GB2234327A - Valve - Google Patents

Abstract

A ceramic three disc type valve assembly is able to control the on/off function and flowrate of two separate fluid supplies without the flows becoming mixed. The flows enter and exit the disc mechanism as separate supplies. It is possible to regulate the flows at the same rate (Fig. 2) or at different rates for any degree of valve actuation. One use is envisaged to be in the plumbing context with the fluids being water.

Description

Ceramic independent twin supply fluid cut off and regulating device.

This invention relates to a ceramic disc type valve which is able to control the on/off function and flowrate of two separate fluid supplies without the flows becoming mixed. It is envisaged that the principle use of such a device would be in the plumbing context wherein the fluid would be water. The following description refers to the valve used within this context.

The use of ceramics in water control devices in now well established. Devices, whether they be taps or mixer valve units have become sophisticated and reliable thanks to advances in the ceramics technology. Typically, these devices consist of two circular discs with one or more passageways.

The discs have a well machined, honed mating surface which provides a seal. When closed, water is prevented from passing through the two disc arrangement. Rotation of one disc relative to the other by means of a suitable mechanism allows the passageways in the two discs to become aligned.

Typically, full flow is obtained when the devices are rotated through 90 degrees with reduced flow at lesser angles.

Turning forces can be reasonably low and movement is often brought about by a direct actuator without gearing or mechanical advantage. Sealing requires about an 80% contact area between two honed surfaces. Lubricant is spread on the surfaces before they are assembled together and this finds its way into the void filled remaining 20% of the surface. A compression force is applied to the discs. A "wringing force" is created between the two discs which is caused by intermolecular attraction of the two surfaces. As the area of contact is increased so do these two forces. If the actuation force, sometimes known as "stiction" becomes too great for the young, elderly or disabled, then levers can be used or a simple gearing mechanism can be built in to the device.

These twin disc devices do not need to be circular or have rotary motion for their actuation. Some have rectangular shaped ceramic "slabs" and linear actuation possibly by means of a lever. This allows a mechanical advantage albeit at the expense of excessive travel of the control lever.

To date, the ceramic valve devices have found an application in two main areas. The first is in simple taps. The conventional style mechanism is replaced with two concentric ceramic discs. The flow of water is controlled by rotating one disc with respect to the other stationary disc. Typical actuation is over 90 degrees. Some taps are now available with more than 90 degrees actuation. It is said that these allow larger ports and a better flow path to low head supplies. The second application is in mixer units such as kitchen taps. Once again a two disc mechanism is required, but this time it controls the flow path of two supplies. The supplies blend as they flow through the passageways. These devices often make use of just one lever which is able to arrange the disc or slab ports to control both flowrate and temperature.

Some modern showers are now making use of ceramic discs for flow control. It is desirable to have well proportioned ports so that the mixer/flow control function does not restrict performance on low head supplies. This can be achieved by enlarging the discs or slabs beyond the size found commonly in taps and sink mixers. Under these circumstances it is possible that the force required for actuation may increase beyond an acceptable level. Under these circumstances it may become necessary to use gearing or levers for actuation.

With the publication of the latest Model Water Bye-laws a new regime in domestic and industrial plumbing applications has emerged. Situations can now arise whereby it may be desirable to have devices operating on mains fed cold and stored low pressure hot water. In these instances it may be necessary to control the separate flows by means of one control before they are mixed at a later stage. The regulations do not allow flows of this nature to blend without very stringent backflow prevention devices.

There may be possible situations whereby it is required to control the flow of two separate supplies in a single unit with a preset, non user variable,-ratio between the two.

One specific application of the valve function discussed above is in a mains cold water powered pumped shower unit.

In this context it is necessary to control the flow of the hot and cold supply from off to fully on in a preset manner.

It is fundamental to this type of device that the flows do not mix before they enter the cold water powered booster device. It is desirable, from the point of safety, convenience and cost that the flows are controlled with one actuator and a ceramic disc type valve as described below can perform this function.

Conventional mixers, which make use of two discs, are unable to prevent the flows from merging in the valve. The use of a third disc makes this possible. It means that there are two rubbing surfaces within the valve with the actuator disc sandwiched between two stator discs. Once again the disc could be replaced by a slab.

The use of a third disc which creates two mating surfaces may cause a significant increase in the valve actuation force required. It could be that the actuator disc would be mounted within a gear. This would provide a mechanical advantage.

Alternatively, a slab actuator could be used with a linear travel.

Before looking at the three disc ceramic valve described in this application, it is worth looking at a typical two disc configuration. Figure 1 shows a typical embodiment. Dise B rotates on the same axis as disc A which is stationary. Full opening is achieved in 90 degrees. Flow passes through both ports, but is from a single supply.

Referring now to Figure 2, this shows one embodiment of the independent supply control valve. As in Figure 1, the necessary housing is not shown. This would vary according to the application.

"Flow 1" enters the valve at 1 and "flow 2" at 2. These are sealed by means of "O" rings on the inlet side of the lower disc (stator) 3, as is appropriate. With the middle disc (actuator) 4, in the closed position, shown, the passage of water in either supply is prevented.

As the actuator is rotated anti-clockwise it begins to uncover ports 5 and 6 in 3. Simultaneously, water begins to flow into ports 7 and 8 in the upper disc (stator) 9. A sealing surface fit exists on both sides of the actuator 4.

As the actuator 4, is rotated further, the ports 10 and 11 allow a greater area for the water to flow through and out of the valve.

The assembled unit 12, shows how the three concentric discs 3, 4 and 9 fit together. In the simplistic embodiment shown, the actuator 4, is rotated by means of a bonded stainless steel shaft, 13. This is rotated on the splines, 14. In practice, the actuator disc 4, would probably be rotated on its periphery. This would reduce stresses in the disc. A geared circumferential insert would provide mechanical advantage as well.

The valve shown in Figure 2 is one of the most simple embodiments envisaged for the concept of a three disc ceramic valve. It would allow an equal volume of flow 1 and flow 2 to pass for any angle setting if both supplies were at an equal pressure. Maximum rotation is 90 degrees. The valve is rotated anti-clockwise to open it.

A very useful feature of the valve is that it can have the ports modified to allow different volumes of water to flow through ports 1 and 2 for a particular angle setting. This feature is demonstrated in Figure 3.

As before, flow enters the valve on the underside of the lower disc (stator) 17, at 15 and 16. With the middle disc (actuator) 18, in the closed position, shown, the passage of water in either supply is prevented. As the actuator is rotated anti-clockwise it begins to uncover ports 19 and 20 in 17. Simultaneously, water begins to flow into ports 21 and 22 in the upper disc (stator) 23. A sealing surface fit exists on both sides of the actuator 18. As the actuator 18, is rotated further, the graduated ports 24 and 25 allow a greater area for the water to flow through. The action of the valve can be described in more detail. For an anti-clockwise motion, port 19 is opened at a greater rate than port 20. The snail shaped port 25 causes a reduced flow out of port 22.

In this way an imbalanced flow path can be achieved as is desired.

Figure 4 shows an alternative configuration for the ports in the valve. It may be desirable to replace the snail-like cross section port, 25, with a series of individual holes, 26. Manufacturing considerations may make this essential.

Furthermore, the use of discrete holes may allow more accurate control of cross sectional area and hence flowrate.

The mechanism for actuation could be as before.

Various modifications may be made within the scope of this invention. The discs may be rectangular or any other convenient shape. The actuation may be by lever, gear or belt.

Claims (10)

Claims:

1. A ceramic valve assembly which is able to control the passage of two independent supplies of fluid without the fluids becoming mixed in the control process.

2. A valve according to claim 1 in which the two flows are regulated from fully off to fully on, at the same rate by means of equivalent rate of area change of the ports.

3. A valve according to claim 1 in which the two flows are regulated from fully off to fully on, at different rates by means of different rates of area change of the ports.

4. A valve according to claim 3 in which the flow path offering restricted flow is in the form of a conical snail cross sectional area.

5. A valve according to claim 3 in which the flow path offering restricted flow is in the form of discrete reduced cross sectional area holes.

6. A valve according to claim 1 in which the fluids are water.

7. A valve according to claim 1 in which one fluid is cold water and the other fluid is hot water.

8. A valve according to claim 1 which comprises two stator discs, one rotor disc and means by which the assemblies can be rotated to cause actuation.

9. A valve according to claim 1 in which the ceramic components are in the form of slabs and actuation is caused by either linear motion, rotary motion or a combination thereof.

10. A unit as claimed in claim 1 substantially as herein described with reference to the accompanying drawings.