JP2024070026A - Anti-loosening screw - Google Patents

Abstract

To provide a screw which achieves excellent anti-loosening effect.SOLUTION: An anti-loosening screw 1 which achieves the above object is a male screw to be threadedly engaged with a female screw 12 provided at a fastened member 8. Two or more screw components 3 are connected so that axes of the screw components 3 correspond with each other to form the anti-loosening screw 1. The screw components 3 can be connected by a connecting screw 4 having a diameter smaller than an outer diameter of the screw component 3. The axis of the screw component 3 corresponds with an axis of the connecting screw 4. A pitch C4 of the connecting screw 4 is larger than a pitch PC3 of the screw component 3. A spiral direction of the connecting screw 4 is the same as a spiral direction of the screw component 3. In a state that the anti-loosening screw 1 is threadedly engaged with the female screw 12 of the fastened member 8, a boundary 9 between the screw components 3 in an axial direction of the anti-loosening screw 1 is located in the female screw 12 of the fastened member 8.SELECTED DRAWING: Figure 3

Description

The present invention relates to a screw with an anti-loosening function.

Screws are used to fasten objects together, and with continued use the fastening parts can loosen. If the screw continues to be used while loose, there is a risk that it may come loose, posing a safety issue. For this reason, various methods have been proposed to prevent screws from loosening.

One of these methods is to fix the fastened parts with adhesive to prevent loosening. The fastened parts are fixed by applying adhesive to the threads and then tightening the screw. Since adhesive is sensitive to heat, the screw can be removed by heating the fastened parts.

This method is used when there is no need to remove the fastener frequently or even at all once it is fastened. For example, it is used for promotional displays that are never intended to be disassembled after assembly and will be discarded after use.

Many methods of preventing loosening that incorporate ingenuity into the structure of the screw itself have also been proposed for a long time. For example, the following Patent Documents 1 and 2 disclose a bolt in which a single bolt is divided into two, top and bottom, and the first bolt having the bolt head and the second bolt having the bolt tip are fitted together eccentrically to prevent loosening. The un-eccentric bolt is fitted into the bolt hole as if it were a single bolt, and then only the second bolt is made eccentric, preventing loosening through a locking effect caused by radial misalignment.

Also, methods of preventing loosening that utilize factors other than eccentricity have been disclosed. As shown in FIG. 15, the following Patent Document 3 discloses a locking bolt 17 having a spring washer 18 and a first bolt 21 and a second bolt 22 that are screwed into the female threaded portion 20 of the member to be fastened (the member to be fastened 19) in two stages, one above the other. The female threaded portion 20 is a right-handed thread. The first bolt 21 has a smaller diameter and pitch than the female threaded portion 20, and has a small-diameter male threaded portion 23 that is a left-handed thread. The second bolt 22 has a small-diameter female threaded portion 24 into which the small-diameter male threaded portion 23 is screwed. The bolt with the small-diameter male threaded portion 23 screwed into the small-diameter female threaded portion 24 is screwed into the female threaded portion 20 of the member to be fastened 19.

When the first bolt 21 is turned to the right, the first bolt 21 receives a force in the direction of the arrow C. The force of turning the first bolt 21 to the right is also transmitted to the second bolt 21 through the small diameter male thread portion 23. Since the small diameter male thread portion 23 is a left-handed thread, when the first bolt 21 is turned to the right, it moves in the direction of the arrow C relative to the second bolt 22, creating a gap 25 between the first bolt 21 and the second bolt 22. At this time, the second bolt 22 presses the female thread portion 20 of the fastened member 19 in the direction of the arrow D, opposite to the first bolt 20. Therefore, the female thread portion 20 receives a pressing force from the first bolt 21 in the direction of the arrow C and a pressing force from the second bolt 21 in the direction of the arrow D, so that a force in the tensile direction acts. In this way, a locking force acts between the locking bolt 17 and the female thread portion 20 of the fastened member 19, and an excellent locking effect can be obtained.

JP 2020-091019 A JP 2020-183772 A JP 2010-043678 A

One method of preventing screws from loosening is to fix the fastening part of the screw with adhesive, but this method has the disadvantage that it is time-consuming as it requires applying adhesive to the threads before tightening the screw, and additional costs are required for the adhesive. In addition, the adhesive is fixed by reacting with the surface of the screw, so the surface of the screw must be made of a material that can react with the adhesive, which limits the materials that can be used. For example, many adhesives react with specific metal ions to bond, so if the surface of the screw is treated with stainless steel, aluminum, or plating, the adhesive cannot react and the adhesive strength will be weak.

In addition, in the anti-loosening structures described in Patent Documents 1 and 2, when tightening the bolts, it is necessary to first tighten the first bolt and then make the second bolt eccentric. This two-step procedure is required, which creates the problem of poor workability.

Furthermore, in the bolt of Patent Document 3 shown in FIG. 15, there is a problem that the locking bolt 17 cannot exert its locking effect if it is loosened significantly. This is because the locking bolt 17 exerts its locking effect only when a gap 25 is generated between the first bolt 21 and the second bolt 22 after it is screwed into the female threaded portion 20. As the first bolt 21 turns left and loosens, the gap 25 gradually narrows and becomes zero, just like when assembled. As a result, there is no locking force between the locking bolt 17 and the female threaded portion 20. As the first bolt 21 turns further left and loosens, the second bolt 22, which is left-handed, also turns smoothly, and the locking bolt 17 comes off the fastened member 19. In other words, the locking bolt 17 exerts its locking effect only when a gap 25 is generated between the first bolt 21 and the second bolt 22 after it is screwed into the female threaded portion 20 and a locking force is acting, and there is a problem that it cannot prevent any loosening beyond that.

The present invention was made to solve the above problems, and aims to provide a screw that exhibits excellent anti-loosening properties.

Representative aspects of the present invention that solve the above problems are as follows.
<First aspect>
A locking screw that is a male screw that is screwed into a female screw provided in a fastened member,
The locking screw can be formed by connecting two or more threaded fasteners so that the axes of the threaded fasteners are aligned,
The threaded fasteners can be connected to each other by a connecting screw having a diameter smaller than an outer diameter of the threaded fasteners,
The axis of the screw part and the axis of the connecting screw are aligned,
The pitch of the connecting thread is greater than the pitch of the threaded component;
The helical direction of the connecting screw and the helical direction of the threaded part are the same direction,
When the locking screw is screwed into the female thread of the workpiece, a boundary between the threaded parts in the axial direction of the locking screw is located within the female thread of the workpiece.
A locking screw characterized by:

(Action and Effect)
In this embodiment, two or more threaded parts connected by a connecting screw form one locking screw. This locking screw is screwed into a female thread provided on a member to be fastened (hereinafter referred to as a "fastened member"; an example of the fastened member is a plate). Hereinafter, this female thread is referred to as a "fastened member female thread." In addition, when fastening the locking screw to the fastened member, an auxiliary part such as a nut may be used. In terms of the member to which the locking screw is fastened, such an auxiliary part such as a nut is also a type of fastened member, and the female thread provided on the auxiliary part such as a nut is also referred to as a fastened member female thread. In addition, when the auxiliary part is used when fastening the locking screw, the main fastened member such as a plate is referred to as a main fastened member, and the fastened member that is the auxiliary part is referred to as a secondary fastened member. In addition, the female thread provided on the main fastened member is referred to as a main fastened member female thread, and the female thread provided on the secondary fastened member is referred to as a secondary fastened member female thread.

Next, the locking effect of the present invention will be explained. In the following explanation, a screw part having a screw head of a locking screw will be referred to as a head screw part, and a screw part having a screw tip of a locking screw will be referred to as a tip screw part. In addition, in the axial direction of the locking screw, the side with the screw head will be referred to as the head side, and the side with the screw tip will be referred to as the tip side.

When the locking screw of this embodiment is continued to be used and the head screw component loosens and starts to rotate, the rotational force is transmitted to the connecting screw, which is connected so that its axis is aligned. Since the helical directions of the connecting screw and the head screw component are aligned, the connecting screw tries to move in the same direction as the head screw component (towards the head). However, since the pitch of the connecting screw is larger than the pitch of the head screw component, the axial movement distance of the connecting screw when the locking screw rotates once is greater than that of the head screw component. In other words, the head screw component can only move a small distance compared to the connecting screw which tries to move a large distance towards the head side. Therefore, although the connecting screw generates a force towards the head side, the head screw component acts as a stopper, suppressing the movement of the connecting screw towards the head side.

When this happens, the connecting screw, which cannot move toward the head side, tries to move in the opposite direction to the head side, i.e., toward the tip side. However, because the pitch of the connecting screw is larger than the pitch of the tip screw part, the connecting screw generates a force toward the tip side, but the tip screw part acts as a stopper for the connecting screw, and movement of the connecting screw toward the tip side is also suppressed.

Because the head screw part and tip screw part are screwed into the female thread of the fastened member, the forces on the head and tip sides generated by the connecting screw press the head screw part and tip screw part against the head and tip sides, respectively, of the female thread of the fastened member. These pressing forces increase the frictional force between the head screw part and tip screw part and the female thread of the fastened member, preventing the locking screw from rotating and providing an anti-loosening effect.

In addition, in order for the threaded parts to generate a pressing force against the female thread of the fastened part and to exert an anti-loosening effect, the boundary between the threaded parts in the axial direction of the anti-loosening screw must be located within the female thread of the fastened part. If the boundary between the threaded parts is not located within the female thread of the fastened part, it is difficult to obtain a pressing force in both directions toward the head and tip, making it difficult to exert an anti-loosening effect.

<Second aspect>
The connecting screw extends axially outward from one axial end side of one of the threaded fasteners connected by the connecting screw,
The other axial end of the other threaded fastener has a female thread that threadably engages with the connecting screw,
The connecting screw is screwed into the female thread of the screw part, so that the screw parts are joined together via the connecting screw to form a locking screw.
The locking screw according to the first aspect.

(Action and Effect)
Of the threaded fasteners connected by a connecting screw, one of the threaded fasteners has a connecting screw extending axially outward from one axial end side, and the other axial end side of the other threaded fastener has a threaded fastener female thread that screws into the connecting screw. The connecting screw is screwed into the threaded fastener female thread to form a single anti-loosening screw.

In this embodiment, the connecting screw is formed on one axial end of the threaded part, so that when the connecting screw is screwed into the female thread of the threaded part, a single locking screw is formed. The user of the locking screw can form the locking screw simply by screwing the connecting screw into the female thread of the threaded part, which has the advantage that there are fewer parts to be connected and it is easy to work with.

<Third aspect>
The threaded fastener has a female thread into which the connecting screw is screwed,
With the connecting screw threadedly engaged with the female thread of the threaded part,
A gap is provided between the tip of the screw and the bottom of the female thread of the screw part.
The locking screw according to any one of the first and second aspects.

(Action and Effect)
In this embodiment, when the connecting screw is threadedly engaged with the female thread of the threaded fastener, a gap is formed between the tip of the threaded connecting screw and the bottom of the female thread of the threaded fastener. In the following description, the tip of the threaded connecting screw is referred to as the connecting screw tip, and the bottom of the female thread of the threaded fastener is referred to as the female thread bottom.

In other words, in this embodiment, even when the connecting screw is screwed into the female thread of the screw part, the bottom of the female thread of the screw part is not in contact with the tip of the connecting screw, but is separated from it. The existence of this space has the advantage of increasing the allowable error during manufacturing. In other words, when the bottom of the female thread of the screw part is in close contact with the tip of the connecting screw, the axial length of the connecting screw must be exactly the same as the axial length of the female thread of the screw part. On the other hand, when the bottom of the female thread of the screw part is configured to be separated from the tip of the connecting screw without contacting it, as in this embodiment, it is sufficient that the axial length of the connecting screw inserted into the female thread of the screw part is shorter than the axial length of the female thread of the screw part, and it is not necessary for these lengths to be exactly the same, so the allowable error in these lengths during manufacturing is greater.

<Fourth aspect>
The locking screw has three or more of the threaded parts,
The screw parts are connected by the connecting screw,
all of the boundaries between the threaded parts in the axial direction of the locking screw are located within the female thread of the fastened workpiece;
The locking screw according to any one of the first and second aspects.

(Action and Effect)
The locking screw of this embodiment has three or more threaded parts connected by a connecting screw. Therefore, when the threaded parts loosen, the number of places where a pressing force acts on the female thread of the fastened workpiece increases, and the frictional force generated increases. Therefore, a locking screw having a stronger locking effect can be achieved compared to a locking screw made of two threaded parts.

<Fifth aspect>
At least one of the outer circumferential surface of the connecting screw, the axial end face of the connecting screw, and the axial end face of the threaded part on the connecting screw side is subjected to a rust prevention treatment.
The locking screw according to any one of the first and second aspects.

(Action and Effect)
In order for the locking effect of the present invention to be exerted, as described above, it is necessary that only the head screw fastener first loosens and starts to rotate. If the boundaries between adjacent screw fasteners or the boundaries between adjacent screw fasteners and connecting screws rust and the adjacent screw fasteners become integrated, when the head screw fastener starts to loosen, the tip screw fastener will also loosen together, and the locking effect as described above will not work.

Therefore, in the case of screws made of a material that may rust, it is preferable to apply rust prevention treatment to at least one of the contact surfaces between the screw part and the connecting screw: the outer circumferential surface of the connecting screw, the axial end face of the connecting screw, and the axial end face of the connecting screw side of the screw part. This rust prevention treatment can prevent rust even after a long time has passed since the screw is fastened, so the anti-loosening effect can be continued. In order to continue to exert the anti-loosening effect, it is preferable to apply rust prevention treatment to all of the outer circumferential surface of the connecting screw, the axial end face of the connecting screw, and the axial end face of the connecting screw side of the screw part. In addition, it is preferable to apply rust prevention treatment to as large an area as possible.

<Sixth aspect>
a fixing groove for fixing an elongated removal member for removing the locking screw is provided at an axial end of the connecting screw;
The threaded fastener having the female thread has an insertion hole for inserting the removal member along an axial direction of the threaded fastener,
the insertion hole extends from an axial end of the threaded fastener having the female thread opposite the connecting screw to at least a position where the fixing groove of the connecting screw is located when the threaded fasteners are connected to each other,
A length in a short direction in a cross section of the insertion hole is shorter than a length in a long direction in a cross section of the removal member,
By inserting the removal member into the insertion hole and fixing a tip end of the removal member in the fixing groove of the connecting screw, the removal member can be rotated to simultaneously rotate the screw fastener having the insertion hole and the screw fastener having the connecting screw, thereby removing the anti-loosening screw.
The locking screw according to the second aspect.

(Action and Effect)
According to this aspect, when the removal member (which refers to a tool used for removal; the same applies below) is rotated to loosen the anti-loosening screw, the screw fastener with the female thread (which is the same as the screw fastener with an insertion hole; the same applies below) and the screw fastener with the connecting screw become integrated into one piece, just like a single ordinary screw, making it easy to remove the anti-loosening screw.

When the locking screw is removed by rotating only the connecting screw with the removal member, as the screw fastener with the connecting screw rotates and moves toward the head, it rotates and moves while pushing the screw fastener with the female thread toward the head. As a result, both the screw fastener with the connecting screw and the screw fastener with the female thread move toward the head, and the locking screw is removed.

In such cases, however, the screw fastener with the connecting screw thread rotates while pushing the screw fastener with the female thread toward the head side, making it difficult for the screw fastener with the female thread to move toward the head side. Also, when using a removal member to rotate only the screw fastener with the connecting screw, a small removal member is inevitably used. Because small removal members do not easily transmit rotational force, the worker must apply a large force to rotate the screw fastener with the connecting screw, and the effort required to remove the locking screw is great.

In this embodiment, the screw fastener having the connecting screw is rotated by the removal member, and the screw fastener having the female thread is also directly rotated by the removal member, making it easier to move the screw fastener having the female thread toward the head side. In addition, according to this embodiment, since there is no restriction to only rotating the screw fastener having the connecting screw by the removal member, the insertion hole provided in the screw fastener can be made larger. As a result, a larger removal member can be used, and the operator does not have to use a large force to rotate the screw fastener having the connecting screw.

As described above, the present invention provides a locking screw that exhibits excellent locking properties.

FIG. 1 is a side cross-sectional view showing a locking screw according to a first embodiment of the present invention, illustrating the state before two screw parts are connected by a connecting screw. FIG. 2 is a side view of the locking screw of FIG. 1 . 2 is a side cross-sectional view showing the locking screw of FIG. 1 in a state after fastening members. FIG. FIG. 13 is a side view showing a locking screw according to a second embodiment of the present invention, showing the connecting screw extending from the head side of the tip end screw fastener before being screwed into the female thread of the head screw fastener. 5 is a side cross-sectional view of the screw parts after they have been fastened together via a connecting screw, following the state shown in FIG. 4 . FIG. FIG. 13 is a side view showing a locking screw according to a third embodiment of the present invention, showing the connecting screw extending from the tip end side of the head screw fastener before it is screwed into the female thread of the tip screw fastener. 7 is a side cross-sectional view of the screw parts after they have been fastened together via a connecting screw, following the state shown in FIG. 6; FIG. FIG. 13 is a side view of a locking screw according to a fourth embodiment of the present invention, the locking screw having an insertion hole in a head threaded part. FIG. 13 is a side view of a locking screw according to a fourth embodiment of the present invention, the locking screw having an insertion hole in a threaded part at its tip end. FIG. 9 is a plan view showing the head side of the locking screw in FIG. 8 . 11 is a plan view showing the head side of the locking screw, showing a different form from that shown in Fig. 10. (11-1) shows the state in which the removal member is inserted into the insertion hole, and (11-2) shows the state in which the removal member is rotated. FIG. 13 shows a locking screw according to a fifth embodiment of the present invention, and is a side cross-sectional view of the locking screw in which the end faces of threaded parts do not come into contact with each other in a fastened state. FIG. 13 is a side view showing a locking screw according to a sixth embodiment of the present invention, the locking screw having three threaded parts before they are connected together by a connecting screw. FIG. 14 is a side cross-sectional view showing the locking screw having the three threaded parts of FIG. 13 after they have been connected together by a connecting screw. FIG. 11 is a side cross-sectional view showing a conventional anti-loosening bolt.

An example of a locking screw will be described below with reference to the attached drawings. The following description and drawings are merely an example of an embodiment of the present invention, and the contents of the present invention are not limited to this embodiment.

(First embodiment)
An example of a first embodiment of a locking screw 1 according to the present invention is shown in Figures 1 to 3. The locking screw 1 includes two or more screw fasteners 3 (head screw fastener 3A, tip screw fastener 3B), a connecting screw 4 that connects the screw fasteners 3, a screw fastener female thread 5 into which the connecting screw 4 is screwed, a screw head 6 of the locking screw 1, and a screw tip 7. Figure 1 is a side cross-sectional view of the locking screw 1 before the screw fasteners 3 are connected by the connecting screw 4. Figure 2 is a side view of Figure 1.

Figure 3 is a side cross-sectional view of the anti-loosening screw 1 of Figure 1 after it has fastened the workpiece. From the state of Figure 1, the connecting screw 4, which is an internal thread, is screwed into the female thread 5 of the threaded parts 3 to connect the threaded parts 3 together, and the ends of the threaded parts 3 are brought together to form a single anti-loosening screw 1. The single anti-loosening screw 1 thus formed is then screwed into the female thread 12 of the workpiece 8 provided in the workpiece. The diameter and pitch of the female thread 12 of the workpiece 8 match those of the anti-loosening screw 1.

The anti-loosening screw 1 is not only screwed into the female thread 12 of the fastened member, but may also fasten the fastened member 8 using additional parts (auxiliary parts) such as washers and nuts. The anti-loosening screw 1 is shown as a parallel thread in the figure, but it may also be a tapered thread, and the shape is not limited.

The details of each part are explained below.

(Anti-loosening screw 1)
The locking screw 1 is a male thread with a groove provided on its outer circumferential surface so as to screw into the female thread 12 of the fastened member. The helical direction of this locking screw 1 may be right-handed or left-handed, but the locking screw 1 shown in the figure is right-handed. However, the helical direction of the threaded part 3 and the helical direction of the connecting screw 4 must be the same. The locking screw 1 may be a full thread in which the groove is provided over the entire length of the locking screw 1, or a half thread in which the groove is provided partially.

As shown in FIG. 3, two or more screw parts 3 connected by a connecting screw become a single locking screw 1 that screws into the female thread 12 of the fastened member. Therefore, two or more screw parts 3 must have a groove that, when connected by a connecting screw 4, becomes a single locking screw 1 that can screw into the female thread 12 of the fastening member. In other words, the screw parts 3 must have a groove that connects the spirals at the boundary between them.

Such groove alignment can be achieved by devising a manufacturing method. For example, the threaded components 3 before the groove of the locking screw 1 is cut can be connected with a connecting screw 4 first, and then the groove can be cut. In this way, grooves with connected spirals can be cut on the outer periphery of two or more threaded components 3. Another manufacturing method is to cut a groove into a single thread having a screw head 6 and a screw tip 7, and then cut the thread to make two or more threaded components 3.

(Screw part 3)
The threaded fastener 3 has a groove on its outer circumferential surface. Two or more threaded fasteners 3 are connected by a connecting screw 4, and the ends of the threaded fasteners 3 are grounded to each other to form the locking screw 1. The threaded fasteners 3 have a threaded fastener female thread 5 on one end side in the axial direction AD, and the connecting screw 4 is screwed into the threaded fastener female thread 5. The axial centers of the threaded fasteners 3 and the connecting screw 4 are aligned.

Figures 1 to 3 show a locking screw 1 according to a first embodiment, which has two screw components 3A and 3B. The head screw component 3A is a screw component 3 with a screw head 6, and the tip screw component 3B is a screw component 3 with a screw tip 7. The screw component 3 is a general term for the screw components 3 including the head screw component 3A and the tip screw component 3B. The diameters of the head screw component 3A and the tip screw component 3B and the spiral direction of the grooves are the same. The connecting screw 4 is an internal thread located inside the head screw component 3A and the tip screw component 3B.

In the case where the head screw part 3A, the tip screw part 3B and the connecting screw 4 are each separate parts as in the first embodiment, it is preferable that the length of the axial direction AD of the connecting screw 3 is longer than the length of the axial direction AD of the head screw part female thread 5A of the head screw part 3A. By doing so, when the head screw part 3A and the connecting screw 4 are connected, the connecting screw 4 is embedded inside the head screw part female thread 5A of the head screw part 3A, and the connecting screw 4 does not protrude from the axial direction AD end of the head screw part 3A. Similarly, it is preferable that the length of the axial direction AD of the connecting screw 3 is also longer than the length of the axial direction AD of the tip screw part female thread 5B of the tip screw part 3B. By doing so, when the tip screw part 3B and the connecting screw 4 are connected, the connecting screw 4 is embedded inside the tip screw part female thread 5B of the tip screw part 3B, and the connecting screw 4 does not protrude from the axial direction AD end of the tip screw part 3B. In other words, the threaded parts 3A and 3B are connected to each other only when both ends of the connecting screw 4 in the axial direction AD are screwed into the separate threaded part female threads 5A and 5B.

(Connecting screw 4)
The connecting screw 4 connects two or more screw components 3 together to form the locking screw 1. The diameter DM4 of the connecting screw 4 is equal to the diameter DM5 of the female thread 5 of the screw component. The groove pitch PC4 of the connecting screw 4 is equal to the groove pitch PC5A of the female thread 5A of the head screw component. Similarly, the groove pitch PC4 of the connecting screw 4 is equal to the groove pitch PC5B of the female thread 5B of the tip screw component. The connecting screw 4 has a smaller diameter than the screw component 3, but if the connecting screw 4 is too thin, the screw strength decreases and it becomes easy to break. Furthermore, the larger the diameter of the connecting screw 4, the higher the screw strength. Therefore, it is desirable that the diameter DM4 of the connecting screw 4 is 40% to 60% of the diameter DM3A of the head screw component 3A (or the diameter DM3B of the tip screw component 3B).

The groove pitch PC4 of the connecting screw 4 is set larger than the groove pitch PC3A of the head screw part 3A and the groove pitch PC3B of the tip screw part 3B. The larger the groove pitch PC4 of the connecting screw 4, the greater the anti-loosening effect. However, if the pitch PC4 is increased, the length of the axial direction AD of the connecting screw 4 becomes longer, so there is a limit to how long the pitch PC4 can be. The greater the difference between the groove pitch PC3A of the head screw part 3A and the groove pitch PC4 of the connecting screw 4, the greater the anti-loosening effect, and conversely, if the difference between the pitches PC3A and PC4 is too small, a sufficient anti-loosening effect cannot be obtained. The same can be said about the difference between the groove pitch PC3B of the tip screw part 3B and the groove pitch PC4 of the connecting screw 4. Therefore, it is desirable that the pitch PC4 of the connecting screw 4 be 2 to 5 times the groove pitch PC3A of the head screw part 3A (or the groove pitch PC3B of the tip screw part 3B).

The cross-sectional shape and inclination angle of the threads of the head screw part 3A, the tip screw part 3B, and the connecting screw 4 are not particularly limited. Examples include triangular threads such as metric threads, unified threads, and pipe threads, as well as trapezoidal threads and square threads.

The materials and surface treatment methods of the connecting screw 4 and the screw fastener 3 are not particularly limited. Examples of screw materials include iron, stainless steel, aluminum, titanium, copper, synthetic resin, and wood, but it is preferable to use a material that is resistant to rust. Examples of surface treatment methods include electroplating, electroless plating, and painting. The materials and surface treatment methods of the connecting screw 4 may be the same as or different from the materials and surface treatment methods of the screw fastener 3.

(Screw head 6 and screw tip 7)
The shape of the screw head 6 of the locking screw 1 is not particularly limited, and examples thereof include hexagonal, square, truss, bind, flat head, round flat head, pan head, low head, and the like.

The shape of the recess in the screw head 6 is also not limited, and examples include cross recess, slot, hexagon, etc.

The shape of the screw tip 7 is not particularly limited, and examples include a round tip, flat tip, rod tip, half rod tip, rod tip, fully pointed tip, pointed tip, and concave tip.

(Anti-loosening effect)
The locking effect of the present invention will now be described. The direction of the screw head 6 in the axial direction AD of the locking screw 1 is called the head side HS, and the direction of the screw tip 7 is called the tip side ES. When the locking screw 1 shown in Fig. 3 is used continuously, the head screw part 3A having the screw head 6 loosens and starts to rotate. Then, the rotational force is transmitted to the connecting screw 4 connected so that their axes coincide. Since the spiral directions of the grooves of the connecting screw 4 and the grooves of the head screw part 3A coincide, the connecting screw 4 tries to move in the head side HS, which is the same as the movement direction in the axial direction AD when the head screw part 3A rotates.

However, because the pitch PC4 of the connecting screw 4 is set larger than the pitch PC3A of the head screw component 3A, the movement distance in the axial direction AD when the anti-loosening screw 1 rotates once is greater for the connecting screw 4 than for the head screw component 3A. In other words, the head screw component 3A can only move a small distance compared to the connecting screw 4 which attempts to move a large distance toward the head side HS. Therefore, although the connecting screw 4 attempts to move toward the head side HS, the head screw component 3A acts as a stopper, suppressing the movement of the connecting screw 4 toward the head side HS.

Then, the connecting screw 4, which cannot move to the head side HS, tries to move in the opposite direction to the head side HS, that is, to the tip side ES. However, the pitch PC4 of the connecting screw 4 is set larger than the pitch PC3B of the tip screw part 3B, just like the head screw part 3A, so although the connecting screw 4 tries to move to the tip side ES, the tip screw part 3B acts as a stopper for the connecting screw 4, and movement to the tip side ES is also suppressed.

Because the head screw part 3A and the tip screw part 3B are screwed into the female thread 12 of the fastened member, the force of movement toward the head side HS and the tip side ES generated by the connecting screw 4 presses the head screw part 3A and the tip screw part 3B against the head side HS and the tip side ES, respectively, of the female thread 12 of the fastened member. These pressing forces increase the frictional force between the head screw part 3A and the tip screw part 3B and the female thread 12 of the fastened member, preventing the locking screw 1 from rotating and providing an anti-loosening effect. In Figure 3, the force moving toward the head side HS is indicated by arrow A, and the force moving toward the tip side ES is indicated by arrow B.

This anti-loosening effect is exerted regardless of the pitch ratio, so long as the pitch PC4 of the connecting screw 4 is slightly larger than the pitch PC3A of the head screw component 3A and the pitch PC3B of the tip screw component 3B. For example, when the ratio of the pitch PC3A of the head screw component 3A to the pitch PC4 of the connecting screw 4 to the pitch PC3B of the tip screw component 3B is 1:2:1, at first glance it appears that the pressing forces in the directions of arrows A and B generated by the connecting screw 4 and the moving forces of the head screw component 3A and the tip screw component 3B are offset, and no anti-loosening effect is exerted. However, in reality, when the connecting screw 4 rotates once, a force equivalent to two rotations in the direction of arrow A is applied to the head screw component 3A, so the forces are not offset and the anti-loosening effect is exerted.

In order for the screw part 3 to generate a pressing force against the female thread 12 of the fastened member and to exert an anti-loosening effect, the boundary 9 between the screw parts in the axial direction AD of the anti-loosening screw 1 must be located within the hole of the female thread 12 of the fastened member. If the boundary 9 between the screw parts is not located within the hole of the female thread 12 of the fastened member and only the head screw part 3A or the tip screw part 3B is within the hole of the female thread 12 of the fastened member, the pressing force in both directions of arrows A and B cannot be obtained, and the anti-loosening effect cannot be exerted.

(Comparison with prior art documents)
As mentioned above, Fig. 15 shows the locking bolt 17 of Patent Document 3. The locking bolt 17 of Patent Document 3 and the locking screw 1 of the present invention have the same force direction when the locking effect occurs, but the helical direction of the thread grooves and the pitch of the thread grooves that make up each of them are different, and the process by which the locking effect is exerted is different.

In Patent Document 3, the first bolt 21 and the second bolt 22 of the locking bolt 17 are right-handed threads, while the small-diameter male thread portion 23 is left-handed threads. Also, the pitch of the small-diameter male thread portion 23 is smaller than the pitch of the female thread portion 20. Therefore, the locking bolt 17 of Patent Document 3 uses a spring washer as described above to create a gap 25 between the first bolt 21 and the second bolt 22 when fastened, thereby generating a pressing force in the directions of arrows C and D.

On the other hand, in the present invention, the grooves of the two or more screw parts 3 and the groove of the connecting screw 4 are in the same spiral direction, and the pitch PC4 of the groove of the connecting screw 4 is larger than the pitch PC3 of the grooves of the two or more screw parts 3. Therefore, as shown in FIG. 3, when the locking screw 1 is fastened to the female thread 12 of the fastened member, the two or more screw parts 3 are integrated with each other, and no gaps are generated between the connected screw parts 3. Then, when the locking screw 1 is continued to be used after fastening and the head screw part 3A begins to loosen, it generates a pressing force in the directions of arrows A and B for the first time. This is a major difference from Patent Document 3, in which pressing forces are generated in the directions of arrows C and D at the time of fastening. Therefore, the locking bolt 17 of Patent Document 3 has the problem of being unable to handle a large amount of loosening that would eliminate the gap 25, but the present invention can solve this problem. Contrary to Patent Document 3, the present invention has the effect that the greater the loosening of the head screw part 3, the greater the pressing force in the directions of arrows A and B.

(Second embodiment)
4 and 5 show a second embodiment of the locking screw 1 according to the present invention. The second embodiment differs from the first embodiment only in that the connecting screw 4 extends from the head side HS to the head side HS in the axial direction AD of the tip-end threaded part 3B, and is otherwise similar to the first embodiment.

The head screw part 3A has a female thread 5 (female thread 5A) on the tip side ES in the axial direction AD into which the connecting screw 4 is screwed.

When the connecting screw 4 is screwed into the female thread 5A of the head screw part from the state shown in FIG. 4, a single anti-loosening screw 1 is formed. The anti-loosening screw 1 formed in this way is then screwed into the female thread 12 of the fastened member as shown in FIG. 5.

(Third embodiment)
6 and 7 show a third embodiment of the locking screw 1 according to the present invention. In this third embodiment, among the screw components 3 connected by a connecting screw 4, the connecting screw 4 extends from the tip side ES in the axial direction AD of the head screw component 3A toward the tip side ES. In addition, the head side HS in the axial direction AD of the tip screw component 3B is provided with a tip screw component female thread 5B into which the connecting screw 4 is screwed.

As in Figures 4 and 5, when the connecting screw 4 is screwed into the female thread 5B of the tip screw part from the state shown in Figure 6, a single anti-loosening screw 1 is formed. The anti-loosening screw 1 formed in this way is screwed into the female thread 12 of the fastened member as shown in Figure 7.

In the second and third embodiments, the locking screw 1 can be formed simply by screwing the connecting screw 4 into the female thread 5 of the screw part. This has the advantage that there are fewer parts to be joined together, and workability during fastening is superior compared to the first embodiment.

In the first to third embodiments, if the length of the axial direction AD of the connecting screw 4 is too short, the screwed portion will be too short and the screw strength will be weakened. For this reason, it is desirable for the connecting screw to have two or more threads, and it is desirable for the length of the axial direction AD of the connecting screw 4 to be at least one-third of the length of the axial direction AD of the locking screw 1.

(Fourth embodiment)
Since the locking screw 1 of the present invention has a locking function, it cannot be removed even if the screw head 6 of the locking screw 1 is rotated as it is. This is because, as described above, when the head screw component 3A loosens and rotates, the rotational force is transmitted to the connecting screw 4, and a pressing force against the female thread 12 of the fastened workpiece is generated due to the difference in pitch between the grooves of the connecting screw 4 and the head screw component 3A (and the tip screw component 3B).

However, as in the fourth embodiment, if an insertion hole 14 is provided in the locking screw 1 and the screw part 3 and the connecting screw 4 are rotated simultaneously, the locking screw 1 can be easily removed as described below.

The insertion hole 14 is provided in the screw fastener 3 having the female thread 5. For example, as shown in FIG. 8, when the head screw fastener 3A has the female thread 5, the insertion hole 14 is provided in the head screw fastener 3A. As shown in FIG. 9, when the tip screw fastener 3B has the female thread 5, the insertion hole 14 is provided in the tip screw fastener 3B.

The through hole 14 is provided along the axial direction AD of the screw fastener 3 having the female thread 5, and passes through the screw fastener 3 having the female thread 5.

As shown in the example in FIG. 10, the shape and size of the insertion hole 14 in cross section can be approximately the same as the removal member 15. That is, in FIG. 10, the cross-sectional shapes of the insertion hole 14 and the removal member 15 are both rectangular, and the size of the insertion hole 14 is approximately the same as the removal member 15. Note that the size of the insertion hole 14 needs to be slightly larger than the removal member 15 so that the removal member 15 can be inserted inside the insertion hole 14.

Also, as in the example shown in FIG. 11, the size of the insertion hole 14 may be larger than the size of the removal member 15 in cross section. However, it is desirable to make the short-side length 14S of the insertion hole 14 in cross section shorter than the long-side length 15L of the removal member 15 in cross section. This is because by making the short-side length 14S of the insertion hole 14 shorter than the long-side length 15L of the removal member 15, a part (or all) of the side of the removal member 15 will catch on a part (or all) of the insertion hole 14 when the removal member 15 is rotated.

For example, in the example shown in Figure 11, when the removal member 15 is rotated counterclockwise from the state (11-1) in which it is inserted into the insertion hole 14, it changes to the state (11-2). In this state (11-2), the corners of the removal member 15 (the lower left corner and the upper right corner in Figure 11) abut against the inner surface of the insertion hole 14 (the upper and lower long sides of the insertion hole 14 in Figure 11), and the rotational force of the removal member 15 is transmitted to the head screw part 3A via this abutment. As a result, the head screw part 3A can be rotated by the removal member 15.

In the example shown in FIG. 10, the entire outer surface of the removal member 15 abuts the entire inner surface of the insertion hole 14, which has the advantage that it is easier to rotate the head screw part 3A than in the example shown in FIG. 11.

In addition, a fixing groove 26 for fixing the removal member 15 is provided at the axial end of the connecting screw 4. In the example shown in FIG. 8, the fixing groove 26 is provided at the HS end of the connecting screw 4 on the head side in the axial direction AD, and in the example shown in FIG. 9, the fixing groove 26 is provided at the ES end of the connecting screw 4 on the tip side in the axial direction AD. The depth of this fixing groove 26 is not particularly limited, but can be, for example, about 1 to 5 mm. In addition, the position where the fixing groove 26 is provided in a plan view is also not particularly limited, but it is preferable to provide it so that it passes through the axis of the connecting screw 4 from the viewpoint of making it easy to rotate the connecting screw 4. For example, in the examples shown in FIG. 8 and FIG. 9, a linear fixing groove 26 passing through the axis of the connecting screw 4 is provided across the circular connecting screw 4 in a plan view.

When removing the locking screw 1, the removal member 15 is inserted into the insertion hole 14, and the tip of the inserted removal member 15 is fixed inside the fixing groove 26 of the connecting screw 4. When the removal member 15 is rotated in this state, it simultaneously rotates the screw fastener 3 with the insertion hole 14 and the connecting screw 4. As a result, the screw fastener 3 with the connecting screw 4 and the screw fastener 3 with the female thread 5 become integrated together, just like a single normal screw, and the locking screw 1 can be easily removed from the female thread 12 of the fastened member.

When removing the locking screw 1, the insertion direction of the removal member 15 differs between Figures 8 and 9, but in both the forms shown in Figures 8 and 9, the removal member 15 moves the locking screw 1 to the head side HS.

The shape of the through hole 14 in plan view is not particularly limited, and examples include a cross hole (plus sign) and a slot (minus sign). The shape of the aforementioned through hole 14 can be the same at all points in the axial direction AD of the through hole 14. For example, if the shape of the head side HS of the screw fastener 3 having the through hole 14 is a slot, the shape of the tip side ES can also be a slot.

In addition, if the shape of the insertion hole 14 and the removal member 15 is made different from that of commercially available screwdrivers, the locking screw 1 cannot be removed unless a special tool is used, providing excellent theft prevention effects.

In order to remove the locking screw 1, the connecting screw 4 must be rotated, so the insertion hole 14 must reach at least the position where the fixing groove 26 of the connecting screw 4 is located (more precisely, the inside of the fixing groove 26) when the screw parts 3, 3 are completely connected to each other via the connecting screw 4.

For example, in the example shown in Figure 8, the insertion hole 14 is formed starting from the head side HS edge of the head screw part 3A (the head side HS edge of the screw head 6), passing over the head side HS edge of the female thread 5A of the screw part, and further to the tip side ES. In more detail, in the example shown in Figure 8, the axial length AD4 of the connecting screw 4 and the axial length AD5A of the female thread 5A of the screw part are the same, so the position of the tip side ES edge of the insertion hole 14 is closer to the tip side ES than the head side HS edge of the female thread 5A of the screw part by the depth of the fixing groove 26.

Similarly, for example, in the example shown in Figure 9, the insertion hole 14 is formed starting from the tip side ES edge of the tip screw part 3B, passing over the tip side ES edge of the female thread 5A of the screw part, and further to the head side HS. In more detail, in the example shown in Figure 9, the axial direction AD length AD4 of the connecting screw 4 and the axial direction AD length AD5B of the female thread 5B of the screw part are the same, so the position of the head HS side edge of the insertion hole 14 is closer to the head side HS than the tip side ES edge of the female thread 5B by the depth of the fixing groove 26.

As described above, when the axial AD length AD4 of the connecting screw 4 and the axial AD length AD5 of the female thread 5 of the threaded part are the same, it is necessary to provide the insertion hole 14 up to a position obtained by subtracting the axial AD length AD26 of the fixing groove 26 from the axial AD length AD5 of the female thread 5 of the threaded part.

On the other hand, as shown in Figures 4 to 7, there is also a form in which a predetermined gap 16 is created inside the female thread 5 of the threaded fastener 3. In this case, the axial length AD5 of the female thread 5 of the threaded fastener is longer than the axial length AD4 of the connecting screw 4. In such a case, it is necessary to provide the insertion hole 14 at least up to a position obtained by subtracting the axial length AD16 of the gap 16 and the axial length AD26 of the fixing groove 26 from the axial length AD5 of the female thread 5 of the threaded fastener.

For example, when providing the through hole 14 in the embodiment shown in Figures 4 and 5, it is necessary to form the through hole 14 from the head side HS edge of the head screw part 3A (the head side HS edge of the screw head 6) as the starting point, beyond the head side HS edge of the female thread 5A of the screw part, and further to the tip side ES. In detail, the position of the tip side ES edge of the through hole 14 must be closer to the tip side ES than the head side HS edge of the female thread 5A of the screw part by the axial length AD16 of the gap 16 and the axial length AD26 of the fixing groove 26. When providing the through hole 14 in the embodiment shown in Figures 6 and 7, the same concept as in Figures 4 and 5 can be adopted.

In the above description, an example has been given in which the edge of the insertion hole 14 is provided up to the depth of the fixing groove 26, but the present invention is not limited to this example. For example, in the example shown in FIG. 8, the edge of the tip side ES of the insertion hole 14 in the axial direction AD may be positioned further toward the tip side ES than in FIG. 8. Similarly, in the example shown in FIG. 9, the edge of the head side HS of the insertion hole 14 in the axial direction AD may be positioned further toward the head side HS than in FIG. 9.

(Fifth embodiment)
FIG. 12 shows a fifth embodiment, in which the sum of the axial length AD5A of the female thread 5A of the head screw fastener 3A and the axial length AD5B of the female thread 5B of the tip screw fastener 3B is shorter than the axial length AD4 of the connecting screw 4, and the end face 3T of the head screw fastener 3A and the end face 3T of the tip screw fastener 3B do not come into contact with each other.

The end face 3T of the head screw part 3A and the end face 3T of the tip screw part 3B do not come into contact with each other, so rusting of the boundary 9 between the head screw part 3A and the tip screw part 3B can be prevented. In order for the locking screw 1 to exert its locking effect, as described above, only the head screw part 3A must first loosen and start rotating. However, if the end faces 3T, 3T of the screw parts 3, 3 rust, the screw parts 3, 3 will become one with each other and the locking effect will not be exerted. Therefore, as in this fifth embodiment, in order to maintain the locking effect for a long period of time, it is effective to prevent the end faces 3T, 3T of the screw parts 3, 3 from coming into contact with each other, and to prevent the screw parts 3, 3 from becoming one with each other due to rusting of the end faces 3T, 3T.

In order to prevent the threaded parts 3, 3 from becoming integrated with each other due to rust, rust-proofing may be applied instead of adopting the form of the fifth embodiment. Specifically, by applying rust-proofing to at least one of the following: (1) the outer peripheral surface 4S of the connecting screw 4, (2) the axial AD end surface 4T of the connecting screw 4, (3) the inner peripheral surface 5S of the female thread 5 of the threaded part, (4) the axial AD end surface 5T of the female thread 5 of the threaded part, (5) the end surface 3T of the threaded part 3, rust can be prevented even after a long time has passed since the thread is fastened, and the loosening prevention effect can continue to be exerted. The more the locations among the above (1) to (5) that are subjected to rust-proofing, the higher the rust-prevention effect. There is no particular limitation on the rust-proofing, but a method such as applying grease can be adopted.

(Sixth embodiment)
13 and 14 show a sixth embodiment in which the locking screw 1 has three threaded fasteners 3. This sixth embodiment has the same features as the first embodiment, except for the number of threaded fasteners 3.

The sixth embodiment has a stronger anti-loosening effect than the first embodiment, which has two threaded fasteners 3. This is because when the threaded fastener 3 loosens, the number of locations where a pressing force acts on the female thread 12 of the fastened member increases, and the frictional force that is generated becomes stronger.

When the number of screw parts 3 is increased to three, the number of boundaries 9 between the screw parts becomes two, but in order to exert an anti-loosening effect, both of these boundaries 9, 9 must be located within the hole of the female thread 12 of the fastened member. The number of screw parts 3 may be increased to four or more. As the number of screw parts 3 in the anti-loosening screw 1 increases, the screw strength decreases, but the anti-loosening effect can be increased.

(others)
It is desirable that the locking screw 1 generates a gap 16 between the end 10 of the connecting screw 4 and the end 11 of the female thread of the threaded fastener when the connecting screw 4 is screwed into the female thread of the threaded fastener. In Figures 3, 5 and 7, the gap 16 generated between the end 10 of the connecting screw 4 and the end 11 of the female thread of the threaded fastener is shown by a grid.

When the connecting screw 4 is completely screwed into the female thread 5 of the screw part (when there is no gap between the screw parts 3, 3), the female thread end 11 of the screw part does not contact the connecting screw end 10 and is separated from it, which increases the allowable error during manufacturing. In other words, when the female thread end 11 of the screw part is in contact with the connecting screw end 10, the axial length AD4 of the connecting screw 4 must be exactly the same as the axial length AD5 of the female thread 5 of the screw part. However, when the connecting screw 4 is completely screwed into the female thread 5 of the screw part and the female thread end 11 of the screw part is not in contact with the connecting screw end 10 and is separated from it, the axial length AD4 of the connecting screw 4 only needs to be shorter than the axial length AD5 of the female thread 5 of the screw part, and the lengths do not need to be exactly the same, so the allowable error in length during manufacturing increases.

In addition, because the female thread end 11 of the screw part does not come into contact with the connecting screw end 10, there is also the advantage that rusting between the axial AD end face 5T of the female thread 5 of the screw part and the axial AD end face 4T of the connecting screw 4 can be prevented.

The present invention can be applied to screws that are screwed into various fastened members, and can provide excellent anti-loosening effects.

1...locking screw, 3...screw part, 3A...head screw part, 3B...tip screw part, 3C...middle screw part, 4...connecting screw, 5...female screw part, 5A...female screw part, 5B...female screw part, 5C...female screw part, 6...screw head, 7...tip of screw, 8...workpiece to be fastened, 9...boundary between screw parts, 10...connecting screw end, 11...female screw part end, 12...female screw part to be fastened, 14...through hole, 15...removal part, 16...gap, 17...locking bolt, 18...spring washer, 19...workpiece to be fastened, 20...female screw part, 21...first bolt, 22...second bolt, 23...small diameter male screw part, 24...small diameter female screw part, 25...gap, 26...fixing groove, AD...axial direction, WD...radial direction, HS...head side, ES...tip side

Claims (6)

A locking screw that is a male screw that is screwed into a female screw provided in a fastened member,
The locking screw can be formed by connecting two or more threaded fasteners so that the axes of the threaded fasteners are aligned,
The threaded fasteners can be connected to each other by a connecting screw having a diameter smaller than an outer diameter of the threaded fasteners,
The axis of the screw part and the axis of the connecting screw are aligned,
The pitch of the connecting thread is greater than the pitch of the threaded component;
The helical direction of the connecting screw and the helical direction of the threaded part are the same direction,
When the locking screw is screwed into the female thread of the workpiece, a boundary between the threaded parts in the axial direction of the locking screw is located within the female thread of the workpiece.
A locking screw characterized by: The connecting screw extends axially outward from one axial end side of one of the threaded fasteners connected by the connecting screw,
The other axial end of the other threaded fastener has a female thread that threadably engages with the connecting screw,
The connecting screw is screwed into the female thread of the screw part, so that the screw parts are joined together via the connecting screw to form a locking screw.
The locking screw according to claim 1. The threaded fastener has a female thread into which the connecting screw is screwed,
With the connecting screw threadedly engaged with the female thread of the threaded part,
A gap is provided between the tip of the screw and the bottom of the female thread of the screw part.
The locking screw according to claim 1 or 2. The locking screw has three or more of the threaded parts,
The screw parts are connected by the connecting screw,
all of the boundaries between the threaded parts in the axial direction of the locking screw are located within the female thread of the fastened workpiece;
The locking screw according to claim 1 or 2. At least one of the outer circumferential surface of the connecting screw, the axial end face of the connecting screw, and the axial end face of the threaded part on the connecting screw side is subjected to a rust prevention treatment.
The locking screw according to claim 1 or 2. a fixing groove for fixing an elongated removal member for removing the locking screw is provided at an axial end of the connecting screw;
The threaded fastener having the female thread has an insertion hole for inserting the removal member along an axial direction of the threaded fastener,
the insertion hole extends from an axial end of the threaded fastener having the female thread opposite the connecting screw to at least a position where the fixing groove of the connecting screw is located when the threaded fasteners are connected to each other,
A length in a short direction in a cross section of the insertion hole is shorter than a length in a long direction in a cross section of the removal member,
By inserting the removal member into the insertion hole and fixing a tip end of the removal member in the fixing groove of the connecting screw, the removal member can be rotated to simultaneously rotate the screw fastener having the insertion hole and the screw fastener having the connecting screw, thereby removing the anti-loosening screw.
The locking screw according to claim 2.

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