Trw Limited

Thomas S Piwonka

William S Blazek

James D Jackson

Philip N Atanmo

Michael Cybulsky

Virgil R Brittain

To cast an article, a mold is lowered into a body of molten metal with an open end of the mold facing downwardly so that the molten metal fills a mold cavity. The mold is then withdrawn form the body of molten metal. As the mold is withdrawn, the molten metal in the mold cavity is solidified. During withdrawal of the mold from the body of molten metal, the level of the upper surface of the body of molten metal is maintained substantially constant. The economical production of castings is promoted by simultaneously lowering a plurality of molds into the molten metal and withdrawing them from the molten metal to simultaneously form a plurality of castings. A strengthening agent may be added to the molten metal by dispensing the strengthening agent to form a dispersoid a short distance beneath the surface of the molten metal as the mold is withdrawn from the molten metal.

Controlled solidification, method of distributing strengthening

A plurality of mold wall segments are positioned in a circular array in an adjustable fixture to form a mold assembly. The fixture includes a base with a plurality of upstanding pin members. Two of the pin members engage the bottom portion of each mold wall segment. Each pin member is eccentrically mounted on a disc. By rotating the discs relative to their base, the mold wall segments may be moved inward or outward. This movement varies the diameter of the lower portion of the mold assembly. The pin members have threaded end portions which enable the pin members to be moved along their upstanding central axes. This movement varies the height of the lower portion of the mold assembly. In addition, the fixture includes a plurality of radially extending adjusting rods, each rod engages a radially inner side surface of a mold segment. By moving the rods radially inward or outward, each mold wall segment is caused to tilt or rotate about an axis extending through the upper end portions of the pin members which engage the bottom portions of that mold wall segment. This movement varies the diameter of the upper portion of the mold assembly. In one embodiment of the invention, the mold segments of inner and outer annular arrays of mold segments are independently movable relative to each other.

Method and apparatus for use in casting an article

A segmented mold assembly is utilized to cast a turbine engine component having a relatively heavy hub from which relatively light vanes project. The mold assembly includes a plurality of sections which are formed of a ceramic mold material and are interconnected at flange joints. The mold sections are advantageously formed by repetitively dipping patterns in a slurry of liquid ceramic mold material to form wet coatings on the patterns. These wet coatings are dried and separated from the patterns to form the mold sections. The mold sections which are used to cast the vanes retard the removal of heat from the vanes to provide time for the hub to solidify. This can be accomplished by using relatively thick walled mold sections to form the mold cavities in which vanes are cast and relatively thin walled mold sections to form the cavity in which the hub is cast. This could also be accomplished by forming the vane mold section of material having a relatively low rate of heat removal and the hub mold section of a material having a relatively high rate of heat removal.

Mold assembly and method of making the same

A segmented mold assembly is utilized to cast a turbine engine component having an annular inner wall and an annular outer wall which are interconnected by a plurality of struts or vanes. The mold assembly includes a plurality of sections which are formed of a ceramic mold material and are interconnected at flange joints. A pair of mold sections are advantageously formed simultaneously by repetitively dipping a single pattern in a slurry of liquid ceramic mold material to form a wet coating on the pattern. This wet coating of ceramic mold material is then dried. After a covering of the desired thickness has been built up by repetitively dipping and drying the coatings on the wax pattern, the wax pattern is destroyed. To facilitate separating the mold sections after destroying the wax pattern, at least some of the wet coatings are wiped away in an area between portions of the wet coatings which will eventually form the mold sections.

Growing community of inventors

Solon, OH, United States of America

Thomas S Piwonka