JPS61148036A - Manufacture of double wall pipe - Google Patents

Abstract

PURPOSE:To save labor hour and cost for application of the titled manufacture, by a method wherein after an outer wall having an outer layer part of a port and an inner wall on the inside of a trough part of the outer wall have been molded continuously, the same is cut off at an end part of the outer layer part of the port, the diameter of one end part of the inner wall positioning at the inside of the outer layer part of the port of a double wall molded member is made to expand by heating and softening the same and the port is molded. CONSTITUTION:When pressure welding of molten resin is performed on a mold surface of a molding block 21', an outer layer part 33 of a port wherein a trough part 32' whose inside diameter is larger than that of a trough part 32 by about twice as thick as a thickness of an inner wall 4 and a crest part 31' are connected alternately with each other is molded. Thus an outer wall wherein the crest part 31 and the trough part 32 are connected alternately with each other and possesses the outer layer parts 33 of the ports at fixed intervals is molded continuously. Simultaneously with molding of an outer wall 3 molten synthetic resin is extruded cylindrically into the outer wall 3 through an annular second resin passage 12 of a molten resin extruding part 1 and the cylindrical inner wall 4 which is made to fuse to the inside of a trough part 32 is molded continuously. The diameter of one end part of this double wall molded member A is expanded by softening the one end part 41 after the double wall molded member A has been cut off at an end part of the outer layer part 33 of the port.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing double-walled pipes used for drainage pipes and the like.

(Prior Art) Conventionally, when manufacturing double-walled pipes, a mold consisting of a large number of two-piece molding blocks with uneven molding surfaces is used, and the molding blocks are run at a constant speed, and the molding Molten synthetic resin is extruded into a mold to continuously form a corrugated outer wall with alternating annular peaks and valleys, and molten synthetic resin is extruded into this outer wall in a cylindrical shape to form the inner surface of the valley of the outer wall. A method has been adopted in which the inner wall to be fused is continuously molded and the thus obtained double wall molded body is cut into predetermined dimensions.

As shown in FIG. 6, the double-walled tube obtained by this method has annular peaks 101 and valleys 102 alternately formed over the entire length of the outer wall 100, and a cylindrical inner wall 103 between the valleys 102. The crest 101 and the inner wall 103 are fused and integrated on the inner surface.
It has a structure in which air is sealed between the two.

Double-walled pipes with this structure have high pressure resistance and smooth water flow, so they are prized as drainage pipes, etc. However, they have the following problems when constructing the pipes.

(Problem to be solved by the invention) That is, since the outer wall 100 of such a double-walled pipe is corrugated,
When connecting, it is necessary to use a special joint, which causes problems such as increased construction costs and troublesome connection work.

To solve this problem, one end of the double-walled pipe is heated and softened to expand its diameter to form a socket, and the other end of the double-walled pipe to be connected is inserted into the socket. However, in the case of double-walled pipes, it is not easy to form the socket.

This is because air is sealed between the peaks 101 of the outer wall 100 and the inner wall 103 of the double-walled pipe, so it takes a long time to heat (preheat) due to the insulating effect of this air. When a sizing member is inserted later to expand the diameter, the inner wall 10
3 is successfully expanded in diameter, whereas the peak 101 of the outer wall 100
is not sufficiently expanded, so the peak 1
This is because the 01 will be crushed and the appearance will be significantly impaired, and the remaining distortion will be large, causing problems such as severe shrinkage.

The present invention aims to provide a method for manufacturing a double-walled tube that can solve these problems.

(Means for Solving the Problems) That is, the method for manufacturing a double-walled pipe according to the present invention involves extruding a molten synthetic resin into a mold consisting of a large number of moving two-part molding blocks, Continuously molding an outer wall having socket outer layer parts at regular intervals in which peaks and valleys are arranged alternately and having an inner diameter larger than the outer diameter of the peaks by approximately twice the thickness of the inner wall described later, and this outer wall. A step of continuously molding the inner wall by extruding the molten synthetic resin in a cylindrical shape and fusing it to the inner surface of the valley of the outer wall, and cutting the double-walled molded product obtained in this step at the end of the outer layer of the socket. The process includes heating and softening one end of the inner wall of one end of the cut double-walled molded body located inside the outer layer of the socket, expanding the diameter so as to contact the inner surface of the outer layer of the socket, and forming a socket. The gist of this method is to form a socket into which the other end of the molded body is inserted.

(Operations and Effects) According to the manufacturing method of the present invention, one end of the inner wall located inside the socket outer layer of one end of the cut molded body is heated and expanded, and this inner wall is a cylindrical part. shape, does not contain air,
Because it has good heat conduction efficiency, like ordinary synthetic resin pipes, it can be sufficiently softened by short heating (pre-heating), and when a sizing member is inserted, the diameter can be expanded evenly and the outer layer of the socket can be easily and uniformly expanded. It comes into contact with the inner surface of the steel and produces almost no residual distortion. Therefore, the molded socket hardly shrinks, and the outer layer of the socket on the outside is not expanded in diameter at all, so there is no risk of deterioration of the appearance due to deformation or the like.

As described above, according to the manufacturing method of the present invention, it is possible to obtain a double-walled pipe having a socket at one end, and the other end of the double-walled pipe to be connected is inserted into the socket of this double-walled pipe. This makes it possible to connect easily with just one piece, and therefore, there is no need for the dedicated joints that have been used in the past, so it is possible to save time and money in construction.

Hereinafter, the present invention will be explained in detail with reference to Examples.

(Example) FIG. 1 is a cross-sectional view of a molding device used in the first molding process of a double-walled molded product. A molten synthetic resin is extruded from the mold, and the extruded resin is pressed against the molding surface of the mold 2 by the pressure of air sent from the air supply passage 13.

This mold 2 is composed of a large number of two-part molding blocks 21, and each upper molding block and each lower molding block are connected in an endless caterpillar shape, and are fixed in the direction of the arrow X. It is configured to run at speed.

This molded block 21 has an annular concave portion 211 and a convex portion 212.
Among them, only the molding block 21' for molding the outer layer of the socket has a recessed part 211.
' and the inner diameter of the protrusion 212' are slightly different, and the inner diameter of the protrusion 212' is larger than the inner diameter of the protrusion 212 of the molded block 21 by approximately twice the thickness of the inner wall 4, which will be described later. ing. Therefore, when the molten synthetic resin is pressed against the wave-formed surface of the forming block 21 running at a constant speed, alternating annular peaks 31 and troughs 32 are formed, and the molten synthetic resin is also applied to the forming surface of the forming block 21'. When the resin is pressed, a trough 32' with an inner diameter larger than the trough 32 by approximately twice the thickness of the inner wall 4 described later and a peak 31 with a larger inner diameter are formed.
A receptacle outer layer portion 33 having alternating numbers 1 and 2 is formed. In this way, the outer wall 3 having the above-described socket outer layer portions 33 in which the peak portions 31 and the valley portions 32 are arranged alternately and at regular intervals is continuously molded.

At the same time as this outer wall 3 is formed, the molten synthetic resin is extruded into the outer wall 3 in a cylindrical shape from the annular second resin passage 12 of the molten resin extrusion section 1 to form a cylindrical inner wall that is fused to the inner surface of the trough 32 of the outer wall 3. 4 is continuously molded.

In this case, the distance from the pressure air reservoir section 14 where air from the air supply road 13 is stored to the tip extrusion port of the second resin passage 12 is set to be larger than the length l of the socket outer layer section 33, When the inner wall 4 is extruded inside the socket outer layer 33, the socket outer layer 33 is cut off from the air reservoir 14, so the inner wall 4 is formed into a right cylindrical shape without being bent inward by air pressure. be done. The inner wall 4 extruded into a right cylindrical shape and fused to the inner surface of the valley 32 of the outer wall 3 is sent toward the cooling tube 5 together with the outer wall 3 as the molded block 21, 21' moves. After cooling and hardening, the molded block 21, 21' is demolded.

The molded product obtained by the above molding process is shown in Figure 2 (a).
As shown in FIG. 3, annular peaks 31 and valleys 32 are arranged alternately, and valleys 32' have an inner diameter larger than the valleys 32 by approximately twice the thickness of the inner wall 4, and ridges have a larger inner diameter than the valleys 32'. A long double-walled molded body A consisting of an outer wall 3 having socket outer layer parts 33 in which parts 31' are arranged at regular intervals, and a cylindrical inner wall 4 fused to the inner surface of the valley part 32 of this outer wall 3. Air is sealed between the peak portion 31 of the outer wall 3 and the inner wall 4 and between the socket outer layer portion 33 and the inner wall 4.

This double-walled molded product A is cut along the cutting line I-1 at the end of the socket outer layer portion 33 by a cutting machine (not shown) that moves at the same speed as the feed speed, and unnecessary cuts are removed. The remaining end 331 is also cut along the cutting line -H, thus making the second
The double-walled molded body B has a predetermined length and has a socket outer layer portion 33 at one end as shown in FIG.

Finally, the outer layer part 3 of the socket at one end of this double-walled molded body B
One end 41 of the inner wall 4 located inside the inner wall 3 is softened by heating, and a sizing member (not shown) having an outer diameter approximately the same as the outer diameter of the peak 31 of the outer wall 3 is inserted. The double-walled pipe C is obtained by expanding the diameter of the socket so that it contacts the inner surface of the trough 32' of the socket outer layer 33, and forming the socket 6 as shown in FIG. 2(C). In this case, one end 41 of the inner wall to be heated and expanded has a cylindrical shape and does not contain air and has good heat conduction efficiency, so it can be heated (preheated) for a short time like a normal synthetic resin pipe. When the sizing member is sufficiently softened and the sizing member is inserted, it is easily and uniformly expanded in diameter and comes into contact with the inner surface (trough portion 32') of the socket outer layer portion 33, causing almost no residual strain. Therefore, the molded socket 6 hardly shrinks, and since the outer socket outer layer 33 is not expanded in diameter at all, there is no deformation or the like that would spoil the appearance.

As shown in FIG. 2(c), the double-walled tube C obtained by the above manufacturing method of the present invention has a socket 6 having an inner diameter approximately equal to the outer diameter of the outer wall peak 31 at one end of the double-walled tube. Socket outer layer part 33
Since it is formed in contact with the inner surface of the trough 32', the connection can be made easily and neatly by simply inserting the other end of the double-walled pipe C to be connected to this socket 6, as shown in Fig. 3. It can be performed. Therefore, there is no need for any dedicated joints that have been used in the past, so construction efforts and costs can be saved.

FIGS. 4(a), (b), and (c) show molded bodies obtained in each step of another embodiment of the manufacturing method of the present invention. That is, in this embodiment, instead of the molding block 21' for socket molding having the wave-formed surface in the previous embodiment, a molding block 21' having a wave-formed surface is used, which is larger than the outer diameter of the outer wall peak portion 31 by approximately twice the thickness of the inner wall 4. A molding block for socket molding having a cylindrical molding surface with an inner diameter is used, and as shown in FIG. Cylindrical (its inner diameter is naturally larger than the outer diameter of the outer wall peak 31)
It is designed to be molded so that it is approximately twice as thick as the The rest is exactly the same as the previous embodiment.

This double-walled molded body A is also cut along the cutting line I-■ at the end of the cylindrical socket outer layer 33' as in the previous embodiment, and the unnecessary uncut end 331' is cut off. It is cut along the line nm to form a double-walled molded body B having a predetermined length and having a socket outer layer portion 33' at one end as shown in FIG. 4(b). Finally, one end 41' of the inner wall inside the molded body B is heated and softened, and expanded in diameter so as to be in contact with the inner surface of the socket outer layer part 33'. C'
It is said that

In the case of such a double-walled pipe C', there is an advantage that the connection can be easily made by simply inserting the other end of the double-walled pipe C' to be connected to the socket 6', as in the case of the previous embodiment. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a molding device used in the first molding step in an embodiment of the manufacturing method of the present invention; FIG. 2 (a);
(B) and (C) are half-sectional views of the molded body obtained in the molding process, cutting process, and socket forming process of the same example, respectively, and FIG. 3 is the connection state of the double-walled pipe obtained in the same example. FIGS. 4(a), 4(b), and 4(c) are half-sectional views of molded bodies obtained in the molding step, cutting step, and socket molding step in other embodiments of the manufacturing method of the present invention, respectively. FIG. 5 is a half-sectional view of a conventional double-walled tube, and FIG. 6 is a partial half-sectional view of the double-walled tube in which the end portion of the same double-walled tube is expanded in diameter. 1... Molten resin extrusion section, 2... Molding die, 21.21
'... Molded block, 3... Outer wall, 31... Peak, 32... Valley, 33.33'... Outer layer of socket,
4... Inner wall, 41... One end of inner wall, 6.6'...
Socket, A...double-walled molded body, B...cut double-walled molded body, C...double-walled pipe.

Claims (1)

[Claims] (1) Molten synthetic resin is extruded into a mold consisting of a large number of moving two-part molding blocks, and annular peaks and valleys are arranged alternately, and the thickness of the inner wall described below is greater than the outer diameter of the peaks. An outer wall having socket outer layer portions with an inner diameter approximately twice as large as the diameter of a step of molding, a step of cutting the double-walled molded body obtained in this step at an end of the outer layer of the socket, and a step of cutting the double-walled molded body obtained in this step at the end of the outer layer of the socket; A double process consisting of the step of heating and softening one end of the inner wall to expand the diameter so as to contact the inner surface of the outer layer of the socket, and forming a socket into which the other end of the molded body serving as the socket is inserted. Method of manufacturing wall tubes.