GB2282957A - Water boiling device - Google Patents

Abstract

Portable water boiling device e.g. an electric kettle has a vessel (10), an electric heater (11) for heating water in the vessel, and switch means (12) comprising a switch (16) and a thermal actuator (25) responsive to steam for actuating the switch to switch off the electrical current to the heater. The device is characterised by a manually operable control (40) to control the switch (12) to enable the user to determine selectively the length of a boil period between commencement of boiling of the water and the moment of response of the switch (12) to switch off the heater (11). Control (40) is preferably in the form of a steam flow adjuster and may be a baffle or restrictor. <IMAGE>

Description

WATER BOILING APPARATUS This invention concerns electrically heated apparatus for boiling water.

Portable water boiling apparatus, such as electric kettles, are known of a kind comprising a vessel, an electric heater for heating water in the vessel, and switch means comprising a switch and a thermally actuable device responsive to exposure to steam for actuating the switch to switch off the electrical current to the heater.

One problem with such apparatus concerns the time taken by the device to respond to exposure to steam. On the one hand over-sensitivity of the device can give premature switch-off especially in instances where the vessel is operated to give successive boilings without any cooling-off interval; and on the other hand any under sensitivity can give rise to prolonged boiling which is wasteful of electricity and produces excessive quantities of steam. During production of such vessels considerable costs are incurred in achieving a satisfactory compromise setting of the individual devices, but nevertheless in a small percentage of such vessels the settings will alter to an unsatisfactory extent during use.

To overcome the problem, the present invention provides apparatus generally of said kind which is characterised in that a manually operable control means is provided to control the switch means to enable the user to determine selectively the length of a boil period between commencement of boiling of the water and the moment of response of the switch means to switch off the heater.

Preferably, the control means is adjustable to enable the rate -of steam heating of the device to be selected by the user of the vessel.

The vessel of the invention offers the user the further advantage of being able to increase the duration of boiling of the water, e.g. for sterilisation of the water or an article immersed in the water, and of being able to reduce the duration of boiling, e.g. for simply re-heating previously boiled water so as to reduce energy costs. The control means preferably comprises a steam flow adjuster.

The adjuster may comprise a baffle which is mounted in a part of the vessel so as to lie in a steam flow path between the chamber and the device, and which is movable deflect steam from, or to vary the proportion of the steam deflected from, a straight line flow path from the chamber to the device.

The adjuster may instead comprise a restrictor which is mounted in a part of the vessel so as to lie in a steam flow path between the chamber and the device, and which is movable to vary the flow cross-sectional area of said flow path. In an embodiment, the flow path is divided into major and minor portions and the restrictor is movable to and from a position blocking said major portion for varying said flow cross-sectional area. The major portion preferably extends direct from the chamber to the device; whereas the minor portion is preferably indirect.

In an embodiment the adjuster is movable between a minimum boil duration position, wherein it leaves open a direct line steam flow path between the chamber to the device, and a maximum boil duration position, wherein it obstructs said direct line steam flow path but leaves open or defects steam to the flow along an indirect steam flow path from the chamber to the device.

The adjuster preferably includes a movable control part which is exposed externally of the vessel (preferably adjacent to a switch-on control part for resetting the switch means) so as to be readily accessible to a user of the vessel.

The vessel may be of any suitable form, and may incorporate the heating means, or may be arranged to be heated when suitably located in or upon a support unit of the apparatus by heating means in the support unit.

The switch may be of electrical form, e.g. a relay or other heating current switch; and the device may be of electrical form, e.g. a thermistor, and may be remote from or integral with such a switch.

In a simple embodiment, the switch is mechanically operable and the device is a mechanism including a bimetallic or memory metal actuator which moves the mechanism to mechanically actuate the switch.

The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings, wherein FIGURE 1 is a sectional view showing a vessel of apparatus of the invention with a first embodiment of switch means and thermally actuable device; FIGURES 2 and 3 are enlarged sectional view of part of the vessel employing a second embodiment of switch means and thermally actuable device shown in on" and "off" positions respectively; FIGURES 4 and 5 show details of control means employed in the first and second embodiments; FIGURES 6 and 7 show details of a second form of control means; and FIGURES 8 and 9 show details of a third form of control means; and FIGURES 10, 11 and 12 show a modified form of the third form of control means.

The portable water boiling apparatus in these embodiments primarily comprises a vessel 10, in the form of an electric kettle, having heating means 11, switch means 12, an actuating device 13 and manually operable control means 14 for varying the duration of boiling of water in the vessel 10.

The heating means 11 includes an electrical immersion heater 15, which may be of known form, in a lower part of the vessel. The electrical heating current for the heater 15 is controlled by the switch means 12 which in the first embodiment of switch means (FIGURE 1) comprises a switch unit 16 disposed in an upper part of a side handle 18 of the vessel and connected by wires 19 to electrical connectors in the head 17 of the heater 15, and in the second embodiment the switch means comprises a switch unit of known form in the head of the heater 15.

In the first embodiment, the actuating device 13 comprises a bimetallic member 25 which bends suddenly or otherwise changes shape when heated by steam to shift a thrust member 25 upwards to shift a bistable rocker member 26 of an actuating mechanism 27 from a stable "on" position (shown in FIGURE 1) to a stable "off" position in which the rocker member 26 holds down a switch operating pin 28 to hold the switch unit 16 in an open condition to switch off the heater 15. The rocker member 26 protrudes through the handle so as to be manually actuable.

In the second embodiment of switch means FIGURES 2 and 3, the actuating device 13 comprises a memory metal coil 20 which, when heated to a predetermined temperature, increases rapidly in length to strike an abutment 18A and to shift a bistable actuating mechanism 21 from an "on" position (FIGURE 2) to an "off" position (FIGURE 3). The actuating mechanism includes a lever 21A which extends downwards in the handle to control the known form of switch unit in the head 17 in known manner. The coil 20 is located on an arcuately movable rocker member 22 of the mechanism 21, and the member 22 has a part 23 which projects through an opening in the handle so as to be manually actuable for moving the mechanism from either of said positions to the other, e.g. for resetting the switch.

In both embodiments, the upper part of main body wall 30 of the vessel 10 is slotted to provide a vertically elongate steam vent 31 to allow steam to flow from within the vessel to within the upper part of the handle for heating the actuating device 13, and a drain path for condensate is provided in the handle.

The control means 14 comprises a steam flow adjuster.

In a first form, the adjuster is a slider member 40 movable to vary the effective flow cross-sectional area in a direct line between the vent 31 and the actuating device.

The slider member 40 has a shaped aperture 41 therein, is located in the handle adjacent to the body wall 30 and has end portions -42 which extend through guide openings in opposite sides of the handle to enable the slider member 40 to be moved manually transversely of the handle to vary the area of the aperture 41 which registers with the vent 31.

The rate of flow of the steam which impinges upon the actuating device 13 will determine the rate of heating of the device, and thus the time taken by the device to react to such heating, after boiling commences, to cause the switch unit to switch off the current to the heating element. The slider member 40 is shown in its mid-position in FIGURES 4 and 5, in which position the mid-portion of the aperture 41 is interposed in said direct line flow path between the vent 31 and the coil 20 or bimetallic member 25, so that the steam flow path is minimally impeded to give the shortest settable boil duration.The slider is movable to the right (in FIGURE 5) to bring only the small triangular left-hand end portion of the aperture 41 into said direct line, for maximum boil duration; and is movable to the left to bring the larger right-hand end portion of the aperture 41 into said direct line to give an intermediate "normal" boil duration.

In the embodiment shown in FIGURES 6 and 7 the vessel can be similar to either the first or second embodiment, but a second form of control means 14 is employed, in which the adjuster, instead of varying the steam-flow crosssectional area, varies the steam flow path between conditions giving maximum and minimum deflections of the flow of steam emerging from the vent.In this form control means, the adjuster comprises a pivotally mounted vane 43 in the handle adjacent the vent, and a slider 44 exposed at and slidably mounted on one side of the handle, which slider 44 is connected by a joint 45 to the vane 43 to move the vane between a minimum boiling time position shown in full lines in FIGURE 7, in which the flow path extends linearly from the vent 31 to the coil 20 or bimetallic member 25, and a maximum boiling time position, shown in broken lines, in which it extends transversely across at least part of the vent 31 so that the steam flow path is impeded and the direct line steam is deflected so that some thereof passes upwards and over the upper edge of a portion 49 of the vane offset from the vent.

FIGURES 8 and 9 show a third form of control means 14 for use in the vessel, in which the adjuster comprises a pivotally mounted shutter member 47 which can be arcuately raised and lowered to vary the effective size of the vent 31, by means of an integral arm 48 which projects through one side wall of the handle 18. The shutter is shown in full lines in the position giving minimum boil duration, and the maximum boil duration position is shown in broken lines.

In the second and third forms of the control means 14, an upper part of the vent 31 is left unobscured even in the maximum boil duration setting, but, whereas in the second embodiment steam passing through this upper part is deflected upwards by steam passing upwardly over the top of the vane, in the third embodiment the shutter member 47 abuts the vessel wall so that there is no deflection from the direct line flow path of the steam emerging from said upper part.

In the embodiment shown in FIGURES 10 to 12, a modified form of the control means 14 having a sliding shutter member 50 is employed to abut the wall of the vessel adjacent to a main vent 3lA. The shutter member 50 has a body 51 which is slidably supported by an extension of the abutment 18A (not shown in FIGURE 11) against which the coil 20 reacts, and has a recess 52 in which the abutment is received when the shutter member 50 is in a maximum boil duration position in which it substantially completely closes the vent 31A as shown in FIGURE 10. In this position of the shutter member, the direct line steam flow path A to the coil 20 is blocked.The main vent 31A is supplemented by a further vent 31B offset from said direct line to provide an indirect steam flow path B in which the steam flow is deflected within the handle to reach the coil, to give a deflection effect similar to that achieved by the vane 43 in or near to its maximum boil duration position.

The shutter member 50 is slidable from the maximum boil duration position to a minimum boil duration position in which, as indicated in FIGURE 11, it is clear of the main vent 31A so that the path A is open. The further vent 31B remains open at all times.

The body 51 carries, via a stem 53, an exposed manually movable slider 54 located at the top of the handle adjacent to the part 23.

The wall 30 is provided with a pair of slots 55 to receive hinges 56 of a lid 57, which slots 55 lead into blind hinge reception cavities (not shown) in the handle.

The invention is not confined to details of the foregoing examples and many variations, modifications and/or functional equivalents are possible within the scope of the invention.

Claims (14)

1. Portable water boiling apparatus comprising a vessel, an electric heater for heating water in the vessel, and switch means comprising a switch and a thermally actuable device responsive to exposure to steam for actuating the switch to switch off the electrical current to the heater; and characterised in that a manually operable control means is provided to control the switch means to enable the user to determine selectively the length of a boil period between commencement of boiling of the water and the moment of response of the switch means to switch off the heater.

2. Apparatus as claimed in Claim 1 wherein the control means is adjustable to enable the rate of steam heating of the device to be selected by the user of the vessel.

3. Apparatus as claimed in Claim 1 or 2 wherein the control means comprises a steam flow adjuster.

4. Apparatus as claimed in Claim 3 wherein the adjuster comprises a restrictor which is mounted in a part of the vessel so as to lie in a steam flow path between the chamber and the device, and which is movable to vary the flow cross-sectional area of said flow path.

5. Apparatus as claimed in Claim 4 wherein the flow path is divided into major and minor portions and the restrictor is movable to and from a position blocking said major portion for varying said flow cross-sectional area.

6. Apparatus as claimed in Claim 3 wherein the adjuster comprises a baffle which is mounted in a part of the vessel between the chamber and the device, and which is movable to deflect steam from, or to vary the proportion of the steam deflected from, a straight line steam flow path between the chamber and the device.

7. Apparatus as claimed in Claim 3 wherein the adjuster is movable between a minimum boil duration position, wherein it leaves open a direct line steam flow path between the chamber to the device, and a maximum boil duration position, wherein it obstructs said direct line steam flow path but leaves open or deflects steam to flow along an indirect steam flow path from the chamber to the device.

8. Apparatus as claimed in any preceding claim wherein the adjuster includes a movable control part which is exposed externally of the vessel.

9. Apparatus as claimed in Claim 8 wherein the movable control part is adjacent to a switch-on control part for resetting the switch means.

10. Apparatus as claimed in any preceding claim wherein the switch is mechanically operable and the device is a mechanism including a bimetallic or memory metal actuator which moves the mechanism to mechanically actuate the switch.

11. Apparatus as claimed in any one of Claims 1 to 9 wherein the switch is of electrical form, such as a relay or other heating current switch.

12. Apparatus as claimed in any one of Claims 1 to 9 wherein the device is of electrical form, e.g. - a thermistor.

13. Apparatus as claimed in Claim 12 wherein the device is integral with or remote from the switch.

14. Apparatus substantially as hereinbefore described with reference to FIGURE 1, FIGURES 2 and 3, FIGURES 4 and 5, FIGURES 6 and 7, FIGURES 8 and 9 or FIGURES 10 to 12 of the accompanying drawings.