GB2372001A - Improvements relating to thermally responsive controls - Google Patents

Abstract

Controls for electrical heating elements of water boiling vessels such as jugs and kettles are conventionally constructed with a moulded plastics or metal chassis onto which switch parts and bimetallic actuators are assembled. The invention provides an alternative method in which a metal sheet is stamped to form a blank 1 having parts destined to form spring terminals 5,5'', switch parts 66 and mountings for bimetallic actuators etc., the sheet metal blank is insert moulded with plastics material 10 so as to leave windows in the plastics through which the spring terminal parts etc of the blank are accessible, and then these accessible parts are bent up out of the plane of the blank or otherwise shaped to be capable of performing their intended functions. The invention enables a lower profile control to be manufactured in a series of readily controllable and reproducible steps and, by virtue of the encapsulation of current carrying parts of the control in plastics material which acts as a heat sink, can provide a control which experiences lower, internally generated operating temperatures.

Description

IMPROVEMENTS RELATING TO THERMALLY RESPONSIVE CONTROLS Field of the Invention : This invention concerns improvements relating to thermally responsive controls and more particularly, though not exclusively, concerns controls for electrically heated water boiling vessels such as, for example, electric kettles and hot water jugs.

Background of the Invention: It has for many years been the practice, especially in the domestic environment, to provide electric kettles and hot water jugs with an element protector control designed to switch off the power supply to the electric heating element of the appliance in the event of the heating element temperature rising above a predetermined safe level, for example as a result of the appliance being switched on empty or being allowed to boil dry. Such controls are also referred to as"dry boil"controls.

It has furthermore been the practice for many years to provide such appliances with controls responsive to the boiling of water in the appliance to switch-off or reduce the power output of the electric heating element. Most such controls operate on the basis of sensing the generation of steam when water boils in the appliance, though controls are also known or have been proposed which respond to the changing rate of temperature rise as the boiling

temperature is approached and/or attained and other controls are known or have been proposed which detect a boil condition by simulation of a dry boil condition at a certain, limited part of the heating element.

There are two principal manufacturers of dry boil and boil detection controls in the UK, namely ourselves, Otter Controls Limited of Buxton, Derbyshire, England, and Strix Limited who are located in the Isle of Man. Our most modem dry boil control is the X4 series which is described in GB-A-2339088 and the competing control from Strix is their U series which is described in WO-A-95/34187. These controls are designed for use particularly with appliances incorporating modem thick film heating elements and of the cordless type comprising a vessel part and a base part upon which the vessel part has to be seated in order to enable the heating element to be powered through mated connectors that are provided on the vessel and base parts of the appliance. Both the X4 and U series controls have two spaced-apart dry boil bimetals and both can support the provision of a steam sensor comprising a third bimetal. Both furthermore incorporate the vessel mounted connector of a 3600 cordless connector set.

The X4 and U series of controls illustrate the different manufacturing philosophies of Otter Controls and Strix. The X4 controls are based upon relatively complex plastics mouldings into and onto which the bimetals and associated switch and conductor components of the control are assembled.

The U series controls, in contrast, make use of a metal control chassis onto which the other control components are assembled. The design of the Otter

Controls plastics mouldings is a complex operation requiring superlative design skills in the selection of appropriate materials and the arrangement of the material in the moulding to ensure that the tightest of manufacturing tolerances will be satisfied and maintained throughout a range of different temperature operating conditions. The Strix metal chassis similarly has to meet the same kind of tolerance considerations and suffers from the problems associated with the bending of unavoidably somewhat resilient materials to micrometre tolerances. In the highly competitive kettle control environment, where counterfeit controls from China in particular are a continuing problem, these manufacturing difficulties continue to cause concern.

Objects and Summary of the Invention: It is accordingly the principal object of the present invention to overcome or at least substantially reduce the abovementioned problem.

According to the present invention the abovementioned object can be achieved by a new control manufacturing philosophy which takes advantage of both the moulded plastics material philosophy favoured heretofore by ourselves and the metal chassis philosophy favoured by Strix, the new philosophy comprising the formation of the metal parts of the control, or at least some of them, together with their interconnections, as a sheet metal blank, formed by stamping for example, the insert moulding of such blank into a plastics material support moulding which is apertured to provide access to predetermined parts of the blank, and the formation of such predetermined

parts into electrical contacts and/or terminations and/or into bimetal or other sensor support elements. By use of this method, the various metal conductor parts of the control can be supported, electrically separated from each other and protected by the plastics moulding, advantageously with a minimum of height and horizontal spacing, whilst the plastics moulding in turn is supported by the metal parts. Furthermore, on account of the heat sink effect of the plastics material, the conductor parts of the control can be cooler in operation of the control.

The invention envisages that parts of the blank may be designed to form contact springs for electrically connecting the finished control to terminal pads of a thick film heating element for example, the metal of the blank, the thickness of the blank and the dimensioning and form of the relevant parts being selected to provide the requisite spring function. Such contact spring parts would be bent out of the plane of the blank after the insert moulding step and might have silver or other high electrical conductivity contacts affixed thereto for making contact with silver or other high electrical conductivity terminal pads of the heating element.

Other parts of the blank may be designed to form switch contact sets of the control, one part for example being designated a fixed contact or a carrier or mounting therefor and being formed to be relatively stiff and the other part of the contact set being designated a moving contact or a carrier or mounting therefor and being formed to be relatively resilient. The two parts

would be bent out of their positions in the original blank so as to bring them into appropriate operative relationship with each other.

Yet further parts of the blank may be designed to carry bimetals or other switch actuators and again may be bent so as to position the actuator in operative relationship with the moving contact of an appropriate switch contact set of the control and so as to be in operative heat transfer relationship with the heating element with which the control is to be used. Dry boil and steam sensor (boil) controls may be arranged in this fashion or the control may alternatively have provision made for attachment of a separate steam control thereto by appropriate formation of the blank with appropriate connector parts or with parts to be formed subsequently into appropriate connector parts. The blank and/or the encapsulating plastics material moulding may furthermore be formed to provide for the assembly of an overcentre mechanism with any of the thermal sensors, the respective sensor being arranged to operate its associated switch contact set via the overcentre mechanism which prevents the switch contact set from resetting until the overcentre mechanism is manually reset.

Various parts of the blank, particularly those destined to be formed into movable spring parts, will preferably be stabilized in the blank by being connected at both ends, for example, to other parts of the blank. This ensures the correct positioning of such parts during insert moulding of the plastics material. The relevant connecting parts that are redundant to operation of the finished control can be left exposed by the moulding operation and can be

cropped out to liberate the relevant part. The same technique can be employed to allow different control configurations to be manufactured from the same insert moulded blank component by provision of optional links in the blank which can either be left intact for one control configuration or can be removed for a different control configuration. For example, the blank can be formed with two terminals connected together by a link which can be removed for a control configuration designed to be used with a separate steam (boil) control, or can be left intact if no steam control is to be connected. In the same way, connections may be provided to enable a control to accommodate different heating element configurations, for example heating elements with and without keep warm tracks (ie. lower power heating element portions arranged to be powered after operation of a boil control to keep the boiled water hot), alternative thermostatic controls and/or indicators.

The metal blank preferably is such as to enable the control to be formed with cordless connector parts, particularly 3600 connector parts enabling a cordless vessel to be seated on its base in any orientation relative thereto in the horizontal plane. To accomplish this, the blank would be provided with parts designed according to the form of the cordless connector parts. For example, the blank might be formed with parts designed to be coupled with a 3600 connector part comprising a central pin terminal surrounded by two cylindrical terminals of different diameters. The two cylindrical terminal parts of the connector might for example be arranged to be mounted to respective arcuate parts of the blank, for example by virtue of

coupling tabs of the cylindrical terminals being received in slots in the arcuate parts and being twisted to make the connection secure, advantageously with the slots and/or tabs and/or adjoining parts of the moulding being formed to effect a pulling together of the parts as the tabs are twisted. Such a control could be used with a base connector similar to the Strix P72 3600 cordless connector component. An alternative method of forming a 3600 cordless connector similar to our CP7 3600 vessel connector component which is adapted for use with our CS4 3600 base connector would be to form the blank with parts destined to be formed into leaf springs similar to those of our CP7 component and with a central platform for an earth pin.

In either case a plastics material support moulding would necessarily or preferably be provided for the connector parts.

The base connector part for such a control including a 3600 cordless connector component may be similarly manufactured by provision of a blank comprising three terminal parts and insert moulding of the blank into a plastics material carrier. The three terminal parts are interconnected in the blank by links which are removed after the insert moulding. The terminal parts may then be bent to form appropriately shaped springs designed for contacting respective terminal parts of the vessel connector when the vessel is set down onto its base. The plastics material carrier may advantageously be formed to make a snap-fit into an accommodating recess of a plastics material moulding defining the body of the base connector and having formations

appropriately locating the three spring terminals to be contacted by the three terminals of the vessel connector.

The above and further features of the invention will best be appreciated by consideration of the following detailed description of an exemplary embodiment of the invention which is illustrated in the accompanying drawings.

Description of the Drawings : Figure 1 shows a perspective view of a stamped sheet metal blank designed for the manufacture of two identical controls side-by-side according to an exemplary embodiment of the present invention; Figure 2 shows the sheet metal blank of Figure 1 after insert moulding of plastics material around the blank; Figure 3 shows the insert moulded blank of Figure 2 with various parts of the blank cropped out and others formed into spring contacts and other components of the finished control, the thus formed and insert moulded blank constituting a chassis for the control; Figure 4 is an enlarged view of part of Figure 3 showing the formation of spring terminals from the blank for contacting terminating tabs of a thick film heating element track; Figures 5A and 5B are enlarged views of another part of Figure 3 showing electrical tab connectors formed on the blank for the optional configuration of the control for the attachment thereto of a boil control,

Figure 5A showing the blank with the tab connections linked as originally formed and Figure 5B showing the link removed ; Figures 6A and 6B are enlarged views of yet another part of Figure 3 showing a part of the blank formed into a mounting for a bimetallic actuator and showing other parts formed into fixed and moving switch parts of a switch associated with the bimetallic actuator, Figure 6A showing the arrangement of the bimetallic actuator and the switch, and Figure 6B showing how one part of the blank is folded over to constitute a fixed contact carrier of the switch co-operating with a moving contact carrier ; Figure 7A is an enlarged view showing the attachment of 360 connector components to a central part of one of the control chassis parts of Figure 3, and showing furthermore the provision of an overcentre arrangement (trip lever) assembled thereto, and Figure 7B illustrates the electrical and mechanical coupling of a cylindrical conductor of the 3600 connector to the control chassis; Figures 8A, B and C are perspective views of a slightly different finished control, Figures 8A and 8B showing alternative positions of the trip lever and otherwise being identical and Figure 8C showing the other side of the control, and Figures 8D, E and F are enlarged showings of respective parts shown circled in Figures 8A, B and C; Figures 9A, B, C and D are views of a base connector component adapted to connect to the 3600 connector part of the control when a cordless

water heating vessel to whl-l the control is affixed to set down upon a power base in which the base connector component is affixed ; and Figures 10A, B and C are respectively a side elevation view showing the control juxtaposed with a cordless base, a top plan view and a cross-sectional side elevation view taken on the line A... A shown in Figure

10B.

Detailed Description of the Embodiment: Referring first to Figure 1, shown therein is a brass stamping 1 designed to form the basis for two controls, the brass stamping comprising two conjoined parts 1A and 1B each identically configured and each formed as a blank designed to be formed into a respective control. Depending on the capacity of the insert moulding machine and subsequent machines to be utilized in the formation of the blanks into controls, the stamping 1 could have more or less conjoined parts.

Each blank lA, 1B is formed centrally with a set of concentric conductors generally designed 2 which are designed to have mounted thereto a central terminal pin and inner and outer cylindrical conductors comprising a 3600 appliance power input connector; these will be described in more detail hereinafter. On each side of the central conductor set 2 there is provided respective conductor sets 3A and 3B which are designed to be formed into mountings for respective bimetallic actuators and into respective switching contact sets associated therewith; again these will be described in more detail

hereafter. Other conductors 4A and 4B are designed to be formed into contact springs for physically and electrically contacting respective termination pads of the heating element track of a thick film heating element with which the finished control is used. Still further conductors generally designated 5 provide for the connection, if required, of a boil (steam) control to the finished control, and yet further conductors generally designed 6 provide for the connection of indicators and the like to the finished control. Parts 7 of the blank are destined to become control fixing points.

As shown in Figure 1, silver contacts 8 are shown affixed to various of the conductors. It is convenient to affix these contacts to the brass stamping before it is further processed, or even to affix them to the basic sheet metal before it is stamped, but they could alternatively be affixed subsequently.

Figure 2 shows the form of the blank after it has been insert moulded with synthetic plastics material, and Figure 3 shows how the plastics encapsulated blank appears after certain parts of the conductors have been cropped out and other parts bent into their required final form. To maintain the structural integrity of the Figure 1 blank various conductors which in the final form of the control will be cantilever structures, fixed at one end and with the other end free, have their designated free ends attached to the blank by means of redundant straps and these have to be cut (cropped) out. This is done after the insert moulding step of Figure 2.

The insert moulding is effected so as to encase the stamped metal blank of Figure 1 within a generally planar plastics material web 10 having a

transverse, reinforcing wall 11 around its periphery and with various internal, transverse walls 12 providing physical and electrical separation between respective parts of the control. A central boss 13 encapsulating the central concentric conductors 2 of the stamping provides a strong foundation for the attachment, physically and electrically, of the 3600 appliance power inlet conductors to the control. Formations 14 in the plastics material co-operate with formations in the blank to facilitate the attachment of these power inlet conductors, as will be described more fully hereafter. Other formations 15 again co-operate with the formations 7 in the blank to provide for the attachment of the finished control to a planar heating element. The plastics material is moulded around the sheet metal blank so as to leave exposed those portions of the blank that are required subsequently to be cropped out or otherwise bent and formed in the progress towards the finished control.

Additionally, the plastics material moulding is effected so as to provide the control with an integral mounting 16 for an overcentre mechanism as will hereinafter be described.

Referring now to Figure 4, this is an enlarged view showing how the conductors 4A and 4B of the blank are formed into heating element contact springs as shown in Figure 3. Figure 1 shows the relevant conductors affixed at both ends to the metal stamping, and Figure 3 shows how the contact bearing end of each conductor has been freed by cropping off a respective forward part and how the resulting cantilever conductors have been bent out of the plane of the blank to form contact springs.

Figures 5A and 5B illustrate how the blank of Figure 1 can be provided with links which can be left in place or alternatively can be cut out in order to customize the control for particular applications. Shown in Figures 5A and 5B is an enlarged view of the part of the blank that is generally designated 5 in Figure 1, and it can be seen that the blank as originally formed has two spade terminals 5'and 5"which are interconnected by links 51 and 52. When the controls are cropped from the blank, namely when the Figure 3 product is cut into two separate controls by appropriately cropping the blank outside of the peripheral plastics material wall portions 11, the external link 51 is removed but the option remains to retain the internal link 52, as shown in Figure 5A, if the control is not to be used with a separate, plug-in steam control or to remove it, as shown in Figure 5B, if it is.

Figures 6A and 6B are an enlarged showing of one of the regions 3A, 3B of the Figure 1 blank which are destined to constitute in the finished control a carrier for a bimetallic switch actuator and an associated switch contact set comprising a fixed contact and a movable contact operated by operation of the bimetal in response to a sensed overtemperature situation. Referring first to Figure 6A, this shows a snap-acting bimetallic actuator 61 of a well known type secured to the free end of a cantilever support member 62, for example by spot welding of the bimetal tongue portion 63 to the support member. The bimetallic actuator 61 co-operates with a switch mechanism constituted by a fixed contact carrier 64 and a moving contact carrier 65, the rim of the bimetal being arranged to operate the moving contact carrier 65

through the intermediacy of a push rod 66 which, in the described arrangement, is affixed to the end of the moving contact carrier 65, but is electrically insulated therefrom, as will be more fully described hereinafter. Also shown in Figure 6A is one of the heating element contact springs 4B of the control.

The component parts of the blank of Figure 1 which form the parts 62, 64 and 65 are correspondingly labelled in the control part IB of the Figure 1 blank and are also shown in Figure 3. Figure 6B shows how the conductor part 64 of the blank is folded over in order to constitute the fixed contact carrier co-operating with moving contact carrier 65 which, in the blank, is constituted by a conductor extending parallel to the major part of the conductor of which the folded-over part 64 is the tip.

Although not shown in the drawings, the push-rod 66 is formed from an extension of that part of the blank which is destined to form the moving contact carrier. Reference to the part IB of the Figure 1 blank shows the conductor 65 at the top of the figure extending rightwards beyond its attached silver contact, and it is this extension 67 that is formed into the push-rod 66. However, to provide electrical isolation of the tip of the push-rod from the moving contact carrier, the extension 67 is divided before the insert moulding step of Figure 2 and the moulding is effected so as to bridge the division. In the finished control and as shown in Figure 6A the tip of the push-rod 66 which contacts the bimetal 61 is thus a separate metal piece which is adhered

to the rest of the extension part 67 by plastics material bridging part 68. For the sake of clarity, this is not shown in Figure 6B.

The attachment to the control of a central pin terminal and first and second concentric cylindrical terminals of a 3600 appliance power input connector is shown in Figures 7A and 7B. Figure 7A shows, in enlarged fragmentary view, the central pin terminal 70 and the first and second cylindrical terminals 71 and 72 mounted to the central boss 13 (see Figure 2) that is formed during the insert moulding step. The central pin terminal 70 is riveted to the central part 73 of the Figure 1 blank, and the cylindrical terminals 71 and 72 are physically and electrically coupled to the arcuate parts 74 and 75 respectively of the blank (see the upper part 1B of the Figure 1 blank). As shown in Figure 1, the arcuate parts 74,75 of the blank have through slots 76 which are designed to receive twist tabs 77 formed on the respective edges of the cylindrical terminals 71 and 72 (see Figure 7B) and the plastics material that is provided around the slots is formed with inclined ramps 78 such that when the twist tabs are twisted, they ride up the ramps so that not only are the cylindrical terminals held captive by the twisting of the tabs, but also the ramps serve to pull the cylindrical terminals firmly into place. The insert plastics material moulding preferably includes supportive features designed to provide support against impact damage to at least the outer one of the two cylindrical terminals 71 and 72, though this could be separately provided, for example as separate plug-in mouldings.

Figure 7A also shows the provision of an overcentre trip lever mechanism 79 affixed to the control, for example for affording a manual ON/OFF facility or for enabling switch-off on boil to be effected through the same set of switch contacts as are used for dry boil protection. In the illustrated arrangement, the trip lever mechanism 79 is formed of stainless steel and includes an integrally formed, cantilevered C-spring 80. The trip lever 79 mounts with the free end of its C-spring 80 lodged in a V-groove provided in the insert moulded mounting part 16 and with an opposing part (not shown) lodged in an opposing V-groove of the insert moulding. As is well known, this mounting arrangement provides for pivotal movement of the trip lever with a snap action between two stable positions on either side of an intermediate unstable position.

The trip lever 79 is bifurcated with two limbs 81 which extend on opposite sides of the 3600 appliance power input connector and terminate at the locations of the dry boil switching arrangements where they are arranged to interact with the moving contact carriers 65 of the respective switching arrangements. As shown in Figure 7A, the trip lever limb 81 engages loosely at its free end with a formation 82 that is provided on the moving contact spring 65 of the respective switching contact set during the insert moulding step (see Figure 6A for an alternative view of the formation 82). By virtue of this arrangement, the trip lever follows the movement of the moving contact carriers of the dry boil switching arrangements and can be employed as an ON/OFF control and/or, by provision of an actuator responsive to boiling of

the contents of an associated liquid heating appliance and coupled to the trip lever, can serve to switch off the appliance on boiling.

An illustrative reset arrangement 83 is shown in Figure 7A as comprising an element arranged to co-operate with the part 82 to cause it to be depressed for mechanically resetting the bimetal 61 (see Figure 6A) to its cold condition. Resetting might for example be accomplished as a result of lifting an appliance off its base and subsequently replacing it.

Figures 8A through 8F illustrate a more developed version of the control described hereinabove, but manufactured by the same method from an initial sheet metal blank. The principal difference between this control and that previously described resides in the formation of the trip lever as a plastics material moulding utilizing a separately provided C-spring. The same reference numerals are used in Figures 8A through 8F as were used in the description of the first embodiment to designate like parts.

Figures 9A through 9D illustrate the construction of a 3600 power outlet connector part adapted to be incorporated into the base of a cordless electrical appliance and to co-operate with the 3600 power inlet connector of the embodiments of the present invention that have been described in the foregoing. Referring first to Figures 9C and 9D these show three spring components 91,92 and 93 captured in a moulded plastics material block 94 and it is to be understood that the springs 91,92 and 93 are originally formed as a stamped, sheet metal blank which is then insert moulded to form the block 94. The blank is then cropped to separate the spring terminals from one

another and the springs are formed into their desired shapes as shown. Spring terminal 91 is adapted to contact the end of central terminal pin 70 of the 360 appliance power input connector, spring terminal 92 is adapted to contact the side of first cylindrical terminal 71, and spring 93 is adapted to contact the side of second cylindrical terminal 72.

As shown in Figures 9A and 9B, the plastics material block 91 is adapted to be snap-fitted into an accommodating recess in a plastics material moulding 95 shaped complementarily to the central terminal pin and surrounding concentric cylindrical terminals of the 3600 power input connector, namely to have a central recess for accommodating the terminal pin of the input connector and concentric annular recesses for accommodating the cylindrical terminals. As shown, the moulding 95 also is formed with recesses and guideways for accommodating the spring terminals 91,92 and 93 and keeping them separate from each other. The curved end portions of the spring terminals 92 and 93 preferably project into annular recesses of the connector through respective apertures formed in wall portions of the connector.

The base connector shown in Figures 9A to 9D is adapted to be secured into a base component of a cordless appliance in the manner shown in Figure 10C which is described hereinafter. Alternatively, the plastics material moulding 95 of the above-described arrangement could be formed integrally with the base component of the appliance, in which case the component shown in Figures 9C and 9D need only be snap fitted into an appropriate

recess of the integrated base component to complete its manufacture. This feature is attractive to appliance manufacturers since it provides them with freedom to design appliance bases without having to concern themselves about colour matching of moulded plastics connector parts to the appliance.

Referring now to Figures 10A, 10B and 10C, these show, respectively, the control of Figures 8A through 8F juxtaposed with a cordless appliance base component 100, a top plan view of this juxtaposed arrangement and a cross-sectional view. Again, the same reference numerals are used to designate like parts as have been used in the preceding description. With the control secured to the underside of a planar heating element of a water boiling vessel for example so that the bimetallic actuators 61 are in close thermal contact with the heating element, the control will execute an overtemperature protection function, as will be well understood by those possessed of relevant skill and knowledge of this art. No further description of Figures 10A, 10B and 10C is considered necessary.

Claims (30)

1. CLAIMS : 1. A method of manufacturing a thermally-responsive control for an electrically powered heating element, said method comprising: (a) forming a sheet metal blank having cut-outs defining in the blank parts of the finished control; (b) moulding a synthetic plastics material about said blank with parts of the blank exposed at windows in the plastics material; and (c) forming parts of the blank exposed at said windows into switch parts of the control and associated mounting (s) for thermally-responsive actuator (s).
2. 2. A method as claimed in claim 1 wherein parts of the blank are designed to form contact springs for electrically connecting the finished control to terminal parts of the heating element.
3. 3. A method as claimed in claim 2 wherein said contact springs comprise elongate parts of the blank which, in said moulding step, are left exposed and subsequently are bent out of the plane of the blank.
4. 4. A method as claimed in claim 3 wherein said elongate contact spring parts are attached at both ends to the blank, and after said moulding step, one end is detached so as to enable bending of the respective parts out of the plane of the blank.
5. 5. A method as claimed in any of the preceding claims wherein said switch parts comprise a fixed contact and a movable contact adapted to be operated by a thermally-responsive actuator, said blank having a part defined to be relatively stiff which, in the finished control, constitutes the fixed contact and a part defined to be relatively flexible which, in the finished control, constitutes the movable contact, and said fixed and movable contact parts being formed into operative relationship in said forming step.
6. 6. A method as claimed in claim 5 wherein a relatively short part of the blank is bent back on itself to comprise the fixed contact.
7. 7. A method as claimed in claim 5 or 6 wherein an elongate part of the blank designated to form said movable contact is attached to the blank at both ends prior to and during the moulding step and, after the moulding step, one end is detached from the blank and the respective elongate part is bent out of the plane of the blank.
8. 8. A method as claimed in claim 5 or 6 wherein an elongate part of the blank designated to form said movable contact has a break therein which is bridged by plastics material during said moulding step, the subsequent forming of said elongate part into the moving contact being such as to provide

   the moving contact with an integral push-rod comprising said plastics material bridge.
9. 9. A method as claimed in any of the preceding claims wherein the blank includes an elongate part adapted to be formed into a mounting for a bimetallic switch actuator.
10. 10. A method as claimed in claim 9 wherein said elongate mounting part is attached to the blank at both ends prior to and during the moulding step and, after the moulding step, one end is detached from the blank and the respective elongate part is bent out of the plane of the blank.
11. 11. A method as claimed in claim 9 or 10 comprising attaching a bimetallic switch actuator to said mounting.
12. 12. A method as claimed in any of the preceding claims wherein the blank is formed with one or more connecting links enabling the control to be customized for predetermined applications by selective retention or removal of said link (s).
13. 13. A method as claimed in any of the preceding claims wherein said blank comprises parts designed to form, or to have affixed thereto, electrical

    terminal parts of a power supply input connector forming an integral part of the finished control.
14. 14. A method as claimed in claim 13 wherein said parts of the blank are designed to have affixed thereto concentric electrical terminals of a 3600 power supply inlet connector.
15. 15. A method as claimed in claim 14 wherein said parts comprise a first part designed to have affixed thereto a central pin terminal of the 360 connector, at least one second part designed to have affixed thereto a cylindrical terminal concentric with said pin terminal, and at least one third part designed to have affixed thereto a further cylindrical terminal concentric with said pin terminal.
16. 16. A method as claimed in claim 15 wherein said second and third parts of the blank are slotted for receiving twist tabs provided on the respective cylindrical terminals.
17. 17. A method as claimed in claim 16 wherein the plastics material that is formed around the slots of said slotted parts during said moulding step comprises ramps serving, on assembly of said first and second cylindrical terminals to the control by insertion of said tabs into the slots and twisting of the same, to pull the cylindrical terminals towards the blank.
18. 18. A method as claimed in any of claims 14 to 17 comprising fixing said concentric electrical terminals to the plastics encapsulated blank.
19. 19. A method as claimed in claim 13 wherein said parts of the blank comprise a first part designed to be formed into or to have affixed thereto a central terminal pin of a 3600 power supply inlet connector, a second part designed to be formed into a first spring contact finger spaced apart from said central terminal pin and extending generally parallel thereto, and a second part designed to be formed into a second spring contact finger spaced apart from said central terminal pin by a distance different from that by which the first spring contact finger is spaced from the central terminal pin and extending generally parallel to said central terminal pin.
20. 20. A method as claimed in claim 19 wherein a plastics material support moulding is provided for supporting said first and second spring contact fingers after bending of the same into a configuration perpendicular to the plane of the blank.
21. 21. A method as claimed in any of the preceding claims wherein plural spaced apart regions of said blank are formed to define respective switch parts of a plural switch control comprising plural spaced apart thermally-responsive actuators each determining the condition of a respective one of said switches.
22. 22. A method as claimed in any of the preceding claims comprising forming a mounting for a trip lever during said moulding step, and subsequently assembling a trip lever with said mounting.
23. 23. A method as claimed in claim 22 wherein said trip lever is arranged to interact with switch means formed in the control.
24. 24. A method as claimed in claim 23 comprising arranging said trip lever so that said switch means is operated, in use of the control fitted in a water boiling vessel as a heating element overtemperature protection control, when water is boiled in the vessel.
25. 25. A method as claimed in claim I and substantially as herein described with reference to the accompanying drawings.
26. 26. A thermally-responsive control manufactured by a method as claimed in any of the preceding claims.
27. 27. An electrically powered appliance including a heating element and a control therefor as claimed in claim 26.
28. 28. An appliance as claimed in claim 27 comprising a water heating vessel.
29. 29. An integrated control and 3600 power input connector for a cordless water heating vessel provided with a thick film heating element, said control comprising first and second bimetallic switch actuators spaced on either side of said 3600 power input connector for thermally contacting said heating element when the control is juxtaposed therewith, said control comprising a plastics material encapsulated sheet metal blank having parts thereof deformed out of the plane of the blank to define switch components and mountings for said bimetallic switch actuators.
30. 30. An integrated control and 3600 power input connector as claimed in claim 29 comprising blank parts deformed out of the plane of the blank to define spring terminals for contacting terminal parts of a heater track of said thick film heating element.