| 摘要 |
PROBLEM TO BE SOLVED: To provide a foreign matter intrusion-preventing plate surely preventing the flow of foreign matters into a rotary vacuum pump while achieving a target opening rate. SOLUTION: An opening 300 of the foreign matter intrusion-preventing plate 30 is formed into a flat rectangular or hexagonal shape to prevent the inflow of foreign matters including an O-ring while securing the target opening rate. When the opening 300 is in the rectangular shape, the target opening rate is set to beα, the width of a portion of a beam 300a to be (t), a short-side size (b) of the opening 300 to be smaller than the diameter of the O-ring, and a long-side size (a) of the opening 300 to be [a>t/äR/α(R+t)-1}]. When the opening 300 is in the hexagonal shape, the long-side size (a) in relation to the width (b) of the smaller opening 300 is set as the expression (1): a>[αt(b+t)tan(θ/4)+äα(b+t)2-b2}/2tan(θ/2)]/äb-α(b+t)}. COPYRIGHT: (C)2007,JPO&INPIT
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