Method and apparatus for casting metal articles with counter-gravity supply of metal to moulds

• US 6,505,677 B1
• Filed: 11/06/2000
• Issued: 01/14/2003
• Est. Priority Date: 05/07/1998
• Status: Expired due to Fees

• Current Assignee: Georg Fischer Waga N.V. (Georg Fischer AG)
• Original Assignee: Georg Fischer Waga N.V. (Georg Fischer AG)
• Inventors: Iversen, Peter M¥ller, Andersen, Uffe
• Primary Examiner(s): Elve, M. Alexandra
• Assistant Examiner(s): Kerns, Kevin P.
• Application Number:
  US09/674,715
• Time in Patent Office: 799 Days
• Field of Search: 164/119, 164/113, 164/120, 164/133, 164/285, 164/363, 164/4.1, 164/457, 164/151, 164/151.3, 164/155.2, 164/155.3, 164/306
• US Class Current: 164/457
• CPC Class Codes: B22D 18/04 Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
• CPC Class Codes: B22D 18/08 Controlling, supervising, e.g. for safety reasons controlling or regulating in general G05

Abstract

When casting metal articles in a mould by forcing molten metal upwardly through a filling tube by gas pressure in a closed chamber, the datum level just below that of a connector connecting the filling tube to the mould is registered by a level sensor in a sensing tube while the latter'"'"'s upper end is connected to atmosphere through a vent tube. At the same moment, the pressure is measured by a pressure sensor and recorded by a control unit and maintained constant by the latter after the emptying of the sensing tube, by connecting its upper end to the chamber through an equalizing tube, until the pressure is increased to fill the mould according to a predetermined function of time programmed into the control unit. The starting point for the filling of all moulds in succession is the same, regardless of the amount of metal in the supply unit.

Claims

1. Apparatus for casting articles of metal in moulds having inlets at the side or bottom, the apparatus comprising

a) a supply unit for molten metal comprising a closed chamber containing a mass of molten metal in a bottom region thereof and a gas above the mass,

b) a filling tube extending from the bottom region upwardly to a connector for temporary connection to a filling duct in a mould for casting an article of metal,

c) pressure-varying means to vary the pressure in the gas between (i) low values, at which metal from the mass when rising though the filling tube does not reach the connector, and (ii) higher values, at which molten metal is made to flow through the connector into the filling duct in the mould,

d) a sensing tube, the lower end of which extends into the mass,

e) a level sensor placed in the sensing tube which reacts when the level of metal in the sensing tube is slightly lower than that of the connector,

f) automatic control equipment to which the level sensor and the pressure-varying means are connected for controlling the operation of the apparatus including the pressure-varying means, and

g) a switchable connecting system which alternately connects an upper end of the sensing tube to a space outside the closed chamber and to the gas above the mass in the closed chamber.

2. A method of casting articles of metal in moulds having inlets at the side or bottom comprising the steps of:

using a sensing conduit of very small cross-sectional area compared to a surface area of molten metal in a closed chamber with gas above the molten metal, the sensing conduit extending from a bottom region of the closed chamber to an outside of the closed chamber,

increasing a pressure of the gas until the level of the molten metal in the sensing conduit reaches a datum level, upon which the pressure of the gas is maintained at this datum value,

connecting a mould to a connector connected to a filling tube in the closed chamber,

increasing the pressure of the gas into a higher range above the datum value,

switching an upper end of the sensing conduit from the outside to the gas in the closed chamber as the pressure is increased from the datum value to prevent backflow in the sensing conduit,

when the mould has been filled with molten metal through the connector, reducing the pressure to or below the datum value, and

disconnecting the mould from the connector.

3. A method according to claim 2:

a) wherein the sensing conduit is a separate sensing tube which includes a level sensor set at the datum level and connected to automatic control equipment for controlling the casting operation,

b) further including the step of measuring the pressure of the gas in the closed chamber with a pressure sensor connected to the automatic control equipment, and

c) further including the step of maintaining the pressure of the gas at the datum value measured when the level sensor reacts until the pressure of the gas is increased for filling the mould connected to the connector.