GB2179544A - Improvements in electrical kettles - Google Patents

Abstract

An electrical kettle comprises a vessel (1) with a handle (4) and part of a control mechanism for the connection and disconnection of the electrical mains supply to a heating element (8) is located within a hollow portion of the handle (4). The control mechanism includes a mechanical assembly for moving a movable member (17) to make or break electrical contact of the heating element, the mechanical assembly comprising a steam responsive means (40,41) located in a steam chamber (18), a rocker control ON/OFF switch (25), a lever arrangement (28) and spring biassing means (36,37,38) for enabling the rocker control switch (25) and lever arrangement (28) to be locked in two stable conditions in which the lever arrangement (28) is effective to act upon a member (17) of a mains control unit (10) effective on movement to connect and disconnect the electrical mains supply to the heating element (8). The mechanical assembly is mounted to the vessel body by two discrete mounting elements, each of the mounting elements being separately provided on the vessel body and the rocker control switch (25) and lever arrangement (28) being mounted on the vessel body by respective ones of the two mounting elements (23,33). Thus, a stable arrangement is provided which is mechanically isolated from a cover member forming a closure of the handle (4), the cover member being removable to allow access to the control mechanism in its operatively assembled condition. <IMAGE>

Description

SPECIFICATION Improvements in electrical kettles This invention relates to electrical kettles, particularly but not exclusively to electrical kettles of the kind in which the vessel for boiling the liquid is of plastics material and now commonly referred to as jug kettles.

A known electrical kettle comprises a vessel for heating liquid having the vessel having a body comprising a base, a sidewall and a handle extending from the side wall; an electrical resistance heating element within the vessel adjacent the base; an electrical control unit connected to the heating ele mentandsecuredtothevesselatan opening in a lower part ofthe vessel side wall adjacent the base, said electrical control unit including a mechanically movableswitching memberforenablingthe making and breaking of the electrical supply to the heating element; a steam chamber extending adjacent an upper part of the vessel side wall which has an opening for enabling ingress of steam from the vessel into the chamber; a mechanical assemblyfor moving the mechanical movable switching member, the mechanical assembly comprising a manuallyoper- able ONIOFF control switch situated partly within or adjacentthevessel handle, a lever assembly extend- ing at least partly within the vessel handle and forming a mechanical linkage between the control switch and the switching element of the electrical control unit and spring biassing means operatively associated with the control switch and lever assembly for enabling the control switch and lever assemblyto be locked in first and second stable positions in which the switching member ofthe control unit is operative respectively to connect and disconnectthe electrical supply to the heating element; and a steam responsive element situated within the steam chamberand effective to cause movement of the control switch and lever assembly from the first stable position to the second stable position in the presence of steam emanating from liquid when boiling in the vessel. Such a kettle, hereinafter referred to as a kettle ofthe kind described, is available commercially in the United Kingdom and manufactured by Philips Electronic and Associated Industries Limited underthe type number HD4355. A kettle ofthis kind is also shown in Figure 4 of United Kingdom PatentSpecification No.2102205 B.

In such kettlesthevessel handle is of a generally hollow configuration and is closed by a cover member upon which is mounted the control switch and the lever assembly. In the commercial product HD4355 referredto above the steam responsive member additionally is mounted on the cover member and consists of a thermally responsive expandable metal coil member located on a part ofthe control switch with an abutment surface forthe coil member in its expanded position being constituted by a part of the cover member.By the mounting of at least the control switch and the lever assembly on the cover member there is provided a separable unit containing the ON/OFF control switching means for the kettle. I nthe designing of such kettlesth is was considered to be an advantageous feature as it enabled an easy assembly of these component parts to the main body of the vessel and furthermore the sensitive switching mechanism was mounted on the cover memberwhich was separate from the main body ofthe vessel and thereby had some thermal separation from the main body ofthe plastics material ofthe vessel. Additionally, the provision ofthese component parts as a separable unit was considered to be important in regard to the servicing ofthe kettle.However, in practice it has been found that this particular construction gives rise to certain problems. This is due two the fact that one ofthe commonly used plastics materials for moulding the vessel and also the cover member, namely acetal copolymer, has a high dimensional instability. Thus it is difficult to mould vessels and cover members from such a material within acceptable tolerance limits and furthermore the material has a high coefficient of expansion.With the described structure in which some ofthe components associated with the making and breaking ofthe electrical supply to the heating element, namely the steam responsive means, the control switch and the lever assembly are mounted on the separable cover member and another component, namely the switching member ofthe control unit, are mounted on the vessel body it is found that in order to obtain a satisfactory mechanical arrangementthe component parts must be manufactured to a very high tolerance as otherwise the effect of the high thermal expansion ofthe plastics material in the operation of the kettle can lead to an unreliable switching action.

It is an object ofthe present invention to provide an electrical kettle of improved construction where the aforesaid disadvantages are at least partly mitigated.

According to the present invention there is provided an electrical kettle comprising a vessel for heating liquid, the vessel having a body comprising a base, a sidewall and a handle extending from the sidewall; an electrical resistance heating element within the vessel adjacentthe base; an electrical control unit connected to the heating element and secured to the vessel at an opening in a lower part ofthe vessel side wall adjacentthe base, said electrical control unit including a mechanically movable switching member for enabling the making and breaking ofthe electrical supply to the heating element, a steam chamber extending adjacent an upper part ofthe vessel side wall which has an opening for enabling ingress of steam from the vessel into the chamber; a mechanical assembly for moving the mechanical movable switching member, the mechanical assembly comprising a manually operable ON/OFF control switch situated partly within oradjacentthevessel handle, a lever assembly extending at least partly within the vessel handle and forming a mechanical linkage between the control switch and the switching element ofthe electrical control unit and spring biassing means operatively associated with the control switch and lever assembly for enabling the control switch and lever assembly to be locked in first and second stable positions in which the switching member of the control unit is operative respectively to connect and disconnect the electrical supply to the heating ele ment;; and a steam responsive element situated within the steam chamber and effective to cause movement ofthe control switch and lever assembly from the first stable position to the second stable position in the presence of steam emanating from liquid when boiling in the vessel, in which electrical kettle the mechanical assembly is mounted to the vessel body by two discrete mounting elements the mounting elements being separately provided spaced-apart on the vessel body, the lever assembly being pivotally mounted to one ofthe mounting elements and the control switch being pivotally mountedtothe other of the mounting elements, and the handle has a removable cover which when removed enables access via the remainderofthe handle to the mechanical assembly mounted to the vessel body.

Thus as in an electrical kettle embodying the invention the control switch and the lever assembly are mounted to the vessel body by respective discrete mounting elements, tolerances due to the dimensional instability ofthe moulded plastics material ofthe vessel may be significantly reduced compared to those of an arrangementwhere the mechanical assembly is mountedto a detachable integral unit, for example the cover member in the arrangement described above, which is then mounted to the vessel body. The tolerance requirements thereby imposed on the switching means consisting ofthe control switch, lever assembly and the mounting ofthe steam responsive element are far less critical.This results in a significant reduction in the number of kettles which have to be rejected dueto failure on test during manufacture or in subsequent operational use. Additionally, the testing ofthe switching mechanism and inspection, particularlythevisual inspection, of the kettle durng manufacture is much morn readily facilitated because this can now be carried out without the cover member in postition. Testing of samples and inspection in the operative mode by boiling a liquid in the vesel can be more readily facilitated. The mechanical arrangement ofthe component parts consisting of the steam responsive means, the control switch and theleverarrangementandtheirmountingcanfurth- ermore be much simplified.

The one mounting element may comprise a lever pivot member within which the lever assembly is pivotally mounted, the lever pivot member being secured within a hollow portion ofthe vessel handle so as to be removable therefrom . In this form the location ofthe lever assembly in manufacture is simplified andthe pivot member being removable enables the simple replacement ofthe lever assembly for servicing purposes. Furthermore, by the use of appropriate plastics mouldingsthe pivotal mounting ofthe lever assembly can be provided without employing a metal pivot pin.Alternatively, the one mounting element may comprise two opposed supporting members projecting toward one anotherfrom opposite sides of an inner surface of a hollowportion ofthe handle, each supporting member having a recess in which a respective pivot pin of the lever assembly is supported, the recesses being closed by a web provided on the removable cover so as to complete a pivotal mounting forthe lever assembly, again enabling the use of a metal pivot pin to be avoided.

The other mounting element may comprise a switch pivotmemberwhich is secured within an upper portion ofthe vessel handle,the control switch being a rocker control switch pivotally mounted within the switch pivot member. In this form the advantage arises that the inspection ofthis part ofthe control mechanism in the finally assembled position is readily facilitated. Furthermore by the use of plastics moulding techniques the pivotal mounting ofthe rocker control switch can be provided withoutthe use of a metal pivot pin.The steam responsive element may comprise athermally responsive extendable metal coil memberslidably mounted on a stem forming part ofthe control switch and in the first stable position of the control switch extension ofthe metal coil member is limited by an abutment surface ofthe said other mounting element.

An embodiment ofthe present invention will now be described with reference to the accompanying diagrammatic drawings in which: Figure 1 shows a perspective view of part of a so-called jug kettle in accordance with the present invention and is shown with a cover member removed and with a side memberwhich forms part of a handle partly broken away, Figures 2 and 3 show vertical part cross-sectional views of the jug kettle shown in Figure 1 taken through the centre ofthe handle and in the two different stable positions of a rocker control switch and leverassem- bly and, Figure 4 shows a rear elevation of the jug kettle shown in Figure 1 with the rocker control switch and lever arrangement shown partly broken away and with the cover member removed.

Referring to the drawings there is shown a jug kettle comprising a vessel in this example of substantially rectangular section, formed by injection moulding of plastics material, in this example acetal copolymer.

The vessel 1 has a base 2 and a sidewall 3 within which there is a volume of .7 litresforcontaining liquid to be heated. Integrally moulded with the side wall 3 and extending therefrom there is a handle 4. The handle 4 is defined by a channel cross-section extension consisting of a base wallwith two integral side members extending therefrom and a cover member 44 which closes the channel and defines with the extension a hollow portion 5 ofthe handle. An apertureforfacilitating gripping ofthe handle is defined between the extension and the remainder of the side wall. The vessel 1 is closed by a lid 7 which is a push fit in the upper end ofthe vessel 1. Towards the handle 4 and on the surface ofthe sidewall 3there is a liquid level indicatorchamber7Ahaving a communicating passage to the interior ofthe vessel 1.

In the lower part of the vessel 1 there is located an electrical heating element8which is positioned above a metal base plate 9 on the base of the vessel. The heating element 8 is secured to an electrical control unit l0which is secured to thevessel at an opening 11 in a lower part ofthe side wall 3. The control unit 10 has an internallythreaded locking ring member 12 which engages an externally threaded portion on a head part 13 of the heating element 8. The control unit 10 has external terminai pins i4for connection of a mains supply connector and lead.

Within the control unit 10 there is incorporated sets of contact members for enabling the mains supply to be connected and disconnected to the heating ele- ment. A mechanically movable switching member in the form of a spring loaded button 17 extending from the rearsurface ofthe control unit 10 acts on one set of contact members. The control unitfurthercomprises thermal cut-out means which are effective on another set of internally provided contact members to discon nectthemainssupplytotheheating elementin an overheating situation when no liquid is present or remains in the vessel, the latter means being referred to as the "boil-dry" safety cut-out means.As the particular configuration of internal contact members and the "boil-dry" safety cut-out present in the control unit 10 do notform an essential part ofthe invention theywill notbefurtherdescribed. Inthefully depressed position of the spring loaded button 17 as shown in Figure 2 the mains supply to the heating element is disconnected. In the fully extended position of the spring loaded button 17 as shown in Figure 3 the mains supply to the heating element is connected.

Atthe upper hollow part ofthe handle a steam chamber 18 is formed adjacent the side wall 3 and an opening 19 is present inthe side wall to enable ingress of steam from the vessel into the chamber 18.

On the lower surface 20 ofthe chamber 18 which forms part of the base wall ofthe channel crosssection extension there is secured by means of two screws 21 one of two mounting element. The mounting element is a switch pivot member 23 of moulded plastics material, in this example of glass filled nylon.

the switch pivot member 23 has two lateral upstanding shoulders 24. An ON/OFF control rocker switch 25 of moulded plastics material is pivotally mounted in the switch pivot member by means of lateral projections 26 on the rocker switch 25 extending in openings 27 in the shoulders 24 ofthe pivot member 23.

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.

A lever assembly 28,in this example also of glass filled nylon, extends within the vertically disposed hollow partofthe handle4and has a lower end portion 29with averticalsurfaceforengagingthe button 17. At the upper end ofthe lever assembly 28 on oppositesidesthere are two slots 30 in which cylindrical projections 31 on the lower part of the rocker switch 25 can slide. The lever assembly 28 has on opposite sides two lateral cylindrical projections 32 (Figure 4) and these are located in apertures in the opposite internal surfaces of the second of the two mounting elemenstwhich is a U-shaped lever pivot member 33 of the same glass filled nylon plastics material. This arrangement forms the pivot point for the lever arrangement 28.The lever pivot member 33 hastwo slots 34 on opposite external surfaces which engage ribs 35 moulded on the internal surfaces ofthe two side members 6 of the channel cross-section extension which together with the cover member 44 forms the handle. The lever pivot member 33 is a push fit on these ribs and can be readily removed together with the lever assembly 28 pivotally mou ntedthereon via the cylindrical projections 32 extending in aper tures in the opposite internal surfaces ofthe member 33. Alternatively, although not shown, the lever pivot member 33 may be replaced by a lever pivot mounting element formed by two opposed supporting members projecting from and integrally formed with respective opposite internal surfaces of the channel cross section extension.In particular, although not shown, each supporting member may provide a U-shaped recess within which is pivotally supported a respective pivot pin provided on the lever assembly. Each U-shaped recess may be closed by a respective web projecting from an inside surface of the cover member 44 so as to retain the respective pivot pin in the recess and complete the pivotal mounting.

Atthe lower part ofthe rocker control switch 25 there is a peg 36 having thereon as a push fit one end of a coil spring 37. The other end ofthe coil spring 37 is located in an aperture 38 in a cross member part39 of the lever assembly 28. The coil spring 37 serves to lock the rocker control switch 25 and the lever assembly 28 in one of two stable positions, these beingthe positions shown in Figure 2 and 3 which respectively are the OFF and the ON conditions ofthe mains supply to the heating element 8. Although not shown, the coil spring 37 may alternatively be located within a recess or hollow in the rocker switch 25. In such an arrangement one end ofthe coil spring 37 would be located on an interior surface of the rocker switch 25 while the other end would be located on the rocker switch pivot member 23.In one particular example, a spring-biassed cam follower arrangement may be used. Thus, the rocker switch pivot member 23 may provide a passage extending upwardly from the su rface 20 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 rockerswitch is moved toward the ON or OFF positon, the combination ofthe spring biassing and cam surface biasses the rocker switch into the ON or OFF position respectively. Of course, it should be appreciatedthatanyappropriatespring biassing means connectable between the rocker switch and the lever assembly or the rocker switch pivot member 23 could be used.

The rocker control switch further comprises a stem 40 which is situated in the steam chamber 18. On the stem 40 there is slidably mounted a steam responsive element consisting of metal coil 41 of a material available commercially as Memory Metal. The thermal response ofthe coil 41 is maximum atthe boiling point of water. rn the ON position ofthe rocker control switch and lever assembly as shown in Figure 3the expansion ofthe coil 41 islimited by an internal abutment surface 42 formed on a part 43 ofthe switch pivot member23through which thestem40 can extend.

Thus, in operation, with liquid present in the vessel the rocker control switch 25 is manually set to the ON position as shown in Figure 3 and in this position the switch 25 and the lever 28 are spring-toaded by the coil spring 37 and thereby locked in a first stable position.

When the liquid boils steam entersthe steam chamber 18 and the metal coil 41 expands and due to the expansion being limited by the engagement with the surface 42 the rocker control switch 25 and lever assembly 28 are urged about their pivot points to move and thus release the spring loading provided by the coil spring 36 and to be finally locked in the second stable position (OFF) as shown in Figure 2.

From Figure 1 it can be seen thatthe rockercontrol switch 25 and the lever assembly 28 fixedly mounted on the vessel body as described via the switch pivot member 23 and the lower pivot member 33 are enclosed in the final assembly ofthe kettle by a removable cover member 44 which is formed of moulded plastics material and which, as described above, also forms part ofthe kettle handle.The cover member 44 is attached to the vessel body by means of (a) two screws each located at the base of a slot 45 in the lower part of the cover member 44 and secured in a moulded hole tapping 46 in the base of the vessel and (b) two screws each extending in a slot 47 in the upper wall ofthevessel and secured in a moulded hole tapping (not shown) in the upper part ofthe cover member 44.The cover member 44 has an aperture 49 for insertion of a mains supply lead, an aperture 50 providing access to the rocker control switch 25 and laterally extending vent apertures 51 which enable exit of steam from the chamber 18, it being noted that the boundaryofthesteam chamber 18 is formed in part by an upper surface part of the cover member 44 and internal vertical walls formed in the upper part of the cover member44. Apertures in these internal walls provide openings for passage of steam from the steam chamber 18to the vent apertures 51.

It will be appreciated thatthe assembly operation in the manufacture ofthis so-called jug kettle is made relatively simple by the provision ofthe mounting of the rocker control switch 25 and lever assembly 28 on the vessel body as described herein. Testing and inspection of the switching mechanism can be carried out without the cover member 44 in position. Operational testing of samples on manufacture can be effected with a temporary closure member provided tocompletethesteam chamberand enabling visual monitoring ofthe switching mechanism. This has to be compared with the described prior art structures in which testing could only be done with the cover member in its finally assembled position.However the principal advantage ofthe structure resides in the increased reliability obtainable and the facility to employ components with wider manufacturing tolerances.

Thus, in the arrangement described above, the control switch and the lever assembly are mounted to respective discrete and independent mounting elements separately provided on the vessel body so that, when the vessel ofthe kettle is formed of plastics material having a high coefficient of thermal expansion, a reliable and stable switching action may be obtained and the manufacturing tolerances imposed on component parts of the control mechanism can be less critical than in prior art structures where the components are assembled as a detachable integral unit which is then mounted to the vessel body, for example when the components are assembled as a detachable integral unit on a cover memberforthe handle.

Also, in the arrangement described above, the spring biassing element does not require a separate mounting element but is located atone end bypartof the rockerswitch and atthe other end by partbythe lever assembly or part of the said other mounting element.

It will be appreciated that various modifications to the structure described may be made within the scope ofthe invention, for example in an alternative form the steam responsive means comprise a bi-metallic element located in the steam chamber 18 and operative to cause movement ofthe control switch when subjected to steam emanating from liquid when boiling inthevessel 1. Furthermore, other materials may be employed in the construction ofthe vessel.

Claims (10)

1. An electrical kettle comprising a vessel for heating liquid, the vessel having a body comprising a base, a side wall and a handle extending from the side wall; an electrical resistance heating element within the vessel adjacent the base; an electrical control unit connected to the heating element and secured to the vessel at an opening in a lower part ofthe vessel side wall adjacent the base, said electrical control unit including a mechanically movable switching member for enabling the making and breaking ofthe electrical supply to the heating element; asteam chamber extending adjacent an upper part of the vessel side wall which has an opening for enabling ingress of steam from the vessel into the chamber; a mechanical assembly for moving the mechanical movable switching member,the mechanical assembly comprising a manually operable ON/OFF control switch situated partly within oradjacentthevessel handle, a lever assembly extending at least partly within the vessel handle and forming a mechanical linkage between the control switch and the switching element ofthe electrical control unit and spring biassing means operatively associated with the control switch and lever assembly for enabling the control switch and lever assembly to be locked in first and second stable positions in which Xa) switching member ofthe control unit is operative respectivelyto connect and disconnect the electrical supply to the heating element; and a steam responsive element situated within the steam chamber and effective to cause movement ofthe control switch and lever assembly from the first stable position to the second stable position in the presence of steam emanating from liquid when.

boiling in the vessel, in which electrical kettle the mechanical assembly is mounted to the vessel body by two discrete mounting elements the mounting element being separately provided spaced-apart on the vessel body, the lever assembly being pivotally mounted to one ofthe mounting elements and the control switch being pivotally mounted to the other of the mounting elements, and the handle has a removable coverwhich when removed enables access via the remainder of the handleto the mechanical assembly mounted to the vessel body.

2. An electrical kettle as claimed in Claim 1, wherein the one mounting element comprises a lever pivot member within which the lever assembly is pivotally mounted, the lever pivot member being securedwithin a hollow portion of the vessel handle so asto be removable therefrom.

3. An electrical kettle as claimed in Claim 1, wherein the one mounting element comprises two opposed supporting members projecting toward one anotherfrom opposite sides of an inner surface of a hollow portion ofthe handle, each supporting member having a recess in which a respective pivot pin of the lever assembly is supported, the recesses being closed by a web provided on the removable lever so as to complete a pivotal mounting for the lever assembly.

4. An electrical kettle as claimed in Claim 1,2 or3, wherein the other mounting element comprises a switch pivot memberwhich is secured within an upper portion ofthe vessel handle, the control switch being a rocker control switch pivotally mounted with in the switch pivot member.

5. An electrical kettle as claimed in Claim 2,3 or4, wherein the handle consists of a channel cross-section extension ofthe side wall, the extension having a base wall and integrally formed side members extending from the base wall, the removable cover closing the channel to define with the base wall and side members of the extension the hollow portion of the handle.

6. An electrical kettle as claimed in any one of the preceding claims, wherein the steam responsive elementcomprisesathermally responsiveextendable metal coil memberslidablymountedonastem forming part ofthe control switch and inthefirst stable position of the control switch extension ofthe metal coil member is limited by an abutment surface ofthe said other mounting element.

7. An electrical kettle as claimed in any one ofthe preceding claims, wherein the spring biassing means comprise a coil spring having one end located on a projection on the control switch and the other end located by a part of the lever assembly.

8. An electrical kettle as claimed in any one of Claims 1 to 6, wherein the spring biassing means comprises a coil spring having one end located on or in the control switch and the other end located by the said other mounting element.

9. An electrical kettle as claimed in any one ofthe preceding claims, wherein the mechanically movable switching element ofthe control unit consists of a spring loaded button extending from the control unit and engagable by an endsurfaceofthe lever assembly.

10. An electrical kettle substantially as herein described with reference to, and as illustrated in,the accompanying drawings.