US3022555A - Molds - Google Patents

Description

i l r United States Patent Ofiice 3,ZZ,555 Fee-tented Feb. 27, 1%52 3,022,555 MOLDS Noel Shaw, Northumberland, England, assignor to Shaw Process Development Corporation, Port Washington, N.Y., a corporation of New York No Drawing. Filed Sept. 11, 1957, Ser. No. 683,218 4 Claims. (Cl. 22-193) compacting, i.e., with the gelling being allowed to proceed with'a minimum of disturbance, followed by ignition thereof, are described in'the patent of Noel Shaw No. 2,795,022. The art i now familiar with the manufacture of such molds as are used in the Shaw process.

I have found that such molds, when made for the production of long slender castings, sometimes have a tendency to twist or warp. I discovered that in such extreme instances, the tendency of the mold to undergo twisting can be overcome by incorporating in the mass that undergoes gelling, fragments of a finished mold made in accordance with the Noel Shaw patent aforesaid. Con

-veniently, such fragments are made by crushing a mold iafter it has been used for making a casting.

For larger molds and cores where general reinforcing is required, slabs or suitably shaped inserts made by thegelation and firing of a slurry in accordance with the process of the Shaw Patent No. 2,795,022 are excellent. The crushings of a used mold aforesaid and the slabs or suitably shaped inserts will be referred to hereinafter as Shaw material. In the case of, for instance, a

rectangular mold measuring by 16'' by 4", a slab,

as aforesaid, approximately 18" by 16" by 1" may be made and fired (that is, ignited and, if desired, subjected to even higher temperatures in an oven or a furnace) and allowed to cool off. When the actual mold is being made, the slab may be pushed into the back of the mold 'box containing the slurry and held there until the slurry sets or gels. On subsequent handling of the mold piece and the firing thereof, the slab insert very effectively prevents distortion.

When large-size precision cores made made, an insert therefor can be readily made by'lining a core box with a layer of clay to a thickness of about A, filling it with the slurry aforesaid, allowing the slurry to gel, removing the gelled mass, and firing it.

In making such large-size precision cores, the thus prepared insert of Shaw material is floated centrally in the core box and then faced with the slurry aforesaid, followed by the gelling and ignition thereof. On final firing of the face, the insert efiectively prevents distortion even in the most complicated of core shapes. When a large number of such cores is required, two core boxes may be used, one of slightly smaller dimensions than the second, the smaller one being used in the manufacture of the insert in accordance with the technique of manufacturing Shaw material, and the larger one for the facing opera tion, as has just been mentioned.

In its fundamental aspects, this novel mode of manufacturing molds or cores, the objective of which is to avoid possibility of twisting, is accomplished by embodying prefired or used Shaw material Within the slurry as it gels. When crushings of prefired or used Shaw material? are employed, the procedure may be that of initially covering the pattern with a portion of the aforesaid slurry of comminuted refractory and binder; covering this initial deposition of the slurry with the crushings aforesaid and then filling the mold box with an additional portion of the slurry. The gelling accelerator employed is used in an amount which will allow adequate time for pouring the initial portion of the slurry; covering this initial portion with the crushings; and then covering the crushing with the balance of the slurry so that both portions of the slurry will undergo gelation at the same rate; and accordingly set at the same time;

Upon setting of the slurry, the two portions are found to be firmly and integrally bound with each other, and the mass constitutes an integral piece which incorporates the crushings. The mold form is then separated from the pattern, followed by ignition in accordance with the rocedure of the Shaw patent aforesaid.

The particles or crushings of a used Shaw mold may range in size from an average diameter of about A; inch to 1 inch. From the standpoint of easy Working, I prefar to use particles or crushings having an average size of about /4 inch in diameter. Where, however, the molds being manufactured are quite large, the particles or crush ings of the used Shaw mold may be of an even greater size than that just mentioned. I have found that the crushings of the used mold may be employed in an amount to constitute approximately 1/10 to 1/2 of the mass oi the mold. in terms of volume, the crushings may constitute from ten to fifty of the volume or the mold. At this time it seems to me that the preferred volume of the crushed pieces is approximately 25% of the volume of the mold itself.

The following is an illustrative example in accordance with thi invention:

Example 1 A pattern is placed in a mold box. Then a sluiry of comminuted refractory, binder and a suitable gelling accelerator, such as the slurry used in Shaw Patent No. 2,795,022 or Prange Patent No. 1,909,008, is poured over the pattern so as to cover the surface thereof with a layer having a depth of about /s to /2. Then crushings of a used mold made in accordance with Shaw Patent No. 2,795,022 having an average size of about are spread over the slurry. Then a further portion of the slurry used in making the initial layer that covers the pattern is poured into the mold box.

When the slurry gels, the integral mold form is separated from the pattern in accordance with the procedure of Shaw Patent No. 2,795,022 and immediately ignited, as described in the Shaw patent aforesaid.

It will'be apparent that the improved mold produced by the instant invention possesses the desirable porosity of the Shaw process mold. Any tendency of the mold form undergoing gellation, when formed solely from the gellation of a slurry aforesaid, to manifest twisting in consequence especially of the evolution of the volatiles from the interior thereof or for any other reasons, is overcome by the instant novel technique, since the crushings are completely stable dimensionally.

eter by 17 /2" long.

precision core.

Example 2 (a) A slurry of comminuted refractory, binder :and Ia suitable gelling accelerator, such as used in Example 1, is poured into a mold box measuring 18" by 16' by 1". When the slurry gels, the gelled mass is removed, placed on a support, and ignited as described in Shaw Patent No. 2,795,022.

(12) In making the mold from the particular pattern used, the pattern is placed in the mold box measuring 20 by 16" by 4". The slurry aforesaid is poured into this mold box, thereby covering the pattern; and the cooled slab of Shaw material prepared in (a) above is inserted therein. When the slurry gels, the whole mass is separated from the pattern; and the finished mold prepared in accordance with the technique that has already been described.

. Example 3 (a) A slurry of a comminuted refractory, binder and 'a'suitable gelling accelerator, such as used in Example 1, is poured into a core box to produce a core in diam- When the slurry gels, thegelled mass is removed,-placed on a support, and ignited as described in Shaw Patent No. 2,795,022' to produce a core reinforcing insert used in the next step '(b). V

(b) In making the ultimate core, a new core box is used, being of 1" in diameter by 1'8" long. 'The reinthe slurry gels, the whole mass is separated from the core box and the finished core prepared in accordance with the technique that has already been described.

Example 4 (a) A core box is prepared for making a large-size This core box is lined with clay to a thickness of A" and is then filled with slurry such as is used in Example 1. When the slurry gels, the gelled mass, which is approximately A! smaller all around than the core box, is removed, placed on a support and ignited as described in Shaw Patent No. 2,795,022, to provide a core reinforcing insert used in the next step (b).

V (b) In making the ultimate core, this core reinforcing insert produced in foregoing step (a) is positioned in the core box. The slurry aforesaid is then poured into the core box, thereby covering the reinforcing insert and filling out the rest of the core box. When the slurry gels, the whole mass is separated from the core box, and the finished core prepared in accordance with the technique that has already been described.

.(c) This entire procedure is applicable for the manufacture of molds of any type of pattern, as well as cores,

except that a mold box is used instead of a core box initially. i

lt wiiibe apparent that the improved molds produced in accordance with the instant invention possess the desirable porosity of the Shaw process mold. Any tendency of the mold form which undergoes gellation, whenformed solely from a single mass of slurry that gels, to manifest twisting in consequence especially of the evoltuion of the sional stability ofthe insert of the Shaw material, either as crushings or as a-single piece, aforesaid; and (b) the possible absorption by such inserted Shaw material of any excess liquid binder in the subsurface.

As has been mentioned, the instant improvement in Shaw process molds is advantageous in producing molds for making metal castings of long slender objects and also larger molds and cores where general reinforcing is desirable or required. In the production of molds or cores having large variations in thicknesses, the instant improvement provides, among other things, for relative equalization of the amount of volatiles evolving from difierent areas of cross-sectional dimensions.

The term Shaw'process as .described'in the aforesaid :Patent No. 2,795,022 briefly comprises: preparing a slurry comprising comminuted refractory materials and a binder of liquid lower alkyl silicate, water'and a gelling accelerator, pouring said slurry overa pattern, allowing the slurry to gel, separating the gelled mass of the slurry from the pattern, and thereafter igniting the surfaces of the gelled mass and allowing the dunes resulting from said ignition to burn until the fiammables are consumed thereby obtaining a mold of porous structure.

Thev term Shaw material, is the product resulting from the completion of the process just described. 7 The term Shaw material encompasses both the virgin material so produced (without investing a pattern with the slurry) or material reclaimed from a used mold.

It will be understood that the foregoing description of the invention and the examples set forth are merely illustrative of the principles thereof. Accordingly, the

appended claims are to be construed as defining the invention within the full spirit and scope thereof.

.1 claim:

1. In the method of manufacturing "a mold which comprises preparing a slurry comprising comminuted refractory materials and a binder of a liquid'lower alkyl silicate,

water and a gelling accelerator, pouring said-slurry over a pattern, allowing the slurry to gel, separating the gelled mass fromthe pattern, thereafter igniting the surfaces of the gelled mass and allowing the .flamesfrom said ignition to burn until the fiammables are consumed thereby to obtain amold having .a porous structure, the improvement which comprises incorporating porous material in the aforesaid slurry that undergoes .gellation, said porous material having been prepared by the steps comprising 7 forming a slurry of comminuted refractory materials and a binder of a liquidlower alkyl;silicate,'waterJand 'aigelling accelerator, allowing'the slurrytogel, ignitingihe surface of the gelled mass and allowing the .ilames from said ignition to burn until the .flammables' are consumed, said porous material having an average-diameter of at least about Ms inch.

2. Method 'in accordance with claim :1 wherein the porous material is incorporated in the .form of atslab.

3. Molds and cores as made by .themethod ofrclaim 1.

4. in the method of manufacturing a mold which comprises preparing a .slurry comprising comminuted irefractory materials and a binder of a'liquidlower alkyl .isilicate, water and a gelling accelerator, pouring said slurry over 'a pattern, allowing the slurry to gel, separating the gelled mass from the pattern, thereafter igniting the surfaces of the gelled mass and allowing the Thames from said ignition .to burn until the ifiammables are consumed thereby to obtain a mold having a porous structure, the improvement which comprises covering the pattern with a layer of said slurry, spreading fragments of porous material on said layer, said porous material having been prepared by the steps comprising forming 'a slurry of comminuted refractory materials and a binder of "a liquid lower alkyl silicate, water and agelling accelerator, allowing the slurry to gel, igniting the surface of the gelled mass and allowing the flames from said ignition to burn until the flammables are consumed, said porous material having an average diameter of at least about References Cited in the file of this patent UNITED STATES PATENTS Patterson et a1 June 27, 1905 Campbell June 15, 1937 Passelecq Jan. 30, 1945 6 2,434,780 Wiss et a1 I an. 20, 1948 2,441,695 Feagin May 18, 1948 2,732,600 Hanink et a1 Jan. 31, 1956 2,795,022 Shaw June 11, 1957 OTHER REFERENCES Wyman et 211.: Metal Industry, Apr. 7, 1944, pages 219-220.

Cady: Precision Investment Castings, pages 184, 185, 186, published in 1948 by Reinhold Publ. Corp., N.Y.

Claims (1)

1. IN THE METHOD OF MANUFACTURING A MOLD WHICH COMPRISES PREPARING A SLURRY COMPRISING COMMINUTED REFRACTORY MATERIALS AND A BINDER OF A LIQUID LOWER ALKYL SILICATE, WATER AND A GELLING ACCELERATOR, POURING SAID SLURRY OVER A PATTERN, ALLOWING THE SLURRY TO GEL, SEPARATING THE GELLED MASS FROM THE PATTERN, THEREAFTER IGINTING THE SURFACES OF THE GELLED MASS AND ALLOWING THE FLAMES FROM SAID IGNITION TO BURN UNTIL THE FLAMMABLES ARE CONSUMED THEREBY TO OBTAIN A MOLD HAVING A POROUS STRUCTURE, THE IMPROVEMENT WHICH COMPRISES INCORPORATING POROUS MATERIAL IN THE AFORESAID SLURRY THAT UNDERGOES GELLATION, SAID POROUS MATERIAL HAVING BEEN PREPARED BY THE STEPS COMPRISING FORMING A SLURRY OF COMMINUTED REFRACTORY MATRERIALS AND A BINDER OF A LIQUID LOWER ALKYL SILICATE, WATER AND A GELLING ACCELERATOR, ALLOWING THE SLURRY TO GEL, IGNITING THE SURFACE OF THE GELLED MASS AND ALLOWING THE FLAMES FROM SAID IGNITION TO BURN UNTIL THE FLAMMABLE ARE CONSUMED, SAID POROUS MATERIAL HAVING AN AVARAGE DIAMETER OF AT LEAST ABOUT 1/8 INCH.