Patent GB-946883-A (GB)
Title: Process and apparatus for forming a glass roving resin pipe
IPC: B29C53/80
Filed: 1962-01-16
Abstract: 946,883. Making non-metallic pipes. ISLAND OIL & REFINING CO. Jan. 16, 1962 [Jan. 23. 1961], No. 1512/62. Heading F2P. A process for forming a glass roving resin pipe includes the steps of applying a parting layer to a rotatable pipe form, applying a layer of curable resin to the parting layer and curing the layer of resin, applying glass roving under tension and additional uncured resin to the cured resin layer until a pipe of desired dimensions has been formed, the additional uncured resin being applied so as to impregnate the glass roving, and curing the additional uncured resin. As shown, the apparatus for making the pipe includes a mandrel 22 of aluminium having a reduced end portion 20 engaged in a collet connected to a shaft 14 provided with a driving pulley 16, and the opposite end portion 24 of the mandrel rests in a half-bearing 26 and a roller bearing 28; the lengths of the supported portions 20, 24 of the mandrel are approximately 10 to 15% of the length of the pipe to be formed to avoid sagging of the mandrel at the middle thereof. Spools 32 from which glass rovings 44 are withdrawn are mounted on a platform 30 longitudinally reciprocated on a screw shaft 36 rotatably driven by a reversible motor 34, the horizontal disposition of the platform being maintained by guides 35. Mounted on the platform is a dispensing means 40 from which a curable resin admixed with hardener flows on to the rovings 44 as the latter are applied to the mandrel. To tension the helical wound rovings, bolts 58 are threadedly engaged in a support plate 61 and frictionally engage the sides of the spools 32 by means of end limits 63 composed of an asbestos or other long-wearing composition. The completed pipes are placed under a radiant heat source and on a curing table, Figs. 6 and 7, comprising a table 84 utilizing drive wheels 86 geared to each other by sprockets 88 and a drive shaft 90 on which one of the sprockets is mounted, the shaft also having mounted thereon a drive pulley 92 driven by a motor 94 through a belt 96. By rotating sprocket 88 on the shaft the drive wheels 86 are rotatably driven to rotate the mandrel portions 24 resting on each pair of wheels 86; idler wheels 98 rotate with the end portions 20 of the mandrels. To counteract flexing of the mandrel during the winding of the rovings thereon an electromagnet 118 is disposed opposite the middle of the mandrel and the latter has mounted therein an iron insert 120, and in operation the winding 122 of the electromagnet is energized with current of a magnitude in proportion to the deflection forces exerted on the mandrel by the tensioned rovings 44; accordingly, the current is a maximum as the platform 30 reaches the middle of the mandrel and decreases to a minimum as the platform 30 approaches the ends of the mandrel. In a modification, a ball 146, Fig. 5, of magnetically attractable material is disposed within the mandrel 122a and an electromagnet 118a simultaneously movable with the platform 30, is mounted on a drive shaft 148 driven by the motor 34. In making a pipe a layer of paraffin wax 52 is applied over a helically-wound paper or other liner 50 wrapped around a mandrel and a silicathickened epoxy resin composition is applied over the solid wax, this resin layer being cured. The mandrel is mounted in the pipe-making apparatus and a tensioned, helically-wound resin-impregnated layer of glass rovings is applied over the resin layer. Longitudinally disposed rovings are incorporated in the pipe and such rovings are secured at the ends thereof to anchor rings 62 moved on a movable trolley to place the assembly of rovings in the desired position relative to the initial helical layer 48. The rings are locked in position by bolts 67 or other conventional clamping devices, a pneumatic piston-cylinder device 72 being then actuated to move the collet 12 away from the anchor ring 62 mounted on the collar 70 so as to place the rovings under a uniform tension and a further helically wound layer 80 of resin-impregnated rovings is applied. As many longitudinal and helical layers of rovings are applied to obtain a pipe of the desired strength. The completed pipe is placed on the curing table, Figs. 6 and 7, to partially cure the resin and final curing of the resin is effected by passing steam through the pipe the paraffin layer 52 being melted and allowing removal of the paper liner.