| 摘要 |
1,156,078. Vehicle braking cylinders. ALFRED TEVES G.m.b.H. 13 Nov., 1967 [16, Nov., 1966], No. 51506/67. Heading F2F. An actuating cylinder for a dual-circuit braking system has a stepped piston 1 (Fig. 1) with a second pot-shaped piston 2 sliding on the stem of the first, the two pistons having the same external diameter, one pressure line 6 being connected between the second piston 2 and the casing 7, and the other pressure line 5 being connected via a double-acting valve 4 to the space between the two pistons. If the first line 6 fails, the piston 2 will be forced against the casing and the pressure in line 5 will move the inner valve member 17 to the right to close a bore 9 (Fig. 2). The whole valve member 11 then moves to the right against a spring 16a unseating the edge 11a so that fluid passes through longitudinal grooves 10 into the chamber 3 (Fig. 1) to displace the piston 1 to the left and apply the brakes. On release, fluid from chamber 3 returns partly by the same path and partly via longitudinal grooves 15 in the inner valve member 17 and in the valve stem 14. If there is no pressure in line 5, movement of piston 2 displaces the inner valve member 17 to the left against a spring 16 until it seats at 12. The chamber 3 is now sealed and both pistons move together. If the pressure in line 5 fails after application, the pressure in chamber 3 seats the inner valve member 17 as before. On release, the pressure in chamber 3 is relieved and the inner valve member 17 is unseated by the spring 16. The brake reservoir preferably contains an indicating device to show when the liquid level or pressure has fallen below a particular value. Modifications.-The spring 16 may be located at the end of the valve stem 4 (see 20 in Fig. 1). The inner valve member 17 may be without the longitudinal grooves 15, in which case pressure relief in chamber 3 occurs by displacement of this member towards the seal 12. The valve stem 14 may be a clearance fit instead of having longitudinal grooves. |
