Tennis Ball Having An Electrically Conducting Surface

Abstract

A ball for playing games such as tennis, having an outer surface which is electrically conducting so that it can short-circuit or bridge wires laid on the surface of the court in order to enable a decision to be given as to whether the ball is "in" or "out" when it strikes the court on or near the lines defining the area of play.

Description

This invention relates to sporting equipment, especially to a ball for use in the game of lawn tennis, subsequently referred to as tennis.

As is well known, tennis is played on a court marked out by lines and the rules provide that if at various stages of the game the ball bounces outside particular lines, then it is considered out of play. There is in each half of the court on each side of the net an area into which a ball must be served, the area being bounded on one side by the net and on the other three sides by lines painted or attached to the court. After the service has been returned, the ball, if it bounces, only remains in play if the bounce is within the lines marking out the full singles or doubles court.

Difficulties in umpiring tennis arise when the ball bounces on or near one of the lines bounding either one of the service areas or the full court. It can be difficult to judge by eye whether the ball is in or out because of the high speeds at which the ball can travel. A tennis ball may travel at 120 m.p.h. which may mean a contact time with the surface of the court of as little as 100 microseconds.

It is an object of this invention to provide a ball with means enabling its position of bounce to be sensed by suitable means such as those disclosed in my co-pending Application No. which has been divided out of this Application.

According to one aspect of this invention there is provided a ball, preferably a ball for the game of tennis, having an outer surface incorporating electric conducting means. The conducting means are preferably in the form of metal woven or stitched into a cloth covering for the ball. Wires or fibres which may be of steel may be stitched into a length of cloth to be cut into panels for covering the ball or may be stitched into panels already cut for the ball, the stitching being performed, e.g., by a multiple sewing machine. The stitching may be on both sides, or on one side only with textile stitching on the other side. Alternatively the wires may be woven into cloth in zig-zag or crisscross lines and suitable panels then cut from the cloth. In each case, the wire should be exposed at least intermittently at the cloth surface which will become the ground-contacting surface of the ball. Single strand steel wires or multi-strand steel threads or fibres may be used.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawing, wherein:

FIG. 1 indicates in plan view part of a lay-out of tapes on one side of a tennis court the view being partly broken away and consequently not to scale; and

FIGS. 2, 3 and 4 represent tennis balls provided with conducting means according to the present invention.

Referring to FIG. 1 a service line for the court is formed in two separate parts 10 and 11. The centre line is indicated at 12 and single court side lines in separate parts 14a, 15a (right-hand side of court) and 14b, 15b (left-hand side of court). Auxiliary sensing tapes 16a, 16b and 17 shown cross-hatched to indicate that they have a different colour from line tapes 10, 11, 12, 14a, 14b, 15a, 15b lie on each side of lines 10, 11 and 12. Similarly auxiliary tapes 18a, b, c, d, e and f are laid on both sides of the lines 14a, 15a, 14b, 15b, and on both sides of the centre line. Parts of the court surface are shown at 20a and 20b, all the tapes being adhesive so as to be stuck to the surface along the appropriate lines. The width of the above-mentioned line tapes is the regulation width for tennis and these tapes are made from suitable coloured material for use as lines on the court. The colour of the above-mentioned auxiliary tapes is of the same or similar colour to that of the court surface.

As indicated for part of the length of tapes 10, 11, 12, 14a and 14b, both the line tapes and the auxiliary tapes have a plurality of parallel conducting steel wires 22 running throughout their length in zig-zags which are in phase with each other. The wires may alternatively be disposed in straight parallel lines. By way of example only, a suitable separation between the wires is approximately one-fourth inch. At the end or edges of the tennis playing area, the wires in the individual tapes are connected to a source of potential, switch means and indicating apparatus so that when desired, the short-circuiting of two or more of the parallel wires will be sensed and indicated. The potential of each wire 22 when the switch means is operative may differ from the potential of the wire on each side of it. As hereinafter explained, a tennis ball for use with the tapes has conducting means to short-circuit two or more of the wires when it comes into contact with the surface of the particular tape. Where neighbouring wires are contacted by the ball, a pulse will be produced and means to amplify the pulse received by the closing of the circuit between wires 22 may be incorporated if necessary and also control means for the switch means. Alternatively the closing of the circuit may be sensed by a device to measure the resistance between the wires.

Each tape is arranged to give an individual response, and where the tapes cross they are insulated from each other. An adhesive layer in the form of a tape without wires is indicated at 24 between the centre line 12 and the service lines 10 and 11, the tape 12 being broken away to show the insulating layer 24.

In place of the tapes indicated in FIG. 1, it is possible to provide broader tapes or sheets which perform a similar function. For example, the centre line 12 could be provided by a tape having the combined widths of the two tapes 18c, 18d and the tape 12 being divided by colour into three bands, e.g., a white band equivalent in width to 12 and green bands on either side equivalent in width to 18c and 18d. Similarly, two or three band tapes could be used for other lines on the court.

Referring to FIGS. 2 and 3, there are shown examples of how the surface of a tennis ball may be made conducting. In FIG. 2, the surface of the ball is provided in customary manner by two panels of Melton cloth stuck under pressure and heat to the centre of the ball. The Melton cloth has woven into it conducting steel wires 28 in a criss-cross pattern in such manner that the wires appear intermittently at the surface of the ball. Wires are used which are of suitable strength and flexibility characteristics to enable the weaving to be carried out and to give the required lifetime in play. The cloth may be woven with steel on one side (the outer surface thereof) or on both sides so that the inner surface is conducting as well as the outer surface when stuck to a ball.

In FIG. 3, the surface of the ball is provided by two panels 26 of Melton cloth as before. After cutting, the panels have stitched into them suitable steel fibres, filaments or wires 28 in a zig-zag pattern to provide conducting elements at the surface. As shown in the drawing, a single wire is formed over the whole surface of one panel in a closed loop.

In an alternative form (not shown) an electrically conducting paint is sprayed or otherwise applied onto the outer surface of the ball.

In a further alternative form, instead of using steel wires, filaments or fibres as the conducting means, aluminium, copper or another electrically conducting metal may be used instead.

Referring now to FIG. 4, the electric conducting means, may be derived using "staple sliver steel" which in appearance looks somewhat like wool off a sheep's back. As in the previous embodiments the surface of the ball is divided with two panels 26 of cloth. The cloth is woven from steel and wool with the possible addition of nylon, the steel being uniformly distributed as indicated by the series of dots 27 in the drawing.

When the balls indicated in FIGS. 2 and 3 are used with the lay-out in FIG. 1, the separations of the conducting means in the balls and the tapes are such that a circuit will be created between adjacent wires 22 when the ball strikes one of the tapes.

The balls embodying the invention may be of the usual type, gas filled or otherwise.

The use of the tapes in a line detection system for indicating whether a service is in or out will now be described. Referring to FIG. 1, the right-hand service area is bounded by the net and the line tapes 10, 12 and 14a. If the ball strikes one of these lines or strikes the auxiliary tapes 18b, 18c or 16a or the court inwardly of these tapes the service is in. If it strikes elsewhere, the service is out.

It will be relatively easy for the umpire to make a decision if the ball strikes the exposed part 20a of the court surface or a part of the court outside the tapes surrounding the service area. However, the more difficult task is to decide whether the ball strikes the line or strikes very near to the line and for this purpose the tapes 10, 11, 12, 14a, 15a, 16a, 17, 18a, b, c and d, are arranged to indicate if the ball lands on any one of them. The wires in the individual tapes are connected to sources of potential and suitable detecting, switching, amplifying and indicating or recording means, the system being controlled so that if the ball lands on 16a, 18b, 18c, 10, 12 or 14a, the ball is given as in, but if the ball lands on 17 or 18d for example it is given as out.

The balls embodying the invention may be used with indicator means besides the tapes here described for the court surface. For example, indicator means may be provided in the net of a court to indicate a net call. Such a system can be used at the same time as the system of line detection. Alternatively in conjunction with the line detection system a pressure sensitive tape can be used at the net with suitable means to indicate a net call.

The invention may be applied to the game of squash or Royal Tennis in which conducting means are incorporated at and near the surface of the ball and in the lines used to mark out the court and appropriate indicator and control means are linked to the conductors in the boundary lines and any adjacent conductive means.

In addition it can also be applied (with appropriate modifications) to such games as football, golf, hockey, badminton, billiards, snooker, table tennis and baseball.

Claims

What I claim and desire to secure by Letters Patent is:

1. A tennis ball comprising: flexible material in the form of a hollow sphere; a surface consisting of two panels of cloth stuck to the flexible material so as to cover the entire outer surface of the material of the hollow sphere; and staple sliver steel uniformly woven into the cloth to form an electrically conducting surface to the tennis ball.