US3333455A - Cold die casting malleable metals - Google Patents

Description

g- 1, 1967 1.. J. RATTE ETAL 3,333,455

cow DIE CASTING MALLEABLE METALS Filed Nov. 1, 1 63 v 5 Sheets-Sheet 1 s1 V r 52 y Hj 57 56 o INVENTORS ROBERT W. RAT TE LEON J. RATTE 1, 1967 L. J. RATTE ETAL 3,333,455

com um CASTING MALLEABLE METALS Filed Nov. 1 196s s Sheets-Sheet 2 INVENTORS ROBERT W. RATTE LEON J. RATTE I g- 1967 1.. J. RATTE ETAL. 3,333,455.

COLD DIE CASTING MALLEABLE METALS Filed Nov. 1, 1963 5 Sheets-Sheet 3 i'ihillli 22 INVENTORS ERT W. RA'ITTE N J. RATTE Aug. 1, 1967 L. J. RATTE ETAL 5 COLD DIE CASTING MALLEABLE METALS Filed Nov. 1. 1963 5 Shets-Sheet 4 FlG.lO

INVENTORS LEON J. RATTE Aug. 1, 1967 L. J. RATTE ETAL COLD DIE CASTING MALLEABLE METALS 5 Sheets-Sheet 5 Filed Nov.

FIG. l2

FIG.

INVENTORS ROBERT W. RATTE BY LEON J. RATTE United States Patent 3 333 455 COLD DIE CASTING MALLEABLE METALS Leon J. Ratte, 1686 Whitaker St., and Robert W. Ratte, 212 Krech St., both of White Bear Lake, Minn. 55110 Filed Nov. 1, 1963, Ser. No. 320,715 4 Claims. (Cl. 72-354) This invention is directed toward die casting metals and specifically it is directed toward a method for cold die casting malleable metals, the product resulting from said method and apparatus constructed to produce articles in accordance with said method.

Certain advantages are to be gained by cold die casting metals according to this invention. One advantage is that articles can be produced faster than by more conventional processes of molding with hot molten metal. A single die casting machine constructed according to the teachings of the invention can produce the same quantity of articles in a given period of time that is normally produced by a plurality of hot molding machines. A further advantage is that no metal flashing occurs on the articles formed by the cold die casting process of this invention so there is no necessity for trimming the finished product. Furthermore, articles of precise dimensions may be formed by the cold die casting process of this inven tion by controlling to a precise degree the feeding of the material being cast. The latter results in a further advantage since the amount of material for forming the finished product can be accurately predetermined and fed in as required so that no waste results. Other advantages are achieved by not subjecting the material to a heating and cooling cycle so there is no shrinkage of the finished product, no adverse change in the characteristics of the material due to heating and cooling, and the product may be handled immediately after fabrication.

These and other features and advantages will be evident from the detailed description of the process of this invention and an embodiment of an apparatus for producing articles in accordance with said process as contained in the following specification with reference to the accompanying drawings in which:

FIGS. 19 schematically illustrate the process steps of the invention;

FIG. 10.is a perspective view of an embodiment of an apparatus for performing the process;

FIG. 11 is a partially broken front elevation view of the apparatus shown in FIG. W

FIG. 12 is a horizontal sectional view of the apparatus;

FIG. 13 is a View along section line A-A of FIG. 12;

FIG. 14 is a view along section line BB of FIG. 12;

FIG. 15 is a view along section line CC of FIG. 12;

FIG. 16 is an enlarged view of the encircled area D of FIG. 12;

FIG. 17 is an enlarged view taken along section line E-E of FIG. 11;

FIGS. 18 and 19 are two views of an article produced by an apparatus constructed according to the teachings of this invention.

The process requires that a volume of malleable metal be injected into a closed cavity of a mold with continuous compression force applied, such that when the metal strikes the cavity-defining wall surface of the mold it shapes in a homogeneous mass to the contour of the cavity. The volume of material injected is equal to the volume of metal in the desired formed article so it can be readily predetermined. No pre-treatment, such as heating to soften the metal, is required. Preferably, a length of a cold cylinder of the malleable metal, having a uniform cross-section along its length, is injected lengthwise into the cavity to impact the cavity wall with the required force.

The process of this invention is most clearly described by a series of illustrations, FIGS. 1-9, schematically showing the functioning of an apparatus for mechanically producing articles according to the process.

A spherical cavity for forming a solid spherical article is defined by a pair of hemispherically shaped molding dies 10 and 11, respectively contained in a fixed die block 12 and a movable die block 13. The spherical cavity formed by the two sections when joined is most clearly illustrated in FIG. 5. An ejector rod 14 is shown disposed between the separated sections of the mold in FIG. 1, and its function will be subsequently described. The ejector rod is normally withdrawn from the area of the cavity.

An elongated rod 15 of malleable metal such as aluminum, copper, or lead, for example, having a uniform crosssection along its length is transported from a source (not shown) down a passageway to the fixed die block 12, and a predetermined length 18 thereof is severed from rod 15 by cutting die 16 as it passes downward into chamber 17 in the die block. The required length of material is readily determined knowing its cross section dimension and the volume of the cavity to be filled. The length 18 of the rod material is conveyed to injection chamber 19 by the cutting die 16 until it is firmly seated in the injection chamber, as most clearly illustrated in FIG. 3. The cutting die 16 is then drawn back up cham ber 17 and the length of material 18 is injected along the injection chamber 19 into the cavity by plunger 20. Concurrently therewith, the movable die block 13 moves rightward toward the fixed die block during this injection phase, as most clearly illustrated in FIG. 4. In FIG. 5 it can be seen that at the time the leftmost end of the rod material 18 impacts the cavity-defining wall surface of the hemispheric die section 11, die blocks 12 and 13 are juxtapositioned along their separation line 21 so as to completely close the mold. The two die sections of the mold are brought together concurrently while the material is being injected so that air in the cavity which is displaced by the injected material may be exhausted. At the instant of initial impact of the material against the inner wall of die 11 there may be some small separation of the two die blocks to facilitate exhaustion of entrapped air. However, by the time the material reaches the separation line while conforming to the contour of the cavity, the two die blocks are completely closed together so that no flashing occurs along the separation line. It has been found that there are suflicient minute openings, such as where the injection chamber 19 joins die 10, through which air can escape while the material completely fills the cavity. The force applied to the length of malleable metal at the time of impact and continuously for a period of time thereafter by plunger 20, effectively causes the metal to flow away from the point of impact to completely fill the cavity in a homogeneous mass shaped to the contour of the cavity as indicated at 22.

The amount of applied force is dependent upon various factors, foremost of which is the malleability of the injected material. Related to the malleability is a phenomenon which will be referred to as cold flow. Obviously, the more malleable solid metals, such as lead and lead alloys, require less amount of compression force than metals of relatively lower malleability. Less malleable metals, such as copper and aluminum based metals, may have to be injected at a high velocity to impact the wall of the cavity with an explosive-like force to initiate cold flow of the metal. A constant force applied thereafter will cause the metal to continue the cold flow and form to the cavity in a homogeneous mass. Lead and lead alloys will flow with less pressure applied at a more gradual rate.

It has also been found that the force and velocity of injection depends upon the size and shape of the article to be formed. For example, greater force is required to form an article having sharp indentations or protrusions than one having an uninterrupted outer surface, such as a sphere. Although some orders of magnitude are recited hereinafter for illustrative purposes, in general these must be determined empirically for each situation.

To remove the formed article 22, the mold cavity is opened by withdrawing the movable die block 13 in a leftward direction to separate the two die sections, and 11. As illustrated in FIG. 7, the formed article has a tendency to adhere to the surface of the cavity as a result of the forceful injection of the material. Further leftward motion of plunger pushes the formed article away fr m the inner surface of die section 10 as shown in FIG. 8. Since the formed article may also have a tendency to adhere to the end of plunger 26, it is freed by being struck by ejector .pin 14 which can be brought into position after the mold has been opened.

FIGS. 1017 show various views of an embodiment of an apparatus constructed to produce solid sphericalshaped articles of lead or lead alloy at a rapid rate of production by the cold-die casting method of this invention. Identical parts shown in the various figures are identified with identical item numbers.

A mean housing generally designated 24, has a base 25, a top 26 and additional strengthening structure, not separately identified, which may be considered generally as wall supports between the base and top. The housing is preferably constructed as a unitary structure either by casting it as a single item or by welding or bolting together the various sections.

It is intended that FIG. 10 convey the concept of the massiveness and strength of the main housing 24 and the other component parts which are necessitated by the relatively large motivating forces and the speed of the machine when in operation. The main drive shaft 27 is journaled in the housing and is rotationally driven by a motivating power source, not shown, which is preferably located rearward of the main housing. Externallytoothed spur gear 28 which is axially attached to shaft 27 meshes with spur gear 29 to drive spur gear 30 and drum or cylinder cam 31 coaxially attached, along with gear 29, to shaft 32, journaled in the main housing. Spur gear 33 is meshed with idler gear 34 diametrically opposite gear 36 and is axially attached to shaft 35, suitably journaled in the housing.

Attached to shaft 27 at its forward extremity is cam 36 linked to impeller arm 37 by cam follower rollers 38 and 39 which are positively driven by engagement with the inner and outer surfaces respectively of cam 36. Extending leftward from its attachment to impeller arm 37 is injector plunger 40. As cam 36 rotates it causes impeller arm 37 to reciprocally slide leftward and rightward along guide ways in the forwardly located wall support 41 of main housing 24. Correspondingly, plunger 40 injects and withdraws along cylindrical injection chamber 42 which opens into the cavity at the die section 43 contained in fixed die block 44. The portion of the profile of cam 36 which drives injector plunger towards the cavity during injection is designed to provide a general constant acceleration-constant deceleration motion to the plunger and the lead material being injected. The maximum displacement effected by the cam profile during injection is such that continuous pressure is applied to the injected metal so that it flows to fill the cavity. Shortly after the maximum displacement position of the contour of cam 36 is a small hump, 23 (FIG. 11) which, as will be later described in greater detail, aids ejection of the formed article. The remainder of the cam profile controls withdrawal of the plunger and includes a dwell section.

As most clearly shown in FIG. 16, a feed passage 45 in the fixed die block 44 runs parallel to the injection chamber 42 to receive the rod 46 of malleable metal to be formed. Chamber 47 provides a passageway for cutting die 48 to carry the severed section of the rod into injection chamber 42. The cutting end 49 of die 48 is curved in correspondence with a portion of the peripheral surface of the rod 46 to ensure that the severed section is properly seated in the injection chamber. Plunger 46 is constructed from extremely hard tool steel with a high resistance to fatigue. Its surface is polished to a fine finish so that even though it sits snugly in the injection chamber it can be driven along the chamber with sufficient acceleration to impart the required force to the material being injected. The end of the plunger which is in contact with the material during injection has a curvature since it closes the opening through which the material is injected into the cavity and therefore forms part of the cavity wall. Injection chamber 40 is formed to a highly polished finish in a different material such as tungsten carbide.

Attached to the front end of shaft 35 is another cam 53. Impeller arm 51 is linked to cam by cam follower rollers 52 and 53 respectively engaged with the inner and outer surfaces of cam Stl. Attached to impeller arm 51 is movable die block 54 containing the other hemispheric section 55 of the mold. As cam 53 rotates, it causes impeller arm 51 to cyclically slide rightward and leftward, respectively corresponding to the injection and withdrawal phases of the cyclical operation, along guideways 56 and 57 (FIGS. 13 and 14) in support members of the main housing 24. The cam profiles and gear driving arrangements are such that plunger 40 and movable die block 54 operate substantially concurrently in the respective injection and withdrawal phases.

Cam follower 58 rides in the cam channel 59 on drum cam 31 and is attached to stop member 60 mounted to a pair of elongated shafts 61 and 62 which slidably pass through their respective cylindrical bores 63 and 64 in the main housing 24, as most clearly shown in FIG. 15. As drum cam 31 is rotationally driven by shaft 32, the cam follower 58 is positively driven to impart linear reciprocating forward and backward motion to shafts 61 and 62 along their respective bores. In general, the profile of cam channel 59 is such that when injector plunger 40 is positioned in the vicinity of its rightmost or furthest withdrawn position by cam 36, shafts 61 and 62 are being driven rearwardly and as movable die block 54 is being driven leftward during the withdrawal phase by cam 50, shafts 61 and 62 are being driven in the forward direction. Attached to the front end of shafts 61 and 62 is block 65 containing cutting die 48 and stop members 66 and 67. Extending forward from its attachment to stop member 60 parallel to rods 61 and 62 is ejector pin 68. When cutting die 48 is being driven rearward to sever the rod of malleable metal and position the severed piece in the injection chamber 42 in preparation for the injection phase, ejector pin 68 is being removed from between the die blocks. During the withdrawal phase, ejector pin 68 is driven forward to strike the formed article and free it from the end of plunger 40.

Each cycle of operation of the machine basically comprises two phases, an injection phase and a withdrawal phase. However, to achieve maximum production rates there is some overlap of these two basic phases. For example, machine operations which prepare the malleable metal for injection are considered to be part of the injection phase. Additionally, as will be subsequently 'described in greater detail, the injection plunger is used to aid in ejecting the article so even though ejection is part of the withdrawal phase, the plunger may not yet be withdrawn.

The operation of the machine can best be described by considering a typical operation to produce lead balls having a diameter of .250 inch. Each of the hemispheric sections 43 and 55 of the spherical cavity are suitably formed to the required corresponding dimensions in their respective die blocks 44 and 54 and an elongated solid rod of lead having a diameter of .100 inch is positioned in feed chamber 45 with a suitable length opposite the cutting face of cutting die 48. It will be assumed that the machine has been operating normally at its cyclical rate with considered to be the start of the injection phase which is substantially as illustrated in FIG. 11. The operative portion of the profile of cam 36 is such that plunger 40 will either be dwelling in its furthest withdrawn position or will be withdrawing so that it does not block the opening where chamber 47 joins injection chamber 42. Similarly, the operative section of the profile of cam 50 will be such that the movable die block 54 will be dwelling in its furthest withdrawn position or may be starting to close toward the fixed die block 44 at a relatively slow rate. As drum cam 31 is rotationally driven by the main drive shaft 27 through the gear train comprising spur gears 28 and 29, cam follower 58 in following track 59 causes block 65 to move rearward by its connection thereto via stop member 60 and shafts 61 and 62 (FIG. 15). Cutting die 48 is thereby driven down chamber 47 toward the injection chamber 42 and cuts off a one inch length of the rod of lead and delivers it to the injection chamber. Concurrently, of course, ejector pin 68 is being moved rearward away from the general vicinity of the mold. As the severed length of the rod is seated in the injection chamber the now operative portion of the profile of cam 36, which is brought into play by the rotation of the main drive shaft 27, initiates injection travel of plunger 40 via cam followers38 and 39 and impeller arm 37, such that the leading edge of the injection plunger is in contact with the piece of lead in the injection chamber. At the same time, cam 50 has been rotated by main drive shaft 27 via the gear train comprising gears 28,

29, 30, 34 and 33 so that the operative portion of its profile is moving the movable die block 54 via cam followers 52 and 53 and impeller arm 51 toward the fixed die block 44 to close the spherical cavity of the mold. As the cutting die 48 is moved forward away from injection chamber 42 while movable die block 54 has been positioned to almost completely close the cavity except for a small gap along the separation line between the two sections of the cavity, the injection-controlling portion of the profile of cam 36 becomes operative to inject the metal into the cavity 43, where it joins injection chamber 42, with the required force. With the cavity completely closed, the leading edge of the injected material impacts the smooth surfaced wall of cavity section 55 and is subjected to pressure ranging in the order of 30,000 to 100,- 000 p.s.i. and is compressed to flow as a homogeneous mass completely filling the now closed cavity and shaped to conform with the cavity contour. It should be noted that 'by accurate machining of the profile of cam 50, the movable die block 54 can be gapped from the fixed die block 44 for a suificient length of time to allow maximum escape of entrapped air. The cavity is completely closed by the controlling action of cam 50 when the compressed material reaches that part of the cavity wall containing the separation line between the two sections of a mold. This can be considered to be the termination of the injection phase of the cycle of operation.

The withdrawal phase is initiated by that portion of the profile of cam 50 which now becomes operative to open the cavity by separating the movable die block 54 from juxtaposition with the fixed die block 44.

Correspondingly, the ejector pin 68 is brought forward into the area of the cavity under control of the drum cam 31. This forward movement of the ejector pin, which is considered to be part of the withdrawal phase, is actually initiated during the injection phase since it is driven forward at the same time that the cutting die 48 is being moved away from the injection chamber. This is a part of the operation which illustrates overlap between the two phases of the cycle of operation. While the cavity is being opened and ejector pin 68 is being moved forward, the operational portion 23 of the profile of cam 36 directs the injection plunger 40 further leftward so that it presses against the formed spherical lead ball to separate it from the wall of the hemispheric section 43 of the cavity. As the ball is pushed away from the wall of the cavity, the front end of ejector pin 68 strikes it to dislodge it from the plunger 40 so that it falls free into a receiving chamber, not shown. The forceful ejection action by plunger 40 and ejector pin 68 is required since the force with which the material is compressed in the cavity is such that the formed article has a tendency to adhere to the wall of the cavity and the contacting end of the plunger.

The force applied to the movable die block 54 to open the cavity must be sufiicient to overcome this adhering force.

There is a possibility that the ball will adhere to the wall of die section 55 when the movable die block 54 is separated from the fixed die block. To compensate for this possibility, a holding pin which is spring biased and extends through the movable die block into communication with the hemispheric section 55 is incorporated to apply sufficient force on the lead ball to separate from the cavity Wall in the movable die block. When the lead ball has been ejected, the withdrawal phase is considered terminated and a new injection phase initiates another cycle. Overlap of the phases is again illustrated since the plunger "40 is being withdrawn along injection chamber 42 by the operative portion of cam 36 after the injection phase I begins.

Although the description of the process and apparatus for cold die casting malleable metals has been directed toward the formation of spherical shaped object, it is evident that articles of various precise sizes and shapes can be fabricated according to the teachings of this invention. For example, a more complex shaped article, shown in side andfront views respectively in FIGS. 18 and 19, comprises a pair of hemispheric jaws 69 and 70 hinged together at 72 to form a gap 71 when in the open position. A pair of tongues 73 and 74 extend downward below the hinge. The jaw faces are indented to provide more effective clamping action when the jaws are closed together. This is indicated by the dashed lines in FIGS. 18 and 19.

This article is formed from lead and the depth of the cut forming gap 71 is critical so that the jaws may be manually opened and closed many times without use of a special tool while the hinge retains its strength. A quantity of articles of this configuration have been produced according to the method of this invention by an apparatus substantially similar to that described herein at a production rate in the order of 200 per minute. Suitable lengths of a solid lead rod to provide the required volume of material were injected with sufficient force to develop pressures in the range previously recited, at the production rate into a cavity defined by a pair of separable sections, each section having an internal cavity wall contour conforming to the desired configurations of the corresponding part of the article. The die section in the movable die block had a protrusion corresponding to the desired gap between the jaws and the end of the ejection plunger was tapered to the configuration of the V-shaped slot between the tongue members 73 and 74 since the end of the plunger forms part of the closed cavity, as previously described.

It should be evident that the required compression forces depend upon the type of material being injected and the shape and size of the article being formed. This further has a bearing on the selection of appropriate length and diameter of the injected rod of material. In general, there may be a range of choices and a suitable choice can be determined empirically. Obviously, the more malleable the metal, for example, lead as compared to copper, the wider is the range of selection.

Selection of metals which can be formed according to this inventive process is dependent upon various characteristics of the metal, such as its hardness, modulus of elasticity, crystalline structure, etc. Without attempting to make a rigorous analysis of the behavior of the metal when subjected to pressures in the manner taught by the invention, it is theorized that the above characteristics (and others) determine the metals susceptibility to flow empirically.

We claim:

1. A method for forming an article from malleable metal by die casting, comprising the steps of:

(a) forming a slug by cutting a length from the end of an elongated rod of malleable metal having a longitudinal uniform solid cross section, the volume of said slug being substantially equal to the volume of the article to be formed;

(b) feeding the slug into an injection chamber through an opening located away from the die cavity;

(c) injecting said slug into the cavity of a separable sectioned mold from the injection chamber through an opening in a wall of the mold only after the cavity has been substantially closed with the injection force being such to compress the metal into a homogeneous mass conforming to the cavity contour by impact with the cavity-defining surface of the mold.

2. A machine for cold die casting malleable metals, comprising: a fixed die block and a movable die block each containing a section of a mold cavity; means for reciprocatingly driving said movable die block toward and away from said fixed die block to correspondingly close and open said cavity; means for feeding a solid piece of malleable metal into an injection chamber at a location away from the die block opening, plunger means for injecting said solid piece of malleable metal into the cavity from the injection chamber through an opening in the wall of the fixed die block only after the cavity is substantially closed to impact the cavity wall on the movable die block within a compression force causing the metal to flow and form to the cavity in a homogeneous mass; said plunger advancing further into the cavity after the injection stroke 3 while said die blocks are separating to push the formed piece away from the wall of the fixed die block.

3. The machine as described in claim 2 further including: means for reciprocatingly driving said plunger between said feeding location and said cavity for injecting the fed metal from the feeding location into the cavity with compression force to form it and for pushing the formed piece away from the wall of the fixed die block when the die blocks are separating.

4. A machine for cold die casting malleable metals comprising: a fixed die block and a movable die block each containing a section of a mold cavity; means for reciprocatingly driving said movable die block toward and away from said fixed die block to correspondingly close and open said cavity; an injection chamber opening into the cavity section through the wall in said fixed die block; a plunger slidingly engaged in said injection chamber; means for reciprocatingly driving the plunger in said injection chamber toward and away from said cavity for providing compression force on the metal as it impacts the cavity wall on the movable die block when it is injected into the cavity after the cavity is substantially closed; feed chamber means for feeding an elongated solid rod of malleable metal; and a cutting tool for cutting off a prescribed length of the rod at one end thereof to form a slug and for feeding the slug through the feed chamber into said injection chamber, the cutting edge of said cutting tool forming part of the wall of the injection chamber when it is positioning the slug therein.

References Cited UNITED STATES PATENTS 1,613,595 1/1927 Abel 72353 2,687,660 8/1954 Friedman 72-346 2,800,814 7/1957 Lewis 7236O 3,036,367 5/1962 Ricks 72356 CHARLES W. LANHAM, Primary Examiner.

L. A. LARSON, Assistant Examiner.

Claims (1)

1. 2. A MACHINE FOR COLD AIR CASTING MALLEABLE METALS, COMPRISING: A FIXED DIE BLOCK AND A MOVABLE DIE BLOCK EACH CONTAINING A SECTION OF A MOLD CAVITY; MEANS FOR RECIPROCATINGLY DRIVING SAID MOVABLE DIE BLOCK TOWARD AND AWAY FROM SAID FIXED DIE BLOCK TO CORRESPONDINGLY CLOSE AND OPEN SAID CAVITY; MEANS FOR FEEDING A SOLID PIECE OF MALLEABLE METAL INTO AN INJECTION CHAMBER AT A LOCATION AWAY FROM THE DIE BLOCK OPENING, PLUNGER MEANS FOR INJECTING SAID SOLID PIECE OF MALLEABLE METAL INTO THE CAVITY FROM THE INJECTION CHAMBER THROUGH AN OPENING IN THE WALL OF THE FIXED DIE BLOCK ONLY AFTER THE CAVITY IS SUBSTANTIALLY CLOSED TO IMPACT THE CAVITY WALL ON THE MOVABLE DIE BLOCK WITHIN A COMPRESSION FORCE CAUSING THE METAL TO FLOW AND FORM TO THE CAVITY IN A HOMOGENEOUS MASS; SAID PLUNGER ADVANCING FURTHER INTO THE CAVITY AFTER THE INJECTION STROKE WHILE SAID DIE BLOCKS ARE SEPARATING TO PUSH THE FORMED PIECE AWAY FROM THE WALL OF THE FIXED DIE BLOCK.

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