Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – With bimetallic elements
Reexamination Certificate
2001-02-20
2002-10-29
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
With bimetallic elements
C337S012000, C337S013000, C337S055000, C337S056000, C361S102000, C361S115000, C335S035000, C335S173000, C335S191000, C200S401000
Reexamination Certificate
active
06472971
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a circuit breaker, such as a molded case circuit breaker for actuating and stopping an electric motor and protecting it from overcurrent, and more specifically, to an assembly structure of a contact opening and closing mechanism therefor.
An assembly structure such as that shown in
FIG. 4
is known as the circuit breaker referred to above. In
FIG. 4
, reference numeral
1
denotes a circuit breaker case as a resin molded article comprising a lower case
1
a
and an upper cover
1
b
,
2
is a power-side main circuit terminal corresponding to each pole, and
3
is a load-side main circuit terminal. The lower case
1
a
has a main circuit contact section integrated thereinto and comprising an assembly of fixed contact shoes
4
and
5
connected to the corresponding main circuit terminals, a movable contact shoe
6
bridging the fixed contact shoes
4
and
5
, a contact spring
7
, a contact shoe holder
8
, and arc extinguishing plates
9
.
In addition, the upper cover
1
b
includes an opening and closing lever
10
made of an insulating material and having a journaled rear end and a tip facing a top surface of the contact shoe holder
8
, an opening and closing handle
11
projecting from a top surface of the upper cover
1
b
, a contact opening and closing mechanism section
12
linking between the opening and closing handle
11
and the opening and closing lever
10
, an overcurrent tripping device
13
including a thermal tripping device
13
a
operating in response to a load current through the main circuit and an electromagnetic tripping device
13
b
operating instantaneously in response to a short circuit current, and others. All these components are integrated into the upper cover
1
b.
In this case, the contact opening and closing mechanism section
12
of the conventional circuit breaker comprises an assembly of a toggle link that couples two links together in the form of “V” in such a manner as to sandwich a toggle shaft in a vertical direction of the circuit breaker, to link between the opening and closing handle
11
and the opening and closing lever
10
, an opening and closing spring or a main spring extending between the toggle link and a lever of the opening and closing handle
11
, and a latch with which the overcurrent tripping device
13
is linked via a trip cross bar (not shown).
The opening and closing operations of such a circuit breaker are well known. When the opening and closing handle
11
is manually operated to the ON side, accumulated force from the opening and closing spring lifts the opening and closing lever
10
. This causes the movable contact shoe
6
, urged by the contact spring
7
, to rise with the holder
8
to bridge the fixed contact shoes
4
and
5
. In this contact-closed state, a main circuit current flows from the main circuit terminal
2
through the fixed contact shoe
4
, the movable contact shoe
6
, the fixed contact shoe
5
, and the overcurrent tripping device
13
to the main circuit terminal
3
.
Additionally, when the opening and closing handle
11
is operated to the OFF position, the accumulated force of the opening and closing spring of the contact opening and closing mechanism section
12
moves the toggle link reversely to drive the opening and closing lever
10
clockwise from a receding position to push the movable contact shoe
6
downward against the force of the contact spring
7
together with the holder
8
, thereby separating the movable contact shoe
6
from the fixed contact shoes
4
and
5
to open the main circuit contact. On the other hand, when an overcurrent or a short-circuit current flows through the main circuit in a conductive state, the overcurrent tripping device
13
operates to release the latch of the contact opening and closing mechanism section
12
to drive the opening and closing lever
10
counterclockwise by the accumulated force of the opening and closing spring. Thus, the movable contact shoe
6
is opened to shut off the main circuit current, i.e. tripping operation.
The above-described conventional circuit breaker structure has problems in regard to the external dimensions of the entire circuit breaker, manual opening and closing operations, and a circuit opening operation.
(1) In the structure shown in
FIG. 4
, which incorporates the bridging contact-shoe type main circuit contact section located at the bottom of the case
1
, and the opening and closing lever
10
, the opening and closing handle
11
, the contact opening and closing mechanism section
12
and other components located above the main circuit contact section, the entire circuit breaker has a large height H. In particular, if the toggle link of the contact opening and closing mechanism section
12
comprises two links coupled together in the form of a “V” in the vertical direction of the circuit breaker, the toggle link has a large height in an extended state, and moves over a wide range when each link, which has been extended, is bent and moved reversely. Consequently, it is difficult to design a small and compact circuit breaker.
(2) Additionally, in the conventional circuit breaker, when the main circuit contact shoe is closed as shown in
FIG. 4
, a tip of the opening and closing lever
10
abuts against a top surface of the contact shoe holder
8
. When the contact shoes are then opened, an opening and closing spring force from the contact opening and closing mechanism section
12
is applied to the opening and closing lever
10
as a static pressure to push the top surface of the contact shoe holder
8
downward, which has been pressed upward by the contact spring
7
, thereby opening the movable contact shoe
6
. Thus, if the contacts of the fixed and movable contact shoes have been welded or fixed together due to conduction of a high current, an error in the shutting-off operation may occur. For example, the movable contact shoe may not open or its opening may be delayed. To prevent such error, it is contemplated that the opening and closing spring integrated into the contact opening and closing mechanism section
12
may be enhanced. A stronger force of the opening and closing spring, however, results in the necessity of a stronger force for manually operating the opening and closing handle
11
, thereby preventing a user from operating the circuit breaker easily.
The present invention has been made in view of the above points, and it is an object of the invention to solve the above-described problems and to provide a circuit breaker with an improved contact opening and closing mechanism that serves to reduce the size of the circuit breaker, to simplify circuit-opening operations and to facilitate operations.
Other objects and advantages of the invention will be apparent from the following description of the invention.
SUMMARY OF THE INVENTION
In order to attain the above object, the present invention provides a circuit breaker comprising a main circuit contact section disposed in a case at a bottom thereof and including an assembly of a fixed contact shoe, a movable contact shoe held in a contact shoe holder, and a contact spring that presses and urges the movable contact shoe toward the fixed contact shoe; a movable opening and closing lever located above the main circuit contact section and having a journaled rear end and a tip located at a portion facing a top surface of the holder; a contact opening and closing mechanism also located above the main circuit contact section and including a combination of a toggle link linked with the opening and closing lever, an opening and closing handle, an opening and closing spring extending between a handle lever for the opening and closing handle and the toggle link, and a latch linked with the toggle link; and an overcurrent tripping device located above the main circuit contact section to detect an overcurrent through a main circuit to release the latch.
In the first aspect of the invention, the toggle link comprises a first link having a lower end coupled to the openin
Asakawa Koji
Ohshima Isamu
Toyama Kentaro
Uchida Naoshi
Fuji Electric & Co., Ltd.
Kanesaka & Takeuchi
Vortman Anatoly
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