Rotary media valve

Abstract

A blast cleaning apparatus containing a rotary media valve with a rotor, which contains depressions on the surface thereof, delivers blast media from a supply vessel into a pressurized gas stream upstream of a nozzle for blast cleaning. As the rotor revolves, the depressions align with the supply vessel where the particulate blast media cascades into the depressions. The media is transported from the supply vessel to the pressurized gas stream as the rotor spins.

What is claimed:  
     
         1 . An apparatus for blast cleaning, comprising: 
 a vessel means for containing a quantity of particulate abrasive blasting medium;    a source of pressurized gas;    a gas conveying line being in fluid communication with said source of pressurized gas;    a rotary media valve for feeding said blasting medium from said vessel to a location of said gas conveying line to form a mixture of blasting medium and pressurized gas;    a blast nozzle at the end of said conveying line and downstream of said location.    
     
     
         2 . The apparatus for blast cleaning of  claim 1  wherein said vessel comprises an open vessel for containing abrasive blasting media.  
     
     
         3 . The apparatus for blast cleaning of  claim 1  wherein said pressurized gas comprises air, nitrogen, inert gas, or blends thereof.  
     
     
         4 . The apparatus for blast cleaning of  claim 1  including a mix chamber positioned between said location and said blast nozzle to form a more uniform mix of said blasting media in said pressurized gas stream.  
     
     
         5 . The apparatus for blast cleaning of  claim 1  wherein said rotary media valve comprises a rotor with at least one depression on the surface thereof capable of delivering media from said vessel into said gas conveying line.  
     
     
         6 . The apparatus for blast cleaning of  claim 4  wherein said rotor has a plurality of said depressions arranged in a spaced configuration around substantially the entire circumference of the rotor.  
     
     
         7 . The apparatus for blast cleaning of  claim 5  wherein said depression is a slot.  
     
     
         8 . The apparatus for blast cleaning of  claim 5  wherein said depression is round.  
     
     
         9 . The apparatus for blast cleaning of  claim 5  wherein said depression depth ranges from 0.05 to 1.0 inch.  
     
     
         10 . The apparatus for blast cleaning of  claim 5  wherein said rotor is contained within a bore of a valve housing.  
     
     
         11 . The apparatus for blast cleaning of  claim 10  wherein said rotor and said bore of said valve housing are sized to create a metal-to-metal dry seal.  
     
     
         12 . The apparatus for blast cleaning of  claim 11  wherein said rotor and said bore have a clearance space there between of 0.0001″ to 0.002″.  
     
     
         13 . The apparatus for blast cleaning of  claim 5  wherein rotation speed of said rotor is controlled by means of a variable speed or indexing servomotor communicating with said rotor.  
     
     
         14 . The apparatus for blasting of  claim 1  wherein said blast nozzle has an orifice diameter of up to ⅝″.  
     
     
         15 . The apparatus for blasting of  claim 1  wherein said blast nozzle has an orifice diameter of at least 0.01″.  
     
     
         16 . The apparatus for blasting of  claim 5  wherein said rotor is contained within a housing, said housing containing a vent communicating with said rotor and positioned to relieve any pressure in said at least one depression before said at least one depression on said rotor is rotated to said supply vessel.  
     
     
         17 . The apparatus of  claim 5  wherein said rotor is placed below said vessel means and above said gas conveying line.  
     
     
         18 . The apparatus for blasting of  claim 1  wherein said rotary media valve feeds said blast medium to said gas conveying line without impeller action.  
     
     
         19 . The apparatus for blast cleaning of  claim 1  wherein said rotary media valve acts as a mechanical volumetric pump.  
     
     
         20 . A method for blast cleaning, comprising: providing a quantity of blasting medium within a vessel; 
 feeding said blasting medium from said vessel, through a rotary media valve into pressurized gas to form a blast steam;    discharging said blast stream through a nozzle placed downstream of where said blasting medium is fed into said source of pressurized gas.    
     
     
         20 . The method for blast cleaning of  claim 20  wherein the blasting medium comprises sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium sesquicarbonate, sodium chloride, sodium sulfate or mixture thereof.  
     
     
         21 . The method for blast cleaning of  claim 20  wherein the pressurized gas is between about 20 to 125 psig.  
     
     
         22 . The method for blast cleaning of  claim 21  wherein said blasting medium is fed from said blast nozzle at a flow rate of from about 0.1 to 10 pounds per minute.  
     
     
         23 . The method for blast cleaning of  claim 23  wherein said blasting medium to pressurized gas weight ratio is about 0.1 to 0.4.  
     
     
         24 . The method for blast cleaning of  claim 20  wherein said rotary media valve comprises a rotor with at least one depression on the surface thereof capable of delivering media from said vessel into said source of pressurized gas, rotating said rotor such that said media is transported from said supply vessel to said at least one depression and subsequently from said at least one depression into said pressurized gas.  
     
     
         25 . The method for blast cleaning of  claim 24  wherein said rotor delivers said blasting medium via a plurality of said depressions arranged in a spaced configuration around substantially the entire circumference of the rotor.  
     
     
         26 . The method for blast cleaning of  claim 25  comprising controlling the RPM of said rotor by means of a variable speed motor or servo motor.