Amusement devices: games – Aerial projectile game; game element or accessory therefor... – Target
Patent
1983-06-30
1987-05-12
Pinkham, Richard C.
Amusement devices: games
Aerial projectile game; game element or accessory therefor...
Target
273371, 273 61R, 364411, 340323R, 340551, A63B 6100, G08B 1324
Patent
active
046643761
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a sports ball for use with electronic ball detection systems and to a ball detection method and apparatus.
The invention will herein be described with particular reference to a tennis ball and a tennis ball detection system, but it will be understood that the invention is applicable to other ball games and is not limited to use for tennis.
BACKGROUND ART
As is well known, tennis is played on a court marked with lines. When a ball bounces on or close to certain of the lines an umpire must rule on whether the ball is within a designated area bounded by the lines, and hence in-play ("in") or is out-of-play ("out"). Because the tennis ball may be travelling at high speed, it is often difficult to judge by eye whether the ball is "in" or "out". When tennis is being played professionally the umpire's rulings may have considerable importance for players and/or sponsors.
A number of systems have been proposed for automatically detecting whether a tennis ball is "in" or "out". Most such systems utilize a tennis ball which is provided with a conductive outer surface. A plurality of closely spaced parallel exposed electrical conductors extend on and/or adjacent the lines and along the full length thereof. Contact of the conductive outer surface of the ball with adjacent conductors completes an electrical circuit. If the conductors of the circuit completed by the ball are within an "in" area of the court the apparatus signals the ball is "in". Such systems are exemplified in U.S. Pat. No. 3,883,860.
Tennis balls having an electrical conductive exterior for use in those systems are described in U.S. Pat. Nos. 4,299,384, 4,299,029, 4,071,242, and 3,854,719.
Systems dependent on conductive connection between exposed conductors on the court surface are susceptible to failure as a result of resistive corrosion either of the conductors of the court or of the ball, or covering of the conductors by insulators such as dirt, and to failure as a result of short circuits for example by moisture. Moreover the balls do not behave as do normal tennis balls or cause undue wear of racquets or the conductive surface of the ball fails as a result of wear prematurely in the ball life.
In U.S. Pat. No. 3,774,194 there is described a system which does not require exposed conductors. Instead a receiving antenna wire extends longitudinally of a court line and is buried beneath the line. There is provided a radio transmitter and a ball containing three coils at right angles acting as a resonant circuit tuned to the radiofrequency of the transmitter. The ball when in the vicinity of the court antenna acts as a coupler causing vertically polarised radiowaves from the transmitter to be sensed in the horizontal court antennae. In another embodiment a ball having a ferromagnetic metal or metal oxide included in the rubber composition thereof or having a thin layer of metal deposited on the outer surface of the rubber ball beneath a felt is used to unbalance a balanced bridge circuit.
That system is subject to interference by external signals and the balls required for use in the system do not have the properties of normal tennis balls and are expensive to manufacture.
None of the systems so far proposed has won wide acceptance and there is a continuing need for a satisfactory system of ball detection.
An object of the present invention is to provide a system which avoids at least some of the previously discussed disadvantages.
SUMMARY OF THE INVENTION
According to one aspect the invention consists in detection apparatus for sensing the proximity of a ball to a boundary when the ball comprises a metallic or ferromagnetic substance, said apparatus comprising:
a plurality of coils disposed each adjacent another along the boundary,
an oscillator associated with each coil for generating an oscillating field in the coil vicinity, and
a detector associated with each oscillator and responsive to a disturbance, if any, of the oscillating field by the metallic or ferromagnetic material of the
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patent: 4054987 (1977-10-01), Forlenza
patent: 4062008 (1977-12-01), Carlsson et al.
patent: 4071242 (1978-01-01), Supran
patent: 4299029 (1981-11-01), Van Auken
patent: 4299384 (1981-11-01), Van Auken
patent: 4375289 (1983-03-01), Schmall et al.
patent: 4432058 (1984-02-01), Supran
Lastova MaryAnn Stoll
Pinkham Richard C.
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