| 摘要 |
<p>1446949 Valves SULZER BROS Ltd 24 Sept 1973 [22 Sept 1972] 44634/73 Heading F2V A valve comprises an inlet 13, outlet 14 and a valve member 16 biased to the open position by springs 32 and driven to the closed position by an electric motor 30 through a pair of gears 28, 29 and a threaded spindle 26. The electric motor is supplied with current by a circuit 35 in which is a switch 36 actuated in response to fluid pressure. If the fluid pressure exceeds a predetermined value the switch is actuated by a pressure-sensitive device 11 which breaks the supply circuit of the motor 30 and puts it in shunt with a resistor 40. Thereafter the springs 32 drive the valve member to the fully open position with the spindle 26 acting as a worm drive and the motor damping the motion. In an alternative embodiment (Fig. 5, not shown) an electromagnetic clutch is incorporated between the motor and gear drive, and the pressure switch serves to disconnect the clutch when fluid pressure rises above a predetermined value. The pressure switch may take the form of three sensors (11<SP>1</SP>) any two of which, when registering an over-pressure, serve to actuate the switch. In a further embodiment (Fig. 6, not shown), the motor is provided with an electromagnetic brake which is released during normal operation of the motor and when the control pressure exceeds the predetermined value.</p> |
