US3472306A - Process for forming an arcuate metal punch plate - Google Patents

Description

Oct. 14., 1969 A, c, ug- 1 ETAL 3,472,306

PROCESS FOR FORMING AN ARCUATE METAL PUNCH PLATE Filed March 23, 1966 2 Sheets-Sheet 1 INVENTORS Arthur C. Ausiin Norbert WfKuleio ATTORNEY Oct. 14., 1969 A. c. AUSTIN T PROCESS FOR FORMING AN ARCUATE METAL PUNCH PLATE Filed March 23, 1966 PROCEDURE 1 2 Sheets-Sheet 2 PROCEDURE 11 FORM FLAT, RIGID FEMALE MOLD IN SOFT, EASILY WORKED MATERIAL FORM FLAT, RIGID FEMALE MOLD IN SOFT, EASILY WORKED MATERIAL;

FORM FLAT, RIGID MALE PATTERN FROM FEMALE MOLD MALE PATTERN FROM FORM SECOND FLAT, RIGID FEMALE MOLD FR M MALE PATTERN FORM FLAT, RIGID FEMALE MOLD FORM FLAT, FLEXIBLE FEMALE MOLD FROM MALE PATTERN I COAT FLEXIBLE FE MALE MOLD WITH SUITABLE RELEASE AGENT I FILL RECESS IN FEMALE MOLD wITI-I FLEXIBLE MATERIAL I FORM FLAT, FLEXIBLE MALE PATTERN I I I I FLEXIBLE MALE PATTERN SECURED TO CURVED SUPPORTING BASE FORM ARCUATE REFRACTORY =FEMALE MOLD V CAST MOLTEN METAL INTO REFRACTORY MOLD TO FORM ARcuATE METAL OIE PLATE WEAR-RESISTANT COATING MAY BE APPLIED TO ARCUATE METAL DIE PLATE Fig.4

IM'ENTORS ArIhur C. AusIin Norbert W. KOIe'IO ATTORNEY United States Patent 3,472,306 PROCESS FOR FORMING AN ARCUATE METAL PUNCH PLATE Arthur C. Austin, Kenmore, and Norbert W. Kaleta,

Tonawanda, N.Y., assignors to National Gypsum Company, Buffalo, N.Y., a corporation of Delaware Filed Mar. 23, 1966, Ser. No. 536,819 Int. Cl. B22c 9/06, 1/22 US. Cl. 164-15 9 Claims ABSTRACT OF THE DISCLOSURE An arcuate punch plate, and the method of forming it, including starting with a mineral Wool acoustical tile with a plurality of fissures in the surface, forming there on a hardenable liquid eutectic alloy, forming thereform a plastic female mold, forming thereon a flexible, room temperature curing, silicone rubber male pattern which is subsequently bent to a uniform desired arc, forming therefrom an arcuate refractory female mold by a gelation of comminuted refractory molding materials, followed by firing, and subsequently forming an arcuate metal punch plate therefrom. The punch plate is coated on the wearing surface with an abrasion resistant material.

This invention relates to the manufacture of an arcuate metal punch. More particularly, it relates to the manufacture of a curved metal plate having integral projections of a predetermined pattern on one surface, the curved plate being adapted to be mounted on a rotata ble cylinder for use in punching, embossing or other surface treating operations.

In the production of acoustical products, such as fibrous acoustical tile or panels, the surface of the product is usually opened in order to expose the fibrous structure in the interior of the product, thereby greatly increasing the sound absorbing efficiency of the product. One method used in opening the surface of fibrous acoustical products is to punch holes or fissures into the tile or panels. In such an operation, a flat plate is usually pressed into the surface of the dry fibrous product, the fiat plate having in relief thereon the design of the openings desired to be formed in the finished product. In order to increase the speed and efiiciency of such a punching operation, it has been suggested heretofore to replace such plates with rotatable metal cylinders, the cylinders having on their outer surface projections of the design or pattern desired to be formed in the finished product. In this manner, the product, such as acoustical tile or other material to be punched or embossed, may be passed beneath the rotatable cylinder and be subjected to surface treatment in a continuous operation. However, methods used for forming the cylindrical punches available heretofore have a number of disadvantages which make the use of cylindrical metal punches unattractive in a commercial operation. For example, according to one method, individual irregularly shaped projections are fabricated by hand from steel or other suitable metals and welded individually to a metal cylinder in a desired pattern. Not only is the cost of producing cylindrical punches by this method prohibitive, but it is also extremely difficult to replace or duplicate the pattern in the event it is damaged. As a result, While the use of cylindrical punches is more efiicient than the previously used flat metal punches, the use of such cylindrical metal punches has been limited.

It is therefore an object of this invention to provide a method for making an arcuate metal punch plate.

Another object of the invention is to provide a method for making a curved metal plate having integral projec- 3,472,306 Patented Oct. 14, 1969 tions of a predetermined design on one surface, the curved plate being adapted to be mounted on a rotatable cylinder for use in punching, embossing, or other surface treating operations.

Another object of this invention is to provide a process for forming an arcuate punch plate suitable for use in forming openings in the surface of .fibrous acoustical products.

Another object is to provide a process for forming a curved plate having integral projections of a predetermined pattern on one surface thereof.

These and other objects and advantages of the invention will become apparent from the following description and drawings of an embodiment of the invention.

FIGURE 1 is a perspective view of the arcuate punch plate of the present invention showing: some of the integral projections on the curved surface of the plate.

FIGURE 2 is a perspective view of a cylindrical punch formed by mounting the arcuate punch plates of this invention on a rotatable cylinder.

FIGURE 3 is a cross-sectional view of the cylindrical punch taken through section lines 3-3 of FIGURE 2.

FIGURE 4 is a flow sheet of the process of the present invention illustrating two alternative procedures which may be used in forming the arcuate punch plate.

According to the present invention, there is provided an arcuate punch plate 1, formed of a curved metal plate 2 having a plurality of integral projections 3 of any desired shape and pattern on the convex surface 4 of the plate. These projections conform in size, shape and pattern to the design desired to be imparted to the material to be surface treated. The plate may be provided with a plurality of spaced holes 5 extending therethrough for securing the punch plate to a rotatable cylinder. As shown in FIGURES Q and 3, a number of the punch plates are mounted on a rotatable cylinder 6 so that the punch plates extend around the circumference of the cylinder, thereby forming a cylindrical punch. The size of the punch plate, including the integral projections, may be varied depending upon the type of surface treating operation to be performed, the size of the rotatable cylinder, the material to be treated, and the like. For punching fissures into dry fibrous acoustical tile or panels, it has been found that excellent results may be obtained by using a punch plate in which the plate 2 has a thickness of between about and and irregularly shaped elongate projections, extending between about A" and /2" above the surface of the: plate and about A" to 2" or more in length, are integrally formed on the convex surface of the curved plate, the projections being formed over the entire surface of the plate. The size and pattern of the projections are, of course, dependent on the fissured design desired to be imparted to the acoustical product. The size and degree of curvature of the punch plate are determined primarily by the size of the rotatable cylinder on which the punch plates are to be mounted. Thus, it is generally preferred that the length and degree of curvature of the punch plates be such that between two and six plates will extend around the circumference of the rotatable cylinder. The width of the punch plates may be varied as desired, de-

ending upon the width of the cylinder. The punch plate, including the projections, preferably is formed of steel or any of the conventional alloys suitable for withstanding the stress and wear resulting from a continuous surface treating operation. If desired, the arcuate punch plate may, before mounting on the cylindrical roll, be coated with a metal or other abrasion resistant material for increased wear resistance. According to a preferred embodiment, the punch plate, including the projections, is coated with a deposit consisting of a metal matrix,

such as nickel, cobalt, nickel-cobalt, copper, iron, brass, platinum, chromium, cadmium, silver, gold or zinc, the matrix containing from about 10% to 50% by volume of one or more finely divided, abrasion resistant materials, such as silicon car-bide, boron carbide, diamond, aluminum oxide, tungsten carbide, chromium carbide metallic powders, and the like. For example, a suitable wear resistant coating may be applied by coating the punch plate with a layer of 1000 mesh silicon carbide in a hard nickel matrix, the coating having a thickness of about 0.002 to 0.015 inch with the coating forming a continuous layer over the integral projections 3 as well as the curved plate 2.

As shown in FIGURES 2 and 3, the arcuate punch plates are mounted on and secured to a rotatable cylinder for use in a number of surface treating operations, such as embossing, punching, printing and the like. It has been found that the arcuate punch plates are especially well suited for use in punching fissures and/r holes in dry fibrous acoustical tile or panels, such as mineral wool or mineral wool-cellulose fiber products. Thus, the punch plates are mounted on the rotatable cylinder to form a cylindrical punch and the acoustical tile passed beneath the cylinder. As the tile pass beneath the cylinder, the projections on the surface of the curved plate are pressed into the surface of the dry fibrous tile, pushing a portion of the surface of the tile into the tile, thereby forming sound-absorbing openings in the product. These openings correspond in design and pattern to the projections on the die plate and contribute to the attractive and decorative appearance of the acoustical tile in addition to increasing its sound absorption. It is to be understood, however, that the arcuate punch plates of this invention may be used for other surface treating operations, such as, for example, printing lates, for embossing plastic film or thin gauge metal, punching designs into thin gauge metal, and the like.

The process of the present invention, according to which the arcuate punch plates are formed, is set forth in FIGURE 4 and generally includes the steps of forming a flat, flexible male pattern having projections conforming in size, shape, and pattern to the design desired on the punch plate and which is to be imparted to the material to be surface treated. This flat male pattern is formed of a material which is flexible and can be bent into an are without cracking or rupture of the pattern or appreciable distortion of the design. The procedures which may be used to form this flat, flexible male pattern will be described in more detail hereinbelow. The flat male pattern is then placed in a suitable jig and bent into an arc of a desired curvature. While the flexible male pattern is held in this position, it is covered with a slurry of a refractory casting material. When the refractory casting material has set, the male pattern is stripped, thereby providing a curved refractory female mold which is subsequently treated to burn off volatiles in the binder to remove moisture. After curing, the refractory female mold is placed in a core box and molten metal poured into the cavity to form the arcuate punch plate. Upon cooling, the metal punch plate is removed and may then be plated for additional wear resistance, if desired. In this manner, there is produced a curved punch plate having integral projections on the surface thereof, the plate providing an accurate reproduction of the desired design or pattern.

Two alternative procedures for forming the arcuate punch plate are shown in FIGURE 4, with the process steps designated Procedure I generally being preferred. It is to be understood, however, that the formation of the arcuate punch plate is not limited to the procedures set forth in the flow sheet, as other equivalent procedures may be used.

Referring now in more detail to the preferred process of the present invention, as illustrated in Procedure 1 in FIGURE 4, a flat, rigid female mold, having recesses conforming in size, shape, and pattern to the projections to be provided on the finished arcuate punch plate, is first constructed. This female mold is formed by cutting, pressing, routing, or otherwise milling out recesses, forming the desired pattern, in a relatively soft, easily worked material, such as, for example, balsa wood or other soft wood, insulation board or sheathing, mineral Wool or cellulose fiber acoustical tile or panels, plaster, foamed synthetic resins, soft metal, and the like. Preferably, this first female mold is made by routing out the desired pattern to form recesses having a depth of between about 0.01 to about 0.5 inch in a dry, fibrous, mineral-wool acoustical tile. The recesses may, of course, have a greater or lesser depth depending on the material used to form the mold, the surface treating operation for which the punch plate is to be used, the material to be surface treated, and the like. Mineral wool acoustical tile, generally containing about 60% to of mineral wool fibers in a starch binder, with or without additional cellulose fibers, has been found to provide the best combination of integrity, softness and workability for use in forming the flat, rigid female mold. Also, in some instances, a material may occur naturally or be formed by casting or similar techniques and have on its surface a pattern or design desired to be reproduced. Such material may also be used as the female mold.

After the female mold has been formed and the debris removed from the mold, a rigid male pattern is reproduced from this first female mold, the male pattern having a flat base plate and integral projections on one surface thereof, the projections conforming in size, shape, and location to the recesses formed in the female mold. Thus, a casting box is constructed around the female mold to form a mold cavity above the surface of the female mold having the recesses formed therein, and the mold cavity filled with a hardenable liquid casting material which is capable of hardening to provide a permanent rigid male pattern. Thus, the hardenable liquid casting material completely fills the recesses in the female mold and forms a base portion of substantially uniform caliper over the surface of the female mold. Preferably, a low melting or fusible alloy having a melting point of below about 200 F. is liquefied and poured into the mold cavity to completely fill the cavity. Suitable low melting alloys which may be used to form this pattern are Woods metal, containing about 50% Bi, 24% Pb, 14% Sn and 12% Cd; Woods alloy, containing about 50% Bi, 25% Pb, 12.5% Sn and 12.5% Cd; Lipowitzs metal, containing about 50% Bi, 27% Pb, 13% Sn and 10% Cd; Cerrobend alloy, containing about 50% Bi, 26.7% Pb, 13.3% Sn and 10% Cd; Cerrolow alloy, which is bismuth alloys containing indium; Cerrosafe alloy, containing about 45% Bi, 38% Pb, 11% Sn and 9% Cd; and the like. Such low melting alloys are preferred in order to avoid the necessity of using heat resistant materials for construction of the first female mold. If this first female mold is formed of a relatively non-porous material, resins, such as epoxy resins, phenolic resins and the like, may be used to form this male pattern. G nerally, it is preferred to use Cerrobend alloy, an eutectic alloy of bismuth, lead, tin and cadmium, in forming the male pattern. This alloy, which has a melting point of about 158 F., provides excellent pattern reproduction and, due to its low melting point, can be cast directly into female molds formed of materials which contain combined water and/or organic binders or other materials which would melt or burn above about 225 F. In forming the male pattern of this material, the alloy is heated to about 200-300 F. to liquefy it and the molten alloy poured into the mold cavity, completely filling the recesses in the female 'mold. Suflicient molten alloy is poured into the mold cavity to fill the recesses and to form a plate of substantially uniform caliper about Me" to A" or more in thickness above the surface of the female mold. Liquid resinous casting materials, such as,

for example, epoxy and phenolic resins, may also be used to form this rigid male pattern.

When the male pattern has become hardened, it is removed from the mold, the resulting male pattern being a flat plate having on one surface integral projections conforming in size, shape and pattern to the recesses in the first female mold.

After the male pattern has been formed, a second rigid, flat female mold is prepared from this male pattern. This second female mold may be formed of any resinous liquid casting material capable of producing accurate mold reproductions and which hardens, sets or cures within a relatively short period of time to form a hard, rigid mold. Generally, it is preferred to form this second female mold of a filled epoxy casting resin, for epoxy resins have a low degree of shrinkage and provide accurate pattern reproduction. Other suitable molding resins, such as acrylonitrile-butadiene-styrene terpolymers, phenolic resins, urea-formaldehyde resins, and the like, may also be used. In forming this second flat, rigid female mold, a dam is built around the periphery of the flat male plattern to provide a mold cavity, with the projections on the pattern extending upwardly into the mold cavity and the pattern invested with the resinous casting material. Thus, the liquid resinous casting material, such as a conventional filled epoxy casting resin, is charged into the mold cavity to a depth at least suflicient to cover all the projections extending from the surface of the male pattern.

When the casting material has hardened and/or cured, the rigid female mold, having recesses conforming in size, shape and location to the projections on the male pattern, is separated from the male pattern and used to form a flat, flexible male pattern. This male pattern consists of a flat base portion of substantially uniform caliper having integral projections on the surface thereof and is made of a material which is flexible and may be bent into an arc of the desired curvature without cracking or rupture of the base portion or appreciable distortion of the pattern. Preferably, a liquid room temperature vulcanizing silicone rubber, such as Silastic 521 or Silastic 588 obtained from the Dow Corning Corporation, and the like, is used to form this flexible male pattern. This material is preferred for it has the properties of resiliency, flexibility, resistance to mechanical fatigue, providing accurate reproduction of mold details, and may be readily stripped from the mold. Thus, in forming the flexible male pattern, a dam is built around the periphery of the second flat, rigid female mold to form a mold cavity and the liquid silicone rubber poured into the mold cavity. Suflicient room temperature vulcanizing silicone rubber is charged into" the mold cavity to completely fill the recesses in the female mold and provide a continuous, integral, flat base portion at the base of the projections. Since this flexible male pattern displaces the area that becomes the finished arcuate punch plate, the base portion and the projections of this flexible male pattern must be of the same size, shape and design as that desired in the completed punch plate. In addition, the caliper of the flexible male pattern must be substantially uniform to ensure that the finished punch plate has a uniform caliper, free from warping, distortion and variations in thickness. Other suitable flexible materials may, of course, be used in forming this male pattern. Thus, rubber or rubber-like materials which vulcanize, polymerize or cure at about room tempera ture and which remain flexible in that state and may be bent into an arc of up to about 180 without being subject to cracking or rupture or appreciable pattern distortion may also be used. The room temperature vulcanizing silicone rubber cures at room temperatures in about 24 to 48 hours. When it is no longer tacky, the flexible male pattern is stripped from the rigid female mold and is then suitable for use in the next step in the process, that is, forming an arcuate refractory female mold. In this rrfanner, the rigid female mold may be used as a master pattern for producing a large number of flexible male patterns. Thus, since the rigid female mold is not damaged or adversely affected when the flexible male pattern is produced from it, it may be used many times to produce male patterns of the desired design.

In forming the arcuate refractory female mold, the flexible male pattern is first mounted on and conformed to a curved supporting base. This supporting base has the same curvature as the rotatable cylinder on which the finished punch plate is to be mounted for operation. The flexible male pattern is held in position on the curved base by any suitable means, such as mechanical fasteners, vacuum, and the like. After mounting the flexible male pattern on the curved supporting base, a suitable frame is constructed around the male pattern, and a refractory molding material charged into the mold cavity thus formed, to invest the pattern, thereby providing a curved, refractory female mold having recesses conforming in size, shape and design to the projections on the flexible male pattern. Preferably, the refractory female mold is formed by the Well-known Shaw Casting Process, as disclosed in US. Patents 2,795,022; 2,811,760; and 2,931,081. Briefly, this Shaw process includes the steps of forming a free-flowing slurry of a comminuted refractory material, such as sillimanite, zircon, chamotte, and the like, a binder of a lower alkyl silicate, alcohol and water, and a gelling accelerator. This slurry is poured over the male pattern to a depth sufficient to at least cover all the projections, thereby investing the pattern. The refractory slurry gels Within a short period of time and then is immediately stripped from the male pattern. The gelled refractory mold is ignited to burn ofi volatiles and fired to remove all traces of moisture. The arcuate female mold thus formed has excellent dimensional stability and resistance to thermal shock and provides excellent pattern reproduction. The refractory female mold, which is in the form of an arc, is now ready for casting of the metal punch plate.

Thus, the refractory female mold is placed in a suitable core box and molten steel or other suitable metals or alloys capable of withstanding stress and wear in a continuous surface treating operation is poured into the cavity. The molten metal completely fills the recesses in the female mold and forms a smooth, curved base portion, about As to %1 thick, and of uniform caliper. When the metal has solidified and is removed from the female mold, there is produced a rigid metal plate having an arcuate cross-sectional shape and having on its surface integral projections of the desired design or pattern, the projections extending from about 0.01 to about 0.5 inch above the surface of the plate and conforming in shape, size and location to the recesses in the female mold. Holes may then be drilled through the metal plate for securing the plate to a rotatable cylinder. Thus, as shown in FIGURES 2 and 3, the punch plate is mounted on and secured to a rotatable cylinder and is ready for use in printing, punching, embossing or other surface treating operations.

If desired, the arcuate plate may be coated with an abrasionresistant material before mounting on the cylindrical roll. One preferred method for coating the plate with a wear-resistant material is disclosed in US. Patent 3,061,525.

The flat, flexible male pattern may, of course, be formed by steps other than described hereinabove. For example, the flexible male pattern may also be formed by the steps set forth in Procedure II in FIGURE 4. According to this procedure, the first rigid female mold is prepared in a soft, easily worked material and the flat, rigid male pattern formed from this first female pattern in the same manner as described in the steps of Procedure I. A flexible female mold is then prepared from this rigid male pattern, the flexible female mold being formed of room temperature vulcanizing silicone rubber. Thus, a

.suitable frame is built around the periphery of the male pattern and the male pattern invested 'with the silicone rubber. Thus the liquid, room temperature vulcanizing silicone rubber is poured into the mold cavity thus formed,

with the silicone rubber covering all of the projections on the surface of the male pattern. When the silicone rubber has cured, it is separated from the male pattern and used to form the flat, flexible male pattern.

Since both the flexible female mold thus formed and the flexible male pattern to be cast from it are both preferably made of silicone rubber which will vulcanize at room temperature, it is necessary to coat the female mold with a suitable release agent to enable the male silicone rubber pattern to be readily separated from the female mold. It was found that conventional release agents, such as waxes, wax-xylene emulsions, flurocarbon sprays, and the like, usually used as release agents for silicone rubber were not effective in preventing the silicone rubber male pattern from vulcanizing to the silicone rubber female mold, and, in addition, in some cases caused distortion of the silicone rubber parts. It was discovered, however, that these parts could be easily separated when the female mold was coated with a parting agent selected from the group consisting of shellac and varnish. Thus, these materials are effective release agents for the silicone rubber. Any conventional shellac or varnish, including spray varnish, may be used as the release agent in this step. One preferred release agent was a spray varnish having the composition:

Percent Dehydrated castor oil alkyd resin 8.5 Acrylic resin 2.0 Aromatic thinner 4-4.5 Propellant (Freon 12) 45.0

and available commercially under the designation Fiesta Spray Varnish. In order to be effective, the shellac or varnish release agent must be coated relatively uniformly over the entire surface area, including the recesses, of the female mold.

In order to obtain accurate pattern reproduction, it is essential that the liquid silicone rubber used to form the flexible male pattern completely fills the recesses formed in the flexible female mold. This is frequently diflicult when the female mold also is formed of silicone rubber, with the result that when the recesses are irregularly shaped or relatively deep, the liquid silicone rubber does not completely fill the recesses. It has been found that accurate pattern reproduction may be obtained by forming small openings from the bottom of each recess through the back of the flexible female mold and then pouring a skim coat of the silicone rubber over the female mold while it is positioned on a vacuum box. Thus, the vacuum draws the liquid silicone rubber down into the recesses so that the rubber completely fills the recesses. The female mold, with the skim coat on it, is then removed from the vacuum box and the remainder of the silicone rubber charged into the mold cavity to form the base portion of the flexbile male pattern, this base portion having a substantially uniform thickness. The silicone rubber forming the base portion of the flexible male pattern readily vulcanizes to the silicone rubber already filling the recesses to provide, upon curing, an integral male pattern. Alternatively, the recesses may be filled by injecting the silicone rubber individually into the recesses by any suitable means and then casting the remainder of the rubber over the female mold. When the rubber is cured, the male pattern is readily separated from the female mold and the arcuate metal punch plate prepared from the flexible male pattern according to the procedure described hereinabove.

In some instances, a material may occur naturally or be formed by casting or similar techniques and have on its surface a pattern or design desired to be reproduced for use in a surface treating operation. If such material is relatively nonporous and is not adversely affected by contact with liquid, room temperature vulcanizing silicone rubber, the flexible male pattern may be obtained by casting the rubber directly onto such material. Alternatively, the hardenable liquid casting material, such as,

for example, the Cerrobend alloy, could be cast directly on such naturally occurring material to provide a rigid pattern, and the flexible male pattern formed from this rigid pattern in the manner described hereinabove.

It will be understood that various changes in the de tails, materials, steps and arrangements which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art, within the principle and scope of the invention as set forth in the appended claims.

We claim:

1. A process for forming an arcuate metal punch plate having integral projections of a predetermined pattern on the surface thereof, said punch plate being suitable for mounting on a rotatable cylinder, for use in a surface treating operation, which process comprises forming a flexible male pattern consisting of a flat base portion of substantially uniform caliper and integral projections on the surface of said flat base portion and formed of rubber-like materials by a process of vulcanization, polymerization or curing at about room temperature, said integral projections conforming in size, shape and design to the design to be imparted in the surface treating operation, forming an arcuate refractory female mold from said flexible male pattern by investing the pattern with a refractory molding material while said male pattern is bent into an arc of a desired curvature to provide an arcuate refractory female mold hav ing recesses conforming in size, shape and design to the projections on the flexible male pattern, removing said flexible male pattern from said arcuate refractory female mold, forming the arcuate metal punch plate by filling the arcuate female mold with molten metal so that the molten metal completely fills the recesses in said female mold and forms a base plate of substantially uniform caliper on the surface of the female mold, and removing said metal punch plate from said female mold upon solidification of the molten metal, whereby there is provided an arcuate metal punch plate having on its surface integral projections conforming in size, shape and design to the recesses in said female mold.

2. The process as defined in claim 1 in which the flexible male pattern is formed of cured, room temperature vulcanizing silicone rubber, wherein the step of forming said refractory female mold being formed from said silicone rubber male pattern is accomplished by conforming and securing said male pattern to an arcuate supporting base having the same curvature as the curvature of the rotatable cylinder on which the arcuate punch plate is to be mounted, investing the male pattern with a refractory slurry comprising comminuted refractory material, a binder, and a gelling accelerator, and firing said refractory mold after gelation of said refractory slurry, and wherein the step of filling the arcuate female mold includes casting molten steel into said arcuate refractory female mold to completely fill the recesses in said female mold and provide a smooth curved base portion having a uniform thickness of between about A; and A 3. The process as defined in claim 1 in which'said flexible male pattern is formed by forming a first flat, rigid female mold having recesses conforming in size, shape and design to the design to be imparted in the surface treating operation by milling out said recesses forming the desired pattern in a relatively soft, easily worked material, forming a flat, rigid male pattern having integral projections conforming in size, shape and design to the recesses formed in said rigid female mold by filling said female mold with a hardenable liquid casting material, so that said material completely fills the recesses in said female mold and forms a base portion of substantially uniform caliper over the surface of the female mold, separating said flat male pattern from said rigid female mold upon hardening of the casting material, forming a second flat, rigid female mold from said male pattern by investing said male pattern with a resinous, hardenable liquid casting material, said second fiat female mold having recesses conforming in size, shape and design to the projections on said flat, rigid male pattern, separating said flat, rigid female mold from said male pattern upon hardening of said resinous casting material, forming said flexible male pattern from said second rigid female mold by filling said female mold with a liquid casting material which upon hardening remains flexible and may be bent into an arc of up to about 180 without being subject to cracking, rupture or pattern distortion, said casting material completely filling the recesses in said female mold and extending over the surface of the female mold in a substantially uniform thickness, thereby providing, upon hardening of said casting material, a flat, flexible male pattern having a base portion of substantially uniform caliper and integral projections on the s-urface of said base portion, said projections conforming in size, shape and design to the recesses in said second rigid female mold and removing said flexible male pattern from said second rigid female mold.

4. The process as defined in claim 3 in which the said first rigid female mold consists of a mineral wool acoustical tile in which the desired pattern is formed by routing out the recesses in said mold, and wherein the step of forming said flat, rigid male pattern is accomplished by casting a molten eutectic alloy of bismuth, lead, tin and cadmium having a melting point of below about 180 F. into said first rigid female mold, and wherein the step of forming said second flat, rigid female mold is accomplished by investing said rigid male pattern with a filling epoxy casting resin.

5. The processes as defined in claim 1 in which said flexible male pattern is formed by forming a flat, rigid female mold having recesses conforming in size, shape and design to the design to be imparted in a surface treating operation by milling out said recesses, forming the desired pattern in a relatively soft, easily worked material, forming a flat, rigid male pattern having integral projections conforming in size, shape and design to the recesses formed in said rigid female mold by filling said female mold with a hardenable liquid casting material so that said material completely fills the recesses in said female mold and forms a base portion of substantially uniform caliper over the surface of the female mold, separating the flat male pattern from said rigid female mold upon hardening of the casting material, forming a flexible female mold from said rigid male pattern by investing said pattern with liquid, room temperature vulcanizing silicone rubber, said flexible female mold having recesses conforming in size, shape and design to the projections on said flat, rigid male pattern, separating said flexible female mold from said rigid male pattern, coating the surface of said flexible female mold with a release agent capable of preventing liquid, room temperature vulcanizing silicone rubber from vulcanizing to cured liquid, room temperature vulcanizing silicone rubber, completely filling the recesses in said flexible female mold, pouring additional liquid, room temperature vulcanizing silicone rubber over the female mold to form a base portion of substantially uniform thickness which is vulcanized to the silicone rubber filling i the recesses in the female mold, thereby providing, upon curing of the silicone rubber, a flat, flexible male pattern having a base portion of substantially uniform caliper and integral projections on the surface of said base portion, said projections conforming in size, shape and design to the recess in said flexible female mold and removing said flexible male pattern from said flexible female mold.

6. The process as defined in claim 5 in which the said flat, rigid female mold consists of a mineral wool acoustical tile in which the desired pattern is routed out to form the recesses in said mold, and wherein the step of forming the said flat, rigid male pattern is accomplished by casting a molten eutectic alloy of bis- ..muth, lead, tin and cadmium having a melting point of below about 180 F. into said female mold.

7. The process as defined in claim 1 inwhich the step of forming said flexible male pattern is accomplished by casting liquid, room temperature vulcanizing silicone rubber over a relatively non-porous material having on its surface a design conforming to that desired to be impaired in the surface treating operation.

8. The processes as defined in claim 5 in which said flat flexible male pattern is formed of a liquid, room temperature vulcanizing silicone rubber which upon hardening remains flexible and may be bent into an arc of up to about 180 without being subject to cracking, rupture or pattern distortion.

References Cited UNITED STATES PATENTS 1,022,067 4/1912 Dow 164-2 2,181,452 11/1939 Ford 264-227 2,517,701 8/1950 Oettinger 264-220 3,061,525 10/1962 Grazen 204-9 3,065,511 11/1962 Leitzel 164-45 3,277,541 10/1966 Wilton et al.

3,379,813 4/1968 Austin 264-227 I. SPENCER OVERHOLSER, Primary Examiner R. D. BALDWIN, Assistant Examiner US. Cl. X.R.

gg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION October 14, 1969 Patent No. 306 Dated Invent0r(s) Arthur C. Austin and Norbert W. Kaleta It is certified .that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 54 "flexbile" should be --flexible--.

Column 10, line 10 "recess" should be -recesses--; line 26 "impaired" should be -imparted--; line 38 "eulectic" should be --eutectic--.

SlfiNED AND SEALED JAN 6 4970 (SEAL) Attest:

Edward WILLIAM E. sonuyLBR, .m. Attestingmfiom' commissioner of Patents

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