JPH03480Y2 - - Google Patents

Description

[Detailed explanation of the invention] Technical field of the invention The lock bolt of the invention, more specifically NATM (New Austrian Tunneling)
This invention relates to lock bolts that can be used as supports for tunnel construction, underground power plants, oil storage facilities, and other underground cavernous construction works, or as anchors for slope reinforcement work.

Prior Art This type of lock bolt has a mechanism in which a hole is drilled in a construction surface such as a tunnel wall, a bolt is inserted into the hole, and a fixing device is installed at the tip of the bolt, or the hole is filled with adhesive for anchoring. The other end is threaded, and a washer and nut are attached to the threaded part of the bolt.

Conventionally, this type of lock bolt has two types: one in which the bolt thread part is formed by rolling and the thread part is a normal thread (mainly metric thread) similar to a general bolt that is not a lock bolt, and the other in which the bolt thread part is formed by rolling. A deformed reinforcing bar with a spiral protrusion formed over its entire length by hot rolling on the surface is cut to the required length and used as a lock bolt (thus, the threaded part of the bolt is formed by the spiral protrusion). It has been known.

The former conventional lock bolt described above has the following drawbacks.

Because the corners of the bolt threads are sharp,
Easy to injure workers' fingers and hands. In particular, if the rolling of the threaded part is incomplete, the thread will have a serrated cross-section, making it more likely to be damaged, and the height of the thread will be relatively high, and the bolt material that has been ground before rolling will be curved. If there is, there is a high possibility that the rolling will be incomplete.

Due to the shape of the screw thread, it easily deforms when it comes into contact with other objects. If the threads are even slightly deformed, the nut will not fit. Moreover, the construction site for lock bolts is an environment where they are likely to collide with other objects, and the actual packaging is simple, consisting of several lock bolts wrapped together and the threaded part wrapped in cloth. The protection of the parts is insufficient.

The slope of the thread is steep and there is a lot of resistance when inserting the nut.

Since the height of the thread is relatively high, the height of the thread at the beginning of the thread is also high, making it difficult to thread the nut onto the threaded part of the bolt, and sometimes the thread may become jammed.

The thread pitch of the bolt thread part is relatively small,
In addition, since the height of the thread is relatively high, the surface area of the thread is large, and the frictional resistance against the threading of the nut is correspondingly large, resulting in poor workability.

The strength of a lock bolt is determined by the strength of the threaded portion, or in other words, the cross-sectional area of the threaded portion, but the cross-sectional area of the threaded portion is not sufficient. In other words, in order to roll the threaded portion of a lock bolt, it is first necessary to prepare the lock bolt material with protrusions to improve the anchoring effect, and of course the cross-sectional area of the portion corresponding to the threaded portion is reduced by the preparation. In order to obtain the required relatively high thread height by rolling, the pre-cut diameter must also be relatively small.

On the other hand, compared to the former, the latter conventional lock bolt has a better nut stiffness and is superior in workability, but on the other hand, the threads formed by rolling do not all have the correct shape, so there is a large amount of play between the bolt and the nut.
Introducing prestress to lock bolts is undesirable because the torque coefficient when screwing the nut is more than twice that of a metric screw. In relatively narrow and limited areas, it is often impossible to use a large tightening machine that requires a large output to apply the necessary prestress load. Because it is extremely large and has a large pitch, it has less engagement with the nut, so the nut needs to be 4 to 5 times the size of a metric thread nut, which increases the cost and makes it difficult to install tunnels, etc. There is a significant economic disadvantage in terms of the total number of lock bolts to be used for the object to be constructed.

Purpose of the invention Therefore, the present invention has a nut with good stiffness and excellent workability, does not injure the hands or fingers even if the threaded part is held with bare hands, is difficult to damage the threaded part, and has a cross-sectional area of the threaded part in meters. It can be increased significantly compared to screws,
Moreover, the torque coefficient is almost the same as that of metric screws,
The purpose is to provide an economical locking bolt that can introduce prestress with a small tightening force.

Structure of the invention The lock bolt of the invention is characterized in that the threaded portion of the bolt is a light bulb screw (that is, the screw of the E-shaped cap and receiver), and the threaded portion may be formed by rolling.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the figure, 1 is a lock bolt, and the lock bolt 1 has a threaded portion 2 that is a light bulb screw. In this example, the other parts of the lock bolt 1 are conventionally known SN
It is the same as that of a lock bolt using an anchor. 3 is Wasshya, 4 is Natsuto.

Effects of the invention In the present invention, the threaded portion 2 is a light bulb screw, that is, its thread is round and low, so the height of the nut 4 is of course lower than that of a conventional regular threaded lock bolt, and it is also a modified reinforcing bar type. It is better than that of the lock bolt, and excellent workability can be obtained, and even if the threaded part 2 is held with bare hands, it will not injure the hands or fingers, and the thread shape and height are suitable for rolling workability. It is also excellent, allowing perfectly formed screws to be rolled, and there is no injury to hands or fingers due to poor thread rolling. In addition, the threaded portion 2 is less susceptible to damage than either a conventional regular thread type lock bolt or a deformed reinforcing bar type lock bolt.

Furthermore, according to the present invention, the cross-sectional area of the threaded portion 2, in other words, the strength of the lock bolt can be greatly increased compared to that of a metric thread.
By the way, the SN anchor TD24 (nominal diameter: 23.8 mm) is in the form shown (however, JIS C 7709, which specifies the standards for light bulb screws, does not have a standard (size) for E24, and is one step higher than the standard for E17. Since it is E26,
The eight types of standards listed in JIS C 7709 above,
E10, E12, E14, E17, E26, E27, E39 and E40
According to the step above, the outer diameter, root diameter, pitch, γ, etc. were determined proportionally, and the bolt thread part 2 was made to be equivalent to E24. ), the inventor's experimental results revealed that a light bulb screw with good threads could be obtained by rolling a material with a pre-cut diameter of 22.70 mm.
With this pre-cut diameter, the cross-sectional area of the threaded part 2 after rolling is
394 mm ² , which is 11.6 mm compared to the M24 metric thread with a pre-cut diameter of 21.90 mm and a cross-sectional area of 353 mm ² .
% increase. That is, if the threaded portion 2 is a light bulb screw, the undercut required for thread rolling can be reduced to a diameter almost close to the base circle of the lock bolt material,
This allows the cross-sectional area of the lock bolt material to be utilized to its maximum potential.

Furthermore, in the present invention, the torque coefficient is almost the same as that of a metric thread when the thread diameter is the same, and prestress can be introduced into the lock bolt with a small tightening force. To explain this with specific numerical values, in the inventor's experiments, the locking bolt of the light bulb screw of E24 (the sample shown above, the SN anchor) was found.
TD24), the torque coefficient K=0.18,
The M24 metric thread lock bolt had K=0.17. This torque coefficient, 0.18 is generally M24
A locking bolt with a metric thread has a torque coefficient of K.
Considering that the actual situation is 0.2, it can be said that it is almost the same as the torque coefficient of a metric thread.

The experimental conditions for determining the torque coefficient are as follows.

In both the present invention and the comparative example, the samples were made by rolling the required screws on a steel bar material, the tip of the sample was fixed with mortar in a steel pipe that was gripped and fixed in a vise, and the load cell was applied with washer back and forth. Then, set it on the other end of the sample, attach a nut to the threaded part of the sample, tighten it with a torque wrench, read the axial force load generated at that time with the load cell, and graph the relationship with the tightening torque. Then calculate the torque coefficient.

In addition, the present invention is economical because it is possible to roll a screw with a maximum diameter that is not much different from the cross-sectional area of the base circle of the lock bolt material, as described above. The strength of the lock bolt depends on the cross-sectional area that is reduced by the preliminary cutting required for rolling the threaded part. Therefore, the strength of the thread part, that is, the cross-sectional area, is preferably closer to the cross-sectional area of the material, and the strength and price of the lock bolt Considering this, it can be said that it is most economical to roll the largest screw as close to the cross-sectional area of the material as possible.

[Brief explanation of drawings]

The drawing is a front view showing an embodiment of the present invention. 1 is the lock bolt, 2 is the threaded part, 3 is the washer, and 4 is the nut.

Claims (1)

[Scope of utility model registration request] A lock bolt with a light bulb screw as the bolt thread.