Sewing principle of sewing machine

Like a car, the basic principles of most sewing machines are the same. The core of the car is the engine of the internal combustion engine, and the core of the sewing machine is the coil stitching system.

The stitching method of the coil differs greatly from ordinary hand sewing. In the simplest hand stitching, the sewer attaches a thread to the small eye at the end of the needle, then passes the needle through the two fabrics completely, from one side to the other, and then back to the original side. In this way, the needle drives the wires in and out of the fabric and stitches them together.

Although this is very simple for handwork, it is extremely difficult to pull with a machine. The machine needs to release the needle on one side of the fabric and then grab it again on the other side. Then, it needs to pull all the loose lines out of the fabric, adjust the direction of the needle, and then repeat all the steps in the opposite direction. This process is too complicated for a simple machine, and it is not practical, and even for manual use, it is only useful when using a shorter line.

Instead, the sewing machine simply passes the needle portion through the fabric. On the needle, the needle eye is behind the tip, not at the end of the needle.

The needle is attached to the needle bar, which is pulled up and down by the motor through a series of gears and cams (described in more detail later).

When the tip of the needle passes through the fabric, it pulls a small coil on one side of the other. A device under the fabric grabs the coil and wraps it around another wire or another coil of the same wire. In the next two sections, we will see how this system works.

The simplest stitch stitching is chain stitching. To sew out the chain stitching, the sewing machine is looped with the same length of thread behind the line. The fabric is placed on a metal plate below the needle and secured with a presser foot. At the beginning of each stitching, the needle pulls a coil through the fabric. A device for making a coil grasps the coil before the needle is pulled out, and the device moves in synchronism with the needle. Once the needle is pulled out of the fabric, the feed device (described later) will pull the fabric forward.

When the needle passes through the fabric again, the new coil will pass directly through the middle of the previous coil. The device that makes the coil will grab the wire again and make a coil around the next coil. In this way, each coil will hold the next coil in place.

The main advantage of chain stitching is that it can be sewn very fast. However, it is not particularly strong, and if one end of the thread is loosened, the entire sewing may be loose. Most sewing machines use a stronger stitch, called a lock seam. You can see how the typical lock stitching works in the animation below.

The most important components of the locking device are the shuttle hook and spool assembly. The spool is a roll of wire placed under the fabric. It is located in the center of the shuttle, which is rotated by the motor and synchronized with the movement of the needle.

As with chain stitching, the needle pulls a coil through the fabric, and as the feed dog moves the fabric forward, it rises again and then inserts another coil. However, this stitching mechanism does not connect the different coils together, but rather connects them to another length of wire that is loosened from the spool.

When the needle puts the thread into the coil, the rotating shuttle catches the coil with the crochet. As the shuttle rotates, it pulls the coil around the wire from the spool. This makes the stitching very strong.

This kind of hook is also evolved through a straight shuttle.

The stitching principle of the sewing machine has evolved from a straight shuttle to a rotary hook, and it has entered a mature stage.