Information
-
Patent Grant
-
6806449
-
Patent Number
6,806,449
-
Date Filed
Wednesday, July 3, 200222 years ago
-
Date Issued
Tuesday, October 19, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 219 707
- 219 716
- 219 703
- 219 704
- 219 705
- 219 710
- 219 715
- 219 719
- 219 754
- 219 728
- 219 682
- 219 685
- 219 482
- 099 325
-
International Classifications
-
Abstract
An apparatus and a method of controlling a microwave oven includes performing a first heating until detection values of a humidity sensor reach a reference value, wherein the humidity sensor senses humidity of water vapor discharged from a cooking chamber. A second heating is performed, lower than the first heating, after the detection values reach the reference value using an output power from a magnetron. A surrounding humidity condition of the microwave oven is determined. The reference value of the first heating is reset so as to cook food appropriately according to the determined humidity condition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 2002-18377, filed Apr. 4, 2002, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to microwave ovens, and more particularly to an apparatus and a method of controlling a microwave oven, which can cook foods under optimal cooking conditions regardless of surrounding humidity conditions by compensating for variation of cooking conditions due to the surrounding humidity conditions.
2. Description of the Related Art
Generally, when rice is cooked in a conventional microwave oven, a first heating is performed until rice water reaches a boiling point of 100° C., and then a second heating is performed for a predetermined period of time after the rice water reaches the boiling point using an output power of a magnetron lower than that of the first heating.
The microwave oven is not equipped with a temperature sensor and thus, detects the boiling of the rice water using a detection value from a humidity sensor, which senses a humidity value of water vapor discharged from a cooking chamber so as to detect the boiling point of the rice water.
FIG. 1A
is a waveform diagram showing a relationship between sensing voltages of a humidity sensor and time in the conventional microwave oven.
FIG. 1B
is a waveform diagram showing a relationship between output powers of a magnetron and time in the conventional microwave oven.
FIG. 1C
is a waveform diagram showing a relationship between boiling temperatures of water and time in the conventional microwave oven. As shown in
FIG. 1A
, at a beginning of heating food, the output power of the magnetron is maximized to rapidly heat the food, and then, the output power is gradually lowered while continuing to heat the food. If the rice water boils, rice continues to be heated using low output power suitable for steaming boiled rice, so the rice is cooked. Accordingly, the humidity value sensed by the humidity sensor is a constant value at the start of cooking, rapidly increasing when rice water reaches the boiling point, and gradually decreasing thereafter.
A sensing voltage graph of the humidity sensor, as shown in
FIG. 1A
, shows a variation of the humidity value. A reference value (T1 FACTOR) of the humidity sensor, corresponding to the boiling point (100° C.) of the rice water, is estimated on a basis of sensing voltage values. Generally, the reference value is uniformly set at a value of, for example, 85% of a maximum voltage MAX of the sensing voltages on a basis of a normal surrounding humidity condition.
However, a sensor for sensing relative humidity, not absolute humidity, is mainly used as the humidity sensor due to problems such as cost, etc. Then, if the surrounding humidity condition of the microwave oven is lower than that of a normal state, that is, a dry state, such as during Winter, the maximum voltage MAX sensed by the humidity sensor is relatively increased. Therefore, the voltage at 85% of the maximum voltage does not reflect the boiling point of rice water. Consequently, the output power of the magnetron is decreased to output a low output power suitable for steaming the rice before the rice water boils, thus causing rice to be half-cooked.
SUMMARY OF THE INVENTION
Various objects and advantages of the invention will be set forth in part in the description that follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a method of controlling a microwave oven to cook foods under optimal cooking conditions regardless of a surrounding humidity condition, by compensating for a variation of cooking conditions due to the surrounding humidity condition.
To achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: performing a first heating until detection values of a humidity sensor reach a reference value, wherein the humidity sensor senses humidity of water vapor discharged from a cooking chamber; performing a second heating, lower than the first heating, after the detection values reach the reference value using an output power from a magnetron; determining a surrounding humidity condition of the microwave oven; and resetting the reference value of the first heating so as to cook food appropriately
Further, to achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: performing a first heating until detection values of a humidity sensor reach a reference value, wherein the humidity sensor senses humidity of water vapor discharged from a cooking chamber; performing a second heating, lower than that of the first heating, for a set period of time after the detection values reach the reference value using an output power from a magnetron; determining a surrounding humidity condition of the microwave oven; and resetting a period of time for the second heating so as to cook food appropriately according to the determined humidity condition.
To achieve the above and other objects, the present invention provides a control method of a microwave oven, including: maximizing an output power; counting a first heating time; reading sensing voltages from a humidity sensor during the first heating time; comparing the sensing voltages sensed by the humidity sensor with each other to determine a maximum voltage; setting a first reference value at a predetermined voltage level from the maximum voltage; determining whether a current sensing voltage sensed by the humidity sensor has reached the first reference value; decreasing the output power to a low power; determining whether the current mode is in a dry mode or a normal mode; setting a preset time as a reference period of time for a second heating time corresponding to the counted heating time; outputting the low power for a predetermined period of time of the second heating time; increasing the output power of the microwave oven to perform a cooking operation after the predetermined period of time of the second heating time elapses; and stopping the cooking operation of the microwave oven after the second heating time has elapsed.
To achieve the above and other objects, the present invention provides an apparatus to control a microwave oven, including: a control unit counting a time from a start of heating to a time point when a first reference value is detected, comparing the counted heating time with a predicted heating time preset; and determining a current mode as a dry mode when the counted heating time is shorter than the predicted heating time.
To achieve the above and other objects, the present invention provides an apparatus to control a microwave oven, including: a control unit determining a surrounding humidity condition of the microwave oven, and compensating for a variation of heating time due to the surrounding humidity of the microwave oven according to seasons or areas in which the microwave oven is used to provide an optimal heating time enabling the microwave oven to optimally cook food, regardless of surrounding conditions.
To achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: counting a time from a start of heating to a time point when a first reference value is detected; comparing the counted heating time with a predicted heating time preset; and determining a current mode as a dry mode when the counted heating time is shorter than the predicted heating time.
To achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: determining a surrounding humidity condition of the microwave oven; and compensating for a variation of heating time due to the surrounding humidity of the microwave oven according to seasons or areas in which the microwave oven is used to provide an optimal heating time enabling the microwave oven to optimally cook food, regardless of surrounding conditions.
These together with other objects and advantages, which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1A
is a waveform diagram showing a relationship between sensing voltages of a humidity sensor and time in the conventional microwave oven when a surrounding humidity of the microwave oven is in normal and dry states;
FIG. 1B
is a waveform diagram showing a relationship between output powers of a magnetron and time in the conventional microwave oven when the surrounding humidity of the microwave oven is in the normal and dry states;
FIG. 1C
is a waveform diagram showing a relationship between boiling temperatures of water and time in the conventional microwave oven when the surrounding humidity of the microwave oven is in the normal and dry states;
FIG. 2
is a top sectional view showing a construction of a microwave oven according to an embodiment of the present invention;
FIG. 3
is a block diagram of the microwave oven of
FIG. 2
;
FIG. 4
is a flowchart of a method of controlling the microwave oven according to an embodiment of the present invention;
FIGS. 5A and 5B
are graphs showing first and second reference values of
FIG. 4
;
FIG. 6
is a flowchart of another microwave oven control method to change a second heating time in a dry mode, according to another embodiment of the present invention; and
FIG. 7
is a waveform diagram showing sensing voltages of a humidity sensor to describe a method of determining a mode of
FIGS. 4 and 6
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.
FIG. 2
is a top sectional view showing the construction of a microwave oven according to an embodiment of the present invention. Referring to
FIG. 2
, the microwave oven of the present invention includes a body
10
, which constitutes an external shape of the microwave oven and defines a cooking chamber
12
and a machine room
11
separately partitioned. A door
13
is connected to the body
10
by a hinge to open and shut the cooking chamber
12
, a control panel
14
is installed on a front of the body
10
and provided with a plurality of functional buttons thereon, and a humidity sensor
17
senses a humidity of the cooking chamber
12
.
The cooking chamber
12
opens at the front of the body
10
, where a cooking tray
12
a
in a form of a turntable is installed on a bottom portion of the cooking chamber
12
and a motor is installed under the cooking tray
12
a
to rotate the cooking tray
12
a.
Further, an inlet
15
a,
communicating with the machine room
11
to suck the external air into the cooking chamber
12
, is formed on a front portion of one sidewall
15
of the cooking chamber
12
. Further, an outlet
16
a
is formed on a back portion of another sidewall
16
of the cooking chamber
12
to discharge the air in the cooking chamber
12
to the outside.
Further, in the machine room
11
, a magnetron
1
a
is installed to oscillate microwaves, a cooling fan
11
b
is installed to suck the external air to cool the machine room
11
and the cooking chamber
12
, and a guide duct
11
c
is installed to guide the air in the machine room
11
to the inlet
15
a.
The cooling fan
11
b
is disposed between a magnetron
11
a
and a back wall of the machine room
11
. A plurality of suction holes
11
d
are formed on the back wall of the machine room
11
to suck the external air into the machine room
11
.
The humidity sensor
17
is mounted on the sidewall
16
of the cooking chamber
12
adjacent to the outlet
16
a
to be disposed along the air discharging path of the cooking chamber
12
. Therefore, the humidity sensor
17
senses the humidity of the air being discharged from the cooking chamber
12
through the outlet
16
a.
The humidity sensor
17
is electrically connected to a control unit formed on the control panel
14
, as will be described later.
FIG. 3
is a block diagram of the microwave oven according to an embodiment of the present invention. Referring to
FIG. 3
, the microwave oven includes a control unit
30
to control operations of the microwave oven. The control unit
30
is connected to an input unit
14
a
arranged in the control panel
14
to allow a user to input operation commands, such as rice cooking for one person and two persons. Further, the control unit
30
is connected to the humidity sensor
17
to sense humidity.
Further, the microwave oven has a storage unit
20
electrically connected to the control unit
30
, to store various data for cooking. Furthermore, the control unit
30
is electrically connected to a magnetron driving unit
41
to drive the magnetron
11
a,
a fan driving unit
42
to drive the cooling fan
11
b,
a motor driving unit
43
to drive a motor
12
b
for rotating the cooking tray
12
a,
and a display driving unit
44
to drive a display unit
14
b
arranged on the control panel
14
to display information. When the user manipulates the input unit
14
a
of the control panel
14
to operate the microwave oven, the microwave oven according to an embodiment of the present invention cooks food placed on the cooking tray
12
a
by radiating microwaves that are oscillated by the magnetron
11
a
to the cooking chamber
12
.
Further, the external air is sucked into the machine room
11
through the suction holes
11
d
to cool the machine room
11
by the action of the cooling fan
11
b
during a cooking operation of the microwave oven, and is provided to the cooking chamber
12
through the guide duct
11
c
and the inlet
15
a.
Then, the air in the cooking chamber
12
is discharged to the outside through the outlet
16
a,
together with water vapor generated from the food, as shown by an arrow in FIG.
3
. Accordingly, odor and water vapor can be eliminated from the cooking chamber
12
. In this case, the air in the cooking chamber
12
is discharged to the outside while being brought into contact with the humidity sensor
17
, so the humidity sensor
17
senses water vapor contained in the discharged air and transmits the sensed water vapor to the control unit
30
as electrical signals. The control unit
30
recognizes such electrical signals as voltage values. The control unit
30
drives the magnetron
11
a,
the motor
12
b
and the cooling fan
11
b
to automatically cook the food based on the electrical signals received from the humidity sensor
17
.
Hereinafter, a method of controlling a microwave oven to cook rice according to an embodiment of the present invention will be described in detail.
FIG. 4
is a flowchart of a method of controlling the microwave oven according to an embodiment of the present invention. Referring to
FIG. 4
, the user places a bowl, in which rice and a suitable quantity of water are mixed, in the cooking chamber
12
so as to cook the rice. The user then selects a cooking course for one person or two persons through the input unit
14
a.
At S
10
, the control unit
30
heats the food by driving the magnetron
11
a
to maximize its output power. At S
11
, the control unit
30
counts a first heating time.
At S
12
, the control unit
30
reads sensing voltages from the humidity sensor
17
for a predetermined period of time of the first heating time. At S
13
, the control unit
30
compares the sensing voltages sensed by the humidity sensor
17
with each other and determines a maximum voltage.
If the maximum voltage is determined, at S
14
, the control unit
30
sets a voltage at 85% of the maximum voltage as a first reference value. At S
15
, the control unit
30
determines whether a current sensing voltage determined from the humidity sensed by the humidity sensor
17
has reached the first reference value. In this case, the first reference value is a humidity value when the temperature of water reaches the boiling point (100° C.), the humidity value being obtained through experiments to determine the humidity and the temperature of water when a surrounding humidity condition of the microwave oven is normal.
At S
15
, if the current sensing voltage has reached the first reference value, at S
16
, the control unit
30
determines whether a current mode is in a dry mode or a normal mode by a mode determining method to be described later.
If it is determined that the current mode is in the normal mode, at S
19
, the control unit
30
decreases the output power of the magnetron
11
a
to a low power suitable for steaming boiled rice, and stops the counting of the heating time. Then, at S
20
, the control unit
30
sets a preset time as a reference period of time for a second heating (second heating time) corresponding to the counted heating time.
If the second heating time is set, during the second heating time, at S
21
, the control unit
30
operates the magnetron
11
a
to output the low power required to steam boiled rice for a predetermined period of time of the second heating time, while the control unit
30
increases the output power of the magnetron
11
a
to perform a cooking operation after the predetermined period of time of the second heating time elapses. At S
22
, after the second heating time has elapsed, the control unit
30
stops the driving of the magnetron
11
a.
At S
23
, the control unit
30
finishes the cooking.
Further, at S
16
, if the current mode is in the dry mode, at S
17
, the control unit
30
sets a second reference value (a voltage at 83% of the maximum voltage) lower than the first reference value, instead of the first reference value, so as to heat the food a little longer, as shown in
FIGS. 5A and 5B
. Accordingly, as shown in
FIGS. 5A and 5B
, a reference value is decreased to a voltage at 83%, lower that the previous 85%, of the maximum voltage, such that a time taken for the sensing voltage to reach the reference value is lengthened, thus allowing the food to be heated a little longer.
At S
17
, if the second reference value is set, at S
18
, the control unit
30
determines whether the current sensing voltage has reached the second reference value. At S
18
, if the current sensing voltage has reached the second reference value, at S
19
, the control unit
30
decreases the output power of the magnetron
11
a
to the low power suitable to steam boiled rice, and stops the counting of the heating time. At S
20
, the control unit
30
sets a preset time corresponding to the counted heating time as the second heating time.
During the second heating time, at S
21
, the control unit
30
operates the magnetron
11
a
to output the low power required to steam boiled rice for a predetermined period of time of the second heating time, while the control unit
30
increases the output power of the magnetron
11
a
to perform the cooking operation after the predetermined period of time of the second heating time elapses. At S
22
, after the second heating time has elapsed, at S
23
, the control unit
30
stops the driving of the magnetron
11
a
and finishes the cooking.
FIG. 6
is a flowchart of another microwave oven control method of changing the second heating time in a dry mode instead of the reference value during the first heating, according to another embodiment of the present invention.
Referring to
FIG. 6
, at S
100
, the control unit
30
heats the food by driving the magnetron
11
a
to maximize the output power, and, at S
101
, counts the first heating time. At S
102
, the control unit
30
reads the sensing voltages from the humidity sensor
17
for a predetermined period of time of the first heating time. Further at S
103
, the control unit
30
compares the sensing voltages sensed by the humidity sensor
17
with each other, and sets the maximum voltage.
If the maximum voltage is set, at S
104
, the control unit
30
sets a voltage at 85% of the maximum voltage as a first reference value. At S
105
, the control unit
30
determines whether the current sensing voltage determined from the humidity sensed by the humidity sensor
17
has reached the first reference value.
At S
105
, if the current sensing voltage has reached the first reference value, at S
106
, the control unit
30
decreases the output power of the magnetron
11
a
to a low power suitable for steaming boiled rice, and stops the counting of the heating time. Then, at S
107
, the control unit
30
determines whether the current mode is in the dry mode or the normal mode by a mode determining method to be described later If the current mode is in the normal mode, at S
108
, the control unit
30
sets a preset time as the second heating time corresponding to the counted heating time.
If the second heating time is set, at S
109
, during the second heating time, the control unit
30
operates the magnetron
11
a
to output low power required to steam boiled rice for a predetermined period of time of the second heating time, while the control unit
30
increases the output power of the magnetron
11
a
to perform a cooking operation after the predetermined period of time of the second heating time elapses. After the second heating time has elapsed, at S
110
and S
111
, the control unit
30
stops the driving of the magnetron
11
a
and finishes the cooking.
Further at S
106
, if the current mode is in the dry mode, at S
120
, the control unit
30
sets the second heating time to be longer than the preset time. If the second heating time is set, at S
109
, during the second heating time, the control unit
30
operates the magnetron
11
a
to output low power required to steam boiled rice for a predetermined period of time of the second heating time, while the control unit
30
increases the output power of the magnetron
11
a
to perform a cooking operation after the predetermined period of time of the second heating time elapses. After the second heating time has elapsed, at S
110
and S
111
, the control unit
30
stops the driving of the magnetron
11
a
and finishes the cooking.
Hereinafter, the dry mode determining method of
FIGS. 4 and 6
is described. There are two methods to determine the dry mode of
FIGS. 4 and 6
.
A first method is performed by determining the current mode as the dry mode if a voltage waveform between points A and B ascends as shown in
FIG. 7
, and by determining the current mode as the normal mode if the voltage waveform is constant or descends. That is, sensing voltages sensed by the humidity sensor
17
for a predetermined period of time are compared with each other, such that the current mode is determined as the dry mode if the sensing voltages are gradually increased. Alternatively, the maximum voltage is set by comparing sensing voltages sensed by the humidity sensor
17
for a predetermined period of time with each other, and if a voltage at the start of heating is less than the maximum voltage, the current mode is determined as the dry mode. This determination is due to a phenomenon where if the surrounding humidity of a microwave oven is decreased, the humidity within the cooking chamber is affected to cause the waveform of the sensing voltages of the humidity sensor
17
to ascend.
A second method is performed by counting a time from the start of heating to a time point when the first reference value is detected, comparing the counted heating time with a predicted heating time preset for a case where the surrounding humidity of the microwave oven is normal, and determining the current mode as the dry mode if the counted heating time is shorter than the predicted heating time. The second method considers that, when the surrounding humidity of the microwave oven is in the dry mode, heating time becomes shorter than that of a normal mode.
As described above, the present invention provides a method of controlling a microwave oven, which provides an optimal heating time by compensating for a variation of heating time due to surrounding humidity of the microwave oven according to seasons or areas in which the microwave oven is used, thus enabling the microwave oven to optimally cook food, regardless of surrounding conditions.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims
- 1. A method of controlling a microwave oven having a cooking chamber, a magnetron, and a humidity sensor adapted to sense a humidity of water vapor discharged from the cooking chamber, comprising:performing a first heating at a maximum output power level; reading a detection value outputted from the humidity sensor; determining, based on the read detection value, whether or not a surrounding humidity condition of the microwave oven corresponds to a dry state; if it is determined that the surrounding humidity condition of the microwave oven corresponds to the dry state, setting a reference value, at which the first heating is to be stopped, to be lower than a corresponding value predetermined for a normal surrounding humidity condition of the microwave oven; determining whether or not the read detection value corresponds to the set reference value; if it is determined that the read detection value corresponds to the set reference value, stopping the first heating, and performing a second heating for a predetermined time at an output power level lower than the output power level at the first heating; and stopping the second heating after the predetermined time has elapsed.
- 2. The method according to claim 1, wherein the determining of the surrounding humidity condition comprises:detecting a variation in the detection value outputted from the humidity sensor until the detection value reaches a maximum value during the first heating; determining whether or not the detection value variation has an increment gradient; and if it is determined that the detection value variation has an increment gradient, determining the surrounding humidity condition of the microwave oven as the dry state.
- 3. The method according to claim 1, wherein the determining of the surrounding humidity condition comprises:counting a time taken until the detection value reaches a predetermined reference value during the first heating; determining whether or not the counted time is shorter than a count time predetermined for the normal surrounding humidity condition of the microwave oven; and if the counted time is shorter than the predetermined count time, determining the surrounding humidity condition of the microwave oven as the dry state.
- 4. A method of controlling a microwave oven having a cooking chamber, a magnetron, and a humidity sensor adapted to sense a humidity of water vapor discharged from the cooking chamber, comprising:performing a first heating at a predetermined output power level; reading a detection value outputted from the humidity sensor; determining whether or not the read detection value corresponds to a reference value, at which the first heating is to be stopped; if it is determined that the read detection value corresponds to the reference value, determining whether or not a surrounding humidity condition of the microwave oven corresponds to a dry state; if it is determined that the surrounding humidity condition of the microwave oven corresponds to the dry state, re-setting the reference value to a value lower than the reference value; determining whether or not the read detection value corresponds to the re-set reference value; if it is determined that the read detection value corresponds to the re-set reference value, stopping the first heating, and performing a second heating for a predetermined time at an output power level lower than the output power level at the first heating; and stopping the second heating after the predetermined time has elapsed.
- 5. The method according to claim 4, whereindetecting a variation in the detection value outputted from the humidity sensor until the detection value reaches a maximum value during the first heating; determining whether or not the detection value variation has an increment gradient; and if it is determined that the detection value variation has an increment gradient, determining the surrounding humidity condition of the microwave even as the dry state.
- 6. The method according to claim 4, wherein the determining of the surrounding humidity condition comprises:counting a time taken until the detection value reaches a predetermined reference value during the first heating; determining whether or not the counted time is shorter than a count time predetermined for the normal surrounding humidity condition of the microwave oven; and if the counted time is shorter than the predetermined count time, determining the surrounding humidity condition of the microwave oven as the dry state.
- 7. A control method of a microwave oven, comprising:maximizing an output power; counting a first heating time; reading sensing voltages from a humidity sensor during the first heating time; comparing the sensing voltages sensed by the humidity sensor with each other to determine a maximum voltage; setting a first reference value at a predetermined voltage level from the maximum voltage; determining whether a current sensing voltage sensed by the humidity sensor has reached the first reference value; decreasing the output power to a low power; stopping the counting of the first heating time; setting a preset time as a reference period of time for a second heating time corresponding to the counted heating time; outputting the low power for a predetermined period of time of the second heating time; increasing the output power of the microwave oven to perform a cooking operation after the predetermined period of time of the second heating time elapses; and stopping the cooking operation of the microwave oven after the second heating time has elapsed.
- 8. The control method according to claim 7, further comprising determining whether the current mode is in a dry mode or a normal mode.
- 9. The control method according to claim 8, wherein when the current mode is in the dry mode, the method further comprises:setting a second reference value lower than the first reference value heating food in the microwave oven longer; and determining whether the current sensing voltage has reached the second reference value.
- 10. The control method according to claim 7, wherein the first reference value is a humidity value when a surrounding humidity condition of the microwave oven is normal.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2002-18377 |
Apr 2002 |
KR |
|
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A |
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A |
5889264 |
Kidblad et al. |
Mar 1999 |
A |
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6642491 |
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