Metal founding – Means to shape metallic material – Pressure shaping means
Patent
1982-12-16
1987-01-27
Lin, Kuang Y.
Metal founding
Means to shape metallic material
Pressure shaping means
164410, B22D 1700
Patent
active
046388486
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a metal mould for use mainly in die casting and more particularly to a venthole arrangement in the metal mould adapted to discharge the air within the metal mould without spouting molten metal.
DESCRIPTION OF THE PRIOR ART
It has been known that a metal mould is provided with a venthole in communication with the cavity so that the air within the metal mould can be discharged out of the mould when a charge of molten metal is poured into the mould for carrying out a casting operation. However the conventional gas discharge out of metal moulds has been performed by providing a clearance having a thickness or cross-section area on the order of 0.15 mm between the opposing or inner surfaces of the mating half portions of the metal mould. The reason for which the gas discharge clearance thickness or cross-section aarea is limited to 0.15 mm is that when molten metal comes to contact the cold inner or opposing surfaces of the two half portions of the metal mould, the molten metal instantly assumes a partially solidified state and increases its viscosity. The partially solidified molten metal with increased viscosity instantly becomes a laminar flow, the mould surface contacting portion of which tends to solidify to thereby form a thin solidified metal film. Since the inner portion of the molten metal advances upwardly at a higher speed than the mould surface contacting portion, the pressure within the metal mould drops and the contact between the mould surfaces and solidified metal film becomes an undesirable condition resulting in insufficient heat transfer between the molten metal and mould surfaces whereby the inner portion of the molten metal spouts out of the metal mould while maintaining its high temperature.
SUMMARY OF INVENTION
A metal mould of the invention comprises a plurality of first inclined gas escape grooves formed in an inner surface of a removable half portion of the metal mould, and a plurality of second inclined gas escape grooves formed in an inner surface of a fixed half portion of the metal mould in opposing relationship to the first inclined gas escape grooves and extending in a direction opposite to that of the first inclined gas escape grooves, the first and second inclined gas escape grooves communicating with a cavity in the metal mould. With the arrangement of the invention, since the first and second inclined gas escape grooves cross each other at many points, the molten metal flowing through the gas escape grooves impinges at the cross points is prevented from flowing out of the metal mould while the gas within the cavity is positively discharged out of the metal mould because of the large cross-sectional area of the inclined grooves.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of one preferred embodiment of a metal mould constructed in accordance with the present invention with a portion thereof broken away;
FIG. 2 is a fragmentary perspective view of a removable half portion of the metal mould as shown in FIG. 1;
FIG. 3 is a vertically sectional view of the metal mould as shown in FIG. 1; and
FIG. 4 is a fragmentary perspective view showing the flow pattern of molten metal in an inclined gas escape groove arrangement in the metal mould of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described referring to the accompanying drawings in which one preferred embodiment of the metal mould of the invention is shown for purpose of illustration,
As shown in FIG. 1, the metal mould generally comprises a removable half portion 1 and a mating fixed half portion 2 which portions 1 and 2 are adapted to be assembled together in spaced face-to-face relationship. The two half portions 1 and 2 are held in their assembled condition by conventional fastening means (not shown). The removable half portion 1 is integrally formed on the inner surface with a trapezoidal-shaped cross-sectional projection 3 extending inwardly from the inner surface. As shown in FIG. 3, the fixed half portio
REFERENCES:
patent: 4154285 (1979-05-01), Yamasaki
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