GB1604427A - Expansion boilers - Google Patents

Description

(54) EXPANSION BOILERS (71) We, W. M. STILL & SONS LIM ITED, a British Company, of Fellows Road, Hastings, East Sussex, TN34 3TX, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to water heaters or boilers of the type known as "expansion boilers" in which during use water is heated continuously to boiling temperature.

Expansion boilers of the type to which this invention relates comprise a water container or vessel connected to a cold water supply tank or cistern and heated either by gas or electricity, a tray or the like being located in the upper region thereof with the side and end walls of the tray extending above the predetermined normal water level in the vessel. A draw-off tap communicates with the tray. When the draw-off tap is opened to discharge water from the tray and hence from the boiler, additional heat is automatically supplied to heat the water in the vessel causing it to expand and the level to rise in the vessel until it overflows the top edges of the walls of the tray which act in effect as a 'weir'. This acts to keep the tray full of boiling water. When the draw-off tap is closed the heat supplied to the vessel is automatically reduced.Cold water is fed into the vessel from a supply tank, cistern or the like to replace that discharged from the boiler. Such a boiler will hereafter be referred to as "an expansion boiler of the type described".

An expansion boiler of the type described in accordance with this invention is characterised in that the water vessel or container is provided with external fins over at least a portion (preferably the lower portion) of the side faces of the vessel to enhance the heat exchange between an external heater and the water contained within the vessel, the crosssection of the water vessel or container being substantially triangular with the apex portion positioned above the heater. Such an arrangement is thermally very efficient and hence enables a more compact heater vessel to be used. This has the advantage of using less counterspace if the boiler is to be used as part of standard catering equipment and also means that the vessel can be shorter so that its top can readily be reached and hence used to keep teapots and the like, warm.

The top of the heater vessel can be open or provided with a removable lid giving easy access to clean, de-scale and overhaul the boiler. For example, the tray which is located in the top part of the heater vessel can readily be removed through the top portion thereof.

A removable filter is preferably provided between the tray and the inlet to the draw-off tap to enable hard, loose pieces of scale and other water contamination to be removed from the water before this is discharged from the tap.

Because the boiler or heater vessel is of smaller volume than presently existing comparable vessels less heat energy and time is required to reach the operating conditions with the water at boiling temperature.

The cold water supply tank or cistern may be positioned at the side of the water heater vessel as described and claimed in the specification of our co-pending Application No. 26002/78 (Serial No 1604428 and may be provided with a relatively small and silent water float valve to control the water level in the cistern. For example, a 'torbeck' equilibrium float valve may be used.

Since such small float valves would tend to oscillate rapidly when connected to mains water supply resulting in 'water hammer' or the like, a needle valve regulating device is preferably fitted to the main supply pipe leading to the cistern which regulating device may be adjusted depending upon the pressure of the water in the mains.

The invention will now be further described by way of example with reference to the drawings accompanying the Provisional Specification in which: Figure 1 is a diagrammatic sketch of an expansion boiler apparatus of the type described in accordance with this invention; and Figure 2 is a section through the water heater vessel, or boiler.

Referring to Figure 1, the expansion apparatus comprises a vessel 2 which is heated by means of a gas burner 4. Cold water is fed to a heating chamber within the vessel from a cistern 6 through a U-shaped connecting tube 8 the connection to the heated chamber being through a cleaning eye 10 and being open to atmosphere through a vent pipe 9.

The cistern 6 which is positioned adjacent to, and at the side of, the heating chamber, is connected to mains water supply through an inlet pipe 12 having a needle water flow regulator 14 which can be adjusted in accordance with the pressure of the mains supply.

The water lever within the cistern which is generally indicated at 16, is maintained at that level by means of a silent small water float valve generally indicated at 18 which may for example be of a 'Torbeck' equilibrium float valve. The water level 20 within the heater vessel or chamber 2 is maintained the same as that in the cistern 6 and the level occurs approximately half way up a water collecting tray 22 mounted within the top portion of the heater chamber. The top edge 24 of the side and end walls of the tray 22 constitute a weir, and normally the water in the tray is maintained separate from the water in the body of the heater chamber.

A drw-off tap 26 is connected to an outlet 28 at the bottom of the tray through a pipe 30, a removable filter 32 being positioned between the water in the tray and the outlet 28 so as to remove impurities from the water such as loose pieces of scale.

Gas for the burner 4 is fed from a gas supply through a pipe 34 containing a 'relay' valve 36. A by-pass pipe 38 extends from the relay valve 36 through a 'weep' valve 40 which is interlocked with the valve of the tap 26 and returns to the pipe 34 on the other side of the relay valve 36.

When the draw-off tap is closed and the water level is at the position indicated, gas flows to the burner 4 at a sufficient rate to maintain the temperature of the water in the heater chamber at approximately 100"C.

This gas passes through the relay valve 36 and through the 'weep' valve 40.

When the tap 26 is opened to discharge boiling water from the tray 22, the 'weep' valve 40 is also adjusted causing the relay valve to open so that full gas supply is fed to the burner.

With the resulting increase in the temperature of the water in the heater chamber its volume expands, causing the level of the hot water to rise until it spills over the 'weir' 24 filling the collecting tray. As water is drawnoff this is replaced from the cistern 6 which remains cold since it is separated from the hot water in the heater chamber by means of the U-shaped pipe. The cold water entering the bottom of the heater chamber is again heated and subsequently discharged from the collecting tray. As the level of the water in the cistern drops the float valve 18 operates to allow fresh mains water to refill the cistern to the desired level.

When the draw-off tap is closed and the gas flow to the burner is only at the by-pass flow rate. hot water will slowly evaporate from the heating chamber the water being replaced from the cistern.

Referring to Figure 2, it will be seen that the vessel generally indicated at 2, has an inner heated water vessel 42 which is triangular in cross-section with the apex of the triangle being positioned above the burner.

The heating container or vessel 42 is, as can be seen in Figure 2, positioned within the casing 2 and is provided with a number of copper fins 44 brazed to its outer surface over the lower portion thereof. These fins act substantially to increase the heat exchange between the water in the vessel 42 and the hot gases flowing up around the vessel as indicated by the arrows, from the burner 4.

This enables the efficiency of the boiler to be very significantly increased resulting in a lower heat-up time and a more compactly dimensioned boiler.

The upper end of the vessel 42 is open but is provided with a removable cover 46.

When it is desired to clean, repair or maintain the boiler, the cover 46 can be removed and the tray 24 readily lifted out from the open top of the vessel giving access to the interior of the boiler. This enables the boiler to be cleaned without having to disconnect the appliance from the gas and water supplies.

WHAT WE CLAIM IS: 1. An expansion boiler of the type described characterised in that the water vessel or container is provided wih external fins on at least a portion of the side faces of the vessel to enhance the heat exchange between an external heater and water contained within the vessel, the cross-section of the water vessel or container being substantially triangular with the apex portion positioned above the heater.

2. A boiler as claimed in Claim I in which the fins are provided over the lower portion of the side faces of the vessel.

3. A boiler as claimed in either of the preceding claims wherein the water heater vessel or container is located within an outer container to convey hot gases from the heater around the inner container, the heat exchange fins being provided on the outer side face of the inner container and projecting into the space between the inner container and the outer vessel.

4. A boiler as claimed in any one of the preceding claims wherein a filter is provided between the tray and the inlet to the draw-off tap.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (1)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   Referring to Figure 1, the expansion apparatus comprises a vessel 2 which is heated by means of a gas burner 4. Cold water is fed to a heating chamber within the vessel from a cistern 6 through a U-shaped connecting tube 8 the connection to the heated chamber being through a cleaning eye 10 and being open to atmosphere through a vent pipe 9.

   The cistern 6 which is positioned adjacent to, and at the side of, the heating chamber, is connected to mains water supply through an inlet pipe 12 having a needle water flow regulator 14 which can be adjusted in accordance with the pressure of the mains supply.

   The water lever within the cistern which is generally indicated at 16, is maintained at that level by means of a silent small water float valve generally indicated at 18 which may for example be of a 'Torbeck' equilibrium float valve. The water level 20 within the heater vessel or chamber 2 is maintained the same as that in the cistern 6 and the level occurs approximately half way up a water collecting tray 22 mounted within the top portion of the heater chamber. The top edge 24 of the side and end walls of the tray 22 constitute a weir, and normally the water in the tray is maintained separate from the water in the body of the heater chamber.

   A drw-off tap 26 is connected to an outlet 28 at the bottom of the tray through a pipe 30, a removable filter 32 being positioned between the water in the tray and the outlet 28 so as to remove impurities from the water such as loose pieces of scale.

   Gas for the burner 4 is fed from a gas supply through a pipe 34 containing a 'relay' valve 36. A by-pass pipe 38 extends from the relay valve 36 through a 'weep' valve 40 which is interlocked with the valve of the tap 26 and returns to the pipe 34 on the other side of the relay valve 36.

   When the draw-off tap is closed and the water level is at the position indicated, gas flows to the burner 4 at a sufficient rate to maintain the temperature of the water in the heater chamber at approximately 100"C.

   This gas passes through the relay valve 36 and through the 'weep' valve 40.

   When the tap 26 is opened to discharge boiling water from the tray 22, the 'weep' valve 40 is also adjusted causing the relay valve to open so that full gas supply is fed to the burner.

   With the resulting increase in the temperature of the water in the heater chamber its volume expands, causing the level of the hot water to rise until it spills over the 'weir' 24 filling the collecting tray. As water is drawnoff this is replaced from the cistern 6 which remains cold since it is separated from the hot water in the heater chamber by means of the U-shaped pipe. The cold water entering the bottom of the heater chamber is again heated and subsequently discharged from the collecting tray. As the level of the water in the cistern drops the float valve 18 operates to allow fresh mains water to refill the cistern to the desired level.

   When the draw-off tap is closed and the gas flow to the burner is only at the by-pass flow rate. hot water will slowly evaporate from the heating chamber the water being replaced from the cistern.

   Referring to Figure 2, it will be seen that the vessel generally indicated at 2, has an inner heated water vessel 42 which is triangular in cross-section with the apex of the triangle being positioned above the burner.

   The heating container or vessel 42 is, as can be seen in Figure 2, positioned within the casing 2 and is provided with a number of copper fins 44 brazed to its outer surface over the lower portion thereof. These fins act substantially to increase the heat exchange between the water in the vessel 42 and the hot gases flowing up around the vessel as indicated by the arrows, from the burner 4.

   This enables the efficiency of the boiler to be very significantly increased resulting in a lower heat-up time and a more compactly dimensioned boiler.

   The upper end of the vessel 42 is open but is provided with a removable cover 46.

   When it is desired to clean, repair or maintain the boiler, the cover 46 can be removed and the tray 24 readily lifted out from the open top of the vessel giving access to the interior of the boiler. This enables the boiler to be cleaned without having to disconnect the appliance from the gas and water supplies.

   WHAT WE CLAIM IS:

   1. An expansion boiler of the type described characterised in that the water vessel or container is provided wih external fins on at least a portion of the side faces of the vessel to enhance the heat exchange between an external heater and water contained within the vessel, the cross-section of the water vessel or container being substantially triangular with the apex portion positioned above the heater.

   2. A boiler as claimed in Claim I in which the fins are provided over the lower portion of the side faces of the vessel.

   3. A boiler as claimed in either of the preceding claims wherein the water heater vessel or container is located within an outer container to convey hot gases from the heater around the inner container, the heat exchange fins being provided on the outer side face of the inner container and projecting into the space between the inner container and the outer vessel.

   4. A boiler as claimed in any one of the preceding claims wherein a filter is provided between the tray and the inlet to the draw-off tap.

   5. A boiler as claimed in any one of the

   preceding claims in which the cold water supply tank or cistern is positioned at the side of the water vessel, the level of water within the cistern being controlled by a valve or the like and being at the same level as the water within the vessel or container, the height of the water level being such as to lie within the tray but below the top edge thereof when the boiler is operating at its normal storage temperature.

   7. An expansion boiler substantially as hereinbefore described with reference to the drawings accompanying the Provisional Spe cification.