FR2613981A1 - Method and head for extruding profiled elements made of synthetic material having coloured stripes (strips) - Google Patents

Abstract

The subject of the invention is an extrusion method and an extruder head enabling, conveniently and economically, elements made of synthetic material to be manufactured, the surface of which has longitudinal or helical coloured stripes (strips). <??>The extruder head 10 includes an inlet orifice 12 and distribution conduits for a synthetic base material 22 intended to form an inner layer 2 which constitutes the major portion of the extruded section. The head furthermore includes at least two other inlet orifices 13, 14 connected to auxiliary extruders delivering coloured synthetic materials. Distribution conduits 25, 26, 31, 32 distribute these materials in the form of contiguous coloured stripes (strips) around the base material in order to form an outer layer 3. The base material may or may not be coloured and may have optimum dielectric characteristics. <??>The invention is applicable in order to produce, especially, jackets for electrical optical conductors, as well as tubes or profiles.

Description

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PROCESS AND HEAD FOR EXTRUDING PROFILED ELEMENTS IN MATERIAL

SYNTHETIC WITH COLORED BANDS.

The present invention relates to an extrusion head of profiled elements in synthetic material having colored bands, comprising an outlet die defining the profile of the element, a punch arranged coaxially upstream of this die, at least two orifices of intake of respective plastics supplied under pressure by separate sources, and distribution means disposed between the intake ports and the

punch to distribute the synthetic materials around the periphery of the punch.

The invention also relates to a method of manufacturing an element.

lU profiled by means of such an extrusion head.

To obtain extruded elements having colored bands of identifi-

cation, therefore at least two different colors on their outer surface, for example to make an insulating sheath of an electric wire or cable, it is known practice to simultaneously extrude a basic insulating material, having a first color and completely surrounding the conductor , by means of a main extruder, and a synthetic material having a color different from the base material, by an auxiliary extruder and separate ducts in the extrusion head. One thus forms bands of the

second color that are embedded in the surface of the base material.

However, this requires the use of a base material which is colored so that the surface bands are clearly visible in contrasting colors. This results in various drawbacks. First of all the colored matter

is relatively expensive compared to a natural colored material.

Whenever you want to manufacture a product with other colors, you have to purge and clean the entire installation. On the other hand, the materials

dyes generally have the effect of modifying the electromagnetic characteristics.

triques of the material, which is inconvenient in the case of insulating sheaths!

electrical conductors.

The basic idea of the invention consists in avoiding these drawbacks by using a base material which is not colored and by simultaneously extruding, -2 - around this base material, surface bands of at least two plastics. colored differently from each other, to cover

the basic material.

More particularly, the present invention provides an extrusion head of the type indicated above, characterized in that the inlet ports comprise at least one inlet port of a base material and at least two inlet ports of a base material. colored materials, and in that the means for distributing the colored materials comprise a distribution member having a tubular shape, an outer surface provided at least with a respective cavity for the entry of each colored synthetic material, an inner surface provided with 'a series of outlet orifices distributed around the periphery of this surface, and distribution conduits connecting the inlet cavities to the outlet ports so that

Adjacent outlet ports are connected to different inlet cavities.

Preferably, these distribution conduits comprise bores passing through the distribution member and forming said outlet orifices, and grooves formed in the outer surface of this member to connect the inlet cavities to the respective bores. These grooves have bifurcations, and the lengths of the grooves between a bifurcation and each

bores connected to this bifurcation are preferably equal.

In a preferred embodiment, the interior surface of the dispensing member is a surface of revolution, and the respective outlet orifices for each color are distributed substantially in a respective radial plane. All these orifices can also be located in the same radial plane. In addition, the outer surface of the dispensing member is a surface of revolution, the inlet cavities of materials of two different colors are offset both axially and angularly one by one.

relative to each other, and the inlet ports of the respective bores correspond

laying in each of these colors are grouped in two respective radial planes located between the two inlet cavities, these two radial planes

which may be distinct or confused.

The extrusion head may include a distribution sleeve housed in the distribution member and provided, on its outer surface, with a respective channel facing each of said outlet orifices, the outlets of these

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distribution channels being distributed around the periphery of an annular passage for the base material around the punch. Preferably, the outlets of the distribution channels are contiguous, so as to form a continuous layer of colored material around the base material in the area of the punch. Preferably, the outlet die is incorporated into the distribution sleeve. The distribution member may be rotary, for the purpose of extruding an element having helical colored bands, as well as a shape.

helical if its profile is not circular.

lu Extrusion heads according to the invention can be provided for

manufacture of a wide variety of profiled elements, either with superficial strips

contiguous skirts, or with bands which are separated from each other, revealing the base material. However, the first case constitutes a particularly advantageous innovation. Thus, the present invention provides a method of manufacturing a profiled element having at least two colored surface bands, by extrusion of synthetic materials, characterized in that one extrudes, simultaneously and in a single extrusion head, a layer interior made of a basic synthetic material, and an outer layer completely covering the inner layer and formed of juxtaposed colored bands. This profiled element may in particular be an electric wire or cable, or an optical fiber or cable, comprising an extruded sheath. This element can also be a

tubular or solid profile.

The present invention and its advantages will be better understood with the aid of the

following description of an exemplary embodiment, with reference to the drawings

appended, in which FIG. I is a schematic view in axial section of an extrusion head according to the invention, the section being taken along the lines I-I of FIGS. 3 and 4, fig. 2 is an exploded view showing in perspective two of the parts of this head, namely a distribution cartridge and a distribution sleeve, FIG. 3 is a schematic view in partial cross section taken along the line III-III of FIG. 1,

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fig. 4 is a schematic view in partial cross section taken along the line IV-IV of FIG. 1, and fig. 5 to 7 represent different elements in cross section

which can be extruded by means of such a head.

The exemplary embodiment illustrated by the figures relates to the manufacture of an electrical conductor by extrusion of an insulating sheath around a metal wire 1. This insulating sheath comprises a first layer 2 which completely surrounds the wire 1 and which is made of a synthetic material referred to here as a base material. This layer accounts for most of the thickness and cross section of the sheath. On this first layer, the sheath comprises on the outside a second layer formed of several colored longitudinal bands, the colors being arranged alternately. In the example illustrated here, four bands 3 of yellow color are provided which are arranged symmetrically around the periphery of the sheath and between which are interposed four bands 4 of green color, to form a conductor indicated by the conventional code yellow / green. . In this way, the base material can be completely covered by colored bands 3 and 4 which are contiguous as shown in Figs. 5 and 6 and its color can be any. In particular, it is possible to use a base material whose composition is optimal from the point of view of its dielectric and / or mechanical characteristics, without the addition of coloring material. As this uncolored base material costs less than a colored material and constitutes the major part of the volume of the sheath, this results in a substantial reduction in the overall cost of the materials used in the manufacture of the conductor. In addition, in the case described here of an electrical insulation sheath, the gain achieved in the insulation properties allows a slight reduction in the diameter of the sheath, that is to say a gain in weight, volume and cost of the finished product. However, it is understood that the present invention also relates to the cases where it is desired to use a

colored base material.

The extrusion head schematically illustrated by FIGS. I to 4 and generally designated by the reference 10 essentially comprises a body 11 provided with three intake ports 12, 13 and 14, a distribution cartridge 15 mounted inside the body 11, a distribution sleeve 16 provided with a die 17 and mounted coaxially in the cartridge 15, and a central punch 18 which is also mounted coaxially in the cartridge 15 and which is provided with a central passage for the thread 1, so as to serve as a thread guide . Die 17 and punch 18 can be constructed in a variety of ways and are not described in detail here. In particular, the die 17 can be formed directly in the sleeve 16, or be constituted by a part added in this sleeve. The parts 15 to 18 are held in the body 11 in a known manner, using plates

front panels 19 and 20.

The intake ports 12, 13 and 14 are arranged radially in the present case. The orifice 12 is located in the rear part of the head 10 and it is connected to a main extruder providing a relatively large flow of uncolored synthetic material 22. This flow of material is distributed in a conventional manner over the entire periphery of the punch 18. by means of suitable conduits arranged in the dispensing cartridge 15, in order to then flow convergently on the conical anterior surface 18a of the punch, then to completely coat the wire 1. The inlet openings 13 and 14 are located in the part front of the head 10 and they are offset axially with respect to each other. As shown in Figs. 3 and 4, they are also angularly offset by 45, for a reason which will appear later. The port 13 is connected to an auxiliary extruder providing a relatively low flow rate of colored synthetic material 23, for example yellow, and likewise the port 14 is connected to an extruder

Similar auxiliary delivering colored material 24, for example green.

The distribution cartridge 15 is provided with respective distribution conduits for dividing these two flows of colored materials in a symmetrical manner with respect to the longitudinal axis of the head 10 and of the wire 1, while the distribution sleeve 16 comprises distribution channels intended

in distributing all of these divided flows around the base material 22.

The distribution ducts for colored materials 23 and 24 appear in FIGS. I to 4 and they include the following elements, among which similar elements bear the same reference numbers but are assigned the letter b for the conduits intended for yellow material 23, and the letter c for the conduits intended for the material green 24. Two respective inlet cavities 25 are formed in the outer surface of the

distribution cartridge 15, opposite the intake ports 13, 14.

Each of the cavities 25 is connected to four respective oblique bores 26 passing through the sleeve 15, by means of a network of grooves 27 arranged

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symmetrically with respect to the cavity 25 and having bifurcations 28

preferably located at an equal distance from the bores 26 which correspond to them.

On a cylindrical inner surface 29 of the sleeve 15, the bores 26 open in the present case through eight outlet orifices 30 which are regularly distributed over a circle, that is to say are located in the same radial plane and are spaced apart. angularly 45, the orifices 30b provided for one color being alternated with the orifices 30c provided for the other color. On the other hand, the inlet orifices of the bores 26b and 26c can be located in different radial planes, the bores then being oblique with respect to the longitudinal axis as seen in FIG. 1. The symmetrical arrangement of each of the distribution networks obviously makes it possible to ensure an equal flow rate of material at each outlet orifice 30. The realization of these symmetrical networks by means of the grooves 27 and the bores 26 constitutes a particularly simple construction and little

expensive, while allowing safe operation and easy cleaning.

In addition, their nested arrangement allows them to occupy a short length of the cartridge 15. The two networks have identical flow characteristics, which makes it easy to obtain at the outlet orifices 30 flow rates which are equal for both. colors. Thanks to the angular offset between the inlet ports 23 and 24, each array of grooves 27 has a symmetrical shape and the auxiliary extruders can

be conveniently connected to the head 10.

The distribution sleeve 16 has a generally cylindrical shape and its rear face has, in this example, a conical cavity placed opposite the conical tip 18a of the punch. On its peripheral surface are provided eight distribution channels 31 which are identical and distributed symmetrically around the socket. The front ends of the channels 31 are located opposite the outlet orifices 30b, 30c, while their outlets are flared and contiguous along the rear edge of the socket, so that the two flows of colored materials 23 and 24 form a vein. continuous 32 (FIG. 1) injected from the outside into the passage of the base material 22 to form around this material a second continuous layer. With this construction, if the respective flow rates of the colored materials 23 and 24 are equal, the section shown in FIG. 5, in which the colored bands 3 and 4 are all the same width. If, for example, the flow of yellow material 23 is increased, the yellow bands 3 will be wider than the green bands 4. Another possibility of obtaining bands

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more or less wide is given by the use of a socket with different flares. If a socket similar to socket 16 is used, but with distribution channels whose outlets are not contiguous, the section illustrated in FIG. 7, in which the yellow 3 and green 4 bands are not contiguous, but separated by bands 33 formed by the base material 2 appearing on the surface. It is therefore sufficient to use a colored base material, with the same extrusion head 10, to produce a profiled element whose surface comprises strips of

three different colors.

The invention is not limited to the exemplary embodiment described above, but may be the subject of multiple variants as regards both the construction and the various uses for the manufacture of all kinds of elements. It is understood that it is possible to extrude more than two colored materials in addition to the base material, thanks to suitable distribution conduits. Helical bands or a helically shaped member can also be produced by mounting the dispensing cartridge in a rotatable manner in the body of the extrusion head, for example by means of an intermediate sleeve of the type described in the publication. WO 86/07562. The rotation can be continuous to form helical bands with constant pitch, or be oscillating to form bands with alternating pitch, as it is known to proceed for the extrusion of grooved rods to carry optical fibers. A particular application of an extrusion head according to the invention is the manufacture of tubes or profiles in

synthetic material having colored longitudinal stripes.

Another interesting application is the extrusion of protective sheaths around optical fibers or optical cables. A sheath can thus be produced in a single operation, the inner layer of which has optimal optical properties, while the outer layer has marks.

colored offering a wide range of codes.

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Claims (13)

Claims 1. Head of extrusion of profiled elements in synthetic material having colored bands, comprising: - an outlet die defining the profile of the element, - a punch arranged coaxially upstream of this die, - at least two orifices d 'admission of respective plastics supplied under pressure by separate sources, - and distribution means arranged between the inlet orifices and the punch to distribute the plastics around the periphery of the punch, characterized in that - the orifices of admission comprise at least one inlet orifice (12) of a base material and at least two inlet orifices (1.3, 14) of colored materials, - the means for distributing the colored materials comprise a distribution member (15 ) having a tubular shape, an outer surface provided with at least one respective cavity (25b, 25c) for the entry of each colored synthetic material (23, 24), an inner surface provided with a series of orifi these outlet (30b, 30c) distributed around the periphery of this surface, and distribution conduits (26, 27) connecting the inlet cavities to the outlet ports so that adjacent outlet ports are connected to different inlet cavities. 2. Extrusion head according to claim 1, characterized in that said distribution conduits comprise bores (26b, 26c) passing through the distribution member and forming said outlet orifices, and grooves (27b, 27c) formed in the outer surface of this member for connecting the inlet cavities (25b, 25c) to the respective bores, and in that said grooves have bifurcations (28b, 28c). 3. An extrusion head according to claim 2, characterized in that the lengths of the grooves between a bifurcation (28b, 28c) and each of the bores (26b, 26c) connected to this bifurcation are equal. 4. Extrusion head according to claim 1, characterized in that the inner surface of the dispensing member is a surface of revolution, 9 2 62613981 (29) and the respective outlet ports (30b, 30c) for one of the Colored materials are distributed substantially in a radial plane. 5. An extrusion head according to claim 4, characterized in that all the outlet openings (30b, 30c) of the colored materials are distributed substantially in the same radial plane. 6. Extrusion head according to one of claims 2 and 5, characterized in that that the outer surface of the dispensing member is a surface of revolution, in that the inlet cavities (25b, 25c) of materials of two different colors are offset both axially and angularly with respect to one another 'other, and in that the inlet orifices of the respective bores (26b, 26c) corresponding to each of these colors are grouped in two respective radial planes located between the two inlet cavities, these two radial planes being distinct or merged. 7. An extrusion head according to claim 4, characterized in that it comprises a distribution sleeve (16) housed in the distribution member (15) and provided, on its outer surface, with a respective channel (31). ) facing each of said outlet openings, and in that the outlets of these distribution channels are distributed around the periphery of an annular passage of the base material around the punch (18). 8. An extrusion head according to claim 7, characterized in that said outlets of the distribution channels (31) are contiguous, so as to form a continuous layer of colored materials around the base material in the punch area. 9. An extrusion head according to claim 7 or 8, characterized in that the outlet die (17) is incorporated in the distribution sleeve. 10. An extrusion head according to claim 1, characterized in that said distribution member (15) is rotatable about its longitudinal axis. 11. A method of manufacturing a profiled element having at least two colored surface bands, by extrusion of synthetic materials, characterized in that one extrudes simultaneously and in a single extrusion head, an inner layer (2) made of a synthetic base material, and an outer layer completely covering the layer interior and formed by juxtaposed colored bands (3, 4). 12. The method of claim 11, characterized in that said profiled element is a wire or an electrical cable, or a fiber or an optical cable, comprising an extruded sheath. 13. The method of claim 11, characterized in that said element profile is a tubular or solid profile.