US2985928A - Method and apparatus for die casting and moulding - Google Patents

Description

y 1961 K. D. HESKETT 2,985,928

METHOD AND APPARATUS FOR DIE CASTING AND MOULDING Filed Nov. 18, 1958 /4- A i /5 \W [729 lnvenior KENNETH DAV 1 D HESKETT 5W Attorney United States Patent METHODtAND APPARATUS FOR DIE CASTING AND MOULDING Kenneth David Heskettg. Lower Edmonton, London, England, assignor to SparkletsLi'mited, aBritish company FiledNon 18,, 1958., Ser. No. 774,722.

Claims prlority, application Great Britain Nov. 22,1957 1 Claim. (CI. 22-73) This invention relates to apparatus for the die casting of metals and for the moulding of othermaterials such, for example,as synthetic; thermoplastic materials.

It is an object ofthis invention to provide improved apparatus for feeding flowable material such as molten metal or other mouldable material from a reservoir to a die in which the die casting or moulding operation takes place.

According to the invention, apparatus for feeding flowable material to the charging chamber of a die casting or moulding machine comprises a feed conduit which extends from a reservoir for the flowable material to a port in the charging chamber, a vacuum conduit which extends from a second port in the charging chamber and which is connected to a source of vacuum via a vacuum valve, and a charging plunger which is slidable in the charging chamber for delivering flowable material therefrom, said charging plunger acting to close the ports during its delivery stroke and to uncover them during its return stroke, and means being provided for preventing flowable material from being sucked along the vacuum conduit into the source of vacuum.

Preferably the means for preventing flowable material from reaching the source of vacuum consists of arranging the vacuum conduit to extend upwardly from the charging chamber for at least a sulficient portion of its length to render this sucking in of flowable material unlikely to occur. For example, the vacuum conduit could extend upwardly to a minimum vertical height of, say, one third of the height at which a column of the flowable material would be supported by a perfect vacuum, so that the source of vacuum would need to produce a degree of vacuum in excess of 33 /3 before flowable material could reach the top of the upwardly extending portion of the vacuum conduit, a condition which is unlikely to occur in practice.

However, as an additional safety measure in this connection, and for rapid production of vacuum conditions in the charging chamber, a vacuum reservoir may be located between the source of vacuum and the vacuum valve, said vacuum reservoir being of volume greater than the volume of the charging chamber and acting to receive any flowable material which may be sucked along the vacuum conduit and thereby prevent it from reaching the source of vacuum.

An embodiment of the invention will now be described with reference to the accompanying drawing, which is a diagrammatic sectional side elevation, showing those parts of a die casting machine to which the invention is applicable.

Referring to the drawing, the fixed die plate of a die casting machine carries the usual fixed die part 11. The movable die part which mates with the fixed die part 11 is indicated at .12, and the said die parts 11 and 12 provide a die cavity 1'3 between them when in the closed condition illustrated, as well as the usual gate 14 and sprue l5.

Mounted horizontally in the fixed die plate 10 is a ice cylindrical charging chamber 16, having slidable therein a charging plunger 17 which is shown in the drawingin its fully retracted position. A heated pot or crucible 18 for molten metal 19', such as aluminium or zine base alloy, is disposed below the charging chamber 16, and a. feed conduit 20 having its lower end immersed in the molten metal '19 extends upwardly from the crucible -18 to a port 21 in the bottom of the charging chamber 16. Note that the charging plunger 17 uncovers the port 21 when in its. fully retracted position, and that the plunger will obturate the port 21 during its delivery stroke.

A second port 22 is provided in the upper part of the charging chamber 16, substantially opposite the first port 21 so that the plunger 17' acts to uncover and obturate both these. ports, and this port 22 has a vacuum conduit 23 extending vertically upwardly therefrom to a height of, say, fifteen feet above the charging chamber 16. The vacuum conduit 23 is joined to a. horizontal extension 24 thereof which contains a, vacuum valve 25, whereby the vacuum conduit can be connected to or isolated from a source of vacuum such as a vacuum pump indicated at 26.

A vacuum reservoir 27 is located between the vacuum pump and the vacuum valve, and it will be appreciated that in operating the machine the vacuum pump will operate continuously, so that when the valve 25 is closed the pump 26 continuously produces vacuum conditions in the reservoir 27 for rapidly producing a degree of vacuum in the vacuum conduit 23 when the valve 25 is opened.

With the parts of the apparatus in the positions shown in the drawings, i.e. ready for a cycle of operations to begin, said cycle commences with the opening of the vacuum valve 25. The reservoir 27 ensures that a good degree of vacuum is produced virtually instantaneously in the vacuum conduit 23 and all spaces which are in communication therewith, viz. the feed conduit 20, the charging chamber 16 and the die cavity 13.

Molten metal enters the charging chamber 16 from the crucible 18 via the feed conduit 20 under the influence of the vacuum until the chamber is charged, and the end of this charging period is determined by the cutting off of the vacuum, either by closing the valve 25 or by effecting the charging stroke of the charging plunger 17 so that the plunger obturates the ports 21 and 22 before the valve 25 is closed. Thus the valve 25 may be closed either before or immediately after the plunger 17 obturates the ports 21, 22.

An air seal is indicated at 28, between the piston 17 and the charging chamber 16, and gas heating flames acting on the feed tube 20 are indicated at 29.

The plunger 17 is provided with a projection 30 which lies between the opposed ports 21 and 22 when the plunger is in its retracted position, said projection acting to prevent the molten metal from passing directly from the feed conduit 20 to the vacuum conduit 23 in uninterrupted flow by deflecting the incoming molten metal horizontally along the chamber 16.

It will be appreciated that the duration of the charging period during which molten metal is being sucked into the chamber 16' will ideally be of such duration that the chamber 16 is charged. The height of the vacuum conduit 23 provides a means whereby molten metal will normally be prevented from being sucked into the vacuum pump 26, as already referred to previously, and the vacuum reservoir 27 provides a further safeguard in that it will receive any molten metal which may pass the valve 25 and thereby prevent it from reaching the pump 26.

It will be appreciated that in accordance with normal practice in die casting machines the closing of the dies 3 11 and 12 will be effected by power-operated means, as also will the actuation of the plunger 17 in timed relation with the die movements. It will therefore be obvious that the vacuum valve 25 will also be power-operated, and in timed relation with the other operations 'of the ma-, chine, to be opened immediately after the dies have been closed and to be closed either just before or just after the plunger 17 commences its charging stroke.

While one arrangement in accordance with the present invention has been described as applied to a metal die casting machine it will be appreciated that similar principles can be applied to other types of moulding machine in which a molten or fluid metal including, for example, synthetic resinous materials is delivered to a die.

What I claim is:

In a pressure die-casting machine of the class operating by the known process of feeding a charge of molten metal by vacuum suction into a charging chamber through an inlet port in front of a retracted charging plunger and forcing the charge of molten metal into a die cavity by means of said charging plunger, the improvements providing for better and higher speed operation of the machine, and comprising the combination with said charging chamber and charging plunger of vacuum-creating 4 mechanism including vacuum reservoir and conduit means connected with a vacuum port in the charging chamber which is substantially opposite the molten metal inlet port for rapid creation of vacuum conditions in said chamber, and a projection on the face of the charging plunger operative to deflect molten metal entering said charging chamber through said inlet port away from said vacuum port, wherein the conduit means leading from the vacuum port to the vacuum-creating mechanism has a vertical height relevant to said charging chamber in excess of the theoretical head of the molten metal obtained with a perfect vacuum, so that the degree of vacuum induced in the chamber cannot possibly suck molten'metal through said conduit means and intosaid mechanism.

References Cited in the file of this patent UNITED STATES PATENTS 1,954,775 During et a1 Apr. 10, 1934 2,243,835 Brunner et a1. June 3, 1941 2,514,390 Hagen July 11, 1950 2,837,792 Ring July 10, 1958 2,837,794 Ring .L June 10, 1958

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