GB1568456A

GB1568456A - Impact fuse device

Info

Publication number: GB1568456A
Application number: GB7791/78A
Authority: GB
Original assignee: Saab Scania AB
Current assignee: Saab AB
Priority date: 1977-03-02
Filing date: 1978-02-28
Publication date: 1980-05-29
Also published as: CH628979A5; SE7702285L; IT7848254A0; SE416679B; BE864385A; DE2807239A1; FR2382671B3; FR2382671A1; IT1102701B

Abstract

In the case of known impact fuzes, the opening at the end of the fuze housing (1) is closed for the purpose of sealing against moisture during storage and water penetration in flight. In order to simplify the production and in order to improve the response sensitivity, the fuze housing (1), with a cylindrical recess (2) for the axially displaceable impact plunger (3), is closed by an end wall (6). This end wall (6) is integrally connected to the fuze housing (1) and has a nose part (8) which is connected to the fuze housing (1) via a ring (7) of reduced wall thickness (t). This ring (7) forms a weak point for the nose part (8) and can be dimensioned in accordance with the required response sensitivity. <IMAGE>

Description

(54) IMPACT FUSE DEVICE (71) We, SAAB-SCANIA AB, S-581 88 Linköping, Sweden, a Swedish Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statment The present invention relates to impact fuse devices of the kind comprising a fuse body defining a cavity having an end wall at the front impact end of said body, and an impact rod located in said cavity and having a front end surface adjacent to said end wall, the latter being adapted for deformation when a projectile incorporating said fuse device meets its target to bear against the end surface of the impact rod to cause the latter to detonate the projectile.

In known devices, said end wall consists of a separately manufactured part usually formed as a thin diaphragm. When assembling such a fuse, the diaphragm is inserted in an annular groove provided in the cavity, whereafter the diaphragm is fastened to the fuse body by the material at the front end of the body being axially upset by a rolling or similar operation.

Such a composite assembly is expensive to produce and there is hardly any possibility of fully automating its manufacture. Also, there is the risk that the joint between the fuse body and the diaphragm will not be completely tight, which can have the result that, during protracted storage periods, moisture can penetrate into the fuse device and damage its delicate internal components.

Functionally, a fuse device of the above kind normally has the disadvantage that it is difficult to arrange for the diaphragm to have a great sensitivity on impact against the target, since it must also be insensitive to drops of water or other objects which may impinge on the diaphragm during trajectory. With the intention of overcoming this disadvantage, it is known to provide the diaphragm on its front face with washer-like and dished means which provide for protection during trajectory, said means having forwardly facing openings whereby the diaphragm can communicate with the surroundings to obtain the desired level of sensitivity for impact. However, such a construction naturally has a cost-increasing and complicating effect on manufacture, particularly in the case of small-bore projectiles.

An object of the present invention is to provide an impact fuse device of the aforesaid kind having a diaphragm construction which eliminates the abovementioned disadvantage.

According to the present invention, an impact fuse device of the aforesaid kind is characterised in that said end wall is integrally formed with the fuse body so as to define a central unbreakable nose portion which is united with the fuse body via an annular, axially thin portion which constitutes a breakable diaphragm, said portion being defined by an annular groove extending concentrically with the axis of said fuse body.

Thus, by providing the diaphragm as an integral part of the fuse body (which can readily be produced by a turning operation), the construction is substantially simpler and therefore cheaper to manufacture. Also, it ensures that the cavity is hermetically sealed at its front end.

With an impact fuse device according to the invention. it is also possible to adjust the sensitivity of the device simply by machining the thin annular portion of the end wall to be of such dimensions that the front end of the device will be proof against rain and the like during trajectory, but will rupture when the nose portion strikes its target.

In order that the invention will be readily understood, two embodiments thereof will now be described in detail with reference to the accompanying drawing, in which: Figure 1 is a longitudinal fragmentary sectional view of one form of impact fuse, and Figure 2 is a view similar to Figure 1 of an alternative form of the fuse.

Referring to Figure 1, the numeral 1 designates the front part of a body for the impact fuse. The body defines a cylindrical cavity 2, in which an axially displaceable impact rod 3 is located. In a manner known per se, the rod 3 has its front part shaped to provide a striking plate 4, having a diameter somewhat less than the diameter of the cavity 2 and a flat front surface 5 for absorbing impact energy when the projectile strikes its target.

In a position directly in front of the surface and parallel thereto, the fuse body provides an end wall 6 of the cavity 2. In accordance with a characterizing feature of the invention this end wall is an integral part of the fuse body 1, and is united to the latter by means of an axially thin portion 7, having the shape of an annulus. The thin annular portion 7 is dimensioned so as to be situated in front of the circumferential portion of the end surface 5, while the central portion of the end wall is formed into a nose portion 8, which is extended forwardly to lie in the same plane as a front annular shoulder 9 of the fuse body. The shoulder 9 functions to provide protection for the fuse during its transport and handling.

The thin annular portion 7, which in the embodiment shown in Figure 1 is formed by machining an axially extending annular groove 10 into the front end of the fuse body, functions in principle as a breakable diaphragm with a line of weakness for rupture (a stress concentration location) defined at the inner groove edge. Thus, in use, when the nose portion 8 comes into contact with the target when the projectile strikes, impact energy is transferred thereby to the breakable diaphragm so as to cause it to rupture along its line of weakness.

The strength of the end wall 6 depends upon the dimensions of the annular portion 7. Thus, the breaking load will decrease with a decreasing thickness t and/or a decreasing diameter d of the nose portion.

By suitably adapting these dimensions the sensitivity of the fuse can be adjusted. viz.

increased or decreased. to comply with the operational demands applicable to the particular kinds of projectiles it is to be used on, thereby ensuring that rupture will not arise during trajectory but only on impact.

Referring to Figure 2, in this embodiment. the front end of the fuse body 1 is of hemispherical shape, and has a radial groove 11 extending in depth perpendicular to the axis of the fuse to provide the annular portion 7. As shown in the Figure, the annular portion 7 has a thickness t1, whilst the nose portion 8 has a diameter dl.

Provided that an impact takes place directly from the front and towards the centre of the nose portion 8, said nose portion ruptures by shearing along the diameter d, at a breaking load which, for equivalent dimensions, is approximately as great as that applicable to the embodiment shown in Figure 1. The nose portion 8, and thereby the impact rod 3, is then pressed rearwardly a distance corresponding to the axial dimension of the groove 11. In practice, however, the embodiment of fuse according to Figure 2 has a greater sensitivity, due to its ability to react to oblique strikes as well as direct frontal strikes. Even if the strike takes place so that the impact occurs at a point on the side of the nose portion 8. this portion will nevertheless transfer impact energy to the diaphragm 7.

On the other hand, the structure of the embodiment according to Figure 2 requires greater demands for protection against injury during transport and handling. Such protection can be obtained by placing a transport safety clip in the groove 11, in the shape of a plate or a wishbone having a thickness corresponding to the axial dimension of the groove 11.

It will be appreciated that the invention is not limited to the embodiments shown here, but can also include modifications thereof within the scope of the following claims. For example, the thin annular diaphragm portion 7 may be provided by machining a groove at an angle, e.g. 45" to the axis. In this case the shape and depth of the groove would be selected to ensure that a nose portion 8 is formed of the desired strength.

The line of weakness for rupture may also be formed by providing an internal forwardly extending recess. for example, during boring of the cavity 2, in the circumferential portion of the inside face of the end wall 6.

In this way the nose of the fuse would provide an unbroken outer surface.

WHAT WE CLAIM IS: 1. An impact fuse device of the kind comprising a fuse body defining a cavity having an end wall at the front impact end of said body. and an impact rod located in said cavity and having a front end surface adjacent to said end wall, the latter being adapted for deformation when a projectile incorporating said fuse device meets its target to bear against the end surface of the impact rod to cause the latter to detonate the projectile, characterized in that said end wall is integrally formed with the fuse body so as to define a central unbreakable nose portion which is united with the fuse body via an annular, axially thin portion, which constitutes a breakable diaphragm, said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. now be described in detail with reference to the accompanying drawing, in which: Figure 1 is a longitudinal fragmentary sectional view of one form of impact fuse, and Figure 2 is a view similar to Figure 1 of an alternative form of the fuse. Referring to Figure 1, the numeral 1 designates the front part of a body for the impact fuse. The body defines a cylindrical cavity 2, in which an axially displaceable impact rod 3 is located. In a manner known per se, the rod 3 has its front part shaped to provide a striking plate 4, having a diameter somewhat less than the diameter of the cavity 2 and a flat front surface 5 for absorbing impact energy when the projectile strikes its target. In a position directly in front of the surface and parallel thereto, the fuse body provides an end wall 6 of the cavity 2. In accordance with a characterizing feature of the invention this end wall is an integral part of the fuse body 1, and is united to the latter by means of an axially thin portion 7, having the shape of an annulus. The thin annular portion 7 is dimensioned so as to be situated in front of the circumferential portion of the end surface 5, while the central portion of the end wall is formed into a nose portion 8, which is extended forwardly to lie in the same plane as a front annular shoulder 9 of the fuse body. The shoulder 9 functions to provide protection for the fuse during its transport and handling. The thin annular portion 7, which in the embodiment shown in Figure 1 is formed by machining an axially extending annular groove 10 into the front end of the fuse body, functions in principle as a breakable diaphragm with a line of weakness for rupture (a stress concentration location) defined at the inner groove edge. Thus, in use, when the nose portion 8 comes into contact with the target when the projectile strikes, impact energy is transferred thereby to the breakable diaphragm so as to cause it to rupture along its line of weakness. The strength of the end wall 6 depends upon the dimensions of the annular portion 7. Thus, the breaking load will decrease with a decreasing thickness t and/or a decreasing diameter d of the nose portion. By suitably adapting these dimensions the sensitivity of the fuse can be adjusted. viz. increased or decreased. to comply with the operational demands applicable to the particular kinds of projectiles it is to be used on, thereby ensuring that rupture will not arise during trajectory but only on impact. Referring to Figure 2, in this embodiment. the front end of the fuse body 1 is of hemispherical shape, and has a radial groove 11 extending in depth perpendicular to the axis of the fuse to provide the annular portion 7. As shown in the Figure, the annular portion 7 has a thickness t1, whilst the nose portion 8 has a diameter dl. Provided that an impact takes place directly from the front and towards the centre of the nose portion 8, said nose portion ruptures by shearing along the diameter d, at a breaking load which, for equivalent dimensions, is approximately as great as that applicable to the embodiment shown in Figure 1. The nose portion 8, and thereby the impact rod 3, is then pressed rearwardly a distance corresponding to the axial dimension of the groove 11. In practice, however, the embodiment of fuse according to Figure 2 has a greater sensitivity, due to its ability to react to oblique strikes as well as direct frontal strikes. Even if the strike takes place so that the impact occurs at a point on the side of the nose portion 8. this portion will nevertheless transfer impact energy to the diaphragm 7. On the other hand, the structure of the embodiment according to Figure 2 requires greater demands for protection against injury during transport and handling. Such protection can be obtained by placing a transport safety clip in the groove 11, in the shape of a plate or a wishbone having a thickness corresponding to the axial dimension of the groove 11. It will be appreciated that the invention is not limited to the embodiments shown here, but can also include modifications thereof within the scope of the following claims. For example, the thin annular diaphragm portion 7 may be provided by machining a groove at an angle, e.g. 45" to the axis. In this case the shape and depth of the groove would be selected to ensure that a nose portion 8 is formed of the desired strength. The line of weakness for rupture may also be formed by providing an internal forwardly extending recess. for example, during boring of the cavity 2, in the circumferential portion of the inside face of the end wall 6. In this way the nose of the fuse would provide an unbroken outer surface. WHAT WE CLAIM IS:

1. An impact fuse device of the kind comprising a fuse body defining a cavity having an end wall at the front impact end of said body. and an impact rod located in said cavity and having a front end surface adjacent to said end wall, the latter being adapted for deformation when a projectile incorporating said fuse device meets its target to bear against the end surface of the impact rod to cause the latter to detonate the projectile, characterized in that said end wall is integrally formed with the fuse body so as to define a central unbreakable nose portion which is united with the fuse body via an annular, axially thin portion, which constitutes a breakable diaphragm, said

annular, axially thin portion being defined by an annular groove extending concentrically with the axis of said fuse body.

2. An impact fuse device according to Claim 1, characterized in that the nose portion is defined by an axially extending annular groove provided in the front face of the fuse body, the depth of said groove being such as to leave an appropriately dimensioned annular, axially thin circumferential portion in said end wall.

3. An impact fuse device according to Claim 1, characterized in that the nose portion is defined by a radial groove extending transversely of the axis of the fuse body at a position selected to leave an appropriately dimensioned annular, axially thin circumferential web portion between the inner face of said end wall and the adjacent wall of said groove.

4. An impact fuse device constructed, arranged and adapted for use substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.

5. A projectile incorporating an impact fuse device according to any one of Claims 1 to 4.