METHOD OF FORMING A CASTING MOLD PATTERN

Abstract

A method of forming a casting mold pattern that includes a core comprises mounting the core in a fixture such that the core is free of flexing imposed by the fixture. Material is removed from and/or added to a first and/or second mounting surface of the core. The core is then positioned in a die, and wax is conducted into the die to form the pattern. The amount of material removed from the first and/or second mounting surface is such that the core will be within a predetermined range of acceptable positions when the core is in the die with the first mounting surface engaging a first core locating surface of the die end with the second mounting surface engaging a second core locating surface of the die. The range of acceptable positions is determined relative to an ideal position of an ideal core.

Description

FIELD OF THE INVENTION

The present invention relates to a method of forming a casting mold pattern that includes a core and, more particularly, to a method of forming a casting mold pattern in which a core can be disposed in an acceptable position in a pattern forming die by removing material from and/or adding material to the core.

BACKGROUND OF THE INVENTION

Articles, such as turbine blades or airfoils, have been formed by a lost wax investment casting process. The process includes forming a pattern having the configuration of a space or cavity to be formed in a mold in which an article is to be cast. A core portion of the pattern has a configuration corresponding to the configuration of a space to be formed in the article itself.

To form the casting mold pattern, the core is positioned in a die cavity. Wax is injected into the die cavity around the core. The resulting pattern is subsequently covered with a ceramic mold material.

Once the pattern has been covered with a ceramic mold material, the wax portion of the pattern is melted. The wax is removed from the mold to leave a cavity into which metal is cast. The core is at least partially enclosed by the cast metal. The core is subsequently removed to form space in the cast metal article. The space formed by the core may be a complex arrangement of passages.

Cores for casting mold patterns used to manufacture articles such as airfoils may experience twisting during the core manufacturing process. A core that experiences such twisting may not be usable to form a pattern to create a mold in which an article such as an airfoil is to be cast.

SUMMARY OF THE INVENTION

The present invention is directed to a method of forming a casting mold pattern that includes a core and, more particularly, to a method of forming a casting mold pattern in which a core can be disposed in an acceptable position in a pattern forming die by removing material from and/or adding material to the core.

In accordance with an embodiment of the present invention, a method is provided of forming a casting mold pattern that includes a core. The core has a length, a first end, and a second end. The second end is spaced apart from the first end by the length. The core also has a first mounting surface adjacent the first end of the core and a second mounting surface adjacent the second end of the core. The method comprises the steps of (a) removing material from and/or adding material to the first mounting surface and/or the second mounting surface; and (b) positioning the core in a pattern forming die after removing material from and/or adding material to the first mounting surface and/or the second mounting surface. The pattern forming die has a first core locating surface to support the first end of the core and a second core locating surface to support the second end of the core. The core is positioned in the pattern forming die with the first mounting surface in engagement with the first core locating surface and with the second mounting surface in engagement with the second core locating surface. The method further comprises the step of conducting a flow of wax into the pattern forming die to form a casting mold pattern while the core is positioned in the pattern forming die with the first mounting surface in engagement with the first core locating surface and with the second mounting surface in engagement with the second core locating surface. The material removed from the first mounting surface and/or the second mounting surface is in an amount such that the core will be within a predetermined range of acceptable positions when the core is positioned in the pattern forming die with the first mounting surface in engagement with the first core locating surface and with the second mounting surface in engagement with the second core locating surface. The predetermined range of acceptable positions is determined relative to an ideal position in the pattern forming die of an ideal core.

In accordance with another embodiment of the present invention, a method is provided for adjusting a core to be at least partially covered by wax to produce a casting mold pattern. The core has a length, a first end, and a second end. The second end is spaced apart from the first end by the length. The core also has a first mounting surface adjacent the first end of the core and a second mounting surface adjacent the second end of the core. The method comprises the steps of (a) mounting the core in a fixture such that the core is free of any flexing along the length of the core imposed by the fixture and (b) removing material from the first mounting surface and/or the second mounting surface. The material being removed from the first mounting surface and/or the second mounting surface is in an amount such that the core will be within a predetermined range of acceptable positions when the core is positioned in a pattern forming die with the first mounting surface in engagement with a first core locating surface of the pattern forming die and with the second mounting surface in engagement with a second core locating surface of the pattern forming die. The predetermined range of acceptable positions is determined relative to an ideal position in the pattern forming die of an ideal core with an ideal twist along its length.

In accordance with a further embodiment of the present invention, a fixture is provided for adjusting a core to be at least partially covered by wax to produce a casting mold pattern. The core has a length, a first ends and a second end. The second end is spaced apart from the first end by the length. The core also has a first mounting surface adjacent the first end of the core and a second mounting surface adjacent the second end of the core. The fixture comprises (a) a first gripping device configured and dimensioned to grip the core adjacent its first end and (b) a second gripping device configured and dimensioned to grip the core adjacent its second end. The first gripping device is spaced apart from the second gripping device and is able to rotate relative to the second gripping device. The fixture also comprises a locking device for locking the first gripping device against rotation relative to the second gripping device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the present invention will become apparent to one skilled in the art upon consideration of the following description of the invention and the accompanying drawings, in which:

FIG. 1 is a perspective view of a core for use in forming a pattern to produce a die for a lost wax investment casting;

FIG. 2 is a schematic sectional view of the core of FIG. 1 positioned in a die for forming a pattern;

FIG. 3 is a schematic sectional view of a pattern formed around the core of FIG. 1 as positioned in the die of FIG. 2;

FIG. 4 is a schematic sectional view of a mold formed around the pattern and core of FIG. 3;

FIG. 5 is a schematic sectional view of the mold of FIG. 4 with the pattern removed and the core remaining;

FIG. 6 is a schematic illustration of a prior art die that incorporates mechanisms for positioning a core in the die;

FIG. 7 is an elevation view of a fixture for holding a core to permit selective removal of material from the core;

FIG. 8 is a plan view of the fixture of FIG. 7;

FIG. 9 is a perspective view of a portion of the fixture of FIG. 7;

FIG. 10 is a perspective view of a core mounted in the fixture of FIG. 7;

FIG. 11 is a schematic illustration of another die that is free any mechanism for positioning a core in the die; and

FIG. 12 is a flow chart of a method of forming a pattern such as the pattern of FIG. 3.

DETAILED DESCRIPTION

FIG. 1 illustrates a core 10 for use in forming a casting mold pattern 12 (FIG. 3), in accordance with an example of the present invention. The illustrated core 10 and pattern 12 are configured to form a mold for fabricating or casting a high pressure turbine blade (not shown) for a gas turbine engine or jet engine (not shown). More particularly, the pattern 12 has the configuration of a space or cavity to be formed in a mold 76 (FIGS. 4 and 5) in which such a high pressure turbine blade (not shown) is to be cast. The core 10 has a configuration that corresponds to the configuration of a cavity in such a high pressure turbine blade. The core 10 and pattern 12 may, however, be configured to form other components of a gas turbine engine or jet engine, such as other turbine blades, airfoils, and blade outer air seals, which have internal cavities. The gas turbine engine may be used, for example, as a propulsion device for a vehicle, such as an airplane, or as a power generating device in a stationary power plant. More generally, the pattern 12 and the core 10 may be configured to form a mold for fabricating any article that has an internal cavity and that is formed by a lost wax investment casting process.

The core 10 may be made of any suitable material. The illustrated core is made of a known ceramic material, which may have a composition similar to the composition of the core disclosed in U.S. Pat. No. 5,580,837. The core 10 may, however, be made of different materials and may have different compositions, including, for example, the composition disclosed in U.S. Pat. No. 4,583,581. When the core 10 is to be used in forming a ceramic mold for casting of gas turbine engine components, the core 10 may be made of a ceramic material that is compatible with the ceramic material forming the mold. The core 10 may have any one of many different configurations, including, for example, the configurations illustrated in U.S. Pat. No. 5,580,337 and U.S. Pat. No. 5,599,166. The core 10 may be molded using any of several different known molding techniques including, but not limited to, injection molding, transfer molding, compression molding, die pressing, and extrusion, and may thereafter be fired at an elevated temperature, such as 2,000° F. to 3,000° F., to develop the strength required for the core's intended use.

The core 10 is made in one piece and has a root end 13, an adjacent root end portion 14, a tip end 15, and an adjacent tip end portion 16. The root end 13 is spaced apart from the tip end 15 by the length of the core 10. The root end portion 14 includes a first mounting surface 18. As shown, the first mounting surface 18 includes two optional datum pads 20, which may be circular portions of the first mounting surface raised above the level of the remainder of the first mounting surface 18. The two datum pads 20 effectively function as two mounting surfaces, as will become apparent from the description below. The first mounting surface 18 may not have any raised datum pads 20, may have more or fewer than two raised datum pads 20, or may have depressions with bottom surfaces below the level of the remainder of the first mounting surface. The tip end portion 16 includes a second mounting surface 22.

A body portion 24 of the core 10 extends lengthwise or along the length of the core from the root end portion 14 to the tip end portion 16. The body portion 24 of the core 10 includes an airfoil portion 26, which extends for only pad of the length of the body portion. When viewed in cross-section taken perpendicular to the length of the core 10, as shown schematically in FIG. 2, the airfoil portion 26 has an arcuate cross-sectional configuration. The airfoil portion 26 of the core 10 thus has a convex major side surface 28 and a concave major side surface 30 (FIG. 2), which is spaced apart from and presented in a direction away from the convex major side surface. The airfoil portion 26 also has a leading edge 32 and a trailing edge 34, as does the tip end portion 16. Each of the convex major side surface 28 and the concave major side surface 30 of the airfoil portion 26 has a configuration that is a function of the desired configuration of a cavity to be formed in the high pressure turbine blade (not shown). The convex major side surface 28 of the airfoil portion 26 also corresponds to the first mounting surface 18 of the root end portion 14 and to the second mounting surface 22 of the tip end portion 16.

Holes or openings 36 may be formed in the core 10. The holes or openings 30 extend entirely through the body portion 24 and the airfoil portion 26 of the core 10 from the convex major side surface 28 to the concave major side surface 30. The holes or openings 36 may be in the form of elongated slots 38, as shown in FIG. 1. The slots 38 may extend for substantially the entire length of the body portion 24 of the core 10 from the root end portion 14 to the tip end portion 16. Alternatively, the slots 38 may extend for only part of the entire length of the body portion 24, such as, for example, the length of the airfoil portion 26 of the core 10. Elongated sections 37 of the core 10 separate the slots 38 from one another. The elongated sections 37 may be joined to one another, as shown adjacent the tip end portion 16 of the core 10 in FIG. 1. The elongated sections 37 may also be joined to and supported by either or both the tip end portion 16 and the root end portion 14s as is also shown in FIG. 1. Although the holes or openings 36 are shown in FIG. 1 as slots 38, the holes or openings 36 may have slot configurations other than the specific configurations of the slots 38 shown in FIG. 1 or configurations other than slots.

Like the core 10, the casting mold pattern 12 has an arcuate cross-sectional configuration. The pattern 12 thus has a convex major outer side surface 40 and a concave major outer side surface 42, which is spaced apart from and presented in a direction away from the convex major side surface. The pattern 12 also has a leading edge 44 and a trailing edge 46. Each of the convex major outer side surface 40 and the concave major outer side surface 42 of the pattern 12 has a configuration that is a function of the desired configuration of a corresponding outer surface of the high pressure turbine blade (not shown) that is to be cast The pattern 12 further has a convex major inner side surface 48 and a concave major inner side surface 50. As can be seen in FIG. 2, the convex major inner side surface 48 abuts and is defined by the concave major side surface 30 of the core 10. The convex major inner side surface 48 also extends generally parallel to the concave major outer side surface 42 of the pattern 12. Similarly, the concave major inner side surface 50 of the pattern 12 abuts and is defined by the convex major side surface 28 of the core. The concave major inner side surface 50 of the pattern 12 also extends generally parallel to the convex major outer side surface 40 of the pattern.

The core 10 is used to form the pattern 12 by positioning the core in a die 60. The die 60, which is shown schematically in FIGS. 2 and 3, includes a first die section 62 and a second die section 64, which are movable relative to one another. The first die section 62 has a first die surface 66 configured to form the convex major outer side surface 40 of the pattern 12. The second die section 64 has a second die surface 68 configured to form the concave major outer side surface 42 of the pattern 12. When the first die section 62 and the second die section 64 are moved into contact with one another adjacent their outer peripheries to close the die 60, the first and second die surfaces 66 and 68 remain spaced apart from one another to define a die cavity 70. When the core 10 is positioned in the die 60 and the die is closed, the core occupies a portion of the die cavity 70. The remainder of the die cavity 70 is the space in which the pattern 12 is formed.

To form the pattern 12, the core 10 is positioned in the die 60 and the die is closed. A known natural or artificial wax 72 is introduced into the die cavity 70 through an inlet passage (not shown) formed in the die 60. The wax 72 at least partially covers the core 10 and fills the holes or openings 36 in the core. When the wax 72 hardens, the wax at least partially encloses the core 10 and forms the portion of the pattern 12 not formed by the core. After the wax 72 hardens, the die 60 is opened, and the pattern 12 is removed from the die. Thereafter, the pattern 12 is at least partially enclosed or invested with a suitable investment or mold material 74 (FIG. 4). For example, the pattern 12 may be coated with multiple layers of a slurry formed of a ceramic material. The slurry coats and ultimately at least partially encloses the pattern 12. The slurry then solidifies over the outside of the pattern 12 to form a casting mold 76,

To provide a cavity for casting the high pressure turbine blade, the wax 72 forming the pattern 12 is removed from the mold 76 by, for example, melting the wax. The core 10, however, remains in the mold. The cavity resulting from the removal of the wax is filled with a molten metal, which solidifies around the core 10 to form the high pressure turbine blade (not shown). The core 10 is subsequently removed from the high pressure turbine blade to provide cooling passages or other space in the turbine blade. More particularly, the openings 36 in the form of slots 38 in the core permit the flow of metal to result in metal supports connecting opposite sides of the high pressure turbine blade (not shown), while the elongated sections 37, when removed, will result in passages, such as cooling passages, in the high pressure turbine blade.

To produce a pattern 12 that can be used to generate an acceptable mold 76 that can, in turn, be used to produce an acceptable turbine blade or other cast article, it is important both to produce an acceptably configured and dimensioned core 10 and also to position the core 10 in an acceptable orientation and location in the die 60 for producing the pattern. Among other things, a core must include a certain amount or degree of twist because the gas turbine blade that will ultimately be fabricated using the core must have a certain amount or degree of twist in order to function properly. One type of core deviation arises from either excessive or insufficient twist in the core, which can also affect the camber of the core.

Broadly, the twist of the core and the gas turbine blade relates to the orientation of a chord line or axis defined by the cross-section of the core and the cross-section of the gas turbine blade, respectively, relative to an axis that extends generally along the length of the core and the gas turbine blade. As indicated in FIG. 1, an axis 100 extends from the root end 13 of the core 10 to the tip end 15, which is along the length of the core 10. More particularly, the axis 100 extends radially outward from an axis of rotation of a gas turbine (not shown) in which the turbine blade (not shown) to be fabricated using the core is mounted. As indicated in FIG. 2, a chord line or axis 102 extends between the leading edge 32 and the trailing edge 34 of the core 10, in successive cross-sections taken along the length of the core 10 from the root end portion 14 to the tip end portion 16, the arcuate lengths of the convex and concave major side surfaces 23 and 30 of the core increase, and the angular position of the chord line or axis 102 relative to the axis 100 changes. The camber of the core and the gas turbine blade relates to the curvature of the camber line 104 or the axis extending along the geometric centerline of the cross-section of the core. If an actual core 10 is produced with too much twist or too little twist as compared to the twist of a theoretical as-designed or ideal core or if the actual core is produced with too much or too little camber, it may not be possible to position the actual core in a die, such as the die 80, in a position adequate to produce an acceptable pattern 12 and thus an acceptable mold 76.

Various techniques and mechanisms have been proposed for producing cores, such as core 10, within acceptable shape and dimensional tolerances, and various techniques and mechanisms have also been proposed for positioning a core in a die to produce a pattern within acceptable shape and dimensional tolerances. Recognizing that individual cores produced by commercially viable manufacturing techniques or processes vary from a theoretical or ideal core, one technique and an associated mechanism for positioning a core in a die is shown in FIG. 6 and is disclosed in greater detail in U.S. Pat. No. 7,913,743.

As shown in FIG. 6, a core, such as the core 10, is positioned in a die, such as die 60, in an orientation in which the airfoil portion 26 of the core is inverted as compared to the orientation shown in FIG. 2. Specifically, the concave major side surface 30 of the airfoil portion 26 is presented in an upward direction, as viewed in FIG. 6, and is positioned above the convex major side surface 28. The convex major side surface 23 of the airfoil portion 26 of the core 10 is spaced appropriately relative to or away from the first die surface 66 of the first die section 82 by core positioning members 78. Each core positioning member 78 includes a core locating surface 80. The foregoing general description is common to both the die 60 shown in FIG. 6 and the die 80a shown in FIG. 7.

In the die 60 shown schematically in Fig, 8, each core positioning member 78 is an elongated pin or shaft that has a core locating surface 80 at or adjacent to an upper end or tip of the pin or shaft. Five core positioning members 78 are shown in a line or row under the airfoil portion 26 of the core 10 to position the core 10 in a vertical direction relative to the first die surface 66. In addition, a sixth core positioning member 78 is shown adjacent the leading edge 32 of the airfoil portion 26 to position the core 10 laterally (to the left and right, as viewed in FIG. 6) relative to the first die surface 86. A greater or lesser number of core positioning members 78 may be used to position the core 10 relative to the die 60.

Each core positioning member 78 is associated with a reversible drive motor 82 so that the core positioning member may be moved in opposite axial directions, which are either upward and downward or left and right, as viewed in FIG. 6. Each individual core positioning member 78 is operatively connected to a corresponding individual drive motor 82 by a reversible drive train 84. The drive trains 84 may have any desired construction. The illustrated drive trains 84 have internally threaded members that are disposed in engagement with externally threaded members. The internally threaded members may be connected with the drive motors 82 through suitable reduction gearing. The externally threaded members are connected with the core positioning members 78. Rather than using internal and external thread convolutions to effect movement of the core positioning members 78, the drive trains 84 may have cam surfaces to move the core positioning members relative to the first die surface 66 of the first die section 62 of the die 60.

The drive motors 82 are controlled by a controller 86, which may be a microprocessor or, as shown schematically in FIG. 6, a computer with a display 88 and an internal memory 90. Communication between the controller 86 and each drive motor 82 may be via wires 92, as shown in FIG. 6, or may be wireless. Operation of the drive motors 82 by the controller 86 may be based on information about the individual actual core 10 being positioned in the die 60, as well as information and calculations regarding the configuration and dimensions of a theoretical or ideal core and the theoretical or ideal pattern to be produced using such an ideal core. Thus, as described in greater detail in U.S. Pat. No. 7,913,743, the actual core 10 may be scanned with a laser-based or a mechanical probe-based coordinate measuring machine to measure the actual dimensions and configuration of the core. This information may then be used by the controller 86 to determine, using commercially available software, a best fit spatial relationship of the actual core 10 to a spatial envelope for an ideal core and/or to the die 80 and the die cavity 70 and thereafter to operate the drive motors 82 to adjust the positions of core locating surfaces 80 of the core positioning members 78 relative to the first die surface 66 of the die 60 to place the actual core 10 in the calculated best fit spatial relationship. Thus, drive motors 82 may be operated to move the core positioning members 78 to positions in which the core locating surfaces 80 are offset from the positions in which they would be disposed if the core 10 had the dimensions and configurations of an ideal core.

Although the use of best fit software and a die with adjustable core positioning members, such as the core positioning members 78 of the core 60 shown in FIG. 6, can permit the production of an acceptable pattern 12 and thus an acceptable mold 76 with an actual core 10 produced with too much twist or too little twist as compared to the twist of a theoretical, as-designed or ideal core, the use of best fit software and a die with adjustable core positioning members can be time consuming and expensive. The present invention reflects the discovery that cores produced with a twist that is greater or less than the twist of a theoretical, as-designed or ideal core can be used to produce acceptable patterns, such as the pattern 12, without investing the time and cost involved with best fit software and/or a die with adjustable core positioning members. In particular, a core, such as the core 10, may he allowed to assume an unflexed or unstressed condition in a fixture or jig and, when the core is in its unflexed condition, an empirically-determined amount of material may be removed from or added to one or both of the first mounting surface 18 of the root end portion 14 of the core 10 and the second mounting surface 22 of the tip end portion 16 of the core. After removing material from or adding material to the first mounting surface 18 and/or the second mounting surface 22, the core 10 may then be placed in a die in which the core positioning members are fixed in position to produce an acceptable pattern, such as the pattern 12, without best fit software and/or a die with adjustable core positioning members.

In accordance with an embodiment of the invention, as shown in FIGS. 7 through 10, a fixture 110 is provided in which or into which a core 10 may be mounted so that at least one of the first and second mounting surfaces 13 and 22 is positioned and presented in a location and orientation in which the required amount of material can be removed and/or added by causing a tool to move along a predetermined path. More particularly, the fixture 110 is constructed such that the core 10 may be mounted in a manner first to permit the core to assume an unstressed or unflexed condition and then to hold the core in its unstressed or unflexed condition for material removal and/or addition.

The fixture 110 comprises a first gripping device 112 and a second gripping device 114, which is spaced apart from the first gripping device. Both the first gripping device 112 and the second gripping device 114 are mounted on a fixture support member or base plate 116. As shown, the first and second gripping devices 112 and 114 are both mounted on the base plate 116 in fixed positions. One or both of the first and second gripping devices 112 and 114 may, however, be movably mounted on the base plate 116 so that one or both the first and second gripping devices may be moved, for example, slid, along the base plate from a first position to a second position and then clamped or locked in the second position so as to accommodate cores of different lengths.

The second gripping device 114 includes a locator block 118, a clamp mechanism 120, and a clamp mounting block 122. The locator block 118 engages and is mounted on an upper surface 124 of the base plate 116. The locator block 118 includes a support surface 126 (FIG. 10) that is oriented at an angle to the upper surface 124 of the base plate 116. The support surface 126 receives and supports the tip end portion of a core, such as the tip end portion 16 of the core 10. More particularly, as shown in FIG. 10, a metal edge locator 128 and a metal mounting surface locator 130 are attached to the locator block 118 such that they project outward and away from the support surface 126. When a core 10 is mounted in the fixture 110, the edge locator 128 receives and engages the trailing edge 34 of the tip end portion 16 of the core, while the mounting surface locator 130 engages the tip end surface 26 of the tip end portion. The mounting surface locator 130 may be attached to the locator block 118 via a screw thread (not shown) so that the distal end (not shown) of the mounting surface locator may be moved toward and away from the support surface 126 for fine adjustment of the position of a core 10 mounted in the fixture 110. The support surface 126 is oriented at an angle to the upper surface 124 of the base plate 116 so that when the tip end portion 16 of the core 10 is supported on the support surface and, more specifically, on the edge locator 128 and the mounting surface locator 130, the root end portion 14 of the core is approximately horizontal and parallel to the upper surface 124 of the base plate 116 due to the twist in the core.

The clamp mounting block 122 also engages and is mounted on the upper surface 124 of the base plate 116. The clamp mounting block 122 has a greater height than the locator block 118 and is located behind and in contact with the locator block. The clamp mounting block 122 also includes a support surface 132 that is oriented at an angle to the upper surface 124 of the base plate 116. The support surface 132 is substantially parallel to the support surface 126 of the locator block 118. The clamp mechanism 120 is mounted on the support surface 132 of the clamp mounting block 122. The clamp mechanism 120 includes a support bracket 134 secured to the clamp mounting block 122 using fasteners (not shown), such as screws. Three bars or links 136, 138 and 140 of a three-bar linkage are pivotally attached to the support bracket 134 to permit manual clamping and unclamping of the core 10. A handle 142 is attached to one end of the link 136, and a clamp pad 144 is attached to one end of the link 140. When the handle 142 is grasped by an individual and pushed upward toward the position shown in FIG. 10, the clamp pad 144 is moved toward the support surface 126 to grip or clamp the tip end portion 16 of a core 10. Conversely, when the handle 142 is pulled downward away from the position shown in FIG. 10, the clamp pad 144 is moved away from the support surface 126 to unclamp the tip end portion 16 of the core 10. The position of the clamp pad 144 relative to the link 140 and thus to the support surface 126, when the handle 142 is pushed upward, can be adjusted via a threaded portion of a post 145 connecting the clamp pad to the link 140.

As best seen in FIGS. 9 and 10, the first gripping device 112 includes a support or bearing block 146, a carriage 148, and a locator block or cradle 150. The bearing block 146 engages and is mounted on the upper surface 124 of the base plate 116 and thus maintains a fixed rotational position relative to the second gripping device 114. The carriage 148 is pivotally mounted on the bearing block 146 via a pin or shaft 147 (FIG. 7) and a bearing (not shown). The carriage 148 is thus pivotable or rotatable relative to the bearing block 146 and the second gripping device 114. To limit the extent to which the carriage 148 can pivot relative to the bearing block 146 and also relative to the second gripping device 114, a stop block 152 is mounted on the upper surface 124 of the base plate 116 adjacent to the bearing block and below the carriage, as viewed in FIGS. 9 and 10. The stop block 152 includes a groove or notch 154 that is presented toward and opens toward the carriage 148. A dowel 156 projects radially outward and away from a curved outer surface 158 of the carriage 148 and is received in the notch 154. The width of the notch 154 is greater than the diameter or width of the dowel 156 so that the dowel can move to a limited extent in the notch and thus the carriage 148 can pivot to a limited extent relative to the bearing block 146 and the second gripping device 114. A set screw 159 can be used to adjust the effective width of the notch 154.

The cradle 150 is attached to the carriage 143 for pivotal movement with the carriage. The cradle 150 includes a support surface 160 and a lateral guide surface 162. The support surface 160 is recessed into the cradle 150 so that a U-shaped wall 164 is formed by the cradle around three sides of the support surface. The fourth side of the support surface 160 is open to the outer periphery of the cradle 150 and is presented toward the second gripping device 114. The support surface 160 extends for most of the lateral dimension or width of the cradle 150. The lateral guide surface 162 is a portion of the U-shaped wail 164 and extends outward from the U-shaped wall toward the central portion of the support surface 160 from one leg or upright of the U-shape. Across the U, projecting through the U-shaped wall 164 toward the lateral guide surface 162, as viewed in FIG. 9, is a threaded clamping member 166. The clamping member 166 can be advanced toward the lateral guide surface 162 and unscrewed away from the lateral guide surface to enable an article, such as the root end portion 14 of a core 10, to be clamped or guided between the clamping member and the lateral guide surface.

Also attached to the carriage 148 for pivotal movement with the carriage is a clamp arm 168. The clamp arm 168 is pivotally attached at one end 170 to the carriage 148. The clamp arm 168 may be pivoted from a first, upright or vertical position substantially in the plane of the carriage 148 through approximately 90° into a second, horizontal position (shown in FIGS. 9 and 10) in which the opposite end 172 of the clamp arm projects over, overhangs or overlies the support surface 160 of the cradle 150. A spring plunger 174 extends through the opposite end 172 of the clamp arm 168. When the clamp arm 168 is in its second position, as shown in FIG. 9, the spring plunger 174 projects toward the support surface 160 to enable an article, such as the root end portion 14 of a core 10, to be gripped or clamped between the spring plunger and the support surface. To hold the clamp arm 168 in its second position, a half-turn screw member 176, which is mounted on a bracket 178 attached to the carriage 148, may be turned to a first position in which the half-turn screw member overlies the clamp arm 168 and prevents the clamp arm from moving to its first, vertical position. To release the clamp arm 168 to pivot relative to the carriage 148 into its first position, the half-turn screw member 176 may be rotated through 180° so the clamp arm is free to pivot relative to and past the half-turn screw member.

To permit the carriage 148 to be looted in position against pivotal movement relative to the bearing block 146 and relative to the second gripping device 114, the fixture 110 includes a locking mechanism or device. The locking device includes two shoulder screws 186 that extend through the carriage 148 into the bearing block 146. The head 188 of each shoulder screw 186 abuts a washer 190 that is in contact with an outer surface 192 of the carriage 148, while the shaft 194 of each shoulder screw passes through an arcuate slot (not shown) in the carriage, through a cylindrical bore (not shown) in the bearing block 146, and into one of two pancake-style, pneumatic piston-cylinder units 184.

The piston-cylinder units 184 are operable to draw the heads 188 of the shoulder screws 186 and thus the washers 190 against the outer surface 192 of the carriage 148 to press the carriage against the bearing block 146 and lock the carriage in position relative to the bearing block or hold the carriage against pivotal movement relative to the bearing block 146 and the second gripping device 114. The piston-cylinder units 184 are also operable to release the shoulder screws 186 and the washers 190 from contact with the carriage 148 so that the carriage is free to move, rotate or pivot relative to the bearing block 146. When the shoulder screws 186 and, thus, the washers 190 are released from contact with the carriage 148, the piston-cylinder units 184 end the shoulder screws 186 may allow compressed air to leak or bleed into the interface between the carriage 148 and the bearing block 146 to form, in effect, an air bearing between the carriage and the bearing block.

To provide clean, dry air to the two pancake-style piston-cylinder units 184, the fixture 110 may include a quick connect fitting 180 for connection to a supply of compressed air (not shown) and an air filter and pressure regulator assembly 182. Air that passes from the fitting 180 through the air filter and pressure regulator assembly 182 is supplied to the two pancake-style piston-cylinder units 184.

In use, a core is mounted in the fixture 110 with the tip end portion 16 in the second gripping device 114 and the root end portion 14 in the first gripping device 112. More specifically, the tip end portion 16 is positioned with its trailing edge 34 resting against the edge locator 128 and with its tip end surface 25 resting against the mounting surface locator 130. The clamp mechanism 120 is actuated so that the clamp pad 144 is moved into contact with the second mounting surface 22 to clamp the tip end portion 16 against movement relative to the second gripping device 114 of the fixture 110. The root end portion 14 of the core 10 is placed in the first gripping device 112 with its surface 19 opposite the first mounting surface 18 resting on and supported by the support surface 160 of the cradle 150. The root end portion 14 is also positioned between the lateral guide surface 162 and the clamping member 166. The clamp arm 168, which has been in its first, upright position, is pivoted into its second, horizontal position with the spring plunger 174 in engagement with the first mounting surface 18. The half-turn screw member 176 is twisted into its first position to hold the clamp arm 168 in its second, horizontal position. The shoulder screws 186 are loosened.

The core 10 is now able to assume an unstressed or unflexed condition free of any stress or deflection imposed by the fixture 110. In particular, the carriage 148 and the cradle 150 of the first gripping device 112, together with the root end portion 14 of the core 10 held in the cradle, are ail free to rotate relative to the second gripping device 114 and the tip end portion 16 of the core in response to the twist or other shape inherent in the core after being molded and fired. When the root end portion 14 of the core and the first gripping device have ceased to move relative to the tip end portion 16 and the second gripping device 114, which should occur in a few seconds, the shoulder screws 186 are tightened so that movement between the root end portion 14 of the core 10 and the tip end portion 16 and between the first and second gripping devices 112 and 114 is no longer possible. Material may now be removed from the root end portion 14 and, more particularly, from one or both of the datum pads 20 or from the tip end portion 16 so that the core 10, after the removal of the material, may be placed in a die without movable core positioning members. The amount of material removed from each datum pad 20 may be the same or different from one datum pad to the other. The adjusted or modified datum pads 20 will be the surfaces in engagement with core locating surfaces of core positioning members in a pattern forming die.

The amount of material to be removed from and/or added to the first mounting surface 18 of the root end portion 14 of a core 10 and/or the second mounting surface 22 of the tip end portion 16 of the core can be determined in various ways. For example, if the dimensions and configuration of the core are measured or determined by, for example, scanning the core with a laser-based or a mechanical probe-based coordinate measuring machine, the measured dimensions and shape may be used to calculate or determine the amount of material to be removed and/or added through the use, for example, of commercially available software. The amount of material to be removed from and/or added to the first mounting surface 18 and/or the second mounting surface 22 may, however, be determined empirically such that the core 10 will be within a predetermined range of acceptable positions when the core is positioned in a pattern forming die with the first mounting surface 18 in engagement with a core beating surface or surfaces and with the second mounting surface 22 in engagement with a core locating surface or surfaces. The predetermined range of acceptable positions is determined relative to a theoretical as-designed or ideal position in the pattern forming die of a theoretical, as-designed or ideal core with a theoretical, as-designed or ideal twist along its length.

If the amount of material to be removed from and/or added to the first mounting surface 18 and/or the second mounting surface 22 is determined empirically, the empirically-determined criteria for removing material will be same for all cores in a group or set of cores, such as an entire production run or lot of cores. With particular reference to the core 10, the amount of material to be removed from and/or added to the raised datum pads 20 of the first mounting surface 18 will the amount needed to bring each datum pad to an empirically determined level or height above the support surface 160 of the cradle 150, on which the surface 19 of the root end portion 14 of the core 10 is supported. Because the datum pads 20 that have been adjusted or modified by the removal and/or addition of material will be the surfaces in engagement with core locating surfaces of core positioning members in a pattern forming die, the position of the root end portion 14 of the core 10 in the pattern forming die will have been established. Because the second mounting surface 22 of the tip end portion 16 of the core 10 will be the only other surface in engagement with core locating surfaces of core positioning members in the pattern forming die, and because the core has been allowed to assume an unflexed or unstressed condition prior to removal of material from the datum pads 20, the position of the tip end portion of the core, together with the overall position of the core, in the pattern forming die will have been established.

The determined amount or depth of material to be removed and/or added to bring the datum pads 20 to a determined height or level above the support surface 160 of the cradle 150 may be communicated to and used by a CNC machine to remove, for example, by grinding or sanding, the determined amount of material from the datum pads of the first mounting surface 18. More specifically, the fixture 110 in which a core has been placed is itself positioned in a location and orientation in which the determined amount of material can be removed by simply causing a tool, such a grinding or sanding tool, to move along a predetermined path. The material removal tool (not shown) may be both moved and operated by a machine, such as, for example, a CNC machine, or may be moved by an individual with the aid of a guide or jig. If the first mounting surface 18 does not have any raised datum pad 20, material may be removed directly from the first mounting surface. Alternatively, if the first mounting surface 18 has depressions (not shown) with bottom surfaces below the level of the remainder of the first mounting surface, a predetermined amount or depth of material may be added to the depressions so as to raise the level of the bottom surfaces of the depressions, which will be the surfaces in engagement with core locating surface of core positioning members in a pattern forming die. The added material may be a liquid that will quickly dry or harden and may be a plastic material.

After material has been removed from or added to an actual core 10, the core may be placed in a die, such as the die 60a of FIG. 11. The die 60a is similar in construction and operation to the die 60 of FIG. 6, but lacks the movable core positioning members 78 and associated motors and drive trains 84 of the die 60 of FIG. 6. In the die 60a, there are not lines or rows of movable core positioning members 78 that supped the airfoil portion 26 of the core 10, but rather only two fixed core positioning members 78a located adjacent the left end of the die 60a, as viewed in FIG. 11, and two additional fixed core positioning members 78b located adjacent the right end of the die 60a. The core positioning members 78a are identical in shape to the core positioning members 78 of FIG. 6. The core positioning members 78a are located, however, so that their respective core locating surfaces 80a engage the tip end portion 16 of the core 10, rather than the airfoil portion 26, and, more particularly, the second mounting surface 22 of the tip end portion. The core positioning members 78b have L-shaped core locating surfaces 80b so that the core locating surfaces 80b are capable of positioning the core 10 in both in a vertical direction relative to the first die surface 66a of the first die section 62a and in a lateral direction relative to the first die surface 66a. The lateral or horizontal portions of the core locating surfaces 80b engage the root end portion 14 of a core, such as the core 10, and, more particularly, the datum pads 20 of the first mounting surface 18 of the root end portion 14. The core positioning members 78b may be in the form of plastic chaplets that can melt into or otherwise be incorporated into a pattern, such as the pattern 12.

The die 60a of FIG. 11 may also include optional pins or core support members 79 in the first die section 62a, which do not engage a core, such as the core 10, when it is initially positioned in the first die section. The core support members 79 engage the core 10 in the event of slight deflection of the core. In particular, the core support members 79 may engage and be effective to help support the core 10 if there is deflection of one or more portions of the core during the injection of wax 72 into the die 60. The core support members 79 thus may limit the range of deflection of the core 10.

Also shown in FIG. 11 is the lower half of a passage 96 for conducting wax 72 into the die 60a when the die is closed. The lower half of the passage 96 is formed in the first die section 62a and the upper half (not shown) of the passage is formed in the second die section (not shown). The passage 96 is completed when the second die section (not shown) is moved into contact with the first die section 62a, and the die 60a is thus closed. The passage 96 has an inlet 98 through which wax 72 is injected into the passage.

FIG. 12 is a flow chart detailing a process or method 300 of forming a casting mold pattern that includes a core. The pattern may be a pattern such as pattern 12, as shown in FIGS. 3 and 4. Similarly, the core may be a core such as the core 10, as shown in FIGS. 1-6. The method of FIG. 12 involves the use of a die, such as die 60 or die 60a, and a fixture, such as fixture 110.

The method 300 starts at block 310. The method 300 then proceeds to step 312, in which a core, such as the core 10, is mounted in a fixture, such as the fixture 110. The fixture has a first gripping device and a second gripping device. The first gripping device is spaced apart from the first gripping device and is free to rotate relative to the second gripping device. The core is mounted in the fixture with the first gripping device gripping the core adjacent a first end of the core and with the second gripping device gripping the core adjacent a second end of the core.

At step 314, the first gripping device and the first end of the core are permitted to rotate freely relative to the second gripping device and the second end of the core so that the core is free of any twisting along the length of the core imposed by the fixture. After the first gripping device and the first end of the core have been allowed to rotate relative to the second gripping device and the second end of the core, the method proceeds to step 316 in which the first gripping device is locked against rotation relative to the second gripping device.

The method 300 next proceeds to step 318, in which material is removed from and/or added to either or both a first mounting surface and a second mounting surface so that the core will be within a predetermined range of acceptable positions relative to a position of a theoretical, as-designed or ideal core when the core is positioned in a die. After step 318, the next step 320 of the method 300 is positioning the core in a die that has at least one first core locating surface to support the first end of the core and at least one second core locating surface to support the second end of the core. The first mounting surface of the core is positioned in engagement with the first core locating surface or surfaces of the die, and the second mounting surface of the core is positioned in engagement with the second core locating surface or surfaces of the die. Lastly, the method 300 proceeds to step 322, in which a flow of wax is conducted into the die while the core is in engagement with the first and second core locating surfaces. When the wax hardens, the casting mold pattern has been formed.

Although the core 10 has been described as having a first mounting surface 18 with two raised datum pads 20 that effectively function as two mounting surfaces, the first mounting surface may not have any raised datum pads. The first mounting surface 18 may alternatively have more or fewer than two raised datum pads 20 or may have depressions with bottom surfaces below the level of the remainder of the first mounting surface. If the first mounting surface 13 is formed with depressions having bottom surfaces below the level of the remainder of the first mounting surface, the depressions would be filled in as required to implement the present invention. Also, while the core 10 and the method of using the core 10 to form the casting mold pattern 12 have been described with particular reference to adjusting or removing material from the first mounting surface 18 or potentially adding material to the first mounting surface, the core may be formed and the method may be implemented by adjusting or removing material from or adding material to the second mounting surface 22 or from or to both the first mounting surface 18 and the second mounting surface 22. Further, although the looking device has been shown and described as comprising two shoulder screws 186 operable by piston-cylinder units 184, the locking device could comprise a variety of other structures. For example, instead of two shoulder screws 186, the locking device could comprise two shafts that are each threaded at one end to receive a wing nut, which would be tightened against the surface 192 of the carriage 148. The locking device might alternatively comprise a clamping mechanism, such as a set screw, for engaging the curved outer surface 158 of the carriage 148.

From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes, and/or modifications within the skill of the art are intended to be covered by the appended claims.

Claims

1. A method of forming a casting mold pattern that includes a core, the core having a length, a first end, and a second end, the second end being spaced apart from the first end by the length, the core also having a first mounting surface adjacent the first end of the core and a second mounting surface adjacent the second end of the core, said method comprising the steps of: (a) removing material from and/or adding material to the first mounting surface and/or the second mounting surface:(b) positioning the core in a pattern forming die alter removing material from and/or adding material to the first mounting surface and/or the second mounting surface, the pattern forming die having a first core locating surface to support the first end of the core and a second core locating surface to support the second end of the core, the core being positioned in the pattern forming die with the first mounting surface in engagement with the first core locating surface and with the second mounting surface in engagement with the second core locating surface; and(c) conducting a flow of wax into the pattern forming die to form a casting mold pattern while the core is positioned in the pattern forming die with the first mounting surface in engagement with the first core locating surface and with the second mounting surface in engagement with the second core locating surface, the material being removed from and/or added to the first mounting surface and/or the second mounting surface being in an amount such that the core will be within a predetermined range of acceptable positions when the core is positioned in the pattern forming die with the first mounting surface in engagement with the first core locating surface and with the second mounting surface in engagement with the second core locating surface, the predetermined range of acceptable positions being determined relative to an ideal position in the pattern forming die of an ideal core.

2. The method of claim 1 further comprising the step of supporting the core such that the core is free of externally applied flexing, the step of removing material from and/or adding material to the first mounting surface and/or the second mounting surface including removing material from and/or adding material to the first mounting surface and/or the second mounting surface while supporting the core such that the core is free of externally applied flexing.

3. The method of claim 2 wherein the step of supporting the core such that the core is free of externally applied flexing comprises mounting the core in a fixture such that the core is free of flexing along the length of the core imposed by the fixture.

4. The method of claim 3 wherein the fixture has a first gripping device and a second gripping device, the first gripping device being spaced apart from the second gripping device and being able to rotate relative to the second gripping device, the step of mounting the core in a fixture including (i) mounting the core with the first gripping device gripping the core adjacent the first end and with the second gripping device gripping the core adjacent the second end and (ii) permitting the first gripping device and the first end of the core to rotate relative to the second gripping device and the second end of the core so that the core is free of flexing along the length of the core imposed by the fixture.

5. The method of claim 4 also comprising the step of locking the first gripping device against rotation relative to the second gripping device after the first gripping device and the first end of the core have been allowed to rotate relative to the second gripping device and the second end of the core.

6. The method of claim 1 wherein the core has a twist along its length

7. The method of claim 1 wherein the first mounting surface is one of a plurality of first mounting surfaces and wherein the first core locating surface is one of a plurality of first core locating surfaces, the step of positioning the core in a pattern forming die including positioning the plurality of first mounting surfaces in engagement with the plurality of first core locating surfaces.

8. The method of claim 1 wherein the core has a convex major side surface extending from a tip end portion of the core to a root end portion of the core, the core also having a concave major side surface extending from the tip end portion of the core to the root end portion of the core, the concave major side surface being spaced apart from and presented in a direction away from the convex major side surface.

9. The method of claim 1 wherein the core is molded from a ceramic material and fired at an elevated temperature before removing material from and/or adding material to the first mounting surface and/or the second mounting surface.

10. The method of claim 1 wherein the pattern forming die includes a first die section and a second die section, the pattern forming die being in a closed condition to receive and contain the flow of wax when the second die section is moved toward and into contact with the first die section, the pattern forming die being in an open condition to receive the core when the second die section is moved away from and out of contact with the first die section.

11. The method of claim 1 wherein the first and second core locating surfaces are fixed in position relative to the pattern forming die.

12. The method of claim 1 wherein the step of removing material from and/or adding material to the first mounting surface and/or the second mounting surface consists of removing material from the first mounting surface and/or the second mounting surface.

13. A method of adjusting a core to be at least partially covered by wax to produce a casting mold pattern, the core having a length, a first end, and a second end, the second end being spaced apart from the first end by the length, the core also having a first mounting surface adjacent the first end of the core and a second mounting surface adjacent the second end of the core, said method comprising the steps of: (a) mounting the core in a fixture such that the core is free of flexing along the length of the core Imposed by the fixture; and(b) removing material from the first mounting surface and/or the second mounting surface; the material being removed from the first mounting surface and/or the second mounting surface being in an amount such that the core will be within a predetermined range of acceptable positions when the core is positioned in a pattern forming die with the first mounting surface in engagement with a first core locating surface of the pattern forming die and with the second mounting surface in engagement with a second core locating surface of the pattern forming die, the predetermined range of acceptable positions being determined relative to an ideal position in the pattern forming die of an ideal core.

14. The method of claim 13 wherein the fixture has a first gripping device and a second gripping device, the first gripping device being spaced apart from the second gripping device and being able to rotate relative to the second gripping device, the step of mounting the core in a fixture including (i) mounting the core with the first gripping device gripping the core adjacent the first end and with the second gripping device gripping the core adjacent the second end and (ii) permitting the first gripping device and the first end of the core to rotate relative to the second gripping device and the second end of the core so that the core is free of flexing along the length of the core Imposed by the fixture.

15. The method of claim 14 also comprising the step of locking the first gripping device against rotation relative to the second gripping device after the first gripping device and the first end of the core have been allowed to rotate relative to the second gripping device and the second end of the core.

16. The method of claim 13 wherein the core has a convex major side surface extending from a tip end portion of the core to a root end portion of the core, the core also having a concave major side surface extending from the tip end portion of the core to the root end portion of the core, the convex major side surface being spaced apart from and presented in a direction away horn the concave major side surface.

17. The method of claim 13 wherein the core is molded from a ceramic material and fired at an elevated temperature before being mounted in the fixture.

18. A fixture for adjusting a core to be at least partially covered by wax to produce a casting mold pattern, the core having a length, a first end, and a second end, the second end being spaced apart from the first end by the length, the core also having a first mounting surface adjacent the first end of the core and a second mounting surface adjacent the second end of the core, said fixture comprising: (a) a first gripping device configured and dimensioned to grip the core adjacent its first end;(b) a second gripping device configured and dimensioned to grip the core adjacent its second end, the first gripping device being spaced apart from the second gripping device and being able to rotate relative to the second gripping device; and(c) a locking device for locking the first gripping device against rotation relative to the second gripping device.

19. The fixture of claim 13 wherein the first gripping device includes (i) a support that maintains a fixed rotational position relative to the second gripping device, and(ii) a carriage pivotally mounted on the support for pivotal movement relative to the support and the second gripping device, the locking device locking the carriage against pivotal movement relative to the support and the second gripping device.

20. The fixture of claim 19 wherein the first gripping device also includes a support surface carried by the carriage for engaging and supporting a surface of the core opposite the first mounting surface.