Abstract: A check valve assembly for use in a plastic injection molding machine injection unit is disclosed. The check valve utilizes a free-floating poppet member which has tapered angularly spaced-apart tapered flutes on the outer surface thereof and a self-aligning spherical valve seating surface at one end thereof. When a predetermined shot volume in front of the check valve has been filled, forward advancement of the feed screw within the injection unit causes the molten thermoplastic material to grippingly engage the tapered surfaces of the flutes causing the poppet member to move along with the backflow of thermoplastic material closing the check valve.