(Fig. 2)

The igniter, mainly of aluminium, is brown in colour as the result of vanishing and is cylin-drical with three steel pronges in the top of the plunger which protrudes at the head. For safety in transport a lateral safety bolt is fitted in the plunger where is emerges from the body.

The aluminium body is 0.7 inch deep in diameter and is made up of three sections screw-ed on into the other. The top section forms a casing for the supporting spring and has a hole in the head for the plunger. At its lower end it is screwthreaded internally to receive the middle section. After assembly the two sections are locked by a plug inserted bet-ween coinciding semi-circular recesses formed in the two sections. The middle section has a band of milling around the centre of exterior. Internally, at the upper part, it is re-duced in diameter to locate the two steel retaining balls in the plunger and to act as guide for the plunger. Screwthreads are formed externally at the upper end for insertion in the top section and internally at the lower end to receive the bottom section. The bottom section also has a milled band is locked to the middle section by a plug inserted between semi-circular recesses. A diaphragm in the top of this section has a central hole in which the cap assembly is fitted. The lower end is screwthreaded internally for as-sembly with the mine. For transport the fuze is closed at the base by a screwed plug of the moulded plastic type.

The aluminium plunger is cylindrical with an external flange at the centre which limits its upward movement and engages one end of the supporting spring. From the base the plunger is recessed to accommodate the striker with its spring and has two radial holes in which steel balls are located to engage a groove in the striker. In the upper port of the plunger there is a lateral channel to receive the safety bolt. A screwthreaded channel, drilled from the head, leads into the centre of this channel and contains a spring-loaded ball which engages a groove in the centre of the bolt. The ball and spring are retained in position by a screwed plug which also retains two steel washers securing the steel prongs. The prongs are inserted in holes in the head of the plunger and are splayed by notches in the inner circumference of the lower washer and in the outer circumference of the upper washer.

The safety bolt is of aluminium and has a steel split ring at one end and a retaining nut at the other. A groove of semi-circular section is formed in the bolt to engage the ball in the head of the plunger.

The steel spiral supporting spring fits around the plunger below the flange and is held in compression between the flange and the upper end of the middle section of the body.

The steel striker has a stem formed on its upper end over which its steel spiral spring is assembled. The spring is held under compression between the body of the striker and the end of the recess in the plunger. A groove, with the upper side inclined, is formed in the striker body to engage with two steel retaining balls.

The cap assembly consists of a copper sheath containing the cap and the anvil. The sheath is flanged at the top and is turned in at the base to secure the anvil. The anvil is formed by a bent brass strip with half collars formed on each end under which the sheath is turned inwards. The copper cap contains 0.8 grains of composition consisting of 40.8 per cent. of lead styphante, 40.7 per cent. of barium nitrate, 2.9 per cent. of antimony sulphide and 15.6 per cent. of calcium silicide.

The safety bolt is withdrawn by removing its retaining nut and pulling the bolt out of the plunger against the resistance of the spring-loaded ball.

When pressure is applied to the prongs the plunger is forced down into the body against the resistance of the supporting spring. When the two steel balls in the plunger have moved down sufficiently to lose the support of the low diameter portion of the body, there are ejected by the inclined surface in the striker groove, under the pressure of the striker spring, which drives the striker to the cap assembly. The weight required to ope-rate the fuze is approximately 7 lb.

fig. 2