Electric lamp and discharge devices – With envelope – Having base and connector
Reexamination Certificate
1998-12-01
2001-05-29
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With envelope
Having base and connector
C313S318020, C313S318090, C313S025000
Reexamination Certificate
active
06239539
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an insulating plug for an electric discharge lamp apparatus having a structure in which a lamp-side connector, to which a connector for supplying electric power can be connected and disconnected, is integrally provided for the rear end of the main body of an insulating plug having a front end to which an arc tube is secured and held.
As shown in
FIG. 15
, a conventional electric discharge lamp apparatus has a structure that an arc tube
3
is, through a metal lead support
2
a
and a ceramic disc
2
b
, integrally secured to the front end of an insulating plug body (an insulating base)
1
made of synthetic resin.
Note that a hole, through which a rear end of the arc tube is inserted, is formed in the front surface of the insulating plug body
1
.
The arc tube
3
has a structure that an ultraviolet-ray shielding globe
5
is, by welding, integrated with an arc tube body
4
having an enclosed glass bulb
4
a
which is a light emitting portion in which electrodes
4
b
are disposed opposite to each other. Thus, the enclosed glass bulb
4
a
is surrounded and hermetically sealed by the ultraviolet-ray shielding globe
5
. The electrodes
4
b
are connected to lead wires
4
e
extending from the arc tube
3
through molybdenum foil members
4
d
bonded to pinch seal portions
4
c.
On the other hand, a cylindrical portion
1
a
extending rearward is formed at the rear end of the insulating plug body
1
. A belt-shape negative-side terminal
6
electrically connected to a front-end lead wire of the arc tube
3
through a lead support
2
a
is exposed on the outer surface of the cylindrical portion
1
a.
In the central portion of the cylindrical portion
1
a,
a positive-side terminal
7
electrically connected to a rear-end lead wire of the arc tube
3
is exposed. The foregoing elements (the cylindrical portion
1
a,
the terminal
6
and the terminal
7
) constitute a lamp-side connector C
2
to which a connector C
1
for supplying electric power can be connected and disconnected.
A ceramic insulating sleeve
2
c
is fitted to a lead support
2
a
forwards projecting over the insulating plug body
1
. Thus, insulation between a lead support
2
a
which is a positive-side passage for electric power and a lead wire at the rear end of the arc tube
3
is maintained, the rear-end lead wire being a positive-side passage for electric power.
As shown in
FIG. 16
, the insulating plug body
1
is formed by injection molding such that the front end surface having a relatively large thickness of the insulating plug body
1
faces a gate
9
of the molds
8
a
and
8
b.
A slide mold
8
c
is provided for forming a recessed groove for receiving a negative-side terminal
6
which is formed into an undercut portion.
However, the conventional insulating plug
1
has a problem in that hollow portions B (hereinafter called “voids”) which cause dielectric breakdown are formed at the base portion of the rear-end cylindrical portion
1
a.
The inventors of the present invention have conducted investigations, resulting in the following fact being detected. Resin injected through the gate
9
is introduced from the front-end cylindrical portion into the rear-end cylindrical portion
1
a
so that the cylindrical portion
1
a
is filled with the resin. In the rear-end cylindrical portion
1
a
which is apart from the gate
9
and which has a large thickness, resin cannot sufficiently be supplied. Moreover, the molding pressure in the foregoing portion is made to be lower than that in the portions in the vicinity of the gate
9
. Therefore, gas cannot sometimes sufficiently be removed. The resin injected into the cavity is solidified such that the peripheral portion which is brought into contact with the mold is first solidified. In the thick wall portions, contraction and solidification occur slowly as compared with thin wall portions when the molding process is performed. Therefore, resin is pulled by the peripheral portion which has first been contracted and solidified and, therefore, deformation takes place. Thus, an estimation is made that voids B are formed.
Therefore, the inventors have formed an inner cylindrical portion and a cylindrical portion for surrounding the inner cylindrical portion which are provided for the front end portion of the insulating plug. Thus, the thickness of the overall portion from the front end portion of the insulating plug body to the base portion is reduced as compared with that of the conventional structure so that a uniform thickness is realized. In addition, the extending end surface of the rear-end cylindrical portion
1
a
having the largest thickness in the insulating plug body
1
is caused to face the gate
9
. As a result, no void was observed in the overall portion of the insulating plug body
1
including the inside portion of the rear-end cylindrical portion
1
a
and the front-end cylindrical portion (the inner cylindrical portion and the outer cylindrical portion).
The present invention is established to solve the above-mentioned problems experienced with the conventional technique and on the basis of the facts detected by the inventors.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an insulating plug for an electric discharge lamp apparatus, the weight and cost of which can be reduced, and in which insulation can be maintained.
To achieve the above-mentioned object, an insulating plug for an electric discharge lamp apparatus according to the present invention includes a front portion having an outer cylindrical portion and an inner cylindrical portion, the inner cylindrical portion having a substantially unique thickness and an opening to receive an arc tube of an electric discharge lamp; a focusing ring extending form the outer cylindrical portion of the front portion; and a rear portion having a rear-end cylindrical portion and a center portion, wherein a thickness t
1
of the rear-end cylindrical portion of the rear portion, and the thickness t
2
of the inner cylindrical portion of the front portion satisfy a following condition:
t
1
>t
2
.
Preferably, the thickness t
1
of the rear-end cylindrical portion of the rear portion, the thickness t
2
of the inner cylindrical portion of the front portion and a thickness t
3
of the outer cylindrical portion of the front portion satisfy a following condition: t
1
>t
2
>t
3
.
The thickness of the insulating plug is enlarged in a direction toward the gate. That is, the passage in the cavity through which the resin flows is widened toward the gate. Therefore, the resin can smoothly be introduced into the overall body of the cavity. Also the injection molding pressure can be uniformed in the overall body of the cavity.
The rear-end cylindrical portion has the largest thickness t
1
in the overall body of the insulating plug. Thus, insulation can be maintained between the belt-shape negative terminal exposed on the outer surface of the rear-end cylindrical portion and the positive terminal exposed in the center portion in the cylindrical portion. Moreover, the mechanical strength which endures connection and disconnection of the connector for supplying electric power can be realized.
The front-end cylindrical portion has the next largest thickness t
2
in the overall body of the insulating plug to that of the rear-end cylindrical portion. Therefore, insulation between the positive-side passage (the rear-end lead wire of the arc tube) for electric power disposed on the inside of the inner cylindrical portion and the negative-side passage (electricity carrying members, such as, a lead support, which are electrically connected to the front-end lead wire of the arc tube) disposed on the outside of the inner cylindrical portion can be maintained. Moreover, the mechanical strength can be realized to reliably secure and hold the rear end portion of the arc tube.
Since the outer cylindrical portion of the front portion is a portion which does not considerably affect the insulation, the foregoing portion has the thic
Fukuyo Takeshi
Harazaki Masato
Irisawa Shinichi
Mochiduki Kunimasa
Numajiri Yasuyoshi
Koito Manufacturing Co. Ltd.
Patel Vip
Quarterman Kevin
Sughure, Mion, Zinn, Macpeak & Seas, PLLC
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