Patent GB-826694-A (GB)
Abstract: 826,694. Engine turning gear. GRATZMULLER, J. L. Jan. 25, 1957 [Jan. 27, 1956], No. 2761/57. Class 7(5) Hydraulic apparatus for turning a driven shaft having a. ratchet toothed claw coupling element comprises an axially displaceable driving rotary member having a ratchet toothed claw-coupling element complementary to that of the driven shaft, an hydraulic motor device for imparting rotary motion initially slow and of limited extent and thereafter faster to the driving member in the sense to rotate the driven shaft, a control valve system for admitting liquid under pressure to the hydraulic motor device to energize it for rotating the driving member in the required sense, the valve system being operative to admit initially a limited quantity of liquid at a relatively slow flow rate and thereafter more liquid at a faster flow rate and means separate from the hydraulic motor device for axially displacing the driving member to establish initial contact between the claw coupling elements and for maintaining such contact by axial pressure while engagement of the claw coupling elements is completed. As shown, a driven coupling member 13 forming part of an engine which it is desired to start has ratchet teeth 12 which co-operate with ratchet teeth 11 on a driving coupling member 8. The driving coupling member 8 is driven by a toothed rack 6 and pinion 7 the rack being actuated by means of a main hydraulic jack 3 shown diagrammatically in Fig. 6. The coupling member 8 is displaceable axially to engage the teeth 11, 12 by means of a pusher rod 4 which is operated by an auxiliary hydraulic pack 28 manual actuation of a pilot valve 48 (to the right Fig. 6) initiates the first phase of the starter motor operation in which the auxiliary jack 28 is energised to displace the pusher rod 4 and thereby press the driving coupling member 8 into engagement with the drivable coupling member 9. Concurrently the pilot valve 48 by disconnecting the control jack 49 from the exhaust line 52 and admitting liquid to it through the calibrated orifice 42 initiates the second phase of operation which begins as soon as the two stage valve 50 actuated by the control jack 49 has uncovered the port 46 connected with the feed branch 44 containing the calibrated orifice 45. The second phase ends and the third phase begins when the two stage valve 50 uncovers the port 47 and allows the main jack 3 to be fed at a high flow rate. The angle through which the coupling member 8 is rotated in the second phase of operation is at least as great as the angular spacing of the teeth 11, 12. The pusher rod 4 tends to hold the coupling member 8 in engagement until the end 31 of the pusher rod runs off the high part 32 of the cam of the coupling member. The angular extent of the high part 32 of the cam is not less than the tooth spacing of the claw coupling elements 11, 12 and at least equal to the smallest fraction of a revolution that must be imparted to the driven member 13 to ensure starting of the engine but is preferably less than that of the low part 33. The structural details of the valve means V are preferably such as are fully described in Specification 818,533 [Group XXIX]