Liquid device having filter

Abstract

A liquid containing receptacle having a filter is disclosed that in one form includes a nozzle. The filter includes a passage having a portion with a size that restricts the flow of a liquid there through unless sufficient pressure is applied to overcome a liquid and filter property such as surface tension. The pressure in the liquid at the filter can be varied by changing a gas overpressure above a surface of the liquid, changing a head height of the liquid, and/or changing the liquid and filter property, among possible others. In one embodiment the liquid containing receptacle can be used to contain a molten metal that is used in an investment casting mold. The molten metal can be selectively poured into a mold by selectively changing pressure of the molten metal at the filter or by changing the pressure at which molten metal flows through the filter.

1 . An apparatus for discharging a melt comprising:
 a molten metal container for holding a liquid and a nozzle located near a bottom of the molten metal container operable to dispense the liquid, the nozzle having an exit aperture through which the liquid passes when being dispensed from the molten metal container;   a filter having a portion positioned within the molten metal container upstream of the nozzle exit aperture and operable to extract an impurity from the liquid as the liquid passes through the filter before being dispensed from the molten metal container; and   wherein during operation a filter-fluid interaction discourages liquid from passing through the filter at a non-flow pressure present in the liquid and the filter-fluid interaction permits liquid from passing through the filter at a flow pressure.   
     
     
         2 . The apparatus of  claim 1 , which further includes a heater coupled in thermal communication with the molten metal container, wherein the molten metal container is a crucible. 
     
     
         3 . The apparatus of  claim 1 , which further includes:
 a conduit for the passage of a relatively pressurized gas to pressurize the molten metal container;   a pressure source that provides the relatively pressurized gas;   wherein the relatively pressurized gas is capable of altering a pressure present in the liquid; and   wherein the molten metal container is operable to hold a molten metal.   
     
     
         4 . The apparatus of  claim 3 , wherein the molten metal container is positioned within a housing, a seal is provided between the molten metal container and the housing, and a heater is operable to provide heat to the molten metal container. 
     
     
         5 . The apparatus of  claim 1 , which further includes a device insertable into a space that contains the liquid and that raises the head height of the liquid during operation. 
     
     
         6 . The apparatus of  claim 1 , wherein the filter-fluid interaction is a surface tension of the fluid as it interacts with the filter. 
     
     
         7 . The apparatus of  claim 6 , which further includes a supply of an agent formulated to alter the surface tension of the fluid. 
     
     
         8 . An apparatus comprising:
 a container operable to hold a molten metal liquid and having a dispensing orifice capable of flowing the molten metal liquid from the container;   a plurality of flow paths disposed within the container and so dimensioned that the molten metal liquid is discouraged from flowing through at least some of the plurality of flow paths at a first liquid pressure and permitted to flow through at least some of the plurality of flow paths at a second liquid pressure; and   wherein the plurality of flow paths are structured to extract an impurity from the molten metal liquid before the molten metal liquid is dispensed from the container.   
     
     
         9 . The apparatus of  claim 8 , wherein at least some of the flow paths have dimensions to constrict a flow of molten metal liquid when a surface tension of the molten metal liquid interacts with the flow path dimension. 
     
     
         10 . The apparatus of  claim 9 , wherein the flow paths are formed internal to a filter. 
     
     
         11 . The apparatus of  claim 9 , wherein a cover is used to enclose a space within the container, the cover including a passage operable to flow a gas to relatively pressurize the space. 
     
     
         12 . The apparatus of  claim 11 , which further includes a gas seal operable to discourage the gas from escaping the enclosed space, wherein the container is a crucible. 
     
     
         13 . The apparatus of  claim 9 , which further includes a plunger operable to extend and retract to increase the head height of the molten metal within the container. 
     
     
         14 . An apparatus comprising:
 a casting crucible having a nozzle for dispensing a molten metal and a pressure-operative control device positioned upstream from an outlet of the nozzle, the pressure-operative control device operable to flow the molten metal at a first molten metal pressure and to discourage flow of molten metal at a second molten metal pressure; and   means for changing a flowable pressure of a molten metal at the pressure-operative control device to cause the molten metal to flow from the nozzle.   
     
     
         15 . The apparatus of  claim 14 , wherein the means includes a device operable to increase head height of the liquid. 
     
     
         16 . The apparatus of  claim 14 , wherein the means includes a source of gas for increasing overpressure of a gas above the surface of the molten metal. 
     
     
         17 . The apparatus of  claim 14 , wherein the means includes an agent formulated to change the flowable pressure from a first flow pressure value to a second flow pressure value. 
     
     
         18 . A method comprising:
 depositing a metal within a crucible having an internal filter;   heating the metal within the crucible during a liquid state of the metal; and   selectively flowing the metal through the internal filter to remove impurities prior to being discharged from the crucible, the selectively flowing dependent upon whether a pressure in the metal is above or below a flowable pressure of the filter.   
     
     
         19 . The method of  claim 18 , which further includes modulating the pressure in the metal relative to the flowable pressure to selectively flow the metal through the filter. 
     
     
         20 . The method of  claim 19 , wherein the modulating includes varying an overpressure of a gas within the crucible. 
     
     
         21 . The method of  claim 19 , wherein the modulating includes varying a head height of the metal in the crucible. 
     
     
         22 . The method of  claim 18 , which further includes including an agent with the metal to alter the flowable pressure of the filter.