GB2125500A - Push-fit plumbing fittings - Google Patents

Abstract

A push-fit plumbing fitting including a deformable grab ring (22) of slotted form made of pressed metal sheet and adapted to engage the surface of a tube or tubular connecting piece. So that the sharp corners adjacent the slot in the ring do not contact the surface of the tube or tubular connecting piece to score the surface, the corner portions (34) are bent outwards from the otherwise frusto-conical shape of a portion (30) of the ring which contacts the surface of the tube or tubular connecting piece. <IMAGE>

Description

SPECIFICATION Push-fit plumbing fittings The invention relates to push-fit plumbing, fittings of the kind for producing a leak-proof seal on a tube or tubular connecting piece, for example a tubular connecting piece on a water tap or valve.

Various kinds of compression type plumbing fittings are already known. For example, in one prior proposal a combination of parts for making a compression type fitting has included male and female screwthreaded members, a ferrule and an O-ring seal, the female screwthreaded member having a portion with a tapered bore within which the ferrule, having a complementary external taper, can be located before the screwthreaded members are connected together, the arrangement being such that when the two screwthreaded members have been assembled together the male member bears against the end of the ferrule to urge it against the tapered bore within the female member so that the ferrule is inwardly compressed to tightly embrace a tube or tubular connecting piece which has been entered into a bore in the male screwthreaded member, the end of said male screwthreaded member which is to abut against the end of the ferrule having a counterbore which forms a groove for the reception of the O-ring seal, one wall of said groove being formed by a radially inner part of the end surface of the ferrule against which the end of the male screwthreaded member is to bear.Such an arrangement has been found to work quite well, primarily because in such an arrangement the mechanical connection function is quite separate from the leak-proof seal function. (It has been found that mechanical joints which have attempted to perform the additional function of a leak-proof seal have been unreliable and difficult to seal against leakage, particularly when the tube or tubular connecting piece has been a relatively weak walled tube, that is to say when it has been a relatively thin walled metal tube or a synthetic plastics tube, due to the high crushing pressure which it has generally been necessary to apply to said tube).Various other kinds of fittings, including push-fit connections which are factory assembled and tightened and only require the push-fit connection of a length of tube or tubular connecting piece thereto, have been used in which the mechanical connection and leak-proof seal functions have been quite separate. However, it is often found, particularly when the mechanical connection includes a deformable grab ring of slotted form, that the surface of the tube or tubular connecting piece concerned is deeply scratched or scored when being connected to the fitting, such scratching or scoring sometimes being sufficient, when the tube or tubular connecting piece concerned is made of synthetic plastics material, to cause leakage of fluid from the fitting.On the other hand, such scratching or scoring may be caused when the tube or tubular connecting piece concerned is being disconnected from the fitting and this might then cause leakage of fluid from some other similar fitting with which that length of tube or that tubular connecting piece is subsequently used.

The object of the invention is to provide a push-fit plumbing fitting which whilst having these same advantages of separate mechanical connection and leak-proof seal functions has a mechanical connection function such -# that the surface of the tube or tubular connecting piece concerned is unlikely to be deeply scratched or scored during its connection to or disconnection from the fitting so that leakage of fluid from the fitting (or from another similar fitting with which the tube or tubular connecting piece concerned might subsequently be used) is unlikely to be a problem.

According to the invention, there is provided a push-fit plumbing fitting including means whereby, on a tube or tubular connecting piece, there is obtained a mechanical connection and a separate leak-proof seal, the mechanical connection being obtained by a deformable grab ring of slotted form made of pressed metal sheet, the grab ring including a tapered inner portion providing a sharp edge adapted to engage the surface of the tube or tubular connecting piece concerned, corner portions of said tapered inner portion of the ring adjacent the slot therein being bent outwards from the otherwise frusto-conical shape of said inner portion so that the sharp corners adjacent the slot in the ring do not contact the surface of the tube or tubular connecting piece concerned.The grab ring may also include a tapered outer portion, this being tapered in the opposite sense to the taper of the inner portion, the fitting in this case including an element having a tapered bore portion in which the tapered outer portion of the grab ring is partly received, the element referred to being a part of an end cap or being an abutment ring. In this case, the tapered outer portion may be provided with a plurality of scallop portions so that the abutment edge of the grab ring is not of circular shape but of sinuous form so that it can seat itself more securely against an abutment surface. The leak-proof seal will preferably be provided by a resilient O-ring which may be located on the inner side or the outer side of the grab ring.If located on the outer side of the grab ring, the resilient O-ring will preferably be located between a portion of an end cap and an abutment ring within which the grab ring is partly received. The end cap may have screwthreaded connection with a body part of the fitting and in this case a skirt portion of the end cap may be provided with at least one ratchet element capable of cooperating with a complementary ratchet stop on the body part, the arrangement being such that the ratchet element or ratchet elements engage with the at least one ratchet stop on the body part during a final part of the screwthreaded connection of the end cap on said body part and prevent the subsequent inadvertent slackening of said end cap.The co-operable faces of the or each ratchet element of the skirt portion and of the or each ratchet stop on the body part may be located in planes containing the axis of the joint. On the other hand, the co-operable faces of the or each ratchet element of the skirt portion and of the or each ratchet stop on the body part may be located in planes inclined to planes containing the axis of the fitting, the arrangement being such that the engagement of the ratchet element and ratchet stop faces prevents slackening of the retaining cap or sleeve until a substantial slackening torque is applied thereto, that is to say a slacking torque substantially greater than the torque applied to tighten the fitting.Preferably, the skirt portion of the end cap will be provided with a plurality of ratchet elements and the body part will preferably be provided with a plurality of complementary ratchet stops. The body part will preferably be provided with an abutment, against which the skirt portion of the end cap can abut when fully tightened.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which:~ Figure 1 is a part sectional side view through an assembled double ended push-fit plumbing fitting embodying the invention, Figure 2 is an exploded view, Figure 3 is an end view of a component part of the fitting, Figure 4 is a sectional view on the line 4-4 in Fig. 3, Figure 5 is a view similar to Fig. 2 which illustrates a possible modification of the fitting, Figures 6 and 7 are views respectively similar to Figs. 1 and 2 which illustrate a somewhat different construction of fitting embodying the invention, Figures 8 and 9 are views respectively similar to Figs. 3 and 4 which illustrate a modification of that component part, Figure 10 is a view similar to Fig. 1 which illustrates a still further construction of fitting, Figure ii is a sectional view on the line 11-11 in Fig. 10, and Figure 12 is a view which will be referred to in relation to a possible modification of the Fig. 10 construction.

Referring now to Figs. 1 and 2 of the drawings, the double ended push-fit plumbing fitting there illustrated is the same at each end. The fitting at the left hand will therefore be described. This includes a body part 10 with stepped bore portions 12 and 14. In use, the bore portion 12 receives an end portion of a tube or tubular connecting piece (shown chain-dotted in Fig. 1) whilst the bore portion 14 contains means generally indicated 16 which provide a mechanical connection function and a resilient O-ring 18 which encircles the tube or tubular connecting piece concerned to provide a leak-proof seal. An annular end cap 20 surrounds the tube or tubular connecting piece and closes the end of the bore portion 14, the end cap having an internally screwthreaded skirt portion which engages a screwthreaded portion of the body part and abuts against a shoulder formed on said body part.A part of the external surface of the skirt portion of the end cap is serrated so that it can be tightened or slackened by hand.

The means generally indicated 16 which provide the mechanical connection function on the tube or tubular connecting piece concerned are constituted by a deformable grab ring generally indicated 22 and an abutment ring 24, the latter having a cylindrical external surface and being slidably located in the bore portion 14 of the body part. The abutment ring has a tapered bore portion 26 within which is partly received the deformable grab ring, the latter having a similarly tapered outer portion 28.In addition, the abutment ring has an internal flange portion 25 which closely surrounds the tube or tubular connecting piece entered into the fitting, the arrangement being such that the end surface of the ring remote from the grab ring extends substantially the full width across the annular space in which the O-ring 18 is disposed so that in the assembled condition of the fitting it deforms the O-ring as shown in Fig. 1.

The deformable grab ring, which is of slotted form, is made of pressed metal sheet.

It is provided, in addition to its tapered outer portion 28, with a tapered inner portion 30 this being tapered in the opposite sense to the taper of its outer portion and providing a sharp edge 32 adapted to engage the surface of the tube or tubular connecting piece on which the fitting is connected.

Referring now to Figs. 3 and 4, these illustrate in greater detail the form of the pressed metal grab ring. In particular, it will be seen that, in the region of the slot, the corner portions 34 of the tapered inner portion 30 have been very slightly bent outwards from the otherwise frusto-conical shape of said inner portion. Consequently, although the tapered inner portion 30 provides the sharp edge 32 which extends around and bites into the plain surface of the tube or tubular connecting piece on which the fitting forms a seal, the sharp corners adjacent the slot in the ring do not contact the plain surface referred to.

In use of the fitting (which will have been factory assembled together as shown in Fig. 1 with the grab ring abutting against the shoulder between the bore portions 12 and 14 of the body part) it will be understood that when a length of tube or tubular connecting piece of appropriate diameter has been push fitted into the fitting, a very slight axial pull on the tube or tubular connecting piece, against the body part and end ring, would tend to cause the grab ring to slide down the internal tapered surface of the abutment ring so that the sharp edge 32 of the grab ring tends to bite into the surface of the tube or tubular connecting piece concerned. In practice this action of pulling the tube or tubular connecting piece against the body part and end ring is not necessary.The internal water pressure within the pipe gives rise to an axial force out of the fitting which causes the pipe to move outwards very slightly and to activate the grab ring. Consequently, it has been found that the amount of inward crushing of the grab ring onto the surface of the tube or tubular connecting piece concerned is very slight and is not sufficient to damage the tube or the ferrule. The component parts of the fitting and the tube itself can therefore be re-used. A plumber can make a joint and then dismantle it again if he finds that the tube is fractionally too long.

The assembled fitting can very quickly and easily be dismantled by the simple process of unscrewing the end cap and withdrawing the tube or tubular connecting piece from within the body part together with the O-ring 18, abutment ring 24 and grab ring 22. As the grab ring is withdrawn away from the shoulder against which it has previously abutted and is freed from contact with the abutment ring, it is able to expand and can then be released from the tube or tubular connecting piece concerned. The fact that the sharp corners of the tapered inner portion of the grab ring, adjacent the slot therein, do not contact the surface of the tube or tubular connecting piece concerned has been found to protect said surface when the tube or tubular connecting piece is being entered into the grab ring and also when being withdrawn therefrom.In other words, the sharp corners of the ring do not tend to dig into and score the surfaces concerned.

In Fig. 5 there is illustrated a minor modification of the fitting just described, the modification residing in the fact that the abutment ring is no longer provided with an internal flange. In other words, the tapered bore portion 26 extends the full width of the abutment ring, the end surface of the ring being sufficiently wide to effect a required deformation of the O-ring when the fitting is assembled.

Referring now to Figs. 6 and 7, the fitting there illustrated is basically similar to that described above in that it includes a resilient O-ring 18 which provides a leak-proof seal function and means which provide a separate mechanical connection, said means including a deformable grab ring 22 exactly the same as that of the previously described arrangement. However, in this case, the resilient 0ring is not located outside the mechanical connection as in the previously described arrangement but is located on the inside of the mechanical connection, that is to say in a bore portion 36 formed between the stepped bore portions 12 and 14. The O-ring is retained in position in the bore portion 36 by means of a flanged retaining ring 38.The tapered outer portion 28 of the grab ring abuts against the flange of the retaining ring which in turn abuts against the shoulder between the bore portions 14 and 36 of the body part.

It will be seen that in this case the abutment ring 24 has been omitted, but the tapered bore portion in which the deformable grab ring is partly received is now provided in a male portion 40 formed integrally within the end cap 20.

In operation, the fitting is very like the fitting previously described, the deformable grab ring being arranged to allow a tube or tubular connecting piece to be plugged into the fitting but to prevent its extraction. However, by virtue of the fact that the O-ring is located on the inside of the mechanical connection, it is even more important than before that the sharp corners of the tapered inner portion of the grab ring should not be able to dig into and score the surface of the tube or tubular connecting piece concerned as it is entered into the fitting because this could cause leakage of fluid past the O-ring 18. As before, this is guarded against by the fact that said corner portions have been very slightly turned out so that they cannot contact the surface referred to.

Referring now to Figs. 8 and 9, there is there illustrated a modified form of the pressed metal grab ring shown in Figs. 3 and 4. As in the case of the grab ring of Figs. 3 and 4, it is of slotted form and made of pressed metal sheet. It is also provided with a tapered outer portion 28 and with a tapered inner portion 30 having a sharp edge 32 adapted to engage the surface of a tube or tubular connecting piece which has been entered into the fitting concerned, and the corner portions 34 of the tapered inner portion 30 have been very slightly bent outwards for the same purpose as before.In this case, however, it will be seen that the tapered outer portion 28 is not a plain tapered portion but has a plurality of scallop portions 29 as shown, the result being that the abutment edge of the grab ring, which in a fitment of the kind illustrated in Fig. 6 will abut against the flanged retaining ring 38, is not of circular shape but of sinuous form so that it can seat itself more securely against the retaining ring.

In Figs. 10 and 11 there is illustrated a still further construction of double ended push-fit plumbing fitting embodying the invention which has been found to be particularly advantageous both from a manufacturing point of view and functionally; this is generally similar in certain respects with the construction of Figs. 6 and 7 and like parts are given the same reference numbers. It will also be seen that the fitting has been provided with a pressed metal grab ring of the modified form just described. However, the tapered bore portion 26 is in this case formed within a tapered nose portion of the end cap 20.

A further variation from the earlier described embodiments, and one which could of course be applied to any of them, is visible in particular in Fig. 11 where it will be seen that the skirt portion of the end cap is provided with a plurality of ratchet elements within the diameter remote from the tapered bore portion, said ratchet elements being capable of co-operating with a plurality of complementary ratchet stops 42 on the body part adjacent a central abutment flange 44. It will be seen that the axial width of the ratchet elements and of the ratchet stops is relatively small, that is to say less than twice the pitch of the screwthread on which the end cap is threaded, and the arrangement is such that the ratchet elements engage the ratchet stops on the body part during the final part of the screwthreaded connection of the end cap on said body part.It has been found that the ratchet elements prevent the subsequent slackening of the end cap even though the joint may be subjected to vibrations and/or water hammer and even when the temperature of water flowing through a water system in which the joint has been used has fluctuated.

It has been said that the ratchet elements 40 of the embodiment just described have prevented the subsequent slackening of the end cap and this is of course because the cooperating surfaces of the ratchet elements and of the ratchet stops are disposed in planes containing the axis of the fitting. However, in Fig. 12 there is illustrated a possible modification, that is to say the slight inclination of the co-operating surfaces of the ratchet elements and of the ratchet stops as shown. In this way it can be ensured that the end cap can subsequently be slackened if desired, but of course by the application of a slackening torque substantially greater than the torque applied to tighten the fitting. The slackening torque required will of course depend upon the inclination of the co-operating surfaces referred to and can be determined by trial and experiment.

It will be seen in Fig. 11 that the ratchet stops are equally spaced around the circumference of the body part but that the ratchet elements within the skirt portion of the end cap are arranged in pairs one pair being offset through 45 relative to the other pair. In this way the end cap is always held by an oppositely disposed pair of ratchet elements and the end cap can ratchet around in 45 increments. A further advantage of this arrangement is that the deformation which must take place to allow the ratchet action to occur, that is to say the deformation of the end portion of the end cap to a somewhat oval shape from its normally circular shape, can easily take place when the operative ratchet elements are oppositely disposed.It will however be understood that the ratchet elements and ratchet stops could be different in number, for example there could be a single ratchet element within the end cap and a greater number of ratchet stops on the body part.

Various other modifications may be made.

For example, it may be advantageous, particularly in the embodiments illustrated in Figs. 6 and 7, and in Figs. 10 to 12 where the screwthreaded end cap is in direct contact with the grab ring, for means to be incorporated to prevent the rotation of the grab ring in the body part. Such means could be constituted by apertures in the outer periphery of the grab ring and moulded key pieces in the body part. In this way there will be prevented the grooving or scoring of the tube or tubular connecting piece concerned which might be caused by rotation of the grab ring.Furthermore, it is not essential for the body part and end cap to be connected together by means of a screwthreaded connection; they could be connected by means of a plug-in connection constituted, for example, by a pair of oppositely disposed slots extending through the wall of the body part and a pair of oppositely disposed elements extending radially inwardly of the skirt portion of the end cap.

It will of course be understood that one or the other of the tubes or tubular connecting pieces shown in chain-dotted lines in Fig. 1 may be a tubular spigot portion formed on some kind of apparatus, for example on a water tap or valve. It will also be understood that although in the fitting illustrated by way of example the body part is shown to be double ended and forming the body part of two such fittings whereby two lengths of tube may be connected together end to end, the body part of the fitting (that is to say one half of the body part illustrated in the drawings) may be formed integrally with some kind of apparatus to which a tube of tubular connect ing piece is to be connected.

All of the fittings hereinbefore described have been primarily designed as push-fit con nections but it will be understood that they could be used as compression type fittings. If they were to be intended to be used as compression fittings, their grab rings could be slightly greater than the outside diameter of the tube or tubular connecting piece concerned such that when tightened the external taper of the grab ring would be brought into contact with the complementary frusto conical surface against which it is to abut, thus causing the grab ring to bite into the surface of said tube or tubular connecting piece. Any additional outward movement caused, for example, by internal water pressure would of course enhance the grip of the grab ring on the surface concerned.

Claims (11)

1. A push-fit plumbing fitting including means whereby, on a tube or tubular connecting piece, there is obtained a mechanical connection and a separate leak-proof seal, the mechanical connection being obtained by a deformable grab ring of slotted form made of pressed metal sheet, the grab ring being retained within the fitting by means of an end cap and including a tapered inner portion providing a sharp edge adapted to engage the surface of the tube or tubular connecting piece concerned, corner portions of said tapered inner portion of the ring adjacent the slot therein being bent outwards from the otherwise frusto-conical shape of said inner portion so that the sharp corners adjacent the slot in the ring do not contact the surface of the tube or tubular connecting piece concerned.

2. A push-fit plumbing fitting according to claim 1, in which the grab ring also includes a tapered outer portion, this being tapered in the opposite sense to the taper of the inner portion, the fitting in this case including an element having a tapered bore portion in which the tapered outer portion of the grab ring is partly received, the element referred to being a part of the end cap or being an abutment ring.

3. A push-fit plumbing fitting according to claim 2, in which the tapered outer portion is provided with a plurality of scallop portions so that the abutment edge of the grab ring is not of circular shape but of sinuous form so that it can seat itself more securely against an abutment surface.

4. A push-fit plumbing fitting according to any one of the preceding claims, in which the leak-proof seal is provided by a resilient O-ring which is located on the inner side or the outer side of the grab ring.

5. A push-fit plumbing fitting according to claim 4, in which the resilient O-ring is located on the outer side of the grab ring between a portion of the end cap and an abutment ring within which the grab ring is partly received.

6. A push-fit plumbing fitting according to any one of the preceding claims, in which the end cap has screwthreaded connection with a body part of the fitting, a skirt portion of the end cap being provided with at least one ratchet element capable of co-operating with a complementary ratchet stop on the body part, the arrangement being such that the ratchet elements or ratchet elements engage with the at least one ratchet stop on the body part during a final part of the screwthreaded connection of the end cap on said body part and prevent the subsequent inadvertent slackening of said end cap.

7. A push-fit plumbing fitting according to claim 6, in which the co-operable faces of the or each ratchet element of the skirt portion and of the or each ratchet stop on the body part are located in planes containing the axis of the joint.

8. A push-fit plumbing fitting according to claim 6, in which the co-operable faces of the or each ratchet element of the skirt portion and of the or each ratchet stop on the body part are located in planes inclined to planes containing the axis of the fitting, the arrangement being such that the engagement of the ratchet element and ratchet stop faces prevents slackening of the retaining cap or sleeve until a substantial slackening torque is applied thereto, that is to say a slackening torque substantially greater than the torque applied to tighten the fitting.

9. A push-fit plumbing fitting according to any one of claims 6 to 8, in which the skirt portion of the end cap is provided with a plurality of ratchet elements and the body part is provided with a plurality of complementary ratchet stops.

10. A push-fit plumbing fitting according to any one of claims 6 to 9, in which the body part is provided with an abutment, against which the skirt portion of the end cap can abut when fully tightened.

11. A push-fit plumbing fitting constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated by Figs. 1 to 4, or Fig. 5, or Figs. 6 and 7, or Figs. 8 and 9 or Figs. 10 and 11, or Fig. 12 of the accompanying drawings.