Method and apparatus for removing a fugitive pattern from a mold

Abstract

A fugitive pattern, such as wax or other meltable pattern material, residing inside of a refractory mold, which can be unsupported or supported in a particulates bed, is removed by discharging steam or other condensable vapor that may include a surfactant inside the mold to contact and melt the pattern while an exterior of the mold is subjected to a non-condensing gas atmosphere such as air outside of the mold. Regardless of whether the condensable vapor includes surfactant or not, the mold can be tilted relative to gravity and rotated while it is tilted to improve the pattern removal. Condensable vapor is condensed inside the mold where the vapor has contacted the pattern while the exterior of the mold remains free of condenate. The condensed vapor and melted pattern material are drained out of the mold with the surfactant, if present, improving drainage.

1 . A method of removing a fugitive pattern from inside a refractory mold, comprising introducing a condensable vapor and a surfactant inside the mold to contact and melt the pattern material, condensing said condensable vapor inside the mold where it contacts and melts the pattern, and draining the melted pattern material and condensed vapor out of the mold wherein the surfactant improves said draining.  
   
   
       2 . A method of removing a fugitive pattern from inside a refractory mold, comprising introducing a condensable vapor and a surfactant inside the mold to contact and melt the pattern material while an exterior of the mold is subjected to a non-condensing gas atmosphere outside of the mold, condensing said condensable vapor inside the mold where it contacts and melts the pattern while the exterior of the mold remains free of condensed vapor, and draining the melted pattern material and condensed vapor out of the mold wherein the surfactant improves said draining.  
   
   
       3 . The method of  claim 2  where the type and amount of surfactant is selected to reduce the surface tension between the condensed vapor and the pattern material.  
   
   
       4 . The method of  claim 2  where the condensable vapor is steam.  
   
   
       5 . The method of  claim 2  where the pattern material is wax, either with or without a non-wax filler  
   
   
       6 . The method of  claim 2  where the surfactant is added to the condensable vapor before the condensable vapor exits a discharge tube and enters inside the mold.  
   
   
       7 . The method of  claim 2  where the surfactant is added to the condensable vapor after the condensable vapor exits a discharge tube and enters inside the mold.  
   
   
       8 . The method of  claim 7  where the surfactant is carried into the condensable vapor stream in a diluted form using a vehicle compatible with the condensable vapor being used.  
   
   
       9 . The method of  claim 2  wherein a pressure differential between the condensable vapor inside the mold and the non-condensing gas atmosphere outside of the mold is small enough as to prevent the condensable gas from exiting outside the mold exterior and the non-condensing gas from entering a mold cavity in the mold.  
   
   
       10 . The method of  claim 2  wherein the condensable gas and the noncondensing gas atmosphere are at substantially the same pressure.  
   
   
       11 . The method of  claim 2  wherein the condensable vapor comprises steam.  
   
   
       12 . The method of  claim 2  wherein the non-condensing gas is air.  
   
   
       13 . The method of  claim 2  wherein the condensable vapor is supplied from a source to a discharge tube from which it is discharged inside the mold.  
   
   
       14 . The method of  claim 2  wherein the condensable vapor is discharged inside the mold at atmospheric pressure.  
   
   
       15 . The method of  claim 2  wherein the condensable vapor is discharged inside the mold at superatmospheric or subatmospheric pressure and a non-condensing gas at substantially the same superatmospheric or subatmospheric pressure is provided exterior of the mold in a vessel containing the mold.  
   
   
       16 . The method of  claim 15  including preventing the condensable vapor from entering the vessel exterior of the mold using a seal between the mold and the vessel.  
   
   
       17 . The method of  claim 2  wherein the fugitive pattern comprises wax.  
   
   
       18 . The method of  claim 2  wherein an axis of the mold containing the fugitive pattern is tilted with respect to the direction of gravity during the melting of the fugitive pattern or after the fugitive pattern has been melted and the mold is rotated about a second axis.  
   
   
       19 . The method of  claim 2  including initially discharging the condensable vapor inside a hollow sprue of the pattern.  
   
   
       20 . The method of  claim 19  wherein the hollow sprue is preformed in the fugitive pattern prior to the discharging of the condensable vapor.  
   
   
       21 . The method of  claim 20  wherein the hollow sprue is formed by condensable vapor discharged against an exposed end of the solid sprue.  
   
   
       22 . The method of  claim 2  wherein the exterior of the mold is surrounded by a support particulate media in a container.  
   
   
       23 . The method of  claim 2  wherein the exterior of the mold is not surrounded by a support particulate media.  
   
   
       24 . Apparatus for removing a fugitive pattern from inside of a refractory mold, comprising means for introducing a condensable vapor at atmospheric, superatmospheric or subatmospheric pressure inside the mold to contact and melt the pattern material and means for providing a surfactant in the condensable vapor.  
   
   
       25 . The apparatus of  claim 24  wherein the means for introducing a condensable vapor comprises a discharge tube communicated to the inside of the mold.  
   
   
       26 . The apparatus of  claim 24  including a surfactant supply conduit for supplying the surfactant to the discharge tube.  
   
   
       27 . The apparatus of  claim 24  including a surfactant discharge tube for introducing surfactant to the condensable vapor after it is discharged from the discharge tube.  
   
   
       28 . A method of removing a fugitive pattern from inside a refractory mold, comprising melting or dissolving the fugitive pattern and subjecting the mold to a combination of rotation and tilting to improve draining of pattern material from the mold.  
   
   
       29 . The method of  claim 28  wherein the mold is rotated about its longitudinal axis while the longitudinal axis is tilted with respect to gravity.  
   
   
       30 . The method of  claim 28  wherein the refractory mold comprises a shell mold.  
   
   
       31 . The method of  claim 30  wherein the shell mold is not surrounded by particulates media.  
   
   
       32 . The method of  claim 30  wherein the shell mold is surrounded by particulates media.  
   
   
       33 . The method of  claim 28  wherein the fugitive pattern is melted by introducing steam or a condensable vapor inside the mold.  
   
   
       34 . Apparatus for removing a fugitive pattern from inside of a refractory mold, comprising a mold clamp and rotation mechanism and a mold support mechnism between which the mold is disposed, a pivotable shaft on which the mold clamp and rotation mechanism and the mold support mechnism are disposed, means for pivoting the shaft to tilt the mold clamp and rotation mechanism and the mold support mechnism relative to gravity, and means for removing the fugitive pattern.  
   
   
       35 . The apparatus of  claim 34  wherein the mold clamp and rotation mechanism comprises a rotatable shaft having an end frictionally enagaged to an end of the mold to impart rotation thereto.  
   
   
       36 . The apparatus of  claim 36  wherein the mold clamp and rotation mechanism is movable up and down relative to the mold to engage the end with the mold.  
   
   
       37 . The apparatus of  claim 35  wherein the mold support mechanism comprises a rotatable nest that receives an opposite end of the mold.