EP1114287A1

EP1114287A1 - Snowmaker

Info

Publication number: EP1114287A1
Application number: EP99946082A
Authority: EP
Inventors: Olivier Seuret
Original assignee: Dicc Realisation Sa; Dicc Realisation S A; Dicc Realisation SA
Current assignee: Dicc Realisations Sa
Priority date: 1998-09-11
Filing date: 1999-08-31
Publication date: 2001-07-11
Anticipated expiration: 2019-08-31
Also published as: FR2783310A1; ATE220193T1; WO2000016026A1; DE69902048D1; FR2783310B1; EP1114287B1

Abstract

The invention concerns a snowmaker including a hollow body (1) comprising a mixing and expansion chamber (2) defined by a peripheral wall (3) and communicating with outside through a ring-shaped coaxial outlet (4) around a central core (26). Water is introduced under pressure into the mixing and expansion chamber (2) through a plurality of helical ducts (6, 7) peripherally distributed about the longitudinal axis (I-I) to inject water along the peripheral wall (3) with a rotating motion. The pressurised air is introduced in the mixing and expansion chamber (2) in a central zone in one or several jets directed obliquely towards the peripheral wall (3) through a plurality of divergent air passages (11, 12). Such a snowmaker structure enables to produce quality snow from water and air at a lower pressure then in known snowmaker structures.

Description

The present invention relates to snow cannons for the production of artificial snow by spraying a mixture of air and water. The development of winter sports has given rise in recent years to the need to produce artificial snow to charge or recharge the ski slopes during periods of insufficient snowfall.

To date, three main families of snow cannons have been developed for the production of artificial snow.

According to the first family, there is at a sufficient height above the ground, at the end of a pole, at least one air spray nozzle and an adjacent water spray nozzle. Air and water mix in the atmosphere and form fine droplets which turn to snow before reaching the ground. According to the second family, water spray nozzles project fine droplets into a flow of air produced by a fan.

According to the third family, a two-fluid gun has a mixing chamber in which air and water are sprayed, and the mixture leaves the mixing chamber through an outlet orifice. This third family is for example illustrated by document EP 0 018 280. In such a two-fluid gun, a hollow body comprises a mixing chamber limited by a coaxial peripheral wall and communicating with the outside by an axial outlet orifice. Air intake means inject compressed air into the mixing chamber. Water intake means inject water under pressure into the mixing chamber. The mixing chamber is an elongated tube, with a section much smaller than the section of the air supply and water supply pipes.

In this third family of two-fluid gun, the document DE 29 41 052 A teaches to mix air and water in a mixing and compression chamber limited by two conical inner and outer coaxial walls converging. By their converging conical shape, the walls of the mixing chamber gradually compress water and air during their mixing. Water is injected in several peripheral jets, according to a rotary movement. The air is injected from the conical inner wall of the mixing and compression chamber, in several jets in substantially longitudinal directions. The mixing chamber is connected directly to the outlet orifice, by its zone of smaller section, without additional narrowing.

The documents FR 2 376 384 A and JP 06 074627 A also teach to mix air and water in a conical mixing and compression chamber.

In document EP 0 084 186 A, the water enters a mixing chamber according to an annular flow regularly distributed around the axis, and receives diverging air jets. The mixture is suddenly compressed by an annular collar engaged in the outlet passage.

The devices of the first family, ensuring a high spraying at the end of a pole, need an inlet air pressure of 8 to 10 X 10 ⁵ Pa, and a water pressure of at least 16 to 20 X 10 ⁵ Pa. Spraying at height often leads to dispersing the snow outside the runway surface to be recharged, in the event of wind, even a weak one. The support structure necessary to hold the pole leads to a unitary installation whose weight is generally greater than 100 kilograms.

The second family fan gun devices can deliver 400 to 800 liters of water per minute for a unit installation weight of 400 to 1000 kilograms. These devices also require an inlet water pressure of between 16 and 20 X 10 ⁵ Pa approximately, as well as an electrical connection of 20 to 50 kilowatts. It is therefore necessary to provide expensive power cables to bring the energy to the snow production site. Two-fluid cannons of the document type

EP 0 018 280, DE 29 41 052 A, FR 2 376 384 A, JP 06 074627 A or EP 0 084 186 A, also need a high water pressure, greater than 10 X 10 ⁵ Pa. The pressure of inlet air must be of the order of 8 X 10 ⁵ Pa. Otherwise, the production of snow is defective and the cannon mainly spits droplets of liquid water. Thus, all these known devices require a large infrastructure, most often a pumping station with high pressures at the start to guarantee a pressure of 8 to 16 × 10 ⁵ Pa at the top of the tracks. The pipes in which the fluids flow must hold pressures of more than 40 X 10 ⁵ Pa on average, which makes them heavy and expensive to purchase and to set up. The guns themselves are also heavy and bulky, difficult to transport along rugged ski slopes. The devices for producing compressed air capable of reaching the pressures necessary for the guns currently used are relatively expensive, since the pressures are higher than those of the versatile compressors generally used on construction sites for feeding jackhammers.

There is therefore a permanent need for a device for producing artificial snow which can operate with reduced air and water pressures, and which is of reduced weight and size to facilitate its transport to the snow producing areas along the ski slopes.

The problem proposed by the present invention is therefore to design a new snow cannon structure making it possible to produce good quality snow from a lower pressure of air and water at the inlet, so as to be satisfy a lighter infrastructure for the production of pressurized air and water, and so as to use lighter and less expensive air and water transport pipes.

The invention results from the surprising observation that it is possible to produce artificial snow from lower pressures of air and water thanks to a particular form of mixing chamber and of expansion of air and water, of larger diameter, in which a maximum of turbulence is created while undergoing a reduced pressure drop, and the mixture is brought out by a passage with reduced section after progressive compression.

To achieve these and other objects, the present invention provides a snow cannon for the production of snow. artificial spraying of air and water mixture, comprising a hollow body having a mixing chamber oriented along a longitudinal axis, bounded by a lateral peripheral wall and communicating with the outside by a front outlet passage, having means water inlet for injecting pressurized water into the mixing chamber in one or more preferential directional flows in the peripheral zone of the mixing chamber along the peripheral wall and in a rotary movement around the axis longitudinal of the mixing chamber, and having shaped air intake means for injecting compressed air into the mixing chamber from the central zone of the mixing chamber; according to the invention, the air intake means are shaped to inject air in the form of one or more air jets each directed to cut off one of said preferential directional flows of water; in addition, the mixing chamber comprises an upstream expansion section followed by a downstream compression section, the upstream expansion section communicating with the water intake means and with the air intake means and having a cross section greater than that of the water and air intake means to allow the expansion of the fluids during their mixing, the downstream compression section having a section which gradually decreases in the direction of the outlet to compress the mixture and drive it to the exit passage. Thanks to such a mixing chamber structure, the two-fluid gun according to the invention can be compact and light, according to a weight of 2 to 3 kilograms, which is easily moved. Such a gun is capable of operating at variable flow rates as a function of the outlet passage section, and with water inlet pressures of the order of 4 × 10 ⁵ Pa and an air pressure of order of that produced by the usual site compressors for supplying jackhammers. Under certain conditions, it is possible to snow with an inlet water pressure which can go down to around 3 X 10 ⁵ Pa. The compressed air pressure is slightly higher than that of water. According to an advantageous embodiment, in the upstream section of expansion of the mixing chamber, the lateral peripheral wall is substantially cylindrical.

Also, according to an advantageous embodiment favoring the obtaining of snowflakes at the outlet, it can be provided that, in the upstream section of expansion of the mixing chamber, the air intake means inject the air in the form of one or more jets directed obliquely towards the peripheral wall.

Preferably, in the downstream compression section, the lateral peripheral wall forms a frustoconical narrowing connecting to the outlet passage.

It is also advantageous to provide that the outlet passage is an orifice of annular shape.

Thanks to such an annular form of outlet orifice, the mixture of air and water exits through the orifice in tubular and rotating form, and it pushes the outside air forwards, inducing a central depression which favors the entry of outside air currents towards the center. This likely promotes the fragmentation of the droplets and causes better heat exchange with the outside air and the droplets. The mixture cools faster and freezes quickly before it hits the ground.

Also, as the mixture changes pressure between the mixing chamber and the outside, the air expands rapidly and separates the parts of water which are close to it. This likely promotes the formation of snowflakes.

According to one embodiment, the water intake means comprise a plurality of helical channels distributed at the periphery around the longitudinal axis, and the helical channels can be connected, upstream, to an annular water distribution chamber. communicating with a peripheral water inlet.

According to one embodiment, the air intake means can comprise a plurality of air channels. The air channels can advantageously be divergent to direct the air obliquely towards the peripheral wall. In practice, the air channels can communicate with the mixing chamber by injection orifices distributed along a ring of a rear front wall. This favors substantially the formation of snowflakes at the outlet, probably due to the swirling expansion of the fluids during their mixing in the upstream section of the mixing chamber.

According to a particular embodiment, an adjustment plate is provided pierced with an annular series of through holes, the adjustment plate coming to bear against the rear front wall and being able to be pivoted about the longitudinal axis between a position of complete opening in which each air channel outlet orifice faces a through hole in the adjustment plate, and partial shutter positions in which the adjustment plate is slightly pivoted about the longitudinal axis to offset at least partially the plate holes with respect to the outlet openings of the air channels. This creates air turbulence entering the mixing chamber, and also regulates the air flow. Indeed, in certain cases, it is useful to be able to reduce the air flow which arrives in the mixing chamber to reduce the risks of freezing at the exit of the chamber.

Preferably, the outlet passage is internally limited by the central core and is externally limited by an internal radial annular lip.

According to an advantageous embodiment, the central core is elongated longitudinally and is adjustable in longitudinal position along the longitudinal axis, and its cross section is variable longitudinally. It is thus possible to adjust to a certain extent the diameter of the mixing jet a few centimeters from the outlet, to adapt to the external conditions of humidity and temperature to optimize the quality of the snow, and to adjust the shooting distance. In this case, according to one possibility, the central core can also comprise several external radial annular ribs, of different diameters, separated by a frustoconical section.

Alternatively, the central core can advantageously be conical, allowing continuous adjustment of the section of the outlet passage.

An additional function of the central core can be obtained by providing a central core in the form of a nut reversible engaged by screwing and selectively locked in an axial position on an axial threaded rod of the body. By the same central core, it is thus possible to substantially modify the shape of the outlet passage. The larger the section of the outlet passage, the higher the possible flow rate for a given pressure of fluids at the inlet. Depending on the shape of the passage between the mixing chamber and the outlet, it is possible to create an average speed of exit of the air and water masses, of divergent or convergent shape, and thus to adapt the spraying for the formation. optimized snow and shooting distance setting.

For a given outlet passage form, it is naturally possible to modify the flow rate by varying the fluid pressure at the inlet. Also, for a given inlet pressure, it is possible to choose the shape of the outlet passage most suitable for producing quality snow as a function of external humidity and temperature conditions.

Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, given in relation to the attached figures, among which:

- Figure 1 is a side view in longitudinal section of a snow cannon structure according to an embodiment of the present invention;

- Figure 2 is an end view of the snow cannon of Figure 1; - Figure 3 is a front sectional view along the plane A-A of Figure 1; and

- Figure 4 is a top view in partial horizontal section along the plane B-B of Figure 1.

In the embodiment illustrated in the figures, a snow cannon according to the invention comprises an elongated hollow body 1, for example generally cylindrical, having a mixing chamber

2 limited by a peripheral wall 3 and communicating with

1 outside by a front outlet passage 4.

The hollow body 1 generally develops along a longitudinal axis II, the peripheral wall 3 is of revolution and coaxial around the longitudinal axis II, and the outlet passage 4 is arranged symmetrically along the longitudinal axis II. However, without significant loss of efficiency, it is possible to provide an outlet passage 4 which is off-center with respect to axis II, which is not symmetrical, and to provide a mixing chamber 2 which is not of revolution. The mixing chamber 2 comprises an upstream expansion section 201, having a cross section substantially greater than that of the outlet passage 4, and followed by a downstream compression section 202. The downstream compression section 202 has a reduced cross section , and is connected to said outlet passage 4 by forming a constriction 5, for example a frustoconical constriction as illustrated in FIG. 1. In the upstream expansion section 201, illustrated in the figures, the peripheral wall 3 is cylindrical.

In the mixing chamber 2, the water is introduced by means of water intake comprising a plurality of helical channels such as channels 6, 7, 8, 9 and 10, distributed regularly at the periphery around the axis longitudinal II. Each channel injects the water in a jet, creating in the mixing chamber 2 a directive preferential flow occupying only part of the cross section of the mixing chamber. The circulation of fluids in a cross section of the mixing chamber thus exhibits strong speed gradients. Thus, the channels 6-10 constituting the means for admitting water under pressure are shaped to inject the water under pressure according to a plurality of preferential directional flows of water in the peripheral zone of the mixing chamber 2 along the peripheral wall 3 and in a rotary movement around the longitudinal axis II of the mixing chamber 2. For example, the channels 6-10 consist of peripheral helical grooves distributed around a central cylindrical part forming an intermediate transverse wall 21 and engaged in a tube forming the peripheral wall 3.

Compressed air is introduced into the mixing chamber 2 by air intake means comprising a plurality of air channels such as channels 11, 12, 13, 14, 15 and 16, distributed in the central area of the hollow body 1 around the longitudinal axis II. For example, as shown in Figure 1, the air channels 11-16 are divergent and form an angle with the longitudinal axis II of about 15 degrees, gradually moving away from the longitudinal axis II as they approach the mixing chamber 2. Each air channel 11-16 is positioned and shaped to direct an air jet so that it cuts off one of the preferential directional flows of water.

Thus, the air intake means constituted by the air channels 11-16 are shaped to inject the compressed air from the central zone of the mixing chamber 2 according to one or more air jets directed obliquely towards the wall peripheral 3. In this way, the compressed air jets penetrate into the preferential directional flow (s) of rotary water in the upstream expansion section 201 of the mixing chamber 2.

Upstream, the helical water intake channels 6-10 connect to an annular water distribution chamber 17, externally limited by an external cylindrical wall 18 extending rearward the peripheral wall 3 of the mixing chamber 2, and internally limited by an inner cylindrical wall 19. The inner cylindrical wall 19 is connected to the outer cylindrical wall 18 upstream by a posterior crown 20, and downstream by an intermediate transverse wall 21 comprising the helical channels 6-10 and the divergent channels 11-16. In Figure 4, the outer cylindrical walls 3 and 18 are cut along the plane BB of Figure 1, while the intermediate transverse wall 21 is not cut to reveal, according to its periphery, the helical channels such as the channels helical 6 and 8.

Upstream, the air channels 11-16 are connected to an axial air supply pipe 22, externally limited by the internal cylindrical wall 19.

The axial air supply pipe 22 communicates with a central air inlet 23, while the annular water distribution chamber 17 communicates with a peripheral water inlet 24. The upstream expansion section 201 of the chamber of mixing 2 communicates with the water intake means and with the air intake means, and has an upper cross section to that of the water and air intake means, to allow the fluids to expand during their mixing.

In the embodiment illustrated in the figures, the mixing chamber 2 is limited upstream by a rear front wall 203, which is for example formed by the intermediate transverse wall 21 itself.

As can be seen in particular in FIG. 3, the air channels 11-16 communicate with the mixing chamber 2 by injection orifices distributed in a coaxial ring on the rear front wall 203.

According to an embodiment as illustrated in FIG. 1, an adjustment plate 25, pierced with an annular series of through holes, bears against the coaxial crown of the rear front wall 203. The adjustment plate 25 can be pivoted about the longitudinal axis II between a fully open position in which each air channel outlet orifice 11-16 faces a through hole of substantially the same cross section of the adjustment plate 25, and partial shutter positions in which the adjustment plate 25 is slightly pivoted about the longitudinal axis II to at least partially offset the plate holes relative to the outlet orifices of the air channels 11-16. The adjustment plate 25 thus makes it possible both to create turbulence in the air entering the mixing chamber 2, and to regulate the air flow. In the embodiment of FIGS. 1 and 2, the outlet passage 4 is an orifice of annular shape, around a central core 26. As an alternative, one could use, for example, a plurality of outlet orifices, distributed in a ring annular, or in matrix. In the illustrated embodiment, the central core 26, engaged in the outlet passage 4, comprises a first external radial annular rib 27, and a second external radial annular rib 28 of diameter greater than that of the first external radial annular rib 27 from which it is separated by a frustoconical section 29.

The central core 26 is preferably adjustable in longitudinal position along the longitudinal axis II. For example, like illustrated in FIG. 1, the central core 26 is in the form of a reversible nut engaged by screwing and selectively locked in the axial position on an axial threaded rod 30 of the body 1.

For example, the axial rod 30 is screwed into a threaded axial bore 31 of the intermediate transverse wall 21. By more or less significant screwing of the central core 26 on the threaded axial rod 30, the longitudinal position of the central core 26 is adjusted relative to an internal radial annular lip 32 of the body 1 which externally limits the outlet passage 4. Thus, the outlet passage 4 is limited externally by the internal radial annular lip 32 of the body 1, and internally by the central core 26. According to the position of the central core 26 along the longitudinal axis II, it is thus possible to modify the shape of the outlet passage 4. For example, in the position illustrated in FIG. 1, the outlet passage 4 is substantially limited by the annular lip internal radial 32 and by the first external radial annular rib 27 of the central core 26.

Preferably, the internal radial annular lip 32 is an edge limited by two faces forming between them an angle of less than approximately 110 °. This promotes abrupt swirling of the outlet fluids, for the formation of snowflakes. This effect is further increased in the presence of an external radial annular rib 27 of the central core 26 facing the internal radial annular lip 32.

If the central core 26 is turned over, an outlet passage 4 of smaller cross section can be produced, limited by the internal radial annular lip 32 and by the second external radial annular rib 28 of the central core 26. In the embodiment illustrated on FIG. 1, the axial rod 30 also serves to hold the adjustment plate 25: the rod 30 passes through a central hole in the adjustment plate 25, and the adjustment plate 25 is held pressed against the intermediate transverse wall 21 by a nut clamp 33 screwed onto the axial rod 30.

The present invention is not limited to the embodiments which have been explicitly described, but it includes some the various variants and generalizations contained in the field of claims below.

Claims

1 - Snow cannon for the production of artificial snow by spraying a mixture of air and water, comprising a hollow body (1) having a mixing chamber (2) oriented along a longitudinal axis II, limited by a peripheral wall (3) lateral and communicating with the outside via a front outlet passage (4), having water intake means for injecting pressurized water into the mixing chamber (2) in one or more flows preferential directives in the peripheral zone of the mixing chamber (2) along the peripheral wall (3) and in a rotary movement around the longitudinal axis (II) of the mixing chamber (2), and having means d air intake (11-16) shaped to inject compressed air into the mixing chamber (2) from the central mixing chamber area (2), characterized in that the air intake means (11-16) are shaped to inject air in the form of one or more directed air jets c each to cut one of said preferential directional flows of water, and in that the mixing chamber (2) comprises an upstream expansion section (201) followed by a downstream compression section (202), the upstream section expansion (201) communicating with the water intake means and with the air intake means and having a cross section greater than that of the water and air intake means to allow the expansion of the fluids during their mixing, the downstream compression section (202) having a section which progressively reduces in the direction of the outlet to compress the mixture and lead it to the outlet passage (4).

2 - Snow cannon according to claim 1, characterized in that, in the upstream expansion section (201) of the mixing chamber (2), the peripheral peripheral wall (3) is substantially cylindrical.

3 - Snow gun according to one of claims 1 or 2, characterized in that, in the upstream expansion section (201) of the mixing chamber (2), the air intake means (11- 16) inject the air in the form of one or more jets directed obliquely towards the peripheral wall (3). 4 - Snow cannon according to any one of claims 1 to 3, characterized in that, in the downstream compression section (202), the peripheral peripheral wall (3) forms a tapered narrowing (5) connecting to the passage of outlet (4).

5 - Snow cannon according to any one of claims 1 to 4, characterized in that the outlet passage (4) is an orifice of annular shape.

6 - Snow cannon according to any one of claims 1 to 5, characterized in that the water intake means comprise helical channels (6-10) connecting, upstream, to an annular distribution chamber d water (17) communicating with a peripheral water inlet (24).

7 - Snow cannon according to any one of claims 1 to 6, characterized in that the air intake means comprise a plurality of air channels (11-16) distributed in the central zone of the hollow body ( 1) around the longitudinal axis (II).

8 - Snow gun according to claim 7, characterized in that the air channels (11-16) are connected, upstream, to an axial air supply pipe (22) communicating with an air inlet central (23).

9 - Snow cannon according to one of claims 7 or 8, characterized in that the air channels (11-16) communicate with the mixing chamber (2) by injection orifices distributed according to a ring of a posterior front wall (203).

10 - Snow cannon according to claim 9, characterized in that it comprises an adjustment plate (25) pierced with an annular series of through holes, the adjustment plate (25) coming to bear against the rear front wall ( 203) and can be pivoted about the longitudinal axis (II) between a fully open position in which each air channel outlet orifice (11-16) faces a through hole in the plate adjustment (25), and partial shutter positions in which the adjustment plate (25) is slightly pivoted about the longitudinal axis (II) to at least partially offset the plate holes relative to the air channel outlet holes (11-16).

11 - Snow cannon according to any one of claims 1 to 10, characterized in that the outlet passage (4) is internally limited by a central core (26) and externally limited by an internal radial annular lip (32).

12 - Snow cannon according to claim 11, characterized in that the internal radial annular lip (32) is an edge limited by two faces forming between them an angle less than 110 °.

13 - Snow gun according to one of claims 11 or 12, characterized in that the central core (26) is elongated longitudinally and is adjustable in longitudinal position along the longitudinal axis (II), and its cross section is longitudinally variable.

14 - Snow cannon according to claim 13, characterized in that the central core (26) further comprises several external radial annular ribs (27, 28), of different diameters, separated by a frustoconical section (29). 15 - Snow cannon according to one of claims 13 or

14, characterized in that the central core (26) is a reversible nut engaged by screwing and selectively locked in the axial position on a threaded rod (30) axial of the body (1).