GB2348842A

GB2348842A - Cable jointing tool attachment

Info

Publication number: GB2348842A
Application number: GB9908314A
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: GB9908314D0

Abstract

An attachment for clamping to the grip portion 21 of a cable jointing tool provides an additional handle 34 spaced from the grip portion. In use, tightening of a shear bolt may be effected by gripping a driving tool 36, and the additional handle in one hand, and squeezing these two parts together to effect final tightening to failure of the shear bolt. Alternatively the attachment may be mounted to a driving tool 36.

Description

Cable ioint holder attachment 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 such as a socket spanner, a tapered neck region 10, and a threaded end portion 11. The crosssectional 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 cross-sectional 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 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 generally comprise a flat 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 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 head 9 of the shear bolt 8. Conventional socket drivers comprise a substantially straight shaft having a ratchet mechanism at one end, from which the socket extends substantially perpendicularly to the direction of the shaft. When engaged on the head 9 of the shear bolt 8, the shaft 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 shaft of 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 an attachment for a cable joint holder, or for a socket driver, 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.

According to a first aspect of the present invention there is provided an attachment for use with a substantially planar cable joint holder 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 and a grip portion in a first plane for engagement with respective end surfaces of the cable clamp, the attachment comprising clamping means for fixing the attachment to the grip portion of the cable joint holder, handle means extending in a plane spaced from the clamping means, and a riser extending between, and rigidly connected to, the clamping means and the handle.

According to a second aspect of the invention, there is provided an attachment for use with a socket driver in combination with a substantially planar cable joint holder for tightening a shear bolt of a cable clamp, wherein the socket driver comprises and elongate socket engageable at one of its ends with the head of the shear bolt and a shaft extending from the other end substantially perpendicularly to the socket, the attachment comprising clamping means for fixing the attachment to the shaft of the socket driver, handle means extending in a plane spaced from the clamping means, and a riser extending between, and rigidly connected to, the clamping means and the handle means.

The clamping means may be a tubular element through which the grip portion of the cable joint holder or the shaft of the socket driver may extend, the clamping means including a releaseable securing element operable to fix the clamping means securely to the grip portion or shaft.

The tubular element may be split in a longitudinal direction, and may have a threaded securing element extending across the split and operable to reduce its width.

The riser may be attached to the handle at one of its ends, or at an intermediate point along its length.

Preferably, the spacing between the clamping means and the handle of the attachment is such that, when the attachment is mounted on the grip portion of the joint holding tool and the socket driver is engaged with the head of the shear bolt, the handle of the attachment extends in a plane substantially adjacent to the plane of the shaft of the socket driver. In the alternative embodiment, when the attachment is mounted to the shaft of the socket driver, the spacing between the clamping means and the handle of the attachment is so arranged that the handle of the attachment extends adjacent the grip portion of the joint holding tool.

Most preferably, the arrangement is such that in use the handle of the socket driver passes slightly above the handle of an attachment mounted to 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 the a cable joint holder comprising a pair of opposed workpiece engaging surfaces and a grip portion extending in a first plane for applying a torque in a first sense to the cable clamp, and the shear bolt of the cable joint is engaged by a socket driver so that the shaft of the socket driver extends in a plane spaced from the first plane, and wherein an attachment is mounted either to the grip portion of the cable joint holder or to the shaft of the socket driver so that a handle of the attachment lies in a plane adjacent the shaft of the socket driver or the grip portion of the cable joint holder, respectively, and relative rotation of the socket driver and cable joint holder is effected by the user single-handedly grasping the handle of the attachment and either the shaft of the socket driver or the grip portion of the cable joint holder, respectively, 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 attachment according to the present invention, mounted on a cable joint holding tool; Figure 4 is a perspective view of the cable joint holding tool and attachment of figure 3, in use; Figure 5 is a perspective view of an alternative embodiment of the cable joint holding tool attachment; Figure 6 is a perspective view of an attachment for the shaft of a socket driver; and Figure 7 is a side view of a socket driver with the attachment of figure 6 mounted to it.

Referring to figure 3, there is shown a conventional cable jointing tool 20. The tool has a grip portion 21 and a head 22 integrally formed with the grip portion 21. The head 22 is generally C-shaped, and comprises a pair of jaws 23 and 24 having oppositely-facing workpieceengaging 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.

Mounted to the grip portion 21 of the joint holding tool 20 is the attachment of the present invention. The attachment comprises a generally tubular clamping portion 27 which extends across the upper and lower surfaces of the grip portion 21 and is slit along one side at 28, and is formed with a pair of opposing flanges 29 and 30 extending along respective sides of the slit 28. A securing element 31 in the form of a threaded bolt extends from the upper flange 30 through a clearance hole in the lower flange 29, and has a butterfly nut threadedly engaged at its free end. The tubular clamping portion 27 is preferably a close fit over the grip portion 21 of the joint holding tool, so that by tightening the butterfly nut 32 on the threaded bolt 31, the clamping portion 27 may be firmly fixed to the grip portion 21. It is preferable that the grip portion 21 be non-circular in cross-section, to provide resistance to the clamping portion 27 rotating about the axis of the grip portion 21.

Extending from the clamping portion 27, and in this embodiment inclined obliquely away from the head 22 of the cable joint holding tool 20, is a riser 33. At the end of the riser 33 remote from the clamping section 27 is a handle 54, in this embodiment arranged to extend parallel to the axis of the tubular clamping portion 27.

When the attachment is mounted to the joint holding tool, the handle 54 extends substantially parallel with the grip portion 21 of the cable joint holding tool 20, but is spaced therefrom by a distance H.

In figure 4, the tool 20 and attachment of figure 3 are shown in use. The head 22 engages the block 1 of a cable clamp, with the jaws 23 and 24 situated adjacent the ends of the block. The shear bolt 8 of the cable clamp is engaged by a socket 35 of a socket driver 36, while the shaft 37 of the socket driver 36 extends in a plane spaced by a distance S from that of the grip portion 21 of the joint holding tool 20. The distance S is slightly greater than the distance H separating the grip portion 21 and the handle 54 of the attachment. Thus, the handle 34 is positioned close to the plane of rotation of the shaft 37 of the socket driver 36.

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 21 of the cable jointing tool 20 in one hand, and the shaft 37 of the socket driver in the other hand. As the torque to be applied to the shear bolt 8 increases, the user brings the shaft 37 of the socket driver to a grasping position spaced from the handle 34 of the attachment by an amount sufficiently small as to enable the user to grasp both the shaft 37 and the handle 34 in one hand. The user then uses that hand to squeeze the shaft 37 and handle 34, so as to bring the shaft 37 closer to the handle 34, further tightening the shear bolt 8. The user repeatedly returns the socket driver shaft 37 to the grasping position, and squeezes the shaft 37 and the handle 34 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 shaft 37 and the handle 34 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 attachment is seen in figure 5, in perspective view. In this embodiment, the attachment comprises a tubular clamping portion 27 with a longitudinal slit 28 and flanges 29 and 30 as before, with a clamping bolt 31 and butterfly nut 32 arranged so as to be able to draw the flanges 29 and 30 together to mount the clamping portion 27 securely on the grip portion 21 of the cable jointing tool. The riser 33 and handle 34 are formed from tubular metal, the riser 33 extending perpendicularly to the clamping portion 27 and to the handle 54. The riser 33 is attached to the handle 34 at its mid-region, rather than at an end of the handle 34 as in the figure 3 embodiment.

The mode of use of the attachment shown in figure 5 is similar to that described in relation to figure 4.

Figures 6 and 7 show an alternative attachment for use with cable jointing tools. The attachment 40 comprises a tubular clamping portion 47, shaped so as to receive the shaft 37 of a socket driver 36. In the embodiment shown, the clamping portion 47 is generally circular in cross-section but may have any cross-sectional shape to conform to that of the socket driver shaft 37.

Alternatively, the tubular clamping element 47 may have a polygonal cross section, for example triangular or hexagonal, to accept a variety of socket driver shafts 37. The clamping portion 47 is formed with a longitudinal slit 48, and flanges 49 and 50 extend along the sides of the slit 48. A clamping bolt 51 extends through a clearance hole 52 in the flange 49, and engages an aligned threaded hole in the flange 50. Tightening the clamping bolt 51 draws the flanges 49 and 50 together, and secures the clamping portion 47 to the shaft 37 of the socket driver 36.

Extending from the clamping portion 47 is a crank arm 53, to which is mounted a handle 54. In the embodiment shown, the crank arm 53 and handle 54 are integrally formed from a bent rod. The length of the crank arm 53 is so arranged that, when the clamping portion 47 is mounted to the shaft 37 of the socket driver, and a socket 35 is mounted to the socket driver, then the handle 54 extends in a plane adjacent the free end of the socket 35. This arrangement ensures that, in use, the handle 54 is situated in a plane adjacent that of the grip portion 21 of a cable joint holding tool 20.

In use, the attachment 40 provides a similar effect to the attachment for the cable jointing tool 20 shown in figure 4, in that the handle 54 may be placed close to the grip portion 21 of the cable jointing tool, so that final tightening of the shear bolt is effected by drawing the handle 54 towards the grip portion 21 by squeezing the two together with one hand. The gross arm and shoulder movements associated with the use of the conventional cable joint holder 20 and socket driver 36 are thus avoided.

The cable jointing tool attachment of figures 3 to 5, and the socket driver attachment of figures 6 and 7 preferably fabricated from metal. The exterior surfaces of the attachments may be coated with an insulating material, but since the cable jointing tool 20 and socket driver 36 are already insulated, further insulation of the attachment is not essential. The interiors of the clamping portions 27 and 47 may be provided with a protective coating, to prevent damage to the insulating material of the cable jointing tool and the socket driver.

The embodiments of the cable jointing tool attachment and socket driver attachment described above are exemplary, and are not intended to limit the scope of the present application. For example, the cable jointing tool attachment shown in figures 3 and 4 may be mounted to the cable jointing tool by positioning the clamping portion 27 at the extremity of the grip portion 21 of the tool.

Likewise, the clamping portion 47 of the socket driver attachment 40 may be positioned adjacent the ratchet head end of the shaft 37, with the crank arm 53 extending downwardly in parallel to the socket 35 and the handle 54 extending away from the socket 35. The attachment may be made from solid metal strip, or from hollow tubular or channel-section materials. It is also foreseen that high-strength plastics or fibre-reinforced resin materials may be used to mould or otherwise form the attachments.

Claims

Claims 1. A handle attachment mountable to a cable jointing tool having a workpiece-engaging head and an elongate grip portion extending therefrom, the handle attachment comprising mounting means engageable with the grip portion to fix the attachment thereto, spacing means extending away from the mounting means, and handle means extending from the spacing means in a plane spaced from the mounting means.
2. A handle attachment according to claim 1, wherein the mounting means comprises a substantially tubular element adapted to surround the grip portion of the cable jointing tool, the mounting means including clamping means capable of drawing the tubular element into tight engagement with the grip portion.
3. A handle attachment according to claim 2, wherein the clamping means includes a threaded clamping element.
4. A handle attachment mountable to a socket driver having a socket for coaxially engaging a shear bolt of a cable clamp and a grip portion extending substantially perpendicularly to the socket, the handle attachment comprising mounting means engageable with the grip portion to fix the attachment thereto, spacing means extending away from the mounting means, and handle means extending from the spacing means in a plane spaced from the mounting means.
5. A handle attachment according to claim 4, wherein the mounting means comprises a substantially tubular element adapted to surround the grip portion of the socket driver, the mounting means including clamping means capable of drawing the tubular element into tight engagement with the grip portion.
6. A handle attachment according to claim 5, wherein the clamping means includes a threaded clamping element.
7. A handle attachment according to any preceding claim, wherein the spacing means is joined to the handle means at one end of the handle means.
8. A handle attachment according to any of claims 1 to 6, wherein the spacing means is joined to the handle means intermediate the length of the handle means.
9. A handle attachment according to any of claims 1 to 3, or claims 7 or 8 when dependent on claims 1 to 3, in combination with a cable jointing tool having a pair of opposed jaws for engaging a cable clamp.
10. A handle attachment according to any of claims 4 to 8, in combination with a socket driver for engaging the shear bolt of a cable clamp.
11. A handle attachment for a hand tool substantially as herein described with reference to figures 3 and 4, figure 5, or figures 6 and 7 of the accompanying drawings.
12. A method of tightening a shear bolt to failure substantially as herein described, using hand tools and an attachment as claimed in any of the preceding claims.