GB2065995A

GB2065995A - Electric connection method and tool for use therein

Info

Publication number: GB2065995A
Application number: GB8039552A
Authority: GB
Original assignee: BICC BURDNY Ltd
Current assignee: BICC BURDNY Ltd
Priority date: 1979-12-12
Filing date: 1980-12-10
Publication date: 1981-07-01

Abstract

A tool for making a connection between a main conductor 21, which may be overhead, and a branch conductor 20 by means of a tapered receptacle and wedge comprises a massive base (1, 2) that provides means for securing the receptacle (19) of the connector and supports a ram (11) carrying the wedge in appropriate alignment with it. The ram may be mounted on a boom (2) pivoted to allow freer access for conductor insertion. The wedge is driven home by hammering the ram. <IMAGE>

Description

SPECIFICATION Electric connection method and tool for use therein This invention relates to a method of, and a tool for, making connections to an electric conductor (hereinafter called the 'main' conductor), which will usually, but not invariably, be an overhead-line conductor. The conductor to be connected to the main conductor (hereinafter called the tapping conductor) may be for example be a branch conductor, a jumper cable connecting a transformer or other equipment, a 'Bail' for subsequent connection of either, or a loop conductor bypassing an existing connector that has become unsatisfactory.

The conductors may independently be bare, insulated but locally bared, or in special cases insulated and not bared.

The usual current practice for making such connections is to use either a crimped connection or a screw clamp. These are perfectly effective provided the conductor surface is sufficiently clean when the connection is made, but there are cases in which this is difficult to ensure (especially on an old main line with surface corrosion when working with the line energised), and if it is riot the resulting poor connection may be difficult or impossible to rectify.

One technique that has been known for many years and avoids this difficulty by providing an inherent self-cleaning action entails locating the main conductor and the tapping conductor in a tapered receptacle (which is normally open at one side so that access to an end of each conductor is not essential) and then driving a wedge between them to complete the connection. This technique has only been used on a small scale for special purposes, however, because the only reliable way to driving the wedge has been to use an explosiveactuated tool, with consequent security and other risks.Simple hand hammering has been used in North America for some large sizes, but is not attractive because preliminary assembly of the parts is difficult, limited access makes hammering difficult and risks damage to the conductors, the receptacle is liable to be displaced by the first hammer blow, and generation of correct contact pressure depends on the linesman observing the relative position of wedge and receptacle.

In accordance with the present invention, a method of making an electrical connection between a main conductor and a tapping conductor using a tapered receptacle and a wedge comprises first securing the receptacle to a base that is massive compared with the receptacle; second positioning the main conductor in the receptacle; and third driving the wedge between the main conductor and the tapping conductor positioned in the receptacle by a series of hammer blows applied to a ram slidably supported on the base and bearing on the back of the wedge, after which the base and ram are removed.

The inertia of the base, which is preferably a little more massive than the hammer to be used in the third step, minimises the risk of the receptacle being displaced during hammering, and the end of the ram can be much more accessible than the wedge; furthermore it is easy to provide a stop for the ram that defines the required insertion of the wedge and prevents over-tightening; if required it can also be fitted with a ratchet mechanism (of the kind often used on crimping tools) that prevents withdrawal until the intended stroke has been completed.

The invention includes a tool comprising a massive base with means for securing a tapered receptacle to it with its axis in a predetermined position, a ram, and means supporting the ram for axial sliding movement in alignment with the said axis position.

Preferably the wedge is attached to the tool before the main conductor is positioned in the receptacle; and in some cases it may be feasible also for the tapping conductor to be pre-fixed in the receptacle, or even integral with it (eg. when the tapping conductor is a bail), or in other cases for the tapping conductor to be inserted in the receptacle before the main conductor so that (assuming overhead line use) only one positioning step off the ground is required.

As a further aid to easy positioning, the ram and its supports are preferably pivotally mounted on the body so that they can be positioned (on the ground) to give maximum clearance for entry of the main conductor; and guides for the main conductor could be mounted on the support if desired.

Preferably suitable spring grips are used to secure the receptacle and (when desired) the wedge. The wedge may be secured to the end of the ram, or to a separate support on the base and/or on the ram; when a separate support on the base is used it will usually need to be slidable with respect to the base to follow the first part of the ram stroke.

In most cases it is preferable for the hammer blows to be applied directly to the ram, but there may be instances in which access is particularly difficult and in which it may be desirable to use blows directed laterally with respect to the conductors; a toggle mechanism or a transverse wedge, bearing (in either case) on a fixed abutment on the support, can be used for this purpose.

Usually the tool will be fitted with a handle, preferably elongate and of insulating material, or else be suitable for gripping in a standard 'hot rod' clamp.

In the accompanying drawings: Figures 1-3 are mutually perpendicular views of a tool in accordance with the invention; Figures 4 and 5 are fragmentary views illustrating the operation of a wedge-gripping clip therein; and Figures 6 and 7 are further fragmentary views illustrating alternative wedge-gripping devices.

The massive base of the tool shown in figures 1-5 is made up to two main parts, namely a body 1 and a boom 2. These are secured together by a pivot pin 3, and in the working position the boom is rigidly held in a recess in the body; however by withdrawing it from the recess against the action of spring 4 it becomes rotatable around the pin 3 and can be placed in any convenient angular position (at least in a certain range) to get best access for conductor insertion (for example the position shown in dashed lines). The total mass of these parts is about 1.5kg.

On the body is mounted a spring clip, for securing a receptacle 5, consisting essentially of two gripping jaws 6 biassed inwardly, by springs 7 acting on appropriate fixed abutments 8.

The body also supports a stop 9 for the narrow tfront) end of the receptacle; this is reversible to cater for two receptacle sizes and is so positioned that, for each size of receptacle and wedge in a chosen range, the rear end of the wedge will be in substantially the same position when correctly driven home.

The boom 2 carries a guide 10 in which a ram 11 is a sliding fit, and which provides an abutment surface 12 which acts as a stop to forward movement of the ram by engaging a head 13 thereon. A circlip 14 makes the ram captive.

A wedge gripping unit 1 5 is mounted on the ram 11 and frictionally engaged with it; it also engages the boom 2 so as to be prevented from rotation. The assembly includes a rigid cantilever support 1 6 to define the required position of the wedge and a pair of cantilever springs 1 7 to grip it.

The receptacles and wedges to be used with the tool are preferably of the kind described in our British Patent Applications 791/4543 and 791/9682, but traditional designs can be used.

In a typical operating procedure, the boom 2 is with drawn from its recess in the head of the tool and rotated to the position shown in dashed lines in figure 1. The ram 11 is fully retracted and an appropriate wedge 1 8 (figure 4) inserted between the cantilever support 1 6 and springs 1 7 in engagement with the front end of the ram. The stop 9 is set in the appropriate position and a receptacle 1 9 clipped to the body of the tool in engagement with it. In some cases the tapping conductor 20, if not already present as an attachment to the receptacle, can now be inserted into the receptacle.

The total assembly is now presented to the main conductor 21 so as to seat it in the receptacle 1 9. If the main conductor is energised, an insulating handle or 'hot rod' 22 will be used for this purpose and if desired a suitabiy shaped guide 23 can be fitted to one or each end of the body 1 to facilitate correct positioning. The tapping conductor 20, if not already present, is now inserted.

The boom 2 is now pushed upwards until it snaps into its recess under the action of the spring 4. This can conveniently be done using the hammer required for the next operation, which is to drive the wedge home by striking the head 1 3 of the ram until it engages the stop surface 12. A hammer of about 1.25 kg is suitable, and if the conductor is energised it should of course be of a suitably insulated (or insulating) design. The wedge gripping unit 1 5 initielly advances with the ram and the wedge, but as the wedge enters the receptacle (19, figure 5) the cantilever support 16 abuts the receptacle and the gripping unit comes to rest while the wedge 1 8 is driven on into the receptacle. The tool can then be unclippped from the completed assembly.

Figures 6 and 7 illustrate two other ways in which the wedge might be attached to the ram. In the first arrangement the end of the ram 11 bears a resilient ring 24 which is a force-fit in a blind bore 25 in the back of the wedge, and in the second a moulding 26 force-fitted on the ram has resilient fingers 27 that engage the faces of and/or recesses in the wedge. In both cases it is desirable for the ram to be positively held against rotation, and it will be apparent that the arrangement of figure 6 cannot be used with an unmodified conventional wedge.

A wedge connector for use with unstripped insulated conductors is the subject of a separate application filed on the same day as this application.

Claims

1. A method of making an electrical connection between a main conductor and a tapping conductor using a tapered receptacle and a wedge comprising first securing the receptacle to a base that is massive compared with the receptacle; second positioning the main conductor in the receptacle; and third driving the wedge between the main conductor and the tapping conductor positioned in the receptacle by a series of hammer blows applied to a ram slidably supported on the base and bearing on the back of the wedge, after which the base and ram are removed.

2. A method of making an electrical connection between a main conductor and a tapping conductor using a tapered receptacle and a wedge comprising first securing the receptacle to a base that is massive compared with the receptacle and securing the wedge to a ram slidably supported on the base and bearing on the back of the wedge; second positioning of the main conductor in the receptacle; and third driving the wedge between the main conductor and the tapping conductor positioned in the receptacle by a series of hammer blows applied to the ram, after which the base and ram are removed.

3. A method as claimed in Claim 1 or Claim 2 in which the tapping conductor is inserted in the receptacle in the first step.

4. A method as claimed in Claim 1 or Claim 2 in which the tapping conductor is inserted in the receptacle between the second and third steps.

5. A method of making an electrical connection between a main conductor and a tapping conductor, substantially as described with reference to the drawings.

6. A tool for making an electrical connection between a main conductor and a tapping conductor using a tapered receptacle and a wedge, the tool comprising a massive base with means for securing a tapered receptacle to it with its axis in a predetermined position, a ram, and means supporting the ram for axial sliding movement in alignment with the said axis position.

7. A tool for making an electrical connection between a main conductor and a tapping conductor using a tapered receptacle and a wedge, the tool comprising a massive base with means for securing a tapered receptacle to it with its axis in a predetermined position, a ram, means supporting the ram for axial sliding movement in alignment with the said axis position, and means for securing a wedge to the ram at the end adjacent to the receptacle-securing means.

8. A tool as claimed in Claim 6 or Claim 7 in which the means for supporting the ram comprises a boom rotatable between a position providing the said alignment and a position allowing freer access for insertion of a conductor in the receptacle.

9. A tool for making an electrical connection between a main conductor and a tapping conductor using a tapered receptacle and a wedge, substantially as described with reference to and as shown in (a) figures 1-5 or (b) figures 1-3 and 6 or (c) figures 1-3 and 7