Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Distributed parameter resonator-type magnetron
Reexamination Certificate
1998-04-07
2001-04-24
Lee, Benny T. (Department: 2502)
Electric lamp and discharge devices: systems
Combined load device or load device temperature modifying...
Distributed parameter resonator-type magnetron
C445S035000
Reexamination Certificate
active
06222319
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetron apparatus for use in microwave ovens and the like, and a manufacturing method for the same.
The magnetron apparatus is a microwave oscillating tube which operates at a fundamental frequency of, for example, 2,450 MHz, and is used as a high frequency source in electric apparatuses using microwaves such as microwave heaters and microwave discharge lamps. A typical configuration of the magnetron apparatus is such that a cathode and an anode are disposed coaxially cylindrically. More specifically, the magnetron apparatus comprises a coiled cathode, an anode cylinder disposed with the cathode as the central axis, and plural anode segments radially arranged around the central axis in a space inside the anode cylinder for defining a resonant cavity. The magnetron apparatus further comprises a pair of magnetic pole pieces disposed at upper and lower open ends of the anode cylinder and magnetically associated with an annular permanent magnet, plural strap rings for electrically interconnecting the anode segments, and an antenna with one end connected to one of the anode segments for discharging microwaves.
In the above-mentioned magnetron apparatus, after the anode cylinder, the anode segments, the antenna, the strap rings and the magnetic pole pieces are integrally assembled as an anode assembly, the cathode is disposed in the central portion of the anode assembly. In the magnetron apparatus, as well known, the precision with which the components are assembled greatly influences the performance of the apparatus, and the arrangement of the plural anode segments for defining a desired resonant cavity inside the anode cylinder are particularly important. Therefore, it is a technical problem of the magnetron apparatus to coaxially and radially secure the plural anode segments with high precision so as to be equally spaced on the inner surface of the anode cylinder with a predetermined distance from the cathode.
As a conventional manufacturing method for the magnetron apparatus, a brazing and soldering method is known in which the anode segments are pressed against the inner surface of the anode cylinder by use of a temporary assembling pin and all the anode segments are secured to the inner surface at once with a brazing filler metal as disclosed in, for example, examined and published Japanese patent application TOKKO Sho 57-18823.
Hereinafter, the conventional magnetron apparatus and the manufacturing method will be described with reference to FIG.
16
and FIG.
17
.
FIG. 16
is a partially cutaway perspective view showing a configuration of a principal part of an anode assembly in a conventional magnetron apparatus before a brazing filler metal is melted.
FIG. 17
is a cross sectional view showing the configuration of the principal part of the anode assembly in the conventional magnetron apparatus after the brazing filler metal is melted.
As shown in FIG.
16
and
FIG. 17
, plural anode segments
52
(
52
a
,
52
b
,
52
c
,
52
d
, as depicted in
FIG. 16
) are coaxially radially arranged inside an anode cylinder
51
. Specifically, for example, ten anode segments
52
are equally spaced inside the anode cylinder
51
. Each of the anode segments
52
is formed into a substantial rectangular shape having a longitudinal size of 9.5 mm and a lateral size of 13 mm, for example. In each of the anode segments
52
, one end surface on the shorter side is secured to the inner surface of the anode cylinder
51
. These anode segments
52
are pressed against the inner surface of the anode cylinder
51
by a jig pin
40
, which is a temporarily used assembling pin, shown by the dash and dotted line of the figure, and the above-mentioned one end surface is secured to the inner surface of the anode cylinder
51
by melting a wire-form brazing filler metal
56
(FIG.
16
).
When a non-illustrated coiled cathode is disposed along the central axis of the anode cylinder
51
, each end surfaces of the anode segments
52
on the central side in the direction of the arrangement, i.e. an end surface each of the anode segments
52
opposed to the above-mentioned one end surface (hereinafter, the end surface on the central side will be referred to as an “inner end surface”) is situated with a predetermined distance from the cathode, so as to define a desired resonant cavity inside the anode cylinder
51
.
At opposite end surfaces (i.e., upper surface and lower surface) on the longer side of each of the anode segments
52
, strap ring grooves
53
a
and
53
b
are provided for brazing two pairs of strap rings
54
(
54
a
and
54
b
) and
55
(
55
a
and
55
b
). At the upper end surface of each of the anode segments
52
where the strap ring groove
53
a
is provided, a terminal groove
53
c
is provided for connecting one end of a non-illustrated antenna.
The strap rings
54
b
and
55
a
are brazed to every two anode segments
52
a
,
52
c
, - - - , and the strap rings
54
a
and
55
b
are brazed to the remaining anode segments
52
b
,
52
d
, - - - . A plating layer (not shown) of the brazing filler metal
56
is formed on the surface of each of the strap rings
54
and
55
, and when the brazing filler metal
56
is melted to secure the one end surfaces of the anode segments
52
to the inner surface of the anode cylinder
51
, the plating layer is also melted, so that the strap rings
54
and
55
are secured to the corresponding anode segments
52
.
The above-mentioned anode cylinder
51
, anode segments
52
, strap rings
54
and
55
, and antenna (not shown) are made of, for example, oxygen free copper. The jig pin
40
is made of a metal member containing silicon nitride (Si
3
N
4
), and the surface of a cylindrical portion which comes into contact with the inner end surface of each of the anode segments
52
is formed so as to be as smooth as the mirror finished surface. The brazing filler metal
56
is made of an alloy of silver and copper, and the strap rings
54
and
55
and the antenna (not shown) are made of copper having a silver plating layer provided on the surface thereof.
In such a conventional manufacturing method for the magnetron apparatus, first, the plural anode segments
52
and the strap rings
54
and
55
are placed in the respective positions inside the anode cylinder
51
by use of a non-illustrated temporary assembling jig. Then, the jig pin
40
is moved along the central axis of the anode cylinder
51
and press-fit from below into the central portion in the direction of the arrangement of the anode segments
52
(the central portion of the anode cylinder
51
) as shown by the arrow Y of FIG.
16
. So that the jig pin
40
contacts with the inner end surfaces of the anode segments
52
. Thereby, the anode assembly is maintained in a preassembled condition where the one end surface each of the anode segments
52
are pressed against the inner surface of the anode cylinder
51
by the jig pin
40
. Hereafter, only the temporary assembling jig is detached, and the brazing filler metal
56
is placed on the end surfaces on the longer side of the anode segments
52
so as to be in contact with the inner surface of the anode cylinder
51
as shown in FIG.
16
. After one of the magnetic pole pieces (not shown) is attached to an upper open end of the anode cylinder
51
, one end of the antenna (not shown) is attached to one of the anode segments
52
. Then, the anode assembly in the preassembled condition is heated to a predetermined temperature (for example, 800 to 900° C.) in a non-illustrated furnace. Thereby, the brazing filler metal
56
is melted and flows into a clearance between the inner surface of the anode cylinder
51
and the one end surface each of the anode segments
52
caused by expansion. At this time, the plating layers on the strap rings
54
and
55
and the antenna (not shown) are also melted. Hereafter, by taking the anode assembly out of the furnace while maintaining the preassembled condition, and cooling it, the inner surface of the anode cylinder
51
and the one end surface e
Nakano Yasunobu
Ochiai Hiroshi
Yoshihara Masanori
Lee Benny T.
Matsushita Electronics Corporation
Sheridan & Ross P.C.
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