CA1174718A - Vessels for heating liquids - Google Patents

Abstract

A B S T R A C T
IMPROVEMENTS RELATING TO VESSELS
FOR HEATING LIQUIDS

The vessel for heating liquids includes a hollow body and an electrical heater together with control means which comprises steam responsive means, a switch assembly electrically connected to the heater, and a cover; fastener means secures said heater and switch assembly to said body.
In this vessel the cover comprises a housing secured to or integral with the body and a separable closure member releasably secured to the housing so that the housing and closure member define at least part of a main chamber; and the steam responsive means comprises a thermally responsive device and a mechanism, which mechanism is mounted on said closure member and is arranged to actuate said switch assembly when actuated by the thermally responsive device when the latter is subjected to steam entering the main chamber from the hollow body.

Description

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This invention concerns irnprovernents relating to vessels for heating liquids, which vessels are provided with an electrical immersion heater assembly and a switch assembly responsive to overheating of the electrical immersion heater assembly and to boiliny of li~uid in the vessel to switch off the electrical supply to the immerslon heater assembly~

It is known, for example, from the published SpeciEication of British Patent Application No. 7928416 (G.B. 2036541A) to provide a hole or vent in an upper part of the wall of the vessel and to provide the switch assembly with a steam responsive actuating mechanism which is actuable by a bimetal device disposed adjacent to the hole or vent so as to be subjected to steam issuing from the vessel vla the hole or vent. In this switch assembly, -the electrical components, such as the switch contacts and the conductors connecting the switch contacts to the immersion heater device and to electrical input terminal pins, are located in a chamber adjacent to a head of the imrnersion heater device, which head extends through a lower aperture in the wall of the vessel, some distance below the hole or vent. The electrical components are thus protected from exposure to dirt and water.

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The steam responsive actua-ting rnechanism extends a considerable vertical distance from adjacent to the hole or vent to the head, and is carried on a body of the switch assembly, which body also carries the electrical components and is mounted on the head so as to clamp a dry overload ac-tuating mechanism to -the head, so -that the dry overload actua-tiny mechanism is responsive to overheating of the immersion heater device to actuate the switch contacts. The body is an assembly comprising a vertically elongate main moulding, on which the steam responsive actuating mechanism is mounted, and a carrier moulding on which the elec-trical components are mounted, which carrier moulding can be fitted -to the head to enable the irnmersion heater, dry overload responsive actuating mechanism and electrical components to be tested tPrior to being fitted to the vessel and prior to the main moulding being connected to the carrier moulding).

However, some considerable skill is needed to assemble the vessel so as to ensure that the head is secured to the vessel in a predetermined position so as to locate the bim~tal device in position adjacen-t the vent or hole and to locate the main moulding in a position to receive an outer cover.

The skill required to assemble the vessel can be reduced by utilsing jigs to pre-align the vessel and immersion heater assembly, or by providing cooperating 4'~

-3 means on the head and vessel wall to ensure that the head is located properly prior to being secured in position, but such expedients are costly.
In our co-pending Application No. 391,448, filed on December 3, 1981, there is disclosed a switch means for use with an electrical immersion heater having a head adapted to be secured to - the wall of a vessel for heating liquids; wherein the switch means comprises a steam responsive mechanism mounted on a body to form a first assembly, and comprises a second assembly comprising a dry overload responsive actuating mechanism and a carrier member on which are mounted live and neutral electrical supply connectors, switch contacts, and conductors to connect electrically the connectors and the switch contacts with cold tails of the immersion heater; wherein the second assembly is securable to the head of the immersion heater so that a switch actuating member protrudes from the second assembly;
and wherein the first assembly is securable to the head independently of the second assembly by clamping means;
wherein the clamping means is arranged' to allow the first assembly to be rotated or moved arcuately relative to the head and the second assembly prior to being secured non-rotatably to the head; and wherein a part of the steam responsive mechanism extends to cooperate with the switch actuating member so as to be effective to open said contacts, when the steam responsive mechanism is s~bjected to steam, when the said part and actuating 74~8 member are in predetermined mutually relative positions ¦ and in relative positions adjacent to said predetermined relative positions.

This la-t-ter switch means facilitates assembly of a vessel and can be constructed so as to afford the advantages of reliability, ease of manufacture, protection of the electrical components, and ease of testing which are afforded by the switch assembly described in the aforesaid Specificati.on No. 2036541A.

Concerning repalrs, however, such switch assemblies and switch means are similar to other known switch assemblies in that the steam responsive actuating mechanism has to be removed before or together with the rest of -the assembly to provide access to the assembly to enable, for example, the switch contacts to be replaced; and therefore the steam responsive actuating mechanism has ; to be repositioned as the repair is completed.

According to the present invention there is provided control means for a vessel for heating liquids, the control means comprising, a cover, a switch assembly, and a steam responsive means; wherein the cover comprises a housing adapted to be secured to a portion of a wall of a vessel for heating liquids, a separable closure member ; releasably secured to the housing so that the housing and closure member define at least part of a main chamber;
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wherein the switch assembly is adapted to be electrically connected to an electrical heater element, and has fastener means to secure the switch assembly and electrical heater element to said wall; and wherein said steam responsive means comprises a thermally responsive device and a mechanism mounted on said closure member and arranged to actuate said switch assembly when the thermally responsive device is subjec-ted to s-team enteriny said main chamber.

The invention also provides a vessel for heating liquids comprising a hollow body, an electrical heater, and control means, wherein the hollow body is adapted to contain a liquid to be heated and has a wall upstanding from a bottom of said body; wherein the heater comprises an electrical resistance heating element disposed alongside said bottom; wherein the control means comprises steam responsive means, a switch assembly electrically connected to said element, and a cover; and . wherein fastener means secures said heater and switch assembly to said body; and characterised in that the cover comprises a housing secured to or integral with said wall, and a separable closure member releasably secured to the housing so that the housing and closure member define at least part of a main chamber; in that the steam responsive means comprises a thermally responsive device and a mechanism, which mechanism is mounted on said closure member and is arranged to actuate said switch assembly when actuated by the thermally -6- ~7~7~
responsive device when the latter is subjected to stearn entering the main chamber from the hollow body.

The mechanisrn preferably comprises a lever pivotally mounted on the closure member, and a manually movable part which extends through the closure member so as to be exposed for manual actuation to move the lever from a stable off position to a stable on position via an unstable intermediate position, whereby to cause the lever to move said switch member.

The heating element is preferably secured to a head of the heater so that cold tails of the element extend through a main panel of the head; the head is preferably provided with an externally threaded cylindrical portion and a peripheral flange around a junction between the main panel and the cylindrical portion; and said fastener means preferably includes fasteners clamping the switch assembly to the main panel, and includes an internally ~hreaded clamping member engayeable around the cylindrical portion to secure the head to the wall.

The switch assembly and fastener means are preferably accomrnodated in the main chamber above a drain opening, and the housing preferably defines an access opening which is normally covered by the closure member and which is disposed and dimensioned to provide access to the fastener means and the switch assembly -to permit the latter to be installed and removed through said access 7~3 opening.

The cover may serve as or form part of a handle of the vessel.
s It will be readily appreciated that the invention avoids the necessity to align the element with extreme accuracy in relation to the body thus obviating the use of jigs or expensive means for aligning the elements;
and enables the housing to be located accurately and rapidly so as to be corr!ectly aligned with a steam vent or hole in the wall for admitting steam to the main chamber. The correct alignment of the housing also facilitates the fitting and re-fitting of the closure member and steam responsive means or the mechanism.

There is also disclosed herein a vessel for heating liquids, comprising a body, a heater and switch assembly to control the supply of electricity to the heater, and a steam responsive means adapted to mechanically actuate the switch assembly when subjected to a flow of steam emerging from the body, characterised i.n that the vessel has a pivotally mounted ].id which cooperates mechanically wi-th the steam responsive means to cause the switch mechanism to switch off said supply when the lid is opened; and in this vessel the steam responsive means has a mechanism which preferably includes a pivotally mounted lever movabl.e, via an unstable -8- ~74 ~
intermediate position, between a first stable position, in which the switch assembly can switch on the supply, and a second stable position, in which the switch assembly is actuated to switch off the supply; the lever being manually movable between said positions and being held in said second position when the lid is open.

In use, the lid restricts -the escape of steam from the body so as to give a copious flow of steam to the steam responsive mechanism.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein:-Figure 1 shows a vertical section through a portion of a vessel in the form of an electric kettle provided with control means, in accordance with the invention;
Figure 2 shows a vertical section through part of a modified form of the vessel shown in Figure l;
Figure 3 shows a vertical section through a portion of a vessel in the form of a first embodiment electric jug provided with control means, in accordance with the invention; and Figure ~ is a view similar to Figure 3 showing a modified form of the jug in accordance with the invention.

1.

9 ~7~7~3 The electric kettle body has a wall 10 ar~d is provided with a handle 11, an immersion heater 12, an earth pin connector 13 and control means. The control means comprises a switch assembly including a dry overload responsive mechanism 14 and an electrical connector and swi-tch arrangement 16; a steam responsive actuating means 18; and a cover 15.

The cover 15 comprises a housing which is secured to the kettle body ].0 as hereinafter described, and a closure member 19 which is releasably secured to the housing 17.

The immersion heater 12 comprises an element 20 having a metal sheath 21; a metal head having a main panel 22;
a peripheral rim flange 23 and an externally threaded cylindrical portion 24 perpendicular to the main panel;
and an elongate post arrangement. The elongate post arrangement comprises a first post 25 which is secured perpendicularly to the main panel above a central axis 26 of the head, and a longer second 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 of fastener means, one of which fasteners 30 clamps the earth pin connector 13 directly to the post 27. The ends of the sheath 21 are secured to the main panel so as to leave cold tails of the element projecting into a socket defined by the cylindrical portion 24 and the main panel 22, and ~7~

an intermediate portion of the sheath is secured across one face of the main panel to provide a hot spo-t 29.

The immersion heater 12 is secured in a predetermined position in the body by an in-ternally threaded clamping I rnember 31 of the fastener means which clamping member is screwed onto the portion 24 so as to clamp the rim 23 and a seal 32 to one side of the wall 10 and to clamp a lower portion of the housing 17 of the cover 15 to the other side of the wall lO. The switch assembly is secured ¦ in the socket prior to the immersion heater being fitted ¦ to the kettle.

In the switch assembly the dry overload responsive 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 to provide passages through which the posts 25 and 27 and cold tails extend, and to receive projections or pegs of the switch arrangement 16. Said : 25 one side of the member 40 provides a flat abutment face which confronts and abuts the rnain panel 22, and is shaped to allow the bimetal 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 ho-t spot.

The electrical connector and switch arrangement 16 comprises a carrier member 61 together with a set of switch contacts, and elec-trical connectors which comprise a live electrical supply connector terminal pin, and a similar neutral pin 63. The live pin extends through the carrier member and is rivetted over to secure one end of a first spring connector 64 to an inside face of the carrier member. Said one end is further held by a projection of the carrier member. The neutral pin 63 similarly extends through the carrier member and is rivetted over to secure a neutral connector to the carrier member which neutral connector has an extension which is clamped to one of the cold tails by a cylindrical collar. A second spring connector 69 is secured to the inside face by two projections of the carrier member, and similarly has an extension whlch is secured to the other cold tail by a further collar. The set of switch contacts comprises a first contact mounted on a free end of the connec-tor 64 and a second contact mounted on a free portion of the second spring connector 69.

The first connector 64 is arranged 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 which can be moved by a mechanically movable switch member in the form of a second push rod 74 in a direction towards the ~74~

main panel so as to open the contacts.

The spring connectors 64 and 69 are arranged so that when the first contact 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 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 extenslon of the moulded member 40. 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 carrier member and the other side of the moulded member 40 are shaped to interengage and define therebetween a switch contact chamber 75, and projections on the carrier member extend through the member 40 and are provided with terminal heads, after assembly, to secure together the carrier member and the moulded member 40. The peripheral surfaces of the member 40 and an adjacent portion of the carrier member 61 are shaped so as to be a close sliding Eit in the socket, and the outside face of the carrier member is provided with a recess and an abutment 76 which enables the carrier memb er and member 40 to be clamped to the head by the second of the two fasteners 30, independently of the earth pin connector 13 which is partially accommodated in said recess.

The second push rod 74 of stepped cylindrieal form extends through a stepped eylindrieal way in the earrier member. A plug socket 52 is provided to receive an electrical supply connector (not shown), for connecting to the earth, live and neutral pins which pins extend from the carrier member through a wall of a plastics protective member 55 having an extension 53 which defines the socket 52. The plastics protective member 55 is secured to the rear or outside face of the carrier member by screws 28, and is provided with an aperture for the thrus-t rod 74.

The plastics protective member 55 has an inwardly or forwardly directed annular peripheral flange 56 which engages in a peripheral rebate in the rear of the carrier member. The clamping member 31 is internally grooved to receive a sea~ing ring 51 which engages a plain peripheral portion of the e~ternal surface of the flange 56.

The steam responsive means~18 comprises a mechanism mounted on the closure member 19, and a thermally responsive device in -the form of a steam actuable bimetal 82, the latter comprising an upper part, an elongate lower part and, between said parts, a U-shaped 7~

part. The member 19 is secured by fasteners 80 to the housing 17 to close an access opening in the housing 17, and so as to confront the wall 10 of the kettle body to define, together with the housing 17, a main chamber.
The bimetal 82 is mounted, by its upper par-t, on a top part 83 of the closure member 19 so as to depend wi-thin the main chamber alongside that side of the closure member 19 which confronts the wall 10. The mechanism comprises lever 81 pivotally mounted, on a pivot 91 on the closure member 19, so as to have an upper portion 85 which lies alongside the said side of the closure member 19, and is engaged by a spring 86. The spring is located by the top part 83 of the closure member 19, and is arranged so that the lever 81 is movable between a first stable positionl in which a lower portion 88 of the lever abuts an adjustable abutment 87 on a lower part of the closure member, and a second stable position, in which the abutment 87 is spaced apart from the lower portion 88.
In the first position the lower portion 88 is spaced apart from -the second push rod 74, and in the second position abuts the push rod so as to hold the second contact away from the first contact. In the second position the upper portion 85 abuts the closure member 19.
The upper portion 85 is shaped to provide a knob 90 which projects through the closure member 19 to allow the lever to be moved manually to the first position.

The lower part of the closure member 19 is apertured to allow the extension 53 of the protective member 55, which defines the plug socket, to ex-tend through the closure member to enable a supply connector to be inserted into the plug socket. The lower portion 88 of the lever is of ring form and extends around the plug socket.

The spring 86 is o~ 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 connec-ted 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 firs-t and second positions so as to urge the lever out of said intermediate position.

The wall 10 has an upper steam vent or hole 33 which allows steam to pass from the kettle into the main chamber 8~ so as to heat the bime-tal 82, whereby to cause the bimetal to bend outwards away from the wall 10 to contact an abutment 92 on the upper portion 85, so that the movement of the bimetal is transmitted to the lever to cause the lever to move to the second position vla an unstable intermediate position.

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The vessel is assembled by assembling, and individually testing, -the immersion heater, the switch assembly a second assembly comprising the closure member and the steam responsive mechanism. The switch assembly is then inserted into the head of the immersion heater and the earth pin is inserted and secured in place. The plastics member 55 is then secured in position. The immersion heater together wi-th the switch assembly is then inserted into the kettle vla the opening for the lid of the kettle, and the rear parts of the switch assembly and the cylindrical portion 24 of the head are inserted through the ~ower aperture in the wall lO until the seal 32 abuts the wall around the aperture.

The housing 17 is located against the wall 10 so that a bottom part 93 of the housing is located around the portion 24, and so that an upper part of the housing is aligned with an end part of the handle ll.

The element is then held so that the major part of the heating portion of the element lies in a plane which is substantially parallel to the bottom of the kettle, and the head and bottom part 93 are secured to the wall by means of the threaded clamping member 31, af-ter the sealing ring 51 has been inserted into the clamping member.

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The upper part 94 of the housing may enyage in a recess 95 in the handle 11, as shown, or may be fastened to or integral with the handle, whereby to locate said upper part 94 in relation -to the steam vent 33.

The immersion heater and switch assembly may be tested together as a unit prior to the unit being inserted into the kettle.

At this stage in -the assembly the element is secured in a predetermined position, or in a position which is angularly close to the predetermined position, and the interior of the kettle can be inspected visually to ascertain whether or not the positioning of the element is acceptable.

The second assembly comprising the closure member and steam responsive mechanism are then secured by fasteners to the housing to close the access opening and thereby substantially closing the main chamber except for the clearances at the junction between the housing and the vessel wall and handle, the clearances around the knob and socket, and a water drain aperture at the bottom of the housing.

As shown in Figure 2 adjustable clamping means lQO
may be provided to secure the bottom part 93 of the housing to the clamping member 31. The latter has an ` 1~7~7~

external flange which is clamped between the housing and a clamp ring 35 by screws as shown, so that the housing can be secured in position after the clamping member 31 has been tightened.

In use any knocks or bumps applied to the cover 15, and the shock loads generated by the operation o~ the steam responsive mechanism are transmitted directly to the wall of the vessel without being imparted to the second assembly except for the load applied by the lower portion 88 of the lever to the second push rod 74. Furthermore any steam, water or condensate draining down from the steam space 84 will be allowed to drain away around the clamping member 31 and will be prevented from entering the second assembly by the sealing ring 51 and the plastics protective member 55, which extends across the main chamber and effectively provides a barrier between the electrically conductive components and the main chamber.

Furthermore, the portion 88 has a considerable area which is available for abutting the push rod 74, so that the portion 88 can cooperate which the push rod not only when said switch and second assemblies are in their predetermined positions, but also when the second assembly is in a position which is displaced fractionally from said predetermined position so that the positioning of the element is no longer critical.

The jug constituting the second embodiment shown in Figure 3 differs from the first embodiment firstly in the form of the body, housing and second assembly, but employs the same heater switch assembly, and fastener means;
and -the jug shown in Figure 4 has a further modified steam responsive means.

In Figures 3 and 4 the same reference numbers are given to parts which are identical to the same parts shown in Figure 1 or 2 and are not hereinafter described, whereas modified parts which are similar or èquivalent to parts shown in Figure 1 are indicated by the same reference numbers with the suffix B in Fiqure 3 and the suffix C in ~igure 4. Some of the parts common to all embodiments are omitted from Figures 3 and 4.

Referring to Figure 3, the body has a wall lOB, which may be made of metal, glass, ceramics or plastics, to which the cover 15B is secured. The cover 15B
comprises a housing 17B and a closure member l9B which cooperate to serve as a handle llB for the jug, the housing servlng to define a large opening 110 to accommoda-te part of a user's hand. The upper part 94B
of the housing is secured to the top of the wall lOB
by the fastener 36, and serves as a mounting for a pivot pin 111 on which a lid 112 of the jug is carried.
The bottom part 93B has an extension 113 which serves as a wide base for the body, so as to provide thermal -20~ 7~
insulation and an air gap below the body.

The closure member l9B carries a steam responsive means 18B to Eorm the second assembly, and the top part 83B serves as a mounting for both the adjustable abutments 87Band 92B,whereas the lower part of the closure member provides one of the confronting grooves in which the spring 86 is located, the other groove being provided at the bottom of the lever 81B. The lever 81B
carries the bimetal 82B, and the knob 90B is disposed at the top of the lever to project through the cover. The upper part of the lever abuts the abutment 8;Bin the first position, and the bimetal 82B bends, when heated by steam entering the chamber 84B vla the steam vent 33, to abut and react against the abutment 92B 7hereby moviny the lever towards the second position.

The upper part of the lever 81B carries an extension 114 which extends towards a hinge part 115 of the lid, which part 115 incorporates a cam 116 to engage the extension 114 to move the lever from the first to the second position when the lid is opened and to prevent the - heater being switched on whilst the lid is open.

In both embodiments the closure member 19 or l9B
can be removed to allow the switch assembly to be removed and replaced without disturbing the housing or the heater, thereby avoiding the need to re-align the heater and the ~7~

cover with the vessel after replacement of the sr"itch assembly. Furthermore, the use of a single switch assembly enables the vessel to be used as a non-automatic vessel if the steam responsive mechanism fails or is removed; and enables all the electrically conductive components, except for the pins which extend into -the socket, to be located within a switch chamber in the switch assembly r which chamber is substantially sealed except for the small clearance around the push rod 74 and the clearances, if any, between the pins and the plastics member 55.

Referring -to Figure 4, the modified form of the jug is designed for low cost production and comprises a moulded plastics ~ody in which the wall lOCis integral with the housiny 17C, and has a lid 120 of push on form.
The steam responsive means 18C is mounted on a modified closure member l9C.

The bimetal 82C is mounted on a part 121 of the member 19C which engages in the steam opening 33C. The mechanism comprises a lever 81C of idler form which does not incorporate a knob, and the spring 86C acts on a manually movable part 122 which is mounted on a pivot 123 so as to be movable between the off and on positions via the unstable position. The part 122 carries abutments which engage the upper end of the lever 81C for moving the lever 81C, and a further abutment 12~ engageable ~7~B

with the bimetal 82C. In this Figure the mechanism is shown in the off position. An extension 90C extends through the closure member.

The protective member 55C is integral with the closure member 19C and sealingly engages the switch assembly and is provided with a slot 125 for the portion 88C to engage the push rod 74.

A metal heat shield 126 lines the bottom of the jug.

The invention is not confined to the precise details of the foregoing examples, and many variations are possible.

A plurality of flanged clamping members, each of limited length, may be used in place of the clamp ring 35.

If desired, in the firs-t and second embodiments, the plastics member 55 can be also mounted on the closure member and provided with enlarged apertures for the pins, and in this variation a sealing member may be applied to the switch assembly so as to protect the rear face of the carrier member, and this sealing member may engage closely around the pins and carry the sealing ring 51 or be provided with a peripheral portion which serves as the sealing xing 51.

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In all embodiments, the earth pin may be formed as part of the head instead of being secured to a post on the head, but the arrangement of the earth pin described is preferred because the earth pin is used to centralise the plug socket connector as the latter is inserted into the plug socket.

Also, if the body is moulded or cast, e.g. from plastics, ceramics or metal, the housing may be integral with the body or part thereof.

!

The heater may be an immersion heater, as shown, or may be of external form in which the element is clamped or secured to or in the bottom of the body.

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A vessel for heating liquids comprising a hollow body, an electrical heater, and control means, wherein the hollow body is adapted to contain a liquid to be heated and has a wall upstanding from a bottom of said body;
wherein the heater comprises an electrical resistance heating element disposed alongside said bottom;
wherein the control means comprises steam responsive means, a switch assembly electrically connected to said element, and a cover; and wherein fastener means secures said heater and switch assembly to said body;
and characterised in that the cover comprises a housing secured to or integral with said wall, and a separable closure member releasably secured to the housing so that the housing and closure member define at least part of a main chamber; in that the steam responsive means comprises a thermally responsive device and a mechanism, which mechanism is mounted on said closure member and is arranged to actuate said switch assembly when actuated by the thermally responsive device when the latter is subjected to steam entering the main chamber from the hollow body.

2. The vessel as claimed in Claim 1, wherein the switch assembly includes a mechanically movable switch member which extends from within the switch assembly to project into said main chamber.

3. The vessel as claimed in Claim 2, wherein the mechanism comprises a lever pivotally mounted on the closure member, and a manually movable part which extends through the closure member so as to be exposed for manual actuation to move the lever from a stable off position to a stable on position via an unstable intermediate position, whereby to cause the lever to move said switch member.

4. The vessel as claimed in Claim 1, 2 or 3, wherein the switch assembly and fastener means are accommodated in the main chamber, above a drain opening, and the housing defines an access opening which is normally covered by the closure member and which is disposed and dimensioned to provide access to the fastener means and the switch assembly to permit the latter to be installed and removed through said access opening.

5. The vessel as claimed in Claim 1, 2 or 3, including a pivotally mounted lid which cooperates mechanically with the steam responsive means to cause the switch mechanism to switch off said supply when the lid is opened.

6. The vessel as claimed in Claim 1, 2 or 3, wherein a plastics protective member defines a plug socket and extends from the switch assembly across the main chamber to the outside of the closure member.

7. Control means for a vessel as claimed in Claim 1, 2 or 3, wherein the cover comprises a housing adapted to be secured to a portion of a wall of a vessel for heating liquids, a separable closure member releasably secured to the housing so that the housing and closure member define at least part of a main chamber; the switch assembly is adapted to be electrically connected to an electrical heater element, and has fastener means to secure the switch assembly and electrical heater element to said wall; and said steam responsive means comprises a thermally responsive device and a mechanism mounted on said closure member and arranged to actuate said switch assembly when the thermally responsive device is subjected to steam entering said main chamber.