GB2348542A

GB2348542A - Electric kettle

Info

Publication number: GB2348542A
Application number: GB9907255A
Authority: GB
Inventors: John William Mcclean
Original assignee: Breville Pty Ltd; Breville R&D Pty Ltd
Current assignee: Breville Pty Ltd; Breville R&D Pty Ltd
Priority date: 1999-03-29
Filing date: 1999-03-29
Publication date: 2000-10-04
Anticipated expiration: 2019-03-29
Also published as: CN1271556A; GB2348542B; GB9907255D0; CA2267871A1

Abstract

An electric jug kettle having a heating element 11, a manually operated switch 16 and a control mechanism to open the switch 16 when the kettle boils. The control mechanism comprises a reaction plate 24 having an upwardly extending arm 26, the reaction plate 24 being positioned above the heating element 11 to be acted upon by bubbles generated by boiling the liquid by the heating element 11. The reaction plate 24 and arm 26 are slidable between a lower position (fig 2) and an upper position (figs 1 and 3) to which it is raised by the action of the bubbles on the reaction plate 24 and by moving to the upper position the arm 26 opens the switch 16.

Description

Electric Kettle The present invention relates to an electric kettle suitable for boiling water.

In the field of electric kettles a number of switch control systems are in use which include the use of temperature sensitive bimetallic strips to trigger a switch to open circuit an electrical supply to a heating element.

Typically, the bimetallic strip is actuated by the temperature of steam rising from the boiling water which is directed to contact the bimetallic strip and thus trigger a switching mechanism.

It is also known to employ floats to trigger a switch to open circuit an electrical supply to a heating element to prevent a kettle from boiling dry.

The use of vibration sensors and ultrasonic wave reflection is also known in the control of apparatus for boiling water.

The applicants earlier application describes generally the use of the lifting force of bubbles which form in a boiling liquid to switch off a kettle.

According to the present invention, there is provided an electric kettle, including a jug, an electric heating element in the bottom of the jug, a manually operable switch and a control mechanism to open the switch when the kettle boils; wherein, the mechanism comprises a reaction plate having an upwardly extending arm, the reaction plate is positioned above the heating element to be acted upon by bubbles generated by the heating element, the reaction plate and arm are slidable between a lower position to which they fall by gravity, and a higher position to which they are raised by action of the bubbles on the reaction plate and in which the arm opens the switch.

This arrangement enjoys the significant advantage that it can be fitted to current kettle designs without any need to redesign the jug or the space housing the switching mechanism. The arm may pass through the aperture through which steam is vented to heat the bimetallic strip of current kettles.

The reaction plate may have any shape and configuration, and may be placed at any location, provided it will react to the bubbles generated by the heating element to rise. In one arrangement, the reaction plate extends continuously above the heating element, except for a gap around the edges which separate it from the wall of the jug.

It is advantageous if the reaction plate is designed and positioned so that it is raised, not so much by the buoyancy of bubbles trapped under the cover, but by their vigorous expansion and the turbulence they generate in the, relatively small, space beneath the plate.

Embodiments of the invention enjoy the advantage that the switch is opened by a movement of the mechanism that is directly related to the vigour with which the kettle boils.

Formations may be provided on the arm, the wall of the jug, or both, to provide interengagement between them so that the arm is maintained in vertical alignment as it slides up and down.

An example of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional schematic view of a domestic electric kettle with its control switch open; Fig. 2 is the same view as Fig. 1 with the control switch closed; Fig. 3 is the same view as Fig. 2 but configured as when the kettle has boiled.

Referring first to Fig. 1, the electric kettle 1 comprises a jug 10 in the bottom of which is positioned an electrical water heating element 11. Elermnt 11 is selectively connected to an electrical power supply via a microswitch 12. In accord with electrical authority requirements an auto reset thermal cut-out 13 is series connected in the power supply circuit to heating element 11 while a non-resetting thermal cut-out switch 14 is also in series with the heating element 11 as an overriding safety device.

Neon indicating light 15 is fitted in parallel with the heating element 11 to display when electrical energy is being supplied to heating element 11.

Nlanually operable switch control knob 16 coupled to switch arm 17 effects opening and closing of microswitch 12. Microswitch 12 being in the opencircuited position in Fig. 1 resulting from the interaction between arm 17 and switch lever 18 of microswitch 12.

Arm 17 biases control knob 16 to the power off position under the action of spring 19 while there are two fixedly settable recesses 20 and 21 on arm 17 which are able to be held against the varying bias forces of spring 19 by means of their interaction with spring loaded detent 22.

As shown, the switch mechanism is typically housed in the kettle handle.

In Fig. 2, jug 10 is shown to be filled with a body of water 23. At the bottom of jug 10 just above heating element 11 there is positioned a reaction plate 24.

The reaction plate 24 can take numerous shapes but is schematically represented here as a flat plate-like body extending continuously above the element except for a gap 25 around the wall of the jug. The reaction plate may be made from expanded polystyrene. An arm 26 extends above reaction plate 24 up the wall of the jug 10. At the top, arm 26 turns and passes through an opening 27 in the wall and engages the control knob 16. Some retaining means may be provided to keep arm 26 aligned down the side of the wall, but if any part of it is submerged it should be designed to operate despite a build up of scale.

The reaction plate 24 and arm 26 may be removable for cleaning and descaling.

To use the kettle it is first filled with water and switched on by actuating control knob 16. In Fig. 2 control knob 16 has been actuated by pressing it down until detent 22 enters recess 21 and the lower end of switch arm 17 has depressed microswitch 12. The heating 11 is now supplied with electrical energy and begins to heat the water 23. Note that the reaction plate 24 has been moved down close to heating element 11.

After a while the water 23 begins to boil and bubbles are gently formed under reaction plate 24. These bubbles will readily pass up through the gap 25 into the main body of water 23.

As the water begins to boil more vigorously larger bubbles are formed with greater frequency. These bubbles expand vigorously and generate turbulence beneath reaction plate 24, causing it to rise. As reaction plate 24 rises it causes arm 26 to rise and in turn raises control knob 16. As control knob 16 begins to rise, detent 22 leaves recess 21 and spring 19 draws up switch arm 17 until it returns to its Fig. 1 position and shown in Fig. 3. In this position the kettle has been switched off and it is safe to pour out the hot water.

Typically, the mechanism will be arranged so that reaction plate 24 will rise to switch off the power supply to heating element 11 once a rolling boil has been established.

Although the invention has been described with reference to a particular example, it should be appreciated that it may be exemplified in a variety of ways. In another example the reaction plate could take the form of an inverted cup or container which surrounds heating element, and it need not be continuous, it is only important that the action of the water boiling off the element is able to cause it to rise.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. An electric kettle, including a jug, an electric heating element in the bottom of the jug, a manually operable switch and a control mechanism to open the switch when the kettle boils; where, the mechanism comprises a reaction plate having an upwardly extending arm, the reaction plate is positioned above the heating element to be acted upon by bubbles generated by the heating element, the reaction plate and arm are slidable between a lower position to which they fall by gravity, and a higher position to which they are raised by action of the bubbles on the reaction plate and in which the arm opens the switch.

2. An electric kettle according to claim 1, where formations are provided on the arm, the wall of the jug, or both, to provide interengagement between them.

3. An electric kettle, including a jug for holding a liquid to be heated, an electric heating element in the jug, a manually operated switch and a control mechanism to open the switch when the kettle boils; wherein, the mechanism comprises a reaction plate having an upwardly extending arm, the reaction plate being positioned above the heating element to be acted upon by bubbles generated in boiling the liquid by the heating element, and the reaction plate and arm being slidable between a lower position and a higher position to which they are raised by action of the bubbles on the reaction plate and moving to which the arm opens the switch.

4. An electric kettle substantially as specifically described herein with reference to the accompanying drawings.