US3172177A

US3172177A - Continuous method of preparing foundry sand

Info

Publication number: US3172177A
Application number: US342742A
Authority: US
Inventors: Herbert C Brauchla
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-02-05
Filing date: 1964-02-05
Publication date: 1965-03-09
Anticipated expiration: 1982-03-09

Description

March 9, 1965 c. BRAUCHLA CONTINUOUS METHOD oF Examine FouNDRY SAND 4 Sheets-sheet 1 Filed Feb. 5., 1964 INVENTOR Herbert C. Brauchla ATTORNEYS H. c. BRAUCHLA coNTINuous METHOD oF PREPARING FouNoRY SAND Filed Feb. 5, 1964 March 9, 1965 4 Sheets-Sheet 2 INVENTOR Herbert C. Brouchlo and ATTORNEYS March 9, 1965 H. c. BRAucl-ILA 3,172,177

CONTINUOUS METHOD oF PREPARING FouNDRY SAND Filed Feb. 5. 1964 1 4 sheets-sheet :s

I INVENTOR Herbert C. Brauchla @www ATTORNEYS March 9, 1965 H.'. BRAUCHLA 3,172,177-

` CONTINUOUS METHOD oF PREPARING FouNDRY SAND Filed Feb. 5, 1964 4 Sheets-Sheet 4 l lIllu INVENTOR l Herben c. Brauchla www ATTORNEYS United States Patent O 3,172,177 CNTINUOUS WETHE) F PREPARDJG FUNDRY SAND Herbert C. Brauchla, PE. Box 349, (Bair Harbor Road, Fremont, (Ehio Filed Feb. 5, 1964, Ser. No. 342,742 9 Claims. (Cl. 22-217) The present invention is related to applicants U.S. Patent No. 3,141,844 issued July 2l, 1964, and entitled Method and Apparatus for Dry Sizing.

The present application relates to a method of preparing foundry sand, particularly a continuous method for effectively sizing, iluling and blending foundry sand with a binder in a casting operation;

In foundry operations, sand and binder are conventionally sized or mulled in an enormous mixer or mullet wherein huge plows or agitators are employed to move or beat a great quantity of hot sand while introducing sutticient quantities of bentonite and sea coal binder and the necessary water as temper. A typical mulling installation may cost as much as $50,000 and require a 125 HP. driving means. The mixing or mulling process, of course, generates friction which contributes to the heat problem and compounds the diiiiculty of tempering the already hot sand which requires normally 4 percent moisturization. Needless to say, the longer conventionally mulled hot sand sits before molding the more the moisture is burned off by the heat. Conventional mullers do not attempt to size the sand and binder so as to remove oversized aggregate and daily shutdown is required for the two or three hour job of cleaning from the drum the undesired quantity of sand and binder which has set up therein. Also, the tempered sand produced by conventional mullers almost always contains large-sized lumps of incompletely mixed clay and sand. Unquestionably such clay agglomerates upset the temper formulization requiring the addition of greater amounts of clay than are actually necessary to produce a mold material having the desired characteristics.

In applicants U.S. Patent No. 3,141,844, sizing is accomplished by advancing matter lto be sized in a horizontal plane and attacking said `advancing matter with a plurality of obliquely7 aligned rotatable, vibrating'combs extending transversely of said plane. Oversized matter is thrown to one side in front of the combs and finer sized Vmatter is advanced through the combs. Applicant in adapting this sizing method to the preparing of foundry sand has developed a more economical and eiiicient blending of binder and sand, andhas substantially eliminated the sand heat problem, since sand and binder are blended and iiuifed while superposed in thin layers. Also, oversized coarse aggregate such as balls of bentonite and charred resin and sand are removed from the blend. The actual blending of sand and binder is more eiiicient since the binder is actually poured as a thin layer on top of an advancing thin layer of sand, then the two layers are simultaneously sized, fiuifed and blended by the combing action. Due to this more efcient blending, substantially every sand particle is covered with the desired layer of binder resulting in a spectacular reduction in the amount of binder required to produce molds having the requisite green strength, permeability, moisture and steam. Also, there are totally eliminated the objectionable lumps of incompletely mixed clay and sand. The tempering process itself is accomplished either by kneading sand and binder while moisturizing or by fogging with water while cascading the blended sand and binder. As a consequence there is provided at less cost a more finely sized, more even temperatured and more homogeneous foundry sand of low moisture content. Without doubt such sand provides a more valuable casting.

Edili?? Patented Mar. 9, 1965 lCe Accordingly, it is an object of invention to provide a more economical and etlicient method of preparing foundry sand.

Another object of invention is to provide a method for continuous sizing, flutiing and blending of foundry sand and binder.

Another object of invention is to provide a method for more efiicient cooling of foundry sand.

Another object is to provide a continuous method for more e'icient mixing of sand and binder and regulating of their mixed strength characteristics.

Yet additional objects of invention willl become apparent from the ensuing speciiication and attached drawings wherein:

FIG. 1 is a flow sheet depicting the present method; including the step of tempering by moisturizing while kneading the intimately mixed sand and binder;

FIG. 2 is a liow sheet depicting the modied method wherein the sized, fluifed and mixed sand is cascaded then tempered by fogging prior to formation of the molds;

FIG. 3 is a side elevation of a modified cascading installation, showing binder introduction at the right side, medially positioned sizing, flufling and blending comb elements and a sequentially positioned fogging element on the left side;

FIG. 4 is an enlarged side elevation of the rotating drum wherein a fogging nozzle is axially positioned for fogging of the blending sand and bindercascading within the drum; `and Y FIG. 5 is an enlarged end'elevation of the fogging or cascading drum showing the fogging element axially positioned therein.

In FIG. 1 there is depicted a flow sheet illustrating the present methodA of preparing foundry sand by advancing same upon an `endless belt conveyor in a substantially thin layer, introducing binders or other agents from

hoppers

68, 70 and 72 and blending'into the layer of foundryV sand, passing the resulting mixture through a grille if desired, Vand sizing, flufing and mixing by repetitively combing the layer of sand and binder throughout a sustained horizontal plane with vibrating cones 66. According tothe present unique sizing method of attacking by rotating a plurality of vibrating combs 66 which transversely engage the layers of sand and binder, oversized matter such as balls of bentonite and the like are conveyed off the belt at side 62v by the combs, While the liner sized matter is advanced through combs 66 for tempering by moisturizing while kneading (FIG. l) in hopper 56. Alternately,rcascading (FIG. 2), may replace kneading. The foundry sand together with the layer of binder, such as a mixture of bentonite, and foundry facing, such as a mixture of sea coal, may be introduced onto the belt by meansY o'f a sieve end-feed such as that manufactured by Christy Machine Company and trademarked Christy Siv-O-Duster. Normally such devices have both agitating and dispensing rollers positioned trans-` versely in a hopper together with a dispensing roller brush. It has been found that the sand may be advanced in a one-half inch layer with a much thinner layer of the binder. inasmuch as the sizing, fluli'ing and mixing take place prior to the tempering or introduction of water, a more homogeneous mixture is completed because the sand and binder are dry and in thin layers. Thus, a comb rotating device of small horse power may effect continuous mixing of large quantities of sand and binder. Since the combs while liutiing and mixing effect aeration and cooling of the sand, it is submitted that a more precise temperirig can be obtained. Because the sand so mixed and tempered is cooler, there does not exist the conventional hazard of heat of the sand evaporating the water temper as the sand sits prior to molding. Also, since the individual sand particles are substantially covered with a film of bentonite, less water is actually required to enable the bentonite to act as a binder. Since less Water is required the moisture content can be readily held below 3%. This is significant for General Motors Corporation is reputed to give their mix men a cash bonus for keeping moisture under 4%. Due also to the intimate mixing of sand and bentonite, it has been found that far less quantities of bentonite are required, applicants molding operation having been carried out several times continuously without the insertion of additional bentonite into the system while consistently producing a mold sand having the following characteristics:

Green strength 12.6 to 12.7. Permeability 113. Moisture 2.7 to 2.9. Shear 3.4 to 3.5.

Manifestly, `scraping elements may be employed to adjust the level of the sand being introduced and as in the parent application controls may consist in the rate of introduction of sand and binder, the rate of advancing both sand and binder along the endless belt, the spaces between proposed comb teeth, the rate of rotation and vibration of combs, the distance between the ends of the comb teeth and the advancing belt. Temper control consist in the FIG. l method in the amount of water added and rate of kneading, and in the FIG. 2 modified method principally in the pressurization and spray adjustment of water that is directed onto the cascading sand and binder.

It is found that by treating and preparing foundry sand according to applicants method, VAthere are eliminated sand holes, blisters and scale whicheresult in imperfect casts. Low moisturization is readily achieved and in actual fact three days of run have beencornpleted while reusing the sand without the addition of any more bentonite into the system.

A proposed installation for preparing foundry sand is illustrated in side elevation in FIG. 3 wherein there is shown a sand and binder conveyor stand 120 supporting

rollers

124 and 126. Endless belt 132 is connected by pulley means to roller 126 and is driven by motor 130 supported upon motor base bracket 34 attached to one ofthe conveyor stand 120 legs.

Sand may be introduced by bin 136 as a thin layer 13S on belt 128. Normally this sand is quite hot, as it is received subsequent to the break-up of the mold, and includes a certain amount of charred binder and other undesirable and oversized particles. A binder such as bentonite and seall coal may be introduced in feeding bin 140 having clearing and dispensing

rollers

142 and 144 with a brush element 146 attached to the bottom of the bin and contacting rollers 144. Thus the binder is introduced as a thin layer 148 on top of layer 138 of foundry sand. This dual layer of material is conveyed to the sizing, fiuing and mixing apparatus 150 including endless belt 152 supported upon table 154 and driven by motor 156 which is connected to roller 158 opposite roller 160 by means of driving belt 162.

Sizing, fluliing and mixing is accomplished by the rotatable combing of combing head 166 which is supported by stand 168 and upon which are mounted a plurality of transversely aligned combs 171 attached to belt 174. Belt 174 is driven by a motor (not shown) supported on the top of stand 168 while combing head 166 is vibrated by eccentric drive motor 178 connected by a clevis 180 which extends through the top of stand 168 and the combing head 166. Combs 171 may be vibrated in the range of 1,400 to 2,000 r.p.m. and in an amplitude of 1/10 to $40,000 of an inch. Though higher frequencies of vibration may be obtained, the vibration must not be so great as to fracture or mill the material to be sized. As in the related applications, adjustments of the height of the comb teeth ends above the conveyor belt 152 may be made by means of hand wheels. Also the distance between the individual comb teeth may be varied readily by interchange of combs 171 having teeth spaced apart at distances suitable to permit sand and binder particles of the desired size to pass through the combing-head, while rejecting and discarding aside the undesired, greater sized particles of individual and agglomerated matter.

Oversized matter incapable of passing between the individual comb teeth is thrown to one side of conveyor belt 152 and then introduced into chute 182 whence it is conveyed to bin 185. Transverse adjustment of the entire combing head is made by means of pivoting stand 150 about base plates 183 by means of studs 184 which extend through base plate foot portion. Finer sized material which is conveyed through the individual combs is dropped into tempering chutes 188 and thence conveyed into the tempering unit 192 which consists of a rotatable drum 194 mounted upon frame 196 by means of rollers 198 and driven by belt means 200 connected to driving motor 202. Rotary drum 194 may have an inwardly extending introductory flange (not shown) at its receiving end to prevent spilling of the finer sized matter and includes braces 206 which support a scraper 208 consisting of two angle irons pinching a resilient member 210 which engages the inside of drum 194 at the mouth thereof for removing caked deposits of finer sized material formed by the high moisture content. Braces 206 also support fogging nozzle 212 which is supplied by airline 214 and Water line 216. As drum 194 rotates the finer sized material is conveyed by centrifugal force, as well as the lifting action of longitudinal inwardly extending flanges 220, to the top of the drum whence gravity permits the finer sized matter to cascade in a vertical plane. Note that flanges 220 are spaced sufliciently inward from the mouth of drum 194 to avoid contact with resilient member 210 of scraper 208. As the finer sized material cascades, fogging is accomplished by nozzle 212 to complete the proper temper. It is believed that this method of fogging while cascading sand provides an eicient tempering method by which virtually every grain of bentonite covered sand is provided with a film of Water. From the open, exit end of drum 194 the tempered sand and binder may be removed by belt conveyor means or the like to the sand molding operation. Various means may be provided for adjusting the speed of drum 194 rotation by tensioning of belt 200 and also the drum 194 itself may be inclined to adjust the speed of advancement of sand and binder therethrough.

Manifestly, various structural changes in the suggested elements may be employed Without departing from the spirit and scope of invention as defined in the subjoined claims.

I claim:

l. Method of preparing foundry sand comprising:

(a) advancing said sand as a thin layer;

(b) blending a layer of binder onto said advancing sand;

(c) sizing, flutiing and mixing by repetitively combing against said sand and binder throughout a sustained horizontal plane;

(d) removing oversized matter from in front of said combing; and

(e) sequentially of said combing, tempering by kneading said sand and binder with liquid.

2. Method of preparing foundry sand as in claim l, said combing being by means of a plurality of transversely reciprocating combs mounted upon an endless belt and traversing said sand and binder being advanced.

3. Method of preparing foundry sand as in claim 2, said binder including bentonite and sea coal.

4. Method of preparing foundry sand as in claim 2, said binder including bentonite and fiber of less than mesh.

5. Method as in claim 4, said combs being vibrated in the range 1,400 to 2,000 r.p.m. and in an amplitude of 2% 0 O 1/40000 Of an llch.

6. Method of preparing foundry sand comprising:

(a) advancing said sand as a thin layer;

(b) blending a layer of binder onto said advancing sand;

(c) sizing, uing and mixing by repetitively combing against said advancing sand and binder throughout a sustained horizontal plane;

(d) removing oversized matter from in front of said combing;

(e) sequentially of said combing, cascading said sand and binder in a vertical plane; and

(f) 4tempering said cascading sand and binder with liquid.

7. Method as in claim 6, said cascading being accomplished by introducing said finer sized sand and binder into a drum rotated at a speed suicient to cascade sand and hinder in a vertical plane within said drum.

8. Method as in claim 7, including retaining said sand in said rotating drum from slipping on the Walls of said drum.

6 9. Method as in claim 8, said tempering including fogging said cascading sand and binder axially Within said rotating drum with air and water.

References Cited bythe Examiner UNITED STATES PATENTS 1,061,160 5/13 Brown 22--89 1,525,634 2/25 Bell 22--89 X 1,985,942 1/35 McIlvaine. 2,134,117 10/38 Floyd et `al 22-89 2,188,798 1/40 Smith 22-89 2,714,953 8/55 Wolski 209-315 2,942,607 6/ 60 Skinner 209-106 FOREIGN PATENTS 21,977 9/ 13 Great Britain. 98,286 3/60 Sweden.

WILLIAM I. STEPHENSON, Primary Examiner.

MARCUS U. LYONS, Examiner.

Claims

1. METHOD OF PREPARING FOUNDRY SAND COMPRISING: (A) ADVANCING SAID SAND AS A THIN LAYER; (B) BLENDING A LAYER OF BINDER ONTO SAID ADVANCING SAND; (C) SIZING, FLUFFING AND MIXING BY REPETITIVELY COMBING AGAINST SAID SAND AND BINDER THROUGHOUT A SUSTAINED HORIZONTAL PLANE; (D) REMOVING OVERSIZED MATTER FROM IN FRONT OF SAID COMBING; AND