Patent GB-164765-A (GB)
Title: Improvements in, or relating to, gunnery computing and predicting apparatus
IPC: G06G7/80
Filed: 1919-03-31
Abstract: 164,765. Willans, P. W. March 31, 1919. Sights and methods of sighting. - Relates to means for directing and controlling the fire of a gun or guns, and consists in means for controlling a short-base range-finder, as regards direction and coincidence, so that it shall automatically, according to set velocity components, follow a target moving with a constant velocity on any fixed course or on any course which is changing at a constant rate and the height of which is constant or changing uniformly. According to the invention, the observed position of the target and the target displacement, in the time of flight of the projectile, are resolved along three rectangular axes and compounded with the components of the reversed velocity of the wind multiplied by the time of flight, and the convergence or parallax, and with the necessary trajectorychart particulars so as to actuate computing mechanisms and effect adjustment of other parts to compute automatically the angles of training and elevation which may be automatically applied to the gun. A potentiometric system, shown diagrammatically in Fig. 3, is employed to solve the various equations and comprises rheostats, whereby differences of potential are obtained proportional to the variables or functions thereof, and relays working in conjunction therewith and controlling motors for operating the computing, &c. mechanisms. The range-finder operator adjusts the rheostat 26 to the horizontal course and the brushes bs, bz, and bo on the rheostats 27, 28 and 29 to the horizontal and vertical speed of target and rate of change of course respectively and the difference of potential resulting is applied to relays Ux, Uy, Uz. Associated with the rheostats 26-29 are rheostats 31, 33<a>, 30 and 30a which are employed to compute corrections for travel of target and have a potential gradient proportional to the time of flight of the projectile. The position of the rheostat 31 is controlled by the rheostat 26 to which it is connected by a differential gear and by a brush b# on a rheostat 32 similar to 30 in order to apply a correction for the difference in course angle. On the assumption that the target travels along the chord of the arc, a correction must be applied for the quantity chord; this is effected by a rheostat constructed in two quadrants having a resistance arc, proportional to " Sin #." These rheostats apply # potential difference to relays L2, M2 and N<2>. The fluxes on relays Ux, &c. are reduced to zero by magnetic speedometers Ix &c., associated with motors Jx &c., which drive brushes l3, m3, n3 along rheostats 13, 14 and 15 so as to intercept resistances between brushes l<1>3, &c., which have been set to a position depending on the parallax and apply potential differences to relays L3, M3 and N3 proportional to co-ordinates of target referred to the range finder. Potential differences are also obtained between points l2 &c., and equipctential points l<1>2 &c., and applied to the relays L2, M2 and N2, proportional to the co-ordinates of the target referred to the gun. The fluxes on L3, M. and N3 are reduced to zero when the rheostats 16a, 16b, and the brush bR have taken up their correct position being connected respectively to the elevating, training, and coincidence working head of the range finder. The fluxes on relays L2, M2, and N2 are reduced to zero when the rheostats 8, 9 and the brush bR have taken up their correct position under the control of their motors. Rheostats 3 and 4 are connected through a differential gear with the rheostats 8 and 9, the inner and outer members of each pair being caused to turn through equal angles in opposite directions. The pairs 3, 8 and 4, 9 are set at angles corresponding to the tangent elevation # and drift # respectively and the central members of the differential gears carry brushes b#, b#, movable over rheostats 10, 11 and adjusted to the computed values of # and #. The E.M.F. applied to the rheostats 3 and 4 varied by a motor driving a brush bv, along the rheostat 7 and potential differences from brushes on these rheostats are applied to relays L<1>, M<1>, and N' to which are also applied in opposition thereto potential differences from the rheostats 1, 2 associated with the elevating and training mechanism of the gun and from the rheostat 5 which applies a correction for the wind. A constant E.M.F. from a fixed brush by proportional to the muzzle velocity v of the projectile is applied to the relay 1. Equilibrium is established on all the relays by means of motors which are directly under the control of their relays excepting in the case of the velocity v, the observed range R, and predicted range R, where the control is interchangeable. This latter adjustment is necessary in the motors associated with the rheostats for the muzzle case of a target passing through the gun zenith; a diagram of the connection for the v rheostats is shown in Fig. 5, the relays L1, M1 have commutator switches and supply current to pairs of contact strips 17 and the relay N1 controls the motor Jv, driving the brush bv. The circular rheostats 1, 2 &c. are constructed so that their resistances are proportional to the sines of the angles described at the centre by the movable member; mechanical equivalents such as the " slider-crank " and " swash-plate " are described for producing this result. The method of computing the time of flight of projectile T, tangent-elevation #, fuze setting F, or drift # consists in depositing copper strips on an insulating surface in such a manner as to lie along curves representing the loci of points of equal values of T.#.F. or # and interposing resistances to form a rheostat in which the resistance intercepted between the origin h<1>, Fig. 4. and the plotted point b will be proportional to the values of T &c. for that point. The rheostats for these variables are shown at 19 and have associated therewith other rheostats 20. 21 for correcting changes of muzzle velocity and ballistic coefficient; the values are set on rheostats 24, 23 and 22.