A needle bar 4 is supported by a needle bar supporter in a manner freely movable up and down relative to a frame. A crank 2 is fixed to an upper shaft 1, rotates with the upper shaft 1, and an output end thereof moves circularly. A crank rod 3 is connected to the crank 2 in a freely rotatable manner. A connection rod 8 is connected to an intermediate portion of the crank rod 3 in a freely rotatable manner, and is connected to the needle bar 4 in a freely rotatable manner. A length of the needle bar 4 and a length from a connecting position of the connection rod 8 and the crank rod 3 to a slider 7 differ. When the crank 2 circularly moves, the connecting position of the connection rod 8 and the crank rod 3 draws a trajectory of an ellipse.

A sewing machine moves a needle up and down relative to a cloth based on drive force from a rotating upper shaft to form a stitch. A first output generating unit reciprocates a first output point along an output axis so as to convert the rotational motion of the upper shaft into a linear motion. An assist rod that serves as a connection portion links the first output point with a needle bar. A needle-bar swing unit swings the needle bar. An output shaft moving unit moves a guide that is the output axis in a cloth feeding direction in accordance with the motion of the needle-bar swing unit. The assist rod changes the inclination in accordance with the movement of the output axis, and reciprocates the needle bar in substantially parallel with the output axis while maintaining the inclination.

A sewing machine moves a needle up and down relative to a cloth based on drive force from a rotating upper shaft to form a stitch. A first output generating unit reciprocates a first output point along an output axis so as to convert the rotational motion of the upper shaft into a linear motion. An assist rod that serves as a connection portion links the first output point with a needle bar. A needle-bar swing unit swings the needle bar. An output shaft moving unit moves a guide that is the output axis in a cloth feeding direction in accordance with the motion of the needle-bar swing unit. The assist rod changes the inclination in accordance with the movement of the output axis, and reciprocates the needle bar in substantially parallel with the output axis while maintaining the inclination.

A sewing system comprises a sewing machine, a camera that captures an image of a reference position for sewing, a robot arm that holds the sewing machine and the camera, and a controller. The controller controls operations of forming a first stitch position that results from stitching of the sewing machine, and forming a second stitch position that results from stitching of the sewing machine after rotating the sewing machine at a prescribed angle about a rotation axis that passes through a needle center position stored by the controller. The controller further performs calibration processing that calibrates the needle center position stored by the controller, based on each position of the first stitch position and the second stitch position within image capture ranges of capture images that are obtained by capturing images of the first stitch position and the second stitch position using the camera.

A sewing system comprises a sewing machine, a camera that captures an image of a reference position for sewing, a robot arm that holds the sewing machine and the camera, and a controller. The controller controls operations of forming a first stitch position that results from stitching of the sewing machine, and forming a second stitch position that results from stitching of the sewing machine after rotating the sewing machine at a prescribed angle about a rotation axis that passes through a needle center position stored by the controller. The controller further performs calibration processing that calibrates the needle center position stored by the controller, based on each position of the first stitch position and the second stitch position within image capture ranges of capture images that are obtained by capturing images of the first stitch position and the second stitch position using the camera.

A method for preventing seam ravel of multi-thread chain stitches is provided. After normal sewing is terminated with a looper set in a forward movement state, a state in which a needle thread loop caught by the looper is subjected to position-holding at a position closer to a forward movement end of the looper than a descent position of a needle is maintained until the needle descends through the needle thread loop caught by the looper. Thereafter, the position-holding of the needle thread loop is released to permit a sewing action for at least one stitch, thereby allowing the needle thread loop to be self-looped with a needle thread held by the needle. This surely strongly prevents the seam ravel of multi-thread chain stitches formed by the single needle, irrespective of the dimension of tension applied to the needle thread and the looper thread.

A method for preventing seam ravel of multi-thread chain stitches is provided. After normal sewing is terminated with a looper set in a forward movement state, a state in which a needle thread loop caught by the looper is subjected to position-holding at a position closer to a forward movement end of the looper than a descent position of a needle is maintained until the needle descends through the needle thread loop caught by the looper. Thereafter, the position-holding of the needle thread loop is released to permit a sewing action for at least one stitch, thereby allowing the needle thread loop to be self-looped with a needle thread held by the needle. This surely strongly prevents the seam ravel of multi-thread chain stitches formed by the single needle, irrespective of the dimension of tension applied to the needle thread and the looper thread.

A needle drive assembly for a sewing machine includes a drive shaft rotatable about a drive shaft axis and a needle drive cam operably connected to the drive shaft and rotatable therewith. A needle drive race is slidably connected to the needle drive cam via a cam pin secured to the needle drive cam and at least partially extending through the needle drive race. A needle is assembly affixed to the needle drive race and includes a needle bar and a needle secured to the needle bar. Rotary motion of the drive shaft and needle drive cam about the drive shaft axis is translated into a needle path via the needle drive race, the needle path including a substantially vertical downstroke from a stroke peak to a stroke depth, a horizontal carry portion from the stroke depth and a curvilinear or linear upstroke from the horizontal carry portion to peak.

A needle drive assembly for a sewing machine includes a drive shaft rotatable about a drive shaft axis and a needle drive cam operably connected to the drive shaft and rotatable therewith. A needle drive race is slidably connected to the needle drive cam via a cam pin secured to the needle drive cam and at least partially extending through the needle drive race. A needle is assembly affixed to the needle drive race and includes a needle bar and a needle secured to the needle bar. Rotary motion of the drive shaft and needle drive cam about the drive shaft axis is translated into a needle path via the needle drive race, the needle path including a substantially vertical downstroke from a stroke peak to a stroke depth, a horizontal carry portion from the stroke depth and a curvilinear or linear upstroke from the horizontal carry portion to peak.

A sewing machine assembly includes a sewing machine frame, a needle bar, a drive shaft, and a vibration dampener system. The needle bar configured to linearly reciprocate relative to the sewing machine frame along a needle bar axis. The drive shaft is coupled to the needle bar and configured to rotate about a drive axis to drive linear reciprocation of the needle bar along the needle bar axis. The vibration dampener system is coupled to the drive shaft to reduce vibration of the sewing machine assembly caused by linear reciprocation of the needle bar during use of the sewing machine assembly.