A sheave bracket directs a trailing cable of a mining vehicle. The bracket is hingedly secured to the vehicle and includes a plate and a plurality of sheaves coupled to and extending from the plate. The sheaves are arranged to guide the cable. The sheave bracket also includes a force control mechanism movable between two positions to adjust tension in the cable. The force control mechanism dampens strain in the cable when the direction of the bracket is changed.

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/569,874, filed Dec. 13, 2011, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to movable electric machinery having a trailing cable connected to a source of power, and, more particularly, to a sheave bracket assembly for preventing the cable from contacting the movable electric machinery. 
         [0003]    Haulage equipment, such as shuttle cars, in the mining industry efficiently removes cut material from a working face in such a manner so as to enhance the performance of a continuous miner and maximize productivity. A conventional rigid sheave bracket attached to a front of a shuttle car has no means to absorb the inertial force (from cable direction change) while passing the shuttle car trailing cable tie-off point. Damage caused to the cable by shock resulting from this change of direction is one of the largest costs associated with maintenance of shuttle cars. 
       SUMMARY OF THE INVENTION 
       [0004]    In one embodiment, a sheave bracket directs a trailing cable of a mining vehicle. The bracket is hingedly secured to the vehicle and includes a plate and a plurality of sheaves coupled to and extending from the plate. The sheaves are arranged to guide the cable. The sheave bracket also includes a force control mechanism coupled between the plate and a wall of the vehicle. The force control mechanism dampens strain in the cable when a direction of the bracket is changed. 
         [0005]    In another embodiment, a sheave bracket assembly is hingedly secured to a mining vehicle and includes a plurality of first sheaves coupled to and extending from a first plate hingedly secured to the vehicle, a second sheave coupled to and extending from a second plate, the second plate coupled to an arm member hingedly secured to the vehicle, and a force control mechanism coupled between the second plate and the arm member. The force control mechanism dampens strain in the cable when the direction of the bracket is changed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a partial top plan view of a right front corner of a shuttle car. 
           [0007]      FIG. 2  is a top view of a swinging sheave bracket with a force control mechanism according to one embodiment of the invention, with the force control mechanism in a first position. 
           [0008]      FIG. 3  is a top view of a swinging sheave bracket with the force control mechanism of  FIG. 2  in a second position 
           [0009]      FIG. 4  is a top view of a swinging sheave bracket with a force control mechanism according to another embodiment of the invention. 
           [0010]      FIG. 5  is a perspective view of the swinging sheave bracket of  FIG. 4 . 
       
    
    
       [0011]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the above-described drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       DETAILED DESCRIPTION 
       [0012]      FIG. 1  illustrates an electric vehicle  10  (such as a shuttle car) useful in hauling material in underground mines. The shuttle car  10  includes a vehicle frame  14 , an electrical motor  18  supported on the frame  14 , and a cable  22 , which is electrically connected to the motor  18  and configured to be connected to a power source  19 . The shuttle car  10  further includes a cable reel  26  on the frame  14  between the electric motor  18  and one end of the frame  14 . In the illustrated embodiment, the reel  26  is located near a front  30  of the shuttle car  10 , that is a rear portion of the vehicle frame  14 , and is rotatable about an axis. 
         [0013]    As the shuttle car  10  moves (e.g., backwards, forwards, and around corners, toward to or away from the power source), the cable  22  is either wound onto or paid out of the reel compartment  26 . The cable  22  extends from a front  34  of the shuttle car  10 , and, at times, either runs along the side  38  of the shuttle car  10 , when the shuttle car  10  is moving forward or backward, or extends straight back from the shuttle car  10 , when the shuttle car  10  is moving forward or backward (not shown). When the shuttle car  10  moves right around a corner, as shown in  FIG. 1 , the cable  22  runs along either the front  34  or the side  38  of the shuttle car  10 . 
         [0014]    The shuttle car  10  further includes a cable guide or spooling device  42  positioned between the reel  26  and the rear  34  of the shuttle car  10 . However, the cable guide  42  could be positioned at other points along the shuttle car as well. A sheave bracket assembly  46  is hinged to the right front  30  of the shuttle car  10  at joint  47  to allow the sheave bracket assembly  46  to swing relative to the right front  30  of the shuttle car  10 . As shown in  FIGS. 2-3 , the sheave bracket assembly  46  includes a lower mounting plate  50 , and two spaced apart sheaves  54  and  58  rotatably mounted on the lower mounting plate  50 . 
         [0015]    With continued reference to  FIG. 1 , the cable  22  extends from the cable reel  26  through the cable guide  42 , and then between the sheaves  54 ,  58 . In certain applications, the cable  22  may have a length of between  500  and  1000  feet. The cable may be an AC cable or a DC cable. 
         [0016]      FIGS. 1-3  illustrate the swinging sheave bracket  46  with a force control mechanism  100 . In the illustrated embodiment, the force control mechanism  100  is a liquid medium type shock or strut element  100  (hereinafter, “strut”). In further embodiments, other types of shock or strut elements may also be used. The strut  100  minimizes the strain in the trailing cable  22  while passing the shuttle car trailing cable tie-off point by dampening or reducing the strain in the cable  22  when the direction of the cable reel  26  is changed. The tie-off point is a point in the mine where the cable is affixed to the wall. The tie-off point may be near the power source  19  or elsewhere along the travel path of the shuttle car  10 . It is at the tie off point where the cable  22  changes direction, which in turns causes a shock on the cable  22 . It is this shock that the strut  100  minimizes. 
         [0017]    As best shown in  FIGS. 2-3 , the strut  100  has a generally cylindrical shape. A first end  101  of the strut  100  is secured to the right front  30  of the shuttle car  10  near a compartment for the cable reel  26 . A second end  102 , opposite the first end  101 , is secured to the cable sheave bracket  46 . 
         [0018]    As discussed above, motion of the sheave assembly  46  is controlled by the strut  100 . In a first position, shown in  FIG. 3 , the strut  100  is in a substantially extended position and the sheave bracket assembly  46  is shown in a retracted position in relation to the right front  30  of the shuttle car  10  forming an obtuse angle (for example approximately 135°) with the right front  30  of the shuttle car  10  relative to a side of the sheave assembly  46  adjacent the strut  100 . The strut  100  is configured to be in full extension when the tension in the cable  22  is light. As the cable tension increases at a regular rate to a certain point, the strut  100  begins to contract into a second position, shown in  FIG. 2 , in which the sheave bracket assembly  46  pivots with respect to the shuttle car  10  and extends substantially perpendicular to the right front  30  of the shuttle car  10 . Movement of the sheave bracket assembly  46  results in increased cable tension at a substantially reduced rate until the strut  100  is fully contracted. At this time, cable tension increases at a regular rate. This configuration provides a “virtual” cable lengthening effect, meaning the overall distance covered by the cable  22  lengthens as the strut  100  compresses (or the distance decreases as the strut  100  extends) due to the geometry of the linkage of the bracket assembly  46 . 
         [0019]      FIGS. 4-5  illustrate a sheave bracket  146  with a roller guide swing arm assembly  210  with a force control mechanism  200  according to another embodiment of the invention. The combination of sheave bracket  146 , roller guide assembly  210 , and cable guide arm  147  shown in  FIGS. 4-5  reduces strain in cable  22  similar to the sheave bracket  46  shown in  FIGS. 1-3 . The differences will be discussed below and like structure will be given the same reference number plus “ 100 .” The force control mechanism  200  is connected to the right front  30  of the shuttle car  10  and includes a second end  202  of the strut  200  that is fixed to a roller guide swing arm assembly  210 . The swing arm assembly  210  includes a roller guide  211  and swing arm  212 . The roller guide  211  includes a top plate  215 , a bottom plate  216 , and a sheave  217  therebetween. 
         [0020]    In the sheave bracket  146 , one end of the swing arm  212  is hinged to the right front  30  of the shuttle car  10  and the other end of the swing arm  212  is fixed to the roller guide  211 . One end  201  of the strut  200  is hinged to the right front  30  of the shuttle car  10  and the other end  202  of the strut  200  is fixed to the swing arm  212 . Thus, the cable  22  extending from the cable reel  26  passes through the assembly  210  before entering the sheave bracket assembly  146  and cable guide arm  147 . 
         [0021]    During operation, the sheave bracket  146  functions similarly to the sheave bracket  46 , except that the additional assembly  210  in  FIGS. 4-5  provides the cable  22  with additional force control. 
         [0022]    Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention as described. Various features and advantages of the invention are set forth in the following claims.