Tube couplings

Abstract: The disclosure relates to a tube coupling having a coupling body (11) with a throughway (12) open at one end (13) to receive a tube. A cap (32) mounted on the body extends over said one end with an end wall of the enclosure spaced from the end of the coupling body and having an aperture to receive the tube. A collet (36) is mounted in the enclosure for limited axial movement between the end wall and the coupling body and the collet has a head (37) adjacent the coupling body and resilient fingers (38) projecting towards the end wall of the enclosure to snap over an annular abutment (51) on the tube (50) inserted through the enclosure into the coupling body. Release means (42) are mounted on the enclosure (32) to release the collet fingers (38) from the abutment to allow extraction of the tube from the coupling body.

Description: This invention relates to tube couplings and particularly, though not exclusively applicable to couplings for metal tubing such as fuel or brake fluid lines as used in motor vehicles. Reference should be made to EP-A-93309027.6 from which the present case is divided. WO-92/08074 discloses a tube connector having a cylindrical body into which a tube with a shoulder can be inserted to form a locked, fluid type joint. The tube is first inserted into a collar which provides the locking function and the collar and tube are then slid further into a cylindrical body portion until the end of the tube is sealed against O-rings. During the sliding movement and once the seal is made, the collar is prevented from moving in a direction out of the connector body by sprag teeth supported on the collar which bite into the connector body. This invention provides a tube coupling comprising a coupling body having a throughway open at one end to receive a tube, an enclosure on the body extending over said end with an end wall of the enclosure spaced from the end of the coupling body and having an aperture to receive the tube, a collet mounted in the enclosure for limited axial movement between the end wall and the coupling body, the collet having a head adjacent the coupling body and resilient fingers projecting towards the end wall of the enclosure to snap over an annular abutment on the tube inserted through the enclosure into the coupling body and release means on the enclosure to release the fingers from the abutment to allow extraction of the tube: wherein in that the end wall of the enclosure has an annular inwardly facing abutment encircling the aperture with which the ends of the resilient fingers are engageable to restrain the fingers against outward movement to release the tube abutment and said release means on the enclosure acts to displace the collet towards the coupling body to disengage the resilient fingers from within said annular abutment and thereby allow expansion of the fingers to release the tube. More specifically the annular inwardly facing abutment on the end wall may comprise a bevelled face around the inside of the aperture in the end wall and the outer sides of the finger ends are chamfered to engage the bevelled face. Further the head of the collet may have an angled annular cam surface on the side adjacent the end wall of the enclosure and the enclosure wall has resiliently mounted presser members at diametrically opposed locations around the wall extending radially into the enclosure and formed with inclined faces which engage the cam face or the collet to displace the collet towards the coupling body with depressing of the presser members to release a tube from the collet. In any of the above arrangements one or more O-ring seals may be mounted in the throughway in the coupling body to seal the external surface of the tube inserted in the coupling body. Also in any of the above arrangements the resilient fingers of the collet may taper towards the head of the collet to increase the radial flexibility of the fingers adjacent the collet head. In the latter arrangement the collet may have three resilient fingers the free ends of which are closely spaced and which taper in width towards the head of the collet. According to a further feature the collet may be aligned with the throughway in the coupling body by means of an intermediate sleeve extending between the throughway and collet. In the latter arrangement the sleeve may extend into the head end of the collet and may be provided with an encircling shoulder which is seated in a counterbore at the end of the collet. 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 sectional view through a tube coupling; Figures 2 to 5 illustrate step by step insertion, engagement and release of a tube in the coupling; Figure 6 illustrates a further construction in accordance with the invention. Figure 7 is a cross sectional view through a tube coupling embodying the further features of the invention; and Figure 8 is an exploded view of the collet and intermediate sleeve of the coupling shown in Figure 7. Figures 1 to 5 of the drawings show a tube coupling which forms the subject of EP-A-93309027.6. The coupling is indicated generally at 10 and comprises a moulded coupling body 11 having a throughway 12 which has an open end 13 to receive a tube to be secured and sealed in the body. The coupling body includes a central portion 14 the internal diameter 15 of which corresponds generally to the outer diameter of the tube to be secured in the coupling body. The central portion 14 terminates in an annular shoulder 16 facing towards the open end of the body with which an end of a tube to be located in the body is engageable. The central portion 14 of the body gives way to an enlarged diameter portion 17 and a step 18 in which a pair of O-ring seals 19 are located with a washer 20 disposed between the seals to seal with the outer surface of the tube to be located in the body. The enlarged diameter portion 17 of the body gives way to a further increase diameter portion 21 having an open end 22 in which a separate moulded annular insert 23 is secured which provides the end opening 13 to the throughway referred to above. A collet 24 is mounted in the open end of the throughway comprising an annular head 25 disposed outside the throughway and a plurality of resilient fingers 26 projecting into the throughway and terminating in heads 27. The collet is moulded in plastics and the heads 27 have metal barbs 28 projecting through the heads to bear against and grip the surface of a tube extending through the collet. The annular insert 23 is formed with an internal tapered cam surface 29 converging towards the open end 13 provided by the insert with which the heads 27 of the collet are engageable when the collet is drawn in a direction outwardly of the throughway to cause the heads to be pressed inwardly into gripping engagement with a tube passing through the collet. Conversely, displacement of the collet inwardly into the throughway releases the heads from the tapered cam surface to release the gripping action of the heads on the tube. To facilitate release of the heads from the tube a ring 30 is mounted in the enlarged part of the coupling body formed with an external tapered cam surface 31 facing toward the heads of the collet. Displacement of the collet into the throughway causes the heads to engage the cam face 31 to expand the heads outwardly away from the surface of the tube to facilitate release of the tube from the coupling body. The coupling body 11 has a cap or enclosure 32 comprising an annular wall 33 secured to the enlarged diameter portion 21 of the coupling body and an end wall 34 spaced from the end of the coupling body 11. The end wall 34 has an aperture 35 through which a tube to be engaged in the coupling body is inserted. The enclosure 32 contains a second collet 36 having an annular head 37 and resilient fingers 38 projecting from the head. The second collet is mounted head-to-head with the first collet so that the resilient fingers 38 of the second collet project away from the coupling body towards the end wall 34. The ends of the resilient fingers 36 of the second collet have inturned heads 39 which are engageable with a bevel 40 formed around the aperture 35 of the inside of the end wall 34 so that when the heads 40 are engaged with the bevel, they are prevented from expanding radially. The side of the head 37 of the second collet facing towards the end wall 34 has an angled cam face 41 facing towards the end wall 34. The encircling wall 33 of the enclosure is formed with apertures at diametrically opposite locations in the enclosure and plunger elements 42 are connected integrally with the wall of the enclosure by flexible webs 43 to project into the enclosure. The plunger elements have angled faces 44 engageable with the cam face 41 on the head 37 so that depressing the plungers radially inwardly deflects the second collet towards the head of the first collet releasing the heads 39 of the second collet from the bevel 40 on the end wall of the enclosure to allow the fingers to expand. Once the clearance between the heads of the collets has been taken up, continuing to depress the plungers 42 causes the first collet to be driven into the throughway to release the fingers of the first collet from a tube passing through the collet as described earlier. Thus the plunger 42 provides one release means for both the first and second collets. Referring now to Figures 2 to 5 of the drawings, there is shown the sequence of operations of the coupling when a tube to be gripped in the coupling is to be inserted. The tube is indicated at 50 and it should be noted that the tube has an integral rounded encircling abutment 51 formed part-way from the end of the tube specifically for engageable by the second collet of the coupling. In Figure 2, the end of the tube is shown inserted through the aperture 35 of the enclosure on the coupling body and through the tube collet. As can be seen, the heads 27 of the collet within the coupling body have separated to accommodate the tube and are engaged with the tapered cam surface 29 so that the end of the tube is already gripped at this stage and any attempt to draw the tube would be resisted by the colllet. Figure 3 shows the tube further inserted into the coupling body so that the end of the tube is located in the first of the O-ring seals 19. Figure 4 shows the tube fully inserted into the coupling body with the end of the tube in the central portion 14 of the coupling body. The tube is in fact inserted until the end of the tube engages the shoulder 16. When the annular abutment 51 on the tube engages the heads 40 of the second collet, the second collet will be displaced from the position shown in Figure 3 until the collets come head-to-head as shown in Figure 4 and the collets are moved inwardly together until the heads 39 of the second collet are clear of the bevel 40 and the heads can then separate to allow the abutment 51 on the tube to pass through. Once the abutment has passed through, the heads close around the abutment 51 as shown in Figure 4. A small movement of the tube outwardly of the coupling body as indicated by the gap between the shoulder 16 and end of the tube illustrated in Figure 4 draws the first collet outwardly of the coupling body sufficiently to cause the heads 27 of the collet to be deflected inwardly by the tapered cam surface 29 into positive gripping engagement with the tube and at the same time the heads 39 of the second collet are engaged in the bevel face 40 on the end wall of the enclosure to lock the heads firmly inwardly against the abutment 51. The tube is therefore doubly locked to the coupling body. To release the tube from the coupling body, the plungers 42 on the enclosure are depressed inwardly as illustrated in Figure 5 to draw the first collet towards the coupling body thereby releasing the heads 39 from the bevel face 40 and at the same time to depress the first collet inwardly into the coupling body to engage the heads 27 of the collet with the annular cam face 31 to release the heads from the tube which can then be extracted from the coupling body. The arrangement thus provides a coupling for a tube which is effected simply by pushing the tube into the coupling body which grips, clips and seals the tube in place so that even if the main gripping collet in the coupling body should fail for any reason, the tube will still be held by the second collet in sealed engagement with the coupling body. At the same time, the tube can readily be extracted from the coupling body by simply depressing the plungers on the enclosure which enable both collets to be released from the tube. Figure 6 shows a modified arrangement in accordance with the present invention in which the tube is not gripped in the coupling body but is simply held by the external collet 36 in the enclosure 32. The tube coupling shown in Figures 7 and 8 is a modification of the arrangement shown in Figure 6 and like parts have been allocated the same reference numerals. The principal differences in the further arrangement relate to the collet 36. The collet is formed with three resilient fingers 38 only of arcuate cross sectional form. At their free ends, the resilient fingers 38 are closely spaced from one another but they are heavily tapered towards the annular head 37 of the collet to increase the resilience of the fingers in the radial direction. An intermediate alignment sleeve 53 has one end engaging in the open end 17 of the throughway and abutting the outermost of the O-ring seals 19 and the other end engaging in the opening in the head of the collet. The sleeve has an encircling shoulder 54 which engages in a counter bore 52 around the opening into the collet. The sleeve 50 aligns the collet 36 with the throughway in the coupling body to facilitate insertion of the tube through the collet into the coupling body. To that end, the ends of the bore through the sleeve are chamferred as indicated at 55 to facilitate entry of a tube end into the sleeve.

Claims: A tube coupling comprising a coupling body having a throughway open at one end to receive a tube, an enclosure on the body extending over said end with an end wall of the enclosure spaced from the end of the coupling body and having an aperture to receive the tube, a collet mounted in the enclosure for limited axial movement between the end wall and the coupling body, the collet having a head adjacent the coupling body and resilient fingers projecting towards the end wall of the enclosure to snap over an annular abutment on the tube inserted through the enclosure into the coupling body and release means on the enclosure to release the fingers from the abutment to allow extraction of the tube; characterised in that the end wall of the enclosure has an annular inwardly facing abutment encircling the aperture with which the ends of the resilient fingers are engageable to restrain the fingers against outward movement to release the tube abutment and said release means on the enclosure acts to displace the collet towards the coupling body to disengage the resilient fingers from within said annular abutment and thereby allow expansion of the fingers to release the tube. A tube coupling as claimed in claim 1, characterised in that the annular inwardly facing abutment on the end wall comprises a bevelled face around the inside of the aperture in the end wall and the outer sides of the finger ends are chamfered to engage the bevelled face. A tube coupling as claimed in claim 1 or claim 2, characterised in that the head of the collet has an angled annular cam surface on the side adjacent the end wall of the enclosure and the enclosure wall has resiliently mounted presser members at diametrically opposed locations around the wall extending radially into the enclosure and formed with inclined faces which engage the cam face or the collet to displace the collet towards the coupling body with depressing of the presser members to release a tube from the collet. A tube coupling as claimed in any one of the preceding claims, characterised in that one or more O-ring seals are mounted in the throughway in the coupling body to seal the external surface of the tube inserted in the coupling body. A tube coupling as claimed in any of claims 1 to 4, characterised in that the resilient fingers of the collet taper towards the head of the collet to increase the radial flexibility of the fingers adjacent the collet head. A tube coupling as claimed in claim 5, characterised in that the collet has three resilient fingers the free ends of which are closely spaced and which taper in width towards the head of the collet. A tube coupling as claimed in any one claims 1 to 6, characterised in that the collet is aligned with the throughway in the coupling body by means of an intermediate sleeve extending between the throughway and collet. A tube coupling as claimed in claim 7, characterised in that the sleeve extends into the head end of the collet and is provided with an encircling shoulder which is seated in a counterbore at the end of the collet.

Inventors: GUEST JOHN DEREK, GUEST, JOHN DEREK
Applicants: GUEST JOHN D, GUEST, JOHN DEREK
Application year: 1993
Main classification: F16L37
IPC codes: F16L37