Patent GB-699039-A (GB)
Title: Improvements relating to change-speed gears comprising fluid clutches
IPC: F16D67/00
Filed: 1951-05-23
Abstract: 699,039. Change-speed gear. DAIMLERBENZ AKT.-GES. May 23, 1951 [May 23, 1950], No. 12100/51. Class 80 (ii). A change-speed gear, particularly for motor vehicles, comprising a fluid clutch which drives one gear shaft and a bridging-over clutch therefor which serves also as a gear-change clutch and drives another gear shaft, is characterized by the inner one of the two gear shafts, which are arranged concentrically one in another, being coupled, or being capable of being coupled, direct to the driven shaft of the gear. In one form, a variable-speed transmission device comprises a driving shaft 1, a fluid clutch 2 of which the driven part 4 is mounted on a hollow shaft 10, a hydraulically operated friction plate clutch 6 which can connect the driving part 3 of the fluid clutch direct to an inner shaft or torsion bar 9, and change-speed mechanism 13 having a driven shaft 24. The changespeed mechanism consists of a constant gear train 14, 15, and of meshing gear pairs 17, 21; 18, 22; 27, 28. The gear 14 is fast on the shaft 10, the gears 15 and 27 are fast on a countershaft 16, and the gears 21, 22 are fast on a shaft 23 which is coupled to the shaft 9 and the driven shaft 24. The gears 17, 18 are selectively clutchable for rotation with the countershaft 16, by hydraulically operated friction plate clutches 19, 20 which are dimensionally similar to the clutch 6. The gear 28 is free for rotation on the driven shaft 24 and contains a free wheel device 29, the inner ring of which is formed by a clutch part 30 having dogs 31. The dogs 31 can be connected to dogs 32 of a coupling member 33. The latter acts as a hydraulically operated piston and as a gear wheel 34 for reverse drive. The reverse drive may be obtained through a pair of toothed gear-wheels (not shown), longitudinally displaceable to mesh with the gear 34 and the gear 27 on the countershaft 16, or by other suitable means employing obliquely-toothed gears. The gear 34 carries a dog-crown 35 engageable by an externally operated member 36 which forms a parking lock. The free-wheel 29 allows the gear 28 to drive the driven shaft 24, when the dogs 31, 32 are engaged, but also permits the driven shaft 24 to overrun the gear 28: The dogs 31, 32 may be bevelled on their opposed faces and on one flank to facilitate their engagement and disengagement. The clutches 6, 19, 20 and the free-wheel 29 are controlled by an oilpressure system, not shown, the pressure oil being supplied by a primary gear pump connected to the driving half 3 of the fluid clutch and a secondary gear pump 43 connected to the driven shaft 24. Provision may be made for driving a speedometer from the driving-means of the gear pump 43. First speed is obtained through train 1, 3, 4, 10, 14, 15, 16, 27, 28, 29, 24, the clutches 6, 19, 29 being disengaged and dogs 31 engaging dogs 32. Second speed is obtained by engaging clutch 19, the train then being 1, 3, 4, 10, 14, 15, 17, 21, 23, 24, free-wheel 29 overrunning. Third speed is obtained by.disengaging clutch 19 and engaging clutch 20, the train being 1, 3, 4, 10, 14, 15, 18, 22, 23, 24, with free-wheel 29 overrunning. Fourth speed is obtained by disengaging both clutches 19, 20, and engaging clutch 6, which thus bridges over the fluid clutch 2 to give a direct drive through train 1, 3, 6, 9, 23, 24. On engaging reverse drive the connection of the dogs 31, 32 is broken. Under all other conditions the dogs 31, 32 may be engaged, thus preventing the possibility of turning the shaft 24 backwards (as would occur if a vehicle in which the device is mounted were to run backwards) so long as one of the higher speeds is engaged, the drive then being locked in itself. Means may also be provided for locking the gear 28 rigid with the shaft 24. In one modification, Fig. 2 (not shown), the constant gear train corresponding to gears 14, 15 is mounted at the rear of the gear box and the second-speed clutch is mounted on the shaft 10 driven through the fluid clutch, this shaft extending nearly to the end of the gear box. A parking lock is provided at the front end of the countershaft. In another modification, Fig. 3 (not shown), the gear pairs for the gear transmission lie between the gear-change clutches, the latter being mounted at the ends of, or externally to, the gear chamber. The second-speed clutch is disposed inside a housing-like part of a hollow shaft connecting the driven part of the fluid clutch to a gear wheel of the constant geartrain. Provision may be made for bridging-over the fluid clutch in, say, third speed, as well as in fourth speed. Alternatively, the fluid clutch may be arranged to remain operative in direct drive, but to the bridged over for an overdrive. Specification 699,040 is referred to.