EMERGENCY AND HANDBRAKE CONTROL SYSTEM

摘要

A combined emergency and handbrake system employs a friction brake actuator having a spring motor in addition to a hydraulic service motor. The spring motor is restrained from operation by a second hydraulic motor which is normally maintained at operating pressure. By venting the second motor, the spring motor applies the friction brake. This provides failsafe operation for the emergency system, and a positive handbrake system when the car is parked with a de-energized or uncoupled pressure source. The second fluid motor is normally pressurized by application of fluid pressure to the hydraulic service motor. The handbrake may therefore be released by cycling the service brake. This eliminates a need for a second hydraulic or pneumatic actuator for the emergency and handbrake system and assures the safe operation of the car by operation of the service brake before the parking brake can be released. A mechanical retraction device is also provided for special situations.