Patent GB-634380-A (GB)
Title: Improvements in toothed couplings
IPC: F16D23/10
Filed: 1946-12-05
Abstract: 634,380. Change-speed gear ; claw-clutches and detents. SINCLAIR, H. Dec. 5, 1946, No. 36081. [Classes 80 (ii) and 80 (iv)] In a double selective positive clutch or detent for a change-speed gear, of the kind described in Specification 486,589, wherein an intermediate member 58, helically splined on a driven shaft 51, has clutch-teeth 60 engageable selectively with clutch-teeth 66 or 67 on the members, e.g. a driving shaft 50 and a second-speed wheel 64, to be clutched to the driven shaft 51, and a lock-sleeve 69, operated resiliently by control-means, is provided for bidirectionally locking the intermediate member 58 to the driven shaft 51 in at least one clutched position, the arrangement is such that, when the intermediate member 58 is in at least the majority of positions in its range of movement between the two clutched positions, free relative rotation of the clutch-members 66, 67 is permitted in both directions, and the controlmeans act resiliently through the lock-sleeve 69 to urge the intermediate member towards the clutchengaging positions. Either the intermediate member 58 or the clutch-members 66, 67 may be provided with oppositely-directed take-up pawls 99, 102, to co-operate with the clutch-teeth of the other member to wind the intermediate member 58 helically along the shaft 51 towards clutch-engagement after synchronism, as in the prior Specification above referred to, but the present arrangement avoids the possibility of the pawls, when provided, being subjected to full transmission torque such as might otherwise occur when torque is suddenly reversed whilst the intermediate member 58 is moving between the clutch members 66, 67 during a change. During part of this movement both pawls 99,102 may be free of the clutch members 66, 67, or, to reduce overall length, they may make simultaneous momentary contact in passing through the central position. The lock-sleeve 69 has a limited movement in the unlocking position, and in the absence of take-up pawls, this movement brings the clutch-teeth 60 of the intermediate member 58 into facial rubbing contact with the clutch-teeth 66 or 67, the confronting tooth-faces being bevelled to reject mesh until the direction of relative rotation reverses, whereupon the lock-sleeve initiates mesh and the teeth themselves complete it. The clutch-operating lock-sleeve 69 is operated by a two-position shift-lever 84, moving, over a locking quadrant 98, and acting on the spindle 80 of a shift-fork 79 through a spring-loaded splined member 88, fig. 3, having a projection 93 engaging a V-notch in the freely-mounted lever 84, which permits the lock-sleeve to be pre-selectively biased for movement in either direction. The take-up pawls 99; 102, pivoted on opposite sides of the clutch-teeth 60 of the intermediate member 58, are pressed out by springs into a position in which they partly mask adjacent tooth-flanks. In the low-speed position, forward drive-torque, passing throughthe clutchteeth 67, 60 and helical-splines 57, maintains the intermediate member 58 hard against a rear stopcollar 68 on the driven shaft 51. Overrun torque passes through the lock-sleeve 69, which is also in its rearmost position, its forward splines 70, which permanently engage splines 71 on the intermediate member 58, also engaging with play splines 73 fast on the driven shaft 51. To shift to high speed under drive-load, the control-lever 84 is preselectively moved to and locked in its high-speed position, which immediately causes the lock-sleeve 69 to move forwards to an unlocked position, Figs. 6 and 7, in which its forward splines 70 disengage the driven-shaft splines 73 and further forward movement is obstructed by abutment of long splines 74A in the rear end of the lock-sleeve 69 against inclined rear faces 76 of the shaft-splines 73. In this position release of drive-torque creates overrun, which screws the intermediate member forward on the helical spline until its clutch-teeth 60 disengage the low-speed clutch teeth 67, leaving it wholly free. The lock-sleeve 69 is still biased for forward movement, and its splines 74A act on the inclined rear faces 76 of the shaft-splines 73, causing the lock-sleeve 69 to turn and thus to screw the intermediate member 58 further forwards until the pawls 99 align with and are overrun by the more quickly rotating high-speed clutch-teeth 66 (or until the faces of the clutch-teeth 60, 67 come into rubbing contact in the absence of take-up pawls). As the clutch-teeth 66 slow down beyond synchronism they pick-up the pawls 99 and screw the intermediate member 58 to its extreme forward position with the clutch-teeth 60,66 in full engagement (or in the absence of pawls, the locksleeve produces initial engagement and the teeth themselves complete it). At the same time the lock-sleeve splines 74A ride clear of the shaft-splines 73, permitting the lock-sleeve 69 to be moved to its extreme forward position in which its long-splines 74A and additional short splines 74B fully engagÚ the shaft splines 73 for transmitting bi-directional drive when the drive-torque is restored. Downshift is similar except that the rearward movement of the lock-sleeve 69 is now obstructed by abutment of the rear faces of its forward splines 70 on the inclined front faces 75 of the shaft-splines 73. These inclined front faces 75, as well as the rear faces 76 if desired, have a step 75A, the inclined portion being only of sufficient width to cause the pawls 99, 102 to be brought into action by the axial movement of the lock-sleeve 69. Alternatively the end-faces of the splines may be all square and the lock-sleeve 69 resiliently biased to a predetermined position on the intermediate member. Specification 634,289 is referred to. The Provisional Specification states also that the invention may be applied to the synchro-coupling shown in Specification 513,974 which controls three ratios, in which case take-up pawls may be provided on one side only of the intermediate member. A single coupling is also described.