GB2521919A

GB2521919A - Improvements in fluid control devices

Info

Publication number: GB2521919A
Application number: GB1419791.7A
Authority: GB
Inventors: Gareth Richards; Simon Timothy Spencer
Original assignee: Salamander Pumped Shower Systems Ltd
Current assignee: Salamander Pumped Shower Systems Ltd
Priority date: 2013-11-06
Filing date: 2014-11-06
Publication date: 2015-07-08
Also published as: GB201319587D0; GB201419791D0

Abstract

An insert 10 is provided for a fluid control device, such as a pump. The insert which may be metal such as brass, is designed to be integrally attachable to a body 13 of the device, which may be plastics material such as acytal. The insert comprises formations 12, conveniently screw threads, for enabling the device to be connected to a supply of fluid. The insert comprises an axially extending annular recess 17, which forms an axially extending ring of plastics material which allows the interface to compensate for differences in coefficients of thermal expansion of the different materials whilst maintaining a permanent watertight connection. The insert is preferably keyed to provide an irregular configuration to the contacting surface between insert and the body of the device; this may comprise undercut regions 14 and circumferential components (16, fig 1) extending parallel to the longitudinal axis of the insert to improve resistance to torsional forces.

Description

Improvements in fluid control devices This invention relates to fluid control devices such as in particular, although not exclusively, water pumps.

The invention provides an insert for a fluid control device which is designed to enable connection to a supply of fluid in use, in which the insert is designed to be attachable to a body of the device in a permanent, watertight manner, with the insert having an axis and comprising formations for enabling said connection to a supply of fluid, and with the contacting surface between the insert and the body in use forming an interface therebetween, wherein the interface comprises a first portion extending around the axis in which the surface of the insert faces towards the axis, and a second portion extending around the axis in which the surface of the insert 13 faces away from the axis.

By way of example, embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates a form of insert according to the invention, Figure 2 is a sectional view illustrating the insert of Figure 1 in position in a fluid control device, Figure 3 is a larger scale view showing in greater detail the interface 3 between the insert and the body of the device, and Figures 4 to 7 are larger scale views showing alternative interface configurations.

Fluid control devices such as water pumps and valves have traditionally been made with metal bodies, typically cast and/or machined brass, with screw-threaded formations for attachment of pipework fittings.

More recently, other materials such as injection moulded plastics have been used instead for these devices. This offers a lighter and cheaper alternative.

13 With plastics, however, it is difficult to ensure that the pipework connections will remain reliably watertight, particularly after they have been loosened and re-tightened a number of times, e.g. for maintenance or repair of the device. There is also a greater risk of cross-threading than with traditional connections.

The present invention proposes a solution in which the attachment formations for the pipework connections are provided by means of special inserts which are integrated into the body of the device.

3 An example of such an insert lOis seen in Figure 1. The insert 10 is made of brass and has a plain bore 11 therethrough for passage of water. At one end, the insert 10 has external screw-threaded formations cut or otherwise formed into it. In the finished article, the screw-threaded end of the insert 10 is designed to extend out of the body 13 of the device (see Figure 2) to allow it to be connected into pipework using suitable fittings, such as standard compression fittings.

It will be understood that instead of the screw-threaded formations shown in this example, the formations could take other forms, for example 13 internal screw-threaded formations for female type couplings or plain-ended formations for push-fit type couplings.

At its other end, the insert 10 is designed to be integrated into the body 13 of the device. This is conveniently achieved by means of an insert moulding process. Such processes are known per se and involve forming material in a mould tool around a component by suitable means such as injection moulding, compression moulding or die casting. In this case, the component is the brass insert 10. and the material is what forms the body of the device. Here, the material is of plastics, conveniently acytal.

To enhance the integrity of the connection between the insert 10 and 3 the body 13 of the device, the insert is keyed. The keying is designed to provide an irregular configuration to the contacting surfaces between the insert 10 and the body 13 of the devide, ie the interface between them. The keying has an axial component, which here takes the form of undercut regions 14. These extend around the outer surface of the insert 10 and have a series of recesses 15 formed in them. As will be understood from the cross-sectional view in Figure 2, the plastics material is designed to fill the undercut regions and the recesses in the insert moulding process. The effect is to strengthen the resistance of the insert 10 to being pulled out of the body 13 of the device.

The keying of the insert 10 also comprises a circumferential component, which here takes the form of plain sections 16. These extend parallel to the longitudinal axis of the insert 10, lying in between and standing proud of the undercut regions 14. As will be understood from Figure 1, this strengthens the resistance of the insert 10 to the torsional forces that it will experience whenever the pipework connections are loosened or tightened. Other keying features or configurations, such as knurling, could of course be used in addition orin the alternative.

The composite construction described above has the advantage of allowing the body of the device to be made out of plastics material, which is lighter and cheaper than suitable metals such as brass, whilst providing that the pipework connections to the device are made via metal attachments such as brass, with its inherent suitability for forming reliably strong and watertight joints.

The construction is particularly suitable for use with devices such as water pumps, for their inlet and outlets connections. However, the principle can be extended to other components of such devices and/or to other devices, such as valves.

Many of the devices on which the construction described above is suitable for use will be subject to high working pressures in use. For example, water pumps for domestic use are typically tested for operation at pressures of 15 bar. It is of course important that the construction is able to maintain its integrity at such working pressures, without leaks or mechanical damage occurring.

Devices of this nature are also likely to have to work within a fairly wide range of temperatures, typically from around 00 C to around 700 C. This variation in temperature can cause difficulties with the sort of construction described above, due to the different coefficients of thermal expansion of 3 the insert and body materials respectively. This is catered for in the example seen in Figures 1 and 2 by means of a further feature in the keying of the insert 10, namely an axially extending annular recess 17 in its inner end face.

As seen in more detail in Figure 3, this is designed to allow plastics material to flow into the recess 17 during the insert moulding process. The effect is to form an axially extending annular ring 18 of plastics material between radially inner and outer axially extending rings 19, 20 of metal formed by the recess 17 in the end of the insert 10. This gives the interface between the insert 10 and the body 13 a deliberately complex configuration.

13 In particular, the interface includes axially extending annular portions A, B that effectively face in opposite radial directions. That is to say, in one portion A, the metal surface of the insert 10 faces radially outwardly, whereas in the other portion B, it faces radially inwardly. The net effect is that the interface as a whole is able to compensate for differences in coefficients of thermal expansion of the different materials. In particular, if at one of the interface protions A, B there is a tendency for the materials to move radially apart as the temperature rises, the same differential expansion effect will cause the opposite movement at the other interface portion, ie the materials will press radially together. The net effect is to maintain a solid connection between the two materials at at least one interface portion, thus ensuring the sealing integrity of the construction.

The provision of radially opposing axially extending interface portions A, B between the two materials can be realised in many different ways. For example, as seen in Figure 4, the configuration can be arranged the opposite way round, with an axially extending annular ring 21 being formed on the end of the insert 10 to be sandwiched between axially extending annular sections 22, 23 of the body 13. Other features or variations of these basic arrangements can be incorporated, such as by adding a circular shaped bead 24 at the end of the annular ring 25 on the end of the insert 10, as seen in Figure 5, or by sloping or otherwise modifying one or both interface portions 13 A, B, as seen in Figures 6 and 7.

Claims

Claims 1. An insert for a fluid control device which is designed to enable connection to a supply of fluid in use, in which the insert is designed to be 3 attachable to a body of the device in a permanent, watertight manner, with the insert having an axis and comprising formations for enabling said connection to a supply of fluid, and with the contacting surface between the insert and the body in use forming an interface therebetween, wherein the interface comprises a first portion extending around the axis in which the surface of the insert faces towards the axis, and a second portion extending around the axis in which the surface of the insert faces away from the axis.
2. An insert as claimed in claim 1 wherein one or both of said first and second interface portions extend parallel to said axis.
3. An insert as claimed in claim 1 wherein one or both of said first and second interface portions extend irregularly with respect to said axis.
4. An insert as claimed in any preceding claim wherein the body of the device is a moulded component and is formed integrally with the insert in an insert moulding process.
5. An insert as claimed in any preceding claim wherein the insert is designed to have the body of the device formed partly around it and is keyed so as to resist movement relative to the body.

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6. An insert as claimed in claim 5 wherein the keying of the insert has a component designed to resist pulling out of the body of the device.
7. An insert as claimed in claim 5 or claim 6 wherein the keying of the insert has a component designed to resist rotation relative to the body of the device.
8. An insert as claimed in any preceding claim wherein the formations on the insert are arranged to lie externally of the body of the device.

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9. An insert as claimed in any preceding claim wherein the formations on the insert are in the form of a screw-threaded connection.
10. An insert as claimed in any preceding claim wherein the insert is formed of metal, preferably brass.
11. An insert as claimed in any preceding claim wherein the body of the device is made of a plastics material, such as acytal.
12. An insert substantially as herein described with reference to the accompanying drawings.
13. A fluid control device incorporating an insert as claimed in any 3 preceding claim.
14. A water pump incorporating an insert as claimed in any one of claims ito 10.