WO2013160330A1

WO2013160330A1 - Noise attenuator for a mortar

Info

Publication number: WO2013160330A1
Application number: PCT/EP2013/058451
Authority: WO
Inventors: Anne DESTREZ; Vincent Hubert; Denis Salignon
Original assignee: Tda Armements S.A.S
Priority date: 2012-04-24
Filing date: 2013-04-24
Publication date: 2013-10-31
Also published as: FR2989773A1

Abstract

The invention concerns a noise attenuator intended to be fitted to a mortar for projecting shells in an initial direction, the mortar comprising a tube (12) extending along an axis forming the initial direction, the attenuator (10) being intended to be mounted to a free end of the tube (12), called the mouth of the tube (12), an axis (11) of the attenuator (10) then coinciding with the axis of the tube (12). According to the invention, the attenuator comprises a plurality of partitions (14, 15, 16 and 17) extending in a substantially annular manner relative to the axis (11) of the attenuator (10), so as to allow the passage of a blast of gas between the partitions (14, 15, 16 and 17), the blast of gas being generated when a shell is projected.

Description

Noise attenuator for mortar

The invention relates to a noise attenuator for equipping a mortar. Mortars are typically used on the battlefield to launch a projectile over an obstacle.

A mortar includes a tube for guiding a projectile at the beginning of its trajectory. The projectile is ejected from the tube in its direction. The orientation of the tube is one of the parameters for defining the trajectory of the projectile. Another parameter is the thrust exerted on the projectile inside the tube. This thrust can be obtained by means of solid explosives surrounding the projectile or by means of a chamber made in the mortar and pressurized for example by means of a propellant ensuring a chemical reaction generating a pressure increase or by injecting a liquid fuel and an associated oxidant into the chamber. An operator adjusts the various parameters in order to obtain the best possible accuracy and to do this he stands in the immediate vicinity of the mortar and can be hindered by the noise generated during the shooting. This discomfort can even be harmful to the health of the operator. More specifically, the noise generated during the shooting comes largely from the mouth of the tube.

When the mortar is installed on the ground, to protect against noise, the operator can move away from the mortar when firing. A mortar can also be installed on an armored vehicle. In this case, the operator may not have enough space to protect himself from the noise.

Devices were mounted at the mouth of the tube and to protect the operator from noise. These devices tend to direct the sound wave emitted during firing in the direction of the tube by limiting the propagation of this wave in the directions perpendicular to the axis of the tube. Thus the operator can more easily stay in an area near the base of the tube during firing. To achieve a sufficient level of efficiency, these devices are generally bulky. In particular, they have a large dimension along the axis of the tube. These devices may interfere with the storage of the tube in the armored vehicle when the mortar is not used.

The invention aims to overcome all or part of the problems mentioned above by providing a noise attenuator whose dimensions, in particular in the axis of the tube, are reduced compared to known devices, while maintaining the same efficiency. Moreover, the guidance of the sound wave uses part of the energy generated for the thrust of the projectile. The invention makes it possible to limit this loss of energy.

For this purpose, the invention relates to a noise attenuator intended to equip a mortar for projecting shells in an initial direction, the mortar comprising a tube extending along an axis forming the initial direction, the attenuator being intended to be mounted on a free end of the tube, called the mouth of the tube, an axis of the attenuator then being merged with the axis of the tube, characterized in that it comprises several partitions extending substantially annularly with respect to the axis of the attenuator, so as to allow the passage of a breath of gas between the partitions, the gas breath being generated during the projection of a shell.

The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, a description illustrated by the attached drawing in which:

Figure 1 shows in section the principle of an attenuator according to the invention;

Figures 2 and 3 show two embodiments of partition construction belonging to an attenuator according to the invention;

Figures 4 to 6 show several variants of holding means in position of the partitions between them.

For the sake of clarity, the same elements will bear the same references in the different figures.

FIG. 1 represents in section an attenuator 10 with symmetry of revolution about an axis January 1. The section plane of Figure 1 contains the axis 1 1. The attenuator 10 is intended to be assembled on the mouth of a tube 12 of mortar. The attenuator 10 is intended to be mounted in the extension of the tube 12. In other words, the axis 1 1 of the attenuator 10 coincides with the axis of the tube 12. The tube 12 is cylindrical and the attenuator 10 comprises a tubular portion 13 of axis 1 1, bored and intended to be adjusted to the outside diameter of the tube 12. The attenuator 10 comprises a plurality of partitions extending substantially annular with respect to the axis 1 January. For example, in the figure

I, four partitions, 14, 15, 16 and 17 are shown. The attenuator 10 comprises means for holding the various partitions integral with each other. To avoid overloading Figure 1, these holding means are not shown and different variants will be presented later. It is simply shown the maintenance of the partition 14 secured to the tubular portion 13. In the example shown, the partition 14 and the tubular portion 13 are made in a single mechanical part.

The attenuator 10 comprises a channel 18 passing through, centered on the axis

I, so as to allow the passage of a shell fired by the mortar. The channel 18 passes through the tubular portion 13 and the various partitions 14 to 17. The attenuator 10 comprises several substantially radial channels arranged between each of the partitions 14 to 17. A channel 21 is located between the partitions 14 and 15, a channel 22 is located between the partitions 15 and 16 and a channel 23 is located between the partitions 16 and 17. The channels 21 to 23 open into the central channel 18 and open to the open air in an area surrounding the attenuator 10. channels 21 to 23 allow the passage of a breath of gas between the partitions 14 to 17, the gas breath being generated during the projection of a shell fired by the mortar.

Each of the channels comprises a first zone 21 1 for the channel 21, 221 for the channel 22 and 231 for the channel 23. This first zone, the closest to the channel 18, allows to relax the gas breath between the respective partitions. For this expansion, the zone 21 1 is formed between a face 21 1 a perpendicular to the axis 1 1 and a face 21 1 b frustoconical with respect to the axis 1 1. The truncated cone is oriented so that a radial section 215 of the portion 21 1 opens away from the channel 18. The zones 221 and 231 are similar to the zone 21 1. The radial sections of the first zones 221 and 231 respectively bear the markers 225 and 235. The opening of the radial section allows the gas to relax partially in each of the zones 21 1, 221 and 231. The relaxation of the breath is performed between two partitions, which improves the control of the relaxation.

Each of the channels comprises a second zone, 212 for the channel 21, 222 for the channel 22 and 232 for the channel 23. This second zone, the farthest from the channel 18 to guide the expanded gas breath between the partitions in a frustoconical direction relative to the axis 1 1 so as to bring the breath of gas to the direction of fire. A radial section of the second zone is substantially constant away from the channel 18. The radial sections of the second zones 212, 222 and 232 respectively carry the marks 216, 226 and 236. Thus, an operator serving the mortar may remain at foot of mortar during firing without being directly subjected to gas blast. Figures 2 and 3 show two embodiments of an attenuator. In FIG. 2, the partitions between which the gas blast passes are formed by a helix winding around the axis 1 1 of the attenuator 30. It is possible to maintain a constant radial cross section of the partition we wind around the axis 1 1. The pitch of the helix determines the section of the passage channels of the gas blast between two partitions. The pitch of the helix can be constant in a central part. At the ends of the helix, it is possible to reduce the pitch in order to arrange the end walls substantially perpendicularly to the axis 11.

In Figure 3, the partitions are each formed by a ring centered on the axis 1 1 of the attenuator 40. Advantageously, the various partitions are identical, which facilitates their realization. The partitions of the attenuator 40 are similar to the partitions 14 to 17 previously described. Advantageously, the attenuator comprises means for holding the partitions in position relative to one another.

A first variant of these means for holding in position is shown in FIGS. 2 and 3. The attenuators, for FIG. 2 and 40 for FIG. 3, comprise several tie rods 35, four by way of example, intended to maintain the partitions spaced from each other, the tie rods extending parallel to the axis 1 1 of the attenuator considered. A tie 35 is for example formed of a threaded rod passing through all the partitions. Between each partition is placed a spacer 36 on which two neighboring partitions support. The rod passes through the spacers 36. Two nuts, no shown, hold the rod on the end bulkheads, ensuring the clamping of partitions and spacers.

A second variant of the means for maintaining the position of the partitions is shown in FIGS. 4 to 6. In this variant, an attenuator 50 comprises plates intended to keep the partitions at a distance from each other, the plates extending radially relative to each other. to the axis 1 1 of the attenuator 50. In the example shown, the attenuator 50 comprises the four annular partitions 14 to 17. Eight identical plates 51 separate the partitions 14 and 15. It is of course possible to vary the number of plates. A larger number of plates 51 provide rigidity to the attenuator. On the other hand, increasing the number of plates 51 reduces the section of the channels in which the flow of gas circulates. The plates 51 are advantageously distributed in a constant manner around the axis 1 1 in order to ensure a symmetry of revolution of the attenuator 50 about the axis 1 January. It would be possible to distribute them differently if one wishes to preferentially orient the flow of gas around the axis 1 1. Similarly plates 52 are disposed between partitions 15 and 16 and plates 53 are disposed between partitions 16 and 17. The plates 51, 52 and 53 may be identical. Alternatively, it is possible that their respective dimensions along the axis 1 1 differ in order to vary the size of the channels separating the partitions 14 to 17.

Figure 5 shows the attenuator 50 in section. This figure makes it possible to visualize the fixing of the partitions 14, 1 5, 16 and 17 with the plates 51, 52 and 53. The attenuator 50 comprises tie rods 55 passing through the four partitions 14 to 17 and three plates 51, 52 and 53 aligned. . The tie rod 55 may be formed of a screw, a head 56 bears against the partition 17 and a thread 57 is screwed into the plate 14. There is a tie rod across each row of plates 51, 52 and 53 aligned . Tightening the screw keeps the plates and partitions fixed together. To prevent any possible movement of the plates relative to the partitions, for example a rotation about the axis of the screw, one can complete the positioning of the plates by means of centering pins 58 arranged in bores arranged opposite and made in the plates 51, 52 and 53 and in the partitions 14, 15, 16 and 17. The installation of the pins 58 allows more to obtain a much more accurate positioning of the plates 51, 52 and 53 relative to the partitions 14, 15, 16 and 17 with the tie rods 55 alone.

The attenuator 50 further comprises means allowing a removable assembly on the tube 12. The end of the tube 12 may be threaded. To achieve the assembly, the tubular portion 13 is threaded so as to be screwed on the thread of the tube 12. In order to lock the position of the attenuator 50 relative to the tube 12, it is possible to set up a stop screw in a tapping 59 made in the tubular portion 13 perpendicular to the axis 1 January. The stop screw bears against the end of the tube 12 in order to immobilize their relative position of the tubular part 13 with respect to the tube 12.

Fig. 6 shows an attenuator 60 in which the plates 51 to 53 joining the partitions 14 to 17 are not all aligned. In the example shown, eight plates 51 are arranged between the partitions 14 and 15, six plates 52 are arranged between the partitions 15 and 16 and four plates 53 are arranged between the partitions 16 and 17. It is understood that the numbers of plates separating the partitions are given only as an example. Other numbers are possible. This arrangement makes it possible to adapt the precision of the guiding of the gas flow as a function of the distance from the mouth of the tube 12.

Claims

1. Noise attenuator for equipping a mortar capable of projecting shells in an initial direction, the mortar comprising a tube (12) extending along an axis forming the initial direction, the attenuator (10, 30, 40, 50, 60 ) being intended to be mounted on a free end of the tube (12), called the mouth of the tube (12), an axis (1 1) of the attenuator (10, 30, 40, 50, 60) being then merged with the axis of the tube (12), characterized in that it comprises a plurality of partitions (14, 15, 16, 17) extending substantially annular with respect to the axis (1 1) of the attenuator (10, 30, 40, 50, 60), so as to allow the passage of a gas blast between the partitions (14, 15, 16, 17), the gas blast being generated during the projection of a shell, in the partitions (14, 15, 16, 17) are configured to expand the gas flow between the partitions (14, 15, 16, 17) in an annular direction relative to the axis (1 1) of the attenuator (10, 30, 4 0, 50, 60) and for guiding the gas blast between the partitions (14, 15, 16, 17) after its expansion in a frustoconical direction with respect to the axis (1 1) of the attenuator (10, 30). , 40, 50, 60).

2. Attenuator according to claim 1, characterized in that it comprises an axial channel (18) passing through and centered on the axis (1 1), so as to allow the passage of a shell fired by the mortar, several channels. substantially radial (21, 22, 23) disposed between each of the partitions (14, 15, 16, 17), in that each of the substantially radial channels (21, 22, 23) comprises a first zone (21 1, 221, 231 ), a radial section (215, 225, 235) opens away from the axial channel (18) for expanding the gas breath between the respective partitions (14, 15, 16, 17).

3. Attenuator according to claim 2, characterized in that each of the substantially radial channels (21, 22, 23) comprises a second zone (212, 222, 232) of which a radial section (216, 226, 236) is substantially constant. away from the channel (18), and in that the second zone (212, 222, 232) is further away from the axial channel (18) than the first zone (21 1, 221, 231).

4. Attenuator according to one of the preceding claims, characterized in that the partitions are formed by a helix winding around the axis (1 1) of the attenuator (30).

5. Attenuator according to one of claims 1 to 3, characterized in that the partitions (14, 15, 16, 17) are each formed by a ring centered on the axis (1 1) of the attenuator (10) .

6. Attenuator according to one of the preceding claims, characterized in that it comprises tie rods (55) for maintaining the partitions at a distance from one another, the tie rods (55) extending parallel to the axis (1 1) of the attenuator (50).

7. Attenuator according to one of claims 1 to 5, characterized in that it comprises plates (51, 52, 53) for keeping the partitions at a distance from one another, the plates (51, 52 , 53) extending radially with respect to the axis of the attenuator (50, 60).

8. Attenuator according to one of the preceding claims, characterized in that it comprises means for a removable assembly on the tube (12).