Patent GB-323217-A (GB)
Title: Improvements in and relating to variable-speed gearing
IPC: F16H3/72
Filed: 1928-06-26
Abstract: 323,217. Thomson, H. J. June 26, 1928. Electromechanical power transmission systems .-A variable-speed power transmission system comprises a three-member epicyclic gear with one or both of two dynamo-electric machines geared to the gear shafts and means for varying the gear ratio at a point in the control cycle at which the machines change their functions. Clutches may be provided to connect a machine alternatively to the power-shaft or the load shaft at different parts of the cycle. The power-shaft may drive one member of each of two three-member epicyclic gears, one member of one gear driving the load shaft, a member of the other gear being connected to a dynamo-electric machine and the remaining members, one in each gear, being interconnected. The various systems described admit of reverse driving and starting of the prime mover. In the system shown in Fig. 2 the power shaft P drives the load shaft L through the gear i, p, s at slow speed when the brake 6 is applied, the geared machine G supplying power to the machine M until the lay shaft A is stationary, whereupon brake B is applied and the load is driven wholly mechanically. Clutch 7 then couples machine G directly to the member i and, the gear 3 being such that the parts of clutch 5 are rotating then at the same speed, clutch 5 is engaged; power is now supplied from machine M to machine G to accelerate to top-speed whereupon clutch T is engaged and the gear drives solid. For starting the prime mover the machine M is battery driven, clutch 5 being engaged. Reverse drive is obtained by engaging clutches 5, T the machine G then driving the load either direct or through the gear 4. In a modification, machines M and G are both connected by chain and sprocket gears to the epicyclic gear members and the machine M may be connected to the prime mover shaft or to the load shaft with change of gear ratio. Two reverse speeds are provided in this modification. Fig. 4 shows a form in which the machine M may be coupled to the load shaft by way of the road wheels and clutch 18 or to the prime mover shaft. In a train of vehicles other machines such as M may be provided on the trailers and likewise supplied with power. The machine G has a tworatio chain gear; it may be used to start the prime mover 1 in this modification. In Fig. 5 the machines are not geared, clutches 5, 21 enabling the machine M to be coupled to the power or load shafts directly. A dog clutch 22 is provided for reversing. Specification 1582/09 is referred to. To increase the range of electrical control between the stages when the drive is wholly mechanical a variable gear may be arranged between shaft L and the wheels of a vehicle. A second epicyclic gear may be employed as in the following modifications. In Fig. 6 the shaft P first drives the load shaft L through the gear s, p, i with brake B applied, next through an additional gear s<1> p<1>, i<1> with brake B<1> applied; next, power is supplied through machines M, G to the member i<1> and finally clutch T' is engaged and the gears drive solid. A bevel wheel type of epicyclic gear may be used in place of the spur wheel type. Modifications of the arrangement shown in Fig. 6 are described in which the machine M is placed upon or connected to the member A interconnecting the gear members p<1>, i, with, and without, means for coupling it to the power shaft, and in a further modification an additional machine is placed on the prime mover shaft. Another modification permits the machine M to be coupled to the member A or to the power shaft and in a further form, with this feature, the machine M is geared to the member A and a clutch is provided for locking the gear. Fig. 12 shows the power shaft P connected by two epicyclic gears s, s' to the load shaft with brakes B, B' and clutch T<1> for giving three mechanical drives at different speeds. A machine G is connected by chain and sprocket change speed gear to the member i<1> of the second gear and a machine M may be connected by reducing gear to the member A interconnecting the gears or by clutch 5 to the power shaft P. The clutches 9, 12 are engaged until the machines M, G are required to reverse their functions, whereupon the gear ratios are changed, clutches 5, 14 being engaged. At top speed clutch T<1> is engaged and clutches 5, 14 released so that the machines M, G are not then rotated. Fig. 13 shows, a form in which the machine M is upon the load shaft and the epicyclic gears are brought together so that they may be enclosed in one box. Provision may be made in this form for disconnecting machine M and connecting it with the power shaft. Specifications 25386/07, [Class 78, Lifting &c.], and 9996/13 also are referred to.