Abstract:
A method and apparatus for guarding a cargo on a trailer without a peripheral sidewall against rock damage. The method involves tensioning a sheet of flexible non-supporting material to form a protective shield.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for guarding a cargo on a trailer without a peripheral sidewall against rock damage and a rock guard for a trailer constructed in accordance with the teachings of the method. 
     BACKGROUND OF THE INVENTION 
     As a trailer is pulled along a road by a tow vehicle, rocks invariably are thrown up from the road surface. The rocks may originate from passing vehicles, or may originate from the tow vehicle. Some trailers have a peripheral sidewall that protects the cargo on the trailer from rock damage. With trailers that do not have a peripheral sidewall, the cargo is exposed and can sustain rock damage. For that reason, rock guards have been developed that mount onto trailers in order to protect cargo from rock damage. These rock guards are commonly positioned on trailers used to haul boats, motor vehicles, and snow mobiles; to name just a few of many applications. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a method for guarding a cargo on a trailer without a peripheral sidewall against rock damage and a rock guard for a trailer constructed in accordance with the teachings of the method. 
     According to one aspect of the present invention there is provided a method of guarding a cargo on a trailer without a peripheral sidewall against rock damage. The method involves tensioning a sheet of flexible non-supporting material to form a protective shield. 
     According to another aspect of the present invention there is provided a rock guard for a trailer which is constructed in accordance with the teachings of the method. The rock guard includes at least one tensioning cable and at least one sheet of flexible non-supporting material having sufficient tensile strength to withstand tensioning. The sheet of material has means for accommodating the tensioning cable. At least one support member is provided having a first end and a second end. The first end is adapted to receive the tensioning cable. The second end is adapted for attachment to a trailer frame. At least one cable tensioning member is provided, whereby the sheet of material is tensioned with the tensioning cable to form a protective shield. 
     The invention, as described, involves tensioning a sheet of non-supporting material and positioning the sheet on a trailer to provide protection to the cargo from any rocks or debris rising from the road or the wheels of the towing vehicle. 
     Although beneficial results may be obtained through the use of the rock guard, as described above, it is desirable that the sheet of material be shaped to match the contours of the trailer. Even more beneficial results may, therefore, be obtained when at least one secondary support member is provided. The secondary supports help the sheet of material maintain a desired shape. Each secondary support has a first end and a second end. The first end is adapted to receive the tensioning cable. The second end is adapted for attachment to a trailer frame. It assists in promoting the desired shaping of the protective shield when the secondary support member is in an angularly offset orientation. 
     Although beneficial results may be obtained through the use of the invention, as described above, boat trailers have a front mounted winch that is used to pull a boat out of the water and onto the trailer. It is, therefore, preferable that the protective shield be removable in order to allow unfettered access to the front of the trailer when launching or recovering the boat. Even more beneficial results may, therefore, be obtained when the second end of each support member has a detachable trailer frame attachment bracket. This allows the attachment bracket to be attached to the trailer frame, and the support member to be attached to and detached from the attachment bracket, as required. For this purpose it is preferred that the attachment bracket have a male coupling and the support member a female coupling. It has been found that it is most convenient when the secondary support members are positioned in pockets in the sheet of material. The tensioning cable can be extended through an aperture at the first end of the secondary support member to prevent the secondary support member from being withdrawn from the pocket in the sheet of material. 
     There are various cable tensioning mechanisms that can be used with the rock guard, as descried above. Beneficial results have been obtained through the use of a cable tensioning member that has a pivotally mounting cam member. The tensioning cable can be tensioned by moving the cam member about a pivot. 
     Although beneficial results may be obtained through the use of the invention, as described above, even more beneficial results can be obtained when the sheet of non-supporting material has a plurality of secondary attachment straps by which an edge of the sheet adjacent the frame of the trailer can be secured to the trailer, whereby the non-supporting material can be tensioned between the straps and the tensioning cable. 
     Although beneficial results may be obtained through the use of the invention, as described above, even more beneficial results can be obtained when the sheet of non-supporting material is divided into two sheets of non-supporting material, each of the two sheets being a mirror image of the other, one of the two sheets being securable at one side of the trailer and another of the two sheets being securable at another side of the trailer, the two sheets thereby severing to protect a load on the trailer from rock chips. The two sheets allow more ready access to the primary support member without reducing the level of protection afforded by the invention. 
     Although beneficial results may be obtained through the use of the invention, as described above, even more beneficial results can be obtained when the tensioning cable has a first end and a second end, both of the first end and the second end having attachment loops by which the tensioning cable is detachably securable to each of the support member and one of the cable tensioning members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein: 
     FIG. 1 is side elevation view of a rock guard for a trailer constructed in accordance with the teachings of the present invention, mounted on a trailer. 
     FIG. 2 is a perspective view of the rock guard for a trailer illustrated in FIG. 1, mounted on a trailer carrying a boat. 
     FIG. 3 is a side elevation view of the rock guard for a trailer mounted on a trailer carrying a boat illustrated in FIG.  2 . 
     FIG. 4 is a top plan view of the front of trailer on to which is mounted the rock guard for a trailer illustrated in FIG.  1 . 
     FIG. 5 is an exploded side elevation view of a male support member for supporting a female support member at a side of the rock guard for a trailer illustrated in FIG. 1, mounted to a side of a trailer. 
     FIG. 6 is a side elevation view of one cable tensioning member for a rock guard for a trailer illustrated in FIG. 1, secured to a trailer. 
     FIG. 7 is an exploded side elevation view of the primary support member for the rock guard for a trailer shown in FIG.  1 . 
     FIG. 8 is a side elevation view of a strap securing the rock guard for a trailer mounted on a trailer to the frame of a trailer as shown in FIG.  1 . 
     FIG. 9 is a detailed side elevation view of the primary support member for the rock guard for a trailer shown in FIG. 1, mounted on the frame of a trailer. 
     FIG. 10 is a detailed side elevation view of a tensioning cable secured to the first end of the primary support member for the rock guard for a trailer shown in FIG.  1 . 
     FIG. 11 is a detailed side elevation view of a tensioning cable secured to the first end of a secondary support member for the rock guard for a trailer shown in FIG.  1 . 
     FIG. 12 is a detailed side elevation view of a cable tensioning member for the rock guard for a trailer shown in FIG.  1 . 
     FIG. 13 is an end elevation view of the cable tensioning member illustrated in FIG. 12, in the secured position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment, a rock guard for a trailer generally identified by reference numeral  10 , will now be described with reference to FIGS. 1 through 13. 
     Referring to FIGS. 2 and 3, rock guard  10  is mountable on a trailer  12  that does not have an enclosed peripheral sidewall, such as is used to transport a boat  13 . Trailer  12  has a hitch end  60 , a loading end  62 , and a pair of opposed sides  64 . A preferred embodiment of rock guard  10  includes a pair of tensioning cables  14 , a pair of sheets of non-supporting material  20 , each of pair of sheets  20  being a mirror image of the other, a primary support member  34 , a pair of cable tensioning members  36 , and a pair of secondary support members  38 . 
     Referring to FIG. 1, each tensioning cable  14  has an attachment loop  15  at each of a first end  16  and a second end  18 . Each of pair of sheets  20  has sufficient tensile strength to withstand tensioning. Each of pair of sheets  20  has a first portion  19 , a second portion  21  and a peripheral edge  22 . Peripheral edge  22  has a first portion  24 , a second portion  26 , a third portion  28 , and a fourth portion  29 . First portion  24  of peripheral edge  22  has a cable sleeve  30  with a channel  32  for accommodating tensioning cable  14 . Cable  14  emerges from channel  32  through eyelets  33 . 
     Primary support member  34  has a first end  40  and a second end  42 . Referring to FIG. 10, first end  40  of primary support member  34  has an hook attachment  44  for loop  15  at first end  16  of tensioning cable  14 . Referring to FIG. 7, second end  42  of primary support member  34  is in the form of a female coupling  43  which detachably receives a male member  45  of a primary trailer frame attachment bracket  46 . Referring to FIG. 9, attachment bracket  46  is secured to a frame  52  at hitch end  60  of trailer  12  in a male-female engagement. Referring to FIG. 4, primary attachment bracket  46  is positioned on frame  52  between hitch end  60  and a winch  72  secured by a post  74  to frame  52 . Winch  72  is used for loading boat  13  on to trailer  12 , as illustrated in FIGS. 2 and 3. 
     Referring to FIGS. 12 and 13, each cable tensioning member  36  has a detachable cam  48  pivotally mounted by a pivot rod  49  extending from each of opposed sides  51  of cam  48  to a cam support  50 . Referring to FIG. 6, cam support  50  is secured to frame  52  at one of opposed sides  64  of trailer  12 . Referring to FIG. 12, cam  48  is pivotally moveable between a released position, shown as dotted lines  100 , and a tensioned position, shown as solid lines  102 . Referring to FIG. 1, when cam  48  is in the released position  100 , cable  14  is not tensioned, and first end  16  of cable  14  is releasable from primary support member  34 . When cam  48  is in the tensioned position  102 , cable  14  is securely tensioned between cable tensioning member  36  and primary support member  34 . 
     Referring to FIG. 5, each secondary support member  38  has a first end  54  and a second end  56 . Referring to FIG. 1, each secondary support member  38  is housed within a sleeve or pocket  58 . Pocket  58  has an opening  59  adjacent second portion  26  of peripheral edge  22  of sheet  20  from which second end  56  of secondary support member  38  extends. Referring to FIG. 11, cable  14  passes through a passage  66  at first end  54  of each secondary support  38 . Referring to FIG. 5, second end  56  of secondary support member  38  is in the form of a female coupling  67  that detachably receives in a male-female engagement a male member  68  of a secondary trailer frame attachment bracket  70 . Referring to FIGS. 1 and 8, secondary trailer frame attachment bracket  70  is secured to frame  52  at one of opposed sides  64  of trailer  12 . When secondary trailer frame attachment bracket  70  is secured to frame  52 , male member  68  is outwardly inclined, thereby affecting the orientation of secondary support member  38 . 
     First straps  76  are secured to second edge  26  adjacent third edge  28  of one of pair of sheets  20 . First straps  76  extend under frame  52  of trailer  12  and are detachably securable to second edge  26  of another of pair of sheets  20 , thereby tensioning second edge  26  of each of pair of sheets  20 . Second straps  77  extend from fourth portion  29  adjacent each of first portion  24  and second portion  26  of peripheral edge  22  of each of sheets  20 . Second straps  77  loop around cam support  50  to tension second portion  21  of sheets  20  between cam support  50  and secondary support member  38 . 
     The method of use of rock guard  10  will not be described with reference to FIGS. 1 through 13. Rock guard  10  as described above is provided. Referring to FIG. 4, primary trailer frame attachment bracket  46  is secured at hitch end  60  of trailer  12 . One each of secondary trailer frame attachment brackets  70  and cam support  50  are secured to frame  52  at each of opposed sides  64  of trailer  12 . Winch  72 , illustrated in FIG. 1, is used to load boat  13  onto trailer  12 . When boat  13  is secured in place on trailer  12 , as illustrated in FIGS. 2 and 3, second end  42  of primary support member  34  is mounted on male member  45  of trailer frame attachment bracket  46 , illustrated in FIG.  7 . Second end  54  of each of secondary supports  38  carrying one each of cables  14  and sheets  20  is mounted on one of outwardly inclined trailer frame attachment brackets  70 , illustrated in FIG.  5 . Referring to FIG. 1, each of sheets  20  is extended between primary support member  34  and cable tensioning member  36 . Loop  15  at first end  16  of each of cables  14  is secured to first end  40  of primary support member  34  as illustrated in FIG.  10 . First straps  76  are secured under frame  52  of trailer  12  between second edges  26  of each of sheets  20  as illustrated in FIG.  1 . Referring to FIG. 6, each of cams  48  is mounted on one of cam supports  50 . Second straps  77  are looped about cam support  50 . Loop  15  at second end  18  of cable  14  engages cam  48  of cable tensioning member  36  as illustrated in FIG.  6 . Cam  48  moves pivotally to tension cable  14  between cable tensioning member  36  and primary support member  34 . Referring to FIG. 1, tensioned cable  14  maintains first edge  24  of sheet  20  in a taught and elevated position, and prevents secondary support  38  from inadvertently detaching from secondary trailer frame attachment bracket  70 . Rock guard  10  so installed prevents rocks or other debris from striking boat  13  while trailer  12  is being towed. 
     The method of unloading boat  13  from trailer  12  and storing rock guard  10  will now be described. Cam  48  is moved pivotally to release tension in cable  14 . Loops  15  are detached from primary support member  34  and tensioning member  36 . Straps  76  are detached from second edges  26  of each of sheets  20 . Primary support member  34  is detached from primary trailer frame attachment bracket  46  and secondary support members  38  are each detached from secondary trailer frame attachment brackets  70 . Rock guard  10  is then out of the way as boat  13  is unloaded from trailer  12 . Sheets  20  containing secondary support members  38  can then be rolled up into a small bundle and stored with primary support member  34  and cams  48  and stored in a storage bag. 
     It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claims.