| 摘要 |
PURPOSE:To cause a device to surely display its seal function, by containing a seal ring made of elastic material in an annular housing groove, fromed gradually spreading toward a rotary shaft, further arranging a means which presses this seal ring to be deformed contracting its diameter. CONSTITUTION:A seal housing 1 forms in its circular peripheral part 1b an annular housing groove 7 gradually spreading its groove width toward a rotary shaft 2, and this housing groove houses a seal ring 8 made of elastic material under a condition such that it is fitted moving contactlessly with the rotary shaft 2. If pressure air is supplied from a supply hole 11 of pressurized fluid acting on a peripheral part 8a of the seal ring 8 when any abnormality is cuased in a main shaft seal device, the pressure air forces an internal peripheral part 8b of the seal ring 8 to be brought into contact with a peripheral surface of the rotary shaft 2 fully over its periphery by deforming the seal ring 8 contracting its diameter.
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