GB1563712A

GB1563712A - Wire cables

Info

Publication number: GB1563712A
Application number: GB3213976A
Authority: GB
Original assignee: Bowden Controls Ltd
Current assignee: Bowden Controls Ltd
Priority date: 1977-11-02
Filing date: 1977-11-02
Publication date: 1980-03-26

Description

(54) WIRE CABLES (71) We, BOWDEN CONTROLS LI MITED, a British Company of Llanelli, Carmarthernshire, South Wales do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to flexible covered wire cables of the kind comprising a plurality of wires together covered by a continuous protective sheath of synthetic polymeric material which is formed in situ on the wire cable by extrusion.

In such covered cables the wire cable proper may for example be composed solely of a plurality of wires or groups of wires which are helically interwound, or it may be composed of such interwound wires or groups of wires in combination with a core, which latter may e.g. consist of a smaller diameter wire cable or a single wire.

Another example of a wire cable construction is one comprising a plurality of straight or helically interwound wires and a surrounding helically wound binder wire.

Wire cables are useful inter alia for the transmission of forces for mechanical remote control purposes. For example, such cables are often used in combination with cable-guiding pulleys or sheaves or in combination with an outer guiding conduit to provide a transmission linkage between actuating and actuated parts. In those and other uses the cables are often subjected to repetitive flexure which may give rise to fatigue failure. The incidence of fatigue failure can be avoided or retarded by the application of lubricant for reducing rubbing friction between constituent wires of the cable.

It is a common practice to extrude a sheath of synthetic polymeric material onto wire cables for protective purposes. Depending on its composition, such a sheath can serve for example to protect the cable wires from dirt or corrosion, to provide electrical insulation and/or to reduce friction or otherwise improve contact conditions between the cable and a guiding conduit, pulleys or other components when the cable is installed for use.

The invention is concerned with a method of producing a flexible covered wire cable of the kind referred to, in lubricated condition, and basically lies in the step of applying lubricant to the wire cable by injection after formation of the protective sheath. The method according to the invention is defined in claim 1.

As compared with the conventional method wherein the sheath is extruded onto the wire cable after application of lubricant to the wire cable, the new method affords the advantage that it is easier to manufacture a lubricated covered cable containing a predetermined amount and/or distribution of any required lubricant. If, contrary to the invention, a wire cable is charged with lubricant before the protective sheath is extruded onto such cable, the lubricated condition of the cable is liable adversely to affect, or to be adversely affected by, the formation of the sheath. The extrusion of the sheath has normally to be carried out at elevated temperature. The loss of the required lubricated condition during extrusion covering of some wire cables made prior to the present invention has been found to be the unsuspected cause of later premature fatigue failure of the cables.

It is permissible, within the scope of the invention, for a small amount of lubricant to be present when the wire cable is covered.

For example, the cable wires may have been lubricated prior to or during formation of the cable and the wires may still bear superficial coatings of such lubricant.

However, even if lubricant is present in the wire cable during the covering thereof, lubricant is injected afterwards. Preferably the whole or at least the greater part of the amount of lubricant required in the finished product is injected after formation of the covering.

The invention can be applied with advantage in the production of lubricated covered wire cables for various purposes. Particular importance is attached to the use of the method in the production of lubricated covered wire cables for use as the inner motion-transmitting members of flexible remote control mechanisms known as Bowden (Trade Mark) mechanisms.

Suitable polymeric materials for use in forming the extruded sheath are nylon, polyacetals, polyolefins and high density polyethylene. These materials are given only as examples. Various other materials known in the cable coating art can be used.

The lubricant can be selected solely or mainly with regard to the nature and intended conditions of use of the covered cable. Suitable lubricants for various conditions include light oils, heavy oils, and greases. It is preferable to employ a grease e.g. a grease based on petroleum jelly.

Preferably a grease or other lubricant is employed having such viscosity that it will remain in place in the between-wire spaces of the cable during the intended normal working life of the cable. On the other hand it is preferable for the viscosity of the lubricant when injected to be such that it can be forced to penetrate along the between-wire spaces of the wire cable over a distance of at least a few inches. preferably at least 6", from an injection point. It is preferable to inject the lubricant under a pressure of an order of magnitude attainable by conventional manual grease guns. The injection preferably takes place while the lubricant is at ordinary ambient temperature.

The injected lubricant may penetrate over the whole length of the wire cable within the covering. However this is not an essential feature of the invention. Some mechanical control cables are installed and used so that the cable wires are worked wholly or mainly at one or more zones along the length of the cable. This may be due for example to such zone(s) passing over a pulley or pulleys and/or to such zone(s) being subject to marked bending or flexure when the cable is installed. The invention accordingly includes methods wherein the injected lubricant penetrates into the covered cable along one or more portions but not along the whole of its length.

In certain methods according to the invention the injection of lubricant takes place via at least one end of the extruded sheath.

Depending on the length of the covered cable, the viscosity of the lubricant, the crosss-sectional dimensions of the betweenwire channels in the cable and the injection pressure, lubricant injected via one end of the covering will penetrate along the entire length or along only a part of the length of the covered cable. Covered cables are often supplied or installed for use in circumstances such that lubrication of one end portion or of each opposed end portions of the wire cable suffices to ensure that the cable will have a satisfactory performance life. This is sometimes true, for example, of covered wire cables forming the inner member of Bowden mechanisms supplied for particular control functions, particularly clutch, hand-brake and other remote control mechanisms employed in the automobile industry. Preferably injection takes place via each end of the cable covering, the injection at the opposed ends being carried out simultaneously or in successive operations.

The endwise injection of lubricant may be accomplished by injecting lubricant through an injection nipple which is temporarily fluid-tightly clamped onto an end portion of the protective sheath. As an example, use can be made of an injection nipple with a screw-threaded counter-bore engaged by a screw-threaded tubular plug which becomes clamped onto the sheath when the nipple and plug are screwed together.

As an alternative to endwise injection of lubricant, injection can take place at one or more points within the length of the covered cable via one or more openings formed for that purpose in the cable covering. By this method (hereinafter called "between-end injection") lubricant can be provided along any required portion or portions within the length of the covered cable or along the whole of that length. Between-end injection may be employed for example for lubricating covered cable which has subsequently to be cut into shorter lengths e.g. to suit individual mechanisms. For that purpose there may be one or more injectors disposed along a path along which the covered cable is conveyed to bring successive lengths of the cable into position for receiving injected lubricant.

To permit between-end injection one or more openings must be present in the cable covering. Such an opening or openings may be formed, e.g., by slitting the covering at one or more positions along its length and flexing the cable to cause such slit(s) to open sufficiently to permit passage of injected lubricant therethrough. On subsequent straightening of the cable the opening(s) close(s) up. The cable covering can if desired be sealed up again, e.g. by fusionjointing the material of the covering across the slit or slits or by using an appropriate adhesive or sealant. However it will normal ly be unnecessary for the slit(s) to be sealed up.

The invention can be applied in the manufacture of cables of a wide range of different thicknesses. The invention is however considered to afford most advantage when applied to cables of diameters from 1 to 10 mm. and particularly when applied to cables which are from 1 to 6 mm.

in diameter. In optimum embodiments the wire cable does not exceed 5 mm. in diameter.

The invention includes a lubricated covered wire cable produced by a method according to the invention as hereinbefore defined.

Preferably the lubricant is present in the between-wire spaces of the cable along the whole of the length of the wire cable or along at least one portion thereof which is at least 6" in length.

Before a covered wire cable is used it is usually necessary for the wire cable to be bared over end portions thereof. The end lengths of cable covering to be removed in this operation must be taken into account in deciding the minimum distances over which end-injection of lubricant must take place if such injection is carried out before end portions of the wire cable are bared by removing surrounding portions of the covering.

Certain methods according to the invention will be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure I is a cross-section of a covered wire cable; Figure 2 shows an assembly of parts for use in carrying our lubrication by endinjection; Figure 3 is a part cross-sectional elevation of apparatus used in between-end injection.

Figure 1 is a cross-section of a typical covered wire cable which comprises a multiplicity of helically interwound metal wires 1 and a tubular casing or covering 2 formed of synthetic polymeric material which has been hot-extruded onto the wire cable.

In carrying out one method according to the invention, the wire cable is lubricated after formation of the covering 2 thereon by injecting the lubricant via one or each end of the covering 2 into between-wire spaces 3 of the wire cable, using an injection device illustrated in Figure 2. This device comprises an injection nipple 4 having a counterbore 5 with a tapered screw-threaded entry portion into which a correspondingly tapered threaded spigot 6 of a tubular plug 7 is screwed to cause the plug to be clamped fluid-tightly onto the cable covering. The bottom portion of the counterbore 5 in the nipple is formed to substantially the same diameter as the cable and receives an end portion of the covered cable. The nipple and plug may be made of metal. The spigot 6 may be peripherally continuous and be deformed by the screw action into sealing engagement with the cable casing 2. It is preferable however for the spigot to be longitudinally slitted or slotted to provide fingers which can be elastically displaced against the casing 2. A plug of that form can be repeatedly used without difficulty.

A selected lubricant is forced under pressure through the nipple so that the lubricant penetrates into and along the between-wire spaces 3 in the wire cable. In one method according to the invention a covered wire cable of the kind represented in Figure 1 having a wire cable diameter of 5 mm. and a length of 1 metre, was lubricated as described with reference to Figure 2, using as lubricant a grease marketed under the Trade Mark "Walkers 952", under ordinary manual grease gun pressure. The grease was injected at each end of the cable and along the spaces 3 up to a distance of 6" from each end.

An alternative method according to the invention makes use of between-end injection performed as illustrated in Figure 3. A die 8 is formed in two components 9 and 10 which co-operate to define a curved cablereceiving passage shown occupied by a portion of a covered cable II. The die can be opened by linearly displacing the lower die component 10 downwardly, away from the upper component 9. The broken lines show the position of the lower die component 10 when the die is open. This lower component has guide rods 12 which extend through guideways in the upper component.

The upper die component is fitted with an injector 13 which is screwed into such component at a central position.

Prior to inserting the covered cable into the die, or at least prior to closure of the die, an incision is made in the cable covering.

Due to the flexure of the covered cable this incision opens and the tip of the injector enters the opening thus formed. The incision can be made by a tool inserted through the injector aperture in the die component 9 before the injector is screwed into position.

As a further alternative the injector could be formed so that it makes its own injection opening in the cable covering as the die 8 is closed or during a subsequent screwing movement of the injector relative to the upper die component ied out 9.

Injection can be carried out as represented in Figure 3 at any required number of positions along the cable and for injecting lubricant along the whole of the length of the wire cable or along one or more portions of such length.

WHAT WE CLAIM IS: 1. A method of producing a flexible

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ly be unnecessary for the slit(s) to be sealed up. The invention can be applied in the manufacture of cables of a wide range of different thicknesses. The invention is however considered to afford most advantage when applied to cables of diameters from 1 to 10 mm. and particularly when applied to cables which are from 1 to 6 mm. in diameter. In optimum embodiments the wire cable does not exceed 5 mm. in diameter. The invention includes a lubricated covered wire cable produced by a method according to the invention as hereinbefore defined. Preferably the lubricant is present in the between-wire spaces of the cable along the whole of the length of the wire cable or along at least one portion thereof which is at least 6" in length. Before a covered wire cable is used it is usually necessary for the wire cable to be bared over end portions thereof. The end lengths of cable covering to be removed in this operation must be taken into account in deciding the minimum distances over which end-injection of lubricant must take place if such injection is carried out before end portions of the wire cable are bared by removing surrounding portions of the covering. Certain methods according to the invention will be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure I is a cross-section of a covered wire cable; Figure 2 shows an assembly of parts for use in carrying our lubrication by endinjection; Figure 3 is a part cross-sectional elevation of apparatus used in between-end injection. Figure 1 is a cross-section of a typical covered wire cable which comprises a multiplicity of helically interwound metal wires 1 and a tubular casing or covering 2 formed of synthetic polymeric material which has been hot-extruded onto the wire cable. In carrying out one method according to the invention, the wire cable is lubricated after formation of the covering 2 thereon by injecting the lubricant via one or each end of the covering 2 into between-wire spaces 3 of the wire cable, using an injection device illustrated in Figure 2. This device comprises an injection nipple 4 having a counterbore 5 with a tapered screw-threaded entry portion into which a correspondingly tapered threaded spigot 6 of a tubular plug 7 is screwed to cause the plug to be clamped fluid-tightly onto the cable covering. The bottom portion of the counterbore 5 in the nipple is formed to substantially the same diameter as the cable and receives an end portion of the covered cable. The nipple and plug may be made of metal. The spigot 6 may be peripherally continuous and be deformed by the screw action into sealing engagement with the cable casing 2. It is preferable however for the spigot to be longitudinally slitted or slotted to provide fingers which can be elastically displaced against the casing 2. A plug of that form can be repeatedly used without difficulty. A selected lubricant is forced under pressure through the nipple so that the lubricant penetrates into and along the between-wire spaces 3 in the wire cable. In one method according to the invention a covered wire cable of the kind represented in Figure 1 having a wire cable diameter of 5 mm. and a length of 1 metre, was lubricated as described with reference to Figure 2, using as lubricant a grease marketed under the Trade Mark "Walkers 952", under ordinary manual grease gun pressure. The grease was injected at each end of the cable and along the spaces 3 up to a distance of 6" from each end. An alternative method according to the invention makes use of between-end injection performed as illustrated in Figure 3. A die 8 is formed in two components 9 and 10 which co-operate to define a curved cablereceiving passage shown occupied by a portion of a covered cable II. The die can be opened by linearly displacing the lower die component 10 downwardly, away from the upper component 9. The broken lines show the position of the lower die component 10 when the die is open. This lower component has guide rods 12 which extend through guideways in the upper component. The upper die component is fitted with an injector 13 which is screwed into such component at a central position. Prior to inserting the covered cable into the die, or at least prior to closure of the die, an incision is made in the cable covering. Due to the flexure of the covered cable this incision opens and the tip of the injector enters the opening thus formed. The incision can be made by a tool inserted through the injector aperture in the die component 9 before the injector is screwed into position. As a further alternative the injector could be formed so that it makes its own injection opening in the cable covering as the die 8 is closed or during a subsequent screwing movement of the injector relative to the upper die component ied out 9. Injection can be carried out as represented in Figure 3 at any required number of positions along the cable and for injecting lubricant along the whole of the length of the wire cable or along one or more portions of such length. WHAT WE CLAIM IS:

1. A method of producing a flexible

covered wire cable in lubricated condition, such covered cable comprising a plurality of wires together covered by a continuous protective sheath of synthetic polymeric material which is formed in situ on the wire cable by extrusion, characterised in that lubricant is applied to the wire cable by injection after the formation of the sheath thereon.

2. A method according to claim 1, wherein said synthetic polymeric material is selected from nylon, polyacetals, polyolefins and high density polyethylene.

3. A method according to claim 1 or 2, wherein said lubricant is selected from light oils, heavy oils and greases.

4. A method according to claim 3, wherein said lubricant comprises a grease based on petroleum jelly.

5. A method according to any preceding claim, wherein the injected lubricant is caused to penetrate into the covered cable over a distance of at least 6 inches from an injection point.

6. A method according to claim 5, wherein the injected lubricant is caused to penetrate over the whole length of the wire cable.

7. A method according to any preceding claim, wherein injection of lubricant takes place via at least one end of the sheath.

8. A method according to claim 7, wherein injection of lubricant via one or each end of the sheath is effected through an injection nipple which is temporarily fluidtightly clamped onto the corresponding end portion of the protective sheath of the cable.

9. A method according to any preceding claim, wherein injection of lubricant takes place at one or more points within the length of the covered cable via one or more openings formed in the sheath.

10. A method according to claim 9, wherein the or at least one said opening is a slit.

11. A method according to claim 10, wherein the cable is flexed to open the or a said slit to allow injection of lubricant.

12. A method according to any of claims 9 to 11, wherein the or at least one said opening is sealed after such injection.

13. A method of producing a lubricated covered wire cable substantially as herein described with reference to Figure 2 and/or Figure 3 of the accompanying drawings.

14. A flexible lubricated covered wire cable produced by a method according to any preceding claim.

15. A lubricated covered wire according to claim 14, the diameter of the wire cable being from 1 to 10 mm.

16. A lubricated covered wire cable according to claim 15, the diameter of the wire cable being not more than 6 mm.

17. A lubricated covered wire cable according to any of claims 13 to 16 and forming the inner motion-transmitting member of a flexible remote control mechanism.