Abstract:
Apparatus for facilitating the loading and unloading of heavy ladders from the roof of a motor vehicle comprises a pair of crossbar members affixed to the roof of the vehicle that extend transversely to the length dimension of the vehicle. A four-bar linkage arrangement affixed to the rearmost crossbar member is adapted to be driven by a shaft journaled for rotation in the spaced-apart crossbar members is arranged to displace a ladder support bar to which ladder hooks are attached. A front ladder hook is attached by a coupler to the elongated shaft at the forward facing end of the ladder rack assembly where the coupler is designed to allow the shaft to be rotated through a predetermined angle before the front ladder hook will rotate with the shaft and in this way the front and rear hooks remain parallel to one another through their range of motions.

Description:
I. CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a 371 of International application no. PCT/US2010/050501, filed Sep. 28, 2010, and claims priority from that application which is also deemed incorporated by reference in its entirety in this application 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    II. Field of the Invention 
         [0003]    The present invention relates generally to vehicle-mounted roof racks for transporting loads, and more particularly to a movable ladder rack that can be used to readily load a ladder onto the roof area of a truck or van and to lower it from the roof area to a position allowing the ladder to be manually carried away to a worksite. 
         [0004]    III. Discussion of the Prior Art 
         [0005]    In my earlier U.S. Pat. Nos. 5,297,912; 6,092,972; 6,099,231; and 6,427,889, the teachings of which are hereby incorporated by reference, there are described different designs of truck or van-mounted ladder racks that facilitate the loading and unloading of one or more ladders with respect to the vehicle&#39;s roof. These devices comprise front and rear four-bar linkage assemblies that include a stationary member which is adapted to rigidly affixed to the vehicle&#39;s roof or to cross-members that clamp to the vehicle&#39;s roof, and a ladder support member pivotally joined to the stationary member by a pair of transversely spaced links. A drive shaft is journaled for rotation in the stationary members of the front and rear four-bar linkage assemblies and is rigidly affixed to one of the pair of links of the front and rear four-bar linkage assemblies. Thus, when the drive shaft is rotated, either manually with a crank or automatically by means of a motor, ladders resting on the front and rear ladder support members are lifted and rotated from a position parallel to the vehicle&#39;s roof to a position parallel to the vehicle&#39;s side during an unloading maneuver. When reloading ladders onto the vehicle, the drive shaft is rotated in an opposite direction to raise and rotate the ladder load onto the vehicle&#39;s roof. 
         [0006]    In my earlier designs described in the aforereferenced patents, the four-bar linkages have been designed such that the top and foot of the ladders remain generally horizontal throughout their range of motion as the drive shaft is rotated. 
         [0007]    While the earlier designs reflected in the above-listed patents greatly simplify the loading and unloading of heavy extension ladders onto and from transport vehicles, it is deemed advantageous to provide a rotatable ladder rack assembly for a motor vehicle that requires less force to be applied during the unloading and reloading operations. My U.S. Pat. No. 6,764,268 describes a ladder rack arrangement in which the frontmost four-bar linkage assembly allows a ladder to be transferred from the vehicle&#39;s roof to a position alongside the vehicle where the upper end of the ladder is at a raised elevation relative to the ladder&#39;s foot such that the ladder is inclined relative to the horizontal. The height drop from the rooftop position to its lowered disposition is reduced such that less force is required to operate the ladder rack. Furthermore, with the inclined position, the ladder feet are lowered further such that a workman is better able to grasp the ladder at its foot end while the top or front end of the ladder is still engaged and supported by the front ladder support member. This permits the foot of the ladder to be lifted free of the rear ladder support member and lowered to the ground with the top end of the ladder still being supported by the front ladder support member. This also reduces the manual effort and ultimately standing the ladder vertically. 
         [0008]    With the arrangement described in the aforereferenced U.S. Pat. No. 6,764,268, the contents of which are hereby incorporated by reference, it is still necessary for the user to manually lift the front end of the ladder to loop its upper rail onto the hook arm 41 followed by the step of lifting the rear end of the ladder so that its upper rail is cradled by the hook arm 19 on the rear four-bar linkage assembly. This has proved to be somewhat challenging for users having limited upper body strength. 
         [0009]    It is a purpose of the present invention to provide a movable ladder rack assembly that eliminates the foregoing drawback of the ladder rack described in my &#39;268 patent. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention comprises a ladder rack for a motor vehicle to facilitate the loading and unloading of ladders onto and from the roof area of the vehicle. It comprises a front and a rear crossbar member that is attachable to the roof of a motor vehicle in parallel, spaced-apart relation where the crossbar members extend transversely to a longitudinal axis of the motor vehicle. An elongated shaft extends between the front and rear crossbar members and is journaled for rotation therein. A four-bar linkage, including a rear ladder support bar that is pivotally joined by a first link member to the rear crossbar member and by a second link member to the elongated shaft such that rotation of the shaft in a first direction displaces the ladder support bar to a ladder loading and unloading position alongside the motor vehicle and rotation of the shaft in a second direction displaces the ladder support bar from the ladder loading and unloading position to a position atop the vehicle&#39;s roof area. At least one, and preferably two, rear ladder hooks are affixed to the rear ladder support bar. Completing the assembly is a front ladder hook that is affixed to and rotatable with the elongated shaft adjacent to the front crossbar by a coupler that is operative to maintain the front ladder hook parallel with the rear ladder hooks on the rear ladder support bar over a path of travel of each upon rotation of the shaft. 
         [0011]    In accordance with the present invention, I have eliminated the front most four-bar linkage assembly and replaced it with a simple L-shaped hook that is joined to the rotatable elongated shaft by a specially designed coupler that ensures that the front hook and the hooks on the rear four-bar linkage assembly remain in a parallel relationship during their entire path of travel between a rooftop position and a position straddling the vehicle&#39;s side. A person wishing to load a ladder onto the vehicle&#39;s roof must merely lean the ladder against the rotatable elongated shaft and then push the ladder from its side to cause the upper portion of the ladder to tip and slide along the elongated shaft toward the front of the vehicle until the forward facing ladder rail abuts the front hook. At this point the ladder will be inclined to the vertical with the foot of the forward facing ladder rail still resting on the ground. The user may then lift the lower end of the ladder to hook one or both of the ladder rails onto the ladder hooks affixed to the rear ladder support bar of the rear four-bar linkage. Once this is done, the user may manipulate the crank arm to rotate the elongated shaft and thereby raise the ladder load to the roof area of the vehicle. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]    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 in the several views refer to corresponding parts. 
           [0013]      FIG. 1  is a perspective view of a cap or topper for a pick-up truck type work vehicle having the ladder rack of the present invention affixed to the roof area thereof; 
           [0014]      FIG. 2  is a rear view of the assembly of  FIG. 1 ; 
           [0015]      FIG. 3  is a perspective view of one-half of the ladder rack assembly shown in  FIG. 1  with that segment in its closed condition; 
           [0016]      FIG. 4  is a perspective view of the ladder rack segment of  FIG. 3  but shown in its open condition; 
           [0017]      FIG. 5  is an enlarged view of the rear four-bar linkage assembly in its open condition; 
           [0018]      FIG. 6  is an enlarged perspective view showing the details of the coupler used for attaching the front hook member to the rotatable shaft and with the front hook assembly engaging ladder rails of an extension ladder; and 
           [0019]      FIGS. 7 and 8 , along with  FIG. 1 , illustrate the method used to raise an extension ladder onto the roof area of a work vehicle using the ladder rack assembly of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    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 the 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 expressly described otherwise. 
         [0021]    Keeping the above in mind and turning now to  FIG. 1 , there is indicated generally by numeral  10  a vehicle ladder rack constructed in accordance with the present invention. It is seen to comprise a front crossbar member  12  and a rear crossbar member  14  that are attachable to the roof  16  of a motor vehicle, such as a truck or van. The front and rear crossbar members  12 ,  14  are in parallel, spaced-apart relation and extend transversely to the longitudinal axis of the motor vehicle. In the view of  FIG. 1 , left and right ladder racks  18  and  20  are mounted to the crossbar members  12  and  14  with the ladder rack assembly  20  shown as containing an extension ladder  22  of conventional design. 
         [0022]      FIG. 2  is a rear view of  FIG. 1  and shows the rear crossbar member  14  being affixed to the roof  16  of the vehicle by mounting brackets  24 . The front crossbar member is similarly attached to the vehicle&#39;s roof. 
         [0023]      FIG. 3  shows the ladder rack segment  20  by itself and without the ladder included so as not to obscure the working parts of the assembly. As seen in  FIG. 3 , an elongated shaft  26  extends between the front crossbar member  12  and the rear crossbar member  14  and is journaled for rotation in these crossbar members by bushings as at  28  and  30 . In order to adapt the ladder rack to a variety of vehicles which may differ somewhat from model to model, it has been found expedient to make the elongated shaft  26  into segments as at  32 ,  34  and  36  which are joined together by telescoping ends secured by bolts  38  extending diametrically therethrough. The length of segment  34  may be chosen to suit the particular application. 
         [0024]    The elongated shaft  26  is adapted to be rotated by a crank  40  that connects to the elongated shaft  26  at an articulated joint  42 . In  FIG. 3 , the crank is shown in its latched position relative to the elongated shaft  26 , the latch being identified by numeral  44 . A padlock (not shown) may be used to secure the crank  40  in place to prevent unauthorized persons from actuating the ladder rack and removing a ladder therefrom. 
         [0025]    Mounted to the rear crossbar member  14  is a four-bar linkage assembly that includes a rear ladder support bar  46  that is pivotally joined by a first link member  48  to the rear crossbar member by means of a hinge pin  50  and by a second link member  52  by a pin  54 . The other end of link member  52  connects to an ear welded to the elongated shaft  26 . The connection of the linkage  52  to the shaft  26  is obscured from view in  FIG. 3  but those skilled in the art can appreciate that when the shaft  26  is rotated in a first direction, the linkage  52  will lift the ladder support member  46  and through kinematic action will move the ladder support member  46  to the end position illustrated in  FIGS. 4 and 5  of the drawings. 
         [0026]    A speed limiting air spring  56  is pivotally connected at one end by a pin  58  to the crossbar member  14  and its output rod  60  connects to a lever arm  62  that is welded to the elongated shaft  26 . 
         [0027]    In  FIG. 3 , the ladder rack assembly is shown in its closed condition which it assumes when securing a ladder in place on the roof of the vehicle.  FIG. 4  shows the same assembly in its open condition wherein a ladder being supported thereby would be in its ladder loading and unloading position along the side of the vehicle. 
         [0028]    Bolted or otherwise attached to the ladder support bar  46  are hooks, as at  64  and  66 , designed to cooperate with the rails of a ladder, the two hooks being spaced accordingly along the length of the ladder support bar  46 . 
         [0029]    With continued reference to  FIGS. 3 and 5 , also affixed to the rear crossbar member  14  is a generally vertically extending post  68  projecting up from a pedestal  70  that is bolted to the crossbar member  14 . The post supports a roller  72  on the top thereof. The roller  72  is designed to cooperate with a ladder retainer  74  that is hinged to the ladder support bar  46  by a pin  76 . As can be seen in  FIG. 3 , when the ladder rack assembly is in its closed disposition, the ladder retainer  74  will partially surround a rail of the ladder being carried by the hook  66 . There, the rail is captured by the retainer  74  as it descends onto the vehicle&#39;s roof. 
         [0030]    Rather than employing a second four-bar linkage assembly at the front end of the ladder rack as in my earlier designs, there is attached to the end portion of the elongated shaft  26  that projects through the bushing  30  in the front crossbar member  12  a coupler block  76  to which is bolted a bracket  78 . An L-shaped hook  80  is attached to the bracket  78  by fasteners  82  projecting through a vertical slot in the bracket  78 . Thus, the elevation of the hook  80  relative to the crossbar member  12  is adjustable over a range to accommodate ladder rails of varying width dimension. The hook member  80  is designed to cooperate with a vertical post  84  that is clamped onto the front crossbar member when the assembly is in its closed condition to effectively enclose a ladder rail in the opening defined between the hook  80  and the post  84 .  FIG. 6  is a greatly enlarged perspective view taken from a point below the crossbar member  12  illustrating the shape of the coupler block  76  showing that it has an arcuate semicircular base portion  86  concentrically surrounding a bore  88  into which is fitted a bushing  90  for journaling the end of the elongated shaft  26  therein. The arcuate portion includes a groove  92  that extends through to the bore  88  and a pin  94  is swaged into the shaft  26  projects outward through the slot  92 . The arcuate length of the slot  92  is such that the coupler  76  and its attached hook  80  will remain stationary until the shaft  26  is rotated to the point where the pin strikes or engages one or the other of the opposed ends of the slot  92  formed in the base  86  of the coupler. Without limitation, the slot length may be such that the shaft  26  may rotate about 130° before the hook  80  will begin to rotate with the shaft. 
         [0031]    Also seen in  FIG. 6  is a stop bar  98  which clamps to and projects laterally outward from a side surface of the crossbar member  12  that interact with the coupler  76  to limit the angle of rotation of the coupler and, therefore, the shaft  26 . In this way, the front hook  80  can remain parallel to the rear hooks  64  and  66  through their path of travel as the shaft  26  is rotated in either a clockwise or a counterclockwise direction in moving a ladder between its loading/unloading position adjacent the side of the vehicle and the stowed position atop the vehicle&#39;s roof. With reference again to  FIG. 3 , it will be seen that there is clamped to the end of the extrusion comprising the ladder support member  46  a bracket  100  having legs  102  and  104  straddling the sides of the ladder support bar  46  and where the legs each include an inwardly extending arcuate recess for receiving the crank arm  40  therein when the crank arm is folded about the articulated joint  42  so as to extend parallel to the elongated shaft  26 . Thus, when the latch  44  is secured by a padlock, the ladder support bar cannot be moved in a way that would allow anyone to remove the ladder from its stowed position atop the vehicle roof. 
         [0032]    Referring next to  FIGS. 7 ,  8  and  1  in that order, the steps involved in loading a ladder onto the roof area of a vehicle will next be explained. 
         [0033]    A worker carrying the ladder  22  from a worksite to the vehicle will lean the ladder against the elongated shaft  26  with the bottom of the ladder on the ground. He or she will then slide the upper portion of the ladder along the shaft  26  until the rightmost ladder rail is received in the hook  80  as illustrated in  FIG. 7 . Following that, the worker will lift the ladder feet from the ground and position a lower portion of the ladder rails within the hooks  64  and  66  of the rear four-bar linkage when the ladder rack assembly  18  or  20  is in its open or loading/unloading position adjacent the side of the vehicle. This is the position represented by  FIG. 8  of the drawings. Following that, the worker will grasp the crank handle  40  and rotate it in the counterclockwise direction as indicated by the arrow on  FIG. 8  which rotates the shaft  26  so as to cause the linkages  48  and  52  to elevate and rotate the ladder support bar  46  to a top dead center position. At this point, further rotation of the crank  40  in the counterclockwise direction will bring the weight of the ladder load over center such that gravity will act against the force of the air spring  56  so that the ladder can be more gently lowered into the position shown in  FIG. 1  of the drawings. Finally, the worker will fold the crank arm  40  into the clasp  44  and the bracket  100  such that a first ladder rail will be captured between the hook  80  and the post  84  at the front end of the ladder rack assembly while the other ladder rail will be lodged between the hook  66  and the post  74  to prevent shifting of the ladder load during transit. 
         [0034]    Unloading of a ladder from the roof of the vehicle occurs in just the reverse order described for the ladder loading operation and need not be described herein in further detail. 
         [0035]    Those skilled in the art will appreciate that the effort involved in proceeding from the step shown in  FIG. 7  to that shown in  FIG. 8  requires a reduced effort because the upper portion of the ladder extending beyond the hook  80  acts as a counterweight offsetting the force needed to lift the foot end of the ladder onto the hooks  64  and  66 . 
         [0036]    While there has been shown and described the preferred embodiment of the present invention, it is to be understood that the invention may be embodied otherwise than is herein specifically shown and described and that, within said embodiment, certain changes may be made in the form and arrangement of the parts without departing from the underlying idea or principles of the invention as set forth in the Claims appended herewith.