GB2397011A

GB2397011A - A liquid heating device having a keep-warm facility

Info

Publication number: GB2397011A
Application number: GB0300305A
Authority: GB
Inventors: Robert Andrew O'neill; Peter Hallam Wright
Original assignee: Otter Controls Ltd
Current assignee: Otter Controls Ltd
Priority date: 2003-01-07
Filing date: 2003-01-07
Publication date: 2004-07-14
Also published as: GB0300305D0

Abstract

A liquid heating appliance (eg a kettle) which includes a keep-warm mode that follows a boil mode, comprises a thermostat that is arranged to switch the appliance heating element on and off in cyclical fashion after boiling has been established thereby reducing the power output of the heating element. The appliance preferably includes a single heating element. The liquid-heating appliance may also include a boil control that is responsive to the boiling of the liquid in the appliance to switch the thermostat into circuit with the heating element. The device preferably includes first and second vessels in a heat transfer relationship with the liquid in the first vessel being kept hot by the heater thus keeping the liquid in the second vessel warm. The appliance is preferably cordless with a base part that is connected to the electrical supply, with complementary 360 degree input and output connectors being placed on the base and appliance. A rectifier may also be present.

Description

I

239701 1 Improvements Relating to Liquid Heating Vessels

Field of the Invention:

This invention concerns improvements relating to liquid heating vessels and more particularly concerns liquid heating vessels arranged to bring water to boiling and then to apply a reduced heating power so as to keep the water hot.

Background of the Invention:

It is well known to provide two heating elements in such a vessel, namely a main heating element with a high power output for heating the vessel contents quickly to boiling and a keep-warm heating element with a lower power output for keeping the vessel contents hot once they have boiled.

The change from high powered heating to relatively low powered heating can be triggered by a boil control responsive to the generation of steam when water boils within the vessel and the boil control can be arranged to switch between the main and keep-warm heating elements, to switch the keep-warm heating element in series with the main heating element, or to switch the main heating element out of a parallel arrangement of the main and keep-warm heating elements.

In TR 2001 02825U there is disclosed an appliance of a kind which is popular in Turkey and is used for making tea. The appliance consists of a water-boiling vessel having a teapot serving as a lid for the vessel. Water is boiled in the vessel and is used to make tea in the teapot. Not all of the boiled water is used for making the tea and, to keep the tea hot, the teapot is sat on / top of the vessel and the water remaining in the vessel is kept hot so as to keep the teapot hot.

The arrangement that is described in TR 2001 02825U has an underfloor sheathed heating element with parallel-connected first and second discrete sheathed element portions which are initially both powered and one of which is disconnected to reduce the heating power in the keep-warm mode of the appliance. In practice, the proprietors of TR 2001 02825U do not use this arrangement, probably on account of the fact that a sheathed heating element with only such a low power output as to be usable as a keep-wan heating element cannot easily be manufactured. Instead, a series arrangement of two sheathed heating elements is employed to achieve the required power reduction. When connected in series, the two heating element portions have a combined power output of about 140Watts and, since this would otherwise boil the water remaining in the vessel after the tea has been made, the keep-warm heating element is mounted on outriggers from the aluminium mounting plate of the heating element so as to reduce its thermal contribution to the heating of the vessel by isolating it, to a degree, from the vessel.

Clearly this arrangement is inefficient in its energy utilization.

Furthermore, as previously mentioned, the manufacture of low power output sheathed heating element is not without its difficulties since, to achieve the high electrical resistance that is required, a long heating coil of fine resistance wire is required and problems arise of reliability and size (projected diameter) of the element sheath. l l

Objects and Summary ofthe Invention:

It is thus the principal object of the present invention to overcome or at least substantially reduce the abovementioned problems of the appliance described in TR 2001 02825U.

According to the present invention, a liquid heating appliance having a keep-warm reduced heating mode following a boil mode has a thermostat which is arranged to switch the operation of the appliance heating element in cyclical fashion after boiling has been established thereby effectively to reduce the average power output of the heating element for the keep-warm mode.

An appliance in accordance with the present invention, for example an appliance of the kind described in TR 2001 02825U, might only have a single sheathed heating element providing both the main heat output required to bring the vessel contents quickly to boiling and the reduced heat output required for the keep warm mode. The boil control of the appliance would be arranged to respond to the boiling of the vessel contents, at the end of the heating to boiling phase of the appliance operation, by switching a suitably calibrated thermostat, a contactstat for example, in series with the single heating element so as to cause the element to cycle between ON and OFF conditions with a periodicity such as to produce the requisite heat output required for the keep-warm phase of the appliance operation.

A half-wave rectifier device, a diode for example, could be arranged to be connected in series with the heating element and the thermostat as a further adjunct to reduction of the power output of the heating element in keep-warm mode.

By use of a single sheathed heating element, the abovementioned problems of manufacturing, reliability and size can be overcome with the further advantages of enabling a smaller diameter heating element to be used with accompanying appliance design flexibility and reduced costs.

Further features of the invention are set forth in the appended claims and, together with the abovementioned features, will be well understood from consideration of the following description of an exemplary embodiment.

Description of an Exemplary Embodiment:

Referring to the drawings and description of the appliance described in TR 2001 02825U abovementioned, the boil control 8 is said to act to switch the heating element 3 out of circuit when water boils in the vessel 1, keep-warm heating then being effected by the heating element 4 which remains in circuit.

An embodiment of the present invention would comprise the arrangement disclosed in TR 2001 02825U but modified as follows, namely instead of the two heating elements 3 and 4 there would be just a single high powered heating element and, to reduce the power output of this single heating element for the keep-warm operating mode of the appliance, the boil control 8 would be arranged to switch a contactstat in series with the heating element, the contactstat being arranged to be responsive to the temperature of the heating element or of its mounting plate and being calibrated to switch ON and OFF in cyclical fashion as the heating element cools down and then heats up again so that the average power output of the heating element is correspondingly reduced. Otherwise, the appliance of TR 2001 02825U As mentioned previously herein, a rectifying diode could also be switched in series with the heating element by the boil control. This would substantially halve the power output of the heating element just by its own operation, thereby facilitating the task of the contactstat.

No further description of an embodiment of the present invention is considered to be necessary. A person of appropriate skills can readily understand the disclosure of TR 2001 02825U and can readily understand how to modify the disclosed appliance in accordance with the teachings of the present invention.

Whereas the appliance described in TR 2001 02825U makes use of sheathed heating elements, an embodiment of the present invention could instead use a thick film heating element. Furthermore, whereas the boil control 8, the dry boil (element overtemperature) protection control 6 and the 360 cordless connector set of the appliance described in TR 2001 02825U are products of Strix Ltd., in an embodiment of the present invention they would preferably be replaced by a Z5 boil control, an X4 dry boil protection control and a CS4/CP7 cordless connector set, all manufactured by Otter Controls Ltd.

Claims

Claims; 1. A liquid heating appliance in operation of which a keep-warm

reduced heating mode follows a boil mode, and wherein a thermostat is arranged to switch the appliance heating element ON and OFF in cyclical fashion after boiling has been established thereby to reduce the power output of the heating element during the keep-warm mode.
2. A liquid heating appliance as claimed in claim 1 having but a single heating element.
3. A liquid heating appliance as claimed in claim 1 or 2 wherein a boil control is responsive to the boiling of liquid in the appliance to switch said thermostat into circuit with the appliance heating element.
4. A liquid heating appliance as claimed in any of the preceding claims wherein a rectifier device is also switched into circuit with the heating element after boiling has been established.
5. A liquid heating appliance as claimed in any of the preceding claims wherein the appliance comprises a first vessel part for boiling liquid and thereafter keeping the boiled liquid hot, and a second vessel part for placement in heat transfer relationship with the liquid being kept hot in the first vessel part.
6. A liquid heating appliance as claimed in any of the preceding claims comprising a cordless appliance, a base part of the said cordless appliance being adopted to be connected to the electrical supply and a S power output connector being provided in said base part for supplying power to an appliance proper part having a complementary power input connector when the appliance proper part is operatively associated with said base part and the input and output connectors are operatively connected.
7. A liquid heating appliance as claimed in claim 6 wherein said power input and output connectors are 360 connectors such as to enable the appliance proper part to be seated on the base part in any rotational orientation relative thereto.
8. A liquid heating appliance as claimed in any of the preceding claims including control means associated with the heating element of the appliance for switching OFF the same in the event of a sensed heating element overtemperature condition.
9. A liquid heating appliance as claimed in claim 8 as dependent upon claim 6 or 7 and wherein said control means comprises at least one sensor device integrated with said power input connector.
10. A liquid heating appliance substantially as herein descnbed.