| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a valve unit that can suppress valve leakage occurring when a butterfly valve 4 is held at a full closing position. <P>SOLUTION: A valve leakage prevention means comprises: a nozzle (first nozzle 16 and second nozzle 17) pressed in and fixed to an inner circumference of a valve passage 2a; two seal rings 19 and 20 which are disposed in a circumferential groove 18 formed in the nozzle; and a backup ring 21 disposed between both seal rings 19 and 20. When the butterfly valve 4 is held at a full closing position, ring inner circumferential surfaces of the two seal rings 19 and 20 are pressed and adhered onto an outer circumferential surface of the butterfly valve 4 with own elastic restoration force of the seal rings acting in a diameter reduction direction. The backup ring 21 shuts off a closed gap formed between both seal rings 19 and 20. Even if the full closing position is varied a little, the outer circumferential surface of the butterfly valve 4 in a radial direction is formed in a spherical surface shape so as not to generate a gap between the seal rings 19 and 20. <P>COPYRIGHT: (C)2013,JPO&INPIT |
