Patent GB-559153-A (GB)
Title: Improvements in or relating to extrusion machines
IPC: B29C48/51
Filed: 1942-07-31
Abstract: 559,153. Extrusion machines. HENLEY'S TELEGRAPH WORKS CO., Ltd., W. T., and GRIFFITHS, F. T. July 31, 1942, Nos. 10783, 14214 and 14215. [Class 87 (ii)] [Also in Group XXII] An extrusion machine comprises two or more pairs of screw-thread impelling devices, the two devices of each pair being in axial alignment with their delivery ends together and having their rotating parts integral with one another or coupled together at their delivery ends, whereby the axial thrust on the bearings of the rotating parts is eliminated. Two or more pairs are so distributed around the axis of the extrusion chamber as to feed in material from a number of points. The pairs may have their axes parallel to the extrusion chamber axis or, as shown, at right angles thereto. When there are two pairs, their axes may lie parallel to each other, as shown. When there are three pairs, their axes may lie at an angle of 60 degrees to each other and in three separate planes at right angles to the extrusion chamber axis. When there are four pairs, two pairs may have their axes parallel to each other in one plane, the other two pairs having their axes parallel to each other in another plane, e.g. a plane parallel tothe first plane, the axes of the first two pairs lying at an angle, e.g. 45 degrees, to those of the other two pairs. Fig. 1 shows a machine for making tubing of lead or lead alloy or for sheathing an electric cable with such metal. Two parallel pairs of screws 121, 122 and 123, 124 lie one above and one below an extrusion chamber 2 (or they may lie behind the chamber). Each pair of screws is constituted by a single shaft 10 having formed thereon right and left hand screw thread portions which are separated by a plain portion 18. The portion 18 serves as a central bearing for the shaft, and access of lead to the bearing is prevented by screw thread glands 21 thereon. The bushes 8 in which the screws rotate are interiorly screw-threaded, of opposite hand from the screws with which they co-operate ; or the linings may be rifled or grooved longitudinally. Molten lead is fed in at 14 and discharged at 19 into ports 20 leading in to the extrusion chamber. To enable the screws to grip the lead, air, steam or water is circulated through channels 16 to cool the lead. Electric heaters 15, 22 heat the feed chambers 14 and the extrusion chamber 2 respectively. The screws are housed in barrels A which are integral with the central extrusion-chambercontaining part B. Figs. 5 and 7 show a modification, suitable for extruding plastics such as polyvinyl chloride or lead, in which the casing is built up of two end blocks 31 and a central block 33. The block 33 is held stationary by projections (or recesses) 38 thereon entering recesses (or projections) 37 on the screw cylinders 32 ; transverse tie bolts extending from cylinder to cylinder may additionally secure the block 33 ; the co-operating surfaces of the block 33 and cylinders 12 may be wedge-shaped. The cylinder bores may be as in Fig. 1 or, as shown, plain. The screw shaft bearings 44 are housed in comparatively isolated brackets 45, to reduce the flow of heat to the bearings. Electric resistance heating elements 91 are clamped on the cylinders. Heat insulation 93 surrounds the central parts of the machine. Thermostats 94, 95 control the temperature at feed and delivery ends respectively. For extruding natural rubber mixes, the heating arrangements are replaced by water-cooling jackets. Particoloured rubber &c. products may be produced by charging each screw section with differentlycoloured stock, the extrusion chamber being divided into four compartments by plates 73, 74, Fig. 7, located on each side of a two-part screen 67, 68. These plates help to restrain the die point 58 from movement relative to the point holder 57. The point 58 may be longitudinally adjusted by movement relatively to a tube 70 on which it is screwed. The die 63 is held by a cap 64 against a tapered opening 62 in an inner sleeve 53 telescoped within an outer sleeve 52. The inner sleeve is pressed inwardly by hand-operated clamps 69 to hold the screen against a seating in the outer sleeve. The extrusion chamber may be pushed out as a whole (to the left, Fig. 7) by rotating a hand wheel 88 carrying a member 82 which bears on the outer sleeve 52. In a modified removable extrusion chamber (not illustrated by drawings) the die 63 is adjustably positioned on the outer sleeve and the point holder 57 is integral with the inner sleeve. The single orifice chamber of Fig. 7 may be modified to provide for two or more extrusion orifices. The screw shafts 40 may be withdrawn from the left, Fig. 5, without dismantling the gear drive 99.