GB719062A - Improvements in and relating to the production of yarns and filaments - Google Patents

Abstract

Solid particles of a filament-forming material are supplied to and held against a plate containing a multiplicity of apertures and maintained at a constant temperature sufficient to melt the filament-forming material, and the melt is forced in a stream through the plate and along ducts to a metering pump which <PICT:0719062/IV (a)/1> <PICT:0719062/IV (a)/2> <PICT:0719062/IV (a)/3> pumps the melt to a spinneret or spinnerets. In one form of the invention the solid particles are held against the heated plate by a ram acting in a cylinder. By providing the ram with holes or hinged apertures and imparting to it a reciprocating motion, replenishment of the material beneath it is effected. In order to avoid irregularities in the flow of material to the pump, the cylinder may be divided into at least two parts by a wall or baffle, with a ram working in each part in such a way that on the downward stroke the rams are out of step. In a modification the solid particles are fed downward in a cylinder and held against the heated plate by a rotating screw, driven through a friction clutch in order to maintain a substantially constant pressure against the plate. Alternatively the screw may be driven pneumatically, hydraulically or electrically. In order to prevent the cylinder from becoming hot through contact with the heated plate, it may be insulated by quartz or asbestos. The cylinder may also be provided with a cooling system. The heated plate is preferably made of silver, aluminium or other good thermal conductor which does not degrade the polymeric material. The rows of apertures in the plate may be connected on the underside by parallel slots, which in turn may be connected by a further slot which has a cross-sectional area substantially equal to the combined area of the parallel slots and bisects them at right angles, the molten material being conducted from this slot to the pump. The plate may be heated electrically or by circulating fluids, and its temperature may be considerably higher than the melting point of the polymer, to reduce the time of contact between plate and polymer as much as possible. The polymer chips in the supply hopper may be blanketed with an inert gas or kept in a vacuum. As shown (Fig. 1), the heating plate 6 of silver is drilled with holes 16 which are countersunk to form sharp edges 17. The melt is collected in parallel slots 18. A heating element 9 is fastened to the outer rim of the plate. In Fig. 4, the silver plate is connected to an intermediate block 8 of aluminium which carries the heating element 9 on its lower surface. The melt is conducted from slots 18 to a slot 12 and then by a central conduit 11 to the pump. The heated plate structure is clamped to the base of a cylinder 1 with a layer of asbestos 7 between the contacting surfaces. The cylinder is divided into two equal parts 15 by a baffle wall 2 and is surrounded by a cooling jacket. Segmental rams 14 formed with holes 33 to permit the polymer particles to pass through and operated by rods 19 reciprocate in the cylinders 15. A hopper 20 provided with an inspection and filling cover 22 and an entry port 23 for supplying inert gas is connected directly to cylinder 1 by a gas-tight joint. The rods 19 pass through the lid and are sealed by bellows. Hollow cylindrical sleeves 26 bearing slots 29, in which work rods 27 connected by pins 28, are attached to the top of the rods 19. Between the top of the sleeves 26 and a collar carried by the rods 27 compression springs 30 are provided. These springs enable a constant pressure to be maintained on the particles regardless of the amount of polymer particles beneath the rams. The rods 27 are driven by an eccentric mechanism not shown. Fig. 6 shows a modification using a substantially vertical rotating screw formed by a rotating shaft 34 carrying a continuous flight 35 and driven by an electric motor 36 through a slipping clutch. The solid particles are supplied to the heated plate by gravity. Preferably the cylinder is formed with a roughened or grooved interior surface to ensure that the polymer does not rotate with the screw. Specification 533,307 is referred to.