A sewing machine includes an arm portion, a thread spool mounting portion, a bobbin winder, a first guide portion, a second guide portion, and a partition wall member. The arm portion is provided with a drive shaft extending in a first direction. The thread spool mounting portion includes a thread spool pin to be inserted through a through hole of a thread spool. The bobbin winder is provided further to one end side of the arm portion than the thread spool mounting portion. The first guide portion is provided further to another end side of the arm portion than the thread spool mounting portion. The second guide portion is provided further to another end side in the first direction of the arm portion than the first guide portion. The partition wall member is disposed between the thread spool pin and the first guide portion in a second direction.

A sewing machine includes an arm portion, a thread spool mounting portion, a bobbin winder, a first guide portion, a second guide portion, and a partition wall member. The arm portion is provided with a drive shaft extending in a first direction. The thread spool mounting portion includes a thread spool pin to be inserted through a through hole of a thread spool. The bobbin winder is provided further to one end side of the arm portion than the thread spool mounting portion. The first guide portion is provided further to another end side of the arm portion than the thread spool mounting portion. The second guide portion is provided further to another end side in the first direction of the arm portion than the first guide portion. The partition wall member is disposed between the thread spool pin and the first guide portion in a second direction.

In thread cutting mechanism portions of a lower thread winding device, two groove portions of an inner threading groove portion and an outer threading groove portion are formed on a holder. In the inner threading groove portion, one end portion is opened to one of an intersecting direction intersecting with a radial direction of the holder at an outer peripheral portion of the holder and another end portion is located at an inner side of a small-diameter bobbin in the radial direction. The outer threading groove portion is located at an outer side of the inner threading groove portion in the radial direction of the holder. In the outer threading groove portion, one end portion is communicated with the inner threading groove portion and located at the outer side of a large-diameter bobbin in the radial direction and another end portion is located at the inner side of the large-diameter bobbin in the radial direction.

In thread cutting mechanism portions of a lower thread winding device, two groove portions of an inner threading groove portion and an outer threading groove portion are formed on a holder. In the inner threading groove portion, one end portion is opened to one of an intersecting direction intersecting with a radial direction of the holder at an outer peripheral portion of the holder and another end portion is located at an inner side of a small-diameter bobbin in the radial direction. The outer threading groove portion is located at an outer side of the inner threading groove portion in the radial direction of the holder. In the outer threading groove portion, one end portion is communicated with the inner threading groove portion and located at the outer side of a large-diameter bobbin in the radial direction and another end portion is located at the inner side of the large-diameter bobbin in the radial direction.

A sensing system for detecting motion of a bobbin used in a chain stitch type sewing machine using a needle on one side of a textile workpiece and a rotary bobbin positioned on an opposing side of the textile workpiece includes the bobbin being held in a bobbin case having a side panel forming an aperture. The rotary bobbin has a side surface with arcuate regions around a perimeter of the side surface. In addition, the sensing system includes the first and second optical sensors aligned to detect the presence of the first or second bobbin surface. The sensing system further includes a controller adapted to receive signals from the first and second optical sensors related to the presence of the first or second bobbin surface in the first or second regions and interpret the signals to provide the detecting motion of the bobbin.

A sensing system for detecting motion of a bobbin used in a chain stitch type sewing machine using a needle on one side of a textile workpiece and a rotary bobbin positioned on an opposing side of the textile workpiece includes the bobbin being held in a bobbin case having a side panel forming an aperture. The rotary bobbin has a side surface with arcuate regions around a perimeter of the side surface. In addition, the sensing system includes the first and second optical sensors aligned to detect the presence of the first or second bobbin surface. The sensing system further includes a controller adapted to receive signals from the first and second optical sensors related to the presence of the first or second bobbin surface in the first or second regions and interpret the signals to provide the detecting motion of the bobbin.

In the large-diameter bobbin mode of the bobbin winding device, the switching lever is arranged at the switching position, and the interlocking lever is rotated to the blocking position blocking the lowering of the thread trimming holder at the raised position. Therefore, the small-diameter bobbin is arranged above the regular mounting position if it is mounted on the spool shaft. Thus, the engaging hook of the bobbin stopper does not engage with the upper end portion of the core portion of the small-diameter bobbin, and the engaging hook and the thread trimming holder do not sandwich the small-diameter bobbin vertically. Therefore, when the spool shaft is rotated by the spool motor in this state, the bobbin thread is not wound around the small-diameter bobbin since it idles with respect to the spool shaft.

A bobbin winding device has a switching motor and a switching lever connected to the switching motor. The switching motor is driven by the control unit, and the switching lever is rotated, so that the intermediate position of the detection lever is changed to one side in the rotation direction of the detection lever. This allows changing the winding diameter of the bobbin thread wound on different bobbin diameters. Here, the bobbin winding device has a color sensor which detects the outer diameter of the bobbin mounted on the spool shaft. The control unit drives the switching motor to rotate the switching lever based on the detected outer diameter of the bobbin. Therefore, the user can wind the bobbin thread around the bobbins having different outer diameters without rotating the switching lever from the initial position based on the outer diameter of the bobbins to be mounted.

A bobbin winding device has a switching motor and a switching lever connected to the switching motor. The switching motor is driven by the control unit, and the switching lever is rotated, so that the intermediate position of the detection lever is changed to one side in the rotation direction of the detection lever. This allows changing the winding diameter of the bobbin thread wound on different bobbin diameters. Here, the bobbin winding device has a color sensor which detects the outer diameter of the bobbin mounted on the spool shaft. The control unit drives the switching motor to rotate the switching lever based on the detected outer diameter of the bobbin. Therefore, the user can wind the bobbin thread around the bobbins having different outer diameters without rotating the switching lever from the initial position based on the outer diameter of the bobbins to be mounted.

In a lower thread winding device, a motor rotates a thread winding shaft on which a bobbin is mounted. A sensor lever includes a contact portion contactable with a lower thread wound on the bobbin, and a cam piece. A contact includes a pin configured to contact the cam piece and rotates between a first position at which the pin contacts a first outer peripheral portion of the cam piece, and a second position at which the pin contacts a second outer peripheral portion of the cam piece. A lever shifts a position of the pin located when the contact is at the first position. The controller drives the motor when the contact is at the first position and stops driving the motor upon receipt of a detection result, by the detector, indicating that the contact is at the second position.