| 摘要 |
<p>1359219 Extruder crosshead BAYER AG 16 June 1971 [20 June 1970] 28169/71 Heading B5A Heat plasticized thermoplastics material, from a single or a twin screw extruder 26, is fed to a die extrusion passage 33, from a crosshead inlet 29, into an annular passage 30 around the extrusion die 23 and then in a direction, opposite to that of extrusion through the passage 33, around an upstream lip 32 of the die and into an annular frusto-conical passage 31 defined between the die 23 and a member 21 and communicating with the passage 33. The extrusion may entirely comprise material from the extruder 26, but in the Fig. 2, embodiment this is applied as a pencil covering to a pencil lead composition delivered by a screw 20 through an extrustion passage 22, extending axially through the member 21 and with respect to which the die 23 is radially adjustable, by 120 degrees spaced apart screws 39. The die 23 is attached to a member 35, which is screw threadedly engaged with the die head 24 and 36 and provided with bland bores 37 for engagement by rotating means to effect axial displacement of the die 23 towards the member 21 to vary the depth of the frusto-conical passage 31. The depth of the frusto-conical passage may alternatively be adjusted by displacement of the die head with respect to the die. The die 23 is slideable within the die head 24 at a seal 38. The inlet 29 is surrounded with heating elements 28. The material may also be extruded around a colour pencil or eraser pencil core. The thermoplastics material by comprise polyolefins, A.B.S. polymers, cellulose thermoplastics, polymethanes, polyamide, polycarbonate, polyvinyl chloride, chlorinated polyvinylchloride, ethylene vinyl acetates, polyacetal, and P.V.C. modified ethylene vinyl acetates, and the materials may be coloured by pigment or may be foamable by colouring agents such as diphenyl-3, 3-disulphahydrazide, hydrocarbons, fluorinated hydrocarbons, argon, nitrogen, and carbon dioxide. The quantity of material supplied to the extrusion passage may be periodically changed to produce a correspondingly thickened or constricted section. The material may also be extruded around one or more cores of circular, slit, or trapezoidal shape, or around a preformed wire, rope, tube, band, fabric web, or a foil, or around members delivered through a plurality of mandrel bores, and more than one layer of material may be sequentially applied during passage through the die.</p> |
