US2521520A - Mold gating system - Google Patents

Description

Sept. 5, 1950 c. G. JANCURA MOLD GATING SYSTEM 5 Sheets-Sheet 1 Filed July 15, 1947 :m m W 0 w/w m M M w vW5 u a 2 J m H Sept 5, 1950 c. G. JANCURA 2,521,520

MOLD GATING SYSTEM Filed July 15, 194'? 5 Sheets-Sheet 5 'i 48 e 54, l 1 Fig. 9.

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W a n I? g 57 H n flwuc-nkwz v Charles G. Jcncuru permanent and sand molds.

Patented Sept. 5,1950

MOLD GA'IING SYSTEM Charles G. Jancura, Cleveland, Ohio, alsignor to Aluminum Company of America, Pittsburgh, Pa., a corporation oi Pennsylvania Application J uly 15, 1947, Serial No. 761,087

4 Claims. I

This invention relates in general to problems encountered in the casting of metals and, in parconditions of the molten metal, are all variables, control of any one of which'has a direct bearing on the quality of the final cast article. In many 1 cases the particular article to be cast is fixed in design by engineering requirements, and manipulation of the remaining variables entering into its production must be so governed to provide the highest quality finished product possible under the circumstances. As a result of the characteristic or property known as shrinkage, those skilled in the art of casting have directed their attention to providing various types of casting technique, including pressure and die casting methods and equipment, mold and gating designs, as well as providing a variety of types of gravity feed permanent, semi- In all instances'the art has fully recognized the deleterious results of shrinkage, which normally exhibit themselves in the form of sinks, voids, and excessive porosity, but there still remains much to be done to alleviate the shrinkage problems confronting the art today. Many metals and alloys, such as aluminum,

magnesium, and their alloys. because of their advantageous weight and workability properties,

v have become very desirable in the fabrication of numerous parts and articles, as complete elements and component parts of many designs.

The use of these metals and alloys will undoubtedly increase many fold, and in so far as castings are concerned, will only be limited by the ability or inability to produce any given cast article or part, for a particular use, in a sound acceptable condition. I

An example of a well established use of aluminum and its alloys is found in the production of cast pistons for internal combustion engines, fluid-operated systems, and the like, where mass production has been developed to a high degree, and the overall efllciency of the particular machine or system employing the pistons is a direct measure of the quality of the cast pistons. The same applies to numerous other cast parts and components, and any improvements in present A z casting technique in a direction to improve the quality of castings, in general, will lead to an advance in the art as it exists today.

Regardless of the particllar shape of any casting, the introduction of molten metal to a mold cavity defining the same must make provision for shrinkage encountered during setting or freezing of the molten metal. It is, therefore, an object of the present invention to provide a gating system which will insure control of the flow of molten metal to mold cavities in general in a man-'- ner conducive to proper setting or freezing to produce sound castings free from voids, sinks, porosity, and attendant characteristics resulting from crystallization shrinkage and-occluded gases or air.

Another object is to-provide a gate. riser, and

spruc arrangement for a mold that will produce a general class or sound articles, referred to herein as cup-shaped articles, with their closed ends uppermost withinthe mold.

Another object is to provide a gating system,

in combination with a. gravity fed mold, for producing cup-shaped articles with their closed ends uppermost in the mold that will eliminate coldshuts, blow holes, and porosity when employed-in the casting of readily shrinkable metals such as aluminum, its alloys, and similar metals.

A further object of the invention is to provide a' will be apparent to those skilled in the molding art following a full consideration of the following description, reference being made to the drawings in which:

Fig. 1 illustrates a permanent mold mecha-.

nism incorporating the gating system of th invention in top plan view, portions being broken away to more clearly showlts mode of construction;

Fig. 2 illustrates a partial sectional elevation taken along line II1I of Fig. l, with the mold parts and internal cores shown in position for removal of a casting from the mold cavity;

Fig. 3 illustrates apartial sectional elevation to enlarged scale taken along the line III-III, or mold parting line, of the mechanism of Fig.1,a cast piston being shown in side elevation;

Fig. 4 illustrates a partial sectional view taken along the line IVIV of Fig. 3

Fig. 5 illustrates a sectional view similar to Fig. 4 and showing a modified form of the invention;

Figs. 6, "I, and 8 illustrate sectional views taken along lines VI-VI, VII-VII, and VIII-VIII, respectively, of Fig. 3;

Fig. 9 illustrates a sectional elevation similar to that of Fig. 3 with the exception that the piston of Fig. 3 has been replaced by a cup-shaped article, such as a motor housing, hub cap, or the like, shown in sectional elevation; and 1 Fig. 10 illustrates a sectional elevation similar to that of Fi 3 and Fig. 9 with the exception that the casting cavity is devoid of internal core devices.

In general terms, the invention relates to new and improved gating systems, which are characterized by certain features that can be defined generally as follows:

1. Structural means for delivering molten metal to a mold cavity at at least two levels considered in terms of the depth of the mold cavity;

2. Structural means for controlling the flow and introduction of molten metal into a mold cavity in such a marmer that the mold cavity is, at least partially, filled from an incoming stream of molten metal delivered at a level below the top of the mold cavity, and preferably at the bottom thereof, and completing the filling of the mold cavity by a second stream of molten metal delivered at a higher elevation than the firstmentioned stream;

3. Structural means for feeding or pouring molten metal downwardly through an entrance gate, diverting the fiow inwardly and substantially laterally towards a mold cavity, continuing the downward fiow and delivering the molten metal into the mold cavity below the plane of inward flow to raise its level within the mold cavity to substantially the plane of the diverted inward flow, whereby continued pouring or feeding of molten metal through the gate entrance serves to extend the initiated inward fiow into communication with the mold cavity to complete filling of the same and, if desired, to establish a reserve of high temperature molten metal in shrinkage, gravity feed relationship with the molten metal previously introduced into the mold cavity.

By following the teaching of the invention, as expressed immediately above, it will be observed that the invention is capable of application in any type of mold cavity in which normal gravity feed or pouring is employed. It will also be seen that a bottom-fed or substantially bottom-fed, mold cavity, employing the gating, systems and methods of the invention, incorporates the feature of transforming normal downward to substantially lateral fiow of molten metal delivered to the mold cavity at some level between the entrance gate and initial delivery to the mold cavity. This transformation in the metal now serves the dual purpose of converting the normal velocity head to static head, insofar as the initial molten metal delivered to the mold cavity is concerned, which insures relatively smooth flow and delivery of the molten metal. It also serves to establish a directional fiow, substantially lateral, of molten metal into the mold cavity following the initial filling, or partial filling, thereof. The net result, as established in practice, has been to produce sound castings, which is probably a direct result of the two-directional flow and sequential delivery of molten metal into a mold cavity, whereby at least partial filling of the mold cavity takes place from initial molten metal delivered thereto,

and continued pouring insures delivery of relatively hot molten metal into a zone of partially chilled molten metal. Thls condition, in itself, insures a maximum temperature differential between the first and last molten metal delivered to a mold cavity, and the thermal effects of such a practice have produced sound castings free from deleterious solidification shrinkage characteristics.

Numerous arrangements and combinations will suggest themselves to those versed in this art, and the specific equipment and cast articles selected for purposes of hereinafter describing the invention in more detail are to be taken as illustrative only, and in no sense limiting the scope or practice of the invention.

The casting of cup-shaped articles, and in particular pistons, in molds with the head or closed end of the article uppermost in the mold, has certain advantages which do not prevail where the mold matrix is formed with the closed end towards the bottom of the mold. One of the chief advantages accruing from positioning the closed end of a cup-shaped article uppermost in the mold lies in the fact that the core or cores forming the interior contour of the article may be withdrawn downwardly out of the bottom .of such a mold. This feature lends itself to a high degree of mechanization of casting mechanisms, as distinguished from the soecalled bench molds which are relatively slow in production as gauged today.

Positioning of the closed end of cup-shaped articles, or for that matter any castings, and particularly those which exhibit relatively heavy section thickness as compared to the remainder of the casting, uppermost in a mold, likewise results in superior soundness in the cast article when coupled with the gating system of this invention that permits the molten metal to preferably be introduced into the bottom of the mold to fill, or sustantially fill, the same and thereafter provides an additional source of molten metal, such as in the form of a central riser, adjacent the closed end or heavy section of the article being cast, as will be hereinafter described in more detail.

Referring now to the drawings forming a Dart of the application, in which like reference numerals identify similar parts, Figs. 1 through 8 illustrate a permanent molding mechanism for the production of pistons. The mechanism comprises a bed plate l0 preferably supported above floor level upon four leg'members i2. Mounted upon the bed plate are two mold halves l4 and it which are slidably guided within guides it and removable keeper plates H on the top surface of bed plate in. The mold halves I4 and ii are each machined to provide cavities l8 and I9 which cooperate to impart the exterior contour to the piston 20 to be cast. For forming the piston wrist pin bores, projecting core members 2| are provided, which are shown integrally formed on the inner surface of each. mold cavity. These wrist pin cores 2| may be separate inserts projecting through the mold halves, as well known in this art.

Each mold half is provided o its exterior surface with projecting lugs 22, which support therebetween a link 24 adjustably connected to a second link 25, which is pin-connected at 26 to a bifurcated crank 21. secured to a shaft 28. Each shaft 1! is suitably supported for oscillatory movement in bearings 29 on the upper surface of bed plate ill. Hand levers l3 secured to shafts 29 provide means for manipulating mold halves M and I! to open and close the same.

A, three-piece sectional core has been illustrated as suitable for imparting the interior coutourto the piston 29 to becast. The core comprises a central member 39 and lateral, interior bossforming cores 3|. The central member 39 is mounted in any suitable manner for vertical rec'iprocation-into and out of the mold cavity. The lateral boss-forming core members 3|v are slidably mounted for movement in guides 32 formed on the under side of the bed plate ll. Each side core II is substantially L-shaped with its lower extending portion bifurcated and guided within the aforementioned guides 92. Links 33 pin-connect the bifurcated ends of the cores ii to cranks secured to cross shafts 35, which are supported in bearings 96 formed on the under side of bed plate It. Operating handles 31, secured to the projecting ends of shafts 35, provide means for manipulating the interior boss-forming cores 3| into and out of position within the casting cavity, subject, of course, to the withdrawal or introduction of center core 39 therein.

For adescription of the improved gating structure or system, specific reference should now be made to Figs. 3 through 8. Fig. 3 illustrates a sectional elevation in the plane of the parting line, or line of separation, of the mold halves I4 and ii, the particular mold half shown being Ii. A cast piston 20 is shown in place within the cavity of mold half l5 and the internal cores II and 3| areiilustrated in position within the interior of the casting. p

The improved gating system comprises an entrance gate or channel 40 that is preferably downwardly and inwardly inclined towards the mold cavity from a point in the top surface of the mold, radially disposed'with respect to the outer boundary of the mold cavity. The gate 49 preferably terminates in a discharge elbow or hook bend 4|, the lower level of which is slightly below a horizontal plane passing through the head or uppermost portion of the piston.

Extending-downwardly from elbow 4|, and in direct communication therewith, a runnerorsprue 42 connects the elbow 4| with a ring gate 43 located at the lower edge of the piston skirt. Ring gate 43 may completely surround the lower edge of the piston skirt (Fig. 4) be interrupted, as at 9 Similarly the riser cavity 44 and pe or passages are preferably machined within the meeting surfaces of mold halves i4 and II.

' Figs. 9 and 10 illustrate further modifications of the invention, thus far described, in thatthe improved gating system has been incorporated in a mold for the production. of a cup-shaped article 92 (Fig. 9), such as a motor housing. hub cap. or the like, in which a single or one-piece internal core 52 hasbeen employed, and in a mold for the production of an irregular object Ii (Fig. 10) of varying section thickness, which does not require any interior core or cores. In both the molds of Figs. 9 and 10 the gating system is, for all practical purposes, identical with that illustrated to best advantage in Fig. 3, and the same reference numerals have been employed to identify similar parts.

With specific reference to Fig. 10, the irregular casting I6 is illustrated as having a relatively heavy body section with integral thin web or flange sections 51, 58, and 59. The mold cavity is so formed to position the heavy body section uppermost in the mold and a riser cavity 63 is provided in gravity feed relationship through a reduced or narrow slot or passage 5|, as in the case of the previously discussed and illustrated embodiments of the invention. The ring gate entrance 49 to the mold cavities for the production of piston 20 and cup-shaped article 82 has been dispensed with in the mold of Fig. 10, it being only essential to insure initial introduction of the molten metal into the mold cavity through runner 42 and entrance elbow 50 at some point in the depth of the mold cavity below the heavy body section of the article 56 to substantially fill the mold cavity. Continued pouring of the molten 45 (Fig. 5), or be any arcuate portion of a comand preferably central thereto, is a riser cavity 46. The riser 46 is connected to the mold cavity through one or more narrow slots or. passages 41, and is also in communication with gate 49 through the medium of an inwardly directed runner 49, which preferably takes the form of a continuation of the inwardly directed elbow 4|.

It is to be noted that the connection between elbow 4| and runner 42 is in the form of a convex surface as a result of the arcuate juncture 49. It is to be also noted that runner 42 blends into the ring gate 43 through a smooth curved surface 59 that is substantially horizontal at its point of juncture with the ring gate. The purpose of these, and other described features of the gating system, will be more clearly described in the operation of the invention.

For convenience in forming the gating structure thus far described, cooperating semi-circular grooves (Figs. 6, 7, and ,8) which lend themselves readily to relatively inexpensive machining opmetal insures filling of the cavity in accordance with the practice to now be described.

In the practice of the invention, mold halves i4 and ii are brought into closed relationship around the interior core members 39 and II (Figs. 1 through 5) or 52 (Fig. 9). The molten metal is thereafter teemed or poured into gate 49 in a manner to provide quiet transfer of the molten metal. A lipped ladle has been found satisfactory for this purpose and the entranceto gate 49 is preferably slightly flared, as at 54, to assist in the pouring operation, The normal downward direction of the molten metal flow is interrupted and a laterally inward flow imparted thereto by the hook-shaped bend or elbow 4|, continued downward flow through runner 42 being quite analogous to liquid flow over a submerged weir, effected by the action of the convex curvature of'surface 49. The molten metal now enters the mold cavity through thesmooth curved entrance 9., a narrow connection or restriction 55 being employed, if desired, between the entrance 59 and ring gate 43. At approximately the time that the molten metal reaches the top of the casting cavity the metal flow from the gate 40 is substantially, entirely laterally inward through runner 48 into riser 46. This sequential metal pouring action supplies relatively hot molten metal in the riser and provides a maximum temperature differential between the body metal of the casting and riser supply metal. This condition further insures a continuous feed of the hot riser metal downwardly into the body portion of the casting as the same undergoes shrinkage through solidification. To this end proportioning of the gate and elbow 4| and runner 42 to substantially equal eratlons and equipment, are preferably employed. cross section (Figs. 6 and 7), and decreasing the 7 cromsectionalareaoi'runnerll (Fig.8),hasbeen found to assist in the sequential mold cavity fillherein described.

' It has been stated that the operation and use of the improved gating structure of the invention insures a supply of hot molten metal in direct gravity communication with the body metal of a casting during its solidification. This condition naturally overcomes the voids, sinks. and porosity which would otherwise prevail if the body metal of any particular casting was to set or freeze before the riser metal reached the mold cavity. Cup-shaped articles, in many instances, incorporate relatively heavy metal sections adjacent their closed ends, as evidenced in a piston by the wrist pin bosses, head and ring groove belt, as distinguished from the section thickness of the skirt below the wrist pin bosses. However, this condition of varying section thickness in a casting is not limited to pistons or cup-shaped articles. Fig, 10 clearly illustrates this fact wherein the gating system has been applied to an article to be cast which is devoid of any interiorly core portions. It will be readily understood that filling, or substantial filling, of the mold cavity of Fig. 10 through the downwardly directed runner 42 is followed by delivery of hot molten metal to the riser 63 in the same manner as previously described for the operation of the invention as applied to the fabrication of piston 20 and cupshaped article 52.

Although the specific examples of the application of the gating structure and system of the invention have all included a riser cavity above the mold cavity, in. which case it is preferred to employ restricted mold venting passages, 6| (Figs.

3 and 9) and 82 (Fig. 10), the gating structure and practice of the invention operates and functions equally well in association with mold cavities in which no riser cavities are employed. In such latter cases the gating structure is identical with that already described and illustrated with the exception that the lateral runner 48 leads into the casting cavity proper at its uppermost level, or thickest portion, which should likewise be located uppermost in a mold.

The improved gating structure, wherein. the molten metal is turned inwardly to impart a substantially lateral flow, and thereafter spill over a convex surface, which acts in the nature of a submerged weir, insures a transformation from a strictly velocity head to one of substantially static head feeding the lower portion or bottom of the mold cavity, This in itself insures smooth, non-agitated delivery of molten metal to the mold cavity with its attendant freedom from gas. or air occlusions, normally associated with high velocity metal transfer as applied to mold filling.

The further provision of maximum temperature differential adjacent the uppermost portion of a mold cavity, or heavy section-defining portion thereof, asprovided for by a riser fed directly from the gate entrance, following substantial filling of a mold cavity upwardly from an entrance to the same below the uppermost or heavy section thereof, insures a ready supp y of high temperature molten metal in direct communication with the first metal introduced into the mold. The molten metal first into the mold will obviously have been subjected to the greatest amount of chilling, and the subsequently fed hot molten metal will serve to produce the aforesaid temperature differential, as well as serve to supply a reserve and maintain a rate of solidification that will avoid the formation of sinks, hot-spots,

a cold-shuts, ind otherwise eliminate excessive porosity in the article being cast.

The gating system of the invention also insures a minimum amount of scrap metal as compared to the numerous gating systems now em ployed. wherein riser and runners are provided in integral connection with the articles being cast over the entire depth or height of the cast articles. These latter forms of gating systems have been used quite extensively in an attempt to provide the temperature difi'erential between the solidifying body portion of a casting and molten metal supply feeding a casting cavity.

Although the invention has been described in terms of its adaptation to the production of specific types of articles, and has been further described in its adaptability to permanent molds, it is not intended that the invention should be limited to these specific descriptions and should in no other way be limited except as it has been defined in the appended claims.

What is claimed is:

1. In a gating system for a mold defining a mold cavity and a riser cavity above the mold cavity and connected thereto, an entrance gate in the mold surface extending downwardly substantially to the plane of the upper part of the mold cavity and offset laterally from the cavity, an inwardly directed elbow in communication with the lower end of the gate and communicating with the riser cavity. and a downwardly and inwardly directed runner communicating with the elbow at a point intermediate its connection with the gate and the riser cavity and terminating in communication with the lower end of the mold cavity.

2. In a gating system for a mold having a cavity defining an article of varying cross section with a heavy section uppermost in the mold and a depending thinner section below the same, an entrance gate in the moldsurface above the mold cavity extending downwardly substantially to the plane of the upper part of the mold cavity and offset laterally in respect thereto, an inwardly directed elbow in communication with the lower end of the gate and communicating with the mold cavity adjacent its upper end, and a downwardly and inwardly directed runner communieating with the elbow at a point intermediate its connection with the gate and mold cavity and terminating in communication with the mold cavity adjacent its lower end.

3. In a gating system for a mold defining a mold cavity for casting a cup-shaped article with its closed end uppermost in the mold, an.entrance gate in the mold surface above the mold cavity and extending downwardly to substantially the plane of the closed end defining portion of the mold cavity and offset laterally therefrom, an inwardly directed elbow in communication with the lower end of the gate and communicating with the mold cavity adjacent its upper end, and a downwardly and inwardly directed runner communicating with the elbow at a point intermediate its connection with the gate and mold cavity and terminatin in communication with the lower end of the mold cavity.

4. In a gating system for a mold defining a mold cavity for a piston with its head uppermost in the mold and a riser cavity above the mold cavity and connected thereto, an entrance gate in the mold surface extending downwardly substantially to the plane of the piston head defining portion of the mold cavity and oflset laterally therefrom, an inwardly directed elbow in communication with the lower end of the gate and communicating with the riser cavity, and a downwardly and inwardly directed runner communicating with the elbow at a. point intermediate its 5 connection with the gate and the riser cavity and terminating in communication with the mold cavity adjacent its lower end.

CHARLES G. JANCURA.

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

UNITED STATES PATENTS Number Name Date Norton et al. Feb. 4. 1938 Schmeller Nov. 8, 1938 Kohl Sept. 2, 1941 Fahlman Dec. 15, 1942

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