GB2363971A

GB2363971A - Conducting steam to a control of an electric liquid boiling vessel

Info

Publication number: GB2363971A
Application number: GB0013778A
Authority: GB
Inventors: John Crawshaw Taylor
Original assignee: Strix Ltd
Current assignee: Strix Ltd
Priority date: 2000-06-06
Filing date: 2000-06-06
Publication date: 2002-01-16
Anticipated expiration: 2020-06-06
Also published as: GB0013778D0; GB2363971B

Abstract

An electric liquid heating vessel comprises a moulded plastics body 4 having an opening in its base 12 which is closed by a planar electric heater 14. A steam sensitive control 30 for interrupting the power supply to said heater in the event of liquid in the vessel boiling, is arranged under the base 12 of the vessel and a steam duct conducts steam from the vessel to the control. The steam duct is formed by a channel integrally moulded with the body 4 and a cover (48, Figure 4) and extends downwardly through an aperture 54 in the heater 14 by means of a spigot 52 extending within a seal 56 which itself extends to and engages with the control 30.

Description

2363971 ELECTRIC LIQUID BOILING VESSELS The present invention relates to

electric liquid boiling vessels, and in particular, but not exclusively, to electric kettles, hot water jugs and the like used for boiling water.

Whilst traditionally in the United Kingdom kettles and hot water jugs have been provided with electric sheathed heating elements which project into the vessel through an opening in the side wall or base of the vessel, there has in more recent years been a move to providing the heating element externally of the vessel itself In such arrangements, a sheathed heating element may be suitably attached to the underside of the base of the liquid heating vessel, for example through a thermal diffusion plate bonded onto the vessel base (which is typically of stainless steel), or a so-called thick-film heating element be provided on the underside of the vessel base.

The base of the vessel on which the heating element is provided may be an integral part of the vessel or, more commonly, a separate plate which is mounted to close an opening provided in the vessel bottom The opening may cover a small portion of, or substantially the whole of, the vessel base, and suitable means are provided for mounting the base in the vessel.

Kettles and hot water jugs are also normally provided with steam sensitive controls which act to interrupt the supply of electrical energy to the element when liquid in the vessel boils This can be achieved by providing a steam sensitive switch in an upper part of the vessel, typically at the top of the vessel handle This switch is wired in series with a further thermally sensitive control which protects the vessel in the event of it being switched on dry or boiling dry.

However, such arrangements are costly, and it is more usual to integrate the steam sensitive control with the overheat protection control under the base of the vessel In such arrangementsl-a steam duct is provided between an upper part of the vessel and the steam sensitive control.

The present invention seeks to provide a new way in which a steam duct may be formed and suitably brought to a steam sensitive control.

From a first aspect, therefore, the invention provides a liquid heating vessel comprising a moulded plastics body having an opening in the base thereof, a planar electric heater mounted to close said opening; a steam sensitive control for interrupting the power supply to said heater in the event of liquid in the vessel boiling, said control being arranged under the base of said vessel; a steam duct formed at least partially integrally with said moulded body and having a steam outlet which extends downwardly through an aperture provided in said heater to conduct steam to said steam sensitive control.

Thus in accordance with the present invention, a steam duct is formed at least partially integrally with the moulded vessel body and has a portion which extends through an aperture in the heater to conduct steam to the steam sensitive control.

Preferably the portion of the steam duct which extends through the heater is formed as a hollow spigot, the hollow spigot engaging within a seal which itself extends through the aperture in the heater A seal is required to prevent leakage of water from the vessel into the control area under the vessel base.

Preferably the seal comprises a generally cylindrical body with a flange at one end which engages the wet side of the heater Preferably the seal is a sliding fit within the aperture in the heater for ease of assembly The inner bore of the sealing member is -3 preferably provided with an annular projection, or is tapered so as to engage with a cylindrical outer wall portion of spigot This acts to deform the seal outwardly so as to make sealing engagement with the heater aperture Preferably the arrangement is such that the seal expands around the lower edge of the aperture to seal therearound This acts to assist in locating the seal during use Preferably the sealing member extends to and engages with the steam sensitive control, thereby obviating the need for a further component to link the steam duct with the control This in itself is a novel and useful arrangement which has utility in arrangements in which the steam duct is both formed integrally with the vessel and as a separate member extending through the heater So from a further aspect, the invention provides a liquid heating vessel comprising a vessel body having an opening in the base thereof, a planar electric heater mounted to close said opening; a steam- sensitive control for interrupting the power supply to said heater in the event of liquid in the vessel boiling, said control being arranged under the base of said vessel; a steam duct extending downwardly through an aperture provided in said heater to conduct steam to, said steam-sensitive control, and sealing means arranged between said steam duct and said aperture and extending from said heater to said steam sensitive control of the vessel.

In order further to facilitate the construction of the steam duct, in a preferred embodiment of the invention the steam duct comprises a channel formed by a plurality of walls integrally moulded with the vessel body, the channel being closed by a separate member to form the duct This is advantageous because it facilitates manufacture of the steam duct It means that a steam duct of a constant cross section can be produced even in a tapering moulded vessel without the need for complicated mould arrangements The channel can be closed to form the duct by any suitable cover, for example a clip-on cover, or more preferably, an adhesive tape applied along the length of the channel.

thereof From a further aspect, therefore, the present invention provides an electric liquid boiling vessel comprising a steam duct for conducting steam to a thermally sensitive control of the vessel, said steam duct being formed by a plurality of walls integrally formed with the body of said vessel to form a channel, and a cover closing the open face of said channel to form said duct a preferred embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a sectional view of a kettle embodying the present invention; Figure 2 is an enlarged view of the lower portion of the kettle of Figure 1; Figure 3 shows a side view of the vessel body of the kettle of Figures 1 and 2; and Figure 4 shows a section along the line a-a of Figure 3.

With reference to the figures, an electric kettle 2 comprises a moulded plastics vessel body 4 of polypropylene or similar material The body 4 is provided with a pivotable lid 6 and also mounts a separate moulding 8 which provides a handle 11 for the kettle.

The body 4 is generally elliptical in cross section, as can be seen for example from Figure 4, and has an elliptical opening 10 formed in its bottom 12.

The opening 10 is closed by an elliptical planar thick- film electric heater 14 The body 4 is provided with a peripheral flange 16 for receiving a C-shaped seal 18 which engages the periphery 20 of the heater 14 The heater 14 is maintained in position by a plurality of springs 22 which engage the seal 18 and a shoulder 24 provided at the lower end of the vessel body 4 Such a mounting provides a flexible clamping for the seal 18 under thermal distortion of the vessel in use Further details of such a mounting can be found in our copending application GB 0010088 3.

Arranged under the base of the vessel is a thermally-sensitive control unit 30 The control unit is in fact a combined thermally-sensitive control and a cordless electrical connector and is available commercially as the Applicant's U 2930 control.

As is known in the art, the control 30 comprises a steam sensitive bimetallic actuator (not shown) which is arranged at one end of an arm 32 of the control unit 30.

When steam is conducted onto the actuator, it operate to trip a trip lever 34 of the control unit 30 (which is shown in its on and off two positions) to open a set of contacts to interrupt the power supply to the heater 14.

The trip lever 34 of the control 30 is coupled to an on- off knob 36 mounted at the upper part of the vessel body 4 by a link 37 which is arranged between the vessel body moulding 4 and the handle moulding 8 a moulded duct 38 is provided on the arm 32 for receiving steam for the control 30, as will be described further below.

The vessel body 4 has a generally elliptical inner wall, but with a re-entrant rear portion 40 a pair of ribs 42, 44 extend rearwardly from the wall 40 to define a channel 46 The channel 46 defined between the ribs 42, 44 is closed by a cover moulding eg a clip on cover or a heat and moisture resistant adhesive tape 48 which, together with the walls 40, 42 and 44, define a steam duct 50 which extends from an opening 51 in the upper part of the vessel body 4 to the control 30.

The lower part of the steam duct 50 is integrally formed with the body 4 as a hollow cylindrical spigot 52 depending therefrom The spigot 52 extends through an aperture 54 in the heater 14 a seal 56 is arranged between the spigot 52 and the aperture 54.

The seal 56 is of a heat resistant material such as silicone rubber and comprises an upper flange 58 for engagement with the upper surface of the heater 14 and the area of the vessel body 4-around the spigot 52 The seal is a non-interference fit within the aperture 54.

When properly assembled, the heater 14 may compress the flange 58 to form a seal The inner surface 60 of the seal 56 tapers so as to ensure a seal between the cylindrical outer surface of the spigot 52 and the seal.

In fact, the spigot 52 acts to deform the lower part of the seal 56 outwardly around the lower edge of the aperture 54 so as to seal around that edge The seal 56 will in fact expand beyond the diameter of the aperture 54 so as to assist in firmly locating the seal in position.

The lower end 62 of the seal 56 extends into the upper end of the moulded duct 36 provided in the control unit 30 This conducts steam from the vessel into the control unit 30 without a further coupling member.

It will be appreciated that various modifications can be made to the described embodiment without departing from the scope of the invention For example while the embodiment described employs a thick film heater a heater comprising a sheathed heating element attached to the underside of a heater plate may also be used, or indeed a heater in which a heating element is cast into a heater body.

Also whilst the invention has been described with reference to an electric kettle, it will be appreciated that it may find wider application, for example in coffee makers and other beverage & food preparation apparatus.

Claims

1 A liquid heating vessel comprising a moulded plastics body having an opening in the base thereof, a planar electric heater mounted to close said opening; a steam sensitive control for interrupting the power supply to said heater in the event of liquid in the vessel boiling, said control being arranged under the base of said vessel; a steam duct formed at least partially integrally with said moulded body and having a steam outlet which extends downwardly through an aperture provided in said heater to conduct steam to said steam sensitive control.

2 A liquid heating vessel as claimed in claim 1 wherein the portion of the steam duct which extends through the heater is formed as a hollow spigot which engages within a seal which itself extends through the aperture in the heater.

3 A liquid heating vessel as claimed in claim 2 wherein the seal comprises a generally cylindrical body with a flange at one end which engages the wet side of the heater.

4 A liquid heating vessel as claimed in claim 3 wherein the seal is a sliding fit within the aperture in the heater.

A liquid heating vessel as claimed in claim 2, 3 or 4 wherein the inner bore of the sealing member is provided with an annular projection or is tapered to engage with a cylindrical outer wall portion of the spigot.

6 A liquid heating vessel as claimed in any of claims 2 to 5 wherein the sealing member extends to and engages with the steam sensitive control.

7 A liquid heating vessel comprising a vessel body having an opening in the base thereof, a planar electric heater mounted to close said opening; a steam-sensitive control for interrupting the power supply to said heater in the event of liquid in the vessel boiling, said control being arranged under the base of said vessel; a steam duct extending downwardly through an aperture provided in said heater to conduct steam to said steamsensitive control, and sealing means arranged between said steam duct and said aperture and extending from said heater to said steam sensitive control of the vessel.

8 A liquid heating vessel as claimed in any preceding claim wherein the steam duct comprises a channel formed by a plurality of walls integrally moulded with the vessel body, the channel being closed by a separate member to form the duct.

9 A liquid heating vessel as claimed in claim 8 wherein the channel is closed by a clip-on cover or adhesive tape applied along the length of the channel.

An electric liquid boiling vessel comprising a steam duct for conducting steam to a thermally sensitive control of the vessel, said steam duct being formed by a plurality of walls integrally formed with the body of said vessel to form a channel, and a cover closing the open face of said channel to form said duct.