US3410942A - Casting method - Google Patents

Description

Nov. l2, 1968 H, Q, BAYER '3,410,942

CASTING METHOD Filed May 24, 1965 INVENTOR.

HELMUT O` BAYER RONALD E 'BARRY Ahorney United States Patent Office 3,410,942 Patented Nov. 12, 1968 3,410,942 CASTING METHOD `Helmut O. Bayer, Mulheim (Main), Germany, assignor ABSTRACT OF THE DISCLOSURE Disclosed herein is a method of removing a cellular t plastic pattern from a mold forming material by incorporating a solvent in either mold forming material or into the cold casting resin.

This invention relates to an improved method of cold casting of resins using cellular plastic patterns.

The recent development of the cavityless casting process using cellular plastic patterns has been used effectively in the casting of molten metals. This process contemplates the combustion or vaporization of a cellular plastic pattern embedded in a forming material by the heat of the molten casting charge. Since the pattern can be left in the mold, it is possible to cast articles of complicated shapes. This process is limited, however, to the casting of molten metals since the pattern is burned or vaporized by the heat from the molten casting charge.

It is also known that castings can be made from temperable resins. This is done by casting the resin into heated dies which consist of several expensive parts. The cast resin is hardened in the die by heat or catalyzed chemically, and then removed by taking the die apart. This process has not been found to be too practical where castings are to be made in small numbers because it requires a considerable amount of time to complete the casting.

One of the principal objects of the present invention is to provide an improved process for casting cold resins.

Another object of the present invention is to provide an improved process for casting resins wherein the pattern is left embedded in the forming material and is removed by a solvent dispersed in the forming material or in the resin to be cast.

Another object of the present invention is to provide a simplified process for cold casting of resins, utilizing vaporization patterns that can be left embedded in the forming material.

Still another object of the present invention is to provide an inexpensive process for forming cold castings of resins that can be used for molding complicated parts.

A further object of the present invention is to provide a process for casting resins that produces products having a finished or polished surface.

These objects are accomplished by forming a pattern of cellular plastic material and embedding the pattern in a gas permeable forming material. A solvent such as monomer resin can be dispersed throughout the forming material or can be added to the casting resin prior to pouring into the mold. The vapor from the solvent whether in the forming material or in the resin will penetrate the forming material and will dissolve the pattern, leaving a cavity in the forming material which can be lilled with the resin. The gaseous content of the cells in the pattern will penetrate the forming material and will not have any eiect on the resulting casting.

If the solvent is incorporated in the forming material of the pattern rather than in the casting resin, a casting resin of lhigh viscosity can be used. If the casting resin is provided with the solvent the casting resin material must be used shortly after mixing since it has little stability.

If a forming material is used which is only poorly wetted by the casting resin, eg., moist molding sand or the like, and by use of a relatively viscose casting resin, the pattern material does not need any special preparation. Otherwise, it is better to cover the pattern with a thin, extremely porous coat which might be composed of plaster, cement, bentonite, etc. These materials can be applied by either dipping or spraying. If necessary, binding, film forming materials, wetting agents as Well as porous materials like starch, wetting agents, resin dispersions, sawdust or corn particles could be added and also separating agents. A porous coating could also be used if it is punctured at its lower end.

In another modification of the present invention, the foamed pattern could be wrapped in plastic foil and then embedded in the forming material. The foil should be perforated and should consist of a material which would not be attacked by the casting resin. The vapors from the solvent will penetrate the pattern through the perforations and dissolve the pattern. A hole is provided in the foil to allow for the admission of the resin to be cast. Other objects and advantages will become more readily apparent from the following detailed description when read in connection with the accompanying drawings, in which:

FIG. l is a perspective View of a pattern with the coating partly broken away.

FIG. 2 is a side view in elevation showing the pattern embedded in a mold forming material.

Referring to the drawing, a pattern 10 of foamed polystyrene is shown covered with a very thin layer 12 of polyvinyl, acetate dispersion. The pattern 10 was then embedded in a forming material 14 such as sand, and rammed up in mold 16 to produce a rigid mold structure. A filling funnel or gate 18 was provided in the forming material to aid in filling the forming material with the casting resin.

A casting resin containing 38% by weight of monomer styrol can then be poured into the filling funnel 18 and as it comes into contact with the pattern, the pattern 10 will be dissolved and the gases in the cells of the pattern dispersed through the sand.

Other coating materials could also be used such as urea formaldehyde adhesive, gypsum, cement and similar coatings, or synthetic or metal foil. In each instance holes must be provided in order to allow the casting resin to enter the chamber and the gases created by the dissolution of the pattern to leave.

Where a particularly intricate metal casting is to be cast with molten metal it may be advisable to remove the pattern before pouring the molten casting charge. This could be done by using a solvent with the forming material. The solvent would dissolve the pattern and the molten metal could then be cast in the cavity.

-Although only a few modifications have been described, it should be apparent that various other changes and modifications can be made herein without departing from the scope of the appended claims.

What is claimed is:

1. A method of cold casting resins, comprising the steps of wholly embedding a cellular plastic form in a body 0f mold forming material, said form being shaped for exact reproduction as a casting,

forming a gate in said mold forming material,

mixing a cellular plastic solvent with cold casting resin,

and

pouring said cold casting resin containing said solvent into said gate, said form being dissolved by said solvent, whereby said cold resin lls the space in the `forming material created on dissolving the form.

2. -A method of cold casting resins, comprising the steps of -forrning a pattern of cellular plastic material which is shaped for exact reproduction as a casting,

coating said pattern with a layer of solid gas permeable material,

embedding said coated form in a body of forming material having a cellular plastic solvent dispersed throughout the forming material,

allowing sufficient time for the solvent to dissolve the pattern, and

pouring a cold casting resin into the cavity left by the pattern.

3. A 4method of cold casting resin comprising the steps of wholly embedding a cellular plastic pattern in a body of forming material, said pattern being shaped for exact reproduction as a resin casting, forming a gate in said forming material, pouring a cold `casting resin containing up to 50% by weight of a monomer styrol, I

allowing a sufficient time for the monomer styrol to dissolve the pattern, whereby said cold casting resin lls the space in the forming material left by the dissolved pattern.

4. A method of cold casting resin, comprising the steps of forming a pattern of cellular plastic material shaped for exact reproduction as a casting,

dispersing a cellular plastic solvent throughout a mold 4 forming material,

embedding said pattern in said forming material,

allowing sufficient time for the vapors from the solvent to dissolve the cellular plastic pattern and ll the space left by the pattern with a `cold casting resin. 5. A method of cold casting resin, comprising the steps forming a pattern of cellular plastic material shaped for exact reproduction as a casting,

covering said pattern with a plastic foil, y

perforating said foil to allow for'the ingress and egress of vapors from within the foil,

embedding the covered pattern informing material with a gate to allow for the lling of the pattern,

and pouring a casting resin containing a cellular plastic solvent into the gateat a rate suicient to allow for the dissolution of the pattern by the solvent and the filling of the space left by the pattern with the resin.

6. A method of casting, comprising the steps of forming a pattern of cellular plastic material shaped for exact reproduction as a casting, Y

mixing a pattern solvent in a forming material,

embedding said pattern in said forrn material,

allowing suicient time for the solvent to dissolve the pattern, and

casting a molten casting charge into the cavity left by the dissolved pattern.

References Cited UNITED STATES PATENTS 2,632,922 3/1953 Kish. 2,830,343 4/ 1958 Shroyer. 3,136,831 6/1964 Zinn 264-22 3,301,935 1/1967 Stoeckhert 264-321 JULIUS FROME, Primary Examiner.

J. R. THURLOW, Assistant Examiner.

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