DE102005053347B4 - Method and plant for producing a multilayer composite pipe - Google Patents

Abstract

method for producing a multilayer composite pipe, in which a Metal strip in a tubular shape body reshaped, the overlapping longitudinal edges of the tubular body welded and subsequently at least the inside of the tubular body with a plastic inner layer is provided, which by means of a disposed within the tubular body extrusion die supplied is characterized in that the metal strip is initially in deforming a tubular body deviating from the circular shape, the area of the overlapping longitudinal edges is asymmetrical outward is shaped, hereinafter the longitudinal edges of the tubular body laser welded be and then the tubular body formed into a circular shape becomes.

Description

The Invention relates to a method for producing a multilayer composite pipe, in which a metal band is formed into a tubular body, overlapping Welded longitudinal edges of the tubular body and then at least the inside of the tubular Body with a plastic inner layer is provided, which by means of a inside the tubular Body arranged extrusion die supplied becomes.

Further The invention relates to a plant for producing a multilayer composite pipe with a forming device for forming a metal strip in one tubular Body, with a welding device for welding the adjacent overlapping Longitudinal edges of the tubular body as well with an extrusion device, which at least one extrusion nozzle for feeding at least a plastic inner layer in the tubular body, wherein the cross section the at least one flow channel the extrusion nozzle above the entire length the extrusion nozzle in the Is substantially constant, and wherein the outside of the extrusion die as an abutment for the welding head of welding equipment is trained.

A multilayer composite pipe with an inner tube made of plastic, an inner layer of the tube, longitudinally overlapped welded intermediate layer of metal and an outer tube made of plastic is made, for example DE 195 07 224 A1 known. This known multilayer composite pipe has an intermediate layer of an aluminum foil whose edges are arranged longitudinally overlapped and welded by means of electron radiation. Such welding by means of electron irradiation is very expensive in terms of control since it must be avoided that the electrons penetrate into the plastic inner layer. A similar multi-layer composite pipe of this kind is made DE 200 14 466 U1 known, wherein the metal strip may be welded butt or overlapped. The metal strip is preferably made of aluminum, on the type of welding nothing is predicated.

Out DE 200 05 621 U1 a multilayer composite pipe is known in which the edges of the metal strip are glued in the overlap region to avoid the described problems in the welding area. Furthermore, it is off DE 43 23 838 B4 It is known to butt-weld the metal strip of such a multilayer composite tube. However, it can not be avoided that the plastic inner layer is damaged during the welding process, so that additional measures are virtually required to repair the plastic.

Out DE 42 25 011 A1 are a generic method and a generic system known. In this document, an extrusion line is described, which is equipped for producing multilayer composite pipes with a forming device for forming a metal strip to a metal tube with overlapping longitudinal edges and with a welding device for welding the overlapping longitudinal edges, wherein the outer wall of the extrusion die as an abutment for a welding head for welding the overlapped longitudinal edges of the rolled strip material is used to produce the metal tube.

at This known system is preferably an ultrasonic welding device used. However, such an ultrasonic welder has the Disadvantage that only soft non-ferrous metals can be processed. A Processing a metal strip of steel would only be possible if stronger welding generators would be used, what but ever higher contact forces the sonotrode and thus a stiffer extrusion die, the as an anvil would require. This would mean that the as Counter bearing serving extrusion die significantly strengthened would have to be. This could be done but only by a flow cross-sectional narrowing the ring channels the extrusion nozzle realize. This would be only a lower production speed of the system possible because at constant production speed with reduced flow cross-section a damage of the plastic material by exceeding the permissible shear rates would occur.

Out DE 44 04 492 C2 a multilayer composite pipe is known in which the longitudinally overlapped edges of the intermediate layer of the composite pipe are laser welded. The intermediate layer consists of a metal foil, preferably of aluminum.

Out DE 297 13 049 U1 is a multi-layer composite pipe with an inner tube made of plastic, an inner tube sheathing intermediate layer of metal and an outer tube made of plastic, wherein the intermediate layer may consist of steel.

task The invention is a solution to deal with with as possible high production speeds and the lowest possible use of materials gastight multi-layer composite pipes can be created.

This object is achieved in a method of the type described in the present invention that the metal strip is first transformed into a deviating from the circular shape tubular body such that the area of the overlapping longitudinal edges asymmetrically outward Shen, the longitudinal edges of the tubular Kör pers are subsequently laser welded and then the tubular body is formed into a circular shape.

By this first deviating from the circular shape asymmetric deformation of the metal strip Is it possible, in the welding area a back To provide clearance, the use of a laser welding process with a conventional one Fiber laser allows without a connection with the anvil takes place. By the asymmetric Shape changes in the welding area of the Flow area the extrusion nozzle only insignificant, so that the desired high production speed guaranteed remains.

there the sequence is preferably such that during the deformation of the tubular body in a circular shape, the plastic inner layer is fed from the extrusion die. This is realized by the extrusion nozzle starting from the welding area goes to its free end in a circular outer contour.

In Particularly preferred embodiment is provided that a metal strip made of stainless steel is used. For example, as stainless steel Stainless steel 1.4301 or 1.4401 can be used. Such a stainless steel foil is extensible in the radial direction, which offers the great advantage that a such multi-layer composite pipe in the connection area, e.g. to the connection with fittings or the like., Can be spread radially. The wall thickness of Steel, especially stainless steel foil, can be chosen very low, it amounts to preferably between 0.03 and 0.15 mm.

The surface roughness the stainless steel foil is chosen that when using a suitable adhesion promoter, a reliable adhesion is ensured with the plastic inner and outer layer. The plastic material used is preferably RT-PE.

Of course you can too other metals are used, since the process is a laser welding device used.

Further sees the invention to the solution the task also a generic system before, which is characterized that distinguishes the welding device as a laser welder is formed and the extrusion die at least in the region of the welding device a deviating from the circular shape outer contour with on the welding device facing side has increased wall thickness, where the outer contour the extrusion nozzle to turns into a circular shape at its free end.

The extrusion die The system thus deviates from the ideal round in the area of the welding device Shape off and is in their serving as an abutment, the laser welding device opposite Area asymmetrically outward thickened, leaving the wall thickness larger in this area and it possible is, without the cross section of the at least one flow channel the extrusion nozzle significantly reduce the space required for use the laser welding device to accomplish. Because of this external shape the extrusion nozzle Thus, a non-circular tubular body is created from the metal strip, the first non-round welded and then is transformed into the round shape. Elaborate changes to existing equipment are not required, it only has a modified extrusion nozzle for the plastic inner layer and a change the forming device performed become. With such a plant can without reducing the Production speed all metals are welded. Depending on the application, that metal can be selected for the multilayer composite pipe to be produced, which needs becomes. A limitation on non-ferrous metals does not exist.

Around the for the laser welding device necessary To create space, it is preferably provided that the extrusion nozzle in the area opposite with increased wall thickness to the welding device has a Queraufnahmenut. Due to the increased wall thickness in this area the extrusion nozzle is not through the Queraufnahmenut the flow area of the extrusion die impaired.

Further is preferably provided that in the extrusion die at least provided two longitudinal bores are that extend into the Queraufnahmenut. These longitudinal bores serve, in the welding area to supply a protective gas and remove this and any burnup.

In Another advantageous embodiment is provided that the forming device in the field of welding equipment Form rollers for pressing the overlapping Longitudinal edges of the tubular body the extrusion nozzle in the area with increased wall thickness as well Seen in the direction of production behind the welding device forming rollers for forming having the formed metal tube in a circular shape.

The The invention is explained in more detail below with reference to the drawing by way of example. These shows in:

1 partly in longitudinal section the essential parts of a plant for producing multilayer composite pipes,

1a to 1c Sections according to the lines AA, BB, CC in 1 .

2 a perspective view of the extrusion device of the system from behind,

3 a perspective view of the extrusion device from the front,

4 a perspective view of an enlarged detail of the extrusion die of the extrusion device,

5 a section through a finished multilayer composite pipe and in

6 an enlarged detail of the 5 ,

A The plant shown in the figures used for the production of multi-layer composite pipes. Among such multi-layer composite pipes, metal pipes are preferred understood, the inside and outside are each provided with a plastic layer, with both sides on the metal tube in each case preferably applied a bonding agent is.

In the figures, only the essential parts of the invention for such a system are shown. In 1 is from a non-illustrated metal belt transport device in the direction of the arrow 1 (Production direction) a metal band 2 , preferably made of stainless steel, fed first by first forming rollers 3 with counterform 4 is transformed into a U-shaped shape.

Seen in the direction of production behind the first form rollers 3 the forming device is an extrusion device 5 arranged, which has a retaining bar 6 with an extrusion nozzle 7 connected is. This extrusion nozzle 7 has inside a preferably circular flow channel 8th whose cross-section over the entire length of the extrusion die 7 is essentially constant. The flow channel 8th stands over the jetty 6 , in which a corresponding flow channel is integrated, with the extrusion device 5 in conjunction and serves to supply plastic for the production of the plastic inner layer of the multilayer composite pipe to be produced.

If a bonding agent is also supplied, the extrusion die has 7 concentric with the flow channel 8th radially outside the same a further flow channel, not shown, whose cross-section is then also over the length of the extrusion die 7 essentially not changed.

Seen in the direction of production behind the extrusion device 5 , but still in the area of the extrusion nozzle 7 , is a laser welding device 9 trained welding device provided, the two other form of roles 10 associated with the forming device.

Essential is now the outer design of the extrusion die 7 , The extrusion nozzle 7 points at least in the area of the welding device 9 but preferably, as shown in the drawing, from the rear end 7a into the area of the welding device 9 a deviating from the circular shape outer contour with on the welding device 9 facing side increased wall thickness. This area with increased wall thickness is with 11 designated. Starting from this area 11 the extrusion nozzle 7 goes the outer contour of the extrusion die 7 in a transition area 12 in the freiendseitig in a circular outer contour, this area is with 13 designated.

By the particular in the field of welding device 9 intended area 11 with increased wall thickness of the extrusion die 7 It is possible without reducing the cross-section of the flow channel 8th in this area below the laser welder 9 to provide a free space, which by a Queraufnahmenut 14 in the extrusion die 7 in the area with increased wall thickness 11 is formed. This Queraufnahmenut 14 is opposite the laser welder 9 arranged. As the area 11 with increased wall thickness of the extrusion die 7 as an abutment of the form rollers 10 the forming device in the welding device 9 serves, becomes the metal band 2 initially starting from the U-shape ( 1a ) into an in 1b to recognize, one-sided oval shape with overlapping longitudinal edges 2a brought and welded in this position.

Seen in the direction of production behind the welding device 9 and behind the free end of the extrusion die 13 are more form roles 15 the forming device is provided, which transform the already welded, provided with a plastic inner layer metal tube in the desired circular shape. To the form rollers 15 the forming device is followed by a further extrusion device for feeding the plastic outer layer, which is not shown.

The through the Queraufnahmenut 14 formed space under half of the laser welder 9 not only serves to enable the use of the laser welding device without reducing the cross-section of the flow channel 8th the extrusion nozzle 7 but also for the supply of inert gas in the welding area and the discharge of the same and any burnup. These are in the extrusion die 7 at least two longitudinal bores 16 . 17 provided in the transverse nahmenut 14 end up.

For the production of the desired multi-layer composite pipe is thus procedurally first a metal strip 2 from the form rollers 3 transformed into a U-shape and then from the forming rollers 10 during the welding process against the asymmetric area 11 the extrusion nozzle 7 in an oval shape with overlapping longitudinal edges 2a deformed and welded. About the same time or a little later, the plastic inner layer is through the free end 13 the extrusion nozzle 7 supplied to the inner wall of the thus formed tubular body, preferably in addition with the aid of a bonding agent. Following this, the thus formed oval tube with plastic inner layer of the forming rollers 15 formed into the desired circular shape and subsequently provided by a further extrusion device with a plastic outer layer.

In the 5 and 6 is a finished multi-layer composite pipe according to the invention 18 shown in section. The multi-layer composite pipe 18 has a plastic inner layer 19 and a plastic outer layer 20 on, which preferably consist of RT-PE. Between the two layers 19 and 20 is the one out of the metal band 2 formed intermediate layer 21 arranged, which preferably consists of stainless steel foil with a wall thickness between 0.03 and 0.15 mm. This intermediate layer 21 has longitudinally overlapped edges 21a . 21b on, which are laser welded. The intermediate layer is on both sides each with a primer layer 22 . 23 Mistake.

Claims (7)

A method of manufacturing a multi-layer composite tube in which a metal strip is formed into a tubular body, welded to the overlapping longitudinal edges of the tubular body, and then at least the inside of the tubular body is provided with a plastic inner layer by means of an extrusion die located within the tubular body is supplied, characterized in that the metal strip is first transformed into a deviating from the circular tubular body in such a way that the region of the overlapping longitudinal edges is formed asymmetrically outwards, then the longitudinal edges of the tubular body are laser welded and then the tubular body in a Circular shape is transformed. Method according to claim 1, characterized in that that while the forming of the tubular body in a circular shape, the plastic inner layer is fed from the extrusion die. Method according to claim 1 or 2, characterized that a metal band made of stainless steel is used. Plant for producing a multi-layer composite pipe with a forming device for forming a metal strip into a tubular body, with a welding device for welding the adjacent overlapping longitudinal edges of the tubular body and with an extrusion device which has at least one extrusion nozzle for feeding at least one plastic inner layer into the tubular Kör has, wherein the cross section of the at least one flow channel of the extrusion die over the entire length of the extrusion die is substantially constant, and wherein the outside of the extrusion die is formed as an abutment for the welding head of the welding device, characterized in that the welding device ( 9 ) is designed as a laser welding device and the extrusion die ( 7 ) at least in the area of the welding device ( 9 ) deviating from the circular shape outer contour with on the welding device ( 9 ) facing side of increased wall thickness ( 11 ), wherein the outer contour of the extrusion die ( 7 ) to its free end in a circular shape ( 13 ) passes over. Plant according to claim 4, characterized in that the extrusion die ( 7 ) in the area ( 11 ) with increased wall thickness opposite to the welding device ( 9 ) a Queraufnahmenut ( 14 ) having. Plant according to claim 5, characterized in that in the extrusion die ( 7 ) at least two longitudinal bores ( 16 . 17 ) are provided, which extend into the Queraufnahmenut ( 14 ). Installation according to claim 4, 5 or 6, characterized in that the forming device in the region of the welding device ( 9 ) Form rollers ( 10 ) for pressing the overlapping longitudinal edges ( 2a ) of the tubular body ( 2 ) to the extrusion die ( 7 ) in the area ( 11 ) with increased wall thickness and in the production direction ( 1 ) seen behind the welding device ( 9 ) Form rollers ( 15 ) for forming the formed metal tube in a circular shape.