Patent ID: 6971437

Claim:
In a pattern for the lost foam casting of a metal melt in a bed of unbonded sand comprising a fugitive polymeric foam having discrete portions configured to form: (1) a pouring basin that receives melt from an external supply thereof and dispenses it through an outlet from the basin; (2) a vertical sprue underlying said basin and formed by a sprue-forming portion, said sprue-forming portion having a sprue-lightener extending the length of the sprue-forming portion; (3) at least one mold-cavity laterally adjacent said sprue, for forming a casting; (4) a plurality of runners vertically arranged along and between said sprue and said cavity for delivering said melt to said cavity; and (5) a plurality of gates each communicating a said runner with said cavity for admitting melt into said cavity; the improvement comprising: (a) said sprue-forming portion comprising an inverted cone having a wall that tapers from an upper end adjacent said basin to a lower end that defines a first included angle between about 4° and about 8° to minimize turbulence of said melt at said lower and upper ends, respectively, during pouring of said melt; (b) said sprue-lightener comprising a tapering blade-lightener configured to substantially simultaneously initiate flow of said melt through said gates into said cavity, said blade-lightener having a pair of opposing edges that lie inboard said wall and define a pair of opposing faces that are each significantly wider than said blade-lightener is thick, and fill the majority of the vertical cross section of said sprue when viewed in a plane of a said face; and (c) a plurality of runner-lighteners each extending into a said runner from a said edge for rapidly advancing said melt into said runners.