Patent GB-918521-A (GB)
Title: Change speed gearing
IPC: F16D23/02
Filed: 1961-01-13
Abstract: 918,521. Change-speed gear; ratchet clutches. VOITH G.m.b.H., J. M. Jan. 13, 1961 [Jan. 13, 1960], No. 1621/61. Class 80 (2). To permit rotation in either direction without locking-up occurring, in a change-speed gear incorporating free-wheel clutches for synchronous engagement of ratios, particularly for powered rail vehicles following a conventional change speed gear, and preferably following a reversing gear, controllable, positive, I, II (Fig. 1), or friction III, IV (Fig. 3), freewheel clutches, each associated with a power path capable of being synchronized, may be set to freewheel or run free in either direction of rotation, and, to change ratio, firstly input speed is relatively reduced, secondly the then freewheeling clutch is set to run free, thirdly the clutch of the gear to be engaged is set from running free into the free-wheel condition corresponding to the direction of rotation, and finally the input speed is relatively increased and the required gear engaged. The clutches may also be bi-directionally locked in any gear, such locking being necessarily released before gear change. The clutch control means is arranged so that only one clutch is capable of power transmission, and may comprise a single lever or mechanically or electrically interlocked levers. Automatic means controlling the timed sequence of gear changing may be provided. In Fig. 1, a two-speed gear comprises wheels 3, 4 loose on an input shaft 1 and meshing wheels fast on a driven shaft (not shown). Positive freewheel clutches I, II comprise sleeves 9, 10 which have clutch teeth 7, 8 meshing those 5, 6 of the wheels 3, 4 and oppositely directed spring-urged pawls 26-29 engaging or ratcheting over the teeth 5, 6. The sleeves 9, 10 are internally threaded for helical movement along the shaft 1 which movement is limited by stops 12-15 or by spring rings 16-19 which can be moved into the sleeve path by radial pins 20, 21 and 22, 23 respectively, controlled by levers 37, 36 through axially moving cam-shafts 24, 25 rotating with the shaft 1. The levers 37, 36 have positioning notches not shown. Radially actuated bolts or locking teeth may replace the rings 16-19 and chamfered teeth freewheel clutches may replace the pawl-actuated type shown. In operation, with the shaft 1 rotating in the direction of arrow A, in low gear clutch II is engaged; the spring ring 18 is raised and is abutted by the leftwardly urged sleeve 10 to engage the teeth 6, 8, andthe sleeve 9 is moved completely leftwards against the stop 12, the pawls 27 ratcheting. On reduction of input speed (or increase of output speed), sleeve 10 moves to the freewheeling position completely rightwards against the stop 15, the pawls 28 ratcheting; and if the input speed falls below that of the wheel 3 then the sleeve 9 also moves rightwardly to the freewheeling position. If in this latter condition the spring rings 18 and 16 are respectively retracted and raised then upon increase of input speed (or reduction of output speed) the sleeve 9 moves leftwardly to abut the ring 16 to engage the teeth 5, 7 for high gear, the sleeve 10 remaining in the rightwards ratcheting position due to the overrunning of the wheel 4. If on reduction of input speed effecting rightwards movement of the sleeve 9 to its freewheeling position, the spring rings 16, 18 are respectively retracted and raised, on increase of input speed the sleeve 9 moves completely leftwards to the stop 12 and on further input speed increase resulting in the shaft 1 overrunning the wheel 4 the sleeve 10 moves leftwardly to abut the ring 18 to again engage low gear. For bi-directional drive, e.g. in high gear with the ring 16 raised, the complementary spring ring of the clutch 17 must be raised. For the direction of rotation B, the sleeve movements are reversed and the spring ring movements are interchanged. To prevent locking-up the one or two spring rings must be actuated at one sleeve only. In Fig. 3, friction, freewheel clutches III, IV are arranged between loose wheels 104, 105 and an input shaft 101, and each, e.g. IV, comprises friction discs 136 alternately splined to the wheel 105 and to sleeves 116, 117 helically movable on the shaft 101 between stops 122- 125. Springs 128, 129 press the sleeves against the stops 123, 124. Rings 134c, 134d secured to the sleeves take the disc pressure. To allow for working play between the sleeves, a thick intermediate outer disc 135a is provided. Independently and axially movable control rings 140, 141, rotatable with the wheel 105 and actuated by levers 144, 145, serve to press the discs of the clutch IV against the springs 128, 129 to produce slight friction between the discs. Further rings 138, 139 control the clutch III. The control levers have each three positioning notches, not shown. In operation, in the direction of rotation A, to engage low gear the control rings 140, 141 are shifted to the right. The sleeve 117, held back in relation to the shaft 101 by the slight frictional torque in clutch IV, is helically moved leftwards to engage the clutch. For bidirectional drive in low gear the control ring 141 is additionally moved into its left-hand position to grip the discs between the rings 140, 141. To change to high gear during freewheeling in low gear, the input speed is reduced, the rings 140, 141 are brought into the freerunning condition as shown, the rings 138, 139 are shifted rightwards and the input speed increased to engage clutch III. For the direction of rotation B, the corresponding control rings are leftwardly moved. Specification 513,974 is referred to.