GB2051280A

GB2051280A - Improvements in or Relating to Couplings for Tubes

Info

Publication number: GB2051280A
Application number: GB7921482A
Authority: GB
Original assignee: John Guest Ltd
Current assignee: Reliance Worldwide Corp UK Ltd
Priority date: 1979-06-20
Filing date: 1979-06-20
Publication date: 1981-01-14
Also published as: GB2051280B

Abstract

A tube coupling for holding a resilient tube 25 comprises a body member 10 containing an integral or separate part 20 which fits into the inside of the tube 25, the tube being forced against the part 20 by arms 16 of a collet 11. Pull on the tube 25 to withdraw it from the collet 11, by engagement of surfaces 17 on the arms with an internal surface 18 in the body member tightens the arms onto the tube 25. Sealing is obtained by the part 20, which is preferably externally tapered, engaging in the tube 25 to give effective sealing at low pressures in the fluid passing through the tube 25. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Couplings for Tubes This invention relates to couplings for tubes and is more particularly concerned with a tube coupling of the kind having a collet with resilient arms arranged to co-operate with a cam surface on a member surrounding the collet which member has an internal surface tapering in one axial direction and engaging the arms of the collet so that the arms are forced radially inwardly by axial movement of the collet in said one direction.

With such a tube coupling, the end of the tube may be pushed into the coupling through the collet from the end thereof remote from the arms.

Any outward pull on the tube with respect to said member surrounding the collet tends, by the engagement between the collet and the tube, to pull the collet in the direction to remove it from said member and thereby causes the arms, by engagement with the cam surface, to grip the tube more tightly.

Such a coupling thus serves to hold the tube in said member; the end of the tube can be inserted directly into the coupling and is engaged thereby in a manner which prevents withdrawal of the tube merely by any pull thereon. The tube can be released however by pushing the collet inwardly into said member whilst pulling the tube outwardly. This release can only be effected by a deliberate action and not by an accidental pull on the tube.

It is commonly required to seal the tube in said coupling and it is the usual practice to provide an O-ring within the bore in said member inwardly of the collet, the O-ring fitting tightly around the end of the tube. If there is any leakage of fluid between the end of the tube and said member, the fluid pressure tends to force the O-ring back against the collet and thus serves not only to apply pressure to the collet in a direction tightening the grip of the collet arms on the tube but also serves to deform the O-ring to hold it more tightly against the tube and the surrounding surface of said member.

The above-described construction thus provides a coupling in which good sealing is obtained for fluids under high pressure. It is an object of the present invention to provide an improved seal for use in a tube coupling of the kind described above which carries low pressure fluids, for example for use with garden hoses and other devices carrying water at domestic supply pressures which are usually less than 20 p.s.i.

According to this invention, in a tube coupling for holding a resilient tube comprising a body member having an internal bore, a collet fitting in said bore from one end thereof, the bore having a tapered portion tapering from a larger diameter down to a smaller diameter and the collet having resilient arms with surface portions engaging the tapered surface on said body member so that the collet arms are forced radially inwardly to grip the tube as the collet is moved towards said end, a sealing tube is provided for sealing against the inside of said resilient tube, said sealing tube extending through the collet and having an external surface of which the diameter decreases towards said one end, the sealing tube being integral with the body member or sealed thereto axially inwardly of the inner ends of the collet arms so that a fluid-tight seal is formed between the body member and the resilient tube, when the resilient tube is inserted in the coupling, by the engagement of the outer surface of the sealing tube with the inner surface of the resilient tube.

With this construction, the sealing tube can be integral with the body member or may be sealed thereto. Such a seal is a permanent seal between parts of the coupling and it is much more readily possible to make such a seal fluid-tight under low pressures than an O-ring seal on the outside of the inserted tube, such as has been employed heretofore in couplings of the type described. Such an O-ring has to seal against any tube which might be inserted in the coupling. The tube may be removed and replaced and it may have a damaged or mis-shapen outer surface. The O-ring is subjected to wear and is liable to deteriorate.

With the arrangement of the present invention, on the other hand, the seal is effected using the inner surface of the resilient tube which is forced onto the sealing tube; the latter tube has a diameter which is larger at the axially inner end of the coupling so that the seal becomes tighter as the resilient tube is forced further inwardly. The resilient tube can be pushed on to the sealing tube as far as it can be forced. The collet arms bear against the outer surface of the resilient tube and thus press a part of that tube radially inwardly onto the sealing tube so thereby further improving the seal.

The sealing tube may have a straight taper with the diameter decreasing towards the end over which the resilient tube is pushed. In many cases however it may be preferred to provide circumferential ribs on the sealing tube. These may be shaped with gently sloping flanks on the sides of the ribs facing the free end of the sealing tube to facilitate insertion of the resilient tube onto the sealing tube and steeper flanks on the other sides of the ribs so as to increase resistance to withdrawal of the resilient tube.

In the following description of a number of embodiments of the invention, reference will be made to the accompanying drawings in which:~ Figure 1 Is a longitudinal section through part of a tube coupling with a tube shown outside the coupling; Figure 2 is a longitudinal section through the coupling of Figure 1 with the tube inserted in the coupling; Figures 3 and 4 are views similar to Figures 1 and 2 but of another construction of coupling; and Figures 5 and 6 are views similar to Figures 1 and 2 but of a third construction of coupling.

Referring to Figures 1 and 2, there is shown a coupling comprising a body portion 10, formed of metal or other relatively hard material, and a collet 11 which fits within a bore 12 within the oody portion. The collet 11 comprises an annular portion 13, fitting within a cylindrical portion 14 of the bore 12, and, outside this bore, the collet has a flange 15. Inwardly of the annular portion 13, the collet has a number of arms 16, typically four or six, each of which extends in the axial direction of the assembly from the portion 13. In transverse cross-section, each arm is arcuate and there are gaps between the arms 16 to permit of the arms being forced radially inwardly sufficient to enable the collet to be inserted through the open end of the bore 12.The radially outer surfaces of the arms 1 6 each have a tapered portion 17 which engages with a corresponding internal taper 18 in the bore 12 so that an axially outward pull on the collet, that is to the right in Figures 1 and 2, causes the collet arms 16 to be forced radially inwardly.

Integral with the body portion 10 is a sealing tube 20 which lies axially of the assembly and extends through the collet 11 from a part of the body inwardly of the inner ends of the collet arms.

The outer surface 21 of the sealing tube 20 is tapered to have a smaller diameter towards the outer end of the collet.

In use, a resilient tube 25 to be coupled to the body portion is forced over the sealing tube as shown in Figure 2. The tapered surface 21 enables a fluid-tight seal to be obtained which will readily withstand low fluid pressures, such as for example those employed in domestic water supplies. The collet 11 grips the tube and, in the known way, has, on each arm, a projection 26 which bites into the outer surface of the tube 25 so securing it against withdrawal. Pull on the tube 25 causes the collet to move in the body; the tapered surfaces 1 7, 1 8 cause the collet arms to be forced harder against the tube 25 so gripping it more firmly with the projections 26 biting into the tube. A tube can be released however by pressing the flange 15 axially inwardly into the body portion 10 so permitting the collet arms 16 to spring apart.

It will be noted that no O-ring seal is required in this construction. No sealing is effected against the outer surface of the tube 25.

Figures 3 and 4 illustrate a modification of the construction of Figures 1 and 2 and, in Figures 3 and 4, the same reference characters are used to indicate corresponding features. In the following description mention will only be made of the modified features. In this construction the sealing tube is formed as a separate component having a tube portion 30 with a generally tapered external surface 31, this tube portion being integral with an enlarged head portion 32 which fits closely within the bore 12 in the body portion and is preferably secured therein so as to prevent any leakage around the head portion 32 into the bore 12. A close fit will be sufficient to prevent leakage of low pressure fluids.

Figures 3 and 4 also illustrate ribs 33 on the tapered surface 31 , these ribs having gently sloping flanks 34 facing the open end of the bore 12 and steeper flanks 35 facing inwardly so as to facilitate insertion of a tube 25 onto the surface 31 but to impede withdrawal. The coupling of Figures 3 and 4 operates in the same way as the coupling of Figures 1 and 2, the required fluid-tight seal being effected on the internal surface of the tube 25.

Figures 5 and 6 illustrate a further modification of the previously-described construction. In Figures 5 and 6, a sealing tube 40 with a generally tapered outer surface 41 is integral with a head portion 42 which is axially slidable in the bore 12, being sealed therein by an O-ring 43 retained in a groove 44 in the head portion 42.

This sealing may readily be effected to give a good seal for low pressure fluids since the surface engaged by the O-ring is a smooth surface forming part of the coupling. The O-ring forms a permanent seal and is not liable to damage by insertion of the tube 25, as is the case with 0rings engaging the external surface of the inserted tube in conventional couplers. Any leakage of fluid onto the face of the head portion 42 causes the the head portion to be pushed outwardly (to the right in Figures 5 and 6) so pushing the collet outwardly causing the collet arms to grip the tube 25 more tightly, so increasing both the grip and the seal potential.

Claims

1. A tube coupling for holding a resilient tube comprising a body member having an internal bore, a collet fitting in said bore from one end thereof, the bore having a tapered portion tapering from a larger diameter down to a smaller diameter and the collet having resilient arms with surface portions engaging the tapered surface on said body member so that the collet arms are forced radially inwardly to grip the tube as the collet is moved towards said end and wherein a sealing tube is provided for sealing against the inside of said resilient tube, said sealing tube extending through the collet and having an external surface of which the diameter decreases towards said one end, the sealing tube being integral with the body member or sealed thereto axially inwardly of the inner ends of the collet arms so that a fluid-tight seal is formed between the body member and the resilient tube, wherein the resilient tube is inserted in the coupling, by the engagement of the outer surface of the sealing tube with the inner surface of the resilient tube.

2. A tube coupling as claimed in claim 1 wherein said sealing tube has circumferential ribs on its external surface.

3. A tube coupling as claimed in either claim 1 or claim 2 wherein said sealing tube is integral with a head portion in said bore.

4. A tube coupling as claimed in claim 3 wherein said head portion is secured in said bore.

5. A tube coupling as claimed in claim 3 wherein said head portion is slidable in said bore with a peripheral seal between the head portion and the inner surface of the bore.

6. A tube coupling as claimed in claim 5 wherein said peripheral seal is an O-ring seal.

7. A tube coupling for holding a resilient tube substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 and 4 or Figures 5 and 6 of the accompanying drawings.