Patent GB-735950-A (GB)
Title: Improvements in or relating to gear systems
IPC: F16H3/08
Filed: 1953-01-29
Abstract: 735,950. Change-speed gearing. MACDONALD, J. S. Jan. 21, 1954 [Jan. 29, 1953; Sept. 10, 1953], Nos. 2597/53 and 25084/53. Class 80(2). In a constant-mesh fourspeed gear, with a countershaft 8 constantly geared at 9, 12 to the driven shaft 3 and carrying loose gears 43 ...46 meshing with gears 34 ... 37 fast on a driving-shaft 2, each gear 43 ... 46 has axial and helical splines adapted to be engaged selectively, through a pair of slidable sleeves 47- 48, 49-50, 51-52, or 53-54 splined internally and externally, with axial and helical splines 41, 42 on countershaft 8, which latter is movable axially. The arrangement is such that, with one gear, say 44, operative, the axial splines of that gear 44 are engaged with the axial splines on shaft 8 through sleeve 49, and, to effect a gear change by a lever 106 operated manually or by a governor, the helical splines of that gear 44 are engaged by moving sleeve 50, sleeve 49 is disengaged, shaft 8 is moved axially so that, due to the helical engagement, shaft 8 is synchronized with the next gear 43 or 45, whereupon the axial splines of said next gear 43 or 45 are engaged by moving sleeve 47 or 51 and the helical splines of gear 44 are disengaged by moving sleeve 50. When the top gear ratio is unity, sleeve 53 may, as shown, be splined on shaft 2 and engageable with splines in gear 12 so as to give direct drive. During a gear change, shaft 8 performs one reciprocation to the right and back, and in an up change synchronization is effected during the movement to the right, the return movement being idle, while in a, down change the rightward movement is idle and synchronization is effected during the return movement. A crosshead 86, movable longitudinally on guide rods 87, carries a cross-slide 100 formed with two half-nuts 104, 105 engageable with a pair of screwed spindles 98, 99 constantly rotated in opposite directions from shaft 2. The transverse movement of slide 100 is effected by lever 106 fast on a spindle 107 formed with a longitudinal rib 108 engaging between a pair of projections 109 on slide 100, lever 106 being normally held central by opposing springs 110 and being movable up or down, for up or down gear changes, so as to engage nut 105 or 104 with spindle 99 or 98 and thus cause cross-head 86 to move right or left. Slide 100 and lever 106 are maintained in position throughout the gear change by a projection 118 on slide 100 cooperating with a gapped guide rail 111. During the downward or upward movement of slide 100, toothed racks thereon turn spindles 144, 145 in the cross-head 86, which spindles engage racks on pins 85, 88, 89, 90 so that, during an up change, pins 85, 89 are projected to operate on the top faces of rockers 82 on spindles 79 to which are secured forks 78 controlling the sleeves 47 ... 54, while, during a down change, pins 88, 90 are projected to operate on the bottom faces of the rockers. Similarly, one or other of two pins 119, 120 is projected from the cross-head to engage an undulating slot 121 in a spindle 122 connected by linkage 123, 124, 125 to a spindle 126 having a rib engaging a slot in a ring 129 encircling a yoke 64, which latter is loose on shaft 8 between collars 66 and in which are journalled inclined rollers 76. The latter are adapted to be pressed inwards selectively, by forks 133 controlled by cam slots 130, 131 in the ring 129, into engagement with helically-grooved spindles 67, 68 geared at 70 to, gear 9 and passing through the yoke 64, the pitch of the helical grooves increasing progressively from zero at one end to a maximum and then decreasing rapidly to zero at the other end, the grooves of the two sets being of opposite hand. This arrangement is such that, as the cross-head moves during a gear change, spindle 122 is turned in the appropriate direction and, through the forks 133, causes rollers 76 first to engage spindles 67 to move shaft 8 to the right and then to engage spindles 68 to return shaft 8 to the left. The direct-gear spindle 76 is connected to the fork controlling sleeve 53 by linkage 150, 151, 152. Means may be provided for moving cross-head 86 to an extreme left position in which all the sleeves 47 ... 54 are disengaged, giving neutral. Gear 34 may be splined on shaft 2 so that it may be moved out of mesh with gear 43 and a reverse train 147, 148 engaged. The movement of the cross-head 86 may also be arranged to control the engine output during a gear change.