Automatic slack adjuster

An automatic, single acting, clearance sensing slack adjuster for maintaining a predetermined running clearance between the selectively engageable and disengageable friction surfaces of a brake comprising:

• a housing;
• a displaceable brake actuation means displaceable relative to said housing;
• a rotatable driving member rotationally received in said housing;
• means for rotating said driving member in response to greater than predetermined displacement of said brake actuation means;
• a rotatable intermediate member rotationally received in said housing and coaxial with said driving member, said intermediate member rotatable relative to said driving member;
• a rotatable driven member rotationally received in said housing and coaxial with and adjacent said intermediate member, said driven member rotatable relative to said intermediate member;
• a rotatable adjustment member rotationally received in said housing, rotation of said adjustment member in a given direction of rotation effective to decrease slack in the brake and in the other direction of rotation to increase slack in the brake;
• a normally engaged, positive clutch for rotationally coupling said driven member to said rotatable adjustment member;
• a one-way clutch for rotationally coupling said driving member to said intermediate member, said one-way clutch effective to transfer torque in the direction causing rotation of said adjustment member in said given direction;
• a force limiting coil clutch for rotationally coupling said intermediate member to said driven member, the torque transfer capacity of said coil clutch in said given direction of rotation greater than the torque required to rotate said adjustment member when said brake friction surfaces are not in contact but less than the torque required to rotate said adjustment member when said brake friction surfaces are in contact;
• and
• means accessible from the exterior of said housing for disengaging said normally engaged positive clutch and for simultaneously rotating said rotatable adjustment member.

A disc brake actuation assembly including an automatic single-acting clearance sensing slack adjuster for maintaining a predetermined running clearance between the brake friction pad and the disc, said assembly comprising:

• a support;
• a disc rotatable relative to said support;
• an actuator housing nonrotationally fixed to said support;
• at least one friction pad axially movable relative to said support for selective engagement with said disc to retard rotational movement of said disc relative to said support;
• a plunger assembly axially movable in said housing, said friction pads mounted to one end of said plunger assembly, said plunger assembly comprising a nut member and a rod member threadably engaged at one end thereof to said nut member and carrying said friction pad at the other end thereof, one of said nut and rod members being rotationally fixed to said housing whereby rotation of the other of the nut and rod member in a given direction of rotation will result in axial movement of said pad relative to said nut member towards said disc and rotation in the other direction of rotation will result in axial movement of said pad relative to said nut member away from said disc;
• a wedge actuator assembly mounted to said housing, said wedge actuator assembly comprising an actuator motor, a push-rod and a roller assembly mounted to said push-rod, said roller assembly engaging the other end of said plunger assembly and effective upon extension from said actuator motor to force said plunger assembly towards said disc;
• a return spring biasing said plunger assembly toward said roller assembly;
• a driving member rotatable in said housing;
• means for rotating said driving member in response to greater than predetermined axial displacement of said plunger assembly;
• an intermediate member rotatable in said housing, said intermediate member coaxial with said driving member, said intermediate member rotatable relative to said driving member;
• a driven member rotatable in said housing, said driven member coaxial with and adjacent said intermediate member, said driven member rotatable relative to said intermediate member;
• a normally engaged positive clutch for rotationally coupling said driven member to the rotatable one of said rod and nut member;
• a one-way clutch for rotationally coupling said driving member to said intermediate member, said one-way clutch effective to transfer torque in the direction of rotation causing rotation of said rotatable one of said nut and rod member in said given direction of rotation, said one-way clutch inoperative to rotate said intermediate member in the direction of rotation causing rotation of the rotatable ones of said nut and rod member in said other direction of rotation against the frictional resistances to such rotation;
• a torque limited coil clutch for rotationally coupling said intermediate member to said driven member, said coil clutch wound to transfer torque from said intermediate member to said driven member in the direction of rotation causing rotation of the rotatable one of said nut and rod member with a torque transfer capacity greater than the torque required to rotate said rotatable one of said nut and rod members when said brake friction pad and disc are not in contact but less than the torque required to rotate said rotatable one of said nut and rod members when said friction pad and disc are in contact;
• and
• means accessible from the exterior of said housing for selectively disengaging said normally engaged positive clutch and for rotating the rotatable one of said nut and rod member.

A disc brake actuation assembly including an automatic single acting clearance sensing slack adjuster for maintaining a predetermined running clearance between the brake friction members and the disc, said assembly including;

• a support;
• a disc rotatable relative to said support;
• an actuator housing nonrotationally fixed to said support;
• at least one friction member axially movable relative to said support for selective engagement with said disc to retard rotational movement of said disc relative to said support;
• a plunger assembly axially movable in said housing, said friction member mounted to one end of said plunger assembly, said plunger assembly comprising a nut member and a rod member threadably engaged at one end thereof to said nut member and carrying said friction member at the other end thereof, said rod member being rotationally fixed to said housing whereby rotation of said nut member in a given direction of rotation will result in axial movement of said friction member relative to said nut member towards said disc and rotation of said nut member in the other direction will result in axial movement of said friction member relative to said nut member away from said disc, said plunger assembly additionally comprising a generally hollow adjuster bushing abutting said nut member at one end thereof and abutting a tappet at the other end thereof, said adjuster bushing rotationally and axially movable relative to said housing;
• a wedge actuator assembly mounted to said housing, said wedge actuator assembly comprising an actuator motor, a push-rod and a roller cage assembly mounted to said push-rod, said roller cage assembly engaging the tappet of the plunger assembly and effective upon extension from said actuator motor to force said plunger assembly towards said disc;
• a driving member rotatable in said housing, said driving member axially movable with said adjuster bushing and rotatable relative thereto;
• means for rotating said driving member in response to greater than predetermined axial displacement of said plunger assembly;
• an intermediate member rotatable in said housing, said intermediate member coaxial with said driving member, said intermediate member rotatable relative to said driving member;
• a driven member rotatable in said housing, said driven member coaxial with and adjacent said intermediate member, said driven member rotatable relative to said intermediate member, said driven member rotatably and axially connected to the adjuster bushing;
• a manual adjustment barrel supported in an inner bore of said adjustment bushing, said manual adjustment barrel axially and rotationally movable relative to said adjustment bushing, one end of said manual adjustment barrel abutting said nut member and the other end of said manual adjustment barrel abutting said tappet;
• the end of said nut abutting said manual adjustment barrel defined by a face carrying a plurality of clutch teeth for axial engagement with axially engageable clutch teeth carried by said manual adjustment barrel and simultaneous engagement with clutch teeth carried by said adjustment bushing;
• a first spring biasing said driven member and adjustment bushing toward said tappet;
• a second spring biasing said nut member toward said tappet and thereby biasing said clutch teeth carried by said nut member into engagement with the clutch teeth carried by said adjustment bushing and the clutch teeth carried by said manual adjuster barrel;
• a one-way clutch for rotationally coupling said driving member to said intermediate member;
• a force limited coil clutch for rotationally transferring torque from said intermediate member to said driven member, the torque transfer capacity of said force limited clutch in the direction which will rotate said nut member in said given direction of rotation being greater than the torque required to rotate said nut member when said brake friction member and said disc are not in contact but less than the torque required to rotate said nut member when said brake friction member and said disc are in contact;
• a fitting provided in said manual adjustment barrel and accessible from the exterior of said housing by a tool for applying an axial and a rotational force to said manual adjustment barrel.

An automatic single acting slack adjuster for a cam actuated expanding shoe drum brake for maintaining a predetermined running clearance between the brake shoe friction pads and the brake drum, said adjuster comprising:

• an actuating lever housing adjustably rotationally fixed to said cam, rotation of said lever housing about an axis effective to operate said brake, said lever housing connectable to a brake operating means;
• a worm gear rotationally received in said lever, said worm gear rotationally fixed to said cam;
• a worm rotatably received in said lever, said worm engaged with said worm gear whereby rotation of said worm in a given direction relative to said lever housing is effective to vary the rotational orientation of said cam relative to said lever housing to reduce the slack in the brake;
• a driving member rotatably received in said housing;
• means for rotating said driving member in response to greater than predetermined angular displacement of said lever housing;
• an intermediate member coaxial with and adjacent said driving member rotatably received in said housing, said intermediate member rotatable relative to said driving member;
• a driven shaft coaxial with and adjacent said intermediate member rotatably received in said housing, said driven shaft rotatable relative to said intermediate member;
• a worm shaft nonrotationally carrying said worm coaxial with and adjacent said driven shaft rotatably received in said housing, said worm shaft coupled to said driven shaft by a normally engaged positive clutch;
• a one-way clutch for rotationally coupling said driving member to said intermediate member;
• a force limited coil clutch for rotationally transferring torque from said intermediate member to said driven member, the torque transfer capacity of said force limited clutch in the direction of rotation which will rotate said worm in said given direction of rotation being greater than the torque required to rotate said worm when said brake shoe friction pads are not in contact with said drum but less than the torque required to rotate said worm when said brake shoe friction pads are in contact with said brake drum;
• and
• means accessible from the exterior of said lever housing for applying a rotational and an axial force to said worm shaft.