GB1095606A - Fluid flow control valves - Google Patents

Abstract

1,095,606. Valves; fluid pressure brakes. WAGNER ELECTRIC CORPORATION. July 1, 1966 [Sept. 28, 1965], No. 29647/66. Headings F2F and F2V. A valve for providing a differential braking effect on the front and rear wheels of a road vehicle comprises, a port 25 connected to the master cylinder and the front brake cylinders, a port 26 connected to the rear brake cylinders, a differential piston 29 urged to the position shown by opposed springs 35, 36, and a differential piston 45 slidable in piston 29 and urged by springs 52 to the position shown where a valve head 48, 51 integral therewith is spaced from a seat 39 on piston 29. During initial displacement of the brake pedal fluid passes from port 25 to port 26 via ports 42, 54 and the interior of piston 29. The increasing pressure acts on areas A 3 , A 4 of piston 29 to move the latter to the left against spring 36 and out of contact with spring 35. When the fluid pressure reaches a first predetermined value, it acts on areas A 1 , A 2 of piston 45 to move the latter to the right to seat valve head 48, 51, thereby disconnecting ports 25, 26. Up to this point the front and rear braking pressures are equal but further depression of the brake pedal to increase the fluid pressure at port 25, and thus at the front brake cylinders, to a second, higher predetermined level causes both pistons 29 and 45 to move to the right to increase the pressure supplied to the rear brake cylinders. During this latter stage, the differential areas A 3 , A 4 and the spring 36 cause the rear brake pressure to increase non- linearly with respect to, and at a lower rate than the front brake pressure. The said second predetermined pressure is reached when the spring 36 is in a relaxed state and if the pressure at port 25 is raised above this level the pressure at 26 will be increased proportionally in the ratio of the areas A 3 , A 4 . In the alternative embodiment of Fig. 4 (not shown), spring 36 is replaced by two springs (102, 104) which act in opposition on a flanged sleeve (106) slidable on piston (29) and engageable with shoulder (23) of the housing.