To prevent leakage of a viscous material and prevent compressed air leakage in a discharge stage from a pneumatic dispenser while achieving air-venting in a filling stage of the viscous material to a cylinder, with a plunger fitted to the cylinder of the pneumatic dispenser for discharging the viscous material.
A plunger 10 has a first part 80 positioned at the front and a second part 82 positioned at the back. The second part has a hollow structure, has a peripheral wall part 84, and an inner peripheral surface 86 of the peripheral wall part has a tapered surface. The peripheral wall part has thick wall dimension which is reduced as going away axially from the first part, and consequently the peripheral wall part has bending rigidity which is reduced as going away axially from the first part, and is easily deformed elastically in the diametrical direction. The first part has a solid structure, functions as a rigid body relatively to the second part, and has a partition wall surface 89 separating an inner space of the second part from a solid part of the first part.
TSUJIKAWA JIN
IMAI KYOTA
