GB2231732A

GB2231732A - Wire stripping tool

Info

Publication number: GB2231732A
Application number: GB8909956A
Authority: GB
Inventors: Barry Peter Liversidge
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-04-29
Filing date: 1989-04-29
Publication date: 1990-11-21
Also published as: GB8909956D0

Abstract

A wire stripping tool has a body 10 with a through-bore 11 for receiving a wire e.g. double-insulated, to be stripped, and cutting blades (28 Figs 4a, 4c, 5) whose angle and depth of penetration are controlled by rotating portion 13 (& 18 Fig. 1) around the body 10 to set the blades across the wire, Fig. 4b or aligned with the wire, Fig. 4c or at an angle to produce a helical cut. Carriers (20 Figs. 5, 6) for the blades have pins (21) which are mounted in slots (22) in a sleeve (17), the pins follow a cam surface 15 which controls the angle and depth of cut of the blades. In use the tool is rotated around the wire to give a circumferential cut, the blade angle and depth changed, and then pulled towards the end of the wire to remove the severed insulation. <IMAGE>

Description

WIRE STRIPPING TOOL This invention relates to a wire stripping tool - that is to say, a tool adapted to assist the removal of an outer sheath from a cable or wire. In particular - though not exclusively - the tool of this invention is intended to assist the removal of an outer insulating sheath from an electrical cable consisting of one or more individual insulated wires encased within such an outer sheath.

Many electrical cables are of a "double-insulated" construction - that is to say, one or more individually insulated current-carrying wires are enclosed within an outer sheath also of an insulating material. Sometimes, one or more of the conductors within the outer sheath may not be individually insulated - for example, an uninsulated earthing conductor may be provided, and in other types of cable a relatively strong filament may be provided to support the weight of the cable when suspended between two points, which filament may be a conductor, optionally insulated.

When a cable as has been described above is to be electrically terminated, it is necessary first to remove a length of the outer sheath, in order to give access to the wires therewithin. Once the outer sheath has been stripped away, then appropriate terminating techniques may be employed on the exposed wires. The satisfactory removal of the outer sheath often is difficult to perform rapidly if all risk of damage to the inner conductors is to be avoided. Moreover, for cables which are intended for external use - such as overhead telephone wires - a relatively tough outer sheath is often employed, which tends to be particularly difficult to remove - especially if the termination is to be effected by an operator working in a difficult situation, such as on a ladder or up a telegraph pole.

An aim of the present invention is to provide a tool adapted to assist the removal of an outer sheath from a cable, so as to facilitate the subsequent electrical termination of the cable conductors.

Accordingly, one aspect of the present invention provides a wire stripping tool comprising: a body having a through-bore within which a cable to be stripped may be received; a sleeve mounted on the body with the axis thereof substantially normal to the through-bore axis, which sleeve is rotatable about its axis with respect to the body and the sleeve has a pair of ports registrable with said through-bore by relatively rotating the sleeve and the body, the ports having a greater circumferential extent than the through-bore diameter; a cutting blade mounted for rotation with the sleeve, which cutting blade is adapted to cut a cable received in the through-bore and the blade being movable axially with respect to the sleeve; and cam means co-acting between the blade and the body whereby relative rotation between the sleeve and the body controls the projection of the blade into the through-bore.

It will be appreciated that in the wire stripping tool of the present invention, the outer sheath of a cable to be stripped is severed by means of the cutting blade when that blade is moved to a position where it projects into the through-bore defined by the body. A stripping operation is effected by the performance of the following steps: a) the tool is primed by relatively rotating the body and the sleeve until the cam means moves the blade to a position where it does not project into the through-bore, and the ports are in register with the through-bore; b) a cable to be stripped is passed through the through-bore; c) the body and sleeve are relatively rotated so that the cam means no longer holds the blade clear of the through-bore, so that the blade cuts into the cable; and then either dl) the tool is rotated about the cable, so that the blade effects a circumferential cut into that cable; or d2) the tool is pulled towards and off the free end of the cable, so that the blade effects a longitudinal cut along the sheath.

In a case where the tool is rotated about the cable (step (d1) above), and depending upon the nature of the outer sheath, it may for some cables thereafter be possible merely to pull the entire tool towards the free end of the cable, so pulling the outer sheath of that cable, by virtue of the engagement of the blade in the circumferential cut. On the other hand, for other types of sheath, the following further steps may be employed: e) the body and sleeve are relatively turned through 900, so that the cutting blade is now aligned with the length of the cable; and f) the tool is then pulled towards and off the free end of the cable, whereby the blade forms a longitudinal cut in the sheath, from the circumferential cut to the cable free end.

Once the longitudinal cut has been made, either with or without a circumferential cut, and the tool has been removed from the cable, the outer sheath may be split along the longitudinal cut, and removed from the inner wires.

In order to allow the tool to operate as described above, the blade must appropriately be configured and mounted with respect to the sleeve. In a case where the tool is to be rotated (step (d1) above), the blade should lie in a circumferential plane immediately after the relative rotation of step (c); but where a longitudinal cut is immediately to be effected (step (d2) above) then the blade should lie in an axial plane immediately after the relative rotation of step (c). In the alternative, a very thin pointed blade could be used, at least for certain types of sheath, to permit performance of steps (d1) or (d2), at will.

Yet another possibility is for there to be provided means defining a pre-determined angular setting between the sleeve and body, whereat the blade lies at a small angle to a true radial plane. Such means, for instance provided by the cam means, may hold the blade at a suitable angle whereby a helical cut is formed along the sheath during rotation of the tool therearound; the sheath may subsequently be removed by an 'unwinding action.

Most preferably, the sleeve is rotatably mounted co-axially within a further bore formed in the body, with the through and further bore axes intersecting.

The cutting blade may then be mounted in a carrier itself mounted for sliding movement within the sleeve along the axis thereof, the cam means acting indirectly on the blade through the blade carrier.

The cam could wholly control the carrier positions, but it is preferred for the carrier to be spring-urged to a position where the blade projects into the bore, the cam means serving to withdraw the carrier from that position, dependent upon the relative angular setting of the sleeve and body. Advantageously, relatively high spring forces are used, to ensure adequate penetration of the sheath by the blade.

Preferably, the blade projects beyond the carrier by a predetermined amount, whereby the depth of penetration of the blade into the outer sheath of a cable to be stripped is defined by the projection of the blade beyond the carrier, so long as the cam means is not serving to hold the blade clear of the through-bore.

Advantageously, the end face of the carrier from which the blade projects has a pair of abutment surfaces arranged at substantially 900 with respect to each other, which surfaces are selectively engageable with the cable by effecting relative rotation through substantially 900 between the carrier and the cable. By having one of said surfaces further from the cutting edge of the blade than the other on the other surface, the depth of penetration of the blade into the outer sheath will thus depend upon the orientation of the blade with respect to the cable sheath. This allows the tool to provide a greater depth of cut for one of the circumferential and longitudinal cuts than for the other of said cuts. For certain types of cable having particularly tough outer sheaths, it is found that stripping of the sheath is much facilitated by performing the longitudinal cut to a greater depth than the circumferential cut.

It will be appreciated that the circumferential extent of the ports in the sleeve, and their disposition relative to the blade carrier, must carefully be selected to ensure that the sleeve can be turned sufficiently with respect to the body, once a cable has been passed through the through-bore, for the full performance of the cutting sequence. Thus, the ports must also have a sufficient circumferential extent to permit the sleeve to be turned through about 1200 with respect to the body following the entry of a cable into the through-bore.

The cam means may comprise a cam surface formed on the body, there being a cam follower associated with the blade and which engages that cam surface. In the preferred form of tool, the cam means is in the form of an annular face, cam surrounding the sleeve and engaged by a follower which passes through an axial slot in the sleeve, the follower being mounted on the blade carrier.

The face cam surface should be formed to lift the blade clear of the through-bore to prime the tool ready for use, against the spring bias acting on the blade or its carrier; thereafter a further slight rotation of the sleeve with respect to the body should free the cam follower from the cam surface, to permit the blade carrier to be driven by the spring bias to a position where the blade penetrates the outer sheath of a cable inserted into the bore. After a circumferential cut has been made, by rotating the body about the cable, a further rotation through 900 of the sleeve with respect to the body will cause alignment of the blade with longitudinal direction of the cable to permit the elongate cut to be effected.At the same time, if the end face of the blade carrier has appropriately been shaped, the blade will penetrate to a different depth of cut, whilst remaining free of control by the cam means.

In an alternative form of the tool, the further rotation of the sleeve causes the blade to be lifted clear of the cable after the performance of a circumferential cut, to permit removal of the tool without forming a longitudinal cut.

The cam surface advantageously is formed with a notch for the carrier to define positively the position where the blade carrier has been withdrawn to the greatest extent, and so to indicate to a user that priming of the tool has been completed.

A preferred form of tool of this invention has a second cutting blade, carrier and cam means arranged generally symmetrically with respect to the firstmentioned cutting blade, carrier and cam means, about the through-bore axis. In this way, the amount of rotation required in order to form a circumferential cut is reduced, and moreover two longitudinal cuts are formed as the tool is pulled towards the free end of the cable, so enhancing the ease with which the outer sheath may be removed from the conductors.

By way of example only, one specific embodiment of wire stripping tool constructed and arranged in accordance with the present invention will now be described in detail, reference being made to the accompanying drawings, in which: Figure 1 is a side view of the embodiment of tool; Figure 2 is a view similar to that of Figure 1, but with certain parts removed or cut away for clarity; Figure 3 is an enlarged end view taken in the direction of arrow A marked on Figure 2; Figures 4A to 4C are enlarged views on the central portion of the body of the tool of Figure 1, with the tool adjusted to three different settings; Figure 5 is a side view of the blade carrier and cutting blade used in the tool of Figure 1; Figure 6 is an end view of the blade and carrier shown in Figure 5; and Figure 7 is a developed view of the central region of the sleeve employed in the tool.

The embodiment of wire stripping tool illustrated in the drawings comprises a main body having a central portion 10 of generally cylindrical form, and a throughbore 11 extending transversely through that central portion. Bosses 12 are formed on the central portion around the through bore 11, the entry into the bore being eased by chamfers to facilitate use of the tool.

At one end of the central portion 10, the body is provided with a cylindrical holding portion 13, which portion is formed with external serrations in order to assist a user gripping the tool. A further bore 14 extends axially through the body 10, the axis of the further bore intersecting the axis of the through-bore 11, and the further bore being enlarged within the holding portion 13. An internal cam surface 15 is formed around the shoulder between the central portion 10 of the body and the holding portion 13, for a purpose to be described in detail below; a similar cam surface 16 is formed at the opposite end of the central portion 10 of the body.

A hollow sleeve 17 extends through the further bore 14 and is rotatable with respect to the body 10.

The sleeve 17 projects from both ends of the central portion 10 of the body by approximately the same amount1 and the free end of the sleeve within the holding portion 13 is fitted with an end cap (not shown) which cap fits closely within the end region of the holding portion 13. A second holding portion 18, of generally similar external dimensions and shape to the holding portion 13, is secured on to the opposed end of the sleeve 17 by means of a pin (not shown) passing through the holding portion 18 and through a transverse bore 19 provided adjacent the end of the sleeve 17. When the tool is assembled, as shown in Figure 1, it therefore has a generally symmetrical appearance, and the sleeve 17 can be rotated with respect to the central body portion by a user grasping the two holding portions 13 and 18 and effecting relative turning movement therebetween.

A pair of blade carriers, each as shown in Figures 5 and 6, is mounted within the bore of the sleeve 17, such that the blades thereof are directed towards each other. Each blade carrier 20 has a tranverse bore in which is received a mounting pin 21, having a length slightly smaller than the internal diameter of either holding portion 13 or 18. The sleeve 17 is provided with two pairs of diametrically opposed elongate slots 22 to receive the pins 21, such that when the two blade carriers have been fitted into the sleeve 17, two pins 21 may be passed one each through the respective slot 22 and respective carrier. Each blade carrier may thus move axially with respect to the sleeve 17, but is held against relative rotation with respect thereto. A spring 23 is disposed between the upper blade carrier 20 (in Figure 2) and the pin passed through the transverse bore 19; a similar spring 24 is disposed between the lower blade carrier 20 and the end cap for the sleeve 17. The springs thus urge the pin 21 associated with the lower blade carrier to engage the cam surface 15, and the pin 21 associated with the upper blade carrier to engage the cam surface 16.

The end face 25 of each blade carrier is formed with a pair of transverse arcuate grooves 26 and 27, arranged mutually at right angles. A cutting blade 28 is mounted within the carrier so as to project in alignment with groove 27, which groove has a greater depth than groove 26. The cutting edge of the blade may be curved, or linear.

The sleeve 17 is provided with a pair of ports 30, each of a relatively large circumferential extent, as shown in the developed view of the sleeve (Figure 7).

The axial extent of each port 30 is however only slightly greater than the diameter of the through-bore 11.

Referring to Figures 2 and 3, it can be seen that each cam surface 15 and 16 has a pair of ramp portions 31, each having a small notch 32 disposed adjacent the highest point of that cam surface. Immediately adjacent that notch, the cam surface drops axially to a lower land 33, extending in a generally radial plane. Each pair of ramp surfaces 31, notches 32 and lands 33 are disposed symmetrically with respect to the through-bore 11, as can be appreciated from Figure 3.

In use, the tool is primed to receive a cable by turning holding portions 13 and 18 relatively, until the pins 21 of the two blade carriers ride up and are received in the notches 32 of the respective cam surfaces. This action withdraws the carriers against the bias provided by springs 23 and 24, such that the through-bore 11 is not obstructed by the cutting blades 28, as shown in Figure 4A. A cable from which the sheath is to be stripped may then be passed through the through-bore 11, the cable passing also through the elongate ports 30 in the sleeve 17, to lie in the position indicated in Figure 7.

Once the cable has been positioned at the point back to which the sheath is to be stripped, the holding portions 13 and 18 are turned relatively through only a small angle, so that the pins 21 ride out of the notches 32 and drop down from the ramp surfaces 31 to overlie the lands 33. The presence of the cable in the ports 30 prevents the relative rotation being performed in the wrong sense. When thus set, the cutting blades 28 lie in a generally radial plane of the through-bore 11, with the cable received in the grooves 26 in the end faces 25 of the two blade carriers; this position is illustrated in Figure 4B, but the cable has been omitted for clarity. The depth of cut of each blade is limited by the depth of the associated groove 26, and a relatively shallow circumferential cut may be made by turning the tool about the cable, through at least 1800.

Next the holding portions 13 and 18 are further rotated relatively, through 900, such that the blades lie longitudinally of the cable and the cable is received in the grooves 27 of the two blade carriers.

Relative rotation in the wrong sense is prevented by the pins 21 abutting the shoulders in the cam surfaces between ramps 31 and lands 33. By now, the cable is located at the ends of the ports 30 in the sleeve 17 opposed to that shown in Figure 7. Since the grooves 27 are of a greater depth than grooves 26, each blade now may cut to a relatively deeper extent into the cable.

On pulling the tool towards and off the free end of the cable, a pair of opposed elongate cuts are thus formed through the outer sheath of the cable. Subsequently, it is a relatively easy matter to split the sheath along at least one of the longitudinal cuts, and then to peel the sheath from the inner conductors of the cable.

It will be appreciated that the cam does not serve to prevent relative rotation between the sleeve and body when the pins 21 overlie the lands 33; however, the engagement of the cable in one of the grooves 26 and 27 coupled with the spring forces acting on the blade carriers serves to restrain that relative rotation until the holding portions 13 and 18 are deliberately turned one with respect to the other.

Claims

1. B wire-stripping tool comprising: a body having a through-bore within which a cable to be stripped may be received; a sleeve mounted on the body with the axis thereof substantially normal to the through-bore axis, which sleeve is rotatable about its axis with respect to the body and which sleeve has a pair of ports registrable with said through-bore by relatively rotating the sleeve and the body, the ports having a greater circumferential extent than the through-bore diameter; a cutting blade mounted for rotation with the sleeve, which cutting blade is adapted to cut a cable received in the through-bore and the blade being movable axially with respect to the sleeve; and cam means co-acting between the blade and the body whereby relative rotation between the sleeve and the body controls che projection of the blade into the through-bore .

2. h tool according to Claim 1, wherein the sleeve is rotatably mounted co-axially within a further bore formed in the body, with the axis of the through and further bores intersecting.

3. A tool according to Claim 2, wherein the cutting blade is mounted in a carrier, which carrier is mounted for sliding movement within the sleeve along the axis thereof, the cam means acting indirectly on the blade through the blade carrier.

4. A tool according to Claim 3, wherein the carrier is spring-urged to a position where the blade projects into the bore, and the cam means serves to withdraw the carrier from that position, dependent upon the relative angular setting of the sleeve and body.

5. A tool according to Claim 3 or Claim 4, wherein the blade projects beyond the carrier by a predetermined amount, whereby the depth of penetration of the blade into the outer sheath of a cable to be stripped is defined by the projection of the blade beyond the carrier.

6. A tool according to any of Claims 3 to 5, wherein the end face of the carrier from which the blade oects has a pair of cable abutment surfaces arranged at substantially 900 with respect to each other, which surfaces are selectively engagab]e with the cable by effecting relative rotation through substantially 900 between the carrier and the cable, and one of said surfaces being disposed further from the cutting edge of the blade than the other of said surfaces.

7. A tool according to any of the preceding Claims, wherein the cam means comprises a cam surface formed on the body, and a cam follower associated with the blade and which engages that cam surface.

8. A tool according to Claim 7, wherein the cam surface is in the form of an annular face-cam surrounding the sleeve and engaged by a follower which passes through an axial slot in the sleeve, the follower being mounted on the blade or blade carrier, if provided.

9. A tool according to Claim 7 or Claim 8, wherein the cam surface is formed with a notch for the follower to define positively the position where the blade has been withdrawn from the through-bore to the greatest extent.

10. A tool according to any of the preceding Claims, wherein there is provided a second cutting blade and associated cam means, arranged gen rally symmetrically about the through-bore axis with respect to the first mentioned cutting blade and associated cam means.

11. A wire-stripping tool substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.