High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Air-current blowout
Reexamination Certificate
1998-05-26
2004-03-09
Donovan, Lincoln (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Air-current blowout
C218S149000, C218S155000, C218S157000
Reexamination Certificate
active
06703575
ABSTRACT:
FILED OF THE INVENTION
The present invention relates to an arc-extinguishing system for a contact switching apparatus.
BACKGROUND OF THE INVENTION
FIG.
12
and
FIG. 13
show an arc-extinguishing system for a contact switching apparatus based on the conventional technology. The contact switching apparatus comprises a movable contact
2
comprising an electrically conductive bar with contact points
1
at both ends thereof, fixed contacts
4
with contact points
3
provided opposite to the contact points
1
of the movable contact
2
, a cross bar
5
for supporting the movable contact
2
and switching the contact points by conveying movement of an electromagnet device to the movable contact
2
, and an arc box
6
made from heatproof resin for covering a contact switching mechanism section comprising the movable contact
2
, fixed contacts
4
and the cross bar
5
to insulate electro-conducting sections of electrodes from each other.
The contact switching apparatus further comprises a plurality pieces of arc-extinguishing grid plate
7
inserted into a plurality of longitudinal concave grooves
6
a
formed on the internal surface of the arc box
6
and being vertical to the movable contact
2
, an arc cover
10
fixed to the top surface of the arc box
6
by screws
8
and constituting a gas blow-off opening section
9
opening to an external wall section with the arc box
6
, heatproof spacer pieces
11
between the arc box
6
and teeth
10
a
of the arc cover
10
for fixing the arc-extinguishing grid plates
7
, and arc runners
12
.
The arc-extinguishing system for a contact switching apparatus having the configuration described above cuts off a current between the contact points by driving arc generated between the contact points
1
and
3
of the movable contact
2
and the fixed contact
4
by means the arc-extinguishing grid plates
7
when the cross bar
5
is returned and separating the arc so as to be led into spaces between the arc-extinguishing grid plates
7
provided in parallel. In the above processes, gas generated when the arc sublimates peripheral parts with its thermal energy passes through the spaces between the arc-extinguishing grid plates
7
to the space above the arc-extinguishing grid plates
7
, and further proceeds along the arc cover
10
, and then is discharged from the gas blow-off opening section
9
to the outside.
The gas having passed through the spaces between the arc-extinguishing grid plates
7
is cooled down by hitting the arc cover
10
with a radiating surface widely provided on the outside thereof and going on through a space comparatively far from the place where the arc is generated, and the temperatures in the gas is left, ideally, to decrease as far as a temperature which does not give any damage to the outside, and then the gas is discharged.
Also, when the cross bar
5
closes or opens a contact according to the suction force of an electro-magnet, severe shock vibrates the arc-extinguishing grid plates
7
. For this reason, the arc-extinguishing grid plates
7
inserted in the longitudinal concave grooves
6
a
are fixed through the spacer pieces
11
to prevent occurrence of rattling other than a switching sound as well as abrasion due to the vibration. The arc cover
10
covers the upper section of the arc box
6
so as to apply pressure to the arc-extinguishing grid plates
7
and is secured by the screws
8
near the arc-extinguishing grid plates
7
.
When opening and closing the contact point, the cross bar
5
slides along a sleeve-shaped guide member
13
attached to the arc box
6
so as to avoid contact with the arc box
6
which is easily worn out.
In the conventional type of arc-extinguishing system for a contact switching apparatus, the arc box
6
and the arc cover
10
are formed with heatproof and thermosetting resin, so that the arc-extinguishing grid plates
7
are not melted even at an elevated temperature due to heat of arc, and on the other hand, those components have no elasticity, so that any method of fixing the arc-extinguishing grid plates
7
such as press fitting can not be employed to prevent rattling thereof.
For this reason, the arc-extinguishing grid plates
7
can not be fixed unless there are spacer pieces
11
having elasticity among the plates, or unless the arc-extinguishing grid plates
7
are bent or crimped, so that the shape of the arc-extinguishing grid plates
7
has to be complicated, which may cost quite a lot for assembly thereof.
Also, foreign matters such as chips of wires produced during works easily enter from the gas blow-off opening section
9
, and if some of the matters have a size less than a space between the arc-extinguishing grid plates
7
, the fine matters can enter into sections where the movable contact
2
and fixed contact
4
are provided, which causes burning of an electro-magnet due to imperfect contact or imperfect charge to be generated.
In the conventional type of arc-extinguishing system for a contact switching apparatus, gas generated by arc passes through the spaces between the arc-extinguishing grid plates
7
, and is discharged from the gas blow-off opening section
9
as it is, so that gas with high temperature is discharged unless the arc-extinguishing grid plates
7
are made as large as a distance so as to enable sufficient cooling down of the gas.
To solve the problems as described above, the arc box
6
and the arc cover
10
are formed with heatproof and thermosetting resin in the conventional type of arc-extinguishing system, so that fine projections or the like can not be made in a narrow space due to the flowing characteristic as well as strength of resin at the time of molding, and for this reason the arc-extinguishing system becomes disadvantageously larger in accordance with the size of the arc-extinguishing grid plates
7
.
Also, in the conventional type of arc-extinguishing system for a contact switching apparatus, discharged gas is diffused from the gas blow-off opening section
9
, which causes insulation outside the adjacent arc-extinguishing systems to be reduced. Shorting between phases easily occurs in this section at the time of abnormality such that arc is not completely cut off, and grounding may occur when a distance from the arc extinguishing system to a control board is short.
In the conventional type of arc-extinguishing system for a contact switching apparatus, name plates for conveying various information are attached to a surface of the arc cover
10
as a front surface of the electromagnetic contactor, but heat is also conveyed to the arc cover
10
with heated gas, so that, when an ordinary paper name plate is used, it is easily peeled off. And for this reason, information is directly printed onto the arc cover
10
in many cases. However, printing onto the surface of a molded component made of resin is quite difficult and printed color is easily changed due to heat.
Also, in the conventional type of arc-extinguishing system for a contact switching apparatus, there are many cases where the cross bar
5
is constructed by heatproof resin and is reinforced with grass fibers like in cases of the arc box
6
and the arc cover
10
. And for this reason, the cross bar
5
is poor in the sliding capability which promotes its abrasion, so that the guide member
13
has to be added to the bar.
SUMMARY OF THE INVENTION
It is an object of the present invention to obtain an arc-extinguishing system in which arc-extinguishing grid plates having a simple form which can be built with low cost by properly fixing the arc-extinguishing grid plates without using any spacer or the like, to obtain an arc-extinguishing system in which intrusion of foreign matters to the inside of the system is prevented, to obtain a compact type of arc-extinguishing system with a path in which a gas is easily cooled down before the gas is discharged to the outside for the purpose to make the arc-extinguishing grid plates smaller, to obtain an arc-extinguishing system in which diffusion of gas can be prevented without using any external shield, to obtain
Donovan Lincoln
Mitsubishi Denki & Kabushiki Kaisha
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