Title of Invention: THERMAL TRIPPING MECHANISM OF CIRCUIT BREAKER
Technical Field [0001]
The present invention relates to a thermal tripping mechanism of a circuit breaker such as a wiring breaker or an earth leakage breaker. Background Art [0002]
The circuit breaker (hereinafter abbreviated as a breaker) such as the wiring breaker or the earth leakage breaker includes a terminal for receiving electric power supplied to the breaker, a terminal for supplying the electric power to a load side, a switching contact for cutting off electrical current between the terminals and a thermal electromagnetic tripping mechanism as shown, for example, in Fig. 1 of Patent Literature 1. Moreover, an electric path for the above is covered with, an insulating cover for securing safety when being operated by a human and for keeping line-to-line insulation thereinside. The thermal tripping mechanism is formed by a bimetal and a heater which is joule-heated by a rated current flowing in the device for bending the bimetal as shown in Fig.

,"*'.'—.. . *^.' '"'.. ■'-"' "-" '•■ " '-"- -c:V'.-"'.'-'■''■'■.'■-•'■
■• -j of Patent Literature 1, which has a configuration in which
"■ '1 an adjuster disposed at a tip of the bimetal pushes a switching
•■> '. ..;.." ■■;■.
mechanism and releases a latch to thereby open the switching
contact when electrical current higher than the rated current
flows.
[00.03] ^
"■■ " V Also in the breaker, electric wires or bus bars
corresponding to the rated current are respectively fixed to
respective terminals by screws and so on though not shown, which
function as paths for feedipg, power to the breaker as well as - .
which feed power also to a subsequent load-side circuit.
Citation List
Patent Literature ,
[0004]
Patent Literature 1: WO2014/Q100 4 0 v
Patent Literature 2: JP-A-2014-13699
i, * , .-
Summary of Invention *■'' ■ _'.,--
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Technical Problem . .- . - . ■ "
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:- |0005] ■. '"- -r - s< '-'■ .,■ i/*. .'. -""" '-.'. --* ";,;*•■'■..■ '$;': ; .'. '^; '■•:
In the thermal tripping mechanism of the breaker, when
electrical current higher than the rated current flows, a - •■■ .
* *. 1
function of breaking a circuit is required after a certain period of time delay. In the case of Patent Literature 1, heat ■ ' generation by the heater installed in the electric path is used
for detection of the electrical current. A heat generation *

amount of the heater and the electrical current are in
one-to-one correspondence from a relation of: heat generation amount of heater=R*I2 by a resistance R of the heater and an electrical current
I. However, a bending amount of the bimetal which operates
ft
in an absolute temperature is used as a method of detecting the heat generation, therefore, the mechanism is affected by : an outdoor air temperature in addition to the heat generation amount at the.time of detection. That is, when the outdoor air temperature is higher than a prescribed outdoor air temperature, the bimetal bends more, therefore, the mechanism is affected such that the circuit is broken by less electrical current or cut off in earlier time. Due to such characteristics, certain restrictions are placed on the outdoor air temperature of the breaker and an installation place is managed at present. . [0006]
There is a case where a compensation means for the outdoor air temperature is introduced as in Patent Literature 2 is adopted in addition to the above, however, the inside of the breaker with respect to the outdoor air is covered with an insulating cover. This cover has not only high electrical insulation properties but also high thermal resistance, and high thermal resistance is generated between a compensation bimetal for measuring an outdoor air temperature and the outdoor air, therefore, it is difficult to correct the outdoor

air temperature with high accuracy. [0007]
The present invention has been made in view of the above problems, and an object thereof is to provide a thermal tripping mechanism of a circuit breaker capable of detecting a heaL generation amount used for detecting electrical current with high accuracy to be transmitted to a switching mechanism without being affected by an outdoor air temperature. Solution to Problem [0008]
In order to solve the above problems, a thermal tripping mechanism of a circuit; breaker according to a first aspect of the present invention includes a heater that generates heat in accordance with energizing current, a high-temperature side bimetal and a low-temperature side bimetal that are deformed by heating in directions opposite to each other and that have the same characteristics as each oLher, a thermal resistor that thermally couples the high-temperature side bimetal to the low-temperature side bimetal and a holding means for mechanically coupling the high-temperature side bimetal to the low-temperature side bimetal and that fixes positions of connecting portions between the high-temperature side bimetal and the low-temperature side bimetal, in which the high-temperature side bimetal is arranged closer to the heater than the low-temperature side bimetal is, and a mechanism parL

for opening switching contacts is operated in accordance with movement of the holding means due to deformation of the high-temperature bimetal and the low-temperature bimetal. [0009]
Moreover, a thermal tripping mechanism of a circuit breaker according to a second aspect of the present invention includes a heater that generates heat by electrical current flowing from a power-supply side terminal to a load-side terminal, a high-temperature side bimetal and a low-temperature side bimetal that are thermally coupled so as to be deformed by heating in directions away from each other and that have the same characteristics as each other, a thermal resistor connected between the high-temperature side bimetal and the low-temperature side bimetal, a holding means for fixing tip end positions of the high-temperature side bimetal and the low-temperature side bimetal, an adjuster that moves with movement of the holding means and a trip bar that is driven with movement of the adjuster and that operates a mechanism part for opening switching contacts, in which the high-temperature side bimetal is arranged in the heater's side and the low-temperature side bimetal is arranged in the load-side terminal's side. [0010]
Moreover, a thermal tripping mechanism of a circuit breaker according to a third aspect of the present invention

includes a heater that generates heat by electrical current
flowing from a power-supply side terminal to a load-side
terminal, a high-temperature side bimetal and a
low-temperature side bimetal that are thermally coupled so as
to be deformed by heating in directions away from each other
and that have the same characteristics as each other, a thermal
resistor that is connected between a connecting portion of the
heater and the high-temperature side bimetal and a connecting
portion of the load-side terminal and the low-temperature side
bimetal and that has rigidity with which an interval between
the connecting portions of the high-temperature side bimetal
and the low-temperature side bimetal is capable of being
maintained, a holding means formed of the bridge-shaped piece
that has sufficient high electrical resistance with respect
to the thermal resistor and that has rigidity with which an
interval between tip ends of the high-temperature side bimetal
and the low-temperature side bimetal is capable of being
maintained, an adjuster that moves with movement of the holding
means and a trip bar that is driven with movement of the adjuster
and that operates a mechanism part for opening switching
contacts, in which the high-temperature side bimetal is
arranged in the heater's side and the low-temperature side
bimetal is arranged in the load-side terminal's side.
Advantageous Effects of Invention
[0011]

In the thermal tripping mechanism of the circuit breaker according to the present invention, the thermal resistor that thermally couples the high-temperature side bimetal to the low-temperature side bimetal is provided, thereby directly measuring a status of a heat flow flowing in the thermal resistor and detecting electrical current with high accuracy as the mechanism is not affected by the outdoor air temperature, as a result, highly accurate breaking can be realized. Brief Description of Drawings [0012]
[Fig. 1] Fig. 1 is a side view showing a schematic structure of a thermal tripping mechanism of a circuit breaker according to Embodiment 1 of the present invention.
[Fig. 2] Fig. 2 is a view for explaining operations of bimetals in the thermal tripping mechanism of the circuit breaker according to Embodiment 1 of the present invention. [Fig. 3] Fig. 3 is a side view for explaining operations of bimetals in a thermal tripping mechanism of a circuit breaker according to Embodiment 8 of the present invention. [Fig. 4] Fig. 4 is a top view for explaining operations of bimetals in the thermal tripping mechanism of the circuit breaker according to Embodiment 8 of the present invention. Description of Embodiments [0013] Embodiment 1

A thermal tripping mechanism of a circuit breaker according to Embodiment 1 of the present invention will be explained with reference to Fig. 1 and Fig. 2. Fig. 1 is a side view showing a schematic structure of a thermal tripping mechanism of a circuit breaker according to Embodiment 1. Fig. 2 is a view for explaining operations of bimetals in the thermal tripping mechanism of the circuit breaker according to Embodiment 1. The structure of the circuit breaker is approximately the same as one disclosed in Patent Literature
T
1, and Fig. 1 corresponds to Fig. 3 in Patent Literature 1.
[0014]
In Fig. 1, a conductor 21 connected to an external power
supply is engaged with a power-supply side terminal 22 made of a conductive metal by screws, and a power supply side contact 23 made of a silver alloy is brazed at an end of the power-supply side terminal 22. A mover-side contact 24 made of a silver alloy that makes contact with the power supply side contact 23 with a certain contact pressure and a mover 25 fixed to the mover-side contact 24 by brazing or caulking are arranged. The mover 25 is moved by a trip bar 6 being pushed by an adjuster 5, which is connected to a mechanism part 26 opening between respective contacts when movement of a certain degree or more occurs. [0015]
The mover 25 is connected to a relay part via a conductor

11. The relay part is electrically connected to a load-side terminal 7 via a heater 8 that generates heat proportional to
■ ■ '-- ' -"- ■ -■ Z? V ■ X '' . '' * ■'■.
a square ol energized electrical current and a thermal res'is'libr
1 cpntinued from the heater 8. An external conductor 28 is
engaged with the load-side terminal 7 by screws, and the power
is supplied to the load circuit through the external conductor
28. A high-temperature side bimetal, 2 is thermally connected
to the thermal resistor on the heater 8 side by a caulking 10.
A low-temperature, side bimetal 3 is thermally connected to the
*'^/load-side terminal 7 side by a caulking 9. ' -
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Moreover, as shown in a deformation operation in Fig.
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2; the''nign-temperatiire bimetal 2 is arranged so as to be deformed in .a -direction of the trip bar 6 by heating and the-
■""■■ low-temperature bimetal 3 is arranged so as; to be deformed in
an opposite direction of the- trip bar 6 by heating.
[0017] " ' •
A bridge-shaped piece 4 is fixed to tip ends of the high-temperature bimetal 2 and the low-temperature bimetal 3. The bridge-shaped piece A is formed of a material having high tnernial resistance and high electrical resistance as compared with materials of the thermal resistor 1 and the heater 2 as
' well as a material havinq high rigidity so that deformation of the high-lemperature side bimetal 2 and the low-temperature side bimetal 3 is transmitted to each other. Respective
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electrode components and the mechanism part are fixed by a base 27 formed of resin so that positions are fixed while being electrically insulated.
[0018] , ,., .. ; ' \... '"'''. "', . . _. r_ . __.
■ . Electrical current flowing from the external power
, - "supply to the power-supply side terminal 22 flows into the
conductor 11 through the switching contacts 23 and 24 via the
mover 25 and is connected to the conductor 28. in the outside
of the breaker at a set place via the heater 8, the thermal
conductor ' 1 and the load-side terminal 7. The external , .
conductor 28 adopts a copper cable having a sufficient girth
in advance or a corresponding bus bar made of copper so.that
i the cable itself does not generate heat by Joule heat and is , ■
not fused. As the external conductor 28 is made of copper,
the conductor 28 is not only an electrical conductive conductor
but also a thermally.high conductor, and further, the conductor
28 contacts the air over a very long length until reaching the
next device, therefore, the conductor 28 is a heat radiator
that is thermally synchronized with temperature.
[0019] '. "
When the heater 8 is Joule-heated by the electrical current flowing in the electric path, a temperature of the heater 8 is increased, which is transmitted to the high-temperature side bimetal 2 via the caulking portion 10 and increases a temperature of the high-temperature side

bimetal, therefore, the high-temperature side bimetal 2 is going to bend in a direction of the trip bar 6. The adjuster 5 can arbitrarily set an interval between the adjuster 5 and the trip bar 6. When a heat amount generated in the heater 8 reaches a set rated current, the adjuster 5 sufficiently pushes the trip bar 6 to drive the mechanism, moving the mover 25 to a position of 25' to open the contacts, [0020]
In the thermal tripping mechanism of the circuit breaker according to the embodiment, the low-temperature side bimetal 3 is thermally and electrically connected to the load-side terminal 7 made of copper having high electrical and thermal conductivity, or corrosion resistance of which is increased by performing tin-plating and so on together with one end portion of the thermal resistor 1 made of stainless steel or iron through the fastening mechanism 9 such as caulking. Moreover, the other end of the thermal resistor 1, the high-temperature side bimetal 2 and the heater 8 formed of a nickel-chrome heating band such as NCHR2 are thermally and electrically connected by the fastening component 10 such as caulking. As the thermal resistor 1 is formed of a high strength material such as stainless steel or iron, there is an effect of keeping an interval between a root of the high-temperature side bimetal 2 and a root of the low-temperature side bimetal 3 constant due to strength of

itself. The low-temperature side bimetal 3 is connected to an external conductor which is the heat radiator that is synchronized with the air via the load-side terminal 7 having good thermal conductivity, therefore, low-temperature side bimetal 3 is affected by a temperature of the external conductor, namely, an air temperature, but is hardly affected by heat generation inside the breaker. [0021]
The high-temperature side bimetal 2 and the low-temperature side bimetal 3 are set to have shapes so that bending amounts at tip ends are the same at the same temperature and loads at the tip ends necessary for maintaining initial positions are the same when a holding means formed of the bridge-shaped piece 4 is not provided. They are called bimetals having the same characteristics. When temperature becomes high, the high-temperature side bimetal 2 is formed to be deformed in the direction of the trip bar 6 as shown in Fig. 2, whereas the low-temperature side bimetal 3 is formed to be deformed in the direction of the load-side terminal 7. [0022]
The high-temperature side bimetal 2 and the low-temperature side bimetal 3 are connected by the holding means formed of the bridge-shaped piece 4 that is made of non-thermal conductive and electrical conductive resin in a flame-retardant grade, for example, PBT (Polybutylene

Terephthalate) or the like, thereby constantly maintaining an interval between tip ends of the high-temperature side bimetal 2 and the low-temperature side bimetal 3 as well as preventing disturbance of a heat generation amount of the heater by occurrence of electrical conduction or preventing reduction in a temperature gradient due to thermal conduction between the high-temperature side bimetal 2 and the low-temperature side bimetal 3. [0023]
A heat generation amount generated in the heater 8 by an electrical current I passing through the breaker is RI2 when an electrical resistance of the heater 8 is R. The generated heat is transmitted through the electric path or radiated through the air to be contacted, the base 27 for holding, a cover for covering a series of components and so on. [0024]
The thermal conductivity of the base 29 and the cover is extremely lower than copper which is the material for the electric path as described above, and the air inside the cover is the same, therefore, most heat is transmitted through the electric path. The switching contacts 23 and 24 are provided before the conductor 11, and the switching contacts are conducted by a point contact and thermal resistance is high, and heat generated in the heater 8 is substantially radiated to the external conductor through the load-side terminal 7.

That is, a primary heat radiation path of the heater 8 is configured by the heater 8, the thermal resistor 1, the load-side terminal 7 and the external conductor 28 in this order. [0025]
Assuming a case where the outdoor air temperature is increased now, the high-temperature side bimetal 2 and the low-temperature side bimetal 3 have the same temperature as heat is not generated in the heater 8 when not energized, but the high-temperature side bimetal 2 and the low-temperature side bimetal 3 are respectively going to bend in directions away from each other. However, as bimetal characteristics are the same, respective forces cancel each other out and the position of the adjuster 5 is not moved. Both in cases where the temperature is increased and where the temperature conversely changes to the low-temperature side, the position of the adjuster 5 is not changed as there is not a temperature difference between both ends of the thermal resistor 1. [0026]
Next, a case where electrical current which should be cut off is flowing is considered. As electrical current flows, Joule heat is generated in the heater 8. The heat is radiated to the external conductor 28 via the thermal resistor 1 and via the load-side terminal 7. As the thermal resistor 1 has thermal resistance, a thermal gradient proportional to the heat

generation amount, namely, electrical current is generated, therefore, a difference occurs between a temperature in a portion of the high-temperature side bimetal 2 and a temperature in a portion of the low-temperature side bimetal 3, and the temperature in the portion of the high-temperature side bimetal 2 is increased. Then, the high-temperature side bimetal 2 is going to bend more as compared with the low-temperature side bimetal 3, therefore, the adjuster 5 moves in the direction of the trip bar 6 side as a whole. When electrical current which should be cut off flows, the adjuster 5 is adjusted so that the adjuster pushes the trip bar 6 and moves the mover 25 to a position of a broken line 25' in the drawing to open the switching contacts 23, 24, as a result, electrical current can be cut off by an appropriate breaking current. [0027]
The thermal gradient is proportional only to the heat amount generated in the heater 8 because the primary heat radiation path is configured by the heater 8, the thermal resistor 1, the load-side terminal 7 and the external conductor 28 in the order, and due to the thermal resistance of the thermal resistor 1, therefore, the thermal gradient is not affected by the outdoor air temperature. That is, the present structure can directly measure a generated heat amount because the structure measures a thermal gradient by generated heat, not

an absolute temperature by generated heat, therefore, it is possible to detect electrical current with high accuracy, as a result, the switching contacts can be opened with high accuracy. [0028]
In the present structure, a deformation amount with respect to the temperature is reduced to 1/2 as compared with a case of using one bimetal, however, the accuracy is comprehensively improved as the structure is not affected by the outdoor air temperature. This improves not only operation accuracy of the breaker body incorporating the present structure but also accuracy for adjusting cutoff operation timing at the time of manufacturing the breaker, therefore, there are advantages that rework at the time of manufacture is reduced and manufacturing accuracy is also improved. [0029]
A thermal tripping mechanism of a circuit breaker according to the embodiment includes the heater 8 that generates heat by energizing current flowing from the power-supply side terminal 22 to the load-side terminal 7, the high-temperature side bimetal 2 and the low-temperature side bimetal 3 that are thermally coupled so as to be deformed by heating in directions opposite to each other and in directions away from each other and that have the same characteristics, the thermal resistor 1 that is thermally connected between a

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"'■'. ."''connecting portion of the heater 8 and the high-temperature
-■ _" side bimetal 2- and a connecting portion of the load-side .:
j. terminal 7 and the low-temperature side bimetal 3 and that has"
,"^ frigidity with which an- interval between the connecting portions
■'i" -"";of the high-temperature side bimetal 2 and the low-temperature
■ . side bimetal 3 is capable of being maintained/ the holding means
■'" ■ ■' '*'-formed of the bridge-shaped piece 4 that has sufficient high
electrical resistance with respect: t'o the thermal resistor 1-
'■'and that has rigidity with which an interval between "tip ends
.■ .v ;i.as deforming portions, of; the high-temperature side bimetal 2
-!fc ''and the low-temperature side bimetal 3 is capable of being
l
** maintained, the adjuster 5 that moves with movement of the
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. holdi'ng. means and the" trip bar 6 that is driven with movement
of . th» adjuster .5 and that operates, the contact ■opening
mechanism part 26 for opening switching contacts, in which Lhe
■ y ■ ".*■ '' ,-.
f.:" " 'high-temperature side bimetal 2 is arranged in the heater B side and the low-temperature side bimetal 2 is arranged in the load-side terminal 7 side so that: the high-temperature side ^ 4 ,r bimetal 2 is arranged closer to the heater 8 than the • . low-temperature side bimetal 3 is, ' and the contact opening >'' .'mechanism part 26 for opening the switching contacts is ...operated in accordance with the movement of the holding means . /formed of the bridge-shaped piece 4 due to deformation of the high-temperature side bimetal 2 and the low-temperature bimetal 3. ' " " ~ ■
j i

[0030]
According to the above, a heat flow flowing in the thermal resistor 1 that thermally connects high-temperature side bimetal 2 to the low-temperature bimetal 3 and .that has the thermal gradient from one end to the other end can be directly measured, therefore, energizing current can be detected with high accuracy because not affected by the outdoor air temperature and a highly accurate circuit breaking function can be realized.
i
[0031] ■ .
i '• i
Here, the thermal resistor 1 is formed of a heat transfer body having an appropriate thermal resistance such as iron or stainless steel, one end of which is thermally coupled to Lhe heater 8 that .generates heat in accordance with energizing current. The other end of the thermal resistor 1 is thermally coupled to the load-side terminal 7 that is electrically and thermally connected to the conductor 28 for external connection as the heat radiator to the air. The thermal gradient exists between one end and the other end of the thermal resistor 1. In one end of the thermal resistor 1, a high temperature area where a temperature is determined by a generated heat temperature corresponding to energizing current and an outdoor air temperature is formed. In the other end of the thermal resistor 1, a low temperature area where a temperature is determined by the outdoor air temperature is formed. The

high-temperature side bimetal 2 is thermally coupled to the high temperature area and the low-temperature side bimetal 3 is thermally coupled to the low temperature area. [0032]
Effects due to the outdoor air temperature are cancelled out by conflicting deformation actions of the high-temperature side bimetal 2 and the low-temperature bimetal 3 having the same characteristics as each other. A difference of temperature conditions due to the heat generation amount corresponding to energizing current in the high temperature area and the low temperature area at one end and the other end of the thermal resistor 1 having the thermal gradient is expressed in a form of movement of the holding means formed of the bridge-shaped piece 4 as a difference of temperature deformations between the high-temperature side bimetal 2 and the low-temperature side bimetal 3, and the holding means formed of the bridge-shaped piece 4 is moved to thereby open the switching contacts. A status of a heat flow phenomenon by heat loss proportional to energizing current in the thermal resistor 1 having the thermal gradient is directly measured and detected to thereby perform an opening action and to thereby perform a circuit breaking action corresponding to an energizing current value with high accuracy without being affected by the outdoor air temperature. [0033]

Embodiment 2
In Embodiment 1, a distance between roots of the high-temperature side bimetal 2 and the low-temperature bimetal 3 is held by the thermal resistor 1. In Embodiment 2, a soft body product such as a carbon flexible stranded wire is used instead of the thermal resistor 1 and the distance is held by a reinforcing means different from the soft body product. The structure not affected by a material strength of the thermal resistor can be obtained and choices of the thermal resistor can be increased by adopting the above structure. [0034] Embodiment 3
In Embodiment 1, the heater 8 and the thermal'resistor 1 are formed of different materials. In Embodiment 3, the heater 8 and the thermal resistor 1 can be formed of the same material by devising a shape of a heater portion such as by narrowing the width, by changing a thickness or by providing a through hole. Moreover, the load-side terminal 7 and the thermal resistor 1 may be integrally formed by the similar devices. It is possible to reduce the number of components and reduce a unit price for product assembly by adopting the above structure. [0035] Embodiment 4
In Embodiment 1, the bridge-shaped piece 4 is a PBT molded

article. In Embodiment 4, a structure in which electrical conduction and thermal conduction are kept sufficiently lower than the thermal resistor 1, for example, a resin coated metal product, an insert molding resin product of metal and so on are used. Both insulation properties and strength are realized and a light structure can be obtained by adopting the above structure. [0036] Embodiment 5
In Embodiment 1, the heater 8 is formed of a nickel-chrome heating band. In Embodiment 5, a function of the heater is given to the high-temperature side bimetal by allowing electrical current to flow in the bimetal itself by a rated current to generate heat. As materials for the heater can be reduced by adopting the above structure, it is possible to further reduce a product price. [0037] Embodiment 6
In Embodiment 1, the energizing electric path is configured by the conductor 11, the heater 8, the thermal resistor 1 and the load-side terminal 7 in this order. In embodiment 6, the thermal resistor 1 is fixed in a position of the bridge-shaped piece 4 by the rated current, and the energizing electric path is configured by the conductor 11, the heater 8, the high-temperature side bimetal 2, the thermal

resistor 1, the low-temperature side bimetal 3 and the load-side terminal 7 in this order, thereby reducing strength of the bridge-shaped piece 4 by a degree corresponding to strength of the thermal resistor 1, therefore, materials to be used for the bridge-shaped piece 4 can be reduced. It is possible to reduce a product price by adopting the above structure. [0038] Embodiment 7
In Embodiment 1, a space is formed between the high-temperature side bimetal 2 and the low-temperature side bimetal 3. In Embodiment 7, a shielding wall is provided between the high-temperature side bimetal 2 and the low-temperature side bimetal 3 to prevent the air in a product casing from being heated by heating by the heater 8, to prevent the air from circulating in the low-temperature side bimetal 3 and heating the low-temperature side bimetal 3. It is possible to alleviate effects of heating due to circulation of the air and to detect the thermal gradient with higher accuracy by adopting the above structure. [0039] Embodiment 8
In Embodiment 1, the high-temperature side bimetal 2 and the low-temperature side bimetal 3 are sequentially arranged along the electric path. In Embodiment 8, the

high-temperature side bimetal is formed by two high-temperature side bimetals 2, and the high-temperature side bimetals 2 are arranged in a straight line respectively on both sides of the low-temperature side bimetal 3 as shown in a side view of Fig. 3 and a top view of Fig. 4. According to the structure, a distance in a direction of the electric path is reduced though a width in a direction perpendicular to the electric path is increased, therefore, a length in the direction of the electric path can be shortened. Though the bridge-shaped piece 4 and the adjuster 5 are omitted for making the drawings easy to see in Fig. 3 and Fig. 4, the bridge-shaped piece 4 is disposed so as to fix top portions of the high-temperature side bimetals 2 and the low-temperature side bimetal 3 to one another, and the adjuster 5 is provided at one end of the bridge-shaped piece 4, therefore, the same operation as Embodiment 1 can be expected. [0040] Embodiment 9
In Embodiment 8, the high-temperature side bimetals 2 are arranged on both sides of the low-temperature side bimetal 3. In Embodiment 9, the low-temperature side bimetal is formed by two low-temperature side bimetals 3, and the low-temperature side bimetals 3 are arranged in a straight line respectively on both sides of the high-temperature side bimetal 3. Accordingly, the same operation as Embodiment 8 can be

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part, 27: base, 28: external conductor :'"
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[Claim 1]
A thermal tripping . mechanism of a circuit breaker comprising:
a heater that generates heaL in accordance with '
energizing current; . ■
a high-temperature side bimetal and a low-temperature .''"
side bimetal that are deformed by heating in directions
opposite to each other and that have the same characteristics
as each other; , . *
a thermal resistor that thermally couples the , high-temperature side bimetal to the low-temperature side
i
bimetal; and _ -.
a holding means for mechanically coupling the
high-temperature side bimetal to the low-temperature side
bimetal and that fixes positions of connecting portions between
the high-temperature side bimetal and the low-temperature side
bimetal, . ■ •
wherein the high-temperature side bimetal is arranged closer to the heater than the low-temperature side bimetal is, and
a mechanism part for opening switching contacts is operated in accordance with movement of the holding means due to deformation of the high-temperature side bimetal and the

low-temperature side bimetal. [Claim 2]
A thermal tripping mechanism of a circuit breaker comprising:
a heater that generates heat by electrical current flowing from a power-supply side terminal to a load-side terminal;
a high-temperature side bimetal and a low-temperature side bimetal that are thermally coupled so as to be deformed by heating in directions away from each other and that have the same characteristics as each other;
a thermal resistor connected between the high-temperature side bimetal and the low-temperature side bimetal;
a holding means for fixing tip end positions of the high-temperature side bimetal and the low-temperature side bimetal;
an adjuster that moves with movement of the holding means; and
a trip bar that is driven with movement of the adjuster and that operates a mechanism part for opening switching contacts,
wherein the high-temperature side bimetal is arranged in the heater's side and the low-temperature side bimetal is arranged in the load-side terminal's side.

[Claim 3]
A thermal tripping mechanism of a circuit breaker comprising:
a heater that generates heat by electrical current flowing from a power-supply side terminal to a load-side terminal;
a high-temperature side bimetal and a low-temperature side bimetal that are thermally coupled so as to be deformed by heating in directions away from each other and that have the same characteristics as each other;
a thermal resistor that is connected between a connecting portion of the heater and the high-temperature side bimetal and a connecting portion of the load-side terminal and the low-temperature side bimetal and that has rigidity with which an interval between the connecting portions of the high-temperature side bimetal and the low-temperature side bimetal is capable of being maintained;
a holding means formed of a bridge-shaped piece that has sufficient high electrical resistance with respect to the thermal resistor and that has rigidity with which an interval between tip ends of the high-temperature side bimetal and the low-temperature side bimetal is capable of being maintained;
an adjuster that moves with movement of the holding means; and
a trip bar that is driven with movement of the adjuster

and that operates a mechanism part for opening switching contacts,
wherein the high-temperature side bimetal is arranged in the heater's side and the low-temperature side bimetal is arranged in the load-side terminal's side. [Claim 4]
The thermal tripping mechanism of the circuit breaker according to claim 2,
wherein the thermal resistor is formed of a stranded wire, and
a reinforcing means for maintaining a distance between the connecting portions between the high-temperature side bimetal and the low-temperature side bimetal. [Claim 5]
The thermal tripping mechanism of the circuit breaker according to claim 2,
wherein the heater and the thermal resistor are formed of the same material by changing a width or a thickness or by providing a through hole. [Claim 6]
The thermal tripping mechanism of the circuit breaker according to claim 2 or 5,
wherein the load-side terminal and the thermal resistor are formed of the same material by changing a width or a thickness or by providing a through hole.

[Claim 7]
The thermal tripping mechanism of the circuit breaker according to claim 2,
wherein electrical current is allowed to flow in the high-temperature side bimetal to thereby give a function of the heater to the high-temperature side bimetal itself. [Claim 8]
The thermal tripping mechanism of the circuit breaker according to claim 2 or 7,
wherein the thermal resistor is connected to tip ends of the high-temperature side bimetal and the low-temperature side bimetal to thereby maintain a distance between tip ends of the high-temperature side bimetal and the low-temperature side bimetal. [Claim 9]
The thermal tripping mechanism of the circuit breaker according to claim 2,
wherein a shielding wall for blocking heat is provided between the high-temperature side bimetal and the low-temperature side bimetal.