Brake Adjusters

Claim 2

In a hydraulic brake actuator which has two components relatively movable apart by the application of hydraulic pressure therebetween, an automatic slack adjuster which comprises an auxiliary stepped piston having first and second external cylindrical surfaces of larger and smaller diameter respectively and having a hollow interior, first and second sealing means slidably sealing one of the actuator components to said first and second cylindrical surfaces such that the hydraulic pressure acts on said one actuator component and said auxiliary piston in opposite directions so that said auxiliary piston is urged towards the other actuator component by the hydraulic pressure, a spring biassing said auxiliary piston away from said other actuator component, an adjuster member associated with said other actuator component, and an adjuster mechanism disposed essentially in said hollow interior of said auxiliary piston and operative between said one actuator component and said adjuster member, said adjuster mechanism being automatically adjustable responsively to relative axial movement between said auxiliary piston and said other actuator component in excess of a desired movement.

Claim 3

An adjuster according to claim 1 in which said spring acts between said auxiliary piston and said one actuator component.

Claim 4

An adjuster according to claim 1 in which said adjuster mechanism includes an encapsulating container member and said auxiliary piston has a bore, said adjuster mechanism being disposed in said bore.

Claim 5

An adjuster according to claim 3 in which said container member is force fit in said bore in said auxiliary piston.

Claim 6

An adjuster according to claim 1 in which said adjuster mechanism comprises a mechanism of adjustable length, operative between said auxiliary piston and said other actuator member and comprising intermediate members having an axis common with the actuator axis, and connections between said auxiliary piston and said intermediate members, one of said connections being a non-reversible screw-thread connection and another of said connections comprising at least one helically inclined surface means providing an axial interengagement.

Claim 7

An adjuster according to claim 5 in which said axial interengagement comprises a reversible screw thread connection.

Claim 8

An adjuster according to claim 5 in which said axial interengagement comprises a reversible face cam.

Claim 9

An adjuster according to claim 3 in which said adjuster member comprises a strut member and in which said adjuster mechanism comprises a nut member having an internal screw thread adapted to mate with an external screw thread on said strut membeR to form a non-reversible screw thread connection, said encapsulating container member surrounding said nut member and said nut and container members having cooperating axial abutment surfaces, an annular member disposed within said container member and encircling said nut member, said annular member and one of said nut and container members having a reversible screw thread connection therebetween, said annular member and the other of said nut and container members having cooperating friction surfaces therebetween, and resilient means disposed within said container member and axially biassing said annular member in a direction to urge said friction surfaces towards one another.

Claim 10

An adjuster according to claim 8 in which said reversible screw thread connection is between said annular and nut members and comprises an internal thread in the former and an external thread on the latter.

Claim 11

An adjuster according to claim 3 in which said adjuster member comprises a strut member and in which said adjuster mechanism comprises a nut member having an internal screw thread adapted to mate with an external screw thread on said strut member to form a non-reversible screw thread connection, said encapsulating containing member surrounding said nut member and said nut and container members having coaxial abutment surfaces, an annular member disposed within said container member, said annular member and one of said nut and container members having a reversible face cam therebetween, said annular member and the other of said nut and container members having cooperating friction surfaces therebetween, and resilient means disposed within said container member and torsionally biassing said annular member in a direction to develop an axial force at said reversible face cam to urge said friction surfaces towards one another.

Claim 12

An adjuster according to claim 10 in which said face cam is between said annular and nut members and the last-mentioned resilient means comprises a torsion spring also operative between said annular and nut members.

Claim 13

An adjuster according to claim 11 which further comprises a one way clutch mechanism operative between the nut and container members.

Claim 14

An adjuster according to claim 12 in which said one way clutch mechanism comprises a ratchet mechanism.

Claim 15

An adjuster according to claim 1 in which said adjuster mechanism comprises a linear ratchet mechanism and means for positively holding said ratchet mechanism in interengagement when the ratchet mechanism is under load.

Claim 16

An adjuster according to claim 14 in which said ratchet mechanism comprises at least one pawl having a free end engageable with a row of ratchet teeth, an inclined surface on said pawl free end and a thrust surface normally engaging said free end of said pawl through said inclined surface to urge said pawl more firmly into engagement with the ratchet teeth.

Claim 17

An adjuster according to claim 15 in which said ratchet mechanism has several pawls in the form of fingers constituted by a longitudinally slit sleeve which encircles the row of ratchet teeth.

Claim 18

An adjuster according to claim 15 in which said thrust surface is on said auxiliary piston.

Claim 19

In a hydraulic brake actuator which has first and second components relatively movable apart by the application of hydraulic pressure therebetween and which has an auxiliary mechanical actuator in said second component, an automatic slack adjuster which is operative between said first component and said auxiliary mechanical actuator and which comprises an auxiliary stepped piston having first and second external cylindrical surfaces of larger and smaller diameter respectively and having a hollow interior, first and second sealing means slidably sealing said first actuator component to said first and second cylindrical surfaces such that the hydraulic pressure acts on said first actuator component and said auxiliary piston in opposite directions so that said auxiliary piston is urged towards said second actuator componeNt by the hydraulic pressure, a spring biassing said auxiliary piston away from said second actuator component, an adjuster member disposed to receive thrust from said auxiliary mechanical actuator, and an adjuster mechanism disposed essentially in said hollow interior of said auxiliary piston and operative between said first actuator component and said adjuster member, said adjuster mechanism being automatically adjustable responsively to relative axial movement between said auxiliary piston and said second actuator component in excess of a desired movement.

Claim 20

In a hydraulic brake actuator which has first and second components relatively movable apart by the application of hydraulic pressure therebetween and which has an auxiliary mechanical actuator in said second component, an automatic slack adjuster which is operative between said first component and said auxiliary mechanical actuator and which comprises an auxiliary stepped piston having first and second external cylindrical surfaces of larger and smaller diameter respectively and having a hollow interior, first and second sealing means slidably sealing said first actuator component to said first and second cylindrical surfaces such that the hydraulic pressure acts on said first actuator component and said auxiliary piston in opposite directions so that said auxiliary piston is urged towards said second actuator componeNt by the hydraulic pressure, a spring biassing said auxiliary piston away from said second actuator component, an adjuster member disposed to receive thrust from said auxiliary mechanical actuator, and an adjuster mechanism disposed essentially in said hollow interior of said auxiliary piston and operative between said first actuator component and said adjuster member, said adjuster mechanism being automatically adjustable responsively to relative axial movement between said auxiliary piston and said second actuator component in excess of a desired movement.

Claim 21

An actuator according to claim 18 in which said auxiliary mechanical actuator comprises a cam journalled in said second actuator component.

Claim 22

An actuator according to claim 19 in which the rotary axis of said cam is perpendicular to the longitudinal axis of the adjuster mechanism.

Claim 23

An actuator according to claim 19 which includes a lever fitted to an end of said cam projecting outwardly of said second actuator component and a retention member attached to said second actuator component and bearing against said lever to resist outward movement of the cam along its axis.

Claim 24

An actuator according to claim 21 in which said retention member is resilient.

Claim 25

A hydraulic actuator according to claim 1 in which said one actuator component comprises an actuator piston.

Claim 26

An actuator according to claim 23 in which said other actuator component comprises a cylinder body having a cylinder bore in which said actuator piston is slidable.