Abstract:
A car lifting platform including a plurality of “L” shaped forks in a parallel mounting arrangement with plates interconnecting the forks. The plates are secured (typically by welding) to the forks and extend substantially along the horizontal leg of the “L”, around the ell portion of the “L and at least part way up the vertical leg of the “L”. The ell portion of the plate may include oval-shaped through openings to allow foreign objects to fall off of the platform and to receive a projection from the object to be carried on the platform in order to limit sliding motion of the object carried on the platform.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a car lifting platform. More particularly, it relates to a car lifting platform wherein the platform mounts to a mast which in turn allows the mounting of the lifting platform to a motorized, heavy-duty piece of equipment, such as a wheel loader. 
   In certain applications, heavy duty equipment, such as wheel loaders, are used to move and place heavy pieces of machinery. Typically, this heavy machinery is picked up using a fork lift type of attachment. These forks are mounted to a mast which in turn mounts onto the wheel loader. 
   Specifically in highwall mining operations, conveyor cars (or auger transporting cars) are picked up from a storage area using car lifting platforms and are transported to a launch vehicle where the cars are hooked up to a continuous miner which engages and advances these cars as it mines an ore seam. These cars are typically 40 feet long and quite heavy. 
   Prior art car lifting platforms used in the highwall mining industry are fabricated from fork-lift forks with flat plates welded in between each fork in order to form a high strength, continuous platform. The fork-lift forks are “L” shaped elements, with one leg of the “L” being shorter and extending in the substantially vertical direction (and referred to as the riser) and the other leg of the “L” being longer and extending in the substantially horizontal direction to form the platform itself. 
   In prior art car lifting platforms, the flat plates welded between each fork extend only along the horizontal legs of the “L”, stopping just short of the 90 degree angle (hereinafter called the “ell” of the fork) which connects the platform to the risers. This allows dirt or other foreign objects to fall through the forks in order to keep the platform clean. It also permits a locating tab or pawl, projecting from the car or other object being lifted, to engage the opening between two of the forks in order to limit the amount of slipping (along the longitudinal axis of the car) allowed of the car during transportation. 
   In the prior art design, the ells are the point of stress concentration of these car lifting platforms. Fatigue cracks develop at these stress points, and, in short order, the fatigue cracks propagate and the forks break. 
   SUMMARY 
   The present design provides a lift platform with longer life than the prior art design, even using the same thickness or gauge of materials. In this design, the plates which extend along the horizontal legs of the “L” shaped forks are bent to conform to the “ell” shape of the fork and extend at least part of the way up the riser portion of the fork. These plates are welded between the forks. 
   In a preferred embodiment, through openings are located at the “ells” of the plates to allow for debris removal and to provide a locking window to accommodate a projection from the car or other object being lifted (to prevent the car from sliding on the lifting platform, along the longitudinal axis of the car). These openings are preferably oval-shaped to eliminate stress risers which could more readily initiate fatigue cracks. 
   Despite these through openings, the bent plates, welded not only along the horizontal platform portion but also along the riser portion and the ell portion of the forks, reduce the magnitude of the stresses. In a preferred embodiment, the stresses are more evenly distributed, and they are reduced approximately in half from the prior art design. Some of the stress is transferred up to the riser portion of the car lifting platform. Based on this reduction and redistribution of the stresses, the life of the car lifting platform made in accordance with the present invention is substantially longer than that of prior art car lifting platforms. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a car lifting platform and mast of the prior art; 
       FIG. 2  is an exploded, perspective view of the car lifting platform and mast of  FIG. 1  (prior art); 
       FIG. 3  is a perspective front view of a car lifting platform and mast made in accordance with the present invention; 
       FIG. 4  is an exploded, perspective view of the car lifting platform and mast of  FIG. 3 ; 
       FIG. 5  is a rear perspective view of the car lifting platform of  FIG. 3 ; and 
       FIG. 6  is an end view of the car lifting platform of  FIG. 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2  show a prior art car lifting platform  10  and a mast  12  for adapting the platform  10  to be mounted on a wheel loader (not shown). The car lifting platform  10  includes a plurality of fork-lift forks  14 , which are interconnected in a parallel mounting arrangement as shown. 
   Each fork  14  defines a substantially horizontal fork platform portion  16 , a substantially vertical fork riser portion  18 , and a fork “ell” portion  20  which is a curved portion that interconnects the platform portion  16  to the riser portion  18  of each fork  14  roughly at right angles. The forks  14  are interconnected by a mounting bar  22 , which extends through openings in the ends of the riser portions  18 , and by a wear plate  24 , which connects together the free ends of the platform portions  16 . 
   In addition, substantially flat plates  26  are inserted into the gaps between the forks  14 , substantially filling the gaps between the platform portions  16  of adjacent forks  14 . The plates  26  are secured, typically by welding, to the respective platform portions  16  of adjacent forks  14 , as shown best in  FIG. 2 . Each plate  26  extends substantially the length of the platform portions  16 , from the wear plate  24  to the ell portion  20  of the forks  14 , to define a plate platform portion  30 . 
   Other than the mounting bar  22  (which not so much connects as extends through the ends of the risers  18 ), there are no plates or other mechanisms bridging the gaps  28  between the riser portions  18  or between the ell portions  20  of the forks  14 . These gaps  28  are left open so that any debris (such as gravel or dirt, for instance) may readily fall off of the platform portion  30  of the lifting platform  10 . Typically, one of the gaps  28 A between two adjacent riser portions  18  serves as a window which engages a pawl or other projection (not shown) on a car being lifted so as to limit the amount of sliding of the car when the car is on the platform  30 . 
   The mast  12  is a standard mast, as is well known in the industry, adapted for mounting the car lifting platform  10  to a wheel loader (not shown). The car lifting platform  10  mounts to the mast  12  by means of the mounting bar  22 , which extends through openings in the mast  12  and through openings in the car lifting platform  10 . The vertical legs  18  of the car lifting platform  10  rest against upper and lower horizontal bars  12 A,  12 B of the mast  12 . 
     FIGS. 3-6  depict an example of a car lifting platform  10 ′ made in accordance with the present invention. This car lifting platform  10 ′ is very similar to the car lifting platform  10  described earlier, with the main difference being that the plates  26 ′ are bent and extend up into the space between the riser portions  18 ′ of the forks  14 ′. Please note that corresponding items in the two embodiments  10 ,  10 ′ are similarly labeled with the same item or reference numbers, but followed by a “superscript prime” (′) to designate this second embodiment  10 ′. Examples of this are the mast  12 ′, the gaps  28 ′ and  28 A′, and the openings  36 A′. 
   Each fork  14 ′ defines a substantially horizontal fork platform portion  16 ′, a substantially vertical fork riser portion  18 ′, and a fork “ell” portion  20 ′ which connects the platform portion  16 ′ to the riser portion  18 ′ at approximately right angles. The forks  14 ′ are interconnected by a mounting bar  22 ′, which extends through openings in the ends of the riser portions  18 ′, and by a wear plate  24 ′, which connects together the free ends of the platform portions  16 ′. 
   The plates  26 ′ are inserted into the gaps between the forks  14 ′ and are connected to the forks  14 ′. Unlike the prior art design, the plates  26 ′ are not substantially flat plates. Instead, the plates  26 ′ are bent so as to conform to the ell portion  20 ′ of the forks  14 ′ and extend approximately half-way up the risers  18 ′ of the forks  14 ′. Each plate  26 ′ substantially fills the gap between the platform portions  16 ′, the ell portions  20 ′ and the riser portions  18 ′ of its two respective forks  14 ′ and is secured, typically by welding, to the platform portions  16 ′, the ell portions  20 ′, and the riser portions  18 ′, respectively, of the adjacent forks  14 ′. 
   The platform portions  16 ′ of the forks  14 ′ and the horizontal portions of the plates  26 ′ together form the platform portion  30 ′ of the car lifting platform  10 ′. The substantially vertical portions  32 ′ of the plates  26 ′ are welded to the riser portions  18 ′ of the forks  14 ′, and together they form the riser portion of the car lifting platform  10 ′. This riser portion  32 ′ of each plate  26 ′ extends at least partially along the height of the riser portion  18 ′ of the forks  14 ′ (and in a preferred embodiment it extends approximately half way up the riser portion  18 ′) and is welded to the riser portion  18 ′ of the forks  14 ′. 
   Finally, each plate  26 ′ includes an ell portion  34 ′, which extends along and is welded to the ell portions  20 ′ of the adjacent forks  14 ′. The ell portions  34 ′ of the plates  26 ′ define through openings  36 ′ which are oval shaped and are elongated a greater distance in the side-to-side horizontal direction than in the vertical direction. These openings  36  allow any foreign objects (such as gravel or dirt) to fall off of the platform  30 ′ in order to keep the platform relatively clean. The oval shape of the openings  36 ′ reduces the opportunity for stress risers, thereby greatly reducing the initiation of stress cracks which could lead to premature fatigue failure of the platform  10 ′. Typically, one of the through openings  36 A′ serves as a window which engages a pawl or projection (not shown) on a car being lifted so as to limit the amount of sliding of the car when on the platform  30 ′. 
   The extended length of each plate  26 ′, which not only extends along the platform portions  16 ′ of the forks  14 ′, but also bends to follow the bend of the ell portion  20 ′, and extends at least part way up the riser portion  18 ′, lends additional rigidity and strength to the platform  10 ′. The amount of stress experienced by the platform  10 ′ is reduced, and the location and distribution of these reduced stresses are changed, resulting in an improved design with an extended fatigue life over that of the prior art. 
   As was the case for the previously described prior art platform  10 , the mast  12  is a standard mast, as is well known in the industry, adapted for mounting the car lifting platform  10 ′ to a wheel loader (not shown). 
   It will be obvious to those skilled in the art that modifications may be made to the embodiment described above without departing from the scope of the present invention.