GB2575620A

GB2575620A - A collet for locking a tube in a coupling body

Info

Publication number: GB2575620A
Application number: GB1806917.9A
Authority: GB
Inventors: Steven Guest Timothy
Original assignee: John Guest International Ltd
Current assignee: John Guest International Ltd
Priority date: 2018-04-27
Filing date: 2018-04-27
Publication date: 2020-01-22
Also published as: WO2019207321A1; GB201806917D0

Abstract

A collet for locking a tube in a coupling body, the collet comprising an annular body 1 and a plurality of legs 2 formed separately from the annular body, each having a head at its distal end 6 spaced from the annular body, and a proximal end 5 via which it attaches to the annular body. Preferably the body is formed of a different material to the legs, and comprises a series of openings 4 into which the proximal end of the legs are accepted.

Description

A COLLET FOR LOCKING A TUBE IN A COUPLING BODY

The present invention relates to a collet for locking a tube in a coupling body.

Connectors are known which have a tubular body receiving a collet. The collet has a collet ring from which a number of legs extend axially each terminating at a head at the distal end furthest from the ring. The body has an inclined inner surface (known as a cap angle) such that, in use, when a tube inserted in the connector is pulled in a direction tending to pull it out of the connector, the heads of the collet legs will grip the tube and are then forced radially inwardly by the inclined surface to grip the tube. The larger the force tending to pull the tube out of the connector, the greater the extent to which the collet grips the tube because it is being forced into an ever narrower portion of the body.

In order to remove the tube from the connector, the collet is pushed inwardly into the body and held such that the collet is prevented from riding up the inclined surface and gripping the tube as described above.

Collets are currently produced by insert injection moulding stainless steel teeth into an otherwise all plastic collet. This is very effective, but is also capital intensive in requiring complex and expensive press tools, moulds and work hardening automation. The stainless steel teeth are pressed from a ring of flat steel. Because of this, the steel of the ring which is not required for the teeth is recycled or wasted. This becomes a greater problem if large collets are produced as the amount of steel which is wasted/recycled increases as the gap between the legs increases.

EP1600682 discloses a collet which is moulded from two different materials. In particular, the head of the collet is made from a stronger and more rigid material from the remainder of the collet. This is done with the object of withstanding higher loads, particularly at higher temperatures.

The present invention is aimed at providing a collet with a new design which provides for greater flexibility.

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

- 2 Forming the annular body separate from the legs provides a number of advantages.

The body and legs can be made of different materials from one another. Previously, they were constrained to be of the same material. In EP1600682, the legs and the annular body are constraint to be the same material. It is only the head which is made of a different material and this is done for reasons which have no relevance to the present invention. The legs are required to be flexible at the point where they meet the annular body such that, in previous designs, the legs are significantly narrower at this position to provide the necessary flexibility. This is no longer necessary with the present invention as the flexibility at the proximal end of the leg can be provided (mostly or entirely) by the material of the annular body to allow the leg to be made of a more rigid material.

There is also no need for all of the legs to be of the same material. This allows more flexibility in meeting the required design criteria and/or reducing cost.

With a conventional collet which is provided with metal teeth, all of the teeth are necessarily formed in the same radial plane as they are stamped from the same sheet. This provides relatively little resistance to rotation of the tube within the connector as the teeth will tend to cut a single groove in the outer wall of the tube. The present invention allows legs of different lengths to be attached to the annular body such that the teeth will engage at different axial portions of the tube thereby providing increased resistance to rotation of the tube within the connector.

Each head is preferably provided with a tooth made from a different material from the rest of the leg which is positioned for engaging the tube. With the present invention, the material forming the teeth no longer needs to be stamped from a ring of material. Instead, as the legs are formed separately, rather than using a ring of material, the legs can be formed in a mould which uses a strip of material to form the teeth. Adjacent legs can be moulded closer to one another such that the amount of material for the teeth which is wasted between adjacent legs is minimal as the distance between the teeth and the mould can be far less than the distance between the teeth in the finished collet.

The present invention also allows the possibility that at least one head is provided with a tooth at an angle which differs from the tooth of at least one other head. This allows, for example, one or more of the teeth to be positioned at a plane which is inclined with respect

-3to a radial plane. The present invention can therefore take advantage of the benefits associated with such a design as disclosed in our earlier EP2860435.

The legs can be connected to the annular body by any suitable attachment process such as adhesion or welding. However, the annular body is preferably provided with a plurality of slots to receive the proximal end of the legs. These are preferably through slots.

The connection between the annular body and the proximal end of each leg is preferably provided with a mechanical interlock via which it is attached to the annular body. Preferably the mechanical interlock is provided by at least one barb to locate on the annular body, for example in one of the above described slots.

The annular body may be provided with at least one sleeve extending towards the distal end to receive a respective leg, the sleeve being flexible to allow deflection of the respective leg.

The present invention is also easy to scale up as a single leg can be produced for a range of collet sizes which can then be attached to annular bodies of different diameter in order to provide collets of different sizes. It is much simpler to produce an annular body of different sizes as this is a very simple moulding as compared with moulding a complete collet which requires a new complex mould including a new press for the teeth for each collet size. Instead of providing a single leg, there may be a limited number of different legs to provide different materials or different lengths as described above.

The present invention also extends to a method for forming a collet for a locking tube according to claim 10.

Preferably the method further comprises attaching the legs to the annular body by a press fit.

Preferably the method further comprises the step of indexing the annular body through a plurality of positions and attaching a respective leg at each indexed position.

Preferably the step of forming the plurality of legs comprises forming a plurality of legs in a single moulding step including in a plurality of mould cavities, wherein a single sheet of

-4material is inserted across all of the mould cavities and is subjected to a pressing operation during the moulding process to sever the material from the strip thereby forming a respective tooth on each leg formed in a respective mould cavity.

The present invention also extends to a leg for a collet according to claim 16 and a ring for a collet according to claim 19. The leg is preferably provided with a mechanical interlock in the form of at least one barb.

Examples of a collet and method of assembling a collet will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a first example from one end;

Fig. 2 is a perspective view of a first example from a second end;

Fig. 3 is a view from the same perspective as Fig. 2 showing the assembly process;

Fig. 4 is a view of four different collets from the same perspective as Fig. 2 showing how the collets of different sizes are formed;

Fig. 5 is a view similar to Fig. 4 demonstrating the assembly process for collets of different sizes;

Fig. 6 is a view similar to Fig. 1 of a second example; and

Fig. 7 is a view similar to Fig. 2 of a second example

The collet forming the subject of the present invention is intended for use in a coupling which consists of a body and cap which are assembled to one another to provide a throughway for a tube. A collet in the open end of the connector is provided to grip the tube. A force on the tube tending to pull it out of the connector will cause the heads of the collet to be deflected radially inwardly to grip the tube with a force which increases as the force tending to pull the tube out of the connector increases. Depressing the collet into the body allows the tube to be removed as it prevents the collet from being compressed as described above. The connector may be optionally provided with a locking ring which

-5prevents the collet from being inadvertently moved into the release position. An example of such a connector is produced by the applicant, John Guest International Limited under the Speedfit (RTM) trade mark.

The present invention relates to a new design of collet which has applications to any such connector. It is, however, particularly applicable to collets which have a large diameter.

The collet design and manufacturing process will subsequently be described.

The first example is shown in Figs. 1 to 5.

This collet consists of an annular body 1 and a plurality of separately formed legs 2. The annular body 1 is in the form of a complete ring and also has an optional annular skirt 3 extending from the radially innermost face of its proximal side. The annular body is provided with a plurality of through slots 4 to receive a plurality of legs as shown in Figs. 1 and 2. Fig. 3 illustrates the manner in which an individual leg 2 is inserted into the annular body 1.

Each leg has a proximal end 5 and a distal end 6. The distal end 6 is provided with a tooth 7 which is formed from a metal sheet as described below. The proximal end has a pair of barbs 8 such that, as the proximal end 5 is inserted through the slot 4, the barbs 8 spring out as shown in Fig. 1 to hold the legs 2 in place. The skirt 3 resists inward movement of the proximal end and hence limits the outward deflection of the distal end.

The legs 2 can be made of a material which is much stiffer than the material of the annular body 1 such that all of the flexibility required when the legs are deflected in use can be provided by the annular body 1 such that the annular body 1 effectively forms the hinge around which the legs pivot. This avoids placing undue bending stress on a relatively stiff plastic.

The legs may be simply a press fit as described above. The press fit may be enhanced by welding or gluing. Alternatively, welding or gluing may be used as an alternative to the slot. Other retaining mechanisms such as having a two-part annular body between which a portion of the legs is sandwiched may be used.

-6The legs shown in the example all have the same length. They may, however, be formed of two or more different lengths. Also, each of the legs may be of the same of a different material depending upon the requirements of the collet.

Each leg is preferably formed as a moulded plastic. The tooth 7 is preferably formed of a different material such as a metal.

This is preferably done by having a single mould to form a plurality of legs in close proximity to one another and with a strip of metal to form the teeth 7 extending across the mould for the plurality of legs. A press tool is provided to cut the individual teeth during the moulding process. Because, the legs can be moulded close to one another, the amount of metal wasted/recycled between the adjacent teeth can be minimised.

Fig. 4 shows four different sizes of collet. As can be seen, all of these have the same leg 2 such that only one moulding is required to form the teeth for any size of collet. The only difference is that a different size of ring 1, 1 ’, 1 ” and 1 is used in each case.

In order to assembly the collet, a supply of legs are sequentially provided to an assembly station and a ring 1, 1 ’, 1 ” and 1 of the required size is provided on a rotating chuck. The ring is then indexed through all positions in which each slot 4 is presented at the assembly position and the leg is inserted as shown in Fig. 5. Thus, the process can easily be automated. Further, any size of collet can be assembled on the same equipment. It is simply a matter of changing the position where the annular ring 1 is supported and the amount of the positions through which it needs to be indexed to create the fully assembled collet.

Figs. 6 and 7 show a second example in which the annular body 1 is provided with a sleeve 10 extending distally from each slot 4 this provides enhanced support for the legs 2 and the flexible material creates an enhanced hinge thereby allowing the individual legs to remain rigid.

Claims

1. A collet for locking a tube in a coupling body, the collet comprising:

an annular body; and a plurality of legs formed separately from the annular body, each leg having a head at its distal end spaced from the annular body for engaging a tube, and a proximal end via which it is attached to the annular body.

2. A collet according to any preceding claim, wherein the annular body is formed of a material which is different from the material of the legs.

3. A collet according to claim 1, wherein the annular body is provided with a plurality of slots each configured to receive the proximal end of a respective leg.

4. A collet according to claim 2, wherein each slot is a through slot in the annular body.

5. A collet according to any preceding claim, wherein the proximal end of each leg is provided with a mechanical interlock via which it is attached to the annular body.

6. A collet according to claim 5, wherein the mechanical interlock is provided by at least one barb.

7. A collet according to any preceding claim, wherein at least one leg has a length which differs from the length of another leg.

8. A collet according to any preceding claim, wherein at least one leg is made from a material which differs from the material of at least one other leg.

9. A collet according to any preceding claim, wherein each head is provided with a tooth made from a different material from the rest of the leg which is positioned to engage the tube.

10. A collet according to claim 9, wherein at least one head is provided with a tooth at an angle which differs from the tooth of at least one other head.

11. A collet according to any preceding claim, wherein the annular body is provided with at least one sleeve extending towards the distal end to receive a respective leg.

12. A method of forming a collet for a tube in a coupling body, the method comprising forming an annular body; separately forming a plurality of legs, each leg having a head at its distal end spaced from the annular body for engaging a tube and a proximal end, the method further comprising attaching the proximal end of each leg to the annular body.

13. A method according to claim 12, wherein the legs are attached to the annular body by a press fit.

14. A method according to claim 12 or claim 13, further comprising the step of indexing the annular body through a plurality of positions and attaching a respective leg at each indexed position.

15. A method according to any of claims 12 to 14, wherein the step of forming the plurality of legs comprises forming a plurality of legs in a single moulding step in a plurality of mould cavities, wherein a single sheet of material is inserted across all of the mould cavities and is subjected to a pressing operation during the moulding process to sever the material from the strip thereby forming a respective tooth on each leg formed in a respective mould cavity.

16. A leg for a collet according to claim 1, the leg having a head at one end with means to grip a tube; and at a second end opposite to the first end being provided with an attachment interface for attachment to an annular body.

17. A leg according to claim 16, wherein the attachment interface is a mechanical interlock for engagement with an annular body.

18. A leg according to claim 15, wherein the mechanical interlock is at least one barb.

19. An annular body for a collet according to claim 4, the annular body being provided with a plurality of through slots in the annular body.