GB2348843A - Cable jointing tool - Google Patents

Abstract

The tool comprises relatively movable workpiece-engaging surfaces eg jaws 29 arranged in a first plane for engagement with cable clamps of a number of different sizes, and a grip portion 21 extending in a second plane parallel to and spaced from the first plane, such that the grip portion of the cable jointing tool is positioned adjacent the handle of a tightening tool 40 when the cable jointing tool engages a cable clamp and the tightening tool engages the shear bolt 8. The jaws can be clamped at their set spacing.

Description

Adiustable Offset cable tool 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 (not shown) 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 a shear bolt 8, with a head 9 and neck 10 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 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 substantially planar, and is formed from a metal strip or plate. The joint holding tool 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.

Furthermore, when using the conventional planar joint holder, the user must hold the joint holder in one hand and the socket driver in the other hand in order to tighten the bolt 8. It has become apparent, however, that users are suffering injury to the arm and shoulder through the use of the conventional tools. Such injuries are caused by the sudden nature of the failure of the shear bolt 8. As the user tightens the shear bolt 8, the resistance to turning increases as the cables are progressively clamped, and the user thus applies and ever-increasing torque in a first sense to the joint holding tool and in the opposite sense to the socket driver. At the instant of failure of the shear bolt 8, the user is applying maximum opposing forces to the tools in his respective hands. The sudden failure of the shear bolt 8 often takes the user by surprise and causes a violent movement of the arms and shoulders of the user which can lead to injury.

An objective of the present invention is to provide a single tool which can accommodate cable jointing blocks of a variety of sizes, and which enables the user to effect the tightening of the cable joint clamp bolt without risking injury to the arm and shoulder.

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.

A yet further objective of the present invention is to provide a method of tightening a shear bolt of a cable clamp of one of a number of different sizes to failure using hand tools, without provoking gross arm movements by the user at the instant of failure.

According to a first aspect of the present invention there is provided a cable joint holder for use in combination with a socket driver for tightening a shear bolt of a cable clamp, wherein the cable joint holder comprises a handle having a grip portion, first and second jaws mounted to the handle and movable relatively one to the other, and releasable 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 positioned in a first plane for engagement with respective end surfaces of the cable clamp, and a grip portion extending in a plane parallel to and spaced from the first plane.

Preferably, the spacing between the plane of the grip portion and the plane of the workpiece-engaging surfaces is such that, when the socket driver is engaged with the head of the shear bolt, the grip portion of the cable joint holder extends in a plane substantially adjacent to the plane of the handle of the socket driver. Most preferably, the arrangement is such that in use the handle of the socket driver may pass adjacent the grip portion of the cable joint holder on its side remote from the cable clamp.

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

The spacing between the plane of the grip portion and the plane of the workpiece-engaging surfaces may be fixed, or may be adjustable. In a further advantageous embodiment, the grip portion is adjustably mounted to a first one of the jaws, and the other jaw is movably mounted relative to the first jaw. The grip portion may be adjustable mounted to the first jaw so that the distance between the plane of the grip portion and the plane of the workpiece-engaging surfaces may be varied, and optionally the relative angular orientation of the grip portion and the first jaw may also be varied.

A second aspect of the invention provides a method for tightening the shear bolt of a cable joint to failure, wherein the cable joint has a pair of spaced end surfaces, and a cable joint holder comprising a pair of opposed, relatively movable workpiece-engaging surfaces situated in a first plane and a grip portion extending in a second plane parallel to and spaced from the first plane has the spacing between its workpiece-engaging surfaces adjusted for engagement with said spaced end surfaces of the cable clamp, and the shear bolt of the cable joint is engaged by a socket driver so that the handle of the socket driver extends in a plane adjacent to said second plane, and wherein relative rotation of the socket driver and cable joint holder is effected by the user single-handedly grasping the grip portion of the cable joint holder and the handle of the socket driver and urging them together.

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 adjustable is a perspective view of a first cable jointing tool; Figure 4 is a perspective view of the cable jointing tool of figure 1, in use; Figure 5 is an underneath perspective view of the head of a second cable jointing tool; Figure 6 is a sectional to on the line VI-VI of figure 5; Figure 7 is a partially-exploded view of a third cable jointing tool; Figure 8 is a perspective view of the third cable jointing tool in a first position for use; and Figure 9 is a perspective view similar to figure 8, showing the cable jointing tool in a second alternative configuration for use.

Referring to figures 3 to 5, there is shown a first cable jointing tool 19 comprising three main components. The first main component is a handle section 20, comprising an elongate grip 21, a riser section 22, and a rectangular-section guide tube 23 those axis extends substantially perpendicularly to the longitudinal direction of the grip 21 and riser 22. In the illustrated embodiment, the grip 21, riser 22 and guide tube 23 are formed from a metal strip which is bent at one end to form the riser 22, guide tube 23 and a flange 24. The flange 24 overlies the handle 20, and is slightly spaced therefrom. A clamping bolt 25 extends from the handle 20 through a clearance hole in the flange 24, and is engaged at its free end by an insulated nut 26.

Extending through the guide tube 23 are a pair of substantially identical jaw components 27. Each jaw component comprises a slide bar 28 and a jaw 29 having a workpiece-engaging surface 30 extending substantially perpendicularly to its respective slide bar 28. To ensure that the workpiece engaging surfaces 30 of the jaws 29 are directly opposed one to the other, each jaw 29 is offset from its slide bar 28 in the thickness direction of the slide bar 28, by an amount equal to half the thickness of the slide bar. As seen in the figure, the jaw 29 on the right of the figure is offset upwardly from its slide bar 28, while the jaw 29 on the left of the figure is offset downwardly from its slide bar 28.

The thickness of the jaws 29 is less than the distance D (see figure 2) so 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.

The dimensions of the slide bars 28 are such as substantially to fill the interior of the guide tube 23.

While the insulated nut 26 is loosened, the slide bars 28 may be moved in the longitudinal direction of the guide tube 23 to vary the spacing between the workpieceengaging surfaces 30. When the surfaces 30 are set to the correct spacing, the insulated nut 26 may be tightened to draw the flange 24 towards the grip 22 and thus clamp the slide bars 28 to prevent relative movement.

It will be appreciated that, when the surfaces 30 are set to the correct spacing, the grip 22 and guide tube 23 may be moved longitudinally of the overlapping slide bars 28, to vary the relative position of the grip 22 and the gap between the surfaces 30. This allows the operative to select a preferred relative position for the grip 22 in relation to the block 1 of the screw clamp when the cable jointing tool is in use.

The cable jointing tool of figures 3 and 4 is preferably fabricated from sheet metal, and all surfaces of the three components of the tool are coated with an insulating material, the only exception being the workpiece-engaging surfaces 30. The tool in use thus presents no exposed live conductive surfaces, and thus ensures operator safety.

In Figure 4, the cable jointing tool is seen in use, with the spacing between its workpiece-engaging surfaces 30 adjusted to the length of the block 1 of a cable clamp, and engaging the end surfaces of the block. The grip 2 is aligned with the shear bolt of the cable clamp, and a socket driver 40 is fitted to the shear bolt 8.

The socket driver 40 comprises a ratchet head 41 and an elongate handle 42, and has a driving socket 43 engageable with the head 9 of the shear bolt 8. The driving socket 43 extends substantially perpendicularly to the handle 42 of the socket driver, and in use spaces the plane of rotation of the handle 42 axially from the head end of the shear bolt.

As can be seen from figure 4, the riser 22 is so dimensioned as to position the grip 21 adjacent the plane of rotation of the handle 42 of the socket driver 40.

In the view shown, the grip 21 is slightly below the handle 42 of the socket driver 40.

In use, the cables C are assembled in the channel section 2 of the screw-clamp, and the block 1 is then slid into position. The insulated nut 26 of the cable jointing tool 20 is loosened, and the workpiece engaging surfaces 30 of the jaws 29 are positioned adjacent the ends of the block 1 of the screw clamp. The grip 21 is positioned in alignment with the shear bolt 8 of the clamp, and the insulated nut 26 is then tightened to fix the jaws 29 and grip 21 in position. The operative may then grasp the grip 21 with one hand, while with the other hand he applies the socket driver 40 to the shear bolt 8. By applying opposing moments to the cable jointing tool 20 and the driver 40, the shear bolt 8 is driven into the block 1 and clamps the cables C against the channel section 2.

In the initial stages of the tightening operation, the user may hold the grip 21 of the cable jointing tool 20 in one hand, and the handle 42 of the socket driver in the other hand. As the torque to be applied to the shear bolt 8 increases, the user brings the handle 42 of the socket driver to a grasping position spaced from the grip 21 by an amount sufficiently small as to enable the user to grasp both the grip 21 and the handle 42 in one hand.

The user then uses that hand to squeeze the grip 21 and handle 42, so as to bring the handle 42 closer to the grip 21, further tightening the shear bolt 8. The user repeatedly returns the socket driver handle 42 to the grasping position, and squeezes the grip 21 and the handle 42 together until the shear bolt 8 fails. The joint is then complete, and the jointing tool 20 is removed from the clamp. The broken-off head 9 and neck 10 of the shear bolt 8 are removed from the socket 43 of the driver 40 and discarded, readying the driver for the next tightening operation.

Figures 5 and 6 show a second jointing tool of the invention, different from the first embodiment in that only one of the two jaws is movable relative to the grip.

The jointing tool of Figures 5 and 6 comprises two main components, the first main component being a grip 51, which is integrally formed with a riser 52. Integrally formed with the riser 52 is a guide channel 53 which comprises two side flanges 54 and 55, and a web 56. The grip 51 and riser 52 extend substantially perpendicularly from one end of the side flange 55 of the guide channel 53. Extending from the other end of the other side flange 54 of the guide channel 53 is a fixed jaw 57. The fixed jaw 57 has a first workpiece-engaging surface 58 extending perpendicularly relative to the guide channel 53 and facing towards the first end of the guide channel 53.

The second main component of the tool is a movable jaw 59, which comprises a slide bar 60 receivable in the guide channel 53. The movable jaw 59 comprises a second workpiece-engaging surface 61 which faces towards the first workpiece-engaging surface 58 when the slide bar 60 is in the guide channel 53.

The web 56 of the guide channel 53 is formed with a longitudinally extending slot 62, seen in figure 6. The slide bar 60 is formed with an opening 63 aligned with the slot 62, and a clamp bolt 64 passes through the slot 62 and the opening 63. The clamp bolt 64 has a head 65 which underlies the web 56, and may be formed with a squared section 66 to prevent the clamp bolt 64 from rotating relative to the guide channel 53 while allowing the clamp bolt 64 to move longitudinally of the guide channel 53 in the slot 62. An insulated nut 67 is threadedly engaged with the end of the clamp bolt 64, to overlie the slide bar 60.

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 58 and 61. On the underside of the web 56, and insulated housing 68 provides a clearance for the head 65 of the clamp bolt 64 to move along the slot 62, while preventing an operative from touching any exposed live metal part.

As before, the thickness of the jaws 57 and 59 is such 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.

The use of the tool is substantially as described in relation to the tool of figures 3 and 4, in that the spacing between the surfaces 58 and 61 is adjusted to suit the clamp, and the grip 51 is grasped with, and squeezed towards, the handle of a socket driver applied to the shear bolt until the neck 10 of the shear bolt fails.

If the operative then has to complete a joint using a different size of screw clamp, he simply loosens the insulated nut 26 or 67 of the cable jointing tool, and repositions the jaws 29 or the jaw 59, respectively, so that the workpiece engaging surfaces 30 or 58 and 61 are appropriately spaced for the new clamp.

A further alternative embodiment of the cable jointing tool is seen in perspective view in figures 7 to 9. In this embodiment, the cable jointing tool has three main components: a handle 70, a fixed jaw 57 and guide channel, and a movable jaw 59. The fixed and movable jaws are similar to those of the figure 5 and 6 embodiment, and like parts are given like references for brevity of description.

The handle 70 comprises an elongate grip 71, to one end of which is joined a first end of a riser 72. The riser 72 is circular in cross-section, and is formed at its other end remote from the grip 70 with a key or spline 73 extending along the riser.

To the sidewall 55 of the guide channel 53, opposite the jaw 57, a mounting ring 74 is integrally attached. The mounting ring 74 is split at 75, and a clamping bolt 76 with an insulated head 77 extends through a clearance hole in a flange 78 adjacent the split 75. A number (in this example three) of slots 79 are formed in the inner surface of the mounting ring 74.

The mounting ring 74 defines a circular opening 80 into which the end of the riser 72 may be inserted, with the key or spline 73 being received in one of the slots 79 to locate the riser in one of a number of angular positions relative to the guide channel 53. By tightening the clamp bolt 76, the mounting ring 74 may be closed to grip the riser 72, once the distance between the grip 71 and the guide channel 53 is suitably adjusted.

The use of the tool is substantially as described in relation to the tools of figures 3 to 6, in that the spacing between the jaws 57 and 59 is adjusted to suit the clamp, and the grip 51 is grasped with, and squeezed towards, the handle of a socket driver applied to the shear bolt until the neck 10 of the shear bolt fails.

Additionally, the spacing between the planes of the grip 71 and the jaws 57,59 can be adjusted to suit the socket driver by loosening the clamp bolt 76, moving the clamping ring 74 along the riser 72 to the required position, and retightening the clamp bolt 76. When the socket 43 of the socket driver is changed to fit a different diameter shear bolt, the axial length of the socket may change, altering the spacing between the block 1 of the clamp and the plane of rotation of the handle 42 of the socket driver, in use. By adjusting the position of the mounting ring 74 on riser 72, the user can alter the effective length of the riser 72 to ensure that grip 71 is always correctly positioned with respect to the socket driver handle.

Figures 8 and 9 show the grip 71 and riser 72 in different angular positions relative to the guide channel 53. In figure 8, the grip 71 extends obliquely away from the guide channel 53, whereas in figure 9 the grip 71 extends substantially perpendicularly relative to the guide channel. This adjustment allows the user to align the grip 71 so that it extends substantially tangentially with respect to the shear bolt, when the tool is applied to a clamp 1. In such a position, the riser height may be adjusted to bring the grip 71 into the same plane as the handle 42 of the socket driver, in use, and still permit the grip 71 and handle 42 to be close enough for the user to grip with one hand during final tightening.

Placing the grip 71 of the jointing tool and the handle of the socket driver in the same plane substantially eliminates asymmetric forces or moments being applied to the clamp and cables during final tightening of the shear bolt to failure.

The embodiments of the cable jointing tool described above are exemplary, and are not intended to limit the scope of the present application. Alternative forms of clamping means to secure the parts against relative movement are 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 relatively movable parts are held captive, i. e. they are not removable from the tool. In the embodiments shown, this may be achieved by riveting the ends of the clamping bolts so that the insulated nuts are not removable therefrom. Likewise, end stops 81 may be provided the end of each slide bar 27 opposite its jaw 29 to prevent the slide bars 27 from leaving the guide tube 23 of the tool of figures 3 and 4. The end stops 81 may be machine screws received in tapped holes in the slide bars 27, with their exposed heads insulated.

Claims (13)

1. Claims 1. An insulated cable jointing tool comprising a head portion including a pair of oppositely-facing workpieceengaging surfaces for applying a torque to a workpiece, and a grip portion for manually grasping the tool to apply a force thereto; wherein the workpiece-engaging surfaces are relatively movable to vary a spacing therebetween and the tool further comprises releasable clamping means for securing the workpiece-engaging surfaces relative one to the other; and wherein the workpiece-engaging surfaces are in a first plane and the grip portion extends in a second plane substantially parallel to the first plane and spaced therefrom.
2. 2. A tool according to claim 1, wherein the oppositely- facing workpiece-engaging surfaces comprise a pair of jaws.
3. 3. A tool according to claim 2, wherein one of the jaws is movable relative to the grip portion.
4. 4. A tool according to claim 2, wherein both of the jaws are movable relative to the grip portion.
5. 5. A tool according to any preceding claim, wherein the spacing between the first and second planes is adjustable.
6. 6. A tool according to claim 5, wherein the grip portion is connected to the workpiece-engaging surfaces by a riser whose effective length is adjustable to vary the spacing between the first and second planes.
7. 7. A tool according to claim 6 wherein the grip portion is positionable in a number of angular positions relative to the workpiece-engaging surfaces.
8. 8. 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.
9. 9. A method of tightening a shear bolt of a cable joint to failure using a tool according to any preceding claim, comprising the steps of: adjusting the spacing of the workpiece-engaging surfaces of the tool to suit the cable joint, and securing the workpiece-engaging surfaces relative one to the other; engaging the cable joint with the workpiece-engaging surfaces of the tool; engaging the shear bolt with a driver having a handle extending in a plane of rotation substantially perpendicular to the axis of the shear bolt and adjacent the plane of the grip portion of the tool; grasping the driver handle and the grip portion of the tool in one hand; and squeezing the driver handle and the grip portion to bring them closer together.
10. 10. A method according to claim 9, wherein the shear bolt is engaged with a socket driver.
11. 11. A cable jointing tool substantially as described herein, with reference to figures 3 and 4, figures 5 and 6, or figures 7 to 9 of the accompanying drawings.
12. 12. A method of tightening a shear bolt, substantially as herein described.
13. 13. A method of jointing cables, substantially as herein described with reference to figures 1 to 9 of the accompanying drawings.