Die Casting Method

Abstract

A method of casting high temperature melting point metals and a die arrangement and molten metal feed mechanism for a die casting machine. The method includes gravity filling a shot cylinder with molten metal, cutting off the inlet to the shot cylinder when it is full and then forcing the molten metal in the air-free cylinder into the mold cavity. The machine includes die elements adapted to mate and define a mold cavity at a parting line defined by parting surfaces between the opposed faces of the elements. The die arrangement and molten metal feed mechanism includes a sprue and runner complex also disposed at a parting line, and a molten metal injection or shot cylinder which extends into the parting line or lines. The metal shot cylinder is filled through the sprue with the dies closed. In one aspect of the invention, a molten metal injection plunger acts to seal off the sprue from the shot cylinder during a casting operation, while in another aspect of the invention a separate sprue plunger is utilized to perform this function.

Parent Case Text

This application is a division of co-pending application Ser. No. 865,397, filed Oct. 10, 1969. Reference is also made to application Ser. No. 769,598, filed Oct. 22, 1968, now abandoned, of which the aforementioned co-pending application Ser. No. 865,397 is a continuation-in-part.

Description

BACKGROUND OF THE INVENTION

This invention relates in general to die casting. It deals particularly with a die casting machine and method especially suited to the casting of high temperature melting point metals.

One of the most critical facets of a die casting operation, regardless of the metal being cast, is the injection of molten metal into the mold. It becomes ultimately critical where high temperature melting point metals are being cast. Conventional methods and equipment for die casting and metal injection have generally been inadequate, or barely adequate, to the task, and little die casting of such metals is presently done.

Referring specifically to conventional machines and methods, there are two types of die casting machines presently in general use. Each is similar in respect to the mechanism for holding the die in position, opening and closing it, and exerting the necessary pressure to hold it shut during casting. Each differs in the mechanism for forcing the metal into the die.

An older type of machine is known as the hot-chamber machine. In this type of machine, the molten metal is retained in a pot. A "goose-neck" extends upwardly and out of the pot and has a generally horizontally extending nozzle immediately above the pot. The nozzle extends through a fixed platen in a die casting machine, perpendicular thereto, into communication with a sprue extending perpendicularly through the fixed die. A plunger is introduced into a suitable cylinder connected to the goose-neck, and the plunger forces molten liquid out of the goose-neck, through the nozzle, into the sprue and the mold cavity. The hot-chamber type machine is normally limited to use with relatively low temperature alloys, zinc and the now unimportant lead and tin alloys, which do not rapidly attack the cast iron metal pot, cylinder, and plunger, as do the copper based alloys, for example.

The second type of machine generally used today for casting is known as the "cold-chamber" machine. In the cold-chamber machine, a generally tubular shot sleeve is mounted in and extends perpendicularly through the fixed or stationary platen. A shot cylinder in the sleeve is in communication at its inner end with a runner leading to the mold cavity. A shot plunger is slidably inserted in the outer end of the cylinder. Immediately in front of the plunger, with the plunger in its retracted or withdrawn position, a pouring slot is provided in the top of the sleeve. In the casting operation, a measured shot of molten metal is ladled through this pouring slot into the cylinder. The plunger is then operated to force the metal through the cylinder and runner into the mold cavity.

The cold-chamber die casting machine is the type presently used for casting aluminum, magnesium, and even the higher temperature melting point copper-base alloys. It does, however, have distinct disadvantages when these higher temperature melting point metals are cast. For example, it will be recognized that when a measured molten shot is poured into the horizontally disposed shot cylinder, it immediately disperses along the base of the cylinder, heating only the lower portion of the cylinder defining sleeve. The sleeve, unevenly and rapidly heated, distorts somewhat. As a result, it is not uncommon to find that the plunger fits poorly when it is introduced, sometimes permitting "blow back," or metal leakage past the plunger during the injection stroke.

In addition, in such cold-chamber machines, it will also be recognized that when the shot of molten metal flows along the bottom portion of the injection sleeve, air occupies the upper portion. Accordingly, when the plunger is operated, it is not uncommon for air to be forced with the metal into the mold cavity. This produces objectionable porosity in the casting.

SUMMARY OF THE INVENTION

The present invention is embodied in a greatly improved die casting machine and method, especially suited to casting high temperature melting point metals, such as the iron and copper alloys, for example. In this respect, the melting point of copper is 1,981.4.degree.F. and that of iron 2,797.degree.F. Aluminum-bronzes, for example, melt at approximately 2,200.degree.F., while some brasses melts at approximately 2,400.degree.F. Ferrous alloys melt at temperatures of 3,000.degree.F. and higher. Any metals in the melting point range of approximately 2,000.degree.F. and above are, for purposes of this invention, considered high temperature melting point metals. It is an object of the invention to provide such a die casting machine which obviates expansion distortions of the injection sleeve due to metal covering only the bottom portion of the sleeve. As a result, the plunger maintains a close fit with the sleeve and blow back or metal leakage past the plunger during the injection stroke is forstalled.

It is another object to provide such a die casting machine wherein air is displaced in the injection sleeve, being replaced by the liquid metal itself, thus preventing objectionable porosity in the casting. The present machine eliminates the necessity for pouring the molten metal shot in a vacuum; a current practice with some machines to avoid this air-entrapment problem.

Still another object is to provide a die casting machine of the aforedescribed character which is a simple modification of present commercial machines. In this light, presently known liquid metal handling methods and mold designs are employed.

Yet another object is to provide a greatly improved method of die casting high temperature melting point metals which results in better castings as well as simpler and less expensive casting operations.

In addition to the foregoing, the die casting machine embodying features of the present invention has, inherent in its construction, a substantially reduced machine length over conventional die casting machines.

The foregoing and other objects are realized in accord with the invention by providing a die casting machine and method of die casting high temperature melting point metals wherein molten metal is poured into the mold through a sprue extending along parting surfaces of the die elements. An injection cylinder, wholly enclosed within the mated die elements, receives the molten metal, is gravity filled with the metal, and acts as a temporary reservoir for it. In a first form of the invention, the sprue is then closed off from the outside by a sprue plunger, thus capturing a full reservoir of molten metal, after which an injection plunger whose tip forms one closed end of the cylinder forces the metal in the injection cylinder through a runner on the parting surfaces into the mold cavity or cavities. In this form of the invention, both the sprue plunger and the cylinder, and injection plunger and cylinder, extend through the fixed platen and die perpendicular to the parting surfaces.

In a second form of the invention, the shot cylinder, pouring sprue, and casting gate are formed at parting surfaces of the die elements. More precisely, these sprues and the shot cylinder are formed at the opposed faces of the fixed die element and the movable die element, the injection plunger being slidable in the shot cylinder sleeve on an axis lying in the parting surfaces. The sprue plunger extends through the fixed die element and platen, perpendicular to the parting surfaces and intersects the pouring sprue to close it off in the aforedescribed manner once molten metal has been introduced to the pouring sprue and has filled the shot cylinder sleeve.

In a third form of the invention, the pouring sprue, shot cylinder and sleeve, and the casting gate are all formed at parting lines at separate pairs of parting surfaces of the die elements. In this form of the invention, however, as opposed to the horizontal arrangements of the shot sleeve cylinders in the aforedescribed forms of the invention, the shot sleeve cylinder and plunger are vertically disposed on the parting surfaces of the die elements and, in addition, the pouring sprue intersects the cylinder below the plunger, intermediate the upper and lower ends of the cylinder. As a result, when molten metal is introduced to the pouring sprue, it flows downwardly into what is defined here as the shot cylinder section, filling it up to a point above the sprue access aperture. The shot plunger coming down then acts also as a sprue plunger, cutting off the pouring sprue from the cylinder without capturing air in the cylinder section as it forces the molten metal through the casting runner to the mold cavity.

A fourth form of the invention also utilizes the shot plunger as a sprue plunger for cutting off the pouring sprue from the cylinder as it forces molten metal through the casting runner to the mold cavity. In this embodiment, however, the shot cylinder and plunger are arranged horizontally in the die elements.

A fifth form of the invention is similar in concept to the fourth form referred to immediately above. The shot plunger is utilized as a sprue plunger to cut off the pouring sprue from the cylinder as it forces molten metal through a casting runner to the mold cavity. In this fifth form of the invention, however, a three plate die system is employed. A fixed die element, a movable die element, and a floating die element between the fixed and movable die elements, provide two parting surfaces between the die elements. The pouring sprue is disposed at the parting surfaces between the fixed and floating die elements, while the mold cavity and casting runner are disposed at the parting surfaces between the movable and floating die elements. The shot cylinder is disposed in the floating die element in horizontal relationship. The shot plunger extends through the fixed die element to enter the shot cylinder, thus cutting off the pouring sprue and forcing molten metal through the casting runner into the mold cavity.

In all forms of the invention, the molten metal injection system works in the parting plane so that if malfunctions do occur, solidified metal can easily be removed at a parting plane from all cavities. In this light, the injection or shot cylinder is defined as being "in" the die elements, which terminology is generic to various embodiments of the invention wherein the injection cylinder extends into the die element along opposed parting surfaces of the die elements and thus lies partially in the opposed surfaces, for example, or extends through one or more of the die elements at an angle to the parting surfaces. Similarly, where the sprues, runners, and mold cavities are referred to or defined as being in the die elements, it should be understood that they might be disposed entirely in one of the die elements at parting surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, both as to its construction and method of operation, along with other objects and advantages, is illustrated more or less diagrammatically in the drawings, in which:

FIG. 1 is a perspective view of a die arrangement and molten metal feed mechanism embodying features of a first form of the invention, with parts removed;

FIG. 2 is a sectional view through the mated die elements of the die arrangement shown in FIG. 1;

FIG. 3 is a perspective view similar to FIG. 1 illustrating a die arrangement and molten metal feed mechanism embodying features of a second form of the invention;

FIG. 4 is an elevational view of a die element face in a die arrangement and molten metal feed mechanism embodying features of a third form of the invention;

FIG. 5 is a perspective view of a die arrangement and a molten metal feed mechanism embodying features of a fourth form of the invention, with opposed die elements rotated 90.degree. to fully expose the mating die element faces; and

FIG. 6 is a sectional view through the mated die elements of a die arrangement and molten metal feed mechanism embodying features of a fifth form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, and particularly to FIGS. 1 and 2, a die arrangement and molten metal feed mechanism embodying features of a first form of the present invention is illustrated generally at 10. The die arrangement and feed mechanism 10 is specially suited to the casting of high temperature melting point metals, such as the iron and copper alloys, for example. However, its many advantageous features also make it eminently suitable for casting lower temperature melting point metals.

The die arrangement and feed mechanism 10 includes a fixed die element 11 and a movable die element 12 which meet and mate on a parting line P at opposed planar faces 13 and 14, respectively, to form a mold cavity 15. The fixed die element 11 is mounted, in a generally conventional manner, on a fixed platen (not shown) of a die casting machine, while the movable die element 12 is, correspondingly, mounted in a generally conventional manner on its movable platen (not shown). The movable die element 12 is, in this manner, movable into and out of engagement with the fixed die element 11, in a well-known manner.

The mold cavity 15 is actually formed in the "hot half" or fixed die element 11. When the die segments 11 and 12 are moved into mating relationship with opposed faces 13 and 14 in intimate engagement, the mold cavity 15, here shown empty of a casting, is closed.

The die arrangement and molten metal feed mechanism 10 also includes a sprue and runner complex 20 through which molten metal is delivered to the mold cavity 15. The complex 20 includes an inclined pouring sprue 21 having a pouring spout 22 at its upper end opening to the top of the die element 11. The spout 22 might actually be formed in a separate attachment 23, as illustrated, for maintenance purposes. A horizontal sprue 25 joins the lower end of the pouring sprue 21 to a vertically disposed casting runner 26 through an injection cylinder 30. The runner 26 communicates with the mold cavity 15.

According to the invention, the sprue complex 20, including the sprues 21, 25 and the runner 26, is formed entirely at the parting line P of the mated die elements 11 and 12. In the die arrangement and feed mechanism 10, the corresponding sprues and the runner are formed in the face 13 of the fixed die element 11. With the die elements 11 and 12 in mating relationship, the sprues and runner are enclosed.

Intersecting the sprue and runner complex 20 at the juncture of the sprue 25 and the runner 26, is the injection cylinder 30. The injection cylinder 30 extends perpendicular to the sprue and runner complex 20, through the fixed die element 11 (and platen), from the back of the platen to its inner end 32 at the parting line P, where it opens into the sprue complex 20 at the juncture of the sprue 25 and the runner 26.

The injection cylinder 30 is actually defined by an injection sleeve 35 fabricated of a high-strength, high-temperature resistant metal alloy. The sleeve is mounted in suitable bores extending through the die element 11 and platen. Slidable in the sleeve 35, in close fitting relationship therewith, is an injection plunger 38. As will be recognized, the full diameter of the sleeve opens onto the parting line P.

The injection plunger 38 is inserted from the open rear end of the sleeve behind the platen and is slidable through the sleeve 35 toward the front end 32 of the cylinder at its juncture with the sprue 25 and runner 26. It is the tip of the plunger 38 which, in a manner hereinafter discussed in detail, forces molten metal upwardly through the runner 26 into the mold cavity 15 to form the casting.

Also intersecting the sprue complex 20, at a point approximately intermediate the ends of the inclined sprue 21, is a sprue locking cylinder 40. The locking cylinder 40 extends perpendicular to the sprue complex, through the die element 11 (and platen), from the back of the platen through the sprue 21 to its inner end 42 in the die element 12. The cylinder 40 is actually defined by a segmented sleeve 43 which extends through and is mounted in suitably formed bores in the die elements 11 and 12 and the fixed die platen.

A sprue plunger 45 is slidable in the locking cylinder 40 from the rear end of the sleeve 43 behind the platen into a position in the cylinder 40 wherein it extends across the sprue 21 into the die element 12 and forms a liquid lock in the sprue 21. The plunger 45, like the injection plunger 38 hereinbefore described, is operated through the mounting platen of the die element 11 by suitable hydraulic motor means (not shown).

In operation of the die arrangement and molten metal feed mechanism 10, the plungers 38 and 45 are initially retracted into retracted positions in the injection cylinder 30 and locking cylinder 40, respectively. Molten metal, such as one of the ferrous alloys, is poured into the pouring spout 22 of the sprue complex 20, whereupon it courses downwardly through the sprue 21, across the horizontal sprue 25, and into the sleeve 35 of the injection cylinder 30 between the plunger 38 and the front-end 35 of the cylinder. Sufficient molten metal is introduced to the sprue complex 20 to fill the cylinder 30 and the sprue 25, as well as some portion of the upwardly inclined sprue 21 and the runner 26. All air has thus been evacuated from the injection cylinder 30 and the molten metal is in contact with the sleeve 35 around its entire circumference.

The sprue plunger 45 is then moved inwardly to its actuated position to lock or block off the sprue 21 above the level of the molten metal therein. At this point, the injection plunger 38 is forced inwardly to its actuated position in the cylinder and sleeve 35, forcing the molten metal through the runner 26 into the mold cavity 15, to fill the mold cavity. The allow hardens quickly in the mold cavity 15, and the die elements 11 and 12 are separated.

Once the die elements 11 and 12 have been separated, conventional ejector pins (not shown) extending through each of the die elements are forced inwardly to eject the cast part and attached casting sprue scrap sometimes referred to as the "gate." Since the casting sprue is, like the die cast part, formed at the parting line P of the separated die elements 11 and 12, the gate is readily ejected from whichever die element it remains on when the die elements 11 and 12 are separated. The ejector pins extend through corresponding die elements 11 and 12, perpendicular to corresponding faces 13 and 14, into communication with the sprues 21, 25 and the runner 26.

Turning now to FIG. 3, a die arrangement and molten metal feed mechanism embodying features of a second form of the present invention is illustrated generally at 110. The die arrangement and feed mechanism 110 includes a fixed die element 111 and a movable die element 112 which meet and mate on a parting line P at opposed planar faces 113 and 114, respectively, to define a mold cavity 115.

The die elements 111 and 112 are mounted, also in a well-known manner, on platens (not shown) of a die casting machine. The movable die element 112 is movable into and out of engagement with the fixed die element 111. The mold cavity 115 is actually formed in the die elements 111, as illustrated.

The die arrangement and molten metal feed mechanism 110 includes a sprue complex 120 through which molten metal is introduced to the mold cavity 115. The sprue complex 120 comprises a vertical pouring sprue 121 having a pouring spout 122 at its upper end opening to the top of the die element 111. A casting runner 126 communicates at one end with the lower end of the vertical sprue 121, and at its opposite end with the mold cavity 115.

Again, according to the invention, the sprue complex 120 is formed entirely at the parting line P of the mating die elements 111 and 112. The corresponding sprue and the runner are actually defined in the face 114 of the die element 111. With the die elements 111 and 112 in mating relationship, they form the corresponding sprue 121 and the runner 126.

Intersecting the sprue complex 120 at the juncture of the sprue 121 and the runner 126 is an injection cylinder 130. The injection cylinder 130 also lies in the parting line P extending from outside the die elements to an inner end 132 where it opens into the sprue complex 120 at the juncture of the sprue 121 and the runner 126.

The injection cylinder 130 is defined by an injection sleeve 135 fabricated in two half-sections 135a and 135b of high strength, high temperature resistant metal alloy. The sleeve sections 135a and 135b are mounted in suitable semi-cylindrical channels in the faces 113 and 114 of the die elements 111 and 112, respectively.

Slidable in the sleeve 135, in close fitting relationship therewith, is an injection plunger 138. The injection plunger 138 is inserted from the open end of the sleeve 135 and is slidable through the sleeve toward the front end 132 of the cylinder at its juncture with the sprue 121 and the runner 126.

Also intersecting the sprue complex 120, at a point approximately intermediate the ends of the vertical sprue 121, is a sprue locking cylinder 140. The sprue locking cylinder 140 extends perpendicular to the sprue complex, through the die element 111 and the fixed platen (not shown) from in back of the fixed platen to its inner end 142 extending through the sprue 121 into the die element 112. The cylinder 140 is actually defined by a segmented sleeve which extends through and is mounted in a suitably formed bore in the die element 111, its fixed platen, and a portion of the die element 112.

A sprue plunger 145 is slidable in the locking cylinder 140 from the rear end of the sleeve 143 behind the fixed platen into a position in the cylinder 140 where it extends through and forms a liquid lock in the sprue 121. The sprue plunger 145 and the injection plunger 138 are operated by suitable hydraulic motor means (not shown).

The operation of the die arrangement and molten metal feed mechanism 10 embodying a second form of the invention is substantially identical to that of the die arrangement and feed mechanism 10. The molten metal is poured into the sprue 121 until the injection cylinder 130 is filled. The plungers 138 and 147 are then sequentially operated in the manner hereinbefore discussed. This second form of the invention is distinguished in that the injection cylinder 130 is arranged at the parting line P so that its sleeve 135 can more easily be inserted, removed and maintained.

A third form of the die arrangement and molten metal feed mechanism embodying features of the present invention is illustrated generally at 210 in FIG. 4. It includes a fixed die element 211 and a movable die element (not shown) which meet and mate on a parting line at opposed planar faces 213 (only one shown in the plane of the drawing) to form a mold cavity receptacle 215. The die elements are mounted in the conventional manner on fixed and movable die platens in a die casting machine.

In the die arrangement and molten metal feed mechanism 210, the mold cavity 215 and the sprue complex 220 into which molten metal is introduced and through which it courses to the mold cavity 215 are formed entirely at the parting line of the mating die elements. The sprue complex 220 includes an inclined sprue 221 having a pouring spout 222. The remainder of the sprue complex, itself, consists of the inclined runner 226. The sprue 221 and the runner 226 are formed in the die element 211 and are closed by mating of the die element 211 with the movable die element.

Vertically disposed at the parting line of the die elements is a combination injection and sprue locking cylinder 230. The cylinder 230 extends from its upper end 231 atop the die elements to its lower end 232 where it joins the lower end of the runner 226. The sprue 221 intersects the cylinder 230 at an opening substantially intermediate the upper and lower ends of the vertically disposed cylinder. That portion of the cylinder 230 extending downwardly to the lowermost point of the sprue opening 233 functions as a sprue locking cylinder. The portion of the cylinder 230 extending downward from the opening 233 functions as the injection cylinder.

The cylinder 230 is defined by a sleeve 235 fabricated in half-sections of high strength, high temperature resistant metal alloys. The half-sections are, in the manner of the second form of the invention hereinbefore discussed, mounted in suitably formed semi-cylindrical channels in the opposed faces of the die elements.

A sprue locking and injection plunger 238 is inserted from the open upper end of the sleeve 230 and is slidable in the sleeve 235 toward the lower end 232 of the cylinder at its juncture with the runner 226. With the die arrangement and metal injection mechanism 210 ready for a casting operation, the plunger 238 is in its upper or retracted position, as illustrated, with the sprue 221 communicating with the cylinder 230 below the plunger 238.

In operation, molten metal is poured into the pouring spout 222, whereupon it courses down the sprue 221, the lower half or injection section of the cylinder 230, and up through the runner 226. Sufficient molten metal is introduced to the mated dies in the foregoing manner to cause it to fill the injection section of the cylinder 230; i.e., until it reaches or exceeds the level L at the inlet 233 from the sprue 221 to the cylinder 230.

The plunger 238 is then forced downwardly, locking off the sprue 221 as it passes, without trapping air below it in the cylinder 230. As it moves to its fully actuated position, it forces molten metal downwardly from the cylinder 230, through the runner 226, to fill the mold cavity 215.

Turning now to FIG. 5, the die arrangement and molten metal feed mechanism embodying features of the fourth form of the invention is illustrated generally at 310. The die arrangement and feed mechanism 310 includes a fixed die element 311 and a movable die element 312 which meet and mate at opposed planar faces 313 and 314, respectively. A mold cavity 315 is formed in the face 313 of the fixed die element 311, the cavity being opposed by the face 314 of the movable die element 312 when the die elements are mated. The movable die element 312 is movable into and out of engagement with the fixed die element 311 in a well-known manner.

A molten metal feed complex 320 formed between the die elements 311 and 312 provides means for delivery of molten metal to the mold cavity 315 from a pouring sprue 321 having a pouring spout 322 formed at its upper end. The pouring sprue 321, as will be noted, is formed solely in the face 313 of the fixed die element 311, while the pouring spout 322, at its open end, is segmented into both die elements 311 and 312.

At the inner end of the pouring sprue 321, a frusto-conical recess 325 is formed in the face 313 of the fixed die element 311. The base of the frusto-conical recess 325 is defined by an annular, planar die element closing face 326. Extending axially from the frusto-conical recess 325 through the fixed die element 311, and communicating with the recess through the closing face 326, is the sprue locking cylinder portion 329 of the combination molten metal injection and sprue locking cylinder 330.

The combination injection and sprue locking cylinder 330 or, more specifically, the sprue locking cylinder portion 329 of it, is actually defined by a segmented sleeve in a manner discussed in relation to the aforedescribed embodiments of the present invention. The sleeve is mounted in suitable bores extending through the die element 311 and its mounting platen (not shown). Slidable in the sleeve-defined cylinder 330, in close fitting relationship, is a sprue locking and injection plunger 338, operated hydraulically from behind the die element 311 and its mounting platen (not shown) by a plunger shaft 339.

The closing face 326 forming the base of the conical recess 325 is notched on the top on its vertical radial at 340. The notch 340 affords communication between the cylinder 330, in front of the plunger 338, and an inclined extension 341 of the pouring sprue 321 formed in the upper surface of the conical recess 325. As will hereinafter be discussed, the pouring sprue 321, its extension 341 and the notch 340, provide access for the molten metal from the pouring spout 322 to enter the cylinder 330.

Extending from the face 314 of the movable die element 312 is a frusto-conical projection 350 which is adapted to mate with and seat in the frusto-conical recess 325 when the die elements 311 and 312 are brought into mating relationship. In this relationship, the closing face 351 forming the annular outer end of the projection 350 seats in sealing relationship against the mating closing face 326 in the base of the frusto-conical recess 325. With the frusto-conical projection 350 thus seated in the frusto-conical recess 325 and the die element faces 313 and 314 pressed together in mating relationship, the molten metal feed passage defined by the pouring sprue 321, its extension 341, and the fill notch 340 is formed.

The frusto-conical projection 350 has the cylindrical injection cylinder portion 355 of the cylinder 330 extending into it in the manner illustrated. The shot well 355, as it is referred to herein to define that portion of a combination injection and sprue locking cylinder 330 which is filled with molten metal when the sprue 321 is blocked off, extends to the mating closing faces 326 and 351 when the die elements are properly mated.

Extending radially through the frusto-conical projection 350 from the shot well 355 to the outer surface of the projection 350 is a molten metal runner notch 357. The molten metal runner notch 357 is angularly displaced in the frusto-conical projection 350 from the pouring sprue extension 341 and the fill notch 340. The significance of this angular displacement will hereinafter be discussed in relation to the operation of the die arrangement and molten metal feed mechanism 310.

In radial registry with the runner notch 357, and formed in the planar surface 314 of the movable die element 312, is a molten metal feed runner segment 360. With the die elements in properly mated relationship, the runner segment 360 communicates at its upper end with a runner segment 361 formed in the surface 313 of the fixed die element 311 and, in turn, with the mold cavity 315.

In operation, with the die elements 311 and 312 in mated relationship and the plunger 338 retracted in the manner illustrated in FIG. 5, molten metal introduced to the pouring spout 322 courses downwardly through the pouring sprue 321, its extension 341 and the fill notch 340, into the cylinder 330. Sufficient molten metal is introduced in this manner to fill the cylinder 330 at least up to and into the fill notch 340. At this point, the plunger 338 is hydraulically actuated and forced inwardly toward the shot well 355 through the cylinder 330.

The plunger 338 forces excess molten metal back up through the fill notch 340 until it passes the fill notch in its travel. As it passes the fill notch 340, the plunger 338 closes off the pouring sprue connection and moves toward its fully actuated position, forcing the molten metal filling the cylinder 330 out through the runner notch 357 into the runner segment 360, and from thence into the runner segment 361 and the mold cavity 315.

The high temperature alloy hardens quickly in the mold cavity 315 and the die elements 311 and 312 are separated. Once they have been separated, conventional ejector pins in each of the die elements are forced inwardly to eject the cast part and attached casting sprue, or gate scrap. An example of such an ejector pin is illustrated at 365 communicating with the base of the shot well 355. The scrap casting sprue complex is, like the die cast part, formed at the parting plane between the surfaces 313 and 314 of the die elements 311 and 312, and the outer surface of the projection 350 and the inner surface of the frusto-conical recess 325. As such, it will be recognized that in the description of this embodiment of the invention, the term "parting lines" is inclusive of the opposed frusto-conical surfaces of the recess 325 and the projection 350, and the closing faces 326 and 351, as well as the die elements 313 and 314.

Referring finally to FIG. 6 of the drawings, a die arrangement and molten metal feed mechanism embodying features of a fifth form of the invention is illustrated generally at 410. The die arrangement 410 includes a fixed die element 411, and a movable die element 412 bracketing a floating die element 413.

The fixed die element 411 and the floating die element 413 are adapted to mate at opposed planar faces 415 and 416, respectively, on parting line P.sub.1, while the movable die element 412 and the floating die element 413 are adapted to mate on opposed planar faces 418 and 419, respectively, at parting line P.sub.2.

The floating die element 413 is actually slidably mounted on the fixed die element 411 through the medium of mounting pins 425 seated in the fixed die element and extending perpendicularly out from its mating face 415. The floating die element 413 is adapted to slide outwardly away from the fixed die element 411 on the mounting pins 425 when a keeper lock arrangement 425 connecting the die elements 411 and 413 is opened. As will hereinafter be explained, however, normally the keeper lock arrangement 426 securely locks the fixed die element 411 and floating die element 413 together.

The fixed die element 411 is mounted in a conventional manner on a fixed platen (not shown) of a die casting machine while the movable die element 412 is, correspondingly, mounted in a conventional manner on its movable platen (not shown). The movable die element 412 is movable into and out of engagement with the floating die element 413 and, accordingly, the fixed die element 411 in a well-known manner.

A mold cavity 430 is formed in the face 418 of the movable die element 412, in the manner illustrated. When the movable die element 412 mates on the parting line P.sub.2 with the floating die element 413, the mold cavity 430 is closed. In FIG. 6, it is shown in closed relationship, empty of a casting.

In the die arrangement and molten metal feed mechanism 410, molten metal is delivered to the mold cavity 430 through a pouring sprue 435 from a pouring spout 436. The metal poured into the sprue 435 enters and fills a horizontal combination injection and sprue locking cylinder 440 extending transversely through the floating die element 413. The molten metal cylinder 440, which is actually defined by a segmented cylindrical sleeve 441 extending through the floating die element 413, extends at its inner end into a shallow shot well 445 formed in the face 418 of the movable die element 412. This shallow well 445 is in communication, through a runner 446, with the mold cavity 430.

Slidably mounted in a continuation of the cylinder 440 extending through the fixed die element 411 is a plunger 450. The plunger 450 is hydraulically actuated in a conventional manner by suitable means in the stationary platen which mounts the fixed die elements 411.

With the plunger 450 in its retracted position as illustrated in FIG. 6, operation of the die arrangement and feed mechanism according to the invention is begun by introducing molten metal through the pouring sprue 435 into the cylinder 440 until the cylinder 440 is full. The plunger 450 is then actuated so as to be forced inwardly into the cylinder 440 toward the shot well 445. As the plunger 450 passes the opening of the sprue 445 into the cylinder 440, it seals off the sprue 445. In effect, that portion of the cylinder 440 through which the plunger 450 passes to seal off the sprue 435 is the sprue locking cylinder portion, while the remainder of the cylinder 440 functions as the injection cylinder portion of the cylinder.

The plunger 450 continues to move inwardly toward the shot well 445 into its fully actuated position, forcing molten metal upwardly through the runner 446 to fill the mold cavity. The alloy hardens quickly in the mold cavity 430 and the die elements 412 and 413 are then separated, the keeper lock 426 normally remaining closed unless molten metal has frozen in the pouring sprue 435 so as to necessitate separating the die elements 411 and 413 to remove it. With good pouring technique, however, it is only infrequently necessary to separate the fixed die element 411 and the floating die element 413.

The separation of the movable die element 412 and the floating die element 413 is effective to free the casting from the mold cavity 430. Conventional ejector pins (not shown) are hydraulically activated in a well-known manner to eject the gate or casting and casting sprue or runner from the runner 446 and the well 445.

In each embodiment disclosed, molten metal is gravity poured into a sprue inlet disposed at an exterior surface of the closed die elements from which it courses to an injection cylinder. The inlet is, in turn, disposed externally of the injection cylinder so that the molten metal may be introduced with the injection plunger (FIGS. 1-3) or combination injection-sprue plunger (FIGS. 4-6) inserted into the injection cylinder or combination injection-sprue cylinder, respectively.

In each embodiment of the invention, molten metal fills the injection cylinder (or injection cylinder section) to the extent that it contacts the cylinder wall around its entire circumference along the axial length of the molten metal shot in the cylinder. Uneven heat distortion of the cylinder is thus avoided and the plunger fits uniformly in the cylinder, preventing "blow back."

Each form of the invention affords all of the advantages hereinbefore discussed. In addition, it should be recognized that the overall length of the machine is reduced considerably in machines constructed according to the invention since the injection and sprue cylinders, and plungers, are entirely within the fixed platens and die elements.

While several embodiments described herein are at present considered to be preferred, it is understood that various modifications and improvements may be made therein.

Claims

What is desired to be claimed and secured by Letters Patent of the United States is:

1. A method of die casting metals having high temperature melting points in the range of or in excess of approximately 2,000.degree.F., comprising the steps of:

a. providing mating die elements which separate at parting surfaces wherein a molten metal pouring sprue, runner, and mold cavity are each formed at parting surfaces and wherein a separate cylinder extends through at least one of said elements into communication at said parting surfaces with said sprue and the runner,

b. closing said die elements into mated relationship,

c. positioning a plunger in said cylinder so that access to said cylinder for introduction of molten metal thereto is afforded only through said sprue,

d. introducing molten high temperature melting point metal to said sprue with the die elements closed and permitting it to flow unchecked into said cylinder to fill said cylinder at least to the point where said sprue enters the cylinder without any molten metal flowing into the mold cavity,

e. causing said sprue to be blocked so that molten metal cannot flow back through said sprue,

f. forcing the plunger through said cylinder without capturing gas in the cylinder in advance of the plunger until sufficient molten metal has been forced out of the cylinder through the runner to fill the mold cavity, and

g. separating the die elements after the metal has hardened to remove the gate including the casting.

2. The method of claim 1 wherein the plunger has a tip, further characterized by and including the step of:

a. introducing molten metal to said cylinder until it uniformly engages the tip of the plunger before moving the plunger through the cylinder to inject molten metal into the die cavity.

3. The method of claim 1 further characterized by and including the step of:

a. employing only the force of gravity to prevent molten metal from flowing into the die cavity before the plunger forces it out of the cylinder.

4. The method of claim 1 further characterized in that:

a. said high temperature melting point metal is a ferrous alloy.

5. The method of claim 1 further characterized by and including the step of:

a. filling said cylinder so that molten metal uniformly contacts the wall of said cylinder around its circumference along the length of the molten mass in the cylinder.