GB2051314A

GB2051314A - Mixing valve

Info

Publication number: GB2051314A
Application number: GB8017591A
Authority: GB
Original assignee: IMI Santon Ltd
Current assignee: IMI Santon Ltd
Priority date: 1979-05-31
Filing date: 1980-05-29
Publication date: 1981-01-14
Also published as: GB2051314B

Abstract

A water mixing valve for use with a displacement type water heater a single control spindle 31 which carries a seat closure 32 and a piston 33 which progressively obstructs a cold water outlet 20 whilst progressively opening an outlet 25. Upon rotation of the spindle 31, the closure 32 opens to permit flow of cold water from the inlet 14 to the outlet 20 via passageways in the piston 33 and to the water heater via outlet 25. Displaced hot water is passed to the outlet 20 via a duct 23. <IMAGE>

Description

SPECIFICATION Improvements in fluid mixing valves This invention relates to improvernents in fluid mixing valves. It is particularly concerned with fluid mixing valves for use in mixing hot and cold water. Such mixing valves may be employed in combination with or affixed to a water heater.

In fluid mixing valves of known type, there are frequently provided two separate controls, one for the volume flow rate and the other for the final temperature of the mixed water. These controls are normally provided by separate rotatable handles or levers or other settable or fixable devices installed on or adjacent the valve.

It is an object of the invention to provide a mixing valve suitable for use with a displacement fluid heating unit, which has one control which can be used to supply fluid at any temperature between the fluid input temperature and a predetermined maximum temperature.

According to one aspect of the invention a fluid mixing valve for use with a displacement fluid heating unit has an inlet for connection to a cold fluid source, a first outlet for said cold fluid, a second outlet for delivery of said cold fluid to the displacement heating unit, and a conduit for supplying heated fluid from the heating unit to the first outlet to mix with the cold fluid exiting therefrom, the temperature of said mixed fluid being controllable between cold and a predetermined maximum temperature by a singly operable means, as hereinbefore defined, moveable within the valve body.

By singly operable, we mean, for example, a single rotatable valve spindle with a knob or handle, or a single lever mechanism such that only one control is required to operate the valve and to provide fluid at varying temperatures. The most suitable application for the valve is in mixing water, and the term water is used interchangeably with fluid in this specification.

By a displacement fluid or water heating unit, we mean a heating unit having in normal use a single inlet for cold water and a single outlet for heated water. Heated water will only leave the unit when cold water is admitted to displace the same volume of heated water from the unit.

According to a second aspect of the invention a water mixing valve for use with a displacement water heating unit comprises a body having a chamber extending between a cold water inlet port and a first water outlet port, said body having a seat adjacent the cold water inlet port, a second water outlet port for connection to the inlet of the water heating unit and extending into said chamber intermediate the cold water inlet port and the first water outlet port, and a hot water conduit for connection to the outlet of the water heating unit and arranged to communicate with the first water outlet port such that in use the heated water can mix with the water from the first water outlet port; a valve spindle extending along said chamber and carrying both a closure adapted to engage the seat adjacent the cold water inlet port and a piston moveable along said chamber to obstruct the first and second water outlet ports, said piston having a passageway through which water admitted to the chamber from the cold water inlet port can in use pass to the first water outlet port, the arrangement being such that when the valve spindle is moved in a direction to move the closure away from the seat, the piston progressively removes the obstruction to the second water outlet port, thereby in use permitting increasing quantities of cold water to pass to the heating unit and hence displacing increasing quantities of heated water through the hot water inlet port, whilst progressively increasing the obstruction to the first water outlet port so as to reduce the flow of cold water to the first water outlet port and thereby in use increasing the temperature of the mixed water.

The arrangement of the piston within the chamber may be such that initial movement of the spindle to move the closure from the seat takes place before the piston commences to remove the obstruction to the second water outlet port, with the result that initial opening of the valve results in substantially cold water only being supplied, since no displacement of water in the associated water heating unit will occur. The dimensions of the passageway through the piston and the dimensions of the seat may be arranged to ensure that substantially full flow of cold water to the first water outlet port takes place before heated water is displaced from the water heating unit.

According to a further aspect, the invention comprises a displacement fluid heating unit in combination with a fluid or water mixing valve as hereinbefore defined. The mixing valve is preferably mounted directly to the heater plate which supports the water heating unit from below.

The valve can then be positioned within a downwardly extending portion of the casing for the water heating unit, so that only a suitable control knob for the spindle is seen from outside the casing.

There is preferably sufficient clearance between the piston and the walls of the-chamber to provide a leakage path for cold water from the first inlet port to the first outlet port between the piston and the walls of the cylinder. The piston and the chamber enclosing it are preferably cylindrical.

The presence of the leakage path enables the thermostat in the heating unit to have a higher setting than the maximum temperature of water required, eg 750C where 550C maximum water temperature is required, since when the valve is in any open position there will always be cold water passing through the leakage path to the first outlet port even when the piston has completely obstructed the first outlet port. This cold water mixes with the heated water from the hot water inlet port to provide the warm water at, say, 550C maximum. The operation of the water heating unit at a higher thermostat setting is more efficient in its use of energy, but this is practicable from the safety point of view only if it can be ensured that there is no possibility of the higher temperature water leaving the valve without the admixture of sufficient cold water.The size of the leakage path is such as to provide mixed water at, say, 550C, with the valve fully open. The maximum mixed water temperature is settable by the heater user, if the temperature is found to be too high. The user simply resets the thermostat in the water heating unit at a lower temperature.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing which is a side elevation in section of a fluid mixing valve for use with a displacement water heating unit.

A longitudinally extending body 10 made from a machined metal casting or machined bar has a cylindrical chamber 11 extending along parts of its length. A cold water inlet port 12 enters the chamber 11 at one end. The inlet port 12 is of smaller diameter than, and aligned with the longitudinal axis of chamber 11, and the shoulder between chamber 11 and inlet port 1 2 provides a valve seat 1 3 extending radially relative to the longitudinal axis of chamber 11.

The cold water inlet port 12 turns through 900 adjacent the end of the body 10 and is drilled in this region to provide fixture for a suitable cold water inlet pipe 14.

At the end of chamber 11 spaced from the cold water inlet port 12, the interior of body 10 is stepped radially outwardly in three separate positions before opening at the end of body distant from the cold water inlet port 12. This provides three cylindrical portions 1 5, 16 and 1 7 respectively to the interior, each co-axial with the chamber 11.

The first co-axial portion 1 5 adjacent to chamber 11 is fitted with an annular ring 18 which is recessed on its external cylindrical face to provide a water channel 1 9 and has a radially extending orifice providing a first water outlet port 20 communicating with the channel 1 9 and positioned opposite a corresponding orifice 21 in the wall of body 10. Orifice 21 is drilled to provide a fixture for a mixed water outlet pipe 40. The external cylindrical face of ring 18 has a diameter slightly larger than that of chamber 11 which it adjoins.

On the diametrically opposite side of body 10 from orifice 20, a hot water inlet port 22 is provided communicating with the water channel 1 9. Hot water inlet port 22 has a drilled portion providing fixture for a hot water pipe 23 extending into a water heating unit indicated generally by dashed line 24.

A second water outlet port 25 extends radially outwardly through the body 10 from chamber 11 between the cold water inlet port 1 2 and the first water outlet port 20 and on the same side of the body 10 as the hot water inlet port 22. A threaded pipe 26 is connected into the second water outlet port 25, and leads into the water heating unit 24, terminating in the upper portion thereof. Pipe 26 has a cap 27 to direct the incoming cold water to the bottom portion of the water heating unit 24.

The cap 27 has a small orifice 41 towards its upper portion to prevent back-syphonage.

Returning to the description of the interior of body 10, the second cylindrical portion 1 6 threadediy receives a sleeve 28 which extends outwardly of body 10. Sleeve 28 has a radially outwardly extending flange 29 which abuts an annular face on the end of body 10 distant from the cold water inlet port 1 2. The third cylindrical portion 17 of the interior of body 10 provides an annular recess between the sleeve 28 and body 10, which houses a sealing ring 30 arranged to provide a seal between the body 10 and the flange 29 of the sleeve 28.

A spindle 31 passes through sleeve 28 into chamber 11 and carries a support plate with a resilient washer 32 at its end adjacent the cold water inlet port 12. In the position shown in the drawing the washer 32 is pressed against the seat 13 providing a closure against the cold water in the inlet port 12 which will normally be under pressure.

A piston 33 is also carried on the spindle 31, the piston being spaced along chamber 11 from the support plate and washer 32. Piston 33 is cylindrical, being arranged co-axially with chamber 11, but is dimensioned so that there is a clearance between the chamber 11 and the cylindrical surface of piston 33. This clearance provides a leakage path for cold water from that part of chamber 11 adjacent the seat 13 to the first water outlet port 20. The piston 33 has one or more passageways, shown in dashed line in the drawing, extending axially therethrough, whereby cold water from the cold water inlet port can pass to the first water outlet port 20 when the piston 33 is in the position shown in the drawing.

The axial length of the piston 33 and its position on spindle 31 is such that when washer 32 is pressed against seat 13, the piston cuts off the second water outlet port 25 to the water heating unit from the chamber 11 (with the exception of the leakage path), and does not obstruct the first water outlet port.

Spindle 31 is rotatably supported by the cylindrical wails of sleeve 28, and sealing ring 34 provides the seal between the spindle 31 and the sleeve 29. A relatively highly pitched threaded portion of spindle 31 engages a mating thread on the inner cylindrical walls of sleeve 28, such that anti-clockwise rotation of spindle 31, eg by means of a handle or knob (not shown) causes movement of spindle 31 along the longitudinal axis of chamber 11 in a direction away from the cold water inlet port 1 2. This movement progressively permits increasing quantities of cold water under pressure from the cold water inlet port 12 to enter the chamber 11. Initially cold water will flow directly through piston 33 (and the leakage path) to the first water outlet port 20, since the piston 33 by virtue of a slight overlap of the second water outlet port 25 still substantially prevents cold water from entering the water heating unit 24. The dimensions of the valve parts are such that substantially full flow of cold water can be obtained through the valve at a first spindle position, before water is displaced from the water heating unit 24. Upon further movement of the spindle in the same direction, the piston 33 progressively removes the obstruction to the second water outlet port 25 whilst at the same time progressively increases the obstruction of the first water outlet port 20.An increasing proportion of the cold water from the cold water inlet port 12 flows into the water heating unit 24 thereby displacing increasing quantities of heated water via the hot water inlet port 22 and annular channel 1 9 to mix with the cold water leavingg the first water outlet port 20. Thus, at different spindle positions, hotter or colder water can be obtained.

When rotation of the spindle 31 has moved the piston 33 such that the second water outlet port 25 is substantially unobstructed by piston 33, the first water outlet port 20 is completely obstructed by piston 33, such that all the cold water entering the chamber 11 passes into the water heating unit 24 with the exception of that passing through the leakage path between the piston 33 and the wall of the chamber 11. In this position the valve provides the maximum temperature of the mixed water. The leakage path enables the water heating unit to be operated with a higher thermostat setting than the maximum water temperature required in the mixed water outlet pipe 40. The overlap of the second water outlet port 25 by piston 33 also provides that when the valve is first opened one does not have an outflow of hot water at its maximum temperature.

Claims

1. A fluid mixing valve for use with a displacement fluid heating unit, said valve having an inlet for connection fo a cold fluid source, a first outlet for said cold fluid, a second outlet for delivery of said cold fluid to the displacement heating unit, and a conduit for supplying heated fluid from the heating unit to the first outlet to mix with the cold fluid exiting therefrom, the temperature of said mixed fluid being controllable between cold and a predetermined maximum temperature by a singly operable means, as hereinbefore defined, moveable within the valve body.

2. A fluid mixing valve as claimed in Claim 1 comprising a body having a chamber extending between a cold water inlet port and a first water outlet port, said body having a seat or sealing region adjacent to or at the cold water inlet port, a second water outlet port for connection to the inlet of the water heating unit and extending into said chamber intermediate the cold water inlet port and the first water outlet port, and a hot water conduit for connection to the outlet of the water heating unit and arranged to communicate with the first water outlet port such that in use the heated water can mix with the water from the first water outlet port; a valve spindle extending along said chamber and carrying both a closure adapted to engage the seat or sealing region adjacent to or at the cold water inlet port and a piston moveable along said chamber to obstruct the first and second water outlet ports, said piston having a passageway through which water admitted to the chamber from the cold water inlet port can in use pass to the first water outlet port, the arrangement being such that when the valve spindle is moved in a direction to move the closure away from the seat or sealing region, the piston progressively removes the obstruction to the second water outlet port, thereby in use permitting increasing quantities of cold water to pass to the heating unit and hence displacing increasing quantities of heated water through the hot water inlet port, whilst progressively increasing the obstruction to the first water outlet port so as to reduce the flow of cold water to the first water outlet port and thereby in use increasing the temperature of the mixed water.

3. A water mixing valve as claimed in Claim 2 wherein the arrangement of the piston within the chamber is such that initial movement of the spindle to move the closure from the seat takes place before the piston commences to remove the obstruction to the second water outlet port.

4. A water mixing valve as claimed in Claim 2 or Claim 3 in which the dimensions of the passageway through the piston and the dimensions of the seat are arranged to ensure that substantially full flow of cold water to the first water outlet port takes place before heated water is displaced from the water heating unit.

5. A water mixing valve as claimed in any of Claims 2 to 4 in which there is sufficient clearance between the piston and the walls of the charnber to provide a leakage path for cold water from the first inlet port to the first outlet port.

6. A water mixing valve as claimed in any of Claims 2 to 5 in which the piston and the chamber enclosing it are cylindrical.

7. A fluid mixing valve as claimed in any preceding claim in combination with a displacement fluid heating unit.

8. The combination of Claim 7 wherein the mixing valve is mounted directly to a heater plate which supports the water heating unit from below.

9. The combination as claimed in Claim 8 in which the valve is positioned within a downwardly extending portion of the casing for the water heating unit, with the spindle having a manual control knob operable from outside the casing.

1 0. A fluid mixing valve as hereinbefore described with reference to and as shown in the accompanying drawing.