Electricity: circuit makers and breakers – Electric switch details – Latches
Reexamination Certificate
2003-05-19
2004-10-05
Donovan, Lincoln (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Latches
C200S308000
Reexamination Certificate
active
06800822
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a circuit breaker for a power supply circuit of an electric motor, and, in particular, to an opening-and-closing operation handle-mechanism for the circuit breaker.
Japanese Patent Publication (Tokkai) No. 2001-23499 has disclosed a configuration of an opening-and-closing mechanism for a circuit breaker. With reference to
FIGS. 9 and 10
, a structure and operation of the opening-and-closing mechanism will be explained.
As shown in
FIGS. 9 and 10
, reference numeral
1
denotes an opening-and-closing mechanism, and reference numeral
2
denotes a locker handle installed at a top of an assembly frame of the opening-and-closing mechanism for an opening-and-closing operation. Reference numeral
3
denotes an opening-and-closing lever for turning on and driving the main-circuit contacts (not shown) to an open position, and reference numeral
4
denotes a main spring (torsion coil spring) provided around a support shaft
3
a
of the opening-and-closing lever
3
to urge the main-circuit contacts in an opening direction. Reference numeral
5
denotes a transmission plate having a lower end linked to the opening-and-closing lever
3
, and reference numeral
6
denotes a latch receiver for responding to an output from an over-current tripping device (not shown).
The locker handle
2
is linked to the transmission plate
5
and the latch receiver
6
via a toggle-link mechanism comprising a combination of a toggle link
7
, a latch
8
, and a U-shaped pin
9
. The toggle-link mechanism and the locker handle as a whole constitute a four-node link. Reference numeral
10
denotes an alarm output plate, and reference numeral
10
a
denotes a spring extending between the alarm output plate
10
and a pin of the toggle-link mechanism.
The locker handle
2
is also known as a see-saw-type handle. A handle knob (molded resin) having an M-shape is rotatably supported on the assembly frame
1
a
of the opening-and-closing mechanism
1
at the middle thereof via a handle pin
2
a
(support shaft). A handle link projecting downward and having a rotational center shifted from the pin
2
is connected to an upper end of the toggle link
7
through a pin
11
. A lock hole
2
b
is formed in the handle knob of the locker handle
2
so that a padlock (not shown) can be inserted into the lock hole
2
b
to lock the handle at the OFF position.
Further, one end of the latch
8
is pivotally supported on the pin
2
a
and the tip pawl is engaged the latch receiver
6
. Furthermore, the U-shaped pin
9
has one end coupled to a central portion of the latch
8
and the other end connecting the lower end of the toggle link
7
to the upper end of the transmission plate
5
.
An operation of the opening-and-closing mechanism will be described with reference to FIGS.
11
(
a
)-
11
(
c
). FIGS.
11
(
a
)-
11
(
c
) show an ON operation of the opening-and-closing mechanism during, an OFF operation thereof, and a trip operation thereof, respectively. The opening-and-closing lever
3
provided in the opening-and-closing mechanism
2
is linked to the main-circuit contacts of the circuit breaker as shown in FIG.
12
(
a
). In FIG.
12
(
a
), reference numerals
12
,
13
, and
14
denote a fixed contactor, a movable contactor (bridging contactor), and a contact-pressure spring for the movable contactor, respectively.
Reference numeral
15
denotes a driving block coupled to the movable contactor
13
so as to face the opening-and-closing lever
3
. When a rotational operation force F is exerted on the locker handle
2
in the direction indicated by the arrow in FIG.
12
(
b
), the main-circuit contacts are closed or opened via the opening-and-closing lever
3
of the opening-and-closing mechanism
1
.
When the locker handle
2
is rotated counterclockwise to perform the ON operation as shown in FIG.
11
(
a
) via the toggle link
7
, the transmission plate
5
pushes down a rear end of the opening-and-closing lever
3
. Thus, a tip of the opening-and-closing lever
3
retreats upward while accumulating an urging force of the main spring
4
. In response to this, the movable contactor
13
(see FIG.
12
(
a
)) contacts the fixed contactor
12
under pressure from the spring force of the contact-pressure spring
14
. The main-circuit contacts are thus closed.
In this state, when the locker handle
2
is rotated clockwise to perform the OFF operation as shown in FIG.
11
(
b
), the transmission plate
5
releases the opening-and-closing lever
3
. The spring force accumulated by the main spring
4
is thus released. Therefore, the opening-and-closing lever
3
pushes down the block
15
, as shown in FIG.
12
(
a
), to open and separate the movable contactor
13
from the fixed contactor
12
.
When an over-current flows through the main circuit of the circuit breaker to actuate a tripping device (not shown), the latch receiver
6
is tilted to release the latch
8
as shown in FIG.
11
(
c
). The latch
8
rotates clockwise to tilt the transmission plate
5
via the U-shaped pin
9
in order to unbind the opening-and-closing lever
3
. As a result, the opening-and-closing lever
3
is rotated under the spring force of the main spring
4
to push down the block as shown in FIG.
12
(
a
). The movable contactor
13
is thus opened and separated from the fixed contactor
12
. In this case, as the latch
8
is released, the locker handle
2
is stopped by the spring force of a trip spring
10
a
(see
FIG. 9
) at a trip display position of halfway between an ON position and OFF position, and the locker handle
2
extends in a horizontal direction.
The locker handle
2
can be switched with one finger. However, the circuit breaker provided with the locker handle has the following problems.
When the circuit breaker is turned on, the rotating operation force is exerted on the knob of the locker handle
2
as shown in FIG.
12
(
b
) to rotate the locker handle
2
around the handle pin
2
a
from the OFF position (solid line) to the ON position (hidden line). The main-circuit contacts are thus closed. A characteristic line F in
FIG. 13
represents a handle load during this turn-on operation. In this case, the handle load is substantially constant at a value F
1
between the OFF position and a point A at which the movable contactor
13
abuts against the fixed contactor
12
. Once the movable contactor
13
reaches the point A from the open position, the spring force of the contact-pressure spring
14
, which urges the opening-and-closing lever
3
to push up, is applied to the fixed contactor
12
. As a result, the handle load increases from F
1
to F
2
in a stepwise manner. Beyond the point A, the handle load decreases toward the ON position.
When an operator rotates the locker handle
2
with an operation force corresponding to the handle load F
1
for turning on the circuit breaker, there is a sudden increase in the handle load at the point A. It is necessary for the operator to increase the operation force in order to rotate the handle further to the ON position. Accordingly, after the point A, the handle is slowly operated to shift the main-circuit contacts to the closed position.
When the circuit breaker is turned on to activate the motor, a starting current six times larger than the rated current flows. Therefore, when the circuit breaker is turned on slowly, it is possible that an arc is generated between the fixed and movable contacts, thereby damaging or wearing the contacts, or melting the contacts to stick with each other.
For this reason, when the circuit board is turned on, it is important to move the handle from the OFF position to the ON position quickly so as to shift the main-circuit contacts from the open position to the closed position without stopping. However, with the conventional locker handle, when the ON operation is started, the handle can move without a large operation force. When the main-circuit contacts contact with each other at the point A, the handle load suddenly increases. Accordingly, it is difficult to
Asakawa Koji
Hamada Yoshinobu
Kuboyama Katsunori
Takahashi Tatsunori
Donovan Lincoln
Fishman M.
Fuji Electric & Co., Ltd.
Kanesaka Manabu
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