Double-bellows vacuum variable capacitor

Details Double-bellows vacuum variable capacitor Double-bellows vacuum variable capacitor

2000-06-08

2001-07-31

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrostatic capacitors

Variable

C361S277000, C361S278000, C361S279000, C361S282000

Reexamination Certificate

active

06268995

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is directed to variable capacitors and, more particularly, to double-bellows vacuum variable capacitors.
A known water-cooled vacuum variable capacitor
10
previously marketed by Jennings Technology, the owner of this patent, having a double-bellows configuration is shown partially in section in FIG.
1
. The capacitor
10
generally included a variable end assembly
12
and a fixed end assembly
14
connected together by a body assembly
16
. The end assemblies
12
,
14
were typically fabricated from steel and, in some instances, were partially silver plated. The body assembly
16
was an insulator such as, for example, ceramic that mechanically coupled the end assemblies
12
,
14
while keeping the end assemblies
12
,
14
electrically insulated from one another.
Inside the capacitor
10
was a fixed can structure
20
that formed the first half of the capacitor
10
. The second half of the capacitor
10
was formed by a variable can structure
22
, which was mounted to a variable can plate
24
. To change the capacitance of the capacitor
10
, the variable can structure
22
and the can plate
24
were moved with respect to the fixed can structure
20
through the use of an adjustment mechanism
30
.
A vacuum bellows
36
was used to seal the adjustment mechanism
30
from the rest of the capacitor
10
. The vacuum bellows
36
was sealed to both the variable end assembly
12
and the variable can plate
24
so that any volume outside the vacuum bellows
36
, shown generally as reference numeral
38
in
FIG. 1
, could be evacuated by attaching a vacuum source to one or both cap seals
40
,
42
.
To facilitate cooling, the capacitor
10
included a water jacket bellows
44
. The water jacket bellows
44
was disposed between the vacuum bellows
36
and the adjustment mechanism
30
and was sealed between the variable can plate
24
and the variable end assembly
12
. To cool the capacitor
10
, water was circulated through the volume between the vacuum and water jacket bellows
36
,
44
(shown generally as reference numeral
46
), via inlet/outlet ports
50
,
52
.
Typically, the vacuum and water jacket bellows
36
,
44
were fabricated from C510 phosphor bronze and had no perforations or holes therein because holes or perforations would either make it impossible to establish the vacuum or would allow water to escape from between the bellows
36
,
44
. As shown in
FIG. 1
, the bellows
36
,
44
were convoluted, or corrugated, to allow the bellows
36
,
44
to flex as the variable can plate
24
was moved.
The force required to move the can plate
24
was proportional to the product of the cross sectional area of vacuum bellows
36
and the pressure differential across the vacuum bellows
36
. Additionally, the current carrying capacity of the capacitor
10
was directly proportional to the diameter of the vacuum bellows
36
, because the vacuum bellows
36
carried the current in the capacitor
10
. Accordingly, the more current that the capacitor
10
needed to carry, the more force it took to move the can plate
24
of the capacitor
10
.
During operation, the variable end and fixed end assemblies
12
,
14
were connected into a circuit requiring capacitance. Current would flow between the variable end assembly
12
and the fixed end assembly
14
through the bellows
36
,
44
, which connected the variable end assembly
12
to the variable can plate
24
. The variable can plate
24
was, in turn, capacitively coupled to the fixed end assembly
14
, via the fixed and variable can structures
20
,
22
. As the capacitor
10
was operated, water was circulated through the volume
46
between the bellows
36
,
44
, via the inlet/outlet ports
50
,
52
. Additionally, a motor was usually coupled to the adjustment mechanism
30
to tune the capacitor
10
by moving the variable can plate
24
.
SUMMARY OF THE INVENTION
The present invention is directed to variable capacitors, and more particularly to double-bellows vacuum variable capacitors.
According to a first aspect, the present invention may include a first electrical terminal structure, a second electrical terminal structure, a housing and a vacuum bellows disposed in the housing, the vacuum bellows having a first diameter, the vacuum bellows and at least a portion of the housing defining an interior vacuum chamber having a pressure disposed therein that is less than atmospheric pressure. Additionally the present invention may include a current-carrying bellows disposed in the housing, the current carrying bellows having a second diameter larger than the first diameter, the current-carrying bellows comprising a conductive material and surrounding the vacuum bellows, the current-carrying bellows being disposed in the interior vacuum chamber, the current-carrying bellows being conductively coupled to the second electrical terminal structure, a fixed-position capacitor structure conductively coupled to the first electrical terminal structure and a variable-position capacitor structure conductively coupled to the second electrical terminal structure, the variable-position capacitor structure being movable relative to the fixed-position capacitor structure to generate a variable capacitance between the capacitor structures.
The invention may also include a vacuum bellows fabricated from stainless steel and a current-carrying bellows fabricated from a metal having a high copper content, such as phosphor bronze. Additionally, the current-carrying bellows may be fabricated from a porous material or may be perforated.
According to a second aspect, the present invention may include a first electrical terminal structure, a second electrical terminal structure, a housing and a substantially air-tight separation member disposed in the housing, the substantially air-tight separation member and at least a portion of the housing defining an interior vacuum chamber having a pressure disposed therein that is less than atmospheric pressure. The present invention may also include a perforated current-carrying structure disposed in the housing, the current-carrying structure comprising a conductive material and being conductively coupled to the second electrical terminal structure, a fixed-position capacitor structure conductively coupled to the first electrical terminal structure and a variable-position capacitor structure conductively coupled to the second electrical terminal structure, the variable-position capacitor structure being movable relative to the fixed-position capacitor structure to generate a variable capacitance between the capacitor structures.
According to a third aspect, the present invention may include a first electrical terminal structure, a second electrical terminal structure, a housing and a substantially air-tight separation member disposed in the housing, the substantially air-tight separation member having a first diameter, the substantially air-tight separation member and at least a portion of the housing defining an interior vacuum chamber having a pressure disposed therein that is less than atmospheric pressure. The present invention may also include a current-carrying structure disposed in the housing, the current carrying structure having a second diameter larger than the first diameter, the current-carrying structure comprising a conductive material and surrounding the substantially air-tight separation member, the current-carrying structure being disposed in the interior vacuum chamber, the current-carrying structure being conductively coupled to the second electrical terminal structure, a fixed-position capacitor structure conductively coupled to the first electrical terminal structure and a variable-position capacitor structure conductively coupled to the second electrical terminal structure, the variable-position capacitor structure being movable relative to the fixed-position capacitor structure to generate a variable capacitance between the capacitor structures.
The features and advantages of the invention will be apparent to those of ordin

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