Metal founding – Process – Shaping a forming surface
Reexamination Certificate
2001-04-12
2002-11-12
Lin, Kuang Y. (Department: 1725)
Metal founding
Process
Shaping a forming surface
C164S132000, C164S369000
Reexamination Certificate
active
06478073
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally related to cores used in the casting process to provide cavities in a cast metallic object and, more particularly, to a composite core that comprises both soluble and insoluble portions.
2. Description of the Prior Art
Those skilled in the metal casting process, and particularly the high pressure die casting processes, are well aware that cavities in cast metal objects are often provided by using a soluble core that is inserted into a mold prior to causing a molten metal to flow into the mold. The soluble core, which is typically made of a salt compound, reserves space in the mold as the liquid metal flows around it and, after the molten metal has solidified, the soluble core can be dissolved to leave a cavity of the desired shape and size. The soluble cores are typically made of a salt compound and can be removed from the solidified metal casting by causing water or another liquid to flow in contact with the soluble core. This liquid dissolves the salt core, leaving a cavity having a size and internal surface configuration generally identical to the outer surface configuration of the salt core prior to the casting process.
U.S. Pat. No. 4,586,553, which issued to Allen et al on May 6, 1986, describes a process for pressure casting a piston with a crown insert and a cavity. The crown is placed in the mold before casting and the soluble salt core forms a cavity in the piston. The salt core is held by a crown insert to position the salt core in the mold to prevent the salt core from moving during the pressure casting procedure.
U.S. Pat. No. 5,803,151, which issued to Carden on Sep. 8, 1998, describes a soluble core method for manufacturing metal cast products. The improved soluble core for die casting metals or metal matrix composites is formed of a mixture of salt and up to about 20 weight % of ceramic material blended together to produce a homogeneous mixture and compacted under pressure to product a soluble core having little or no porosity. The ceramic material can be in the form of fibers, particulates, whiskers, and/or platelets, and has a melting temperature greater than that of the salt.
U.S. Pat. No. 3,963,818, which issued to Sakoda et al on Jun. 15, 1976, describes a water soluble core for pressure die casting and process for making the same. The process includes pre-drying a granular water soluble salt having grain size of less than about 1000 microns so that the moisture content thereof becomes less than 1%. It also comprises the step of molding under pressure the granular water soluble salt into a desired shape and volume at a pressure of between about 1.5 to 4 tons per square centimeter and, if necessary, sintering the molded salt at a temperature of between about 100°-300° C. The core for pressure die casting acts as a cavity former within a casting and substantially consists of a water soluble salt having a compressive strength of between about 800-1480 kg per square centimeter, a bending strength of between about 200-370 kg per square centimeter, and a density of between 2.05-2.12.
U.S. Pat. No. 4,252,175, which issued to Whipple on Feb. 24, 1981, describes a cylinder block having a cast in core unit and a process for manufacturing the same. A core unit for use in casting a cylinder block of an internal combustion engine which core unit comprises a preformed cylinder liner which includes a cylindrical sidewall defining an interior bore and having a port in the sidewall is disclosed. A first core unit is formed of a reducible material molded upon the preformed liner, which first core unit includes a first main core portion which partially occupies the bore and a port core portion which extends through the port. A second core unit is formed of the reducible material separately from the first core unit and is assembled upon the cylinder liner, which second core unit includes a second main core portion in the bore and in mating alignment with the first main core portion, thereby forming a composite core assemblage.
U.S. Pat. No. 4,361,181, which issued to Wischnack et al on Nov. 30, 1982, describes a casting core and process for the production thereof. A casting core for the creation of difficultly accessible cavities in castings of aluminum or of one of its alloys, is produced from a water soluble salt as base substance and burnt sugar as a binding agent, and a process for the production of such a casting core wherein the base substance is mixed with burnt sugar in aqueous or organic solution, pressed into molds, and baked at elevated temperature.
U.S. Pat. No. 4,743,481, which issued to Quinlan et al on May 10, 1988, describes a molding process for articles having an irregular shaped internal passage. The process for making an article having an irregular internal passage utilizes a hollow polymer preform. The preform is filled with a relatively incompressible filler material such as a powder or a fluid, which supports the preform when it is placed in a mold, such as an injection mold. The filler enables the preform to withstand high molding pressures and prevents deflection and movement of the internal passage within the preform. The shell, a layer of a polymer material is then molded about the preform. After the final article has been formed, consisting of the preform and the shell, the filler is removed for possible reuse.
U.S. Pat. No. 4,840,219, which issued to Foreman on Jun. 20, 1989, describes a mixture and method for preparing casting cores and cores prepared thereby. Casting cores are fabricated from a mixture comprising a molten salt having dispersed therein a particulate material which includes a first refractory material having a mesh size of 60-120 and a second refractory material having a mesh size of at least 200. The salts are preferably halides, carbonates, sulfates, sulfites, nitrates or nitrites of Group Ia and Group IIa metals and the refractory material may be selected so as to be non-reactive with the molten salt. Some preferred refractory materials include alumina and magnesium silicate.
U.S. Pat. No. 4,922,863, which issued to Adams on May 8, 1990, describes a cast engine cylinder having an internal passageway and method of making same. A cast cylinder for an internal combustion engine having an intake valve cavity located on one side of the piston bore, an intake bore for communication with a carburetor located on the other side of the piston bore, and an internal passageway cast there in communicating the intake bore and the intake valve cavity is disclosed. The internal passageway is curved and circumscribes a portion of the intake bore. A walled hollow tube having initially closed ends is embedded in the cast cylinder during casting as a permanently retained casting core. Subsequently, the ends of the embedded tube are machined open to communicate with the intake valve cavity and the intake bore, respectively, to define the internal passageway.
U.S. Pat. No. 4,904,423, which issued to Foreman et al on Feb. 27, 1990, describes a pressure molding process using salt cores and composition for making cores. The process for pressure molding an article around a hardened salt mold core made from a mixture of relatively low melting temperature salt and sand, wherein the core is removed from the finished article by immersion of the article containing the core into a molten bath mixture of the core material to thereby melt the core out of the article, is disclosed. The process also recovers the core material and thus replenishes the bath for use in making additional cores. The bath is originally constituted by melting a suitable quantity of a dry premix of the salt and sand.
U.S. Pat. No. 5,303,761, which issued to Flessner et al on Apr. 19, 1994, describes a die casting process using casting salt cores. A process of providing a disposable core for use in die casting processes is described. A salt material is molten and cast into a core of a desired configuration under exacting conditions. The fluidity of the molten salt is controlled enabling casting the s
Cleary Terrance M.
Grebe David E.
Hesterberg William G.
Potratz Mark P.
Brunswick Corporation
Lanyi William D.
Lin Kuang Y.
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