IL87694A

IL87694A - Device for connection between a projectile and a cartridge

Info

Publication number: IL87694A
Application number: IL8769488A
Authority: IL
Original assignee: Giat Ind Sa
Priority date: 1987-09-09
Filing date: 1988-09-07
Publication date: 1994-05-30
Also published as: NO884007D0; NO165893B; NO884007L; EP0307307B1; DE3872805D1; FR2620214B1; EP0307307A1; DE3872805T2; IL87694A0; NO165893C; FR2620214A1; ATE78332T1

Abstract

The technical sector of the invention is that of connecting devices between a projectile and a case. The device according to the invention comprises a ring (6) which has a front part (8) connected to the projectile by a first fastening means and a rear part (7) fixed to the case (2) by a second fastening means. The device is characterised in that the second fastening means is shaped in such a way that the action of the pressure of the combustion gases of the propellant charge exerted on the projectile (1) causes the separation of the latter, carrying the ring, and of the case, and in that the rear part (7) then comes into contact with an inner surface of the chamber (4) so as to ensure gastightness. The invention is used for ammunition of the backswept type fired from a smooth barrel. <IMAGE>

Description

Device for connection between a projectile and a cartridge GIAT INDUSTRIES, C: 75571 RING CONNECTING A PROJECTILE TO A CASE The present Invention relates to devices linking an ammunition round case containing a propulsive charge with a projectile, and more particularly a combustible case and an arrowhead type projectile fired through a smooth gun barrel .

The most common way of securing a metal case to a projectile is to crimp the case annularly around the projectile. This crimping is in fact possible, despite the difference in diameter between the two elements, because of the convenient way metal cases are constructed, with the conic forward part tapering inward to adapt to the outer diameter of the projectile.

Combustible cases, which are coming more and more frequently into use because of the high rate of fire they allow, prohibit such a mode of connection because of the mechanical fragility of this type of case and the difficulty of obtaining combustible cases with a conic forward part.

Various solutions have therefore been proposed to connect the combustible case with the projectile. United States patent 4,487,131 describes a ring glued to the combustible case and having elastic tabs to grasp the rearward part of an arrowhead projectile sabot. The elasticity of the tabs thus provides the assembly with good mechanical toughness.

An arrowhead projectile consists of a subcalibrated penetrator made of a heavy material such as tungsten, surrounded by a fragmentable sabot including several (generally three) parts. Assembling such a projectile requires the integration of the sabot elements around the penetrator. which is partly obtained by the assembly of the leakproof collar around the sabot.

It was tempting to try to combine the gas-proofing function resulting from the combustion of the propulsive charge with the projectile-case linking function, in a single connection ring.

United States patent 4, AAA.113 describes a high-pressure seal Joint for a fragmentable-sabot projectile. This Joint consists of a skirt that locks by elastic deformation onto the rearward part of the sabot and onto the opening of a case. The case Is separated from-'the projectile by the initiation of an annular rupture groove, under the effect of the pressure from the propulsive gases. This pressure, applied to the internal surface of the skirt, imparts a translational motion to the said skirt on ramps integral with the sabot, and bring it into contact with the internal surface of the gun barrel, where it provides an effective gas pressure seal of the order of several hundred megapascals in the barrel. The main problem with such a device is its lack of effectiveness for low pressures of the order of a few megapascals, whereas this low pressure seal is indispensable in the first tenths of a millisecond following the ignition of the propulsive charge; and this is especially true in the case of a combustible case, as the confinement provided by such a case is less than what is obtained with a metal case, and the projectile then moves under a lower pressure. Any Joint that is insufficiently sensitive to be operational at the time of ignition risks allowing gases to pass through toward the front of the projectile, and such a leak can damage the outer surface of the Joint and cause a pressure drop decreasing the efficiency of the propulsive charge. This is why the present patent proposes to add, in front of the high pressure seal skirt, a guide collar and rubber ring squeezed between the skirt and collar, as this arrangement offers the desired low pressure seal. Such an assembly is relatively complex to construct, and also the ramps that must be provided on the sabot and which must also be covered with rubber to avoid any gas leakage between the sabot and skirt, require additional machining and assembly operations.

The purpose of the present invention is to propose a device to connect a case with a projectile while providing a seal at a low level of pressure. Another purpose of the Invention is to propose a connection device that also provides a high pressure seal, thereby avoiding the addition of auxiliary systems. Moreover, the device in accordance with the invention simplifies the assembly of an arrowhead projectile and makes it easier to secure this projectile to a combustible case, while, providing the ammunition round with good impact toughness.

The invention therefore proposes a connection device between a case containing a propulsive charge and a projectile intended to be fired by a gun including a firing chamber communicating with a barrel, with the said device consisting of a ring having a forward part made integral with the projectile by a first means of attachment, and a rearward part integrated with the case by a second means of attachment, wherein the said second means of attachment is shaped in such a way that the pressure of the gases resulting from the combustion of the propulsive charge and exerted on the projectile causes the said projectile, carrying the ring, to separate from the case, and wherein the rearward part then comes Into contact with an inner surface of the chamber, to provide a gas seal .

Preferably, the forward and rearward parts are separated by at least one incipient fracture groove, with this groove being shaped in such a way as to break and thereby cause the forward and rearward parts to separate, with this separation occuring after the separation of the case from the projectile, and consecutive to the contact of the projectile with the gun barrel, while the forward part then comes to press against the inner surface of the barrel under the pressure of the gases.

The rearward part can include at least two embrittlement areas arranged along generatrix lines, and the forward part at least one circular groove on Its outer surface.

The first means of attachment may consist of matching shapes between the forward part of the ring and the lateral surface of the projectile, and in particular the forward part may fit into an annular groove provided on the lateral surface of the projectile or may be screwed into the projectile.

In one preferred embodiment, the second means of attachment consists of a cylindrical surface provided on the rearward part of the ring, on which the case Is adjusted and riveted and/or glued.

In accordance with another embodiment the second means of attachment Includes a cylindrical Intermediate part thay can be glued to the inner surface of the case.

A better understanding of the present Invention may be had from a consideration of the following detailed description, taken in conjunction with the accompanying drawing In which: FIG. 1 is a partial sectional drawing of an ammunition round placed in the firing chamber of a gun and equipped with the connection device in accordance with the Invention; FIG. 2 is a view of the connection ring seen from direction A in FIG. 1; FIG. 3 is a partial representation of the projectile in the gun barrel after separation of the forward and rearward parts of the connection ring; FIG. 4 Is a representation of a second embodiment of the invention.

Referring to figure 1, the schematically represented projectile 1 (here a sabot carrying an arrowhead-type subprojectile) is made integral with a combustible case 2 by means of a connection ring 6. The case- ring-proJectlie assembly is shown here placed in the firing chamber 4 of a weapon system, with the projectile 1 then being partially engaged in the gun barrel 3. The forward part of the chamber is shaped as a connecting cone 5 and the barrel is smooth.

The connection ring 6 includes one forward part 8 which is made integral with the projectile by a first means of attachment, which is in this case a concordance of shape between the forward part of the ring and an annular groove 10 provided in the lateral surface of the projectile 1. The outer diameter of the ring 6 at the level of this forward part 8 is slightly greater than the diameter of the barrel 3 (the difference in diameter is of the order of 1 % of the caliber). The cylindrical outer surface of this ring is provided with circular grooves 14 , the function of which will be specified below.

The ring also has a rearward part 7 that is made, integral with the case 2 by a second means of attachment, which here includes a cylindrical intermediate piece 12 glued to the cylindrical inner surface of the case. This piece may be made of cellulose with or without a charge of nitrocellulose, and such a material is particularly easy to glue onto a combustible case. The intermediate piece is secured to the rearward part 7 of the ring 6 by rivets 13 , regularly distributed around a circular generatrix of the ring. At the level of the intermediate piece 12, the outer diameter of the rearward part of the ring 6 is therefore roughly equal to the outer diameter of the case and the connection ring therefore exhibits a conic portion 15 connecting this rearward part with the forward part 8.

The forward and rearward parts are also separated by an incipient fracture 9 , which s here a circular groove provided on the inner surface of the ring forward of the conic portion 15.

The rearward part includes an embrittlement area 1 on both its conic and cylindrical portions, arranged along generatrix lines and regularly spaced with each other. The distribution of these embrittlement areas 11 , which are four in number here, obtained by reductions In the thickness of the ring, is easier to see in PIG. 2.

When the case carrying the ammunition is placed in the chamber, the projectile is only partially engaged in the gun barrel, and Is therefore not in contact with it. The forward part of the ring 6, the outer diameter of which is slightly greater than the barrel diameter, is found facing the connection cone 5. When the propulsive charge In the case 2 is ignited, gases are produced and the resulting pressure is exerted at the same time on the case, the ring and the projectile and will cause tensile stresses both In the ring and In the attachment means, the Incipient fracture and the case. The ring and the means of attachment will be dimensioned In such a way that the second means of attachment will break befo(re incipient fracture 9 breaks. To ensure this, it suffices to adjust the thickness of the intermediate piece and the depth of the circular groove constituting the incipient fracture 9.

The separation of the case from the projectile carrying the ring allows the projectile to advance In the barrel, pushed by the gases. As the gas pressure Is exerted on the Inner surface of the ring, it places the rearward part 7 of the ring in contact with an Inner surface of the chamber at the level of the connection cone 5, and does so in the first tenths of a millisecond following the separation (this time can be adjusted if needed by changing the thickness of the ring, the distance between the first and second means of attachment, and the number and distribution of the embrittlement areas 11, so that the rearward part 7 of the ring provides a low pressure gasproof seal at a few megapascals, a seal provided almost Instantaneously, which puts the propulsive charge to optimum use.

When the forward part 8 of the ring enters the barrel and comes nto contact with it, thereby centering the projectile, the resistance of the barrel opposing the passage of the rearward part will create tensile stresses in the ring which will cause the forward and rearward parts to separate at the level of the incipient fracture 9. At this point in time, the pressure of a few tens of megapascals in the firing chamber is high enough for the contact between the forward part and the inner surface of the smooth barrel to suffice as a seal between the barrel and the projectile. PIG. 3 shows the projectile carrying the forward part of the ring in the gun barrel. It Is further possible to adjust the effectiveness of the high pressure Joint thereby obtained by changing the thickness of the forward part 8 and the distance between the first means of attachment and the Incipient fracture. Moreover, the circular grooves 14 provided on the outer cylindrical surface, by acting as baffles, provide an additional seal function (any leakage of gases toward the front of the projectile is stopped as soon as it starts, since the gases expand in the baffles).

The rearward part of the ring, as well-as the intermediate piece 12 and the rivets 13, are expelled from the gun barrel aIons, with the combustion gases, following the projectile. The embrittlement area 11 allow a dislocation of the rearward part subsequent to the passage of the connection cone, thereby facilitating its ejection from the barrel. A decrease in the size of the ejected pieces is also an appreciable way of avoiding damage to the tail empennage of the arrowhead subprojectile.

We therefore see that the device in accordance with the Invention has made it possible, firstly, to obtain a low pressure seal by means of the rearward part of the ring, and secondly to ensure the high pressure seal in the smooth gun barrel by means of the forward par of the ring.

Another advantage of the invention is due to the simpli ication of the manufacturing process. For this reason, the ring will preferably be made of a thermosetting plastic polymer that will be injected around the projectile. This will integrate the various elements constituting the sabot with the subprojectile, in the case of an arrowhead projectile. The intermediate piece will then be riveted on the. ring, and then this assembly is integrated with the case by gluing. Dy making the intermediate piece of cellulose or cardboard, with or without a nitrocellulose charge, the gluing of the said intermediate piece to the combustible case is made easier and this link then exhibits a certain flexibility, which is Indispensable to avoid breakage of the combustible case at this level.

PIG. * shows another embodiment of the Invention in which the only difference with the preceding one is the second means of attachment used.

The ring 6 here includes on the rearward part 7 a cylindrical surface 16 which delimits an area of reduced thickness. This area is therefore weaker and will play a role analogous to that of the cylindrical intermediate piece 12 of the previous example. The case adjusts on the ring at the level of the said surface and is made integral with it by rivets or glue. The said rivets and/or glue and cylindrical surface 16 thus constitute the second means of attachment of the rearward part 7 of the ring 6 with the case.

The operation is the same as described previously. The tensile stresses born by the case-attachment means-ring assembly cause the case to separate from the ring. This separation occurs either by the rupture of the cylindrical surface 16, the fragility of which can be adjusted by changing its thickness or the number of rivets, or by the rupture of the combustible case at the level of the said surface.

After separation, the rearward part 7 of the ring plays the role of low pressure seal already described. The flexibility of the case-projectile connection, which avoids breakage of the combustible case, is ensured here by the ring itself.

The mode of manufacture is the same as the one described previously, i.e. the ring made of thermosetting polymer is injected around the projectile and provides the integration of the various elements making up the sabot.

Other variants of the invention are possible within the framework of the invention. It is possible to imagine other means of attachment: other types of shape matching between the forward part of the ring and the lateral surface of the projecitle, e.g. a threaded or rivet connection. The intermediate piece -can be integrated in the ring by placing It in the ring injection mold or by gluing it to the ring. The forward and rearward parts may constitute two distinct pieces that are integrated during assembly, either by means of rivets squeezing these two parts simultaneously, or by a second cylindrical intermediate piece glued to both the forward and rearward parts. The incipient fracture 9 will then consist of these rivets or of this intermediate i piece, the essential point being that the attachment means be dimensioned so that - the gas pressure causes the second means of attachment to break first, and thereby separate the case from the projectile carrying the two parts of the ring; - then the separation of the forward and rearward parts occurs once the projectile has come into contact with the gun barrel, in particular because of the resistance the gun barrel applies to the passage of the rearward part.

It is possible to apply the invention to any type of projectile. In the case of projectiles designed to be fired through a smooth barrel (arrowhead or shaped-charge projectiles), an incipient fracture will be provided between the forward and rearward parts of the ring, and the forward part of the ring will then provide the high pressure seal described above.

For projectiles fired through rifled barrels, the invention makes it possible to use combustible cases, despite the fact that with such cases the projectile moves under a lesser firing chamber pressure, which could cause gases to leak toward the front of the projectile before the rifling begins. The rearward part of the ring of the device in accordance with the invention provides a low pressure seal prior to the point at which the projectile collar enters the rifling.

In such a configuration, the forward part of the ring can be made Integral with the collar or not, and the Incipient fracture between the forward and rearward parts can be omitted, as the high pressure seal function is fulfilled by the collar Itself. For arrowhead projectiles intended to be fired into rifled barrels and therefore carrying a slip collar, the forward part of the ring will preferably be integral with the collar. - 10 - 87694/3

Claims

1. Connection device between a case containing a propulsive charge and a projectile designed to be fired by a weapon system with a firing chamber communicating with a barrel, wherein said device consists of a ring including a forward part made integral with the projectile by a first means of attachment, and a rearward part made integral with the case b a second means of attachment, wherein the said second means of attachment is shaped such that the pressure - of- the gasesi of combustion of the propulsive charge exerted o the projectile cause the projectile carrying the ring, to separate from the case, whereby the case being combustible, the rearward part when separating from the case jcomes into contact with an internal surface of the chamber, in such a way as to provide a gasproof seal, and in that the forward and rearward parts are separated by at least one incipient fracture, the said incipient fracture being shaped in such a way as to break, thus causing the said parts to separate, this separation occurring after that of the case and projectile and consecutive to the contact of the said projectile with the gun barrel, the forward part then coming to press against the internal surface of the barrel under the action of the gas pressure.

2. The connection device of Claim 1, wherein the said rearward part includes at least two embrittlement areas arranged along generatrix lines.

3. The connection device of Claim" 1 or 2, wherein the ring includes on the outer surface of its forward part at least one circular groove.

4. The connection device of Claims 1 to 3 including a first surface contour in the internal face of the forward part of the ring and second surface contour in the lateral surface of the projectile, where said first and said second contours are in register with one another. - 11 - 87694/2

5. The connection device of Claim 4, wherein the forward part fits into an annular groove provided in the lateral surface of the projectile.

6. The connection device of Claim 4, wherein the forward part is screwed onto the projectile.

7. The connection device of Claims 1 or 2, wherein the second means of attachment consists of a cylindrical surface provided on the rearward part of the ring, on which the case is riveted or glued.

8. The connection device of Claims 1 to 6, wherein the second means of attachment includes a cylindrical intermediate piece.

9. The connection device of Claim 8, wherein the intermediate piece is glued to the internal surface of the case. For the Applicants DR. REIJJHQLD COHN AND PARTNERS By: