Abstract:
A locking mechanism is provided for a tarping system having a flexible cover deployable from a roller assembly for covering a container and a mechanism for extending and retracting the cover from the roller assembly. The locking mechanism includes a locking element, such as a taut cable, mounted to the roller assembly and spanning the width of the cover. The locking element is arranged on the roller assembly with a portion of the length of the cover less than the entire length of the cover wound around the locking element. This portion of the cover corresponds to an extended length of the cover. The locking mechanism prevents further advancement of the cover from the roller assembly once the locking mechanism is uncovered when the cover is unwound.

Description:
BACKGROUND 
     The present invention relates to flexible cover or tarping systems for open-topped containers and particularly concerns a mechanism for locking the flexible cover or tarp extended over the container. 
     Many hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. In a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel and the like, as well as organic materials, such as grain or produce. Depending upon the nature of the materials stored in the open-topped container, it is often desirable to provide a cover for the container. A cover is particularly valuable when the containers are part of a vehicle, such as a dump truck. Rigid covers have given way to flexible cover systems that utilize a flexible tarpaulin (tarp) that can be drawn from a stowed position at one end of the container to a deployed position covering the open top of the vehicle container or bed. The flexible cover or tarpaulin is preferable in this arena because it can be easily stowed when the cover is not necessary, such as when a dump truck is being loaded or emptied. In addition, the flexible cover is generally easier to deploy than a rigid cover. 
     A variety of flexible cover or tarping systems have been developed that are geared toward particular hauling vehicle applications. One such tarping system is the Easy Cover® Tarping System manufactured and sold by Aero Industries, Inc. An example of one form of the Easy Cover® Tarping System is shown in  FIG. 1 . The vehicle  10  includes a dump body  11  with a flexible cover or tarp  13  sized to cover the entire open top of the dump body when in the deployed position shown in the figure. The vehicle is provided with a deployment and retraction mechanism that is operable to extend the tarp over the container and to retract the container to a stowed position. The tarp is stored within a storage assembly  14  that may be mounted toward the front of the vehicle  10 , as reflected in  FIG. 1  or that may be mounted on a movable bail arm assembly  16  used to extend the tarp to its deployed position. The storage assembly includes a roller assembly  15  that may rotatably mounted to the vehicle or to the movable bail arm, and is configured to roll up the tarp  13  to its stowed position and to unfurl the tarp as it is pulled away from the roller assembly. The bail arm assembly  16  is connected to a free end of the tarp  13  and is configured to draw the tarp out of the roller assembly  14  as the bail arm assembly sweeps over the dump body. In the illustrated embodiment, the storage assembly includes a housing  18  mounted to the front of the dump body  11 . A drive assembly  12  may be mounted to the housing  18  that is operable to retract the tarp back into the housing. The drive assembly may be motorized or manual but is configured to rotate the roller assembly to continuously wind the tarp thereon. 
     One problem that is persistently faced with tarping systems of the type shown in  FIG. 1  is the effect of air flow or wind as the vehicle is traveling. This problem becomes especially acute at high speeds. If the tarpaulin  13  is not properly restrained in its deployed position it can be damaged by flapping and whipping over the top of the dump body. Road vibration can have a similar effect on the tarp. This excess movement of the tarp can cause it to unroll from the roller assembly  15  even when the free end of the tarp is held at the rear end of the dump body. This unrolling leads to more flapping of the tarp, particularly when traveling at highway speeds, causing more damage to the tarp and even to the storage assembly  14  and dump body. 
     In order to address this problem, various systems have been devised to hold the tarp down against the container body. In one common system, a web of cords is laid over the tarp cover along the length of the container body and attached to mounts fixed to the side of the body. In other systems, the bail member includes a tie down that can be manually attached to mounts at the rear of the body. Still other systems rely upon a complicated array of mechanical, electrical or hydraulic structures to apply a constant tension along the length of the tarp. However, in most cases, the tension along the length of the tarp does not alleviate the problem of bellowing of the side edges of the tarp or bouncing of the bail member. 
     In other systems, a separate hold-down arm assembly is provided that bears against a forward portion of the tarp to hold it against the top rail of the dump body. This type of hold-down system is typically self-deployed and less complicated than the other approaches discussed above. However, even with this type of system tarp billowing or vibration can still cause the tarp to gradually unroll. Moreover, these types of hold-down systems have difficulty in generating enough force or torque to keep the cover pressed against the top rail of the dump body, especially at highway speeds. Consequently, there is a need for a system that can positively lock the tarp or cover in its deployed position, even under extreme wind loads and road vibration. 
     SUMMARY 
     According to one embodiment, a cover or tarping system is provided having a flexible cover deployable from a roller assembly for covering a container and a mechanism for extending and retracting the cover from the roller assembly. The locking mechanism includes a locking element mounted to the roller assembly and spanning at least a portion of the width of the cover. The locking element is arranged on the roller assembly with a portion of the length of the cover less than the entire length of the cover wound around the locking element. This portion of the cover corresponds to an extended length of the cover. The locking mechanism prevents further advancement of the cover from the roller assembly once the locking mechanism is uncovered when the cover is unwound 
     In one embodiment, the locking element is a taut cable spanning the entire width of the cover. The cable may be removably mounted to the hubs of the roller assembly. In another embodiment, the locking element is a pair of rods extending inward from the roller assembly hubs but each spanning less than half the width of the cover. The removable locking elements allow the elements positioned at a certain number of windings of the cover onto the roller assembly. More particularly, the locking elements can be mounted to the roller assembly at a predetermined extended length of the cover. That extended length is then wound around the locking element onto the roller assembly. When the cover is unwound from the roller assembly, the locking element prevents further extension of the cover once the locking element is fully exposed. 
     In another feature, the hubs of the roller assembly may be configured to provide multiple locations for mounting and fastening the locking element. In one embodiment the hubs are square with an opening at each corner that is configured to receive the locking element and a fastening element for fastening the locking element to the hub. 
    
    
     
       DESCRIPTION OF THE FIGURES 
         FIG. 1  is a top perspective view of a hauling vehicle utilizing a flexible tarping system. 
         FIG. 2  is a perspective view of a roller assembly incorporating locking mechanism as disclosed herein, shown in the fully deployed position of the flexible tarp. 
         FIG. 3  is a perspective view of the roller assembly shown in  FIG. 2  with the tarp in a partially stowed position. 
         FIG. 4  is a perspective view of a roller assembly incorporating locking mechanism according to a further embodiment disclosed herein, shown in the fully deployed position of the flexible tarp. 
         FIG. 5  is a perspective view of a roller assembly incorporating a locking mechanism according to another embodiment disclosed herein, shown in the fully deployed position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates. 
     In accordance with one aspect of the invention, a locking element is provided that locks a flexible cover or tarp at a particular deployed length. Referring to  FIG. 2 , the roller assembly  15  includes a roller  20  supported between two hubs  23 . The hubs support a roll bar  21  that supports the roller  20  and defines the axis of rotation for the roller assembly. The roll bar is connected to a drive mechanism  12  to roll the tarp  13  up onto the roller  20 . The entire roller assembly  15  is rotatably mounted within the housing  18  to deploy or roll up the tarp. The roller assembly  15  as thus far described may be of any known construction, provided that the hubs  23  flanking the tarp rotate with the tarp as it is wound up or unwound. 
     The roller assembly  15  includes a locking element  30  that spans the width of the tarp and is anchored to the opposite hubs. In one embodiment the locking element  30  is a cable that extends through openings  33  in each hub  23 . A fixing component in the form of a set screw  35  is threaded into a bore  36  in each hub that intersects the opening  33  so that the set screw can bear against the cable passing through the opening. The set screw  35  is tightened onto the cable  30  to fasten it to the hubs  23  and maintain the cable in tension. As shown in  FIG. 2 , the cable  30  passes across the tarp  13 , separating the tarp into an extended segment  13   a  and a segment  13   b  that remains on the roller  20 . The extended segment  13   a  is the portion of the tarp that is deployed over the open top of the dump body  11 . The cable is offset from the surface of the roller  20  or more particularly from the surface of the non-extended segment  13   b  of the tarp wound onto the roller, so that an angle a is formed between the extended and non-extended segments of the tarp. In order to achieve this offset, the hubs  23  may be provided with an eccentric portion  24  which includes the openings  33  for the cable  30 . 
     It can be appreciated that without the locking element  30  the tarp would unwind from the roller assembly  15  generally tangential to the diameter D of the roller assembly. The locking element in essence creates the angle a between direction of extension E ( FIG. 3 ) of the tarp and the tarp as it is unrolled from the roller  20 . 
     The locking element or cable  30  is sized so that it does not impede rolling the extended segment  13   a  onto the roller  20  when the tarp is retracted, as shown in  FIG. 3 . Thus, in one specific embodiment the cable is a 1/8  in. steel cable. When the tarp is unwound from the roller  20 , by pulling in the direction of the arrow E in  FIG. 3 , the extended segment  13   a  gradually unwinds from the roller. The extended segment  13   a  unwinds generally tangentially to the diameter D of the roller. As the roller rotates in the direction of the arrow R ( FIG. 3 ) the cable becomes exposed and gradually bears against the extended segment  13   a  until the cable  30  reaches the position shown in  FIG. 2  in which the cable is generally aligned with the extension direction E of the tarp from the housing  18 . At this point the cable  30  stops any further movement of the tarp or rotation of the roller assembly  15 . It can be appreciated that the locking element/cable gradually moves the direction of extension E from tangential to the roller  20  to essentially radial to the roller. At this point, any pulling force attempts to rotate the roller and tarp further, but this further rotation causes the cable to rotate as well, so that the cable bears with even greater force against the extended segment  13   a . The cable thus becomes self-locking. On the other hand, the locking element  30  does not impede retraction of the tarp because the extended segment  13   a  is wound over the cable. An angle α of less than about 160° is believed to be sufficient to lock the tarp  13  and prevent any further deployment of the tarp from the housing  18  under any working conditions. 
     It is important that the locking element/cable  30  be aligned with the opening in the housing  18  through which the tarp is deployed. In order to facilitate proper orientation the hubs are eccentrically shaped, with an extended portion  24 . The opening  33  is positioned within the extended portion. The opening  33  is offset from the central axis A through the roll bar  21  by a distance L that is generally equal to or greater than the diameter D of the hub. This offset produces the angle a between the extended and non-extended segments discussed above. It can be appreciated that this distance L is sufficient to accommodate different lengths of the non-extended segment  13   b  wound onto the roller  20 , based on the length adjustment as described below. 
     One attribute of the locking element  30  is that it can be used to adjust the deployed length of the tarp  13 . The cable  30  can be easily threaded through the openings  33  in the hubs  23  and fastened in place with the set screws  35 . In order to establish the length of the extended segment  13   a  the installer can extend the tarp to the desired length and then attach the cable  30  by passing it through the openings  33  and tightening the set screws  35 . Once the cable is installed the tarp  13  can be wound back onto the roller  20  and the roller assembly  15  can be mounted within the housing  18 . It can be noted that the same adjustment process is used to adjust the deployed length where the roller assembly is mounted to the bail arm, rather than to the vehicle. Other fastening elements are contemplated for fastening the cable to the hubs. 
     Other forms of locking element may be implemented, such as the mechanism  130  depicted in  FIG. 4  that is mounted to a roller assembly  115  that is similar in most respects to the assembly  15  described above. In this embodiment, the mechanism includes two rods  130  that pass through openings  133  in the hubs  123  of the roller assembly  115 . The rods do not extend across the entire width of the tarp  13 , but must span a sufficient portion of the tarp width to prevent the tarp from slipping through the gap G between the free ends of the rods. In addition, the rods and their engagement to the hubs must be sufficiently rigid to prevent the rods from deflecting under load from the tarp. 
     Rather than include the set screw ( FIG. 2 ), other fastening elements may be provided to fasten the locking element to the hubs. For example, the engagement end  132  of each rod  130  may be configured to engage the respective opening  133 , such as by way of a threaded engagement. Thus, the opening  133  may be internally threaded while the engagement end  132  of the rod  130  includes mating external threads. Alternatively, the end of the rod  130  may include internal threads and the engagement end  132  may include a bolt that passes through the opening  133  to engage the internal threads of the rod and fasten the rod to the hubs. Other fastening elements are contemplated that allow the rods  130  to be removed and re-installed to adjust the deployed length of the tarp  13 . In addition, a single rod  130  may be utilized projecting from only one of the hubs  123 . The rod may span the entire width of the tarp  13  or just a portion of the width, provided that it spans a sufficient distance to prevent the tarp from shifting away from the rod. With respect to the embodiment of  FIG. 4  and the variations discussed above, the rod or rods preferably span over half the width of the tarp, and preferably at least 75% of the width. 
     In another embodiment shown in  FIG. 5 , a locking mechanism  150  includes hubs  153  with multiple positions for engaging the locking element  30  (or  130 ). In particular, the hubs  153  include openings  160   a - 160   d  distributed at different locations on the hubs. In the illustrated embodiment the hubs are square with the openings  160   a - d  situated at the four corners of the square. Other hub shapes are contemplated with the opening appropriately position, provided that the hub shape allows the openings to be positioned outside the diameter of the tarp  13  when it is in the fully deployed position depicted in  FIG. 5 , such as at the distance L ( FIG. 2 ). The multiple openings  160   a - d  facilitate engagement of the locking element to the hubs of the roller assembly. Moreover, the multiple openings allows adjustment in the length of the tarp in its deployed position. For instance, engagement of the locking element in openings  160   a  can permit an extended portion  13   a  of tarp of a certain length, while moving the locking element to the next clockwise opening  160   b  leads to a reduced length of the extended portion. 
     In the illustrated embodiment, each opening  160   a - d  is provided with an intersecting bore  162  for receiving a locking screw  35  to clamp the locking element  30  within the corresponding opening. Of course, other locking elements and means for fastening the locking element to the hubs  153  are contemplated, as discussed above. For instance, the locking elements may be a cable or a generally rigid rod that spans the width between the hubs, or may be configured like the rods  130  to extend only part way across that width. The means for fastening the locking elements to the hubs may be the set screw  35 , mating threads between the openings  160   a - d  and the locking element  30 , a bolt or screw extending through the openings to engage a corresponding threaded bore in the locking element, or other structure suitable for fixing the locking element firmly to the hubs so that the element does not become dislodged when the tarp  13  is fully extended.