GB2099357A

GB2099357A - Extruding around a metal pipe, a sheathing incorporating identifying strips

Info

Publication number: GB2099357A
Application number: GB8215803A
Authority: GB
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1981-05-29
Filing date: 1982-05-28
Publication date: 1982-12-08
Also published as: GB2099357B; ATA138482A; DE3122043C2; IT1151169B; CA1200665A; CH656090A5; DE3122043A1; NL8202038A; BE893344A; IT8221356A0; AT384990B; CS229932B2; FR2506664A1; DD202118A5; JPS5833439A; HU183940B; FR2506664B1

Abstract

Longitudinally extending identifying strips (24) of polyethylene, are distributed around the circumference, on the surface of a steel pipe (17) or like elongate article sheathed with polyethylene, the sheating of which is formed by simultaneous extrusion of a tubular foil (19) of ethylene copolymer serving as contact adhesive and of a tubular polyethylene foil (24) lying over it, using an extruder head with two ring channels (6,11) from which the foils are extruded. The labelling strips are applied in the longitudinal direction during the extrusion process, by delivery into the extrusion channel (11) of the tubular foil (24), at an extrusion pressure greater than that of the tubular foil, via an extruder head inlet (20), ring channel (21), and openings (23) into the channel (11). <IMAGE>

Description

SPECIFICATION Method and device to produce coloured labelling strips on steel pipes sheathed with synthetic material The invention relates to a method and a device for applying several label strips of polyethylene, distributed over the circumference, on the surface of steel pipes or like elongate articles sheathed with polyethylene. Particularly it relates to the application of such strips simultaneously with the sheathing of the pipes.

For the labelling of pipes, cables and leads of solid material bus-bars for the conduction of earth connections, many diverse methods are used. Examples are, simple labels with technical information or pictures and trademarks as advertisements, waterproof labels with the same texts or identification functions, texts stencilled on with colouring matter (water soluble or containing solvents), produced by a stamping process with colour inserts, longitudinal labels produced by spray painting, and also an extrusion can be made with a colouring in a different shade from the base material. Generally, these techniques do not produce weather-resistant labels or they are susceptible to failure on UV- or temperature load with changing climatic conditions.

The invention seeks to provide a method and a device with which it is possible, during the extruding of the tubular contact adhesive- and sheathing foil, to apply coloured label strips in longitudinal direction onto the sheathing, which visibly identify the pipes laid in the ground. To this end the invention provides a method of applying a plurality of longitudinally extending labelling strips to the surface of a pipe simultaneously with sheathing the pipe with polyethylene wherein a contact adhesive and a tubular polyethylene foil are extruded over the pipe surface from a single extruder head; and wherein polyethylene labelling strips are extruded into the path of the tubular foil extrusion at an extrusion pressure greater than that of the tubular foil.

It is preferred that the method is carried out such that the label strips are not completely pressed through the thermoplastic sheathing and that the physical and chemical properties of the sheathing are not impaired, for example by notch effects, alteration of the elongation at rupture and of the chemical behaviour, through UV-radiation or heat.

The invention enables linear strips, which are durable, stable to UV and heat and weather-resistant and are produced by colouring in the most diverse way to be applied to sheathed pipes in a continuous operation in extruded form. In a typical process the labelling strips are each extruded in a width of substantially 8mm and a thickness of 50 to 100 u, and at a pressure of 10 to 50 bar greaterthan the extrusion pressure of the tubular foil.

Flush, smooth formation of the labelling strips can be achieved in the method of the invention if the strips are extruded at a pressure of substantially 100 bar and the sheath foil at a pressure of substantially 150 bar. Strips of lenticular cross-section can be achieved with a smaller pressure differential. For example, if labelling strips are extruded at a pressure of 130 to 140 bar and the sheath foil at a pressure of substantially 150 bar. The fashioning of an extruded labelling is limited in sheathing in width and depth, being continually impressed into the layer bearing the labelling. A raised lenticular or a plane design of the label can thus be achieved through a corresponding pressure regulation.

The invention also provides a device for applying a plurality of longitudinally extending labelling strips to the surface of a pipe comprising an extruder head having two inner and outer concentrically arranged ring slots through which to extrude respectively a contact adhesive and a tubular polyethylene foil wherein a distributor ring is mounted in the anterior housing wall of the extruder head, the distributor ring having a ring channel connected to a duct extending through the anterior housing wall for the supply of the labelling polyethylene and at least three circumferentially spaced outlet openings which open out into the ring slot for the tubular foil extrusion.With the double conical head used according to the invention, in the region of the smoothing zone, i.e. in the upper third of the outer ring slot (from which the sheath foil is extruded), an annular slot is normally provided for receiving the distribution ring. The design of the distributor channels prevents a recessed penetration of the sheath during extrusion.

To achieve best results we have found that the labelling polyethylene (abbreviated below as PE) should have a melting index i2,q6 close to that of the sheathing PE to be labelled. In one preferred embodiment that of the sheathing-PE is 0.4 - 0.5 g/10 min, and that of the Labei-PE is 0.6 - 0.9 g/10 min.

To provide selective identification of the pipes sheathed according to the invention, a colourant is normally included in one or more of the labelling strips, the colourant typically comprising at least one of phosphorescent, UV -stabilized, and heat stabilized. In the extruding process a UV-and/or heatstabilized colourant must remain of fast colour. This task is all the easier, the less admixtures (copolymer of the PE) are present. In addition, the possibility arises to design the label fibres, heat- and UVstabilized, not only with colouring, but phosphorescent as a luminous colour. With these steps the result is that the physical properties, tensile strength, rupture strength and elongation at rupture remain fully maintained and comply with the accepted DIN.

In addition or as an alternative to colouring, a tracer thread may be extruded in, to identify the object sheathed in synthetic material.

Appropriate selection of the label-PE and the sheathing-PE allows processing and distribution of the label-PE-S without the need for additional thermal insulation between the extruders, since the extruding process can be carried out in a uniform temperature working.

The invention will now be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 shows a longitudinal section through the extruder head and the pipe to be sheathed; Figure 2 shows a longitudinal section, to a larger scale, through the anterior housing ring of the extruder head; Figure 3 shows a section taken along line A-B of Figure 2; and Figure 4 shows a further longitudinal section of a portion of the extruder head, to the same scale as Figure 2.

The extruder head used for the extruding of two tubular-shaped foils is known per se in accordance with the German Patent No.1957078 and consists of three housing rings. The extruder head illustrated in the drawings herewith is largely similar and as shown, a first housing ring 1 is designed in one piece with a mandrel 2. Viewed in the direction of working, an intermediate ring 3 connects axially to the housing ring 1, and forms a ring slot 5 with the conically tapering end section 4 of the mandrel 2 for the inner contact adhesive tube 19. Also, between the intermediate ring 3 and the ring channel 6 a baffle ring 7 is fixedly and interchangeably arranged.

While the housing ring 1 serves to apply the inner contact adhesive tube 19 emerging from the ring slot 5 onto the pipe 17 which is to be sheathed and for this purpose is connected to the inlet 8, a second housing ring 9 is arranged for the application of the outer polyethylene tube 18 and is designed in a similar way to the housing ring 1 and is closely connected with the side of the intermediate ring 3 facing away from the latter. The ring slot 5 opens out directly in front of the ring opening of a second ring slot 10, which is formed by the tapered outer surface of the intermediate ring 3 and by the inner surface of the housing ring 9 parallel to this. The ring slot 10 communicates with a ring channel 11,which is connected to a polyethylene inlet 12 and the crosssection of which, as with the housing ring 1, can be altered by means of a baffle ring 13.The housing ring 1, the intermediate ring 3 and the housing ring 9 are connected with each other by bolts 14. The heating of the extruder head up to operating temperature takes place with the controllable heating elements 15.

In the front housing ring 9 of the extruder head a distributor ring 22 is arranged. This has a ring channel 21 (see Figures 2 and 3) in the region of the flattening zone, i.e. in the region of the upper third of the outer ring slot 18. This ring channel 21 is connected to a channel 20 which passes through the front housing wall 9 and serves for the supply of the labelling-PE's. As can be seen from Figure 3, the distributor ring 22 (in this example) has four outlet openings 23 uniformly distributed over the circumference, which open out in the upper third of the ring slot (Figure 4). Thus, on extruding, four labelling strips are produced simultaneously and in this way it is ensured that in every pipe position at least one of the strips is visible.

Claims

1. A method of applying a plurality of longitudin ally extending labelling strips to the surface of a pipe simultaneously with sheathing the pipe with polyethylene, wherein contact adhesive and a tubu lar polyethylene foil are extruded over the pipe surface from a single extruder head; and wherein polyethylene labelling strips are extruded into the path of the tubular foil extrusion at an extrusion pressure greater than that of the tubular foil.

2. A method according to Claim 1 wherein the melting index i2.16 = 0.4to 0.5 g/10 min for the tubularfoil, and = 0.6 to 0.9 g/10 min forthe labelling strips.

3. A method according to Claim 1 or Claim 2 wherein the labelling strips are each extruded in a width of substantially 8 mm and a thickness of 50 to 100 CL, and at a pressure of 10 to 50 bar greater than the extrusion pressure of the tubular foil.

4. A method according to any preceding Claim wherein the labelling strips are extruded at a pressure of substantially 100 bar and the sheath foil at a pressure of substantially 150 bar.

5. A method according to any of Claims 1 to 3 wherein the labelling strips are extruded at a pressure of 130 to 140 bar and the sheath foil at a pressure of substantially 150 bar, the strips have a lenticular cross section.

6. A method according to any preceding Claim wherein one UV- and heat-stabilized colourant is added to the material of the labelling strips.

7. A method according to any preceding Claim wherein a phosphorescent colourant is added to the material of the labelling strips.

8. A method of applying a plurality of longitudinally extending labelling strips to the surface of a pipe substantially as described herein with reference to the accompanying drawings.

9. A device for applying a plurality of longitudinally extending labelling strips to the surface of a pipe comprising an extruder head having two inner and outer concentrically arranged ring slots through which to extrude respectively a contact adhesive and a tubular polyethylene foil, wherein a distributor ring is mounted in the anterior housing wall of the extruder head, the distributor ring having a ring channel connected to a duct extending through the anterior housing wall for the supplying of the labelling polyethylene and at least three circumferentially spaced openings which open out into the ring slot for the tubular foil extrusion.

10. A device according to Claim 9 when the distributor ring is located in the upper third of the outer ring slot.

11. A device for applying a plurality of longitudinally extending labelling strips to the surface of a pipe substantially as described herein with reference to the accompanying drawings.