US2583036A

US2583036A - Forming foundry cores

Info

Publication number: US2583036A
Application number: US759719A
Authority: US
Inventors: Robert S Wolf
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-07-08
Filing date: 1947-07-08
Publication date: 1952-01-22
Anticipated expiration: 1969-01-22

Description

Patented Jan. 22, 1952 Robert S. Wolf, Chicago, Ill.

No Drawing. Application July 8, 1947, Serial No. 759,719

9 Claims. 1

This invention relates to the formation of foundry cores and is an improvement upon the methods and products described in my co-pending application, Serial No. 733,921, filed April 2, 1947, now abandoned.

The common adhesive heretofore used to impregnate core sand is a form of oil. It has the disadvantage of causing a disagreeable irritating smoke and odor when the casting is poured. It also generates gases which cause defects in the castings. Likewise the cores when baked have solid crusts which can be broken only with difficulty.

As set forth in my aforesaid application, I have found that by using soluble cellulose derivatives and particularly methyl cellulose and its derivatives such as carboxy methyl cellulose and its salts, the defects of the oil from the adhesives may be eliminated.

The new adhesives are introduced into the sand in any suitable manner, normally by dissolving at least a portion of the adhesive in a solvent, such as water, and then mixing the sand and the adhesive.

I have found that an improved core may be produced if an unbaked core produced by the process of my aforesaid application is exposed, in at least its outer section, to an atmosphere consisting substantially of a solvent for the adhesive and this exposure is continued long enoughsubcore in which the exterior is substantially harder and tougher than the interior.

This process also has the advantage that it permits the use of more highly viscous adhesive solutions, which may not otherwise wet and bind the sand particles. It thus permits the use of higher solid content solutions of the adhesive.

The preferred method of creating an atmosphere of the solvent is to place cores within an enclosed chamber such as a steam kettle wherein vapors of the solvent may be generated, pref erably under super-atmospheric pressure. Usually one or two pounds atmospheric pressure is necessary and a treatment of only five to ten minutes is adequate.

The core may be placed within the kettle on the usual plates but in such case it is preferred to pre-heat the kettle and plates to approximately 212 F. in order to avoid condensation thereon.

The atmosphere of solvent may be generated within the core as by the use of high frequency current, but under present conditions this is not economical.

It is also possible to employ a steam tunnel or direct jets of steam, saturated or superheated.

Where the solvent is other than water, it is usually desirable to use an enclosed system so that the solvent may be recovered.

The preferred adhesive. is a cellulose derivative able to withstand 212 F. without becoming insoluble. Sodium carboxy methyl cellulose is particularly suitable. The present invention is not necessarily limited to such cellulose derivatives but is applicable to other soluble adhesives.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, for some modifications will be obvious to those skilled in the art.

I claim:

1. The method of forming foundry cores which comprises treating foundry sand with a soluble adhesive, forming the so treated sand into a coherent core, and then exposing the outer portions of the core, prior to baking, to an atmosphere containing solvent in proportion and at a temperature to condense upon the adhesive upon the sand, and continuing the exposure until the flowability of the adhesive in the exposed portions of the core has substantially increased.

2. The method as set forth in claim 1, in which the adhesive is water soluble and the atmosphere is one consisting essentially of steam.

3. The method as set forth in claim 1, in which the adhesive comprises a cellulose derivative.

4. The method as set forth in claim 1, in which the adhesive comprises a salt of carboxy methyl cellulose.

5. The method as set forth in claim 1 in which the adhesive comprises a water soluble compound and the atmosphere consists substantially of steam.

6. The methods as set forth in claim 5 in which the atmosphere comprises steam under super-atmospheric pressure.

7. A method as set forth in claim 1 in which the cores are preheated to a non baking temperature substantially above atmospheric prior to exposure to the solvent atmosphere.

8. The method of forming foundry cores which comprises treating foundry sand with a soluble adhesive, forming the so treated sand into a coherent core, and then exposing the outer portions of the core, prior to baking to an atmosphere con- 3 4 taining solvent in proportion and at a temperature to condense upon the adhesive upon the UNITED STATES PATENTS sand, and continuing the exposure until the fiow- Number m Date ability of the adhesive in the exposed portions 7 Lane June 10 7 of the core has substantially increased, and then 5 9 355 Bean 25 1945 ba t Core- 2,398,047 Schmidt Apr. 9, 1946 9. The method as set forth in claim 8, in which 2,435,353 Whitehead 10, 1948 the adhesive is a salt of carboxy methyl cellulose.

- ROBERT 5. W013 OTHER REFERENCES 10 "New Binders Improve Core Performance," REFERENCES CITED by Gebharclt, article in The Iron Age, December The following references are of record in the 26, 1946- Pages file of this patent: