FR2620210A1 - ANTI-ARRANGEMENT DEVICE FOR AN ARM TUBE - Google Patents

Abstract

The technical sector of the invention is that of anti-bending devices for gun barrels, especially of large calibre. The device according to the invention consists of at least one sleeve (1) fixed to the barrel (2) and delimiting around the latter and over some of its length at least one annular cavity (3). It is characterised in that it comprises a ventilation system intended for dissipating the heat which accumulates in the annular cavity (3) in the vicinity of the upper generatrix of the barrel (2). The invention is used for barrels equipping armoured vehicles.

Description

The technical field of the present invention is that of the devices

  anti-arcure intended for barrels of heavy weapons weapons and more particularly cannons equipping

armored vehicles.

  We know that a barrel tube is subjected to thermal constraints of two origins: -outside related to climatic conditions (rain, wind, sun); endogenous, ie due to firing (combustion of the propellant charge and friction of the projectile in the tube); each of these constraints can generate a temperature gradient between two opposite generators, gradient causing a difference in expansion between these generatrices thus inducing a deformation of the tube called thermal arc, which is detrimental to the accuracy of the shot,

mainly in tense shooting.

  For example, for a 120 mm gun, a temperature gradient of 1'C causes a deviation of the axis of the tube of the order of 0.35 thousandths (the thousandth being the unit proper to the artillery such as 6400 thousandths = 2x radians). One can imagine the same cannon between two shots and subject to a side wind: the wind generator will be colder than its opposite. We will then have a bow and a lateral deviation of the tube. It is therefore easy to conceive, under these conditions, that during the firing there are important dispersions, and all the more so that the arcs will be constant neither in absolute value nor in direction; these deviations may also take unacceptable values in the case of severe weather conditions combined with a significant heating of the barrel as it may occur after a sustained rate of fire. It has therefore sought to overcome these disadvantages by providing various systems for isolating all or part of the tube from the ambient air so as to homogenize the temperature thereof, and whatever the conditions of the shot. Thus, US Pat. No. 4,424,734 proposes a composite sheath of which at least one element is a thermal insulator covering the tube of the barrel. This type of protection has the serious disadvantage of storing heat in the tube, particularly at the level of the combustion chamber. This results in a risk of self ignition (a phenomenon known as "cook-off") of an ammunition remained stationary; risk

  incompatible with the safety of the gunmen.

  Another proposed solution is to use several tubular sleeves juxtaposed axially, linked in rotation and in translation to the barrel tube and closed at their ends, thus forming as many concentric cavities to the tube. Each sleeve is constituted by a casing made of material having a high thermal conductivity (greater than 100 W / (m × K)), for example an alloy of

  magnesium, allowing it a quick isothermal setting.

  Under these conditions, the layer of air trapped between the tube and the sleeve is a thermal insulator between the barrel of the weapon and the ambient air. The main disadvantage of this provision is that during firing, the temperature rise of the tube (the peripheral temperature of the tube reaches nearly 100 'for 10 shots fired in 30 minutes), will cause a heating of this layer of air thus causing convection movements of the air molecules. These movements will cause an accumulation of calories in the vicinity of the upper generatrix of the tube, thus creating a temperature gradient between this and the lower generator, such

dissymmetry causing a bow.

  The present invention aims to overcome these disadvantages by providing a simple device, lightweight and inexpensive, allowing on the one hand to isolate all or part of the gun -3 tube of ambient air by means of a layer of insulation, and on the other hand to avoid thermal gradients

at this layer.

  The anti-arcure device for a tube of a weapon, in particular of large caliber, according to the invention is constituted by. at least one sleeve, secured to the tube in translation and in rotation by a connecting means, delimiting, around the latter and over a part of its length, at least one annular cavity, closed at its ends, it is characterized in it includes a ventilation system to evacuate the calories that can accumulate in the annular cavity in the vicinity of

  the upper generator of the tube.

  According to a particular embodiment, the ventilation system is constituted by at least one evacuation orifice, integral with the sleeve, and disposed in the vicinity of the upper generatrix of the tube cooperating with at least one intake orifice situated in the vicinity of the generator. lower the tube, these orifices communicating the annular cavity with the ambient air, the total surface of the or the discharge orifices being between one time and 20 times the total surface of the inlet or ports. In a preferred manner, the sleeve is cylindrical and has several intake orifices regularly spaced along one of its generatrices, the minimum distribution density of these orifices being 15 orifices per meter, the maximum diameter of each orifice of intake being 5 mm, and the minimum diameter of each orifice

10 mm evacuation.

  According to another characteristic, the device comprises a protection system for the evacuation orifice (s), constituted by at least one cap, arranged vertically of the latter, so as to cover them in the following projection.

a vertical direction.

  The protection system also has cheeks, located on either side of the discharge ports, and pierced with lights having a surface greater than that of these. It will be advantageous to arrange the lights alternately with the drain holes along the direction

axial of the sleeve.

  According to another particular embodiment, the ventilation system comprises a compressor connected to the annular cavity in the vicinity of the upper generatrix of the tube, and at least one vent, arranged on the sleeve in the vicinity of the lower generatrix of the tube, making

  communicate the annular cavity with the ambient air.

  In particular, the ventilation system may comprise a duct, integral with the sleeve, disposed in the annular cavity in the vicinity of the upper generatrix of the tube and extending substantially over the entire length of the sleeve, this duct being connected to the compressor

  and having at least one injection hole.

  The compressor may be such that it creates pressure

of air in the pipeline.

  According to a variant of the invention, the device is such that the distance separating the sleeve from the lower generatrix of the tube is greater than that separating it from the

  superior generator of it.

  Other advantages of the invention will become apparent

  reading of the description which will follow, made with regard to

  attached drawings and in which: FIG 1 is a cross section of a first embodiment of the device according to the invention; FIG. 2 is a simplified longitudinal section showing a particular application of this first embodiment; FIG. 3 is a cross-section of a second embodiment;

  embodiment of the device according to the invention.

  FIG. 4 is a simplified longitudinal section showing a particular application of this second embodiment

26202 1 0

  The device represented in FIG. 1 comprises a sleeve 1, cylindrical and coaxial with a tube 2 of a barrel, for example of large caliber, an annular cavity 3 is thus arranged between the tube and the sleeve, which cavity is closed at its two ends by partitions integral with the sleeve (not shown here), that to avoid axial air currents especially at the time of recoil. At least one inlet port 4 is formed on the sleeve in the vicinity of the lower generatrix of the tube, and at least one discharge orifice 5 in the vicinity of the upper generatrix of the latter. These orifices constitute a ventilation system for evacuating the calories that can accumulate (especially during firing) in the annular cavity, in the vicinity of the upper generatrix of the barrel of the weapon. The surface of the outlet orifice (s) 5 is between once and twice the surface of the intake orifice (s) 4.

  for a reason that will be explained later.

  When the temperature increases in the cavity 3, and more particularly during a firing, the convection movements of the air molecules will have the effect of causing the hot air to escape through the evacuation orifice (s). , thus creating a depression in the cavity 3 and consequently a call for fresh air therein, through the at least one intake orifices 4, fresh air whose flow

  turbulent favors the distribution in cavity 3.

  The surface of the outlet or openings will be greater than that of the intake ports so as to allow the renewal of the air contained in the cavity 3; a contrary arrangement, braking the evacuation of hot air while promoting the entry of cold air, would have the effect of increasing the thermal gradient between the upper and lower generatrices of the tube and thus the arcure. Preferably, the diameter of the inlet orifices 4 will not exceed 5 mm, in order to avoid

  excessive cooling of the lower generator.

  For a similar reason, the diameter of the discharge orifices 5 will be greater than or equal to 10 mm, thus facilitating the exit of the hot air. It will also be useful to regularly distribute the intake and discharge ports along their respective generatrices, so as to regulate the convection movements occurring throughout the annular cavity in steady state. A minimum distribution density of 15 holes

  intake per meter will give good results.

  For example, comparative tests were conducted between a tube of a large caliber weapon, equipped with four identical sleeves, covering substantially its entire length, and having no outlets or ports intake, and a tube equipped with four sleeves according to the invention, having the same geometry as the previous but each having 17 inlet ports of diameter 4 mm and 5 discharge holes of diameter 32 mm regularly spaced. After a series of 6 shots fired in a time interval of 20 minutes, the tube according to the state of the art presented a total deformation of 0.8 thousandths, whereas the total arc of the tube equipped with

  sleeves according to the invention did not exceed 0.3 thousandths.

  Another advantage of the invention is that it makes it possible to use materials other than magnesium for producing the sleeves. Indeed, the sleeves not drilled, according to the state of the art, had to have a significant thermal conductivity, both radial and circumferential, that in order to be able, on the one hand, to homogenize the temperature of the air contained in the cavity annular, and on the other hand evacuate, by exchange with the ambient air, the calories transferred by the tube to the annular cavity and which might cause excessive heating thereof. A thermal gradient due to

  endogenous thermal stresses nevertheless remained.

  The convection movements and the renewal of the air contained in the annular cavity, possible with the ventilation system of the device according to the invention, allowing to evacuate the calories that can accumulate in the vicinity of the upper generatrix of the tube, permit

  the use of any thermal conductivity material.

  Possibly an insulating material could even be used, thus making it possible to limit the effect of the gradients

  thermals of external origin on the barrel of the weapon.

  In order to isolate the tube 2 from external climatic stresses to the right of the discharge orifices 5 (rain, snow, etc.), stresses likely to disturb the homogeneity of the temperatures, the sleeve has at its upper part a protection system which consists of a gutter 6 composed of a cap 7, disposed vertically of the discharge orifices, resting on cheeks 8, located on either side of these orifices, and having lights 9 allowing the exhausting the hot air, these lights each having a surface equal to or greater than that of the discharge orifice 5 so as not to disturb the movement of the hot air outlet. The cap 7 has dimensions such that in projection in a vertical direction it covers completely the

orifices 5.

  It will be advantageous to alternately ax the lights 9 and the discharge orifices 5, this in order to reduce the disturbances that can be caused by a side wind. It will also be interesting to equip the tube by means of several sleeves, identical or not, in order to facilitate the manufacture, storage and transport, or even optimize the performance. FIG. 2 is a simplified representation of an anti-arcure device consisting of four sleeves 1 juxtaposed axially and

  thus covering substantially the entire length of the tube.

  The sleeves 1 will be secured to the tube in rotation and in translation in known manner by a connecting means not shown here. It will be possible in particular to make sleeves consisting of two symmetrical shells hinged and closing around the tube by a quick coupler, see EP183432 and DE1918422 which describe such binding means applied

anti-arcure devices.

  r It will be possible to vary the number, the surface and the distribution of the intake ports 4 as well as the outlets 5, the surface and the position of the lights 9 with respect to the evacuation ports 5, the volume of the the cavity 3, so as to adapt the device according to the characteristics (size, thickness of the tube,

  temperature after shooting ...) specific to each type of weapon.

  In particular, it is conceivable to use sleeves such that the distance separating the sleeve from the lower generatrix of the tube 2 is greater than that separating it from the upper generatrix thereof, for example by adopting cylindrical sleeves whose axis is located offset and parallel to the axis of the tube. This results in a smaller volume of air at the upper generatrix of the tube, resulting in faster evacuation of hot air and a greater volume of air at the lower generator, hence better homogenization of the suction air temperature

  with the one already contained in the cavity.

  Other ventilation systems are possible.

  FIG. 3 represents a second particular embodiment of such a system, in which the sleeve 1 is cylindrical and coaxial with the tube 2 of the weapon as previously. A cylindrical pipe 10, integral with the sleeve and extending substantially the entire length thereof, is closed at one of its ends and connected at its other end to a compressor 11 (see FIG. 4), integral with the weapon . The pipe 10 is disposed in the annular cavity 3 and in the vicinity of the upper generatrix of the tube 2, it carries along one of its own generatrices (for example that facing the tube), injection holes 13 (here 3 holes diameter 3 mm, regularly distributed along a generatrix of the pipe with a density of 5 holes per meter). The sleeve also carries vents 12 (here 10 vents of diameter 2 mm), arranged in the vicinity of the lower generatrix of the tube which communicate the annular cavity.

with the ambient air.

  The compressor 11, the pipe 10 and the vents 12 constitute a ventilation system according to the invention. The compressor will send a fluid under pressure, for example air, into the pipe. This fluid will diffuse through the injection holes 13 in the annular cavity 3. In steady state the outlet temperature of the fluid is homogeneous along the pipe and is lower than the temperature of the air present in the annular cavity in the vicinity of the upper generatrix of the tube, (a device for stabilizing the fluid temperature may also be provided between the compressor and the pipe). The effect of this ventilation system is twofold: it acts on the one hand thermally, cooling the air contained in the annular cavity at the very place where the temperature could be the highest, on the other hand mechanically the fluid stream thus created expels hot air to the lower zone of the annular cavity, the hot air then escapes through the vents

  12, because the sleeves are waterproof otherwise.

  Figure 4 is a simplified representation of an anti-arcure device covering substantially the entire length of the tube 2 of the weapon, and for this purpose the sleeve is constituted by four sections 14 whose decreasing diameters take into account the taper of the tube . Each section is separated from its neighbors by a sealed partition 15, the sleeve 1 thus delimits around the tube four annular cavities 3. The duct 10 passes through these partitions and thus extends over substantially the entire length

of the sleeve 1.

  It is possible, as in the case of the first embodiment of the invention, to vary the number, the area and the distribution of the injection holes 13 as well as the vents 12, the diameter of the pipe 10, the flow rate of the compressor It and the temperature of the fluid supplied by the latter, and finally the volume of the cavity 3, so as to adapt the device according to the characteristics (caliber, thickness of the tube, temperature after firing ...)

specific to each type of weapon.

  It will also be possible to design a device of an architecture similar to the previous one but in which the compressor 11 draws air contained in the annular cavity through the injection holes 13 instead of injecting a fluid. The goal is always to evacuate the calories that can accumulate in the vicinity of the upper generatrix of the tube. In the latter case the depression thus created in the annular cavity will cause an air intake through the vents 12, and it will be useful to provide a distance between the sleeve and the lower generatrix of the tube which is greater than that separating it from the upper generator of the latter. The larger volume of air then facing the vents 12 will provide a better homogenization of the temperature of

  the air sucked with that already contained in the cavity.

Claims (10)

  1. anti-arcure device for a tube (2) of a weapon, in particular large caliber, constituted by at least one sleeve (1), secured to the tube in translation and in rotation by a connecting means, delimiting, around the tube and over a part of its length, at least one annular cavity (3), closed at its ends, characterized in that it comprises a ventilation system for evacuating the calories that can accumulate in the annular cavity   (3) in the vicinity of the upper generatrix of the tube (2).   2. Device according to claim 1, characterized in that the ventilation system is constituted by at least one discharge orifice (5), integral with the sleeve (1), and disposed in the vicinity of the upper generatrix of the tube, cooperating with at least one inlet opening (4) situated in the vicinity of the lower generatrix of the tube, these orifices making the annular cavity communicate with the ambient air, and in that the total surface of the outlet orifices (5) is between once and 20 times the   total area of the intake port (s) (4).   3. Device according to claim 2, characterized in that the sleeve is cylindrical and has a plurality of inlet orifices (4) regularly spaced along one of its generatrices, the minimum density of distribution of these orifices being 15 orifices per meter, the maximum diameter of each inlet port (4) being 5 mm, and in that the minimum diameter of each discharge port (5) is 10 mm.   4. Device according to claims 2 or 3, characterized   in that it comprises a protection system for the at least one discharge opening (5) consisting of at least one cap (7) arranged vertically therefrom so as to   cover in projection in a vertical direction.   5. Device according to claim 4, characterized in that the protection system comprises cheeks (8), located on either side of the discharge orifices (5), and pierced with lights (9) having a top surface to that of the evacuation holes. 6. Device according to claim 5, characterized in that the slots (9) are arranged alternately with the discharge orifices (5) along the axial direction of the tube. 7. Device according to claim 1, characterized in that the ventilation system comprises a compressor (11) connected to the annular cavity (3) at the upper generatrix of the tube, and at least one vent (12), arranged on the sleeve in the vicinity of the lower generatrix of the tube and communicating the annular cavity with the ambient air. 8. Device according to claim 7, characterized in that the ventilation system comprises a pipe (10), integral with the sleeve (1), disposed in the annular cavity (3) in the vicinity of the upper generatrix of the tube (2) and extending substantially over the entire length of the sleeve, in that this pipe is connected to the compressor (11) and has at least one hole injection (13).   9. Device according to claim 8 characterized in that the compressor (11) creates an air pressure in the channeling (10).   Device according to claims 2 to 6, characterized   in that the distance separating the sleeve (1) from the lower generatrix of the tube (2) is greater than that of the   separating from the upper generator of the tube.