Melt-spinning

摘要

Apparatus for extrusion of thermoplastic materials comprises a heated jacket through which the material is fed by a rotatable screw into an extrusion chamber, the rotatable screw being positioned in a predetermined working position and being resiliently urged into such position and towards the extrusion chamber. The screw is preferably tapered towards the extrusion chamber and is urged by adjustable spring means. The material may be fed to the heated jacket from a vessel having means for agitating and feeding the material to the jacket and in which a vacuum duct opens beneath the surface of the comminuted material, to remove water and occluded gases. As shown, comminuted thermoplastic material is fed from hopper 10 under a vertically adjustable gate 12 to cylindrical vessel 16. In the vessel 16 the material is agitated by rotating wire frame 81, fixed to rotating shaft 41, and the material is also lifted and dropped continuously by three helical blades 86, 86a, 86b. Adjacent the upper end of each blade is a radial duct communicating with a pipe 76 connected to an air pump, whereby removal of moisture and occluded gases is effected. The material is fed downwardly by screw 19 on driven shaft 41, past the spreader 28 and sand filter 29 to spinneret 31, the material being melted by heater coils 24, 32, heated electrically or by circulating hot fluid. The lower portion of screw 19 is preferably tapered, the inner surface of jacket 21 being tapered to match, whereby the material is compressed. The tendency for screw 19 and hence shaft 41 to rise under heavy feeding pressure is resisted by spring 51, one end of which abuts against collar 52 fixed to the shaft, and the other end of which abuts against thrust bearing 54, the top of which presses against stationary cap 55, threaded into fixed sleeve 57. By screwing cap 55 in or out, the spring pressure on feed screw 19 may be adjusted. The conical portion of feed screw 19 is kept just clear of its conical seat by limiting the downward movement of shaft 41 through thrust bearing 61 which rests on fixed sleeve 57, whose vertical position can be adjusted by shims 62. Small vertical movements of shaft 41 are accommodated without affecting the drive by providing gears 66 and 67 on the driving shaft and shaft 41 and embracing the two gears with an internally toothed annular gear 72.