Strings for racquets

a technology of strings and racquets, applied in the field of strings for racquets, can solve the problems of individual strings sliding over one another, wear against each other, and weakening of the tensile strength of the string,

Inactive Publication Date: 2006-04-20
WL GORE & ASSOC INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In a tennis racquet, for example, the principal requirements are playability and durability and it is difficult to satisfy both requirements in a single racquet string type.
This brushing action causes the individual strings to slide over one another and wear against each other.
These notches are the primary reason for string breakage; as the notching becomes more severe, the tensile strength of the string weakens and eventually it breaks.
The friction between the ball and the string during contact with the string surface also causes some string wear.
Unfortunately, gut strings have a short life due to notching and wear.
Few recreational players use gut strings because they are expensive and wear quickly.
Such synthetics generally are more durable than gut, but are not as playable.
Nylon strings demonstrate improved durability over gut, but even nylon strings are subject to frequent breakage by certain players, particularly power hitters and those who hit the ball with a lot of spin.
Such coatings have generally failed because they are inelastic and do not adhere well to the nylon surface as the string stretches in use.
However, the addition of stiff aramid fibers to a string matrix dramatically reduces the playability of the strings.
Nomex, which has better elastic properties than other aramids, has been added to the core of nylon strings with some success with regards to durability, but with a significant tradeoff with regard to playability.
The resultant friction between strings causes energy loss.
This energy loss may also affect playability.

Method used

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  • Strings for racquets
  • Strings for racquets
  • Strings for racquets

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0076] An example of a string according to the present invention was prepared by helically wrapping a 1.19 mm diameter multi-filament nylon string that was obtained from Prince Mfg. Co. with a polymer film impregnated with UV-curable adhesive. The string was made in the following manner:

[0077] Expanded PTFE film with a thickness of about 0.015 mm was obtained from WL Gore and Associates, Inc., Newark, Del. The expanded PTFE film had a bulk density of 0.7 g / cc, and was further characterized by a matrix tensile strength of about 41,000 psi in the longitudinal direction and a Bubble Point of 68 psi.

[0078] A 30 wt. % adhesive solution was prepared in isopropyl alcohol for impregnating the expanded PTFE film. The adhesive composition is 60 wt. % aliphatic polyester based urethane diacrylate oligomer blended with ethoxylated trimethylol propane triacrylate (available from Sartomer Company, Exton, Pa. as CN963E75), 32 wt. % triacrylate acid ester (available from Sartomer Company as CD905...

example 2

[0084] A second, slightly smaller example string was made according to the present invention by helically wrapping a 1.13 mm diameter multi-filament nylon string that was obtained from Prince Mfg. Co. with a polymer film impregnated with UV-curable adhesive. The string was made in the manner described above in Example 1 by wrapping the base string with the same ePTFE film impregnated with a low temperature adhesive used in Example 1.

[0085] The final string diameter was 1.18 mm. As reflected in Table 1, the inventive string shows much better durability than a comparable diameter nylon string, and a similar dynamic modulus.

Test Methods

Durability

[0086] The durability test apparatus is depicted in FIG. 10. Tennis balls were alternatively fired at 60 MPH from two ball machines 15, 15′ such that the balls contacted a simulated racquet frame 17 at a rate of one every 4 seconds. Ball speed was measured at each ball machine using laser speed recording equipment. The simulated racquet st...

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PUM

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Abstract

Novel racquet strings and methods for making the same. A polymer cover combined with a low temperature adhesive is provided to the strings. The string of the present invention may employ a conventional string, such as a string having a center core comprising gut or synthetic material such as nylon, and a polymer cover impregnated with low temperature adhesive. The polymer cover covers the string along at least a portion of the length of the string.

Description

BACKGROUND [0001] The present invention relates to strings for sporting applications, and particularly to strings for racquets such as tennis racquets, badminton racquets, squash racquets, racquetball racquets and the like. [0002] Racquet strings must satisfy competing requirements. In a tennis racquet, for example, the principal requirements are playability and durability and it is difficult to satisfy both requirements in a single racquet string type. String construction and material selection has heretofore required a compromise between acceptable playability and durability. [0003] During play, particularly in tennis, the ball is usually hit with some degree of spin. To generate spin, the strings are brushed against the ball to impart a tangential force to it. This brushing action causes the individual strings to slide over one another and wear against each other. The rubbing action of one string against another as well as the impact of the ball creates notches in the strings at ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): A63B49/00A63B51/02
CPCA63B51/02A63B51/10A63B59/0074A61M2205/3653A61B17/3474A61M2205/3372A61M2205/8206A61M13/003A63B60/42
Inventor CHU, CHAOKANGGAMBALE, DEAN J.
Owner WL GORE & ASSOC INC
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