Patent GB-712231-A (GB)
Title: Improvements in or relating to hydraulic power transmissions
IPC: F16H61/14
Filed: 1949-07-21
Abstract: 712,231. Variable-speed gear; clutch combinations. AKTIEBOLAGET LJUNGSTROMS ANGTURBIN. July 21, 1949 [July 22, 1948], No. 19211/49. Class 80 (2) [Also in Group XXIX] In a power transmission device comprising a hydraulic variable-speed torque converter having a liquid-filled working chamber 24, a mechanical coupling 72 ,engageable between, the driving member 16 and the driven member 28, a servomotor 80 actuated by pressure liquid for providing engagement of the mechanical coupling. between the primary member 26 and the secondary member 36 of the hydraulic torque converter, and a liquid pump 152, a valve and conduit system for liquid under pressure consists of a main valve 168 distributing pressure liquid either to the working chamber 24 of the hydraulic torque converter or to the servomotor 80 of the mechanical coupling and alternatively opening the discharge from the other thereof and at least one throttling device 198 located between the liquid conduit to the servomotor and the conduit to the working chamber of the hydraulic torque converter or to a chamber communicating with said working chamber. The mechanical coupling 72 between the driving member 20 and the turbine shaft 28 is actuated by the servomotor 80 to provide direct drive. The turbine member 28 has a gear 86 engaging a gear 88 on a shaft 90 carrying a gear 92. A ring 104, shown in its neutral position in Fig. 1, may be moved to the left by a lever 110, post 112, and yoke 114 to engage the gear 86 thereby establishing forward drive between the turbine member and the tail shaft 94. Movement of the ring 104 to the right causes it to mesh with an idler gear driven by the gear 92, so that reverse drive to the tail shaft is effected. A normally open clutch 116 between the turbine member and the tail shaft is closed by a member 122 actuated by liquid supplied through a normally closed valve 124. During the period the lever 110 is moved from neutral to a drive position it moves a plate 128 and ring 126 to open the valve 124 to admit liquid to engage the clutch, thereby synchronising the turbine member and the tail shaft. Liquid is supplied by the pump 152 through a valve 164 at a pressure governed by a high-pressure relief valve 180. When the valve member, 168 is in the hydraulic drive. position shown in the Figures the liquid flows via a conduit 172, chamber 182, channels 186, and ports 190 and 192 into the working chamber 24 of the converter, at the same time passing through the housing 32 and ports 194 into the clutch 72 to disengage the plates. There is a leakage past a sealing ring 198, which acts as a throttling member, this leakage flowing to a chamber 200, bores 204 and 206, groove 208 and conduits 170 and 176, back to the sump. The desired pressure differential in the system is maintained by a low-pressure. relief valve 178. When the valve member 168 is moved to the right direct drive is obtained since liquid is then supplied from conduits 162 and 170 to bore 204, chamber 200, and bores 202 to the plate 80 to engage the. clutch 72. Leakage occurs from the chamber 200 past the seal 198 into the conduits 172 and 174, the desired minimum pressure of the leakage liquid being maintained by the valve 178 which also prevents the working space 24 being emptied and maintains a desired static pressure therein. The position of the valve member 168 is controlled by a lever 214, Fig. 2, which is urged by a spring 222 to move the member to the direct drive position. The yoke 114 attached to the reversing lever 110 has an extension which engages one arm of a lever 230 in such a manner that the other arm 230b provides a stop for the portion 220b of the lever 214 when reversing lever 230 is set at neutral or reverse drive, but retracts the stop when the latter lever is set for forward drive, thus ensuring hydraulic drive only when the lever 110 is at neutral or reverse and that direct mechanical drive cannot be obtained unless the lever is set for forward drive. The shaft 50 of the reaction member of the converter provides the inner race of a freewheel clutch having elements 58, the outer race 64 having teeth 66 adapted to engage teeth 60 on the stationary housing member. A rod 68 mounted in the housing is actuated by an abutment 70 on the outer race 64. With the lever 110 at forward drive, the impeller and turbine of the converter rotate counter clockwise as indicated by arrow 254, and at low speeds reaction torque will be applied to the reaction member so that members 62 and 68 will be actuated to move lever 214 clockwise against the spring 222 thus holding the valve 168 in the hydraulic drive position even though it is free to move outwards as far as the stop 230b is concerned. As the turbine speed increases so that torque multiplication is reduced, the torque reaction on the reaction member decreases and the rod 68 4s no longer able to prevent the spring 222 from rotating the lever 214, with the result that the valve 168 is automatically moved to effect direct drive. A manually controllable overrule mechanism is provided comprising a lever 234 actuating a member 236 normally held in position by a spring-loaded pin 244. The member 236 has an arm 236b, which is located in a slot 248 in the lever 214 in such a manner that when the overrule lever 234 is in its neutral position the freedom of movement of the lever 214 under the influence of the automatic control is unaffected. The overrule lever may be rotated in one direction to positively lock the lever 214 to hold the valve 168 set for hydraulic drive. When the overrule lever is rotated in the other direction the arm 236b engages a spring-loaded pin in the slot 248, to turn the lever 214 against the resistance of the rod 68. Consequently, depending upon the strength of the spring in relation to the reaction resistance exerted through the rod 68, the overrule shift to direct drive may be effective or ineffective. An electric switch 256 is provided so that when changing from hydraulic to direct drive, the upper limb of lever 214 momentarily closes an electrical circuit to provide an impulse which is used to decrease the engine speed, thereby diminishing the surge in the operation of the mechanism which may occur at the change over.