This invention relates to pipe connectors, such as plastics pipe connectors of the type typically used to connect pipes underground, such as water pipes supplying water to buildings,

A common method of connecting plastics water pipes of the type described above is by the use of compression fittings in which the tubular connector has threaded ends onto which respectively opposite threaded compression collars may be received, the collars themselves being rotatable with respect to the connector to capture the end of the pipe to both mechanically secure it to the connector fitting as well as sealing the connection therebetween by, typically, an 'Ο' ring or similar compressible seal Given that the typical working pressure is 18 bar, requiring ^' the application of considerable turning forces, it will be understood that installing such compression fittings below ground can be time consuming and difficult. This problem is exacerbated where the free ends of the pipe have to be cut or otherwise prepared but are already below ground and hence difficult to access. In the case of contaminated ground pipework, where the pipe itself is sheathed with a, typically, wound aluminium cover to prevent the ingress of chemical contaminants into the plastics piping and hence into the water itself, this problem is compounded because of the need to ensure that there is no gap between the compression seal and the outside of the pipe where the connection is made.

The foregoing disadvantages are largely overcome by the use of push-fit fittings the type described in GB2206569 to a connector fitting having a tapered chamber within which is disposed a radially expandable correspondingly tapered collar, and associated '0 ^s ring, the collar acting to grip the pipe with increasing force in response to positive pressure within the pipe tending to force the pipe out of the fitting, in a manner similar to a Chinese fingerloek. To prevent the pipe from buckling under the compressive load of the collar as it is squeezed against the outside of the pipe, the end of the pipe is provided with an internal ferrule and associated flange for ensuring that the position of the ferrule is maintained relative to the connector fitting. However, whilst this general arrangement is an improvement on compression fittings in terms of ease of installation and accessibility, it exposes the cut end of the pipe to the internal water pressure, and where the pipe is of laminate construction, such as in the case of contaminated ground water piping, it allows the ingress of water- between and along the laminated layers, even though the outside of the pipe is securely held by the push-fit coupling.

The present invention is derived from the realisation that there is a need for an alternative approach to couplings required for laminated pipework in which the foregoing disadvantages are obviated.

According to a first aspect of the invention there is provided onnecfor system for connecting laminated pipes, such as contaminated ground plastics pipes, the connector system including a plurality of sets of connectors, each set comprising or including a tubular connector fitting and respective pipe-end spigot(s}, each spigot having a first end for fitting into and supporting the end of a pipe and a second end for fitting into a correspondingly shaped bore in the connector fitting, an Ό' ring seal within the connector for sealing the outside of the pipe end spigot and/or the pipe, the first end of the spigot including one or more continuous teeth for gripping and sealing the inside of the pipe end, a radially expandable split collar having an outer taper corresponding to a correspondingly shaped tapered chamber in the connector fitting whereby upon positive pressure being applied from the inside of the pipe tending to force the pipe out of the connector the tapered collar slides towards the narrower end of the tapered chamber to thereby grip the pipe end and hence the toothed first end of the spigot to thereby collectively prevent or inhibit the pipe end from delaminating as a consequence of water ingress due to high internal water pressure.

With this arrangement, the split tapered collar (which may have one or several splits) and tapered chamber collectively act like a Chinese finger lock as the collar grips the end of the pipe in that, the more force exerted from without or within to disconnect the pipe from the connector fitting the tighter is the grip between the fitting and the pipe by virtue of the split ring/collar sliding to the narrower, open, end of the connector fitting. However, more importantly the tapered collar squeezes the end of the pipe against the one or more continuous teeth on the first end of the spigot which, in turn, seals it and thereby prevents de!amination of the pipe caused by internal water pressure such that the higher the pressure the greater the seal integrity.

With this arrangement the connection of e.g. underground water pipes simply requires that for each such connection the end of the pipe is cut off generally at 90 degrees to the major axis of the pipe, whereafter the first end of the spigot is then pushed or tapped into the pipe end, the second end is inserted all the way into the bore of the connector fitting beyond the split collar and Ό' ring, thereby completing the connection.

A further significant advantage is thai the spigot effectively acts as an extension piece for the pipe which, by virtue of having a smooth outer surface can be completely sealed by the Ό ^! ring against the ingress of water or other contaminants entering through the open end of the connector fitting.

According to a second aspect of the invention there is provided a connector for connecting laminated pipes, such as contaminated ground plastics pipes, the connector including a tubular connector fitting and respective pipe-end spigot, the spigot having a first end for fitting into and supporting the end of a pipe and a second end for fitting into a correspondingly shaped bore in the connector fitting, an Ό' ring seal within the connector for sealing the outside of the pipe end spigot and/or the pipe, the first end of the spigot Including one or more continuous teeth for gripping and sealing the inside of the pipe end, a radially expandable spilt collar having an outer taper corresponding to a correspondingly shaped tapered chamber in the connector fitting whereby upon positive pressure being applied from the inside of the pipe tending to force the pipe out of the connector the tapered coiiar slides towards the narrower end of the tapered chamber to thereby grip the pipe end and hence the toothed first end of the spigot to thereby collectively prevent or inhibit the pipe end from delaminafing as a consequence of water ingress due to high internal water pressure,

According to a third aspect of the invention there is provided a method of connecting pipes below ground including the steps of cutting the end of each pipe to be connected to a connector fitting substantially normal to the major axis of the or each pipe, Inserting into the or each pipe the first end of a spigot according to the first aspect of the invention and thereafter push fitting the second end of the or each spigot into the open end of the connector fitting beyond the Ό' ring in the fitting to thereby seal the end of the pipe and locking and sealing the pipe in position via the split collar and spigot system according to the first aspect of the invention.

The invention in all its aspects will now be described, with reference to the accompanying drawings, in which:

Figure 1 is an exploded half-cut out perspective view of a connector set adjacent a pipe to be connected thereto,

Figure 2 is a cross-sectional side elevation of Figure 1 ,

Figure 3 is a partly cut out perspective view of the connector set and pipe of Figure i shown in their connected condition, and Figure 4 is a cross-sectional view of Figure 3.

Referring firstly to Figures i and 2, a connector set shown generally at 1 comprises a tubular connector fitting 2 (only part of which is shown) and a pipe- end spigot 3, the latter having a first pipe-connecting end 4 for fitting within the cut end of a laminated pipe 5 and a second connection end 8 for fitting within and through the open end 7 of the connector fitting 2, which second end 8 is itself receivable within a bore 8 at the other end of the connector fitting 2, The outside of the first end of the spigot 4 includes a number of circular ribs or teeth 9 which, in use, act as seals in a manner to he described.

The connector fitting 2 has a tapered or frusfo-conicai chamber 10 between the open end 7 and the bore 8 for containing an annular hut split collar 11 and an 'Ο' ring seal 12.

As can be seen more clearly with reference to Figure 2 the collar 11 has a smooth outwardly tapering outer surface corresponding to the inside of the tapered chamber 10 whereas on the inside of the collar 11 there are circular gripping surfaces in the form of ribs or teeth 13 by which the collar 11 can both radially grip the pips 5 in a manner to be described, and slide along and against the inner surface of the tapered chamber 10 in response to axial pressure on the pipe in a direction towards the open end 7 of the fitting 2, or in response to water pressure within the pipe 5,

Figure 3 shows the fully assembled condition of the connector set 1 and pipe 5 in which it will be seen that the second end of spigot 3 is fully received within the bore 8 of the connector fitting 2, in which condition the Ό' ring 12 operates to seal the assembly from the ingress of water or other contaminants through the opening 7 whereas, as it is more clearly seen with reference to Figure 4, the annular spilt collar 11 has radially expanded to accommodate the diameter of the pipe 5 to the extent that its smooth but tapered outer surface bears against the smooth and correspondingly tapered inner surface of the tapered chamber 9, in the position shown, corresponding to no, or negative pressure being applied to the joint, the Ό' ring 12 serves to seal the joint against, the ingress of contaminants, such as groundwater, as weli as stopping water leaking out. However, in the event of positive pressure being applied to the contents of the pipe 5 the Ό' ring seal 12 pushes against the thick end of the collar 11 , forcing it, and the pipe 5 and spigot 3 towards the open end ? of the fitting 2 _S but in so doing is increasingly resisted by the gradually narrowing space within the tapered chamber 10, which both resists further axial movement of the collar 11 and increases the grip of the collar on the pipe 5, thereby collectively preventing with increasing force the tendency of the pipe 5 to be ejected from the opening 7, This is countered by the circular teeth 9 pressing into the inside of the pipe 5 to thereby collectively form a watertight seal in this region such that, in particular, water under high pressure cannot travel along the laminations of the pipe 5.

In this description the lerrn 'connector fitting' is intended to include all types of pipe fittings including, without limitation, straight couplings, elbow couplings and T-shaped couplings.