GB2040027A - An igniter for an explosive device - Google Patents

Abstract

An igniter for an explosive mine includes a main body 1 having an upper cup-shaped portion presenting an annular edge 2 on which bears an actuating cap 3 able to pivot about the tangent at any point on the circumference of edge 2. Main body 1 has a bottom annular flange 19 connected to the rest of the body by a thin bridge, whereby the igniter can be connected to the mine by a suitable bush 20. A striker 5 biased by a spring 8 is held in an inoperative position in body 1 by a retaining sleeve 7 carrying balls 6 engaging in a groove 5' on the striker. Sleeve 7 is connected to the cap by a link 11 for withdrawing sleeve 7 upwardly and releasing striker 5 on pivoting of the cap 3. A detonator 10 is mounted in the path of the striker 5 by a bush 17 screwed to the main body 1. A retractable safety pin is provided to hold the cap 3, and body 1 relatively immovable until the mine is used. The described igniter construction enables the igniter to be stored separately from the mine and also permits the detonator to be stored separately from the rest of the igniter. <IMAGE>

Description

SPECIFICATION An igniter for an explosive device such as a mine This invention relates to an igniter for an explosive device such as a mine.

As is known, the term "igniter" is normally used for the part of an explosive mine, or other device, which comprises actuating means, a striker operated by the actuating means and an explosive capsule or detonator disposed in the path of the striker.

Normally, the parts of the igniter, except for the capsule or detonater, are mounted on the body of the explosive mine during manufacture, to form a unit which is stored as such until use.

An object of the invention is to construct an igniter, operating under tension or pressure, adapted to form a separate unit completely independent from the rest of the mine or device, which can remain separate therefrom until shortly before use.

Accordingly, the present invention provides an igniter for an explosive device, such as a mine, including: a main body terminating at the top in an annular edge and having a bottom annularfiangefor securing to the explosive device, the flange being secured to the main body by a thin bridge constituting a predetermined breaking line; an actuating cap bearing on the annular edge of the main body and pivotable at any point around the annular edge, about a horizontal axis coinciding with a tangent to the corner of the annular edge; a striker disposed inside the main body and controllen by the motion of the cap; and a detonator mounted on a bush which can be screwed into a threaded projection extending below the main body beneath the striker.

The main advantages of an igniter embodying the invention are as follows.

Firstly, the igniter can remain separate from the body of an explosive mine or other device until used.

This has clear advantages of safety, particularly in stores.

The fuse (capsule or detonator) can be kept separate from the igniter when associated with the body of an explosive mine or other device. The capsule or detonator, mounted in a bush which can be screwed to the main body, is not associated with the igniter until the moment of use.

Finally, the igniter can be manufactured as a unit having standard dimensions and shape and can therefore be used with various mines or other devices.

In order that the invention may be readily understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an elevational view, partly in axial section of an igniter means embodying the invention; Figure 2 is a detailed view in axial section on a larger scale showing how the detonator or capsule is mounted; and Figures 3 and 4 are diagrammatical partial views in elevation and plan respectively of the igniter means and an associated safety pin.

Referring to Figure 1 of the drawings, an igniter embodying the invention comprises a main body 1 and an actuating cap 3. The main body 1 has a cup-shaped upper portion terminating in an annual edge 2 on which an internal annual shoulder 4 of the cap 3 bears.

As a result of this arrangement, when cap 3 is driven in a manner described in detail hereinafter, it can pivot freely around a horizontal axis coinciding with a straight line at a tangent to edge 2, at any point around 360 of its external perimeter.

The bottom part of body 1 has an internal seat or axial bore receiving a striker 5, which thus can move only in the axial direction.

The top end of striker 5 has an annular groove 5' for engagement by retaining balls 6 retained in respective radial bores in a retaining sleeve 7.

Acompression spring 8 is disposed between a shoulder 1A of body 1 and a plate 9 mounted on the bottom end or head of striker 5. Spring 8, which is very slightly pre-stressed, tends to press the striker towards a capsule or detonator 10, against and retaining action of balls 6 and sleeve 7.

Sleeve 7 has a top eyelet 7A engaged by the bottom end of a link in the form of a double hook 11, constituted by an S-shaped bent rod, the top end of the link being hooked to another eyelet 12 secured to cap 3.

Eyelet 12 projects from the widened base 13A of a shaft 13, which projects from cap 3 through an axial paerture. Shaft 13 has a threaded part 13B on to which a securing nut 14 is screwed. Bush 14 can be tightened to a varying extent in order to adjust the initial prestress (normally very small) of the compression spring 8, as will be explained more fully hereinafter.

A radial seal 15 is disposed between (a) the inner wall 3B of a cylindrical projection of cap 3, projecting therefrom downwards inside body 1 and (b) the outer wall 13C (the cylindrical portion), of shaft 13.

Aflexible second seal 16 is disposed between the inner wall of the top region of the cup-shaped part of body 1 and the outer wall 3A of the cylindrical projection from cap 3.

The two seals are toroidal and completely protect the mechanism inside body 1, more particularly without seal 16 preventing the cap from oscillating.

Below the tip of striker 5, the detonator or capsule 10 is held by a plug comprising a bush 17 which is screwed to a threaded cylindrical projection 1 B extending from the bottom of body 1.

Detonator 10 is in the form of a frusto-conical or substantially cylindrical capsule having a top retaining collar 10'. As clearly shown by Figure 2, detonator capsule 10 is mounted in bush 17 simply by engaging the detonator capsule in an axial aperture in bush 17 and pressing it to the bottom until a collar 10' on the capsule is brought against a shoulder or abutment formed at the end of the bore. In the resulting position, two resilient hooked securing tongues 18 formed integrally with bush 17 firmly retain the collar 10' of the capsule.

Body 1 also has an annular bottom flange 19 which co-operates with a bush 20 to secure body 1 to the body of a mine or other explosive device (not shown). Flange 19 is secured to body 1 by a thin bridge 19' constituting a predetermined breaking line.

Bush 20, which surrounds the main body 1, has a substantially L-shaped cross-section; its radial limb bears on the securing flange 19 and its axial limb is adapted to be screwed to the threaded mouth (not shown) of the body of the mine or device. The inner diameter of bush 20 is substantially the same as, or slightly greater than, the diameter of the aforementioned predetermined breaking line 19', so that the igniter can be ejected as described in detail hereinafter.

As shown in Figures 3 and 4, cap 3 is locked and made safe by a pair of safety plugs or pins 21A and 21 B engaging in matching apertures formed in pairs of radial lugs 23 projecting in diametrically directions from the cap 3, the pins also pass through respective bored stirrups 22 projecting from body 1, likewise in diametrically opposite directions.

Pins 21A and 21B are constituted by free end portions of a rigid, shaped safety fork 21 having two loops 21C particularly suited for gripping with the index finger and middle finger. Between the two loops 21C, the fork forms another loop 21 D which can be easily forced into one of two retaining hooks or tooted members 24A or 24B formed on respective stirrups 24 on body 1,thus additionally preventing the fork from accidentally slipping off.

Preferably, one pin 21A or 21B is longer than the other, to facilitate inserting the pins into the matching apertures in eyelets 23 and stirrups 22.

The complete igniter is assembled by mounting detonator capsule 10 in bush 17 as already stated and and separately assembling all the mechanical components in body 1.

This second operation is done firstly by inserting spring 8, striker 5 and plate 9 from the bottom. Then, sleeve 7 and balls 6 are inserted from the top so as to engage one another in known manner. Next, link 11 is secured in eyelet 7A and then eyelet 12 is secured to hook 11. Next, cap 3 is introduced from the top, thus driving shaft 13 into its axial bore. Finally, bush 14 is screwed to the threaded part 1 3b, thus clamping shaft 13 and causing itto project when necessary in order to tighten the chain of components comprising eyelets 12 and 7A and link 11 and, if required, slightly prestressing spring 8.

The aforementioned mechanical assembly can be stored separately from bush 17 and detonator 10, thus improving safety and the two components need not be joined until shortly before use. Furthermore, the igniter assembly need not be associated with the body of the explosive mine or device until just before use or directly before the mine or device is placed in position.

Operation is very simple. After the safety fork 21 has been extracted so that the cap 3 is free to oscillate or pivot at any point on the circumference of edge 2 triggering of the explosive device is caused by pressure exerted in known manner on oblique shanks 25 secured to cap 3, or alternatively by the cap being pulled by trip wires (not shown) secured to the top of shaft 13. The resulting movement of cap 3 raises eyelet 12 in known manner and consequently raises link 11 and sleeve 7. Thereupon, balls 6 come out of their bores or recesses, since they are no longer held by the side wall 1 B of the seat of body 1.

Striker 5 is then free and, under the pressure of spring 8 which has been loaded by raising the chain of components 12, 11, 7A, and 9, it slides downwards and strikes the detonator capsule 10, so that the latter operates and an explosion occurs.

Claims (17)

1. An igniter for an explosive device, such as a mine, including; a main body,termi- nating at the top in an annular edge and having a bottom annular flange for securing to the explosive device, the flange being secured to the main body by a thin bridge constituting a predetermined breaking line; an actuating cap bearing on the annular edge of the main body and pivotable at any point around the annular edge, about a horizontal axis coinciding with a tangent to the corner of the annular edge; a striker disposed inside the main body and controlled by the motion ofthe cap; and a detonator mounted on a bush which can be screwed into a threaded projection extending below the main body beneath the striker.

2. An igniter according to claim 1, in which the cap has an internal annular shoulder which bears on the annular edge of the main body, and beyond the annular shoulder the cap has at least two oppositelydisposed lugsformed with diametrical apertures and disposed adjacent respective bored stirrups secured to the main body, respective safety pins being provided for engagement in aperture of each lug and the bore of the respective stirrups.

3. An igniter according to claim 2, in which the safety pins are constituted by two free end portions of a single safety fork.

4. An igniter according to claim 3 in which the said free end portions of the safety fork are of different lengths.

5. An igniter according to claim 3 or 4, in which an intermediate part of the safety fork has a retaining portion adapted to engage a securing hook formed integrally with the main body.

6. An igniter according to any one of claims 3 to 5, in which the safety fork is formed with a pair of loops for gripping with the fingers.

7. An igniter according to any preceding claims, including a bush having an L-shaped cross-section surrounding the main body, the limb of the L extending perpendicular to the axis of the igniter bearing on the annular securing flange and the limb extending along the axis being for screwing to a threaded mouth of the explosive device, the predetermined breaking line of the annular flange having a diameter substantially equal to the internal diameter of the bush.

8. An igniter according to any preceding claim, in which, in the inoperative position, the striker is secured to an axial retaining sleeve by retaining balls, the sleeve being connected to the actuating cap by a link having a double hook.

9. An igniter according to claim 8, in which the link engages in a bottom eyelet secured to the top of the retaining sleeve and also engages a top eyelet associated with the actuating cap.

10. An igniter according to claim 9, in which the top eyelet is secured to the widened base of a shaft extending through an axial aperture in the cap and secured to the exterior thereof by a threaded nut.

11. An igniter according to claim 10, in which a toroidal seal is disposed between the inner wall of the cylindrical projection from the cap and a cylindrical wall of the shaft.

12. An igniter according to any one of claims 8 to 11, in which a compression spring is disposed between a bearing shoulder inside the main body and a plate borne directly by the head of the striker.

13. An igniter according to any preceding claim, in which the detonator is mounted on the associated bush screwable to the main body by engagement in a central aperture in the bush and is retained by securing tongues.

14. An igniter according to claim 13, in which the securing tongues are integral with the body of the bush.

15. An igniter according to any preceding claim, in which the annular edge bearing the actuating cap is formed at the top of a cup-shaped portion of the main body, inside which a cylindrical projection projects directlytowardsthe bottom of the cap, a flexible toroidal seal being inserted between the internal wall of the cup-shaped part and the outer wall of the projection.

16. An igniter for an explosive mine substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

17. Any novel feature or combination of features herein disclosed.