US2569899A

US2569899A - Mold for casting crankshafts

Info

Publication number: US2569899A
Application number: US69659A
Authority: US
Inventors: Howard W Miner
Original assignee: Fairbanks Morse and Co
Current assignee: Fairbanks Morse and Co
Priority date: 1949-01-07
Filing date: 1949-01-07
Publication date: 1951-10-02
Anticipated expiration: 1968-10-02

Description

Oct. 2, 1951 H, w, MlNER 2,569,899

MOLD FOR CASTING CRANKSHAFTS Filed Jan. 7, 1949 2 sheets-sheet 1 INVENTOR FIG. 4. HOWARD W. MINER a A, /ofu/ ATTORNEY Oct. 2, 1951 HV1/.MMR 2,569,899

MOLD FOR CASTING CRANKSHAFTS Filed Jan. 7, 1949 2V sheets-sheet 2 FIG. 6.

FIG. 7.

lNvEN'roR HOWARD W. MINER ATTO RNEY Patented Oct. 2, 1951 UNITED STATES MOLD Fon CASTING CRANKSHAETS.

Howard W. Miner, Belair, Wise., assigner .to `franlianks, Morse a tion ef Illinais Application J anuary 7, 1949,:.Se17ia1 IXe-.695.519

l This invention relates vto the casting of. irregular shaped objects, `such as crankshaftsand the like, and one o f ythe importantobjects 'is `tdirnll prove upon the method 'of'a'casting and the "teen` nique for arranging a mold for. casting slii'ch' obl jects.

' It is also an important object to provide improvements in the vmethod of and `ari@angemer'1t for gating and risering thecasting `mold.cavities to optain a uniform flow and deposit affine-casta. ing metal, and assure an adequate supply of c alsftL ing metal to compensate for shrinkageduring solidification.

Another object of the invention resides in the improved technique of supplying casting` 'metal to the risers to avoid undueagitation ofthe inolten metal collecting the mold cavities, and to the further technique of maintaining' the `fluid condition of the casting metal in the risers at least until the solidication and shrinkage Iof the metal has occurred in the mold cavities.

Other objects and` advantagesof the invention will become obvious from the detailed descrip relating to certain preferred embodiments hereof,

the same being disclosed `in the accompanying drawing, wherein:

Fig. 1 is a longitudinal sectional elevation, through a mold assembly for casting 'amcrankl shaftjand in which the cavities and risers are shown to advantage;

Fig. 2 is a top plan view of the lower or drag portion of the mold of Fig. 1;

Fig. 3 is a bottom view of the upper or cope portion of the mold of Fig. 1, showing the arrangement and disposition of runners, gates and risers; Fig. 4 is a sectionalelevational view taken at line 4 4 of Fig. 1;

Fig. 5 is a transverse sectional elevational view of a somewhat modied arrangement of mold assembly;

Fig. 6 is a top plan view of the lower or drag portion of the mold of Fig. 5; and, A

Fig. 7 is a bottom view of the upper or cope portion of the mold assembly shown byFig. 5, `and in which the arrangement of runners, ingates and risers have been clearly indicated.'

In Figs. 1 and 4 of the drawing, the mold assembly is seen to include a cope Ill and a drag'll Vlongitudinally divided in the plane of the crankshaft axis, so that parts of the mold cavities'which define the crankshaft article to be cast are located in each of the cope and drag portions of the mold.

`More specically, the cavities formed in the drag I l have been shown in Fig. 2, while those in the cope are clearly illustrated in Fig. 3. It is understood that the cavities in the sand of the cope and drag are formed by packing and ramming sand .about the cope and drag patterns and then withdrawing the patterns. In the following descrip- 1 einer. (o1. ca -134) 2 tion ofl the rnold aseeniblv, thematching parts oi' the." ieee in 'eerderegedegen; lee-identifi@ enumeran, since such cavity cavityl haveb'eenp videdl" Inasimilar'rnaneer, beire'ef eefjlk 24 2.5i and 28"`are`provdd," p neetedbv .respeetive @1eme Rie Cei/.ities 29 3.0', `3A 20 @refiere flzhe scheef ene-pieve Cremeren is r nd ed t o heres'pective an-l V`lirovvs `which, als may be seen 1n 1, pl 'es certain of the cavi "es sulos:i'ialntiazlly'"w e1157 in" "fcopejand'ether 25 c .i .1 1v.' :y il'. 5 w' 'It' is an important featune of the prese provments to previ hi. "geek ehek .anw-smaad i ascasee ingates above noted, the mold cope is formed with shrinkage make-up reservoir means lin the nature of a series of enlarged 4riser openings (Fig. 1)

which communicate with the mold cavities at or,

have been indicated in Fig. 3, and may beidentified by reference numerals having the suflix a. In addition to these risers, the cope also provides other risers (not shown) ywhich connect with and open to the pin cavity 29 at opening Gta and to the pin cavity 33 at opening 6Ia. The general relation of riser and riser opening to a mold cavity is illustrated in FigLll, in connection with the sectional view of riser 55 in Fig.' l.

The described system of runners, ingates and risers provides a flow of molten casting metal to all of the mold cavities substantially uniformally and together, enables the feeding of the lowest cavity areas which tends to maintain a uniform ylevel of molten metal and reduces appreciable ,endwise flow disturbances, and the upper riser connections permit rapid and complete venting of the mold cavities whereby the molten metal may fillV up such zones as the general level of casting metal rises to and begins flow into the several risers, which collectively constitute the reservoir means.

It is a further preference in the present method and technique of casting, to establish characteristics of directional solidication of the casting metal so that the final article may be free of imperfections at any part throughout its length. Such imperfections heretofore encountered, have usually been occasioned by imperfect venting of the cavities, to'o rapid chilling ofthe metal in certain mold cavities or Zones, disturbances in the flow of casting metal between cavities, and improper feeding of the metal from the risers back to the mold cavities during solidication shrinkage. These usual diiculties have now been obviated bythe application of directional solidification Within the mold cavities, and by means enabling the maintenance of fluidity of the casting meta] in the risers such that the same may be free to feed back to the mold during shrinkage, without restriction at the riser openings.

The directional solidii'lcation of the casting metal is cared for by the use of metallic chills located in the surfaces of i certain mold cavities in such positions as to be contacted by theincoming molten metal and immediately extract the heat therefrom to initiate solidication. The use of chills has already been suggested, however such prior use has been to position the chills near the central Zone of a mold cavity to initiate internal solidication ahead of any solidication taking place at the outer surfaces of the mold cavity. As a consequence, the chills become a part of the final casting, being completely embedded in the casting, and in some cases fusing into the casting metal. In the fpresent case, the chills are not so employed to initiate chilling or solidiiication at internal zones of the'casting, and as such do not become a part of the final product. By preference, the chills are positioned in the mold sand to provide heat absorbing zones in the surfaces of the mold cavities, and to initiate solidication of the casting metal'from the low points of the mold cavities." In this manner, the

4 object to be cast is caused to begin its solidication in its lowest areas, and the solidication progresses toward the risers -where the still fluid metal may freely feed back to the cavities to compensate for shrinkage and maintain the cavities completely filled throughout the process of solidication.

In the example illustrated in Figs. 1 to 4, the outer surfaces of the several mold cavities have been provided with embedded chills, and these chills have been located to attain the desired directional solidification of the casting metal. A representative case of the present use of chills may be observed in Fig. 4, wherein the lower or drag surfaces of the mold cavity I4 have embedded metallic chil1 elements I4c. In each instance where a mold cavity is provided with embedded chills, as in Figs. 1, 2 and 3, the chill or chills have been identified by the numeral designating the cavity with the addition of the suffix letter c. It is believed that this will obviate any further detailed reference to the chills.

A further feature hereof resides in the means for prolonging the fluidity of the casting metalcin the

several mold risers

53, 54, etc. Referring to Figs. 1 and 4, it will be observed that the walls of the riser 55 are provided with and are defined by embedded insulation blocks or elements 55b. In each instance, the insulation blocks associated with the

respective risers

53, 54, etc. have been indicated by the sufx letter b. These blocks may be formed of any suitable material which will stand up under direct contact by the high temperature molten metal, and it is preferred that the several blocks for each of the risers extend over a maximum vertical height of the riser so that the volume of metal therein may be maintained in a uid state until the solidilcation in the mold cavities has progressed into the riser bottom openings. It is also important to prevent premature or untimely solidication within each riser to preclude any obstruction forming in the riser openings 53a, 54a, etc. which could cause or result in incomplete feed back during shrinkage, or shrinkage breakaway of the -metal neckin these openings.

This last consideration is prevented bythe improved technique of boosting or increasing the temperature of the riser metal following completion of the pouring step and after the general level of casting metal in all of the risers has become established. Prior technique has involved the step of adding a quantity ofVv molten metal to each riser from the original ladle or by use of hand ladles. This prior technique is commonly referred to as riser touch-up, and when carried out in the usual manner results in a pronounced disturbance of the metal in the mold due to the gravitational unbalancing of the level of metal between risers and from .end to end of the mold. The presently improved method is to deposit a suitable quantity of thermite on the surface of the metal in each riser. This thermite may be ignited by a primer ma terial, in the usual manner, and upon ignition imparts a sudden charge of heat to the riser metal whereby to boost its temperature. The use of thermite, which is a well known compound, has the important advantages that itV does not disturb the level of the metal in any of the risers, and may be applied quickly and easily.V Thus the combination of insulating the risers by the block elements 53h, 5419, etc., and the application of therinite to boost the temperature of the riser metal will result in maintenance of theV fluidity of the metal until the mold cavities have become completely lled out and all shrinkage has been compensated.

The above described method and technique of casting is excellently suited to large articles, and has been carried out successful in the production of large crankshafts. When applied in the casting of smaller articles, the same general principles may be followed with Vcertain modications, as will now be described in connection with thel disclosure of a single throw crankshaft of Figs. 5, 6 and 7. In these latter views, the mold drag B5 contains portions of the cavities and the mold cope 55 contains the remainder of the cavities together with the sprue, ingates and reservoir means or riser. Following the saine system of indicating the cooperating portions of the cope and drag cavities by similar reference numerals, it can be seen that the article to be produced is characterized by such mold cavities as the end bearing cavities Bl' and 68, spaced crank cheek cavities 69 and a crank pin cavity 10. The mold drag 65 also contains the riser pocket 'H and the lower part of the runner opening 72, whereas, the mold cope 65 is provided with the sprue 'I3 leading from the pouring box 14 to a longitudinal runner passage 75. The runner 75 connects with the end bearing cavity 61 at spaced zones by means of ingates 'i6 and 17, and with the opposite cavity 98 by

ingates

18 and 79. The mold cavity' 79 is connected to the riser by means of the runner opening 72, it being clear that the complete riser is constituted by the respective drag and cope portion 'll and 8|.

During pouring, the molten metal substantially simultaneously flows into the cavities -67 and 58, and this, it will be observed, establishes the general flow trends from the end zones of the

cavities

67 and 68 toward the crank cheek cavities 69, and finally into the pin cavity 79. Since the molten metal is fed thereto at a number of ingates, it can be appreciated that very little endwise ow disturbances can occur in the

cavities

68 and 69, except that which is due to the ordinary and slow shrinkage process during solidilcation. The riser pocket 1l is by preference, given a suicient volumetric capacity to regulate its lling with molten metal in time with the lling of the mold cavities, so as to` provide ample opportunity for venting of such cavities to the riser portion 8l through the runner opening 12.

As the pouring continues, the level of the metal will eventually rise above the opening l2 and, as

this takes place, the metal in the runner 15 will back up and seek a flow path through the auxiliary passage or up-gate 82 (Fig. 5) where it may enter the upper zone of the riser 3|. The provision of up-gate 82 allows a direct flow of hot metal onto the riser metal to maintain or boostI its temperature for prolonged fluidity. Thus no riser touch-up is required to boost the temperature of such metal, and the gravitationally quiescent condition of the metal in the mold cavities is preserved during the solidification process. Further retention of the heat of the metal in the riser 8| is obtained by the use of a number of blocks 83 of insulation in the riser 6 endwise flow disturbances by preserving gravita tional balance of the metal level, and main'- tenance of luidity of the casting metal in the reservoir means or risers by insulating the same and by imparting thereto a temperature boost, is fully carried out in the preferred forms of the mold assembly shown by Figs. 1 to 4 or by Figs. 5 to 7. I-Iaving now fully and clearly described the features or the present invention, it should be understood that the method or technique in practicing the invention shall be limited only in accordance with the scope of the following claim.

I claim:

In a mold for horizontal casting of crankshafts, the combination of a mold drag section having a pattern impression of the crankshaft to be cast, arranged horizontally therein such that the longitudinal center line of the crankshaft lies substantially in the plane of the face surface of the drag section, and a mold cope section having a pattern impression of the crankshaft complementary to the impression in the drag section, the drag and cope pattern impressions forming a horizontal, communicating series of molding cavities to receive the casting metal; the cope section being provided with runner passages extending longitudinally thereof on opposite sides of the series of molding cavities, vertical sprue passages opening to the opposite ends of each runner passage, vertical riser passages individual to certain of the molding cavities, each communicating at its lower end with the associated molding cavity substantially in the uppermost zone of the cavity, and opening at its upper end through the top surface of the cope, and a plurality of ingate passages relatively spaced along each runner passage and extending horizontally therefrom to communication with said series of molding cavities, certain of said ingate passages leading directly to certain of said molding cavities having riser passages associated therewith and opening to such cavities in zones thereof relatively near the zones of cavity communication of the riser passages; said riser passages providing for the escape of gases from the molding cavities in crankshaft casting, and serving as reservoirs for the accumulation of excess casting metal rising therein from the molding cavities, and insulation means embedded in the interior surfaces of the riser passages to prolong fluidity of the excessV casting metal accumulated in the riser passages, until solidication of casting metal in the molding cavities is substantially complete.

HOWARD W. MINER.

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

UNITED STATES PATENTS Number Name Date 1,543,657 Bohn June 23, 1925 1,992,677 Sorensen Feb. 26, 1935 2,014,224 Campbell Sept. 10, 1935 2,135,537 Schmeller Nov. 8, 1938 FOREIGN PATENTS Number Country Date 497,628 Great Britain Dec. 22, 1938 OTHER REFERENCES American Foundryman, October 1947, pages 51-64.