AU2003100939A4 - Boomerang - Google Patents

Description

P001 Section 29 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Application Number: Lodged: Invention Title: BOOMERANG The following statement is a full description of this invention, including the best method of performing it known to us:

BOOMERANG

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a boomerang for sports, and more particularly, to a boomerang made of an excellent material with low specific gravity and high cushioning properties.

DESCRIPTION OF THE PRIOR ART Boomerangs, for sports and as toys, are thrown in the air and return to the launching point through a continuous curved path. Even though, the boomerangs in market now have been designed with various novel shapes, the profile of the boomerang's arm is basically similar to that of the airfoil so as to produce lift force on the arms when they fly in the air. Because of the resultant lift force normal to the arm section and the associated spinning torque, the boomerangs will rotate continuously, fly along a curved path and finally return to the launching location.

However, there still exist many safety-concerned problems, thus the following improvements and innovations declare the main points of the present invention: Most boomerangs are made of wooden or plastic material that have enough thickness and weight for the boomerang arms. It is to have suitable inertia and produce enough lift force when it moves in the air. However, the safety problem is the most serious issue when the boomerangs are made of hard materials. Further, the users' age for playing this kind of boomerangs need to be limited.

As depicted in Figs .3 and the prior boomerang, disclosed in the U.S. Patent 5,490,678, is essentially characterized by multiple boomerang arms extending in radial direction from the central part of boomerang. Each arm face is also symmetric about its individual axis that is distributed at equal space in circumferential direction. The main defects of this afore-mentioned boomerang are as follows: the cross-section profiles of the boomerang's arm are symmetric to the individual axis of each boomerang arm. Based on this design, the lift force produced on each arm would make the boomerang climb up to much higher altitude when the boomerang rotates and advances through a curved path in the air. Further, based on this design, the radius of the continuous curved path will be large and the boomerangs are not easy to return to the launching location.

Accordingly, the afore-mentioned boomerang is not a proper design and still exist some defects to be improved.

After intensive studies and trials for many years, the inventor has successfully developed the present invention of boomerang to overcome the disadvantages associated with the disclosed boomerang mentioned in US patent.

SUMMARY OF THE INVENTION The first object of the present invention is to declare a new design of boomerang made from a foaming plastic (or soft) material with low density and high cushioning properties. The second object of the present invention is to declare a new design boomerang having different centerline angle of the tip-blade that enables to fly at different altitudes and along various curved paths.

The new invention of the boomerang essentially comprises a central body with three arms. The center-of-gravity of the spinning axis coincides with the center of boomerang body. Each arm contains a root-blade portion and a tipblade portion. The root-blades are extended in radial direction and equally spaced in the circumferential direction. The tip-blades connect with the root-blades at the location half of the radius of the whole arm. As depicted by the dashed lines in Fig. 1, the bottom surface of the tip-blade portion is inclined at an angle from its leading edge that extends from the leading section to the tip section of the tipblade. Besides, the center axis of the tip-blade is inclined at an angle relative the symmetric axis of the root-blade portion, originating from the location at half the radius of the whole arm. The cross-sectional profiles of the tip-blade and rootblade are illustrated in Fig. 2A, 2B. They basically contain a leading edge, trailing edge and a platform portion. Further, the profile along the cross-section C-C is also illustrated in Fig. 2C to clearly describe the detailed structure. By adjusting the inclined angle and the inclined bottom surface of the tip-blade, the resultant lift force on the arm will be enhanced and the radius of the continuous curved path will be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings disclose an illustrative embodiment of the present invention that serves to exemplify the various advantages and objects hereof, and as follows: Fig. 1 is a top view showing the central body, the arms and the inclined angle of the centerline of the tip-blade relative to the symmetric line of the rootblade in the present invention; Fig. 2 depicts a top view of the boomerang; Fig. 2 is a cross sectional view of the boomerang taken along line A-A of the present invention; Fig. 2 is a cross sectional view of the boomerang taken along line B-B of the present invention; Fig. 2 is a cross sectional view of the boomerang taken along line C-C of the present invention; Fig. 3 shows the top view of the disclosed boomerang of the US patent; Fig. 4 illustrates the shape symmetric to the centerline of the boomerang arm of the US patent and the profiles at some selected cross sections in Fig. 4 Fig. 4 Fig. 4 and Fig. 4 Fig. 4(A) is a cross sectional profile of the US patented boomerang taken along line A-A; Fig. 4(B) is a cross sectional profile of the US patented boomerang taken along line B-B; Fig. 4(C) is a cross sectional view profile of the US patented boomerang taken along line C-C; and Fig. 4(D) is a cross sectional profile of the US patented boomerang taken along line D-D.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in Figs. 1 and 2, the boomerang 1 of the present invention essentially contains a central body 11 and three arms 12 where the center-ofgravity of the body coincides with the spinning axis of the boomerang. Each arm includes two parts, a root-blade 121 and a tip-blade 122. The root-blades extend radially and space equally in the circumferential direction. The tip-blade originates from the end of the root-blade, located at half the radius of the whole arm, and extends to the tip 123. The critical parameters of the tip-blade 122 are an inclined angle 01 of the center line and a inclined bottom surface 14. The inclined bottom surface 14 of the new-design boomerang extends from the leading edge 131 of the root-blade 121 to the leading edge 123 of the tip-blade 122.

Referring to Figs. 2 the cross-sectional profile of tip-blade 122 includes a leading edge 131, a platform portion 132 and a trailing edge 133, respectively. Besides, other important terminologies used are listed as follows: The blade's chord width this width is measured from the leading edge 131 to the trailing edge 133 of the tip-blade 122. Typical chord width is around The blade thickness the thickness of tip-blade 122 is around 8mm-20mm; Tip of the tip-blade 123: the most outward extending point of the tip-blade 122.

Accordingly, this design can have two types of the boomerangs, namely, the right-hand and the left-hand boomerangs. For both types of boomerang, the slightly convex surface must be faced inward (or faced to the user), and the plane surface is faced outward. In the following, the described embodiment of the present invention is based on the right-hand boomerang. When the user launches the boomerang, the angle of boomerang surface of the foaming body 1 must be nearly vertical to the ground. Note that this angle may vary when the wind speed and critical parameters of this new-design boomerang change. After the boomerang has been launched, the blade cross-section of the root-blade portion 121 and the tip- 122 (or this cross-section is close to airfoil shape) and the inclined angle 01 of the center line will generate a thrust on one side of boomerang surface through airflow, and create a buoyant force on the other side of the surface. The resultant force on each arm is called the net lift force. This net lift force on each arm is directed from the right to the left, viewing from the launcher. The net lift force produced on the advancing arm (namely, when the blade 122 is located above the center of gravity) is larger than that produced on the retreating arm (when the blade 122 is situated below the center of gravity) owing to the higher tangential speed of the advancing arm. The difference of the net lift forces created on the advancing and the retreating arms would result in an inward-directed resultant lift force and an equivalent torque that enforce the boomerang to turn along a curved path. In this invention, the inclined angle6l of the center line of tip-blade 121 and the root-blade 122 ranges between 12 degrees and 30 degrees. The boomerang body 1 can climb up to higher altitude more easily and fly back to the launching point with a steeper curved path when the inclined angle 01 of the center line is small, and the boomerang body 1 would fly in a lower path and fly back to the launching point nearly horizontally when the inclined angle 91 of the center line approach 30 degrees.

Moreover, each tip-blade 122 will produce disturbance depending on the location ahead or behind the center of gravity of the boomerang, resulting in different net lift force. In general, the lift force is large when the arm is located behind the center of gravity, and the lift force is small when the arm is situated ahead the center of gravity, an equivalent torque formed by these different lift forces would push the boomerang body 1 to turn right gradually. The inclined angle 1el of the centerline is between 12 degrees and 30 degrees. Such design can make the boomerang fly in a less steeper curved path; In other words, different inclined angle 1el can make the boomerangs fly along any curved path having different height. Thus, when the boomerang body 1 was thrown out with spin, it will climb up first due to gradually turning of the boomerang to the right, and fly back horizontally with the remaining spinning inertia. Therefore, the radius of the flying path of the boomerang body 1 will be directly proportional to the spinning inertia and inversely proportional to the net lift force. The inclined bottom surface 14 of the present invention extends from the leading edge 131 of the rootblade 122 to the leading edge 131 of the tip-blade 123., This inclined bottom surface can increase the net lift force of the boomerang, and further affect the curvature and range of the flying path.

The boomerang of present invention has advantages over the prior disclosed US patented boomerang as follows: Since the boomerang body of the present invention is made of soft material through foaming process instead of wooden or plastic material. Making the product only needs to heat the raw material first to a foam state as popcorn, and then be expanded and filled inside the mold. This organic boomerang is not only light-weighted but also possesses high cushioning property that will not cause hurt upon hitting.

The inclined angle between the centerline of the tip-blade and the rootblade of the invention is designed between 12 degrees and 30 degrees. The above design collocated with the soft foaming, low specific gravity material makes the boomerang body climb up more easily and fly back to the launching point with 6 a much steeper angle when the inclined angle of the center line is small, and vice versa.

The above-description represents only one of the embodiments of this invention, but is not limited only by the scope of the appended claims. Any changes or equivalent replacements without major progresses or improvements will be included within the disclosed range of this invention.

Claims (1)

1. 1. A boomerang which includes: a foaming body having a central portion, with a spinning axis coinciding with the center of gravity of the center portion thereof, and three arms; wherein each arm includes a root-blade and a tip-blade, said root-blade extends outward radially and spaces equally in the circumferential direction, said root- blade is symmetrically distributed about the individual radial axis, and said tip- blade originates from the end of said root-blade at a location half of the radius of the whole arm, the centerline of said tip-blade is inclined at an angle relative that of said root-blade; the main geometry parameters of said tip-blade are an inclined angle of the centerline between the tip- and root-blades and an inclined bottom surface, the inclined angle ranges between 12 degrees and 30 degrees, and the inclined bottom surface of the boomerang extends from the leading edge of said root-blade to the leading edge of said tip-blade. DATED this 1 lth day of November 2003 ING-CHUN CHEN WATERMARK PATENT TRADE MARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA