GB778494A - Improvements in or relating to delay-action self-destroying percussion fuzes - Google Patents

Abstract

778,494. Projectile fuzes. SOC. PER AZIONI FRATELLI BORLETTI. Feb. 20, 1956 [Feb. 18, 1955 ; Sept. 10, 1955], No. 5235/56. Class 9 (1). A delay-action percussion fuze intended more particularly for A.-A. projectiles and having a clockwork controlled self-destruction device has safety means for preventing arming on the first part of the trajectory comprising a toothed rack 2 interposed between a detonator 3 and the firing pin 4, the rack movement being controlled by the clockwork mechanism M through a pinion 7. Locking bolts 8, which are held by the rack prevent flash from the detonator passing to the igniter 23. During transport a bolt 9 pressed inwards by a spring 11 houses a pin 10 which engages a recess in the rack 2, Fig. 3, to lock the rack. On firing the projectile, when the angular velocity exceeds a predetermined value, the bolt 9 moves outwards due to centrifugal force and releases the rack. Screwed into the fuze body 1 is a nose 12 closed by a disc 13 and housing a striker 14 together with selfdestruction mechanism. This mechanism comprises a hammer mounted in a spring-stressed sleeve 15 supported by balls 17 which bear against a conical surface of a ferrule 21 fixed in the body 1. Into a ring 22 closing the body 1 is screwed the igniter 23 separated from the detonator 3 by a labyrinth delay device 24. Surrounding the sleeve 15 is a frusto-conical cap 19, which extends into a ring 20 and is thrust inwards by an amount proportional to the initial acceleration of the projectile to stress the hammer spring 18. The cap 19 and ring 20 may be replaced by a small cylinder supported by a spring. In this modification, centrifugally driven bolts move outwards from the cylinder, as the cylinder sets back on firing the projectile, to lock the cylinder and so maintain the stress on the hammer spring. The locking bolts are helically arranged in the cylinder so that the cylinder may be locked in the position which corresponds to the initial acceleration of the projectile. On firing the projectile, the bolt 9 moves outwards freeing the clockwork-controlled rack which then moves to free the striker. When the rack has completed its movement, the locking bolts controlling the flash passage move and the projectile is armed for action on impact. If the projectile does not strike the target, as the spin decreases the equilibrium between the balls 17 and the spring 18 ceases and the balls move inwards releasing the sleeve 15, which then drives the hammer on to the striker to initiate the fuze.