GB2246673A

GB2246673A - Electrical cable protection

Info

Publication number: GB2246673A
Application number: GB9116379A
Authority: GB
Inventors: Michael Ralph Forman; Florence Doreen Forman
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-07-30
Filing date: 1991-07-30
Publication date: 1992-02-05
Anticipated expiration: 2011-07-30
Also published as: GB9116379D0; GB9016667D0; GB2246673B

Abstract

A cable 17 for connecting a hand held electrical power tool 10 e.g. a hedge trimmer, to a power supply has a length of reinforced flexible plastics sleeve 20 or hose e.g. PVC with braided nylon, fastened to that part of the cable which is most likely to contact the moving parts of the tool. The sleeve may be only 1 to 2.5 m long, 10 to 16 mm thick and brightly coloured, and have an anti-friction surface. The sleeve is fastened in position by releasable fastening means 21 disposed at opposite ends of the sleeve so that it may be moved along the cable. Alternatively helical or split ring fastening means may be used (Figs 3 & 4). In a modification (Fig 5), instead of a reinforced plastics sleeve, the cable may be formed with a region of thicker insulation adjacent one end. This region may be moulded integrally with the insulation of the cable or may be formed by bonding an additional layer of insulating material; the thicker region may be of the same or a different insulating material. <IMAGE>

Description

ELECTRICAL CABLE PROTECTION The present invention relates to the protection of insulated electrical cables used for connecting portable or hand-held electrical power tools to electrical power supplies and, more particularly, to protecting such cables from damage as a result of accidental contact with moving blades or other moving parts of the tools and consequent risk to the user of electrocution.

Safety is an extremely important consideration in relation to the use of hand-held electrical power tools, such as, hedge trimmers, chain saws and other saws of all types, sanders, grinders, planes, files and rotary mowers, which are connected to electrical mains supplies by cables.

When using such a tool, there is always a risk of the cable being cut, trapped, chafed or entangled with the moving parts of the tool because the cable is extremely flexible and not easy to control whilst manoeuvring the tool. For example, when using an electrical hedge trimmer, it is not uncommon for the cable to catch in the gate of the oscillating cutting blades and sever the cable. The most vulnerable part of the cable is the length of cable immediately adjacent or proximal the tool. Various means have been devised to reduce the risk of electrocution in the event of cable damage, such as, residual current devices, fast acting fuses, circuit breakers and insulated grips, and brightly coloured cable has been used in an effort to provide a readily visible indication as to the position of the cable relative to the tool.However, whilst these prior devices reduce the risk of electrocution when a cable is accidentally damaged, none of them are designed to prevent damage to the cable in the event of contact with moving parts of the tool and the additional inconvenience and expense of having to replace or repair the damaged cable.

It is an object of the present invention to provide means for protecting the electrical cable of a hand-held electrical power tool against damage as a result of accidental contact with moving parts of the tool.

From one aspect, the invention consists in an insulated electrical cable for connecting a hand-held electrical power tool to a power supply, having a region of thicker insulation than the remainder of the cable surrounding the cable and extending over a short length thereof from a position adjacent one end.

The cable may have an electrical connector at the said one end for connecting the cable to the power tool, and the region of thicker insulation extends from a position adjacent and spaced from the connector so that it does not interfere with any rewiring of the connector which may be required, and necessitating removal of insulation from around the wires.

The region of thicker insulation serves to protect the proximal length of the cable which is most likely to contact the moving parts of the tool. In the event of contact, the added thickness reduces the risk of cutting.

The thicker insulation has inherent resiliency, which tends to cause it to bounce off the. moving parts of the tool, and its strength provides resistance to severing of the cable should contact occur.

The region of thicker insulation may be moulded integrally with the normal insulation of the cable or may be formed by bonding to the latter an additional layer of the same or different insulating material. Preferably, the region of thicker insulation is formed by a strong, light resilient plastics material, such as silicon plastics material, or any other suitable material.

The thicker region of insulation should extend over a short length of the cable which is most likely to contact the tool, and should be of a thickness appropriate to the danger of severance by the tool. Depending on the tool for which the cable is to be used, the region may be 0.5m, 2m or up to 6m in length, and it may have a diameter of from 10 to 16mm.

From another aspect, the invention consists in an insulated electrical cable for connecting a hand-held electrical power tool to an electrical power supply, having a reinforced, or at least not readily flattenable, flexible tube or sleeve of insulating material fastened in surrounding relation with the cable and extending over a short length of the cable from a position at or adjacent one end thereof.

The cable may have an electrical connector at the said one end for connecting the cable to a mating connector of the tool. The tube or sleeve, which is preferably a reinforced plastics tube or sleeve such as reinforced PVC hose, is made of sufficient length and external diameter relative to the type of electrical tool so as to protect the proximal length of cable which is most likely to contact the moving parts of the tool. In most cases, this protective tube or sleeve will need to be at least 1 metre in length to achieve the desired result. For example, electrical cable for small electrical hand tools, such as sanders, planes and small saws, may have a protective tube or sleeve which is from 1 to 1.25m in length and 16mm in external diameter.Cable for other tools, such as hedge trimmers and chain saws, may have protective sleeves of approximately 1.5m in length and 18mm in external diameter, and a cable for a lawn mower may have a protective sleeve which is approximately 2.5m in length and 18mm in external diameter.

Whilst the protective tube or sleeve is flexible, it is stiffer and heavier than the cable so that it serves to improve control over the cable and tends to guide the cable away from the moving parts of the tool during normal usage, even if the cable is simply allowed to hang from the tool rather than the user manually supporting the tube or sleeve. Should the protected part of the cable contact the moving parts of the tool, the protective tube or sleeve protects the cable against contact with cutting blades, for example, it resists movement of the cable into the cutting gate of a hedge trimmer and tends to bounce off the cutting edges of tools, such as, chain saws.

The protective tube or sleeve should be of a suitable internal diameter so as freely to house the insulated electrical cable and the external diameter depends on the nature of the tool. For example, in the case of a hedge trimmer, the tube or sleeve should be of sufficient external diameter so as to prevent it entering the cutting gate of the hedge trimmer.

Preferably, the protective tube or sleeve is a loose fit on the cable and is fastened in position by means disposed at opposite ends of the sleeve. Such fastening means is advantageously releasable so that the protective sleeve is not permanently fixed in position but may be readily moved along the cable and be refastened in a fresh position, if desired. For example, the fastening means may take the form of bushes at opposite ends of the sleeve which are an interference fit about the cable and within the adjacent open ends of the sleeve. In another embodiment, the means for fastening the sleeve to the cable comprises helical clamping or gripping devices made from plastics and/or rubberised material which can be disposed on the cable and wedged into the opposite open ends of the sleeve by a screwing action in order to provide an interference fit between the sleeve and the cable. Such clamping or gripping device may be of variable length and diameter appropriate to the electrical cable and the individual requirements of the particular tool.

The region of thicker insulation or the protective sleeve may be brightly coloured, for example it may be bright yellow, in order to provide an obvious visible indication as to the position of the cable.

From yet another aspect, the invention consists in a kit of parts for protecting an electrical cable for a hand-held electrical power tool, comprising a length of reinforced, or at least not readily flattenable, plastics tube or sleeve for surrounding the cable with a loose fit, and means for fastening the tube or sleeve to the cable to retain it in a preselected position on the cable.

From still another aspect, the invention consists in a hand-held electrical power tool having an electrical cable according to the invention for connecting the tool to an electrical supply.

In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Figure 1 is a perspective view of a hedge trimmer having an electrical power cable embodying the invention, the protective sleeve being shown particularly in section, Figure 2 is an enlarged sectional view of the protective sleeve showing one embodiment of fastening means for securing the sleeve to the cable, Figure 3 is a view similar to Figure 2 showing a second embodiment of fastening means, Figure 4 is a perspective view of a third embodiment of fastening means, and Figure 5 is a view similar to Figure 1 illustrating an embodiment in which the power cable is provided with a region of thicker insulation in place of a protective sleeve.

Referring to Figure 1 of the accompanying drawings, the hedge trimmer 10 is of known construction and comprises a double-sided cutting 11 having cutting gates 12, insulated grips or handles 13, 14, and a short inlet cable 15 having a plug or socket connector 16 as its free end.

Electrical mains power is supplied to the hedge trimmer via a long electrical cable 17, which may, for example, be 6.5 to 7mm in diameter, having a socket or plug connector 18 at one end for fitting to the connector 16 of the hedge trimmer, and a plug 19 at its opposite end for connecting the cable 17 to a suitable mains supply.

A protective tube or sleeve 20 made from reinforced plastics hose, for example, PVC hose reinforced with braided nylon, is fastened in surrounding relation with a length of the cable adjoining the connector 18. The sleeve 20 is a loose fit on the cable 17 and is fastened in position by means of flanged bushes 21 at opposite ends of the sleeve.

These bushes are an interference fit about the cable and within the adjacent open ends of the sleeve. As shown in more detail in Figure 2, each bush 21 comprises a cylindrical collar portion 22 engaged in the adjacent end of the sleeve and an outwardly tapering flange portion 23 projecting from the sleeve end. The latter abuts the shoulder 24 between the collar and flange portions and is flush with the flange portion so that the bush provides a neat termination to the sleeve end. The sleeve 20 is an interference fit on the collar portion 22 and this enhances the grip of the bushes on the cable in order adequately to resist sliding movement of the sleeve relative to the cable.

The sleeve 20 may be brightly coloured to improve its visibility and, for a hedge trimmer, should be approximately 1.5m in length. In the case of a hedge trimmer in which the maximum width of the cutting gates 12 is approximately 12mm, the sleeve 20 should have an external diameter of approximately 18mm so as to prohibit the sleeve and, hence the length of cable protected thereby, from entering a gate. The sleeve should have a shiny or anti-friction external surface, and not a rubberised or frictional external surface, so that the sleeve has a tendency to be eject ed away from the cutter 11 should it accidentally engage the mouth of a gate 12.

When a hedge trimmer 10 is being operated, it is normal for the user to hang the cable over one shoulder with a view to maintaining it clear of the cutter 11. When used in a similar manner with a protective sleeve 20 according to the invention is supported over one shoulder, the sleeve serves more positively to guide the cable away from the trimmer and hold the unprotected part of the cable away from the cutter. Even if the cable with its protective sleeve is simply allowed to hang from the inlet lead 15 without being guided over the user's shoulder, the stiffer and heavier sleeve 20 tends to maintain the cable hanging away from the cutter under normal usage of the hedge trimmer.Furthermore, even if the proximal length of cable accidentally contacts the cutter, it is protected by the sleeve 20 which being of larger external diameter than the width of the gates 12 resists entry into the gates, thereby avoiding cutting of the cable even if some damage is sustained to the protective sleeve.

Another embodiment of fastening means for securing the loose fitting protective sleeve 20 to the cable 17 is illustrated in Figure 3. In this embodiment, the fastening means comprises two helical grippers 25 (only one being shown in Figure 3) each of which is formed from laminated strip material or elastomeric material. The external lamination 26 is a flexible plastics material whilst the internal lamination 27 is a rubberised material. When not installed, the helical gripper has an internal diameter slightly smaller than the external diameter of the cable 17 so that it may grip the cable and an external diameter slightly greater than the internal diameter of the sleeve 20. The thickness of the strip from which the helix is formed is slightly greater than the annular spacing between the external surface of the cable and the internal surface of the sleeve.Each helical gripper 25 is firstly fitted onto the cable 17 at opposite ends of the sleeve 20 fitted by screwing it on to the cable if there is not a convenient free end over which it can slide. Thereafter, each gripper is inserted into the space between the cable and the adjacent end of the sleeve by pushing the gripper into the end of the sleeve whilst turning in a direction to tighten the helix. In this manner, the helical gripper is tightly inserted into the end of the sleeve and wedges between the sleeve and the cable to produce an interference fit therebetween which resists movement of the sleeve relatively to the cable.

Figure 4 illustrates another fastening device 28 which operates in a similar manner to that described with reference to Figure 3 except that, instead of being helical, it is formed by a multiplicity of interconnected split rings 29 made of laminated strip material or elastomeric material. The splits 30 in the rings enable the device readily to be fitted on to a cable and, thereafter, it may be tightly wedged between the cable and an adjacent open end of the protective sleeve, in a similar manner to that described with reference to Figure 3, to produce an interference fit resisting relative movement of the sleeve and cable.

The gripping devices 25,28 described with reference to Figures 3 and 4 are suitable for securing a protective sleeve to a wider range of cable diameters than the flanged bush 21. For example, they may be used for fastening protective sleeves to cables having diameters in the range from 5 to 7mm.

Figure 5 illustrates a hedge trimmer and cable combination similar to Figure 1 and like reference numerals in Figures 1 and 5 indicate similar parts. However, in the embodiment illustrated in Figure 5, the electrical cable 17 is protected by a region of thicker insulation. Over a major portion of its length, the cable 17 is insulated in the normal way, and is about 6.0 to 7.5mm in diameter.

Extending over the region 31 of the cable, for example for 1.5m, from a position adjacent but spaced from the connector 18, there is an additional thickness of insulation, preferably comprising silicon plastics insulating material, which increases the diameter of the cable over the region to about 15mm. This region 31 is less likely to enter a gate 12 of the hedge trimmer 10 and, in the case of accidental contact, tends to be thrown away from the moving blades due to the resilience of the silicon plastics forming the region 31.

Whilst a particular embodiment has been described, it will be understood that modifications can be made without departing from the scope of the invention as defined by the appended claims. For example, whilst the protective sleeve 20 is conveniently made from reinforced plastics hose, any plastics tube which is not readily flattenable may be utilised as the protective sleeve.

Claims

1. An insulated electrical cable for connecting a hand held electrical power tool to an electrical power supply, having a region of thicker insulation than the remainder of the cable surrounding the cable and extending over a length thereof from a position at or adjacent one end.

2. An electrical cable as claimed in claim 1, in which the region of thicker insulation is moulded integrally with the normal insulation of the cable or is formed by bonding to the latter an additional layer of the same or a different insulating material.

3. An electrical cable as claimed in claim 1 or 2, in which the region of thicker insulation is formed by silicon plastics material or other strong light resilient plastics material.

4. An electrical cable as claimed in claim 1, 2 or 3, in which the region of thicker insulation is from 0.5m to 6m in length and has an outside diameter of from 10-16mm.

5. An electrical cable for connecting a hand held electrical power tool to an electrical power supply, having a reinforced, or at least not readily flattenable, flexible tube or sleeve of insulating material fastened in surrounding relation with the cable and extending over a length thereof from a position at or adjacent one end.

6. An electrical cable as claimed in claim 5, in which the tube or sleeve is a reinforced plastics hose having such an internal diameter as freely to house the electrical cable therein.

7. An electrical cable as claimed in claim 5 or 6, in which the tube or sleeve is at least one metre in length and has an external diameter of from 16mm to 18mm.

8. An electrical cable as claimed in any one of the preceding claims, having an electrical connector at said one end of the cable for connecting the cable to the power tool, the region of thicker insulation or the tube or sleeve extending from a position adjacent and spaced from the electrical connector.

9. An electrical cable as claimed in any one of the preceding claims, in which the region of thicker insulation or the tube or sleeve is brightly coloured in order to provide an obvious visible indication as to the position of the cable adjacent the tool.

10. A hand held electrical power tool having an electrical cable as claimed in any one of the preceding claims for connecting the tool to an electrical power supply.

11. A kit of parts for protecting an electrical cable for a hand held electrical power tool, comprising a length of reinforced, or at least not readily flattenable, flexible tube or sleeve of insulating material for surrounding the cable with a loose fit, and means for fastening the tube or sleeve to the cable to retain it in a selected position on the cable.

12. An electrical cable, power tool or kit of parts as claimed in claim 5 or 11 or any one of the preceding claims 6 to 10 as appendant to claim 5, in which the tube or sleeve is fastened in position on the cable by means disposed at opposite ends of the tube or sleeve.

13. An electrical cable, power tool or kit of parts as claimed in claim 12, in which said fastening means is releasable so that the tube or sleeve is movable along the cable and fastenable in a selected position.

14. An electrical cable, power tool or kit of parts as claimed in claim 12 or 13, in which the fastening means is in the form of bushes disposable at opposite ends of the tube or sleeve and being an interference fit about the cable and within the adjacent open ends of the tube or sleeve.

15. An electrical cable, power tool or kit of parts as claimed in claim 12 or 13, in which the fastening means comprises helical clamping or gripping devices made from plastics and/or rubberised material which are disposable about the cable and wedged into the opposite open ends of the tube or sleeve by a screwing action in order to provide an interference fit between the tube or sleeve and the cable.

16. An electrical cable, power tool or kit of parts constructed substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

17. An electrical cable or power tool constructed substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.