GB2122245A

GB2122245A - Cable anchorages

Info

Publication number: GB2122245A
Application number: GB08217335A
Authority: GB
Inventors: John Charles Crownshaw
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1982-06-15
Filing date: 1982-06-15
Publication date: 1984-01-11
Also published as: FR2547641A1; JPH0320963B2; GB2122245B; FR2547641B1; JPS5937823A

Abstract

Helically applied armour wires (1) of a cable or the like are anchored to a plate (3), for attachment to a jointing chamber or repeater, for example, by gripping between an inner member (6) and an outer member (7). The outer member is longitudinally split such that axial movement of a locking collar (8) during fastening thereof to plate (3) causes radial movement of the outer member (7) towards the inner member (6) for gripping the anchor wires (1) therebetween. Due to the matching tapered faces (10) of the outer member (7) and the locking collar (8) increased load on the armour wires increases the gripping force effective thereon, thus minimising cable elongation and, for example, possible damage to optical fibres contained therein, The faces of the inner and outer members are suitably machined to ensure gripping of the anchor wire therebetween. <IMAGE>

Description

SPECIFICATION Cable anchorage This invention relates to armoured cables, stranded wire ropes or the like, and in particular to the anchorage of one or more layers of such cables or ropes.

According to one aspect of the present invention there is provided a method of securing a substantially cylindrical layer of an elongate member to an anchor member therefor, including the steps of arranging an annular first gripping member under the cylindrical layer, arranging a second gripping member on the cylindrical layer and over the first gripping member, urging the second gripping member radially of the elongate member towards the first gripping member, whereby to grip the layer therebetween, by means which serve also to secure the first and second gripping member to the anchor member and which are such that upon subsequent increased axial load on the elongate member the gripping force applied to the layer by the first and second gripping member is increased.

According to another aspect of the present invention there is provided an anchorage arrangement, for the securement of a substantially cylindrical layer of an elongate member, comprising an anchor member wall portion, an annular first gripping member adapted to be arranged on the elongate member under the cylindrical layer with one end abutting the wall portion, a second gripping member adapted to be arranged on the cylindrical layer and over the first gripping member with one end abutting the wall portion, which second gripping member is movable radially with respect to the first gripping member, and a locking collar adapted to be fastened to the wall portion, whereby to secure the first and second gripping members, and adapted to cause the radial movement of the second gripping member upon axial movement towards the wall portion, and wherein in use the first and second gripping members and the locking collar co-operate to increase the gripping force applied to the cylindrical layer upon increased axial load applied to the elongate member.

Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows a section through an armour wire anchorage arrangement according to one embodiment of the present invention: Fig. 2 shows an end view, looking in the direction of arrow A of Fig. 1 and on a larger scale, of one version of inner gripping member which can be employed with the arrangement of Fig. 1; Fig. 3 shows an end view, looking in the direction of arrow A of Fig. 1 and on a larger scale, of one embodiment of external gripping member which can be employed with the arrangement of Fig. 1; and Fig. 4 schematically illustrates a part crosssection through a cable with two layers of armour wires and an inner gripping member.

The anchor arrangement illustrated in Fig. 1 is employed to anchor a cylindrical layer of an elongate element, which layer is comprised by a single layer of helically applied plough steel armour wires 1, laid up over a cable core 2, to an anchorage plate 3 which is to be secured to, for example, a repeater housing or jointing chamber (not shown). The cable core 2 may be jointed to a tail cable 4 with the use of a conventional tapered dielectric moulding, as at 5. The cable core 2 may, for example, be of the light weight coaxial submarine cable type or it may incorporate optical fibres. In the case of submarine optical fibre cables, in particular, it is necessary to have minimum elongation, of the fibres, to avoid breakages, particularly during cable laying and cable recovery when the tensile loads on the cable are greatest.It is thus desirable that increased cable loads at the armour anchorage points do not result in the armour wires slipping relative to the anchorage and thereby putting strain on the optical fibres. The present anchorages are thus designed to generate increased anchor wire gripping forces with increased cable loads.

The armour wires 2 are gripped between a first (internal) grip member 6 and a second (external) grip member 7 which are urged together by means of a locking collar 8. The locking collar 8 is located on studs 9 fastened to the anchorage plate 3 and has an internally tapered bore which mates directly with an externally tapered surface 10 presented by the external grip member 7. The external grip member 7 is longitudinally split and thus comprised of a plurality of separate segments; four identical segments 11 in the version shown in Fig. 3. The internal grip member 6 is cylindrical with the internal bore 12 shaped to conform with the underlying cable core with which it is to be used.In the example illustrated the bore 1 2 is cylindrical over the majority of the length and of a diameter comparable with the tail cable 4, the remaining portion being tapered to conform to the tapered shape at 5 between the sea cable core 2 and the tail cable 4.

The outer surface 1 3 of the internal grip member 6 is adapted to facilitate gripping of the anchor wires 1 between the internal and external grip members. As illustrated in Fig. 2, the outer surface 1 3 may be provided with machined outer part-helical grooves 14, one for each armour wire, which are such as to maintain the armour wires at their cable pitch diameter and lay angle. This ensures minimal bedding down of the wires during initial loading and that the wires are subjected to purely tensile loads up to the anchorage. Such an internal grip member is, however, expensive to produce due to the machining required. Alternatively, therefore, the outer cylindrical surface 1 3 may be provided with a screw thread, preferably one specifically adapted for gripping.

The internal bore of the external grip member 7, formed by the four segments 11 (Fig. 3), is a threaded parallel bore, the thread profile being such as to provide a bite into the armour wires 2.

The thread profile of external grip member 7 is preferably the reverse of that provided on cylindrical surface 13, where appropriate, for maximum gripping effect. In use, the external grip member 7 is forced radially towards the internal grip member 6 upon fastening of lock nut pairs 1 5 onto studs 9 due to the segmental nature of the grip member 7, the co-operating tapered surfaces of the locking collar 8 and the grip member 7, and the engagement of the inner and outer grip members with the plate 3. With the anchor wires thus gripped in the anchorage, any increase in cable load tending to pull the armour wire ends away from the anchorage plate 3 will, due to the co-operating tapered surfaces of the anchorage, generate corresponding higher gripping forces within the anchorage itself.

As shown in Fig. 3, each external grip member segment 11 is axially slotted at 1 8 from its external circumference to provide three sections which are effectively hinged together by the thus reduced radial thickness portions 1 9. The external grip member of Fig. 3 is designed for use with twenty armour wires and the slotted structure of each segment is such that no one section bridges more than two wires in order to ensure an even overall gripping effect on the wires.

In order to facilitate assembly of the anchorage the inner grip member is provided with two threaded bores 1 6 and the outer grip member segments 11 are each provided with a threaded bore 1 7. The armour wire anchorage shown in Fig. 1 is assembled and employed as follows. The cable with core 2 and armour wires 1 to be terminated or jointed is connected to the tail cable 4 in a conventional manner. The internal grip member 6 is secured to the anchorage plate 3 by means of screws (not shown) engaging threaded bores 1 6. With the armour wires 1 cut to the appropriate length the tail cable 4 is threaded through the bore 12 of internal grip member 6 and the armour wires 1 each laid into the appropriate part helical groove 14.The outer grip member sections 11 are secured to plate 3 by means of screws (not shown) engaging threaded bores 1 7 to hold the located armour wires in place. The locking collar 8, which if necessary is slipped over the cable end before threading the tail cable through the internal grip member 6, is located on studs 8 with the first nut of locking nut pairs 1 5 initially only loosely threaded thereon. The screws securing the internal and external gripping elements to the anchorage plate are then removed and the first nuts of the lock nut pairs 1 5 screwed onto the studs to a predetermined torque at which the armour wires are securely gripped between the internal and external gripping members with the thread of at least the external member biting into the wire.The second nuts of the pairs are subsequently screwed onto the studs 9 to lock the collar 8 in place relative to the plate 3.

Preferably the anchorage plate 3 is of BS970EN25 steel, the locking collar 8 is of BS970EN25 steel, and the internal and external gripping members are of a high carbon steel to BS4659 BD3.

The description so far has been concerned with the anchorage of a single layer of helically applied steel armour wires, the same basic anchorage arrangements as described with reference to Figs.

1 to 3 can, however, also be employed with two layers of contra lay or same lay direction steel armour wires. In the case of a cable with two layers of armour wires 21 and 22 it is preferable, however, to arrange an intermediate member, such as comprised by suitably sectioned members 20 (Fig. 4), in each of the outer interstitial spaces of the innermost layer 21 of armour wires in the vicinity of the anchorage such that the innermost layer then presents a smoother cylindrical surface for engagement by the outermost layer, which is forced there against by the external gripping member 7 (not shown) during use of the anchorage, thereby spreading the gripping force more evenly. Alternatively, the intermediate member may be comprised by a multi-segment support tube (not shown) arranged on the innermost layer 21 of armour wires in the vicinity of the anchorage and such as to space the layers 21 and 22 apart. The tube may be comprised of four segments.

Whereas the invention has been described with reference to the anchoring of armoured cables, it is alternatively applicable to the anchoring of stranded wire ropes or like member, other elongate members having a cylindrical layer to be gripped, such as one or more layers of outer stranded steel strength members which elongate members may, for example, incorporate a fluid flow tube with or without optical or electrical communications conductors.

Claims

1. A method of securing a substantially cylindrical layer of an elongate member to an anchor member therefor, including the steps of arranging an annular first gripping member under the cylindrical layer, arranging a second gripping member on the cylindrical layer and over the first gripping member, urging the second gripping member radially of the elongate member towards the first gripping member, whereby to grip the layer therebetween, by means which serve also to secure the first and second gripping member to the anchor member and which are such that upon subsequent increased axial load on the elongate member the gripping force applied to the layer by the first and second gripping member is increased.

2. A method as claimed in claim 1, wherein the second gripping member is longitildinally split into a plurality of segments.

3. A method as claimed in claim 1 or claim 2, wherein the radially outermost surface of the second gripping member tapers in the direction away from the anchor member and the said means includes a locking collar, arranged around the second gripping member, having a tapered radially innermost surface co-operable directly with the radially outermost surface of the second gripping member.

4. A method as claimed in claim 3, wherein the anchor member includes a wall portion against which a respective end face of each of the first and second gripping members abut, and wherein the second gripping member is urged radially towards the first gripping member upon urging of the locking collar towards the wall portion.

5. A method as claimed in claim 4, wherein the locking collar is located on and secured to studs fastened to the wall portion.

6. A method as claimed in any one of the preceding claims, wherein the cylindrical layer is comprised by a plurality of armour wires applied helically to the elongate member in a single layer.

7. A method as claimed in claim 6, wherein the radially outermost surface of the first gripping member includes a plurality of grooves with a helical lay substantially equal to the helical lay of the armour wires.

8. A method as claimed in claim 6, wherein the radially outermost surface of the first gripping member is threaded whereby to bite into the armour wires to provide a gripping effect.

9. A method as claimed in any one of claims 6 to 8, wherein the radially innermost surface of the second gripping member is threaded whereby to bite into the armour wires to provide a gripping effect.

10. A method as claimed in any one of claims 1 to 5, wherein the cylindrical layer is comprised by a plurality of armour wires applied helically to the elongate member in two layers, the wires in the two layers having the same or differing lay directions.

11. A method as claimed in claim 10, wherein the radially outermost surface of the first gripping member includes a plurality of grooves with a helical lay substantially equal to the helical lay of the innermost layer of armour wires, there being a respective groove for each wire of the innermost layer.

12. A method as claimed in claim 10, wherein the radially outermost surface of the first gripping member is threaded whereby to bite into the innermost layer of armour wires to provide a gripping effect.

13. A method as claimed in any one of claims 10 to 12, wherein the radially innermost surface of the second gripping member is threaded whereby to bite into the outermost layer of armour wires to provide a gripping effect.

14. A method as claimed in any one of claims 10 to 13, including the step of arranging appropriately sectioned members in each of the outer interstitial spaces of the innermost layer of armour wires in the vicinity of the first gripping member whereby the innermost layer of armour wires presents a smoother cylindrical surface to the outermost layer of armour wires.

1 5. A method as claimed in any one of claims 10 to 13, including the steps of arranging a multisegment support tube between the innermost and outermost layers of armour wires in the vicinity of the first gripping member, which support tube serves to space the armour wire layers apart.

1 6. An anchorage arrangement, for the securement of a substantially cylindrical layer of an elongate member, comprising an anchor member wall portion, an annular first gripping member adapted to be arranged on the elongate member under the cylindrical layer with one end abutting the wall portion, a second gripping member adapted to be arranged on the cylindrical layer and over the first gripping member with one end abutting the wall portion, which second gripping member is movable radially with respect to the first gripping member, and a locking collar adapted to be fastened to the wall portion, whereby to secure the first and second gripping members and and adapted to cause the radial movement of the second gripping member upon axial movement towards the wall portion, and wherein in use the first and second gripping members and the locking collar co-operate to increase the gripping force applied to the cylindrical layer upon increased axial load applied to the elongate member.

1 7. An anchorage arrangement as claimed in claim 16, wherein the second gripping member is longitudinally split into a plurality of segments.

18. An anchorage as claimed in claim 16 or claim 17, wherein the radially outermost surface of the second gripping member tapers in a first direction which in use of the arrangement is away from the wall portion, and wherein the radially innermost surface of the locking collar also tapers in the first direction and in use of the arrangement co-operates directly with the radially outermost surface of the second gripping member.

19. An anchorage arrangement as claimed in any one of claims 16 to 18, including studs fastened to the wall portion for location and securement of the locking collar.

20. An anchorage arrangement as claimed in any one of claims 16 to 19, and for use with a cylindrical layer comprised by armour wires applied helically to the elongate member, wherein the outermost surface of the first gripping member includes a plurality of grooves with a helical lay.

21. An anchorage arrangement as claimed in any one of claims 16 to 19, wherein the outermost surface of the first gripping member is threaded whereby in use to bite into the cylindrical layer to provide a gripping effect.

22. An anchorage arrangement as claimed in any one of claims 16 to 21, wherein the radially innermost surface of the second gripping member is threaded whereby in use to bite into the cylindrical layer to provide a gripping effect.

23. An anchorage arrangement as claimed in any one of claims 16 to 19, and for use with a cylindrical layer comprised by armour wires applied helically to the elongate member in two layers, the wires in the two layers having the same or differing lay directions, including a plurality of appropriately sectioned elements for arrangement in the outer interstitial spaces of the innermost layer of armour wires such that the innermost layer of armour wires can present a smoother cylindrical surface to the outermost layer of armour wires than otherwise.

24. An anchorage arrangement as claimed in any one of claims 16 to 1 9, and for use with a cylindrical layer comprised by armour wires applied helically to the elongate member in two layers, the wires in the two layers having the same or differing lay directions, including a multisegment support tube for arrangement between the innermost and outermost layers of armour wires such as to space them apart.

25. A method of securing a substantially cylindrical layer of an elongate member to an anchor member therefor substantially as herein described with reference to Figs. 1 to 3 or Figs. 1 to 4 of the accompanying drawings.

26. An anchorage arrangement, for the securement of a substantially cylindrical layer of an elongate member, substantially as herein described with reference to and as illustrated in Figs. 1 to 3 or Figs. 1 to 4 of the accompanying drawings.