Flexible circular waveguide utilizing helical windings

Abstract

A circular helical wave guide in which, with a view more particularly to preventing a turn of wire from parting with the cylinder thus constituted, more particularly in the case of bending of the guide, the said wire has a quadrangular cross-section, preferably with oblique sides. That wire may also be cemented to the external insulating sheath of the guide and the turns of wire may also have their adjacent faces cemented together. The wire may previously be pasted with a layer of polymer on its face on the external side of the guide and it may also be bi-metallic.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns wave guides whose essential element consists of an insulated conductor wire wound in contiguous turns in a helical configuration.

2. Description of the Prior Art

In the usual technique, these wires have a circular cross-section, so that each turn is in contact with the adjacent turn only along a simple tangency line, that is, on a very small surface.

Under these conditions, when the guide is bent, the turns which are on the inside of the bend are subjected to forces tending to bring them closer to one another and it sometimes happens that one of the turns is driven out by the neighboring turns towards the inside of the guide.

SUMMARY OF THE INVENTION

The invention has for its object a wave guide which is not subject to the drawback that same turns of wire forming the wave guide are displaced towards the inside of the wave guide when it is bent.

That wave guide is characterised in that the wires constituting the guide have a guadrangular cross-section, preferably with oblique sides; due to that arrangement, when the guide is bent, the sides of adjacent turns have a tendency to jam in relation to one another, this preventing the turns from coming out of the cylinder which they constitute.

BRIEF DESCRIPTION OF THE DRAWING

The specific nature of the invention, as well as other objects, uses and advantages thereof, will clearly appear from the following description and from the accompanying drawing, in which:

FIG. 1 is a part transversal cutaway view of a wave guide of known type;

FIG. 2 is a part cutaway view of a wave guide according to the invention;

FIG. 3 is a cross-sectional view illustrating one variation of the invention;

FIG. 4 is cross-sectional view illustrating another variation of the invention; and

FIG. 5 is a cross-sectional view illustrating yet another variation of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawing, and more particularly to FIG. 1, a wave guide of known type consists of cylindrical wires such as 1 under an insulating sheath 2. It will be seen that, when the wave guide is bent, certain wires such as 3 may part from the cylinder on which the wires are wound.

As illustrated in FIG. 2, the present invention avoids the disadvantage of the prior art by forming the wave guide of a wire 4 having a quadrangular cross-section and oblique sides. Because of this geometry, when the wave guide is bent, the sides of adjacent turns have a tendency to jam in relation to one another.

To great advantage, these wires may be covered with a suitable thin varnish, or be coated with, before their winding, with a layer of plastic material, such as a polyamide or, for example, polyethylene dissolved in xylene, which makes them slightly rough and consequently increases the coefficient of friction between their sides.

According to a variant of the invention, the wires constituting the guide are cemented to the insulating sheath, formed by taping or by extrusion, arranged on the winding which they constitute. For that purpose, a layer of cement is applied by any method between the face of the conductor wires, on which the said insulating sheath should come and the internal face of the said insulating casing.

FIG. 3 shows that the wires 4 are cemented to the sheath 2 by a layer 5 which may be either a layer of cement applied to at the time of manufacturing the guide or a layer of polymer previously pasted on the face of the wire 4 on the external side of the guide.

According to another variant, applicable separately or in combination with the preceding variant, the faces of the wires, intended to come opposite the faces of the neighboring turns, are also coated with a layer of cement in order to ensure a mechanical connection between the various turns and to form, thus, a compact assembly, without the possibility for the turn to escape.

FIG. 4 shows wires 4 whose opposite faces are cemented together at 6.

By way of an example, the fixing cement for the insulating sheath may be based on usual polyethylene and the fixing cement between the various turns may be a grafted copolymer of acrylic acid or polyisocyanate or an epoxy resin.

According to another embodiment of that variant, the quadrangular metallic wire constituting the guide is pasted on its face on the outside of the guide, with a layer of copolymer, on which will be cemented or welded the insulating sheath applied to the guide or one or several insulating tapes laid with an appropriate pitch.

According to a variant of that latter embodiment, the quadrangular wire is a bi-metallic wire, whose face on the internal side of the guide is made of a metal having good conductivity and whose face on the external side is made of a metal such as aluminum or steel pasted with a layer of polymer such as polyethylene.

FIG. 5 shows the use of a bi-metallic wire, whose layer 7 on the internal side of the guide is made of a metal which is a good conductor, such as copper, and whose layer 8 on the external side is made of a metal such as aluminum or iron, subsequently cemented at 5 to the sheath 2.

In these different variants, the close connection between the pasted polymer layer and the insulating casing of the guide may be produced by any method, for example by a thermal action obtained either by the actual heat of the extrusion if the casing is roved, or by an outside heat source, for example by a generator of infra-red radiation.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

Claims

I claim:

1. A circular wave guide consisting of a helical winding in contiguous turns of a conductor wire having a quadrangular cross-section with oblique and parallel sides and being coated with an insulating sheathing material, whereby certain turns are prevented from parting with the cylinder which they constitute when the wave guide is bent.

2. A circular wave guide according to claim 1, wherein the conductor wire is a bi-metallic wire whose face on the internal side of the wave guide is made of copper, whereas its face on the external side is made of steel.

3. A circular wave guide according to claim 1, wherein the conductor wire is a bi-metallic wire whose face on the internal side of the wave guide is made of copper and its face on the external side is made of aluminum.

4. A circular wave guide according to claim 1, wherein a polymer coating is applied to at least the parallel, contiguous sides of said conductor wire.

5. A circular wave guide according to claim 4, wherein said polymer coating consists of polyethylene dissolved in xylene.

6. A circular wave guide according to claim 1, wherein the conductive wire is cemented to the sheathing material.

7. A circular wave guide according to claim 6, wherein the opposite faces of adjacent turns are cemented together.

8. A circular wave guide according to claim 6, wherein the conducting wire is pasted at least on its face on the external side of the wave guide with a layer of polymer which is fixed to the insulating sheating material of the wave guide.

9. A circular wave guide according to claim 8, wherein the connection between the pasted polymer layer and the insulating sheathing material of the wave guide is produced by the heat due to the roving when the insulating sheathing material is extruded.

10. A circular wave guide according to claim 8, wherein the connection between the pasted polymer layer and the insulating sheathing material is effected by infrared heat.