Patent GB-493441-A (GB)
Title: Improvements in and relating to change speed gear controls
IPC: F16H61/02
Filed: 1937-03-05
Abstract: 493,441. Controlling change speed gearing and clutches. BROWN, G. L. March 5, 1937, No. 6553. [Class 80 (ii)] Change-speed selector control means comprises an internally-cammed arcuate shell 25, angular displacement of which selectively moves dogs A, B and C, D, mounted respectively on gear-striking carriers 23, 24, radially into engagement with left- or right-handed screwthreads 20, 21, Fig. 5, on a continuously rotating shaft 17, so as to produce an appropriate axial movement of the carriers 23, 24 in either direction. The dogs A ... D are radially slidable in their carriers, and have teeth 52 for engaging the screw-threads. The dogs A, C overlie the left-hand thread 20, whilst those B, D overlie the right-hand thread 21, so as to produce leftward and rightward movement respectively of their carriers 23, 24. The change-speed gear itself comprises a lowspeed and reverse pinion 11, and a second- and high-speed pinion 10, both splined on the driven shaft 3, and actuated respectively by forks 49, 48, connected to the respective carriers 23, 24 through springs 51, Fig. 5, which yield at the commencement of a change, to allow the main clutch to be first disengaged by a mechanical relay described below. The selector cam-shell 25 surrounds the relay shaft 17 and the carriers 23, 24, and its internal cam projections are arranged in four groups 1a, 1b, 1c, 1d, Figs. 16 and 19, which selectively press the corresponding dogs A, B, C, D radially into operative engagement with the relay-shaft 17. The cam groups, which are shown in development in Fig. 16, include short and long cams for effecting neutralizing and gear-establishing movements respectively. At the completion of such movements, the tails of the dogs A ... D ride off the cam ends and are lifted radially, by springs 53, Fig. 15, out of engagement with the relay shaft 17 so that movement of their carriers 23, 24 ceases. The relay shaft 17 is continuously driven, through a slipping coupling 19, which yields to excessive resistance, by a pinion 9<1>, loosely mounted on the gear-driving shaft 2 and fast to the engine flywheel 11<1> so that the relay shaft 17 is always driven even when the main-clutch is disengaged. The driving shaft 2 of the gear is driven, in the usual manner, by the driven member of the main-clutch. During a change, the axial movement of the gear-shifting carriers 23, 24 is also caused to disengage and re-engage the main-clutch in the following manner. Each gear-shifting carrier 23, 24 carries a vertically slidable rack 32, which, as the carrier moves axially, tracks over and rotates a pinion 47, the pivot 41 of which is guided in a slot in a vertical arm 34. Fast to the pinions 47 are arms 42, carrying rollers 43, 44, which, at the commencement of a change, Fig. 1, are horizontal, the main-clutch being engaged. The axial movement of either carrier 23, 24 during a change turns the corresponding arm 42 into a vertical position, Fig. 4, in the attainment of which, one or other of the rollers 43 or 44 fulcrums on an upper horizontal bearing-surface 45, fixed to the carriers 23 or 24, whilst the other roller 44 or 43 bears on a horizontal surface 40 on the vertical arm 34. thereby forcing the said arm vertically downwards and disengaging the main-clutch through linkage including a rock-shaft 37 carrying an arm 35, pinned at 36 to the vertical arm 34, and lever 38 acting directly on the main-clutch throw-out collar 5. Each carrier 23, 24 has a clutch-acting rack 32, there being two vertical arms 34, arranged one on each side of the camshell 25, and pinned together at 36. Whilst the arms 42 are being moved to the vertical clutch-disengaged position, Fig. 4, the springs 51, Fig. 5, connecting the carriers to the gearstriker forks, yield until the clutch is disengaged. The new gear then engages under the spring-influence, and the continuing axial movement of the carrier 23 or 24 causes the rack 32 to turn the pinion 47 through a further 90‹ and restore the roller-carrying arm 42 to the horizontal position, thus allowing the mainclutch to re-engage. The main-clutch throwout collar 5 has also a manual control 6, and clutch engagement is always cushioned by a dashpot 39. In the construction shown in Figs. 1-19, the cam selector-shell 25 is turned manually or by a centrifugal governor 55, Fig. 3, driven by a worm 54 from the driven shaft 3. The collar 56 of the governor is biassed into a central neutral position, Fig. 3, by springs 57, 58, and acts on the selector-shell 25 through step-by-step mechanism comprising a coil-spring 72, Fig. 8, secured at one end to a sleeve 60, rocked by the governor-arm 59, and at its other end to a disc 65, slidably keyed to an inner shaft 66, which rigidly carries an arm 67, connected by a link 68, Fig. 3, to the selector shell 25. The disc 65 has a lateral extension passing through the sleeve 60, and having a series of holes 73, Figs. 3, 12 and 13, corresponding to gear and neutral positions, and engaged by a fixed peg 74 on the gearcasing. The proximate end-faces of the sleeve 60 and disc 65 have complementary camrecesses 70, Figs. 12 and 13, which, before a change, engage each other as shown in Fig. 12. When a change is to take place, the governor turns the sleeve 60, so that its cam recesses rideup those of the locked disc 65, stressing the spring 72, Fig. 8, in torsion and compression, and forcing the disc 65 axially until one of the holes 73 is freed from the locking-peg 74, as shown in Fig. 13. The torsion of the spring 72 then turns the disc 65, so that the shaft 66 follows the sleeve 60, and the cam-recesses 70 re-engage, the locking-peg 74 engaging in the next hole 73. An upper extension 61 of the governor-arm 59 is connected to means for manually operating the selector-shell 25 through the step-by-step mechanism. In the modification shown in Figs. 26-54. two axially movable carriers 62<1>, 63<1>, each yieldingly carrying a gear-striking fork, pivotally carry a pair of dogs A<1>, B<1> and C<1>. D<1>, Fig. 54, adapted to be selectively moved radially inwards into engagement with left- and right-handed screwthreads 49', 50<1>, Fig. 29, on a relay-sleeve 36<1>, continuously driven from the engine-flywheel 15<11> through friction-wheels 24<1>, 30<1>, 31<1>, 32'. As before, the dogs A', C' co-operate with the left-hand thread 49<1> to produce rightward movement, and B<1>, D' with the right-hand thread 50<1> to produce leftward movement of their carriers. In Fig. 26, the relay-sleeve 36<1> is shown in front of the driven shaft 5<1> of the gear, which shaft carries sliding-gears such as 10, 11 in Fig. 1. The dogs A' ... D<1> are selectively controlled in the same manner as in the first construction described above, by internal cam-groups 1a<1>&c., Figs. 29 and 54, in an angularly movable cam selector shell 79<1>. In this form, however, the dogs A<1> ... D<1> are centrally pivoted in pairs to the carriers 62<1>. 631, are lifted away from the relay-sleeve 36<1> by blade-springs 76<1>, and their tails carry rollers 72<1>, for engagement with the cam-shell. The selector shell 79<1> is controlled manually and by a centrifugal-governor through step-by-step mechanism described below. During a change, the main-clutch 3<1> is automatically disengaged by axial movement of an inner shaft 35<1> acting on the throw-out collar 16<1> through levers 20<1>, 18<1>, such axial movement being produced as follows. The friction-wheel 17<1> is splined on the shaft 35<1>, and the relay sleeve 36<1> receives its drive from the shaft 35<1> through co-operating screw-threads 37<1> between the shaft 35<1> and sleeve 36<1>, conical rollers 40<1> being inset in threads of the shaft to reduce friction. Axial clutch-disengaging movement of the shaft 35<1> is produced by temporarily stopping the rotation of the sleeve 36<1>, whereupon inner shaft, continuing its rotation, screws on the thread 371 and so moves axially and disengages the clutch. Stopping of the relay-sleeve 36<1>, to produce clutch-disengagement, is effected by means of a stop-wheel 51<1>, frictionally mounted on the relay-sleeve 36<1> and having triangular teeth 58<1>, Fig. 29, which in neutral and gear positions of the selector-carriers 62<1>, 63<1>, are received in notches 68<1>, 69<1>, 70<1> in the dogs so as to allow the stop-wheel to rotate freely. When a change is to take place, the initial movement of the carrier 62<1> or 63<1> moves the notches 68<1>, 69<1> or 70<1> out of registry with the teeth of the stop-wheel 51<1>, thereby preventing rotation of the latter together with the relaysleeve 36<1> and effecting clutch-disengagement. A yielding connection is provided between the carriers 62<1>, 63<1> and their selector-forks so that no movement of the latter takes place in this interval. The leftward clutch - disengaging movement of the shaft 35<1> is positively limited by a collar 48<1>, Fig. 26, whereupon the frictional connection between the stop-wheel 51<1> and the relay-sleeve 36' slips, permitting the sleeve 36<1> to continue its rotation and move the carriers 62<1>, 63<1> to selected gear or neutral positions. In such positions, the teeth of the stop-wheel 51<1> again register with one of the notches 68<1>, 69<1> or 70<1>, freeing the stop-wheel and permitting a compression spring 47<1> to return the shaft 35<1> to the right of Fig. 26, thus allowing the clutch to re-engage under control of a dashpot formed by a piston-head 44<1> on the shaft 35<1>, and an adjustable escape-valve 45<1>. Manual servo-control of the clutch is possible at any time by a hand-lever 153' which turns a shaft 155' and pivots a cam into the path of the teeth of the stop-wheel 51<1>, stopping the latter and causing clutch disengagement. The rotatable cam selector shell 79<1>, determining engagement of the dogs A<1> ... D' with the threaded relay-sleeve 36<1>, is controlled through step-bystep mechanism by manual means acting directly on the step-by-step mecha