GB2308501A - Electric kettle - Google Patents

Description

DESCRIPTION IMPROVED ELECTRIC KETTLE This invention relates to electric kettles, which may be either in the form of a conventional kettle of very approximately cylindrical shape, or a jug kettle having a height greater than its diameter.

Both types of kettle comprise a hollow body to contain a liquid to be heated; an electrical resistance heating element within the body; a temperature sensitive switch, often a bimetallic element, arranged to disconnect the heating element from an electrical supply when it reaches a pre-determined temperature; and a steam chamber arranged to convey steam from the body to the temperature sensitive element, the temperature sensitive element providing automatic switch-off on boiling.

Various arrangements of steam chamber are known. For example, in a jug kettle, in which the body is made of plastics material, a channel can be moulded into the side of the jug adjacent the handle to convey steam to a temperature sensitive element arranged towards the base of the kettle.

A common factor in all arrangements is that the steam in the chamber adjacent the temperature sensitive element must cool and condense before the element can be reset. It may therefore be irritating to a user that the kettle cannot be switched on and reboiled immediately after automatic switch-off, and that a short time delay is inevitable. Further, there may be a considerable amount of steam to condense and drain from the base.

One method of reducing the amount of condensation is to make the steam chamber narrow in dimensions, but this requires a small diameter insert in the moulding tool in which a plastics material kettle body is moulded.

Other arrangements are known in which the steam path to the bimetallic element is modified.

In GB Patent Application no: 2252875 Strix Ltd., a steam aperture between the boiling vessel and the steam channel is provided with a flap which closes the aperture when the water boils, but the reset time delay is not thereby reduced, and nor is the quantity of steam which must condense.

In GB Patent Application No: 2282957, Fast Forward Design Ltd., the period of boiling before automatic switch-off is adjustable by providing a baffle in the steam path with a variable aperture to provide a variable impedance to the passage of the steam, but the reset time delay is not thereby reduced, and nor is the volume of steam which must condense.

According to the invention, an improved electric kettle comprises a hollow body for containing a liquid to be heated; an electrical resistance heating element within the body adjacent its base; an electrical control unit connected to the heating element and secured to the kettle external to the hollow body and adjacent its base, said electrical control unit including a moveable temperature-sensitive switching member arranged to make and break an electrical supply to the heating element; a steam chamber for conveying steam from the hollow body to the vicinity of the switching member; and a venting device operable with the switching member between a first position in which the steam chamber is closed and current is supplied to the heating element, and a second position in which the steam chamber is open and current is disconnected from the heating element.

Preferably the venting device comprises a hinged flap arranged to cover an aperture in the steam chamber.

Preferably the switching member is a bimetallic disk forming part of a rocker mechanism, and the hinged flap is mechanically connected to the rocker mechanism.

Preferably the steam chamber is moulded integrally with the hollow body, and optionally extends above the switching member substantially to the top of the vessel, the chamber having a first aperture at its upper end connecting the chamber to the hollow body, and a second aperture at its lower end on its side remote from the hollow body, which second aperture is covered by the venting device.

The invention will now be described with reference to the accompanying drawings in which Figure 1 is a partial view of a jug kettle having a venting device in the closed position; Figure 2 is a partial view of a jug kettle having a venting device in the open position; Figure 3 illustrates a standard bimetallic disc and rocker mechanism cooperable with the venting device.

Figures 4 and 5 shows in a frontal view and a side view respectively the venting device shown in Figures 1 to 3 in greater detail.

In Figure 1, a jug kettle comprises a hollow body 10 for containing water, the body being of plastics material, and there being a heating element 11 (see Figure 3) near the bottom of the body. Electrical current is supplied to the element through a socket 12 to which a plug (not shown) can be connected; the socket is connected to the element 11 through a controller 14.

Above the controller 14 and socket 12 there is a steam chimney 16 in the form of a vertical tube of rectangular cross section moulded as part of and external to the body 10, and having at its upper end an aperture 18 by which the chimney is connected to the inside of the hollow body 10. The chimney 16 conveys steam passing through the aperture 18 down to the controller 14, as indicated by the arrows A.

The chimney 16 terminates at its base with a housing portion 29. The housing portion 29 defines a control chamber within which a steam sensing element 28 (Figures 4 and 5) of the controller 14 is located. The lower end of the chimney 16, at the housing portion 29, has on its outer face a vent aperture 20 (see Figure 2) which enables venting of the control chamber, the aperture being covered by a vent plate 22. The steam chimney 16 and control chamber may together be considered as a steam chamber.

The vent plate 22 is supported by a horizontal hinge pin 24, and is moveable between the position in Figure 1 in which the plate closes the vent aperture 20 and the position shown in Figure 2 in which the plate rotates on the hinge pin and opens to allow steam within the control chamber and the chimney 16 to vent to the atmosphere. When the vent plate 22 is open steam may escape in the manner represented by arrows in Figure 2. This allows the steam sensing element 28 of the controller 14 to cool more quickly than has previously been possible, allowing very rapid reset of the sensor and minimising the delay between automatic switch off and permitted reboil.

Figure 3 illustrates the controller 14 with the vent plate 22 removed; any conventional controller, such as that made by Strix Ltd. may be used.

The controller 14 has a bimetallic steam sensing element 28 arranged at the base of the steam chimney 16 and within the control chamber. A rocker body 30 has a first, upper, arm 32 which can contact the element 28, and a second, lower, arm 34 which can contact a current-disconnect device 36 of known type.

When the first arm 32 contacts the sensing element 28, current flows to the heating element 38 until water in the kettle boils. Steam then passes down the chimney 16 into the control chamber, and the steam sensing element 28 operates on the rocker body which rocks so that the second arm 34 contacts the disconnect device, and current is disconnected from the heating element 38. As the rocker moves, it carries the vent plate 22 with it. Figure 1 corresponds to the current-connected position and Figure 2 to the currentdisconnected position.

The rocker body 30 pivots about the axis 24, which is fixed positionally relatively to the controller, by means not shown in the drawings. As in conventional steam responsive switches for kettles, the rocker body 30 may require manual resetting to return from the open position of Figure 2 to the closed position of Figure 1. For this purpose, the rocker body 30 and vent plate 22 may be mechanically coupled to a manual on/off switch of the kettle.

The rocker body is biased so that it will occupy only one of the two positions described above, thereby functioning as a bistable switching device.

Figure 4 shows, in greater detail, the steam chimney 16, control chamber defined by the housing 29 and controller 14 from a front view. The cross hatched area represents the vent aperture 20, from which steam can escape, as shown by arrows. The steam sensor 28 is positioned at the base of the chimney 16 where the chimney 16 opens into the control chamber. As shown in side view in Figure 5, when the vent plate 22 is closed, the steam sensing element 28 is at the base of the chimney 16 and the remainder of the controller 14 substantially fills the control chamber defined by the housing portion 29. All steam within the chimney 16 is thereby directed to the steam sensing element 28.

The advantages of an improved electric kettle according to the invention are that all steam passing into the steam chamber is directed to the bimetallic switch, giving swifter operation of the switch with a reduced volume of condensation; that the switch can be reset more quickly than has previously been possible; that a wide steam chamber integral with the kettle body can be used, which permits easier manufacture than the narrow steam tubes previously used; and that the cover can be designed to fit any standard controller, even controllers at different sizes, allowing easy interchangeability of controllers. The invention can be applied to a jug kettle, as illustrated, or to a conventional form of kettle.

Claims (6)

1. CLAIMS 1. An electric kettle comprising a hollow body for containing a liquid to be heated; an electrical resistance heating element within the body adjacent its base; an electrical control unit connected to the heating element and secured to the kettle external to the body and adjacent its base, said electrical control unit including a moveable temperature-sensitive switching member arranged to make and break an electrical supply to the heating element; a steam chamber for conveying steam from the hollow body to the vicinity of the switching member; and a venting device operable with the switching member between a first position in which the steam chamber is closed and current is supplied to the heating element, and a second position in which the steam chamber is open and current is disconnected from the heating element.
2. 2. An electric kettle according to claim 1 in which the venting device comprises a hinged flap arranged to cover an aperture in the steam chamber.
3. 3. An electric kettle according to claim 2 in which the switching member is a bimetallic disc forming part of a rocker mechanism, and the hinged flap is mechanically connected to the rocker mechanism.
4. 4. An electric kettle according to any preceding claim in which the steam chamber is moulded integrally with the hollow body.
5. 5. An electric kettle according to claim 4 in which the steam chamber extends above the switching member substantially to the top of the vessel, and has a first aperture at its upper end connecting the chamber to the hollow body and a second aperture at its lower end on a side remote from the hollow body which second aperture is covered by the venting device.
6. 6. An electric kettle substantially as described herein, with reference to, and as shown in, the accompanying drawings.