Patent GB-620737-A (GB)
Title: Improvements in or relating to variable speed gears
IPC: F16D23/08
Filed: 1946-12-16
Abstract: 620,737. Change-speed gear ; ratchet clutches. NAPIER & SON, Ltd., D., and CATFORD, A. L. Dec. 16, 1946, No. 37009. [Class 80 (ii)] In a constant-mesh two-speed supercharger-drive of the kind, e.g. as described in Specification 599,234, in which helix-mounted facially toothed high- and low - speed one - way clutch-members F<2>, E<2> are torque-actuated by temporarily introducing during shift an overspeed ratio through an otherwise inoperative fluidcouplng D<1>, and the clutches are controlled by a two-position axially-slidable actuating sleeve H, the function of which is solely to lock the high-speed clutch F<2> out of engagement in one position when the low-speed drive is required and to release it in its other position for engaging high-speed when required, there is provided a rotatable axially-fixed locking-ring J, permanently splined at J<2> to the high-speed clutch member F<2> and having baulk-teeth J3 to prevent movement of the actuating sleeve H from either of its two positions unless the clutch-member F<2> is fully disengaged. The clutch-members E<2>, F<2> engage teeth on opposite faces of a common clutchmember G<2> secured to the final driven shaft G, and are helix-mounted on sleeved extensions of wheels E, F, which are freely mounted on the driven shaft G and constantly mesh wheels B, C. on a parallel driving shaft (not shown). The fluid-coupling D1 connects the driven shaft to a third smaller -freely-mounted wheel D meshing a driving-wheel A to give the highest speed used only during shift. Friction-shoes E5, F5 on the clutch-members E<2>, F<2> act constantly on the inside of a shell G<5> fast to the driven shaft G to provide the drag for screwing the clutch-members into and out of engagement in accordance with appropriate speed differences and the end-faces of the clutch-teeth are inclined to assist the helix in disengaging the clutch. The actuating sleeve H has internal splines H<5> which permanently mesh splines on a sleeve F<6> keyed to the high-speed wheel F arid are axially spaced from 'an additonal set of aligned splines H<6>, also on the actuating sleeve H, for co-operating with the baulkteeth J<3> of the locking-ring J to lock-out the high-speed clutch F<2>, as described below. In Figs. 1 and 17 the gear, and a fluid-pressure servomotor control K are shown in the high-speed position, with the clutch-member F<2> engaged, the actuating-sleeve H being in its-leftward position in which the clutch-member F<2> is free to engage. To shift to low speed, a valve O is moved manually to the left, supplying pressure-fluid from an inlet P<1>, through ports P<2>, Q<3>, to act simultaneously on the right face of a central piston, which, through a lever H<4>, biases the actuating- sleeve H to the right ; and on the left face of a piston L, which immediately moves to the right, acting through a lever M to open a sleeve-valve M3, supplying fluid to the constant-leak fluidcoupling D<1>. This overspeeds the driven shaft G, screwing the high-speed clutch-member F<2> to a disengaged position at the extreme left, the rotational component of this movement also turning the locking-ring J to permit passage of the previously detained splines H<6>, whereupon the actuating sleeve H moves to its extreme rightward position in which its splines H<6> engage with circumferential play (see below) with splines F<9> on the high-speed clutch-member F<2>. This rightward movement, through the lever H<4>, also shifts the central piston to the left so that a valve N, associated with it, exhausts the piston L, which is then returned by a spring L3 to the position shown, closing the supply-valve M3 to the fluidcoupling D<1> which drains, thereby allowing the driven shaft G to decelerate. This causes the high-speed clutch-member F<2> to screw back to the right sufficiently to turn the locking-ring J within the limits of the circumferential play permitted between the splines H<6>, F<9>, so that further movement of the actuating-sleeve H in either direction is prevented by the locking-ring teeth J<3> which now lie in the gap between the axially-spaced splines H<5>, H<6> and are out of register circumferentially with them. This positively locks out the high-speed clutch F<2> and the driven shaft decelerates further until low-speed drive is picked up by screwing the low-speed clutch E<2> into engagement. Upshift is by movement of the shift valve O back to the Fig. 17 position, biasing the actuating sleeve H for movement to the left (Fig. 1 position) and also immediately supplying pressure past the valve N<1> (now at the left of Fig. 17) to the left face of a second lower piston L<1> which opens the supply-valve M3 filling the fluid-coupling D<1>. The over-run thus created disengages the lowspeed clutch E and also screws the high-speed clutch. F<2> back to the extreme left sufficiently to turn the locking-ring teeth J<3> into alignment with the splines H<6> of the actuating-sleeve H which is then permitted to return to its left unlocked position, shown in Fig. 1, thus exhausting the pressure on the piston L<1> which is returned by its spring L3 to close the supply-valve M<3> of the fluidcoupling D<1>. With drainage of the latter, the driven shaft G decelerates sufficiently to enable the now unlocked high-speed clutch F<2> to be screwed into engagement to pick-up high-speed drive. To obtain the two-directional locking-action the splines and locking-ring teeth are proportioned circumferentially as follows: The width of the teeth J<3> of the locking-ring J and of the splines on the adjacent wheel-member F<6> is twice that of their corresponding tooth and spline spaces ; the width of the spline-spaces of the actuating-sleeve splines H5 and H<6> and of the clutch-member splines F9 is twice that of the corresponding splines. This permits the relative circumferential movement between the splines F<9>, H<5> which turns the locking-ring J into a locking position with the splines H<5>, H<6> on each side of it, as above described.