| 摘要 |
880,128. Change-speed control; clutches. HURTH, H., HURTH, F., and HURTH, L. Sept. 24, 1959 [Oct. 18, 1958], No. 32483/59. Class 80 (2). Change-speed gearing includes a two-speed constant-mesh gear having the ratios introduced by hydraulically engaged friction clutches 18, 20 under the control of a distributing valve 41, the low ratio clutch 28 being formed as an over-running clutch, and the valve 41 in an intermediate position supplying liquid to engage both clutches so there is no interruption of drive during change from low to high gear. Constant-mesh gear.-A gear 12 is fast on a driving shaft 10 and meshes a gear 25 on an intermediate shaft 24 clutchable to a gear 26 fast on an output shaft by the clutch 28. Gear 26 meshes a gear 13 connectable to the input shaft by the clutch 18. A second constant mesh gear may be in series with the first as shown in dotted lines in Fig. 1. Clutches.-The clutches are of the multi-disc type and are engaged by hydraulic pressure in a chamber 21 or 37 of a moving cylinder 20 or 36 co-operating with a stationary piston formed on the input shaft of the clutch. The clutches are disengaged by springs 22, 38. Clutch 28 has plates 30 splined to a casing 29 fast with the gear 26 and plates 31 splined to a sleeve 32 having a reversible screw-threaded connection with the intermediate shaft 24. The sleeve 32 is spring-loaded to the left so that the clutch can be engaged by hydraulic pressure, but when the clutch 18 is engaged the sleeve screws along the intermediate shaft so that the clutch 28 disengages. Control.-Hydraulic pressure is provided by a pump 51 supplying liquid through a solenoidoperated pilot valve 48 to the valve 41 loaded by a spring 43 to the position shown in which liquid is supplied to the chamber 37 to engage clutch 28 for low gear. A pilot valve 60 is actuable by a solenoid to a position in which liquid is supplied through an adjustable throttle 54 to a valve chamber 73 to move the valve spool to its uppermost position in which chamber 21 is pressurized to engage clutch 18 and chamber 37 is exhausted to disengage clutch 28. During movement of the valve spool between its end positions both chambers 21, 37 are open to pressure so that both clutches are engaged and clutch 28 over-runs. A switch 70 is closed to actuate the pilot valve 48 and switches 70, 71 are closed to actuate the valve 60. If the equipment being driven is stopped, e.g. due to current failure, with the control switches 70, 71 left in the high gear position, the valve 41 will be moved to its lowest position since the pump 51 is stopped; on restarting, the valve 41 will remain in this position until the pressure has built up sufficiently to actuate the valve 41. Low gear is thus engaged initially so that the engine is unlikely to stall. In a modification the pilot valves are controlled by a cam. |
