GB2196403A - Improvements in or relating to pipe fittings - Google Patents

Abstract

A pipe fitting incorporating a retaining means for preventing the displacement of a sealing ring in the pipe fitting during the insertion of a pipe end into the pipe fitting, the retaining means either being integral with the body of the pipe fitting or being in the form of an independent insert. In both cases the retaining means has a substantially radial first portion and a radially innermost second portion inclined at an acute angle of between about 5 DEG and 20 DEG to a radial plane where it merges with the interior wall of the fitting, which combine to confine the sealing ring in its intended position.

Description

SPECIFICATION Improvements in or relating to pipe fittings This invention relates to pipes and pipe fittings and in particular to means for preventing unwanted sealing ring displacement during insertion of a pipe into a push-in type pipe fitting.

The assembly of push-in type pipe fittings needs to be carried out with care in order to avoid damage to, or displacement of, the elastomeric sealing member. These sealing members are, in their simplest form, often rubber '0' rings.

If the pipe is inadequately prepared or incorrectly inserted into the fitting, as can occur due to carelessness or working in confined conditions, then the sealing member may be displaced from its correct position on assembly, and damaged, such that it fails to provide a fluid tight seal.

These problems are common to all types of pipe fittings using an elastomeric sealing ring.

However, push-in type fittings have to be designed to overcome these problems, but the assembly forces must be maintained within reasonable limits.

One way of improving the end of the pipe, which is to be inserted into the pipe fitting, is to use a specially shaped pipe support liner with a frusto-conical nose portion, as disclosed in our Patent Application No.8612695.

The frusto-conical portion of the liner both guides the pipe end through the rubber sealing ring and protects the sealing ring from the rough and abrasive end portion of the pipe end.

In spite of the pipe support liner, the insertion of a pipe end into a pipe fitting is still not devoid of problems. In particular, as the pipe end is pushed into the pipe fitting, the sealing ring is easily displaced from its correct position. This occurs when the pipe is entered into the fitting at an angle, such that one part of the pipe end pushes on the grip ring at one point on its circumference, causing it to tilt out of square. The grip ring then pushes on the sealing ring at one point, causing it in turn to be displaced. Further force on the pipe causes it to enter the fitting, and push the sealing ring further out of position, such that it fails to make a fluid seal.

The aim of the present invention is to prevent a sealing ring in a push-in type pipe fitting from being forced out of its intended position during the inertion of a pipe end into the pipe fitting.

According to the present invention, there is provided a pipe fitting comprising a hollow body having a bore therein to receive an end of a pipe, a sealing ring located within the bore for forming a seal between the pipe and the body, means to hold the pipe within the body, and retaining means for preventing displcement of the sealing ring when the pipe end is pushed into the hollow body, said retaining means having a generally concave surface facing the sealing ring against which the sealing ring bears when the end of the pipe is pushed into the fitting, said surface including a generally axially extending portion extending towards the sealing ring and engageable with an inner peripheral area of the ring correctly to locate the ring within the body.

In a preferred embodiment of the invention the hollow body of the pipe fitting has a central bore at one end, a generally cylindrical counterbore at a central location, and a tapered bored portion at the other end, all of which are co-axial, and wherein the retaining means is located at the juntion between the counterbore and tapered bored portion, and the sealing ring is located within the tapered bored portion.

It is preferred that the retaining means is integral with the body of the pipe fitting, but where necessary the retaining means may be in the form of an insert within the body,and in this case the retaining means is preferably made of a plastics material.

It is also preferred that the concave surface is arcuate and of a radius of curvature similar to that of the sealing ring. However, other concave shapes are possible.

Three embodiments of the invention are now described by way of example with reference to the accompanying drawings in which: FIGURE 1 shows in cross-section a prior art pipe fitting assembled with a pipe; FIGURE la shows schematically how the fitting of Figure 1 can behave during fitting of the pipe; FIGURE 2 is a schematic cross-section of a pipe fitting incorporating a first embodiment of the invention; FIGURE 3 shows in cross-section a pipe fitting, incorporating a second embodiment of the invention; and FIGURES 4a and 4b are cross-sections of a pipe fitting incorporating a third embodiment of the invention.

In the various Figures of the drawings, like parts are identified with the same reference numerals.

Referring first to Figure 1, a prior art fitting has a body 3 provided at one end with a central bore 4 merging at one end with an enlarged central counterbore 4a, which itself merges with a further tapered bore portion 4b at its opposite end. A sealing ring or O-ring 5 is located in the enlarged inner end of bore portion 4b, and between this and its outer end a grip ring 7 is provided. A pipe P is shown in full lines correctly inserted into the fitting. Unfortunately, as the end of the pipe P is pushed into the pipe fitting 1, it may easily snag or catch on a portion of the grip ring 7 especially if its longitudinal axis is slightly out of alignment with that of the fitting 1.If this occurs, the grip ring 7 is forced into engagement with the sealing ring 5, which in turn can be displaced, until eventually it is forced into the broken line position shown in Figure 1 so that eventually part of it will be located in the central counterbore 4a. It cannot then form a satisfactory seal between pipe P and the fitting 1.

Referring now to Figure 2, it will be seen that, in accordance with one embodiment of the invention, the body 3, where the bore 4a and tapered counterbore 4b merge, is formed with an arcuate, concave wall 11 (instead of the normal radially extending wall 12) (Figure 1a) the radius of curvature of which corresponds with that of the sealing ring 5, to provide a retaining means 9 for the ring 5, and prevent it from being displaced during pipe insertion. It is not essential that the retaining means 9 is arcuate, and any re-entrant shape which has an axially extending portion 13 which can engage with an inner peripheral area of the sealing ring 5 to urge it into its intended position is sufficient.Such a construction is shown in Figure 3, where the wall between counterbore 4a and bored portion 4b has an outer radial portion 12 of standard construction and a radially innermost portion which is inclined towards the mouth M of the fitting, as shown at 13.

It is important, however, where the wall between the counterbore 4a and tapered bore portion 4b joins the wall of the counterbore 4a that it subtends an angle a of at least 50 and preferably between 5 and 200 with a radial plane through the fitting.

Sometimes, manufacturing needs may preclude the formation of integral retaining means 9 as shown in Figure 2 or Figure 3. In a third embodiment of the invention shown in Figures 4a and 4b the body 3 is of standard, known construction, but is provided with an insertable retaining means or backing ring 29, one face of which locates against the radial wall between the counterbore 4a and bored portion 4b, and as in the first embodiment, has an arcuate concave wall on its opposite face, or a wall 31, the radially innermost portion of which is inclined to a radial plane, to provide an annular locating flange 33 for the ring as shown in Figure 4a.

As in the previous embodiment, the ring 29 prevents snagging or catching when the end of a pipe P is inserted into the pipe fitting.

The insertable retaining means 29 may adjust its position slightly, as a result of the pressure applied by the sealing ring 5, but it cannot adjust very far, and will eventually embrace the ring 5, and ensure it is aligned with the counterbore 4a.

The insertable retaining means 29 is made of a material that is sufficiently resilient to allow it to deflect to the position shown in Figure 4b, but is also sufficiently rigid to restrain the sealing ring 5 from moving radially inwards. The material is normally a plastics material. Also, it must of course have a suffi ciently large bore to accommodate the end of pipe P and have an outside diameter slightly less than the maximum internal diameter of the bored portion 4b. The arcuate wall 31 need not be arcuate or even as shown exactly in Figures 4a and 4b. However, it should have the same properties as wall 11 of the first embodiment, i.e. be able to confine the ring 15 to an approximately central position, by bearing on an inner peripheral area of the ring to prevent it moving out of alignment.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims (11)

1. A pipe fitting comprising a hollow body having a bore therein to receive an end of a pipe, a sealing ring located within the bore for forming a seal between the pipe and the body, means to hold the pipe within the body, and retaining means for preventing displacement of the sealing ring when the pipe end is pushed into the hollow body, said retaining means having a generally concave surface facing the sealing ring against which the sealing ring bears when the end of the pipe is pushed into the fitting, said surface including a generally axially extending portion extending towards the sealing ring and engageable with an inner-peripheral area of the ring correctly to locate the ring within the body.

2. A pipe fitting according to claim 1 wherein the hollow body has a central bore at one end, a generally cylindrical counterbore at a central location, and a tapered bored portion at the other end, all of which are co-axial, and wherein the retaining means is located at the junction between the counterbore and tapered bored portion, and the sealing ring is located within the tapered bored portion.

3. A pipe fitting as claimed in claim 1 or 2 wherein the retaining means is integral with the body of the pipe fitting.

4. A #pipe fitting as claimed in claim 1 or 2 wherein the retaining means is in the form of an insert within the body.

5. A pipe fitting as claimed in claim 4 wherein the retaining means is made of a plastics material.

6. A pipe fitting as claimed in any one of the preceding claims wherein the concave surface is arcuate and of a radius of curvature similar to that of the sealing ring.

7. A pipe fitting according to any one of claims 1-5 wherein the concave surface has an outer radially extending portion and a radially innermost portion which is inclined towards a mouth of the fitting through which a pipe is inserted, the inclined portion facing the inner periphery of the ring.

8. A pipe fitting according to any one of the preceding claims wherein the surface of the retaining means where it merges with the counterbore in the body subtends an angle of at least 5 with a radial plane through the fitting.

9. A pipe fitting as claimed in claim 8 wherein said angle is between 5 and 200.

10. A pipe fitting as claimed in any preceding claim wherein the retaining means has a bore sufficiently large to accommodate the pipe end.

11. A pipe fitting substantially as hereinbefore described with reference to Figures 2, 3 or 4a and 4b of the accompanying drawings.