US2068875A - Pressure casting machine - Google Patents

Description

Jan. 26 1937. N sMlTH Z,@68,875

PRESSURE CASTING MACHINE Filed Nov. 19, 1932. I 2 Sheets-Sheet 1;

INVENTOR dnnes N. SM/TH.

fiTTO RNEY Jan 2%, 1937. J N SMITH 2,068,875

' PRESSURE CASTING MACHINE Filed Nov. 19, 1932 2 Sheets-Sheet 2 INVENTOR JA MES N. \SM/T'H.

ATTO RNEY.

Patented Jan. 26, 1937 UNITED STATES PATENT OFFICE PRESSURE CASTING MACHINE Application November 19, 1932, Serial No. 643,430

3 Claims.

The invention relates to pressure casting machines particularly adapted to the fabrication of castings from the light metals aluminum and magnesium and their alloys and also useful in casting low melting point metals such as tin, zinc and lead.

Pressure castings of the type generally referred to in the art as die casting are generally produced with machines which fall into one of two general classes known as the plunger and gooseneck types The former usually comprises, in addition to the permanent mold or die in which the casting cavity is formed, a mechanical pump submerged in a pot of molten metal, this pump consisting of a cylinder and piston arrangement in which the cylinder is provided with an inlet port below the level of the metal in the pot and a passage connecting with the cylinder which has an outlet port above the.

metal level, which outlet port leads into the gate of the die. The piston or plunger operates in the cylinder in such a manner that at one end of the stroke the inlet portis exposed, allowing the metal to flow into the cylinder. The plunger is moved by external mechanical means, first passing and closing the inlet port and thereafter ejecting the metal from the cylinder and forcing it into the mold or die. This type of machine usually operates at metal pressures of 1000 to 1500 pounds per square inch and is commonly used for low melting point metals such as tin, lead and zinc base alloys. It has not been used for aluminum or other high melting point metals and alloys because of the difficulties experienced with the cylinder and plunger when in contact with metals at the higher temperatures which obtain in the casting of aluminum. Some of these higher melting point alloys have a corrosive action on the pump which is obviously a disadvantage.

Undoubtedly it is for reasons such as these that the plunger type of machine has not been used to any extent in the production of aluminum and magnesium die castings and that the gooseneck type of machine has been universally used instead. Machines of the latter type Which utilize-a trunnion ladle or an immersed pressure chamber shaped like a gooseneck are well known to those skilled in the die casting art. Such machines usually operate at a pressure of about 250 pounds to 500 pounds per square inch, being limited in "this respect by the hazards in handling air. at the higher pressures as well as the excessive' cost of higher compression. Thusit'will be seen that there are serious limitations in the use of either of the principal types of machines known to the die casting or pressure casting art.

It is an object of the present invention to provide a pressure casting apparatus which overcomes certain of these limitations and by means of which die castings of the higher melting point light aluminum and magnesium alloys (or other metals or alloys of relatively high melting points) can be made under higher pressures than have heretofore been practicable. of the invention to provide a pressure casting machine which is simple in construction and which is relatively inexpensive to build and maintain. A further object is to provide a machine of the class described which, by permitting the use of considerably higher pressures, makes it possible to keep the casting temperature of the metal very close to the freezing point or even slightly below the freezing point, and at the same time to avoid the expense and hazards involved in the use of air at the higher pressures.

It is known that the combination of high pressure casting with low metal temperature produces a casting characterized by its soundness and freedom from porosity. It is accordingly an object 2 of the invention to provide a machine which makes it possible to attain the advantages incident to this combination of high pressure and low metal temperature.

A specific object of the invention is the provision of a pressure casting machine of the plunger type which is designed to eliminate the use of special sprue-cutting devices, and being so constructed that all of the excess metal is removed along with the casting in-the form of sprue. 3

Other objects and advantages will appear in connection with the following description of certain preferred embodiments of the invention when taken in connection with the accompanying drawings in which; i

Fig. 1 isa vertical cross-sectional view-taken on the parting line of the mold illustrating in its preferred embodiment a pressure casting machine constructed in accordance with the principles of the present invention. In this view the parts are shown in the position occupied at the end of the casting operation.

Fig; 2 is a side elevational view of the machine shown in Fig. 1, partly brokenaway along the line IIII of Fig. 11 and with the partsshown in the position occupied after ejection of the casting. it

Fig. 3' is a view'similar 'toFig. 2; but showing the parts in the position'occupied at the begin ning of the casting operation.

It is also an object 1 Fig. 4 is a view similar to Fig. 3, but illustrating another embodiment of the invention in which the plunger is arranged above the mold instead of below it.

The apparatus consists in its general arrangement of a mold or die I, a pressure cylinder 2, and a plunger 3,- operable in the pressure cylinder. The mold or die I is mounted in a die carrying frame or press of convention-a1 design which is indicated generally by the reference numeral 4. The press 4 is provided with suitable mechanism for opening and closing the die and locking it in closed position to resist the pressure of the metal which is injected into the die cavity upon operation of the plunger 3. This opening and closing mechanism is indicated diagrammatically at 5. It will be unnecessary to describe in detail either the die carrying press or the die opening and closing mechanism, since these may be of any desired construction which may be found suitable for the purpose, and the design and construction of these elements is thoroughly understood by those who are familiar with this art.

In the preferred embodiment of Figs. 1-3 the mold or die I consists of two complementary die portions 6, l, which are parted in a vertical plane or parting line 8. A casting cavity 9 is formed in one or partly in each of the die members 6, I. The casting cavity 9 is gated at ill in the customary manner. In the particular construction which has been chosen for the purpose of illustration and which I have found most adv-antageous in realizing the benefits of my improved apparatus, the mold or die is edge-gated. That is to say, the gate I0 is arranged on or adjacent to the parting line 8 of the mold. The edgegated type mold is peculiarly adapted to that feature of the present invention which makes it possible to remove all of the excess metal along with the castings, thus eliminating the necessity for special sprue-cutting devices.

Adjacent the lower edge of the die I, and lying in or adjacent to the plane of parting 8 thereof, is formed a cylindrical recess ll connected with the gate ID by a conically shaped portion l2. It will be noted that the pressure cylinder 2 also lies substantially in the plane of parting of the mold and is in alignment with the aforesaid cylindrical recess ll formed in the die members 6 and 1. This pressure cylinder or container 2 is preferably i'ormed at its upper end with a conic-ally or spherically shaped nozzle l3 fitting into or against a similarly shaped recess M in the mold I. In the claims, the term bevelled end as employed with reference to the end l3 of the pressure cylinder 2, is used in a generic sense, and is intended to include both conically and spherically shaped ends and their equivalents, as distinguished from a fiat end. The term complementary bevelled surface refers to the similarly shaped recess M in the mold, and has a like significance. Suitable means are provided for holding the pressure cylinder 2 tightly against the edge of the die 1 during the casting operation. Since the die members 6 and l are arranged to be separated in a horizontal direction as will be seen best in Fig. 2, it is unnecessary to provide means for periodically advancing and withdrawing the pressure cylinder 2. It is, however, preferable to provide a suitable vertical adjustment for the cylinder 2 in order that the press may be made to accommodate dies of'varying sizes properly mounted in asubstantially central position with respect to the horizontal axis of the press. Such a vertical adjustment may take the form :mo'wn by way of example in Fig. l of the drawings in which the pressure cylinder 2 is arranged to engage at its lower end a cross-head l5 slidably mounted for movement in a vertical direction on the connecting rods I6 and is vertically adjustable by means of the nuts [1. The operation of the plunger 3 is controlled by suitable valve mechanism (not shown).

An important feature of the present invention resides in making the diameter of the cylindrical recess II in the edge of the die I of a diameter substantially equal to or greater than that of the interior of the pressure cylinder 2. The purpose of this is to allow all of the excess metal to be ejected from the pressure cylinder 2 coincidentally with the casting operation. As will be seen upon examination of Fig. 1, the plunger 3 may be raised to the extent that its forward end is flush with the nozzle l3 of the pressure cylinder 2 or even beyond this point until it advances an appreciable distance into the cylindrical recess ll of the die itself. It will be readily understood that if the exact amount of metal required to completely fill the casting cavity 9, gate l0 and recess H could always be accurately measured out and ladled into the cylinder 2 (plus the amount of metal which might be lost as flashing or through the vent holes quite commonly employed in the dies), then (and only then) all of the metal would be ejected from the pressure cylinder 2 when the top of the plunger 3 was flush with the top of the pressure cylinder. In this case the cylindrical recess I I might be replaced by a conical recess or a recess of some other shape and yet all of the excess metal would be removable with the casting in the form of sprue. This might be true even where a slightly greater amount of metal was used, in which case the finished casting with its attached sprue might be left sticking out of the end of the pressure cylinder 2 when the die halves were parted. The casting with its attached sprue could then be pulled out of the cylinder. Thus, with such an alternative construction, the advantages of my invention may be realized to a certain extent in that by arranging the pressure cylinder and connecting gate portion of the mold on the parting line it becomes possible by proper manipulation to remove all of the excess metal along with the casting without use of special sprue-cutting devices or similar means, and without retracting the pressure cylinder.

I prefer, however, to make the entrance portion ll of cylindrical form as has been described, so that the plunger 3 may penetrate a certain distance into the mold itself. With this arrangement, the charging of the pressure cylinder or container 2 prior to casting and the elimination of all excess metal after casting is greatly simplified. For example, relatively slight variations in the amount of metal ladled or otherwise introduced into the pressure cylinder 2 prior to casting affects only the extent to which the plunger 3 advances into the cylindrical recess ll of the die. If a little less metal is put into the cylinder 2 on one particular occasion, it simply means that the plunger 3 will advance a somewhat greater distance into the recess H; and if a greater amount is used, the plunger will not advance so far; but within certain easily controllable limits as to the amount of metal charged into the pressure cylinder 2 prior to casting, it is assured that all of the excess metal will be ejected from the cylinder 2 and thus be readily removed from the mold along with the finished casting in the form of attached sprue, without necessitating retraction of the pressure cylinder to free it from the sprue.

The operation of the apparatus shown in Figs. 1 to 3, inclusive, is as follows:

In Fig. 1 the parts are shown in the position occupied at the completion of the casting operation. The plunger 3 is first retracted and the die I opened by separating the die halves 6 and I to eject the finished casting. It will be quite obvious to those skilled in the art that manually or mechanically-operated ejector pins commonly employed to assist in the removal of the casting may be employed in connection with my machine if so desired. Fig. 2 shows the parts in the position just referred to in which the die members 6 and l are separated and the plunger 3 withdrawn to a position below the original pouring position. The plunger 3 is now raised to an intermediate position, as shown in Fig. 3, but with the die members 6 and 1 remaining in the separated position shown in Fig. 2. Molten, semi-molten, or semi-plastic metal is now ladled from a melting pot (not shown) into the pressure cylinder 2 in an amount sufficient for one gate of castings. The die is then closed and locked in the position shown in Fig. 3 and the plunger 3 driven upwardly by means of the hydraulic ram, the cylinder of which is shown at l8, injecting the metal into the die where it solidifies. The plunger again occupies the position shown in Fig. l, and the cycle is complete.

Fig. 4 illustrates another embodiment of the invention in which the die 2| is edge-gated at the top of the mold for cooperation with a pressure cylinder 22 positioned thereabove and having a plunger 23 operable therein. 'The press 4 and mold opening and closing mechanism may be the same as that employed in the arrangement described in connection with the embodiment of Figs. 1-3. A gate shut-off member is provided which may consist of a valve 24 slidably arranged in one of the .die members 25. Valve 24 is provided at its forward or inner end with an upwardly facing inclined surface 26 disposed in a gate 21 when the die 2| is closed and the valve is in position to close the gate. Valve 24 is arranged to be moved into its closed position by means of the ejector mechanism 28.

The operation of this form of apparatus is as follows: Y

The die is closed, the valve 24 being in such a position that it closes the passage between the casting cavity 29 and the gate runner 30'. The metal to be cast is poured into pressure cylinder 22 and the plunger 23 is forced downwardly against the metal in the cylinder. When willoient pressure is developed by the plunger, the valve 24, by reason of the provision of the inclined upwardly facing end surface 26 against which the metal bears under the pressure exerted by gravity and by the plunger 23, is forced outwardly and to one side, opening the passageway between the gate runner 30 and the casting cavity 29, allowing metal to be forced into the mold. The valve 24, with its inclined face 26, thus constitutes means operable by the pressure produced within the metal to automatically open the gate and allow the metal to flow through into the mold.

Excess metal after the die cavity is filled remains in the recess 30, which, as in the form described in connection with"Figs. 1-3, is cylindrical in form and of a diameter not less than that of the pressure cylinder 22, thereby forming an offsets the reduction in temperature.

extension of the pressure cylinder, so that the plunger 23 is adapted to enter the cylindrical recess 30 to remove all excess metal from the' cylinder proper (22). Thus, with this form of the apparatus as in the embodiment previously described, all of the excess metal is removable with the finished casting in the form of sprue attached thereto. As the die is opened to eject the casting, the ejector mechanism 28 returns the valve 24 to its original position, so that when the'die is again closed the passageway between the casting cavity 29 and the gate runner 30 will be closed. The principal advantage of this form of the invention resides in the arrangement whereby the plunger 23 may be completely withdrawn from the pressure cylinder 22 to allow introduction of the metal to the cylinder prior to the casting operation but after the die has been closed. With the cylinder positioned below the mold, it is necessary to separate the die halves in order to allow introduction 'of the metal into the pressure cylinder, so that it is necessary to close and lock the die after the metal has been poured. Thus, with the form illustrated in Fig. 4, the elapsed time between pouring and casting may be reduced somewhat and a slight reduction in pouring temperature is possible. On the other hand, the embodiment of Figs. l-3 possesses the advantages of greater simplicity because of the elimination of any necessity for a valve mechanism in the gate.

With a pressure casting machine constructed in accordance with the principles of the present invention, it has been found possible to produce castings of aluminum alloys under a pressure on the order of between 5000 pounds and 10,000

pounds per square inch. It has been found possible by the use of these higher pressures to maintain the casting temperature of the metal close to the freezing pointor even slightly below the freezing point, since the use of higher pressures The castings produced are characterized by soundness and freedom from porosity. When the machine is used for casting easily oxidizable metals, the reduction in metal temperatures becomes particularly important, which means that my improved machine is well adapted to the production of magnesium die castings. Yet the construction of the machine is extremely simple, and because of the novel arrangement of parts, the problem of removing excess metal after the casting operation is greatly simplified.

It is to be distinctly understood that various modifications may be made in the invention as described, without departing from the invention defined inthe appended claims. For example, the machine might be designed for operation by hand instead of by power as has been suggested. Again, while I have shown and described a two-part die, it would be feasible to employ a multi-part mold in which there is more than one plane of parting, in which case the axis of the pressure cylinder will be arranged in one of the planes of parting or at the intersection of the various planes of parting.

I claim:

1. Apparatus for the pressure casting of meals comprising a separable mold parted in a substantially vertical plane and being provided with a casting cavity having a gate disposed thereabove, a pressure cylinder above the mold cavity and connected with said gate when in position for casting, said pressure cylinder being formed in part in a separate member adapted to receive metal for introduction into the mold and in part in the mold, a plunger operable in the cylinder to completely eject the metal from said separate member, said plunger being removable from the cylinder to allow introduction of the metal while the mold is closed and in casting position, and a gate shut-off member slidably arranged in the mold and having an upwardly facing inclined face disposed in the gate when in closed position whereby upon application of sufiicient pressure said shut-oil member will be caused to slide out of closed position and allow the metal to enter the mold.

2. Apparatus for the pressure casting of metals comprising a separable mold having a plurality of sections and provided with a casting cavity and a gate arranged at the parting of the sections, a pressure cylinder in alignment with said gate and a plunger operating therein, said pressure cylinder provided with a bevelled end for contact with a complementary bevelled surface provided on a mold section, and means for withdrawing said mold section from the axis of the pressure cylinder to allow removal of the finished casting without movement of the pressure cylinder relative to the remainder of said mold.

3. Apparatus for the pressure casting of metals comprising a separable mold having a plurality of sections and provided with a casting cavity and a gate arranged at the parting of the sections, a pressure cylinder adapted to receive metal for introduction into said mold cavity and a plunger operating in the pressure cylinder, said pressure cylinder arranged in alignment with said gate and formed in part in a separate member positioned adjacent to but exteriorly of the mold and in part in the mold proper whereby said plunger is operable to completely eject the metal from that part of the cylinder which lies exteriorly of the mold, said pressure cylinder having a bevelled end for contact with a complementary bevelled surface provided on a mold section, and means for withdrawing said mold section from the axis of the pressure cylinder to allow removal of the finished casting and attached sprue without movement of the pressure cylinder relative to the remainder of said mold.

JAMES N. SMITH.

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