Abstract:
A covering system for a container body of a dump truck or roll-off dumpster with a rollable cover uses a pair of pivot arms attached to a leading edge of the cover. A shaft is transversely disposed and rotatably supported by an underside of the container body. Each pivot arm has a lower end fixedly attached to ends of the shaft for rotation with the shaft. A hydraulic or pneumatic rotation actuation mechanism operative to rotate the shaft is mounted to the underside of the container body, where it is not likely to be damaged during loading operations. The pivot arms are also readily kept in synchronization by operation of a single rotation actuation mechanism. A hydraulically or pneumatically actuated cover hold-down tensioning device is also provided, which may be operative in cooperative sequence with the covering system.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicant claims priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/170,930, filed Dec. 14, 1999, and to U.S. Provisional Application No. 60/176,286, filed Jan. 14, 2000, the disclosures of which are incorporated by reference hereon. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     BACKGROUND OF THE INVENTION 
     Open top container bodies or receptacles such as those used on dump trucks and roll-off trash dumpsters often hold loads that are easily agitated by forces from bumpy roads, external winds, and the air stream created by vehicular movement. Accordingly, a flexible cover is often secured on top of these container bodies to shield the contents. Container bodies are often up to forty feet long and as wide as the vehicle upon which they are carried, and the covers for such large bodies are themselves large and unwieldy. Some form of mechanical assistance is thus often used to furl and unfurl the covers over the bodies. 
     Prior art truck covering systems typically provide a flexible cover that is attached at one end to a crossbar that extends transversely across the open top of a container body. The other end of the cover is attached to a roller, which is mounted to a cab shield at the front edge of the container body. A pair of pivoting arms connected to the crossbar is mounted on the sides of the container body and is actuated by hydraulic or pneumatic cylinders, also mounted on the sides of the container body. Pivoting actuation of the arms causes the cover to be drawn from the roller over the open top of the container body. 
     Because the arms and cylinders are mounted on the sides of the container body, they are vulnerable to being hit during loading operations. Also, some mechanism to keep the arms in synchronization during movement is preferably provided to minimize wear on the covers. 
     A truck cover system having a hold down tensioning device is also known. In this system, spring biased arms attached to a tensioning bar urge the cover toward the top edge of the container body, keeping the tensioned cover close to the top edge of the sides of the body. See U.S. Pat. No. 5,957,523, the disclosure of which is incorporated by reference herein. 
     SUMMARY OF THE INVENTION 
     In the present invention, a covering system is provided having pivot arms connected to a common shaft that runs from side to side underneath the container body and that ensures the arms move in synchronization. The pivot arms are connected to the shaft at the outboard ends. The shaft is rotated by a mechanism that converts linear motion to rotary motion, such as a hydraulically or pneumatically operated bell crank. This mechanism is connected to the center of the shaft underneath the truck body, thereby keeping the mechanism out of harm&#39;s way and transmitting equal amounts of torque to the pivot arms, which in turn deploy the cover or tarp over the load. The covering system may be run with compressed air from the truck&#39;s air supply or hydraulic fluid provided by the truck&#39;s hydraulic system if the truck is equipped with a central hydraulic system that is used to run other functions, such as sanders and plows. 
     In a further embodiment, a tensioning device is provided comprising a hoop rotatably mounted to a front of the container body to travel an arcuate path between an uncovered position near a top of the roller mechanism and a covered position holding down the cover close to a top of the container body. The tensioning device may be actuated by the hydraulic or pneumatic circuit provided for actuating the covering system, or may be a standalone system. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a side view of a hydraulically actuated covering system according to the present invention; 
     FIG. 2 is an exploded view of the covering system of FIG. 1; 
     FIG. 3 is a partial rear view of the covering system of FIG. 1; 
     FIG. 4 is a bottom view of the covering system of FIG. 1; 
     FIG. 5 is a partial side view of a rotation actuation mechanism operative with the system of FIG. 1; 
     FIG. 6 is an exploded view of the rotation actuation mechanism of FIG. 5; 
     FIG. 7 is a schematic of a hydraulic circuit operative to actuate the rotation actuation mechanism of FIG. 1; 
     FIG. 8 is a side view of a pneumatically actuated covering system according to the present invention; 
     FIG. 9 is a partial rear view of the covering system of FIG. 8; 
     FIG. 10 is a bottom view of the covering system of FIG. 8; 
     FIG. 11 is a partial side view of a rotation actuation mechanism operative with the system of FIG. 8; 
     FIG. 12 is an exploded view of the rotation actuation mechanism of FIG. 11; 
     FIG. 13 is a schematic of a pneumatic circuit operative to actuate the rotation actuation mechanism of FIG. 8; 
     FIG. 14 is a side view of a cover hold down tensioning device according to the present invention; 
     FIG. 15 is a front view of the tensioning device of FIG. 14; 
     FIG. 16 is a hydraulic circuit operative to actuate the covering system and tensioning device according to the present invention; 
     FIG. 17 is a pneumatic circuit operative to actuate the covering system and tensioning device according to the present invention; 
     FIG. 18 is a further embodiment of a pneumatic circuit operative to actuate the tensioning device according to the present invention; 
     FIG. 19 is a still further embodiment of a pneumatic circuit operative to actuate the tensioning device according to the present invention; and 
     FIG. 20 is a partial cross-sectional view of a further embodiment of the tensioning device using a rolling cross bar. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-7 illustrate a covering or tarping system for a dump truck container body  10  according to the present invention. The covering system includes two pivot arms  12 , one on each side of the container body. The pivot arms include bows  14  at their upper ends that are connected to a leading edge of a cover or tarp  16 . Typically, a stiffening rod  18  is provided through a pocket along the leading edge; the bows are connected to the ends of the stiffening rod. The trailing edge of the cover is mounted to a spring-biased roller mechanism  22  mounted at the front of the container body, as known in the art. 
     A rotatable shaft  24  extends transversely underneath the container body  10  at generally the midpoint between the front and rear ends of the container body. The shaft  24  is supported for rotation along its longitudinal axis in any suitable manner to the container body, as by bushings  26  mounted to brackets welded to the underside surface of the container body. Four bushings are shown; it will be appreciated that any suitable number of bushings, or any other rotational support mechanism, may be provided. The shaft also passes through openings formed in the long sills or longitudinals  28  on the underside of the body  10 . The area around the holes is preferably reinforced. On Canadian or heated bodies, cross tubes are welded into the sills to form protective passages for the shaft  24  and to contain the exhaust gases and stiffen the body at the holes in the sills. 
     The pivot arms  12  are rigidly connected in any suitable manner at their lower ends to the rotatable shaft  24 . For example, a plate  30  may be welded or otherwise affixed to the lower end of the arm  12  and to the shaft. In this manner, when the shaft  24  is rotated, the pivot arms  12  pivot about the axis of the shaft. 
     A rotation actuation mechanism  34  is also mounted underneath the container body, generally in the middle thereof. In the presently preferred embodiment, the mechanism includes at least one hydraulic or pneumatic cylinder  36  and a bellcrank assembly  38  connected between the cylinder  36  and the shaft  24  for converting linear motion of the cylinder to rotary motion of the shaft. The size and number of cylinders are selected to achieve the desired actuation based on the available hydraulic or pneumatic pressure, as would be known in the art. 
     According to a first embodiment, the rotation actuation mechanism  34  is hydraulically actuated. For example, the cylinder  36  is hydraulic and is provided with a clevis  40  at the base end of the cylinder for mounting to a bracket  42  that is fixed to the underside  44  of the container body  10 , for example, by welding or bolting. A clevis pin  46  with cotter fits through aligned openings on the clevis and the bracket to allow pivoting motion about the axis of the pin. A U-shaped yoke  48  is provided at the rod  50  of the cylinder  36 . The bellcrank assembly  38  is pivotably attached to the yoke  48  with a clevis pin  52  with cotter. The bellcrank assembly is rigidly fastened to the shaft  24 , for example, with a scalloped end  54  that fits the curvature of the shaft and that is welded thereto. Actuation of the hydraulic cylinder to extend or retract the rod  50  causes the bellcrank assembly  36  to pivot about the axis defined by the clevis pin  52 , thereby causing rotation of the shaft. 
     A hydraulic circuit suitable for operating the rotation actuation mechanism is illustrated in FIG.  7 . Hydraulic fluid stored in a reservoir  60  is supplied via a pump  62 , operated by a suitable motor  64 , to a solenoid-operated fluid valve  66 . The fluid reservoir  60  may be part of the truck&#39;s central hydraulic system, or may be separately provided for the covering system. In a first position  67  of the solenoid valve  66 , the fluid flows to the base end  37  of the cylinder to extend the rod  50 . Fluid from the yoke end  39  flows toward the reservoir  60 . In a second position  69  of the solenoid valve  66 , fluid flows in the opposite direction to the yoke end  39  of the cylinder to retract the rod. Fluid from the base end  37  flows toward the reservoir. Appropriate flow controllers  68  and check valves  70  are provided in the fluid lines. The flow controllers  68  limit the speed of the arm movement and prevent the arms  12  from slamming into bow rests  72  on the container body  10 . The check valves  70  are fluidly coupled such that, during actuation, both check valves open in response to flow on either line toward the cylinder  36 , which allows flow in either direction along the fluid lines. When the flow is stopped, the check valves close to prevent fluid from leaking back toward the reservoir, thereby maintaining the cylinder in the appropriate position. The pump motor  64  and the solenoid valve  66  are electrically coupled to be actuated concurrently such that the solenoid valve  66  opens when the pump  62  turns on, to prevent fluid pressure build up in the lines. Preferably, a switch is provided in the cab of the truck to be convenient for the operator. For example, the operator pushes and holds in an appropriate button until the cover reaches the end of its stroke. In this embodiment, the solenoid valve  66  returns to the middle position when the button is released and the pump  62  turns off. The check valves  70  ensure the cylinder  36  is maintained in the appropriate position by hydraulic pressure. 
     When it is desired to cover the load, the operator pushes the button on the switch, which in turn energizes the pump motor  64  and fluid valve  66  to pump hydraulic fluid to the base end  37  of the cylinder  36 , extending the rod  50 . The rod and yoke push against the bell crank assembly  38 , which causes the shaft  24  to rotate, thereby moving the arms  12  from the uncovered to the covered position. As the cover and arms move toward the rear of the body, the spring contained within the roller assembly  22  becomes biased, thereby storing energy for the uncover operation. When the arms  12  reach the rear of the truck, the operator releases the switch, and the arms  12  stop moving and are held in place by hydraulic pressure. 
     When it is desired to uncover the load, the operator pushes the uncover button on the switch, which in turn energizes the pump motor  64  and fluid valve  66  to pump hydraulic fluid to the rod end  39  of the cylinder  36 , retracting it. The cylinder pulls against the bell crank assembly  38 , which causes the shaft  24  to rotate in the opposite direction, thereby moving the arms  12  from the covered to the uncovered position. As the cover and arms move toward the front of the truck, the energy that was previously stored in the roller assembly  22  becomes available to wind the cover onto the roller for storage. When the arms  12  reach the front of the body, the operator releases the switch and the arms  12  stop moving and are held in place by hydraulic pressure. 
     In a further embodiment of the invention, illustrated in FIGS. 8-13, a pneumatically operated rotation actuation mechanism is provided. The pivot arms  12  and shaft  24  are similar to the hydraulically operated embodiment described above. The rotation actuation mechanism  34  is also mounted underneath the container body  10 , generally in the middle thereof. The mechanism preferably includes two pneumatic cylinders  36   a  and  36   b.  A clevis  40   a,    40   b  is provided at one end of each cylinder for mounting to a bracket  42   a,    42   b  that is fixed to the underside  44  of the container body, for example, by welding or bolting. Clevis pins  46   a,    46   b  with cotters fit through aligned openings on the devises and brackets to allow pivoting motion about a common axis defined by both pins. A U-shaped yoke  48   a,    48   b  is provided at the rod end  39   a,    39   b  of each cylinder. A bellcrank assembly  38   a  is pivotably attached to the yokes with clevis pins with cotters. The bellcrank assembly includes two members  43   a,    43   b  attached with a crossbar  41   a  and rigidly fastened to a midpoint of the shaft  24 , as by welding. Actuation of the pneumatic cylinders  36   a,    36   b  to extend or retract the rods  50   a,    50   b  causes the bellcrank assembly  38   a  to pivot about a common axis defined by the clevis pins  52   a,    52   b,  thereby causing rotation of the shaft. 
     A pneumatic circuit suitable for operating the rotation actuation mechanism is illustrated in FIG.  13 . Compressed air from a compressed air source (not shown) is supplied via a pressure protection valve  80  and air line  82  to an inlet port  86  of an air valve  84 . Because the compressed air source is used by a truck&#39;s braking system, which requires maintenance of a minimum air pressure in the air lines to prevent brake lock-up, the pressure protection valve  80  shuts off air to the covering system if the air pressure drops below the preselected minimum air pressure. 
     From the air valve  84 , a line  87  leads from a port  88  to the base end  37   a,    37   b  of the pneumatic cylinders  36   a,    36   b  for extension of the rods  50   a,    50   b  and yokes  48   a,    48   b.  A line  90  leads from the rod end  39   a,    39   b  of the pneumatic cylinders to a port  92  on the air valve for retraction of the rods and yokes. Exhaust ports  94 ,  96  for each line are provided on the air valve. Flow controllers  98  are provided in the lines  87 ,  90  to the air valve  84  to limit the speed of the arm movement and prevent the arms from slamming into the bow rests  72  on the container body  10 . A knob  102  is provided on the air valve for operator actuation. For example, the operator pushes the knob in to cover the container body and pulls the knob out to uncover the body. Preferably, the air valve is mounted in the cab of the truck. 
     In another embodiment of the present invention, a powered tensioning device  110  is provided, illustrated in FIGS. 14-19. The tensioning device includes a hoop  112  formed of a cross bar  114  fixed to the ends of two bowed arms  116 . The bowed arms are rigidly connected to a shaft  118  that is mounted for rotation transversely across the front of the container body  10 . The shaft may, for example, be mounted to the container body directly underneath the cab shield  120 . Any suitable rotatable mounting mechanism may be used, such as bushings  122  bolted or welded to the body. Upon rotation about the pivot axis, the cross bar  114  travels along an arcuate path between an uncovered position near the top of the roller mechanism  22  and a covered position adjacent the top  124  of the container body  10 . In the covered position, the hoop  112  holds the cover  16  down close to the top of the container body. 
     When the cover  16  is rolled up within the roller mechanism  22 , the hoop  112  is stored in a retracted position, in which the bowed arms  116  are preferably vertical, so that the hoop  112  does not interfere with extension or retraction of the cover  16 . After the cover has been extended over the top of the container body, the hoop  112  is rotated downwardly, sliding over the cover until the cover is held in tension close to the top  124  of the container body  10 , as best illustrated in FIG.  14 . 
     The cross bar  114  may be rigidly fixed to the arms  116 , for sliding contact with the cover  16 . Alternatively, the cross bar  114  may be rotatably mounted to the arms  116  with, for example, a suitable rotatable bearing  117 , indicated in FIG.  20 . The rolling cross bar rolls as it contacts the cover, minimizing friction with and subsequent wear of the cover. 
     A rotation actuating mechanism  140  is provided to cause rotation of the shaft  118 . In the preferred embodiment, the mechanism includes a cylinder  142 , which may be hydraulic or pneumatic, and a bellcrank assembly  144  connected between the cylinder  142  and the shaft  118  for converting linear motion of the cylinder to rotary motion of the shaft. The cylinder is fixedly mounted at the base end by a bracket  146  to the front bulkhead  148  of the container body, for example, by welding or bolting. The cylinder may be mounted to the bulkhead anywhere that does not interfere with existing equipment. A U-shaped yoke  150  is provided at the rod end of the cylinder  142 . The bellcrank assembly  144  is pivotably attached to the yoke  150  with a clevis pin with a cotter. The bellcrank assembly  144  includes a scalloped end that fits the curvature of the shaft and that is rigidly fastened to the shaft, as by welding. Actuation of the cylinder to extend or retract the rod causes the bellcrank assembly to pivot about the axis defined by the clevis pin, thereby causing rotation of the shaft. 
     The tensioning device  110  may be actuated using the hydraulic circuit provided to actuate the covering system, described above. See FIG.  16 . Fluid lines  160 ,  161 ,  162  continue from the covering system cylinder  36  to the tensioning device cylinder  142 . A flow sequencer  164  is provided to ensure that, during extension, the tensioning device is not actuated until the cover is extended over the container body  10  and to ensure that, during retraction, the tensioning device is retracted before the cover is retracted. For example, the flow sequencer  164  prevents hydraulic fluid from entering the base end of the cylinder  142  until a preselected pressure is reached, preferably the pressure when the pivot arms  12  are at the back end of the container body. During retraction, hydraulic fluid flows preferentially into the tensioning device cylinder  142  before flowing into the covering system cylinder  36 , due to less resistance in the cylinder  142 , thereby retracting the tensioning device before retracting the cover. Alternatively, a separate hydraulic circuit may be provided for the tensioning device. 
     In another embodiment, the tensioning device  110  may be actuated using the pneumatic circuit provided to actuate the covering system, described above. See FIG. 17. A flow sequencer  170  is provided in the line from the air valve to the cylinder. During extension of the cover, the sequencer  170  senses air returning from the rod ends of the cylinders  36   a,    36   b.  When the return air flow from the cylinders  36   a,    36   b  has ceased, indicating that the cover is fully extended, the sequencer opens to allow air flow to the base end of the cylinder  142  on line  172 , causing the tensioning device to rotate downwardly onto the cover. During retraction, air flows preferentially to the rod end of the cylinder  142  due to less resistance, causing the tensioning device to retract before the cover. After the tensioning device retracts, air flows to the rod ends of the cylinders  36   a,    36   b,  causing retraction of the cover. Flow controllers  174  are provided at the cylinder  142  to control the speed of movement. Alternatively, a separate air valve  180  may be provided to operate the tensioning device cylinder, for example, if the tensioning device is installed on a truck with a preexisting manual or electric covering system. See FIG.  18 . If an existing pneumatic covering system is already installed on the truck, a supply line  190  may be provided from the existing supply line to deliver air to the air valve of the tensioning system. See FIG.  19 . 
     It will be appreciated that the rotation actuation mechanism and tensioning device can be embodied in other manners, as would be apparent to those of skill in the art. The invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.