Patent GB-1343805-A (GB)
Title: Method of and apparatus for manufacturing cylindrical hollow articles of hardenable moulding materials
IPC: B29C41/22
Filed: 1971-04-19
Abstract: 1343805 Moulding tubes H MAIHART 19 April 1971 [4 March 1970] 23116/71 Heading B5A [Also in Division F2] Cylindrical hollow articles of any desired length are produced in a rotating shell mould by introducing hardenable material, e.g. thermosetting resin, from one or more nozzles, on to the inner surface of the rotating mould to form a cylindrical layer and withdrawing the layer so formed as it hardens, the speed of the process being controlled in accordance with thickness and setting time of the material of the thusformed layer. A cylindrical shell mould 1 is formed with rounded ends 2, 3, around which pass a plurality of longitudinally extending flexible belts 5 (Fig. 5) which together form an axially movable mould wall, centrifugal force and moulding pressure being sufficient to cause them to conform to the cylindrical contour of the inside of the shell. The belts may be of silicon rubber, polytetrafluoroethylene or polyethylene or they may be coated with one of these. The mould is supported on two sets of 120 degrees spaced rollers which engage in races 8 and 9, the bottom roller 10 of each set being driven by motor 18 and thus rotating the mould, whilst the other two rollers 11 and 12 (Fig. 4, not shown) are carried by pivoted arms. The roller 10 may be raised or lowered by screws 28, 29 to accommodate moulds of different diameters. Hardenable material is sprayed on to the rotating mould inner wall by nozzles 49-56 which may be advanced, or reciprocated, longitudinally, and several layers, one or more of which may be coloured, cellular, or reinforced with granular, fibrous or filamentary material may be applied by appropriately arranging the nozzles. A roller 55 may be provided for smoothing and pressing. At the delivery end of the mould two stationary rings 59, 60 carry a series of rollers 61 on spindles arranged to rotate in sleeves or ball bearings 65 which are pivotable about their radial axes so that the rollers may be skewed relative to the vertical plane of the device, this being accomplished by rotating the ring 60 relative to ring 59, the tie bolt holes being slotted to allow this. A cylindrical connector 58 is inserted into the delivery end of the mould so that the hardenable material will be sprayed on to one end of it at the commencement of the operation and its other end projects into concentric engagement with the array of skewed rollers. Rotation of the mould thus results in these rollers exercising a screw effect upon the connector, and the moulded workpiece to which it is attached, so withdrawing the latter from the mould. The rate of withdrawal is determined by the angle of skew of the rollers 61. Several sets of this advancing device may be provided at intervals to support the moulded cylinder as it is drawn off. Examples of materials of the layers are polyester resin, which may be reinforced with glass or steel fibres, carbon or asbestos filaments, quartz sand, vermiculite or expanded clay;  or polyurethane foam.. Annular ribs, e.g. of polyurethane foam may be provided on the inner surface by an extra nozzle. Hardening may be assisted by such means as heat, ultra violet radiation or neutron bombardment.