WO2002003159A1

WO2002003159A1 - Thermostatic mixing valve

Info

Publication number: WO2002003159A1
Application number: PCT/GB2001/002956
Authority: WO
Inventors: William Reid
Original assignee: The Horne Engineering Co. Ltd.
Priority date: 2000-07-05
Filing date: 2001-07-05
Publication date: 2002-01-10
Also published as: AU2001270754A1; GB0016481D0; GB0116417D0

Abstract

There is provided a thermostatic mixing valve (1) for eliminating uneven mixing of hot and cold fluid flows comprising a casing (2) including ducts (3, 4) for cold and hot feeds into the cold and hot portions, an annular cold inlet port (9) being present at the seat (6) while a corresponding annular hot inlet port (10) is present at seat (7), the size of these ports (9, 10) determined by valve member (8) which in turn is controlled by a thermostatic actuator (11) coupled to the valve member (8) via a spool device (12), divided into upper and lower parts (12A, 12B) each defining a fluid conduit, the wall of the upper part (12A) carrying first annularly arranged apertures (31A) for location at the top end of the valve member (8) at the level of the cold inlet port (9), while lower similar second apertures (32A) are located at the level of the hot inlet port (10). Hot fluid passes radially inwards between the valve member (8) and hot valve seat (10) to meet the cold fluid passing radially outwards from apertures (32A) so that the fluids are evenly mixed.

Description

THERMOSTATIC MIXING VALVE

The present invention relates to thermostatic mixing valves.

Thermostatic mixing valves (TMVs) are well established and serve to provide a fluid (water) supply at a desired temperature. For this purpose, TMVs have a thermostatic device to control the relative proportions of hot and cold fluids passing in the valve to a mixing zone whence the mixed fluids are caused to impinge on a temperature responsive element of the thermostatic device, control of the hot and cold flows being achieved by the thermostatic device being operatively coupled to a valve member controlling fluid flows through hot and cold inlet ports of the valve. Consequently, when there is an undesirable rise in the temperature of the mixed fluid the thermostatic device expands to cause the valve member to reduce the hot flow via the hot inlet port and increase the cold flow via the cold inlet port to restore the fluid supply temperature condition to that desired, with a converse operation when there is a fall in the mixed fluid temperature .

It is established practice to have the hot and cold inlet ports (controlled by the valve member) of a substantially 360° form, with the valve member constituted by a slide or poppet valve device, and for the provision of a suitable fluid flow to the 360° port the TMV usually employs fluid feed ducts extending laterally to the TMV casing and each feeding to a respective annular gallery within the valve casing, appropriate wall formations being present in the casing to contain fluid flow in each gallery. In a known design the galleries surround their respective hot and cold inlet ports of the TMV. GB-A-2096274 and FR-A-1310027 show such an arrangement.

Standard arrangements as discussed above suffer from distinct drawbacks. Problems arise from imperfect mixing of the hot and cold fluids with consequential creation of high and low temperature zones in the mixed fluid. This leads to difficulties in the

TMV maintaining accurate temperature control. Ideally the temperature responsive element of the TMV should be responsive to a thoroughly mixed fluid of uniform temperature and which has not always been achievable in prior TMV's for the above mentioned reason.

FR-A-1310027 has the hot and cold fluid feed ducts on the same side of the casing whereas GB-A- 2096274 has these ducts on opposite sides of the casing, but in both valves the above disadvantages can arise.

US-A-4164321 shows a TMV wherein the above discussed galleries (at the hot/cold feed ducts) are rather spaced from their respective inlet ports, with passages of substantial length within the valve casing for delivery of the hot and cold feed fluids from the galleries to the ports, and it is possible that this arrangement could minimise or remove the above drawback, in particular by substantially removing the high pressure zone at each gallery, although it would appear that the manner of mixing the hot/cold feeds in US-A-4164321 will hardly be conducive to the temperature responsive element receiving a thoroughly mixed fluid. However the arrangement of the TMV shown in US-A- 4164321 does create a rather bulky valve, and this disadvantage is especially severe in larger sizes of TMV e.g. of 40mm or 50mm size (supply/outlet diameter), and the present invention is particularly concerned with these larger sizes of TMV.

It has also been proposed to provide ribbing on a casing wall surface at the gallery with a view to disturbing the fluid flow in the gallery. However, this will entail the use of ribbing of suitable geometry otherwise any benefit obtained may be only minimal. Also, there could be difficulties in applying appropriate ribbing from valve size to valve size and making ribs which are suitable for all flow rates. A major disadvantage in building ribs into a valve body is the increase in the pressure drop through the TMV producing undesirable effects. Further, the actual thermostatic element used in such devices is an averaging device and needs to be relatively long in order to provide temperature control. It is an additional problem that the level of temperature control provided by previous approaches to the problem cannot provide the level of finesse of control that may be required.

It is the principal object of the present invention to provide a device for use in a TMV, and in particular larger TMVs, which meets the above discussed drawback in a more advantageous manner.

The invention provides a thermostatic mixing valve comprising housing parts and operating parts accommodated within an operating space defined by the housing parts, said operating space and operating parts being generally cylindrical and having rotational symmetry about an axis of the valve, said parts including: a valve slider movable axially between first and second valve seats so as to define first and second annular valve ports respectively, said first valve port tending to open while the second valve port is closing and vice versa, depending on the direction of movement of said slider; and a temperature-sensitive actuator arranged centrally and extending along the axis of the valve, at least a sensing part of the actuator being located within a sensing space within said operating space, said sensing space being in communication with both of said first and second valve ports thereby to receive a mixture of fluids, said actuator being arranged to cause axial movement of the valve slider so as to counteract temperature changes of said fluid mixture; wherein the housing parts and operating parts together further define: three openings communicating with the exterior of the valve to form first and second fluid inlets and a mixed fluid outlet, the first and second fluid inlets communicating with said first and second valve ports respectively, at least one of said openings being arranged asymmetrically relative to said axis such that fluid therein flows radially at one side of the axis only; at least one gallery space whereby said asymmetrically arranged opening communicates with said operating space from substantially all radial directions; said sensing space wherein a temperature-sensing part of said actuator is located, the sensing space being in communication with said gallery space indirectly via at least a first intermediate space; a first cylindrical baffle separating said first intermediate space from said gallery space at a first set of angular positions around said axis while permitting radial fluid flow at intervening angular positions via apertures in the first baffle; a second cylindrical baffle separating said first intermediate space (or further intermediate space) from said sensing space at a second set of angular positions around said axis while permitting radial fluid flow at intervening angular positions via apertures in the second baffle; and said first set of angular positions being generally aligned with the intervening positions of the second baffle and vice versa.

By this arrangement, fluid flow between said first gallery space and said sensing space requires flow in circumferential directions, while the general direction of flow is axial. Fluid flowing through each aperture in the first baffle will be divided between plural apertures in the second baffle. These plural streams are divided and parts of each mixed with parts of the other. Thus good mixing can be assured tliroughout the full range of flow rates.

The valve may include means for fixing said first and second sets of angular positions relative to the angular position of said asymmetrical opening. The first baffle may in particular be oriented so that there is no aperture at the part of the gallery most remote from the asymmetrically arranged opening. The first and second sets of angular positions may be fixed only relative to each other, and oriented at random relative to the housing.

Each set of angular positions may total between 150° and 200°, so as to minimise pressure loss while restricting the degree of overlap between said first and second sets of angular po sitions . In the embodiment specifically detailed herein, each baffle comprises two apertures diametrically opposite one another, the positions of the apertures in the second baffle being at ninety degrees to the positions of those in the first baffle. There may be two apertures per baffle, each extending over approximately 90°, for example. Large numbers of small apertures would achieve the desired result but are not necessary, reducing both cost and pressure drop across the baffle.

The baffles need not all have the same number of apertures. The number of apertures in each baffle may be even or odd.

The first and second baffles may be formed at separate axial positions in a single cylindrical baffle member, with said first intermediate space being within said baffle member and said gallery space being outside said baffle member. The relative angular positions of the first and second apertures can be fixed simply by providing the first and second baffles as part of a single cylindrical baffle member. The apertures may be formed simply by cutting a cylindrical notch into a cylindrical baffle member.

Third and, optionally fourth baffles can be formed at further axial positions in the same baffle member, each baffle having apertures at positions rotated relative to those of the previous baffle.

In one embodiment said asymmetrically arranged opening forms the first inlet, while the gallery space surrounds said first baffle, such that fluid from said first inlet opening will flow via at least the first and second baffles prior to mixing with fluid from said second inlet opening. The first inlet may for example be the cold fluid inlet.

In such an embodiment, the first valve port may be located in terms of fluid flow between said first gallery and said first baffle. Said sensing space may be located within said baffle member but separated axially from said first intermediate space, fluid communication between the two being via a second intermediate space outside said baffle member.

The second intermediate space may further be in communication with said second valve port so as to form a mixing space communicating with said sensing space but separated therefrom by a third baffle. The third baffle may also be cylindrical and may separate the second intermediate space from said sensing space at a third set of angular positions with apertures providing said communication at intervening angular positions.

Said actuator may be arranged to act between said baffle member and part of the housing, axial movement of the baffle member in turn effecting the axial movement of the slider.

In the embodiment detailed herein, the first and second inlet openings are asymmetrically arranged and diametrically opposite one another across the valve axis, the second opening communicating with the operating space via a second gallery space and said second annular valve port. The second valve port and the apertures in the second baffle may open into a mixing space. The apertures in the second baffle may be arranged so as to face the second inlet opening and the part of the gallery remote from the second inlet opening.

Said mixing space may form a second intermediate space separated from said sensing space by a third cylindrical baffle at a third set of angular positions around said axis and communicating radially with said sensing space at intervening angular positions via apertures in the third second baffle.

Any combination of the three openings may be asymmetrically arranged relative to the axis of the operating space. The invention is equally applicable in arrangements where the asymmetrically arranged opening referred to forms the mixed fluid outlet. That is to say, the fluid flow through the intermediate spaces may in principle be in the direction from the sensing space to the first gallery space, rather than from the gallery space to the sensing space as in the embodiments detailed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, by reference to the accompanying drawings, in which:

Fig. 1 shows a thermostatic mixing valve in accordance with the prior art;

Fig. 2 shows a cross-sectional front view of a thermostatic mixing valve embodying the present invention;

Fig. 3 is a sectional side view of the valve of Fig. 2 through section K-K of Fig. 2.

Fig. 4 to 7 show respectively cross sections through F-F, G-G, H-H and J-J of

Fig. 2; and

Fig. 8 shows to a larger scale in cross sectional view the cartridge unit of the

Fig. 2 valve including the thermostatically actuated valve member.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Firstly referring to Fig. 1, the casing C of a prior art thermostatic mixing valve TMV has a gallery surrounding an inlet port (e.g. for the cold feed) controlled by a cylindrical valve member VM, movement of the valve_, member VM being effected from a thermostatic actuator TA in response to changes in fluid temperature while a feed duct D extending laterally to the casing C deϊiyers fluid feed F to the gallery G, the gallery being partly defined by a wall portion of the valve member VM. Thus in the TMV the ducts D supply relatively hot and cold feed fluids (e.g. water) respectively while mixed water is discharged via the discharge portion DP. The temperature of the mixed water is controlled by the thermostatic elements TE of the actuator TA. The actuator TA moves the valve member VM against the return spring RS. When the temperature of the water surrounding the elements TE rises, the elements expand and move the valve member VM towards the hot valve seat HVS and away from the cold valve seat CVS to reduce the inflow of hot water and increase the inflow of cold water. Conversely, when the temperature of the water surrounding the elements falls, the elements contract and the return spring moves the valve member towards the cold valve seat and away from the hot valve seat thereby reducing the inflow of cold water and increasing the inflow of hot water, so as to maintain the desired discharge temperature.

As explained above, a drawback in this arrangement is that uneven mixing of the hot and cold fluid flows can lead to insufficient mixing and as a result the element receives a false signal and is unable to control the mixed water temperature satisfactorily.

When there is a high demand for mixed water the hot and cold water streams at the hot and cold water inlets are moving at relatively high velocity. The streams impinge on the valve member and divide to pass round either side of the valve member. Some of the stream passes between the valve member and the hot or cold seat, as appropriate. The momentum of the stream, however, results in a build-up of pressure behind the valve member diametrically opposite to the inlet port. This build up of pressure is sufficient to lead to an uneven distribution of the stream around the gap between the valve member and the seat. There is therefore an uneven distribution of water passing through the valve and this leads to incomplete mixing of the hot and cold water streams. As a result, the element cannot control the mixed water temperature satisfactorily.

It is possible to add deflectors DF to encourage mixing. However, the presence of these causes an increase in turbulent flow leading to an increase in pressure drop across the TMV, particularly at high flows rates, which is undesirable. This leads to difficulties in supplying mixed fluid at the desired temperature, particularly over a wide range of flow rates.

Figs 2 to 8 show a thermostatic mixing valve (TMV) 1 including a device to eliminate the above drawback. The TMV 1 which embodies a design suitable for larger sizes of TMV e.g. of 40mm or 50mm in size, comprises a casing 2 including a main body 2A, a cover 2B and a discharge portion 2C, the main body 2 A including lateral ducts 3, 4 for the cold and hot feeds (water) respectively and a partition wall 5 dividing the body 2A into the cold and hot portions. The cover 2B and discharge portion 2C provide facing seats 6, 7 engageable by end seating surfaces on a cylindrical valve member 8 of slide valve type, an annular (360°) cold inlet port 9 being present at the seat 6 while a corresponding annular hot inlet port 10 is present at seat 7, the size of these ports 9, 10 being controlled by the valve member 8. Controlling movement of the valve member 8 is effected by a thermostatic actuator 11 coupled to the valve member 8 via a spool device 12 ( to be described). To cater for the larger size of TMV, the thermostatic actuator 11 comprises two back-to-back thermostatic devices 13 (i.e. operating in tandem) so enabling the actuator 11 to enjoy the necessary expansion for desired movements of the valve member 8. Each thermostatic device 13 comprises a temperature responsive (expandable) element 14 extending from a flange 15 with a further (non-active) locating part 16 extending from the other side of the flange 15.

The cover 2B has a temperature setting spindle 18 threaded therein with a gland seal 19 between the spindle 18 and the cover 2B, and the spindle 18 reacts with the thermostatic actuator 11 via a rod device 20 for positional setting of the actuator 11. Outward movement of the actuator 11 being resisted by a return spring 21 located between a shoulder 22 on the discharge portion 2C and an annular rib 23 in the valve member 8 while a further outwardly located spring 24 catering for over-expansion of the actuator 11 is positioned between the rib 23 and a top flange on the spool device 12.

The cold feed duct 3 feeds cold feed to an annular gallery 25 surrounding the cold inlet port 9, the inner boundary of gallery 25 being partly defined by a wall of the valve member 8, while a similar gallery 26 is present to receive hot feed supplied via the hot feed duct 4 and surrounds the hot inlet port 10.

Considering now the spool device 12, this device forms the baffle member referred to in the introduction, and comprises an elongate cylindrical body 27, an upper cap 28 including a sleeve 28A to locate the thermostatic actuator 11 and the rod device 20, and a bottom cap 29 having a cup portion 29A to receive the lower end of the actuator 11. A transverse wall 30 located intermediate the ends of the spool body 27 divides the interior of the spool 12 into upper and lower, parts 12A, 12B each defining a fluid conduit. The wall of the upper part 12A carries first annularly arranged apertures 31A (two shown) for location at the top end of the valve member 8 i.e. at the level of the cold inlet port 9, while lower similar second apertures 32A are located at the level of the hot inlet port 10. In this example the apertures 31 A, 32A (two of each) are of elongate slot form, and the apertures 32A are angularly displaced by 90° relative to the apertures 31 A. The spool lower part 12B has similar first and second apertures 3 IB, 32B these apertures 3 IB, 32B being located adjacent the top and bottom ends of the tandem thermostat elements 14 respectively as more clearly shown in Fig. 8, the spool device 12 is linked to the valve member 8 by means of a retainer ring 33, the spool device 12, valve member 8 and actuator 11 forming a valve cartridge unit as can be seen in Fig. 8, while full retention of the parts is effected by the return spring 21 bearing on washer 34, and by the spring 24.

The operation of TMV 1 is substantially as described above wherein the actuator 11 moves the valve member 8 in response to temperature changes in the water surrounding the thermostatic elements 14.

The cold water feed entering through duct 3 passes into the gallery 25 i.e. round the circumference of the valve member 8 and the cold valve seat 6.

The hot water feed entering through duct 4 passes into the gallery 26 i.e. round the circumference of the valve member 8 and the hot valve seat 10. There is a tendency, at high flowrates, for the cold water to pass down the side of the thermostat elements 14 diametrically opposite the cold water supply inlet 3 and for the hot water to pass down the side of the thermostat elements 14 diametrically opposite to the hot supply inlet 4. If this happens, the hot and cold supplies will not be thoroughly mixed and the thermostat actuator 11 will be unable to control the mixed water temperature accurately because the hot and cold supplies are not thoroughly mixed and the temperature at the surface of the thermostat elements 14 does not represent the true mixed water temperature.

Enhanced mixing of hot and cold supplies is achieved in the present valve TMV 1 by the two feed supplies passing through the apertures 31A B, 32A B in the spool device 12 such that they have to change radial direction of flow, in particular by 90 degrees.

After the cold water supply passes between the valve member 8 and the cold valve seat 6, it must find its way to pass radially inwards through apertures 31A in the upper part 12A of the spool device 12. The cold water then passes downwards through the fluid conduit in the spool device 12 and then radially outwards through apertures 32A.

Hot water passes radially inwards between the valve member 8 and hot valve seat 10 to meet the cold water passing radially outwards from apertures 32A.

Mixing takes place. The mixed water passes longitudinally downwards through a chamber 35 between the casing portion 2C and the spool device 12. The mixed water then finds its way to pass radially inwards through apertures 3 IB in the lower spool part 12B.

After passing through apertures 3 IB, the mixed water passes across the thermostat elements 14 and then radially outwards through apertures 32B in the lower part 12B then through chamber 36 in portion 2C, and then to discharge outlet 37.

Apertures 31A are at right angles to apertures 32A while apertures 32A are at right angles to apertures 3 IB. Apertures 3 IB are at right angles to apertures 32B. There is, therefore, no direct route for cold water to pass to the thermostat elements 14 or for hot water to pass to the thermostat elements 14. Consequently by this arrangement the hot and cold feed supplies are thoroughly mixed before passing over the thermostat elements 14. The flow paths of the hot and cold supplies are shown by arrows in Figs. 2 to 8.

In an alternative embodiment (not shown), the spool device 12 is shown rotated through 90° relative to the arrangement shown in Fig. 2 but this has no real affect on the operation of the device: indeed the spool device 12 may be located in the TMV1 at any angular setting.

The skilled reader will appreciate that the invention is not limited to the specific implementations and applications detailed above. Modifications are of course possible. In particular, the form and arrangement of the apertures 31A/B and 32A/B could be different. Only part of the benefit could be applied by utilising only one of the above mentioned stages provided by the spool device 12.

Claims

1. A thermostatic mixing valve comprising housing parts and operating parts accommodated within an operating space defined by the housing parts, said operating space and operating parts being generally cylindrical and having rotational symmetry about an axis of the valve, said parts including: a valve slider movable axially between first and second valve seats so as to define first and second annular valve ports respectively, said first valve port tending to open while the second valve port is closing and vice versa, depending on the direction of movement of said slider; and a temperature-sensitive actuator arranged centrally and extending along the axis of the valve, at least a sensing part of the actuator being located within a sensing space within said operating space, said sensing space being in communication with both of said first and second valve ports thereby to receive a mixture of fluids, said actuator being arranged to cause axial movement of the valve slider so as to counteract temperature changes of said fluid mixture; wherein the housing parts and operating parts together further define: three openings communicating with the exterior of the valve to form first and second fluid inlets and a mixed fluid outlet, the first and second fluid inlets communicating with said first and second valve ports respectively, at least one of said openings being arranged asymmetrically relative to said axis such that fluid therein flows radially at one side of the axis only; at least one gallery space whereby said asymmetrically arranged opening communicates with said operating space from substantially all radial directions; said sensing space wherein a temperature-sensing part of said actuator is located, the sensing space being in communication with said gallery space indirectly via at least a first intermediate space; a first cylindrical baffle separating said first intermediate space from said gallery space at a first set of angular positions around said axis while permitting radial fluid flow at intervening angular positions via apertures in the first baffle; a second cylindrical baffle separating said first intermediate space (or further intermediate space) from said sensing space at a second set of angular positions around said axis while permitting radial fluid flow at intervening angular positions via apertures in the second baffle; and - said first set of angular positions being generally aligned with the intervening positions of the second baffle and vice versa.

2. A valve as claimed in claim 1 including means for fixing said first and second sets of angular positions relative to the angular position of said asymmetrical opening.

3. A valve as claimed in claims 1 or 2 wherein the first baffle is oriented so that there is no aperture at the part of the gallery most remote from the asymmetrically arranged opening.

4. A valve as claimed in any of claims 1 to 3 wherein the first and second sets of angular positions are fixed only relative to each other, and oriented at random relative to the housing.

5. A valve as claimed in any of claims 1 to 4 wherein each set of angular positions total between 150° and 200°, so as to minimise pressure loss while restricting the degree of overlap between said first and second sets of angular positions.

6. A valve as claimed in any of claims 1 to 5 wherein each baffle comprises two apertures diametrically opposite one another, the positions of the apertures in the second baffle being at ninety degrees to the positions of those in the first baffle.

7. A valve as claimed in claim 6 wherein there are two apertures per baffle, each extending over approximately 90°.

8. A valve as claimed in any preceding claim wherein the baffles need not all have the same number of apertures.

9. A valve as claimed in any preceding claim wherein the number of apertures in each baffle are even or odd.

10. A valve as claimed in any preceding claim wherein the first and second baffles are formed at separate axial positions in a single cylindrical baffle member, with said first intermediate space being within said baffle member and said gallery space being outside said baffle member.

11. A valve as claimed in claim 10 wherein the relative angular positions of the first and second apertures are fixed by providing the first and second baffles as part of a single cylindrical baffle member.

12. A valve as claimed in any preceding wherein the apertures are formed by cutting a cylindrical notch into a cylindrical baffle member.

13. A valve as claimed in any preceding claim wherein third and, optionally fourth baffles are fonned at further axial positions in the same baffle member, each baffle having apertures at positions rotated relative to those of the previous baffle.

14. A valve as claimed in any preceding claim wherein said asymmetrically arranged opening forms the first inlet, while the gallery space surrounds said first baffle, such that fluid from said first inlet opening will flow via at least the first and second baffles prior to mixing with fluid from said second inlet opening.

15. A valve as claimed in claim 14 wherein the first inlet is the cold fluid inlet.

16. A valve as claimed in claims 14 or 15 wherein the first valve port is located in terms of fluid flow between said first gallery and said first baffle.

17. A valve as claimed in any preceding claim wherein said sensing space is located within said baffle member but separated axially from said first intermediate space, fluid communication between the two being via a second intermediate space outside said baffle member.

18. A valve as claimed in any preceding claim the second intermediate space is in communication with said second valve port so as to form a mixing space communicating with said sensing space but separated therefrom by a third baffle.

19. A valve as claimed in any preceding claim wherein the third baffle is also cylindrical and separates the second intermediate space from said sensing space at a third set of angular positions with apertures providing said communication at intervening angular positions.

20. A valve as claimed in any preceding claim wherein said actuator is arranged to act between said baffle member and part of the housing, axial movement of the baffle member in turn effecting the axial movement of the slider.

21. A valve as claimed in any preceding claim wherein the first and second inlet openings are asymmetrically arranged and diametrically opposite one another across the valve axis, the second opening communicating with the operating space via a second gallery space and said second annular valve port.

22. A valve as claimed in claim 21 wherein the second valve port and the apertures in the second baffle open into a mixing space.

23. A valve as claimed in claims 21 or 22 wherein the apertures in the second baffle are arranged so as to face the second inlet opening and the part of the gallery remote from the second inlet opening.

24. A valve as claimed in any preceding claim wherein said mixing space forms a second intennediate space separated from said sensing space by a third cylindrical baffle at a third set of angular positions around said axis and communicating radially with said sensing space at intervening angular positions via apertures in the third second baffle.

25. A valve as claimed in any preceding claim wherein any combination of the tliree openings are asymmetrically arranged relative to the axis of the operating space.

26. A valve as claimed in any preceding claim wherein the asymmetrically arranged opening referred to forms the mixed fluid outlet.