Abstract:
An apparatus for remotely operating a heavy duty tailgate on a heavy-duty dump truck body incorporates a power-assisted mechanism to remotely unlatch the tailgate for unloading of the truck body contents and to remotely latch the tailgate during transit. Another power-assisted mechanism remotely positions the tailgate so that it either pivots about either a horizontal axis or rotates about a vertical axis as desired for unloading of the contents of the truck body. The controls for the power-assisted mechanisms are situated in the cab of the truck so that the driver has full control of the tailgate positioning and dump of the load from within the cab of the dump truck.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to vehicles having heavy-duty tailgates such as those employed on trucks, towed trailers, and containers used for transporting and discharging bulk materials such as rock, sand, mulch, bark, and the like. The invention, more specifically, relates to apparatus for remotely operating a heavy-duty tailgate on a dump truck as either a tailgate rotatable about a vertical axis at one side of the tailgate or as a power-assisted conventional tailgate pivotal about a horizontal axis along the top of the tailgate. 
     BACKGROUND OF THE INVENTION 
     In light duty hauling applications, such as carried out on automobiles of the station wagon style, it has been known to mount a tailgate in such a way that it can be employed as either a manually positioned door or as a manually positioned drop gate. U.S. Pat. No. 3,387,406 to Coker et al; U.S. Pat. No. 3,592,504 to Sandor; and U.S. Pat. No. 4,076,301 to Gergoe exemplify patents which teach manually operated tailgates for automobile station wagons and which are mounted in such a way that the tailgate can manually swing about either a vertical or horizontal axis. 
     Dump trucks, having conventional tailgates pivoted about a horizontal axis at the top and latched at the bottom, are frequently used for transporting and discharging large debris such as tree stumps, large and heavy rocks, dirt, and sand. However, tailgate apparatus of this kind requires the vehicle operator to leave the cab of the truck and manually unlatch the tailgate each time the dump truck body is to be emptied and manually re-latch the tailgate once the load is discharged. 
     U.S. Pat. No. 4,691,956 to Hodge; U.S. Pat. No. 3,027,188 to Eichstadt; and U.S. Pat. No. 2,260,504 to Barrett provide dump trucks with tailgates which can be top or bottom hung so that the tailgates may be swung pivotally from the top or bottom as the conditions may require. 
     U.S. Pat. No. 2,953,408 to Koenig provides a dump truck that permits dumping of the contents of the truck body to either side or to the rear of the dump truck. 
     More recently, dump trucks are now being equipped with tailgates which are pivoted about a horizontal axis at the top and which also can be opened by rotating about a vertical axis at one side sometimes referred to as the “barn door” type. However, the operator still must leave the cab of the truck and manually unlatch the tailgate each time the dump truck body is to be emptied and manually relatch the tailgate once the dump truck body has been emptied. 
     With the above background in mind, the present invention has as its primary object that of providing an improved apparatus for operating a tailgate on a dump truck, or the like, which enables the operator with powered assistance to remotely unlatch and position the tailgate for pivoting on a horizontal axis or to allow rotation on a vertical axis. Other objects will become apparent as the description proceeds. 
     SUMMARY OF THE INVENTION 
     A dump truck or the like, according to the present invention, utilizes a heavy-duty tailgate which can be opened as referred to above like a “barn door” and can be easily switched back to a conventional tailgate as the need arises. The tailgate can be unlatched, opened, released, closed, and re-latched with time saving efficiency since the operator remains in the cab of his truck and remotely operates the dumping of material from the truck bed. The tailgate is remotely operated by activation of a power-assist mechanism to control rotation about a vertical axis at one end of the tailgate or pivot about a horizontal axis at the top of the tailgate. Provision is also made for power-assisted remote latching of the invention apparatus during transit and power-assisted remote unlatching of the invention apparatus at the site at which the dump truck contents are discharged. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of a conventional dump truck embodying the apparatus of the present invention. 
     FIG. 2 is a side elevation view of a conventional dump truck of FIG. 1 illustrating the dump truck tilted into a conventional rear dumping position. 
     FIG. 3 is an enlarged end view of the rear tailgate area of the dump truck of FIGS. 1 and 2 incorporating the present invention. The tailgate is in a typical tailgate operating mode. 
     FIG. 4 is an side elevation view similar to that of FIG. 1 but with the tailgate switched into the open “barn door” operating mode. 
     FIG. 5 is a side elevation view similar to that of FIG. 2 illustrating the dump truck tilted into a dump position with the tailgate in the “barn door” mode. 
     FIG. 6 is a schematic view showing the pneumatic arrangement employed by the present invention. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring now to FIG. 1 of the drawings, a conventional dump truck  10  is shown having a chassis or frame  12 , a cab  14 , a tiltable load or cargo carrying dump body  16  with vertical sides  18 ,  20  (not shown), and vertical back  22  to form a storage space, and conventional dumping mechanism  24  (FIG.  5 ). The rear of load carrying dump body  16  is open but the opening is fitted with a heavy-duty, rectangular tailgate  26  (FIGS. 2 and 3) which can be opened to gain access to the cargo or allow the cargo to be removed and which is mounted so that it can be opened as a tilt door which pivots about a horizontal axis “HA” (FIG.  3 ), or as a “barn door” rotatable about a vertical axis “VA” (FIG.  3 ). The cargo, to be removed, slides by gravity down the bed of load carrying body  16  of truck  10 , when it is in the tilted or elevated position, as shown in FIG. 2, by actuating conventional dumping mechanism  24  which is illustrated in the form of a hydraulic lift mechanism. Activation of dumping mechanism  24  takes place in cab  14  of dump truck  10 . Activation does not require the operator to get out of cab  14  of dump truck  10 . 
     First, operation of the subject invention as a pivotal tailgate is best seen in FIGS. 1 and 2. Tailgate  26  is pivotal about horizontal axis HA (FIG.  3 ). Standing at the back and facing the rear of dump truck  10 , tailgate  26  has a top left side pin  31  affixed thereto and pivots with tailgate  26  as it is tilted. Top left side latch  32 , mounted in left sidewall rail  20   a , is normally closed thus latch  32  holds pin  31  in place while allowing pivoting of tailgate  26  about pin  31 . Latch  32  is independently controlled, closed or opened, by use of control C- 1  and a pneumatic cylinder  34  and will be discussed further when discussion of tailgate  26  functioning as a “bam door” takes place. 
     Again, if one is facing the rear of dump truck  10 , a two-way hinge  40  is fixedly secured to the top right corner of sidewall rail  18   a . Tailgate  26  has a top right side pin  41  affixed thereto which rotates with tailgate  26  as it is pivoted or tilted. Thus, tailgate  26  can pivot at its top outward away from the rear of dump truck  10  (see FIG.  2 ). Tailgate  26  pivots about horizontal axis HA by pivoting on pins  31  and  41 . Two-way hinge  40  will be discussed further when discussion of tailgate  26  functioning as a “barn door” takes place. Tailgate  26  is prevented from constant free swinging about pins  31  and  41  by a pair of normally closed bottom left and right latches  45 ,  46  respectively. Latch  45  is mounted in the outward lower end of left sidewall rail  20   a  and receives in a pivoting relationship a pin  47  affixed to the lower left hand end of tailgate  26 . Latch  46  is mounted in the outward lower end of right sidewall rail  18   a  and receives in a pivoting relationship a pin  48  affixed to the lower right hand end of tailgate  26 . When latches  32 ,  45 , and  46  are closed, tailgate  26  cannot move and is fixed in a closed position for travel. Latches  45 ,  46  are controlled by a single pneumatic cylinder  49  which is controlled by control C- 2  from within cab  14  of dump truck  10  by the dump truck operator. Latches  45 ,  46  are normally in a closed position thus holding pins  47 ,  48  thereby and in turn maintaining tailgate  26  in a closed position. When pneumatic piston  49  is activated by control C- 2  from within cab  14  of dump truck  10  by the dump truck operator, then latches  45 ,  46  are opened thus freeing pins  47 ,  48 . As dump truck  10  is positioned for dumping of its load, latches  45 ,  46  are released, hydraulic lift mechanism  24  is activated, and dump body  16  is raised or tilted as illustrated in FIG.  2 . Activation of hydraulic lift mechanism  24  also takes place from within cab  14  by the operator. Tailgate  26  pivots about axis HA on pins  31 ,  41  thus allowing the contents of dump body  16  to spill through open tailgate  26 . Once dump body  16  is free of its contents, dump body  16  is lowered into a travel mode by hydraulic lift mechanism  24  from within cab  14  of dump truck  10 . Once dump body  16  is lowered to its horizontal position, tailgate  26  pivots back into a vertical position and latches  45 ,  46  are closed. Closing of latches  45 ,  46  is achieved from within cab  14  of dump truck  10  by the operator activating cylinder  49  by use of control C- 2  without having to exit the cab. Tailgate  26  is now closed and dump body  16  is ready for a new load for transport. 
     Description will now shift to operation of the subject invention for swinging tailgate  26  in a “barn door” type operation. Operation as a “barn door” begins by causing normally closed top left side latch  32  to be unlatched without the necessity of manual manipulation, i.e. the operator getting out of cab  14  of dump truck  10  to release tailgate  26  for dumping. This is accomplished by use of control C- 1  and activation of pneumatic cylinder  34 , by the operator from within cab  14 , to open top left side latch  32 . Tailgate  26  is now free at its top left end. Next, pneumatic cylinder  49  is activated by the operator through use of control C- 2  from within cab  14  of dump truck  10 . The operator is thus able to unlatch and simultaneously release bottom left latches  45  and bottom right latch  46 . Pneumatic cylinders  34  and  49  are operated independently of each other through use of controls C- 1  and C- 2  but from within cab  14 . A two-way hinge  40  is fixedly secured to the top right corner of right sidewall rail  18   a . Tailgate  26  has a top right pin  41  affixed thereto and rotates with tailgate  26  as it is pivoted or tilted. Two-way hinge  40  thus allows tailgate  26  to open as a “barn door” when tailgate pins  31 ,  47 , and  48  are released from their latched positions. 
     A hinge shaft  50  (FIG. 3) having a tapered geared sprocket  52  formed with splines  52   a  at its bottom and a taper  52   b  at its top inserts into the eyelets of two fixed tailgate hinges  53 ,  54  that are fixedly attached to right sidewall rail  56  by any suitable means, e.g. welding. Shaft  50  is preferably at least one inch in diameter and should be made of solid steel to ensure rigidity. Two holes (not seen) are drilled into the center of shaft  50  at precise locations of fixed hinge holes or eyelets  53   a ,  54   a  simultaneously to ensure the accuracy of each hole and that they are aligned with each other. Two steel pins  52   e ,  52   f  preferably of at least {fraction (5/16)} inch in diameter are inserted into holes  53   a ,  54   a  to lock tailgate hinges  53 ,  54  to shaft  50 . This enables tailgate  26  to open as a “barn door” when shaft  50  is being rotated by a powered tailgate drive  62 . 
     Shaft  50  is driven by means of a reversible air motor comprising tailgate drive  62  connected to shaft  50  through a gearbox  64 . Gear box  64  is fixedly secured under the right hand corner of right sidewall rail  56  of dump truck  10  by any suitable means. Gearbox  64  may be bolted or welded to right sidewall rail  56  for sturdiness, and has a tapered, splined sprocket (not shown at one end to mate with sprocket  52  on shaft  50 . Reversible motor  62  is preferably at least ½ to 1 horsepower to turn shaft  50  and thus rotate tailgate  26 . Motor  62  is controlled by control C- 3  mounted inside cab  14  of dump truck  10  which makes this operation fully automatic from within cab  14 . Motor  62 , whether of an electric, hydraulic, or pneumatic type may be used to make this operation fully automatic. 
     After tailgate  26  has been rotated back against sidewall  18  of dump body  16  by motor  62 , it is latched into position by means of what is referred to as the “Barn Door” sidewall latch  75 . Latch  75  which is fixedly secured to sidewall  18  engages a mating latch portion  76  (see FIG. 3) of tailgate  26 . Latch  75  is controlled by a pneumatic cylinder  77  which in turn is remotely controlled from within cab  14  by the operator through use of control C- 4 . Latch  75  and latch portion  76  hold tailgate  26  against sidewall  18  (FIGS. 4 and 5) when tailgate  26  is operated as a “barn door” until closing by deactivating cylinder  77  to release tailgate so that upon activating motor  64 , tailgate  26  returns to its closed position. Latches  32 ,  45  and  46  are closed thus placing truck  10  in readiness for another load transfer. 
     From the foregoing description, it can be seen that the operator of dump truck  10  is allowed to remain seated in cab  14  of truck  10  and activate the necessary controls to operate tailgate  26  as either a rotatable “barn door” type apparatus or as a tailgate tiltable about a horizontal axis along the top of tailgate  26 . The remotely operated apparatus of the present invention is adapted for faster dumping time and thus faster turn-around time to the job site for additional hauling/dumping of loads of material. 
     While a representative system has been shown, it is recognized that variations in the switches, override switches, controls, or override controls are within the spirit and scope of the present invention. Further, the system may be pneumatic, hydraulic, or electrical and still fall within the scope of the present invention.