JP2004017083A - Method for drilling hole in pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for drilling a hole in a pipe which can avoid the collapse of a hole drilling part, does not generate burrs and flash and chip and, in addition, can shorten the drilling time. <P>SOLUTION: In this method for drilling a hole in a pipe, a front end face (13a) of a punch (13), to which voltage has been applied from a power source (14), is brought into contact with the surface of a pipe (11) to form a closed electric circuit. Next, while pushing the front end face (13a) of the punch into the pipe (11), the pipe (11) in its part in contact with the punch (13) is superheated by taking advantage of resistance heating upon the contact of the punch (13) with the pipe (11). The above contact part of the pipe (11) softened by the superheating is punched by the pressing force of the punch (13) to form a hole in the pipe (11). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pipe drilling method for drilling a thick wall portion of a pipe.
[0002]
[Prior art]
Conventionally, this type of pipe is drilled by cutting with a drill, fusing with laser or plasma, or by inserting a mandrel 2 into the pipe 1 as shown in FIG. Press punching using a punch 3 is generally known.
[0003]
However, the above-mentioned method of drilling a pipe has a problem in that the pipe is slightly crushed, burrs or burrs are generated on the surface, and the sealing performance when performing a packing seal near the hole is reduced.
Furthermore, cutting by cutting and fusing using a laser or plasma require a long processing time, and also cause problems such as generation of minute chips and spatter chips.
Also, in the press punching process, the mandrel 2 may not be inserted depending on the bent shape of the pipe 1 and the processing position of the hole, and if the press punching is performed without using the mandrel 2, the hole processed portion is crushed. There is a problem.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems, and has as its object to avoid crushing a drilled portion, without generating burrs, burrs, and chips, and processing It is an object of the present invention to provide a pipe drilling method capable of reducing time.
[0005]
[Means for Solving the Problems]
That is, in the method for drilling a pipe according to the present invention, a closed electric circuit is formed by bringing the tip end face of the punch to which a voltage is applied into contact with the pipe surface, and the punch is brought into contact with the pipe while pushing the tip end face into the pipe. The contact portion of the pipe with the punch is overheated by the resistance heating accompanying with the above, and the contact portion of the softened pipe is punched out by the pressing force of the punch to form a hole in the pipe.
[0006]
As described above, the drilling method of the present invention reduces the shear strength by thermally softening the drilled portion of the pipe, and punches a hole in this state, so that the drilled portion of the pipe does not collapse. In addition, it is possible to reduce the time required for drilling without generating burrs on the periphery of the hole, burrs on the hole surface, and minute chips.
[0007]
And in the pipe drilling method of the present invention, it is preferable that the tip end surface of the punch is flat. By using such a flat punch, the shearing point moves sequentially from the top to the outside on the curved surface of the pipe, so that the current flows to the shearing point and heat is efficiently generated.
It is preferable that the power supply to the punch is stopped almost simultaneously with the punching of the hole. Thereby, the discharge in the pipe due to the cut off of the current supply path is avoided, and the deformation of the hole due to the discharge can be avoided.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 to 4 show an example of a method for drilling a pipe according to the present invention. Here, a method for drilling a hole in a wall surface of a cylindrical steel pipe is shown.
[0009]
That is, as a method for drilling the pipe 11, first, as shown in FIG. 1, the pipe 11 is horizontally supported by a pipe receiver 12, and a punch 13 having a flat end surface 13a is directed downward on the pipe receiver 12. Place. In this case, a voltage is applied from the power supply 14 between the pipe receiver 12 and the punch 13, and an electric circuit including the pipe receiver (receiving electrode) 12, the pipe 11, the punch (punch-side electrode) 13, and the power supply 14 is configured. You.
[0010]
Next, the punch 13 is lowered vertically toward a position where a hole is formed in the wall surface of the pipe 11 and pressed with a force that does not cause crushing. At this time, when the tip surface 13a of the punch 13 contacts the top of the curved surface of the pipe 11, the electric circuit is closed and a current A flows from the power source 14 to the pipe 11, and the contact portion of the pipe 11 with the punch 13 by resistance heating. Is instantaneously locally heated and softened, and the shear strength of the pipe 11 decreases. Then, as shown in FIG. 2, the sheared portion 11a of the pipe 11 moves outward, and the entire distal end surface 13a of the punch 13 comes into contact with the wall surface of the pipe 11. In this case, since the distal end surface 13a of the punch 13 is formed flat, the shearing point 11a sequentially moves outward from the top on the curved surface of the pipe 11, and the current A concentrates on the shearing point 11a. The part will be heated efficiently.
[0011]
Further, when the punch 13 is continuously pressed, as shown in FIG. 3, the movement of the shearing portion 11a of the pipe 11 progresses, and the shearing of the contact portion extends to the entire thick portion, and soon, the punching process is performed as shown in FIG. Then, a hole 11b is formed in the wall surface of the pipe 11.
[0012]
Here, when a discharge occurs in the pipe 11 after the punch 13 punches the hole 11b, the shear surface is melted and the roundness of the hole 11b is reduced. Therefore, in the present invention, the displacement of the punch 13 is detected by a position sensor (not shown), and control is performed so that the energization is stopped at the same time as the hole 11b is punched out. That is, as shown in FIG. 5, energization starts when the position sensor detects a position (S) where the punch 13 contacts the pipe 11, and energizes when the position sensor detects a position (E) where the hole 11b is punched. Is controlled so as to stop.
Note that a timer is used instead of the position sensor, and when the punch 13 comes into contact with the pipe 11, the timer is started at the same time as the energization is started, and the time is up after a predetermined time required to complete the punching of the hole 11b. You may make it stop.
Further, as shown in FIG. 6, the shear strength of the pipe 11 starts to drop sharply from around 500 ° C. Therefore, it is preferable to set the heating current A so that the temperature of the portion of the pipe 11 in contact with the punch 13 becomes 500 ° C. or higher.
[0013]
As described above, in the method for drilling a pipe according to the embodiment of the present invention, the pipe 11 is heated while being pressed by the punch 13, and the hole 11b is drilled at the moment when the shear strength is reduced. Eleven roundness can be maintained. Further, since the conventional mandrel is not required, it can be applied to the drilling of a complicated hollow structure. Furthermore, the processing time is about 1/10 of press punching at room temperature, and there is no generation of minute chips and spatters unlike drilling, and there is no need for cleaning because processing oil is not required. . Further, drilling can be realized with a resistance welding machine, equipment costs are low, and mass productivity is excellent.
[0014]
Next, the present invention will be described more specifically with reference to examples.
A pipe made of steel (STKM 11A) having a diameter of 12.7 mm and a thickness of 1.2 mm was used as the pipe 11, and was horizontally supported by a chromium copper pipe receiver 12 having a radius of curvature of 6.9 mm. Using a spot welder made of copper tungsten having a diameter of 8.0 mm, the punch 13 having a flat tip surface, the pipe receiver 12 and the punch 13 were electrically connected, and a high voltage at a frequency of 5 cycles / min was applied.
The punch 13 is pushed vertically downward into the wall of the pipe 11 with a pressing force of 240 kgf, and the application of the voltage is stopped at the moment when the pipe 11 is pierced. No steel chips are generated and the roundness of the pipe 11 is maintained. It had been. The current flowing through the pipe 11 was 11,000A.
[0015]
The present invention is not limited to the pipe drilling method shown in the above embodiment, and various changes can be made without departing from the spirit of the invention described in the claims.
For example, in the embodiment, the tip end surface 13a of the punch 13 is flat. However, as shown in FIG. 7, the tip end 15a may have a stepped shape. It is effective for narrowing. The pressing force of the punch 13 on the pipe 11 varies depending on the material of the pipe 11, but is generally in the range of 100 to 500 kgf, preferably in the range of 200 to 300 kgf.
Note that the shape of the pipe is not limited to a cylindrical shape, and the cross-sectional shape may be, for example, a square or an ellipse. The material of the pipe is not particularly limited as long as it is a metal or an alloy having a characteristic according to various uses and having a high electric resistance. Further, as a material of the pipe receiver, chromium copper, beryllium copper alloy, or the like can be cited, and a punch made of copper tungsten is usually used.
In the present invention, a pipe to be drilled is used as a gas supply pipe connected to a gas inlet provided in a gas control device such as a gas cock or a gas valve attached to a gas appliance.
[0016]
【The invention's effect】
As understood from the above description, according to the present invention, burrs around the hole and burrs and chips on the pipe surface are not generated, and a hole is formed in the pipe in a short time while maintaining the roundness of the pipe. Can be.
[Brief description of the drawings]
FIG. 1 shows an example of a pipe drilling method according to the present invention, in which (a) is an explanatory view showing a state where a punch contacts a pipe, and (b) is orthogonal to (a). It is explanatory drawing seen from the direction.
2 (a) is an explanatory view showing a state where a sheared portion of a pipe is expanded outward from the state shown in FIG. 1, and FIG. 2 (b) is an explanatory view when (a) is viewed from a direction perpendicular to the pipe. .
3 (a) is an explanatory view showing a state where the sheared portion of the pipe has further moved from the state shown in FIG. 2, and FIG. 3 (b) is an explanatory view showing (a) as viewed from a direction perpendicular to FIG.
4A is an explanatory view showing a state in which the drilling of a pipe has been completed from the state shown in FIG. 3, and FIG. 4B is an explanatory view of FIG.
FIG. 5 is an explanatory diagram showing the timing of starting and stopping the energization of the pipe shown in FIG. 1;
FIG. 6 is a graph showing a relationship between a shear strength of a pipe and a heating temperature.
FIG. 7 is a front view showing the tip of another punch used in the method for drilling a pipe according to the present invention.
FIG. 8 is an explanatory diagram showing an example of a conventional pipe drilling method.
[Explanation of symbols]
11 ... Pipe, 11a ... Shearing point, 11b ... Hole, 12 ... Pipe receiver, 13 ... Punch, 13a ... Tip surface, 14 ... Power supply.

Claims (4)

The tip of the punch to which the voltage is applied is brought into contact with the pipe surface to form a closed electric circuit. A method for drilling a pipe, comprising heating a portion and punching out the contact portion of the softened pipe with a pressing force of a punch to form a hole in the pipe. 2. The method according to claim 1, wherein a tip surface of the punch is flat. 3. The method according to claim 1, wherein the power supply to the punch is stopped almost at the same time when the contact portion of the pipe is punched. The method according to any one of claims 1 to 3, wherein the pipe is used as a gas supply pipe connected to a gas inlet of a gas control device in a gas appliance.

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