Contactor device for circuit breaker

A contactor device for a circuit breaker includes a stationary contactor having a stationary contact, and a stationary conductor secured with the stationary contact and constituting an electricity path extending from an external terminal to the stationary contact, and a movable contactor having a movable contact movable to detachably touch the stationary contact, and a movable conductor secured with the movable contact and constituting an electricity path extending from the movable contact to another external terminal. The contactor device further includes a stationary core made of a ferromagnetic material with a gap between both ends of the stationary core and surrounding the stationary conductor, a movable core provided at a distance from said stationary core to be attracted toward the stationary core by a magnetic flux generated in the stationary core by an excessive overcurrent flowing through the circuit breaker, and an electrically insulating plate movable in a direction perpendicular to that of separation of the movable contact from the stationary contact, so that the insulating plate is moved together with the movable core and inserted into a space between the stationary contact and the movable contact at the time of the attraction of the movable core toward the stationary core, when the breaker cuts off the overcurrent.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a contactor device for a circuit breaker, 
which comprises a stationary contactor composed of a stationary contact 
and a stationary conductor secured with the stationary contact and 
constituting an electricity path extending from an external terminal to 
the stationary contact, and a movable contactor composed of a movable 
contact movable to detachably touch the stationary contact, and a movable 
conductor secured with the movable contact and constituting an electricity 
path extending from the movable contact to another external terminal. 
2. Prior Art 
FIG. 17 shows the contactor device of a conventional circuit breaker, which 
includes a stationary conductor 4 shaped as a U-shaped plate and having 
two mutually parallel portions 4a and 4b. A stationary contact 5 is 
secured to the outside surface of the portion 4a. A movable contact 6, 
which is moved into and out of touch with the stationary contact 5, is 
secured to a movable conductor 7 provided in parallel with the two 
mutually parallel portions 4a and 4b of the stationary conductor. The 
stationary conductor 4 and the stationary contact 5 constitute a 
stationary contactor. The movable conductor 7 and the movable contact 6 
constitute a movable contactor. The stationary contactor and the movable 
contactor constitute the contactor device of the circuit breaker. 
When the circuit breaker with the contactor device thus constituted cuts 
off a heavy current such as an overcurrent at a relatively high voltage, 
an arc generated between the stationary contact 5 and the movable contact 
6 at the time of the cut-off of the heavy current needs to be quickly 
driven in between arc extinguishing plates 14a in an arc extinguishing 
chamber 14 and cooled by the arc extinguishing plates to heighten the arc 
voltage to the voltage of a power supply. For that reason, the relative 
portions of the contacts 5 and 6 and the arc extinguishing plates 14a, the 
number and dimensions of the plates and so on are determined so that the 
arc generated between the contacts 5 and 6 is quickly driven in between 
the plates and cooled by the plates to heighten the arc voltage to the 
voltage of the power supply while the arc is moved and lengthened in the 
order of a, b and c as shown in FIG. 18. 
However, if the property of recovery of insulation between the stationary 
contact 5 and the movable contact 6 has only a small margin for the 
circuit voltage or is insufficient therefor, an arc is generated again 
between the contacts 5 and 6 at the time of appearance of a recovery 
voltage therebetween after the current cut-off action of the circuit 
breaker or the former arc continues to exist without a clear no-current 
period present before the generation of the latter arc, so that the arc 
repeatedly takes sequential states shown by a, b and c in FIG. 18. In that 
case, it is impossible to cut off the current finally. In order to prevent 
such a phenomenon to surely cut off the current, the gap between the 
contacts 5 and 6 needs to be enlarged as shown by a one-dot chain line in 
FIG. 18. As a result, however, the circuit breaker becomes larger and more 
expensive if it is for a relatively high voltage circuit, resulting in 
drawback. 
SUMMARY OF THE INVENTION 
The present invention was made in order to eliminate the above-mentioned 
drawback with the conventional contactor device. 
Accordingly, it is an object of the present invention to provide a 
contactor device which makes it possible to surely cut off a current at a 
relatively high voltage, without making a circuit breaker larger and more 
expensive. 
The above-mentioned object is achieved by a provision of a contactor device 
which includes a stationary contactor composed of a stationary contact and 
a stationary conductor secured with the stationary contact and 
constituting an electricity path extending from an external terminal to 
the stationary contact; a movable contactor composed of a movable contact 
movable into and out of touch with the stationary contact and a movable 
conductor secured with the movable contact and constituting an electricity 
path extending from the movable contact to another external terminal; a 
stationary core made of a ferromagnetic material, which is formed so as to 
surround the stationary conductor through a gap between both ends of the 
stationary core; a movable core provided at a distance from the stationary 
core near the gap between both ends of the stationary core so as to be 
attracted toward the stationary core by a magnetic flux generated in the 
stationary core by an overcurrent flowing through the circuit breaker; and 
an electrically insulating plate provided to be movable in a direction 
perpendicular to that of separation of the movable contact from the 
stationary contact, so that the electrically insulating plate is moved 
together with the movable core and inserted into the gap between the 
stationary and the movable contacts at the time of the attraction of the 
movable core toward the stationary core, when the circuit breaker cuts off 
the overcurrent. 
The present invention is created in view of the experimental result that 
the property of recovery of insulation after the current cut-off action 
depends upon the period of time maintaining an arc between the stationary 
contact and the movable contact in the state of a shown in FIG. 18. 
In the contactor device thus constituted according to the present 
invention, since an arc generated between the stationary and movable 
contacts is forcibly driven toward an arc extinguishing chamber by the tip 
portion of the electrically insulating plate, the time throughout which 
the arc stays between or near both the stationary and movable contacts is 
much shortened. Since the electrically insulating plate is evaporated by 
the heat of the arc, the vapor of relatively low temperature retards the 
rise in the temperature of the contacts to suppress the melting or 
evaporation thereof. The vapor of relatively low temperature also cools 
the arc to quickly heighten the voltage across the arc to limit the 
excessive overcurrent. As a result, the energy of the arc is decreased so 
that the property of recovery of insulation between both the contacts 
after the current cut-off action of the circuit breaker is improved. Since 
the electrically insulating plate covers the whole stationary contact when 
the distance between the movable and stationary contacts is still minimum, 
the property of recovery of insulating therebetween is improved further so 
that the arc does not continue to exist or another arc is not generated 
again, even if a relatively high transient recovery voltage is applied 
between both the contacts at the instant of the end of the cut-off of the 
overcurrent. For that reason, the overcurrent can be always cut off 
easily, surely and stably without increasing the distance between the 
stationary and movable contacts at the time of separation thereof, namely, 
without enlarging the circuit breaker. The size and cost of the circuit 
breaker can thus be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The contactor device for the circuit breaker according to the present 
invention will be described in detail with reference to the drawings 
attached hereto. 
FIGS. 1 through 8 show a contactor device according to one embodiment of 
the present invention. The contactor device includes a stationary 
conductor 44 shaped as a strip. A stationary core 39 is formed so as to 
surround the stationary conductor 44 through a trapezoidal gap Ga between 
both ends of the stationary core 39, as shown in FIG. 2. The stationary 
core 39 extends in a direction perpendicular to the longitudinal direction 
of the stationary conductor 44 so as to hold both sides of the stationary 
conductor 44 and is provided with a pair of grooves 39c opposite to each 
other to be coupled to the bottom of the stationary conductor 44 in a 
magnetically and mechanically rigid manner. An electrically insulating 
plate 40, which is inserted into the gap between a stationary contact 5 
and a movable contact 6 when the movable contact 6 is detached (separated) 
from the stationary contact 5, is inserted into the opening between the 
stationary conductor 44 and the grooves 39c of the stationary core 39 in 
the direction of the thickness thereof to be movable along one surface of 
the stationary conductor 44. The electrically insulating plate 40 is 
coupled to a plate-like trapezoidal movable core 41 by a stepped pin 42, 
which is movable while being guided by a slot 44b penetrating the 
stationary conductor 44 in the direction of the thickness thereof and 
extending in the longitudinal direction thereof as shown in FIGS. 3 and 4. 
When an overcurrent flows through the stationary conductor 44 so that the 
movable core 41 is attracted toward the stationary core 39 by a magnetic 
flux generated in the stationary core, the electrically insulating plate 
40 coupled to the movable core 41 by the stepped pin 42 is moved toward 
the stationary contact 5 as the initial direction of the movement of the 
electrically insulating plate 40 toward the stationary contact is kept by 
the inner surfaces of the opposite grooves 39c of the stationary core 39, 
so that the electrically insulating plate 40 is surely inserted into the 
gap between the stationary contact 5 and the movable contact 6 and closely 
covers the whole stationary contact. As a result, an arc generated between 
both the contacts 5 and 6 is forcibly driven toward an arc extinguishing 
chamber by the tip portion of the electrically insulating plate 40, and 
the electrically insulating plate made of an arc extinguishing dielectric 
material such as an aromatic polyester is partly evaporated by the heat of 
the arc to cool the stationary contact 5 and the arc around the stationary 
contact 5 to quickly heighten the arc voltage and to limit the excessive 
overcurrent thereby to decrease the energy of the arc. The property of 
recovery of insulation between both the contacts 5 and 6 after the current 
cutoff action of the contactor device is thus made high. 
FIGS. 9 through 12 show a contactor device according to another embodiment 
of the present invention. The contactor device includes a stationary 
conductor 21 of a U-shape. As shown in FIG. 11, a pair of pins 34 and a 
pin 37 different in height from each other are planted in a lower portion 
21b of the stationary conductor 21. The small-diameter portions of the 
pins 34 and 37 are fitted in slots 35 provided in a thin movable plate 25 
made of nonmagnetic metal, as shown in FIG. 12. A helical tension spring 
32 is extended between the pair of pins 34 and a pair of engaging lugs 30 
provided on one end portion of the movable plate 25 so that the movable 
plate 25 is normally kept in a position shown in FIG. 9. As shown in FIG. 
11, the lower portion 21b of the stationary conductor 21 is closely 
surrounded by a stationary core 23 with a trapezoidal gap widening in the 
longitudinal direction of the stationary conductor 21. As shown in FIG. 
12, a trapezoidal movable core 24 having a pair of oblique sides 36 
parallel with those of the trapezoidal gap between both ends of the 
stationary core 23 is secured to the bottom of the movable plate 25, and 
an electrically insulating plate 26 is secured to the right-hand (as to 
FIG. 12) end portion of the movable plate 25 by means of adhesive or the 
like. When an overcurrent flows through a circuit breaker so that a 
tripping mechanism (not shown) can act to move a movable contact 6 to be 
detached from a stationary contact 5, a movable conductor 22 secured with 
the movable contact 6 receives a strong electromagnetic repulsive force 
because the upper portion 21a of the stationary conductor 21 constitutes 
an electricity path in the reverse direction to the movable conductor 22, 
so that the movable contact 6 is quickly moved to be detached from the 
stationary contact 5 as shown in FIG. 10. At the same time, a magnetic 
flux is generated in the stationary core 23 and the trapezoidal movable 
core 24 by the overcurrent flowing through the lower portion 21b of the 
stationary conductor 21, to apply an attractive force to the movable core 
24 to move it together with the movable plate 25 leftward (as to FIG. 10) 
against the forces of the springs 32 to insert the electrically insulating 
plate 26 into the gap between the stationary contact 5 and the movable 
contact 6. The property of recovery of insulation between both the 
contacts 5 and 6 after the current cut-off action of the contactor device 
is thus made high. 
FIGS. 13 through 16 show a contactor device according to a further 
embodiment of the present invention. A U-shaped stationary core 8 has a 
gap Gb provided between both ends thereof as shown in FIG. 15, and 
surrounds the U-shaped stationary conductor 4. The stationary core 8 is 
U-shaped so that both sides of the stationary conductor 4 are put between 
a pair of mutually parallel sides 8a of the stationary core 8. The inside 
surface 8b of the base of the U-shaped stationary core 8 is opposed to the 
inside surface of the U-shaped stationary conductor 4, that is, to the 
inside surface of the base of the stationary conductor 4. The movable core 
11 is formed of a flat plate so that it is attracted toward both ends of 
the U-shaped stationary core 8. An electrically insulating plate 10 made 
of an arc extinguishing dielectric material such as an aromatic polyester 
is secured to the tip portion of the movable core 11 by adhesive or the 
like. The movable core 11 is pivotally supported by a shaft 12 provided 
immediately under a stationary contact 5, so that the movable core 11 is 
kept in a non-operative position by a spring 13 in the normal application 
of the electrical current. 
When a heavy current such as an overcurrent flows through a circuit breaker 
including the contactor device, the movable contact 6 of the contactor 
device is moved to be detached from the stationary contact 5 by a tripping 
mechanism (not shown), so that a gap is made between both the contacts 5 
and 6, as shown in FIG. 14. At the same time, a magnetic flux is generated 
in the stationary core 8 and the movable core 11 by the current flowing 
through the stationary conductor 4, to attract the movable core 11 toward 
the stationary core 8 to short-circuit the air gaps of the magnetic 
circuit at both ends of the U-shaped stationary core 8. Since the 
electrically insulating plate 10 secured to the movable core 11 is in the 
form of a circular arc with the center of the shaft 12, the insulating 
plate 10 closely covers the whole stationary contact 5 as the insulating 
plate 10 is inserted into the gap between the stationary contact 5 and the 
movable contact 6 as a result of the attraction of the movable core 11 to 
the stationary core 8. The property of recovery of insulation between both 
contacts 5 and 6 after the current cut-off action of the contact device is 
thus made high. 
As described above, the contactor device according to the present invention 
is arranged so that the electrically insulating plate is inserted into a 
gap between the stationary contact and the movable contact at the time of 
breaking of an overcurrent. As a result, an arc generated between the 
stationary and movable contacts is forcibly driven toward the arc 
extinguishing chamber by the tip portion of the electrically insulating 
plate so that the present invention has the following advantages. 
The time when the arc stays between or in the vicinity of the stationary 
and movable contacts is remarkably reduced. Since the arc around the 
stationary and movable contacts is cooled by the evaporation of the 
electrically insulating plate due to the heat of the arc, the voltage 
across the arc is quickly heightened to limit the overcurrent. As a 
result, the energy of the arc is decreased so that the property of 
recovery of insulation between both the stationary and movable contacts 
after the current cut-off action is improved. Since the electrically 
insulating plate covers the whole stationary contact when the distance 
between the stationary and movable contacts is still minimum, the property 
of recovery of insulation therebetween is further improved so that the arc 
does not continue to exist or another arc is not generated again, even if 
a relatively high transient recovery voltage is applied between both the 
contacts at the instant of the end of the cut-off of the overcurrent. For 
that reason, the excessive overcurrent can be always cut off easily, 
surely and stably without increasing the distance between the stationary 
and movable contacts at the time of separation thereof, namely, without 
enlarging the circuit breaker.