Patent GB-455083-A (GB)
Title: Improvements in or relating to variable speed gearing
IPC: F16H61/02
Filed: 1935-01-09
Abstract: 455,083. Variable-speed gearing. ASPINWALL, R. B., 3659, Oakman Boulevard, Detroit, Michigan, U.S.A. Jan. 9, 1935, No. 729. [Class 80 (ii)] [See also Group XXIX] A fluid-controlled variablespeed gear comprises two cooperating valves, one of which is movable by an automatic speed governor to cause displacement of the other into positions corresponding to the different gear ratios, the movement of the second valve being subject, when desired, to the action of an over-riding control, such as an escapement which is operated whenever the accelerator pedal is released. A servomotor operated by engine suction may over-ride the governor so as to change down when the load increases. In the form shown as applied to a motor vehicle, low speed is transmitted from the driving shaft 11 through countershaft 13, gears 23, 36 and freewheel clutch 37 to the driven shaft 12. Second speed is obtained through gears 22, 35 and a friction clutch 50 mounted between the hub 53 of the gear 35 and a casing 46 carried by a flange 45 on the driven shaft 12, while the clutch 37 overruns. To obtain direct drive, a friction clutch 51 is engaged, which is situated between the end 11<a> of the driving shaft 11 and the casing 46, the clutch 50 being disengaged. The freewheel clutch 32 incorporated in the gear 22 avoids wear of the clutch plates 50 due to relative rotation in top gear. The clutches 50, 51 are actuated by pistons 160, 161, acting in cylinders 162, 163, which may be supplied with pressure oil through passages 166, 168 in the shaft 12. Oil is compressed during forward rotation of the shaft 12 by a gear pump 75 constantly driven therefrom through gears 70, 71. The distributing valve mechanism, Fig. 5, controlling the actuation of the clutches 50, 51 is controlled (1) according to the speed of the driven shaft by a centrifugal governor 92 driven from the shaft 12 through the gear-pump shaft 85 ; (2) during forward running only by an overriding engine-suction-actuated servomotor 220, whose movements are thus a measure of the load on the driven shaft in relation to the throttle opening ; and if desired (3) by an escapement device which over-rides the two previous controls and is such that gear change in the upward direction takes place only when the accelerator pedal 213 is momentarily released. The rod 94 of the governor 92 acts on a bell-crank lever 100 which actuates the pilot valve 110 of the valve mechanism. Engine suction is applied through a reservoir 227 below the servomotor piston 221, which is thus normally drawn downwards to the position shown against the action of a spring 225. If, however, the throttle is opened wide when the load on the driven shaft is considerable, the engine vacuum falls and the piston 221 is raised by the spring 225, thus lifting a lever 223, Fig. 3, on the piston rod 222 so as to move the lever 100 to, or keep it in, the low gear position. When the handle 193 is in the " forward " position shown, and the engine is inoperative, the motor spring 225 keeps the valve 110 in low gear position and the clutch 37 permits the shaft 12 to freewheel, so that the vehicle can be pushed along by hand. If the hand control 193 is moved to engage notch 195, a rod 191 is shot to the right by a Bowden cable 192. The rod 191 carries a fork 190 engaging the gear 36, which together with its freewheel clutch 37 is slid to the right along the splined part 39 of the shaft 12 out of engagement with the gear 23. At the same time a pin 231 on the rod 191 rocks the lever 223 out of engagement with the lever 100, so that the servomotor is inoperative. The vehicle may, however, be started, by towing it at the high speed, which brings in the clutch 51 If the hand control 193 is moved further to the notch 194<a>, the gear 36 is moved into engagement with the reverse idler 33, the pump 75 being then inoperative. Valve operation. The gear pump 75 delivers oil under pressure through the passages 102 103 to the chamber 115 of the pilot valve 110, which in Fig. 5 is shown in the low gear position in which neither of the clutches 50, 51 are engaged. Pressure fluid passes from the chamber 115 through passage 120 to the chamber 105 of the main distributing valve 125. Fluid also passes (1) through the internal passage 118 and chamber 117 in the valve 110 and through passage 121 to the chamber 129 in the valve 125 ; and (2) through the passage 130 in the valve 125 to the chamber 126. The valve 110 is therefore in equilibrium under fluid pressure, and the valve 125 is held to the left. For second speed, the valve 110 is shifted to the right until chamber 117 comes opposite the port 122, thus admitting pressure to the piston 138, which slides to the right in the cylinder formed by the plugs 133, 139 and carries the stem 135 of the valve 125 with it. The chamber 126 is thus brought into registry with the port 178, and pressure fluid supplied through passage 176, Fig. 1, to operate clutch 50. For top speed, the valve 110 is shifted further to the right, so that its chamber 117 registers with a port 123 and supplies fluid to the piston 136, which then pulls valve 125 still further to the right, so that its chamber 126 supplies fluid through port 179 and passages 177, 168 to clutch 51. Escapement. The accelerator pedal 213 is connected through a rod 212, and lever 211 to a shaft 205, Fig. 3, which carries a projection 207 acting on a pair of spring connected arms 203, 204 with ratchet ends engaging grooves 201, 202 in the main distributing valve 125. The lever 203 is slightly longer than 204, so that if, in the position shown in Fig. 1, the pedal 213 is depressed, 204 is disengaged and 203 engaged. Gear change does not now take place as soon as the valve 110 moves to second gear position, but does so when the pedal 213 is released, when the arm 204 slips into notch 201 in valve 125. On again accelerating, arm 203 replaces arm 204 in notch 201, and on again releasing the pedal 213 the valve 125 is permitted to move into the top gear position. The escapement may be put out of action by shifting shaft 205 bodily laterally by a manual control 237.