Abstract: A brake cooling circuit which includes a pump for circulating cooling fluid to the brakes in a scraper portion of a tractor scraper combination is driven by a motor powered by hydraulic fluid communicated through conduits leading to one of the implements of the scraper. Selective actuation of the brake cooling circuit may be accomplished manually by the operator. Automatic actuation of the brake cooling circuit is also provided upon a signal of a high temperature condition in the brakes. The vehicle hydraulic circuit is designed to override the cooling circuit upon actuation of the implement by the operator. Upon completion of the work cycle of the implement, the cooling circuit is reactuated. The cooling circuit is comprised of the motor driving the pump and the fan, a radiator, conduits for communicating cooling fluid through the radiator and to the brakes, a control assembly, and a separate source of cooling fluid.

Abstract: A brake pressure modulating control valve for a hydraulically operated brake system. The control valve includes a spool associated with an air spring chamber. The system includes equipment for modulating the air pressure in the air chamber for constantly and concurrently modulating the pressure of the hydraulic fluid in the brake system.