Note: Descriptions are shown in the official language in which they were submitted.
114V~73
FIl~LD AND BACKGROUN~ OF THE INVENTION
Cooking units such as electric hobs, electric
co~kers, portable eleetrie,cookers or the like are
usually provided with from tw~ to four electric cooking
plates eaeh of whieh has an output of from 1000 to 2000 W
so that food can be heated up relatively quiekly on these
eooking plates, A four-plate unit can therefore have a
max~mum output of 7 to 8 kW. This is often too mueh
for a normal domestic mains supply, particularly if the
mains voltage is only 120 volts. In addition, it is
not possible to eonnect such a unit to a soeket which is
~used in the normal way. Cooking units have already
been proposed whieh eontain a power eooking plate with
a hlgh :Load and three cooking plates with a very low loa~
whieh are intended Ior eontinued eooking, With this arrange-
ment, the house-wife has to heat up eaeh pan in sueeession on
the one hi~h power plate, e.g. bring the contents thereof
to the boil, then transfér the pans to the three plates
of lower power for eontinued eooking, This makes the
eooking more diffieult and demands partieular attention.
j SUMMARY OF THE INVENTION
The object ol the invention is to provide a cooking
unit with at least two electrie~ooking plates, at least
one of which is rhythmically regulated or controlled by a
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switching device which manages with a small connected
load and contains cooker plates which can be used fully.
According to the invention there is provided a
cooker unit comprising at least two electric cooking
plates, means for supplying electrical power to the
plates, and a switching device for regulating or con-
trolling the supply of power to at least one of the
plates rhythmically, the switching device of at least
one favoured cooking plate being such that when at least
one portion of its power is switched off, at least one
subsequent cooking plate is supplied with power.
In accordance with a particular embodiment of
the invention a cooking unit includes at least one
cascade cooking unit, the cascade cooking unit including
a favored cooking plate having at least two electric
heating elements and at least one additional cooking plate
having at least one heating element. A thermal sensor is
associated with the favored plate and is responsive to
at least one of the heating elements of the favored
cooking plate. Thermostatic switching means are res-
ponsive to the thermal sensor, the switching means oper-
ating in a first mode to supply power solely to the
elements of the favored plate and in response to a pre-
determined temperature sensed by the sensor operating in
a second mode to supply power to only one of the elements
of the favored plate and to supply power to at least one
of the elements of the at least one additional plate
through a series connection.
A specific order of priority is thus deter-
mined (which can however be changed or eliminated bymeans of changeover switches) so that the subsequent
electric cooking plates are supplied with current when
the first cooking plate switches off the power at least
partially owing to its control or regulating procedure.
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Since the initial cooking process takes place quickly
when using a cooking plate having a high connected load
and the power needed for continued cooking often does
not exceed 10 to 15% of the connected load, sufficiently
long periods are available in which the subsequent cook-
ing plates are switched on, In particular, when the
intervals or switching periods are very short, the
cooking procedures on the subsequent cooking plates
are rarely disturbed and the consumer will hardly
notice the inevitable disconnection pauses of the
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subsequent cooking plates. This applies particularly
when the cooking plates are arranged~patially in the
cooking unit in their priority grading in such a way
that the cooking plates which are used most on the basis
of this arrangement are the first in the priority grading.
A rhythmic mode of operation of the switching devices
is important in the favoured electriccooking plates, but
a subsequent cooking plate could also have a different
type of regulation, for example a filter pulse clrcuit.
10 The thermostat is preferably a so-called automati-c
controller which operates with a hydraulic sensor box
which is arranged in the central zone of the cooking
plate and is pressed on to the bottom of the cooking pot.
In this arrangement, the electric cooking plate has two
15 heating reslstances and the controller has two associated
contracts which switoh off at successive temperature values.
An additional cooking plate can be supplied completely
or partially with current as soon as the first partial
current is switched off.
In a particularly advantageous embodimcnt which not
only keeps the connected load low but also saves energy,
the switching device is a condition controller which
responds to the steam produced in the cookin~ container.
When this condition controller, of the type described
25 in German Patent No. 1,029,502, is allocated to the
favourod electric cooking plate, it is evell possiblc to
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^ ll~V9~73
- prepare a meal con~sting Or several individual dishes
on one eooking plate by stacking up,cooking containers,
- ' the lower cont~n~s eæh heating the one above it, and
using an additional subsèquent c,ooking plate, for example
f~r frying purposes.
BRIEF DESC RIPTION OF THE DRAWINGS
Figures 1 to 3 are schematic circuit diagrams of
~th~ee cooking units;
Figure 4 shows a detail of a modified form of unit;
Figure' 5 shows the side view of a cooking unit; and
Figure 6 shows the cireuit diagram of the cooking
unit aecording to Figure 4.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
, The circuit illustrated in Figure 1 com~rises a cooking
15 unit 11 having four electric cooking plates 12, 13, 14 and 15,
whieh ean be oonneeted to the domestie mains at a socket 17.
by means of a plug 16. The eooking unit ean be an electric
eooker, an eleetrie~Db or a ~ortable eleetric cooker.
Eaeh eleetric cooking plate can be a eonventional cooking
20 plate made of oast material, each having two heating
elements 18,19, which can be connected individually or
together by two contaet arms 20,21 or switehing springs
of'a switching device 22. The switching device 22 is a thormo-
stat whieh ean be adjusted manually to the desired temperat,ure
25 by means of an adjusting head 23. Eaeh thermostat is provided
with a sensor bo~ 2ll, whieh is spring-mounted in a conventional
way (not shown) in the eentre ol' the eooking plate and can
rest against the bottom of a cooking eontainer in order to
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114V973
detect its temperature. It is generally connected to
the internally arranged heating element 19. The scnsor
box 2~ is filled with an expansion fluid and connected
via a capillary tube 25 with an expansion box 26 which
5 acts upon the contact arms 20,21 as a function of the
- temperatur~ of the sensor box and the manual adjustment.
'The contact arms 20,21 are adjusted relative to each
other in such a way that they switch in succession as
the temperature rises, the contact arm 20 switching a
, 10 few degrees before the contact arm 21. This substantially
pre~ents the,desired temperature from being exceeded.
rrhe thermostat can be constructed in accordance
with German Offenlegungsschrift No. 2,058,512 or German
Patent No. 2,~ ,813. 'rhe contact arms 20,21 are also
15 electrically s,eparated on the input side and can havc
two separate switching springs. 'rhe flxed contacts
27,28 of the switching device 22 leading to the hcating
elements 18,19 are each provided with a fixed transYer
contact 29,31 which c~operates with the corresponding
20 switching springs when the respective heating resista~e
is switched oIf.
he he~tin~ resistances oI all cooking plates are
connected via a return line 36 to one pole of the domestic
mains and the contact arms 2~21 oY the switching device
Yor the first cooking plate 12 to the other pole.
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The transfer,contact 29 is connected to the contact..
. .arm 21 of the next switching device and the transfer
', contact 31 is connected to the.contact arm 20 of the
. ,next switchin~ device, so that the transfer contact -
, 5 of the internal heating resistance of each cooking
plate is allocated to the external heating resistance
. . . of another cooking plate. Owing to this-cross-over
. circuit, the heating resistance which controls the
.temperatuPe sensor 24 is charged at, any time.
10 , . Tlle cooking unit according to Figure 1 operates
in the following manner. The connecting plug 16 is
.connected to a soc~et whose fu-e corresponds to the '
maximum power of the highest rated cookin~ plate, for
example 2000 W. Figure 1 shows a condition in which
15 the cooking plates 12,13 and 14 are switched on by
activatin6 the adjusting button 23. With the,cooking
plate 12, the initial cookin~ process ,in which both
heating resistances .were switched on has already ended
and the switchin~ device has received an ïndication from
20 the temperature,sensor 24 that thc adjusted temperature
has been reached. An avera~e power of up to only about
,' 500 W is needed for continued cookin~, and this is
supplied by switching the he~tin6 resistance 19 on and
, off by means of contact arm 21 ,which in so daing switches
2~ ovcr between the contacts 28 and 51. With the cookin~
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73
plate 12, both contacts 27 and 28 are disconnected
so that both contact arms 20,21 are connected to the
transfer contacts 29,31 which are connected to the
contact arms 20,21 of the subsequent cookingplate 13.
The subsequent cooking plate 13 has also completed the
initial cooking operation. Cooking plate 13 illustrates
the condition in which the internal heating element 19
receives current (drawn in black), the heating up o~
which charges mainly the temperature sensor. The
transfer contact 29 is open and the~eatin~ resistance 18
of the cooking plate 1ll does not receive any current
although, like heating element 19, it is switched on
by the switching device 22 an~ the cooking plate has
not yet reached the sct temperaturc.
The condition illustrated does not last long because
the cooklng plate 13 is switohed oii agnin by the contact 21
after a very ~hort period so that both heating resistanoes
18,19 of the cooking plate 1ll then receive current
Since, in the case ol cooking plate 13, the heating
~esistance 18 is disconnected and the contact arm 20
is connected to thc transier contact 29, the contact
arm 21 receives current Irom the cooking plate 1ll and
its heating roYistanco 18. The initial cooking operation
is delayed somewhat by cooIcing plate 1~l during the period
when the cooking plate 13 receives its continucd cooking
power. IIowevér, when cooking pla-tc 13 switches oIi
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shortly aIterwards, cooking plate 1~-l receives full power.
When cooking plate 12 is-switched on, cooking plate 13
and the subsequent cooking plates act accordingly. rrhe
cooking plates 12 to 15 are thereIore favoured over
5 each other in the sequence of their connection. Although
three cooking plates operate, the maximum connected
output is;not higher than for a single one. There is
still sufficient switching time available for the last
cooking plate owing to the small relative switching
10 r times
The cooking unit 11l in Figure 2 also has four
cooking plates, the cooking plates 12~ and 15t hawng
a smaller diameter and a power of 1500 W, and the remaining
cooklng plates 13l and ~ having a larger diameter and
15 a power of 1500 and 2000 W respectively. rrhe thermostats
22~ dlïfer lrom tho~e in Figure 1 only in that their
structuré is that of a simple snap switch. rrho snap
switch has a movable catch spring 37 and cons~sts of two
contact halves 20t and 21~, made of resilient material,
20 from which are bent spring tongues which arc supportod
in rigid supporting bearings 38,39 by means of which
the current is supplied. rrhe spring halves are insorted
into a central insulating block 55, upon which the
expansion box 26 acts. rrhe contacts 27,28,29,31 cooperate
25 with contacts at the end OL~ the spring halves 20~,21~.
rrhiS double cat~h spring 37 is adjusted in such a way
that the oontact half 21' switches off at a lower temperature
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114~9'73
than the current half 20~.
Current is supplied from the domestic mains by a
socket 16 via a manually activatable switch~6 which has
two contact arms which switch on the cooking plates
5 in one position, switch on a socket 57 for additional
appliances, for example a mixer, in a second position,
and separate the cooking plates from the two poles
of the domestic mains in a third position. In Figure 2,
the thermostats 22~ of the two favoured cooking plates
10 121 and 14' preferably arranged in the front portion of
the cooking unit 11' are connected to one pole of the
mains while the cooking plates 13',15' with their heating
resistances are connected to the transfer contacts 29,31
oI' their thermostats. As in Figure 1, the current
15 supply lines 38,39 to the contact arms 20',21', are
eleotrloally connected together in the case of the
Iavoured cooking plates 12t,1~l~, so that a normal double
snap switch could be usod here without elcctric insulation
between the two contact halves 20 t, 21' while although
20 t'he electric separation of the two contact arms'from
each other is important in the subsequent cooking plates
13~',15~, the transfer contacts could be dispensed with.
It is assumed in the condition illustratcd in
F~re 2 that all cooking plates are switched on. The
25 cooking plates 12',1~l~ have reached théir set temperature
range. The continued cooking power 18' is just supplied
to cooking plate 12~, while cooking platc '1ll' has
switche~d off completely Accordingly, only one heating
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element 18 is switched on in the cooking plate 13'
eonnected downstream of cooking plate 12', while both
~eating elements are switched on at cooking plate 15
because it is still heating up.
Although the cooking ~unit 11' has two completely
usable favoured cooking plates 12~,14l and the two
subsequent pIates can be used almost always completely
outside the heating up time of the favoured cooking plates,
the eonneeted load is only 3500 W, say 16 Amperes at
220 V, providing that the heating resistances 18,19
are the same. The servieeability is there~ore ino~ased
by dividing into two branches 12',131 and 14',151.
The switch 56 ensures bipolar disconneetion and
ensures that the socket 57 is only used when the cooking
plates ~re not switehed on. It eould also be connected
to the free transfer eontaets of the eooking plates 13~,
15l, nnd thus be ineluded in th~ priority eireuit.
Figure 3 show~ a eooking unit with a manual switch
56, a soeket 57 as in Figure 2 and a cooking plate 12
as well as a thermostat 22 as in Figure 1. In this
arrangement, a manual filter pulse switeh 58 is connected
to the -first transfer contact 31 used and a filter pulse
switeh 59 to the transfer eontaet 29, and these swigches
eaeh control three heating elemen1;s ol cooking plates
13a~ via switching springs activated by cams. In this
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114Q~73
embodiment, therefore, the cooking plate 13a is put
into full operation once the heating resistance 19
o~ the cooking plate 12 has been switched of~ and the
cooking plate 14a is put into operation completely once
the heating resis-tance 18 has also been switched oIf.
The maximum connected power is 2500 W, although
the combined wattage of the cooking plates is 4500 W.
Figure 4 shows a modified switching deyice 22"
whose cooking plate 12b has only one heating element 18
for the entire output. The expansion socket 26 acts on
a bimetallic member 33 which is heated by a low power
control heating resistance 3~l and is connected in parallel
to~he heating resistance 18~. This heating resistance
18~ and the control heating resistance 34 ~e controlled
by a gnap switch 35 which supplics the two heating
résistances ln its "on~ positlon as illustrated, whereas,
in the ~ofY" position, it is connected to the transfer
oontact 29~ which i8 itself' connected to the I-ed line
30~ ~ the switching device of the next cooking plate
which is completely switched on in this way.
The embodiment according to Figure ~ operates in
the following manner. The thermostat oI this embodiment
is rhythmic in operation and can be adjusted manually to
a speciIic temperature value by the adjusting knob 23~. The
bimetallic member 33 which is heated as the cooking plate
is heated producès a rhythm, i.o. successive switching on
and off of the single heating elements 18~, the relative
switching on period changing in accordance wi-th the temperature
adjustment (knob 23~) and the actual temperature on the cooking
conainer. This relativ~ switching on period will diminish
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from about 100% during the lnitial cooking phase
to about 10 to 20% during the continued cooking phase.
The-fuli power is available for the subsequent cooking
plates in the pauses i.e. during the continued cooking
phase between 80 and 90% of the time.
If the thermostat 24; 25, 26 illustrate~ in broken
lines is omitted, a step-less rhythmic power control device
is formed which supplies the subsequent cooking plate in
its disconnected periods.
Figures 5 and 6 show a cooking unit lla which is designed
as a portable unit and possess two cooking plates 12a and
13a. The cooking plate 12a is provided with a condition
controller 40 which is connected to the cooking un~t lla
via a flexible line 41 and is suitable for being placed on
a lld 42 of a cooking pot 50 which has an opening 47 for
the passage of steam,
Three superi~posed cooking pots 50 which are designed
so that they fit on to each other with the two lower cooking
pots each heating the one above it, are placed on to the
cooking plate 12a. Several different dishes can be cooked
irI different cooking containers using a single cooking plate
by means of this "tower" cooking.
The steam issuirlg out of the upper cGoking pot lid
42 shows that all cooking pots have reached the coGkir,g
temperature. The steam acts on a barometric cell 43 which
is filled with a liquid having a boiling point which is
somewhat lower than the boiling point of water. The
Issuing stea~ therefore
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causes rapid evaporation in the cell 43 so that a switch
- 44 in the condition controller 40 is activated via a
membrane, this switch being designed as a snap switch
and switching over between a contact 45 and a contact 46.
A change-over switch 48 is provided to allow the
condition controller 40 and therefore the cooking plate
12a to be switched off completely. In the illustrated
switch position of the change-over switch 48, the
electric cooking plate 12a, which has only one heating
resistance 18a, is switched on via the switch 44 and a
control switch 49 as well as a temperature protection
switch 52. The control switch 49 can be either a
simple on/off switch, a 7-time switch oP even a stepless
power control device. The temperature protection
switch protects the cooking plate and cooking pots if
the condition controller is accidentally not put on
or if food has been put on without water.
The cooking plate 13a has a switching device 22
of the type shown in Figure 1. The common line 30
from the switching device 22 is connected to the transfer
contact 46 of the condition controller 40 as well as
to a contact of the change-over switch 48. Additional
cooking plates, sockets or appliances can be connected
in series with the cooking plate 13.
The cooking unit lla operates ln the following manner.
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In order to prepare a complete meal with, for example,
-four different dishes, three dishes to be cooked are
poured into the three cooking pots 50 which are
placed on top of each other and closed with the lid
42. The cooking plate 12a is switched on via the
adjusting knob 5~ of the control switch 49 once the
cooking pots 50 have been placed on the cooking plate
12a and the condition controller 40 has been placed
on to the lid 42. The heating resistance 18' heats
the three cooking po~s with its total output until the
cooking temperature prevails in the uppermost cooking
pot 50, steam issuing through the opening 47 heats
the barometric cell 43 and switches the switch 44 from the
contact 45 over to the contact 46. The cooking plate
12a is thus switched off and the cooking plate 13a,
on which a further boiling or frying operating can be
performed is supplied via the line 30. ~fter initial
cooking, the continued cooking power is very low so
that the cooking plate 13a is ready for use over 80%
of the time. The condition controller 40 functions in
cooperation with the cooking plate 12a with a small
time lag 50 that it switches off again seconds ater
it has been switched on again. Such a short power
surge is sufficient to allow steam to be evolved again.
It is therefore actually controlled to the "cook"
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condition and not to the associated temperature which
can only be detected imprecisely. The short interuptions
of power are hardly noticeable in the cooking plate 13a.
This embodiment allows a meal with four or more different
dishes to be cooked at the same time using one two-plate
stove which has the connected load of only one cooking
plate .
The change-over switch 48 ensures that the priority
which the cooking plate 12a normally has over the
cooking plate 13a is given to the latter and therefore
that the cooking plate I2a is disconnected. It is also
possible to change only the priority. Instead of using
the condition controller 40 which is connected to the
cooking unit lla via a flexible line 41, it is a].so
possible to use a condition controller which transmits
its on and off signals to the coGking unit without the
use of wires (see German Auslegeschrift No. 2161371).
Numerous variations of the embodiments described
and illustrated are possible within the scope of the
invention. Although the cast cooking plates described
are particularly advantageous in conjunction with the
invention owing to their temperature-compensating properties,
other cooking points can also be used, for example, each
electric cooking plate can be formed by a heating unit
beneath a glass ceramic plate, or the electric cooking
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plates can be formed by tubular heating bodies.
It is also possible to connect one or more independent
cooking plates in parallel wlth the cooking plates
which are connected in cascade.
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