Relase Switch No. 12 Mk I (Service)

Diameter

Length

Explosive

Minimum safe load

Description: The switch consists of a shallow, tapered explosive container, 3 in. in diameter by ¾ in. deep, from the center of which protrudes a short tube containing a striker release mechanism. This tube fits into the main housing tube, which terminates in a spike enabling it to be forced into the ground. A flange is fitted to the top end of the main housing tube and abuts against the base of the explosive container.

The tube of the striker release mechanism houses a striker head, attached to a hollow spindle which terminates in a small split head. The striker spring is placed between the striker head and a bush on the end of the short tube. The bush has a hole in its center just large enough to allow passage of the spindle's split head when collapsed. The split head protrudes through the bush and has a retaining rod inserted into the split end to hold it in position. When so located, the striker spring is compressed.

The retaining rod, which has a smaller washer on its bottom end, is located in the housing tube and surrounded by the lift spring. The striker release mechanism fits above it in the main housing tube. The lift spring tends to force the explosive container up and the release-mechanism tube out of the main housing tube unless prevented by a suffi-cient weight resting on top of the explosive container.

The detonator unit consists of a 4-gr. detonator spun into a tubular, windowed holder containing C.E. pellets. It is inserted through the center of the explosive container above the striker.

A self-trapping safety pin passes through a turned-over protion of the flange secured to the main housing tube, and also through an eyelet attached to the bottom of the ex-plosive container. When in place, this safety pin prevents separation of the two parts and the resultant release of the striker. The safety pin has an annular groove in its stem which engages the eyelet of the explosive container if an attempt is made to remove the pin when the load on the explosive container is insufficient to overcome the pressure maintained by the lift spring. A split transit pin is inserted through the end of the safety pin to prevent its withdrawal before preparation for use.

Functioning: When the weight is removed from the explosive container, the lift spring forces the container and release-mechanism tube upward. This disengages the retaining pin from the split striker spindle, and allows the striker to be carried forward by the com-pressed striker spring. The striker fires the detonator unit, which explodes the main ex-plosive charge.

Use: This switch is employed as an anti-lifting device. It is ideal to prevent removal of land mines.

Installing: Force the spike of the switch into the ground. Place a sufficient weight on the explosive container, and withdrawn the safety pin.

Disarming: If the switch is accessible, insert a safety pin through the flange and eye. If it is not readily accessible, destroy it in place.