| 摘要 |
1,152,055. Brake master cylinders. FORD MOTOR CO. Ltd. 4 Nov., 1966 [20 Dec., 1965], No. 49445/66. Heading F2F. A brake master cylinder, having separate chambers 50, 86 for supplying independently front and rear braking circuits 102, 108, comprises a single piston 26, having an annular area acting on the fluid in chamber 50 and the remaining area acting on the fluid in chamber 86, and a balancing piston 65 arranged in a blind bore 60 in the piston, the inner end of which communicates with the chamber 50 via passages 62 so that pressures in the two chambers act on opposite sides of the balancing piston, there being a trapped spring 74 so arranged that it normally centralizes the balancing piston in the position shown but, should a failure occur in the circuit 108, is arranged to be compressed and allow the balancing piston to move to the end of the blind bore where a conical end face of the balancing piston engages a conical face of the blind bore, the conical face being designed to produce a wedging action to retain the balancing position at the end of the blind bore during subsequent strokes of the piston 26, whereby pedal travel is restored to normal. Should failure occur in the circuit 102, a stem 68 of the piston 65, around which the spring 74 is coiled, is projected by movement of the balancing piston beyond the end of the master piston 26 and so contacts end cap 24 before the end of the master piston stroke. As a result, the loss of fluid in the circuit 108 during movement of the piston 65 is made up towards the end of the stroke of the master piston, since the piston 65 is pushed back into the bore 60, whereby pedal travel is not substantially increased. In order that spring 74 may act to resist movement of piston 65 both ways from its central position, the spring is trapped between a washer 72 held on the stem 68 and a cup member 78 which has an out-turned flange 82 engageable with a shoulder between an enlarged diameter portion 80 and the remainder of the blind bore 60. The cylinder housing 10 is formed with separate reservoirs 12, 14 sealed by a flexible diaphragm 16 and cover-plate 18, and communicating by way of usual ports 52, 54, associated with a trapped seal 44, with the chamber 50 and by way of a tilting valve assembly 88 with the chamber 86, respectively. A seal 58 isolates the chambers from one another. |
