Abstract:
A ladder rack for a motor vehicle similar to what is shown in U.S. Pat. No. 6,764,268, but differing therefrom in that the top surfaces of the stationary bar member and the movable bar member are coplanar and in a side-by-side relationship when the load being carried is atop the vehicle&#39;s roof rather than being stacked, one-above-the-other, as in the prior art. As such, the ladder rack of the present invention exhibits a reduced height profile.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    None 
       STATEMENT OF GOVERNMENT SPONSORSHIP 
       [0002]    None 
       BACKGROUND OF THE INVENTION 
       [0003]    I. Field of the Invention 
         [0004]    This invention relates generally to an apparatus to facilitate the loading and unloading of ladders onto and from the roof of road vehicles and, more particularly, to an improvement over the prior art that reduces the height profile of such apparatus to thereby decreases wind resistance and allows entrance to certain work sights having height restrictions. 
         [0005]    II. Discussion of the Prior Art 
         [0006]    The closest prior art to the present invention are U.S. Pat. Nos. 5,297,912; 6,427,889 and 6,764,268 to Avraham Y. Levi. Each comprise front and rear 4-bar linkages. In each, a first stationary bar is adapted for attachment to the vehicle&#39;s roof and a second movable bar is pivotally joined to the stationary bar by a pair of linkages. An elongated shaft is journaled for rotation in the stationary bars of the front and rear 4-bar linkages and one of the pair of linkages is clamped to the shaft whereby rotation of the shaft results in the rotation of the movable bar on which the ladder(s) being transported are disposed from their position atop the vehicle to a position straddling the side of the vehicle where it is within reach of a workman on the ground. 
         [0007]    In each of these prior art designs, the movable bar rests atop the stationary bar when the load is located on the vehicle&#39;s roof. This stacked relation of the stationary and movable bars necessarily adds to the overall height of the ladder load while being transported. The height above the vehicle&#39;s roof not only results in greater wind resistance and noise at higher speeds of the vehicle, but there are also job sites, like parking garages, that have height restrictions that may be violated. 
         [0008]    It is therefore a principle object of the present invention to modify the ladder racks of the prior art so as to reduce the overall height of the ladder rack mechanism by over 50%. 
       SUMMARY OF THE INVENTION 
       [0009]    The instant invention comprises a ladder rack for a motor vehicle. It comprises a front and a rear 4-bar linkage assembly. Each includes a stationary bar member adapted to be attached to the roof of a motor vehicle so as to extend transverse to the longitudinal axis of the motor vehicle. A movable bar member comprising a ladder support is pivotally coupled and offset from the stationary bar member by a pair of rigid links arranged such that rotation of one of the pair of rigid links on each of the front and rear 4-bar linkage assemblies results in the movable bar members of the front and rear 4-bar linkage assemblies moving between a first disposition in which a top surface of the movable bar member is in coplanar relation with a top surface of the stationary bar member to a second disposition aligned and spaced from one side of the vehicle. A connecting rod extends longitudinally between the two 4-bar linkage assemblies, the connecting rod being journaled for rotation in the stationary member of each. One of the pair of rigid links in each of the 4-bar linkage assemblies is coupled to the connecting rod whereby rotation of the connecting rod results in the movable bar members rotating between a position on the roof of the vehicle to a position along and parallel to one side of the vehicle. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings in which like numerals and the several views refer to corresponding parts. 
           [0011]      FIG. 1  is an isometric view of the ladder rack of the present invention as it would appear atop the roof of a motor vehicle during transport of the vehicle to a work site; 
           [0012]      FIG. 2  is an isometric view like  FIG. 1 , but without a ladder in place; 
           [0013]      FIG. 3  is a partial view showing the ladder rack in its open position; and 
           [0014]      FIG. 4  is a partial view showing the rear 4-bar linkage in a state between its full closed and full open position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    This description of the preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top” and “bottom” as well as derivatives thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “connected”, “connecting”, “attached”, “attaching”, “join” and “joining” are used interchangeably and refer to one structure or surface being secured to another structure or surface or integrally fabricated in one piece, unless expressively described otherwise. 
         [0016]    Referring now to  FIG. 1 , indicated generally by numeral  10  is a ladder rack assembly used to facilitate loading and unloading of one or more ladders  11  onto and from the roof of a motor vehicle, such as a pickup truck with a topper unit or a commercial van, neither of which is shown. The view of  FIG. 1  shows the ladder  11  in place on the ladder rack  10  as it would appear when positioned on the vehicle&#39;s roof, such as when it is being transported to or from a work site. 
         [0017]    Switching momentarily to  FIG. 2 , which is like that of  FIG. 1  except with the ladder missing, the ladder rack  10  itself is seen to comprise a front  12  and a rear  14 , 4-bar linkage assembly, each including a stationary bar member  16 ,  18  and a movable bar member  20 ,  22 , the two being linked together by a pair of linkages better seen in the close-up view of  FIG. 4 , which shows the rear 4-bar linkage  14  of  FIG. 1 . The pair of linkages are identified by numerals  24  and  26  in  FIG. 4 . A connecting rod  28  is journaled for rotation proximate the outer ends of the stationary bar members  16  and  18  and a fold-up crank member  30  is joined to the connecting rod  28 , which when manually manipulated, applies a rotational torque to the connecting rod. 
         [0018]    As seen in  FIG. 4 , a first of the linkages  26  is clamped at one end  32  to the connecting rod  28  and its opposite end is pivotally joined to the movable member at pivot point  34 . The linkage member  24  is pivotable about a stub shaft  36  that extends outward from beneath the stationary bar member  18  and the other end of the linkage  24  pivotally joins to an inner end  38  of the movable bar member  22 . An L-shaped hook  40  projects perpendicularly from a top surface  42  of the movable bar member  22  and, as best seen in  FIG. 1 , cooperates with a post  44  extending up from the stationary member  18  to capture a ladder rail between them to preclude shifting of the ladder during transport. 
         [0019]    The present invention achieves its advantage over the prior art in the way that the linkage members  24  and  26  are positioned relative to the stationary bar members  16 ,  18  and the manner in which the linkage  26  joins the movable bar member to the connecting rod  28 . Referring to  FIG. 4 , it is to be noted that the linkage member  24  is able to collapse down to a location sandwiched between the stationary member  18  and the movable member  22  such that the top surface  46  of the stationary member  18  becomes coplanar with the top surface  42  of the movable bar member  22 , as can readily be seen in the view of  FIG. 2 . Rather than being stacked one atop the other as in the prior art, the stationary bar member  18  and the movable bar member  22  in the present invention reside side-by-side with their top surfaces coplanar when the ladder rack is in its closed condition with the ladder load being carried on the vehicle&#39;s roof. 
         [0020]    Furthermore, as seen in  FIG. 2 , a hydraulic cylinder  50  is operatively connected between the stationary bar member  18  and the connecting rod  28  so that it does not extend above the level of the top surfaces of the stationary and movable bar members. 
         [0021]    Referring again to  FIG. 4 , extending laterally from a clamp  52  attached to the bottom surface of the stationary bar member  18  is a short cylindrical rod  54  that supports an elastomeric toroid  56  and similarly a toroid  58  is also provided on an extension of the rod  36 . The toroids  56  and  58  serve as supports or rests for the linkage  24  and movable member  22  when the ladder rack is in its closed disposition. 
         [0022]    This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.