GB2085121A - Mixing valve - Google Patents

Abstract

A valve for mixing steam and cold water to produce hot water of the type in which a valve (32) controlling the steam inlet 17 is connected to a piston (21) which on one side is subject to the full pressure of cold water from the cold water inlet (16) and on the other side is subject to the pressure of cold water coming from a restricted passage (25) connected to the inlet (16), so that when the valve is in operation, the differential pressure upon the piston causes it to move in the direction to open the steam valve (32) is characterised in that substantially constant temperature control is provided by a thermostat inserted in the hot water outlet (13) Fig. 1, (not shown), and operating a push rod (41) via a capillary inside a flexible tube (39) with the push rod engaging the end of the stem (33) of the steam valve (32). <IMAGE>

Description

SPECIFICATION Improved mixing valve This invention relates to a valve for mixing steam and cold water to provide a supply of hot water and is concerned with the type of valve such as shown in our prior Specification No. 1,220,586.

This type of valve comprises a body, a piston working within the body, an inlet in the body to admit cold water to one side of the piston, another inlet in the body to admit steam to the other side of the piston, a steam valve member connected to the piston to control the admission of steam through the steam valve and a passage of restricted crosssection through which cold water can flow from the cold water inlet to said other side of the piston. The piston has an annularwall on said other side, the space within which constitutes a mixing chamber for the cold water and steam and the piston also has a skirt extending from its annular wall defining an annular space between the wall and the inside of the body, there being passages through said wall through which cold water from said restricted passage can pass into the mixing chamber.

When the mixing valve is not in use and there is no flow of waterth rough the valve, the piston is in the position in which the steam valve member closes the steam inlet and a spring acts on the piston to bias it into this position When the mixing valve is put into operation, the flow of cold water through the passage of restricted cross-section creates a differential pressure across the piston which moves in the direction to allow the steam valve member to open and increase and decrease in demand at the outlet results in opening or closing movement respectively of the steam valve member due to increase or decrease respectively of the differential pressure across the piston.

Such a mixing valve is hereinafter referred to as being "a mixing valve of the type specified".

The object of the invention is to provide a valve of the type specified having means to provide additional control over the steam valve member to achieve substantially constant temperature of the hot water supplied by the valve.

According to the invention we provide a mixing valve of the type specified wherein the steam valve member has a slidable connection with the piston and spring means act upon the steam valve member tending to move it in the direction to open the steam inlet when the piston is caused to move upon the mixing valve being put into operation, the steam valve member being additionally under the control of a temperature responsive device which is under the influence of the temperature of the hot water delivered by the mixing valve, said device having a thermally expansible substance or material which transmits movement to the steam valve member via a mechanical connection.

Conveniently the steam valve member engages a valve seating on the steam inlet which is at the end of a tube extending centrally into the mixing valve body, the piston being mounted for axially directed sliding movement on the outside of said tube and the steam valve member having a stem which passes slidably and centrally through the end of the piston which is adjacent the valve seating.

The spring means which acts upon the steam valve member may comprise a coil spring disposed about said stem, having its one end engaging the said end of the piston and its other end engaging an abutment on the stem, so as to urge the steam valve member in the axial direction away from the steam inlet valve seating.

The said mechanical connection may include a push rod mounted in the body of the mixing valve for sliding movement, the push rod being axially in line with said stem and having one end in engagement with the free end of the stem.

The invention is hereinafter described by way of example with reference to one embodiment which is illustrated in the accompanying drawings wherein: FIGURE 1 is a view in plan to show the connections to the valve body for steam and water and the outlet connection for hot water; FIGURE 2 is a section on the line 2-2 of Figure 1; and FIGURE 3 is a section on the line 3-3 of Figure 1.

In the following description reference may be made to upper and lower parts of elements and this is in relation to the mixing valve occupying the position as shown in Figures 2 and 3, although the valve may be mounted on a vertical surface by means of its mounting bracket 10 in which case it occupies a position which is turned through 90" as compared with Figures 2 and 3.

Referring to Figure 1, the inlet connection for cold water is shown at 11 and the inlet connection for the steam at 12, with the outlet connection for delivery of hot water being indicated at 13. Suitable supply lines would be connected to the inlet connections 11 and 12 with their own master on/off controls which are not shown in the drawings and do not form part of the valve according to the invention.

The hot water delivered from the outlet connection 13 may be piped to one or more washing stations (e.g. shower heads) or other types of station where hot water is required on demand. Such station or stations would have their own individual on/off controls.

Referring now particularly to Figures 2 and 3, the mixing valve has a body comprising a lower part 14 and an upper part 15 which is of generally cylindrical configuration, the lower part 14 being provided at one side with an inlet 16 for connection to the cold water inlet connection 11 and at the other side an inlet 17 for connection to the steam inlet connection 12. The lower part 14 of the body also has integrally formed therewith a tube 18 which extends centrally and axially into the upper part 15 of the body and which communicates with the steam inlet 17 as shown in Figure 2. At the upper end of the tube 18 there is a valve seating assembly 19 with the actual valve seat 20 being mounted within the assembly 19 and being engaged by the steam valve member as hereinafter described to control the admission of steam to the mixing valve.

Mounted within the upper part 15 of the body, so as to be slidable upon the outside ofthe tube 18, is a piston 21 which is generally of truncated conical form and has an annular wall 22 extending from its base and a skirt 23 extending from the annular wall and engaging the interior surface ofthe upper part 15 of the body. A number of passages 24 extend through the annular wall of the piston in the part thereof between the base of the piston and the skirt 23.

Cold water passes into the interior of the mixing valve from the inlet 16 via a passage 25 of restricted cross-section as compared with that of the inlet 16 and the cross-sectional area of the passage 25, through which the cold water passes, is controlled by a valve member 26 which can be adjusted to provide for a desired rate of flow of cold waterthrough the passage 25.

The upper end ofthe piston which is indicated at 29 extends around and beyond the valve seating assembly 19 and has fitted into the upper end two plates 27 and 28, the upper plate 27 being engaged by one end of a coil spring 30, the other end of which engages the inner face of an end cap 31 secured to this end of the mixing valve body.

The spring 30 imposes a fixed loading upon the upper end of the piston tending to move it in the downwards direction as shown in the drawings and maintaining the piston and steam valve member in the closed position when the valve is not in operation and there is no flow of fluid through the valve body.

The steam valve member shown at 32 has its lower end engaging the valve seating 20 and has a stem 33 extending upwardly and centrally of the valve body and also a circular flange which engages beneath the lower plate 28 at the top of the piston so that the load imposed by the spring 30 is transmitted via the plates 27 and 28 to the steam valve member to urge it towards a closed position and maintain it in the closed position when the mixing valve is not in operation. When the piston moves upwardly during operation of the mixing valve, the steam valve member 32 follows the movement of the piston and allows admission of steam due to the action of a further coil spring indicated at 34 acting between the plate 27 and an abutment in the form of a ring 35 secured to the upper end ofthe stem 33.

In operation of the mixing valve, when an on/off control at one ofthe stations such as a shower head is opened, the pressure of the cold water via the inlet 16 underneath the piston 21 causes this to move upwardly so that cold water can pass via the passage 25 and a further short passage 36 into the space between the skirt 23 and the base of the piston and then through the passages 24 in the wall of the piston into the interior thereof. There is also a clearance between the outside of the piston 21 and the interior of the housing and a further clearance between the interior of the piston and the tube 78, through which water can pass.At the same time, upward movement of the piston allows the steam valve member 32 to open to admit steam into the space 37 where it immediately mixes with cold water which has passed upwardly into the space 37 past the ring 38 which is secured around the outside of the seating assembly 19. Thereafter during operation of the valve, increase or decrease in the demand for hot water at the outlet results in corresponding move ment ofthe piston to move the steam valve member 32 in the appropriate direction to respectively increase or decrease the flow of steam into the mix ing valve in the generally known manner of operation of this valve.

To provide for substantially constant temperature of the hotwaterdelivered from the mixing valve, a temperature responsive device of thermostat is combined with the valve so far described with the actuator of such thermostat being located in the hot water outlet 13 and connected by a flexible tube 39 to the upper end of a sleeve 40 which is formed as an integral extension at the upper end of the cap 31.

Within the sleeve 40 there is slidably mounted a push rod 41 which at its lower end bears against the upper end of the stem 33, thus providing a mechanical connection between the thermostat and the steam valve member 32. Expansion of the working substance of the thermostat due to rise in temperature of the hot water at the outlet, above a preselected value will produce a corresponding downwards movement of the push rod 41 and corresponding movement of the steam valve member 32 towards a closed position to reduce the admission of steam to the mixing valve. A drop in temperature at the outlet below the said preselected value will allow the steam valve member 32 to make opening movement under the influence of its spring 34 to admit more steam to the mixing valve.

The thermostat comprises a bulb containing the volatile liquid Freon, connected to a capillary tube into which the liquid can expand. The capillary tube extends through the flexible tube 39 and the expansion and contraction of the liquid causes movement of the pushrod 41. The connection between the expanding liquid and the pushrod can be adjusted by rotation of the end cap 42 which is therefore used to pre-set the thermostat operating temperature.

Claims (5)

1. A mixing valve of the type specified wherein the steam valve member has a slidable connection with the piston and spring means act upon the steam valve member tending to move it in the direction to open the steam inlet when the piston is caused to move upon the mixing valve being put into operation, the steam valve member being additionally underthe control of a temperature responsive device which is under the influence ofthetempera- ture of the hot water delivered by the mixing valve, said device having a thermally expansible substance or material which transmits movement to the steam valve member via a mechanical connection.

2. A mixing valve according to Claim 1 wherein the steam valve member engages a valve seating of the steam inlet which is at the end of a tube extend; ing centrally into the mixing valve body, the piston being mounted for axially directed sliding movement on the outside of said tube, the steam valve member having a stem which passes slidably and centrally through the end ofthe piston which is adjacent the valve seating.

3. A mixing valve according to Claim 2 wherein the spring means which acts upon the steam valve member comprises a coil spring disposed about said stem having its one end engaging the said end of the piston and its other end engaging an abutment on the stem so as to urgethe steam valve memberin the axial direction away from the steam inlet valve seating.

4. A mixing valve according to Claim 3 wherein said mechanical connection includes a push rod mounted in the body of the mixing valve for sliding movement, the push rod being axially in line with said stem and having one end in engagement with the free end of the stem.

5. A mixing valve substantially as hereinbefore described with reference to and as shown in the accompanying drawings.