Torque limitation device for a drum brake
OwnerLeslie Cyril Chouingsinventor
Life of this patent
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Abstract
A drum brake, primarily for a trailer, which gives normal braking torque in forward direction and low torque in reverse. This is achieved by having a pivoted lever acting between the one ends of two shoes remote from the ends between which the brake actuator is located. The shoes act on the lever at different effective radii and the forces applied by the shoes to the lever hold it in a first position during forward rotation, thus allowing normal braking torque, and a second position during reverse rotation which allows the ends of the shoes acted on by the actuator to move apart thus allowing a limitation of the reverse braking torque by limiting the stroke of the actuator.
Claims8
A drum brake comprising a drum, two shoes mounted within the drum for movement between operative and inoperative positions, spring means biasing the shoes to their inoperative positions, a shoe actuator interposed between adjacent one ends of the two shoes, a shoe abutment and torque limitation means arranged to provide a clearance having a predetermined value when the shoes are in their operative positions and the drum is rotating in one direction and to eliminate or substantially to eliminate said clearance in response to the reactive forces generated by the shoes due to their engagement with the drum when the shoes are in their operative positions and the drum is rotating in the opposite direction thereby producing a lower torque between said drum and said shoes than when said drum is rotating in said one direction so that, when the drum is rotating in said opposite direction, a greater movement apart is required of said one ends of the shoes by said actuator from the positions said ends occupy when the shoes are in their inoperative positions to obtain a given braking torque than is required to obtain said braking torque when the drum is rotating in the one direction and the torque limitation means being arranged so that, with the drum rotating in either of said directions and with the shoes in their operative positions, said reactive force generated by one of the shoes acts to tend to reduce said clearance, the torque limitation means comprising a lever mounted to pivot with respect to a fixed part of the brake and being connected, with the other ends of the shoes, the engagement of the lever with said shoe ends being at different radii about the lever pivot for the two shoe ends, the lever being biased to a rest position which it takes up when the shoes are in their inoperative positions, whereas when the shoes are in their operative positions said reactive forces (1) hold the lever substantially in its rest position when the drum is rotating in said one direction and (2) pivot the lever to eliminate or substantially eliminate the clearance when the drum is rotating in said opposite direction.
Dependencies are inferred from the claim text.