Abrasive feed system

• US 4,878,320 A
• Filed: 12/04/1987
• Issued: 11/07/1989
• Est. Priority Date: 12/04/1987
• Status: Expired due to Fees

• Current Assignee: Whitemetal, Inc.
• Original Assignee: Whitemetal, Inc.
• Inventors: Woodson, Jerry P.
• Primary Examiner(s): Olszewski, Robert P.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/128,589
• Time in Patent Office: 704 Days
• Field of Search: 51/319, 51/320, 51/321, 51/410, 51/413, 51/436, 51/439, 410/90, 410/136, 410/137, 410/138, 410/140, 410/141, 410/145, 410/146, 410/153, 410/46 X, 410/139
• US Class Current: 451/39
• CPC Class Codes: B05B 7/1404 Arrangements for supplying particulate material
• CPC Class Codes: B05B 7/1472 Powder extracted from a powder container in a direction substantially opposite to gravity by a suction device dipped into the powder
• CPC Class Codes: B24C 7/0053 with control of feed parameters, e.g. feed rate of abrasive material or carrier
• CPC Class Codes: B24C 7/0061 of feed pressure
• CPC Class Codes: B24C 7/0084 the abrasive material being fed in a mixture of liquid and gas B24C7/0038, B24C7/0076 take precedence; blasting medium with additives B24C11/005

Abstract

In accordance with illustrative embodiments of the present invention, a hopper containing a sodium bicarbonate abrasive is pressurized with a dry gas such as nitrogen. The abrasive is fed into a transport line through which compressed air flows toward a nozzle, and pressures in the hopper and transport line are regulated so that the hopper pressure is greater than the transport line pressure by an amount that keeps the abrasive in the hopper very dry so that the same differential pressure causes a precisely metered amount of abrasive flow.

Claims

1. Liquid-propelled abrasive cleaning apparatus comprising:

nozzle means having a body with an interior propulsion chamber having a water inlet, an air and abrasive inlet and an outlet all communicating with said interior propulsion chamber through said housing;

pump and conduit means for furnishing water under high pressure to said nozzle means;

transport line means for conveying a mixture of compressed air and sodium bicarbonate particles to said air and abrasive inlet of said propulsion chamber;

means containing a supply of sodium bicarbonate particles to be delivered under pressure to said transport line means;

nitrogen gas supply means for supplying nitrogen under pressure to said containing means to provide a pressurized flow of sodium bicarbonate particles to said transport line means;

supply means independent of said nitrogen gas supply means for supplying pressurized air to said transport line means, and

regulator means for maintaining a positive pressure differential between the interior of said containing means pressurized by said nitrogen, and said transport line means pressurized by said supply of pressurized air.

2. The apparatus of claim 1 wherein said abrasive is sodium bicarbonate.

3. The apparatus of claim 1 further including dryer means in said transport line means for reducing the moisture content of said compressed air.

4. The apparatus of claim 1 wherein said containing means has a porous membrane therein for separating the interior thereof into an upper region and a lower region, said nitrogen being supplied to said lower region and passing through said membrane to create a fluidized bed of abrasive particles in said upper region.

5. The apparatus of claim 4 further including a pick-up line extending into said containing means to a location adjacent said membrane, said pick-up line being connected to said transport line means, said positive pressure differential causing a metered amount of said abrasive to flow into said transport line means.

6. Apparatus for use in an abrasive blasting system, comprising,

means containing a quantity of abrasive particles;

conduit means for supplying a dry gas under pressure to the interior of said containing means;

transport line means connected to a source of pressurized air for transporting abrasive in said abrasive blasting system;

an abrasive particle feed line connecting the interior of said containing means to said transport line means;

first pressure regulating valve means disposed in said conduit means for controlling the pressure of said dry gas as applied to said interior of said containing means; and

second pressure regulating valve means disposed in said transport line means for regulating the pressure of air in said transport line means;

whereby said first pressure regulating valve means and said second pressure regulating valve means may be adjusted to maintain a pressure in said container means that is greater than the pressure of air flowing in said transport line to permit a controlled amount of flow of said abrasive from said container means via said abrasive particle feed line into said transport line to permit a controlled amount of flow of said abrasive into said transport line.

7. The apparatus of claim 6 wherein said abrasive particle feed line extends from the bottom of said containing means to a point of connection with said transport line.

8. The apparatus of claim 6 further including valve means in said feed line for controlling the flow of abrasive therethrough.

9. The apparatus of claim 8 further including dryer means in said transport line upstream of the point of connection of said feed line thereto for reducing the moisture content of said compressed air.

10. The apparatus of claim 6 further including a porous membrane in said containing means dividing the interior thereof into a lower region and an upper region, said dry gas being supplied to said lower region and passing through said membrane to create a fluidized bed of abrasive particles in said upper region.

11. The apparatus of claim 10 wherein said abrasive particle feed line extends from a location above said membrane out the top of said containing means to a point of connection with said transport line.

12. The apparatus of claim 6 wherein said dry gas is nitrogen.

13. The apparatus of claim 6 wherein said abrasive is sodium bicarbonate.

15. The method of claim 8 wherein said abrasive particles consist of sodium bicarbonate, and said surface has a coating of paint to be stripped away by performing said method.

14. A method of supplying a controlled amount of abrasive particles from a container to a transport line having a stream of compressed air flowing therethrough, comprising the steps of:

pressurizing the interior of said container with a dry gas; and

maintaining a pressure of the gas in said container that is greater than the pressure of the compressed air flowing in said transport line, the difference in said pressures causing abrasive particles to flow from said container into said transport line and preventing the compressed air in said transport line from entering said container.

16. The method of claim 14 wherein said abrasive particles are sodium bicarbonate.

17. The method of claim 14 wherein said gas is nitrogen.

18. The method of claim 14 including the additional steps of transporting the resulting mixture of compressed air, gas and abrasive particles to a nozzle having a water supply inlet;

and propelling said abrasive particles onto a surface to be cleaned with water under high pressure supplied to said inlet.

19. With a propulsion chamber having an outlet, a water inlet and an air/abrasive inlet, the method of cleaning a surface of paint, corrosion or the like, comprising the steps of

applying a source of high pressure water to said water inlet of said propulsion chamber,

applying a stream of bicarbonate of soda particles entrained in air to said air/abrasive inlet of said propulsion chamber,

accelerating said bicarbonate of soda particles with said high pressure water inside said propulsion chamber and directing same in a high energy blast via said outlet of said propulsion chamber, and

directing the outlet of said propulsion chamber against said surface to be cleaned, the hardness of said surface being approximately the same as the hardness of said particles of bicarbonate of soda.

20. The method of claim 19 wherein said surface has a moh hardness of about 3.

21. The method of claim 19 wherein said surface is aluminum.

22. The method of claim 19 wherein said surface is fiberglass.

23. The method of claim 19 wherein said surface is a carbon fiber laminate.