GB2197757A - Apparatus for stripping insulation from cables - Google Patents

Abstract

This invention relates to apparatus for stripping the outer electrical insulation from a predetermined size cable. A blade holder (1 Figs 1a & 1b) comprises two halves 8 which define an open ended slot (2). Two generally planar blades 5 are located between the halves 8, each having a slanted cutting edge 7. The blades are mounted in the holder to define a slot 13 between opposing faces 6. An end portion of a cable 4 is inserted transversely into the slot 14 so that the outer insulation 17 is presented to the blades 7 at the correct angle and is then cut by the blades 7 before the faces 6 are forced into the cut in the insulation. During the stripping process, it is the edges 6 that take the stress separating the end portion outer insulation from the outer insulation of the remainder of the cable so there is a reduced likelihood of the edges 6 breaking. A tool for the holder is also described (Figs 4 & 5) that receives two holders. <IMAGE>

Description

Apparatus tor Stripping Insulation from Cables This invention relates to apparatus for stripping insulation from cables and in particular to a tool for stripping the insulation from a predetermined size cable.

In circumstances where a particular size cable is commonly used, it is often more convenient to have a cable insulation stripping tool engineered for that particular cable rather than a multi purpose adjustable tool. An example of such a tool for a particular size cable comprises a pair of razor blades with blade edges spaced apart in a plane to define an elongate slot therebetweenof predetermined size. The slot is selected to correspond substantially with the cable size after stripping. In this way, when an end portion of cable is inserted transversely of the slot, the opposing cutting edges cut into the outer insulation of the cable but insufficiently to damage any internal wires of the cable. To actually strip the outer insulation from the end portion, the cable is pulled transversely to the slot.One of the disadvantages with this tool is that during pulling of the cable from the slot, the cutting edges of the blades are extremely stressed during separation of the outer insulation of the end portion and the outer insulation of the rest of the cable, especially if the cut into the outer insulation does not entirely sever the outer insulation. These edges are thin so that during the stripping process they can sometimes snap especially after frequent use. This is both hazardous to the user and also renders the tool useless.

It is an object of the present invention to provide an improved apparatus for stripping outer insulation from cables which substantially overcomes the aforementioned disadvantages.

According to the present invention there is provided apparatus for stripping an end portion of outer electrical insulation from an insulated cable comprising: a generally planar blade member having a first open ended slot of predetermined width corresponding substantially to the size of said cable without said outer insulation, and wherein the open end region of the slot has cutting edges and the slot region remote from the open end has edges thicker than said cutting edges; and a blade holder in which said blade member is located, said blade holder having a second open ended slot of predetermined width corresponding substantially to the size of said cable with said outer insulation, and forming an entrance to said first open ended slot. In this way, as the end portion of the cable to be stripped is inserted transversely of the two slots, it first passes through said second slot.

Then, as it enters the first slot, the outer insulation is cut by the cutting edges between said first and second slots, and as the cable is further inserted into the first slot, the relatively thicker edges enter the cut in the insulation. Then, to strip the cable, the cable is pulled from the side remote from the end portion so that it is the relatively thicker faces of the slot that take the stress during separation of the insulation from the cable interior and the remaining cable insulation. Since these edges are relatively thicker, they are less likely to break off.

Preferably, the cutting edges define a generally v-shaped transition between said first and second slots.

Thus the length of said second slot extends from an open end, to a cutting edge and the length of said first slot extends from a cutting edge to a closed end.

Preferably also, the ratio of the length of said second slot to its width is at least 4:1. Ihthis way, as the end portion of the cable to be stripped is inserted transversely of the second slot, at least half of the width of said cable will be contained within said second slot before the outer insulation begins to be cut by the cutting edges. This ensures that the outer surface of the insulation is presented to the cutting edges at the correct angle.

Conveniently, the blade member comprises a pair of mirror image blade pieces located in the blade holder such that the blade holder defines said predetermined width.

This allows an economic production of the stripper.

Preferably, the length of said first slot is at least as long as the width of said cable. In this way, the outer insulation will have been cut along its entire width before the cable is stripped.

In a preferred embodiment of the invention, the apparatus includes a hollow handle formed to recieve and firmly grasp the blade holder and fixing means provided to fixedly retain the holder in the handle. In another preferred embodiment, the hollow handle is formed to received two blade holders with only one blade member exposed for use.

An example of the present invention will now be described with reference to the accompanying drawings in which: Figure l(a) illustrates a plan view of a blade holder.

Figure l(b) illustrates an end view of the blade holder shown in Figure l(a).

Figure 2 illustrates a partial section viewed along the line X-X shown in Figure l(b).

Figure 3 illustrates a view along the arrows Y-Y shown in Figure l(a).

Figure 4 illustrates a plan view of the apparatus embodying the present invention.

Figure 5 illustrates an end view of the apparatus shown in Figure 4.

Referring to Figure 1, a blade holder 1 comprises two halves 8 joined together with suitable fixing means such as adhesive or screws (not shown). The holder incorporates an open ended slot 2 at one end thereof and an aperture 3 at the other end thereof. Referring to figure 2, the blade holder 1 incorporates two generally planar elongate blades 5, which in this case are mirror images of one another. The two blades are generally rectangular and each has a slanted cutting edge 7 cutting off to a corner of one long face 6. The blades are mounted in recesses in holder 1 so that they extend slightly into the slot 2 as shown in the figure with the faces 6 opposite so that the blades define a further slot 13 between opposing faces 6 with a V-shaped transition between slot 13 and the open ended region of slot 2 which forms another slot 14.The slot 13 has a predetermined width corresponding substantially with the cable size after stripping off the outer insulation.

The slot 14, which in figure 2 is the region in which the cable has been inserted, also has a predetermined width which is greater than the predetermined width of slot 13, and corresponds substantially with the cable size before stripping off the outer insulation.

The length of the slot 13, which extends from points 18 to points 19 is at least as great as the width of cable 4.

Figures 4 and 5 illustrate a handle for receiving two blade holders 1. The handle 9 has a generally oval cross section and is hollowed to firmly hold a received holder 1. As can be seen from Figure 4, the handle 9 extends sufficiently to receive almost entirely one blade holder and substantially half another blade holder. The handle 9 incorporates two appertures 10 which may be lined up with the apertures 3 in both blade holders whereby screws 11 can be inserted therethrough to fixedly retain the holders 1 in the handle 9.

In order to strip the outer insulation 17 from a cable 4, the cable is inserted into and transversely of the slot 14 in the direction of arrow A shown in Figure 2. As the cable moves to the left in Figure 2 into slot 13, the outer insulation 17 of the cable encounters cutting blades 7 which cut into the insulation. The length of the slot 14 which extends from points 15 to points 16 is at least four times as great as its predetermined width. This ensures that at least half the width of the cable 4 is within the slot region 14 before the outer insulation 17 of the cable encounters the cutting blades 7. The outer insulation is therefore presented to the cutting blades 7 at the correct angle.

The V-shaped transition between slot 13 and slot 14 gives a good cutting angle to the edges 7 as they encounter the insulation 17. As the cable is pushed into the slot 13 the faces 6 are forced into the cut in the insulation. When the entire width of the cable 4 is contained within the slot 13, cable 4 is pulled from the side remote from the cable end portion so that the insulation to be removed separates from the cable core and is retained on the other side of the blade and the stripped cable is produced.

It can therefore be seen that because it is the edges 6 that take the stress of separating the insulation at the cut and because the edges 6 are thicker relative to the cutting edges 7, there is reduced likelihood of the edges 6 breaking. This can be particularly important when the cable inserted into the groove 13 has a very long thin cross section. For example, telephone wire suitable for placing under carpets comprising six inner cables laid flat with an outer insulation. With this particular type of wire, during manufacture there is an ingress of the outer insulation into the recesses between adjacent inner cables making it difficult to cut entirely through the outer insulation. Thus, when trying to strip an end portion by separating the outer insulation from the inner cables, (the core), there is still a significant joint between the end portion outer insulation and the outer insulation of the remainder of the cable. Consequently, the force required to strip the end portion from the cable is quite high. The present invention enables large forces to be employed without damage to the apparatus since the edges 6 are thicker relative to the cutting edges 7.

Claims (8)

1. Apparatus for stripping an end portion of outer electrical insulation from an insulated cable comprising: a generally planar blade member having a first open ended slot of predetermined width corresponding substantially to the size of said cable without said outer insulation, and wherein the open end region of the slot has cutting edges and the slot region remote from the open end has edges thicker than said cutting edges; and a blade holder in which said blade member is located, said blade holder having a second open ended slot of predetermined width corresponding substantially to the size of said cable with said outer insulation, and forming an entrance to said first open ended slot.

2. Apparatus as claimed in claim 1 wherein said cutting edges define a generally V-shaped transition between said first and second slots.

3. Apparatus as claimed in claim 2 wherein the ratio of the length of said second slot to its width is at least 4:1.

4. Apparatus as claimed in any of the preceding claims wherein the blade member comprises a pair of mirror image blade pieces located in the blade holder such that the holder defines the predetermined width of said first slot.

5. Apparatus as claimed in any of the preceding claims wherein the length of said first slot is at least as long as the width of said insulated cable.

6. Apparatus as claimed in any preceding claim including a hollow handle formed to receive and firmly grasp the blade holder, and fixing means provided to fixedly retain the holder in the handle.

7. Apparatus as claimed in claim 6 wherein the hollow handle is formed to receive two blade holders with only one blade member exposed for use.

8. Apparatus for stripping an end portion of outer electrical insulation from an insulated cable substantially as herein described with reference to the accompanying drawings.