GB2286727A - Spacer damper for electrical cables - Google Patents

Abstract

A spacer damper comprises a frame (1) to which a plurality of arms (4) are mounted (only one arm is shown). Each arm (4) has one extremity (3) designed to grip a cable, the other extremity being provided with an enlarged end portion (6) which is received in and spaced from a cooperating recess in the frame (1) by means of a plurality of semi-conductive cylindrical insulating spacer members (27, 28, 29). In the embodiment there are four arms (4, Figure 1) and each arm can rotate about a bolt (34, Figure 2) and laterally (Figures 6 and 7). <IMAGE>

Description

SPACER DAMPER FOR ELECTRICAL CABLES The present invention relates to spacer dampers of the type typically used for spacing bundled electrical conductors suspended from pylons.

A spacer damper typically comprises at least two clamps which grip respective bundles of conductors, mounted on a frame which separates the clamps. The frame may comprise a straight bar or it may be triangular, rectangular or polygonal, depending on the number of clamps and the number of cable bundles to be separated. The clamps are mounted at the ends or corners bf the frame and comprise an arm portion and a cable grip portion. The mounting of the clamps on the frame permits a limited amount of movement of the clamps with respect to the frame, and also provides a controlled electrically semiconductive path between the clamp arm and the frame, both of which are usually made of metal.

For the purpose of providing the semiconductor path and also to damp any movement of the clamp arm (also known as the conductor arm) with respect to the frame, the arms of a spacer damper are usually attached to the frame via one or more elastomeric members. These members are the weakest part of a spacer damper and in currently available Quad/four bundle spacer dampers, for example, they may wear out after three years in areas subject to high levels of subconductor oscillation so that either the elastomeric members or the whole spacer damper have to be replaced.

It would be advantageous to provide a spacer damper in which the damping members were less susceptible to wear.

Accordinq to an aspect of the present invention, each clamp arm of a spacer damper has one extremity designed to grip a cable and the other extremity provided with an enlarged end portion which is received in and spaced from a cooperating recess in the frame by means of a plurality of spacer members.

The spacer members are preferably made from semiconducting elastomeric material.

Preferably, the spacing members are located in recesses provided in facing surfaces of the arm end portion and the frame recess respectively.

Preferably, the facing surfaces of the arm end portion and the recess are cylindrical. The recess in the frame may then be provided with an opening, preferably in its cylindrical surface, from which the arm itself extends. The opening permits a limited amount of movement of the arm about the axis of the cylindrical surfaces, the maximum amount depending on the size of the opening. Preferably the cylindrical axis is perpendicular to the longitudinal axis of the arm.

Preferably, the spacing members are cylindrical and are arranged, preferably equidistantly, around the cylindrical surfaces. Preferably their circular end surfaces protrude from the frame and the arm. This permits them to be compressed by means of additional plates provided to apply pressure to their protruding surfaces. The plates may be attached to each other, for example by means of a bolt passing through the end portion of the arm. The hole in the end portion for receiving the bolt is preferably larger than the bolt to prevent contact between the arm and the bolt.

The plates may have protruding lugs engaging in recesses provided on the clamp arm and preferably in the arm end portion to prevent the plates from rotating with respect to the arm.

Preferably the spacing members are provided in pairs, one of each pair extending to or beyond a respective end face of the cylindrical end portion. Preferably three equally spaced pairs are provided. The spacing members of each pair may be separated by a shelf provided on the cylindrical ar end portion. Alternatively, each pair may be replaced by a single cylindrical insert extending to both faces of the cylindrical arm end portion.

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which: FIGURE 1 is a plan view of a conventional spacer damper having a square frame usually known as a Quad spacer damper; FIGURE 2 is an exploded partial perspective view of a spacer damper according to the present invention; FIGURE 3 is a perspective view of part of a clamp arm viewed from an alternative angle; FIGURE 4 is an end elevation of the assembled spacer damper in its rest position with the side plate removed; FIGURE 5 is a view corresponding to Figure 4 showing the clamp arm rotated with respect to the frame; FIGURE 6 is a cross sectional view on the line VI-VI of Figure 4; and FIGURE 7 is a cross sectional view taken in the opposite direction to Figure 6 showing the arm laterally rotated.

Referring to the drawings, Figure 1 shows a Quad spacer damper having a generally square frame 1 to which clamps 2 are attached at the four corners of the square.

One of the clamps 2 is shown in cross-section. The clamps each comprise a clamp portion 3 and an arm portion 4, the arm portion being attached to the frame so as to be pivotable to a limited extent. The clamp portion 3 is conventional and will not be described in detail herein.

Figure 2 shows one clamp arm of a spacer damper according to the invention having a generally cylindrical end portion 6 which is received in a generally cylindrical through hole 7 provided at the corner of the frame 1. The through hole 7 has an opening 8 in its cylindric21 surface through which the arm 4 extends. In the assembled configuration the arm 4 is free to pivot by a limited amount with respect to the frame 1 about the axis of the cylindrical portion 6, in directions indicated by arrows X (Figure 4).

The cylindrical portion 6 has three pairs of recesses 1Oa,1Ob,11a,11b,12a,12b equally spaced about its cylindrical surface, the recesses in each pair extending from respective end faces of the cylinder axially opposite each other. The remaining portions of the cylinder between each pair of recesses form shelves 13 separating the recesses from each other.

The cylindrical through hole 7 in the frame 1 is provided with arcuate recesses around its cylindrical surface arranged in three pairs extending from opposite sides of the frame 1 at axially opposed positions. Only three of these recesses 21,22,23 are visible in Figure 2.

The other three, making up the three pairs, extend from the rear side of the frame as shown. With the arm in its normal position, symmetrical with respect to the frame, recess 21 faces recess 10a in the arm cylindrical portion 6, recess 22 faces recess ila and recess 23 faces recess 12a. The recesses not visible face recesses 10b,11b,12b likewise.

The clamp arm 4 is held with its cylindrical portion 6 located within but spaced from the cylindrical through hole 7 in the frame 1 by means of six identical cylindrical elastomeric members 24,25,26,27,28,29. Each elastomeric member is positioned between a recess, 10a,10b,11a,11b,12a or 12b, on the cylindrical end portion 6 of the clamp arm and the facing recess (eg: 21,22,23) in the through hole 7 on the frame 1. Thus, the recesses hold the elastomeric members 24-29 in place and the elastomeric members maintain an annular space 30, shown in Figure 4, between the frame 1 and the cylindrical portion 6.

The elastomeric members 24-29 are held in place by means of two circular side plates 31,32 which are positioned on either side of the frame 1, concentric with cylindrical portion 6. The side plates 31,32 are secured to each other by means of bolt 34, nut 35 and spring washer 36. To prevent the side plates 31,32 from rotating with respect to the frame 1 they are each provided with a pair of rectangular lugs 41,42 which locate in recesses 43,44 provided in the opposing faces of the frame 1. The cylindrical portion 6 of the arm 4 has a hole 45 through its centre which is larger than the bolt 34 to ensure that there is no contact between the bolt and the arm. By virtue of the semiconducting property of the elastomeric members 24-29 and the space 30 between the cylindrical portion 6 and cylindrical hole 7 the arm is not completely insulated from the frame 1.

The elastomeric inserts 24-29 protrude from the cylindrical portion 6 on the end of arm 4. In other words, the length of the cylindrical inserts is greater than the depth of the corresponding recesses 1Oa,b-12a,b. In the assembled configuration the inserts 24-29 are directly adjacent to the side plates 31,32. They are also precompressed laterally by the frame 1 and clamp arm 4 so as to be distorted as shown in Figure 4. Rotation of the arm about the cylindrical axis is resisted due to the increased compression of the elastomeric members. Figure 5 shows the maximum theoretical rotation with the arm 4 touching the frame 1. In practice the shore hardness of the elastomeric members is such that the a predetermined force is met before arm to frame contact is made.

The elastomeric members also permit some lateral movement of the clamp arm, typically +/- 10 degrees about an axis perpendicular to the cylindrical axis in directions indicated by arrows Y (Figure 6). The edges of the side plates 31,32 are slightly bevelled where they face the opening 8 as indicated by numerals 37,38 to ensure that when moving laterally the arm 4 does not touch the plates 31,32.

It will be appreciated from a comparison of Figures 4 and 5 and Figures 6 and 7 that the forces applied to the elastomeric members 24-29 are mainly compressive.

Therefore, wear of the elastomeric members is minimised and their life is prolonged.

It will be noted from Figures 6 and 7 that the edges of the cylindrical members are rounded and in fact the only significant shear forces during movement of the arms are applied to these edges as the arms are rotated laterally.

The number of elastomeric members positioned around the rotation axis may be varied, although three pairs are presently preferred. Each pair could be replaced by one cylindrical insert extending from one side plate to the other, either by omitting the shelves 13 or by providing a slot in the inserts to receive the shelves.

It will be appreciated that the number of arms provided on a frame will vary according to the intended application of the spacer damper. Currently, spacer dampers have up to eight arms mounted on one frame.

As an example of the dimensions of a typical spacer damper according to the invention, the example shown in Figure 2 is roughly to scale and the shelves 13 are 6mm deep.

The frame (l), the arm 4 and the side plates 31,32 may, for example, be formed from aluminium alloy or any other suitable material.

Claims (15)

1. A spacer damper comprising a frame to which a plurality of arms are mounted, each arm having one extremity designed to grip a cable and the other extremity being provided with an enlarged end portion which is received in and spaced from a cooperating recess in the frame by means of a plurality of spacer members.

2. A spacer damper as claimed in Claim 1 in which the spacer members are located in recesses provided in facing surfaces of the arm end portion and the frame recess respectively.

3. A spacer damper as claimedin Claim 1 or Claim 2 in which the facing surfaces of the arm end portion and the recess are cylindrical.

4. A spacer damper as claimed in Claim 3 in which the axis of the cylindrical surfaces is perpendicular to the longitudinal axis of the arm.

5. A spacer damper as claimed in Claim 3 or 4 in which the spacer members are cylindrical and are arranged equidistantly around the cylindrical surfaces of the arm end portion and the recess.

6. A spacer damper as claimed in Claim 3, 4 or 5 in which the spacer members protrude from the frame and the arm.

7. A spacer damper as claimed in Claim 6 in which the spacer members are retained by means of plates pressing on their protruding surfaces.

8. A spacer damper as claimed in Claim 7 in which the plates are attached to each other.

9. A spacer damper as claimed in Claim 8 in which the plates are secured to each other by means of a bolt passing through the cylindrical end portion of the arm.

10. A spacer damper as claimed in Claim 7, 8 or 9 in which the plates have protruding lugs which engage in recesses on the clamp arm.

11. A spacer damper as claimed in any of Claims 3 to 10 in which the spacer members are arranged in pairs, one of each pair extending to a respective end face of the cylindrical end portion.

12. A spacer damper as claimed in Claim 11 in which the spacer members of each pair are separated by a shelf provided on the cylindrical end portion.

13. A spacer damper as claimed in Claim 11 or 12 including three pairs of spacer members extending to both end faces of the cylindrical portion.

14. A spacer damper as claimed in any one of Claims 3 to 10 including three spacer members extending to both end faces of the cylindrical portion.

15. A spacer damper substantially as hereinbefore described with reference to Figures 2 to 7 of the accompanying drawings.