Image Number 4 for United States Patent #8091608.
A method of forming a hollow sand core involves placing a preform into a cavity defined in a mold, where the preform has a predetermined configuration. A granular material is then introduced into the mold cavity and around the preform. The introduced granular material is established around the preform to form the hollow sand core. The preform is deformed in a manner sufficient to enable removal of the preform from inside the hollow sand core, and then is removed from the sand core. The removal of the preform exposes a hollow portion of the sand core.