GB2487596A - Water heating apparatus comprising a safety valve - Google Patents

Abstract

A water heating apparatus comprises a tank (1a, fig.1) having a water supply inlet and a hot water supply outlet. The tank contains a heating tube 7 having a fluid inlet and outlet, where the fluid inlet is connected to a source of heated fluid, such as that provided by a boiler, so that heated fluid flowing through the heating tube heats water in the tank. The water heating apparatus also has a safety device 10 to inhibit or reduce the flow of fluid through the heating tube. The safety device comprises a valve 11 biased to a closed condition, a valve control element biased to a first position in which the valve control element acts against the valve biasing to hold the valve open, and a tank temperature responsive member 12. In operation, if the temperature within the tank exceeds an operating temperature or temperature range, the temperature responsive member moves the valve control element from the first position to a second position in which the valve control member no longer acts against the valve biasing. In a further aspect, a safety device is disclosed comprising a valve biased to either an open condition or a closed condition.

Description

inaaratus This invention relates to a heating apparatus.

Domestic and commercial water heating systems may use unvented and other hot water tanks. Such a water heating tank will have an inlet coupling for connection to a water supply which may be a mains water supply, a header tank or other supply, for example, and an outlet coupling for connection to pipe work to supply hot water to outlet taps (faucets) and/or appliances such as washing machines, dishwashers, showers and the like. The tank contains a coiled pipe or tube known as a primary coil. The primary coil has a coil inlet ("primary flow") and a coil outlet (primary return") to enable the primary coil to be coupled into the hot water feed of a water heating system external to the tank to enable, under the control of a thermostat, water heated by the external heating system to be circulated through the primary coil to heat water within the tank. The external heating system may be for example a gas, oil or electric boiler of a central heating system, an electric heater or a renewable source. The heating of the water in the tank is thus indirect because water already heated by another heating system is used to heat water in the tank.

Building regulaflons require that all such indirect unvented water heating apparatus are provided with a safety device to shut off the flow of hot water from the external heating system to the primary coil in the event of overheating or fault. The safety device is required to be fail safe and non self-resefting. The safety device commonly used is a spring loaded two port motorised valve as shown in for example our UK Patent No 0B2431 461 B. Power to the motor drive of the valve is supplied via a factory prewired, high limit thermal cut-out wired in series with the valve and responsive to the temperature within the tank. When power is applied to the valve, the motor drive keeps the valve open against the spring-biasing. However, in the event of overheating, the thermostat cuts out, removing the power to the valve motor drive and so allowing the spring-biasing to close the valve. Such a device requires an electricity supply which may in some circumstances be inconvenient to provide and moreover could result in the valve inadvertently being closed because of a failure of the electricity supply.

In one aspect, the present invention provides a water heating apparatus in which a safety cut-off device to cut-off flow to a heating tube within the apparatus comprises a valve biased to a closed condition in which flow of fluid through the heating tube is inhibited or reduced, a valve control member to hold the valve open against the valve biasing and a temperature responsive mechanical actuator to move the valve control element to a position in which the valve control member no longer acts against the valve biasing in the event the temperature within the tank exceeds an operating temperature or operating temperature range.

In one aspect, the present invention provides a water heating apparatus comprising a tank having a water inlet coupling to be coupled in use to a water supply and a water outlet coupling to output hot water, the tank containing a heating tube having a fluid inlet and a fluid outlet, the fluid inlet to be coupled to a source of heated fluid such that, in operation, heated fluid flowing through the heating tube heats water surrounding the heating tube in the tank, the water heating apparatus having a safety device to inhibit or at least reduce the flow of fluid through the heating tube, the safety device comprising a valve biased to a closed condition in which flow of fluid through the heating tube is inhibited or reduced, a valve control element biased to a first position in which the valve control element acts against the valve biasing to hold the valve open and a temperature responsive member responsive to a temperature within the tank to move the valve control element from the first position to a second position in which the valve control member no longer acts against the valve biasing in the event the temperature within the tank exceeds an operating temperature or operating temperature range.

Embodiments of the invention enable the provision of water heating apparatus having a safety cut-off device that operates mechanically and does not require an electricity supply.

The valve control element may be a control member which may be biased into the first position and a cam cooperating with the control member and the valve to cause the valve to move towards a closed condition in the event the temperature responsive member moves the valve control member from the first position to the second position. The control member may be latched in the first position. The control member may be received in a slot having a recess into which the control member is biased so as to latch the control arm in the first position. The slot may be provided in a housing of the safety device and a portion of control member may project from the slot to provide a user-operable control to enable a user manually to return the valve control element to the first position in the event the temperature within the tank drops back to an operating temperature or a temperature in the operating temperature range.

The valve control element may be manually resettable to the first position in the event the temperature within the tank drops back to an operating temperature or a temperature in the operating temperature range.

The temperature responsive member may extend into the tank so as in use to be submersed in water in the tank to sense the temperature of the water.

The temperature responsive member may contain a thermally expandable material and a piston which is moved by expansion of the thermally expandable material to move the valve control element from the first position to the second position in the event the temperature within the tank exceeds an operating temperature or operating temperature range. The thermally expandable material may be any appropriate material suitable for the temperature range of the device (for example: -wax). The piston may provide or be coupled to a pin to move, for example push, the valve control etement from the first position to the second position in the event the temperature within the tank exceeds an operating temperature or operating temperature range.

In an embodiment, a water heating apparatus has a tank having a water inlet coupling and a water outlet coupling. A tube within the tank has inlet and outlet couplings for coupling to an external heating system to enable fluid heated by the external heating system to be circulated through the tube within the tank to heat water within the tank. A safety device shuts off the flow of fluid from the external heating system in the event of overheating or fault. The safety device is a thermally responsive mechanical safety device.

In an example, the safety device has a cut-off valve biased into a closed position but held open against the biasing by means of a mechanical arrangement and a temperature probe that is designed to be submersed in water within the tank. Whilst the Temperature sensed by the temperature probe is within required operational limits, the mechanical arrangement is in a first state and holds the cut-off valve open. However, if the temperature sensed by the temperature probe exceeds a required operating limit, then the mechanical arrangement adopts a second state allowing the biasing mechanism to close the cut-off valve. The mechanical arrangement may be re-settable by a user.

In an embodiment, the mechanical arrangement may comprise a control arm that cooperates with a temperature responsive probe, one end of which is inserted into the tank so that it is subject to a temperature within the tank and the other end of which has a movable or expandable element that cooperates with the control arm to move the control arm from a first position in which the control arm counteracts a valve biasing mechanism to hold the valve open to a second position in which the control arm allows the biasing mechanism to close the valve when the temperature experienced by the one end of the probe exceeds the pre-set temperature. In an embodiment, the thermal probe has a thermally conductive body, such as a metal body, containing a chamber of a thermally expandable material, such as a wax, that expands when heated to move the movable or expandable element, which may be in the form of a pin, towards the control arm such that, as the pre-set temperature is exceeded, the pin causes the control arm to move to the second position to allow the biasing mechanism to close the valve. The control arm may cooperate with a cam mechanism that ensures that the valve is held in either the open or the closed state, dependent upon whether the control arm is in the first or the second position. A part of the control arm may extend beyond a housing of the valve to enable it to be returned to the first position by a user when the temperature within the tank no longer exceeds the pre-set temperature.

The present invention also provides a safety device comprising a valve biased to a closed condition, a valve control element biased to a first position in which the valve control element acts against the valve biasing to hold the valve in an open condition and a temperature responsive member responsive to a temperature within an environment to move the valve control element from the first position to a second position in which the valve control member no longer acts against the valve biasing in the event the temperature within the environment exceeds an operating temperature or operating temperature range.

The safety device may have any of the safety device features mentioned above. The safety device could for example be used in a solar station.

An embodiment provides a water heating apparatus having a safety device which without the use of any electrical intervention is in compliance with the requirements of Clauses 3.18, 3.28,3.29 and 3.30 of the Building Regulations 2000, Approved Document Part G3, Sanitation, hot water safety and water efficiency for United Kingdom, Scotland and Northern Ireland.

An embodiment provides a safety device for water heating apparatus that has a temperature limiter which, when a set temperature of a mechanical temperature probe is reached, activates a latch/lever to interrupt the supply of heat to a water vessel of the apparatus. In an embodiment the safety device is a non-self-resetting device that requires user or consumer intervention to reset it.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which; Figure 1 shows a perspective view of a water heating apparatus embodying the invention; Figure 2 shows a schematic diagram to illustrate some of the functionality of a water heating apparatus embodying the invention; Figure 3 shows a side view, part cut-away, of a primary flow safety device of a water heating apparatus embodying the invention; Figure 4 shows a view from below of the primary flow safety device shown in Figure 3; Figure 5 shows a sectional view taken along line A-A in Figure 4 of the safety device without a temperature probe of the safety device; Figures Ba to 6d show perspective views of component parts of the safety device; and Figure 7 shows a very diagrammatic perspective view of part of the primary flow safety device illustrating the relationship between a cam and a swing arm of the primary flow safety device: Figure 7b shows a sectional view taken along line A-A in Figure 7d of the safety device; Figure 7ba shows part of Figure 7b on an enlarged scale; Figure 7c shows a perspective view of part of primary flow safety device further to illustrate the relationship between the cam, swing arm and valve biasing springs; Figure 7ca shows a plan view of the part of primary flow safety device shown in Figure 7c but with the swing arm omitted; Figure 7d shows a cross-sectional view taken along the line C-C in Figure 5 of the primary flow safety device in a normal operating condition; and Figure 7e shows a cross-sectional view similar to Figure 7d but with the primary flow safety device in an abnormal operating condition, that is when the temperature limit has been exceeded.

Referring now to Figures 1 and 2, a water heating apparatus 1 comprises a tank la which may be for example a copper or a stainless steel tank. The tank la has a water inlet coupling 2 to be coupled in use to a water supply such as a main water supply or a header tank and a water outlet coupling 3 to be coupled in use to pipe work for supplying hot water to, for example, taps (faucets) and/or appliances. A primary coil or tube 7 (Figure 2) is provided within the tank and primary flow and return couplings 4 and are carried by the tank for coupling to an external heating system (not shown) to enable, under the control of a thermostat 6, water heated by the external heating system to be circulated through a primary coil within the tank (see Figure 2) to heat water within the tank, The external heating system may be for example a gas, oil or electric boiler of a central heating system or an electric heater. The heating of the water in the tank is thus indirect because water already heated by another heating system is used to heat water in the tank. The tank may have an electrically powered immersion heater 8 to provide a back up or supplemental (boost') heat source.

The water heating apparatus 1 also has a safety device 10 to shut off the flow of hot water from the external heating system to the primary coil in the event of overheating or fault. The safety device 10 is not motorised but rather is a thermally responsive mechanical safety device. The safety device comprises a cut-off valve 11 (Figure 2) which is biased by a biasing mechanism into a closed position but which is held open against the biasing by means of a mechanical arrangement. The safety device also has a temperature probe 12 that is designed to be submersed in water within the tank. Whilst the temperature sensed by the temperature probe 12 is within required operating limits, the mechanical arrangement of the safety device is in a first state and holds the cut-off valve open against the biasing of the biasing mechanism. However, if the temperature sensed by the temperature probe 12 exceeds a certain pre-set temperature, then the mechanical arrangement adopts a second state allowing the biasing mechanism to close the cut-off valve 11. The mechanical arrangement may be re-settable by a user.

Referring now to Figures 3 to Sd, the safety device 4 has a valve control 40 mounted within a housing and coupled to the temperature probe 12. The temperature probe 12 contains a thermally expandable material, such as a wax, that expands as the temperature of the water in the tank increases to push a pin 13 of the temperature probe outwardly from the other end of the temperature probe. )

A swing arm 14 of the valve control 40 extends from a slot 26 of the valve housing 20 and is spring-biased into a recess 27 of the slot 26.

The swing arm 14 cooperates with a cam 15 mounted in the housing 20 which in turn cooperates with the valve (not shown). The swing arm 14 is biased by a swing arm spring (not shown) into a swing arm retaining recess 27 of the slot 26, so holding or latching the swing arm and thus the cam 15 in a first position. ln this first position, the valve is held open against the valve spring biasing force allowing heating water to flow through the primary coil.

As the water within the tank la heats up, the thermally expandable material within the temperature probe 12 heats up pushing out the pin 13 of the temperature probe. The configuration is such that if the temperature of the water exceeds the operating position of the temperature probe 12, the pin 13 pushes on the swing arm 14 counteracting the biasing force of the swing arm spring and causing the swing arm 14 to move out of the swing arm retaining recess 27, so unlatching the swing arm 14 and thus the cam 15. Once the swing arm 14 is unlatched, the spring biasing force of the valve causes the cam 15 to rotate to a second position causing the valve to close to cut-off the flow of heating water to the primary coil. This is the second state of the safety device.

Once the temperature of the water in the tank la drops below the operating position of the temperature probe 12, then a user or consumer can move the swing arm 14 back to its normal position so that the swing arm 14 and thus the cam 15 are latched in the first position to again hold the valve open against the valve spring biasing force, allowing the heating water again to flow through the primary coil.

In this example the operating position of the temperature probe is 85 degrees Celsius ± 5 degrees Celsius, that is the valve will close when the temperature reaches 90°C and will reset at 80°C, this temperature difference resulting from the hysteresis of the thermally expandable material, for example wax, within the temperature probe. The temperatures at which the valve is designed to close and then re-open or reset may be adapted to meet different requirements and for example may vary dependent upon the particular thermally expandable material used within the temperature probe.

Further details of the example shown in Figures 3 to 6d will now be described. It will however be appreciated that these details are simply one way in which the safety device may be implemented and that the principle may be implemented in different ways.

As shown by Figures 3 to 5 and 6a, the housing or main body 20 of the valve control 40 has a rectangular frame member 24 having two opposed major faces 24a and 24b coupled by opposed minor faces 24c and 24d. The slot 26 is formed in one of the minor faces 24c. An aperture formed in the major face 24b is coupled to the valve coupling 30a of a two port valve body 30 which may be of a commercially available standard type. A body 21 is mounted within the housing to hold the cam 15, the swing arm 14 and valve biasing springs 210 and 220. As shown a tubular projection 28 of the cam 15 is received in a tubular recess 22 of the body 21 so that the cam can rotate relative to the body about an axis defined by the tubular projection 28. The swing arm 14 has a 90 degree bent flange 14a at the end which projects from the housing 20 to facilitate manipulation by a user. An aperture 14b is provided closer to the other end 14e of the swing arm 14 to enable it to be mounted to a pin 25 of the cam. The swing arm has a nose 14d projecting from a region of one long edge adjacent the aperture 14b.

The valve biasing springs are best shown in Figures 7b to 7e. As is evident from these Figures, each valve biasing spring 210 and 220 has end hooks 210a and 21Db and 220a and 220b. End hooks 210a and 220a are mounted to respective posts 140 and 141 projecting from the cam 15 whilst and end hooks 21 Ob and 220b are mounted to respective posts 21a and 21 b of the body 21. The valve biasing springs bias the cam into a position holding the valve closed.

As can best be seen from Figures 7a and 7c, the end 14e of the swing arm 14 has opposed notch 14g which receives one, 29b, of two off-centre pins 29a and 29b provided on a support element 29c mounted to the cam 15 so that the end 1 4e is positioned between the two off-centre pins 29a and 29b and the second pin 29a is adjacent the nose 14d. The arrangement of the pins 25, 29a, 29b and the swing arm 14 ensures that a rotation of the cam 15 leads to a rotation of the swing arm 14 and vice versa.

The pin 13 of the temperature probe contacts the nose 1 4d of the swing arm 14 at a distance from the support element 29c. Figure 7d shows a cross-sectional view taken along the line C-C in Figure 5 to illustrate the position of the swing arm 14 when the valve is in a normal operating condition, that is when the temperature of the water does not exceed the temperature at which the temperature probe 12 is designed to operate to close the valve.

If the water temperature increases the beyond the operating range of the valve, the expansion of the thermally expandable material causes the pin 13 to push on the nose 14d of the swing arm 14 in the direction indicated by arrow 40 in Figure 7a against the biasing force 43 of the swing arm biasing spring (not shown) so that the swing arm 14 is tilted about the support element 29c towards the cam 15. This causes the end of the swing arm 14 comprising the bent flange 14a to be pushed out of the recess 27 in the direction indicated by arrow 41 As soon as the swing arm 14 is no longer constrained by the edge of the recess 27, the spring biasing force provided by the valve biasing springs 210 and 220 (see for example Figure 7c) rotates the cam 15 to the second position in the direction indicated by arrow 42. The rotation of the cam 15 also causes a rotation of the swing arm 14 about the axis defined by pin 25 and causes the end of the swing arm 14 comprising the bent flange 14a to move along the slot 26 in the direction indicated by arrow 43, as illustrated by Figure 7e.

In the example described above, the temperature probe contains a material which expands with temperature to cause a pin to push the swing arm form its latched position. Other approaches may be possible such as a simple thermally expanding rod or a bimetal device provided that they meet any relevant standards regulations.

It might also be possible for the temperature probe to extend only part way into the wall of the cylinder, that is not into the water, or to contact the outside of the tank cylinder (underneath any lagging) provide that a sufficiently rapid response time could be achieved.

Although the above-described arrangement has been shown to be particularly robust, it may also be possible to combine or integrate the cam and swing arm.

The tube for transporting the heated fluid through the tank need not necessarily be a coil, other shapes are possible. It may also be possible in some circumstances to use other heating liquids/fluids for circulation through the tube, such as oil. Also the fluid may or may not be recirculated.

Although the above describes application to a water heating apparatus, the present invention may be used in other heating apparatus and in temperature regulating circumstances, for example in heating apparatus for liquids other than water or in solar heating stations to control the glycol mixture.. It may also be possible to use the safety device in circumstances where a fluid such as water is being cooled rather than heated. Where appropriate the word Water" should be read as "water or other media" that the apparatus or device embodying eth invention may come into contact with during its application. It will of course be appreciated that the type of media" that that the temperature probe may come into contact with, the construction of the temperature probe and that of the main body of the device will be such as to be suitable for the application in which it would be required to operate.

The present invention may also be used to control closing rather than opening of a valve.