System for interrupting a flow and method for interrupting a flow

Abstract

The cutting system of the present application has: a straight pipe composed of a polyolefin-based material; and a knife gate having a semicircular arc-shaped first cutting edge that forms an opening in the form of a slit by cutting the straight pipe on the distal end side of the knife gate, and a circular arc band-shaped sealing portion that comes into contact with the cut surface of the straight pipe on the proximal end side of the knife gate, the knife gate having a pair of side edge portions that connect between the first cutting edge and the sealing portion, the first cutting edge and the side edge portions intruding into the inner circumferential surface along the straight pipe, the knife gate being formed in a flat plate shape having a first surface and a second surface between the first cutting edge and the sealing portion, and between the pair of side edge portions, the opening extending in the circumferential direction in the straight pipe, the sealing portion extending from the end portion on one side of the opening to the end portion on the other side, and in the interval from the end portion on one side to the end portion on the other side, extending from the inner circumferential surface to the outermost circumferential surface that is the outermost side of the straight pipe.

Description

[0001] This application is a divisional application of the invention patent application filed on February 19, 2021, with application number 202180015073.6 and invention title "Fluid Interception System and Interception Method". Technical Field

[0002] This invention relates to a fluid shut-off system and method for a straight pipe made of polyolefin-based material with a knife gate installed. Background Technology

[0003] Previously, it was known to have a process and apparatus for installing a knife gate in existing or newly installed polyethylene (PE) pipes (see Patent Documents 1 and 2). In the inventions disclosed in Patent Documents 1 and 2 below, a bottomed groove is formed in a straight pipe beforehand using an end mill, and after a thin skin is formed in the straight pipe, the knife gate penetrates the thin skin to form an opening, and the knife gate enters the straight pipe to prevent the flow of fluid.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: WO2020 / 013008 (Figure 16)

[0007] Patent Document 2: WO2019 / 167646 (Figure 16) Summary of the Invention

[0008] In all the prior art techniques mentioned above, the groove must be pre-formed. Therefore, not only are end mills and power tools needed to form the groove, but the number of construction steps is also increased, and the construction time is also longer.

[0009] Furthermore, in the aforementioned prior art, the groove formed by pre-cutting the tube with an end mill and the opening cut by a tool gate require sealing with a tool gate. Therefore, a tool gate with a rubber seal needs to be glued and fixed, which complicates the water-stopping structure.

[0010] Therefore, the object of the present invention is to provide a fluid cutoff system and method capable of solving these problems.

[0011] In the aforementioned prior art, the following is not disclosed: the tube is not pre-cut, that is, the opening is cut with a knife gate without forming a thin skin on the tube.

[0012] On the other hand, the applicant proposed using a punching tool to form an elongated opening in the PE pipe (JP2013-199991A). However, in this pilot application, the elongated, cylindrical punching tool could not advance to cut the PE pipe, and the attempt failed. The reasons for this failure are examined below.

[0013] In this pilot example, when the slender, cylindrical punch cutter cuts into the PE pipe, the PE pipe needs to avoid an amount corresponding to the thickness of the punch cutter's blade. However, the portion of the PE pipe surrounded by the cylindrical punch cutter is neither easily deformed nor compressed; therefore, it is presumed that the punch cutter was unable to advance and cut the PE pipe.

[0014] The cutting-off system of the present invention comprises: a straight pipe 2 made of a polyolefin-based material; and a flat-plate-shaped knife gate 1 that prevents the flow of fluid within the straight pipe 2, wherein...

[0015] A semi-circular first cutting edge 13 is formed on the distal end of the knife gate 1. This first cutting edge 13 cuts the straight pipe 2 to form a slit-like opening 20 that extends elongatedly along the circumferential direction R of the straight pipe 2.

[0016] An arc-shaped sealing portion 14 is formed on the proximal side of the knife gate 1. This sealing portion 14 is in contact with the cut surfaces 21 and 22 of the straight pipe 2 that define the opening 20.

[0017] The knife gate 1 has a pair of side edges 15, 15 connecting the semi-circular first cutting edge 13 and the arc-shaped sealing part 14.

[0018] The semi-circular first cutting edge 13 of the knife gate 1 and the pair of side edges 15, 15 penetrate the inner circumferential surface 23 of the straight pipe 2 along the inner circumferential surface 23.

[0019] The knife gate 1 is formed as a flat plate having a first surface 11 and a second surface 12 opposite to the first surface 11 between the first cutting blade 13 and the sealing portion 14, and between the pair of side edges 15, 15.

[0020] The slit-shaped opening 20 extends along the circumferential direction R in the straight tube 2.

[0021] The sealing portion 14 of the knife gate 1 extends from one end 25 of the opening 20 in the circumferential direction R to the other end 26, and is formed as an arc-shaped band extending from the inner circumferential surface 23 to the outermost circumferential surface 24 of the straight pipe 2 in the interval from the one end 25 to the other end 26.

[0022] On the other hand, the cutting-off method of the present invention is a fluid cutting-off method that uses a flat blade gate 1 to stop the flow of fluid in a straight pipe 2 made of polyolefin material, wherein,

[0023] The flat-shaped knife switch 1 has a first surface 11 and a second surface 12 opposite to the first surface 11.

[0024] A semi-circular first cutting edge 13 is formed on the distal end of the knife gate 1. This first cutting edge 13 cuts the straight pipe 2 to form a slit-like opening 20 that extends elongatedly along the circumferential direction R of the straight pipe 2.

[0025] An arc-shaped sealing portion 14 is formed on the proximal side of the knife gate 1. This sealing portion 14 is in contact with the cut surfaces 21 and 22 of the straight pipe 2 that define the opening 20.

[0026] Here, the truncation method includes the following steps:

[0027] The top 13T of the first cutting blade 13 abuts against the outermost peripheral surface 24 of the straight tube 2;

[0028] The first cutting blade 13 advances and cuts the straight tube 2 from the outermost peripheral surface 24 toward the internal space 27 of the straight tube 2;

[0029] The entire semi-circular first cutting edge 13 penetrates the half-circumference portion of the inner circumferential surface 23 of the straight tube 2.

[0030] After the above process, the semi-circular first cutting edge 13 of the knife gate 1 penetrates the inner circumferential surface 23 of the straight pipe 2, and the sealing part 14 is in contact with the cutting surfaces 21 and 22 to prevent the flow of fluid in the straight pipe 2.

[0031] According to the present invention, a flat blade gate is used instead of a punching tool to cut an opening in a straight pipe. Therefore, the straight pipe has room to avoid or deform relative to the first and second surfaces of the blade gate, enabling the blade gate to cut into the straight pipe.

[0032] Furthermore, in this invention, the first cutting edge abuts against the outermost circumferential surface of the straight pipe without a pre-formed groove, and cuts the straight pipe. Therefore, the process and tools for pre-forming a groove in the straight pipe are unnecessary. Consequently, the system is inexpensive and construction time is significantly reduced.

[0033] Furthermore, the first cutting edge and side edge of the flat-plate knife gate penetrate the inner circumferential surface of the straight pipe, and the arc-shaped sealing part contacts the cut surface of the straight pipe, thereby stopping the flow. Therefore, the knife gate's construction is simplified by eliminating the need for a rubber seal, resulting in a significant cost reduction.

[0034] In this invention, polyolefin materials refer to polyethylene, polypropylene, polybutene, etc. Attached Figure Description

[0035] Figure 1 This is a simplified perspective view of the system illustrating the contact process and the advancing cutting process of the cutting method of the present invention.

[0036] Figure 2This is a simplified three-dimensional diagram of the system, showing the cutting and penetration processes in the same manner.

[0037] Figure 3 (a), (b) and (c) are respectively a simplified top view, cross section view and longitudinal section view of an embodiment of the system.

[0038] Figure 4 This is a simplified cross-sectional view of the system illustrating one embodiment of the truncation method.

[0039] Figure 5 This is a cross-sectional view showing another example of this system.

[0040] Figure 6 This is a cross-sectional view of the system that can be used as an experimental example.

[0041] Figure 7 Similarly, this is a longitudinal sectional view.

[0042] exist Figure 3 of (b) Figure 5 (a) and Figure 5 In (b), the contact area between the knife switch and the PE pipe is marked with dotted patterns.

[0043] Explanation of reference numerals in the attached figures

[0044] 1: Knife switch

[0045] 11: First Page

[0046] 12: Second page

[0047] 13: First cutting edge

[0048] 13T: Top

[0049] 14: Sealing part

[0050] 15: Lateral edge

[0051] 16: Stopping component

[0052] 17: Second cutting edge

[0053] 18: Third cutting edge

[0054] 2: Straight pipe

[0055] 20: Opening

[0056] 21, 22: Cross-section

[0057] 23: Inner circumferential surface

[0058] 24: Outermost circumference

[0059] 25, 26: End

[0060] 27: Interior space

[0061] 30: Shell

[0062] 31, 32: First segmented shell and second segmented shell

[0063] 33: Valve box

[0064] 43: Valve stem

[0065] 50: Operating valve

[0066] 51: Slit for insertion

[0067] R: Circumferential direction

[0068] T: Wall thickness

[0069] φ: Inner diameter. Detailed Implementation

[0070] In a preferred system, a second cutting blade 17 connected to the first cutting blade 13 is formed on each of the pair of side edges 15, 15.

[0071] In this case, a second cutting edge is formed on each side edge connected to the first cutting edge, so that each side edge smoothly enters the end of the slit-like opening cut by the first cutting edge.

[0072] More preferably, the two ends of the sealing portion 14 that connect with the pair of ends 25, 26 of the opening 20 are sharp in the shape of cutting edges.

[0073] In this case, the top view shape of the sealing portion 14 of the knife switch matches the top view shape of the ends 25, 25 of the opening 20. Therefore, the water-stopping function is improved.

[0074] Preferably, the width between the second cutting edge formed on the pair of side edges 15, 15 is larger than the inner diameter φ of the straight tube 2.

[0075] In this case, the width between the second cutting blades of a pair of side edges is larger than the inner diameter of the straight pipe 2, so that even if the knife gate is eccentric relative to the straight pipe, it can still stop the water.

[0076] Preferably, it also has:

[0077] Housing 30, which surrounds a portion of the straight pipe 2 and the knife switch 1; and

[0078] The valve stem 43 moves the knife gate 1 until the first cutting edge 13 of the knife gate 1, which is disposed in the housing 30, cuts through the straight pipe 2 to form the opening 20, and the first cutting edge 13 penetrates along the inner peripheral surface 23.

[0079] In this system, a knife gate is used to stop the water flow through the PE pipe. Therefore, as long as the force required to cut into the PE pipe is sufficient, a sealed casing is not necessarily needed. However, if a casing and valve stem are provided for cutting into the PE pipe, the installation is easy even for those who are not skilled in the field.

[0080] In the preferred cutting method, the straight tube 2 is not pre-cut to form a groove, and the top 13T of the first cutting edge 13 abuts against the outermost circumferential surface 24 of the straight tube 2.

[0081] In this case, there is no need for equipment or procedures that require cutting straight pipes, which can reduce costs and shorten construction time. Moreover, the construction is simple and can be carried out even by unskilled workers.

[0082] More preferably, after the intrusion process, the following process is performed: the stop 16 installed on the knife gate 1 abuts against the outermost peripheral surface 24 of the straight pipe 2 to prevent the knife gate 1 from further advancing and cutting.

[0083] A feature described and / or illustrated in connection with the various embodiments or the examples described below can be used, or used in place of, the same or similar form and / or in combination with features of other embodiments or examples in one or more other embodiments or other examples.

[0084] Example

[0085] The present invention can be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for mere illustration and description and should not be used to define the scope of the invention. The scope of the invention is determined solely by the technical solutions. In the drawings, the same component numbers in multiple figures represent the same or equivalent parts.

[0086] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0087] First, a brief explanation of the truncation method.

[0088] Figure 1 and Figure 2 This provides a brief overview of the truncation method.

[0089] This truncation method includes Figure 1 (a) The process in which the top 13T of the first cutting edge 13 of the knife gate 1 abuts against the outermost peripheral surface 24 of the straight pipe 2. Figure 1 (b) ~ Figure 2 (b) The process of advancing and cutting and Figure 2 The intrusion process of (c).

[0090] It should be noted that, in Figure 1 and Figure 2 In the middle, a profile line is applied to the surface of the straight pipe 2 that is not cut by the knife gate 1.

[0091] Figure 1 The straight pipe 2 is made of a polyolefin material such as PE pipe. On the other hand, the knife switch 1 is made of metal such as stainless steel or ceramic.

[0092] Next, an example of this truncation system will be described.

[0093] Figure 3 The straight pipe 2 of (c) has an inner circumferential surface 23 with a uniform and constant inner diameter φ, an outermost circumferential surface 24 with a uniform and constant outer diameter, and a uniform and constant wall thickness T. Figure 3 (a) That is, the straight tube 2 is a resin tube obtained by extrusion from the extrusion port. An opening 20 is formed in such a straight tube 2.

[0094] like Figure 3 As shown in (a), the straight pipe 2 has a slit-like opening 20 formed by the knife gate 1. Figure 3 As shown in (b), the opening 20 extends along the circumferential direction R of the straight tube 2. Figure 3 The ends 25, 26 of the opening 20 in (a) are sharp (conical) in shape, just like the knife gate 1.

[0095] Figure 3 The knife gate 1 is formed as a flat plate that blocks the flow of fluid flowing in the internal space 27 within the straight pipe 2. The knife gate 1 has a first cutting edge 13, a sealing portion 14, and a pair of side edges 15, 15.

[0096] Figure 3 (b) The first cutting edge 13 is formed in a semi-circular arc shape protruding outward on the distal side of the knife gate 1, cutting the straight tube 2 to form a slit-like opening 20 that extends elongatedly along the circumferential direction R of the straight tube 2.

[0097] The sealing portion 14 is formed in an arc-shaped strip on the proximal side of the knife switch 1, as defined. Figure 3 The cut surfaces 21 and 22 of the straight pipe 2 of the opening 20 in (a) are connected.

[0098] Figure 3The pair of side edges 15, 15 of (b) are disposed between the semi-circular first cutting blade 13 and the arc-shaped sealing portion 14, connecting the sealing portion 14 and the first cutting blade 13.

[0099] The semi-circular first cutting edge 13 of the knife gate 1 and the side edges 15, 15 penetrate the inner circumferential surface 23 of the straight pipe 2 along the inner circumferential surface 23.

[0100] Figure 3 The knife gate 1 of (b) is formed such that, between the first cutting edge 13 and the sealing portion 14, and between the pair of side edges 15, 15 Figure 3 It is a flat plate having a first surface 11 and a second surface 12 located on the opposite side of the first surface 11, as in (a).

[0101] As mentioned above, Figure 3 The slit-shaped opening 20 of (a) and (b) extends along the circumferential direction R in the straight pipe 2. On the other hand, the sealing portion 14 of the knife gate 1 extends from one end 25 of the opening 20 in the circumferential direction R to the other end 26, and is formed in a semi-circular arc shape from the inner circumferential surface 23 to the outermost circumferential surface 24 of the straight pipe 2 in the interval from the one end 25 to the other end 26.

[0102] exist Figure 3 In (b), a second cutting edge 17 connected to the first cutting edge 13 may also be formed on the pair of side edges 15, 15 respectively.

[0103] exist Figure 3 In (a), the two ends of the sealing portion 14 of the knife gate 1 that connect with the pair of ends 25, 26 of the opening 20 are sharp in the shape of cutting blades.

[0104] like Figure 3 As shown in (b), the distance between the second cutting edge 17 formed on the pair of side edges 15, 15 is... Figure 3 The inner diameter φ of the straight pipe 2 in (a) is large.

[0105] like Figure 3 As shown in (b) and (c), a stop 16 may also be installed on the knife gate 1. This stop 16 prevents the first cutting edge 13, which has penetrated half of the inner circumferential surface 23 of the straight pipe 2, from further cutting after the first cutting edge 13 has penetrated the inner circumferential surface 23. The stop 16 is preferably made of metal and has internal threads for valve stem engagement.

[0106] Next, the details of the truncation method will be explained.

[0107] like Figure 4 As shown in (a), firstly, the top 13T of the first cutting edge 13 abuts against the outermost circumferential surface 24 of the straight tube 2. At this time, the straight tube 2 is pressed down by the first cutting edge 13 and deformed into a slightly flattened shape.

[0108] There is no need to pre-cut grooves in the straight pipe 2; the top 13T of the first cutting blade 13 abuts against the outermost circumferential surface 24 of the straight pipe 2.

[0109] Next, as Figure 4 (b) ~ Figure 4 As in (d), the first cutting edge 13 cuts into the straight tube 2 from the outermost circumferential surface 24 toward the space 27 inside the straight tube 2 and then advances to cut. During this advancing cut, the straight tube 2 also undergoes some deformation.

[0110] After that, as Figure 4 As in (d) and (e), the entire semi-circular first cutting edge 13 penetrates half of the inner circumferential surface 23 of the straight pipe 2. That is, the entire length of the semi-circular first cutting edge 13 penetrates half of the inner circumferential portion 23 of the straight pipe 2.

[0111] Thus, the semi-circular first cutting edge 13 of the knife gate 1 penetrates the inner circumferential surface 23 of the straight pipe 2, and Figure 3 The sealing part 14 is in contact with the cut surfaces 21 and 22 to prevent the flow of fluid in the straight pipe 2.

[0112] like Figure 3 As in (b) and (c), after the intrusion process, the stop 16 installed on the knife gate 1 abuts against the outermost peripheral surface 24 of the straight pipe 2 to prevent the knife gate 1 from further advancing and cutting.

[0113] Figure 5 (a) and (b) represent another example of this system.

[0114] like Figure 5 As in (a), the pair of cutting edge-shaped side edges 15, 15 of the knife gate 1 can also be constructed with a slight taper to cut into the straight pipe 2. In this case, the water-stopping performance will be further improved.

[0115] like Figure 5 As in (b), a third cutting edge 18 can also be provided at both ends of the sealing part 14.

[0116] Next, an example of the construction of a truncation system will be described.

[0117] Figure 6 and Figure 7 The system shown is a suitable construction for use as an experiment, where only a single item is produced.

[0118] exist Figure 6 and Figure 7 In the middle, the sealed housing 30 surrounds a portion of the straight pipe 2 and the knife switch 1 in a watertight state. The housing 30 can also be divided into a first divided housing 31 and a second divided housing 32. A valve box 33 is integrated into the second divided housing 32.

[0119] The valve housing 33 houses the knife gate 1 in the open state and the valve stem 43. The valve stem 43 is constructed in a well-known manner to move the knife gate 1 until the first cutting edge 13 of the knife gate 1, which is disposed in the housing 30, cuts through the straight pipe 2 to form the opening 20, and the first cutting edge 13 penetrates along the inner circumferential surface 23.

[0120] Alternatively, a well-known operating valve 50 may be provided within the sealed housing 30 to separate the second partition housing 32 from the valve box 33. The operating valve 50 may be a rod valve and have an access slit 51 for the knife gate 1 to enter.

[0121] It should be noted that the shell 30, etc., can also be a casting. Additionally, in Figure 7 The figure shows the state of the knife gate 1 returning to the valve box 33 after the opening 20 is formed in the straight pipe 2.

[0122] The applicant modified the shell of the casting (Water Research & Development Co., Ltd.), utilizing... Figure 6 and Figure 7 The knife gate 1 was used to cut the straight pipe 2, and a water-stopping test was performed. The result confirmed that the knife gate 1 could be used to cut the straight pipe 2 (PE pipe) and penetrate into the pipe until the first cutting edge 13 reached the inner circumferential surface 23. The reason why the cutting proceeded without producing chips can be inferred to be because the PE pipe deformed during the cutting process.

[0123] In addition, water was used to fill the PE pipe and its water-stopping performance was confirmed. No leakage was found that would hinder construction.

[0124] Preferred embodiments have been described above with reference to the accompanying drawings, but various changes and modifications will be readily conceived by those skilled in the art upon viewing this specification.

[0125] For example, knife switches can also be made of ceramic.

[0126] In addition, no stop is required.

[0127] Therefore, the above-mentioned changes and modifications can be interpreted as falling within the scope of the present invention as defined by the technical solution.

[0128] Industrial availability

[0129] The system and method of the present invention can be used to insert a knife switch into the piping of waterways, gas lines, etc., and use the inserted knife switch to stop the flow of fluid.

[0130] In addition, the process method of the present invention can also be used when valve insertion is performed without interruption of flow, in addition to the newly installed piping.

Claims

1. A cutoff system comprising: a straight pipe (2) made of a polyolefin material; and a flat-plate gate (1) that prevents the flow of fluid within the straight pipe (2), wherein, A semi-circular first cutting edge (13) is formed on the far end side of the knife gate (1). The first cutting edge (13) cuts the straight tube (2) to form a slit-like opening (20) that extends elongatedly along the circumferential direction (R) of the straight tube (2). An arc-shaped sealing portion (14) is formed on the proximal side of the knife gate (1), and the sealing portion (14) is in contact with the cut surface (21, 22) of the straight pipe (2) that defines the opening (20). The knife gate (1) has a pair of side edges (15, 15) connecting the semi-circular first cutting edge (13) and the arc-shaped sealing part (14). The semi-circular first cutting edge (13) of the knife gate (1) and the pair of side edges (15, 15) penetrate the inner circumferential surface (23) of the straight tube (2) along the inner circumferential surface (23). The knife gate (1) is formed as a plate having a first surface (11) and a second surface (12) opposite to the first surface (11) between the first cutting edge (13) and the sealing part (14) and between the pair of side edges (15, 15). The slit-like opening (20) extends circumferentially (R) within the straight tube (2). The sealing portion (14) of the knife gate (1) extends from one end (25) of the opening (20) in the circumferential direction (R) to the other end (26), and extends from the inner circumferential surface (23) to the outermost circumferential surface (24) of the straight pipe (2) in the interval from the one end (25) to the other end (26) to form an arc-shaped strip. A second cutting edge (17) connected to the first cutting edge (13) is formed on each of the pair of side edges (15, 15). A stop (16) is installed on the knife gate (1). The stop (16) abuts against the outermost circumferential surface (24) of the straight pipe (2) to prevent the first cutting edge (13) that has penetrated the inner circumferential surface (23) of the straight pipe (2) from further cutting after the first cutting edge (13) has penetrated the inner circumferential surface (23). The second cutting edge (17) extends to the stop (16).

2. The truncation system according to claim 1, wherein, The two ends of the sealing part (14) that connect with the pair of ends (25, 26) of the opening (20) are sharp in the shape of cutting blades.

3. The truncation system according to claim 2, wherein, It also has: Housing (30), which surrounds a portion of the straight pipe (2) and the knife gate (1); and The valve stem (43) moves the knife gate (1) until the first cutting edge (13) of the knife gate (1) disposed in the housing (30) cuts the straight pipe (2) to form the opening (20) and the first cutting edge (13) penetrates along the inner circumferential surface (23).

4. The truncation system according to claim 1, wherein, The width between the second cutting blades (17) formed on the pair of side edges (15, 15) is larger than the inner diameter (φ) of the straight tube (2).

5. The truncation system according to claim 4, wherein, It also has: Housing (30), which surrounds a portion of the straight pipe (2) and the knife gate (1); and The valve stem (43) moves the knife gate (1) until the first cutting edge (13) of the knife gate (1) disposed in the housing (30) cuts the straight pipe (2) to form the opening (20) and the first cutting edge (13) penetrates along the inner circumferential surface (23).

6. The truncation system according to claim 1, wherein, It also has: Housing (30), which surrounds a portion of the straight pipe (2) and the knife gate (1); and The valve stem (43) moves the knife gate (1) until the first cutting edge (13) of the knife gate (1) disposed in the housing (30) cuts the straight pipe (2) to form the opening (20) and the first cutting edge (13) penetrates along the inner circumferential surface (23).

7. A method for cutting off fluid flow, wherein a plate-shaped knife gate (1) is used to prevent the flow of fluid within a straight pipe (2) made of a polyolefin material, wherein, The flat knife switch (1) has a first surface (11) and a second surface (12) opposite to the first surface (11). A semi-circular first cutting edge (13) is formed on the far end side of the knife gate (1). The first cutting edge (13) cuts the straight tube (2) to form a slit-like opening (20) that extends elongatedly along the circumferential direction (R) of the straight tube (2). An arc-shaped sealing portion (14) is formed on the proximal side of the knife gate (1), and the sealing portion (14) is in contact with the cut surface (21, 22) of the straight pipe (2) that defines the opening (20). The knife gate (1) has a pair of side edges (15, 15) connecting the semi-circular first cutting edge (13) and the arc-shaped sealing part (14). A second cutting edge (17) connected to the first cutting edge (13) is formed on each of the pair of side edges (15, 15). A stop (16) is installed on the knife gate (1) to prevent the first cutting edge (13) that has penetrated the inner circumferential surface (23) of the straight pipe (2) from further cutting after the first cutting edge (13) has penetrated the inner circumferential surface (23). The second cutting edge (17) extends into the stop (16). Here, the fluid cutoff method includes the following steps: The top (13T) of the first cutting blade (13) abuts against the outermost peripheral surface (24) of the straight tube (2). The first cutting edge (13) advances and cuts the straight tube (2) from the outermost circumferential surface (24) toward the interior space (27) of the straight tube (2); The entire semi-circular first cutting edge (13) penetrates the half-circumference portion of the inner circumferential surface (23) of the straight tube (2). After the above process, the semi-circular first cutting edge (13) of the knife gate (1) penetrates the inner circumferential surface (23) of the straight pipe (2), and the sealing part (14) is in contact with the cutting surface (21, 22) to prevent the flow of fluid in the straight pipe (2).

8. The fluid cutoff method according to claim 7, wherein, Instead of pre-forming a groove obtained by cutting the straight tube (2), the top (13T) of the first cutting edge (13) abuts against the outermost circumferential surface (24) of the straight tube (2).

9. The fluid cutoff method according to claim 8, wherein, After the intrusion process, the following process is performed: the first cutting blade (13) further advances to cut after the stop (16) installed on the knife gate (1) abuts against the outermost peripheral surface (24) of the straight pipe (2) to prevent intrusion into the half-circumference of the inner peripheral surface (23) of the straight pipe (2).

Images