Hot sprue valve assembly for an injection molding machine

In an injection molding machine for producing centrally apertured record discs, a valve assembly for controlling the flow of molten disc-forming material through a sprue bushing into a disc-shaped mold cavity, comprising:

• a poppet valve positioned at the end of the sprue bushing adjacent the mold cavity and movable between an open position disposed at the side of the mold cavity generally opposite and spaced from the sprue bushing to allow the molten disc-forming material to flow through the sprue bushing into the mold cavity, and a closed position seated upon the end of the sprue bushing adjacent the mold cavity to prevent flow of the molten disc-forming material through the sprue bushing into the mold cavity;
• a valve stem extending from said poppet valve into the sprue bushing generally along the axis of the sprue bushing;
• means for guiding said valve stem for sliding movement within the sprue bushing along the axis of the sprue bushing, and for defining a plurality of axially extending openings for passage of the molten disc-forming material past said valve stem and said guide means;
• spring means for biasing said poppet valve to a normally closed position, the biasing forced applied by said spring means being overcome when the molten disc-forming material is supplied under pressure to the sprue bushing whereby the material under pressure urges said poppet valve to said open position;
• a ram positioned on the side of the mold cavity generally opposite the sprue bushing for engaging said poppet valve;
• and
• means for moving said ram between a retracted position wherein said ram is retracted from the mold cavity and defines a stop for said poppet valve when said poppet valve is in said open position, and an advanced position advanced toward the mold cavity for positively moving said poppet valve through the mold cavity to its closed position to prevent further flow of the molten disc-forming material into the mold cavity and to cause said poppet valve to mold an aperture in the record disc formed in the mold cavity.

In an injection molding machine for producing centrally apertured record discs, a valve assembly for controlling the flow of molten disc-forming material through a sprue bushing into a disc-shaped mold cavity, comprising:

• a poppet valve positioned at the end of the sprue bushing adjacent the mold cavity and movable between an open position disposed at the side of the mold cavity generally opposite and spaced from the sprue bushing to allow the molten disc-forming material to flow through the sprue bushing into the mold cavity, and a closed position seated upon the end of the sprue bushing adjacent the mold cavity to prevent flow of the molten disc-forming material through the sprue bushing into the mold cavity;
• a valve stem extending from said poppet valve into the sprue bushing generally along the axis of the sprue bushing;
• a plurality of arms projecting radially outwardly from said valve stem and angularly spaced from each other, said arms slidably engaging the sprue bushing for guiding said valve stem for accurate sliding motion along the axis of the sprue bushing;
• spring means for biasing said poppet valve to a normally closed position, the biasing force applied by said spring means being overcome when the molten disc-forming material is supplied under pressure to the sprue bushing whereby the material under pressure urges said poppet valve to said open position;
• a ram positioned on the side of the mold cavity generally opposite the sprue bushing for engaging said poppet valve;
• and
• means for moving said ram between a retracted position wherein said ram is retracted from the mold cavity and defines a stop for said poppet valve when said poppet valve is in said open position, and an advanced position advanced toward the mold cavity for positively moving said poppet valve through the mold cavity to its closed position to prevent further flow of the molten disc-forming material into the mold cavity and to cause said poppet valve to mold an aperture in the record disc formed in the mold cavity.

A mold assembly for an injection molding machine, comprising:

• first and second mold halves movable toward each other to define a disc-shaped mold cavity, and movable away from each other to allow a molded disc to be removed from said mold cavity;
• a sprue bushing mounted on said first mold half and defining a flow path for passage of molten disc-forming material in a direction generally normal to the plane of said mold cavity and generally along the central axis of said mold cavity;
• a poppet valve positioned at the end of said sprue bushing adjacent said mold cavity and movable between an open position disposed at the side of said mold cavity opposite said sprue bushing to allow the molten disc-forming material to flow through said sprue bushing flow path into said mold cavity, and a closed position seated upon said end of said sprue bushing to prevent flow of the molten disc-forming material into said mold cavity;
• a valve stem carrying said poppet valve and positioned within said sprue bushing flow path, and including means for guiding said valve stem for movement along the axis of said flow path and for allowing flow of the molten disc-forming material through said flow path;
• spring means for biasing said poppet valve to a normally closed position, the biasing force applied by said spring means being overcome when the molten disc-forming material is supplied under pressure to said sprue bushing whereby the material under pressure urges said poppet valve to said open position;
• a ram positioned on the side of said mold cavity generally opposite said sprue bushing for engaging said poppet valve;
• and
• means for moving said ram between a retracted position wherein said ram is retracted from said mold cavity and defines a stop for said poppet valve when said poppet valve is in said open position, and an advanced position advanced toward said mold cavity for positively moving said poppet valve through said mold cavity to its closed position to prevent further flow of the molten disc-forming material into said mold cavity and to cause said poppet valve to mold an aperture in the record disc formed in said mold cavity.