Abstract: A low-cost sewing machine capable of achieving a desired balance between needle thread consumption and bobbin thread consumption is described. A memory section stores needle thread requirement data having precorrected needle thread requirement and postcorrected needle thread requirement. In a torque control zone, rotating force is imparted to a turning arm so as to impart a tension on the needle thread according to a torque value, while closing an upstream grip section main body and while opening a downstream grip section main body. In a first position control zone, the needle thread is drawn according to the postcorrected needle thread requirement, while opening the upstream grip section main body and while closing the downstream grip section. In a second position control zone, the turning arm is returned to an initial position, while closing the upstream grip section main body and while opening the downstream grip section main body.

Abstract: A low-cost sewing machine capable of achieving a desired balance between needle thread consumption and bobbin thread consumption is described. A memory section stores needle thread requirement data having precorrected needle thread requirement and postcorrected needle thread requirement. In a torque control zone, rotating force is imparted to a turning arm so as to impart a tension on the needle thread according to a torque value, while closing an upstream grip section main body and while opening a downstream grip section main body. In a first position control zone, the needle thread is drawn according to the postcorrected needle thread requirement, while opening the upstream grip section main body and while closing the downstream grip section. In a second position control zone, the turning arm is returned to an initial position, while closing the upstream grip section main body and while opening the downstream grip section main body.

Abstract: Disclosed is a sewing machine which evaluates sewing quality using a stitch tightness index. During sewing operation, a used length of an upper thread per stitch is detected, and a stitch tightness index per sewn stitch is calculated on the basis of a stitch length per stitch defined by sewing pattern data, a fabric thickness of a sewing workpiece, and detected data of the used length of the upper thread. Then, notification is made which corresponds to the calculated stitch tightness index per sewn stitch (such as a visual display of the stitch tightness index). After that, acceptability/non-acceptability of the thread tightness per sewn stitch can be determined by comparing the calculated stitch tightness index per sewn stitch against a reference value, and a result of the determination can be notified.

Abstract: A presser foot 12c of a sewing machine is provided with a main body 210, a swayingly reciprocating mechanism section 230, and a thread hooking rod drive motor 240. The swayingly reciprocating mechanism section 230 has a thread hooking rod 236, and a needle thread receiving section for fixing a needle thread together with the thread hooking rod 236 is provided inside a leading-end structure section 216 of the main body 210. As a result of driving of the thread hooking rod drive motor 240, the swayingly reciprocating mechanism section 230 reciprocally moves while swaying with respect to the main body 210. When a thread take-up lever pulls up the needle thread, a circular movement arm which performs rotation movement while hooking the needle thread adjusts a rotational angle of the circular movement arm, thereby enabling adjustment of a length of a needle thread in one preceding stitch.

Abstract: Disclosed is a sewing machine which evaluates sewing quality using a stitch tightness index. During sewing operation, a used length of an upper thread per stitch is detected, and a stitch tightness index per sewn stitch is calculated on the basis of a stitch length per stitch defined by sewing pattern data, a fabric thickness of a sewing workpiece, and detected data of the used length of the upper thread. Then, notification is made which corresponds to the calculated stitch tightness index per sewn stitch (such as a visual display of the stitch tightness index). After that, acceptability/non-acceptability of the thread tightness per sewn stitch can be determined by comparing the calculated stitch tightness index per sewn stitch against a reference value, and a result of the determination can be notified.

Abstract: A presser foot 12c of a sewing machine is provided with a main body 210, a swayingly reciprocating mechanism section 230, and a thread hooking rod drive motor 240. The swayingly reciprocating mechanism section 230 has a thread hooking rod 236, and a needle thread receiving section for fixing a needle thread together with the thread hooking rod 236 is provided inside a leading-end structure section 216 of the main body 210. As a result of driving of the thread hooking rod drive motor 240, the swayingly reciprocating mechanism section 230 reciprocally moves while swaying with respect to the main body 210. When a thread take-up lever pulls up the needle thread, a circular movement arm which performs rotation movement while hooking the needle thread adjusts a rotational angle of the circular movement arm, thereby enabling adjustment of a length of a needle thread in one preceding stitch.

Abstract: In relation to a sewing machine having a function of rotating a sewing needle in order to prevent occurrence of hitch stitches, there is provided a needle bar that obviates a necessity for an additional rotation mechanism for rotating the sewing needle. A needle bar includes: a needle bar body having a vertically-movable sleeve and a guide bush; a sleeve provided in the needle bar body and having openings, and the like, where balls are to be placed; a cam shaft that has a disc-shaped portion which is provided in the needle bar body, an upper shaft which is provided with a pair of grooves or the like having helical grooves and which is inserted in the sleeve, and a lower shaft which is formed so as to protrude downward from a guide bush; and a joint secured to the lower shaft for securing a sewing needle.

Abstract: In relation to a sewing machine having a function of rotating a sewing needle in order to prevent occurrence of hitch stitches, there is provided a needle bar that obviates a necessity for an additional rotation mechanism for rotating the sewing needle. A needle bar includes: a needle bar body having a vertically-movable sleeve and a guide bush; a sleeve provided in the needle bar body and having openings, and the like, where balls are to be placed; a cam shaft that has a disc-shaped portion which is provided in the needle bar body, an upper shaft which is provided with a pair of grooves or the like having helical grooves and which is inserted in the sleeve, and a lower shaft which is formed so as to protrude downward from a guide bush; and a joint secured to the lower shaft for securing a sewing needle.

Abstract: To provide a sewing machine that can control tension on a needle thread and tension on a bobbin thread on a per-stitch basis; that enables even heads of a multi-head embroidery sewing machine to form an identical embroidery; and that enables even a plurality of sewing machines to form identical embroidery. A memory device stores for each stitch of embroidery data a needle thread control torque value and a bobbin thread control torque value. In a needle thread torque control zone, an upstream grip section main body is closed, and a downstream grip section main body is opened. A needle thread motor is subjected to torque control in accordance with the needle thread control torque value. In the meantime, in a position control zone, the upstream grip section body is opened, and the downstream grip section body is closed, thereby subjecting the needle thread motor to position control.

Abstract: Each of front-back direction actuation blocks for actuating a sewing frame in a front-back direction has ball screws, motors, and movable members. An engagement roller of each of the movable members engages with a long side of the sewing frame, and an engagement roller of each of the movable members engages with a long side. The movable members of respective front-back direction actuation blocks are connected to short sides of the sewing frame. In each of the front-back direction actuation blocks, the ball screw and the ball screw are joined together by means of a joint member. Movable members of respective right-left direction actuation blocks support the respective front-back direction actuation blocks.

Abstract: To provide a sewing machine that can control tension on a needle thread and tension on a bobbin thread on a per-stitch basis; that enables even heads of a multi-head embroidery sewing machine to form an identical embroidery; and that enables even a plurality of sewing machines to form identical embroidery. A memory device stores for each stitch of embroidery data a needle thread control torque value and a bobbin thread control torque value. In a needle thread torque control zone, an upstream grip section main body is closed, and a downstream grip section main body is opened. A needle thread motor is subjected to torque control in accordance with the needle thread control torque value. In the meantime, in a position control zone, the upstream grip section body is opened, and the downstream grip section body is closed, thereby subjecting the needle thread motor to position control.

Abstract: [Problem] To provide a sewing frame actuator for a sewing machine capable of positioning a sewing frame with high accuracy by preventing occurrence of distortion of the sewing frame. [Means for Resolution] Each of front-back direction actuation blocks 70 for actuating a sewing frame 50 in a front-back direction has ball screws 86 and 106, motors 84 and 104, and movable members 87 and 107. An engagement roller 92 of each of the movable members 87 engages with a long side 52 of the sewing frame, and an engagement roller 112 of each of the movable members 107 engages with a long side 54. The movable members 87 and 107 of respective front-back direction actuation blocks 71 are connected to short sides 56 and 58 of the sewing frame 50. In each of the front-back direction actuation blocks 70 and 71, the ball screw 86 and the ball screw 106 are joined together by means of a joint member 124.