WO2008034975A2

WO2008034975A2 - Undergage projectile with asymmetric shoe

Info

Publication number: WO2008034975A2
Application number: PCT/FR2007/001519
Authority: WO
Inventors: Franck Melendez
Original assignee: Nexter Munitions
Priority date: 2006-09-22
Filing date: 2007-09-19
Publication date: 2008-03-27
Also published as: WO2008034975A3; FR2906360A1; FR2906360B1; EP2069711A2

Abstract

The invention relates to an undergage projectile (1) comprising a gaged shoe (2) made of at least three segments (2a, 2b, 2c) contacting each other two by two at junction planes (10a, 10b, 10c) and surrounding an undergage shaft (3) with a longitudinal axis (8). The projectile is characterised in that the segments (10a, 10b, 10c) are made so that the geometrical intersections (11, 12, 13) of their different junction planes (10a, 10b, 10c) are located away from the longitudinal axis (8) of the shaft, each segment thus having an asymmetric geometry. Application in the field of armament.

Description

SUB-CALIBER PROJECTILE COMPRISING AN ASYMMETRIC SHAFT

The technical field of the invention is that of sub-calibrated projectiles, and more particularly that of sub-calibrated projectiles stabilized by empennage.

These projectiles (more commonly known as arrow projectiles) comprise a gauge shoe formed of at least three segments in contact two by two at the level of joint planes, a shoe that surrounds a sub-calibrated bar. The shoe is most often made of a light material (such as an aluminum alloy or a composite material), while the bar is made of a dense material (such as steel or tungsten).

The shoe increases the speed of the bar when firing the projectile.

The patent FR2521717 describes a sub-calibrated projectile with a detachable shoe according to the prior art.

At the exit of the tube of the weapon the segments of the shoe open radially and they release the bar. One of the problems with known projectiles is that the segments of the shoe impact the rear part of the projectile when opening the shoe.

This results in shocks at the bar which disturb the trajectory of it. It has been proposed by US Pat. No. 4,724,770 to provide, at the rear of the bar, a bead forming a hinge and preventing the sliding of the segments of the shoe relative to the bar.

However, such a solution is complex and requires specific machining of the bar and the shoe.

The object of the invention is to propose a projectile making it possible to overcome such disadvantages.

Thus the projectile according to the invention reduces interference between the shoe and the bar when opening the shoe at the exit of the barrel of the weapon. The subject of the invention is therefore a sub-calibrated projectile comprising a shoe of gauge formed of at least three segments in contact two by two at the level of planes of joints and surrounding a sub-calibrated bar having a longitudinal axis, a projectile characterized in that that the segments are made so that the geometric intersections of their different joint planes are located at a distance from the longitudinal axis of the bar, each segment then having an asymmetrical geometry. The joint planes of a segment may form an angle between them equal to 360 ° / N, where N is the total number of segments of the shoe.

The bar may be connected to the shoe by a thread and the joint planes of each segment will be arranged so that the direction of the thread promotes the ejection of the segment.

According to a particular embodiment, and with a bar introduced by the rear of the shoe and having a right-hand threading, the joint planes of each segment are arranged relative to the bar so that each segment comprises, by observing the shoe at its front portion and in the direction of clockwise, a first joint plane forming an obtuse angle with a first tangent to the bar. According to another embodiment, when the shoe comprises at least one radial arm on each segment, the arms are positioned angularly on each segment so as to ensure a locking of the shoe on the bar.

Thus, for each segment, the arm or arms are positioned angularly closer to the joint plane which delimits with the bar a thinned zone of the segment in question.

Other advantages of the invention will appear on reading the following description of various modes embodiment, a description given with reference to the accompanying drawings and in which: FIG. 1 is an external side view of a projectile according to a first embodiment of the invention,

FIG. 2 is a view of this same projectile in cross-section, made at the level of the plane whose track AA is marked in FIG. 1,

FIG. 3 is a view similar to FIG. 2, but in which a segment of the shoe has been removed, FIG. 4 is an external lateral view of a projectile according to a second embodiment of the invention,

FIG. 5 is a view of the same projectile in cross-section, section made at the level of the plane whose trace

BB is identified in Figure 4.

Referring to FIG. 1, a projectile 1 according to the invention comprises, in a conventional manner, a shoe 2 made of a light material (such as an aluminum alloy or a composite material), a shoe which surrounds a 3-membered bar. calibrated.

The bar is made of steel or a dense alloy based on tungsten.

The bar carries at its rear part empennage 4 ensuring stabilization trajectory.

The shoe carries at a rear portion a belt 5, made of plastic material, and which seals the propellant gas when firing into the barrel of a weapon (not shown). The shoe 2 also has a front seat 6 on which is disposed a friction strip 7 also made of plastic.

Such a general configuration of a stabilized stabilized projectile projectile (arrow projectile) is well known. In particular, it will be possible to consider the patents FR2521717 and FR2661739 which describe known arrow projectiles.

The shoe 2 is intended to allow the shot of the projectile in the weapon. It consists of several segments (usually three) which surround the bar 3 and which are in contact two by two at joint planes.

At the exit of the barrel of the weapon the segments of the shoe 2 deviate from the bar 3 under the action of the aerodynamic pressure exerted on the front portion (AV) of the shoe 2.

The spacing of the segments leads to the rupture of the belt 5 and the band 7 and the shoe thus releases the bar 3 which continues its trajectory.

Figure 2 shows a section of the projectile according to the invention. This figure shows three lines 9a, 9b and 9c all passing through the axis 8 of the projectile and forming with each other angles of 120 °.

These three straight lines embody the usual positions of the inter-segment joint planes in the arrow projectiles according to the prior art.

It is indeed usual to make shoes having three segments each having a plane of symmetry which is the bisecting plane of the dihedron formed by the two joint planes of the segment in question. In section, this bisecting plane traces the bisector (not shown) of the angle separating the two consecutive directions 9 considered.

This figure shows that the projectile according to the invention differs significantly from the prior art. Indeed the joint planes 10a, 10b and 10c are made such that their geometric intersections are located at a distance from the longitudinal axis 8 of the bar.

Thus in FIG. 2, the planes 10a and 10b have a theoretical geometric intersection located at the point 11, the planes 10b and 10c have their intersection located at the point 12 and the plans 10c and 10a have their intersection located at the point 13.

The theoretical geometrical intersections of the three joint planes are thus no longer confused with the axis 8 of the projectile 1 but form a trihedron whose trace in the plane of section of FIG. 2 is a triangle of vertices 11,

12 and 13.

It is thus noted that for each segment, the geometric intersection of the two joint planes is on one of the two joint planes of the segment considered. The intersection 11 is thus on the plane 10b, the intersection 12 on the plane 10c and the intersection 13 on the plane 10a. Each segment therefore has an asymmetrical geometry, that is to say devoid of plane of symmetry.

The different segments 2a, 2b and 2c, however, are identical and they therefore all have the same mass. The center of gravity of the projectile 1 is always located on the axis 8 of the projectile and the latter is not unbalanced during firing.

As can be seen in FIG. 2, each joint plane 10a, 10b or 10c is parallel to one of the symmetry planes 9a, 9b and 9c and situated at a distance d from the latter.

The joint planes of a segment therefore always form between them an angle equal to 120 °.

The asymmetrical shapes of each segment lead to a shift in the center of gravity of each. The centers of gravity Ga, Gb and Gc are thus closer to the joint planes 10c, 10b and 10a, respectively.

This asymmetry leads during the separation of the segments of the shoe to a rotation of each segment about an axis which is parallel to the axis 8 of the projectile. There is therefore no longer as in the prior art a separation of the segments with interference with one rear of the bar 3, but a pivoting of each segment which leads to its spacing along a path that away from the tail empennage 4. This avoids any mechanical sabot / empennage interference during the release of the bar.

The bar 3 could be connected to the shoe by circular grooves.

According to another embodiment, when the bar is connected to the shoe by a thread, we will have the joint planes of each segment so that the direction of the thread promotes the ejection of each segment.

As is more particularly visible in Figure 3 (on which the segment 2c of the shoe has been removed), the joint planes of each segment 2a, 2b, 2c are arranged relative to the bar 3 so that each segment comprises, by observing the hoof at the level of its front part

(AV) and in the direction of clockwise, a first joint plane 10a, 10b, 10c which forms an obtuse angle α with a tangent to the bar Ta, Tb, Tc.

The angles are obtuse because we consider here the tangents oriented in the direction of clockwise.

Such an arrangement is favorable to the ejection of the segments when it is in combination with the establishment of a bar screwed by the back of the shoe (which is generally the case) and whose thread has a right step

(screwing clockwise).

FIG. 3 shows by the arrow F the screwing direction of the bar in the shoe when the bar thread has a step to the right and that the shoe is observed at its front portion (AV in FIG. 1). .

Indeed, it avoids any jamming segments of the shoe at the neighboring areas of the bar 3 where said segments are the thinnest (zones marked Z in Figures 2 and 3).

In a known manner, the fins of the empennage 4 have a slight deflection which slightly rotates the projectile around its axis 8 (of the order of a few tens of revolutions per second).

This rotation causes a centrifugal effect which is exerted on the different segments.

The centers of gravity Ga, Gb and Gc being closer respectively to the joint planes 10c, 10b and 10a, thus the joint planes delimiting the thin zones Z, the centrifugal force exerted on the segments of the shoe at the exit the tube of the weapon leads (at least in the first moments of the opening of the shoe) to a radial sliding of each segment relative to its neighbor along the joint plane delimiting with the bar a thinned zone Z.

Thus the segment 2c slides radially on the joint plane 10a, the segment 2b slides on the joint plane 10b and the segment 2a slides on the joint plane 10c. The segments therefore do not lock each other at the Z-thinned zones and the shoe opens with a rotary movement of each segment.

Different variants are possible without departing from the scope of the invention. A shoe with three segments has thus been described. It is of course possible to define a shoe according to the invention and having more segments, for example four.

If N denotes the total number of segments of the shoe, the joint planes of the segments preferably form an angle of 360 ° / N between them. This ensures identical masses for each segment of the shoe.

Figures 4 and 5 show another embodiment of a projectile according to the invention. According to this embodiment, the shoe 2 of the projectile 1 is very long and each segment 2a, 2b, 2c comprises a rear radial arm 14a, 14b or 14c. These arms 14 are the caliber of the weapon and they provide a complementary guide support for the projectile 1 in the barrel of the weapon. This support is arranged at a distance from the back of the belt 5.

Such a general shoe configuration is well known to those skilled in the art. For example, it is possible to consult the patent FR2842897 which describes such a type of shoe.

According to this particular embodiment of the invention, the segments of the shoe are again asymmetrical.

The arms 14 are therefore not arranged either symmetrically with respect to the joint planes 10.

As is more particularly visible in Figure 5, each arm 14 is disposed in the vicinity of the parting plane defining the thinned zone Z of the segment in question.

Thus the arm 14a of the segment 2a is close to the joint plane 10c, the arm 14b of the segment 2b is close to the joint plane 10b, and the arm 14c of the segment 2c is close to the joint plane 10a.

Such an arrangement makes it possible to improve the maintenance of the bar in the tube of the weapon during firing. Indeed, the force communicated to each segment by the tube at each arm 14 then has the effect of increasing the locking of the segments relative to each other.

The skilled person will determine precisely the optimal angular position of the arms as a function of the forces experienced by the shoe during firing and the geometry of the shoe (including the angles between the different joint planes).

From a mechanical point of view, it suffices for the clamping to be ensured that the resultant of the forces exerted radially on the shoe at the level of each arm 14 has not to slide the segments relative to each other along the joint planes 10.

We have seen in the description of the previous embodiment, that the asymmetrical geometry of the shoe led to a shoe opening mechanism in which the segments slide relative to each other along a preferred plane which is (for a given segment) the joint plane delimiting with the bar the thinned zone Z.

Thus the segment 2c slides on the joint plane 10a, the segment 2b slides on the joint plane 10b and the segment 2a slides on the joint plane 10c.

From a mechanical point of view, the more the arm 14 is angularly removed from the sliding plane (defining the thinned zone Z of the segment in question), the greater the risk of initiating the opening of the shoe is important.

Conversely, the more the arm 14 is close to this sliding plane, the more the locking of the shoe is closed.

Mechanical equilibrium is ensured if each force exerted by the arm has its component on the sliding plane considered (geometric projection on said plane) which is directed towards the bar 3.

The theoretical extreme angular position for each arm 14 is therefore that corresponding to the directions 15a, 15b and 15c which are perpendicular to each of the sliding planes considered (10a, 10b, 10c).

Thus for the segment 2c the arm 14c can be positioned angularly between the directions 10a and 15c (the arrow λ has the maximum positioning amplitude of the arm 14c for the segment 2c). Concretely and to facilitate the opening of the shoe, it will be preferred (as shown in the figure) to place the arm in the vicinity of the radial direction passing through the center of gravity Ga, Gb or Gc of the segment in question. As a variant, it will of course be possible to make a shoe comprising guide arms disposed at the front of the shoe. The angular positioning of these front arms will be carried out according to the same rules as previously described.

A shoe may also (as described by the patent FR2842897) have arms in front of the shoe and arms at the rear of the shoe (shoe with three supports).

Claims

1- sub-calibrated projectile (1) comprising a shoe (2) with a gauge formed of at least three segments (2a, 2b, 2c) in contact two by two at joint planes (10a, 10b, 10c) and surrounding a sub-calibrated rod (3) having a longitudinal axis (8), projectile characterized in that the segments (2a, 2b, 2c) are made such that the geometric intersections (11, 12, 13) of their different planes joints (10a, 10b, 10c) are located at a distance from the longitudinal axis (8) of the bar (3), each segment then having an asymmetric geometry.

2- projectile according to claim 1, characterized in that the joint planes (10a, 10b, 10c) of a segment form between them an angle equal to 360 ° / N, N being the total number of segments of the shoe (2 ).

3- projectile according to one of claims 1 or 2, characterized in that the bar (3) is connected to the shoe (2) by a thread and in that the joint plane (10a, 10b, 10c) of each segment are arranged so that the direction of the threading promotes the ejection of the segment (2a, 2b, 2c).

4- Projectile according to claim 3, characterized in that with a bar (3) introduced from the rear of the shoe (2) and having a right-hand thread, the joint planes (10a, 10b, 10c) of each segment is arranged relative to the bar (3) so that each segment comprises, by observing the shoe at its front portion and in a clockwise direction, a first joint plane forming an angle (α ) obtuse with a first tangent (Ta, Tb, Tc) to the bar (3).

5- Projectile according to one of claims 1 to 4, characterized in that the shoe (2) comprises at least one radial arm (14a, 14b, 14c) on each segment (2a, 2b, 2c), the arms being positioned angularly on each segment so as to ensure a locking of the shoe (2) on the bar (3).

6. Projectile according to claim 5, characterized in that for each segment, the arm or arms (14a, 14b, 14c) are positioned angularly closer to the joint plane which defines with the bar a thinned zone (Z) of the segment

(2a, 2b, 2c) considered.