GB847679A - Hydraulically actuated friction clutch - Google Patents

Abstract

847,679. Reverse gearing; friction clutches; gearing for stopping and starting machinery. TWIN DISC CLUTCH CO. Nov. 7, 1957, No. 34765/57. Class 80 (2). [Also in Group XXIX] To select and engage forward and reverse multiplate friction clutches 20, 45, Fig. 16, in a countershaft reverse gear for fishing boats, a selector valve spindle 72 is turned one way or the other from the position shown to connect an oil pump 138 and a pipe 144 with one or other of two ports 101, 102 leading to the two clutches, turning the selector valve spindle simultaneously connecting the pipe 144 to a pipe 85 leading through a restriction to a valve piston 95 thereby biased leftwards to the Figure to compress springs 96-97 which then bias a pressure-regulating piston valve 98 to close a port 145 bleeding off the pump pressure through a pipe 84 to a sump. Accordingly the pressure in the pipe 144 and the selected port 101 or 102 gradually builds up as the compression of the springs 96, 97 increases, to give a cushioned clutch engagement. In the preferred embodiment shown, the valve spindle 72, Fig. 6, 9, is formed with a boss containing axial passages 75, 76 in constant communication with an inlet port 74. On turning the selector spindle 72, one of the passages 75, 76 connects the inlet port 74 with the appropriate port 101, 102 leading to the forward and the reverse drive clutches, and the other' axial passage connects the inlet port with a port 82 leading through the pipe 85 to a restriction 92. Pressure in a space 93 at the end of the piston valve 95 gradually builds up as oil seeps through the restriction 92, to compress the springs 96, 97 and bias the pressure-regulating piston valve 98 leftwards, thereby tending to close the venting port 145 leading through the pipe 84 to the gear-box sump. A cushioned engagement of the selected clutch is thereby obtained. On returning the selector valve spindle 72 to its neutral position, a central passage 81 therein connects the port 82 and the pipe 85 to a port 83 and the sump return pipe 84, so that the pressure of the oil in the space 93 unseats a spring-biased one-way ball valve 88. The valve piston 95 is then returned rapidly to the position shown, with consequent sudden reduction of the pressure in the circuit and disengagement of the engaged clutch. A second valve 103, Fig. 16, is included as a by-pass from the pipe 147 between the selector valve 72 and the forward drive clutch 20, operation of this valve by turning a handle 109 anticlockwise opening an outlet port 130. Oil then passes through an inlet port 128 and the valve to a pipe 160 which supplies the oil as lubricant between the discs of the clutch, the simultaneous reduction of the engaging pressure in the pipe 147 allowing the clutch to slip continuously. A reduced speed drive of the fishing boat is thus obtained when trawling &c. The preferred embodiment of the valve described comprises a valve spindle 106, Fig. 12, to which the operating lever 109 is connected. The inlet port 128 supplies oil under pressure to act upon the left-hand face of a pressureregulating valve piston 119 biased against the oil pressure by a spring 120. On movement anticlockwise of the controlled lever 109, the port 130 leading to the forward-drive clutch is uncovered and the spring 120 effects regulation of the pressure of the oil passed therethrough. The valve spindle 106 is formed with a central bore 115 having an end hole 123 and transverse ports 126, 127 connecting the various parts of the valve so that they shall be at the same pressure, and a port 131 in parallel with the outlet port 130 counter-balances the pressures on the two sides of the valve piston. Accordingly the hydrostatic forces acting upon the valve assembly are balanced out, and the control lever 109 can be turned without effort. The countershaft reverse gear to which the control system is applied comprises an input shaft 12, Fig. 1, carrying the forward drive clutch 20, an output shaft 37 and a countershaft 41, Fig. 2, carrying the reverse drive clutch 45. Engagement of the forward drive clutch 20 transmits drive from the input shaft 12 to a gear 35 meshing a gear 36 fast upon the driven shaft 37. Fast with the input shaft 12 is a gear 39 meshing a gear 40 fast on the counter-shaft 41, engagement of the reverse drive clutch 45 then transmitting drive through a gear 58 to the gear 36 and driven shaft 37. The forward drive clutch 20 comprises multiple friction discs engaged when oil under pressure is supplied as described above to ports 150, 152 to move a piston 26 leftwards against the bias of springs 28 surrounding bolts connecting opposite flanges of the clutch. When continuous slipping of the forward drive clutch is required for trawling &c., oil is supplied through the pipe 160 and passages 162, 164 to the inner periphery of the clutch discs.