US 2383988 A
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Patented Sept. 4, 1945 UNITED STATES PATENT OFFICE No Drawing. Application October Serial No. 507,737
(Granted under the act of amended April 30, 1928;
The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.
The present invention relates to a new and novel abrasive cleaning and polishing material for use in conventional air blast cleaning processes replacing sand or metal shot now in use.
In the overhaul of aircraft engines many of the parts such as the cylinders, crankcase, connecting rods and other motor parts are covered with very adherent films of foreign matter such as oil stains, soft and hard carbon deposits and oil sludge which forms a varnish like coating. Due to the adherent nature of the foreign matter films and stains above noted, vapor cleaners and mild alkaline sprays are of little value and the use of strong alkali or acid. cleaning solutions is ruled out because of damage to the parts being cleaned particularly when such parts are aluminum alloy.
It is obvious that tumbling of the parts in sawdust or mixtures thereof with mild abrasives is not practical with a view to the nature of the parts to be cleaned and sand blasting while very effective causes surface pits and roughness which would ruin the engine parts. It has therefore been necessary to remove the dirt films of the character described by hand scraping and rubbing with steel wool and abrasive cloth which is a very expensive and time consuming procedure particularly when a large number of engine parts are to be cleaned.
It was determined that air blast cleaning was the most practicaly solution if an abrasive material could be found which could be used in place of sand or shot in the conventional sand blasting equipment, the material having only sufficient abrasive action to remove the surface film but having a polishing action so as not to damage the metal surface finish and being of sufficient density to give the desired results without excessive air consumption.
The principal object of the invention is the provision of a material for use in air blast metal cleaning equipment which possesses sufficient abrasive properties to remove oil stains, carbon deposits, sludge and the like without causing damage to the surface finish of the metal.
Another object of the invention is the provision of an improved abrasive material for use in air blast metal cleaning equipment which consists of finely divided starch killed and dehydrated cereal grain 6f the character having a hard outer hull such as Wheat, barley, rice and com.
A further object of the invention is the process for preparing an abrasive of the character described from cereal grains.
In the preparation of the abrasive material in accordance with the invention, whole grain wheat has been found to be an excellent raw material though other grains having a hard outer hull March 3, 1883, as 370 0. G. 757) such as barley, rice or corn as above noted may be employed. The raw material such as Whole grain wheat is cooked by boiling with water for a period of approximately one and one half hours to hydrolyze the starch in the grain, i. e. to break down all of the starch granules so that the starch will gelatinize in the absorbed water, forming a starch paste enclosed by the harder outer hull. The starch paste and gluten in the cooked grain form a glue-like material which, when the grain is dried, becomes a hard horn-like material as distinct from the granular nature of the starch in the uncooked grain. The cooked grain is then dried or dehydrated until it has a moisture content of approximately five percent based on the weight of the dried product. The dried or dehydrated product is then ground or cut in a machine employing steel cutters, it being essential that the product be cut and not crushed or pulverized. The product is cut so that each grain is divided into twelve or fourteen parts and these granules are then ready for use in conventional sand blasting equipment of either the suction or gravity feed type. The granules, after use, may be screened to remove dirt and dust and thus are ready for reuse.
In use the granules have sufficient density and hardness to be impelled with sufiicient velocity against the metal surfaces to be cleaned that the granules will bite into the films of foreign matter and will effectively remove the same by abrading action, but the granules lack any sharp cutting edges such as are characteristic of sand and hence will not scratch, pit or chip the metal parts being cleaned. The granules are elastic so they do not indent the metal being cleaned but are sufficiently abrasive to give a definite polishing action so that the metal is polished as well as being cleaned. Continuous use of the new material has indicated it to have no detrimental action on engine parts and has effected large savings in time over previously employed methods.
While I have disclosed the use of wheat as the preferred raw material for an abrasive in accordance with the invention, other grains having a hard hull such as barley, rice and corn may be treated and granulatedinto particles of a similar size in the manner above described.
Having described my invention what I declare to be new and wish to secure by Letters Patent is:
A process for preparing whole grain wheat to make a mild abrasive material adapted for use in air blast cleaning of metals consisting of the steps of cooking the Wheat with water at boiling temperature for a period of approximately one to two hours, drying the cooked wheat to a moisture content of substantially five per cent and cutting the dried product into granules of a convenient ize for use.
FRANK R. PERRY.