Patent GB-615175-A (GB)
Title: Improvements in variable speed power transmission
IPC: F16D67/00
Filed: 1946-07-31
Abstract: 615,175. Change-speed gearing ; clutches. FORD MOTOR CO., Ltd. July 31, 1946, No. 22806. Convention date, Aug. 22, 1945. [Class 80 (ii)] A change speed gear drives at low speed through a hydraulic coupling, a first intermediate shaft and gearing of one ratio, while at higher speeds the gearing is automatically changed to render the hydraulic coupling inoperative and the drive is transmitted through a mechanical coupling, a second intermediate shaft and gearing of another ratio, to the output shaft. The impeller 18 of a Fottinger type fluid coupling is directly connected to an engine crankshaft 16 and is connected through resilient means 44 and splines 42 to the drum 46 of a second speed clutch 40. The runner 23 of the coupling is connected to a main shaft 29 through a one-way clutch 34. Coaxial with the main shaft is a clutch carrier 52 splined at 53 to a clutch sleeve 49 which is rotatable on the main shaft and carries on its outer periphery a sleeve valve 51. This sleeve valve is moved axially against two springs 57, 58, which become operative at different positions of the valve, by centrifugal weights 178 acting through bell crank levers 181. The clutch carrier 52 houses a plurality of pistons 86 in cylinders 79, 80, which selectively overcome the release springs 94 and engage the plates of the friction clutches 40, 50 which connect the drum 46 with the carrier 52, and the carrier 52 with the drum 107 rigid with a planet carrier 99, respectively. The valve 51, carrier 52 and sleeve 49 are ported to allow oil to drain from the cylinders when the valve is in the extreme rearward poistion ; to allow pressure oil from duct 62 to reach the cylinders 40 when the valve is in an intermediate position, and to allow oil to reach both sets of cylinders when the valve is in the extreme forward position. This pressure oil is supplied from the sump through a duct 159 leading to the inlet 126 of a pump 124 having a delivery. 127 connected with the duct 62. A passage 176 (Fig. 11) leads from the delivery to a valve 165 in communication with a metering bleed 174 and with a passage 177 which feeds oil through the tube 73 and passage 68 to the third speed cavity 60. The valve 165 is operated at substantially full travel of the throttle control to shut off the oil supply to the third speed clutch and thereby cause the engagement of second speed, this may also be done by an overriding manual control. The planet carrier 99 is in two parts and carries spindles 111 on which are freely rotatably mounted clusters of three planet gears 104, 105, 106 which are rigid with each other and mesh respectively with teeth on the sleeve 49 the main shaft 29 and the gear 103 rigid with the output shaft 64 which also drives the pump 124. The planet carrier is in oneway clutch connection through the clutch 116 with a brake drum having a forward drive brake 119, a similar reverse drive brake 96 being fitted round the outer drum of the clutch carrier 52. The two brakes, which are similar, comprise a pair of metal bands having several wraps round the drum and anchored at the ends 100 to the casing 12, the other ends have projections 148 engaged by spring-pressed levers 146 operated through a manually controlled camshaft 129 having cams 134, 135 for reverse and forward and a detent plate 143. The reverse lever spring 149 is acted upon by a piston 154 mounted in a cylinder 152 connected with the oil pump by a pipe 153, which prevents the engagement of reverse by counteracting the spring while the final drive shaft is rotating in the forward direction. In operation, low speed is obtained by the drive from the impeller passing to the runner 23 and thence to the main shaft 29 through a one-way clutch 25, at low rotational speeds the spring 57 holds the valve 51 in the rear position so that neither clutch 40 nor 50 is engaged, and the drive is therefore through sun gear 102, planets 105, 106 and driven sun 103, the carrier 99 being being held against backward rotation by the one way clutch 116 and forward brake 119. For reverse, the camshaft 129 is rotated manually to allow the cam 135 to disengage the brake 119, and allow the cam 134 to cause engagement of the brake 96 providing oil pressure generated by forward motion of the vehicle is not acting against the spring 149. This results in the drive passing through the hydraulic coupling to the main shaft 29, to sun gear 102, planets 105, 106 and driven sun 103, the planet carrier rotating to produce the reverse drive by virtue of the rigid reaction sun gear sleeve 49. For second gear, as forward speed increases, the centrifugal force on the weights 178 overcomes the resistance of the spring 57 and the valve 51 moves to a midposition to pass pressure oil from duct 62 to the cylinders of the clutch 50 which engages and transmits the drive directly to the sun gear sleeve 49, thence through planets 104, 106 and driven sun 103, the planet carrier being held against negative rotation by the brake 119. For third speed, the centrifugal force on the weight 178 overcomes both springs 57 and 58 and forces the valve 51 to the extreme forward position, thus allowing oil to pass to both clutches 40, 50, which locks the sun gear sleeve 49 and planet carrier 99 together to give a direct drive. To prevent immediate downward change on slight speed variations, a cushion of oil is built up behind the valve 51 through a metering leak hole. For neutral, both the forward and reverse brakes 119, 96 and the two clutches 40, 50 are released, and the centrifugal force released anti-drag brake 205 locks the clutch carrier 52 with the planet carrier 99 to prevent creep of the vehicle due to the hydraulic coupling.