Patent GB-713238-A (GB)
Title: Three speed transmission
IPC: B61C9/14
Filed: 1952-08-14
Abstract: 713,238. Hydromechanical variable - speed gear. AKT.-GES. FUR UNTERNEHMUNGEN DER EISEN-UND STAHLINDUSTRIE. Aug. 14. 1952 [Aug. 24, 1951], No. 20476/52. Class 80 (2) [Also in Group XXIX] A hydromechanical gear comprising a torque converter driving an output shaft through an epicyclic train is characterized in that one member of the converter which may act as a reactor acts in the lowest velocity-ratio range as a counter-running turbine driving the output shaft through the gear train, whilst the epicyclic gear idles in an intermediate velocity-ratio range, and is connected as a step-up gear between the main turbine of the torque converter and the output shaft in the highest velocity-ratio range. As shown in Fig. 1, the impeller 4 of the torque converter 1 is driven directly by the input shaft 3. Blade rings 5, 6 constituting the main turbine drive a shaft 10 to which is splined a clutch member 28. A blade ring 7 is mounted on a shaft 11 to which is rigidly fixed a brake drum 18 and the sun gear 15 of an epicyclic train 2. A carrier 20 for planet pinions 16, which mesh with the sun wheel 15 and a ring gear 17, is rigidly connected to a brake drum and to a clutch member having teeth 31 for engagement with teeth 42 on the member 28 which member may alternatively engage teeth 32 on the output shaft 40 coaxial with the input shaft. The ring gear 17 is rigidly connected by a casing 23 with the output shaft 40 and may be connected by a friction clutch to the planet carrier 20. The friction clutch plates 24, 27 are normally free but a piston 25 may be moved, by fluid under pressure in a chamber 26, against a release spring 38 to engage the clutch which acts only to synchronize the members 20, 28 when the teeth 42, 32 are engaged and the teeth 42, 31 are to be engaged. The member 28 is actuated by fluid pressure on a double diameter piston 29 connected thereto by a pin 30 traversing a slot in the shaft 10. In the lowest of the three velocity-ratios that the gear provides fluid under pressure from the converter housing flows through a conduit 33 in the shaft 10 to move the piston 29 until the teeth 42, 32 engage and a band 21 is applied to the brake drum on the planet carrier. The output shaft is then driven directly by the turbine 5, 6 and indirectly, through the planetary gear, by the counter-rotating guide ring 7. In the intermediate velocityratio range the brake band 21 is released and another 19 is engaged with the drum 18 to station the sun wheel 15 and the guide ring 7 which then acts as a reactor. The planetary train idles in this range. For the highest velocity-ratio range the brake band 19 remains engaged, the turbine shaft 10 is clutched to the. planet carrier and the output shaft is driven by the ring gear 17. In changing from the intermediate to the high range the brake band 19 is temporarily released and the friction clutch engaged to synchronize the teeth 42, 31 of the positive clutch the member 28 of which is then moved by fluid pressure applied to the piston 29 via conduits 34, 36. It is stated that a ratio of torques in the lowest to the highest ranges of fourteen to one is obtained. In a modification (Fig. 2, not shown), the positive clutch 42, 32, 31 is replaced by a one-way clutch between the shafts 10, 40 which overruns in the highest ratio range when a friction clutch is engaged to connect the turbine shaft 10 to the planet carrier 20.