Patent GB-485573-A (GB)
Title: Improvements in and relating to percussion fuzes for projectiles
IPC: F42C15/26
Filed: 1936-11-18
Abstract: 485,573. Projectile fuzes. LOUHIA, V. V. P. Nov. 18, 1936, No. 31610. Convention date, Nov. 18, 1935. [Class 9 (i)] Relates to projectile percussion fuzes of the kind having at least two safety devices, one of which is adapted to secure the movable firing pin and another to close the passage leading to the detonator. According to the invention, both the safety devices are constrained in their locking position with the aid of a central longitudinally movable member and are both arranged to be unlocked or released independently of centrifugal force by the combination of an initial set-back movement of an axially movable inertia member due to the acceleration of the projectile upon firing and the subsequent forward movement, consequent upon the said set-back movement, of the central member. As shown in Fig. 1, a conical part 6 of the firing pin 1 is engaged by balls 5 held in holes 4 in a fixed sleeve 2 by a flange 7 on a movable sleeve or central member 8 which is screwthreaded into the fuze body part 10 and carries a percussion cap 9 at the forward end of a bore 16 therein. In this position of the sleeve 8, the cap 9 is situated so far from the firing pin that the latter could not reach and strike against the cap even if the balls 5 should be removed. A spring 11 connected on the one hand with the sleeve 8 and on the other hand with the body part 10 tends to turn the sleeve forwardly out of the threads in the body part. This turning of the sleeve is, however, prevented by an inertia member in the form of a spring- pressed locking sleeve 12 provided with lugs 13 which project through holes 14 in the part 10 into recesses 15 in the sleeve 8. A ball 17 normally closing the passage 18 in a bottom member 19 of the fuze body leading to the detonator 20 of the booster charge 21 is held in position between the lower edge of the bore 16 and the upper edge of the passage 18. In operation, when the shell is fired, the sleeve 12 sets back against its spring so that the lugs 13 are withdrawn from the recesses 15. The sleeve 8 is now free to be turned by the spring 11 so as to be moved towards the firing pin 1. Owing to this movement, the percussion cap 9 is brought within contact range of the pin 1, the balls 5 pass behind the flange 7 so that the firing pin is unlocked and the ball 17 is also released thus opening the passage 18 to the detonator 20. Fig. 2 shows a modification in which the set-back of the inertia sleeve 12 unlocks the balls 5. The sleeve 12 is provided at its rear end with inclined inner surfaces 25 which, when the sleeve sets back, lock themselves on correspondingly inclined exterior surfaces 26 on the sleeve 8. Consequently, as soon as the acceleration of the shell decreases sufficiently and the sleeve 12 moves forward again under the action of its spring 22, the sleeve 8 is carried forward with the sleeve 12 and the percussion cap 9 is brought into the range of contact of the firing pin 1, the balls 5 are pushed over the conical part 6 of the pin 1 out of the holes 27 in the sleeve 8 thereby unlocking the firing pin, and the ball 17 is released, thus opening the passage 18 to the detonator 20. In a modification of this construction, Fig. 3 (not shown), the percussion cap 9 is dispensed with and the firing pin extended so as to act directly on the detonator. A further modification is also described, Fig. 4 (not shown), in which a third sleeve surrounding the sleeve 12 and operated by a separate spring is provided. When the sleeve 12 sets back, this third sleeve also sets back and locks the balls 5. When the acceleration of the shell decreases sufficiently, the third sleeve is returned first by its spring unlocking the balls 5 and thereafter the sleeves 12, 8 advance together as previously described so as to unlock the firing pin and open the passage to the detonator.