Process and apparatus for low pressure casting

Claim 1

In a process of low-pressure casting a metal in a mould which is fed with metal from below by means of an electromagnetic pump, the process comprising the following stages, starting from an initial position in which the metal to be moulded is at a height which is slightly lower than that of the inlet of said mould: (a) filling said mould with metal, at a predetermined acceleration, by applying an increasing voltage to said pump until a voltage is reached which corresponds to a delivery height which is slightly greater than that of the top of said mould; (b) holding said voltage until a skin forms on the inner walls of said mould; (c) applying an increased pressure to the metal in said mould until the solidification front reaches the inlet of said mould; and (d) at the end of the solidification, reducing the pressure to said initial pressure and opening said mould; the improvement comprising measuring the temperature of said mould and the temperature of the metal in the melting furnace, and filling said mold at an acceleration greater than said predetermined acceleration when the respective temperatures are lower than a predetermined value, and filling said mold at an acceleration smaller than said predetermined acceleration when the respective temperatures are higher than said predetermined value.

Claim 5

A device for controlling the low-pressure casting of a metal in a mould which is fed with metal from below by means of an electromagnetic pump, said device comprising: means for generating a plurality of supply voltages for an electromagnetic pump; first, second, third and fourth clock counters with preselection, which are a connected in series sequence to determine the duration of respective casting operations including: mould filling; skin formation on mould wall interior; formation of solidification in mould inlet; opening of said mould; respectively; an analog switch associated with means for controlling the supply voltage of said pump, and connected to be controlled by output signals from said first, second and third clock counters for selectively applying the corresponding voltages to said pump; means for controlling the opening of the mould and which is controlled by said fourth clock counter; at least one temperature sensor for said mould and one temperature sensor for the metal in the melting furnace; a variable time base means for said first and second clock counters; and a reversing amplifier associated with each said temperature sensor and connected to said variable time base means.

Claim 6

A device for controlling the low-pressure casting of a metal in a mould which is fed with metal from below by means of an electromagnetic pump, said device comprising: means for generating a plurality of supply voltages for an electromagnetic pump; first, second, third and fourth clock counters with preselection, which are a connected in series sequence to determine the duration of respective casting operations including: mould filling; skin formation on mould wall interior; formation of solidification in mould inlet; opening of said mould; respectively; an analog switch associated with means for controlling the supply voltage of said pump, and connected to be controlled by output signals from said first, second and third clock counters for selectively applying the corresponding voltages to said pump; means for controlling the opening of the mould and which is controlled by said fourth clock counter; at least one temperature sensor for said mould and one temperature sensor for the metal in the melting furnace; a variable time base means for said first and second clock counters; and a reversing amplifier associated with each said temperature sensor and connected to said variable time base means.