Resin pipe for rubber ring joint and rubber ring joint structure

Abstract

To provide a resin pipe for a rubber ring joint that is difficult to come off from a rubber ring joint, and a rubber ring joint structure to which the resin pipe is connected by the rubber ring joint.SOLUTION: A resin pipe 10 for a rubber ring joint of the present invention is connected to a rubber ring joint 30 having a rubber ring 50 disposed on an inner surface of a receiving port 33, and at least an outer periphery thereof is made of resin, where a surface roughness Ra of the outer periphery is 0.5 μm or more. A rubber ring joint structure 20 of the present invention is formed by connecting the resin pipe 10 for a rubber ring joint to the rubber ring joint 30 having the rubber ring 50 disposed on the inner surface of the receiving port 33.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin pipe for a rubber ring joint that can be connected by a rubber ring joint, and a rubber ring joint structure formed by connecting the resin pipe for a rubber ring joint and a rubber ring joint. [Background technology]

[0002] Plastic pipes, such as multi-layer pipes, are typically connected to fittings. Two common methods for connecting fittings to plastic pipes are adhesives and heat fusion. However, adhesives raise concerns about the impact of solvent cracking on the pipe material caused by the solvent in the adhesive and the impact of organic solvent evaporation on the construction environment. Heat fusion requires significant construction work, including the preparation of a welding device and securing a power source. For this reason, rubber ring fittings are used to connect plastic pipes in non-pressurized pipelines, such as sewer and drainage pipes, where pressure is not normally generated. Rubber ring fittings are used to connect plastic pipes. Rubber ring fittings have a rubber ring on the inner surface of the socket into which the pipe is inserted. By inserting the pipe into the socket and compressing the rubber ring inside the socket, a rubber ring fitting structure is created, hermetically connecting the fitting and the pipe.

[0003] In such a rubber ring joint structure, if the pipe is not prevented from coming out of the joint, the pipe may come out of the joint. Therefore, for example, Patent Document 1 discloses that a locking member and a locking member are attached to the rubber ring joint to improve the locking ability. A metal wire is exemplified as the locking member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-156431 Summary of the Invention [Problem to be solved by the invention]

[0005] The rubber ring joints require not only the rubber ring but also other components such as locking and retaining members, which increases the joint structure and costs. In addition, the use of metal locking members can scratch the outer surface of the plastic pipe.

[0006] The inventors have invented a rubber ring joint structure that makes it difficult for the resin tube for the rubber ring joint to come loose by improving the configuration of the resin tube for the rubber ring joint rather than improving the structure of the rubber ring joint itself.

[0007] An object of the present invention is to provide a resin pipe for a rubber ring joint that is difficult to come loose from the rubber ring joint, and a rubber ring joint structure in which a resin pipe is connected by a rubber ring joint. [Means for solving the problem]

[0008] The resin pipe for rubber ring joint of the present invention is A resin pipe for a rubber ring joint is connected to a rubber ring joint having a rubber ring disposed on the inner surface of the receiving port, and at least the outer periphery is made of resin, The outer periphery has a surface roughness Ra of 0.5 μm or more.

[0009] The outer periphery surface roughness Ra is preferably 6 μm or less.

[0010] It is desirable to use a multi-layer pipe consisting of multiple layers in the pipe thickness direction.

[0011] The outer periphery preferably includes a resin and a reinforcing material such as glass fiber.

[0012] Further, the rubber ring joint structure of the present invention is The rubber ring joint is formed by connecting the above-described resin pipe for a rubber ring joint to a rubber ring joint having a rubber ring disposed on the inner surface of the receiving port. [Effects of the Invention]

[0013] The resin pipe for rubber ring joints of the present invention has a large outer surface roughness Ra, which increases the frictional force against the rubber ring, making it difficult for the resin pipe for rubber ring joints to come off the rubber ring joint. Also, because the resin pipe for rubber ring joints has a large outer surface roughness Ra, it is difficult for a worker to slip when gripping it, making it easy to handle.

[0014] In the rubber ring joint structure of the present invention, the outer surface roughness Ra of the resin pipe for the rubber ring joint is large, so that the resin pipe for the rubber ring joint can be prevented from coming loose without making the rubber ring joint more complicated. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a photograph showing the appearance of a resin pipe for a rubber ring joint according to the present invention. [Figure 2] FIG. 2 is a partial cross-sectional view of a resin pipe for a rubber ring joint and a rubber ring joint before being fastened together. [Figure 3] FIG. 3 is a partial cross-sectional view after fastening. [Figure 4] FIG. 4 is a schematic diagram of a production line for the resin pipe for rubber ring joints of the present invention. [Figure 5] FIG. 5 is an explanatory diagram of a pressure resistance test device. [Figure 6] FIG. 6 is a graph showing the results of the pressure resistance test. DETAILED DESCRIPTION OF THE INVENTION

[0016] The resin pipe 10 for a rubber ring joint (hereinafter simply referred to as "resin pipe") and the rubber ring joint structure 20 of the present invention will be described below.

[0017] <Resin pipe 10> The resin pipe 10 is a resin pipe having a hollow flow path formed therein.

[0018] The resin to be used can be selected depending on the temperature of use, and examples thereof include heat-resistant plastic materials such as polybutene resin, cross-linked polyethylene resin, polypropylene resin, and heat-resistant polyvinyl chloride for high-temperature applications of 80°C to 120°C, and high-density polyethylene, semi-rigid or flexible polyethylene, and polyvinyl chloride for low-temperature applications of 80°C to -50°C.

[0019] The resin pipe 10 can be a single-layer pipe or a multi-layer pipe having multiple layers in the pipe thickness direction. In the case of a multi-layer pipe, the outer layer can be a layer of resin containing a reinforcing material such as glass fiber.

[0020] The inclusion of a reinforcing material, such as glass fiber, can increase the strength, rigidity, and tensile elongation of the plastic pipe 10. The lower limit of the glass fiber content in the outer layer is preferably 5% by mass or more, and more preferably 10% by mass. Increasing the glass fiber content in the outer layer can increase the outer surface roughness Ra of the plastic pipe 10, as described below. Therefore, in this case, the glass fiber content is preferably 5% by mass or more, and more preferably 10% by mass or more. Incidentally, an excessive glass fiber content reduces the moldability of the outer layer, so the upper limit of the glass fiber content is 45% by mass or less, and more preferably 40% by mass or less, of the outer layer.

[0021] The average fiber length of the glass fibers is preferably 150 μm or more, more preferably 200 μm or more, in order to ensure low linear expansion, rigidity, and the orientation described below. On the other hand, in order to ensure moldability, the average fiber length of the glass fibers is 700 μm or less, preferably 650 μm or less. For the same reasons, the lower limit of the average fiber diameter of the glass fibers is preferably 1 μm or more, preferably 5 μm or more, and the upper limit is preferably 30 μm or less, preferably 15 μm or less.

[0022] To suppress thermal expansion and contraction of the resin pipe, it is preferable that 50% or more of the glass fibers are axially oriented, and more preferably 70% or more. "Axis-oriented glass fibers" means that, among the fibers having a length of 10% or more of the average fiber length of the glass fibers, at least 50%, preferably at least 70%, have a fiber orientation within ±15° of the axial direction. When molding a resin pipe using an extrusion molding machine, molding conditions such as the type and shape of the extrusion molding machine and the molding mold, and the resin temperature are not particularly limited. Orientation of the glass fibers can generally be achieved by passing a resin composition containing glass fibers through a flow path of any shape within the mold, so that the glass fibers naturally orient along the axial flow of the resin composition. The resin composition is then extruded from the outlet of a cylindrical mold and cooled in a water tank (while the resin remains fluid) to be shaped. The orientation rate can be adjusted by applying stretching, diameter contraction, diameter expansion, or other processes.

[0023] The inner diameter, outer diameter, and pipe thickness of the resin pipe 10 are determined appropriately depending on the required application. For example, in the case of resin drainage pipes for building facilities, those with an inner diameter (nominal diameter) of 40 mm to 300 mm and a pipe thickness of 1.8 mm to 17.3 mm are generally used as JIS K6741 products.

[0024] The resin pipe 10 of the present invention is characterized in that its outer circumferential surface roughness Ra is 0.5 μm or more. By increasing the outer circumferential surface roughness Ra of the resin pipe 10, friction with the rubber ring 50 can be increased when the resin pipe 10 is connected to the rubber ring joint 30, improving the ability of the resin pipe 10 to prevent slippage. The surface roughness Ra was measured in accordance with "7. Evaluation method and procedure using a stylus surface roughness measuring instrument" in JIS B0633 (2001) "Geometrical Product Specifications (GPS) - Surface Quality: Profile Curve Method - Method and Procedure for Surface Quality Evaluation," and the measured value was the average of four axial surface roughness Ra measurements taken at four equal positions circumferentially dividing the outer surface of the pipe.

[0025] In order to improve the ability of the resin pipe 10 to prevent it from slipping out, the outer circumferential surface roughness Ra of the resin pipe 10 is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more.

[0026] On the other hand, if the outer peripheral surface roughness Ra of the plastic pipe 10 is large, a gap may form between the rubber ring 50 and the outer peripheral surface of the plastic pipe 10 when connected to the rubber ring joint 30. This gap may lead to leakage of the fluid flowing inside the plastic pipe 10. Furthermore, if the surface roughness Ra is large, when the rubber ring joint structure 20 is used over a long period of time, the rubber ring 50 may wear and deteriorate due to contraction or vibration of the pipe, which may also lead to leakage of the fluid. Therefore, the outer peripheral surface roughness Ra of the plastic pipe 10 is preferably 6 μm or less, more preferably 5.7 μm or less, and even more preferably 5 μm or less.

[0027] FIG. 1 is a photograph showing the appearance of a plastic pipe 10 according to one embodiment of the present invention. The illustrated plastic pipe 10 has a surface roughness Ra of 4.4 μm. Referring to FIG. 1(a), it can be seen that wrinkle-like irregularities similar to those produced by a graining process are formed on the outer surface of the plastic pipe 10. FIG. 1(b) is a photograph of the plastic pipe 10 in which a portion 11 on the end side of the pipe has been polished to reduce the surface roughness Ra to 1.2 μm so that the irregularities become more apparent. Referring to FIG. 1(b), it can be seen that the plastic pipe 10 of the present invention has relatively large irregularities.

[0028] The outer peripheral surface roughness Ra of the resin pipe 10 can be set, for example, by adjusting the manufacturing conditions of the resin pipe 10. Specific examples include methods such as lowering the molding temperature of the mold, increasing the surface roughness of the cooling cylinder 65, lowering the temperature of the cooling water tank 64, or decreasing the degree of vacuum in the cooling water tank 64 in a manufacturing line 60 (see FIG. 4) for the resin pipe 10, which will be described later. Furthermore, if the resin pipe 10 is a multi-layer pipe containing glass fibers on the outer periphery, the surface roughness Ra of the resin pipe 10 can be increased by increasing the amount of glass fibers. Naturally, the surface roughness Ra can also be adjusted by forming irregularities on the surface of the resin pipe 10 by embossing, or by machining the surface of the resin pipe 10.

[0029] By adjusting the outer periphery surface roughness Ra of the resin pipe 10 of the present invention as described above, it is possible to increase the frictional force against the rubber ring 50 of the rubber ring joint 30 described below, making it difficult for the resin pipe 10 to come off the rubber ring joint 30. Furthermore, because the surface roughness Ra of the resin pipe 10 is large, it is difficult for a worker to slip when gripping it, making it easy to handle.

[0030] <Rubber Ring Joint 30> The rubber ring joint 30 to be connected to the resin pipe 10 of the present invention is a joint in which a rubber ring 50 is arranged on the inner surface of the receiving port 33. Examples of the rubber ring joint 30 include, but are not limited to, anti-corrosion joints for drainage tank ventilation piping (joints for kitchen drainage piping: so-called RD joints) and flexible joints for steel drainage pipes (so-called MD joints).

[0031] 2 and 3 are partial cross-sectional views showing an embodiment in which an MD fitting 31 is used as a rubber ring fitting 30 to connect a plastic pipe 10, with Fig. 2 showing the state before tightening and Fig. 3 showing the state after tightening. The MD fitting 31 is mainly composed of a fitting body 32 with sockets 33 (only one socket 33 is shown in the figure) formed on both ends of a cast iron tubular body, a rubber ring 50 placed in the socket 33 of the fitting body 32, and a pressure ring 40 that compresses the rubber ring 50 in cooperation with the fitting body 32.

[0032] The socket 33 of the joint body 32 is designed so that the edge of the resin pipe 10 can be inserted into it, and the inner periphery of the opening side is formed with a tapered pressure contact surface 34 that narrows in diameter toward the back. Also, the outer periphery of the joint body 32 is formed with a bolt hole 35 through which the tightening bolt 21 passes.

[0033] The pressure ring 40 that compresses the rubber ring 50 is formed with a tapered pressure surface 41 that narrows in diameter from the joint body 32 toward the back. In addition, a bolt hole 42 is opened through the outer periphery of the pressure ring 40 at a position opposite the bolt hole 35 of the joint body 32 described above.

[0034] The rubber ring 50 inserted between the joint body 32 and the press ring 40 is an annular sealing member. Examples of materials for the rubber ring 50 include synthetic rubbers such as styrene butadiene rubber (SBR), chloroprene rubber (CR), ethylene propylene diene rubber (EPDM), fluororubber (FKM), and silicone rubber (VMQ). For heat-resistant applications, ethylene propylene diene rubber, silicone rubber, and fluororubber are used.

[0035] In the illustrated embodiment, a push pin 51, a retaining ring 52, and a retaining piece 53 are arranged on the pressing ring 40 side of the rubber ring 50, facing rearward from the joint body 32 side. The push pin 51 can be made of, for example, SUS304, the retaining ring 52 can be made of ethylene propylene diene rubber, and the retaining piece 53 can be made of SUS410. When tightened, the push pin 51 pushes the retaining piece 53 toward the rear of the pressing surface 41.

[0036] <Rubber ring joint structure 20> In the MD joint 31 configured as described above, as shown in FIG. 2, the plastic pipe 10 is inserted into the joint body 32, rubber ring 50, and pressure ring 40, the bolt 21 is fitted into the bolt holes 35, 42, and the nut 22 is tightened. As a result, as shown in FIG. 3, the rubber ring 50 is compressed by the joint body 32 and the pressure ring 40, airtightly connecting the socket 33 and the outer periphery of the plastic pipe 10. Furthermore, as the rubber ring 50 is compressed, the push pin 51 presses the retaining piece 53 into the inner side of the pressing surface 41 of the pressure ring 40. Furthermore, the retaining piece 53 fits between the plastic pipe 10 and the pressure ring 40, thereby performing a retaining function. In this way, a rubber ring joint structure 20 is formed in which the plastic pipe 10 is connected by the rubber ring joint 30.

[0037] Similarly, for rubber ring joints 30 other than the MD joint 31, by inserting the plastic pipe 10 into the receiving port 33, the rubber ring 50 is compressed and the plastic pipe 10 and the rubber ring joint 30 are airtightly connected.

[0038] In the rubber ring joint structure 20 of the present invention, the outer surface of the plastic pipe 10 has a rough surface roughness Ra, so the plastic pipe 10 can have a higher frictional force with the rubber ring 50 than a plastic pipe with a small surface roughness Ra, for example, a surface roughness Ra of about 0.2 μm. In other words, the pressure resistance of the rubber ring joint structure 20 can be improved without complicating the pull-out prevention structure of the rubber ring joint 30.

[0039] By making the resin pipe 10 of the present invention from a heat-resistant resin, it can be suitably used for high-temperature drainage applications in kitchens, etc. In this case, by using it in combination with an MD joint 31 made of cast iron, which is less susceptible to thermal expansion and contraction, it can follow the thermal expansion and contraction of the pipe caused by changes in drainage temperature. [Example]

[0040] <Manufacturing method and standard manufacturing conditions for resin pipe 10 (multilayer pipe)> Hereinafter, a method for adjusting the surface roughness Ra of the outer periphery of the resin pipe 10 will be described using a production line 60 for a multi-layer pipe having a two-layer structure consisting of an inner layer and an outer layer as the resin pipe 10 shown in Figure 4. Of course, the production method for the resin pipe 10 is not limited to this embodiment.

[0041] 4 is a plan view schematically showing a production line 60 for the resin pipe 10 (multilayer pipe). The production line 60 can include an inner layer extruder 61, an outer layer extruder 62, a molding die 63, a cooling water tank 64, a take-up machine 66, and a cutter 67.

[0042] The inner layer extruder 61 and the outer layer extruder 62 melt-knead the resin materials to be used for the inner and outer layers, extrude them, and discharge them into a molding die 63. The discharge rate is set as desired depending on the capacity of the extruders. The molding die 63 forms the outer layer material on the outer periphery of the inner layer, thereby forming a resin pipe 10 consisting of the inner and outer layers. The molding temperature of the molding die 63 is 200°C to 240°C under standard manufacturing conditions, but by setting the molding temperature to 180°C to 210°C, preferably 180°C to 200°C, the fluidity of the mold surface of the molten resin decreases as it passes through the die, making it less slippery, and therefore the surface roughness Ra of the outer periphery of the resin pipe 10 can be increased.

[0043] The resin pipe 10 is sent to a cooling water tank 64. The cooling water tank 64 has a cooling cylinder 65 through which the resin pipe 10 passes, and the resin pipe 10 entering the cooling water tank 64 has its outer diameter regulated as it passes through the cooling cylinder 65, and is cooled in the cooling water tank 64. The cooling water tank 64 stores a non-corrosive fluid with high heat exchange properties, such as water, air, oil, or polyethylene glycol.

[0044] The outer periphery surface roughness Ra of the resin pipe 10 can be made rough by increasing the surface roughness Ra of the cooling cylinder 65. Furthermore, the water temperature in the cooling water tank 64 is 30°C to 50°C under standard manufacturing conditions, but by lowering the water temperature to 10°C to 20°C, the molten resin solidifies before it becomes smooth, thereby making it possible to make the outer periphery surface roughness Ra of the resin pipe 10 rough. Furthermore, the degree of vacuum in the cooling water tank 64 is -20 to -60 kPa, preferably -25 to -55 kPa under standard manufacturing conditions, but by setting the degree of vacuum in the cooling water tank 64 lower to -20 to -35 kPa, preferably -20 to -30 kPa, the force pressing the resin against the cooling tower is weakened, making it possible to make the outer periphery surface roughness Ra of the resin pipe 10 rough.

[0045] The resin pipe 10 taken up by the take-up machine 66 is then sent to a cutter 67 where it is cut to a predetermined length.

[0046] <Pressure test> Resin pipes of Example 1 and Comparative Example 1, which have different outer periphery surface roughness Ra, were prepared, connected to rubber ring joints, and subjected to a pressure resistance test.

[0047] Invention Example 1 is a multi-layer pipe that uses a resin containing glass fiber on the outer periphery, and has a surface roughness Ra of 4.4 μm, an outer diameter of 89 mm, an inner diameter of 79 mm, and a length of 500 mm. The surface roughness Ra was adjusted by adjusting the temperature of the molding die and the degree of vacuum in the cooling water tank.

[0048] A VP pipe (hard polyvinyl chloride pipe) having an outer diameter of 89 mm, an inner diameter of 77 mm, and a length of 500 mm was used in Comparative Example 1. The surface roughness Ra of Comparative Example 1 was measured and found to be 0.2 μm.

[0049] The rubber ring joint 30 used was an MD joint (S(MD) nominal diameter 2; Daidore Co., Ltd.) shown in Figures 2 and 3. The material of the rubber ring 50 was EPDM.

[0050] The pressure test can be carried out using a pressure test device 70 shown in Figure 5. The pressure test device 70 is an apparatus that measures the degree of displacement of the plastic pipe 10 relative to the rubber ring joint 30 when the tip of the plastic pipe 10 is sealed with a cap 71 and various water pressures are applied to the plastic pipe 10 from the open end of the rubber ring joint 30 using a pump 72. The displacement of the plastic pipe 10 is measured by attaching a dial gauge 73 to the cap 71 that measures displacement in the direction along the pipe axis.

[0051] The applied water pressure was increased by 0.5 MPa every 10 minutes from 0 MPa by adjusting the output of the pump 72, up to a maximum of 0.35 MPa. The results are shown in Table 1 and Figure 6. Displacement measurements using the dial gauge 73 were carried out every 10 minutes starting 20 minutes after the start of the test.

[0052] [Table 1]

[0053] 6, it can be seen that Example 1 was able to reduce displacement compared to Comparative Example 1. In Example 1, for example, at 0.25 MPa, the displacement of the plastic pipe 10 was reduced to less than half. This is because the outer periphery surface roughness Ra of the plastic pipe 10 in Example 1 was large at 4.4 μm, which increased the frictional force with the rubber ring 50 of the rubber ring joint 30. On the other hand, in Comparative Example 1, the outer periphery surface roughness Ra was small at 0.2 μm, which reduced the frictional force with the rubber ring 50 and made it unable to withstand displacement due to water pressure.

[0054] When water pressure was applied, no water leakage was observed from the connection between the resin pipe 10 and the rubber ring joint 30 up to 0.3 MPa in either Inventive Example 1 or Comparative Example 1. As an inventive example, a resin pipe 10 with a surface roughness Ra of 5.7 μm was manufactured and subjected to the same test as above, but no water leakage was observed from the connection between the resin pipe 10 and the rubber ring joint 30. On the other hand, with a resin pipe 10 with a surface roughness Ra of 6.2 μm, a small amount of water leakage was observed between the resin pipe 10 and the rubber ring 50 at a water pressure of 0.3 MPa.

[0055] <Adjusting the surface roughness Ra> The surface roughness Ra of the resin pipe 10 employed in the above-mentioned invention example 1 could be adjusted in the following manner. Note that the following conditions indicate changes from the above-mentioned standard manufacturing conditions in the manufacturing line 60 shown in FIG.

[0056] By setting the molding temperature of molding die 63 to 190°C (10°C lower), the surface roughness Ra could be adjusted to 4.5µm.

[0057] By lowering the temperature of the cooling water tank 64 by 5°C to 20°C from the standard, the surface roughness Ra could be adjusted to 5.1 μm.

[0058] By increasing the degree of vacuum in the cooling water tank 64 by 20%, the surface roughness Ra could be adjusted to 3.6 μm.

[0059] By increasing the molding temperature of the mold by 10°C, the surface roughness Ra could be adjusted to 4.0 μm. Also, by increasing the molding temperature of the mold by 20°C, the surface roughness Ra could be adjusted to 3.7 μm.

[0060] By increasing the mold molding temperature by 20°C and the degree of vacuum in the cooling water tank 64 by 20%, the surface roughness Ra could be adjusted to 3.5 μm. By increasing the mold molding temperature by 20°C and the degree of vacuum in the cooling water tank 64 by 35%, the surface roughness Ra could be adjusted to 3.2 μm.

[0061] The above description of the embodiment is for the purpose of explaining the present invention, and should not be construed as limiting the invention described in the claims or narrowing its scope. Furthermore, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope described in the claims. [Explanation of symbols]

[0062] 10. Resin pipe for rubber ring joints 20 Rubber ring joint structure 30 Rubber Ring Joint 50 rubber rings 60 production lines 70 Pressure Test Equipment

Claims

1. A resin pipe for a rubber ring joint is connected to a rubber ring joint having a rubber ring disposed on the inner surface of the receiving port, and at least the outer periphery is made of resin, The outer periphery has a surface roughness Ra of 0.5 μm or more and 6 μm or less. Resin pipe for rubber ring joints.

2. A multi-layer pipe consisting of multiple layers in the pipe thickness direction. The resin pipe for a rubber ring joint according to claim 1.

3. The outer periphery includes a resin and a reinforcing material. The resin pipe for a rubber ring joint according to claim 2.

4. The resin pipe for a rubber ring joint according to any one of claims 1 to 3 is connected to a rubber ring joint having a rubber ring disposed on the inner surface of a receiving port. Rubber ring joint structure.

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