The invention relates to a method for manufacturing a thermally insulated conduit pipe which comprises at least an inner pipe, arranged at a distance therefrom an undulated outer pipe made of plastic and a layer made of foamed plastic filling the space between the inner pipe and the outer pipe, wherein the inner pipe is first enclosed by foam and the outer pipe is extruded onto the inner pipe enclosed by foam. Furthermore, the invention relates to a thermally insulated, undulated conduit pipe as well as an installation for carrying out the method.
A method according to the preamble of claim 1 is known from EP-A-0 897 788. This method has proven itself and leads to thermally insulated conduit pipes of high quality. Conduit pipes manufactured with the method are for example used in the local and district heating supply or in industrial applications. The undulation created according to EP-A-0 897 788 in the process of foam enclosure of the inner pipe or of the inner pipes allows small bending radii of the finished pipe, which are different depending on pipe dimensions and which allow an easy pipe laying. For example, a conduit pipe for the heat supply known as CALPEX® has in a dimensioning with an outer pipe of 162 mm a bending radius of 1.2 meters. There may exist applications for which an even smaller bending radius of the thermally insulated pipe is required. A method for forming thermally insulated plastic conduit pipes is known from DE-A 195 07 110, in case of which an outer plastic pipe of only 0.3 to 0.5 mm wall thickness is extruded coaxially to an inner pipe, wherein this outer pipe is pulled into the molds by vacuum by means of a mold chain arranged in vacuum, like in the case of a corrugator machine for the manufacturing of undulated plastic pipes. At the same time, a PE-foam containing propellant is extruded into the empty space between the outer thin pipe and the inner pipe, wherein the foam fills the empty space. By pulling-in a thin outer pipe into the molds by means of vacuum, only an undulation with a low depth can be reached. The manufacturing of a thermally insulated conduit pipe is known from WO-A 02/07948, in case of which an inner pipe is provided with an insulation layer onto which an outer pipe is overlaid. Solely the outer pipe is then provided with a rib structure by means of a rib structure maker. It is for example known from U.S. Pat. No. 5,522,718 that in the case of manufacturing simple undulated pipes mold halves are conveyed on a return section by means of grapplers and slides.
The invention has the task of improving a thermally insulated conduit pipe and its manufacturing method.
This is reached with the method mentioned at the beginning by creating the undulated shape by means of molding tools, after completed extrusion of the outer pipe, on the inner pipe which is enclosed by foam.
It has been seen that in this way, in the case of the special compound consisting of inner pipe, foamed thermal insulation and outer pipe with the undulation valleys, an undulation which extends deep into the conduit pipe can be brought into the outer pipe and the thermal insulation, resulting in a higher bendability. The deep undulation is thereby pressed into the extruded thermally insulated conduit pipe. It extends deep inside the conduit pipe and therefore into the thermal insulation. This is contrary to the described methods with corrugator machines by using vacuum (or over-pressure) for creating the undulated shape, by means of which only a comparatively small depth of the undulation is reached.
The deep undulation by pressing-in is preferably done directly after the completed extrusion of the outer pipe, after which the conduit pipe has a temperature which allows the plastic deformation by the molding tools. It is thereby preferred that the extruded conduit pipe is tempered to a suitable temperature for this on the way to the deep undulation, for example by means of a spray bath with water. By this, the extruded conduit pipe has an optimum temperature for the pressing-in of the deep undulation when it gets to the tools provided for this. However, a later bringing-in of the deep undulation may also take place in a separate manufacturing step, for which the conduit pipe is brought to a temperature allowing the pressing-in of the undulation by heating means.
A first undulation may be created by usual means already for the foamed thermal insulation, as described in EP-A-0 897 788, wherein the deep undulation is molded around and deepens this first undulation after the extrusion according to the present invention. One may also provide an evenly foamed pipe extruded with an even outer pipe with the pressed-in undulation according to the present invention. The procedure according to the first option, in case of which the molding with the deep undulation is done for an already undulated conduit pipe after the extrusion, is preferred because the undulation normally yields a higher material thickness in the undulation valleys of the outer pipe in the case of foaming and subsequent extrusion of the outer pipe onto this first undulation. It is then available for the deep second undulation by means of the molding tools after the extruder, such that even in the case of a deeper undulation no imperfections arise in the outer pipe. Thereby, a detection of the first undulation, particularly prior to the extruder, and an adapted positioning of the molding tools for the deep undulation may take place.
It is preferred that the undulation depth is greater or equal to 4 mm and it is therefore at least 33% higher that in case of the mentioned CALPEX® conduit pipe which is manufactured according to the prior art. An undulation depth of 4 to 10 mm is particularly preferred. According to the invention it is possible to create substantially U-shaped undulation valleys which are separated from each other particularly by means of even upper side sections. This shaping results in a good material distribution of the outer pipe material during the molding after the extrusion. In a preferred embodiment, the molds used for the deep undulation are cooled, particularly by providing water cooling. In order to detach the molds for the deep undulation from the conduit pipe it may be provided that the molds have channels allowing the blowing-in of air for supporting the detaching.
The task is further solved by a conduit pipe according to the invention.
In the following, examples of the invention are explained by means of the drawings. Thereby it is shown in
A plastic foil 5, particularly a polyethylene foil, is removed from a supply spool 4 and shaped into a slotted tube with a glued or welded longitudinal seam around the inner pipe 2 concentrically to it. A foaming-up plastic mixture is brought into the still open slotted tube 6, particularly on a polyurethane basis or a polyethylene basis, for example by means of the nozzle 7. The closed slotted tube is inserted into a molding tool 9 which is formed by a plurality of molding halves 9a and 9b which form together a “traveling molder” for the inner pipe which is provided with the insulation layer under the foil 5.
The surfaces of the molding halves 9a and 9b facing the foil 5 or the slotted tube 6 respectively may have an undulated profile, inside of which the foil 5 is molded in due to the foaming pressure. In this case, which is shown in the figure, the pipe 10 coming out of the molding tool 9 has an undulated surface. The surfaces of the molding halves 9a and 9b facing the foil 5 may however also be even. The pipe 10 coming out of the molding tool 9 has in this case an even surface. In this case the molding tool 9 could also replaced by an idle hollow cylindrical shape.
The pipe 10 may afterwards travel through the x-ray installation 11 known from EP-A-0 897 788 by means of which the pipe 10 is continually checked for an exact centered position of the inner pipe.
In the next manufacturing step the outer pipe 13 made of plastic is extruded onto the pipe 10 by means of an extruder 12. For this, a vacuum causing the fitting of the outer pipe on the foamed pipe 10 is generated in a known way. In the case of the undulated pipe 10, the outer pipe 13, which can also be called an outer shell, fits to the undulation of the pipe. In case of the even pipe 10 the outer shell fits to the even pipe and becomes also even. Thereby, the outer shell glues to the plastic foil 5 because of its high temperature which was kept up by the extrusion.
Preferably, the deep undulation is brought into the extruded conduit pipe directly following the extrusion step in the manufacturing process of the conduit pipe, such that a continuous manufacturing results. The deep undulation takes place by pressing the undulation mold into the conduit pipe. This is done for example in such a way that the deep undulation is brought in according to the present invention by means of molding tools 16-21 at a distance from the extruder 12 which may for example be 3-4 m. This bringing-in is done in the pipe 10, which is still moldable because of the process heat due to the foaming and the extrusion, being provided with the outer pipe 13. The process heat of the preceding manufacturing steps of foaming and of extruding may be used or one may ensure by using heating means or cooling means respectively, that the pipe 10, 13 still has a temperature when entering the molding tools, which allows the pressing of the deep undulation into the conduit pipe. It is preferred to provide a spray bath 23 which brings the extruded conduit pipe to a temperature which is suitable for the deep undulation and which is then kept. The temperature depends on the plastic material of the conduit pipe and is therefore easy to determine for the skilled person or it is determinable by tries. The molding tools used to bring in the deep undulation may for example be endless molding tools traveling along, as they were shown for the molding tool 9 in case of the foaming or they may be other molding tools known to the skilled person. An example for other molding tools is explained in the following.
The pressing in of the deep undulation by means of molding tools may also be carried out in a separate manufacturing step, after the extruded conduit pipe has been cooled down and temporarily stored, such that a discontinuous manufacturing results. However, this subsequently requires a heating-up of the conduit pipe from the storage temperature to the temperature allowing the pressing-in of the deep undulation.
In the following, an example for the bringing in the deep undulation by means of molding tools is described according to
The molding tool with the molding halves 20 and 21 which form the undulation on the top and the bottom works the same way. A closure in the direction of the arrow a or in the opposite direction respectively is carried out, such that both molding halves 20 and 21 form the closed mold. After that the method is carried out in the direction of the arrow b for the same retention time as for the molding halves 18 and 19. After that the demolding in the direction of the arrow c or in the opposite direction respectively and the fast driving back of both molding halves in the direction of the arrow d is carried out. These movements are obviously done synchronized with the movements of the molding halves 18 and 19, such that all molding halves execute the shifting together in the direction of the arrows b or together the fast driving back in the direction of the arrows d.
Preferably, the molding halves are cooled, particularly by providing fluid channels in the molding halves, into which a cooling fluid (preferably water) is fed into the molding halves via a (not shown) supply port and may be drained off via a (not shown) drain port. Furthermore it is preferred that the molding halves are provided with air passages and a port for pressurized air, such that pressurized air can be blown into the molding space of the molding halves in order to support the demolding of the deep undulated pipe.
It may preferably be made sure that the deep undulations are brought in each in an undulation valley of the previously undulated conduit pipe by providing a detection device which detects the existing undulation before the molding tools and controls the molding tools such that they execute the pressing-in of the deep undulation aligned to the previous undulation. This is shown in
Number | Date | Country | Kind |
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090012170 | Jan 2009 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CH2010/000021 | 1/27/2010 | WO | 00 | 9/6/2011 |