Patent GB-1158999-A (GB)
Title: Improvements in Dynamic Pressure Converter, Especially Applicable to the Braking System of an Automobile Vehicle.
IPC: B60T11/10
Filed: 1967-01-06
Abstract: 1,158,999. Hydraulic brakes; valves; springs. SOC. ANON. FRANCAISE DU FERODO. 6 Jan., 1967 [7 Jan., 1966; 9 Aug., 1966], No. 890/67. Headings F2F, F2S and F2V. In a dynamic pressure-converter, particularly for hydraulic braking systems of motor vehicles, a hollow body 20 is provided with at least two bores within which slide a piston 37 and a rod 40, the piston-rod being subjected to a variable axial force dependent upon the loading on the motor vehicle, and the piston 37 being provided with a control communication in the form of a ball valve which controls the flow of fluid under pressure from a source via connection 19 to the outlet connection 119 leading to the rear wheel brakes 23, 24 of a vehicle. In operation, fluid is supplied from a pedal-operated master cylinder 10 directly to the front wheel brakes 17, 18 of the vehicle and via connection 19 pressure converter 20 and the connection 119 to the rear wheel brakes 23 and 24 of a vehicle. Depending on the loading of the vehicle a blade spring 60 secured at one end 61 to the rear axial 62 of the vehicle and at its other end to the connecting rod 56 of the pressure converter causes the piston 37 and the piston-rod 40 of the converter to take up positions described below which govern the supply of fluid under pressure to the rear wheel brakes of the vehicle. When the vehicle is empty and stationary a force is applied in the direction of the arrow 76 (Fig. 2) so that feet 53 of the piston 36 come into contact against the bottom 52 of the bore 33 of the body of the pressure converter and a ball valve 73 is held open by means of a spigot member 75. This permits fluid to be supplied to the rear wheel brakes of the vehicle without restriction via the open ball valve and connection 119. As the pressure in the chamber 70 is applied over a larger section S1 than the pressure applied to the opposite end of the piston in the chamber 71 the piston tends to move towards the right as shown in Fig. 2 to close the communication between the chambers 71 and 70 via the ball valve 73. As the pressure in the chamber 71 increases a ring member 41, interposed between the piston-rod 40 and a bore 34 in the body 31, bears against a calibration spring 50 so that the force of a calibration spring 50 is overcome and the ring member 41 is displaced to the right to abut the shoulder 48 of the piston. This phase of the operation determines a new rate of increase of pressure in the chambers 70 and 71 less than the previous pressure ratio; should the vehicle run in a more loaded condition the blade spring takes up the position shown in chain dotted lines by condition Y and when the axle 62 is completely freed from load the blade spring 60 takes up the dotted line position Z shown in Fig. 1 to alter the pressure ratio in accordance with the load on the vehicle. The blade spring 60 may be reinforced by an elastic backing blade 63. An alternative embodiment is disclosed in Fig. 4 wherein the blade spring 60 is replaced by a multi-spring arrangement housed in a cylindrical casing 200 pivoted at its lower end with an adjustable connection to the chassis of the vehicle 32. A rod 215 is coupled to a guide member 216 operating in the casing 200 and relative loading on the vehicle causes adjustment of a bell crank lever 219 to adjust the pressure converter 31 similar to that disclosed in Fig. 2. Also described in the Specification (Fig. 6, not shown) is a pressure converter suitable for use in vehicles provided with hydraulic suspension.