Patent GB-750768-A (GB)
Title: Improved method and apparatus for fabricating pipe
IPC: B29C53/60
Filed: 1954-08-30
Abstract: 750,768. Making pipes. GANAHL, C. DE. Aug. 30, 1954 [Dec. 14, 1953], No. 25157/54. Class 99(2). One or more continuously advancing multi-filament glass fibre rovings is or are heated to a temperature substantially above 200‹F. and immersed while still at a temperature above 125‹F. in a bath of uncured, liquid plastic composition and then applied in one or more helically wound layers to a continuously advancing mandrel; on which the layers are treated to set the plastic composition, the mandrel being removed from the resulting glass-fibre-reinforced plastic pipe. Preferably, the plastic material employed is a synthetic thermosetting resin, such as polyester or epoxy resin compositions and blends thereof, and which can be dissolved in one or more solvents in the monomeric or low polymeric form to yield a viscous solution and which is afterwards converted to an insoluble, infusible, high polymeric form by heating. As shown, motor-driven rubber-tyred wheels 6, Fig. 1, below a rotatable circular table 5 advance a mandrel 1 upwardly at a uniform rate through an opening 4 in the table which is supported in a horizontal plane on rollers 7 mounted on a framework 8 and carries a number of packages 9 of glass fibre rovings 10. A ring 12, Fig. 3, carrying a number of radially-extending supports 13 is removably mounted at the upper end of a cylinder 11 arranged in the opening 4 and secured to and rotatable with the table 5, the inner ring 14 of an open annular pan 20 for dispensing the plastic composition being secured to the ring 12 and resting on the upper edge of the cylinder. Attached to the bottom plate 18 of the pan 20 is an outer ring 19 and a number of radially extending supporting arms 22 lie on the plate, a series of annular rings 21 being secured to those arms and the arm and ring assembly being removable ; alternatively, the rings 21 are secured to an annular plate. A series of rings 23 are secured to a frame comprising radially extending arms 24 which carry upwardly extending hooks 26 resting upon shoulders 30 of vertical shafts 29 screwed into a nut 31 secured to the ring 19 and mounting handwheels 28 for controlling the vertical position of the rings 23 and therefore the winding tension on the rovings 10 which pass between the rings 21, 23. The plastic composition is delivered to the pan 20 by gravity flow from a supply tank and through a stationary trough 32 mounted on the framework 8, the plastic being guided from the trough into the pan by an annular cone 33. Any excess of plastic overflowing from the pan 20 collects in a cone 35 secured to the cylinder 11 and flows through openings 36 in the cylinder to a collecting vessel 37 and from that vessel to a stationary trough 39 and a collecting tank for recirculation. Vertical roving-spacing pins 42 are mounted in a collar 40 lying on the plate 18 and fixed by pins 41 to the ring 14, the pins 42 serving to guide the rovings leaving the pan 20 and preventing rotation of the pan about the mandrel from pulling the rovings into a skewed path of travel through the pan. Control over the uniformity with which the rovings 10 are distributed about the mandrel 1 is achieved by a ring 48 which guides the rovings onto the mandrel and is carried on a series of vertically adjustable bars 45 passing through a centering ring 44 affixed to flexible rods 43 secured to the framework 8, the ring 44 ensuring that the ring 48 is accurately centred about the mandrel. Excess plastic wiped and squeezed from the rovings as the latter pass under the ring 48 is caught by a deflector cone 49, the resin passing through openings 50 in the cone and down the inner surface of the cylinder 11 to the trough 39. Removably supported on the supports 13 are a series of segment-shape, electrically-heated ovens 52 spaced around the pan 20, each oven comprising a hot-plate 54 having a smooth upper surface 55 and an upwardly curved section 57 provided with transversely spaced openings 62 through which the rovings pass, and a closed box 63, filled with insulating material and having a lower exterior reflecting surface 64, removably mounted over the plate 54. The rovings 10 are drawn across the surface of the plate 54 and heated to a temperature in the range from 400‹F. to 800‹F., and such cooling of the rovings as results from exposure thereof to the air after passing through the openings 62 and before the rovings come into contact with the plastic in the pan 20 is such, under normal conditions that the rovings are still at a temperature in the range from 125‹F. to 175‹F. A series of tables 5 may be arranged one above the other whereby a number of layers of plastic coated rovings are applied to the mandrel. When an adequate thickness of rovings and plastic has been built up on a convenient length of mandrel the pipe is heated or otherwise treated to cure the plastic and stripped from the mandrel. Where there are at least two layers of rovings the pitches of those layers may be opposite in direction but substantially equal in magnitude ; also, there may be one or more layers of rovings applied substantially parallel to the axis of the mandrel. Specification 687,552 is referred to.