JPS61286605A - Equalizing screw - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a screw, and particularly to a pressure equalizing screw that equalizes the load screw blood pressure during tightening.

[Prior art and its problems]

The flank angle of the threads of bolts, nuts, etc. for the purpose of fastening is set at 30 degrees for both male and female threads in the case of standard metric threads, and it is conventional wisdom that both should be geometrically the same angle. Met. However, when the threads are loaded due to tightening, the threads of the male thread are more likely to be elastically deformed than the threads of the female thread due to the difference in three-dimensional shape, so the surface pressure generated between the loaded thread surfaces is not equal. , the load is always biased towards the root of the male thread. As a result, fitting is lost, the torque radius becomes smaller, and there is a tendency for the material to loosen easily.

Figure 2 shows the shape of the thread of a standard metric thread. ), the flank angle for both male thread 1 and female thread 2 is 3011.
1, and under no load, the male thread 1 and the female thread 2 are in contact with each other at their thread surfaces. When a load is applied to the threads by tightening, each thread deforms elastically. 3 and 4 show transverse planes of the male thread 1 and the female thread 2. In each figure ', the circumferential length of the roots of the threads sandwiched by a certain angle θ is AB in the case of the male thread 1 and CD in the case of the female thread 2, and naturally the relationship AB<CD holds true.

Therefore, when the same load is applied to the threads separately, the elastic deformation of the threads of the male thread 1 is greater than that of the threads of the female thread 2, so the fall of the threads due to the load is greater for the male thread 1. When the thread surfaces of the male thread 1 and the female thread 2 are elastically deformed while being in contact with each other, the front center of action moves toward the smaller radius side and tries to balance. Therefore, the distribution of contact surface pressure between the threads is not uniform, and the pressure is biased towards the root 1a of the male thread 1. This condition impairs the fitting of the thread on the contact surface and reduces the torque radius when the nut loosens and rotates, resulting in a tendency for the nut to loosen easily.

[Purpose of the invention]

The present invention has focused on the above-mentioned drawbacks of the prior art, and has been made with the aim of improving this, and the flank angle of one thread is adjusted relative to the other so that the crest corner of the male thread contacts when there is no load. By making slight changes, it is possible to equalize the surface pressure under load and eliminate the above-mentioned problems.

[Summary of the invention]

In order to achieve the above object, the present invention sets the flank angles of the loaded thread surfaces of a male thread and a female thread that fit together to be approximately 1'20' relative to the other so that the flank angles of the loaded thread surfaces of the male thread and the female thread that are fitted into each other are in contact with each other at the crest corner of the male thread when no load is applied. It is characterized by changing the range of ~3°30'.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on one embodiment shown in FIG. 1, using the same reference numerals for parts common to those in FIG.

As shown in FIG. 2, the flank angle of the female thread 2 on the loaded thread surface 2a side is set to a value (+α) slightly larger than 30 degrees. As a result, the distribution of the contact pressure between the threaded surfaces is made uniform, resulting in good fitting, and the effect of preventing the torque radius from decreasing and loosening.

Regarding the value of α, according to the results of a loosening test when a hexagonal nut with a metric coarse thread with a nominal diameter of 10 shoes is tightened with 20ON9f-cj+, it is about 20 minutes for one turn to 30 minutes for three degrees, and is preferably 2°30' to 3"O'.

The table below shows the test results when the present invention was applied to the female thread of a nut.

In the table above, ``Nut A'' has α of 1°20', ``Nut B'' has α of 3°30', and r-Nut C'' has α of 5'45.
'.

Nuts A and B both leave considerable residual torque even when the "standard nut" is completely loosened, while nut C has the opposite result. This is thought to be due to the fact that α was increased to 5°45', which did not allow a good fit with the bolt. Therefore, the value of α that achieves the object of the present invention is preferably within the range of 1°20' to 3°30'.

In FIG. 2 used for the above description of the present invention, 1-α is given to the female thread 2 side, but this may be given to the load thread surface side 1b of the male thread 1 as -α.

In addition, if it is difficult to determine the load thread during use, +α (when applied to a female thread) or -α (when applied to a male thread) may be added to both thread surfaces.

〔Effect of the invention〕

As explained above, the present invention adjusts the flank angle between the load thread surfaces of the male thread and the female thread that fit into each other so that one side is approximately 1.0 angle with respect to the other so that the flank angles of the load thread surfaces of the male thread and the female thread that fit into each other are brought into contact at the crest corner of the male thread when no load is applied.
By changing the range between °20' and 3°30', it is possible to equalize the surface pressure on the loaded screw surface during load during tightening, and thereby increase the torque radius. It is possible to use a screw that does not easily loosen.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a thread showing an embodiment of a pressure equalizing screw according to the present invention, Fig. 2 is a sectional view showing the shape of a thread of a standard metric thread, and Figs. 3 and 4 are a male thread and a female thread. FIG. 3 is a cross-sectional view for explaining the difference in elastic deformation of the screw thread. 1... Male thread, 1a... Valley bottom, 2... Female thread, 1
b. 2a... Load thread surface. Applicant's agent Inomata Qing Party 1 Figure 2 Procedural amendment 1985 Patent application No. 129660 October 2 Relationship to the name of the invention case Patent applicant Tokyo Chiyoda Shobakutsu 5 H T) 几, 21 disaster Fissure “2°00”
’” and corrected. (3) Same as above, No. 5 Manazuru front side column (NO, II> Correct rXJ in the bottom row to rYJ.

Claims (1)

[Claims] The flank angle between the loaded thread surfaces of the male and female threads that fit into each other was changed by approximately 1°20' to 3°30' relative to the other so that they would contact each other at the crest corner of the male thread when no load was applied. Features a pressure equalizing screw.