Electrically conductive tennis ball

• US 4,664,378 A
• Filed: 12/12/1983
• Issued: 05/12/1987
• Est. Priority Date: 04/23/1975
• Status: Expired due to Fees

• Current Assignee: Accu-Call As
• Original Assignee: John A Van Auken
• Inventors: Van Auken, John A.
• Primary Examiner(s): Marlo, George J.
• Application Number:
  US06/560,239
• Time in Patent Office: 1,247 Days
• Field of Search: 273/61 R, 273/61 B, 273/61 C, 273/61 D, 273/58 B, 273/58 BA, 428/242, 428/113, 428/283, 428/227, 428/229, 340/323 R, 139/11
• US Class Current: 473/570
• CPC Class Codes: A63B 2071/0611 Automatic tennis linesmen, i.e. in-out detectors
• CPC Class Codes: A63B 2102/02 Tennis
• CPC Class Codes: A63B 43/004 electrically conductive, e.g. for automatic arbitration
• CPC Class Codes: A63B 71/0605 Decision makers and devices using detection means facilitating arbitration

Abstract

An electrically conductive tennis ball comprising a cover of woven fabric in which the yarn used for weaving the fabric in at least one direction is made by twisting together a blend of electrically conductive and electrically nonconductive filament fibers. The electrically nonconductive fibers may predominate, and the woof yarn may be thicker than the warp yarn which may be so woven with the woof yarn that the latter occupies the major part of the ball'"'"'s surface. To promote continuity of the electrical paths in the ball'"'"'s cover, an electrically conductive adhesive, or mat, or scrim or other base may be interposed between the woven cover, and an electrically conductive coating may be applied to the inner, or back, side of the cover. Needling may also be employed to reorient the fibers in the cover and thereby enhance the conductivity of the electrical paths along the inner side of the cover. Features of the invention such as those just described reduce the number of electrically conductive fibers needed to make the ball operate satisfactorily, eliminating objectionable discoloration of the ball attributable to those fibers and also eliminating changes in the playing characteristics of the ball which a greater number of those fibers might create. Tennis balls as just described may be made more conductive than water to keep water on the court from generating a false signal.

Claims

1. An electrically conductive tennis ball for use with an electrical detection circuit in which touchdown of the ball in a selected area is detected by completion of a circuit between spaced apart electrical conductors extending along said area, said electrically conductive tennis ball comprising an elastically deformable sphere, a cover of woven fabric covering said sphere, said fabric being woven with a set of warp strands interlaced with a set of woof strands, the strands of one of said sets comprising a quantity of electrically conductive fibers and a quantity of electrically nonconductive fibers, and the strands of the other of said sets being composed entirely of electrically nonconductive fibers.

2. The electrically conductive tennis ball defined in claim 1 wherein said fabric has a weave in which the area occupied by the strands of said one of said sets on the outer surface of said cover is greater than the area occupied by the strands of said other of said sets.

3. The electrically conductive tennis ball defined in claim 2 wherein the strands of said one of said sets are thicker than the strands of the other of said sets.

4. An electrically conductive tennis ball for establishing a current-conducting path across spaced apart electrical conductors extending along a selected area of a tennis court and/or the top surface of a net, said electrically conductive tennis ball comprising an elastically deformable sphere and a cover of woven fabric covering said sphere, said fabric being uniform over the entire surface of the ball and:

(a) having a set of strands of warp yarn interlaced with and extending transversely of a set of strands of woof yarn with the yarn for the strands in at least one of said sets being formed of a plurality of electrically conductive fibers with metal surfaces and electrically nonconductive fibers which are twisted together and the number of said electrically nonconductive fibers exceeding the number of said electrically conductive fibers in the yarn for the strands of said at least one of said sets to the extent that excessive discoloration of said cover by said electrically conductive fibers is avoided, or (b) having a set of warp strands interlaced with a set of woof strands with the strands of one of said last mentioned sets comprising a quantity of electrically conductive filament fibers with metal surfaces and of random lengths and a quantity of electrically nonconductive filament fibers mixed with said conductive fibers, said conductive and nonconductive filament fibers being twisted together to form the yarn for said one of said sets of strands.

5. The electrically conductive tennis ball defined in claim 4 comprising a base of electrically conductive material formed separately of said cover and lying between said cover and said sphere without passing through said cover, said base being in contact with and electrically interconnecting at least some of said electrically conductive fibers to provide at least one electrically conductive network for conducting electrical current through one or more of the electrically interconnected electrically conductive fibers from the outer side of the cover to said base, through said base along the inner side of the cover, and through one or more additional ones of the electrically interconnected electrically conductive fibers from said base to the outer side of said cover.

6. The electrically conductive tennis ball defined in claim 5 wherein said cover comprises a pair of panels which are divided by a seam, and wherein said base bridges said seam to establish electrical continuity between said panels.

7. The electrically conductive tennis ball defined in claim 6 wherein said base is an electrically conductive adhesive which adheres said panels to said sphere.

8. The electrically conductive tennis ball defined in claim 6 wherein said base is a scrim comprising unwoven electrically conductive fibers, there being an adhesive for adhering the composite of said cover and scrim to said sphere.

9. The electrically conductive tennis ball defined in claim 6 wherein said base is an electrically conductive mat.

10. The electrically conductive tennis ball defined in claim 4, wherein said electrically conductive fibers form a part of the woof of said fabric, wherein the warp strands of said fabric are composed entirely of electrically nonconductive fibers, and wherein said fabric has a weave in which the area occupied by the woof of said fabric on the outer surface of said cover is greater than the area occupied by the warp of said fabric.

11. The electrically conductive tennis ball defined in claim 4 wherein the yarn defining the strands in the other of said sets is formed by electrically conductive and electrically nonconductive fibers which are intermixed and twisted together.

12. The electrically conductive tennis ball defined in claim 4 wherein at least some of said electrically conductive fibers each have at least one portion which is reoriented after said fabric is woven to extend transversely of the plane of the fabric.

13. The electrically conductive tennis ball defined in claim 4 wherein said fabric has a weave in which the area occupied by the strands of said one of said sets on the outer surface of said cover is greater than the area occupied by the strands of the other of said sets.

14. The electrically conductive tennis ball defined in claim 4 wherein only the yarn in said woof contains electrically conductive fibers and wherein each of said woof strands is passed over a larger number of warp strands than it is passed under to increase that portion of the exposed surface of the covering that is covered by the woof.