GB578816A - Improvements in electrical means for regulating the amplitude of vibratory motion - Google Patents

Abstract

578,816. Automatic control systems. JENNINGS, R. E., and FOSTER TRANSFORMERS & SWITCHGEAR, Ltd. April 19, 1944, No. 7205. [Class 38 (iv)] Amplitude of vibration.-In an automatic control system the amplitude of an electric motor-driven vibrator is maintained constant in accordance with the direction of rotation of a secondary electric motor, which is driven in alternate directions according to the increase or decrease in amplitude in relation to a predetermined value thereof, through a vibrating member arranged to control a circuit, in which a direct current bias is imposed upon an alternating current voltage, controlling a thermionic valve by the action of which other thermionic valves control the direction of rotation of the secondary motor and the speed of the main motor. The vibration of a member C, consisting, for example, of a flexible member fitted to the vibrator and adapted to make contact at the end of its travel with a fixed contact, produces a direct current voltage across a resistance R2, the mean value of which depends upon the closed and open periods of contact, such voltage being smoothed and applied across a condenser C3 to be opposed by an adjustable voltage across a resistance R1 and supplied in series with an alternating current voltage from a winding W2 to control the grid potential of a gas-filled relay valve V1. The anode of the valve Vl is supplied through a thermal switch S1 to cause a short delay at starting until the valve filaments are heated. The valve V1 will pass current when the direct current negative grid bias component is reduced due to prolonged duration of contact of the controlling switch which causes an increased voltage across the condenser C3. The condition of the anode circuit of the valve Vl is used to control the working of two other gasfilled relay valves V2 and V3, which are arranged so that if the valve V1 does not fire, the valve V2 passes current through a load M, representing the secondary motor, and if the valve V1 does pass current a negative bias is applied to the grid of the valve V2 to prevent that valve from firing. To prevent the valve V3 from firing when the valve V2 passes current, a resistance R8 is used to produce a voltage drop between the cathode and grid of the valve V3. When the valve V2 does not fire. the grid of the valve V3 is at zero potential, so that current passes through the load in the opposite sense to that previously obtaining.