Spool, Spool Unit, and Spool Unit Production Method

A spool comprising:

• a main body of which a first main wall and a second main wall are disposed in parallel to each other, one end of the first main wall and one end of the second main wall are connected to each other by a connector, the other end of the first main wall and the other end of the second main wall serve as open ends;
• a first projection member disposed on an inner surface of the first main wall and projected toward the second main wall, of which at least a portion near the open end is curved to project toward the open end;
• a second projection member disposed on an inner surface of the second main wall and projected toward the first main wall, of which at least a portion near the open end is curved to project toward the open end;
• a first piece member extending from the connector on the inner surface of the first main wall toward the open end, of which a back surface on an intermediate portion is connected to a projected end face of the first projection member, a front rim near the open end is curved to project toward the open end, and at least a tip portion near the open end is flexible;
• and
• a second piece member extending from the connector on the inner surface of the second main wall toward the open end, of which a back surface on an intermediate portion is connected to a projected end face of the second projection member, a front rim near the open end is curved to project toward the open end, and at least a tip portion near the open end is flexible.

A spool unit comprising:

• a base plate in the form of an elongated rectangle having a central portion and end portions and capable of changing its posture between a folded posture in which the base plate is bent at the central portion so that the end portions are opposed to each other and an expanded posture in which the end portions depart from each other symmetrically;
• a pair of thread retaining members disposed on the end portions of the base plate in such a fashion that the thread retaining members are opposed to each other when the base plate is in the folded posture, each of which is in the form of a column with the peripheral surface being in the form of a circular arc;
• an auxiliary plate being provided on each of end faces of the thread retaining members that are opposed to each other when the base plate is in the folded posture;
• a long thread-like substance;
• a casing for housing and retaining the thread-like substance, the thread retaining members, and the base plate with the base plate being in the folded posture;
• and
• a guiding member for guiding the thread-like substance from inside to outside of the casing,
• wherein
• the auxiliary plate has flange portions and fixing portions, the flange portions being fixed to the end faces of the thread retaining members and one end of each of the fixing portions being formed continuously form the flange portion;
• and
• each of the fixing portions extends from the flange portion in a longitudinal direction of the base plate so that the other end is fixed to the central portion of the base plate, a length of each of the fixing portions in a direction orthogonal to the longitudinal direction of the base plate being reduced gradually toward the center of the base plate;
• and,
• the thread-like substance is wound on one of the thread retaining members and subsequently on the other thread retaining member in a state where the base plate is in the expanded posture so that the thread-like substance is wound on the pair of thread retaining members as being crossed between the pair of thread retaining members.