WO1979001125A1

WO1979001125A1 - Openable,tubular sheath with two or more channels for insertion of longitudinal elements,and a method of producing such a sheath

Info

Publication number: WO1979001125A1
Application number: PCT/DK1979/000015
Authority: WO
Inventors: A Andersen
Original assignee: Nordiske Kabel Traad; A Andersen
Priority date: 1978-05-26
Filing date: 1979-05-17
Publication date: 1979-12-27
Also published as: DK233778A; BE876587A; NO791656L; FI791676A; NL7904132A; IT7968127A0

Abstract

An openable, tubular sheath (1) with two or more channels separated by one or more longitudinal, preferably radially arranged partitions (2) and designed to receive longitudinal elements, such as optical fibres, electric cables and/or tubes, wherein the outer wall of one or more channels is provided, along its entire length, with readily openable, rectilinear or helical, longitudinal slots (3) to form adjoining wall portions (4) which are preferably substantially symmetrical about the slot (3) and will, upon opening of the slot, return to their original positions by themselves. The sheath may be produced by extruding a polymeric material in the desired multi-channel profile and cutting the outer wall in one or more of the channels to form one or more self-closing slots, preferably immediately upon the extrusion, optionnally inserting at the same time the longitudinal elements into one or more of channels before the slots close.

Description

Openable, tubular sheath with two or more channels for insertion of longitudinal elements, and a method of producing such a sheath

The present invention relates to a tubular sheath with two or more channels separated by one or more partitions and designed to receive longitudinal elements such as fibre- optical cables or metal cables, for advancing them to- gether.

It is known to extrude profiles, such as square strip profiles with channels into which cables and/or tubes may be inserted and which are closed by strips.

Another type of a strip profile is described in the U.S. Patent 2,066,242 where a square profile having a base face for attachment to a wall is divided into two channels formed by a centrally located, two-branched rib and two side walls whose upper edges are extended in parallel with the base face and abut on the outer sides of the rib to form a top face onto which there is secured a tape by an adhesive.

It is also known in the art to extrude circular profiles with longitudinal cavities formed in various ways, cables or conduits being inserted into said cavities during the process of extrusion. In particular, said profiles may be extruded with longitudinal strands in the wall of the profile, the strands protruding into each cavity, access to the cavities being obtained by tearing out the strands, cf. DE-OS 2523738. Additionally, it is known to extrude an essentially Hshaped profile and place fibre-optical ribbon cables on one side and copper cables oh the other side of the central section and then wind a plurality of tapes around the H-profile and subsequently apply a plurality of additional layers of metal or plastics in the usual manner in the cable technique. The U.S. Patent 2,440,668 discloses a cable construction preferably constructed by forming a rubber strip with circular extensions at the ends which form a substantially H-shaped profile, vulcanizing electric conductors onto either end of the strip, folding the end extensions in pairs in engaging relationship and welding them to form a waterproof conduit through which cooling liquid may be passed.

The U.S. Patent 2,435,956 discloses a streamlined cable for towing aircraft or watercraft, a strength element and one or more electrical conductors being surrounded by a solid, streamlined covering with longitudinal bores. The covering is either divided into two sections or is cut along most of the symmetry plane. The covering is closed by cementing and/or wire staples.

A similar towing cable is described in the German Offen-legungsschrift 2,201,195 where a substantially flat, solid sheath having longitudinal recesses is folded around a strength element and one or more conductors to form a streamlined towing cable.

It applies to the constructions mentioned above that they are either adapted to very specific purposes, such as the above towing cables, or involve a large number of separate working steps which are laborious and/or expensive.

It applies in particular to the constructions described in USP 2,440,668 and DE-OS 25 23728 and to other similar constructions that the necessity of passing the material inserted in the cavities through the extruder makes the process more difficult and involves risks of damage owing to the mechanical and thermal strains in the extruder. As regards the above H-profile for fibre-optical cables, the windings for closing the cavities invariably increase the costs of production and render it more difficult, and they also hinder access to the cable for repairs and/or branching off.

The object of the present invention is to provide a tubular sheath with two or more channels which are much simpler to produce than the constructions described above, are easier to open when the longitudinal elements are to be inserted into the channels and also later on, and which moreover are self-closing without the use of special closing devices, such as cover plates, adhesive tape and wire staples or by winding tape or the like around them.

This is achieved by the sheath of the invention which is characterized in that the outer wall of one or more channels is provided, along its entire length with readily openable, longitudinal slots to form adjoining wall portions which, upon opening of the slot will assume their original positions by themselves. The sheath of the invention may easily be produced by extrusion and be cut to form one or more slots.

The sheath is thus distinguished from the prior art by longitudinal slots in the outer wall of one or more of the channels, which cause the formed wall portions, to assume, after their being cut or upon a subsequent opening, the shape they had before they were cut.

The slot may be cut so that its edges are smooth or serrated. Serrated edges provide a torsionally stable sheath because longitudinal desplacemehts are obviated. Moreover the serrated edges provide a good securing when individual elements are to be branched off, as will be illustrated below.

As comprised in the state of the art when evaluating the novelty of the invention should also be regarded a method of producing unitary elements for telecommunication cables and the unitary elements produced thereby, disclosed in the Danish Patent Application 1948/78 filed on May 3, 1978 claiming priority from the Italian Patent Application 23147A/77 filed on May 4, 1977, and the files of which became available to public inspection on November 5, 1978. Applications with the same priority have been filed i.a. in Sweden under No. 78,05036 and in the Federal Republic of Germany (DE-OS 2819484 laid open to public inspection on November 9, 1978).

The method disclosed in said application for producing a so-called unitary element, which comprises one or more optical fibres located loosely in a tube with a greater internal diameter than the outside diameter of the fibres, is characterized by comprising the following steps:

"feeding, with a uniform advancement of the tube previously extruded and stabilized,

applying a first traction to a zone of .the tube for putting the part of the tube upstream under tension and for setting a straight path downstream of the tube,

cutting the tube longitudinally, and without a solution of continuity, to a depth that is equal to one time the thickness of the tube itself, on the cutting plane,

a first widening apart of the edges formed immediately downstream of the cutting operation,

inserting into the tube through the said widening, at least said fibre or fibres; said fibre (fibres) also advancing in a uniform manner,

uniting the cut edges, by exploiting the elasticity of the tube material, at least downstream of the inserting of the fibre (or fibres), but upstream of the said zone of application of the said first traction,

collecting the said tube with fibre or fibres inserted inside (unitary element)."

Thus, in the method of application 1948/78 there is employed a previously extruded tube which has been stabilized, which is defined as a thermal and mechanical treatment, preferably a stretching process. The tube is advanced from a feeder, illustrated by way of a bobbin, and cut to a depth just equal to the thickness of the material. The fibres, too, are advanced from a feeder and are inserted into the tube as explained above.

A unitary element according to application 1948/78 comprises a tube loosely enclosing one or more fibres produced by the above method, and is characterized in that the tube comprises a longitudinal cut equal to only one time the tube thickness.

The explicit object of the above application is to reduce the risk of the optical fibres locally adhering to the inner side of the tubes extruded around the fibre, in particular tubes with outside diameters of a few mm. This problem is said to become ever more important because within the field of telecommunication there is an increasing wish for miniature tubes, the inside diameters of which, however, are still greater than the diameter of the enclosed fibre or fibres.

Conclusively, it may be said that application 1948/78 provides an improved method for producing unitary elements, preferably having a small diameter and consisting of a tube into which one or more, optical fibres are inserted.

The novelty of the present invention over application 1948/78 may be ascertained with respect to construction as well as to use. Application 1948/78 discloses a tube into which one ormore optical fibres are inserted. Said application failsto describe other elements which might be inserted, and the advantages of the construction are explained in relation to fibres.

The tube is not shown or explained as being divided by means of one or more partitions, and there is no suggest of this possibility. On the contrary, the purpose is miniature elements with a very small diameter where partitions would make the production difficult both in terms of extrusion and cutting.

As opposed to this the present invention relates to a tubular sheath with two or more channels separated by on or more longitudinal partitions. Longitudinal elements, such as optical fibres, may be inserted into the channel but also for example conventional leads and water pipes, as will be elaborated below.

Besides providing these concrete differences the sheath of the invention overcomes some drawbacks from which the construction of application 1948/78 suffer.

When spooling a tube of application 1948/78 the tube tends, even at a rather small diameter, to become flattened, whereby the cutting opens and the fibre may easily get jammed. The problem may be somewhat diminished by a helical, cut, but it cannot be eliminated. On the other hand, the helical cutting causes the tube to open at insignificant tensile forces. Unless the tube has a rather large wall thickness, which is at variance with the explanation in the application and increases considerably the costs of producing the tube, the cut edges will tend to overlap each other when the tube is twisted or flexed.

The partitions used in the sheath of the invention bring about a substantial shape stability so that the sheath will not be pressed flat when spooled. This is particularly so if the partitions, as explained below, are twisted about the longitudinal axis of the sheath.

Moreover, the partitions entail that the closing pressure exerted by the tube walls on each side of the slot, will be increased over the closing pressure of a slotted tube of application 1948/78 with the same diameter and wall thickness. In this manner there is achieved an improved self-closing effect which combined with the improved shape stability in respect of spooling and torsional forces, reduces the risk of the inserted, longitudinal elements getting jammed in the slot.

The subject sheath has the additional advantage that any conceivable, longitudinal elements may be inserted, including such as do not stand or do not very well stand the temperature at which the tubular sheath is extruded, the elements being inserted only after the extrusion of the sheath itself. This eliminates, like application 1948/78, also the risk of the elements adhering to the inner sides of the channels. However, the sheath may also be extruded similtaneously with the elements being inserted into one or more of the channels, the fibres being inserted upon the cutting of a channel.

The outer walls of the sheath and the partitions defining the channels have preferably a thickness which is comparatively small compared to the cross sectional dimension of the sheath. This means saving in material and a large number of longitudinal elements to be arranged and/or buffer layers to protect them. The latter circumstance is particularly important where the longitudinal elements are wholly or partly constituted of optical fibres, which are very fragile as is well-known.

It is preferred to cut the slot so that the wall portions formed thereby are substantially symmetrical around the slot.

This provides the greatest amount of certainty of the wall portions returning to their original positions after the cutting or later openings, and also the easiest access to the channel.

Preferably, the cross section of the sheath is substantially circular; however, it may also be for example oval or semi-circular if circumstances of installation or the shape of the longitudinal elements make it desirable.

The partitions which together with the outer wall of the sheath form the channels, are advantageously arranged radially relative to the cross section of the sheath. This provides the most expedient internal bracing of the sheath and the most uniform forces on the wall portions formed by the cutting; this in turn enhances the certainty of their assuming their original positions after cutting and/or later opening.

The partitions may be given a substantially rectilinear or twisted course relative to the axis of the sheath. The rectilinear course is the simplest to produce and provides the easiest insertion of the longitudinal elements as well, but diminishes flexibility in the plane of the partitions.

By imparting a twisted course to the partitions, which can be done by twisting the sheath about its axis when advancing it during the process of extrusion, there is obtained a sheath which has approximately the same flexibility in all directions and a very great stability of shape.

The invention relates also to a method of producing the subject sheaths; the method of the invention is characterized by extruding a polymeric material in the desired multi-channel profile and cutting the outer wall in one or more of the channels to form one or more self-closing slots, by means of a tool whose lower edge abuts on and is guided by the partition.

Any extrudable, polymeric material may in principle be used for producing the sheath, such as polyethylene, polypropylene, ethylene-propylene copolymers or polyvinyl chloride. For special uses also polymers may be used, meeting for example special requirements on stability or strength. The invention is not restricted in this respect, and the choice of materials for a given use is within the skills of the artisan.

A preferred material is ID-polyethylene (PEL) because it has a good workability, its price is reasonable and its properties are satisfactory for most purposes.

As explained above the slot is preferably cut so that the formed wall portions are substantially symmetrical about the slot.

It is preferred to perform the cutting immediately upon the extrusion. If desired, the longitudinal elements may simultaneously be inserted in a manner known per se by means of a tool capable of inserting the elements before the slot closes again.

However, the sheath may also be extruded and spooled uncut in particular where special considerations of production make it expedient. Then the sheath may for example be transported to the location where one or more ox τne elements are produced, for example optical fibres, and where the sheath is cut and the elements are inserted, if desired, at the same time.

Alternatively one or more of the channels may be cut upon the extrusion and the elements may be inserted simultaneous- ly, while one or more channels are left uncut. At a later stage in the process of production the uncut channel or channels may then be cut and the desired elements be inserted. As mentioned, the sheath may moreover be extruded at the same time as elements, which can stand the extrusion, are inserted into one or more of the channels, and then the last channel or channels may be cut and the desired elements may be inserted at the same time, if desired.

Precisely this flexibility in production and in the elements that may be inserted, constitutes a valuable feature of the present invention.

As examples of such elements may be mentioned optical fibres, for example in the form of ribbon cabls or as individual fibres, conventional electric cables or conduits of any type, pipes for the supply of water or other liquids, pressurized air pipes, etc. If desired, buffer or padding layers of any type may be inserted, such as powders, high viscosity liquids, cellular materials or their combinations. Hereby the sheath may be made waterproof in the longitudinal direction.

The flexibility of the use of the sheath is illustrated by that fact that there is no requirements for inserting . longitudinal elements along the entire length of the sheath, it being possible for example to branch off one or more of the elements at any point on the sheath.

As explained above, the sheath of the invention has a sufficient strength and impervioύsness for most uses. If, however, special requirements are made on imperviousness orstrength the sheath may be enclosed by additional coverings of plastics or metal in a manner known per se in the cable technique. Here, too, the skilled person will be able to select the most suitable materials and shapes for the use concerned.

The invention is illustrated in more detail in the drawing, in which

fig. 1 is a cross sectional view of a cut sheath according to the invention, with two channels and a rectilinear partition,

fig. 2 is a cross sectional view of a cut sheath according to the invention, with three channels and rectilinear partitions,

fig. 3 is a cross sectional view of a cut sheath according to the invention, with four channels and rectilinear partitions,

fig. 4 is a longitudinal view of the profile shown in fig. 11, tthhee sshheeaatthh bbeeiinngg flexed 90°, and individual elements being branched off,

fig. 5 shows a sheath with two channels where the partition is twisted and the slot extends helically,

figs. 6 and 7 show sheaths having three and four channels, respectively, where the partitions are twisted and the slots extend helically,

fig. 8 shows a longitudinal view of a two-channel sheath having a helical partition and serrated slot, respectively, and figs. 9 and 10 are two different cross sectional views A-A and B-B of the sheath shown in fig. 8.

In fig. 1 there is shown an example of an embodiment of a sheath according to the invention. The sheath 1 has two channels and a partition 2 and cuts 3. The profile may for example be extruded in PEL. One channel contains insulated Cu-conductors 11, and in the other there is inserted an optical or copper ribbon cable 12, openable by means of flaps 4, with a surrounding foamed buffer inserted to gether with the ribbon cable.

Another embodiment is shown in fig. 2 where the sheath 1 comprises three channels with an element 13 inserted into one channel, the other two channels being available for subsequent use.

Fig. 3 shows the use of a sheath with four channels for different elements, for example two pressurized air pipes 14, a water pipe 15, four conductors 16 for telecommunication and a cable 17 for heavy current, respectively.

Fig. 4 shows a two-channel sheath 1 with Cu-conductors 18 and 19, the conductors 19 being branched off through the slot for various connections, such as in casings for electrical wiring. The edges of the slots are advantageously serrated for securing the conductors branched off.

Figs. 5, 6 and 7 show analogously with figs. 1, 2 and 3 sheaths with helical partitions.

Fig. 8 shows a sheath 1 with a serrated slot 20, seen from the side, while figs. 9 and 10 are two sections through this sheath, taken along A-A and B-B.

Claims

CLAIMS:

1. An openable, tubular sheath (1) with two or more channels separated by one or more longitudinal partitions (2) and designed to receive longitudinal elements, char a c t e r i z e d in that the outer wall of one or more channels is provided, along its entire length, with readily openable, longitudinal slots (3) to form adjoining wall portions (4) which, upon opening of the slot, will assume their original positions by themselves.

2. A sheat according to claim 1, c h a r a c t e ri z e d in that the thickness of the outer wall and the partitions is small relative to the cross sectional dimension.

3. A sheath according to claim 1 or 2, c h a r a c t e ri z e d in that the wall portions (4) are substantially symmetrical about the slot (3).

4. A sheath according to claim 1, 2 or 3, c h a r a c t e r i z e d in that its cross section is substantially circular.

5. A sheath according to claim 4, c h a r a c t e ri z e d in that the partitions (2) are arranged radially.

6. A sheath according to claim 1, 2, 3, 4 or 5, c hara c t e r i z e d in that the slots (3) and the partitions (2) extend substantially rectilinearly relative to the axis of the sheath.

7. A sheath according to claim 1, 2, 3, 4 or 5, c h a r a c t e r i z e d in that the course of the slots (3) and the partitions (2) is helical and twisted, respectively, relative to the axis of the sheath.

8. A sheath according, to any of the preceding claims, cha r a c t e ri z e d in that the edges of the slots (3) are serrated.

9. A method of producing a sheath according to claim i, cha r a c t e ri z e d by extruding a polymeric material in the desired multi-channel profile and cutting the outer wall in one or more of the channels to form one or more self-closing slots, by means of a tool whose lower edge abuts on and is guided by the partition.

10. A method according to claim 9, c h a r a c t e i z e d by performing the cutting immediately upon the extrusion.

11. A method according to claim 9 or 10, c h a r a c t e r i z e d by performing the cutting so that the wall portions formed are substantially symmetrical about the slot.