Provided is a sewing machine that can be reduced in size by employing a simple configuration for a feed dog drive device. A lateral feed drive unit (8) and a vertical drive unit (9) transmit rotation of a drive shaft (7) to a feed dog (3). The feed dog (3) is supported by a swingable feed base (5). A square piece (18) is provided at a lower end of a raising and lowering link (15) of the vertical drive unit (9). A guide member (19) including a guide groove (20) configured to guide the square piece (18) is disposed right under the feed base (5). An upper end of the raising and lowering link (15) is connected to a part of the feed base (5) between the swinging shaft (6) and the feed dog (3).

A sewing machine according to the present invention includes: an upper shaft that drives a needle and a balance; a lower shaft that drives a hook and a feed dog; an upper and lower shaft belt that synchronizes rotation of the upper shaft with rotation of the lower shaft; and an idler unit that pushes an idler into the upper and lower shaft belt to change a tension side belt length, in which the idler unit includes a transmission mechanism connected to the upper shaft or the lower shaft, and a rotating body mechanism provided with the idler and having a rotating body that rotates in synchronization with the upper shaft or the lower shaft by the transmission mechanism, and a pushing amount of the idler into the upper and lower shaft belt is changed according to rotation of the rotating body.

Provided is a sewing machine that can be reduced in size by employing a simple configuration for a feed dog drive device. A lateral feed drive unit (8) and a vertical drive unit (9) transmit rotation of a drive shaft (7) to a feed dog (3). The feed dog (3) is supported by a swingable feed base (5). A square piece (18) is provided at a lower end of a raising and lowering link (15) of the vertical drive unit (9). A guide member (19) including a guide groove (20) configured to guide the square piece (18) is disposed right under the feed base (5). An upper end of the raising and lowering link (15) is connected to a part of the feed base (5) between the swinging shaft (6) and the feed dog (3).

Provided is a sewing machine that can be reduced in size by employing a simple configuration for a feed dog drive device. A lateral feed drive unit (8) and a vertical drive unit (9) transmit rotation of a drive shaft (7) to a feed dog (3). The feed dog (3) is supported by a swingable feed base (5). A square piece (18) is provided at a lower end of a raising and lowering link (15) of the vertical drive unit (9). A guide member (19) including a guide groove (20) configured to guide the square piece (18) is disposed right under the feed base (5). An upper end of the raising and lowering link (15) is connected to a part of the feed base (5) between the swinging shaft (6) and the feed dog (3).

Provided is a sewing machine capable of positioning feed dogs with a sufficient distance below the upper surface of a throat plate when the feed dogs are retracted. Feed dogs 3 protrude and retract from a throat plate 1. A horizontal feed drive unit 8 converts the rotation of a drive shaft 7 into a reciprocating motion in the horizontal direction and transmits the horizontal reciprocating motion to the feed dogs 3. A vertical drive unit 9 converts the rotation of the drive shaft 7 into a reciprocating motion in the vertical direction and transmits the vertical reciprocating motion to the feed dogs 3. A vertical position changing part moves turn-back points P at both ends of a forward path and a return path when the feed dogs 3 reciprocate in the horizontal direction below the throat plate 1.

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.

In feed dog mounting/unmounting mechanism, lever is slidably provided to feed base in the front-rear direction, and is forced backward by a lever force-applying spring. Upon sliding lever rearward, fixing target portion of feed dog 22 is fixedly held by base-side fixing portion of feed base and lever-side fixing portion of lever arranged in the front-rear direction. Stopper is provided to feed base so as to be movable in the upper-lower direction, and holds lever. When feed dog is mounted, stopper is pressed downward by feed dog, which moves stopper so as to allow lever to slide. With this, lever is slid due to force applied by the lever force-applying spring, thereby allowing fixing target portion to be held, interposed between base-side fixing portion and lever-side fixing portion.

A sewing machine comprises a crank shaft, a first drive shaft, a second drive shaft, a needle assembly, a presser foot, and an upper walking foot. A first crank arm assembly is connected to the crank shaft to the first drive shaft. A first linkage assembly is connected to the first drive shaft to the needle assembly. A second crank arm assembly is connected to the first drive shaft to the second drive shaft. A second linkage assembly is connected to the second drive shaft to the presser foot and the upper walking foot. The second linkage assembly is configured to cause out-of-phase reciprocatory movement of the presser foot and the upper walking foot. The second crank arm assembly has a variable length that is selectably adjustable by an operator to yield at least first and second different stepping heights of the upper walking foot.

A sewing machine comprises a crank shaft, a first drive shaft, a second drive shaft, a needle assembly, a presser foot, and an upper walking foot. A first crank arm assembly is connected to the crank shaft to the first drive shaft. A first linkage assembly is connected to the first drive shaft to the needle assembly. A second crank arm assembly is connected to the first drive shaft to the second drive shaft. A second linkage assembly is connected to the second drive shaft to the presser foot and the upper walking foot. The second linkage assembly is configured to cause out-of-phase reciprocatory movement of the presser foot and the upper walking foot. The second crank arm assembly has a variable length that is selectably adjustable by an operator to yield at least first and second different stepping heights of the upper walking foot.

A feeding device of an industrial sewing machine comprises a shell base, a main connecting rack having a first bar portion and a second bar portion, a terminal driven rack mounted at the first bar portion and the second bar portion, a first driven rack, a raising-driven mechanism and a driving shaft. The first driven rack is mounted at the first bar portion and connected to the shell base, and has a first sliding recess. The raising-driven mechanism has a second driven rack mounted at the second bar portion and having a second sliding recess. A raising-connecting rod is mounted at the second driven rack and the terminal driven rack. The driving shaft has a first crank mounted through the first sliding recess and a second crank mounted through the second sliding recess. The feeding device has a compact volume to facilitate ease in maintenance.