Pipes for underground drainage and the like are now almost universally joined by push-fit spigot and socket joints, in which a pipe end is pushed into a socket provided with a flexible internal seal. The socket may be an end region of a pipe length, or a socket member fitted to an end of a pipe length. The latter arrangement can be used for pipes of clay, cement, concrete. Alternatively, for joining pipes of such materials, pipe coupling sleeves are provided, having a socket and seal at each end, for joining two adjacent plain pipe spigot ends; this arrangement permits the use of completely plain pipe lengths.

The pipe couplings or sockets are commonly made of plastics.

Pipe joints of the above described kind have been very successful. Joints of this kind are disclosed for example in British patents 1182769, 1572099, 2179584 and 2181201.

These pipe joints have been extremely successful for pipes of smaller diameters. An object of the invention is to provide an improved pipe coupling particularly adapted for use with pipes of larger diameters, although the present invention is not limited to use with large diameter pipes.

The present invention is applicable to pipe joints in the form of separate double-ended coupling sleeves, socket members fitted to pipe ends, and sockets integral with pipe ends.

The invention is particularly applicable to the jointing of pipes of clay, cement, asbestos and the like but is also applicable to the jointing of pipes made of metal or of plastics.

According to one aspect of the present invention a pipe joint comprises a socket having an internal annular seal for sealing against an inserted pipe end, and a guide element or guide elements extending axially outwardly away from the seal over an appreciable distance, for guiding a pipe end into the socket and into contact with the seal.

This arrangement makes it much easier for labourers on site to locate the pipe end in the joint, before forcing it through the seal. This is particularly advantageous in the case of larger and therefore heavier pipes; it has been found that the manipulation of these into pipe couplings of current design can be extremely difficult because the seal is very close to the outer end of the coupling and a large heavy pipe can easily miss the

opening of the coupling or even be dropped, causing damage to the pipe and/or coupling and causing a risk that contamination will be picked up from the surroundings on the pipe end (which is commonly provided with a lubricant) and introduced into the coupling, impairing the performance of the seal. By providing a guiding and supporting surface extending outside the seal, the present invention largely eliminates these problems.

Instead of lubricant on the pipe end we may provide a body of lubricant in the socket axially outside the seal, to be picked up on an inserted pipe end.

Preferably the lubricant is provided on the inside of the guide element(s).

According to a second aspect of the invention, a pipe joint with an internal seal is provided with a flexible internal wiper, axially external to the seal, for wiping contaminants off an inserted pipe end. This measure can reduce the risk of accidental introduction of solids into the seal when the pipe end is inserted, by wiping the external surface of the pipe before it reaches the seal. This measure is also particularly valuable in the

case of larger heavier pipes, which are more liable to be dropped by the labourer and therefore pick up sand or other contaminants from the trench in which they are laid, in particular sand used for bedding the pipes.

A coupling provided with the wiper may also be initially provided with a body of lubricant, preferably placed between the wiper and the seal, so as to lubricate the wiped pipe end as it enters the seal.

The first and second aspects of the invention can be used together in one and the same pipe coupling.

The invention will be further described with reference to the accompanying drawings in which:

Fig. 1 is a cut away perspective view of a pipe coupling sleeve embodying the invention, and

Fig. 2 shows an assembled pipe joint using this coupling sleeve, and

Fig. 3 is a section on the pipe axis, of a pipe end carrying a plastics socket.

Figs. 1 and 2 show a pipe coupling composed of a plastics sleeve 1 with slightly enlarged regions 3 at its ends. The sleeve provides two sockets, one at each end, separated by a central register rib 5. In use, a respective end of a respective plain pipe length 7 is

inserted into each socket-forming end of the coupling sleeve, as shown in Fig. 2.

The outermost rim at each end of the sleeve has an external circumferential rib 9. At each end of the sleeve there is fitted a plastics end cap 11. This has an outer skirt 13, joined by an inwardly extending wall 15 to an inner lip 17. An internal annular groove within the skirt defines a tooth 19 at the free edge of the skirt. In use, this is snap-fitted over the tooth or rib 9 on the end of the plastics sleeve 1. An elastomer seal ring 21 has a fixing region 23 which is trapped between the end of the plastics sleeve 1 and the regions 13, 15, 17 of the end cap, and an inwardly projecting seal region or lip 25 of smaller internal diameter than the external diameter of the pipe lengths to be joined.

To the extent that it has been described thus far, the illustrated pipe coupling corresponds to well known conventional pipe couplings.

In use, pipe ends are inserted as already mentioned, deflecting the seals 21 which then make sealing contact with the external surfaces of the pipe ends. This can be clearly seen in figure 2.

It will be seen that the distance between the seal and the outermost surface of the wall region 15 is quite short. In use, the labourer has to insert the pipe end into this short outer region of the end cap and then force the pipe end through the seal. This presents relatively few problems for small pipes, but is extremely difficult for large heavy pipes. Labourers tend to drop these before they are safely located in the coupling. Even if the labourer successfully gets the pipe end into the end caps so as to rest on the inner lip region 17, there is a distinct risk that the weight of the pipe will dislodge it before it can be pushed home into the seal.

This leads to a risk of damage. Also, particularly where the pipes are bedded in sand, the pipe end becomes contaminated. The pipe ends are normally lubricated, to facilitate entry into the seal. The lubricant is sticky and picks up grains of sand and other dirt from the surroundings if the pipe end is dropped. This contamination is then carried into the seal and can destroy its effectiveness.

Conventional types of pipe coupling have therefore been less than fully satisfactory for use with large-diameter pipes.

To overcome this, the present coupling is provided with an axially outwardly extending annular guide 31, which in the illustrated embodiment is an extension of the inner lip region 17 of the end cap. This provides an extended sleeve-like region in which the inserted pipe end can be initially located and supported, before being forced home into the seal. The long sleeve 31 at the front of the cap enables the pipe end to be inserted and located before jointing and sealing actually take place. This ensures that the pipe is centrally positioned without extra assistance and enables jointing more easily by one person. This materially reduces the risk that the pipe end will be incorrectly aligned with the coupling socket, while it is being manipulated by the labourer, and the risk that the pipe end will be dropped or become dislodged from the coupling, and consequently contaminated by the surrounding material, before it is fully inserted. The risks of damage and contamination are therefore significantly reduced.

The added guide 31 can take other forms, for example a plurality of projecting tongues instead of the illustrated ring, and may for example be flared, or provided with a bevelled edge at its lip, to make insertion of the pipe end even easier.

Further to reduce the risk of contaminating material being carried into the seal, the illustrated pipe coupling has, on the internal surface of its guide portion 31, an inwardly projecting flexible oblique rib 33, which slants inwardly towards the seal position. This acts as a wiper to remove any gross contamination from the external surface of the pipe end as the latter is inserted. The internal diameter of the wiper 33 is somewhat less than the pipe diameter so that the wiper is deflected by the inserted pipe, as can be seen in figure 2. As a still further measure to reduce problems caused by contamination picked up from the surroundings, the illustrated pipe coupling is intended to be used with unlubricated pipe ends. Instead of the lubricant usually applied to the pipe end on site, a body of soft lubricant jelly or paste is provided on the inner side of the wiper 33, between it and the seal, as shown at 35. This can be applied on site, but is preferably provided at the factory, which has the further advantage that better quality control is possible and the amount of lubricant provided can be closely controlled and ensured to be correct.

The lubrication may be contained in a carrier for example a sponge which is then placed in the position shown. This will have the advantage of containing a fairly fluid lubricant until needed.

When the pipe end is inserted, it deflects the wiper 33 which in turn squeezes the lubricant 35 towards the seal 21 and onto the external surface of the pipe end, which- then carries the lubricant onto and through the seal.

In a modification, the radially inner region of the wiper may be designed to act as a scraper on the pipe surface, for example by being provided with a bead, or with a rib or lip directed outwards towards the exterior, or having its radially inner region hook-shaped in cross section with the hook on the axially outer side of the wiper, so as to scrape the pipe surface as the pipe is inserted.

While the wiper shown slants inwardly towards the seal, it may alternatively be substantially perpendicular to the axis of the coupling or even be slanted outwardly at least before the pipe end is inserted.

Figure 3 shows an alternative embodiment of the invention, in which a socket member 43 made of PVC or other suitable plastics material is secured on the plain end of a clay pipe length 41. The other end of the pipe length is left plain.

The outer end region 55 of the socket member 43 has an internal diameter slightly greater than the external

diameter of a pipe length, and contains an internal rubber seal ring 45. In use, a plain pipe end is inserted into the projecting 55 portion of the socket member, which constitutes a pipe joint socket, through the seal ring 45, thereby forming a sealed pipe joint. The arrangement is analogous to the use of the coupling sleeve shown in figures 1 and 2 except that in this case the plastics coupling or socket member 43 is permanently secured on one pipe end.

The socket member can be secured on the pipe end in any convenient manner, for example by an interference fit and/or adhesive, or by shrink fitting. Preferably, the plastics socket member is secured on the end of a clay pipe length in the manner set out in GB-A-2181201. That is to say, the socket member 43, at least in the skirt portion 53 which fits over the clay pipe end, is softened by heating and expanded, is fitted over the pipe end in this condition, with a rubber sealing ring or band 51 between it and the external surface of the clay pipe, and then is allowed to cool and shrink while compression is applied externally at least in the region of the rubber ring or band 51. A sealing or bonding compound may be provided at the interface of the skirt 53 and the clay pipe 41, in addition or as an alternative to the rubber ring or band 51.

At the other or outer end of the socket member 43, the seal ring 45 for the inserted pipe end is retained by a snap-on end cap 47 made of polypropylene or other suitable plastics material. The seal ring 45 may be bonded in position, for example by an adhesive or by being co-moulded with the socket member 43. It will be seen that the seal and shown in figure 3 are not configured as shown in figures 1 and 2 to provide a strong positive lock for the seal ring. However the member 43 has a seat for the seal ring, with an undercut surface 57, and preferably the cap 47 also has an opposed undercut surface, to provice mechanical retention of the seal ring.

The end cap 47 is provided with an axially outwardly extending annular guide 49, of which the internal diameter is the same as the internal diameter of the socket-forming region 55 of the socket member 43. As in the case of figures 1 and 2, this guide extension 49 provides an extended sleeve-like region in which an inserted pipe end can be initially located and supported before being forced home into the seal 45 and socket 55".

By way of example only, figure 3 shows a design suitable for clay pipes of 225mm (9 inch) diameter.

The present invention is believed to be particularly advantageous, as already indicated, in the case of the larger pipe diameters (heavier pipes), in particular pipes of 150 millimeter (6 inches) diameter and upwards, more especially those of 200 millimeters (8 inches) and upwards. However, the invention can equally well be used for pipes of smaller diameters, with particular advantage when such pipes are to be bedded on or in sand with the resulting risk of contamination of the pipe ends.

Numerous variations of the coupling employing the disclosed principles will naturally occur to the skilled person and will not be described in detail.