US2887744A - Pattern for impeller core - Google Patents

Description

May 26, 1959 2,887,744

D. HALLIDAY v PATTERN FOR IMPELLER CORE Filed Sept. 20, 1957 3 Sheets-Sheet 1 /NVNTO R. 0/9 V/D HALL/Dav May 26, 1959 D. HALLIDAY PATTERN FOR IMPELLER com:

Filed Sept. 20, 1957 3 Sheets-Sheet 2 INVENTOE. DAV/0 HALL/DAY BY HIS HTTORNEYS HARRIS, K/ECH, Fosrae 3; HARQ/s D. HALLIDAY PATTERN FOR IMPELLER CORE May 26, 1959 3 Sheets-Sheet 3 Filed Sept. 20, 1957 INVENTOR- DAV/D HALL/DAY United States Patent 2,887,744 PATTERN FOR IMPEIJLEREORE David Halliday, Huntington =Park, oann, assignor, by

me'sne assignments, to Dresser Industries, Inc, a corporation of Delaware Application'September -20, "1957,Seriril Not-685,7 81

4 Claims. (Cl. 22-158) The present invention relates in general to patterns for making molds or cores and, more particularly, to

a pattern for making a mold or core which is to be used in the casting of an article including components having complex configurations, or components arranged in complex fashion.

Since the present invention was initially embodied in and is particularly applicable to a pattern for making a core to be used in the casting of a centrifugal pump impeller having internal, outwardly spiralling passages, the invention will be considered herein in connection with such an impeller for convenience in effecting a disclosure thereof.- However, it will be understood that the invention is applicable to patterns for making molds or cores utilized'in the casting of other articles as Well.

In a centrifugal pump impeller of the type under consideration herein, the internal, outwardly spiralling passages receive the fluid to be pumped through an axial inlet and discharge the fluid radially outwardly by centrifugal action. These internal passages are separated by integral, outwardly spiralling blades which are twisted from their inner ends toward their outer ends and which thus have complex curvatures. In making a core for use in casting such a centrifugal pump impeller, the core sand or other material of which the core is made must be provided with cavities conforming in configuration to the desired blade configuration and conforming in arrangement to the desired bladearrangement. Because of the intricate blade shapes and'blade arrangements involved in impellers of this kind, the making of cores from which impellers with the proper blade configurations and arrangements may be cast presents difiicult core-making problems, a primary object of the invention being to overcome such problems in a simple and straightforward manner.

One conventional way of making cores for use in the casting of centrifugal pump impellers involves making each core in a plurality of circumferentially arranged sections suitably secured together with gaps therebetween to form the blades. This procedure is open to objection because of the time and expense involved in making and piecing together a plurality of core-sections.

Another conventional practice is to mount a plurality of blade patterns in a core box and fill the spaces therebetween with core sand. Subsequently, the blade patterns are removed from the core box manually one at a time to leave the desired blade cavities in the core. This practice requires extreme care and skill on the part of the core maker in twisting or threading the blade patterns out of the cavities in the core without damaging the core. This practice is time consuming and thus expensive, and is open to the additional disadvantage that-the core may be damaged to such an extent that discarding thereof is necessary.

An important .object of the invention is to provide a pattern capable of making .a one-piece core, thereby avoiding the disadvantages of a sectional core, and capable of mechanically guiding the blade .patterns out figurations of the blade patterns, and thus conforming to the configurations of the cavities in the core.

Still more particularly, an important object of the invention is to provide interengageable means solely on the'guidemember and the blade patterns for twisting or .threadingthe blade patterns out of engagement with the guide member along curved paths the curvatures of which conform to the curvatures of the blade patterns, and thus conform to the curvatures of the cavities in the core.

With the foregoing impeller corepattern ofythe invention, the guide member and the blade patterns cooperate to twist or thread the blade patterns out of the cavities in the corein such a manneras to minimize the possibility of damageto the core, which is an important feature.

Another objectof the invention is to provide a guide member having curved guide slots therein which receive-the curved bladepatterns and through. which the bladepatterns extend from one side ofthe guide member to the other, the blade patterns being adapted to form the desired core on one side of the guide member and beingprovided on the other side of the guide member with heads or handles by means of which they may be removed from the cavities in the core through the guide slots in the guide member.

Anotherobject is to provide guide slots and blade patterns the configurations of which are so related that the blade patterns can be removed from the cavities in 'the core only along paths the curvaturesof which conform to the curvatures of the cavities in the core so that the. possibility of damage to the core is minimized.

A further object of the invention is to provide a pattern wherein the interengageable means mentioned for guiding the blade patterns out of engagement with the guide member include interengageable cam surfaces respectively located at theedges of the guide slots and on the blade patterns. Therelated object is to provide such cam surfaceswhi ch comprise beveled edges of the guide slots and complementary beveled surfaces on the blade patterns.

The foregoing objects, advantages, features and results of the present-invention, together with various other objects, advantages, features and results thereof which will be evident to those skilled in this art in the light of the present disclosure may be attained with the exemplary embodiment of the invention described in detail hereinafter and illustrated in the accompanying drawings, wherein:

Fig. 1 is a perspective viewof one side of an impeller core pattern of the invention;

Fig. 2 is a perspective view ofthe opposite side of the impellercore pattern;

Fig. 3 is a view, partially inlon-gitudinal section and partially in elevation, of a core box incorporating the impeller core patterm-Fig. 3 being taken substantially along-the irregular arrowed line -3-3 of Fig. ltwith respect to the impeller core pattern;

Fig. 4 is a view, partially in longitudinal section and partially-in-elevatiomwvhich is-similar to Fig. 3, butwhich 3 of shown in Fig. 3 and shows part of the core box housing removed; and

Figs. 5, 6, and 7 are partially sectional and partially perspective views illustrating the manner in which an impeller blade pattern of the invention is removed from a guide member thereof and from a cavity formed in an impeller core by the blade pattern, Figs. 5, 6, and 7 being somewhat diagrammatic and thus subject to some distortion.

In the drawings, the numeral 10 designates an impeller core box which includes two housing members 12 and 14 adapted to receive therebetween a guide member 16 and impeller blade patterns 18 of the invention. As will be described in more detail hereinafter, these components cooperate to make a core 20 for use in the casting of a centrifugal pump impeller having internal, radially outwardly spiralling passages.

Considering the core box 10 in more detail, the guide member 16 and the housing member 12 are spaced apart axially of the core by a central boss 22 on the housing member 12 and an annular rib 24 on the guide member. The housing and guide members 12 and 16 are adapted to be clamped together by a nut 26 seated against the housing member 12 and threaded on a stud 28 carried by the guide member 16. The housing member 14 is adapted to seat on another annular rib 30 on the guide member 16 and is provided with a marginal flange 32 which telescopes over the annular rib 30.

The housing and guide members 14 and 16 are provided with annular surfaces 34 and 36, respectively, which are convex and concave, respectively, in cross section and which provide the core 20 with axially spaced surfaces 38 and 40, respectively, corresponding to axially spaced walls of the outwardly spiralling internal passages through the centrifugal pump impeller ultimately to be formed by the core. The blade patterns 18 provide the core with surfaces 42 which correspond to radially spaced walls of the outwardly spiralling internal passages of the ultimate impeller, the surfaces 42 of the core being the walls of impeller blade cavities 44 formed in the core by the patterns 18.

Considering generally the relationship between the guide member 16 and the blade patterns 18, it will be noted that the blade patterns have rather complex configurations and may perhaps best be described as curving or spiralling generally radially outwardly away from the axis of the guide member to provide the surfaces 42 of the core 20 with the configurations necessary to form the corresponding walls of the internal passages of the centrifugal pump impeller with the requisite shapes. Because of the complex configurations of the blade patterns 18 and the cavities 44 in the core 20 formed thereby, it is necessary to guide the blade patterns out of the cavities 44 along curved paths the curvatures of which conform to the curvatures of the blade patterns and the cavities so as to prevent damage to the core 20, the present invention providing interengageable means on the guide member and the blade patterns for guiding the blade patterns out of the cavities in the core in an accurate and positive manner.

More particularly, the guide member 16 is provided therethrough with a plurality of guide slots 46 which curve or spiral generally radially outwardly from the axis of the guide member and which are spaced apart circumferentially about such axis. The blade patterns 18 are insertable into the guide slots 46 and extend therethrough from one side of the guide member 16 to the other, the blade patterns having edges 48 which are engageable with the convex surface of the housing member 14. Thus, the blade patterns 18 divide the core 20 into radially outwardly spiralling sections 50 corresponding in configurations to the configurations of the internal passages in the centrifugal pump impeller which is ultimately cast from the core 20.

The blade patterns 18 are provided, on the side of the guide member 16 which is adjacent the housing member 12, with enlarged heads 52 serving as handles by means of which the blade patterns 18 may be grasped manually to remove them from the guide slots 46 in the guide member 16 and from the cavities 44 in the core 20. The heads 52 of the blade patterns 18 seat against the housing member 12 of the core box 10, as shovm in Fig. 3 of the drawings, when the core box is assembled, whereby the housing member 12 prevents inadvertent removal of the blade patterns 18 from the guide slots 46.

The heads 52 of the blade patterns 18 are provided with beveled or tapered cam surfaces 54, 56, 58 and 60 which converge generally toward the edges 48 of the blade patterns and which are adapted to seat on complementary cam surfaces 64, 66, 68 and 70, respectively, forming the edges of the guide slots 46. As will become apparent, the relationships between the curvatures of the blade patterns and the guide slots 46 and the relationships between the configurations of the beveled surfaces 54, 56, 58 and 60 on the blade-pattern heads 52 and the beveled surfaces 64, 66, 68 and 70 on the guide member 16 are such that the blade patterns may be disengaged from the guide member only by movement of the blade patterns axially and generally radially outwardly out of the cavities 44 in the core 20 along curved paths conforming in curvature to the curvatures of the cavities 44. Thus, damage to the core 20 as the blade patterns 18 are withdrawn from the cavities 44 therein is prevented, which is the important feature of the invention.

Considering the operation of the invention, the housing member 12, the guide member 16 and the blade patterns 18 are assembled with the housing member 12 resting on a suitable supporting surface, the blade patterns 18 thus projecting upwardly through the guide member 16. In other words, the housing member 12, the guide member 16 and the blade patterns 18 are assembled and oriented in the manner shown in Fig. 3 of the drawings, with the housing member 14 removed.

Core sand of any suitable composition is then packed around the blade patterns 18 above the guide member 16 within the confines of the annular rib 30 on the guide member, this being accomplished by any suitable process. Thereafter, the housing member 14 is placed on the guide member 16 and the blade patterns 18 with the convex surface 34 of the housing member 14 in engagement with the edges 48 of the blade patterns 18 and in engagement with the rib 30 on the guide member, the marginal flange 32 of the housing member 14 being telescoped over the annular rib 30. Subsequently, the interior of the housing member 14 is packed with core sand to the level 72 in any suitable manner, thereby completing the formation of the core 20.

Before baking the core 20, the blade patterns 18 are withdrawn from the cavities 44 which they form in the core. Considering how this is accomplished, the core box 10 is first inverted and the housing member 12 is removed, thereby leaving the heads 52 of the blade patterns exposed, as shown in Figs. 2 and 4 to 7. Then, the blade patterns 18 are withdrawn from the cavities 44 through the guide slots 46, as will now be described.

Referring to Figs. 5 to 7, the operator grasps the head 52 of a" blade pattern 18 and withdraws it from the corresponding guide slot 46 and core cavity 44 along a curved path which conforms in curvature to the curvature of the blade pattern, the path in question being determined by i'nterengagement of portions of the blade pattern and the edges of the corresponding guide slot. As will be apparent from Fig. 6, the curvatures of the blade pattern 18 shown and the corresponding guide slot 46 require combined axial and generally radially outward movement of the blade pattern to achieve withdrawal of the blade pattern, it being impossible to withdraw the blade pattern by subjecting it to anything other than combined axial and generally radially outward movement. As clearly shown in Fig. 6, the beveled surfaces 54 and 64 in particular assist in guiding the blade pattern shown out of the corresponding cavity 44 and guide slot 46 along the prescribed path.

The net result of the interaction of each blade pattern 18 and the guide member 16 in guiding the blade pattern axially and generally radially outwardly along a curved path which conforms in curvature to the curvature of the blade pattern and the corresponding guide slot in this fashion, is that the sides of the blade pattern move generally parallel to the surfaces 42 of the cavity 44 at all times. In effect, each blade pattern 18 is unscrewed from its cavity 44 in the core 20. Thus, the possibility of damage to the core as the blade patterns 18 are withdrawn is minimized, and no particular skill in removing the blade patterns is required in view of the positive and accurate guiding action resulting from interengagement of the blade patterns and the guide member 16, which are important features of the invention.

After the blade patterns 18 have been withdrawn in the foregoing manner, the guide member 16 is removed and the core 241 is baked in the usual manner. Thereafter the core 20 is utilized in the casting of a centrifugal pump impeller in accordance with conventional practices unnecessary to relate herein.

While the blade patterns 18 and the guide member 16 may be formed in various ways, it is convenient to make the blade patterns in wood first and then cast them in brass. Subsequently, the guide member 16 is cast around the blade patterns 18 in aluminum, which will not fuse to the brass. In this fashion, the guide slots 46 are formed automatically.

Although an exemplary embodiment of the invention has been disclosed herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims which follow.

I claim:

1. In an impeller mold pattern, the combination of: a guide member having an axis; a plurality of spirally curved blade patterns circumferentially spaced apart about said axis and engageable with said guide member, said blade patterns spiralling generally radially outwardly away from said axis; and a plurality of spirally curved interengageable means on said guide member and on said blade patterns, respectively, for guiding said blade patterns axially and generally radially outwardly out of engagement with said guide member along spirally curved paths the curvatures of which conform to the curvatures of said blade patterns.

2. In an impeller mold pattern, the combination of: a guide member having an axis and provided therethrough with a plurality of spirally curved guide slots which spiral generally radially outwardly from said axis and which are spaced apart circumferentially about said axis; a plurality of spirally curved blade patterns receivable in said guide slots, respectively, and adapted to extend therethrough from one side of said guide member to the other; and guide means including guide edges of said guide slots and complementary guide surfaces of said blade patterns, respectively, for guiding said blade patterns axially and generally radially outwardly out of said guide slots along spirally curved paths conforming in curvature to the curvature of said blade patterns.

3. In an impeller mold pattern, the combination of: a guide member having an axis and provided therethrough with a plurality of spirally curved guide slots which spiral generally radially outwardly from said axis and which are spaced apart circumferentially about said axis; a plurality of spirally curved blade patterns receivable in said guide slots, respectively, and adapted to extend therethrough from one side of said guide member to the other; and guide means, including guide edges of said guide slots and complementary guide surfaces of said blade patterns, respectively, for guiding said blade patterns axially and generally radially out of said guide slots along spirally curved paths conforming in curvature to the curvature of said blade patterns, said guide edges of each of said guide slots and said complementary guide surfaces of the corresponding blade pattern being beveled.

4. In a impeller mold pattern, the combination of: a guide member having an axis and provided therethrough with a plurality of spirally curved guide slots which spiral generally radially outwardly from said axis and which are spaced apart circumferentially about said axis; a plurality of spirally curved blade patterns receivable in said guide slots, respectively, and adapted to extend therethrough from one side of said guide member to the other; and guide means, including guide edges of said guide slots and complementary guide surfaces of said blade patterns, respectively, for guiding said blade patterns axially and generally radially out of said guide slots along spirally curved paths conforming in curvature to the curvature of said blade patterns, said guide edges of each of said guide slots and said complementary guide surfaces of the corresponding blade pattern being beveled and diverging in the direction of withdrawal of the blade pattern from the guide slot.

References Cited in the file of this patent UNITED STATES PATENTS 165,237 Jones July 6, 1875 416,333 Hogan Dec. 3, 1889 1,443,341 Brown Ian. 30, 1923 2,361,140 Pfeiffer Nov. 3, 1942 2,611,161 Paul Sept. 23, 1952 2,702,418 Miner Feb. 22, 1955 2,741,817 Wilkins Apr. 17, 1956 2,782,477 Bean Feb. 26, 1957

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