GB1291089A - Pressure proportioning valve for hydraulic brake systems - Google Patents

Abstract

1291089 Dual hydraulic braking systems; valves KELSEY-HAYES CO 12 Nov 1969 [10 Dec 1968] 55461/69 Headings F2F and F2V In a dual hydraulic braking system having front and rear wheel cylinders 28, 34 separately pressurized by a master cylinder 20, a pressure proportioning valve 10 in the line between the master cylinder 20 and the rear wheel cylinders 34 regulating the pressure to the rear cylinders minimizes the reduction in fluid pressure to the latter when the front brakes fail. Hydraulic fluid passes to the front brake cylinders 28 by way of conduit 26 which has a branch 24 leading to a port 16 of the valve 10, pressure acting through this port on the cylindrical extension 78 of a piston 54 having a flange 62 acted upon by fluid pressure from the master cylinder by way of conduit 18 and port 14, a stepped portion 76 of the piston controlling with a valve seat 68 the flow of fluid to the rear brakes via port 30. At a predetermined pressure in conduit 24 piston 54 moves leftwardly to engage seat 68 thereby reducing the pressure to the rear cylinders. If the pressure to the front brake cylinders fails the seat 68 and portion 76 disengage to pass hydraulic fluid to the rear wheel cylinders. In a further embodiment, Fig. 2 (not shown), in which the delivery of pressure to the front brakes is delayed the valve has a further port (100) connected to the front brakes which communicate with the master cylinder through this port and a port (94) controlled by valve piston (112) having an elastomeric valve head, the piston moving leftwardly under fluid pressure to connect the master cylinder and front brakes only when the pressure exceeds a predetermined value.