This invention relates to a tube coupling device of the kind comprising a body having a terminal portion for receiving a tube, sealing means for sealingly engaging the external surface of the tube, and tube gripping means for gripping the external surface of the tube to retain it in the body.

Such coupling devices are used in pneumatic systems for coupling a tube to one or more other tubes, or, via an adaptor, to a fluid flow port of an apparatus. The tube is normally inserted by hand through the gripping means, which is normally a grab ring, and the sealing means, typically an

O-ring, until the end of the tube reaches a stop provided in the body.

With systems designed for pressures up to about 20 bar and for tube diameters of 4 to 16 mm (OD) , the forces exerted on the inserted tube by the gripping means and seal in order to retain it in the body in use do not need to be very great, so that the insertion force is relatively low.

However, even with a low insertion force it can be difficult for the user to know when the tube is fully inserted, as its engagement with the stop may not be evident, for example if the end of the tube is not straight. It is important for the tube to be inserted fully, in order to ensure that the seal engages with the outside of the tube to provide proper sealing.

Further, some devices include a tube support, over which the tube fits for support and retention in the correct place in the body, to ensure that the gripping means and seal engage properly on the external surface of the tube. This may increase the insertion force and the difficulty of determining when the tube is fully inserted.

According to the invention, a tube coupling device of the kind set forth includes a tube support member, over which the end of the tube fits,

wherein the coupling includes co-operating means on the body and the tube support member movable axially relative to the body on insertion of the tube to provide an audible indication of the fully-inserted position of the tube.

Thus, with the audible indication. , such as a click, when the tube is in the correct position, proper insertion and sealing of the tube is assured.

The co-operating means could be on the tube itself, or indeed on any other part which moves axially on insertion of the tube.

Preferably the co-operating means comprises a projection on one of the body and the movable part, and a groove on the other. The engagement of the projection in the groove provides the click, and also acts to retain the movable part against removal . Preferably the projection is an internal projection on the body, while the groove is an external groove on the movable part. The end of the movable part forward of the groove (in the insertion direction) is then constructed so that it can deflect to move over the projection, until the groove is reached. Thus, the external surface of the end may be profiled, and the end may have axial slots.

Conveniently, the projection and the groove are constructed to allow for easy insertion but resistance to removal of the movable part.

The coupling device may be releasable, being provided with means for releasing the gripping means from the external surface of the tube to allow its removal.

The body may itself have further terminal portions, for receiving other tubes or adaptors, or be inserted in a housing which has the further terminal portions.

An embodiment of the invention is illustrated in the accompanying drawing, in which:

Figure 1 is an end view of a tube coupling device;

Figure 2 is a section along the line 2-2 of Figure 1 without a tube; and

Figure 3 is similar to Figure 2, but shows the tube in the fully- inserted position.

The tube coupling device 1 shown in the drawings is of the releasable push-in type, and is intended for use in pneumatic systems, to connect a tube to one or more other tubes, or adaptors.

The device 1 comprises a body 2 adapted to receive a tube 3 (see Figure 3) , sealing means 4 for sealingly engaging the external surface of the tube 3, and tube gripping means 5 for gripping the external surface of the tube 3 to retain it in the body 2. The device 1 also has a stepped tube support member 6 which co-operates with the body 2 to provide an audible tube insertion indicator 7. The body 2 is itself sealingly mounted by means (not shown) in a port of a connector 8, enabling the tube 3 to be connected to other tubes or adaptors of the pneumatic system.

The body 2 is of plastics material and of annular construction, with a stepped internal bore 9 and a stepped external surface 10. The internal bore 9 has a larger diameter portion 11 at its outer end, in which the gripping means 5 and sealing means 4 are received, and a portion 12 of smaller diameter at its inner end in which trie inner end of the support

member 6 is received, and which is also adapted to receive the end of the tube 3 in use.

The gripping means 5 comprises a collet member 13, in the form of a cylindrical metal tube with an enlarged inner end 14. At its inner end the tube has slits 15, and has triangular projections 16 extending radially inwardly to form gripping teeth. A conical surface 17 is provided externally on the enlarged end 14. The collet member 13 is retained in the body 2 by an annular plug 18 fixed in the outer end of the bore 9. The collet member 13 is adapted to slide axially in the plug 18, which has a conical internal surface 19 which engages the conical surface 17 of the collet member 13 to urge the gripping teeth radially inwardly to grip the tube 3 in use. In the position shown in Figure 2 thte teeth do not exert a great deal of force, and the collet member 13 can be moved inwardly to allow the tube 3 to be removed.

The sealing means 4 comprises a lip seal 20 mounted at the shoulder 21 between the diameter portions 11, 12 of the bore 9 . The seal 20 has an external sealing surface 22 to seal against the bore 9, and an internal lip 23 to seal against the tube 3 in use. In the position shown in Figure 2, there is an axial clearance between the collet member 13 and the seal 20. The seal 20 may be an O-ring instead.

The tube support member 6 is of plastics material, and is of stepped cylindrical outline. A longer outer end portion 24 is of smaller diameter to fit into the tube 3, while a shorter inner end portion 25 is of larger diameter to slide in the bore portion 12. A shcmlder 26 between the portions 24, 25 forms a stop for the end of the tube 3.

The audible insertion indicator 7 is formed by co-operating parts on the tube support member 6 and the body 2. These comprise a groove 27 on

the external surface of the inner portion 25, and a complementary projection 28 on the internal surface of the bore 9. The .groove 27 and projection 28 have a small cylindrical central section 2-9, a radially- extending forward edge 30, and an angled rearward edge 31. The forward or inner end of the tube support member 6 is profiled to allow it to deflect as it passes over the projection 28.

Figure 2 shows the coupling device 1 before insertion of a tube 3, with the tube support member 6 in a retracted position. On insertion of a tube 3, its end is fitted over the outer end portion 24 of th.e tube support member 6, and within the collet tube. As the tube is pushed in, it moves along the tube support member, past the collet teeth 16 and the seal 20, moving the lip 23 radially outwardly, until it reaches the stop 26. Further force applied to the tube 3 then moves the tube support member 6 as well, until the projection 28 engages in the groove 27, with an audible click. This provides the indication that the tube 3 is fully inserted, in the position shown in Figure 3.

When the system is pressurised the tube 3 may move outwardly again. It takes with it the collet member 13, causing the teeth 16 to grip more tightly to prevent its removal. However, the tube support member 6 is held in place by the engagement of the projection 28 in the groove 27.

If the tube 3 is to be released, the collet member 13 can. be pushed in manually, or with a special tool, to release the teeth 16 and allow the tube 3 to be pulled out.