US20090260533A1

US20090260533A1 - Fuse for a projectile

Info

Publication number: US20090260533A1
Application number: US12/391,772
Authority: US
Inventors: Markus Kopf; Frank Weisser; Frank Martin Kienzler
Original assignee: Junghans Microtec GmbH
Current assignee: Junghans Microtec GmbH
Priority date: 2008-02-26
Filing date: 2009-02-24
Publication date: 2009-10-22
Also published as: EP2096402A3; ZA200901311B; DE102008011081B4; DE102008011081A1; EP2096402A2

Abstract

A fuse for a projectile has a primary firing assembly and a secondary firing assembly. The secondary firing assembly, which is separated from the primary firing assembly by a barrier, has a firing relay with a relay explosive in a sleeve component and a firing booster. When using insensitive explosive for the secondary firing assembly, little energy should be lost in the relay from the primary to the secondary firing assembly, with enhanced safety against inadvertent firing in the secondary firing assembly. For that purpose, the sleeve component forms a gas-tight seal for the secondary firing assembly with respect to the primary firing assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. § 119, of German application DE 10 2008 011 081.7, filed Feb. 26, 2008; the prior application is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a fuse for a projectile having a primary firing assembly and having a secondary firing assembly, which is separated from the primary firing assembly by a barrier and has a firing relay with a relay explosive in a sleeve component, and has a firing booster.
Fuses for artillery projectiles, mortar shells or direct projectiles are normally fitted with a primary firing assembly with a primary firing chain, or a primary firing element and a secondary firing assembly with a secondary firing chain, or a secondary firing element. A barrier is arranged between the firing chains or firing elements and prevents inadvertent crossover from the primary firing chain to the secondary firing chain. The barrier may be formed by a plate which is arranged between the firing chains when in the safe position, and is pivoted out of the area between the firing chains when in the armed position. The barrier is frequently formed by a detonator for the primary firing chain, which is pivoted out of a firing line when in the safe position, in such a way that a firing impulse from an initial detonator cannot strike the detonator and no firing impulse from the detonator can strike the second firing chain.
In order to avoid inadvertent firing within the secondary firing chain, it is advantageous for the firing elements for the secondary firing assembly to be provided with insensitive explosive. In accordance with the international STANAG standard (NATO standard), an insensitive explosive is an explosive which does not fire when a standard initiator is detonated at a distance of at most 15 mm, water column. It must therefore withstand the pressure wave transmitted by a water column of 15 mm, without firing. This results in a high degree of insensitivity of the explosive to an accidental impact of a bullet or shell fragment, or to an adjacent explosion, in such a way that, for example, an ammunition depot can withstand being fired at.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a fuse for a projectile which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a reliable firing fuse, which has a high degree of safety against inadvertent firing.
With the foregoing and other objects in view there is provided, in accordance with the invention, a fuse for a projectile, comprising:
a primary firing assembly;
a secondary firing assembly adjoining the primary firing assembly, the secondary firing assembly having a firing relay with a relay explosive disposed in a sleeve component, and having a firing booster;
said sleeve component forming a gas-tight seal of said secondary firing assembly with respect to said primary firing assembly and a barrier separating said secondary firing assembly from said primary firing assembly.
In other words, the objects of the invention are achieved in that the sleeve component forms a gas-tight seal for the secondary firing assembly with respect to the primary firing assembly.
The invention is in this case based on the idea that insensitive explosive is relatively difficult to fire. A firing element in the primary firing chain, for example a detonator, should therefore be fitted as closely as possible to the insensitive explosive to be fired, for example a firing relay of the secondary firing chain. This requirement is contrary to detonator safety requirements, for example in accordance with AOP Standard 20 which, in addition to the barrier, require that the secondary firing chain be sealed from contact with the hot gases which are developed when a primary initiating device is fired. No fragments, perforations, combustion points, smoke, carbonization or singeing or melting damage may therefore occur on the secondary firing assembly, which in addition must not exhibit any evidence of glowing. A seal must therefore be provided between the primary and the secondary firing assembly which is sufficiently gas-tight when it reliably prevents the damage mentioned above. The barrier can generally not provide a seal such as this since it is intended to allow intentional crossover, that is to say it must be open for example. The seal must therefore be provided by an additional component.
The invention is based on the further idea that, in order to form an insensitive firing relay, its relay explosive must be pressed into a housing and must be held in a housing in the fuse. Intentional crossover must therefore pass through both the seal and the housing of the firing relay and sufficient energy must then still be available for crossover to the insensitive firing relay. In order to reliably ensure crossover to an insensitive firing relay, any energy loss caused by the seal and the housing should therefore be as little as possible.
If the housing for the relay explosive and/or the sleeve component intrinsically itself forms a gas-tight seal, then there is no need for a separate seal and energy loss is less than that of two separate components. More energy is therefore available for firing the firing relay, which can therefore be designed to be less sensitive. The sealing sleeve component therefore makes it possible to enhance the safety against inadvertent firing of the firing relay, since this can be kept insensitive.
The projectile may be an artillery projectile, a mortar shell or a direct projectile, in particular in the caliber range from 30 mm to 70 mm. The barrier may be a detonator which can be pivoted out of an armed position, or a shield in the form of a plate. It is expediently provided in addition to the sleeve component. Gas-tightness is achieved if, when a detonator in the primary firing assembly is fired when in the safe position, no fragments, perforations, combustion points, smoke traces, carbonization or singeing or melting damage occurs on the secondary firing assembly. The sleeve component is expediently formed integrally. It may be a component of the gas-tight seal, but need not carry out this function on its own. The firing assemblies may each comprise firing chains, in which case the primary firing assembly may be provided with just one firing element instead of the firing chain. The secondary firing assembly comprises the firing relay which is provided in order to fire the firing booster. The firing booster is used to fire the main charge of the projectile.
In one advantageous embodiment of the invention, the sleeve component forms a housing for booster explosive of the firing booster. The booster explosive can thus be held in a defined manner on the relay explosive without the two explosives being held by two components. An undesirable distance between the two explosives can be avoided, as could occur, for example, as a result of manufacturing tolerances of two components. Since the crossover is caused by a pressure wave, the firing relay can be designed to be smaller, with a very small gap being provided or no gap reliably being provided, than when a relatively large gap must be calculated in for safety reasons or tolerance reasons. In the case of a small firing relay, a detonator for the primary firing device can be pivoted, in a physically small form, out of the firing line or the area of the firing relay.
The sleeve component advantageously clasps the booster explosive at least from two directions, in particular from the front and on all sides, in which case the expression sides should be understood as meaning with respect to the fuse alignment. Only at the rear—which in this context should not be understood as meaning a side—can the sleeve component remain open for filling, and can be closed by a closure, for example a plate, after being filled, and can be sealed against moisture.
The sleeve component expediently forms at least a part of hermetically sealed encapsulation of the relay explosive and of the booster explosive for the firing booster. There is no need for any additional, for example side, seals and a high degree of safety can be achieved.
In a further embodiment of the invention, the sleeve component forms a housing for the primary firing assembly. This allows the primary firing assembly, and therefore its detonator as well, to be shielded well from the outside, so that no combustion gases pass from the primary firing assembly to the secondary firing assembly.
The booster explosive of the firing booster can be particularly insensitive and can thus be designed to be particularly safe while it can nevertheless be fired reliably, if the relay explosive has different firing characteristics than the booster explosive of the firing booster. If the relay explosive can be fired more easily, this makes it possible to ensure reliable relaying. Since the firing relay is considerably smaller than the firing booster and it is therefore considerably more difficult for shell fragments or the like to strike it, it is not necessary for the relay explosive to be completely insensitive, in accordance with STANAG. However, the booster explosive is expediently insensitive, in particular in accordance with STANAG. The relay explosive is therefore advantageously a different substance than the booster explosive of the firing booster.
A high degree of safety can nevertheless be achieved if the relay explosive is at least insensitive to a temperature of up to 200° C., since high temperatures can also pass through to a small firing relay.
In a further advantageous embodiment variant of the invention, the sleeve component forms the only material barrier between the relay explosive and an armed detonator for the primary firing assembly. Reliable crossover can be achieved when the primary firing assembly is in the armed position.
The fuse has a fuse housing which shields the components arranged in it from the outside and ensures stability on firing and impact. Good shielding of the secondary firing assembly without the use of additional components can be achieved if the sleeve component forms a load-bearing housing part of the fuse housing. The shielding characteristic of the fuse housing can be used to shield the secondary firing assembly. The relay explosive can be introduced directly into the sleeve component, and therefore directly into the fuse housing.
The fuse is subject to extremely high accelerations on firing and impact of the projectile, which mechanical and if appropriate electrical components in particular in the primary firing assembly should withstand with as little damage as possible. For this purpose, the components can be held firmly by a solid supporting plate in a fuse housing. A compact arrangement can be achieved if the sleeve component is a supporting plate for supporting the primary firing assembly. The supporting plate may be the firmest element which holds fuse components arranged further forwards on the fuse housing. It may itself be a component of the fuse housing which surrounds all the elements of the fuse except for the secondary firing assembly, which can be arranged externally on the load-bearing part of the fuse housing and can be protected from the outside just by a cover.
The sleeve component expediently forms a bottom screw of the fuse, as a result of which the described secure mounting can be linked to the compact design.
It is also proposed that the sleeve component forms a tab in the direction of the primary firing assembly, in which, in particular, relay explosive is arranged. An embodiment such as this allows the relay explosive to be moved towards the primary firing assembly, that is to say allows it to be arranged closer to the primary firing assembly than without the tab. A greater distance between the detonator and the firing relay can be avoided, and absorption of pressure-wave energy by an air space can be kept minor.
A compact design of the fuse and robust mounting of assemblies of the primary firing assembly can be achieved if the tab engages in a recess in an assembly mount for the primary firing assembly. The assembly mount allows robust mounting to be achieved and, as a result of the engagement, a distance which absorbs only a small amount of energy.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a fuse for a projectile, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a partly sectional view of a fuse for a projectile according to the invention;

FIG. 2 is an enlarged detail from FIG. 1, with a sleeve component of the secondary firing assembly; and

FIG. 3 is a sectional view of an alternative sleeve component of the secondary firing assembly.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a fuse 2 for a projectile with a fuse housing 4. A rear portion 8 is illustrated partially broken away and in section. In the forward portion 6, the fuse housing 4 may, for example, surround an impact mechanism and possibly electronic components while, in contrast, a primary firing assembly 10 and, behind it, a secondary firing assembly 12 are disposed in the rear portion 8.
The two firing assemblies 10, 12 are illustrated enlarged in FIG. 2. The primary firing assembly 10 comprises a detonator 14 which is illustrated in its armed position in FIG. 2. The detonator can be pivoted by means of a mechanism 16 from a safe position to the armed position, with the detonator 14 being arranged laterally offset with respect to the center axis 18 of the fuse 2 when in the safe position, in such a way that it is not aligned with an opening 20 in a plate 22 which is used as an assembly mount for supporting assemblies of the first firing assembly 10. The mechanism 16 can be interlocked by means of an interlock 24, for example a double-bolt system, such that it reliably holds the detonator 14 in its safe position.
The secondary firing assembly 12 comprises a firing relay 26 with relay explosive 28 which rests directly on the booster explosive 30 of a firing booster 32. The relay explosive 28 is mounted in a sleeve component 34 which surrounds it at the front and on all four sides and is open only at the rear towards the booster explosive 30. The sleeve component 34 also forms a housing for the booster explosive 30, which holds this in the form of a pot with side walls 36 which provide shielding in all lateral directions. At the rear, the housing for the booster explosive 30 is closed by a cover 38 and additional sealing composed of a lacquer, so that the relay explosive 28 and the booster explosive 30 are hermetically sealed from the exterior.
The fuse housing 4 of the fuse 2 is fitted with all the assemblies that are present in it and is responsible for the mechanical robustness of the fuse 2 and the mechanically stable position of the assemblies in the fuse 2 during storage, firing, flight and impact. For this purpose, the fuse housing 4 has, inter alia, a base plate 40 which is screwed from the inside into a housing section which is arranged further forwards. The greatest part of the base plate 40 is formed by a bottom screw 42 which is screwed into the circumferential part of the base plate 40. The bottom screw 42 is formed by the front plate part of the sleeve component 34 and supports assemblies of the fuse 2 at the rear. The sleeve component 34 therefore forms a part of the fuse housing 4 of the fuse 2. The relay explosive 28 is therefore inserted or pushed directly into the fuse housing 4.
The sleeve component 34 is provided with a tab 44 which engages in a recess 46 in the plate 22. The opening 20 in the plate 22 is incorporated in this recess 46. The tab 44 ends at the front in a cover 48 which is directly adjacent to the opening 20, or alternatively may be located in the opening 20. This results in the sleeve component 34 being very close to the detonator 14, as a result of which little relay energy is lost from the detonator 14 to the firing relay 26.
When the fuse 2 is launched, the interlock 24 is unlocked by the launch acceleration, and releases the mechanism 16 which moves the detonator 14 out of a peripheral position to its armed position, in which it is arranged on the center axis 18, as is illustrated in FIG. 2. On impact of the fuse 2 or at a time which is predetermined by electronics, an initial detonator which is not illustrated is fired, and passes its relay energy through a channel 50 to the detonator 14. Its conventional explosive is fired and its pressure wave destroys the cover 48 of the sleeve component 34, in such a way that the pressure wave can reach the insensitive relay explosive 28.
As a result on the one hand of the close proximity of the relay explosive 28 to the detonator 14 and on the other hand the separation of the relay explosive 28 and the detonator 14 by just a single component, specifically the cover 48, little relay energy is lost and the detonator 14 is able to fire the firing relay 26. It is also feasible for the relay explosive 28, although it is not an insensitive explosive in accordance with STANAG, but is also not a conventional explosive, nevertheless to be characterized by at least being insensitive to high temperatures, for example up to 200° C.
The fired relay explosive 28 now itself fires the booster explosive 30, which is insensitive in accordance with STANAG and in turn fires the main charge of the projectile. As a result of the direct contact on the relay explosive 28 with the booster explosive 30, which is also regarded as being present when only a layer composed of air or material, for example lacquer of less than 300 μm is present between the relay explosive 28 and the booster explosive 30, no relay energy or only a small amount of relay energy is lost, as a result of which the energy of the relatively small firing relay 26 is sufficient to fire the insensitive booster explosive 30. Its pressure wave blows off the cover 38 and a cover 52 which is screwed to the fuse housing 4, in order to protect the secondary firing assembly 12, and fires the main charge.
If a large amount of energy is applied to the fuse 2 when in its safe position, for example by a high temperature resulting from the influence of combustion or by impact of a bullet or of a fragment on the fuse 2, then no explosive in the secondary firing assembly 12 is fired since both the relay explosive 28 and the booster explosive 30 are insensitive in accordance with STANAG. If the relay explosive 28 is only temperature-insensitive, then it could admittedly be fired, for example, by a fragment striking it directly, but such an impact will with a high degree of probability be suppressed because of the highly protected position of the firing relay 26 in the sleeve component 34 and in the plate 22. This also results in a high level of safety.
Less protected and furthermore more sensitive are the explosive of the detonator and of the initial detonator which may be present. In the event of inadvertent firing of the detonator 14 or of the initial detonator, the firing relay 26 and its relay explosive 28 must not be adversely affected. This is achieved by the hermetic sealing of the secondary firing chain by the sleeve element 34, which surrounds the secondary firing chain and is formed integrally, in conjunction with the cover 38.
FIG. 3 shows an alternative sleeve element 54 with a firing relay 56 inserted in it with relay explosive 58. The following description is restricted essentially to the differences from the exemplary embodiment in FIGS. 1 and 2, to which reference is made with regard to features and functions which remain the same. Components which remain substantially the same are in principle provided with the same reference symbols, and features which are not mentioned have been adopted in the following exemplary embodiment although they will not be described again.
The sleeve element 54 forms a housing for the primary firing assembly 10 at the front, by means of a circumferential wall 60 at the side. The sleeve component 54 forms a part of the fuse housing 4 and can be screwed with the aid of a thread 62 to a section of the fuse housing 4 which is located further forwards. A rearward thread 64 is used for screwing on the cover 52. As in the case of the sleeve component 34, the relay explosive 58 is inserted, for example pressed, directly into the sleeve component 54 and therefore into the fuse housing 4. The firing booster 32 can be attached to the sleeve element 54 behind the firing relay 56, for example with the aid of screw holes 66. It is likewise feasible to provide a side wall 36 on the sleeve element 54, as in the case of the sleeve element 34, in particular integrally.
As a result of the primary firing assembly 10 being surrounded like a pot and the screw connection to the section of the fuse housing 4 which is located further forwards, the secondary firing chain with the firing relay 56 and the firing booster 32 located further to the rear is separated in a gas-tight manner from the detonator 14.

Claims

1. A fuse for a projectile, comprising:

a primary firing assembly;

a secondary firing assembly adjoining said primary firing assembly, said secondary firing assembly having a firing relay with a relay explosive disposed in a sleeve component, and having a firing booster;

said sleeve component forming a gas-tight seal of said secondary firing assembly with respect to said primary firing assembly and a barrier separating said secondary firing assembly from said primary firing assembly.

2. The fuse according to claim 1, wherein said sleeve component forms a housing for booster explosive of said firing booster.

3. The fuse according to claim 1, wherein said sleeve component forms at least a part of a hermetically sealed encapsulation of the relay explosive and of booster explosive for said firing booster.

4. The fuse according to claim 1, wherein said sleeve component forms a housing for said primary firing assembly.

5. The fuse according to claim 1, wherein said relay explosive has different firing characteristics than a booster explosive of said firing booster.

6. The fuse according to claim 1, wherein said relay explosive is a different substance than a booster explosive of said firing booster.

7. The fuse according to claim 1, wherein said firing booster has an insensitive booster explosive.

8. The fuse according to claim 1, wherein said relay explosive is insensitive to a temperature of up to 200° C.

9. The fuse according to claim 1, wherein said sleeve component forms an exclusive material barrier between said relay explosive and an armed detonator for said primary firing assembly.

10. The fuse according to claim 1, which comprises a fuse housing, and wherein said sleeve component forms a load-bearing housing part of said fuse housing.

11. The fuse according to claim 1, wherein said sleeve component is a supporting plate for supporting said primary firing assembly.

12. The fuse according to claim 1, which comprises a fuse housing, and wherein said sleeve component forms a bottom screw of said fuse housing.

13. The fuse according to claim 1, wherein said sleeve component forms a tab in a direction of said primary firing assembly.

14. The fuse according to claim 13, wherein said tab engages in a recess formed in an assembly mount for said primary firing assembly.