GB2145201A - Mechanical mine-triggering device actuated by a trip wire or the like - Google Patents

Abstract

A mechanical mine-triggering device actuated by a trip wire (41) or the like and comprising: a casing (1); a striker (6) movingly guided in a seat (4,5) in the casing (1) from an armed position to a released position; spring means (7) permanently biassing the striker (6) towards the released position and means for releasably retaining the striker (6) in the armed position against the force of the spring means, characterised in that the means for releasably retaining the striker (6) in the armed position against the force of the spring means comprise: a throat (16) in the striker (6); an aperture (12) with which the casing (1) is formed opposite the seat (4, 5); a ball (15) received in the aperture (12) and movable from a first position, in which the ball is in engagement with the throat (16), into a second position, in which it is clear of the throat (16); and removable stop means for maintaining the ball in its first position, the stop means being mechanically actuated by the strip wire (41). <IMAGE>

Description

SPECIFICATION Mechanical mine-triggering device actuated by a trip wire or the like This invention relates to a mechanical mine-triggering device actuated by a trip wire or the like and comprising: a casing; a striker movingly guided in a seat in the casing from an armed position to a released position; spring means permanently biasing the striker towards the released position; and means for releasably retaining the striker in the armed position against the force of the spring means.

The basic requirements for a device of this kind are of course reliable operation -- i.e., the certainty that the mine will explode -- and the safety of the person installing the device.

Various kinds of mechanical triggering devices for use with trip wires are known, but all of them are based on the same idea; the striker is retained by a mechanical element against an opposing spring force and the trip wire is so secured to the element that when any object or person interferes with the device, the element moves and releases the striker.

Unfortunately, the sensitivity and, therefore, the reliability of operation of all the known triggering devices are unsatisfactory, for friction between contacting parts means that appreciable forces are required to produce the necessary movements.

Friction between the striker and the striker-retaining element is particularly high, for the force with which the striker must be hurled on to the detonator to which the triggering device is fitted must be high and so, therefore, must the force needed to retain the striker.

Consequently, minor impacting of the trip wire may fail to release the striker.

It is the object of this invention to provide a mechanical mine-triggering device whose constructional and operating features are such as to obviate the disadvantages of the prior art.

The invention accordingly relates to a mine-triggering device of the kind outlined wherein the means for releasably retaining the striker comprise: a throat in the striker; an aperture with which the casing is formed opposite the seat; a ball received in the aperture and movable from a first position, in which the ball is in engagement with the throat, into a seond position, in which it is clear of the throat; and removable stop means for maintaining the ball in its first position, the stop means being mechanically actuated by the trip wire.

Advantageously, the aperture is open towards the outside of the casing and its length is less than the diameter of the ball, the stop means comprising a closure member disposed on the casing for rotation around an axis and movable between a first position, in which it closes the aperture, and a second position, in which it is clear of the aperture.

A preferred embodiment of the invention will be described hereinafter with reference to the accompanying drawings wherein: Figure 1 is a perspective view of a triggering device according to the invention at a time when it has just been actuated by cutting of the trip wire; Figure 2 is a cross-section of the device of Figure 1 with the moving arm in its inoperative position and with the safety key inserted; Figure 3 is a section on the line Ill-Ill of Figure 2, and Figure 4 is a section through the device of Figure 2 after it has been actuated by the trip wire.

A triggering device according to the invention comprises a casing 1 which is of substantially cylindrical symmetry and which terminates at the top in a circular surface 2. The casing 1 has at the top a substantially cylindrical projection 3 which projects from the surface 2 and which is coaxial of the casing 1.

Two cylindrical orifices - a top orifice 4 of relatively narrow diameter and a bottom orifice 5 of relatively large diameter -- which are contiguous with and coaxial of one another extend vertically through the casing 1 and projection 3. The orifices 4, 5 form a seat receiving a striker 6 guided for vertical movement against the force of a spring 7 compressed between an abutment 8, associated with the junction between the two orifices 4 and 5, and a disc 9 connected to the striker 6. Orifice 5 is closed at the bottom by a screwthreaded cover 10 formed with a central aperture 11 of smaller diameter than the striker 6. The same is therefore movable from a top armed position, in which the spring 4 is fully compressed, and a bottom released position in which it bears on the cover 10.

Projection 3 is formed with a radial aperture 12 adjacent the aperture 4. In the part distal from the aperture 4 the radial aperture 12 is adapted to be closed by a pivoted closure member 13 in shape resembling a C and extending three-quarters of the way around the projection 3. The ends of member 13 are pivotally connected to the projection 3 along a horizontal axis 14; the member 13 can therefore pivot between a substantially horizontal bottom position, in which it closes the aperture 12, and a raised position, in which it clears the aperture 12.

Aperture 12 receives a ball 15 whose diameter is greater than the length of the aperture 12 and which, with the member 13 in its bottom position, extends into the aperture 4 to engage with a rounded throat 16 in the striker 6 to retain the same in its top armed position.

Also secured to the surface 2 is a vertical cylindrical pin 17 which is disposed beside the projection 3 and distal from the aperture 12. An arm 19 is secured by a screw 18 to the pin 17 and can move angularly parallel to the surface 2 against the force of a torsion spring 20 operative between the surface 2 and the casing 1. The arm 19 is gantryshaped and has a securing end 21, used to secure it to the pin 17, and an operating end 22, the ends, 21, 22 being interconnected by a horizontal crosspiece 23.

The operating end 22 has a tooth 24 which projects towards the securing end 21. Tooth 24 engages in a recessed part 25 contrived externally in the central part of the closure member 13. The part 25 has a cross-section substantially in the shape of a very flat U; the part 25 is bounded at the top by a horizontal edge 26 and two inclined edges 27 and by two downwardly inclined edges 27 which extend the edge 26, while at the bottom the part 25 is bounded by a short horizontal edge 28.

Arm end 22 is formed with a cylindrical vertical aperture 29 and the surface 2 is formed with a rectangular-section groove 30 disposed radially opposite the aperture 12; the aperture 29 has a diameter substantially equal to the width of the groove 30.

The aperture 29 receives a safety key 31 in the form of a cylindrical shank 32 terminating at the top in an eye 33.

The arm 19 is formed with a top longitudinal recess 34 which extends in the crosspiece 23 and in the end 22. Near the centre of the crosspiece 23 two transverse apertures 35 are disposed in alignment with one another on either side of the recess 34. The apertures 35 receive a screwthreaded pin 36 which is screwed to a knurled nut 37 placed between the two apertures 35 as a means for adjusting the position of the pin 36 relatively to the arm 19.

A further two registering transverse apertures 38 are disposed on either side of the recess 34 in the end 22 and are in alignment with the eye 33 of the key 31 when the same is in its inserted position. A small pin 39 is inserted in the apertures 38 and eye 33.

A first ring 40 is secured to the end of the pin 36 for connection to a trip wire 41. A second ring 42 is secured to the pin 39 to facilitate the operation thereof.

The operation of the triggering device hereinbefore described will now be explained.

The device is first secured to the detonator of an already installed mine (not shown) in completely conventional manner, then connected by way of the ring 40 to the trip wire 41. At this juncture the tension of the wire must be adjusted agains the force of the spring 20 so that the arm 19 is accurately balanced in the inoperative position with the tooth 24 in the middle of the recessed part 25; fine adjustment of wire tension is by means of the nut 37 which is turned to move the pin 36 in the apertures 35.

After the arm 19 has been balanced in the inoperative position the safety devices can be removed, the pin 39 first being removed from the apertures 38 to release the eye 33, whereafter the safety key 31 is withdrawn from the aperture 29.

The triggering device is now in the activated state and pulling or cutting of the trip wire 41 will operate the device and therefore explode the mine; for when the wire 41 is pulled, the arm 19 turns and the tooth 24 moves in the part 25, its movement first being horizontal between the edges 26 and 28 until it strikes one of the two inclined edges 27 and thus raises the closure member 13.

As it rises the member 13 clears the aperture 12, so that the ball can be pushed out from the rounded walls of the throat 16 of the striker 6, the same therefore being forced downwards abruptly by the spring 7 and striking the detonator to explode the mine.

Operation is of course very similar if the wire 41 is cut; in this case the spring 20, which is no longer opposed by the tension of the wire, turns the arm 19 at the opposite end.

As will be appreciated, the device according to the invention is very sensitive and is therefore very reliable in operation; the point is that release of the striker is controlled through the agency of elements (arm 19, closure member 13, ball 15) between which there is very little friction; more particularly, the striker-retaining force is transmitted from the rounded throat 16 to the ball 15, which presses against the closure member 13 but with a very reduced force and therefore with very little friction.

Also, the closure member 13, since it is pivoted in the part distal from the inclined edges 27 acted on by the pull of the trip wire relatively to the place where the ball 15 presses, acts as an amplifier of the pull (or release) force of the trip wire itself, thus improving the sensitivity of the device.

In confirmation of these statements, tests have shown that the force necessary to release the striker 6 (moving the arm 19 and closure member 13) is really very slight.

A mechanical triggering device according to the invention therefore achieves the objective of the invention by overcoming all the disadvantages of the prior art as set out in the opening part hereof.

Claims (4)

1. A mechanical mine-triggering device actuated by a trip wire (41) or the like and comprising: a casing (1); a striker (6) movingly guided in a seat (4,5) in the casing (1) from an armed position to a released position; spring means (7) permanently biasing the striker (6) towards the released position; and means for releasably retaining the striker (6) in the armed position against the force of the spring means, characterised in that the means for releasably retaining the striker (6) in the armed position against the force of the spring means comprise: a throat (16) in the striker (6); an aperture (12) with which the casing (1) is formed opposite the seat (4, 5); a ball (15) received in the aperture (12) and movable from a first position, in which the ball is in engagement with the throat (16), into a second position, in which it is clear of the throat (16); and removable stop means for maintaining the ball in its first position, the stop means being mechanically actuated by the strip wire (41).

2. A device according to claim 1, characterised in that the aperture (12) is open towards the outside of the casing (1) and its length is less than the diameter of the ball (15), the stop means comprising a closure member (13) disposed on the casing (1) for rotation around an axis (14) and movable between a first position, in which it closes the aperture (12), and a second position, in which it is clear of the aperture (12).

3. A device according to claim 2, characterised in that the closure member (13) has a shaped recessed part (25) in the part distal from the axis (14) around which the closure member (13) is rotatably mounted in respect of the ball (15), a tooth (24) being provided on an arm (19) mechanically actuatable by the trip wire (41), the tooth (24) engaging in the shaped recessed part (25).

4. A device as claimed in Claim 1 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.