GB1037513A - Change speed gearboxes - Google Patents

Abstract

1,037,513. Ratchet clutches; change speed gear. S.S.S. PATENTS Ltd. March 5, 1963 [March 15, 1962; May 21, 1962], Nos. 10022/62 and 19524/62. Headings F2C and F2D. In a change speed gear wherein the lowest ratio is established by a synchro self-shifting clutch which comprises an intermediate member 12 (or 63) that moves along helical splines 11 on a clutch member 4 (or 61) to engage teeth 17 (or 68) on the intermediate member 12 (or 63) synchronously with teeth 8 (or 59) on a clutch ring 7 (or 58), and a pawl and ratchet mechanism 9, 19 or 69, between the intermediate member 12 (or 63) and clutch ring 7 (or 58) which initiates the helical movement, control means 26 (or 70) are provided to disengage the clutch for both directions of rotation and thus provide a neutral condition of the gear. As shown the gear, which is driven through a fluid coupling or torque converter, provides two ratios, the lower of which is established by engaging the above clutch whilst the higher ratio is established by engaging a synchro self-shifting clutch 31 ... 37 which is locked engaged by a servo 27<SP>1</SP> ... 29<SP>1</SP> operated locking mechanism 40 ... 47. In Figs. 1 and 2 the control means comprises a servo 27 ... 29 operated control sleeve 22 having splines 21 and teeth 23, 24 which respectively constantly engage splines 20 on the intermediate member 12 and co-act with teeth 15, 16 on a sleeve 14 fast with an output shaft 4. When the control sleeve 22 is in the neutral position shown, slow rotation of an input shaft 1 due to converter or coupling drag causes a ratchet wheel 10 of a second ratchet mechanism, which is directed oppositely to ratchet mechanism 9, 19, to ratchet overpawls 18 and for pawls 37 of the high speed clutch to ratchet over a ratchet wheel 33. To establish the low speed ratio the servo 27 ... 29 is energized to urge the control sleeve left, which movement is prevented by the teeth 23, 22 abutting the ends of the teeth 15, 16. An input brake 55 is energized and a servo 56 rotates the input shaft 1 backwards through a limited angle (e.g. 30 degrees) whereupon the ratchet mechanism 33, 37 engages the high speed clutch 32, 36 and the ratchet mechanism 10, 18 moves the intermediate member 12 helically left, its teeth 17 passing through the clutch teeth 8, until it abuts a stop 13 whereupon the pawls 19 engage the ratchet 9. The helical movement of the intermediate member 12 rotates the control sleeve 22 causing the teeth 23, 22 to engage, with lost motion, the teeth 15, 16. On release of the brake 55 forward rotation of the input shaft 1 disengages the high speed clutch 32, 36 and causes the ratchet mechanism 9, 19 to move the intermediate member 12 right until its teeth 17 engage the clutch ring teeth 8, the accompanying rotation of the control sleeve 22 takes up the lost motion and brings the teeth 23, 22, 15, 16 into driving engagement. For high ratio the servo 27<SP>1</SP> ... 29<SP>1</SP>is energized and on torque reversal, effected by accelerator release, the ratchet mechanism 33, 37 engages the clutch 32, 36 which is locked engaged. For a shift from low to neutral with the vehicle stationary the servo 27 ... 29 is actuated to urge the control sleeve 22 right, which movement is prevented until the toothed coupling 23, 22, 15, 16 and splines 20, 21 are relieved of torque by actuating the back-turning and brake means 55, 56. The ratchet mechanism 10, 18 may be replaced by sprig pressed plungers which urge the teeth 17 into light nuzzling end contact with the teeth 8. In Fig. 4 the control means comprises a servo-operated sleeve 61 which is splined on the output shaft 4 and has the intermediate member 63 helically splined thereon. Rightward movement of the control sleeve 70 completely disengages the clutch 59, 68. In a modification (not shown) the intermediate member is helically splined on the output shaft and the teeth on the clutch ring are axially movable to completely disengage the clutch.