Electric heating – Microwave heating – With control system
Reexamination Certificate
2001-05-07
2003-02-18
Walberg, Teresa (Department: 3742)
Electric heating
Microwave heating
With control system
C219S702000
Reexamination Certificate
active
06521875
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a microwave oven, and more particularly to a microwave oven having a conducting member for controlling the supply of electrical power, which is capable of simplifying a structure of the switching system, according to controlling the electrical power supplied to a high voltage transformer by using a conducting member installed in a door.
BACKGROUND ART
FIG. 1
shows a microwave oven for heating/cooking food using microwaves. The microwave oven contains a case
20
for forming a cooking chamber
22
, a door
21
for opening/closing the cooking chamber
22
, a tray
24
being installed in the cooking chamber
22
, and a panel
25
for controlling operations of the microwave oven.
FIG. 2
is a partial cutaway view of
FIG. 1. A
pair of latch hooks
28
a
,
28
b
are installed in the door
21
, catch openings
27
a
,
27
b
are formed corresponding to each latch hook
28
a
,
28
b
at a front plate
26
of the case
20
. If the door
21
is pushed shut, the latch hooks
28
a
,
28
b
will engage the catch openings
27
a
,
27
b
to hold the door
21
shut.
At the back side of the panel
25
is provided a device chamber (not shown). In the device chamber are installed a magnetron for generating microwaves and a high voltage transformer HVT for generating a high voltage supplied to the magnetron, and so on. In supplying an AC power to the high voltage transformer HVT, this high voltage transformer HVT generates a predetermined high voltage to drive the magnetron. Then, the magnetron radiates microwaves of about 2,450 MHz frequency to heat/cook food.
As shown in
FIG. 2
, micro switches MS
1
, MS
2
, MS
3
are installed at the back side of the front plate
26
of the case
20
.
FIGS. 3
a
and
3
b
are schematic diagrams and symbols of each micro switch MS
1
, MS
2
, MS
3
, respectively. The micro switches MS
1
, MS
2
, MS
3
have a slight interval at the point of contact, and a mechanism of a snap action. The micro switches MS
1
, MS
2
, MS
3
have a mechanism at the point of contact to open/close by the determined operation and force in a sealing case, and is a small switch for arranging a pushing mechanism of the actuator switch located on the outside of the case. That is, the micro switch is one of the contact type detectors, which detects something contacted according to releasing the inside point of contact when something
6
closes to a push button
1
, and begins to push the push button
1
, and applies more than a predetermined force F to the push button
1
. In
FIG. 3
a
, the reference numeral
2
is a movable spring, and the reference numeral
3
is a movable point of contact. The reference numeral
4
is a fixed point b of contact, and the reference numeral
5
is a fixed point a of contact. COM, NO, and NC are a common terminal, a normally open terminal, and a normally closed terminal, respectively. In
FIG. 3
b
, a point a of contact
7
is the point of contact which conducts first when the micro switch is operated, and which connects the common terminal COM into the normally open terminal NO. A point b of contact
8
is the point of contact which conducts when the micro switch is not operated, and which connects the common terminal COM into the normally close terminal NC.
The micro switches MS
1
, MS
2
, MS
3
each have an operating button
31
,
32
,
33
, respectively. At the back side of the front plate
26
are installed a pair of movable members
29
a
,
29
b
to adjoin the catch openings
27
a
,
27
b
. Then, the movable members
29
a
,
29
b
are fixed for pivoting by each pin
23
a
,
23
b
, and are fixed elastically by each spring
41
a
,
41
b.
In
FIG. 2
, if the door
21
is pushed closed, the micro switches MS
1
, MS
2
, MS
3
are operated by the latch hooks
28
a
,
28
b
which are inserted in the catch openings
27
a
,
27
b
. That is, when the movable members
29
a
,
29
b
are pushed by each latch hook
28
a
,
28
b
, the movable members
29
a
,
29
b
are rotated against the elasticity of the springs
41
a
,
41
b
. Therefore, the operating button
31
is pushed by the upper movable members
29
a
, and the operating buttons
32
,
33
are pushed by the lower movable members
29
a
, respectively.
Meanwhile, since the conventional microwave oven has been made to be operated using the AC common power source of 110V/220V for supplying high alternating current, the microwave oven cannot be used in a place where alternating current is not available.
To overcome the above described problem, an AC/DC type microwave oven has been developed, as shown in FIG.
4
. In
FIG. 4
, an AC/DC type microwave oven includes an AC driving load
30
, a DC driving load and DC/AC converting part
40
, and a microwave oscillator
50
. The AC driving load
30
is driven by an AC input power. The DC driving load and DC/AC converting part
40
includes the DC driving load being driven by a DC input power, and the DC/AC converter converting the DC input power into an AC power. The microwave oscillator
50
is supplied by only one of the AC input power or the DC/AC power converted by a DC/AC converter, and generates microwaves.
The AC driving load
30
is driven by alternating current, which includes a lamp and a fan motor, etc., which are connected to the AC power source. A power switch (not shown) to determine the supplying status of AC is connected to the AC power source. The DC driving load being driven by direct current, which includes a lamp and a fan motor, etc., which are connected to the DC power source. A power switch (not shown) to determine the supplying status of DC is connected to the DC power source. The direct current forms a differential DC circuit net discriminated as an AC circuit net. Then, the direct current is connected to the input side of the DC/AC converting part
40
which supplies alternating current. The microwave oscillator
50
includes a high voltage transformer HVT which receives the AC power, a high voltage condenser HVC, a high voltage diode HVD, and a magnetron MGT. The operation of the microwave oscillator
50
is described the same way as shown in FIG.
1
.
Therefore, as the AC power source supplies alternating current to the AC driving load
30
, and as the DC power source supplies direct current to the DC driving load and DC/AC converting part
40
, respectively, the conventional AC/DC type microwave oven is operated.
That is, in case the large amount of current is supplied through the micro switches MS
1
, MS
2
, the points of contact of the micro switches MS
1
, MS
2
can remain in the contacting status. When the user pulls the door
21
so that the cooking chamber is open, the operating buttons
31
,
32
of the micro switches MS
1
, MS
2
can remain in the pushed status. Accordingly, as the primary switch PC and secondary switch SD of the DC driving load and DC/AC converting part
40
are held in the closed status, current is supplied to the DC driving load and DC/AC converting part
40
, so the AC/DC type microwave oven has the problem of encountering a malfunction.
According as the primary switch PC and secondary switch SD of the DC driving load and DC/AC converting part
40
are held there closed status, and then current is supplied to the DC driving load and DC/AC converting part
40
, so the AC/DC type microwave oven has the problem of encountering a malfunction.
FIG. 5
is a block diagram of a conventional AC/DC type microwave oven operated by many micro switches. For preventing the threat of electromagnetic waves, the microwave oven is capable of isolating the supply of the power not to generate electromagnetic waves when the door
21
is open. For insuring the isolation of the supply of power, the microwave oven includes many micro switches PA, SA, MA, PD, SD, MD for multi-switching operations.
The structure of the microwave oven, however, becomes very complicated by many micro switches PA, SA, MA, PD, SD, MD, and by the peripheral parts for driving the micro switches. Furthermore, as the number of parts of the microwave increases, the manufacturing cost of the microwave oven inc
Han Yong-woon
Jang Seong-deog
Kim Chul
Sung Han-jun
Bushnell , Esq. Robert E.
Van Quang
Walberg Teresa
LandOfFree
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