GB2421642A

GB2421642A - Electrical connector

Info

Publication number: GB2421642A
Application number: GB0427997A
Authority: GB
Inventors: Gary Barnett; David Mark Eaton
Original assignee: Tyco Electronics Corp
Current assignee: TE Connectivity Corp
Priority date: 2004-12-21
Filing date: 2004-12-21
Publication date: 2006-06-28
Anticipated expiration: 2024-12-21
Also published as: GB0427997D0; GB2421642B

Abstract

An electrical connector (1) is disclosed comprising first and second bodies (10, 12). The first and second bodies (10, 12) are formed respectively with complementary first and second extensions (14, 16) that may be brought together such that the first extension (14) overlies the second extension (16). The first extension (14) is provided with an opening (15) having an internal shoulder (15a) and the second extension (16) is provided with a threaded bore (17) in registration with said opening (25) when said first and second extensions (14,16) are so brought together. A bolt (20) may be passed through the opening (15) and engaged with the threaded bore (17), to bring an enlarged portion of the bolt (20) into abutment with the shoulder (15a). The shoulder (15a) is configured such that the enlarged portion (23) of the bolt (20) exerts upon the shoulder (15a) a force parallel to the longitudinal axis of the bolt (20) and a force perpendicular thereto.

Description

Title - Electrical Connector This invention relates to electrical

connectors, in particular (though not exdusively) to electrical connectors for use with electrical power distribution cables.

The distribution of electrical power within the United Kingdom involves distribution networks operating at a number of particular voltages. Power is distributed from power stations at very high voltages, typically 400kV, 275kV or 132kV, via overhead power lines. Further distribution then takes place through networks operating at voltages typically and principally of 11kV or 33kV, before the electricity is finally supplied to consumers at normal "mains" voltages of 240V (single-phase) or 415V (three-phase).

Cables operating at the intermediate voltage range of 11kV - 33kV are commonly installed underground. From time to time, it is necessary for joints to be created in such cables, either for maintenance purposes or to create branch connections or the like. Among the problems that are encountered in creating such joints are that the cables may be of relatively large diameter and hence may be inflexible and difficult to manipulate. These problems may be exacerbated by the environment in which the cables are installed (eg underground chambers or ducting) or the confines of a trench excavated around the cable.

Conventionally, one form of electrical connector that has been used for the end-to- end connection of two electrical conductors in such circumstances comprises a cylindrical body having blind bores at each end into which the conductor ends are inserted. Threaded bores are provided in the wall of the cylindrical body for bolts to secure the conductors.

Known conductors of this type suffer from a number of disadvantages. For example, the large diameter and relatively inflexible nature of the conductors means that it is sometimes difficult to fit both conductors into opposite ends of the connector.

GB-A-2272803 describes an electrical connector which also comprises a pair of complementary socket bodies which can be individually connected to the ends of two conductors and then clamped together to make an electrical connection. When properly assembled, with correctly aligned socket bodies, the connector has a smooth overall shape which reduces the risk of undesirable electrical discharges. The socket bodies fit together via extensions with abutting, complementary surfaces which in the specific connectors described are V-shaped to provide keying engagement which aligns the connector bodies and improves the electrical contact between them. The extensions are clamped together by means of a bolt that extends through an opening in one of the extensions and engages a threaded bore in the other extension. An enlarged head of the bolt engages a shoulder within the opening, so that tightening of the bolt draws the complementary surfaces of the two extensions together. The underside of the head of the bolt, and the shoulder that it engages, are flat so that the clamping force exerted by the bolt is entirely directed parallel to the longitudinal axis of the bolt. The bolt thus acts to fasten the two extensions together, but alignment of the extensions is dependent entirely on the relatively complex form of the complementary surfaces.

Thus, the connector disclosed in GB-A-2272803 addresses the problem of jointing of inflexible conductors, but suffers from the disadvantage of requiring high precision machining of the complementary surfaces to ensure their correct engagement.

It would thus be desirable to provide a connector that facilitates connection of inflexible cables, in a similar manner to that of GB-A2272803, but the manufacture of which does not involve relatively difficult and costly machining operations.

There has now been devised an improved form of electrical connector which achieves this objective and thereby overcomes or substantially mitigates the above-mentioned and/or other disadvantages associated with the prior art.

According to a first aspect of the invention, there is provided an electrical connector comprising first and second bodies, the first and second bodies being formed respectively with complementa,.y first and second extensions that may be brought together such that the first extension overlies the second extension, the first extension being provided with an opening having an internal shoulder and the second extension being provided with a threaded bore in registration with said opening when said first and second extensions are so brought together, such that a bolt may be passed through said opening and engaged with said threaded bore, to bring an enlarged portion of the bolt into abutment with said shoulder, wherein said shoulder is configured such that the enlarged portion of the bolt exerts upon said shoulder a force parallel to the longitudinal axis of the bolt and a force perpendicular thereto.

The electrical connector according to the invention is advantageous primarily in that the force exerted upon the shoulder parallel to the longitudinal axis of the bolt urges the first and second extensions into abutment with each other, and, at the same time, the force exerted perpendicular to the longitudinal axis of the bolt draws the first and second bodies together. Appropriate configuration of the first and second bodies, and of the first and second extensions, then enables tightening of the bolt to bring the first and second bodies not orgy into tight engagement but also into good alignment. The connector may therefore be considered to be self-aligning. These effects are achieved even where the abutting surfaces of the first and second extensions are simple, flat surfaces. Hence, the effects may be achieved without the formation of extensions with complex complementary surfaces. The connector may offer the further advantage that the length of the overlapping first and second extensions may be relatively short, enabling the connector to be more compact than would otherwise be the case, which offers significant advantages, particularly where the connector is used in the jointing of underground electrical distribution cables.

Preferably, the opening formed in the first extension is generally circular in cross- section, the upper part of the opening being of increased dimension so as to accommodate the enlarged (head) portion of the bolt. The lower portion of the opening is preferably of only slightly greater diameter than the shank of the bolt that extends, in use, through the opening. The shoulder formed in the opening most preferably forms an inclined transition region between the upper and lower parts of the opening.

The threaded bore in the second extension preferably extends through the full thickness of the second extension.

In order that the bolt exerts the desired force perpendicular to the longitudinal axis of the bolt, it is necessary that abutment of the head portion of the bolt with the shoulder does not occur around the whole circumference of the bolt. Most preferably, such abutment occurs only at that part of the circumference of the bolt that is closest to the second connector body (so that the effect of such abutment is to urge the first and second connector bodies towards each other). This can be achieved by means of the shoulder being formed only at that part of the circumference of the opening. For reasons of manufacturing simplicity, however, it is preferred that the shoulder be formed around the full circumference of the opening, ie that the shoulder should be frustoconical in form. In such a case, so that the force is exerted in the desired direction, it is preferred that the opening should be of sufficient diameter that the head portion of the bolt can be brought into abutment with the shoulder at the desired point, but is spaced from (and hence does not bear upon) the shoulder at the diametrically opposite point. In such an arrangement, the longitudinal axis of the opening is preferably slightly offset from that of the threaded bore in the second extension when the opening is brought into registration with that threaded bore.

It is strongly preferred that the enlarged, head portion of the bolt should have an abutment surface that corresponds in form to that of the shoulder. Thus, the head portion of the bolt is most preferably provided with a frustoconical abutment surface, and that surface is most preferably inclined to the longitudinal axis of the bolt at an angle that matches the angle at which the corresponding surface of the shoulder is inclined to the longitudinal axis of the opening.

Most preferably, the bolt is provided with a drive head that is adapted to shear off when a predetermined torque is applied to it. Such a drive head may, for instance, be of non-circular cross-section (eg square or hexagonal cross-section) so that it may be engaged by a drive tool such as a spanner or socket wrench. Alternatively, the drive head may have an internal recess of non-circular cross-section into which a tool such as an Allen key may be inserted. In either alternative, the drive head is preferably connected to the head portion of the bolt by a weakened region that is designed to shear at the predetermined torque. The weakened region may, for instance, be of reduced thickness.

Bolts suitable for use in the invention and having the above characteristics are believed to be novel and represent a further aspect of the invention, which thus provides a bolt having a threaded shank with an enlarged head portion having a frustoconical undersurface, and a drive head with drive formations adapted to be engaged by a drive tool, the drive head being adapted to shear from the head portion upon application to the drive head of a predetermined torque.

Apart from the particular features that are the essence of the invention, the electrical connector may otherwise be generally conventional in form. Thus, the first and second bodies are preferably formed in electrically conductive material, most preferably in aluminium or brass.

The connector may be for the end-to-end connection of two conductors, in which case the first and second bodies are preferably of generally similar form, each having a single socket that receives, in use, an end of one of the conductors. The sockets are most preferably blind bores formed in the ends of the bodies and extending along the majority of the length of the respective bodies. As is conventional, the walls of the first and second bodies are preferably provided with threaded bores with which bolts may be engaged to fasten the conductor ends within the sockets. As for the bolt that is used to fasten together the first and second extensions, such bolts are preferably provided with shearable heads.

In another commonly-used variant, the connector is of the branch or socalled breech type, in which one of the first and second bodies receives the end of one conductor and the other receives the ends of two conductors.

Whatever overall form the connector takes, the first and second bodies are preferably configured such that when they are brought together with the first extension overlying the second extension the first and second bodies fit closely together, and the assembled connector has a smooth overall configuration. By this is meant that the connector has an overall shape which is free of protrusions or sharp edges that could give rise to electrical discharges. The edges of the connector are therefore preferably rounded.

The first and second extensions are preferably formed integrally with the first and second bodies. Most preferably, the form of the extensions is such that when they are brought together during use, the resulting assembled connector has a generally continuous, smooth external profile. A connector for the end-to-end connection of two conductors, for instance, will preferably have a generally cylindrical external aspect.

In such a case, the two extensions are each preferably generally hemicylindrical.

Breech-type connectors are preferably of generally similar construction, though deviating from a cylindrical shape. The overlapping extensions of the first and second bodies are commonly referred to as palms, and the abutting surfaces of the two palms are most preferably flat. The ends of the palms are preferably also flat and, in use, come into abutment with correspondingly shaped surfaces of the other one of the first and second bodies.

As discussed above, the electrical connector according to the invention is particularly useful in relatively high voltage applications, particularly in the jointing of electrical distribution cables, especially underground distribution cables. The electrical connector is thus particularly suited for use with electrical conductors that operate at voltages in the kV range, ie from 1kV to several tens of kV, eg up to 50kV. Particular voltages at which such cables may operate are 11 kV and 33kV.

According to a further aspect of the invention, there is thus provided an electrical power distribution cable, preferably such a cable operating at a voltage between I kV and 50kV, eg 11 kV or 33kV, the power distribution cable induding a joint comprising an electrical connector in accordance with the first aspect of the invention.

The invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which Figure 1 is a perspective view of an electrical connector in accordance with the invention; Figure 2 is an exploded side view of the connector of Figure 1, showing the three components of the connector in a disassembled state; Figure 3 is sectional view of the assembled connector, along the line Ill-Ill in Figure 1; and Figure 4 is a perspective sectional view of the connector, again taken along the line Ill-Ill in Figure 1.

Referring first to Figure 1, an electrical connector for use in high voltage applications is generally designated 1 and is of the branchconnector or "breech" variety. As is most clearly apparent from Figure 2, the connector I is made up of two principal components, viz a singlesocket body 10 and a double-socket body 12. One end of the connector 1 is thus formed with a single socket 2, which in use receives a single conductor (not shown), and the other end of the connector I is formed with two sockets 4,6, which in use receive the ends of two conductors (not shown).

The sockets 4,6 in the double-socket body 12 are not clearly visible in the drawings (only the positions of the open ends of those sockets being indicated in Figure 1, but are similar in form to the socket 2 in the single-socket body 10. As is conventional, each of sockets 2,4,6 comprises a blind bore extending from the outward (in the assembled connector) end of the respective body 10,12. The blind bore is formed with a helical groove that gives the socket 2,4,6 a ridged internal surface that enhances mechanical fixing of connectors within the sockets 2,4,6. Pairs of threaded bores 3,5,7 are formed in the walls of the respective bodies 10, 12, each pair of bores 3,5,7 being associated with a respective one of the sockets 2,4,6. Thus, the single-socket body 10 is formed with one pair of threaded bores 3, and the double- socket body 12 has two pairs of threaded bores 5,7. The threaded bores 3, 5,7 receive, in use, shearable damping bolts (not shown) that are used to fix the ends of conductors within the sockets 2,4,6 in the manner described below.

The single-socket body 10 and double-socket body 12 are each formed, at the ends of the respective bodies 10,12 that, in use, abut, with palms 14, 16 that fit closely together. The palms 14,16 are configured and dimensioned such that, when the two bodies 10,12 are brought together in the manner that is described in greater detail below, the ends 14a,16a of each palm 14,16 abut the corresponding faces lOa,12a of the other one of the two bodies 10,12, and the juxtaposed underside surface 14b of one palm 14 and the upper surface I 6b of the other palm 16 also abut each other (it should be understood that all references herein to "underside", "upper surface" and the like refer to the arrangement depicted in the Figures, and do not necessarily, unless the context requires otherwise, imply that strict compliance with such a term is essential).

The palm 14 of the single-socket body lOis formed with a plain bore 15, and the palm 16 of the double-socket body 12 is formed with a threaded bore 17. When the two bodies 10,12 are brought together with the two palms 14,16 overlapping, the plain bore 15 and threaded bore 17 are brought into registration, though the central axes of the plain bore 15 and the threaded bore 17 are not perfectly aligned. The two bodies 10,12 may then be fastened together by means of a securing bolt 20, the tip of which is passed through the plain bore 15 in the upper palm 14 and engaged with the threaded bore 17 in the lower palm 16.

As can be seen from Figure 2, the securing bolt 20 has a shank 21, that is threaded for the majority of its length, and an enlarged head 22, the transition from the upper part of the shank 21 to the head 22 forming a chamfered shoulder 23. The surface of the shoulder 23 is disposed at an angle of approximately 25 to the longitudinal axis of the bolt 20. A drive head 24 of hexagonal cross-section is attached to the head 22 by a neck 25 of reduced dimension.

As is most clearly apparent from Figure 3, the plain bore 15 is of slightly greater diameter than the threaded bore 17, and the upper part of the plain bore 15 is dimensioned to form a countersink that receives, in use, the head 22 and chamfered shoulder 23 of the bolt 20. In particular, the uppermost part of the plain bore 15 is of slightly greater diameter than the head 22 of the bolt 20, and the lowermost part of the plain bore 15 is of slightly greater diameter than the shank 21 of the bolt 20. The uppermost and lowermost parts of the plain bore 15 are connected by a transition region that forms a frustoconical abutment I 5a. The surface of the abutment I 5a is disposed at an angle that matches that of the shoulder 23 on the bolt 20, ie an angle of approximately 25 to the longitudinal axis of the plain bore 15.

The connector 10 may be used to create a branch connection to an existing high voltage electrical conductor. To achieve this, the existing connector is cut and stripped of insulation in a conventional manner, so that two exposed ends are created. The connector 10, in its disassembled condition, is then fitted as follows: First, one exposed end of the conductor is inserted into the socket 2 of the single- socket body 10 and the other exposed end of the conductor is inserted into one of the sockets 2 of the double-socket body 12. The conductor ends may be loosely held in place by means of one or two shearable clamping bolts engaged with the respective threaded bores 3,5 associated with the sockets 2,4.

The two bodies 10,12 are then brought together, with their palms 14,16 overlapping, so that the plain bore 15 and threaded bore 17 are brought into registration. The securing bolt is then inserted into the plain bore 15 and its threaded shank engaged with the threaded bore 17. Rotation of the bolt 20 (by means of a suitable wrench applied to the drive head 24) eventually brings the chamfered shoulder 23 of the bolt 20 into engagement with the abutment 1 5a of the plain bore 15. Continued rotation of the bolt 20 exerts a downward force upon the abutment 15a (in the direction of the arrow A in Figure 3), which clamps the palms 14,16 of the two bodies 10,12 together. In addition, however, a lateral force is exerted (in the direction of the arrow B in Figure 3) that urges the end 14a of the upper palm 14 against the corresponding surface 12a of the double-socket body 12. This also urges the end 1 6a of the lower palm 16 against the corresponding surface 1 Oa of the single- socket body 10.

The forces exerted by the bolt 20 securely clamp together the singlesocket body 10 and the double-socket body 12. Moreover, the lateral force that draws the ends 14a,16a of each palm 14,16 into abutment with the juxtaposed surface of the other body 10,12 brings the bodies 10,12 into good alignment without the need for the presence of any mating or otherwise cooperating formations on the palms 14,16.

Once the torque exerted on the bolt 20 exceeds a predetermined limit, the bolt 20 shears at the base of the neck 25, preventing further rotation of the bolt 20, and hence preventing the application of excessive force. The dimensions of the bolt 20 are such that after the drive head 24 has sheared off, the tip of the shank 21 lies substantially flush with the underside of the connector I and the upper surface of the head 22 lies substantially flush with the upper surface of the connector 1.

The two ends of the existing conductor are then fixed in place by tightening of clamping bolts engaged with the threaded bores 3,5. Clamping bolts loosely engaged with the threaded bores 3,5 to hold the conductor ends temporarily in place while the connector bodies 10,12 are clamped together may be loosened to permit fine adjustment of the position of the connector 1 on the conductor ends, and then tightened, and any further clamping bolts engaged with the threaded bores 3,5 so that each conductor end is held in place by two such bolts. As is conventional, the clamping bolts will generally be shearable bolts, dimensioned and designed to shear in a plane substantially flush with the connector surface.

An exposed end of the intended branch connection is then inserted into the remaining socket 6, and clamped in place by means of shearable clamping bolts engaged with the associated threaded bores 7.

Finally, the completed connection may be encased in insulating material, which may be done in a conventional manner.

Claims

Claims 1. An electrical connector comprising first and second bodies, the

first and second bodies being formed respectively with complementary first and second extensions that may be brought together such that the first extension overlies the second extension, the first extension being provided with an opening having an internal shoulder and the second extension being provided with a threaded bore in registration with said opening when said first and second extensions are so brought together, such that a bolt may be passed through said opening and engaged with said threaded bore, to bring an enlarged portion of the bolt into abutment with said shoulder, wherein said shoulder is configured such that the enlarged portion of the bolt exerts upon said shoulder a force parallel to the longitudinal axis of the bolt and a force perpendicular thereto.
2. An electrical connector as claimed in Claim 1, wherein the shoulder formed in the opening forms an inclined transition region between the upper and lower parts of the opening.
3. An electrical connector as claimed in Claim 1 or Claim 2, wherein abutment of the head portion of the bolt with the shoulder occurs only at that part of the circumference of the bolt that is closest to the second connector body, so that the effect of such abutment is to urge the first and second connector bodies towards each other.
4. An electrical connector as claimed in Claim 3, wherein the shoulder is frustoconical and the opening is be of sufficient diameter that the head portion of the bolt can be brought into abutment with the shoulder at the part of the circumference of the bolt that is closest to the second connector body, but is spaced from the shoulder at the diametrically opposite point.
5. An electrical connector as claimed in any preceding claim, wherein the enlarged, head portion of the bolt has an abutment surface that corresponds in form to that of the shoulder.
6. An electrical connector as claimed in Claim 5, wherein the head portion of the bolt is provided with a frustoconical abutment surface.
7. An electrical connector as claimed in Claim 6, wherein the abutment surface is inclined to the longitudinal axis of the bolt at an angle that matches the angle at which the corresponding surface of the shoulder is inclined to the longitudinal axis of the opening.
8. An electrical connector as claimed in any preceding claim, wherein the bolt is provided with a drive head that is adapted to shear off when a predetermined torque is applied to it.
9. An electrical connector as claimed in any preceding claim, which is for the end- to-end connection of two conductors, and the first and second bodies each have a single socket that receives, in use, an end of one of the conductors.
10. An electrical connector as claimed in any one of Claims 1 to 8, which is of the branch breech type, and one of the first and second bodies has a single socket that, in use, receives the end of one conductor and the other has two sockets that, in use, receive the ends of two conductors.
11. An electrical connector as claimed in Claim 9 or Claim 10, wherein the sockets are blind bores formed in the ends of the bodies and extending along the majority of the length of the respective bodies.
12. An electrical connector as claimed in any one of Claims 9 to 11, wherein the walls of the first and second bodies are provided with threaded bores with which bolts may be engaged to fasten the condudor ends within the sockets.
13. An electrical connector as claimed in any preceding claim, wherein the first and second extensions are formed integrally with the first and second bodies.
14. An electrical connector as claimed in any preceding claim, wherein the abutting surfaces of the extensions are flat.
15. An electrical connector as claimed in any Claim 14, the ends of the extensions are flat and, in use, come into abutment with correspondingly shaped surfaces of the other one of the first and second bodies.
16. An electrical power distribution cable, preferably such a cable operating at a voltage between 1 kV and 50kV, eg 11 kV or 33kV, the power distribution cable including a joint comprising an electrical connector in accordance with any preceding claim.
17. A bolt having a threaded shank with an enlarged head portion having a frustoconical undersurface, and a drive head with drive formations adapted to be engaged by a drive tool, the drive head being adapted to shear from the head portion upon application to the drive head of a predetermined torque.
18. A bolt as claimed in Claim 17, wherein the drive head is of noncircular cross- section 50 that it may be engaged by a drive tool such as a spanner or socket wrench.
19. A bolt as claimed in Claim 17, wherein the drive head has an internal recess of non-circular cross-section into which a tool such as an Allen key may be inserted.
20. A bolt as claimed in any one of Claims 17 to 19, wherein the drive head is connected to the head portion of the bolt by a weakened region that is designed to shear at the predetermined torque.
21. A bolt as claimed in Claim 20, wherein the weakened region is of reduced thickness.