Hydraulic actuator assemblies for vehicle brakes

A brake of the spreading type comprising a housing having spaced opposed radial surfaces, friction discs provided with friction linings, pressure plates equipped with lugs located between said discs, stationary pilots to centre said pressure plates, co-operating oppositely inclined recesses being provided in adjacent faces of said pressure plates, end faces of said recesses defining ramps and balls located in said recesses, said friction linings are brought into engagement with said radial surfaces by means of said pressure plates being adapted to move angularly in opposite directions which causes them to move axially away from each other due to the tendency for said balls to ride up said ramps in said recesses, angular movement of said pressure plates in opposite directions being initiated by an actuator assembly acting between said lugs on said pressure plates, said actuator assembly comprising a housing having a bore, a piston working in said bore and movable between a retracted position and an advanced brake-applying position, means for applying hydraulic brake-applying pressure to said piston in said bore to generate a brake-applying force, an adjuster assembly for determining said retracted position of said piston and braking clearances, and a strut through which said adjuster assembly acts on said piston, wherein said adjuster assembly comprises a first clamp member movable with said piston, an adjuster member, a first part on said first clamp member, and a second part on said adjuster member, said first and second parts being movable into engagement with each other to form a releasable detent, a resilient means acting between said piston and said clamp member normally to bias said first part and said second part into said engagement, a first inclined face on said piston, a second inclined face on said clamp member complementary to said first inclined face and engageable therewith, said inclined faces being so constructed and arranged that axial movement of said clamp member with respect to said piston in an outward brake-applying direction in response to said hydraulic brake-applying pressure in said bore enhances said engagement of first and second parts, a stop provided in said bore and with which said adjuster member is adapted to co-operate when movement of said adjuster member in a brake-applying direction exceeds a distance sufficient to take up said braking clearances, and a spring loading said stop, additional movement of said clamp member in the said brake-applying direction causing said clamp member to move axially with respect to said adjuster member to increase the effective length of said strut and define an adjusted retracted position for said piston with said detent released against said bias of said resilient means until the said force of said engagement of said interengaging parts at a predetermined point exceeds the force of said spring-loaded stop, whereby to re-engage said detent and prevent further relative axial movement between said adjuster member and said clamp member whereafter further movement of said strut with said piston is accommodated by movement of said stop against said loading in said spring, said adjusted retracted position defining a position to which said piston can retract when said brake pressure is relieved and which determines said braking clearances, no relative movement between said clamp member and said adjuster member taking place when said brake pressure is so relieved.

An internal shoe-drum brake for a vehicle wherein arcuate shoes carry friction linings for engagement with a rotatable drum, said arcuate shoes are mounted on a backing plate, and said shoes are adapted to be separated at adjacent ends to apply said brake by means of an hydraulic actuator assembly comprising a housing having a bore, a piston working in said bore and movable between a retracted position and an advanced brake-applying position, means for applying hydraulic brake-applying pressure to said piston in said bore to generate a brake-applying force, an adjuster assembly for determining said retracted position of said piston and braking clearances, and a strut through which said adjuster assembly acts on said piston, wherein said adjuster assembly comprises a first clamp member movable with said piston, an adjuster member, a first part on said first clamp member, and a second part on said adjuster member, said first and second parts being movable into engagement with each other to form a releasable detent, a resilient means acting between said piston and said clamp member normally to bias said first part and said second part into said engagement, a first inclined face on said piston, a second inclined face on said clamp member complementary to said first inclined face and engageable therewith, said inclined faces being so constructed and arranged that axial movement of said clamp member with respect to said piston in an outward brake-applying direction in response to said hydraulic brake-applying pressure in said bore enhances said engagement of first and second parts, a stop provided in said bore and with which said adjuster member is adapted to co-operate when movement of said adjuster member in a brake-applying direction exceeds a distance sufficient to take up said braking clearances, and a spring loading said stop, additional movement of said clamp member in the said brake-applying direction causing said clamp member to move axially with respect to said adjuster member to increase the effective length of said strut and define an adjusted retracted position for said piston with said detent released against said bias of said resilient means until the said force of said engagement of said interengaging parts at a predetermined point exceeds the force of said spring-loaded stop, whereby to re-engage said detent and prevent further relative axial movement between said adjuster member and said clamp member whereafter further movement of said strut with said piston is accommodated by movement of said stop against said loading in said spring, said adjusted retracted position defining a position to which said piston can retract when said brake pressure is relieved and which determines said braking clearances, no relative movement between said clamp member and said adjuster member taking place when said brake pressure is so relieved.

A disc brake for a vehicle wherein friction pads for engagement with opposite faces at a rotatable disc are located in a caliper which straddles said disc and at least one of said friction pads is applied directly to said disc by means of an hydraulic actuator assembly comprising a housing having a bore, a piston working in said bore and movable between a retracted position and an advanced brake-applying position, means for applying hydraulic brake-applying pressure to said piston in said bore to generate a brake-applying force, an adjuster assembly for determining said retracted position of said piston and braking clearances, and a strut through which said adjuster assembly acts on said piston, wherein said adjuster assembly comprises a first clamp member movable with said piston, an adjuster member, a first part on said first clamp member, and a second part on said adjuster member, said first and second parts being movable into engagement with each other to form a releasable detent, a resilient means acting between said piston and said clamp member normally to bias said first part and said second part into said engagement, a first inclined face on said piston, a second inclined face on said clamp member complementary to said first inclined face and engageable therewith, said inclined faces being so constructed and arranged that axial movement of said clamp member with respect to said piston in an outward brake-applying direction in response to said hydraulic brake-applying pressure in said bore enhances said engagement of first and second parts, a stop provided in said bore and with which said adjuster member is adapted to co-operate when movement of said adjuster member in a brake-applying direction exceeds a distance sufficient to take up said braking clearances, and a spring loading said stop, additional movement of said clamp member in the said brake-applying direction causing said clamp member to move axially with respect to said adjuster member to increase the effective length of said strut and define an adjusted retracted position for said piston with said detent released against said bias of said resilient means until the said force of said engagement of said interengaging parts at a predetermined point exceeds the force of said spring-loaded stop, whereby to re-engage said detent and prevent further relative axial movement between said adjuster member and said clamp member whereafter further movement of said strut with said piston is accommodated by movement of said stop against said loading in said spring, said adjusted retracted position defining a position to which said piston can retract when said brake pressure is relieved and which determines said braking clearances, no relative movement between said clamp member and said adjuster member taking place when said brake pressure is so relieved.