Apparatus for cleaning ducts

Claim 1

A BLAST CLEANING APPARATUS FOR CLEANING THE INTERIOR SURFACE OF A DUCT, COMPRISING: A HOLLOW ROTATABLE SHAFT, CLOSED AT ONE END; MEANS FOR SUPPLYING BLAST-CLEANING FLUID UNDER SUITABLE PRESSURE AT THE OTHER END OF SAID HOLLOW SHAFT; EXTERNAL BEARING MEANS ROTATABLY SUPPORTING SAID HOLLOW SHAFT, AND ADAPTED SUBSTANTIALLY FOR AXIAL ALIGNMENT IN SAID DUCT; MEANS FOR ADVANCING SAID BEARING MEANS AND HOLLOW SHAFT LONGITUDINALLY WITHIN SAID DUCT; A MULTIPLICITY OF CLOSED-ENDED TUBULAR ARMS EXTENDING RADIALLY FORM SAID HOLLOW SHAFT IN FLUID-COMMUNICATING RELATIONSHIP THEREWITH; A SUBSTANTIALLY TANGENTIAL PROPULSION NOZZLE ON EACH OF SAID ARMS, HAVING SUITABLY LIMITED FLOW CAPACITY AND BEING ADAPTED TO PRODUCE SUFFICIENT TANGENTIAL THRUST FOR ROTATION OF SAID HOLLOW SHAFT AT A SUITABLE SPEED; AND A BLAST NOZZLE ON EACH OF SAID ARMS, SO DIRECTED AS TO POSSESS PRINCIPALLY AXIAL AND RADIAL COMPONENTS, AS WELL AS A TANGENTIAL COMPONENT OPPOSED TO THAT OF SAID PROPULSION NOZZLE BUT INSUFFICIENT TO OVERCOME THE THRUST OF THE LATTER NOZZLE, WHILE BEING SUITABLY ORIENTED TO EMIT A BLAST JET AGAINST THE WALL OF SAID DUCT AT A SUBSTANTIAL ANGLE FROM THE NORMAL THERETO.