Gas circuit breaker

In a gas circuit breaker of the type in which compressed gas is blasted about an arc generated by the separation of at least a pair of relatively movable contacts, there are provided an arc extinguishing chamber, a stationary contact mounted on the inside wall of the chamber, an operating rod located in the chamber, a movable contact disposed to oppose the stationary contact and moved by the operating rod, a device for creating a blast of compressed gas when the contacts are separated, and a plurality of partition plates separated from each other in the direction of the movement of the movable contact. The partition plates are provided with gas passing passages and function to channel the compressed gas and blast it about the arc at a plurality of spaced apart interrupting points.

BACKGROUND OF THE INVENTION 
This invention relates to a gas circuit breaker and more particularly a 
compressed gas circuit breaker employing multi-stage gas blasting about an 
arc generated by the separation of relatively movable contacts thereby 
improving the interrupting capacity. 
Recently, demand for a circuit breaker with large interrupting capacity and 
compact size has been increased because of the enlargement of a power 
system and due to the limited space of installation. Furthermore, it has 
also been required to provide a simple and accurate circuit breaker 
construction in view of the cost and the reliability thereof. 
In a conventional puffer-type (single gas-flow-type) gas circuit breaker 
the arc interruption is performed such that an operating rod is first 
pulled by means of an operating mechanism, and in accordance with the 
movement of the rod, a cylinder located within an arc extinguishing 
chamber of the circuit breaker is also moved, whereby the gas in the 
cylinder is compressed to a high pressure and the compressed gas is 
blasted through a nozzle part across, or about the arc gererated at the 
nozzle part thereby interrupting the arc. The breaking efficiency of this 
type of breaker is determined by the strength of the blasting action. In 
another conventional double gas-flow-type circuit breaker the blasting 
efficiency is duplicated in comparison with that of the single 
gas-flow-type mentioned above. However, in order to obtain a breaking 
efficiency higher than that of the former type, the latter type must 
increase the blast pressure or increase the number of serially connected 
interrupting points. This causes an enlargement in the structural 
configuration of the circuit breaker and an increase in the driving force 
which involves much cost making such a breaker uneconomical. 
SUMMARY OF THE INVENTION 
Accordingly, the principal object of this invention is to provide a 
compressed gas circuit breaker which can improve the interrupting capacity 
by blasting gas in a multi-stage gas flow about an arc at nozzle parts 
without increasing either the blast pressure of the gas or the number of 
serially connected interrupting points. 
Another object of this invention is to provide an improved compressed gas 
circuit breaker with a simple construction and high reliability and such 
can be manufactured at a low cost. 
According to this invention, there is provided a gas circuit breaker of the 
type in which compressed gas is blasted about an arc generated by the 
separation of at least a pair of relatively movable contacts. The gas 
circuit breaker comprises an arc extinguishing chamber, a stationary 
contact mounted on the inside wall of the chamber, an operating rod 
located in the chamber, a movable contact disposed opposingly to the 
stationary contact and moved by the operating rod, a device for creating a 
blast of compressed gas when the contacts are separated, and a plurality 
of partition plates separated from each other in the direction of the 
movement of the movable contact between the contacts, whereby the blast of 
the compressed gas is directed about the arc generated by the separation 
of the movable and stationary contacts so as to form a cylindrical gas 
flow enclosing the arc and to interrupt the arc at nozzle parts formed by 
the partition plates.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates one embodiment of a puffer-type gas circuit breaker 
according to this invention and shows the manner of arc extinguishment. 
This circuit breaker comprises an arc extinguishing cylindrical chamber 1 
(filled with an insulating gas such as sulfur hexa fluoride (SF.sub.6)) 
and end plates 2 and 3. In the cylindrical chamber 1 there is provided a 
movable member including an assembly of an operating rod 4 driven by well 
known external operating means such as a link mechanism, a puffer cylinder 
5, a tubular movable contact 6 and an insulating nozzle member 7. There 
are also provided a stationary contact 8 secured to the end plate 2 to 
oppose the movable contact 6 and a puffer piston 9 movable within the 
cylinder 5. The piston 9 is fixed at one end to the inner surface of the 
end plate 3. p The insulating nozzle member 7 is provided with three 
partition plates 10, 11 and 12 spaced from each other in the longitudinal 
direction of the cylindrical chamber 1 and positioned between the movable 
and stationary contacts when they are opened. A nozzle 13 is formed 
between the rightmost partition plate 10 and the contact 6. A plurality of 
pipes 14 extend through the space between the partition plate 10 and the 
intermediate partition plate 11, and the periphery of the space between 
the partition plates 11 and 12 is closed by a circumferential wall 17. 
A puffer chamber 18 is defined by the puffer cylinder 5 and the puffer 
piston 9, and in the breaking operation the insulating gas in the puffer 
chamber 18 is compressed according to the movement of the operating rod 4 
and blasted through small openings 15 provided in the cylinder 5. The 
blasted gas is then guided to the nozzle 13 by the insulating nozzle 
member 7. Because a slide contact 16 connected to the end plate 3 at one 
end thereof is slidably contacting the outer peripheral surface of the 
puffer cylinder 5, in the closed condition, a current path is formed from 
the end plate 2 to the end plate 3 through the stationary contact 8, the 
movable contact 6, the puffer cylinder 5 and the slide contact 16. 
The breaking operation of the circuit breaker shown in FIG. 1 is as 
follows. 
When the movable member is moved to the left by the operating rod 4 
connected to the external operating means such as a link mechanism, the 
space between the contacts 6 and 8 are separated widely and the insulating 
gas in the puffer chamber 18 is compressed. The compressed gas under high 
pressure is blasted through the small openings 15 of the cylinder 5 and 
guided by the insulating nozzle member 7 so as to be blasted about the arc 
struck between separated contacts 6 and 8. At this moment, the compressed 
gas is blasted about the arc at four nozzle parts formed by the movable 
contact 6, and the partition plates 10, 11 and 12, through the pipes 14. 
The circuit breaker construction according to this invention increases the 
blasting efficiency 2 to 4 times in comparison with a conventional circuit 
breaker. In other words the same efficiency can be assured as in the case 
where the number of the serially connected interrupting points is larger. 
The insulating nozzle member 7 shown in FIG. 1 may be constructed as an 
integral unit or as an assembly of a plurality of individual members. 
FIG. 3 shows a dual pressure-type circuit breaker constructed in accordance 
with this invention in an arc extinguishing condition. In FIG. 3, an arc 
extinguishing chamber is formed by an arc extinguishing cylinder 21 made 
of insulator and end plates 22 and 23 closing gas-tightly the end openings 
of the cylinder 21 and filled with an insulating gas such as SF.sub.6. In 
the cylinder 21 there are provided a movable member comprising an 
operating rod 24 driven by external operating means (not shown), a 
cylindrical movable contact 25 and a movable electrode 26, which are 
secured to the rod 24, and a stationary contact 27 connected to the end 
plate 22 to oppose the movable electrode 26. 
The cylindrical movable contact 25 is provided with a valve member 29 
facing to a packing 28 disposed at the periphery of the base of the 
stationary contact 27 and with a valve member 32 facing to a packing 31 
located on an end plate 30 on gas exhausting side. Inside the cylindrical 
movable contact 25 are formed three partition plates 33, 34 and 35 
separated from each other in the direction of movement of contact 25. The 
space between partition plate 33 adjacent the stationary contact 27 and 
the partition plate 35 is communicated with the exhaust side through a 
passage 37, and a plurality of pipes 36 extend through the partition plate 
33 and the intermediate partition plate 34, whereby compressed gas 
introduced from an inlet port 41 into the cylinder 21 is fed into the 
space between the partition plates 33 and 34 around the inner edge of the 
partition plate 33 and to the space between the partition plates 34 and 35 
through the pipes 36. 
To the end plate 23 there is fixed a slide contact 38 at one end thereof 
and the other end of the slide contact 38 is slidably engaging the outer 
peripheral surface of the movable contact 25. In the closed condition, 
there is formed a current path from the end plate 22 to the end plate 23 
through the stationary contact 27, the movable electrode 26, the movable 
contact 25 and the slide contact 38. An arc root 39 is formed on the 
movable contact 25 when an arc is struck as shown. An exhaust chamber 40 
is formed between the end plate 23 and the plate 30, and a perforated 
cover 40a is provide to surround the exhaust chamber 40 for communicating 
it with the outside atmosphere or gas recovering device (not shown). In 
the closed condition, the inside of the cylinder 21 defined by the inner 
surface of the cylinder 21 and the outer surface of the movable contact 25 
is filled with insulating gas under high pressure which is fed from the 
gas inlet port 41. 
The inlet port 41 is communicated with a well known compressed gas tank 
(not shown) disposed externally of the cylinder 21 through an 
electromagnetic valve (not shown) and when the operating rod 24 is moved, 
the valve is opened and the compressed gas in the tank is introduced into 
the cylinder 21 through the inlet port 41. 
The breaking operation of this embodiment shown in FIG. 3 is as follows. 
When the operating rod 24 is moved by the external operating means to the 
right as viewed in FIG. 3, the space between the contacts 25 and 27 is 
separated widely and the space between the valve member 29 and the packing 
28 is also separated, whereby the insulating gas under high pressure fed 
from the inlet port 41 is blasted towards the center of the movable 
contact 25. The arc generated between the contacts 27 and the electrode 26 
is transferred between contacts 27 and 24 by the blast of the insulating 
gas. During the transfer of this arc the compressed gas is blasted to 
surround the arc at three nozzle parts formed by the partition plates 33, 
34 and 35 through the pipes 36 and the passage 37 so as to form a 
cylindrical compressed gas flow under high pressure enclosing the arc and 
to interrupt the arc at nozzle parts formed by the partition plates. Thus, 
the structure of the circuit breaker shown in FIG. 3 can improve the 
blasting efficiency by a factor of three over a conventional circuit 
breaker. 
As a further modification of the circuit breaker there may be provided a 
double gas-flow-type circuit breaker including a hollow stationary contact 
through which compressed gas is passed or the same type of circuit breaker 
provided with a further partition plate disposed on the side of the 
stationary contact. Furthermore, the structure of this circuit breaker can 
be applied for a three-phase circuit breaker by providing barriers between 
respective arc extinguishing chambers. 
As is clear from the above, the merits or advantages of this invention may 
be summarized as follows. 
According to this invention, a plurality of partition plates are located so 
as to provide multi-stage gas blasting with respect to the nozzle parts 
formed by the partition plates, and the partition plates are provided with 
pipes and/or passage through which compressed gas is blasted to the 
respective nozzle parts, so that the interrupting capacity can be 
remarkably improved without increasing the blasting gas pressure or the 
number of the interrupting points. Moreover as the circuit breaker has a 
simple and compact construction, it can be installed in a limited space. 
Furthermore, since the blasting gas flow is reduced by selecting properly 
the diameter of the nozzle during the generation of the arc in the nozzle 
part, the comsumption of the gas is substantially equal to that of the 
conventional double gas-flow-type circuit breaker. 
There is described herein embodiments employing only three partition 
plates, but the present invention is not limited thereto. Rather, the 
invention covers other modifications and changes obvious to those skilled 
in the art which do not depart from the scope and spirit of the invention.