Core for an investment casting process

Abstract

A core for an investment casting process in which a component to be cast has an internal passageway, the internal passageway being provided by the core. A first core passage having a first point and a second point and including no straight path between the first point and the second point; a first core bridge which extends away from the first core passage between the first and second points, and has a first pillar and a second pillar which connect to the first and second points respectively, and a bridge portion which extends between the first and second pillars; wherein the first pillar has a core inlet portion having a thickness at the first point and the second pillar has a thickness at the second point, the thickness of the core inlet portion at the first point being less than the thickness of the second pillar at the second point.

1 . A core for an investment casting process in which a component to be cast has an internal passageway, the internal passageway being provided by the core, the core comprising: a first core passage having a first point and a second point therein and including no straight path between the first point and the second point; and a first core bridge which extends away from the first core passage between the first and second points, wherein the first core bridge comprises a first pillar and a second pillar which connect to the first and second points respectively, and a bridge portion which extends between the first and second pillars; wherein the first pillar comprises a core inlet portion having a thickness at the first point and the second pillar has a thickness at the second point the thickness of the core inlet portion at the first point being less than the thickness of the second pillar at the second point. 
     
     
         2 . A core according to  claim 1 , wherein the core passage has a height, width and breadth wherein the width and breadth are greater than the height, wherein the chimney portion extends in the direction of the height. 
     
     
         3 . A core according to  claim 2 , wherein the core passage is planar. 
     
     
         4 . A core according to  claim 2 , wherein the core passage is arched. 
     
     
         5 . A core according to  claim 1 , wherein the core inlet portion has a height H 1  at the first point and the second pillar has a height H 2  at the second point , H 1  being less than H 2 . 
     
     
         6 . A core according to  claim 1 , wherein the first core bridge comprises a transition region between the core inlet portion and the second pillar. 
     
     
         7 . A core according to  claim 6 , wherein the transition region is part of the first pillar, the bridge portion and/or the second pillar. 
     
     
         8 . A core according to  claim 6 , wherein the transition region comprises a sloping upper surface, which connects an upper surface of the core inlet portion to an upper surface of the second pillar. 
     
     
         9 . A core according to  claim 6 , wherein the transition region comprises one or more transition region side walls connecting one of the side walls of the core inlet portion to one of the side walls of the second pillar. 
     
     
         10 . A core according to  claim 1 , wherein the core inlet portion comprises at least one indent, groove or recess extending in a transverse direction at least partially across a side wall of the core inlet portion. 
     
     
         11 . A core according to  claim 1  comprising one or more shell lock features. 
     
     
         12 . A core according to  claim 1  comprising more than one core bridge. 
     
     
         13 . A core according to  claim 12 , wherein the core inlet portion is common to more than one core bridge. 
     
     
         14 . A ceramic shell for an investment casting process in which a component to be cast has at least one internal passageway, the internal passageway(s) being provided by a core, the ceramic shell comprising: a core comprising: a first core passage having a first point and a second point therein and including no straight path between the first point and the second point; and a first core bridge which extends away from the first core passage between the first and second points wherein the first core bridge comprises a first pillar and a second pillar which connect to the first and second points respectively, and a bridge portion which extends between the first and second pillars;
 wherein the first pillar comprises a core inlet portion having a thickness at the first point and the second pillar has a thickness at the second point, the thickness of the core inlet portion at the first point being less than the thickness of the second pillar at the second point, the core having an outer layer of a sacrificial material within the ceramic shell, wherein the first core bridge extends between the first core passage and the ceramic shell through the sacrificial material.   
     
     
         15 . A cast component comprising: at least one internal passageway formed by a core comprising: a first core passage having a first point and a second point therein and including no straight path between the first point and the second point; and a first core bridge which extends away from the first core passage between the first and second points, wherein the first core bridge comprises a first pillar and a second pillar which connect to the first and second points respectively, and a bridge portion which extends between the first and second pillars; wherein the first pillar comprises a core inlet portion having a thickness at the first point and the second pillar has a thickness at the second point; the thickness of the core inlet portion at the first point being less than the thickness of the second pillar at the second point, the cast component having an aperture to the internal passageway at a first point and a cap sealing an aperture at a second point, wherein the apertures at the first and second points respectively correspond to the connections of the core inlet portion and second pillar ( 412 ) provided by the core. 
     
     
         16 . A cast component according to  claim 15 , wherein the cast component is a seal segment for bounding a portion of a main gas path of a gas turbine engine. 
     
     
         17 . A cast component according to  claim 15 , wherein the cast component is a combustion tile. 
     
     
         18 . A cast component according to  claim 15 , wherein the at least one internal passageway has a local area contraction corresponding to an indent, groove or recess on the core.