Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
1999-08-09
2001-10-23
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S306100, C361S307000
Reexamination Certificate
active
06307729
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a vacuum capacitor and its manufacturing method for the same, the vacuum capacitor being suitably used for an oscillation circuit of a high power transmitter, a high-frequency power supply of a semiconductor manufacturing device, or a tank circuit of an inductive heating device.
b) Description of the Related Art
A previously proposed vacuum capacitor includes an insulating envelope made of ceramics or glass having upper and lower ends to which upper and lower end electrodes each made of copper are hermetically sealed via upper and lower metal fittings so that a vacuum vessel is formed. A plurality of copper made, cylindrically shaped electrode plates of different diameters are extended vertically from an inner surface of the upper end electrode concentrically at equal intervals to form first cylindrical electrodes.
In addition, another plurality of copper made, cylindrically shaped electrode plates of different diameters are extended vertically from an inner surface of the lower end electrode and interposed between each of the first cylindrical electrodes to form second cylindrical electrodes.
It is noted that a hole is penetrated through a center portion of the upper end electrode to be used for exhausting air from the vacuum vessel described above, an exhaust tube made of copper is fitted around the hole, and an exhaust tube cover covers the exhaust tube is screwed into a tap hole installed on an outer surface of each end electrode.
Next, a previously proposed manufacturing method will be described below.
First, a plurality of concentrically arranged circular grooves are provided on the inner surface of the lower end electrode. Each cylindrical electrode plate constituting the second cylindrical electrode is mounted on the circular groove so that each cylindrical electrode plate is concentrically arranged. Thereafter, each cylindrical electrode plate is brazed or welded to the lower end electrode.
Thereafter, the metal fittings are conjoined to the respective ends of the insulating envelope.
Thereafter, another plurality of concentrically arranged circular grooves are formed on the inner surface of the upper end electrode. Each cylindrical electrode plate constituting the first cylindrical electrode is mounted on the circular groove so that each cylindrical electrode plate is concentrically arranged. At this time, the exhaust tube is fitted around the hole. The upper end electrode, each cylindrical electrode plate, and exhaust tube are brazed or welded.
Next, the insulating envelope with the respective metallic fittings are mounted on the inner surface of the lower end electrode having the cylindrical electrode and the inner surface of the upper electrode with the one metallic fittings having the cylindrical electrode and exhaust tube is mounted on the inner surface of the lower end electrode. Then, a plurality of jigs to concentrically arrange the end electrodes are fitted into the inner surface of the upper end electrode.
In this state, the brazing or welding is performed between the metal fitting and the upper end electrode and between the metallic fitting and the lower end electrode.
Next, a vacuum exhaust device is attached to the exhaust tube, a heat vacuum is performed with the vacuum vessel, and, thereafter, the exhaust tube is pinched to be hermetically sealed.
It is noted that the circular groove may not be provided on the lower end electrode and, in place thereof, a convex portion may be provided on a center portion of the inner side of the lower end electrode, a letter-U shaped portion which is bent in the inner side of a diameter direction is provided on a junction end between each cylindrical electrode plate constituting the second cylindrical electrode and the end electrode is provided, and each cylindrical electrode plate may concentrically be arranged so that the letter-U shaped portion is fitted to the convex portion and adjacent letter-U shaped portion. The same thing is applied equally well to the upper end electrode.
SUMMARY OF THE INVENTION
It is, however, necessary to carry out a heat evacuation (heat air exhausting) to render the vacuum vessel in the vacuum state for each of the previously proposed vacuum capacitors and manufacturing method described in the BACKGROUND OF THE INVENTION for the same.
This causes a prevention of the previously proposed vacuum capacitor from a mass production.
On the contrary, to produce a large quantity of the previously proposed vacuum capacitors, a large quantity of the heat evacuation (air exhaust) device are required. Furthermore, since the air exhaust tube and the exhaust tube covering are required, an installation limitation on the attachment of the vacuum capacitor is placed. In addition, although each of the first and second cylindrical electrodes is important to equalize the spatial intervals in their radial directions of the respective first and second cylindrical electrodes, it is also important to equalize the spatial intervals in their axial directions of the respective first and second cylindrical electrodes in terms of a performance of the vacuum capacitor.
It is therefore an object of the present invention to provide improved vacuum capacitor and manufacturing method for the same which are suitable for the mass production, are cost effective, do not receive the installation limitation, and can easily equalize the spatial intervals in the axial directions of the cylindrical electrodes.
The above-described object can be achieved by providing a vacuum capacitor comprising: an insulating envelope; a pair of end electrodes, each end electrode being brazed to a corresponding end of the insulating envelope and being formed together with the insulating envelope to constitute a vacuum vessel; a plurality of cylindrical electrode plates constituting a pair of cylindrical electrodes, each cylindrical electrode plate constituting one of the pair of cylindrical electrodes having a mutually different diameter and being extended along the insulating envelope from an inner surface of the corresponding one of the pair of end electrodes so as to be inserted into a space between the mutually adjacent cylindrical electrode plates constituting the other of the pair of cylindrical electrodes; and a positioning member to position one of the pair of cylindrical electrodes to the other of the pair of cylindrical electrodes in such a manner as to equalize a spatial interval between each cylindrical electrode plate constituting the one of the pair of cylindrical electrodes and that constituting the other of the pair of cylindrical electrodes.
The above-described object can also be achieved by providing a manufacturing method for a vacuum capacitor, comprising: a) brazing at least one of a pair of cylindrical electrodes to an inner surface of a corresponding one of a pair of end electrodes, the pair of end electrodes being attached on respective ends of an insulating envelope to form a vacuum vessel and each of the pair of cylindrical electrodes having a plurality of cylindrical electrode plates, each cylindrical electrode plate having a different diameter, being extended from the inner surface of the corresponding one of the pair of end electrodes, and being inserted into a space between the mutually adjacent cylindrical electrode plates constituting the other of the pair of cylindrical electrodes; b) provisionally assembling the vacuum capacitor with at least the other of the pair of end electrodes having the other of the pair of cylindrical electrodes provisionally mounted on the corresponding other of the respective ends of the insulating envelope via a brazing material; and c) heat brazing the provisionally assembled other of the pair of end electrodes to the corresponding one of the respective ends of the insulating envelope under a non-oxidization atmosphere to make an inner space of the vacuum vessel in a vacuum state.
REFERENCES:
patent: 3576479 (1971-04-01), Oeschger
patent: 4177495 (1979-12-01), Perret
patent: 5-41335 (1993-02-01), N
Fukai Toshimasa
Ito Takamitsu
Dinkins Anthony
Foley & Lardner
Kabushiki Kaisha Meidensha
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