US2137764A - Apparatus for casting metal under pressure - Google Patents

Description

Nov. 2-2, 1938. K. F. WAGNER 2,137,764

APPARATUS FOR CASTING METAL UNDER PRESSURE Filed March 4, 1937 2 Sheets-Sheet 1 Nov. 22, 1938. K. F. WAGNER Y APPARATUS FOR CASTING METAL UNDER PRESSURE Filed March 4, 1937 2 Sheets-Sheet 2 Patented Nov. 22, 1938 I 2,137,754 APPARATUS FOR CASTING METAL UNDER PRESSURE Karl Friedrich Wagner, Friedrichshai'en,

Bod

ensee, Germany Application March 4", 1937, Serial No. 128,896 In Germany March 19, 1936 3 Claims.

My invention relates to the casting of metals and more especially to means for casting metal under pressure in permanent metal molds, as described for instance in my copending application for Letters Patent of the United States Serial No. 124,978, filed February 10, 1937, these apparatus being particularly useful when casting readily oxidizable metals such as magnesium and its alloys.

I have described an apparatusin which the pres-' sure chamber is directly combined with a filling chamber partly submerged in the melting pot, this system being delimited on one side by the pressure piston, on the other side by a counterpiston, which can be withdrawn altogether for the purpose of expelling the waste metal from the pressure chamber. In all cases the casting metal in the pressure chamber is compressed by means of a single pressure piston.

I have now found that I can obtain a better and quicker pressing eifect, if the metal enclosed in the pressure chamber before compression is forced towards the pistons simultaneously, which are moved in op- ,posite directions. In contradistinction to the apparatus disclosed in my copending applications, the pressure chamber is here delimited by at least two movablepistons which at the start of the pressure operation are spaced equally from the gate and are moved toward the gate in opposite sense and under equal pressure and with velocities such that. the casting metal is forced at high speed through thegate into the mold and that, when the pistons have reached the end of their stroke, the waste metal islocated below the gate. I prefer imparting to the piston moving above the filling chamber a certain lead relative to the counter-piston from its outer end position up to the position in which it covers the point where the filling cylinder joins the pressure chamber. In this position the two inner end faces of the two pistons are spaced equally from the center of the gate. Fromthis point on the two pistons are moved towards the gate in a uniform manner, preferably by a common source of energy and by means of a coinon control.

I have taken care that themovements of the two pistons, occur in absolute relative dependency in such manner that the influence of frictional resistances of different degree, which might arise gate by a plurality of pressure I lated in a well known manner.

during the sliding of the pistons in the pressure chamber and between the driving members is paralyzed by the selection of suitable constructions and an exact distribution of forces. Thus for instance the two opposed pistons may be connected with each other in the usual manner by a system of levers, with the aid of which the compression movement as well as. the return movement can be started by means of eccentric disks orcams mounted on a driving shaft which is driven by some suitable source of power. I may however also drive the two pistons in both directions by means of stationary power cylinders and a system of levers. Since these driving means are of a well known kind, it does not appear necessary to enter into a detailed description thereof. I have found the hydraulic drive to be the most suitable for the purpose of this invention, as it allows of controlling the operation of the two pistons in the simplest manner.

As mentioned above, it is essential that the movements of the pistons are controlled exactly and altogether positively in order to provide that uniform quantities of casting metal be always displaced from the pressure chamber by the two pistons. I thus obtain that the waste metal is .kept as small as possible and for the same purpose care is taken to arrange the runner midways of the waste metal.

I further provide the two pistons with adjustable means for limiting their stroke in order to prevent the pistons from passing beyond their end positions relative to the gate.

I prefer cooling the pressure pistons by means of water or some other suitable liquid supplied to cavities provided in the pistons through borings, the-circulation of the cooling liquid being regu- I thus avoid any accumulation of heat and consequent undesirable expansion of the pistons.

In 'the drawings afiixed to this specification and forming part thereof a casting device embodying my invention is illustrated diagrammatically by way of example.

In the drawings Fig. 1 is a vertical section of the smelting oven with the casting device disposed on top of it, while Figs. 2 to 7 illustrate the coaction of the two pressure pistons in the pressure chamber in their most important positions.

Fig. 2 is a longitudinal section of the pressure chamber showing the filling chamber filled with molten metal. a

Fig. 3 is a similar view showing the same parts after the pressure chamber has been filled with metal.

Fig. 4 illustrates the position of the parts at the beginning of the compression operation.

Fig. 5 shows the position of the pistons at the end of the operation.

Fig. 6 shows the position of the parts, while the waste metal is being expelled.

Fig. 7 shows their position during their return strokes and Fig. 8 illustrates on a larger scale the relative position of the waste metal and the runner.

Referring to the drawings and flrst to Fig. 1. ll is a smelting oven and 2| the melting pot filled with a body 22 of molten metal. 28 is the oven cover and 21 is a case forming part of the cover and enclosing the metal feeding and compressing means. I is a cylinder extending downwardly from the pressure chamber into the molten metal, this cylinder being formed with a lateral intake opening 9. 3 is the filling piston reclprocable in this cylinder by means of rods I4 governed by a piston 33. I is the cylinder forming the pressure chamber in communication with the fllling cylinder 8 and I and 2 are two pistons reciprocable in the pressure chamber, being governed by pistons SI and 32, respectively. I is the gate leading to the riser 35 formed in the mold 23 which is seated on top of. the pressure chamber and is closed by a cover 24 gove'rned by a piston 26. 3!

is a cooling or heating jacket surrounding the pressure chamber 34.

The pressure piston 2 is shown in Fig. 2 in its extreme end position, which is spaced a distance from the inner edge of the mouth 4 of the fllling cylinder 4 in the pressure chamber 1. In order to make the piston stroke as short as pos sible, the mouth 4 is partly covered by the piston 2 already in the extreme position of the piston.

The filling piston 3 now moves upwardly, cover-.

ing first of all the intake opening and lifting the metal I4 in the cylinder into the pressure chamber I (Fig. 3). After the metal has entered the space left between the two pistons in the pressure chamber, the piston 2 is started in the direction towards the gate 5, completely covering the mouth 4 (Fig. 4). When the piston 2 has moved into this position, the gate 5 is located exactly in the middle of the space III which is now delimited by the two pistons I and 2 (Fig. 4).

From this moment on the two pistons move in opposite-directions towards the gate 5 and compress the metal between them. The velocity of the two pistons during this movement is equal and so are the lengths of stroke and the pressures required for the compression.

Bythe control system indicated at 4| in Fig. 1 the two pistons are so connected with each other, that during the pressing operation they always move together and simultaneously, being driven either by hydraulic or by mechanical means.

On the mold having been filled through the gate I, the pistons I. and 2 come to a stillsiiand and now take up the positions shown in Fig. 5. Since the two pistons have carried out the compression work altogether uniformly, the runner I I now takes up exactly a position in the middle of the waste metal I! (Fig. 8).

In order to prevent the two pistons from moving beyond the desired end positions, stroke limiting devices are provided, as shown for instance in Fig. 2, where II is a collar mounted on the piston rod II and abutting in its end position against stops it fixed to the machine frame, whereby the piston, is stopped when the waste metal has reached a predetermined minimum thickness.

The piston I is now moved outwardly, the piston 2 following it in the same direction until it has exp lled the waste metal I2 from the pressure chamber (Fig. 6) Now first the piston I and thereafter also piston 2 move towards the right (Fig. 7) until the two pistons have reached their initial positions shown in Fig. 2.

In order to accurately control the temperature of the pistons, inflow and outflow conduits I1, I8 are formed in the piston rods and pistons, throug which a suitable cooling or heating agent may be;

passed (Fig. 3).

A material advantage of this combination of the pistons as compared with the devices disclosed in my copending applications consists therein, that in contrast to the apparatus operated by a single piston the piston stroke, when two pistons are provided, is reduced to one half and in the case of more than two pistons to a corresponding fraction. Furthermore the outflow velocity of the metal through the gate is greatly increased at equal piston velocities. This design further involves a. smaller overall length of the apparatus, in consequence of which also the parts enclosing the pressure chamber can be made smaller and lighter.

Obviously this casting apparatus is not limited to the casting of magnesium or its alloys, but may be used with equal advantage in the casting of other metals and alloys.

The gate 5 which connects the pressure chamber I with the mold may be arranged above, laterally of or obliquely to and at any desired angle relative to the pressure chamber. The pistons I', 2 and I and the power cylinders driving them are actuated by means of-a common controlling system H at a predetermined rate.

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

I claim:-

1. A metal casting apparatus comprising in combination, a cylinder forming a pressure chamber, two opposed pistons arranged in said chamber for reciprocation in opposite directions,

means for feeding molten metal into said chamber intermediate said pistons, a gate formed in the wall of said cylinder and means for holding said pistons equally spaced from said gate before compression begins, and for moving same towards said gate with equal pressures and speeds.

2. The metal casting apparatus of claim 1, m which the gate is located in the middle of the pressure chamber between'the inner edge of the mouth of the fllling cylinder and the outer end position of the outer pressure piston.

3. A metal casting apparatus comprising in combination a melting pot, a cylinder forming a pressure chamber secluded from air arranged outside said melting pot, two opposed pistons arranged in said chamber for reciprocation in opposite directions, a cylinder forming a fllling chamber secluded from air associated with and opening into said pressure chamber, a gate formed in the wall of said pressure chamber intermediate said filling chamber and one of said pistons, means for moving, in the starting operation, the other, pressure, piston until it covers the opening of said fllling chamber and means for thenmoving both pistons in opposite direction and about an equal distance toward said gate;

KARL FRENCH WAGNER.

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