| 摘要 |
A spring applied, hydraulically released (SAHR) parking and emergency brake system 1) can be manually overridden to permit towing or assisted vehicle transport when charge pump pressure is unavailable for the brakes, and 2) is reset either a) automatically when charge pump pressure becomes available or b) manually. Override is made possible by a manual override assembly that includes a manually-actuated hand pump and an override valve. The override valve is manually actuated to isolate the brake release actuators and the outlet of the hand pump from the system's reservoir and is reset to its open position in response to the presence of hydraulic pressure at a designated location of the braking system. Automatic reset of the override valve preferably is effected by the supply of pressurized fluid to a previously-unpressurized port of the override valve. The hand pump, override valve, and any other brake control valve(s) of the braking system preferably are incorporated into a single control module.
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