Sewing-machine bobbin thread tension controller, and sewing machine

A sewing-machine bobbin thread tension controller, comprising:

• an outer shuttle that includes a guide groove formed on an inner peripheral surface thereof;
• a middle shuttle that rotates along the guide groove of the outer shuttle, to thus hook a needle thread, and that includes
• a race formed into a circular arc along a circumferential edge of the middle shuttle and slidably supported by the guide groove,
• a main middle shuttle that continually extends from an inner end of the race and that includes
• a rear portion continually extending from a rear-side end which is one end of an inner circumferential edge of the race achieved in an axial direction, and
• a front-side tapered portion which continually extends from a front-side end which is a remaining end of the inner circumferential edge of the race, and which is tapered so as to have a smaller diameter toward the front, wherein the rear portion further includes
• a substantially circular plate-like rear-side body which is perpendicular to an axial line serving as a center of rotation of the middle shuttle and whose outer diameter is smaller than an inner diameter of the race and
• a rear-side tapered portion which is formed between a surrounding area of the rear-side body and the race and which is tapered so as to have a smaller diameter from the race toward the rear-side body,
• a bobbin accommodation section that is formed in a front surface of the rear-side body and that includes
• a shaft formed so as to extend from a center of the rear-side body along the center of rotation of the middle shuttle and
• a cylindrical tubular portion provided on a front surface of the rear-side body, and
• a third magnet disposed on a front or rear surface of the rear-side tapered portion, wherein the middle shuttle except the third magnet is made of a non-magnetic substance;
• a middle shuttle presser that is disposed on a front side of the outer shuttle in order to prevent the middle shuttle accommodated in the outer shuttle from falling from the outer shuttle;
• a bobbin that is accommodated in the bobbin accommodation section of the middle shuttle and that has a first magnet disposed on a plane perpendicular to an axial line serving as a center of rotation;
• a bobbin thread tension control mechanism that includes
• a bobbin thread tension control motor which is disposed at a rear of the middle shuttle, which has a rotary shaft concentric to the center of rotation of the middle shuttle, and which rotates the rotary shaft in a direction opposite to a rotating direction of the bobbin achieved when a bobbin thread wound around the bobbin is withdrawn, and
• a rotary disc which is attached to a rotary shaft of the bobbin thread tension control motor and positioned in close proximity to the rear portion of the middle shuttle and which has a second magnet for rotating the first magnet as a result of rotation of the rotary disc;
• a shuttle actuation unit that includes
• a shuttle actuation motor which is provided at a rear of the bobbin thread tension control motor and which has a second rotary shaft serving as a rotary shaft concentric to the center of rotation of the middle shuttle,
• a substantially L-shaped arm attached to the second rotary shaft and including
• a base end attached to the secondary shaft and perpendicular to an axial center core of the second rotary shaft and
• a leading end continually extending from the base end in parallel to the axial center core of the second rotary shaft, and
• a fourth magnet attached to an extremity of the arm and in close proximity to the third magnet;
• and
• a control section for controlling rotation of the shuttle actuation motor such that the middle shuttle makes substantially half forward and backward rotations.

A sewing-machine bobbin thread tension controller, comprising:

• an outer shuttle that includes a guide groove formed on an inner peripheral surface thereof;
• a middle shuttle that rotate along the guide groove of the outer shuttle, to thus hook a needle thread, and that includes
• a race formed into a circular arc along a circumferential edge of the middle shuttle and slidably supported by the guide groove,
• a main middle shuttle that continually extends from an inner end of the race and that includes
• a rear portion continually extending from a rear-side end which is one end of an inner circumferential edge of the race achieved in an axial direction, and
• a front-side tapered portion which continually extends from a front-side end which is a remaining end of the inner circumferential edge of the race, and which is tapered so as to have a smaller diameter toward the front, wherein the rear portion further includes
• a substantially circular plate-like rear-side body, perpendicular to an axial line serving as a center of rotation of the middle shuttle, that has an outer diameter which is smaller than an inner diameter of the race and
• a rear-side tapered portion that is formed between a surrounding area of the rear-side body and the race and that is tapered so as to have a smaller diameter from the race toward the rear-side body,
• a bobbin accommodation section formed in a front surface of the rear-side body and that includes
• a shaft formed so as to extend from a center of the rear-side body along the center of rotation of the middle shuttle and
• a cylindrical tubular portion provided on a front surface of the rear-side body, and
• a third magnet disposed on a front or rear surface of the rear-side tapered portion, wherein the middle shuttle except the third magnet is made of a non-magnetic substance;
• a middle shuttle presser disposed on a front side of the outer shuttle in order to prevent the middle shuttle accommodated in the outer shuttle from falling from the outer shuttle;
• a bobbin that is accommodated in the bobbin accommodation section of the middle shuttle and that has a first magnet disposed on a plane perpendicular to an axial line serving as a center of rotation;
• a bobbin thread tension control mechanism that includes
• a bobbin thread tension control motor which is disposed at a rear of the middle shuttle, which has a rotary shaft concentric to the center of rotation of the middle shuttle and which rotates the rotary shaft in a direction opposite to a rotating direction of the bobbin achieved when a bobbin thread wound around the bobbin is withdrawn, and
• a rotary disc which is attached to a rotary shaft of the bobbin thread tension control motor and positioned in close proximity to the rear portion of the middle shuttle and which has a second magnet for rotating the first magnet as a result of rotation of the rotary disc;
• a shuttle actuation unit that includes
• a shuttle actuation motor which is interposed between the bobbin thread tension control motor and the middle shuttle and which has
• an insert hole enabling insertion of a rotary shaft of the bobbin thread tension control motor and
• a second rotary shaft, which is a rotary shaft of the shuttle actuation motor, is formed into a tubular shape so as to enable insertion of the rotary shaft of the bobbin thread tension control motor;
• wherein an axial line of the second rotary shaft is concentric to an axial line of the rotary shaft of the bobbin thread tension control motor,
• a substantially L-shaped arm which is attached to the second rotary shaft and which includes
• a base end attached to the secondary rotary shaft perpendicular to an axial center core of the second rotary shaft and
• a leading end continually extending from the base end in parallel to the axial center core of the second rotary shaft, and
• a fourth magnet attached to an extremity of the arm and in close proximity to the third magnet;
• and
• a control section for controlling rotation of the shuttle actuation motor such that the middle shuttle makes a full rotation.