JPH0245071B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention comprises low density polyethylene (LDPE),
Polyethylene such as medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE), polymethacrylate (PMMA), and polyvinyl chloride (PVC)
It is made of cross-linked plastic material such as polyvinyl acetate or ethylene-vinyl acetate copolymer (EVA), and has a straight pipe portion with a constant thickness and a deformed portion that is curved or changes in thickness. This invention relates to tubular parts and methods of manufacturing the same.

For example, in the field of heating and hygiene, plastic tubular parts are frequently used for transporting fluid media. The plastic material used to form this tubular part has excellent long-term stability at high temperatures and pressures, and is stable against most additives used in the heating and sanitary fields. .

In order to construct a curved part in the middle of piping with these tubular parts, it is necessary to bend a straight tubular part to fit the curved part and fix it in the bent state. This is because straight plastic tubular parts have a strong restoring force against bending, so they resist bending and try to return to a straight position, and it takes a lot of effort to fix them in a bent state. Yes.

Furthermore, even if a straight tubular component can be bent, for example, at a right angle and fixed in that state, the cross-sectional area of the section of the tubular component that is bent at right angles will be smaller than the straight section; The flow inside the pipe becomes difficult.

The present invention relates to a plastic tubular part having such a curved part or a part whose thickness changes, and a method for manufacturing the same. Therefore, it is possible to obtain a tubular component that does not have a small cross-sectional area.

Therefore, the plastic tubular part of the present invention can be made of low density polyethylene, medium density polyethylene,
Straight pipes of constant thickness made of cross-linked plastic materials such as linear low-density polyethylene and high-density polyethylene, polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, and ethylene-vinyl acetate copolymers. It has a deformed part that is curved or whose thickness changes, and the wall thickness of the deformed part gradually decreases toward the straight pipe part so that it is connected to the wall of the straight pipe part.

Furthermore, the method for producing tubular plastic parts of the present invention can be applied to polyethylenes such as low density polyethylene, medium density polyethylene, linear low density polyethylene, and high density polyethylene, polymethyl methacrylate, polyvinyl chloride, and polyvinyl acetate. or,
A cross-linked plastic material, which is an ethylene vinyl acetate copolymer, is first formed into a tube, and then the first formed tube is formed into a straight tube having a different diameter and whose diameter can be expanded or contracted. In order to form a deformed part that curves or changes in thickness in a part of this second-formed straight pipe, the part of the straight pipe where the deformed part is to be formed is heated to a temperature exceeding the crystal melting point of the plastic material. It is characterized in that it is heated locally at a temperature, whereby the thickness of the tube wall of the deformed portion is gradually reduced toward a straight tube and connected to the tube wall of the straight tube.

Next, an embodiment of the method of manufacturing a plastic tubular part according to the present invention will be described.

The dispersed polyethylene is mixed with 2.5% by weight dicumyl peroxide, and if necessary other crosslinking agents, additives, and auxiliaries, and the mixed material is placed in a pressure chamber and high pressure is applied. The temperature of the mixed material at the outlet of the pressure chamber is approximately 110°C. This mixed material is passed through the passages of an extrusion device and heated to approximately 160°C. This temperature allows the crosslinking reaction of the material to proceed rapidly and completely in the extrusion device, and a preformed tube of crosslinked polyethylene is extruded from the outlet of the forming tool of the extrusion device.

Using this tube, in order to expand the diameter of the tube and manufacture a tubular part having a deformed portion curved at right angles as shown in Fig. 1, the above-mentioned primary formed tube is subsequently subjected to the same working process. Pass through a forming tool and then stretch by drawing through a water bath and cool to obtain a secondary formed tube. Note that the radius of the forming tool is at least 10% smaller, preferably 20% smaller. Therefore, if the original tube formed by primary forming is A, then the tube B which is stretched and reduced in diameter by secondary forming can be expressed as B = A - ΔA, where ΔA is between 10% and 20%. be.

To make the tubular part shown in FIG. 1 from this tube B, hot air of 140° C. or higher is applied to the side 1 of the tube for a while.
During heating, the section of the section expands and the plastic material from which the tube was formed tends to assume the original shape of tube A. Uneven heating around the tube results in a deformed section of the tube that bends at right angles. This is due to the well-known memory effect of plastics, where the peripheral side 1 of the tube tends to assume the original thickness of the tube A, while the cooler side 2 does not. This is because it will not happen. Therefore, the radii R ₁ and R ₄ of the straight pipe sections on both sides of the curved deformed section are:
The radius of the stretched tube B remains the same, but the radius of the deformed part expands to larger R ₂ and R ₃ ,
R ₃ which is larger than R ₂ is close to the radius of the original tube A. The same thing can be said about the wall thickness of the pipe. The wall thickness D ₁ of the straight pipe portion remains the same as that of pipe B, but the wall thickness of the deformed portion changes to D ₂ and D ₃ , which are larger than D ₁ , with the thickest D ₃ being the original. The thickness approaches that of the tube wall of tube A. In this curved deformed part, the radius becomes larger and the wall thickness increases, so that the cross-sectional area does not decrease and the flow resistance does not increase. This deformed part maintains its deformed shape and does not elastically return to its original shape.
Even more conveniently, the curved deformation is D ₂
As can be seen from the wall thickness of D ₃ , which is thicker than that of D 3, the more curved the area, the thicker the wall thickness and reinforcement, which prevents abrasion caused by the flow inside the pipe and other damage.
This prevents damage from impact.

Deformed portions with enlarged diameters, such as the socket portion and collar portion 12 of the tubular component shown in FIG. 1, can also be molded in the same manner.

FIG. 2 shows another tubular part formed according to the invention. This tubular part is a ventilary tube having a waist with a minimum radius R ₅ and tapered parts 3 and 4 that gradually reduce in diameter towards this waist. To manufacture this, the diameter of the tube 5 with radius R ₄ is reduced by heat treatment to form a constricted portion with radius R ₅ and both tapered portions 3 and 4. As a result, the pipe wall has the maximum wall thickness at the constriction with the minimum radius R ₅ ,
The wall thickness of each tapered portion 3, 4 gradually increases toward the constriction. Therefore, the constriction that restricts the flow inside the pipe and its vicinity are reinforced. The constricted portion and both tapered portions of this ventilate tube maintain their deformed shapes.

In order to obtain a tube 5 with a reduced radius in this way, a mold is used which is formed into this tube 5, into which the original tube of the tube 5 is laid and subsequently defined by the mold. Heat until it takes on the shape. As a result, the original tube is transformed into a tube 5 that can return to its original shape. The mold can thus be used to mass produce preformed tubes 5 of precise dimensions for forming deformed parts of decreasing radius.

Now, among the straight pipe part referred to in claim 1 of the present invention and the deformed part that is curved or changes in thickness, the straight pipe part is defined as the radius of the tubular part shown in FIG.
The portions R ₁ and R ₄ are the portions of the tube 5 with radius R ₄ in the tubular component shown in FIG. Also, the deformed parts that are curved or change in thickness are the right-angled curved parts with radii R ₂ and R ₃ in Fig. 1, and the constricted parts with the minimum radius R ₅ and the tapers on both sides of the constricted parts in Fig. 2. This refers to parts 3 and 4.

In addition, the fact that the wall thickness of the deformed part gradually decreases toward the straight pipe part and connects to the wall of the straight pipe part means that in the case of Fig. 1, the maximum wall thickness of the pipe wall of the deformed part D ₃ is D ₂
It is said that it connects to the pipe wall of the straight pipe part with radius R ₁ or R ₄ while decreasing to In addition, in the case of Fig. 2, the constricted part where the wall thickness of the pipe wall is the largest is connected to the pipe wall of the straight pipe section 5 with radius R ₄ in the front and rear while reducing the wall thickness at both tapered parts 3 and 4. It is.

The procedure according to the invention can also be used to make connections between pipe fittings and fittings, in which case a packing ring may be unnecessary. To do this, use a hose with a slightly reduced radius, heat it appropriately at the connection, expand it through this heat treatment, and install it in place.

The method of the invention can also be used to cover repaired areas, such as damaged areas or holes in existing pipes, from the inside with plastic.

To do this, for example, a polyethylene tube reduced in diameter by 10% as described above is extruded and inserted into the tube to be repaired. The length of the polyethylene pipe to be inserted should be sufficiently longer than the repair area. After inserting the polyethylene tube in this manner, the fitting portions of both tubes are joined, and the inner polyethylene tube, which has been reduced in diameter in advance, is expanded and brought into close contact with the inner wall of the outer tube. The outer periphery of the polyethylene tube whose diameter has been expanded thereby covers the inner surface of the outer tube, including the repaired area.

Furthermore, the method of the present invention can also be used to make a tubular component in which an air chamber is provided between the inner and outer double tubes, as shown in FIGS. 3 and 4. .

In Fig. 3, an inner tube 6 passing into an outer tube 8 that can be expanded in diameter is used, and the diameter expands at predetermined intervals around the inner tube 6, and expanded diameter portions are closely attached to the inner surface of the outer tube. form 7. This creates an air chamber between the inner tube 6 and the outer tube 8, which is closed by the enlarged diameter portions 7 on the front and rear, and this air chamber provides an excellent insulation effect or heat insulation effect to the tubular component.

In addition, in FIG. 4, a tube whose diameter can be reduced is used as the outer tube 10 through which the inner tube 11 passes, and recesses 9 are formed around it at predetermined intervals, the inner surface of which is in close contact with the outer surface of the inner tube. . In this case as well, the inner tube 11 and the outer tube 10
An air chamber that exhibits a heat insulating effect is formed between the front and rear recesses 9.

The outer tube 8, which does not deform in FIG. 3, and the inner tube 11, which does not deform in FIG. 4, may be made of plastic or metal.

FIG. 5 shows a T-shaped tubular part with a coupling tube 16 connected thereto, the coupling tube 16 passing through the hole 15 of the tube 13. The end of the joint pipe is provided with a molded part 17 that contacts the inner surface of the pipe 13, and a thread is formed on the outer periphery, so that the pressure part (washer) 18 shown in the figure is formed.
is fitted into the joint pipe, and a nut (not shown) is screwed onto the thread of the joint pipe.Since there is a molded part 17, the nut can be sufficiently tightened.

To make this T-shaped tubular part, a tube 13 with an expandable diameter is used, and the wall section 14 of the tube 13, which is in contact with the forming part 17 of the coupling tube from the inside, is heated according to the method of the invention. , the tube wall portion 14 is inflated to the original tube condition of the tube 13. Next, a hole 15 is made in this tube wall portion 14, and the diameter of the hole 15 matches the diameter of the joint tube 16. Molding part 17
It is integrated with the joint pipe and has an oval shape. The joint tube 16 is passed through the hole 15 from the inside of the tube while the tube wall portion 15 in which the hole 15 has been drilled is still warm. This allows the tube wall section 14 to fit snugly into the molding 17 when cooled. After the area around the hole has cooled, the pressurizing part 18 is fitted into the joint pipe 16 and tightened with a nut as described above. There is no leakage from the hole 15 and the joint pipe 16 is firmly attached to the T-shaped tubular shape shown in the figure. Becomes a part. The molded portion 17 is formed by the swollen tube wall portion 14 of the tube 13.
Since it is located inside the tube 13, there is no resistance to the flow flowing through the tube 13, or even if there is resistance, it is only slight.

The method for manufacturing a T-shaped tubular component described above can connect a joint pipe to an existing pipe in a T-shape without disassembling it. In addition, it is preferable that the joint pipe 16, the pressurizing component 18, and the nut are made of metal.

Next, the effects of the present invention will be described.

In the first aspect of the tubular component, the wall thickness of the deformed portion that is curved or changes in thickness gradually decreases toward the straight tube portion, and is continuous with the wall of the straight tube portion. As a result, the pipe walls of the deformed portion and the straight pipe portion smoothly transition from inside to outside, and maintain the deformed form. When the deformed part is curved, the wall thickness of the pipe wall in the deformed part is the strongest, and gradually becomes thicker towards the part where the flow inside the pipe comes into intense contact, and the thickness of the pipe wall changes in the deformed part. In this case, the thickness varies the most in size, and it gradually becomes thicker toward the part that restricts the flow inside the pipe or causes turbulence. Therefore, the wall thickness of the area affected by the flow is increased and reinforced, preventing wear and tear caused by the flow.
Damage caused by other impacts can be prevented.

Further, according to the method for manufacturing a tubular component according to the second aspect of the present invention, a deformed portion that is curved or whose thickness changes can be easily formed at a desired location on the straight pipe of the tubular component. The wall of the deformed portion gradually reduces its wall thickness and connects to the wall of the straight pipe, so that the deformed portion and the wall of the straight pipe smoothly transition from inside to outside, and maintain the deformed form.

[Brief explanation of drawings]

FIG. 1 is a side view of a tubular component having a right-angled curved part manufactured according to the present invention, FIG. 4 is a sectional view of a heat-insulating double pipe whose outer pipe is manufactured according to the present invention, FIG. 5a is a plan view of the molded part of the joint pipe, and FIG. 5b is a cross-sectional view taken along the line Vb-Vb of FIG. 5c. Cross-sectional view of the joint pipe, No. 5c
The figure is a cross-sectional view of a T-shaped tubular component obtained by processing a pipe according to the present invention, FIG. 5d is a plan view of a pressurized part for connecting a joint pipe, and FIG.
FIG. In the figure, 1 and 2 are the sides of the right-angled curved part of the tube, 3 and 4 are the tapered part of the ventilate tube, 5 is the straight tube, 6 is the inner tube, 7 is the enlarged diameter part, 8 is the outer tube, and 10 is the outer tube,
9 is the recess, 11 is the inner tube, 12 is the flange,
13 is a tube, 14 is an inflated tube wall portion, 15
16 is a hole, 17 is a molded part thereof, and 18 is a pressurized part.

Claims (1)

[Claims] 1. Low density polyethylene, medium density polyethylene,
Straight pipes of constant thickness made of cross-linked plastic materials such as linear low-density polyethylene and high-density polyethylene, polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, and ethylene-vinyl acetate copolymers. In a plastic tubular part having a deformed part that is curved or whose thickness changes, the wall thickness of the deformed part gradually decreases toward the straight part, and the wall thickness of the deformed part gradually decreases toward the straight part. A plastic tubular part characterized by its continuous structure. 2 Low density polyethylene, medium density polyethylene,
A tube is first formed from a cross-linked plastic material such as linear low-density polyethylene or high-density polyethylene, polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, or ethylene-vinyl acetate copolymer. The first-formed pipe is second-formed into a straight pipe that has a different diameter and can be expanded or reduced in diameter, and a part of the second-formed straight pipe is curved or has a different diameter. In order to form a deformed portion that changes, the portion of the straight pipe where the deformed portion is to be formed is locally heated at a temperature exceeding the crystalline melting point of the plastic material, thereby directly changing the wall thickness of the pipe wall in the deformed portion. A method for manufacturing a plastic tubular part, characterized in that the plastic tubular part is gradually reduced toward the pipe and connected to the pipe wall of the straight pipe.