Metal founding – Process – Shaping liquid metal against a forming surface
Reexamination Certificate
1999-12-10
2003-05-20
Elve, M. Alexandra (Department: 1725)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S120000, C164S061000, C164S312000
Reexamination Certificate
active
06564853
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to pressure casting of multiple parts and, more specifically to simultaneous pressure casting of lead and lead alloy battery terminals to inhibit the formation of cracks and tears during the solidification of the battery terminal.
BACKGROUND OF THE INVENTION
Battery terminals, which are typically made of lead or a lead alloy, are usually cold formed in order to produce a battery terminal that is free of voids and cracks. If lead or lead alloy battery terminals are pressure cast, air is left in the battery terminal cavity in the mold so that as the lead solidifies, the air bubbles prevent the battery terminal from cracking. That is, the air bubbles act as fillers so the lead remains distributed in a relatively uniform manner throughout the battery terminal. Unfortunately, air bubbles within the battery terminal cause the battery terminal to be rejects as the air bubbles can produce large voids in the battery terminal. In order to minimize the air bubbles in the battery terminal, a vacuum can be drawn in the battery terminal cavity mold; however, although the vacuum removes air from the mold and inhibits the forming of air bubbles in the battery terminal, the battery terminals cast with a vacuum in the battery terminal cavity oftentimes solidify in an uneven manner producing battery terminals with cracks or tears which makes the battery terminal unacceptable for use. In the present process, a battery terminal is cast which is substantially free of cracks and tears by pressure casting a lead alloy while a vacuum is being applied to the battery terminal cavity. After the lead in the battery terminal cavity reaches the liquid-to-solid transformation stage, a piston is driven into the mold to rapidly reduce the volume of the mold. By precisely controlling the time of application of an external compression force to the lead in the battery terminal cavity, and consequently, the time at which the volume of the battery terminal cavity is reduced, one can force the into a smaller volume while the pressure on the battery terminal cavity is maintained. By maintaining the pressure on the battery terminal cavity during the solidification process, the battery terminal can be cast in a form that is substantially free of cracks and tears.
In the present invention a plurality of molds are connected to a runner to allow one to simultaneously form a plurality of battery terminals followed by using an external compression force to intensify the pressure of the lead to produce a battery terminal substantially free of cracks and tears.
SUMMARY OF THE INVENTION
Briefly, the system comprises an apparatus and method for simultaneously pressure casting a plurality of battery terminals to produce a plurality of battery terminals substantially free of tears and cracks. A gate formed by a retracting piston extends into each of the plurality of battery terminals molds to maintain the battery terminal mold in a closed condition so that molten lead cannot enter any of the molds until a specified time. When the molten lead has filled the runners to all the battery terminal molds and while the lead is still in the molten state the gates to each of the battery terminal are opened simultaneously so that all the battery terminal molds can receive the molten lead at the same time. After a predetermined time sufficient to allow for filling of the molds the set of retractable pistons are simultaneously driven into their respective molds to thereby increase the pressure on the lead therein. As the lead in each of the molds solidifies under the reduced volume and pressure it simultaneously produces a plurality of battery terminal that are substantially free of both tears and cracks.
REFERENCES:
patent: 4497359 (1985-02-01), Suzuki et al.
patent: 4753283 (1988-06-01), Nakano
patent: 4967827 (1990-11-01), Campbell
patent: 5048590 (1991-09-01), Carter
patent: 5244033 (1993-09-01), Ueno
patent: 6202733 (2001-03-01), Ratte
patent: 0559920 (1993-09-01), None
Elve M. Alexandra
Tran Len
Water Gremlin Company
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