US2435858A - Core manufacture - Google Patents

Description

Feb. l0,I 1948. v l 4D. E. wHl'rEHEAD 2.435.858

" i conn muF-Ac'rxm Filed oct. 4, 1944 iNvENToR DONALU E h/H/reuefna WIM RNEYS hama m. 1o, ma

UNITED STATES PATENT i OFFICE Y Cona Manormmucm Donald E. Whitehead, New York. N. Y. Appliclll October 4, 1944, Suhl N0. 557,18?

Claims. (Cl. 22-194) My present invention relates to core manufac- "ture and comprises an improved method of forming cores which is superior to methods now in use in that it substantially reduces the time required in the production of cores and in that cores made thereby are superior to cores made by prior processes. The new method requires but slight change in standard core producing machinery for its practice. 4

In the usual foundry practice, core material comprising sand combined with water, oil or v.other wetting agent, is forced under air pressure into a core box to form the core, which is thereafter baked to evaporate the wetting agent and set the binder. This'baking of the moist core requires a substantial period of time, depending upon the size ofthe core, the particular wetting .agent employed, and the relative proportions of the wetting agent and the sand. The method of the present invention eliminates or substantially COl'e.

In accordance with the invention a thermosetting synthetic resin which is solid at room temperatures and melts at the temperature of steam or of superheated steam. as for example urea formaldehyde, is mixed with sand to form a dry core material. Live steam superheated under pressure is then applied to this dry mix to liquefy the resin and force the mix into the core box. The resin both in its fluid or semi-fluid state while subjected to the temperature of the steam and in its solid state upon resolidiflcation and setting in the core box after formation of the core serves as an adhesive to bind the particles of sand together in a ilrm c ore. The core' made as above described contains little if any water and hence may be used immediately or stored for future use without preliminary drying. During the molding operation the high heat of the molten metal liquefies or burns the resin, insuring ready flowing of the core material from the cored holes of the metal.

Standard core blowing machines may be readily modified for use in the practice of the invention as it is only necessary to use steam under pressure instead of air, toprovide suitable heat insu reduces this nal baking or heating of the formed lation about the parts of the machine head into which the steam is admitted and to include heating means in the path of the steam to the core material in order to maintain the temperature of In the attached drawing the single 'figure illustrates diagrammatically in cross-section the head of a conventional core blowing machine suitably equipped for practice of the invention. The machine as sh'own in the drawing includes the usual bin 2 for the core material, the-funnel l mounted for reciprocation from the position shown in the drawing to one beneath the outlet 8 from the bln 2 by means of the piston 8 and -rod Il under the opposing actions of a spring .i2

and pressure fluid admitted to the piston cylinder i4 through a pipe i6, the fixed casing section i8 provided lwith the communicating chambers 20 and 22 for admission of operating fluid to the funnel l and the core plate 24 secured to the funnel l for engagement with the top of the core box (not shown). In order to practice the invention on the conventional machine above briefly described, it is only necessary to provide suitable heat insulation 28' over the surface of the casing il and to provide suitable grid and strip Iheaters 28 within the chambers 20 and 22. A dry mix comprising, for example, 99 per cent. by weight of sand and I per cent. by weight of uncured urenI formaldehyde, preferably in comminuted or powdered form, is placed in the bin 2 and steam under pressure is admitted to theV chamber 2l. The steam after passage about the heaters 28 heats the core material in the funnel l suiilciently to cause the resin therein to become fluid and wet the sand, whereupon the plastic cores and results in a core in which the sand and resin are firmly bound together into a substantially homogeneous mass.

As heretofore indicated, any thermo-setting` resin that is solid at room temperature and becomes uid at the temperatures of steam or of superheated steam,say from 212 to 3U0 F., could be used in the process. For example, instead of urea formaldehyde, lthe melamine condensates or phenol formaldehyde could be mixed with sand to form the core material. The relative amount of resin in the core mixture is not critical but in general'the quantity of resin employed should be between l and 1% per cent. by weight of the total mixture.` -This range'may vary with the development oi' 4new resins. When less resin is employed. the core material does not become sumeietly strong when the resin soiidiiies. When anfexcessgot resin is used, the oost of the cores is materially incre '111e following is claimed: A

1. The method of forming coreslwhich coinprises mixing dry sandI with a comminuted thermo-setting resin to form a dry core material, and then applying steam under pressure to the core material to heat and liquei'y the resinV and to force the materialsinto a core box for formation of a core.

2. The method of forming cores which comprises` mixing sand and a comminut '.uncured thermo-setting resin together to i'orm a dry core material. heating thel material with live steam to render the resin fluid and finally forcing the material while hot into a core box by steam pressure whereby upon cooling and setting of the resin a rm core comprising sand bound togrther with cured resin is produced.

8. The method of forming cores-which com.-l prises making a dry mixture of sand and a thermo-setting resin with the resin comprising vis li'rom .one-half to one and one-half per cent. by weight of the total mixture. heating the mixture with live steam to render the resin i'iuid andz inally applying steam pressure to the heated mixture to force the mixture into a core box.

4. The method of forming' -eores which comprises mixing dry sand with eomminuted urea formaldehyde and then applying steam under pressure lto themixture to heat the mixture and render the resin i'iuid and to torce the mixture while heated into a core box for formation of a core. 5. The'method o t forming cores according to claim 4 wherein the urea formaldehyde comprises substantially one per cent. of the mixture.

DONALD E. WHITEHEAD.

msrEnENCEs CITED The following references are of record in the ille of this patent:

` UNITED STATES PATENTS Number Name Date 875,228 Witham Dec. 31, 1907 1,573,346 Kissam Feb. 18, 1926 1,777,9987 Dent Oct. 7, 1930 1,808,630 Brown June 2, 1931 1,831,555 Earl Nov. 10, 1931 1,866,301 Goodun .July 5, 1932 2,133,027 Honig Oct. 11, 1938 2,148,642 Ricard Feb. A28, 1939y FOREIGN PATENTS Number Country Date 118,781 f Australia Aug. 7, 1944 1 CTI-1ER REFERENCES Plastics in Engineering," 2nd edition, 1943, page 368, by Delmonte.

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