Patent ID: 7198477

Claim:
A shut-off valve assembly for a plastic injection molding system, said assembly comprising: a housing member having an internal cavity, an orifice at a first end of said cavity, and an opening at the second end of said cavity; a piston member slidingly positioned in said cavity, said piston member having an internal passageway therein for at least part of its length for passage of plastic material, said passageway having a first opening in the direction of said orifice at the first end of the cavity and at least one second opening distal to said orifice; said piston member having a head member at one end positioned adjacent said second end of said cavity; a plate member attached to said housing member and having an opening positioned for passage of plastic material into said opening in the second end of said cavity; and a biasing member positioned in said cavity and biasing said piston member in a direction toward said second end of said cavity; wherein said piston member has a first position biased by said biasing member with said head member in contact with said plate member for preventing passage of plastic material through said opening in said plate member, and a second position forced away from said plate member by pressure of the injected plastic material to allow passage of plastic material through said opening in said plate member.