GB2198074A

GB2198074A - Making plastics channelling for electrical cables

Info

Publication number: GB2198074A
Application number: GB08629009A
Authority: GB
Inventors: Frank Harold Ferguson
Original assignee: Grawater Ltd
Current assignee: Grawater Ltd
Priority date: 1986-12-04
Filing date: 1986-12-04
Publication date: 1988-06-08
Anticipated expiration: 2006-12-04
Also published as: GB2198074B; GB8629009D0

Abstract

The material e.g. semi-rigid plastics, (polyvinylchloride) is extruded in the shape of the channelling 1, and is then indented by rolling between knurled and plain rollers 14, 15, to render it flexible, so that it can be coiled for storage. The sides of the channelling are stepped so that, when coiled, adjacent loops of the coil are nested together. The semi-rigid plastics material is shatterproof, with a "memory" for remembering shape. The sides of the channelling may be inclined together towards their free ends, with the web being arcuate between the sides (Fig 4 ) to compensate for distortion due to the coiling. <IMAGE>

Description

Channelling for electrical cables This invention relates to channelling made from plastics material for covering electrical cables during installation.

In the construction industry, channelling is used to contain electrical cabling against surfaces. When a cable is required to be fixed against a planar surface, such as for example a wall or roof the channelling is affixed to the planar surface over the electrical cable so that the cable is contained within the channel.

Channelling is generally provided in relatively rigid lengths which must be cut to size before use. Ihis can lead to storage problems and to significant wastage.

According to the present invention there is provided a method of manufacturing channelling comprising the steps of a) extruding plastics material through a die to form a member of predetermined generally shaped cross-sectional shape with the side walls joined by a web and the free ends of the side walls extending outwardly to form flanges; b) shaping the side walls to form steps therein between the web and the flanges; c) indenting the surfaces of the web and/or flanges whereby to permit curvature of the channelling about an axis transverse to its length; and d) coiling the indented channelling.

In order that the present invention be more readily understood, an embodiment thereof will now be described by way of example with reference to the accompanying drawings.

in which Figure 1 is a perspective view of a length of channelling.

Figure 2 is a perspective view of two pieces of channelling nested together; Figure 3 shows a block diagram of a process of manufacture; Figure 4 is a perspective view of a length of channelling: Figure 5 is a schematic side elevation of an indentation means.

Figure 6 is a schematic front elevation along the line VI - VI of Figure 5.

In Figure 1. a length of channelling is of general ly inverted Shape with the free ends of the arms or side members 5 extending outwardly to form flanges 3. The side members 5 are jointed together by a web 4. The flanges 3 have sections of reduced thickness 7 to facilitate the driving of nails therethrough. whilst the web 4 is shown provided externally with elongate ribs R to facilitate adhesion of plaster to the channelling.

The two arms or side members 5 are shown as being stepped with the external width dl of an upper portion of the channelling 1 less than the internal width .d2 of the lower portion, so that one length of channelling may be fitted over a further length, as shown in Figure 2. The reason for this will become apparent.

In a preferred embodiment of the invention, the channelling is of uniform wall thickness, generally of the order of 1.4 to 1., millimetres. A suitable material for the channelling is a semi-rigid plastics material. such as polyvinylchloride. with a 'memory" for remembering shape.

The material is advantageously stable at temperatures below 00C and is resistant to shattering.

A suitable material is commercially available from Polycol (PVC) Limited under the grade reference FC i5/#5T and has the following approximate properties. A Cold Flex temperature of -30C, a Cold Bend temperature of -250C and a Tensile Strength of 15.3 MN/m2.

A further suitable material is available from Norsk Hydro Polymers Limited under the grade reference XN 75467 and has the following approximate properties. A maximum Cold Flex temperature of -60C, a maximum Cold Bend temperature of -200C, a minimum Tensile Strength of 15.2 MN/m2 and a nominal Shore A Hardness of 92.

To form the basic shape of the channelling the material may be extruded through a main die 9 (Figure 3), shaped to produce a section similar to that shown in Figure 1. The extruded material may then be cooled 10. To compensate for the fact that bending the channelling into an arcuate form can distort the cross-sectional profile of the channelling, the channelling may then be passed through a further sizing die 1I to form the channelling into the shape shown in Figure 4 with the web 4 now arcuate rather than straight and the free ends of the side walls 5 being closer together to define a sector shape. The flanges 3 extend normally from the lower side walls 5. Alternatively, the main die 9 may be shaped to produce the section shown in Figure 4 to eliminate the need for a further sizing die.

After the channelling is formed into the shape of Figure 4, it may then be cooled further 12 to record the shape of Figure 4 in the memory of the material.

To facilitate coiling of the channelling into rolls, it is desirable to pass the channelling through means 13 whereby at least the bottom surfaces of the flanges and/or web 4 may be indented. One such method of achieving this is shown in Figures 5 and 6 where two rollers 14. lj are provided with generally corresponding cross-sectional profiles at their circumference. The profile of one of the rollers i4 is provided with a straight knurled finish, whilst the surface of the other roller 15 is generally smooth.By suitably adjusting the gap between the rollers and passing the channelling between them, the knurling on roller 14 may be impressed into the undersurface of the channelling to elastically deform it so as to form a multitude of small transverse indentations which act like hinges to facilitate rolling the channelling into coils upon exit 16 from the rollers.

During the first stage of rolling 16 the channelling into coils, the process of bending it into a generally arcuate form before it joins the coil biases the channelling from being of the section shown in Figure 3, to that shown in Figure 1. Consequently, when the channelling is incorporated into the coil it is able to nest over the previously rolled loop of the channelling as shown in Figure 2.

When a sufficient length of channelling has been rolled into a coil, the coil may be bound and stored until it is needed for use. The nesting effect of the adjacentloops of the coil provide a reasonable degree of resistance to the coil being inadvertently uncoiled through rough handling.

To remove an amount of channelling from the coil.

the necessary amount is unrolled and may be cut off to length. Because of the memory of the material, the length of channelling may be straightened into a generally elongate form. When the channelling is offered up to the surface against which it is to be fitted,the cross-sectional shape thereof is similar to that shown in Figure 4. When the channelling is suitably positioned over the cable to be contained therein, the web 4 of the channelling may be placed under pressure, for example by the fitter's thumb.

to distort the channelling into a profile similar to that of Figure 1. The channelling may then be readily affixed to the surface by driving a suitable fixing means, such as nails, into the surface through sections 7.

Claims

Claims:

1. Method of manufacturing channelling comprising the steps of a) extruding plastics material through a die to form a member of predetermined generally U-shaped cross-sectional shape with the side walls joined by a web and the free ends of the side walls extending outwardly to form flanges; b) shaping the side walls to form steps therein between the web and the flanges; c) indenting surfaces of the web and/or flanges whereby to permit curvature of the channelling about an axis transverse to its length; and d) coiling the indented channelling.

2. A method according to claim 1, wherein the web is formed to adopt an arcuate shape in cross-section prior to indenting with the side walls adopting a position corresponding to radii of the circle on whose circumference lies the web.

A Amethod according to claims 1 or 2, wherein the side walls are stepped to permit the web of one coil to be received in the U-shaped channel of the immediately adjacent outer coil.

4. A method according to claim 1,2 or 3, wherein the plastics material is polyvinylchloride.

5. A method according to claim 4, wherein the wall thickness of the channelling is of the order of 1.4 to 1.7 millimetres.

6. A method as hereinbefore described with reference to the accompanying drawings.

7. Plastics channelling when made by the method according to any one of the preceding claims.

8. Plastics channelling as claimed in claim 7, wherein the width of the channelling across the web is less than the internal width of the channelling between the flanges.

9. Plastics channelling substantially as herein before described with reference to the accompanying drawings.