Electric lamp and discharge devices – Cathode ray tube
Reexamination Certificate
2000-07-12
2002-12-31
Dawson, Robert (Department: 1712)
Electric lamp and discharge devices
Cathode ray tube
C445S022000, C445S023000, C445S024000, C445S036000, C445S045000, C106S287100, C106S287150, C525S474000, C525S477000, C525S478000, C528S015000, C528S024000, C528S031000, C528S032000, C528S034000, C528S037000, C528S033000, C156S329000, C252S500000
Reexamination Certificate
active
06501212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of insulating a cathode ray tube used for electrical equipment having high voltage electrodes, in particular color television receivers, video and computer monitors, etc., applied to the insulation between stem pins to which a high voltage is supplied and to an electrical insulator composition for a cathode ray tube used for insulation between high voltage stem pins of a cathode ray tube and between other electrodes to which a high voltage is supplied.
2. Description of the Related Art
Generally, as shown in
FIGS. 1B and 1C
, a stem
20
is integrally attached to a neck of a cathode ray tube by fusing together the glass at is periphery and the glass around the end edge of the neck
1
a
. A stem base
30
is attached to the stem
20
. The stem
20
is provided with a plurality of stem pins
21
at its periphery serving as electrodes in a predetermined pin circle shape and with a tip
22
projecting from its center portion. Note that the illustration of the stem pins
21
is omitted in FIG.
1
C.
The stem base
30
is made of a polycarbonate or other plastic having an excellent insulating property and comprises, as shown in
FIGS. 1A
,
1
B, and
2
, a circular base
31
, a tip holder
32
provided at the center portion of the base
31
for holding the tip
22
of the stem
20
, a sector-shaped stem pin holder
33
provided on the base
31
in a state also serving as a part of a side wall of the tip holder
32
for holding the high voltage stem pins
21
, and a skirt portion
34
extending downward from the peripheral edge of the base
31
. The base
31
is formed, corresponding to the stem pins
21
, with pin through holes
35
through which the stem pins
21
are inserted at the time of attaching the stem base
30
to the stem
20
.
As a method of the related art for electrical insulation between the stem pins
21
of the stem
20
to which the stem base
30
is attached, a method of interposing an electrical insulator
40
shown in
FIGS. 3A and 3B
between the stem
20
and the stem base
30
as shown in
FIG. 1B
is known. The electrical insulator
40
is formed as a thick disk shape and is formed at its center portion with a tip through hole
41
for inserting the tip
22
of the stem
20
. Further, pin through holes
42
through which all of the stem pins
21
including the high voltage stem pins are inserted at the time of placing the electrical insulator
40
on the stem
20
are formed corresponding to the stem pins
21
.
The electrical insulator
40
is prepared by, for example in Japanese Unexamined Patent Publication (Kokai) No. 8-111191, extruding into a tape shape a viscous electrical insulator composition comprising
100
parts by weight of a silicone compound having an electrical insulation property plus 2 parts by weight of a silane coupling agent and 1.5 parts by weight of an organic peroxide (hereinafter referred to as the “insulator composition”) and punching out a disk shape using a die set. Further, Japanese Unexamined Patent Publication (Kokai) No. 7-94100 discloses a method of obtaining an electrical insulator by molding a viscous insulator comprising a silicone compound similar to the above publication into a flat plate of a large area and punching out disk shapes by a molding tool.
In both publications, first, the electrical insulator
40
shown in
FIG. 4A
is adhered to the back of the base
31
of the stem base
30
shown in
FIG. 4B
as shown in FIG.
4
C. Then, the stem pins
21
are inserted through the pin through holes
42
of the electrical insulator
40
and the pin through holes
35
of the stem base
30
and the tip
22
is inserted through the tip through hole
41
of the electrical insulator
40
and the tip holder
32
of the stem base
30
. In that state, the stem base
30
is attached to the stem
20
of the cathode ray tube
1
, then pressed and heated to bond it so as to achieve electrical insulation between the stem pins
21
.
Summarizing the problems to be solved by the present invention, in the inventions disclosed in Japanese Unexamined Patent Publication (Kokai) Nos. 8-111191 and 7-94100, however, since both punch out disk shapes from an insulator composition of a tape shape or a flat plate shape by a die set or a molding tool, the portion remaining after punching becomes wasted, that is, there is a disadvantage of a loss of the material loss.
Also, because the disk is produced by punching, it is difficult to mold the electrical insulator into a shape corresponding to a complicatedly shaped stem or stem base of a cathode ray tube. As a result, it ends up allowing air to become entrained between the stem base and the stem at the time of attaching the two. When air is entrained, disadvantages are caused such as a decline in the insulation property between the stem pins
21
due to the entrained air, an inability to draw out 100% of the electrical characteristics of the cathode ray tube, and insufficient bonding force between the stem and the stem base.
Note that since it is difficult to mold an electrical insulator into a complicated shape in the related art as explained above, an electrical insulator of substantially the same size as the base of the stem base has been prepared to provide insulation between all stem pins projecting from the stem. However, in actuality, it is possible to achieve sufficient electrical characteristics of the cathode ray tube by just insulation between the high voltage stem pins among the plurality of stem pins.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of insulating a cathode ray tube enabling production of an electrical insulator without loss by efficiently using the electrical insulator composition.
Another object of the present invention is to provide a method of insulating a cathode ray tube enabling easy molding of an electrical insulator into a shape corresponding to a complicatedly shaped stem and stem base of the cathode ray tube by transfer molding and thereby enabling attachment of the stem base to the stem without entrainment of air.
A still other object of the present invention is to provide an electrical insulator composition for a cathode ray tube which is very effective in realizing a cathode ray tube improved in bonding of the stem and the stem base and improved in the insulation property between the high voltage stem pins by the above method of insulating a cathode ray tube.
According to a first aspect of the present invention, there is provided a method of insulating a cathode ray tube for insulation between stem pins using an electrical insulator when attaching to a stem, which is provided at the cathode ray tube and has a tip and stem pins projecting therefrom, an insulating stem base, which comprises a base through which pin through holes are formed and has provided projecting from the front surface thereof a tip holder, in a state with the stem pins inserted through the pin through holes and the tip held in the tip holder, comprising the steps of molding an electrical insulator composition comprising an uncured self-adhesive silicone rubber into a predetermined sheet shape by using a transfer mold to obtain an electrical insulator, arranging the electrical insulator in a state extending from the positions of the pin through holes on the back of the base of the stem base to the tip holder and adhering it to the back of the base, folding back the portion of the electrical insulator extending to the tip holder to the inside surface of the tip holder, and attaching the stem base to the stem.
According to the above aspect of the present invention, since an electrical insulator composition is molded by using a transfer mold (hereinafter the molding will be referred to as “transfer molding”) to obtain an electrical insulator, there is no loss of the electrical insulator composition such as when obtaining an electrical insulator by using a die set or molding tool. Also, due to the transfer molding, it becomes possible to easily mold the electrical in
Kanno Hirokazu
Setsuda Takashi
Tomaru Kazuhiko
Yamaguchi Hisaharu
Yoneyama Tsutomu
Dawson Robert
Kananen, Esq. Ronald P.
Rader & Fishman & Grauer, PLLC
Robertson Jeffrey B.
Sony Corporation
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