GB2348841A - Cable jointing tool - Google Patents

Abstract

The tool is for applying a torque to a cable clamp while a shear bolt of the cable clamp is being tightened to failure. The cable jointing tool comprises surfaces eg jaws or pins arranged in a first plane 24 to engage the cable clamp, and a grip portion 22 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 30.

Description

Cable ioint 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 screwclamp. 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 inter-engaging 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 such as a socket spanner, 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 a shear bolt, with a head of a predetermined size and a neck region having a predetermined minimum crosssectional area.

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 5 and 6 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. Conventional joint holding tools are generally flat, and comprise a straight handle section having at one end a head, the head including a substantially rectangular cut-out whose sides are spaced apart by a distance equal to the length of a 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 tool is formed from a substantially planar 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.

Conventional socket drivers comprise a substantially straight handle section having a ratchet mechanism at one end, from which the socket extends substantially perpendicularly to the direction of the handle section.

When engaged on the head 9 of the shear bolt 8, the handle section of the socket driver extends substantially perpendicularly to the axial direction of the bolt 8, and is spaced from the head of the bolt 8 by approximately 50 mm.

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.

And objective of the present invention is to provide a cable joint holder 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 method of tightening a shear bolt to failure using hand tools, without provoking gross arm movements by the user at the instant of failure.

A further objective of the present invention is to provide a cable joint holder of simple construction, capable of accommodating cable joint fittings of different sizes.

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 pair of opposed workpiece engaging surfaces in a first plane for engagement with respective oppositely facing surfaces of the cable clamp, and a grip portion extending in a plane parallel to and spaced from the first plane.

The workpiece-engaging surfaces may be a pair of jaws spaced apart by a distance corresponding to a dimension of the cable clamp. In an alternative embodiment, the workpiece-engaging surfaces may be a pair of studs extending substantially perpendicularly from a planar tool head.

Preferably, the spacing between the grip portion and 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 passes slightly above the grip portion of the cable joint holder.

A second aspect of the invention provides a method for tightening the shear bolt of a cable joint to failure, wherein the cable joint is engaged by a cable joint holder comprising a pair of opposed workpiece engaging surfaces in a first plane for engagement with respective end surfaces of the cable clamp and a grip portion extending in a second plane parallel to and spaced from the first plane, 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 grasping the grip portion of the cable joint holder and the handle of the socket driver in one hand 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 is a perspective view of a cable jointing tool according to the present invention; Figure 4 is a perspective view of the cable jointing tool of figure 3 in use; Figure 5 is a side view of the arrangement shown in figure 4; and Figure 6 is a perspective view of a cable jointing tool according to a second embodiment of the invention, in use.

Referring to figure 3, there is shown a first cable jointing tool 20. The tool has a handle section 21 comprising a grip portion 22 and a riser section 23. The riser section 23, is integrally formed with the grip portion 22 and with a head 24. The head 24 is generally Cshaped, and comprises a pair of jaws having oppositelyfacing workpiece-engaging surfaces 25 and 26, spaced apart by a distance L which corresponds to a dimension of the cable joint. Generally, the distance L corresponds to the length of the block 1 of the cable joint.

The workpiece-engaging surfaces 25 and 26 are situated in a first plane, and due to the presence of the riser section 23, the grip portion 22 is situated in a second plane spaced from the first plane by a distance H. The length of the riser section 23 is so arranged that, in use, the grip portion 22 is positioned close to the plane of rotation of the handle of a bolt-tightening tool, as will be described in detail below.

Figures 4 and 5 illustrate the cable joint holder of figure 3 engaging the block 1 of a cable clamp, while a socket driver 30 engages the head 9 of the shear bolt 8 of the cable clamp. The socket driver 30 comprises a handle 31, a ratchet head 32, and a socket 33 to engage the shear bolt 8. The socket 33 extends substantially co-axially with the shear bolt 8, and the ratchet head 32 and handle 31 extend perpendicularly to the axis of the shear bolt 8. As is clear from figures 4 and 5, the riser section 23 ensures that when the head 24 of the joint holding tool engages the block 1 of the cable clamp, the grip portion 22 is positioned in a plane adjacent that of the handle 31 of the socket driver 30.

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 cable jointing tool 20 is offered up to the cable joint such that the workpiece-engaging surfaces 25 and 26 are positioned adjacent the ends of the block 1.

The socket driver is then offered up to the shear bolt 8.

By applying opposing moments to the cable jointing tool 20 and the socket driver 30, 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 portion 22 of the cable jointing tool 20 in one hand, and the handle 31 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 31 of the socket driver to a grasping position spaced from the grip portion 22 by an amount sufficiently small as to enable the user to grasp both the grip portion 22 and the handle 31 in one hand. The user then uses that hand to squeeze the grip portion 22 and handle 31, so as to bring the handle 31 closer to the grip portion 22, further tightening the shear bolt 8. The user repeatedly returns the socket driver handle 31 to the grasping position, and squeezes the grip portion 22 and the handle 31 together until the shear bolt 8 fails. The joint is then complete.

At the moment of failure of the shear bolt 8, when the resistance felt by the user suddenly ceases, the muscular effort being exerted by the user is one of gripping the handle 31 and the grip portion 22 in one hand. The sudden failure of the shear bolt thus only causes the user's hand to be tightly clenched, and does not lead the user to make gross movements of the arms and shoulders which can cause injury.

An alternative embodiment of the cable jointing tool is seen in perspective view in figure 6. In this embodiment, the cable jointing tool comprises a grip portion 22 and a riser 23, but the riser is attached to a generally annular head 40. The head 40 lies in a plane substantially parallel to the plane of the grip portion 22, and is placed therefrom by a distance H. As before, the distance H is arranged so that the grip portion 22 of the cable jointing tool is positioned, in use, adjacent the plane of rotation of the handle 31 of a socket driver engaging the shear bolt 8 of the cable clamp.

Extending axially from the head 40 on its side remote from the grip portion 22 are a number of studs 41,42. The studs 41,42 function as workpiece-engaging surfaces to apply the torque to the cable joint. The positions of the studs 41,42 may be permanently fixed to the annular head 40. Alternatively, the studs may be adjustably mounted to the head so that the circumferential positions of the studs relative to the riser 33 may be altered. In a further alternative embodiment, the head 40 may be formed with a number of threaded openings into which screw-threaded studs may be selectively driven. In this way, the positioning of the studs on the head 40 may be adjusted to suit different cable joints. It is, however, foreseen that the diameter of the head 40 may be so arranged at a pair of diametrically opposed studs can effectively engage cable joints of a number of different sizes.

In use, the head 40 of the cable jointing tool of figure 6 is placed over the cable joint and the studs 41,42 are brought into engagement with the sides of the block 1 of the cable joint so as to enable the jointing tool to exert a torque on the block 1 to counter the tightening torque applied to the shear bolt 8 by the socket driver 30. The shear bolt 8 is then tightened as before, until the resistance felt by the user indicates that failure of the shear bolt is imminent. The user then switches to singlehanded operation, drawing the handle 31 of the socket driver 30 toward the grip portion 22 of the cable jointing tool by squeezing them together with one hand, and repeats this operation until the shear bolt 8 fails.

The cable jointing tools of figures 3 to 6 are preferably fabricated from metal sheet or plate, and all surfaces of the tool are coated with an insulating material, the only exception being the workpiece-engaging surfaces 25 and 26 of the tool shown in figures 3 to 5, and the workpieceengaging sides of the studs 41,42 of the tool shown in figure 6. 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.

Claims (10)

1. Claims 1. An insulated cable jointing tool comprising a head portion including a pair of oppositely-facing workpieceengaging surfaces situated in a first plane for applying a torque to a workpiece, and a grip portion for manually grasping the tool to apply a force thereto, the grip portion extending in a second plane substantially parallel to the first plane, but spaced therefrom.
2. 2. A tool according to claim 1, wherein the oppositelyfacing workpiece-engaging surfaces comprise a pair of jaws.
3. 3. A tool according to claim 1, wherein the head portion is generally annular, and the oppositely-facing workpiece-engaging surfaces comprise a pair of studs projecting from the head portion in a direction away from the second plane.
4. 4. A tool according to claim 3, wherein the circumferential positions of the studs relative to the annular head portion are adjustable.
5. 5. 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.
6. 6. A method of tightening a shear bolt of a cable joint to failure, comprising: engaging the the shear bolt with a driver having a handle extending in a plane of rotation substantially perpendicular to the axis of the shear bolt; engaging the cable joint with a joint holding tool comprising engaging surfaces for applying a torque to the cable joint, and grip means extending substantially radially of the shear bolt in a plane adjacent to the plane of rotation of the driver handle; grasping the driver handle and the grip means of the joint holding tool in one hand; and squeezing the driver handle and the grip means to bring them closer together.
7. 7. A method according to claim 6, wherein the shear bolt is engaged with a socket driver.
8. 8. A cable jointing tool substantially as described herein, with reference to figures 3,4 and 5, or figure 6, of the accompanying drawings.
9. 9. A method of tightening a shear bolt, substantially as herein described.
10. 10. A method of jointing cables, substantially as herein described with reference to figures 1 to 6 of the accompanying drawings.