PLUNGER AND APPARATUS USEFUL IN EXTRUDING OR DISPENSING VISCOUS MATERIALS

摘要

The invention is a plunger useful in extruding or dispensing viscous material which comprises a thin disc of a material which is capable of deforming when subjected to back pressure during use. The edge of the disc has a circular shape and a cylindrical lip attached to the edge of the disc, which lip is disposed perpendicular to the edge of the disc. The disc has a face and a back surface located on opposite sides of the sheet. The disc also has a symmetrical convex portion which protrudes beyond the plane defined by the edge of the disc in the direction of the face and the peak of the convex portion disposed in the center of the disc. The disc further comprises a symmetrical concave portion which protrudes beyond the plane defined by the edge of the disc in the direction of the back surface. The concave portion of the disc surrounds the convex portion of the disc and the convex portion starts at the bottom of the concave portion. The radius of the convex portion, measured from the peak to the bottom of the concave portion, is sufficient to withstand the back pressure exerted during use without inverting. The slope of the wall of the concave portion from the edge to the bottom of the concave portion is disposed such that, when back pressure is exerted on the plunger, the edge deforms radially outward.