Electromagnetic relay

Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Polarity-responsive

Reexamination Certificate

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Details

C335S083000

Reexamination Certificate

active

06781490

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic relay for use as a small electromagnetic relay that can be mounted on a printed-circuit board, for example.
In general, this kind of small electromagnetic relay has the following structure. Specifically, the electromagnetic relay includes a resin spool having flange portions formed at both sides of its cylindrical portion. The spool has coils wound thereat to form a coil assembly. The spool has an iron core inserted into its central axis position. The iron core exposes its head portion from the flange portion and this head portion serves as a portion to magnetically attract an armature by an electromagnet.
A yoke is shaped like a plate portion having a length nearly equal to the length of the spool in the axial direction. This yoke is attached to the spool in such state in which it may extend to the flange portions of both sides of the spool. The yoke has a movable contact spring attached to its plate portion. This movable contact spring is shaped at its flange portion side in which the head portion of the iron core is located such that it may be bent in the direction nearly perpendicular to the yoke. An armature made of a square steel plate is attached to the movable contact spring at it surface side in which its bent portion oppose the head portion of the iron core. Further, the movable contact spring includes a portion projecting to the direction parallel to the plate surface direction of the armature, and this projecting portion has a movable contact formed thereon.
A break (i.e., normally closed) fixed contact terminal and a make (i.e., normally open) fixed contact terminal are narrow L-like plates having predetermined widths and a break contact and a make contact are provided at tip end portions of the L-like plates. The break fixed contact terminal and the make fixed contact terminal are fitted into the grooves formed at the flange portion of the spool with pressure and thereby attached.
In the case of the conventional electromagnetic relay having the above-mentioned structure, since the break fixed contact terminal and the make fixed contact terminal are directly fixed to the resin spool, there is a risk that the following problems arise.
Specifically, while a drive current is flowing through the coils of the electromagnetic relay, when the movable contact and the make contact are connected and an excess current flows through the movable contact and the make contact due to an accident, the drive current causes the coils to generate heat and conductor portions such as the movable contact spring and the fixed contact terminal generate heat. When the coil and the conductor portions generate heat, the heat thus generated fuses the resin spool. When the resin spool is fused by heat, there occurs an abnormal state in which the movable contact and the make contact are fixed in the “ON mode” which is the connected state.
Thereafter, even when an interlayer short circuit (i.e., so-called coil layer short) occurs in the coil, the movable contact does not return to the break contact side and the movable contact is still connected to the make contact.
If the mode of the electromagnetic relay is “ON mode” when such trouble occurred in the electromagnetic relay, then an excess current continues to flow through the make contact, There is then a risk that other trouble will occur.
In the case of the above conventional electromagnetic relay, the break fixed contact terminal and the make fixed contact terminal are fitted into the grooves of the flange portions of the spool with pressure. When the break fixed contact terminal and the make fixed contact terminal are fitted into the grooves with pressure, the fixed contact terminals made of made of copper alloys cut the resin spool to produce shavings, and shavings are scattered around the fixed contact terminals. Contact sets of the movable contact, the break contact and the make contact exist near the pressure engagement portions (i.e. groove portions formed at the flange portions of the spool). Since scattered shavings lie between these contacts, there is a risk that a trouble of contact failure will occur between these contacts.
As an electromagnetic relay which can solve the above-mentioned problems, the inventors of the present application has previously proposed the following electromagnetic relay (see Japanese laid-open Patent Publication No. 162712/1998).
The previously-proposed electromagnetic relay comprises a main body assembly, formed by combining an electromagnet assembly comprising a coil assembly comprising of a spool and coils wound around the spool and an iron core and a yoke with a movable contact and an armature, and a terminal board assembly having fixed contact terminal attached to a terminal board. These main body assembly and terminal board are separate members and engage with each other to comprise an electromagnetic relay.
FIGS. 1A
to
1
D of the accompanying drawings are diagrams to which reference will be made in explaining the outline of this previously-proposed electromagnetic relay. In the electromagnetic relay of this example, a main body assembly
1
shown in
FIG. 1A and a
terminal board assembly
2
shown in
FIG. 1B
are assembled to form an electromagnetic relay main body
3
shown in FIG.
1
D.
In the example shown in
FIGS. 1A
to
1
D, the electromagnetic relay main body
3
is formed by assembling the two members of the main body assembly
1
and the terminal board assembly
2
. The electromagnetic relay main body
3
is housed within a cover
4
shown in FIG.
1
C. Then, a sealant seals the opening portion of the cover
4
to complete the electromagnetic relay.
The main body assembly
1
comprises an electromagnet assembly
20
and an armature assembly
30
. The electromagnet assembly
20
comprises a coil assembly
10
and an iron core (not shown) and a yoke
21
, both of which are attached to the coil assembly
10
. The coil assembly
10
comprises a resin spool
11
including square plate-like flange portions
11
a
and
11
b
provided at respective ends thereof, a coil
13
wound around the spool
11
and coil terminals
12
a
and
12
b
, made of copper alloys, for example, attached thereof.
The flange portion
11
a
has a projection portion
11
c
projecting in the direction perpendicular to the plane of the plate thereof. This projection portion
11
c
serves as an engagement portion when the coil assembly
10
is fitted into the terminal board assembly
2
. The flange portion
11
b
has a projection portion
11
d
serving as an engagement portion when the coil assembly
10
is fitted into the terminal board assembly
2
, as will be described later on. The projection portion
11
d
projects from the upper surface of the flange portion
11
b
to the direction parallel to the central axis direction of the coil winding portion.
The armature assembly
30
comprises a substantially L-like movable contact spring
31
made of a copper alloy, for example, and a square plate-like armature
32
made of steel attached to the movable contact spring
31
.
The terminals strip assembly
2
includes a terminal board
40
shown in
FIG. 2A
into which a make fixed contact terminal
50
shown in
FIG. 2B and a
break fixed contact terminal
60
are fitted and is shaped as shown in FIG.
2
D.
The terminal board
40
is made of resin and shaped like a thin plate by molding. Specific shape and structure of the terminal board
40
will be described with reference to
FIGS. 3A
to
3
I and
FIGS. 4A and 4B
.
FIG. 3A
is a front view showing the terminal board
40
from a surface
40
a
of the side from which the make fixed contact terminal
50
and the break fixed contact terminal
60
are fitted into the terminal board
40
(i.e. opposite side of a surface
40
b
shown in FIG.
2
A).
FIG. 3B
is a side view of the terminal board
40
, and
FIG. 3C
is a top view of the terminal board
40
.
FIG. 3D
is a cross-sectional view taken along the line D—D in FIG.
3
A.
FIG. 3E
is a cross-sectional view taken along the line E—E in FIG.

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