Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – With bimetallic elements
Reexamination Certificate
2001-11-20
2003-09-16
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
With bimetallic elements
C337S101000, C337S111000, C337S039000, C335S145000, C335S141000, C335S031000, C335S044000
Reexamination Certificate
active
06621403
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a bimetal overload tripping device installed in a circuit breaker, such as an autobreaker.
Taking the autobreaker as an example, a configuration of a circuit breaker in which the present invention is implemented will be described with reference to FIGS.
3
(
a
) and
3
(
b
). In these figures, reference numeral
1
denotes a main body case of a circuit breaker (in the figures, the cover has been removed from the case),
2
is a power supply side main circuit terminal,
3
is a load side circuit terminal,
4
is a handle for opening and closing operations, and
5
is an adjustment dial for adjusting a current flowing through a thermal overload/open-phase tripping device to a rated value described below. The case
1
internally has a breaking section
8
formed of a movable contact shoe
8
a
, a fixed contact shoe
8
b
, and an arc extinguish chamber
8
c
, an opening-and-closing mechanism section
9
for driving the movable contact shoe
8
a
of the breaking section
8
to an open or a closed position, a thermal overload/open-phase tripping device
10
, an electromagnetic instantaneous tripping device
11
, and other parts.
The thermal overload/open-phase tripping device
10
is formed of a combination of a heater-mounted main bimetal
12
connected to each phase of a main circuit, a differential shifter mechanism
13
linked with an operating end of the main bimetal of each phase to detect operational displacement of the bimetal, and a temperature-compensating bimetal
14
interposed between the differential shifter mechanism
13
and a latch receiver incorporated in the opening-and-closing mechanism section
9
to transmit an output signal from the differential shifter mechanism to the latch receiver in order to trip the opening-and-closing mechanism section
9
, with the temperature-compensating bimetal also acting as a tripping lever.
Furthermore, the differential shifter mechanism
13
includes a combination of a slide push shifter
15
and a pull shifter
16
located on opposite sides of the arrangement of the main bimetal
12
of each phase, and fitted and supported in a groove in an interphase partition wall
1
b
of the case
1
, with an output lever
17
extending across the top surfaces of the push shifter
15
and pull shifter
16
and coupled to these shifters
15
and
16
with pins so as to move therewith. Arm portions projecting from the push shifter
15
and pull shifter
16
face each other, with the main bimetal
12
of each phase located between the arm portions.
The temperature-compensating bimetal
14
in the illustrated example is formed by bending a piece of bimetal like a hair pin, and has one end journaled on a bearing
18
linked with the adjustment dial
5
and the other end facing the output lever
17
of the above-described differential shifter mechanism
13
. Moreover, an operating piece extending from near the bearing toward the opening-and-closing mechanism section
9
faces the latch receiver of the opening-and-closing mechanism section.
When the overload tripping device configured as described above is operated, an overload current flows through the main circuit to bend the main bimetal
12
in a predetermined direction, and the push shifter
15
and pull shifter
16
of the differential shifter mechanism
13
are displaced so as to follow the bending of the main bimetal
12
. Then, the output lever
17
pushes a tip of the temperature-compensating bimetal
14
. Therefore, the temperature
5
compensating bimetal
14
rotates clockwise around a shaft support point of the bearing
18
, causing the operating piece thereof to push the latch receiver to a released position. Synchronously with this movement, the opening-and-closing mechanism section
9
is tripped to open the movable contact shoe
8
a
of the breaking section
8
, thereby interrupting the main circuit current. Furthermore, if an open phase occurs in the main circuit, the push shifter
15
and pull shifter
16
of the differential shifter mechanism
13
differentially operate to cause the output lever
17
to rotate counterclockwise around the pin coupling the output lever to the pull shifter. Thus, the temperature-compensating bimetal
14
is pushed to trip the circuit breaker, as described above.
Since the driving force or displacement of the main bimetal, which is effected when the main bimetal is bent to swing the temperature-compensating bimetal
14
, is small, the latch receiver of the opening-and-closing mechanism section
9
is designed to move to its release position under a weak driving force.
In contrast, the electromagnetic instantaneous tripping device
11
includes a tripping coil
11
a
connected to the main circuit, a yoke
11
b
, a plunger
11
c
, and a tripping lever
11
d
following a movement of the plunger
11
c
. When an overcurrent flows through the main circuit due to a short circuit or the like, the plunger
11
c
carries out a sucking or pulling operation, causing the tripping lever lid to release the latch receiver of the opening-and-closing mechanism section
9
, thereby instantaneously tripping the circuit breaker.
Furthermore, the temperature-compensating bimetal
14
in the illustrated example is bent like a hairpin and has one pivotally supported end. However, the temperature-compensating bimetal may be linearly formed so as to have a longitudinally intermediate point thereof journaled by the bearing so as to swing therearound, with one end thereof facing the output lever of the differential shifter mechanism and the other end facing the latch receiver of the opening-and-closing mechanism section via the intermediate lever. Alternatively, the tip of the temperature-compensating bimetal may extend toward the latch receiver without using the intermediate lever, or another metallic arm portion may be welded to the tip of the temperature-compensating bimetal so as to directly push the latch receiver, thereby allowing signals to be transmitted more efficiently.
In the above conventional configuration for the temperature-compensating bimetal, also acting as the tripping lever, opposite sides extending from the swinging shaft support point thereof toward the differential shifter and the latch receiver, respectively, have different lengths and masses.
In this case, if the temperature-compensating bimetal is linearly formed so as to have the longitudinally intermediate point journaled by the bearing to swing therearound, and the tip of the temperature-compensating bimetal is extended toward the latch receiver or another metallic arm portion is welded to the tip of the temperature-compensating bimetal so as to face the latch receiver, then the tip side with respect to the swinging shaft support point has a larger mass and thus a larger inertial moment than the opposite end. Consequently, the opposite sides of the temperature-compensating bimetal with respect to the swinging shaft support point are imbalanced.
Therefore, if an external stimulus, e.g., vibration or impact, is applied to a circuit breaker during use, the temperature-compensating bimetal may swing around the swinging shaft support point like a pendulum due to the difference in the inertial moment described above, pushing the latch receiver of the opening-and-closing mechanism section to its released position. Thus, although no overload current is flowing through the main circuit, the circuit breaker may be tripped to interrupt the main circuit.
The present invention is designed to resolve these issues, and an object of the invention is to provide an overload tripping device for a circuit breaker having an improved vibration-resisting performance so as to prevent the circuit breaker from being inadvertently tripped due to an external stimulus, such as a vibration or impact.
SUMMARY OF THE INVENTION
To attain this objective, the present invention provides an overload tripping device for a circuit breaker formed of a combination of a main bimetal for detecting overloads, a differential shifter mechanism linked with
Kuboyama Katsunori
Nagahiro Isamu
Oyama Jun
Uchida Naoshi
Fuji Electric & Co., Ltd.
Kanesaka & Takeuchi
Vortman Anatoly
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