Patent GB-730497-A (GB)
Title: Improvements relating to fuses for projectiles
IPC: F42C15/28
Filed: 1953-03-03
Abstract: 730,497. Projectile fuzes. AKTIEBOLAGET BOFORS. March 3, 1953 [March 26, 1952], No. 5847/53. Class 9(1). Clockwork fuze for projectiles fired from one medium into another has a domed cap 1 seated on an annular flange 2 of a two-part tube 3, 4 which is closed by a head 5 integral with coaxial cylinders 6, 7 as described in Specifications 730,323 and 730,324. The annular chamber surrounding the cylinder 7 communicates with the exterior of the fuze through a passage 9 which has a groove 10 to receive a closure plate or a threaded plug. Leading from the chamber is a channel or channels 11. Sealing the cylinder 7 is a disc 12, preferably of phosphor bronze, held in place by a plate 13 through which extend openings 14, 15, Below the disc 12 is a plate 20 carried by a rod 16 which is secured in the passage 8 by a shear pin 17. The rod has a frustoconical part 18 adapted to engage the complementary surface of a liner 19 in the cylinder 6. Axial movement of the tube part 4 is prevented by a set-screw 21 extending through the cap 1 into an annular groove 23 in the head 5. At the lower end of rod 16 is a stop member 28 which bears against arms 29, 30 secured in rotatably mounted shafts 31, 32. Helical springs 35, 36 surrounding the shafts are fixed at one end to the tube part 3 and bear at their outer ends against the arms 29, 30. The inner end of each shaft carries an arm 37, 38 respectively adapted to engage pointers 39, 40 rotatable by clockwork mechanisms 41, 42 respectively. Above the pointers are hollow cylinders 43, 44 the inner end of each cylinder having a recess to receive the adjacent pointer. When the pointers enter the recesses the strikers of the clockwork mechanisms are released and contact detonators 48, 49 in charges 50, 51 respectively. On the hollow cylinders 43, 44 are mounted fixed gears 54, 55 meshing with a gear 56 fixed to the output shaft 57 of a magslip element 58 which contains stator and rotor windings and is connected by a cable 59 to a source of electrical energy, so that the shaft can be set in any required position. Before firing the projectile the closure plate is removed from the groove 10. After firing as the projectile passes from air into water, air is forced out of the annular chamber through passages 11 by water entering the nose. When a certain hydrostatic pressure is reached the disc 12 is ruptured and the pressure on the plate 20 causes the pin 17 to shear, and the parts 18, 19 to engage to prevent entry of water into the fuze. The stop 28 moves out of the path of the arms 29, 30 which then rotate thus turning the shafts 31, 32 and disengaging the arms 37, 38 from the pointers 39, 40. The clockwork mechanisms 41, 42 then start, the mechanism 41 being faster than the mechanism 42. After a certain time interval, dependent on the setting given by the synchronizing element 58, the pointers 39, 40 snap into the recesses of cylinders 43, 44. It is arranged that after a certain time interval only the pointer of the fast clock mechanism enters its recess and for a longer time interval only the pointer of the slower mechanism enters its recess, so that either the detonator 48 or 49 is initiated. For this purpose a sector carried by mechanism 41 extends between pointer 39 and member 43.