JPS5935304B2 - Operating rod with threaded part - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an external operating rod and a fastening member for a wristwatch, and materials used for manufacturing them.

Conventionally, external operating rods and fastening members for wristwatches are made of precipitation-hardening stainless steel for the purpose of rust prevention and high torsional strength.

These members are manufactured by automatic lathes using rod-shaped materials, and the finishing accuracy and processing efficiency are greatly influenced by the quality of the rigidity of the materials.

For this reason, the materials &i, Pb used for manufacturing these members
Precipitation-hardening free-cutting stainless steels whose machinability has been improved by adding appropriate amounts of (lead), Se (selenium), P (phosphorus), S (sulfur), etc. are often used.

However, the addition of the above-mentioned elements induces internal defects (cracks), which are considered to be fatal to the material.

Therefore, precipitation-hardened free-cutting stainless steel bars are subjected to two different destructive internal defect inspection methods: overcurrent flaw detection and ultrasonic flaw detection, and only those that pass are shipped. Generally, about 0.5% to 1.5% of defective materials are detected and discarded.

Describing the typical forms of internal defects and the capabilities of the flaw detector, in FIG. 1, 1 is the outer diameter of the material, and the crack 2 of the internal defect opens at the outer diameter of the material.

The inner end 3 of the crack then reaches close to the center 4 of the material,
The maximum center portion 5 of the crack is about 30μ.

For such internal defects, thorough flaw detection is performed.

However, as shown in Fig. 2, the crack 2a due to the internal defect has closed in the outer diameter part 1 of the material, and the inner end 3a of the crack has stopped at a distance of about 0.2 nm from the center 4 of the material. For products with a maximum crack size 5a of 10 to 20 microns, the limit of detection power for internal defects is sometimes exceeded, and defective products may be shipped without being detected.

As shown in Figure 3, these cracks are cracks 2a that exist continuously along the longitudinal direction of the material over a length of approximately 30,000 to 1,200 degrees and close at the outer diameter of the material.
can hardly be detected even when observed under a microscope.

However, when the part is completed as shown in FIG. 4, the largest crack 5a appears on the surface of the part, and it becomes clear that the part is internally defective.

By the way, when I investigated external operating rods such as watch winding stems, I found that if 12 million pieces are produced per year, it will cost about 3.
There were 0 cases of internally defective products, and each time we spent a lot of time and effort sorting out defective products, finding 0.2% to 1.5% of defective products and discarding them.

When compared to normal crystals, these defective products have a bending strength of 80%.
%, the torsional strength will break at a load of 46%, so improvement is necessary, but the reliability of material manufacturing technology and non-destructive testing is still not perfect, and it is difficult to obtain materials without internal defects. I'm in a situation like this.

In order to eliminate the above-mentioned drawbacks, the present invention allows the opening 2 of the crack and the maximum width 5 of the crack to be brought into close contact with each other as much as possible by twisting the member in advance in accordance with the threading direction of the member. The purpose is to prevent the crack from expanding due to twisting of the material due to the torsional force that is applied during thread cutting, and to prevent a significant decrease in strength.

Hereinafter, the present invention will be explained in detail with reference to FIGS. 5 to 8.

FIG. 5 shows an external operating rod for a wristwatch according to the present invention, which is made of a material with a right-handed twist.

If an internal defect exists in this material, the crack 6 will appear with a clockwise twist angle of θ corresponding to the number of twists.

Next, the threaded portion 7 has an outer diameter of 0.9rIjl and a pitch of 0.
When a 2251 ut right-handed thread is rolled, the crack 6 at the threaded portion 1 has a larger right-hand twist (as shown in 6a in FIG. 6), and the twist angle has also become larger as shown in θ1.

That is, 2 to 7 per 100 ma of operating rod length in advance.
When torsion is applied at a rate of 1.5 times, the maximum crack due to an internal defect (Fig. 1) is compressed to 5a (Fig. 2) or smaller, and due to thread rolling, It has been given a deformation that further promotes close contact.

After all machining, the external operating rod is carefully heat treated and tempered to a hardness of I(v(300S')) 550±3.
0 (Hv is the hardness measured by the Vickers hardness tester) and used for practical use, but there are normal products with no internal defects, products with cracks as shown in Figure 2 that have not been twisted, and genuine products. A comparison of the strengths of internally defective products with twisting according to the invention is as follows.

First, the bending strength was investigated using the method shown in FIG. 1, and the results shown in Table 1 were obtained.

To explain the test model shown in Fig. 1, the external operating rod 8 is fixed with a chuck 9, the span l is set to 5.5 mm, a load W is applied to the arrow part, and a clear deformation occurs. This is a count of the load.

As is clear from Table 1, the products of the present invention exhibit approximately 90% of the bending strength of normal products, but conventional abnormal products with cracks can withstand only 80% of the load of normal products. It shows.

In addition, the test model shown in FIG. 8 was used to investigate the strength of the external operating rod against the torsional force it receives during practical use and the repeated stress equivalent to winding a mainspring for about 10 years.

In FIG. 8, a torsional load is applied to Maryuse 10 clockwise with a torque of 200 ff-am, and then counterclockwise with a torque of 10,100 ft-am.

This is regarded as one cycle, and the load is applied repeatedly until it breaks, and three types are examined: a normal product, a product with cracks as shown in Figure 2 but not twisted, and an internally defective product that is twisted according to the present invention. The results shown in Table 2 were obtained.

As is clear from Table 2, even if the product of the present invention has internal defects, it is twice as durable as the conventional product with internal defects.

And the repeated operation 40 is the target of the strength of the external operation lever.
It was also proven that it could withstand loads of 00 times with ease.

In addition, sample A4 (red stamp) of normal crystal was broken from the V groove part 11 in Figure 8, but there was no abnormality except that the W groove diameter was made at the lower limit of the tolerance, and the other 13 nearby pieces were broken. The crown mounting portion 12 was all bent.

Next, the torsion diagram of the present invention will be explained.

FIG. 9 &L is a graph showing how much twist is applied to the outer diameter of the external operating rod (13 in FIG. 8) and the length of the external operating rod of 10 om.

As shown in many embodiments, when the outer diameter 13 is around 1.
7 times per 4100 fights, 10 when the outer diameter 13 is 3 to 5
By applying twisting around 2 times per zero force, even if internal defects exist, there will be no significant decrease in strength.

In addition, if the number of twists is insufficient, the effect of preventing strength loss will be greatly reduced, and if the number of twists is inadvertently large, the external operating member after heat treatment will be bent, which is harmful in practice. The number of twists must be determined carefully.

As described above, according to the present invention, even if an external operating rod has an internal defect, it is possible to prevent a fatal decrease in strength, and even if the fastening part is made from a material that was not detected by non-destructive testing. The fear of breaking the product during use has been greatly reduced, providing maximum user satisfaction.
Moreover, even when the existence of internal defects is discovered during processing,
This has the effect of ensuring complete quality assurance without having to spend a huge amount of time on sorting work or discarding internally defective products as defective.

[Brief explanation of the drawing]

Figure 1 shows a specimen of precipitation hardening free-cutting stainless steel with internal defects large enough to allow for perfect flaw detection.
Double sectional view. Figure 2 is a 50x cross-sectional view of precipitation-hardening free-cutting stainless steel, which has internal defects so large that complete flaw detection is difficult to perform. Figure 3 is a sketch of the materials shown in Figure 2. Figure 4 & ζ A sketch of the cracked part of the external operating rod made from the material shown in Figure 2. FIG. 5 is a side view of the external operating rod that is twisted to the right according to the embodiment of the present invention. FIG. 6 is a side view of the external operating rod that has been machined in an embodiment of the present invention. FIG. 1 is a model diagram for testing the bending strength of an external operating rod. FIG. 8 is a model diagram of the torsional strength test of the external operating rod. FIG. 9 is a graph showing the outer diameter of the external operating rod and the appropriate number of twists per 100wn length. 1... Outer diameter of the material, 2... Internal defect opening at the outer diameter of the material, 3... Inner end of the crack, 4... Center of the material, 5... Maximum center of the crack (approximately 30μ), 2a... Internal defect closed at the outer diameter of the material, 3a... Inner end of crack, 5a... Maximum center of crack (approximately 10 to 20μ), 6
... Clockwise twisted crack, 7... Right-handed threaded part, θ
...The angle between the right-handed twisting crack and the center line, 6a...
Right-handed crack emphasized by thread rolling, θ1... Angle between the right-handed crack highlighted by thread rolling and the center line, 8... External operating rod, 9... Chuck, l...
Span, W...Load, 9a...Square hole chuck, 1
0... Lew's, 11... Normal crystal sample A4 (
12... Part broken due to torsional stress (crown attachment part); 13... Maximum part of the outer diameter of the external operating rod.

Claims (1)

[Scope of Claims] 1. An operating rod having a threaded portion, characterized in that the operating rod is twisted in the same direction as the thread cutting direction. 2. The torsion of the operating rod is 100. per N
An operating rod having a threaded portion according to claim 1, which is capable of being twisted twice (N=2 to 7).