Blast cleaning apparatus and method with laterally moving conveyor

A blast cleaning apparatus comprising:

• a blast cleaning chamber;
• a conveying means comprising a conveying surface moveable horizontally in a first direction into, through and out of the blast cleaning chamber to convey through the cleaning chamber a workpiece to be cleaned;
• and wherein the conveying surface has a plurality of openings therethrough and adjacent openings aligned in a second direction transverse to the first direction of movement of the conveying surface are separated by a separating material;
• at least one blast cleaning means located within the cleaning chamber and oriented to direct abrasive cleaning material upwardly through the openings of the conveying surface to clean at least a portion of the workpiece;
• a moving means capable of causing lateral movement of the conveying surface, this lateral movement being within the cleaning chamber at a region where the abrasive cleaning material cleans the workpiece, wherein the lateral movement is relative to the workpiece and in a second direction which is horizontal and transverse to the first direction of movement of the conveying surface so as to expose to the cleaning at least some material area of the workpiece that would otherwise be protected from the cleaning materials by the material separating the openings in the conveying surface;
• wherein the lateral movement of the conveying surface is a back to forth movement relative to the piece;
• wherein the lateral movement comprises a lateral acceleration of the conveying surface during each of the back and forth movements so as to overcome frictional forces between the workpiece and the conveying surface in each of the back and forth directions;
• and wherein the accelerations in each of the back and forth directions are substantially equal such that the workpiece remains substantially in the same location on the conveying surface after a period of movement.