Seal component manufacturing method and mold

A method of manufacturing a seal component obtained by integrally molding an endless shaped gasket made of an elastomeric material on a base member, comprising the steps of:

• setting the base member between split molds of a mold;
• injecting an injection amount of a molding rubber material to an endless shaped cavity defined between a base surface of the base member and an inner surface of one of the split molds opposed to the base surface of the base member;
• making the injection amount of the molding rubber material be an amount such that the molding rubber material completely fills the cavity, completely fills an air vent hole open to a confluence position of the molding rubber material within the cavity, and thereafter flows through an orifice and into a surplus material reservoir provided at a downstream side of the air vent hole but does not completely fill the surplus material reservoir;
• causing a pressure drop with only the orifice on the basis of flow resistance to the molding rubber material flowing into the surplus material reservoir from the air vent hole through the orifice;
• and
• keeping an internal pressure of the cavity to be equal to or more than a first lower limit value of pressure for molding the gasket and to be less than a second lower limit value of pressure which causes leakage from the cavity, on the basis of the pressure drop.