Patent GB-760494-A (GB)
Title: Improvements in automatic safety firing control systems for gun mountings
Inventor: FRY MICHAEL GEORGE JOSEPH
IPC: F41A17/08
Filed: 1954-01-18
Abstract: 760,494. Firing control systems for gun mountings. BREVETS AERO-MECANIQUES SOC. ANON. Feb. 25, 1955 [Jan. 18, 1954], No. 1453/54. Class 92. Relates to automatic safety firing control systems for gun mountings to prevent firing when a gun on a ship is aimed at the superstructure. According to the invention a pair of separate and distinct control elements are arranged to move angularly with movements of the gun in azimuth and elevation, respectively, and are connected to the gun firing circuit so as to set the circuit in readiness or otherwise in accordance with the instantaneous combination of their angular positions. Each control element is formed to represent a function of one of the rectangular co-ordinates of the point of aim of the gun within a plane representation of the field of fire, the rectangular co-ordinates corresponding to the instantaneous angles of azimuth and elevation of the gun, means being provided for combining the functions and making the setting of the firing circuit dependent on the instantaneous value of the combined functions, the functions being related and each either a stepped function with more than two steps or a continuously varying function, determined by the shape of an outline of a prohibited zone of fire in the plane representation of the field of fire. In one form Fig. 1, a pair of control elements in the form of an azimuth cam d with a follower e and an elevation cam f with a follower g are mounted on the training and elevation axes T-T, E-E respectively to operate switches T<SP>1</SP>, T<SP>2</SP>, T<SP>3</SP> and E<SP>1</SP>, E<SP>2</SP>, E<SP>3</SP> in parallel cross-connected conductors of a gun firing circuit between the firing button h and the gun. The superstructure of the ship represented at S is bounded by training sectors T<SP>1</SP>, T<SP>2</SP>, T<SP>3</SP> and elevation sectors El, E2, E<SP>3</SP> and the cams d and f are stepped to correspond to these sectors to open the conductor switch corresponding to the sector in which the gun is aimed in azimuth and elevation. In the position shown the line of fire passes through training sectors T<SP>1</SP>, T<SP>2</SP>, T<SP>3</SP> and elevation sectors E<SP>2</SP>, E<SP>3</SP> and the corresponding switches T<SP>1</SP>, T<SP>2</SP>, T<SP>3</SP>, E<SP>2</SP> and E<SP>3</SP>  are  therefore open. The firing circuit is thus interrupted and the gun cannot fire. If now the gun is trained to the right without change of elevation to bring it to bear on the point X, the line of fire passes through training sector T<SP>3</SP> only and elevation sectors E<SP>2</SP>, E<SP>3</SP>. Corresponding switches T<SP>3</SP>, E<SP>2</SP>, E<SP>3</SP> are thus open and the firing circuit is now completed through switch E<SP>1</SP>, the cross-connection, switches T<SP>2</SP>, T<SP>1</SP> and the gun is free to fire. The diagram S may be regarded as a plane representation of the outline of the superstructure and that any point thereof has rectangular co-ordinates which can be represented by functions of azimuth and elevation angles and the stepped contours of the cams d, f represent functions of the gun azimuth and elevation angles. The arrangement is such that whenever the pointof-aim lies outside the prohibited zone the sum of the values of the functions represented by cams d and f is 3 or more and when the point-of-aim is inside the prohibited zone the sum is 2 or less, and the cross-connected switches provide a means of closing the firing circuit when the sum of the two functions is 3 or more and opening it when the sum is 2 or less, the number 3 corresponding to the number of " steps in the superstructure outline. In a modified form, Fig. 2 (not shown), the superstructure has an outline with five separate co-ordinate values and it may be regarded as having five " steps ", and the functions of azimuth and elevation represented by the control elements are drawn as graphs on electrical contact drums d, f, Fig. 3 (not shown) arranged to move with the guns in the same way as the cams d, f, Fig. 1. The shape of each graph is represented by a segment of insulating material i bounded by conducting metal m, and the drums engage stationary sets of cross-connected contact brushes T<SP>1</SP>-T<SP>5</SP> and E<SP>1</SP>-E<SP>5</SP>, the drums being arranged in the firing circuit of the gun as in the case of the cams. The arrangement is such that the firing circuit is closed when the sum of the two functions is 5 or more and opened when the sum is 4 or less, i.e., when the sum of the brushes in contact with the metal part m of the two drums is 5 or more or 4 or less. In another form the superstructure, Fig. 4, has a smooth outline without steps, and the cam d, Fig. 5, has a radially reciprocating follower e and the cam f a similar follower g which drive respectively the sliders of electric - potential dividers T, E and control the outputs therefrom to coils RT and RE in, and operative in the same direction in, a relay R. A fixed potential divider F provides a selected constant output to a coil RF in the relay R in the opposite direction to coils RT, RE. Current in the coil RF operates in a direction to open an armature switch RA in the firing circuit and the current in the coils RT, RE operate in the opposite direction to close the switch RA. The profiles of cams d, f, represent functions of the azimuth and elevation angles respectively which are arranged to vary from zero to an arbitrary limiting value k corresponding to the limiting values of the co-ordinates of the superstructure as represented in Fig. 4, so that when the point-ofaim is outside the prohibited zone, the sum of the values of the two functions is equal to or greater than k but when inside the prohibited zone the sum is less than k. Thus when the followers e, g are bearing simultaneously on portions of their cams representing a point within the superstructure, the currents in the coils RT, RE are so reduced that their combined effect cannot overcome the opposite effect of the coil RF and the switch RA is opened to prevent the gun firing. Under any other circumstances the effect of coils RT, RE overcomes that of coil RF and the switch RA is closed to make the firing circuit ready to fire. Instead of an electrical control system, a pneumatic or hydraulic system with valves in place of switches may be used. Moreover the setting of the firing circuit could be made to depend upon the difference of the two functions, their product or other mathematical combination instead of their sum.