GB2335588A - Percolator - Google Patents

Abstract

An electrically powered percolator makes use of a thick film electric heating element 10 having a printed circuit track arranged to define two or more discrete heating zones 2-1, 2-2 each of which has an associated percolator structure 21-1, 22-2 delivering hot water to the filter basket 23 of the percolator. By this means, and taking advantage of the high power output of thick film heating elements, percolation time can be significantly reduced. Control of percolation is also facilitated since a bimetallic sensor on the underside of the heating element will sense the temperature of the water in the percolator with only a small thermal lag. The bimetallic sensor can advantageously be employed additionally to switch on a keep warm element portion of the thick film element when it switches off the element portions responsible for effecting percolation.

Description

11 2335588 1 IMPROVEMENTS RELATTNG TO ELECTRTC WATER HEATING APPLIANCES

Field of the Invention:

This invention concerns improvements relating to electric water heating appliances and particularly concerns percolator appliances, for example for domestic use, wherein an electric heater is arranged to heat to boiling a small volume of water which is expelled from the boiling space and replaced by water from a cold water reservoir, the expelled water being delivered by a pipe to a filter basket containing ground coffee or tea for example which is infused by the hot water, the infusion in some instances being returned to the main volume of liquid in the reservoir to be recycled and in other instances being collected after a single passage through the filter basket.

Background of the Invention:

Conventional electric percolators of the recirculatory type commonly use a heatina element which is formed as a well at the bottom of a liquid 0 reservoir vessel, the heatincy element generally comprising a die cast member incorporating a conventional beating element, for example a metal sheathed heating element comprising a resistance beating wire within a tubular sheath with a mineral insulating material packed between the wire and the sheath.

The well is capped with a perforated cover which permits water to flow ftom the reservoir vessel into the well, and a central pipe rises from the cover so that boiling water ejected from the well spills from the top of the pipe into the filter 2 basket. The hot water trickles throu-h the -round coffee or tea leaves in the filter basket and falls back into the main liquid reservoir. This process is repeated and the infusion becomes progressively stronger and at the same time the main volume of liquid heats slowly, it being appreciated that the liquid is heated only while it is briefly within the well. A thermostat which is located close to the heating element is arranged to switch off the heating element when 0 Z:1 the temperature of the main liquid body is about 95T, the thermostat being responsive, via a thermal delay, to the liquid temperature.

Non-recirculatory percolators operate in substantially the same manner except that there is additionally provided a hot plate upon which stands a separate vessel arranged to receive the percolated beverage after passage through the filter. The hot plate temperature is controlled by a thermostat which cycles so as to keep the percolated beverage at an appropriate temperature, and a separate thermostat operates to switch off the well heater when the water in the reservoir is exhausted and the heating element temperature beings to rise above its normal operating level.

It is a problem of known recirculatory and non-recirculatory percolators that the time required for preparation of a beverage is quite long which does not comfortably accord with today's pace of life. For example, with currently available percolator appliances it takes about 10 minutes to prepare 1.0 to 1.5 litres of beverage. The reason for this is that it is necessary to limit the element power to below about 700 watts to ensure that the 1 percolation activity does not become excessively violent leading to boiling water splashing out of the appliance and, depending on the construction of the appliance, dislodgement of the appliance lid. Obsects and Summary of the Trivention:

It is the principal object of the present invention to overcome or at least substantially reduce the abovementioned problem.

According to the present invention the heating element of an improved percolator appliance comprises a so-called thick film heating element having a plurality of heating, areas and a separate percolator structure is associated with each of said heatinu areas, the percolator structures and their respective heating areas each operating to deliver boilina water to the filter basket of the percolator.

Thick film heating elements comprising a substrate, formed of stainless steel for example, upon which there is formed a resistance heating track or layer together with appropriate electrical insulation, are currently a popular replacement for the more conventional sheathed heating elements commonly used in domestic kettles and hot waterjugs. The Russell Hobbs "MlleniumT"4" kettle for example incorporates such a thick film element. Although relatively expensive by comparison with conventional sheathed heating elements, thick film heatina elements have the advanta.e of increased watts density and more simple and more aesthetically pleasing incorporation into the appliance.

C> 4 Hereinafter described is an exemplary embodiment of the present invention wherein a thick film heatina element has two heating areas conjoined in a floure-of-elght form, and associated with each heating area is a percolator structure comprising an inverted saucer-shaped member defining with the respective heating area a boiling zone or volume and a vertical tube or pipe for conveying boiling water upwardly from the boiling zone, the upper ends of the Z two pipes being secured to a common filter basket. The total power of the heatina element miorht, for example, be 1300 to 1400watts with half the total concentrated under each of the two inverted saucer-shaped members of the percolator structure. Each boiling zone and associated saucer-shaped member and vertical pipe acts as a separate percolator which can be as powerful as the prior art percolators hereinbefore described and the percolation will only take half as Ion. to perform on a given volume of water.

The invention is not limited to the provision of just two heating areas and just two associated percolator structures, though for normal domestic applications two would most likely be sufficient. For commercial or catering percolators, three or more heating areas and associated percolator structures all working in parallel could be provided.

The thick film heating element can additionally be formed with a part designed to keep the beverage hot once it has been made. For recirculatory type percolators, such part of the heating element might be arranged to be switched into operation only after percolation had been completed and might be switched in series with those parts of the heating element which define the percolation zones so that the whole beating element operates at reduced power so as to keep the beverage hot. For such an arrangement, control of the percolator might simply be effected with a single sensor responsive to the temperature of the main volume of liquid, sensed for example at an appropriate part of the heating element. For a non-circulatory type of percolator appliance, the additional heating element part could be employed to keep the hot plate at an appropriate temperature and might be powered, under thermostatic control, so]on. as the percolator appliance was switched on, the control of the percolation zones of the heating element being separately effected by means of a sensor responsive to the temperature at said zones rising above their normal operating temperature when the water reservoir has been emptied by percolation into the separate vessel on the hotplate.

The above and further features of the present invention are set forth with particularity in the appended claims and, together with the advantages thereof, will become clear to those possessed of appropriate skills from consideration of the followine detailed description given with reference to the accompanying drawings.

Description of the Drawings:

Figure 1 shows a plan view of a thick film heating element according to 0 an exemplary embodiment of the present invention, the figure-of-eight form of 1 P 6 the two percolation zones and the provision of a keep warm element portion being schematically shown; Figure 2 is a perspective view of an exemplary form of recirculatory percolator structure adapted for use with the heating element of Figure 1, the percolator structure being shown in Figure 2 spaced above the heating element surface by a greater distance than would be normal., Figure 3 is a perspective view similar to Figure 2 but showing the percolator structure in Its normal spacing from the heating element surface; and Figure 4 is a further perspective view, but taken from the underside of the heating element.

Detailed Description of the Embodiment:

Referrina to Fiaure 1, the heatincy element shown therein consists of a flat stainless steel substrate 1 of about 1.5mm thickness having on its underside a resistance beating track pattern sandwiched between electrically insulating layers, the track pattern being formed of electrically conductive ink by printing for example and the Insulating layers being formed of glass for example by electrodeposition. A protective layer of glass for example can also be formed over the upper surface of the substrate if so desired. The track pattern, as shown, comprises a figure-of-cight portion 2 consisting of conjoined areas 2-1 and 2-2 and a portion 3) extending around near to the periphery of the substrate outside of the portion 2. Terminal portions 4, 5 and 6 are provided, as shown, 7 and windows are provided in the uppermost layer of glass insulation for enabling the terminal portions to be accessed for powering the heating element.

As is well known, the terminal portions may be silvered so as not to be subject to resistive heating.

Although not shown, it will be understood that within the areas 2-1 and 2-2 the heating element track has a serpentine configuration such as to provide each area with a power output in use of the order of 700 watts. The heating element portion 33 may comprise a single track or a serpentine track or may comprise several tracks in parallel, and has a power output of the order only of 50 watts. With an appropriate control device coupled to the terminal portions 4,5 and 6 of the heating element, power can be supplied to the element portions 2-1 and 2-2 during percolator operation, as hereinafter described, and during this time period the heating element portion 3) is switched off. When percolation is determined to have been completed, the control device operates is to switch the heating element portion 3 in series with the portions 2- 1 and 2-2 across the power supply so that the whole heating element then operates at reduced power so as to keep the percolated beverage hot.

Figure 2 shows the heating element 10 of Figure 1 and a dual n percolator structure 20, the structure 20 being shown more widely spaced from the upper surface of heating element 10 than it would normally be. The 0 view of Figure 3 shows the percolator structure 20 and heating element 10 in normal operative relationship. As shown, the percolator structure 20 8 comprises two inverted saucer-shaped members 21-1 and 21-2 which, like the heating element portions 2-1 and 2-2, are conjoined in a figure-of-eight formation and, when the percolator structure 20 is assembled with the heating element 10, co-operate with the heating element portions 2-1 and 2-2 to define boiling zones or volumes within the surrounding water containing volume of the percolator.

The percolator structure 20 further comprises two outlet pipes 22-1 and 22-2 havine, their lower ends coupled to the saucer-shaped members 21- 1 and 21-2 respectively and their upper ends secured to a perforated filter basket 23 having a removable lid 24 In operation of the thus-described arrangement when fitted in the water reservoir of a percolator appliance, water entering the boiling zones defined by the heating element portions 2-1 and 2-2 and the inverted saucer-shaped members 21-1 and 21-2 will rapidly be boiled and expelled up the pipes 22- 1 and 22-2 and into the filter basket 23. Hot water filtering down through 0 ground coffee or tea leaves in the filter basket 23 will fall back into the main volume of liquid in the appliance and will be recirculated. The temperature of the brewing beverage in the main body of the percolator will rise as it is progressively pumped through the two boiling zones by the percolator action.

At a predetermined temperature, a control device responsive to the liquid temperature in the main body of the percolator will switch the keep warm heating element portion 3 into series circuit with the heating element portions 0 1 1 1 9 2-1 and 2-2 so that the output power of the heating element falls to a low level sufficient only to keep the contents of the percolator hot.

When the water is percolating, the heat from the heating element is limited to below the inverted saucer-shaped members 21-1 and 21-2 and there is little direct heating of the body of water contained in the appliance, the gradual heating of this body of water resulting from its progressive recirculation through the percolator structure. This makes sensing of completion of percolation as a function of the temperature of the overall body of liquid in the appliance an entirely practical approach, since percolation will start with the body water at a relatively low temperature as compared with the final temperature reached at completion of percolation, so that the control device only has to be sensitive to a relatively large temperature change. In the described embodiment, a sensor might advantageously be mounted over the keep warm track 3), for example at the position 50 indicated in Figure 1. With a sensor mounted in this position, the control will sense the temperature of the main body of water in the percolator appliance, albeit through the heating element which will introduce a thermal delay, so long as the keep warm heating element portion 3 is not powered. When the control operates at the sensed completion of percolation, the energisation of the keep warm element portion 3 underlying the control will supply heat to the control and ensure that it cannot reset until such time as the appliance is switched off. This will allow the use of a control with a narrow differential, that is to say only a small j difference between its operating temperature and the temperature at which it will reset, which will ensure a rapid reset when the heating element cools and will allow reset simply by refilling the percolator with cold water. The thermal delay abovementioned will tend to slow reset, but because the control is responsive to the water temperature with a close thermal coupling, any such delay would only be slight.

In conventional electric percolator appliances as hereinbefore described, the control for sensing completion of percolation is generally attached to the die cast heating element and does not sense the body water temperature directly. This introduces a considerable thermal delay into the operation of the control and poor thermal feedback from the water, and results in the reset times for such appliances being relatively long. Even refilling of the appliance with cold water does not result in the control being cooled and reset sufficiently quickly. In addition, to prevent incorrect resetting during use, the reset temperature of the control is generally set at a relatively low temperature, which exacerbates the problem. As described above, the present invention enables this problem to be overcome.

The control can conveniently comprise a bimetallic actuator arranged, as shown at 50 in Figure 1 for example, to be responsive to the temperature of the main body of water in the percolator appliance. A push-rod associated with the bimetallic actuator would be arranged to operate a change-over switch arranged so that in the "cold" condition of the bimetallic actuator the 11 keep warm portion 3) of the heating element was out of circuit and so that when the bimetallic actuator operated in its "hot" condition the heating element portion 3 was brought into circuit in series with the parts 2-1 and 2-2 of the heatina element. Contact type thermostats capable of satisfying these requirements are known. In this connection, it is to be appreciated that the locations of the heating element terminals 4, 5 and 6 as shown in Figure 1 are schematic only and would be rearranged in a practical version of the embodiment to suit the construction of the control device. Preferably the control device would be provided with spring terminations arranged to make z 0 the necessary electrical connections with the terminals 4, 5 and 6 when the control was appropriately juxtaposed with the heating element.

Having thus described the present invention in the foregoing by reference to a specific embodiment, it is to be appreciated that the described embodiment is exemplary only and that modifications and variations are possible without departure from the spirit and scope of the invention as set forth in the appended claims. For example, whereas the described embodiment has twin percolator structures, three or more such structures operating in parallel could be provided especially in larger percolator appliances for cateriner applications. Furthermore, whereas the described embodiment is a recirculatory type of percolator appliance, the invention could alternatively be applied to a non-recirculatory type of percolator appliance, in which case the keep warm heating element portion 3 could be arranged to be on the hot plate 12 which keeps the prepared beverage hot and might comprise a number of selectable, different output power heating elements. With a non- recirculatory type of percolator appliance, the hot plate would be arranged to be heated throughout the operation of the appliance, but different output power heating element portions might be selected in dependence upon the condition of the percolator appliance control. In such an arrangement, the keep warm heating element(s) could be provided on the same heating element substrate as the heating element portions responsible for effecting percolation, or altematively could be on a separate substrate, depending upon the physical arrangement of the appliance. Additionally, whereas in the described embodiment the heating element has a flat, planiform structure, the stainless steel (or other) substrate of the heating element could be dished at the locations of the active heating element portions 2-1 and 2-2 so as to contribute to the definition of the percolation zones underlying the inverted saucer-shaped members 21-1 and 21-2.

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Claims (1)

1. CLAIMS..

   1. A percolator appliance having a plurality of parallel-operating percolator structures.

   2. A percolator appliance as claimed in claim 1 comprising electric heating elements associated with said parallel-operating percolator appliances.

   3. A percolator appliance as claimed in claim 2 wherein said electric heating elements comprise thick film heating elements.

   4 A percolator appliance as claimed in claim 3 wherein a plurality of said electric beating elements are formed on a common substrate.

   5. A percolator appliance as claimed in claim 4 wherein said plurality of beating elements are spatially distributed on the substrate so as to define localized percolation zones, and said percolator structures have corresponding parts completing the definition of said percolation zones.

   6. A percolator appliance as claimed in any of the preceding claims incorporating a heating element arranged to keep warm a beverage prepared in W 0 C> the appliance.

   14 7. A percolator appliance as claimed in claim 6 wherein the keep warm heating element is arranged to be energised only after percolation has been completed.

   8. A percolator appliance as claimed in claim 6 wherein the keep warm heatina element is arranced to be energised so long as the appliance is switched on.

   9. A percolator appliance as claimed in any of the preceding claims including control means responsive to completion of percolation.

   10. A percolator appliance as claimed in claim 9 as dependent upon claim 6 wherein the control means is arranged to switch off the heating elements responsible for percolation operation upon sensed completion of percolation, and to switch on the keep warm heating element- A percolator appliance as claimed in claim 9 or 10 where the control means includes a bimetallic actuator.

   12. A percolator appliance as claimed in claim 11 as dependent upon claim 3 wherein the bimetallic actuator is arranged to sense the temperature of the main body of water in the percolator through the thick film heating element.