Games using tangible projectile – Projectile – per se; part thereof or accessory therefor – Arrow – dart – or shuttlecock; part thereof
Reexamination Certificate
2000-03-01
2001-06-26
Ricci, John A. (Department: 3712)
Games using tangible projectile
Projectile, per se; part thereof or accessory therefor
Arrow, dart, or shuttlecock; part thereof
Reexamination Certificate
active
06251036
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention belongs to the field of carbon fiber composite material technology and relates to an improvement for a carbon fiber arrow shaft.
Prior arrow shafts include wooden arrow shafts, aluminum arrow shafts and carbon fiber arrow shafts. Wooden shafts have heavier masses and are not uniform thus influencing their effect on usage. Aluminum arrow shafts have lower masses but they have poor stiffness and are subject to permanent deformations. Glass fiber arrow shafts have less strength and are easily broken.
The appearance of the carbon fiber reinforced material has introduced advanced composite material into sports equipment. Such material has superior performances: lighter masses, higher strengths, and good stiffness. In making current carbon fiber arrow shafts, both carbon fibers and resins initially form a pre-impregnated material, which is then cut and twist-wound onto mandrels, and then formalized by thermosetting. Due to the overlapping joints of pre-impregnated material, surface protrusions are easily formed which affect the uniformity of arrow shafts. The non-uniform shaft wall thickness will affect the uniformity of forces applied to arrow shafts, thus resulting in bending and deformation of the shafts, and lowering the linearity of the shaft. The non-uniform shaft wall thickness will result in instability of the flight path of the arrow.
Within a certain period after shooting of the arrow, besides forward movement, the arrow shaft will have radial vibration which becomes weaker due to the damping produced by the arrow shaft stiffness and which approaches zero after a certain period of time. If the shaft wall thickness is not uniform, the stiffness along each radius direction is not symmetrical which results in an imbalance of the damping effect. The imbalanced damping will affect the motion of the arrow producing some unexpected changes in the flight path. Moreover, the arrow that is in flight will be subject to air resistance which will result in deflection from the flight path when the shaft wall thickness is non-uniform. Therefore, the non-uniform shaft wall thickness will increase the aiming errors.
U.S. Pat. No. 4,234,190 entitled “Carbon Fiber-Reinforced Plastic Arrow” has disclosed an improved carbon fiber arrow shaft (FIG.
1
), which has a two-layered construction. The interior layer
12
,
14
utilizes a winding method, which comprises two oppositely wound carbon fiber winding layers with a winding angle between 30-45 degrees. The outer layer
16
is made by twist-winding of one to four layers of 0 degree pre-impregnated fiber material. The performance of such an arrow shaft construction are higher than those of an arrow shaft formed by complete twist-winding. However, due to the need of twist-winding one to four layers of 0 degree fiber to increase its strength, the protrusions appearing on the surface cannot be avoided. This will result in a non-uniform shaft wall thickness. Furthermore, the thickness of the carbon fibers wound on the inner layer of the arrow shaft is small such that the twist-resistance and shear-resistance are poor. When the arrow shafts are shot or aimed at the targets, the impact on hard material objects causes the two ends of the shafts to be easily cracked or broken due to greater forces imposed thereon.
One disadvantage of the manufacture technology with respect to the above-mentioned “Carbon Fiber-Reinforced Plastic Arrow” is the need for two steps in formalizing the carbon fiber tubes. The interior layer is processed on winding machines, while the outer layer is processed on twist-winding machines. Moreover, the twist-winding needs pre-impregnated materials. Thus, in the winding and twist-winding technological procedures, two fiber raw materials, namely carbon fibers and pre-impregnated materials, are needed. This results in complexity of technology, discontinuity of winding, high costs and low production efficiency.
Based on the usage features of the arrow shaft, the requirements for the stiffness at the two ends of shafts and at the central part of the shafts are different. For an ideal arrow shaft, the central part or middle section of the shaft needs a greater degree of stiffness than at the ends. Thus, when the arrow is launched, the deformation of the shaft during flight is small, the flight path is stable, and aiming precision is higher. There are large forces imposed on the arrow shaft head and tail ends during launch and impact, such that the two ends are easily cracked. Therefore, appropriate elasticity, flexibility and enough circumferential strength are needed.
SUMMARY OF THE INVENTION
The object of this invention is to provide a carbon fiber arrow shaft, which has a reasonable construction, meets the requirements for stiffness distribution of the arrow shaft and has uniform shaft wall thickness, thereby overcoming the weakness of the conventional carbon fiber arrow shafts, i.e., non-uniformity of shaft wall thickness, unreasonable stiffness distribution and low performances.
Another object of the present invention is to provide a directly and continuously winding method for a carbon fiber arrow shaft, which guarantees a uniform shaft wall thickness and strength thereof, and which increases productivity and decreases cost.
According to the present invention, a carbon fiber arrow shaft has a hollow tube formed with a length of between 500-900 mm, an inner diameter of between 2-10 mm, and a tube wall thickness of between 0.3-2 mm. A carbon fiber is used as a reinforced material and a resinoid is used as a binder. The arrow shaft is formed by directly and continuously winding the resin-impregnated carbon fibers. The winding angle of the carbon fiber at a head section (L
1
) is shown as being changed from a large winding angle to a small winding angle, a winding angle at a middle section (L
2
) is kept constant and a winding angle at a tail section (L
3
) is changed from a small winding angle to a large winding angle. The length of the head section (L
1
) is between 25-250 mm with the initial winding angle at the head section (L
1
) being between 30-90 degress and the winding angle at the head section (L
1
) is gradually decreased to between 2-30 degrees at the boundary of the head section (L
1
) and the middle section (L
2
). In the middle section (L
2
), the winding angle is kept constant. The length at the tail section (L
3
) is between 25-250 mm with the winding angle at the tail section (L
3
) being gradually increased to between 30-90 degrees at the end of the tail section (L
3
). The winding angles at the head section (L
1
) and the tail section (L
3
) are at least two times of the winding angle at the middle section (L
2
).
A continuously winding method for a carbon fiber arrow shaft includes the following steps:
(1) selecting the materials of a carbon fiber and a binder wherein 3K-24K carbon fiber is used as a reinforced material and a themoset epoxy is used as a binder for the winding of arrow shafts;
(2) setting up the winding program for a winding machine as follows: the full length of the arrow shaft is divided into three sections, i.e. a head section (L
1
), a middle section (L
2
) and a tail section (L
3
), the length of the head section (L
1
) being between 25-250 mm, and the length of the tail section (L
3
) being between 25-250 mm; the initial winding angles at the head section (L
1
) being set between 30-90 degrees, and being gradually decreased to between 2-30 degrees at the boundary of the head section (L
1
) and the middle section (L
2
); the winding angle at the middle section (L
2
) being kept constant; the winding angle at the tail section (L
3
) being gradually increased from the range of 2-30 degrees at the boundary of the middle section (L
2
) and the tail section (L
3
) to the range of 30-90 degrees at the end of the tail section (L
3
) and the winding angles of the head section (L
1
) and the tail section (L
3
) being at least two times of that of the middle section (L
2
);
(3) initiating the winding machine to form a carbon fiber arrow shaft blank by c
Chen Weifang
Chen Wenhao
Liu Minyong
Mao Qingzhu
Sun Dahai
Beijing Institute of Aeronautical Materials
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Ricci John A.
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