Note: Descriptions are shown in the official language in which they were submitted.
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Liquid heating apparatus
This invention relates to a liquid heating apparatus for heating/boiling
liquids such
as water.
There is a common need almost all over the world to heat water in order to
make
beverages. In the UK and other parts of Europe, it is common for most
households
to own a kettle which is used to boil water for making occasional beverages.
In
larger establishments and also in other parts of the world, it is more common
to keep
a body of water hot or boiling for a prolonged period of time - possibly all
day - in
order to be able to make such beverages "on demand", i.e. without having to
wait for
the water to heat up from room temperature. An example of this would be a
traditional electric urn or, more commonly in Asia, a so-called airpot.
Both of these arrangements have their disadvantages. In the case of the
kettle, the
time taken for the water to heat from cold (i.e. the temperature from which it
is
drawn from the tap) is seen as inconvenient to users, even those using very
high
power kettles (of the order of 3 kilowatts). This is particularly so given the
difficulty in estimating the volume of water required when the kettle is being
filled
and the attendant tendency to boil more water than is needed which of course
increases the time taken for it to boil. On the other hand, if water is kept
for a
prolonged period of time either at or just below boiling, a significant amount
of
energy will be required to counter the unavoidable heat loss.
Recently, devices attempting to bridge this gap have been commercialised.
These
are said to be able to deliver a cupful of hot water from a reservoir of cold
water
within a matter of seconds. However, these devices are typically based on a
tubular
flow heater and the applicant has appreciated some significant drawbacks to
this
arrangement. Firstly, as is typical of tubular flow heaters, heating must be
ceased
before the water in the tube reaches boiling point in order to avoid the
danger of the
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heater overheating through hot spots created by pockets of water vapour and/or
the
pressure inside the tube building up too high. Another drawback is that
although the
heater heats up relatively quickly, there is inevitably an initial volume of
water
which passes through the heater which is not heated to the target temperature.
This
mixes with the water produced later, itself still not at boiling point, to
reduce the
average temperature of the water. The combination of these two factors means
that
in practice the water provided by such devices is at well below boiling point
by the
time it is dispensed making it unsuitable for example for making tea and
thereby
limiting its consumer appeal.
The Applicant has further appreciated that most users will still need to keep
a
conventional kettle in addition to a one-cup hot water dispenser of the type
discussed above, for when a larger quantity or truly boiling water is needed.
This
creates problems in terms of space taken up in the kitchen.
When viewed from a first aspect the present invention provides a liquid
heating
apparatus having a first mode of operation in which a first volume of water
can be
heated and a second mode of operation in which a second, smaller volume of
water
can be heated and automatically dispensed.
It will be seen by those skilled in the art that in accordance with the
invention a
single apparatus can be used either to heat and dispense a small volume of
water
rapidly, or to heat or boil a larger quantity of water more conventionally.
This has
the advantage of allowing the user to select the appropriate mode of operation
according to the volume of water required at any particular time, but without
the
cost associated with separate appliances for these tasks or the need to find
space for
multiple appliances on a kitchen worktop. Of course it should be understood
that
the relative volumes of water that can be heated in either mode is determined
by the
relative maximum capacities; at least in preferred embodiments the first mode
of
operation could be used to heat a volume of water that is sufficiently small
that it
could have been heated in the second mode instead. The volume of water that
can
be heated in the second mode may be fixed or might be variable - e.g. by a
user.
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The apparatus could be provided with separate reservoirs for the two
respective
modes of operation, but in preferred embodiments a common reservoir is
provided.
This could be arranged to dispense water (or another liquid) to respective
heating
arrangements depending upon whether the first or second mode of operation was
being employed, but in preferred embodiments the apparatus is arranged to heat
all
the water in the reservoir in the first mode of operation, or a smaller,
predetermined
amount of water from the reservoir in the second mode of operation.
The apparatus preferably comprises a removable reservoir which is advantageous
in
facilitating filling, since the reservoir can be removed from the rest of the
apparatus
and taken e.g. to a tap to fill it. In particularly convenient embodiments,
the
apparatus is also arranged such that water heated in the first mode of
operation can
be manually dispensed from the removable vessel. The removable vessel can,
preferably, resemble an ordinary kettle and it will be appreciated therefore
that in
these embodiments the apparatus essentially comprises a standard water boiling
kettle but the apparatus is also configured to be able to heat and dispense
water "on
demand" if the volume required is small enough.
A common heating means could be employed to heat water in either the first or
second mode of operation. For example, a reservoir could comprise means to
divide
off a small volume therefrom which can be heated in the second mode of
operation.
In other embodiments, independent heating means are provided for the first and
second mode of operation respectively. This might have some advantages in
terms
of optimising each heater for its particular use and also lends itself
particularly to
embodiments where essentially a complete water boiling kettle is provided for
operation in the first mode but which, when placed on the apparatus, allows
water
from the kettle to enter the heater for the second mode of operation. It will
be
appreciated that in such embodiments the kettle could be operated
independently of
the rest of the apparatus, only needing to be placed on the rest of the
apparatus when
the second mode of operation was required.
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Such arrangements are novel and advantageous in their own right and thus when
viewed from a further aspect the invention provides an apparatus for heating
liquid
comprising a removable liquid heating vessel comprising a heater for heating
liquid
therein, the apparatus further comprising a second heating chamber arranged to
heat
liquid and dispense it through an outlet, wherein said second heating chamber
is
filled with liquid from the removable liquid heating vessel.
Preferably one or both heaters are arranged to heat water to boiling. In
comparison
with the first aspect of the invention the removable liquid heating vessel
provides
the first mode of operation and the second heating chamber provides the second
mode.
In accordance with all the aforementioned embodiments, it is preferred for the
heater
for heating liquid in the first mode of operation, e.g. the heater of the
liquid heating
vessel in the aspect of the invention set out above, to comprise a heater
plate with a
resistance heating element, e.g. a sheathed element, formed on or mounted to
the
underside of the plate. Preferably the heater is arranged to close an opening
in the
base of the vessel as is well-known in the art of kettles.
Where an independent heater for the second mode of operation is provided, e.g.
the
heater of the second heating chamber in the aspect of the invention set out
above this
could take any convenient form, e.g. a tubular heater or some other form of
flow
heater, but preferably a chamber is provided in which the liquid is heated to
the
desired temperature and then dispensed.
The automatic dispensing in the second mode of operation could be effected by
any
suitable means. For example, a pump could be employed or the apparatus might
be
arranged such that the liquid is heated in an upper part thereof and dispensed
lower
down through hydrostatic pressure. In preferred embodiments, however, the
water
is arranged to be boiled in the second mode of operation and is dispensed from
the
apparatus with the aid of steam pressure generated during boiling.
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In some embodiments of the invention a common mechanism is provided to cease
heating of the liquid when it has reached a predetermined temperature,
regardless of
whether this is in the first or the second mode of operation. This could take
any
convenient form, e.g. electronic, and may be dependent upon the temperature to
which the liquid is being heated. In preferred embodiments in which water is
boiled
in both modes of operation, the common means preferably comprises a steam
switch, e.g. one comprising a snap acting bimetallic actuator, as is well-
known in the
art.
In other embodiments independent means are provided to cease heating in the
respective modes. For example where a removable liquid heating vessel is
provided,
a conventional steam switch could be provided. This for example allows such a
removable vessel to be as close as possible to a standard kettle which is
beneficial
both in terms of user acceptance and in being able to minimise re-tooling.
The removable liquid heating vessel preferably comprises valve means for
selectively allowing liquid into the second heating chamber when the vessel is
installed on the appliance and preventing leaking when it is removed. The
valve
means could be provided in the vessel body, but preferably it is provided in a
heater
plate closing an opening in the base of the vessel. This is beneficial in
having the
valve lowermost in the vessel but also means that a standard heater plate
incorporating the valve can be produced thereby allowing appliance
manufacturers
to use appliance bodies that have already been tooled.
Although not essential, preferably valve means are also provided on the second
heating chamber. Preferably such valve means are configured to close when
there is
a predetermined amount of water in the second heating chamber. This allows the
second heating chamber to fill automatically to the required level. It could
for
example comprise a float valve. In accordance with one set of embodiments, a
freely floating valve member is employed, which is more robust than a flap
valve.
Advantageously, such a valve member is received in a housing which permits
liquid
flow through it but retains the valve member, the valve member having an upper
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position in which it is against a valve seat to close the valve and a lower
position
where it is retained in the lower part of the housing. The valve member might
take
any convenient form. For example it could comprise a ball. Alternatively it
could
be pill, discus or squat-cylindrical in shape. In a preferred set of
embodiments the
valve member is downwardly tapering, e.g. frusto-conical. This has been found
to
minimise the chance of the valve member sticking during use.
Preferably the second heating chamber valve means is configured such that
increasing pressure in the heating chamber tends to increase the closure
pressure on
the valve arising from the buoyancy of the valve member. Preferably it
comprises a
resilient collar against which the valve member is pressed by internal
pressure in the
second heating chamber. This helps to prevent leakage of water or steam when
the
removable vessel is removed.
Where, as is preferred, separate heaters are provided for the two respective
modes of
operation, preferably the apparatus comprises a switching arrangement which
only
permits energisation of one of said elements at time. This is advantageous as
it
allows each heater to be high power without running the risk of overloading
the
mains electrical supply by both being energised at once. In a simple exemplary
embodiment the switching arrangement could comprise a change-over switch such
as a rocker switch. Where provided the steam switch preferably acts on the
aforementioned switching arrangement to switch off whichever heater is being
energised.
The above-mentioned arrangement is considered to be novel and inventive in its
own right and thus when viewed from another aspect the invention provides a
switching arrangement for an electrical appliance, said switching arrangement
comprising a switch having a first position in which a first circuit can be
powered, a
second position in which a second circuit can be powered and a third position
in
which neither of said circuits is powered, said arrangement further comprising
a
thermally responsive actuator arranged to act on said switch so as to move the
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switch from either of said first or second positions to said third position
upon said
actuator reaching a predetermined temperature.
In other embodiments an electronic or electro-mechanical arrangement is
employed
to prevent simultaneous energisation. For example in one set of embodiments a
relay is employed in series with the electrical supply to one of the heaters
and is
arranged such that the contacts thereof are opened when power is supplied to
the
other heater. Of course the skilled person will readily conceive of equivalent
means
for achieving the same function electronically. Preferably the arrangement is
such
as to cut off power to the removable liquid heating vessel when the heater of
the
second heating chamber is energised. This is beneficial in that it allows the
electrical arrangement in the liquid heating vessel to be entirely standard.
For
example the relay or other switching arrangement could simply cut power. to a
cordless connector such as the Applicant's P72 connector which is used to
supply
power to the liquid heating vessel.
A preferred embodiment of the invention will now be described, by way of
example
only, with reference to the accompanying drawings in which:
Fig. 1 is a schematic diagram showing the main parts of an apparatus embodying
the invention;
Fig. 2 is a schematic circuit diagram illustrating the electrical switch
arrangement
for the two heaters;
Figs. 3a to 3d are a series of schematic diagrams showing use of an embodiment
of
the invention;
Fig. 4 is a further schematic diagram of a second embodiment;
Fig. 5 is a perspective view of a third embodiment of the invention;
Fig. 6 is a perspective view, from a different angle, of the embodiment of
Fig. 5
with the jug kettle part removed;
Fig. 7 is a view similar to Fig. 6 with the outer cover removed;
Fig. 8 is a partly exploded view of the parts above the heating chamber;
Fig. 9 is cross-sectional view through the heating chamber;
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Fig. 10 is a different section through the heating chamber;
Fig. 11 is an enlarged sectional view of the valve between the jug kettle and
the
heating chamber;
Fig. 12 is a perspective view of the lower part of the dispensing chamber;
Fig. 13 is a sectional view through the dispensing chamber; and
Fig. 14 is schematic circuit diagram for the appliance.
Fig. 1 shows the basic parts of an apparatus embodying the invention. In this
embodiment there is an almost-standard jug kettle 2 having a lifting handle 4
and a
pouring spout 6. The kettle is fitted with a heater arranged to close an
opening in the
base thereof and comprises a sheathed heating element mounted to the underside
of
a metal plate. The kettle 2 also comprises the Applicant's standard U17
control unit
in order to switch off the heater in the event that it overheats due to being
switched
on dry or boiling dry. As is well known in the art such a control unit
includes the
male part of a 360 degree cordless electrical connector. The female part of
the
connector 8 is visible on the base part of the apparatus 10.
Where the kettle 2 differs from an ordinary one is that on its base it
comprises a self-
closing valve (not visible) which can be opened by penetration of a tube 12
protruding from the base 10 when the kettle 2 is placed on the base 10. At the
lower
end of the tube 12 is another valve in the form of a float valve 13,
controlling the
entry of water from the kettle 2 to a heating chamber in the base 10.
The heating chamber inside the base of the apparatus 10 has another heater 30
at the
underside thereof which is similar to the heater in the kettle 2. As well as
the inlet
controlled by the float valve 13 as just described, the base heating chamber
is
connected to a dispensing spout 14 which protrudes from the base part 10 and
ends
with a downward loop for dispensing heated water into a cup 16 or other
receptacle
placed beneath it.
Also communicating with the heating chamber and rising from the base 10 of the
apparatus is a vertical steam tube 18 with a narrow neck at its upper end,
beyond
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which is a thermally responsive snap-acting bimetallic actuator 20. Although
not
shown in the schematic representation of Fig. 1, the bimetal 20 is positioned
such
that it also lies above the spout 6 of the kettle 2 when it is positioned on
the base unit
10.
Fig. 2 is a schematic circuit diagram showing the switching arrangement. It
will be
noted from this that the bimetal 20 acts on a change-over type rocker switch
36. The
rocker switch 36 has three positions. In the left and right positions it can
complete a
circuit between a common terminal 22, connected to the live side of the mains
supply, and either one of two other terminals 24, 26, connected respectively
to the
element 28 in the kettle 2 and the element 30 in the base heating chamber. In
the
central position of the switch 36, neither circuit is completed.
This arrangement allows either element 28, 30 to be energised, or neither to
be
energised, but does not physically allow both elements to be energised at the
same
time. Consequently each element can be at the maximum power rating for the
mains
supply - e.g. 3 kW in the UK. The bimetallic actuator 20, when it reaches its
operating temperature (e.g. ninety degrees C), after coming into contact with
steam,
acts on the switch 36 to return it to the central, open position (depicted in
Fig. 2) in
which neither element is energised.
In series with the kettle element 28 are the respective live and neutral pole
switch
contact sets 32 of the U17 control unit. In series with the base heating
chamber
element 30 are a simple bimetallic thermostatic switch and a thermal fuse
switch or
two bimetallic switches (not shown). These respective further switches ensure
that
the elements are de-energised in the event of overheating - e.g. due to being
switched on dry or boiling dry.
Operation of the apparatus will now be described with additional reference to
Figs.
3a to 3d. Fig. 4a shows the apparatus with the kettle 2 placed on the base
part 10
and with a cup 16 placed beneath the dispensing spout (not visible). In use
the user
removes the kettle 2 from the base unit 10 and fills it from a tap in the
conventional
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way (Fig. 4b). It is then replaced on the base part 10, thereby allowing the
tube 12
to penetrate the bottom of the kettle and so allow water to be drawn out from
it
subject to the float valve 13 being open (i.e. if the base heating chamber is
empty).
In a first mode of operation a user can boil a relatively large volume of
water (e.g.
up to two litres). This is done by selecting the appropriate position for the
rocker
switch 36. This energises the kettle element 28 so that it boils the whole
contents of
the kettle 2. When the water has boiled, the steam produced will cause the
bimetal
20 to operate which in returns the rocker switch 36 to the central, off
position which
interrupts power to the cordless connector 8 and so de-energises the element
28 in
the kettle. Of course, instead of this arrangement a more conventional steam
switch
arrangement could be employed in the kettle 2 itself. With a 3 kW heating
element
it would take approximately 4 minutes to boil two litres of water. Once the
element
has been switched off after the water has boiled, the kettle 2 can be picked
up and
the water poured out in the normal way (Fig. 3c).
If instead the user requires only a cupful of boiling water, a second mode of
operation can be employed. This is done by selecting the other position of the
rocker switch 36 (Fig. 3d) and thereby energising the in the base chamber
heater 30.
This rapidly heats the small volume of water in the chamber to boiling, with
the
steam thereby produced entering the steam tube 18 and actuating the bimetal 20
and
returning the switch 36 to the central position so switching off the element.
The
increase in pressure associated with the water in the chamber being boiled
forces it
up through the dispensing spout 14 and into the cup 16. A cupful of water can
be
boiled and dispensed in approximately 30 seconds.
Fig. 4 shows schematically a further embodiment. This has a similar
arrangement of
a removable kettle 2' with its own element (not shown) and a side-entry water
feed
tube 12' for drawing water from the kettle 2' for rapidly heating and
automatically
dispensing a small, predetermined body of water through the spout 14' to the
cup 16.
In this embodiment however, instead of a heater on the underside of an
enclosed
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base heating chamber, there is a flow heater 30' for heating the water for the
second
mode of operation.
Thus it will be appreciated by those skilled in the art that the embodiment
described
above allows a user the flexibility to be able to boil a cupful of water very
rapidly, or
to boil a kettle full of water in the usual way, but without having to buy,
and find
storage space for, two separate appliances.
The embodiment described is merely one example of how the invention can be
implemented. Many variations and modifications can be made. For example rather
than having two separate heating elements for the two modes of operation, a
single
common element could be provided.
Fig. 5 shows a perspective view of a further embodiment of the invention. This
broadly comprises a removable liquid heating vessel in the form of a jug
kettle 40
which is placed on a stand 42 which also serves to support a hot water
dispensing
chamber 44 with its dispensing spout 45 by means of a pillar 46. The kettle 40
is
shown with the lid and outer handle moulding removed. This reveals a standard
steam switch 48 such as the applicant's R48 steam control which is used to
switch
the kettle off when water inside it boils.
Fig. 6 shows the apparatus with the kettle removed. This reveals a 360
cordless
electrical connector 50 such as the applicant's P72 connector located
centrally within
the region of the base 42 which receives the kettle. To one side of the
cordless
electrical connector 50 is the outer housing of water valve 52, the purpose of
which
will be described later.
Also more easily visible in this drawing is the on/off switch 54 on top of the
hot
water dispensing chamber 44 and the drip tray 56 which is directly beneath the
spout
45 (not shown in Fig. 6).
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Fig. 7 shows a view of the main parts of the appliance with the outer covers
removed. Thus in the lower part of the appliance there can now be seen a
heating
chamber 58 with which the valve 52 selectively communicates. Extending from
the
side of the heating chamber 58 are two tubes 60, 62 which connect the interior
of the
heating chamber 58 to the interior of the dispensing chamber 44. The purpose
of
these two tubes will be described later.
Fig. 8 shows a partially exploded view of the parts above the heating chamber.
This
shows that the 360 cordless connector 50 is received in a special recess 60
in the
top face of the heating chamber 58. A channel 62 is provided to accommodate
the
wires coming from the connector 50. The connector 50 is held in place by a
plate 64
which is screwed, riveted or otherwise attached to the top of the heating
chamber 58.
The securing plate 64 also provides the outer valve housing 52. The outer
valve 52
housing fits over an upstanding annular wall 66 on the top of the heating
chamber
with a novel resilient annular sealing member 68, which will be described in
more
detail later, interposed between them.
The heating chamber 58 is formed from upper and lower parts which are clamped
together by clamp rings 70, 72 which are screwed together by a series of boss
and
screw arrangements 74.
Fig. 9 shows a vertical cross-section through the heating chamber 58. From
this
figure can be seen the sheathed resistance heating element 76 bonded to an
aluminium diffuser plate 78 which is in turn bonded to the underside of a
stainless
steel heater plate 80, the foregoing construction being similar to that
conventionally
used in water-boiling kettles. The heater plate 80 is attached to the upper
body of
the heating chamber 58 by means of a peripheral channel 82 which is crimped
over a
downwardly depending wall portion of the heating chamber in accordance with
the
applicant's Sure Seal system which is described in greater detail in WO
96/18331.
Also visible in this figure is a section through one of the tubes 60
connecting the
heating chamber 58 to the dispensing chamber (not shown). This is the outlet
tube
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for conveying boiling water from the heating chamber 58 to the dispensing
chamber
It will be apparent from the Figure that inside the chamber the outlet tube 60
extends
in a right angle arrangement to terminate in a downwardly depending tube
portion
84 the end of which is a few millimetres above the heater plate 80.
Fig. 10 also shows a vertical cross-section through the heating chamber 58,
although
in this instance the section is taken through a plane parallel to that of Fig.
9. This
shows the other tube 62 connecting the heating chamber 58 to the dispensing
chamber which is a vent tube. The lower end of the vent tube 62 fits over a
spigot
86 which opens into a hole at the top of the interior of the heating chamber
58.
Fig. 11 shows a vertical cross-section through the kettle 40 seated on top of
the
heating chamber 58. In this figure, the view has been enlarged to show the
valve
arrangement more clearly and some components have been omitted to enhance
clarity further. The kettle 40 has a side wall 88. The underside of the kettle
is
closed by a circular stainless steel heating plate 90, on the underside of
which is
provided an aluminium diffuser plate 92 and a sheathed resistance heating
element
(not visible).
A hole is formed towards the edge of the heater plate 90 to accommodate the
vertically protruding spigot portion 94 of the kettle part of the valve
mechanism.
This spigot portion 94 is sealed against the hole in the heater plate 90 by
means of a
grommet 96. Beneath the spigot portion 94, the kettle valve part comprises two
concentric annular shrouds: an inner shroud 98 and an outer shroud 100. The
diameter of the outer shroud 100 is such that it fits over the outer housing
52 of the
heating chamber valve part and it has a bevelled edge to aid location.
Between the spigot 94 and the inner shroud 98 is a sprung valve arrangement
comprising a vertically movable valve member 102 which has at the top a valve
head 104 which is biased towards a corresponding valve seat 106 by a
compression
coil spring 108. The coil spring acts between the underside of the valve seat
106
and a ring 110 at the bottom of the valve member 102. In the configuration
shown
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in Fig. 11, an upward force is being applied to the lower ring 110 of the
valve
member thus lifting the valve head 104 away from the valve seat 106 to permit
water to pass through the valve. Equally, however, it will be seen that when
this
force is removed, the coil spring 108 acts to close the valve and therefore
prevent
further passage of water.
The components provided on the heating chamber side of the valve arrangement
comprise the outer housing 52 (mentioned previously with reference to Figs. 6,
7
and 8) having a central, chamfered opening which receives the inner shroud 98
of
the kettle valve housing. This outer housing 52 therefore passes, during
coupling of
the two valve parts, between the inner and outer shrouds 98, 100 of the upper
part.
Inside the outer housing 52 is the annular sealing member 68 which provides a
fluid-
tight seal against the upwardly projecting annular wall 66 which is an
integral part of
the top of the heating chamber 58. The sealing member 68 has a central annular
protrusion which forms an upwardly open annular channel which receives and
seals
against the lower edge of the inner shroud 98 of the kettle valve part.
On the lower face of the sealing member 66 is an angled annular flange 112
which
extends radially outwardly so that it has a degree of flexibility in the axial
direction.
Beneath the sealing member 66 is a generally frusto-conical float valve member
114
which is able to move vertically but which is constrained in its downward
travel by a
valve stop member 116. The top surface of the float valve member 114 presses
against the angled annular flange 112 when it in the upper portion or its
travel.
Fig. 12 shows a perspective view from above of the dispensing chamber 44 with
the
upper cover removed. Fig. 13 shows a vertical cross-section through part of
the
chamber with the upper cover in place. The main part of the dispensing chamber
44a is broadly bowl-shaped with the dispensing spout 45 in a distinct recess
44c at
the centre. Extending round part of the rear edge is a raised, generally
horizontal
platform portion 44b into which the outlet pipe 60 and vent pipe 62 from the
heating
chamber emerge. It will be noted that these two tubes 60, 62 extend vertically
some
way into the dispensing chamber.
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Mounted outside the dispensing chamber (but shown in Fig. 12 for reference) is
an
R48 steam switch 188 to which is attached the on/off rocker switch 54. A
vertical
chimney 120 extends through, but is isolated from, the dispensing chamber 44
and
opens just beneath the bimetallic actuator (not clearly visible in Figs. 12
and 13) of
the steam switch 118. This allows cool air to pass over the bimetallic
actuator after
it has operated in order to allow it to reset relatively quickly.
As maybe seen most clearly from Fig. 13, the tube forming the outlet spout 45
extends vertically some way into the dispensing chamber 44 inside a concentric
downwardly open tube 122 of slightly larger diameter which is mounted to the
upper
cover of the dispensing chamber. The downwardly open tube 122 extends down
just
short of the annular recess 44c in the centre of the main part of the
dispensing
chamber 44a.
Fig. 14 shows a schematic circuit diagram showing the main electrical
connections
between various parts of the appliance. To the left of the diagram may be seen
the
line, neutral and earth connections from the mains lead (not shown). The
switch
contacts of the steam switch 118 provided in the dispensing chamber are
connected
electrically in series between the line pole and the coil of a relay 124
(although not
shown in this schematic diagram, some form of rectification might be
provided).
The contacts of the relay 126 are of the change-over type with the common
contact
126a connected to the line pole. The normally-off relay contact 126b is
connected
to the heating element 76 provided on the base of the heating chamber 58.
Although
not shown in the Figures, the electrical connection to this element 76 is made
by
means of a modified U-series control having its characteristic pair of
overheat-
protection bimetallic actuators which act on respective normally-closed
contacts
128a, 128b on the line and neutral side respectively of the element. An
indicator
neon 130 is connected, in series with a suitable resistor 132, across the
element 76 to
indicate when the element is energised.
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The normally-closed relay contact 126c is connected to the central, line
terminal of
the cordless electrical connector 50. The neutral and earth terminals are
connected
directly to the corresponding inputs from the mains lead.
To the right of the diagram in Fig. 14 is depicted the conventional electrical
arrangement found in a kettle. Thus, the heating element 134 is connected in
series
with the normally-open contact of the steam switch 48 and also in series with
the
normally-closed contacts 136a, 136b which are acted on by the overheat
bimetals of
a U17 control. Again, an indicator neon 138 and corresponding resistor 140 are
connected across the element 134 to indicate when it is energised.
Operation of the embodiment described above with reference to Figs. 5 to 14
will
now be described.
As with the previous embodiments, the appliance of this embodiment can be
operated in two separate modes. In the first mode, the kettle 40 can be
removed,
filled and then replaced on the base. To start boiling, the on switch (not
shown) is
pressed to close the contacts of the steam switch 48. In the normal state
shown in
Fig. 14, power can then be supplied through the cordless connector 50 to
energise
the element 134. Unless the user switches off again, heating will continue
until the
water in the kettle boils which causes the steam switch 48 to operate and
disconnect
the power to the element. The kettle 40 can then be lifted up again and the
boiling
water poured out of its spout in a conventional manner.
However, if a user wishes to boil and dispense just a cupful of water, he or
she can
operate the appliance in a second mode of operation which will be described
below.
When the appliance is first used, or the heating chamber 58 has otherwise been
allowed to become empty, it must be filled with water. This is done by filling
kettle
40 with water and replacing it the stand 42. This allows the water in the
kettle 40 to
drain through the valve arrangement shown in Fig. 11 into the heating chamber.
More particularly, as the kettle 40 is replaced on the stand, the lower end
ring 110 of
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the valve member 102 in the kettle valve part is forced up against the force
of the
coil spring 108 by its contact with the inner annular projection of the
sealing
member 68. This allows water to flow from the inside of the kettle 40, through
the
valve spigot portion 94, past the valve member 102 and into the heating
chamber 58
through the centre of the sealing member 68 and over the edges of the float
valve
member 114. The vent tube 62 allows air to be displaced from the chamber even
after the lower part 86 of the outlet tube has been covered.
As the level of water in the heating chamber 58 rises, the float valve member
114
will gradually be raised by the water until such time as it seals against the
annular
flange 112 on the lower face of the sealing member 68 with sufficient force to
prevent any further water entering the heating chamber 58. If the kettle 40
should
now be lifted up again, the coil spring 108 will close the valve head 104
against the
valve seat 106 inside the kettle valve housing, thus preventing leakage of
water from
the kettle. Similarly, the buoyancy pressure of the float valve member 114
against
the compliant annular flange 112 at the bottom of the sealing member 68 will
prevent water from spurting out of the lower part of the valve arrangement.
When
the kettle 40 is replaced, although the kettle side of the valve 104, 106 will
be
opened again, no further water will flow since the float valve member 114 will
remain pressed against the annular flange 112.
In order to operate the appliance in the second mode, the user must switch on
the
switch 54 provided at the top of the dispensing chamber. As will be
appreciated by
considering the circuit diagram of Fig. 14, this energises the relay coil 124
to
disconnect relay contacts 126a and 126c and connect contacts 126a and 126b.
This
has two consequences. The first is that the kettle 40 cannot be operated since
power
is no longer being supplied to the cordless connector 50, thereby ensuring
that the
two elements 76, 134 cannot be energised at the same time which would drain an
excessive current for an ordinary domestic mains socket. The other consequence
is
that the element 76 on the underside of the heating chamber 58 is energised
and
begins to heat the water in the heating chamber.
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During the initial stages of heating, the build-up of pressure inside the
heating
chamber 58 is limited by the vent tube 62 connected to the dispensing chamber
44
which is essentially at atmospheric pressure. This prevents water which has
not
been sufficiently heated from being ejected via the outlet tube 60
prematurely. It
also reduces any tendency of the float valve member to 114 to 'wobble' against
the
sealing member 68. Together with the compliant annular flange, 122 this helps
prevent further cold water entering the heating chamber during heating.
As the temperature of the water in the heating chamber 58 approaches boiling,
the
pressure builds up and begins to force water up the outlet tube 60 and so into
the
dispensing chamber 44. As this continues, almost all of the boiling water in
the
heating chamber 58 is forced up the outlet tube 60 to fill the dispensing
chamber 44.
Water will continue to be forced up the outlet tube until the water level in
the
chamber 58 falls below the lower end of the downward extension of the outlet
tube
88.
Turning to Figs. 12 and 13, it will be seen that boiling water initially
enters the side
chamber 44b and thereafter drains into the main part of the chamber 44a
towards the
annular recess 44c in the centre and so starts to fill the chamber main part
44a. As
water continues to enter the dispensing chamber 44, the level between the
downwardly open tube 122 and the upwardly extending outlet spout 45 rises
until
the water begins to flow over the top edge of the outlet tube 45 and so down
through
the spout into a user's cup. This sets up a siphon which causes virtually all
of the
water in the dispensing chamber 44 to be dispensed through the spout 45.
Once all the water has been forced up from the heating chamber 58 via the
outlet
tube 60, steam from the heating chamber 58 will be ejected from the top of the
outlet
tube 60 (as well as form the vent tube 62) and into the dispensing chamber 44.
This
causes the steam switch 118 to switch off, thereby interrupting power to the
relay
coil 124 and so disconnecting the heating chamber element 76.
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When pressure in the heating chamber has subsided, the float valve member 114
drops down against its stop 16 which automatically refills the heating chamber
58
with water from the kettle 40, assuming it is there and has sufficient water
in it. If
the kettle 40 is not there, the heating chamber 58 will be refilled next time
it is
replaced. The kettle 40 therefore acts as a convenient removable reservoir for
the
heating chamber. This allows a user to produce cups of boiling water
repeatedly
throughout the day without having to refill the kettle each time, without re-
boiling
the same water several times (which is often considered to harm its taste by
removing dissolved oxygen) and, importantly, without wasting energy by boiling
more water than is necessary.
If the heating chamber 58 is operated without any water in it, for example if
there is
no water in the kettle 40 to refill the chamber after a previous use, then one
or other
of the bimetals in the modified U-series control protecting the element 76
will
operate to open the respective contacts 128a, 128b.
Thus it will be seen that a highly versatile appliance is provided which can
either be
used as an ordinary kettle to heat a relatively large quantity of water or, if
only a
single cupful of water is required, it can be heated and dispensed very
quickly and
efficiently by means of the second mode of operation. The kettle 40 then acts
as a
removable reservoir in this mode of operation which is in itself convenient as
it
allows easy refilling. The provision of a relay to switch between the two
elements
avoids an electrical overload.
