GB2156027A

GB2156027A - Flexible control cable and feed tube

Info

Publication number: GB2156027A
Application number: GB08425210A
Authority: GB
Inventors: Horst Buchholz
Original assignee: Stoessel & Co Kommanditge GmbH
Current assignee: Stoessel & Co Kommanditge GmbH
Priority date: 1984-03-14
Filing date: 1984-10-05
Publication date: 1985-10-02
Also published as: ES285223U; SE8402334D0; ES285223Y; SE8402334L; BE900287A; DE3409193A1; FR2561329A1; FR2561329B1; GB8425210D0

Abstract

In a flexible control cable, for example a brake or clutch cable for motor vehicles, with a protective guide sheath and a force transmission element arranged therein for longitudinal movement, for example a steel wire cable, the protective guide sheath consisting of a wire spiral which is lined on the inside with a plastic tube and shrouded on the outside with plastic, the problem of coping with relatively large compressive forces in the sheath arises. In order to achieve the resulting object of preventing individual windings of the wire spiral from breaking out in the curved state of the control cable, the wire spiral (13) is firmly wound in spaced windings on the plastic lining tube (12) and the plastic shroud (14), which may be produced by injection under pressure, fills the spaces (15) between the windings and surrounding the spiral so that the lining (12) and the shroud (14) cohere between the windings. The invention may also be applied to a flexible feed tube, for example a welding rod guide tube, without a force transmission element arranged therein for longitudinal movement. <IMAGE>

Description

SPECIFICATION Flexible control cable and feed tube In one aspect the invention relates to a flexible control cable, for example a brake cable or clutch cable for motor vehicles, with a protective guide sheath and a force transmission element, arranged therein for longitudinal movement, for example a steel wire cable, the protective guide sheath consisting of a wire spiral which is lined on the inside with a plastic tube and shrouded on the outside with plastic.

Flexible control cables, also quite generally called Bowden cables, though not always correctly, are used as control devices for many applications in land vehicles, aircraft and watercraft, in industrial process engineering, in domestic technology, and the like. The force transmission element in the form of a wire, cord or cable and also called the core, as a rule takes up only tensile forces, whilst the protective guide sheath for the core is exposed predominantly to compressive forces because, due to the pull on the force transmission element, it tends to move back from the curved shape into a straight line.

These compressive forces can increase to such an extent that one winding, or even several windings, of the wire spiral breaks out of its intended line, that is to say it bends as such in an uncontrolled manner and thus not only the desired line of the control cable is changed, but the force transmission element in the sheath is also jammed and likewise bent. Such an occurrence can cause serious traffic accidents or other disasters.

With respect to its protective guide sheath, a known flexible control cable is made in such a way that a spiral of round steel wire is wound with the windings in mutual contact, the spiral as a whole being coated on the outside with plastic, for example polyvinyl chloride, in order to form a seamless sheath.

The plastic thus penetrates into the approximately triangular wedges between the windings of the wire spiral, but not in between the individual windings as such, since these are in tight mutual contact as a result of the production process. A separately prefabricated plastic lining tube of finite length is then pushed into the interior of the wire spiral, where the latter appears as bare metal. This tube consists, for example, of polyethylene and forms the actual guide for the force transmission element or the core.

When the known control cable is laid in a curve, in the usual way, the windings of the wire spiral on the outside of the curve move away from one another to a greater or lesser extent, whereby the cohesion of the parts including the outer shroud is loosened. This has no disadvantageous effects until a defined tensile force on the force transmission element and hence also a compressive force on the protective guide sheath is exceeded. However, as soon as this happens, the sheath breaks out, and the disadvantage of the known construction is that the critical limit is comparatively low.

It is therefore an object of the invention to provide a flexible control cable, the protective guide sheath of which can, without breaking out, absorb substantially greater compressive forces, while at the same time the diameter of the sheath as compared with conventional devices of this type must not be increased but, rather, should be smaller if possible.

According to one aspect of the invention there is provided a flexible control having a protective guide sheath and a force transmission element arranged therein for longitudinal movement, the protective guide sheath consisting of a wire spiral which is lined on the inside with a tube and surrounded on the outside by a shroud, wherein the wire spiral is firmly wound in spaced windings on the lining tube, and the material of the shroud fills the spaces between the windings and surrounds the spiral, so that the lining tube and the shroud cohere between the windings.

In another aspect the invention relates to a flexible feed tube, for example a welding rod guide tube, in that the protective guide sheath of the above flexible control cable has been found useful for this purpose.

Thus, according to a second aspect of the invention there is provided a flexible feed tube comprising a wire spiral which is lined on the inside with a tube and surrounded on the outside by a shroud, wherein the wire spiral is firmly wound in spaced windings on the lining tube, and the material of the shroud fills the spaces between the windings and surrounds the spiral, so that the lining tube and the shroud cohere between the windings.

The invention has the advantage that a kind of supporting corset for the windings of the wire spiral of the protective guide sheath is provided, which corset prevents breaking-out of the sheath at the curve even under comparatively higher compressive forces. At the same time, a relatively smaller diameter of the sheath and its connectors can be obtained in this way, and this is in turn associated with a saving in weight.

Certain embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a view of an axial crosssection of a short piece of a flexible control cable, Figure 2 shows a sectional view corresponding to the area II in Fig. 1 on an enlarged scale, and in fact with a different wire spiral, and Figure 3 shows a sectional view similar to Fig. 2 with a wire spiral of round wire.

The control cable shown in Fig. 1 consists in principle of a protective guide sheath 10 and a steel wire cable 11, arranged for longitudinal movement therein, as a force transmission element. The further necessary and possible constituents of the control cable, for example sheath fitting, end pieces, coupling ring, nipple, spring, sleeve and the like are not shown. The force transmission element 11 can be in the form of a cable, cord or single wire.

The protective guide sheath 10 is built up from three components and, in production, it is assembled from a plastic tube 12, a wire spiral 13 and a plastic shroud 14 which are joined with one another to form an inseparable unit. The properties of the plastic pairings of the components 1 2 and 14 of the sheath 10 must be matched in the usual way.

The plastic tube 1 2 has a smooth cylindrical surface on the inside in order to allow easy running of the wire cable 11. The wire spiral 1 3 would around the outside of the plastic tube 12 consists, according to Fig. 1, of flattened steel wire; however, this can also be round wire (Fig. 3) or any transitional form between a flattened wire and a round wire, for example a wire of barrel-shaped cross-section.

A typical round wire diameter is of the order of size of 1.2 mm. A typical internal diameter of the plastic tube 12 to 4.2 mm.

The overall diameter of the control cable, measured across the outer plastic shroud 14, may be 9 mm, for example.

The wire spiral 1 3 is wound onto the plastic tube 1 2 in such a way that the individual windings of the spiral run at a mutual spacing 1 5. With a width of the flattened wire of, for example, 4 mm this spacing can be of the order of size of 1 mm. Since the wire spiral 1 3 is firmly wound onto the lining tube 12, which is carried out at a comparatively high speed in the production machine, the inside of the spiral is forced, due to the heat generated and the softening of the tube 12, into the outer surface thereof, so that the windings of the spiral 1 3 are recessed into the outer surface of the tube 1 2. The extent of the recess can vary and depends on the conditions during production.In the illustrative embodiment shown in Fig. 1, the depth of the recess is about one quarter of the wire thickness of the wire spiral 13. In this way, a spiral-like groove or track forms on the tube 12, which groove or track is here designated as the recess 1 6 and has continuous side edges 17, which mate with the relevant side edges of the wire spiral 1 3.

Subsequent to the production step of winding on the wire spiral 13, the outer plastic shroud 14 is applied under pressure by an injection-moulding process. The shroud material then flows into the space of the intervals 1 5 between the windings of the wire spiral 1 3 and is welded to the surface, present there, of the plastic of the lining tube 1 2. In the crosssection according to Fig. 1, this gives a toothlike internal outline of the shroud 14, leading to further clamping of the windings of the wire spiral 1 3. The wire spiral is immovably solidly and tightly surrounded on all sides by the materials of the components 1 2 and 14.

As a consequence, individual windings of the wire spiral cannot break out.

As can be seen from Fig. 2, the windings of the flattened steel wire of the wire spiral 1 3 have assumed, on winding, a cross-sectional shape in which the outer edges of the flattened wire are slightly bent upwards. This phenomenon can be influenced by production factors. In this way, continuous undercuts 18 are formed in the spacings 1 5 between the windings close to the outer surface of the lining tube 12, the plastic of the shroud 14 penetrating from above into these undercuts so that, in cross-section, a kind of anchorage 1 9 results, whereby the cohesion of the components can be promoted. This formation occurs more markedly if the wire spiral 1 3 is made from round wire, in accordance with Fig. 3, where the material of the shroud 14 forms an anchorage 1 9 in the spacings 1 5 between the windings. This enhances the effect of the supporting corset already mentioned and formed by the tube 1 2 in conjunction with the shroud 14.

A certain stiffening of the control cable with a completely embedded wire spiral, in comparison with conventional cables, has been found to be not important, but rather even advantageous.

Claims

1. A flexible control cable having a protective guide sheath and a force transmission element arranged therein for longitudinal movement, the protective guide sheath consisting of a wire spiral which is lined on the inside with a tube and surrounded on the outside by a shroud, wherein the wire spiral is firmly wound in spaced windings on the lining tube, and the material of the shroud fills the spaces between the windings and surrounds the spiral, so that the lining tube and the shroud cohere between the windings.

2. A flexible feed tube comprising a wire spiral which is lined on the inside with a tube and surrounded on the outside by a shroud, wherein the wire spiral is firmly wound in spaced windings on the lining tube, and the material of the shroud fills the spaces between the windings and surrounds the spiral, so that the lining tube and the shroud cohere between the windings.

3. A control cable as claimed in claim 1, or a feed tube as claimed in claim 2 wherein the wire spiral is made of flattened steel wire.

4. A control cable as claimed in claim 1 or a feed tube as claimed in claim 2 wherein the wire spiral is made of cylindrical steel wire.

5. A control cable as claimed in any of claims 1, 3 and 4 or a feed tube as claimed in any of claims 2, 3 and 4 wherein the shroud and the lining tube are made from a plastics material.

6. A control cable as claimed in any of claims 1 and 3 to 5 or a feed tube as claimed in any of claims 2 to 5 wherein the shroud is formed by an injection moulding process.

7. A control cable as claimed in any of claims 1 and 3 to 6 or a feed tube as claimed in any of claims 2 to 6 wherein the windings of the wire spiral are recessed into the lining tube.

8. A control cable as claimed in any of claims 1 and 3 to 7 or a feed tube as claimed in any of claims 2 to 7 wherein the recess has a depth of up to approximately one quarter of the thickness of the wire of the wire spiral.

9. A control cable as claimed in any of claims 1 and 3 to 8 or a feed tube as claimed in any of claims 2 to 8 wherein the shroud material extends underneath the windings on one or both sides thereof, to form an anchorage therebetween.

10. A control cable as claimed in any of claims 1 and 3 to 9 or a feed tube as claimed in any of claims 2 to 9 wherein the lining and the shroud are welded between the windings of the wire spiral.

11. A control cable as claimed in any of claims 1 and 3 to 10 wherein the control cable is a brake cable or a clutch cable for use in motor vehicles.

12. A feed tube as claimed in any of claims 2 to 11 wherein the feed tube is a welding rod guide tube.

1 3. A control cable substantially as herein described and with reference to any of the accompanying drawings.

1 4. A feed tube substantially as herein described and with reference to any of the accompanying drawings.