Games using tangible projectile – Projectile – per se; part thereof or accessory therefor – Boomerang
Reexamination Certificate
2001-01-04
2001-09-25
Wong, Steven (Department: 3711)
Games using tangible projectile
Projectile, per se; part thereof or accessory therefor
Boomerang
Reexamination Certificate
active
06293879
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
This invention relates to boomerangs, an aerodynamic shaped implement that when thrown into the air, with a degree of skill, will return to the person throwing it.
BACKGROUND—DESCRIPTION OF PRIOR ART
Most boomerangs are patterned after the ancient aboriginal boomerang that was used as a weapon. See
The World Book Encyclopedia
, 1997 edition. These boomerangs have a bend, called an elbow, near the middle, that forms two wings shaped like airplane wings. This type of boomerang, because of its far flying capability, is still favored for outdoor use. The shape and rotational speed make this type nearly impossible to catch and poses a risk of injury to bystanders. Manufacturers of this type often place warning labels on them. If one were hit in the head or eye most prior art boomerangs could inflict serious injury. Because of this hazard crowded areas must be avoided and younger children can't participate in the sport.
There are a variety of modern toy or sport boomerangs ranging from small, indoor types made of foam to larger, outdoor types made of wood or plastic. All of these boomerangs have from two to five wings or rotor blades connected at a center point. Since boomerangs must rotate as they fly, to produce stability and the gyroscopic precession which cause them to return, these wings must be considered more like the rotor blades of a helicopter.
A rotor blade consists of an upper and lower surface which are essentially parallel with respect to one another along a center line drawn from wing root to wing tip. The lower surface is essentially flat and the upper surface arched from leading edge to trailing edge, forming an airfoil along the length of the blade. With this type of boomerang the rotor blades fly and the central hub is only a means for holding the blades in position.
The prior art continues to reinvent the rotor blade. Many have enlarged or bulbous ends where the weight is concentrated at the tip of the blades in an effort to prolong the duration of the boomerang's axial rotation. The elongated blades and greater tip speed, however, produce more drag which defeats this purpose. This is especially so where more than three blades are utilized since each blade must pass through the more disturbed air of the preceding blade. More than three blades only adds redundancy and unnecessary weight to a flying implement the size of a boomerang.
One disadvantage with this type of boomerang is that a wing or rotor blade airfoil produces maximum lift when the advancing blade rotates to a position where its leading edge is approximately perpendicular to the relative wind. When blade rotates to a position where the centerline heads to the wind no lift is produced and as it rotates further and becomes the retreating blade, depending on the forward speed, little or no lift is produced. Lift is mainly produced in one quadrant of boomerang's rotation and is unevenly distributed over boomerang's surface. Therefore, this type of boomerang is inherently unstable and relies on centrifugal force produced by the rotational speed to maintain stability. Another disadvantage with this type of boomerang is that a very precise flick of the wrist is required to match rotational speed to forward speed to accomplish this. If rotational speed slow beyond a certain RPM boomerang's flight path becomes erratic.
These boomerangs have no particular aesthetic appeal which would make an interesting child's wall hanging when not in use.
OBJECTS AND ADVANTAGES
Accordingly, several objects and advantages of the invention are:
1. to provide a safer boomerang so that crowded areas need not be avoided and younger children may participate.
The present invention solves the safety problem of the bladed type boomerang by providing a more compact boomerang with a small radius of gyration which produces a slower tip speed. This, combined with the more rounded contours, presents little or no danger to bystanders.
2. to provide a boomerang that is easier to throw and catch.
The unique circular or circular and elliptical combination of airfoils produce a continuous and more uniform lift throughout 360° of boomerang's rotation, the result being better balance, stability, and greater ease of operation.
3. to provide a boomerang with larger market appeal.
In addition to the ease of operation and safety features The specific shape of the invention provides an ideal surface for application of a variety of cartoon faces with ears which make it desirable as a child's wall hanging.
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.
REFERENCES:
patent: D. 219158 (1970-11-01), Gray et al.
patent: D. 241361 (1976-09-01), Crew
patent: D. 340480 (1993-10-01), Cummings
patent: 4222573 (1980-09-01), Adler
patent: 4452461 (1984-06-01), O'Brien
patent: 4772030 (1988-09-01), Hunt
patent: 5490678 (1996-02-01), Darnell
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