Patent GB-1336207-A (GB)
Title: Propeller coupling arrangement
IPC: F16D48/04
Filed: 1971-11-04
Abstract: 1336207 Clutches; controlling clutches GENERAL MOTORS CORP 4 Nov 1971 [30 Nov 1970] 51283/71 Headings F2C and F2L [Also in Division B7] In a propeller coupling in which a propeller 13  is to be selectively coupled to an engine 10 also driving a helicopter rotor by axially moving a shaft 24, splined to the shaft connected to the propeller, so that external splines 23 engage a driving shaft 18, the engagement of splines and shaft is controlled by an hydraulically actuated disc clutch 51, 45 and a synchronizing clutch (Fig. 4). The hydraulic circuit comprises a pump 86, shuttle valves 92 and 93 and a solenoid valve 91. Clutch construction.-The multiple clutch comprises discs 51 splined to a ring 53 in turn splined to shaft 24, the other discs 45 being splined to a member 38 which in its turn is splined to part (Fig. 2, not shown) of the drive member 18, A piston 63, receiving fluid from a port 83 puts this clutch into engagement. The synchronizing clutch comprises a friction ring 78 helically splined to the shaft 24 and biased by a spring 79 between it and a piston 64. A spring 71 biases this piston to the left, which force is counteracted by fluid from port 84. On movement of the piston 64 to the left the friction ring 78 abuts a conical part of member 47, between which the reaction, in conjunction with the helical splines, prevents further movement to the left of the piston (and so of the shaft 24 to which it is attached) until member 47 and ring 78 rotate at the same speed and synchronization can be completed, splines 23 engaging teeth 22 of driven member 18. Clutch operation.-The circuit is shown (Fig. 4) with the propeller coupling disengaged, the pump 86 producing fluid at pressure which passes through conduits 135, 151 and 148 to hold back piston 64, 131 and 134 to a vent valve 85 and 136 to a port 102 in shuttle valve 92. On operation of the solenoid valve 91 the land 95 moves to the right so that high pressure hydraulic fluid flows via valve 92 and conduit 152 to port 84. A port 105 in valve 92 receives Pitot pressure dependent on the rate of rotation of the propeller (allowed to rotate freely, i.e. "windmill", by the pilot of the helicopter) which when it is great enough moves the spool 102, cuts off the pressure to one side of the piston 64 (and vents this pressure) and allows this to move to the left. Simultaneously the pressure on the left side of spool valve 93 drops which allows pressure to be supplied, via port 83 to piston 63 to actuate the disc clutch (this actually occurring before piston 64 operates the synchronizing clutch drive to friction in piston 64 and a constriction 149 in the conduit leading thereto). When the synchronizing clutch has operated, and the coupling complete, the piston 64 uncovers a vent port 85 (due to its shape) which vents the right side of the shuttle valve 93 and centres it, this venting the pressure to the disc clutch piston and disengaging it. To disengage the propeller the solenoid valve 91 is returned to the position shown in Fig. 4, supplying fluid to the left side of valve 93, which re-engages the disc clutch and then disengages the synchronizing clutch, the resultant covering of port 85 returning valve 93 to the position shown and disengaging the disc clutch. A lock pin (not shown) engages a notch 64b in piston 64 when no pressure is supplied by the pump 86 so that the synchronizing clutch does not become actuated by the switching off of the helicopter engine.