GB612652A - Improvements in or relating to automatic clutch mechanisms - Google Patents

Abstract

612,652. Gearing for stopping and starting machinery. READ, J. R. May 28, 1946, No. 16250. [Class 80 (ii)] [Also in Group XXXIII] In gearing for stopping and starting machinery, particularly applicable to the driving of a single airscrew from two gas turbines, an intermediate member 20 is driven by the driving member 10 through a lost-motion connection 22 and is clutchable through a main driving clutch 24 to the driven member 26, synchronizing means 34, 35 bias the member 20 to rotate with the driven member 26 and relative movement of the driving and intermediate members causes, through a main power device 17, engagement of the main clutch 24 when the intermediate member lags, and disengagement when the intermediate member leads, the driving shaft. The driving shaft 10 is hollow and comprises the cylinders 14, 15 for the main power-device piston 17 and the cylinder 16 for the piston of the auxiliary power-device 18, and has journalled on its outer surface the intermediate member 20 which is splined to drive the inner plates of the main clutch 24, the outer plates of which are connected to the driven shaft 26 through the member 25. The intermediate member has splined to it a support member 21 which is formed with spaced teeth 22 to engage cooperating teeth on a driving shaft member with lost motion, and which carries centrifugal bob-weights 27 for the engagement of the main clutch 24. The bob-weights 27 are moved to either side of the dead-centre position by a sleeve 28 operated by the piston 17 through a pin 29 having sufficient clearance to allow for the lost motion between driving shaft 10 and the sleeve 20. The piston 18 carries a pin 32 having lost-motion clearance in the slot in the shaft 10, but not in the sleeve 20, and which engages the synchronizing clutch member 34. Each engine-clutch unit is provided with a pump 36 which feeds the cylinder 16 via a relief valve 38, a pilot-controlled valve 39, a pressure responsive warning device 64 and a pipe 40. From the cylinder 16 oil is led through a passage 41 to a port 43, which is only open to the passage 45 when the intermediate member 20 lags the driving shaft, and thence to the cylinder 14 from which it can exhaust through a port 451 when the member 20 leads, and through a port 46 when the piston 17 has moved sufficiently to shift the levers 27 over dead-centre to allow them to engage the clutch 24. Oil from the pump 47, driven from the airscrew gearing, passes to each clutch unit through pipes 49, 501; pipe 49 supplying oil through a passage 50 to a port 51, open only when the sleeve 20 leads the driving shaft 10, and thence to the cylinder 15 for disengagement of the main clutch 24, exhaust from the cylinder being possible through the ports 54 when the sleeve 20 lags and the ports. 540 when the piston 17 is rearward of the dead-centre position. In operation, when starting from rest, one engine is started and run up to idling speed, the high-pressure shut-off cock is then opened by the lever 56 which also energizes the solenoid 60 to open the valve 39 and allow pressure oil to cylinder 16 to engage the synchronizing clutch 34. As the driven shaft 26 is stationary the lost-motion connection 22 moves until the sleeve 20 is lagging the driving shaft, and thus oil is admitted to the cylinder 14 to engage the main clutch 24. This causes pressure oil to be delivered from the pump 47 which prevents, by its admission to the corresponding cylinder 15 of the other clutch units, the engagement of the other main clutch 24 until the driving shaft leads the driven shaft and so closes port 51 and opens port 43. Should one engine fail, the appropriate sleeve 20 will lead and the ports will open to disengage the main clutch. The engaging pressure of one clutch is made higher than that of the other so that in the event of the airscrew overrunning both turbines only one clutch disengages, disengaging pressure for the other being prevented from building up as, when the piston 17 has moved to a disengaging position, the oil discharges freely through the port 540.