WO2006037967A1

WO2006037967A1 - Seals

Info

Publication number: WO2006037967A1
Application number: PCT/GB2005/003774
Authority: WO
Inventors: Michael Roberts
Original assignee: Norgren Limited
Priority date: 2004-10-01
Filing date: 2005-09-30
Publication date: 2006-04-13
Also published as: GB0421816D0

Abstract

A seal (4, 4a, 4b) for use in a pneumatic system, being at least partially formed of resilient material, having radially inner and outer (49) sealing surfaces and front and back faces (45, 50), comprising a body part (20), the outside of which forms the outer sealing surface, and a lip (23), which extends radially inwardly from the body part (20), in which the lip (23) is provided with at least one sealing portion (47) that protrudes inwardly from the lip (23) at its free end and which is arranged to form the inner sealing surface. The invention also relates to a tube-coupling device incorporating such a seal.

Description

SEALS

This invention relates to seals for use in pneumatic systems, and a tube- coupling device comprising such a seal.

It is known in the art of pneumatic systems to seal interlocking parts of such a system. In one common example, tube coupling devices are used for coupling a tube to one or more other tubes, or to a fluid flow port of an apparatus. The tube is normally inserted by hand through gripping means, normally a grab-ring, and a seal, typically an O-ring, until the end of the tube reaches a stop in the body. The O-ring is of conventional design, comprising a thin toroid of resilient flexible material. With systems designed for pressures up to about 20 bar (2 MPa) , 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, it is desired to use such connectors with higher pressures, up to 60 bar (6 MPa) . In such a case, the O-ring seal is unlikely to hold unless it is so stiff that the insertion force is unacceptably high; if the seal does not hold the connector may leak. This is obviously inefficient and may lead to improper operation of the pneumatic system or even be dangerous if the gas being transferred is harmful or the supply of pressure is for a safety-critical purpose, such as a braking system for a vehicle.

In hydraulic systems, lip seals are known. These comprise a body section forming a ring around the area to be sealed. From a front face of the body section, a lip depends and extends backwards into the interior of the ring. In use, the lip lies along the periphery of the tube to be sealed and is pushed against the tube by the resilient nature of the seal material. Furthermore, once the tube has been inserted and the system pressurised, the hydraulic fluid will be present around the back of the seal. As the lip depends from the front face of the body section, the pressurised hydraulic fluid can flow into a gap between the body and lip sections. There therefore exists a pressure difference between the two sides of the seal and so extra force is applied on the lip portion to force it against the periphery of the pipe.

However, such lip seals have been tried in pneumatic systems and found to be unsatisfactory; they leak more readily than the O-rings previously used.

According to a first aspect of the invention, there is provided a seal for use in a pneumatic system, being at least partially formed of resilient material, having radially inner and outer sealing surfaces and front and back faces, comprising a body part, the outside of which forms the outer sealing surface, and a lip, which extends radially inwardly from the body part, in which the lip is provided with at least one sealing portion that protrudes inwardly from the lip at its free end and which is arranged to form the inner sealing surface.

The provision of such a sealing portion ensures that the seal is air (or gas) tight. Being angled away from the remainder of the lip towards the interior of the seal ensures that the sealing portion presses against the object to be sealed.

Preferably the sealing portion comprises an annular rounded projection. Alternatively, the sealing portion may comprise a projection of substantially rectangular cross-section. Preferably, two sealing portions are provided on the lip. Preferably the two sealing portions are adjacent to each other. The lip may comprise a shoulder, which is arranged to, in use, engage the object to be sealed such that as the object to be sealed is inserted through the seal the lip is urged towards the body part. This may be achieved by the lip extending into the interior of the seal at a non-perpendicular angle to a plane in which the seal lies. Preferably, the resilience of the seal material ensures that the lip being urged towards the body part biases the lip against the object to be sealed.

The body part may be of the form of a generally cylindrical tube, typically having an outer surface of constant cross section. However, in a preferred embodiment the body part has first and second regions of differing outer radius. Having a section of wider radius has been found to be advantageous as this improves the quality of seal around the outer sealing surface. The second section may be of wider radius and may be at the back face of the seal. There may be provided a transition section over which the radius changes from that of the first section to that of the second section. Alternatively, the second region may comprise an annular, preferably rounded, projection that has a wider radius to that of the first region.

An internal edge of the front face of the body part may be chamfered. This aids insertion of a tube or other item to be sealed in use.

The seal may be formed of any suitable resilient material such as a nitrile rubber. It may be of unitary construction, and may be formed entirely or substantially of resilient material. Preferably, the lip extends from or from near the front face of the body part.

According to a second aspect of the invention, there is provided a pneumatic tube- coupling device for coupling a tube to a pneumatic system, comprising a seal according to the first aspect of the invention. The coupling device may comprise a body having a terminal portion for receiving a tube and tube gripping means for gripping the external surface of the tube to retain it in the body. The seal preferably engages the body around the outer sealing surface of the seal.

The coupling device may comprise an internal bore in which the seal is seated. The bore may define a seat, which may be step in diameter of the bore. The second region may engage a wall of the bore. The wall may have a portion of widened diameter compared to the surrounding area in order to accommodate the second region of the seal. This ensures the outer sealing surface can make a good seal on the wall of the bore.

The seal may be seated so as to present the front face towards the direction from which a tube is to be inserted.

There now follows by way of example only, embodiments of the present invention described with reference to the accompanying drawings, in which:

Figure 1 shows a cross-sectional view of a seal according to the present invention;

Figure 2 shows a cross-sectional view of the seal of Figure 1 installed in a pneumatic tube-coupling device;

Figure 3 shows a cross-sectional view of another seal according to the present invention; and

Figure 4 shows a cross-sectional view of a further seal according to the present invention. The tube coupling device 1 shown in Figure 2 of 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 device 1 also has a stepped tube support member 6. The body 2 is itself sealingly mounted by means (not shown) in a port of a connector 8, enabling the tube 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, 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 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 proj ections 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 axdally in the plug 18, which has a conical internal surface 19 that 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.

The seal 4 shown in Figures 1 and 2 of the accompanying drawings is arranged (as will be described below) so as to enable a reliable substantially gas-tight seal. The seal is of the form of a lip seal as are common in hydraulic systems but which have been tiitherto considered unsatisfactory for use in pneumatic systems. The seal is annular, to seal round a tube (not shown) . In use, the tube is inserted into an interior of the seal in order to provide an air- (or other gas-) tight fit.

The seal 4 is mounted at the shoulder 21 between the diameter portions 11, 12 of the bore 9. The seal 4 has an outer sealing surface 22 to seal against the bore 9, and an inner sealing surface being a lip 23 to seal against the tube in use. In the position shown in Figure 2, there is an axial clearance between the collet member 13 and the seal 4.

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.

Turning to the seal 4 in more detail and with reference to Figure 1 particularly, the seal 4 comprises a body part 20 and a lip 23 depending therefrom, to form the outer and inner sealing surfaces respectively. The body part 20 is of annular form with front 45 and rear 50 faces. The lip 23 extends inwardly from the body part, and overtiangs the body part

20 in a backward direction. The seal 4 is made from a resiliency flexible material (such as nitrile rubber) such that the lip 23 can articulate relative to the body part. The internal edge of the front side 45 of the seal 4 - the edge that will, in use, first engage the tube - is provided with a chamfered corner 4-4 so as to guide the tube into the interior of the seal. As the tube is inserted further into the interior of the seal, it will engage a shoulder 46 of the lip 23. The shoulder 46 extends from a point between the front face 45 and the free end of the lip 23 to the free end. The action of tlie tube pressing against the shoulder 46 is to push the lip 23 away from the tube and back towards the body part 20. However, the resilience of the seal material is such that the lip 23 resists this and pushes back. As the tube progresses further through the seal 4 the lip 23 will get further pushed back and so this force will increase.

At the free end of the lip 23 is a sealing portion 47, being a small protuberance at the end of the lip that turns away from the body part 20 towards the interior of the seal. Thus, the inclination of the inwardly facing surface of the lip 23 to the body part 20 increases in the region of the sealing portion 47. The sealing portion 47 comprises a rounded annular projection that extends radially inwardly beyond the extent of the lip 23. The sealing portion 47 thus forms an annular ridge on an inwardly facing surface of the lip 23 that is adapted to seal agains t a tube in use. When a tube is inserted into the seal 4, the sealing portion 47 faces inwards in contact with and pressing against the tube. This increases the force due to the resilience of the seal material at the sealing portion 47 and hence ensures an airtight seal.

The body part 20 is generally of cylindrical annular form. The exterior width of this part increases at its back face (that is, the face furthest from that into which the tube is inserted) through a graduation 48 to a wider part 49. This assists with making a seal to the tube coupling device as will become apparent below. In operation, the tube is fitted into the tube coupling device over the tube support member 6 and supplies high-pressure gas through the interior of tube support 24. The seal 4 ensures that no gas leaks out from the pneumatic system to the outside. The space defined by the internal bore 9, the tube support member 26 and the seal 4 is at high pressure, whereas the space the other side of seal 4 is generally at atmospheric (or locally prevalent) pressure. The pressure differential over the seal acts on lip 23 to add to the resilience force pushing the lip 23, and especially the sealing portion 47, against the tube. This helps ensure a good seal. Similarly, the outer sealing surface, and particularly the widened portion 49 of the body part 20, is urged outwards against the internal bore 11 to form the seal with the body 2.

Figure 3 shows an alternative embodiment of the seal 4a of the present invention, in which like items to the first embodiment are indicated with like reference numerals. The sealing portion 47 extends less far from the lip 23 and is less rounded. The shoulder 46 starts closer to the front face of the body part 20 and the interior edge of the front face 45 is less chamfered. The wider portion 49 of the back end of the seal is comparatively less extensive than in the first embodiment. However, the functioning of the seal 4a is the same as described above.

Figure 4 shows a further embodiment of the seal 4b of the present invention, in which like parts of the first and second embodiments are designated like reference numerals. In this embodiment the lip 23 includes two sealing portions 47 and 47' . The sealing portions 47, 47' comprise rounded protuberances facing towards the interior of the seal and arranged adjacent to each other. The shoulder 46 of this embodiment extends from the chamfered corner 44 to the sealing portion 47' . The annular groove 51, formed between the body part 20 and the inwardly extending lip 23, has a base comprising a radial annular surface 52. The presence of the surface 52 improves the resilience of the lip 23. Thus, in use, the pressure in the coupling can act over surface 52 and lip 23 to urge the sealing portions 47, 47' into contact with the tube. The wider part 49 of this embodiment comprises a rounded annular projection 54, similar in form to the sealing portion 47. Thus, the rounded form of the projection 54 replaces the graduation 48.

Claims

1. A seal for use in a pneumatic system, being at least partially formed of resilient material, having radially inner and outer (49) sealing surfaces and front and back faces (45,50) , comprising a body part (20) , the outside of which forms the outer sealing surface, and a lip (23), which extends radially inwardly from the body part (20) , in which the lip (23) is provided with at least one sealing portion (47) that protrudes inwardly from the lip (23) at its free end and which is arranged to form the inner sealing surface.

2. A seal according to claim 1, in which the sealing portion (47) comprises an annular rounded projection.

3. A seal according to claim 1 , in which the sealing portion (47) comprises a projection of substantially rectangular cross-section.

4. A seal according to any preceding claim, in which two sealing portions (47, 47') are provided on the lip (23) .

5. A seal according to claim 4, in which the two sealing portions (47,47') are adjacent to each other.

6. A seal according to any preceding claim, in which the lip (23) comprises a shoulder (46) , which is arranged to, in use, engage the object to be sealed such that as the object to be sealed is inserted through the seal the lip (23) is urged towards the body part (20) .

7. A seal according to any preceding claim, in which the lip (23) extends into the interior of the seal (4, 4a, 4b) at a non-perpendicular angle to a plane in which the seal lies .

8. A seal according to any preceding claim, in which the resilience of the seal material ensures that the lip (23) being urged towards the body part (20) biases the lip (23) against the object to be sealed.

9. A seal according to any preceding claim, in which the body part (20) is of the form of a generally cylindrical tube.

10. A seal according to claim 9, in which the body part (20) has an outer surface of constant cross section.

11. A seal according to any preceding claim, in which the body part (20) has first and second regions (53, 49) of differing outer radius.

12. A seal according to claim 11 , in which the second section (49) is of wider radius and is located toward the back face (50) of the seal.

13. A seal according to claim 11 , in which there is provided a transition section (48) over which the radius changes from that of the first section (53) to that of the second section (49) .

14. A seal according to claim 11 , in which the second region (49) comprises an annular rounded projection (54) that has a wider radius to that of the first region.

15. A seal according to any preceding claim, in which an internal edge (44) of the front face (45) of the body part (20) is chamfered.

16. A seal according to any preceding claim, in which the seal (4, 4a, 4b) is formed of any suitable resilient material such as a nitrile rubber.

17. A seal according to any preceding claim, in which the seal (4, 4a, 4b) is of unitary construction.

18. A seal according to any preceding claim, in which the seal (4, 4a, 4b) is formed entirely of resilient material.

19. A seal according to any of claims 1 to 17, in which the seal (4, 4a, 4b) is formed substantially of resilient material.

20. A seal according to any preceding claim, in which the lip (23) extends from or from near the front face (45) of the body part (20) .

21. A pneumatic tube-coupling device for coupling a tube to a pneumatic system, comprising a seal (4, 4a, 4b) according to the first aspect of the invention.

22. A pneumatic tube-coupling device according to claim 21, in which the coupling device comprises a body (2) having a terminal portion for receiving a tube and tube gripping means (5) for gripping the external surface of the tube to retain it in the body (2) .

23. A pneumatic tube-coupling device according to claim 21 or claim 22, in which the seal (4, 4a, 4b) preferably engages the body (2) around the outer sealing surface (49) of the seal.

24. A pneumatic tube-coupling device according to any of claims 21 to 23, in which the coupling device comprises an internal bore (9) in which the seal (4, 4a, 4b) is seated.

25. A pneumatic tube-coupling device according to claim 24, in which the bore (9) defines a seat (21) to receive the seal.

26. A pneumatic tube-coupling device according to claim 24, in which the seat (21) comprises a step in diameter of the bore (9) .

27. A pneumatic tube-coupling device according to any of claims 24 to 26, in which the second region (49) of the seal (4, 4a, 4b) engages a wall of the bore (9) .

28. A pneumatic tube-coupling device according to claim 27, in which the wall has a portion of widened diameter compared to the surrounding area in order to accommodate the second region (49) of the seal.

29. A pneumatic tube-coupling device according to any of claims 21 to 28, in which the seal (4, 4a, 4b) is seated so as to present the front face (45) towards the direction from which a tube is to be inserted.