Abstract:
An open-topped vehicle body, such as a dump body, includes a tarping system that is deployed over the body by a pivoting bail member. An actuation mechanism applies a torque to the bail member to automatically pivot the member and deploy the tarp. The actuation mechanism includes a number of double coil spiral torsion springs anchored on a shaft attached to the dump body. The springs each include a right hand and a left hand coil portion concentrically wound about an integral center anchor portion. The shaft includes an elongated slot to receive and support the center anchor portion of each spring within the mechanism. The actuation mechanism includes a housing attached to the bail member. The housing contains the double coil springs and supports a pair of reaction posts extending therethrough. The coil portions of each spring include a left and right reaction end configured to contact and provide a torsional force against a corresponding reaction post within the housing.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to covers or tarping systems for open-topped containers. The invention concerns an apparatus for pivotably mounting a flexible cover over the bed of truck, such as a dump truck, and more specifically to an actuation mechanism for pivoting the cover over the truck bed.  
           [0002]    Some hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. For example, in a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel, aggregate or similar products. In addition, some hauling vehicles carry organic materials, such as grain or produce.  
           [0003]    Depending upon the nature of the materials stored in the open-topped container, it is often desirable to provide a cover for the container. Of course, rigid covers are well known that may be hinged from one end of the container body. These rigid covers have gradually given way in the industry to flexible tarping systems because the flexible tarpaulin can be easily stowed when a cover is not necessary, such as when the dump bed is being loaded. Moreover, the flexible tarp is much easier to deploy than a rigid cover.  
           [0004]    A variety of tarping systems have been developed that are geared to particular hauling vehicle applications. One such tarping system for use with dump trucks is the Easy Pull® Tarping System of Aero industries, Inc. The Easy Pull® System includes a flexible tarp that is wound around a spool at one end of the dump bed. A rope attached to the free end of the tarp can be used to unwind the tarp from the roller to span the length of the dump bed.  
           [0005]    Another cover system particular suited for open-topped containers on hauling vehicles, is the Easy Cover® Tarping System, also of Aero Industries, Inc. The Easy Cover® Tarping System includes a U-shaped bail that is pivotably mounted at its ends to the base of the container body. The horizontal section of the U-shaped bail is attached to the tarp, while the free ends of the vertical elements are pivotably mounted. In one application, the Easy Cover® Tarping System allows the tarp to be manually pulled in a sweeping arc over the container load.  
           [0006]    In another application of the Easy Cover® System, an actuation mechanism is provided that automatically pivots the U-shaped bail member to deploy the tarp over the load within the open-topped container. When the actuation mechanism is released, it automatically pivots the bar, thereby unfurling the tarp from the tarp roller at the front of the vehicle. A hand crank or powered motor can be provided to rotate the tarp roller to wind the tarp when it is desired to open the container top. The hand crank or motor mechanism must be capable of providing sufficient mechanical advantage to overcome the deployment force of the actuation mechanism.  
           [0007]    A vehicle  10  is depicted in FIG. 1 having an open-topped body  13  As illustrated in FIG. 1, the vehicle can be a dump truck, with the open-topped container comprising a dump body. A tarpaulin cover  16  is shown in its deployed configuration spanning the length of the container and covering the load within. The tarp cover  16  can be wound onto a tarp roller  19 . Both the tarp  16  and the roller  19  can be of a variety of known constructions, such as the Easy Cover® Tarping System.  
           [0008]    A bail member  22  is connected to one end of the tarp  16  in the manner described above. The bail member is pivotably mounted to the truck body  13  by way of an actuation mechanism  25 . This actuation mechanism can take a variety of forms in the prior art. For instance, one such mechanism relies upon extension springs that apply a linear force at some point along the bail member  22 , to cause the bail member to pivot when the tarp roller  19  is released. In a similar configuration, a compression spring is used to push the bail member outward, thereby pivoting it about its pivot mount at the base of the truck body  13 .  
           [0009]    In other applications, a coil torsion spring applies a torque or moment to the lower ends of the U-shaped bail member  22 . One advantage of the coil torsion spring is that it can be mounted substantially under the truck body  13  so that the actuation mechanism is clear of the working area around the truck body. In some instances an under-body mount cannot be accomplished. In these instances, a spiral torsion spring assembly can be used to apply torque at the pivot mount of the bail member  22 .  
           [0010]    Once such spiral torsion spring of the prior art as depicted in FIGS. 2 and 3. In particular, the actuation mechanism  25 ′ is mounted to the vehicle bed by a mounting plate  27 . The actuation mechanism  25 ′ includes a post  29  that projects from the mounting plate  27 . The post is configured to extend through openings at the pivot mount for the bail member  22 ′. A torsion spring pack  31  is disposed within the pivot end  23 ′ of the bail member  22 ′.  
           [0011]    As shown most clearly in FIG. 3, the spring pack  31  can include a number of individual springs, such as torsion spring  31   a . Each spring includes an anchor end  33  that is configured to fit within an anchor groove  35  defined along the length of the post  29 . The opposite end of the torsion spring constitutes a reaction end  37  that reacts against a post  39  extending through the interior of the bail member  22 ′.  
           [0012]    With any of the various actuation mechanisms described above, the amount of force generated by the mechanism depends upon the nature of the tarp cover  16  and the length that it must reach in its deployed position. Obviously, the longer the open-topped body  13 , the longer distance the tarp  16  must cover. This translates to longer arms for the bail member  22 . The longer the arms, the stronger the force or torque needed to pivot the arms from the stowed to the deployed position.  
           [0013]    In order to generate this increased force using a spiral torsion spring configuration, such as that shown in FIGS. 2 and 3, additional springs, such as spring  31   a , must be added to the spring pack  31 . In one typical prior art spiral spring system, between three and six such springs are utilized, depending upon the length of the bail member arms. In the configuration depicted in FIG. 2, four such springs are provided. Each of the springs is aligned axially along the length of the post  29 . Obviously, additional springs added to the pack  31  will require a longer post  29 .  
           [0014]    It has been found in practice that any spring pack using more than three springs projects too far from the side of the vehicle body  13 . This excessive projection presents two problems: (1) since the arms of the bail member  22  necessarily project farther from the side of the body  13 , they are more easily struck or damaged; and (2) federal law prohibits tarping system hardware from exceeding three inches from the side of the truck body. Since each spiral torsion spring is typically about one inch in width, it can be easily be appreciated that no more than three such springs can fit within the federally mandated envelope.  
           [0015]    Consequently, there remains a need for an actuation mechanism that can utilize spiral torsion springs for a wide range of bail member dimensions, while still avoid the problems of the prior art system shown in FIGS. 2 and 3.  
         SUMMARY OF THE INVENTION  
         [0016]    In order to address this unresolved need, the present invention contemplates a spiral torsion spring configuration that incorporates two spring coils within the same envelope. In one feature of the invention, the spring is a double coil spring in which two concentrically wound coil portions are connected at a center anchor portion. An actuation mechanism according to a preferred embodiment of the invention includes a shaft defining an elongated slot that is configured to receive the center anchor portion of a number of such double coil springs.  
           [0017]    The actuation mechanism can further include a housing that surrounds the double coil springs and mates with a pivot end of an arm of the bail member. Each coil portion of each spring terminates in a reaction end that is configured to engage a post passing through the housing. In the preferred embodiment, two such posts are situated within the housing at diametrically opposite positions. Each spring element, then, includes a left coil portion and a right coil portion, each having a corresponding reaction end that contacts a respective one of the diametrically opposite posts. Thus, each coil portion can exert a torsional force against each post, which results in a pivoting moment being applied to the arms of the bail member through the housing.  
           [0018]    In one aspect of the actuation mechanism, the housing can include a male and a female half that are connected together about the double coil springs. The two halves can be combined to define a pair of peg holes at diametrically opposite sides of the housing. The set of peg holes mate with similar pairs of pegs projecting from the pivot end of the arms of the bail member when the housing halves are clamped about the pivot end. The pegs and peg holes hold the bail member arms to the housing.  
           [0019]    Each housing half can also define a shaft bore through which the slotted shaft extends. Preferably, the shaft projects from a mounting plate that can be mounted to the open-topped container to support the actuation mechanism. A pair of bushings can be disposed between the shaft and the housing halves to reduce friction as the housing rotates about the shaft under the torsional force applied by the double coil springs. The free end of the shaft projects beyond the housing and can receive a retaining ring to hold the housing on the shaft.  
           [0020]    Likewise, the reaction posts can extend through reaction bores defined in the male and female housing halves. In one embodiment, the reaction posts include an enlarged head at one end and receive a retaining ring at the other end to hold the reaction posts within the housing. in one aspect of the invention, the double coil springs reduce by half the number of spiral torsion springs required to achieve a desired deployment torque. Thus, when six prior art torsion springs are called for, only three double coil springs of the present invention are required. Each double coil spring can be formed of wound flat stock, with the number of windings of each coil portion being determined by the desired torsional force. Preferably, the flat stock has a width of about one inch or less, so a combination of three double coil springs easily falls within the federally mandated prominence guidelines.  
           [0021]    It is one object of the present invention to provide an actuation mechanism for use in deploying a cover over an open-topped container. A more particular object is to provide such a mechanism for use with a flexible tarping system for vehicle, such as a dump truck.  
           [0022]    One advantage achieved by the present invention over prior art devices is that a requisite amount of deployment torque can be generated by a spring pack that fits within an acceptable envelope. A further benefit is that the number of parts that must be assembled to form the actuation mechanism is reduced.  
           [0023]    Other benefits and objects of the present invention can be readily discerned upon consideration of the following written description and accompanying figures.  
       
    
    
     DESCRIPTION OF THE FIGURES  
       [0024]    [0024]FIG. 1 is a perspective view of a vehicle utilizing a tarping system to cover the open-topped body of the vehicle.  
         [0025]    [0025]FIG. 2 is a side perspective view of an actuation mechanism of the prior art.  
         [0026]    [0026]FIG. 3 is a partial cross-sectional view of the actuation mechanism shown in FIG. 2.  
         [0027]    [0027]FIG. 4 is a top elevational view of a spiral torsion spring in accordance with one embodiment of the present invention.  
         [0028]    [0028]FIG. 5 is a top perspective view of a shaft bracket for use with the spiral torsion spring shown in FIG. 4 to constitute an actuation mechanism in one embodiment of the invention.  
         [0029]    [0029]FIG. 6 is a top exploded view of an actuation mechanism according to one embodiment of the present invention utilizing the spiral torsion spring of FIG. 4 and the shaft bracket of FIG. 5.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    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.  
         [0031]    In accordance with certain aspects of the present invention, an actuation mechanism  25 ″ is provided for use with the pivoting bail member  22  shown with the vehicle  10  in FIG. 1. The actuation mechanism utilizes a number of spiral torsion springs to apply a torque moment at the pivot end of each arm of the bail member  22 . In one aspect of the invention, each spiral torsion spring includes double concentric coil portions connected by a center anchor section that is held fixed relative to the pivoting bail member arms. The novel spiral spring incorporates two reaction ends that each provide a restoring or deployment torsional force to the bail member arms.  
         [0032]    More specifically, one preferred embodiment of the invention utilizes a double concentric coil spiral spring  50  shown in FIG. 4. The spring  50  includes a left coil portion  52  and a right coil portion  54 . The two portions  52  and  54  are connected at the center of the spiral by a center anchor portion  56  and are concentrically wound about this anchor portion. The two coil portions are disposed in a common plane passing through the anchor portion, so the entire spiral spring  50  presents the same envelope as a prior art spiral spring. The concentric winding of the two portions  52 ,  54  means that segments of the left and right portions alternate along a radial line emanating from the center anchor portion.  
         [0033]    The free end of each coil portion  52  and  54  includes a corresponding reaction end  58 ,  60  that reacts against or provides a torsion force against an element connected to the arms of the bail member  22 . Preferably, the two reaction ends  58 ,  60  are diametrically opposite, and in a most preferred embodiment are aligned with the center anchor portion  56 , as depicted in FIG. 4.  
         [0034]    Each of the coil portions  52 ,  54  are wound in the same direction, such as counter-clockwise in the illustrated embodiment. Of course, the coil portions can be wound in a clockwise sense; however, it is important that the portions be wound in the same direction so that they can provide a torsion force in the same direction, as represented by the arc arrow T. It is understood that when the spring  50  is installed within an actuation mechanism  25 ″, the spring is wound in a direction opposite the direction of the arrow T as the tarp is moved to its stowed position around the tarp roller  19 . In this instance, the diameter of the two coil portions  52 ,  54  is reduced as the spring  50  is tightly wound. Of course, moving the bail arms to their stowed position, tightens the coil portion of the spring  50 , thereby storing potential energy for future deployment.  
         [0035]    Another element of the actuation mechanism is the shaft bracket  65 , depicted in FIG. 5. The shaft bracket includes a mounting plate  71  configured to be mounted to the side of the vehicle body  10 . A shaft  67  projects perpendicularly outward from the mounting plate  71 . The shaft  67  defines an anchor slot  69  that extends along a substantial portion of the length of the shaft. This anchor slot  69  has a width sufficient to accommodate the center anchor portion  56  of each of the double coil spiral springs  50  included with the actuation mechanism. This arrangement of the center portion  56  relative to the shaft  67  is depicted in dash lines in FIG. 4.  
         [0036]    In accordance with the preferred embodiment, the double coil spiral spring  50  and shaft bracket  65  form part of an actuation mechanism  25 ″ as shown in FIG. 6. In order to integrate the springs with the bail member, the actuation mechanism  25 ″ includes a housing  80  formed by a male housing half  82  and a female housing half  83  that can be connected together about a number of spiral springs  50 . The two housing halves can be at least initially snap-fit together, and ultimately held together by some type of fastener, such as a bolt and nut.  
         [0037]    The two housing halves  82  and  83  combine to define a leg engaging portion  84 . The leg engaging portion  84  is elongated and hollow to receive the pivot end  23 ″ of a leg of the bail member  22 ″. The two halves  82 ,  83  also combine at the shaft engagement portion  84  to define a pair of peg holes  85  on opposite sides of the portion. These peg holes are configured to clamp about a pair of pegs  86  projecting from opposite sides of the pivot end  23 ″ of the bail member  22 ″. Thus, when the two housing halves  82 ,  83  are combined about the end portion  23 ″ of the bail member  22 ″, the pegs  86  are solidly retained within the peg holes  85 , to prevent translation and rotation of the bail member leg relative to the leg engagement portion  84 .  
         [0038]    Each of the housing halves  82 ,  83  defines a shaft bore  88  projecting therethrough. This shaft bore  88  is configured to pivotally receive the shaft  67  of the shaft bracket  65 . Preferably, a pair of shaft bushings  89  are provided at each of the housing halves  82 ,  83 . These bushings can reduce the amount of friction between the shaft  67  and the housing  80  of the actuation mechanism as the housing, (together with the bail member  22 ″) pivots relative to the shaft  67 .  
         [0039]    It is understood that the shaft bore  88  is arranged so that the anchor slot  69  of the shaft  67  can engage the center anchor portions  56  of each spiral spring  50  contained within the housing  80 . In the illustrated embodiment, three such springs are provided, although one or two springs may be contained within the housing depending upon the amount of pivoting torque required for the particular bail member  22 ″ and tarp system.  
         [0040]    The reaction ends  58  and  60  of each of the coil portions  52  and  54  react against corresponding posts  92 . Each post  92  passes through combined post bores  93  defined in each of the housing halves  82 ,  83 . Preferably, the reaction ends  58 ,  60  are configured to bend around a corresponding post, in the manner depicted in FIG. 4. Since the reaction post  92  does not pivot, no bushing is required between the post and the housing halves.  
         [0041]    In order to retain the combined housing  80  on the shaft  67 , the shaft defines a retaining ring groove  75  at its free end. This groove  75  projects just outside the male housing half  82 , as shown in FIG. 6. A retaining ring  90  is provided that can be engaged within the groove  75 . The retaining ring  90  can be in the form of a snap ring or other mechanism sufficient to hold the housing  80  on the shaft  67 . For instance, instead of a retaining ring  90 , a cotter pin arrangement can be implemented.  
         [0042]    A similar arrangement is applied to each reaction post  92 . Specifically, each post can include a groove  94  at its free end that can be engaged by a retaining ring  95 . Preferably, the reaction post  92  can have an enlarged head  96  at the end opposite the retaining ring. This enlarged head  96  can fit within an undercut portion of the post bores  93  in the female housing half  83 . It is understood, of course, that other means for mounting the reaction post  92  to the housing halves  82 ,  83  are contemplated. For instance, the free end of each of the reaction post  92  can be threaded to engage corresponding threads in the post bores  93  within the male housing half  82 .  
         [0043]    The present invention provides an actuation mechanism  25 ″ that can be easily assembled. Specifically, each of the housing halves can be readily engaged about the pivot end  23 ″ of the bail member  22 ″. The springs  50  forming a spring pack can be contained within the housing  80  in their free state as the shaft  67  is passed through the shaft bores  88  and the anchor slot  69  engaged about the center anchor portion  56  of each of the springs  50 . Attachment of the reaction posts  93  to the housing halves  82 ,  83  can require some torquing or winding of the spiral springs  50 . It is preferable that the spring pack have some residual torque when the bail member  22 ″ is in its deployed position.  
         [0044]    The orientation of the shaft  67  relative to the bail member  22 ″ can be adjusted by positioning the mounting bracket  71  on the vehicle body  13 . To accomplish this adjustment, the mounting plate  71  defines an array of mounting holes  73 . The array of mounting holes allows the shaft bracket  65  to be affixed to the truck body  13  with the anchor slot  69  at different angular orientation relative to the truck body. These different angular orientations impact the residual torque exerted on the bail member  22 ″ when the tarp cover  16  is fully deployed. In addition, this angular orientation of the shaft  67  and anchor slot  69  also determines the amount of initial torque applied to the tarp cover when it is released from the tarp roller  19 .  
         [0045]    The actuation mechanism  25 ″ can be assembled by first extending the reaction posts  92  through the post bores  93  in the female housing half  83 . The requisite number of springs  50  can be placed within the housing half  83  with the reaction ends  58 ,  60  engaged about a corresponding one of the posts. The pivot end  23 ″ of the bail member  22 ″ can be situated within the shaft engaging portion  84  of the female housing, with the pegs  86  extending into the female housing portion of the peg holes  85 .  
         [0046]    At this point, the male housing halve  82  can be combined with the female housing half  83  to form the complete housing  80 . Of course, the posts  92  extend through the male housing post bores  93  and the pegs  86  extend into the male housing peg holes. The housing assembly can be completed by bolting the two halves together. The retaining rings  95  can be engaged within the grooves  94  at the exposed end of each post  92 .  
         [0047]    The shaft bracket  65  can be fastened to the truck body  13  at a suitable pivot location for the bail member  22 ″. The assembled housing can mounted on the shaft  67  with the slot  69  sliding around the center anchor portion  56  of each spring in the spring pack. When the shaft extends beyond the male housing half  82 , the retaining ring  90  can be engaged within the groove  75  of the shaft to hold the housing on the shaft.  
         [0048]    In one specific embodiment of the invention, each of the double coil spiral springs  50  can be formed from flat steel wire having a thickness of 0.187 in. and a width of 0.625 in. A spring sized in this manner is capable of generating 900 in.lbs. of torque at 120° of deflection.  
         [0049]    Preferably the shaft  67  has a diameter of about 1.25 in. Thus, the working length of the center anchor portion  56  must be at least 1.25 in. to accommodate the shaft.  
         [0050]    Preferably the shaft  67  and the reaction post  92  are formed from steel bar stock. The male and female housing halves  82 ,  83  can be die cast in steel or other suitable material. The shaft bushings  89  can be formed of bronze or other similar low friction material.  
         [0051]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It should be understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.  
         [0052]    For instance, the reaction posts  92  can be integrally formed within one or both of the housing halves  82 ,  83 . The reaction posts themselves can also provide a means for fastening the male and female halves together, such as by externally threading a free end of the posts for engagement by a machine nut, or internally threading the posts to receive a bolt.