Patent GB-1104539-A (GB)
Title: Improvements in and relating to hollow reinforced plastic rods
IPC: A63B53/10
Filed: 1966-07-15
Abstract: 1,104,539. Pipes and tubes. S. M. SHOBERT. 15 July, 1966 [16 Nov., 1965], No. 31904/66. Heading F2P. A hollow reinforced plastic rod suitable for a golf club shaft comprises a plurality of contiguous layers of reinforcement which surround a given imaginary axis, the layers being embedded within and bonded to each other by a cured resinous material; two of the layers each comprising tensioned strands extending in the form of a first helix in one circumferential direction and a second helix in the opposite circumferential direction, a third of the layers being clamped between the two layers and comprising a plurality of longitudinally extending substantially straight circumferentially adjacent tensioned strands, the two layers holding the strands of the third layer in position, the strands of the first and second helices being interlocked together and thereby held in position with respect to each other and the strands of the third layer. As shown, a first layer of braid formed from glass strands 54 is applied to a mandrel 37 by starting a braiding apparatus 26 during which the spools 28 and glass thread are moved at a uniform speed through respective guiding grooves 34 and 36, whilst mandrel 37 is slowly raised at a uniform speed, the spools 28 passing alternately inside and outside of each adjacent spool as they move in opposite directions in the respective guiding grooves. The braid is thus formed on the mandrel 37, the braiding operation being continued until the entire mandrel is covered with a braid layer from one end to the other. When the strands 54 at the bottom of mandrel 37 are cut and the free ends are tied securely to the mandrel so as to prevent the strands forming the braid from relaxing. The mandrel 37 with the first braid layer 62 thereon is lowered in the distributing ring 40 to a position at which the upper end 64 of the mandrel is adjacent to the upper side of ring 40. The free ends of the strands 48 which have been passed through apertures 46 in the ring 60 are now attached securely to the upper end 64 of the mandrel. The mandrel is axially raised slightly without rotation so as to apply tension to all of the strands 48 which now extend longitudinally of the mandrel 37 at which time the strands are equally spaced apart and lie in vertical planes, the strands 48 being wet with resin from being passed through the tank 10. The strands 54 from spools 28 are once again tied to the top end 64 of the mandrel 37 over the strands 48, these longitudinally extending strands being denoted by the numeral 48a. The braider is operated as before so as to apply a second layer of braid 66 over the longitudinally extending strands 48a while the mandrel 37 is raised at the same rate as previously during the application of the first layer 62. The holes 46 are of larger size than the apertures 24 in bar 22 and made large enough to pass the individual threads 48 without wiping therefrom any more resin than is desired in the strands 48a. By reason of the additional resistance between the apertures 46 and the strands 48, the strands 48a on the mandrel are further tensioned and maintained in substantially straight lines. Thus, the longitudinally extending strands 48a are always evenly distributed around the circumference of the mandrel, which provides a uniform radial thickness in the finished tube. After the full length of the mandrel 37 has been moved upwardly through distributing ring 40, the braiding and pulling operations are stopped and the strands on the lower end of the mandrel are tied with a cord as before. All of the strands applied to the mandrel are tied at the ends of the latter so as to maintain the strands in tension. As the outer layer 66 of braid is being applied, the liquid resin in the strands 48a is squeezed therefrom into the strands of both braid 62, 66 so that all of the strands of both braids as well as strands 48a become thoroughly impregnated. The strands are then cut off and the mandrel-layer assemblage is pressurewrapped with a cellophane tape 68 from one end to the other, the edges of this tape 68 being slightly overlapped to make certain the entire outer surface of the braid 66 is covered, and the assemblage with the tape 68 thereon is next inserted into a curing oven, where it is heated until the resin has completely cured or hardened after which the tape 68 is removed and then the mandrel 37 is removed, leaving the hollow finished structure shown in Fig. 7.