Method of and apparatus for vacuum casting
First Claim
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1. A method of vacuum casting comprising:
- a first step of closing, with a gate member, a sprue of a cavity formed in a die;
a second step of feeding molten metal stored in a molten metal storage tank through a molten metal passage to a molten metal reservoir which is communicated with the sprue through the gate member and is also communicated with the molten metal storage tank via the molten metal passage, until the lowest head of the molten metal fed into the molten metal reservoir becomes higher than the level of the sprue;
a third step of reducing the pressure in the cavity, the third step being executed either before, simultaneously with or after the second step;
a fourth step of communicating the sprue with the molten metal reservoir and also with the molten metal passage by moving the gate member when the pressure in the cavity has been reduced to a predetermined pressure; and
a fifth step of having the interior of the molten metal reservoir isolated from the atmosphere and held gas tight while the molten metal having been fed into the molten metal reservoir is introduced into the cavity as a result of the communication brought about in the fourth step between the sprue and the molten metal reservoir, with the lowest head of molten metal in the reservoir being held to be higher than the level of the sprue during this time.
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Abstract
In a method of vacuum casting wherein when the molten metal previously introduced into a molten metal reservoir is fed into a cavity, the lowest head of the molten metal in the molten metal reservoir is held to be higher than the level of a sprue, so that the cycle time of casting may be shortened and the quality of cast products may be improved. To this end, the interior of the molten metal reservoir is held gas tight while the sprue is opened by a gate member of straight tubular shape.
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Citations
17 Claims
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1. A method of vacuum casting comprising:
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a first step of closing, with a gate member, a sprue of a cavity formed in a die; a second step of feeding molten metal stored in a molten metal storage tank through a molten metal passage to a molten metal reservoir which is communicated with the sprue through the gate member and is also communicated with the molten metal storage tank via the molten metal passage, until the lowest head of the molten metal fed into the molten metal reservoir becomes higher than the level of the sprue; a third step of reducing the pressure in the cavity, the third step being executed either before, simultaneously with or after the second step; a fourth step of communicating the sprue with the molten metal reservoir and also with the molten metal passage by moving the gate member when the pressure in the cavity has been reduced to a predetermined pressure; and a fifth step of having the interior of the molten metal reservoir isolated from the atmosphere and held gas tight while the molten metal having been fed into the molten metal reservoir is introduced into the cavity as a result of the communication brought about in the fourth step between the sprue and the molten metal reservoir, with the lowest head of molten metal in the reservoir being held to be higher than the level of the sprue during this time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for vacuum casting comprising:
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a die having an internal cavity; a gate member for switching a sprue of the cavity between a closed state and an open state; a molten metal storage tank for storing molten metal; a molten metal passage communicated with the molten metal storage tank; a molten metal reservoir communicated with the sprue via the gate member and also communicated with the molten metal passage; a change-over valve operable to be switched between a state to hold the molten metal reservoir interior gas tight and a state not to hold the molten metal reservoir interior gas tight; an evacuating pump for reducing the pressure in the cavity; molten metal introducing means for introducing the molten metal in the molten metal storage tank through the molten metal passage into the molten metal reservoir with the sprue held closed by the gate member and the molten metal reservoir interior not held gas tight by the change-over valve, the molten metal being introduced until the lowest head of molten metal introduced into the molten metal reservoir becomes higher than the level of the sprue; and gate member drive means for switching the gate member to an open state after the pressure in the cavity has been reduced to a predetermined pressure by the evacuating pump, molten metal has been introduced by the molten metal introducing means into the molten metal reservoir, and the change-over valve has been switched to hold the molten metal reservoir interior gas tight. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification