JPS6168067A - Conductive tennis ball - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a tennis ball having excellent electrical conductivity.

[Background of the invention]

In tennis trials, trouble often arises over the judgment of a ball that flies over the boundary line.

In particular, the ball hit by a -style player flies at about 165 km/h,
Furthermore, since the service pole flies at approximately 198km/h,
It is extremely difficult to visually determine whether the ball is in play or out of play. For this reason, in official games, there are 10 2-insers in addition to the referee who make decisions about the ball, but their decisions are not accurate because they have to watch from a position about 9 meters away from the ball and because the net gets in the way. Missing, more accurate calls are desired.

Therefore, if line calls could be made accurately using a mechanical device, the players would be satisfied with the decision and troubles between referees and players could be resolved. It will also be possible to reduce the number of referees to at least one.

At the tennis courts at Wimbledon in the UK, infrared detection devices are installed only on the service line as a sub-call for tennis. In this device, infrared rays pass slightly above the line surface, and when the ball crosses the line, it is detected electrically.

However, this device has the drawback that it cannot always accurately determine whether the ball is in or out when it hits the court from the side, cutting off the infrared rays. For this reason, the current practice is to use it only during service.

Additionally, at the U.S. Oven Tennis Championships, infrared detection devices are used as an official call only during service.

Recently, as a better device, a thin metal mt-meter is implanted in the line tape installed on the boundary line of the court and on the service line in a tennis court at intervals of about 5 mm, and when conductive poles come into contact with the metal line. , a device that forms a circuit and lights up a lamp provided on an electronic device at the umpire's hand to indicate that it is in play; for example, British Patent No. 1370332 [Automated M
Onitoring and Orbitration
There is System for ballgameJ.

One possible method for manufacturing conductive balls used in such devices is to needle-punch metal fibers from the top of felt for tennis balls. Since black fibers such as metal fibers and carbon fibers are punched in bundles, the appearance becomes a mottled pattern. Furthermore, punching metal fibers increases the weight per unit area of the felt, which may reduce the weight of the core of the ball or the thickness of the core, which also increases the price of the felt. Furthermore, when we used a tester to measure the resistance at intervals of 10 on the ball surface, we found that 43% of the resistance was above 50, and 40% was below 10,000. There are drawbacks.

Therefore, in order to eliminate the above-mentioned drawbacks, it is conceivable to mix conductive fibers into 7ELT for tennis balls in advance to obtain a tennis ball with uniform electrical conductivity on the surface. Examples of conductive fibers include stainless steel fibers, fibers with metal plating such as nickel on the surface of the fibers, fibers with metal kneaded into polymers, fibers with metal powder deposited in the pores of the fibers, fibers mixed with carbon, etc. is common. but,
All of these have various defects in processing, and carbon fiber in particular has a high specific resistance of 102 to 10" ntm and is black in color, making it unsuitable for tennis balls that require a bright color. Metallic Plated fibers and fibers mixed with metal fibers have good conductivity, but they require many steps such as pre-treatment to improve plating adhesion, and there are various problems in the spinning process. As mentioned above, the color tone is dark and it is not suitable as a material for the felt that forms the surface of tennis balls, especially for indoor tennis balls.

[Purpose of the invention]

An object of the present invention is to provide a conductive tennis ball with uniform surface electrical conductivity and a bright color.

[Summary of the invention]

The characteristic of the conductive tennis ball of the present invention is that the surface felt layer of the tennis ball is made of a mixture of conductive acrylic fibers with conductive metal chemically attached to the fiber surface, and wool and/or synthetic fibers. This is because it is made of conductive felt.

The conductive fiber used in the present invention is an acrylic synthetic fiber having metallic silver or metallic steel adhered to its surface, and has excellent conductivity. This conductive fiber is manufactured by, for example, "Method for Manufacturing Conductive Fiber"
No. 3). This conductive fiber has a wide color range, which is important for tennis balls.
If the content is within 15%, it is possible to produce felt with a fairly bright color using dyeing techniques. However, if the content is less than 5%, the specific resistance value is high and the variation is large, and the ball cannot function as a conductive tennis ball. Therefore, the amount of conductive fiber mixed into the felt is preferably 5 to 15%.

Ordinary felt for tennis balls is made from 70 to 90% wool and 10 to 30 strands of nylon fibers, which are made through the following processes: opening, carding, hardening, fulling, dyeing, and hair conditioning. Some of the products are used as felts for needle felt tennis balls, which have gone through various processes such as compounding (opening), carding, wrap formation, base fabric insertion, needle punching, drying, and heating. The felt for tennis balls of the present invention can be made using either of the above methods, but in the case of felt for needle corbels, "needle felt for hard tennis balls" (Utility Model No. 58-1)
No. 51689). In other words, the opening process (spreading process) of the felt manufacturing process
Sometimes, wool and synthetic fibers, mainly nylon fibers, and acrylic fibers with metal silver or copper chemically attached to the fiber surface are uniformly mixed in a range of 5 to 15 wt%, and then carded, zipped, and needled. punching,
Needle felt is made by dyeing and drying, and then used to manufacture tennis balls.

To manufacture a tennis ball, first, two pieces of felt are punched out into the shape of a gourd and attached to a center ball using adhesive.

Next, fill the gap between the two gourd-shaped pieces of felt with a thin string-like stitched rubber. It is preferable that the rubber padding also has conductivity, so that no matter which side of the ball comes into contact with the court line, a circuit will be formed and the ball will be called correctly.

[Embodiments of the invention]

Examples of the present invention will be described below.

Felt for tennis balls mixed with wool, sweet acid fibers and conductive fibers according to the proportions shown in Table 1 (Utility Model No. 58-1516)
89 "Felt for Rigid Tennis Balls") was used to produce a rigid f=nispol. The color tone, electrical resistance, etc. of these balls were investigated.

The color tone of the felt was slightly dark yellow in Invention Example 3, dark yellow in Comparative Example 3, and yellow in the others. The brightness of the felt determined by direct visual comparison with the standard color chart ("Color Standard" published by the Japan Color Research Institute) was 4 for Comparative Example 3 and 5 for the others.
That was it.

In addition, when we measured the resistance at 10 wm intervals on the ball surface using a tester (randomly 100 times), it was 8,000 to 12,000 Ω in Comparative Example 1, and 2,000 to 5 Ω in Comparative Example 2.
The resistance value was as large as 000Ω, and its variation was also large.

The above results are summarized in Table 1 below.

Table 1 Note 1) Thunderon 5S-N; Japan Microhair Dying ■Example 2.3 of the present invention exhibited extremely good conductive properties, with resistances in the range of 10,000 or less in 100 resistance measurements using a tester.

Furthermore, it was confirmed that there was also relatively no variation within the 3000Ω range for Inventive Example 1, and there was no problem in use.

Therefore, it can be seen that the tennis ball of the invention example is preferable from the color tone and surface resistance value of the ball.

In an outdoor court and an indoor court, lines with copper wires planted at 5 mm intervals were installed on the court, and the balls of these invention examples were subjected to a ball batting test using an automatic electronic judgment device. Ball No. 3 had a good judgment and had the same feel and life as a normal ball.

〔Effect of the invention〕

The conductive tennis ball according to the present invention is disclosed in the above-mentioned British Patent No. 137.
As a result of a practice match between first-class professional players using the automatic judgment device for tennis games based on No. 0332, the difference in the color tone of the ball from that of a normal tennis ball was extremely small, and the ball was easy to see while in flight. The conductivity of the wires confirmed that on-line determination of "in" and "out" was extremely accurate.

Claims (1)

[Claims] The surface felt layer of the tennis ball is made of conductive felt made by mixing conductive acrylic fibers with conductive metal chemically attached to the fiber surface and wool and/or synthetic fibers. A conductive tennis ball.