WO1997024966A2

WO1997024966A2 - Domestic kettle

Info

Publication number: WO1997024966A2
Application number: PCT/GB1996/003253
Authority: WO
Inventors: William Thomas Large; Stylianos Panaghe
Original assignee: Delta Theta Limited
Priority date: 1996-01-11
Filing date: 1996-12-27
Publication date: 1997-07-17
Also published as: WO1997024966A3; GB9600562D0; AU1384497A

Abstract

An electric kettle has settings for boiling (for making tea) and a lower temperature (for making coffee). The kettle may be maintained at temperature by a simmer control. A liquid crystal or other thermochromic substance may be incorporated in a ceramic transfer to give visual indication of temperature.

Description

DOMESTIC KETTLE

This invention relates to domestic kettles.

The primary use for domestic kettles is for boiling water for making tea and coffee. Electric kettles are conventionally provided with a sensor that switches off the element once the kettle has boiled, as well as a safety cut-out to prevent overheating if operated without water. Some kettles have indicator lights telling when switched on. Attainment of boiling temperature is normally indicated by an audible click as the sensor switches off the element, and by the on-off switch button moving to the "off position.

Acting, perhaps, on the principle that a watched kettle never boils, users, having filled and switched on the kettle, tend to turn to other tasks or return to watching television, so that the kettle might have boiled and, having switched off, cooled down before being re-attended for the purpose of making the chosen beverage, necessitating reboiling. In most cases, the switch will not latch on until the kettle has cooled down quite a bit below boiling, requiring manual holding down until boiling temperature is reattained.

Ideally, for tea-making, it is recommended, the water be at boiling point. On the other hand, for French coffee, the water should be just below boiling point when it is poured over the coffee. (Laroussee Gastro nomique, 1988. Paul Hamlyn, publ., pp 1070. 285). With conventional kettles, the water may well have cooled down, since the kettle boiled and switched off. to a temperature suitable for making coffee, yet because there is no way of knowing this, the kettle is reboiled, clearly to a temperature above what is recommended for coffee-making, and may not be allowed to cool back down sufficiently before being poured on to the grounds, or may be let to cool down too far.

The present invention provides an improved kettle that avoids this latter disadvantage and can accommodate optional further improvements.

The invention provides a domestic kettle for heating water comprising a heating element and a temperature sensor with a control arrangement adapted to heat the water only to a given temperature below boiling temperature.

The kettle may be optionally adapted, and will, in fact, usually be adapted, also to heat the water to boiling temperature, so as to be equally suitable for tea or coffee.

Ideally, the kettle is adapted to maintain the water at said given temperature, and, indeed, to maintain it at said given temperature only for a certain time.

The kettle may incorporate a signal device indicating attainment of said given temperature.

In another aspect, the invention comprises a domestic kettle for heating water comprising an external ceramic coating on a substrate kettle shell.

The ceramic coating may comprise a ceramic transfer. Such a coating may comprise a temperature sensitive ingredient that changes colour with temperature. The colour change may indicate boiling point, and may differentiate between boiling point and a slightly lower temperature suitable for making coffee. The ingredient may comprise a thermochromic liquid crystal.

The invention also comprises a domestic kettle for heating water comprising an external ceramic coating on a substrate kettle shell.

The ceramic coating may comprise a ceramic transfer and may comprise a temperature-sensitive ingredient that changes colour with temperature.

The colour change may indicate boiling point, or may differentiate between boiling point and a slightly lower temperature, suitable for making coffee.

The temperature-sensitive ingredient may comprise a thermochromic liquid crystal.

The ceramic coating may comprise nano-particulate ceramic. The coating may also be applied to the heating element.

Embodiments of kettles according to the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is a circuit diagram of a first embodiment. Figure 2 is a circuit diagram of a second embodiment, and

Figure 3 is a view of a kettle with a ceramic coating temperature indicator.

The drawings illustrate domestic kettle arrangements for heating water comprising a heating element 11 and a temperature sensor 12 with a control arrangement 13 adapted to heat the water only to a given temperature below boiling temperature.

The kettle arrangements illustrated are also adapted optionally to heat the water to boiling temperature.

The sensor 12 is illustrated as a simple thermostatic switch, but could be any equivalent arrangement such as a platinum resistance thermometer in a bridge circuit with a discriminator to emit a control signal, on the attainment of the given temperature, to switch off the element current.

A simple thermostat switch and, if desired, the equivalent arrangement, will operate also to switch the element current back on when the water temperature falls a degree or so in order to maintain the water temperature at or around a temperature (say, 95 °C) suitable for pouring on to coffee grounds.

To heat the water to boiling temperature, in the embodiment of Figure 1. an additional switch 14 is arranged in parallel with the thermostat 12. The kettle first brings the water up to the given, thermostatically controlled temperature, at which is maintained by the thermostat so that coffee can be made immediately and without further ado. If, however, tea is required, the "boil" or override switch 14 can then be operated. This switch 14 may be a conventional, switch-off-at-boil switch, or may be another, higher-set thermostatic control.

Figure 2 illustrates a pre-select switch 21 which is set on first filling and switching-on the kettle to "C" for coffee or "T" for tea, the thermostats 12, 22 being set to the given temperature and boiling temperature respectively.

In both embodiments, a timer 15 picks up a "current-off ' signal from the element 11 lead and turns off a switch 16.

The two embodiments, as well as other variants, can be realised in simple format in a domestic kettle, which can be provided with a "boil" override switch or a pre¬ select switch as the main overt control for tea or coffee selection.

In addition, an adjustment 17 can be provided for pre-selection of the given temperature setting, say between 90° and 97 °C.

Visual and/or audible signal devices, such for example as light emitting diodes and chimes can be incoφorated.

Figure 3 illustrates a kettle 31 which may include the heating element 11 and sensor 12 as above described but which has a ceramic coating 32 in the form of a ceramic transfer applied to the substrate shell 31a of the kettle 31. The transfer is in the form of a thermometer scale and includes thermochromic liquid crystal material that changes colour up the scale to indicate temperature. "Coffee" and "tea" temperature levels are printed on the kettle or incoφorated into the transfer. If desired, the "coffee" indicator could highlight the word "coffee" and the "tea" indicator the word "tea" at the appropriate temperatures by incoφorating the colour-changing material in or surrounding the lettering of those words.

It is particularly advantageous if the ceramic coating is a selected nano- particulate coating in which desired properties can be "engineered". Such coatings can be made to have non-stick properties so that the kettle can be easily cleaned. Such coatings, again, can themselves have colour without the use of dyes and can change colour with temperature.

Inside the kettle (and this also would apply to kettles without the temperature and external decoration provisions described above) a nano-particulate ceramic coating could be applied to the heating element, and even over the entire inside of the kettle to eliminate build-up of limescale.

Claims

OAIMS

1. A domestic kettle for heating water comprising a heating element and a temperature sensor with a control arrangement adapted to heat the water only to a given temperature below boiling temperature.

2. A kettle according to claim 1 , adapted optionally to heat the water to boiling temperature.

3. A kettle according to claim 1 or claim 2, adapted to maintain the water at said given temperature.

4. A kettle according to claim 3, adapted to maintain the water at said given temperatures only for a certain time.

5. A kettle according to any one of claims 1 to 4, incoφorating a signal device indicating attainment of said given temperature.

6. A domestic kettle for heating water comprising an external ceramic coating on a substrate kettle shell.

7. A kettle according to claim 6, the ceramic coating comprising a ceramic transfer.

8. A kettle according to claim 6 or claim 7, in which the ceramic coating comprises a temperature-sensitive ingredient that changes colour with temperature.

9. A kettle according to claim 8, in which the colour change indicates boiling point.

10. A kettle according to claim 9, in which the colour change differentiates between boiling point and a slightly lower temperature, suitable for making coffee.

11. A kettle according to any one of claim 8 to 10, in which the temperature- sensitive ingredient comprises a thermochromic liquid crystal.

12. A kettle according to any one of claims 6 to 11, in which the ceramic coating comprises nano-particulate ceramic.

13. A kettle according to any preceding claim having a ceramic coating on the heating element.