Patent GB-752153-A (GB)
Title: Improvements in self-propelled projectiles
IPC: F42C11/00
Filed: 1954-06-15
Abstract: 752,153. Projectile fuzes. BRINRO, Ltd. June 15, 1954 [June 29, 1953], No. 17570/54. Class 9(1) An electrically operated projectile fuze includes a condenser which is charged by connecting an insulated contact 3 on the casing to a source of direct current 4, the charging circut being closed through a contact 5 and the shell casing. When the projectile is fired or launched the condenser is disconnected from the contact 3 by a switch U, which then connects the condenser to the fuze system. The switch U includes a pivoted arm 7 prevented from moving to the closed position by a fusible wire 9 in series with the contact 3 and condenser 2. The inertia of the arm 7 is such that even after fusion of the wire, the arm does not move until the acceleration of the projectile reaches a predetermined value. To fuse the wire, an alternating current source 13 is connected to a transformer 11, 12 and a switch 14, which is closed when the projectile starts to move forwards by a pushrod 15 bearing against the shell casing. As soon as condenser 2 is charged, the projectile is ready for launching and during its forward movement closes switch 14. An impulse is then sent through transformer 11, 12 to the charging circuit, the wire 9 fuses and cuts condenser 2 off from the charging contact. Should a misfire occur. switch 14 remains open and the condenser 2 can be discharged through a resistance 17 by closing a switch 16. When switch arm , 7 moves against contact 8 a second arm 7a coupled to the first, Fig. 2, moves against a contact 8a closing the battery circuit to a, thyratron 18. Closure of the switch 7, 8 also completes the circuit through the thyratron 18, an ignition condenser 20 and a primer 21, and charging of the condenser 20 begins, the time of charging being controlled by resistances R 1 , R 2 . When the condenser 20 is, charged the fuze is armed and when the negative bias voltage of a grid 22 of the thyratron is eliminated the fuze can be operated by a firing member 23, which may be a firing pin or a device operated by visible radiation or infra-red rays. If member 23 is not actuated, a condenser 24, after a delay, primes a glow tube 25 and hence supplies a positive voltage to the grid 22. The condenser 20 then discharges through the primer 21 and the .projectile explodes. As a further safety precaution the primer 21 is short-circuited by a conductor connected to a switch, which opens when switches 7, 8 and 7a, 8a are closed. Instead of the wire 9 a locking device, Fig. 3, may be used which comprises a member sheared by a primer charge on passage of an electric impulse. The device has an outer casing 26 of insulating material from which project three pairs of contacts, contacts a, a, and b, bi being at right angles to contacts c, c,. A piston 27 slidable in the casing 26 has diametral passages 28, 29, each housing balls 30, 31 urged into contact with the casing by a spring 32. Extending from the casing into a recess 34 in the piston is a safety locking wire 33, holding the piston with balls 30, 31 and spring 32 in the hole 28 in circuit with contacts a, a 1  and the charging circuit of condenser 2. The wire 33 is sheared when a detonating charge 35, e.g. lead trinitroresorcinate, is exploded by a current through wires. 36, which may be in series with contacts a, a 1 . Piston 27 then moves upwardly to shear the wire 33 and later sets back due to inertia bringing the balls in passage 28 against contacts b, b 1  and the balls in passage 29 against contacts c, c 1 . These contacts b, b 1  and c, c, correspond to the switch elements 7, 8 and 7a, 8a of Fig. 2, while a, a 1  correspond to 7, 9 of Fig. 1. To lock the piston in the position of Fig. 6, a recess 38 may be provided in the casing 26.