Patent GB-831999-A (GB)
Title: Improvements relating to clutches
Inventor: DARLINGTON WILLIAM HENRY
IPC: F16D11/10
Filed: 1957-05-08
Abstract: 831,999. Positive and friction clutches; securing together rotary parts. METROPOLITAN-VICKERS ELECTRICAL CO. Ltd. May 7, 1958 [May 8, 1957], No. 14676/57. Class 80 (2). A positive clutch comprises two rings of clutch teeth fast on one clutch element and aligned with each other, a pair of toothed clutch members slidably mounted upon a second clutch element and each having a ring of teeth, the members being capable of axial movement both with respect to each other and the second clutch element, the teeth on the slidable members being angularly displaced so that the teeth of one ring are aligned with the spaces between the teeth of the other ring, spring-loaded rods passing axially through holes in the slidable members so that the slidable members can be biased to engage their clutch teeth with the rings of fixed teeth, the slidable clutch members normally being biased away from each other, and means enabling the slidable members to be moved from a position of engagement to a position of disengagement with respect to the fixed rings of teeth. The clutch may be used between two shafts connecting a steam and a gas turbine. In one form, a driving shaft 1, Fig. 1, carries upon helical splines 4 a ring 5 connected to one member of a ratchet clutch 6 (not further described) in turn connected through a small friction clutch 2<SP>1</SP> to a driven shaft 2. When the speed of the driving shaft 1 increases to such an extent that it tends to overrun the driven shaft 2, the ratchet clutch 6 engages and screws the ring 5 rightwards along the helical splines 4, so that rods 11 are similarly moved rightwards and cause springs 14 mounted on the rods to bias two clutch members 9, 10 rightwards along splines 3 to engage their teeth 9<SP>1</SP>, 101 with rings of teeth 7, 8 upon the driven shaft 2. The teeth of the two rings 7, 8 are axially aligned while the teeth 9<SP>1</SP>, 10<SP>1</SP>, Fig. 2, are angularly displaced so that the teeth 9<SP>1</SP> are aligned with the gaps between the teeth 10<SP>1</SP>, the width of the gaps between the teeth 9<SP>1</SP>, 10<SP>1</SP> being approximately three times the width of the teeth. Similarly, the gaps between the teeth on each of the rings 7, 8 are approximately three times the width of the teeth. In the event that the teeth 9<SP>1</SP>, 10<SP>1</SP> are not exactly aligned with the gaps between both rings of teeth 7, 8 at the moment of engagement, one or other of the rings of teeth 9<SP>1</SP>, 10<SP>1</SP> slides into engagement, the separation of the clutch members 9, 10 varies as one or other of the sets of springs 14 is compressed, and the other of the sets of teeth 9<SP>1</SP>, 10<SP>1</SP> slides into engagement after slight relative rotation of the driving and driven shafts 1, 2 has taken place. The clutch is disengaged by operation of a lever 15. When used between a gas and a steam turbine, it is sometimes desired for the shaft 2 to be rotatable completely independently of the shaft 1. Accordingly, the friction clutch 2<SP>1</SP> is disengaged, so that the ratchet clutch 6 is rendered inoperative. As a modification, instead of the rings of fixed teeth 7, 8 being rigid with the driven shaft 2, they may be formed upon a ring 20, Fig. 4, connected to the driven shaft 2 through tangentially disposed spring struts 23. Again, the rings of teeth 7, 8 may be formed upon the inner and outer peripheries of a ring 42, Fig. 6, fast with the driven shaft 2, the ring of teeth 10<SP>1</SP> then being on the inner periphery of a flange 40 on the clutch member 10. In another modification, a driving shaft 1, Fig. 5, carries upon helical splines a similar ring 5 driving through a ratchet clutch 6 which picks up on synchronism to slide the ring and coacting rods 33 rightwards, thus opening a valve 34 which admits oil under pressure through a passage in the driving shaft to a space between pistons 32, 32, which separate and engage multi-disc friction clutches 30, 30 in parallel between the driving shaft and the driven shaft 2. Engagement of the teeth on clutch members 9, 10 with rings of fixed teeth 7, 8 on the driven shaft 2 in a positive clutch according to the invention is then obtained by manually sliding the clutch member 10 leftwards.