IE33885L - Tennis rackets. - Google Patents

Abstract

1,266,531. Steel tennis rackets. DUNLOP HOLDINGS Ltd. 31 Dec., 1969 [2 Jan., 1969], No. 367/69. Heading A6D. A tennis racket is made of hollow steel tube whose cross section is such that its maximum external dimension M, divided by the maximum wall thickness, WT, is at least 26 and the minimum external dimension, M', divided by the maximum wall thickness, WT, is at least 13. Preferably, also, the point H of the frame will not be displaced by more than 3/4" when the last 6" of the handle is clamped and a load of 50 1b. is applied to point L; the angular distortion of the head about the longitudinal axis is not more than 4‹ under a torque of 150 inch 1b. applied along the line YZ; the vertical displacement of point E of the frame is not more than 1 3/4" when the head of the racket to line FG is clamped and a load of 20 1b. is applied to point E; and the load/ deflection ratio at a deflection 1/10" is greater than 450 when the frame is gripped in a tension testing machine and I and J. The crosssectional shape of the tube may be elliptical, circular or rectangular and may be grooved in the middle portion to facilitate stringing. The racket frame is made from a length of tube filled with bitumen supporting material and bent into shape, the stringing groove lying on the outer edge of the logs. A series of string- ing apertures are drilled in the loop, the bitumen material is melted and drained, and a bridge piece (C) and braces (D) are brazed onto the frame loop and between the parallel ends of the frame respectively. The racket is completed by a leather-bound wooden handle and stringing. [GB1266531A]