The fuze mechanism consists of a striker, with spring under initial compression, held off an igniferous detonator by a steel shearing pin. Two safety devices are included to re-lieve the shearing pin of the spring pressure, a safety bolt passing through a hole in the stem of the striker and a safety lug engaging the head of the striker.

The brass body of the fuze is screwthreaded externally below the flange for insertion in the cover plate of the Tellermine and is recessed from the base to receive the striker with its guide and the spindle of the safety lug. The recess is designed to permit the guide to move further into the body when the fuze functions. A cylindrical projecting sleeve, screwed into the side of the body, is aligned with a radial channel which inter-sects the upper part of the striker recess for the insertion of the safety bolt. A stop pin is fitted inside the sleeve at the lower side near the outer end to limit the withdrawal of the safety bolt. A recess formed in the top of the body is connected by a short channel with the interior and accommodates the setting head for the spindle of the safety lug. A stop pin on the top of the body, underneath the igniter top plate, limits the turning mo-vement of the setting head.

The striker assembly consists of the striker, spring, shearing pin and striker guide. A transverse hole is drilled in the cylindrical stem of the striker to receive the safety bolt. A collar formed near the head supports one end of the spring and is stepped to engage the safety lug. A radial recess in the collar coincides with a channel in the guide for the in-sertion of the steel shearing pin. A vertical recess is also formed in the periphery of the collar, this is probably intended for the escape of air as the striker is forced downwards. The striker guide protrudes from the base of the body and is retained in the body recess by a screwed collar, which does not prevent it moving inwards. The collar screws into the body recess and has an internal flange which engages a step formed round the exte-rior of the guide. The guide is in the form of an inverted cup with an internal diameter to suit the collar formed on the striker. The closed end of the cup engages the upper end of the spring and has a hole at the centre for the striker stem. A hole is formed in the side of the spring case portion of the guide for the escape of air pressure and a slot is provi-ded through which the safety lug protrudes to engage the step in the striker head. The guide is closed at the base by a screwed detonator plug which carries an igniferous de-tonator. The detonator includes an anvil and the 0.3 grain filling consists of mercury ful-minate 14.2 per cent, potassium chlorate 37.8 per cent, antimony sulphide 41.7 per cent and glass 6.3 per cent.

The safety lug is formed near the lower end of the spindle which is reduced in diameter and enters a recess formed in the guide. The lug is fan shaped and extends through 130 degrees. The surface of the lug is inclined so that as it is rotated away from the striker (anti-clockwise) the pressure exerted by the spring is gradually transferred to the shear-ing pin. The sprindle has flats formed near the upper end to engage with the setting head and a pint-leat the top locates one end of a spiral spring. The setting head has a tool slot in the top and a red spot which is the setting index. A stepped flange formed round the head has a projection which, in conjunction with the stop pin in the top of the body, limits the rotary movement of the setting head. The lower part of the head is cy-lindrical and fits into the recess in the top of the body. The cylindrical portion is recessed and has two slots, diameterically opposite, which engage the flats on the spindle. A spi-ral contained in the recess permits the spindle to move further into the setting head when it is forced in with the striker guide during the functioning of the fuze.

The top plate is secured to the body of the fuze by three screws and is marked to indi-cate the armed and safe setting positions of the setting head. The armed setting poisi-tion is indicated by a red rectangular patch and the word "Scharf". The safe position is indicated by a white rectangular patch and the word "Sicher". Rotation of the setting head, clockwise, so that the red index spot is moved from "Sicher" to "Scharf" causes the safety lug to disengage from the step in the collar on the striker. Two recesses in the edge of the top plate correspond with similar recess in the fuze body to form key slots.

The safety bolt consists of a slotted cylindrical body with a hook attachment which is contained in the sleeve projecting from the side of the fuze body and a stem which pas-ses through a hole in the striker. The cylindrical body portion has a vertical slot extend-ing from its outer end along the greater part of its length to receive the claw which en-gages a pin inserted transverly in the slot. The claw is a flat key with a hook at its inner end to engage the pin in the slot and has about 5 feet of flexible wire attached at its outer end. The outward movement of the safety bolt is limited by the end of the slot coming into contact with the stop pin near the outer end of the sleeve.

After the mine has been laid the setting head is turned so that the red spot on the set-ting head is aligned with the red rectangular patch marked "Scharf", thus disengaging the safety lug from the striker, and the safety bolt is withdrawn from the striker by pulling the claw wire. When the bolt has been withdrawn to the extent permitted by the stop pin in the sleeve the claw becomes detached from the bolt and the striker is then sup-ported only by the shearing pin. When pressure is applied to the fuze, or the cover plate of the mine, the spring supporting the cover plate is compressed and the fuze is forced downwards. The striker guide, supported by the mine beneath, enters further into the fuze body. The movement of the striker guide, relative to the striker, breaks the shearing pin and the striker is driven down by its spring and fires the igniferous detonator. The flash produced passes through the channel in the closing discs of the detonator socket of the mine and initiates the main detonator which with the amplifying effect of the ex-ploder pellet detonates the bursting charge.

The load required to actuate the fuze in the mine has been found by experiment to be approximately 350 lb. Five fuzes were used in the trial and the required loads were found to vary between 342 lb. and 357 lb. With the fuze removed from the mine, so that the resistance of the spring under the cover plate is excluded and only the shearing pin has to be severed, the load required is approximately 231 lb. The loads required with ten fuzes at a trial varied between 225 lb. and 239 lb.

Fig. 2