THE «ETERNAL» DISADVANTAGES OF THE EXISTING TECHNOLOGIES OF FORMING LOCKSTITCH TYPE 301 AND DOUBLE THREAD CHAIN STITCH TYPE 401, CURRENTLY USED FOR STRAIGHT STITCH SEWING.

As you know, the straight stitch is the most commonly used seam in the production of a wide range of sewn products compared to other seam types. 

In addition, straight stitching can be performed under the most demanding conditions, as straight stitching often involves sewing different materials with different thicknesses, densities, rigidity and elasticity, as well as through thick areas and cross seams. 

Therefore, the sewing technology must be ideal for this type of sewing under these harsh conditions. However, the current technologies for forming lockstitch type 301 and double thread chain stitch type 401 used for straight stitching are not ideal.  

This is because the technology for forming the lockstitch type 301, using a hook (shuttle) with a bobbin containing the bottom thread inside, and the technology for forming the double thread chain stitch type 401, using looper carrying the bottom thread, invented in the 19th century, have disadvantages associated with the forming of these stitches that can be described as «eternal», since they cannot be improved, no matter how much these technologies develop in the future.

As you know, most straight stitches are currently made with a lockstitch type 301 and there are relatively few opportunities to use a double thread chain stitch type 401. 

This is mainly due to the fact that existing technologies for forming a double thread chain stitch type 401 with loopers carrying the bottom thread cannot guarantee a tight join between materials and cannot sew qualitatively different materials with different thicknesses, densities and stiffness. 

Thanks to our revolutionary ideal ZARIF 2023 revolutionary ideal ZARIF double thread chain stitch technology with rotary looper, we can now perform most straight stitches with our new double thread chain stitch type 401 instead of the lockstitch type 301.

The «eternal» disadvantages of the existing technologies for forming a lockstitch type 301, which are not present in the ZARIF 2023 sewing technology. 

1. Frequent changer of the bottom thread wound on the bobbin of hook (shuttle), due to the small size of the bobbin.

2. A very large number of types of hooks (shuttles), differing in mechanical design, size, movement and direction of the axis of oscillation or rotation.

3. All types of hooks (shuttles) have a very complex mechanical design and require high precision manufacturing and assembly.

4. Deflection of the needle when the needle moves down while sewing through thick seams may cause the needle to collide with the needle plate and hook (shuttle), resulting in breakage of the needle or deformation of the needle point.

5. To obtain a high-quality seam with a lockstitch of type 301, the threads must be intertwined in the middle of the stitched materials, the threads must tightly join the materials, it is necessary to obtain a smooth seam on light materials and an elastic seam on elastic materials, which requires adjusting the tension of the threads when changing the thickness, stiffness and elasticity of the materials being stitched, while it is impossible to obtain a highly elastic seam.

6. With a small stroke length of the needle bar equal to 32 mm, it is impossible to sew materials up to 8 mm thick.

7. The maximum allowable gap between the hook point and the needle is 0.1 mm, which requires adjusting the hook relative to the needle when switching from needle Nm. 130/21 to needle Nm. 60/8.

8. All existing technologies of forming a lockstitch type 301 cannot guarantee sewing without skipping a stitch and without breaking threads.

9. During sewing, the top thread loses its mechanical strength with increasing sewing speed, due to the large number of repeated movements of the top thread through the eye of the needle, the stitched material and thread guides, since even a standard hook consumes a sufficiently large length of the top thread to form a stitch.

10. All types of thread take-ups unevenly shorten and tighten the loop of the top thread and it is impossible to evenly shorten and tighten the loop of the top thread.

11. All types of hooks (shuttles) require lubrication, and non-lubricated hooks limit the sewing speed.

12. All types of hooks (shuttles) must be cleaned of dirt, and getting thread segments into the hook slip zone can lead to jamming of the hook and sudden braking of the sewing machine.

The «eternal» disadvantages of the existing technologies for forming a double thread chain stitch type 401, which are not present in the ZARIF 2023 sewing technology. 

1. All existing technologies for the formation of a double thread chain stitch type 401 using a looper with an eyelet, where the bottom thread is filled, are not able to tightly join materials, as well as qualitatively sew combinations of various materials, such as textile-leather, textile-plastic, knitwear-leather and knitwear-plastic.

2. For high-quality sewing of various materials, it is necessary to adjust the tension of the threads, i.e. it is impossible to sew various materials qualitatively under normal tension of threads.

3. To form a double thread chain stitch, it is necessary to use a special needle with two long grooves, which is less durable for longitudinal bending than a conventional needle with one long groove.

4. To increase the reliability of stitch formation, it is necessary to use movable and fixed needle guards. 

5. Deflection of the needle when the needle moves downwards, during sewing through thickened seams, can lead to a collision of the needle with the body of the looper and the needle guards, which can lead to needle breakage or deformation of the needle point.

6. With a small stroke length of the needle bar equal to 32 mm, it is impossible to sew materials up to 8 mm thick.

7. The maximum allowable gap between the looper point and the needle is 0.1 mm, which requires adjusting the looper relative to the needle when switching from needle Nm. 130/21 to needle Nm. 60/8.

8. All existing technologies for the formation of a double thread chain stitch type 401 cannot guarantee sewing without skipping a stitch and without breaking threads.

9. Loopers with an eyelet, where the bottom thread is filled, have rather complex mechanisms.

10. All existing technologies for forming a double thread chain stitch of type 401 do not allow reducing the stitch length to 0.5 mm in order to securely tack the end of the chain seam.