Abstract:
A self-returning aerial glider is disclosed, which can be launched to travel outwardly away from the point of launching and subsequently reverse its flight and return to the location of launching. The object is comprised of a generally ring-shape planar body conforming to specific dimensional proportions and mass-to-projected-area ratios optimized to producing favorable return glide behaviors.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to flying disc toys and more particularly to circular, generally flat, aerial devices that are thrown and return to the thrower.  
         BACKGROUND OF THE INVENTION  
         [0002]    There have been available a variety of different flying disc devices that may be thrown back and forth between two or more participants. See, for example, U.S. Pat. Nos. 4,944,707, 4,560,358, 4,456,265, 4,104,822, 3,765,122, 1,986,937, and 248,901. One drawback with this type of devices is that at least two participants are required to use, so the device may be tossed back and forth. The unintended one-person game possibilities are limited to flinging a flying disc forwardly at a tilt, ideally into a strong wind, so that with the aid of the wind force the disc may partially slide back to the thrower. One drawback is that if the proper wind condition does not exist, such practice would be difficult to execute. Ultimately, these traditional flying disc devices are not designed to be self-returning and are not intended to be used by only one person.  
           [0003]    Some variants of flying disc devices have non-linear flight paths and, if thrown just right, can either partially or substantially return to the thrower. See, for example, U.S. Pat. Nos. 5,816,879, 5,340,347, 4,506,894, 4,337,950, and 4,203,249. However, the flight paths of this type of devices are typically not linear and, therefore, less predictable. In addition, these devices usually can only be used in large, open spaces and, when used indoors, tend to be somewhat dangerous.  
           [0004]    Another type of flying disc devices relies on a tether line to cause the disc to change direction and return to the thrower. Such flying disc devices are disclosed for example in the U.S. Pat. Nos. 5,275,417, 5,254,077, 5,066,258, and 3,976,297. These devices tend to contain many parts and are more complicated to use. In general, these devices are also not suitable to use indoors.  
           [0005]    The boomerang is a widely know device having the property of returning. The boomerang flies in a circle because the upper wings, which are rotating into the wind, develop greater lift than the lower wings, which are rotating with the wind. This creates a banking moment, which is converted by gyroscopic precession to a turn. See U.S. Pat. Nos. 5,213,539, 4,934,713, 4,479,655, and 3,955,817 for examples that employ this operational principle. By the nature of its operational principle, the boomerang is a relatively heavy article being thrown with a significant force and is usually used in large, open spaces. Thus, one drawback is that the boomerang tends to be dangerous to use, especially within a relatively small space.  
           [0006]    As can be summarized from the prior art described above, a common disadvantage of known flying disc devices is that they are not suitable to be thrown indoors or in small spaces.  
           [0007]    A further disadvantage is that most conventional flying disc devices, when being used in the presence of bystanders, especially children, tend to be dangerous.  
           [0008]    Another common disadvantage of known flying disc devices is that by design they typically require convex surfaces or other complex surface features to maintain lift throughout the flight. This requirement precludes the use of low-cost manufacturing processes by witch an article is created by stamping out the desire contour from a flat sheet of lightweight material, such as a sheet of Styrofoam, other foam materials, or rigid paper.  
           [0009]    A further disadvantage of conventional flying disc devices is the limitation of appropriate image imprinting methods that can be used on the typically convex surfaces or other complex surface features. Therefore, imprinting high-quality images or messages, such as corporate identities or advertising, is either difficult or expensive.  
           [0010]    Yet another common disadvantage of known flying disc devices is that an individual typically can throw only one disc at a time. The game possibilities of stacking together multiple discs and throwing them all at once, while novel and appealing in exhibitions, are either impossible or awkward to perform with traditional flying disc devices, again due to the less stackable convex surfaces or other complex surface features.  
           [0011]    There has thus been a need for an aerial device that can be used by one individual, can successfully return to the thrower without wind, can be thrown in a small space, is safe to operate among bystanders, can provide single- and multi-disc game possibilities, can be manufactured cheaply, and can be imprinted easily.  
         OBJECTS AND ADVANTAGES  
         [0012]    Accordingly, a general object of the present invention is to provide an aerial device having superior self-returning characteristics for use by one individual.  
           [0013]    A more specific object is to provide such an aerial device conforming to the dimensional proportions and mass-to-projected-area ratios that are optimized to producing favorable return glide paths back to the thrower in absence of wind.  
           [0014]    Another object of the present invention is to provide such an aerial device in a form that is suitable to be used indoors, for examples, at home, in the office, or in enclosed public spaces.  
           [0015]    Yet another object is to provide such an aerial device in a form that is generally safe to use in the presence of bystanders, especially children.  
           [0016]    Another object is to provide such an aerial device in a form that is substantially thin and flat, so multiple discs can be stacked together and thrown all at once, offering novel game possibilities, which can be especially appealing in public exhibitions.  
           [0017]    Yet another object is to design such an aerial device in such way that only flat surfaces are used. Therefore, the aerial device can be manufactured by stamping out the device from a flat sheet of lightweight material such that extremely low manufacturing cost can be achieved.  
           [0018]    Another object is to design such an aerial device in such way that the surface characteristics facilitate easy imprinting of messages and high-quality images, such as logos and advertisements.  
           [0019]    Further objects and advantages of the present invention will become apparent from a consideration of the drawings and ensuing description. 
       
    
    
     DESCRIPTION OF DRAWINGS  
       [0020]    For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings.  
         [0021]    [0021]FIG. 1 is a perspective view of an exemplary embodiment of the present invention.  
         [0022]    [0022]FIG. 2 is a plan view of the aerial device illustrated in FIG. 1.  
         [0023]    [0023]FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2.  
         [0024]    [0024]FIG. 4 is a side view of the aerial device illustrated in FIG. 1.  
         [0025]    [0025]FIG. 5 is a schematic representation of the flight of the aerial device when thrown so as to return to the thrower.  
         [0026]    [0026]FIG. 6 is a schematic representation of an alternative game possibility where multiple aerial devices of the same size are stacked together and thrown.  
         [0027]    [0027]FIG. 7 is a schematic representation of an alternative game possibility where multiple aerial devices of different sizes are stacked together and thrown.  
         [0028]    FIGS.  8 A-G show several examples of possible variations of the present invention. In FIG. 8A the outer perimeter is a circle, but the inner perimeter is an oval. In FIG. 8B the outer perimeter is an oval, but the inner perimeter is a circle. In FIG. 8C the outer perimeter is an oval, and the inner perimeter is also an oval. FIGS.  8 D-F illustrate further perimeter contour variations. FIG. 8G shows the plan view of one example where the center of the inner perimeter and the center of the outer perimeter are different.  
         [0029]    [0029]FIG. 9 is a perspective view of an exemplary embodiment of a variation of the present invention where multiple aerial devices are joined together.  
     
    
     SUMMARY  
       [0030]    A self-returning aerial glider is disclosed, which is comprised of a thin, lightweight planar body, conforming to the dimensional proportions and mass-to-projected-area ratios according to the ensuing disclosed data. When the ensuing disclosed dimensional proportions and mass-to-projected-area ratios are followed to manufacture the invention, optimal return glide behaviors would be achieved. The aerial device can be launched to travel outwardly away from the point of launching and subsequently reverse its flight and return to the location of launching.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    [0031]FIG. 1 is a perspective view of an exemplary embodiment of the present invention. It includes a thin, planar body  1 , having a substantially flat upper surface  2 , a substantially flat lower surface  3 , a central opening  4 , an outer perimeter  5 , and an inner perimeter  6 . The outer perimeter has a center  7 , and the inner perimeter has a center  8 . Note that in this exemplary embodiment the center of the outer perimeter and the center of the inner perimeter are the same point in space. However, these two centers are not required to be the same in all embodiments of the present invention; in other variations of the present invention the center of the outer perimeter and the center of the inner perimeter may be different points. Other details of the invention will be discussed while referencing the remaining figures.  
         [0032]    A factor that enables the performance of this invention is the employment of extremely lightweight materials—lighter than prior art by approximately one to two orders of magnitude per unit of projected area. This practice is contrary to the teaching of traditional flying disc designs, which rely on a certain amount of mass to maintain linear and rotational moment, and thus further require the use of a convex airfoil to generate lift to counter the resulting weight. This invention, on the other hand, is constructed of a flat sheet of material of less than 0.15 grams per square centimeter of projected area. The preferred embodiment presented in this description, at 0.0151 grams per square centimeter of projected area, is approximately 150 to 500 times lighter than the typical plastic materials used in traditional flying disc devices. Some examples of such materials include Styrofoam, other foam materials, and various lightweight plastics. The low weight-to-projected-area ratio helps keep the cumulative vertical drop throughout the return flight to minimum.  
         [0033]    The achievement of minimal cumulative vertical drop throughout the return flight eliminates the need for a convex airfoil, typically found in traditional flying disc devices. Thus, contrary to prior art devices, which generally require a convex airfoil or other complex surface features to maintain lift, the surface of this invention is substantially flat in most embodiments. As can be seen in FIG. 3, a cross-sectional view taken along line A-A, the upper surface  2  and the lower surface  3  are substantially flat. FIG. 4, a side view of the aerial device, also shows that the upper surface  2  and the lower surface  3  are substantially flat. The ability of this invention to use only flat surfaces means that the aerial device can be manufactured by stamping out the article from a flat sheet of lightweight material such that extremely low manufacturing cost can be achieved.  
         [0034]    Another factor that enables the performance of this invention is the aerodynamic characteristics produced by the dimensions that conform to the specific ratios between the radius of the inner perimeter and the radius of the outer perimeter. FIG. 2 shows the aerial device according to FIG. 1 in a planar projection. The outer perimeter has the radius of r, and the inner perimeter has the radius of s. For a given size of the aerial device there is a corresponding range of optimal ratios between the inner perimeter radius and the outer perimeter radius. When constructing the aerial device, this range must be conformed in order to achieve favorable return glide behaviors. That is to say, given a value of r, the value of s must fall within a critical range in order to achieve favorable return glide behaviors. Note that the value range for this ratio is not constant; the value range varies depending on the size of the aerial device being constructed.  
         [0035]    The following data discloses these parameters.  
                                                                 r &lt; 12 cm   s = 0.833 r to 0.900 r           r &gt;= 12 cm and r &lt; 24 cm   s = 0.750 r to 0.892 r           r &gt;= 24 cm and r &lt; 48 cm   s = 0.667 r to 0.884 r           r &gt;= 48 cm   s = 0.634 r to 0.875 r                where           r = radius of said outer perimeter           s = radius of said inner perimeter                      
 
         [0036]    The present inventor systematically experimented with multitude of experimental articles. When experimental articles that do not conform to the above formula were thrown, on the return flight the articles would tend to bank to one side and fall to the ground, failing to return to the location of launching. Systematic experiments with different prototypes of different dimensional proportions lead to the discovery that when an aerial device was constructed in conformance to the proper ratios between the inner perimeter radius and the outer perimeter radius, a beautiful, straight, and stable return path back to the thrower was produced. A genuine breakthrough in return flight performance had been achieved. Without the requirement of any convex surfaces or complex surface features, using only properly proportioned dimensions to generate the desired aerodynamic characteristics, here was a cheap-to-manufacture aerial device that achieved stable, substantially straight, return flight back to the thrower.  
         [0037]    While flat sheets of lightweight materials should be used in manufacturing the present invention, slightly defective sheets that are not perfectly flat are sometimes unavoidable when acquiring large quantities of raw materials. When one must make use of sheets that have an unavoidable minute curvature, the resulting aerial device should be thrown with the convex side facing down.  
         [0038]    Detailed specifications of a preferred embodiment of the present invention are presented below:  
         [0039]    Outer and inner perimeters are substantially circular.  
         [0040]    Outer and inner perimeters are substantially concentric.  
         [0041]    Outer perimeter radius=22.86 cm  
         [0042]    Inner perimeter radius=19.04 cm  
         [0043]    Thickness=0.35 cm  
         [0044]    Mass=7.59 g  
         [0045]    Mass per square centimeter of projected area=0.0151 g  
       OPERATION OF INVENTION  
       [0046]    Referring to FIG. 5, a schematic representation of the flight of the present invention, in use the aerial device is thrown with a snap of the wrist to impart a rotational velocity. The direction of travel is inclined slightly at an angle above the horizon. For most angles of inclination at launch, the aerial device can be launched to travel along a substantially straight path outwardly away from the point of launching and subsequently reverse its flight and return to the thrower.  
         [0047]    The ability to maintain a stable, substantially straight, beautiful, return flight is attributed to the lasting gyroscopic stability. Because the invention&#39;s substantially smooth outline is free of any large protruding physical features, the air friction caused by the rotation of the aerial device is kept to minimum. Consequently, the rotational velocity imparted to the aerial device by the thrower is maintained substantially throughout flight. This rotational velocity generates gyroscopic stability, witch helps the aerial device maintain its incline angle. This gyroscopically stabilized incline facilitates the aerial device to glide back to the thrower on air cushion.  
         [0048]    In addition to the lasting gyroscopic stability, the lightweight of the device further contributes toward achieving the exceptional return glide path. For a given projected area, this invention is approximately 150 to 500 times lighter than typical prior art devices. The low weight-to-projected-area ratio helps keep the cumulative vertical drop throughout the return flight to minimum. As a result, when thrown correctly, the height at which this aerial device returns is typically only slightly lower then the height at launch.  
         [0049]    Furthermore, in operation the invention is reasonably safe to the thrower as well as the bystanders because the total mass of the aerial device is relatively small.  
         [0050]    Additionally, the present invention has novel operational possibilities. Because the surface of the present invention is substantially flat, multiple aerial devices can be stacked together and thrown all at once, offering novel game possibilities, especially in public exhibitions. FIG. 6. shows that multiple aerial devices of the same size can be stack together and thrown all at once. FIG. 7. shows that multiple aerial devices of different sizes can be stack together and thrown all at once.  
       CONCLUSION, RAMIFICATIONS, AND SCOPE OF INVENTION  
       [0051]    Thus the reader will see that the present invention provides high entertainment value where an individual can throw the aerial device outwardly along a nice straight path away from the point of launching, and the aerial device will subsequently reverse its flight and return to the location of launching, also along a nice straight path. Furthermore, the present invention has the additional benefits in that the present invention  
         [0052]    can be used by one individual,  
         [0053]    can successfully return to the thrower without wind,  
         [0054]    can be used in a small space,  
         [0055]    is safe to operate among bystanders,  
         [0056]    can provide single- and multi-disc game possibilities,  
         [0057]    can be manufactured cheaply,  
         [0058]    and can be imprinted easily.  
         [0059]    While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible.  
         [0060]    For example, the inner perimeter, the outer perimeter, or both may be defined by various geometric contours while the overall close-figure shape of the device is still substantially maintained. FIGS.  8 A- 8 F show the plan views of some examples of perimeter variations in accordance with this invention. In FIG. 8A the outer perimeter is a circle, but the inner perimeter is an oval. In FIG. 8B the outer perimeter is an oval, but the inner perimeter is a circle. In FIG. 8C the outer perimeter is an oval, and the inner perimeter is also an oval. FIGS.  8 D-F illustrate further perimeter contour variations. For the purpose of computing the radius of a perimeter in conformance to the formula disclosed previously, when a perimeter used is not a perfect circle, the average of the distances taken along the perimeter from its mass center would be used as the value for the radius of the perimeter.  
         [0061]    In other variations of the invention, the aerial device may be constructed such that the centers of the outer and inner perimeters offset from each other while the aerial device still conforms to the aforementioned formula that governs the ratios between the average inner radius and the average outer radius. FIG. 8G shows the plan view of one example where the center of the inner perimeter and the center of the outer perimeter are different.  
         [0062]    Another variation is to construct the invention in extreme sizes, which is appealing in public exhibitions. Yet another variation is to link multiple copies of the aerial devices together. FIG. 9 shows the perspective view of an exemplary embodiment of a variation of the present invention where multiple aerial devices are joined together. Further variations include applying neon-like surface paint, using night-glowing materials, or attaching electric illuminators, just to name a few.  
         [0063]    Accordingly, the scope of the invention should be determined not by the embodiment illustrated, but by the appended claims and their legal equivalents.