Patent GB-191417567-A (GB)
Title: Improvements in Mechanism for Controlling Movement at a Distance Electrically.
Filed: 1914-07-24
Granted: 1915-02-11
Abstract: 17,567. HarlÚ et Cie. July 28, 1913, [Convention date]. Systems for controlling travel for a fixed distance or number of revolutions.-Relates to apparatus of the kind in which the controlling-member varies the resistance in two arms of a Wheatstone bridge, and a relay in the bridge arm controls the circuit of a motor which drives the controlled member over two similar arms until the bridge balance is restored. In order to avoid changes in the direction of the current in the bridge arm as the controlling member moves over the end of one arm of the bridge, two or more bridges are provided, and each bridge is cut out of action before the controlling-member reaches the end of its resist ance arm. A similar arrangement may be provided for obtaining greater accuracy of working. In the form shown in Fig. 2, the controlling-member a moves over the resistances of two bridges, one comprising parts of the resistance c1 and the resistances d, d1, and the other comprising the parts of the resistance c<1>1 and the resistances d<1>, d1. The controlled member g moves similarly in relation to the other resistance arms of the two bridges and is driven by a motor h which is controlled by the relays i in the bridge arms j, j<1>. In order to avoid the change of direction of current in the bridge arm that would be caused as the switch member b passed over the corresponding points in its resistance ring. the contact bars r, r<1> at the controlled station are arranged not to extend through a complete circle so that each bridge is cut out when the controlling-member reaches a critical point on it. The movement is at these times controlled by the bridge that is not broken. In modified forms, only one relay i is provided, but each bridge is connected to one winding on it. In other forms, the resistances c1, c<1>1 are semicircular in shape, but the controlling-member a is provided with four arms. In one form, only one resistance ring c1 is provided for two bridge systems, and in another form, three bridge systems are used. The bridges may also be placed out of action by means of circuits which are controlled by switches actuated by the controlling and controlled members, as they pass through critical positions. The arrangement shown in Fig. 8 is designed to give great accuracy of movement. The controlling-arm a is connected to the handle a<1> in such a way that this makes several turns while the arm a makes one turn. The controlled bars q, y' are similarly connected, and three bridge wires j, j<1>, j<1>1, are used. When the angle between the members a, g is small, the current in the bridge arm j is not sufficient to actuate the relay i, but a larger angle exists between the members b<1>, g<1> and the motor h is connected into circuit through the relay i2. When the members a, g are at a larger angle and the relay i is energized, the relay z opens the bridge wires j1, j<1>1 thus preventing the reversal effect that might arise if the members a', g<1> were at a large angle to each other. In another form, the controlling-member drives two other arms, the third arm rotating still more rapidly than the second. Relays similar to relay z, Fig. 8, are provided to cut out the bridges of the second and third arms when the bridge of the first arm is in action and to cut out the bridge of the third arm when the bridge of the second arm is in action.