A string suitable for use in game rackets such as for tennis contains from two to four heavy denier monofilaments of an oriented synthetic polymer. Each monofilament has at least two opposite flattened sides throughout its length. The monofilaments are ply-twisted and bonded together along their lengths with each being bonded along a flattened side to at least one other such monofilament. Particularly suitable monofilaments have a substantially ribbon-shaped cross-section with a length-to-width ratio of from two to four.
A composite structure comprises at least one ply comprising approximately parallel unidirected twines comprising helically-configured matrix-impregnated continuous strands of filament reinforcements to provide a flanged composite cantilever spring which serves as the principal constituent of a coupling structure. An interior ply of a coupling structure body member comprises unidirected longitudinal twines configured at a body member extremity to provide a flange member connected to a cantilever spring. An exterior ply is disposed transversely of and superimposed upon the interior ply to provide the cantilever spring hinge line. The composite cantilever spring can be constructed to deflect about either a straight or curved hinge line. A preferred tubular form of the coupling structure comprises at least one end configured as a polygonal array of flanged cantilever springs which serve as the socket end of a spring-lock coupling used to connect mating flanged spigot-end structures. A preferred segmented form of coupling structure comprises two semi-circular flanged cantilever spring members assembled and deflected by an encircling retaining sleeve. The method and apparatus for making a composite in the form of a preferred coupling structure comprises placing first ply loops of longitudinal twines upon a pin-ended forming surface, transversely placing a second ply of twines upon the first ply twines to deflect them into flange-forming cavities, hardening the twine-impregnating matrix, removing and slotting the flanged spring members to provide the desired coupling structure.
A yarn of a synthetic, fibre-forming, polymeric material comprising a plurality of filaments having a substantially rectangular cross-section and having a birefringence assymetry across the width of the filaments, each of the filaments being twisted about the longitudinal axis of the filament in such a manner that the overall lateral dimension of the twisted filament corresponds substantially with the length of the rectangular cross-section of the filament.
An integrated string primarily for use in connection with athletic rackets, such as tennis, badminton, squash and the like, but also usable for fishing line, musical strings, etc., said string in one embodiment comprising a thermoplastic core having a thermoplastic sheath covering same and integrated thereto, said core material and said sheath comprising strands therein having substantially different melting points, and in a second embodiment said string consisting of a braided sheath, with no inner core, said sheath comprising thermoplastic strands having substantially different melting points.
The invention concerns a composite synthetic delaminated string in particular for a tennis racket. The string includes central monofilaments surrounded by multifilament yarns, the assembly being impregnated and coated with polyurethane and is subjected to tensile bending after it has been formed. The invention is useful for tennis strings with novel appearance, with long life span and quick reaction when hitting a ball.
A polyhexamethylene adipamide yarn characterized by a tenacity greater than 4.5 g/den., an elongation of from 25-40% constituent ribbon cross-section filaments having a length to width ratio greater than 3 is disclosed. Also disclosed is the process for making such yarn including a delayed quench and a two-stage hot chest draw.
