Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B15/00—Self-propelled projectiles or missiles, e.g. rockets; Guided missiles
  • F42B15/36—Means for interconnecting rocket-motor and body section; Multi-stage connectors; Disconnecting means
  • F42B15/38—Ring-shaped explosive elements for the separation of rocket parts

Definitions

• the present invention relates to the field of pyrotechnic separation, in particular to the separation of two elements of aeronautical or spacecraft, such as for example the cap or protective panels of measurement devices of a rocket and the body of the rocket.
• It relates to a method of assembling a pyrotechnic separation device, as well as a pyrotechnic separation device obtained by the implementation of this assembly method.
• the document WO 87/07006 describes a pyrotechnic separation device which comprises at least one charged tube formed of an envelope containing over its entire length a detonating cord.
• the loaded tube is arranged between two machine elements which must be separated from each other, along a cutting area between the two machine elements.
• the envelope is made of a deformable metallic material, and has in a first operating configuration a flat cross section, for example oblong or oval. It is filled with a flexible material within which the detonating cord is placed.
• the separation device is held in place inside a housing running through the cutting area.
• the wall of this housing has, distributed over its entire length, areas of weakness, which are areas where said wall is thinned.
• the firing of the detonating cord at at least one of the ends of the separation device and the propagation of a subsequent shock wave inside the charged tube cause the deformation thereof, step by step.
• Said loaded tube then tends to take a second operating configuration in which it has a circular cross section. This radial expansion of the loaded tube has the consequence that the weakening zones of the housing break along the cutting area between the two machine elements, which, gradually, separates these two machine elements .
• Document O-87/07006 does not provide any indication of the ends of the pyrotechnic separation device.
• FIG. 5 A conventional pyrotechnic separation device of the prior art, seen at its ends, is illustrated in Figure 5 in top view.
• the separation device 110 comprises at each of its ends an initiation nozzle 120, which is connected on the one hand to one end of a charged tube 112 and on the other hand to a connecting cord 180, itself connected to a firing device (not shown in Figure 5), through which the initiation is initiated fire from the detonating cord, and which is distant from the separation device.
• the separation device 110 is received in a housing 106 which is continuous over the entire length corresponding to the loaded tube 112, and which has a discontinuity corresponding to the location of the initiation nozzle 120 associated with said end of the separation device 110. This discontinuity results in an opening 108 made in the wall 109 of at least one of the two machine elements which must be separated.
• the firing is caused at both ends of the loaded tube 112, in order to counter the possibility of a firing failure which would occur at one of these ends, which requires the presence of two initiation tips 120 and two connections with a firing cord 180.
• the positioning of the separation device 110 in the housing 106 is such that the two end caps 120 are in close proximity to each other, which requires an opening 108 having a greater length in the cutting plan.
• the initiation nozzle 120 of the prior art is a segment of substantially straight tube, which has at one end an assembly orifice 126 for its assembly with the envelope, and at the other end a firing orifice 124 for its connection with the firing cord 180.
• a method of manufacturing a conventional pyrotechnic separation device of the prior art takes place as follows:
• an initiation nozzle 120 is assembled at each end of the envelope, by a conventional assembly process, for example by screwing into the assembly orifice 126 of the initiation nozzle 120,
• the sheath containing the detonating cord is introduced, through an introduction orifice 124 of the initiation nozzle 120, said introduction orifice 124 being for this purpose oriented in such a way that its axis is parallel to the longitudinal direction common to the initiation end piece and to the envelope, then said sheath is moved step by step inside the initiation end piece and the envelope,
• a firing cord 180 is connected to each initiation nozzle 120, for example by screwing, in the firing orifice 124 of the initiation nozzle 120,
• the tube loaded with the flexible sheath containing the detonating cord is deformed, to bring it into its first operating configuration in which it has a flattened shape over its entire length, by an appropriate deformation process, for example by a process pressing or other calibrated crushing process.
• the shape of the initiation tip 120 is conditioned by the manufacturing process which has just been recalled. For reasons of convenience, the introduction orifice is merged with the firing orifice 124.
• the firing orifice 124 and the assembly orifice 126 of the initiation nozzle 120 are aligned with each other in the longitudinal direction thereof, so that we can introduce and slide the flexible sheath containing the detonating cord in the initiation tip 120 and then in the envelope, according to the longitudinal direction common to the initiation tip 120 and to the casing.
• the firing orifice 124 therefore serves both to connect the firing cord to the initiation tip 120, and to introduce the flexible sheath containing the detonating cord.
• This introduction function requires that the initiation nozzle has a certain length, designated by D in FIG. 5, in order to be able to guide the flexible sheath.
• connection between the initiation tip and the firing cord is made on a connection portion, designated by 140 in Figure 5, which occupies a certain length Dl, in the longitudinal direction of the tip initiation, which accordingly increases the length L, in the cutting plane, of the opening 108 made in said wall 109 of at least one of the two machine elements which must be
• the tube deformation operation is done after its assembly with the initiation tip, because otherwise it would not be possible, or in any case very difficult, to introduce the flexible sheath containing the detonating cord into an already flattened envelope .
• the loaded tube has a transient portion, designated by 150 in FIG. 5, along which its section passes progressively in a substantially circular shape, near the end piece. initiation, to a substantially flattened shape, where it has been deformed.
• This transient portion 150 occupies a certain length D2, which consequently increases the length L, in the cutting plane, of the opening 108 made in said wall 109 of at least one of the two machine elements.
• An object of the present invention is to obtain a pyrotechnic separation device which retains the main advantage of the separation device of the prior art, namely allowing a clean separation of the elements, that is to say that the residues explosive material remains inside the tube. Indeed, one of the two machine elements to be separated is very often a compartment in which there are sophisticated, fragile and expensive electronic equipment, which must not be polluted during the separation of the elements.
• a further object of the present invention is to minimize the stresses on the edges of openings in the wall of the at least one machine component to be separated. For this, it is necessary to reduce the length of these openings in the cutting plane. To do this, we seek to reduce the length D of each initiation nozzle and / or the length D1 of the associated connection portion, and / or to reduce the length D2 of the associated transient portion.
• a solution consists in previously loading an envelope having a substantially circular cross section with the flexible sheath containing the detonating cord, then in deforming the loaded tube to give its cross section a flattened shape on its entire length, and finally to assemble the initiation nozzle on one end of said loaded tube, through the assembly orifice of the initiation nozzle. Consequently, the firing orifice of the initiation nozzle only serves to connect the latter with the firing cord, and no longer serves to introduce the flexible sheath containing the detonating cord. It follows on the one hand that the transient portion is eliminated, since the deformation of the loaded tube takes place over its entire length. The length D2 can thus be deleted.
• the elimination of the transient portion also has the advantage of reducing the manufacturing costs of the separation device.
• Another object of the present invention is to guarantee that the assembly between the loaded tube and the initiation nozzle ensures good sealing conditions to preserve the detonating cord from the humidity of the ambient air.
• the heating of the parts during welding must not cause inadvertent ignition or destruction of the detonating cord which is already inside the envelope at the time of assembly.
• the present invention therefore provides a method of assembling a pyrotechnic separation device by which at least one initiation nozzle is directly assembled at one end of a tube. previously loaded and deformed, said initiation nozzle having a reduced longitudinal dimension compared to the initiation nozzles of the prior art, and said assembly method ensuring the tightness of the assembly. It also proposes a pyrotechnic separation device obtained by this process.
• the method of assembling a pyrotechnic separation device comprises:
• the method comprises a prior step during which the loaded tube is deformed to give its cross section a flattened shape over its entire length.
• said flattened cross section has an oblong or oval or elliptical shape.
• the method comprises an initial step during which an envelope having a cross section of substantially circular shape is loaded with a flexible material and a detonating cord, said flexible material forming a sheath for said detonating cord.
• the separation device comprises more than one initiation nozzle, the succession of the above-mentioned steps is repeated for each assembly of an initiation nozzle with an end of tube previously loaded and deformed.
• said weld bead is produced between a thinned peripheral zone of an assembly wall surrounding an assembly orifice of the initiation nozzle and the envelope.
• Said welding points pass through the thinned peripheral zone of the assembly wall and penetrate into the envelope without passing through it.
• this spot welding is carried out by means of a laser welding apparatus of the pulsed YAG laser type. Its operating parameters are adjusted in such a way that the temperature rise at the detonating cord is perfectly controlled.
• the pyrotechnic separation device comprises at least one tube loaded with a detonating cord and at least one initiation tip assembled on said charged tube by the implementation of a conforming assembly process to the first aspect of the invention.
• the initiation nozzle is provided with an assembly orifice delimited by an assembly wall which comprises a thinned peripheral zone.
• the initiation nozzle has a bent shape, for example forming substantially a right angle.
• FIG. 1 is a perspective view of part of a cutting area between two machine elements, showing two initiation tips assembled on two respective ends placed end to end of two tubes loaded with a device pyrotechnic separation;
• FIG. 2 illustrates in longitudinal section an initiation nozzle assembled on one end of a tube loaded with a pyrotechnic separation device
• FIG. 3 is an enlarged partial view illustrating the assembly by welding between the initiation tip and the loaded tube of Figure 2; and - the.
• Figure 4 is a close-up view of a welding spot to illustrate its shape and dimensions;
• FIG. 5 already described, is a top view of part of a cutting area between two machine elements, showing two initiation tips assembled on two ends put end to end of a tube loaded with a pyrotechnic separation device of the prior art.
• FIG. 1 illustrates only part of the two elements 2, 4, which each have an overall shape of a substantially circular crown.
• This cutting area is traversed by a peripheral housing 6 which comprises, in the example illustrated, a wall 62 belonging to the machine element 2 and a wall 64 belonging to the machine element 4.
• Said peripheral housing 6 receives.
• pyrotechnic separation devices 10. These are, in this example, two in number and arranged end to end. They each include a loaded tube 12 and two initiation tips 20. Due to the substantially circular configuration of the cutting zone of the present example, it has two substantially diametrically opposite locations, in which there are two initiation tips.
• FIG. 2 illustrates, in longitudinal section, one end of a pyrotechnic separation device 10, which comprises a charged tube 12 and an initiation nozzle 20.
• the charged tube 12 comprises a metal casing 13, preferably made of stainless steel. It is equipped over its entire length with a detonating cord 14 constituting a core of said charged tube 12, and with a flexible sheath 16 which fills the space between the casing 13 and the detonating cord 14.
• the charged tube 12 has was obtained by introducing into the envelope 13 a flexible material containing the detonating cord 1, said flexible material forming a sheath 16 for said detonating cord 14.
• Said flexible sheath 16 is made of a damping material, such as for example silicone.
• the loaded tube 12 has been previously deformed over its entire length. It has a flattened cross section, for example oblong, oval or elliptical. A firing of the detonating cord will cause a radial expansion of the loaded tube 12 which will tend to adopt a configuration in which it will have a substantially circular cross section.
• the initiation tip 20 is a metal tip, preferably made of stainless steel refined under vacuum, which has a length D along its longitudinal direction which is also the longitudinal direction of the loaded tube 12. It comprises: - a tip body 22 a firing orifice 24 intended for connection with a firing cord 80
• FIG. 1 (represented by broken lines in FIG. 1), which in the example illustrated is a screw-type connection, and an assembly orifice 26 for its assembly with the loaded tube 12.
• the tip body 22 preferably has an angled shape.
• the firing orifice 24 and the assembly orifice 26 have axes which intersect, forming, in the example illustrated, an angle substantially equal to 90 °.
• the assembly orifice 26 has a cross section whose shape and dimensions are adapted to that of the cross section of the end of the loaded tube 12. It is delimited by an assembly wall 28 which is part of the body d end piece 22.
• the assembly wall 28 has a thinned peripheral zone 30 and ends in a reinforcing ring 32.
• the thinned peripheral zone 30 is shown on a larger scale in FIG. 3, which illustrates the actual assembly of the initiation nozzle 20 on the loaded tube 12.
• the method of assembling the separation device 10 comprises a step for fitting the end of the loaded tube 12 into the assembly orifice 26, and a step of joining by welding the thinned peripheral zone 30 to the flattened envelope 13. These two steps can be preceded by a step of loading the envelope 13 with the detonating cord 14 surrounded by its flexible sheath 16, and / or by a step of deformation of the cross section of the loaded tube 12.
• This deformation is carried out on the entire length of the loaded tube 12, and tends to flatten its cross section, to give it an oblong, or oval, or elliptical, or other flattened shape.
• Welding is a fusion welding of metal, which is carried out by means of a laser welding machine of the pulsed YAG laser type, the operating parameters of which are adjusted, so that the temperature generated at the detonating cord does not exceed not a maximum value T M.
• this maximum value T M is fixed at 100 ° C.
• the main operating parameters are the welding speed, the welding energy, the pulse duration, the pulse frequency of the laser beam, the focal length of the objective, and the shooting distance.
• a vacuum-refined stainless steel has the advantage, compared to a stainless steel that would not be vacuum-refined, of a lower sensitivity to cracking which sometimes occurs during laser welding, due to the rapid solidification of molten areas.
• the welding step consists in making successive welding points 40 on the thinned peripheral zone 30, by overlapping the weld points 40 along the periphery of the thinned peripheral zone 30, so as to form one or more weld bead (s) 42 peripheral (s) and continuous (s).
• the weld points 40 of the same weld bead 42 are regularly distributed over the entire circumference of the thinned peripheral zone 30, so that said weld bead 42 is closed.
• the weld points 40 pass through the thinned peripheral zone 30 of the assembly wall 28, and penetrate into the envelope 13 without passing through it.
• the assembly of the initiation nozzle 20 on one end of the loaded tube 12 is obtained as soon as one has produced a peripheral and continuous weld bead 42.
• a peripheral and continuous weld bead 42 To improve the mechanical strength and tightness of the assembly, it is preferred to produce several peripheral and continuous weld beads 42 which are substantially parallel to one another.
• the number of weld beads 42 is limited by the width of the thinned peripheral zone 30. It is preferably between two and six, and even more preferably equal to four. Said width of the thinned peripheral zone is noted a.
• the weld beads 42 are spaced from each other in the direction of the width a of the thinned peripheral zone 30. According to another preferred variant, illustrated in FIG. 3, the weld beads 42 are contiguous in the direction of the width a of the thinned peripheral zone 30.
• the height of the thinned peripheral zone is denoted hl
• the axial distance between two adjacent weld beads 42 is denoted c
• the distance between each end weld bead 42 and each edge of the thinned peripheral zone 30 is denoted b
• the total welding width is noted 1.
• FIG. 4 is illustrated in section and in an enlarged manner a weld point 40. It has a base portion 44 which opens to the outside at the surface of the thinned peripheral zone 30, and a foot portion 46 which penetrates into the casing 13.
• the base 44 has substantially a dome shape and the foot 46 has substantially a cylindrical shape or a frustoconical shape which decreases as it moves away from the base 44.
• the end of the foot 46 penetrating into the casing 13 ends with a substantially rounded tip 47.
• the surface of the base 44 which opens to the outside has a recess 45.
• the junction between the base 44 and the foot 46 has a substantially funnel-shaped profile.
• the base 44 has a diameter dl and its hollow 45 has a height e.
• the foot 46 has a diameter d2.
• its diameter d2 is axially variable.
• d2p the diameter d2 at the joint plane between the thinned peripheral zone 30 and the envelope 13.
• the weld point 40 has a total height h.2 which is the sum of a through height hl equal to the height of the thinned peripheral zone 30 crossed by the points of weld 40 and a penetrating height h3 which corresponds to the penetration height of the weld points 40 in the casing 13.
• the envelope 13 was loaded with a silicone sheath 13 containing a detonating cord 14.
• the loaded tube thus formed was crushed to have a cross section of oblong shape, with two straight parts and two rounded parts.
• a pulsed YAG laser welding process was used, with a microsoldering center known under the name LASAG PM 300.
• the temperature generated at the detonating cord remained below 80 ° C.
• the weld beads 42 were joined.
• the weld points 40 had the following dimensions:
• - base diameter 1.2 mm ⁇ dl ⁇ 1.6 mm
• An initiation nozzle 20 was used whose length D along the longitudinal direction of the loaded tube was substantially between 30 and 35 millimeters, more precisely substantially equal to 32.7 millimeters, whereas according to the prior art a initiation nozzle having a firing and introduction orifice axially aligned with the assembly orifice, and having a length D of 58.4 mm.
• the length L, in the cutting plane, of the opening made in the wall of the machine element has been reduced to 116 millimeters, whereas with a separation device of the prior art, we should have practiced an opening with a length L of 230 mm.

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Citations (5)

• 2003
  • 2003-01-24 FR FR0300778A patent/FR2850454B1/fr not_active Expired - Lifetime
• 2004
  • 2004-01-26 EP EP04705109A patent/EP1585933B1/de not_active Expired - Lifetime
  • 2004-01-26 WO PCT/FR2004/050032 patent/WO2004068062A1/fr active IP Right Grant
  • 2004-01-26 ES ES04705109T patent/ES2268623T3/es not_active Expired - Lifetime

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