GB2033211A

GB2033211A - Electric Kettles

Info

Publication number: GB2033211A
Application number: GB7932837A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-21
Filing date: 1979-09-21
Publication date: 1980-05-21
Also published as: GB2033211B

Abstract

An automatic vapour-controlled electric kettle having thermally responsive means arranged to actuate switch means to interrupt supply of electric current to the immersion heater of the kettle when vapour emerging from a venting aperture (1) in an upper wall (2) of the kettle impinges on said thermally responsive means, comprises a float valve (3) mounted in relation to said venting aperture (1) so as to close said aperture upon a rise in the water level in said kettle above said aperture to prevent any substantial flow of water through the aperture. A snap-fit member 6 provides the valve seat. <IMAGE>

Description

SPECIFICATION Electric Kettles This invention relates to automatic vapourcontrolled electric kettles having immersion heaters and electrical switch means sensitive to the boiling of the water in the kettle.

It is known to provide such kettles with a vapour venting aperture in the upper wall thereof so that, when the water therein boils, a jet of water vapour discharges through the vent to impinge on thermally responsive means e.g. a bimetallic element, which actuates switch means to interrupt the supply of electric current to the immersion heater element. However, when such kettles are tilted away from their normal upright positions, for example during filling, it is possible for the water to pass through the vent hole into the housing for the switch means, producing electrical safety problems. This is particularly so with a spout filling kettle, or when a kettle is filled up to its maximum water level and tipped back as a considerable volume of water can be ejected under a head of water pressure.

In an attempt to overcome this problem gutters and drains have been provided to try to duct the water away, but none of these have proved wholly successful as the water ejected can be considerable in volume and rate of flow. Also, in an attempt to overcome this problem, kettles have been proposed having a vapour-discharge tube extending from the said venting aperture to a point in the kettle body near the top and towards the centre thereof. However, this does not provide a complete solution to the problem, since the end of the tube is still accessible to water within the kettle and the provision of such a tube within the kettle complicates the manufacturing process.

It is therefore the object of the present invention to provide a simple and reliably effective solution to the aforestated problem. According to one aspect of the invention, there is provided an automatic vapour-controlled electric kettle having thermally responsive means arranged to actuate switch means to interrupt supply of electric current to the immersion heater of the kettle when vapour emerging from a venting aperture in an upper wall of the kettle impinges on said thermally responsive means upon water in the kettle boiling and a valve mounted in relation to said venting aperture so as to close said aperture upon a rise in the water level in said kettle above said aperture to prevent any substantial flow of water through the aperture.

By virtue of the arrangement according to the invention, the valve will not interfere with the passage of vapour through the venting aperture, but will prevent any substantial volume of water from entering the electrical controls.

The valve is preferably a snap fit in the venting aperture so as to facilitate assembly of the kettle.

The valve seat may be the kettle wall itself or a seat member surrounding the aperture which may be a snap fit in an aperture in the kettle wall. The valve preferably comprises a valve member retained in the kettle by means of a member extending through the aperture. Alternatively, the valve member could be hingedly mounted, for example on a snap fit member as described above. The valve member would then normally be pivoted into a position away from the valve seat under its own weight when the kettle is in its normal upright position, but would be pivoted into a position in engagement with the valve seat if the kettle was tilted or filled until the liquid level reached the venting aperture.In another arrangement, the valve member is restrained in a cage which allows the valve member to drop to a position away from the valve seat under its own weight, but which guides the valve member into engagement with the valve seat as the liquid level rises.

Whilst hydrodynamic forces in the liquid will tend to force the valve member into contact with the valve seat, operation of the valve will be improved as the direction of approach of the valve member to the valve seat approaches the vertical, and the valve seat is horizontal in the case in which the density of the valve member is less than that of water. In order to achieve this, the venting aperture may be provided in a portion of the kettle wall formed to have an appropriate orientation, and/or a valve seat member as described above may be provided having a valve seat inclined relative to the aperture in the kettle wall with which it is associated.Thus, since the liquid level in the kettle will normally reach the vent during tipping of the kettle rather than simply by over-filling the kettle while upright, it may be desirable to provide a valve seat which is forwardly and downwardly inclined to the horizontal in the normal standing position of the kettle.

In one preferred arrangement, the valve member is buoyant in water. In this case, closure of the venting aperture is achieved by a combination of buoyant and hydrodynamic forces acting on the valve member. The valve member may then be made of a material which has a density less than that of water, such as polypropylene, or the valve member could be hollow or of a foamed plastics material. However, a solid valve member e.g. of plastics material is less prone to damage at the high temperatures that may occur if the kettle is switched on without any water therein. Alternatively, the valve member may be denser than water, in which case only hydrodynamic forces act on the valve member to effect closure. The valve member may then be made of a solid plastics material such as nylon.The material used should in any case be capable of withstanding such excess temperatures as well as the usual 1 000C of boiling water.

It is not essential for the valve to provide an absolute seal, as the electrical controls are designed to cope with small amounts of water, such as that formed by condensation on the thermally responsive means, by means of an arrangement of gutters and drains. However, it is desirable for any leakage of water through the vent to be kept to a minimum.

The valve preferably comprises a valve member mounted on a structure which is resiliently deformable when it is pushed through the vent aperture from inside the kettle body, but cannot then be pulled back through the aperture.

By virtue of such a construction, assembly costs are minimised whilst producing an arrangement having a long service life.

The structure may comprise a stem having a plurality of arms extending radially from the end thereof remote from the valve member. These arms may be resilient and extend towards the valve member.

In the accompanying drawings: Figure 1 shows a first preferred embodiment of a valve for use in a kettle according to the invention; and Figure 2 shows a second preferred embodiment.

As shown in Figure 1, a venting aperture 1 in a kettle wall 2 has associated therewith a float valve member 3 made of solid polypropylene with a specific gravity of 0.9. The member 3 is thus heavy enough to open the aperture 1 against the surface tension of water. The valve seat is provided by the kettle wall 2. The valve member 3 is connected to a stem 4 which extends through the aperture 1 and has two arms 5 on the upper end thereof. The arms 5 are flexible relative to the stem 4, so that they are resiliently deformable to allow the stem to be pushed through the aperture 1 and thus mount the valve member in the venting aperture.

In the embodiment of Figure 2, the valve seat is provided by a member 6 which is a snap fit in the aperture 1. The provision of such a member results in a more reliably formed valve seat, since it is difficult to punch a clean hole on the inside of a kettle wall.

Claims

1. An automatic vapour-controlled electric kettle having thermally responsive means arranged to actuate switch means to interrupt supply of electric current to the immersion heater of the kettle when vapour emerging from a venting aperture in the upper wall of the kettle impinges on said thermally responsive means upon water in the kettle boiling and a valve mounted in relation to said venting aperture so as to close said aperture upon a rise in the water level in said kettle above said aperture to prevent any substantial flow of water through the aperture.

2. A kettle as claimed in claim 1, wherein the valve is a snap fit in the venting aperture.

3. A kettle as claimed in claim 1 or 2, further comprising a valve seat member surrounding the venting aperture.

4. A kettle as claimed in claim 3, wherein said valve seat member is a snap fit in an aperture in the kettle wall.

5. A kettle as claimed in any preceding claim, wherein the valve comprises a valve member connected to a retaining member extending through the aperture to retain the valve member in the kettle.

6. A kettle as claimed in claim 5, wherein said retaining member comprises a stem having a plurality of arms extending radially from the end thereof remote from the valve member, said arms engaging the kettle wall in the open position of the valve member.

7. A kettle as claimed in claim 6, wherein said arms are resilient and extend towards the valve member so as to enable the stem to be pushed through the aperture.

8. A kettle as claimed in any preceding claim, wherein the valve member is buoyant in water.

9. A kettle as claimed in claim 8, wherein the valve member is made of a solid material having a specific gravity less than that of water.

10. An automatic vapour-controlled electric kettle provided with a valve substantially as herein described with reference to Figure 1 or 2 of the accompanying drawings.