Sand Core Pattern and Method of Forming A Sand Mold

Technical Field This invention relates to a manufacture of a fluid flow deflector such as the stator of a torque converter, a compressor wheel for a turbine, etc.

Background Art

In forming such flow deflectors, a number of different manufacturing techniques have been employed. In one such prior manufacturing technique, the indi¬ vidual blades of the stator were machined in segments and subsequently secured together to form the complete stator structure. In another prior manufacturing method, the blade patterns were pegged into a shell ring prior to forming the sand mold thereabout. A problem arose in such manufacture in that variations in spacing and profile occurred in the patterns so that the stator was not completely uniform for providing a completely balanced flow of the fluid in the torque converter.

Disclosure of Invention

The present invention comprehends an im¬ proved sand core pattern for producing a one-piece cast wheel for use as a fluid flow deflector. The wheel includes a radially inner annular shell, a co¬ axial radially outer annular blade support, and a plurality of angled blades extending in a spaced an¬ nular array between the shell and blade support to define the desired fluid flow deflector.

The improved pattern includes a plurality of segments each having a first end portion defining a portion of the profile of the shell, and a second end

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portion defining the profile of one blade, means for supporting the segments in an annular array to define cumulatively a pattern structure corresponding to the configuration of the wheel shell and blade portion, and a removable outer ring encircling the array of seg¬ ments to define a pattern for the blade support.

The invention comprehends that the segments be configured to permit radially inward removal there¬ of from the array upon removal of the supporting means.

In the illustrated embodiment, the inner end portions of the segments are tapered and, more spe¬ cifically, are alternatively, in the array, tapered to sequentially widen inwardly and narrow inwardly. More ^' specifically, the side faces of the shell-forming portion of the segments define inter- secting planes.

The outer ring illustratively comprises a split ring. In the illustrated embodiment, the ring defines a pattern preselected to permit suitable sub¬ sequent machining of the casting portion defined by the ring pattern to the final desired outer ring con¬ figuration.

The pattern is arranged so that upon removal of the support of the segments, every other segment may be removed by a radially inward movement .thereof as a result of the inwardly widening configuration of the segment shell portion.

The invention comprehends that the segments be mounted annularly about a cylindrical mandrel in effecting the support thereof during the mold-forming steps. Upon removal of the mandrel at the completion of the sand mold formation, the segments may be with¬ drawn sequentially into the axial space previously occupied by the mandrel.

The outer ring may be withdrawn radially out¬ wardly upon completion of the forming of the sand mold.

In the illustrated embodiment, the side faces of the shell portion of the segments taper at an in- eluded angle of approximately 60°.

The side faces of the adjacent segment shell portions resultingly define interlocking means which, in cooperation with the mandrel and outer locking ring, provide a positive, fixed retention of the elements of the pattern during the sand mold forming step.

Each of the segments may be readily formed by identical machining operations so as to provide uni¬ formity in the blade configuration throughout the array. The shell portion of each of the segments may be machined to define selectively the inwardly and outwardly diverging angular configuration discussed

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_. ^• As a result, • the cast wheel may comprise a totally uniform configuration to provide a completely ^• balanced flow of fluid therethrough. The sand core pattern and method of forming the sand mold utilizing the pattern of the invention are extremely simple and economical while yet providing the highly improved cast wheel structure.

Brief Description of the Drawing

FIGURE 1 is a perspective view of a cast wheel manufactured in accordance with the invention;

FIGURE 2 is a side elevation thereof;

FIGURE 3 is a vertical section taken along the line 3-3 of Figure 2;

FIGURE 4 is a perspective view illustrating the sand core pattern in partially assembled rela¬ tionship for use in forming the sand mold to produce the wheel of Figure 1;

FIGURE 5 is a fragmentary radial section il¬ lustrating the interlocked relationship of the shell portions of the segments defining a portion of the pattern; FIGURE- 6 is a side elevation of a pair of ad¬ jacent segments of the annular array thereof illus¬ trated in Figure 4; and

FIGURE 7 is a diametric section of the struc¬ ture upon completion of the flowing of the sand to define the sand mold about the pattern illustrated in Figure 4.

Best Mode for Carrying Out the Invention

In the exemplary embodiment of the invention as disclosed in the drawing, an improved method of manufacture of a stator wheel 10, or the like, is shown to comprise the formation of a pattern generally desig¬ nated 11 for producing the wheel 10 as a one-piece cast wheel in a novel and simple manner.

As shown in Figure 1, the wheel includes a radially inner annular shell portion 12, a coaxial radially outer blade support 13, and a plurality of. angled blades 14 extending in a spaced annular array between the shell and ^" blade support to define a fluid flow deflector, such as for use in _. a torque converter stator structure.

The blades 14 are of complex configuration and it is desirable to arrange the blades in the array illustrated in Figure 1 in accurately positioned and spaced relationship so as to provide a completely bal- anced and uniform wheel 10. The present invention permits the individual blades ^" 14 to be defined by identical segments 15 of the pattern 11 which differ only in the angularity of the circumferentially oppo¬ site side faces 16 and 17 of an inner end portion 18

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of the segments.

As best seen in Figures 4 and 5, segments 18a define planar side faces 16a and 17a which converge radially outwardly from the axis 19 of the segment array. Segments 15b define planar side faces 16b and 17b which converge radially inwardly in facial abut¬ ment with surfaces 16a and 17a of the adjacent seg¬ ments 15a. In the illustrated embodiment, the in¬ cluded angle between faces 16a and 17a and, thus, be- tween faces 16b and 17b, is approximately 60°. As shown in Figure 5, faces 16b and 17b intersect in spaced relationship to axis 19.

Segments 15a, as shown in Figure 6, include a first inner end portion 20a defined by the planar sur- faces 16a and 17a, and segments 16 include a corres¬ ponding first inner end portion defined by surfaces 16b and 17b. Each of the segments defines a similar blade portion 21. As shown in Figure 4, the side sur- • faces of the inner end portions of the segments are curvilinear.

In the illustrated embodiment of Figure 5, an odd number of segments is utilized requiring the pro¬ vision of a third form of segment 15c at one position in the annular array generally designated 22.. Segment 15c includes an inner end portion 18c wherein the side surfaces 17c and 16c extend at an angle suitably to engage the counterclockwise side surface of the adja¬ cent segment 15b and the clockwise side surface of the adjacent segment 15a. As can be seen in Figures 4 and 5, the annu¬ lar array 22 of the segments defines a complete annu- lus wherein the inner portions 18 define an inner con¬ tinuous ring and the blades 21 are spaced apart uni¬ formly at a uniform angle to define a fluid flow de- flector pattern 23.

The annular array 22 is formed about a trans¬ versely split mandrel 25, which, as illustrated in Fig¬ ure 7, has an outer arcuate configuration corresponding to the desired inside configuration of the finished stator wheel. As the segments are being installed, they are held in place by a lock ring 25a positioned in a groove 25b located in the inner portion 18 of the segments 15. After the annular arrangement is com¬ pleted, an outer ring 26, which forms a portion of core box 28, is brought into encircling relationship to the outer tips 24 of the blades, as shown in Fig¬ ure 4. (The mandrel 25 is omitted in Figure 4 to facilitate showing of the arrangement of the segments.) Outer ring 26 and core box 28 preferably comprise a split ring which includes locking means 27 for causing firm embracing of the blade tips 24 in the annular array of the segments.

After the pattern is assembled on the man¬ drel 25 and with the outer* ring 26 installed, as shown in Figure 7, molding sand 29 may be packed around the pattern and subsequently cured to form the desired sand mold M in which the stator wheel 10 is cast.

Sand mold M is then removed from the core box 28 and mandrel 25 and split ring 26 are removed. Removal of mandrel 25 from annular array 22 permits the removal of the segments 15 sequentially from the annular array. More specifically, upon removal of mandrel 25, segments 15a may be removed by a radially inward withdrawal thereof from the annular array as permitted by the inwardly widening side surface con¬ figuration. Upon removal of segments 15a, segments 15b, and segment 15c when used, may then be removed to complete the removal of the pattern from the sand mold for subsequent casting of the stator wheel 10 in the formed mold.

As the. inner portions 18 of the respective segments effectively define a continuous annular ring portion of the pattern, as seen in Figures 4 and 5, the sand mold correspondingly defines a continuous ring cavity for defining the shell 12 of the wheel 10, seen in Figure 1. Further, as each of the segment blade portions 21 was accurately and positively posi¬ tioned in the annular array 22, the resultant cast blades 14 are similarly accurately spaced and posi- tioned in the wheel 10.

As illustrated in Figure 3, the configura¬ tion of the split ring 26 may not correspond exactly to the desired final configuration of the blade sup¬ port 13. Thus, illustratively, the outer portion of the casting may comprise a rectangular section ring which may be suitably machined to the final config- uration of the blade support 13, as shown in Figure 3.

As rther illustrated in Figure 3, the shell 12 may be further machined at its opposite ends 30 and 31, as desired.

Industrial Applicability

The cast wheel structure of the present in¬ vention provides an improved uniform, accurately con¬ figured complex-shaped structure which is adapted for use in a wide range of industrial applications, such as the stator of a torque converter wherein it is de¬ sirable to provide accurate, uniform blade deflectors at low cost.

As the pattern for the casting mold is made up of a plurality of readily repeatable machined seg¬ ments, high accuracy in the configuration of the pat¬ tern and, as a result, the configuration of the cast¬ ing made from the mold formed by the pattern, is obtained.

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As indicated above, the structural and method concepts are adapted for providing either an even num¬ ber of blades or odd number of blades in the cast wheel as desired. As will be obvious to those skilled in the art, where an even number of blades is desired, the segment 15c is omitted and the circumferential ex¬ tent of each of the segments 15a and 15b correspond¬ ingly increased to form the continuous annular array defining the shell portion of the wheel. The invention permits the production of sand cores for castings in such relatively complex-shaped castings as wheel 10 by numerical control machining steps in forming the individual segments. The inter¬ locking angle of the side surfaces of the segments assures that the blade portions thereof are effec¬ tively accurately retained while the molding sand is being packed around the pattern, thereby assuring a uniform blade arrangement. Where the wheel is util¬ ized as a torque converter stator, such uniform stator configuration provides a highly desirable balanced flow of fluid through the diverter means.

While the invention is disclosed in connec¬ tion withthe stator wheel construction of Figure 1, as will be obvious to those skilled in the art, the novel segmented pattern concept and pattern forming process of the invention may be utilized in conjunc¬ tion with a wide range of different annular configur¬ ations.

Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims. The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts compre¬ hended by the invention.

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