DESCRIPTION
TITLE OF INVENTION
CIRCUIT BREAKER
TECHNICAL FIELD
[00011 The invention relates to a circuit breaker.
BACKGROUND ART
[00021 Conventionally, there has been a circuit breaker disclosed in JP
4769263 B2 (hereinafter, referred to as "document 1") for example.
[0003] The circuit breaker disclosed in the document 1 includes: a contact
section that includes a fixed contact and a movable contact; a link
mechanism designed to close or open the contact section according to an on or
off operation; a trip mechanism designed to actuate, in response to detection
of an abnormal current, the link mechanism to forcibly turn off (open) the
contact section; and an arc-extinguishing device. The fixed contact is fixed
to a fixed contact plate that is fixed at a prescribed location in a casing of the
circuit breaker. The movable contact is fixed to a movable contact arm that
is rotatably held in the casing.
[0004] The circuit breaker includes an electromagnetic releasing mechanism
section as the trip mechanism. The electromagnetic releasing mechanism
section includes a coil of which one end is connected to the fixed contact plate.
The electromagnetic releasing mechanism section actuates, when a short
circuit current flows through this coil, the link mechanism to rotate the
movable contact arm in a direction of being separated from the fixed contact,
thereby forcibly turning off the contact section.
[00051 This type of circuit breaker is required to increase an arc voltage as
fast as possible, when the short circuit occurs in an on-state of the contact
section. For that reason, it needs to enhance an opening speed of the
contact section.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a circuit breaker
which can enhance an opening speed of a contact section in occurrence of
short circuit.
[0007] A circuit breaker according to one aspect of the present invention
includes: a fixed contact plate provided with a fixed contact; a movable
contactor provided with a movable contact; and a trip mechanism. The
movable contactor is designed to make the movable contact come into contact
with or separate from the fixed contact. The trip mechanism includes a coil
including a winding wire. The fixed contact plate is connected to one end of
the winding wire. The trip mechanism is designed to actuate, when a short
circuit current flows through the coil, the movable contactor to forcibly
separate the movable contact from the fixed contact. The fixed contact plate
and the movable contactor are designed so that part of the fixed contact plate
is arranged aligned with part of the movable contactor in a state where the
movable contact is in contact with the fixed contact. The fixed contact plate
is connected to a region that is on an opposite side of the one end of the
winding wire from the movable contact.
[0008] According to the aspect of the invention, because the fixed contact
plate is connected to the region that is on the opposite side of the one end of
the winding wire from the movable contact, it is possible to increase a length
of each of the part of the fixed contact plate and the part of the movable
contactor which are arranged aligned with each other in a closed state,
compared with a case where the fixed contact plate is connected to a region
that is on a side close to the movable contact. In the state where the
movable contact is in contact with the fixed contact and a current flows
through the fixed contact plate and the movable contactor, a current
direction at the part of the fixed contact plate is opposite to a current
direction at the part of the movable contactor. Therefore, it is possible to
enhance Lorentz forces that respectively act on the part of the fixed contact
plate and the part of the movable contactor, through increasing the length.
Accordingly, a speed is enhanced, at which the trip mechanism actuates the
movable contactor in a direction of the movable contact being separated from
the fixed contact when the short circuit current flows. Therefore, it is
possible to enhance a speed at which the fixed contact and the movable
contact are opened, and increase an arc voltage as fast as possible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Preferred embodiments of the invention will now be described in
further details. Other features and advantages of the present invention
will become better understood with regard to the following detailed
description and accompanying drawings where:
Fig.1 is an explanatory drawing of a contact section in a circuit
breaker according to an embodiment;
Fig. 2 is a front view showing the circuit breaker in an off-state
according to the embodiment, in a state where a cover is removed;
Fig. 3 is a perspective view showing the circuit breaker in the
off-state according to the embodiment, in the state where the cover is
removed;
Fig. 4 is a front view showing the circuit breaker in an on-state
according to the embodiment, in the state where the cover is removed;
Fig. 5 is a front view showing the circuit breaker, immediately after a
trip operation, according to the embodiment, in the state where the cover is
removed;
Fig. 6 shows the circuit breaker according to the embodiment, A of
Fig. 6 is a front view, B of Fig. 6 is a left side view, C of Fig. 6 is a right side
view, and D of Fig. 6 is a top view;
Fig. 7 is an explanatory drawing of another contact section in the
circuit breaker according to the embodiment;
Fig. 8A is an explanatory drawing of yet another contact section in
the circuit breaker according to the embodiment;
Fig. 8B is an explanatory drawing of yet another contact section in
the circuit breaker according to the embodiment;
Fig. 9 is an explanatory drawing of yet another contact section in the
circuit breaker according to the embodiment; and
Fig. 10 is an explanatory drawing of a contact section in a circuit
breaker of a comparative example.
DESCRIPTION OF EMBODIMENTS
[0010] A circuit breaker according to the present embodiment will be
described with reference to Figs. 1 to 10. In the following description, a
vertical direction and a lateral direction are defined based on directions of
the circuit breaker shown in Fig. 2, and a direction perpendicular to a paper
surface of Fig. 2 is described as a front-back direction, in so far as there is no
particular remark otherwise stated. However, those directions are defined
for convenience of description, and directions of the circuit breaker in a usage
state are not limited to such directions.
[0011] As shown in Figs. 2, 3 and 6, the circuit breaker according to the
present embodiment includes: a casing 1 including a body 2 and a cover 3;
terminal devices 4A and 4B; a contact section 6 including a fixed contact 7
and a movable contact 8; an opening and closing mechanism 9; and an
electromagnetic releasing mechanism section 11 (trip mechanism). In
addition to the above-mentioned configuration, the circuit breaker according
to the present embodiment further includes: a thermal releasing mechanism
section 12; an arc-extinguishing device 13 for extinguishing an arc generated
when the contact section 6 is opened or closed; and a display member 15.
[00121 Each of the body 2 and cover 3 is formed of an insulating synthetic
resin material in substantially a box-shape, of which one surface in a width
direction thereof is open (see Figs. 1, 3 and 6). While an opening part of the
body 2 is aligned with an opening part of the cover 3, and plural bosses 2d
provided at an inner surface of the body 2 are respectively inserted into
plural through-holes (not shown) provided at a side wall of the cover 3, two
locking claws 2c provided at right and left side walls of the body 2 are
respectively locked in two locking hole 3a provided in right and left walls of
the cover 3. Then, the body 2 and cover 3 are coupled to each other by
applying heat to tips of the plural bosses 2d exposed outside through the
plural through-holes of the cover 3 and by deforming the tips.
[0013] As shown in Figs. 2 and 3, the terminal device 4A includes a terminal
plate 5A, a terminal metal fitting 16, a terminal screw 17. To the terminal
device 4A, an electric wire (not shown) &.om a load is connected. The
terminal plate 5A is formed by bending a metal plate in a U-shape, and is
fixed inside the casing 1. The terminal metal fitting 16 is formed by
bending a metal plate in a rectangular tube shape, and is attached, movably
in the vertical direction, inside the casing 1 while a lower piece of the
terminal plate 5A is inserted into the rectangular tube. The terminal screw
17 is designed to be screwed in a screw hole (not shown) provided in an upper
piece of the terminal metal fitting 16 through a through-hole provided in an
upper piece of the terminal plate 5A. Here, when the terminal screw 17 is
screwed through an opening provided in a side surface la of the casing 1
while the electric wire being inserted between a lower piece of the terminal
metal fitting 16 and the lower piece of the terminal plate 5A, the terminal
metal fitting 16 is moved upward, thereby the electric wire being hold
between the lower piece of the terminal metal fitting 16 and the lower piece
of the terminal plate 5A. One end 18a of a winding wire of a coil 18 is fixed
to the terminal plate 5A of the terminal device 4A by welding for example.
The coil 18 is one of components constituting the electromagnetic releasing
mechanism section 11 as described later.
[00141 The terminal device 4B includes a terminal plate 5B, a terminal
metal fitting 16, and a terminal screw 17. To the terminal device 4B, an
electric wire (not shown) from an external power supply is connected.
Because the terminal device 4B has a configuration similar to that of the
terminal device 4A, description thereof is omitted. One end of a braided
wire 23a is fixed to the terminal plate 5B of the terminal device 4B, and the
other end of the braided wire 23a is fixed to a bimetal plate 19.
[0015] The fixed contact 7 is provided on a fixed contact plate 20 that is fixed
at a prescribed position inside the casing I. As shown in Figs. 1 and 2, the
fixed contact plate 20 is formed by bending a metal band plate. The fixed
contact plate 20 includes: a central piece 20a having one surface on which
the fixed contact 7 is fixed; and a mounting piece 20b formed integrally with
the central piece 20a. The mounting piece 20b is formed by being bent from
an upper end of the central piece 20a at a right angle toward an opposite side
from a side on which the fixed contact 7 is provided. A lower end side of the
central piece 20a is bent in the same direction as the mounting piece 20b.
The fixed contact plate 20 is connected to the coil 18 by, for example, welding
in a state where a lower surface of the mounting piece 20b abuts on an upper
surface of the one end 18a of the coil 18.
[0016] The movable contact 8 is formed at one end part of a movable contact
arm 22 (movable contactor) that is formed by subjecting a metal plate having
a prescribed thickness to processing, such as punching processing. The
movable contact arm 22 is supported so that the other end part thereof is
rotatable with respect to a second rotary shaft 21 that is attached movably
along a guide groove 2b (see Fig. 2) that is formed in an inner wall of the
casing 1. One end side of a braided wire 23b is fixed to a middle part of the
movable contact arm 22, and the other end side of the braided wire 23b is
fixed at a middle position of the bimetal plate 19. Therefore, a conductive
path is formed with the terminal plate 5B, braided wire 23a, bimetal plate 19,
braided wire 23b, movable contact arm 22, movable contact 8, fixed contact 7,
fixed contact plate 20, coil 18 and terminal plate 5A in that order. In the
present embodiment, the movable contact 8 is formed integrally with the
movable contact arm 22. However, the movable contact 8 may be formed as
a member separate from the movable contact arm 22, and the movable
contact 8 formed independently may be fixed to the movable contact arm 22.
[0017] The opening and closing mechanism 9 includes a handle 10, a thrust
bar 27, a supporting member 26, a latch member 30, a stop bar 31, a contact
pressure spring 32, and a latch spring 33. The opening and closing
mechanism 9 is designed to turn on or off the contact section 6 in response to
an operation of the handle 10.
[0018] The handle 10 is a molded product made of synthetic resin, and is
supported to be rotatable about a handle shaft 24 provided in the body 2, in a
state where an operation knob 10a projects outside through a window hole 2a
formed in an upper wall of the body 2.
[0019] The supporting member 26 is formed by subjecting a metal plate
having a prescribed thickness to processing, such as punching processing,
and is supported by a first rotary shaft 25 provided in the casing 1 so that a
middle part thereof is rotatable about the first rotary shaft 25.
[0020] The thrust bar 27 is formed in a U-shape by bending, in one direction,
both ends of a metal bar formed in a cylindrical shape. A shaft part of one
end side of the thrust bar 27 is rotatably inserted into a shaft hole lob
formed in the handle 10. A shaft part of the other end side of the thrust bar
27 is locked with a locking part 26a provided on one end side of the
supporting member 26.
[0021] The latch member 30 is formed by subjecting a metal plate having a
prescribed thickness to processing, such as punching processing. The latch
member 30 is supported by the first rotary shaft 25 so that a middle part
thereof is rotatable together with the supporting member 26 about the first
rotary shaft 25. A closed space for locking an end part of the thrust bar 27
is formed between the above-mentioned locking part 26a and an L-shaped
claw piece 28 provided on one end side of the latch member 30. An oblong
link hole 29 is formed on the other end side of the latch member 30, and the
second rotary shaft 21 is inserted into the link hole 29.
LO0221 The stop bar 31 is formed in a U-shape by bending, in one direction;
both ends of a metal bar formed in a cylindrical shape. A shaft part of one
end side of the stop bar 31 is inserted into a guide groove 10c formed, along a
circumferential direction, in the handle 10, and a shaft part of the other end
side of the stop bar 31 is locked with an L-shaped locking part 26b provided
at the supporting member 26.
[0023] The contact pressure spring 32 is a torsion coil spring of which both
ends project mutually in opposite directions. The first rotary shaft 25 is
inserted into a central hole of the contact pressure spring 32. One end part
of the contact pressure spring 32 abuts on a spring receiving projection (not
shown) provided at the body 2, and the other end part of the contact pressure
spring 32 abuts on a spring receiving piece 22a of the movable contact arm
22. The spring receiving piece 22a is provided at an end part of the movable
contact arm 22 that is on an opposite side of the second rotary shaft 21 from
one end side of the movable contact arm 22 on which the movable contact 8 is
provided. When pressing the spring receiving piece 22a toward the right
side in Fig. 2, the contact pressure spring 32 is provided to apply, to the
movable contact arm 22, an elastic force so that the movable contact arm 22
is rotated clockwise about the second rotary shaft 21, thereby a contact
pressure being applied to the contact section 6. Further, the contact
pressure spring 32 is provided to apply, to the supporting member 26, an
elastic force so that the supporting member 26 coupled to the movable
contact arm 22 is rotated counterclockwise about the first rotary shaft 25.
Lo0241 The latch spring 33 is a torsion coil spring. The first rotary shaft 25
is inserted into a central hole of the latch spring 33. One end part of the
latch spring 33 abuts on the display member 15, and the other end part of
the latch spring 33 abuts on the latch member 30. The latch spring 33 is
provided to apply, to the latch member 30, an elastic force so that the claw
piece 28 comes closer to the locking part 26a and the latch member 30 is
rotated in a direction of changing, to a closed space, a space surrounded by
the claw piece 28 and the locking part 26a (that is, a space into which a shaft
part of the thrust bar 27 is inserted). Further, the latch spring 33 is
provided to apply, to the display member 15, an elastic force in a direction of
rotating the display member 15 counterclockwise about the first rotary shaft
25.
LO0251 The handle 10 is provided with a return spring (not shown) to apply
an elastic force for rotating the handle 10 in an off direction (a
counterclockwise direction in Fig. 2), and a link spring 34 to apply an elastic
force in a direction of moving a shaft part of the stop bar 31 to the right side
within the guide groove 10c.
Lo0261 The display member 15 is a molded product made of synthetic resin,
and is provided to display a state of the contact section 6 (any one of an
on-state, an off-state and a trip-state) in a display window 14 that is open in
an upper surface of the body 2.
LO0271 The electromagnetic releasing mechanism section 11 includes the coil
18, an oil plunger 37, and a yoke 39. When detecting an abnormal current,
such as a short circuit current, the electromagnetic releasing mechanism
section 11 is designed to forcibly open the contact section 6. The coil 18 is
formed by winding a flat type wire in a coil shape. The oil plunger 37
includes a casing that is formed of an insulating synthetic resin material in a
cylindrical shape. The coil 18 is located along an outer periphery of this
casing. A fixed iron-core (not shown) made of a magnetic material is located
inside the casing of the oil plunger 37. Further, a movable iron-core (not
shown) made of a magnetic material is located inside the casing to freely
slidably move in an axis direction thereof. A pressing pin 38 coupled to the
movable iron-core projects outside through one end surface of the oil plunger
37 (a surface that faces the latch member 30). A return spring (not shown)
is provided to apply an elastic force to the movable iron-core in a direction of
being separated from the fixed iron-core, and accordingly, the pressing pin 38
is moved in a direction of being separated from the latch member 30 (toward
the left side in Fig. 2) with movement of the movable iron-core. The yoke 39
is formed of a magnetic material in a tubular shape of which both side
surfaces in a front-back direction thereof are open. The yoke 39 is located so
as to surround a periphery of the coil 18 to form a magnetic path.
[0028] Thus, in the electromagnetic releasing mechanism section 11, the
pressing pin 38 (coupled to the movable iron-core by the elastic force of the
return spring) is located at a left end of the electromagnetic releasing
mechanism section 11, in a state where no current flows through the coil 18
(an initial state). On the other hand, when a current flows between the
terminal devices 4A and 4B and thereby the coil 18 is energized, a magnetic
attraction force acts between the movable iron-core and the fixed iron-core so
as to reduce a magnetic resistance of a magnetic path that passes through
the fixed iron-core, yoke 39 and movable iron-core in that order. Here, when
the current flowing through the coil 18 is excessive such as a short circuit
current, the movable iron-core moves to a side of the fixed iron-core against
the elastic force of the return spring. At this time, the pressing pin 38
coupled to the movable iron-core is moved to project in a right direction of Fig.
2, and the latch member 30 is pressed to the right side with a tip of the
pressing pin 38, and accordingly, a trip operation is performed by the opening
and closing mechanism 9. When the contact section 6 is forcibly opened by
the trip operation, the current flowing through the coil 18 is decreased and
the attraction force acting on the movable iron-core is reduced. Therefore,
the movable iron-core is moved to an initial position through the elastic force
of the return spring, and the pressing pin 38 retreats to the left end (an
initial position).
[0029] The thermal releasing mechanism section 12 is designed to forcibly
open the contact section 6, when detecting an abnormal current, such as an
overload current. The bimetal plate 19 constituting the thermal releasing
mechanism section 12 may be a directly heated type of bimetal plate that is
curved by self-heating, or an indirectly heated type of bimetal plate that is
heated and curved by a plate-shaped heater that is laminated thereon. The
bimetal plate 19 is not curved in a state where no current flows through the
bimetal plate 19, and accordingly, a tip of the bimetal plate 19 does not abut
on the latch member 30. On the other hand, when an excessive current,
such as an overload current, flows between the terminal devices 4A and 4B,
temperature of the bimetal plate 19 is increased due to the overload current
flowing through the conductive path, and in response to it the bimetal plate
19 is curved. When the bimetal plate 19 is curved and the tip thereof
presses the latch member 30 toward the right side, the opening and closing
mechanism 9 performs the trip operation. When the contact section 6 is
forcibly opened by the trip operation, the current flowing through the
bimetal plate 19 is decreased and the temperature is reduced. Therefore,
the degree of curvature of the bimetal plate 19 becomes small, and then the
tip of the bimetal plate 19 is returned to the initial state that the tip thereof
is at a position apart from the latch member 30.
[0030] As shown in Figs. 2 and 3, the arc-extinguishing device 13 includes
an arc running plate 13a and an arc-extinguishing grid 13b. The arc
running plate 13a is formed by bending a band-plate-shaped metal plate. A
base of the bimetal plate 19 is coupled to one end of the arc running plate 13a.
The arc running plate 13a is designed to extend toward the left side of the
casing 1 along a lower wall of the casing 1. The other end of the arc running
plate 13a is located on the lower side of the yoke 39. The arc-extinguishing
grid 13b is located between the other end of the arc running plate 13a and a
lower piece of the yoke 39. The arc-extinguishing grid 13b is formed by
alternately stacking a plurality of arc-extinguishing plates 13c, each of which
is formed of a conductive material in a flat plate, and a plurality of insulating
plate pieces. In this way, the plurality of arc-extinguishing plates 13c of the
arc-extinguishing grid 13b are located between the arc running plate 13a
and the lower piece of the yoke 39. Accordingly, when an arc is generated by
the movable contact 8 being separated from the fixed contact 7, the
arc-extinguishing device 13 is designed to extend and extinguish the arc.
Because for the arc-extinguishing device 13 a well-known thing can be used,
detailed description thereof is omitted in the present embodiment.
[00311 Next, an operation of the circuit breaker according to the present
embodiment will be described with reference to Figs. 2 to 5. Figs. 2 and 3
are explanatory drawings for the off-state (opened state), and Fig. 4 is an
explanatory drawing for the on-state (closed state), and Fig. 5 is an
explanatory drawing for the state immediately after the trip operation.
[0032] As shown in Figs. 2 and 3, in the off-state, the handle 10 is rotated in
an off-rotary direction (counterclockwise direction in Fig. 2) by receiving a
spring force of a handle spring, and the operation knob 10a is stopped at a
position of abutting on a left edge of the window hole 2a. The thrust bar 27
and the stop bar 31 are pulled up with the rotation of the handle 10, thereby
a pressing force that the thrust bar 27 applies to the supporting member 26
being eliminated. At this time, by a returning force of the contact pressure
spring 32, the supporting member 26 is rotated counterclockwise about the
first rotary shaft 25, and the movable contact arm 22 is rotated clockwise
about the second rotary shaft 21. The supporting member 26 is stopped at a
position of the second rotary shaft 21 being moved to a terminal position (a
right end in Fig. 2) of the guide groove 2b, and the movable contact arm 22 is
stopped at a position of a stopper piece 22b abutting on the locking part 26b,
and accordingly, the movable contact 8 is separated from the fixed contact 7.
The stopper piece 22b is designed to project from a left edge of an upper end
part of the movable contact arm 22. The latch member 30 is rotated
clockwise in Fig. 2 by receiving the spring force of the latch spring 33. Here,
the latch member 30 is stopped at a position of the claw piece 28 locking with
a shaft part of the thrust bar 27.
i00331 In the off-state (see Fig. 2) of the contact section 6, when the
operation knob 10a of the handle 10 is rotated from an off-position in an
on-direction (clockwise direction in Fig. 2), the shaft part of the thrust bar 27
presses the locking part 26a of the supporting member 26 with the rotation
of the handle 10. Therefore, the supporting member 26 is rotated clockwise
in Fig. 2 about the first rotary shaft 25, and then the second rotary shaft 21
(attached at a rear end of the supporting member 26) slides in a direction of
coming closer to the fixed contact plate 20 (the left side in Fig. 2) along the
guide groove 2b. Because the spring receiving piece 22a is pressed in the
right side direction by the contact pressure spring 32, the entire movable
contact arm 22 is moved to the left side in Fig. 2 with the slide movement of
the second rotary shaft 21, and the movable contact arm 22 is rotated
clockwise in Fig. 2 about the second rotary shaft 21. Here, when a lower
shaft part of the stop bar 31 is moved downward with the rotation of the
handle 10 and abuts on the stopper piece 22b of the movable contact arm 22,
the rotation of the movable contact arm 22 is stopped by the stop bar 31, and
the second rotary shaft 21 slides to the left side in Fig. 2 while the rotation
position of the movable contact arm 22 is kept unchanged with respect to the
casing 1. Then, in response to the slide movement of the second rotary shaft
21, the shaft part of the stop bar 31 (inserted into the guide groove 10c of the
handle 10) is moved to the left side in Fig. 2 over a line segment of connecting
the handle shaft 24 and the other shaft part of the stop bar 31, thereby a
pressing force that the shaft part of the stop bar 31 applies to the stopper
piece 22b being eliminated. Therefore, the movable contact arm 22 is
rapidly rotated clockwise in Fig. 2 about the second rotary shaft 21 by a
biasing force accumulated in the contact pressure spring 32 during the
rotation being stopped by the stop bar 31, and accordingly, the movable
contact 8 is shifted to a state of being in contact with the fixed contact 7 in a
short time (see Fig.4).
[0034] Then, in a state where the handle 10 is rotated to an on-position as
shown in Fig. 4, a shaft part of one end side (a side inserted into the shaft
hole lob) of the thrust bar 27 is moved to the opposite side (lower side) over a
line segment connecting the handle shaft 24 and a shaft part of the other end
of the thrust bar 27. In this state, the spring force of the contact pressure
spring 32 is balanced with the spring force of the handle spring and the like,
and the handle 10 is kept at the on-position, and accordingly, the contact
section 6 becomes in the closed state. The latch member 30 is rotated
clockwise in Fig. 4 by receiving the spring force of the latch spring 33.
However, the rotation of the latch member 30 is stopped at a position of the
claw piece 28 locking with the shaft part of the thrust bar 27. In the
on-state, the contact pressure is generated between the movable contact 8
and the fixed contact 7 by the spring force of the contact pressure spring 32.
[00351 Further, in the on-state (see Fig. 4) of the contact section 6, when the
operation knob 10a of the handle 10 is rotated from the on-position in the
off-direction, the thrust bar 27 and the stop bar 31 are pulled up with the
rotation of the handle 10. At this time, because the pressing force that the
thrust bar 27 applies to the supporting member 26 is eliminated, the
supporting member 26 is rotated counterclockwise about the first rotary
shaft 25 by the returning force of the contact pressure spring 32, and the
movable contact arm 22 is rotated clockwise about the second rotary shaft 21.
The supporting member 26 is stopped at a position of the second rotary shaft
21 being moved to the terminal position of the guide groove 2b, and the
movable contact arm 22 is stopped at a position of the stopper piece 22b
abutting on the locking part 26b of the supporting member 26, and
accordingly, the contact section 6 is opened. When the shaft part (inserted
into the shaft hole lob) of the thrust bar 27 is moved, with the rotation of the
handle 10, to the opposite side over the line segment connecting the handle
shaft 24 and a shaft part of the other end of the thrust bar 27, the handle 10
is rapidly rotated in the off-direction by the spring force of the handle spring.
Therefore, the movable contact 8 is shifted to a state of being separated from
the fixed contact 7 in a short time, and accordingly it is possible to prevent
occurrence of the arc. In the off-state of the contact section 6, the rotation of
the latch member 30 is stopped at a position of the claw piece 28 locking with
the shaft part of the thrust bar 27.
LO0361 Next, the trip operation will be described, which is performed by the
thermal releasing mechanism section 12 and the electromagnetic releasing
mechanism section 11. Regarding the trip operation, an operation of the
thermal releasing mechanism section 12 will be first described.
Lo0371 In the on-state of the contact section 6 (see Fig. 41, when an abnormal
current, such as an overload current, flows through the conductive path, the
temperature of the bimetal plate 19 is increased by the excessive current
flowing through the conductive path, and then the bimetal plate 19 is curved.
When the bimetal plate 19 is curved, the latch member 30 is pressed in the
right direction against the spring force of the latch spring 33 with an upper
end part of the bimetal plate 19. At this time, the claw piece 28 is moved in
a direction of being separated from the supporting member 26 by the latch
member 30 being rotated counterclockwise about the first rotary shaft 25,
and accordingly, the space surrounded by the claw piece 28 and the locking
part 26a becomes an opened space (see Fig. 5). When this space becomes
the opened space, the shaft part (inserted into the shaft hole lob) of the
thrust bar 27 is moved outside the space surrounded by the claw piece 28
and the supporting member 26. At this time, because a force that the
handle 10 applies to the supporting member 26 is eliminated, the supporting
member 26 is rotated counterclockwise about the first rotary shaft 25 by the
returning force of the contact pressure spring 32, and the movable contact
arm 22 is rotated clockwise about the second rotary shaft 21. Then, the
supporting member 26 is stopped at a position of the second rotary shaft 21
being moved to the terminal position of the guide groove 2b, and the movable
contact arm 22 is stopped at a position of the stopper piece 22b abutting on
the locking part 26b of the supporting member 26, and accordingly, the
movable contact 8 is forcibly separated from the fixed contact 7. In the trip
operation, the handle 10 is rotated from the on-position to the off-position by
the spring force of the handle spring. The shaft part of the thrust bar 27 is
pulled to the left side in Fig. 5 with the rotation of the handle 10, and is
moved inside the space surrounded by the claw piece 28 of the latch member
30 and the locking part 26a of the supporting member 26. Therefore, the
circuit breaker becomes a state similar to the off-state except for the rotation
position of the display member 15.
[0038] Further, in the on-state of the contact section 6 (see Fig. 41, when an
abnormal current, such as a short circuit current, flows through the
conductive path, a magnetic field is generated by a current flowing through
the coil 18, and a magnetic attraction force acts between the movable
iron-core and the fixed iron-core, and the movable iron-core is moved to the
side of the fixed iron-core. Here, the pressing pin 38 is moved to project in
the right direction in response to the movement of the movable iron-core, and
the latch member 30 is pressed to the right side with the pressing pin 38, and
accordingly, the latch member 30 is rotated counterclockwise in Fig. 4 about
the first rotary shaft 25. In this time, the claw piece 28 is moved in a
direction of being separated from the locking part 26a of the supporting
member 26, and the space surrounded by the claw piece 28 and the locking
part 26a becomes the opened space, and the shaft part of the thrust bar 27 is
moved outside the space. Accordingly, the above-mentioned trip operation
is performed, and the contact section 6 is forcibly opened.
[0039] Here, in the circuit breaker according to the present embodiment, the
fixed contact plate 20 and the movable contact arm 22 are designed so that
part (hereinafter, referred to as a first piece 40) of the fixed contact plate 20
is arranged aligned in parallel with part (hereinafter, referred to as a second
piece 41) of the movable contact arm 22, in the on-state of the contact section
6 (Figs. 1 and 4). Further, the fixed contact plate 20 is connected to a region
60 of the one end 18a (an upper surface of the one end 18a in Fig. 1) that is
on an opposite side of the one end 18a (of the winding wire of the coil 18)
from the movable contact 8.
[0040] Therefore, it is possible to increase a length of each of the first piece
40 and the second piece 41 arranged aligned with each other, compared with
a case where the fixed contact plate 20 is connected to a region of the one end
18a (a lower surface of the one end 18a in Fig. 10) that is on a side close to
the movable contact 8 as shown in Fig. 10 (see Dl in Fig. 1 and D3 in Fig. 10).
Here, when a current flows through the fixed contact plate 20 and the
movable contact arm 22, a current direction at the first piece 40 arranged in
parallel with the second piece 41 is opposite to a current direction at the
second piece 41. Due to this, Lorentz forces that have directions of repelling
each other are generated at the first piece 40 and second piece 41,
respectively. Therefore, when the electromagnetic releasing mechanism
section 11 and the thermal releasing mechanism section 12 forcibly open the
contact section 6, the Lorentz forces generated at the fixed contact plate 20
and the movable contact arm 22 act so as to separate the movable contact 8
from the fixed contact 7. Accordingly, it is possible to enhance an opening
speed of the contact section 6. Further, because an arc voltage is steeply
increased, a short circuit current is decreased. Accordingly, it is possible to
obtain good circuit breaking performance.
[00411 When the handle 10 is rotated from the off-position to the
on-direction (clockwise direction in Fig. 5) to return the circuit breaker from
the trip-state, the shaft part of the thrust bar 27 presses the locking part 26a
of the supporting member 26 with the rotation of the handle 10. At this
time, the supporting member 26 is rotated clockwise in Fig. 1 about the first
rotary shaft 25, and the second rotary shaft 21 (attached at the rear end of
the supporting member 26) slides in a direction of coming closer to the fixed
contact plate 20 (the left side in Fig. 5) along the guide groove 2b. Because
the spring receiving piece 22a is pressed in the right side direction by the
contact pressure spring 32, the entire movable contact arm 22 is moved to
the left side in Fig. 5 with the slide movement of the second rotary shaft 21,
and the movable contact arm 22 is rotated clockwise in Fig. 5 about the
second rotary shaft 21. At this time, when a lower shaft part of the stop bar
31 is moved downward with the rotation of the handle 10 and abuts on the
stopper piece 22b of the movable contact arm 22, the rotation of the movable
contact arm 22 is stopped by the stop bar 31, and the second rotary shaft 21
slides to the left side in Fig. 5 while the rotation position of the movable
contact arm 22 is kept unchanged with respect to the casing 1. Then, in
response to the slide movement of the second rotary shaft 21, the shaft part
of the stop bar 31 (inserted into the guide groove 10c of the handle 10) is
moved to the left side in Fig. 5 over a line segment of connecting the handle
shaft 24 and the other shaft part of the stop bar 31, thereby a pressing force
that the shaft part of the stop bar 31 applies to the stopper piece 22b being
eliminated. Therefore, the movable contact arm 22 is rapidly rotated
clockwise in Fig. 5 about the second rotary shaft 21 by an elastic force
accumulated in the contact pressure spring 32 during the rotation being
stopped by the stop bar 31, and accordingly, the movable contact 8 is shifted
to a state of being in contact with the fixed contact 7 in a short time. Then,
in a state where the handle 10 is rotated to the on-position, a shaft part of
one end side (a side inserted into the shaft hole lob) of the thrust bar 27 is
moved to the opposite side (lower side) over a line segment connecting the
handle shaft 24 and a shaft part of the other end of the thrust bar 27.
Accordingly, the spring force of the contact pressure spring 32 is balanced
with the spring force of the handle spring and the like, and the handle 10 is
kept at the on-position (see Fig. 4).
Lo0421 In the circuit breaker according to the present embodiment, as shown
in Fig. 7, it is preferred that the fixed contact plate 20 includes a projection
part 20c that is formed between a region 70 fixed to the one end 18a of the
coil 18 (winding wire) and a region 80 at which the fixed contact 7 is provided.
In the fixed contact plate 20, the projection part 20c is designed to project to
an opposite side of the region 70 (fixed to the one end 18a of the winding
wire) &.om the fixed contact 7.
lo0431 In this way, a length D2 of each of the part (first piece 40) of the fixed
contact plate 20 and the part (second piece 41) of the movable contact arm 22
arranged aligned with each other can be set to be longer than a length Dl in
the case of Fig. 1, by forming the projection part 20c in the fixed contact plate
20. Accordingly, in the on-state of the contact section 6, it is possible to
more increase the Lorentz forces generated at the fixed contact plate 20 and
the movable contact arm 22 which are arranged in parallel with each other,
and it is possible to more enhance the opening speed in short circuit.
Therefore, because the arc voltage is more steeply increased, the short circuit
current is decreased and it is possible to obtain good circuit breaking
performance.
[00441 In the present embodiment, as shown in Figs. 8A and 8B, it is
preferred that the circuit breaker further includes a reinforcing part 50 that
is provided at the one end 18a of the winding wire connected to the fixed
contact plate 20. In this case, it is preferred that the reinforcing part 50 is
designed to be in contact with the part (first piece 40) of the fixed contact
plate 20 arranged aligned with the part (second piece 41) of the movable
contact arm 22, from an opposite side of the part (first piece 40) of the fixed
contact plate 20 from the movable contact arm 22, in the state where the
movable contact 8 is in contact with the fixed contact 7.
LO0451 In the on-state of the contact section 6, the fixed contact plate 20
receives a force that is applied toward a side of the coil 18 (the left side in
Figs. 8A and 8B) by the movable contact 8 coming into contact with the fixed
contact 7 at a prescribed contact pressure, and accordingly, there is a
possibility that the fixed contact plate 20 is plastically deformed. If the
fixed contact plate 20 is plastically deformed, there is a possibility that a
sufficient contact pressure cannot be obtained between the movable contact 8
and the fixed contact 7. In view of that, as shown in Figs. 8A and 8B, it is
preferred that the reinforcing part 50 is provided at the one end 18a of the
coil 18. It is possible to support the fixed contact plate 20 by the reinforcing
part 50 being in contact with the fixed contact plate 20 from the opposite side
of the fixed contact plate 20 from the movable contact 8. Therefore, the
fixed contact plate 20 is hardly deformed plastically.
LO0461 The reinforcing part 50 may be formed of a conductive material, or an
insulating material. In the case of the reinforcing part 50 with conductivity,
because a tip of the reinforcing part 50 is in contact with the fixed contact
plate 20, a part of a current flowing through the fixed contact plate 20 flows
to the coil 18 through the reinforcing part 50. However, the reinforcing part
50 and the fixed contact plate 20 are only in contact with each other without
being fixed to each other. Therefore, an electric resistance of a contact
portion at which the reinforcing part 50 is in contact with the fixed contact
plate 20 is larger than an electric resistance in the case where those are fixed
to each other. Accordingly, a current flowing to the coil 18 through the
reinforcing part 50 from the fixed contact plate 20 is sufficiently smaller than
a current flowing directly to the coil 18 &om the fixed contact plate 20. For
this reason, similarly to a case where the reinforcing part 50 is not provided,
it is possible to increase the length of each of the part (first piece 40) of the
fixed contact plate 20 and the part (second piece 41) of the movable contact
arm 22, at which the current directions are in parallel and opposite to each
other, and further it is possible to enhance the opening speed by the Lorentz
forces generated at the fixed contact plate 20 and the movable contact arm
22.
[0047] Here, as shown in Fig. 9, the one end 18a of the coil 18 to which the
fixed contact plate 20 is connected may be designed to extend so as to be
directly in contact with the central piece 20a from an opposite side of the part
(first piece 40) of the fixed contact plate 20 from the movable contact arm 22.
That is, the above-mentioned reinforcing part may be configured by an
extension part 18b that is formed by extending the one end 18a of the coil 18.
It is possible to reduce the number of components and the cost of the circuit
breaker, by the reinforcing part being formed of the same material as the
winding wire of the coil 18.
100481 In the circuit breaker according to the present embodiment, as shown
in Figs. 8B and 9, it is preferred that the winding wire of the coil 18 is
connected to the fixed contact plate 20 by caulking with a rivet 51. In this
case, it is possible to connect, at a low cost, the winding wire of the coil 18 to
the fixed contact plate 20.
[0049] The circuit breaker according to the present embodiment includes the
thermal releasing mechanism section 12 in addition to the electromagnetic
releasing mechanism section 11, as described above. However, the thermal
releasing mechanism section 12 is not mandatory. In addition, the terminal
devices 4A and 4B, and the opening and closing mechanism 9 are not limited
to the above-mentioned configurations, and suitable configurations may be
used according to a situation.
[00501 As described above, according to the present embodiment, the circuit
breaker includes: the fixed contact plate 20 provided with the fixed contact 7;
the movable contactor (movable contact arm 22) provided with the movable
contact 8; and the trip mechanism (electromagnetic releasing mechanism
section 11). The movable contactor (movable contact arm 22) is designed to
make the movable contact 8 come into contact with or separate from the
fixed contact 7. The trip mechanism (electromagnetic releasing mechanism
section 11) includes the coil 18 including the winding wire. The fixed
contact plate 20 is connected to the one end 18a of the winding wire. The
trip mechanism (electromagnetic releasing mechanism section 11) is
designed to actuate, when a short circuit current flows through the coil 18,
the movable contactor (movable contact arm 22) to forcibly separate the
movable contact 8 from the fixed contact 7. The fixed contact plate 20 and
the movable contactor (movable contact arm 22) are designed so that the part
(first piece 40) of the fixed contact plate 20 is arranged aligned with the part
(second piece 41) of the movable contactor (movable contact arm 22) in a
state where the movable contact 8 is in contact with the fixed contact 7.
The fixed contact plate 20 is connected to the region 60 that is on the
opposite side of the one end 18a of the winding wire from the movable contact
8.
[0051] In the circuit breaker, preferably, the fixed contact plate 20 includes
the projection part 20c that is formed between the region 70 fixed to the
winding wire, and the region 80 at which the fixed contact 7 is provided. In
this case, preferably, the projection part 20c is designed to project to the
opposite side of the region 70 fixed to the winding wire &om the fixed contact
7.
Coo521 Preferably, the circuit breaker further includes the reinforcing part
50 that is provided at the one end 18a of the winding wire connected to the
fixed contact plate 20. In this case, preferably, the reinforcing part 50 is
designed to be in contact with the part (first piece 40) of the fixed contact
plate 20, from the opposite side of the part (first piece 40) of the fixed contact
plate 20 from the movable contactor (movable contact arm 22), in the state
where the movable contact 8 is in contact with the fixed contact 7.
[0053] In the circuit breaker, preferably, the reinforcing part 50 is formed of
the same material as the winding wire of the coil 18.
100541 In the circuit breaker, preferably, the winding wire of the coil 18 is
connected to the fixed contact plate 20 by caulking.
[0055] In the circuit breaker, preferably, the movable contact 8 is formed
integrally with the movable contactor (movable contact arm 22), alternately,
the movable contact 8 is formed separately from the movable contactor
(movable contact arm 22) and fixed to the movable contactor (movable
contact arm 22).
LO0561 Although the present invention has been described with reference to
certain preferred embodiments, numerous modifications and variations can
be made by those skilled in the art without departing from the true spirit
and scope of this invention, namely claims.

CLAIMS
1. A circuit breaker, comprising:
a fixed contact plate provided with a fixed contact;
a movable contractor provided with a movable contact, the movable
contractor being designed to make the movable contact come into contact with
or separate from the fixed contact; and
a trip mechanism comprising a coil including a winding wire, the
fixed contact plate being connected to one end of the winding wire, the trip
mechanism being designed to actuate, when a short circuit current flows
through the coil, the movable contractor to forcibly separate the movable
contact from the fixed contact,
wherein the fixed contact plate and the movable contractor are
designed so that part of the fixed contact plate is arranged aligned with part
of the movable contractor in a state where the movable contact is in contact
with the fixed contact, and
wherein the fixed contact plate is connected to a region that is on an
opposite side of the one end of the winding wire from the movable contact.
2. The circuit breaker according to claim 1,
wherein the fixed contact plate comprises a projection part that is
formed between a region fixed to the winding wire, and a region at which the
fixed contact is provided, and
wherein the projection part is designed to project to an opposite side
of the region fixed to the winding wire from the fixed contact.
3. The circuit breaker according to claim 1 or 2, further comprising a reinforcing part that is provided at the one end of the winding wire connected to the fixed contact plate,
wherein the reinforcing part is designed to be in contact with the part of the fixed contact plate, from an opposite side of the part of the fixed contact plate from the movable contractor, in the state where the movable contact is in contact with the fixed contact.
4. The circuit breaker according to claim 3,
wherein the reinforcing part is formed of the same material as the winding wire of the coil.
5. The circuit breaker according to any one of claims 1 to 4, wherein the winding wire of the coil is connected to the fixed contact plate by caulking.
6. The circuit breaker according to any one of claims 1 to 5, wherein the movable contact is formed integrally with the movable contractor.
7. The circuit breaker according to any one of claims 1 to 5, wherein the movable contact is formed separately from the movable contractor, and fixed to the movable contractor.
wherein the