GB2278658A

GB2278658A - Compression fitting

Info

Publication number: GB2278658A
Application number: GB9410666A
Authority: GB
Inventors: David Digby
Original assignee: Pegler Ltd
Current assignee: Pegler Ltd
Priority date: 1993-06-02
Filing date: 1994-05-27
Publication date: 1994-12-07
Also published as: GB9410666D0; GB9311349D0

Abstract

A compression filling, in particular for use with flexible tubes (T), has a body (10), a nut (12), a ferrule (14) and a stiffener element (16). A tube (T) inserted into the filling is engaged by the ferrule (14) whereupon tightening of the nut (12) causes deformation of the tube (T) into contact with engagement formations such as ribs (17) and/or grooves (17') on the stiffener element (16) which serve to retain the tube (T) within the filling. The stiffener element (16) may be received within a bore (24) of the body part, an O-ring seal (18) being provided to form a fluid-tight seal between the stiffener element (16) and the body part (10). <IMAGE>

Description

COMPRESSION The invention relates to compress ion fittings for producing a fluid-tight seal between a tube or pipe and a tubular connecting piece on, for example, a tube or pipe connector, a water tap inlet or the connections to valvework and the like designed to accept the tube. It will be understood that the term "tube" as used herein is intended to extend to tubes and pipes of all types, both flexible and rigid.

Various kinds of compression fittings are already known. For example, in one prior proposal a compression fitting includes a tubular body part and an end cap, the body part having a bore with a groove for an O-ring seal and the end cap having a tapered bore portion within which is received a deformable ferrule, the latter being arranged to bite into the surface of a tube entered into the fitting. However, this kind of compression fitting is intended for use with tube of a fairly rigid nature and is not capable of being used with tube of a more thin-walled or flexible nature.

According to the invention, there is provided a compression fitting comprising a tubular body portion for receiving an end portion of a length of tube inserted into the fitting; a compression part in threaded engagement with the body; a deformable ferrule disposed between the body and the nut and surrounding the tube; and a stiffener element arranged to enter an end portion of the tube, and having a retention formation for engagement with an inner wall surface of a tube, the fitting being arranged such that tightening of the compression part on the body part cases radially inward deflection of the ferrule, so as to deform the ferrule such that the inner wall surface of the tube is urged into contact with and gripped and/or sealed by the retention formation.

The compression part will typically be a nut.

The stiffener may be formed separately from the body part, being adapted for insertion into the body part for use. In such arrangements, sealing means (such as an O-ring seal) may be provided to form a fluid-tight seal between the stiffener element and the body part.

Conveniently, the body part may have a bore into which the stiffener is received as described above, the bore preferably being formed (for example with a step-change in its diameter) to limit the extent to which the stiffener element may be inserted.

The engagement formation may comprise a groove in the stiffener element, a rib on the stiffener element, or a combination of these. Preferably, a plurality of such engagement formations are provided, one or more of which serve to retain the tube within the fitting.

Preferably, the body part and/or the nut each has a formation adapted to engage the ferrule and urge it radially inwardly on tightening of the nut. Such formations may be frusto-conical surfaces for example being formed by a tapered portion of a bore within the body part and/or the nut, as the case may be.

Normally, the stiffener element will have a fluid passage through which fluid may flow into or out of the tube.

The deformable ferrule will preferably be inwardly deformed at both ends when the compression nut is tightened. The bore of the tubular body part will preferably be a stepped bore into which the tubular stiffener element can be entered to a limited extent.

The tubular stiffener element will preferably have a plurality of circumferential grooves constituting engagement formations defined by a series of circumferential ribs, each groove preferably being of Vshape in cross section.

In order that the invention may be fully understood and readily carried into effect, an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a sectional view through an assembled compression fitting embodying the invention, the left and right hand halves of the drawing showing the assembly before and after tightening, respectively, and Figure 2 is an exploded view thereof.

Referring now to the drawings, the compression fitting there illustrated includes a tubular body part 10 having a bore 29 extending therethrough; a compression nut 12 (constituting a compression part) engaging an externally screwthreaded end portion 11 of the body part 10; a deformable ferrule 14; and a tubular stiffener element generally indicated 16. The stiffener element has a series of external circumferential ribs 17 and an enlarged diameter end portion 15 in which is formed a circumferential groove for the location of an O-ring seal 18. Pairs of adjacent ribs 17 define a series of circumferential grooves 17' spaced along the exterior surface of the stiffener element, each groove being of Vshape in cross section.

The nut 12 has an axial through bore 20 extending between first and second faces. A first portion 20' of the bore 20, extending from the first face, is internally threaded and adapted for threaded engagement with the screwthreaded portion 11 of the body part 10, as described above. A tapered portion of the bore extends from the screwthreaded portion 20' towards the second face, this taper forming an annular frusto-conical surface 20'' directed generally towards the first face.

From the tapered portion, the bore extends, generally cylindrically, to the second face.

The bore 24 of the body part 10 has a tapered end portion which tapers inwardly to form an outwardly directed, frusto-conical annular surface 22. From the tapered portion the bore 24 extends cylindrically, as shown at 24', at a diameter suitable for engagement with the O-ring seal 18 (and likewise with the tube) on insertion ofthe stiffener element 16 into the bore 24 of the body part 10. Inwardly of the cylindrical portion 24', the bore 24 undergoes a step reduction in diameter, as shown at 24''.

In its free condition, that is to say before any compression has been applied to it (see the left hand side of.Figure 1) the deformable ferrule 14 is seated at its outer end against the frusto-conical surface 20'' of the compression nut 12 and at its inner end is in contact with the frusto-conical surface 22 of the tapered end portion of the bore 24 of the tubular body part 10. The inner end portion of the ferrule 14 is of slightly lesser wall thickness than the end which abuts the compression nut 12.

On assembling the fitting for use, a length of flexible tube T, which is to be connected to the fitting, is forced along the circumferentially ribbed portion of the tubular stiffener element 16 to its fullest extent, that is to say until the end of the tube T abuts against a shoulder 26 formed by the enlarged diameter end portion 15 (an end portion 28 of the stiffener element 16 is tapered and the taper leads onto a plain diameter portion 30 to facilitate the fitment of the flexible tube on the stiffener element 16.) The enlarged diameter end portion 15 of the stiffener element 16, together with an end length of the flexible tube T, is then entered into the bore 24 of the tubular body part 10 to the fullest extent possible, (insertion being limited by the step reduction 24'' in bore diameter) the O-ring seal 18 being compressed to form a fluid tight seal within the stepped bore 24.

Having assembled the components of the fitting as shown in the left hand portion of Figure 1 and as described above, the tightening of the compression nut 12 forces the deformable ferrule 14 along the inwardly tapering portion of the bore 24, such that it is compressed between the frusto-conical surfaces 20,22 of the body part 10 and the compression nut 12. This causes the end portions of the ferrule 14 to be deformed radially inwardly whereby, in these regions, the wall of the flexible tube T is deformed inwardly to partially occupy and seal within the grooves 17' between pairs of ribs 17 of the stiffener element 16.

It has been found that, by virtue of the manner in which the ferrule 14 is caused to deform the wall of the flexible tube radially inwardly upon the ribs 17 of the stiffener element 16, a very secure attachment of the tube T within the fitting is possible without excessive tightening of the nut 12 being required. The fitting is sealed against the leakage of fluid under pressure from within the flexible tube T by the deformation of the tube into the stiffener element grooves 17' and by the O-ring seal 18, so resisting the passage of fluid from the tube to a position in which it could contact a cut end of the tube.

Various modifications may be made. For example, although it is preferable for the O-ring seal 18 to be accommodated in a circumferential groove around the stiffener element 16, as in the illustrated embodiment, it could quite possibly be accommodated in an undercut groove in the bore of the tubular body part to encircle a plain cylindrical portion of the stiffener element 16 (the wall thickness of the body part 10 being enlarged somewhat to allow the provision of such an undercut groove). Also, instead of the nut 12, an externallythreaded nipple could be provided for engagement with an internally-threaded portion of the bore 29, the nipple having an end surface adapted for engagement with the ferrule 14.

The deformable ferrule 14 could be modified in various ways. For example, it is not essential for its inner end portion to be of lesser wall thickness than the end which abuts the compression nut 12. The deformable ferrule 14 may be deformable at either one of its ends or at both ends or indeed art some point between its ends.

Although the fitting has been designed specifically for use with flexible tube of the kind including a thin walled metal tube sheathed both internally and externally with plastics, it may be used with any other kind of tube capable of being radially inwardly deformed without the application of undue force.

When used with flexible tube of the kind including a thin walled metal tube sheathed both internally and externally with plastics, the O-ring 18 and the grooved stiffener element 16 prevents the fluid being handled from coming into contact with the end face of the tube, thus protecting the bonding of the metal to plastics and preventing corrosion of the metallic layer of the tube.

Claims

CLAIMS:

1. A compression fitting comprising a tubular body portion for receiving an end portion of a length of tube inserted into the fitting; a compression part in threaded engagement with the body; a deformable ferrule disposed between the body and the nut and surrounding the tube; and a stiffener element arranged to enter an end portion of the tube, and having a retention formation for engagement with an inner wall surface of a tube, the fitting being arranged such that tightening of the compression part on the body part causes radially inward deflection of the ferrule, so as to deform the tube such that the inner wall surface of the tube is deformed into contact with and gripped and/or sealed by the retention formation.

2. A compressing fitting according to claim 1, in which the compression part is a nut.

3. A compression fitting according to claim 1 or claim 2, in which the stiffener element is formed separately from the body part, its being inserted into the body part in use.

4. A compression fitting according to claim 3, comprising sealing means to effect a seal between the stiffener element and the body part in use.

5. A compression fitting according to claim 2 or claim 3, in which the stiffener element is received within a bore of the body part.

6. A compression fitting according to any preceding claim, in which the retention formation comprises a groove in a circumferential wall of the stiffener element.

7. A compression fitting according to any preceding claim in which the retention formation comprises a rib projecting from a circumferential wall of the stiffener element.

8. A compression fitting according to any preceding claim, comprising a plurality of retention formations, one or more of which being effective to retain the tube in the fitting.

9. A compression fitting according to any preceding claim in which the nut and/or the body part each has a formation adapted to engage the ferrule and cause its radial deformation on tightening of the nut.

10. A compression fitting according to claim 9, in which the formations comprise frusto-conical surfaces.

11. A compression fitting according to claim 9, in which the body part and/or the nut has a bore, a tapered portion of which is bounded by a wall which constitutes a frusto-conical surface.

12. A compression fitting according to any preceding claim, in which the stiffener element has a fluid passage through which fluid may flow into or out of the tube.

13. A compression fitting substantially as described herein with reference to the accompanying drawings.