Composite plastics pipes comprising an inner core and an outer protective layer are known. The outer protective layer may, for example, provide environmental the pipe is laid in a trench. In joining sections of such a pipe, it has been proposed to remove the outer protective layer in the regions surrounding the pipe ends to be joined in order to permit the installation of a pipe coupler, such as, for example, an electrofusion pipe coupler. Examples of such pipes with outer protective layers are described in WO-A-9300212, WO-A-9215818, EP-A- 0474583 and in WO-A-9622485 the entire disclosures of which are incorporated herein by reference for all purposes.

In practice it has proved to be extremely difficult to remove the outer protective layer cleanly from the pipe inner core without damaging the inner core when using conventional tools such as knives, scrapers etc.

In GB1487033 there is described a tube cutting and chamfering tool comprising an adjustable C-shaped frame,

a pair of spaced cutting wheels arranged in a common plane, supporting rollers for the tube, and a chamfering cutter adjustably located between the two cutting wheels. This tool is quite complex in design and is not readily adapted to remove the outer protective layer of a composite pipe.

GB1458366 describes a tool for cutting a cable sheath which comprises a loop-like frame, including at least two hingedly connected parts, means for releasably holding the frame parts in closed loop form, a handle connected to the frame, and a cutter assembly mounted for adjustment both inwardly and outwardly of the loop and angularly about the axis of its inward and outward movement. The cable sheath is supported by rollers mounted on the frame and, in some embodiments, also on the cutter assembly. This tool is complex both in design and operation.

In GB2296886 there is described and claimed a pipe preparing tool which comprises: a frame having an opening adapted to receive a pipe or a portion thereof; a first tapered roller means mounted transversely on the frame;

a second tapered roller means mounted transversely on the frame and spaced apart from the first tapered roller means; the arrangement being such that the first and second tapered roller means have opposed directions of taper; a cutting, scoring or penetrating means mounted on the frame and spaced apart from the first and second roller means; and clamping means adapted to apply a clamping force to the pipe such that the first and second tapered roller means and the cutting, scoring or penetrating means are brought into contact with the pipe and the cutting, scoring or penetrating means penetrates a surface layer of the pipe; the arrangement being such that the pipe and the tool can be rotated relatively to one another about the axis of the pipe whereby the cutting, scoring or penetrating means produces a helical groove in at least a surface layer of the pipe.

This tool works well in practice, and can be used to strip off the outer layer of a composite pipe, but again some further simplification of the design would be

desirable. In particular, it would be desirable to provide a cheaper tool and one wherein the number of moving parts, such as rollers, can be reduced or eliminated.

The present invention provides a pipe preparing tool of relatively simple construction which, in a preferred embodiment, is capable of cutting or scoring a helical groove in a pipe outer surface. In appropriate embodiments, the outer protective layer only is penetrated, so that it can readily be peeled cleanly away from the inner core without any substantial damage to the inner core.

In a first aspect, the present invention provides a wraparound pipe preparing tool which comprises: a C-shaped clip of resilient material having on one end thereof a tool receptor for a cutter assembly, the clip being adapted to snap onto the pipe to be prepared so that the cutter assembly is pressed against the surface of the pipe.

Preferably said clip is formed from spring material and said receptor comprises a C-shaped clip-element of the clip adapted to snap onto the cutter assembly, the assembly comprising a substantially cylindrical body.

Preferably, the cylindrical body has a flat or concave face in the cylindrical surface of the body and in which a cutter element, carried by the body, protrudes through a slot in said face, the flat or concave face being adapted to bear against the surface of the pipe and to maintain the cutter element in contact with the pipe.

Preferably, the clip-element opens in a plane substantially tangential to the curve of the C-shaped clip, so that a user gripping the clip-element to hold the cutter assembly increases the security of the grip on the assembly by the clip-element reducing any tendency of the cutter assembly to rotate in the clip-element as the clip is drawn around the pipe.

Preferably the body comprises a housing mounting a shaft on which said cutter element is mounted the cutter element protruding through a slot in the housing. The shaft may be rotatable between discrete positions whereby different parts of the cutter element may protrude through the slot.

Preferably said different parts have cutting edges at different angles to a plane normal to the axis of clip, which axis corresponds with the long axis of the pipe when the tool is in use.

Preferably a knob of the shaft at the end of the housing may be employed to rotate the shaft in the housing.

Preferably a ratchet is formed on the shaft against which a pawl in the housing bears to lock the shaft against rotation in one direction. In use, the tool will be rotated around the pipe in said one direction.

In accordance with a different aspect of the present invention there is provided a cutter assembly, comprising a housing mounting a shaft on which a cutter element is mounted, the cutter element protruding through a slot in the housing, the shaft being rotatable between discrete positions, whereby different parts of the cutter element protrude through the slot, and wherein said different parts have cutting edges at different angles to a plane normal to the axis of the shaft. Any suitable means of mounting such an assembly on a pipe for drawing around the pipe to score the pipe may be employed.

In accordance with another different aspect of the present invention there is provided a skin preparing tool comprising a housing and a rotary cutter element in the housing, the cutter element having a central point and peripheral cutters protruding a predetermined distance from an opening of the housing, whereby a circular cut

can be made in the surface of the pipe by pressing the tool against the pipe so that the point and cutters penetrate the pipe up to said opening of the housing and by rotating the tool.

If the distance is arranged equal to or slightly greater than the thickness of a skin on the pipe, then a fillet of the skin can be removed.

Preferably said skin preparing tool includes or comprises a skin lever.

The invention is further described hereinafter by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded view of a pipe preparing tool in accordance with the first aspect of the present invention; Figure 2 is a perspective view of the assembled tool of Figure 1; Figure 3 is a plan view of the cutter assembly of the tool of Figure 1, part of the housing having been removed; Figure 4 is a section through the cutter assembly of Figure 3; Figure 5 shows a variety of different sized clips for the tool of Figure 1;

Figures 6a, b and c are, respectively, an exploded view of a different embodiment of a cutter assembly of a pipe preparing tool in accordance with the first aspect of the present invention, an end view in the direction of the arrow A in Figure 6a, and a perspective view of the tool; Figure 7 is a perspective view of a pipe having a skin which is partly peeled back exposing a core of the pipe; Figures 8a, b and c are, respectively, a side view of a pipe skin preparing tool in accordance with the second aspect of the present invention, a surface view of a pipe showing a fillet removed therefrom, and a side view, partly in section, of the tool of Figure 8a; Figures 9a and b are perspective views of different, hand operated, embodiments of the tool illustrated in Figure 8a; and, Figures 10a, b and c are perspective views of skin levers in accordance with the present invention.

In Figures 1 to 4, a pipe preparing tool 10 comprises a clip 12 formed from a band of spring steel formed into a C-shape. A cutter assembly 14 is retained in a clip-element 16 which comprises a C-bend in the clip 12. The cutter assembly 14 comprises a housing 18 in two parts, an upper housing 18a and a lower housing 18b.

Captured between the upper and lower housings 18a, b is a shaft 20 which is rotatable in the housing 18.

On a square section 22 of the shaft is mounted a cutter element 24 having a square section aperture 26.

The cutter element 24 has three cutting parts 24a, b, c, anyone of which can protrude through a slot 28 in the lower housing 18b. A ratchet 30 retains the cutter element 24 on the shaft 22. A knob 32 is mounted on the end of the shaft 20 and by means of which the shaft may be rotated to expose different ones of the cutter parts 24a, b, c through the slot 28.

The housing 18 is substantially cylindrical so that it is rotatable within the clip-element 16. However, when the clip 12 is snapped onto a pipe (not shown) the cutter assembly is pressed against the pipe surface. By rotating the cutter assembly in the clip-element 16 a flat face 34 of the housing 18 will snap into engagement against the surface of the pipe, a lip 36 accommodating the curvature of the pipe. In this position, further rotation of the cutter assembly in the clip-element 16 is inhibited. The slot 28 is formed in the face 34.

Shoulders 38a, b on the housing 18 prevent the cutter assembly moving axially with respect to the clip-element 16.

Turning to Figure 3, the housing 18 comprises two moulded plastic components having retaining elements 40, by means of which the two parts can be detachably clipped together. When unclipped, the shaft 20 with its knob 32, cutter element 24 and ratchet 30, can be removed from the housing 18.

Turning to Figure 4, it can be seen that the ratchet 30 is retained on the shaft 20 by means of two hooked prongs 42 formed at the end of the shaft 20. By pressing the prongs together, the ratchet 30 can be removed from the shaft 20 so that the cutter element 24 can be released. This enables replacement of the cutter element 24 should it become blunt in time.

The ratchet 30 has ratchet teeth 44 which engage a pawl 46 formed as a leaf in the upper (or lower) housing 18a.

The shaft 20 is located by flanges 25 thereon which seat on either side of webs 27 in the housings 18a, b.

The webs 27 have semicircular seats which carry the shaft 20.

With reference to Figure 5, the clip 12 can be provided in numerous sizes having various radii rl, r2... r5. The radii ri to rS correspond with different sized pipes commonly employed. Each clip 12 is, however,

provided with an identical clip-element 16 so that the same cutter assembly 14 can be employed to score different sized pipes.

Indeed, it is for this reason that the cutter element 24 is provided with a plurality, preferably 3, cutting parts 24a, b, c. When fixed in position by the ratchet 30, each cutter part is arranged so that its cutting surface is substantially tangential to the curvature of the clip 12, and hence the curvature of the pipe it is intended to score. However, each cutting part 24a, b, c is arranged at a different angle with respect to the radial plane of the pipe, that is to say, the plane which is normal to the axis of the clip 12, which corresponds with the axis of the pipe on which the clip 12 is snapped. At least one of the cutter parts (for example, part 24a) will be parallel that plane, so that, in use, when the clip 12 with a cutter assembly received in the clip-element 16 is snapped onto a pipe with the face 34 against the pipe surface and the cutter assembly 14 drawn around the pipe within the confines of the clip- element 16 (the clip 12 sliding around the pipe), the cutter part scores a groove or cut in the pipe surface which is circular and which stays in the radial plane, ie the ends of the cut will meet.

However, a second 24b of the cutter parts is inclined with respect to the radial plane, so that, as the cutter assembly rotates around the pipe, the inclination of the cutter moves the tool progressively along the pipe, so that a helical groove is scored into the pipe surface. The width of the helical band scored by the cutter depends on the angle of inclination of the cutter part 24b and also the diameter of the pipe.

Thus the third cutter part 24c has a different angle of inclination with respect to the cutter part 24b, for example a greater inclination with the respect to the radial plane, so that on small radius pipes, a band of similar width is scored compared with the cutter 24b on larger diameter pipes.

The width of the band is not critical, but nevertheless should be large enough so that a reasonable quantity of skin is peeled from the pipe for any one rotation of the tool about the pipe, but not so much that the force required to peel is excessive.

Turning to Figures 6a, b and c a slightly different embodiment of the tool described above with reference to Figures 1 to 4 is shown. One difference to be appreciated is in the shape of the knob 32'. Also, not all the flanges 25 on the shaft 20'are provided.

Turning to Figure 7, a pipe 60 comprises a core 64 and a skin 61 which provides abrasion resistance and other characteristics to the pipe 60. When two pipes 60 are to be joined by electrofusion, the skin 61 near the end of the pipe is removed so that clean unoxidised material is exposed which is immediately suitable for electrofusion without the need for any scraping to expose unoxidised material. A tool in accordance with the present invention is employed to score the pipe around its circumference to form a helical score 62. However, a circumferential cut 65 is also made at the end of the exposed region of the pipe.

Once the scoring of the pipe has been completed, there is still a practical difficulty in lifting sufficient of the skin 61 to enable a band 63 to be peeled from the pipe by hand.

Turning to Figures 8 to 10, a pipe skin preparing tool 100 is shown comprising a housing 110 and a cutter 112. The cutter 112 can comprise a standard wood drill bit having a point 114 and wing cutters 116. The cutter 112 is mounted in the housing so that just a tip of the cutter 112 protrudes through an opening 118 of the housing 100. The depth of protrusion should be sufficient to penetrate completely the skin 61 of the pipe 60, as shown in Figure 8a. In Figure 8a, the tool

100 is inserted in a drill chuck 120 which can be employed to quickly score a circular patch, shown removed in Figure 8b.

In Figures 9a and b, the tool 100'is provided with different handles 122a, b for hand operation. In Figure 10, a skin lever 124 is shown for lifting a first lip of the skin 61. In Figure 10a, skin lever 124a is shown as a detachable element fixed in a slot 126 of skin preparing tool 100a. In Figure lOb, the skin lever 124b is shown as a protrusion on the end of skin preparing tool 100b. In Figure 10c the skin lever is shown as a separate tool. ~