WO2012016550A2

WO2012016550A2 - Method of production of artificial snow and apparatus for carrying out this method

Info

Publication number: WO2012016550A2
Application number: PCT/CZ2011/000073
Authority: WO
Inventors: Adéla VORÁČKOVÁ
Original assignee: Vorackova Adela
Priority date: 2010-08-02
Filing date: 2011-07-28
Publication date: 2012-02-09
Also published as: CZ2010594A3; SI2601462T1; CZ304511B6; WO2012016550A3; PL2601462T3; EP2601462B1; EP2601462A2

Abstract

The invention deals with the problem of production of artificial snow (7) by means of snow guns (1,2, 2') when the streams of water (5, 5') or drops of water in a stream of water or water fog (6) leaving the output of the snow gun (1, 2, 2') crystallize after landing on the landing area (3) where they either crystallize in a large piece of ice resulting in creation of dangerous icy plates in the neighborhood of snow guns (1, 2, 2') or they fail to crystallize and flow away. The subject matter of the invention consists in creation of at least one impact area (4) in the distance of at least 2 m from the output of a snow gun (1, 2, 2') between the output of at least one snow gun (1, 2, 2') and the landing area (3). The individual streams of water (5, 5') and/or drops of water carried in a stream of air and or droplets of water fog (6) are directed in the impact area (4) so that they hit each other and/or a fixed obstacle to reduce their internal energy and on the route between the impact area (4) and landing area (3) they subsequently crystallize in their whole volume and form artificial snow (7) falling on the landing area (3) in a fully crystallized state. Artificial snow (7) produced according to this method does not form icy plates, is easy to manipulate with and can be stored in piles when it is maintained in a loose state.The apparatus for production of artificial snow (7) can be formed by a tubular snow gun (1) with a fan (8) and nozzles (9) provided with a routing extension (10) or with a routing mouth (11) to direct the output in the impact area (4). The apparatus for production of artificial snow (7) can also be formed by a tubular snow gun (1) or a shower snow gun (2, 2') provided with a hydrophobic sieve (12). The impact area (4) can also be created by directing the streams of water (5, 5') from two shower snow guns (2, 2') against each other.

Description

Method of production of artificial snow and apparatus for carrying out this method

Field of the invention

The present invention relates to a method of production of artificial snow and to an apparatus for carrying out this method especially for down-hill or cross-country skiing and for other winter sports.

Background and summary of the invention

Artificial snow is made by spraying water from nozzles of a machine commonly designated as "snow gun". Small drops freeze in ambient air the temperature of which must be under 0°C to allow the small drops to fall on the ground in the form of ice crystals. The ambient temperature influences positively creation of the ice crystals. The colder is the ambient air, the more efficient is the snow gun.

At present there are two principal types of snow gun for production of artificial snow: the stick snow gun, called also "shower" according to the principle of its function and its design. Water is sprayed by fine nozzles in the cold ambient air. The second type is a tube type snow gun provided with nozzles and a fan blowing the water drops away from the nozzles in the ambient air. The fan creates a stream of air carrying the drops long enough to cause them to freeze before they fall on the ground. This property allows for the mobility of this type of the snow gun restricted solely by the length of the water conducting pipe and the length of the electrical cable supplying electric energy to the engine of the fan.

It is characteristic of the stick snow gun that the nozzles are placed at a stationary stick 6 to 11 m high. The pressure of the water distribution network in the proximity of the snowed area is applied the value of which is from 1 to 9 MPa. The disadvantage of this type of snow guns consists in their stationary placement, its function being dependent on the direction and speed of wind which can blow the produced snow away from the target area. Its advantage lies in the fact that the stick snow gun does not need a supply for electric energy.

In the system of tubular shape snow guns provided with a fan and nozzles, water is supplied from the water distribution network in the neighborhood of the snowed area the pressure of the connecting points having the value of 0,8 to 5 MPa. The snow gun has a tubular shape with a relatively large diameter (about 50 cm) and inside the tubular body there is placed a fan powered by an electrical motor sucking the air and blowing it out at a high speed. In the mouth there is placed a large number of water nozzles. Water is sprayed into the stream of air made by the fan the stream of air carrying the drops long enough to make them freeze. The disadvantage of this type of snow gun is the need of electric energy for the propulsion of the fan. The advantage of this type of snow gun is its mobility.

Low efficiency is the disadvantage of both types of snow guns.

The efficiency of the above described types of snow gun is reduced by a physical property of water, which allows for its undercooling. In nature, under normal conditions, spontaneous crystallization of water contained in a cloud occurs at a temperature of about -15°C. But in practice it is necessary to produce high-quality artificial snow under much higher temperatures, amounting to about 0°C. However in these higher temperatures non-crystallized drops of water flow off in fluid state or crystallize after they fall on the ground and form a layer of ice there, which is dangerous because ice is harder than beaten snow. Falls and injuries of athletes occur on such places. The behavior of undercooled water after hitting the ground depends on ambient temperature.

All of the following patents teach the increase in efficiency of the known snow guns by production of crystallizing nuclei.

Document WO01/86216 is an improvement to the basic type of the shower snow gun. It uses a turbine which sucks and compresses ambient air which is subsequently propelled to the output mouth set with nozzles spraying pressured water to the expanding air cooled by the expansion, which allows for the production of artificial snow even when the ambient air temperature is higher than 0°C. The disadvantage of this solution is the need of supply of compressed air as well as the complicated construction and price of such device.

Document WO96/09505 describes the principle of production of artificial snow by means of two types of nozzles. External high pressure nozzles create special microclimate rich in crystallizing nuclei to which drops sprayed from internal nozzles freeze. Disadvantage of this solution is that it is not guaranteed that the whole mass of the blown water fog will be mixed sufficiently with crystallizing nuclei. Mixing of drops of water in water fog with crystallizing nuclei is the important principle increasing the efficiency of the snow gun. Its disadvantage may be the complicated construction and price. Document W097/26493 discloses nozzles and the angles of their placement according to the longitudinal axis of the air streaming from the fan described in WO96/09505.

WO2009/018319 describes the principle of production of artificial snow when crystallizing nuclei created by means of expansion of a mixture of air and water compressed beforehand in special nozzles are injected in the stream of air. Drops propelled in the stream of the air from common nozzles at the end of the tubular body freeze to these crystallizing nuclei. Special nozzles for creation of crystallizing nuclei are located at the output part of the tubular body of the snow gun in the center of the stream of the air propelled by the fan situated at the input edge of the tubular body of the snow gun.

WO2009/125359 uses for production of crystallizing nuclei special nozzles placed at the output edge of the tubular body of the snow gun. These nozzles are set on the same circle of the pipe as the nozzles spraying water in the stream of air propelled by the fan placed at the input part of the snow gun.

Document WO95/04906 describes a method of production of artificial snow by means of a snow gun provided with a fan, the snow gun comprising two types of nozzles. At the output edge of the conical body of the snow gun there are nozzles mounted spraying water in the stream of air sucked by the fan placed on the input part of the snow gun, the stream of air being enriched by crystallizing nuclei produced by high pressure nozzles mounted in the center of the body of the snow gun.

The disadvantage of the above stated inventions is the complicated construction of the crystallizing nuclei nozzles and the requirements on material from which they are made. The requirement on the high quality of the purity of water supplied to the crystallizing nuclei nozzles. Their fine diameter could be plugged, which could even destroy the nozzles. To reach the necessary quality of water is demanding and requires regular checking and careful maintenance of the filters.

Document WO2008/075689 deals with subcooling of the supplied air which is sucked by the fan of the snow gun, after which water is sprayed into it to freeze and form artificial snow. The disadvantage of this invention consists in the need of an apparatus for subcooling the air that is supplied in the gut.

Inventions known from the present state of the art solve the difficulty concerning subcooling water during production of artificial snow by producing crystallizing nuclei by means of compressing and subsequent expansion of the air. During the expansion the air is cooled, which enhances the formation of crystallizing nuclei necessary for creation of snowflakes.

All the above referenced methods and apparatuses for enhancement of efficiency of snow guns aim at production of crystallizing nuclei to increase the efficiency of snow guns. The above referenced patents solve the problem by reducing the temperature of the air, in which the crystallizing nuclei are created. The disadvantage common to all solutions cited in the state of the art consists in the fact that despite the increase in efficiency of the snow guns to a certain degree, such snow guns are complicated to construct and expensive and the problem of creation of ice plates nearby the snow guns resolved.

The object of this invention is to create a method of production of artificial snow and an apparatus for carrying out this method which would eliminate the above cited deficiencies, would impede the creation of ice plates in the vicinity of snow guns and would improve operation of the snow gun under temperatures in the scale from -1°C to -15°C.

Summary of the invention

A method of production of artificial snow and an apparatus for carrying out this method eliminates to a high degree the deficiencies of above described methods and apparatuses for production of artificial snow.

The present invention addresses the problem of crystallization of water drops in a different physical way than the inventions cited above. The cited inventions deal with the problem of crystallization by reducing the temperature of the air and/or the water fog in which the crystallization nuclei are created. In the present invention the supercooled water is taken its heat by a mechanical motion.

The invention applies a physical property of water which is its instability in a supercooled state when only a small movement in a given volume of water suffices to induce a spontaneous crystallization.

The movement inside the drops of water is ensured by directing all drops leaving the snow gun in one spot in a certain distance from the output mouth of the snow gun where the drops hit each other. The impact provokes movement in the given volume which takes sufficient amount of internal energy and induces the process of spontaneous crystallization. The object of the present invention is the method of production of artificial snow which consists in the fact that at least one impact area is created between the output nose and the landing area. In the impact area individual streams of water and/or drops of water carried in the stream of the air and/or droplets of water fog in a supercooled state are directed. They are guided to hit into one another and/or in a fixed obstacle, which takes away their internal energy keeping them in a liquid state. The internal energy keeps the atoms in a grid far enough to maintain the water liquid. The movement of the liquid in a given volume causes the release of this energy. Because the temperature of water in a drop is lower than 0°C, the crystallization process is induced releasing the surplus heat, heating the drop of water. During the flight in cold air the crystallizing heat is taken by the environment and the drop crystallizes properly and lands in the form of a snow flake. This method causes the water drops to crystallize in full volume on their route between the impact area and landing area and to form artificial snow landing on the landing area in fully crystallized state. This method impedes the water drop to lose its surplus heat after hitting the ground where it would crystallize with other drops in the form of ice (ice plates) or flows away when the ambient temperature is that high (even though under the freezing point) that there is so much heat released by crystallization that the temperature of the water/drop gets above 0°C and the drop will not freeze, which is the disadvantage of all presently known methods of production of artificial snow and snow guns for its production.

In an advantageous embodiment of the method according to the invention the stream leaving the output of a tubular snow gun provided with a fan and nozzles is guided in the impact area by means of a routing extension arranged at the output of the snow gun or by means of a routing mouth of the snow gun. This solution does not require new snow guns to be produced. The extensions are easily mounted on existing snow guns, which saves costs to owners of ski resorts and other winter sport resort regions where the need arises to supply artificial snow.

In another advantageous embodiment of the present invention the outputs of at least two shower snow guns are oriented in such manner that the streams of water leaving them meet in the impact area. Even this embodiment applies existing apparatuses for production of artificial snow, eliminating the necessity to invest in new types of snow guns.

There is also advantageous a method of production of artificial snow according to the present invention when a fixed obstacle in the impact area is formed by a hydrophobic sieve. This means can be used for both above cited types of snow guns, i.e. for both the tubular snow gun with a fan and shower snow guns. A subject of the present invention is also an apparatus for production of artificial snow applying at least one snow gun with a fan and nozzles the subject matter of which consists in the fact that at least one snow gun comprises a means for creating an impact area for individual streams of water and/or drops of water carried in the stream of air and/or droplets of water fog to hit each other or to hit in a fixed obstacle and the impact area extending between the output of a snow gun and the landing area in the direction of at least 2 m from the output of a snow gun. This secures that the crystallization heat will be taken from the drops of water, falling afterwards on the ground as small crystals of ice. Artificial snow of high quality is thus produced which can be easily manipulated with, e.g. it can be transported to areas with lesser snow coverage where due to technical reasons snow guns cannot be installed. The quality artificial snow produced by means of the apparatus according to this invention can also be stored in piles on an appropriate location.

In an advantageous embodiment of the apparatus according to the present invention the means for creating the impact area is formed by a routing extension arranged on the output of a snow gun provided with a fan and nozzles, the routing extension being of a conical shape and in its central area being provided with at least one reflective body to direct the water fog from the center of the output of the snow gun in the direction of the walls of the routing extension. The extension guiding the stream of drops is very easy to construct and it is not demanding on the choice of material. The main advantage of the routing extension is that it is applicable on existing tubular snow guns with a fan.

In another advantageous embodiment of the apparatus according to the present invention the means for creating the impact area is formed by a routing mouth with at least two guiding slots and with a reflective body for directing the water fog in the directing slots and the routing mouth is arranged on the output of a tubular snow gun provided with a fan and nozzles. The guiding slots can also advantageously be provided with movable flaps to allow for directing individual streams of drops of water carried in the stream of air and/or droplets of water fog in the impact area in variable distance from the routing mouth of the snow gun in dependence on the temperature of the ambient air. The routing mouth can be also applied on existing snow guns.

Thus it is possible to modify the distance of the impact area from the routing mouth in dependence on the temperature of ambient air.

It is also advantageous that the guiding slots are formed with a possibility to change the angles of the output of the drops of water in the stream of air or water fog from the routing mouth of the snow gun. A greater precision of the trajectory of the water drops thus can be achieved.

It is also advantageous that the routing extension or the routing mouth are provided on the walls of the reflective body with guiding grooves to guide the drops in the stream of air or water fog. The precision of their flight trajectory is thus increased to reach the impact area with greater precision, which allows for the reduction in size of the impact area. The drops are thus not dispersed which could cause their failure to hit into each other.

In further advantageous embodiment of the apparatus according to the present invention the means for creating the impact area is formed by at least one hydrophobic sieve arranged between the output of a tubular snow gun or a shower snow gun and the landing area.

In another advantageous embodiment of the apparatus according to the present invention the means for creating the impact area is formed by a set of at least two shower snow guns the outputs of which are oriented so that the streams of water or water drops leaving them meet in the impact area.

The advantages of the present invention consist in that it significantly improves the efficiency of existing snow guns of all types, quality of artificial snow is also improved without an increase in the costs of its production for owners or operators of winter sports resorts. It it particularly advantageous that ice plates do not occur beneath snow guns and the artificial snow produced according to the present invention is easy to manipulate and easy to store in piles.

Brief description of the drawings

The invention will be explained in detail by means of the drawings on which Fig. 1 shows a schematic side view of a snow gun with a fan and nozzles, with a mounted routing extension directing the stream of water fog into the crashing area, fig. 2 shows a front view of the routing extension, fig. 3 a side view of the routing extension, fig. 4 a rear view of the routing extension, fig. 5 a rear view at the routing mouth of a tubular snow gun fitted with two guiding slots, equipped with routing flaps, fig. 6 a side view of the routing extension, fig. 7 a front view of the routing extension, fig. 8 a detail of routing flaps, fig. 9 a side view of two shower snow guns on one carrier pillar, with outputs directed in the crashing area, fig. 10 a rear view of a shower snow gun shown in fig.9, fig. 11 a side view of a shower snow gun with a hydrophobic sieve, fig. 12 a rear view on a shower snow gun with a hydrophobic sieve, fig. 13 a plan view of a hydrophobic sieve with a structure, fig.14 a side view of the hydrophobic sieve with a structure. Preferred embodiments of the invention

The below described and depicted particular examples of the invention embodiments are considered illustrative and they in no way limit the invention embodiment to the examples herein presented. Professionals in the technology sphere will find or will be able to find more or fewer equivalents to the specific embodiments of the invention herein described in their routine experimental work. These equivalents will also be included in the following claims.

Example 1

Fig. 1 and fig. 2 show a classical tubular snow gun 1 with a fan 8 situated on the air input 18 side and nozzles 9 mounted in a circle on the inner perimeter of the output mouth. Water supply 19 is brought to the nozzles 9. The routing extension 10 is mounted on the output of the tubular snow gun 1. The routing extension 10 is made of metal sheet or plastic. The routing extension 10 extends the tubular mouth of the snow gun 1, is hollow and is conically narrowed in the direction from the mouth of the snow gun 1. The central part of the routing extension 10 is filled by the reflective body 15 also made from metal sheet or plastic, having the shape of a rotary body, an ellipsoid in this case. The reflective body 15 is fastened to the casing by means of four bracings 20. Its convex ellipsoid surface is situated against the output of the snow gun 1 from which the fine droplets of water fog 6 leave. The stream of water fog 6 or the stream of drops of water in the stream of air has a circular cross section but after hitting the convex surface of the reflective body 15 it assumes the shape of an annulus and is guided between the casing of the routing extension 10 and the surface of the reflective body 15 with guiding grooves 17 to the output of the routing extension 10 from which it also leaves as an annulus but due to the conical shape of the routing extension 10 the diameter of the annulus gradually diminishes resulting in the water fog 6 or drops of water in the stream of air hitting in each other in the impact area 4. In the impact area 4 the decrease in internal energy of drops of water hitting each other occurs and the crystallization begins, accompanied by the release of heat. Subsequently, the drops of water are further cooled on their trajectory between the impact area 4 and landing area 3 so that they fall fully crystallized as artificial snow 7 of quality on the landing area 3.

In another not depicted embodiment a hydrophobic sieve 12 can be fixed in front of the snow gun 1 to form a fixed obstacle in the impact area 4 inducing the same effect as when the drops hit each other. Example 2

The tubular snow gun 1 described in the first preferred embodiment and depicted in fig. 1 is not provided with the routing extension 10 but with a routing mouth 11 made of metal sheet or plastic and shown in fig. 5 to fig. 8. The routing mouth 11 has a similar function as the routing extension 10, but it does not have a conical but a circular shape on the side that extends to the snow gun 1 with a fan 8 and nozzles 9 and on its output side there are guiding slots 13, 13'. Inside the body of the routing mouth 11 is a reflective body 15 to guide the water fog 6 or drops of water in the stream of air in two guiding slots 13, 13' of a rectangular shape, slanted under such angle to cause the outputs of water fog 6 or drops of water in the stream of air leaving the guiding slots 13, 13' meet in the impact area 4 where they hit each other. The process of crystallization of the artificial snow 7 before landing on the landing area 3 is the same as in example 1. To regulate simply the distance of the impact area 4 from the snow gun 1 the guiding slots 13, 13' are provided by routing flaps 14, 14' pivotally mounted on pivot hinges 22 and provided with set screws 23 by means of which the angular setting of the routing flaps 14 is possible, which regulates the distance of the impact area 4. The distance of the impact area 4 from the output of the snow gun 1 is set in dependence on the temperature of the ambient air.

Example 3

Fig. 9 and fig. 10 show another embodiment of the present invention, where artificial snow 7 is produced by means of two shower snow guns 2, 2', the arms of which are fixed in one carrier pillar 24, which is advantageous due to common water supply. The heads with nozzles of the snow guns 2, 2' are oriented so that the streams of water 5, 5', drops of water respectively, meet in the impact area 4 situated above the landing area 3. In the impact area the internal energy of drops of water hitting each other is reduced, and the process of crystallization begins followed by the release of heat. Subsequently, the drops of water are cooled on their trajectory from the impact area 4 to the landing area 3 and they land in the form of quality artificial snow 7 with required properties.

Example 4

In this embodiment as shown in fig. 11 to 14 application of a fixed obstacle in the impact area is shown that is to reduce the internal energy of drops of water. A hydrophobic sieve 12 forms the fixed obstacle fixed in front of the output of the shower snow gun 2. The hydrophobic sieve 12 can be fixed in a similar way in front of the tubular snow gun 1 as we described in example 1. The hydrophobic sieve 12 is preferably made from plastic or from metal provided with a surface treatment. It is fixed to the shower snow gun 2 by means of a bearing structure 25 with an upper sleeve 26 and a button sleeve 26' in a position between the head with nozzles of the shower snow gun 2 and the landing area 3. The stream of water 5, drops of water respectively, hits the sieve and is sprayed by the impact on the meshes of the sieve 12. The internal energy of individual drops of water is not reduced by the impact caused by the drops of water hitting each other but first due to the impact of the drops of water on the fixed obstacle, the hydrophobic sieve 12 in this embodiment of the invention. The process of crystallization is similar as in the previous embodiments of the invention, i.e. after the internal energy is reduced due to the movement of water in the volume of the given drop, the crystallization process begins by the release of heat. The drops are further cooled on their trajectory from the impact area 4 to the landing area 3 and land in the form of artificial snow, crystallized in their whole volume. It is evident that the fixed obstacle is not limited only to the hydrophobic sieve 12 and can be formed by other devices.

Industrial applicability

Method of production of artificial snow and apparatus for carrying out this method according to this present invention can be applied for production of artificial snow in winter sports resorts for skiing, snowboarding, tobogganing etc. and anywhere where the need is to create artificial snow the properties of which would be similar to natural snow.

List of references used in the drawings

1 tubular shape snow gun with fan and perimeter nozzles

2 Shower snow gun

2^' Shower snow gun

3 landing area

4 impact area

5 Streams of water (drops of water)

5 ' Streams of water (drops of water)

6 fine drops of water in air stream or water fog

7 artificial snow

8 fan

9 nozzles

10 routing extension snow gun

11 routing mouth

12 hydrophobic sieve

13 guiding slot

13' guiding slot

14 routing flap

14' routing flap

15 reflective body

17 guiding groove

18 air (supply)

19 water (supply)

20 bracing

22 pivot hinges

23 set screw

24 carrier pillar

25 bearing structure

26 upper sleeve

26' button sleeve

Claims

PATENT CLAIMS

1. Method of production of artificial snow (7) by spraying of water or water in a stream of air by means of at least one snow gun (1, 2, 2') on a landing area (3) characterized in that at least one impact area (4) is created in the distance of at least 2 m from the output of a snow gun (1, 2, 2') between the output of at least one snow gun (1, 2, 2') and the landing area (3); the individual streams of water (5, 5') and/or drops of water carried in the stream of air and or droplets of water fog (6) are directed in the impact area (4) so that they hit each other and/or a fixed obstacle to reduce their internal energy and on the route between the impact area (4) and landing area (3) they subsequently crystallize in their whole volume and form artificial snow (7) falling on the landing area (3) in a fully crystallized state.

2. Method of production of artificial snow according to claim 1 characterized in that the stream leaving the output of a tubular snow gun (1) provided with a fan (8) and nozzles (9) is guided in the impact area (4) by means of a routing extension (10) arranged on the output of the snow gun (1) or by means of a routing mouth (11) of the snow gun (1).

3. Method of production of artificial snow according to claim 1 characterized in that the outputs of at least two shower snow guns (2, 2') are oriented in such manner that the streams of water (5, 5') leaving them meet in the impact area (4).

4. Method of production of artificial snow according to claim 1 characterized in that a fixed obstacle in the impact area (4) is formed by a hydrophobic sieve (12).

5. An apparatus for production of artificial snow (7) in outdoor environment by spraying water by means of at least one snow gun (1, 2, 2') on a landing area (3) characterized in that at least one snow gun (1, 2, 2') comprises a means for creating an impact area (4) for individual streams of water (5, 5') and/or drops of water carried in the stream of air and/or droplets of water fog (6) to hit each other or to hit a fixed obstacle and the impact area (4) extending between the output of a snow gun (1, 2, 2') and the landing area (3) in the direction of at least 2 m from the output of a snow gun (1, 2, 2').

6. Apparatus according to claim 5 characterized in that the means for creating the impact area (4) is formed by a routing extension (10) arranged on the output of a snow gun (1) provided with a fan (8) and nozzles (9), the routing extension (10) being of a conical shape and in its central area being provided with at least one reflective body (15) to direct the water fog (6) from the center of the output of the snow gun (1) in the direction of the walls of the routing extension (10).

7. Apparatus according to claim 5 characterized in that the means for creating the impact area (4) is formed by a routing mouth (11) with at least two guiding slots (13, 13') and with a reflective body (15) for directing the water fog (6) in the guiding slots (13, 13') and the routing mouth (11) is arranged on the output of a tubular snow gun (1) provided with a fan (8) and nozzles (9).

8. Apparatus according to claim 7 characterized in that the guiding slots (13, 13') are formed with a possibility to change the angles of the output of the drops of water in the stream of air or water fog (6) from the routing mouth (11) of the snow gun (1).

9. Apparatus according to at least one of claims 6 to 8 characterized in that the routing extension (10) or the routing mouth (11) are provided on the walls of the reflective body (15) with guiding grooves (17) to guide the drops of water in the stream of air or water fog (6).

10. Apparatus according to claim 5 characterized in that the means for creating the impact area (4) is formed by at least one hydrophobic sieve (12) arranged between the output of a tubular snow gun (1) or a shower snow gun (2, 2') and the landing area (3).

11. Apparatus according to claim 5 characterized in that the means for creating the impact area (4) is formed by a set of at least two shower snow guns (2, 2') the outputs of which are oriented so that the streams of water (5, 5') or water drops leaving them meet in the impact area (4).