WO2005104321A1

WO2005104321A1 - Improved cable stripping tool

Info

Publication number: WO2005104321A1
Application number: PCT/GB2005/001316
Authority: WO
Inventors: Michael Joseph Maguire
Original assignee: Michael Joseph Maguire
Priority date: 2004-04-24
Filing date: 2005-04-06
Publication date: 2005-11-03
Also published as: GB2413440B; GB0409167D0; GB2413440A

Abstract

A tool is described which in use will cut through the outer PVC sheath of S.W.A. cable and thereafter make a circumferential cut around the armour layer of steel reinforcing wires surrounding the central core of the cable. It comprises a pair of adjustably movable jaws, a pair of rollers on one of the jaws and a cutting blade on the other jaw with its cutting edge facing the rollers, and generally orthogonal to the axes about which the rollers rotate. In use the blade is stationary relative to its supporting jaw. The cutting edge of the blade is formed with teeth, and is typically similar to a saw blade. Stop means is provided on at least one side of the blade which makes contact with the outer surface of the cable as the blade cuts into the cable and controls the depth to which the blade can penetrate the cable. The blade is removable to allow it to be replaced by another blade for sharpening or replacement or replacements by a blade from a range of blades, each of which when fitted will protrude by a different amount beyond the stop means. In addition or instead the stop means is adjustable to allow the maximum depth of blade penetration to be adjusted. The blades and the blade receiving groove in the jaw are adapted to ensure that a blade can only be fitted in one position relative to the jaw and the stop means.

Description

Title: Improved cable stripping tool

Filed of the invention

This invention concerns cable stripping tools and in particular an improved stripper for removing the outer insulating sheath and steel wire armour around heavy-duty electric cable. The device is of particular use in connection with so-called S.W.A. cable and enables an electrician to expose the internal conductor or conductors making up the inner core of the cable, to allow a connection to be made between the conductor(s) and electrical equipment.

Background

Steel reinforced S.W.A. cable is employed when it is necessary to convey electric current underground or below the surface of a river or other area of water. The outer casing of PVC prevents the ingress of water and other liquids, and the inner sleeve of steel wire protects the inner core of conductors and insulating material from accidental damage.

Making a joint using such cable involves stripping away from an end of the cable the outer PNC sheath, and then half cutting the steel wire armouring close to the cut end face of the PVC sheath and flexing the reinforcing wire tails about the half cuts until each of the wire tails breaks off at the half cut. This exposes the inner sleeve of insulating material surrounding the conductors part of which can then be removed to expose the copper conductors which can then be secured in manner known per se to the terminals of the electrical equipment which is to feed or be fed by the cable. At the same time the end of the S.W.A. cable is sleeved and terminated in the conventional manner and sealingly joined to the cover of a metal casing containing the equipment, so that moisture cannot penetrate the cable via the opened-up end thereof. Although it is relatively easy to form a circumferential cut in the outer PVC sheath using for example a knife, it is quite difficult to make a circumferential half cut through the steel wire armouring, to enable the wire tails to be flexed and broken off. If a knife is used there is a risk that the knife will slip and cut the engineer, and in any case the knife edge will rapidly become blunted.

More commonly a small hacksaw has been used by the electrician, to make the circumferential half cut through the wires. While this, is less hazardous than using a knife, it is difficult to judge when the wires have been half cut through and if the hacksaw blade is new and sharp it is quite easy to sever the wires completely and damage the insulating material below the wires.

With these problems in mind a conventional pipe cutter was used. Such a device includes fixed and movable jaws, one housing a rotatable cutting wheel and the other a pair of rollers. In use a length of pipe is located between the jaws which are then moved together to embrace the pipe between the two rollers and the cutting wheel. Rotating the device around the pipe and simultaneously adjusting the jaws so that they move closer together causes the cutting wheel to cut through the pipe wall in manner known per se.

If the rotating cutting wheel was sharp enough, the outer PVC could be cut through, but it was found that however sharp, the cutting wheel of the pipe cutter simply deformed and seemingly work hardened the steel reinforcing wires, instead of making the half-cut needed to enable the wire tails to be flexed and broken off.

It is an object of the present invention to. provide a tool, similar to a conventional pipe cutter, which can be used to remove the outer PVC sheath of S.W.A. cable and to reliably make a circumferential cut in the reinforcing wires making up the armour layer, to allow the reinforcing wire tails to be removed to expose the insulating material surrounding the central core of the cable and thereby facilitate the making of a connection between electrical equipment and the conductor (s) of the central core. Summary of the invention

According to the present invention a tool which in use will cut through the outer PNC sheath of S.W.A. cable and thereafter make a circumferential cut around the armour layer of steel reinforcing wires surrounding the central core of the cable, comprises a pair of adjustably movable jaws, a pair of rollers on one of the jaws and a fixed cutting blade on the other jaw with its cutting edge facing the^' rollers, and generally orthogonal to the axes about which the rollers rotate, so that in use the blade is stationary relative to its supporting jaw, characterised in that the cutting edge of the blade is formed with teeth which in use will cut through the PNC sheathing and thereafter cut into but not through the steel reinforcing wires.

Preferably the cutting edge of the blade comprises a saw blade.

Preferably stop means is provided on at least one and preferably both sides of the blade which makes contact with the outer surface of the cable as the blade cuts into the cable and controls the depth to which the blade can penetrate the cable.

The blade may be removable to allow it to be replaced by another blade from a range of blades, each of which when fitted will protrude by a different amount beyond the stop means so that different depths of PNC sheath and reinforcing wire diameter can be accommodated by one tool, be merely selecting and fitting the appropriate blade.

Alternatively the stop means or the blade may be adjustable to allow the maximum depth of blade penetration to be adjusted.

Where the blade or stop means is adjustable as aforesaid one or other (or the means by which they are adjustable) may be calibrated or otherwise marked so as to indicate the depth to which the blade will penetrate and/or the size of S.W.A. cable which can be used with that setting of the blade or stop means. Alternatively a selection of blades may be provided and the blade containing jaw is adapted to receive and secure a blade in place, and the blades are dimensioned so that when secured in place, they protrude to a greater or lesser extend beyond the stop means and towards the rollers. The different blades may be calibrated or coloured or otherwise marked to indicate the depth of cut, or the S.W.A. cable size(s) with which the blades can be used.

Each of the jaws may be C-shaped and describe an arc of a circle which subtends somewhat less than 180°, and one end of one jaw is hingedly joined to one end of the other so that they can be swung open to allow a cable to be positioned therebetween and then closed so as to embrace the cable. If they are then squeezed firmly by the operator as the assembly is rotated around the cable, the cutting edge will first cut through the PVC sheath and thereafter cut into the steel wires to a depth determined by the stop means.

Alternatively one of the jaws is generally U-shaped, one limb constituting a fixed jaw and providing a support for the blade and stop means (or the rollers) and the other limb containing a threaded passage within which a screw threaded rod is received, the latter being rotatably joined to a movable jaw carrying the rollers (or the blade and stop means) which is slideable relative to the bridge of the U-shaped jaw as the rod is rotated, movement being towards or away from the fixed jaw depending on the direction of rotation of the threaded rod, and the remote end of the latter includes a knob to facilitate its rotation. In use the movable jaw is moved away from the fixed jaw to allow a length of S.W.A. cable to be located therebetween, after which the knob is rotated until the blade and rollers engage opposite sides of the cable at the point where a cut is to be made, after which the unit is rotated about the cable and the knob is slowly twisted during the rotation, so as to move the jaws closer and cause the blade to first cut into and through the PVC sheath and thereafter cut into the wires of the armour layer to a depth determined by the stop means. In each case, after the stop means engages the PVC sheath, no further squeezing of the two C-shaped jaws, or twisting of the knob will cause the blade to cut deeper into the reinforcing wires, and at that stage the jaws can be opened to allow the cable to be removed. The severed length of PVC sheath can be slid off or cut off leaving the tails of the partially severed wires which can then be flexed in known manner about the line of the circumferential half cut and broken off, exposing the inner core of the cable.

Where the thickness of the outer PVC sheath and the diameter of the reinforcing wires is constant for a range of cable sizes no adjustment of the stop means or blade will be necessary and one tool can be used for all the S.W.A. cables in the range. Instead it is merely necessary for the blade to protrude beyond the stop means by a distance equal to the thickness of the PVC sheath and a given percentage (typically 50%) of the diameter of the reinforcing wires. From experience it has been found that a range of S.W.A. cable sizes can be accommodated if the blade protrudes by 1.5mm beyond the stop means.

Whether or not the blades are removable to allow different sizes of blade to be employed, it is preferable for the blades to be removable to allow for sharpening, or replacement with a fresh blade, as a blade becomes blunted with use.

The blades and a blade receiving groove in the said other jaw may be adapted to ensure that a blade can only be fitted in one position relative to the jaw and the stop means. However, as a further alternative to replacing blades or adjusting the stop means or a blade when fitted in place, the means for securing each blade in position may be adapted to allow a blade to be reliably secured in two or more different positions each of which correspond to a given protrusion of the cutting edge of the blade beyond the stop means, so as to accommodate different PVC sheath thicknesses and/or reinforcing wire diameters.

The invention also lies in a method of stripping an end of a S.W.A. cable using a tool as aforesaid wherein a length of S.W.A. cable is positioned between the blade and the rollers, with the cylindrical outer surface of the cable nested between the two rollers and the blade aligned with the point at which the PVC sheath is to be cut, after which the jaws are moved together so that the cable is gripped between the blade and the rollers, and thereafter rotating the tool around the cable and incrementally reducing the spacing between the jaws during the rotation, whereby the blade will cut through the PVC sheathing and thereafter cut into but not through the steel wires of the armour layer.

The invention will now be described by way of example with reference to the accompanying drawings in which:-

Fig 1 is a side elevation of a cable stripping tool constructed as one embodiment of the invention,

Fig 2 is a perspective view showing the tool in use,

Fig 3 is a side elevation of another tool embodying the invention,

Fig 4 is a front elevation of the tool of Fig 3, and

Fig 5 is a side elevation of an alternative design of tool embodying the invention.

Fig 1 shows how a conventional pipe cutter can be modified to serve as a cable stripping tool.

In place of the rotatable cutting blade (not shown) a stationary saw blade 10 is fixed to the stationary jaw 12 of the pipe cutter housing. The movable jaw 14 is slidable on a track 16 and its position relative to the fixed jaw 12 is determined by the extent to which a screw 18 has been rotated so as to protrude beyond the threaded boss 20 towards the fixed jaw 12. A knob 22 facilitates the rotation of the screw 18.

The movable jaw carries two parallel freely rotatable rollers 24, 26 which together with the saw tooth edge of the blade 10 form a 3-point location within which a circular section cable (not shown) can be nested, and between which the cable can be pinched by tightening the screw 18. Thereafter rotation of the tool about the cable and incrementally moving the jaw 14 towards the jaw 12 causes the saw blade 10 to first cut through the outer PVC layer and thereafter to cut into the steel reinforcing wires of S.W.A. cable. The blade 10 is secured by a screw or bolt 28 between two side cheeks of the fixed jaw 12 one of which can be seen at 30 in Fig 1.

In Fig 2 the tool is shown rotated through 180° from the position shown in Fig 1, this time secured around a length of S.W.A. cable 32. The circumferential cut in the outer PVC sheath 33 formed as the tool is rotated around the cable is clearly shown at 34. Also in Fig 2 can be seen the steel wire reinforcing (or armouring) layer 36 and the central core 38 containing in this case four copper conductors one of which is denoted by reference numeral 40.

Fig 2 also shows the circumferential half-cut in the steel wires created after the tool has been used to cut through the outer PVC sheath 33. This can be seen at 42 immediately adjacent the cut end of the outer sheath 33, the latter and the wires 36 having been revealed by removing the cylindrical sleeve of PVC which surrounded the now exposed length of the armour layer 36 after a first cut had been made using the tool at the position denoted by 44 in Fig 2. After making this first cut at 44, and removing the outer PVC sheath to expose the wires 36, the. tool was opened up and moved along the cable to the position shown in Fig 2 where it has been used to make a second cut 34, this time only through the outer PVC sheath, so as not to score the wires. This permits a second length of the PVC sheath 33 to be removed to expose the reinforcing wires.

Preferably the second length is only removed after the reinforcing wire tails to the right of the half-cut 42 have been flexed about the half-cut 42 and broke off therearound.

The cable end will be ready to make a joint, since a length of the inner central core has now been exposed from the end face 46 back to the position 44 and a length of the wire layer 36 will be exposed between 44 and 34 after the second length of the outer PVC sheath is removed. The cable is now ready to receive the gland to make a sealed joint between the outer sheath and a metal housing (not shown), containing equipment to which the conductors such as 40 are to be connected. A more preferred form of construction of the tool is shown in Fig 3 and 4. Here parts that are common to the earlier design of Figs 1 and 2 are denoted by the same reference numerals.

In this embodiment a saw blade 50 is shown secured in a clamp one part of which can be seen in Fig 3 at 52. The other part of the clamp can be seen at 54 in Fig 4. The blade is shown detached from the tool in the scrap view of Fig 4A and can be seen to have two slots 56, 58 along its inboard edge. The blade is positioned in the clamp 52, 54 so that the slots align with the positions of two securing bolts or screws 60, 62. By pushing the blade 50 into the groove 64 between the two parts of the clamp 52, 54 as far as the slots and screws/bolts will allow, and then tightening the bolts/screws to secure the blade in place in the clamp, the blade will protrude below the clamp 52, 54 by a given amount.

The two parts 52, 54 of the clamp therefore also constimte stops, since as will be seen from Fig 4, once the tool has been closed and rotated around the cables so that the two clamp parts are now in contact with the outer PVC sheath 33 of the cable 32 (best seen in Fig 4), further tightening of the screw 18 will not cause the saw blade to cut any deeper.

Fig 3 shows an S.W.A. cable in cross section between the tool jaws supported by two rollers 66, 68 and partially cut through by the blade 50. The outer PVC sheath can be seen at 33, the steel wire armour layer at 36, an inner sleeve of rubber or plastics material at 35, the central core of rubber or plastics at 46 and in this case, three copper conductors 40, 41 and 43 embedded in the core material.

As already noted, by ensuring that the depth by which the blade 50 extends below the undersides of the two parts 52, 54 making up the blade clamp, so the depth of the cut can be controlled. In the example shown, this is 1.5mm which is found to be sufficient to cut through the outer PVC layer and reliably score or half-cut through, the steel wires in the layer 36 of a range of S.W.A. cable sizes. In the Fig 3 and 4 embodiment the boss 20 is omitted and the screw 18 is merely screwed into and through a threaded hole in the lower limb 70 of the U-shaped tool housing.

Likewise the sliding jaw 72 which carries the rollers differs from the jaw 14 of Figs 1 and 2. However the principle of operation is the same.

A third variation of the design is shown diagrammatically in Fig 5.

Here a blade 72 is carried between two parts of a clamp similar to that shown at 52, 54 in Figs 3 and 4. Only one part is visible in Fig 5 and this is identified by reference numeral 74.

The blade is held in place as before by two screws or bolts 76, 78. The clamp parts extend from the inner curved surface of a first arcuate jaw 80 which is hinged at 82 to a second similar arcuate jaw 84. Within the latter are mounted two parallel spaced apart freely rotatable rollers 86, 88.

The two arcuate jaws 80, 84 are held in their open position (as shown) by a spring 90 shown in dotted outline as extending around and on opposite sides of the hinge 82.

In use the device is moved in the direction of arrow 92 until the jaws surround a cable 94 to be cut and stripped (and shown in dotted outline in Fig 5). At this point the two jaws can be closed around the cable by squeezing by hand. Whilst continuing to squeeze the two jaws together, the device can be rotated around the cable (or the cable rotated within the device) so that the saw blade 72 cuts into the cable as previously described. The depth of cut is determined by the amount by which the blade 72 extends below the clamp 74.

In order to accommodate a wide range of cable diameters the free end of one arcuate jaw may be bifurcated to form a parallel sided slot 96 and the similar opposed end of the other jaw is rebated to form a thinner end section 98 which will slide into the groove 96 in the other jaw. A further refinement may be provided if the faces of the section 98 are ribbed as shown dotted at 100 and the inner faces of the groove 96 are formed with one or more ribs which engage when 98 is pushed into the groove 96 and co-operate to prevent the two jaws from springing open if the squeezing force is removed (to allow the operator to reposition his/her hand around the device during rotation around a cable).

As the jaws are moved closer together the ribs on the jaw 80 will engage different ribs on the end 98 nearer to the shoulder 102, so that once closed the two jaws 80, 84 are retained in their progressively more closed-up condition around the cable, as the latter is penetrated by the blade thereby allowing the two jaws to move closer together. In this event a device (not shown) is provided for releasing the engagement of the ribs after the cutting action has been completed to allow the jaws 80, 84 to be pivoted into their open position to be removed from the cable.

The ribs preferably form a one-way clutch which keeps the two jaws closed until released.

Claims

1. A tool which in use will cut through the outer PVC sheath of S.W.A. cable and thereafter make a circumferential cut around the armour layer of steel reinforcing wires surrounding the central core of the cable, comprising a pair of adjustably movable jaws, a pair of rollers on one of the jaws and a fixed cutting blade on the other jaw with its cutting edge facing the rollers, and generally orthogonal to the axes about which the rollers rotate, so that in use the blade is stationary relative to its supporting jaw, characterised in that the cutting edge of the blade is formed with teeth which in use will cut through the outer PVC sheath and thereafter cut into but not through the steel reinforcing wires.

2. A tool as claimed in Claim 1 wherein the cutting blade comprises a saw blade.

3. A tool as claimed in Claims 1 or 2 wherein stop means is provided on at least one side of the blade which makes contact with the outer surface of the cable as the blade cuts into the cable and controls the depth to which the blade can penetrate the cable steel wires.

4. A tool as claimed in Claim 3 wherein stop means is provided on both sides of the blade.

5. A tool as claimed in Claims 3 or 4 wherein the stop means is adjustable to allow the maximum depth of blade penetration to be adjusted.

6. A tool as claimed in Claim 5 wherein the stop means, or any means by which it is adjustable, is calibrated or otherwise marked so as to indicate the depth to which the blade will penetrate and/or the size of S.W.A. cable which can be used with that setting of the stop means.

7. A tool as claimed in any of Claims 1 to 6 wherein the blade is removable to allow for sharpening or replacement with a fresh blade, as a blade becomes blunted with use, or to allow it to be replaced by another differently dimensioned blade.

8. A tool as claimed in Claim 7 in combination with a plurality of differently dimensioned blades.

9. A tool and plurality of different blades as claimed in Claim 8 wherein the different blades are calibrated or coloured or otherwise marked to indicate the depth of cut, or the S.W.A. cable size(s) with which the blade can be used.

10. A tool as claimed in Claim 8 or 9 wherein the blades and a blade receiving groove in the said other jaw are adapted to ensure that a blade can only be fitted in one position relative to the jaw and the stop means.

11. A tool as claimed in any of Claims 1 to 10 wherein in use a length of S.W.A. cable is positioned between the blade and the rollers, with the cylindrical outer surface of the cable nested between the two rollers and the blade and with the latter aligned with the point at which the PVC sheath is to be cut, after which the jaws are moved together so that the cable is gripped between the blade and the rollers.

12. A tool as claimed in any of Claims 1 to 11 wherein each of the jaws is curved and describes an arc of a circle which subtends somewhat less than 180°, and one end of one jaw is hingedly joined to one end of the other which in use can be swung open to allow a cable to be positioned therebetween and then closed so as to embrace the cable, and thereafter squeezed firmly by the operator as the tool is rotated around the cable, so that the cuttmg edge will first cut through the PVC sheath and thereafter cut into the steel wires to a depth determined by the stop means.

13. A method of stripping an end of a S.W.A. cable using a tool as claimed in any of claims 1 to 12 wherein a length of S.W.A. cable is positioned between the blade and the rollers, with the cylindrical outer surface of the cable nested between the two rollers and the blade with the latter aligned with the point at which the PVC sheath is to be cut, after which the jaws are moved together so that the cable is gripped between the blade and the rollers, and thereafter the tool is rotated around the cable and the spacing between the jaws is incrementally reduced during the rotation, whereby the blade will cut through the PNC sheathing and thereafter cut into but not through the steel wires of the armour layer, whereafter the severed length of PNC sheath is slid off or cut off leaving tails of partially severed wires which are flexed about the line of the half cut and broken off.

14. A tool for cutting through the outer PNC sheath and thereafter into but not through the steel reinforcing wires of S.W.A. cable constructed, arranged and adapted to be used as herein described with reference to and as illustrated in Figs. 1 and 2 or Figs. 3 and 4 or Fig. 5 of the accompanying drawings.