JPH10156419A - Manufacture of lock bolt made of steel tube by cold drawing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a lock bolt made of a steel tube easily and at a low cost. SOLUTION: In the manufacturing method of the lock bolt made of the steel tube which is closed at both end parts, has the inlet for fluid and has a tubular shape which is expandable in a drilled hole of base rock by being pressurized through the inlet, at the time of manufacturing the lock bolt made of the steel tube, intervals in the opening parts of the recessed parts 6 are spreaded as advancing in the inside so that the cross-sectional shape of the tube becomes a cross having the recessed parts 6 in four directions, from a round tube by a cold drawing method, in the shape of a die, projections from the four directions are gradually made larger on an inlet taper side, projections are eliminated at the point of time when the shape is approached to the final shape in the vicinity of the center and, furthermore, the final shape is made by reducing the outside diameter of the tube in the tapered part. Consequently, the lock bolt is manufactured by single cold drawing method and at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a steel pipe lock bolt.

[0002]

2. Description of the Related Art Generally, there is a method of driving a steel bolt having a length of about 3 m into a bedrock for reinforcing a bedrock such as a tunnel. In this method, a rock is drilled and bolts are inserted, but mortar must be further filled and fixed in order to fix the bolts. Therefore, work efficiency and cost also become very poor.

[0003] In recent years, in many cases, lock bolts made of steel pipe have been used. As described in JP-B-2-5238 and JP-B-2-520, the cross-sectional shape of the pipe is circular as shown in FIG.
There is one that is bent at an angle of 180 ° or more inside one place, and the bent inside extends to almost the outside part.

[0004] Therefore, both ends of the pipe are closed, and the end is provided with an inlet through which a fluid is introduced, from which a pressure medium is sealed, and the pipe is expanded and fixed to the bedrock. According to this method, the necessary mortar filling can be omitted in the ordinary bolt, and the working efficiency and cost are greatly improved. Generally, a bent portion is formed by repeatedly pressing a round pipe several times with a lock bolt made of a steel pipe having this shape.

[0005] A method of using a conventional steel pipe lock bolt will be described with reference to Figs. As shown in FIG. 3, a hole having a circular cross-section having a circumference smaller than that of the cross-section of the steel pipe lock bolt 1 is formed in the bedrock 2. A steel pipe lock bolt 1 having both ends closed is inserted into this hole, and a pressure device 3 is inserted from the entrance side.
Apply pressure to the inside of the pipe with water pressure. This causes the pipe 1 to expand and be fixed to the bedrock 2 as shown in FIG.

A prerequisite for such a method is that it has a perimeter longer than the perimeter of the hole in the rock and is smaller than the diameter of the hole before insertion into the hole, ie before pressure expansion. For this purpose, the cross-sectional shape of a conventional steel pipe lock bolt is shown in FIG.
The shape is as shown in FIG. That is, the outer circumference is 18
A substantially sub-circumferential area spanning an angle of more than 0 ° and only one depression opposing the sub-circumferential area, wherein the depression is a part of the circumference of which the sub-circle is a part. It has a cross-sectional shape that extends beyond the center. When this is inserted into the hole and then pressurized and expanded, it has a cross-sectional shape as shown in FIG. 4 and can be fixed to the bedrock.

[0007]

In a lock bolt made of a steel pipe having a conventional shape, the cross section of the pipe has a circular outer periphery as shown in FIG.
゜ It has a shape that is bent more than once and the bent inside extends to almost the outer part. Generally, a bent portion is formed by repeatedly pressing a round pipe several times with a steel pipe lock bolt of this shape. But,
This shape is very difficult to make in manufacturing.

[0008] Two methods are conceivable as a method of manufacturing the same. The first method is a pressing method. As shown in FIG. 5, first, a circular tube 1 is depressed at one place by a press jig 4. Further, as a second step, as shown in FIG. 6, the entire tube 1 is pressed from the depression side or the side 5 of the depression. The press method requires at least two steps as described above, and increases the manufacturing cost. Moreover, the length of the normal pipe is 3
In the pressing method, a pressing machine having the entire length must be used, or in the case of a pressing machine having a short length, pressing must be repeated several times. In any case, the manufacturing cost is high.

[0009] The second method is a cold drawing method. FIG.
The drawing between the die 8 and the plug 9 is performed by a cold drawing machine as shown in FIG. First, in order to form a depression in a tube, the tube is pulled out with a die having a cross section (the same cross-sectional shape as in FIG. 5) having a projection corresponding to the depression. Then, it is pulled out with a die having a final diameter and processed into a predetermined shape. Also in this cold drawing method, at least two or more cold drawing operations are required in the conventional shape, and the cost increases accordingly. This indicates that even if the construction using the steel pipe lock bolts is more efficient and the cost is lower than that of the bolts, the cost of the steel pipe lock bolts themselves increases, and the total cost does not decrease.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lock bolt made of steel pipe in order to solve the above-mentioned problems, to provide a cross-sectional shape that is easy to manufacture, and to manufacture the lock bolt in a simple manner and at low cost.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and its gist is that the invention is closed at both ends, has a fluid inlet at the end, and is pressurized therethrough. In the method for manufacturing a steel pipe lock bolt having a pipe shape that can be expanded in a drilled hole in a rock or the like, the interval between the openings of the recesses is set at the center axis of the bolt so that the pipe cross section has a cross shape having a recess in four directions. When manufacturing a steel pipe lock bolt that is expanding as it approaches, by cold drawing from a round pipe, the shape of the die is gradually increased from the four directions on the taper side at the entrance to the die, and the center is the final part. A method for manufacturing a steel pipe lock bolt by a cold drawing method, wherein a projection is eliminated when the shape approaches the shape, and the outer diameter of the tube is further reduced at a tapered portion to obtain a final shape.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
According to the method of the present invention, the cross-sectional shape of a steel pipe lock bolt is changed from the conventional shape so that it can be manufactured at low cost. First, the cross-sectional shape will be described. As shown in FIG. 1, the cross-sectional shape is a so-called cross shape having a recess 6 in four directions. Although the relative relationship between the crosses is shifted by 90 ° from the central axis, an error of ± 10 ° is acceptable. If there is an error larger than this, bending is likely to occur during manufacturing.

Next, the opposite sides 7 forming the depressions 6
As shown in FIG. 1, the distance is increased as the distance from the central axis approaches. The diameter of the outermost periphery is smaller than the diameter before processing and smaller than the diameter of the hole drilled in the rock. The reason for increasing the distance between the opposing sides in this way is to make the diameter of the outermost peripheral portion as small as possible so that the rock can be inserted even if the diameter of the hole preceding the rock is small.

Next, a method of manufacturing a steel pipe lock bolt having this sectional shape will be described. The manufacturing method is a cold drawing method shown in FIG. 7, but in the case of the present invention, no plug is required. FIG. 8 shows the change in the drawing direction of the cross section of the die. The shape of the die is such that the projection 11 from four directions is gradually increased from the cross-sectional shape 12 to 13 on the inlet taper side 10 and the processing is performed until the vicinity of the center approaches the final shape. At this time, the protrusion is eliminated, and the outer diameter of the tube is further reduced at the tapered portion so that the cross-sectional shape becomes 14 to 15.

Normally, if the projections are left as they are,
Although processing can be performed only to reduce the diameter, the distance between the sides can be increased by continuously reducing the diameter.
After the tapered portion 10, the parallel portion 16 is used to stabilize the shape.
Is provided. The tube 17 indicates the outermost periphery, and the tube 18 indicates the locus and shape of the depression.

As described above, by using such a die of the present invention, it is possible to manufacture a shape at a low cost by a single cold drawing method even in the case of a shape which conventionally required cold drawing several times. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional steel pipe lock bolt shown in FIG.
The production method of the steel pipe lock bolts according to the method of the present invention shown in FIG. 1 was compared, and the produced steel pipe lock bolts were actually inserted into the rock to compare the performance. They are shown in Table 1. The raw tube before processing was φ42.7 × t2.5, and each having a cross-sectional shape shown in FIGS. 1 and 2 was manufactured by a cold drawing method.

[0018]

[Table 1]

As a result, in the case of the conventional method, the number of times of drawing was three times, whereas in the case of the method of the present invention, it was possible to perform one time. In addition, when the rock was actually drilled in the bedrock, the steel pipe lock bolt was inserted, and the inside of the tube was pressurized and expanded and fixed to the bedrock, there was no difference in both workability and fixing performance, and good results were obtained. Was.

[0020]

According to the conventional steel pipe lock bolt,
In general, a bent portion is formed by repeating pressing from a round tube several times. This means that even if the construction using the steel pipe lock bolts is more efficient and the cost is lower than that of the bolts, the cost of the steel pipe lock bolts themselves becomes higher and the cost is not reduced as a whole. Therefore, the present invention makes it possible to manufacture a low-cost steel pipe lock bolt by a single cold drawing method by making the cross-sectional shape easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a sectional view of a steel pipe lock bolt of the present invention.

FIG. 2 is a cross-sectional view of a conventional steel pipe lock bolt.

FIG. 3 is a cross-sectional view showing a method for fixing a steel pipe lock bolt to rock.

FIG. 4 is a diagram showing a cross-sectional shape of a conventional steel pipe lock bolt when inserted into rock and when expanded.

FIG. 5 is a cross-sectional view showing a first-stage working method during press working in a conventional method.

FIG. 6 is a cross-sectional view showing a second-stage working method at the time of press working in a conventional method.

FIG. 7 is a cross-sectional view showing a cold drawing machine in a conventional method.

FIGS. 8A and 8B are diagrams showing the shape of the die of the present invention, wherein FIG. 8A is a cross-sectional view of a cold drawing machine, and FIGS.

[Explanation of symbols]

1: steel pipe (or steel pipe lock bolt) 2: rock mass 3: pressurizing device 4: press jig 5: pressing direction 6: depression 7: side 8: die 9: plug 10: die taper portion 11: die protrusion 12, 13, 14, 15: sectional shape of die 16: parallel part of die 17: outermost peripheral part of pipe 18: hollow part of pipe

Claims (2)

[Claims] 1. A method for producing a steel pipe lock bolt having a tubular shape which is closed at both ends, has a fluid inlet at the end, and is pressurized therethrough and expandable in a borehole such as rock. When manufacturing by a cold drawing method from a round pipe, a steel pipe lock bolt which has an opening interval between depressions that becomes wider as approaching the bolt center axis so that the cross section of the pipe becomes a cross shape having depressions in four directions. On the taper side of the entrance to the die, gradually increase the protrusions from four directions, eliminate the protrusions when the center nears the final shape, and reduce the outer diameter of the tube at the tapered portion to the final shape A method for producing a steel pipe lock bolt by a cold drawing method. 2. The rock bolt made of steel pipe by the cold drawing method according to claim 1, wherein the cross-sectional shape of the cross section of the pipe having recesses in four directions is within 90 ° ± 10 °. Manufacturing method.