Electric heating – Microwave heating – Enclosed cavity structure
Reexamination Certificate
2000-03-09
2001-04-03
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
Enclosed cavity structure
C219S702000, C219S718000, C126S27300R, C126S29900R
Reexamination Certificate
active
06211504
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my two applications WALL MOUNTED TYPE MICROWAVE OVEN AND HOOD MOTOR SPEED CONTROLLING METHOD THEREOF filed with the Korean Industrial Property Office on Mar. 9, 1999 and there duly assigned Ser. No. 7718/1999, and WALL MOUNTED TYPE MICROWAVE OVENAND HOOD MOTOR SPEED CONTROLLING METHOD THEREOF filed with the Korean Industrial Property Office on Mar. 9, 1999 and there duly assigned Serial No. 7720/1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wall-mounted microwave oven and a method for controlling a hood motor, and more particularly, to a wall-mounted microwave oven and a method for controlling a hood motor, to vary the speed of the hood motor.
2. Description of the Related Art
A wall-mounted microwave oven is installed on the upper wall over a gas range, and functions as a hood for inhaling vapor and fumes generated during cooking foods in the gas range and discharging the inhaled vapor and fumes to the outside.
As shown in
FIGS. 1 and 2
, the wall-mounted microwave oven includes a main body
53
and a casing
56
enclosing the main body
53
. Between the casing
56
and the main body
53
is formed a hood duct
65
as a path for discharging vapor and fumes. On the lower surface of the casing
56
is formed an inlet
58
for inhaling vapor and fumes into the hood duct
65
. On the upper surface of the casing
56
is formed an outlet
59
to which a discharging tube
61
is connected. The discharging tube
61
is connected to a discharging path
67
which penetrates the wall and communicates with the outside. Also, on the upper portion of the main body
53
adjacent to the outlet
59
is formed a hood fan
63
for discharging the vapor and fumes inhaled in the hood duct
65
via the inlet
58
to the outside via the outlet
59
, as indicated by arrow marks.
The hood fan
63
operates by a user's selection through a select button provided in a control panel
35
. As it being the case, a hood sensor
57
(
FIG. 7
) which turns on or off the hood fan
63
according to air temperature or smoke detection is provided to the inlet
58
of the hood duct
65
or the inside thereof, thereby controlling operation of the hood fan
63
. Here, the hood sensor
57
is generally made of a bimetal.
FIG. 7
is a circuit diagram of a hood driver for a conventional wall-mounted microwave oven. The hood motor
95
is installed on an electric power line which mutually and serially connects first and second commercial alternating voltage (AC) electric power lines
51
and
52
which extend from an external power source
55
. On the electric power line where the hood motor
95
is installed, are formed a hood fan switch
72
which turns on or off the hood motor
95
and a speed select switch
73
for selecting a driving speed of the hood motor
95
at low or high speed. Here, the speed select switch
73
has a high speed contact
73
a
and a low speed contact
73
b
for turning on the hood motor
95
, with a result that the hood motor
95
operates at high speed or at low speed, respectively. The speed selection switch
73
is normally connected to the low speed contact
73
b.
The hood sensor
57
is connected in parallel with the hood fan switch
72
. As described above, the hood sensor
57
detects heat or gases transferred from a gas range
100
and is turned on when heat or gases is detected.
By this configuration, a selection button for driving the hood fan can be selected to discharge heat and fumes emitted from foods during cooking. Here, if a user presses the selection button once, a microcomputer
60
turns on the hood fan switch
72
, in which case the speed selection switch ordinarily in contact with the low speed contact
73
b
drives the hood motor
95
at low speed. If the selection button is pressed twice, the microcomputer
60
directs the speed selection switch
73
to contact the high speed contact
73
a
to drive the hood motor
95
at high speed. If the selection button is pressed once again, the microcomputer
60
turns off the hood fan switch
72
to stop the hood motor
95
.
Meanwhile, although the user does not manipulate the selection button, if the hood sensor
57
detects heat or fumes during cooking, the hood sensor
57
is turned on to drive the hood motor
95
at low speed.
However, the conventional hood motor
95
can be controlled only at two levels, that is, at low speed and high speed. Thus, if a user wishes the hood motor
95
to be driven faster than at high speed, or wishes the hood motor
95
to be driven at intermediate speed, such user needs cannot be met. That is, the driving speed of the hood motor
95
cannot be adaptively controlled according to the degree of heat or fumes emitted.
To solve these problems, the winding number of coils is increased to enlarge the capacity of the hood motor
95
, thereby controlling the rotational speed of the hood motor
95
in multiple steps. In the case that the winding number of coils is increased, the volume of the hood motor
95
also increases. In addition, as the number of steps are increased, the number of contacts in the speed selection switch
73
should be increased. As a result, a production cost increases and an assembling work is complicated.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a wall-mounted microwave oven which is adaptively controlled according to a cooking condition under which the speed of a hood motor is diversified.
It is another object of the present invention to provide a hood motor speed controlling method in a wall-mounted microwave oven which is adaptively controlled according to a cooking condition under which the speed of a hood motor is diversified.
To accomplish the above object of the present invention, there is provided a wall-mounted microwave oven having a main body forming a cavity for accommodating foods to cook, a casing enclosing the main body and forming a hood duct having an inlet located on a bottom area and an outlet located on an upper area, and a hood fan installed in the hood duct, the wall-mounted microwave oven comprising: a hood motor driving the hood fan; a first switching unit for interrupting a supply current supplied to the hood motor, a hood sensor connected in parallel with the first switching unit, said hood sensor detecting whether or not the hood fan need to be turned on or off; a microcomputer for controlling the rotational speed of the hood motor by controlling an on and-off time of the first switching unit, in response to an external control signal; and a second switching unit transmitting a control signal supplied from the microcomputer to the first switching unit.
Preferably, the wall-mounted microwave oven further comprises a rectifying unit rectifying the supply current supplied from a power unit.
Preferably, the wall-mounted microwave oven further comprises a filtering unit connected between the first switching unit and the hood motor, each end of the filtering unit connected to the rectifying unit, the filtering unit filtering rectification current rectified in the rectifying unit.
Preferably, the first switching unit comprises a transistor.
The wall-mounted microwave oven further comprises a second switching unit for transmitting a control signal supplied from the microcomputer to the first switching unit. The second switching unit comprises a first transistor connected to the microcomputer and turned on or off according to a driving signal supplied from the microcomputer and a second transistor operating reversely to the on-and-off operation of the first transistor and transmitting a driving signal to the first switching unit.
Preferably, when the speed of the hood motor is increased, the first switching unit is controlled to have a short duty cycle.
Preferably, the wall-mounted microwave oven further comprises a selection switch connected serially to said hood sensor, having a first pole conne
Bushnell , Esq. Robert E.
Leung Philip H.
Samsung Electronics Co,. Ltd.
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