Games using tangible projectile – Player held and powered – nonmechanical projector – per se,... – With sound-deadening – vibration-damping – or shock-absorbing...
Reexamination Certificate
2002-06-27
2003-12-16
Chiu, Raleigh W. (Department: 3711)
Games using tangible projectile
Player held and powered, nonmechanical projector, per se,...
With sound-deadening, vibration-damping, or shock-absorbing...
C473S546000, C473S535000, C473S537000
Reexamination Certificate
active
06663514
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a racket frame and in particular, a tennis racket frame. More particularly, the present invention is intended to increase the vibration-damping performance of the racket frame by improving a connection portion of a frame body of the racket frame and that of a yoke thereof.
2. Description of the Related Art
In recent years, the racket frame is demanded to have a light weight, a high rigidity, a high strength, and a high durability. The fiber reinforced resin (hereinafter referred to as FRP) is the most popular material for the racket frame. Normally the racket frame is formed by molding a thermosetting resin reinforced with a fiber such as a carbon fiber having a high strength and elastic modulus.
The FRP containing the thermosetting resin as the matrix resin is superior owing to its high rigidity, but the FRP is apt to vibrate when it is subjected to a shock, thus causing a tennis player to suffer tennis elbow frequently.
Therefore an organic fiber such as an aramid fiber or an ultra-high-molecular-weight polyester fiber may be used to improve the vibration-damping performance of an FRP composed of an epoxy resin serving as the matrix resin and a continuous carbon fiber serving as the reinforcing fiber. However, the FRP reinforced with the organic fiber has a vibration-damping performance of less than 0.6 that is not so high and a low rigidity and strength. Thus the FRP reinforced only with an organic fiber has a problem with respect to its rigidity.
To overcome the problem, in recent years, there is proposed a racket frame composed of a fiber-reinforced thermoplastic resin containing a thermoplastic resin, superior in its vibration-damping performance, serving as the matrix resin. For instance, the fiber-reinforced resin contains a polyamide resin and a continuous fiber or a short fiber serving as the reinforcing fiber. Methods for manufacturing the fiber-reinforced thermoplastic resin are classified into the following three methods. In each case, the frame body of the racket frame made of the fiber-reinforced thermoplastic resin has a vibration-damping factor not less than 0.9.
(1) The polyamide resin containing the short fiber is injection-molded (vibration-damping factor: 1.9%).
(2) A fibrous material serving as the matrix resin and the reinforcing fiber are layered on each other in a fibrous configuration. An internal pressure is applied to the laminate at a high temperature to fuse the matrix resin and mold the laminate (vibration-damping factor: 0.92%).
(3) A reaction injection molding (RIM) of the polyamide resin monomer is performed, with the reinforcing fiber set in a die (vibration-damping factor: 1.1%).
The frame body of the racket frame made of the fiber-reinforced thermoplastic resin reflects the high toughness of the thermoplastic resin, thus having characteristics such as a high resistance to shock and a high vibration-damping performance that cannot be attained by the conventional frame body made of the thermosetting resin.
However, a thermoplastic resin depends on an environment for its elastic modulus and strength more than a thermosetting resin. Thus depending upon the environment in which the frame body of the racket frame is used, the characteristic of the thermoplastic resin such as rigidity is liable to change.
To solve these problems of a frame body of a racket frame composed of a matrix resin consisting of a thermoplastic resin and a frame body composed of a matrix resin consisting of a thermosetting resin, a frame body containing a combination of a thermoplastic resin and a thermosetting resin is proposed.
For example, in Japanese Patent Application Laid-Open No. 6-63183, the region from the throat part to the grip part is formed of a thermoplastic resin as the matrix resin, and the string-stretched part (face part) surrounding the ball-hitting face is formed of a thermosetting resin as the matrix resin.
In Japanese Patent Application Laid-Open No. 2000-70415, the yoke is formed of nylon made by reaction injection molding and a carbon fiber. Then the yoke is set in a die for the frame body to integrally mold the yoke and a laminate of an unhardened prepreg of the carbon fiber and an epoxy resin.
In the racket frame disclosed in Japanese Patent Application Laid-Open No. 6-63183, half of the body thereof is formed of a thermoplastic resin, as the matrix resin, which is liable to change in its characteristic depending upon the environment in which the frame body of the racket frame is used, and the vibration mode of a tennis racket composed of the racket frame is not considered. Thus this racket frame does not have effective vibration-damping performance.
In the racket frame disclosed in Japanese Patent Application Laid-Open No. 2000-70415, the connection portion of the yoke and of the frame body is subjected to a string tension and a load applied to the string by a tennis ball. Thus it is necessary to firmly bond the yoke and the frame body to each other by one-piece molding. Actually the connection portion of the yoke and of the frame body crack. Further a shear stress is generated on the interface of the connection portion. It is impossible for the connection portion to suppress the vibration of the racket frame.
The art demands a racket frame having increased vibration-damping performance. In addition, a tennis racket having high operability to cope with a play style of giving a tennis ball a spin is demanded. Therefore there is a growing demand for development of a lightweight (reduced moment of inertia) racket frame.
A player gives the tennis ball a spin by using a wide portion of the ball-hitting face as a hitting point. Thus the player desires a tennis racket having a large sweet spot.
It is desired that a tennis racket for a contestant have a stable ball-hitting face. It has been revealed that the rigidity in the in-plane direction is important.
As described above, a racket frame is demanded having light weight, high operability, high rigidity, high strength, high durability, high restitution performance, high stability in its ball-hitting face, and high vibration-damping performance.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described demands. Thus, it is an object of the present invention to provide a racket frame that is lightweight, stable in rigidity, has a proper vibration-damping performance, and can control the degree of the vibration-damping performance.
In order to achieve the object, according to the present invention, a connection portion of the yoke and the frame body thereof is improved so that the connection portion suppresses vibrations effectively. To do so, materials can be arbitrarily selected for the frame body to allow the frame body to be lightweight and have an appropriate rigidity and strength.
More specifically, the present invention provides a racket frame in which a frame body is formed separately from a yoke connecting right and left parts of the frame body to each other; and the yoke and the frame body are connected to each other by a mechanical connection means or/and an adhesive agent, with both ends of the yoke in contact with the right and left parts of the body in an area of not less than 10 cm
2
(1.6 in
2
).
It is preferable that a shear force generated when the racket frame deforms is collectively applied to a connection surface of the frame body and the yoke to increase the vibration-damping performance of the racket frame.
In the conventional racket frame composed of a FRP, the portion where the yoke and the frame body are connected to each other is integrally formed when the frame body is formed by molding a material. The resin for the yoke and the resin for the frame body are fused and integrated with each other to a high degree. Therefore a stress is collectively applied to the connection surface (boundary) of the frame body and that of the yoke when a tennis racket deforms.
On the other hand, in the case where the yoke and the frame body are bonded to each other to a low degre
Ashino Takeshi
Niwa Kunio
Takeuchi Hiroyuki
Chiu Raleigh W.
Sumitomo Rubber Industries Ltd.
LandOfFree
Racket with vibration damping yoke does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Racket with vibration damping yoke, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Racket with vibration damping yoke will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3137792