JPS6344962B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention has a non-circular cross section, which allows screwing into a pre-threaded hole pre-prepared in a workpiece and completing tightening while forming a female thread through plastic working. , relates to the shape of the threaded portion of tightening screws, mainly tatsupin screws.

According to the terminology for screws in the Japanese Industrial Standards, ``a screw thread is a protrusion with a uniform cross section formed in a coil shape on the surface of a cylinder or cone,'' and ``a screw refers to the entire cylinder or cone with threads.'' It says "I say." From this terminology, this invention does not require that the cross section of the protrusion is necessarily uniform.
A thread can be referred to as a thread-like protrusion, and the overall shape of this invention, which has such a thread-like protrusion and is further given a twist to the entire thread material, is more appropriately called a thread-like body. It seems so. Since the other terms do not seem to be particularly inconvenient for explanation, we will apply the screw terms as they are.

Normally, this type of tatsupin screw requires a small screw-in torque and a good locking effect after tightening, but if you place emphasis on reducing the screw-in torque, Normally, it is difficult to expect the effect of this, and placing emphasis on preventing loosening inevitably results in an increase in screwing torque. In other words, items with a large screw-in torque also have a large return torque, and almost all items whose screw-in torque is reduced in response to demands for improved workability also have a small return torque and tend to loosen. In order to satisfy both of these two contradictory requirements, various improvements have been made in the past, but in the end, it all came down to finding the appropriate point between the two in response to the purpose of use. It was difficult to find something that satisfied them at the same time.

An object of the present invention is to obtain a threaded body with a novel shape that can satisfy both of the two contradictory requirements as fully as possible. Another purpose is to obtain a threaded body with a shape that provides good bite at the initial stage of screwing and allows for good workability even in small pilot holes. The object of the present invention is to obtain a new shape of a screw-like body in which the force gradually increases. Another object of the present invention is to obtain a threaded body having a shape that can be easily mass-produced by rolling.

The structure of the present invention made to achieve these objects will be explained with reference to the drawings. FIG. 1 is an embodiment showing the general appearance shape of a threaded body according to the present invention, and the overall appearance is almost the same as that of a conventional tut pin screw, except for the threaded portion. There is. That is, the head 1 has a known shape, and connected thereto is a threaded part 2. This threaded portion 2 is given a gentle coil-like twist over its entire length, and the cross-section perpendicular to the axis of the threaded portion 2 has various shapes as shown in FIGS. 2, 3, and 4. It has a shape selected from non-circular shapes such as . The threaded portion 2 in FIG. 1 is shown to have a left-handed coil-like twist, and is loosely twisted by approximately one full turn over its entire length. In other words, although the conventionally conceived threaded rod is very loosely twisted, it is further twisted into a coil shape, creating a shape that can be called a double coil. Therefore, when looking at the total length of the threaded portion 2, it can be seen that the outer diameter WD of the coil is represented by the maximum width of the twist in the twisted helical winding X. This WD corresponds to the outer diameter of a coil spring and corresponds to the outer diameter or nominal diameter of a general screw, and is distinguished from the outer diameter in a cross section perpendicular to the axis of the material.

Regarding the threaded body of the present invention, for convenience of explanation,
Hereinafter, unless otherwise specified, the three diameters of the thread, the outer diameter, the effective diameter, and the root diameter, will be simply referred to as the outer diameter.

Reference numeral 5 denotes a tapered guide portion provided at the tip of the threaded portion 2. The shape of the cross section perpendicular to the axis of the material of the threaded portion 2 is approximately circular in the one shown in Fig. 2, almost oval in the one shown in Fig. 3, and slightly oval with rounded corners in the one shown in Fig. 4. It bulges into an almost triangular shape. The shapes of the cross-sections perpendicular to the axis of the materials of these threaded portions 2 are straight lines 2A, 2B, 3A, 3B and 4A, 4C, 4D passing through the centers O ₂ , O ₃ , O _4
2P , _3P , _3Q and
The number of 4P, 4Q, and 4R is 1, 2, and 3, respectively.
I can see that they have become individuals. In the case of FIG. 2, in a circle, the maximum part is the same and indeterminate everywhere on the circumference, but it is assumed to be one in the sense of extracting a specific one from it. In the case of this invention, the term "approximately circular" is used on the premise that the radii (O ₂ -2P) and (O ₂ -2Q) are not equal. Non-circular shapes are not limited to geometrically regular shapes like this, but can be any other shape if necessary, but are generally made using machining techniques. Considering the above difficulty, a geometrically regular shape is more advantageous. Ultimately, these non-circular shapes should be determined in accordance with the usage conditions, taking into account the number of the maximum parts, the reduction of screw-in torque during use, and the effect of preventing loosening after tightening.

A continuous thread-like protrusion 3 is carved over the entire length of the threaded portion 2 on the outer circumferential surface of the above-described threaded material having a non-circular cross section perpendicular to the axis. The thread-like protrusion 3 does not need to have a uniform cross section everywhere. Non-circular maximum part 2P, 3P, 3Q, 4P,
It is only necessary to match the outline shape of the thread groove of the female thread to be machined or tightened around 4Q and 4R, and in other parts, the angle of the thread should be adjusted with the upper limit of the outline of the perfect thread shape. It doesn't matter if the heights are different. It is common to transform the threads so that the angle is obtuse and the height of the threads is low. Such a shape is shown in Prior Patent No. 771130 (see Japanese Patent Publication No. 45-30853), "Non-circular screw".

Non-circular maximum part 2P, 3P, 3Q, 4P, 4
Of the one or more helical windings formed by sequentially connecting the highest points of the thread-like protrusions 3 in Q and 4R, that is, the peaks 4, only the helical winding X formed by 2P, 3P, and 4P is the 5th one. O ₁ −O ₁ as shown in the figure
An imaginary cylinder centered at (the outer diameter of the coil W.
The non-circular centers O ₂ , O ₃ , O ₄ and the center O ₁ −O ₁ of the virtual cylinder are eccentrically arranged to maintain a required distance so that they contact the inner surface of a cylinder (with a diameter equal to D). I'll keep it. That is, the non-circular centers O ₂ , O ₃ ,
The structure is such that O ₄ does not coincide with the center O ₁ of the virtual cylinder.

FIG. 5 schematically shows the relationship between the helical winding X and the non-circular cross section perpendicular to the axis of the material.
In FIG. 5, one helical winding X in contact with the inner surface of the virtual cylinder 6 whose center axis is O ₁ -O _{1 has a diameter of O 1 −O 1} and rotates from the lower surface 7 of the cylinder 6 in a slightly counterclockwise direction about 1 turn to reach the upper surface 8. However, the maximum part 2P of the almost circular axis-perpendicular cross section centered on O ₂ is a circle at the lower surface 7.
While contacting O ₁ and maintaining this state, it gradually rotates counterclockwise along the helical winding X and rises,
It reaches the upper surface 8.

The screw-shaped body according to the present invention is constructed as described above, so when it is inserted into a pre-screw hole previously provided in a workpiece and rotated while pressing the head 1, Following guide section 5, first,
The tip of the non-circular screw material comes into contact with the inner wall of the screw hole, and the action of forming a female screw thread begins. The initial working outer diameter of the threaded part 2 that acts at this time is equal to the diameter of the circle including the two points 2P and 2Q in the one in Fig. 2, and 3 in the one in Fig. 3.
It is equal to the diameter of the circle containing the two points P and 3Q, and in the case of FIG. 4, it is equal to the diameter of the circle containing the three points 4P, 4Q, and 4R, which are all the diameters of the circumscribed circles of the non-circular materials.

As the threaded part 2 is being screwed in, the head 1
When the screws are all screwed in to the bottom of the
The working outer diameter is the maximum width of the twist in the helical winding X and is the outer diameter of the coil WD, which is the final working outer diameter. At this time,
This threaded body contacts the inner wall of the screw hole with the helical winding X, and the threaded portion 2 is screwed into the screw hole over its entire length.

In this way, the contact state of the threaded body with the inner wall of the pilot hole gradually changes as the screwing action progresses, and the working outer diameter starts from the minimum working outer diameter of the thread material itself, and finally changes. The outer diameter of the coil reaches WD.

The center of the screwing action of this screw-shaped body is
At the beginning of screwing, the center of the non-circular material O ₂ ,
O ₃ and O ₄ , and as the screwing progresses, the center moves and finally reaches the center O ₁ of the virtual cylinder 6. At intermediate positions of screwing, the center of screwing action will gradually move between the lengths of each turn of the coil, which is determined by the lead angle of the helical winding. . Therefore, the lead angle of the helical winding X, the length of one turn of the coil, the number of turns of the coil in the entire length of the threaded portion 2, etc. must be designed in accordance with the actual purpose of use.

In the embodiment shown in FIG.
is wrapped around the entire length of the threaded portion 2 for about one full turn, and the final working outer diameter is the same as the diameter of the virtual cylinder 6, and the center of the screwing action at that time is naturally the center _O1 of the virtual cylinder 6. The movement of the center during screwing work naturally manifests itself as a change in the working outer diameter. That is, as will be repeated, in the case of Fig. 2, the initial working outer diameter is the line segment 2P-2.
It has a length of Q and contacts the side wall of the screw hole at two points, 2P and 2Q. As the screwing progresses,
Point 2Q gradually moves away from the side wall in the pilot hole, and the working outer diameter finally reaches the outer diameter WD of the coil at the end of one rotation of the coil. In the case shown in FIG. 3, the initial working outer diameter has a length of line segment 3P-3Q, and contacts the side wall of the screw hole at two points 3P and 3Q. As screwing progresses, point 3Q gradually moves away from the side wall in the prepared hole, and the working outer diameter becomes
Eventually, the outer diameter WD of the coil is reached at the end of one rotation of the coil. In the case of Fig. 4, the initial working outer diameter is centered at O ₄ and points 4P, 4Q,
It is equal to the diameter of the circle passing through 4R, and is in contact with the side walls 4P, 4Q, and 4R at three points in the screw hole. As screwing progresses, points 4Q and 4R gradually move away from the side wall in the prepared hole, and the working outer diameter eventually becomes
At the end of one rotation of the coil, the outer diameter WD of the coil is reached.

The amount of movement of the center of screwing action corresponds to the eccentric distance H between the centers O ₂ , O ₃ , O ₄ of the non-circular materials and the center O ₁ of the virtual cylinder 6, and the outer diameter of the action is twice the eccentric distance H. It's going to change. This eccentric distance H is a design matter that should be set in relation to the lead angle of the helical winding X based on the nominal diameter and working length of the threaded body, that is, the total length of the threaded portion 2, and is 0 ( If necessary, it is possible to take a larger value than the value close to zero (0), but it is usually set to about 0.1 mm to 0.25 mm for nominal diameters of M3 to M6. This eccentricity can also be set by setting the value of the eccentricity distance H at the beginning of the helical winding X to 0 (zero) and gradually increasing the value to reach a desired final value.

The threaded body of the present invention changes its working outer diameter as the screwing operation progresses, so even if the screw hole is quite small at the beginning of screwing, the work can be carried out while adapting to this. However, as the work progresses, the working outer diameter gradually increases, and the contact state of the threaded protrusion 3 in contact with the side wall of the screw pilot hole gradually changes along the twist of the helical winding X. Therefore, the forming action of the female thread is carried out gradually and extremely smoothly.
As the screwing progresses further, the repulsion effect of the elasticity due to the gentle coiled twist of the threaded portion 2 is gradually added, causing an effect of increasing the axial force.
Even after tightening is complete, this elasticity remains and acts to prevent loosening.

The coil-like twist given to the threaded portion 2 is usually left-handed in the case of a right-handed thread, and is considered to be effective. This is because when the clockwise screwing operation begins and processing resistance occurs at the tip of the threaded part 2, the left-handed coil is twisted in the direction of winding the coil, so the outer diameter of the coil tends to decrease. When the threaded part 2 is turned in the opposite direction, the left-handed coil tends to expand its outer diameter and the threaded protrusion 3 bites into the female thread, creating a locking effect. It is from.

Overall, the threaded body of this invention has a non-circular shape that is suitable for mass production by rolling rather than a round bar material. Rolling can be easily carried out by using a flat thread rolling die having a thread surface of the shape that can be obtained at the time of rolling.

This threaded body is normally used as a quench-hardened tuft pin screw, but it is not necessary to quench it when it is used only for tightening or when it is used in plastic materials or the like.

[Brief explanation of drawings]

Fig. 1 is a plan view showing the general external shape of the present invention, and Figs. 2, 3, and 4 are cross-sectional views perpendicular to the axis of the threaded portion, and are shown slightly enlarged without leads for convenience of explanation. be. FIG. 5 is an explanatory diagram schematically showing the relationship between the non-circular material and the virtual cylinder. 1 is the head, 2 is the threaded part, 3 is the thread-like projection, 4
is the top of the mountain, 5 is the guide section, 6 is the virtual cylinder, 7 is the bottom surface of the virtual cylinder, and 8 is the top surface of the virtual cylinder. X is a helical winding, O ₁ is the center of the virtual cylinder, and O ₂ , O ₃ , and O ₄ are the centers of the noncircular shapes in FIGS. 2, 3, and 4, respectively. 2A, 2B, 3A, 3B, 4A, 4C, 4D
are straight lines passing through the center of each non-circular shape, 2
P, 2Q, 3P, 3Q, 4P, 4Q, and 4R are the maximum points in each of the noncircular shapes, WD is the outer diameter of the coil, and H is the eccentric distance.

Claims (1)

[Claims] 1. A continuous thread-like protrusion is carved on the outer peripheral surface of a non-circular material that is gently twisted in a coil shape over the entire length, and Only one of the helical windings formed by sequentially connecting the tops of the thread-like projections is in contact with the inner surface of the imaginary cylinder, and all other parts of the non-circular material are separated from the inner surface of the cylinder. 1. A coiled non-circular screw, characterized in that the center of the non-circular material and the central axis of the cylinder are eccentric so as to maintain a required distance. 2. The coiled non-circular screw according to claim 1, wherein the non-circular material has a substantially circular cross section perpendicular to the axis. 3. The coiled non-circular screw according to claim 1, wherein the non-circular material has a substantially elliptical cross-section at right angles to the axis. 4. The coiled non-circular screw according to claim 1, wherein the non-circular material has a triangular cross-section perpendicular to its axis with rounded corners and a slightly outward bulge.