US2206211A - Casting press - Google Patents

Description

y 2, 1940- K. F. WAGNER 2,206,211

CASTING mass Filed Feb. 10, 1937 2 sheets shee 1 frz aenfor War/1282M k6 liywer I am r Jaw July 2, 1940.

K. F. WAGNER CASTING FRISS 2 Sheets-Sheet 2 Filed Feb. 10. 1937 Ill IIHH ll HHIH Patented July 2, 1940 UNITED STATES 2,206,211 CASTING mmss Karl Friedrich Wagner, Friedrichshafen, Bodensee, Germany,

Application February 10, 1937, Serial No. 124,978 In Germany February 13, 1936 Claims.

My invention relates to casting presses, i. e. to machines for casting metal and more especially light metals under pressure. It has more particular reference to the pressure-casting of read- 5 ily oxidisable metals such as magnesium or aluminum in such manner that the molten metal is not oxidized in contact with the air.

Hitherto, 'when feeding readily oxidisable metals of the kind here in view into casting presses with a pressure chamber located outside of the crucible the metal has as a rule been ladled out by hand and has thus been exposed to oxidation. The protective matter covering the surface of the molten metal in the crucible had to be partly removed before entering the ladle in the metal, which was thus likely to become oxidized. Moreover the danger arose that together with the ladle obnoxious constituents of the protective cover might enter the pressure chamber together with the metal and that the metal and more especially the residual metal adhering to the ladle might come to burn during the operation. All these drawbacks impaired the quality of the metal and the castings made from it, which enclosed oxides and nitrites. These drawbacks also necessitated expensive interruptions of the work and led to considerable metal losses by continuous oxidation. The burning metal may further endanger the health and life of the operators. i

The present invention relates to means whereby the casting of light metals including magnesium, aluminum, etc., and their alloys is greatly facilitated. The invention is applicable to casting presses with a pressure chamber extending vertically, horizontally or obliquely. In accordance with this invention the molten metal is metered and conveyed from the melting pot into the pressure chamber located outside of the melting pot 1 L0 through closed spaces inaccessible to the outer air, which are arranged partly above and partly below the level of the molten metal and the melting pot. The quantity of molten metal to be pressed is metered below the metal level and lifted, by means of a piston operated from without, above the metal level until the molten metal enters the casting channel. When a predetermined quan-v tity of metal has been displaced in this channel,

the metering piston will come to a standstill and 0 the feed piston sliding in the channel now shifts the metal lying in front of it into the pressure chamber adjoining the channel. Both the metering and the feed piston are actuated from without the melting pot, preferably by positively 5 operated cylinders and pistons acted upon by hydraulic or pneumatic pressure. Other mechanical means may however also be provided for actuating the pistons. Since the pistons are required to operate at exactly predetermined periods, they are preferably actuated in connection with the means actuating the casting press proper, however, in manually operated presses the two pistons might also be manually operated.

The cylinder enclosing the metering piston is formed with a lateral opening through which fluid metal may enter the cylinder whenever the metering piston has been lowered to the extent of uncovering the opening. While the lower part of the metering cylinder is always submerged in the fluid metal, the charging channel formed integral with it is always arranged above the metal level. Preferably the cylinder and channel are combined with a cover closing the melting pot. They may be made in one or several pieces. V

The inner spaces thus formed above the metal level may be filled with inert gases or vapors or may be partly evacuated and part of the oxygen and nitrogen removed by evacuating the air therein." In contradistinction to similar devices the joint faces between the melting pot and the top covering same simply abut against each other without any packing. Preferably the melting pot is formed with a marginal wall surrounding its top and the space enclosed between the top and this wall may be filled with material, such as carnallite, forming gases. If the interior of the melting pot is evacuated, the ambient air entering through the carnallite and the joints will carry carnallite vapors into the melting pot, the

air in which takes up such vapors and consequently prevents oxidation of the metal. Since the carnallite 'or similar material does not permanently develop vapors, the supply must be replenished from time to time, preferably by in- 40 serting in the space enclosed between the top of the melting pot and the cover some receptacles containing carnallite, which snugly fit this space. The melting pot and the header cover are heated uniformly so that also the carnallite is heated for evaporation. 1 Particular importance is attached to that part of the charging channel which projects from the melting pot. above the metal level and connects the melting pot with the pressure chamber arranged in the casting press. This connection is so arranged that in spite of the close connection between the melting pot and the casting press no obnoxious convection of heat to the press takes place, although the charging channel is as I further provide a protective sleeve surrounding the press stamp, which permanently prevents 15 the access of air to the space between the pressure chamber and the press stamp, except during the time when the discard is expelled from the pressure chamber. The protective sleeve is preferably arranged for displacement in parallel to 20. the press stamp either by hand or by means of a controlled or uncontrolled hydraulic or pneumatic power cylinder and piston. The interior, inaccessible to the outer air, of the protective sleeve may be connected with the interior of the 25 melting pot by a pipe system, so that also the interior of the sleeve may be evacuated and filled with a gas poor in oxygen and nitrogen. The protective sleeve may however also be stationary and be formed with apertures, which may be 30.closed, for expelling the discard and it may be provided with means, independent of the melting ,pot, for evacuating air and introducing gas.

Obviously this invention does away with the injurious consequences of the modes of operation 35 hitherto used when casting light metals such as magnesium or aluminum or its alloys incasting presses, since the fiuid metal is charged from the melting pot into the pressure chamber in such manner, that the quantity of metal about to be '40 charged does not come'in contact with the outer air and soiling of the metal and losses by the formation of oxides and nitrites are avoided. The

invention further renders the charging of thepress more eflicient, since the quantity of metal 45 to be pressed is uniformly predetermined and fed to the pressure chamber, independently from the operator, by the mechanically actuated metering device. In this manner the hitherto unavoida ble wasting of metal by discards of different sizes 59 and by the metal adhering to the ladle are avoided. Similar losses are hitherto encountered when removing the metal adheringto the ladle and returning it into the melting pot. This metal contains a high percentage of impurities and l 55 greatly impairs the qualities of the molten metal.

Apart from the light metals proper such as magnesium and aluminum, also zinc and its alloys can be cast with advantage in the manner here described.

In the drawings afllxed to this specification and forming part thereof an embodiment of my invention is illustrated? diagrammatically by way of example. t

In the drawings:

65 Fig. 1 isalongitudinal section and Fig. 2 a cross-section of the melting pot, the

charging device and pressing device, while Fig. 3 illustrates on a larger scale the means for adjusting the metering piston.

Referring to the drawings, is the melting oven and 2' is the melting pot removably mounted therein, while 3 is the metering cylinder, the .in-

take'opening 4 of which is arranged below the metallevel 5, which ispermanently maintained 7 at uniform level by well-known means (not shown). The intake opening 4 is preferably located near the center of the body of molten metal where the metal is known to be purer than in other parts. The charging channel 6 is preferably formed integral with the metering cylinder. I is 5 the hood covering the metering cylinder and charging channel and closing up the melting pot,

at the same time preventing access of air to the metal. The heating gases flowing around the melting pot rise above the hood 1 whereby the metal in the pot as also the parts arranged above the metal are heated uniformly. 8 is a cover cov ering the oven as a whole and serving to lead the heating gases in the desired direction and to reduce the radiation of heat. 9 is a piston reciproeating in this metering cylinder 3, rods l0 and II connecting the piston with the power cylinder |2,

a cross piece I3 connecting the two rods, which are extended upwardly at |4, -|5 carry nuts l6, whereby the stroke of the piston l1 can be adjusted in accordance with the quantity of metal to be pressed.

In the channel 6, which is here formed with rectangular cross-section, the piston I8 is reciprocated by means of the level 20 and power cylinder IS. The piston l8 serves for forcing the metal lifted by the metering piston into the pressure chamber 2|, the end of the charging channel 6, which projects from the melting pot, forming a mouthpiece fitting exactly a notch in the wall of the pressure chamber 2|.

The wall of the melting pot is extended upwardly and this extension 23 encloses with the part of the charging channel 6 and the hood I a chamber 24, in which are mounted iron receptacles 25, containing bodies of carnallite 26 or the like. The vapors developed by the heated carnallite are sucked, in consequence of the partial vacuum in the interior 21 of the melting put, across the joints into the pot and serve to protect 40 the metal surface against oxidation. The am-- bientair as such has no access to the metal surface in view of the very limited passage and since the air would have to first flow through the heatinggases in the oven chamber 28 and the chamber 24 filled with carnallite. I may however also introduce into the melting pot inert gases or vapors under slight pressure above normal.

The press stamp 29 is surrounded by an axially displaceable sleeve governed by a power. cylinder 33, to which it is connected by an arm 32. This sleeve serves for preventing air from entering the pressure chamber 2| and. the charging channel as soon as the discard has been expelled from the chamber, the sleevebeing lowered, for this purpose, upon the pressure chamber, which may thus be evacuated'and filled with inert gases and may also communicate by a pipe system with the space 21 above the metal in the melting pot. I thereby succeed in preventing contact of the air with the molten metal with ensuing oxidation.

This device operates as follows:

The mold mounted in the casting press (not 2 shown), .the bottom end 34 of which is shown in Fig. 1', being closed and in operative position,

the sleeve 3| is lowered by the piston 33 and airtightly seated on the pressure chamber 2|, while its interior is evacuated and filled with an inert gas flowing also into the charging channel 6. The metering cylinder. 3 is filled with metal. The piston 9 is now lifted by the cylinder |2 until the nuts l6 meeting the stop 3] prevent the piston II from rising further. In rising the piston 9 first covers the intake opening I and on rising further lifts the metal into the charging channel 6. The quantity of metal above the piston 9 can be predetermined exactly, by adjusting the nuts IE to form the casting with discard as desired. Directly the ascent of the metering piston 9 has come to an end, the charging piston l8 will force the metal into the pressure chamber 2 I, where the metal is now pressed by the lowered press stamp 29. While this is going on, the metering piston is lowered again, uncovering the intake opening land allowing the cylinder 3 to be refilled. The piston l8 also, returns into its initial position. During .the pressing it closes the mouth piece 22 in order to prevent any residual metal from entering the channel. As thepiston I8 is withdrawn, the protective sleeve 3| is also lifted, uncovering the aperture 35 of the pressure chamber, so that the discard can be expelled ina well-known manner, whereupon the sleeve 3! is lowered at once into operative position. On the mold being returned into casting position, the cycle of movements is gone through again.

I wish it to be understood that I do not desireto be limited to the exact details of construction I shown and described for obvious modifications will occur to a person skilled in the art. I claim:

1. Apparatus for casting under pressure readily oxidizable metals, comprising in combination, a closed melting pot, a charging cylinder extending above said melting pot, a metering device permanently extending from said cylinder into said melting pot, a pressure chamber communicating with said cylinder, a charging piston reciprocable in said cylinder for conveying metal raised by said metering device from said melting pot towards said pressure chamber. andmeans for preventing air from entering said melting pot, said charging cylinder and said pressure chamber while the metal isso conveyed. g 2. The apparatus of claim 1 in combination with a press stamp above and arrangedto be lowered into said pressure chamber and'a sleeve surrounding said press stamp and adapted to be lowered. onto said chamber to temporarily prevent air from entering said chamber and-the charging cylinder.

.3. The apparatus of claim l in combination 7 and communicating with said arranged to be heated together with said pot.

opening, a metering piston arranged for reciprocation'in the bottom part of said tube and past said opening, and means for reciprocating said piston,

with a gas developing chamber pro'videdabove melting potand 20 4. 'Iheapparatusof claim lwherein the meteringdevicei comprises a tube, having an-intake 5. .The apparatus of claim 1 combination I with a. cooling jacketsurrounding the charging KARL FRIEDRICH WAGNER. so

cylinder. 7

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