Paintball having reduced drag

Abstract

A paintball comprising a thin-walled capsule filled with paint, wherein the surface of the capsule is formed as a polyhedron, for example, a dodecahedron. The angled surface faces of the polyhedron cause turbulent air flow over a greater percentage of the paintball surface than in a prior art smooth, spherical paintball. The air flow thus remains “attached” over more of the paintball surface, thereby reducing form drag of the paintball. An added benefit of a paintball formed in accordance with the invention is that the structure includes a plurality of intrafacial edges which are currently believed to be preferred lines of impact breakage of the paintball.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/580,608, filed Jun. 17, 2004

TECHNICAL FIELD

The present invention relates to aerodynamic spheroids; more particularly, to paintballs for use in hunting sport games; and most particularly, to an improved paintball having a polyhedral outer surface for reduced drag and greater range.

BACKGROUND OF THE INVENTION

So-called “paintballs” are an integral element of a well-known mock hunting sport wherein players attempt to deliver paintballs into rupturing contact with other players. See, for example, U.S. Pat. Nos. 5,001,880; 5,018,450; 5,393,054; 5,353,712; 5,448,951; 5,640,945; 5,762,058; 5,823,173; 5,936,190; 6,082,439; 6,145,441; 6,230,630; 6,375,981; 6,530,962; 6,574,945; and 6,615,739, the relevant disclosures of which are hereby incorporated by reference.

The sport or recreational activity known as “War Games” is currently one of the fastest growing sports in North America. Typically, players are arranged into two or more teams and shoot paintballs at members of the opposing teams in a hide-and-seek setting. When a paintball strikes a player of an opposing team, the paintball ruptures and releases the fill material or “paint” onto that player. Any player who has been struck by a paintball is marked and thus disqualified from continuing in the game.

A paintball comprises a generally spherical capsule having a typical thickness of about 0.010 inch and enclosing a charge of a colored liquid, referred to generally as “paint.” The paint, while typically liquid in most paintballs today, may be in any phase. The current invention is not limited to liquid fill materials, or to single-phase fill materials. Typically, the capsule is formed of gelatin and the paint is a dyed aqueous sugar solution that may include additives such as starch and polyethylene glycol to improve breakage resistance in handling and firing.

In the sport, a paintball typically is fired from a hand-held gun employing a compressed-gas charge which can accelerate the paintball without causing it to rupture within the gun. In organized paintball activities, the discharge velocity of a paintball is limited to 300 feet per second; at higher paintball velocities, human injury can result. Thus, a typical paintball gun can discharge a paintball at about 298 feet per second.

The limit on initial muzzle velocity creates a resulting limit in range of fire of a regulation paintball from a regulation gun.

The flight of a paintball is typically ballistic, following paraboloid path dictated by gravitational acceleration in the vertical direction and muzzle velocity in the horizontal direction. The path is not ideally parabolic, however, because a projectile is subject to both frictional drag forces and form drag forces in the horizontal direction, causing a progressive reduction in velocity during the flight. The practical result is that the range of a paintball is significantly less than theoretical, typically only about one-tenth the ideal range in the absence of drag. A greater range from the same initial velocity is highly desirable.

What is needed in the art is a means for increasing the range of a paintball within the initial velocity limitations of the sport.

It is a principal object of the present invention to provide an improved paintball that can travel farther than prior art paintballs.

SUMMARY OF THE INVENTION

Briefly described, a paintball in accordance with the invention comprises a thin-walled capsule filled with paint, wherein the surface of the capsule is formed as a polyhedron, for example, a dodecahedron. The angled surface faces of the polyhedron cause turbulent air flow over a greater percentage of the paintball surface than in a prior art smooth, spherical paintball. The air flow thus remains “attached” over more of the paintball surface, thereby reducing form drag of the paintball.

An added benefit of a paintball formed in accordance with the invention is that the structure includes a plurality of interfacial edges which are currently believed to be preferred lines of impact breakage of the paintball. The manufacturing processes used to create the paintball also may be used to induce false mold markings along the interfacial edges, such that the parting line from the manufacturing process does not introduce asymmetry into the paintball shape. Further, the edges may be preferentially raised, or indented, to control the impact breakage characteristics and the deformable body characteristics of the ball during firing and flight.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an isometric view of a paintball in accordance with the invention having an outer surface in the form of a regular dodecahedron;

FIG. 2 is a wire-frame perspective view of a paintball similar to the one shown in FIG. 1 illustrating a concave face, a convex face, and a septa positioned within the paintball chamber forming first and second sub-chambers;

FIG. 3 is a wire-frame perspective view of a paintball having a buckyball shape;

FIG. 4 is a wire-frame perspective view of a paintball having a triacontahedron shape;

FIG. 5 is a wire-frame perspective view of a paintball having a pentagonal dodecahedron shape;

FIG. 6 is a wire-frame perspective view of a paintball having a icosahedron shape;

FIG. 7 is a wire-frame perspective view of a paintball having a hexakisoctahedron shape;

FIG. 8 is a wire-frame perspective view of a paintball having a triakisoctahedron shape;

FIG. 9 is a wire-frame perspective view of a paintball having a icositetrahedron shape;

FIG. 10 is a wire-frame perspective view of a paintball having a octahedron shape;

FIG. 11 is a wire-frame perspective view of a paintball having a cube shape;

FIG. 12 is a wire-frame perspective view of a paintball having a hexakistetrahedron shape;

FIG. 13 is a wire-frame perspective view of a paintball having a tetrahedron shape;

FIG. 14 is a wire-frame perspective view of a paintball having a deltoid dodecahedron shape;

FIG. 15 is a wire-frame perspective view of a paintball having a diakisdodecahedron shape;

FIG. 16 is a wire-frame perspective view of a paintball having a pentagonal icositetrahedron shape;

FIG. 17 is a wire-frame perspective view of a paintball having a tetrahedral pentagonal dodecahedron shape;

FIG. 18 is a wire-frame perspective view of a paintball having a deltoid dodecahedron shape;

FIG. 19 is a wire-frame perspective view of a paintball having a trigonal dipyramid shape;

FIG. 20 is a wire-frame perspective view of a paintball having a tetragonal dipyramid shape;

FIG. 21 is a wire-frame perspective view of a paintball having a rhombohedron shape; and

FIG. 22 is a graphical representation of drag coefficients (CD) for three-dimensional ellipsoidal bodies of revolution as a function of aspect ratio.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, paintball 10 in accordance with the invention includes a semi-rigid capsule shell 12 defining a closed chamber 13 for enclosing a liquid charge of paint (not visible in FIGS. 1 and 2). Shell 12 is formed in a generally spheroid shape defining a closed polyhedron on at least the outer surface of shell 12, the polyhedron comprising faces 14 intersecting at interfacial edges 16. Faces 14 may be planar, convex outwards 14a, or concave outwards 14b, or combinations thereof. While one of the faces 14 of paintball 10 in FIG. 2 is shown as convex outward 14a, and one of faces 14 is shown as concave outward 14b, it will be understood that more than one of faces 14 may be either convex outward 14a or concave outward 14b. This includes an embodiment where all of faces 14 on paintball 10 are either convex outward 14a or concave outward 14b. Moreover, faces 14 may be identical or non-identical.

A currently-preferred polyhedron is a regular dodecahedron, as shown in FIGS. 1 and 2, although other closed polyhedra are fully comprehended by the invention. For instance, as best seen in FIGS. 3-21, the invention all includes, but is not limited to, polyhedra such as a buckyball 10a, triacontahedron 10b, pentagonal dodecahedron 10c, icosahedron 10d, hexakisoctahedron 10e, triakisoctahedron 10f, icositetrahedron 10g, octahedron 10h, cube 10i, hexakistetrahedron 10j, tetrahedron 10k, deltoid dodecahedron 10l, diakisdodecahedron 10m, pentagonal icositetrahedron 10n, tetrahedral pentagonal dodecahedron 10c, deltoid dodecahedron 10p, trigonal dipyramid 10q, tetragonal dipyramid 10r, and rhombohedron 10s, respectively.

As best seen in FIGS. 1 and 2, interfacial edges 16 are currently believed to be preferred lines of impact breakage of the paintball. The manufacturing processes used to create paintball 10 also may be used to induce false mold markings 18 along one or more of interfacial edges 16, such that the parting line from the manufacturing process does not introduce asymmetry into the paintball shape. It will be understood that false mold markings 18 may extend generally around the circumference of paintball 10 along one or more of interfacial edges 16. Further, interfacial edges 16 may be preferentially raised, or indented, to control the impact breakage characteristics and the deformable body characteristics of paintball 10 during firing and flight.

Paintball 10 may include a plurality of similar or dissimilar liquid or other material charges within the closed chamber of shell 12 which may be separated internally by one or more septa 20 that divide the chamber into at least first and second sub-chambers 13a, 13b as best seen in FIG. 2. The one or more septa 20 are intended to rupture at impact, along with shell 12, thereby mixing the liquid charges. The internal septa 20 can also cause the liquid charges to rotate with the shell, preventing paintball rotation from being viscously damped out, as disclosed in U.S. Pat. No. 5,640,945.

The purpose of providing shell 12 as a closed polyhedron is to reduce form drag, thereby promoting longer flight of a paintball so equipped. The benefits of reduced drag are well known for spherical and ellipsoidal bodies, and are equally applicable to polyhedral bodies, for the same reasons. A currently-preferred polyhedral shaped shell can reduce form drag on a paintball by between 25% and 50% as compared to an unfeatured, spherical paintball of otherwise identical weight, size, and composition.

TABLE 1
Aspect Ratio	Laminar Flow	Turbulent Flow
1:1	0.47	0.27
2:1	0.27	0.06
4:1	0.2	0.06
8:1	0.25	0.13
Drag coefficients for three-dimensional ellipsoidal bodies of revolution. Source: Mechanics of Fluids, By Irving H. Shames, 2nd edition, © 1982, Table 10.3, Page 409, McGraw Hill, ISBN 0-07-056385-3. FIG. 22 is a graphical representation of the data presented in Table 1.

With reference to FIG. 22, for a sphere, with an aspect ratio of 1:1, the drag coefficient is dramatically reduced by causing a transition from laminar to turbulent flow. In addition, whether the flow is turbulent or laminar, slightly increasing the aspect ratio of the projectile, such that it is somewhat elongated in the direction of motion, causes a reduction in total drag on the body. This is due to the fact that the streamlined flow on the trailing edge of the body results in better pressure recovery. However, if the aspect ratio is increased too far, then the overall drag begins to increase again, and skin friction affects overtake the importance of the pressure recovery. The important thing to note from the figure below is that the total drag coefficient, CD, on the projectile decreases nearly linearly with increasing aspect ratio, as the projectile becomes less spherical in shape.

The results illustrated in Table 1 and FIG. 22 are demonstrated in Table 2 set forth below, which shows the positive influence that deforming the shape of the projectile body can have upon the drag coefficient. For a spherical shape having an aspect ratio of 1:1, which is the shape used by virtually all paintballs today, the drag coefficient, CD, is 0.47. If transition to turbulence can be induced, then the drag coefficient can be reduced dramatically to approximately 0.27. Such a reduction will result in extended range of the projectile flight. Note that whether the flow regime is laminar or turbulent, a reduction in the drag coefficient, C_D, can be achieved by increasing the aspect ratio of the projectile. For example, in laminar flow conditions, elongating the projectile to an aspect ratio of 1.1:1 reduces the drag coefficient by approximately 5%. As the deformation becomes more pronounced, for example with an aspect ratio of 1.25:1 under laminar flow conditions, the drag coefficient CD can be reduced by approximately 11%. Even better reductions in drag coefficient are achieved for a given deformation when the flow is in the turbulent range. Thus, a paintball that can cause the boundary layer flow to transition from laminar flow to turbulent flow will have a decreased drag coefficient, C_D, and a corresponding increase in range for a given muzzle velocity. Additionally, a projectile which is deformed into an oblong shape will have a lower drag coefficient, C_D, and a corresponding increase in range for a given muzzle velocity than a projectile which is generally spherical in shape.

TABLE 2
Estimated drag coefficients for three-dimensional
ellipsoidal bodies of revolution of various aspect ratios, obtained by
linear interpolation of the data presented in Table 1.
				Approximate %	Approximate %
Ellipsoidal	Aspect	Approximate	Approximate	Reduction in	Reduction in
Shape	Ratio	Laminar CD	Turbulent CD	Laminar CD	Turbulent CD
	1:1	0.47	0.27	Not Applicable	Not Applicable
	1.11:1	0.45	0.25	5%	9%
	1.25:1	0.42	0.22	11%	19%
	1.43:1	0.38	0.18	18%	33%
	1.67:1	0.34	0.13	29%	52%
	2:1	0.27	0.06	43%	78%

It is desirable to have a paintball projectile that is generally spheroidal in shape during the process of storage, transportation, and loading from the paintball feeder into the breech of a paintball gun. The generally spheroid shape has numerous materials handling advantages, including the primary advantages of being able to load the projectile into the gun without need to orient the projectile in a particular fashion, and for compatibility with the large installed user-base of paintball guns which have the ability to manipulate and fire only those projectiles that are generally spheroid. At the same time, a paintball which can be initially fired in a generally spheroid shape, and can be caused to deform into an elongated aspect ratio as illustrated in Table 2 during the process of firing the paintball from the gun or during its flight from the muzzle to the target, can exhibit reduced total drag coefficient, C_D, and hence improved range. The present invention meets these needs.

While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Claims

1. A paintball for discharge from a paintball gun, comprising:

a) a semi-rigid shell defining a closed chamber; and

b) a material charge contained within said chamber,

wherein said shell is formed in a shape defining a closed polyhedron on at least the outer surface thereof, said polyhedron comprising a plurality of faces intersecting at a plurality of interfacial edges.

2. A paintball in accordance with claim 1 wherein said faces are selected from the group consisting of planar, convex outwards, concave outwards, and combinations thereof.

3. A paintball in accordance with claim 1 wherein said plurality of faces is identical.

4. A paintball in accordance with claim 1 wherein said plurality of faces is non-identical.

5. A paintball in accordance with claim 1 wherein said polyhedron is selected from the group consisting of buckyball, triacontahedron, pentagonal dodecahedron, icosahedron, hexakisoctahedron, triakisoctahedron, icositetrahedron, octahedron, cube, hexakistetrahedron, tetrahedron, deltoid dodecahedron, diakisdodecahedron, pentagonal icositetrahedron, tetrahedral pentagonal dodecahedron, deltoid dodecahedron, trigonal dipyramid, tetragonal dipyramid, and rhombohedron.

6. A paintball in accordance with claim 1 further comprising at least one internal septum dividing said chamber into at least first and second sub-chambers.

7. A paintball in accordance with claim 6 further comprising at least first and second material charges disposed in said first and second sub-chambers, respectively.

8. A paintball in accordance with claim 7 wherein said first and second charges are identical in composition.

9. A paintball in accordance with claim 7 wherein said first and second charges are non-identical in composition.

10. A paintball in accordance with claim 1 wherein the aerodynamic form drag of said paintball is at least 25% less than the aerodynamic form drag of an unfeatured prior art paintball.

11. A paintball in accordance with claim 1 wherein the manufactured shape of said shell is aerodynamically deformable during firing and flight of said paintball from a firing means.

12. A paintball in accordance with claim 1 further comprising false molding marks on the surface thereof.

13. A paintball in accordance with claim 12, wherein the false molding marks are positioned on the interfacial edges.