WO1987007006A1

WO1987007006A1 - Device for the pyrotechnic separation of two elements

Info

Publication number: WO1987007006A1
Application number: PCT/FR1987/000157
Authority: WO
Inventors: Hubert Vaillant De Guelis; Jean Langlois
Original assignee: Aerospatiale Societe Nationale Industrielle
Priority date: 1986-05-16
Filing date: 1987-05-15
Publication date: 1987-11-19
Also published as: EP0246958A1; DE3764311D1; FR2598796A1; FR2598796B1; ES2018281B3; EP0246958B1

Abstract

Device for the pyrotechnic separation between two elements (2, 4), for example panel-shaped elements. The first element (2) comprises two projecting parts (6, 8) connected to the remainder portion of the element by areas of reduced thickness (10, 12). The projecting parts (6, 8) are secured to the second element (4) by means of screws (30) and nuts (32). A deformable envelope (20) containing a detonating fuse is placed into the cavity (16) formed by the projecting parts (6, 8), the body of the first element (2) and the second element (4). Upon firing, the envelope (20) deforms and causes the rupture at the connection areas (10, 12). The thin areas (10, 12) being close to the extremity of the cavity (16) which is remote from the fixing point of the projecting parts (10, 12) to the second element (4), a greater lever arm and therefore an improved efficiency are obtained. Application to the aeronautical or spatial field.

Description

SISPOSITI £ _ ^ _ SEPARATigN_PYRO ^

The present invention relates to a device for the separation of two elements by means of a pyrotechnic charge which can be used in particular for separating elements in the form of panels in aeronautical or spacecraft. The use of a pyrotechnic charge to separate elements of an aeronautical or spacecraft is known and widely used at present. For example, document US-A-3 698 281 describes a system of this kind in which the explosive charge is in the form of two detonating cords placed inside a deformable envelope of oblong shape, the space between the detonating cords and the envelope being filled with a flexible material, such as rubber for example. The panels to be separated are connected to each other by two metal plates, one on each of their faces, these plates being bolted to the panels. The deformable envelope is placed between these plates in a housing formed by recesses provided on the plates and which matches the shape of the envelope. In addition, the plates have, on their faces opposite to this housing, grooves defining a thinned zone, therefore weakened, along which the fracture must be made. These grooves are located at the central part of the plates, therefore towards the middle of the cavity in which the deformable envelope which contains the detonating cords is placed. When the detonating cord is ignited, this causes the deformable envelope to expand. This tends to take a circular configuration, which has the effect of deforming the central part of the two plates connecting the panels to be separated and causing rupture along the weakened sections. If such a device is satisfactory, it does however allow breaking only relatively small sheet thicknesses, for example of the order of 1 mm.

The present invention aims to remedy these drawbacks by proposing a separation device pyrotechnic between two elements, for example elements in the form of panels, making it possible to cut a greater thickness of sheet metal with the same charge of explosive.

More specifically, the invention relates to a pyrotechnic separation device between a first element and a second element using a pyrotechnic charge placed in a deformable envelope.

In known manner, the first element has two projecting parts which define a certain space between them, the device further comprising first fixing means for fixing the first element to the second by means of said projecting parts, thus defining a cavity in Which is placed said deformable envelope, this cavity having a first end close to said first fixing means and a second end remote from these first fixing means, and the first element has thinned parts which break when the charge explodes pyrotechnic.

According to the invention. The thinned parts are located approximately at the second end of said cavity.

Thus, during the ignition, the envelope deforms and causes rupture at these thinned parts. As the latter are at the end of the cavity furthest from the first fixing means, the deformable envelope ag t at the time of the explosion on a relatively large lever arm corresponding to the length of the projecting parts: this makes it possible to have better efficiency, for a given load, than with a device such as that described in document US-A-3 698 281. Indeed, in the latter case, the: weakened parts of the connection plates are in the middle of these, so halfway between the plate attachments on the elements to be separated, and the lever arm is weaker. According to a preferred embodiment of the present invention, the first fixing means comprise at least one screw passing through a hole formed in each protruding part and a hole formed in the second element, and a nut, the tightening of this nut on the screw causing the application of said protruding parts on the second element. In this case, it is also possible to provide at least one stirrup, a part of which at least partially surrounds the deformable envelope while being in contact with the latter and of which another part has a hole through which the screw can pass.

In the general case where the elements to be separated are in the form of panels, the detonating cord and the deformable envelope are of elongated shape and there are several fixing devices such as that which has just been described with ^' screws, nuts and possibly stirrups, regularly distributed along the separation zone.

In a first embodiment, the projecting parts form an integral part of the first element and are connected to the rest of this element by thin connection zones which constitute said thinned parts.

In a second embodiment, the projecting parts are constituted by plates fixed to the first element by second fixing means, each of these plates having a thin zone which constitutes one of said thinned parts.

The invention will be better understood on reading the description which follows, given by way of purely illustrative and in no way limiting example, with reference to the appended drawings in which: - Figure 1 is a schematic sectional view of a device in accordance with the invention before the ignition of the charge,

FIG. 2 is a schematic perspective view showing how the deformable envelope can be maintained using stirrups, and - Figure 3 is a view similar to Figure 1 showing the device object of the invention after firing of the load.

If we refer to FIG. 1, we see The two elements to be separated which bear the references 2 and 4. In the embodiment described here, the first element 2 has two projecting parts 6 and 8, connected respectively to the body of element 2 by thin zones 10 and 12. In this example, the projecting parts 6 and 8 are not attached elements, but form an integral part of the body 2, the latter having been machined in order to produce the protruding parts 6 and 8. It can also be seen in FIG. 1 that the element 2, including the protruding parts 6 and 8, has, seen in section, a symmetry with respect to a plane P perpendicular to the plane of the figure, represented schematically in dashed lines.

On the other hand, the second element 4 presents. Along its edge closest to the first element 2, an enlarged part 14 whose width is slightly less than the width of the cavity 16 defined between the protruding parts 6 and 8. The pyrotechnic charge is in the form of a detonating cord 18 placed inside a deformable envelope 20, the space between the detonating cord and the deformable envelope being filled with a flexible material 22, for example a silicone rubber sheath. The sheath 22 performs several functions. First of all, it supports and maintains the detonating cord 18 in the correct position, that is to say substantially along the axis of symmetry of the envelope 20. In the particular case described here, this envelope has two parts flattened connected by semi-circular parts, but it would not depart from the scope of the invention by giving it another shape, oval for example. In addition, if silicone rubber is used, it behaves like a thermal insulator and protects the cord 18 from sudden temperature variations that the components of a spacecraft can undergo. Finally, the damping qualities of rubber protect the detonating cord from external shocks to which a spacecraft may be subjected upon departure or when certain propulsion engines are ignited.

In the particular case described here, there is only one detonating cord 18, but it would not go beyond the scope of the invention by putting several, two for example, so that the second can operate in the event of failure from the first. In this case, the flexible sheath 22 also has the role of preventing the ignition of the second cord by shock waves due to the explosion of the first.

FIGS. 1 and 2 also show the means for fixing the first element 2 to the second element 4 by means of the projecting parts 6 and 8. It can be seen that the latter have, at their ends opposite to the connection zones 10 and 12, holes 24 and 26 respectively, which can be aligned with a hole 28 formed in the enlarged part 14 of the element 4, these different holes being of the same diameter. A screw 30 passes through the holes 24, 28 and 26 and it is held by a nut 32, the tightening of the nut 32 on the screw 30 having the effect of applying the protruding parts 6 and 8 of the first element on the part enlarged 14 of the second element. Optionally, a dou lle 34 can be placed inside the passage formed by the holes 24, 28 and 26, in order to better adjust the screw 30. It can also be seen in FIGS. 1 and 2 that the fixing device can be completed using one or more stirrups such as 36, distributed from place to place along the deformable envelope 20. These can be made of any ductile material such as mild steel. It can be seen in FIG. 2 that each stirrup 36 consists of an upper part 38 in the form of a semicircle extended by two branches 40 and 42. The upper part 38 is in contact with the upper part of the deformable envelope 20 which is also in the shape of a semicircle. As for the branches 40 and 42, they are substantially parallel and their spacing is such that they can be placed between the internal face of the projecting parts 6 and 8 and the external face of the widened part 14 of the element 4 (FIG. 1). The branches 40 and 42 of the stirrup 36 also have holes 44 and 46 respectively (FIG. 2) of the same diameter as the holes 24, 26 and 28, the screw 30 also passing through the holes 44 and 46.

If we refer again to FIG. 1, we see that the deformable envelope 20 is held against the internal faces of each protruding part 6 and 8, against the wall of the cavity 16 situated on the body side of the element 2 and, finally, against a boss 48 provided on the enlarged part 14 of element 4. This arrangement means that the envelope 20 is held on all sides, but it would not go beyond the ambit of the invention to use an equivalent assembly, provided that the casing 20 is maintained so that the energy of the explosion causes the tearing at the connection zones 10 and 12.

We will now describe the operation of this device with reference to ^' Figure 3. When fired, the detonating cord 18 explodes and the energy of the explosion is transmitted through the flexible sheath 22 to the deformable envelope. It therefore deforms and tends to take a more or less circular section. A force is therefore exerted on the internal faces of the projecting parts 6 and 8, substantially perpendicular to these faces. The projecting parts 6 and 8 undergo a torque and tend to pivot around an area close to their end held against the element 4 (areas 6a and 8a in FIG. 3). The greatest torque is exerted at the end of the projections 6 and 8 furthest from the screw 30, that is to say at the level of the connection zones 10 and 12 because it is where the lever arm is most important. This is where the rupture occurs.

Thus, the device which is the subject of the invention has interesting advantages, the main one of which is that it allows, for a given explosive mass, to cut a greater thickness of sheet metal than with the devices of the prior art. Tests comparisons were made with a device in accordance with that described in document US-A-3,698,281 and with a device in accordance with that of the invention, as illustrated in FIG. 1. In the first case, there is no was able to cut a set of two sheets of small thickness, that is to say for each of the order of 0.85 mm, while with the device of the invention, it was possible to cut a element in which the thinned zones 10 and 12 each had a thickness of 1.70 mm, or a cutting capacity doubled. The zones 10 and 12 can therefore have a relatively large thickness, which contributes to maintaining the rigidity of the assembly of the element 2.

Finally, it is understood that the invention is not limited to the single embodiment which has just been described, but that it is possible to envisage variants without thereby departing from the scope of the invention. For example, the projecting parts can be an integral part of the first element, as in the embodiment described above, but can also be produced in the form of independent plates. In this case, the plates are fixed to the first element by second fixing means, which can be identical to the first. Each plate has an external face and an internal face, the internal faces of the plates constituting walls of the cavity containing the deformable envelope. The plates have longitudinal grooves or grooves (that is to say substantially parallel to the detonating cord) formed from their external face and located approximately at the second end of the cavity. The thinned parts are then formed by the zones located between the bottom of the grooves and the internal face of the plates.

Claims

1. Pyrotechnic separation device between a first element (2) and a second element (4) Using a pyrotechnic charge (18) placed in a deformable envelope ⁽ 20 ⁾ , the first element (2) comprising two parts projections (6, 8) which define between them - a certain space, the device further comprising first fixing means ⁽ 30, 32) for fixing the first element (2) on the second (4) by means of said parts protruding (6, 8), thus defining a cavity (16) in which is placed said deformable envelope (20), this cavity (16) having a first end close to said first fixing means (30, 32) and a second end remote of these first fixing means, the first element (2) having thinned parts (10, 12) which break during the explosion of the pyrotechnic charge (18), characterized in that said thinned parts (6, 8) are located approximately level of the second end of said cavity (16).

2. Device according to claim 1, characterized in that the first fixing means comprise at least one screw (30) passing through a hole (24, 26) formed in each projecting part (6, 8) and a hole (28 ) formed in the second element (4), and a nut (32), the tightening of this nut (32) on the screw (30) causing the application of said projecting parts on the second element (4).

3. Device according to claim 2, characterized in that the first fixing means further comprise at least one stirrup (36) of which a part at least partially surrounds the deformable envelope (20) while being in contact with the latter and whose another part has a hole ⁽ 44) through which said screw (30) can pass.

4. Device according to claim 1, characterized in that said projecting parts (6, 8) are an integral part of the first element (2) and are connected to the rest of this element (2) by thin connection zones which (constitute said thinned parts (10, 12).

5. Device according to claim 1, characterized in that said projecting parts (6, 8) consist of plates fixed to the first element by second fixing means, each of these plates having a thin area which constitutes the one of said thinned parts (10, 12).