Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SNOW MAKING MACHINE
The manufacture of man-made snow at commercial ski areas is widely
practiced, as a means for not only extending the useful season of the ski area,
but also improving the quality and uniformity of the surface during the primary
season. Typically, in the production of man-made snow, the snow making areas
are furnished with supplies of compressed air and water under pressure. Usually,
these are in the form of permanent distributional installations, with provisions
being made for connection of the snow making equipment at appropriate locations.
The Pierce, Jr. U.S. Patent No. 2,676,471 is representative of such an installation.
One of the common techniques for the production of man-made snow
is the mixture and discharge of water and compressed air through a simple
discharge gun as, for example, the type shown in the Lindlof U.S. Patent No.
3,716,190. The water is partially atomized within the gun, when it is mixed with
the high pressure compressed air, and the high velocity discharge of the
water/compreæed air mixture serves to complete the atomization and to convey
the atomized water particles then an appropriate distance from the discharge
nozzle. Snow making guns of this type are simple and reliable, but suffer a
disadvantage in requiring a substantial consumption of compressed air, which is
an expensive component of the snow making process.
Another common form of snow making apparatus incorporates an engine
driven fan, which directs a stream of air at relatively high velocity through a
confining shroud and out over the snow making area. A plurality of atomizing
water nozzles are distributed around the periphery of the shroud, discharging
streams of atomized water at an angle, forwardly and into the fan~riven air
stream. Typically, small amounts of compressed air are injected into the water
streams immediately prior to discharge from the atomizing nozzles, to facilitate
the atomizing process. This technique either eliminates or greatly minimizes the
requirement for a compressed air distribution system over the ski area, but in
turn suffers the disadvantage that the equipment is both very expensive, and
inconvenient to operate. Typically, such equipment incorporates a self-contained
internal combustion engine. Thus, each snow making unit requires a substantial
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capital investment. Moreover, the equipment is large, heavy and difficult to
move easily around the snow making site. There is an additional inconvenience
of having to provide constant maintenance for the internal combustion engines,
as well as constant delivery of fuel, etc. Thus, although snow making equipment
provided with engine-driven fans has certain significant advantages, it also has
important compensating disadvantages. Illustrative of snow making equipment
utilizing self-contained engine-driven fan is the Dewey U.S. Patent No. 4,083,492.
In an effort to avoid the inconvenience and investment cost of providing
internal combustion engines with each snow making unit, some of the commercially
available fan-type snow making units have employed electric motors for powering
the fan. While this has certain conveniences in comparison to the use of
self-contained internal combustion engines, it requires the installation and
maintenance of heavy~uty electrical service throughout the ski area, and also
presents certain maintenance and safety problems. Accordingly, notwithstanding
the apparent advantages, the use of electrically driven fans has not proven to
be particularly successful commercia~ly. Illustrative of snow making equipment
utilizing electrically driven fans is the Jakob, et al. U.S. Patent No. 3,760,598,
the Hanson U.S. Patent No. 4,004,732, and the Kircher et al. U.S. Patent No.
4,105,161.
It has also been proposed heretofore, as for example in the Rambach
U.S. Patent No. 3,945,567, to utilize compressed air from the primary compressed
air supply source to supply motive power to a fan-type snow maker. Insofar as
the applicant is aware, however, such a technique has never achieved any degree
of commercial success, possibly because of limitations imposed on the operation
of the system by the use of compressed air as a driving medium. In this respect,
the relationship of air to water in the atomizing process, for optimum results,
is a variable function of temperature and humidity, particularly temperature.
Thus, the utilization of compressed air as a motive source for the fan tends to
impose limitations upon the flow of compressed air to the system, requiring that30 the pressurized water serve as the primary variable on the control of the process.
This leads to significant inefficiencies in the overall operation and importantly
limits the capacity of the equipment to make snow under marginal conditions.
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In accordance with one of the significant aspects of the present
invention, a novel and improved high efficiency, fan-type snow making apparatus
is provided, which derives motive power for driving a fan from the high pressure
water supply, prior to discharging of the water through snow making nozzles.
This utilization of a turbine powered by the high pressure water source produces
unigue and advantageous results in reducing or eliminating the difficulties
associated with the prior snow making equipment listed above.
In accordance with a separate advantageous feature of the apparatus
of the invention, the snow making nozzles are of the compressed air-water type,
10 similar in principle to the conventional snow making guns that do not use fans.
In this respect, the compressed air is introduced into the water supply upstream
of the nozzle discharge, enabling mixing and partial atomization to occur prior
to discharge from the nozzle extremity. ~ one form of the invention, the
atomized mixture is discharged directly into the fan-driven stream of distributional
air.
The use of motive power from the high pressure water supply,
advantageously when combined with the nozzle arrangement, provides for the
making and effective widespread distribution of a high quality snow with
outstanding efficiencies in terms of the consumption of high pressure compressed
20 air from the primary source. Of course, there is energy utilization from the
water supply, but this is more than offset by significant reductions in the
consumption requirements for compressed air, the most expensive component of
the snow making process.
In one form of the invention, all of the compressed air-water atomizing
nozzles are placed directly in the faninduced air stream, and preferably within
the confines of a shroud which surrounds the fan. ~ this particular embodiment,
the atomized air/water mixture is discharged directly into the distributional air
stream for atomization and snow particle formation. When this feature is present,
the constant bathing of the atomizing nozzles in the distributional air stream
30 serves to keep the nozzles clean and free of ice accumulation, which can otherwise
have a deleterious effect on the atomizing efficiency and effectiveness of the
nozzles.
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For a more complete understanding of the above and other features
and advantages of the invention, reference should be made to the following
detailed description of a preferred embodiment of the invention and to the
accompanying drawing.
Fig. 1 is a simplified, side elevational view of a snow making Qpparatus
of the type incorporating principles of the invention.
Fig. 2 is a front elevational view of the atomizing and discharging
unit of the apparatus of Pig. 1.
Fig. 3 is a longitudinal sectional view as taken generally on line 3-3
10 of Fig. 2.
Fig. 4 is a simplified top plan view of the apparatus of Fig. 1.
Fig. 5 is a simplified schematic flow diagram of the apparatus of the
invention.
Referring now to the drawing, the reference numeral 10 designates
generally a support structure for the snow making equipment~ which typically
may be a skid suitable for being towed into position for use, either manually or
by the usual snow cat equipment normally available at commercial ski areas.
The support structure 10 advantageously may include a swivel arrangement 11,
for accommodating rotational movement of the snow generator, generally
20 designated by the numeral 12. A support frame 13 is mounted on the swivel
unit 11 and is adapted for adjustable angular positioning by a pivoted support 14,
enabling the snow generator to be disposed at a desirable angle to the ground
surface.
Mounted on the frame 13 is a generally cylindrical metal shroud 15
having a downstream or discharge end 16 and an upstream or intake end 17.
Desirably, the intake end is provided with an outwardly flared collar 18 to
accommodate a relatively efficient flow of air through the shroud.
Internally the shroud is a support tube 19, which is positioned
concentrically within the shroud by means of a plurality of radial fins 20. The
30 support tube 19 has a bearing platform 21 mounted rigidly within, to which are
bolted a pair of spaced bearing blocks 22, 23. The bearing blocks journal a shaft
24 which carries, positioned just within the upstream end of the shroud 15 and
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axial fan 25. In the illustrated structure, the shaft 24 carries at its upstream
extremity a pulley 26, which is driven from a turbine motor 27 via the output
shaft 28 of the latter, a drive pulley 29 and a i1exible belt 30.
In a practical embodiment of the invention, an axial fan may be a
twelve inch Vaneaxial fan, as manufactured by Hartzell Propeller Fan Co., Piqua,
Ohio, designed to move approximately 2400 cmf of air at approximately 3500
rpm, with a power input of approximately one horsepower.
This level of power is easily derived from a multistage turbine 27
having a water flow-through of approximately 33 gallons per minute at a pressuredrop of approximately 140 psi. In a prototype unit, the turbine 27 was a Gould
multistage pump, modified slightly for operation as a turbine motor. Desirably,
a~l of the water flow to the snow generator is supplied through a line 31 leading
to the intake of the turbine 27. The use of the water turbine 27 has proven
most advantageous in the efficient production of man-made snow. The discharge
outlet 32 of the turbine is connected to a circular manifold 33, mounted at the
back of the shroud 15 and connected, in a manner to be described, to a plurality
of water atomizing nozzles.
In the illustrated form of the snow generator, there are shown a series
of nine (for example) atomizing nozzles 34, arranged in a generally circular array,
at the forward end of the shroud 15, and, in this illustrated form of the invention,
slightly inside the inner wall of the shroud. To this end, discharge lines 35 for
the outgoing air/water mixture may pass through the wall of the shroud, near
the discharge end thereof. In this particular form of the invention, the discharge
nozzles may be located tota~ly within the confines of the shroud, or slightly in
front of the end thereof, as shown in Fig. 3, for example.
To advantage, the water atomizing arrangements comprise an elongated
mixing tube 36 for each discharge nozzle, which may be mounted along the
outside of the shroud 15, extending axially forward from the water manifold 33.
Each mixing tube is of relatively large diameter (eg., 1.5. inches) than the
discharge line leading therefrom and is connected at its upstream end to the
water manifold 33 through a short delivery tube 37 provided with a restricted
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orifice. Also entering the upstream end of the mixing tube 36 is an air nozzle
38 carrying compressed air and discharging through a nozzle or orifice 39. Within
the mixing tube, there is highly turbulent mixing of the water and compressed
air which then exits the mixing tube through the outlet tube 35 leading to the
discharge nozzle 34. Typically and desirably, the discharge nozzle 34 is provided
with a plurality (e.g., seven) of discharge orifices, from which issue a plurality
of streams of air mixed with highly atomized water particles, expelled at rel~tively
high velocity by the compressed air.
In a typical ski area installation with snow making facilities, valved
10 water and air supplies 40, 41 (Fig. 5) are provided adjacent the snow making
areas, arranged with quick detachable couplings 42, 43 for connection to the snow
making apparatus. In a typical operational system, the water inlet system of
the snow maker may include an inlet pressure gauge 44, a flow meter 45, a
throttling valve 46, turbine inlet pressure gauge 47 and outlet pressure gauge 48.
Downstream of the turbine 27, the water supply divides and enters the manifold
33 from opposite ends, for maximum uniformity of water distribution to the
several nozzles. As refleeted in the schematic of Fig. 5, all of the incoming
water supply is, in the illustrated apparatus, directed through the turbine 27.
The compressed air system of the snow making apparatus includes an
20 incoming pressure gauge 49, flow meter S0, throttling valve 51 and manifold
pressure gauge 52 on the downstream side of the throttling valve. The air
manifold 53, which may be a circular manifold similar to the water manifold 33,
is arranged to distribute the incoming compressed air uniformly to the several
air injector nozzles 38.
In typical operation of the illustrated embodiment of the novel system,
approximately 33 gallons per minute of water was delivered to the inlet of the
turbine 27 at a pressure on the order of 250 psi. In this prototype unit,
approximately 140 psi was dropped through the turbine to drive the fan at around
3200 rpm. The discharge water, at a pressure on the order of 100 psi, was then
30 directed to the water manifold and discharged into the mixing chambers 36, from
which the air/atomized water mixture is discharged from the nozzles 34. In the
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illustrated form of the invention, the mixture is discharged directly into the
distributional stream of ambient air.
As is well known and recognized, the percentage of compressed air
required to be mixed with water in the snow making process is highly variable,
as a function of both the temperature and humidity. The higher the temperature
and/or relative humidity, the greater proportions of air are required to form ice
crystals from the water particles. In all cases, however, the amounts of compressed
air per unit of water required with the apparatus of the invention are significantly
lower than with conventional air/water atomizing guns under corresponding
conditions. For example, under relatively favorable snow making conditions, it
is possible, with the illustrated embodiment of the apparatus of the invention,
to produce large quantities of quality snow utilizing as little as 90 cfm of air
to approximately 33 gallons per minute of water, an extremely favorable ratio.
Under extremely unfavorable snow making conditions, approximately 180 cfm of
air is used with approximately 33 gallons per minute of water. Compressed air
is supplied to the generator at pressures in the range of 85-110 psi.
Desirably, some of the output of the turbine unit 27 may be utilized
for other functions, such as driving a small alternator 55. The output of the
alternator may be utilized to provide for electrical control functions and/or toeffect oscillation of the snow generator for wider distribution of the snow over
the area to be covered. In this respect, it is anticipated that a high efficiency
turbine unit may readily derive approximately one horsepower via a pressure drop
of less than 100 psi at 33 gallons per minute, such that the system can easily
accommodate the extraction of minor amounts of energy to service an alternator
55.
One of the advantageous aspects of the system of the invention is
that it enables the production of snow to be maximized under all conditions. In
this respect, one feature of the illustrated embodiment of the present invention
is that the flow of water to, and its discharge from, the snow generator may be
maximized at a constant value, and the primary variable in the process is the
amount of air supplied. This, of course, is adjusted to a level as low as the
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ambient conditions will permit. This feature, which exists in the particular
illustrated embodiment, is most advantageous when these particular ambient
conditions exist. In general, the volumes of compressed air required to be supplied
are significantly less than would have to be supplied to a conventional air/water
gun of similar capacity.
In the illustrated embodiment, the arrangement of the atomizing nozzles
directly within the distributional air stream issuing from the fan 25 also serves
to increase the overall efficient operation of the system. ~3ecause the nozzles
are continuously bathed in a relatively high velocity flow of air through the
shroud, the nozzles remain clean and free of ice build up, which can significantly
substantially degrade performance of the nozzles.
A rather surprising characteristic of the snow generator of the invention
is the fact that it is extremely quiet in operation. Typically, the operation of
air/water snow making guns is accompanied by a great deal of penetrating,
annoying noise. In the operation of the snow generator of the invention, possibly
because of the reduced requirements for compressed air usage, the noise level
of the equipment in operation was sufficiently low as to not be disagreeable and
annoying even at locations immediately adjacent to the discharge nozzles.
It should be understood, of course, that the specific form of the
invention herein illustrated and described is intended to be representative only,
as certain changes may be made therein without departing from the clear teachings
of the disclosure. Accordingly, reference should be made to the following appended
claims in determining the full scope of the invention.
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