CN114630982B

CN114630982B - Pipe coupling

Info

Publication number: CN114630982B
Application number: CN201980100227.4A
Authority: CN
Inventors: G·安塞尔
Original assignee: Integrity Global Co Uk Ltd
Current assignee: Integrity Global Co Uk Ltd
Priority date: 2019-07-10
Filing date: 2019-12-18
Publication date: 2025-03-25
Anticipated expiration: 2039-12-18
Also published as: GB2585668B; KR20220088406A; CN114630982A; GB201909906D0; GB2585668A; EP3997374A1; WO2021005319A1; AU2019456730A1; KR102722373B1

Abstract

A tube coupling includes a coupling body (1) having an open-ended through passage for receiving a tube (T). A collet (41) is located in the open end of the through passage having a ring (52) and a plurality of flexible arms (53) extending generally axially from the ring into the through passage. The through passage has a tapered surface (43) converging toward the open end, and the collet arms have heads at their distal ends for engaging both the tapered surface and a tube extending through the collet into the through passage to be compressed against the tube by the tapered surface with outward movement of the collet relative to the through passage to secure the tube in the through passage. A collet lock is formed on the collet (41) having a locked rotational position in which the lock retains the collet in the outward tube securing position and an unlocked rotational position in which the collet is movable axially relative to the through passage to release and engage the tube through the collet. One of the body (1) and the collet (41) is provided with a cam surface (46) and the other is provided with a cam follower (56), the cam surface being arranged to provide a locked position and an unlocked position. The invention also extends to the collet (41).

Description

Pipe coupling

Technical Field

The present invention relates to pipe couplings. The pipe coupler has particular application as a fiber optic cable connector for use above or below ground. However, the concept is more broadly applicable to other types of connectors.

Background

Such fiber optic cable connectors are used in the laying of fiber optic cables. Cables are used, for example, for providing fiber optic cable connections from a junction box to a building such as an office or home in order to provide a connection for internet data.

Fiber optic cables are provided in bundles of individual fibers, which may be up to several kilometers in length. The fiber bundles are packed through tubes (often referred to as microcatheters), which are typically 100 meters long, but can also be up to 500 meters long. Thus, a plurality of tubes need to be connected together in order to support the full length fiber bundle.

Because of their manner of use, there are many requirements for fiber optic cable connectors.

The outer diameter must be as small as possible in order to minimize the volume, as the connectors are often clustered together in large numbers.

The connector also needs to be highly impact resistant. Cables are typically buried underground, and they need to be dug out for maintenance. This is typically done by a worker with a spade, and the first time the worker knows whether a cable is present is when the cable is impacted by the spade. Thus, the connector needs to be robust enough to resist such impacts. In practice, they need to pass the "15J impact test".

The connector has a connection at each end that attaches to and holds the tube within the connector. This is accomplished using a collet or snap ring. Which grips onto the outer wall of the tube and any movement which tends to pull the tube out of the connector will cause the collet to tighten its grip on the tube in a well known manner. To release the tube, the collet can be manually displaced toward the interior of the connector. This prevents the collet from gripping the tube, allowing the tube to be withdrawn from the connector.

A requirement of fiber optic cable connectors is that the collet must be locked in place to prevent accidental release of the tube.

This is conventionally accomplished using a locking clip that is clamped between the end of the body of the connector and the collet ring, thereby preventing axial movement between the body and the collet.

These clips have a number of disadvantages. They are fragile and exposed components and often break. Because they are exposed, they can become clogged with dirt, which can make them potentially difficult to remove. During installation they may accidentally come out of place and then be easily lost, so that the connector will not be usable unless a spare clip is carried. The clip will then also shift during installation. The installer will not necessarily know that this has occurred, as this may only occur when the connector is covered with dirt.

Disclosure of Invention

The present invention aims to address at least some of these problems.

An alternative method of locking the collet within the connector is disclosed in our own earlier EP 2131089. The invention discloses a concept of a locking ring rotatably mounted on a body. The body is provided with a cam surface which cooperates with a cam follower on the locking ring. Rotation between the body and the locking ring changes the axial spacing between the two components. The end of the locking ring abuts the collet ring. In the locked position, the axial spacing between the locking ring and the body is at its maximum. The engagement between the locking ring and the collet ring prevents axial movement of the collet such that the collet cannot be displaced inwardly to a position where the tube can be released.

Such connectors are not designed for use with fiber optic cable connectors and, in fact, are not suitable for such purposes. The locking ring is fitted on the outer surface of the body. This increases the volume of the connector, which is contrary to the requirement that the outer diameter of the fiber optic cable connector be as small as possible. The locking ring is exposed to dirt such that in use dirt particles may enter the locking ring and catch the locking ring in a locked position. Furthermore, the locking ring may also be damaged during installation and maintenance operations, which may result in the locking ring failing or jamming in the locked position.

According to the present invention, there is provided a pipe coupling according to claim 1.

With the present invention, locking of the collet is now achieved solely by the interaction between the body and the collet. This eliminates the prior art locking clip. It also eliminates the locking ring of EP 2131089.

While the motivation for the present invention is to provide an improved fiber optic cable connector, it may also be used in any environment for which EP2131089 is designed, because it provides improvements over EP2131089 in terms of low profile nature of the connector and a reduction in the number of parts (because it does not require a locking ring). In particular, it is suitable for use in a wide range of plumbing applications that provide fluid communication.

Because the locking is accomplished by the interaction between the body and the collet, the locking mechanism may be physically internal to the body. This may provide a low profile design and also protect the locking mechanism from impact damage and dirt ingress.

The cam surface may be provided on the body or on the collet but is preferably provided on the body. In this case, the cam surface may be molded directly into the body as part of the body molding process. However, this requires relatively complex tools. Thus, preferably, the body comprises a cap retained by the main body portion, the cap being provided with a cam surface. The cap may fit over or within the body portion. It may be held by teeth that grip the body portion, ultrasonic welding, snap fit, screw fit, or in any other manner.

For prior art fiber optic cable connectors, it was necessary for the collet to protrude beyond the body to allow for an annular gap in which the locking clip is inserted. This is not necessary in the present invention. The collet ring may still protrude axially beyond the body, but preferably, in the locked position, the collet ring does not protrude axially beyond the body. It may be flush with the body but is more preferably recessed into the body. This protects the collet ring from impact damage and from fouling.

The collet ring may be a conventional annular collet ring that a user grasps to rotate the collet between the locked and unlocked positions. However, an unlocking feature is preferably provided in the collet ring. This may take the form of one or more openings in the axial end face of the collet ring. However, these require the use of tools and can become clogged with dirt.

Thus, preferably, at least one lug projects from the collet ring axially away from the open end of the through passage. This provides a tip where the collet can be easily grasped for rotation.

The or each lug may not protrude axially beyond the body. However, the or each lug preferably protrudes beyond the end of the body in the axial direction. This makes it easier to grip them. In addition, these lugs may provide a burr removal function. For example, they may be shaped with sharp edges so that lugs may be inserted into the cut end of the tube and scraped around the inner edge to remove any burrs left by the flocking (tufting) process. These may create a risk of hooking during use, so it will be very useful in practice for the operator to have a tool at hand to remove these burrs.

A single lug may be present. Preferably, however, there are two or more spaced apart lugs, as this provides improved grip and also allows the grip function to be maintained in the event that one of the lugs is damaged. As stated above, it is preferred that the collet ring does not protrude axially beyond the body. The or each lug preferably protrudes beyond the axial end of the body so that it can be easily gripped.

At least one of the body and/or the collet is preferably provided with a visual indication of the locked and/or unlocked position.

In the vicinity of the locking position, the cam surface is preferably provided with a bump over which the cam follower will pass. This serves to ensure that the cam follower remains in the locked position and also provides a tactile indication to the user that the locked position has been reached.

When the coupling is used as a pipe connector, the connector body is preferably made of a non-opaque plastic.

Further, the body preferably includes an outer sleeve and an inner sleeve configured to receive the distal ends of the respective tubes, an outer wall of the inner sleeve being generally spaced apart from an inner wall of the outer sleeve to define a gap, the inner sleeve being supported on the outer sleeve by a separate web of material that supports the inner sleeve and maintains the gap between the inner sleeve and the outer sleeve. This provides an impact protection feature as the gap allows any impact to the outer sleeve to deform the outer sleeve which will deform into the gap before the impact deforms the inner sleeve.

Preferably, the connector is free of external ribs and has a continuous outer surface of constant radius. This eliminates the ribs provided on prior art connectors, but also provides areas of stress concentration and dirt accumulation.

Preferably, an annular flange extends radially into the through passage, each end face of the annular flange providing a stop surface for a respective pipe end, wherein the annular flange is undercut such that its end face is inclined such that the axial dimension of the flange increases towards the axis. Such undercut ensures that the inner edge of the tube can be closer to the annular flange and preferably abut the annular flange. This eliminates or minimizes the possibility of the fibers (which then pass through the connector once the tube is in place) getting caught on the tube or annular flange.

Preferably, a plurality of annular splines are provided adjacent the annular flange to deflect the outer wall of the tube as the tube approaches the flange. In practice, the tubes are supplied on coils and have often been flattened to an oval cross section. In the region of the widest part of the oval shape, the inner diameter is larger than it was, and this exposes a portion of the annular flange in this region. This provides the fiber with a risk of hooking, which is significantly reduced by the use of splines.

Drawings

Examples of connectors according to the invention will now be described with reference to the accompanying drawings, in which:

FIGS. 1A-1C are cut-away perspective views of a connector showing the gradual insertion of a tube;

FIG. 2A is a cross-sectional view of the connector body in a plane perpendicular to the main passageway of the connector body through line A-A in FIG. 2B;

FIG. 2B is a cross-sectional view of the connector body in a plane passing through the main axis of the body, through line B-B in FIG. 2A;

Fig. 2C is a view showing a second example of the connector in the same plane as fig. 2A;

Fig. 2D is a view showing a second example in the same plane as fig. 2B;

FIG. 3 is a cross-section of the connector in the plane of FIG. 2B, with the tube connected and the fiber bundle passing through;

FIG. 3A shows the center portion of FIG. 3 in more detail;

FIG. 3B shows a view similar to FIG. 3A with a different tubing configuration and no fibers passing through;

Fig. 4A and 4B correspond to fig. 3A and 3B, showing a prior art arrangement;

fig. 5 is an exploded perspective view of the connector as seen from one end of the connector body;

FIG. 6A is an equivalent of FIG. 5 in a non-exploded form, showing the cartridge and collet in a first angled configuration;

FIG. 6B is a cross-section through the plane of the locking tab of FIG. 6A;

FIGS. 7A and 7B are views corresponding to FIGS. 6A and 6B, respectively, showing the cartridge and collet in a second angled configuration, and

Fig. 8A and 8B correspond to fig. 7A and 7B, but show the tube in place.

Detailed Description

The connector comprises a connector body 1, which connector body 1 has a substantially hollow cylindrical configuration centred on a main axis X. A connector 2 (described in more detail below) is provided at each end to receive and grip a tube T sealed by an O-ring 3 at each end.

The body 1 is moulded from a non-opaque plastic. The plastic must be sufficiently light transmissive so that an external visual inspection of the connector allows the operator to determine whether a fiber or fiber bundle F is present at the center of the connector. Ideally, the body should be as nearly transparent as possible. However, practical considerations mean that the body will not be completely transparent. Instead, the body may be translucent to the point where the fibers are sufficiently visible. Suitable materials are polycarbonate, polystyrene, polyester, acrylic and nylon. The body 1 is formed during the moulding process and may optionally be polished to improve the light transmission of the body. As can be seen from the various figures, the outer profile of the body is a smooth configuration, which has no external ribs, thereby eliminating any stress concentrations and dirt accumulation apertures.

The body 1 is formed by an outer sleeve 5 and an inner sleeve 6, said outer sleeve 5 and inner sleeve 6 being connected by at least one web 7 as described below.

The outer sleeve 5 has an axial bore 8, which axial bore 8 is open at the distal end 8 and has a first step 10 and a second step 11 which receive the connector 2, as described below.

The inner sleeve 6 is held by the web 7 so as to form a gap 12 having a substantially uniform thickness, as best seen in fig. 2A.

As will be appreciated from fig. 2A and 2B, the web 7 extends across only a small portion of the inner sleeve 6 such that the gap 12 exists for a majority of the length and circumference of the inner sleeve 6.

Any impact on the outer sleeve 5 that occurs during installation of the pipeline or when the pipeline is dug out for maintenance may result in deformation of the outer sleeve 5.

By providing the gap 12, the effect of any external impact on the outer sleeve 5 is to a significant extent isolated from the inner sleeve 6 and thus any variations in the diameter of the inner bore 14 of the inner sleeve 6 are largely prevented from being caused. Preliminary experiments have shown that this design is effective against external impacts. Furthermore, this can be achieved in a manner that does not require the addition of ribs and does not require the increase in the outer diameter of the connector.

The use of a very small size of the web 7 means that the chance of the impact being transmitted directly from the outer sleeve 5 to the inner sleeve 6 via the web 7 is greatly reduced. Even if this happens (i.e., an impact is applied in the vertical downward direction in fig. 2A at the center point connector in fig. 2B), the inner sleeve 6 may deflect an amount equivalent to the width of the gap 12 before any stress is generated on the inner sleeve that would adversely affect the inner bore 14 of the inner sleeve 6.

To mould the body 1 all the plastic required for the inner sleeve 6 needs to pass through the webs 7, 15. This represents a fairly significant amount of plastic flowing into a relatively complex and narrow flow path. To alleviate this, we envisage providing one or more added webs 13, schematically depicted in fig. 2A, which are angularly offset with respect to the web 7 and may also be axially offset to ensure that there is no point at which the inner sleeve 6 is supported on diametrically opposite sides. The added webs 13 provide a further flow path for the plastic into the inner sleeve during the molding process. The plurality of webs may be made weaker than the single web such that the web closest to the impact breaks preferentially under the applied load, leaving the remaining ribs to support the inner sleeve 6.

Instead of extending in a radial sense as shown in fig. 2A, the or each web 15 may extend in a tangential direction as shown in fig. 2C, or in any other direction across the gap 12. As shown in fig. 2D, the webs 15 are offset in the axial direction relative to the annular flange 20, so that they do not impair the visibility of this region.

The manner in which the connector is configured to avoid hooking the fiber F will now be described with reference to fig. 3, 3A and 3B, wherein fig. 4A and 4B are used to provide a comparison with the prior art.

Fig. 3 shows a connector body 1 with a tube T fixed and sealed at each end. Once connected in this way, the fibers F are blown from one end through the tubes T, across the joints between the tubes, and into the adjacent tubes.

The tube T abuts the annular flange 20 at the midpoint of the inner sleeve 6. The connector 2 and the O-ring 3 have substantially the same inner diameter as the inner diameter of the inner sleeve 6, so that when the tube T is pushed into the body 1, it will be guided into the inner sleeve 6. Then, the end of the tube T abuts the annular flange 20. As best seen in fig. 3A and 3B, the annular flange 20 is provided with an undercut portion 21 such that the thickness of the annular flange 20 in the axial direction increases towards the axis X.

Thus, the innermost corner 22 of the tube T is the first portion of the tube T that abuts the annular flange 20. This means that there is no gap between the inner face 23 of the tube T and the annular flange 20.

As shown in fig. 3A and 3B, the undercut portion 21 is rounded. Similarly, the radially innermost corner 24 of the annular flange is rounded to present a smooth surface to the fiber.

In contrast to the prior art arrangement shown in fig. 4A, eliminating the gap G between the end of the tube T and the annular flange 20 means that there is no exposed abrupt edge of the tube T on which the fiber F hooks.

Fig. 3B depicts the case where the left tube is cut at an angle slightly oblique to a plane perpendicular to the axis X. Thus, the uppermost edge 25 of the tube T enters the undercut region 21 and seats on the annular flange 20.

By comparison with fig. 4B, it can be seen that the gap between the tube T and the annular flange 20 is eliminated in the upper half of the figure, and the gap at the bottom is significantly reduced compared with fig. 4B.

As will be apparent from fig. 3A and 3B, the radially inward extent of the annular flange 20 is greater than the inner diameter of the tube T. Thus, the annular flange 20 projects slightly inwardly beyond the inner face 23 of the tube T. From a comparison of fig. 3B and 4B, if it is assumed that the fibre F is loaded from right to left, the end of the fibre, which in fig. 3B will first encounter a corner of the annular flange 20 that protrudes slightly beyond the inner surface 23 of the tube T, will run along the lower part of the inner face 23 in fig. 3B and 4B in the vicinity of the connector 1. However, the fiber F can easily pass over this curved corner, and in so doing, this deflection should push the end of the fiber over the exposed edge 28 of the tube T. In contrast, in fig. 4B, the annular projection S does not protrude beyond the inner surface 23 of the tube, so nothing begins to deflect the fiber F back toward the center of the bore. Furthermore, the gap G' in fig. 4B is significantly larger than the corresponding gap in fig. 3B. In this way, not only does the fibers not deflect away from the gap, the presence of a large gap provides a significantly greater opportunity for the fibers to enter the gap and become caught on the edge 28 of the tube T.

A further feature to prevent hooking of the pipe is the listed arrangement of splines, as best shown in fig. 1 and 2.

As can be seen from these figures, six axially extending splines 30 are equally spaced around the circumference of the inner sleeve 6. These are shown as having a constant cross-section in a plane perpendicular to the axis. However, they may have a thickness that increases toward the annular flange 20.

As shown in fig. 1A and 1B, the tube T from the coil has been filled and has assumed a flat oval shape. When the tube T enters the inner sleeve 6, the tube T engages with an enlarged portion of the tube T and tends to push the tube T back into a more rounded shape as shown in fig. 1C.

Any number of splines may be used. However, six is considered a reasonable number. This allows engagement with flat tubes inserted in any orientation. A smaller number of flanges has the risk that an enlarged portion of the tube may enter between adjacent splines. On the other hand, adding more splines increases the insertion resistance of the tube T into the connector 1.

The spline 30 is sized such that where it is present, it is slightly smaller than the outer diameter of the tube. Thus, the spline 30 will bite into the material of the tube T in these areas. This ensures a reliable and robust fit of the tube T and also provides the greatest opportunity for the spline to reduce tube eccentricity.

The connector 2 (one connector 2 at each end of the body 1) will now be described in more detail with reference to fig. 5 to 8.

The connector 2 is formed of two parts, namely a cartridge 40 and a collet 41.

The cartridge 40 has a generally annular configuration. The outer surface is provided with a plurality of flexible metal teeth 42. The cartridge 40 is inserted into the end of the body 1 until it seats against the second step 11. The teeth 42 grip the walls of the body 1 to ensure that the cartridge 40 is permanently held in the body 1. At the end of the cartridge 40 adjacent the second step 11 there is a tapered cam surface 43, which cam surface 43 cooperates with a collet as described below. At opposite ends, the end faces of the cartridge 40 are provided with pairs of ramp surfaces 44. Although two such surfaces are shown, there may be a single surface or there may be more than two surfaces. Each ramp surface has a low point 45 in the middle inclined surface 47 corresponding to the unlocked configuration and a high point 46 corresponding to the locked configuration. A bump 48 is provided at the junction between the high point 46 and the inclined surface 47. A similar bump may be provided at the junction between the inclined surface 47 and the low point 45. The low point 45 terminates at a first end stop 49 and the high point 46 terminates at a second end stop 50.

Most of the features of the collet 41 are conventional. It has a collet ring 52 with a plurality of flexible arms 53 extending from the collet ring 52. Each arm has a head 54 at its distal end, with inwardly projecting metal teeth 55.

With the tube T inserted (e.g., as shown in fig. 8B), any movement tending to pull the tube T out of the connector results in the teeth 55 gripping into the tube, which pulls the head 54 toward the tapered cam surface 43 on the cartridge 40 which deflects the arms 53 inwardly to provide a progressively increasing gripping force on the tube T. This force serves to hold the tube T firmly in place. This is a conventional manner of collet operation.

The improvement provided by the present invention is the presence of a pair of cam followers 56 extending from the collet collar 52 toward the ramp surface 44 on the cartridge 40. Although two followers 56 are shown, there are in fact as many followers 56 as ramp surfaces 44. Alternatively, the cam arrangement may be reversed such that the ramp surface(s) are on the collet and the follower(s) are on the cartridge.

The collet ring 52 is also provided with a pair of lugs 57, the pair of lugs 57 extending from the collet ring 52 in a direction opposite the follower 56. As shown in the drawings, the positions of the projections 57 correspond to the number and positions of the followers 56. However, this may not be the case. The components may be offset relative to each other and the number of both need not be the same.

The operation of the collet will now be described with reference to fig. 6 to 8. The position shown in fig. 6A and 6B is the unlocked position. In this position, the collet 41 has been rotated such that the cam follower 56 abuts the first end stop 49 such that the cam follower is at the low point 45. As will be apparent from fig. 6B (particularly when compared to fig. 7B), in this position the collet 41 has a relatively large axial degree of freedom as it can move all the way to the left from the position where the head 54 engages the tapered cam surface 43 to the position shown in this figure (see fig. 6B). If held in this position by the user, the tube T can be withdrawn because the head 54 is held away from the tapered inclined surface 43 so that the collet cannot grasp the tube. The collet 41 is then rotated in the direction of arrow 60 to the locked position shown in fig. 7A. In so doing, follower 56 moves up inclined surface 57 over bump 48 (thereby providing the user with a tactile sensation that the position has been reached) to high point 46.

As will be appreciated from a comparison of fig. 6B and 7B, in the locked position shown in fig. 7B, the collet does not have the same degree of freedom as in fig. 6B, such that it cannot be moved and held to an unlocked position in which the teeth 55 are disengaged from the tube T. This is more apparent from fig. 8A and 8B, with fig. 8A and 8B showing the collet in the same locked position as in fig. 7A and 7B, but with the tube in place. Here, it can be seen how the presence of the tube pushes the head 54 back onto the tapered cam surface 43.

In this locked configuration, the only way to remove the tube T is for the user to grasp the tab 57, rotate the collet 41 in the direction of arrow 61 in fig. 6A to the unlocked position, and manually hold the collet in the position shown in fig. 6B while pulling the tube out of the body 1.

The tube T will typically be inserted with the collet 41 in the unlocked position shown in fig. 6A and 6B, as this allows a greater range of deflection of the arm 53 upon tube insertion. However, as can be seen in fig. 7B, even in the locked position, there is a small gap between the head 54 and the tapered cam surface 43. Thus, it is possible to insert the tube T with the collet in the locked position. This provides a simple assembly process as the user only needs to be informed of the insertion of the tube into the collet. They do not have to bother themselves with the locking operation.

As can be seen best in fig. 1A to 1C and 3, the collet ring 52 is arranged to recede axially inside the body 1. However, the projection 57 extends beyond the end of the body 1. In this position, the collet 41 is protected from external impact from the body 1. Furthermore, because it is recessed within the body 1, it is protected to some extent from contact with the soil in which the cable is buried. With this connector, dirt can potentially enter the connector at the only points of the interior working area between the collet ring 52 and the tube T and between the collet ring 52 and the body 1. However, these are joints that can apply tight tolerances. Any dirt entering here does not impair the visibility of the fibres F in the body 1. Moreover, due to the rotational action required to unlock the collet, it is unlikely that even some dirt will actually enter into these gaps, the collet 41 will become stuck, as the rotational movement can easily generate enough torque to overcome any such sticking.

Bump 57 has a right angle corner. This allows them to be inserted into the cut end of the tube T and scraped around the inner edge of the tube to remove any burrs that form during the cutting operation and may otherwise create a hooking hazard to the fibers F. The edges may be shaped in different ways to provide more efficient burr removal.

The connector 2 described above combines an outer sleeve 5 and an inner sleeve 6 supported by a web 7 with an unconventional arrangement of annular flanges 20 and splines 30. However, the connector may also be used in couplings having conventional interiors without these features.

Claims

1. A pipe coupling, comprising: a coupling body having an open-ended through passage for receiving a pipe; a collet located in the open end of the through passage, the collet having a ring and a plurality of flexible arms extending axially from the ring into the through passage, the through passage having a tapered surface converging toward the open end, and the flexible arms having heads at their distal ends for engaging both the tapered surface and a pipe extending through the collet into the through passage in use, so as to be compressed against the pipe by the tapered surface by outward movement of the collet relative to the through passage to secure the pipe in the through passage; and

a collet lock integrally formed on the collet, the collet having a locked rotational position in which the collet lock retains the collet in an outward tube securing position and an unlocked rotational position in which the collet is axially movable relative to the through passage to release and engage a tube through the collet;

One of the body and the collet is provided with a cam surface, and the other of the body and the collet is provided with a cam follower, wherein the cam surface is configured to provide a locked position and an unlocked position.

2. The coupling of claim 1, wherein the cam surface is on the body.

3. A coupling according to claim 2, characterized in that the body includes a cap retained by the main body portion, the cap being provided with the cam surface.

4. The coupling of claim 1, wherein the ring does not protrude axially beyond the body.

5. The coupling of claim 4, wherein the ring is recessed into the body.

6. The coupling of claim 1, wherein an unlocking feature is provided on the ring.

7. The coupling of claim 6, wherein at least one lug projects from the ring axially away from the open end of the through passage.

8. The coupling of claim 7, wherein the at least one lug protrudes axially beyond the body.

9. The coupling of claim 8, wherein the at least one lug has an abrupt edge.

10. A coupling according to any one of claims 1 to 9, characterised in that at least one of the body and/or the collet is provided with a visual indication of the locked position and/or the unlocked position.

11. A coupling according to any one of claims 1 to 9, wherein adjacent the locked position the cam surface is provided with a raised bump over which the cam follower rides.

12. The coupling according to any one of claims 1 to 9, wherein the coupling body is made of non-opaque plastic.

13. A connector according to any one of claims 1 to 9, characterized in that the body includes an outer sleeve and an inner sleeve, the inner sleeve is configured to receive the distal end of the corresponding tube, the outer wall of the inner sleeve is spaced apart from the inner wall of the outer sleeve to define a gap, and the inner sleeve is supported on the outer sleeve by a separate material web, the material web supports the inner sleeve and maintains the gap between the inner sleeve and the outer sleeve.

14. A coupling according to any one of claims 1 to 9, characterised in that the coupling has no external ribs and has a continuous outer surface with a constant radius.

15. A connector according to any one of claims 1 to 9, characterized in that an annular flange extends radially into the through-channel, each end face of the annular flange provides a stop surface for a corresponding pipe end, wherein the annular flange is undercut so that its end face is inclined so that the axial dimension of the annular flange increases toward the central axis of the through-channel.

16. The coupling of claim 15, wherein a plurality of annular splines are provided on a wall of the through passage adjacent the annular flange to deflect an outer wall of the tube as the tube approaches the annular flange.

17. A collet for a pipe coupling according to any preceding claim, the head having teeth on a radially innermost face for gripping a pipe in use;

The collet is integrally provided with a collet locking feature in the form of a cam feature arranged so that, in use, the depth to which the collet can be inserted into the coupling body will vary with different angular positions of the collet,

The cam feature is a cam follower extending from the ring in the direction of the flexible arm.

18. The collet of claim 17, wherein the unlocking feature is provided by at least one lug, the at least one lug axially extending from the ring in a direction opposite to the direction in which the flexible arms extend.