Patent GB-878017-A (GB)
Title: Improvements in or relating to automatic change speed gears
Inventor: MILLER ALBERT ARTHUR
IPC: F16H61/02
Filed: 1958-10-15
Abstract: 878,017. Change-speed epicyclic gear. SELFCHANGING GEARS Ltd. Oct. 8, 1959 [Oct. 15, 1958], No. 32899/58. Class 80 (2). Relates to an automatic epicyclic changespeed gear for rail traction or road haulage vehicles of the kind comprising a speed and torque responsive clutch and link device in which friction clutch shoes 10 act as transmitting links in a relatively low ratio and are engaged with an input clutch drum 2 for solid direct drive for high ratio, as described in Specification 740,692. In such an arrangement the overall step-down transmission is arranged with a step-down main portion between an input 1 and the shoes 10 and a step-up auxiliary portion between the shoes 10 and an output 13 so during change up to solid drive the shoes 10 undergo a speed increase to increase the centrifugal clutching force to counterbalance increasing input torque arising from decreasing input speed, and during change-down shoes 10 undergo a speed decrease to reduce the centrifugal clutching force to counterbalance decreasing input torque arising from increasing input speed, thereby opposing any tendency of the clutch to slip after engagement during changeup and of the clutch to re-engage after disengagement during change-down. Whilst the invention is applicable to arrangements wherein the input to the change-speed gear is from an engine through a mechanical or fluid clutch it is particularly applicable to constant input power arrangements wherein input torque and speed are inversely proportional, e.g. a hydrodynamic torque converter or constant power internal combustion engine or electric motor. In Fig. 1 the step-down main portion comprises planets 7 meshing a ring gear 3 of the input clutch drum 2 and a sun 4 reacting on a one-way detent 5, the planets 7 being mounted on a carrier 8 connected to the friction clutch shoes 10, and the step-up auxiliary portion comprises planets 16 meshing a ring gear 14 connected to the shoes 10 and an input sun 15, the planets 16 being mounted on an output carrier 17. The connection of the carrier 8 and the ring gear 14 with the shoes 10, which may be outwardly spring biased, is as described with respect to Fig. 7 of Specification 740,692. The present Specification provides step-up auxiliary sun and ring gear proportions so that during gear change the change in the centrifugal clutch torque capacity, which varies as the square of the shoe speed counterbalances the change in the torque delivered to input. In Figs. 2, 3, 5 (not shown), wherein the stepup auxiliary portions are similar to that in Fig. 1, the step-down main portions comprise: Fig. 2, planets on a friction shoe-connected carrier meshing an input sun and a reactionary ring gear; Fig. 3, interengaging planets on an input carrier, one of each planet pair meshing a reactionary sun and the other meshing a friction shoe-connected ring gear ; and Fig. 5 interengaging planets on a reactionary carrier, one of each planet pair meshing an input sun and the other meshing a friction shoe-connected ring gear. Fig. 4 (not shown) is a series arrangement of the Fig. 3 type wherein the output carrier of the first step-up auxiliary portion is connected to the input carrier of the second step-down main portion, the friction shoes of each train engage a common input drum, and the main portion reactionary suns are mounted on a common sleeve. In Fig. 6 (not shown), which form is also suitable for series arrangements, the step-down main portion comprises planets mounted on a friction shoe-connected carrier meshing an input sun and a reactionary ring gear, and the step-up auxiliary portion comprises planets on a friction shoe-connected carrier meshing a reactionary sun, integral with the main portion reactionary ring gear, and an output ring gear.