IL43634A - Method of manufacturing a tube from thermoplastic material and apparatus for performing this method - Google Patents

Abstract

1456222 Extruding tube N G PETZETAKIS M G PETZETAKIS and I DIAPOULIS 29 Nov 1973 [29 Nov 1972 2 Dec 1972 9 March 1973] 55522/73 Heading B5A A thermoplastics, or natural or synthetic rubber tube 3, Fig. 1, is extruded from the can extrusion head 1 and drawn around an internal sizing mandrel 4 along which its passage is facilitated by a layer of hydraulic lubricant, (is) entrained by the tube 3 from an annular space 9, between the head 1 and mandrel 4, containing the lubricant at a pressure which does not inflate the tube 3, the layer of lubricant, Fig. 3 (not shown), being of progressively decreasing thickness and increasing pressure along the mandrel, produced by radially inwardly directed forces acting on the tube. The radial forces may be produced by cooling of the tube 3, by a widened portion of the mandrel, or by the pressure at extrusion of a further layer around the tube 3. The tube may be of circular or elliptical section. The lubricant 14 is introduced gravitationally from a reservoir 11, at atmospheric pressure, or vacuum, and via lines 7 in the Fig. 1 embodiment, to the space 9. Lubricant may be leaked from the space 9, via pressure relief boxes 12, as shown in Fig. 9. In the Fig. 1 embodiment, the tube 3 is not stretched in being drawn around the mandrel 4, which is cylindrical, and through a cooling means 8 comprising sequential chambers 13, at different temperatures, producing the radial forces on the tube by shrinkage thereof. In the Fig. 4 embodiment, the extruded tube is cooled to a biaxial stretching temperature during passage through a first heat exchanger 8, around an upstream cylindrical portion 4a of the mandrel which is internally cooled. Biaxial stretching is effected around a conically widened part 4b of the mandrel followed by cooling during passage through a second cooling heat exchanger around a cylindrical mandrel part 4c. The radial forces on the tube are produced by the stretching at 4b, and cooling at 4c. Lubricant may also be supplied between the mandrel parts 4a and 4b. In the Fig. 9 embodiment, the extruded tube comprises an internal extruded layer passing around a cylindrical mandrel 4 with lubricant supplied to the chamber 9, and the mandrel 4 being cooled by coolant circulated via passages 20, 21. circumferential, and/or crossed, and/or parallel filamentary reinforcements 19, are applied at 18 prior to extrusion therearound at die 16 of an external layer, at a pressure producing the radial force on the layer 3. [GB1456222A]

Claims (1)

1. CLAIMS WHAT IS CLAIMED IS: " ~ 1 ·. A method of manufacturing a tube from plastic material, especially thermoplastic material, a quasi-liquid moulding being extruded from an, extrusion head having an. internal spigot, and the moulding being hauled off over an. internal calibration mandrel connected to the internal spigot, the said moulding being cooled fro the quasi-liquid range in thsse conditions, a lubricant being introduced between the moulding and the internal calibration mandrel, characterised in that a hydraulic lubricant is introduced in the practically pressure-less state into a space between the internal spigot and the internal calibration mandrel in. the quasi-liquid range of the moulding, the latter entraining a layer of lubricant between the internal calibration mandrel and the moulding, and said layer of lubricant is. progressively tapered off in the longitudinal section on the internal calibration mandrel by radial forces acting on the moulding* 2.. A method according to claim 1, characterised in that the hydraulic lubricant is introduced between the moulding and the intern calibration mandrel immediately after the moulding has left the extrusion head. 3·- A method according to claims 1 and 2, characterised in that the lubricant layer over the. internal calibration mandrel is not cooled. i*. A method according to claims 1 to 3* characterised in that the radial forces acting on the moulding are produced by cooling of the moulding. - 13 - 5- A method according to claims 1 to 3 and in addition to claim , characterised in that the radial forces acting on the mouldin and produced by hauling the moulding off over an internal calibration mandrel which widens out conically towards the haul-off. 6. A method according to claims 1 to 3 and in addition to claim and or claim 5» characterised in that the radial forces acting on the moulding are produced by extraneous forces, 7. A method according to claims 1 to and 6 i the embodiment for manufacturing an internally calibrated non-stretched tube or a tube which is stretched practically only in the longitudinal direction (by the haul-off), characterised in that the moulding: is hauled off over a cylindrical internal calibration mandrel and the lubricant layer is progressively tapered off on said mandrel by cooling the moulding* 8·- A method according to claims 1 to 3 and 5 and 6 in the embodiment for manufacturing a bi-axially stretched tube, characterised in. that the moulding is cooled only to stretching temperature over a cylindrical part of the internal calibration mandrel and then hauled-off over a conically widened part of theiinternal calibration mandrel, and the layer of lubricant is tapered off progressively thereon and, if required, on another cylindrical end part, with simultaneous external cooling of the moulding* 9· A method according to claims 1 to 6 in the embodiment for manufacturing a tube consisting of an inner ply and an outer ply, if required with, filament reinforcement between, the inner ply and the outer ply, characterised in that the moulding is hauled off as an inne ply over a cylindrical internal calibration, mandrel and the outer - H - ply is extruded around the inner ply (by means of a cross-head) and the layer of lubricant is tapered off progressively by this extrusion pressure.. 1o» A method according to claims 1 to 9» characterised in that the moulding is subjected to very intensive external cooling in the region of the end of the internal calibration mandrel, 1 1 .. Apparatus for performing the method according to claims 1 to 1o , consisting of an extruder, an extrusion head with an internal spigot fon extruding the tubular moulding, an. internal calibration mandrel connected to the internal spigot, and means for introducing a lubricant betwee the internal calibration mandrel and the moulding characterised in. that the internal calibration mandrel (if) is connected directly to the internal spigot (2) and lubricant introduction, bores. (7) for the (practically) pressure-less introduction of a hydraulic lubricant lead between the internal spigot (2) and the internal calibration mandrel (if), and thointernal calibration mandrel (½) s" surrounded by at least one heat-exchanger (8) for cooling and/ or heating tihe moulding ( 3) at least over part of its length, 12. Apparatus according.to claim 1 1 , characterised in that the lubricant inttroduction bores (7) lead into an annular chamber (8 ) which- is disposed between the internal spigot (2) and the internal calibration, mandrel (4) and is open towards the moulding O 13* Apparatus according to claims 1 1 and 12, characterised in that the lubricant introduction bores (7 communicate via bores in th internal spigot (2) with a lubricant reservoir ( 1 1 ) which is subjecte only to atmosHheric pressure or no pressure at all. - 15 - 1 · Apparatus according to claims 11 to 13» characterised in that not only the lubricant introduction bores but also pressure relief bores (.12) lead into tftie annular chamber (8). 15· Apparatus according to claims 11 to 1 , characterised in that the heat- exchanger or exchangers (8) are constructed as liquid containers which are sub-divided into chambers (.13 an-cL the chambers (13) are adjustable to different temperatures.. 16. Apparatus according to claims 11 to 15, characterised in that the internal calibration' mandrel (if) at the beginning consists of a cylindrical part (^a), an adjoining conically widened part ( b followed by an end part ( c which is again cylindrical, while lubricant introduction bores may also lead into the zone between the cylindrical part and the conically widened part.. 1?· Apparatus for performing the method according to claims 1 and 9 and lo, consisting of a first exttruder, an extirusion head with an internal spigot for the mouldin of the inner ply and an internal calibration mandrel connected to the internal spigot, a second extruder with a cross-head for the outer ply and means disposed between, the first extruder and the second extruder for applying a circumferentia-L filament reinforcement,, characterised in that an internal calibration mandrel (4) extending as. far as the cross-head (16) is connected to the internal spigot (2) and is surrounded by the cross-head (16), and means for the pressure-less introduction of hydraulic pressuremedium are disposed between the internal spigot (2) and the internal calibration mandrel (A).. C P. O. Box 33116 , Tel-Aviv Attorneys for Applicant