WO2009092857A1

WO2009092857A1 - Method for fastening increment charges to mortar shell, shell and system of increment charges

Info

Publication number: WO2009092857A1
Application number: PCT/FI2009/050050
Authority: WO
Inventors: Eeva Makkonen
Original assignee: Patria Weapon Systems Oy
Priority date: 2008-01-21
Filing date: 2009-01-20
Publication date: 2009-07-30
Also published as: FI121321B; FI20085049A; EP2242985A1; EP2242985A4; FI20085049A0

Abstract

The invention relates to a method of fastening increment charges to a mortar shell, a mortar shell, and an increment charge system. A fin-stabilized mortar shell (1 ) comprises a shell part (2) and a tail shaft (3) on the extension thereof, the tail shaft comprising guide fins (5). The tail shaft is provided with an increment charge system (12) comprising several increment charges (6) arranged around the tail shaft and fastened to the tail shaft in a form-locking manner. In order to ensure the fastening, a tubular flexible fastening sleeve (13) is further arranged around the increment charge system.

Description

METHOD FOR FASTENING INCREMENT CHARGES TO MORTAR SHELL, SHELL AND SYSTEM OF INCREMENT CHARGES

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method of fastening increment charges to a tail shaft of a fin-stabilized mortar shell. The invention further relates to a fin-stabilized mortar shell equipped with increment charges, and further to an increment charge arrangement comprising several increment charges.

[0002] The fields of the invention are defined in closer detail in the preambles of the independent claims of the application.

[0003] A fin-stabilized mortar shell is provided with a shell part which contains the actual explosive charge and on the extension of which in a rear part of the shell typically a tail shaft is provided which includes a tail comprising several guide fins. Inside the tail shaft, a propelling charge is provided which ignites upon launch and provides the shell with its departure speed and trajectory. The trajectory of the shell may be controlled by placing a desired number of increment charges around the tail shaft, which, upon launch, ignite and burn in the shaft of the mortar and provide the shell with an additional propulsive thrust. The trajectory of the shell may be controlled not only by influencing the number of increment charges but also e.g. by selecting increment charges with different burning properties.

[0004] Typically, increment charges are substantially shaped like a horseshoe. An increment charge is dimensioned such that it fits in a shaft of a mortar. For the same reason, the increment charge is substantially circular in its external form. A central section of the increment charges is provided with a central space which may receive a tail shaft. Such an increment charge further includes an installation opening which extends from an outer edge of the increment charge to the central space and through which the increment charge may be pushed in a transverse direction into place so that the tail shaft settles in the central space. The width of the installation opening is dimensioned to be slightly smaller than the diameter of the tail shaft in order to ensure that the increment charge stays around the tail shaft. It has been noticed, however, that increment charges do not always stay in place around the tail shaft but they may fall off when the shells are being handled. This, of course, presents a serious safety risk. BRIEF DESCRIPTION OF THE INVENTION

[0005] An object of the invention is to provide a novel and improved method and arrangement for fastening increment charges to a mortar shell.

[0006] A method according to the invention is characterized by arranging around the increment charges at least one elongated tubular fastening sleeve which is made from a flexible material and which engages the increment charges with one another and prevents them from becoming detached from the tail shaft unintentionally.

[0007] A shell according to the invention is characterized in that the increment charges are surrounded by a substantially tubular elongated fastening sleeve made from a flexible material.

[0008] An increment charge system according to the invention is characterized in that the increment charges are surrounded by a substantially tubular elongated fastening sleeve made from a flexible material.

[0009] An idea of the invention is that a fastening sleeve which is an elongated substantially tubular flexible object has been arranged around the increment charges arranged around the tail shaft of the shell. The fastening sleeve surrounds all increment charges included in the increment charge system of the shell.

[0010] An advantage of the invention is that the fastening sleeve prevents unintentional detachment of the increment charges from the tail shaft. Consequently, dangerous situations caused by increment charges being detached may be avoided. The fastening sleeve thus improves the safety of shell handling, e.g. when shells are being transferred from a shell storage to a charging device or when the shells are handled otherwise. The fastening sleeve is a simple, inexpensive and reliable member. The use of the fastening sleeve requires no changes to the shell, increment charges or mortar. Further, the fastening sleeve is easy to install on the increment charges and remove when necessary. Still further, if desired, one or more increment charges may be detached by removing the fastening sleeve completely or in part or by releasing its fastening force over a desired section, e.g. only over its one end, e.g. by tearing off, unfastening or in another manner.

[0011] An idea of an embodiment is that the fastening sleeve is made from an elastic material. In such a case, the fastening sleeve, when be- ing installed, may be stretched and subsequently allowed to be pressed against the outer edge of the increment charges. The elastic fastening sleeve then generates a fastening force constanly pressing the increment charges in a radial direction. The elasticity enables the same fastening sleeve type to be used in fastening increment charges with slightly different dimensions. If necessary, some increment charge(s) may also be easily removed from the increment charge system since the elastic fastening sleeve is easy to strech and move aside for the duration of the removal.

[0012] An idea of an embodiment is that the fastening sleeve is elastic and its cross section is shaped like a closed loop. The fastening sleeve is installed in place on top of the increment charges such that it is stretched first in the radial direction and subsequently pulled in an axial direction around the increment charges. When the outwards stretching force is released, the fastening sleeve is pressed inwards against the outer surface of the increment charges provided in the tail shaft, keeping them tightly in place. It is easy and quick to install and remove such a fastening sleeve even under difficult conditions.

[0013] An idea of an embodiment is that the fastening sleeve is a netlike member. In such a case, it comprises less material to be burned off in the shaft of the mortar during lauch. In addition, it is possible to see through the netlike fastening sleeve any markings, colours and other identification information possibly provided on the increment charges.

[0014] An idea of an embodiment is that both ends of the fastening sleeve are open. This enables fastening sleeves having a length suitable for each increment charge system to be cut off from a long fastening sleeve preform, which may be e.g. rolled up.

[0015] An idea of an embodiment is that one end of the fastening sleeve is open while the other end is closed. Naturally, the fastening sleeve is installed through the open end. The closed end of the fastening sleeve surrounds the tail of the shell and may thus prevent the increment charges from rotating around the tail shaft. Further, the closed end of the fastening sleeve may surround a lauchning device located in a rear part of the shell and thus participate in holding it as well.

[0016] An idea of an embodiment is that the fastening sleeve is formed from several yarns arranged to criss-cross with one another. The fastening sleeve may then be a netlike structure or it may be made from a fabric which is not dense. The fastening sleeve may be a woven structure, knitted work, braided work or another yarn construction.

[0017] An idea of an embodiment is that the fastening sleeve is made from a fibre material. In such a case, the fastening sleeve may be made e.g. from a flocky material or another non-woven material.

[0018] An idea of an embodiment is that the material of the fastening sleeve is selected such that the fastening sleeve substantially burns off completely in the shaft of the mortar when the shell is lauched. Such a burnable material may be e.g. nitrocellulose or cotton. Also, many plastic materials burn off well during launch of the shell.

[0019] An idea of an embodiment is that for fastening the increment charges a fastening sleeve which has a seam and a longitudinal first connecting edge and a longitudinal second connecting edge is used. The fastening sleeve is arranged as a loop around the increment charges and, subsequently, the connecting edges are connected with one another. The connecting edges may be equipped with suitable fastening means, such as a glue-free Velcro tape, adhesive tape or hooks.

[0020] An idea of an embodiment is that a fastening sleeve is formed around the increment charges such that a sheet-like material is rolled in a transverse direction of the shell around the increment charges. Finally, a free end that has been left outermost is engaged with the outer surface of the rolled section of the fastening sleeve. The free end left on the outer surface may be fastened by a suitable fastening member, such as an adhesive tape or hooks.

[0021] An idea of an embodiment is that several weakened sections are pre-arranged in the fastening sleeve substantially in the direction of the circumference thereof at a distance from one another. This enables a desired part to be easily torn off from the fastening sleeve e.g. when one or more increment charges are later to be removed from the shell.

BRIEF DESCRIPTION OF THE FIGURES

[0022] Some embodiments of the invention are described in closer detail in the accompanying drawings, in which

Figure 1 is a schematic side view showing a fin-stabilized mortar shell, Figures 2a to 2c are schematic views showing an increment charge, as seen from different directions,

Figure 3 is a schematic perspective view showing a mortar shell equipped with several increment charges,

Figure 4 is a schematic perspective view showing a fastening sleeve made from an elastic material,

Figure 5 is a schematic perspective view showing a second fastening sleeve equipped with a longitudinal seam,

Figure 6 is a schematic longitudinal view showing a principle of a third fastening sleeve, and

Figure 7 is a schematic perspective view showing a mortar shell having a netlike fastening sleeve arranged around its increment charge system.

[0023] For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. In the figures, like reference numerals identify like elements.

DETAILED DESCRIPTION OF THE INVENTION

[0024] A mortar shell 1 shown in Figure 1 comprises a shell part 2, a tail shaft 3 on the extension thereof, and further a tail 4 located in a rear part of the shell 1. The tail 4 typically comprises several guide fins 5. The actual explosive of the shell 1 is positioned in the shell part 2. The inside of the tail shaft 3, in turn, is provided with a propelling charge which, upon launch, provides the shell 1 with its departure speed.

[0025] Figures 2a to 2c show an increment charge 6 as seen from different directions. Typically, an increment charge is substantially shaped like a horseshoe. Its outer edge 7 is substantially circular, so it fits in the shaft of the mortar. For the same reason, the outer dimension of the increment charge 6 is to be smaller than the largest diameter of the shell. A central part of the increment charge 6 is provided with a central space 8 which may receive the tail shaft 3. The increment charge 6 is further provided with an installation opening 9 which extends from the outer edge 7 of the increment charge to the central space 8. In such a case, the increment charge 6 may be pushed in a transverse direction of the shell 1 into its place around the tail shaft 3. The width of the installation opening 9 is dimensioned to be slightly smaller than the diameter of the tail shaft 3, whereby a form-locking is provided between the increment charge 6 and the tail shaft 3. Sides 10a and 10b of the increment charge 6 may be provided with projections 11a and 11b which are dimensioned such that they fit in the installation opening 9 of an adjacent increment charge when increment charges 6 have been arranged successively around the tail shaft 3. The adjacent increment charges 6 are naturally arranged contrariwise with respect to one another, i.e. the installation openings of the adjacent increment charges point in opposite directions, as can be seen below in Figure 3. Such an increment charge has been described e.g. in US 2005/075 933 A1. The increment charge 6 may be a casing inside which gunpowder or another burning propellant suitable for the purpose is provided.

[0026] The fin-stabilized shell 1 shown in Figure 3 is equipped with an increment charge system 12 comprising several increment charges 6. The increment charges 6 are fastened around the tail shaft by means of form- locking, but they may become detached if the shell is subjected to external impacts or jolts.

[0027] Figure 4 shows a possible fastening sleeve 13 which is a tubular flexible object which may be arranged around the increment charge system 12. The fastening sleeve 13 may be made from an elastic material, in which case it may be strecthed at least in a radial direction, as shown by arrows in Figure 4. In such a case, cross-section A of the fastening sleeve 13 may be streched larger for installing the fastening sleeve 13. In the figure, the streched position is illustrated by broken line A^'. When the strecthing force is released, the fastening sleeve 13 tries to recover the original situation, whereby it tightens around the increment charges 6. Since the fastening sleeve 13 is made from a flexible material, it may be easily pulled on top of the increment charge system 12 over the tail 4 or the shell part 2, even if it is a seamless tube.

[0028] Figure 5 shows a second fastening sleeve 13 comprising at least one longitudinal seam 14. Thus, the fastening sleeve 13 may be formed from a sheet-like piece by connecting its connecting edges 15a and 15b with one another. The connecting edges 15a, 15b may be provided with suitable fastening members, such as adhesive tapes, Velcro tape, hooks or the like. The material of the fastening sleeve 13 may be elastic. The fastening sleeve 13 may be formed from several yarns 16, whereby it may be e.g. a fabric which is not dense. The fastening sleeve 13 may further comprise weakened sections 17 which are substantially co-directional with the circumference and lo- cated at a predetermined distance from one another, which makes a desired section of the fastening sleeve 13 easy to detach if some increment charges 6 are to be removed later.

[0029] Figure 6 shows a principle of a third fastening sleeve 13. The fastening sleeve 13 may be formed by rolling a sheet-like piece to provide a tubular structure around the increment charge system 12. Finally, the connecting edge 15a that has been left outermost is engaged with the outer surface of the rolled section. The fastening may be carried out by any fastening member or fastening agent suitable for the purpose. The material of the fastening sleeve 13 may be elastic.

[0030] In Figure 7, a netlike fastening sleeve 13 has been arranged around the increment charge system 12. The material of the fastening sleeve 13 may be elastic. The fastening sleeve 13 engages the increment charge into one entity from which no individual increment charge 6 is allowed to become detached unintentionally.

[0031] It is to be noted that the fastening sleeve set forth in the present application may be used in connection with increment charges with different constructions and fastening principles as well. The fastening sleeve is a simple fastening member for all kinds of increment charges being used in mortar shells.

[0032] In some cases, the features disclosed in the present application may be used as such, irrespective of other features. On the other hand, when necessary, the features set forth in the present application may be combined in order to provide different combinations.

[0033] The drawings and the related description are only intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims.

Claims

1. A method of fastening increment charges to a mortar shell (1) comprising a shell part (2) and a tail shaft (3) on an extension of the shell part (2) and, further, several guide fins (5) in a section of an outer end of the tail shaft (3), and the method comprising: installing a predetermined number of increment charges (6) around the tail shaft (3) of the shell (1); fastening the increment charges (6) to the tail shaft (3) by means of form-locking; characterized by arranging around the increment charges (6) at least one elongated tubular fastening sleeve (13) which is made from a flexible material and which engages the increment charges (13) with one another and prevents them from becoming detached from the tail shaft (3) unintentionally.

2. A method as claimed in claim 1, characterized by using for fastening the increment charges (6) a fastening sleeve (13) made from an elastic material.

3. A method as claimed in claim 2, characterized by using for fastening the increment charges (6) a fastening sleeve (13) whose cross-section is shaped like a closed loop; stretching the fastening sleeve (13) in a radial direction and pulling it subsequently in an axial direction around the increment charges (6); and releasing finally the stretching force, whereby the fastening sleeve (13) is pressed against an outer surface (7) of the increment charges (6).

4. A method as claimed in claim 1 or 2, characterized by using for fastening the increment charges (6) a fastening sleeve (13) provided with a seam (14) and a longitudinal first connecting edge (15a) and a longitudinal second connecting edge (15b); and arranging the fastening sleeve (13) around the increment charges (13) and engaging the connecting edges (15a, 15b) with one another.

5. A method as claimed in claim 1 or2, characterized by rolling a sheet-like material around the increment charges and engaging to provide a fastening sleeve (13).

6. A method as claimed in any one of the preceding claims, characterized by arranging a netlike fastening sleeve (13) around the increment charges (6).

7. A method as claimed in any one of the preceding claims, characterized by arranging a fastening sleeve (13) made from a fabric around the increment charges (6).

8. A mortar shell comprising: a shell part (2) provided with an actual explosive of the shell (1); a tail shaft (3) which is provided on an extension of the shell part (2) and inside which a propelling charge of the shell (1) is provided; a tail (4) located at an outer end of the tail shaft (3), the tail (4) comprising several guide fins (5); and an increment charge system (12) comprising several increment charges (6) arranged around the tail shaft (3) and fastened to the tail shaft (3) in a form-locking manner; characterized in that the increment charges (6) are surrounded by a substantially tubular elongated fastening sleeve (13) made from a flexible material.

9. A shell as claimed in claim 8, characterized in that the fastening sleeve (13) is made from an elastic material.

10. A shell as claimed in claim 9, characterized in that the fastening sleeve (13) is a seamless tubular object whose cross- section is shaped like a closed loop.

11. A shell as claimed in any one of the preceding claims 8 to 10, characterized in that the fastening sleeve (13) is made from a netlike material.

12. A shell as claimed in any one of the preceding claims 8 to 10, characterized in that the fastening sleeve (13) is made from a fabric.

13. A shell as claimed in any one of the preceding claims 8 to 12, characterized in that the material of the fastening sleeve (13) is selected such that it burns off substantially completely in the shaft of the mortar when the shell is launched.

14. A mortar shell increment charge system, wherein several incrment charges (6) are arranged around a tail shaft (3) located in a rear part of the shell (1), characterized in that the increment charges (6) are surrounded by a substantially tubular elongated fastening sleeve (13) made from a flexible material.

15. An increment charge system as claimed in claim ^.characterized in that the fastening sleeve (13) is a netlike seamless tube made from an elastic material, which, upon installation, has been stretched to a larger cross- sectional area and pulled around the increment charges (6) and which, subsequently, has been let to recover to a smaller cross-sectional area, whereby it has been pressed against an outer surface (7) of the increment charges (6).

16. An increment charge system as claimed in claim 14 or 15, characterized in that the increment charge (6) is a substantially horseshoe-shaped object which comprises a central space (8) and an installation opening (9) which extends from an outer edge (7) of the increment charge to the central space (8), whereby the increment charge (6) is pushable in a transverse direction of the shell (1) into its place such that the tail shaft (3) settles in the central space (8), and wherein a width of the installation opening (9) is dimensioned to be smaller than a thickness of the tail shaft (3), whereby the increment charge (6) is arranged to become fastened in its place by means of form-locking.