GB2121243A

GB2121243A - Conductor spacers

Info

Publication number: GB2121243A
Application number: GB08311777A
Authority: GB
Inventors: Edwin B Moore; Rodriguez-Solano Mi Estarallas
Original assignee: MATERIAL AUX ELECT
Current assignee: MATERIAL AUX ELECT
Priority date: 1982-05-07
Filing date: 1983-04-29
Publication date: 1983-12-14
Also published as: ES8305165A1; ES512003A0; GB8311777D0

Abstract

In a conductor spacer for multi- conductor electrical overhead transmission lines the conductor clamps are mounted resiliently on their support body by means of resilient bush assemblies. The bush assemblies each comprise an elastomeric bush 40 embraced between inner 41 and outer 45 sleeves, the outer sleeve being secured to the bush by securement means extending inwardly from the outer sleeve, e.g. by punching apertures with inwardly deformed edges. Where the body of the spacer comprises hollow component half- shells 13, 14 the inner sleeve of the bush assembly together with the clamp arm 25 can be used to hold the half-shells together. <IMAGE>

Description

SPECIFICATION Conductor spacers This invention relates to conductor spacers for multi-conductor or bundled electrical overhead transmission lines 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 level 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 annular 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 very cold winter conditions, between the bush and outer sleeve yet avoids the expense of chemical bonding.

In a first aspect the invention comprises 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 elastomeric bush embraced between an inner sleeve and an outer sleeve, the outer sleeve being secured to the bush by securement means extending inwardly from the outer sleeve.

In a second aspect the invention comprises bush assembly for use in the conductor spacers of the first aspect of the invention, comprising a hollow elastomeric bush, an inner sleeve and an outer sleeve between which the bush is embraced, the outer sleeve being secured to the bush by securement means extending inwardly from the oúter sleeve.

The bar or frame of the conductor spacers of this invention 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 particularly, 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 the 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 elastomeric bush is 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 is in contact with 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 securement means conveniently extends radially inwards from that sleeve. In a preferred form of the invention the securement means has been formed by piercing or otherwise deforming the outer sleeve. For example, the piercing can be such as to have produced in the outer sleeve an aperture the edge or edges of which constitute the securement means. Thus, for example, where such an aperture has a circular continuous edge that edge can constitute the securement means; if the aperture is square then normally it will have four separate edges which can together constitute the securement means. In either of these examples the edge or edges of the aperture preferably press against and locally deform the outer periphery of the elastomeric bush without actually piercing the periphery.However, if desired, the securement means can be such as to pierce the periphery of the bush through this arrangement carries with it the risk that the bush may be weakened thereby.

The securement means preferably comprises two or more (for example three or five) like spacedapart component securement means, for example three circular apertures punched in the outer sleeve from the exterior surface thereof, the apertures 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 apertures providing the securement means 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 securement means can be disposed in two or more planes.

In one form of the invention the bar or frame comprises two component shells which preferably abut each other in a plane which is a median plane of the bar or frame. The shells can, for example, be half shells and can be pressings of aluminium, an aluminium alloy or other light-weight metal.

Where such a metal is used it is normal to provide the bar or frame with one or more weights to increase the inertia of the spacer. Where the bar or frame comprises two or more shells, it is a feature of preferred embodiments of the bush assembly of the invention that it can provide the means of holding together the component shells. Thus, where the housing for the bush assembly is provided partly by an aperture in a first half shell and partly by a corresponding aligned aperture in a second half shell, a bush assembly can be used whose inner sleeve has end portions which extend respectively substantially beyond the ends of the bush and are splayed outwardly so as to conform to the surface of the half shells and thereby hold the two shells together.In a particularly advantageous form of the invention this arrangement serves also to retain in position a bifurcated clamp arm as is described below with reference to the drawings.

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 1 is a 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 4 is a cross-section on the line B-B of Figure 1; and FIGURE 5 is a cross-section on a diameter of the bush assembly of the spacer damper prior to incorporation therein.

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. The body 1.0 comprises two jive hollow half-shells 13, 14 held together by means described below. Each end portion of each body shell has formed therein a circular aperture, the apertures in the shells at each end of the body being aligned so as to provide a housing of circular cross-section to accommodate bush 1 5 or 1 6 as is described in greater detail below.

The end portions of the body shells are of a shape such that the thickness of the body at its end portions 1 7, 18 is less than its thickness at the middle portion separating those end portions.

This reduced thickness is to accommodate the clamps within the minimum practicable overall thickness of the spacer damper. The body end portions 17, 18 are separated from the middle portion by shoulders 19, 20 which serve respectively as limit stops for the rotational movement of clamps 1 2,11 with respect to the body.

There is located within the middle portion of body 10 a cylindrical bar 21 (Figure 3) which serves 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 bar is of a diameter slightly less than the minimum internal dimension of the body middle portion and is held in place by means of a packing 22 (or by a suitable local deformation of the body shells 1 3 and 14). The end portions of the body 10 have small apertures 23, 24 formed at the bottom thereof to act as drains to prevent the accumulation of rain water within the body.

The overali 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 and 5, the construction of the clamp 12. In general terms the clamp comprises a bifurcation 25 having a pair of clamp arms 25.1, 25.2 each having formed therein an aligned circular location aperture having a chamfered circumferencen; a clamp cap 26; bush assembly 15; and a shear-head bolt assembly 27.

The clamp is pivotally mounted on body end portion 1 7 and the clamp cap 26 has a floating relationship to clamp arms 25 being connected to the latter by means of the shear-head bolt assembly 27.

The outer end portions of the clamp arms 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 arms, clamp cap and clamp jaws could be of an aluminium alloy.

The shear-head bolt assembly 27 comprises a shear-head bolt 30 the shank end of which carries an externai thread by means of which it is retained in the clamp arm 25. Between the head of the bolt and a recess in the clamp cap 26 there is mounted a galvanised steel washer 31 and a Belleville washer 32 of sheradised steel.

Referring now to Figure 5 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 reduced outside diameter compared with that of the central portion 44 extending between them. The outer sleeve 45 of the bush assembly comprises an aluminium alloy cylinder.

The bush assembly of Figure 5 is 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. This sub-assembly is then presented to the cylindrical member to be used as outer sleeve 45, the inside diameter of the cylinder being such that the sub-assembly is a press fit within it. The sub-assembly is forced into the cylinder so as to be disposed midway between the ends thereof, and a plurality of small apertures 46 are punched in the cylinder, the punching being carried out so as to deform radially inwards the aperture edge and locally to compress the bush 40.These apertures, which can be, for example three or five in number, are spaced equidistant from one another about a circumference of the outer sleeve 45 and lie in a plane which is at a right-angle to the longitudinal axis of the bush. In consequence, bush 40 is firmly gripped between inner sleeve 41 and outer sleeve 45 and the edges of the inturned apertures prevent the bush from moving with respect to the outer sleeve in either a circumferential or longitudinal direction.

The completed bush assembly is then inserted into the housing (referred to above) in end portion 1 7 of the spacer damper body 10, the dimensions of the housing being such that the bush assembly is a push 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 defined by the internal edges of the two body shells 13, 14; and the ends of the outer sleeve 45 are then deformed radially outwardly so as to embrace the curved, and preferably noncircular, periphery of the housing as is shown in Figure 4.

A pair of aluminium alloy washers 47, 48 are located on end portions 42, 43 of inner sleeve 41.

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 the location apertures are aligned respectively with the ends of inner sleeve 41, and the clamp arms are straightened thereby causing their location apertures to engage respectively with the sleeve end portions 42, 43.

The outer ends of inner sleeve 41 are then deformed radially outwards so as to conform to the chamfered edges of the location apertures in clamp arms 25.1, 25.2, preferably of a noncircular shape in order to impede relative movement, as is shown in Figure 4.

The construction 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 45, resulting in a major ecnomy in manufacture. The securement means provided by the pierced apertures in the outer sleeve prevent movement relative to the bush such as occurs with other non-bonded systems under extremes of temperature. The frictional forces arising at the interface between the exterior surface of outer sleeve 45 and the housing in the spacer body is sufficient to prevent relative movement between them.

The bush of the bush assembly of this invention can comprise any suitable elastomer. Very good results have been obtained using, for example, a polynorbornene 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.

If desired, there can be used in the conductor spacers of this invention bush assemblies according to our U.K. Patent Application (Title: Conductor Spacers, Methods of Making Conductor Spacers and Bush Assemblies) of even date instead of the bush assemblies described herein.

Claims

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 hollow elastomeric bush embraced between an inner sleeve and an outer sleeve, the outer sleeve being secured to the bush by securement means extending inwardly from the outer sleeve.

2. A conductor spacer according to Claim 1, in which the clamp is mounted on the inner sleeve of the bush assembly.

3. A conductor spacer according to Claim 1 or 2, in which the outer sleeve is cylindrical and the securement means projects radially inwards from said sleeve.

4. A conductor spacer according to Claim 1,2 or 3 in which the securement means has been formed by piercing the outer sleeve.

5. A conductor spacer according to Claim 4, in which said piercing has produced an aperture the edge or edges of which constitute said securement means.

6. A conductor spacer according to Claim 5, in which said edge or edges press against and locally deform the outer periphery of the bush without piercing it.

7. A conductor spacer according to any of the preceding claims, in which the securement means comprises two or more like spaced-apart means substantia.lly in a plane disposed at a right-angle to the longitudinal axis of the bush.

8. A conductor spacer according to any of the preceding claims, in which the support is a hollow bar or frame and comprises two like component shells.

9. A conductor spacer according to Claim 8 in which the two shells abut each other in a plane which is a median plane of the bar or frame.

10. A conductor spacer according to Claim 8 or Claim 9, in which each bush assembly is located in aligned apertures in the component shells and together the plurality of bush assemblies hold together the two shells.

11. A conductor spacer according to Claim 10, in which the ends of the inner sleeve are formed with end portions which extend respectively beyond the ends of the bush, the respective clamp has a bifurcation by means of which it is mounted on said end portions and the outer extremities of said end portions are splayed and subsequently closed whereby they serve to retain the clamp in place on the inner sleeve and to hold the component shells together.

12. A conductor spacer according to any of Claims 8 to 11, in which the component shells are pressings of a light-weight metal and the bar or frame carriers one of more inertia masses.

1 3. A conductor spacer according to any of the preceding claims, in which end portions of the outer sleeve have been splayed so that the outer surface of said sleeve conforms to the surrounding surface of a housing in the support.

14. A conductor spacer according to any of the preceding claims, in which the inner sleeve is bonded to the bush.

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

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

1 7. A bush assembly for use in the conductor spacer claimed in Claim 1, comprising a hollow elastomeric bush, an inner sleeve and an outer sleeve between which the bush is embraced, the outer sleeve being secured to the bush by securement means extending inwardly from the outer sleeve.

18. A bush assembly according to Claim 17, substantially as described herein with reference to the accompanying drawings.

1 9. A bush assembly substantially as described herein and substantially as shown in Figure 5 of the accompanying drawings.