EP0354088B1

EP0354088B1 - Device for opening projectile fins

Info

Publication number: EP0354088B1
Application number: EP89402060A
Authority: EP
Inventors: Claude Boutet; Daniel Guenin; Jean Rat
Original assignee: Giat Industries SA
Current assignee: Giat Industries SA
Priority date: 1988-08-04
Filing date: 1989-07-20
Publication date: 1992-07-15
Anticipated expiration: 2009-07-20
Also published as: EP0354088A1; IL91102D0; DE68902108D1; IL91102A; CA1334908C; DE68902108T2; FR2635178B1; AT78334T; FR2635178A1

Description

The present invention relates to a device for opening the tail of an artillery projectile.
We already know artillery projectiles with a deploying tail unit fired from cannons with a smooth or striped tube. The deploying tail unit has the advantage of being less bulky in length than a fixed tail unit which, to be effective, must be pushed far behind the body of the projectile; in fact, for a smaller footprint, it allows better stabilization, therefore greater precision.
In addition, this type of empennage allows the shooting by means of a tube with the caliber of the projectile.
On the other hand, in order to avoid any contact of the tail fins with the tube, and therefore any degradation in the interior ballistic phase, these fins must necessarily be locked in the closed position.
They should only be opened after they exit the tube, in the shortest possible time and in a perfectly symmetrical manner, in order to ensure the immediate stabilization of the projectile on its trajectory. Finally, on this trajectory, the fins must be locked in the open position so as to maintain stability and precision with the projectile, but also because they would close by themselves under the pressure of aerodynamic constraints.
More particularly, document FR-A-2 221 707 discloses an artillery projectile tail opening device, of the type defined in the preamble of claim 1 and comprising a mounting body, a control member opening axially movable relative to said body from a first position where it keeps the tail closed to a second position where it keeps the tail open, and control means for said control member, said control means comprising a piston sensitive to gas pressure in the launcher tube and a gas generator arranged to bring the opening control member from its first to its second position.
In this document, the gases act on the fins by means of differential pistons subjected in the tube to the pressure of the propellant gases of the projectile exerted on a large surface of this piston, the gases tending to open the fins n ' acting only on a significantly smaller surface. In the interior ballistic phase, the thrust due to the propellant gases is very significantly greater and therefore keeps the tail closed.
However, there is still a force tending to open the tail while the projectile is still in the barrel. Towards the mouth of the latter, the pressure having dropped sharply, this force may predominate over that keeping the tail closed, hence a possible deployment of the fins causing their degradation in contact with the tube, as well as possible scratching of the latter. In addition, if the barrel is equipped with a muzzle brake, the fins can bend or break while crossing it. Finally, this device consists of complex parts associated with precise assemblies which make it difficult and expensive to produce.
The present invention aims to overcome these drawbacks by providing a simple and therefore inexpensive device allowing an almost instantaneous opening of the tail unit as soon as it leaves the tube, and only outside the tube, in a perfectly symmetrical manner. The invention also aims to provide a device having all the guarantees of storage and handling security.
To this end, the subject of the present invention is a device for opening the tail of an artillery projectile of the type mentioned above, characterized in that said control means comprise:

a striker for the gas generator,
a striker holder member to which the striker is connected by unlockable blocking means,
a locking member arranged to keep the locking means locked in a first relative position of the striker holder and the locking member and to unlock them in a second relative position,
holding means for holding the striker-striker-striker-locking member assembly in a storage position relative to the control member while maintaining the striker holder and the locking member in their first relative position,
said piston, arranged to bring against the action of the means for holding said assembly from said storage position to an arming position when the pressure exerted on said piston exceeds a first predetermined value, while maintaining the striker holder and the locking member in their first relative position as long as said pressure remains above a second predetermined value, and
elastic means for bringing the striker holder and the locking member into their second relative position and causing the striker to strike the gas generator against the action of said piston when said pressure becomes lower than said second predetermined value.

0n understand that such an arrangement has all the desirable security.
Indeed, in the storage position, the striker is kept in the locked position in the striker holder. Only the considerable pressure (of the order of 2000 bars) prevailing in the barrel chamber at the start of the shot can oppose the holding means, and thus bring the assembly constituted by the striker holder the striker and the locking member in the armed position. Again, there is no risk of premature opening of the tail since the striker holder remains locked until the elastic means can oppose the pressure prevailing in the tube. However, when the projectile is about to leave this tube, the pressure is still extremely high (of the order of 400 bars). It is therefore sufficient to calibrate the spring so that it can only oppose a pressure of a few bars (for example 15 bars) to be absolutely certain that it will not cause the striker to be unlocked before the projectile is completely out of the tube.
According to a particular embodiment of the invention, said locking means comprise at least one claw connected to the striker holder and engaged in the locked position in a corresponding recess of the striker, said claw being held in the recess by a stop surface of the locking member when the striker holder and the locking member are in their first relative position, said abutment surface being erased when the striker holder and the locking member are in their second relative position.
Also according to a particular embodiment of the invention, said holding means comprise a first shear piece secured to the striker holder and engaged in the storage position in a recess in the control member, two cooperating stops of the member locking and the control member now, in this storage position the striker holder and the locking member in their first relative position.
Advantageously, the piston and the locking member are integral, the locking member then exercising the function of thrust member to bring the striker-holder-striker-locking member assembly from its storage position to its position d arming by causing the shearing of the holding means.
The elastic means can be produced in the form of a compression spring disposed between the striker and the locking member, and tending to separate them from each other against the action of the piston.
Under these conditions, when the pressure drops below the second predetermined value, the spring draws aside the locking member from the striker holder, consequently clears the abutment surface of the locking member, which releases the striker which is thus projected. under the action of the spring towards the gas generator.
The striker holder and the control member may more particularly comprise cooperating abutment surfaces, these abutments being maintained in contact in said cocking position under the action of the piston.
In an advantageous embodiment of the invention, the striker holder and the locking member are arranged to slide in a bore of the control member, and the striker is arranged to slide in a bore of the striker holder.
The device according to the invention may also comprise a second shear piece integral with the control member, engaged, in the first position of this member, in a recess of the body.
The control member can, for the sake of simplicity, form a piston sliding in a bore of the body under the action of the gases of the gas generator, which cause the shearing of the second shearing part.
A particular embodiment of the invention will now be described by way of nonlimiting example with reference to the accompanying drawings in which:

FIG. 1 is a view in axial section of a device according to the invention in its storage position,
FIGS. 2a and 2b are enlarged views of the details IIa and IIb of FIG. 1, and
Figures 3a to 3d are schematic views in axial half-section illustrating the operation of this device.

The device of Figure 1 comprises a body 1 provided with a thread 2 for mounting on the base of an artillery projectile or on an intermediate piece. It is substantially symmetrical in revolution around an axis 00.
A piston 3 is slidably mounted in an axial bore of the body 1, a shear flange 4 engaged in a peripheral counterbore of the bore and blocked by a bottom plate (not shown) preventing this sliding as long as it is not not sheared. O-rings 5 seal between the piston 3 and the body 1.
Cooperating stops 6 and 7 formed by shoulders on the piston 3 and on the body 1 respectively, limit the rearward movement (to the right of the figures) of the piston 3 relative to the body 1.
An actuating member 8 is screwed to the rear of the piston 3 with the interposition of an O-ring seal 9. A locking nut 10 is itself screwed to the rear part of the actuating member 8, for reasons which will be explained below.
At the junction between the piston 3 and the actuating member 8, a countersink in the piston 3 forms an annular groove 11. This groove allows the engagement of a shear flange 12 formed at the periphery of a carrier member - piercer 13 arranged in a bore 14 of the piston 3.
It will be noted that it is only after fitting the striker holder 13 in the bore 14 that the actuating member 8 can be screwed onto the piston 3. After screwing, the piston 3 forms with the member actuator 8 an integral assembly which axially holds the striker holder 13. This assembly with the nut 10 will be designated in FIGS. 3a to 3d under the name of control member 15.
An axial bore 16 is formed in the striker holder 13, which comprises in the extension of the surface of this bore elastic branches 17 terminated at their ends by claws 18 (FIG. 2b) extending axially inwards relative at bore 16.
The bore 16 also receives a sliding striker 19 comprising at its outer periphery an annular groove 20 of shape complementary to that of the claws 18, so that the claws can engage in the groove.
The actuating member 8 also comprises a bore of the same diameter as the bore 14, and coaxial with the latter, in which is disposed a pushing piece 21 whose front part forms a locking member 22 and whose rear part forms a piston rod 23.
The locking member 22 has a first bore 24 towards the front and a rear bore and a second bore 25 of smaller diameter. The bore 25 has a diameter such that it forms an abutment surface for the radially outer surfaces of the claws 18, thus preventing the latter from leaving the groove 20 when the front part of the thrust piece 21 is in contact with the rear part of the striker holder 13.
When this striker holder is blocked by its flange in the storage position of FIG. 1, the pushing piece 21 is also blocked between the striker holder and two cooperating stop surfaces formed by shoulders 27 and 28 respectively of the actuating member 8 and the pushing piece 21.
Finally, an axial bore of the striker receives a compression spring 29 bearing on the one hand on an internal face of this striker, and on the other hand on the bottom of the bores of the thrust piece 21, thus tending to spread the striker of this room.
The piston rod 23 carries at its rear end the piston 30 proper, which is arranged in a chamber 31 formed in the actuating member 8 and opening into the open air at its rear part through a plug. maintenance.
The piston 30 comprises a front part 30a of reduced diameter allowing a certain radial expansion of the piston and avoiding any jamming of the latter which would prevent the return of the thrust piece 21 and therefore the opening of the tail.
In order to avoid possible jamming of the thrust piece 21, a slightly larger diameter portion 31a is provided in its housing in the actuating member 8.
In addition, the piston 30 has on its front face 30b a coating of a low friction material, in particular PTFE for example with a thickness of 0.1 mm, making it possible to ensure gas tightness.
Finally, a gas generator 32 is placed in a chamber formed at the front of the piston 3 opposite the striker 19.
Figure 3a shows the device described above in its storage position shown in Figure 1, and mounted at the rear part of the base 33 of an artillery projectile deploying tail.
This empennage consists of fins 34 rotatably mounted on an axis 35. Each fin has a tooth 36 whose sides are arranged to cooperate with the sides of an annular groove 37 of the control member 15. It will be noted that these sidewalls are formed on the one hand by an external shoulder of the actuating part 8 and on the other hand, by the nut 10. The latter is screwed onto the actuating part 8 so as to adjust the clearance between the two flanks of tooth 36.
Note also that in Figure 3a, that is to say in the storage position, the groove 37 has an axial position such that it maintains the fins 34 in the folded position towards the axis of the device.
When the projectile is placed in the firing position in the core of a barrel, the chamber 31 is therefore in communication with the chamber of this barrel. When the blow is initiated, an extremely high pressure develops in this chamber, thus pushing the part 21 forward and causing the shearing of the flange 12 of the striker holder 13.
The assembly constituted by the thrust piece 21, the striker holder 13 and the striker 19 are thus propelled in one piece towards the front, leaving in place the flange 12. This movement ceases when the assembly is blocked in the cocking position by two cooperating stops formed respectively from the front face 38 of the firing pin holder and a shoulder 39 produced at the front end of the bore 14. The assembly is thus held in abutment as shown in the FIG. 3b as long as there is sufficient pressure in chamber 31.
(Note that the base 33 and the fins 34 have not been shown in Figures 3b and 3c, the fins retaining in these figures the same positions as in Figure 3a).
When the projectile leaves the tube, the pressure in the chamber 31 abruptly decreases to be reduced to a few bars. At this instant, the force of the spring 29 becomes sufficient to push the part 21 backwards against the action of the residual pressure.
Thus, the abutment surface 25 is erased in front of the claws 18 of the striker holder 13. The spring 29 pushes not only the pushing piece 21 backwards but also the striker 19 forwards, including the rear part 40 pushes the claws 18 axially outwards in the bore 24 under the combined action of two inclined planes 41 and 42 formed respectively on the claws 18 and on the rear flank of the groove 20 (fig.2b).
The striker 19 is thus released from the striker holder 13 and is propelled forward where it strikes the gas generator 32 as shown in FIG. 3c.
The gas pressure generated by the gas generator 32 increasing in the front chamber of the control member 15, this member tends to be pushed back like a piston.
When the pressure becomes sufficient, it causes the flange 4 to shear, thereby releasing the control member 15 which moves backwards until the stops 6 and 7 come into contact. This position is shown in Figure 3d.
This backward movement of the member 15 causes the fins 34 to pivot about the axis 35 by the action of the sides of the groove 37 on the teeth 36. When the control member 15 reaches the end of the race, two abutment surfaces 43 and 44 of the fin 34 come to bear on the external surface of the part 15 (in fact, the surface 43 bears on the piston 3 and the surface 44 bears on the actuating member 8), now thus perfectly the fin 34 in the open position because the pressure of the gas from generator 32 is maintained and thus prevents the control member from turning back.
Even in the case of a reduction in the gas pressure of the generator 32, the fin 34 remains immobilized in the deployed position due to the jamming of the abutment surfaces 43, 44 on the member 15.
This simple, therefore inexpensive embodiment device ensures extremely rapid opening of the tail (less than 5 milliseconds) and effective locking of the fins both in the folded position and in the open position.
Furthermore, there is no risk of inadvertent opening inside the tube, the difference in the opposing forces acting on the control member 15 being such that, even in the event of a fault in the propellant charge, the latter stays down.
On the other hand, less than five meters after the exit of the tube, the tail is deployed and the projectile stabilized on its trajectory thus benefiting from an excellent precision.
Finally, another advantage of the device lies in the high level of security that it provides, due to the importance of the forces necessary for its activation, excluding any risk of opening following falls or other rough handling.

Claims

1. Artillery projectile empennage opening device including one mounting body (1) one opening control element (15), axially mobile with respect to the said body from an initial position where it holds the empennage closed, to a second position where it holds it open, and control means for the said control element, wherein the control means includfe a piston (30) sensitive to the gas pressure in the gun tube, and a gas generator (32) arranged to drive the opening control element from its first to its second position, wherein the said control means include :

- one pin (19) to puncture the gas generator;

- one pinholder (13), to which the said pin is linked by unlockable locking means (18,20),

- one locking element (22), arranged to hold the locked locking means in one position relative to the pinholder and the locking element, and to unlock them in a second relative position;

- securing means (12) to secure the pin-pinholder-locking element assembly in a storage position with respect to the control element, while the securing the pinholder and locking element in their said first relative position;

- the said piston, arranged to drive, against the action of the said securing means, the said assembly from the said storage position to an arming position when the pressure exerted on the said piston exceeds a certain predetermined value, while the securing the pinholder and locking element in their first relative position as long as the said pressure remains greater than the second predetermined value; and

- elastic means (29) to drive the pinholder and locking element to their second relative position and to drive the pin to puncture the gas generator, against the action of the said piston when the said pressure becomes less than the said second predetermined value.

2. The device of claim 1, wherein the said locking means include at least one grip (18) linked to the pinholder and, when locked, fitted into a corresponding recess (20) in the pin, being secured in the said recess by a stop surface (25) on the locking element when the pinholder and locking element are in their first relative position, the said stop surface being retracted when the pinholder and locking element are in their second relative position.

3. The device of either claim 1 or 2, wherein the said securing means include a first shearing piece that is integral with the pinholder and, while in storage position, fits into two cooperating stops (27,28) of the locking element and of the control element, and which secure the pinholder and the locking element in their first relative position.

4. The device of any claim 1 to 3, wherein the piston and the locking element are integral.

5. The device of any claim 1 to 4, wherein the said elastic means include a compression spring arranged between the pin and the locking element, and tending to separate them from each other against the action of the piston.

6. The device of any claim 1 to 5, wherein the pinholder and control element include cooperating stop surfaces (38,39) that are held in contact in the said arming position under the action of the piston.

7. The device of any claim 1 to 6, wherein the pinholder and the locking element are arranged to slide in a bore (14) of the control element.

8. The device of any claim 1 to 7, wherein the pin is arranged to slide in a bore (16) of the pinholder.

9. The device of any claim 1 to 8, wherein it includes a shearing piece integral with the control element, fitted into a recess in the said body, in the first position of this element.

10. The device of any claim 1 to 9, wherein the said control element forms a piston sliding in a bore in the body under the action of the gas generator gases.