KR100484042B1 - Method for manufacturing heat insulating pipes - Google Patents

Abstract

The present invention comprises at least one inner tube, a corrugated plastic outer tube disposed coaxially spaced from the inner tube, and a layer of foamed plastic filling the annular gap between the inner tube and the outer tube. A method of making an insulated conduit. Such methods include spacing the at least one inner tube with a plastic foil formed from a hose, injecting foamed plastic into the space between the at least one inner tube and the plastic foil or hose, the at least one inner tube And supplying the hose to a forming tool consisting of mutually coupled half molds having a corrugated profile formed on the inner surface, wherein the hose is pressed against the inner surface of the half mold closed by the foamed plastic, thereby Causing a corrugated profile of the face to be formed, extruding the outer tube on the corrugated surface of the hose so that the corrugated outer tube is formed on the corrugated surface of the hose immediately after the outer tube exits the exit member of the extrusion tool. Making a step.

Description

METHOD FOR MANUFACTURING HEAT INSULATING PIPES}

The present invention relates to a method for producing an insulated conduit according to the preamble of claim 1.

DE-GM 93 10 530 discloses an insulating conduit consisting of an inner tube for conveying media made of reticular polyethylene, a protective sheath made of plastic with a shallow corrugation and a layer of foam between the inner tube and the protective sheath. Such known conduits are used in long-distance and short-range heating pipeline networks, as water and sewer pipes, and in many other special fields. In addition, such conduits are characterized by having an optimum bending behavior, i.e., a small bending radius, minimum elastic repulsion, high static load carrying capacity and good longitudinal water tightness. Such conduits can be easily installed in excavation trenches.

GB-A-1 482 661 discloses a method for producing an insulated conduit of the type in which a plastic pipe is continuously fed to an extruder. Such extruders form a plastic protective sheath coaxially spaced with respect to the tube being fed. In the same process, foamed plastic is injected into the annular gap between the inner tube and the protective sheath to completely fill the annular gap. The conduit arrives at the cooling and straightening device immediately after passing through the extruder, in which the protective sheath is cooled and corrected to a constant outer diameter. By such a method, an insulating conduit having a plastic inner tube, a plastic protective sheath, and a layer of foam between the inner tube and the protective sheath can be produced long in a continuous working manner.

DE-A-28 03 708 has a smooth thermoplastic inner tube and a thermoplastic outer tube. Disclosed is an apparatus for manufacturing a flexible multilayer insulated conduit having an insulation layer between an inner tube and an outer tube. In such a device, an inner tube is supplied to the tube forming apparatus of the outer tube, and the tube forming apparatus of the outer tube extrudes the outer tube at intervals coaxially with respect to the inner tube. The foamed plastic is extruded into an annular gap between the inner and outer tubes by a worm extruder. The extruded new outer tube is fed into a hollow mold consisting of an endlessly cyclic forming chain, which hollow mold supports and corrects the outer tube. In one embodiment, the shaping chain has a corrugated profile. When a vacuum is applied between the forming chain and the soft protective sheath, the protective sheath enters the corrugation of the shaping chain and forms a wavy surface on the protective sheath.

It is an object of the present invention to improve the manufacturing method of the type mentioned at the outset so that the waveform of the protective sheath is basically simple, i.e., without creating a vacuum in the circulating forming chain.

Such an object is achieved by the features described in the characterizing part of claim 1.

The essence of the present invention is that the plastic foil shaped into a tube acting as a mold of the foam to be expanded is pressed into the half mold of the molding tool having a corrugated profile by the pressure at the time of foaming. Therefore, the surface of the heat insulating material layer is formed in a wave shape. Subsequently, when the outer tube is extruded onto the surface of the heat insulating material layer, the outer tube enters the corrugated wave of the hardened layer of short insulation material, and thus the corrugated surface is formed in the completed heat insulating conduit. Correctly forming the corrugation in the outer tube is preferably performed by underpressure generated between the insulation layer and the soft outer tube extruded.

As the waveform, an annular or helical waveform is used. Such waveform is determined by the half template.

The finished conduit, where both the insulation layer and the outer tube have hardened, engages the caterpillar take-off. The conduits may be in annular bundles or wound on cable drums immediately after passing through the caterpillar take-off.

In the scope of the invention double tubes may be produced by the process according to the invention. That is, two inner tubes separated from each other may be introduced instead of one inner tube. Such a scheme is generally proposed for long distance heating conduits in which both mainstream and reflux tubes are installed.

As the inner tube, for example, a plastic tube (flat tube or corrugated tube) or a metal tube (flat tube or corrugated tube) can be used. The plastic foil used is an LLDPE foil, whose wall thickness is about 0.05-0.5 mm. The plastic foil should be constructed so that the corrugation profile of the half mold can be formed by the foaming pressure.

In the plastic foil, the surface facing the foam material is preferably treated by corona discharge. Thereby, a close bond between the foil and the foam is achieved. Since the extruded skin is also bonded to the plastic foil, a tube having excellent watertightness in the longitudinal direction is formed. As the foam, a polyurethane foam having a short solidification time is preferable. In other words, the foam is preferably foamed inside the molding tool. However, this means that the withdrawal speed for withdrawing the inner tube from the storage drum is determined by the withdrawal speed of the forming tool. In order to arrange the inner tube exactly coaxially with the outer tube, means must be provided to displace the inner tube in at least two mutually perpendicular directions. For this purpose, a pair of rollers is preferably installed. In order to monitor the center position, an inner tube with a layer of foam is irradiated with high energy radiation. In the case of deviation from the center position, the pair of rollers are displaced across the production direction correspondingly.

Hereinafter, the present invention will be described in detail with reference to the embodiments schematically illustrated in the accompanying drawings.

The inner tube 2 is continuously drawn out from the storage drum 1. The inner tube 2 is preferably a networked polyethylene tube with polyvinyl alcohol embedded in its wall. The inner tube 2 is conveyed through a pair of straightening rollers 3 being driven. The pair of straightening rollers 3 are arranged to be movable across the production direction in two directions perpendicular to each other.

The foil 5 made of LLDPE is withdrawn from the storage spool 4 and shaped coaxially with respect to the inner tube 2 around the inner tube 2 to form a slit tube 6, which is a slit tube 6. It has a longitudinal seam that is bonded or welded. In addition, a polyurethane- or polyethylene-based foamed plastic mixture is injected into the slit tube 6 which is not yet bonded. In the case of polyurethane, the components mixed with each other using the pistol 7 are sprayed onto the foil 5.

If necessary, the signal core 8 is supplied into the slit tube 6.

The closed tube is fed to a forming tool 9 consisting of a plurality of half molds 9a and 9b, and the plurality of half molds 9a and 9b to an inner tube 2 with a layer of insulation and a foil 5. Form a waveform as a whole.

The surfaces of the half molds 9a, 9b facing the plastic foil 5 have a corrugated profile, which is shaped into the foil 5 by foaming pressure. Therefore, the corrugated surface is formed in the pipe 10 which exits from the shaping | molding tool 9.

Subsequently, the tube 10 passes through the roentgen irradiation apparatus 11, and the roentgen irradiation apparatus 11 continuously inspects the tube 10 with respect to the exact center position of the inner tube 2. In the case of deviation from the center position, the roller pair 3 is displaced correspondingly. Subsequently, the plastic sheath 13 is extruded onto the tube 10 by the extruder 12, which such shell 13 is introduced into the corrugation of the tube 10 by the negative pressure between the shell and the tube 10. Enter into a waveform. At this time, the shell is adhered to the plastic foil 5 due to the high temperature maintained through extrusion.

The finished tube 14 is then drawn out by the band drawing device 15 and made into an annular bundle in a suitable device.

Alternatively, the tube 14 may be wound on a drum, not shown.

By the method of manufacturing the insulated conduit according to the invention, the waveform can be simply formed in the protective sheath of the insulated conduit without the need to create a vacuum in the circulating molded chain as in the conventional method.

1 shows schematically an embodiment of the invention.

Claims (13)

Insulation consisting of at least one inner tube, a corrugated plastic outer tube disposed coaxially spaced apart from the inner tube, and a layer of foamed plastic filling the annular gap between the at least one inner tube and the outer tube In the manufacturing method of the conduit, a) surrounding said at least one inner tube with a plastic foil molded from a hose at intervals, b) injecting foamed plastic into the space between the one or more inner tubes and the plastic foil or hose, c) supplying said at least one inner tube and said hose to a forming tool consisting of mutually coupled half molds having a corrugated profile formed on an inner surface thereof, d) the hose is squeezed to the inner surface of the half mold closed by the foamed plastic, such that the corrugation profile of the inner surface is formed in the hose, e) extruding the outer tube on the corrugated surface of the hose, such that the corrugated outer tube is molded on the corrugated surface of the hose immediately after exiting the outer tube from the outlet member of the extrusion tool; The manufacturing method of the heat insulation conduit made into. 2. The plastic foil of claim 1, wherein the plastic foil is withdrawn from the storage drum and formed into a hose, the longitudinal edges of the plastic foil are glued or welded, and the plastic foil is bonded before welding or welding the longitudinal edges of the plastic foil. A method of making an insulated conduit, wherein the foamed polyurethane mixture is applied to a foil. The method for producing an insulated conduit according to claim 1 or 2, wherein an LDPE-based material having a wall thickness of 0.05 to 0.5 mm is used as the plastic foil. 3. The method of claim 1 or 2, wherein the surface of the plastic foil facing the foam side is treated by corona discharge. 3. The method of claim 1, wherein the at least one inner tube is made of a plastic, such as a reticulated polyurethane with a diffusion barrier layer. 4. 6. The method of claim 5 wherein the diffusion barrier layer is made of polyvinyl alcohol and is produced together with the polyethylene tube by coextrusion. The method for producing an insulated conduit according to claim 1 or 2, wherein a plastic inner tube having a smooth wall portion or a corrugated wall portion is used. The method for producing an insulated conduit according to claim 1 or 2, wherein a metal inner tube having a smooth wall portion or a corrugated wall portion is used. 3. Insulated conduit according to claim 1 or 2, wherein the one or more inner tubes can be moved in two vertical directions by suitable means perpendicular to the direction of travel before entering the forming tool. Method of preparation. 10. The method of claim 9, wherein horizontally and vertically laterally displaceable roller systems act on the at least one inner tube. The method of claim 1 or 2, wherein the insulating conduit is irradiated with high energy radiation prior to extrusion of the outer tube to indicate the position of the one or more inner tubes, wherein the position of the one or more inner tubes is a predetermined position. And a means for moving the at least one inner tube laterally to control the position when it is displaced from the insulated conduit. 3. A method according to claim 1 or 2, wherein the forming tool is formed by a mold which is provided with a transverse groove which complements the hollow mold and which is guided and divided while rotating. 3. The method of claim 1 or 2, wherein shaping the outer tube into the corrugated surface of the hose is achieved by a negative pressure between the outer tube and the hose on the foam layer exiting the outlet member of the extrusion tool. A method of producing an insulating conduit.

Images