Abstract:
The present invention discloses a lifting mechanism to raise and lower a truck cap relative to a truck box, the mechanism comprising a pair of lifting devices, which comprise a support member for engagement with the truck cap, a base attached to the truck box, at least one first and at least one second guide attached to the base, each of the guides having at least one block slidably engaged therewith, each of the blocks being connected to a link extending to the support member and means for moving the blocks along the guides, the blocks on the second guide being adapted to move in an opposite direction to the blocks on the first guide, whereby movement of the blocks result in scissor-like movement of the links.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims the benefits of U.S. provisional patent application No. 60/423,059 filed Nov. 1, 2002, which is hereby incorporated by reference. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to a lifting mechanism for raising and lowering a truck cap relative to a truck box.  
         BACKGROUND  
         [0003]    Lifting mechanisms for covers and caps of truck beds, also called truck boxes, are well known. Their primary use is to provide more vertical space. The benefits of the additional vertical space are numerous. People may stand up while moving inside the truck box instead of remaining bent over. Taller items may be loaded into the truck box. Items that would fit into the truck box with the cap lowered but are difficult to load into a confined space may be more easily loaded into the truck box with the cap raised. Some examples of prior art are U.S. Pat. Nos. 4,603,901, 4,981,319, 5,364,154, 5,366,266, 5,375,900, 6,086,134, and 6,209,944.  
           [0004]    The liftable tops listed above have most or all of the following drawbacks. Some have a special cover included as part of the lifting mechanism. For users who already own a truck cap, or who want to purchase a certain type of truck cap, having the lifting mechanism already attached to a cover is not commercially acceptable. Some require modifications to either the truck cap, truck box, or both. Modifications to the truck box are highly undesirable while modifications to the cap should be minimal. Others are restricted in the height to which the truck caps may be lifted. Yet others do not include means for automatically lifting the truck cap.  
           [0005]    Accordingly, it is an object of the present application to obviate or mitigate the above disadvantages.  
         SUMMARY  
         [0006]    In one aspect of the present invention, there is provided a lifting mechanism A lifting mechanism to raise and lower a truck cap relative to a truck box, said mechanism comprising a pair of lifting devices, said devices comprising:  
           [0007]    a support member for engagement with said truck cap;  
           [0008]    a base attached to said truck box;  
           [0009]    at least one first and at least one second guide attached to said base;  
           [0010]    each of said at least first and at least second guides having at least one block slidably engaged therewith;  
           [0011]    each of said blocks being connected to a link extending to the support member; and  
           [0012]    means for moving said blocks along said guides, the blocks on said at least one second guide being adapted to move in an opposite direction to said blocks on said at least one first guide; whereby movement of the blocks result in scissor-like movement of the links.  
           [0013]    In another aspect of the present invention, there is further provided a lifting mechanism to raise and lower a truck cap relative to a truck box, said mechanism comprising a pair of lifting devices, said devices comprising:  
           [0014]    a support member for engagement with said truck cap;  
           [0015]    a base attached to said truck box;  
           [0016]    a first and a second threaded rods attached to said base;  
           [0017]    said first and said second threaded rods having at a pair of threaded blocks slidably engaged therewith;  
           [0018]    each of said threaded blocks being connected to a link extending to the support member; and  
           [0019]    means for moving said threaded blocks along said guides, the threaded blocks on said second threaded rod being adapted to move in an opposite direction to said threaded blocks on said first threaded rod;  
           [0020]    whereby movement of the threaded blocks result in scissor-like movement of the links. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0021]    Embodiments of the invention will be described by way of example only with the help of the accompanying figures.  
         [0022]    [0022]FIG. 1 is a side view of a pickup truck with a cap mounted on the truck box.  
         [0023]    [0023]FIG. 2 is a side view of a pickup truck with a cap raised relative to the truck box using.  
         [0024]    [0024]FIG. 3 is a perspective view of a lifting system.  
         [0025]    [0025]FIG. 4A is a cross-sectonal view (along axis IV-IV as shown in FIG. 3) of the lifting device in the lowered position.  
         [0026]    [0026]FIG. 4B is a cross-sectional view (along axis IV-IV as shown in FIG. 3) of the lifting device in the raised position.  
         [0027]    [0027]FIG. 5 is a cross-sectional view (along axis V-V as shown in FIG. 3) of the lifting device base.  
         [0028]    [0028]FIG. 6 is a cross-sectional view (along axis VI-VI as shown in FIG. 3) of the lifting device base.  
         [0029]    [0029]FIG. 7 is a cross-sectional view (along axis VII-VII as shown in FIG. 3) of the lifting device base.  
         [0030]    [0030]FIG. 8 is a perspective view of the lifting device base with means for manually operating the lifting device.  
         [0031]    [0031]FIG. 9 is an exploded perspective view of the inside of a truck cap and truck bed.  
         [0032]    [0032]FIG. 10A is an exploded perspective view of the inside of a truck cap and truck bed showing mounting brackets.  
         [0033]    [0033]FIG. 10B is an exploded perspective view of an alternative embodiment of FIG. 10A.  
         [0034]    [0034]FIG. 11 is a perspective view of the inside of a truck cap and truck bed showing a lifting device.  
         [0035]    [0035]FIG. 12 is a detail view of the securing of the lifting device to the truck cap. 
     
    
     DETAILED DESCRIPTION  
       [0036]    [0036]FIG. 1 shows a pickup truck  20  comprising a box  21 , which is covered by a cap  22 . Using lifting mechanism  23  (partially hidden), cap  22  may be raised relative to box  21 , as shown in FIG. 2.  
         [0037]    Referring to FIG. 3, the lifting mechanism  23  comprises a pair of lifting devices  30 , which are to be preferably placed longitudinally within the truck box  21  along its inside lateral walls. Each lifting device  30  comprises a support member  40 , to be secured to its respective side of truck cap  22 , which is connected to base  49  via links  42 ,  44 ,  46 , and  48 . Base  49  is attached to either the inside walls or the floor of truck box  21 . In one embodiment, the lifting mechanism  23  further comprises a switching circuit  33  for controlling the motion of the lifting devices  30 . Switching circuit  33  includes a switch  36 , for example a toggle switch, a lever or a button, which may be used to control the direction of movement of lifting devices  30 , i.e. to raise or lower truck cap  22 . The switching circuit may also include a lock to stop unauthorized use of the lifting mechanism  23 . Wiring  38  interconnects switching circuit  33  with lifting devices  30 .  
         [0038]    Lifting device  30  is shown in more details in a lowered position in FIG. 4A and in a raised position in FIG. 4B. Base  49  comprises a housing  50 , preferably a box like structure, which includes a pair of guides, in the form of generally parallel threaded rods  51  and  53 , extending along its length, motor  60 , gears  62 ,  64 ,  66  and  68  and threaded blocks  52 ,  54 ,  56  and  58 . Although a pair of guides are shown, more than two guides may be used as well. FIGS. 4A and 4B also show optional biasing members, such as springs  55  and  57  and safety stop switches  63  and  65  which will be described further below.  
         [0039]    Threaded rods  51  and  53  are positioned one above the other in an over-under configuration in order to reduce the overall width of base  49  and are held in position by the base  49  end plates  61  and  69 . Threaded blocks  52  and  54  are threaded onto upper threaded rod  53  while threaded blocks  56  and  58  are threaded onto lower threaded rod  51 . Alternate arrangements such as side-by-side may also be possible.  
         [0040]    In the over-under configuration the threaded blocks  52 ,  54 ,  56  and  58  must be designed such that threaded blocks  52  and  54  positioned on upper threaded rod  53  do not interfere with threaded blocks  56  and  58  positioned on lower threaded rod  51  as they pass by each other while moving in opposite directions during the raising or lowering of support member  40 . FIG. 5 shows a cross-sectional view of housing  50 , illustrating how threaded blocks  54  and  58  are configured such that the do not do not interfere with each other. Threaded blocks  52  and  54  are generally square shaped while threaded blocks  56  and  58  are generally L shaped, allowing threaded blocks  52  and  54  to pass by threaded blocks  56  and  58  unhindered. Preferably, housing  50  also includes ledges  59 , which provide support and guide threaded blocks  52 ,  54 ,  56  and  58  along threaded rods  51  and  53 .  
         [0041]    As mentioned previously, links  42 ,  44 ,  46 , and  48  extend between and interconnect base  49  with support member  40 . To this end, links  42 ,  44 ,  46 , and  48  are pivotally connected to support member  40  with pins  72 ,  74 ,  76  and  78  and to threaded blocks  52 ,  54 ,  56  and  58  with pins  82 ,  84 ,  86  and  88  respectively.  
         [0042]    Additional support may be provided to lifting device  30  when it is in its fully raised position as shown in FIG. 4B. The additional support is achieved when threaded blocks  52  and  58 , and associated links  42  and  48 , partially enter into recessed areas  91  and  99  of end plates  61  and  69 , shown in FIGS. 6 and 7. End plates  61  and  69  further comprise holes  92  and  93  for holding threaded rod  53  and holes  94  and  95  for holding threaded rod  51 . Also shown in FIG. 6 is mounting hole  96  for switch  63 .  
         [0043]    Gears  62 ,  64 ,  66  and  68  provide means for motor  60  to rotate threaded rods  51  and  53  at the same rate and in opposite directions. For example, if motor  60  is rotating clockwise, attached gear  68  will also rotate clockwise and it will cooperate with gear  66 , which will rotate counter-clockwise. Gear  64  and threaded rod  51  attached to gear  66  will thus also rotate counter-clockwise. Gear  64 , rotating counter-clockwise, cooperates with gear  62 , which will rotate clockwise, and so will threaded rod  53 , which is attached to gear  62 . Since threaded rods  51  and  53  have the same thread orientation, threaded blocks  52  and  54  will move in one direction while threaded blocks  56  and  58  will move in the opposite direction, which will cause links  42 ,  46  and  44 ,  48  to move in a scissor-like fashion, raising or lowering support  40 , which is secured to truck cap  22 . With the motor  60  rotating in one direction, the support member  40  may be raised while remaining generally parallel to base  49 . Reversing the direction of motor  60  will lower the support member  40  in a like manner. Of course, reversing the thread orientation of one of the threaded rods  51  or  53  may while also changing the gear arrangement so that the threaded rods  51  and  53  rotate in the same direction will achieve the same results.  
         [0044]    Well known methods exist for selecting gears and threaded rods. An appropriate selection of gear and thread specifications permits the use of a compact and low power motor  60  to lift loads in excess of several hundred pounds. One example is to use a 1 hp motor  60 ,  6  threads per inch threaded rods  51  and  53 ,  42  tooth gears  62  and  64 ,  84  tooth gear  66  and  22  tooth gear  68 . Persons skilled in the art may easily find other configurations that meet their specific requirements.  
         [0045]    As mentioned previously, springs  55  and  57  may be used to assist motor  60  in raising support member  40 . Referring to FIG. 4A, lifting device  30  is shown in the lowered position. In this position the energy required to move the threaded blocks  52 ,  54 ,  56  and  58  for the first several inches may be significantly greater than when the lifting device  30  is approaching the fully raised position, as shown in FIG. 4B. This is due to the fact that in the lowered position, links  42 ,  44 ,  46 , and  48  are almost parallel to the path of threaded blocks  52 ,  54 ,  56  and  58 . To assist in moving the threaded blocks  52 ,  54 ,  56  and  58 , springs  55  and  57  are placed around threaded rods  51  and  53  as shown in FIGS. 4A and 4B. In the lowered position, springs  55  and  57  are compressed, while in the raised position, springs  55  and  57  are expanded.  
         [0046]    Safety stop switches  63  and  65  may also be used to automatically shut off motor  60  when the lifting device  30  reaches the fully raised or fully lowered positions. Switch  65 , in conjunction with switching circuit  33 , will stop motor  60  when threaded block  54  makes contact with switch  65  just as threaded block  54  reaches a position such that the lifting device  30  is fully lowered. Similarly, switch  63 , in conjunction with switching circuit  33 , will stop the motor  60  when threaded block  52  makes contact with switch  63  just as threaded block  52  reaches a position such that the lifting device  30  is fully raised.  
         [0047]    As will be understood by persons skilled in the art, the rotation of threaded rod  51  may be achieved manually as well as with the help of a motor  60 . FIG. 8 shows base  49  with threaded rod  51  protruding from the end plate  69 . In one embodiment, a nut  97  is provided at the end of threaded rod  51  so that it may be rotated manually with the help of a tool. For example, nut  97  may be a standard sized hexagonal automotive wheel lug nut, which may be rotated using a standard tire iron, which is generally issued with all vehicles, including pickup trucks, thereby raising or lowering the support member  40 .  
         [0048]    [0048]FIG. 9 shows an exploded view of the inside of a truck bed  21  and truck cap  22  combination. Generally, truck cap  22  has a cap rail  102 , which serves as a base for truck cap  22 , that rests on truck box rail  104 . Generally as well, a gasket  106  is fixed to the bottom of the cap rail  102  providing a non-abrasive cushion as well as a weatherproof seal between the cap rail  102  and the box rail  104 . Truck box postholes  108  and  109  are generally used for mounting side walls on a truck bed  21 .  
         [0049]    In FIG. 10A, cap rail  102  mounting brackets  110  and posthole mounting brackets  111  are shown. Cap rail  102  mounting brackets  110  may be secured to the cap rail  102  using, for example, standard nuts and bolts, or screws. With a gasket  106  in place, the screw or bolt heads will not touch the box rail  104  surface. Posthole mounting brackets  111  simply drop into the truck box postholes  108  and  109  and hang on the inside of the truck box  21 . Slots  112  are used to fasten the brackets to base  49  while allowing for vertical adjustment of the lifting device  30  during installation. In an alternate embodiment, the mounting brackets  111  may be secured, as shown in FIG. 10B, to the side of box rail  104  and the interior wall of truck bed  21  using, for example, standard nuts and bolts, or screws  113 .  
         [0050]    [0050]FIG. 11 shows the installation of lifting device  30 . Support member  40  is secured to cap rail  102  mounting brackets  110  while base  49  is secured to posthole mounting brackets  111  and adjusted using slots  112 . FIG. 12 shows in more detail the cap rail  102  mounting bracket  110  secured to both the cap rail  102  and support member  40 , thus engaging the lifting device  30  to the truck cap  22 . Switching circuit  33  may be secured to base  49 . The other lifting device  30  (not shown) is installed in a similar fashion but on the other side of the truck bed  21 . In another embodiment, base  49  may be secured directly to the floor or the inside walls of the truck box  21 .  
         [0051]    Alternative embodiments of the invention may use a different number of blocks with associated links. The guides, which is are threaded rods in the described embodiments, may be replaced with a belt entrained about a pair of wheels or with hydraulic cylinders. Pulleys may also be used instead of gears to drive the threaded rods. The blocks may be combined into a single block having two or more spaced apart connection points to which the links are connected. As well, the springs may be replaced by other types of biasing members or may be omitted altogether.  
         [0052]    Although the present invention has been described by way of particular embodiments thereof, it should be noted that it will be apparent to persons skilled in the art that modifications may be applied to the present particular embodiment without departing from the scope of the present invention.