GB2348840A

GB2348840A - Cable jointing tool

Info

Publication number: GB2348840A
Application number: GB9908308A
Authority: GB
Inventors: Walter Snaith Sample
Original assignee: CLYDESDALE Ltd
Current assignee: CLYDESDALE Ltd
Priority date: 1999-04-12
Filing date: 1999-04-12
Publication date: 2000-10-18
Also published as: GB9908308D0

Abstract

An insulated cable jointing tool for holding a cable clamp has a handle 21, first and second relatively movable jaws 23, 25, and releaseable clamping means 28 operable to prevent relative movement of the jaws, each jaw being formed with a respective one of a pair of opposed workpiece engaging surfaces 24 for engagement with respective end surfaces of the cable clamp. The handle may be fixed relative to one of the jaws or both jaws may move, and the releaseable clamping means may comprise a screw clamp or a cam-action clamp.

Description

CABLE JOINT HOLDER The present invention relates to hand tools, and is particularly concerned with electrically insulated hand tools for use in jointing high-voltage cables.

Electricity cables are conventionally joined at underground locations by clamping the cables together using a screw-clamp. A conventional screw clamp is illustrated in figures 1 and 2, and comprises a block 1 and a channel section 2 formed from metal, preferably aluminium. The block 1 and channel section 2 are so dimensioned that the block 1 is receivable between the side walls 3 and 4 of the channel section 2, and interengaging undercut rib and groove formations 5 and 6 enable the block 1 to slide in the longitudinal direction of the channel 2 while preventing the block from moving laterally out of the channel 2 in the vertical direction as seen in figure 1. The block 1 is formed with a threaded bore 7 in which is received a shear bolt 8. The shear bolt 8 comprises a bolt head 9 engageable by a driving tool, a tapered neck region 10, and a threaded end portion 11. The cross-sectional area of the neck region 10 of the shear bolt 8 is related to the amount of tightening torque which is to be applied to the threaded end portion to clamp the cable to the channel section.

The block may be formed with a longitudinally extending bore 12, intersected by a transverse bore 13 in which a grub screw 14 is accommodated. Additional cables may be secured in the bore 12, to make electrical connections to the main cable or cables held between the channel section 2 and the block 1. The screw clamps are available in a variety of different sizes, to suit different diameters of cable C and to accommodate different numbers of cables to be joined. Each size of screw clamp has a correspondingly designed shear bolt, with a head of a predetermined size.

In use, the cables C to be jointed are laid into the channel section 2 and the block 1 is then slid into the channel 2 over the cables. The shear bolt 8 is then tightened down onto the cables, compressing them together and bringing the undercut rib and groove formations of the block 1 and the channel 2 into tight gripping engagement. When sufficient torque is applied to the shear bolt to ensure a reliable joint between the cables, the narrower end of the neck region 10 of the shear bolt snaps, leaving the threaded end portion 11 of the shear bolt firmly engaging the block 1 and the cables. The bolt head 9 and neck 10 are discarded, leaving a permanent joint between the cables C.

In order to enable operatives to work on live cables at minimum risk, insulated hand tools have been developed to enable a worker to hold the screw clamp with a first tool, and to engage the shear bolt 8 with a second tool so that driving torque can be applied to the head 9 of the shear bolt 8 while an opposing torque is applied to the block 1 of the screw clamp. This arrangement prevents any lateral force being applied to the cable itself, and thus avoids damage to the cable. As can be seen from figures 1 and 2, the block 1 protrudes above the channel 2 by only a small distance, and since there may be a wire present in the bore 12 and extending out of one end of the block 1, the available height D for a tool to engage the block 1 is limited. Conventional mechanic's spanners having the required spacing between the jaw faces are too thick to fit between the upper edges of the side walls 3 and 4 of the channel section 2 and the lower edge of the bore 12, and such spanners are not electrically insulated.

Joint holding tools have been developed to engage the end surfaces of the block 1 between the bore 12 and the upper edges of the side walls of the channel section 2, and these conventional joint holding tools generally comprise a straight flattened handle section having at one end a head, the head including a substantially rectangular cutout whose sides are spaced apart by a fixed distance equal to the length of the block 1. The orientation of the handle and the head is such that when the head engages a block of a cable clamp, the handle extends substantially perpendicularly to the longitudinal direction of the cable clamp. The conventional joint holding tool is formed from a metal strip or plate, and is coated with an electrically insulating material over its entire surface with the exception of the cut-out, where the metal is exposed to engage the metal of the block, in use.

The bolt head 9 of the shear bolt 8 is conventionally tightened by engaging it with an insulated socket driver, the driver having interchangeable sockets to suit each particular size of the head 9 of the shear bolt 8.

However, to provide a purchase on the block 1 of the screw clamp, the operative requires a different holding tool for each size of screw clamp, since the tool comprises a pair of fixed opposing engagement surfaces spaced apart by a distance equal to the longitudinal dimension of the block 1 of a particular screw clamp.

The operative thus has to carry with him selection of tools to suit all of the sizes of screw clamps which he may encounter during the course of his work.

The provision of a selection of tools for each operative is thus expensive, and unnecessarily burdens the operative with a heavy tool bag. It has also been found in practice that one or more tools from a set may become mislaid, and the operative then arrives at the work site with an incomplete set of tools, and may be without the correct tool to carry out the task.

An objective of the present invention is to provide a single tool which can accommodate cable jointing blocks of a variety of sizes.

A further objective of the present invention is to provide a cable jointing tool with a handle which can, in use, occupy a number of different positions relative to the cable joint being held.

According to a first aspect of the invention, there is provided an insulated cable jointing tool for holding a cable clamp having a pair of spaced end surfaces, the tool comprising a handle or grip, first and second jaws movable relatively one to the other, and releaseable clamping means operable to prevent relative movement of the jaws, each jaw being formed with a respective one of a pair of opposed workpiece engaging surfaces for engagement with respective end surfaces of the cable clamp.

In a preferred embodiment of the invention, one of the jaws is fixed relative to the handle or grip. In a further advantageous embodiment of the invention, the releaseable clamping means comprises a screw clamp.

Embodiments of the present invention will now be described in detail, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a cable clamp prior to tightening the shear bolt; Figure 2 is a longitudinal section of the cable clamp of figure 1; Figure 3 is a perspective view of a head of a cable jointing tool according to the present invention; Figure 4 is an underneath perspective view of the head of the cable jointing tool of figure 3; Figure 5 is a sectional view on the line V-V of figure 4; Figure 6 is a perspective view of a cable jointing tool according to a second embodiment of the invention.

Referring to figures 3 to 5, there is shown a first cable jointing tool 20 comprising two main components. The first main component of the tool is a handle section 21, which is integrally formed with a guide channel 22 which comprises two side flanges 22a and 22b, and a web 22c.

The handle section 21 extends substantially perpendicularly from one end of the side flange 22a of the guide channel 22. Extending from the other end of the other side flange 22b of the guide channel 22 is a fixed jaw 23. The fixed jaw 23 has a first workpieceengaging surface 24 extending perpendicularly from the guide channel 22 and facing towards the first end of the guide channel 22.

The second main component of the tool is a movable jaw 25, which comprises a slide bar 26 receivable in the guide channel 22. The movable jaw 25 comprises a second workpiece-engaging surface 26 which faces towards the first workpiece-engaging surface 24 when the slide bar 26 is in the guide channel 22.

The web 22c of the guide channel 22 is formed with a longitudinally extending slot 27, seen in figure 5. The slide bar 26 is formed with an opening 33 aligned with the slot 27, and a clamp bolt 29 passes through the slot 27 and the opening 33. The clamp bolt 29 has a head 30 which underlies the web 22c, and may be formed with a squared section 31 to prevent the clamp bolt 29 from rotating relative to the guide channel 22 while allowing the clamp bolt to move longitudinally of the guide channel 22 in the slot 27. An insulated nut 28 is threadedly engaged with the end of the clamp bolt 29, to overlying the slide bar 26.

The first and second main components of the cable jointing tool are preferably formed from metal plate, and are covered with an insulating material on all sides with the exception of the first and second workpiece-engaging surfaces 24 and 26. On the underside of the web 22c, an insulated housing 32 provides a clearance for the head 30 of the clamp bolt 29 to move along the slot 27, while preventing the operative from touching any exposed live metal part.

The thickness of the fixed jaw 23 and movable jaw 25 are so arranged that the jaws may engage the end surfaces of the block 1 of a screw clamp, and may extend between the upper edges of the side walls 3 and 4 of the channel section 2 of the screw clamp and the lower edge of the bore 12 in the block 1.

In use, the cables C are assembled in the channel section of the screw-clamp, and the block 1 is then slid into position. The insulated nut 28 of the cable jointing tool 20 is loosened, and the workpiece engaging surfaces 26 and 24 of the jaws 25 and 23 are positioned adjacent the ends of the block 1 of the screw clamp. The insulated nut 28 is then tightened to fix the jaw 25 relative to the jaw 23. The operative may then grasp the handle section 21 with one hand, while with the other hand he applies the tightening tool to the shear bolt 8.

By applying opposing moments to the cable jointing tool 20 and the tightening tool, the shear bolt 8 is driven into the block 1 and clamps the cables C against the channel section 2. The operative continues to tighten the shear bolt 8 until the neck 10 of the shear bolt 8 fails. The joint is then complete.

If the operative then has to complete a joint using a different size of screw clamp, he simply loosens the insulated nut 28 of the cable jointing tool 20 and repositions the movable jaw 25 so that the workpieceengaging surfaces 24 and 26 are appropriately spaced for the new joint.

An alternative embodiment of the cable jointing tool is seen in perspective view in figure 6. In this embodiment, the cable jointing tool has three main components.

The first main component is a handle section 40, comprising an elongate grip 41 and a rectangular-section guide tube 42 those axis extends substantially perpendicularly to the longitudinal direction of the grip 41. In the illustrated embodiment, the grip 41 and guide tube 42 are formed from a metal strip which is bent at one end to form the guide tube 42 and a flange 43. The flange 43 overlies the grip 41, and is slightly spaced therefrom. A clamping bolt extends from the grip 41 through a clearance hole in the flange 43, and is engaged at its free end by an insulated nut 44.

Extending through the guide tube 42 are a pair of substantially identical jaw components. Each jaw component comprises a slide bar 45 and a jaw 46 extending substantially perpendicularly to the slide bar 45. To ensure that the workpiece engaging surfaces 47 of the jaws 46 are directly opposed one to the other, each jaw 46 is offset from its slide bar 45 in the thickness direction of the slide bar 45, by an amount equal to half the thickness of the slide bar. As seen in the figure, the jaw 46 on the right of the figure is offset upwardly from its slide bar 45, while the jaw 46 on the left of the figure is offset downwardly from its slide bar 45.

The dimensions of the slide bars 45 are such as substantially to fill the interior of the guide tube 42.

While the insulated nut 44 is loosened, the slide bars 45 may be moved in the longitudinal direction of the guide tube 42 to vary the spacing between the workpiece engaging surfaces 47. When the surfaces 47 are set to the correct spacing, the insulated nut 44 may be tightened to draw the flange 43 towards the grip 41 and thus clamp the slide bars 45 to prevent relative movement.

It will be appreciated that, when the surfaces 47 are set to the correct spacing, the grip 41 and guide tube 42 may be moved longitudinally of the overlapping slide bars 45, to vary the relative position of the grip 41 and the gap between the surfaces 47. This allows the operative to select a preferred relative position for the grip 41 in relation to the block 1 of the screw clamp when the cable jointing tool is in use.

The cable jointing tool of figure 6 is preferably fabricated from sheet metal, and as before all surfaces of the three components of the tool are coated with an insulating material, the only exception being the workpiece-engaging surfaces 47. The tool in use thus presents no exposed live conductive surfaces, and thus ensures operator safety.

The embodiments of the cable jointing tool described above are exemplary, and are not intended to limit the scope of the present application. Alternative embodiments are envisage wherein one or both of the workpiece-engaging surfaces is movable relative to a handle part of the tool, and other forms of clamping means to secure the parts against relative movement are also foreseen. For example, cam-operated clamping means may replace the screw clamps described in relation to the exemplary embodiments.

In preferred embodiments of the cable jointing tool, the movable parts are held captive, i. e. they are not removable from the tool. In the embodiment shown in figures 3 to 5, this may be achieved by riveting the upper end of the clamping bolt 29 so that the insulated nut 28 is not removable therefrom. Likewise, the insulated nut 44 of figure 6 may be held captive to its clamping bolt, and end stops 48 may be provided at the end of each slide bar 45 opposite its jaw 46 to prevent the slide bar 45 from leaving the guide tube 42. The end stops 48 may be machine screws received in tapped holes in the slide bars 45, with their exposed heads insulated.

Claims

CLAIMS: 1. An insulated cable jointing tool for holding a cable clamp having a pair of spaced end surfaces, the tool comprising grip means, first and second relatively movable jaws, and releaseable clamping means operable to prevent relative movement of the jaws, each jaw being formed with a respective one of a pair of opposed workpiece engaging surfaces for engagement with respective end surfaces of the cable clamp.
2. A tool according to claim 1, wherein the grip means is fixed relative to one of the jaws.
3. A tool according to claim 1 or claim 2, wherein the first and second jaws are both movable relative to the grip means.
4. A tool according to any preceding claim, wherein the releaseable clamping means comprises a screw clamp.
5. A tool according to any of claims 1 to 3, wherein the releaseable clamping means comprises a cam.
6. A tool according to any preceding claim, wherein the external surfaces of the tool are provided with an electrically insulating coating, with the exception of the workpiece engaging surfaces.