Abstract:
A park brake linkage includes a pivotable park brake actuating handle, a park brake bell crank rotatably mounted on a cross shaft, an arm extending radially from the park brake bell crank, and a single connector between the handle and the firs arm to transmit pivoting movement of the handle to rotational movement of the park brake bell crank. A second arm may extend radially and laterally from the park brake bell crank, which may be used to turn a left brake bell crank and a right brake bell crank, each of which may be secured to a separate brake camshaft. Each camshaft has a cam lobe extending therefrom to apply a brake.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to park brake systems for tractors and other vehicles, and more specifically to mechanical linkages for park brake systems. 
   BACKGROUND OF THE INVENTION 
   Conventional tractors and other vehicles, including vehicles suited for off-road use, may have a park brake system which includes a manual or hand-operated lever connected through a pair of mechanical linkages to brake units on each of two wheels. Each of the two linkages may include several components that transfer forces necessary to apply and securely hold a brake on a wheel. 
   For example, each linkage may include one or more bell cranks, wire cable and/or rods. Each linkage for the left and right brake may duplicate one or more components. 
   Manufacturing costs and assembly time for linkages in park brake systems may relate, at least in part, to the number of components in the linkage. A park brake system is needed that has fewer components in the linkage, lower manufacturing cost, and reduced assembly time. 
   Park brake systems are serviced periodically for several reasons including or related to wear and tear. For example, cables in both linkages may need to be adjusted or tightened so that both brakes may be applied and will engage with equal pressure. This is one example of an adjustment to a park brake linkage that may be difficult and time intensive. A park brake linkage is needed that will reduce or minimize service requirements. 
   SUMMARY OF THE INVENTION 
   A park brake linkage is provided that eliminates duplication of components, reduces manufacturing cost, and shortens assembly time. The park brake linkage also helps reduce or minimize service requirements. Fewer components are used than in conventional park brake linkages. 
   A single connector extends from the park brake actuation handle to left and right bell cranks on a brake cross shaft. The connector, which may be a rod, extends between the handle and an arm extending radially from a park brake bell crank. The connector transmits pivoting movement of the handle to rotational movement of the park brake bell crank. A second arm may extend radially and laterally from the park brake bell crank, which may be used to turn a left brake bell crank and a right brake bell crank, each of which may be secured to a separate brake camshaft. Each camshaft has a cam lobe extending therefrom which, when rotated, may apply a brake to a separate wheel. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a rear perspective view of a brake system for a tractor showing a first embodiment of the park brake linkage. 
       FIG. 2  is an expanded rear perspective view of the park brake linkage according to the first embodiment. 
       FIG. 3  is an expanded front perspective view of the park brake linkage according to the first embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As shown in  FIG. 1 , brake system  100  may be in a tractor or other vehicle, including an off-road vehicle. When the park brake is operated, left and right brakes may be applied together. When brake pedals are operated, the left and right brakes may be applied independently of each other. 
   Park brake actuation handle  101  may be, and in normal use will be, used to apply the brakes on two wheels (i.e., the left and right wheels) of a vehicle. The park brake actuation handle may be positioned at or in the operator station of the vehicle. In one embodiment, handle  101  may be pivotably attached to mounting plate  104  secured to the body or frame. 
   Brake pedals  102 ,  103  also may be used to apply brakes independently to each of the left and right wheels. Left brake pedal  102  and right brake pedal  103  may be floor mounted or hanging in the operator station. For example, as shown in  FIG. 1 , the brake pedals may be floor mounted over brake pedal pivot shaft  105  which may be rotatably mounted to the tractor body or frame. Alternatively, the brake pedals may be positioned to hang below the brake pedal pivot shaft. Stop  106  may be provided to locate both brake pedals at a rest position. 
   In one embodiment, one of the brake pedals may rotate with respect to the brake pedal pivot shaft, and the other brake pedal may be secured to and rotate together with the shaft. For example, left brake pedal  102  may be attached to sleeve  107  and right brake pedal  103  may be attached to sleeve  108 . Sleeve  107  may rotate on the brake pedal pivot shaft, and sleeve  108  may be secured to the brake pedal pivot shaft. 
   In one embodiment, sleeve  107  may have radially extending arm  109 . Left brake rod  110  may extend between arm  109  and left brake main bell crank  111 . Left brake rod  110  may include turnbuckle  112  which may be used to change the rod length. When the left brake pedal is applied, sleeve  107  rotates on the brake pedal pivot shaft, moving left brake rod  110  longitudinally to rotate left brake main bell crank  111 . The left brake main bell crank may be secured to and rotate together with left brake camshaft  113 . As shown in  FIG. 2 , rotating the left brake camshaft urges cam lobe  115 , which is on the left brake camshaft&#39;s outer circumference, against projection  116  on plate  117 , and then rotates plate  117 . Rotation of plate  117  will apply the left wheel brake in a conventional manner understood by those skilled in the art. Return spring  159  may urge the left brake pedal toward the rest position. 
   In one embodiment, left brake main bell crank  111  may fit around and be secured to left brake camshaft  113 . For example, a key may engage slots in the internal diameter of the left brake main bell crank and the external diameter of the left brake camshaft. As shown in  FIGS. 2 and 3 , the left brake main bell crank may have a generally sleeve-shaped body with first end  118 , second end  119 , and arms  120 ,  121 , and  122  extending radially from the body. Arm  120  may be connected to return spring  123 , to urge the left brake main bell crank toward the rest position. Arm  121  may have slot  124  which may pivotably receive one end of left brake rod  110 . Slot  124  may be dimensioned to provide a lost motion mechanism so that application of the park brake does not alter the position of the left brake foot pedal. When the park brake is applied, park brake bell crank  141  may contact arm  122  and rotate the left brake bell crank to apply the left brake. 
   In one embodiment, right brake rod  125  may extend between right brake front bell crank  126  and right brake main bell crank  127 . Right brake rod  125  may include turnbuckle  128  which may be used to change the rod length. When the right brake pedal is applied, brake pedal pivot shaft  105  and right brake front bell crank  126  rotate together, moving right brake rod  125  longitudinally and rotating right brake main bell crank  127 . Right brake main bell crank  127  may be secured to right brake camshaft  129 , both of which may be secured to brake cross shaft  114  with a key or similar device. Rotating the right brake camshaft urges cam lobe  130 , which is on the right brake camshaft&#39;s outer circumference, against projection  131  on plate  132 , and then rotates plate  132 . Rotation of plate  132  will apply the right wheel brake in a conventional manner understood by those skilled in the art. Return spring  133  may be connected to arm  134 , to urge the right brake pedal back toward the rest position. 
   In one embodiment, right brake main bell crank  127  may fit around and be secured to right brake camshaft  129 . For example, a key may engage slots in the internal diameter of the right brake main bell crank and the external diameter of the right brake camshaft. The right brake main bell crank and the right brake camshaft may be secured to brake cross shaft  114 , and may rotate together with the brake cross shaft. As shown in  FIGS. 2 and 3 , right brake main bell crank  127  may have a generally sleeve-shaped body with first end  135 , second end  136 , and arm  137  extending radially from the body. Arm  137  may have slot  138  which may pivotably receive one end of right brake rod  125 . Slot  138  may be dimensioned to provide a lost motion mechanism so that application of the park brake does not alter the position of the right brake foot pedal. 
   Park brake actuation handle  101  may be used to apply both the left and right brakes. When the handle is pulled, it may pivot on axis  139  adjacent the first end of the handle, and move connector  140  longitudinally to rotate park brake bell crank  141 . In one embodiment, connector  140  may be a rod that connects the first end of the handle to park brake bell crank  141 . The connector may include turnbuckle  160  to adjust the length. Rotating the park brake bell crank rotates the left and right brake camshafts so that cam lobes  115 ,  130  on the outer circumference of the camshafts abut projections  116 ,  131  on plates  117 ,  132 , and then rotate the plates to apply the left and right brakes. A latch (not shown) may releasably lock the park brake actuation handle in the park brake position. 
   In one embodiment, park brake bell crank  141  may be dimensioned to fit around left brake camshaft  113 . A bearing may be pressed into the internal diameter of the park brake bell crank. For example, the bearing may be a dry bearing made from or including an elastomeric material. As shown in  FIGS. 2 and 3 , park brake bell crank  141  may have a generally sleeve-shaped body, first end  142 , second end  143 , and arms  144 ,  145  extending from the body. Arm  144  extends radially from the park brake bell crank adjacent the first end. Arm  144  may include slot  146  which may pivotably receive one end of connector  140 . Slot  146  may be dimensioned to provide a lost motion mechanism so that application of either or both brake pedals does not alter the position of the park brake bell crank and park brake actuation handle. 
   In one embodiment, as shown in  FIG. 3 , arm  145  may extend radially and longitudinally from the second end of park brake bell crank  141 . When handle  101  is actuated and park brake bell crank  141  is rotated, arm  145  may abut and push against arm  122  extending radially from left brake main bell crank  111  and arm  147  extending radially from right brake secondary bell crank  148 . Arm  145  may push against arms  122  and  147  sufficiently to turn the left brake main bell crank and right brake secondary bell crank, rotating the left and right brake camshafts to apply the left and right brakes. 
   In one embodiment, adjustment device  149  may set the relative position of park brake bell crank  141  with respect to left brake main bell crank  111  and right brake secondary bell crank  148 . The adjustment device may be used to equally distribute force from the park brake actuation handle to the left and right brakes. For example, the adjustment device may be an externally threaded member that may engage an internally threaded passage in arm  145 , and a nut to lock the externally threaded member in a desired position. The position of the park brake bell crank with respect to each of arms  122 ,  147  then may be adjusted as needed. 
   Right brake secondary bell crank  148  may have an internal diameter dimensioned to fit around brake cross shaft  114 , and may be secured to the brake cross shaft. For example, roll pin  150  may be inserted through corresponding holes in the right brake secondary bell crank and brake cross shaft. The right brake secondary bell crank may have a generally sleeve-shaped body with first end  151 , second end  152 , and arms  147 ,  153  extending from the body. When the park brake bell crank is rotated, arm  145  (acting through adjustment device  149  extending from arm  145 ) may abut and push against arm  147  which extends radially and longitudinally from the right brake secondary bell crank, rotating the right brake secondary bell crank and right brake camshaft to apply the right brake. Arm  153  may extend radially from the right brake secondary bell crank and be connected to return spring  154 , for urging the right brake secondary bell crank toward the rest position. 
   In one embodiment, left brake camshaft  113  and right brake camshaft  129  may be generally sleeve-shaped members having internal diameters dimensioned to fit over brake cross shaft  114 . Left brake camshaft  113  may extend through park brake bell crank  141  and left brake main bell crank  111 . Left brake camshaft  113  may terminate at or adjacent second end  119  of left brake main bell crank  111 , so that it is spaced from first end  155  of the brake cross shaft. Right brake camshaft may extend through right brake main bell crank  127 . Right brake camshaft may terminate at or near second end  156  of the brake cross shaft. Left brake camshaft  113  may rotate on brake cross shaft  114 , and right brake camshaft  129  may be secured to brake cross shaft  114 . For example, roll pin  157  may be inserted through corresponding holes in the right brake camshaft and brake cross shaft. 
   One or more lock rings may be positioned and locked on camshafts  113  and/or  129  to locate and maintain their axial positions with respect to a transmission and/or one or more other components. For example, lock rings may be placed between left brake bell crank  111  and right brake secondary bell crank  148 . 
   The park brake linkage described above significantly reduce the number of components compared to conventional park brake systems. Instead of a pair of linkages, a single linkage connects the park brake actuation handle and a left and a right bell crank on a brake cross shaft. As a result, manufacturing costs may be reduced and assembly time may be lower than with conventional park brake systems. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.