Patent GB-617326-A (GB)
Title: Improvements in or relating to apparatus for the practice of gun sighting
IPC: F41G3/26
Filed: 1944-11-02
Abstract: 617,326. Apparatus for gun-sighting practice. TAPP; E. T. J., and STEPHENS, H. C. Nov. 2, 1944, No. 21511. [Class 119] [Also in Group XL (b)] An apparatus for the practice of gun-sighting comprises a sight 10, Fig. 1, adapted to be directed by the operator on to a target produced on a spherical screen by a cinematograph and connected by link and lever mechanism to a lever 18 carrying projectors in an assemblage 19 also directed on the screen. The assemblage 19 comprises a projector 41, Fig. 2, for producing a spot of light representing a tracer projectile, a projector 48 producing a flash indicating a hit and a light-sensitive device 47 such as a photo-electric cell to control the projectors. The assemblage 19 is pivoted on a horizontal axis and held in upper position by solenoid 28. When the operator has sighted on the target, he presses the gun trigger which closes a switch 32 and clutches, by means of an electromagnet 24, the arm 18 to a fixed part 25 and also renders the light-sensitive device 47 operative by means of a coil 35 and breaks the circuit of the solenoid 28, thus allowing the projectors to swing down under the control of a dash pot so that their rate of movement corresponds to the known rate of fall of a tracer projectile. The projector circuits are controlled by an electromagnetic switch 46 controlled by the light-sensitive device 47 and a bridging member 40 controlled by a cam 38 driven by the cinematograph and having a profile varying with the range of the target and a cam 39 driven at constant speed when the trigger is pulled and having a profile varying with the constantly increasing range of the projectile. If the apparatus is correctly aimed the light-sensitive device 47 registers with the dark target and de-energizes the switch 46, breaking the tracer projector circuit and making the circuit of the hit projector 48 to produce a flash indicating a hit, through contacts 51, 52, and cams 38, 39 which both contact the bridging member 40. If the apparatus is sighted too far in advance of the target the tracer projector circuit is broken, so as to simulate the tracer passing behind the target, as the device 47 again registers with the target and the circuit of the projector 48 is not closed as only the cam 39 engages the bridge member 40. If not sighted far enough in advance of the target the tracer projector remains illuminated, simulating tracer passing in front of the target, as its circuit is completed through the cam 38. The assemblage 19 is returned to its original position by energization of the solenoid 28, the circuit of which is closed by contacts 36 on de-energization of electromagnet 24 brought about by the opening of conducts 34, which is caused either by energization of a solenoid 53 through the circuit of the flash projector when a hit is made or by the armature of the solenoid 28 when it reaches its limit of movement due to the fall of the assemblage 19. The lever and link mechanism connecting the sight 10 and the projector assemblage 19 comprises a reciprocable shaft 13 in a bore in the shaft 12 connected to a collar 16 slidable on the shaft 12. A spring link 17 connects the collar 16 to a lever 54 connected by a pivot 56 to the lever 18. On a member 55 rotatable on the shaft 12, the levers 18, 54 are mounted by means of pivots 58, 59, the ratio of the distance between which to the distance between pivots 59, 56 is the same as the ratio of pivots 11, 58 to the distance between the pivot 11 and the target screen, thus the intersection of the line of the sight with the optical axis of the assomblage 19 is maintained on the screen. A spring- pressed roller 21 engaging a V-depression on the member 55 moves the lever 18 and the assemblage 19 into line with the sight again when the magnet 24 is de-energized. The shaft 13 may operate a number of similar mechanisms carrying assemblages 19, brought into operation by successive operations of the trigger to simulate a number of tracers.