GB2215143A

GB2215143A - Wire stripper

Info

Publication number: GB2215143A
Application number: GB8802628A
Authority: GB
Inventors: Barry Peter Liversidge
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-02-05
Filing date: 1988-02-05
Publication date: 1989-09-13
Anticipated expiration: 2008-02-05
Also published as: GB8802628D0; GB2215143B

Abstract

A self-adjusting tool arranged to remove insulation from a wire or cable, which tool has a first body portion 10 slidably receiving second body portion 11. Portion 10 has a circular aperture 24 for receiving a cable to be stripped, and portion 11 has a tongue 22 with a planar end surface 34, a cutting blade 31 being mounted on the tongue 22 so as to project from the planar surface, but at an acute angle thereto. The depth of penetration of the blade 31 into the insulation of a cable on rotation of the tool therabout is defined by the projection of the blade beyond the planar surface, by the angle of the edge with respect to the surface, by the cable diameter, and by the sense of rotation of the tool about the cable (Figs 7 & 8). The blade lies across aperture 25 to permit a guillotining action to be pertormed on a cable in that aperture. <IMAGE>

Description

WIRE STRIPPER This invention relates to a tool intended to assist the removal of an outer layer from an elongate member having at least one core surrounded by such an outer layer. In particular - but not exclusively - this invention relates to a tool for assisting the stripping of a layer of insulation from a wire or cable.

Though the tool of this invention may be used to strip the outer layer from various kinds of elongate member having such a layer - for example, a fibre optic cable having an outer sheath - the invention will primarily be described with specific reference to the stripping of an insulating layer from an electric wire or cable. References to the stripping of insulation from wires or cable should therefore in the context of this Specification be construed broadly to cover such wider applications.

There has been a great number of proposals for tools intended to assist the removal of insulation from insulated wires or cables, in order to facilitate the electrical termination thereof: these tools are conventionally known as wire (or cable) strippers. One common design of wire stripper is somewhat plier-like, and has a pair of cutting blades intended to cut through the insulating layer, prior to the removal of the insulation by pulling the pliers towards the free end of the wire whilst the blades are still engaged in the cut in the insulation. Many of these designs of wire strippers have a stop arrangement, intended to prevent the cutting edges closing to an extent which would cut or otherwise damage the wire conductor.A disadvantage of wire strippers of this kind is that the stop arrangement is usually inconvenient to use and set accurately, with the result that many operators leave the stop set at the minimum value, the operator then relying on his own skill and judgement to minimise damage to the conductors during a stripping operation.

To mitigate this problem, some stripper tools of this kind are provided with a certain number of pre-set positions for the stop, in an attempt to facilitate the setting thereof, but the disadvantage of these tools is that the pre-set positions are unlikely to be exactly right for all of the many different sizes of wire usually encountered. In any event, there is still the disadvantage that each time a different wire size is to be stripped, the tool must be adjusted. Moreover, these designs of wire stripper cannot easily be used to facilitate the removal of the outer sheath from a double-insulated cable, prior to the stripping of the insulation from the or each inner conductor.

Another known form of wire stripper has a body defining an aperture in which a wire or cable may be received, a blade being suitably mounted on the body such that rotation of the body around a wire or cable located in the aperture causes the blade to cut into the insulation, whereafter the insulation may be removed by an axial pull applied to the tool. Typically, the cutting blade is mounted on the body by means of a screw-threaded adjuster, to permit adjustment of the tool to suit different wire or cable sizes. Also, if a wide range of wire or cable sizes are to be accommodated, it may be necessary to fit inserts into the aperture, appropriately to configure the tool to suit the wire or cable to be stripped.

Another known form of wire stripper has two relatively-movable parts arranged generally in the form of a pistol grip, the tool having a pair of jaws which are adapted firstly partially to cut through the insulation and then to apply an axial pull to that insulation, as the two tool parts are squeezed together.

Again, either complex adjustments are required to ensure the tool adequately cuts through the insulation but not the conductors, or the tool will operate with only a narrow range of wire sizes. Again, this tool has only limited usefulness in removing the outer sheath from a double-insulated cable.

All the above-described known forms of wire stripping tools suffer from various disadvantages.

Typical tools are relatively complex and hence expensive to manufacture, and/or the tools are difficult or inconvenient to adjust to suit different wire sizes, especially if a wide range of wires is to be stripped.

Yet another disadvantage is that none of the known forms of wire stripping tools-as described are able to accommodate the removal of the outer sheath from a wide range of double-insulated cables, and then immediately and without adjustment of the tool are able to effect stripping of the insulation from an inner conductor contained within the outer sheath.

It is a principal aim of the present invention to provide a self-adjusting tool for assisting the removal of an outer layer from an electric wire cable (as defined herein) which tool is very simple to use and which is able to accommodate a wide variety of wire sizes without requiring specific adjustment.

Accordingly, one aspect of the present invention provides a self-adjusting tool for assisting the removal of an outer sheath from an elongate member having at least one core surrounded by such an outer sheath, which tool comprises co-operating first and second body portions having respective opposed surfaces defining a member-receiving aperture therebetween, the first and second body portions being relatively movable to vary the size of the aperture, said surface on one of said first and second body portions being substantially planar and that one body portion having a cutting blade secured thereto, the cutting blade having an elongate cutting edge which projects beyond the plane of said surface and at an acute angle thereto, whereby the depth of penetration of the cutting blade into an elongate member located in the aperture is defined by said substantially planar surface engaging the outer surface of the elongate member.

The following further description of this invention will refer exclusively to the stripping of electric wires and cables, though it will be appreciated that many of the preferred features are applicable to tools of this invention and intended for use with elongate members other than electric wires and cables such as fibre optic cables.

In order to use the tool of this invention, the first and second body portions are moved relatively to increase the separation between the respective opposed surfaces of said body portions, and thereby increasing the size of the aperture defined thereby. The insulated wire (or cable) to be stripped is then located in the aperture, with the cutting blade aligned with the position at which the strip is to be effected. The two body portions are then urged together and are rotated about the wire, so causing the cutting edge to cut into the insulating layer, but the depth of penetration of the cutting blade is limited by the engagement of the substantially planar surface of said one body portion with the outer surface of the wire being stripped.

After the tool has been rotated at least once around the wire, to complete a circumferential cut into the insulating layer, the tool may be used to remove the severed insulating layer, by leaving the blade engaged -in the cut, and applying an axial pull to the tool in the direction of the free end of the wire. In the alternative, the tool may be removed from the wire simply by relatively separating the two body portions, soincreasing the size of the wire-receiving aperture and permitting removal of the tool. Bending of the cable in the vicinity of the cut will complete the severance of the insulation and commence the removal thereof.

A great advantage of the wire stripping tool of the present invention is that it is fully self-adjusting to suit a very large range of wire (or cable) diameters, without the need for the operator to perform any alteration in the configuration of the tool. A typical embodiment of tool of this invention may be capable of effecting a satisfactory insulation stripping operation on electric wires or cables having outer diameters ranging from 1.5 to 10 mm.

This leads to yet another advantage of the tool of this invention, in that the tool may be used not only to strip a layer of insulation provided directly over the conductors of a wire, but also to remove the outer sheath provided around a double-insulated electric cable, where such a sheath is moulded around a group of two, three or even more separately insulated electric wires. Thus, the tool may be used without the need for any operator adjustment firstly to remove a suitable length of outer sheath from the end portion of a typical domestic two or three core double-insulated electric cable, and immediately thereafter be used to strip from the ends of each of the insulated wires exposed by the stripping of the outer sheath an appropriate length of the insulating layer.

It will be understood that within the context of the present Specification, a "satisfactory strip is regarded as being one in which the insulating layer is severed to a depth which enables that layer easily to be removed from the underlying core (be it a conductor or a further insulating layer on a conductor), but which does not penetrate deeper than the thickness of the layer being removed, so as that the integrity of the underlying core is not damaged in any way. This is of course especially important when removing the outer sheath from a double-insulated cable, where it is most important that no cutting of the insulation on the individual conductors occurs at the point at which the outer sheath is cut.

Automatic adjustment of the depth of cut may be obtained by providing a stop to one side of the aperture, and by carefully selecting the included angle between the substantially planar surface of said one body portion and the cutting edge of the blade, as well as the projection of the blade from that surface, adjacent the stop. Presuming that a round wire is to be stripped, and that the wire when located in the aperture engages the stop side the point along the length of the substantially planar surface at which contact with the wire occurs depends upon the diameter of the wire.

Since the cutting edge of the cutting blade lies at an angle to that substantially planar surface, the depth to which that blade may penetrate the wire equally depends upon the wire diameter. With relatively small wires, where the point of contact of the wire with the substantially planar surface is relatively close to said stop the depth of penetration of the cutting blade also will be relatively small, whereas for a relatively large cable, where the point of contact of the wire with the substantially planar surface is further from said stop, the depth of penetration of the blade will be relatively greater.

Empirical trials for performing a satisfactory strip on a wide range of types of wires and cables have shown that the angle between the cutting edge of the blade and the substantially planar surface should be less than 250, with a more preferred range being from 50 to 120. For such a configuration, the projection of the cutting edge from said substantially planar surface at the stop should lie in the range of 0 to 2 mm, though most preferably the projection of the cutting blade is no greater than 1.5 mm at the stop.

When operating the tool, the engagement of the wire or cable with the stop can be assured by rotating the tool in the correct sense around the wire or cable.

The friction between the insulating layer and the blade will cause the cable to be driven along the blade, either to engage the stop or towards. the other side of the aperture aperture, as tool rotation proceeds. As a consequence, and provided a second stop is provided at the opposite end of the aperture to the first-mentioned stop, rotation of the tool in the sense opposite to that which drives the cable engage the first stop will cause the wire to be driven to engage the second stop, where the blade projection is greatest. This gives rise to a further advantage, in that should a relatively deep cut be required - for instance to remove a relatively thick outer insulating sheath from a multi-core cable or when preparing a co-axial cable - the tool may be rotated in the opposite sense to that normally employed, so achieving a greater than normal cut into the outer layer.

Experimental trials and tests have shown that it is possible for the tool of this invention as defined above to be modified by reducing the angle between said substantially planar surface and the cutting edge of the cutting blade to substantially 00, provided that the projection of the cutting edge beyond said surface is closely controlled to lie within a very narrow range; if this is done, a satisfactory strip may be achieved for a wide range of typical domestic electric mains cables and wires. Thus, a second aspect of the present invention wires.Thus, a second aspect of the present invention provides a modified form of self-adjusting tool for assisting the removal of an outer sheath from an elongate member having at least one core surrounded by such an outer sheath, which tool comprises co-operating first and second body portions having respective opposed surfaces defining a member-receiving aperture therebetween, the first and second body portions being relatively movable to vary the size of the aperture, one of said first and second body portions having a cutting blade secured thereto, the cutting blade having an elongate cutting edge which extends substantially parallel to said surface and which is spaced beyond said surface by a distance of from 0.25 mm to 1 mm, whereby the depth of penetration of the cutting blade into an elongate member located in the aperture is limited by said surface of said one of the body portions engaging the outer surface of the elongate member. More preferably, the projection of the cutting edge is within the range of 0.4 mm to 0.65 mm.

In either form of the present invention as defined above, any curvature of the surface from which the blade projects should be small enough not significantly to affect the stripping operation of the tool. The surface of said second body portion opposed to the surface from which the blade projects may be arcuate, with a radius of curvature equal to the radius of the largest diameter cable which is to be stripped by the tool, whereby the surface itself defines the first and second stops at the sides of the aperture. The surface may however be substantially planar, in which case that surface preferably lies essentially parallel to the corresponding surface of said one body portion.

A preferred construction for a tool of this invention has the first body portion defining a socket in which may be received a part of the second body portion, for sliding movement with respect to the first body portion. The first body portion may define a bore for receiving a wire or cable to be stripped, a section of the periphery of that bore defining said surface of said one body portion.

Most advantageously, the first body portion includes a second aperture also configured to receive a wire or cable, there being a cutting edge provided on the second body portion and arranged to perform a guillotining action across that second aperture, as the two body portions are moved closer together.

Conveniently, the cutting edge for this purpose is constituted by an extension of the cutting blade adapted to perform the stripping operation. In this way, the tool may be used to achieve the further function of cutting through a wire cable at a required position, prior to performing a stripping operation thereon.

Preferably, resilient means are provided to urge the first and second body portions in a sense which reduces the size of the aperture between said surfaces.

For example, a resilient band may pass around both body portions, which band is extended when the two body portions are moved relatively to increase separation between said opposed surfaces. Moreover, at least one of the body portions preferably has a finger-hole, to facilitate the rotation of the tool around a wire or cable to be stripped.

By way of example only, two specific embodiments of tools of this invention will now be described in detail, reference being made to the accompanying drawings, in which: Figure 1 is a front view of the first embodiment of a tool of this invention; Figure 2 is a rear view of the tool of Figure 1; Figure 3 shows the second body portion, as used in the tool of Figures 1 and 2; Figure 4 is a front view on the first body portion, but with a cover plate removed; Figure 5 is a side view on the first body portion of Figure 4; Figure 6 is a side view on the cover portion forming a part of the first body portion; Figure 7 is a detailed view on an enlarged scale showing the insulation cutting action of the tool of Figure 1; and Figure 8 is a detailed view on an enlarged scale of a modification of the tool of Figures 1 to 7.

Referring initially to Figures 1 to 6, there is shown a first embodiment of cable stripping and cutting tool constructed and arranged in accordance with the present invention. This tool comprises a first body portion 10 and a second body portion 1t having a tongue which is received in a socket in the first body portion 10, whereby the two body portions may relatively be separated by sliding movement of the tongue in the socket, in the direction of arrow A shown on Figure 1.

An elastomeric band 12 fits around the entire periphery of the tool, so as to urge the first and second body portions to the relative positions illustrated in Figures 1 and 2, where the two portions are closest together.

The first body portion has a base member 13 (Figure 4) and a cover 14 (Figure 6) which cover has legs 15 provided with barbs 16, the barbs being engageable in slots 17 provided in the side wall 18 of the base member 13. In this way, once the cover 14 has been pressed into engagement with the base member 13, the removal of the cover 14 is inhibited by the interengagement of the barbs 16 and slots 17. In order to provide the correct relative alignment between the cover 14 and the base member 13, pins 19 project from the cover 14, which pins are received in corresponding bores 20, in the base member 13.

The side walls 18 of the base member 13 define therebetween a slot 21 in which is received the tongue 22 of the second body portion 11. The back plane 23 of the base member 13 has a pair of bores 24 and 25 formed therethrough, the cover 14 having a pair of corresponding bores axially in alignment with the bores 24 and 25 when the cover 14 has been fitted on to the base member 13. The outer faces of the back plane 23 and cover 14 are provided with thumb and finger grips 26.

The second body portion 11 has in the main part 28 thereof a finger-hole 29, and also a panel 30 for carrying identification information, or the like. The tongue 22 projects from the main part 28 of the second body portion 11, and carries a cutting blade 31 having a cutting edge 32. The blade is secured in the required position against movement with respect the tongue 22 by means of a pair of pins 33 pressed into the tongue 22 and received in corresponding openings in the blade 31.

The free end of the tongue 22 has a substantially planar reference surface 34, and also an arcuate recess 35, disposed to one side of the surface 34. The cutting edge 32 lies at an acute angle to the reference surface 34, as will be described in greater detail below.

When the tool has been assembled and the two body portions are closest together, the cutting edge 32 of the blade 31 extends chordally across the bore 24. The planar surface 34 also extends chordally across that bore, with the angle between the surface 34 and the cutting edge 32 being g0 which typically, is about 100 (Figure 7). Relative separation of the two body portions allows the cutting edge to be moved clear of the bore.

In order to use the tool to effect a stripping operation, a user places his middle finger in the finger-hole 29, and thumb and index finger are pressed on to the grips 26; the two body portions may then be separated, so sliding the cutting blade 31 clear of the bore 24. A cable to be stripped, such as cable 35 (Figure 7), is then located in the bore 24 with the blade 31 at the position where the strip is to be performed, whereafter the two body portions are released, so as to allow the band 12 to urge the two portions closer. Next the tool is rotated about the cable in the clockwise sense (arrow B in Figure 7) and the blade cuts into the insulating layer, to an extent defined by the engagement of the surface 34 with the outer circumference of the cable. During this rotation of the tool around the cable, the friction between the cutting blade and the insulation urges the cable towards the left (in Figure 7) of the cable receiving aperture, defined jointly by the bore 24 in co-operation with the surface 34.

As is apparent from Figure 7, relatively small diameter cable 35 will be located during this rotational step closer to the left-hand side of the aperture than will be a larger diameter cable, such as cable 36 illustrated in long-chain lines. As a consequence, the depth of penetration (D and d) of the cutting blade 31 will be greater for the larger diameter cable 35 than for the smaller diameter cable 36.

When the cutting action has been completed, an axial pull on the tool towards the free end of the cable will pull off the severed insulation. On the other hand, if the insulation has not completely been cut through, tool may be removed from the cable, whereafter the insulation may be broken through by flexing of the cable in the region of the cut; thereafter, the insulation may be pulled off in any convenient manner.

When severing the outer insulating sheath from a double insulated cable, this would be the normal method of operating.

If the tool should be rotated in the counterclockwise sense (Figure 7) about the cable, then it will be seen that the friction between the blade and insulation will tend to drive the cable 37 towards the right-hand side (in Figure 7) of the cable-receiving aperture, and so the depth of cut will be relatively deep (D2). This may be performed particularly where an outer sheath of a double insulated cable is to be cut through, and the outer sheath has an abnormally high wall thickness, such as may be encountered for certain types of double insulated mains cables.

It should be noted that Figure 7 is diagrammatic, and somewhat exaggerates the cutting effects as well as the positioning of the cable, in order to illustrate clearly the tool operation. In practice, the angles, wire positions and so on would not be as significant as illustrated.

Should it be desired to sever a cable completely, the cable may be placed into bore 25, after opening the tool as described above. Then the tool may be rotated about the cable whilst the band 12 urges the two parts of the tool together so that the extension of the blade cutting edge 32 across bore 25 will gradually sever by a guillotining action through the entire cable. The force of the band, in urging together the two parts of the tool, may be augmented by manual pressure applied endwise of the tool, and in the case of a small cable, it may be possible to sever the cable just by applying such pressure, without the need to effect any rotation of the tool.It should be noted that any damage to the cutting edge, which might occur after cutting through a considerable number of cables, will not in any way affect the performance of the stripping part of the cutting blade which is located across bore 24, so that satisfactory stripping may still be achieved.

Figure 8 is a view similar to that of Figure 7, but of a modified form of tool of this invention. Like parts with those of the embodiment of Figures 1 to 7 are given like reference characters and will not be described again here. In the arrangement of Figure 8, the angle &commat; e between between the cutting edge 40 of the cutting blade 31 and the surface 34 is reduced to zero so that the cutting edge extends parallel to that surface.

Here, the distance between the cutting edge 40 and that surface 34 is set at substantially 0.5 mm. Thus, the maximum depth of cut into the insulation of any cable 41 located in the aperture will be 0.5 mm. Empirical tests have shown that this allows a satisfactory strip to be achieved for a very wide range of cable diameters as used for domestic mains electricity. This is because the insulation must have a minimum thickhess to give adequate insulation from the electrical point of view, and so a setting of the projection of the cutting edge 40 beyond surface 34 by just less than that thickness will ensure that with the smallest types of cables, the blade will not cut the conductors. With larger cables, the insulation may have an increased thickness to give sufficient strength, but a satisfactory strip may be obtained initially by partially severing the insulation with the blade, whereafter severing may be completed by removing the tool and then flexing the cable in the region of the cut. An advantage of the tool of Figure 8 is that the tool may be rotated in either sense about the cable, without affecting the depth of cut. In other respects, the tool of Figure 8 corresponds to that of Figures 1 to 7.

Claims

1. A self-adjusting tool for assisting the removal of an outer sheath from an elongate member having at least one core surrounded by such an outer sheath, which tool comprises co-operating first and second body portions having respective opposed surfaces defining a memberreceiving aperture therebetween, the first and second body portions being relatively movable to vary the size of the aperture, said surface of one of said first and second body portions being substantially planar and that one body portion having a cutting blade secured thereto, the cutting blade having an elongate cutting edge which projects beyond the plane of said surface and at an acute angle thereto, whereby the depth of penetration of the cutting blade into an elongate member located in the aperture is defined by said substantially planar surface engaging the outer surface of the elongate member.

2. A tool according to claim 1, wherein there is provided a cable stop to one side of the aperture.

3. A tool according to claim 2, wherein the projection of the cutting edge of the cutting blade beyond the plane of the surface increases with distance from the stop.

4. A tool according to claim 2 or claim 3, wherein the angle between the cutting edge of the blade and the substantially planar surface is less than 250.

5. A tool according to claim 4, wherein said angle lies in the range of from 5 to 120.

6. A tool according to claim 4 or claim 5, wherein the projection of the cutting edge from said substantially planar surface at the stop lies in the range of 0 to 2 mm.

7. -A tool according to claim 6, wherein the projection -of the cutting blade is no greater than 1.5 mm at the stop.

8. A tool according to any of claims 2 to 7, wherein a second stop is provided at the side of the aperture opposed to said first-mentioned cable stop.

9. A tool according to claim 8, wherein the aperture is defined by a substantially circular opening formed in at least one of the first and second body portions, the sides of the opening defining the first and second stops.

10. A tool according to any of claims 1 to 4, wherein the angle between the cutting edge of the blade and the substantially planar surface is substantially at 00.

11. A self-adjusting tool for assisting the removal of an outer sheath from an elongate member having at least one core surrounded by such an outer sheath, which tool comprises co-operating first and second body portions having respective opposed surfaces defining a memberreceiving aperture therebetween, the first and second body portions being relatively movable to vary the size of the aperture, one of said first and second body portions having a cutting blade secured thereto, the cutting blade having an elongate cutting edge which extends substantially parallel to said surface and which is spaced beyond said surface by a distance of from 0.25 mm to t mm, whereby the depth of penetration of the cutting blade into an elongate member located in the aperture is limited by said surface of said one of the body portions engaging the outer surface of the elongate member.

12. A tool according to claim 11, wherein the projection of the cutting edge lies within the range of from 0.4 mm to 0.65 mm.

13. A tool according to any of the preceding claims, wherein the first body portion defines a socket in which may be received a part of the second body portion, for sliding movement with respect to the first body portion.

14. A tool according to claim 13, wherein the first body portion defines a bore for receiving an elongate member to be stripped, a section of the periphery of that bore defining said surface of said one body portion.

15. A tool according to any of the preceding claims, wherein the first body portion includes a second aperture also configured to receive a wire or cable, there being a cutting edge provided on the second body portion and arranged to perform a guillotining action across that second aperture, as the two body portions are moved closer together.

16. A tool according to claim 15, wherein the cutting edge for performing said guillotining action is constituted by an extension of the cutting blade adapted to perform the stripping operation.

17. A tool according to any of the preceding claims, wherein resilient means are provided to urge the first and second body portions in a sense which reduces the size of the aperture between said surfaces.

18. A tool according to any of the preceding claims, wherein at least one of the body portions has a fingerhole, to facilitate the rotation of the tool around an elongate member to be stripped.

19. A tool substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 7, or in Figures 1 to 7 as modified by Figure 8, of the accompanying drawings.