US2261947A - Foundry practice - Google Patents

Description

Nov. 11, 1941. A. J. BARNEBL am. 2,261,947

FOUNDRY PRACTICE Filed July 27, 1940 Patented Nov. 11, 1941 FOUNDRY PRACTICE August J. Barnebl, Chicago, Ronald Webster, Evanston, and Alfred W. Gregg, Chicago, Ill.

Application July 27, 1940, Serial No. 348,044

3 Claims. (Cl. 22-217) Our invention relates to foundry practice.

Heretofore in foundry practice it has been feasible to re-employ only to a limited extent the sand from used casting-molds and cores. Good molds and cores can be produced only from a base of clean, highly refractory graded sand which is. within rather narrow limits, free from undersize particles or fines Best results are secured when sand of the proper character is available to the molders and core makers in what is termed bone dry condition, i. e., containing not to exceed 2% of moisture. However, the disintegration of sand particles by heat l of the molten metal, by abrasion and other causes and the coating of sand particles with various substances such as clay, oil, molasses and other ingredients used principally for bonding in the production of cores-and with heat derivatives of such bonding materials-results in the production of fines being increased and the cleanliness of the sand being reduced.

In order to compensate for and minimize the deleterious eects of the increasing nes and the decreasing cleanliness, it has been the customary practice to add new sand, having the proper characteristics, to the old or used sand in quantities from a few hundred pounds to one and one-half tons for each ton of castings produced. Probably the most common practice is to add the new sand by first using it in the production of cores and for mold facings. at least to the extent that it can be so added. Of course,` this repeated addition of new sand usually requires the discarding of used sand in substantially the amounts of the additions.

For many years attempts have been made, and with some success, to remove fines by means of air currents and dust collectors, but the mere ,removal of fines by no means solves the foundry v sand problem. Sand so cleaned of nes may possess satisfactory permeability qualities-1i. e., the ability properly to permit escape of gases from the molds during pouring; but itv does not possess the refractory characteristics of new sand. Thus, the particles of used sandLeven when of satisfactory sizes-become coated with films of the bonding material used in mold and core production and of heat derivatives 'of such materials, with the result that the resistance of the particles to high temperatures such as obtain in casting is lowered. In other words, the used sand becomes less refractorythan the original, new sand. And this problem of refractability has become more acute in recent years, because of the .extensive use of alloy metals, the

v satisfactory pouring temperatures of which in k many instances have well nigh approached the limit which even clean, withstand.

It has been known for many years that sand cleaned or scrubbed in water would be cleaner and more resistant to high temperatures than either sand as it comes from the pit or sand that has been treated by so-called dry cleaning pure, silica sand can processes. However, the addition of the quantities of water required for scrubbing, and which was utilized for no .otherspurposa presented problems of dewatering and drying in order to reduce the water content of the scrubbed sand to produce bone dry sand and was entirely too expensive to be practicable.

Very recently there has been developed and commercially employed a process of cleaning castings and of removing and disintegrating cores from castings by a high pressure jet of water and -Wet sand. United States Patent No. 2,200,587 granted May 14, 1940, discloses such a system.

The combination of this high pressure blast water and sand removal of mold sand adhering to castings and of core sand (which will be generally termed casting cleaning), with classilcation, water scrubbing, the return of some sand to the blast, the dewatering and drying of other parts of the sand, and the return of the. dried sand tothe molding floor for re-use in making molds and cores, which is the gist of our invention, isnow for the first time advanced.

One of the objects of our invention is to provide a process of casting cleaning with sand recovery which is economical, clean, and effective.

Another object is to provide a method whereby the sand used in cleaning castings and that removed from the castings in the cleaning operation is water-cleaned and classified and then in part returned for-re-'use in cleaning and impart dried and returned for re-use in molds and cores.

In the high pressure water and sand blasting operation, the sand particles adhering to the 4castings and comprising the cores, and also those that may have been cracked or otherwise weakened by the high temperatures obtaining in the molds during casting or from other causes are broken down into fines and as such removed before reuse, either in the blast or in the molds and cores. Thus, the water blasting operation in eifect helps to remove nim from, scour and cleanvthe sand particles and also facilitates the subsequent selection and retention of the strongerparticles for re-use and the discard of the weaker particles.

Our invention is illustrated diagrammatically in the accompanying drawing which is a route diagram for core and molding sand, water, waste material, and reclaimed sand-some of which reclaimed sand is re-used in the cleaning operation and some in the molding room for making molds and cores.

In the particular embodiment here shown, cores and molding sand adhering to castings pass from the molding room I to the blastingV room or `location 2. This movement may be through l mechanical devices, such as traveling belts, moving platforms, cranes, and the like, or by cars or even by manual portage.

In the blasting room 2, the castings are cleaneddgg,

' and the cores are removed therefrom by means of -a high pressure stream of water and sand projected from gun's 3, which are supplied with wet and fiowable sand from the basin 4 and with fresh water at high pressure from the pump 5.

The floor of the blasting room 2 slopes-to a coarse grating 6 through which all of the material blasted from the castings passes under the inuence of the water from the blast gun. This material is made up largely of sand, but also contains nails, wire and other objects used to strengthen the cores and molds; clay, used as a binder for the foundry sand; scale, fines; and coke and other coarse materials used to make up the interior of cores: oil, molasses, pitch, bentonite, and like material used as binders in making cores, some of which is burnedor heat affected.

`The material passing through the grating 6 is carried by gravity onto a vibrating screen 1 of such mesh as to permit the passage of sand of the size desired formolding and to reject al1 coarser materials which 'are carried to waste or to furtherclassification for recovery of the metal parts as may be desired.

The goodsand. water, clay, soluble material, and fines fall into the transfer sump 8, from which this material flows by gravity or is pumped by a pump 9 to a classier I0.

This classifier comprises a spreader flume II for causing the material to fall substantially evenly over the surface of the hopper. Extending downwardly from the bottom of the hopper are a plurality of tapering sand discharge chutes I2, each restricted to such an extent as to per- -mit a discharge under the head of the classiiler just sufficient to cause some water continuously to flow from the top of the classifier down the spillway I3. Near the bottoms of the chutes I2, water is continuously supplied from rings surrounding the bottoms of the chutes, the water being supplied in such quantity that it continuously ows upwardly through the sand in the classifier, carrying with it the more buoyant lines, clayor soluble materials which, because of the up current. flow oif the surface of the classifier and down the spillway I2. The size of the sand grains retained in the classifier may be predetermined by the velocity of flow of water up the chutes I2. The -heavy material which 7.5.'

passes down the spillway I3 is separated from the water in the sludge settling tank I4, overflowing through the pipe I5 tothe seal tank I6 hereinafter described.

The thin mixture of sand and water which passes out of the bottoms of thechutes I2 enters the storage hopper Il, from which a part. usually about one-half, is returned through pipe I8 to the'wet sand basin 4, to be used as hereinabove described as the abrasive for the blasting gun 2. The passage of sand and water from the storage hopper I'I to the wet sand basin 4 may be by gravity or by pump 20, as conditions require.

All of the sand and water not required by the sand blasting guns 3 passes out of the storage hopper Il into the feed hopper 2| of the dryer 22. In order to keep the'sand which passes into the dryer 22 at requisite dilution with water so that it will spread properly uponthe dryer drum 23, additional water is supplied through the pipe 24 and regulated by the valve 26. The dryer here shown may be of the type illustrated in the application of August J. Barnebl and Howard D. Grant and August C. Barnebl', Serial No. 257,922, filed February 23, 1939, and will not be hereindescribed in detail. Suiiice it to say that the sand is first dewatered by very rapidly removing water therefrom by means of suction applied within the drum 22, as the layer of sand is rotated on the surface of the drum.

'I'he suction Ior reduced pressure within the drum 23 is maintained by an exhauster 21 whiclr not only draws water out of the sand veryI rapidly, but also\ aids the ilow of heated air through the sand. The water and air pass into a separator 28 from the bottom of which the water is drawninto the seal tank I8 and from the top of which the hot air and vapor pass oi! through the exhauster 21. It has been found that this rapid removal of water from the sand results in the further removal Aof films from the sand'particles and of nnes released by the removal of such iilms and also nes which may not have been removed by the classifier.

Thus, it will be apparent that the nes, resulting from the removal of illms from sand particles and otherwise, may be removed in part yat the classifier and in part -at the dewateringl iines is recirculated by means ofa water pump4 i 30, the excess being allowed periodically to ow to waste. The undesirable fines removed in the dryer are eventually discharged from the top of the classier.

Valves are provided-in the water lines so that the supply may be regulated and so that various pieces of apparatus may be shut oii temporarily, as for repairs or cleaning, without interruption of the entire system. Ordinarily the water brought to the system by the guns 2 and the water seals, not shown, for the various pumps is sufiicient for the entire system, but should the sludge discharging from the settling tank be of such .character as to retain an excessive amount of water, additional water may be admitted by opening the valve 3| which. will ordinarily be left closed.

- After the removal of th`e major part of the water in dryer 22, hot air supplied by a hot air furnace the dryer drum 23 to evaporate additional amounts of water until the sand finally leaves the dryer in what is called bone dry? condition, that is to say, with a moisture content of not more than 2%. The sand leaving the dryer is deposited upon a traveling belt 36 which moves along a path indicated by the dotted arrows 31 to carry the dry sand back to the molding room I, where it is again made into cores and used in the molds, after which it again enters the cycle hereinbefore described. Of course, instead of employing a conveyor belt to convey the classied, washed and dried sand back to the molding door, this transfer umay be accomplished by cars, wheelbarrows, or in any other appropriate manner, and the sand may be passed to bins from which it may be removed as needed in the molding room.

Having thus illustrated and explained a typical embodiment of our invention, what We claim and desire to secure by United States Letters Patent is as follows:`

1. The foundry method comprising removing from a casting location to a cleaning location castings containing sand cores and adhering sand 25 'cation with u continuous upward flow 0f Water from the molds. removing from the castings'at the cleaning location and by means of a stream of high pressure water and wet sand the adhering sand, scale and cores, separating out the bulky material from the sand, fine scale and water, owing the wet sand and ne scale to a classifier for removal of superbuoyant sand particles from the heavier particles, returning part of the heavier sand to the high pressure water streams, passing the remainder of the heavier sand through a del I 3 waterer and dryer, and returning the dried sand for re-use in making molds and cores,

2. 'I'he foundry method comprising removing from a casting location to a cleaning location the castings containing sand cores and adhering sand from the molds, removing from the castings atthe cleaning location and by Ameans of a stream of high pressure waterand wet sand the adhering sand, scale and cores, separating out the bulky material from the sand, ne scale and water, fiowing the wet sand and fine scale to a classifier for removal of superbuoyant sand particles from the heavier'particles, returning part of the heavier sand to the high pressure water streams, passing the remainder of the heavier sand and water through a dewaterer and dryer, returning the dried sand for re-use inmaking molds and cores,

and returning water and solids removed with it to the classifier.

3. The foundry method comprising removing core and molding sand from castings, treating the used mold and core sand which includes the steps of separating smaller lighter particles from the larger heavier .particles by hydraulic classificontinuously removing the smaller `lighter par.l ticles by overiiow of the water carrying them upward, passing through a dewaterer and dryer the separated larger heavier particles which settle against the upward ow of lthe water, and reusing the dried sand to produce molds and cores for additional castings.

AUGUST J. BARNEBL.

. RONALD WEBSTER. ALFRED W. GREGG.

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