Abrasive blasting apparatus

Claim 1

IN AN APPARATUS FOR TUMBLING A BATCH OF WORK PIECES COMPRISING A TROUGH-SHAPED CONVEYOR ON WHICH THE WORK PIECES ARE TUMBLED, A HOUSING ENCLOSING SAID CONVEYOR, A LOADING AND UNLOADING DOORWAY FOR SAID HOUSING, ABRASIVE PARTICLE BLASTING MEANS EXTENDING INTO SAID HOUSING FOR PROJECTING ABRASIVE AGAINST THE WORK PIECES, THE IMPROVEMENT OF A DOORWAY IN WHICH THE UPPER PORTION THEREOF IS INCLINED TO FACE UPWARDLY, A DOOR TRACK THAT EXTENDS ALONG THE SIDES OF THE DOORWAY, A ROLLER SUPPORTED DOOR IN THE TRACK, SAID DOOR HAVING A RIGID UPPER PANEL PORTION, THE LOWER PORTION OF SAID DOORWAY BEING INCLINED TO FACE DOWNWARDLY, SAID DOOR HAVING A LOWER FLEXIBLE PANEL DEPENDING FROM THE BOTTOM EDGE OF THE UPPER DOOR PANEL TO COMPLETE THE CLOSURE FOR THE DOORWAY, A PLURALITY OF CLOSELY SPACED TRANSVERSE STIFFENERS EXTENDING CROSS THE LOWER FLEXIBLE DOOR PANEL, AND SEALING ELEMENTS ON THE SIDES OF THE UPPER DOOR PANEL PORTION AND THAT UPPER PORTION OF THE TRACK ACCOMMODATING THE UPPER DOOR PANEL COOPERATING TO MINIMIZE THE ESCAPE OF PROJECTED PARTICLES AROUND THE UPPER DOOR PANEL, THE LOWER PORTION OF THE TRACK ACCOMODATING THE LOWER FLEXIBLE PANEL HAVING CONNECTED OUTER AND INNER PLATES ON EACH SIDE OF THE LOWER DOOR PANEL, THE INNER PLATES LYING IN SPACED RELATIONSHIP FROM THE ADJACENT OUTER PLATES BY A DISTANCE GREATER THAN THE THICKNESS OF THE LOWER DOOR PANEL TO GUIDE THAT DOOR PANEL.