Boomerang for sport

Information

  • Patent Grant
  • 6659832
  • Patent Number
    6,659,832
  • Date Filed
    Wednesday, February 12, 2003
    21 years ago
  • Date Issued
    Tuesday, December 9, 2003
    20 years ago
Abstract
A boomerang is made from a flat sheet material, and includes a plurality of blades connected to a central body by a plurality of interconnecting portions, and angularly displaced from one another about a center point. Each blade includes leading and trailing edges that are symmetrical relative to a middle line. Each interconnecting portion extends along a radial axis which intersects the middle line to form an obtuse included angle therewith. Each blade has a bent line that is positioned between the middle line and the trailing edge thereof, and cooperates with the trailing edge to define a bent portion which faces towards the leading edge and which forms an obtuse included angle with a horizontal plane. Varying the position of the bent lines and the included angles of the bent portions can change flight patterns and flight range of the boomerang.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




This invention relates to a boomerang for sport, more particularly to a boomerang made from a flat sheet material of a reduced weight so as to ensure safety.




2. Description of the Related Art




Boomerangs, which have been used for sport in recent years, are devices capable of being thrown by a user, flying in a continuous path, and returning to the point of launching. Referring to

FIGS. 1

to


3


, two conventional boomerangs


5


,


6


are shown to include two arms


51


,


52


and three arms


61


, respectively. Each arm


51


,


52


,


61


is designed to have an airfoil thickness such that, when the boomerang


5


,


6


is thrown, air flows over its leading edge


511


,


521


,


611


and its trailing edge


512


,


522


,


612


to produce a lift force according to Bernoulli's law, and the boomerang


5


,


6


continues rotation until it returns to the point of launching. As such, the boomerang


5


,


6


is required to have a sufficient thickness in order to produce the desired lift, thereby resulting in a greater weight thereof, which in turn results in a larger flight range. Therefore, the conventional boomerangs


5


,


6


generally cannot be used in a relatively narrow area.




To overcome the above problem, referring to

FIGS. 4 and 5

, another conventional boomerang


7


was proposed. The boomerang


7


is made from a thin plate, and is shown to include four arms


71


, each of which has two bent portions


711


,


712


so as to reduce the overall weight of the boomerang


7


. However, as the flight path of the boomerang


7


is monotonous, the boomerang


7


is not interesting to play with.




SUMMARY OF THE INVENTION




The object of the present invention is to provide a sport boomerang which is capable of adjustable flight patterns and which has an adjustable flight range.




According to this invention, the boomerang is made from a flat sheet material, and includes a central body with an outer periphery surrounding a center point. The central body has top and bottom surfaces that are substantially parallel to each other and that are symmetrical relative to a horizontal plane. A plurality of interconnecting portions are integrally formed with the outer periphery of the central body, and are angularly displaced from one another about the center point. Each of the interconnecting portions extends outwardly and along a radial axis, and terminates at a boundary region. A plurality of blades are integrally and respectively formed with the interconnecting portions, and are angularly displaced from one another. Each of the blades includes leading and trailing edges which are opposed to each other in one of clockwise and counterclockwise directions when the blades are turned about an axis that is normal to the horizontal plane and that passes through the center point, and which are symmetrical relative to a middle line. Each of the blades further includes a distal end which is opposed to the boundary region along the middle line and which joins the leading and trailing edges, respectively, at leading and trailing junctures. The middle line intersects the radial axis to form an obtuse included angle therewith, which faces towards the leading edge. Each blade further includes a bent line which extends towards the distal end and which is positioned between the middle line and the trailing edge. A bent portion, which faces towards the leading edge, is defined by the bent line and the trailing edge. The bent portion forms an obtuse included angle with the horizontal plane.











BRIEF DESCRIPTION OF THE DRAWINGS




Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which:





FIG. 1

is a fragmentary perspective view of a conventional boomerang with two arms;





FIG. 2

is a top view of a conventional boomerang with three arms;





FIG. 3

is a cross-sectional view of the boomerang shown in

FIG. 2

, taken along lines


3





3


thereof;





FIG. 4

is a top view of a conventional boomerang with four arms;





FIG. 5

is a cross-sectional view of the boomerang shown in

FIG. 4

, taken along lines


5





5


thereof;





FIG. 6

is a top view of a preferred embodiment of a boomerang according to this invention;





FIG. 7

is a cross-sectional view of the boomerang shown in

FIG. 6

, taken along lines


7





7


thereof;





FIG. 8

is a top view illustrating the preferred embodiment in a state of flight;





FIG. 9

is a schematic view illustrating how the preferred embodiment is held by the thrower; and





FIG. 10

is a top view of another preferred embodiment of the boomerang according to this invention.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring to

FIGS. 6 and 7

, the preferred embodiment of a boomerang


1


according to the present invention is formed from a thin, flat sheet material of a substantially uniform thickness that is less than 2 mm, and has a single-piece construction. The boomerang


1


is shown to be throwable by a right-handed user, and comprises a central body


10


, three interconnecting portions


21


, and three blades


22


.




The central body


10


has an outer periphery surrounding a center point


11


, and top and bottom surfaces that are substantially parallel to each other and that are symmetrical with respect to a horizontal plane. The interconnecting portions


21


are integrally formed with the outer periphery of the central body


10


, and are angularly displaced from one another about the center point


11


. Each of the interconnecting portions


21


extends outwardly and along a radial axis


31


, and terminates at a boundary region. The blades


22


are integrally and respectively formed with the interconnecting portions


21


, and are angularly displaced from one another. Each of the blades


22


includes leading and trailing edges


223


,


224


which are opposed to each other in one of clockwise and counterclockwise directions when the blades


22


are turned about an axis that is normal to the horizontal plane and that passes through the center point


11


. In this embodiment, the leading and trailing edges


223


,


224


are opposed in the counterclockwise direction. The leading and trailing edges


223


,


224


are symmetrical with respect to a middle line


32


. Each of the blades


22


further includes a distal end


221


which is opposed to the boundary region along the middle line


32


and which joins the leading and trailing edges


223


,


224


, respectively, at leading and trailing junctures


2231


,


2241


.




The middle line


32


intersects the radial axis


31


to form an obtuse included angle


0




1


therewith, which faces towards the leading edge


223


. In other words, each of the blades


22


curves toward an adjacent one of the blades


22


that is disposed forwardly thereof in turns of the direction of a spin. Each of the blades


22


includes a bent line


222


which extends towards the distal end


221


, which is in parallel to the middle line


32


, and which is positioned between the middle line


32


and the trailing edge


224


. Thus, a bent portion


226


, which faces towards the leading edge


223


, is defined by the bent line


222


and the trailing edge


224


. Referring to

FIG. 7

, the bent portion


226


forms an obtuse included angle θ2 with the horizontal plane. In addition, a plane portion


225


is defined between the bent line


222


and the leading edge


223


. The central body


10


, the interconnecting portions


21


and the blades


22


are of substantially the same thickness.




With reference to

FIG. 9

, in combination with

FIGS. 7 and 8

, the thrower can hold the plane portion


225


of one of the blades


22


, and then throw the boomerang


1


in a direction indicated by arrow (I). The boomerang


1


will rotate about the axis passing through the center point


11


in a direction indicated by arrow (II), and then return to the point of launching.




In particular, when the boomerang


1


is thrown with a spin in an almost vertical state (i.e. the axis passing through the center point


11


is parallel to the ground) so as to rotate through the air, due to the presence of the included angle θ2 between the bent portion


226


and the horizontal plane, a thrust is generated by airflow to act upon one side of the bent portion


226


, thereby creating a lift at the other side of the bent portion


226


from right to left (as viewed by the thrower). Since there is more lift at the top of the spin than that at the bottom, the difference in lift forces results in a first torque that acts upon the substantially vertical boomerang


1


to cause it to fly leftward in a curve path. At the same time, as more lift is generated in front of the center point


11


(center of mass of the boomerang


1


) than behind the center point


11


, a second torque results to cause the boomerang


1


to lay down horizontally and rightwardly in a gradual manner while the boomerang


1


climbs to a highest point. Thereafter, the boomerang


1


will returns to the point of launching by virtue of residual rotational inertia. Therefore, the flight range of the boomerang


1


is in a direct proportion to the rotational inertia, and is in an inverse proportion to the lift.




Accordingly, referring to

FIG. 8

, since the bent line


222


of each blade


22


is offset from the center point


11


by an offset distance (X), and since the offset distance (X) can decrease the second torque, the height of flight of the boomerang


1


can be varied by adjusting amount of the offset distance (X). Besides, the flight range can be varied by adjusting length and width of the bent portions


226


and the included angle θ2.




Moreover, since the boomerang


1


according to this invention is made from a thin flat sheet material, it has a smaller rotational inertia so that a relatively small lift force is required for rotation thereof. Therefore, the boomerang


1


of this invention is lighter and safer.




Referring to

FIG. 10

, another preferred embodiment of the boomerang


1


according to this invention is shown to be similar to the aforesaid embodiment in construction, except that the top surface of the central body


10


has a circular through hole


12


which extends through the bottom surface of the central body


10


and which surrounds the axis passing through the center point


11


. As such, the weight of the boomerang


1


is decreased, and the gyration stability of the boomerang


1


is increased. It is noted that the through hole


12


can have a rectangular or triangular shape.




Further, the boomerang


1


of this invention can be configured to have four interconnecting portions and four blades which are angularly displaced from one another so as to achieve similar flight characteristics.




The advantages of the boomerang


1


of this invention are as follows:




1. Since the blades


22


are provided with the bent portions


226


that are defined by the bent lines


222


and the trailing edges


224


so as to create lift during flight of the boomerang


1


, compared to the conventional boomerang with the complicated airfoil structure, the boomerang


1


of this invention is easy to fabricate, and can be manufactured at a relatively low cost. Besides, the boomerang


1


has a reduced weight to ensure safety of the thrower and bystanders.




2. The offset distance (X) can be determined according to the thickness and material of the boomerang


1


so as to vary the height of flight of the boomerang


1


. In addition, the length and width of the bent portion


226


and the included angles θ2 can be varied to change the flight range of the boomerang


1


. Thus, the boomerang


1


can be designed to perform different flight patterns, and is suitable for use in spatial and narrow spaces.




While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.



Claims
  • 1. A boomerang made from a flat sheet material, comprising:a central body with an outer periphery surrounding a center point, said central body having top and bottom surfaces that are substantially parallel to each other and that are symmetrical relative to a horizontal plane; a plurality of interconnecting portions integrally formed with said outer periphery, and angularly displaced from one another about the center point, each of said interconnecting portions extending outwardly and along a radial axis, and terminating at a boundary region; and a plurality of blades integrally and respectively formed with said interconnecting portions, and angularly displaced from one another, each of said blades including leading and trailing edges which are opposed to each other in one of clockwise and counterclockwise directions when said blades are turned about an axis that is normal to the horizontal plane and that passes through the center point, and which are symmetrical relative to a middle line, each of said blades further including a distal end which is opposed to said boundary region along the middle line and which joins said leading and trailing edges respectively at leading and trailing junctures, wherein, the middle line intersects the radial axis to form an obtuse included angle therewith, which faces towards said leading edge of a respective one of said blades, each of said blades further including a bent line which extends towards said distal end and which is positioned between the middle line and said trailing edge such that said bent line and said trailing edge define a bent portion which faces towards said leading edge, said bent portion forming an obtuse included angle with the horizontal plane.
  • 2. The boomerang of claim 1, wherein said plurality of interconnecting portions include three of said interconnecting portions, and said plurality of blades include three of said blades.
  • 3. The boomerang of claim 1, wherein said central body, said interconnecting portions and said blades are of substantially the same thickness.
  • 4. The boomerang of claim 1, wherein said top surface has a through hole which extends through said bottom surface and which surrounds the axis.
  • 5. The boomerang of claim 4, wherein said through hole is a circular hole.
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Number Name Date Kind
3881729 Block et al. May 1975 A
5199717 Wimmer Apr 1993 A
5615892 Miller Apr 1997 A
D389878 Tylor Jan 1998 S
6179738 Perthou Jan 2001 B1
Foreign Referenced Citations (3)
Number Date Country
112382 May 1996 JP
159604 Jun 2002 JP
WO 9826844 Jun 1998 WO
Non-Patent Literature Citations (2)
Entry
US 20030083160A1, Ben-Hador, May 2003.*
US 20010024923A1, Streit, Sep. 2001.