GB2056778A - Electric kettles - Google Patents

Abstract

An electric kettle comprises an electrical immersion heater 12 mounted on a metal head 22 having an externally threaded extension 24 on which a clamping ring 31 is engaged to secure the immersion heater to the kettle body 10; switch contacts 71, 72 mounted on a mounting 61 secured to the head 22 by a fastener 30; a dry overload responsive actuating mechanism 41, 43 located within the extension 24 for opening the contacts 71, 72 upon overheating of the head 22; steam responsive actuating means 82 located on a body 80 secured to or integral with the mounting 61; and switch sealing means which includes a flexible seal 51 embraced between the body 80 and the clamping ring 31, to prevent steam or water entering the extension 24. <IMAGE>

Description

SPECIFICATION Improvements relating to switch sealing arrangements for electric kettles This invention concerns improvements relating to electric kettles of the kind having a kettle body, an electrical immersion heater and switching means for controlling the immersion heater. The immersion heater comprises a metal sheathed heating element which is mounted on a metal head, and the head is mounted on the kettle body so as to project through a hole in the kettle body. The switching means projects outwardly from the kettle body and is electrically connected to the heating element which projects into the kettle body from the head.

There are known a very large number of different switching means for electric kettles of the above kind, for example, there are "steam actuated switching means" to switch the kettle off when it boils, "dry overload switching means" to switch the kettle off if the immersion heater overheats, and manually operable "on/off switching means".

There are sold a very large number of electric kettles which have only a dry overload switching means, because they are relatively inexpensive and because the dry overload switching means are usually small enough to be inserted between the metal head and a moulded plastics plug socket for an electrically supply cable connector, thereby to avoid having a large switch housing projecting from the kettle body. This type of kettle is known as a "non-automatic" kettle, and has the advantages of low manufacturing cost, simple manufacture, easy repair and durability; and only occasionally are there any warranty (guarantee) claims due usually to overheating.

There are also sold very large numbers of electric kettles of the type known as "automatic" kettles, which include steam actuated switching means, and usually also dry overload switching means. The steam actuated switching means normally controls the kettle so that the dry overload switching means becomes of secondary importance. In most automatic kettles there is a small vent near the top of the kettle body to allow steam to flow to the steam actuated switching means, and therefore there is a need to provide means for excluding steam and water condensate from the electrical contacts and electrical conductors of the switching means, thus making automatic kettles complicated and expensive to manufacture.

In order to reduce the cost of such automatic kettles it is known to use an on/off switching means which is manually operable to close or to open and close a single set of electrical switch contacts, and to mechanically (but not electrically) interconnect the mechanism of on/off switching means with a dry overload responsive actuating mechanism and a steam respbnsive actuating mechanism. This reduces the number of electrical components but gives rise to problems because steam and water can follow the mechanical interconnections of the actuating mechanisms to the electrical switch contacts, giving rise to expensive warranty claims.

Other automatic kettles have employed the more expensive alternative of using separate sets of electrical switch contacts in separate dry overload and steam actuated switching means, each set of contacts being individually protected from steam and condensate. However, these kettles are very expensive, difficult to repair and can suffer from electrical problems due to the large number of electrical contacts and connections, with resultant warranty costs.

There is a further problem with automatic kettles, in that if they are overfilled with water or tilted when full, water can flood out of the steam vent at a rate sufficient to flood the switching means, and hitherto the best answer to this problem has been to place the steam actuated switching means in the handle well above the water level, but this answer is expensive and requires lengthy electrical connections to the immersion heater.

An object of the invention is to provide means enabling a kettle manufacturer to produce improved automatic electric kettles at a reduced total manufacturing and warranty cost.

According to the present invention there is provided an electric kettle, comprising a kettle body, an electrical immersion heater, a clamping ring and switching means, wherein the immersion heater comprises a metal sheathed element permanently mounted on a metal head so as to produce a hot spot on the head, wherein the head has an externally threaded cylindrical extension, wherein the clamping ring is engaged around the extension to secure the immersion heater to the kettle body, wherein the switching means comprises a set of electrical switch contacts and a dry overload responsive actuating mechanism responsive to overheating of the hot spot to open the set of switch contacts and a steam responsive actuating mechanism, and wherein the switch contacts are mounted on an electrical insular ing mounting, characterised in that:: (a) said extension serves to define the periphery of a socket and said mounting is secured to said head by fastener means so as to locate the dry overload responsive actuating mechanism in said socket; (b) said steam responsive actuating means is mounted on a body secured to or integral with said mounting; and (c) sealing means is provided, and comprises a flexible seal disposed between said body and said clamping ring, to prevent any steam or water which flows down the outside ofthe kettle body from entering said socket.

The steam responsive actuating mechanism preferably actuates the switch contacts by means of a thrust member which extends slidably through a way in the mounting and body, and said thrust member preferably serves as part of, or co-operates with a portion of, the sealing means to prevent ingress of steam or water along the way.

A sealing arrangement is preferably included in the sealing means to close a recess provided in the switching means for access to said fastener means, and said sealing arrangement preferably sealingly engages an earth pin which projects from that side of the switch means remote from the head In preferred embodiments of the kettle the sealing means can be constructed so as to substantially preclude any of the steam or water which may flow from the steam vent from entering said socket or contacting the switch contacts, irrespective of how the kettle is held, and may possibly be effective to prevent water entering the socket or contacting the switch contacts even if the lower portions of the kettle are accidentally immersed in, for example, a sink or bowl full of water.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein: Figures 1 and 2 show vertical cross sections through an immersion heater and first and second embodiments of switching means, secured to the body of a kettle; Figure 3 shows an inside face of the switching means of Fig. 1, with portions of the immersion heater removed, to show portions of the switching means which are common to all of the embodiments of the switching means; Figure 4 shows an inside face of a mounting and electrical components common to all said embodiments; Figure 5 shows a cross section taken on the line V-V in Fig. 4, with an element and a steam responsive actuating mechanism removed; Figure 6 shows a vertical cross section similar to Figs. 1 and 2, and shows a third embodiment of switching means; and Figure 7 shows a part sectional general arrangement of an automatic kettle incorporating the third embodiment.

The electric kettle body has a wall 10 and is provided with a handle 11, an immersion heater 12, an earth pin connector 1 3 and a switching means. The switching means comprises an assembly of a dry overload responsive actuating mechanism 14, an electrical connector and switch arrangement 16, a steam responsive actuating mechanism 1 8, and is provided with a cover 15 or housing.

The immersion heater 1 2 comprises an element 20 having a metal sheath 21: a metal head having a main panel 22, a peripheral rim 23 and an externally threaded cylindrical extension 24 perpendicular to the main panel; and an elongate post arrangement. As shown in Figs. 1, 2, 3 and 6 the elongate post arrangement comprises a first portion in the form of a first post 25 which is secured perpendicularly to the main panel above a central axis 26 of the head, and a second portion in the form of a longer post 27 secured to the main panel so as to be parallel with and slightly above the post 25. The free end parts of the posts are internally threaded to receive two fasteners 30 one of which clamps the earth pin connector 1 3 directly to the post 27.The ends of the sheath 21 are secured to the main panel so as to leave cold tails 28 of the element projecting into a socket defined by the extension and the main panel, and an intermediate portion of the sheath is secured across one face of the main panel to provide a hot spot 29.

The immersion heater 1 2 is secured in a predetermined position in the body by a internally threaded clamping ring 31 which is screwed onto the extension 24 so as to clamp the rim 23 and a seal 32 to the wall 10. The alignment of the heater 1 2 with respect to the body can be maintained as the ring is tightened by locating the kettle in a jig (not shown) which holds the posts 25 and 27 in a predetermined position so as to prevent the head being turned by the turning of the ring.

The dry overload responsive actuating mechanism 14 comprises a moulded member 40 of a heat resistant thermal insulating material, a bimetal 41 of stressed snap-acting dished form located on one side of the member 40 by a cylindrical flanged metal retainer 42, and a push rod 43 which extends perpendicularly from the bimetal through a cylindrical guideway through the member 40 to project from the other side of the member 40.

The member 40 is apertured as shown in Fig.

3, to provide passages through which the posts 25 and 27 and cold tails 28 extend, and to receive projections or pegs 60 of the switch arrangement 1 6. Said one side of the member 40 provides a flat abutment face 44 which confronts and abuts the main panel 22, and is shaped to allow the bi-metal to snap from a convex dished form to a concave dished form, upon being heated to a predetermined temperature by the hot spot 29, to thrust the push rod 43 away from the hot spot.

The electrical connector and switch arrangement 1 6 comprises a mounting 61 together with a set of switch contacts, and electrical connectors which are arranged on the mounting as shown in Figs. 4 and 5. The connectors comprise a live electrical supply connector pin 62, and a similar neutral pin 63. The pin 62 extends through the mounting and is rivetted over to secure one end of a first spring connector 64 to an inside face 65 of the mounting. Said one end is further held by a projection 66 of the mounting. The neutral pin 63 similarly extends through the mounting and is rivetted over to secure a neutral connector 67 to the mounting which neutral connector has an extension which is clamped to one of the cold tails 28 by a cylindrical collar 68.A second spring connector 69 is secured to the inside face by two projections 70, and similarly has an extension which is secured to the other cold tail by a further collar 68. The set of switch contacts comprises a first contact 71 mounted on a free end of the connector 64 and a second contact 72 mounted on a free portion of the second spring connector 69.

The first connector 64 is arranged as shown in Fig. 5 so that it can be displaced by the push rod 43 to move the first contact away from the main panel so as to open the contacts, and the second spring connector 69 has an extension 73 which can be moved by a second push rod 74 in a direction towards the main panel sa as to open the contacts.

The spring connectors 64 and 69 are arranged so that when the first contact 71 is moved outwards away from the head, the second contact is prevented from following the first contact for more than a slight distance by the extension 73 abutting either the push rod 74 or the mounting adjacent the push rod; and similarly when the second contact is moved inwards towards the head, any movement of the first contact is restricted by the connector 64 abutting the push rod 43, or optionally an extension 45 of the moulded member 40 (shown in broken lines in Fig. 5). Furthermore the contacts are caused to wipe across each other slightly during the initial part of each opening movement and the final part of each closing movement, so as to be self cleaning.

The inside face of the mounting and the other side of the moulded member 40 are shaped to interengage and define therebetween a switch contact chamber 75, and the projections 60 are provided with terminal heads, after assembly, to secure together the mounting and the member 40. The peripheral surfaces of the member 40 and an adjacent portion of the mounting 61 are shaped so as to be a close sliding fit in the socket, and the outside face of the mounting is provided with a recess 77 and an abutment 76 which enables the mounting and member 40 to be clamped to the head by the second of the two fasteners 30, independently of the earth pin connector 1 3 which is partially accommodated in said recess.

The second push rod 74 of stepped cylindrical form extends through a stepped cylindrical way in the mounting.

The steam responsible actuating mechanism 18 comprises a body 80, a lever 81, and a steam actuable bimetal 82. The body 80 has an upper portion 83 which extends upwards from adjacent the ring 31 so as to confront the wall 10 of the kettle body to define a steam space 84 therebetween as shown in Fig. 7. The bi-metal 82 is mounted, at its upper end on a top part of the upper portion 83 so as to depend within the steam space alongside that side of the upper portion which confronts the wall 10.The lever 81 is pivotally mounted, as hereinafter described, so as to have an upper portion 85 which lies alongside the other side of the upper portion 83, and a top part of the portion 85 is engaged by a spring 86 which is located by the top part of the body, and is arranged so that the lever 81 is movable between a first stable position in which an abutment 87 of the lever abuts the upper portion 83 and a second stable position in which the abutment 87 is spaced apart from the upper portion 83. The lever has a lower portion 88 which in the first position is spaced apart from the second push rod 74, and in the second position abuts the push rod so as to hold the contacts 72 away from the contact 71, and further abuts a lower portion 89 of the body.As shown in Fig. 7 the upper portion 85 is shaped to provide a knob 90 which projects through the cover 1 5 to allow the lever to be moved manually to the first position.

The spring 86 is of round wire formed to S or Z shape so as to have top and bottom parallel limbs which are self centring in V or U shaped confronting grooves in the top parts of the body and lever, which limbs are connected by an intermediate transverse limb, and the arrangement is such that the compression on the spring is increased to a maximum when the lever is in an intermediate position between the first and second positions so as to urge the lever out of said intermediate position.

The wall 10 has an upper steam vent 33 which allows steam to pass from the kettle into the steam space 84 so as to heat the bimetal 82, whereby to cause the bi-metal to bend outwards away from the wall 10 to contact an abutment 92 on the upper portion 85, which abutment extends through an aperture in the upper portion 83 into the steam space, so that the movement of the bi-metal is transmitted to the lever to cause the lever to move to the second position via an unstable intermediate position.

The foregoing description applies generally to all the embodiments shown in the drawings, but these embodiments differ in some details, and in the protection of the switch contact chamber 75 from ingress of steam and water.

As shown in Figs. 1, 2 and 6 the clamping ring 31 is provided with an extension 34 which extends into an annular recess 50 in the body 80, and a sealing ring 51 is com pressed between the body and the extension 34 so as to seal the joint therebetween and close the recess 50 whereby to prevent steam, condensate water and flood water, which flows down the steam space 84 from entering the socket in the head and the switch contact chamber 75, furthermore the second push rod 74 is a close sliding fit in the aforesaid way so as to effectively seal the way against ingress of any steam or water which may, upon rare occasions, pass round the body to the side remote from the wall 10, but if necessary the push rod or way may have a small- amount of silicone grease applied thereto to serve as further seal in said way.

In each of the embodiments an outwardly open plug socket 52 is provided to receive an electrical supply connector (not shown), for conn-ecting tithe live, neutral and earth pins, 62, 63 and 1 3 which extend into said plug socket 52.

In the first embodiment shown in Fig. 1 the mounting and body are constituted by a single moulding of electrically insulating material, and the plug socket is provided on an extension 53 of the cover 15, which is secured to the integral moulding by two screws 54 so as to clamp a soft flexible plastics member 55 to the outside face of the integral moulding whereby to provide a seal arrangement which embraces the live, neutral and earth pins and serves to close the recess 77 which is provided in the integral moulding to provide access to and accommodation for the fasteners 30.

In the second embodiment shown in Fig. 2 the mounting and body are again integral, but the plug socket is defined by a hollow moulding 56 of flexible plastics material which serves as a sealing arrangement by embracing the pins and closing the recess 77, this sealing arrangement may optionally include a sealing ring 57 which is trapped between the outside face of the integral moulding and a peripheral portion of the hollow moulding 56.

The hollow moulding is clamped in place by the cover 15.

In the third embodiment shown in Fig. 6 the mounting 61 and the body 80 are separate mouldings held together by screws 58, so as to trap a sealing member 59 around the second push rod to seal the way. The plug socket 52 is formed integrally with the body moulding, and the recess 77 is filled with a sealing material so as to provide a sealing arrangement which closes the recess.

As shown in Figs. 1, 2 and 6 the lever 81 is supported on a pivot 91 which is located on the body 80 above the socket 52, and the lower portion 88 of the lever extends around the plug socket. The abutments 87 and 92 are threaded inserts in the upper portion 85 so as to be presettable or adjustable to determine the first position and to permit the relationship between the lever and the bimetal 82 to be adjusted or preset so that the switch contacts are opened when the bi-metal 82 reaches a predetermined temperature.

These inserts may be locked in position by the application of a sealing compound to the outside face of the upper portion 85 to close the openings in which the outside ends of the inserts are disposed.

The invention is not confined to the foregoing details and many variations are possible within the scope of the invention as defined by the appended claims. For example, whilst it is convenient to form the plug socket integrally in the body of the embodiment shown in Fig. 6, the plug socket could be moulded in the cover or moulded separately, and the body shown in Fig. 6 modified accordingly.

The embodiment shown in Fig. 6 has the advantages that a non-automatic kettle can be constructed, utilising the same immersion heater and dry overload switch means, simply by substituting a simple cover for the steam responsive actuating mechanism and cover 1 5. The simple cover preferably incorporates the plug socket 52 and the recess 50 to cooperate with the sealing ring 51 and clamping ting 31.

The seals, sealing members and mouldings 51, 56, 57 and 69 can be of any suitable flexible or resilient rubber or plastics material, or even, with the exception of the moulding 56, a silicone or like grease or a sealing compound.

The socket for the lower fastener 54 could be blind or sealed by the fastener or a plug to render the socket and the interior of the switching means substantially watertight.

It will be readily appreciated that the construction of the switching means and the provision of the seal 51 between the body and the clamping ring effectively prevents any ingress to the socket or switch chamber 75 of any steam or flood water which may descend within the steam space, and the other portions of the sealing means prevent any of such steam or water which may pass around the body to the outer space between the body and the cover 1 5 from entering the socket or switch chamber via any aperture, recess or way in the switching means directed towards said outer space.

The sealing of the pins to the plug socket is of lesser importance in some embodiments in so far as this steam and flood water is concerned, because the mouth of the plug socket is not accessible from either the steam space or the outer space but only from outside the cover; but if it is desired to protect the switch contacts against damage caused by accidental immersion of the lower parts of the kettle in water, the sealing of the pins can be helpful.

However, it should be understood that some leakage into the switch chamber could possibly arise if a hot kettle was immersed in cold water for a period sufficient to generate a vacuum within the switching means (due to thermal contraction of the enclosed air) sufficient to overcome some part of the sealing means.

Furthermore, with the exception of the head rim seal 32 of well proven form, the invention obviates the use of vulnerable diaphragm and other seals in contact with heated components, and seals clamped between the kettle body and the switching means, all of which seals are subjected to thermal or thermally caused mechanical stresses which can give rise to failure of the seals, whilst allowing a steam vent, rather than the alternative of the vunerable and easily blocked known steam tube, to be employed.

Claims (16)

1. An electric kettle, comprising a kettle body, an electrical immersion heater, a clamping ring and switching means, wherein the immersion heater comprises a metal sheathed element permanently mounted on a metal head so as to produce a hot spot on the head, wherein the head has an externally threaded cylindrical extension, wherein the clamping ring is engaged around the extension to secure the immersion heater to the kettle body, wherein the switching means comprises a set of electrical switch contacts and a dry overload responsive actuating mechanism responsive to overheating of the hot spot to open the set of switch contacts and a steam responsive actuating mechanism, and wherein the switch contacts are mounted on an electrical insulating mounting, characterised in that:: (a) said extension serves to define the periphery of a socket and said mounting is secured to said head by fastener means so as to locate the dry overload responsive actuating mechanism in said socket; (b) said steam responsive actuating means is mounted on a body secured to or integral with said mounting; and (c) sealing means is provided, and comprises a flexible seal disposed between said body and said clamping ring, to prevent any steam or water which flows down the outside of the kettle entering said socket.

2. A kettle as claimed in claim 1, wherein said clamping ring extends into a recess in said body, and wherein said flexible seal is disposed in said recess.

3. A kettle as claimed in claim 1 or 2, wherein said flexible seal is a resilient rubber or plastics sealing ring embraced between said body and said clamping ring.

4. A kettle as claimed in any preceding claim, wherein the steam responsive actuating mechanism is arranged to actuate the switch contacts via a movable member which is slidably located in a way, wherein said switch contacts and the dry overload responsive actuating mechanism are disposed at one side of the mounting, and wherein said way extends through the mounting from said one side.

5. A kettle as claimed in claim 4, wherein said movable member serves as part of, or cooperates with a part of, said sealing means to prevent ingress of steam or water along said way.

6. A kettle as claimed in claim 4 or 5, wherein the body and mounting are separate mouldings secured together so that the body is supported on the side of the mounting remote from said one side, and wherein said movable member extends through said body.

7. A kettle as claimed in claim 6, wherein live, neutral and earth electrical connector pins extends, from the side of the mounting remote from said one side, into a plug socket provided by the body to receive an electrical supply connector.

8. A kettle as claimed in claim 4 or 5, wherein said mounting and body are formed as an integral moulding, and wherein said way extends through said moulding.

9. A kettle as claimed in claim 8, including a plug socket to receive an electrical supply connector, and wherein live, neutral and earth electrical connector pins extend, from the side of the integral moulding remote from said one side, into said plug socket.

10. A kettle as claimed in claim 7 or 9, wherein the sealing means includes a sealing arrangement adapted to prevent water or steam entering the plug socket from entering said socket provided by the head.

11. A kettle as claimed in claim 10 as appended to claim 9, wherein said switch means is provided with a cover or houding, wherein said plug socket is provided in said cover or housing, and wherein said sealing arrangement comprises a flexible member clamped between the plug socket and said body.

12. A kettle as claimed in claim 10 as appended to claim 9, wherein said switch means is provided with a cover or housing, wherein said plug socket is a moulded plastics member clamped between the cover or housing and said body.

1 3. A kettle as claimed in claim 12, wherein said moulded plastics member serves as said sealing arrangement.

14. A kettle as claimed in any preceding claim, wherein a recess is provided in said mounting to provide access to said fastener means.

15. A kettle as claimed in claim 14 as appended to claim 7 or 9, wherein the earth pin extends from said recess, and wherein said recess provides access to a fastener securing said earth pin to the head.

16. A kettle as claimed in claim 14 or 15 as appended to claim 10, wherein said sealing arrangement serves to close said recess.

1 7. A kettle as claimed in any preceding claim, wherein the sealing means is substantially as hereinbefore described with reference to- Figs 1, 2 or 6 of the accompanying drawings