Patent Description:
Gas turbine engines are widely used in aircraft propulsion, electric power generation, shift propulsion and pumps. Many gas turbine engine components are cast components. One example casting process is known as investment casting. Investment casting can form metallic parts having relatively complex geometries, such as gas turbine engine parts requiring internal cooling passageways. Blades and vanes are examples of such parts.

The investment casting process typically utilizes a casting system that includes a mold having one or more mold cavities that define a shape generally corresponding to the part to be cast. A wax or ceramic pattern of the part is formed by molding wax or injecting ceramic material around a core assembly of the casting system. A shell is formed around the core assembly in a shelling process to assemble the casting system. The shell is fired to form the casting system including the shell having one or more part defining compartments that include the core assembly. Molten material is communicated into the casting system to cast the part. The shell and core assembly are removed once the molten material cools and solidifies.

Maintaining wall thicknesses to specification during the casting process can be difficult because of the relatively thin-walled constructions of parts that are cast to include relatively complex internal cooling passageways. The spacing between the core assembly and the surrounding shell is one area that must be controlled to maintain wall thicknesses during the casting process. <CIT> discloses a core assembly according to the preamble of claim <NUM>. <CIT>, <CIT> and <CIT> disclose other casting systems.

According to a first aspect, there is provided a core assembly for a casting system according to claim <NUM>.

In a non-limiting embodiment of the foregoing core assembly, the core is a refractory metal core (RMC).

In a further non-limiting embodiment of either of the foregoing core assemblies, the core is a ceramic core.

In a further non-limiting embodiment of any of the foregoing core assemblies, the chaplet portion is conical.

In a further non-limiting embodiment of any of the foregoing core assemblies, the chaplet portion includes a second stud portion and a skirt that is positioned between the stud portion and the second stud portion.

In a further non-limiting embodiment of any of the foregoing core assemblies, the skirt is conical or rounded.

In a further non-limiting embodiment of any of the foregoing core assemblies, at least one filleted cutout is formed in either the stud portion or the chaplet portion.

In a further non-limiting embodiment of any of the foregoing core assemblies, the stud portion includes at least one depth indicator.

In a further non-limiting embodiment of any of the foregoing core assemblies, the chaplet portion is a bent portion of the spacer.

In a further non-limiting embodiment of any of the foregoing core assemblies, the core is assembled to a second core and is spaced from the second core by a bumper or a second spacer.

In a further non-limiting embodiment of any of the foregoing core assemblies, the core is assembled to a second core or a shell and is spaced from the second core or the shell by a second spacer received in a recess of the second core.

In a further non-limiting embodiment of any of the foregoing core assemblies, the spacer and the second spacer are threadably attached together.

In a further non-limiting embodiment of any of the foregoing core assemblies, the spacer and the second spacer are riveted together.

According to a second aspect, there is provided a casting system according claim <NUM>.

The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

This disclosure relates to a casting system. The casting system includes a core assembly having a core that includes a body and at least one hole formed through the body. A spacer extends through the hole and includes a stud portion and a chaplet portion. The chaplet portion abuts a portion of the body that circumscribes the hole. One or more spacers may be used to control the spacing between the core and a surrounding shell of the casting system during a casting process. In another embodiment, a spacer assembly is employed to sandwich a core of a core assembly and to space the core from other casting articles of a casting system.

Alternative engines might include an augmenter section (not shown) among other systems or features.

It should be understood that various bearing systems <NUM> at various locations may alternatively or additionally be provided, and the location of the bearing systems <NUM> may be varied as appropriate to the application.

The inner shaft <NUM> and the outer shaft <NUM> are concentric and rotate via the bearing systems <NUM> about the engine central longitudinal axis A which is collinear with their longitudinal axes.

The gear system <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans and turboshafts.

The "Low corrected fan tip speed" as disclosed herein according to one non-limiting embodiment is less than about <NUM>,<NUM> ft/second (<NUM> meters/second).

Each of the compressor section <NUM> and the turbine section <NUM> may include alternating rows of rotor assemblies and vane assemblies (shown schematically). For example, the rotor assemblies can carry a plurality of rotating blades <NUM>, while each vane assembly can carry a plurality of vanes <NUM> that extend into the core flow path C. The blades <NUM> may either create or extract energy in the form of pressure from the core airflow as it is communicated along the core flow path C. The vanes <NUM> direct the core airflow to the blades <NUM> to either add or extract energy.

<FIG> illustrates a part <NUM> that can be cast in a casting process, such as an investment casting process. In one embodiment, the part <NUM> is a turbine vane. Although the part <NUM> is illustrated as a turbine vane, the various features of this disclosure are applicable to any cast part, including parts located elsewhere within a gas turbine engine, such as blades, blade outer air seals (BOAS), combustor panels, etc..

In one embodiment, the part <NUM> includes an inner platform <NUM>, an outer platform <NUM>, and an airfoil <NUM> that extends between the inner platform <NUM> and the outer platform <NUM>. The airfoil <NUM> includes a leading edge <NUM>, a trailing edge <NUM>, a pressure side <NUM> and a suction side <NUM>. The pressure side <NUM> and the suction side <NUM> generally meet at both the leading edge <NUM> and the trailing edge <NUM>. Although a single airfoil is depicted, other parts are also contemplated, including parts having multiple airfoils (i.e., vane doublets).

The part <NUM> can include internal cooling passages 74A, 74B that are separated by a rib <NUM>. The internal cooling passages 74A, 74B may include core formed cavities that exit the airfoil <NUM> at slots <NUM>. The internal cooling passages 74A, 74B and their respective core formed cavities define an internal circuitry <NUM> for cooling the part <NUM>. The internal cooling passages 74A, 74B and the internal circuitry <NUM> of the part <NUM> represent but one example of many potential cooling circuits. In other words, the part <NUM> could be cast to include various alternative cooling passages and internal circuitry configurations within the scope of this disclosure.

In operation, cooling fluid, such as bleed airflow from a compressor section of a gas turbine engine, is communicated through the internal cooling passages 74A, 74B and is expelled out of the slots <NUM> to cool the airfoil <NUM> from the hot combustion gases that are communicated across the airfoil <NUM> between the leading edge <NUM> and the trailing edge <NUM> on both the pressure side <NUM> and the suction side <NUM>. The cooling fluid may circulate through the internal circuitry <NUM> to cool the part <NUM>.

<FIG> illustrates a wax pattern <NUM> that can be used to manufacture the part <NUM> of <FIG>. The wax pattern <NUM> surrounds a core assembly <NUM> made up of one or more cores. In one non-limiting embodiment, the core assembly <NUM> includes multiple refractory metal cores (RMC's) <NUM> (i.e., a first core(s)) attached to a ceramic core <NUM> (i.e., a second core). This disclosure is not limited to RMCs and ceramic cores, however, and it should be understood that the core assembly <NUM> can be made up of cores of any size, shape, number and type. Once removed from the part <NUM> post-cast, such as via a leaching operation, the ceramic core <NUM> forms the internal cooling passages 74A, 74B of the part <NUM> and the RMC's <NUM> form the slots <NUM> and associated near-wall geometries of the internal circuitry <NUM> of the part <NUM> (see, e.g., <FIG>).

<FIG>, <FIG> and <FIG>, with continued reference to <FIG>, illustrate multiple features of the core assembly <NUM>. For example, <FIG> illustrates the core assembly <NUM> with the wax pattern <NUM> of <FIG> removed, <FIG> depicts volume A-A of <FIG>, and <FIG> depicts volume B-B of <FIG>.

The RMC's <NUM> interface with troughs <NUM> formed in the ceramic core <NUM>. The troughs <NUM> are receptacles for receiving the RMC's <NUM> to assemble the core assembly <NUM>. The length, depth, geometry and configuration of the troughs <NUM> can vary and can be cast or machined into the ceramic core <NUM>. The RMC's may include various holes <NUM> or other openings (formed through a body <NUM>) that define pedestals and other features of the internal circuitry <NUM> ultimately cast into the part <NUM> of <FIG>.

<FIG> illustrates a cross-sectional view of a casting system <NUM> that includes the core assembly <NUM> described above. The core assembly <NUM> of the casting system <NUM> is illustrated in this embodiment through plane P of <FIG>. The casting system <NUM> may include the core assembly <NUM> and a shell <NUM> that generally surrounds the core assembly <NUM>. The shell <NUM> may completely or partially surround the core assembly <NUM>.

In one embodiment, a spacer <NUM> (also shown in <FIG>) is received through a hole <NUM> formed in the RMC <NUM>. Although only a single spacer <NUM> is illustrated in <FIG>, it should be understood that the core assembly <NUM> may employ a multitude of such spacers or any combination of spacers. The spacer <NUM> spaces and properly positions the RMC <NUM> relative to the shell <NUM>. The spacer <NUM> may include a stud portion <NUM> and a chaplet portion <NUM>. In one non-limiting embodiment, the stud portion <NUM> extends through the hole <NUM> toward the ceramic core <NUM> of the core assembly <NUM>. The stud portion <NUM> may or may not contact the ceramic core <NUM>.

Once the spacer <NUM> is positioned within the hole <NUM>, the chaplet portion <NUM> may abut a surface <NUM> of the body <NUM> that generally circumscribes the hole <NUM> of the RMC <NUM>. The chaplet portion <NUM> may extend to and abut against the shell <NUM>. In one embodiment, a nose <NUM> of the chaplet portion <NUM> is in direct contact with the shell <NUM>.

A bumper <NUM> may be formed on the ceramic core <NUM>. The bumper <NUM> may be radially offset from the spacer <NUM> and extend in a direction toward the RMC <NUM>. The bumper <NUM> maintains the spacing between the ceramic core <NUM> and the RMC <NUM> and helps to keep the spacer <NUM> from falling out of the hole <NUM> during the casting process.

In an alternative embodiment, shown in <FIG>, another spacer <NUM>-<NUM> can be used in place of the bumper <NUM>. A recess <NUM> may be formed in a core <NUM>-<NUM>. The stud portion <NUM> of the spacer <NUM>-<NUM> may be inserted into the recess <NUM>. The chaplet portion <NUM> spaces a surface <NUM>, such as a surface of another core or a shell, from the core <NUM>-<NUM>.

<FIG> illustrates the spacer <NUM> described above in <FIG>. As described, the spacer <NUM> includes a stud portion <NUM> and a chaplet portion <NUM> that extends from the stud portion <NUM>. In one non-limiting embodiment, the chaplet portion <NUM> is conical. The spacer <NUM> is made of platinum.

<FIG> illustrates another exemplary casting system <NUM>. In this disclosure, like reference numbers designate like elements where appropriate and reference numerals with the addition of <NUM> or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding original elements.

In this embodiment, the casting system <NUM> may include a core assembly <NUM> that is at least partially surrounded by a shell <NUM>. The core assembly <NUM> may include a first core <NUM>. A surface <NUM> may be positioned adjacent to the first core <NUM> on an opposite side from the shell <NUM>. In one embodiment, the first core <NUM> is a ceramic core or a RMC. In another embodiment, the surface <NUM> is part of either the shell <NUM> or a second core, such as a ceramic core.

Spacers <NUM> may be positioned to extend through holes <NUM> of the first core <NUM> to control a positioning of the first core <NUM> relative to both the surface <NUM> and the shell <NUM>. In one embodiment, chaplet portions <NUM> of the spacers <NUM> are positioned to extend in opposing directions. In other words, a first chaplet portion <NUM>-<NUM> abuts a surface <NUM> of the shell <NUM> and a second chaplet portion <NUM>-<NUM> may abut the surface <NUM>. Such a configuration may be particularly suited for use with cores that do not include the bumpers <NUM> shown in <FIG>, or for use with trailing edge cores, or between two adjacent RMC's.

<FIG> illustrates another exemplary spacer <NUM>. In this embodiment, the spacer <NUM> includes a chaplet portion <NUM> that extends between a first stud portion <NUM>-A and a second stud portion <NUM>-B. The chaplet portion <NUM> may include a skirt <NUM>. In one non-limiting embodiment, the skirt <NUM> is round. However, other shapes are also contemplated (see, for example, <FIG>).

The first stud portion <NUM>-A may include a first diameter D1 and the second stud portion <NUM>-B may include a second diameter D2. In one embodiment, the second diameter D2 of the second stud portion <NUM>-B is larger than the first diameter D1 of the first stud portion <NUM>-A. The difference in the diameters D1, D2 helps ensure that the spacer <NUM> is properly positioned relative to the core assembly, such as by denoting to an assembler which stud portion is intended to abut against a shell of a casting system.

Referring now to <FIG>, the first stud portion <NUM>-A of the spacer <NUM> may extend through the hole <NUM> of a first core <NUM> and extend toward a second core <NUM>. The skirt <NUM> may abut a surface <NUM> of the first core <NUM>. The second stud portion <NUM>-B extends toward and may abut a shell <NUM>. The second core <NUM> may optionally include a bumper <NUM>.

Another non-limiting embodiment of a spacer <NUM> is illustrated in <FIG>. The spacer <NUM> includes a chaplet portion <NUM> that extends between a first stud portion <NUM>-A and a second stud portion <NUM>-B. The chaplet portion <NUM> may include a skirt <NUM>. In one non-limiting embodiment, the skirt <NUM> is conical. The sizes of the stud portions <NUM>-A, <NUM>-B may be tailored depending on the desired wall thickness of the part being cast.

<FIG> illustrates yet another spacer <NUM>. The spacer <NUM> includes a stud portion <NUM> and a chaplet portion <NUM>. The stud portion <NUM> may include one or more depth indicators <NUM>. The depth indicators <NUM> indicate to an assembler different lengths for achieving different wall thicknesses in a cast part.

The spacer <NUM> may additionally include one or more filleted cutouts <NUM>. The filleted cutouts <NUM> provide space for avoiding interference with the corners of a core that receives the spacer <NUM>. In one embodiment, the filleted cutouts <NUM> are formed in the stud portion <NUM> (see <FIG>). In another embodiment, the filleted cutouts <NUM> are formed in the chaplet portion <NUM> (See <FIG>).

<FIG> illustrates yet another exemplary spacer <NUM>. In this embodiment, the spacer <NUM> includes a stud portion <NUM> and a chaplet portion <NUM>. The chaplet portion <NUM> may be formed by bending an end of the spacer <NUM> to a position that is transverse to the stud portion <NUM>. For example, the spacer <NUM> may be made of a bendable platinum wire.

<FIG> schematically illustrates a casting method <NUM> that includes the use of a casting system that includes a core assembly. The exemplary method <NUM> may be utilized with respect to any of the casting systems, core assemblies and/or spacers described above.

First, at block <NUM>, a wax or glue is applied to a spacer or to a hole in a first core (e.g., a RMC or ceramic core). A core assembly that includes at least the first core may optionally be assembled prior to block <NUM>. For example, an RMC may be attached to a ceramic core.

At block <NUM>, the spacer is positioned within the hole of the first core. The spacer is positioned such that a chaplet portion abuts a surface of the first core which surrounds the hole. The core assembly, including the spacer, is inserted into a wax die at block <NUM> and then a wax pattern is injected around the core assembly at block <NUM>.

The shell is formed around the wax pattern at block <NUM> to construct the casting system. Once the shell has been formed, the wax pattern is burned or melted out leaving the core assembly and the spacers inside the shell. The spacers may contact the shell to space the first core therefrom. Finally, at block <NUM>, molten metal is poured into the casting system to cast a part. The spacers maintain the proper spacing between the shell and the core assembly (or between cores) during the casting process to maintain wall thicknesses in the cast part. The core assembly may be leached out, with the metal of the spacers being incorporated into the final part alloy.

<FIG> illustrate portions of another casting system <NUM>. The casting system <NUM> utilizes a spacer assembly <NUM> that includes a first spacer <NUM>-<NUM> and a second spacer <NUM>-<NUM>. The second spacer <NUM>-<NUM> is secured relative to the first spacer <NUM>-<NUM> (or vice versa) to sandwich a core <NUM> of the casting system <NUM>. The core <NUM> may be a RMC, a ceramic core or any other core. Although not shown, the core <NUM> may be positioned and/or assembled relative to other casting articles including but not limited to a shell or an additional core. The first spacer <NUM>-<NUM> and the second spacer <NUM>-<NUM> position and space the core <NUM> relative to adjacent casting articles.

The first spacer <NUM>-<NUM> is positioned at a first side <NUM> of the core <NUM> and the second spacer <NUM>-<NUM> is positioned at a second side <NUM> of the core <NUM>. Each spacer <NUM>-<NUM>, <NUM>-<NUM> is received within a hole <NUM> formed through a body <NUM> of the core <NUM>. The first spacer <NUM>-<NUM> and the second spacer <NUM>-<NUM> may be inserted into the hole <NUM> of the core <NUM> in any order. That is, either the first spacer <NUM>-<NUM> or the second spacer <NUM>-<NUM> may be inserted into the hole <NUM> before the other spacer is engaged thereto. The hole <NUM> could be any opening, including a slotted opening.

The first spacer <NUM>-<NUM> and the second spacer <NUM>-<NUM> may both include a stud portion <NUM> and a chaplet portion <NUM>. In one non-limiting embodiment, the second spacer <NUM>-<NUM> is engaged to the first spacer <NUM>-<NUM> by receiving the stud portion <NUM> of the first spacer <NUM>-<NUM> within a bore <NUM> that extends through the second spacer <NUM>-<NUM>. Of course, an opposite configuration is also contemplated in which the first spacer <NUM>-
<NUM> is equipped with a bore that receives the stud portion <NUM> of the second spacer <NUM>-<NUM>.

The bore <NUM> may extend completely through the second spacer <NUM>-<NUM>, including through the stud portion <NUM> and the chaplet portion <NUM>. In one embodiment, the stud portion <NUM> of the first spacer <NUM>-<NUM> extends beyond a nose <NUM> of the chaplet portion <NUM> of the second spacer <NUM>-<NUM> (see <FIG>) such that an end <NUM> of the stud portion <NUM> protrudes out of the bore <NUM>. In another embodiment, the stud portion <NUM> of the first spacer <NUM>-<NUM> extends to a position that is flush with the nose <NUM> of the chaplet portion <NUM> of the second spacer <NUM>-<NUM> (see <FIG>).

In one embodiment, the first spacer <NUM>-<NUM> and the second spacer <NUM>-<NUM> are threadably connected to one another. In another embodiment, the first spacer <NUM>-<NUM> and the second spacer <NUM>-<NUM> are riveted to one another. The first spacer <NUM>-<NUM> and the second spacer <NUM>-<NUM> may be attached to one another using any attachment method to form the spacer assembly <NUM>. Once the spacer assembly <NUM> is positioned to sandwich the core <NUM> by engaging the first spacer <NUM>-<NUM> to the second spacer <NUM>-<NUM> (or vice versa), the chaplet portions <NUM> may abut surfaces of the first side <NUM> and the second side <NUM> of the core <NUM> that generally circumscribe the hole <NUM>. The two-sided spacer assembly <NUM> may reduce the likelihood of a spacer becoming displaced or dislodged from the core <NUM> during a casting procedure.

Although the different non-limiting embodiments are illustrated as having specific components, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

Claim 1:
A core assembly (<NUM>; <NUM>) for a casting system, comprising:
a core (<NUM>; <NUM>; <NUM>) that includes a body and at least one hole (<NUM>; <NUM>; <NUM>) formed through said body; and
a spacer (<NUM>-<NUM>) that extends through said at least one hole (<NUM>), said spacer (<NUM>-<NUM>) including a stud portion (<NUM>) and a chaplet portion configured (<NUM>) to abut a surface (<NUM>; <NUM>) of said body that circumscribes said at least one hole (<NUM>; <NUM>; <NUM>); and characterized by
a second spacer (<NUM>-<NUM>) that engages said spacer (<NUM>-<NUM>) to sandwich said core (<NUM>) between said spacer (<NUM>-<NUM>) and said second spacer (<NUM>-<NUM>);
wherein the first spacer and second spacer are made of platinum;
wherein said core (<NUM>; <NUM>; <NUM>) is assembled to a second core (<NUM>; <NUM>) and is spaced from said second core (<NUM>; <NUM>) by a bumper (<NUM>), wherein the bumper (<NUM>) is formed on the second core, wherein the bumper (<NUM>) is radially offset from the spacer (<NUM>-<NUM>) and extends in a direction toward the core.