Improvements in or relating to tube couplings

Abstract: The disclosure relates to a tube coupling (10) comprising a coupling body (14)having a throughway (15) open at one end (16) to receive an end part (12) of a tube, a sealing ring assembly (21) in the throughway to form a sealing engagement with the end part of the tube located in the throughway, and a collet (24) in the throughway entrance engageable with an annular bead (13) on the tube adjacent to the end part of the tube to hold the end part of the tube in the coupling body in engagement with the sealing ring. Resistance to entry of the tube into the throughway prior to engagement of the collet with the tube bead is provided by an annular deformable diaphragm (31) mounted in the coupling body in front of the sealing assembly so that a force applied to the tube to overcome the resistance also overcomes any resistance offered by the locking device to ensure that the tube bead is engaged and held by the collet.

Description: This invention relates to tube couplings. More particularly, the invention is concerned with tube couplings comprising a coupling body having a throughway open at one end to receive an end part of the tube, sealing means in the throughway to form a sealing engagement with the end part of the tube located in the throughway, and a locking device engageable with an annular bead on the tube adjacent to said end part to hold the end of the tube in the coupling body in engagement with said sealing means. A problem which can arise with such an arrangement is that a tube can be pushed into the coupling body and the resistance offered to entry of the tube by the seal may appear to indicate to the operator that the tube has been locked in the coupling body but this may not be so and the bead on the tube may not have engaged the locking device. Thus, when pressure is applied to the coupling, the tube may be simply blown out of the coupling resulting in loss of fluid and potential danger where the fluid is either flammable or corrosive. DE-A-3631812 discloses a tube coupling body having a throughway open at one end to receive a tube with a locking device and an annular seal located in the throughway in succession from its open end. A diaphragm extends across the throughway beyond the seal itself from the open end of the coupling body so that the diaphragm is engaged by a tube inserted through the coupling body after the tube has engaged in the seal. This invention provides a tube coupling comprising a coupling body having a throughway open at one end to receive an end part of a tube, sealing means in the throughway to form a sealing engagement with the end part of the tube located in the throughway, a locking device engageable with an annular bead on the tube adjacent to the end part of the tube to hold the end part of the tube in the coupling body in engagement with said sealing means and resistance means on the body between the sealing means and said open end of the throughway which offer a greater resistance to entry of the tube into the throughway than said engagement of the tube with said locking device and said sealing means, the resistance means being engageable with the tube prior to engagement of either the locking device or the sealing means with the tube and the arrangement being such that application of a force to the tube sufficient to overcome said resistance also overcomes any resistance offered by the locking device and sealing means to ensure that when such a force is applied the tube bead engages with the locking device and the tube engages with the sealing means. The means to provide a resistance to entry of the tube into the throughway may comprise a deformable member located in the throughway in the path of the tube between said sealing means and said open end of the throughway to be engaged and deformed by entry of the tube and thereby to provide resistance to entry of the tube. More specifically the deformable member may comprise an annular component mounted in the throughway between said sealing means and the open end of the throughway and having a inner peripheral portion engageable with the tube to be deformed thereby. For example the annular element may be of simple diaphragm form having a plain inner periphery to be deformed by the tube passing through the element. In another embodiment the annular element may be of diaphragm form having spaced fingers or teeth around its inner periphery which are deformed by the tube passing through the annular element. In a further arrangement the annular element may have arcuate slots between its inner and outer peripheries to allow deformation of the element when the tube is passed through the element. More specifically the element may have an oval shaped inner aperture to be deformed by the tube passing through the element. Alternatively the annular element may have an internal diameter smaller than the outside diameter of the tube whereby the inner portion of the element is deformed by passing the tube through the annular element. In a further arrangement according to the invention the locking device for holding the tube in the coupling body may comprise a annular collet mounted on the coupling body having resilient fingers projecting outwardly of the coupling body to engage over and snap behind the bead on the tube to retain the tube in the coupling body, the annular portion of the collet having an internal diameter less than that of the outside diameter of the tube to provide said resistance to entry of the tube into the throughway in the coupling body. In the latter case the collect may be of dual form, having one set of resilient fingers projecting into the coupling body for engagement with a tapered cam surface in the coupling body to grip and engage the tube within the coupling body and a second set of fingers projecting outwardly of the coupling body to engage and lock with the bead on the tube. 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 known form of coupling body and tube prior to assembly of the tube in the coupling body; Figure 2 is a diagrammatic view of a coupling and tube of Figure 1 shown partly assembled; Figure 3 is a diagrammatic view of a coupling body similar to that of Figure 1 modified to incorporate the present invention; Figure 4 shows the coupling body of Figure 3 and a tube to be located in the coupling body; Figure 5 shows the tube and coupling body of Figure 4 with the tube partially inserted into the coupling body; Figure 6 shows the tube and coupling body of Figure 4 with the tube fully inserted in the coupling body; Figures 7 to 9 are diagrammatic illustrations of tubes and various different forms of annular resistance elements; Figure 10 is a diagrammatic illustration of a dual form collet modified to provide resistance to entry of the tube with a tube partially and more fully inserted into the collet; and Figure 11 shows the collet of Figure 10 incorporated in a tube coupling body; and Figures 12 to 15 show various further arrangements. Reference is made firstly to Figures 1 and 2 of the drawings which show a tube coupling indicated generally at 10 and a tube 11 to be engaged in the coupling. The tube 11 has an end part 12 which is inserted into the coupling and an integral annular bead 13 encircling the tube adjacent the end part to engage with a locking device in the coupling to hold the tube in engagement in the coupling. The coupling comprises a coupling body 14 having a throughway 15 having an enlarged open end 16 to receive the end part 12 of the tube. The diameter of the throughway is increased at a first step 17 facing towards the open end of the throughway to form a first enlarged section 18 and by a second step 19 also facing towards the open end of the throughway to form a second enlarged section 20. The diameter of the first enlarged section 18 corresponds to that of the end part 12 of the tube so that when the tube is inserted in the coupling body, the end of the tube engages in the enlarged section 18 and abuts the step 17. The second enlarged section 20 of the coupling body contains a seal assembly indicated generally at 21 lying in engagement with the shoulder 19 and comprising a pair of O-ring seals 22 separated by a washer 23. The seals are dimensioned to engage the outer surface of the end part 12 of the tube when the latter is inserted in the coupling body to form a fluid tight seal therewith. The end part of the coupling body is formed with an integral collet comprising resilient arms 24 which extend axially over the coupling body and terminate in heads 25 which are shaped to snap over and engage behind the raised bead 13 on the tube when the latter is inserted in the coupling body. The coupling body/collet are enclosed in an end cap 26 the end wall 27 which extending over the collet is formed with an aperture 28 to receive the pipe 11. Figure 2 of the drawings illustrate the coupling body with the tube 11 partially engaged. The end part 12 of the tube is inserted into the coupling body through the collet 24 into the second enlarged section 20 and through the seal assembly 21. The seal assembly provides some resistance to insertion of the tube as the seals grip the surface of the tube which may result in the assembly believe, mistakenly, that the tube has been fully engaged in the coupling whereas the bead 13 of the tube has not been snapped through the heads 25 of the collet as is apparent from Figure 2. This may not be visually apparent because the bead 13 is within the end cap. If a significant pressure where applied to the fluid within the tube/coupling, there would be a serious risk that the tube would be blown out of the coupling resulting in an escape of fluid at pressure. This could be particularly dangerous in the case of an inflammable fluid such as petrol in a fuel line in a motor vehicle or a chemically corrosive fluid. Reference is now made to Figure 3 of the drawings which illustrates a modified form of the coupling of Figures 1 and 2 adapted to overcome the above difficulties. Firstly the second section 20 of the throughway in the coupling body is formed with an integral annular guide 30 adjacent the open end 16 of the coupling body to align the end part 12 with the tube with the seal assembly and section 18. An annular deformable diaphragm 31 is mounted on the wall of the coupling body between the guide 30 and seal assembly and has an internal diameter 32 which is less than the outside diameter of the end part 12 of the tube. Thus, when the tube is inserted in the coupling body, the tube deforms the inner part of the diaphragm 31 as shown in Figure 7 of the drawings as it passes through the diaphragm thus a positive resistance to entry of the tube is provided by the diaphragm which requires a significant force from the assembler to overcome. Once the diaphragm has been deformed, the tube can slide through the diaphragm and then the seal assembly 21 into the section 18 of the throughway but the force applied to "break through" the diaphragm is sufficient to carry the tube fully into the coupling body snapping the bead 13 through the heads 25 of the collet 24 to retain the tube positively in the coupling body. The sequence of the assembly of the tube in the coupling body is shown in Figures 4, 5 and 6. Figure 8 shows a further form of diaphragm in which the inner periphery is formed with spaced teeth 33 which are deflected or deformed by the insertion of the end part of the tube as illustrated. Figure 9 shows a further arrangement in which the diaphragm 31 is formed with a spaced pair of arcuate slots 34 within its wall thickness at diametrically opposite locations. The slots allow the inner part of the diaphragm to be displaced immediately outwardly by the tube as it is driven through the diaphragm closing up the slots as illustrated. The inner opening of the diaphragm may be circular or oval shaped. Figure 10 of the drawings shows an application of the invention to the dual collet form described and illustrated in our UK Patent Application No 9400585.7. The central annular portion 40 to which the two sets of collet arms 41 are mounted has a restricted opening provided by an annular shoulder 42. Pressing the tube end 12 through the collet deforms the shoulder as illustrated in Figure 10. Figure 11 of the drawings shows the dual collet of Figure 10 assembled on a coupling body ready for insertion of the tube. Figures 12 and 13 show a further form of collet described in greater detail in our UK Patent Application No 9419003.0 in which a skeletal metal insert 50 is embodied. The insert has an annular part 51 embodied in the annular part of the collet and integral arms 52 embodied in the arms of the collet. Inturned tabs are formed on the annular part which extend through the inner surface of the collet at spaced locations around the collet to provide the resistance to insertion in a tube through the collet. The tabs are encapsulated in the plastics of the collet to prevent scratching of the tube surface. The tabs remain in tact and functional even when the plastics of the collet has been destroyed by heat or chemical action. Figures 14 and 15 show a further modified form of the collet of Figure 10. The collet of Figures 14 and 15 is formed as a plastics moulding and comprises an annular part 60 having longitudinal slots 61 at one end to form resistent arms 62 to engage and grip a tube in the collet. The annular part of the collet is formed with pairs of circumferentially extending slots 63, 64 and 65, 66 at diametrically opposed locations across the collet. The wall portions 67, 68 within the slots are flexible and are moulded to a larger radius than that of the remainder of the collet so that they project into the interior of the collet as best seen in Figure 15. The wall portions provide an obstruction to the entry of a tube through the collet until the tube is formed into the collet spreading the wall portions 67, 68 apart. The arrangement thus provides a positive resistance to entry of a tube until sufficient force is applied to drive the tube through the collet fully into the coupling body in which it is located as described in connection with the other embodiments above.

Claims: A tube coupling comprising a coupling body (14) having a throughway (15) open at one end (16) to receive an end part (12) of a tube (11), sealing means (21) in the throughway to form a sealing engagement with the end part of the tube located in the throughway, a locking device (24, 25) engageable with an annular bead (13) on the tube adjacent to the end part of the tube to hold the end part of the tube in the coupling body in engagement with said sealing means and resistance means (31,32) on the body between the sealing means and said open end of the throughway which offer a greater resistance to entry of the tube into the throughway than said engagement of the tube with said locking device and said sealing means, the resistance means (31,32) being engageable with the tube (11,12,13) prior to engagement of either the locking device or the sealing means with the tube and the arrangement being such that application of a force to the tube sufficient to overcome said resistance also overcomes any resistance offered by the locking device and sealing means to ensure that when such a force is applied the tube bead engages with the locking device and the tube engages with the sealing means. A tube coupling as claimed in claim 1, characterised in that the means to provide a resistance to entry of the tube (12) into the throughway (15) comprises a deformable member (31,32) located in the throughway in the path of the tube between said sealing means (21) and said open end (16) of the throughway to be engaged and deformed by entry of the tube and thereby to provide resistance to entry of the tube. A tube coupling as claimed in claim 2, characterised in that the deformable member comprises an annular component (31) mounted in the throughway between said sealing means (21) and the open end (16) of the throughway and having an inner peripheral portion (32) engageable with the tube to be deformed thereby. A tube coupling as claimed in claim 3, characterised in that the annular element (31) is of simple diaphragm form having a plain inner periphery (32) to be deformed by the tube passing through the element. A tube coupling as claimed in claim 3, characterised in that the annular element (31) is of diaphragm form having spaced fingers or teeth (33) around its inner periphery which are deformed by the tube passing through the annular element. A tube coupling as claimed in claim 3, characterised in that the annular element (31) has arcuate slots (34) between its inner and outer peripheries to allow deformation of the element when the tube is passed through the element. A tube coupling as claimed in claim 6, characterised in that the element (31) has an oval shaped inner aperture (32) to be deformed by the tube passing through the element. A tube coupling as claimed in claim 6, characterised in that the annular element (31) has an internal diameter (32) smaller than the outside diameter of the tube whereby the inner portion of the element is deformed by passing the tube through the annular element. A tube coupling as claimed in claim 1, characterised in that the locking device for holding the tube in the coupling body comprise an annular collet (40) mounted on the coupling body having resilient fingers (41) projecting outwardly of the coupling body to engage over and snap behind the bead (13) on the tube (11) to retain the tube in the coupling body, the annular portion (40) of the collet having an internal diameter (42) less than that of the outside diameter of the tube to provide said resistance to entry of the tube into the throughway in the coupling body. A tube coupling as claimed in claim 9, characterised in that the collet (40) is of dual form, having one set of resilient fingers (41) projecting into the coupling body for engagement with a tapered cam surface in the coupling body to grip and engage the tube (12) within the coupling body and a second set of fingers (41) projecting outwardly of the coupling body to engage and lock with the bead (13) on the tube.

Inventors: GUEST JOHN DEREK, GUEST, JOHN DEREK
Applicants: GUEST JOHN D, GUEST, JOHN DEREK
Application year: 1995
Main classification: F16L37
IPC codes: F16L37, F16L21