Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Distributed parameter resonator-type magnetron
Reexamination Certificate
2000-09-08
2003-12-30
Lee, Benny T. (Department: 2817)
Electric lamp and discharge devices: systems
Combined load device or load device temperature modifying...
Distributed parameter resonator-type magnetron
C315S039510
Reexamination Certificate
active
06670761
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetron, and more particularly, to a strap in a magnetron.
2. Background of the Related Art
Referring to
FIG. 1
, a general magnetron is provided with a cylindrical anode. body
11
, anode vanes
12
fitted to an inside wall of the anode body
11
in a radial direction, a resonant cavity (not shown) having straps
13
connected to the anode vanes
12
alteratively through two holes
12
a
and
12
b
in each of the anode vanes, a cathode
15
on a central portion of the magnetron having a helical filament
14
serving as a cathode
15
, an antenna
16
fitted to one of the anode vanes
12
, a plurality of cooling fins
17
fitted to an outer circumferential surface of the anode body, a yoke
18
a
and
18
b
divided into upper and lower plates for protecting the cooling fins and guiding external air into the cooling fins
17
, permanent magnets
19
of N-S poles on top and bottom of the anode body
11
for forming static manetic fields, and a filter box
20
(See
FIGS. 2A
,
2
B.)
The operation of the general magnetron will be explained.
Electrons emitted upon heating the filament
14
receive forces of the static electric field provided between the cathode and the resonant cavity and the static magnetic fields provided in up and down direction of the resonant cavity by the permanent magnets
19
, to evolve into a cycloidal movement in an operation space between the cathode and the resonant cavity, when the electrons interact with a high frequency electric field already provided between the anode vanes
12
, to move toward the resonant cavity gradually during which most of electron energy is converted into a high frequency energy. The high frequency energy is accumulated in the resonant cavity (not shown) and emitted to outside of the magnetron through an antenna
16
. On the other hand, the energies, the electrons are holding, are converted into thermal energies in the resonant cavity. The heat generated at the anode vanes
12
is cooled down by the plurality of cooling fins
17
fitted to the outer circumferential surface of the anode body
11
, thereby preventing deterioration of performance of the magnetron caused by the heat.
A first exemplary related art magnetron will be explained based on the foregoing general
Referring to
FIGS. 2A and 2B
, the first exemplary related art magnetron is provided with two ring form of straps
13
of stainless steel, and a plurality of anode vanes
12
each having two holes
12
a
and
12
b
in up and down portions of central portions thereof with the straps
13
passed therethrough. Two pieces of the strap
13
will be called as a first strap and a second strap
13
a
and
13
b
, and the two holes
12
a
and
12
b
in each of the plurality of anode vanes
12
will be called as a first hole
12
a
for the smaller one and a second hole
12
b
for the larger one, which will be explained in more detail. The first strap
13
a
passes through the first hole
12
a
in the odd numbered anode vane
12
with contact thereto, and the second hole
12
b
in the even numbered anode vane without contact thereto according to an order of disposal of the plurality of anode vanes
12
, to connect the plurality of the anode vanes
12
at fixed intervals. The second strap
13
b
passes through the first hole
12
a
in the even numbered anode vane
12
with contact thereto, and the second hole
12
b
in the odd numbered anode vane
12
without contact thereto according to an order of disposal of the plurality of anode vanes
12
, to connect the plurality of the anode vanes
12
at fixed intervals. The first and second straps
13
a
and
13
b
are connected alternatively to odd numbered and even numbered anode vanes respectively, for forming different polarities between adjacent anode vanes
12
, to form static electric fields.
However, the related art a magnetron has the following problems.
The straps
13
(hereafter called as “center type strap”) of stainless steel applied to the related art magnetron with a power higher than 1.7KW requires to pass through the anode vanes
12
disposed at fixed intervals one by one, that results in a significant amount of productivity loss. Moreover, the center type strap
13
is required to cut for inserting into the holes
12
a
and
12
b
in the anode vanes
13
, and to weld the cut ends together once the insertion is completed, when, for good appearance sake, the welding is made at the first hole
12
a
in the anode vane
12
or the two cut ends are welded the same as an original state, which are inconvenient and complicated in fabrication. Therefore, a simple strapping method is in need, which can solve the foregoing fabrication problem to improve a productivity while characteristics of the strap and the magnetron are equal, or similar to the related art.
Referring to
FIGS. 3A and 3B
showing a second exemplary related art magnetron for a microwave oven of i KW, the second exemplary related art magnetron is provided with one pair of two ring formed straps
22
with different diameters(the greater diameter strap is called as “outer strap
22
b
”, and the smaller diameter strap is called as “inner strap
22
a
”) of oxygen free copper(hereafter called as “side type inner and outer straps”), and a plurality of anode vanes
21
each having a notch in top and bottom to form circular grooves in top and bottom of the plurality of anode vanes in overall such that every other anode vane
21
is in contact with the one of the outer strap
22
b
and the inner strap
22
a
for inducing a static electric field, which will be explained in detail. The notches in odd numbered anode vanes
21
and even numbered anode vanes
21
are formed to have different shapes(a first notch shape
21
a
and a second notch shape
21
b
), such that, with respect to the top side groove, the first notch. shape
21
a
for the odd numbered anode vane
21
is not come into contact with the inner strap
22
a
, but with the outer strap
22
b
, and the second notch shape
21
b
for the even numbered anode vane
21
is come into contact with the inner strap
22
a
, but not with the outer strap
22
b
. The notches in the bottom side have shapes opposite to the top side notches, such that fashion of contact of the inner strap and the outer strap to the odd number and even numbered anode vanes is opposite. Thus, the second exemplary related art strap requires neither the cutting of the strap, nor the insertion of the strap into the holes in the anode vanes, both of which are required in the first exemplary related art magnetron, to permit a high productivity and convenience in fabrication.
However, if a high voltage is applied to the magnetron with the second exemplary related art magnetron for providing a power higher than 1.7KW will cause the following problems. That is, in general, the magnetron has an efficiency of 70% to waste about 30% as heat such that the higher the power of the magnetron, the greater the heat loss wasted at the anode, to cause a problem in securing a thermal stability of the high powered magnetron, particularly, the resonant cavity is subjected to a high thermal stress, of which the most intense part is the very side type inner and outer straps
22
, because the inner and outer straps
22
are next to the thermal electrons emitted from the cathode, directly affected by the cycloidal movement of the thermal electrons, and formed of oxygen free copper.
Though the oxygen free copper is used widely owing to its good thermal conductivity, the material is liable to deformation and has a weak strength, such that, if the material is subjected to a relatively high thermal stress, the material is deformed, and the side type strap
22
is broken as fatigue is accumulated from prolonged use. That is, though a stable lifetime of the inner and outer strap
22
of oxygen free copper can be secured within a usual power range of the microwave oven magnetron, it is impossible to apply the inner and outer strap
22
of oxygen free copper to a magnetron having an aver
Lee Jong Soo
Lee Yong Soo
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