JPH036293Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to hooks such as a horizontal full-rotation hook and a vertical full-rotation hook for sewing machines.

BACKGROUND ART In general, when sewing with a sewing machine, a seam is formed by rotating an outer hook around an inner hook that is restrained to the sewing machine body. At this time, the raceway of the outer hook and the raceway of the inner hook are sliding in contact with each other, and this frictional resistance causes the hook to generate heat.If the hook is operated continuously for a long period of time, even on high-speed or low-speed sewing machines, the hook will may get burned. For this reason, there is a problem in that frictional resistance increases, leading to thread breakage and poor thread tightening, and abnormal friction and noise in the sliding parts. Furthermore, when sewing with a strong synthetic fiber thread, there is a problem in that the part of the hook that the thread comes into contact with becomes abnormally abraded, leading to thread breakage and poor thread tightening.

In order to solve this problem, prior art has applied hard chrome plating or Teflon coating to the outermost surfaces of the outer hook and inner hook. It is desired to reduce the amount of oil supplied as much as possible, and such movements cannot be adequately accommodated. There are manufacturing disadvantages such as uneven thickness of the plating or coating and unstable adhesion.

Problems to be solved by the invention In summary, conventional hooks have poor abrasion resistance and impact resistance, and cannot provide good sewing performance.

The purpose of the present invention is to provide a sewing machine hook that has a high degree of abrasion resistance and impact resistance, and as a result, improves sewing performance.

Means for Solving the Problems The present invention is a sewing machine hook characterized by a combination of a carburized, quenched and tempered outer hook, a nitrocarburizing treatment, and an inner hook plated with hard chrome.

Effect According to the present invention, abnormal friction can be reduced as much as possible by creating a combination structure in which the outer hook has been carburized, quenched and tempered, is subjected to nitrocarburizing treatment, and the inner hook is plated with hard chrome. It is possible to eliminate this problem and improve sewing performance.

Embodiment FIG. 1 is a plan view of a horizontal full-rotation hook according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the vicinity of the track 7 of the inner hook 3. A shaft 2 is formed in the outer hook 1 and is driven to rotate around an axis extending vertically. An inner hook 3 is attached to the outer hook 1 and fixed by an inner hook retainer 4. The track 7 of the inner hook 3 fits into the track groove 8 of the outer hook 1 with an appropriate spacing, allowing the outer hook 1 to be rotated. The outer hook 1 is formed with a tip 5, and the inner hook 3 is formed with a rotation stopper projection 6.

A method of manufacturing the outer hook 1 will be described with reference to FIGS. 1 and 2. The outer hook 1 is formed by precision casting or cutting using case hardened steel such as carbon case hardened steel or chromium molybdenum case hardened steel. This outer hook 1 is separately carburized and quenched and tempered to obtain surface hardness.

In the present invention, after such carburizing and quenching and tempering treatments are performed, soft nitriding treatment is further performed.
The aim is to obtain higher levels of abrasion resistance and impact resistance, as well as to improve sewing performance. The soft nitriding process heats and hardens the surface layer of the outer hook 1 that has been carburized in a high nitrogen state. Although the hardness decreases due to the influence of the above, a thin and extremely hard nitrided layer 9 is formed on the outermost surface of the carburized hardened layer 12. This nitrided layer 9 has superior wear resistance compared to the carburized hardened layer 12 of the outer hook 1, and thereby also reduces sliding resistance. In particular, outer hook 1
It is effective in areas where the track groove 8 of the inner hook 3 slides into contact with the track 7 of the inner hook 3, and where the sewing thread constantly comes into contact during sewing. 3. Prevents heat generation and burn-in. A hard chrome plating layer 11 is formed on at least the track 7 of the inner hook 3.

The invention can not only be implemented in connection with a horizontal full-rotation hook, but also in connection with a vertical full-rotation hook.

Effects As described above, according to the present invention, the outer case is carburized, quenched and tempered, then nitrocarburized, and the inner case is plated with hard chrome, resulting in a combination structure that has excellent wear resistance and impact resistance. As a result, it is possible to prevent the sliding parts of the outer hook and inner hook from seizing, and to prevent abnormal wear and tear of the outer hook and inner hook due to contact with the sturdy sewing thread. This increases the durability of the hook of the sewing machine, prevents sewing defects such as thread breakage and poor thread tightening, and improves sewing performance.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a state in which the track 7 of the inner hook 3 is fitted into the track groove 8 of the outer hook 1. 1...Outer hook, 2...Shaft of outer hook, 3...Inner hook, 4...Inner hook holding down, 5...Tip of outer hook, 6
. . . Inner rotary rotary locking protrusion, 7 . . . Raceway, 8 . . . Raceway groove, 9 .

Claims (1)

[Scope of utility model registration request] A sewing machine hook characterized by a combination of an outer hook that has been carburized, quenched and tempered, an outer hook that has been nitrocarburized, and an inner hook that is hard chrome plated.