GB752737A - Improvements in or relating to electric ignition devices for projectiles - Google Patents

Abstract

752,737. Projectile fuzes. MOTHA TREUINSTITUT. Aug. 30, 1954 [Aug. 31, 1953; Jan. 5, 1954], No. 25092/.54. Class 9(1) An impact-operated electromagnet fuze comprising a, casing 2 housing a condenser 1 and an induction coil 6 wound on a support 7 and placed between permanent magnets 8, 9 is provided with a movable core' 10. The magnets 8, 9 are segments of a ring and their upper surfaces are of the same polarity, e.g. south, so that the magnetic field is a torus surrounding the coil. A disc 3 supporting the magnets and coil has a flanged aperture into which extends the core 10, the core being suspended from an apertured disc 5 by a copper strip 11 secured on an axial stem 13 of the core. On firing a projectile equipped with the fuze, the core 10, due to inertia, sets back bending the strip 11 and lodging in the flange 4. The resultant change in magnetic field induces an e.m.f. in the coil 6, which has an end 16 connected to the condenser. The other end 17 of the coil is connected to a blade 14 mounted on an insulating member 15 and earthed by contact with the stem 13. The second terminal of the condenser is earthed by a wire 18 attached to a screw 19 which secures the member 15 on the disc 5. On set-back of the core 10, the connection between the blade 14 and stem 13 is broken and the .coil 6 disconc nected from the condenser. The ends of the strip 11 engage the underside of the disc 5 to prevent return of the core. A safety device to delay discharge of the condenser 1 through a priming detonator comprises a toothed sector 20 of insulating material connected by a gear train 24, 25 to a pivoted mass 23. As the sector rotates; a contact 26, electrically connected to the condenser 1, is carried into engagement with a contact 27 depending from the cover 28 of the casing. A pin 29 projecting from the core prevents rotation of the sector 20 until set-back of the core after firing. Whereupon, the sector is driven by its spring 22, the motion being braked by the mass 23. When the contacts 26, 27. touch, the condenser 1 can be discharged through a detonator 36, Fig. 6, containing a detonating composition 37 in which are embedded the ends of conductors 30, 31 connected in series with the condenser and a key closed after a given time delay or on impact. The delay given by the safety device is adjusted by varying the mass 23 or the strength of the driving spring 22. The contact 14 may be replaced by a rectifier. The core 10 may be a permanent magnet and the magnets 8, 9 are then replaced by a sleeve of ferro-magnetic. material. In rotated projectiles, the driving spring 22 may be replaced by a, centrifugal mass. The core 10 may be lightened by an axial recess. An alternative arrangement is described in which the condenser before firing is connected in circuit with an impact-operated member. Should this member be actuated accidentally before the end of the safety period; the condenser is short-circuited and no discharge can take place through the primer.