GB2218768A

GB2218768A - Pipe coupling with compressible sleeve

Info

Publication number: GB2218768A
Application number: GB8910580A
Authority: GB
Inventors: Stephen Lane
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-05-16
Filing date: 1989-05-08
Publication date: 1989-11-22
Anticipated expiration: 2009-05-08
Also published as: GB8910580D0; GB2218768B; AU4476589A; AU625643B2

Abstract

A pipe coupling comprising a tubular body 1 of a plastic material; two sealing rings 2; two gripper rings 3 each having gripping ridges on the inner surface; an enclosure ring element 4 and means 5 for drawing inwards the enclosure ring element 4. Insertion of the pipe ends into the coupling is achieved with a minimum of resistance because of the clearance between the pipe and the gripping edges, and the loose fit between the pipe and the seals. When the enclosure ring element/enclosure ring segments 4 are drawn radially inwards the gripping edges are also deflected inwards so that they grip into the pipe surface. At the same time the tubular body 1 deforms inwards until the inner surface bears against the pipe outer surfaces and a fluid tight seal is formed by each sealing ring 2 within the confines of each groove in the tubular body and the outside of the pipe. <IMAGE>

Description

TITLE " A PIPE COUPLING " BACKGROUND OF THE INVENTION This invention relates to a coupling or joint for connecting co-axial lengths of piping.

It is often difficult to provide a coupling which embodies all of the following features, particularly on large diameter pipes: (a) Is easy to fit.

(b) Has good sealing characteristics, especially at high pressures.

(c) Can be easily removed.

(d) Does not require special preparation of the pipe ends.

(e) Will resist angular deflection of the pipe ends.

(f) Will accommodate rotational misalignment.

(g) Will accommodate a variable gap between the pipe ends or allow the pipe ends to butt closely together.

(h) Will withstand both radial and axial pressure components, thus preventing axial separation of the pipes at the coupling at all operational pressures whilst maintaining a leak tight seal.

Known pipe couplings which have been used for this purpose include pipe couplings of the kind to which this invention relates, namely pipe couplings consisting essentially of three main components, i.e. a tubular housing having an externally threaded portion and adapted to receive the pipe ends, two axially split gripping sleeves with an outer tapered surface and designed to surround the pipe ends and two tubular compression sleeves each having an internally threaded axial portion adapted to be screwed onto the externally threaded portion of the housing and having an internal tapering surface adapted to engage the tapering portion of the gripping sleeve in such a manner that, when the sleeves are screwed onto the housing, the relative displacement of the sleeves with respect to the housing causes the gripping sleeves to contract and thereby grip the pipe ends.

It has been found in practice that difficulties arise as follows: 1) Difficulties in attaching or removing the coupling to or from the pipe, since such couplings use sealing rings which may impose a great resistance, particularly in large diameter pipes, to the insertion of the pipe into the housing bore.

2) Difficulties in ensuring both the effective gripping and sealing of the coupling at high pressures especially on large diameter pipes.

3) Difficulties in the economical production of such couplings again especially on larger sizes where quantities may not warrant expensive tooling and moulds.

SUMMARY OF THE INVENTION The invention provides a coupling for two pipes which includes a tubular body and which is formed with two spaced annular grooves on an inner surface, two sealing rings which are located respectively in the two annular grooves, abutting ends of the two pipes being located within the tubular body with each sealing ring surrounding a respective pipe, and means for applying a compressive force to the tubular body thereby to deform the tubular body so that its inner surface bears against outer surfaces of the two pipes, and so that a fluid tight seal is formed by each sealing ring within the confines of the respective annular groove and an outer surface of the respective pipe.

The tubular body is preferably of a material having a low modulus of elasticity, as hereinafter defined.

The pipe coupling may include gripping means adapted to engage respectively with an outer surface of each pipe when compressive force is applied to the tubular body.

In one form of the invention the means for applying a compressive force to the tubular body includes at least a first pair of opposed shells which are located on an external surface of the tubular body, and means for drawing the shells towards one another.

In one embodiment the shells are longer than the tubular body, in the axial direction, and the gripping means includes gripping formations at opposed ends of the shells.

Alternatively the gripping means includes two gripping rings located respectively at opposed ends of the tubular body, the shells being engaged with the gripper rings thereby to restrain relative axial separation of the gripping rings.

Use may also be made of first and second pairs of the shells, the first pair of shells being located at one end of the tubular body, and the second pair of shells being located at an opposing end of the tubular body.

The pipe coupling, whilst comprising the aforelisted basic components and elements, may thus take a number of forms: i) Each described component or element may be made in one, two or more parts which are fixed together during manufacture or located together during assembly.

ii) The gripper means may form part of an enclosure ring element.

iii) The enclosure ring element may be of two separate rings situated one at each end of the tubular body and designed to grip or locate into the outside of the tubular body to prevent axial displacement during operation.

iv) The enclosure ring element may be of two separate rings situated one at each end of the tubular body but joined together by tie members to prevent axial displacement during operation.

v) Tne gripper means may be enclosed within the ends of the tubular body and have external gripping edges or a shoulder which locates within the ends of the tubular body and cannot be axially displaced during operation.

vi) The means for applying the compressive force may be bolts and nuts, toggle clamps, or other means.

The gripper means may be omitted completely when axial separation of the pipes can be prevented by other means.

DESCRIPTION OF PREFERRED EMBODIMENTS Six embodiments of the invention described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a partially sectioned side elevation of a pipe coupling according to the invention, and pipe ends, showing the coupling in an untightened condition, Figure 2 is an end elevation of the pipe coupling of Figure 1 but in a tightened condition, Figure 3 is a partially sectioned side elevation of a pipe coupling and pipe ends showing the coupling in a tightened condition, Figure 4 is a partially sectioned side elevation of a pipe coupling according to a second form of the invention, and Figures 5 to 8 are similar views of four other pipe couplings according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENT Figures 1, 2 and 3 show a pipe coupling according to a first form of the invention.

The coupling includes a tubular body 1 and, located in an annular groove within each end of the tubular body 1 and around the abutting ends of each pipe is an annular sealing ring 2 the shape of which ensures a seal between the body and the respective pipe when the coupling is tightened and under pressure.

The tubular body is made from a material with a modulus of elasticity which is sufficiently low to enable the material to deform to the required amount without exceeding its yield stress. As will become apparent hereinafter the body is deformed into contact with the outer walls of the pipes. Initially there is a clearance of say 1,5% of pipe diameter between the bore of the body anc the pipes. This facilitates assembly of the coupling.

The modulus of elasticity of the material of the body should have a low enough value to ensure that the body can deform,, as required, without failure. One such suitable material is high density polyethylene which has a modulus of elasticity of the order of 0,9 GPa. Unplasticized polyvinylchloride may also be used and its modulus of elasticity being of the order of 3,0 GPa. By way of contrast the modulus of elasticity of steel is in the region of 209 GPa. It is to be understood though that other materials which deform to the required amount can be used, even though the yield stress is exceeded, provided the materials do not fail or fracture.

At each end of the tubular body and around the inner end of each pipe is an annular gripper ring element 3.

Enclosing the tubular body 1 and the gripper ring element 3 is an annular enclosure ring 4. As is apparent from Ficure 2 the enclosure ring 4 consists of two shells with mating flanges which can be clamped, and drawn inwardly, by means of suitable fasteners. In this example fasteners in the form of bolts and nuts 5 achieve this purpose.

In use the coupling is assembled as shown with the clamping fasteners 5 in the untightened position. Ends of two co-axial pipes are inserted into each end of the coupling and positioned centrally, abutting one another.

Insertion of the pipe ends into the coupling is achieved with a minimum of resistance because there is a clearance between the gripper ring gripping edges and the outside of the pipes, and the sealing rings have a clearance between their inner edges and the outside of the pipes, or at worst a light interference fit.

In tne case where a damaged section of pipe is to be removed from a pipeline and replaced, the coupling can be slid completely over one of the pipes before final positioning.

Once the pipes and coupling are in the correct position the clamping fasteners 5 are progressively tightened. This tightening has two effects: 1) The gripping edges of the gripper rings are deflected radially inwards towards the pipe surfaces and then into the pipe surfaces.

2) The tubular body is compressed and so deforms and deflects radially inwards towards the pipe surfaces until circunferential contact is made with the outer surfaces of the pipes.

During this deforming operation the sealing rings 2 which are captive within the grooves in the tubular body 1 press against the outside of the pipes to form fluid tight sea's. '0' ring seals are one example of the type of seal which can be used.

During operation it will be appreciated that the gripping action prevents axial separation of the pipe ends.

Figure 3 shows the position of the gripper ring elements and other components when the coupling is in an operational and pressurized condition.

Flexible sealing rings used in pipe couplings are subject to tie problem of being extruded through the small gaps between the adjacent components or the components and the pipes themselves when subjected to very high pressures.

When the pipe coupling is used to connect pipes of a plastic type material, the pipes tend to increase in diameter as the pressure increases. In this invention by usinc a tubular body of material which has a sufficiently low wzulus of elasticity, as hereinbefore described, and an enclosure ring of a much stronger material such as steel any small gaps retaining in the unpressurized condition reduce and finally disappear when the pipes and coupling are subjected to increased pressure. This feature ensures that each sealing ring is fully contained and minirizes the possibility of extrusion.

Also as the pipe diameters increase under pressure this causes each gripper ring, which is captive within the enclosure ring, to dig further into the respective pipe surface.

The second, third, fourth, fifth and sixth embodiments of the invention as shown respectively in Figures 4,5,6,7 and 8 operate on the same principle as the first but take differing physica forms.

Thus in Figure 4 opposing ends of the shells extend beyond the body 1 and carry gripping formations 6. The rings 3 are therefore dispensed with.

Figure 5 shows that two sets of shells, 7 and 8 respectively, are used. The shells include projections 9 which engage in recesses 10 in the body 1, and shoulders 11 which abut respective gripper rings 3, thereby to prevent axial separation of the pipes.

The Figure 6 arrangement is similar to that of Figure 5 except that the gripper rings 3 are omitted and replaced by gripping formations 12 on the outer ends of the two sets of shells.

Figure 7 shows a modification to the coupling of Figure 6 wherein the projections 9 are omitted and the two sets of shells 7 and 8 are fixed to one another by tie members 13, to prevent axial separation of the components when the pipes are pressurized.

In the Figure 8 pipe coupling gripper rings 3 are located within inner recessed formations 14 at opposed ends of the tubular body 1. These rings include inner and outer gripping formations which engage respectively with the tubular body 1, and opposing surfaces of the pipe respectively.

It will be appreciated that in all the embodiments the material being conveyed in the pipes comes into contact only with the seals and the tubular body.

The couplings of the invention are suitable for use with plastic pipes or pipes of any other material which is softer than the gripper ring material. This allows the gripper rings to dig into the pipe outer surface and prevent axial separation.

Furtherm#re, the couplings are simple to install and may easily and rapidly be installed where a damaged or perforated section has been removed from a pipeline and a new section replaced as is the case when a pipe develops a leak.

The gripper rings exert a compressive force on the two pipes. On pipes having thin walls, to minimize the likelihood of the pipes collapsing under this force a liner may be inserted into each pipe. A single liner may be used, which extends into both pipes, or each pipe may have a liner, with a locating flange, as shown in dotted lines marked 15 on Figure 3.

Claims

1. A coupling for two pipes which includes a tubular body which is formed with two spaced annular grooves on an inner surface, two sealing rings which are located respectively in the two annular grooves, abutting ends of the two pipes being located within the tubular body with each sealing ring surrounding a respective pipe, and means for applying a compressive force to the tubular body thereby to deform the tubular body so that its inner surface bears against outer surfaces of the two pipes, and so that a fluid tight seal is formed by each sealing ring within the confines of the respective annular groove and an outer surface of the respective pipe.

2. A pipe coupling according to claim 1 which includes gripping means adapted to engage respectively with an outer surface of each pipe when compressive force is applied to the tubular body.

3. A pipe coupling according to claim 2 wherein the means for applying a compressive force to the tubular body includes at least a first pair of opposed shells which ate located on an external surface of the tubular body, and means for drawing the shells towards one another.

4. A pipe coupling according to claim 3 wherein the shells are longer than the tubular body, in the axial direction.

5. A pipe coupling according to claim 4 wherein the gripping means includes gripping formations at opposed ends of the shells.

6. A pipe coupling according to claim 4 wherein the gripping means includes two gripping rings located respectively at opposed ends of the tubular body, the shells being engaged with the gripper rings thereby to restrain relative axial separation of the gripping rings.

7. A pipe coupling according to claim 6 wherein gripping rings are located within the shells which have shoulders respectively abutting the gripping rings.

8. A pipe coupling according to claim 2 which includes first and second pairs of the shells, the first pair of shells being located at one end of the tubular body, and the second pair of shells being located at an opposing end of the tubular body.

9. A pipe coupling according to claim 8 wherein each pair of shells and the tubular body includes inter-engaging formations.

10. A pipe coupling according to claim 9 wherein the inter-engaging formations comprise grooves or recesses in the tubular body and complementary projections on the shells.

11. A pipe coupling according to claim 8 which includes means securing shells of the first pair to respective shells of the second pair.

12. A pipe coupling according to any one of claims 8 to 11 wherein the first pair of shells extends beyond one end of the tubular body and the second pair of shells extends beyond an opposing end of the tubular body.

13. A pipe coupling according to claim 12 wherein the gripping means includes gripping formations on the two pairs of shells adjacent the respective ends of the tubular body.

14. A pipe coupling according to claim 12 wherein the gripping means includes two gripping rings located res#ectively at opposed ends of the tubular body and engaged respectively with the two pairs of shells.

15. A pipe coupling according to claim 2 wherein the gripping means includes two gripping rings located respectively within two recesses at opposed ends of the tubular body, each gripper ring including inner and outer gripping formations which engage with the tubular body and an opposing pipe surface respectively.

16. A pipe coupling according to any one of claims 1 to 15 which includes liner means within the two pipes.

17. A pipe coupling according to any one of claims 1 to i6 wherein the tubular body is of a material which has a low modulus of elasticity, as hereinbefore defined.

18. A pipe coupling according to any one of claims 1 to 17 wherein the tubular body has a modulus of elasticity which is not greater than 3,0 GPa.

19. A pipe coupling according to any one of claims 1 to 18 wherein the tubular body is made from unplasticized polyvinylchloride or high density polyethylene.