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GB939954A
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Combined impeller and closure
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US2998765A
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Pivotal louver assembly
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US2974731A
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Combined impeller and closure
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US2862438A
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Automatic louver control mechanism
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US2673681A
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Combined fluid impeller and self-sealing closure
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US2656971A
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Combined fluid impeller and selfsealing closure
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US2624265A
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Spring counterbalanced louver mechanism
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US2632377A
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Louver actuating and fan motor control mechanism
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US2383004A
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Combined impeller and closure
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US2383003A
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Forced ventilation apparatus
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US2383001A
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Combined impeller and closure
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US2383002A
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Impeller and governor for same
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US2311950A
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Pivoted louver with seating pad
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US2314003A
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Counterbalanced louver construction
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US2299833A
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Louver mechanism for attic ventilation
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US2299832A
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Louver construction
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US2061162A
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Louver construction
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US1996340A
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Louver construction
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US2009740A
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Louver construction
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CA411553A
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Counterbalanced louver
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