WO2006082376A1

WO2006082376A1 - Tube coupling

Info

Publication number: WO2006082376A1
Application number: PCT/GB2006/000291
Authority: WO
Inventors: Christopher Edward Narborough
Original assignee: Norgren Limited
Priority date: 2005-02-01
Filing date: 2006-01-31
Publication date: 2006-08-10
Also published as: GB0501995D0

Abstract

A removable cartridge (3) for a tube coupling allows the components of the coupling to be removed for servicing. The tube coupling comprises a body (2) having a terminal portion for receiving a tube, sealing means (4) for sealingly engaging the external surface of the tube and tube gripping means (5) for gripping the external surface of the tube to retain it in the body (2). The removable cartridge (3) retains the gripping means (5) and sealing means 4 in the body (2), the cartridge (3) having a screw-threaded portion (41) adapted to engage, with rotation, a complementary screw-threaded portion (45) on the body to removably secure together the cartridge (3) and the body (2).

Description

TUBE COUPLING

This invention relates to a cartridge for a tube coupling and, in particular relates to a removable cartridge for a tube coupling that allows components of the coupling to be serviced. The invention is particularly applicable to tube couplings in a pneumatic system.

Pneumatic systems comprise pneumatic lines, to transfer the pneumatic fluid, as well as pneumatically operated devices that are powered or controlled by the pneumatic fluid. Tube coupling devices and fittings are used in pneumatic systems to connect pneumatic lines together, in order to alter their direction or make up longer lengths, and also to connect them to fluid flow ports of pneumatically operated devices. Such coupling devices usually comprise a body having a terminal portion to receive the end of a tube which forms part of a pneumatic line, and gripping means and sealing means for the tube. An end plug, usually of brass, is used to retain the gripping and sealing means within the body. The tube is normally inserted by hand through the end plug and gripping means, which is normally a grab ring or collet, and also through the sealing means, which is typically an O-ring, until the end of the tube reaches a stop provided in the body.

The body and the external surface of the end plug are normally press- fitted together. Thus, the end plug is permanently fixed within the body to ensure the coupling is robust and the gripping and sealing means are retained securely. The end plug also has a conical internal surface, which, in use, engages the grab ring or collet to urge the gripping teeth radially inwardly to grip the tube. It is therefore important that the end plug is securely in place to ensure the integrity of the coupling. In certain applications it is desirable that the gripping means and sealing means can be removed from the assembled coupling. This is of particular importance when the tube coupling is required to be serviced, as it allows a user access to inspect or replace component parts such as the gripping means or the sealing means.

According to the invention we provide a tube coupling 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 and a removable cartridge for retaining the gripping means and sealing means in the body, the cartridge having a screw-threaded portion adapted to engage, with rotation, a complementary screw-threaded portion on the body to removably secure together the cartridge and the body.

Thus, the cartridge provides the means to retain the gripping means and sealing means within the body obviating the need for an end plug. Further, as the cartridge securely engages the body by a screw-threaded connection, it provides the necessary integrity for the coupling while being easily removable, to allow servicing.

Preferably, the screw-threaded portion of the cartridge is on an external surface thereof and the screw-threaded portion of the body is on an internal surface. Thus, the cartridge is removably received within the body making the coupling compact. Further, the cartridge may have a conical surface that interacts with the gripping means in use.

The screw-threaded portion may comprise a single-start thread. Preferably, it is a multi-start thread. A multi-start thread allows the cartridge and the body to fully engage with less rotation. Also, the use of multiple threads improves the shear strength of the connection. Preferably the cartridge and the body have complementary parts of an engagement means. The engagement means is adapted to become engaged at least when the cartridge is fully inserted in the body. The engagement means therefore secures the screw-threaded connection to prevent the cartridge becoming accidentally disengaged from the body in use. Furthermore, the engagement means may provide an indication to a user that the cartridge is fully inserted in the body. Thus, the engagement means may 'snap' together to provide an indication that can be felt or heard by the user when the cartridge is screwed into the body. This is advantageous as it improves the reliability of the assembly of the coupling and therefore its integrity.

The engagement means may comprise at least one projection on one of the components and at least one complementary recess on the other. Preferably, four equally spaced projections are provided that are received within four complementary recesses. Preferably, the projections are provided on the cartridge and the recesses are provided in the body.

Preferably, the cartridge requires the use of a tool to disengage it from the body.

Preferably the gripping means comprises a collet. Alternatively, the gripping means comprises a grab ring.

Preferably, the cartridge includes a flange that is adapted to engage the gripping means. The flange can be used to appropriately axially position gripping means.

Preferably, the cartridge is of plastics. There now follows by way of example only a detailed description of the present invention with reference to the accompanying drawings in which;

Figure 1 shows an exploded perspective view of the coupling incorporating the cartridge of the invention; and

Figure 2 shows a section through the tube coupling of Figure 1 when assembled.

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 (not shown) , sealing means 4 for sealingly engaging the external surface of the tube, and tube gripping means 5 for gripping the external surface of the tube to retain it in the body 2. The sealing means 4 and gripping means 5 are retained in the body 2 by a cartridge 3. The device 1 also has a stepped tube support member 6, which engages with the body 2 by means 7. The body 2 is itself sealingly mounted, by means 8, in a port of a connector (not shown) , enabling the tube to be connected to other tubes or adaptors of the pneumatic system.

The cartridge 3 is of plastic material, and comprises an annular ring 18, which retains the sealing and gripping means 4, 5 in the body 2. The ring 18 comprises a collar portion 19 and a screw-threaded portion 41, which has a multi-start thread on an external surface thereof. The ring 18 also has a conical internal surface 42 that is adapted to interact with the gripping means 5 in use. The collar portion 19 has part of an engagement means in the form of four equally circumferentially spaced projections 44. The projections 44 are positioned relative to the thread such that when .cartridge 3 is screwed into the body 2, the projections engage with another part of the engagement means in the form of complementary recesses (not shown) in the body 2 when the cartridge 3 is fully inserted.

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 45, 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 the inner end of the support member 6 is received, and which is also adapted to receive the end of the tube in use. The internal surface of the bore 9 has a complementary screw-threaded portion 45 at its outer end 48.

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 in use. The seal 20 may be an O-ring instead.

The gripping means 5 comprises a collet member 13 having a tubular member portion 35 with an enlarged inner end 14. The tubular member portion 35 extends from the bore 9 and allows a tube to be removed from the tube coupling. At its inner end the collet 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 the cartridge 3. The cartridge 3 is mounted to the body 2 such that it extends within the outer end of the bore 9 and the screw-threaded portion 41 is engaged with the threaded portion 45. As the cartridge 3 is screwed into the body 2, the projections 44 of the engagement means approach the outer end 48 of the bore 9. The arrangement of the threaded portions 41, 45 and position of the projections 44 around the circumference of the collar portion 19 is such that the engagement means interengages when the cartridge 3 is fully screwed into the bore 9 of the body 2. This ensures the coupling 1 is robust and correctly assembled, as the engagement means makes an audible sound when it engages and also prevents the cartridge from becoming unscrewed.

The collet member 13 is adapted to slide axially within the retaining means 18. The collar portion 19 of the cartridge 3 has an inwardly facing annular flange 51, which engages an annular channel 52 in the collet member 13. The flange 51 ensures that the collet member 13 is appropriately positioned within the bore 9 for effective gripping of the inserted tube. However, the engagement between the flange 51 and the collet member 13 is such that with sufficient axial force the collet member 13 is allowed to slide to ensure the integrity of the coupling as discussed below.

The conical internal surface 19 of the cartridge 3 engages the conical surface 17 of the collet member 13 to urge the gripping teeth radially inwardly to grip the tube in use. In the position shown in Figure 2, the teeth do not exert a great deal of force, and the collet member 13 can be moved inwardly to allow the tube to be removed. Thus, a user can move the collet member 13, and therefore allow the tube (not shown) to be removed, by applying a force to the part of the release means 35 that extends from the bore 9.

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, while a shorter inner end portion 25 is of larger diameter to slide in the bore portion 12. A shoulder 26 between the portions 24, 25 forms a stop for the end of the tube.

A dust cap 40 is provided for reducing the ingress of moisture and dust into the tube coupling device 1. The cap 40 has a tube-insertion aperture 43 therein. The dust cap 40 includes an annular ridge 46 on its inside surface that engages with a complementary annular groove 47 on the external surface of the body 2. When mounted on the body 2, the dust cap 40 covers the cartridge 3.

On insertion of a tube, its end is fitted over the outer end portion 24 of the 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.

When the system is pressurised the tube may move outwardly again. It takes with it the collet member 13, causing the conical surface 17 of the collet 13 to bear against the conical surface 19 of the retaining means 18 of the cartridge 3. This, causes the teeth 16 to grip the tube more tightly to prevent its removal.

If the collet member 13 and seal 20 are to be removed for servicing, the dust cap 40 is first removed, and then the tube, as described above, by pushing the collet member 13 inwardly. The cartridge 3 can then be removed, unscrewing it from the body thereby causing the projections 44 to snap out of the recesses (not shown) , so that the cartridge 3 can be moved outwardly off the body 2. Access is thereby provided to the collet member 13 and the seal 20, which can be removed for inspection or replacement.

Claims

1. A tube coupling comprising a body (2) having a terminal portion for receiving a tube, sealing means (4) for sealingly engaging the external surface of the tube and tube gripping means (5) for gripping the external surface of the tube to retain it in the body and a removable cartridge (3) for retaining the gripping means and sealing means in the body, characterised in that the cartridge (3) has a screw-threaded portion (44) adapted to engage, with rotation, a complementary screw-threaded - portion (45) on the body (2) to removably secure together the cartridge (3) and the body (2) .

2. A tube coupling according to claim 1, characterised in that the screw-threaded portion (41) of the cartridge is on an external surface thereof and the screw-threaded portion (45) of the body is on an internal surface .

3. A tube coupling according to claim 1 or claim 2, characterised in that the cartridge has a conical surface that interacts with the gripping means (5) in use.

4. A tube coupling according to any preceding claim, characterised in that the screw-threaded portion (41 ,45) comprises a single-start thread.

5. A tube coupling according to any of claims 1 to 3, characterised in that the screw-threaded portion (41 ,45) comprises a multi-start thread.

6. A tube coupling according to any preceding claim, characterised in that the cartridge (3) and the body (2) have complementary parts of an engagement means (44) , which is adapted to become engaged at least when the cartridge is fully inserted in the body.

7. A tube coupling according to claim 6, characterised in that the engagement means (44) provides an indication to a user that the cartridge is fully inserted in the body.

8. A tube coupling according to claim 6 or claim 7, characterised in that the engagement means comprises at least one projection (44) on one of the components and at least one complementary recess on the other.

9. A tube coupling according to claim 8, characterised in that the projections (44) are provided on the cartridge (3) and the recesses are provided in the body (2) .

10. A tube coupling according to any preceding claim, characterised in that the gripping means (5) comprises a collet (13) .

11. A tube coupling according to any of claims 1 to 9, characterised in that the gripping means comprises a grab ring.

12. A tube coupling according to any preceding claim, characterised in that the cartridge (3) includes a flange (51) adapted to engage the gripping means (5) .