Abstract:
A combined control unit/connector for a cordless electrical water heating appliance for connection in use to a heating element thereof, comprising a housing, thermally sensitive control means for switching of said heating element and a protrusion extending vertically from directly beneath the housing on which are disposed electrical contacts for making connection to a separate base.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a combined control/connector for cordless electrical water heating appliances such as hot water jugs and kettles.  
           [0002]    Such appliances are provided with a base or stand upon which the appliance may be placed for the supply of electrical power to the appliance. The base is normally provided with a female socket connector which is connected to the mains electrical supply and with which a male pin connector of the appliance engages when the appliance is placed on the base to supply power to the appliance.  
           [0003]    It is also normal to provide such cordless water heating appliances with a thermally sensitive control including a set of switch contacts which open in the event that for example, liquid within the vessel boils, or the electric heater element of the appliance overheats should the appliance boil dry or be switched on without water, to interrupt the electrical supply to the heater element. Such controls are often self-contained units which are mounted onto the appliance and which, for maximum manufacturing flexibility may be used in either corded or cordless appliances. An example of such a control is shown in applicant&#39;s co-pending GB Application No. 0109777.3.  
           [0004]    The present invention is a development of this control the contents of the GB Application No. 0109777.3 being incorporated herein by reference.  
           [0005]    In cordless appliances the male pin connector may be conveniently and commonly formed by a terminal pin connector of the thermally responsive control or by a terminal pin connector serving as an adapter, mounted on the male pin connector of a thermal control unit.  
           [0006]    In each case the standard I.E.C. plug pin configuration of the horizontally-extending pins is placing constraints on the overall size and shape of connectors, resulting in a connector of unnecessarily large dimension and cost.  
           [0007]    For example, both GB 2241390 of Otter Controls Ltd and GB 2263364 of Strix Ltd shows three terminal pins which project rearwardly from the control unit which make engagement with spring contacts in the female connector part. In EP 0490762 of S.E.B. SA the three pins extending from the control unit are of a “L shape”, the depending portions engaging the contacts in the female connector part. In GB 2209633 of Strix Ltd the terminal pins of the control unit extend rearwardly and by means of sleeves are connected to “L-shaped” pins. In GB 2221104 of Strix Ltd the horizontal terminal pins of the control unit are connected to vertical terminal pins through a sleeve-type arrangement.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention seeks to provide a connector which overcomes these drawbacks.  
           [0009]    Embodiments of the invention are now described by way of example only, with reference to the following drawings in which:  
           [0010]    According to a first aspect of the invention there is provided a combined control unit/connector for a cordless electrical water heating appliance for connection in use to a heating element thereof, comprising a housing, thermally sensitive control means for switching of said heating element and a protrusion extending vertically from directly beneath said housing on which are disposed electrical contacts for making connection to a separate base.  
           [0011]    This structure is thereby able to utilise the space directly below the control for making connection to the power-supplying base.  
           [0012]    The protrusion is preferably unitarily formed with the housing, and comprises a tongue-like protrusion having a width greater than its thickness with the conductors disposed spaced across the width of the protrusion, and having a non-linear-shaped section.  
           [0013]    More particularly, the protrusion may be shaped so that adjacent contacts are displaced relatively to each other in the direction of the thickness of the protrusion. For example, the shape may comprise a pair of channels facing in one direction with a channel therebetween facing in the opposite direction, the contacts being disposed at the base of each channel. This results in a shape which can be of very small thickness, whereby the corresponding slot in the female connector can be made very thin and therefore safe, whilst the protrusion is still rigid.  
           [0014]    In the preferred embodiment the contacts comprise thin metal strips which extend from the control unit over a lower free end of the protrusion and back up an opposite face of the protrusion, which may be of thickness less than  0 . 5 mm and formed of copper or an alloy thereof. They may be formed unitarily with or directly connected to switching spring contacts with the control unit.  
           [0015]    The contacts may comprise live, neutral and earth conductors wherein one of the live and neutral conductors is arranged to extend in a direction further from the control unit than the other. This ensures that if the kettle is put on the base or removed therefrom whilst being switched on there is sequential electrical connection or breaking of live and neutral connections. This minimises the rate of change of potential and hence the risk of sparking or arcing which can lead to damage of the control unit and connectors as well as being a safety hazard. Such has been found to be particularly important where the kettle has a heating element which comprises a long coil as the resulting high inductance can greatly increase the susceptibility to arcing.  
           [0016]    The housing may be provided with water-shielding walls which depend from the t p housing spaced from the protrusion, which may extend down opposite sides of the protrusion or may totally surround it.  
           [0017]    The thermally sensitive control means may include a steam sensing trip lever to switch off the appliance on boiling of water and sensing means adapted to switch off the appliance at an elevated temperature corresponding to a dry boil condition, i.e. dry boil protection.  
           [0018]    In a further aspect the invention resides in a combined control unit/connector as defined above in combination with a female connector for fitting to a power-supplying base, the female connector having an opening for receiving the protrusion and electrical contacts which engage the electrical contacts of the control unit/connector on mating of the connectors.  
           [0019]    In a still further aspect the invention resides in a cordless electrical kettle having a combined control unit/connector as defined above.  
           [0020]    In a still further aspect the invention resides in a female connector for use in a power-supplying base of a cordless water-heating appliance comprising a housing defining a single continuous slot at an upper region thereof through which a male connector can be inserted and electrical contacts disposed beneath the slot.  
           [0021]    Preferably, the slot has a non-linear shape. In one embodiment the slot has a shape comprising straight portions extending in the general direction of the extent of the slot where adjacent straight portions are laterally displaced with respect to each other, with the electrical contacts are disposed beneath said straight portions. The slot has a pair of substantially co-linear portions disposed above live and neutral contacts with the laterally displaced portion arranged therebetween above an earth contact.  
           [0022]    The live and neutral contacts may be disposed in the housing beneath the slot with one of the live or neutral contacts disposed closer to the slot than the other. Thus, sequential live and neutral connection/disconnection can be arranged through the adaptation of the female connector.  
           [0023]    The invention in further aspects also resides in a power-supplying base being a female connector as defined above; in a combined control unit/connector as defined above when combined with a female connector as defined above; and in an electrical kettle with control unit/connector as defined above in combination with a power supplying base as defined above. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 shows a cordless kettle and base with an outer cover part for the combined control/connector partly removed;  
         [0025]    [0025]FIG. 2 is a vertical section through the control/connector and a female connector;  
         [0026]    [0026]FIG. 3 is a rear view of the control unit/connector, and the female connector;  
         [0027]    [0027]FIG. 4 is a front view of the control unit/connector, and the female connector;  
         [0028]    [0028]FIG. 5 is a front view of the control unit/connector with the cover removed, and also showing the contacts of the female connector;  
         [0029]    [0029]FIG. 6 is a view of a second embodiment with alternative male connector;  
         [0030]    [0030]FIG. 7 is a view of a third embodiment with an alternative form of female connector;  
         [0031]    [0031]FIG. 8 is a perspective exploded view of part of a dry boil protector;  
         [0032]    [0032]FIG. 9 is a perspective view from below of the control unit/connector;  
         [0033]    [0033]FIG. 10( a ) is a perspective view of the female connector;  
         [0034]    [0034]FIG. 10( b ) is a view of the electrical contacts from the female connector;  
         [0035]    [0035]FIG. 11 is a view of the female connector from below; and  
         [0036]    [0036]FIG. 12 is a view of the female connector from above. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0037]    Turning to the drawings and firstly in particular FIG. 1 this shows an appliance being a water heating kettle or jug generally indicated  1 . On the rear of the kettle  1  is arranged a  
         [0038]    combined control unit and male connector  2  having a connecting portion  5  which is enclosed within a cover  4  formed by two housing parts which also form a handle for the kettle.  
         [0039]    A separate base  6  is provided through which power is supplied. A power cord is connected to the base and in use connected to a mains power supply. A female connector  8  of the base mates with the male connector portion  5  to supply power to the kettle  1 .  
         [0040]    The control  2  is of a general type which is used in an electrical water heating appliance such as a kettle or jug, which includes an immersed heating element. As is conventional, when fitted such an element extends laterally into water carrying body of the kettle from a head plate which is fitted into an opening in the side wall near the base of a water carrying body of the kettle. Extending through the head plate are the cold tails of the heating element to which the control is electrically connected. The control  2  provides both the automatic switch-off of the kettle when water has reached the required temperature, typically at boiling, as well as providing overheat protection in the event of failure of automatic switch-off or in the event of operation of the kettle with no water inside, i.e. so-called “dry-boil” protection.  
         [0041]    The control has a generally cylindrical cup-like hollow housing  10  formed of moulded plastics from which upstands a plate-like support  12 . The housing  10  contains or supports the majority of the switching components and is closed at the frontwardly-facing opening (where the front indicates the direction facing the kettle main water carrying body) by a circular cover  14 .  
         [0042]    On the front of the cover  14  is arranged part of the switching means for providing the dry boil protection, namely, a number of bimetallic elements discussed as further below which are held beneath a metallic cap  16  having a circular opening through which the foremost bimetallic element  18  is visible. In use, the control is disposed so that the cap  16  lies adjacent or in close thermal contact with a hot spot on the heating element head, as is well-known in the art.  
         [0043]    Disposed on the front of the control  2  at an upper region of the support  12  is a bimetallic switch element  20 . In the assembled kettle the element  20  is disposed in a steam passageway in communication with the interior of the kettle, whereby steam passes over the element  20 . The element  12  is of a well-known construction comprising a thin bimetallic disc which is slightly dished so as to be rearwardly concave when cold having a generally U-shaped opening cut therein defining a central tongue  22 . At a predefined temperature the element snaps to an inverted position in which it is dished in the opposite direction. The element  20  is held at its periphery, whereby the central tongue  22  moves rearwardly with respect to the support  12  at the defined temperature.  
         [0044]    On the rear of the support  12  is a bi-stable lever  24  most clearly seen in FIGS. 2 and 3 arranged to pivot about an upwardly directed knife edge which engages in a shallow slot in rearwardly protruding fingers on the support  12 , and more particularly, to snap between a first (“on”) position where the upper end of the lever lies closest to the support  12  and a second (“off”) position (FIG. 2 a ) where a lower end of the lever lies against formations on the housing  10 . A C-spring  26  is constrained in compression between a shoulder on the support  12  and beneath a claw at an upper end of the lever  24 . The upper end of the lever  24  is also provided with a nose extending towards the element  20  so that the tongue  22  of the element  20  engages the nose when it snaps to its hot position, causing the over-centre lever to trip from the ON position to the OFF position. The lower end of the lever  24  is provided with actuating surfaces  28  which bear on the ends of a pair of actuating rods  30 , the end of one being visible in FIG. 2, which extend through respective bores provided in the rear of the housing  10 . The function of the rods  30  is further described below.  
         [0045]    The control  2  provides conducting electrical paths between the male connector portion  5  and contacts connected in use to the heating element head. Switches are provided in both the live and neutral side of the control  2 . In the live side of the control a movable live contact spring strip  32  (see FIG. 5) which has a contact piece at its upper end forms a contact switch pair with fixed live strip  34  which likewise has a contact piece. The opposed contacts pieces may comprise discs of silver or other electrical contact alloy. The fixed strip  34  has an upstanding leg which terminates in a bent over region  36  at which the strip  34  is in use secured to the live cold tail of the heating element (not shown).  
         [0046]    The movable live contact spring strip  32  has a lower rectangular aperture through which an insulative peg  35  extends and at which the contact spring strip  32  is supported as a cantilever. An enlarged actuating surface  38  is provided about two thirds of the distance up the contact spring strip from the peg  35 .  
         [0047]    An identical switch structure is also provided in the neutral side of the control by means a neutral fixed contact strip  42  having a bent over end portion  44  at which the contact strip is secured to the opposite neutral cold tail of the heating element extending through the element head (not shown). Movable neutral contact spring strip  40  is of similar construction to the live spring strip  32  and has an enlarged actuating surface  46 , with opposed ends of the neutral contacts strips  42 ,  46  being provided with silvered contact pieces. The movable spring contact strip  40  is secured at its lower end to insulative peg  48  which extends through a rectangular opening therein.  
         [0048]    The dry boil switching elements comprise, as described in detail in applicant&#39;s co-pending GB Application No. 0109777.3 a series of bimetallic disc elements held within cap  16  of known type which when cold are dished with concave surfaces facing to the switch rear, and which snap to an inverted configuration at predetermined temperatures. Such discs have a relatively small distance of movement (typically about  1 mm) but provide a large force (typically 500 gf). More particularly, there is provided the first bimetallic disc  18  selected to snap (switch) at about 140° C. and to re-set automatically when it has cooled to a lower temperature typically below about 70° C. to 100° C. A second bimetallic disc  52  is separated from the first disc by a metal heat-conductive spacer ring  54 , this disc switching at a similar temperature to the first disc  18 , and likewise being reversible on cooling. Third disc  56  interposed between first and second discs  18 ,  52  is selected to switch at a rather higher temperature, typically about 260° C. serving as a back-up switch, and being of a type which does not automatically snap back on cooling, thereby essentially disabling the kettle. The bimetal discs are operatively connected to the switch contact pairs through actuating means as now described. First bimetal disc  18  acts on a push rod  50 , which extends through central openings in the second and third discs, and through an axial opening in a push rod sleeve  58  for the second and third discs. Both push rod  50  and sleeve  58  extend through an opening in the cover  14  to extend into the interior of the housing  10 . As can be seen in FIG. 5, live and neutral dry boil switch levers  60 ,  62  are provided between the push rod  50  and sleeve  58  and the switch contacts. Both levers  60 ,  62  are pivotably mounted on shaft  64 . The live switch lever  60  has at its lower end a flat surface against which an end of the push rod  50  engages and at its upper end a ring-like formation which bears against the rear side of the actuating surface  38  of the contact  32  and through which the actuator rod  30  of the trip lever  24  passes in an unobstructed manner so that this can likewise engage the rear of surface  38 . Neutral lever  62  has at its lower end a ring-like formation dimensioned to allow push rod  50  to pass unobstructed therethrough to reach the end of the live lever  60 , but obstructing the push sleeve  58 . An upper end of the lever  62  engages beneath region  46  of the neutral contact, likewise having an upper ring formation through which an actuator rod  30  extends unobstructed to bear against the neutral movable contact spring strip  40 .  
         [0049]    In normal use of a kettle incorporating such a control  2 , from an OFF position the user manually moves a button on the kettle exterior which is operatively connected to the lever  24  to cause it to snap over-centre to an ON position where the top of the lever lies adjacent the tongue  22  of the bimetal. On boiling, the bimetal  20  senses the steam and snaps to its hot position, the tongue  22  causing the lever  24  to snap over-centre to its OFF position in which the lower end of the lever urges actuating rods  30  to bear against surfaces  38 ,  46  and opening the contact pairs. It is arranged by appropriate construction and relative disposition of the various element described that the contact pairs be opened in a sequential manner, that is that the neutral contact pair opens momentarily before or after the live contact pair, thereby isolating the kettle element on both neutral and live sides in a sequential manner, reducing the changes in potential which are occurring at any instant of switching and thereby reducing the risk of arcing on the second contact pair.  
         [0050]    In the event of a dry situation, in the absence of steam the steam-sensing bimetal  20  will not switch. In this case the temperature of the heating element will rise above its normal operating temperature. The first bimetal  18  of the dry boil switch elements which is closest to the element head will switch first, causing the central region of the bimetal to move rearwardly, pushing push rod  50  into the housing  10  and causing lever  60  to pivot, opening the live contact pair thereby switching off the power to the element at the live side. Very shortly thereafter bimetal  56  will switch, moving push-sleeve  58  to the rear, causing lever  62  to pivot opening the neutral contact pair.  
         [0051]    On cooling, the bimetals  18 ,  56  revert to their cold position, the resilience of movable contact spring strips  32 ,  40  closing the contact pairs.  
         [0052]    The structure of the connector is now described. As can be seen in FIGS. 3, 4 and  5 , the lower region of the control unit supports the male contacts which comprise a central earth  60 , and on opposite sides the live and neutral contacts  62 , 64  each of which extend directly vertically downwardly from the control unit. Each comprise thin conductive members in the form of conductive strips secured to or bent over a thin tongue  65  of insulating material which constitutes a lower extension of the control unit housing  10 . The earth strip  60 , as best seen in FIG. 3 comprises a strip which curves from a securing point  66  where in use it is clamped to the head part of the heating element having a straight portion wrapped over the end of the central region of tongue  65  and back on itself being to secured to itself through aligned openings through the earth strip  60  and tongue  56  by riveting or other suitable means. The live and neutral conductive strips  62 ,  64  extend from the interior of the control unit, as best seen in FIG. 5, being secured to the movable contact strips  32  and  40  respectively at the insulative pegs  35 ,  48  which are hot staked to hold the parts in conductive contact. The strips  62 ,  64  extend through openings in the lower region of the housing, being bent about the leading (lower) end of the tongue  65  and each secured back on itself by riveting or other suitable means. As best seen in FIG. 9 the tongue has a non-linear bent configuration with the plane of the earth contact spaced rearwardly with respect to the plane of the live and neutral contacts. More particularly, the tongue essentially is shaped as a pair of rearwardly facing channel sections (on which the live and neutral contacts are held) with a forwardly facing channel section therebetween (on which the earth contact is held). This construction ensures that a tongue of very rigid form and yet of minimal thickness can be provided. It will be appreciated that other shapes of tongue could be employed providing a rigid non-linear (in cross-section) structure of small thickness is achieved.  
         [0053]    The structure whereby the movable live and neutral switch contacts  32 ,  40  are joined to separate live and neutral contacts  62 ,  64  of the connection portion means that the high quality conductive spring alloy demanded by the switch contacts can be confined thereto, and the contacts  62 ,  64  made of inexpensive metal such as copper, or copper alloy such as bronze. However, the spring contacts  32 ,  40  could readily be unitarily formed with the contacts  62 ,  64  for ease of manufacture.  
         [0054]    Turning now to the female connector  8  as best seen in FIGS.  10 ( a ) and  12 , this has an upstanding shaped housing  70  of moulded plastics material secured at its lower periphery to a generally planar support which is provided with moulded openings  74  for receiving screws for fixing the female connector to the main body of the appliance base  6 . An upper end of the housing  70  defines a continuous but non-straight slot  76  which has a shape corresponding to the cross-sectional shape of the tongue  65  and which receives the tongue  65  of the male connector.  
         [0055]    As best seen in FIG. 10( b ) there are provided a pair of L-shaped electrical contacts  78 ,  80  being the neutral and live contacts respectively having spade terminals at their lower ends and at their upper ends extending upwardly within the housing towards the slot  76 . The contacts  78 ,  80  including regions  82 ,  84  at which they are bent slightly downwardly near the bottom of their upstanding portions to give these enhanced springiness or flexibility. The upper ends of the contacts terminate in contact portions  86 ,  88  of highly conductive metal such as silver contacts, as is well-known in the art in order to ensure a good electrical connection. The silver contacts remain a minimum distance below the slot as required by safety standards. A central earth contact  90  has a slightly different structure, and instead of having a silvered contact region having a wrapped over end region  92 . The non-linear slot  76  ensures that thin flat objects cannot be inserted into the slot in a manner which could make electrical contact with more than one of the contacts  78 ,  80 ,  90  at any one time.  
         [0056]    On mating of the connectors  5 ,  8  the end radii of the connector strips  62 ,  64  and  60  where these are wrapped over the lower leading end of the tongue  65  engage the contact pieces  88 ,  86  and the earth contact  90  respectively. It is deliberately arranged that there is at least a small vertical distance of travel of the contacts whilst engaged and that there is at least a small amount of laterally relative through slight sliding or rolling movement therebetween which serves to clean the male contact strips each time they mate with the live contact of the female connector.  
         [0057]    As can be seen in FIG. 5 the earth contact  90  extends upwardly beyond the live and neutral contacts  80 ,  78  so that on mating of the connectors the electrical connection of the earth is made first, and on disengagement, broken last.  
         [0058]    [0058]FIG. 6 illustrates an alternative embodiment identical in all respects except that a neutral strip  64 ′ and supporting region of the tongue  65  of the male connector  5  is disposed slightly higher than the live strip  62  set back from the leading end of the tongue  65 , whereby the live connection is made before the neutral connection on mating, and broken later on disengagement. This ensures a sequential electrical connection of live and neutral supply, minimising incidences of arcing which can lead to deterioration of the contacts, and at worst in case of high-inductance heating elements, severe arcing to earthed metal.  
         [0059]    [0059]FIG. 7 illustrates a further alternative embodiment identical in all respects with the exception of the neutral contact  78 ′ in the female connector which extends higher than the live contact, to ensure the neutral electrical connection is made first and broken last, and that the electrical connections are sequentially made.  
         [0060]    It will be appreciated that other adaptations with respect to relative positioning of contact strips  62 ,  64  and contacts  80 ,  78  could be made to ensure this sequential electrical connection.  
         [0061]    The described structure employing a combined control and connector, in departing from the conventional structures dictated by the arrangement of three plug pin required by I.E.C. standards, allows a control and connector of particularly compact and robust construction.