WO1991008414A1

WO1991008414A1 - Conduit coupling

Info

Publication number: WO1991008414A1
Application number: PCT/AU1990/000562
Authority: WO
Inventors: Maurice Kevin Fiddler
Original assignee: Vulcan Australia Limited
Priority date: 1989-11-23
Filing date: 1990-11-23
Publication date: 1991-06-13

Abstract

A flexible conduit coupling such as for coupling of a water inlet flexible hose (8) of a diswashing machine to a water main, in which the coupling comprises a spigot (6), a collet (20) and a ferrule (14). In use, the spigot is inserted in the end of the hose, the collet is located over the hose outside of the spigot and the ferrule is located over and permanently deformed in a state of inward compression over the collet and spigot to maintain the collet and hose in tight contact with the spigot so clamping the hose, whilst also making a first end (16) of the ferrule captive in a slot (22) of the spigot. Any force applied to the hose tending to pull it out from the coupling is resisted by a tendency also to move the collet with the hose into a region of the ferrule, the inner wall of which has an inward taper (24) which complements an inward taper (24) of the outside of the collet such that any axial pull out movement tendency is accompanied by a radially inward deflection of the collet into tighter engagement with the hose. The spigot preferably is provided with ribs (12) and projection (10) whilst the inside surface of the collet preferably is provided with rib (29) and lip (30). The ribs, projection and lip assist in gripping the end of the hose, further resisting any tendency for it to be pulled out of the coupling.

Description

CONDUIT COUPLING-

BACKGROUND

This invention relates to a conduit coupling. An example of its use is for coupling a water inlet hose of a dishwashing machine to a water main.

The object of the present invention is to provide a conduit coupling which is more resistant to failure by the conduit being separated from the coupling by pulling or under the influence of excessive internal pressure in the conduit.

SUMMARY

According to the present invention there is provided a flexible conduit coupling comprising a spigot one end of which is, in use, inserted in the end of a flexible conduit, the other end of the spigot having connecting means for connecting the conduit coupling to another body, a collet located, in use, over the end of a conduit, and a ferrule which is, in use, compressed inwardly so as to cause the end of the conduit to be clamped between the collet and the spigot, the arrangement being such that when the conduit is pulled in the direction away from the spigot, the collet will tend to move with the conduit and wherein the coupling includes a constriction which forces the collet into tighter engagement with the conduit.

Preferably, the ferrule has an inwardly sloping wall and the outer surface of the collet has a complementary wall the arrangement being such that when the collet moves with the conduit in an axial direction, the sloping wall and complementary wall cause radial deflection of the collet into firmer engagement with the conduit.

DESCRIPTION OF THE DRAWINGS

The invention will now be further described with reference to the accompanying drawings, in which:

FIGURE 1 is a longitudinal section through a known form of conduit coupling;

FIGURE 2 shows the known form of coupling when subjected to excessive pressure;

FIGURE 3 is a side view of the coupling, partly in section, of the invention prior to compression of the ferrule; FIGURE 4 shows the coupling after compression;

FIGURE 5 is a perspective view of the collet;

FIGURE 6 is an end view of the collet;

FIGURE 7 is a cross-sectional view taken along the lines 7-7; and

FIGURE 8 shows the collet after compression.

DETAILED DESCRIPTION.

The coupling 2 illustrated in Figure 1 comprises a body 4 in which is normally provided with internal or external threads. Extending from the body 4 is a hollow spigot 6 which is inserted in the end of a flexible conduit or hose 8. The spigot is provided with a sloping projection 10 and a number of circumferentially extending ribs 12. The coupling includes a ferrule 14 which is usually made of metal and is compressed inwardly so as to clamp the end of the hose 8 between it and the spigot 6. The ribs and to some extent the projection 10 assist in gripping of the hose within the ferrule. During assembly the end of the hose is inserted in the ferrule and the spigot with the assistance of the sloping projection 10 enters the hose. The f entile is then pressed so as to clamp the hose between it and the spigot. One end of the ferrule is pressed inwardly so as to lie adjacent to the spigot 6 and the other end includes a flared portion 18 which is directed away from the hose so as to minimise contact of the hose with the end of the ferrule. That contact could cause damage to the hose.

When a coupling of the type illustrated in Figure 1 Is subjected to excessive internal pressures either static or transient, the hose tends to expand to a position as diagrammatically illustrated in Figure 2. It has been found that the end of the hose 10 tends to work free from the spigot and eventually pulls from the spigot and the coupling fails. The shape of the flared end 18 does not impede the removal of the hose from the coupling.

It will be appreciated that in some circumstances the failure of the coupling can lead to damage. For instance where the hose is used in connection with domestic appliances say for connecting a dishwasher or clothes washer to a hot or cold water supply, the failure of the coupling can cause expensive water damage and this can lead to claims against appliance manufacturers. Figures 3 and 4 show a coupling constructed in accordance with the invention. Similar reference numerals will be used to denote parts which correspond to those of the arrangement shown in Figure 1.

Generally speaking, the principal distinction between the known arrangement and that of the invention is the interposition of a collet 20 between the ferrule 14 and the spigot 6. The collet 20 of the invention is constructed so that it can be radially compressed, as will be described hereinafter.

Figure 3 shows the coupling of the invention prior to compression of the ferrule 14 and Figure 4 shows the coupling after compression. The assembly of the coupling is similar to the known arrangement. The spigot is fully inserted into the end of the hose until the end of the hose is located within the collet 20. The ferrule is then compressed by pressing or rolling or the like so that the hose is clamped between the spigot and the collet.

It will be noted that the body 4 includes a circumferential slot 22 adjacent to the inner end 16 of the ferrule. After compression, the end 16 of the slot is captive in the slot 22. This effectively prevents axial movement of the ferrule 14 relative to the body 4, except for the slight movement which might be possible owing to the clearance between the slot 22 and the end 16 of the ferrule. When the ferrule is compressed, it is formed with an inwardly inclined wall portion 24 and an outwardly flared portion 26. The outer surface of the collet 20 includes inclined faces 24 which are complementary in shape to the inwardly inclined surface 24, as best seen in Figure 4. The inner surface of the Collet 20 when compressed includes at least one circumferential projection 28 and a rib 29 projecting therefrom which bite into the hose 8. The inner surface of the collet also includes an inwardly directed tapering lip 30 which is inwardly adjacent to the inclined surface 27. As best seen in Figure 3, the inner edges of the rib 29 and lip 30 are about the same diameter as the end of the hose when on the spigot 6 so as not to impede the insertion of the end of the hose into the coupling.

When the coupling is completed by inward compression of the ferrule 14, the collet is inwardly compressed so as to clamp the end of the hose between it and the spigot 6. The rib 29 and lip 30 as well as the ribs 12 and projection 10 assist in gripping the end of the hose. When the coupling of the invention is subjected to forces which tend to pull the hose away from the coupling, axial movement is resisted by virtue of the clamping action described above. When, however, the loads are increased and movement of the hose on the spigot 6 begins to occur, the collet 20 will move with the end of the hose. This takes place because the rib 29 is embedded in the hose and the outer surface of the collet and the adjacent inner surface of the ferrule are smooth and free of projections so that the collet can move relative to the ferrule. The ferrule 1 is restrained by virtue of its inner end 16 being captive in the slot 22. Thus the inclined faces 27 will slide down the inwardly directed wall 24 of the ferrule and so cause the lip 30 to bite harder into the hose 8. The lip 30 is located axially inwardly relative to the projection 10 so as when the collet moves the hose is constricted between the lip 30 and the projection 10. This very significantly increases the resistance of the coupling to pulling away of the hose.

Figure 5 schematically illustrates the preferred form of collet 20 for use in the coupling. It is essentially comprises a hollow cylindrical body 40 which is formed with tapering slots 42 and 43 extending generally axially from opposed ends. The slots 42 and 43 are circumferentially staggered so as to form a somewhat zig-zag sidewall structure for the collet. When the collet is compressed, the geometry is such that it forms a generally complete cylindrical wall as diagrammatically illustrated in Figure

8. This has been found to be particularly advantageous in the coupling of Figures 3 and 4 because if the inner wall of the collet does not have at least one complete cylindrical surface leakages can occur under higher statis pressures because the liquid can slowly pass through any small gaps which might occur in the inner wall of the collet. In the illustrated arrangement the geometry is such that the segments of the sidewall structure which form the rib 29, and preferably the projection 28, form continuous cylindrical surfaces.

Figure 7 shows a slightly modified collet 45 which is similar to that shown in Figure 5 except that the outer profile of the body 40 is straight as indicated by reference numeral 45 rather than curved as is the case in Figure 5. In addition the widths of the ends of the slots 43 are wider than the ends of the slots 42. When the collet 45 is compressed such that the rib 29 is a complete cylindrical surface there will be some clearance between the sidewall segments adjacent to the segments 31 which form the lip 30. In the assembled coupling when the collet moves axially, the inward deflection of the lip 30 is facilitated because of the presence of gaps between the segments 31.

The body 4 and collet 20 are preferably injection molded from nylon or other suitable plastics material. The ferrule 14 would normally be made from steel. The internal diameter of the ferrule would be say 26mm before compression and 23.5mm after compression. The inner edge of the lip 30 is initially 18mm and is compressed to 15.5mm in the assembled coupling. The inwardly inclined surface 24 is 10° to the axial and preferably In the range 5 to 15°. This angle does not impede axial movement of a collet and gives the inward compression at the end where the lip 30 is located.

A prototype coupling has been tested with hot water (90°C) and was capable of withstanding pressure of 10 Megapascals.

Many modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A flexible conduit coupling comprising a spigot one end of which is, in use, inserted in the end of a flexible conduit the other end of the spigot having connecting means for connecting the conduit coupling to another body, a collet located, in use, over the end of the conduit, and a ferrule which is, in use, compressed inwardly so as to cause the end of the conduit to be clamped between the collet and the spigot, the arrangement being such that when the conduit is moved in the direction away from said one end of the spigot, the collet will tend to move with the conduit and wherein the coupling includes a constriction which forces the collet into tighter engagement with the conduit.

2. A coupling as defined in claim 1 wherein the spigot and compressed ferrule have interlocking formations which prevent or limit axial relative movement.

3. A coupling as defined in claim 2 wherein the interlocking formations include a groove in the spigot and an inwardly directed flange on the ferrule.

4. A coupling as defined in claim 3 wherein the flange is located at one end of the ferrule, the flange being radially deformed into said groove on compression of the ferrule.

5. A coupling as defined in claim 4 wherein the constriction includes a first frustoconical face which tapers inwardly in a direction towards the other end of the ferrule.

6. A coupling as defined in claim 5 including a second frustoconical face which tapers outwardly to the free end of the ferrule.

7. A coupling as defined in claim 6 wherein the frustoconical faces are formed on compression of the ferrule.

8. A coupling as defined in any preceding claim wherein the outer surface of the collet has an inwardly sloping wall which engages said first frustoconical face when the collet is moved in said direction so that the collet is radially compressed into tighter engagement with the conduit.

9. A coupling as defined in any preceding claim wherein the collet includes axial slots to facilitate compression thereof.

10. A coupling as defined in any preceding claim wherein the inner surface of the collet includes projections which bite into the conduit on compression of the ferrule.

11. A coupling as defined in claim 8 or claim 9 or 10 as appended to claim 8 wherein the collet includes projection which extends inwardly and is inwardly adjacent to the said sloping wall.

12. A coupling as defined in claim 11 wherein the spigot includes a projection which is located such that the projection lies between the inwardly extending projection of the collet and said one end of the spigot the arrangement being such that when the collet is moved in said direction the conduit is compressed between said projections.

13. A coupling as defined in claim 12 wherein the projection on the spigot is V-shaped in axial section.

14. A coupling as defined in claim 12 wherein the projection on the spigot tapers toward said one end of the spigot.

15. A coupling as defined in claim 12 or 13 wherein the spigot includes projecting ribs spaced axially between said projection on the spigot and the other end of the spigot.