Braking system with non-spring parking brake actuator

摘要

A braking system is provided that enables application and release of a parking brake with fluid control and that also maintains application of the brake during a loss of fluid pressure—all without using springs and using only a single fluid control conduit. The brake actuator for the system includes a housing defining service and parking chambers. A pushrod in the parking chamber is configured for movement with a diaphragm in the chamber. The parking brake is applied by introducing fluid on one side of the diaphragm. A clutch surrounds the pushrod and includes a tooth configured to engage corresponding teeth on the pushrod to hold the position of the pushrod even during a loss of fluid pressure. The clutch is rotated under fluid control to move the clutch tooth into and out of alignment with the teeth on the pushrod to hold and release the parking brake.