Automatic adjusters for vehicle brakes

Claim 2

An automatic adjuster for a vehicle brake comprising a housing, a screw-threaded strut assembly movable with respect to said housing between an inoperative retracted position and an advanced operative position to transmit a brake applying force to a friction member from brake applying means, abutment means disposed in one datum position for defining said inoperative retracted position, a first part of said adjuster for engagement with said abutment means when said strut assembly is in said inoperative retracted position, a second part of said adjuster spaced from said first part for moving said abutment means from said one datum position to a second datum position when said strut assembly moves from said inoperative retracted position into said operative advanced position through a distance exceeding the spacing between said second part and said abutment means which spacing defines a desired braking clearance, and adjuster means for increasing automatically the effective length of said strut assembly to compensate for wear of said friction member after said abutment has moved to said second datum position.

Claim 3

An automatic adjuster as claimed in claim 1, wherein said housing is provided with a bore, and a tappet for transmitting a brake applying force to said friction member works in said bore, said tappet being provided with an annular groove extending axially between an inner wall and an outer wall, and said abutment means comprising a ring received in said groove and of an axial length less than the distance between said walls whereby, in said retracted position, said outer wall engages with said ring and a clearance, corresponding to a desired braking clearance, is defined between said ring and said inner wall.

Claim 4

An automatic adjuster as claimed in claim 2, wherein said ring is an interference fit in said bore and said ring is constructed and arranged to be movable with said tappet after said clearance has been taken up and to be held against movement in the opposite direction.

Claim 5

An automatic adjuster as claimed in claim 2, wherein the face of the ring and said outer wall which engages with it in said retracted position are inclined to define a wedge-like engagement adapted to enhance the grip of said ring against said bore in that position.

Claim 6

An automatic adjuster as claimed in claim 1, wherein said housing is provided with a bore and an annular groove in the wall of said bore extending axially between an inner wall and an outer wall, and a tappet for transmitting a brake applying force to said friction member works in said bore, said abutment means comprising a ring which encircles said tappet and which is received in said annular groove, and said groove being of an axial length greater than that of said ring so that, in said retracted position, said inner wall engages with said ring and a clearance, corresponding to a desired braking clearance, is defined between said ring and said outer wall.

Claim 7

An automatic adjuster as claimed in claim 5, wherein said tappet is an interference fit in said ring and said ring is constructed and arranged so that, although said tappet is movable relative to said ring after said clearance has been taken up, said tappet and said ring are held against relative movement in the opposite direction.

Claim 8

An automatic adjuster as claimed in claim 1, wherein said housing is provided with a bore, and a tappet for transmitting a brake applying force to said friction member works in said bore, and wherein said tappet comprises a hollow piston having a closed outer end, a sleeve accomodated within said piston, a thrust assembly, a spring-loaded clutch ring defining a screw-threaded engagement between said sleeve and said thrust assembly and rotatable relative to said thrust assembly when said tappet is arrested by said abutment means, said spring-loaded clutch ring being so constructed and arranged on the next brake application to rotate said sleeve with respect to said tappet to increase the effective length of said strut assembly.

Claim 9

An automatic adjuster as claimed in claim 7, wherein said thrust assembly comprises a single thrust component and said sleeve has a screw-threaded engagement in said piston.

Claim 10

An automatic adjuster as claimed in claim 7, wherein said sleeve is slidably received within said piston and said thrust assembly comprises two components of which one has a screw-threaded engagement with said clutch ring and is slidably received within the other component, the said other component having a screw-threaded engagement in said sleeve.

Claim 11

An automatic adjuster for a vehicle brake comprising a housing member, a screw-threaded strut assembly movable with resPect to said housing member between an inoperative retracted position and an advanced operative position to transmit a brake applying force to a friction element from brake applying means, said housing member being provided with a bore, and a tappet member incorporated in said strut assembly being adapted to work in said bore, and abutment means adapted to be engaged by a part of the adjuster to define said inoperative retracted position, one of said members being provided with a groove extending axially between an inner wall and an outer wall, and said abutment means comprising a ring received in said groove and of an axial length less than the distance between said walls whereby, in said retracted position, said outer wall engages with said ring and a clearance, corresponding to a desired braking clearance, is defined between said ring and said inner wall, and adjuster means for increasing automatically the effective length of said strut assembly to compensate for wear of said friction element when the braking clearance between the friction element and a rotatable braking surface exceeds a predetermined value.

Claim 12

An automatic adjuster for a vehicle brake comprising a housing member, a screw-threaded strut assembly movable with resPect to said housing member between an inoperative retracted position and an advanced operative position to transmit a brake applying force to a friction element from brake applying means, said housing member being provided with a bore, and a tappet member incorporated in said strut assembly being adapted to work in said bore, and abutment means adapted to be engaged by a part of the adjuster to define said inoperative retracted position, one of said members being provided with a groove extending axially between an inner wall and an outer wall, and said abutment means comprising a ring received in said groove and of an axial length less than the distance between said walls whereby, in said retracted position, said outer wall engages with said ring and a clearance, corresponding to a desired braking clearance, is defined between said ring and said inner wall, and adjuster means for increasing automatically the effective length of said strut assembly to compensate for wear of said friction element when the braking clearance between the friction element and a rotatable braking surface exceeds a predetermined value.