GB2121244A - Conductor spacers, methods of making conductor spacers and bush assemblies - Google Patents

Abstract

In a conductor spacer for multi- conductor electrical overhead transmission lines the conductor clamps are mounted on the support body of the spacer by means of resilient bush assemblies each comprising a resilient bush embraced between inner 41 and outer 46 sleeves. The outer sleeve is fast with the body of the spacer, for example as a result of the body having been cast directly onto the outer sleeve and before assembly with the bush and inner sleeve. The outer sleeve preferably has inwardly directed projections or deformations to grip the bush. The clamp arms 25.1, 25.2 are mounted on a pivot tube 49 received within the inner sleeve. <IMAGE>

Description

SPECIFICATION Conductor spacers, methods of making conductor spacers and bush assemblies This invention relates to conductor spacers for multi-conductor or bundled electrical overhead transmission lines, to a method of making conductor spacers and to resilient bush assemblies for use therein. In particular, the invention relates to spacers carrying two, three, four or more spaced apart clamps each to clamp an individual conductor, the clamps being mounted resiliently with respect to a supporting structure. Such spacers are commonly referred to as "spacer dampers". Spacer dampers serve to maintain the conductors of a bundle in spaced relationship while resisting forces resulting from the action of the wind, ice accumulation and short circuit current. They further serve to control to an acceptable ievel conductor vibration and oscillation.

Resilient bush assemblies by means of which the clamps of a spacer damper are mounted resiliently with respect to the supporting structure normally comprise a resilient bush of annuiar cross section, the inner surface of which is chemically bonded to a metal inner sleeve and the outer surface is chemically bonded to a metal outer sleeve. However, the bonding of the bush to the sleeves involves a multi-stage process which adds considerably to the cost of the spacer damper. In order to obviate at least part of this expensive procedure there has previously been proposed the use of bush assemblies in which the bush is a press fit within an outer sleeve but without any chemical bonding between them.However, in practice it has been found that under very cold winter conditions such as are met in Canada and Sweden contraction of the bush results in it becoming loosened from the outer sleeve thereby allowing unwanted relative movement between them which results in defective performance of the spacer damper.

The present invention now provides a novel resilient bush assembly for use in conductor spacers, in which a resilient bush is firmly attached to an outer sleeve without the need to use chemical bonding. The assembly provides excellent attachment even under cold winter conditions, between the bush and outer sleeve yet avoids the expense of chemical bonding.

In a first aspect the invention provides a conductor spacer for a multi-conductor electrical overhead transmission line, the spacer comprising a support carrying two or more spaced-apart clamps each to clamp one of the conductors, the clamps each being mounted resiliently with respect to the support by means of a resilient bush assembly, said assembly comprising a resilient bush embraced between an inner sleeve and an outer sleeve, the outer sleeve being fast with said support.

In a second aspect the invention provides a method of making a conductor spacer for a muiticonductor electrical overhead transmission line, the spacer comprising a support carrying two or more spaced apart clamps each to clamp one of the conductors, the clamps each being mounted resiliently with respect to the support by means of a resilient bush assembly comprising a hollow resilient bush embraced between an inner sleeve and an outer sleeve, in which method the support is formed so that it has a housing for the outer sleeve of the bush assembly, making the outer sleeve fast with the support and then pressing into engagement in the outer sleeve a bush subassembly comprising the resilient bush mounted on the inner sleeve.

This method is applicable inter alia to the production of conductor spacers of the first aspect of the invention. In a preferred form of the method the support is of cast metal and is formed by casting in a mould in which there has previously been located the outer sleeve of a bush assembly so that in the cast product the outer sleeve is not only fast with, but integral with, the support; thus the need to machine a housing in the support to take the outer sleeve is obviated.

In a third aspect the invention provides a conductor spacer for a multi-conductor electrical overhead transmission line, the spacer comprising a support carrying two or more spaced-apart clamps each to clamp one of the conductors, the clamps each being mounted resiliently with respect to the support by means of a resilient bush assembly, said assembly comprising a hollow resilient bush embraced between an inner sleeve and an outer sleeve, the outer sleeve having a plurality of elongate projections or deformations disposed about the periphery of the sleeve and substantially parallel to one another and to the longitudinal axis of the outer sleeve and extending inwardly thereof so as locally to compress the bush and prevent relative rotational movement between the bush and the outer sleeve.

In a fourth aspect the invention provides a bush assembly for use in the conductor spacer of the first or third aspect of the invention, comprising a hollow resilient bush, an inner sleeve and an outer sleeve between which the bush is embraced, the outer sleeve having elongate projections disposed about the periphery of the sleeve and substantially parallel to one another and to the longitudinal axis of the outer sleeve and extending inwardly thereof so as locally to compress the bush and prevent relative rotational movement between the bush and the outer sleeve.

The support of the conductor spacers of this invention is conveniently a bar or frame which can take a variety of forms. If in the form of a bar it can, for example, be of linear construction and normally adapted to hold spaced apart two conductors. However, the bar can be of a branched construction suitable for holding, for example, three or four conductors. If the spacer is one having a frame construction it can be one suitable for holding, for example, three or four conductors.

If desired, a frame construction can be used where there are only two conductors in the transmission line but in general this is more expensive than a comparable bar construction.

The invention is particulariy, though not exclusively concerned with conductor spacers whose clamps each comprise a clamp arm having at one end thereof adjustable jaws to clamp a conductor of circular or other cross-section and having at the other end thereof a bifurcation by means of which the clamp is mounted on a support bar, and it is with particular reference to such clamps that the following description particularly relates.

In a preferred form of the invention both the inner and outer sleeves of the bush assembly are of circular cross-section (normally in the form of a right cylinder) and the resilient bush is an elastomeric bush of annular cross-section and is bonded at its interior surface to the exterior surface of the inner sleeve. This bonding can, for example, take a form conventionally used in the art for bonding together rubber bushes to an adjacent metal sleeve. The elastomeric bush conveniently has a cross-section (see for example Figure 5 of the accompanying drawings) in which the longitudinal dimension at its interior surface in contact with the inner sleeve is substantially greater than its longitudinal dimension at its exterior surface where it contacts the outer sleeve.

The difference between said two longitudinal dimensions is such as to avoid any substantial bulging of the bush along its longitudinal axis when placed under radial compressive stress in use.

Where the outer sleeve of the bush assembly is of circular cross-section the elongate projections or other deformations conveniently extend radially inwards from that sleeve. In a preferred form of the invention each deformation has been formed by piercing or otherwise deforming the outer sleeve. For example, a deformation can be produced by making cuts or slits in the outer sleeve and deforming inwards the metal disposed between those cuts or slits. In this example, when a bush sub-assembly comprising resilient bush and inner sleeve is pressed into the outer sleeve the deformation presses against and locally deforms the outer periphery of the bush without, normally, actually piercing the periphery.However, if desired, the deformation means can be such as to pierce the periphery of the bush though this arrangement carries with it the risk that the bush may be weakened thereby, The deformations preferably comprise two or more (for example three or five) like spaced-apart component deformations for example three elongate projections punched in the outer sleeve from the exterior surface thereof, the projections being spaced about the circumference of the outer sleeve at an angular spacing of 1200. In the embodiment of the invention described with reference to the accompanying drawings the projections are spaced apart in a plane disposed at a right angle to the longitudinal axis of the bush but the invention is not so limited and, if desired, component deformations can be disposed in two or more planes.

In one form of the invention the bar, frame or other support can be of aluminium, an aluminium alloy or other light-weight metal. Where such a metal is used it is normal to provide the support with one or more weights to increase the inertia of the spacer. If desired, the bar, frame or other support can comprise two or more shells. Where two shells are used they conveniently abut each other in a plane which is a median plane of the support.

Bush assemblies according to the fourth aspect of this invention can be used in the conductor spacers of our U.K. Patent Application (Title: Conductor Spacers) of even date in place of bush assemblies described therein.

There is now described, by way of example and with reference to the accompanying drawings, a twin spacer damper according to an embodiment of the invention. In the drawings: FIGURE lisa side elevation of the spacer damper; FIGURE 2 is a plan view of the spacer damper; FIGURE 3 is a cross-section on the line A-A of Figure 1; FIGURE 5 is a cross-section on the line B-B of Figure 1; FIGURE 5 is a cross-section on a diameter of the bush sub-assembly of the spacer damper; and FIGURE 6 is a cross-section of the outer sleeve of the bush assembly of the spacer damper on the centre line of Figure 4.

With reference to Figures 1 and 2, in general terms the spacer damper comprises a bar body 10 having resiliently mounted at each of its respective end portions clamps 11 and 12, clamp 12 being shown in greater detail in Figure 4. Clamp 11 is identical with clamp 12 in this preferred embodiment. There are located in the middle portion of body 10 two recessed cylindrical plates 13, 14 which serve to increase the mass of the body and the inertia of the spacer damper as a whole. As can be seen from Figure 3, the plates are held in place by means of a fixing assembly comprising bolt 13.1, nut 13.2 and washer 13.3, the shank of the bolt being accommodated in a transverse aperture in body 10, and the head of the bolt and the nut being housed respectively in recesses 13.4, 14.1 in the cylindrical plates so as to minimise risk of accidental electrical discharge from them. The body 10 is of cast aluminium alloy, and each end portion of the body has formed therein a circular aperture to provide a housing to accommodate bush 1 5 or 16, as is described in greater detail below.

The end portions 1 7, 18 of the body are of a shape such that the thickness of the body there is less than its thickness at the middle portion separating them. This reduced thickness is to accommodate the clamps within the minimum practicable overali thickness of the spacer damper.

End portions 17, 18 are separated from the middle portion by shoulders 19, 20 having formed thereon bosses 19.1, 20.1 which serve respectively as limit stops for the rotational movement of the clamps 12, 11 outwardly with respect to the body, and bosses 22, 23 which serve as limit stops for rotational movement of the clamps inwardly with respect to the body. The overall shape of the body (and of the clamps) is such as to avoid the presence of sharp promontories which could act as local concentration areas for electrical discharge.

There is now described, with particular reference to Figures 1, 4, 5 and 6 the construction of the clamp 12. In general terms the clamp comprises: a clamp body 25 having a pair of clamp arms 25.1,25.2 each having formed therein an aligned circular location aperture having a chamfered circumference at the outer surface of the arm; a clamp cap 26; bush assembly 15; and a shear-head bolt assembly 27.

The clamp is pivotally mounted on body end portion 17 and the clamp cap 26 has a floating relationship to clamp body 25 being connected to the latter by means of the shear-head bolt assembly 27.

The outer end portions of the clamp body 25 and clamp cap 26 are provided with concave jaws 28, 29 whose shape and dimensions are such that, when closed they can firmly grip between them a conductor of the appropriate diameter. The clamp body, clamp arms, clamp cap and clamp jaws can be of an aluminium alloy. The shear-head bolt assembly 27 comprises a shear-head bolt 30 the shank end of which carries an external thread by means of which it is retained in the clamp body 25. Between the head of the bolt and a recess in clamp cap 26 there is mounted a galvanised steel washer 31 and a belleville washer 32 of sheradised steel.

Referring now to Figures 4, 5 and 6, the bush assembly comprises an elastomeric bush 40 which has previously been firmly bonded to a cylindrical inner sleeve 41 of aluminium alloy the outer end portions 42, 43 of which have a semicircular rebate providing diametrical shoulders 44, 45. Referring to Figures 5 and 6, the outer sleeve 46 of the bush assembly comprises an aluminium alloy cylinder having a plurality of deformations 47 formed by pressing, the pressing being carried out so as locally to deform the cylinder 46 radially inwards and locally to compress the bush 40. The deformations can be formed, for example, by making two slits in the outer sleeve, parallel to each other and to the longitudinal radial axis of the sleeve and, either concurrently or subsequently, pressing the portion of the sleeve lying between the slits so as to deform it inwardly of the sleeve.

These deformations which can be, for example, three or five in number, are spaced equidistant from one another about a circumference of the outer sleeve 46 and lie in a plane which is at a right-angle to the longitudinal axis thereof. Outer sleeve 46 can have a plurality of dimples or like depressions 48 which can, for example, be spaced intermediate the deformations 47 and can, if desired, be on the same plane or planes as them.

in a preferred embodiment of the invention outer sleeve 46 is installed in the spacer damper separately from the remainder of the bush assembly.

For example, the outer sleeve having previously had formed therein the locking deformations 47 (but not, in this embodiment, depressions 48) is made fast with body 10 by prior introduction into the mould used in casting the body, thus providing an integral assembly of body 10 and sleeve 46. This procedure obviates the need of machining body 10 to accommodate a bush assembly. It is with reference to this procedure that the following description particularly relates.

The components of the bush sub-assembly (that is the bush assembly without outer sleeve 46) can be assembled as follows. The bush 40 is bonded, for example by means of a conventional technique for bonding a rubber bush to metal, to the central portion 44 of inner sleeve 41 (or is formed in situ thereon). This sub-assembly is then presented to the outer sleeve 46, the inside diameter of which is such that the sub-assembly is a press fit within it, and is forced into the sleeve 46 so as to be disposed midway between the ends thereof. In consequence, bush 40 is firmly gripped between inner sleeve 41 and outer sleeve 46. The edges of the sleeve 46 are then inturned to prevent the bush from moving with respect to the outer sleeve in a longitudinal direction; the inwardly directed deformations 47 prevent rotary movement.

In another embodiment of the invention the bush assembly is installed as a whole in the body 10 as follows. The bush assembly is inserted into the housing in end portion 1 7 of the body 10, the dimensions of the housing being such that the bush assembly is a press fit therein.

The bush assembly is centrally located within the housing so that the ends of inner sleeve 41 are spaced equidistant from the median plane of the body 10 and the ends of the outer sleeve 46 are then deformed radially inwards so as to embrace the bush 40. In this embodiment of the invention the frictional forces arising at the interface between the exterior surface of outer sleeve 46 and the housing in the spacer body is sufficient to prevent relative movement between them.

A pivot tube 49 whose external diameter is such that the tube is a free fit in the inner sleeve 41 is inserted into that sleeve and positioned symmetrically therein. Then a precursor form of the clamp assembly, in which the two spaced apart clamp arms 25.1, 25.2 are divergent from each other and not parallel as shown in the complete spacer damper of the drawings, is presented to the bush assembly so that its location apertures are aligned respectively with the ends of the pivot tube. The periphery of the location apertures in the clamp arms includes projections to engage with the shoulders 44 and 45 of the inner sleeve, and the arms are presented to the pivot tube so that those projections are aligned with the shoulders.

The clamp arms are then straightened thereby causing their location apertures to engage respectively with the end portions of the tube, and the outer ends of pivot tube are deformed radially outwards so as to conform to the chamfered edges of the location apertures in clamp arms 25.1, 25.2. Said outer ends can be, for example, circular (as in the drawings) or oval.

The embodiment described above provides a simple yet most effective means of mounting the bush assembly in the clamp arms. It will be seen that no separate fixing devices are required to hold the bush assembly or the clamp arms in place with respect to the spacer body. Even more important is the avoidance of bonding the bush 40 to outer sleeve 46, resulting in a major economy in manufacture. The securement means provided by the deformations in the outer sleeve prevent rotational movement relative to the bush such as occurs with other non-bonded systems under extremes of temperature.

The structure described above as being a preferred embodiment of the invention prevents relative movement between adjacent components, both under normal temperature conditions and under extreme winter conditions. Thus, shoulders 44, 45 of the inner sleeve co-act with the projections on the clamp arms so as to prevent relative movement; inner sleeve 41, being chemically bonded to a bush 40, precludes relative movement between them; the inwardly directed deformation or projections of the outer sleeve prevent relative rotary movement between it and the bush; and the inturned edges of the outer sleeve prevent relative axial movement between that sleeve and the bush. As explained above, in the embodiments where body 10 has been cast on to the outer sleeve relative movement between those two components is impossible.

The bush of the bush assembly of this invention can comprise any suitable elastomer. Very good results have been obtained using, for example, a poiynorbornene elastomer. When a polynorbornene elastomer is used it can be, for example in the form of a homopolymer or in the form of a copolymer or otherwise in conjunction with one or more other elastomers, for example natural rubber or polyisoprene.

Claims (20)

1. A conductor spacer for a multi-conductor electrical overhead transmission line, the spacer comprising a support carrying two or more spaced-apart clamps each to clamp one of the conductors, the clamps each being mounted resiliently with respect to the support by means of a resilient bush assembly, said assembly comprising a resilient bush embraced between an inner sleeve and an outer sleeve, the outer sleeve being fast with said support.

2. A conductor spacer according to Claim 1 in which the support has been produced in situ so as to embrace the outer sleeve.

3. A conductor spacer according to Claim 1 or 2, in which the outer sleeve has elongate projections or deformations disposed about the periphery of the sleeve and parallel to one another and to the longitudinal axis of the outer sleeve.

4. A conductor spacer according to Claim 1, 2 or 3, in which the clamp is mounted for pivotal movement with respect to the support.

5. A conductor spacer according to any of the preceding claims, in which the outer sleeve is cylindrical and the deformations project radially inwards from said sleeve.

6. A conductor spacer according to any of the preceding claims, in which the deformations lie in a plane disposed at a right-angle to the longitudinal axis of the outer sleeve.

7. A conductor spacer according to any of the preceding claims in which the clamp has bifurcated clamp arms which are arranged to pivot about the longitudinal axis of the inner sleeve and the outer ends of the inner sleeve have engagement means to engage co-operating means carried by the clamp arms, whereby pivotal movement of the clamp arms with respect to said axis results in corresponding rotation of the inner sleeve about that axis.

8. A conductor spacer according to Claim 7, in which the engagement means comprises a ledge disposed diametrically across an end of the inner sleeve and the co-operating means comprises a member adapted to bear against the ledge for transmission of rotational movement from the clamp arm to the inner sleeve.

9. A conductor spacer according to Claim 7 or 8, in which the inner sleeve is rotationally mounted on a tube concentric with the inner sleeve, the end portions of the tube extend respectively beyond the ends of the inner sleeve and the clamp arms are pivotally mounted on said tube end portions and secured thereon to prevent outward axial movement.

10. A conductor spacer according to any of the preceding claims in which the ends of the outer sleeve have been turned radially inwards so as to embrace the ends of the bush and prevent relative axial movement between the bush and the outer sleeve.

11. A conductor spacer according to any of the preceding claims, in which the support is of a light-weight metal and carries one or more inertia masses.

12. A conductor spacer according to Claim 1, substantially as described herein with reference to the accompanying drawings.

13. A conductor spacer substantially as described herein and substantially as shown in the accompanying drawings.

14. A method of making a conductor spacer for a multi-conductor electrical overhead transmission line, the spacer comprising a support carrying two or more spaced apart clamps each to clamp one of the conductors, the clamps each being mounted resiliently with respect to the support by means of a resilient bush assembly comprising a hollow resilient bush embraced between an inner sleeve and an outer sleeve, in which method the support is formed so that it has a housing for the outer sleeve fast with the support and then pressing into engagement in the outer sleeve a bush sub-assembly comprising the resilient bush subassembly comprising the resilient bush mounted on the inner sleeve.

1 5. A method according to Claim 14, substantially as described herein with reference to the accompanying drawings.

1 6. A conductor spacer obtained by the method of Claim 14 or 15.

1 7. A conductor spacer for a multi-conductor electrical overhead transmission line, the spacer comprising a support carrying two or more spaced-apart clamps each to clamp one of the conductors, the clamps each being mounted resiliently with respect to the support by means of a resilient bush assembly, said assembly comprising a hollow resilient bush embraced between an inner sleeve and an outer sleeve, the outer sleeve having a plurality of elongate projections or deformations disposed about the periphery of the sleeve and substantially parallel to one another and to the longitudinal axis of the outer sleeve and extending inwardly thereof so as locally to compress the bush and prevent relative rotational movement between the bush and the outer sleeve.

1 8. A bush assembly for use in the conductor spacer claimed in Claim 1 or 16, comprising a hollow resilient bush, an inner sleeve and an outer sleeve between which the bush is embraced, the outer sleeve having elongate projections or deformations disposed about the periphery of the sleeve and substantially parallel to one another and to the longitudinal axis of the outer sleeve and extending inwardly thereof so as locally to compress the bush and prevent relative rotational movement between the bush and the outer sleeve.

1 9. A bush assembly according to Claim 18, substantially as described herein with reference to the accompanying drawings.

20. A bush assembly substantially as described herein and substantially as shown in Figures 4 and 6 of the accompanying drawings.