Single point actuated self-adjusting brake mechanism in a vehicle driven

Abstract

A cross-drive transmission has a hydraulic brake apply system and a mechanical brake apply system actuated through the same rotary input shaft of the vehicle operator. Rotation of the input shaft rotates a cam which controls a brake control valve which causes a regulated brake apply pressure to be delivered to the hydraulic portion of the brake system for service brake actuation. The cam is moved angularly through a desired angular range which will normally deliver the maximum hydraulic pressure used to actuate the brakes. After the angle is achieved, further rotation of the input shaft causes the cam to enter a dwell phase which permits additional stroke of the mechanical brake apply system if required. This may be required at times because of inadequate hydraulic pressure available from a suitable hydraulic pressure source or the inability of the hydraulic brake apply system to achieve the required braking effort. The mechanical system is driven through a differential gear assembly with differential output members acting to drive the brake pack actuators. One-way clutch mechanisms allow the differential output members to move without limitation in the brake applying direction but limit the return stroke of them, and therefore the return stroke of the ball ramp cam apply rings and the brake torque arms actuating them so as to establish brake adjustment.