Abstract:
A method and apparatus for continuously making snow at all times of the year comprises the creation of countless ice crystals from a mist in a controlled environment. The mist may have a ice crystal nucleus added to it to facilitate the development of the ice crystal at higher temperatures. The ice crystals are directed into an ultrasonic field generated by an transducer where the fall rate of the crystals levitated. While the crystals are within the ultrasonic field, the crystals grow into snowflakes as a result of collisions with other crystals. The snowflakes eventually fall out of the ultrasonic field as snow having a more natural appearance than more conventional snow-making techniques.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a novel method and apparatus for making snow and particularly to a method and apparatus for making snow in all seasons. 
     One method and apparatus for making snow utilizes blocks or cakes of ice which are shaved into fine ice flakes by a rotating cutter. The snow-like ice flakes are blown off, together with a gas, by a blower or compressed air blast. A disadvantage of the shaving method and apparatus is the form of shaved ice which is far from naturally formed snowflakes. 
     Another method and apparatus for making snow involves a snow making chamber having a screen- or brush-like member on which frost is formed by a spray, ultrasonic atomizer or the like. The frost is then scraped by suitable means to form the snow. A disadvantage of the device is the long time required for frost development, since the frost is formed on the screen- or brush-like member by the mist. Once the frost has been scraped, considerable time is required before new frost can develop, making it impossible to produce snow on a continuous basis. A further disadvantage associated with this method is that the frost, once scraped, tends to harden to a state much different from that of naturally formed snow crystals. 
     A third method and apparatus provides a mist which is supplied to a snow making chamber to generate ice crystals. The ice crystals are suspended within the chamber by an air stream. As the ice crystals are suspended, they continue to grow into snowflakes. The ice crystals become heavier as they grow and eventually fall out of the air stream due to their weight. 
     Following this method, it is difficult to suspend the fine ice crystals and grow them into snowflakes having a diameter of several millimeters. An extremely sophisticated control of the air stream is required to achieve the desired suspension density. Accordingly, the ice-crystal growth chamber must be of a height substantially equal to a building five stories high in order to achieve an effective control of the air stream. As a consequence, the apparatus is inconveniently bulky and impractical to use. Moreover, the method requires a time cycle on the order of 20 to 30 minutes to grow the ice crystals in the same manner as in nature, so it is difficult to realize continuous snowfall. 
     In view of the problems and disadvantages associated with the former methods of making artificial snow, the present invention provides a method for continuously and rapidly making snowflakes which more closely resembles naturally formed snow. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, a method for making snow comprises the steps of generating ice crystals using an ice crystal generator means having a liquid atomizer and freezer. This step is followed by guiding the ice crystals into an ultrasonic field generated by ultrasonic levitating means and levitating the ice crystals within the ultrasonic field so as to make snowflakes. 
     An apparatus for carrying out the method for making snow comprises an ice crystal generator mechanism having a liquid atomizer mechanism and a freezer mechanism to generate ice crystals. A collector chamber is provided within the freezer to collect the ice crystals from the generator mechanism. An ultrasonic levitating mechanism, located below the collector, is adapted to generate an ultrasonic field and suspend the crystals within the freezer so they may grow. Coupled to the crystal generator is a guiding means used to guide the ice crystals into the collector chamber and the ultrasonic levitating mechanism, respectively. 
     With the method and the apparatus of the present invention, the ice crystals formed by the ice crystal generator means or mechanism are levitated within the ultrasonic field which is, in turn, generated by the ultrasonic levitating means or mechanism so that the individual ice crystals are combined with the adjacent ice crystals or mist particles to form the snow-like flakes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Method and apparatus of the present invention will be more apparent from the following description of preferred embodiments made in reference with the accompanying drawings wherein: 
     FIG. 1 is a schematic diagram illustrating a basic arrangement of the snow making apparatus according to the invention; 
     FIG. 2 is a perspective view illustrating one embodiment of the ultrasonic levitating mechanism; 
     FIG. 3 is a perspective view illustrating one embodiment of the apparatus constructed according to the invention; 
     FIG. 4 is a perspective view illustrating a preferred embodiment of the ultrasonic levitating mechanism; 
     FIG. 5 is a perspective view illustrating another embodiment of the apparatus constructed in accordance with the invention; 
     FIG. 6 is a perspective view illustrating a preferred embodiment of the mist guiding means; 
     FIG. 7 is a perspective view illustrating an embodiment of the annular ultrasonic transducer; and 
     FIGS. 8 through 10 are perspective views illustrating various embodiments of the reflectors. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In referring to the drawing figures, like reference numerals will be used to indicate like components, wherein FIG. 1 is a schematic diagram illustrating a basic arrangement of the snow making apparatus according to the invention. The snow making device 10 has a liquid atomizer means or mechanism 12, most preferably in the form of an ultrasonic atomizer. Alternatively, a combination of high pressure pump and nozzle or a steam generator may work as the liquid atomizer mechanism so far as an effective mist generator can be obtained. A freezer means or mechanism 14 cools a freezing chamber 16 within an insulated cabinet 18 comprising an ice crystal generator means or mechanism. The crystal generator 18 is adapted to generate countless ice crystals. The insulated cabinet of the crystal generator may be constructed from a variety of materials including polyvinyl chloride sheeting or stainless steel. The cabinet may be insulated using polyurethane foam or the like to maintain the preferred environment within the cabinet. It is preferred that portions of the cabinet contain windows. Such window should be insulated windows having triple panes to provide an insulated window that will not cloud or fog while the snow making apparatus is functional. 
     Ice crystals are generated in an environment at a temperature lower than approximately -5° C. if crystal nuclei are present. Even in the absence of such ice crystal nuclei, it has been found that ice crystals are generated from mist in an environment at a temperature lower than -40° C. Accordingly, freezer mechanism 14 having an ability of cooling the environment to a temperature lower than -40° C., may be combined with the liquid atomizer mechanism 12 to provide an ice crystal generator 18 which is effective to generate countless ice crystals. 
     It will be possible to generate ice crystals even by using a freezer mechanism 14 having a limited ability to cool to a temperature of -5° C. if the crystal generator 18 is combined with a crystal nucleus generator means or mechanism 20. Preferably nucleus generator 20 is adapted to atomize a mixture of colloidal silver iodide solution and water having a concentration of silver iodide between 0.1 to 0.4 grams per liter. Alternatively, the colloidal silver iodide solution may be mixed into the liquid contained in liquid atomizer mechanism 12 to achieve the desired generation of ice crystal nuclei. Other ice nucleus material may be used such as salt, clay and certain ice nucleus bacillus. 
     It may be contemplated that a temperature lower than -40° C. be established within freezing chamber 16 to generate the ice crystals. This may be achieved by utilizing, for example, a Peltier element or dry ice. Alternatively, cooling may be achieved by adiabatic expansion (an increase in volume without heat loss) by the discharge of a high pressure fluid (gas). 
     Referring to FIG. 1, reference numeral 22 refers to a collector chamber adapted to collect mist particles generated by liquid atomizer mechanism 12 and passed through a mist conduit 24. Within collector chamber 22, the mist droplets are being converted to ice crystals in a sub-zero environment generated by freezer mechanism 14. While it will suffice to maintain the temperature within collector chamber 22 below -5° C. if the ice crystal nucleus generator mechanism 20 is used, it will be necessary to maintain the temperature within collector chamber 22 at approximately -40° C. or provide an inlet of collector chamber 22 with a suitable means such as a Peltier element for establishing a super-cooled environment having a temperature on the order of -40° C. 
     Reference numeral 26 designates a mist guiding chamber adapted to guide the mist, together with the ice crystals, into an ultrasonic field generated by an ultrasonic levitating mechanism 28 described in greater detail below. The conical shape of the chamber 26 is positioned above the ultrasonic levitating mechanism 28 such that the outlet to the guide is above the area where the ultrasonic field is generated. 
     The ultrasonic levitating mechanism 28 introduced above is comprised of an ultrasonic transducer assembly 30 and a reflector 32. As illustrated in FIG. 2, an ultrasonic transducer assembly 30 is basically comprised of ultrasonic transducer 34 having a cylindrical metallic horn 36 and distant therefrom is reflector 32 so as to be opposed to cylindrical metallic horn 36. Generated between cylindrical horn 36 and reflector 32 is an ultrasonic standing wave through which ice crystals 38 are passed. The temperature within the standing wave is preferably maintained at approximately -15° C. Opposing surfaces of cylindrical horn 36 and reflector 32 may be slightly concave to generate a linear standing wave field, as illustrated in FIG. 1, and thereby levitate the ice crystals 38 in the air within the ultrasonic standing wave to provide sufficient time for the crystals to grow into snowflakes. Reflector 32 is preferably position-adjustable so as to vary the distance to horn 36 and change the amount of reflected energy between the horn and reflector. 
     FIG. 3 is a perspective view illustrating one embodiment of the apparatus 10 constructed according to the invention in which the same reference numerals are used to show the same parts shown in FIG. 1. In this embodiment, colloidal silver iodide solution is mixed with a quantity of water contained in liquid atomizer mechanism 12 to obtain a concentration of colloidal silver iodide between 0.1 and 0.4 grams per liter. The mixture within atomizer 12 serves as the ice crystal nucleus generator means. As a consequence, no additional space is required for the ice crystal nucleus generator mechanism if liquid atomizer mechanism 12 is provided with a refill port 40 for the mixed solution. 
     Reference numeral 42 designates a fan provided within liquid atomizer mechanism 12 to direct the mist generated by the liquid atomizer, through conduit 24 and into collector chamber 22. The flow rate of the air within conduit 24 may be in the range of 0.2 to 0.8 meters per second. Located within mist conduit 24 is a valve 52 used to control the airflow rate within the conduit and thereby regulate the mist stream. In this specific embodiment, there is provided within collector chamber 24 a Peltier element 44 adjacent the point where mist conduit 24 enters collector chamber 22 serving to achieve a partial supercooling effect. Extending downwardly from the bottom of collector chamber 22 is a cylindrical mist guiding chamber 26 for directing the mist and ice crystals into the ultrasonic field. Concentrically received about guiding chamber 26 and adapted to slide about the guide is a sleeve 48 which may be fixed in position by a fastener 50 such as a winged screw. FIG. 6 illustrates another embodiment of mist guiding chamber 26 disposed beneath collector chamber 22. More specifically, mist guiding chamber 26 is a bellows allowing the outlet of chamber 22 to be position-adjusted above the ultrasonic standing wave generated by the transducer horn 36. 
     The ultrasonic levitating mechanism 28 shown in FIG. 3 comprises ultrasonic transducer assembly 30 and annular metallic horn 36 mounted to a bracket 29 and adapted to generate the standing wave used to levitate the ice crystals. The ice crystals 38 together with the mist particles, also shown as 38, are levitated or suspended in the horn by the ultrasonic standing wave. The ultrasonic energy causes the ice particles to collide with the mist particles and freeze thereon and grow to form the snowflakes. The growth of the snowflakes continue by way of ultrasonic cohesion until the size of the snowflakes cause them to fall from the ultrasonic field. Annular metallic horn 36, shown in FIG. 3, may be made of DURALUMINUM 56S with the annulus having a height of 35 mm, an inner diameter of 50 mm and an outer diameter of 58 mm. FIG. 7 illustrates an alternate embodiment of ultrasonic tranducer 120 in the form of an annular transducer. Referring again to FIG. 3, reference numeral 54 designates a toy house placed immediately below annular metallic horn 36 so that the artificial snow falls directly onto its roof to create the sense of real snowfall. 
     Referring to FIG. 5, there is illustrated another embodiment of the apparatus 10 constructed in accordance with the present invention, in which freezing chamber 16 is defined by a cylindrical wall 56 made of transparent material. An ultrasonic field generated by an ultrasonic generator 58 causes horn 36 to generate standing waves not only within annular metallic horn 36 but also between transparent wall 56 of the freezing chamber and annular metallic horn 36 so that the snow making occurs not only inside but also outside annular metallic horn 36 so as to fall on and around a desired target such as the tree 59. 
     Referring to FIG. 8, an annular metallic horn 36 may be surrounded by an annular reflector 60 which is radially expansible to obtain the snow making effect shown by crystals 38 not only inside but also outside annular metallic horn 36. FIG. 9 illustrates an alternative arrangement of the ultrasonic horn and reflector such that there is provided above annular metallic horn 36 a hemispherical or dome-shaped reflector 62 while FIG. 10 illustrates a spherical ultrasonic transducer assembly 64 surrounded by a hollow spherical transparent reflector 66 to make the snowflakes 38. The spherical reflector also contains a upper and a lower port 68, 70 to allow the mist and ice crystals 38 to enter and the snowflakes to exit the ultrasonic field. 
     The best mode contemplated for making the snowflakes using the method and the apparatus as described above will be described with reference to the schematic diagram shown by FIG. 1 wherein the space within freezing chamber 16 and particularly the space within collector chamber 22 are cooled in advance by the freezer means or mechanism 14. The temperature within collector chamber 22 may be lower than -5° C. if there is provided the ice crystal nucleus generator means or mechanism 20. However, if there is not provided such ice crystal nucleus generator means or mechanism 20, the temperature within the freezing chamber preferably is maintained at a level on the order of -40° C. alternately, the collector chamber may be provided with any suitable super-cooling mechanism such as Peltier element 44 so that the space within said collector chamber is partially maintained at a temparature on the order of -40° C. 
     A quantity of the liquid is sprayed by liquid atomizer mechanism 12 into collector chamber 22. The liquid may be colored, for example wine, fruit juice, or liquor may be used to generate attractively colored snowflakes. Mist particles having been sprayed into collector chamber 26 are partially converted therein into ice crystals and then discharged together with the mist through mist guiding chamber 26 into the ultrasonic field. These ice crystals and mist particles 38 are directed into the ultrasonic field created by ultrasonic levitating mechanism 28 to suspend or levitate both in the standing wavefield while being levitated, the ice crystals and mist particles are bonded together under the effect of ultrasonic cohesion and thereby form snowflakes. The initial snowflakes attract further additional ice crystals and mist particles to form larger snowflakes and remain within a low pressure region in the ultrasonic field under a differential pressure of ultrasonic standing waves without being in contact with any portion of the apparatus. The ultrasonic cohesion effect continues to grow the snowflake until the size thereof reaches the order of several square millimeters and its weight correspondingly increases and falls from the ultrasonic standing wave. Each of such snow making cycles is in the order of several seconds, so the snow making as well as snow fall can be realized in a relatively continuous manner. It should be understood that the size of each snowflake can be more or less adjusted by regulating the ultrasonic output level and/or the frequency and the shape of each snowflake can be varied into two-dimensional or three-dimensional shapes such as spherical shape by changing a distribution of the ultrasonic field using the adjustable reflectors and mist guiding chambers. 
     While the invention has been described with respect to the relatively compact apparatus, a plurality of the ultrasonic levitating mechanisms may be provided side-by-side or a single ultrasonic floating mechanism may be horizontally moved to enlarge the apparatus to some degree and thereby to make a correspondingly larger quantity of snow. 
     As is apparent from the foregoing description, the method and apparatus for making snow according to the present invention allow the artificial snowflakes closely similar to the natural snowflakes to be effectively made in an artificial manner, since the snowflakes are free from contact with any portion of the apparatus during formation thereof and the snowflakes are made as the ice crystals are floated within the ultrasonic field. Furthermore, each of the snow making cycles is in the order of several seconds because the snow making is achieved by utilizing the ultrasonic cohesion effect as has been mentioned above and, therefore, snow making as well as snow fall can be continuously presented in a practically natural manner. Additionally, no large equipment, for example, of a height corresponding to the standard building which is five stories high is required but a very compact apparatus suffices to realize the artificial snow making. Accordingly, the present invention can be effectively and efficiently utilized in a show window display, a snow resisting test for building, science teaching aids, an artificial slope, etc.