GB1444049A - Electric switches - Google Patents

Abstract

1444049 Mechanical switches SABASCHWARZWAELDER APPARATE - BAUANSTALT AUGUST SCHWER SOEHNE GmbH 19 March 1974 [4 May 1973] 12087/74 Heading H1N A retractive switch 1 can be actuated manually by a button (not shown) on the end of a push rod 11 or by a remotely controlled motor (not shown) which is geared to drive a cam plate 5 having a cam surface 6 to displace the movable contact 30 of a change-over set 29, 30, 31 for a predetermined operating phase of the motor, and said cam plate 5 having an eccentric crankpin 8 which engages an actuating member 9 mounted on the push rod 11 to displace it axially and thus actuate the switch 1, the motor being controlled by a thyristor in its circuit, and said change-over contact set ensuring that the motor is brought to maximum torque by connecting full supply voltage to it just before engagement between the crank-pin 8 and the actuating member 9. As shown the actuating member 9 is substantially rectangular and is coupled to push rod 11 by a spring 12 which is stronger than the internal restoring spring in switch 1 and allows for overtravel of member 9. The cam surface 6 extends over approximately 180 degrees so that the motor is maintained energized while push rod 11 moves to the right and back again. In its normal rest position contact 30 connects a thyristor (24, Fig. 4, not shown) in series with a resistor (25) and the motor (28) and also connects a resistor (27) in parallel with the motor such that, when the thyristor (24) is gated on, the motor runs at reduced voltage. When contact 30 moves to engage contact 31 it disconnects the parallel resistor (27) and replaces the thyristor (24) and series resistor (25) by a diode (26) thereby maintaining the motor at half-wave rectified full supply voltage.