Electric lamp and discharge devices – With envelope – Having base and connector
Reexamination Certificate
2001-01-17
2003-03-04
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With envelope
Having base and connector
C313S318030, C313S318050, C313S318120, C439S683000, C439S181000, C439S182000
Reexamination Certificate
active
06528932
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the structure of a CRT (Cathode-Ray-Tube) socket for connecting a cathode ray tube used in a color television, etc., and particularly relates to a CRT socket for reliably insulating a focus contact and a signal contact from each other.
2. Description of the Background Art
Referring now to
FIGS. 9 and 10
, a base insertion hole
101
, in a conventional CRT socket
100
, is formed in an insulating housing
102
. A plurality of signal contacts
103
,
103
, —and focus contacts
104
,
104
, —are formed at predetermined intervals in the insulating housing
102
, around the outside of the base insertion hole
101
, on the same circular circumference concentric to the base insertion hole
101
.
A columnar base
100
a
of a CRT tube is inserted into the base insertion hole
101
and connected from a front face side (an upper side in
FIG. 10
) of the CRT socket
100
to the base insertion hole
101
. A signal pin
100
b
and a focus pin
100
c
, arranged on the same circular circumference around the base
100
a
, respectively, are in physical and electrical contact with the signal contact
103
and the focus contact
104
facing the front face side.
The signal contact
103
and the focus contact
104
both have a conductive metallic plate that has been press-worked and formed in a bottle type (sometimes known as a banana plug) in which a connecting portion has a cylindrical shape and a drawn intermediate portion. The columnar signal pin
100
b
and the focus pin
100
c
are inserted into the drawn portion and are secured in place by a predetermined contact pressure.
A neck diameter of the cathode ray tube is reduced to make the cathode ray tube compact. As a result, the attaching positions of the contacts
103
,
104
in the insulating housing
102
are closely spaced to each other. Accordingly, there is a concern that the focus contact
104
and the signal contact
103
are short-circuited along a surface of the insulating housing
102
since a high voltage of several thousands volts is applied to the focus pin
100
c
. To reduce the chance of such arc-over, the insulating housing
102
includes a ring-shaped portion
105
attached to the signal contact
103
, a cover portion
106
attached to, the focus contact
104
, and a base portion
109
covering the rear of the cover portion
106
.
Creepage is defined as the conduction of electricity across the surface of a dielectric. A creepage distance is the distance along a dielectric that such conduction must occur for an arc to be formed. The creepage distance in the prior-art device is the distance along the surface of the insulating housing
102
between the focus contacts
104
and the signal contacts
103
. The creepage distance is extended by interposing a slit
107
between the ring-shaped portion
105
and the cover portion
106
. The rear face of a focus contact storing chamber
108
for storing a contact portion of the focus contact
104
is covered with the base portion
109
. This construction reduces the chance of the above short circuit.
Referring now also to
FIG. 11
, the gap (L) between the base
100
a
and the focus pin
100
c
is very narrow to reduce the neck diameter of the cathode ray tube. In the conventional CRT socket
100
, the focus contact
104
and a partition wall
106
a
of the cover portion
106
are interposed in this gap (L). Therefore, the thickness of the partition wall
106
a
is limited to a value that is less than desired. As a result, the strength of the partition wall
106
a
for partitioning the focus contact storing chamber
108
and the base insertion hole
101
is insufficient. Therefore, there is a chance that the partition wall
106
a
will be damaged when the cathode ray tube is forced into the socket at a slant when making the connection.
The rear face of the focus contact storing chamber
108
is covered by the base portion
109
. A short-circuited electric current flows to an abutting portion of the cover portion
106
and the base portion
109
, i.e., a rear face side of the ring-shaped portion
105
via a rear face of the partition wall
106
. Accordingly, the distance between the focus contact
104
and the signal contact
103
cannot be made great enough to avoid arc-over.
OBJECTS AND SUMMARY OF THE INVENTION
To solve the above problems, an object of this invention is to provide a CRT socket in which a partition wall for partitioning a focus contact storing chamber and a base insertion hole has sufficient strength, and the creepage distance between a focus contact and a signal contact can be set to a sufficient length.
To solve the above problems, a CRT socket of the invention comprises an insulating housing in which the insulating housing is constructed by a ring-shaped portion in which a cylindrical base insertion hole is bored and plurality of signal contact storing chambers are concavely arranged from a rear face side on an outside circular circumference of the base insertion hole; a cover portion for arranging a focus contact storing chamber on the same circular circumference as the signal contact storing chambers by projecting a projecting portion concavely having the focus contact storing chamber from the rear face side to a portion having no ring-shaped portion; and a base portion for covering the rear face side of the cover portion; and the cover portion and the base portion are integrated with each other by molding the ring-shaped portion integrally with the cover portion or the base portion, and engaging the cover portion and the base portion with each other; a signal contact stored in each signal contact storing chamber; and a focus contact stored in the focus contact storing chamber; wherein a pin insertion hole communicated with the signal contact storing chamber and the focus contact storing chamber from front face sides of the ring-shaped portion and the projecting portion is bored, and a signal pin and a focus pin of a cathode ray tube arranged on an outside circular circumference of a base are respectively electrically connected to the signal contact and the focus contact, the CRT socket includes the focus contact constructed by a conductive metallic plate of a band shape, and an intermediate portion of the conductive metallic plate is bent at an acute angle, a bent basic end side is set to a supporting portion, and a bent tip side is set to a leaf spring contact portion; the supporting portion rises and is supported along an inner wall face of the focus contact storing chamber facing a direction of the base insertion hole, and the leaf spring contact portion faces the pin insertion hole; and an outside face of the projecting portion is covered with a partition wall rising on the front face side from the base portion.
The focus contact is formed in a leaf type in which an intermediate portion of the metallic plate of a band shape is bent at an acute angle. A supporting portion of the focus contact rises and is supported along an inner wall face facing the direction of the base insertion hole. Therefore, there is no focus contact interposed in a gap (L) between the base and the focus pin in the cathode ray tube. Accordingly, it is possible to increase the thickness of the partition wall to a thickness of the focus contact from the base portion, and cover the outside face of the projecting portion.
Since the partition wall of the base portion overlaps the, outside of a partition wall of the projecting portion, increased strength is obtained in the partition wall for partitioning the focus contact storing chamber and the base insertion hole.
The distance between the focus contact and the signal contact is extended by the partition wall rising from the base portion sufficiently to achieve sufficient length for mutual insulation.
The CRT socket of the invention includes the ring-shaped portion and the base portion being integrally molded. The cover portion is engaged with the base portion and is attached to the front face side of the base portion.
The signal contact is stored in the signal
Arai Atsushi
Arakawa Hiroharu
Patel Nimeshkumar D.
Roy Sikha
SMK Corporation
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