GB2064078A - Water boiler - Google Patents

Abstract

The invention provides an electrically heated water boiler for making tea or coffee or for other culinary uses. The boiler includes a main chamber 10 containing electric heating elements 26, 28 for heating the water, and a boiling water reservoir 30 which fills up with boiling water as the main bulk of the water in the chamber 10 is heated. Water may be drawn off from the reservoir via a spout 40, 42. The heating operation is controlled by sensing the level of boiling water in the boiling water reservoir 30 by means of probes 46, 48, 50 so that the heating element 26 is switched on when the level falls below a predetermined value, and is switched off when the level is above a predetermined value. The reservoir has an inverted frusto-conical base 32 with a spout extending upwards and through which boiling water spills. A recirculating pipe 25 passes through the spout with clearance, the top thereof is slightly above the top of the spout so that excess boiling water returns to the main chamber through the said recirculating pipe 25. <IMAGE>

Description

SPECIFICATION Improvements relating to water boilers This invention relates to water boilers which are used for producing hot water for beverages such as tea and coffee, and other culinary uses. The boilers to which the invention relates are sometimes referred to as self-feeding boilers in that they are adapted to replenish automatically any hot water which is drawn from the boiler for producing a hot beverage.

Self-feeding water boilers are of course well known and generally these are provided with electric, gas or steam heating means. The present invention is concerned with an electric heating means boiler.

The known form of electrically heated boiler comprises a heating chamber into which water is supplied via a float controlled valve and in which is located the electric heating means. Also in the chamber is a water reservoir from which the boiling water is drawn in use to provide the beverage. As the water in the chamber is heated it boils and the boiling water spills over into the reservoir until the reservoir fills with boiling water and is ready to be drawn off. The supply of power to the electric heating means is controlled mainly by a thermostat in contact with the water in the chamber so that the power is cut off when the main bulk of the water in the chamber reaches a predetermined temperature. A pilot heating means maintains the water at said predetermined temperature when there is no draw-off of water from the boiler.

To draw off water a dispensing tap is operated, allowing hot water to run from the reservoir, and the opening of said dispensing tap causes switching on of the electric heating means to heat the water in the chamber to compensate for the heat removed from the boiler resulting from the draw-off of the boiling water. Closing of the tap results in switching off of the heating means if the water in the chamber is at or above the said predetermined temperature.

It is desired of water boilers of the type to which the invention relates that the maximum amount of boiling water be drawn off in the minimum time and also that it should be possible to draw off boiling water continuously for as long as possible. These objectives are not attainable, or not economically attainable, because there must of necessity be some time to take account of the thermal storage involved in heating cold water and then raising the temperature of the stored water to boiling point.

The known electrically heated boiler as described above has a disadvantage that if water is drawn off in small amounts, for example in cupfuls, at regular intervals, circumstances which can exist frequently in practice, the reservoir may become depleted without the heating means being switched on other than for the short periods between opening and closing of the tap, which periods are not adequate to compensate for the heat removed from the boiler. If, following such events, there is a demand for the full capacity of the boiler, then there may be a substantial delay before said full capacity of the boiling water can be drawn from the reservoir.

A further disadvantage is that the commercial tolerances found in thermostats used to control the temperature of water in the heating chamber in the known boiler are too wide which results in failure to achieve the maximum thermal storage temperature and potential capacity of the boiler, and water tends to be retained in the reservoir at temperatures below boiling point.

The present invention is concerned with providing a self-feeding water boiler which does not suffer, from the disadvantages of the known water boiler described herein, and will have better draw-off performance and more consistent maximum rapid draw off capacity than the said known water boiler.

According to the invention there is provided an electrically heated, self feeding water boiler for providing boiling water for making beverages such as tea or coffee or for other culinary uses, comprising a chamber for containing a supply of water, an electrical heating means for heating the water In said chamber, a reservoir in the chamber and into which water spills from the chamber when the water is heated to boiling point, means enabling boiling water to be drawn from the reservoir and the boiler for making hot beverages, or for other culinary uses and level detection means to control the switching on and off of the said heating means in response to changes in level in the reservoir, the arrangement being such that the boiler operates at a ready to draw off or quiescent condition in which the level of boiling water in the reservoir is at an intermediate level with the electrical heating element off, and when there is draw off of water to such an extent to drop the level of water in the reservoir to a lower level below the intermediate level the electrical heating means is automatically switched on, and is not switched off again until the level reaches an upper level which is higher than the intermediate level.

By such arrangements, the heating means can be arranged to be switched on almost as soon as there is any draw off of water from the reservoir, and can be made to remain on until the water level has reached the said predetermined level, or even higher. In this way, regardless of how the water is drawn off, the heating means can be switched on to cause replenishment of the reservoir well before the reservoir is depleted. Also regardless of how much water is drawn off, the heating means will not switch off until the reservoir is not only replenished but the thermal storage capacity has been fully restored to a consistent maximum capacity.

Preferably, said level detector means comprises an upper level detecting probe for switching off the heating means when the level of water in the reservoir reaches said upper predetermined level, and a lower level detection probe for switching on the heating means when the water level in the reservoir falls below the lower predetermined level.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, wherein Fig. 1 is a sectional elevation of a water boiler according to the embodiment of the invention; Fig. 2 is a perspective elevation showing the reservoir and detection means of the boiler shown in Fig. 1; and Fig. 3 shows in detail the locations of the probes in relation to the reservoir inlet.

Referring to the drawings, the boiler is shown in developed sectional elevation in Fig. 1 in that a hot water chamber 10 and a cold water chamber 12 are shown side by side. In actual practice, these two units are housed in a neat box-like casing which also houses water feed and overflow pipes and the electrical supply cables and the like which gives the unit a clean and attractive appearance with concealed service connections for electricity, cold water and overflow. The boiler is suitably insulated.

To the cold water chamber 12 is connected a mains water supply pipe 14 through which cold water is supplied to the chamber 12, the amount of water supplied being controlled by an equilibrium float valve 1 6 of known construction.

The cold water chamber 12 is provided with a conventional overflow 18, and there is a cold water outlet pipe 22 which has a U-bend therein before it passes into the hot water chamber 10.

Pipe 22 is connected to the internal water feed pipe 24 whose function will be more readily understood from the description which follows hereinafter.

The electric heating means comprises a main element or elements 26 for heating the water to boiling point and a pilot element 28 which is shown in dotted lines in Fig. 1, which operates continuously to compensate for heat loss, provided that there is water in the chamber 10, and which is situated adjacent to the main element 26 as shown.

Also inside the hot water chamber 10 and immediately above the elements 28 and 26 is a cylindrical boiling water reservoir 30 having in the base thereof a central inverted funnel 32 of which the upper spout end 34 lies at a particular level, and is splayed outwards, for reasons explained hereinafter.

The cylindrical boiling water receiver is provided on its top peripheral edge with an outwardly extending, rectangular flange 36 with fixing holes for attachment to a top sealing flange 36A of the hot water chamber. There is a vent hole or a series of such holes 43 from an annular cavity 43A (which would be otherwise closed were the hole or holes 43 not provided) defined between the reservoir 30 and the wall defining chamber 10. The hole or holes 43 serve to prevent excessive build up of pressure in the hot water chamber but to allow slight build up of pressure for assisting water level rise within the water reservoir.

A circulating return pipe 25 having an outwardly splayed top edge 25A is positioned centrally within and projects slightly above upper spout 34 of the centrally inverted funnel 32.

A cover 44 closes the top of the boiling water receiver and extending downwardly from the underside of the said cover are three electrically conducting level sensing probes 46, 48, and 50 which are of different lengths and as clearly shown in Fig. 1 they are attached to a demountable insulating material flange 53 which is secured to the cover 44. A small electrical voltage is in use applied either to probe 46 and probe 50 or to probe 48 and probe 50, depending upon the mode of operation selected (as will be explained) and when the water contacts end of the probes 46, 48 and 50, when operative, a small electric current flows between the probe and the body of the boiler, which acts as an earth for all probes.The position to which the probes 46,48 and 50 extend are closely related to the internal operational water levels as will be clear from the explanation of the operation of the boiler which follows with reference to Fig. 3. A second cover 45 closes the top of the unit casing as shown.

Finally, the underside of the cover 44 is provided with a cylindrical shield 52 which surrounds the probes 46, 48 and 50 and dips into the boiling water in the reservoir 30 when it is full in order to prevent excessive surface turbulence to the inside of the cylindrical shield 52 which could cause spurious readings of the probes 46, 48 and 50.

The shield 52 has a vent hole or several of such holes 54 in the wall thereof to prevent build up of pressure in the shield 52 and this hole or these holes also serve to keep the water inside the shield calm. An atmospheric vent pipe 55 which extends through covers 44 and 45 provides a means for relieving pressure on the top of the boiling water receiver.

The boiler described has two modes of operation, either of which can be selected by the throwing of a switch provided on the boiler. In the first mode of operation the full storage capacity of boiling water is available for rapid draw off, whilst in the other mode of operation the capacity of boiling water available for rapid draw off is reduced but the requisite preheating period is also reduced and therefore thermal storage will be replenished in a shorter period; the operation is more economical than the first mode as the full capacity is not required. Depending upon which mode of operation is selected, level sensor probes 46 and 50 or probes 48 and 50 will be operational. For the purposes of initial explanation, it is assumed that the mode of operation in which level sensing probes 46 and 50 are in use, has been selected.

Referring now to Fig. 3 which shows the top ends 34 and 25A of spouts 32 and tube 25 and the portions of probes 46, 48 and 50, starting from cold, the boiler is filled automatically from the main supply pipe 14 until the water reaches level L as indicated in Figs. 1 and 3 which is under the edge 54 by the distance A. The main heating element or elements 26 and pilot element 28 are operational at thjs time, and start to heat the water in chamber 1 0. When the water begins to boil, the ebullution causes the water to be lifted and it splashes up through the funnel 32 so that it spills over the spout 34 and into the reservoir 30.

Any resulting fall in level L is compensated by the opening of valve 16, which, being an equilibrium float valve is designed for rapid response. The heating is continued until the reservoir 30 is full of boiling/water, at which point any further hot water is supplied to the reservoir 30 will spill over into and circulate downwards through the circulating return pipe 25. At this time, the end of probe 50 will be in contact with the water as it is above spout 34 by an amount D which is less than the distance F, being the amount by which tube 25 projects above spout 34 and an electric current passes through the water between probe 50 and earth.Provided that no boiling water is being drawn from the boiler, hot water continues to circulate up through the funnel 32, into reservoir 30, down through pipe 25 to the bottom of chamber 10 and back to the underside of funnel 32, and more of the water turns to steam bubbles increasing the turbulence in the water and expanding the total volume of steam and water.

Eventually, due to the expansion the water in the reservoir 30 contacts the end of the shortest probe 46, the ends of probes 48 and 50 being immersed in the water, and this contacting of probe 46 results in a flow of current from probe 46 through the water to earth, and in the main heating element 26 being switched off automatically. Appropriate control means being provided for this purpose. There is an immediate fall back in the level of the water in reservoir 30 but as long as the pilot heating element remains on the fall back level is above the end of probe 50, keeping the main element 26 off.If now some boiling water is drawn from the reservoir 30, the level in said reservoir 30 falls, until such time as, in this case, the level detector probe 50 no longer contacts the water, at which point the heating element 26 is once more switched on so that heat will be added immediately to the water in chamber 30, causing boiling thereof and replenishment of reservoir 30, make up being provided by intaking cold water. The volume of cold water which will be introduced will correspond to the volume of water which is needed to replenish the reservoir 30, less the expansion.The volume of water which represents a change in level from probe 46 to probe 50, is a relative small amount, and therefore the heating element 26 will quickly raise the temperature of the water in chamber 10 (after the addition of the small amount of make-up cold water) to a level representing maximum thermal storage capacity and replenishment of the reservoir 30 will commence almost immediately. If the water is drawn from reservoir 30 in small amounts and intermittently, then it is possible to maintain the full thermal storage capacity and a maximum supply of boiling water for rapid draw off is always available.If all the contents of reservoir 30 are drained off in one operation, then although the apparatus will require some time to heat the resultant mixture of hot and cold water in chamber 10 to return to maximum thermal storage capacity, the replenishment of reservoir 30 will be continuous until the maximum thermal storage available for rapid draw off capacity is attained and thereafter output will be at the hourly rated capacity of the unit. In any event, the main element 26 will be below that of probe 50, and will remain on until the level of water in reservoir 30 once more reaches the bottom of the probe 46. The length of time that the main element or elements operate to restore maximum thermal capacity after boiling water has been drawn off is directly proportional to the amount of boiling water drawn off.These features distinguish the apparatus from the known form of electric water boiler in which the switching on and off of the main element is controlled by the handle of a draw off valve in conjunction with a standard commercial thermostat, having wide operating tolerances within the hot water chamber.

In order to select the second mode of operation which is suitable when there is not a high demand for boiling water, it is a matter of throwing a switch provided on the front face of the casing and in the second mode of operation, the probes 48 and 50 are operative. Probe 48 serves to switch the element 26 off when the probe contacts the water (at a lower level than the lower end of probe 46). This means that the element 26 will be switched off sooner which means that it will be switched off when there is less heat stored in the water in chamber 10 as the heating element 26 is switched off at a lower level of thermal expansion of the water. The lower thermal expansion is caused by the water in the lower region of the chamber 10 being colder.As long as there is no high demand or rapid draw off of the full thermal capacity, the unit will operate more economically than in the first mode.

It will be appreciated from the above that the geometrical configuration of the chamber 10 and reservoir 30, and also the positioning of the probes 46, 48 and 50 are inter-related to ensure that when the boiler is full and is ready for draw off (a quiescent condition), the level of the water in reservoir 30 will be at an intermediate level which is below the end of the operative probe (46 or 48) because of the said fall back in level when the boiling water has expanded up to the end of the operative probe (46 or 48) to cause cut-off of the main heating element 26, and which intermediate level is above the end of probe 50 to ensure that the main heating element is not immediately switched on again.

When the level of water falls from the said intermediate level, as a result of draw off or any other reason such as excess heat loss or failure of the pilot element, to a lower level exposing the end of the probe 50, the main element is operated again until the level of water reaches an upper level, above the intermediate level until the operative probe (46 or 48) is contacted causing the main heating element 26 to be switched off with the resultant fall back in level to the said intermediate level.

It is to be mentioned that in the quiescent condition when boiling water is available the water in the reservoir 30 and chamber 10 is in expanded condition and if the pilot element were to fail, there would be an immediate contraction.

Contraction due to heat loss can also take place if the insulation is insufficient or has failed.

The boiler will of course be provided with the necessary controls, such as thermostatic or pressure switch controls to prevent the elements 26 and 28 from being operational when not covered with water. The probes 46,48 and 50 may be of conventional conductive design or they may be capacitive or of servo or other nonconductive or capacitive design, and appropriate control means electrical in nature will be provided between the probes 46, 48 and 50 and the relays for the switching on and off of the power to the heating elements 26 and 28. The various components of the boiler, apart from the spout 40/42 will be housed in a suitable container, provided with appropriate insulation in order to prevent heat loss.

The apparatus described, in addition to providing a means whereby better boiling water output capacities and flow rates can be obtained, as compared to the known electrically heated water boiler has certain novel and advantageous features. For example:- The splayed periphery of the upper spout end 34 of the centrally inverted funnel 32 is slightly under the splayed periphery at the top 25A of the circulating return pipe 25 so that water rising within the annulus formed is deflected into the boiling water reservoir and will not short circuit down the return pipe before the reservoir is full of boiling water. Additionally, the use of the cylindrical screen 52 with holes 54 provides a quiet surrounding water surface layer within which the probes 46, 48 and 50 can operate.

The equipment described combines a number of features to provide an excellent high demand output, in addition to the features referred to herein. The additional features might be mentioned as follows.

a) The use of an equilibrium float valve improves response and water is made up quickly.

This means that the interior annulus between spout 34 and the circulating return pipe 25 splayed top will be substantially full at all times which makes it easier for the boiling water to be !ifted over the edge of the spout.

b) An advantageous arrangement is achieved if the central spout 34 diameter is made in a predetermined ratio to the diameter of the circulating return pipe 25.

c) Compared to the known arrangement the pipe 25 is arranged inside the centrally inverted funnel 32. This gives more space inside the reservoir for the storage of boiling water, and makes the reservoir easier to clean.

d) There is a tendency in hard water districts for scale to be deposited within the circulating return pipa 25 and the annulus between this pipe and spout 34.

The unit is constructed so that without the use of tools it is a simple matter to remove the outer casing lid 45, reservoir cover 44 and lift out the circulating return pipe 25 for descaling. A reamer can then be inserted into the upper spout 34 to remove scale from this area.

e) The unit is also constructed so that without the use of tools it is a simple matter to remove outer casing lid 45 and control probe flange 53 in order to clean probes 46, 48 and 50.

f) The control of thermal storage temperatures by means of reservoir water level ensures consistently high temperatures at the base of the heating chamber and excellent response. The specific arrangement of the boiler of the present invention as described is extremely advantageous in that it makes use of a level change effect which occurs when the water in the vicinity of the heater 26 starts to boil. In the vicinity of the heater, some of the water is turned to steam as a boiling condition takes place, and the rise of the steam bubbles in effect causes the level of water in the chamber 10 to increase. If the water towards the bottom of the chamber 10 is relatively cold then the amount of level increase is relatively small.

However, when the water at the bottom of the chamber 10 is of the order of 88-960C, then steam bubbles are generated in the region of the heater 26 much more rapidly, and there is a much more rapid increase in the level. The level sensors 46,48 can be made to detect this easily so that an extremely fast response is obtained. The unit therefore is designed to actuate the level sensor and switch off the heater only at a particularly critical temperature range and when the waters in the chamber 10 causes a build-up in pressure under boiling conditions as steam rises into the cavity 43A, and results in an upward balancing movement of the water level in the reservoir 30.

The hole or holes 43 is or are designed as to size to give the desired throttling effect and the limited build up in pressure in the cavity 43A. The holes also provide preventing of sub-atmospheric pressures due to condensation of steam vapour.

Due to thermal stratification this feature ensures also that the water retained in the reservoir is actually boiling which is essential for making good tea. It is not possible to consistently achieve such accurate operation by means of thermostats having a wide "on"/"off" tolerance.

g) By connecting the inflow pipe 22 as a connection to pipe 24, pipe 24 can simultaneously serve as an air vent. The internal diameter of pipe 24 is sufficient to accommodate scale deposits without impairing normal operation of the boiler.

h) An economy selector switch saves electricity by reducing the preheat period and continuous rapid draw off capacity for periods when maximum draw off is not required.

i) By arranging the main and pilot elements close to the underside of the reservoir, response is rapid and controlled.

j) In mounting the Linit on a surface, it may be necessary to provide apertures in that surface for reception of the overflow and supply pipes 1 8 and 14, but the casing can be provided with removable blanks on the side thereof to enable side connections to be made to the said pipes 14 and 18 is desired.

k) The configuration of the assembly is such that the overall depth of the boiler is minimal which enables the unit to be mounted on standard worktop surfaces and still leave enough room in front of the boiler to accommodate drip trays, tea urns, utensils and adequate working space.

Various modifications may be made without departing from the scope of the invention. For example, instead of two spaced probes being used as sensing elements, a single probe coupled to an adjustable delay means could be used. The delay would operate to switch off the main heating element at a predetermined time (adjustable) after being contacted by the expanding boiling water to ensure that the water rises to said level and falls to the first level above the end of the probe when the main heating element is switched off. When the water level falls below the end of the probe, the main heating element is switched on. Additional heating elements may be provided, and the proportions of the various chambers and pipes may be altered.

Although the boiler according to the invention is most suitable for producing boiling water for making tea, of course the end use of the boiling water is at the discretion of the user. It could be used for making such as custard or porridge.

Claims (12)

1. An electrically heated, self feeding water boiler for providing boiling water for making beverages such as tea or coffee or for other culinary uses comprising a chamber for containing a supply of water, an electrical heating means for heating the water in said chamber, a reservoir in the chamber and into which water spills from the chamber when the water is heated to boiling point, means enabling boiling water to be drawn from the reservoir and the boiler for making hot beverages, or for other culinary uses and level detection means to control the switching on and off of the said heating means in response to changes in level in the reservoir, the arrangement being such that the boiler operates at a ready to draw off or quiescent condition in which the level of boiling water in the reservoir is at an intermediate level with the electrical heating element off, and when there is draw off of water to such an extent to drop the level of water in the reservoir to a lower level below the intermediate level the electrical heating means is automatically switched on, and is not switched off again until the level reaches an upper level which is higher than the intermediate level.

2. A water boiler according to claim 1, wherein the said level detector means comprises an upper level detecting probe for switching off the heating means when the level of water in the reservoir reaches said upper predetermined level, and a lower level detection probe for switching on the heating means when the water level in the reservoir falls below a lower predetermined level.

3. A water boiler according to claim 2, wherein there is a second upper level detecting probe qperative to switch off the heating means when the level in the reservoir reaches a second upper predetermined level which is lower than the first mentioned upper predetermined level, and in relation to which there is a second intermediate level which is lower than the first mentioned intermediate level but higher than said lower level, and there is switch means to make the first mentioned upper probe means ineffective so that the boiler operates by sensing of the second upper and lower probes, or selectively ta make the second upper probe ineffective so that the first mentioned and lower probes control the operation of the boiler.

4. A boiler according to claim 2 or 3, wherein the said probes extend downwardly from a support plate which, together with the probes is removable for inspection and/or repair.

5. A water boiler according to claims 4, wherein said probes are surrounded by a cylindrical shield which serves to keep the water around the vicinity of the probe ends calm.

6. A water boiler according to claim 5, wherein the cylindrical shield extends downwardly from the said carrier plate, and is provided with vent holes at a level which will be above the water level in the reservoir over the operational range of the boiler.

7. A water boiler according to any preceding claim, wherein the base of the reservoir is of inverted frusto-conical shape, having an upwardly extending spout over the edge of which the boiling water spills in passing to the said reservoir, the said upper edge being outwardly turned or flanged to facilitate said spillage.

8. A water boiler according to claim 7, wherein there is a recirculation pipe within the said spout, but leaving an annular clearance between the pipe and spout for the passage of boiling water from the chamber to said reservoir, the recirculation pipe having a flanged top end which lies slightly above the flanged top end of the said spout.

9. A water boiler according to claim 8, wherein the recirculation pipe can be removed from the boiler from the top end by removing a removable cover, whereby the recirculation pipe and the interior of the spout can be readily descaled.

10. A water boiler according to any preceding claim, wherein cold water is supplied to the chamber from a cold water make up tank by means of a pipe which, inside the chamber has a section leading to the above the water level in the chamber.

11. A water boiler according to any preceding claim, wherein the reservoir is located in the chamber so as to leave an annular space between the outside of the reservoir and inside the chamber which is closed apart from throttling apertures connecting the interior of the reservoir and the interior of the chamber, said apertures being located above the water level in the chamber.

12. An electrically heated, self-feeding water boiler, substantially as hereinbefore described with reference to the accompanying drawings.