Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Automatic circuit-interrupting devices
Reexamination Certificate
2002-05-21
2002-11-12
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Automatic circuit-interrupting devices
C335S016000, C335S195000, C200S244000
Reexamination Certificate
active
06480080
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a molded case circuit breaker, and in particular, to an assembly structure of a current-interrupting section equipped with a bridging rotary contact shoe.
First, a general configuration of a molded case circuit breaker is schematically shown in FIG.
7
. In this figure, reference numeral
1
denotes a main body case of a circuit breaker,
2
is an opening and closing handle,
3
is a toggle type opening and closing (switching) mechanism, and
4
is an over-current tripping device based on a bimetal method or the like. Reference numeral
5
is a current-interrupting section containing fixed contact shoes, a movable (rotary) contact shoe and arc extinguishing devices of a main circuit, and is linked to the opening and closing mechanism
3
. An opening and closing operation of such a circuit breaker is well known.
Through an ON/OFF operation of the opening and closing handle
2
, the movable contact shoe in the current-interrupting section
5
opens or closes via the opening and closing mechanism
3
. Further, when an over-current flows to activate the over-current tripping device
4
while the main circuit is powered, the opening and closing mechanism
3
performs a trip operation to open the movable contact shoe in the current-interrupting section
5
, thereby interrupting the over-current from flowing through the main circuit.
Here, an interrupting method used for the current-interrupting section
5
includes a single-break method and a double-break method. An example of a double-break method using a bridging rotary contact shoe as a movable contact shoe has been disclosed in Japanese Patent Publications (KOKAI) No. 06-028964 and No. 06-52777. A configuration of this circuit breaker is shown in FIG.
8
. In this figure, reference numeral
6
denotes an insulated case of the current-interrupting section
5
;
7
A and
7
B are power-supply side and load side fixed contact shoes disposed in the insulated case
6
and arranged diagonally opposite to each other;
7
a
is a fixed contact provided at a tip portion of each fixed contact shoe;
8
is a movable contact shoe that bridges the contacts of the fixed contact shoes
7
A,
7
B;
9
is a rotary drum-shaped contact shoe holder that holds the movable contact shoe
8
; and
10
is an arc extinguishing device (grid) positioned at each side of the movable contact shoe
8
and disposed in the insulated case
6
.
The movable contact shoe
8
is urged and held in a position by a pressure spring (tension spring or torsion coil spring)
11
loosely fitted and disposed in a through-hole
9
a
formed on the contact shoe holder
9
. One end of the fixed contact shoe
7
A (a power-supply side) is drawn out from the insulated case
6
to constitute a power-supply-side terminal portion. A terminal portion of the fixed contact shoe
7
B (a load side) is connected to the main circuit conductor of the overload tripping device
4
, shown in
FIG. 4
, at a top surface of the insulated case
6
.
Further, in the illustrated structure, a tip portion of each of the fixed contact shoes
7
A and
7
B is folded in a U-shape to form a fixed contact
7
a
. When an over-current such as a short circuit current flows through the main circuit, the movable contact shoe
8
is substantially instantaneously opened before the overload tripping device
4
(see
FIG. 7
) operates by an electromagnetic resilient force exerted between the tip portions of the fixed contact shoes
7
A and
7
B and the movable contact shoe
8
. Furthermore, the folded portion of each fixed contact shoe has a magnetic yoke
12
to enhance a magnetic field acting on an arc generated between the contacts of the fixed and movable contact shoes during current interruption, thereby increasing the electromagnetic arc driving force to the arc extinguishing devices
10
.
It is preferred for the current-interrupting section
5
to be as compact as possible in order to reduce a size of the molded case circuit breaker. However, in the conventional structure of the current-interrupting section shown in
FIG. 8
, the tip portion of each of the power-supply side and load side fixed contact shoes
7
A and
7
B is folded in the U-shape to generate the electromagnetic resilient force required to drive and open the movable contact shoe
8
when the over-current flows through the circuit. As a result, the insulated case
6
, which contains the fixed contact shoes
7
A and
7
B, needs to have a larger height H, resulting in a larger size of the current-interrupting section
5
.
Further, as shown in
FIG. 9
, Japanese Patent Publication (KOKAI) No. 01-166429 has disclosed a molded case circuit breaker in which the fixed contact shoes
7
A and
7
B, disposed in the insulated case
6
of the current-interrupting section
5
and arranged diagonally opposite to each other, are formed of linear contact shoe conductors. The bridging rotary contact shoe
8
is disposed between the fixed contacts
7
a
provided at the tips of the fixed contact shoes
7
A and
7
B. In this assembly structure, the fixed contact shoes
7
A and
7
B in the insulated case
6
have a linear shape, thereby allowing the height H of the current-interrupting section
5
to be smaller as compared to the configuration in FIG.
8
. On the other hand, a current direction flowing through the fixed contact shoes
7
A and
7
B is the same as that through the movable contact shoe
8
. Therefore, a large electromagnetic resilient force required for driving and opening the movable contact shoe can not be obtained between each of the fixed contact shoes
7
A and
7
B and the movable contact shoe
8
.
It is thus an object of the present invention to provide a molded case circuit breaker having linear shape fixed contact shoes to minimize a current-interrupting section, wherein the contact shoes are arranged so as to generate a large electromagnetic resilient force required for driving and opening a movable contact shoe when an over-current flows through the circuit.
Further objects and advantages will be apparent from the following description of the invention.
SUMMARY OF THE INVENTION
To achieve the objects, the present invention provides a molded case circuit breaker including a current-interrupting section. The current-interrupting section is composed of an insulated case containing arc extinguishing devices; fixed contact shoes on a power-supply side and a load side disposed in the case and arranged diagonally opposite each other; a movable or rotary contact shoe bridging between contacts of the fixed contact shoes; and a rotary contact shoe holder for holding and linking the movable contact shoe and a pressure spring to an opening and closing mechanism of the circuit breaker. The movable contact shoe can be opened by an electromagnetic resilient force exerted when an over-current flows. Contact shoe conductors of the power-supply side and load side fixed contact shoes are substantially linear, and are arranged in parallel and opposite to each other with the movable contact shoe in between. The fixed contact shoes, and the movable contact shoe which is bridging contacts positioned at tips of the fixed contact shoes, are assembled together to form a Z-shape conducting path (the first aspect).
According to this configuration, the fixed contact shoes are composed of linear contact shoe conductors, thereby reducing a height of the current-interrupting section as opposed to the conventional structure having a U-shape fixed contact shoe. Further, when the circuit breaker is powered, a current through the power-supply side and load side fixed contact shoes flows relatively opposite to that through the bridging movable contact shoe. Accordingly, if an over-current flows through the circuit, a large electromagnetic resilient counter force is generated between a tip portion of the power-supply side fixed contact shoe and the movable contact shoe, and between the tip portion of the load side fixed contact shoe and the movable contact shoe. This electromagnetic counter force ac
Asada Tadashi
Isozaki Masaru
Onchi Toshiyuki
Uchida Naoshi
Yonemitsu Kazunori
Barrera Ramon M.
Fuji Electric & Co., Ltd.
Kanesaka & Takeuchi
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