GB714912A - Improvements in electro-mechanism for following a moving body which moves within given limits - Google Patents

Abstract

714,912. Electric follow-up systems. LEBAR, M. L. May 22, 1950 [May 23, 1949], No. 12765/50. Class 40 (1). The control or the follower member of a follow-up switch has an auxiliary member pivoted thereto for' limited movement, and biassed in a direction tending to close two switches located between the auxiliary member and the control or follower member. Both switches are closed at coincidence and are opened selectively to control the follow-up motor according to the sense of the control member movement. A further contact is provided for slowing down the motor as coincidence is approached. As shown, a balance beam 1, Fig. 2, pivoted at 9 carries a pintle 3 whose axis intersects the axis of the pivots 9. Rotatably mounted on the pintle axis is a conducting plate 2 which in the position of balance shown, contacts with both contacts 11, 12 of a follower mechanism 13. Movement of the beam in either direction e.g., from position A, Fig. 1, to positions B or C causes anti-clockwise rotation of the plate 2 and opening of contacts 11 or 12 according to the direction of movement of the beam. The contacts 11, 12 when normally closed bias corresponding triodes 21, 22, Fig. 3, to cut-off. Opening of one of these contacts causes the corresponding triode to conduct and operate associated relay pairs 31, 34 or 32, 33 to drive the follow-up .motor 17 in the corrective sense, the motor moving the follow-up beam 13 along guides 14, 15 through a screw 16. The beam 1 carries a further auxiliary contact lever 6 urged by a spring 8 into contact with the plate 2 at 7. The lever 6 tends to follow any angular displacement of the plate 2 but adjustable stops 4, 18 limit its displacement to a small value, so that for any larger displacement of the plate 2, the auxiliary contacts 7 open. This permits a normally blocked triode 23, Fig. 3, to conduct thereby energising a relay 33 to speed up the servomotor 17 by short circuiting a resistor 36 in the circuit thereof. Similarly the motor is slowed down as coincidence is approached by closure of contacts 7. The motor may actuate a weight indicator. The follow-up mechanism may alternatively be applied to a steelyard in which case the "follower" contacts control the counterweight.