AU2018264057B2

AU2018264057B2 - Improved compression seal

Info

Publication number: AU2018264057B2
Application number: AU2018264057A
Authority: AU
Inventors: Brian Haigh
Original assignee: Haigh Tooling Ltd
Current assignee: Haigh Tooling Ltd
Priority date: 2017-12-15
Filing date: 2018-11-15
Publication date: 2024-05-16
Anticipated expiration: 2038-11-15
Also published as: AU2018264057A1

Abstract

A compression seal for a plumbing fitting, in which one edge of the compression seal is permanently secured around one end of the plumbing fitting, to prevent loss, 5 damage or distortion of the seal; the seal being made of a resilient but compressible material and annular in form, the edge of the seal which is not to be secured permanently around one end of a plumbing fitting being formed with a taper on the interior surface of the seal, such that the seal decreases in thickness towards that edge. 8 3/3 6 CNo CNC 0 G0 Co K) C

Description

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K) C IMPROVED COMPRESSION SEAL

Technical Field The present invention relates to a compression seal for a pipe joint, for use in combination with plastics plumbing fittings. The invention includes plumbing fittings incorporating the seal.

Background Art It is known to use compression seals when joining plumbing fittings together. A compression seal is a seal which is designed to be compressed between components that are being joined together, to provide a secure and watertight seal.

At present, compression seals are formed as separate seals in the form of an annulus of resilient but compressible material, each edge of which is tapered on its outer surface, so as to provide an easy "lead-in" when the seal is being slid onto the outer surface of one of the components to be connected together. Seals of this type are used with an internally screw threaded nut which provides a tapered compression surface at the outer end of the internal screw thread.

In use, the tapered compression surface on the nut engages the complimentary taper on the seal, so that the seal edge is pressed tightly onto the corresponding component. The angles of taper on the compression seal and on the compression surface of the nut are approximately the same.

The above described arrangement works reasonably well in practice, but has the known drawbacks of the compression seals (which are of course separate until connected onto the other components), getting lost, or being damaged or distorted in storage. If the seal is not in good condition and undistorted, it will not provide a good seal and in some cases may not be able to be used at all. For example, the seal, if distorted, may not lie correctly within the tapered compression surface on the nut.

In addition, assembly of such components often is carried out under difficult circumstances and in confined spaces, and the separate seal can be fiddly to fit into place.

Disclosure of Invention An object of the present invention is the provision of a compression seal which avoids, or at least ameliorates, the above described disadvantages.

The present invention provides a compression seal made of a resilient but compressible material, which is annular in form and has a first edge which is formed with a taper on the interior surface of the seal, such that the seal decreases in thickness towards said first edge; the seal having a second edge which is adapted to be permanently secured around the perimeter of one end of a plumbing fitting.

The present invention further provides a plumbing fitting including: • a first component at least one end of which is designed to be releasably secured to another plumbing fitting; • said first component having an external screw thread formed adjacent said at least one end; • an internally threaded nut which is dimensioned and adapted to engage said external screw thread such that a second component may be secured to said first component; • said nut providing an internal tapered compression surface adjacent the end of said internal screw thread furthest from said first component in use; • a compression seal made of resilient but compressible material, which is annular in form and which has opposed first and second edges; • said first edge being formed with a tapered surface on the internal surface of said seal, such that the seal decreases in thickness towards said first edge; • the taper of said internal tapered surface of the seal being approximately the same as the taper of the tapered surface of the nut, such that in use, when the nut is fully engaged with said first component, the tapered surface of the nut presses said first edge of said seal into sealing engagement with said another plumbing fitting; • said one end of said first component having the second edge of the compression seal permanently secured around said one end.

As used herein, the term 'internal surface' means that surface which in use lies closest to the supporting component upon which the seal is mounted.

Preferably, the taper on the internal tapered surface of the nut/tapered surface of the seal is in the range 16 degrees - 30 degrees.

Preferably also, the plumbing fitting further includes a slip ring in the form of a frusto conical portion of low friction material which is tapered to match the internal tapered surface of the nut.

Brief Description of the Drawings By way of example only, a preferred embodiment of the invention is described in detail, with reference to the accompanying drawings in which: Figure 1 is a side view of the end of a pipe incorporating a compression seal in accordance with the present invention; Figure 2 is a longitudinal section through Figure 1; Figure 3 is an end view and partly sectioned side view of a nut in accordance with the present invention; Figure 4 is a longitudinal section through first and second pipes, a nut, and a slip ring partially connected together; and Figure 4A is a detail of Figure 4, but with the components fully connected.

Best Mode for Carrying out the Invention Referring to the drawings, a pipe fitting 10 consists of a length of pipe (only part of which is shown) formed adjacent one end 12 with an external screw thread 13. A compression seal 14 is permanently secured around the end 12 of the pipe:- the end 15 of the seal 14 adjacent the end 12 is moulded onto the end 12 during the process in which the pipe fitting 10 is formed. The pipe fitting 10 is formed with a slight indentation (not visible) on the inner surface 17 of the pipe at the end 12, so that the interior surface 16 of the seal 14 is a smooth continuation of the surface 17.

The opposite end 18 of the seal 14, (i.e. the free end) is internally tapered outwards towards the free end of the seal. Preferably, the taper is in the range 16 degrees - 30 degrees. The angle of the taper is the angle between the inclined wall of the seal and the non-tapered wall of the seal, i.e. angle X as shown in Figure 2.

Referring to Figures 3, 4 and 4A, a nut 20 may be used to secure a second component, (e.g. a pipe 21) onto the pipe fitting 10. The nut 20 has a castellated exterior surface 22, to enable the nut to be gripped by a hand or tool easily, and is internally screw threaded with a screw thread 23 adapted to engage the screw thread 13 on the fitting 10.

On the interior of the nut 20, at the end of the screw thread 23 furthest from the fitting 10, the nut is formed with an inclined surface 24; the angle of the surface 24 is about 25-30 degrees.

Optionally, a slip ring 25 may be fitted into the inclined surface 24. The slip ring 25 is made from a rigid low friction material such as polytetrafluoroethylene or acetal and is frusto conical in shape, so that it fits flat against the inclined surface 24. The material of the slip ring 25 is such that it slips easily against the material of the nut (typically polypropylene or polyvinylchloride) but sticks to the compression seal, which typically is made from a resilient compressible material, preferably a thermoplastic elastomer such as Santoprene (Registered Trademark).

To assemble the components as shown in Figures 4/4A, the slip ring 25 is fitted into the inclined surface 24 (if a slip ring is to be used) and the nut 20, with the slip ring in place, is slid over the pipe 21. The end of the pipe 21 is then slid through the compressible seal 14 into the end of the pipe 10 until the end of the pipe 21 contacts a shoulder 26 formed around the interior of the pipe 10. The taper on the seal 14 provides a "lead-in", making it easy to slide the pipe 21 into place. The internal screw thread on the nut 20 is then engaged with the screw thread 13 on the pipe 10, to secure the components together.

For clarity, Figure 4 shows the above described components with the nut partially tightened onto the pipe 10, so that the seal 14 and the inclined surface 24 and slip ring 25 can be seen clearly. Figure 4A shows the nut fully tightened onto the pipe 10, and shows how the slip ring 25/inclined surface 24 contact the outer end of the seal 14 and bend it onto the surface of the pipe 21 to give a very good watertight seal.

If the slip ring 25 is not used, then the inclined surface 24 contacts the outer end of the compressible seal 14 and bends it inwards onto the surface of the pipe 21.

The fact that the compression seal 14 is fixed in place means that it is held in the correct position and cannot be skewed or misaligned. The additional support provided by moulding the compression sealed to the end of the pipe 10 also means that it is possible to use a softer grade of material for the seal, which also tends to deform more readily under pressure and provide a better seal.

The angle of taper on the seal and on the inclined surface 24 of the nut can be varied to suit particular requirements/particular materials. The limiting factors with the angle of taper of the seal are that a very shallow angle, (e.g. 2 degrees to 5 degrees) means is a very long seal is required, and a correspondingly longer nut, which is impractical. Conversely, a much sharper taper, (e.g. 45 degrees) means that the seal is correspondingly shorter, giving only a small contact area between the nut (or nut plus slip ring) and the seal, and a smaller contact area between the seal and the pipe onto which the seal is being pressed:- this tends to give a less satisfactory seal.

It has been found that an angle of about 16 degrees gives optimum results so far as grip between the components is concerned, but a relatively shallow angle like this means that the components are slower to connect together, because more torque is required to connect them. A greater angle, typically 25 degrees to 30 degrees still gives an excellent seal and means that the components are connected together more rapidly, but does not give as good a grip between the components as a more shallow angle.

Claims

1. A plumbing fitting including: • a first component at least one end of which is designed to be releasably secured to another plumbing fitting; • said first component having an external screw thread formed adjacent said at least one end; • an internally threaded nut which is dimensioned and adapted to engage said external screw thread such that a second component may be secured to said first component; • said nut providing an internal tapered compression surface adjacent the end of said internal screw thread furthest from said first component in use; • a compression seal made of resilient but compressible material, which is annular in form and which has opposed first and second edges; • said first edge being formed with a tapered surface on the internal surface of said seal, such that the seal decreases in thickness towards said first edge; • the taper of said internal tapered surface of the seal being approximately the same as the taper of the tapered surface of the nut, such that in use, when the nut is fully engaged with said first component, the tapered surface of the nut presses said first edge of said seal into sealing engagement with said another plumbing fitting; • said one end of said first component having the second edge of the compression seal permanently secured around said one end; • said plumbing fitting further including a slip ring in the form of a frusto conical portion of low friction material which is tapered to match the internal tapered surface of the nut and which is dimensioned to mount inside said nut, in contact with said internal tapered surface.

2. The plumbing fitting as claimed in claim 1, wherein the taper on the tapered internal surface of the nut and the taper of the tapered surface of the seal both are in the range 16 degrees - 30 degrees.

3. The plumbing fitting as claimed in claim 1 or claim 2, wherein said seal is made from a thermoplastic elastomer.