| abstract |
A syringe having a barrel adapted to receive a plunger with a through passageway from the bottom wall of a groove in which an O-ring seal is positioned to the rear surface of the plunger. Upon insertion of the plunger into the barrel, the O-ring will move to a position adjacent a rear wall defining the groove over the passageway and allow air to escape from within the barrel through the passageway. When the pressure used to seat the plunger against material within the barrel is removed, the plunger will rebound slightly causing the plunger to move relative to the O-ring so that the O-ring makes an air tight seal between the plunger and the barrel. When pressure is again applied to the plunger to press the material out of the barrel, the plunger will again move relative to the O-ring to again position the O-ring over the passageway, however, the O-ring will seal the passageway sufficiently to restrict escape of a significant amount of the viscous material through the passageway. |