Valve stem having a reverse taper

A valve stem for use in an injection machine nozzle in a hot runner system, the valve stem comprising:

• a first end having a diameter, and for plugging an opening in the injection machine nozzle when in a first position;
• and
• a middle section having a bulbous portion, the bulbous portion having a diameter for sealing a clearance between the valve stem and the injection machine nozzle.

A valve stem for use in a sprue bar in a hot runner system, the valve stem comprising:

• a first end having a diameter, and for plugging an opening in the sprue bar when in a first position;
• and
• a middle section having a bulbous portion, the bulbous portion having a diameter larger than the opening of the sprue bar for sealing a clearance between the valve stem and the sprue bar.

A bushing having an internal passage for receiving a valve stem having a reverse taper thereon in a hot runner system, the bushing comprising:

• a face proximate the internal passage, the face having a complementary portion for receiving the reverse taper;
• and
• wherein the reverse taper seals a clearance between the valve stem and the bushing when the reverse taper of the valve stem engages the face of the bushing.

A manifold having an internal passage for receiving a valve stem having a reverse taper in a hot runner system, the manifold comprising:

• a face proximate the internal passage, the face having a complementary portion for receiving the reverse taper;
• and
• wherein the reverse taper seals a clearance between the valve stem and the internal passage of the manifold when the reverse taper of the valve stem engages the face of the manifold.