Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
2002-03-11
2004-10-26
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S272200
Reexamination Certificate
active
06808669
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high voltage transformers for
microwave ovens and manufacturing methods therefor, and more particularly, to an improved high voltage transformer for a microwave oven including a core, and primary and secondary coils, and an improved manufacturing method therefor.
2. Description of the Related Art
A typical microwave oven comprises a casing or housing having a cooking chamber and an electronic component compartment, a door for the cooking chamber, and a control panel installed in front of the electronic component compartment. A plurality of electronic components are housed in the electronic component compartment. These electronic components include a high voltage transformer for generating high voltage when the microwave oven is supplied with power from a power supply, a high voltage capacitor which is charged to a high voltage by the high voltage transformer, and a magnetron for generating microwaves and radiating the microwaves into the cooking chamber when discharge of the high voltage capacitor supplies the magnetron with high voltage.
FIG. 8
is an exploded perspective view of a conventional high voltage transformer, while
FIG. 9
is an enlarged cross sectional view taken generally along line IX—IX of
FIG. 8
, showing a part of a secondary coil. As shown in
FIG. 8
, the conventional high voltage transformer, which is denoted
120
, has an I-shaped core
121
, and an E-shaped core
123
, both of which are made of silicon steel. A primary coil
125
is connected to an external power supply, (not shown) and a secondary coil
129
is connected to a magnetron (not shown). An insulating member or micasheet
127
made of a suitable insulating material is positioned between the primary and secondary coils
125
and
129
, and a heater coil
131
is positioned between the insulating member
127
and the secondary coil
129
. As illustrated, insulating member
127
may be formed as two separate parts.
Each of the primary and secondary coils
125
and
129
is covered with a respective insulating sheet or covering
133
for insulating the coils
125
and
129
from other components. As illustrated, the respective insulating sheets
133
can be formed of multiple parts. Beside the secondary coil
129
is installed a temperature sensor
135
for detecting temperature of the secondary coil
129
so as to protect the secondary circuit for the secondary coil
129
. The temperature sensor
135
is positioned inside the insulating sheet
133
enclosing the secondary coil
129
as shown in FIG.
9
. Alternately, sensor
135
can be fixed between the secondary coil
129
and the core
121
by a tape (not shown). Another insulating sheet
137
is positioned between the temperature sensor
135
and the secondary coil
129
so as to prevent the temperature sensor
135
from contacting the secondary coil
129
.
In the above-described conventional high voltage transformer for a microwave oven, because the temperature sensor
135
is fixed in position by the insulating sheet
133
enclosing the secondary coil
129
, the insulating sheet
133
can detach from the secondary coil
129
when the high voltage transformer
120
is in operation and the temperature of the high voltage transformer
120
can increase beyond a predetermined value. As a consequence, the temperature sensor
135
cannot be securely disposed at its optimum or desired position with respect to the secondary coil, and under conditions such as those outlined above, the temperature sensor
135
cannot precisely detect the temperature of the secondary coil. In addition, with this conventional configuration, the efficiency of insulation is not optimal. Further, because the temperature sensor
135
is fixed to the secondary coil
129
with the insulating sheet, or in the non-illustrated embodiment, to the fixing tape, the insulating sheet or the fixing tape must be removed by hand for inspecting, repairing or replacing the sensor, thereby decreasing the efficiency of any such inspection, repair or replacement.
SUMMARY OF THE INVENTION
To solve the above discussed problems, it is an object of the present invention to provide a high voltage transformer for a microwave oven in which a temperature sensor is securely positioned at its desired position relative to a secondary coil, thereby improving the detecting accuracy of the temperature sensor, and to provide a method of manufacturing such a transformer.
It is another object of the present invention to provide a high voltage transformer, and a manufacturing method therefor, wherein the associated temperature sensor can be installed and removed in a simple manner so as to permit the sensor to be easily repaired or replaced.
To accomplish these and other objects of the present invention, there is
provided a high voltage transformer for a microwave oven including a core, and primary and secondary coils, wherein the high voltage transformer further comprises an insulation molding part which encloses at least a part of said secondary coil and which includes a sensor accommodating portion, and a temperature sensor disposed or accommodated in said sensor accommodating portion for detecting temperature of the secondary coil.
Preferably, the sensor accommodating portion is formed inside of the
insulation molding part, and the temperature sensor is one of a thermostat and a thermistor. Advantageously, when a thermistor is used, a safety device such as a fuse is also employed.
In an alternative preferred embodiment, the sensor accommodating portion has the shape of a pocket, or is otherwise shaped, so that the temperature sensor can be easily put into, and taken out of, the sensor accommodating portion, and the temperature sensor comprises one of a thermostat, a thermistor and a fuse.
According to a further aspect of the present invention, there is provided a method for manufacturing a high voltage transformer for a microwave oven, the transformer including a core, primary and secondary coils, and a temperature sensor for detecting temperature of the secondary coil and the method including the steps of: accommodating the secondary coil and the temperature sensor in a molder member; molding the secondary coil and the temperature sensor accommodated in the molder member into an insulating molding part accommodating the temperature sensor, and enclosing at least part of the secondary coil such that the temperature sensor is fixed in position relative to the secondary coil.
Advantageously, the molding step comprises molding a temperature sensor accommodating portion into the molding part in which the temperature sensor is accommodated. In a beneficial implementation, the sensor and the secondary coil are molded together such that the sensor is disposed directly adjacent to the secondary coil. Advantageously, the external sensor accommodating portion is formed as a pocket defining member on an outside surface of the insulating molding part. Preferably, the temperature sensor is one of a thermostat and a thermistor.
According to another aspect of the present invention, there is provided a manufacturing method of a high voltage transformer for a microwave oven, the transformer including a core, primary and secondary coils, and a temperature sensor for detecting temperature of the secondary coil, and the method comprising the steps of: providing a molder member for forming an insulating molding part including an external sensor accommodating portion; disposing the secondary coil in the molder member; and molding the secondary coil in the molder member to form the insulating molding part with at least a part of the secondary coil molded therein and to form the external sensor accommodating portion in spaced relation to the secondary coil so as to permit placement of the temperature sensor into, and removal of the sensor from, the sensor accommodating portion. Preferably, the temperature sensor is one of a thermostat, a thermistor and a fuse.
REFERENCES:
patent: 4221949 (1980-09-01), Minakawa
patent: 4763095 (1988-08-0
Hunt, Jr. Ross F.
Ortiz Angela
Stites & Harbison PLLC
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