CH286948A - Process for obtaining a plastic tube. - Google Patents

Description

  

  



  Process for obtaining a plastic tube.



   The present invention relates to a process for obtaining a plastic tube, the latter being introduced in the molten state into a die from which it is expelled by compression, characterized in that this tube is passed, at its exit from the die, around a member giving shape to its wall, then a traction is carried out on its end ensuring its stretching, the tube being cooled after sound. passage around said organ.



   The appended drawing shows, by way of example, an embodiment of a device for implementing the method which is the subject of the invention.



   The single figure is a longitudinal sectional view thereof.



   According to this process, is introduced into a die 1, provided with a core 1 * ', a plastic material, for example polyethylene, in the molten state; the latter is expelled from this die 1. by compression and exits at the entrance 2 of the latter in the form of a tube B which is passed around an organ}. in the general shape of a cone, fixed to the core 12 by a threaded rod 5, this core 12 being fixed to a support 13 forming part of the die 1.



   The shape of the base of the member 4 can be round, square or polygonal, this member 1 being coaxial with the die 1.



   Tube 3 rd, is subjected to a treatment which ensures its stretching in the direction of arrow 6: this traction can be exerted by means of a weight attached to a cable connected to clamps tightened at the end of the tube 3 ; said cable can also pass over a return pulley.



   The thickness of the tube 3 can be increased or decreased by increasing or decreasing the magnitude of the tensile weight.



   On leaving the die 1, the tube 3 is heated by means of an electric heating body 7. for example, to prevent premature contraction.



   After his passaye a. ntonr of the orane 1, the tube 3 is subjected to the action of cooling air currents; these are produced, on the one hand, by means of a duct 8 placed inside the tube 3, eoaxially to eelui-ei and, on the other hand. using an annular channel! 'arranged around the tube 3 and supplied by a pipe 10; the channel 9 is pierced opposite the tube 3 with orifices 11 for the outlet of the cold air; the latter ensures an energetic contraction of the tube 3, after its passage over the member 4. and consequently a constant thickness of the wall thereof.

   It is provided in an alternative embodiment to cool the tube 3 only, internally.



   It is possible, with the same die 1, to obtain tubes 3 of different perimeters by changing the shape of the member 4, each tube obtained strictly keeping the profile conferred on it by the latter.



   The duct 8 is assembled by means of a bar 1. 4 to the member 4.


 

Claims (1)

CLAIM: CLAIM: Process for obtaining a plastic tube, the latter being introduced in the molten state into a die from which it is expelled by compression, characterized in that this tube is passed through its exit from the die, around a member giving shape to its wall, and then pulling on its end ensuring its stretching, the tube being cooled after it has passed around said member. SUB-CLAIMS: 1. Method according to claim, characterized in that the tube is heated as it leaves the die. 2. Method according to claim, characterized in that the tube is cooled inté r-ieurement. 3. Method according to claim, characterized in that the tube is cooled internally and externally. 4. Method according to claim, caractÚrisé in that the tube is stretched by means of at least one weight. 5. Method according to claim and sub-claim 4, characterized in that the weight is connected directly to the end of the tube. 6. Method according to claim and sub-claim 4, characterized in that the weight is connected to the end of the tube by means of a cable passing over a return pulley.