Brake actuator with automatic adjustment

A brake actuator with an automatic slack adjuster incorporating a screw and nut actuator mechanism whose elongation is controlled by the combination of a control device having a screw and nut with reversible pitch and a unidirectional clutch sensitive to relative axial displacement between a control piston and a fixed body housing said control piston, characterized in that said unidirectional clutch effects rotational operation of said automatic slack adjuster and incorporates an automatic deivce for momentarily disengaging the automatic slack adjuster when rotational torque of said screw and nut actuator mechanism exceeds a predetermined value, said automatic device for disengaging the automatic slack adjuster including two surfaces facing each other and normally pushed against one another in frictional engagement, one of the surfaces being fixed firmly to the body and the other surface being fixed firmly to said unidirectional clutch, at least one spring pushing said two surfaces into engagement against one another to effect the frictional engagement which defines said predetermined value beyond which the two surfaces are capable of rotational movement relative to one another, and the brake actuator including a reset device for resetting to zero the screw and nut actuator mechanism, the reset device effecting rotation of the nut of the screw and nut actuator mechanism and against frictional resistance defined by frictional engagement of the two surfaces.

A brake actuator with an automatic slack adjuster incorporating a screw and nut actuator mechanism whose elongation is controlled by the combination of a control device having a screw and nut with reversible pitch and a unidirectional clutch sensitive to relative axial displacement between a control piston and a fixed body housing said control piston, characterized in that said unidirectional clutch effects rotational operation of said automatic slack adjuster and incorporates an automatic device for momentarily disengaging the automatic slack adjuster when rotational torque of said screw and nut actuator mechanism exceeds a predetermined value, said automatic device for disengaging the automatic slack adjuster including two surfaces facing each other and normally pushed agianst one another in frictional engagement, one of the surfaces being fixed firmly to the body and the other surface being fixed firmly to said unidirectional clutch, at least one spring pushing said two surfaces into engagement against one another to effect the frictional engagement which defines said predetermined value beyond which the two surfaces are capable of rotational movement relative to one another, said spring being a first compression spring pushing a component of the unidirectional clutch, the component carrying said other surface, the unidirectional clutch including ramp surfaces for jamming rollers and formed on a part of the control device, and springs pushing the rollers into jamming engagement between said ramps and a cylindrical portion firmly fixed to said component of the unidirectional clutch.