GB2150759A - Switch control of vessels for heating liquids - Google Patents

Abstract

A vessel for heating liquids comprises a hollow moulded plastics body (10), a heater (12), an electrical switch assembly (13), steam responsive unit (14) for actuating the switch assembly, and a cover (16). The body (10) has a rear extension (22) (e.g. a handle) shaped to provide an upper support (25) and a lower support (26). The steam responsive unit (14) comprises a thermally responsive device (30), such as a bimetal or memory metal coil; a mechanism (31) and a carrier (32) shaped to engage the supports (25 and 26) to locate the unit (14) in a steam receiving space. <IMAGE>

Description

SPECIFICATION Vessels for heating liquids This invention concerns vessels for heating liquids comprising a body, an electrical heater, a cover and control means, wherein the body is adapted to contain a liquid to be heated and has a wall upstanding from the bottom of said body; wherein the heater comprises an electrical resistance heating element disposed in or alongside said bottom; wherein the control means comprises steam responsive means, and a switch assembly secured to said heater and electrically connected to said element; and wherein fastener means secures said heaterto said body, and such vessels are hereinafter referred to as being "of the kind described".

In our co-pending GB Application No. 21 02205A there are disclosed vessels ofthe kind described, in which vessels the cover comprises a housing secured to or integral with said wall, and a separable closure member releasably secured to the housing so thatthe 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 chamberfrom the body.In these vessels the steam responsive means is disposed adjacent a steam vent adjacent the top of said body whereas the switch assembly is disposed adjacent the bottom so thatthe mechanism and closure member are required to extend through avertical distance which is only fractionally less than the overall heightofthe body.

Whilst the mounting ofthe mechanism on the closure member has proved to be satisfactory in use, the inventor has realised that there are certain disadvantages inherent in such an arrangement of the mechanism and closure member.

An object of the invention isto enable these disadvantages to be avoided or reduced, and to provide an improved vessel ofthe kind described, enabling theverygreat advantages, which arise from employing a switch assembly constructed as a unit which is mechanically mounted on the heater, to be retained.

According to the present invention there is provided a vessel ofthe kind described which is characterised in thatthe steam responsive means is a mechanical assembly comprising a carrier, a thermally responsive device, and a mechanism supported by the carrier; in thatthe body provides upper and lower supports locating the carrier in a steam space between said body and the cover so that the thermally responsive device is located adjacentto a steam vent which extends through an upper part of said wall, and so that a movable member of said mechanism is located to mechanically actuate the switch assembly when the steam responsive means responds to the presence of steam in the steam space.

The carrier provides an upper mounting upon which a manually actuable upper member of the mechanism is pivotally supported and a lower mounting upon which a lower member of the mechanism is pivotally supported. The upper support is preferably at above or adjacent to the level of the upper mounting and the lower support is preferably at below or adjacent to the level of the lower mounting. The upper member preferably carries the thermally responsive device and provides two abutments engageable with stops provided on the carrier to restrict movement of the upper member to a predetermined arc between limits corresponding to an "on" position and an "off" position.

The carrier is preferably a snap, press or push-on fit onto the supports, and the latter are preferably moulded so asto be integral with the body.

The invention will be describedfurther, byway of example, with reference to the accompanying di agrammaticvertical cross-sectional view of an embodiment of a vessel ofthe invention, which embodiment is shown in an "off" condition.

The embodiment shown in the drawing comprises a hollow moulded plastics body 10, a heater 12, an electrical switch assembly 13, steam responsive means 14, a lid 15 and a cover 16.

The body 10 is moulded to provide a bottom 20, a wall 21 and a rear extension 22. The wall 21 has a lower aperture through which the heater 12 extends to permitthe heaterto be clamped in position by a fastener ring 23, in known manner; and the wall has an upper steam vent aperture 24. The rear extension 22 serves as a fixed part of the body which is shaped to provide an upper support 25 and a lower support 26.

The switch assembly 13 is a unit constructed, mounted and arranged to operate as described in our aforementioned co-pending application.

The switch assembly 13 and the steam responsive means 14together constitute control means for the heater. The steam responsive means 14 is a mechanical assembly which comprises a thermally responsive device 30, such asa bimetal ora memorymetatcoil; a mechanism 31 and a carrier 32.

The carrier 32 is a plastics moulding having an upper portion 33 shaped to engage the upper support 25 and in particular to engage in a recess 27 in the support25; alowerportion34shapedtoengagethe lower support 26 and in a further recess 27 in the support 26; and an upstanding intermediate portion 35.

The mechanism 31 comprises an upper member 40 pivotally carried by an upper mounting 36 provided by side parts ofthe carrier; an elongate movable member 41 pivotally carried by a lower mounting 37 provided by side parts of the carrier; and an over-centre spring 42 located between a first arm 43 ofthe member 40 and an abutment 38 provided by the portion 35 of the carrier. The upper end of the member 41 is forked to engage projections on the lower end ofthe arm 43, and the lower end 44 ofthe member 41 mechanically actuates the switch assembly 13 via a push rod 17 (shown in broken lines) ofthe switch assembly. The upper member40 has a second arm 45 which locates the device30 and provides an "off" abutment46 which abuts an "off" stop 28 provided by the carrier; and has an "on" abutment47 which abuts an "on" stop 29 provided by the carrier.

The cover 16 serves substantially to close a gap between projecting side walls 50 (only one of which is partlyvisible in the drawing) of the fixed part 22 so as to define therewith a steam space 51; and the cover has steam release apertures 52, an upper aperture 53 through which a manually operable part 48 ofthe member 40 projects, a lower aperture 49 through which a plug socket part 54 of the switch assembly projects, and a bottom water drain apertures 55.

In use, the vessel can be switched on by moving the part 48 downwards untii the abutment 47 abuts the stop 29, thus moving the end 44 and allowing the push rod 1 7to move rearwards. When the water in the vessel boils, steam passes through the vent aperture 24 into the space 51 to cause the device 30 to change shape, e.g. elongate, and thereby move the arm 45 downwards to an extent sufficientto move the spring 42 over centre. The spring then rapidly restores the mechanism to the "off" condition.

The vessel ofthe invention has many advantages, some of which overcome disadvantages of vessels disclosed in the aforementioned copending application, including: (a) assemblyandtesting ofthevessel aresimplified, e.g.the carrier can be snap or push fitted onto the supports so astoalignthemechanism accurately particularly with respect to the push rod; (b) the carrier is separate from any part, e.g. the cover, of the vessel which is subjected to impacts or similar loads ordamagewhich arise in use;; (c) the carrier can be designed and made from a material selected solely with respect to the mechanical function ofthe carrier, without the aesthetic constraintsto which the coverdesign and material are subject, thereby ensuring that the mountings for the mechanism are precisely located to minimise the risk ofmalfunction ofthe mechanism; and further enabl- ing the cover to be designed and its material selected for appearance and minimum cost; (d) the vertical height ofthe carrier is much less than that ofthe cover minimising the effects of moulding shrinkage or distortion, andthe upper and lower parts ofthe carrier are firmly and accurately supported on positionally stable parts of the fixed part ofthe bodyto fu rther minimise these effects; (e) the need for fasteners to secure the cover is reduced, and the risk of malfunction ofthe mechanism due to overorundertightening of the fasteners of the cover is obviated.In particularthe cover may have an upper part 60 which interengageswith the body and a body engaging top part 61 ofthe carrier, and further and lower parts which interengage e.g. at 62, with the sides ofthe extension to retain the cover in place without requiring fasteners; and (f) the aperture 53 can be made oversize so that dirtaccumulating in the aperture does notrestrictthe movement of the member40.

The invention is not confined to the precise details oftheforegoing example, and many variations are possible within the scope of the invention as defined bytheappendedclaims. For instance the thermally responsive device may be supported upon any suitable part. The fixed part may have an intermediate aperture 64 so as to be able to be gripped to serve as a handle, or may merely comprise supports arranged to locatethecarrierand coverclosetooragainstthe body wall, the body being provided with a handle which extends above the lid. The fixed part may bea discretee memberwhich is secured to the body wall, e.g. by interengagement therewith and/orthefasteners. The fastener ring 23 may be used to clamp a lower portion ofthefixed parttothe body wall around the lower aperture.

Claims (7)

1. A vessel, for heating liquids, comprising a body, an electrical heater, a cover and control means, wherein the body is adapted to contain a liquid to be heated and has a wall upstanding from the bottom of said body; wherein the heater comprises an electrical resistance heating element disposed in or alongside said bottom; wherein the control means comprises steam responsive means, and a switch assembly, which switch assembly is secured to said heater and electrically connected to said element; and wherein fastener means secures said heater to said body.

2. Avessel as claimed in Claim 1, wherein the carrier provides an upper mounting upon which a manully actuable upper member ofthe mechanism is supported, and a lower mounting upon which said movable member of the mechanism is pivotally supported; and wherein the upper mounting is at, adjacent or above the level ofthe uppersupportand the lower mounting is at, adjacent or below the level of the lower support.

3. Avessel as claimed in Claim 2, wherein the upper member carries the thermally responsive device and provides two abutments engageable with stops provided on the carrierto restrict movement of the upper member to a predetermined arc between limits corresponding to an "on" position and an "off" position.

4. A vessel as claimed in Claim 1,2 or 3, wherein the carrier is a snap, press or push-on fit onto the support.

5. Avessel as claimed in any preceding claim wherein the supports are provided by a fixed part of the body integral with or secured to the wall of the body.

6. Avessel as claimed in Claim 5 wherein said fixed part serves as, or as part of, a handle.

7. A vessel substantially as hereinbefore described with reference to the accompanying drawing.