Gas rinsing stopper preventing mixing of air with rinsing gas

in a gas rinsing stopper for use with a vessel containing molten metal, said stopper including a stopper member having therethrough an axial gas passage, a mounting fixture extending into a first end of said gas passage, a gas feed opening at a second end of said gas passage, and a gas supply line extending into said gas passage for supplying rinsing gas thereto and thereby for discharging said rinsing gas through said gas feed opening, the improvement comprising means for preventing said supplying of said rinsing gas to said gas passage from creating a reduced pressure at said first end of said gas passage and causing atmospheric air to be drawn inwardly through said first end of said gas passage and mixing with said rinsing gas within said gas passage, said preventing means comprising:

• a seal member positioned within said gas passage and forming a gas tight seal separating said gas passage into a first section including said mounting fixture and a second section leading to said gas feed opening;
• and
• said gas supply line opening into said second section of said gas passage, whereby said rinsing gas is isolated from said first section of said gas passage.