Patent GB-686436-A (GB)
Title: Improvements in or relating to mechanical time fuze mechanism for projectiles
IPC: F42C9/04
Filed: 1951-05-24
Abstract: 686,436. Projectile fuzes. MEFINA SOC. ANON. May 24, 1951 [July 7, 1950], No. 12157/51. Class 9(i) Clockwork time fuze 'has a striker 6 controlled by a release cup 8 which can make three turns relative to a plate 20 and is provided with a guide rib 7 in the form of an Archimedean spiral The rib extends over an angle less than 360 degrees so that there is a gap between the ends 7a, 7b. Opposite the gap is a part 2 of an actuating lever 9 pivoted on the plate 20. The part 2 has three teeth 9a adapted to engage the spiral 7 and having the same curvature as the spiral. The spacing of the teeth corresponds to the pitch of the spiral and one tooth can engage the part 7b while the next engage: the part 7a. The nose 9b of the part 2 passes freely between the two ends of the spiral. A boss 21 on the lever 9 has a circular contour with the pivot 1 as centre. A striker catch 18 pivoted on the plate 20 has a boss 18a engaging the striker and a nose 22 engaging the boss 21. The free end 17a of a centrifugal pawl 17 pivoted on the plate 20 penetrates a notch 8c of the cup 8 in the position of rest. A projection 23 on this pawl engages with the striker catch 18 and the actuating lever 9. A spring 17<SP>1</SP> tends to push the centrifugal pawl 17 towards the centre while springs 9<SP>1</SP>, 18 'tend to push the members 9, 18 outwards. In the zero position Fig. 2, the end 17a of the centrifugal pawl 17 holds the release cup 8, while the actuating lever is held by its nose 9b against the end 7b of the guide rib 7 and the nose 21 holds the nose 22 of the striker catch 18 which is further held by the projection 23. During setting of the fuze mechanism the parts A, B are turned relatively to each other and the notch 8c leaves the end 17a of the centrifugal pawl. The relative movement of the parts A, B causes the actuating levers 9 to be drawn inwardly by the guide rib 7 engaging in successive gaps in the teeth 9a. The lever 9 slides in proportion to the setting against the ncse 22 of the striker catch which remains stationary during the setting and during running of the mechanism. The nose 21 engages the nose 23 as long as a tooth 9a is in engagement with the guide rib. The actuating lever 9 pushes the centrifugal pawl 17 outwardly so that the point 17a cannot enter the notch 8c until the end of the last turn of the release cup 8. After setting is finished, e.g. after three turns, the fuze is ready for firing. Upon firing a barrel spring 5, Fig. 1, causes a barrel shaft 16 to turn and so drive a member regulating the clockwork movement and also release the cup 8. The pawl 17 is urged outwards against the wall of its seating. When the cup 8 reaches tne end of the last turn the lever 9 is in the position shown in Fig. 2. The lever 9 continues to move outwards under the action of its spring until free of the guide 7, when the nose 21 frees the striker catch 18. The striker catch is urged outwardly by its spring 18<SP>1</SP> when the striker 6 is pushed against the primer (not shown). The mechanism may be regulated for times of 20, 25, 30 sec. &c. per turn.