Patent GB-690592-A (GB)
Title: Improvements in power transmission mechanisms
IPC: F16D25/0638
Filed: 1951-02-21
Abstract: 690,592. Clutches. GENERAL MOTORS CORPORATION. Feb. 21, 1951 [March 2, 1950; July 15, 1950], No. 4171/51. Class 80 (ii). [Also in Groups XXVI and XXXIII] In a multiple friction clutch wherein engagement and disengagement is effected by supplying pressure oil alternatively to cylinder chambers on. opposite sides of a piston, means are provided for preventing supply to the engaging chamber below a certain speed, for maintaining the disengaging chamber full during initial engagement so that the centrifugal effects of oil in the two chambers balance and clutch pressure is due solely to the oil supply pressure, for partially draining the disengaging chamber when, the clutch parts are synchronised so that the predominating centrifugal pressure in the en-, gaging chamber increases the clutch pressure, and for draining the disengaging chamber further at full speed so that the clutch pressure is further increased. During the initial engagement stage, cooling oil is supplied between the clutch plates and to the disengaging chamber. The clutch 30, Fig. 3, arranged between an aircraft engine shaft 16 and a drum 87 geared to the propeller, is engaged by supplying pressure oil from an inlet 143 through a tube 114 and ports 121, 122, 123 to the chamber 110 of a cylinder 106 on the left-hand side of a piston 96 fast on shaft 16, the cylinder 106 being slidable on the shaft and forming the presser plate of the clutch, and is disengaged by supplying the pressure oil from an inlet 138 through a tube 113 and ports 117, 118, 119 to the cylinder chamber 111 on the right-hand side of the piston 96. Cooling oil is circulated through the clutch from an inlet 146 through a tube 126 and ports 129, 133, 134, the tube 126 being also connected by a passage 136 to one of the ports 117 and hence to the chamber 111. The latter has a restricted drain opening 169 in its end wall 107 and also has, nearer its periphery, one or more spring-loaded centrifugally-opened relief valves 175. As shown in Fig. 2, the shafts 16 of two gas turbines arranged side-by-side are geared through individual clutches 30 to a central shaft 19 driving oppositely-rotating dual propellers D through epicyclic reducing gearing C. A starter motor 32, driving through a one-way clutch, can be geared to either engine by means of a double dog clutch 34 controlled by solenoids 42, 43. An oil pump 48, driven both from the starter shaft 33 and from shaft 19 through gears and one-way clutches 53, 54, supplies the two spring-loaded coolant control valves 70 through pipes 61 and the two clutch control valves 60 through a pressure-regulating valve 200 and pipes 201. Control mechanism for each clutch comprises a lever 153 operating a reciprocable rod 161 carrying a plate 162 which engages with lost motion between collars on the rod of valve 60, is adapted to engage the end of the valve 70 and co-operates with a spring-loaded abutment 166, the valve 60 being held in either of its two positions by a detent 67. Solenoid controlled latches 159, 160 co-operate with a projection 158 on the lever 153, the circuit of the solenoids including switches 155 and 156, adapted to be closed at predetermined speeds of the shafts 16 and 19 respectively, and a double-pole double-throw switch 165. The arrangement is such that, with the switch 165 closed on the lower contacts, the latch 159 locks the lever 153 in clutch-disengaged position a, in which valve 60 allows supply to chamber 111 and opens chamber 110 to exhaust, until shaft 16 attains a certain speed (say 11,000 r.p.m.), whereupon lever 153 may be moved to position b in which it becomes locked by latch 160. In this position, valve 60 allows supply to chamber 110 and opens chamber 111 to exhaust, the abutment 166 is compressed and valve 70 is opened to supply cooling oil to the clutch and to the chamber 111, which latter therefore remains full so that the clutch engages under a pressure determined solely by the pressure in the supply line 201. When shaft 19 has been brought up to speed, switch 156 closes to release the latch 160 and the lever 153 is moved back by the abutment 166 to position c, in which the valve 60 remains in clutch-engaged position but valve 70 is closed to stop the supply of cooling oil. The chamber 111 now partially drains through the opening 169, thus increasing the clutch pressure. At full speed (say 12,500 r.p.m.), the valves 175 open to drain the chamber 111 further and the final clutch pressure is considerably increased (say twelve times. that due to the oil supply pressure). If it is desired to start one engine from the other or from the propeller, the switch 165 is closed on its upper contacts. One set of clutch plates may be faced on both sides with friction material provided with spiral grooves to provide circulation channels for the cooling oil; or, as shown in Fig 5, each grooved facing 190 may be divided into sections spaced by supply and discharge channels 191, 192 blocked respectively at the outer and inner ends.