JPS6310890Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a screw tap for threading the female thread of a nut, which has excellent locking performance.

As shown in FIG. 6, in the standard nut 1, the crest 3 and the root 4 of the thread 2 are formed parallel to the axis O.

Therefore, even if we compare the tightening process in which the nut 1 is moved in the direction of the arrow S relative to the bolt 5 as shown in FIG. 7, and the tightening process in which the nut 1 is moved in the direction of the arrow T as shown in FIG. The gap l between the root 4 of the thread 6 of the bolt 5 and the crest 7 of the thread 6 of the bolt 5 is equal, and the leading flanks 8, 9 and the trailing flanks 10, 1 are equal.
1. Since there is no difference in the mutual contact state, the tightening torque and the return torque have the same value. On the other hand, various types of locking nuts have been known in which the internal thread shape has been devised to suppress loosening after tightening, but most of these nuts have a large return torque, but also have a large tightening torque, making it difficult to tighten them. It requires strong force to operate.

The present invention provides a screw tap that can form an ideal internal thread of a locking nut, which has the revolutionary performance of having a large return torque and a relatively small tightening torque.

Embodiments of the present invention will be described below based on the drawings.

In Fig. 1, 25 is the screw tap body;
6 is a shank portion. The screw tap body 25 is
It consists of a threaded blade part 28 divided into four equal parts in the radial direction by four grooves 27 along the axial direction. It consists of a threaded portion 28b extending to the rear end.

As shown in FIG. 2a, the threaded portion 28b is centered on the virtual reference line Q, which is inclined at an angle θ of 1° to 1.5° with respect to the axis O, and extends parallel to the crest of the thread 29. 30 and the root portion 31 are formed at equal pitches, thereby making the crest portion 3 of each thread 29
The distances l ₁ , l ₂ between the shaft center A and the root portion 31 are gradually reduced in diameter as they reach the screwing direction side as shown by the arrow B, and both flanks of each thread 29 are is formed so as to be inclined in the screwing direction B by an angle corresponding to the inclination angle of the virtual reference line Q.

The threaded portion 28'b shown in FIG. 2b has almost the same structure as the embodiment described above, except that in the embodiment described above, the crest 30 of the thread 29 is formed into a curved (R) shape. , mountaintop part 3 of this example
In the case of 0', it is formed into a tapered surface in which the height of the crest becomes lower in the screwing direction B.

However, by using the screw tap having the above-mentioned structure to perform thread cutting in the direction of arrow B on a nut material that has previously been prepared with a pilot hole, a third thread can be cut in the direction of arrow B.
Locking nut 12 shown in Figure a or Figure 3b
a and 12b are manufactured.

That is, FIG. 3a shows the threaded portion 28 shown in FIG. 2a.
This figure shows a vertical cross section of a nut 12a manufactured by a screw tap having a diameter of 12. Thread 1 parallel to this
3, the virtual peak portion 14 is located inside the prepared hole diameter P parallel to the axis O, and therefore the prepared hole diameter P is the inner diameter of the female thread. A flat solid mountain top 16
, and this physical valley bottom 15 and physical mountain top 16
By forming the valley bottoms 1 at equal pitches,
5 is an angle that gradually becomes deeper as it goes in the screwing direction (downward in the figure), and that the leading side flank 17 and the trailing side flank 18 from the valley bottom 15 to the real mountain top 16 correspond to the inclination angle of the reference line Q. It is formed to be inclined in the screwing direction.

Figure 3b shows the threaded section 28' shown in Figure 2b.
Nut 1 made with a screw tap having
2b shows a vertical cross section of the nut 12b. In the nut 12a, the root portion 15 is formed into a curved surface (R) shape, but in the case of this nut 12b, the return direction (upward direction) is shallower, and the screwing direction is shallower. It is formed in a tapered valley bottom portion 15' so that it becomes deeper (in the downward direction).

Figures 4a and 4b show nuts 12a and 12 of the above structure.
b shows the state in the middle of manual tightening without applying torque to the bolts 19, and these nuts 12a or 1
Since the thread 13 of 2b is formed with a slight inclination in the screwing direction, that is, downward in the figure, the advancing side flank 17 of the nut thread 13 and the bolt thread 20
Approximately equal gaps are formed between the trailing flank 22 of the former, and the trailing flank 18 of the former and the leading flank 21 of the latter (although, of course, some of their circumferential surfaces are in contact with each other). ), and since the contact area between the two is small, it can be screwed in with relatively light force. In this regard, in conventional nuts, as shown in FIG. 8, the entire trailing side flank 10 of the nut thread 2 is screwed into contact with the leading side flank 9 of the bolt thread 6, and the mutual contact area between the two is large. Therefore, the sliding resistance during tightening increases accordingly.

Figures 5a and 5b show the final tightening operation of the bolt 19 using a work tool such as a spanner or wrench under a certain tightening torque after the nuts 12a and 12b were tightened by hand as described above. Indicates the operating state, nut 12a or 1
Since the thread ridge bottoms 15, 15' of the bolt 19 are formed to be shallower toward the upper end, the thread crest 23 of the bolt 19 is strongest at the thread ridge bottom 15a or 15'a at the uppermost end of the nut 12a or 12b. It's true. In this case, since the thread 20 of the bolt 19 is not pressed against the nut 12a during manual tightening described above, the thread 20 does not deform elastically and does not come into contact with the thread root 15 of the nut 12a. Therefore, when the nut 12a is screwed into the bolt 19 with a tightening torque exceeding a certain level, since the thread 13 of the nut is slightly inclined in the screwing direction, the advancing side flank 17 will follow the thread 20 of the bolt 19. The side flank 22 is strongly pressed, which causes the thread 20 of the bolt 19 to be elastically deformed slightly in the diametrical direction, whereby the thread crest 23 of the bolt 19 is attached to the root 15a of the uppermost end of the nut 12a. The nut 12a makes strong contact as shown by arrow m and overcomes this strong contact resistance.
By strongly tightening the nut 12a, the nut 12a receives the reaction force of the tightened material W, and the thread 13 of the nut 12a receives the elastic reaction force of the thread 20 of the bolt 19, thereby providing a strong locking mechanism. This will result in the effect of

In particular, as shown in FIG. 5b, the thread valley bottom 1
If the nut 12b has a tapered surface such that the return direction is shallow and the screwing direction is deep, the nut 12b is rotated in the opposite direction to tighten the bolt 1.
9, the crest 23 of the bolt 19 slides into contact with the higher side of the tapered surface of the root 15' of the nut 12b, that is, the shallower side of the root 15'. , Natsuto 1
2b and the bolt 19, and the opposing flanks 17, 22 of both threads 13, 20 are strongly pressed against each other in the direction of the arrow m. Therefore, Natsu 12
The returning action of b requires a significantly larger torque than the tightening action, which causes the nut 12 to tighten.
b provides stronger resistance to loosening after tightening.

According to the invention as described above, the leading flank and the trailing flank of the thread of the nut manufactured by the screw tap are formed to be inclined in the screwing direction, so that when the nut is screwed onto the bolt and tightened. Since the threads of the nut and bolt only partially contact each other, and the contact resistance is small, the nut can be screwed in with relatively light force. In addition, during final tightening, in which the nut is screwed in with a tightening torque above a certain level and pressed into contact with the material to be tightened, the above-mentioned two threads, which were only partially in contact with each other, are brought into strong and full pressure contact with each other, and in addition to this, Since the root of the nut is formed to be gradually deeper in the screwing direction due to the screw tap of the present invention, the top of the bolt thread is brought into strong contact with the root of the uppermost end of the nut. Due to this action, the two ridges stick to each other, creating a strong locking effect.

[Brief explanation of the drawing]

Figure 1 is a front view of an embodiment of the present invention, Figure 2 a
is a longitudinal sectional front view of the same main part, Fig. 2b is a longitudinal sectional front view of the main part of another embodiment, and Fig. 3a is manufactured according to the embodiment shown in Fig. 2a of the present invention. A longitudinal sectional front view of the nut, FIG. 3b, is a longitudinal sectional front view of the nut manufactured according to the embodiment shown in FIG. 2b, FIG. 4a.
and FIG. 4b are longitudinal sectional front views showing the operating state of the nut shown in FIGS. 3a and 3b, respectively. FIGS. 8 are longitudinal sectional front views showing a conventional nut and its operating state. O... Axis line, Q... Virtual reference line, 29... Screw thread, 30, 30'... Mountain top, 31... Valley bottom,
l ₁ , l ₂ ... Distance between the top and bottom of the thread and the shaft center, A ... Shaft center, B ... Threading direction line.

Claims (1)

[Claims for Utility Model Registration] 1. The tops and bottoms of the threads are formed at equal pitches parallel to a virtual reference line that is slightly inclined with respect to the axis. The distance between the crest and the bottom of the shaft and the center of the shaft is gradually reduced in diameter as it approaches the screwing direction, and both flanks of each thread are formed at an angle corresponding to the inclination angle of the virtual reference line. A screw tap formed at an angle in the screwing direction. 2. The screw tap according to claim 1, wherein the crest of the thread is formed into a tapered surface whose crest height decreases in the screwing direction.