EP0367815B1 - Separation device for the aerodynamic braking of a body - Google Patents

Abstract

The invention relates to an aerodynamic device of a body (1) particularly applicable to the rear part of a projectile allowing for the taking away of said rear part with respect to useful charges (3) contained inside the projectile. This economical device, of reduced volume, produces its effects on a body (1) provided with a certain rotational speed. The fixing of blades (4) to the body is made in different ways so as not to be cumbersome and allow the blades (4), by means of a stop system (7, 8), to be fully operative. After unlocking of the system which maintains the blades along the body, the blades are subjected to the centrifugal force as well as to the effects of the speed of the body (1), and when extended, the blades increase the aerodynamic drag of the body, thereby acting as a brake. Application to all bodies, particularly projectiles, for example self-propulsed vectors having a rotational motion.

Description

The invention relates to a device for aerodynamically braking a body, this braking being applicable in particular to the separation of bodies initially linked for example the rear part and the front part of a projectile or the separation of bodies or submunitions initially contained in the projectile.

The main application of this device can be carried out on a projectile rotating on itself containing payloads and the release of which is effected by the separation of the front part and the rear part, kept in contact in particular by a system pin, thanks to the action of propellant gases located at the front of the projectile; the latter having taken place, the rear part of the projectile tends to remain in the vicinity of the payload and thus risks causing discomfort during subsequent sequences: possibility of percussions with the payload preceding it ... To avoid this phenomenon , it is necessary to increase the aerodynamic drag of the rear part of the projectile.

A device performing braking of a rear part initially fixed to a front part of a rocket is described in US Pat. No. 4,648,321. This patent describes a device for separating the payload 16 of a rocket 10 from the engine section 12. This separation is carried out by means of a special section 14. For the present invention we will focus more particularly on the braking device aerodynamics in this section. This device consists of a deployable surface 50 housed in an internal part 30 of the section. This surface 50 is capable of two positions, a first when the section 14 is one with the rest of the rocket and a second deployed radially outwards so as to form an airbrake after separation.

The passage from one to the other of these positions is ensured by a spring which acts after pyrotechnic removal of a retaining lock.

The surface 50 has a shape such that in the first position its outer surface contributes to the continuity of the outer surface of the assembled body of the rocket. To this end, this surface can be defined as a part of the surface generated by a generator parallel to the axis of the rocket. Because of its complexity, such a device is necessarily expensive, so it is only justified to use it on expensive assemblies, for example rockets. In such assemblies the operation of each part must be verified by prior tests reproducing if possible the conditions of the flight. This concern does not concern projectiles which by their nature are intended to be produced in large numbers.

The present invention is essentially applicable to projectiles for which a compromise must be found between reliability and price.

One of the aims of the invention is therefore to produce an economical device ensuring the aerodynamic braking of a first body which it is desired to separate from a second body with which the first body was initially assembled to form an assembled body. Another object of the invention is to conform this device so that its size provides only a minimum reduction in the volume available in the internal part of the first and second assembled bodies so as not to reduce the volume of the payload.

The invention therefore relates to a device for braking an element of a projectile having a longitudinal axis 00 ′ and intended to be driven in a rotational movement, the projectile comprising a front part and a rear part each having a body, an assembly of the two bodies forming a body of the projectile, the external peripheral surface of the body of the projectile delimiting an internal part and an external part, the front and rear parts being separable from each other, the rear part comprising braking means capable of two positions, a first when the front and rear parts are assembled and a second when these parts are separated, the braking means being constituted by surfaces which in the first position are housed in the part internal to the body of the projectile and which in the second position are at least partially deployed outside the body of the rear part, characterized in that the surfaces consist of strips of a material capable of plastic deformation fixed by one of their ends to the periphery of the body of the rear part, the transition from the first to the second position being obtained after separation of the front part and the rear part under the effect of centrifugal forces.

• Fig.1, une coupe transversale de la partie arrière d'un projectile avant la phase de séparation selon l'invention
• Fig.2, une coupe transversale de la partie arrière d'un projectile pendant la phase de séparation selon l'invention ;
• Fig.3, une coupe transversale de la partie arrière d'un projectile après la phase de séparation selon l'invention ;
• Fig.4, une coupe transversale de la partie arrière d'un projectile avant la phase de séparation selon un autre mode de réalisation que celui de l'invention ;
• Fig.5, une coupe transversale de la partie arrière d'un projectile après la phase de séparation selon le dispositif de la figure 4 ;
• Fig.6, une coupe transversale de la partie arrière d'un projectile après la phase de séparation suivant un autre mode de réalisation ;
• Fig.7, un schéma du déploiement des lamelles selon l'invention.
• Fig.8, un schéma d'application du dispositif sur un corps selon l'invention.
• Fig.9, un système de maintien de sous-munitions à l'intérieur d'un projectile, avant et après le largage ;
• Fig.10, un schéma d'un système de retardement à l'ouverture des lamelles fixées sur une sous-munition selon l'invention.

The invention and its characteristics will be better understood on reading the description of a particular example of application which will follow and the figures which represent:

• Fig.1, a cross section of the rear part of a projectile before the separation phase according to the invention
• Fig.2, a cross section of the rear part of a projectile during the separation phase according to the invention;
• Fig.3, a cross section of the rear part of a projectile after the separation phase according to the invention;
• Fig.4, a cross section of the rear part of a projectile before the separation phase according to another embodiment than that of the invention;
• Fig.5, a cross section of the rear part of a projectile after the separation phase according to the device of Figure 4;
• Fig.6, a cross section of the rear part of a projectile after the separation phase according to another embodiment;
• Fig.7, a diagram of the deployment of the slats according to the invention.
• Fig.8, a diagram of application of the device on a body according to the invention.
• Fig.9, a system for holding submunitions inside a projectile, before and after dropping;
• Fig.10, a diagram of a system for delaying the opening of the strips fixed to a submunition according to the invention.

Figure 1 shows a cross section of the rear part of a projectile before the separation phase. This projectile is provided with a braking device according to the invention. The projectile has a rear part 1, a front part 2, a payload 3, a sliding tube 5 on which are lamellas 4 and a support piece 6. The rear part 1 of the projectile is embedded, for example, in the front part 2 thereof in the recess 9 shown in this figure. The two parts 1 and 2 are kept in contact with each other by means of pins 12; it is at this point that the front part 2 of the projectile is separated from the rear part 1. This separation is initialized, for example, thanks to the pulse caused by a gas generator located in the front part 2 of the projectile and not shown in the figure causing the breakage of the pin 12 thus releasing the two front and rear parts of the projectile as well as the payloads contained inside the latter. To allow the insertion of the strips 4 inside the structure of the projectile, an increase in the clearance between the payload 3 and the projectile 2 has been achieved. These strips 4 are arranged side by side inside the projectile thus forming a tube which can slide; they are also fixed at one of their ends to a tube 5 on which is placed a support piece 6; the shape of the latter is determined, for example, to include bosses serving to support the bottom of the payload 3; it is made, for example, from stamped sheet metal and its thickness is determined, for example, according to the resistance of the materials to avoid any deformation. At each of its ends, the support part 6 is provided, for example, with one or more lugs 7 which come, during ejection, to be braced on a shoulder 8 forming an integral part of the rear structure 1 of the projectile and allowing the lamellae 4 to fully play their role; these lugs 7 are made, for example, so that they are elastically erased during integration into the projectile when they pass in line with the shoulder 8; they can also be fixed, for example, on the lamellae (4) or on the tube (5) while retaining their function.

2 shows a cross section of the rear part 1 of the projectile during the separation phase. In fact, when the projectile has left its launch tube, it is rotated around the axis OO ′. The separation of the front structure 2 of the projectile and its rear part 1 causes the release of the payloads contained inside the projectile. The front part 2 of the projectile is propelled forward by means of propellant gases; the latter exert a force on the rear of the projectile facilitating, for example, the separation of the two parts 1 and 2 of the projectile. As the spacing progresses, the lamellae 4 are subjected to centrifugal force due to the rotation of the projectile. They thus exert a force which causes the start of separation between the rear part 1 and the payload 3. This phenomenon is obtained by the sliding of the assembly 4, 5, 6 on the rear part 1 of the projectile. This makes it possible to obtain a greater deployment length than that allowed by the location between the rear part 1 and the payload 3. The sliding of this assembly 4, 5, 6 is carried out up to the stop 8 of the rear part 1 where the pins 7 of the support part 6 lock the assembly 4, 5, 6.

Figure 3 shows a cross section of the rear part of the projectile after the separation phase. The device according to the invention having come to abut against the notches provided for this purpose, the strips 4 are subjected to centrifugal force because the projectile has been rotated in its launching phase; they deploy as a fan, by bending, as shown in Figure 3, the speed of the projectile also producing effects on the latter. The combined effects of aerodynamic forces due to the speed of the projectile and the centrifugal forces, on these strips 4, position them according, for example, to an angle η; this angle η, once reached, varies little or not, this, thanks to the structure of the lamellae produced, for example, in a metallic or plastic material ensuring plastic deformation, that is to say a deformation which is preserved after l action of the combined effects on the lamellae. This principle considerably increases the aerodynamic drag of the rear part 1 of the projectile.

FIG. 4 shows a fixing of the strips 4 according to another embodiment before the phase of separation of the front part 2 of the projectile and its rear part 1. The strips 4 are arranged side by side inside the projectile; they are housed between the rear part of the payload 3 and the rear part of the projectile 1; they are fixed at one of their ends 12, for example, by a fixed fixing system, for example, one can use rivets 13 which pass through the lamellae 4 and come to bear on the rear part 1 of the projectile.

FIG. 5 represents the fixing system, previously described according to FIG. 4, after the separation of the front part 1 of the projectile and its rear part 2. Slats 4 fixed on the rear part 1, during the ejection of the front part 2 of the projectile, deploy and take the position shown in FIG. 5. The non-fixed end 14 of the strips 4 comes to bear on the recess 9 of the rear part 1; it is at this moment that the lamellae 4 begin to play, on the one hand, their role of separation thanks to the action of the self-rotating forces on the lamellae which causes the creation of a pushing force on the front part 1 thus facilitating the separation of the front part 1 and the rear part 2, and on the other hand, their braking role thus allowing the payload 3 contained inside the projectile to be moved away from its rear part 1.

FIG. 6 shows a fixing of the strips 4 according to another embodiment after the phase of separation of the front part 2 of the projectile from its rear part 1. The strips 4 have the same arrangement as in the previous description; the difference is in the fixing system; they are fixed, for example, to a mobile fixing system, for example, an axially sliding fixing which can be produced, for example, by a spiral spring 15 whose large coil 16 is fixed to the rear part 1 of the projectile, by example, by studs 17; the central turn 18 is fixed to the strips 4, for example, by a plate 19 provided with two rivets 20. When the front part 1 of the projectile is ejected, the central turn 18, which superimposed the large turn 16, moves longitudinally in the direction OO ′ and, stabilizes in the position shown in this figure 6 so that part 21 of the lamellae 4 lies in a plane perpendicular to the turn central 18 as well as direction OO ′. The slats 4 then fulfill the function which has been described previously.

; ce dernier doit être réduit pour limiter les risques de vibration dus au fait que le profil aérodynamique des lamelles est instable à grande incidence Dans le même but, par exemple, on peut excentrer le centre de poussée aérodynamique des lamelles 4. Ceci peut être réalisé, par exemple par découpe, par plombage, et par pliage d'un des bords de celles-ci ; de cette manière, on obtient un calage angulaire stable vis-à-vis de la rotation ainsi qu'un moment de roulis modifiant la loi de roulis de la partie freinée en empruntant de l'énergie au mouvement axial ce qui contribue à accroître l'efficacité du dispositif.Figure 7 shows the deployment of the slats 4 according to the invention. These strips 4 are arranged either in a layer, which, in this case, causes a fan-shaped deployment of the latter as shown by the strips 4 in solid lines in FIG. 7, or in several layers, which makes it possible to obtain continuous ring deployment. In the example shown in FIG. 7, two layers of strips were used: the first being drawn in solid lines 4, the other 11 in dotted lines. The two sets of strips each forming a tube in the rest state inside the projectile are offset by a certain angle in order to obtain the largest possible braking surface; the latter is obtained when the spaces 11 between the strips 4 of the first thickness are covered by the strips 10 of the second thickness. The shaping of these strips is given by the rotational movement of the projectile acquired at launch. The strips 4 are located next to each other and form a tube inside the projectile when they are distributed around the payload 3. They are relatively thin and are made, for example, of metallic or plastic material. The shape of these strips 4 is, for example, that of a flat rectangle whose width and length give their orientation which is defined by the ratio $$\frac{\text{Length}}{\text{Width}}$$

; the latter must be reduced to limit the risk of vibration due to the fact that the aerodynamic profile of the slats is unstable at high incidence. For the same purpose, for example, the aerodynamic thrust center of the slats can be offset. This can be achieved, for example by cutting, by sealing, and by folding one of the edges thereof; in this way, a stable angular setting is obtained with respect to the rotation as well as a roll moment modifying the roll law of the braked part in borrowing energy from the axial movement which contributes to increasing the efficiency of the device.

The device operates without the use of an extractor system and only undergoes disturbances due to its surroundings. It can even be used in the case where, for example, the payload 3 of the projectile has air brakes fixed on its rear part and opening under the influence of centrifugal force; these, when inserted inside the projectile before the separation and launching phase, can rest on the tube 5 which prevents them from rubbing against the rear part 1 during the sliding of the assembly 4 , 5, 6 on the latter 1. As a result, the relief stroke with friction of the airbrakes is considerably reduced.

FIG. 8 represents another application of the lamella braking device according to the invention. In this figure, the lamellae (4) are positioned, by one of their ends (22), on a body (23), for example, by embedding the latter in the structure of the body, so that, during the deployment of the strips (4), as shown in the figure, each of them comes to bear on the edge (24) of the body considered for allow to play their full role, namely: the body being rotated, the aerodynamic effects due to the speed of the projectile and the centrifugal forces exerted on the slats, the slats are positioned according to, for example, an angle σ significantly increasing aerodynamic drag and therefore braking the body. The slats (4) will be fixed at the other end (25), for example, by a system of pins (26) which makes it possible to keep the slats in contact with the body to initially increase the piercing of the body in the air and then decrease the bulk; this system for fixing the end (25) of the strips (4), for positioning the strips (4) along the body, can be produced in particular by a control system providing for the unlocking of the fixing system at a precise calculated time beforehand. During the trajectory of the body, the aerodynamic forces act on the tear-off sockets constituted, for example, by the pins, the latter are torn off freely leaving the strips (4) deploying fulfilling their braking function.

The arrangement of the lamellae (4) described in FIG. 7 as well as any other method of fixing the lamellae to a body could be envisaged in the application of the braking device which has just been previously described.

This device according to the invention applies to any body driven by a high speed of rotation and remains effective for speeds of rotation which decrease because once deployed the device remains substantially in this position.

The invention can be applied in particular to any braking of a body in replacement of a braking stage as well as to pyrotechnic devices, for example military ones such as illuminants or infrared which must be braked before the start of their phase. operational.

The invention can also be applied to submunitions on board a projectile. Indeed, in order to disperse each submunition after its ejection from the projectile, the device according to the invention can be fixed on each submunition to brake and therefore separate these submunitions. To do this, each submunition must be provided with a number and a size of lamellae determined to give them different speeds. With reference to FIGS. 9 and 10, the application of the device according to the invention to submunitions contained inside a projectile is as follows. In FIG. 9, each submunition 27 placed inside the projectile 28 is covered with a compact system, in this case spacers 29 and their fixing system, for example weights 30 so as to firstly, during ejection, to avoid causing significant radial stresses against the casing 31 of the projectile due to the centrifugal force created by the projectile rotating around its longitudinal axis, and secondly, to resist the stresses mechanical due to acceleration and imposed on the projectile at the start of the shot likely to damage certain submunitions. The device according to the invention must be placed, for example, on each submunition, that is to say between the compact system and the submunition. Any other means of fixing the lamellae to the body of the submunition may be used. To avoid a collision of the spacers with the lamellae which would in particular cause destruction of the lamellae, a system for delaying the opening of the lamellae 35 has been implemented; this system as shown in Figure 10 consists, for example, to put as many metallic ribbons called foils 32 as elements of spacers not shown. These foils, for example, made of thin sheet metal, are wound around the submunition 33 in the opposite direction of rotation with a winding angle limiting the risk of collision; this winding angle is a function of the number of spacer elements and the position of the junction between two spacer elements relative to the fixing of the foil, for example, on the submunition, for example, by welding 34 at one of its ends. For example, for three 120 ° spacer elements, each foil is surrounded around the submunition with a winding angle of the order of 285 °. The fixing of the foil on the submunition is made so that the tangential resistance is substantial but that the radial resistance is weaker so that the foil fixed, for example, by welding, does not resist the centrifugal force which causes the ejection of its last.

Claims (19)

1. Device for braking an element of a projectile, having a longitudinal axis OO′ and intended to be driven with a rotational movement, the projectile comprising a front portion (2) and a rear portion (1) each having a body, an assembly of the two bodies forming a body of the projectile, the external peripheral surface of the body of the projectile delimiting an internal portion and an external portion, the front (2) and rear (1) portions being able to be separated from one another, the rear portion (1) comprising means of braking capable of two positions: a first position when the front (2) and rear (1) portions are assembled, and a second position when these portions are separated, the braking means consisting of surfaces which in the first position are lodged in the portion internal to the body of the projectile and which in the second position are at least partially deployed outside the body of the rear portion (1), characterised in that the surfaces consist of thin strips (4) made from a material capable of plastic deformation and secured by one of their ends to the periphery of the body of the rear portion, passage from the first to the second position being obtained after separation of the front portion and of the rear portion under the effect of centrifugal forces.
2. Device according to Claim 1, characterised in that the thin strips (4) are secured to a tube (5) of axis OO′.
3. Device according to Claim 2, characterised in that the tube (5) is capable of two positions: a first position before separation, and a second position after separation, passage from the first to the second position consisting of sliding towards the front along the axis OO′.
4. Device according to one of Claims 2 or 3, characterised in that the tube (5) is secured to a support piece (6) which comprises, at each of its ends, studs (7) interacting with the rear portion so as to prevent the piece (6) from leaving the rear portion (1).
5. Device according to Claim 4, characterised in that the locking of the device, effected by the studs (7), during sliding of the tube (5), of the thin strips (4) and of the support piece (6), is performed by setting the studs (7) into a stop (8) fixed on the rear portion.
6. Device according to one of Claims 2 or 3, characterised in that the tube (5) comprises studs interacting with a stop (8) of the rear portion so as to prevent the tube (5) from leaving the rear portion.
7. Device according to Claim 1, characterised in that the thin strips (4) are secured to the rear portion of the projectile (1) by rivets (13).
8. Device according to Claim 1, characterised in that the thin strips (4) are secured to the rear portion (1) by a flat coil spring (14) sliding axially.
9. Device according to Claim 8, characterised in that the flat coil spring (14) is secured to the rear portion (1) of the projectile.
10. Device according to one of the preceding claims, characterised in that the thin strips (4) are, in the first position, arranged in one layer.
11. Device according to one of the preceding claims, characterised in that the thin strips (4) are, in the first position, arranged in several layers.
12. Device according to Claim 10, characterised in that the thin strips (7) are deployed in the form of a discontinuous crown.
13. Device according to Claim 11, characterised in that in the deployed position the thin strips (4) form a continuous crown.
14. Device according to one of the preceding claims, characterised in that the centre of aerodynamic thrust of the thin strips (4) is off-centred by lead weighting or other means so as to obtain a stable angular displacement of the strips.
15. Device according to one of Claims 1 to 14, characterised in that before separation of the front (2) and rear (1) portions, the body of the projectile houses bodies (23) or sub-munitions (27) capable of leaving the body of the projectile after separation.
16. Device according to Claim 15, characterised in that the bodies (23) or the sub-munitions (27) are equipped with thin strips (25, 35) which are plastically deformable and are capable of two positions: a first position when the body (23) or the sub-munition (27) is inside the projectile and a second position when the body (23) or the sub-munition (27) is outside the projectile, and in that in the first position at least a portion of the surface of each thin strip is arranged along the peripheral surface of the munition, and in that in the second position at least a portion of the surface of each thin strip is deployed radially towards the outside of the body or of the sub-munition.
17. Device according to Claim 16, characterised in that metal foil (32) is wound around the sub-munition (33) on the thin strips (35) so as to prevent a rapid opening of the device.
18. Device according to Claim 17, characterised in that the metal foil is secured by one of its ends by welding (34).
19. Device according to one of the preceding claims, characterised in that the securing system is a control system.

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