Patent GB-1161581-A (GB)
Title: Power Shift Transmission
IPC: F16H3/16
Filed: 1966-12-16
Abstract: 1,161,581. Variable-ratio gears; ratchet clutches. MASSEY-FERGUSON Inc. 16 Dec., 1966 [23 Dec., 1965], No. 56340/66. Headings F2C and F2D. A transmission for heavy duty vehicles includes overrunning clutches providing ratio change without interruption of torque transmission. Overrunning clutches.-Each ratchet clutch comprises facial ratchet teeth 261 on an axially fixed member 223 engageable by ratchet teeth 265 formed on a piston 263 splined to a shaft 257 or alternatively splined to a cylinder 225 fast with the shaft. The teeth are shaped so as to disengage against the pressure of a spring 267 when the piston 263 is driven faster than the member 223. The clutch may be locked, to inhibit overrunning, by supplying fluid pressure to a chamber 272. If the teeth are disengaged the lock is disabled since an exhaust path provided by a port 273 in the piston and a port 275 in the cylinder is open. When the teeth are engaged a land 276 on the piston 263 blocks the relief port 275 so that pressure can build up behind the piston to prevent disengagement of the teeth. Transmission.-A transmission providing six forward and three reverse ratios comprises a three speed constant-mesh gear incorporating two ratchet clutches in series with a two speed and reverse constant-mesh gear having one ratchet clutch. An input shaft 205 is connected by a clutch 203 to an engine and power take off shaft 201. A gear-wheel 207 is fast with the input shaft 205, and gear-wheels 213, 217 are selectively clutchable to this shaft by fluid pressure operated friction clutches A, B. The gear-wheels respectively mesh gears 228, 223, 225, the gear 225 being fast on a shaft 227 and the gears 223, 228 being connectible thereto by ratchet clutches E, D. The two-speed and reverse gear comprises gears 229, 253 fast with the shaft 227, and a gear 237 connectible thereto by a fluid pressure operated friction clutch C. The gear 229 meshes a gear 231 connected to a shaft 235 by a ratchet clutch F, gear 237 meshes a gear 233 fast on the shaft 235, and the gear 253 meshes a reverse idler 251. An output shaft 239 is clutchable to the shaft 235 by a positive clutch 243, 245 for forward drive, and a reverse gear 242 which meshes the idler 251 is clutched to the output shaft by a positive clutch 243, 247 for reverse drive. The clutches A-F are controlled by pilot operated valves H, I, J controlled by a sixposition valve G which selectively supplies pilot pressure 305 thereto. Pilot pressure 305 is derived from a pump 301 by way of a reducing valve 303. The pump supplies servo pressure 302 to the valves H-J which selectively supply this pressure to the clutches. The bi-directional looking of the selected ratchet clutches D-F provides engine braking in all ratios. The transmission has an inherent hill holding feature. With a friction clutch engaged and the vehicle pulling up a hill, if the main clutch is disengaged the vehicle will come to a stop and hold its position since a ratchet clutch will engage and the output shaft be connected by two different ratio trains to the transmission input shaft. Reference has been directed by the Comptroller to Specification 1,105,443.