Rotary scraper blade

Claim 1

A SCRAPER SYSTEM FOR A VESSEL HAVING A SUBSTANTIALLY CIRCULAR SIDE WALL AND A FLOOR AT THE LOWER EDGE THEREOF, COMPRISING: (A) A CENTRAL COLUMN ROTATABLE ABOUT ITS AXIS AND EXTENDING ALONG THE AXIS OF SAID VESSEL; (B) POWER MEANS OPERABLE TO ROTATE SAID COLUMN; (C) A PLURALITY OF ARMS OF DIFFERENT LENGTHS FIXED ALONG THE LENGTH OF SAID COLUMN AND PROJECTING OUTWARDLY THEREFROM; (D) AT LEAST ONE FIRST BLADE ROTATABLY MOUNTED ON ONE OF SAID ARMS, TO ROTATE ABOUT AN AXIS SUBSTANTIALLY PARALLEL TO THE AXIS OF THE COLUMN; (E) SECOND BLADES ROTATABLY MOUNTED ON OTHERS OF SAID ARMS, RESPECTIVELY, TO ROTATE ABOUT AXES SUBSTANTIALLY PARALLEL TO RADII EXTENDING FROM THE COLUMN; (F) EACH OF SAID FIRST AND SECOND BLADES HAVING A SCRAPER PORTION EXTENDING BETWEEN ITS ROTATIONAL AXIS AND THE ADJACENT SUBSTANTIALLY PARALLEL VESSEL INNER SURFACE, THE EDGE OF SAID SCRAPER PORTION CONTACTING SAID INNER SURFACE HAVING THE SAME CONTOURS AS SAID SURFACE, AND A TAIL PORTION EXTENDING FROM SAID BLADE AXIS IN THE DIRECTION OPPOSITE TO SAID VESSEL SURFACE; (F) THE RESPECTIVE AREAS OF SAID SCRAPER AND TAIL PORTIONS BEING SUCH AS TO PERMIT ROTARY MOTION OF THE BLADE RELATIVE TO THE TANK ON ENCOUNTERING AN ABNORMAL ACCUMULATION OR OTHERS OBSTRUCTION; (H) THE LENGTHS OF SAID ARMS AND THE SPACING OF SAID ARMS ALONG SAID COLUMN BEING CHOSEN TO PERMIT THE SCRAPING OF THE ENTIRE INNER SURFACE OF SAID SIDE WALLS AND SAID FLOOR.