| 摘要 |
PURPOSE: A butterfly valve is provided to minimize the abrasion of an expansion sheet and to improve the sealing property by combining the expansion sheet to the circumference of an on/off unit. CONSTITUTION: A butterfly valve is operated by the steps of: avoiding the contact of an on/off unit with a valve body(10) by revolving the on/off unit as air is removed from an air chamber(52) of an expansion sheet(50) when desiring to close a butterfly valve; forcibly feeding air to an air hole(21) on the lower part of a rotary shaft(20); feeding the introduced air into the air hole to a channel hole(43) of a combining ring body(40) through an air exhaust port(22); filling the air chamber of the expansion sheet with the introduced air to the channel port; and interrupting the flow of sludge by closely adhering the air to the inner circumference of the valve body(10). The butterfly valve can extend the life span of the expansion sheet by preventing the sheet from being worn away.
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