Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a combination micro-
wave and electric oven and~ more particula~ to a damper
activating mechanism in a combination microwave and electric
oven.
A combined microwave and electric oVen has been devel-
oped which includes a microwave generating source for microwave
cooking purposes and an electric heater for electric cooking
purposes. When cooking in the microwave mode, it is necessary
to introduce an air flow into the oven cavity for recirculation
purposes. Conversely, when cooking electrically there must be
no air flow for otherwise cooking temperatures within the oven
could not be maintained without excessive energy consumption.
Air flow is required, however, outside the oven cavity to
~rotect the microwave generator from the high temperatures
otherwise induced by the electric heater.
To enhance cooking efficien~y~ it is desirable that
the microwave cooking be performed first, followed immediately
afterwards by electric cooking.
Accordingly! an object of the present invention is to
provide a novel damper mechanism in a combination microwave and
electric oven.
Another object of the present invention is to provide
an automatic damper activating mechanism associated with a cook-
ing timer in a combination microwave and electric oven.
Other objects and further scope of applicability of the
present invention will become apparent from the detailed descrip-
tion given hereinafter. It should be understood, however, that
the detailed description and specific examples, while indicating
preferred embodiments of the inVention, are given by way of
illustration only, since various changes and modiications within
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the spirit and scope of the invention will become ~ppaxent to
those skilled in the art from this detailed descxiption.
To achieve the above objects pursuant to an embodiment
of the present invention, a blower fan system is provided for
creating a forced air flow for cooling the microwave generator.
The blower fan system is continuously energized during both
microwave and electric cookin~ operations. A damper mechanism
is provided for selectively introducing the forced air flow into
the oven cavity.
In a preferred form, a microwave control timer mechan-
ism is associated with the damper mechanism so that the damper
mechanism allows the introduction of forced air into the oven
- cavity during periods of microwave cooking but prevents that
air flow during periods of electric cooking.
According to the present invention, then, there is
provided a combination microwave and electric oven comprising:
' an oven wall defining an oven cavity therein; microwave generat-
ing means disposed externally of the oven cavity for microwave
cooking operations;electric heater means for electric cooking
;20~ ; operations; blower means for creating a forced air flow for
cooling the microwave generating means; air flow guide means
for directing the forced air flow toward the oven cavity7
'~ damper means disposed in the air flow guide means, the damper
means being selectively actuatable between a first position
wherein the forced air flow is introduced into the oven cavity
and a second position wherein the forced air flow is not intro-
duced into the oven cavity; first timer means for selecting a
; period of microwave cooking whereby the microwave generating
; means are energized; and drive means associated with the first
timer means for actuating the damper means, whexeby the damper
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means are placed in the first position when the microwave
generating means are energized.
According to a further aspect of the present invention
there is also provided a combination microwave and electric oven
comprising an oven wall defining an oven cavity therein, micro-
wave generatingmeans disposed externally of the oven cavity for
microwave cooking operations, electric heater means for performing
electric cooking operations, blower means for creating a forced
air flow for cooling the microwave generating means, air flow
guide means for directing the forced air flow toward the oven
cavity, damper means disposed in the air flow guide means, the
damper means being selectively actuatable between a first position
wherein the forced air flow is introduced into the oven cavity
and a second position wherein the forced air flow is not intro-
duced into the oven cavity, timer means for selecting a first
time period during which the microwave generating means are
energized, and a second time period during which the electric
heater means are energized, first drive means associated with
the timer means for energizing the blower means during the first
2:0 and second time periods, and second drive means associated with
the timer means for actuating the damper means into the first
position during the first time period.
: According to yet another aspect of the present invention,
there is provided a combined microwave and electric heating
oven comprising an oven wall defining an oven cavity therein,
microwave generating means disposed at the outside of the oven
cavity for introducing microwave energy into the oven cavity
for performing a microwave cooking operation, electric heater
means disposed in the oven cavity for performing an electric
: 30 heating cooking operation, blower fan means operatively
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associated with the microwave generating means for creating a
forced air flow for cooling the microwave generating means, air
flow c3uide means communicating with the oven cavity and a zone
surrounding the oven cavity, the air flow guide means directing
the forced air flow toward the oven cavity and the zone
surrounding the oven cavity, damper means disposed in the air
flow guide means, the damper means being adapted to
selectively channel the forced air flow to either the oven cavity
or the zone surrounding the oven cavity, and time period
determination means operatively associated with the damper means
for automatically changing the position of the damper means within
the air flow guide means depending on the type of cooking cycle
which is being energized.
Embodiments of the present invention will now be
described in greater detail and will be better understood when
read in conjunction with the following drawings in which:
Figure 1 is a front elevational view of an embodiment
of a combination microwave and electric oven as described herein;
Figure 2 is a perspective view of the combination
microwave and electric oven of Figure 1, wherein an outer casing
is removed;
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Figure 3 is a frontal view of an embodiment of a
damper mechanism included in the combination oven of Figure l;
Figure 4 is a schematic circuit diagram of the combina-
tion microwave and electric oven of Figure l; and
Figure 5 is a perspective view of another embodiment
of the damper mechanism included in the combination microwave
and electric oven of Figure 1.
Figures 1 and 2 schematically illustrate an embodiment
of a combination microwave and electric oven.
The combination oven comprises generally a casing 10
and an oven wall 12 defining an oven cavity. A tray 14 is remov-
ably disposed at the bottom of the oven cavity for supporting a
foodstuff to be cooked, and an electric heater 16 is disposed at
an upper section of the oven cavity for performing the electric
cooking operations. The combined microwave and electric oven
further comprises a control panel 18 upon which a first timer 20,
a second timer 22 and a cook start switch 24 are provided.
Timers 20 and 22 are used to select electric and microwave cook-
ing periods, respectively.
A magnetron 26 is secured to side wall 12 of the oven
cavity. The microwave energy generated by the magnetron 26 is
introduced into the oven cavity via a waveguide 28, A blower
fan 30 is provided for drawing fresh air through air inlet open-
ings 32 and developing a forced air flow. The forced air flow
is directed to magnetron 26 for cooling purposes and is also
selectively introduced into the oven cavity via a damper mechanism
34 and an air duct 36. Damper mechanism 34 is associated with
second timer 22 so that the forced air flow is introduced into
the oven cavity only when the oven is in the microwave cooking
mode.
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Air duct 36 includes one inlet 36~ $oX ~eceiving
the forced air flow (X~, and two outlets 362 and 364 for select-
ively developing forced air flows (Y) and (Z).
Referring now to Figure 3, there is shown the relation-
ship between second ti~er 22 and the damper mechanism 34. Like
elements corresponding to those of Figure 2 are indicated by
like numerals.
Damper mechanism 34 includes a damper plate 38 disposed
in air duct 36. The damper plate 38 is rotatably secured to a
shaft 40 and is biased by a spring 42 to normally rest at the
position indicated by solid lines in Figure 3. Accordingly,
forced air flow (X) introduced normally through inlet 360 is
directed to outlet 362 to create forced air flow (Y). Forced
air flow (Y) is passed through a gap formed between the casing
10 and the oven wall 12, and is exhausted through openings 44
formed in the rear wall of casing 10 (see Figure 2). Accordingly,
the air flow (Y) is not normally introduced into the oven cavity.
When timer 22 is rotated to the desired setting through
the use of a timer knob 46, a cam 48 fixed to a timer shaft 50
-is rotated in the clockwise direction, thereby depressing a
~; roller 52 downwardly. Roller 52 is integrally fixed to a roller
lever 54 which is rotatably supported by a sha~t 56. Accordingly,
when second timer 22 is rotated to the desired setting corres-
ponding to a desired microwave cooking period, roller lever 54
is pivoted into the position shown by the broken lines in
Figure 3. Damper plate 38 is thusly pivoted into the position
shown by the broken lines in Figure 3 due to the action of rod
58 and forced air flow (X~ introduced through the inlet 360 is
directed to outlet 364 ko create forced air ~low (Z).
Forced air flow (Z) is introduced into the oven cavity
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for recirculation purposes, The ai~ is then exhausted from the
cavity via exhaust openings 60 formed into an upper portion of
oven wall 12, an exhaust duct 62 secured to oven wall 12, and
exhaust openings 64 formed in the rear wall of casing 10 (see
Figure 2). Accordingly, forced air flow ~Z~ is introduced
into the oven cavity only when microwave cooking operations are
being performed. When microwave cooking is completed following
the lapse of the time period selected by second timer 22, damper
plate 38 is returned to its normal position by spring 42, thereby
preventing any further flow of forced air into the oven cavity.
Referring now to Figure 4, there is schematically
illustrated the circuitr~ of the combination oven referred to
herein. Like elements corresponding to those of Figures 1 and 2
are indicated by like numerals.
A latch switch 66 is associated with the o~en door
such that a movable contact of the switch is connected to a
first terminal 660 when the oven door is opened and to a second
~ termlnal 662 when the oven door is closed. A safety switch 68
; ~ is also associated with the oven door to be closed when the oven
door is closed. ~imer switches 70 and 72 are associated with the
second timer 22 in such a manner that movable contacts thereof
are connected to first terminals 700 and 720, respectively, when
second timer 22 is rotated or wound up. Another timer switch 74
is associated with the first timer 20 so that timer switch 74 is
closed when first timer 20 is wound up. First timer 20 includes
a timer motor 200 for controlling the electric cooking time period
whereby timer switch 74 is opened when the preselected cooking
$ime period has been counted by timer motor 200. The second timer
22 includes another timer motor 220 for controlling the microwave
cooking time period, whereby the movable contacts of timer
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switches 70 and 72 are connected to second terminals 702 and 722,
respectively, when the preselected time period has been counted
by timer motor 220. Figure 4 illustrates the initial condition
wherein neither first timer 20 nor second timer 22 have been
wound up.
The control circuit of Figure 4 further comprises a
transformer 76 for supplying power to magnetron 26, and a
blower motor 300 for activating blower fan 30.
For the purposes of illustration, it will be assumed
that a roast beef is to be prepared. As mentioned previously,
it is preferable that microwave cooking be performed first, to
be followed therafter by electric cooking. Second timer 22 is
rotated to select a desired microwave cooking period and first
timer 20 is then rotated to select a desired electric cooking
period. After placing the meat within the oven cavity, the oven
door is tightly closed to connect the movable contact of latch
switch 66 to second terminal 662, and toclose safety switch 68.
Cook start switch 24 is then closed, and transformer 76 and
timer motor 220 receive power through the first terminal 700 of
~20 timer switch 70. Blower motor 300 is activated through the first
terminal 720 of timer switch 72. Accordingly, microwave cooking
is performed firstly.
While microwave cooking is being per~ormed, damper
plate 38 is positioned as shown by the broken line in Figure 3,
such that forced air flow tZ) is introduced into the oven cavity
for recirculation purposes.
After microwave cooking has been conducted for the
predetermined period of time selected b~ second timer 22, the
movable contacts of timer switches 70 and 72 are connected to
second terminals 702 and 722, respectively, to terminate micro-
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wave generation. At the same time, dampex plate 38 is returned
to its normal position by spring 42 thereby preventing the
introduction of forced air into the oven cavity.
~pon completion of the microwave cooking operations,
electric heater 16 and timer motor 200 receive power through
the second terminal 702 of timer switch 70 and timer switch 74.
Blower motor 300 is activated through the second terminal 722
of timer switch 72. Accordingly, electric cooking operations !
are started automatically immediately upon completion of micro-
wave cooking operations. It will be clear that while electric
cooking operations are being conducted, forced air is not intro-
duced into the oven cavity. However, the area between oven
cavity 12 and casing 10 is cooled by forced air flows (X) and (Y).
When the electric cooking has been conducted for the
period of time selected by first timer 20, timer switch 74 is
switched off to complete the series of cooking operations.
Figure 5 illustrates another example of the damper
; ~ mechanism. Like elements corresponding to those of Figure 3 are
indicated by like numerals.
20 ~ The damper plate 38 is disposed in the air duct 36 and
is rotatably supported by a shaft 80. A damper lever 82 is
secured to one end o~ the shaft 80 whereby the damper plate 38
rotates in unison with damper lever 82. Damper lever 82 is
associated with a roller arm 84 through a communication rod 86.
When second timer 22 is rotated, communication rod 86 is pulled
in the direction shown by the arrow in Figure 5 in response to
the rotation of cam 48. Accordingly, damper plate 38 is urged
into the position shown by the solid lines in Figure 5 to allow
the introduction of forced air (Z) into the oven cavity. A
spring 88 biases damper plate 38 towards the normal position
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shown by the broken lines in Figuxe 5, whereby the flow of
forced air into the oven cavity is prevented during electric
cooking operations.
Where it is desired to $irst perform electric cooking
and then the microwave cooking, the control circuit of Figure 4
may be modified to assign a priority to the electric cooking
operations. Accordingly the damper mechanism may be actuated
by rotation of the timer used to select electric cooking time
periods 60 that it is norma]ly open during periods of microwave
cooking. Upon actuation of the electric timer, then, the damper
is closed to prevent the circulation of air in the oven cavity
during periods of electric cooking.
Although in the foregoing embodiments a mechanical
timer has been described, the present invention can be applied
to a combination oven including a digital timer system. A
plunger mechanism may be associated with the damper mechanism
to be activated during microwave cooking operations to open
the damper mechanism to the oven cavity to allow for the circu-
lation of forced air therein.
~he invention being thus described, it will be obvious
that the same may be varied in many ways. Such variations are
not to be regarded as a departure ~rom the spirit and scope o~
i the invention, and all such modifications are intended to be
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included within the scope of the following claims.
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