GB2125501A

GB2125501A - Conduit end fitting

Info

Publication number: GB2125501A
Application number: GB8320075A
Authority: GB
Inventors: Paul Lewis Williamson; Brian Albert Godley
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1982-08-11
Filing date: 1983-07-26
Publication date: 1984-03-07
Also published as: GB2125501B; GB8320075D0

Abstract

An end fitting for a corrugated conduit has a tubular body member (10) in whose bore the conduit is received and which in part (19) is slotted axially to define flexible, radially- displaceable fingers having projections (22) for engaging, and thus retaining, the conduit. The fingers are maintained in engagement with the conduit by a co-operating sleeve member (20) mounted on the body member by means of a bayonet fitting arrangement enabling axial movement of the sleeve member over the body member to a position in which the projections (22) are held in the conduit corrugations and rotational movement for locking the sleeve member on the body member. <IMAGE>

Description

SPECIFICATION Conduit end fittings This invention relates to end fittings for conduits, and, in particular, to end fittings for use with flexible corrugated conduits.

According to the present invention there is provided an end fitting for a corrugated conduit comprising a generally tubular body member having an axial bore in which an end of the conduit is to be received, a portion of the tubular body member having means thereon for engaging with the conduit corrugations to retain the conduit in said bore and being radially displaceable to facilitate insertion of the conduit end into the bore from one end thereof, and a sleeve member which extends around the outer surface of the tubular body member, wherein the sleeve member is retained on the tubular body member by means of a bayonet fitting arrangement, said bayonet fitting arrangement permitting axial movement of the sleeve member over the body member to a position in which the sleeve member is arranged to co-operate with the body member to inhibit radial displacement of said portion of the body member and thereby maintain said engagement means in engagement with the conduit corrugations, and rotational movement of the sleeve member with respect to the body member to retain the sleeve member on the body member in said position.

The bayonet fitting arrangement may comprise a plurality of pairs of co-operating projections and slots on the body and sleeve members, which preferably are spaced at regular intervals around their peripheries, for example, in the case of two such pairs, at diametrically opposed positions.

Each of the slots may include an axiallyextending lead-in portion and a circumferentially-extending portion terminating in an enlargement. In this case, the fitting may also include resilient means which is arranged to act between the sleeve and body members so as to urge the sleeve member axially with respect to the body member and maintain the projections of the bayonet fitting arrangement in the enlargements of their respective slots, thereby to retain the sleeve member on the body member. The resilient means may comprise a compressible rubber ring or metal annulus disposed between the sleeve member, and preferably the end face thereof, and a shoulder on the body member.

Alternatively, each of the slots may comprise an axially-extending lead-in portion and a circumferentially-extending portion which is formed with a constriction of less width than its respective co-operating projections through which that projection passes during the rotational movement thereby to retain the sleeve member on the body member.

The slots may be formed in the sleeve member such that the lead-in portions thereof open at the end of the sleeve member or, alternatively, may be formed with their lead-in portions closed at the ends thereof remote from the circumferentially-extending portions so that the sleeve member is captively mounted on the body member for limited axial displacement relative thereto by engagement of the projections with the slot ends.

The slots of the bayonet fitting arrangement may comprise recesses in the internal surface of the sleeve member or may extend completely through the wall of the sleeve member.

The radially displaceable portion of the tubular body member, which may conveniently be formed of flexible resilient material, preferably comprises a region of the tubular body member adjacent to, and including, said one end of that member. The tubular body member preferably is provided with a plurality of slots which extend axially thereof from said one end along a length defining the radially displaceable portion to permit radial flexing of the portion.

The sleeve and tubular body members may include respective tapered surfaces which are adapted to co-operate with one another when the sleeve member is moved axially of the body member to said position to inhibit radial movement of the portion of the tubular body member.

The means on the tubular body member for engaging with the conduit corrugations may comprise at least one projection means which extends inwardly of the bore of the tubular body member.

An end fitting for a corrugated conduit in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawing in which Figure 1 shows the end fitting, partly in cross-section, mounted on the end of a flexible corrugated conduit; and Figure 2 is a cross-sectional view through a component of the fitting showing a part of the bayonet fitting arrangement.

The conduit shown in Fig. 1 of the drawing is of plastics material and is annularly corrugated to impart flexibility and a certain amount of axial compressibility although it is sufficiently rigid in a radial sense to resist crushing. As will be described hereinafter, the fitting may alternatively be used on helicallycorrugated conduit.

With reference to Fig. 1, the end fitting includes a one-piece, generally tubular body member 10 of resilient plastics material, for example, nylon, having a bore 11 which extends completely therethrough. The tubular body member 10 is formed with an internal annular shoulder 12 intermediate its ends defining one end of a cylindrical recess 14 of the bore 11 which opens at one end 15 of the body 10 and into which the end of the corrugated conduit, referenced 16, is received.

The annular shoulder 12 is of substantially the same size as the overall thickness of the conduit wall such that when the conduit end is inserted into the cylindrical recess 14, with its end abutting the shoulder 12 as shown in the drawing, the bore of the conduit is aligned and continuous with the remainder of the bore 11.

The tubular body member 10 is formed with an integral cylindrical projection 13 at its end remote from the end 15. The projection 13 is externally screw-threaded and adapted to receive a co-operating lock-nut 17 to facilitate mounting of the end fitting in an aperture in a support member (not shown) with the wall of the support member surrounding the aperture being clamped by the lock-nut 17 against a radially-extending surface 18 provided by a flange 25 on the tubular body member 10.

An end portion of the tubular body member 10, generally designated 19, is provided with a plurality, for example, six, of axially-extending slots (not visible in the drawing) which open at the end 15 thereof and extend part way along the length of the part of the member 10 which surrounds the cylindrical recess 14 to form a split-collet. The slots, which are spaced at regular intervals around the portion 19, allow the part of the body member adjacent the end 15 to be flexed radially inwards and outwards for purposes which will become apparent.

The external surface of the split collet portion 19 of the body member 10 is tapered inwardly at 21 towards the end 15. The internal surface of the body member 10 adjacent the end 15 is provided with integrallyformed projection means 22 for engaging with the conduit corrugations and retaining the conduit in the bore 11 of the fitting. In the case where the conduit is annularly corrugated, as shown in the drawing, these means 22 comprise two rows of teeth which project into the cylindrical recess 14 and are arranged to enter respective troughs in adjacent corrugations of the conduit to prevent axial displacement of the conduit. The rows of teeth, which are formed on the integral fingers of the portion 19 defined by the axially-extending slots and can be regarded as beads made discontinuous by those slots, extend in a circular fashion around the internal surface of the body member 10.

In the case where the fitting is to be used with a conduit having helical corrugations, the conduit engaging and retaining means may be in the form of a discontinuous bead extending helically around the surface of a section of the cylindrical recess 14 adjacent the end 15.

Although two rows of teeth have been shown in the drawing, the conduit engaging and retaining means may comprise one or more than two rows of teeth.

A generally cylindrical sleeve member 20, also of resilient plastics material, surrounds the portion of the body member including the split-collet portion 19, intermediate the annular shoulder 12 and the end 15. The sleeve member 20 is slidably mounted on the external surface of that portion of the body member for axial displacement relative to the body member and has an internal tapered surface 23 which is arranged to co-operate with the external tapered surface 21 of the portion 19 of the body member 10. In its fully assembled position, as shown in the drawing, the cooperating tapered surfaces 23 and 21 of the sleeve member 20 and portion 19 respectively act to prevent radial expansion, that is, displacement radially outwards, of the split collet portion 19.In this way, the corrugation engaging and retaining means 22 on the tubular body is maintained in engagement with the conduit corrugations and axial displacement of the conduit with respect to the fitting is prevented.

The sleeve member 20 is retained in the fully assembled position shown in Fig. 1 by means of a bayonet fitting arrangement acting between the body member 10 and the sleeve member 20. This arrangement comprises a pair of diametrically-opposed cylindrical projections 24, only one of which is visible in Fig. 1, formed on an outer cylindrical peripheral surface of the body member 10 between the portion 19 and the flange 25, and a cooperating pair of diametrically opposed slots 26 in the internal peripheral surface of the sleeve member 20. With reference to Fig. 2, the slots 26, only one of which is shown, are generally L-shape having a lead-in, axiallyextending portion 30 and a transverse, circumferentially-extending portion 31.The portion 31 terminates in an enlargement 32 which, when the sleeve member is fully assembled on the body member 10, is to receive the projection 24 on the body member.

The slots 26, as shown in Figs. 1 and 2, comprise recesses in the internal surface of the member 20. They may alternatively extend completely through the wall of the member 20 such that the projections 24 are visible from the outside of the fitting.

A resilient rubber O-ring 34 is disposed around the periphery of the body member 10 between the end face, 27, of the sleeve member 10 and the flange 25, which in the position shown in Fig. 1, is in compression.

The sleeve member 20 is formed with an annular lip 28 at its end which, in its fully assembled position on the body member 10, overlies the end 15 of the body member 10.

To assemble the end fitting on the end of a corrugated conduit the sleeve member 20 is first slid along the outer surface of the body member 10 towards the end 15 to a position in which the respective tapered surfaces 23 and 21 are out of engagement with one another and limited radial movement of the split collet portion 19 of the body member 10 is allowed. The conduit end is offered to the bore 11 and pushed inwardly. In so doing, the end of the conduit forces the retaining means 22 on the fingers of the portion 19 radially outwards so that the conduit can enter the bore 11. The conduit end is thereafter fed into the cylindrical recess 12, with the retaining means 22 sliding over its outer surface, until it abuts the annular shoulder 12 at which point the retaining means 22 project into the conduit corrugations as shown in Fig.

1. The sleeve member 20, which is externally knurled to facilitate gripping, is then slid axially over the surface of the body member 10 towards the flange 25 with the projections 24 on the body member 10 passing along the lead-in portion 30 of their respective slots 26 on the sleeve member 20. As the projections 24 approach the bottom of the portions 30 of the slots 26, the end face 27 of the sleeve member 20 abuts the O-ring 34. Further displacement of the sleeve member 20 with respect to the body member 10 results in the O-ring being compressed against the flange 25.The sleeve member 20 is thereafter twisted so that the projections 24 of the bayonet fitting arrangement pass along the transverse portions 31 of the slots 26 until they reach the end of the slots at which time the sleeve member 20 is released and, under the action of the compressed O-ring 34 and in a snap-fit manner, is caused to move back very slightly over body member 10 such that the projections 24 locate in the enlarged terminations 32 of their respective slots 26.

In this position, the sleeve member 20 is securely retained on the body member 10.

During this sliding and locking operation the tapered surface 23 co-operates with the tapered surface 21 on the portion 19 to urge the retaining means 22 inwardly. Engagement between the surfaces 21 and 23 thereafter prevents radial expansion of the split collet portion 19 and maintains the retaining means 22 in the conduit corrugations such that axial displacement of the conduit is inhibited.

To unlock the sleeve member 20 from this position it is necessary to force it towards the flange 25 against the O-ring 34 so that the bayonet fitting arrangement can be released.

As deliberate force is required for this action, it is unlikely that the sleeve and body members will be unlocked inadvertently during use.

Unlocking of the sleeve member 20 in this manner allows the member 20 to be slid axially of the body member 10 away from the flange to disengage the co-operating tapered surfaces 21 and 23 and permit withdrawal of the conduit end from the fitting.

The split collet portion 19 of the body member 10 may be formed such that, in its relaxed condition, the conduit retaining means 22 are positioned out of the path of the conduit end in order that the conduit end may be slid into the cylindrical recess 12 without resistance. The respective co-operating tapered surfaces 21 and 23 may be arranged in these circumstances to urge the conduit retaining means 22 radially inwardly to project into the conduit corrugations upon the sleeve member 20 being fully assembled on the body member 10. To remove the conduit from the end fitting, the sleeve member 20 is slid back to allow the split-collet portion 19, being resiliently flexible, to spring outwards, thereby disengaging the retaining means 22 from the conduit corrugations.

Instead of opening at the end 27 of the sleeve member 20 as shown in Figs. 1 and 2, the portion 31 of the slots 26 may alternatively terminate before the end 27 such that the slots 26 are closed at both ends. In such an arrangement the sleeve member 20, once mounted on the body member 10 by physically deforming its wall to enable the projections 24 to pass under its end and locate in the slots 26, is effectively captively mounted on the body member 10 whilst sufficient axial sliding of the member 20 is still permitted to allow proper operation of the collet portion 19 in the manner described.More particularly, the sleeve member 20 is captively mounted for sliding movement between a first, fully assembled position, as shown in Fig. 1, and a second position in which the respective tapered surfaces 21 and 23 on the body and sleeve members 10 and 20 are displaced with respect to one another to allow limited radial expansion of the split collet portion 19 of the body member 10.

It may in some circumstances be desirable to prevent the ingress of moisture, dust, or the like into the bore of the conduit, and to this end sealing means may be disposed between the conduit and the inner bore of the body member 10. This sealing means may take the form of a rubber sealing ring which is either located around the conduit adjacent its end and sealingly engaging in compression with the surfaces of the conduit and the recess 14 of the body member 10, or disposed between the end of the conduit and the shoulder 12.

The rubber O-ring 34 may be replaced by any suitable resilient means, for example, a metal annular of V-shape cross-section.

In an alternative arrangement, the O-ring 34 may be dispensed with and the transverse portion 31 of the slots 26 formed with a constriction immediately adjacent the enlargement 32 of less width than the diameter of the projections 24 whereby, upon twisting the sleeve member 20 during the locking operation, the projections 24 are caused to expand the constrictions by deformation in order to pass therethrough into the enlargements 32 in a snap-fit manner, the constrictions thereafter returning to their original configuration. Force will also be necessary to move the projections 24 back through the constrictions in order to unlock the bayonet fitting, thus preventing the inadvertent release of the sleeve member from the body member.

The sleeve and body members 20 and 10 may be provided with more than two cooperating pairs of slots 26 and projections 24 respectively, for example three pairs spaced at 1 20' intervals around their peripheries.

It is envisaged that the tubular body member 10 may be formed with a V-shaped groove (not shown) extending around its periphery adjacent the inner end of the split collet portion 19, to impart increased flexibility to the fingers of the portion 19.

It is also envisaged that the body member may be formed from a suitably flexible and resilient metallic material such as aluminium instead of plastics.

It will be apparent from the above that the end fitting is particularly simple and convenient to use. Following insertion of a conduit end into its bore 11, all that is necessary for the end fitting to be mounted securely on the conduit end is that the sleeve member 20 be slid axially forward over the body member 10 and twisted to lock it on the body member 10. Similarly, it is only necessary to twist the sleeve member to unlock and release the bayonet fitting and slide the sleeve member back over the body member 10 away from its mounted position to permit removal of the end fitting from the conduit.

Claims

1. An end fitting for a corrugated conduit comprising a generally tubular body member having an axial bore in which an end of the conduit is to be received, a portion of the tubular body member having means thereon for engaging with the conduit corrugations to retain the conduit in said bore and being radially displaceable to facilitate insertion of the conduit end into the bore from one end thereof, and a sleeve member which extends around the outer surface of the tubular body member, wherein the sleeve member is retained on the tubular body member by means of a bayonet fitting arrangement, said bayonet fitting arrangement permitting axial movement of the sleeve member over the body member to a position in which the sleeve member is arranged to co-operate with the body member to inhibit radial displacement of said portion of the body member and thereby maintain said engagement means in engagement with the conduit corrugations, and rotational movement of the sleeve member with respect to the body member to retain the sleeve member on the body member in said position.

2. An end fitting according to Claim 1, wherein the bayonet fitting arrangement comprises a plurality of pairs of co-operating projections and slots on the body and sleeve members.

3. An end fitting according to Claim 2, wherein the pairs of co-operating projections and slots are spaced at regular intervals around the peripheries of the body and sleeve members.

4. An end fitting according to Claim 2, or Claim 3, wherein each said slot of the bayonet fitting arrangement includes an axially-extending lead-in portion and a circumferentiallyextending portion terminating in an enlargement.

5. An end fitting according to Claim 4, wherein the end fitting includes resilient means which is arranged to act between the sleeve and body members so as to urge the sleeve member axially with respect to the body member and maintain the projections of the bayonet fitting arrangement in the enlargements of their respective slots, thereby to retain the sleeve member on the body member.

6. An end fitting according to Claim 5, wherein the resilient means is disposed between the sleeve member and a shoulder on the body member.

7. An end fitting according to Claim 6, wherein the resilient means is disposed between an end face of the sleeve member and the shoulder on the body member.

8. An end fitting according to Claim 6 or Claim 7, wherein the resilient means comprises a compressible rubber ring.

9. An end fitting according to Claim 6 or Claim 7, wherein the resilient means comprises a compressible metal annulus.

10. An end fitting according to any one of Claims 2 to 4, wherein each said slot of the bayonet fitting arrangement includes an axial!y-extending lead-in portion and a circumferentially-extending portion which is formed with constriction of less width than its respective co-operating projection through which that respective projection passes during said rotational movement thereby to retain the sleeve member on the body member.

11. An end fitting according to any one of Claims 4 to 10, wherein the said slots are formed in the sleeve member such that the lead-in portions thereof open at an end of the sleeve member.

12. An end fitting according to any one of Claims 4 to 10, wherein the said slots are formed in the sleeve member with their leadin portions closed at the ends thereof remote from the circumferentially-extending portions so that the sleeve member is captively mounted on the body member for limited axial displacement relative thereto by engage ment of the projections with the slot ends.

13. An end fitting according to any one of Claims 2 to 12, wherein the said slots of the bayonet fitting arrangement comprise recesses in the internal surface of the sleeve member.

14. An end fitting according to any one of Claims 2 to 12, wherein the said slots of the bayonet fitting arrangement extend completely through the wall of the sleeve member.

15. An end fitting according to any one of the preceding claims, wherein the said radially-displaceable portion of the tubular body member comprises a region of the body member adjacent to, and including, said one end of the body member.

16. An end fitting according to Claim 15, wherein the tubular body member is provided with a plurality of slots which extend axially of the body member from said one end along a length thereof defining the radially displaceable portion to permit radial flexing of the said portion.

17. An end fitting according to any one of the preceding claims, wherein the sleeve and tubular body members include respective tapered surfaces which are adapted to co-operate with one another when the sleeve member is moved axially of the tubular body member to said position to inhibit radial movement of the said portion of the body member.

18. An end fitting according to any one of the preceding claims, wherein the sleeve member includes an annular lip at its one end which overlies said one end of the tubular body member when in said position.

19. An end fitting according to any one of the preceding claims, wherein the means of the tubular body member for engaging with the conduit corrugations comprises at least one projection means which extends inwardly of the bore of the tubular body member.

20. An end fitting according to Claim 19, wherein the or each projection means extends around the internal surface of the tubular body member.

21. An end fitting according to any one of the preceding claims, wherein the tubular body member defines a shoulder in its bore against which the end of the conduit is to abut.

22. An end fitting according to any one of the preceding claims, wherein the tubular body member further includes means at its end remote from said one end for facilitating mounting of the end fitting on a member.

23. An end fitting according to Claim 22, wherein said mounting means comprises a screw-threaded cylindrical projection.

24. An end fitting according to any one of the preceding claims, wherein the tubular body member is unitary and formed of flexible resilient material.

25. An end fitting according to any one of the preceding claims, wherein the sleeve member is formed of resilient material.

26. An end fitting substantially as hereinbefore described with reference to the accompanying drawing.