Patent GB-1142199-A (GB)
Title: Improvements in or relating to hydraulic brake control valves
Inventor: HARRIES DAVID ANTHONY
IPC: B60T8/26
Filed: 1965-10-25
Abstract: 1,142,199. Hydraulic braking systems; valves. GIRLING Ltd. 25 Oct., 1966 [25 Oct., 1965; 23 Feb., 1966], Nos. 45086/65 and 7938/66. Headings F2F and F2V. A valve adapted to be inserted in an hydraulic line between a master cylinder and rear wheel brake cylinders of an hydraulic braking system comprises a piston which is normally by-passed by a passage in a member fixed with respect to the valve housing and which is closable by a valve when a predetermined master cylinder pressure is exceeded through the operation of a plunger or second piston responsive to this pressure to overcome spring means or/and means responsive to vehicle load, the piston being movable by further increase in master cylinder pressure against spring means such that pressure rises in the rear wheel brake cylinders at a slower rate, the movement of the piston being limited by a stop to limit maximum wheel cylinder pressure. In the embodiment of Fig. 1, the piston 17 is annular and slides on a sleeve 16 integral with a fixed insert 14 which is bored to provide the by-pass passage and a valve seat 13. A ball valve 12 located by a guide 11 loaded by a spring 9 is normally held away from the valve seat by a rod 24 secured to a plunger 23 which is subjected to master cylinder pressure at inlet 2 so that the plunger moves to allow closure of the valve when the predetermined pressure is reached, blocking flow to outlet 3. Holes (not shown) bored axially through the insert 14, allow the rising master cylinder pressure to continue to act on the right face of piston 17, however, so that the latter moves in opposition to Belleville washers 20 to cause the outlet pressure to increase at a slower rate, until the abutment of castellations on the piston 17 with castellated portions of a block 19 limit this further pressure increase. The guide 11 slides in a bore in a plug 6 but, alternatively (Fig. 2, not shown) the guide may be mounted within the bore in insert 14. In a modification, Fig. 3, the piston 17 is stepped and inlet pressure is arranged initially to act on the total piston area and, after closure of the valve 12, on the step 17A only. Fig. 3 also shows in addition to the Belleville washers 20 a rubber spring one end of which is acted on by an extension 22 of the plunger and the other by  one end of a lever pivoted to a bracket 32, the other end of the lever being connected with the axle of the vehicle to respond to varying load. In the embodiment of Fig. 4, the by-pass passage is partly in plug 6 and partly in the housing itself, as shown at 43, the plunger 23 being in the form of a second piston which is integral with valve 12 and a stem 12A, the valve closing in the opposite direction to the direction of flow of the fluid. A separate plunger 52 in conjunction with a spring 49 is provided for applying a control force to the piston 23 in proportion to vehicle load so that the predetermined pressure at which the valve closes is varied in accordance with the load. In a further embodiment (Fig. 5, not shown) the valve (12) is arranged as in Fig. 4 but the by-pass passage is through an axial bore in the piston (17) which has a step (17A) as in the Fig. 3 embodiment which is the sole area acted on by the fluid after the valve has closed.