EP0426627A2

EP0426627A2 - Ammunition impact fuse

Info

Publication number: EP0426627A2
Application number: EP90850279A
Authority: EP
Inventors: Bengt Carlsson
Original assignee: Bofors AB
Current assignee: Saab Bofors AB
Priority date: 1989-08-25
Filing date: 1990-08-15
Publication date: 1991-05-08
Also published as: SE463436B; SE8902822D0; SE8902822A; EP0426627A3

Abstract

An ammunition unit (1) is provided with a fuze function which is sensitive to impact on both soft and hard targets (19) and comprises a front barrier (2) which effects piercing of a hard target. Mounted behind the barrier is a safety and armament part (6). This is fixed in its longitudinal displacement direction by means of a locking member (14). The locking member yields when the ammunition unit, after striking the target (which causes a certain compression of the ammunition unit in its longitudinal direction), undergoes rearward compression and thus causes a relative movement between the barrier of the part connected to it and the safety and armament part (6). A relative movement is permitted between the safety and armament part and the other parts of the shell, with simultaneous retention of the centring of the safety and armament part in the ammunition unit.

Description

TECHNICAL FIELD

The present invention relates to an arrangement primarily for a long ammunition unit having a fuze function which is sensitive to impact on both soft and hard targets. The ammunition unit is also provided with a front barrier which effects piercing of a hard target, when the ammunition unit penetrates the latter, before triggering of the charge carried. The fuze function comprises a safety and armament part mounted behind the barrier and in the latter and/or in a part connected to the barrier. The ammunition units concerned are chiefly in the form of shells. The invention is particularly applicable to shells of high velocity, for example 500 m/s or higher. Moreover, the shell is of the type which can penetrate thick targets.

PRIOR ART

The invention is a further development of the shell which is described in Swedish Patent 85 02575-7, which corresponds to American Patent 4,690,057. This shell is intended for use against both soft and hard targets. The shell comprises a front barrier of hard material and a fuze part which extends in front of this barrier. The shell also comprises a safety and armament part which is included in or is acted upon by the said fuze function. The armament and safety part is mounted in the barrier.

DESCRIPTION OF THE INVENTION

TECHNICAL PROBLEM

It has been found that shells of the present type function unreliably upon impact against hard targets in cases where the shell is to be designed relatively long, for example with lengths of approximately 1 metre and above. The said lengths may apply especially in the case of large calibres. In connection with the starting point of the invention, it was discovered that the shell may function incorrectly upon impact against a hard target. When the problems surrounding the strike functions against hard targets were analysed, it was observed that, because of its length, the shell on the one hand undergoes a certain compression movement upon impact itself and, on the other hand, executes a subsequent expansion movement when the piercing is complete and the shell is on its way into the target. In this type of shell, which is to function against both soft and hard targets, it is important for the safety and armament part to be arranged in such a way that undesirable ignitions do not occur. Among other things, the incorporation of percussion ignition is essential in this context. In the earlier construction, the safety and armament part was anchored by means of a threaded coupling which it was found could not hold during the said expansion movement of the shell. The safety and armament part can become inclined in its bearing when a threaded coupling of this type breaks. This inclination acts undesirably on the ignition function and results in the said unreliability in initiation of the charge carried.
It is important that the centring of the safety and armament part can be maintained throughout the entire functioning time of the shell in order to permit a reliable and accurate triggering of the charge carried. In this connection it is of no importance if the safety and armament part executes a slight movement, for example a movement of approximately 2.0 mm, relative to the other part of the shell/the barrier.

SOLUTION

The main aim of the present invention is to solve the abovementioned problems, and it provides details regarding a bearing function for the safety and armament part in which a substantially maintained centring of the safety and armament part is obtained throughout the entire functioning time of the shell, even if this is achieved at the expense of a slight relative longitudinal displacement movement between the safety and armament part and the barrier, or part connected to the barrier.
The feature which may principally be regarded as characterizing the new arrangement is that the safety and armament part is fixed in its longitudinal displacement direction by means of a locking member which is designed to yield when the ammunition unit, after striking the target (which causes a certain compression of the ammunition unit in its longitudinal direction), undergoes rearward compression/expands and thus causes a relative movement between the barrier or the part connected to it and the safety and armament part. A further characteristic is that the bearing of the safety and armament part is designed to permit, after the locking member yields, the relative movement between the barrier and the part connected to it while simultaneously retaining the centring of the safety and armament part in the ammunition unit.
In a preferred embodiment the locking member comprises an annular element which is designed to withstand acceleration forces occurring in the ammunition unit when the latter strikes the target. The locking member is moreover provided with a projecting flange which is designed to be sheared off by the barrier, or the part connected to it, when the said rearward compression or expansion occurs. A space is in this respect arranged in front of the shear-off part which can be displaced into the space without disturbing the said centring function. In one embodiment, the locking member is held in position with the aid of a sleeve-shaped nut member which fixes the locking member in its position where the said shearing-off can take place. The locking member can have an L-shaped longitudinal section and comprises a part extending in the longitudinal direction of the ammunition unit and a part at an angle relative to the latter part and thus forming the shear-off part.
In another embodiment the retaining member is designed with an arrow-shaped longitudinal section which connects to a part in the shape of the shaft of an arrow. The part in the shape of the shaft of an arrow extends in the longitudinal direction of the ammunition part, and this part and the part of the locking member extending in the longitudinal direction of the ammunition part have essentially the same outer diameters. The said arrow-shaped part constitutes a delimiting part for the said space which will permit the shearing-off and the relative movement.
In one embodiment, a part is connected to the barrier and effects the shearing-off of the shear-off part of the locking member via a front surface. The part connected to the barrier has an inner diameter which slightly exceeds the said outer diameters of the locking and retaining members.
The locking member is mounted threadlessly on an outer surface of the safety and armament part. The retaining member is screwed securely on the safety and armament part via a threaded coupling and bears with one end surface against the locking member. The part connected to the barrier is threadlessly mounted on bearing surfaces on the safety and armament part and the locking member. The safety and armament part is designed with a pliant section at one surface which bears against a corresponding inner surface of the part connected to the barrier. The pliant section yields at accelerations above a predetermined value in order to prevent inappropriate actuation of the locking member upon impact of the ammunition unit on the target. The yielding is of the order of magnitude of 0.5-1.0 mm.

ADVANTAGES

The above proposal provides a technically simple solution to the above problems. A simple shear-off part can thus be designed as well as a space which permits the said shearing-off and relative movement. The parts of the fuze function which operate with great accuracy can be kept intact and are not disturbed by the new bearing principle for the safety and armament part. In all cases this can provide a distinct trigger function where, for example, undesirable gas leakage due to the said expansion phenomenon in the shell is prevented.

DESCRIPTION OF FIGURES

A presently proposed embodiment of an arrangement which has the features significant to the invention will be described hereinbelow with reference to the attached drawing in which
the figure shows, in a longitudinal section, the front parts of a shell which uses the new bearing principle for the safety and armament part.

PREFERRED EMBODIMENT

Since the function and construction of the shell are well known per se, they will not be described in any great detail here, but only to the extent that they are relevant to the invention. The shell comprises a barrier or piercing part 2 for hard as well as soft targets. The fuze function therefore comprises a front part 3 which is situated in front of the barrier and is contained in a nose cone 1a. A part 4 is connected to the barrier, which part is joined to the barrier via a threaded coupling 5. In the rear part of the barrier and at the said part 4 there is mounted a safety and armament part 6. The safety and armament part comprises a delay primer charge 7, a detonator cap safety 8 and a bottom charge 9. At the front part of part 6 there is a primer charge 10 which constitutes a reinforcement of the flame which occurs in a central channel 11 through the barrier 2 when the initiation charge 12 is initiated from the percussion cap 13 in the nose of the shell or upon direct impact against a hard target. A locking member in the form of an annular locking element 14 is arranged at the front parts of the part 6.
The locking member 14 is held in position by means of a sleeve-shaped nut element 15. The nut-shaped element is screwed securely via a threaded coupling 16 on the front section of part 6. The front end surface of the element 15 bears against an inner wall 2a of the barrier via an elastic member 17. The part 4 is designed with different outer diameters, and the section 4a with the smaller outer diameter is in cooperation with the locking member 14. The section 4b with the larger outer diameter of part 4 partially surrounds an outer surface 6a of part 6. The locking member 14 is designed with an L-shaped longitudinal section, the locking member having a part 14a which extends in the longitudinal direction of the shell and a part 14b which is at an angle relative to the part 14a. The part 6 is provided with an outer surface 6b which is recessed relative to the surface 6a and serves as a bearing surface for section 4a of part 4. The part 6 also has a transverse surface 6c which finishes the said bearing surface 6b. The transverse surface constitutes a surface fixing the longitudinal position for the locking member 14 which bears against the stop surface 6c via an end surface on its part 14a. The part 14a of the locking member 14 has an outer diameter which corresponds essentially to the outer diameter of 6b. In this way the locking member part 14a can function as a bearing surface for the section 4a of part 4. Part 4 is also provided with an end surface 14c which bears against the angled part 14b. Part 4 also comprises a transverse surface 4d which bears against a corresponding rear end surface of the barrier 2 in order to define the relative positions of the barrier and the part 4. The nut-shaped element 15 is provided with an arrow-shaped part 15a and a part 15b in the shape of an arrow shaft. The element 15 cooperates with the locking member via an end surface 15c of part 15b. The part in the shape of an arrow shaft has an outer surface with an outer diameter which corresponds essentially to the outer diameters of the surfaces 6b and section 14a. Behind the arrow-shaped part 15a there is a space (annular) which is delimited at the front by the arrow-shaped part 15a and at the rear by the angled part 14b of the locking member 14. The locking member is made of a material which affords a distinct shearing-off capacity. An example which may be mentioned is light metal BML79, which is a material with distinct shearing properties. The front surface 4c of section 4a is used as a shearing element for the angled part 14b. The material of part 4 is a hard material corresponding to that of the barrier 2.
When the shell expands after penetrating a target 19, the forces of inertia in the safety and armament part result in the barrier 2 and the part 4 moving forwards relative to the part 6. The part 4 thus comes to shear off the angled part 14b which can move in the space 18. In accordance with the above, the shearing-off takes place distinctly and the part 4 also acquires a bearing on the remaining part of 14a and parts of the part 15b formed in the shape of an arrow shaft. The centring of the part 6 can therefore be retained with great accuracy. The movement is of the order of magnitude of approximately 2.0 mm. The retained centring ensures a good triggering function.
The part 6 is provided with an inner transverse surface 6d which is set opposite an inner corresponding surface 4d of part 4. The part 6 is provided with a pliant section 6e at the said surface 6d. The said pliant section will yield upon impact forces of a predetermined magnitude in such a way that the angled part 14b is not inappropriately subjected to actuation forces in conjunction with the striking of the target. The movement of the yield is 0.5-1.0 mm.
The invention is not limited to the embodiment illustrated above as an example, but instead can be modified within the scope of the following patent claims and the inventive concept.

Claims

1. Arrangement primarily for a long ammunition unit (1) having a fuze function sensitive to impact on both soft and hard targets (19) having a front barrier (2) which effects piercing of a hard target, when the ammunition unit penetrates the latter, before triggering of the charge carried, in which respect the fuze function comprises a safety and armament part (6) which is mounted behind the barrier and in the latter, and/or in a part (4) connected to the barrier, characterized in that the safety and armament part is fixed in its longitudinal displacement direction by means of a locking member (14) which is designed to withstand acceleration forces occurring in the ammunition unit when it strikes the target and which is designed to yield when the ammunition unit, after striking the target (which causes a certain compression of the ammunition unit in its longitudinal direction), undergoes rearward compression/expands and thus causes a relative movement between the barrier or the part (4) connected to it and the safety and armament part (6), and in that the bearing of the safety and armament part is designed to permit, after the locking member yields, the relative movement between the barrier and the part (4) connected to it while simultaneously retaining the centring of the safety and armament part in the ammunition unit.

2. Arrangement according to patent claim 1, characterized in that the locking member (14) comprises an annular element which is provided with a projecting flange (14b) which is designed to be sheared-off by the barrier, or the part connected to it, when the said rearward compression/expansion occurs.

3. Arrangement according to patent claim 2, characterized in that a space (18) is arranged in front of the projecting flange or the shear-off part, which space receives the sheared-off flange or the part and permits the relative movement.

4. Arrangement according to patent claim 1, 2 or 3, characterized in that the locking member can cooperate with a sleeve-shaped retaining member (15) which holds the locking member (14) in a fixed position where it permits shearing-off of the projecting part of the locking member.

5. Arrangement according to any one of the preceding patent claims, characterized in that the locking member has an L-shaped longitudinal section with a part (14a) extending in the longitudinal direction of the ammunition unit and a part (14b) at an angle relative to the latter part.

6. Arrangement according to patent claim 5, characterized in that the retaining member has an essentially arrow-shaped longitudinal section (15b) which connects to a part (15b) in the shape of an arrow shaft, in that the part in the shape of an arrow shaft extends in the longitudinal direction of the ammunition unit, in that the part in the shape of an arrow shaft and the part (14a) of the locking member extending in the longitudinal direction of the ammunition part have essentially the same outer diameters, in that the angled part on the locking member can shear-off upon the relative movement, and in that, when the part is sheared off, it moves in the space (18) which is delimited at the front by the said arrow-shaped part (15a).

7. Arrangement according to patent claim 5 or 6, characterized in that the part (4) connected to the barrier effects the shearing-off of the shear-off part of the locking member via a front surface (4c) which, before the relative movement occurs, bears against the said shear-off part, and in that the part connected to the barrier has an inner diameter which slightly exceeds the said outer diameters of the locking and retaining members.

8. Arrangement according to any one of the preceding patent claims, characterized in that the locking member is threadlessly mounted on an outer surface of the safety and armament part, in that the retaining member is secured on the safety and armament part via a threaded coupling (16), and in that the part connected to the barrier is threadlessly mounted on bearing surfaces on the safety and armament part and the locking member.

9. Arrangement according to any one of the preceding patent claims, characterized in that the safety and armament part is designed with a pliant section (6e) at a surface (6d) which bears against a corresponding inner surface on the part connection to the barrier, and in that the pliant section yields at acceleration beyond a predetermined value in order to prevent undesirable actuation of the locking member upon impact on the target.

10. Arrangement according to patent claim 9, characterized in that the said surfaces (4e and 6e) consist of an internal collar surface and a shoulder surface situated behind the locking member.