Tube coupling

Abstract: The disclosure relates to a tube coupling (10) having a throughway (11) open at one end (18) to receive a tube end (17), an annular groove encircling (18) the throughway at a location spaced from said open end and an annular flexible sealing washer (24) mounted in the groove and having an inner peripheral portion (28) which projects through the open mouth of the groove to engage an outer surface of a tube (16) which is a close fit in the throughway. The groove has one side (20) nearest the open end of the throughway which lies in a plane generally transverse to the throughway to limit flexing of the inner part of the sealing washer towards the open end of the throughway and an opposite side (21) of which is relieved (23) at the mouth (22) of the groove to allow the inner part of the sealing washer to take up a curvature in being deformed by forcing a tube through the washer so that the resulting stretching of the inner part (28) of the washer by the tube provides a seal between the washer and tube and fluid pressure on the side of the sealing washer facing into the coupling body enhances the seal between the washer and tube.

Description: This invention relates to tube coupling bodies and in particular to coupling bodies having throughways open at one end to receive a tube and a seal mounted in the throughway to seal with the outer surface of the tube. Conventionally an O-ring seal or seals is provided in the coupling body as described, for example, GB-A-1520742, GB-A-1573757, GB-A-2007322 and GB-A-2150243. US-A-2491004 discloses a coupling comprising an annular form housing having inturned flanges at the ends of the housing within which the pipe ends are received. Within the cavity of the housing there is a resilient packing provided with a centrally located cavity having an annular slot through the inner wall to provide access for the fluid in the pipes to the cavity. The packing has inner cylindrical surfaces on either side of the slot for cooperation with the ends of the pipes to effect a seal therebetween when the packing is subjected to internal pressure. US-3837687 discloses a tube coupling having a body in which a gripping ring is mounted for engaging the tube and a sealing ring of U-shaped cross-section having a inner ring bearing against the tube. FR-1491388, which is considered to be the closest prior art, discloses a tube coupling comprising a plastics sleeve having one or more metal rings incorporated in the sleeve. Each ring has a rim of oblique rigid ribs pointed towards the center of the sleeve and of chisel-shaped section to engage and grip the tubes inserted into the sleeve. The sleeve has annular seats formed towards the open ends of the sleeve in which bearing seals are located to seal with the tube ends inserted into the sleeve. This invention provides a tube coupling having the features of claim 1. In the preferred arrangement according to the invention the outer peripheral portion of the sealing washer is in sealing engagement with the bottom part of the groove. More specifically the sealing washer may be formed with an annular ridge adjacent the outer periphery of the washer which seals with one side of the groove. In one particular construction according to the invention the ridge may project on one side of the washer and a corresponding recess is formed in the other side of the washer and the other side of the groove is formed with an annular ridge which engages the washer adjacent the recess so that both sides of the sealing washer are sealed in the groove. In any of the above arrangements a stack of said sealing washers may be provided having annular sealing ridges on one side thereof, the washers being mounted side by side in the groove so that the ridges form a seal between the washers and also space the washers apart to allow the inner peripheral portions of the washers to flex independently and seal with the outer surface of a tube in the throughway. The sealing washing may be formed from P.T.F.E. strip, nylon, polyethylene or aluminium foil. The following is a description of some specific embodiments of the invention, reference being made to the accompanying drawings in which : Figure 1 is a diagrammatic view of a tube coupling body having a throughway to receive an end part of a tube and an encircling seal mounted in the throughway to seal with the outer surface of the tube shown both with and without the tube present; Figure 2 is a side view of an annular sealing washer for use in the coupling body of Figure 1; Figure 3 is a front view of the sealing washer of Figure 2; and Figure 4 is a similar view to that of Figure 1 showing an alternative arrangement embodying multiple annular seals. Referring firstly to Figure 1 of the drawings, there is shown a tube coupling body 10 having a throughway 11 extending into the coupling body from one end 12 thereof. At a location spaced from the end 12 of the coupling body, the throughway is stepped up in diameter at 13 to form an enlarged end diameter portion 14 which extends to an opening 15 in the end wall 12 of the body. A tube 16 has an end part 17 which is inserted into the enlarged end portion 14 of the throughway. The tube abuts against step 13 in the throughway and the outer diameter of the tube is such that it is a close fit in the enlarged diameter portion of the throughway. The enlarged diameter portion 14 of the throughway is formed partway between the open end 15 and the step 13 with a deep encircling annular groove 18 having a closed bottom wall 19, side walls 20 and 21 and a mouth 22 where the groove opens to the throughway. The side 20 of the groove lies in a plane extending generally transversely of the throughway. The opposing side 21 is closely spaced and parallel to the side 20 adjacent the bottom of the groove and is formed with an annular rebate 23 adjacent the mouth of the groove to form a wider entry to the groove. An annular thin section flexible sealing washer 24 is mounted in the groove, the washer is formed with a moulded or cold-formed ridge 25 adjacent its outer periphery with an annular recess 26 on the opposite side. The one side of the groove 20 is formed with an annular raised ridge 27 in the narrower part of the groove adjacent the groove bottom 19. This raised ridge 27 engages in the recess 26 in the sealing washer and holds the ridge 25 of the sealing washer in sealing engagement with the opposite side wall 21 of the groove. The washer is therefore mounted in its relaxed condition closely spaced from the wall 20 of the groove which limits flexing of the washer towards the open end of the throughway. The washer 24 projects through the mouth of the groove into the throughway and the inner diameter 28 of the washer is formed with a slightly smaller diameter than the outer diameter of the tube 16 with which the washer is to engage. Thus, when the tube is forced into the throughway, as shown in the lower part of Figure 1, the washer takes up the curve formation indicated extending across the rebate 22 at the mouth of the groove and the inner diameter of the washer forms a sealing engagement with the tube. Fluid pressure upstream of the sealing washer in the coupling body bears on the enclave surface of the sealing washer 24 facing into the coupling body to enhance the sealing action of the washer with the tube. Loss of the fluid around the outer side of the washer is prevented by the sealing engagement of the ridge 25 with the side 21 of the groove and the ridge 27 with the recess 26 in the washer. The flexible walled sealing washer 24 is formed by piercing, blanking and then cold-forming out of thin P.T.F.E. sheet or could be moulded in plastics such as a nylon or polyethylene or can be pierced, blanked and formed in a metal such as aluminium foil. Figure 4 of the drawings shows an alternative arrangement in which the outer part of the groove 18 adjacent the groove bottom 19 is widened to accommodate a stack of three sealing washers as described above. The ridge 25 on one washer engages the next washer in the region of the recess 26 but does not enter the recess so that the washers are held spaced apart from one another. This arrangements provides a sealing between adjacent washers and also permits the washers to flex separately when a tube is inserted through them and to seal independently with the surface of the tube, as described for the single washer of the Figure 1 embodiment described earlier. It will be appreciated that because the sealing washer 24 has an internal diameter which is smaller than the tube outside diameter, as the tube is inserted, the washer is deformed by the tube into a curved or conical shape. The conical deformation of the washer creates stresses in the washer which provide the initial sealing pressure on the tube. This sealing pressure is increased as the internal fluid pressure increases thereby maintaining an effectively proof seal. The thin washer 24, being inherently flexible, allows the tube to be inserted with very small effort or force. In addition, a low friction material such as P.T.F.E. further reduces the assembly effort required. This obviously provides an advantage for the connector particularly when coupled with the "avalanche" feature described in EP-A 0667480 where the initial "avalanche" effort can be reduced but still provide a significant difference in level of effort over that of pushing a tube into a conventional seal.

Claims: A tube coupling (10) having a throughway (11) open at one end (12) to receive a tube end (17), an annular groove (18) encircling the throughway at a location spaced from said open end and an annular flexible washer (24) located between spaced sides (20,21) of the groove and having an inner peripheral portion which projects through the open mouth (22) of the groove to engage an outer surface of a tube which is a close fit in the throughway, characterised in that the seal is an inherently flexible sealing washer (24) allowing the tube end (17) to be inserted with very small effort or force and being in sealing engagement with the groove, the groove has one side (20) nearest the open end of the throughway which lies in a plane generally transverse to the throughway and the sealing washer (24) is located in its relaxed position closely spaced from that side (20) of the groove to limit flexing of the inner peripheral portion of the sealing washer (24) towards the open end of the throughway (11) and the opposite side of the groove (21) has annular rebate (23) at the mouth (22) of the groove (18) to increase the width of the groove at the mouth to allow the inner peripheral portion of the sealing washer (24) to take up a curvature adjacent its inner periphery on forcing a tube of slightly greater diameter than the internal diameter of the sealing washer (24) into the throughway and through the sealing washer so that the deformation of the inner peripheral part of the sealing washer seals with the tube and fluid pressure within the throughway can act on the side of the sealing washer facing into the coupling body to enhance the seal between the washer and tube. A tube coupling as claimed in claim 1, characterised in that the outer peripheral part of the sealing washer (24) is in sealing engagement with the bottom part (19) of the groove. A tube coupling as claimed in claim 2, characterised in that the sealing washer (24) is formed with an annular ridge (25) adjacent the outer periphery of the sealing washer which seals with one side (21) of the groove. A tube coupling body as claimed in claim 3, wherein the ridge (25) projects on one side of the sealing washer (24) and a corresponding recess (26) is formed in the other side of the sealing washer and the other side (20) of the groove is formed with an annular ridge (27) which engages the sealing washer adjacent the recess (26) so that both sides of the sealing washer are sealed in the groove. A tube coupling body as claimed in any of the preceding claims wherein a stack of said sealing washers (24) having annular sealing ridges (25) on one side thereof is mounted side by side in the groove so that the ridges form a seal between the sealing washers and space the sealing washers apart to allow the inner peripheral portions of the sealing washers to flex independently and seal with the outer surface of a tube in the throughway. A tube coupling body as claimed in any of the preceding claims wherein the sealing washer (24) is formed from P.T.F.E. strip, NYLON, polyethylene or aluminium foil.

Inventors: GUEST JOHN DEREK, GUEST, JOHN DEREK
Applicants: GUEST JOHN D, GUEST, JOHN DEREK
Application year: 1997
Main classification: F16L37
IPC codes: F16L37, F16L21, F16L17