Patent GB-487544-A (GB)
Title: Electric fuze for submarine mines, grenades, bombs and like ammunition
IPC: F42C11/04
Filed: 1937-06-03
Abstract: 487,544. Fuzes for projectiles and submarine mines; magnetos. SOC. ANON. FAX. June 3, 1937, Nos. 15443 and 15444. Convention dates, June 3, 1936 and Dec. 3, 1936. [Classes 9 (i) and 9 (ii)] [Also in Group XXXV] Relates to an electric fuze for submarine mines, grenades, bombs, and like ammunition projectiles, in which the current for the spark is supplied by a current generator driven by a spring motor provided with means for winding it and fitted with the generator in the mine or projectile. According to the invention, a ratchet holding mechanism for the spring motor is released on impact of the projectile or on the mine and a circuitbreaking device in the spark circuit is controlled by the rotor of the current generator in such manner that it closes as the rotor is set in motion. As shown in Fig. 1, a casing 1 is divided by a partition 2 into two chambers, the upper one of which contains the motor spring 3, one end of which is secured to the casing 1 whilst the other end is attached to a bush 4 loosely mounted on a shaft 5 and provided on its lower end with ratchet teeth meshing with similar teeth on a ring 6 secured on the shaft 5. This shaft passes through the partition 2 into the lower chamber where it carries a coil 10 forming the rotor of the current generator, the stator of which is formed by the U-shaped polepieces 11, 12 of a permanent magnet 9. A pinion 13 on the lower end of shaft 5 meshes with a toothed wheel 14 which carries on its lower face a contact disc provided with a sector of insulating material, one of the terminals 17 for the feed current being arranged to wipe over this disc. One end of the coil 10 is connected to the contact disc whilst its other end is connected to the second feed terminal 19. In its inoperative position, the terminal 17 contacts with the insulating sector and the igniting circuit is open, but as soon as the spring motor 3 is released, rotation of the contact disc brings the conducting portion thereof into contact with terminal 17 and the igniting circuit is closed. If desired, a centrifugal breaking device, the centrifugal masses of which close a circuit when they reach a determined path of oscillation, may be employed. An induction coil may be inserted between the terminals 17, 19 and the spark-gap. The spring 3, which is wound by means of a key fitting on the polygonal end 20 of the shaft 5, is maintained wound by a pawl 8 which engages a ratchet wheel 7 mounted outside the casing 1 at the upper end of the shaft 5. Engagement between the pawl 8 and ratchet wheel 7 so as to release the spring 3 and actuate the current generator may be annulled by means of any suitable device on impact of the projectile or upon the mine. When it is desired to produce ignition only a certain time after impact, the fuze is provided with a delay device as shown in Fig. 3. In this arrangement, the motor spring is mounted in a box 21 having a toothed rim 22 which meshes with the pinion 23 of a winding-up device on a shaft 24 carrying a handle 25. A pawl 26 prevents backward rotation of the pinion 23 and of the box 21 to which the outer end of the spring 3 is secured. The other end of the spring is attached to a shaft 27 carrying a ratchet wheel 28 engaging a pawl 29 carried by an arm 30 pivoted at 31 and carrying at its free end an inertia mass 32 which is held in its inoperative position by a pin 33. After removal of the pin 33 and on impact, the inertia of the mass 32 rocks the arm 30, the pawl 29 is released and the spring is allowed to unwind. The mechanism cannot, however, attain at once the speed required for ignition on account of the provision of the relay device comprising a screw 34 on which a bush 35 fixed to the cover of the casing 1 is screwed. A pinion 36 of a substantial depth on the screw 34 meshes with a toothed wheel 37 mounted on the shaft 27 whilst a toothed wheel 38 also carried by the screw 34 meshes with a pinion 39 controlling a damping wing (not shown). As the spring motor begins to unwind, screw 34 is set in rotation by the gears 37, 36 and is screwed up into the bush 35 carrying with it the pinion 36, the rotational movement being braked by the damping wing as long as pinion 36 is in engagement with the toothed wheel 37. The duration of the ignition delay can be adjusted by varying the initial position of pinion 36 by means of a milled button 40 on the indicator dial 41. If desired, the stator may be in the form of a coil and the armature in the form of a permanent magnet.