| 摘要 |
A push rod assembly having a first section and a second section through which an input force is transmitted to an output member. The first section includes a cylindrical member with a bellows attached thereto. The cylindrical member has a bore therein. The second section includes a piston that is attached to a brake pedal by a pivot pin. The piston divides the bore in the cylindrical member into a first chamber and a second chamber. The piston has a passage therethrough that connects the first chamber with the second chamber. A valve located in the passage controls the communication of fluid from the first chamber to the second chamber. A linkage member which extends into the bore in the cylindrical member is connected to a plate with a slot therein. The pivot pin associated with the brake pedal extends through the slot to attach the plate to the brake pedal. In the rest position, the plate engages a stop and allows the pivot pin to move in the slot and bring the linkage member into engagement with the valve to allow free communication through the passage in the piston. A switch member, responsive to movement of the brake pedal by an input force, allows a source of vacuum to evacuate air from the bellows to create a pressure differential therein with air in the surrounding environment. The pressure differential causes the bellows to contract and thereby move the cylindrical member at a faster rate than the piston and move the valve away from the linkage to interrupt the fluid communication through the passage. With fluid communication through the passage interrupted, a fluid lock is created in the first chamber. Thereafter, the input force from the brake pedal is transmitted to the cylindrical member from the piston through the fluid in the first chamber.
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