Abstract

A valve for controlling flow of abrasive media from a blast tank to a nozzle, utilizes rollers for constricting a straight-through tube. In this way the valve meters the flow of the abrasive media into a blast hose through which air is directed under pressure as a carrier for the media. Contact with the media within the valve is limited to a radially constrictable tube adapted for ready replacement as the only component subject to the destructive characteristics of media such as mineral grit, sand, or the like. In association with the pinch tube housing, means is provided permitting ready interchange of manual and automatic tube-constricting assemblies. In the automatic configuration, the size of the valve orifice through which the media passes can be accurately and swiftly regulated by varying the pressure on a diaphragm. The control air pressure exerted on the diaphragm determines the extent to which the pinch tube may open under pressure directed through the blast hose, against the force of a spring mounted within the diaphragm housing. Fine adjustments, including selective pre-adjustment of the spring tension and tube constriction, aid in precise regulation of the media flow.