Patent GB-1490808-A (GB)
Title: Brake-force regulator in or for a dual-circuit brake system
IPC: B60T8/26
Filed: 1975-12-04
Abstract: 1490808 Braking force regulator ALFRED TEVES GmbH 4 Dec 1975 [11 Dec 1974] 49821/75 Heading F2F A brake force regulator for a dual circuit vehicle braking system comprises a first stepped piston 3 operable to close a fluid connection in one brake circuit between a brake pressure source and at least one wheel cylinder, the piston 3 being subjected to the pressure from the source and to a pressure in a chamber 32 dependent on a control force 7 (viz the biasing force of a spring or an axle-load dependent force) in an opening direction and to the pressure supplied to the wheel cylinder(s) in the closing direction, a second axially displaceable stepped piston 4 operable to close a fluid connection in the second brake circuit between a further pressure source and least one further wheel cylinder, the piston 4 being subjected to opposing forces as the first piston 3. The pistons 3, 4, 6 are coaxially arranged with piston 3 extending into a bore 5 in piston 4. The pistons 3, 4 are respectively formed with valve edges 13, 23 for engagement with respective sealingly slidable sealing members 14, 24 to close the aforesaid fluid connections. The pressure source of the first circuit is connected via an inlet port 12 to a control chamber 19 and the wheel cylinder(s) of the first circuit is connected via an outlet port 11 to a regulator chamber 18, the pressure source of the second circuit is connected via an inlet port 22 to a control chamber 29 and the wheel cylinder(s) of the second circuit is connected via an outlet port 21 to a regulator chamber 28. A channel 31 leads from regulator chamber 28 to a control chamber 32, and a closing member 33 is provided in channel 31, which closing member 33 has a tappet 36 for engagement with the control piston 6 when the regulator is in its inoperative position. Control chamber 32 is vented through an opening 37. In its normal position(as shown) when braking starts the connection between chambers 19, 18 and chambers 29, 28 allows fluid flow to the respective wheel cylinder(s) and fluid also flows from chamber 28 into control chamber 32. As soon as a pre-determined charging pressure is reached in control chamber 32, which pressure depends on the cross-sectional area of piston 6 and the control force acting on piston 6, the piston 6 will move rightwards to cause closing member 33 to close the connection between chambers 28, 32. The pressure forces acting in chambers 32, 19, 18 determine the switching point at which pressure regulation by piston 3 begins (by the cooperation of edge 13 and member 14), the pressure regulation acting so that the pressure in chamber 18 is in a predetermined ratio to the pressure in chamber 19. The pressure forces in chambers 32, 29, 28 control pressure regulation by piston 4. Sealing members 14, 24 act as one-way valves to allow release of excess pressure in chambers 18, 28. If either circuit fails pressure regulation in the other circuit does not begin until a higher than normal switching point since in this case the control piston 6 abuts the piston of the stilloperable circuit so that the full control force acts in a direction to keep the circuit open. Different control characteristics for the circuits may be obtained by altering the ratio of the surfaces of pistons 3, 4, 6.