Patent GB-1422595-A (GB)
Title: Hydraulic unit for an anti-locking braking system
IPC: B60T8/36
Filed: 1973-03-08
Abstract: 1422595 Anti-lock braking systems AUTOMOBILES CITROEN 8 March 1973 [9 March 1972] 11366/73 Heading F2F An hydraulic anti-lock vehicle braking system includes a valve 1 operable by a device responsive to the dynamic rotational state of a wheel to disconnect a conduit 12 leading to a driver-controlled source of fluid pressure from a conduit 13 leading to a brake operator 2 and connect conduit 13 to an exhaust conduit 14 in the event of wheel lock; the conduit 14 is connected to a distributer 9 having a slide 10 operable to close the conduit 13 during exhaust of pressure fluid and a conduit 13a containing a flow limiter 17 and a conduit 13b containing a non-return valve 25 are branched from the conduit 13 on either side of the distributer 9; the conduit 14 is further connected to an accumulator 6 and an accumulator 8, the accumulator 6 having a moving member 6a responsive to the pressure prevailing in the brake operator 2 to change the route which exhausting fluid pressure takes during an anti-wheel lock operation. As shown in Fig. 1 the exhaust conduit 14 has a branch 5 extending via distributer 9 and accumulator 6 to a fluid reservoir 3a constituted by a fluid reservoir 3 connected to conduit 14. The distributer 9 which has a piston 11 is also connected to a branch 12a from conduit 12 which also includes a filter 20. The accumulator 8 comprises two chambers 23, 24 interconnected by an aperture 18 in a piston 8a; a conduit 15 leading to reservoir 3 connects with chamber 24 and in the section of conduit 14 between reservoir 3 and accumulator 8 there is a flow-limiter 7. When wheel lock is detected conduits 12, 13 are disconnected and conduits 13, 14 are connected-the brake operator 2 is exhausted via the non-return valve 25 and then via branch 5 or exhaust conduit 14 depending on the position of member 6a in response to pressure prevailing in the operator 2 at the time. However exhausting pressure will act on piston 11 to move slide 10 rightwards to close conduit 13 where it is subsequently maintained by fluid entering distributer 9 via branch 12a. Thus during the remainder of the braking operation braking fluid can only enter the operators via flow-limiter 17. Fluid exhausted via conduit 14 fills the accumulator 8 and if necessary continues through the flow limiter 7. In the embodiment of Fig. 2 the accumulator 8 is housed in the moving member 6a of accumulator 6, and exhausting flow to reservoir 3 can take place via conduit 5 or via flow limiter 7 depending on the pressure in brake operators 2 which pressure is applied to moving member 6a. Conduits 21, 22 connected to valve 1 ensure emptying of the accumulator 8. Figs. 3-8 illustrate an arrangement similar to Fig. 1 where the bores containing members 6a, 8a, 10 are provided in a single body 30 and the slide 1a of valve 1 is housed in a body 40; the bodies 30, 40 are connected by a joint support plate 50 which ensures the hydraulic interconnections between the valve 1 and the members in body 30. Connections 80, 90 are joined to conduits connected to a reservoir. Covers 60, 70 are interchangeable as abutments for member 6a to alter the maximum volume of accumulator 6.