Cylindrical case for propellant charge powder

Abstract

The invention refers to a cylindrical sleeve (6) for receiving propellant powder (4) with a dimensionally stable jacket wall of combustible, felted fibre material and an insert (5) of a textile fabric in the jacket wall, and to a method of manufacturing a cylindrical sleeve (6).

Claims

1. A cylindrical case (6) for receiving propellant powder (4) with a dimensionally stable jacket wall of combustible, felted fibre material and an insert (5) of a textile fabric in the jacket wall, characterized in that the insert (5) is stretchable.

2. The case according to claim 1, in which the insert (5) is of single-layer construction and is expandable both axially and radially.

3. The case according to claim 1, in which the insert (5) has at least two or three layers, of which a first layer is at least axially stretchable and a second layer is at least radially stretchable.

4. The case according to claim 1, in which the insert (5) consists of knitted fabric.

5. The case according to claim 1, in which the insert (5), with respect to the thickness of the jacket wall, is arranged in the centre of the jacket wall or closer to an inside or an outside of the jacket wall.

6. The case according to claim 1, in which the insert (5) is arranged on an inside of the jacket wall.

7. The case according to claim 1, in which the insert (5) is in the form of a hose whose central axis coincides with the central axis of the case (6).

8. The case according to claim 7, in which the hose is seamless.

9. A method of manufacturing a cylindrical case (6) according to one of the previous claims, comprising: immersing a screen shape in an aqueous pulp containing nitrocellulose and cellulose, applying negative pressure to conform the pulp to the screen shape so that a fleece is formed, pulling a tubular insert onto the screen shape and/or onto the flow formed.

10. The method according to claim 9, whereby the insert is drawn on before applying the negative pressure or as an intermediate step between a first application and a second application of negative pressure, or during the application of negative pressure.

11. The case according to claim 4, wherein the fabric is a warp-knitted fabric.

12. The case according to claim 5, wherein the insert is between the first quarter and the fourth quarter of the thickness of the jacket wall.

Description

[0029] Further advantages and applications of the invention result from the following description in connection with the figures.

[0030] FIG. 1 shows schematically a case according to an exemplary embodiment of the invention as a component of a cartridge.

[0031] FIG. 2 shows a photo of a case from FIG. 1 after a fracture test with its insert partially exposed at the area of fracture.

[0032] FIG. 3 schematically shows a section of the knitted fabric which forms the insert of the case from FIGS. 1 and 2.

[0033] FIG. 1 shows a schematic example of a case 6 as part of a cartridge 1. The case is elongated and circular cylindrical and contains granular propellant powder 4 in its interior. An insert 5 is embedded in the jacket wall of the case 6.

[0034] A bottom 2 with a detonator 3 is attached at the lower end of cartridge 1.

[0035] The case 6 is made of felted cellulose and nitrocellulose fibres as well as conventional additives. The embedded insert 5 is a stretchable hose made seamlessly from knitted fabric 12, here exemplarily from warp-knitted, crocheted and/or weft-knitted fabric. Due to its embedding in the case 6 as shown, its central axis coincides with the central axis of the case.

[0036] The hose is made of 50 percent normal cotton yarn and 50 percent polyurethane-cotton mixed yarn, whereby in experiments a variant with one third cotton yarn and two thirds polyurethane-cotton mixed yarn also turned out to be a good material for the hose. In both cases, the mixed yarn has a polyurethane core coated with cotton. In the exemplary embodiment, the mixed yarn has a composition of 89% cotton and 11% PUR, wherein according to embodiments, a PUR ratio of between 5% and 20% may be considered.

[0037] Due to its knitted construction, the hose forming the interlining is highly stretchable. The elasticity in the axial direction of the hose is additionally supported by the polyurethane-cotton mixed yarn.

[0038] If the case 6 is damaged by mechanical action so that a crack, a gap or another fracture opening occurs in the jacket wall, the insert is exposed in the fracture opening and stretched there to such an extent that it keeps the fracture opening closed against the granular propellant powder inside the case without tearing.

[0039] A typical case according to the invention has an outer diameter of between 50 and 170 mm and a length of between 35 and 75 cm and a, particularly jacket, wall thickness of between 1.5 and 4 mm, in particular 2.5 mm.

[0040] FIG. 2 shows a photo of a case 6 from FIG. 1 after a fracture test with an insert 5 partially exposed at a fracture area 8. The arrangement of the insert 5 between a radially inner part 6a and a radially outer part 6b of the case 6 is clearly visible. A felting 10 formed by the meshes of the insert 5 is also partially visible.

[0041] The dark inscription on the outer part 6b of case 6 originates from the sample marking of the fracture test performed and is irrelevant here.

[0042] FIG. 3 schematically shows a cut-out from the knitted fabric 12, which forms the hose of the insert 5 of the case 6 from FIGS. 1 and 2.

[0043] Tests carried out by the applicant have shown that the insert 5 as knitted fabric 12, here exemplarily as warp-knitted, crocheted and/or weft-knitted fabric, provides very high tensile strength and high elongation values with a relatively low weight per area and a low radial dimension of the hose. Such textile surfaces are produced, for example, on circular knitting machines. With a circular knitting machine, for example, a seamless hose insert as shown in the exemplary embodiment can be produced.

[0044] In order to enable very high stretching of the insert 5, a certain mesh binding 14 is used in the embodiment example. A mash pattern 16 of the mesh binding 14 is shown in FIG. 3.

[0045] The mesh pattern 16 shows an excerpt of a large number of mesh courses 18 arranged one above the other in the vertical direction of the FIG. 3 illustration, and a large number of meshs 20 arranged one next to the other in the transverse direction of the FIG. 3 illustration. In the example, the vertical direction in the representation of FIG. 3 corresponds to a longitudinal direction L of the insert 5 or the case 6; the transverse direction corresponds to the circumferential direction U of the insert 5 or the case 6.

[0046] Each mesh 20.2 is guided at its lower end through the corresponding mesh 20.3 of the lower adjacent mesh course 18.3 and guides the corresponding mesh 20.1 of the upper adjacent mesh course 18.1.

[0047] The corresponding meshs 20 of adjacent mesh courses 18, form a mesh wale 23 and are each guided on the same radial side of the hose of the insert, i.e. either all on the outside or all on the inside.

[0048] Neighbouring meshs 20 of a course 18 are always guided in the opposite radial side; i.e. if one adjacent mesh 20 is guided on the inside, the adjacent meshs 19 and 21 are each guided on the outside, and if one adjacent mesh is guided on the inside, the adjacent meshs are each guided on the inside.

[0049] In the exemplary embodiment of the case, between ten and 13 (thirteen) courses of meshes per centimetre of longitudinal extension are provided in the unstretched state of the insert in the mesh, in particular between 11.5 and 12 courses of meshes (mesh courses number MRZ, FIG. 3 shows its inverse value). It is also customary to specify mesh courses per two centimetres: to this extent, the insert has a fabric pattern with between 20 (twenty) and 26 (twenty-six) mesh courses per two centimetres of longitudinal extension, in particular between 23 and 24 mesh courses per two centimetres.

[0050] With regard to the mesh wales 23, in the unstretched state of the insert, between ten and a half and 13.5 (thirteen point five) mesh wales per centimetre of circumferential extension are provided in the fabric pattern, in particular between 11.75 and 12.25 mesh wales (mesh wales number MSZ, FIG. 3 shows its inverse value). An indication in mesh wales per two centimetres is also customary: to this extent the insert exhibits a fabric pattern with between 21 (twenty-one) and 27 (twenty-seven) mesh wales per two centimetres of circumferential extension, in particular between 23.5 and 24.5 mesh wales per two centimetres.

[0051] In a state mounted on the case, the insert of the exemplary embodiment exhibits a fabric elongation (=stretch), in particular in the circumferential direction U (or radial direction R) of the case and/or in the longitudinal direction L of the case, of 5% to 20% in comparison with the unstretched state, in particular of approx. 11%. This elongation state particularly constitutes the elongation state shown in FIG. 2 with respect to the magnitude, if the slight additional elongation due to the displacement at the point of fracture is neglected.

[0052] The seamless hose-shaped insert 5 used in the embodiment example shows a maximum elongation of approx. 420% in the transverse direction of the representation of FIG. 3i.e. in the circumferential direction U of the hose. In the vertical direction of the representation of FIG. 3i.e. in the longitudinal direction L of the hosethe maximum elongation is approx. 80%. A maximum elongation in the radial direction of the insert 5 hose can be calculated from or with the hose diameter in the unstretched state and the maximum elongation in the circumferential direction U of the hose, taking into account an additional elongation in the longitudinal direction L if necessary.

[0053] Cellulosic fibres are suitable for the material of insert 5, for example used in their pure form (100% cellulosic fibres) or in a fibre blend (for example cotton fibres with a synthetic material such as PUR).

[0054] The desired felting quality of the case (during the felting process through the insert) is achieved by (skilled-in-the-art) coordination of the fibre thicknesses and the technological parameters of the yarn and knitting method, based on the exemplary embodiment. This means that it is ensured that the fibre mass of the textile gets stuck in the mesh legs and thus prevents separation or splitting of the case 6 body.

REFERENCE SIGNS

[0055] 1 cartridge [0056] 2 bottom [0057] 3 detonator [0058] 4 propellant charge powder [0059] 5 insert [0060] 6 case [0061] 6a inner part of the case [0062] 6b outer part of the case [0063] 8 fracture area [0064] 10 felting [0065] 12 mesh fabric [0066] 14 mesh binding [0067] 16 mesh pattern [0068] 18 mesh course [0069] 19, 20, 21 mesh [0070] 23 mesh wale [0071] L longitudinal axis/direction [0072] U circumferential direction [0073] R radial direction [0074] MRZ mesh courses number [0075] MSZ mesh wales number