US1301965A

US1301965A - Mold.

Info

Publication number: US1301965A
Application number: US14071117A
Authority: US
Inventors: Charles Pack
Original assignee: DOEHLER DIE CASTING CO
Current assignee: DOEHLER DIE CASTING CO
Priority date: 1917-01-05
Filing date: 1917-01-05
Publication date: 1919-04-29
Anticipated expiration: 1936-04-29

Description

UNTTE STATES PATEN T @FFTCE S PACK, OF BROOKLYN, NEW YORK, ASSIGNOB TO DQEHLER DIE CASTING 'CQMTANY, OF BROOKLYN, NEW YORK, A CORPORATIQN OF NEW YUM.

Patented Apr, 2% 11%19.

OH H e z morn.

ll,3ll,9afii5, Specification of Letters Patent.

No Drawing. I

T 0 all whom it may concern:

Be it known that l, CHARLES PACK, a citizen of the United States, residing at the borough of Brooklyn, in the city of New York, county of Kings, and State of New York, have invented certain new and useful Improvements in Molds, of which the following is a specification. v

My invention relates to molds and more particularly to a type of mold made of p1as tic material adapted to be used in the casting of fluid m tals.

Molds of the character to which my invention relates are used in the production of intricate castings requiring little or no machining after being drawn from the mold and having sufliciently exact dimensions to permit them to'be incorporated in the diderent mechanisms without requiring material machine work thereon. Castings made in such molds possess all of the surface characteristi'cs of finished castings produced by what is known as the pressure die casting precise as to accuracy of dimensions and Heretofore in the production of molds for making such castings, it has been the practice to employ a mixture composed of the ordinary commercial plaster of Paris and owdered asbestos either with or without a "brous fusible binder for the purpose of securing greater tenacity in the body of the mold, or through the burning out of said fibrous material to form ducts to secure-a more rapid venting of the moldduring the pouringoperation' In making the molds the mixture is formed in suitable frames about patterns which may be made of metal or of low fusing material such as wax. l have found in producing molds of this char actor, there is a tendency of the plastic to imprison air in and about the surface of the pattern, particularly where sharp angles or depressions are presented in the pattern, thus necessitating the agitation of the plastic mass about the pattern to free any such imprisoned air and secure exactitude in the mold cavity. By experiment, l have discovered that the composition consisting of asbestos and plaster of Paris is not suitable for the production of molds of this character because the mixture cannot be satisfactorily handled except when it has thickened or become partially set by reason ofthe tendency of water in excess of that required inform- Application filed January 5, 1917. Serial No. 140,711.

ing a combination with the solids of the plastic material, to stratify and come to the top of the mold.

Furthermore, it have found it necessary to use a composition which may be poured into the frame in a fluid or viscous condition to permit the agitation thereof about the pattern in a manner to prevent the formation of bubbles or blow-holes upon'the surface of the cavity into which the metal is to be poured. With the asbestos and plaster of Paris composition, if the mass be sufliciently fluid to permit of its agitation as above referred to, the water will not. only accumulate at the top of the mold being formed in the manner above referred to, but the plaster of Paris will be precipitated, forming a stratum at the bottom of the mold, the asbestos constituent forming a stratum intermediate the plaster of Paris and the water which stratum is too weak to withstand the stresses incidental to the casting operation and which rapidly cracks in a manner to form fins upon the casting which fins make the casting diflicult to remove, and necessitate complicated machine refinishing of the castings. Furthermore, the stratum of plaster at the bottom of the mold is very much less porous than the stratum of asbestos and has a tendency to warp during the drying out of the mold prior to the casting operation. This condivtion also results in a mold, different portions With these conditions in mind, the object of my invention is to provide a mold of plastic material, the nature of the ingredt outs of which will be such as to have atlinity for each other and have absorptive properties which will avoid the stratification of excess water and of the solid ingredients entering into the composition.

A mold made in accordance with my invention, when the composition sets, will have substantial homogeneity throughout the entire. body thereof and the patterns may be drawn therefrom in a manner to leave smooth surfaces and sharp edges owing to the tenacity of the material of the mold which will be sufficiently great to prevent the breaking or chipping of the material of the mold as a result of theforce applied in removing the pattern; All parts of the mold will be suiiiciently porous to admit a free venting during the casting operation and the uniform porosity of all parts of the mold facilitates the elimination of the moisture in the mold by heat drying without likelihood of the warping of the mold due to the necessity for a prolonged subjection of the mold to heat, after any portion thereof has been thoroughly dried.

In the production of a mold made in accordance with my invention, the ingredients I employ are such as to permit the pouring of the plaster, while in a fluid or viscous state, about the pattern or patterns and within a frame, and the subsequent agitation of'the plastic material about the pattern or patterns in a manner to expelthe air and thus insure the smooth surfaces in the finished mold.

Furthermore, the composition of the mold makes possible the separation of enough of the moisture, either free or in combination with the solids contained in the mold by a uniform application of heat without likelihood of prematurely drying portions there of wlth a resultant warping or distortion of the portions of the molds which are the first to lose their moisture.

The invention consists primarily in a mold formed of plaster of Paris and a granular, porous, non-fibrous and absorptive material having an afiinity'for plaster of Paris; and in the novel steps and practlces in making said mold all as hereinafter set forth and described and more particularly pointed out in the claims hereto appended.

In the practice of my invention, ll form a mold consisting of pulverulent silicious sinter, also called kieselguhr, and cellite, mixed with ordinary commercial plaster of Paris and a suitable fluid such as ordinary water in such proportions as to secure the desired condition of the mixture. In practice, I have found the most satisfactory results are secured by using equal quantities by bulk of kieselguhr or cellite and plaster of Paris, uslng enough water to make the composition sufficiently fluid to readily flow. I do not desire, however, to limit myself to the exact proportlons stated, as the roportions may be varied. I have found that the kieselguhr or cellite has a stron afiinity for the plaster of Paris, and that t e solids entering Into the composition absorb and retain moisture far in excess of that which w ll enter into combination therewith.

In making the molds, I mix the plaster of Paris and kieselguhr or cellite while dry and add thereto the desired volume of Water, thoroughly mixing the composition. The mixture is then poured into a frame having placed therein. one, or a number of patte and by reason. of its fluidity, the composition flows freely about each of the patterns and throughout the frame. After being so poured, it will remain fluid for a suficient time to permit the molder to agitate the plastic about each pattern in a manner to free any imprisoned air and cause the fluid composition to closely hug the pattern. The composition is then allowed to set and there after the patternis drawn therefrom. l have found that in setting, a composition, such as l have described, does not stratify but solidifies intoa substantially homogeneous mass of substantially uniform density or porosity, and that the material is sum- 'ciently tenacious to permit the drawing of the pattern while the molding material is still wet without providing any substantial draft in the patterns to avoid a break down of the walls in or about the mold cavity. This tenacity in the mold is highly desirable where split molds are used, although a matter of secondary importance where fusible patterns are employed. The other characteristics of the mold are of equal importance, however, irrespective of the type of mold made.

After the patterns have been drawn, the mold is subjected to the action of heat for a sufficient time and at sufficiently high temperature to not only remove thefree moisture, or the moisture in suspension, in the mold but also that moisture which has combined with the solid ingredients of the mold, thus avoiding likelihood of injury to the mold when the molten metal is poured thereinto. llhe casting or castings are drawn from the mold by breaking the mold from about same after the have solidified.

The absorptive propertles of the mold, result in uniformity in the drying action throu b all parts of the mold, thus avoiding li elihood of the distortion or working of small parts of themold about the cavity therein.

While the outside ofthe mold has a tendency to dry first, nevertheless, the properties above referred to will gradually bring moisture to the surface. of the mold and this drying of the outside will not have a tendency to injure the molds in any way.

The non-conductive properties of a mold made in accordance with my invention prevent a too rapid chilling of the lighter portions of the castings while the uniform porosity affords ample venting of the mold without the necessity for providing special vent openings.

A completed mold made in accordance with my invention is substantially devoid of 3d 1161' of MP I at Letters Patent is:--'

- i aoi eaa 1 it to work the composition in making the molds in a manner to secure'exactitude in the formation and dimensions of the mold cavity by reason of the possibility of us the com position while in a'fluid or viscous'condition it without likelihood of Stratification of the difl'erent ingredients when the mold sets. Furthermore, Mesel hr or cellite' or an equivalent silicious smter, possesses superior qualities in that it is granular, porous, men 7 to fibrous, absorptive andhas an 'aity for the .plaster o characteristics it has a low specific gravity and is .hlciently bulky to be more-economical in use than jasbestos OP-Slmllfil material. v

p it is not my intention to t the invention-to theexact proportions herein reie to nor to the exact manner of '1: the Mesel and the plaster of Paris, it 1 H apparent hat such proportions and the depa a the spirit and scope at the invention. Hag ,descri the invention what i claim as new and'de'sire to 1.- At mold adapted for the production ot intricate rmetal cast formed oi laster of Paris and a granular, porous, non-. brouaabsorptive material ha i a an :tii m at ny for plaster of Paris. the mateal oil said mold. being devoid of moisture d moisture normally combined with the d el advantage. in the u f the v deity, 7

Paris. in addition to these se may be varied without thereof, the com 'ositionol the mold being a substantiall omogeneous mass of substantiallyuni orm density. 7 2. A mold adapted for the production of intricate finishedfrnetal castings deed of laster otllaris and cellite, in a substantially omogeneous mass oi substantially uniiorinv 3. A mold adapted for the productionot intri te that metal cast formedot.

plaster otiParis. and a silicious sinter, the

material'olt saidm'oldbein'g devoid of tree moisture and moisturefnormally combined to with the-solids thereol, in a substantially homogeneous mass of substantially uniform vdensi y.

t. A mold adapted tor the production oi intricate ed metal cast formed of to plaster of Paris and a 'silicious sinter in substantially equal quantities of bulk, thematerial of said mold being devoid of tree moisture and moisture normally combined with the solids thereot' in a substantially home to geneous'mass of substantially uniform densit A moldxadapted tor the production at intricate shed metal castings formed-oi laster of Paris and cellite in a substantially 7t omoneous mass, the material of said mold being substantiallyih'ee from tree moisture v and moisture normally combined was the solids thereot. 1

ln witness whereof-l1 hereunto my it a w ature in the presence of two subscribing wtnesses, t. it.

onus men w .Wnt. i'tGnr.

till

28th day of December, with K i