Axial fan with adjustable blades

Claim 1

IN AN AXIAL FAN FOR TRANSPORTING DUST LADEN GASES COMPRISING A RADIALLY-EXTENDING CONCENTRIC HUB MOUNTED ON A ROTATABLE SHAFT, A PLURALITY OF ADJUSTABLE-PITCH FAN BLADES DISPOSED ABOUT THE PERIPHERY OF SAID HUB, SAID HUB HAVING RECESSES ABOUT ITS PERIPHERY, A CIRCULAR BASE PLATE AND A ROTATABLE AXLE MOUNTING EACH OF SAID BLADES INTERMEDIATE A RECESS IN SAID HUB AND SAID BLADES, SAID AXLE MOUNTING A LEVER AT ITS INNER END, ADJUSTMENT MEANS COMPRISING A AXIALLY DISPOSED ADJUSTABLE SHAFT MOUNTING A DISK, SAID DISK CONNECTED TO SAID LEVER SO AS TO CAUSE CHANGES OF PITCH IN SAID BLADES UPON AXIAL DISPLACEMENT OF SAID SHAFT, AN ANNULAR COVER DISK CONNECTED TO SAID HUB AND HAVING A CENTRAL TERMINUS DEFINING AN APERTURE TO RECEIVE A CIRCUMSCRIBE SAID ADJUSTABLE SHAFT; A STATIONARY CASING MOUNTED ON THE OUTLET SIDE OF SAID IMPELLER AND HAVING A FRONTAL WALL PORTION CONFRONTING SAID HUB AND SAID COVER DISK AND SPACED THEREFROM SO AS TO DEFINE AN ANNULAR SLOT BETWEEN, AN INWARDLY PROJECTING PAIR OF SPACED WALLS DEFINING A HOLLOW CHAMBER CONNECTED TO SAID FRONTAL WALL PORTION AND HAVING TERMINI ADJACENT TO BUT SPACED FROM SAID COVER DISK, A RADIAL SEAL CONNECTED TO AT LEAST THE REAR ONE OF SAID WALLS AND IN ABUTTING ENGAGEMENT WITH SAID COVER DISK, AND AIR SUPPLY MEANS CONNECTED TO SAID CHAMBER TO PROVIDE A FLOW OF AIR FROM SAID CHAMBER INTO SAID ANNULAR SLOT BETWEEN SAID FRONTAL WALL PORTION AND SAID COVER DISK WHEREBY DUST LADEN GAS IS PREVENTED FROM ENTERING THEREBETWEEN.