Process and equipment for the conveyance of powdered material
The invention concerns a process and a device ( 2 ) for the pneumatic conveyance of powdered material ( 4 ), in which a cylindrical chamber ( 10, 12 ), which can be connected with a reservoir ( 6 ) by a sealable inlet ( 14, 16 ) and with a delivery line ( 28 ) by a sealable outlet ( 18, 20 ), is alternately filled with material from the reservoir ( 6 ) and emptied of this material by applying a negative pressure to the chamber with its outlet ( 18, 20 ) closed and its inlet ( 14, 16 ) open through a bordering wall formed by a gas-permeable filter element ( 50 ) to draw material into the chamber ( 10, 12 ) from the reservoir ( 6 ), and by then admitting a gas under pressure into the chamber ( 10, 12 ) with its inlet ( 14, 16 ) closed and its outlet ( 18, 20 ) open to force the material previously drawn into the chamber ( 10, 12 ) out of the chamber and into the delivery line ( 28 ). To prolong the service life of the filter element ( 50 ) and to avoid contamination of the filter element more easily, it is proposed, in accordance with the invention, that the filter element ( 50 ) be designed as a hollow cylinder and that it surround at least a portion of the chamber ( 10, 12 ).
1. A system for delivering and spraying powder coating materials, comprising:
a powder reservoir;
a feed line connected to said reservoir;
a conveyance device for the pneumatic conveyance of powdered material connected to said feed line;
a delivery line connected to said conveyance device;
wherein said conveyance device includes:
a first conveying chamber and a second conveying chamber, said first conveying chamber comprising a first rigid gas permeable filter element encircled by a first annular housing, said second conveying chamber comprising a second gas permeable rigid filter element encircled by a second annular housing;
a first inlet pinch valve at said inlet of said first conveying chamber;
a first outlet pinch valve at said outlet of said first conveying chamber;
a second inlet pinch valve at said inlet of said second conveying chamber;
a second outlet pinch valve at said outlet of said second conveying chamber;
a first Y-shaped line section having one inlet and two outlets, with said inlet connected to said reservoir through said feed line and said outlets connected to said first inlet pinch valve and said second inlet pinch valve respectively;
a second Y-shaped line section having two inlets and one outlet, with said inlets being connected to said first outlet pinch valve and said second outlet pinch valve respectively, and said outlet connected to said delivery line;
one or more control valves being operable in a first mode of operation to selectively open or close said first and second inlet pinch valves and said first and second outlet pinch valves, and to selectively apply negative pressure or admit compressed gas through said first and second rigid gas permeable filter elements to draw in powdered material from said reservoir through said feed line into said first conveying chamber while said second conveying chamber forces powdered material, which had been previously drawn into said second conveying chamber, out of said second conveying chamber through said delivery line; and to draw powdered material from said reservoir through said feed line into said second conveying chamber, while said first conveying chamber forces powdered material, which had been previously drawn into said first conveying chamber, out of said first conveying chamber through said delivery line;
said one or more control valves being operable in a second mode of operation to clean powdered material from said first and second conveying chambers, said first and second inlet pinch valves, said first and second outlet pinch valves, said first and second Y-shaped line sections, said feed line, and said delivery line by operating said one or more control valves to selectively open said first and second inlet pinch valves and first and second outlet pinch valves while selectively admitting compressed gas through said first and second rigid gas permeable filter elements to allow compressed gas to flow through said first and second conveying chambers, said first and second inlet pinch valves, said first and second outlet pinch valves, said first and second Y-shaped line sections, said feed line, and said delivery line.
2. The system of claim 1 wherein said first and second rigid gas permeable filter elements extend for more than one third of the length of the first and second conveying chambers, respectively.
3. The system of claim 1 wherein said first Y-shaped line section has a leg connected to said inlet and two arms connected to said outlets, respectively, the angles between said leg and said arms being less than 30°, and wherein said second Y-shaped line section has a leg connected to said outlet and two arms connected to said inlets, respectively, the angles between said leg and said arms being less than 30°.
4. The system of claim 3 , wherein the first conveying chamber and the second conveying chamber each have a longitudinal axis, and wherein the angle between each of said arms of said first and second Y-shaped line section and the longitudinal axis of the chamber to which each of said arms is connected is less than 30°.
5. The system of claim 1 wherein the length to inside diameter ratio of the first and second rigid gas permeable filter elements is 10 to 30.
6. The system of claim 1 wherein a vacuum injector is used to apply negative pressure through said first and second rigid gas permeable filter elements.
7. The system of claim 1 further comprising first and second cleaning valves which can supply compressed gas to said first and second conveying chambers, respectively, without passing said compressed gas through said first and second rigid gas permeable filter elements.
8. The system of claim 1 wherein said first conveying chamber further comprises first and second connectors and first and second threaded screw caps, said first annular housing has first and second threaded ends, and said first rigid gas permeable filter element has first and second ends, said first and second ends of said first rigid gas permeable filter element being received within said first and second connectors respectively, said first and second connectors being received within said first and second end caps respectively, and said first and second end caps being threadably engaged with said first and second threaded ends respectively of said first annular housing to secure said first rigid gas permeable filter element within said first annular housing to create an annular space therebetween.
9. The system of claim 8 wherein an inner gasket is supported on the inside surface of each of said first and second connectors and an outer gasket is supported on the outside surface of each of said first and second connectors, said inner gasket being compressed by said first rigid gas permeable filter element and said outer gasket being compressed by said first annular housing.
10. The system of claim 1 wherein said outlet of said second Y-shaped line section is connected to a spray gun through said delivery line.