It is an aim of the present invention to provide a double acting piston and cylinder so that multiple stroking metal dispensing can occur from a molten metal tank. Multiple stroking permits indefinite cylinder capacity. The piston may be reversed to continue filling the die with substantially no pause for refilling the cylinder. In the known processes of low temperature metal casting where a single acting cylinder limits the quantity of metal alloy dispensed, it was sometimes necessary to have more than one stroke to fill a die. There was always a time delay between strokes because it was necessary to refill the cylinder each time. This time delay resulted in a join line or mark occurring in the casting or encapsulation where the new metal from the next stroke joined metal from the previous stroke. In the present application, there is substantially no time delay between strokes so no join line or mark occurs.

The double acting cylinder permits the piston to fill a die from molten metal in the cylinder, while at the same time filling the cylinder on the other side of the piston. Furthermore, the present invention provides an apparatus for filling a die which has more capacity than a single acting cylinder. A single stroke may be used to fill a die or, alternatively, multiple bidirectional strokes may be used to fill a die, thus the machine is suitable for substantially any size of die.

In another embodiment there is provided an apparatus for filling a die with molten metal with valves positioned above the injection cylinder but still within the molten metal tank. This provides easier access to the valves for maintenance. Furthermore, the nozzle attachment on the end of the injection passageway may be positioned above the molten metal level in the tank which prevents leakage of molten metal if a valve should fail to close. In yet another embodiment, a check valve is arranged within the nozzle attachment to interface with the die. Thus, when the nozzle attachment is separated from the die, the check valve closes and there is always molten metal present at the tip of the nozzle outlet regardless of fluctuations of molten metal level in the tank. The check valve in the nozzle attachment acts as a safety valve to prevent molten metal escaping when the nozzle attachment is separated from the die.

The present invention provides an apparatus for filling a die with molten metal comprising: a tank adapted to contain molten metal, a double acting cylinder having both ends closed and an injection piston therein, means to reciprocate the piston in the cylinder, first passage means from one end of the cylinder to a first valve having a first opening to the tank and a second opening to an injection passageway leading to a die, the first valve having a first position wherein the first opening to the tank is open and the second opening to the injection passageway is closed, and a second position wherein the first opening to the tank is closed and the second opening to the injection passageway is open, first valve operating means to transfer between the first position and the second position of the first valve, second passage means from the other end of the cylinder to a second valve having a first opening to the tank and a second opening to the injection passageway, the second valve having a first position wherein the first opening

to the tank is open and the second opening to the injection passageway is closed, and a second position wherein the first opening to the tank is closed and the second opening to the injection passageway is open, second valve operating means to transfer between the first position and the second position of the second valve, and control means for the means to reciprocate the piston in the cylinder, and for the first valve operating means and the second valve operating means to fill the die with the molten metal.

In another embodiment there is provided a method of producing a casting or encapsulation from molten metal or the like, including a double acting cylinder located within a tank containing molten metal, the cylinder having both ends closed and an injection piston therein, means to reciprocate the piston in the cylinder, first passage means from one end of the cylinder to a first valve means with a first opening to the tank and a second opening to an injection passageway leading to a die, second passage means from the other end of the cylinder to a second valve means with a first opening to the tank and a second opening to the injection passageway leading to the die, the method comprising the steps of: closing the first opening to the tank in the first valve means and opening the second opening from the first passage means to the injection passageway, opening the first opening to the tank in the second valve means and closing the second opening from the second passage means to the injection passageway, moving the piston towards the one end of the cylinder having the first passage means therein to draw molten metal into the cylinder through the second passage means and inject molten metal into the die through the first passage means and the injection passageway.

In a further embodiment there is provided a method of producing a casting or encapsulation from a molten metal or the like including: a double acting cylinder located within a tank containing molten metal, the cylinder having first and second closed ends and an injection piston connected to a piston rod extending through the first end of the cylinder, means to reciprocate the piston in the cylinder, first passage means from the first end of the cylinder to a first valve means with a first opening to the tank and a second opening to an injection passageway leading to a die, second passage means from the second end of the cylinder to a second valve means with a first opening to the tank and a second opening to the injection passageway leading to the die, the method comprising the steps of: filling the cylinder wit molten metal through the second passage means with the piston adjacent the first end of the cylinder, closing the first openings to the tank in the first valve means and the second valve means, and opening the second openings from the first passage means and the second passage means to the injection passageway, moving the piston towards the second end of the cylinder to inject molten metal into the die through the second passage means and the injection passageway and recirculate molten metal through the second passage means and the first passage means into the cylinder on the other side of the piston.

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