Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Multiple contact type
Reexamination Certificate
2001-11-16
2003-06-10
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Multiple contact type
C335S202000
Reexamination Certificate
active
06577215
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a circuit breaker, such as an autobreaker, applied to the protection of an electric motor.
Manufacturers of such circuit breakers, which are main components of low-voltage distribution devices, define the products with the construction described below as a standard and produce variations thereof to meet users' various needs.
The construction of the standard circuit breaker is shown in
FIGS. 5
,
6
(
a
), and
6
(
b
), using an autobreaker by way of example. In
FIG. 5
, reference numeral
1
denotes a circuit breaker case (resin mold case),
2
is a power-supply-side main circuit terminal,
3
is a load-side main circuit terminal,
4
is a handle for opening-and-closing operations,
5
is an adjustment dial for adjusting a rated current, with the adjustment dial facing a cover
1
a
of the case
1
,
6
is a test trip slot into which a screwdriver or the like is inserted from the outside for a trip test, and
7
is a name plate. The case
1
has a main circuit breaking section
8
, which is formed of a movable contact shoe
8
a
, a fixed contact shoe
8
b
, and an arc-extinguishing chamber
8
c
; a toggle-link-type opening and closing mechanism section
9
for driving the movable contact shoe
8
a
of the breaking section
8
between an open position and a closed position; a thermal overload/open-phase tripping device
10
corresponding to each phase; and an electromagnetic instantaneous tripping device
11
. These components are arranged as illustrated in FIGS.
6
(
a
) and
6
(
b
).
In this case, the thermal overload/open-phase tripping device
10
and the electromagnetic instantaneous tripping device
11
are integrally assembled together for each phase, to constitute a trip unit. 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 the main circuit, a differential shifter mechanism
13
linked with a main bimetal operating end (upper end) for each phase so as to interconnect with the bimetal, a temperature-compensating bimetal
14
for linking an output end of the differential shifter mechanism
13
with a latch receiver incorporated into the opening and closing mechanism section
9
, with the temperature-compensating bimetal
14
also being used as a tripping lever, and the adjustment dial
5
described previously.
Further, the differential shifter mechanism
13
is formed of a combination of a sliding push shifter
15
and a sliding pull shifter
16
, which are positioned along the main bimetals
12
for the respective phases on the respective sides thereof, and are guided and supported in a groove in an interphase partition wall
1
b
of the case
1
, with an output lever
17
extending over the push shifter
15
and the pull shifter
16
and being pivotally coupled with pins. The push shifter
15
and pull shifter
16
have L-shaped arms
15
a
and
16
a
, respectively, which project toward the main bimetal
12
for each phase, so that in an assembled position, the tips of the arms are located opposite to the respective surfaces of the main bimetal
12
so as to sandwich the main bimetal therebetween. Furthermore, the adjustment dial
5
described above has a groove
5
a
formed in a top surface thereof into which a screwdriver or the like is inserted for operation. A rated current value is printed around the periphery of a dial hole opened in the case cover
1
a
so as to correspond to an arrow printed on the top surface of the dial
5
.
The operation of the thermal overload/open-phase tripping device
10
is well known. When an overload current continuously flows through the main circuit, the main bimetal
12
is bent correspondingly in a predetermined direction under heat by the heater, and the push shifter
15
and pull shifter
16
of the differential shifter mechanism
13
are displaced in the direction indicated by an arrow in FIG.
6
(
a
) so as to follow the bending of the bimetal. The output lever
17
then pushes the tip of the temperature compensating bimetal
14
. This causes the temperature compensating bimetal
14
to rotate clockwise to push the latch receiver into its released position, and in synchronism with this movement, the opening and closing mechanism section
9
performs a trip operation to open the movable contact shoe
8
a
of the breaking section
8
, interrupting the current flowing through the main circuit. If an open phase occurs, the push shifter
15
and pull shifter
16
of the differential shifter mechanism
13
operate in a differential manner to cause the output lever
17
to rotate counterclockwise around the pin for coupling with the pull shifter in order to push the temperature compensating bimetal
14
, thereby causing the circuit breaker to perform a trip operation as described above.
On the other hand, the electromagnetic instantaneous tripping device
11
is formed of a trip coil
11
a
, which is commonly referred to as an “instant coil”, a yoke
11
b
, a plunger
11
c
, and a tripping lever
11
d
that follows the operation of the plunger
11
c.
The trip coil
11
a
and the heater-mounted main bimetal
12
are connected together in series, and are interposed between and connected to the load-side main circuit terminal
3
and the fixed contact shoe
8
a
of the breaking section
8
. When an overcurrent, such as short circuit current, flows through the main circuit, the plunger
11
c
performs a suctioning operation to cause the tripping lever lid to depress a tripping plate incorporated in the opening and closing mechanism section
9
, thereby driving the latch receiver described above into its released position in order to cause the circuit breaker to instantaneously perform a trip operation.
If the opening and closing mechanism section
9
undergoes a trip test in a non-conductive state, a screwdriver or the like is inserted into the test trip slot
6
, shown in
FIG. 5
, from the outside in order to move the output lever
17
(which has a projection to be caught by a tip of the screwdriver) of the differential shifter mechanism
13
(see FIGS.
6
(
a
) and
6
(
b
)). Then, as in the tripping operation for the overload current, the latch receiver of the opening and closing mechanism section
9
moves to its released position via the temperature compensating bimetal
14
to perform a trip operation.
When a standard circuit breaker provided with the thermal overload/open-phase tripping device
10
and the electromagnetic instantaneous tripping device
11
as standard equipments is applied to a distribution circuit using as a load an electric motor requiring an extended period for start-up, the start current and time for the electric motor can not be coordinated with the overload protection characteristics of the circuit breaker. Consequently, while the electric motor is being started up, the thermal overload/open-phase tripping device
10
may operate to cause the circuit breaker to perform a trip operation.
Thus, a feeding circuit using as a load an electric motor requiring a particularly long time for start-up may employ a circuit breaker comprising the standard circuit breaker described above, which does not perform the overload/open-phase tripping function in order to prevent the circuit breaker from inadvertently performing a trip operation while the electric motor is being started up. Instead, a thermal relay is connected to the load side of the circuit breaker to protect the electric motor from overload.
Further, in a variation of a circuit breaker that is adapted for the above application conventionally, the differential shifter mechanism
13
, the temperature compensating bimetal
14
, and the adjustment dial
5
are removed from the standard circuit breaker shown in FIGS.
6
(
a
) and
6
(
b
) in order to disable the overload/open-phase tripping function, and the case cover
1
a
, shown in
FIG. 5
, is modified so that the dial hole and test trip slot therein are blocked.
However, the conventional instantaneous-tripping circuit bre
Asakawa Koji
Emura Takeshi
Kuboyama Katsunori
Nagahiro Isamu
Nomura Koji
Donovan Lincoln
Fuji Electric & Co., Ltd.
Kanesaka & Takeuchi
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