FR3155804A1 - Gas pressure bladder device and ejection assembly - Google Patents

Abstract

Gas pressure bladder device and ejection assembly A charge launcher gas pressure bladder device 5 comprising a bladder 5 made of elastic material arranged along an axis and provided with an orifice 20 at an axial end, and a valve 21 mounted at the orifice 20 in a sealed manner, the bladder 5 having a thick wall 61 extending from a rounded end zone around the lumen, to a large diameter portion of a rounded end zone distant from the lumen, and a thin wall 62 extending over a small diameter portion of the rounded end zone distant from the lumen.

Description

Gas pressure bladder device and ejection assembly

The invention relates to the field of airborne maritime surveillance for which certain missions require dropping sonar buoys from an aircraft: plane, helicopter, drone, etc. A launcher can be placed in the hold or outside the aircraft. Such missions may require dropping numerous sonar buoys. Also, the launchers can be grouped in structures. The invention also relates to the field of launching charges from a support.

To control the ejection of the buoys, several release concepts were considered:

- by gravity from a vertical launcher

- by pyrotechnic ejection from a horizontal or vertical launcher

- by pneumatic ejection from a horizontal or vertical launcher.

Pneumatic ejectors are appreciated for their safety and flexibility in adjusting the ejection speed, compared to pyrotechnic launchers.

FR 2 479 135 describes a barrel buoy launcher capable of launching short or long buoys by gravity ejection. Cylinders are used for triggering and ejection.

FR 2 497 766 describes a pneumatic piston buoy launcher. The ejection causes the rupture of a frangible part.

Multi-launch structures can be integrated into the aircraft hold or externally. When the launchers are installed externally, the structure is in the form of a pod. In the case of a pod-shaped structure, the launcher design imposes mass and size constraints, while requiring high power.

In order to improve these devices, the Applicant has developed pneumatic ejectors equipped with a bladder storing, on the one hand, the compressed air for ejecting the charge and, on the other hand, carrying out this ejection. Propulsion is ensured by an expansion of the bladder under pressure, propelling the charge to be ejected out of the ejector.

FR 3 113 283 Alkan describes a pneumatically propelled buoy launcher equipped with a cap at the end of the tube, the cap being pneumatically unlocked. Pneumatic propulsion is provided by a deformable flexible bladder.

The Applicant analyzed the disadvantages of buoy launchers and realized the need to reduce the cost of use. Here, use means implementing the device by inflating the bladder, whether the load is pulled or not.

The invention improves the situation.

The charge launcher gas pressure bladder bladder device comprises a bladder of elastic material arranged along an axis and provided with an orifice at an axial end, and a valve sealingly mounted at the orifice, the bladder having a thick wall extending from a rounded end region around the lumen, to a large diameter portion of a rounded end region remote from the lumen, and a thin wall extending over a small diameter portion of the rounded end region remote from the lumen. The thin wall is limited to the region seeing the most expansion. The thin wall is remote from the tube, in the uninflated state, in the inflated state and in the pulled state. The thick wall substantially retains its shape in the uninflated state while being flexible to allow its insertion into the tube. The thick wall provides guidance for the thin portion during insertion. Proper positioning during insertion into the tube is repeatable. Reliability is increased.

In one embodiment, the bladder is annular. The construction is robust.

In one embodiment, the bladder has a first thickness proximate the orifice and a second thickness distant from the orifice, the second thickness being less than the first thickness. The area proximate the opening being less prone to expansion than a distal area can be made thicker.

In one embodiment, a bulge is provided on the large diameter portion of a rounded end region distant from the lumen, after inflation. The bulge conforms to the boundary between the tube and the piston. The risk of perforation is reduced.

In one embodiment, a transition zone of monotonic thickness is provided between the thin wall and the thick wall. The stretching stresses are distributed homogeneously.

In one embodiment, the thin wall extends longitudinally over 5 to 15% of the length of the bladder when inflated at ambient pressure. The duration of use of the bladder is increased.

In one embodiment, the thin wall has a thickness of between 0.4 and 1.0 mm, preferably between 0.5 and 0.8 mm, and the thick wall has a thickness of between 1.2 and 4.0 mm, preferably between 1.2 and 3.0 mm in the inflated state at ambient pressure and in the uninflated state. The bladder is robust. The bladder has a free uninflated state resulting in a position with low risk of deformation, wrinkles or residual torsion.

In one embodiment, the rounded end areas have a radius of between 40 and 100 mm, preferably between 50 and less than 65 mm when inflated at ambient pressure. The defect rate of the bladders is low.

In one embodiment, an assembly includes a bladder device and a projectile ejection device. The projectile ejection device includes a tube having a hollow core, a first end and a second end forming a mouth, opposite one another, a yoke capable of closing the first end and having a pressurized fluid supply port, and a retaining member disposed at the second end. The bladder device is disposed in the core. The bladder device is fillable with pressurized fluid. The bladder device can be placed in fluid communication with the supply port. The implementation cost is reduced.

In one embodiment, the rounded end areas have a radius less than the radius of the hollow core of the tube when inflated at ambient pressure. The bladder is reliable.

Other characteristics and advantages of the invention will appear on examining the detailed description below, and the attached drawings, in which:

FIG. 1 schematically illustrates in axial section a buoy launcher device according to one aspect of the invention during inflation.

FIG. 2 schematically illustrates in axial section a guided bladder device according to one aspect of the invention.

FIG. 3 schematically illustrates in side view a buoy launcher device according to another aspect of the invention.

FIG. 4 schematically illustrates in axial section a guided bladder device according to another aspect of the invention.

The attached drawings may not only serve to complete the invention, but also contribute to its definition, where appropriate.

The invention relates to a device for ejecting a load, and more particularly to a pneumatic ejector, in particular for a sonar buoy. Ejection devices may also be referred to as “ejection systems”, “ejectors”, or even “launchers”. Ejectors are widely used in the field of airborne maritime surveillance, some of whose missions involve the dropping of sonar buoys as projectiles. Ejectors are most often armed on the ground, for use in flight. The ejectors are usually arranged in pods housing a plurality of ejectors.

However, the bladders of pneumatic bladder ejection devices are single-use per shot or ejection. Indeed, the expansion of the bladder causes irreversible dilation of the bladder walls, which can lead to bursting of the bladder. Bursting occurs particularly when high projectile ejection energy is required. The bladder must therefore be replaced each time the ejector is reset.

The method of using bladders in a buoy launcher is very specific with opposing desired characteristics: the bladders are used both as a pneumatic energy source and as a hermetic envelope in severe environmental conditions until the ejection operation. Since ejections are not systematic during a mission, the seal must be guaranteed for several missions. Upon return from a mission, the bladder is deflated to avoid an accident in the event of an unintentional launch. This implies that a bladder can withstand several inflations in the absence of ejection. Furthermore, ejection performance requires the thinnest possible envelope and, conversely, maintaining the seal requires a high thickness.

During tests of the ejection system to increase the service life of the bladders, it was observed that the bladders tear in the same areas after durations dependent on vibration or climatic conditions. One objective is to increase the service life of the bladders, particularly in terms of flight hours and number of missions without firing.

The Applicant has conducted tests and discovered that vibrations have a damaging effect even though the bladder is made of flexible material. However, limiting vibrations is a very complicated path.

By analyzing a large number of torn bladders, the Applicant observed that tears often occur in the same places. The Applicant then had the idea of locally reinforcing the bladders to improve their strength. But the tests showed that reinforcing the areas frequently affected by a tear did not improve the strength of the bladders, and sometimes surprisingly reduced it. The Applicant realized that the reinforcements modify the deformations of the bladder in such a way that the reinforcements are not positioned, after inflation, at the desired location in the envelope volume of the ejection tube. Thus, the positioning of the bladder during inflation has a significant influence on its durability.

The tears observed occur in two places, most often at the intersection of the piston and the tube, sometimes at the intersection of the cylinder head and the tube, rarely elsewhere.

The Applicant has developed a bladder with improved inflation positioning.

As illustrated on the FIG. 1 , a projectile launcher 1, such as a sonar buoy, comprises a storage and launch tube 2, a breech 3 and a removable cap 6. The tube 2 is closed at one end by the breech 3 fixed to the tube 2. The tube 2 is closed at the other end by the removable cap 6. Between the two ends, the tube 2 can accommodate a projectile P, with an external section substantially identical to the internal section of the tube 2 with a clearance ensuring sliding of the projectile P relative to the tube 2. The projectile P can be a buoy of cylindrical shape, in particular with a standard of 130 mm in diameter and 914 mm in length.

A pneumatic ejection system maintains pressure in a closed volume during transport phases and, at the desired moment, releases the energy to propel the projectile. The closed volume is delimited in the tube between the breech and the projectile. These operations are carried out with a level of reliability meeting safety requirements, particularly aeronautical. Pneumatic ejection systems are sufficiently robust to take into account the environments encountered in all phases of use: storage, taxiing, flight, harsh landing, etc.

For the grouping of launchers in a pod, the Applicant has developed a buoy launcher capable of operating horizontally, for example when carried externally by a helicopter or a floating drone, or vertically, for example in the hold of an aircraft.

The projectile launcher 1 further comprises a propellant 4 arranged in the tube 2 between the breech 3 and the projectile P. The propellant 4 is capable of applying an ejection force to the projectile P. The ejection force is axial along the axis of the tube 2. The propellant 4 is pneumatic to produce the ejection force.

The propellant 4 comprises a gas reserve in the form of a flexible and deformable bladder 5 capable of receiving a gas, typically air, under pressure. In Figures 1 and 3, the bladder 5 is shown during inflation in order to better distinguish it from the tube 2. In Figures 2 and 4, the bladder 5 is shown in the same state, the tube 2 being omitted, this corresponding to the free state of the bladder at a pressure substantially equal to the ambient pressure. After inflation, the bladder 5 occupies the space in the tube 2 between the breech 3 and the projectile P. The bladder 5 then has a less rounded shape. The arming of the propellant 4 is done by pressurizing the bladder, via a valve 14. This creates a force, channeled longitudinally, i.e. along the axis of the tube 2, which tends to push the projectile P against the plug 6. The bladder, when deployed, pushes the projectile P. A separator/piston 15 can be inserted between the propellant 4 and the projectile P.

The plug 6 has a locked configuration in which the plug 6 engages the inner wall of the tube 2. Thus, the plug 6 is securely attached to the tube 2. The plug 6 thus closes the tube 2 and keeps the projectile P in place in the tube 2, including when the propellant 4 is armed and applies an ejection force. The plug 6 also has an unlocked configuration in which the plug 6 is free relative to the tube 2, and can thus be removed and separated from the tube 1 if the propellant is unarmed and ejected if the propellant is armed.

The launcher 1 further comprises a trigger 7. The trigger 7 has a retracted, resting configuration, in which the trigger 7 is found by default and most of the time. The trigger 7 further has a deployed configuration. In the deployed configuration, the trigger 7 is capable of actuating the cap 6, and of triggering, causing the cap 6 to move from the locked configuration to the unlocked configuration.

Also, a sequence of use of such a launcher 1 comprises the following steps. While the propellant 4 is disarmed, the propellant 4 is installed in the tube 2, then a projectile P is introduced into the tube 2. The projectile P is immobilized inside by the installation of the plug 6 at the end of the tube 2. The plug 6 is secured to the tube 2 by placing it in a locked configuration. The propellant 4 can then be armed, typically by increasing the pressure in the bladder 5 serving as a gas reserve, in particular by compression/inflation using the valve 14. The engagement of the plug 6 with the tube 2 is carried out in a radial direction and thus effectively opposes the force, substantially axial, that the propellant 4 exerts on the projectile P and that the projectile P transmits to the plug 6. The launcher 1 remains loaded and armed until the projectile P is ejected or until it is disarmed upon return from a mission without ejection. When it is desired to eject the projectile P, a command is transmitted to the trigger 7. The trigger 7 then triggers and passes from the folded configuration to the unfolded configuration. In doing so, the trigger 7 actuates the plug 6 which passes from the locked configuration to the unlocked configuration. The plug 6 is then released. The plug 6 separates from the tube 2. The armed propellant 4 continues to exert an ejection force. Also, the propellant 4 pushes on the projectile P. The projectile P itself pushes on the plug 6. The projectile P under the effect of the ejection force, is ejected from the tube 2, pushing the plug 6 in front of it. The plug 6 separates from the tube. The projectile P is ejected at a speed chosen according to the pressure in the bladder.

The operation of the cap 6 is described in FR 3113283 to which the reader is invited to refer.

After firing, reloading is carried out by depressurizing the propellant 4, via the valve 14. The bladder can be inspected. If the bladder is intact, a new projectile P can be placed in the tube 2, then a new plug 6 which is locked in place. The propellant 4 is then armed by pressurizing the bladder 5. The armed state is restored.

If the projectile has not been fired, the propellant 4 is depressurized upon return from the mission. Then the cap 6 is unlocked. The projectile P is removed. The bladder is inspected, then discarded if damaged or reused. Thanks to the invention, the number of missions without firing carried out using the same bladder increases from one to approximately five. The cost of ownership of the launcher in the event of no firing is reduced.

The bladder 5 of the propellant 4 is illustrated in the FIG. 2 .

In one embodiment, the pneumatically triggered buoy ejection system comprises an ejection tube, a pressurized volume, a supply valve, a single-acting distributor electrically controlled by a solenoid, a cylinder head equipped with a Y-shaped pneumatic circuit for connecting the supply valve, the distributor and the pressurized volume, a single-acting pneumatic piston, a pneumatic pipe connecting the piston to the distributor, a releasable plug equipped with a retractable snap ring under the action of the single-acting pneumatic piston and a pusher interfacing between the buoy to be ejected and the pressurized volume. The pressurized volume supplying both the trigger and the ejection allows a triggering force proportional to the pressure and therefore to the ejection power.

During testing, it was found that the bladder does not center itself correctly in the envelope volume formed by the walls of the cylinder head, the ejection tube and the piston. An improvement is to provide a centering system relative to the center of the ejection piston for the bladder at the distal end opposite the valve.

In the illustrated embodiment, the gas pressure bladder device is intended for a charge launcher. The bladder device or propellant 4 comprises a bladder 5 made essentially of elastic material. The bladder 5 is arranged along an axis. The bladder 5 may have a shape of revolution along said axis. The bladder 5 is provided with an orifice 20 at one axial end. The bladder 5 may be made of elastomer. The bladder 5 forms a pressure-resistant interior chamber to form, once inflated, a reserve of ejection energy.

The bladder device comprises a valve 21 mounted at the port 20 in a sealed manner. The valve 21 is analogous to a tire valve. The valve 21 may project outside the bladder 5. The valve 21 is configured to be opened when a higher gas pressure is applied to the outside of the bladder 5 than to the inside, opened when a force is applied to a moving valve part 21 from the outside, and closed in other situations. The bladder 5 may be inflated with a compressed gas such as industrial compressed air. The bladder 5 may be deflated by manually pressing or using a tool on the moving part. The moving part may be a valve core 21.

The bladder 5 has, in the armed state, a shape adapted to the chamber. The armed state corresponds to an internal gas pressure higher than the atmospheric pressure on the ground and to the bladder 5 installed in the projectile ejection device. In practice the inflation pressure is several bars, for example between 4 and 10 bars. The bladder 5 has two opposite poles, one proximal, the other distal. The bladder 5, in the free state at approximately 1 bar of pressure, has two rounded regions or polar zones 51 and 52, for example hemispherical, ovoid or oval, around the poles, and a central region 50 between the rounded regions. In the embodiment shown, the central region 50 may be cylindrical of revolution. The central region 50 follows the shape of the bore of the tube. The polar zones 51 and 52 have a radius less than the radius of the hollow core of the tube, in particular less than 65 mm for a tube of caliber 130 mm. The polar zones 51 and 52 have a radius of between 40 and 100 mm, preferably between 50 and less than 65 mm.

In the variant illustrated on the FIG. 4 , the bladder 5 comprises two rounded regions or polar zones 51 and 52, for example hemispherical or oval, around the poles, connected to each other. The central zone is omitted. The bladder 5 has a generally spherical, ovoid or oval shape.

The bladder 5 is here made in two parts joined together by assembly, for example by vulcanization. The two parts can be joined by two complementary tapered zones 60 located in the central region 50, cf. FIG. 2 , or in a polar zone.

The bladder 5 has the orifice 20 centered on the proximal polar zone 51. The valve 21 is permanently mounted in the orifice 20 of the bladder 5. The valve 21 is tightly mounted in the orifice 20 of the bladder 5.

During inflation, the bladder 5 deforms to press against the walls of the tube. This phase is complex because in the first parts of the bladder 5 which come into contact with the surrounding walls, friction is created which in turn modifies the deformation of the bladder 5.

The first idea to strengthen the bladder was to glue an elastomer ring. This solution proved to be less resistant than the historical bladder because the glue creates a local deformation during inflation which often causes a tear.

During testing and modeling, a deeper understanding of the ejection phase made it possible to establish that during a shot only the thin part of the bladder deforms until it tears. It was concluded that the membrane of bladder 5 could be thickened everywhere except in the area in contact with the piston without reducing ejection performance. Moreover, the thick part, which deforms very little, absorbs less energy than an equivalent part in a bladder of constant thickness, resulting in reduced heating and an improved efficiency between the pressure potential energy stored in the bladder and the kinetic energy of the ejected projectile.

This design eliminates the problem of positioning the reinforcements. The length of the bladder 5 is very slightly greater than the length of the chamber, for example by 1 to 10%. During inflation, the thin area is immediately pressed against the piston wall, which ensures that the energy is released in a directional manner.

The bladder 5 has a first thickness in the vicinity of the orifice 20 and a second thickness opposite, i.e. at the distal polar zone 52. The second thickness is less than the first thickness. In the embodiment shown, the second thickness extends over a portion of the distal polar zone 52. The first thickness extends over a complementary portion of the distal polar zone 52, over the central region 50 and over the proximal polar zone 51.

The second thickness may extend longitudinally over 5 to 15% of the length of the bladder 5 in the inflated state at ambient pressure.

To facilitate the mounting of the valve 21, the bladder 5 may comprise a radial region 55. The radial region 55 forms an annular branch made of a single material with the proximal polar zone 51. The radial region 55 separates from the proximal polar zone 51 going towards the orifice 20. The radial region 55 may have a lumen 56 aligned with the axis of symmetry of the bladder 5. Between the orifice 20 of the proximal polar zone 51 and the lumen 56 of the radial region 55 is formed a chamber 58 for fixing the valve 21. The diameter of the orifice 20 of the proximal polar zone 51 is greater than the diameter of the lumen 56 of the radial region 55. The chamber 58 has a maximum diameter greater than the diameter of the orifice 20 of the proximal polar zone 51 to allow insertion and retention of the valve 21.

In other words, the bladder 5 has a thick wall 61 extending over a rounded end zone around the orifice 20, over a central zone and over a large diameter portion of a rounded end zone distant from the orifice 20, and a thin wall 62 extending over a small diameter portion of the rounded end zone distant from the orifice 20. The thick wall 61 may have a thickness of 1.2 to 4.0 mm. For a reduced mass, a thickness of 1.2 to 3 mm is preferred, in particular between 2 and 3 mm, for example 2.5 mm. The thin wall 62 may have a thickness of between 0.4 and 1.0 mm, preferably between 0.5 and 0.8 mm, for example 0.68 mm. The thickness of the thin wall is less than the thickness of the thick wall. A thin-wall to thick-wall thickness ratio of 3 to 4 is preferred, particularly to ensure good strength, low mass, low thick-wall deformation and high ejection velocity.

The bladder 5 may have an annular bulge 57 after a first inflation to operational pressure in the tube 2, in particular between the breech 3 and the projectile P. Before said first inflation, the bulge is absent. The bulge 57 is permanent. The bulge 57 is caused by creep of the material under the effect of inflation. The bulge 57 remains present in the event of deflation after inflation in the tube 2. The bulge 57 is centered on the axis of the bladder 5. The bulge 57 is arranged on the complementary part of the distal polar zone 52. In other words, the bulge 57 has a diameter greater than the diameter of the thin part of the distal polar zone 52. The bulge 57 has a diameter between 70 and 95% of the diameter of the central region 50. The bulge 57 is local. The bulge 57 may have a thickness of 0.2 to 2 mm at its maximum. The bulge 57 is directed outwards. The bulge 57 may have a rounded section.

The invention also proposes an assembly comprising a bladder device 5 as above and a projectile ejection device, comprising a tube having a hollow core, a first end and a second end forming a mouth, opposite one another, a breech capable of closing the first end and having a pressurized fluid supply orifice, a retaining member arranged at the second end, the bladder device being arranged in the core, fillable with pressurized fluid, capable of being placed in fluid communication with the supply orifice.

In one embodiment, the separator/piston 15 provides a concave surface 70 oriented towards the distal rounded region and the distal pole of the bladder 5, cf FIG. 3 . The concave surface 70 is smooth to preserve the bladder 5. The concave surface 70 comprises a radial central portion and a rounded rim. The rounded rim occupies approximately 10 to 30% of the diameter and the radial central portion 90 to 70%. The rounded rim limits the extension of the bladder 5 during inflation and during firing. Maximum deformations of the bladder 5 occurring in the re-entrant angles are reduced. Thus, the deformation of the bladder 5 is locally less. In other words, the deformation is more homogeneous.

In one embodiment, the cylinder head 3 provides a concave surface 30 oriented towards the proximal rounded region and the proximal pole of the bladder 5, cf FIG. 3 . The concave surface 30 is smooth to preserve the bladder 5. The concave surface 30 comprises a radial portion surrounding the valve and a rounded rim surrounding the radial portion. The rounded rim occupies approximately 10 to 30% of the diameter and the radial central portion 90 to 70%. The rounded rim limits the extension of the bladder 5 during inflation and during firing. Maximum deformations of the bladder 5 occurring in the re-entrant angles are reduced. Thus, the deformation of the bladder 5 is locally less. In other words, the deformation is more homogeneous.

In a manner common to the above embodiments, a life cycle of the bladders includes the operational phases of manufacturing, storage, removal from storage, placement in the ejection tube, pressurization to 4 to 10 bars, maintenance of the pressure either at ambient temperature or in operational conditions, ejection of a load with the required performance or deflation of the bladder.]

Claims (10)

A gas pressure bladder device (5) for a charge launcher comprising a bladder (5) made of elastic material arranged along an axis and provided with an orifice (20) at an axial end, and a valve (21) mounted at the orifice (20) in a sealed manner, characterized in that the bladder (5) has a thick wall (61) extending from a rounded end zone around the lumen, to a large diameter portion of a rounded end zone distant from the lumen, and a thin wall (62) extending over a small diameter portion of the rounded end zone distant from the lumen. Device according to claim 1, wherein the bladder is annular. Device according to claim 1 or 2, in which the bladder (5) has a first thickness in the vicinity of the orifice (20) and a second thickness distant from the orifice (20), the second thickness being less than the first thickness. A device according to any preceding claim, wherein a bulge is provided on the large diameter portion of a rounded end region distant from the lumen, after inflation. Device according to one of the preceding claims, in which a transition zone of monotonous thickness is provided between the thin wall and the thick wall. Device according to one of the preceding claims, in which the thin wall extends longitudinally over 5 to 15% of the length of the bladder (5) in the inflated state at ambient pressure. Device according to one of the preceding claims, wherein the thin wall has a thickness of between 0.4 and 1.0 mm, preferably between 0.5 and 0.8 mm, and the thick wall has a thickness of between 1.2 and 4.0 mm, preferably between 1.2 and 3.0 mm, in the inflated state at ambient pressure and in the uninflated state. Device according to one of the preceding claims, in which the rounded end zones have a radius of between 40 and 100 mm, preferably between 50 and less than 65 mm in the inflated state at ambient pressure. Assembly comprising a bladder device (5) according to one of the preceding claims and a projectile ejection device, comprising a tube having a hollow core, a first end and a second end forming a mouth, opposite one another, a breech capable of closing the first end and having a pressurized fluid supply orifice, a retaining member arranged at the second end, the bladder device (5) being arranged in the core, fillable with pressurized fluid, capable of being placed in fluid communication with the supply orifice. Set according to claim 9, wherein the rounded end regions have a radius less than the radius of the hollow core of the tube when inflated to ambient pressure.