WO1991000757A1

WO1991000757A1 - Returning flying ring toy and improved airfoil

Info

Publication number: WO1991000757A1
Application number: PCT/US1990/003622
Authority: WO
Inventors: Alan J. Adler
Original assignee: Adler Alan John
Priority date: 1989-07-06
Filing date: 1990-06-27
Publication date: 1991-01-24
Also published as: EP0482122A4; AU5943090A; AU641926B2; EP0482122A1

Abstract

A returning flying ring toy (10) of modified triangular-ring planform and an improved airfoil comprising an abrupt transition (49) on the upper surface (15 - 46, 48), near the trailing edge (33).

Description

RETURNING FLYING RING TOY AND IMPROVED AIRFOIL

BACKGROUND OF THE INVENTION

The present invention relates to flying toys which can be thrown and will return to the thrower. The earliest known returning flying toys are boomerangs. It is believed by historians that boomerangs have been used for at least four thousand years. These devices are generally wooden sticks of arc-shaped planform. They are hazardous and reguire a strong and skilled thrower.

SUMMARY OF THE INVENTION:

The present invention is a returning flying toy. Its flight pattern is comparable to a boomerang but it is easier to throw and catch. It is lighter in weight and safer than any known prior art returning flying toy of comparable flight distance.

The toy comprises a body in the form of a substantially triangular ring characterized by an inner perimeter and an outer perimeter. The inner perimeter is substantially triangular with rounded corners. The outer perimeter is substantially triangular but is widened at its three corners to define three wingtip areas, at least two of which are formed to provide lift.

The preferred embodiment of the invention employs a novel airfoil section for the wingtip areas which provides improved aerodynamic performance. The airfoil is defined by the wingtip area being formed with a downwardly depending flap at its trailing edge. The airfoil cross-section is characterized by an abrupt downward transition on the upper surface where the flap joins the main portion of the airfoil. The abrupt transition encourages separation of the airflow near the trailing edge of the upper surface of the wingtip area as the body spins and is well suited to molded plastic or molded rubber manufacture.

A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a preferred embodiment of a flying ring toy according to the present invention;

Figs. 2A and 2B are edge views of two variants of the toy;

^' Fig. 3 illustrates the forces on the toy in flight; Fig. 4A is a cross-section, taken at line 4-4 in Fig. 1, illustrating the preferred embodiment of the toy and the improved airfoil;

Fig. 4B is a fragmented cross-section showing a variant on the embodiment of Fig. 4A; Fig. 5 is a cross-section, taken at line 5-5 in

Fig. 1, illustrating the preferred composite construction of the toy;

Fig. 6 is a cross-section taken at line 6-6 in Fig. 1, further illustrating the preferred composite construction of the toy; and

Fig. 7 is an edge view of an alternative embodiment.

DESCRIPTION OF SPECIFIC EMBODIMENTS Fig. 1 is a plan view of a flying ring toy 10 according to the invention. Toy 10 comprises a thin aerodynamic body 12 of substantially triangular-ring planform with an upper surface 15 and a lower surface 17. The substantially triangular-ring planform is characterized by an inner perimeter 20 of substantially triangular shape with rounded corners, encompassing a center point 22 and central opening 23. The inner perimeter is encompassed by an outer perimeter 25 of substantially triangular shape (except near the corners) to define three sides 27 of body 12.

The triangular outer perimeter is widened in the area of the three corners by laterally broadening the perimeter outward from the normal extensions of the outer perimeter lines defining the triangular sides and rounded at the three corners to define three wingtip areas 30, each having a radially outermost extremity 31, a leading edge 32, and a trailing edge 33. At least two of the wingtip areas 30 are formed so as to produce aerodynamic lift at the wingtips areas as body 12 spins about an axis which is perpendicular to the plane of the body and passes through center point 22. Fig. 2A is an edge view of the basic form of toy 10. In this basic form, wingtips 30 are substantially in the same plane as the main body 12. Fig. 2B is an edge view of the preferred embodiment of toy 10. In this preferred embodiment, wingtips 30 are bent slightly upwards above the plane of the central parts of body sides 27. This upward bend elevates the toy's flight path and makes it easier to catch upon return. The upward bend can take the form of a gentle bow curve distributed over the length of one or more of sides 27. Alternatively, the bend can be concentrated a two locations 28a and 28b along one or more sides of the triangular-ring as shown in Fig. 2B.

Fig. 3 shows the forces that are generated whe the toy is thrown forward with spin (as depicted by arrows 34) wingtip areas 30 produce aerodynamic lift

(shown by arrows 35) in a direction perpendicular to the plane of body 12. A specific wingtip area, designated 30a (which at the instant is at the top of the spin cycle) is spinning into the flow of air 37. Consequently, (because lift is proportional to the squar of the air velocity) wingtip area 30a develops greater lift than the other two wingtip areas. This greater aerodynamic lift of the top wingtip area will produce a rolling moment 40. Gyroscopic precession converts rolling moment 40 into a yawing moment 42 and causes the body to fly in a substantially circular path and return to the thrower.

. Fig. 4A is a section taken at line 4-4 in Fig. 1, and illustrates the preferred method of forming wingtip areas 30 to produce aerodynamic lift as the body spins. trailing portion of the wingtip area is configured with a depending flap 45 having an upper surface segment 46. The portion 47 exclusive of the flap is referred to as the main portion and has an upper surface segment 48. The flap is formed to define an abrupt downward transition 49 in the upper surface of the wingtip area between upper surface segments 46 and 48.

In this context, an abrupt transition is defined as a change in angle of the contour of the surface when viewed in cross-section, wherein the change of angle is accomplished relatively sharply. In the preferred embodiment of the invention the change of the angle is approximately 50°, however, it is believed that any change of angle greater than approximately 20° will achieve the desired flow separation. The abrupt transition 49 is so formed to encourage separation of the airflow over the upper surfaces 15 of the wingtip areas at the abrupt downward transition as the body spins about its center point.

Upper surface segment 48 is non-concave (typically convex or flat over all of its area) as part of an effort to further assist delaying flow separation until the flow reaches the^" abrupt transition. Upper surface segment 46 is flat. However, Fig. 4B shows a variant where the flap, designated 45', has a concave upper surface. - The present inventor has discovered that, with small scale flying objects, the airfoil of Fig. 4A has less drag for a given amount of lift than conventional airfoils. It is believed that flow separation in this airfoil is delayed until the flow reaches abrupt transition 49 near the trailing edge of the airfoil, as opposed to the more common laminar separation which occurs near the leading edge of small scale airfoils. It is anticipated that this improved airfoil will be found advantageous when applied to other flying toys, such as flying rings, boomerangs, propellers, and toy or model airplanes. A further benefit of the improved airfoil depicted in Fig. 4A is that it can be manufactured in a mold having a planar parting line 50, as opposed to twisted wings (such as that of Fig. 7) which require that the mold have a non-planar parting line in order to meet the leading and trailing edges. Molds with planar parting lines can be made with greater precision and lower cost than molds with non-planar parting lines. Figs. 1, 5, and 6 also illustrate another feature of the preferred embodiment of the invention. The body is molded of two different materials. First an inner triangular ring backbone 52 is molded from a relatively rigid, yet springy, thermoplastic material such as polycarbonate. Backbone 52 is then inserted into a second mold and the inner and outer perimeter portions 55 and 57 comprised of a soft resilient material (such as thermoplastic rubber) , are molded over the backbone. The resulting composite body is safer than if made from a single material.

In the preferred embodiment of the planform of body 12, the outer perimeter 25 is widened at the wingtip areas so as to increase the area of the wingtip areas such that the aerodynamic rolling moment (produced by their aerodynamic lift) and the resulting yawing moment will be enhanced. The widened wingtip areas have a crescent-shaped planform with a convex leading edge and a concave trailing edge. The trailing edges 33 of the crescent-shaped wingtip^' areas provides a convenient plac 6 to apply pressure with the tip of the forefinger while throwing and thus impart spin to the body. It is note_d that some recent articles in the aerodynamic literature have suggested that crescent-shaped wingtips have slightly lower induced drag than other tip planforms. However, the primary reason for the use of crescent-shaped wingtip areas on the present invention is to facilitate throwing with spin.

In the preferred embodiment of the invention the thickness of the modified triangular-ring body 12 is 0.125 inches and the chord of the modified triangular- ring, as measured at the side of the modified triangle from the^' nner perimeter to the outer perimeter, is ₁.₁₂₅ inches. The chord of each wingtip area 30 is about ₁.₇ inches. However as can be seen in Fig. l, the chor_d is not constant and diminishes to zero at the extremity of the wingtip. The radius from the center 22 to extremity 31 of the wingtips is 6.375 inches. Lower surface 17 is substantially flat except in the region of the downwardly depending flaps 45. As noted above, upper surface 15 is preferably convex except in the region of the flaps. The total weight is approximately two ounces, yet the returning flying ring can fly a circular path approximately 100 feet in diameter and return to the thrower. Central opening 23 provides an easy means of catching the returning flying ring upon return.

An alternative method of forming wingtip areas 30 so that they produce aerodynamic lift as the body spins is to twist them in the manner of a propeller, as depicted, in Fig. 7, which is an edge view of the _device.

While in the foregoing specification embodiments of the invention have been set forth in detail for,purposes of making a thorough disclosure of the invention, it will be apparent to those skilled in the art that numerous changes can be made in such _details without departing from the spirit of the invention.

Claims

WHAT IS CLAIMED IS:

l. A returning flying ring formed as a thin aerodynamic body with an upper surface and a lower surface, the body being characterized by: an inner perimeter of substantially triangular shape with rounded corners, encompassing a center point and a central opening; an outer perimeter of substantially triangular shape widened and rounded at the three corners to define three wingtip areas; and at least two of said wingtip areas being formed so as to produce aerodynamic lift at said wingtip areas as said body spins about an axis which is perpendicular to the plane of said body and passes through said center point; such that when said returning flying ring is thrown forward with spin, said aerodynamic lift of said wingtip areas will produce a rolling moment which gyroscopic precession will convert into a yawing moment and cause said returning flying ring to fly in a substantially circular path thereby returning to the vicinity from which it was thrown.

2. The returning flying ring of claim l wherein said outer perimeter is formed such that said wingtip areas are crescent-shaped.

3. The returning flying ring of claim l wherein at least two of said wingtip areas are twisted, in the manner of a propeller, so as to produce said aerodynamic lift at said wingtip areas.

4. The returning flying ring of claim l wherein at least one of said wingtip areas is formed wit a main portion and with a downwardly depending flap at the trailing edge of said wingtip area in order to produce said aerodynamic lift at said wingtip area.

5. The returning flying ring of claim 1 wherein portions of said body bounding said inner and outer perimeters are formed of a soft resilient material so as to enhance the safety of said returning flying ring.

6. The returning flying ring claim 4 wherein at least one of said wingtip areas is shaped with a cross-section characterized by an abrupt downward transition on the upper surface of said wingtip area at the intersection of the upper surface of said main portion of said wingtip area and the upper surface of said downwardly depending flap so as to encourage separation of the airflow over said upper surface of said wingtip area at said abrupt downward transition.

7. A returning flying ring having a thin aerodynamic body with an upper surface, the body being characterized by: an inner perimeter of substantially triangular shape with rounded corners, encompassing a center point and central opening; and an outer perimeter of substantially triangular shape, said outer perimeter being widened and rounded at the three corners to define three wingtip areas; each of at least two of said wingtip areas being formed with a downwardly depending flap with an abrupt downward transition between the upper surface of a main portion of said wingtip area and the upper surface of said flap so as to encourage separation of the airflow over said upper surfaces of said wingtip areas at said abrupt transition, and further to produce aerodynamic lift at said wingtip areas as said body spins about an axis which is perpendicular to the plane of said body and passes through said center point; such that when said returning flying ring is thrown forward with spin, said aerodynamic lift of said wingtip areas will produce a rolling moment which gyroscopic precession will convert into a yawing moment and cause said returning flying ring to fly in a substantially circular path thereby returning to the vicinity from which it was thrown.

8. An airfoil for use in a flying toy having a cross-section characterized by: a main portion having a non-concave upper surface; and a downwardly depending flap at a trailing edge of the airfoil, said flap having an upper surface; said upper surfaces of said main portion and said flap coming together in a manner that defines an abrupt downward transition in the upper surface of said airfoil.

9. The airfoil of claim 8 wherein said upper surface of said main portion is convex.

10. The airfoil of claim 8 wherein said upper surface of said flap is flat.

11. A returning flying ring of triangular-rin planform, comprising: an inner triangular-ring backbone molded from relatively rigid, yet springy, thermoplastic material; and inner and outer perimeter portions formed from a soft resilient material, molded over said backbone; said ring being formed with three widened wingtip areas, at least two of which are formed to produce aerodynamic lift as said ring spins around an axis which is perpendicular to said planform and passes through the center of said ring.