Snow production cannon

Abstract: To increase the efficiency of the cannon (1) (ie to increase the artificial snow quantity produced for the same energy expended), upstream of each atomization nozzle (15) there is provided a chamber (5) in which the liquid is pre-mixed with the gas. The gas is injected into the chamber (5) by at least one injection nozzle (3), (Figure 1).

Description: This invention relates to a snow production cannon. EP-A-0 250 425, EP-A-0 084 186 and EP-A-0 084 187 disclose known snow production cannons. In this sector, technical progress is continually aimed at increasing the efficiency of said devices, ie increasing the snow quantity produced for equal energy used. For example, US 2676471 discloses an improved nozzle for use in the making of snow, whereby snow may be economically manufactured and distributed over a desired surface. In particular, mixing of air and water occurs inside a series of nozzles and coarse vapour flows into one enlargement, which constitutes a compression chamber. Even if the distribution of snow is very uniform over various surfaces, however, according to the teaching of US 2676471, it is not possible to provide for a drastic increasing of the efficiency of the known, i.e. an increasing of the snow quantity produced for a given quantity of energy expanded. The main object of the present invention is therefore to provide a snow production cannon of optimum efficiency. This object is attained by a snow production cannon in accordance with the first claim, to which reference should be made for brevity. Briefly, air is injected by at least one injection nozzle into the pre-mixing chamber (or into the pre-hole of the further nozzle), from which it can leave only through the respective further nozzle (this being the atomization nozzle) to atomize the liquid therein in an optimum manner. A further object of the invention is to obtain artificial snow of good quality. A further object of the invention is to provide a cannon of simple and economical structure, ie a structure composed of a relatively small number of elements which are joined together in a manner which enables them to be easily assembled and disassembled. The further objects of the invention are attained by a snow production cannon in accordance with the dependent claims, to which reference should be made for brevity. A possible embodiment of the invention is described hereinafter by way of non-limiting example. This embodiment is illustrated in the accompanying figures. Figure 1 is a longitudinal section through a snow production cannon according to the invention. Figure 2 is a cross-section on the line II-II of Figure 1. Figure 3 is a cross-section on the line III-III of Figure 1. Figure 4 is a longitudinal section through an injection nozzle. Figure 5 is a longitudinal section through an atomization nozzle. Figures 6-17 are cross-sections showing the exit ports of injection and/or atomization nozzles constructed in accordance with further embodiments. It should be noted that the longitudinal direction is that parallel to the direction of fluid flow through the cannon during operation, whereas the transverse direction is that perpendicular to the direction of fluid flow through the cannon during operation. With reference to said figures, and in particular to Figures 1-5, the cannon of the particular embodiment used to describe the invention, indicated overall by 1, is of the type comprising a plurality of nozzles positioned along concentric circles. The cannon 1 comprises essentially the following elements, listed in the order of fluid flow through the elements: a first element 2 distributing gas to injection nozzles 3, a second element 4 distributing liquid to a pre-mixing chamber 5, a third element 6 for injecting gas and a fourth element 7 in which the fluid and gas are mixed to form aerosol, with propelling of said aerosol out of the cannon 1. The first element 2 comprises an annular chamber 8 which can be hydraulically connected to a pressurized gas feed pipe (9) and is hydraulically connected to the inlet of the injection nozzles 3. The first element 2 can also be connected to the pressurized liquid feed pipe 10. The second element 4 is of cone shape, the vertex of which is positioned on the axis 11 of the pressurized liquid feed pipe 10, its base perimeter being tangential to the mouth of the pre-mixing chambers 5. The axis 11 coincides with the axis of the cannon 1. The third element 6 houses the injection nozzles 3 and comprises a conical hole (not clearly visible) loosely housing the second element 4 such that between the outer surface 12 of the second element 4 and the inner surface 13 of the conical hole there is a passageway 14 for liquid feed to the pre-mixing chambers 5. The fourth element 7 comprises the pre-mixing chambers 5 and a plurality of atomization nozzles 15, for which each pre-mixing chamber represents the pre-hole. The pipes 9 and 10 are connected to the first element 2 by respective threads 16 and 17. The first element 2, the second 4, the third 6 and the fourth 7 are joined together by screws 18 all of which can be manoeuvred from the front of the cannon so as to facilitate assembly and disassembly. Annular gaskets 19-21 provide the necessary hydraulic seal between the elements mechanically connected together. With particular reference to Figure 4, each injection nozzle 3 comprises, aligned along the axis of symmetry 22 and listed in the order in which the gas flows through them, a pre-hole 23 and a sized capillary hole 24. The pre-hole 23 comprises three portions 25-27. The first portion 25 is in the form of a cone frustrum converging into the second portion 26. The second portion 26 is cylindrical and has a diameter equal to the minor base of the first portion 25. The third portion 27 is in the form of a cone frustrum converging into the sized capillary hole 24 in which the minor base has a diameter greater than the dimensions of said sized capillary hole 24. With reference to Figure 5, each atomization nozzle 15 comprises, aligned along the axis of symmetry 28 and listed in the order in which the fluid flows through them, a pre-hole 5 and a sized capillary hole 29. The pre-hole of the atomization nozzle is the pre-mixing chamber 5, in the shape of a cone frustum converging into the sized capillary hole 29. To facilitate distribution of the snow produced, the axes of symmetry 28 of each atomization nozzle 15 cut the axis 11 of the cannon 1. In the illustrated example, the angle of incidence α is about 7°. In the example, the ports of the sized capillary holes 29 and 24 of the atomization nozzles 15 and injection nozzles 3 have ports of equal shape, however said ports could be of different shape, and/or of variously assorted forms. In the particular case shown in Figures 1-5, the ports of the sized capillary holes 29 and 24 of the atomization nozzles 15 and injection nozzles 3 are of circular shape. Some of the possible geometrical forms of the ports of the sized capillary holes 24 and 29 of the nozzles 3 and 15 are shown in Figures 6-17. In a first example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: at least two lobes oppositely positioned about the central projection axis of the nozzle. In a second example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: two lobes oppositely positioned about the central projection axis of the nozzle and having right-angled ends. In a third example the ports of the sized capillary holes of the nozzles have the following geometrical plan shape: two lobes oppositely positioned about the central projection axis of the nozzle and having rounded ends. In a fourth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: three lobes positioned 120° apart about the central projection axis of the nozzle and having right-angled ends (Figure 9+10). In a fifth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: three lobes positioned 120° apart about the central projection axis of the nozzle and having rounded ends (Figure 8). In a sixth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: three lobes positioned 120° apart about the central projection axis of the nozzle and having rounded ends, with the width of the lobes decreasing from the central axis towards the outside (Fig.8). In a seventh example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: three lobes positioned 120° apart about the central projection axis of the nozzle and having right-angled ends in which two lobes have equal length, which is less than the remaining lobe (Fig.9+10). In an eighth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: four lobes oppositely positioned about the central projection axis of the nozzle, ie cross-shaped and having right-angled ends (Fig.11). In a ninth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: four lobes oppositely positioned about the central projection axis of the nozzle, and having rounded ends (Fig.12). In a tenth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: five lobes oppositely positioned about the central projection axis of the nozzle, and having right-angled ends. In an eleventh example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: five lobes oppositely positioned about the central projection axis of the nozzle, and having rounded ends (Fig.15). In a twelfth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: six lobes oppositely positioned about the central projection axis of the nozzle, and having right-angled ends. In a thirteenth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: six lobes oppositely positioned about the central projection axis of the nozzle, and having rounded ends (Fig.16). In a fourteenth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: eight lobes oppositely positioned about the central projection axis of the nozzle, and having right-angled ends. In a fifteenth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: eight lobes oppositely positioned about the central projection axis of the nozzle, and having rounded ends (Fig.17). In a sixteenth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: triangular (Fig. 6+7). In a seventeenth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: triangular with rounded vertices (Fig.6). In an eighteenth example the ports of the sized capillary holes 24, 29 of the nozzles have the following geometrical plan shape: at least two lobes oppositely positioned about the central projection axis of the nozzle, and along which pairs of circular holes are provided in symmetrical positions (Fig.14). The use of capillaries with the aforestated geometrical forms enables artificial snow crystals of different shapes to be formed. The opportune choice of the ports and/or combinations of different ports even on the same cannon element enables artificial snow to be produced with different characteristics, so as to be the most suitable possible for the skiing use for which it is usually produced. During operation, the cannon 1 essentially implements a method for artificial snow production comprising a first stage of gas injection into the liquid while this is upstream of the atomization nozzle 15. The injection stage is accomplished by passing the liquid through the injection nozzle 3 which opens into a pre-injection chamber 5 positioned upstream of the atomization nozzle 15. There is then a second stage in which the liquid is atomized into the atmosphere by the previously injected pressurized gas, to obtain said artificial snow when the aerosol produced by the atomization nozzle 15 emerges into the atmosphere. For reasons of economy and ready availability and in order not to result in ecological harm, the gas is air and the liquid is water. The use of other fluid mixtures thereof is however not excluded.

Claims: Snow production cannon (1), comprising means (9, 10) for conveying a liquid and a pressurised gas into a plurality of atomisation nozzles (15), each of them having a first capillary hole (29), a first element (2) which distributes the gas to a plurality of injection nozzles (3), each of them having a second capillary hole (24) and which are integrally provided in a third element (6) for injecting gas, a second element (4) which distributes the liquid to a plurality of pre-mixing chambers (5), and a fourth element (7), which integrally includes said atomisation nozzles (15) and said pre-mixing chambers (5), and in which the liquid and the gas are mixed to form aerosol that is propelled out of the cannon (1), wherein each injection nozzle (3) is associated to a single one of said plurality of said pre-mixing chambers (5) and a single one of said atomisation nozzles (15), so that said injection nozzles (3) inject said gas into said atomisation nozzles (15), facing the injection nozzles (3) through said pre-mixing chambers (5), which face, in turn, the injection nozzles (3) and the atomisation nozzles (15). Snow production cannon (1) as claimed in claim 1, characterised in that said first element (2) comprises an annular chamber (8), which is hydraulically connected to a pressurised gas feed pipe (9), to a pressurised liquid feed pipe (10) and to an inlet of said injection nozzles (3). Snow production cannon (1) as claimed in claim 2, characterised in that said second element (4) is shaped as a cone, with a vertex which is positioned along a longitudinal axis (11) of said pressurised liquid feed pipe (10), said cone having a base perimeter which is tangential to an inlet of said pre-mixing chambers (5). Snow production cannon (1) as claimed in claim 1, characterised in that said third element (6) comprises a conical hole loosely housing said second element (4), so that a conduit (14), connecting an outer surface (12) of said second element (4) with an inner surface (13) of said conical hole, is provided for feeding said liquid to each of said pre-mixing chambers (5). Snow production cannon (1) as claimed in claim 1, characterised in that said first (2), second (4), third (6) and fourth elements (7) are joined together by screws (18), which are provided on a front wall surface of said cannon (1). Snow production cannon (1) as claimed in claim 3, characterised in that each atomisation nozzle (15) has a first axis of symmetry (28), which is inclined with respect to said longitudinal axis (11). Snow production cannon (1) as claimed in claim 1, characterised in that each injection nozzle (3) comprises an inlet pre-hole (23) and said second capillary hole (24), which are aligned along a second axis of symmetry (22) so that said liquid and gas flow from said inlet pre-hole (23) to said second capillary hole (24), said inlet pre-hole (23) also comprising a first portion (25), shaped as a cone frustum converging into a second portion (26), which is cylindrical and has a diameter equal to a minor base of said first portion (25), and a third portion (27), which is shaped as a cone frustum converging into said capillary hole (24), said minor base having a diameter greater than said capillary hole (24). Snow production cannon (1) as claimed in claim 6, characterised in that each atomisation nozzle (15) comprises one of said pre-mixing chambers (5) and said first capillary hole (29), which are aligned along said first axis of symmetry (28) so that said liquid and gas flow from said pre-mixing chamber (5) to said first capillary hole (29), said pre-mixing chamber (5) being shaped as a cone frustum converging into said first capillary hole (29). Snow production cannon (1) as claimed in claim 1, characterised in that said first (29) and second capillary holes (24) of said atomisation (15) and injection nozzles (3) are equally shaped with a prefixed geometrical plan shape. Snow production cannon (1) as claimed in claim 1, characterised in that said first (29) and second capillary holes (24) of said atomisation (15) and injection nozzles (3) are shaped in different forms.

Inventors: CASTAGNERI MICHELANGELO, CASTAGNERI, MICHELANGELO
Applicants: LEITNER SPA, LEITNER S.P.A.
Application year: 1998
Main classification: F25C3
IPC codes: B05B7, B05B1, F25C3