Note: Descriptions are shown in the official language in which they were submitted.
CA 02321652 2004-11-18
09RG19385
COMBINATION OVEN WITH MANUAL ENTRY
OF CONTROL ALGORITHMS
BACKGROUND OF THE INVENTION
This invention relates generally to ovens and, more particularly, to a
control system for a combination oven using both radiant and microwave energy.
Known ovens are either, for example, microwave or radiant cooking
type ovens. For example, a microwave oven includes a magnetron for generating
RF
energy used to cook food in the oven cooking cavity. Although microwave ovens
cook food more quickly than radiant ovens, microwave ovens do not brown the
food.
Microwave ovens therefore typically are not used to cook as wide a variety of
foods
as radiant ovens.
Radiant cooking ovens include an energy source such as lamps which
generate light energy used to cook the food. Radiant ovens brown the food and
generally can be used to cook a wide variety of foods. Radiant ovens, however,
cook
foods slower than microwave ovens.
Microwave and radiant cooking ovens typically include an array of
keypads mounted to a control panel for enabling an operator to enter and
select the
feature options, and a numerical key pad numbered 0-9. The complexity of the
control panel and the number of keypads mounted to the control panel increases
as
the appliance functionality and features increase. Such control panels are
often
complex for users to understand, offer little flexibility to the users, and do
not
provide users with an opportunity to adjust or review in-progress cooking
without
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terminating the cooking. The complexity and inflexibility of such control
systems
increases a likelihood that the food will be cooked correctly.
Accordingly, it would be desirable to provide a user friendly, flexible,
and easily controlled oven which provides the speed advantages of a microwave
oven
with the appealing browning advantage of a radiant ovens to cook a wide
variety of
foods.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention a speed cooking oven
includes a microwave cooking unit for delivering microwave energy and at least
one
radiant cooking unit for delivering radiant energy into a cooking cavity. A
control
panel is operatively connected to the microwave cooking unit and radiant
cooking
unit for user manipulation to select desired oven features including pre-
programmed
cooking algorithms and manually entered cooking algorithms. A microprocessor
is
coupled to the control panel for executing a manually entered control
algorithm based
upon at least one of a user selected total COOK TIME and user selected POWER
LEVEL for the microwave cooking unit and the radiant cooking unit.
The control panel includes a plurality of input keys and a rotary dial
input selector for easy selection of desired features by rotating the dial and
depressing
the dial to enter a selection. An alphanumeric display is provided to prompt a
user for
control information and guide the user through the oven feature selection
process.
The oven is operable in a microwave only cooking mode, a lightwave only
cooking
mode and a speed cooking mode utilizing both radiant cooking units and
microwave
cooking units. Thus, a variety of foods may be quickly cooked and browned in
the
oven, and a flexible and straightforward cooking mode and control selection
process
is provided with the user friendly control panel.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a front view of a combination oven including a control
system;
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Figure 2 is a front view of the control system shown in Figure 1;
Figure 3 is a perspective schematic view of a portion of the oven
shown in Figure 1;
Figure 4 is a schematic illustration of the radiant cooking unit and the
microwave cooking unit relative to the cooking cavity;
Figure 5 is a schematic illustration of the lower lamp of the oven
shown in Figure 3;
Figure 6 is a schematic illustration of the reflector for the upper lamps
of the oven shown in Figure 3;
Figure 7 is -an illustration of a portion of the turntable of the oven
shown in Figure 3;
Figure 8 is a schematic illustration of the cooking cavity of the oven
shown in Figure 3, including a damper to control air flow;
Figure 9 is a functional block diagram of the oven shown in Figure 1;
Figure 10 is a circuit schematic diagram of the oven shown in Figure
1;
Figure.11 is a timing diagram illustrating, target and command times
for energizing the cooking elements;
Figures 12-15 illustrate messages displayed when adjusting/entering
the power level and cooking time;
Figure 16 is a flow chart illustrating process steps executed when
adjusting the cook time;
Figure 17 is a flow chart illustrating process steps for lamp power level
control; and
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Figure 18 is a flow chart illustrating process steps for the soft start of
the Halogen lamps.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed, in one aspect, to operation of an
oven that includes at least two types of cooking elements, such as radiant and
microwave cooking elements. Although one specific embodiment of
radiant/microwave cooking oven is described below, it should be understood
that the
present invention can be utilized in combination with many other such ovens
and is
not limited to practice with the oven described herein.
Figure 1 is a front view of an oven 10 including a control system 12.
Oven 10 includes a body.14 which is constructed of a top 16, a bottom 18 which
is
connected to top 16 with a first side 20, a second side 22, and a rear side
(not shown).
Body 14 houses a cooking cavity (not shown) for receiving food (not shown)
during
cooking. A door 26 is hingedly attached to a front face 28 of body 14 and is
pivotable
to selectively open and close with a handle 29 to access the cooking cavity.
Door 26
includes a window 30 fabricated from dark tinted glass having a thickness of
about
1/8 inches which can withstand high temperatures, as is known in the art.
Window 30
permits a user to visually inspect the cooking cavity during cooking without
exposing
the user to intense light generated while oven 10 is operated. Oven 10 also
includes
an extruded vent gri1132.
Control system 12 includes a control panel 40 for selecting control
information (not shown in Figure 1) and a control interface 44 for providing
visual
information about the cooking to a user. Control panel 40 includes a touch
control
area 46, described in more detail below, which provides the user with many
feature
options available during cooking. Control panel 40 also includes a rotary dial
48
configured to permit a user to select control information for cooking. Control
panel
40 is operatively responsive to any selection of control information the user
inputs
using touch control area 46 and rotary dial 48.
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Figure 2 is a front view of control system 12 including control panel
40 and control interface 44. Control interface 44 is mounted to control panel
40 and
includes alphanumeric display 50. Alphanumeric display 50 displays the current
time
of day when oven 10 is not in operation. Additionally, during entry of control
inputs
by the user, alphanumeric display 50 provides visual prompts that guide the
user
through a selection process to select available options. In one embodiment,
alphanumeric display 50 is a vacuum fluorescent display or LED type of display
which displays multiple lines.
Control panel 40 includes touch control area 46 and rotary dia148. A
user may select control inputs using touch control area 46, rotary dial 48, or
a
combination of rotary dial 48 and touch control area 46. Touch control area 46
includes a face surface 52 which includes a plurality of keys 54 (described in
more
detail below) which extend from face surface 52 and are configured to permit a
user
to enter control inputs and activate feature options. Rotary dial 48 is
rotationally
attached to oven 10 and extends through an opening 56 in surface face 52. Each
key
54 is connected to a control (not shown) which includes a microprocessor (not
shown)
or other electronic elements for executing user selected feature options.
Keys 54 provide a user with oven feature options and various cooking
functions and.are electrically operable when depressed by a user applying a
minimal
amount of pressure. More specifically, keys 54 include a COOK touch control
pad
60, a START/PAUSE touch control pad 62, a MANUAL COOK touch control pad
64, a CLEAR/OFF touch control pad 66, a POWER LEVEL touch control pad 68, a
DELAY START touch control pad 70, a TIMER touch control pad 72, a
MICROWAVE touch control pad 74, a MICRO EXPRESS touch control pad 76, a
VENT FAN touch control pad 78, a REMINDER touch control pad 80, an OPTIONS
touch control pad 82, a HELP touch control pad 84, and a SURFACE LIGHT touch
control pad 86.
Rotary dial 48 interacts with several of keys 54 and is connected to a
control (not shown) which includes a microprocessor (not shown) or other
electronic
elements for executing user selected oven tcatures. Rotary dial 48 is also
connected
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to a select switch (not shown) which is operatively engaged when the user
applies a
moderate pressure to depress rotary dial 48 into opening 56.
Rotary dia148 is configured to be rotated in a clockwise direction 94
or in a counter-clockwise direction 96. Rotation in clockwise direction 94
increments
a numerical selection value (not shown) and scrolls non-numerical selections
in
ascending alphabetical order. Rotation in counter-clockwise direction 96
decrements
the numerical selection value and scrolls non-numerical selections in reverse-
alphabetical order. Rotary dial 48 is configured to provide tactile feedback
to a user
simultaneously as rotary dial 48 is rotated. The tactile feedback allows the
user to
t0 determine an amount of rotation (not shown). In one embodiment, the tactile
feedback has a resolution of approximately 15-25 counts per revolution. As
such,
when rotary dial 48 is rptated, the user will feel approximately 15-25
"stopping
points" and thus, will sense an amount of rotation of rotary dia148.
Oven features may be selected using touch control area 46, rotary dial
48, or a combination of rotary dial 48 and touch control area 46. In
operation,
plurality of keys 54 are configured to function in cooperation with rotary
dial 48.
Initially, a mode of oven 10 is selected from a lightwave only mode, a
microwave
only mode, and a speed cooking mode. Depressing touch control pad 60 results
in the
processor causing control interface 44 to visually prompt the user with
alphanumeric
display 50 for selections for the lightwave mode of oven 10. Depressing
microwave
touch control pad 74 results in the .processor causing control interface 44 to
visually
prompt the user with alphanumeric display 50 for selections for the microwave
mode
of oven 10. Additionally, depressing microwave touch control pad 74 energizes
a
cooking lamp (not shown) to briefly illuminate the food being cooked.
Depressing COOK touch control pad 60 and rotating rotary dial 48
results in alphanumeric display 50 displaying pre-programmed control
information
including a listing of food types commonly cooked with a lightwave mode of
oven
10.
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Depressing MANUAL COOK touch control pad 64 and rotating rotary
dial 48 permits the user to manually input control information before the
cooking of
the food is started, including the length of time for cooking and the power
levels to be
applied by oven 10. Additionally, depressing MANUAL COOK touch control pad 64
and then rotating rotary dial 48 permits the user to select combinations of
non-
preprogrammed cooking information.
Keys 54 also provide additional options and features to the user.
Depressing POWER LEVEL touch control pad 68 enables the user to alter any pre-
programmed suggested power levels. Depressing DELAY START touch control pad
70 permits the user to select a time of day for cooking to begin. Depressing
TIMER
touch control pad 72 permits the user to program the processor to control a
timer.
After an amount of time programmed into the timer has elapsed, the audible
alarm
sounds to indicate that the amount of time has elapsed.
Rubber tactile switch covers are located over each key pad of control
panel 40, and dial 48 is provided for making multiple selections. Selections
are made
using dial 48 by rotating dial 48 clockwise or counter-clockwise and when the
desired
selection is displayed, pressing dial 48. The various selections available, in
an
exemplary embodiment, from dia148 are set forth in Appendix A. Instructions
and
selections are displayed on alphanumeric display 50.
The following functions can be selected by user manipulation of
control panel 40.
CLEAR/OFF Selecting this pad stops all cooking and erases
the current program.
DELAYED Selecting this pad results in a delay in the start
.25 START of cooking.
HELP Selecting this pad enables an operator to find out
more about the oven and its features.
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MICROWAVE Selecting this pad enables defrosting, heating
beverages, reheating leftovers, popcorn,
vegetables, and all types of microwave cooking.
MICROWAVE Selecting this pad enables quick and easy
EXPRESS warming of a sandwich, or reheat of coffee.
OPTIONS Selecting this pad enables access to the auto
ON/OFF night light, beeper volume control, clock, clock
display, and display scroll speed features.
OVEN LIGHT Selecting this pad during microwave cooking
illuminates the cavity.
POWER LEVEL Selecting this pad enables adjusting the power
levels for speed cooking and microwave
cooking.
REMINDER Selecting this pad enables an operator to select a
time at which an alarm is to sound.
REPEAT LAST Selecting this pad facilitates cooking repetitive
items such as cookies and appetizers.
SPEED COOK Selecting this pad enables an operator to
MANUAL manually enter speed cooking time and power
levels.
START/PAUSE Selecting this pad enables an operator to start or
pause cooking.
SURFACE LIGHT Selecting this pad turns ON/OFF the surface
light for the cooktop.
TIMER ON/OFF Selecting this pad controls a general purpose
timer (e.g., minutes and seconds)
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VENT FAN Selecting this pad enables an operator to clear
the cooktop area of smoke or steam.
Figure 3 is a perspective schematic view of a portion of oven 10. Oven
includes a shell 120, and a cooking cavity 122 is located within shell 120.
Cooking
5 cavity 122 is constructed using high reflectivity (e.g., 72% reflectivity)
stainless steel.
Halogen lamps 124 and 126, and a reflective plate 128 are mounted to an upper
panel
130 of shell 120. As described below in more detail, a halogen lamp also is
located at
a lower section of shell 120. An exhaust system 132 also is mounted to shell
120.
Air flows through cavity 122 in a direction indicated by arrow 134. A cooling
system
10 137 is mounted to shell 120 for cooling oven components. Exemplary
dimensions of
oven 10 are set forth below.
Shell '
Exterior Height (front) 15 11/16"
Exterior Height (rear) 16 %z'
Exterior Width 29 4/5"
Exterior Depth 14 4/5"
Cooking Cavity
Cavity Height 8 2/5"
Cavity Width 19 2/7"
Cavity Depth 13 3/5"
Figure 4 is a schematic illustration of oven 10, and particularly of
halogen lamp cooking units 150 and 152 and microwave cooking unit 154 relative
to
cooking cavity 122. As shown in Figure 3, upper cooking unit 150 includes two
halogen lamps 124 and 126 and cooking unit 152 includes one halogen lamp 156.
Lamps 124, 126, and 156, in an exemplary embodiment, are 1500 W halogen lamps
having a color temperature of 2300K, output power of 4.5 kW with 7% in the
light
wave range of 0.4 um to 0.7 um, 20% to 25% in the light wave range less than
1.0
um, and 36% in the light wave range of 0.4 um to 1.35 um. Lamp 124 is referred
to
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as the upper center lamp, and lamp 126 is referred to as the upper exterior
lamp.
Lamp 156 is referred to as the lower lamp. Glass plates 158 and 160 extend
over
cooking units 150 and 152 between lamps 124, 126, and 156 and cavity 122.
Also,
twist mesh screens 162 and 164 having an opening ratio of 80% are provided for
additional protection. Additional details are provided below with respect to
reflector
128. A magnetron 166 of microwave cooking unit 154 is located on a side of
cavity
122. Magnetron 166, in an exemplary embodiment, is rated at 1000 W and
delivers
950 W into cavity 122.
With, respect to lower lamp 156, and referring to Figure 5, lamp 156 is
lo located off center and at an angle relative to a bottom su.rface 172 of
cavity 122. Such
location of lower lamp 156 results, for example, in lowering the temperature
of the
rollers on turntable 136.
Figure 6 is a schematic side illustration of reflector 128. Reflector 128
includes angular side sections 180 and 182 and angular center sections 184 and
186.
The dimensions (in millimeters) indicated in Figure 5 are exemplary and have
been
found suitable for at least one oven. By selecting the reflector dimensions as
indicated in Figure 5, upper lamps 124 and 126 are believed to provide more
even
cooking of items located on ttuntable 136.
Figure 7 illustrates a portion of turntable 136. Turntable 136 has an
open grille construction with a 70% energy transmission. Turntable 136 rotates
at
about 6 r.p.m. and has a diameter of about 11 1/8". Turntable 136 includes
metal
segments 190 with ceramic rollers 192, one of which is illustrated within
circle 194.
Figure 8 illustrates a damper 194 located below microwave cooking
unit 154. Damper 194 is open when in the microwave only mode to enable air to
flow
through cavity 122. In the speed cooking and radiant only mode, damper 194
closes
to prevent air from flowing in a reverse direction and back towards microwave
cooking unit 154.
Figure 9 is a functional block diagram of oven 10. As shown in Figure
8, oven 10 includes a mounting system 200. a structural system 202, a control
system
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204, an electrical system 206, RF generation 208, a component cooling system
210,
halogen lamps 212, and a food containment system 214. Various features of each
system are indicated in Figure 8. Mounting system 200 is provided to enable
mounting oven over the range. Mounting system 200 also provides connection
with
an exhaust to enable removal of fumes from over the cooktop into the exhaust.
Structural system 202 generally refers to shell 120, which provides an
enclosure.
Control system 204 includes an interface, i.e., keypads 112 and dial 48, and
also
distributes power to the other oven systems. Electrical system 206 powers the
control
and safety devices. RF generation 208 is performed by magnetron 166, and RF
energy output by magnetron 166 is selectively used to cook food in food
contaiament
system. Component cooling system 210 is provided to cool the other system and
to
remove moisture from cavity 122. Halogen lamps 212 generate light energy used
for
cooking food in food containment system 214.
Figure 10 is a schematic diagram of oven 10. Power is provided to
oven 10 via lines Li, L2, and N. Relays R1 - R13 are connected to a
microprocessor
or microcomputer which is programmed to control the opening and closing
thereof.
Lower lamp 156 is electrically connected to line L 1 via a thermal cut off
300.
Energization of lower lamp 156 is controlled by relays R1 and R2. A triac is
in series
with relay Ri to provide a soft start, as described below in more detail.
Upper lamps
126 and 124 are connected to line L2 via thermal cut offs 304 and 306. Triacs
308
and 310 are in series with relay R4.
Relays Rl and R4 are air gap type relays, and are in series with triacs
302 and 308, respectively. Relays RI and R4 are closed in the soft start
operation of
respective lamps 124, 126, and 156 to enable energization of triacs 302 and
308. After
completion of the soft start, relays Ri and R4 are open. Relays R2, R3, and R6
are
controlled by the micro computer to close after the soft start is completed to
maintain
energization of lamps 124, 126, and 156 based on the particular power setting.
Oven 10 also includes an upper blower motor 312 and a lower blower
motor 314 for cooling. A rectifier circuit 316 is provided for rectifying an
AC input
signal to a DC output signal to be supplied to a solenoid 317. Solenoid 317,
when
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energized, closes damper 194. Thermal cut outs 318 and 320 and a fuse 322 also
are
provided to protect oven components, e.g., from overheating or an overcurrent
condition. Cooktop lamps 324 are electrically connected in series with a triac
326
and are provided for illuminating the cooktop. Rectifier circuit 316 and
solenoid 317
may be replaced with a small synchronous motor.
A vent motor 328 having low, slow, and high speeds selectable via
relays R7, R8, and R9 is provided for removing fumes from over the cooktop. An
oven lamp 330, a fan motor 332, and a turn table motor 334 are controlled by
separate
relays R10, R11, and R12. A primary interlock switch 336 is located in door
102 and
prevents energization of cooking elements unless door 102 is closed. A relay
R13
controls energization of microwave cooking unit 154. Microwave cooking unit
154
includes a high voltage transformer 338 which steps up the supply voltage from
120V
to 2000V. A high voltage capacitor 340 and a high voltage diode 342 circuit
steps up
the voltage from transformer 338 from 2000V to 4000V. This high voltage is
supplied to magnetron 166 and the output of magnetron 166 is supplied to a
waveguide 344 which directs RF energy into cooking cavity 122. As also shown
in
Figure 9, oven 10 includes a door sensing switch 346 for sensing whether door
102 is
opened, a humidity sensor 348 for sensing the humidity in cooking cavity 122,
a
thermistor 350, and a base thermostat 352.
With respect to speed cooking operation of oven 10, the
microcomputer controls relays Ri - R6 and R13 based on the power level either
associated with the preprogrammed cooking program or manually entered. In the
speed cooking mode, for example, if a power level 9 is selected, the upper
exterior
lamp 124 has a target on-time of 29 seconds of a 32 second duty cycle, upper
center
lamp 126 has a target on-time of 25 seconds of a 32 second duty cycle, lower
lamp
156 has a target on-time of 29 seconds of a 32 second duty cycle, and
magnetron 16
has a target on-time of 29 seconds of a 32 second duty cycle. A duty cycle of
32
seconds is selected for one particular implementation. However, other duty
cycles
could be utilized. Set forth below is a chart which sets forth the target on-
times based
on power level.
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Upper Upper
Exterior Center Lower
Power Level j.a= LA= LA= Magnetron
0 0 0 0 0
1 3 3 3 3
2 6 5 6 6
3 10 8 10 10
4 13 11 13 13
5 16 14 16 16
6 19 16 19 19
7 22 19 22 22
8 26 22 26 26
9 29 25 29 29
10 32 27 32 32
To increase lamp reliability, a soft start operation is used when
energizing lamps 124, 126, and 156. Particularly, in accordance with the soft
start
operation, triacs 302, 308, and 310 are utilized to delay lamp turn-on. For
example,
upper exterior lamp 126 and lower lamp 156 are delayed for one second from
commanded turn-on to actual turn-on. Upper center lamp 124 is delayed for two
seconds from commanded turn-on to actual turn-on. Therefore, the target turn-
on
times are different from the commanded on-times. Set forth below is a table
containing the commanded on-times based on power level selected.
Upper Upper
Exterior Center Lower
Power Level jmp j= LAmR MaeIletrou
0 0 0 0 0
1 4 5 4 3
2 7 7 7 6
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3 11 10 11 10
4 14 13 14 13
17 16 17 16
6 20 18 20 19
5 7 23 21 23 22
8 27 24 27 26
9 30 27 30 29
32 29 32 32
For example, if upper lamps 124 and 126 are to operate at power level
10 7, then upper lamp 124 would be commanded to operate for 21 seconds and
upper
exterior lamp 126 would be commanded to operate for 23 seconds. Lamps 124 and
126 would be commanded to turn-on for 21 and 23 seconds, respectively, at the
beginning of each 32 second duty cycle. Due to the soft-start delays, lamps
124 and
126 would actually be on for 19 seconds (lamp 124) and 22 seconds (lamp 126)
of
each 32 second duty cycle.
Figure 11 is a timing diagram illustrating the state of lamps 124, 126,
and 156, and magnetron 166. In the example, refrigerated crescent rolls are to
be
cooked in accordance with the following:
Total Time: 4:30
Upper Power Level: 10
Lower Power Level: 3
Microwave Power Level: 3
As shown in Figure 11, upper center lamp 124 is commanded on
(dashed line) two seconds before it actually turns on (solid line). Lamp 124
is on for
27 seconds of each 32 second period. Upper exterior lamp 126 is always on
during
this period. Lower Lamp 156 is on one second after it is commanded to tum on,
and
is on for 10 seconds out of each 32 second period. Magnetron 166 has no delay
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between command and execution of on time, and is on for 10 seconds of each 32
second period.
An operator may enter control information, including a selected total
cooking time and power levels for desired cooking units, as well as adjusting
the
cooking time and power level of the upper lamps, the lower lamp, and the
microwave
during operation. For manual entry of parameters to a control algorithm,
MANUAL
COOK control pad 64 is depressed and "Select COOK TIME" is displayed on
alphanumeric display 50. By rotating rotary dial 48 to increment or decrement
the
displayed cooking time, a COOK TIME may be selected and rotary dia148
depressed
to enter the selected COOK TIME. Once COOK TIME is entered, a message "Select
UPPER POWER" is displayed as shown in Figure 11. Rotation of dial 48 then
enables an operator to select the upper power level (clockwise rotation
increases the
power level and counter clockwise rotation decreases the power level). When
dial 48
is pressed to enter the selection, a short beep sounds and "Select LOWER
POWER" is
displayed as shown in Figure 13. Dial rotation then alters the current lower
power
level, and when dial 48 is pressed to enter the selection, a short beep is
sounded.
Then, "Select MICRO POWER" is displayed as shown in Figure 14. Dial rotation
now alters the microwave power level. When dia148 is pressed to enter the
selection,
a short beep is sounded and the OVEN icon flashes and the SELECT icon is
turned
off. "ADJUST TIME or START" is then displayed as shown in Figure 15. The time
may be adjusted or the START pad pressed.
A user may depress control panel POWER LEVEL pad 68 to adjust
power levels of desired cooking units during operation of oven 10. When the
power
level pad is pressed at an acceptable time during lightwave cooking, i.e., one
or more
of -the lamps are energized, the cooking countdown continues and the UPL
(Figure
11), LPL (Figure 12) and MPL (Figure 13) displays appear. The same operation
as
described above is utilized except that after entering the new microwave power
level,
2 short beeps are sounded and the countdown and UPL, LPL and MPL display
continue for 2.0 seconds. After 2.0 seconds, the UPL, LPL and MPL displays are
removed and only the cooking countdown continues. If the power level pad is
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pressed when it is not allowed to change/enter or recall the power level, a
beep signal
(0.5 seconds at 1000 hz) sounds and the message "POWER LEVEL MAY NOT BE
CHANGED AT THIS TIME" scrolls on alphanumeric display 50. After the scroll
has completed, the previous foreground features return. If the power level pad
is
pressed at a time when a change/entry is allowed, but no dial rotation or
entry occurs
within 15 seconds, the UPL, LPL and MPL display are removed and alphanumeric
display 50 returns to the cooking countdown.
Figure 16 is a flow chart 400 illustrating process steps executed when
adjusting the cook, time during cooking operations. During cooking operations,
a
main cooking routine COOK is executed. If dial 48 is not moved 404, the main
cooking routine continues to be executed 406. If dial 48 is moved 404, then
the
microcomputer determines whether a time change can be made, e.g., is the time
remaining within the change limits 408. For example, if only 15 seconds remain
in a
cooking operation, no time change may be allowed to prevent an operator from
shutting down a cooking operation by rotating dial 48 until zero is displayed,
sometimes referred to as a "hard shutdown", which may not be desirable. If the
remaining time is not within the change limits, then the main cooking routine
continues to be executed 406. If the remaining time is within the change
limits, then
the micro computer detennines whether dial 48 was moved clockwise 410. If no
(i.e.,
dial 48 was moved counterclockwise), then for each increment that dial 48 is
moved,
the cook time is decremented by one second 412. If yes, then for each
increment that
dial 48 is moved, the cook time is incremented by one second 414.
Figure 17 is a flow chart illustrating process steps 450 for lamp power
level control. Such control is used to control energization of lamps 124, 126,
and 156
(Figure 9). More particularly, a main cooking routine 452 is executed during
normal
cooking operations. A power counter is incremented 454 for each one second
interval, and the microcomputer then checks whether a power cycle is complete
456.
For example, and as explained above, each duty cycle has a duration of 32
seconds.
If the duty cycle is complete, then the power counter is reset 458. If the
duty cycle is
not complete, or after resetting the counter, then the micro computer checks
whether
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the power count is greater than the "on time" 460. The "on time" is equal to
the time
corresponding to the selected power level for each lamp, as explained above.
If the
power count is greater than the "on time", then the particular lamp is de-
energized
462 and cooking continues with the main cooking routine 464. If the power
count is
less than or equal to the "on time", then the micro computer checks whether
the lamp
is already on 466. If yes, then cooking operations continue 464. If no, then
the micro
computer checks whether the soft start has been completed 468. If the soft
start has
been completed, then operations continue with the cooking routine 464. If soft
start
operations are not complete, then the soft start routine is called 470.
Figure 18 is a flow chart illustrating process steps for the soft start
routine 500. As explained above, the soft start for the halogen lamps is
utilized to
increase the lamp reliability. When routine 500 is called from the power level
control
routine 502, the microcomputer increments a soft start counter 504. The micro
computer then determines whether the soft start is complete (e.g., depending
on the
lamp, the soft start has a duration of 1 or 2 seconds, as explained above). If
soft start
is complete, the microcomputer resets the soft start counter 508, turns on the
lamp
control relay 510, and turns off the lamp control triac 512. Operations then
proceed
to the cooking routine 514. If soft start is not complete, the micro computer
turns on
the lamp control triac for a soft start count x 10% of the line cycle 516.
Operations
then proceed to the cooking routine.
The glass of oven door 26 (shown in Figure 2) is very dark and does
not enable visualization of food within cavity 122 (shown in Figure 2) unless
at least
one of the Halogen lamps is on and sufficiently energized to illuminate cavity
122.
Therefore, in some cooking operations such as the microwave only mode of
cooking
or when radiant cooking at low power levels, and in order to visualize food in
cooking cavity 122, an operator may select the microwave button on control
pane140.
When this pad is selected during cooking, the microcomputer energizes upper
center
lamp 124 for four seconds at full power (i.e., power level 10), with a soft
start, i.e.,
two seconds of soft start and two seconds of power level 10 energization for a
total of
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CA 02321652 2000-08-31
WO 00/42824 PCT/USOO/00840
four seconds, as described above. Lamp 124 illuminates the cooking cavity
sufficiently so that an operator can visualize the food through window 30.
While the invention has been described in terms of various specific
embodiments, those skilled in the art will recognize that the invention can be
practiced with modification within the spirit and scope of the claims.
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