GB2256019A - Seal for pipes - Google Patents

Abstract

A seal for interfitting pipes comprising a gasket (11) of elastically deformable material which progressively increases in thickness from its radially innermost tip (5) to the radially outer most location (12), and which is used to join and seal a wide tolerance and range of pipes. in another seal the gasket is adapted to removably receive a rigid insert which is removed after the spigot is in place. The external diameter of the gasket may be greater than the internal diameter of the socket. <IMAGE>

Description

SEAL FOR PIPES This invention relates to a seal for pipes and in particular it relates to an elastically deformable seal for sealing the joint between two pipes.

It is most important when joining two pipes that joints be secure and well sealed against both the contents of the pipes leaking out and also against the ingress of unwanted material from outside the pipes.

Pipes may be made of material such as concrete, clay or various plastics and thermoplastics materials. It is sometimes required to connect pipes of different sizes and/or materials together. The same conditions for joint integrity apply to such joints.

Previously available elastically deformable seals in the form of gaskets have been designed with one particular diameter of pipe in mind and have not been able to cope with a wide tolerance and range of pipe diameters to be joined.

According to the present invention there is provided a seal for interfitting pipes; comprising a gasket of elastically deformable material having a radially innermost portion adapted to form a lip seal with an inserted member of a first thickness, a radially intermediate portion adapted to form a compression seal with an inserted member of a second, greater, thickness and a radially outermost portion adapted to circumferentially engage the inner wall of a socket.

Preferably, the gasket is of greater outer diameter than the internal socket diameter such that the gasket is insertable into the socket in a pre-compressed state.

The gasket may be adapted to receive one or more rigid non-deformable inserts, which are preferably annular or part-annular. These may be adapted to be removed after a joint between pipes has been made, or to be retained within the joint.

According to the present invention in a second aspect there is provided a seal for inter-fitting pipes; comprising a gasket of elastically deformable material and having means to removably receive a rigid nondeformable annular or part annular insert and to hold said insert in place whilst a spigot member is inserted into the gasket but to enable said insert to be removed after the spigot member is in place.

According to the present invention in a third aspect, there is provided a method for joining pipes comprising locating a gasket according to the first or second aspect of the invention into a socket formed by one pipe, the gasket being of larger diameter than the socket such that it is compressed when located in the socket, and inserting a spigot formed by an end of the second pipe into the aperture of the gasket, the aperture being narrower than the spigot such that rolling or compression of the gasket occurs to form a seal.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a half section of a gasket according to the present invention in situ, showing various alternative structures; Figure 2 shows deformation of the gasket by means of (a) a small wall thickness pipe and (b) a wider wall thickness pipe of substantially the same internal diameter; Figure 3 shows a means of securing a gasket in place; Figure 4 shows a plan view of a gasket which is retained by a split ring; Figure 5 shows a cross-section through A-A of Figure 4; Figure 6 shows an application of the gasket for use with an externally ribbed pipe; Figure 7 shows a gasket retained by a clip; and Figure 8 shows a method of locating a gasket in a plain socket.

It should be noted that Figure 1 shows several alternative constructions by way of brevity and to avoid excessive duplication of drawings. In the figure there is shown a seal 11 mounted within a socket 1 in a concrete component such as a manhole base, gully or pipe 20. The nominal size is defined by the bore 2 of the concrete component and the pipe to be jointed. In this example, the pipes to be joined are of common internal diameter, but the external diameter may vary depending upon the material or supplier of the pipe to be fitted into the socket or the material and performance required.

The cross-sections shown at 3 and 4 show typical spigot thicknesses for, respectively, plastic pipes and clay pipes. It is noted that the clay pipe 4 is of larger thickness than the plastics one, although of similar internal diameter. The invention is not necessarily limited to pipes of similar internal diameter.

The seal or gasket 11 is shown in cross-section and includes a radially outermost location area 12 for circumferentially abutting against the wall 13 of the socket. The socket may include a shoulder 14 against which the seal is located by compression. Alternatively, it may be retained by a cast-in anchor 10 or by means of resilient locking means such as rings mounted in circular voids or recesses 8 and 9 respectively. One or both or these voids 8 and 9 may be omitted if required. The or both locking rings may be made of metal, ceramic, thermosetting plastics, thermo-plastics or any other suitable material. They may be a permanent fixture or may be adapted to be removed after the joint is made, as described below with reference to Figures 4 and 5. The seal 11 may also be located in various differently configured grooves or shoulders in the socket 1.It could alternatively be glued in by means of adhesive.

The seal itself progressively increases in thickness from its radially inner most tip 5 to the radially outer most location area 12. As shown in the figure, in cross-section the seal is of generally Z-shape from the location area 12 to the tip 5.

Figures 2(a) and (b) illustrate how the seal deforms to support and centre a spigot of two different thickness. In Figure 2(a) a plastics spigot of relatively small thickness is shown. As shown, insertion of this spigot causes rolling of the seal 11 about edge 15 which acts as a pivot such that face 6 lies against the edge of the spigot 3 to form a lip seal with it.

Since the tip end 5 is the thinnest portion of the seal, it is the most flexible and hence there is not a large amount of compressive force acting against the pipe, only a lip seal force. This is a very suitable type of sealing for a pipe such as a plastics one which would have a smooth surface and also, being thin, cannot withstand a large compressive inwards force without deforming.

Figure 2(b) shows how the seal would be deformed by a larger thickness spigot such as would be obtained by a concrete pipe 4. In this case, further rolling of the seal occurs and the spigot is held against face 7, which is thicker than face 6 on average and is sufficiently thick to provide a compressive force against the spigot.

Since the larger pipes are generally more rigid and have a rougher surface finish some degree of compression is required to provide a good seal. The compression can be aided by making the diameter of the seal larger than the internal diameter of socket 1, so that the seal is precompressed when fitted into the socket. This also aids in retaining the seal in the socket.

The thicker section of the seal aids in centralising spigots, particularly with the smaller spigots.

Although relatively low insertion forces are required a good seal is made with a wide variety of spigot thicknesses and unwanted removal is difficult.

Figure 3 shows an alternative embodiment in which the seal 11 is held in socket 1 by an additional circular ring 16 which has a peripheral flange 17 which extends into void 8 to secure the seal. The ring may be made of a moulded plastics material or any other material and serves to centralise an inserted pipe 3 and to limit deflection of the seal 11 due to shear. The dotted line in the figure shows the position at which the seal tip 5 is moved into by insertion of the pipe 3.

Figure 4 shows a plan view of a seal in which a discontinuous ring member 18 is inserted into void 8.

The respective ends of the partial ring 18a and 18b are spaced apart by a predetermined distance d. The ring is preferably made of a rigid yet flexible material such as a plastics material, an example of which is a thermoplastics material. In use, after seal 11 has been located with respect to a socket ring 18 is positioned.

A spigot is then inserted into the socket and the ring 18 serves to limit rolling and rotation of the seal whilst retaining the seal in the socket. In some instances, if ring 18 were not present insertion of a spigot, particularly of a larger diameter, could cause the seal to be removed completely from its housing. Ring 18 prevents this. As the seal is rolled in the direction into the paper the ends 18a and 18b of the ring tend to close towards one another. After the joint has been successfully made, the ring can be removed. The removal is facilitated by the discontinuity which enables the ring to be removed merely by pulling in the direction shown by arrow R which causes ends 18a and 18b to pull apart from one another to move around the sides of a pipe and be pulled clear. Figure 5 illustrates more clearly how the member 18 is located with respect to the seal.

Figure 6 shows a seal 11 mounted in a socket 2 and retained by an internal resilient ring 19. An externally ribbed pipe 4 is shown in this figure. The figure shows how a seal according to the present invention is adapted for use with such ribbed pipes since the tip 5 can compress and roll into the space between adjacent ribs as shown to hold and centralise the inserted pipe. The seal of many other embodiments can also, of course, be used with an externally ribbed pipe.

Figure 7 shows a seal 11 mounted against a socket having a much thinner wall. This may be the case where a plastics socket is used which does not require the large wall thickness of a concrete or clay pipe or socket. The seal 11 in this case may be conveniently retained by an external clip 21. The clip may be annular and have a channel portion which is mounted over an end of the socket and the seal and includes a flange which is received in annular void 8 of the seal.

A seal according to the invention can automatically compensate for different pipe materials or size variation by different suppliers of the same nominal pipe dimensions. The joint obtained by using such a seal has very good characteristics of shear deflection and draw. The joint is easy to make and a high degree of skill is not required. In particular, no special tools are required during jointing and the only labour requirement is of locating the spigot in the socket.

A common fault in pipes is that they tend to be oval rather than circular in cross-section. The joint provided by a seal according to the present invention can compensate for such ovality. The seal is particularly, but not exclusively, of use in pre-cast concrete gullies and manhole bases and with branch connectors for concrete pipes. They may be used to seal concrete pipes with socket and spigot type joints or to seal thermo-plastic pipe joints where different materials may be used, requiring different pipe wall thicknesses. They can also be used as an adaptor between a plastic pipe and other materials, in which case a moulding of a thermo-plastic or other material may sometimes be required.

Figure 8 shows a method of locating a seal 11 in a plain socket 2 which has a parallel or slightly tapered internal bore. An annular location ring 22 is fixed in void 9 to locate and space the seal apart from the rear end 2a of the socket. Ring 22 may be continuous or discontinuous and may be fitted before or after location of the seal. It firstly provides a positive location for the seal and secondly serves to transmit the sealing force from a pipe 3 against the socket side wall. It also permits compression of the area marked A if high joint integrity is required. The ring may be made of any appropriate material, such as a plastics material.

Figure 8(b) shows how the seal 11 may bear against ring 22 after insertion of a pipe 3.

Claims (17)

1. A seal for pipes comprising a gasket of elastically deformable material having a radially innermost portion adapted to form a lip seal with an inserted member of a first external diameter, a radially intermediate portion adapted to form a compression seal with an inserted member of a second, greater, external diameter and a radially outermost portion adapted to circumferentially engage the inner wall of a socket.

2. A seal as claimed in Claim 1, having a thickness which progressively increases from its radially innermost part to a portion at or towards its radially outermost part.

3. A seal as claimed in Claim 1 or Claim 2, wherein the gasket is of greater outer diameter than the internal diameter of the socket such that the gasket is insertable into the socket in a pre-compressed state.

4. A seal as claimed in any one of Claims 1 to 3, wherein the gasket is adapted to receive at least one rigid non-deformable insert.

5. A seal as claimed in Claim 4, wherein the rigid non-deformable insert is annular or part annular.

6. A seal comprising a gasket of elastically deformable material and having means to removably receive a rigid non-deformable insert and to hold said insert in place whilst a spigot member is inserted into the gasket but to enable said insert to be removed after the spigot member is in place.

7. A seal as claimed in Claim 6, wherein the rigid non-deformable insert is annular or part-annular.

8. A seal as claimed in any preceding claim, wherein the seal is adapted for engagement with the inner wall of a socket and to be retained thereto by a retaining means.

9. A seal as claimed in Claim 8, wherein the retaining means is a clip.

10. A seal as claimed in Claim 8, wherein the retaining means is a cast-in anchor.

11. A seal as claimed in Claim 8, wherein the retaining means is an adhesive.

12. A seal as claimed in Claim 8, wherein the gasket includes a void or recess and the retaining means includes at least a portion which is located in said void or recess.

13. A seal for pipes as claimed in Claim 11, wherein the retaining means is at least one resilient ring mounted in a circular void or recess of said seal.

14. A method for joining pipes comprising locating a gasket into a socket formed by one pipe, the gasket being of larger diameter than the socket such that it is compressed when located in the socket, and inserting a spigot formed by an end of the second pipe into the aperture of the gasket, the aperture being narrower than the spigot such that rolling or compression of the gasket occurs to form a seal.

15. A method for joining pipes as claimed in Claim 14, wherein further rolling of the gasket occurs as spigots of increasing external diameter are inserted.

16. A method for joining pipes as claimed in Claim 14 or Claim 15, wherein the pipe comprises external ribs.

17. A seal substantially as hereinbefore described with reference to the accompanying drawings.