The present invention generally relates to making artificial snow by means of a snow making machine, and comprising a funnel shaped carrier which at one end thereof, the inlet end, has a fan for blowing a large amount of air there through under high pressure and at high speed, and which at its other end is formed with several rings having a large number of fine distribution (atomizing) nozzles through which water under high pressure is ejected into the air flow passing through the carrier, and whereby the pressure for atomizing the water into small drops can be 30-40 bar. For making said small drops of water become freezed, strongly freezed particles so called nuclei, are introduced into the flow of water drops, which is referred to as the bulk water flow. Said nuclei, which have as low temperature as down to -42°C act as a type of catalysts for freezing the water drops emanating from the ordinary water nozzles The nuclei are created at a place where the air flow has its lowest air speed, in particular at a "back zone" adjacent the nose cone of the funnel shaped carrier at which zone there is a low air speed.

In our Swedish patent No 94031 68-9 (equivalent to WO 96/09505) is described how to make snow crystals in two steps, namely in a first step by creating nuclei in the outer periphery of the air flow in that extremely fine drops of water are sprayed through atomizing nozzles of the said back zone of the nose cone, and in a second step by mixing the nuclei thereby formed with atomized water drops which are ejected into the air flow passing through the snow making machine from the ordinary water nozzles of the snow making machine thereby forming a plume of water drops which are mixed with the nuclei in a turbulent air flow.

A problem has been that a part of the water drops which are ejected from the nozzles fall to the ground in an only party freezed or even non- freezed condition thereby forming a not wanted layer or ice on the ground This problem is increasingly noticeable the higher the temperature of the ambient air is. Until now it has not been possible, in practice, to make artificial snow if the temperature of the ambient air is higher than about -3°C to -2.5°C, and even at such theoretically possible temperatures of the ambient air there have been problems to freeze all water drops ejected from the water nozzles. In many cases it has not been considered practically and economically possible to make artificial snow at higher temperatures than

-3°C to -4°C.

For having the water drops distributing themselves in an optimum way in the air flow of the snow making machine, and for having the snow making machine produce the greatest possible amount of snow crystals it has shown suitable to form the snow making machine with several rings of water distribution nozzles arranged axially on line after each other adjacent the outlet end of the snow making machine. To-day there are generally used at least three nozzle rings and even as much as six nozzle rings.

It has shown that it is of great importance to the formation of snow crystals how the nozzles of the rings are placed, and according to the invention the nozzles of the various nozzle rings are mounted angularly with a successively steeper (less) angle to the flow axis as seen in the flow direction. In a preferred embodiment of the invention, which is illustrated in the accompanying drawings the snow making machine is formed with a ring of nuclei nozzles mounted close to the nose cone of the snow making machine, especially at the above mentioned back zone, and five rings of ordinary water nozzles. The rearmost ring thereof has the most blunt (greatest) angle to the flow axis and the foremost ring has the steepest (smallest) angle to the flow axis. As an example it can be suggested that the nozzles of the rearmost ring are mounted at an angle of about 45°, and that the nozzles of the succeeding rings can be mounted at angles of about 42°, 37°, 32° and 27°, respectively. The nuclei nozzles can be mounted at an angle of about 30° to the axis of the air flow through the snow making machine. Surprisingly it has shown that it is possible to use the snow making machine for making snow crystals having a good quality at lower temperatures than has so far been considered possible in that the water of the various nozzle rings is turned on at stages, and still better according to a specific order of stages. In the illustrated embodiment, in which the nozzles of the various rings are mounted at successively steeper angles to the flow axis it has shown particularly suitable that the water is first turned on in the foremost ring but one, ring II as shown in the drawings, thereafter in the rings II + I, followed by rings II + 1 + III, the rings ll + l + lll + IV and in all rings II + I + III + IV + V. The water to the atomizing nozzles which create the nuclei, is constantly turned on after the air flow through the snow making machine has been turned on.

By this way of starting and proceeding the making of snow crystals it has shown possible to make snow crystals having a good quality and being almost completely freezed throughout at temperatures of the ambient air of even up to + 5°C. This is true at very dry air conditions, for instance air having a moisture content of about 20%, but also at higher moisture contents the invention offers the possibility of making snow crystals at surprisingly high ambient temperatures. The increase of the ambient temperature at which it is possible to make snow crystals of good quality from the previously highest possible temperature level of at least -3°C to -1 °C is very important considering the fact that the snow making machine may thereby be used on many occasions on which it has previously not been possible to artificially make snow crystals of good quality having completely freezed through water drops.

In the preferred embodiment of the invention which is shown in the accompanying drawings, and which is formed with five nozzle rings it has been possible to reach the following capacity at a water pressure of 35 bar ^¬ ring II 1 40 l/mιnute rings II + I 264 l/minute rings II + I -f ill 396 l/minute rings II + I + III + IV 538 l/minute rings II + I + III + IV + V 659 l/minute.

It is not completely made clear what is the reason for the good effect of stage wise turning on the water of the nozzle rings in the said order, but it is believed that the reason is that the separation of the water drops from the nozzles is increased, and that a compact cold mass body is successively built up in the snow making machine following the turning on the various nozzle rings, which cold mass body, after having been fully built up makes it possible to completely freeze practically all water drops from all nozzle rings - even when all nozzle rings operate at full capacity. Now the invention is to be described more in detail with reference to the accompanying drawings which diagrammatically show a preferred embodiment of a snow making machine according to the invention. Figure 1 shows an axial cross section view through a snow making machine having one ring of atomizing nozzles and five rings of ordinary water nozzles arranged successively following each other in the axial direction. Figure 2 is a cross section view through the nozzle rings in the snow making machine of

figure 1 . Figure 3 is a cross section view similar to that of figure 2, and it illustrates the placing and the angular positioning of the nozzles. Figure 4 shows in five successive views, A, B, C, D and E the optimum way, according to the invention, of operating the snow making machine at marginal temperatures of the ambient air of about -2°C and at such high temperatures as up to + 4°C to -t- 5°C.

As conventional the snow making machine shown in the drawings comprises a funnel shaped carrier 1 , which at the inlet end thereof is formed with a diagrammatically sketched fan 2 forcing a flow of air 3 through the carrier 1 , and which at the outlet end thereof is formed with a nose cone 4 of suitable shape and size, which carries both a ring 5 having a series of atomizing nozzles 6 distributed round the carrier 1 , and five rings 7, marked I-V, having a large number of ordinary water distribution nozzles 8 mounted peripherally round the carrier 1 . The nose cone is formed so that the air flow 3 through the snow making machine, in combination with the flow 9 of ambient air which is brought, by suction action, passed the nose cone at the outlet end thereof forms a "back zone" 1 0 having a low air speed and in which there is a sub pressure which makes the atomized water drops from the atomizing nozzles become converted to strongly freezed nuclei 1 1 which distribute in a ring comprising said strongly cooled down, and extremely finely atomized nuclei round the air flow. The nuclei act as catalysts which speed up and facilitate the freezing of the water particles 1 2 which are ejected through the ordinary water distribution nozzles 8 and which mix with the nuclei. The water nozzles 7 are mounted similarly to form a diverging cone or arc 1 3 so that the foremost nozzle ring I has greater diameter than the rings II - V mounted successively rearwardly thereof. The rearmost ring V has the smallest diameter. As best evident from figure 3 the nozzles are mounted at different angles in relation to the flow axis 1 4 of the snow making machine. The nozzles are preferably mounted at successively less angels, as seen in the flow direction, for instance so that the nozzles of the rearmost ring V forms an angle to the flow axis of about 45°, the nozzles IV an angle of about 42°, the nozzles III an angle of about 37°, the nozzles II an angle of about 32° and the nozzles I an angle of about 27°. The atomizing nozzles preferably can be mounted at an angle of about 30° to the flow axis 14. In case of strong cold of the ambient air all water rings I - V can be

pressurized at the same time with water having a pressure of about 35 bar At marginal temperatures of the ambient air of between -2°C and ±0°C there are, however, problems to provide a freezing of all water drops 1 2 ejected from the nozzles 8. At still higher temperatures, for instance temperatures as high as + 4 to + 5°C it has until now been very difficult, if at all possible, to make artificial snow.

According to the invention there is used a method according to which the water distribution rings are, for this reason, pressurized in turn after each other, especially so that the outermost ring but one is pressurized first, whereafter the succeeding rings are pressurized in turn after each other in combination with the previously pressurized ring/rings, that is I, III, IV and V By this method there is obtained a surprisingly effective freezing of the water drops, and thereby it is possible to make artificial snow even at temperatures of up to -2°C to ±0°C, and if the humidity of the ambient air is low at temperatures of up to + 4°C to + 5°C

The method is performed in the following way:

- the fan 2 is started whereby a flow of air 3 having high speed is moved through the carrier 1 , which flow of air brings a flow 9 of ambient air at the exterior side of the snow making machine; - pressurized water is turned on to the ring 5 of atomizing nozzles 6, whereby extremely finely atomized drops of water are ejected into the back zone 1 0 which is formed at the outlet side of the nose cone 4, by the action of the air flow 3 and the flow 9 of ambient air brought by said air flow 3 there is formed a sub pressure in the back zone which contributes to making the extremely finely atomized water drops from the nozzle become very strongly cooled down (freezed) and forming an all around extending curtain of nuclei;

- pressurized water is turned on to the outermost but one ring II of water nozzles 8 (see figure 4A), whereby a flow 1 2 of water drops are ejected into the air flow 3, in the illustrated case preferably an average angle of about 32°;

- when the water flow from the ring II has stabilized, so that the water drops form a body of freezed snow crystals, pressurized water is turned on in the ring I (see figure 4B), and when also said flow has stabilized the rings III, IV and V (see figures 4C, 4D and 4E) are turned on so that the snow making machine ultimately provides a total mass of well freezed snow crystals

It is obvious that the invention is as well useful in snow making machines formed with only three or four rings of water nozzles. It is also obvious that the water nozzles can be mounted at other angles than those mentioned above, and that each of said suggested angles is only one out of many possible examples. It is, however, important that the nozzles of the various nozzle rings are mounted at successively steeper (less) angles to the flow axis 1 4 of the snow making machine, as seen in the flow direction.

REFERENCE NUMERALS 1 funnel shaped carrier

2 fan

3 air flow

4 nose cone

5 atomizing ring 6 atomizing nozzle

7 water ring

8 water distribution nozzle

9 flow of ambient air 1 0 back zone 1 1 nuclei

1 2 water drops

1 3 arc, cone

14 axis