Robert Boschgmbh

James E Doolittle

William Eugene Sherman, Ii

Lawrence W Rusk

Kent Allen Woodiwiss

Leon A Bogucki

A parking brake having first and second brake shoes each of which has a first end that engages an anchor post on a backing plate and a second end that engages an adjuster. An actuator that is located adjacent an anchor post engages a first end and an adjuster engages a second end of webs for the first and second brake shoes. A brake cable that is connected to the actuator provides a force for moving the first and second brake shoes into engagement with a drum to effect a brake application. The adjuster is characterized by the adjuster mechanism including a yieldable member for reducing the space between the second end engagement between the webs to limit braking force to a predetermined maximum. A strut of the adjuster compresses at loads above a predetermined set load to thereby reduces the effective braking diameter, input loads and hence output torque.

Drum-in-hat torque limiter

A drum brake having a disc with a peripheral surface with a plurality of radial guides interspersed between a first radial abutment and a second radial abutment. The plurality of radial guides receive a first arcuate channel member on a first brake shoe and a second arcuate channel member on a second brake to align a first reaction surface on the first channel with the first radial abutment and a second reaction surface with the second radial abutment. An actuator provides a force to move the first reaction surface moves away from the first radial abutment and the second reaction surface from the second radial abutment to initiate a brake application. When a leading edge on a first friction member frictionally contacts a braking surface on a drum the first reaction surface continues to move away from the first radial abutment while second reaction surface associated with a trailing edge is moved back into engagement with the second radial abutment to oppose the braking force developed by the frictional engagement. During the frictional engagement, the plurality of radial guides engage the first and second arcuate channels to retain the first and second friction surfaces in perpendicular alignment with the braking surface.

Drum brake

An adjuster mechanism in a drum brake wherein a rotation of a star wheel on a shaft of an extendable strut is limited to a single increment define the pitch of a plurality of teeth on the star wheel. The limitation is achieved by a lever that is carried by a web of a brake shoe has a first blade that in perpendicular alignment with a first tooth of the plurality of teeth while a second blade is offset from a second tooth and located in a plane that is substantially parallel with the pitch. When the lever is pivoted on the web through a predetermined angle, the first blade slides into engagement with a third tooth while the second blade moves through the offset and into engagement with the second tooth to connect the lever with the star wheel. Any further pivoting of the lever by movement of the web toward the drum results in the lever and star wheel moving together. When a brake application terminated, a return spring acts on the lever to bring the first blade into engagement the third tooth while the second blade is moved to the offset position and the star wheel is rotated an increment defined by the pitch of the plurality of teeth such that a running clearance is sustained for the drum brake.

Adjuster mechanism for a drum brake

An adjustment arrangement for a non-servo drum brake having a hydraulic actuator that engages a first web of a first brake shoe and a second web of a second brake shoe. The hydraulic actuator on receiving a hydraulic input develops an actuation force for moving the first and second brake shoes from a rest position into engagement with a rotatable member to effect a brake application. An extendible member, that is connected to the first web and the second web, is extendable to define a running clearance in a rest position between the first and second brake shoes and the rotatable member. A lever arm, that is mounted on the first web, engages the extendable member. A resilient member extends between the lever to the second web to urge the first and second webs into engagement with the hydraulic actuator. The lever arm pivots on the first web as the first web moves through the running clearance during a brake application. When the running clearance reaches a predetermined maximum gap, the lever pivots sufficiently to rotate the extendible member and extend the extendible member to establish a minimum gap for the running clearance. The adjustment arrangement is characterized by the first web having a first engagement surface connected to the hydraulic actuator and a second engagement surface connected to the extendible member. The first engagement surface receiving the actuation force from the hydraulic actuator to move the first brake shoe through the running clearance and into engagement with the rotatable member to effect the brake application. The first web has a cantilever arm through which the first engagement surface is connected to the second engagement surface such that movement of the second engagement surface in response to the actuation force is limited as a function of the resiliency of the cantilever arm.

Brake shoe

A drum brake assembly ( ) having first ( ) and second ( ) brake shoes retained on a backing plate ( ). Each of the first ( ) and second ( ) brake shoes have an end ( ) aligned on a hydraulic actuator assembly ( ) and an end ( ) aligned on an anchor block ( ). An adjustable strut mechanism ( ) has a extendable shaft ( ) that includes a first end member ( ) that engages the first end ( ) of said first brake shoe ( ), a second end member ( ) that engages the first end ( ) of the second brake shoe ( ) and a rotatable stem ( ). A first resilient member ( ) urges the first ( ) and second ( ) brake shoes toward the hydraulic actuator assembly ( ) and second resilient member ( ) urges the first ( ) and second ( ) brake shoes toward the anchor block ( ). The length of the extendable shaft ( ) is adjusted by ratcheting a pawl ( ) rotating the stem ( ) to establish a predetermined running clearance between the first ( ) and second ( ) friction members and drum ( ).

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Granger, IN, United States of America

James E Doolittle