Patent GB-1065819-A (GB)
Title: Improvements in and relating to clutches
IPC: F16D48/02
Filed: 1964-08-04
Abstract: 1,065,819. Clutch control. SOC. ANON. FRANCAISE DU FERODO. Aug. 4, 1964 [July 30, 1963; July 10, 1964], No. 31257/64. Heading F2L. Automatic take-up of wear in an hydraulic clutch control system is provided by a lostmotion connection. In one form, the clutch 12 of a motor car &c. is disengaged by depression of a pedal 14 energizing a master cylinder 34 connected through a pipe 31 to a slave unit 29, which in turn acts through a thrust bearing 22 upon the clutch. Lost-motion G, which tends to decrease with wear of the clutch, is taken up on initial movement of the pedal 14, the slave unit 29 acting to turn a lever 23 against the bias of a spring 30. Further depression of the pedal 14 takes up lost motion within the hydraulic system, and then disengages the clutch against the bias of springs 13, as well as the bias of the spring 30. The master cylinder includes a piston 35, slidden inwardly against spring bias in a pressure chamber 41, topped up with oil through a pipe 49 and two-way valve (43), Fig. 2 (not shown), from a reservoir 51. The two-way valve (43) is biased to close by springs. Initial depression of the pedal 14, Fig. 1, moves the piston 35 to energize the slave unit 29 and take up the lost motion G in the thrust bearing. The springs of the two-way valve (43) are of such strength that they hold the valve closed during this movement. However, further depression of the pedal 14 against the combined bias of the clutch springs 30, 13 causes the valve (43) to open, so that oil is returned to the reservoir 51, and lost-motion in the hydraulic system is taken up. Ultimately, the piston 35 reaches and passes over a port 42 in the master cylinder through which oil flows to the valve (43) &c., thus shutting off the valve from the pressure chamber. Continued depression of the pedal 14 then actuates the slave unit 29 for clutch disengagement. Thus irrespective of the extent and variation of the lost-motion G, the disengagement of the clutch always occurs at the same position in the pedal travel when the piston closes the port 42. The pedal 14 carries a cam 38 which abuts a roller 37 carried by the rod of the piston 35, and is so sloped as to give a variable ratio transmission of movement to the piston, quick initial movement being followed by a slower follow-up. In one modification, Fig. 6 (not shown), the valve (43) is omitted and the port 42 is connected to an hydraulic accumulator. In another modification, Fig. 8 (not shown), the cam 38 on the pedal arm is dispensed with, and a similar variable ratio effect is achieved by the use of a two-diameter piston in the master cylinder. The larger and smaller parts act together to produce quick take-up of the lost-motion G and the smaller diameter portion then effects clutch disengagement. In further modifications, Figs. 9, 10 (also not shown), a large diameter piston in the master cylinder is initially slidden rapidly to take up the lost-motion G, the oil displaced flowing through a hollow smaller diameter piston until the latter is abutted by the large piston. The two pistons then slide together, the smaller piston energizing the slave unit for clutch disengagement and the larger piston forcing oil through a spring-closed valve to a reservoir. In further modification, Figs. 11, 12, 13 (also not shown), a large diameter piston in the master cylinder is provided at its end with a two-way valve, opened by increasing pressure when the lost-motion G has been taken up to vent liquid to a reservoir. The valve in the piston then abuts the end of a hollow small diameter piston, effectively shutting off the valve from the slave unit 29. The valve is now fully opened, so that continued depression of the pedal 14 moves the larger piston to return liquid directly to a reservoir, while the smaller piston effects disengagement of the clutch. In yet a further modification, Fig. 14 (not shown), a single piston in the master cylinder is provided with an extension which, as the piston moves, shuts off flow of oil to a two-way spring-biased valve. In a similar construction. Fig. 15 (not shown), the piston is provided with a spring-mounted connection which engages a valve in a return circuit.