Abstract: A thread feeding apparatus for a sewing machine which has a simplified mechanism for accuracy of manufacturing and improved durability so as to accommodate high speed sewing. The thread feeding apparatus for the sewing machine has upstream grippers for respectively gripping an upper looper thread and a lower looper thread, closed by a stitch forming device at the time of the stitch forming and opened at the time of the cloth feeding, downstream grippers for gripping the respective threads introduced from the respective upstream grippers, opened at the time of the stitch forming so that the respective threads are pulled by the stitch forming device and closed at the time of cloth feeding, and reciprocators which are respectively driven in a synchronous manner with a left needle, a right needle, an upper looper and a lower looper, at the time of cloth feeding.

Abstract: A needle plate of a cover stitch sewing machine, adapted to introduce double chain stitch chain-off's, which are formed below a needle plate by the intertwining of threads on three needles and a thread on a looper in accordance with actions of the needles and looper occurring when fabrics to be sewn are not fed, onto the portion of an upper surface of the needle plate which is behind needle points, and feed out the chain-off's continuously with the chain-off's held between rear feed dogs on the rear side of the needle points and a chain-off thread gripper, is provided with a thread positioning spreader formed of retainers 10A, 10B having inclined portions indexed to the needle points and provided between recesses of the needle plate so that the chain-off stitches can be sewn continuously in a stable condition by a simple structure.

Abstract: A looper drive mechanism for a sewing machine includes: two loopers; looper drive shafts for driving the loopers; a main shaft extending across one plane transverse to the looper drive shafts; and torque transmission units for transmitting rotation of the main shaft to the looper drive shafts. The transmission units include: two slant grooved cams fixed to the main shaft and having grooves each extending through a full circumference and slanting relative to the main shaft; U-shaped followers each having two rollers, each of the rollers being supported by the looper drive shaft and rotating about its own axis within the groove of the slant grooved cams; and connection pins for pivotally mounting the U-shaped followers on the looper drive shafts so that the U-shaped followers are not rotatable in a direction in parallel with a line connecting the two rollers with each other but rotatable in a direction perpendicular to the line connecting the two rollers with each other.

Abstract: A looper drive cam is formed of a cylindrical cam which is fixed to a main shaft so that its axis is inclined thereto at an angle of .theta.. A looper drive fork forming an U-shaped cam follower is attached to a looper drive shaft, and is engaged with the inclined cam. The fork is attached to the looper drive shaft with a degree of freedom which allows for deviation between axes of the main shaft and the looper drive shaft. As the main shaft rotates, a cam face of the inclined cam changes in a range of .+-..theta. in a plane containing the main shaft, so that the fork rotates to rotate the looper drive shaft. Owing to the freedom of degree of the fork thus attached, the motion is transmitted smoothly, and wear and rattling are prevented.

Abstract: A knife drive mechanism of a sewing machine includes a drive assembly 1 for converting rotary motion of a drive shaft 10 into a swing motion and an upper-knife drive assembly 2 for converting the swing motion into an up-and-down motion of an upper knife 20. The upper-knife drive assembly 2 has a clutch 3 for preventing/permitting transmission of the up-and-down motion to the knife 20. Even during stitching, engagement/disengagement of the clutch 3 can be effected, which permits the knife 20 to be connected to and disconnected from its drive assembly, thereby permitting the scissoring cutting to be started or stopped. When a surface 42 of the first swing member 4 urges a projection 52 of a second swing member 5 to cause the knife 20 to move downward at the completion of cutting, the knife 20 itself serves as a cloth-feed guide to prevent misalignment of the cloth and breakage of the sewing needle or upper and lower loopers.

Abstract: Disclosed is a buttonhole sewing machine which includes an electric motor for driving the sewing machine; a machine body including a bed for holding a workpiece in cooperation with a workpiece clamping means; a stitch forming device for working buttonholes in the workpiece and including a mechanism for driving a needle bar which supports a needle, a looper-spreader mechanism for driving a looper and a spreader, and a turning mechanism for turning the needle bar, the looper and the spreader. The needle bar driving mechanism includes a vertical reciprocation mechanism and a needle lateral vibrating mechanism; and an arm shaft for driving the up/down moving mechanism.

Abstract: A blind stitch sewing machine includes a straight needle, a driving mechanism which gives a linear reciprocating motion to the straight needle, a needle guide which prevents the straight needle from sliding on the surface of the work without sticking therein, and a work raising portion formed on a work raising member so that a raised part of the work is continuously raised until it is stuck with the pointed tip of the straight needle and, after the pointed tip of the straight needle has passed the work raising member, the work raising member is withdrawn from the path of the straight needle by a distance not less than the radius of the trunk of the straight needle.

Abstract: The invention discloses an overlock sewing machine equipped with a threading unit of very simple configuration, which comprises a shaft having a threading member fixed thereon and a mechanism (including arm and disc elements) for determining the rotation timing of the shaft.