WO2007071911A1

WO2007071911A1 - Wire stripping blades and associated tool

Info

Publication number: WO2007071911A1
Application number: PCT/GB2006/004521
Authority: WO
Inventors: Bo-Hwan Lee
Original assignee: Heat Trace Limited
Priority date: 2005-12-22
Filing date: 2006-12-05
Publication date: 2007-06-28
Also published as: CN101361242A; CA2634610A1; GB0526149D0; EP1964223A1

Abstract

Disclosed is a pair of blades for removing insulation from a multi-core electrical cable, each of the pair of blades comprising: a plurality of curved potions, each corresponding to the relative position of a conductor of the cable; and disposed between a pair of the plurality of curved portions, a protruding portion and a recessed portion, arranged to mate with corresponding respective portions on the other of the pair of blades. Also disclosed is a hand tool comprising such a pair of blades.

Description

Wire Stripping blades and associated tool

The present invention relates to blades for a tool for removing a layer of insulation from a multi-core electrical cable. It relates particularly, but not exclusively, to a tool for removing insulation from a twin-core electrical heating cable.

Various tools are known in the prior art for removing an outer layer of insulation from electrical wire or cable. In the case of a single core wire, a simple tool resembles a pair of pliers or scissors and has opposing blades, each blade including a notch such that the wire to be stripped is captured in the notch and further pressure causes the insulation to be severed substantially around its entire circumference. By providing an axial movement towards a free end of the wire, the required quantity of insulation can be simply and quickly removed.

In multi-core cables, a number of individually insulated single wires are further encapsulated in an outer layer of insulation. In such cases, removing the outer insulation, without damaging the inner wires, can be difficult. Often, the only practical solution is to remove the outer insulation with a sharp knife, such as a knife with a retractable blade (e.g. Stanley ^® knife) , and individually strip the wires therein.

Figure 1 shows a prior art automatic wire-stripper 10. Such a device is commonly used to strip the insulation from single-cored electrical cables. The device 10 comprises a pair of handles 26, 28 which are spring biased outwardly and rotate around pivot point 24. In use the single-core wire is inserted into the tool between gripping members 12, 14, with the end of the wire to be stripped extending between blades 16, 18.

The blades 16, 18 comprise a plurality of different-sized apertures, for use with wires of different gauges. The most appropriate gauge is chosen, and the wire is aligned therewith.

When the user squeezes the handles 26, 28, a co-ordinated and synchronised series of events takes place. Firstly, the gripping members 12, 14 are urged towards each other, thus gripping the wire to be stripped.

The blades 16, 18 are then urged towards each other, and the wire is located in the aperture chosen. With increased pressure on the handles, the blades 16, 18 penetrate the insulation of the wire. With further pressure on the handles, portions 20 and 22 move apart from each other, causing the weakened or severed insulation to be pulled away from the inner conductor of the wire.

When pressure is removed from the handles, the gripping members 12, 14 release their grip on the wire and it may be released.

A particular form of electrical cable where a problem removing the insulation is encountered is self-limiting trace-heating cable. Such cable generally comprises two metallic conductors extending along the length of the cable and embedded in apolymeric body manufactured from a material providing a positive temperature coefficient . Thus as the temperature of the cable increases the resistance of the material electrically connected between the conductors increases, thereby reducing power output.

When such cable requires termination, either to control equipment or a further length of similar cable, the insulation from the end of the wire needs to be removed to enable connection to the inner pair of conductors. There is no known tool which provides a simple method of performing the required stripping operation and recourse is normally had to a sharp knife, such as a Stanley ^® knife. This runs the risk of damaging the cable, due to the ad-hoc nature of the operation and poses a risk of injury to the person performing the stripping operation.

An aim of embodiments of the present invention is to address the problems with the prior art, whether mentioned explicitly herein or not .

According to the present invention there is provided an apparatus as set forth in the appended claims . Preferred features of the invention will be apparent from the dependent claims, and the description which follows.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figure 1 shows an automatic wire stripper known from the prior art ; Figure 2 shows a pair of blades which form an operational part of a wire stripper according to an embodiment of the present invention;

Figure 3 shows a further view of the blades of Figure 2;

Figure 4 shows a detailed view of a blade of Figure 2;

Figure 5 shows a sectional view of the blade of Figure 4 ;

A pair of blades forming an embodiment of the invention is shown in Figure 2. Each of the pair of blades includes a curved portion 110, 120, 210, 220 defining respective halves of a circular aperture 310, 320. The circular aperture is formed when the two blades are brought into contact with each other. This arrangement of the two blades 100, 200 is shown in Figure 3.

The distance between the two curved portions 110, 120 and 210, 220 is configured to correspond to the separation of the conductors in a given cable.

The portion of the blade between the two curved portions 110, 120 comprises a zigzag portion comprising two vertices 130, 140. The first vertex 130 corresponds to a generally indented portion of the zigzag section and the second vertex 140 corresponds to a generally protruding portion of the zigzag section.

The second blade 200 comprises complementary first and second vertices 230, 240, such that vertex 230 defines a protruding portion which mates with the indented portion of the first blade defined by vertex 130. Vertex 240 defines an indented portion which mates with the protruding portion of the first blade defined by vertex 140.

Figure 4 shows a more detailed view of blade 100. In particular, it shows that the blade comprises two distinct portions - a body portion 102 and a sharpened portion 104. The body portion is of substantially uniform thickness, and the sharpened portion tapers to a sharpened edge. This arrangement can be more clearly seen in Figure 5 which shows a sectional view along line X-X of Figure 4.

In particular types of cable, particularly the heating cable referred to previously, the brittle nature of the cable can render it difficult to strip.

The zigzag portions of the blades serve to apply a shearing action to the material disposed between the metallic conductors of the cable. In effect as blades 100 and 200 are brought together, vertex 230 and vertex 140 pierce the material of the cable and as continued pressure is applied, the material disposed between the conductors is completely severed at the same time as the insulation surrounding the two conductors is penetrated.

In the description up to this point, no mention has been made of the complete tool which may be used to house the blades described. An advantage of the present invention is that it may be embodied in a variety of different forms .

In a preferred embodiment, the blades 100, 200 are housed in an automatic wire stripper similar to the device 10 shown in Figure 1. Blades 100, 200 may be simply substituted for blades 16, 18 shown. In such a tool, the stripping process is automated, once the user has aligned the pair of conductors with the pair of curved portions 210, 220 (and/or 110, 120) .

As an alternative to the device of Figure 1, a simpler scissors-like tool can be adapted to comprises a pair of blades 100, 200.

Although described herein in relation to a cable having only a pair of conductors, the skilled man will appreciate that the invention can be used with cables having any number of parallel conductors.

Blades according to embodiments of the invention may be provided in a range of different configurations to cater for cables having differently spaced conductors or different gauge conductors, as required.

The blades may be arranged to be interchangeable within a single tool, or a range of dedicated tools may be provided, each corresponding to a different cable configuration .

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification

(including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A pair of blades for removing insulation from a multi-core electrical cable, each of the pair of blades comprising:

a plurality of curved potions, each corresponding to the relative position of a conductor of the cable; and

disposed between a pair of the plurality of curved portions, a protruding portion and a recessed portion, arranged to mate with corresponding respective portions on the other of the pair of blades.

2. A pair of blades as claimed in claim 1, wherein the protruding portion and recessed portion define a zigzag shape .

3. A pair of blades as claimed in claim 1 or 2 arranged to be fitted, in use, into a hand tool.

4. A pair of blades as claimed in any preceding claim wherein each of the plurality of curved portions is of identical size and shape.

5. A pair of blades as claimed in any preceding claim wherein each of the plurality of curved portions defines a semi-circle.

6. A pair of blades as claimed in any preceding claim wherein the plurality of curved portions consists of two curved portions .

7. A hand tool comprising a pair of blades according to any preceding claim.

8. A hand tool as claimed in claim 7 wherein the hand tool comprises a pair of scissor-like members.

9. A hand tool as claimed in claim 7 wherein the hand tool comprises gripping means for securing the cable to be stripped, said gripping means being arranged to grip the cable when pressure is applied to handles of the hand tool and being further arranged to strip the insulation from the cable with increased pressure on the handles.