Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – With housing or support means
Reexamination Certificate
2000-06-30
2001-09-11
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
With housing or support means
C174S034000, C174S034000
Reexamination Certificate
active
06288622
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an electro-magnetic relay and a cover used therefor, and more particularly to an electro-magnetic relay required to have quick response to high frequency signals, and a cover used therefor.
2. Description of the Related Art
One of conventional electro-magnetic relays is illustrated in
FIGS. 1 and 2
. With reference to
FIG. 1
which is an exploded perspective view of the conventional electro-magnetic relay, the illustrated electro-magnetic relay is comprised of a coil assembly
100
, an armature block assembly
200
, and a base assembly
300
.
The coil assembly
100
includes a core
15
covered with coil spool
11
except opposite ends acting as magnetic poles, a coil
12
wound around the core
15
, and a permanent magnet
13
inserted into a hole formed at the center of the coil spool
11
, and thus located at the center of the core
15
. The coil spool
11
is composed of insulating material.
The armature block assembly
200
includes an armature
20
, swingable springs
22
a
and
23
a
each having a contact
22
b
and
23
b
at a distal end thereof, and an armature block
250
made of insulating material and formed integral with the armature
20
and the springs
22
a
and
23
a.
The armature
20
moves like a seesaw by applying a current to the coil
12
or stopping application of a current to the coil
12
. In such seesaw movement of the armature
20
, a center portion thereof located on the permanent magnet
13
acts as a fulcrum. The swingable springs
22
a
and
23
a
are connected to hinge springs
22
and
23
, respectively.
The base assembly
300
includes fixed contacts
30
a
and
31
a
facing to the swingable contacts
22
b,
fixed contacts
32
a
and
33
a
facing to swingable contacts
23
b,
fixed contact terminals
30
,
31
,
32
, and
33
on which the fixed contacts
30
a,
31
a,
32
a,
and
33
a
are mounted, neutral terminals
38
and
39
, coil terminals
34
,
35
,
36
, and
37
, and a box-shaped insulating block (no reference numeral) formed integral with the fixed contact terminals
30
,
31
,
32
, and
33
, the neutral terminals
38
and
39
, and the coil terminals
34
,
35
,
36
, and
37
. The fixed contact terminals
30
,
31
,
32
, and
33
are formed to outwardly project to thereby act as relay terminals.
Ends of the coil
12
are electrically connected to welding portions
11
a
buried in the coil spool
11
, and further electrically connected to coil terminals
34
,
35
,
36
, and
37
by welding. The hinge springs
22
and
23
of the armature block assembly
200
are electrically connected to the neutral terminals
38
and
39
of the base assembly
300
, respectively, by welding.
FIG. 2
is a perspective view showing how the electro-magnetic relay is assembled. The armature block assembly
200
and the coil assembly
100
are assembled to the base assembly
300
. The armature block assembly
200
, the coil assembly
100
, and the base assembly
300
, which are assembled to one another, are covered with a cover
400
made of plastics. Gaps between the cover
400
and the base assembly
300
are filled with electrically insulating sealing material such as epoxy resin. Thus, there is completed the electro-magnetic relay.
The conventional electro-magnetic relay having the above-mentioned structure has a problem of poor response to high frequency signals input to contacts. This is because the cover
400
is made of plastics, and thus, does not have shielding characteristic, which means that it is not possible to match with a transmission path with respect to characteristic impedance.
In order to overcome this problem, Japanese Unexamined Patent Publication No. 4-263508 having been published on Sep. 18, 1992 has suggested an electrically insulating cover to which shield characteristic is provided.
FIGS. 3 and 4
illustrate the cover suggested in the above-mentioned Publication.
FIG. 3
is a perspective view of the cover with portions cut away, and
FIG. 4
is a perspective view of the cover, as viewed from downwardly.
As illustrated in
FIG. 3
, a piezoelectric electronic part P is mounted on a base B, and is covered with an electrically insulating cover C.
As illustrated in
FIG. 4
, the cover C is formed at an entire upper inner surface with a shield electrode C
1
, and at a part of side inner surfaces with shield electrodes C
2
. Furthermore, the cover C is formed at an external surface thereof with a external electrode C
3
and a shield electrode C
4
. The shield electrodes C
4
are designed to electrically connect with the shield electrodes C
1
and C
2
. The reason why the cover C is formed at an external surface thereof with the external electrode C
3
and the shield electrodes C
4
is to use an electro-magnetic relay with the cover C, as a chip component.
However, the above-mentioned cover is accompanied with a problem that since the external electrode C
3
is formed on an external surface of the cover C, it is impossible to ensure a high breakdown voltage between the cover C and the external electrode C
3
, or a high breakdown voltage between the shield electrodes C
1
to C
3
and the external electrode C
3
.
If the electrically insulating cover illustrated in
FIGS. 3 and 4
were used for an electro-magnetic relay, there would be caused a big problem on safety that it is impossible to have a high breakdown voltage between a cover and coil terminals, and between a cover and contact terminals.
In addition, the cover C illustrated in
FIGS. 3 and 4
is formed at just a part of an inner side surface thereof with the shield electrode C
2
, though the cover C is formed at an entire inner upper surface with the shield electrode C
1
. As a result, the cover C is accompanied with a problem of insufficient shield characteristic against electro-magnetic waves entering through a sidewall of the cover C.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems of the conventional cover used for an electro-magnetic relay, it is an object of the present invention to provide an electro-magnetic relay having higher shield characteristic to thereby have improved response to high frequency input signals.
Another object of the present invention is to provide an electro-magnetic relay having sufficiently improved breakdown voltages between a cover and coil terminals, and between a cover and contact terminals.
It is also an object of the present invention to provide a cover to be used for the above-mentioned electro-magnetic relays.
In one aspect of the present invention, there is provided a cover used for an electro-magnetic relay, including (a) an enclosure having both a bottom edge defining an open bottom, and an insulating external surface, (b) a plurality of projections formed on the bottom edge so that the projections can support the enclosure while the enclosure stands, and (c) a shield metal film formed on an inner surface of the enclosure, the shield metal film extending to a bottom surface of each of the projections so that the bottom surface of each of the projections acts as a grounding surface.
Since the cover is designed to have a shield metal film on an inner surface thereof, the cover could have shield characteristic. Hence, it is possible to match with characteristic impedance of a transmission path, resulting in quicker response to high frequency input signals.
In addition, since the shield metal film is formed on a bottom surface of the projections, the projections can act as grounding surfaces. That is, the projections have two functionals, one of which is to support the enclosure, and the other is to provide ground to the enclosure.
Furthermore, since the enclosure has an insulating external surface, it is possible to enhance a breakdown voltage between the enclosure and coil terminals of an electro-magnetic relay, and between the enclosure and contact terminals of an electro-magnetic relay.
It is preferable that the enclosure is formed at the inner surface thereof with an insulating region starting from the bottom edge and having a prede
Barrera Ramon M.
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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