JPS59229255A - Screening method of recovered molding sand - Google Patents

Abstract

PURPOSE:To screen effectively recovered molding sand of a high temp. without clogging of screens by removing lumps with a coarse screen from said sand and cooling the sand to decrease moisture then screening successively the sand with a fine screen and an ultra-fine screen. CONSTITUTION:A casting mold removed after pouring is charged into a separator, by which the mold is collapsed and separated to a casting and molding sand. Iron pieces are separated and removed from the separated molding sand of a high temp. by a magnet separator and thereafter the sand is screened with a coarse screen provided with an opening of about 20-30mm. diameter, by which the lumps of the molding sand are removed. The molding sand is then cooled to a temp. of about atm. temp. +5 deg.C and is decreased in moisture by a sand cooler while preventing the considerable variance in the temp. of the molding sand. The sand is thereafter screend with a fine screen provided with a wire net having about 5mm.X25mm. opening and is screened with an ultra-fine screen provided with a wire net having about 0.5-0.6mm.X2.5-3.0mm. opening. The screened casting mold is kneaded with the water and binder added thereto and is fed to a molding machine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for sieving recovered foundry sand suitable for sieving recovered foundry sand into fine sand.

In general, it is very difficult to sieve recovered foundry sand into fine sand, and when it is sieved through a sieve made of perforated steel plate with about 20 punched holes, the sieve becomes clogged, and even a few birds are found. With an open-mesh sieve, no sand can pass through the sieve, so it was conventionally thought that fine sand such as surface sand could not be sieved from recovered foundry sand.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for sieving recovered foundry sand, which can sieve fine sand from recovered foundry sand.

Hereinafter, one embodiment of the present invention will be explained based on a flowchart. After pouring, the removed mold is put into a vibrating conveyor-type or rotating drum-type separation device, where it is collapsed and separated into a cast product and molding sand. After the separated foundry sand is discharged from the separator, the iron pieces are separated and removed by a magnetic separator, and then it is passed through a coarse knot with a rough opening of about 20 to 39 mm in diameter to form a lump of foundry sand. This allows the lumps of molding sand to be smoothly discharged without being caught in the gate when being cut out from the hopper in the subsequent process by the belt feeder. The coarsely grained foundry sand is temporarily stored in a hopper, cut out by a touch-held feeder, and supplied in fixed quantities to a sand cooler.By supplying a fixed quantity to this sand cooler, the temperature of the foundry sand is prevented from varying over a large IJ. It is then cooled down to a temperature of about +5°C and its moisture content is reduced, after which it is temporarily stored in a hopper. Next, the foundry sand in the hopper is cut out by a belt feeder, placed in a predetermined amount at a time in a narrow tube equipped with a wire mesh having an opening of about 5 mm x 25 πm, and then stored in the hopper. In this case, since the foundry sand has been cooled and its moisture content has been reduced, it can pass through the narrow tube. The foundry sand in the hopper is also cut out by a belt feeder in predetermined amounts, with an opening of 0.5πm to 0.
It is passed through an ultra-fine sieve with a wire mesh of 6×2.5πm to 3.0mm and stored in a hopper. In this case as well, the foundry sand has been cooled and its moisture content has been reduced, so the foundry sand in the hopper that can pass through the ultra-fine sieve is fed in a fixed quantity to the mixer via the belt feeder, and water and binder are removed. The mixed sand is added and kneaded, and after being aerated, it is put into the hopper of a mold making machine.

The rough sand removed by the narrow tube or ultra-fine sieve is crushed by a crusher and then fed via a conveyor into a hopper provided at a downstream stage of the sand cooler.

As is clear from the above description, in the present invention, the recovered foundry sand is cooled to about 5°C above the air temperature by passing it through a sand cooler, and then passed through a narrow tube and an ultra-fine sieve. The water content is reduced at the same time as the sand is cooled, so it does not clog when passed through a narrow tube or ultra-fine sieve, making it possible to obtain fine sand from recovered foundry sand, solving the problems of the conventional method. It produces excellent effects.

[Brief explanation of the drawing]

The drawing is a flow diagram for explaining the present invention.

Claims (1)

[Claims] The high-temperature recovered molding sand that has been separated from the castings is roughly pounded to remove lumps of molding sand, and then cooled to about +5°C in a sand cooler to reduce the moisture content. A method for sifting recovered foundry sand, which is characterized by sequentially passing it through a sieve.