Vent plug for vulcanization

A vent plug for vulcanization installed in a vent hole formed in a vulcanization mold for molding a green tire and configured to discharge air and prevent a raw rubber of the green tire from inflowing, comprising:

• a housing inserted into the vent hole;
• an actuator installed inside the housing;
• and
• an opening/closing drive spring installed inside the housing to provide an elastic force to the actuator,
• wherein the actuator has a head formed at one end thereof, and
• one end of opposite ends of the spring is caught by a step formed on a bottom inside the housing, and the other end is caught by the head, whereby, when the actuator is inserted into the housing, the opening/closing drive spring pushes a portion of the actuator to an outside of the housing;
• wherein the housing comprises:
• a body front end and a body rear end which are formed in a longitudinal direction thereof;
• and an intermediate step which connects the body front end and the body rear end,
• the body front end is first inserted into the vent hole, and then the body rear end is inserted therein, such that the end of the body rear end is installed so as to face the inside of the vulcanization mold, and
• the body rear end is formed to have a larger diameter than the diameter of the vent hole, such that the body rear end is pressed and inserted into the vent hole by forced fit
• wherein the body rear end has a concave-convex structure formed on an outer circumference thereof to reinforce coupling between the body rear end and the vent hole in a circumferential direction;
• wherein the concave-convex structure is tight fitting grooves which are grooves formed in a predetermined length and inserted while a portion of an inner circumference of the vent hole is raised due to a pressure difference generated in a process of the body rear end being pressed and inserted into the vent hole;
• wherein the tight fitting grooves are formed to be inclined at a predetermined angle with respect to the longitudinal direction of the housing and the vent hole, such that in the process of the body rear end of the housing being pressed and inserted into the vent hole, a trajectory due to the raised portion formed on an inner circumference of the vent hole caused by the tight fitting grooves is formed in a spiral shape;
• wherein in the intermediate step formed between the body front end and the body rear end of the housing, a step surface defining the intermediate step is formed to be inclined at a predetermined angle from a right angle with respect to the longitudinal direction of the housing, such that the intermediate step is formed in a shape in which a diameter is gradually increased from a point where the body front end ends to a point where the body rear end starts, and a starting point of the tight fitting groove is a point where the diameter of the intermediate step starts to increase, and wherein the tight fitting groove is formed in a protruding portion, the tight fitting groove has an extension section formed at an end thereof, and the extension section is a tight fitting reinforcement section formed to be inclined with respect to the housing at an angle greater than an angle formed by the tight fitting groove with the housing.