High-voltage variable resistor

Details High-voltage variable resistor High-voltage variable resistor

2002-10-30

2004-01-13

Easthom, Karl D. (Department: 2832)

Electrical resistors

Mechanically variable

Movable contact electrically adjustable over length of...

C338S160000, C338S184000

Reexamination Certificate

active

06677849

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-voltage variable resistor for regulating a focus voltage or a screen voltage of a TV receiver or other suitable device.
2. Description of the Related Art
A known high-voltage variable resistor for regulating a focus voltage or a screen voltage of a TV receiver is disclosed, for example, on pages 5 and 6 and in
FIG. 1
of Japanese Unexamined Utility Model Registration Application Publication No. 6-2610. Such a high-voltage variable resistor includes a high-voltage variable-resistor substrate having a resistor element and land electrodes provided thereon. The front and rear sides of the base of the high-voltage variable-resistor substrate are electrically connected via through-holes provided at corresponding land electrodes, although this method is not specifically disclosed.
Referring now to
FIG. 6
, an undisclosed high-voltage variable-resistor substrate will be described.
FIG. 6
is a plan view of a known high-voltage variable-resistor substrate
51
.
The high-voltage variable-resistor substrate
51
includes a base
52
having a resistor element
61
and two land electrodes
62
and
63
on the front side thereof. The two land electrodes
62
and
63
include through-holes
64
and
65
, respectively, in which a conductive paste or other suitable material is filled so as to electrically connect the front and rear sides of the base
52
of the high-voltage variable-resistor substrate
51
. However, in the high-voltage variable-resistor substrate
51
used in the above-described known high-voltage variable resistor, the through-holes
64
and
65
are often insufficiently filled with the conductive paste or other suitable material depending upon the variations in printing conditions of the land electrodes, causing faulty electrical continuity between the front and rear sides of the base
52
of the high-voltage variable-resistor substrate
51
, and accordingly, reducing the reliability of the high-voltage variable resistor.
Also, another known high-voltage variable resistor having an insulating case formed by fitting first and second insulating cases together is disclosed, for example, in Japanese Patent Application Publication No. 10-74605. The disclosed high-voltage variable resistor includes the insulating case, an insulating substrate provided in the insulating case and having a variable-resistor circuit pattern on the front surface thereof, and a slider arranged between the front surface of the insulating substrate and the insulating case.
The first and second insulating cases of the known high-voltage variable resistor are engaged with each other in the following manner. As shown in
FIG. 7A
, a front case
100
a
defining the first insulating case includes a side wall
122
at each peripheral side thereof. The side wall
122
includes two flat plate members
121
and a fitting depression
120
provided between the two flat plate members
121
. The side wall
122
also includes an engaging hole
140
provided therein. One end of the engaging hole
140
is open at the inner wall of the fitting depression
120
and the other end is open at the outer wall of the front case
100
a.
Also, as shown in
FIG. 7B
, a rear case
100
b
defining the second insulating case includes a side wall
110
defined by a single flat plate member at each peripheral side thereof. The front of the side wall
110
is fitted into the fitting depression
120
of the front case
100
a
. In addition, the side walls
110
include an opening end
111
in which an engaging projection
130
is provided, and the engaging projection
130
elastically engages the engaging hole
140
. More specifically, as shown in
FIG. 7C
, since the engaging projection
130
and the engaging hole
140
elastically engage each other, the front case
100
a
and the rear case
100
b
are attached together, thereby allowing the insulating case
100
to be formed without using a welding technique. Although only one side wall of the insulating case is illustrated in
FIGS. 7A
to
7
C, the other three side walls are formed in substantially the same manner as described above.
The insulating substrate provided in the insulating case
100
includes a slit at each corner thereof, formed by cutting the insulating substrate from the peripheral side surface towards an inner portion thereof. The slits include elastic conductors, such as coil springs or conductive rubbers, fitted therein so as to sandwich the insulating substrate. The conductors are electrically connected to an input-terminal electrode and a ground terminal electrode provided on the front surface of the insulating substrate. Also, the conductors are electrically connected to input terminals and ground terminals inserted from the rear surface of the insulating substrate of the insulating case. As described above, the conductors define electrical conducting members between the input terminals and the ground terminals and the input-terminal and ground-terminal electrodes, respectively. In addition, when the insulating case is formed by fitting, the conductors are pressed by the inner bottom surfaces of the front and rear cases
100
a
and
100
b
such that the insulating substrate is sandwiched and held by this pressing force in the depth direction thereof.
However, in the known high-voltage variable resistor, since the engaging projection
130
of the rear case
100
b
is provided in the opening end
111
of the side walls
110
, and also one end of the engaging hole
140
of the front case
100
a
is open at the inner wall of the fitting depression
120
and the other end is open at the outer wall of the front case
100
a
, the insulating case
100
has a gap
150
, in communication with the inside thereof, provided at the engaging portion between the engaging projection
130
and the engaging hole
140
. Accordingly, there is a risk that dust, moisture, or other impurities will intrude into the inside of the insulating case
100
of the variable resistor through the gap
150
, and a poor connection or deteriorated characteristics may occur. Also, the gap
150
greatly reduces the dielectric strength of the variable resistor.
In addition, the known high-voltage variable resistor has a problem in that not only does fitting the conductors in the slits provided in the insulating substrate require an additional manufacturing step, but also the slits reduce the durability of the insulating substrate and increase the defective ratio of products through breakage.
SUMMARY OF THE INVENTION
In order to overcome the above-described problems, preferred embodiments of the present invention provide a high-voltage variable resistor including front and rear cases defining an insulating case that are reliably brought into close contact and engaged with each other without producing a gap at any engaging portions in the side walls of the front and rear cases, an insulating substrate is fixed in the insulating case without forming a slit therein, and also input terminals and ground terminals are electrically connected with corresponding terminal electrodes on the front surface of the insulating substrate.
A high-voltage variable resistor according to preferred embodiments of the present invention includes an insulating case, having first and second insulating cases, and a high-voltage variable-resistor substrate. The high-voltage variable-resistor substrate includes a base having a resistor element on the front surface thereof, a plurality of through-hole electrodes arranged so as to extend through the base, and at least one land electrode provided on each of the front and rear surfaces of the base and connected to the through-hole electrodes. The plurality of the through-hole electrodes is provided at the land electrode of the high-voltage variable-resistor substrate, the high-voltage variable-resistor substrate is housed in the insulating case, at least one conductor is disposed in the second insulating case, and the conductor and the land electrode on the rear surface of the high-voltage v

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