1.  Technical Field
The invention relates generally to a tarping system for covering open top trailers.  More particularly, the invention relates to such a system in which a support assembly and tarpaulin are mounted thereon and movable between a covered position atop the trailer to an uncovered position beside the trailer.  Specifically, the invention relates to such a device in which the support system and tarpaulin are pivoted between the covered and uncovered positions. 
2.  Background Information
It has been long been necessary to cover trailers in order to keep their contents from blowing out especially when the trailer is being pulled.  Laws and regulations have been adopted in many areas specifying that these trailers be covered during transit for this purpose.  Even where laws to this effect do not exist, it is nonetheless beneficial to cover the trailers to prevent the various negative results of material coming out of the trailers. 
Transfer trailers are typically used to haul refuse from a transfer station to a landfill.  They are typically loaded from the top by a wheel loader or the like, covered to keep the contents therein and uncovered upon arrival at the landfill.  The tailgate of the transfer trailer is then opened and a tipper dumps the trailer to empty its load.  Other dumping mechanisms may be used such as a shuffle floor.  Many trailers may be quite long, for instance 53 feet or even longer.  The maximum trailer widths for highways are typically either 96 inches or 102 inches.  Federal highways allow for 102 inch wide trailer bodies whereas some local areas may restrict the maximum to 96 inches.  Laws and regulations also generally allow for an additional width of 3 inches on each side of the trailer body to allow for safety equipment such as lighting, tarping systems and so forth.  Thus, the overall width of a tarping system for a highway trailer is limited to a maximum of 102 inches for the 96 inch body and 108 inches for the 102 inch body. 
While it is possible to manually cover such trailers, it is time consuming, expensive and often unsafe.  Manual tarping may take 30 minutes or more.  Manual tarping also requires the operator to climb on top of the load to spread the tarp and tie it down, which can be dangerous especially if the load is refuse or the like.  In addition, trailers can be 13 feet tall or more, thus subjecting operators to fall hazards. 
The various types of truck hauling systems typically fall into 3 categories.  The first is cable tarp systems, which are represented in patents such as U.S. Pat.  Nos.  2,469,958; 4,067,603; 4,189,178; 4,725,090; 5,102,182; 5,253,914; 6,142,554 and 6,250,233.  The first category employs a continuous loop of cable along the top of each side wall of the trailer which is revolvable with a sheave at the front or rear of the trailer and a driven sheave at the opposite end.  Bows or other cross members extend across the trailer with the tarpaulin connected thereto.  The bows are rigid rods or the like having an arch shape or the like which extend upwardly and over the trailer.  The rearmost bow is connected to the cable and the other bows are configured to slide or slip along the cable so that movement of the cable during the revolution of the endless cable loop pulls the rear most bow with it whereby the tarpaulin in turn pulls the remainder of the bows to cover the trailer. 
Because trailer walls are typically at or near the maximum height allowed, the use of a bow or arch shaped member may put the trailer over the maximum height.  On the other hand, if the cross members are straight instead of bowed, the tarpaulin tends to be dragged over the load, thus destroying the tarpaulin and preventing the use of the tarpaulin system with loads that are heaped above the trailer walls.  Refuse and other materials tend to destroy tarpaulins relatively quickly and replacement of a tarpaulin is labor intensive on this type of system.  In addition, especially with longer trailers the movements of the two endless loop cables are likely to get out of timing with one another due to cable stretch, which causes the bows to rack, thus making deployment of the tarpaulin difficult and requiring additional maintenance.  This type of system also requires a substantial amount of space to store the tarpaulin in its un-deployed position near the front of the trailer, making complete loading of the trailer more difficult.  In addition, if the side walls belly out, they may hit the cable and make actuation difficult or impossible. 
The second category of tarping systems is a roll type system as shown U.S. Pat.  Nos.  2,976,082; 3,384,413; 3,785,694; 4,302,043; 4,505,512; 4,657,062; 4,691,957; 4,834,445; 5,002,328; 5,180,203; 5,549,347; 5,762,002; 5,765,901 and 6,142,553.  The end of the tarpaulin in the roll system is attached to the side wall of the trailer and the other end is attached to a torque tube or torsion member that rolls the tarpaulin over the width of the trailer.  The tube is held down by means of straps, chains or the like to stretch the tarpaulin over the top of the trailer.  Most of these systems are cranked by hand although some are powered. 
One problem with roll systems is that they are not fully automatic.  The operator must manually tie down the tarp and in most cases manually roll the tarp onto the trailer, which is time consuming.  For longer trailers, the torque tube requires a center support extending across the top of the trailer to prevent deformation of the torque tube, which makes rotating the tube very difficult.  As previously noted, the trailer walls are typically near or at the maximum height and if an arch is used to roll the tarp over, it may cause the trailer to be over the maximum height.  If no arch is used, the tarpaulin must sometimes roll across a heaped load which can cause damage to the tarpaulin and may be impossible without the operator climbing on top of the load to hoist the roll over any pieces which stick up abruptly from the load.  Thus, this type of system is typically time consuming, labor intensive and possibly hazardous. 
The third category of tarping systems is the flip tarp system.  These tarping systems typically have tarpaulins that flip or rotate approximately 270 degrees from a generally horizontal deployed or covered position over the load to a vertical uncovered or stowed position along the side of the trailer.  This type of system allows loading from either side of the trailer.  The flip tarp systems typically have a structure which is hinged on the top of one or both side walls with a tarpaulin connected thereto.  Some of these systems may use a cable extending the length of the trailer to offer additional support to the tarpaulin.  Such systems use an opening mechanism mounted on the front of the trailer to rotate the frame structure about the hinges.  Examples are shown in US Patent Application Publications 20060043755 and 20050127705, as well as in U.S. Pat.  Nos.  6,983,975; 6,402,224 and 5,542,734.  Each of these examples uses hinges on one side of the trailer and opens the covering to one side.  Other flip tarp systems utilize a cover which has been split into two longitudinal sections that hinge on each of the side walls of the trailer, as shown in U.S. Pat.  Nos.  D290,591, 4,767,152, 4,627,658, 4,542,931, 4,210,358, 2,408,132 and 1,209,265.  Although U.S. Pat.  No.  4,627,658 shows an operating mechanism at the rear of the trailer, it is generally unfeasible due to the fact that there is no room on a standard trailer as a result of tailgate, width and height limitations.  Thus, the other prior art configurations use some sort of frame structure or torsion member running from the front of the trailer to the rear of the trailer in order to operate rear portion of the tarping system. 
One disadvantage of the prior flip tarp systems relates to the prior belief that a torsional structure running the length of a trailer was required to flip the entire tarp over.  Because trailers can be 53 feet long or more, using a frame or torsional structure to operate the rear and/or central portions of the tarping system requires substantial structure and the associated weight thereof.  For example, one prior art flip tarp system uses a 1½ inch solid shaft for the torsional member which weighs over 300 pounds.  Due to weight limits imposed by law, this results in reducing the amount of the payload that can be hauled within the trailer. 
In addition, the top rails of these trailers move, deflect and belly outward.  Thus, if the longitudinal frame or torsional member is hinged where the trailer bellies out, the frame structure must also deflect in the center, causing undue stress and premature failure of the tarping system.  If the frame or torsional member is not hinged at the center section of the trailer wall and the wall bows out in the center, the wall can keep the frame or torsional member from swinging all the way around to lie next to the trailer wall.  Either way, this can put the frame or torsional member into a bind, causing the tarping system to cease functioning.  Moreover, a loader may run up against the side of the trailer during loading and damage the frame or torsional member when using the stated position against the side of the trailer.  Furthermore, because a low height is desirable, the frame or torsional member typically is barely adequate to take the torsion from the driven member at the front of the trailer to the rear, and thus it is somewhat flexible.  Thus, although the frame or driven member may be held down by the actuating mechanism at the front of the trailer, only the torsion member serves to hold the tarping mechanism down at the back. 
Prior flip tarping systems typically do not do a very good job of keeping the material or load within the body of trailer.  As the trailer is pulled down the highway causing air to blow relative thereto, the air may blow material out the rear of the trailer.  The light torsion tube or frames as discussed above do not suitably keep the tarping system held down in the rear of the trailer.  The bumping up and down of the tarping system or the upward blowing by wind on the tarp tends to cause cracks therein which create openings through which material can escape.  These prior systems also typically fail to suitably hold the tarping material down along the sides of the trailer body, thus creating gaps through which material may be blown out.  These prior art systems do not allow for holding down the moving side of the tarp over the side of the trailer by a few inches.  If the middle of the trailer bellies out, the tarp will sit on top of the bellied out middle of the wall, leaving a substantial crack between the cable and wall at the front and the rear of the trailer through which material may be blown out.  In addition, tarping systems which require a lateral frame structure at the center portion of the trailer for supporting the tarpaulin can be an impediment to sealing.  More particularly, when the load is heaped up above the side walls of the trailer, the lateral frame structure lies atop the heaped up load so that the tarping system cannot seal around its periphery, thus allowing the material to escape. 
Another disadvantage relates to the use of operating mechanisms which use a roller and track mechanism or sleeve type bearings to operate the torsional structure.  The torsional structure is usually hinged to the wall of the trailer and if the operating mechanism on the front wall and side wall do not stay perpendicular, premature failure of the bearings will occur due to misalignment. 
An additional need is to be able to rotate the tarping system to either one side or the other of the trailer, which is partially addressed by U.S. Pat.  No.  6,983,975.  However, said patent does not provide a tarping system which is capable of handling multiple widths and lengths of trailers without the need for different parts or the welding of components that have been cut to length. 
The tarping system of the present invention addresses these and other problems in the art.