Patent GB-191515390-A (GB)
Title: Improvements in Methods of and Apparatus for Range Finding, Gun Control and the like.
IPC: G01C3/04
Filed: 1915-11-01
Abstract: 15,390. Evershed & Vignoles, Needham, J. C., and Finnis, S. F. W. Nov. 1. Sighting-devices; triangles, solving - Relates to apparatus for obtaining values for the triangles to be determined in range-finding and surveying, guncontrol, and generally where the elements are directed according to such quantities as the base and altitude angles of long home-base range-finders in order to ascertain range and height, and consists in causing the departure from parallel directions of directing-appliances at the ends of a base-line to disturb the balance of wheatstone bridge whereof the balance is restored by shunting the arms of the bridge ; the adjustment of the shunts causes a pointer to indicate directly on a scale any desired information about the triangles concerned which may be determinable by the amount of departure from parallelism. Fig. 4 shows diagrammatically a bridge constituted by uniform resistances A B, C D, joined in parallel across a source of electrical supply, upon which slide contacts connected to a galvanometer. The bridge is balanced when the contacts are in the positions a, b, and also, after the insertion of shunts z<1>, z<2> between opposite ends of the resistances and the contacts, when the contacts are at a<1>, b<1>. The displacements m, k for the contacts vary with the positions of a and b, and a curve showing the sum of the displacements attains a maximum half way between A and B and is symmetrical with respect to this position. In application the resistances are arranged in arcs of circles at each end of a base-line and the contacts are carried by radial arms each moved simultaneously with a sighting- device &c. When the sighting-devices are directed to an object at a given distance and the necessary shunts are inserted to restore balance, the law of the variation of the convergence of the sighting- devices with respect to the direction of the object is found to follow over a very considerable angle the law represented by the displacement curve, and this fact enables such an arrangement to be used for range-finding, gun-control, &c. Fig. 8 shows a range-finder. The arms of the bridge are constituted by two series of uniform resistances between the contacts arranged in semi-circles, contact-arms pivoted to the spindles of telescope mountings moving over the contacts. The shunts are similarly constituted by resistances 24 and contacts 22, 23 arranged in circles, and an arm 28 carries brushes connecting the contacts 22, 23 with conductor rings 25, 26 respectively, the arm being mounted on the spindle of a rotatable handle which moves a pointer over a range scale simultaneously with the adjustment of the shunts. Signal lamps 32, 32a, lighted by switches 33 to be closed by each observer when he has sighted the object are provided at the galvanometer 31, and the shunts are then adjusted manually until the galvanometer reading is zero, whereupon the range from the midpoint of the base is read from the scale, range being assumed proportional to convergence angle. The plane of sight for range-finding, gun-control, &c., may be made rotatable by mounting the telescopes &c. on trunnions the axes of which are in the base-line. The angle through which the apparatus may be used for range-finding and the like may be extended by the use of additional shunts which are included in the circuits when the contact-arms reach given angular positions, one such shunt 34 at each sighting-station being shown in Fig. 8. Additional shunts of variable or fixed value which are included in the circuits when the contact-arms reach certain positions may also be provided to cause the variation of the relative displacement of the contact-arms with their direction to follow any desired law or to represent more closely the relation between range and convergence angle. Apparatus for determining the height of aerial objects may be constructed on this principle, the sighting-devices moving in planes rotatable about horizontal axes at right angles to the base, the balance being restored by means of primary shunts as above together with secondary shunts of which the resistances vary with the height but have a fixed value for any given height. In the case of gun-control the sighting-devices may be represented by the sights of guns at the extremities of the base line, and the laying of the controlled gun is arranged to insert the shunts, the gun being correctly laid when balance has been restored. By providing more than one shunt-box, galvanometer, &c. a number of guns may be controlled together.