AVALANCHE TRIGGERING SYSTEM

Description

FIELD OF THE INVENTION

The invention firstly relates to a component for an avalanche triggering system, in particular for snow avalanches. The invention also relates to an avalanche triggering system as such, in particular for snow avalanches, comprising such a component.

BACKGROUND

Avalanche triggering system are known to be used in areas where snow accumulation could generate avalanches threatening places or people.

To cause an avalanche, it is generally planned to generate a shock wave from an explosion. For example, explosive charges can be placed by an operator at the point where an avalanche is to be triggered. This placement can be done either from a helicopter by launching, or from the ground, where the charge can be dropped, slid or launched to the appropriate location. In both cases, the charge is usually ignited by a slow fuse or electrically. In addition to the risks directly associated with handling explosives, for placing explosive charges directly on the ground the operator is required to travel to often steep areas with unstable snowpack. Additionally, these operations must sometimes be carried out in difficult weather conditions, whether on the ground or by helicopter.

As the movement and handling of explosives is dangerous and regulated, it is preferable to use a mixture of explosive gases to generate the shock wave. In addition, remote-controlled systems are known to be used to enhance operator safety. These systems must offer the same performance as other systems in terms of the area of the snowpack potentially affected. Some devices, such as the commercially available “CATEX”, use a cable system to convey explosives over one or more avalanche paths. While this type of solution limits the risks associated with moving to the site of an avalanche trigger, it does not provide a solution for handling and storing explosives. This device also requires the costly installation of a system of towers to support the conveyor cable over distances that can be very long.

One way of reducing the risks associated with handling explosives is to use an explosive mixture of gases to generate a shock wave used to trigger the avalanche. This approach and the corresponding systems require a confinement enclosure to inject the mixture into before its ignition (which causes the explosion) and avoid premature dilution before explosion in the atmosphere. This confinement function can be achieved by a flexible membrane (such as a balloon) or, more often, by a rigid structure, usually a metal structure. Depending on its characteristics, it also determines the quality of the explosion, so it can be referred to as either a confinement enclosure or an explosion chamber. According to this principle, transportable devices, such as those described in documents WO 2007/096524 A1 and WO 2009/080977 A1, are known which can be brought to site by helicopter. These devices use a mixture of explosive gases to trigger an explosion above the snowpack. Also known is a device in the form of a downward-opening confinement enclosure designed to be suspended from a helicopter by a sling. This enclosure is therefore brought in by helicopter and hovered above the snowpack in the area where an avalanche is to be triggered. To trigger an avalanche, this enclosure is filled with an explosive gas mixture lighter than air. This mixture is then ignited, usually electrically, to generate an explosion. The resulting shock wave then shakes the snowpack, triggering an avalanche. The main advantage of these devices is that they can be used in areas not previously equipped, without the need to handle explosives. The disadvantages remain those inherent in the use of helicopters, namely high operating costs and the impossibility of operating in bad weather.

Another type of device is known under the trade name “GAZEX”. This type of device, described in document FR 2 636 729 A1, comprises an explosion chamber in the form of an explosion tube with a closed bottom and an open, angled end, mounted on a foundation system, the opening of which is directed toward the snowpack. A gas circuit is used to fill the explosion tube with oxidizing gas and fuel gas, which is then ignited by an ignition device mounted at the rear of the explosion tube. The shock wave from the resulting explosion is then directed through the tube opening toward the snowpack, thus triggering the avalanche. The fixed installation of this device further guarantees sufficient, reproducible and long-lasting power to protect large avalanche paths. The main disadvantages of this type of device are the need for complex installation, requiring major civil engineering work for the device itself, the adjacent technical site and the connecting pipes connecting them, and the need to carry out maintenance at the installation site, which is, by definition, difficult or even dangerous to access.

Some additional features of an avalanche triggering device are sought, such as a smaller footprint, integration into the landscape and removability by helicopter. This last feature is particularly important, as it enables said devices to be removed in summer, when their use is not needed, to limit their exposure to lightning and falling rocks, but also to carry out maintenance and repair operations, limiting the operators'exposure to the harsh conditions of the high mountains.

Prior art solutions propose removable remote avalanche triggering system based on the explosion of a hydrogen/oxygen gas mixture inside an open cone. In particular, document FR2958739A1 presents a solution wherein a module comprising the explosion enclosure is placed on a fixed support stand positioned in avalanche initiation zones. This solution is satisfactory in that it provides a removable system capable of triggering avalanches when operated remotely.

However, the performance of avalanche triggering systems traditionally depends not only on the quantity and type of gases used for the explosive gas mixture, but also on the size and volume of the enclosure used to carry out the explosion. It therefore seems preferable to use a large-volume enclosure with a large amount of gas to maximize the explosion, since it is within the enclosure that the effects of the explosion will develop from the ignition of this amount of gas.

In this way, the desire to achieve improved performance can quickly run up against limits of compatibility, particularly in terms of mass capacities suitable for helicopter transport for the removability criterion mentioned above. For an integrated system with a constant helicopter transportable mass, it is therefore necessary to find an optimum way of distributing this removable mass between the various components of the device, such as the enclosure, gas reserves, miscellaneous equipment and control equipment. This optimum way is also limiting and does not allow power to be increased indefinitely, as this requires an increase in mass.

All of the current gas avalanche release systems therefore use explosion chambers of various shapes and sizes. All metal explosion chambers have one thing in common: they have a fairly direct free outlet, and they must have sufficient volume to contain the gas mixture required to power the explosion and reliably trigger an avalanche. However, each device must be adapted to the type of gas used, particularly based on the density of the gases used. This is particularly true of the explosion chamber, most of which has a fairly direct free outlet, that is, apart from the path through the confinement chamber during filling, the outlet is often “in sight” directly from the injection point: in other words, the explosion develops unidirectionally and progressively from the ignition point to the outlet. The gas is therefore only very partially confined, and the shape of the explosion chamber limits the range of gases that can be used: chambers with a larger opening are dedicated to gas mixtures heavier than air (e.g. propane and oxygen), and those with a smaller opening are dedicated to gas mixtures lighter than air (e.g. hydrogen and oxygen). In addition, injection and ignition times must therefore be fast to avoid losses.

SUMMARY

The present invention aims to address the above-mentioned drawbacks by providing an injection chamber suitable for all types of gas mixtures, regardless of their density, while improving the power of the shock wave generated.

To this end, the object of the invention is an explosion chamber for an avalanche triggering system, the explosion chamber comprising:

• • a lower half-chamber closed at its lower end and comprising an opening at its upper end,
  • an upper half-chamber extending above the lower half-chamber, closed at its upper end and comprising an opening at its lower end.

According to the invention, the lower end of the upper half-chamber extends around the upper end of the lower half-chamber, or the upper end of the lower half-chamber extends around the lower end of the upper half-chamber, so as to create at least one gas flow channel between the inside and the outside of the explosion chamber, which air channel comprises at least one baffle formed by the lower end of the upper half-chamber and the upper end of the lower half-chamber.

The result is an explosion chamber which is closed at the upper part and the lower part. With this type of confinement, all types of explosive gas mixtures are compatible with this enclosure, whether heavy or light. This further ensures better maintenance of the gas mixture during the injection phase thereof prior to ignition, particularly with respect to the outside wind, and enables longer procedure times.

Moreover, such an architecture constrains the explosion at the moment of ignition which, depending on the ignition position, can generate different rebounds and internal reflections of the shock wave, with the effect of increasing its power for the same amount of gas: the mixture is better consumed with less being simply ejected and burnt outside, as is the case with prior art enclosures.

The explosion chamber also allows the explosion to be oriented according to the interlocking of the upper and lower parts that make up this new enclosure: as one is more open than the other, it determines the orientation of the explosion as it leaves the enclosure. If the upper half-chamber is wider and covers the lower half-chamber, the explosion is directed downwards. With the reverse, the explosion could be directed upwards. Depending on the symmetry or asymmetry of the interlocking, additional orientation effects can be achieved. The assembly can also be oriented according to the desired effect.

According to other optional features of the explosion chamber, taken alone or in combination:

• • the lower half-chamber and the upper half-chamber are attached to one another by resiliently deformable means,
  • the gas flow channel extends around an entire perimeter of the explosion chamber,
  • the gas flow channel extends over part of a periphery of the explosion chamber,
  • the explosion chamber comprises several distinct gas flow channels extending around an entire periphery of the explosion chamber,
  • the upper half-chamber comprises at least one internal chimney or partition extending inside the upper half-chamber,
  • the lower half-chamber comprises at least one internal chimney or partition extending into the lower half-chamber.

Another object of the invention is an assembly formed by an explosion chamber according to the invention and an explosion chamber support.

According to other optional features of the assembly, taken alone or in combination:

• • the support and the explosion chamber are attached to one another by means of an articulated system,
  • the support is made up of several straight sections telescopically mounted together.

The invention also relates to an avalanche triggering system comprising:

• • an assembly according to the invention, and
  • at least one member for feeding a gas mixture into the explosion chamber.

According to other optional features of the avalanche triggering system, taken alone or in combination:

• • The avalanche triggering system further comprises a technical unit integrating at least one of the following elements:
  • at least one receiving member for receiving bottles of gaseous fuel and oxidizer,
  • at least one gas injection member for injecting gas inside the explosion chamber,
  • at least one control member for controlling gas injection into the explosion chamber,
  • at least one ignition member for igniting the gas mixture inside the explosion chamber,
  • the technical unit is interfaced and placed on the explosion chamber without being attached thereto.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood upon reading the following description, which is provided merely by way of example and with reference to the appended drawings, wherein:

FIG. 1 is a perspective view of an explosion chamber according to the invention,

FIG. 2 is a side view of an explosion chamber according to the invention,

FIG. 3 is a longitudinal cross-sectional view, along section plane A-A of FIG. 2, of an explosion chamber according to the invention,

FIG. 4 is a perspective view of an assembly formed by an explosion chamber according to the invention and a support,

FIG. 5 is a side view of an assembly formed by an explosion chamber according to the invention and a support,

FIG. 6 is a longitudinal cross-sectional view, along section plane B-B of FIG. 5, of an assembly formed by an explosion chamber according to the invention and a support,

FIG. 7 is an exploded view of an assembly formed by an explosion chamber according to the invention and a support,

FIG. 8 is a perspective view of an avalanche triggering system according to the invention,

FIG. 9 is a longitudinal cross-sectional view of an avalanche triggering system according to the invention, and

FIG. 10 is an exploded view of an avalanche triggering system according to the invention.

DETAILED DESCRIPTION

Reference is now made to FIGS. 1 to 3, showing an explosion chamber 2 of an avalanche triggering system. Explosion chamber is understood to mean an enclosure comprising at least one opening wherein at least one fuel, and potentially at least one oxidizer, in this case gaseous, are injected and ignited in such a way as to trigger an explosion, generating a shock wave propagating from the explosion chamber 2 and allowing the triggering of an avalanche, in particular a snow avalanche caused by the detachment of a snowpack. It would be possible to inject no oxidizer, but only one or more fuels, using the oxygen present in the air.

The explosion chamber 2 comprises a lower half-chamber 4 closed at its lower end 6 and comprising an opening at its upper end 8.

In the example shown, the lower half-chamber 4 is substantially tubular in shape. This shape could be different: it could form a cylinder with a non-circular base, a frustoconical hollow body, etc. As shown in FIG. 4, the lower half-chamber 4 can be formed by a main portion 10, here tubular in shape, and an assembly of a solid plate 12 and a first domed flange 14 forming the closed lower end 6 of the lower chamber 4. At least one first attachment flange 16 may be present, the lower half-chamber 4 being assembled, for example, by screwing or any other conventional means known to a person skilled in the art.

Alternatively, the lower half-chamber 4 could be made in one piece.

The explosion chamber 2 further comprises an upper half-chamber 18 extending above the lower half-chamber 4, closed at its upper end 20 and comprising an opening at its lower end 22.

In the example shown, the upper half-chamber 18 has the shape of a frustoconical hollow body. This shape could be different: it could form a cylinder, more particularly a tube, etc.

As can be seen in FIG. 7, the upper half-chamber 18 can be formed by a main portion 24, here of frustoconical shape, and an assembly of a second domed flange 26 and a second attachment flange 28 forming the closed lower end of the lower chamber. In the example shown, an injection hose 30 and an attachment flange of the injection hose 32 are attached to the upper end 20 of the upper half-chamber 18. In this case, a gas injection device is connected to the injection hose 30 so as to close the upper half-chamber 18. Of course, and in the case where the gases are fed into the explosion chamber 2 in some other way, the upper half-chamber 18 may not have an opening, for example by comprising a solid plate closing its upper end 22. In this example, the upper half-chamber 18 is assembled by screwing or any other conventional means known to a person skilled in the art.

Alternatively, the upper half-chamber 18 could be made in one piece.

According to the invention:

• • the lower end 20 of the upper half-chamber 18 extends around the upper end of the lower half-chamber 4, or
  • the upper end 8 of the lower half-chamber 4 extends around the lower end 20 of the upper half-chamber 18,
  • so as to create at least one gas flow channel 34 between the inside and outside of the explosion chamber 2, the gas flow channel 34 comprising at least one baffle formed by the lower end 20 of the upper half-chamber 18 and the upper end 8 of the lower half-chamber 4.

In other words, one of the two half-chambers overlaps the other without being in contact with the latter, so as to form said gas flow channel 34. This configuration allows the effects described above to be achieved. In the example shown in the figures, the half-chamber extending around the other (here the upper half-chamber 18 extending around the lower half-chamber 4) forms an outer skirt around said chamber. Together with the innermost wall of the half-chamber, this outer skirt helps to form the gas flow channel 34. The shape of this skirt, and more broadly of the outer deflectors, helps to guide the shock wave in a desired direction, in whole or in part and symmetrically or not, in order to trigger an avalanche.

Such a configuration implies that one of the two related ends is larger than the other. In the example shown, the lower end 20 of the upper half-chamber 18 is wider than the upper end 8 of the lower half-chamber 4. The reverse is also possible.

Advantageously, the lower half-chamber 4 and the upper half-chamber 18 are attached to one another by resiliently deformable means. In the example shown, the two half-chambers are attached to one another by means of a fastening member comprising fastening bars 36 and fastening nuts 38, together with spring-type return means 40. This allows the half-chambers to move relative to one another at the moment of the explosion, thereby better absorbing the forces exerted on the explosion chamber 2 when the shock wave is generated. It is therefore understood that the dimensioning of the resiliently deformable means allows deformation of the explosion chamber 2 at the moment of said explosion, while allowing a return to its resting shape after explosion. This could also allow the size of the gas flow channel 34 to be varied.

Alternatively, the two half-chambers can be attached via rigid means that prevent any deformation, for example by welding or bolting them to one another.

In the example shown, the gas flow channel 34 extends around the entire periphery of the explosion chamber 2. Depending on the desired result in terms of shock wave power and direction, it is possible to provide that:

• • the gas flow channel 34 extends over part of a periphery of the explosion chamber 2, or that
  • several distinct gas flow channels 34 extending around all or part of a periphery of the explosion chamber.

In general, the position and/or size of the gas flow channel(s) 34 is chosen based on the desired shock wave, both in terms of the power and the direction of the latter. Indeed, the total size of the opening (that is, of a single gas flow channel 34 or the sum of the gas flow channels 34) partly conditions the stress level for the gas outlet and therefore allows modulation of the shock wave power. As far as direction is concerned, it is understood why the position of the gas flow channel(s) 34 determines the latter.

Advantageously, the upper half-chamber 18 and/or the lower half-chamber 4 comprises at least one internal chimney or partition, extending, for example, from its closed end to the interior of said half-chamber or even the other half-chamber. Such a configuration makes it possible to increase the effects of an explosion by refining the orientation of the shock wave, further increasing the stresses on the explosion by generating more rebounds and internal reflections of the shock wave in order to increase its power with an equivalent amount of gas.

The explosion chamber 2 can be formed by two half-chambers made of metal, for example steel, or made of plastic. The shapes of the two half-chambers can be identical or different, as can the materials used to form them.

The explosion chamber 2 may comprise elements to facilitate access to the latter, means for evacuating water ingress, points for securing operators, means for guiding on its support and/or for accommodating a technical unit, etc.

Advantageously, the explosion chamber 2 can be equipped with a handling and/or gripping device. This device can be manual or automatic.

As can be seen from FIGS. 1 to 7, the explosion chamber 2 can further comprise a deflector 39, positioned in the example shown at the lower end 6 of the lower half-chamber 4. This allows the shock wave to be directed in the desired direction, in whole or in part and symmetrically or not, in order to trigger an avalanche. The positioning and shape of the deflector 39 can of course be different from the example shown, while retaining the function of guiding at least part of the shock wave generated by the explosion chamber 2.

Another object of the invention is an assembly 41 formed by an explosion chamber 2 according to the invention and an explosion chamber support 42. This assembly 41 is shown in FIGS. 4 to 7.

The explosion chamber 2 can be fixedly connected to the ground by a support 40, for example a grounded foot system, vertical or otherwise, and connected at a point on the explosion chamber 2, for example at the lower half-chamber 4. This connection can be rigid or articulated to allow a sweeping movement (obtained by the asymmetry of the aforementioned interlocking) during the explosion to better diffuse the shock wave emitted by the explosion.

As an alternative to a fixed connection, the explosion chamber 2 can be installed/embedded via the corresponding parts on a support 42, itself grounded to the ground and allowing seasonal helicopter transportation.

Alternatively, the explosion chamber 2 can be part of a complete system that can itself be transported by helicopter or transported under a cable or pipeline.

In short, the assembly 41 may or may not be removable, and may be transportable by helicopter in one or more parts. It can be made of steel, plastic or any other material.

The assembly 41 can be positioned vertically on a mountainside or inclined in any direction, particularly toward the slope, by being attached directly or by any structure allowing it to be connected to the ground.

Advantageously, the support 42 is formed by several straight sections 44 telescopically or slidably mounted together, for example on a mounting plate 45. Once again, this allows better absorption of the stresses exerted by the shock wave, this time on the assembly 41. More generally, it is advantageous for the support 41 to allow movement of the explosion chamber so as to absorb some of the energy and/or limit stress on the civil engineering structures. This movement can also be used to generate vibrations in the ground to increase the efficiency of the system. Alternatively, and if desirable, it is possible to provide a support that does not allow such vertical movements.

The assembly 41 can be held in place by its own weight or via external means.

The support 42 may comprise a connecting plate 47 attached to a section 44 so as to create an attachment interface with the explosion chamber 2, for example with the lower chamber 4. Rib-forming lugs 49 are arranged at the connection between the section 44 and the connecting plate 47 to reinforce this connection. Such lugs 49 can also be arranged at the plate 45.

A further object of the invention is an avalanche triggering system 46 (visible in FIGS. 8 to 10) comprising:

• • an assembly 41 according to the invention described above, and
  • at least one member for feeding a gas mixture into the explosion chamber.

The member for feeding a gas mixture may, for example, comprise one or more hoses for feeding gas from one or more remote tanks to the assembly 41, and more particularly to the explosion chamber 2.

The explosion chamber 2 may in this case comprise a member for connecting the hose(s) to the assembly, as well as elements for igniting a gas mixture or monitoring the avalanche triggering system 46, for example via sensors.

Advantageously, the avalanche triggering device 46 can comprise a removable technical unit 48, generally installed and interfaced on the upper half-chamber 18. In this specific case, the upper end 20 of the upper half-chamber 18 is open without the placement of the technical unit 48, which closes the upper end 22 of the explosion chamber 2.

The technical unit 48 can be attached to the explosion chamber 2 or simply placed in a movable manner on the latter. A movable placement allows a relative movement of the technical unit 48 with respect to the explosion chamber 2, in particular at said explosion, so as to improve the resistance of the avalanche triggering system 46 over time.

The technical unit 48 may comprise at least one of the following elements:

• • Receiving members 50 for receiving bottles 51 of gaseous fuel and oxidizer.
  • At least one member for injecting gas inside the explosion chamber 2. For example, it may be a diffusion chamber secured to a frame 52, receiving gases from the receiving members 50 and having one end extending into the explosion chamber 2 so as to inject the received gases therein.
  • At least one member for controlling gas injection into the explosion chamber 2. This control member comprises, for example, a power generation member configured to supply electrical power to the equipment, and/or an electrical power storage element configured to store said electrical power, and a communication element configured to exchange instructions with an external control unit. The control member can be configured to control at least one ignition member.
  • At least one ignition member for igniting the gas mixture inside the explosion chamber 2. The latter therefore allows an explosion of the gas mixture to be triggered. In particular, the ignition of the ignition member can be controlled by the control member, and particularly based on instructions communicated by the communication element and/or measurements made by one or more physical sensors, for example a thermometer, an accelerometer, a seismometer or an anemometer.

All these elements can be assembled on a frame 52.

The technical unit 48 is known from the prior art and is described in document WO 2021/255370 A1. It will not be described in greater detail here.

LIST OF REFERENCES

• • 2: explosion chamber
  • 4: lower half-chamber
  • 6: lower end of the lower half-chamber
  • 8: upper end of the lower half-chamber
  • 10: main portion of the lower half-chamber
  • 12: solid plate
  • 14: first domed flange
  • 16: first attachment flanges
  • 18: upper half-chamber
  • 20: upper end of the upper half-chamber
  • 22: lower end of the upper half-chamber
  • 24: main portion of the upper half-chamber
  • 26: second domed flange
  • 28: second attachment flange
  • 30: injection hose
  • 32: attachment flange of the injection hose
  • 34: gas flow channel
  • 36: fastening bars
  • 38: fastening nuts
  • 39: deflector
  • 40: spring
  • 41: assembly
  • 42: support
  • 44: sections
  • 45: mounting plate
  • 46: avalanche triggering system
  • 47: connecting plate
  • 48: technical unit
  • 49: lugs
  • 50: receiving member
  • 51: bottle
  • 52: frame