are prevented from working off the sprockets  12  by the movable shoes  26  that are positioned directly above the sprocket  12  and are held in position by the locking arms  28 . The chain locking mechanism is a positive tag chain-to-sprocket locking device that reduces or essentially eliminates the possibility of the tag chain  66  being pulled off the sprockets  12  when the locking arm  28  is in position.  
      Referring to  FIGS. 2, 7 ,  8 ,  9  and  10 , during the mounting phase of the operation, the movable frame  11  continues being pulled up and forward towards the frame  19  with two tag chains  66  and two roller chain links  62  now in contact with sprockets  12 . The two frame rails  58  begin to slide over the slides  8 . The frame rails  58  and slide  8  take the weight of the front of the movable frame  11 , which removes the weight off the tag chain  66 , the roller chain frame  60 , sprocket  12  and drive axle  14 .  
      Advantageously, as the movable frame  11  moves further forward, the roller chain frame  60  moves under the stationary shoe  23  thereby preventing the movable frame  11  from tipping or rolling off sideways. Furthermore, this prevents the roller chain frame  60  from lifting up to a point where the chain links could slip a tooth on the sprocket  12  and ensures that the movable frame cannot fall back off the slides  8 . This guide system of  58 ,  8  and  16  maintains the movable frame in a straight line with the stationary frame  19 .  
      At this stage, the operator removes the wheels  56  at the front of the moveable frame  11  to prevent them from interfering with the vehicle tires  29 .  
      Referring to  FIGS. 9, 10 ,  11  and  13 . As the vehicle  13  has two essentially identical locking systems  10  mounted rearwardly, only one will be described in detail.  
      The front-end portion  25  of the rail  58  contacts the sensing plate  32  and pivots the sensing plate  32  forwardly and downwardly. The sensing plate  32  rotates the shaft  40  against the spring tension of the main spring  38 . Rotation of the shaft  40  also pivots the arm  28  forwardly and downwardly. The groove  31  in the arm  28  pivots clear of the projection  103  on the arm  22 , thereby releasing the arm  22 . As the movable frame  11  continues advancing, the sensing plate  32  continues to pivot downwardly, which in turn rotates the shaft thereby moving the arm  28  further forwardly and downward and increasing the tensioning of spring  38 . The arm  28  pivots forward and down with the tab  30  on the arm  28  pushing the tag chain  66  forward and off the teeth of the sprocket  12 .  
      Methods other than the sensing plate  32  may be used to sense the frame  11  when loading or off-loading and to activate the locking plate  28 . This timing and activation may be accomplished electrically by the use of limit switches that sense a lower portion of the surface  92  of the rail  58  and in turn the limit switches may control the operation of an electric or mechanical solenoid or small gear motor that closes or opens locking plate  28 .  
      As the chain  66  is being pushed forward off the sprocket  12 , the chain  66  contacts the arm  22  which is still in a closed position. The forward advancement of the chain  66  pushes the movable arm  22  forward and open, which overcomes the force of the spring  36 . The tab  30  of locking arm  28  has now pushed the tag chain  66  forward and off the teeth of sprocket  12  and tab  30  holds the chain forward and away from the sprocket  12 , and in turn the chain  66  holds arm  22  forward and up. With the front of movable frame rail  58  still moving forward, the arm  22  is lifted by the roller chain frame  60  on the side of the frame rail  58  as the roller chain frame  60  slides under the arm  22 . The arm  22  is lifted by the forward sliding action of the roller chain frame  60  and movable shoe  26  rests on the top of the frame  60  as it moves forward. With the frame rail  58  still advancing, the rail  58  slides over the plate  32  and bearing  34 . The bearing  34  rolls along the bottom side  92  of rail  58  for the remainder of the operation.  
      The tab  30  on the arm  28  holds the tag chain  66  forward and away from the sprocket  12 , while the frame rail  58  advances. This prevents the chain  66  from hanging or “welding” to the sprocket  12 . With the forward movement of the frame rail  58 , the tag chain  66  is moved forward and away from the tab  30 .  
      Advantageously, slot  31  is so machined that when the movable shoe arm projection  103  is in a locked position with the locking arm slot  31 , there is a space between the chain  66  and arm  22  to prevent excessive wear.  
      For operation of the chain locking system  10  in reverse, the process described above is essentially reversed. During rearward movement of the frame  11 , for example in the off-loading procedure, the main springs  36  and  38  urge the arm members  22  and  28  into a closed position when the loose tag chain  66  re-engages the sprocket  12 . The shoe  23  that is attached to the first end portion  101  of the support member  88  prevents the chain from skipping the teeth on the sprocket  12 . Furthermore, the stationary shoe  23  prevents body rollover when off-loading the movable frame  11  from the stationary frame  19 . In the fully opened position, the shoe  23 , and the arms  22  and  28  allow the chain  83  to move freely with the sprocket  12 . As the movable frame  11  moves rearward with the tag chain  66  approaching the sprocket  12 , the tag chain  66  contacts the locking arm tab  30 . The roller chain frame  60  begins to slide from under the movable shoe  26  and arm  22 , and the movable shoe  26  and the arm  22  pivots down and contact the top of the tag chain  66  and tag chain  66  is pressured down against the tab  30 . With the sensing plate  32  following the contour of the rail  58 , the tab  30  pivoting down and rearward and to the closed position allows the tag chain  66  to lay onto the teeth of the sprocket  12 . The tag chain  66  is urged on to the teeth of the sprocket  12  by the spring-tensioned arm  22 . With the tag chain  66  engaging on the sprocket  12 , the groove  31  of the spring-tensioned locking arm  28  pivots over projection  103  on the moveable arm  22  and the locking system is again closed and locked.  
      The stationary shoe  23  is positioned such that at any angle of loading, the shoe  23  acts as a secondary hold for the movable frame  11  to the stationary frame  19  and thereby positively locks the roller chain  83  to the teeth of the sprocket  12 . The stationary shoe  23  also acts as a secondary hold of the tag chain  66  to the teeth of the sprocket  12  during lifting and lowering of the front end portion  25  of the movable frame. Advantageously, if the locking system  10  were to fail or a load was loaded or off-loaded with the system unengaged, the tag chain  66  would still be secured by the stationary shoe  23 .  
      Referring to  FIGS. 14, 17 ,  18  and  19 , with the frame  11  still moving forward and the rear wheels  56  still on the ground, the movable frame cross member  65  moves over the elevatable support  17 . With the rearward portion of the elevatable support  17  rotatably attached to the axle  14 , and if the forward portion of the UHMW  50  on top of slide rail  44  is too high for the slot  75  to clear, the slide rail  44  will be pushed, in turn pivoting the elevatable support  17  down by the slot  75  and by the weight of the movable frame  11 . A lift plate  87  enters the rearward disposed end of the channel  54  and alignment plate  73  slides over top of the slide rail  44 . If the slide rail  44  is still too high, the alignment plate  73  pushes on the slide rail  44  and the elevatable support  17  pivots further down. If the elevatable support  17  is low, the lift plate  87  slides along the inside top lip of the channel  54  and lifts and pivots the elevatable support  17  upwardly as the movable frame moves forward. The lift plate  87  slides along and under a tapered internal ramp  33  and lifts and pivots the elevatable support  17  higher. With the elevatable support  17  height finely adjusted, the rail  44  aligns with the receiver  72 . The movable frame  11  slides further forward and the front portion of the receiver  72  slides and interlocks over the rear disposed portion of the elevatable support rail  44 , which is coated with UHMW on both sides. With further forward movement of the movable frame  11 , the receiver  72  slides further forward over the rail  44 .  
      The elevatable support guide system  59  along with the slot  75 , the lift plate  87  and the alignment plate  73  allow various lengths of frames to be loaded on the same stationary frame. When the frame  11  is off-loaded the elevatable support  17  maintains this angle. When a different length of frame  11  is on-loaded the angle of loading changes. The elevatable support may be re-adjusted by the above components allowing this new receiver to align with the elevatable support with no manual labor required.  
      As best seen in  FIG. 21 , the movable frame  11  is balanced above the rear block assembly slide  8  whereupon only the slides  8  on the rear block assemblies  80  are in contact with rails  58 . The receiver  72  is interlocked with the rail  44  and the movable frame rails  58  are straddling the rear portion of the stationary frame rails  16 . As the movable frame  11  is moved forward so that the center of gravity and weight is passed over the slides  8 , the weight is transferred from the rear wheel assemblies  56  to the elevatable support  17 . The elevatable support  17  allows the weight to drop down onto the stationary frame  19  in a controlled manner by the resistance of the hydraulic cylinder  46 , flow restrictors and valves. The movable frame  11  is eased down onto the stationary frame  19  with the movable frame rails  58  resting on top and straddling the rails  16 , thereby preventing lateral movement of the movable frame  11  when travelling ( FIG. 12 ). The tag chains  66  are pulled up onto the storage tracks  84  as the movable frame  11  continues forward. The storage area on top of the roller chain frame  60  is only used when the movable frame  11  is off the vehicle  13 .  
      One skilled in the art will understand that the storage track  84  may be omitted. The top of the roller chain frame  60  along with the side bar  79  on the movable frame  11  may be used in place of the storage track  84 . The side bar  79  makes a storage track for the tag chain  66 . The bar  79  moves through the stationary shoe groove  121  ( FIG. 13 ) when the movable frame  11  is loaded or off-loaded. This track may be necessary when loading and off-loading because when the movable frame  11  is moving on top of the stationary frame, the hanging tag chain  66  may catch, or hang up, on the vehicle suspension on parts of the chassis  9 . In loading the operator may be required to manually place the tag chain  66  into the storage track roller chain frame  60 . In off-loading, the tag chain  66  may be removed from the top of the roller chain frame  60  by the movable shoe  26 . With the movable shoe  26  on the top of roller chain frame  60  the shoe  26  pushes the tag chain  66  off of the roller chain frame  60  as the movable frame moves in rearward direction.  
      As best illustrated in  FIGS. 2, 5 ,  6 ,  11 ,  12  and  21 , the stop plates  68  prevent the movable frame from being pushed forward into the cab of the vehicle  13 . Advantageously, the stationary shoes  23 , the movable shoe arms  22 , the rear upper tie down brackets  85  and the rear lower tie down brackets  86 , the receiver  72  and the elevatable supports  17 , are so configured that they prevent the movable frame stop plates  68  from lifting over the stop plates  81  in an accident. The manual locking mechanism  82  is used to lock the movable frame  11  in the loaded position. Moving the handle  89  into the locked position causes the pins  71  and  78  to move into the locking pin holes in the movable frame  11 .  
      In order to remove the movable frame  11  same procedure is used except that the motor  94  is activated in the reverse direction.  
      Referring to  FIGS. 2, 6 ,  7 ,  14 ,  17  and  18 , the movable frame  11 , may have fender components that hang lower and in front of the rear vehicle tires  29 . The ramp system for on and off-loading of a fender body comprises a pair of lower fender slide frames  95 , a pair of slide posts  69  and a pair of roller posts  91  that are located on the movable frame  11 . A pair of ramps  90  are correspondingly located on the frame  19 . The frame components protect the fenders  99  of the box  105  of the movable frame  11  when loading and off-loading. One skilled in the art will recognize that there are many types of fender bodies, for example, a standard fleet slide or step side pickup box body, a utility box body, catering truck bodies, motor home bodies and passenger bodies to name only a few.  
      The lower fender slide frames  95  protect the fenders  99  of the body. The fender slide frames  95  is slightly lower than the fenders  99 . The slide frame  95  is supported and attached to the movable frame cross members  115  and the cross members  77 . The lower fender frames  95  shown, work as a slide system that slides across the top of the rear tire  29  when loading or off-loading. The balance point of the movable frame  11  at the time of loading or off-loading determines if the slides  95  contact with the tires  29 .  
      The slide posts  69  slide up or down the topside of the rearward angled portion of the ramps  90 . The slide posts  69  are shorter than the roller posts  91  located forward therefrom on the frame  11 . The bottom end of the shorter slide posts  69  is high enough to contact the top side of the sloped rear section of the ramps  90  when the frames  95  are sliding forward on the tires  29 . The front portion  25  and the roller posts  91  of the frame  11  are raised as the slide posts  69  slides forward and up the ramps  90 . The longer roller posts  91  are raised to a position where they contact the top sides of the sloped rear sections of the ramps  90 .  
      The short slide posts  69  allow the most rearward end of the sloped section of ramps  90  to be high above the tires  29  allowing necessary clearance from tires  29  to ramps  90 .  
      The longer roller posts  91  lifts the frame  11  high enough so as to maintain necessary clearance between the front of the wheel wells  98  and the tires  29 . Depending on the weight, the balance point and the speed at which the frame  11  is on or off-loading, the setting of the controls of the hydraulic cylinder  46 , plus the vehicle chassis suspension, slide post  69  may or may not be used.  
      For off-loading, the slide posts  69  carry the movable frame  11  when the roller posts  91  roll off of the sloped rear section end of the ramps  90  to a point where either gravity tilts the movable frame  11  up or the frames  95  contacts the tires  29 . The slide posts  69  could also be equipped with rollers.  
      The roller posts  91  carry the movable frame  11  as it rolls up and down the ramps  90  during loading or off-loading. The roller posts  91  carry the load weight at different times depending upon the weight, balance point and speed at which the frame  11  is on or off-loading, the setting of the controls of the hydraulic cylinder  46 , plus the vehicle chassis suspension.  
      By eliminating the rear sloped section of the ramps  90  and extending the horizontal section of the ramps  90  rearwardly away from the rear of tire  29 , the slide post  69  and the lower fenders&#39; slide frames  95  may be eliminated, providing the design of the vehicle chassis  9  is such that adequate clearance is maintained between the top of the tires  29  and the ramps  90  when the vehicle is loaded and in motion. One skilled in the art would recognize that the balance point is such that the roller posts  91  would be positioned over the ramps  90  when the center of gravity of the fender body  105  is moved over the rear block assembly slide  8 .  
      If the fully loaded movable frame  11  begins to off-load, the roller posts  91  come into contact, rolling rearward and upward on the top side of the front angled portion of the ramps  90 , thus lifting the front portion  25  of the movable frame  11 . The rearward portion  27  of the rails  58  slide and pivot on the rear block assembly slides  8 . The movable frame  11  and the receiver  72  lift the elevatable support  17  up as the receiver  72  slides along the slide rail  44 .  
      Referring to  FIGS. 6, 17  and  18  with the front portion  25  of the movable frame  11  moving up, the front of fender walls  98  clear the top of the tires  29  and the roller posts roll along the horizontal section of the ramps  90 . The roller posts  91  roll rearward and down the rear portion of the ramps  90 . With the roller posts  91  rolling to the end of the ramps  90  the shorter slide posts  69  contacts the ramps  90  and as the movable frame  11  is moved rearward the slide posts  69  slides rearward and down the ramps  90 . The front-end portion  25  of the movable frame  11  continues moving rearward and down, the lower fender slide frames  95  contacts the top of the tires  29 . The weight of the front end portion  25  of the movable frame  11  is removed from the slide posts  69  and ramps  90  to the lower fender slide frames  95  and the top of the rear tires  29 . The frame sliding rearward with the weight of the front portion end  25  of the movable frame  11  on rear tires  29  and the weight of the rear end portion  27  of movable frame  11  on the rear block assembly slides  8  and with the receiver  72  sliding on the elevatable support rail  44 , the point of balance of the movable frame slides over the rear block assembly slides  8  and the front end portion  25  of the movable frame  11  tilts upward and rearward. With the receiver interlocked with the elevatable support rail  44  the tilting action lifts the elevatable slide support. The speed of lift action is controlled by the scissor arms  15  and  37 , the hydraulic cylinder  46  and its associated hydraulic flow controls and valves. The movable frame  11  tilting action occurs at the time the point of balance of the movable frame  11  slides over the rear block assembly slides  8 . The tilting action timing varies depending on the distribution of the payload weight of the movable frame  11 .  
      In on-loading of the moveable frame  11 , the procedure is reversed.