JP3292776B2 - Mold for resin coating on inner surface of metal / resin composite tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for continuously manufacturing a composite pipe in which the inner surface of a metal tube is coated with a resin, by inserting the inside of the metal tube and extruding a molten resin onto the inner surface thereof.
The present invention relates to a mold for forming an inner resin layer.

[0002]

2. Description of the Related Art In a pipe used for transferring a fluid such as water supply, hot water supply, or drainage, an inner surface of a metal pipe is coated with a resin for the purpose of improving corrosion resistance and chemical resistance.
A so-called metal / resin composite tube is known.

[0003] As a method of manufacturing such a metal / resin composite tube, conventionally, a metal tube and a resin tube are separately manufactured, and then a resin tube is bonded to the inner surface of the metal tube via a resin. In addition to the production method, there is a continuous production method in which a resin is extruded and coated on the inner surface at the same time as a continuous production of a strip-shaped metal material.

In the continuous production method, as shown in FIG. 3, a schematic process diagram is provided, in which a band-shaped metal material 11 set on an uncoiler 21 is supplied to a pre-bending portion 23 via a pre-processing portion 22 and has a substantially U-shaped section. After being formed into a U-shape, the metal material 12 having a substantially U-shaped cross section is guided to a pipe-making portion 25 via a heating portion 24 and formed into a tubular shape so as to abut both side edges of the metal material. Are welded by a welding machine 26 to continuously manufacture the metal tube 13. Then, a resin extrusion die 27 is inserted from the opening of the metal material in the process of forming the tube portion 24, and a molten resin is continuously extruded onto the inner surface of the metal tube 13 after welding to form an inner resin layer. (For example, JP-A-4-39032). According to this continuous production method, many advantages can be expected in terms of productivity and the like as compared with the batch production method.

[0005] In the above continuous manufacturing method, conventionally,
A resin extrusion die whose cross-sectional view is illustrated in FIG. 4 is used. That is, the resin extrusion mold used in this type of manufacturing method has a resin passage 31a and a resin outlet 31b at the tip thereof, which are provided with a resin outlet 31b in order to supply a molten resin into the metal tube 13 from an opening during molding. An outer mold 31 having a character shape and an inner mold 32 having a function as a sizing core for regulating the thickness and the like of a resin discharged into the metal tube 13 from the tip of the outer mold 31. . The inner mold 32 has a tip 32a that protrudes from the resin outlet 31b at the tip of the outer mold 31 in the resin outflow direction and functions as the above-described sizing core, and one end has a tip to position and fix the tip 32a. A rod-shaped support portion 32b is fixed to the portion 32a, penetrates the inside of the horizontal portion of the resin flow channel 31a, and is fixed to the outer mold 31 at the upstream end of the resin flow channel 31a via the fixing portion 32c. Have been.

Further, since the inner mold 32 is cantilevered by the fixing portion 32c, and the position of the tip portion 32a with respect to the center of the metal tube 13 is difficult to be determined, usually, the resin outlet 3
A plurality of inner mold gap adjusting positioning bolts 3 for adjusting the position of the tip 32a of the inner mold 32 near 1b.
3 are disposed radially across the resin flow path 31a.

[0007] With such a resin extrusion mold, the molten resin supplied into the resin flow path 31a from an external extruder or the like,
It is extruded into the metal tube 13 from the front end opening portion 31b of the outer mold 31 and the inner peripheral surface of the metal tube 13 and the front end portion 32 of the inner mold 32.
a is formed along the cylindrical gap between the outer peripheral surface of the metal pipe 13 and the resin tube 14.
The metal / resin composite pipe 15 lined with the above.

[0008]

According to the above-described conventional resin extrusion die, the bar-shaped support portion 32b of the inner die 32 penetrates the horizontal portion of the resin flow passage 31a.
As a result, the cross-sectional area of the resin flow path 31a is reduced, and the resin discharge amount is limited. As a result, there is a problem that the pipe production speed is restricted. That is, if the resin discharge amount is forcibly increased in such a structure, the resistance in the resin flow section increases, and the resin pressure increases, so that good lining cannot be performed.

If the positioning bolt 33 for adjusting the clearance between the inner molds is provided in the vicinity of the resin outlet 31b of the resin flow path 31a, the flow of the resin becomes partially non-uniform due to the influence of the bolt. In addition, there are problems that the thickness of the resin layer 14 varies in the circumferential direction and that the surface roughness of the resin layer 14 tends to be non-uniform.

The present invention has been made in view of such circumstances, and it has been possible to increase the resin discharge rate and improve the pipe production speed as compared with a conventional resin extrusion die, and to obtain the present invention. It is an object of the present invention to provide a mold for coating the inner surface of a metal / resin composite tube, which can make the thickness and surface roughness of the resin layer more uniform.

[0011]

The structure for achieving the above object will be described with reference to FIG. 1 which is an embodiment drawing. The mold for coating the inner surface resin of a metal / composite pipe according to the present invention comprises:
The outer mold 1 is inserted into the metal tube 13 from the opening part of the belt-shaped metal material being formed and has a resin flow path 1a formed at the center thereof, and the resin flow path 1a of the outer mold 1 is formed. In the vicinity of the downstream end, one end is fixed via a fixing member 3, and the other end has an inner mold 2 that faces the inner surface of the metal tube 13 beyond the end of the outer mold 1. 3 is a cylindrical outer frame 3a provided with a position adjusting mechanism 4 in the radial direction with respect to the outer mold 1 along the inner wall surface of the resin flow path 1a of the outer mold 1 and between the inner wall surface and the resin flow path 1a. A plurality of arm-shaped members 3b extending from the inner surface of the outer frame 3a toward the center and holding one end of the inner mold 2, and each of the arm-shaped members 3b is streamlined along the flowing direction of the molten resin. It has a cross-sectional shape
The tip B of the outer mold 1 near the resin outlet is
It can be detachably attached to the main part A of the outer mold 1 with screws.
Between the tip B and the body A
In the meantime, with the outer frame 3a of the fixing member 3 inserted,
The outer periphery of the tip portion B of the outer mold 1 is
The diameter of the metal tube is slightly larger than the diameter of the metal tube A.
13 and the outer mold 1 and the metal tube 13 are in contact with each other.
Is characterized by being centered on

[0012]

The inner mold 2 does not penetrate the horizontal portion of the resin flow path 1a of the outer mold 1, but is fixed at one end by a fixing member 3 provided near the downstream end of the resin flow path 1a. Therefore, the resin flow path 1a has a large cross-sectional area in most parts except the vicinity of the outlet part, and as a result, the flow resistance of the resin is reduced, so that the resin discharge amount can be increased.

The inner mold 2 extends from the outer frame 3a along the inner surface of the resin flow path 1a toward the center, and is formed by a streamlined arm-shaped member 3b along the resin flow direction. And the position adjustment is performed by a position adjusting mechanism 4 in the radial direction between the inner surface of the resin flow path 1a and the outer frame 3a along the inner surface, and the resin flow path 1a is adjusted. Is not directly traversed by the bolt, the flow of the resin becomes more uniform, and the thickness and surface roughness of the resin layer can be made uniform.

[0014]

FIG. 1 is a central sectional view (A) showing the overall structure of an embodiment of the present invention, and its II sectional views (B) and (B).
It is II-II sectional drawing (C) of a figure.

The outer mold 1 has a substantially L-shape as a whole, and has a uniform resin flow path 1a formed along the center line thereof. The other end is connected to an extruder or the like to form a resin supply port 1c through which the molten resin is supplied. The outer mold 1 is provided with a tube forming section 2 in the process shown in FIG.
5 from the opening of the strip-shaped metal plate being formed
3 and the resin outlet 1b is arranged so as to extend beyond the welding point by the welding machine 26 to the downstream side in the pipe making direction.

One end of the inner mold 2 is fixed via a fixing member 3 in the vicinity of the downstream end of the resin flow path 1a of the outer mold 1. The inner mold 2 is formed integrally with the tip 2a projecting from the resin outlet 1b of the outer mold 1 into the metal tube 13 and serving as a sizing core, and the tip 2a.
It is constituted by a rod-shaped support member 2b fixed at one end by a fixing member 3.

As shown in FIG. 2B, the fixing member 3 has a cylindrical outer frame 3a along the inner wall surface of the resin flow path 1a of the outer mold 1.
And a plurality of arm-shaped members 3b extending from the inner surface of the outer frame 3a toward the center.
a is fixed in a state where it is positioned with respect to the outer mold 1 by a position adjusting mechanism 4 described later, and the rod-shaped support member 2b of the inner mold 2 is fixed at the tip of the arm-shaped member 3b.

A tip portion of the outer mold 1 near the resin outlet 1b.
B is detachably attached to the main body portion A of the outer mold 1 by a screw , and has a front end portion B and a main body portion.
A is fixed in a state where the outer frame 3a of the fixing member 3 is inserted between the outer frame 3A and the outer frame 3A. That is, a step portion having a diameter larger than that of the resin flow path 1a is formed in the predetermined region at the front end of the main body portion A , and a female screw for screwing the front end portion B is formed at the front end side of the step portion. The outer diameter of the outer frame 3a of the fixing member 3 is slightly smaller than the inner diameter of the step portion of the main body portion A , and the outer frame 3a of the fixing member 3 is moved along the inner surface of the step portion with the distal end portion B removed. Then, by screwing the distal end portion B , the outer frame 3a is sandwiched between the inner end surface of the stepped portion of the main body portion A and the end surface of the distal end portion B. It is fixed to the mold 1.

The outer periphery of the distal end portion B of the outer mold 1 has a slightly larger diameter than the main body portion A , and this large diameter portion comes into contact with the inner surface of the metal tube 13 so that the outer mold 1 and the metal The tube 13 and the tube 13 are centered with each other. And
The outer mold 1 has an outer frame 3a of the fixing member 3 from the outer periphery thereof.
Four (or three) adjustment screws 4a are respectively screwed vertically toward the outer peripheral surface of. The adjusting screws 4a are arranged radially at an equal angle with respect to the center axis of the fixing member 3, and are appropriately screwed or unscrewed to adjust the fixing member 3 with respect to the outer mold 1. The radial position can be adjusted. Here, since the inner mold 2 is fixed to the fixing member 3, after all, each adjusting screw 4 a functions as the adjusting mechanism 4 for adjusting the clearance of the tip 2 a of the inner mold 2 with respect to the metal tube 13. Function.

Each arm-shaped member 3b of the above-mentioned fixing member 3
Has a streamlined cross-sectional shape along the direction in which the resin flows in the resin flow path 1a, as shown in FIG. Also,
The outer diameter of the rod-shaped support member 2b of the inner mold 2 near the portion fixed to the fixing member 3 is smaller than that of the portion adjacent to the tip 2a, and the rod-shaped support member 2b is fixed to the fixing member 3. The end face on the side where the resin flows, that is, the end face facing the flow of the resin in the resin flow path 1a is sharpened in a conical shape.

As a specific method of fixing the inner mold 2 to the fixing member 3, for example, as shown in FIG. 1A, the rod-shaped support member 2b of the inner mold 2 is integrated with the tip 2a. Divided into two parts before and after the part integrated with each arm-shaped member 3b of the fixing member 3, and at the respective butted end faces, an external thread is cut into one side and a female thread is cut into the other side to be integrated with each other. Such a method can be adopted. In this case, for example, a hexagonal hole 2c is provided on the end face of the tip 2a of the inner mold 2, and the fixing member 3 is mounted on the outer mold 1, and then a hexagon wrench or the like is inserted into the hexagonal hole 2c to form the tip 2a.
What is necessary is just to screw in the part containing a.

In the embodiment of the present invention described above, when the molten resin is supplied from the resin supply port 1c of the outer mold 1, the resin flows in the resin flow path 1a and is cylindrically formed in the metal tube 13 from the resin outlet 1b. Extruded, the inner peripheral surface of the metal tube 13 and the inner mold 2
The resin layer 14 is formed along a cylindrical gap defined by the outer peripheral surface of the tip 2 a of the metal tube 13 and covers the inner peripheral surface of the metal tube 13.

In the above-described molding process, there is no object in the resin flow path 1a from the resin supply port 1c to the fixing member 3 or the position where the rod-shaped support member 2b of the inner mold 2 is disposed at all. Therefore, the resistance to the flow of the molten resin is reduced as compared with the case where the conventional extrusion die illustrated in FIG. 4 is used. As a result, the discharge amount of the resin can be further increased, and the pipe forming speed is improved. It becomes possible. The resistance to the flow of the molten resin is such that the outer diameter of the rod-shaped support member 2b of the inner mold 2 is made smaller on the upstream side of the resin than on the downstream side as in the embodiment, and further, on the rod-shaped support member 2b. By making the shape of the end surface facing the resin upstream side conical, the size can be further reduced.

The molten resin discharged from the resin outlet 1b into a cylindrical shape is fixed to the fixing member 3 near the outlet 1b.
Although the arm-shaped members 3b pass through the plurality of arm-shaped members 3b, each arm-shaped member 3b has a streamlined cross section along the flow of the resin, so that the flow is hardly obstructed. The resin flow to be discharged becomes uniform, and the resulting resin layer 14 is less likely to have uneven thickness and uneven surface roughness.

An example in which a metal / resin composite tube is actually manufactured using the embodiment of FIG. 1 will be described below. In the embodiment of FIG. 1, 6 mm substantial dimension L of about 30mm of the inner mold 2 present in the resin flow path 1a, the outer diameter D ₁ of the upstream side of the rod-like support member 2b, the outside diameter of the downstream Dimension D ₂ to 8
mm and the inner diameter of the resin flow path 1a is 12 m
m was compared with a mold having the structure shown in FIG.

In the comparative example shown in FIG. 4, the substantial dimension L 'of the inner mold 32 existing in the resin flow path 31a is 110 mm.
The outer diameter of the rod-shaped support member 32b is constant at 8 mm, and other dimensions, resin pressure and melting conditions of the resin, and other conditions such as the thickness of the resin layer 14 are completely equal. In the invention example, about 1.3 to about as compared with the comparative example.
It was possible to achieve 1.7 times the line speed (pipe production speed).

Further, by examining the cross section of the obtained composite pipe,
As shown in FIG. 2, the thickness t at the position corresponding to the downstream of each arm-shaped member 3b in the embodiment of the present invention, or the position corresponding to the downstream of each inner mold gap adjusting positioning bolt 33 in the comparative example of FIG. The surface roughness was measured, and the thickness t 'and the surface roughness of the other portions were measured, and the difference between the two was determined. As shown in Table 1 below, the thickness was reduced in the examples of the present invention. Both the difference and the difference in surface roughness were smaller than in the comparative example, and it was confirmed that the resin flow was more uniform than in the comparative example.

[0028]

[Table 1]

[0029]

As described above, according to the present invention,
In a mold for continuously inserting a metal pipe from a band-shaped metal material and extruding molten resin by inserting the metal pipe into the inside thereof, a downstream end portion of a resin flow path of an outer mold having a resin flow path formed therein. In the vicinity, one end of the inner mold is fixed via a fixing member, and the fixing member is fixed to a cylindrical outer frame along the inner wall surface of the resin flow path of the outer mold, and the center of the inner frame from the inner surface of the outer frame. And a plurality of arm-shaped members extending toward the inner mold to hold one end of the inner mold, and the cross-sectional shape of the arm-shaped member is streamlined along a resin flowing direction. Since a structure with a position adjustment mechanism in the radial direction with respect to the outer mold is adopted between the frame and the inner wall surface of the resin flow path,
As compared with the conventional mold in which the inner mold is supported by a rod-shaped support member that penetrates the inside of the resin passage of the outer mold, and bolts for adjusting the inner mold clearance are provided near the resin outlet. The resistance of the resin in the inside is reduced, and the discharge amount of the resin can be increased. As a result, it is possible to further improve the pipe production speed, and there are factors that obstruct the flow of the resin discharged from the resin outlet. As a result, a more uniform flow is formed, and as a result, variations in the thickness of the obtained resin layer in the radial direction and variations in the surface roughness are reduced. Could be obtained.

[Brief description of the drawings]

FIG. 1 is a central cross-sectional view (A), its II cross-sectional view (B), and a II-II cross-sectional view in (B) showing the entire configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of evaluation of a resin layer 14 according to an embodiment of the present invention and a comparative example.

FIG. 3 is an explanatory view of a process by a continuous production method of a metal / resin composite pipe to which the present invention is applied.

FIG. 4 is a central cross-sectional view showing the overall configuration of a conventional inner resin coating mold.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 outer mold 1a resin flow path 1b resin outlet 1c resin supply port 2 inner mold 2a tip 2b rod-shaped support member 3 fixing member 3a outer frame 3b arm-shaped member 4 position adjustment mechanism 4a adjustment bolt 13 metal tube 14 resin layer

Claims (1)

(57) [Claims] 1. A metal tube that is continuously formed is welded while being formed into a tubular shape so as to cover the inner surface of a metal tube that is continuously formed with a resin. And a mold for extruding the molten resin, which is inserted into the metal tube from the opening, and
An outer mold having a resin flow path formed at the center thereof, one end of which is fixed via a fixing member in the vicinity of the downstream end of the resin flow path of the outer mold, and the other end is formed of the outer mold. The fixing member is provided along the inner wall surface of the resin flow path of the outer mold and between the inner wall surface thereof and the fixing member. A cylindrical outer frame having a position adjustment mechanism in the radial direction with respect to the mold, and a plurality of arm-shaped members extending from the inner surface of the outer frame toward the center and holding one end of the inner mold, Each arm-shaped member has a streamlined cross-sectional shape along the direction in which the molten resin flows .
The tip of the outer mold near the resin outlet is the outer mold.
It is removable with screws to the main part of the mold
Between the tip and the body.
The fixing member is fixed with the outer frame inserted,
The outer circumference of the mold tip is slightly larger than the body.
The large diameter portion contacts the inner surface of the metal tube,
A mold for coating the inner surface of a metal / resin composite tube, wherein the mold and the metal tube are centered with each other .