US2475396A - Casting apparatus - Google Patents

Description

Juy E949. N. LESTER CASTING APPARATUS 2 Sheets-Sheet l Filed Oct. lO, 1946 mm mw E mL N Hh .w N.

fof ATTORNEYS R E s E L N.

CASTING APPARATUS Filed oct. 1o; 1946 2 Sheets-Sheet 2 INVENTOR. NATHAN LESTER f w ATTO/Neva Patented July 5, 1949 3 Claims.

The present invention relating generally as indicated to a casting'apparatus without regard to either the casting or molding material employed or the article formed thereby is, however, particularly concerned with the forming, for example, of electric motor armatures wherein a onepiece aluminum or other high heat conductive material skeleton in the laminated body of the armature effectively dissipates the heat gener ated in said body and serves as a frame for retaining the laminations in firm abutting relationship. Eective heat dissipation by such a skeleton, even though formed of a material such as aluminum which has a high thermal conductive constant compared to that of the iron laminations, is, nevertheless, largely dependent upon the forming of the skeleton so as to include a series of relatively thin webs and ns which present large heat dissipating surfaces per unit mass of metal.

Prior to the advent of the present invention, the forming of articles of the character indicated was considered impracticable for at least two reasons, viz. (1) because of the partial solidication of the metal in the small cross section mold cavities before being completely filled with metal, thereby producing porous castings with cold shuts and other defects, or (2) because in order to make sound castings without such defects, it was necessary to heat the mold to a temperature approaching that of the metal injected thereinto and then to cool the mold to effect solidication of the metal. The latter procedure, in addition to consuming a lot of time, entailed the added expense of employing elaborate heating and cooling equipment.

In further elucidating on the first reason above which refers to a cold chamber process, itcan be seen that when the article to be cast is annular in form and includes many thin webs as does the armature herein disclosed, a center shot is not feasible because the molten material in the horizontally disposed injection chamber prematurely runs into the mold cavity and partially solidies therein before the entire cavity can be filled. Such incomplete filling4 is especially undesirable in armatures of the character indicated in that the' entire 'unit will be out of balance and the heatgenerated therein will be unevenlyconducted away. Furthermore, cold shuts and other defects at critical points may weaken the skeleton to the point where portions thereof will be thrown oif by centrifugal force and thereby cause serious damage to the surrounding motor housing. An off-center shot will, of course,

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take care of the premature running of the material into the cavity but, on the other hand, the material has to be flowed long distances to the upper corners of the cavity and thus has a chance tov partially solidify and impede complete filling of the cavity.

Accordingly it is one principal object of this invention to provide an apparatus by which articles of the character indicated can be efficiently made, said apparatus being characterized in that a center shot is rendered feasible.

It is another object of this invention to provide a methodand apparatus by which articles of the character indicated can be rapidly produced without encountering the dimculties heretofore experienced.

Another object of this invention is to provide a casting method and apparatus incorporating a novel arrangement for' assuring that the molding material in aheated and liquid state is continuously and quickly injected into the mold cavity so as not to permit cooling and partial solidification of portions thereof before the remaining portions are completely nlled.

4Additional objects and advantages of the invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particu` larly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative. however, of but a few of the various ways in which the principle of the invention may be employed.

In the drawings:

Fig. 1 is a central vertical cross section view of a portion of one form of casting apparatus illustrating the separable die blocks, a portion of the injection chamber in communication with the mold cavity formed by said blocks and the ejector mechanism Fig. 2 is a view similar to Fig. 1 but on a smaller scale and illustrating more fully the injection chamber and the plunger reciprocable therein;

Fig. 3 is a'transverse face view of oneof the die blocks as viewed along the line 33, Fig. 1, with the cast article and sprue adaptor removed;

Fig. 4 is a perspective view of the armature formed by the apparatus illustrated in the foregoing flgures;

Fig. 5 Iis a central vertical crosssection view of the. skeleton of the armature' illustrated in Fig- 4 atrasos taken along a plane transverse to the axis of the armature with the laminated body omitted;

Fig. 6 is a perspective view of one form of sprue adaptor which affords communication between the injection chamber and the mold cavity:

Fig. 7 is a fragmentary cross section view taken along line 'I-l, Fig. 1, illustrating more clearly the passage arrangement between the injection chamber and the mold cavity; and

Figs. 8 and 9 are perspective views of other forms of sprue adaptors.

Referring now to the drawings and first more particularly to Figs. 1, 2, 3, and 6 to 9; there is shown therein only those portions of the apparatus with which the present invention is concerned, viz. the combination of a horizontally disposed injection cylinder with separable die blocks which form a mold cavity therebetween.

As illustrated, the mold cavity for producing an article of the aforesaid character is formed between the several die blocks i, 2 and 3, die block I being preferably carried by a xed platen not shown and die blocks 2 and together being preferably carried by a movable platen not shown. In effect, the intermediate die block l2 is an integral part of die block 3, but in order to facilitate making of the mold cavity, such die blocks 2 and 3 are separately made and then secured together. Although the movement of the die blocks 2, 3 toward and away from die block I is usually guided by sliding the movable platen on suitable Ways and/or tie bars associated with the frame of the machine as for example illustrated in Lester et al. Patent No. 2,365,282 dated December 19, 1944 and Lester Patent No. 2,309,460, dated January 26, 1943, it is preferred that additional means be employed for the purpose of accurately locating the'die blocks I and 2, 3 relative to one another at least when brought together. Such additional locating means in the present case comprises dowels d fixed in die block I and having close 4sliding engagement in bushings 3 fixed in die block 2 Associated with the die block assembly 2, 3 is an ejector mechanism comprising an ejector plate 6 having several push pins 'I projecting therefrom through the die blocks 2, 3 with the ends thereof engaging the parting line face of die block I and ejector pins 6 through die block 3 projected into the mold cavity and adapted to engage the molded article and displace the same from the mold cavity. The ejector plate 6 is actuated in one direction through a plate 9 provided with a gear rack Ill in mesh with a rotatably supported pinion II and in the other direction by engagement of the parting line face of die block I' with the ends of the push pins 1. In operation, after the die blocks i and 2, 3 have opened, the gear II is rotated counter-clockwise, as viewed in Figs. 1 and 2, to cause the ejector plate 6 to be urged toward the leftrelative to die block-2, 3 to thereby displace the molded article from the die block 2, 3 or at least free the article so that it can be readily removed.

The die block I as aforesaid is preferably mounted in a. nxed platen and has tted into a central opening therethrough a plunger bushing I2, said bushing forming an extension of the injection cylinder I3 fixed to the die block i. The

injection cylinder I3, as best shown in Fig.4 2

. comprises an elongated horizontally disposed cylinder having a lateral opening ill through which molding material in a liquid state can be sup- A plunger I5 reciprocable in cylinder I3 and bushing I2 when moved toward the right from the solid line position shown in Fig. 2 will obviously first close the lateral opening I4 and then, in a manner to be explained, force the molding material from the injection chamber into the mold cavity.

The molded article I3 herein illustrated comprises the laminated body made up of a plurality of thin plates Il, and annular rings I8 at each end of said body integrally connected to one another by thin webs I 3 which pass through generally radially disposed slots in the body, such slots extending transversely of the plates I'l from one end to the other of the body. Projecting from each annulus i8 are a plurality of fins 23. The laminated body has a central opening 2d therethrough into which a shaft, not shown, is adapted to be press tted or otherwise/secured to form trunnions for rotatably supporting the same. The armature illustrated is intended for use in a motor of the rotating field type and, of course, as is well known, the laminated body minimizes hysteresis and eddy current losses. Plates I'I are of iron and each is preferably about .025 inch thick and preferably has a thin heat-resisting insulating coating or film on its opposite faces whereby the plates in assembled relation are insulated from one another. Although such laminated structure does materially reduce the hysteresis and eddy current losses, as compared with a, solid iron body, there is yetv considerable heat generated in such body. The reason for incorporating the webs I9, the annuli i8 and the fins 20 in such laminated body is to dissipate such heat. This can be most eectively done by making the aforesaid elements Iii, Id and 23 from a high heat conductive material and proportioning the sameso as to present large heat absorb ing and radiating areas. In this way, the heat generated in the laminated body is picked up by the webs I9 and conducted to the annuli I8 and fins 20 from which it is effectively dissipated during-rotation of the armature. Of course, in some cases it may be desirableto omit the fins on either or both of the annuli I8. Furthermore, it is to be noted that the webs I9 are inclined relative to the axis of the body whereby still greater heat radiating areas are provided. The elements I8, I9 and 20, being integrally connected, constitute a skeleton, see Fig. 5, which, in addition to effectively dissipating the heat generated in the laminated body, serves as a framework to tie the plates II together as a single unit. While it is preferred that this skeleton be made of aluminum because of its light weight (approximately 1/3 that of iron) and good heat conducting properties (approximately 3 to 5 times that of iron) and low melting point (less than 1/2 that of iron), there are other metals such as copper, gold, magnesium, silver, etc. which might be satisfactorily used. However, while the aforesaid metals may have good heat conducting properties, they may be undesirable from the standpoint of high melting point, excess weight, prohibitive cost, etc. In addition to the aforesaid metals, it is also conceivable that many metal alloys could be satisfactorily used and possiblycertain plastic materials particularly those of the thermosetting type.

The mold cavity for forming the above described armature is essentially in three parts, namely, the cavities for the annuli I 8 and ns 20 Y in die blocks I and 3, and the cavity in die block plied into the injection chamber Adefined by the l inner walls of the cylinder and plunger bushing.

2 surrounding the laminated body. Thev cavity .in die block lI is formed in a chamber disposed concentrically about-the plunger bushing I2, in

which chamber the slotted insert 2i defines with die block l and plunger bushing |2 one annulus i8 and the series of ilns 20 projecting therefrom. An identical insert 2l lsecured in an annular chamber defined between die block 3 land a centrally projecting part 22 forms the other annulus it and series of ns 2U. The webs' I9 are delined by slots extending from end to end of the laminated body and the central opening 23 in die block 2 provides an annular chamber into which molding material may flow, such material being usually machined off in finishing the article. Opening 23 is preferably slightly tapered so as to be larger in diameter at its left-hand end to thus facilitate removal of the molded article. It is to be noted that the ends oi the slots defining webs it are in communication with the cavities defining the annuli it and that such latter cavities are in communication with the cavities defining the fins 2d. Likewise, such slots are in communication with the annular chamber surrounding the body.

Surrounding the mold cavity in each die block is a .passage '23 terminating at its ends in an inlet 2t and an outlet 2l', through which passage a suitable cooling medium such as cold w-ater may be circulated to prevent excessive heating of the die blocks and thus provide a relatively cool mold cavity.

`Having thus described the mold cavity, reference will now be made to the means for holding the plates l together during molding and the means for establishing communication between the injection chamber and the mold cavity. As

to the former, the plates il' are snugly itted over a shaft 2t. The projecting end of shaft 2t is adapted to be slip fitted into an opening in the part 22 in die block 3 in order to centrally locate the body in the cavity. As to the latter, the other end of shaft 23 has the reduced end portion M of a sprue adaptor 29 slip fitted thereinto. Said sprue adaptor has la generally frusta-conical head which is adapted to extend into a corresponding frusto-conical bore in the end of the plunger bushing l2 and to make sealed or substantially sealed engagement therewith when the die blocks land 2, 3 are closed. A portion of the outer periphery of the sprue adaptor is cut away 'as at 3d to thus define with the Wall of the bore in the plunger bushing l2 a part annular chamber. Such part annular chamber, for a reason which will :be presently explained, is disposed at the upper portion of the plunger bushing bore. The right-hand end of the plunger bushing l2 which is adjacent one end of the laminated body is likewise provided with a cut away portion 3| terminating at its outer periphery in several channels 32. In register with channels 32 are channels 33 in the insert 2, such latter channels leading into the annular chamber defining the annulus i8. The cut -aw-ay porti-on 3| is in register with the cut away portion 30 and, therefore, it can be seen that molding material from the injection chamber can be forced directly into the mold cavity through the cut away portions 3|! and 3l and the channels 32 and 33.

The sprue adaptor described above is that i1- lustrated in Figs. l, 2, 6 and 7. 'I'he sprue adaptor 35 illustrated in Fig. 8 is not only peripherally cut away at 36 but has a reduced rearward end 3l either all the Way around asshown or only part-way around if desired. Such reduced end 31 defines with the laminated body and the plunger bushing I2 an annular chamber having a portion thereof disposed below the normal level of molten material in the cylinder' I8. Radially outward of such-annular chamber, the plunger bushing |2 and the insert 2| will be provided with further channels 32 and 33 to thus assure uniform and quick distribution of the molten material to all parts of the mold cavity when the plunger l5 is moved to the right as viewed in Fig. 2. The en'd of sprue adaptor 35 is further reduced as at 44 to provide an axial projection adapted to have a sliding nt within shaft 2t.

The sprue adaptor 38 illustrated in Fig. 9 has a cut away portion 39 which, adjacent the rearward end of the sprue adaptor terminates in oppositely extending grooves il! and l, such grooves extending only partway around the periphery. The flange defined between the grooves tu and ill and the rearward end of the sprue adaptor is cutaway as at 42 'and llt to provide diametrically opposed passages in communication with several diametrically opposed channels 32 and 33 in the plunger bushing I2 and insert 2l respectively. With this sprue adaptor the molten material, when the plunger is moved toward the right in Fig. Z, will flow through cutaway portion 39. grooves lll and lll, passages l2 and d3 yand channels 32 and 33 into the mold cavity. By providing such large size diametrically opposed passages leading to the mold cavity, the molten material can be quickly and uniformly fiowed into the mold cavity. Sprue adaptor 33 yalso has a reduced end portion 3ft ad-apted to slidably fit within the shaft 28.

The relationship of the size and location of the inJection chamber to the passage -between the injection chamber and the mold cavity and to the mold cavity is such that molding material in the injection chamber in volume sufficient to fill the cavity, the passage and a small portion of the injection chamber, as indicated by the dotted line 34 in Figs. 1 and 2, can only communicate with the m'old cavity upon movement of the plunger l5 toward the right, as viewed in Figs. 1 and 2. to first close the lateral opening vIll and raise the level of the molding material up to such passage. With an arrangement such as this, no molding material can prellminarlly flow into the relatively cool mold cavity and solidify therein prior to the mold cavity and the passage leading thereto being filled. In fact, the molding material is rapidly and continuously shot into the mold cavity under pressure so as to completely illl the same before portions thereof have par,- tially solidled. Such quick shot action eliminates forming of cold shuts in the casting. Furthermore, such metal solidifies so rapidly in the relatively cool mold cavity, that the die blocks can be separated and thev completed article removed without having to wait any appreciable length of time. A further feature flowing out of the labove arrangement is that the material solidies and cools before the die blocks and laminated body have a chance to appreciably heat up and expand, whereby when the webs I9 cool and contract, such contraction is effective to draw the l5 22 and bushing l2 securely clamp the laminated farmaco body therebetween. vMolding material in a liquid state and in volume suiiicient to nll the mold cavity, the passage leading thereto and a small portion of the injection chamber is then poured into the injection chamber through the l-ateral opening I4. The level of such volume of molding material is, as clearly illustrated in Fig.v 2, well below the cutaway portion of the sprue adaptor so that no material has yet been flowed into the mold cavity. The plunger I is then moved toward the right to close the opening I4 and simultaneously raise the level of the material in. the injection chamber. After the opening I4 has been closed, continued movement of the plunger will raise the level of the material up to the sprue adaptor passage and channels 32 and 33 and permit the material to flow into the mold cavity. The movement of the plunger I5 is relatively rapid and continuous whereby the mold quickly fills up. When the mold cavity and passages are filled, the pressure exerted by plunger I5 will effect a compacting action on the material and further force it into all of the corners of the cavity. Inasmuch as the material quickly solidifies in the cool mold cavity, the plunger can be immediately withdrawn and the die blocks separated to eject the completed article. The slug of material in the channels 32, 33 and in the sprue adaptor passages and in the injection chamber between the left-hand end of the sprue adaptor up to the dotted line 34 can be cut oiT at the inner periphery of the annulus I8. With such slug removed, the sprue adaptor can-then be removed, as can the shaft 28. The armature so formed can then be tted with the shaft forming the trunnions on which it can be rotatably mounted in a motor housing. If the opening 23 in die block 2 is larger than the laminated body as shown in Fig. 1, the layer of material around the periphery of the laminated body can be removed if desired in a lathe or like machine tool. It is to be observed that the clamping of the laminated body between the die blocks I and 3, as described above, assures that the plates I 'I will be compacted together, whereby no material can be squirted between them during the casting operation.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

l. A pressure casting apparatus for forming.

articles, said articles having a cylindrical Ibody and an annular ring portion with circularly arranged radial ilns projecting axially therefrom, comprising separable d ie blocks` forming a chamber for said body and a mold cavity corresponding with such annular ring portion, one of said die blocks being formed with a bore therethrough coaxial with such cavity, a tubular sprue bushing fitted within such bore, one end of such bore 4being enlarged whereby to form an annular recess .formed with `central opening coaxial with said sprue bushing, a shaft adapted to support said body therearound and having one end slidably fitting within such opening, a plug projecting axially into said bushing and including an axially extending groove in its upper surface defining with said bushing a passage leading from within said cylinder to such channels, said plug having a sliding fit with the other end oi said shaft, and a. plunger movable in said cylinder to force material to be cast from said cylinder through said passage .and channels into such cavity and thence from such cavity into the slots of said insert.

2. A' pressure lcasting apparatus for forming articles, said articles having a cylindrical body and an annular ring portion with circularly arranged radial flns projecting axially therefrom, comprising separable die blocks forming a chamber for said body and a m-old cavity corresponding with such annular ring portion, one of said die blocks being formed with a bore therethrough coaxial with such cavity, a tubular sprue bushing ntted within such bore, one end of such bore being enlarged whereby to form an annular recess with said sprue bushing, a one-piece tubular insert snugly iltted in such recess having the end thereof which is adjacent such cavity formed with slots radially therethrough corresponding with such ns, one end of said ybushing and insert- Abeing formed with diametrically opposed channels leading from within the former into such cavity, a horizontally disposed injection cylinder co-axial with such cavity and engaged with vthe other' end of said bushingthe other of said die blocks being formed with a central opening coaxial with said sprue bushing, a shaft adapted to support said body therearound and having one end slidably fitting Within such opening, a plug projecting axially into said bushing and including an axially extending groove in its upper surface defining with said bushing a passage leading 'from`within said cylinder to such channels, said plug having a sliding nt with the other end of said shaft, such groove terminating in diametrlcally opposed branches communicating with such channels, and a plunger movable in said cylinder to force material to be cast from said cylinder through said passage, branches, and channels into such cavity and thence from such cavity into' the slots of said insert.

3. A pressure casting apparatus for forming articles, said articles having a cylindrical body with a skeleton cast thereabout, which skeleton includes an .annular ring portion at each end of said body connected together by circularly arranged radially disposed webs through said body and circularly arranged radial hns' projecting axially from each such ring portion, comprising separable die blocks formed with opposed central hollow, coaxial projections adapted to engage the ends of saidbody and thereby clamp the latter therein,lsaid die blocks together with such projections and body defining annular chambers at each end of such body corresponding .with the aforesaid annular ring vportions of such skeleton, a tubular insert in each su-ch chamber'each having the end thereof which faces the respective. chamber formed with slots radially therethrough corresponding with -such nns of such skeleton, the end of one of such projections and the associated insert being formed with registering channels communicating with the asso ciated chamber, an injection cylinder co-axial with said die blocks having communication with ,said .one/oi .sucht projections, a. shaft vcentralrsaid cylinder to such channels,

ly through such body adapted to support the latter and having one end slidably iitting within the other of such projections, a plug projecting axially from said body into said one of such projections and including an axially extending groove in its upper surface dening with said one of such projections a passage leading from within said plug having a sliding t with the other end of said shaft, and a plunger movable in said cylinder to force material to loe-cast from said cylinder through such passage and channels into the lassociated chamber and thence from such chamber into the slots of one ofV said inserts, through said body into the other of such chambers and into the slots in the other of said inserts.

. NATHAN LESTER.

10 REFERENCES CITED The following references are of record in the le of this patent:

Stern, McGraw-Hill Seventh Avenue, New York, rst edition, 1930.

Book Company, Inc., 370 Y

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