Abstract:
A prolonged release system having a locking member pivotally mounted on a post within a hand brake and having an arm that contacts a clutch assembly to prevent the clutch assembly of the handbrake from engaging after it has been manually released. Rotation of the hand brake wheel causes a pawl on a ratchet gear to move into contact with a cam of the locking member so that the arm of the locking member moves out of contact with the clutch assembly. By maintaining the clutch assembly in a released position, the prolonged release system ensures that the brake chain drum is decoupled from the driveshaft of the hand brake and prevents the inadvertent application of the brakes. When a user turns the hand brake wheel, the locking member is disengaged from the clutch assembly and the hand brake can be set by a user.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. FIELD OF THE INVENTION 
         [0002]    The present invention relates to hand brake release mechanisms for use on railway car braking systems and more particularly, to a prolonged release mechanism. 
         [0003]    2. DESCRIPTION OF THE RELATED ART 
         [0004]    Rail car hand brake mechanisms have a user wheel that is turned to rotate a drum to take up a chain attached to the rail car brake system, this allowing a user to manually engage the brakes. Hand brake mechanisms typically include a quick release mechanism, such as a handle that can be moved by a user, which allows for an immediate and full release of the hand brake. For example, movement of the handle will disengage a clutch assembly that connects the user wheel and drum, thereby the drum to freely rotate and release the brake chain. When the quick release mechanism is released, the clutch assembly reengages and the brake chain drum is reconnected to the wheel. 
         [0005]    A major problem with hand brakes is that if the brake chain has not fully unwound, or if the motion of the rail car causes a loss of the slack in the brake chain, an inadvertent application of the rail car brakes can occur. Unintentional braking is a serious problem and can lead to overheating, the failure of the braking system, and damages truck wheels. To remedy this problem, prolonged release mechanisms have been incorporated into the hand brake to prevent the clutch from reengaging after the quick release handle has been pulled and returned to the original position. For example, U.S. Pat. No. 8,123,004 discloses a prolonged release mechanism that maintains the clutch in the disengaged position even if the quick release handle is moved back. Although the prolonged release mechanism does disengage when the user turns the hand brake wheel, the posts on the ratchet wheel that knock the mechanism out of engagement with the clutch assembly is not a robust design, and thus could be improved to ensure longevity of the system. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present invention comprises a prolonged release system for a rail car hand brake having a locking member that is pivotally mounted on a post within the hand brake and has an arm positioned proximately to a clutch assembly of the hand brake as well as a cam positioned proximately to a pawl that is coupled to a ratchet wheel of the hand brake. The locking member can pivot about the post between a first position, where the arm prevents the clutch assembly from engaging, and a second position, where the arm allows the clutch assembly to engage. The locking member is biased into the prolonged release position and disengaged when rotation of the ratchet wheel causes the pawl to contact the cam of the locking member so that the first arm of the locking member moves from the first position to the second position. 
         [0007]    The locking member of the prolonged release system can be positioned on the same post as the pawl or on a different post that extends in parallel to the post of the pawl. In either case, the locking member selectively engages the yoke assembly of the clutch assembly to retain the axially movable clutch member in the declutched position by pivoting into engagement with the yoke after the yoke has moved the movable clutch member connector plate into a disengaged position. The locking member may have a notch that engages a tab associated with the yoke, or a radius that assists a planar portion to flushly engage the yoke directly. By maintaining the clutch assembly in the released position, the prolonged release system ensures that the brake chain drum is decoupled from the driveshaft of the hand brake. When a user subsequently turns the hand brake wheel, rotation of the driveshaft causes the locking member to disengage from the clutch assembly so that the clutch can reengage, thereby ending the prolonged release and recoupling the brake chain drum to the driveshaft and wheel so that the hand brake can be set by a user. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0008]    The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which: 
           [0009]      FIG. 1  is an exploded perspective view of a rail car hand brake having a prolonged release mechanism according to the present invention; 
           [0010]      FIG. 2  is perspective view of a prolonged release mechanism according to the present invention in the disengaged position; 
           [0011]      FIG. 3  is perspective view of a prolonged release mechanism according to the present invention in the engaged position; 
           [0012]      FIG. 4  is a perspective view of another prolonged release mechanism according to the present invention in the disengaged position; and 
           [0013]      FIG. 5  is a perspective view of another prolonged release mechanism according to the present invention in the engaged position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring now to the drawings, wherein like reference numerals refer to like parts throughout, there is seen in  FIG. 1  a rail car hand brake  10  that has been outfitted with a prolonged release mechanism  12  for maintaining hand brake  10  in the released position until such time as a user manually rotates the wheel  14  of hand brake  10 . The general structure of rail car hand brake  10  is known in the art and disclosed in various publications and will only be discussed herein as it pertains to prolonged release mechanism  12 . 
         [0015]    Referring to  FIG. 1 , prolonged release mechanism  12  comprises a locking arm  16  that pivots about a post  18 , which may be the same post that supports the pawl  20  of a ratchet gear  22  positioned on a hand brake driveshaft  24 . Pawl  20  and ratchet gear  22  are used to prevent counter-rotation of drive shaft  24  if a user releases wheel  14  and shaft  24  is under torque, such as when a brake chain  26  has been wound around a drum  28  to set the rail car brakes in an applied position. Locking arm  16  includes a trigger cam  30  that is positioned proximately to and slightly spaced apart from pawl  20  of ratchet gear  22 . When ratchet gear  22  is rotated, pawl  20  will move up and down as it translates across the toothed surface  32  of ratchet gear  22 . Due to this motion, pawl  20  will contact trigger cam  30  and cause locking arm  16  to pivot about post  18  against the bias of a trigger spring  36 . A trigger tab  34  may be provided on pawl  20  to encourage contact between pawl  20  and trigger cam  30 . 
         [0016]    Locking arm  16  includes a locking end  38  extending outwardly from and positioned on the opposing side of post  18  from trigger cam  30 . Locking arm  16  is biased by trigger spring  36  to rotate locking end  38  toward the prolonged release position. In the prolonged release position, a notch  40  in locking end  38  will selectively retain the hand brake clutching assembly in the released position once it has been manually released by a user. As seen in  FIGS. 2 and 3 , locking end  38  and notch  40  are positioned and configured to releasably lock the clutch assembly by engaging a pivoting yoke  42  used to selectively disengage a clutch  44  that is positioned along driveshaft  24 . Clutch  44 , when engaged, allows the rotation of driveshaft  24  to drive a pinion  46  that is connected to the main gear  48  of a drum  28 . Drum  28  is used to wind up a brake chain  26  connected to the rail car brakes, thus mechanically applying the brakes and allowing a user to set the brakes by hand. Clutch  44  comprises a connector plate  54  that is rotationally fixed about driveshaft  24  but moveable axially along driveshaft  24  into a first position, where connector plate  54  closes clutch  44 , and a second position, where connector plate  54  disengages clutch  44 . For example, connector plate  54  may be biased, such as by a spring  50 , to move a clutch teeth  56  fixedly connected to connector plate  54  (and thus also rotationally fixed to driveshaft  24 ) into engagement with a toothed clutch half  58  that is attached to pinion  46 . Toothed clutch half  58  and pinion  46  are fixed axially along driveshaft  24 , but free to rotate about driveshaft  24  if first clutch half  56  is disengaged from toothed clutch half  58 . 
         [0017]    When clutch  44  is engaged, driveshaft  24  and toothed clutch half  58  are rotationally interlocked so that rotation of driveshaft  24  will cause rotation of pinion  46 . Thus, when clutch  44  is engaged, rotation of pinion  46  will drive main gear  48  and drum  28  to take up brake chain  26  as driveshaft  24  is rotated by wheel  14 , thereby applying or releasing the rail car brakes. Clutch  44  is disengaged by applying a force to connector plate  54  so that connector plate  54  and clutch teeth  56  translate along driveshaft  24  against a bias force provided by spring  50  to separate first clutch half  56  from second clutch half  58 . When clutch  44  is disengaged, pinion  46  is rotationally separated from driveshaft  24  and thus free to rotate relative to driveshaft  24 . As a result, main gear  48  and drum  28  are released from driveshaft  24  and free to unwind if under a load, such as a wound up chain  26 , which will consequently unwind and stay in the unwound or ‘brakes released’ position as main gear  48  and drum  28  are no longer operably connected to driveshaft  24 . 
         [0018]    As seen in  FIGS. 1 and 2 , connector plate  54  is positioned so that it may be moved axially along driveshaft  24  in response to a pivoting of yoke  42 , which has a pair of opposing arms  60  and  62  that are held in spaced relation by connecting rod  64 . A cam  66  may be rotated into and out of engagement with connecting rod  64 , thereby driving yoke  42  so that yoke arms  60  and  62  move from a first position, where yoke arms  60  and  62  are disengaged from connector plate, into a second position, where yoke arms  60  and  62  engage connector plate  54  and push it axially along driveshaft  24  against bias of spring  50  so that clutch  44  disengages.  FIG. 2  depicts yoke  42  in the first position and  FIG. 3  depicts yoke  42  in the second position after being pivoted by cam  66 . Cam  66  is typically interconnected to a lever  68  so that a user can quickly release hand brake  10  by moving lever  68  and rotating cam  66  to disengage clutch  44 . 
         [0019]    Connecting rod  64  includes a tab  52  extending outwardly from an intermediate portion thereof for selective engagement with notch  40  of locking end  38  when yoke  42  has been pivoted into its second position and yoke arms  60  and  62  are pushed against connector plate  54 . When yoke  42  has been fully rotated and connector plate  54  has moved into the second position, as seen in  FIG. 3 , locking end  38  is pivoted under the bias of trigger spring  36  so that notch  40  of locking end  38  engages tab  52  and retains yoke  42  in contact with connector plate  54 . As seen in  FIG. 3 , notch  40  and tab  52  are dimensioned and positioned so that tab  52  will remain seated in notch  40  even if cam  66  rotates out of engagement with connecting rod  64  of yoke  42 . As a result, clutch  44  is maintained in the disengaged position so that hand brake  10  is kept in a released configuration for a prolonged period, i.e., until pawl  20  moves along up and down when it translates along the teeth  32  of ratchet gear  22 . When pawl  20  moves it causes trigger tab  34  to bump trigger cam  30  and pivot locking arm  16  so that notch  40  is moved away from and releases release tab  52 . Yoke  42  is then free to return to the first position, as seen in  FIG. 2 , as connector plate  54  is biased by spring  50  and clutch  44  reengages. 
         [0020]    In operation, prolonged release mechanism  12  automatically retains hand brake  10  in the released position after a user manually releases hand brake  10  using handle  68 , which moves yoke  42  so that clutch  44  disengages to separate brake chain drum  28  from driveshaft  24 . Locking arm  16  is biased into the prolonged release position and will thus pivot so that locking end  38  engages tab  52  of yoke  42  to maintain yoke  42  in engagement with clutch  44  so that drum  28  remains uncoupled from driveshaft  24 . If a user rotates wheel  14 , pawl  20  of ratchet gear  22  will translate across teeth  32  so that trigger tab  34  contacts trigger cam  30 , thereby causing interlock  30  to pivot so that locking end  38  moves out of engagement with yoke  42 . Yoke  42  will move out of contact with clutch  44  so that clutch can return under the bias of spring  50  to the engaged position where driveshaft  24  is again coupled to drum  28 . Thus, prolonged release mechanism  12  automatically prolongs the release of hand brake  10  by preventing reengagement of the clutch assembly until there is subsequent manual rotation of wheel  14 , such as when a user next sets hand brake  10 . 
         [0021]    In another embodiment seen in  FIGS. 4 and 5 , a prolonged release mechanism  70  includes a locking arm  72  that is positioned on and pivots about the end of a post  74  that extends parallel to pin  18  about which pawl  20  of ratchet wheel  22  pivots. Locking arm  72  includes a single tooth gear  76  or cam portion that is positioned to selectively engage a corresponding single tooth gear  78  or cam portion associated with pawl  20 . Locking arm  72  pivots between a first position, where a planar surface  80  of locking arm  72  flushly engages an intermediate portion of connecting rod  64  of yoke  42  and holds yoke  42  in place so that clutch  44  is disengaged, and a second position, where arm  72  releases connecting rod  64  so that clutch  44  can reengage.  FIG. 4  illustrates locking arm  72  in the released position relative to yoke  42  and  FIG. 5  illustrates locking arm  72  in the engaged position relative to yoke  42  so that clutch  44  has disengaged to prolong the release of hand brake  10 . 
         [0022]    Locking arm  72  is biased by a wire spring  82  into the first position so that as soon as yoke  42  is moved to disengage clutch  44 , locking arm  72  will pivot into flush engagement with and hold yoke  42  in place. Wire spring  82  may be connected at one end to locking arm  72  and at an opposing end to a fixed surface such as the housing of hand brake  10 . When ratchet wheel  22  is turned, movement of pawl  20  will cause single tooth gear  78  to contact corresponding single tooth gear  76  of locking arm  72  thereby rotating planar surface  80  of locking arm  72  far enough out of flush engagement with connecting rod  64  of yoke  42  so that yoke  42  can move into the declutched position. Preferably, the bias forces applied to yoke  42  exceeds the bias force moving locking arm  72  into the engaged position so that yoke  42  can move into the declutched position as soon as locking arm  72  has rotated sufficiently to move planar surface  80  out of flush engagement with connecting rod  64 . As seen in  FIGS. 4 and 5 , one end of planar surface  80  of arm  72  may include a radius  84  that allows connecting rod  64  of yoke  42  and planar surface  80  of locking arm  72  to more readily engage and disengage. 
         [0023]    As before, prolonged release mechanism  70  will automatically retain hand brake  10  in the released position after a user manually releases hand brake  10  using handle  68 , which moves yoke  42  so that clutch  44  disengages to separate brake chain drum  28  from driveshaft  24 . Locking arm  72  is biased into the prolonged release position and will thus pivot so surface  80  engages yoke connecting rod  64  to maintain yoke  42  in engagement with clutch  44  so that drum  28  remains uncoupled from driveshaft  24 . If a user rotates wheel  14 , pawl  20  of ratchet gear  22  will translate across teeth  32  so that single tooth gear  78  contacts single tooth gear  76 , thereby causing locking arm  72  to pivot so that surface  80  moves out of engagement with yoke connecting rod  64 . Yoke  42  will then move out of contact with clutch  44  so that clutch  44  can return under the bias of spring  50  to the engaged position where driveshaft  24  is again coupled to drum  28 . Thus, prolonged release mechanism  70  automatically prolongs the release of hand brake  10  by preventing reengagement of the clutch assembly until there is subsequent manual clockwise rotation of wheel  14 , such as when a user next sets hand brake  10 .