Patent GB-306636-A (GB)
Title: Improvements in or relating to power transmission mechanism
IPC: F16D23/02
Filed: 1927-12-06
Abstract: 306,636. Salerni, P. M. Dec. 6, 1927. Facilitating changing speed; clutches, claw.- In the transmission system of mechanicallypropelled vehicles is provided a positive bidirectional clutch which can be disengaged at will, while the remainder of the transmission may be uninterrupted, in order to allow the vehicle to " coast " without undue friction &c., and is adapted to revert automatically to its coupled condition when the driving and driven members substantially synchronize. The clutch members may be held apart during coasting by reason of the limited displacement relative to the driven member of an interposed part or parts having antifrictional contact or connection with the driven member and light contact under spring &c., pressure with the driving member, which restores the part or parts to allow re-engagement as soon as it overtakes the driven member. When the clutch is disposed behind the gearbox, it may be controlled in conjunction with the engine clutch and act to isolate the gearbox to facilitate speed-changing. As shown in Figs. 1, 5, and 6, the gear-box shaft 5, which receives a spigot 7x of the propeller shaft 6, carries the driving-member 7, provided with teeth 7a normally engaging teeth 8a on the driven member 8, which is splined to the shaft 6 and pressed by a spring 9. A ring 8b, having an enlarged opening 8k to enable it to be seated in a groove 8e of the member 8, slides on a stationary pin 3c and is actuated by linkage 10 - - 13 to declutch. A ring 14, secured by a spring-ring 7c on the member 7 and contacting frictionally therewith at the faces 14a, 7d, has stepped fingers 15, which lie in recesses 16 in the part 8 when the clutch is engaged. When, on declutching, the part 8 overruns, the ring 14 lags and each finger 15 comes into the position shown in Fig. 6, where, on release of the actuating-means, a ball 17, seating against a face 16b of the recess 16, obstructs a face 15b of the finger until, when the part 7 overtakes the part 8 and frictionally restores the ring 14, the spring 9 automatically engages the clutch without shock. Oil may be introduced between the faces 14a, 7d through a passage 37. The parts 15 - - 17 may be replaced by ballended struts 17a, Fig. 11, which, during overrunning coact by shoulders with the faces 8j, 14b of the parts 8, 14 to prevent clutch engagement, but collapse into recesses 8h, 14d when the member 7 overtakes. The ring 14 may be omitted, and the parts 7, 8 held apart or released by rollers or balls 20, Fig. 16, which lie either in the flattened shallow ends or the deep ends of recesses 21 in the part 8 according to the speed-relation of the parts. In a further modification, Figs. 18, 19, the balls 24 act also to transmit the drive, replacing the teeth 7a, 8a. On declutching, the balls ride, due to loss of momentum and to centrifugal force, up the slopes 26 of inclined recesses 25 to the flat shallow ends thereof, but when the member 7 overtakes, they roll down into part-spherical portions 28 of the recesses and also into complementary recesses 29 in the member 7, being subjected to shear under drive. To facilitate re-engagement of the claw-clutch teeth 7a, 8a when the part 7 is running slightly faster than the part 8, the meeting faces of the teeth may be bevelled (Figs. 31 to 33, not shown). A plate 43, Fig. 29, coacting with balls 41 and inclines 40a on additional fingers 40 on the ring 14, may be provided, so that, by reverse movement of the control levers, the plate 43 may be pressed in, the ring 14 restored, and the clutch re-engaged prior to synchronism. The bevelling of the clutch teeth prevents damage on such re-engagement, the driving-member being speeded up by a succession of impulses. Fig. 35 shows a form in which the ring 8b carries by lugs 8c a brake ring 18, held against rotation by engagement with the pin 3c. On a full stroke of the control levers 10, the ring 18 is applied to a " Ferodo " &c. facing 19 on the member 7 to arrest the shaft 5. Control gear is shown in Fig. 39. The link 13 connects an extension 2e of the main clutch pedal 2 to an arm 44, which has lost-motion connection 44b, 10b with the rock-shaft 11 carrying the levers 10 and a nose 10a. To change gear, pedal 2 is depressed to the position 2a, where the main clutch 1 is disengaged, a toe 44a on arm 44 striking the front face of a spring plunger 46 in a freelypivoted detent arm 45, so rocking this arm until, just as its lug 45a meets the nose 10a, the toe 44a escapes. Further depression of the pedal to the extreme position 2c takes up the lost motion and actuates the levers 10 to disengage clutch members 7, 8 and apply the brake 18, 19, the nose 10a restoring the detent 45. The gear lever 4 is now shifted, and, on release of the pedal, the brake is taken off, but, due to the balls 17 &c., the clutch 7, 8 does not reengage until the engine is sufficiently accelerated. During this operation, the toe 44a meets the under-face 46b of plunger 46, compresses its spring, and slips past. If ,during coasting, the engine stops and it is necessary to use the momentum of the car to restart it, the pedal is depressed to the position 2b. The toe 44a then strikes the plunger 46 and rocks the detent 45 and nose 10a, so operating plate 43 and balls 41 to shift the friction ring 14. By dwelling at the position 2a, the friction ring 14 will first speed up the declutched gear trains and reduce the shock of positive engagement at the position 2b. The emergency re-engagement may be effected by some abnormal movement of another control element, such as the accelerator or brake pedal or lever. The invention is applicable also to automatically-operated changespeed gears.