EP0036273A2

EP0036273A2 - Method of, and pattern for use in, forming a sand mould, and method of producing an annular casting using the mould

Info

Publication number: EP0036273A2
Application number: EP81300927A
Authority: EP
Inventors: Edward E. Flesburg
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1980-03-13
Filing date: 1981-03-05
Publication date: 1981-09-23
Also published as: JPS57500421A; WO1981002536A1; DE3161348D1; JPH0113941B2; EP0036273A3; EP0036273B1; CA1154570A; BR8009025A

Abstract

A pattern (11) for forming a sand mould for use in producing a one-piece annular casting (1) having a radially inner shell (12), a radially outer blade support (13), and a plurality of angled blades (14) extending in a spaced, annular array (22). The pattern includes a plurality of similar segments (15), each having an inner end portion (18) defining a portion of the profile of the shell, and an outer end portion (21) defining the profile of the blade. The segments are supported in annular array about a mandrel (25) and are circumscribed by a split ring (26) defining the pattern for the outer blade support portion of the wheel (10). The inner portions of the segments are defined by inclined side surfaces (16,17) which, in alternate ones of the segments in the annular array, converge and diverge toward the centre of the array. Upon completion of the forming of the sand mould aboutthe pattern, the mandrel and outer ring are removed, permitting the segments having the inwardly diverging side faces to be withdrawn inwardly from the array and permit the remaining segments then to be withdrawn inwardly therefrom.

Description

This invention relates to sand moulds for producing an annular casting, particularly a fluid flow deflector, such as the stator of a torque converter or a compressor wheel for a turbine.
In forming such flow deflectors, a number of different manufacturing techniques have been employed. In one such prior manufacturing technique, the individual blades of the deflector were machined in segments and subsequently secured together to form the complete deflector.
In another prior manufacturing method, the blade patterns were pegged into a shell ring prior to forming a sand mould thereabout. A problem arose in such manufacture in that variation in spacing and profile occurred in the patterns so that the deflector was not completely uniform and this did not provide a completely balanced flow of the fluid.
In accordance with the present invention, a pattern for use in forming a sand mould for a one-piece annular casting having a radially inner, shell ring, a radially outer, blade support ring and a plurality of angled blades extending in spaced annular array between the rings, comprises a plurality of pattern segments each having a first end portion defining a portion of the profile of one of.the rings, and a second end portion defining the profile of one blade; means for supporting the pattern segments in an annular array to define cumulatively a pattern structure corresponding to the configuration of the one ring and blades; and a removable pattern ring coaxial with the array of segments to provide a pattern defining the profile for the other of the rings.
The pattern segments are preferably shaped to permit selective radially directed removal thereof from the array upon removal of the supporting means. Thus the first end portion of at least one pattern segment may be tapered radially inwardly or outwardly to permit radially outward or inward respectively removal thereof from the array of segments upon removal of the supporting means. Preferably, the first end portions of adjacent ones of the segments are tapered in opposite radial directions. Upon removal of the support for the segments, every other segment may then be removed by a radially directed movement thereof prior to removal of the other segments.
The removable pattern ring may comprise a split ring. In the illustrated embodiment, the ring defines a pattern selected to permit suitable subsequent machining of the portion of the casting defined by the pattern ring, to the final desired configuration.
The first end portions of the pattern segments may define the profile of the radially outer, blade support ring, but preferably define the profile of the radially inner, shell ring. In the latter case radial removal of the pattern segments from the annular array is preferably in the radially inward direction.
The invention also includes a method of forming a sand mould for a one-piece annular casting having a radially inner shell ring, a radially outer blade support ring, and a plurality of angled blades extending in a spaced annular array between the rings and utilizing a pattern as previously defined, the method comprising the steps of supporting the pattern segments in an annular array to define cumulatively a pattern structure corresponding to the configuration one of the rings and the blades; securing the removable pattern ring coaxially with the array of pattern segments; forming a sand mould about the associated parts of the pattern; discontinuing the support of the pattern segments; removing the pattern ring from the mould; and removing the pattern segments from the mould by movement thereof radially with respect to the axis of the annular array of pattern segments.
The segments may be mounted coaxially of an annular supporting surface during the mould-forming steps. Thus when the first end portions define the profile of the shell ring, the annular supporting surface may be provided on a mandrel which preferably urges the pattern segments radially outwards and locks them in the annular array. Upon removal of the mandrel at the completion of the sand mould formation, the segments may be withdrawn sequentially into the axial space previously occupied by the mandrel.
The removable ring,when defining the prcfile of the blade support ring, may be withdrawn radially outwardly upon completion of the forming of the sand mould.
The faces of the adjacent segments fit closely together and may additionally be locked to one another, for example by means of an inner locking ring engaging in a groove in the segments. In cooperation with the annular supporting surface on the mandrel or otherwise, and the removable ring, this provides a positive, fixed location of the elements of the pattern during the sand mould forming step.
Each of the pattern segments may be readily formed by identical machining operations so as to provide uniformity in the blade configuration throughout the array. The first end portion of each of the pattern segments may be machined to define selectively the inwardly and outwardly tapering configuration discussed above.
The resulting annular casting may thus comprise a totally uniform configuration to provide a completely balanced flow of fluid therethrough. The pattern and method of forming the sand mould utilizing the pattern are extremely simple and economical while yet providing the highly improved cast structure.
The formation of a sand mould by means of a pattern in accordance with the invention is illustrated in the accompanying drawings, in which:-

Figure 1 is a perspective view of a casting;
Figure 2 is a side elevation thereof;
Figure 3 is a vertical section taken on the line 3-3 of Figure 2;
Figure 4 is a perspective view illustrating the pattern in partially assembled relationship for use in forming the sand mould to produce the casting of Figure 1;
Figure 5 is a fragmentary radial section illustrating the interlocked relationship of the inner end portions of the pattern segments;
Figure 6 is a side elevation of a pair of adjacent segments of the annular array thereof illustrated in Figure 4; and,
Figure 7 is a diametric section of the structure upon completion of the packing of the sand to form the sand mould about the pattern illustrated in Figure 4.

The manufacture of a stator 10 involves the formation of a pattern 11 for producing the stator 10 as a one-piece casting.
As shown in Figure 1, the stator includes a radially inner annular shell ring 12, a coaxial radially outer blade support ring 13, and a plurality ₃f angled blades 14 extending in a spaced annular array between the shell and blade support rings 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 sc as to provide a completely balances and uniform stator 10. The individual blades 14 are defined by identical segments 15 of the pattern 11 which differ only in the angularity of the circumferentially opposite side faces 16 and 17 of an inner end portion 18 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 abutment with surfaces 16a and 17a of the adjacent segments 15a. In the illustrated embodiment, the included angle between faces 16a and 17a and, thus, between 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 surfaces 16a and 17a, and segments 16 include a corresponding 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 surfaces 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 provision 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 adjacent segment 15b and the clockwise side surface of the adjacent segment 15a.
As can be seen in Figures 4 and 5, the annular array 22 of the segments defines a complete annulus wherein the inner portions 18 define an inner continuous ring and the blades 21 are spaced apart uniformly at a uniform angle to define a fluid flow deflector pattern 23.
The annular array 22 is formed about a transversely split mandrel 25, which, as illustrated in Figure 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. They are then locked in position by the mandrel, the two parts of which urge the segments radially outwards as the parts are brought together. After the annular arrangement is completed, 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 Figure 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 mandrel 25 and with the outer ring 26 installed, as shown in Figure 7, moulding sand 29 may be packed around the pattern and subsequently cured to form the desired sand mould M in which the stator 10 is cast
Sand mould 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 configuration. 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 mould for subsequent casting of the stator 10 in the formed mould.
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 stator 10, seen in Figure 1. Further, as each of the segment blade portions 21 was accurately and positively positioned in the annular array 22, the resultant cast blades 14 are similarly accurately spaced and positioned in the stator 10.
As illustrated in Figure 3, the configuration of the split ring 26 may not correspond exactly to the desired final configuration of the blade support 13. Thus, illustratively, the outer portion of the casting may comprise a rectangular section ring which may be suitably machined to the final configuration of the blade support 13, as shown in Figure 3.
As further illustrated in Figure 3, the shell 12 may be further machined at its opposite ends 30 and 31, as desired.
The casting "structure of the present invention provides an improved uniform, accurately configured 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 desirable 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 segments, high accuracy in the configuration of the pattern and, as a result, the configuration of the cast- ing made from the mold formed by the pattern, is obtained.
As indicated above, the structural and method concepts are adapted for providing either an even number of blades or odd number of blades in the cast stator 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 extent of each of the segments 15a and 15b correspondingly increased to form the continuous annular array defining the shell portion of the stator.
The invention permits the production of sand moulds for castings in such relatively complex-shaped castings as stator 10 by numerical control machining steps in forming the 'individual segments.. The interlocking angle of the side surfaces of the segments assures that the blade portions thereof are effectively accurately retained while the molding sand is being packed around the pattern, thereby assuring a uniform blade arrangement. Where the stator is utilized 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 connection with the stator 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 conjunction with a wide range of different annular configurations.

Claims

1. A pattern for use in forming a sand mould for a one-piece annular casting (10) having a radially inner, shell ring (12), a radially outer blade support ring (13) and a plurality of angled blades (14) extending in a spaced-annular array (22) between the rings (12, 13), the pattern comprising a plurality of pattern segments (15) each having a first end portion (18) defining a portion of the profile of one of the rings (12), and a second end portion (21) defining the profile of one blade; means (25) for supporting the pattern segments in an annular array (22) to define cumulatively a pattern structure corresponding to the configuration of the one ring and blades; and a removable pattern ring (26) coaxial with the array of segments to provide a pattern defining the profile for the other of the rings (13).

2. A pattern according to claim 1, wherein the pattern segments (15) are shaped to permit selective radially directed removal thereof from the array (22) of pattern segments upon removal of the supporting means (25).

3. A pattern according to claim 2, wherein the first end portion (18) of at least one pattern segment (15) is tapered in the radial direction to permit radially directed removal thereof from the array (22) of segments upon removal of the supporting means (25).

4. A pattern according to claim 3, wherein the first end portions (18a, 18b) of adjacent ones of the segments are tapered in opposite radial directions.

5. A pattern according to any one of the preceding claims, wherein the removable pattern ring (26) comprises a split ring.

6. A pattern according to any one of the preceding claims, wherein the first end portions (18) of the pattern segments (15) define the profile of the shell ring.

7. A method of forming a sand mould (M) for a one-piece annular casting (10) having a radially inner shell ring (12), a radially outer blade support ring (13), and a plurality of angled blades (14) extending in a spaced annular array (22) between the rings (12, 13) and utilizing a pattern according to any one of the preceding claims, the method comprising the steps of supporting the pattern segments (15) in an annular array (22) to define cumulatively a pattern structure corresponding to the configuration one of the rings (12) and the blades (14); securing the removable pattern ring (26) coaxially with the array (22) of pattern segments; forming a sand mould (M) about the associated parts of the pattern(ll); discontinuing the support of the pattern segments (15); removing the pattern ring (26) from the mould; and removing the pattern segments (15) from the mould by.movement thereof radially with respect to the axis (19) of the annular array (22) of pattern segments.

8. A method according to claim 7, wherein the pattern segments are supported by providing an annular supporting surface (25) and mounting the pattern segments (15) coaxially of the supporting surface.

9. A method according to claim 8, when dependent on claim 6, wherein the annular supporting surface is provided on a mandrel (25) which urges the pattern segments (15) radially outwards and locks them in the annular array.

10. A method according to any one of claims 7 to 9, wherein the pattern segments (15) have been formed by machining.

11. A method of producing an annular casting wherein the casting is cast in a sand mould which has been formed by a method according to any one of claims 7 to 10, where-after the portion of the casting defined by the pattern ring is subjected to machining.