JPH06330928A - Non-constant pitch screw - Google Patents

Abstract

PURPOSE:To provide unlikelihood of loosening and eliminate necessity for use of any washer or the like by forming threads with ones a little larger than standard and ones a little smaller alternately pitch by pitch, and arranging so that two adjoining threads constitute two in the standard pitch. CONSTITUTION:Two pitches at the tip (on the right) of a bolt 1 are made at the standard pitch, and thereafter it is made with a pitch a little smaller than standard and pitch a little larger alternately pitch by pitch, and therein two adjoining threads constitutes two in the standard pitch. Thereby three types of contacting in standard pitch one another, ordinary, loose, and tight, are generated between the threads of the bolt 1 and nut 2. The tight contacting 5 is produced where the thread width of the bolt is large when nut threads pinching them are distorted so that a restrative force acts. This enlarges the friction force compared with the case with combination of standard bolt and nut, and loosening is precluded without use of any washer etc. To fabricate bolt 1, a computer-controlled lathe is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw used in combination with a male screw and a female screw.

[0002]

2. Description of the Related Art A combination of a bolt (male screw) and a nut (female screw) is generally used for joining two or more objects. Instead of using a nut, the female thread may be cut directly on the object farthest from the head of the bolt.
In order to prevent loosening of these screws, generally, as shown in FIG. 4, flat washers 45, spring washers 46, and the like are fastened with bolts 41 and nuts 42 together with connecting members 43, 44. The washer is clamped and deformed, and the force to return to the original state is constantly working, so that the screw is prevented from loosening. In order to make the loosening prevention stronger, after tightening one nut 52 as shown in FIG. 5,
A double nut method is used in which the nut 52 is fixed with a spanner and another nut 52 '(lock nut) is tightened. In this method, since the nut 52 and the nut 52 'are tightened together via the bolt 51, the threads of the two nuts and the bolt are deformed and fixed with a strong force. Further, in this method, the tightening force between the members 53 and 54 is adjusted, that is, the nut 52 is tightened with an appropriate torque, and then the nut 52 ′ is strongly tightened to the nut 52 to allow rotation between the members. It is possible.

[0003]

In tightening using a combination of a bolt and a nut, a spring washer or the like or an extra nut is used to prevent loosening, which reduces workability, and carelessness causes a washer or the like. If you forget to install it, the bolts and nuts will fall off, which will cause an accident.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a screw capable of securely preventing loosening without using a spring washer or an extra nut. And

[0005]

Therefore, the present invention provides
"The unequal-pitch screw is characterized in that the threads are alternately larger and smaller than the standard pitch for each pitch, and when the two threads are combined, the pitch is two standard pitches. 1) ”is provided.

[0006]

The present invention will be described in detail with reference to FIGS. 1 and 2 which are one embodiment, but the present invention is not limited to this embodiment. In FIG. 1, nut 2 is a standard nut and has standard pitch threads. Bolt 1 is an unequal pitch screw. FIG. 2 shows the bolt 1 of FIG. 1 again in (A), and shows the top and bottom phases of the thread of the bolt 1 in (B). The phases of the mountain peaks are indicated by thin lines and hatches. The hatched area indicates that the top of the mountain is wide. The phase of the valley bottom is indicated by a thick line.

At a phase of 0 or 2π, the pitch is a standard pitch when viewed from a distance between peaks and a distance between valleys. In the phase π, the standard pitch is seen from the distance between the peaks, but the standard pitch is not seen from the distance between the valley bottoms. The first two pitches are standard pitches, and from then on, they are alternately smaller and larger than the standard pitch. In FIG. 2B, the phase of the valley bottom of the standard pitch is shown by a broken line.

Since the bolt 1 has such a shape,
As can be seen in FIG. 1, there are three different degrees of contact between the threads of the bolt 1 and the nut 2. There are three types of contact: standard contact between standard pitches 3, loose contact 4 due to slightly different pitch of bolts, and tight contact 5. Tight contact occurs when the width of the thread of the bolt is large and the thread of the nut that sandwiches the thread is distorted and the restoring force acts.

Since the screw threads are formed in this manner, the bolt 1 enters the nut 2 smoothly for the first three pitches, and then a little tighter. Although the pitch is alternately small and large, it is tight, but as you can see from Fig. 2, when the two are combined, it becomes two standard pitches, so the phase shift alternates between positive and negative. It becomes a small value, and there is no big reason as a whole.

Due to the tight contact 5, the frictional force is greater than in the case of the standard bolt and nut combination and loosening is prevented without the use of washers or the like.

[0011]

EXAMPLE A first example is shown in FIGS. The unequal pitch screw is applied to the bolt 1, and the tip (right side)
The two pitches are the standard pitch, and from then on, the pitches are alternately smaller and larger than the standard by one pitch each, and two adjacent pitches form two standard pitches. There are three different degrees of contact with the standard nut 2.

A computer-controlled lathe is used to manufacture the bolt 1. Since the slope of the hillside and the depth of the valley are constant, the shape of the bolt 1 is adjusted by aligning the front and rear positions of the bite with the tip angle that matches the slope of the hillside to the depth of the valley and changing the feed speed to the left. Is made. If you try to make this shape at once, and the load on the cutting tool is too large, first make the valley shallow and cut only the feed rate change to the design value. From the next time onward, adjust the angular position at the beginning of cutting to the first one, make the valley a little deeper, and cut at the same feed rate change as at the beginning. Thus, finally, the desired shape is obtained. This series of operations is automatically performed by programming the computer.

FIG. 3 shows a second embodiment. The unequal pitch screw is applied to the nut 32. One pitch of the nut inlet (left side) is a standard pitch, the next one pitch is a little smaller than the standard, and the next one pitch is a little larger than the standard. After that, similarly, a pitch slightly smaller than the standard and a pitch slightly larger than the standard continue alternately for each pitch. The standard pitch of the nut inlet makes it easy to insert standard bolts. The nut 32 is also manufactured in the same manner as the bolt 1 of the first embodiment.

In the embodiment, the tip 2 pitch is the standard pitch, but it may be any pitch.
In addition, the following one pitch is a pitch slightly smaller than the standard, and the next one pitch is a pitch slightly larger than the standard.
The pitch does not have to be 1 pitch, but the phase shift from the standard screw thread becomes too large, and an excessive force is required when inserting the bolt into the nut, which in turn reduces workability. Therefore, it is preferable that the number of rotations is about one.

[0015]

EFFECTS OF THE INVENTION By using the unequal pitch screw according to the present invention, loosening is less likely to occur in the combination of the bolt and the nut, so that a spring washer and an extra nut are not required and the workability of screw tightening is improved.

[Brief description of drawings]

FIG. 1 is an example (first embodiment) in which the unequal pitch screw according to the present invention is applied to a bolt (outline view) and combined with a standard nut (cross-sectional view).

FIG. 2 is a development view showing the bolt (A) shown in FIG. 1 and a phase of a thread and a valley of the bolt.

FIG. 3 is an example (second embodiment) in which the unequal pitch screw according to the present invention is applied to a nut.

FIG. 4 shows the conventional prevention of loosening by a flat washer and a spring washer.

FIG. 5 shows a conventional double nut system using a lock nut for preventing loosening.

[Explanation of symbols]

 1 ... Bolt using unequal pitch screw 2 ... Standard nut 3 ... Normal contact 4 ... Loose contact 5 ... Tight contact 6, 26, 36 ... Standard thread 7, 27, 37 ... Small threads 8, 28, 38 ... Large threads 32 ... Nuts using unequal pitch screws 41, 51 ... Bolts 42, 52, 52 '... Nuts 43, 44, 53, 54 ... Members to be joined 45, 55 ... Flat washer 46, 56 ... Spring washer

Claims (1)

[Claims] 1. The threads are alternately pitch-wise and are slightly larger and slightly smaller than the standard pitch,
An unequal pitch screw that is characterized by two standard pitches when combined.