JPH0761390B2 - Manufacturing method of inner pot in sewing machine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an inner hook in a half-turn hook of a sewing machine.

Prior Art The manufacture of an inner kettle has conventionally required a number of steps, which made the kettle extremely expensive. Various attempts have been made so far to reduce the number of steps and reduce the manufacturing cost of the kettle, and there was the idea of integrally molding the kettle with resin, but there were difficulties in strength and wear resistance, and it could not be put to practical use. It was Therefore, the present applicant previously mentioned in Japanese Patent Application No. 59-117691 that a race part having one end of a sword is formed separately from metal, set in a mold, and a resin is injected to integrally mold it. I proposed about a kettle. According to this, since the parts other than the core part are formed of resin, a considerable effect can be obtained in terms of the manufacturing cost of the kettle, such as a reduction in machining and a large number of steps, but on the other hand, during molding in the mold. Due to the difference in cooling rate between the metal core portion and the side resin portion, distortion occurs, the dimensional accuracy decreases, and a problem arises that the shape becomes defective. Especially, the race part requires the most precision, and distortion occurs here, and if the required precision is not obtained, it will be fatal as a middle pot. In addition, if the core part is fitted tightly for accurate positioning even when mounting the core part in the mold, it becomes difficult to separate the molds, and conversely, some play can be provided to facilitate mold separation. However, there is a problem that the positional deviation easily occurs, the positioning is not accurately performed, and the precision of the molded product is further deteriorated.

Problems to be Solved by the Invention The present invention is intended to provide a method for manufacturing an inner pot that solves the above problems.

Means for solving the problem The inner pot is divided into three parts, a core part with a lace part formed at one end as a sword tip and side parts on both sides of the core part, and the core part is made of metal and the side part is injected. Formed separately by molding. Next, each part is assembled and the inner pot is assembled and welded to be integrated.

Here, the metal core portion is formed, for example, by punching, pressing (cold forging), polishing, or the like, or by sintering metal powder.

The welding after assembly is performed, for example, by heating the joint surfaces of both side portions with a high frequency, or by heating the joint surface with the core portion together with the joint surfaces. In the case of the former, since the core portion and the side portion are not integrally connected, locking means for preventing the core portion from falling off, for example, a protrusion or a recess in the core portion,
It is necessary to provide the side portion with recesses or protrusions that are fitted and locked in the protrusions or recesses.

The center post is integrally formed with one of the side parts at the time of molding, or is formed separately as a metal, and is set in the mold at the time of molding of the side part and insert-molded, or a separate step is performed on the side part. Be attached. Incidentally. When insert molding occurs, the same problem as described above occurs, but the center post does not cause distortion in its shape, and since it does not require strict accuracy as in the race portion, it does not cause a problem.

Example As shown in FIG. 1, the inner pot is divided into three parts, a core part 2 having a lace part formed at one end with a sword tip 1 and side parts 3.4 on both sides thereof, and the core part 2 is made of metal powder. The side portions are separately formed by injection molding by sintering. As shown in the figure, the core portion 2 is provided with a plurality of protrusions 5 having a screw head-shaped cross section on the inner peripheral side thereof, and on each side portion, a recess 6 into which the protrusion 5 is fitted is formed. .

Next, the core portion 2 is sandwiched and the side portions 3.4 are fitted from both sides so that the recesses 6 engage the protrusions 5.
Then, in the assembled inner pot, the joint surfaces 7 of both side portions are heated by high frequency and welded.

EFFECTS OF THE INVENTION According to the present invention, since both side portions are formed of resin, machining of the portions is reduced, the number of steps is significantly reduced, and vibration and noise are absorbed and relaxed in the resin portion and reduced. In addition to the effect of reducing the inertial force by making the entire kettle lighter, the cooling speed of the core part and the resin part in the mold during molding compared to injection molding with the core part set in the mold. There is no need to consider the distortion caused by the difference between
The dimensional accuracy is not impaired, and there is no need to consider the positioning of the core in the mold and the separation of the mold, so that the accuracy of the mold is relaxed and the charging time is shortened.

[Brief description of drawings]

FIG. 1 is a perspective view of the inner pot before assembly, and FIG. 2 is a sectional view. 2 ... Core part 3.4 ... Side part 5 ... Protrusion 6 ... Recess 7 ... Joining surface

Claims (1)

[Claims] 1. A core part provided with a lace part, one end of which is formed as a sword tip, and three parts of side parts on both sides of the core part. The core part is made of metal and the side part is made of resin. A method for manufacturing an inner hook in a sewing machine, which is formed separately, and then the side portions are assembled from both sides of the core portion with the core portion sandwiched between them and then welded and integrated.