The British WW2 anti lifting switch No.12 was used to boobytrap mines and other items. It consists of two main parts; the upper part is the explosive charge (1), in which the telescope pipe (3) is mounted. In the top of the telescope pipe the duplex detonator (2) is placed. In the lower part of the telescope pipe are the firing pin (6), the firing pin spring (7) and the lock up ring (8 ). The lower part is the nail (5) with the safety fork (4) pressed on, the blocking pin (10),and the spring (9). Functioning of the switch : A hole is dug to place a mine; in the middle of the hole the switch is pressed into the ground, spike down. the mine is placed , making shure there is good contact between the bottom of the mine and the top of the switch. the mine is than covered with soil. The safety pin is now removed with a lanyard, however, if no good contact is made between mine and switch, the upper part will move upward, thereby locking the switch and prevent premature detonation (see fig.5). If the switch makes good contact , the safety pin can easily be removed (see fig.4). The switch is now fully armed. The lower part of the firing pin has a chamfered edge with four machined slots, each at 90 degrees , each 0,7 mm wide effectively changing it into four flexible lips. The firing pin is held in place by the lock up ring that also has an chamfered edge to fit the chamfered edge of the firing pin, and the blocking pin inside the firing pin. As soon as the mine is lifted the spring (9) pushes the upper part upwards, thereby retracting the blocking pin from the firing pin. The firing pin spring pushes the firing pin upwards, thereby forcing the flexible lips to bend inwards, so it can pass the lock up ring. The firing pin will ignite the duplex detonator that will explode the switch. If the mine is lifted more than 15 mm, the switch will explode. Once a switch is armed it cannot be disarmed anymore.
Regards, DJH
Regards, DJH
