an in - line single nozzle valve gate apparatus for injection molding comprises upper and lower rnatable annular cylinder bodies that house an annular dual sided piston having opposed pressure bearing upper and lower surfaces . the piston has a cross beam to which a valve gate pin is attached for movement therewith . the valve gate pin passes through a sprue bushing flow path to selectively open and close a part cavity gate . an interface is provided to receive molten plastic from the injection machine nozzle and pass it into the sprue bushing flow path . the cylinder bodies reside largely outside of the mold plate architecture to lessen thermal damage too piston seals .