Die-casting process and equipment

A vacuum die-casting machine including, a fill chamber having a bore into which molten metal is drawn by a vacuum, a piston slidably in said bore of the fill chamber to charge said molten metal into a die on a forward stroke of the piston, a thin flexible elongated generally cylindrical skirt seal between said piston and the bore of said fill chamber and having a forward edge secured to said piston and a floating rearward edge, said thin flexible elongated cylindrical skirt seal having a diameter which provides sealing engagement with the bore of the fill chamber.

A vacuum die-casting machine including a die, a fill chamber having a bore, a piston slidable in said bore of the fill chamber to charge molten metal into said die on a forward stroke of said piston, said piston having a generally rearwardly facing shoulder having a preset outer diameter, a thin flexible elongated cylindrical skirt seal between said piston and the bore of said fill chamber made of the same material as said piston and having a forward edge secured to said piston and a floating rearward edge, said thin flexible elongated cylindrical skirt seal having a diameter which provides an interference fit with the bore of said fill chamber, and an annular hem ring having a rearward facing peripheral cutting edge and an inner diameter less than said outer diameter of the shoulder on said piston, said annular hem ring being secured to said rearward edge of said skirt and engaging said shoulder on said piston to transfer loading produced by resistance to rearward movement of the cutting edge upon rearward movement of the piston to the piston rather than to the flexible skirt.

A method of checking seals in a vacuum die-casting machine having a piston slidable in a fill chamber bore with a sliding fit forming a seal, said method comprising:

• introducing a trace gas adjacent one end of said piston, monitoring for the presence of said trace gas adjacent the other end of said piston, and adjusting said sliding fit to reduce the amount of trace gas monitored.

In a die-casting machine having a fill chamber with a bore for communicating with a die, a piston slidable in said fill chamber and a piston rod for moving said piston in the fill chamber bore to inject molten metal into said die, the improvement wherein said piston comprises a cylindrical body and an end wall which together define an internal spherical socket, and wherein said piston rod terminates in a ball which seats in said spherical socket to effect an articulated connection which accommodates for variations in alignment between said piston and said piston rod, said ball having a fully enclosed chamber defined in part by a spherical sector end wall which rotatably engages said end wall of said piston, said piston rod having passages communicating with said fully enclosed chamber in said ball for circulating coolant through said chamber to cool said piston including the end wall of said piston.

A vacuum die-casting machine including a fill chamber having a longitudinal bore and an inlet opening extending generally transversely through a wall of the fill chamber into said bore, a feed tube seated in the inlet opening, means drawing a vacuum in said fill chamber bore to draw molten metal through said feed tube into said fill chamber bore, and heater means in surface contact with the wall of said fill chamber surrounding said feed tube, said heater means comprising an annular housing with an annular groove in one face thereof, an electrical coil in said annular groove, and means clamping said annular housing against said fill chamber wall surrounding the feed tube with said one face with said annular groove therein containing said electrical coil abutting the wall of said fill chamber.

A vacuum die-casting machine including a fill chamber having a longitudinal bore and an inlet opening extending generally transversely through a wall of the fill chamber into said bore, a feed tube seated in said inlet opening, means drawing a vacuum in said fill chamber bore to draw molten metal through said feed tube into said fill chamber bore, a primary vacuum seal between said feed tube and said inlet opening and a redundant secondary vacuum seal in series with said primary vacuum seal between said feed tube and said inlet opening, said primary vacuum seal and secondary vacuum seal each sealing against at least partially axially facing sealing surfaces and one of said primary and secondary seals being crushable to assure sealing of both seals.

A vacuum die-casting machine including a fill chamber having a longitudinal bore and an inlet opening extending generally transversely through a wall of the fill chamber into said bore, said inlet opening having an inner radial shoulder and an outer axially and radially inclined shoulder axially spaced a preset distance from the inner radial shoulder, a feed tube seated in said inlet opening and having an end face aligned with the inner radial shoulder of the inlet opening and a radially outward shoulder aligned with the outer shoulder of the inlet opening and axially spaced substantially said preset distance form the end face, means drawing a vacuum in said fill chamber bore to draw molten metal through said feed tube into said fill chamber bore, a primary vacuum seal located between said end face of the feed tube and the inner radial shoulder of said inlet opening, and a redundant secondary vacuum seal in series with said primary vacuum seal and located between the other axially and radially inclined shoulder of the inlet opening and the radially outward shoulder of said feed tube, one of said primary and secondary vacuum seals being crushable to assure sealing of both seals.