GB726893A - Improvements relating to the extrusion of filament-forming materials - Google Patents

Abstract

<PICT:0726893/IV (a)/1> <PICT:0726893/IV (a)/2> In the extrusion of powdered or granular fusible filament-forming material according to the method of the parent Specification, the moving surfaces are rigidly supported in an early part of the zone into which the material is fed (i.e. early in relation to the travel of the surfaces past the zone), and resiliently urged inwards of the zone in a later part of the zone whereby frictional engagement of the surfaces with the rod is maintained in the later part of the zone. As in the parent Specification the advancing rod can be received, as it leaves the surfaces, into a laterally confined space leading to one or more extrusion orifices, the end of the rod being melted in the confined space whereby the molten material is extruded through the orifices by the pressure of the advancing rod. As shown in Fig. 3, powdered or granular material is fed to the hoppers 74 and passes through the ducts 73 and the passages 71, 72 into the passage 63 (Figs. 1 and 3) between the flexible stainless steel bands 39, 40 and between the upper cheek plates 66, 67. The powder is tamped by the tip of the vibrating tamping-rod 80 into a compacted rod of rectangular section in the part of the passage 63 over which the band 40 is rigidly supported by the block 48 (Fig. 1) and, by the tamping action, is brought into firm frictional engagement with the bands so that the compacted rod is carried by the bands down the passage 63. Below the block 48 the frictional engagement of the bands 39, 40 with the compacted rod is maintained by the resilience of the springs 57 (Fig. 1) which urge the blocks 49, 50, 51 inwards. At the same time the frictional engagement of the other two sides of the rod with the upper cheek-plates 66, 67 (Fig. 3) is relieved as the compacted rod reaches the lower cheek-plates 68, 69. The movement of the bands 39, 40 forces the rod through the guide passage 95 and the inlet tube 97 into the diminishing cross-section of the melt tube 106. In the melt tube the material of the rod is fused and the fused material is extruded by the pressure of the incoming rod, through the holes of the jet 123 to form filaments. The bands 39, 40 cover the faces of block 36 (Fig. 1) which are secured to the middle rollers of a pair of endless triple roller chains 5, 6 driven by sprockets 7, 8 mounted on shafts 9, 10 driven by the train of gears 15-24 (Fig. 3). The chains 5, 6 are each trained round three idler pulleys 30-32, the pulley 30 being a spring-loaded jockey-pulley. The chains move downwards over their operative runs on either side of the passage 63 and the connecting-means between the shafts 9, 10 and the sprockets 7, 8 is provided with replaceable soft metal shear plugs to disconnect the drive if the resistance to the drive of the sprockets becomes excessive. The bands 39, 40 leave the blocks 36 between the pulleys 30, 31 to pass round the spring-load jockey pulleys 41 which maintain the required tension in the bands. The chain 5 is supported over its operative run by means of a fixed supporting block 44 and the operative run of the chain 6 is supported by a series of blocks 48-51 slidably mounted in apertures in a fixed block 52, block 48 being attached thereto by means of screws 54. Blocks 49-51 are mounted resiliently, being backed separately by plates 56, each of which is urged into engagement with its block 49, 50 or 51 by a pair of strong springs 57. The space 63 between the operative runs of the chains 5 and 6 is bounded on two sides of the bands 39 and 40 and on the other two sides by the guide plates 64, 65 (Fig. 3), upper cheek-plates 66, 67 and lower cheek-plates 68, 69. The plates 64-69 are of T-section, the single limb of the T entering between the bands 39, 40 and being closely engaged thereby. The cheek-plates are mounted a little closer together than the cheek-plates 68, 69. The tamping rod 80 is actuated by a pneumatic vibrator 81 and the level of material in the passage 63 is automatically controlled by the automatic feed device described in Specification 726,892. The invention is particularly adapted for the extrusion of organic filament-forming materials that are liable to decompose at or slightly above their melting-points, e.g. synthetic linear polyamides or polyaminotriazoles (such as polyoctamethylene - aminotriazoles) made for example as described in Specifications 612,609 and 613,020, or co-poly-amide-amino-triazoles, made for example as described in Specification 627,124. The invention may also be applied to the extrusion of polyvinyl compounds such as polyvinylidene chloride and copolymers of vinyl chloride with vinyl acetate or acrylonitrile.