GB2195234A

GB2195234A - Improvements in or relating to electrical kettles

Info

Publication number: GB2195234A
Application number: GB08623169A
Authority: GB
Inventors: Lou Beeren; Robert Geoffrey Goodsell
Original assignee: Philips Electronic and Associated Industries Ltd
Current assignee: Philips Electronics UK Ltd
Priority date: 1986-09-26
Filing date: 1986-09-26
Publication date: 1988-04-07
Anticipated expiration: 2006-09-26
Also published as: GB8623169D0; GB2195234B

Abstract

An electrical kettle is described comprising a vessel (1) having a plastics material body defining a receptable (5) for receiving liquid to be heated and an electrical heating element (36) disposed in the receptacle (5) for connection via an electrical control unit (38) of the kettle to an electrical supply. The plastics material body is formed so as to provide inner (3) and outer (9) walls for the receptacle. Thus, a first body portion (2) provides an inner wall (3) having an inner side wall (4a) and a base wall (4b) together defining the receptacle and an outer wall portion (6) formed integrally with the inner wall (3) so as to depend spaced apart from the inner wall (3) and so as to terminate just above the inner base wall (4b). A second body portion (8) engages the outer wall portion (6) to complete an outer side wall and to provide an outer base wall spaced from the inner base wall (4b) so that an insulating gap (13) is provided between the inner and outer walls. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electrical kettles This invention relates to improvements in or relating to electrical kettles.

Electrical kettles are known which comprise a body defining a receptacle for receiving liquid to be heated and an electrical immersion heating element disposed within the receptacle for connection via an electrical control unit of the kettle to an electrical power supply to enable liquid in the receptacle to be heated.

Although plastics materials normaliy have a lower coefficient of thermal conductivity than metals so that the heat loss through the walls of a plastics material kettle should be less than through the walls of a conventional metal-walled kettle, considerable heat may still be lost through the plastics material walls.

According to one aspect of the present invention, there is provided an electrical kettle comprising a vessel having a body defining a receptacle for receiving liquid to be heated and an electrical heating element disposed in the receptacle for connection via an electrical control unit of the kettle to anelectrical supply, characterised in that the body is formed so as to provide inner and outer walls for the receptacle and comprises a first body portion defining the inner wall and an outer wall portion integrally formed with the inner wall so as to depend spaced-apart from the inner wall and a second body portion engaging a free end of the outer wall portion to form a base of the outer wall of the vessel, the inner and outer walls being spaced apart to hinder heat flow from the vessel through the walls of the receptacle.

An electrical kettle in accordance with the invention thus enables the flow of heat through the walls of the vessel to be hindered facilitating an increase in the efficiency of operation of the heating element and thus potentially reducing the costs to the consumer by reducing, compared to conventional kettles, the amount of electricity required to boil a particular quantity of liquid.

Furthermore, because the space between the inner and outer walls hinders heat loss, the outer wall of a kettle in accordance with the invention will not reach as high a temperature as would the wall of a known kettle having a plastics material body so that the risk of a person who accidently touches the wall of the kettle during or immediately after operation of the kettle being burnt is minimised.

Also, because in use of the kettle, the kettle will be supported on a work surface by the outer wall, the inner wall surface can be shaped so as to define any desired shape of receptacle and may for example be shaped so as to minimise the volume of the receptacle beneath the heating element to reduce the minimum volume of liquid which can be heated in the kettle.

The base formed by the second body portion may be spaced-apart from the inner wall so as to define a continuous thermally insulating gap between the inner and outer walls.

Conveniently, the base of the vessel defined by the second body portion is secured to the inner wall by a fastening element or elements.

Normally the inner wall provides an inner side wall and an inner base wall and the outer wall provides an outer side wall and the outer base wall, the outer wall portion depending from the inner wall terminating above the inner base wall so that a part of the outer side wall of the vessel is formed by the second body portion.

Such an arrangement simplifies considerably the construction of the kettle because the outer and inner walls of the vessel are formed basically by the engagement of two body portions. Furthermore, the fact that the outer wall portion is integrally formed with the inner wall so as to depend therefrom means that the join between the first and second body portions is not provided at or adjacent an opening through which liquid is to be introduced into or removed from the receptacle so that the possibility of water entering between the inner and outer walls may be minimised.

The outer wall portion may be integrally formed with at least part of a handle thus enabling possible further reduction in construction costs. The handle may be hollow and may comprise an open channel cross-section extension of the outer wall, which extension defines with the outer wall an aperture for facilitating gripping of the handle, the channel cross-section extension being closed by a closure member so as to define within the handle a passage in communication with the insulating gap between the inner wall and outer walls of the vessel.Conveniently, with such a hollow handle, steam responsive means may be disposed within an upper part of the vessel, possibly within the handle, and a mechanical linkage may be disposed within the handle to move a movable rod of the control unit to disconnect the heating element in response to steam emanating from liquid in the receptacle contacting the steam responsive means.

Usually, the receptacle is provided with a lid, the inner wall and lid defining therebetween a passageway for enabling liquid to be poured from the receptacle. Conveniently, the inner wall is shaped, opposite the handle, so as to define a spout which forms with the lid the aforementioned passageway. In such a case, the outer wall may terminate at or adjacent a lower end of the passageway defined by the lid and the inner wall to facilitate pouring of liquid from the receptacle. Alternatively, the outer wall portion may extend along the spout but so that the gap between the inner wall and the outer wall portion tapers or nar rows toward the lip of the spout.

The present invention also provides an electrical kettle comprising: a vessel having a plastics material body, the body comprising a first body portion having an inner wall providing an inner side wall and an inner base wall together defining a receptacle for liquid to be heated, the inner wall being formed integrally with an outer wall portion which is spaced apart from the inner wall and depends from the inner wall so as to terminate at a free end just above the inner base wall, a second body portion engaging the free end of the outer wall portion so as to define therewith an outer wall having an outer side wall and an outer base wall, the outer base wall being spaced from the inner base wall so as to define a continous insulating gap between the inner and outer walls and a fastening element or elements being provided to secure the outer base wall to the inner base wall, an extension formed integrally with the outer wall portion and engaging a plastics material cover so as to define a hollow handle for the kettle and a plastics material lid closing the receptacle, an upper portion of the receptacle opposite the handle being shaped to provide a spout defining with the lid a passageway for permitting liquid to be poured from the receptacle, the inner wall and the outer wall portion being integrally formed so that the spout is formed only by the inner wall, the outer wall portion merging with the inner wall at or adjacent a boundary of the spout; an electrical heating element- disposed within the receptacle; an electrical control unit electrically connected to the heating element and disposed between the inner and outer walls so as to provide for connection of the heating element to an electrical supply; a mechanical linkage extending through the handle and movable between a first position in which the heating element is electrically connectable to an electrical supply via the electrical control unit and a second position in which the mechanical linkage causes a movable rod of the electrical control unit to move to break electrical contact of the heating element to an electrical supply via the control unit; a manually operable switch mounted partially within or adjacent the handle, which switch is connected to the mechanical linkage to move the linkage between the first and second positions so that the iink- age is in the first position when the switch is in an ON position and the linkage is in the second position when the switch is in an OFF position; a steam responsive device disposed within an upper part of the handle for receiving steam emanating from liquid in the receptacle via an aperture formed in the inner side wall adjacent the steam responsive device and moving the ON/OFF switch to the OFF position is response to steam contacting the steam responsive member to cause the mechanical linkage to move the movable rod to disconnect the heating element; and spring biassing means for biassing the ON/OFF switch toward the ON or the OFF position when the switch moves toward the ON or the OFF position, respectively.

In order that the invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal part cross-sectional view of a first embodiment of an electrical kettle in accordance with the invention; Figure 2 is a top plan view of the electrical kettle shown in Figure 1; Figure 3 is a front view of the electrical kettle shown in Figure 1 taken along the direction of the arrow Ill in Figure 2,; Figure 4 is a back view taken along the line IV in Figure 2 of the electrical kettle shown in Figure 1 with the left hand half of the kettle shown partly in cross-section and with electrical and mechanical internal components of the kettle omitted; and Figure 5 is a part-sectional back view of the kettle shown in Figure 1 showing a handle of the kettle with a cover of the handle and electrical and mechanical components within the handle removed; It should of course be appreciated that the drawings are schematic and are not drawn to scale.

Referring now to the drawings, Figures 1 to 5 illustrate an electrical kettle in accordance with the invention.

As shown in Figure 1 the electrical kettle is of a type commonly known as a jug kettle providing a vessel 1 having a substantially right-cylindrical body which is taller than it is wide.

The vessel body is formed of a heat-resistant plastics material, for example an acetal copolymer by moulding, usually injection moulding. The vessel 1 has a first integrally moulded body portion 2 providing an inner wall 3 formed by an inner side wall 4a and an inner base wall 4b which together define a receptacle 5 for liquid to be heated within the electrical kettle. An outer wall portion 6 is formed integrally with the inner wall so that the outer wall portion 6 depends from and is spaced apart from the inner wall 3. The outer wall portion 6 extends downwardly from or adjacent an edge 3a (Figure 4) of the inner side wall defining an opening 5a of the receptacle to terminate at a free end 7 a short distance about the inner base wall 4b.

A second body portion 8 comprising a flat surface 8a having an upstanding lip 8b engages the free end 7 of the outer wall portion so that respective projections 8"b and 7' provided on the free end 7 and an edge 8'b of the lip 8b overlap and interlock providing an interference fit. The second body portion thus completes an outer side wall 9 (Figure 3) of the vessel and also forms, by means of the flat surface 8a, an outer base wall 10 of the vessel. It should of course, be appreciated that any suitable means for connecting the first and second body portions may be used.

Thus, for example, the lip 8b and free end 7 may be screw-threaded to provide a screw connection. The outer base wall 10 may be secured to the inner base wall 5 as shown by means of a screw 11 which extends through a nut 1 lea and a centrally disposed aperture in the inner base wall 4b to engage in a centrally disposed projection or rubber foot 12 provided on the outer base wall 10. Further such fastening elements may be provided. Of course, the outer base wall 10 will be provided with two or more further rubber feet (not shown) to provide a stable base.

The outer side wall 9 may extend substantially parallel to the inner side wall 4 or may, as shown, extend at a slight angle thereto.

The outer base wall 10 is, as mentioned above, substantially planar to provide a flat supporting surface of the kettle to enable the electrical kettle to stand on a work surface (not shown). However, although the inner base wall 5 is shown in Figure 1 to be nearly parallel to the outer base wall 9 such need not necessarily be the case. Thus, for example, the inner base wall 4b may be curved so as to be continuous as well as integral with the inner side wall 4a. However, whatever the precise relationship between the inner and outer side walls and bases, an air gap 13 is provided therebetween to reduce heat loss through the walls of the vessel. As shown in Figure 1, the air gap 13 is continuous, however it may be possible for the air gap between the second body portion 8 and the inner wall 3 to be separate from that between the outer wall portion 6 and the inner wall 3.

As shown most clearly in Figures 1 and 4, the electrical kettle is provided with an integral handle 15 by means of a lateral extension of the outer wall portion 6. As illustrated in Figures 1, 4 and 5, the extension is in the form of a substantially rectangular cross-section member 16 having side walls 16a and a base wall 16b. The member 16 is integrally formed with the outer wall portion 6 and extends outwardly from the outer wall portion 6 adjacent an upper end 6a thereof, then travels substantially parallel to the outer wall portion 6 for a predetermined distance and returns to join the outer wall portions at a part 6b thereof so that an aperture 17 for facilitating gripping of the handle is defined between the channel member 16 and the outer wall portion 6.The side walls 1 6a of the channel member merge at 6b with the outer wall portion 6 to define therwith two substantially parallel lateral extensions 19 of the outer wall portions 6. The second body portion 8 is provided with a substantially rectangular cross-section laterally extending flange 20 having a free edge 21 which engages free ends 19' of the lateral extensions 19. The free edge 21 and the free ends 19' are of course extensions of the free edge 8'b and the free end 7, respectively, and engage one another in the same manner, that is by means of the interlocking projections 8"b and 7.

A cover plate 22 closes the open channel of the member 16. The cover plate 22 is formed by injection moulding from the same or a similar plastics material as the remainder of the vessel body. As is shown most clearly in Figure 1, the cover plate 22 extends downwardly beyond the handle and is provided with an inwardly directed flange 23 which engages the flange 20 so as to define between the inner plate, the flange 20 and the inner side wall 4a below the handle a relatively large cavity 24 for accommodating the necessary electrical circuitry as will be described hereinafter.

An upper end of the cover plate 22 is provided with a lip 26 which hooks over a lip 27 provided on an outwardly extending periperal shoulder 28 at the edge 3a of the inner wall 3. The lip 26 is secured to the lip 27 by means of a screw connection (not shown). It should, of course, be appreciated that any desired method of securing the cover plate 22 to the body of the kettle may be used.

A lid 29 formed of the same or a similar plastics material as the body is provided to close the opening 5a of the receptacle 5. As shown, the lid 29 is provided with a peripheral depending flange 30 which rests on the shoulder 28. The lid 29 has a centrally disposed recess 31 from which projects a knob 32 to enable the lid 29 to be removed from the kettle.

The knob 32 of the lid 29 may be replaced by a central rib within the recess 31 of the lid. It should, of course, be appreciated that in either case any desired form of gripping means may be provided to enable the lid 29 to be removed. Alternatively, the lid 29 may be permanently secured in place so that no gripping means are required. Of course if a permanent lid is provided, then the kettle will be designed to be filled always via the spout 33.

A region adjacent the edge 3a of the inner wall 3 opposite the handle is moulded so as to extend outwardly to define a substantially part-conical spout 33 for the kettle. The flange 30 of the lid 29 is provided with an extension 34 which, when the lid 29 is correctly positioned on the kettle body, extends into the spout 33 so as to define therewith a passageway 35 through which liquid may be poured from the kettle without removing the lid 29.

The spout 33 is formed only by the inner side wall in the arrangement shown in Figure 1. Thus, in the region of the spout 33 the integral connection between the inner side wall 4a and the outer wall portion 6 is at or adjacent an imaginary line 33a (Figure 3) defining the boundary between the spout and the rest of the inner side wall. It will of course be appreciated that apart from in the region of the spout 33, the outer wall portion 6 is formed integrally with the inner side wall 4a at or adjacent the edge 3a of the inner side wall.

As shown in Figure 1, an electrical immersion heating element 36 is disposed within the receptacle 5 above a metal base plate 37 provided on the inner base wall of the kettle. The heating element 36 is mounted so as to be electrically connected to an electrical control unit 38 via an opening in the inner wall. The electrical control unit 38 is secured to the outer surface of the inner wall adjacent the opening. The control unit 38 may have an internally threaded locking ring member 40 which engages an externally threaded portion on a head part 41 of the heating element 36.

The control unit has terminal pins 42 connectable via an aperture in the cover plate 20 to an appropriate mains electrical supply connector and lead (not shown).

The electrical control unit 38 incorporates sets of contact members for enabling the mains supply to be connected and disconnected from the heating element. The control unit includes thermal cut-out or 'boil-dry' cutout means, usually a bimetallic member in contact with the hot spot of the heating element (not shown), for opening a pair of contacts to disconnect the heating element from the mains supply when no liquid is present in the receptacle. The control unit also includes an automatic cut-out mechanism for switching the kettle off when liquid within the kettle boils. This cut-out mechanism comprises a mechanically movable switching member in the form of a spring biassed pin 44 and a mechanical lever assembly or linkage 45 which extends through the hollow handle to connect with a manually movable ON/OFF rocker switch 46 mounted within the top of the handle 15.Both the mechanical lever asembly 45 and the switch 46 are pivotally mounted to the body of the vessel by respective pivotal mounting elements 45a and 46a. Although the use of a rocker control switch is preferred, it should of course be appreciated that alternative control switches could be used, for example a slidable control switch could be used.

The lever pivot mounting element 45a is formed by two opposed supporting members 45b projecting from an integrally formed with respective opposite internal surfaces of the channel cross-section extension 16. In particular each supporting member 45b provides a U-shaped recess 45c within which is pivotally supported a respective pivot pin 45d provided on the lever assembly. Each U-shaped recess 45c may be closed by a respective web 22a projecting from an inside surface of the cover member 22 so as to retain the respective pivot pin 45d in the recess and complete the pivotal mounting.

The connection between the switch 46 and the lever assembly 45 is such that, when the switch 46 is in the ON position, the lever assembly 45 is in a first position as shown in Figure 1 and when the switch 46 is moved from the ON to the OFF position the lever assembly is pivoted to a second position in which the lever assembly pushes on the pin 44 to cause a set of contacts within the control unit to be opened to disconnect the heating element 36 of the kettle from a mains electrical supply.

A steam responsive member 47 in the form of a coil of a material available commercially and known as memory metal is provided on a stem 48 of the rocker switch 46. The stem 48 of the rocker switch is disposed within a steam chamber 49 provided within the hollow handle into which steam may pass via an aperture 50 formed in the inner side wall 4a.

The memory metal steam responsive member 47 is arranged to expand when steam enters the steam chamber due to boiling of liquid within the receptacle to cause the rocker switch 46 to be moved to the OFF position so causing the lever assembly 45 to push on the movable pin 44 to disconnect the power supply from the heating element.

An overcentre spring 51 is provided to bias the rocker switch 46 toward the ON or OFF position when the rocker switch begins to move toward the ON or the OFF position, respectively. In the arrangement shown, one end of the spring 51 is located on part of the rocker switch 46 and the other end is located within part of the lever assembly 45. Although not shown, the spring 51 may alternatively be located within a recess or hollow in the rocker switch 46. In such an arrangement one end of the spring 51 would be located on an interior surface of the rocker switch 46 while the other end would be located on the rocker switch pivot member 46a. In one particular example, a spring-biassed cam follower arrangement may be used. Thus, the rocker switch pivot member 46a may provide an upwardly extending passage within which passage is received a spring carrying at its free end a ball on which a cam or shaped surface of part of the rocker switch rides so that as the rocker switch is moved toward the ON or OFF position, the combination of the spring biassing and cam surface biasses the rocker switch into the ON or OFF position respectively. Of course, it should be appreciated that any appropriate spring biassing means connectable between the rocker switch and the lever assembly or the rocker switch pivot member 46a could be used.

A kettle embodying the invention may be provided with an optical water level indicator.

Thus, an elongate recess (not shown) may extend longitudinally up the kettle on the outer surface of the outer wall portion 6. The recess is closed by a transparent plastics material cover to form a small chamber. The lower end of the chamber is connected by means of a short plastics tube (not shown) to an aperture (not shown) provided in the inner side wall 4a so that the chamber communicates with the receptable. Thus, as the receptable 5 of the kettle is filled, liquid enters the chamberand the liquid level in the chamber of course rises or falls with the liquid level in the receptacle. A float may be provided in the chamber to indicate the liquid level in the chamber and therefore the liquid level in the receptacle.Alternatively, the surface of the elongate recess may have a pattern provided thereon, which pattern is optically distorted by any liquid in the chamber so that the liquid level in the chamber is clearly indicated by the change in the pattern at the interface between the liquid and air in the chamber.

Although in the arrangement described above, the handle is formed integrally with the outer wall portion, it would of course be possible to have a separately formed handle which is then secured to the outer wall, apertures being provided in both the inner and outer walls to enable electrical connections to be made to the the heating element 36 and to enable steam to enter the steam chamber 49.

Similarly, although the lid 29 has been shown as being single-walled, the lid 29 may also have inner and outer walls to reduce heat loss further. Also, although in the arrangement shown in Figures 1 to 4, the spout 33 is single-walled, the outer wall could be extended up to a lip 33a of the spout 33, the gap between the outer wall tapering or narrowing toward the lip 33a of the spout so as to avoid any deterioration in the pouring abilities of the kettle.

The body of the kettle may of course have any desired shape and may be, for example, of circular, rectangular or elliptical cross-section.

Claims

1. An electrical kettle comprising a vessel having a body defining a receptacle for receiving liquid to be heated and an electrical heating element disposed in the receptacle for connection via an electrical control unit of the kettle to an electrical supply, characterised in that the body is formed so as to provide inner and outer walls for the receptacle and comprises a first body portion defining the inner wall and an outer wall portion integrally formed with the inner wall so as to depend spaced-apart from the inner wail and a second body portion engaging a free end of the outer wall portion to form a base of the outer wall of the vessel, the inner and outer walls being spaced apart to hinder heat flow from the vessel through the walls of the receptacle.

2. An electrical kettle according to Claim 1, wherein the base of the vessel defined by the second body portion is secured to the inner wall by a fastening element or elements.

3. An electrical kettle according to Claim 1 or 2 wherein the inner wall provides an inner side wall and an inner base wall and the outer wall provides an outer side wall and the outer base wall, the outer wall portion depending from the inner wall terminating above the inner base wall so that a part of the outer side wall of the vessel is formed by the second body portion.

4. An electrical kettle according to Claim 1,2 or 3, wherein the outer wall is integrally formed with at least part of a handle for the vessel.

5. An electrical kettle according to Claim 4, wherein the handle is hollow.

6. An electrical kettle according to Claim 5, wherein the handle comprises an open channel cross-section extension of the outer wall, which extension defines with the outer wall an aperture for facilitating gripping of the handle, the channel cross-section extension being closed by a ciosure member so as to define within the handle a passage in communication with the insulating gap between the inner and outer walls.

7. An electrical kettle accoring to Claim 5 or 6, wherein steam responsive means are disposed within an upper part of the vessel and a mechanical linkage is disposed within the handle, the steam responsive means being arranged to cause the mechanical linkage to move a movable rod of the control unit to disconnect the heating element from an electrical supply in response to steam emanating from liquid in the receptacle contacting the steam responsive means.

8. An electrical kettle according to any preceding claim wherein the receptacle is provided with a lid, the inner wall and lid defining therebetween a passageway for enabling liquid to be poured from the receptacle.

9. An electrical kettle according to Claim 8, wherein the outer wall terminates at or adjacent a lower end of the passageway defined by the lid and the inner wall.

10. An electrical kettle comprising: a vessel having a plastics material body, the body comprising a first body portion having an inner wall providing an inner side wall and an inner base wall together defining a receptacle for liquid to be heated, the inner wall being formed integrally with an outer wall portion which is spaced apart from the inner wall and depends from the inner wall so as to terminate at a free end just above the inner base wall, a second body portion engaging the free end of the outer wall portion so as to define therewith an outer wall having an outer side wall and an outer base wall, the outer base wall being spaced from the inner base wall so as to define a continous insulating gap between the inner and outer walls, and a fasten ing element or elements being provided to secure the outer base wall to the inner base wall, an extension formed integrally with the outer wall portion and engaging a plastics material cover so as to define a hollow handle for the kettle and a plastics material lid closing the receptacle, an upper portion of the receptacle opposite the handle being shaped to provide a spout defining with the lid a passageway for permitting liquid to be poured from the receptacle, the inner wall and the outer wall portion being integrally formed so that the spout is formed only by the inner wall, the outer wall portion merging with the inner wall at or adjacent a boundary of the spout; an electrical heating element disposed within the receptacle; an electrical control unit electrically connected to the heating element and disposed between the inner and outer walls so as to provide for connection of the heating element to an electrical supply; a mechanical linkage extending through the handle and movable between a first position in which the heating element is electrically connectable to an electrical supply via the electrical control unit and a second position in which the mechanical linkage causes a movable rod of the electrical control unit to move to break electrical contact of the heating element to an electrical supply via the control unit; a manuaily operable switch mounted partially within or adjacent the handle, which switch is connected to the mechanical linkage to move the linkage between the first and second positions so that the linkage is in the first position when the switch is in an ON position and the linkage is in the second position when the switch is in an OFF position; a steam responsive device disposed within an upper part of the handle for receiving steam emanating from liquid in the receptacle via an aperture formed in the inner side wall adjacent the steam responsive device and for moving the ON/OFF switch to the OFF position in response to steam contacting the steam responsive member to cause the mechanical linkage to move the movable rod to disconnect the heating element; and spring biassing means for biassing the ON/OFF switch toward the ON or the OFF position when the switch moves toward the ON or the OFF position, respectively.

11. An electrical kettle substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 to 5 of the accompanying drawings.

12. Any novei feature or combination of features described herein.