GB2298967A

GB2298967A - Cable stripper

Info

Publication number: GB2298967A
Application number: GB9605448A
Authority: GB
Inventors: Russell Ridley
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-03-15
Filing date: 1996-03-15
Publication date: 1996-09-18
Anticipated expiration: 2016-03-15
Also published as: GB9605448D0; GB9505220D0; GB2298967B

Abstract

A cable stripper comprises two cable-engaging rollers 21, 22 with a cable receiving space 23 therebetween, the axes 25, 26 of the rollers being non-parallel, and an adjustable cutter 28 for cutting the cable as it moves between the rollers. The angle between the axes may be adjustable. In one embodiment, Figure 4, the rollers 40, 41 are cage-like structures with longitudinal blades 42 which allow debris from the cables to fall through the rollers. In another embodiment, Figure 6, the rollers are frusto-conical. The stripper is used to recover metal from cables.

Description

CABLE STRIPPING APPARATUS This invention relates to cable stripping apparatus suitable for removing the covering of cables which surround one or more core elements. The apparatus is particularly, though not exclusively, suitable for recovering core materials such as copper or aluminium from wires and cables.

Cables and wire materials generally comprise one or more core materials surrounded by a protective sheath. Electrical cables comprise one or more electrical conductors surrounded by a tough protective sheath which might comprise a polymeric material or a metallic material or both. Large industrial cables for the supply of electricity are often armoured to improve strength and penetration resistance. These cables comprise segmented copper or aluminium cores surrounded by a number of layers of sheaths reinforced by a wire or armouring layer embedded in the sheath or located between layers.

Recovering metal cores from these cables is extremely difficult particularly because the cables are heavy, very stiff and are armoured with a metal wire layer.

A known construction of cable stripping machine comprises two conical drive members arranged adjacent to each other with their axes of rotation parallel. In use a cable is inserted into the space between the drive members. The drive members grip and pull the cable through the machine while cutting means cut the sheath material. The cutting means usually comprises a cutting edge which penetrates the sheath of the cable and shaped to splay the sheath apart in order to separate the outer sheath from the core material. The cutting means for cutting and splaying the cable apart is commonly known in the trade as a "fish tail". A guide element is sometimes used to assist guidance of the cable through the machine.

Although the known construction of machine is capable of accepting a variety of sizes of cable it is not particularly efficient for stripping all sizes of cable inserted into the machine. Furthermore, the conical drive members are difficult and relatively expensive to produce because of their shape.

The drive members are prone to rapid wear, require frequent replacement to maintain efficiency and are unable to cope with excessive loads imposed, particularly, by the heavier and larger sizes of cable.

The invention provides cable stripping apparatus which comprises two cable engaging rollers with axes of rotation which are non-parallel.

According to the present invention there is provided cable stripping apparatus for removing cable sheathing which comprises: (a) two cable engaging rollers orientated to one another to define a space between the rollers adapted to accept a cable to be stripped, wherein the axes of rotation of the rollers are non-parallel; (b) drive means for rotating at least one of the rollers; and, (c) cutting means for cutting a sheath of a cable as the cable moves through the space defined between the rollers in order to facilitate removal of the sheath from the core elements.

The cable stripping apparatus of the invention has the advantage that it can grip and strip cables of varying sizes more efficiently than known cable stripping machines. In the prior art cable stripping machine the axes of rotation of the conical drive members are parallel. This means that the contact area between the drive members and the cable is large for small sizes of cable but much smaller for large sizes of cable. As a consequence the prior art cable stripping apparatus engages small sizes of cable efficiently but the same efficiency cannot be maintained as the size of the cable increases. This is because the contact area reduces as the size of cable to be stripped increases. This effect is illustrated in Figures la-le of the drawings which depict a pair of parallel conical drive members and compares contact areas for stripping different sizes of cable.Furthermore, as the prior art rollers are only supported at one end, larger forces are exerted on the apparatus at the remote ends of the drive members when stripping a large size cable. This severely limits the range of cable sizes that can be efficiently stripped by the machine.

In practice, when using prior art devices, different sized cable is stripped by using a range of different sized interchangeable pairs of rollers. This is clearly a disadvantage as the machine cannot be used while the rollers are being changed which is time consuming and inconvenient especially as the rollers tend to be heavy and difficult to handle. Furthermore, the numbers of spares is increased and all must be replaced periodically.

Another drawback with the known construction of cable stripping apparatus is that the larger size cable is gripped by a smaller part of the drive member. Therefore, the drive member must rotate more times per length of large cable than per length of small cable. Thus the rollers wear rapidly towards their smaller ends. This wear is exacerbated by the inefficient grip on the larger sized cables and by the excessive loads imposed on the apparatus while stripping the larger sizes.

The orientation of the rollers is selected so that the desired range of sizes of cable can be stripped, preferably also so that the contact area between the rollers and the cable does not decrease with increasing cable size.

The angle between the axes of rotation of the rollers may be greater than about 30, more preferably greater than about 50, more preferably greater than about 100, especially greater than about 150.

The angle between the axes of rotation of the rollers may be less than about 900, more preferably less than about 500, especially less than about 300.

The angle between the surfaces of the rollers is preferably less than about 750, more preferably less than about 500, especially less than about 350.

The angle between the surfaces of the rollers is preferably greater than about 40, more preferably greater than about 100, especially greater than about 150.

The rollers can conveniently be parallel sided rollers.

Parallel sided rollers are relatively easy to manufacture and maintain. The diameter of the roller is constant and there is no decrease in the area of contact between the rollers and the cable for different sizes of cable. Wear is reduced and larger sizes of cable can be stripped more efficiently.

The rollers can be conical (although it is understood that they need not taper to a point in the sense of being frustoconical). Smaller sizes of cable are engaged by the narrow end of the roller and larger sized cables are engaged by the wider end of the rollers. This means that the area of contact is increased for the larger sizes of cable which are heavier1 stiffer and generally harder to strip. Furthermore, the wider end of the roller is heavier and its weight partly counterbalances the higher loads caused by stripping larger cables.

One of the rollers may be adjustable in order to change the angle between the axes of rotation of the rollers. The 'V' shaped space between the rollers can accept any size of cable between its upper and lower limits. The angle formed between the surfaces of the rollers is important for stripping cable and the optimum angle can vary with the type and size of cable being stripped. The adjustable roller has the advantage that an operator may easily 'fine tune' the machine for optimum stripping efficiency.

Preferably, the cutting means comprises a plurality of circumferential cutting edges provided on at least one of the rollers to cut the sheath of a cable to be stripped. The circumferential cutting edges cut into the sheath of the cable as it is engaged and pulled through the apparatus by the rollers.

The spacing between adjacent cutting edges may vary along the length of the roller surface. A finer spacing is more suitable for stripping small cable sizes which might otherwise slip between adjacent cutting edges.

The height of adjacent cutting edges may vary along the length of the roller surface. Larger sized cables tend to have thicker sheaths and in order for the sheath to be removed the cutting edges must penetrate further into the cable.

Similarly, smaller cables require less penetration.

The rollers may comprise an open structure of blades arranged around one or more discs. Cables, particularly cables for supplying electricity, are often buried and can be covered with dirt soil and other contaminants which may affect the efficiency of the apparatus. Particles of sheath material and other debris can fall through the rollers without becoming embedded in or on the surface and reduce the effectiveness of the stripping process.

The cutting means may comprise a blade for cutting into the surface of a cable and a diverging portion for causing the sheath to splay apart so that the core elements can be recovered from the sheath material easily, in addition to or instead of circumferential cutting edges. The blade and the guide can be formed integrally or as separate adjustable tools.

Guide means may be provided to control the position of the cable in the space between the rollers. The cable has a tendency to move out of the apparatus during stripping.

In a preferred arrangement one of the rollers is driven directly from the drive means and the other roller via a coupling from the driven roller. Only one motor or drive means is necessary to turn both rollers. The coupling may be by chain and sprockets, gears or universal joints, however, it must be understood that other known suitable coupling means could also be used.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure la shows a known arrangement of a pair of conical rollers with their axes of rotation parallel and which is capable of stripping a range of sizes of cable, Figure 1b-1c are sections on lines AA and BB respectively of Figure la comparing the contact areas for stripping a small cable and a large cable, Figure 2 is a side elevation of cable str-ipping apparatus according to the invention with angled parallel sided rollers, Figure 3 is a side elevation of the apparatus depicted in Figure 2 with an adjustable roller, Figure 4 is a side elevation of parallel sided rollers with an open structure, Figure 5a is a plan view. of a cutting tool and guide, Figure 5b is a schematic drawing of the location of the cutting tool and guide in relation to the rollers, and Figure 6 is a side elevation of conical rollers with non parallel axes of rotation.

Figure la shows a known construction of cable stripping machine, generally indicated by reference numeral 1, which comprises two spaced apart conical rollers 2, 3 arranged with their axes of rotation parallel. A cable to be stripped is inserted in the 'V' shaped space between the rollers which engage the cable. A guide and cutting means 4 is moved against the cable in the direction of the arrow 6 to cut the sheath as the cable moves through the apparatus to facilitate recovery of the core elements of the cable. Small cables 7 are engaged at the wide end of the rollers 2, 3 and large cables are engaged at the narrow end of the rollers. Stripping large size cable exerts large loads (in the direction of the arrows 8) on the conical rollers and these loads are exerted at a remote, unsupported end of the machine. This places a limit on the actual size of cable that the machine can strip.Furthermore, as shown in Figure 1b and ic the contact area 10 is drastically reduced for the larger size cable thereby reducing the efficiency of the machine. The rollers must perform more rotations per unit length of cable and this, in -combination with the factors already mentioned, produces rapid wear of the rollers in the region where larger size cables are stripped ie.

towards the narrow end of the conical rollers.

Referring now to Figure 2 there is shown cable stripping apparatus, generally indicated by reference numeral 20, which comprises two parallel sided cable engaging rollers 21, 22 orientated to one another to define a space 23 between the rollers adapted to accept a cable 24 to be engaged and stripped. The axes of rotation of the rollers 25, 26 are nonparallel. Drive means (not shown) is provided for rotating the roller 25 which in turn causes rotation of the roller 22 via the coupling 27. In this arrangement the coupling is a gear coupling, although it must be understood that other suitable couplings well known to the skilled man could be used. The roller is driven by drive means via a gearbox (not shown).

Each of the rollers are supported at both ends by bearings 30.

This provides a very stable configuration which can withstand loads imposed by the cable stripping process. Parallel sided rollers provide a constant contact area along the length the roller. This means that the grip on a cable does not vary with cable size as is the case with known cable stripping apparatus.

Cutting element 28 is moveable in the direction of the arrow 29 to engage and cut the sheath 24b of the cable 24 as the cable moves between the rollers. The cutting element also includes a guide for the cable and a diverging portion downstream of the cutting edge which splays the sheath of the cable to facilitate removal of the core elements 24a. Cutting means for cutting into the cable and splaying the sheath apart are commonly referred to in the trade as 'fish tails'.

Each of the rollers 21, 22 is provided with a plurality of circumferential cutting edges 31 along the length of the roller. These penetrate the cable 24 and assist effective removal of the sheath material. The cutting edges have a generally triangular profile but the profile of the edges can be altered to improve penetration. The rollers are formed from an appropriate hard material, for example, hardened or case hardened steel. The size of the cutting edge and the spacing between adjacent edges varies along the length of the roller in order to strip the various sizes of cable effectively. A scraper (not shown) is used to ensure that the rollers do not become clogged with debris and particles of sheath material.

Figure 3 shows the cable stripping apparatus of Figure 2 but with the roller 22 adjustable relative to the roller 21 in order to alter the angle a between the surfaces of the rollers.

An optimum value for the angle a is approximately 100 to 300 but can vary depending on the type of cable being stripped and the diameter of the cable. The adjusting means 35 can be a lockable screw type arrangement.

In another construction the roller 22 can be moved relative to the roller 21 in order to adjust the apparatus to strip a wider range of cable sizes. For example, the arrangement shown in Figure 2 could be used to strip cables of approximately 5mm to 20mm but if the roller 22 was moved away from the roller 21 by a distance of 15mm (position shown in outline 32) it would be able to strip cables from 20mm to 35mm.

Figure 4 shows cable stripping apparatus which uses two parallel sided rollers 40, 41 which comprise a series of cable engaging blades 42 secured to four discs 43 which in turn are fixed to a shaft 44, 45 of the respective rollers. Dirt and debris from the cable stripping process can fall through the open spaces of the roller without adhering to and clogging the rollers.

Figures 5a and 5b show a cutting element 50 and guide member 51. Cutting element 50 comprises a traditional fish tail arrangement with a cutting edge and a diverging portion for splaying the cable apart. Guide member 51 helps to ensure the cable is located in the apparatus. A further guide member can be integral with the 'fish tail' cutting element to prevent the tool from penetrating too far into the cable. Each of the cutting element 50 and guide member 51 are adjustable in the direction of the arrows 52, 53 and are connected to a table 54 which is also moveable towards or away from the rollers.

Figure 5b indicates the positions of the cutting element 50, guide member 51 and cable engaging rollers 21, 22.

Figure 6 shows cable stripping apparatus according to the invention in which the rollers 60, 61 are conical with their axes of rotation 62, 63 non parallel. In this arrangement larger size cable is engaged towards the wide end of the rollers.- This means that the contact area between the roller and the cable increases with cable size further improving the efficiency of the cable stripping process. The angle '3between the surfaces of the rollers is approximately 100 to 300.

Claims

1. A cable stripping apparatus for removing cable sheathing which comprises: (a) two cable engaging rollers orientated to one another to define a space between the rollers adapted to accept a cable to be stripped, wherein the axes of rotation of the rollers are non-parallel; (b) drive means for rotating at least one of the rollers; and, (c) cutting means for cutting a sheath of a cable as the cable moves through the space defined between the rollers in order to facilitate removal of the sheath from the core elements.

2. Apparatus according to claim 1 in which the contact area between the rollers and the cable does not decrease with increasing cable size.

3. Apparatus according to claim 1 or claim 2 in which the angle between the axes of rotation of the rollers is greater than about 30.

4. Apparatus according to any of the preceding claims in which the rollers are parallel sided rollers.

5. Apparatus according to any of claim 1 to 3 in which the rollers are conical or frustoconical.

6. Apparatus according to any preceding claim in which one of the rollers is adjustable in order to change the angle between the axes of rotation of the rollers.

7. Apparatus according to an preceding claim in which the cutting means comprises a plurality of circumferential cutting edges provided on at least one of the rollers.

8. Apparatus according to any preceding claim in which the spacing between adjacent cutting edges vary along the length of the roller surface.

9. Apparatus according to any preceding claim in which the height of adjacent cutting edges varies along the length of the roller surface.

10. Apparatus according to any preceding claim in which the rollers comprise an open structure of blades arranged around one or more discs.

11. Apparatus according to any preceding claim in which the cutting means comprises a blade for cutting into the surface of a cable and a diverging portion for causing the sheath to splay apart.

12. Apparatus according to any preceding claim in which guide means are provided to control the position of the cable in the space between the rollers.

13. Apparatus according to any preceding claim in which one of the rollers is driven directly from the drive means and the other roller via a coupling from the driven roller.

14. Apparatus according to any preceding claim in which one or both rollers are supported at both ends.