GB963697A - Actuators for positioning a fluid flow control valve or other member in accordance with an electrical signal - Google Patents

Abstract

963, 697. Automatic flow control. FOXBOROYOXALL Ltd. May 19, 1961 [Feb. 19, 1960], No. 5982/60. Heading G3R. [Also in Division F2] An actuator comprises an electrically controlled coupling 3b which transmits a torque that varies in accordance with a variable electrical signal fed to the coupling. The input member of the coupling is connected to a constantly rotating electric motor and the output shaft 7b carries a lever arm 15 which positions a member 1b, such as a valve spindle, against a spring loading 12b. The electrical signal is fed to a coil 21 on an iron bar 22 which is pivoted at 23 and connected at one end by a spring 26 to the member 1b. The bar is mounted between two permanent magnets 24, 25 and carries a polepiece 28 located between limbs 29, 30 of a transformer. The transformer is connected by leads 35 to an amplifier 36, which includes a rectifier, and thence by leads 37 to the coupling 3b. In operation a small change in the current fed to :he coil 21 or in the position of the spindle 1b causes rotation of the rod 21 thereby altering the linkage between the primary winding 31 of the transformer and the secondary windings 33, 34. Such a change causes a comparatively large signal to be fed to the coupling to change the position of the spindle. Movement of the spindle also acts through the spring 26 in a direction to restore the movement of the bar 22 and hence a reduction of the signal. Such an arrangement overcomes initial forces of friction. Where the spindle is a valve spindle, the electrical signal may be provided in response to flow in a pipe in which the valve is mounted to maintain a constant flow. Specification 963,698 is referred to.