US 2986797 A
Description (OCR text may contain errors)
June 6, 1961 l. M. AISENBERG 2,986,797
MOLD FoR PREPARATION oF ARTIFICIAL STONE TESI CYLINDERS Filed July 12, 1957 ADHERFNT HFS/IV COAT/IVG ON CASH/V6 SURF/i CF DINVENTOR. /rwzn /Z Awe/25e@ United States Patent O 2,986,797 MOLD FOR PREPARATION OF ARTIFICIAL STONE TEST CYLINDERS Irwm M. `Arsenberg, Washington, D.C., assignor to the United States of America as represented by the Secretary of the Army Filed July 12, 1957, Ser. No. 671,677 3 Claims. (Cl. 25-118) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon.
The present invention relates to separable molds and more particularly to a separable cylindrical mold for the casting of artificial stone test cylinders.
Test cylinders composed of artificial stone material such as gypsum `cement or oxychloride cement, have been used for some time to slush-cast acrylate films or sheets for testing purposes from acrylate (such as butyl acrylateacrylonitrile) copolymers. Ideally, these cylinders are hollow right circular cylinders having one base and a fairly uniform approximate thickness of less than onehalf inch. Prior to the instant invention these test cylinders were prepared by a cumbersome hand procedure, anld uniformity of result was the exception rather than the ru e.
The former method of casting test cylinders required a cylindrical plastic foam form having a smooth outer surface and an upright rod support which was inserted in a centrally located hole in the form to support it at a desired height and position. In the first step, a thin mixture of a gypsum cement, or other type of artificial stone and water, was applied to the surface of the plastic foam form and allowed to harden. In the second step, layers of gauze, soaked in a thick consistency of the artificial stone mixed with water, were wrapped around the base layer of stone so that it was completely reinforced. When the top layer of stone applied in this manner had set, the foam form was carefully removed from the surrounding cast artificial stone leaving the required stone test cylinder. This method demanded considerable alt and experience from the operator or craftsman in order to avoid cracking the inner layer of stone and to obtain a finished test cylinder product which would be sufficiently sturdy for casting acrylate films.
In later advancements in the art of casting artificial stone test cylinders, which eventually led to the full development of the instant invention, an attempt was made to use an aluminum mold casing surrounding the vinyl foam filler as a mold core. It was essential that the mold be as light as possible yet sufficiently strong and durable so that it would not be damaged or deformed by vibrating or jarring, as vibration was used during the pouring of the artificial stone slurry into the mold in order to assure that it would be uniformly distributed from the top to the base of the mold. The use of aluminum for the mold casing was practically mandatory from the standpoint of cost, strength, durability, weight, and machinability; however, it was soon found that the artificial stone rapidly pitted the aluminum and destroyed the efficacy of the mold casing after only a few castings. A further disadvantage encountered with the use of an aluminum mold casing was that after the artificial stone was cast and set, it adhered so strenuously to the aluminum casting surface that its removal in one piece was virtually impossible. The need for a suitable mold release agent to be used in combination with the aluminum mold casing was readily apparent. It was also apparent that an unusual type of mold release agent would have to be found, since it is of major importance that the outside surface of the stone test cylinder have adequate ICC to the mold surface Iby a proper process, the coatingsl would form an acceptable mold release agent.
A satisfactory process for applying an epoxy resin coat-V ing to the casting surface of the aluminum mold includes the following steps: v
l) Solvent cleaning of the mold surface; (2) Sand blasting of the clean surface; (3) Wiping or spraying a solution of epoxy resin on the casting surface of the mold;
(4) Drying the resin film in a force air oven for Onehalf hour at approximately 5 0 C.;
(5 Cooling to room temperature; (6) Repetition of steps 3 and 4; (7) Curing the two resin films thus applied at 100 C. for 20 minutes. p When vinyl resin is used as the coating, each coat is dried for one hour at 50 C. in the force air oven instead of for one-half hour and both coats are then cured separately for one-half hour at C. v The present invention, by creating a light weight aluj minum mold and a satisfactory mold release agentto be used in combination with it has carried the art of molding artificial stone test cylinders forward from a cumbersome, haphazard hand operation to an efficient, dependable and precise means and method for the production/of a quality product having uniform characteristics.
Accordingly, it is 'an object of the presentinvention to provide a means for casting artificial stone test cylinders which makes it possible for even an unskilled operator to prepare uniform test cylinders of high quality at a rapid rate of production. f
It is another object of the instant invention to provide a lightweightmachinable mold having strength, durability,` and low cost that can be used for casting stone cylinders.
Another object of this invention is to provide a metal mold for casting stone cylinders and a release agent which adheres tenaciously -to the casting surface of the mold but releases readily from the stone casting and does not adversely affect the porosity of the outside surface of the stone casting. I
Another object of the linvention is to provide a light, strong, and durable mold that will not be damaged or deformed by heavy vibration or jarring.
Another object o-f the-invention is to provide a mold for casting artificial stone test cylinders having a mold core which will insure that the cast cylinder has a smooth interior surface and which may be readily separated from the cylinder once it has set.
Another object of the invention is to provide a mold lfor casting artificial stone test cylinders having a core which will remain xed in place during heavy vibration of the mold and yet be readily separable from the cast cylinder once it has set. v
A further object of the invention is to provide a mold for casting stone cylinders which may be rapidly and accurately assembled prior to the molding operation and easily and quickly disassembled once the cylinder has set with a minimum danger of breakage or other damage/to the cylinder.
It is va still Ifurther object of this invention toprovide a means and method for casting artificial stone test cylinders which will eliminate the necessity for cumbersome yPatented June 6,y 1961 i hand operation and the need `for highly skilled and experienced operators in order to obtain a quality product having uniform characteristics.
Broadly described, the present invention comprises a receptacle type mold base, a mold core supported by the base and capable of producing a smooth uniform interior surface in the cast test cylinder but readily removable from the cylinder when it is set, and a tubular longitudinally separable mold casing adapted to be received and held by the mold base.
In operation, the tubular mold casing and mold core are assembled on the base, and a gypsum or other artificial stone slurry is poured into the space formed between the mold core and casing of the assembled mold. The mold is vibrated during pouring to insure a uniform distribution of the slurry from the top ot the base of the mold. After the mold is poured, the stone is allowed to set. When the stone cylinder has completely set and hardened, the mold is disassembled by removing the base, separating the mold casing, and withdrawing the mold core from the finished cylinder.
Further objects and a more thorough understanding of the invention may be obtained by referring to the following description and claims taken in conjunction with the accompanying drawings which disclose an illustrative embodiment of the construction forming the basis of the invention, and in which- FIG. 1 is a disassembled perspective View of the mold;
FIG. 2 is a central vertical section of the mold; and
FIG. 3 is a horizontal section taken along the line 33 of FIG. 2.
In accordance with the invention, -a mold is provided for casting stone cylinders having a means forming a base, a means forming a mold casing having an adherent film on its casting surface which makes it readily releasable from the cast stone cylinder, and means forming a semi-pliable, deformable mold core, the mold core having a smooth surface and readily releasable from the interior of the cast cylinder. The means forming the base is adapted to receive and support both the means forming the mold casing and the means forming the mold core.
In the'illustrated embodiment of the invention (FIG. 1), the means forming the base comprises a'cylindrical receptacle 6, the means forming the mold casing comprises a metal tube, preferably of aluminum, split into two separable halves 8 and 10, and the means yforming the mold core comprises a semi-pliable deformable cylinder 12. The cylindrical receptacle 6 has internal threads 14 and several equally spaced external recesses 16 in which a Spanner wrench or similar tool may be secured to aid in tightening or loosening the base or cylindrical receptacle 6 from the rest of the mold.
Thecylindrical semi-pliable deformable mold core 12 is made of vinyl plastic foam 18 and is completely encased by a smooth plasticized vinyl coating 20 which is integral with the foam interior. In the illustrated embodment, the mold core 12 is a right cylinder having a centrally located cylindrical well 22. The well 22 is con? centric with, and its principal axis coincides with, the axis of the mold core itself 12, and the well 22 extends from one base of the mold core approximately nine-tenths of the distance to the other base.
The complete mold includes a cylindrical aligning support 24 which in the present embodiment is approximately nine-tenths as long as the mold core 12. One end of the cylindrical aligning support 24 is a flat surface 26 perpendicular to the axis of the support, and the other end has a concentric cylindrical extension 28 which is equal in length to the thickness of the base receptacle 6 and which hasthreads30 by which it may be screwed into a centrally located threaded hole 32 in the base receptacle 6. The cylindrical aligning support 24 and the cylindrical wall A22 of the mold core '-12 have equal diameters. Thus, the cylindrical wall 22 readily receives the -aligning support '24 when that vsupport is in the operative positionex# tending perpendicularly from the flat portion 34 of the base receptacle 6 (FIG. 2). Since the internal dimensions of the well 22 are approximately equal to the external dimensions of the aligning support 24, a partial vacuum is caused if the mold core 12 is lifted from the support 24. This partial vacuum makes it necessary to exert force in order to separate the mold core 12 from the support 24, a factor which is important in maintaining the mold core 12 in place when the mold is subjected to vibration during pouring of the artifical stone slurry.
The cylindrical mold casing is a split mold formed of two separable halves 8 and 10. The two halves 8 and 10 are so constructed that when they are fitted together aligning pins 36 in half 10 fit into corresponding bores 3S in half 8. The mating of the pins 36 and the bores 38 insures that the two halves of the mold are in proper alignment so that the inside or casting surface 39, which is formed when the halves 8 and 10 are fitted together, constitutes a right circular cylinder. The lower end of the completed mold casing is provided with external threads 40 which coact with the internal threads 14 of the base receptacle 6 to positively lock the mold casing in the base receptacle. A series of bores 42, provided in mold casing half 10 and a series of threaded holes 43 in half 8, are adapted to receive screws 44 by means of which the two halves 8 and 10 of the mold casing can be positively fastened together. A cut 45 is provided in each half 8 and 10 of the mold casing so that when the two halves are joined together to form the complete casing a slot 46 is formed at the juncture of the two cuts 45. The slot 46 makes it possible for a wedge, like a screwdriver, to be used to eciently separate the two halves 8 and 10 of the mold casing after a cast has been made.
In operation, a gypsum slurry or a predetermined mixture of some other artificial stone and water is poured into the space formed between the mold core 12 and casings 8 and 10 of the assembled mold. The mold is subjected to vibration during the pouring process to assure that the slurry is uniformly distributed from the base to the top of the mold. After pouring, the artificial stone cylinder is allowed to harden and set, and when completely set the mold is taken apart. The base receptacle 6 is first removed with the aid of a spanner wrench and vice, if necessary. The screws 44 are next removed, and the halves 8 and 10 of the mold casing are separated from each other and from the completed casting. Finally, the mold core 12 is withdrawn leaving the completed artificial stone test cylinder. As an aid to removal of the completed casting and as protection for the casting surface 39 of the mold casing, the entire casting surface 39 is coated in the manner previously described with either an epoxy or vinyl resin as a combined mold release agent and protective coating for the aluminum casting surface 39. A fitted gasket 50 is provided for the flat portion `34 of the base receptacle 6; this gasket 50 which is made of plasticized polyvinyl chloride in the preferred embodiment, acts both as a seal between the mold casing and the base receptacle 6 and as a release agent or antistick surface between the cast cylinder and the flat portion 34 of the base receptacle 6.
As shown in the illustrated embodiment, the instant invention provides an efficient, light weight mold for artificial stone test cylinders which makes it possible for a relatively unskilled operator to rapidly produce a high quality stone cylinder having desired uniform characteristics. The semi-pliable deformable plastic mold core 12 forms an important part of this invention; its integral smooth plastic exterior 20 makes it possible to cast a stone cylinder having a smooth interior surface with desired porosity characteristics, but its foam interior 18 makes it readily pliable and deformable to permit its easy extraction from the completed stone cylinder once the cylindrical aligning support 24 is removed. The combination of a metallic mold casing with an adherent resin coating on its' casting surface yields a mold of desired strength, durability, weight, and machinability which may be readily released from the cast cylinder and which has its casting surface protected against pitting Which would otherwise be caused by chemical reaction with the articial stone slurry. The instant invention thus provides a long step forward in the art of casting artificial stone cylinders and fulfills along felt need for a precision type mold that would make possible the rapid production of high quality cylinders having uniform characteristics. This need had not been met by the molds of the prior art.
Having thus described my invention, what I claim as new and wish to secure by Letters Patent is:
1. A mold for casting frangible, artificial stone test cylinder specimens of substantially constant wall thickness, having a smooth cylindrical bore and terminating in an integral base portion having an outside diameter equal to the external diameter of the stone cylinder; said mold comprising an internally threaded cylindrical base receptacle, a cylindrical support member threadably and centrally secured to said base receptacle, a deformable and resilient inner core member having an inner central well therein to receive said support member, said central well having an internal diameter approximately equal to the external diameter of said central support, a pair of semicircular casing members of greater diameter than said inner core, bolt means for securing together said casing members, said casing members having a smooth internal casting surface and threadably received and supported by said cylindrical base to extend above and spaced from said inner core to dene a mold space between said core and casing members for forming test cylinders having a tubular portion terminating in a base portion, gasket sealing and mold release means between said base, core, and casing members, and a ilexible resin externally bonded to the surface of said inner core and to the wall surface of said central well and interrelated therewith to assure quick and non-damaging release of a specimen from said mold.
2. A mold for casting articial stone test cylinders comprising an internally threaded cylindrical base receptacle, a cylindrically shaped aligning and support member threadably received centrally in said base receptacle, a deformable and resilient cylindrical core of foraminous material having an inner central well to receive said aligning and support member, said central well having an internal diameter approximately equal to the external diameter of said central support, two semicircular casing members surrounding said core and uniformly spaced therein, each of said casing members having a corresponding plurality of external, integral circumferential rib portions, said rib portions having bolt-receiving recesses extending normal to the meeting edges of said semicircular casing members, bolt means received in said recesses for securing together said casing members, gasket sealing means between said base and casing members, and a continuous layer of liexible resinous material surrounding the external surface of the deformable core and bonded 'to the wall surfaces of said central well and cooperating with said deformable core to facilitate release of a stone test cylinder from said mold.
3. A mold for casting artificial stone test cylinders comprising a righ-t circular cylindrical internally threaded base, a core of foraminous, deformable, resilient material having an outer layer of smooth llexible resinous material, said core having a centrally located well substantially, but less than, the length of said inner core, said central wall having the wall surfaces thereof coated with a smooth, flexible, resinous material, a central aligning support substantially of the shape and dimensions of said well snugly received in said well and threadably secured centrally of said cylindrical base receptacle, a pair of semi-circular longitudinally separable outer mold casing members, said casing members being of a height greater than said core and having external threads at one end for engagement with the internally threaded base and having a plurality of Outer circumferential rib members, said rib members being aligned by integral recesses in a first one of said outer mold casing members and aligning integral dowel pins carried by a second one of said outer mold casing members for accurate assembly of said outer casting members, internally threaded recesses in a first one of said outer mold casing members to threadably receive a plurality of cooperating securing and aligning bolt means received in bores in a second one of said outer mold casing members aligned with the internally threaded recesses of said second outer mold casing member, said outer mold casing members being of greater diameter than and concentric With said core, the difference in diameters delining a space therebetween within which moldable material may be cast.
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