| 摘要 |
947,255. Apparatus for manufacture of flexible tubes of non-uniform wall thickness. F. HOBIGER, and L. HOBIGER. April 6, 1962 [April 7, 1961], No. 13386/62. Heading B5A. A process for the manufacture of tubes of thermoplastic material having a non-uniform wall thickness comprises extruding the material through a nozzle containing a mandrel to form an outlet gap of non-uniform width and bringing the plastic material passing through or emerging from the nozzle in the region of a smaller width of tube wall to a higher temperature than that of another section of the tube wall so that a rectilinear tube is produced. Plastic material is fed to an extruder head 5, to which is secured a nozzle 6 containing an eccentric core 7, and discharges through an annular opening 8 in the form of tube 9, 10. The nozzle 6 consists of at least two ring segments 11, 12 connected together by thin webs 13 such that heat conduction between the two segments is maintained as low as possible, and are made from different thermally conductive materials, segment 12 which is provided with an electric heating element 14 having a higher thermal conductivity than segment 11. Alternatively the nozzle 6 may be formed from more than two segments, the segments being thermally insulated from each other. Alternatively radiant heaters may be used external to the extruded tube. In a further embodiment of the invention the nozzle 6 may be so formed that it has a variable height with respect to its base so that greater heat dissipation may be obtained over one area of the nozzle than in another. |
