Patent Publication Number: US-2002000736-A1

Title: Horizontal positioning of dump truck tailgate

Description:
BACKGROUND OF THE INVENTION  
       [0001] This invention relates to a hinge for a truck body. More specifically, this invention relates to a latchable hinge for securing a tailgate to a dump truck body.  
       [0002] Dump trucks, especially medium and heavy duty trucks adapted for the movement of bulk construction materials, are common and well known. Commonly, this type of vehicle has a generally box shaped dump body to contain the bulk materials during transport. The vehicle also has a lift which can raise the front of the dump body with respect to the rear during unloading. This creates an inclined plane such that the bulk materials slide toward the back of the body and are dumped through an open tailgate.  
       [0003] The tailgate at the rear of the dump body is designed to allow the transport of bulk materials while facilitating the rapid discharge via dumping. The top of the tailgate is usually hinged to the top of the body with pins, and the bottom of the tailgate is usually releasably coupled to the bottom of the body. The result is a solid attachment of the tailgate to the body when the tailgate bottom is coupled, allowing construction materials to be transported without loss. To normally dump the construction materials, the bottom of the tailgate is uncoupled from the bottom of the dump body. The tailgate can then pivot around the top pins, creating an opening between the rear of the dump body and the bottom of the tailgate. As the front of the dump body is raised, the construction materials rapidly flow to the rear of the body and are discharged through the opening. After discharge of the bulk material, the front of the dump body is lowered, with the tailgate pivoting back to its initial position, ready for re-coupling to the dump body.  
       [0004] Some materials carried by the truck cannot be discharged in the normal manner, for instance, boulders too large to fit through the opening created between the tailgate and the dump body, or items too fragile to withstand the fall to the ground. For these materials, it is desirable to allow the tailgate to rotate around the bottom coupling mechanism to a horizontal or lowered vertical position. This allows a larger opening in the back of the dump body for discharging materials which can be dumped, or for carrying off fragile items.  
       [0005] The manipulation of the tailgate to a horizontal or lowered vertical position can present a number of problems. Conventional hinge pins, when new, require tools for removal. In the usual construction environment, the hinge pins quickly rust into place in the body, allowing the tailgate to pivot, but making removal from the body difficult, even with the use of tools. After removal, the pins are easily misplaced. Finally, after unloading of the bulk material, the tailgate must be placed back into the raised vertical position. This requires the operator to manually lift the tailgate to the raised vertical position, at the same time trying to align holes high on both sides of the body with holes in the top of the tailgate. The operator must then hammer the pins back into those holes, while maintaining everything in alignment. At best this process is difficult, and at worst it may be impossible for a single operator to achieve.  
       SUMMARY OF THE INVENTION  
       [0006] An object of the invention is to provide a dump body hinge for a tailgate.  
       [0007] Another object of the invention is to provide a hinge for a dump body tailgate which is easily releasable without tools.  
       [0008] A further object of the invention is to provide a hinge for a dump body tailgate which can be rapidly released and reattached by a single operator.  
       [0009] The present invention achieves these objects by use of a latchable hinge comprising an extendable plunger assembly cooperating at right angles with a movable strike. Preferably a pair of latchable hinges is used, with one plunger assembly mounted to each side of the dump body and one strike mounted cooperatively to each side of the tailgate. It would also be possible to mount the plunger assemblies to the tailgate and the strikes to the dump body.  
       [0010] The plunger assembly includes a bolt biased toward an extended position. In the extended position, the bolt fits within an aperture defined by a strike. In this relationship the bolt can act as a pivot, supporting the weight of the tailgate and allowing the strike, and thereby the tailgate bottom edge, to rotate. The plunger assembly also includes a lever attached to the bolt for moving the bolt against the bias to a retracted position. In the retracted position, the bolt is free of the strike aperture and the tailgate top edge can rotate around the bottom coupling mechanism.  
       [0011] Preferably, the end of the bolt is beveled so that the strike can move past the extended bolt until the bolt fully engages the aperture. The plunger assembly may also comprise a guide to help align the strike with the bolt. The lever, especially if toggled, may also serve to retain the bolt in the retracted position.  
       [0012] An operator uses the invention by toggling the lever of a first latchable hinge on one side of the dump body, locking the bolt into the retracted position. The operator then toggles the lever of a second latchable hinge on the opposing side of the dump body, locking that bolt in the retracted position. The tailgate top edge can now be lowered by rotation around the bottom coupling mechanism. After unloading the material, the operator toggles both levers to their original position, biasing both bolts toward the extended position, and rotates the tailgate back into the raised vertical position. As the tailgate returns to this position, the strikes on each side of the tailgate, traveling in an arc around the lower coupling, move past the bevel on the bolts, until the bolts engage the strike aperture on each side, thus securing the tailgate to the dump body. The release and reattachment of the tailgate to the dump body are rapid and require no tools. Further, the bolt is automatically aligned with, and captured within, the strike aperture during reattachment, without operator attention. 
     
    
    
     DESCRIPTION OF THE DRAWINGS  
     [0013] Other objects and advantages of the invention will be evident to one of ordinary skill in the art from the following detailed description made with reference to the accompanying drawings, in which:  
     [0014]FIG. 1 is a schematic, partially exploded view of a truck dump body, viewed from the rear, showing the tailgate and latchable hinge;  
     [0015]FIG. 2A is a schematic side view of the dump body of FIG. 1 showing the tailgate in the raised vertical position;  
     [0016]FIG. 2B is a schematic side view of the dump body of FIG. 1 showing the tailgate secured in the horizontal position;  
     [0017]FIG. 2C is a schematic side view of the dump body of FIG. 1 showing the tailgate in the lowered vertical position;  
     [0018]FIG. 3 is a partial, exploded perspective view of a single latchable hinge;  
     [0019]FIG. 4 is a partial top view, partly in phantom, of a single latchable hinge with the bolt in the extended position; and  
     [0020]FIG. 5 is a partial top view, partly in phantom, of a single latchable hinge with the bolt in the retracted position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0021] In the following description of the preferred embodiments, like reference numerals represent identical or corresponding parts throughout the different views.  
     [0022]FIG. 1 shows the dump body, designated generally as  10 , as seen from the rear of the truck. The dump body is generally box shaped, with an open top and rear. The dump body comprises a bed  12 , a front wall  14 , a first side wall  16  and a second side wall  18 . The walls are connected to the bed  12 . The side walls  16 ,  18  each have an interior face ( 20  and  21  respectively), facing into the dump body, an exterior face (not shown) and top edges,  17  and  19  respectively.  
     [0023] The tailgate  24  acts as a back wall for the dump body  10 . The tailgate  24  is generally rectangularly shaped and abuts the rear opening of the dump body. The tailgate has an interior face (not shown), an exterior face  35 , a bottom edge  26 , a top edge  28 , a first side  30  and a second side  32 . The tailgate may be double walled, with the interior and exterior walls connected by the sides and edges. Alternatively, the tailgate may have a single wall with reinforcing members surrounding the periphery of the wall to create the sides and edges.  
     [0024] The tailgate bottom  26  is rotatably captured to the dump body  10  by a releasable coupling mechanism  36  as is commonly known in the art. When the bottom coupling mechanism is secured, the tailgate is limited to a pivotal motion, with the tailgate top edge  28  following a circular path around the lower pivot axis created by the coupling mechanism, as shown in FIGS. 2B and 2C.  
     [0025] The tailgate top  28  is secured to the dump body  10  by at least one latchable hinge. Preferably, a pair of latchable hinges is employed, one on each side of the tailgate. Although the use of a pair of latchable hinges is preferred, the description will generally refer to a single latchable hinge. As shown in FIG. 1, the latchable hinge comprises a strike  40  and a plunger assembly  50 . The strike is mounted to either of the tailgate sides,  30  or  32 , adjacent to the top edge  28 . The plunger assembly is mounted to the dump body on either of the top edges,  17  or  19 , adjacent to the rear of the body. While these mounting positions are preferred, other positions will also be suitable to practice the invention. As an example, the plunger assembly  50  may be mounted on the tailgate  24  and the strike  40  may be mounted on the body  10 . The component mounted to the tailgate will follow the circular path of the tailgate top edge as the tailgate is raised and lowered.  
     [0026] The strike  40  defines an aperture  44  parallel with the tailgate side. The plunger assembly  50  has a bolt,  60 . The longitudinal axis of the bolt  60  is perpendicular to the strike aperture  44 . The bolt is biased toward an extended position, shown in FIG. 4. When the tailgate is in the raised vertical position, the strike aperture  44  and bolt  60  are in axial alignment and the bolt is biased into the aperture. With the bolt  60  biased into the aperture  44 , rotation of the tailgate top edge  28  around the bottom coupling mechanism  36  is prevented. The bolt  60  creates an upper pivot axis. When the bottom coupling mechanism is uncoupled, the latchable hinge possesses sufficient strength to support the weight of the tailgate, allowing the strike  40  and the attached tailgate  24 , to rotate around the upper pivot axis created by the bolt  60  for normal dumping.  
     [0027] In one embodiment, shown in FIG. 1, the strike is elongated and has a first end mounted to a tailgate side,  30  or  32 , adjacent to the tailgate top edge  28 . The aperture  44  is defined within an opposing end, which extends beyond the inside face of the tailgate. The strike  40  may also have a bevel,  46  or  48 , as shown in FIGS.  3  or  4  respectively.  
     [0028] It is also possible for the side of the tailgate to act as the strike, with the aperture defined within the side of the tailgate. In this embodiment the plunger assembly  50  is mounted to the dump body  10  such that the strike aperture and the bolt are in axial alignment when the tailgate is in the raised vertical position. In either embodiment, the strike and the aperture will follow a circular path as the tailgate moves from the lowered or horizontal position to the raised vertical position.  
     [0029] Preferably, as shown in FIG. 3, the plunger assembly  50  comprises a bias tab  52 , spaced from the strike  40 , and a first guide tab  56 , located between the bias tab and the strike. The bias and first guide tabs each define apertures,  54  and  58  respectively, which are in coaxial alignment with the strike aperture  44  when the tailgate is in the raised vertical position. Preferably the tabs  52  and  56  are parallel to the strike  40  when the tailgate is in the raised vertical position and are mounted to the top edge,  17  or  19 , of the dump body adjacent to the rear.  
     [0030] A bolt  60  is received within the bias tab and guide tab apertures  54 ,  58 . The bolt is longitudinally displaceable between an extended position, shown in FIG. 4, and a retracted position, shown in FIG. 5. The bolt  60  has a pin end  62 , extending beyond the interior face of the guide tab  56  in the extended position. The pin end  62  may have a rear facing bevel  64 . In the extended position, the pin end  62  of the bolt fits within the strike aperture  44  of the raised vertical tailgate. The bolt also has an opposing actuation end  66 , extending beyond the exterior face of the bias tab  52 .  
     [0031] The bolt  60  has a spring retainer located between the bias tab  52  and first guide tab  56 . In one embodiment, the spring retainer comprises a first aperture  70  transverse to the longitudinal axis of the bolt through which a pin  74  is inserted. A thrust washer  76  may also be incorporated coaxially over the bolt  60  between the pin  74  and the bias tab  52 .  
     [0032] A spring is compressed, with one end trapped by the interior face of the bias tab  52  and the opposing end trapped by the spring retainer. The spring biases the spring retainer, and thereby the bolt pin end  62  away from the bias tab  52  and toward the extended position. In one embodiment, the spring is a coiled spring  72 , surrounding and generally coaxial with the bolt  60 .  
     [0033] A lever is mounted to the bolt  60 . The lever allows an operator to move the bolt  60  from the extended position to the retracted position, thereby freeing the top edge of the tailgate from the dump body. The lever may be rigidly mounted to the bolt so that an operator can pull the lever and bolt against the bias. Alternatively, the lever may be pivotally coupled to the bolt so that the lever pushes against a surface, enhancing the leverage available for moving the coupled bolt against the bias.  
     [0034] In one embodiment, the lever comprises a cam attached to a handle  86 . The cam is coupled to the bolt  60  and abuts the exterior face of the bias tab  52 . In a further refinement, shown in FIG. 3, the cam comprises an eccentric yoke  82  with a pair of axially aligned apertures  85 . The yoke  82  is coupled to the bolt  60 .  
     [0035] The coupling of a lever or cam to the bolt may be at the bolt actuation end  66  such as at a second transverse aperture  68 , located exteriorly to the bias tab  52 . Preferably as shown in FIGS. 3, 4 and  5 , the coupling comprises a pin  84  which rotatably connects the lever or cam to the bolt. The coupling of the lever to the transverse aperture may also be accomplished with other commonly known methods, such as bolts.  
     [0036] In one embodiment, the lever in a first position, shown in FIG. 4, allows the coupling  84  to remain adjacent to the exterior face of the bias tab  52 , thereby allowing the bolt  60  to remain biased toward the extended position. In a second position, shown in FIG. 5, the coupling  84  and bolt  60  are moved away from the bias tab  52 , drawing the bolt into the retracted position. A handle  86  (omitted from FIGS. 4 and 5) is attached to the cam so that an operator has leverage to move the cam  82 , and thereby the bolt  60 , from the retracted position toward the extended position and back.  
     [0037] Preferably, the shape of the cam allows the coupling to be toggled between the first position and the second position. In this embodiment, the bolt  60  is moved to, and retained in, the retracted position by movement of the lever. The bolt remains in the retracted position until the lever is manually returned to its original position.  
     [0038] In another variation, shown in FIG. 3, the plunger assembly further includes a second guide tab  78  spaced from the first guide tab  56  by the strike  40 . The spacing distance is chosen so that the strike  40  can freely enter between the guide tabs  56 ,  78 . The guide tabs can include rear facing bevels,  59  and  79 , to create a funnel-shaped guide for the strike  40 . In the extended position, the pin end  62  of the bolt  60  rests against the exterior face of the second guide tab.  
     [0039] In use of a preferred embodiment, the handle  86  is moved so that the cam  82  is toggled to the second retracted position. The cam toggling moves and retains the bolt  60  in the retracted position. In the retracted position, there is no contact between the bolt pin end  62  and the strike aperture  44 , so the tailgate  24  is free to rotate around the lower pivot axis  36  to the horizontal or lowered vertical positions.  
     [0040] To secure the tailgate in the raised vertical position, the cam is toggled to the first position. This cam toggling allows the bolt to be biased toward the extended position. As the tailgate is rotated to the raised vertical position, the strike  40  and strike aperture  44  travel in a circular path. As the elongated end of the strike  40  approaches the plunger assembly it is guided by the beveled ends,  59  and  79 , of the guide tabs  56  and  78 . As the elongated end of the strike comes into contact with the bolt bevel  64 , the bolt is moved against its bias and the strike slides past. When the path of the strike aperture  44  intersects the longitudinal axis of the bolt  60 , the spring biases the bolt  60  into the strike aperture  44 . With the bolt  60  biased into the strike aperture  44 , the tailgate upper edge  28  is prevented from rotating around the lower pivot axis, although rotation of the strike  40  and thereby the tailgate  24 , around the upper pivot axis created by the bolt pin end  62  is possible.  
     [0041] While preferred embodiments of the foregoing invention have been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present invention.