GB2035518A - Fuze for mines - Google Patents

Abstract

A mine fuze which is sensitive to tipping but insensitive to shock waves comprises a mechanically released detonating mechanism, e.g. a rotor 13 carrying a detonator 6, by means of which the mine can be detonated, a device 15 acting on the detonating mechanism which is designed to arm the detonating mechanism automatically a certain time after the mine has been laid, and a mass 16 acting as a pendulum, which is sensitive to the tipping of the mine and which can move around an axle 17 to trigger the detonating mechanism, wherein the pendulum can freely take up the equilibrium position prevailing for it at the time, as long as the detonating mechanism is not armed, by rotating around the axle, without affecting the detonating mechanism, but the pendulum forming a mechanical operative connection when the detonating mechanism is armed under the effect of the said arming device so that, when disturbed out of its equilibrium position as a result of tipping of the mine, the pendulum triggers the detonating mechanism via the operative connection. <IMAGE>

Description

SPECIFICATION Mine detonator which is sensitive to tipping The present invention relates to a mine detonator which is sensitive to tipping, of the type comprising a mechanically released detonating mechanism by means of which the mine can be detonated, a device acting on the detonating mechanism which is designed to arm the detonating mechanism automatically a certain time after the mine has been laid, and a mass acting as a pendulum, which is sensitive to the tipping of the mine and which can move around an axle to trigger the detonating mechanism.

Conventional anti-troop or anti-tank mines with mechanical triggering are sensitive only to such pressure forces as arise when the mine is trodden on or run over by a tank. The force which is necessary to set-off and detonate the mine is naturally adapted to the target which the mine is intended to combat; for a tank, this force is chosen sufficiently great for the mine normally not to be detonated when it is trodden on.

Accordingly, it can be said that conventional mines of the above mentioned type are relatively insensitive and not particularly difficult to clear and defuse, especially if they can be located. A common way of clearing a road in a mined area is to detonate an elongated charge, known as a mine snake, whereby a number of mines within a specific distance from the charge are detonated by the shock waves which arise. It is also known to protect tanks from mines with a plough-like arrangement mounted on the front of a tank, by means of which any tank mines there may be can be ploughed up and pushed so far to the side that, even if they should be detonated during the process, they cause little or no damage to the tank.

Detonators or detonating devices which are sensitive to tipping and which operate according to electrical or magnetic principles have already been proposed. A ball of magnetic or electrically conducting material is used as the position-detecting device; this can move in pre-determined paths and is set into motion when tipping occurs, thereby effecting contact between two poles which are isolated from one another, or else the movements can be detected by a detector which is sensitive to the magnetic field.

A grave disadvantage of this type of detonator is that it requires some form of electrical power cell, usually a battery. Electrical batteries have a limited life and durability, as is known, and it is therefore expensive and laborious work ensuring that the batteries are constantly capable of functioning when the electrically operating detonators are stored.

Another disadvantage is that the limited life of the electrical batteries determines the time that a mine is capable of functioning after it has been laid.

The object of the present invention is to provide a mechanically-operating mine detonator which is sensitive to tipping but insensitive to shock waves, and this can be accomplished with detonators which have the characteristics set out in the Patent Claims. The detonators can be used both alone or together with the conventional pressure-sensitive trigger device of the mine. A mine equipped with a detonator according to the invention cannot be made harmless in any of the ways described above. With removal by ploughing the mine detonates as soon as it is tipped, and since the detonation is likely to occur near the ploughing arrangement, this and the tank will be destroyed and further removal will be made extremely difficult.

In order that the invention will be clearly understood two embodiments thereof will now be described with reference to the accompanying drawings, in which Figure 1 shows schematically detonators in accordance with the invention, fitted on a mine.

Figure 2a shows a preferred first embodiment of such a mine detonator, viewed from above, Figure 2b is a central longitudinal section through the detonator 2a, Figure 2e shows part of Fig. 2a in detail.

Figures 3a and 3b show a second embodiment of a detonator according to the invention, viewed from one side and from above respectively, and Figures 4a and 4b show an alternative way in which to make the detonators insensitive to clearing by means of mine snakes. In the figures, corresponding parts have been given the same reference numerals.

The mine in Fig. 1 consists of a circular body 1 containing explosive material and a housing 2 arranged in the centre of the body and containing a detonating mechanism which is triggered by pressure, with a trigger component 3, this being a so-called breaking cross. On the housing 2 a tipping-sensitive mine detonator 4 according to the invention is attached by a wire loop round the housing, or in some other appropriate way. Since, as will become clear from the following, the detonator 4 does not have to be placed in a special way or in a particular position when the mine is laid, the way in which the detonator 4 is attached to the mine is quite irrelevant. Accordingly, the detonator can also be installed advantageously in the mine itself.

The detonator in Fig. 2 can be divided up into five co-acting functional parts, namely, a mechanically triggered detonating mechanism by means of which the mine can be deto nated, means acting on the detonating mecha nism, such as a clock mechanism, for exam ple, which is designed to arm the mine automatically a certain time after the mine has been laid, a device which is sensitive to tipping, an operative connection which is effective under certain conditions which will be described later, between the tipping-sensitive device and the detonating mechanism, and means sensitive to acceleration force such as is caused, for example, by detonation shock waves; the task of this means is to prevent the mine from detonating when shock waves occur due to mine snakes, for example.

The detonating mechanism comprises a percussion cap 6 with an initiator charge 7 and a striker pin 8 with a trigger spring 9 and a locking device 10 in the form of a ball. The striker pin can be displaced in a bore 11, which opens out immediately in front of the percussion cap 6 when the detonator is armed. When the spring 9 and with it the detonating mechanism are under compression, the striker pin 8 is held up by the ball 10 which engages in a groove 1 2 around the striker pin 8. The percussion cap 6 is mounted in a rotor 1 3 which is rotatably mounted around an axle 14 which is perpendicular to the movement path of the striker pin 8, in such a way that when the detonator is secured the percussion cap forms an approximate right-angle with the striker pin.It is therefore quite impossible for the detonator to be triggered off accidentally when in the secured state, since the striker pin 8 cannot reach the percussion cap 6, even if it is released.

In the embodiment shown in Fig. 2, the priming device consists of a clock mechanism 1 5 which is connected to the axle 14 of the rotor 1 3 which contains the percussion cap 6.

During priming, the clock mechanism 1 5 turns the rotor 1 3 anticlockwise so that the percussion cap 6 comes into position in line with the movement path of the striker pin 8.

An additional securing arrangement, which will be described later in conjunction with the effective connection between the device which is sensitive to tipping and the detonating mechanism, is thereby actuated. Assuming that the construction of the detonator is suitable in other respects, the arming device can naturally consist of many other types of mechanically-operating delayed mechanism, such as the type which is described in US Patent No. 3 786 750, for example.

The device which is sensitive to tipping consists of a wheel 1 6 acting as a pendulum which is mounted rotatably on a concentric axle 1 7 and is provided with an eccentrically located weight 1 8. So that the wheel 1 6 may rotate freely, it is disposed under the effect of gravity along, thus, in a state of equilibrium in which the weight 1 8 occupies its lowest position.

The operative connection between the pendulum wheel 1 6 and the detonating mechanism consists of a friction wheel 1 9 which is rigidly connected to the axle 1 7 and to the wheel 16, a counter-pressure wheel 21 arranged against the periphery thereof and loaded by a spring 20, and a friction rod 22 clamped by one end between the said wheels 19, 21. On its other end this friction rod has a piston 24 mounted in a bore 23, which, except when the detonating mechanism is triggered, holds the locking ball 10 pressed into the groove 1 2 and thus holds up the striker pin 8.In the secured state, on the friction rod 22 there acts one end of a link arm 26 which is pivotably mounted on an axle 25, and the other end of which is engaged with an entraining pin 27 on the rotor 13 in such a way that, as can be seen in Fig.

2c, the friction rod 22 is held disengaged from the friction wheel 1 9. Due to a groove 28 disposed on the friction rod 22 in which the link arm now engages, the friction rod is secured from moving in its longitudinal direction. The surface of the piston 24 sliding towards the bore 23 is made slightly spherical to make possible the pivoting movements of the friction rod 22 into and out of engagement with the friction wheel 1 9. According to the invention, the described effective connection allows the pendulum wheel to take up freely by itself the equilibrium position prevailing for it at any given moment, as long as the detonating mechanism is not armed, but during arming the pendulum is connected to the detonating mechanism so that this is triggered when the pendulum is displaced out of its said equilibrium position.

The acceleration-sensitive device consists of a body 29 which is displaceably mounted spring-loaded in a housing 30 on one end face 31 of which the axle 17 is mounted. The body is held in a centred position in the housing by a flat spiral spring 32 disposed between the body 29 and the end face 31, the centre of this spring coinciding generally with the centre of the housing 30 and the mounting for the axle 1 7. On the side opposite to the spring 32, in the body 29 there is a conical cavity 33 which opens into a circular opening 34 in the other end face 35 of the housing. A ball 36 rests in the opening 34.

The depth of the cavity 33, the diameter of the ball 36 and the thickness of the end face 35 are adapted to each other so that the ball 36 just projects through the opening 34 out on the side of the end face 35 facing away from the body 29, when the body 29 is held by the spring 32 in a centred position with the cavity 33 lying in the centre of the opening 34. When the detonator is subjected to a lateral acceleration force of such a magnitude that despite the spring 32 there is a relative movement between the housing 30 and the body 29 as a result of the inertia of the latter, the ball 36 is forced out through the opening 34 as a result of the wedge effect of the walls of the cavity 33.Against the opening 34 and on the outer face of the end face 35, under the effect of a spring 37, there rests one arm of a lever 39 mounted on an axle 38, the other arm of which is equipped with a block 40 made of a friction material.

The lever is arranged in such a way that when the ball 36 is pressed out through the opening 34 in the way described above, against the arm of the lever loaded by the spring 37, thus overcoming the spring 37, the friction block 40 presses against the periphery of the pendulum wheel 1 6 so that this is prevented from rotating. It can be said that the spring also has the task, in addition to centring the body 29, of preventing it from being displaced relative to the housing 30 when acceleration forces of such a magnitude arise, i.e.

gravity, to which the body can be subjected when the mine is tipped up.

The mine detonator described above operates in an imaginary practical application in the following way: When the detonator is secured as shown in Fig. 2, the spring 9 is compressed and the striker pin 8 is held up by the ball 10 which is held in place by the piston 24. Since the rotor is turned so that the percussion cap 6 lies out of the movement path of the striker pin, as already mentioned, accidental release is not possible. Due to the pivot position of the rotor, moreover, the friction rod 22 is also fixed via the link arm 26 so that it is both immovable in its longitudinal direction and also out of contact with the friction wheel 19, which means that the pendulum wheel 1 6 can rotate freely according to the position ofthe mine detonator at the time.

When the mine is laid, the clock mechanism 1 5 is started. The pendulum wheel 1 6 can still rotate freely on its axle 17, and after a short time assumes its equilibrium position.

Under the effect of the clock mechanism the rotor 1 3 rotates anti-clockwise, so that when the clock mechanism runs down it takes up a position in which the percussion cap 6 is located immediately in front of the mouth of the bore 11, i.e. right in the displacement path of the striker pin 8. With the anticlockwise movement of the rotor, the friction rod 22 is caused by the link arm 26 to engage with the friction wheel 1 9 at the same time as the lock which is effected by the link arm 26 engaging with the groove 28 on the friction rod 22 ceases to be effective. The mine detonator is now armed. If the mine and with it the detonator 4 should now be tipped, for example as a result of attempts to clear the mine, the pendulum wheel 1 6 tries to take up a new equilibrium position.This causes the friction rod 22 to be displaced in its longitudinal direction and with it also the piston 24, which results in the locking ball 10 no longer being held in place but being forced out of the groove 1 2 in the striker pin 8 which is thereby released. The striker pin is hurled by the spring force towards the percussion cap 6 which then causes the initiator charge 7 and with it the whole mine to detonate.

If instead attempts are made to cause the detonator to trigger the mine by detonating a mine snake or other charge in the vicinity of the mine, thereby making the latter harmless, it will be appreciated from the following that this will not be successful. If the detonation occurs within a certain distance from the mine, both it and the detonator will be shaken and moved as a result of the acceleration forces which arise with the detonation. However, the body 29 will maintain its position, due to its inertia, provided that the lateral acceleration force is sufficiently great to overcome the force from the flat spiral spring 32.

Due to the relative movement between the body 29 and the housing 30 which now occurs, the ball 36 is pressed against the lever 39 which causes the brake block 40 to be pressed against the pendulum wheel 1 6 which is braked thereby, so that release of the detonating mechanism is prevented.

In the mine detonator shown in Fig. 3, some technical structural modifications can be observed in the embodiment of the present invention. The operative connection which is established according to the invention between the pendulum wheel 1 6 and the detonating mechanism when the detonator is armed, is accomplished in this instance by means of a gear-wheel 41 which is axially movable between two terminal positions. In one position, which is shown in Fig. 3, which the wheel 41 occupies as long as the detonator is secured, there is no effective connection between the detonating mechanism and the pendulum wheel 16, which can therefore take up the equilibrium position prevailing for it at the time.In the other terminal position which the gear-wheel 41 is made to occupy when the detonator is armed, the gear-wheel is engaged with a ring of teeth 42 around the periphery of the pendulum wheel 1 6 and also with a device equipped with teeth in the detonating mechanism. This device has a task which is analogous with that of the piston 24 in Fig. 2, namely to hold the locking ball 10 in place in the groove 1 2 and thereby to restrain the striker pin 8. When the detonator is armed, any disturbance of the same which entails a change of the equilibrium position of the pendulum wheel results in the release of the striker pin 8. The gear-wheel 41 is held in the said terminal position by a locking arm 45 which can rotate around an axis 44, and it is pressed upwards away from it by a flat spring 46.

As an additional precaution against accidental setting off, the percussion cap 6 is arranged in a slide 47 which is movable transverse to the movement path of the striker pin 8, the function of which is analogous with that of the rotor 13. As long as the detonating mechanism is secured, the slide 47 is locked by a ball catch 48 with co-acts with arming clock mechanism 15, in such a position that the percussion cap 6 is located to the side of the movement path of the striker pin 8. When the detonator is armed, the slide 47 is freed from the ball catch 48 so that it can move under the effect of a spring 49, so the percussion cap 6 is located immediately in front of the striker pin 8.The locking arm 45 mentioned previously is connected to the slide 47 in such a way that it is rotated around its axis 44 when the slide 47 moves sufficiently to free the gear-wheel 41, and is brought by the spring 46 into the other terminal position in which it engages with the pendulum wheel 1 6 and the locking device 43.

In the acceleration-sensitive device which has the task of preventing the detonator from reacting to shock waves which produce transitory horizontally-directed acceleration forces above a pre-determined magnitude, the inertia body 29 is found again, being mounted as before, movably and also spring-loaded relative to the detonator, being provided with three upwards-pointing pins 50. The said device also comprises a wheel 51 equipped with arms, which is arranged concentrically with the body 29 and between the pins 50 and which engages via the gear-wheels 52, 53 with the ring of teeth 42 and thus also with the pendulum wheel 16. The gear ratio between the pendulum wheel 1 6 and the armed wheel 51 is such that the latter rotates rapidly even when the pendulum wheel is rotating slowly.However, if as a result of a close and adequately powerful detonation this tends to be rotated, a relative movement will also take place between the inertia body 29 and the armed wheel 51, provided that the acceleration force overcomes the force of the spring 32. The wheel 51 is then prevented from rotating by the pins 50, and the pendulum wheel 1 6 is thereby stopped directly and triggering is prevented.

As has already been mentioned, Fig. 4 also shows a way of making the detonator insensitive to clearing by means of shock waves from a mine snake, for example. The accelerationsensitive device is constructed and operates generally in the same way as that described in connection with Fig. 2, but the braking of the pendulum wheel 1 6 is carried out in this instance against the operative connection in such a way that the friction block 40 is made to act on the periphery of a wheel 54 rigidly connected concentrically on the gear-wheel.

Claims (7)

1. A mine detonator which is sensitive to tipping, comprising a mechanically released detonating mechanism by means of which the mine can be detonated, a device acting on the detonating mechanism which is designed to arm the detonating mechanism automatically a certain time after the mine has been laid, and a mass acting as a pendulum, which is sensitive to the tipping of the mine and which can move around an axle to trigger the detonating mechanism, characterised in that the pendulum is designed so that as long as the detonating mechanism is not armed it can freely take up the equilibrium position prevailing for it at the time, by rotating around the axle, without affecting the detonating mechanism, but when the detonating mechanism is armed it forms a mechanical operative connection with this under the effect of the said arming device so that when it is disturbed out of its equilibrium position as a result of tipping of the mine, the pendulum is able to trigger the detonating mechanism via the operative connection.

2. A mine detonator according to Claim 1, characterised in that it comprises a device which acts on the pendulum or the operative connection and is sensitive to acceleration force, and which is designed to prevent the pendulum from trigger the detonating mechanism when the acceleration force exceeds a pre-determined value.

3. A mine detonator according to Claim 2, characterised in that the said pre-determined value is greater than the force of gravity.

4. A mine detonator according to Claim 2, characterised in that the acceleration-sensitive device consists of a body with a specific inertia, which can be moved in the transverse direction relative to the axle of the pendulum against the effect of a spring, and a stopping device which co-acts with the body and is designed to be caused by the body to engage with the pendulum or the operative connection, and thereby to stop or brake the movement of the pendulum when acceleration forces occur which are greater than the force of the spring.

5. A mine detonator according to Claim 1, characterised in that the operative connection consists of a friction wheel connected to the pendulum, a counter-pressure wheel acting in a direction counter to the periphery of the friction wheel, a friction rod arranged between the two said wheels and connected to the detonating mechanism, which rod is designed to be disengaged or engaged with the friction wheel under the effect of the arming device so that as long as the detonator is not armed the pendulum can freely take up the equilibrium position prevailing for it at the time, but after arming entrains the friction rod via the friction wheel.

6. A mine detonator according to Claim 1, characterised in that the pendulum consists of a concentric, rotatably mounted wheel with an eccentrically situated centre of gravity and with teeth around its periphery, and that the operative connection between the pendulum gear-wheel and the detonating mechanism consists of an intermediate wheel which can be put into one of two positions under the effect of the arming device and which is designed so that before arming it takes up an inactive position in which the intermediate wheel is not engaged with the pendulum gear-wheel and so that during arming it is brought by the arming device into the other position in which the intermediate wheel couples together the pendulum gear-wheel and the detonating mechanism.

7. A mine detonator constructed, arranged and adapted to operate substantially as hereinbefore described with reference to Figs. 2a, band c, 3a and 3b, or 4a and 4b of the accompanying drawings.