| 摘要 |
PROBLEM TO BE SOLVED: To prevent the lowering of the insulating proof stress at a peripheral part of a cooling cylinder by forming the cooling cylinder with an opening having a diameter capable of housing the nearly whole quantity of the insulating gas sprayed to an arc in the cutoff of the current at opposite ends of movable parts of the cooling cylinder, and providing an injection gas guide part with a gas discharge port tapered at an angle equal to the angle of spreading of the injection gas from an insulating nozzle at the other end of a barrel part. SOLUTION: A cooling cylinder 28 is formed with an opening part 28a having a diameter capable of housing the nearly whole quantity of the insulating gas sprayed to an arc in the cutoff of the current at opposite ends of a movable main contact 23 and a movable arc contact 25. An injection gas guide part 28b of the cooling cylinder 28 is tapered at an angle equal to the angle of spreading of the insulating gas injected from an insulating nozzle 24 and heated by the arc, and cools the insulating gas with a barrel part 28c of the cylinder 28. Furthermore, the insulating gas is mixed with the normal-temperature insulating gas inside of the cooling cylinder 28, and temperature thereof is lowered and discharged to the peripheral part through a gas discharge port 28d. With this structure, in a fixed main contact 26, progress of corrosion can be prevented while preventing the distribution of the high-temperature insulating gas in the periphery thereof.
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