JPH07290156A - Mandrel of pipe bender - Google Patents

Abstract

PURPOSE:To prevent scratch, etc., at the inside corner of bending at bent part of pipe by notching the part of the inside corner of bending of a mandrel so as not to be brought into contact with the inner wall surface of pipe. CONSTITUTION:A mandrel 1 is constituted of a shank 11, first, second, third mandrel 12, 13, 14. An outside diameter of the shank 11 is about equal to an inside diameter of the pipe to be bent. An outside diameter of plural disk mandrel 12, 13, 14 is about equal to or a little bit smaller than an inside diameter of the pipe to be bent. The shank 11, mandrel 12, 13, 14 are connected through spherical bearing 12a, 13a, 14a. The part corresponding to bending corner 12b, 13b, 14b of mandrel 12, 13, 14 are notched not to be brought into contact with the inner wall surface of pipe. In this way, at pulling out the mandrel 1, the outer peripheral surface of mandrel is not brought into contact with the inner wall surface of pipe of contact with the inner wall surface of pipe of bending part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core metal for a pipe bender used when bending a pipe.

[0002]

2. Description of the Related Art Conventionally, as a core metal of a pipe bender used when bending a pipe, Japanese Patent Publication No. 50-434.
6, JP-A-51-54457, JP-A-62.
As disclosed in, for example, JP-A-33017 and JP-A-3-193220.

As shown in FIGS. 4 (a) and 4 (b), these cores are, for example, three mandrels 101a, 101.
The core metal 100 of a triple mandrel having b and 101c will be described as an example. Three mandrels 101a, 101b and 101c are provided at the tip of the shank 100a.
They are connected via 02, and can be bent in free directions around the respective axes.

That is, as shown in FIG. 4 (a), the mandrels 101a, 101b, 101c are inserted up to the bent portion 104 of the straight pipe 103, and as shown in FIG. If the pipe is bent by (not shown), the mandrel 101 bends together in the bending direction while receiving the inner wall surface of the pipe 103. Therefore, the pipe 103 should be a curved pipe 105 with a smooth curve drawn without being deformed. You can

[0005]

However, when the core metal 100 as described above is used to bend an inner surface resin lining pipe, for example, as shown in FIGS. 5 (a) and 5 (b), bending is performed. Rubbing 106 may occur at the inner corner portion 105 of the bent portion of the processed portion, which may cause a problem in the corrosion resistance of the inner surface of the pipe.

That is, as shown in FIG. 4B, the pipe 1
When the 03 bending process is performed, the resin lining layer 107 is compressed by the core metal 100 and elastically deforms along the surface of the core metal 100. Then, after the bending process is completed, the core metal 100
The resin that has been compressed by the shank 100a is temporarily released from the compression after passing through the shank 100a and is immediately compressed by the first mandrel 101a. Furthermore,
It is opened after passing through the first mandrel 101a, and immediately thereafter, it is compressed again by the second mandrel 101b. In this manner, the resin on the inner surface of the pipe is repeatedly compressed and released until the resin passes from the shank 100a to the third mandrel 101c, resulting in a slight deformation.

In particular, since the distance between the contact points between the core metal 100 and the pipe 103 becomes smaller toward the inner side of the bend, the interval between compression and release of the resin becomes shorter, and the swelling deformation concentrates around the inner side of the bend. Occur. In view of such circumstances, an object of the present invention is to provide a core metal for a pipe bender that does not cause scratches or the like on the inner surface of the bent portion during bending.

[0008]

In order to achieve such an object, a core metal of a pipe bender according to the present invention is installed in a bending portion of a pipe to be bent, and has a pipe inner diameter to be bent. In a core metal of a pipe bender, which has a plurality of disc-shaped mandrels arranged at substantially the same or a slightly smaller diameter and with a predetermined pitch, and adjacent mandrels are connected so as to bend along the bent state of the pipe, the mandrel The inside corner of the bend is cut out so as not to contact the inner wall surface of the pipe.

In the above structure, the material of the core bar is
Although not particularly limited, steel is generally used, and it is preferable that the surface is as smooth as possible.

[0010]

According to the above construction, the mandrel portion is inserted up to the bending portion of the pipe to be bent, and then the pipe is bent using the bender. Since the pipe is received from the inner surface by the mandrel, the pipe can be bent smoothly without being deformed. When the bending process is completed and the core metal is pulled out, the mandrel can be pulled out without coming into contact with the inner corner portion of the bend on the inner wall surface of the pipe of the bent portion.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 shows one embodiment of a cored bar according to the present invention. As shown in FIG. 1B, the core metal 1 includes a shank 11 and a first mandrel 1.
2, a second mandrel 13 and a third mandrel 14.

The shank 11 has an outer diameter substantially the same as the inner diameter of the pipe to be bent. The first mandrel 12 is
As shown in FIGS. 3 (a) and 3 (b), the maximum diameter portion has a diameter substantially equal to the inner diameter of the pipe and is connected to the shank 11 via the spherical bearing 12a. Two
As shown in (a), the portion 12b facing the inner corner portion 2b of the bend of the bent portion 2a is notched with a chord width of an arc of 30 °.

The second mandrel 13 is shown in FIG.
As shown in (b), the maximum diameter part has substantially the same diameter as the inner diameter of the pipe, and is connected to the first mandrel 12 via the spherical bearing 13a, and FIGS. 1 (a) and 2 (b)
As shown in, the portion 13b facing the curved inner corner portion 2b of the bent portion 2a is notched with a chord width of an arc of 45 °.

The third mandrel 14 is shown in FIG.
As shown in (b), the maximum diameter part is substantially the same as the inner diameter of the pipe, and it is connected to the second mandrel 13 via the spherical bearing 14a, as shown in FIGS. 1 (a) and 2 (c). As shown, a portion 14b facing the inner corner portion 2b of the bend of the bent portion 2a is notched with a chord width of an arc of 60 °.

That is, the distance from the center to the notch surface is shorter as the distance goes from the first mandrel 12 to the third mandrel 14. Therefore, even if the resin lining pipe 2 is bent by using the core metal 1, the resin lining layer 21 of the resin lining pipe 2 is not frayed.

That is, as shown in FIG. 3 (a), the core metal 1 has a structure in which the first mandrel 12 to the third mandrel 14 come to the bent portion 2a, as in the conventional core metal 100. 1 can be inserted into the resin lining pipe 2, and can be bent using a bender (not shown) as shown in FIG. Moreover, the first mandrel 12 to the third mandrel 14 are respectively bent portions 2a.
A portion 12b facing the inside corner portion 2b of the bend,
Since 13b and 14b are cut, the outer wall surfaces of the mandrels 12 to 14 do not come into contact with the curved inner corner portion 2b when the core metal 1 is pulled out.

Therefore, the cored bar 1 can be smoothly pulled out without causing the conventional cored bar 100 resin lining layer 21 to wrinkle or the like. The core metal of the pipe bender according to the present invention is not limited to the above embodiment. For example, in the above example, the mandrel is 3
It was continuous, but 4 or more may be used. If the mandrel portion can be flexed in any direction, the connection between the mandrel and the mandrel does not have to be a spherical bearing.

The notch amount (cutting angle, cutting displacement) of the mandrel is changed according to various conditions such as the resin material and the roundness of the pipe. Further, in the above-mentioned embodiment, the core metal is used for bending the resin-lined pipe, but for the pipe whose surface is treated with paint or the like on the inner surface of the metal pipe or the pipe formed of a highly soft metal material, etc. Is also effective. Of course,
It goes without saying that it can also be used for bending ordinary metal pipes.

[0019]

The core metal of the pipe bender according to the present invention is
Since it is configured as above, the bending work is completed,
When pulling out the core metal, the outer peripheral surface of the mandrel does not contact the inner wall surface of the pipe of the bent portion. Therefore, even if a pipe having a resin lining or a coating treatment applied to the inner surface of the pipe is bent by using this core metal, the bent corner portion of the pipe does not have a scratch or the like on the inside corner portion of the bend. .

[Brief description of drawings]

1A and 1B show a core metal of a pipe bender according to the present invention, FIG. 1A is a front view thereof, and FIG. 1B is a side view thereof.

2 is a view of each mandrel of the cored bar of FIG. 1 as seen from the front, in which FIG. 2 (a) is a first mandrel, FIG. 2 (b) is a second mandrel, and FIG. Represents each mandrel.

FIG. 3 is a view for explaining a pipe bending method using the cored bar of FIG. 1, and FIG. 3 (a) shows a state immediately before bending the cored bar by inserting the cored bar into the pipe. (B) shows the state after bending.

FIG. 4 is a diagram for explaining a conventional method of bending a pipe using a core metal, in which FIG. 4 (a) shows the state immediately before bending the pipe by inserting the core metal into the pipe; b) shows the state after bending.

5A and 5B show a resin-lined curved pipe bent by using a conventional cored bar, FIG. 5A is a sectional view thereof, and FIG. 5B is a front view showing a cut-out portion of the bent portion. is there.

[Explanation of symbols]

 1 core metal 2 resin lining pipe (pipe) 2a bending part 2b inner corner part 12 first mandrel 13 second mandrel 14 third mandrel 12b part facing inner corner part 13b part facing inner corner part 14b inner corner part The part facing

Claims (1)

[Claims] 1. A bend of a pipe having a plurality of disc-shaped mandrels which are installed in a bending portion of a pipe to be bent and are arranged at a predetermined pitch with a diameter substantially equal to or slightly smaller than an inner diameter of the pipe to be bent. In a core metal of a pipe bender in which adjacent mandrels are connected to each other so as to bend according to a state, a portion corresponding to an inner corner of bending of the mandrel is notched so as not to contact an inner wall surface of the pipe. Core metal for pipe benders.