Method of manufacturing inter-dental cleaning tool

A method for manufacturing an interdental cleaning tool including:

• a base portion having a shaft portion, which extends in a specific direction and has a shape to be inserted into an interdental space, and a grip portion, which is connected to the shaft portion and has a shape to be gripped by fingers;
• and a cleaning portion configured to clean the interdental space and covering at least a part of the shaft portion, the method comprising:
• a base portion forming step of forming the base portion by using a primary mold having a first space in correspondence to the base portion and filling the first space with a synthetic resin, the primary mold including a first mold member and a second mold member separable from each other on a separation plane which is a reference plane encompassing an axis of the shaft portion;
• and
• a cleaning portion forming step of forming the cleaning portion around the shaft portion by using a secondary mold configured to hold the base portion and having a shape forming a second space in correspondence to the cleaning portion around the shaft portion, and filling the second space with elastomer under a condition in which the secondary mold holds the base portion,
• wherein what is used as the first mold member in the base portion forming step includes a first contact surface defining the separation plane and coming into contact with the second mold member;
• a pair of first spaced-apart portions, each of which has a surface curved so as to be convex toward the separation surface, the surface becoming gradually more distant from the separation plane as the surface becomes more distant along the separation plane from the second contact surface;
• and a first connection portion, which connects the first spaced-apart portions with each other and has a curved shape that is convex so as to become more distant from the separation plane in a direction perpendicular to the separation plane, an angle between a tangential plane at a vertex of each of the first spaced-apart portions and the separation plane being acute, and
• wherein what is used as the second mold member in the base portion forming step includes a second contact surface defining the separation plane and coming into contact with the first contact surface;
• a pair of second spaced-apart portions, each of which has a surface curved so as to be convex toward the separation surface, the surface being gradually more distant from the separation plane as the surface becomes more distant along the separation surface from the second contact surface;
• and a second connection portion, which connects the second spaced-apart portions with each other and has a curving shape that is convex so as to become more distant from the separation plane in a direction perpendicular to the separation plane, an angle between a tangential plane at a vertex of each of the second spaced-apart portions and the separation plane being acute.