EP0990869A1 - Sabot for a subcalibre projectile - Google Patents

Abstract

Holding device (1) for an undergauge projectile comprises at least three segments surrounding the undergauge projectile body (2). It includes first devices, such as a front cavity (6), intended to receive an aerodynamic flow when the weapon tube is released at the time of firing, and second devices (7), such as a rear cavity (7), intended to receive propulsive gas when the weapon tube is released. The first and second devices are positioned and dimensioned with respect to each other such that the holding device (1) moves away from the projectile body (2) in a direction more or less parallel to the latter when the weapon tube is released.

Description

The technical field of the invention is that of hooves for calibrated projectiles, especially large caliber (greater than or equal to 40mm).

Sub-calibrated projectiles have been known since many years they usually have a hoof at the caliber which is formed of at least three segments surrounding a under calibrated bar.

The shoe guides the bar in the tube the weapon when fired. It releases the bar at the exit of the tube of the weapon as a result of the aerodynamic forces which are exerted on him at this moment and which cause the rupture seat belts for the three segments.

Patent FR2694081 describes such a projectile.

Seeking to increase the effectiveness of arrows projectiles leads to the realization of bars of longer and longer (L / D> 10) and whose guidance must be ensured by a shoe also very long.

US Pat. No. 5,289,777 thus describes such a projectile.

Large elongation projectiles (L / D ratio> 10) cause problems with separation shoe / bar. Thus the aerodynamic forces which are exercised on the front hoof pocket (or on the front supports described by US5289777) cause a pivoting of the segments, back and forth, relative to the bar. This results in mechanical interactions (supports, between the rear of the shoe segments and the bar. Such shocks affect the accuracy of the shot (especially in increasing the dispersion) therefore to the effectiveness of the projectile.

It is the object of the invention to propose a shoe for sub-calibrated projectile not exhibiting such disadvantages.

Thus the shoe according to the invention is designed so as not to not interfere with the bar and it separates from the bar in a manner substantially parallel to this one.

Thus the subject of the invention is a shoe for a sub-calibrated projectile comprising at least three segments to the gauge intended to surround an under-calibrated bar, shoe comprising first means, such as a front pocket, which are intended to receive aerodynamic flow at the exit from the barrel of a weapon during firing, hoof characterized by which it also includes second means such as rear pocket, second means for receiving gases propellants at the exit of the barrel of the weapon, the first and second means being positioned and dimensioned by relation to others so that the hoof moves away from the bar substantially parallel to it at the out of the barrel.

According to another characteristic of the invention, the shoe comprises a rear pocket having an external leading edge which is at the level of a first plane normal to the axis of the projectile and disposed at a distance L _AR from the center of gravity of the hoof and a front pocket having an external leading edge which is at the level of a second plane normal to the axis of the projectile and disposed at a distance L _AV from the center of gravity of the hoof, the profile of the front pockets and rear being defined so that the moment M _AR with respect to the center of gravity G of the normal component F _ARN of the result of the aerodynamic forces F _AR exerted at the outlet of the tube on the rear pocket by the propellant gases is substantially equal to the moment M _AV with respect to the center of gravity G of the normal component F _AVN of the result of the aerodynamic forces F _AV exerted at the exit of the tube on the front pocket by the aerodynamic flow.

According to a particular embodiment, the pocket rear may be at the rearmost end of the shoe and its internal diameter may be between 0.4 and 0.7 hoof gauge.

According to another particular embodiment, the rear pocket may be located in the vicinity of the center of gravity of the shoe at a distance L _AR from its leading edge and from the center of gravity G which is less than or equal to 0.75 caliber, the internal diameter of the rear pocket can then be between 0.8 and 0.95 caliber.

The front pocket can be located at the most front of the shoe and its internal diameter can be understood between 0.2 and 0.6 hoof gauge.

According to another embodiment, the front pocket may be located in the vicinity of the center of gravity of the shoe at a distance L _AV from its leading edge and from the center of gravity which will be less than or equal to 0.75 caliber, the diameter internal pocket will then be between 0.8 and 0.95 caliber.

According to another embodiment, the leading edges front and rear pockets may be substantially equal distance from a mean plane of the belt, this distance could then be less than or equal to 0.75 caliber.

The shoe may include a medium support to the caliber arranged in the front part of the hoof and having recesses allowing aerodynamic flow to the pocket before.

Advantageously, the support means may be constituted by at least three arms regularly distributed angularly.

• la figure 1 montre en demi-coupe longitudinale schématique un projectile suivant l'art antérieur,
• la figure 2 montre en demi-coupe longitudinale un projectile équipé d'un sabot suivant un premier mode de réalisation de l'invention,
• la figure 3 montre en demi coupe un projectile équipé d'un sabot suivant un deuxième mode de réalisation de l'invention,
• la figure 4 schématise la séparation du sabot et du barreau à la sortie du tube de l'arme pour un tel projectile,
• la figure 5 montre en demi-coupe un projectile équipé d'un sabot suivant un troisième mode de réalisation de l'invention,
• la figure 6a montre en demi-coupe un projectile équipé d'un sabot suivant un quatrième mode de réalisation de l'invention.
• La figure 6b est une coupe de la vue précédente suivant le plan repéré AA.

The invention will be better understood on reading the following description of different embodiments, description made with reference to the accompanying drawings and in which:

• FIG. 1 shows in schematic longitudinal half-section a projectile according to the prior art,
• FIG. 2 shows in longitudinal half-section a projectile equipped with a shoe according to a first embodiment of the invention,
• FIG. 3 shows in half section a projectile equipped with a shoe according to a second embodiment of the invention,
• FIG. 4 shows diagrammatically the separation of the sabot and the bar at the outlet of the barrel of the weapon for such a projectile,
• FIG. 5 shows in half-section a projectile equipped with a shoe according to a third embodiment of the invention,
• Figure 6a shows in half-section a projectile equipped with a shoe according to a fourth embodiment of the invention.
• Figure 6b is a section of the previous view along the plane marked AA.

Referring to Figure 1, a sub-calibrated projectile according to the prior art (for example as described by FR2694081) includes a shoe 1 to the caliber of the barrel of a weapon (not shown) surrounding a sub-calibrated bar 2.

The shoe is conventionally made up of three segments forming sectors of 120 ° and which are rendered secured to each other by a guide belt 4 which also seals with propellant gases between the weapon barrel and projectile when fired.

The bar is made integral with the hoof for example by thread.

Sealing means are provided at the rear of the shoe in order to prevent any leakage of propellant gases between the joint planes separating the different segments. We for example provide a rear cover 5 made of silicone secured to a rear part of the shoe 1.

The shoe 1 has a front pocket 6 which is intended for receive at the exit of the barrel of the weapon the flow aerodynamic. The result of aerodynamic pressures which exercise in the front pocket 6 causes the tear of the belt 4 and the opening of the hoof.

The downside of such a hoof is that its movement of opening is going to be a pivot around a point of rear contact A between the shoe and the bar. It will result from mechanical interactions with the bar which will disturb the accuracy of the shot by inducing dispersion. The segments may also interfere with the tail of the bar when they opened.

The projectile according to the prior art shown here could be of any caliber greater than 40mm, in particular of 44mm or 120mm.

Figure 2 shows a projectile equipped with a shoe 1 according to a first embodiment of the invention.

This shoe differs from the front shoe in that it comprises a rear pocket 7 which is intended to receive the gases propellants at the exit of the barrel of the weapon. The pressure exerted by these gases has a resultant whose radial component has the effect of opening the hoof following a movement of pivoting with respect to a front point B.

This movement is combined with that caused by the aerodynamic forces exerted on the pocket before 6. This results in opening of the shoe 2 by spacing of the three segments of it in a way substantially parallel to bar 2, therefore without interference nor shock on this one.

The skilled person will size the front pockets and rear according to the following criteria:

It is essential to separate the hoof from the projectile as soon as possible at the exit of the barrel of the weapon in order to limit the problems of mechanical interactions and shocks.

For this, a rear pocket having a sufficient efficiency for the result of the efforts generated by the energy contained in the propellant gases (pressure, speed) has an action instantly out of the barrel.

The efficiency of the opening can easily be quantified by playing on the moment M _AR with respect to the center of gravity G of the shoe of the normal component F _ARN of the resultant F _AR of the aerodynamic forces exerted at the outlet of the tube on the rear pocket by propellant gases. This normal component F _ARN is perpendicular to the axis 9 of the projectile. Its moment M _AR is proportional to the value of F _ARN and it is also proportional to the lever arm of the vector F _AR with respect to the center of gravity G (see Figure 2).

It is the F _ARN component which is predominant for the opening of the hoof.

We will play on the intensity of this moment by modulating the intensity of the force F _ARN (which depends on the shape of the pocket and in particular on its caliber) and by varying the lever arm of this force, it is at say the longitudinal position of the pocket which will be determined by the distance L _AR between the center of gravity G of the shoe and the first plane 8, normal to the axis 9 of the projectile, and in which the leading edge is located outer 10 of the back pocket 7.

In the same way we will play on the moment M _AV with respect to the center of gravity G of the shoe of the normal component F _AVN of the resultant F _AV of the aerodynamic forces exerted at the exit of the tube by the aerodynamic flow on the front pocket in modulating the intensity of the force F _AVN (which depends on the shape of the front pocket and in particular its caliber) and by varying the lever arm of this force.

This normal component F _AVN is perpendicular to the axis 9 of the projectile. Its moment M _AV is proportional to the normal component F _AVN and it is also proportional to the lever arm of the vector F _AVN with respect to the center of gravity G.

We will play on the lever arm of this front force by varying the longitudinal position of the pocket before we determine by the distance L _AV between the center of gravity G of the shoe and the second plane 11, normal to the axis 9 of the projectile, and in which the outer leading edge 12 of the front pocket 6 is located.

Because the action of propellant gases is preponderant at the exit of the barrel, the rear pocket will sized to free the bar as soon as possible while avoiding excessive tilting of the rear shoe forward. The effectiveness of the front pocket is felt when the projectile comes out of the propellants, about 20 calibers of the mouth of the tube (2.4 m in 120mm caliber).

The aerodynamic forces F _AV and F _AR will be quantified by a person skilled in the art, for example by computer calculation of the force resulting from the elementary pressures exerted on the interior surface of the pocket considered.

This resultant has a position and an orientation which depend on the pocket geometry and characteristics flow (speed, pressure, orientation). The component of these forces which is preponderant for the opening of the hoof is the normal component to axis 9 of the projectile.

• pour un profil de poche donné, le calibre de la poche D_AR ou D_AV est important, ou bien
• pour un calibre de poche donné, que la portion de surface de poche sensiblement parallèle à l'axe 9 du projectile est grande.

Overall, the normal force which is effective for opening the hoof will be all the stronger when:

• for a given pocket profile, the pocket size D _AR or D _AV is important, or else
• for a given pocket caliber, that the pocket surface portion substantially parallel to the axis 9 of the projectile is large.

We can therefore vary the location and shape of the front and rear pockets provided that the pockets have a shape and a position such that the moments M _AR and M _AV are substantially equal.

In FIG. 2, the leading edge 10 of the rear pocket is located at a distance L _AR from the center of gravity G of the order of 0.75 caliber. For a rear pocket relatively close to the center of gravity (L _AR less than or equal to 0.75 caliber), the internal diameter of the rear pocket will be between 0.8 and 0.95 caliber. In this example D _AR is equal to 0.9 caliber (D _AR = 0.9 D) taking into account the thickness of the shoe at the edge 10.

The front pocket is located at a maximum distance L _AV . Its leading edge 12 is located as far forward as possible on the hoof (ie at about L _AV = 1.5 calibers).

The size of the front pocket is here equal to 0.9 size (D _AV = 0.9 D), taking into account the thickness of the shoe at the leading edge 12.

This configuration is not optimal since the profile of the front pocket has not been modified with respect to the projectile reference profile according to FIG. 1. This results in an opening moment M _AV still too strong. However, the rear opening moment M _AR already ensures with this hoof configuration an opening of the hoof from the rear which reduces hoof / rudder interference and improves the accuracy of the shot.

Figure 3 shows a projectile equipped with a shoe 1 according to a second embodiment of the invention.

In this embodiment, the efficiency of the front pocket has been reduced. We chose to keep the shape of the internal pocket profile according to Figure 1 and we reduced the efficiency of the pocket by reducing its caliber D _AV which is here equal to 0.58 calibers (D _AV = 0.58 D) .

A guide range 13 to the gauge is connected to the pocket front 6 by a flat face 14.

A rear pocket 7 has been placed at a maximum distance from the center of gravity G. The lever arm L _AR being large (here of the order of 2 calibers), the efficiency of the rear pocket has been reduced by decreasing its caliber (with a constant pocket profile). The rear pocket thus has a caliber D _AR of the order of 0.66 caliber (D _AR = 0.66 D).

The back moment is substantially equal to the front moment ( M AR = M AV ) which leads to an opening of the shoe segments in a manner substantially parallel to the axis 9 of the bar 2 and without mechanical interference, therefore without impact, with the bar.

The presence of a rear pocket 7 also has the effect to accelerate the separation of the hoof and the bar, since it has been verified that aerodynamic forces could not exercise on the pocket before at a distance from the weapon around 20 calibers while the forces exerted on the back pocket by propellant gases intervened from the exit of the barrel of the weapon and thus ensured a rupture fast rollover 5.

The appropriate sizing of the front pocket by compared to the rear pocket as proposed by the invention ensures a space between the shoe and the bar so substantially parallel by minimizing problems interference with the bar, the front pocket balancing the action of the back pocket avoiding interference shoe / bar at the front of it.

Figure 4 thus shows the separation of the bar and the hoof segments (only two hoof segments 1a and 1b are represented). This figure corresponds to a snapshot taken at a distance of around 40 calibers from the tube outlet tear.

Concretely, when as in Figure 3 the rear pocket is located at the rearmost end of the shoe, it will be given an internal diameter D _AR which will be between 0.4 and 0.7 gauge of the shoe.

• projectile selon l'art antérieur (figure 1),
• projectile selon la figure 2,
• projectile selon la figure 3.

Various shooting tests were conducted with 44mm caliber projectiles. The dispersion of the shots was measured for different configurations:

• projectile according to the prior art (FIG. 1),
• projectile according to FIG. 2,
• projectile according to figure 3.

Shots were taken for each configuration to a target located 200 m from the tube.

It was thus possible to verify that the projectile having a hoof according to figure 2 had a dispersion on impact on target 20% lower than that of the projectile according to the prior art (figure 1).

The projectile having a shoe according to FIG. 3 has for its share a dispersion on impact on target less than 50% to that of the projectile according to the prior art (Figure 1).

Such an improvement in results results from the absence mechanical interactions between the hoof and the bar which results from the shoe structure proposed by the invention.

Figure 5 shows a projectile fitted with a sabot according to a third embodiment of the invention.

This shoe again includes a rear pocket 7 disposed at the rearmost end of the shoe. The caliber of this pocket is approximately 0.5 caliber of the hoof (D _AR = 0.5D). The internal profile of the pocket being similar to that of the front pocket according to FIG. 1.

This shoe also includes a front pocket 6 disposed at the frontmost end of the shoe and which is substantially of caliber (D _AV = 0.9 D). However, the efficiency of this front pocket (that is to say the importance of the component normal to axis 9 of the effort resulting from F _AV ) has been reduced by varying the shape of its internal profile. Thus the pocket shown here has a reduced efficiency of the order of 50% compared to that of a pocket as represented by the dotted lines 15 in FIG. 5 and which would correspond substantially to the pocket according to FIG. 1.

This front pocket has substantially the same efficiency as a front pocket as shown in Figure 3 and having a caliber D _AV = 0.5D.

Such a shoe has been tested for a projectile caliber of 120mm. Shoe opening occurred without interference mechanical shoe / bar.

Figure 6a shows a projectile fitted with a sabot according to a fourth embodiment of the invention.

According to this embodiment, the front pockets 6 and rear 7 are arranged in the vicinity of the center of gravity G hoof.

The distance L _AR is around 0.75 caliber and the distance L _{AV around} 0.5 caliber. For such an embodiment of the projectile according to the invention, it is possible to take as an embodiment criterion a symmetry of the lever arms on either side of a mean sealing plane 3 materialized by the belt 4. A distance will be adopted L (distance from the leading edges 10 and 12 to this mean plane 3) less than 0.75 caliber and of the order of 0.5 caliber.

The pocket sizes are close to the hoof size D _AR = 0.9D and D _AV = 0.9D. The profiles of the pockets are similar so as to generate substantially equal moments.

In order to ensure guidance of the projectile in the tube the weapon during firing, a medium support 16 to the caliber is disposed in the front part of the shoe 1. This support means is constituted by at least three arms 16a, 16b, 16c regularly angularly distributed and which each carry at their end a guide shoe 17 (17a, 17b, 17c).

The arms delimit between them recesses which leave pass the aerodynamic flow to the front pocket 6.

This embodiment is the preferred mode. Indeed it allows to communicate a lateral escape speed to the hoof high by reducing on the one hand the tilting of the hoof towards the front at the outlet of the tube (efficiency of the back pocket) and on the other hand the tilting backwards (front pocket effective). Reducing leverage reduces the bending stresses to which the shoe is subjected, therefore to lighten the hoof. This mass gain makes it possible to increase the speed of the bar or its mass. Reducing the arms of lever also allows better reproducibility of the hoof separation movement parallel to the bar.

Different variants are possible without leaving the frame of the invention. So it is possible to vary shapes and positions of the pockets on condition of ensuring opening parallel to the hoof segments and avoid any interaction mechanical during the opening phase. he is also possible to use the shoe according to the invention for any type of calibrated projectiles under calibrated.

Claims (9)

Sabot (1) for a sub-calibrated projectile and comprising at least three caliber segments intended to surround a sub-calibrated bar (2), sabot comprising first means, such as a front pocket (6), which are intended to receive an aerodynamic flow at the outlet of the barrel of a weapon during firing, shoe characterized in that it also comprises second means such as a rear pocket (7), second means intended to receive the propellant gases at the outlet of the weapon barrel, the first and second means being positioned and dimensioned with respect to each other so that the shoe (1) moves away from the bar (2) in a manner substantially parallel to the latter at the out of the barrel. Shoe according to claim 1, characterized in that it comprises a rear pocket (7) having an external leading edge (10) which is at the level of a first plane (8) normal to the axis (9) of the projectile and disposed at a distance L _AR from the center of gravity G of the shoe and a front pocket (6) having an external leading edge (12) which is at the level of a second plane (11) normal to the axis (9) of the projectile and placed at a distance L _AV from the center of gravity G of the shoe, the profile of the front (6) and rear (7) pockets being defined so that the moment M _AR relative to the center of gravity G of the normal component F _ARN of the result of the aerodynamic forces F _AR exerted at the outlet of the tube on the rear pocket (7) by the propellant gas is substantially equal to the moment M _AV with respect to the center of gravity G of the normal component F _AVN of the result of the aerodynamic forces F _AV exerted at the exit of the tube on the front pocket (6) by the ec only aerodynamics. Shoe according to claim 2, characterized in that the rear pocket (7) is located at the rear end shoe (1) and in that its internal diameter is included between 0.4 and 0.7 gauge D of the shoe (1). Shoe according to claim 2, characterized in that the rear pocket (7) is located in the vicinity of the center of gravity G of the shoe at a distance L _AR from its leading edge (10) to the center of gravity G which is less than or equal to 0.75 caliber, the internal diameter of the rear pocket (7) being between 0.8 and 0.95 caliber. Shoe according to one of claims 2 to 4, characterized in that the front pocket (6) is located at the most front of the hoof and in that its internal diameter is understood between 0.2 and 0.6 hoof gauge (1). Shoe according to one of Claims 2 to 4, characterized in that the front pocket (6) is located in the vicinity of the center of gravity G of the shoe at a distance L _AV from its leading edge (12) to the center of gravity G which is less than or equal to 0.75 caliber, the internal diameter of the front pocket (6) being between 0.8 and 0.95 caliber. Shoe according to claims 4 and 6, characterized in what the leading edges (10, 12) of the front pockets (6) and rear (7) are substantially equal distance L from a plane means (3) of the belt (4), this distance L being less than or equal to 0.75 caliber. Shoe according to one of claims 6 or 7 characterized in that it comprises a support means (16) with the gauge arranged in the front part of the shoe (1) and comprising recesses allowing aerodynamic flow to the pocket before (6). Shoe according to claim 8, characterized in that the support means is constituted by at least three arms (16a, 16b, 16c) regularly distributed angularly.

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