Games using tangible projectile – Player held and powered – nonmechanical projector – per se,... – Racket or paddle; accessory therefor
Reexamination Certificate
1999-05-05
2001-05-22
Chiu, Raleigh W. (Department: 3711)
Games using tangible projectile
Player held and powered, nonmechanical projector, per se,...
Racket or paddle; accessory therefor
C473S535000, C473S536000, C473S544000
Reexamination Certificate
active
06234921
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to sports racquets having strings, for example, tennis racquets, squash racquets, badminton racquets, and racquetball racquets.
Aside from strength and durability, weight and weight distribution have always been among the most important physical characteristics in a sports racquet. Tennis is a collision sport, as are other racquet sports, and the momentum and inertia of a racquet upon ball impact are directly related to the power and sweet spot size.
Over the past fifteen years, the speed of the game has changed with bigger, more powerful players resulting in higher ball speeds However, the mass of the ball and court size have remained the same, resulting in shorter rallies and higher impact loads imparted by the ball to the racquet. Over this same time period, due to improvements in materials and manufacturing technology, racquet weights have decreased drastically. In the case of tennis racquets, racquet weights have decreased by over 140 grams, from a typical strung weight of 360 grams to present day strung weights as low as 220 grams.
Lighter racquets tend to be more maneuverable and thus, in such respect, would appear to be better suited to a faster game. However, lighter racquets are less stable, which has a doubly negative effect in the case of any balls which do not land exactly at the racquet's center of mass. First, the racquet tends to twist, either about the longitudinal axis (in the case of balls which land off-axis), or about the center of mass (or both), more than a heavier racquet hitting the same ball. Second, because faster ball speeds mean greater impact momentum, the twisting force will be magnified compared to a heavier racquet. Thus, lighter racquets tend to be harder to control, and for such reason, professional tennis players continue to use heavier racquets.
In the past, proposals have been made to improve the stability of the racquet. For example, Wilson Sporting Goods markets racquets with a “Perimeter Weighting System”, in which small weights are placed at the 3 o'clock and 9 o'clock locations on the racquet head. These weights increase the polar moment of inertia, and thereby improve the resistance to twisting on side-to-side off center hits, but do not improve the stability about the racquet's midpoint.
Nikonow U.S. Pat. No. 1,539,019 discloses a racquet which uses a lightweight handle and in which weight is shifted to the tip region in order to advance the location of the center of percussion. Removing weight from the handle and shaft, and shifting such weight to the head, has two disadvantages. First, the racquet becomes head heavy and thus less maneuverable. Second, the longitudinal stability of the racquet about its midpoint is reduced. Thus, when balls land on the string bed above or below the center of percussion of the racquet, the handle will have a greater tendency to kick out of or towards, respectively, the player's hand. In addition, this weight distribution does not improve the polar moment of inertia of the racquet.
Other companies have tried various weight distribution schemes, all with certain drawbacks.
SUMMARY OF THE INVENTION
The present invention is a sports racquet with improved bi-directional stability, i.e., both about the longitudinal axis (for off-axis hits) and about the center of percussion (for balls hit above or below the center of percussion). The racquet also has improved power for balls hit towards the tip portion of the string bed.
More particularly, a sports racquet according to the invention has a lightweight frame and a pair of pods, having an increased cross-sectional width and perimeter, at the 11 o'clock and 1 o'clock positions of the head. The pods also preferably have an increased wall thickness, or a molded-in weight element, so as to provide increased weight at such regions, Preferably also, the handle has at least one weight pod at the butt portion. The three pod weighting system, i.e., having weight pods located at the 11 o'clock, 1 o'clock, and butt end positions, not only increases the polar moment of inertia of the racquet about its longitudinal axis, but also increases the moment of inertia of the racquet about the center of gravity, providing a very stable racquet. Also, because the pods in the head portion increase the width of the frame, the torsion and rigidity of the frame near the tip region is greatly increased, improving the power of the racquet with respect to balls hit further out on the string bed.
The weight pods at the 11 o'clock and 1 o'clock locations do several things. First, they improve the polar moment of inertia. Second, they improve the longitudinal mass moment of inertia about the midpoint of the racquet. Third, they raise the center of percussion and vibrational node higher in the head of the racquet, i.e., towards the tip, which improves performance in this area.
The weight at the butt end also does several things. First, it improves the longitudinal mass moment of inertia about its midpoint. Improving this property improves the stability of the racquet for balls hit above and below the center of percussion. Second, adding weight to the racquet in the butt increases the overall momentum of the racquet upon ball impact and therefore energy transfer to the ball. It does this without increasing the swing weight of the racquet because of its location in the butt.
The amount of the weights at each weight pod is preferably between 3 and 30 grams. Preferably, the weight pod in the butt has greater weight than either of the two pods in the head portion. Preferably, the weight of the pod in the butt equals the combined weight of the two head weight pods Such weights can be provided by using more material, e.g., carbon or glass fiber, at the pod locations, or by adding a weight element such as steel, lead, or titanium.
Alternatively, in another preferred embodiment, the pods in the head portion are formed by applying a resin-impregnated braided or woven sleeve, or a flat piece of material of such braided or woven material, over the outer surface of the uncured frame tube. The braid or woven material becomes an integral part of the frame as a result of the pressure molding process. The sleeve or other material is comprised of metal coated carbon fibers or glass fibers, respectively, which have a higher density than uncoated carbon or glass fibers. Preferably, the metal material is nickel, copper, brass, or titanium. This alternative has the advantage of increasing weight while maintaining the stiffness of the carbon fiber composite or the strength of the glass fiber composite, respectively.
In the butt, such weight element can be molded into the graphite frame material or molded into the plastic butt cap. Alternatively, the butt cap can be molding out of a plastic containing a heavy metal powder so as to increase the density of the plastic.
For a better understanding of the invention, reference is made to the following detailed description of a preferred embodiment, taken in conjunction with the drawings accompanying the application.
REFERENCES:
patent: Re. 33372 (1990-10-01), Frolow
patent: 1539019 (1925-05-01), Nikonow
patent: 4153249 (1979-05-01), Plagenhoef
patent: 4165071 (1979-08-01), Frolow
patent: 4997186 (1991-03-01), Carr
patent: 5220719 (1993-06-01), You
patent: 5299801 (1994-04-01), Sol et al.
patent: 5310179 (1994-05-01), Takatsuka
patent: 5462274 (1995-10-01), Takatsuka
patent: 5913740 (1999-06-01), Miklos
patent: 9-215780 (1997-08-01), None
P. 95, Tennis Magazine, Jun. 1991, showing Wilson Pro Staff 6.0 si 110 Tennis Racquet wit “perimeter weighting a the sides of the head”.
Blonski Brian J.
Davis Stephen J.
Wolverton Joseph J.
Benetton Sportsystem USA Inc.
Chiu Raleigh W.
Skadden, Arps Slate Meagher & Flom LLP
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