636,108. Hydromechanical. variable-speed gearing; friction and ratchet clutches. BORG-WARNER CORPORATION. Feb. 26, 1946, No. 5956. Convention date, Aug. 15, 1942. [Class 80 (ii)] Means for facilitating the engagement and disengagement of positive clutches in a motor vehicle variable-speed gearing following a hydrodynamic or other slipable power transmitting device comprises means under the control of the engine throttle for rotating the driven shaft of the slipable device reversely when the engine is idling so as to break, as by reverse rotation of the driving member of an interposed freewheel clutch, the power train between the device and the gearing. As shown, the hollow driving shaft 17, Fig. 1, of a three-speed and reverse counter shaft gear is powered from an input shaft 12, either through a hydraulic torque converter whose pump 21 and turbine 26 are connected to the shafts 12, 17 respectively, or directly through a hydraulically-operated friction clutch 37 whose combined piston and presser plate 33 is actuated through conduits 39, 38 and 32'. The converter is of the type having a reactor 28 held by a one-way detent 30 against backwards rotation only. Unitary countershaft gears 51, 52, powered from the shaft 17 by a gear pair 46, 47, mesh directly and through an idler (not shown) respectively with gears 57, 65 alternatively clutchable to the driven shaft 13 by a double positive .clutch element 62 to give indirect forward and reverse drives. The gear 47 drives the gear cluster 51, 52 through a one-way roller clutch 53 having a slidable positive locking member 56. Two forward speeds are available through the gears 46, 47, 51, 57 according to whether the clutch 37 is disengaged or engaged. A direct drive between the shafts 12, 13 is also provided, when the gear 57 is clutched to the shaft 13, by a positive clutch member 61 slidably splined on an axial extension 58 of the gear and engageable with teeth 60 on the end of a central shaft 16 connected to the shaft 12 by a circumferentially sprung coupling 41, the clutch 53 overrunning. A hydraulically-operated multiplate friction clutch 73 has outer and inner discs splined respectively to an extension 48 of the gear 47 and to a shaft 71 driven reversely to the gear 47 from the converter pump 21 by an idler train 20, 77, 76. Engagement of the clutch 73 causes the gear 47 and turbine 26 to rotate backwards, freeing the gear cluster 51, 52 from driving torque, and facilitating engagement and disengagement of the clutch member 62. Fluid acting through conduits 75, 74 on the combined presser plate and piston 70 of the clutch 73 is controlled by a solenoid valve 94, Fig. 2, having an armature 91 slidable against spring pressure on energization of the solenoid to change the connection of a conduit 96, in communication with the conduit 75, from a supply pipe 95 to an exhaust pipe 97 and so to disengage the clutch 73. The solenoid comprises a holding coil 88 and an operating coil 89 cut out by an armature-actuated switch 90, and is in circuit with an earthed battery 82 via a switch 85 closed by energization of a relay 83 also connecting the battery 82 to earth trough switches 78 ... 81 in parallel. These switches comprise a manual test switch 78, a switch 79 closed when the member 56 is engaged to lock the clutch 53, a switch 80 closed by a vehicle speed governor 86 when the vehicle is moving above 5 m.p.h., and a switch 81 closed when the vehicle accelerator 87 is depressed from the engine idling position. The clutch 73 is thus held disengaged during normal running of the vehicle and is only engaged when the vehicle is at rest or moving below 5 m.p.h., with engine idling and the freewheel 53 operative. In the event of an electrical breakdown, a mechanical interlock between the control lever 98 of the clutch member 62 and two pins 100 on the end of the armature 91 is rendered operative by rotating the armature through an arm 101 thereon to bring the pins from a normal position out of the plane of the lever 98 into the plane as shown. Operation of the lever 98 in either direction will then disengage the clutch 73 mechanically.