Winch having automatic brake

Abstract

An automatic brake for vehicle winch that is automatically applied when the applied torque of the drive motor ceases and automatically released upon application of motor torque. The brake features brake pad segments that move radially outward against the interior of the drum to affect braking and retract radially inward to affect releasing of the brake. The pads have tapered ends that mate with opposed frusto-conical shoes. The brake utilizes rotation of a cam rotatable with respect to a cam follower in one direction to force one shoe toward the other to force the pads radially outward to engage the interior surface of the drum. Rotation of the cam with respect to the cam follower in the opposite direction releases the braking action. A wave spring is incorporated to eliminate chatter as the brake is applied and released. The configuration of the brake components provides a conductive path for the dissipation of heat generated by the braking action.

What is claimed is: 
     
       1. In a winch having a rotatable drum rotatable in both rotative directions, a cable wound onto the drum in one rotative direction and off the drum in a second rotative direction, a drive motor having a drive shaft selectively rotated by the motor in either direction of rotation, and interconnecting mechanism interconnecting the drive shaft and the drum for rotatably driving the drum, said interconnecting mechanism including a gear train that reduces the rotative speed of the drum relative to the motor shaft, and brake mechanism for controlling rotation of the drum comprising: said drum having a cylindrical inner surface defining an axis,   a plurality of brake pads cooperatively arranged to provide a cylindrical outer braking surface and arranged adjacent the inner surface of the drum, said brake pads having radial movement toward and away from the inner surface of the drum, a brake shoe cooperatively arranged relative to the pads and axially movable into and away from the pads to induce radial expansion and permit radial retraction of the pads,   a cam and cam follower having cooperative cam surfaces that urge axial separation thereof upon relative rotation of the cam and cam follower in a first rotative direction, and permit axial nesting thereof upon relative rotation of the cam and cam follower in a second rotative direction,   a coupling that independently couples the motor shaft to the cam and cam follower, said coupling initially engaging the cam with the motor shaft driven in one rotative direction and initially engaging the cam follower with the motor shaft driven in the other rotative direction to initiate relative rotation of the cam and cam follower in said second relative rotative direction with the motor shaft driven in either rotative direction,   a first biasing member urging rotation of the cam and cam follower in the first rotative direction, and   said brake shoe arranged relative to said cam and cam follower for axial urging of the brake shoe toward the brake pads upon axial separation of the cam and a cam follower.   
     
     
       2. A brake mechanism as defined in claim 1 wherein one of said cam and cam follower is coupled to said brake shoe for axial movement therewith, and a second biasing member permitting restrictive axial movement of the other of said cam and cam follower in the opposite direction to cushion the effect of repetitive braking in the drum during cable unwinding. 
     
     
       3. A brake mechanism as defined in claim 2 wherein the arranged brake pads form frusto conical end surfaces, a brake shoe fixed adjacent one end and having a frusto conical surface mated to the corresponding brake pad end, and said movable brake shoe adjacent the other end of the pads and having a frusto conical surface mated to the pads and having a frusto conical surface mated to that brake pad end, said separating movement of the cam and cam follower forcing said movable shoe against the frusto conical end of the brake pads, the opposite end thereof being forced against the frusto conical surface of the fixed shoe to force radial movement of the brake pads. 
     
     
       4. A brake mechanism as defined in claim 3 wherein said interconnecting mechanism includes a shaft that extends from one of said cam and cam follower to said gear train, said one of said cam and cam follower spline fit to said shaft whereby rotation of said one of said cam and cam follower forces rotation of the gear train and thereby rotation of the drum, and said coupling including a drive dog and said cam and cam follower including ears rotatively engageable by said drive dog, said rotative positions of the drive dog and ears arranged whereby in one rotative direction of the motor shaft the ear of said one of the cam and cam follower is engaged by the drive dog and urged counter to the urging of the first biasing member, and in the other rotative direction of the motor shaft the ear of the other of the cam and cam follower is engaged by the drive dog and urged counter to the urging of the first biasing member.   
     
     
       5. A brake mechanism as defined in claim 4 wherein engagement by the drive dog with the ear of said one of said cam and cam follower urges cable wind-up rotation of the drum. 
     
     
       6. A brake mechanism as defined in claim 5 wherein the first biasing member is a torsional spring having one end anchored to the shaft and thereby is rotatively fixed to said one of the cam and cam follower, and the other end fixed under tension to the other of said cam and cam follower to urge relative rotation therebetween. 
     
     
       7. A brake mechanism as defined in claim 6 wherein said one of said cam and cam follower is engaged by the resistive second biasing member and said other of said cam and cam follower urges the movable shoe toward the brake pads. 
     
     
       8. A brake mechanism as defined in claim 7 whereby the second biasing member is a wave spring interposed between the shaft end and the said one of said cam and cam follower. 
     
     
       9. In a winch having a drum rotatable in both rotative directions, a cable wound onto the drum in one rotative direction and off the drum in a second rotative direction, a drive motor having a drive shaft, and interconnecting mechanism interconnecting the drive shaft and the drum for rotatably driving the drum, said interconnecting mechanism including interconnected gears reducing the rotative speed of the drum relative to the motor shaft, and brake mechanism comprising: said drum having a cylindrical inner surface,   a plurality of brake pad segments arranged to form a cylinder located inside the drum, said brake pads having radial movement toward and away from the inner surface of the drum,   shoes having tapers mounted on said interconnecting mechanism, said shoes engaging opposite ends of said pads, one of said shoes moveable axially toward and away from the other shoe,   a cam affixed to the moveable shoe, said cam rotatable on said mechanism and moveable axially with said moveable shoe, a cam surface formed on said cam,   a cam follower mounted to said mechanism, a cam surface formed on said cam follower and in abutment with the cam surface of said cam,   a spring connected to said cam, said spring biasing said cam to rotate in a first direction relative to said cam follower whereby said cam surface of said cam acting on said cam surface of said cam follower forces said moveable shoe to move axially toward the other shoe to thereby force said pads to move radially outward to engage the inner surface of the drum. .Iadd.   
     
     
       10.  A winch comprising: a housing;   a cable drum assembly having opposed ends and a cylindrical exterior surface, said drum assembly rotatably mounted to the housing and a cable mounted to the exterior surface of the drum to be wound onto and off of the drum upon alternate rotation of the drum;   a motor having a drive shaft mounted to the housing at one end of the drum, a shaft extension coupled to the motor drive shaft and extended through the center of the drum to the opposite end of the drum, a gear reducer mechanism at said opposite end engaged with the shaft extension, said gear reducer engaged with the drum and configured to reduce the rotational effect of the drive shaft as applied to the drum;   a brake surface on said cable drum assembly, a brake pad, a movable braking member provided on said shaft extension and rotatable therewith and movable between engaged and disengaged positions to frictionally press said pad into braking engagement with said brake surface of the drum assembly whereby, when engaged, the relative rotative movement between the shaft extension and the drum is resisted; and   a cam mechanism actuating said braking member including a cam actuator and a cam follower having mated cam surfaces whereby alternate relative rotation allows axial nesting in one direction and forces axial separation of the cam actuator and cam follower in the other direction, said braking member carried by one of said cam actuator and cam follower whereby axial separation thereof moves the braking member and brake pad into braking engagement with the brake surface of the drum assembly, and a biasing member rotatively biasing the actuator and follower to the axial separation condition, and a driver coupling the motor's drive shaft to the cam actuator and cam follower whereby rotation of the driver in either rotative direction counters the biasing action member to permit axial nesting and disengagement of the braking member..Iaddend.