Patent GB-689694-A (GB)
IPC: F16D43/286
Abstract: 689,694. Friction clutches. SELF-CHANGING GEAR CO., Ltd. Feb. 16, 1951 [Feb. 23, 1950], No. 4699/50. Class 80 (ii). Hydraulic pressure for engaging a friction disc clutch 13, 14 is controlled in accordance with the variation in motion of the output shaft 2 to reduce the pressure and hence the slip-torque when the output shaft is either reversed, brought to rest, or decelerated. A mechanically torque-responsive force also opposes the fluidpressure to minimise the effect of changes in the coefficient of friction. The engaging fluid pressure can also be varied manually and its value is indicated on a pressure gauge which reads in terms of transmitted torque. The friction clutch may be bridged by a manually operated positive clutch when required. The clutch transmits drive between an input wheel 9 on a casing 1, and an output shaft 2 carrying, or driving, a winch of a whale-harpooning line, excessive pull in which latter causes clutch slip, permitting the line to pay out. Sudden overload is prevented by the deceleration-responsive inertia control of clutch-engaging fluid-pressure. The clutch-pack 13, 14 is pressed against an axially-fixed back-plate 18 by a two-part piston 33 acting leftwards through a ball thrust-bearing 19 on an axially-movable front presser-plate 17, in opposition to a rightward force produced by the drive-torque in its passage from the input casing 1, through adjustable inclined struts 26 and spring-loaded pins 24, to the outer drum 16 of the clutch-pack, which drum 16 abuts against the presser-plate 17 and thus provides the torque-responsive opposing pressure, in accordance with the inclination of the struts 26. Such inclination is restricted by the pins 24 engaging circumferential slots 31 in the casing 1. The two-part piston 33 comprises a main inner area between seal-rings 34, 38 and an auxiliary outer area between seal-rings 37, 38, the main inner area 34, 38 being supplied with oil-pressure by an input-driven gear-pump 47, driven by a wheel 49 on the input casing 1, whilst the auxiliary outer area 37, 38 is supplied by an output-driven gear-pump 50, driven by a wheel 52 fast on the output shaft 2, both pumps being carried by a fixed sleeve 40 and both effective in the absence of slip (see below). The input pump 47 is effective in both directions of rotation, the output 50 only in the forward direction, so that if the output shaft 2 slips to a standstill or reverses, the output-pump pressure on the auxiliary piston area 37, 38 vanishes, thus reducing the clutch-loading pressure. Pressure reaches the respective piston-areas through a central control valve 56, which in the position shown permits pressure from the input pump 47 to reach the main piston-area 34, 38 through passages 68, 69, 72. 55, 57 and 58; and pressure from the output pump 50 to reach the auxiliary piston-area 37, 38 through passages 74, 75, 78, 79 and 81. Input pressure from the passage 55 also passes through a groove (not shown) in a valve-collar 62 to a space 61 at the left end of the valve 56, thus tending to move it to the right for its collar 62 to uncover an exhaust passage 63, leading to the casing from the space 61, so that exhausted oil cools and lubricates the clutch. This rightward exhausting movement is resisted by pressure applied leftwards on the valve by a manual lever (Fig. 7, not shown), acting on the end of a sleeve 65, loading the valve 56 leftwards through a ball thrustbearing 67 and spring. The leftward engaging force applied to the manual lever thus meters the exhaust passage 63 and so determines the degree of clutch-engaging pressure on the main piston-area 34, 38, and release of the leverpressure permits clutch disengagement, by exhausting the main piston-area 34, 38 as above, the auxiliary piston-area 37, 38 also exhausting through a non-return valve 103 and passages 58, 57. With this arrangement, the transmitted torque is proportional to the engaging fluid pressure and may be indicated on a pressuregauge, which may be graduated to indicate directly the pull on the winch-line. The valve 56 is also splined to a sleeve 87 secured to a flywheel 88, drivingly connected through tangential springs 91 (see also Fig. 6, not shown) with the output shaft 2. Sudden deceleration of the output shaft 2 thus causes the flywheel 88 to turn relatively forwards against its springs 91, turning the valve 56 in the shaft 2 and aligning an axial groove 83 (dotted) in the valve 56 with a radial passage 82 (dotted) in the shaft 2, thus exhausting the auxiliary piston-area 37, 38 through passages 84, 85 leading to the casing. Both pumps 47, 50 are housed below the shaft 2 in a sump (being shown above only diagrammatically). The input casing 1 may be positively connected to the output shaft 2 by releasing screws 114, permitting a spring-loaded dog 108, splined in the casing 1 to engage teeth 1.11 on the output shaft 2. Specification 652,560 is referred to. The Provisional Specification states also that the output pump may be driven from both input and output shafts through a compound planetary gear, in which case the pump functions in both directions of rotation. The input pump also feeds the auxiliary piston area, this feed being effected during run-out of the winchline at half-pressure through a reducing-valve, allowing a large oil surplus to exhaust for cooling and lubricating the slip. During run-in of the winch-line the reversal of the output pump disables the reducing-valve and full pressure is supplied to the auxiliary area. Either acceleration or deceleration may cause either increase or decrease of the clutch engaging pressure. The clutch casing is fanned for cooling.