The length of a sewing machine stitch is adjustable by varying the effective length of a first bar of a multi-bar linkage operably secured to a feed dog of the sewing machine. The effective length of the first bar is defined between an anchor point and a pivot point, with the pivot point being secured to a slider configured for movement along the length of the first bar. The slider comprises a pinion gear configured to engage a gear rack of the first bar, such that rotation of the pinion gear causes movement of the slider and the pivot point relative to the anchor point. Moreover, to accommodate the adjustable stitch length, the sewing machine additionally comprises an adjustable looper thread eyelet configured to adjust the length of the looper thread path to accommodate increased tension or slack in the looper thread due to the changed stitch length.

A lower thread supply device of a sewing machine includes a bobbin, a bobbin case, a magnetic force member, and a magnetic force change portion. The bobbin has a cylindrical portion for inserting into a spindle of a shuttle, a shuttle side flange portion, and a front surface side flange portion which is magnetic, and a lower thread is wound around an outer circumference of the cylindrical portion between the shuttle side flange portion and the front surface side flange portion. The bobbin case has a non-magnetic cover portion having a front surface side part and a side wall part, housing the bobbin and transmitting a magnetic force. The magnetic force member is arranged at the front surface side of the bobbin case and attracts the front surface side flange portion of the bobbin by a magnetic force via the bobbin case.

A thread feeding device of a sewing machine includes a needle bar movable vertically to pull an upper thread through a fabric, and movable between left and right terminal positions. An imaginary plane to which the needle bar is normal is defined, and includes left and right boundary lines which pass through the left and right terminal positions. An inner rotary hook includes a thread tensing unit disposed on a hook surrounding wall. A lower thread passes through and abuts against the thread tensing unit to define at least one thread abutting point. A final abutting point where the lower thread passes through the thread tensing unit immediately before reaching the fabric is defined, and is projected on the imaginary plane at a point that is interposed between the boundary lines.

Apparatuses, methods, and computer program products for quilting webs without compressing the webs. A quilting machine includes a needle bar to which needles are attached, needle thread passing through each needle, a looper shaft to which loopers are attached, a looper corresponding to each needle and from which looper thread is provided to form stitches, and a retainer bar to which spreaders are attached to facilitate stitching. A drive pulley powered by a first servo motor rotates cranks to move the needles through a cycle and rotates a belt which rotates an indexer pulley. Rotation of the indexer pulley oscillates the looper shaft and reciprocates the retainer bar. Another drive pulley powered by a second servo motor operates to move an input web through the machine between chain stitches.

Apparatuses, methods, and computer program products for quilting webs without compressing the webs. A quilting machine includes a needle bar to which needles are attached, needle thread passing through each needle, a looper shaft to which loopers are attached, a looper corresponding to each needle and from which looper thread is provided to form stitches, and a retainer bar to which spreaders are attached to facilitate stitching. A drive pulley powered by a first servo motor rotates cranks to move the needles through a cycle and rotates a belt which rotates an indexer pulley. Rotation of the indexer pulley oscillates the looper shaft and reciprocates the retainer bar. Another drive pulley powered by a second servo motor operates to move an input web through the machine between chain stitches.

With a overlock sewing machine, when a switching mechanism is switched to a threading-enabled state, and a looper cover is closed, the looper cover is slid toward one side in the hinge shaft axial direction so as to operate a detection lever. In the non-operating state, the detection lever is set to an initial position where it does not press an operation protrusion of a switch. When a side cover is closed, and the detection lever is operated, the operation lever is set to an operation-enabled position where it presses the operation protrusion. When the operation lever is operated, and the side cover is opened, the detection lever is set by passing through the operation-enabled to the operation-disabled position where it does not press the operation protrusion.

With a overlock sewing machine, when a switching mechanism is switched to a threading-enabled state, and a looper cover is closed, the looper cover is slid toward one side in the hinge shaft axial direction so as to operate a detection lever. In the non-operating state, the detection lever is set to an initial position where it does not press an operation protrusion of a switch. When a side cover is closed, and the detection lever is operated, the operation lever is set to an operation-enabled position where it presses the operation protrusion. When the operation lever is operated, and the side cover is opened, the detection lever is set by passing through the operation-enabled to the operation-disabled position where it does not press the operation protrusion.

Apparatuses, methods, and computer program products for quilting webs. A quilting machine includes a cutting edge, a looper from which thread is provided to form stitches, and an adjuster assembly. The adjuster assembly extends an adjuster toward the thread between the looper and the retainer. When the adjuster is moved, a predetermined amount of thread is pulled away from the looper by the adjuster to provide a controlled length of thread between the looper and the cutting edge. The looper assembly may also include an air nozzle that urges the thread away from the adjuster after the thread has been cut. The thread passes through a thread tension monitor that monitors tension in the thread. The tension monitor includes a lift arm that selectively disables the tension monitor so that a loss of tension in the sewing head does not shut down the quilting machine.

Apparatuses, methods, and computer program products for quilting webs. A quilting machine includes a cutting edge, a looper from which thread is provided to form stitches, and an adjuster assembly. The adjuster assembly extends an adjuster toward the thread between the looper and the retainer. When the adjuster is moved, a predetermined amount of thread is pulled away from the looper by the adjuster to provide a controlled length of thread between the looper and the cutting edge. The looper assembly may also include an air nozzle that urges the thread away from the adjuster after the thread has been cut. The thread passes through a thread tension monitor that monitors tension in the thread. The tension monitor includes a lift arm that selectively disables the tension monitor so that a loss of tension in the sewing head does not shut down the quilting machine.

A lower thread supply device of a sewing machine includes a bobbin, a bobbin case, a magnetic force member, and a magnetic force change portion. The bobbin has a cylindrical portion for inserting into a spindle of a shuttle, a shuttle side flange portion, and a front surface side flange portion which is magnetic, and a lower thread is wound around an outer circumference of the cylindrical portion between the shuttle side flange portion and the front surface side flange portion. The bobbin case has a non-magnetic cover portion having a front surface side part and a side wall part, housing the bobbin and transmitting a magnetic force. The magnetic force member is arranged at the front surface side of the bobbin case and attracts the front surface side flange portion of the bobbin by a magnetic force via the bobbin case.