Patent GB-1230738-A (GB)
IPC: F16H3/66
Filed: 1970-04-02
Abstract: 1,230,738. Change-speed gear. GENERAL MOTORS CORP. 2 April, 1970 [1 May, 1969], No 15652/70. Heading F2D. Four widely-spaced forward ratios, including direct-drive and one or two overdrives, and two reverse ratios are provided by three threeelement planet trains, the first two 20, 22 of which are arranged on one side of an input bevel drive 11, 13 from a transversely mounted engine on a heavy vehicle, whilst the third train, 52, which provides both reverse and one overdrive, is arranged on the other side. The widely-spaced ratios enable a gas-turbine to be used over its narrow speed range without necessity for an hydraulic torque converter, the gear being wholly mechanical and the first forward and reverse ratios providing sufficient starting torque at turbine stall. Five embodiments are described and shown, each having different interconnections of the various planetary elements. With the interconnections shown in Fig. 1, ratios are as follows. First, ratio 3: 00 uses the second train 20 alone by applying a brake 44 to the ring gear 28, and engaging a clutch 74 to lock up the reverse train 52. Drive passes from the input bevel shaft 11 to the sun 16 of the second train 20, the carrier of which drives directly to output 72 through an intermediate shaft 32 and the locked reverse train 52. Second, ratio 1: 80 compounds the trains 20, 22, by braking at 46 the ring 36 of the train 22, the reverse train 52 remaining locked as for first. Third, ratio 1: 00, engages a direct clutch 68 for direct drive through the intermediate shaft 32 and locked reverse train 52. Overdrive fourth, ratio 0: 69, changes from the reverse lock-up clutch 74 to a brake 76 for the sun 50 of the reverse train 52. The direct clutch 64 remains engaged so that the ring gear 56 overdrives the output 72, the train 52 acting alone. First reverse, ratio - 6:72, uses trains 20 and 52 in series by applying brakes 44, 64. The train 20 drives as in first forward, 52 reverses. For second reverse, ratio - 4: 04, brakes 46, 64 are applied and the trains 20, 22 compound as in second forward, the train 52 reversing. The brake 44 is applied in neutral. In each of the following four modifications the reverse train 52 is unmodified. In Fig. 2, not shown, in which the bevel gear is angled at other than a right-angle, input is to the connected carrier (78) of the first train (80) and ring (81) of the second (86). The suns are separate, the first (80), together with the second carrier (98), being secured to the intermediate shaft (32 in Fig. 1), the second sun (94) being braked. Second ratio is direct drive, and both third and fourth are overdrives, in the rear train (116) alone and first train (80) alone respectively. In Fig. 3, not shown, the first carrier (154) is connected to the second sun (158) and the second train (148) has intermeshed planets. The two rings (142, 144) are connected together to input. Third ratio, first overdrive, is in the reverse train (178) alone as in Fig. 2, not shown, whilst fourth, second overdrive, is in the second train (148) alone by holding the carrier of the intermeshed planets. In Fig. 4, not shown, input is to the connected ring (214) of the first train (220) and sun (218) of the second (222). The first and second carriers are both mounted on the intermediate shaft (32 in Fig. 1), and the second ring (246) is braked. Third ratio is direct-drive and overdrive fourth in the rear train (254) alone, as in Fig. 1. In Fig. 5, not shown, input is to the second ring (288) and brakes are provided for the connected first and second suns (308,292); the first carrier (316); and the connected first ring (300) and second carrier (290), both mounted on the intermediate shaft (32 in Fig. 1). First ratio is compounded in the first two trains (306, 290); second uses the second train (290) alone; third is direct-drive, and overdrive fourth is in the rear train (328) only, as in Fig. 1. All ratios, including that of the bevel gear, are specified, and the clutches and brakes may be operated by hydraulic, pneumatic, electric or mechanical power. The arrangements of Figs. 2 and 3, not shown, are useful for governed input speeds of 2850 R.P.M., those of Figs. 4 and 5, not shown, for 4,000 R.P.M.