Connection device for metal pipes

Abstract

A connection device for metal pipes, comprising: an insertion part provided at one end of a first metal pipe; an expanded pipe part provided at one end of a second metal pipe; and a locking bolt, wherein: the expanded pipe part is provided with a plurality of locking holes that penetrate through the wall of the expanded pipe part; the insertion part has a ring-shaped protrusion part provided along the outer circumferential surface thereof; the insertion part is inserted into the expanded pipe part to form a coupled state in which the insertion part and the expanded pipe part are joined; in the coupled state, there is a gap space between the inner circumferential surface of the expanded pipe part and the outer circumferential surface of the insertion part; the gap space includes a first gap space located toward the tip of the insertion part with respect to the protrusion part, and a second gap space located toward the tip of the expanded pipe part; two locking holes form a pair; the locking bolt is inserted to pass through the pair of locking holes and the second gap space, to lock the coupled state into a locked state; and, in the locked state, the locking bolt catches on the protrusion part, to prevent the insertion part from arbitrarily moving backward and loosening the coupled state.

Description

Metal pipe connecting device

[0001] The present invention relates to a connecting device provided at the end of a metal pipe to connect the metal pipe and lock the connection.

[0002]

[0003] When transporting fluids over long distances using pipes, multiple pipes are sometimes connected to each other.

[0004] As methods of connecting pipes, there are various methods used, including a method of forming a flange at the end of a pipe and connecting it, a method of inserting the end of a pipe into a coupling and connecting it, and a method of forming a spiral at the end of a pipe and connecting it with a screw.

[0005] When connecting pipes, the clamping force required to maintain the connection is proportional to the pipe cross-sectional area. Therefore, larger diameter pipes are more difficult to secure, making it difficult to ensure airtightness at the connection. Flange connections maintain airtightness by inserting sealant between the flange plates. However, if the connected pipes are not level due to ground settlement or vibration, sufficient joint strength at the flange joint may not be maintained, resulting in compromised airtightness. Cast iron pipes using connecting sleeves maintain airtightness by inserting sealant at the joints of the pipes on both sides within the connecting sleeve. This method relies on the pipe's own weight for fixation, making it unstable. Recently, separate anti-separation members have been used for fixation, but these are expensive and require complex installation. Conventional connecting techniques for large-diameter pipes consistently suffer from both fixation and airtightness issues, so welding is generally used for pipes with diameters greater than 200 mm.

[0006] Furthermore, in the case of large-diameter metal pipes installed horizontally, the downward pressure of the sealing member may be strongly exerted by the weight of the pipe itself and the weight of the fluid passing through it, resulting in excessive compression. If this downward compression occurs, the pressure applied upward to the sealing member may be reduced, and the sealing effect due to the elasticity of the sealing member may not be sufficiently secured in the upward direction.

[0007] Prior art patent No. 10-0909887 relates to a sewer pipe for connection and fixation. A separate connecting device is attached to the pipes to be connected, and the pipes are connected through this connecting device. A groove is formed by digging a portion of the outer surface of the insertion portion of the connecting device, and a locking bolt is inserted into this groove to secure the connection. However, digging the outer surface of the insertion portion may damage the insertion portion, making it unsuitable for pressure pipes. This method of digging the outer surface of the insertion portion can be applied when the wall of the insertion portion is thick. Typically, metal pipes are much thinner than plastic pipes, so the structure of digging the outer surface of the insertion portion to form a groove is difficult to apply. If the wall of the metal pipe is made thick, the pipe becomes excessively heavy.

[0008] (Patent Document 1) Korean Registered Patent KR 10-0909887 B1

[0009]

[0010] The present invention aims to provide a connecting device that can easily connect large-diameter metal pipes having a diameter of about 80 to 500 mm and easily lock the connection.

[0011] The present invention aims to provide a connecting device having excellent pressure resistance and airtightness at a portion where a metal pipe is connected.

[0012]

[0013] A metal pipe connecting device according to the present invention includes an insertion portion provided at one end of a first metal pipe, an expansion portion provided at one end of a second metal pipe, and a locking bolt.

[0014] The expansion member is provided with multiple locking holes penetrating the wall of the expansion member.

[0015] A ring-shaped protrusion is provided along the outer surface of the insert.

[0016] The insertion part is inserted into the expansion part, and the insertion part and the expansion part are combined into a combined state. In the combined state, there is a separation space between the inner surface of the expansion part and the outer surface of the insertion part, and the separation space includes a first separation space at the front end of the insertion part and a second separation space at the front end of the expansion part based on the protrusion.

[0017] The locking holes are paired in two, and the locking bolt is inserted through the pair of locking holes and the second separation space to lock the joint state of the pipe and create a locked state.

[0018] When the pipe joint is locked, the locking bolt catches on the protrusion, preventing the insertion part from moving backward arbitrarily against the user's will and loosening the pipe joint.

[0019] The protrusion height of the protrusion may be greater than or equal to the wall thickness of the insert.

[0020] The locking hole may have a locking hole extension portion protruding from the outer surface of the expansion member.

[0021] The locking bolt may be in tangential contact with the inner periphery of the expansion member or the outer periphery of the insert member.

[0022] A ring-shaped sealing member made of elastic material is installed in the first separation space so that it can come into contact with the outer surface of the insertion part and the inner surface of the expansion part.

[0023] The protrusion may have a protrusion height of the lower section that is higher than the protrusion height of the upper section by an additional protrusion, and the additional protrusion may also function as an anti-overpressure member.

[0024] A foreign matter prevention cap made of resin may be inserted into the annular space between the tip of the expansion member and the insertion member to prevent the inflow of foreign matter. The foreign matter prevention cap may also include a metal overpressure prevention member in its lower section.

[0025] Meanwhile, the connecting device of the present invention may be provided with two sealing members isolated from each other, a pressure check space defined by the two sealing members and the outer surface of the insertion part and the inner surface of the expansion part, and a pressure check hole penetrating the wall of the expansion part and communicating with the pressure check space.

[0026]

[0027] According to the present invention, large-diameter metal pipes can be easily joined and the joining can be easily locked.

[0028] According to the present invention, the pressure and airtightness of the part where the metal pipe is connected are excellent.

[0029] According to the present invention, a metal pipe having a thin wall thickness can be mechanically connected without welding.

[0030] The present invention can solve the problem of leakage due to overpressure and further extend the life of the pipe.

[0031] In particular, the present invention is advantageous in connecting and milling large-diameter metal pipes having a diameter of about 80 to 500 mm.

[0032]

[0033] FIG. 1 illustrates step-by-step a method of connecting a metal pipe using a connecting device according to an embodiment of the present invention.

[0034] Figure 2 is a perspective view of a pipe connecting device according to an embodiment of the present invention.

[0035] FIG. 3 is a longitudinal cross-sectional view showing a state in which an insertion portion of a first metal pipe is inserted into an expansion portion of a second metal pipe according to an embodiment of the present invention.

[0036] Figure 4 is a perspective view of a pipe having a locking hole extension portion according to an embodiment of the present invention.

[0037] Figures 5 and 6 are cross-sectional views of a point where a locking hole is located in a connected pipe according to an embodiment of the present invention.

[0038] Figure 7 is a perspective view of a metal pipe according to an embodiment of the present invention.

[0039] Figures 8 and 9 are cross-sectional views of a connecting device according to an embodiment of the present invention.

[0040] Figures 10 and 11 are cross-sectional views of points where protrusions are located in connected pipes according to embodiments of the present invention.

[0041] Fig. 12 is a perspective view of a metal pipe according to an embodiment of the present invention.

[0042] Figures 13 to 17 are cross-sectional views of a connecting device according to an embodiment of the present invention.

[0043] Fig. 18 is a perspective view of a foreign matter prevention cap according to an embodiment of the present invention.

[0044]

[0045] In the present invention, 'lower' means the direction in which gravity is directed when piping a metal pipe horizontally, and 'upper' means the opposite direction.

[0046] In the present invention, the 'retraction' of the pipe refers to movement in the direction in which the pipe is released from its joint.

[0047] The present invention relates to a connecting device provided in a metal pipe itself, and the metal pipe to be connected is made of a material such as stainless steel, steel pipe, or cast iron.

[0048] The metal pipe connecting device of the present invention may have a sealing member, a pressure sensor, a compression member, an anti-overpressure member, or a foreign matter prevention cap.

[0049] The two ends of the metal pipes to be connected may have the same or different shapes. For example, a metal pipe may have only inserts or only expansions at both ends, or it may have an insert at one end and an expansion at the other end. The objects to be connected are a metal pipe having an insert and a metal pipe having an expansion, and the metal pipes are connected by inserting the insert into the expansion.

[0050] Hereinafter, the present invention will be described with reference to the drawings.

[0051] FIG. 1 illustrates step-by-step a method for connecting metal pipes using a connecting device according to an embodiment of the present invention. FIG. 1 (a) shows a state in which a first metal pipe (1) and a second metal pipe (2) are separated, FIG. 1 (b) shows a state in which the first metal pipe (1) and the second metal pipe (2) are joined, and FIG. 1 (c) shows a state in which the first metal pipe (1) and the second metal pipe (2) are joined in a locked state.

[0052] Figure 2 is a perspective view of a pipe connecting device according to an embodiment of the present invention.

[0053] Fig. 3 is a longitudinal cross-sectional view showing a state in which the insertion portion (110) of the first metal pipe (1) is inserted into the expansion portion (120) of the second metal pipe (2) according to an embodiment of the present invention. This inserted state can be locked using a locking bolt (130).

[0054] FIG. 4 is a perspective view of a pipe having a locking hole extension portion (121a) according to an embodiment of the present invention, and FIGS. 5 and 6 are cross-sectional views of a point where a locking hole (121) is located in a connected pipe according to an embodiment of the present invention.

[0055] Fig. 7 is a perspective view of a metal pipe according to an embodiment of the present invention, and Figs. 8 and 9 are longitudinal cross-sectional views of a connecting device according to an embodiment of the present invention. Figs. 10 and 11 are cross-sectional views of a point where a protrusion (111) is located in a connected pipe according to an embodiment of the present invention, and Fig. 12 is a perspective view of a metal pipe according to an embodiment of the present invention. Figs. 13 to 17 are longitudinal cross-sectional views of a connecting device according to an embodiment of the present invention, and Fig. 18 is a perspective view of a foreign matter prevention cap (180) according to an embodiment of the present invention.

[0056]

[0057] Insert

[0058] The first metal pipe (1) to be connected has an insertion portion (110) at one end.

[0059] The insertion portion (110) has a cylindrical shape and has a ring-shaped protrusion (111) on its outer surface.

[0060] The ring-shaped protrusion (111) may be one or two or more. Fig. 7 is an example of one protrusion (111), and Fig. 12 is an example of two protrusions (111).

[0061] An insertion part (110) having one protrusion (111) is advantageous for connecting metal pipes with a diameter of 80 mm to 500 mm and a maximum pressure of 10 bar. An insertion part (110) having two protrusions (111) can also use multiple U-bolts, for example, as locking bolts (130), and is advantageous for connecting metal pipes with a diameter of 500 mm to 1500 mm and a maximum pressure of 5 bar.

[0062] The side surface of the protrusion (111) may be a plane perpendicular to the longitudinal center line of the first metal pipe (1), but may not be perpendicular or may not be a plane.

[0063] When the insertion part (110) is inserted into the expansion part (120) and the metal pipe is connected, and the locking bolt (130) inserted through the locking hole (121) comes into contact with the side of the protrusion (111), the locking bolt (130) acts as a lock and the protrusion (111) acts as a catch on which the lock is caught, thereby preventing the insertion part (110) from being arbitrarily retracted against the user's will and the pipe connection from becoming loose or released.

[0064] Referring to Fig. 3, the locking function of the locking bolt (130) is advantageous when the protrusion height (h1) of the protrusion (111) protruding from the outer surface of the insertion portion (110) is high, because the lock is locked more securely.

[0065] As in the prior art patent No. 10-0909887, when a locking bolt passes through the inside of the groove and the groove serves as a catch for the locking bolt, the recessed portion of the wall inevitably reduces its ability to resist external force applied to the wall. Furthermore, while the groove must be deep to ensure a more secure locking, it is impossible to make the groove deeper than the wall thickness of the insertion portion. Furthermore, the deeper the groove, the lower the wall's ability to resist external force.

[0066] In contrast, in the present invention, there is no particular limitation on the protrusion height (h1) of the protrusion (111). The protrusion height (h1) of the protrusion (111) may have a size greater than or equal to the wall thickness (t1) of the insertion portion (110). Since there is no limitation on the protrusion height (h1) of the protrusion (111), a locking bolt (130) with a large body diameter can also be used without particular limitation. In addition, compared to the prior art of digging a groove in the wall of the insertion portion (110), forming the protrusion (111) in the wall of the insertion portion (110) as in the present invention improves the resistance of the wall to external force applied to the wall.

[0067]

[0068] Expansion department

[0069] The second metal pipe (2) to be connected has an expansion member (120) at one end. The expansion member (120) has a cylindrical shape and is sized to accommodate the insertion member (110) of the first metal pipe (1).

[0070] The expansion member (120) has two or more locking holes (121) penetrating its wall. The locking holes (121) are formed chordwise along the inner circumference of the expansion member (120). Two locking holes (121) formed on the same axis form a pair, and the expansion member (120) may have two or more pairs of locking holes (121).

[0071] As shown in FIGS. 7, 8, and 12, the expansion member (120) may be a two-stage structure composed of an outer end (120a) and an inner end (120b). The outer end (120a) is the front end portion of the expansion member (120), and the inner diameter of the outer end (120a) is larger than the inner diameter of the inner end (120b), and the inner diameter of the inner end (120b) is larger than the outer diameter of the insertion portion (110). In this case, a sealing member (140), a protrusion (111) of the first metal pipe (1), and a locking bolt (130) may be arranged in the area of ​​the outer end (120a).

[0072] The difference between the inner diameter of the inner end (120b) and the outer diameter of the insertion portion (110) may be less than half the difference between the inner diameter of the outer end (120a) and the outer diameter of the protrusion (111). The inner end (120b), which has a smaller inner diameter than the outer end (120a), stabilizes the connected metal pipe. In addition, the inner end (120b) may also function as an anti-overpressure member (200).

[0073] When the insertion part (110) of the present invention is inserted into the expansion part (120) and connected to each other, a separation space (190) is created between the inner surface of the expansion part (120) and the outer surface of the insertion part (110). The separation space (190) includes a first separation space (191) on the front end side of the insertion part (110) with respect to the protrusion (111) and a second separation space (192) on the opposite side (i.e., the front end side of the expansion part).

[0074] Meanwhile, when pressure is applied internally while the pipes are joined, the pipe receives a force that causes it to retreat in the longitudinal direction. If the internal pressure is high, the locking bolt (130) may be damaged by a strong shear force when the pipe retreats in the longitudinal direction.

[0075] Breakage of the locking bolt (130) can be prevented by expanding the area where the locking bolt (130) comes into contact with the locking hole (121). To this end, in the present invention, the locking hole (121) may be extended from the outer surface of the expansion member (120).

[0076] Figures 4(a) and (b) illustrate examples of a locking hole extension portion (121a) protruding from the outer surface of an expansion member (120) at different viewpoints, respectively, and Figure 4(a) shows the locking hole extension portion (121a) in an enlarged form, separated separately. The locking hole extension portion (121a) is a part of the locking hole (121).

[0077] The locking hole extension portion (121a) can be manufactured separately and attached to the expansion portion (120), or it can be formed integrally with the pipe during the manufacture of the pipe.

[0078] When the locking hole extension portion (121a) is formed integrally with the expansion portion (120), a predetermined length is cut in the longitudinal direction of the expansion portion (120), and one side of the cut portion is pushed outward from the expansion portion (120) so as to protrude, so that the protruding portion becomes the locking hole extension portion (121a), and the locking hole (121) is formed as the cut portion forms an arch.

[0079] FIGS. 5 and 6 are cross-sectional views of a pipe at a point where a locking hole (121) is located when the pipe is connected according to an embodiment of the present invention. FIG. 5 is an example without a locking hole extension portion (121a) protruding from the outer surface of the expansion portion (120), and C1 is an area where the locking hole (121) and the locking bolt (130) come into contact. FIG. 6 is an example with a locking hole extension portion (121a), and a foreign matter prevention ring (122) is installed between the upper and lower ends of the locking bolt (130) and the locking hole extension portion (121a), and C2 is an area where the locking hole (121) and the locking bolt (130) come into contact. The case of C2 is more advantageous than the case of C1 in preventing damage to the housing. In addition, if the extension portion starts from the housing in a curved shape, it is advantageous in preventing damage to the locking bolt (130) due to shear force.

[0080]

[0081] locking bolt

[0082] The locking bolt (130) is inserted into the locking hole (121) and comes into contact with the side of the protrusion (111) provided in the insertion portion (110), thereby preventing the protrusion (111) from accidentally or suddenly retracting and releasing the connection of the metal pipe against the user's intention.

[0083] The locking holes (121) are paired in two, and the locking bolts (130) are inserted so as to penetrate the pair of locking holes (121) and pass through the second separation space (192). The locking bolts (130) penetrating the pair of locking holes (121) may tangentially contact the inner circumference of the expansion portion (120) or the outer circumference of the insertion portion (110).

[0084] The locking bolt (130) may be a straight type penetrating a pair of locking holes (121), a U-bolt type penetrating two pairs of locking holes (121), or may have other shapes.

[0085] The locking bolt (130) inserted into the locking hole (121) can be fixed by tightening a nut.

[0086]

[0087] Absence of confidentiality

[0088] When metal pipes are connected by fitting, a gap (190) is created between the inner surface of the expansion portion (120) and the outer surface of the insert portion (110), which may weaken the airtightness. Therefore, to maintain airtightness, an airtight member (140) such as an elastic O-ring may be used.

[0089] The confidential member (140) is provided in the first separation space (191) and contacts the outer surface of the insertion portion (110) and the inner surface of the expansion portion (120).

[0090]

[0091] Overpressure prevention member

[0092] If the lower part of the sealing member (140) is over-pressed and the upper part is under-pressed due to the load of the metal pipe and the load of the fluid flowing inside the metal pipe, the sealing effect of the sealing member (140) may be reduced.

[0093] Excessive compression is likely to occur in large-diameter metal pipes. However, even in the case of small-diameter pipes, if the connecting portion is bent or bent due to vibration or uneven settlement, excessive compression may occur on one side of the sealing member (140) and the opposite side may become relatively loose, thereby reducing the sealing performance.

[0094] The connecting device of the present invention may be provided with an anti-pressure member (200) to prevent a decrease in airtightness. One or more anti-pressure members (200) may be provided.

[0095] The over-pressure prevention member (200) may have a form indicated by drawing symbols 200a, 200b, 200c, and 200d.

[0096] As shown in FIGS. 9 and 10, if the protrusion height of the lower section of the protrusion (111) on the first metal pipe (1) is made higher than the protrusion height of the upper section, the additional protrusion height portion (200a) of the lower section can function as an over-pressure prevention member (200).

[0097] Additionally, as shown in Fig. 11, a metal plate (200b) inserted into the gap between the lower section of the protrusion (111) and the inner surface of the expansion portion (120) of the second metal pipe (2) may be an anti-overpressure member (200).

[0098] In FIG. 7, FIG. 8 and FIG. 12, among the two-stage structures (120a, 120b) of the expansion member (120), the inner stage (120b) may be an anti-pressure member (200).

[0099] In FIGS. 16 to 18, a metal anti-pressure member (200) forms part of a foreign matter prevention cap (180).

[0100]

[0101] Foreign body prevention cap

[0102] The foreign matter prevention cap (180) prevents foreign substances from entering the separation space (190). The foreign matter prevention cap (180) may be an annular shape made of a resin material, and may be installed in the annular space between the tip of the expansion portion (120) and the insertion portion (110).

[0103] In FIGS. 15 to 18, the foreign body prevention cap (180) has an annular insertion projection (180a), and the annular insertion projection (180a) is inserted into an annular space between the tip of the expansion portion (120) and the insertion portion (110). The upper and lower sections of the annular insertion projection (180a), or at least one of the upper and lower sections, may be a metal anti-pressure member (200). In FIG. 17, the annular insertion projection (180a) is provided with a member insertion groove (180b), and the anti-pressure member (200) is inserted into the member insertion groove (180b).

[0104]

[0105] Pressure measuring means

[0106] The connecting device according to the present invention may also be provided with means for measuring the pressure of the metal pipe.

[0107] The connecting device according to the present invention may have one sealing member (140), but may also have two or more. In Fig. 13, there are two sealing members (140) separated by a metallic isolation member (142). In addition, there is a pressure check space (150) partitioned by these two sealing members (140), the outer surface of the insertion part (110), and the inner surface of the expansion part (120), and there is also a pressure check hole (151) penetrating the wall of the expansion part (120) and communicating with the pressure check space (150). If the pressure check space (150) and the pressure check hole (151) exist in this way, a hydraulic pressure test can be performed to determine the sealing performance by putting water in the pressure check space (150), or a pressure sensor (161) can be attached to the pressure check hole (151) to measure the pressure change in the pressure check space (150). For example, paint can be put in the pressure check space (150) so that the paint comes out when the seal fails, and a sensor that conducts electricity when it comes into contact with water can be put in so that an LED turns on when the seal fails.

[0108] In addition, an annular pressure sensor (161) may be installed on the surface of the annular insertion protrusion (180a) of the foreign substance prevention cap (180) or in the groove of the annular insertion protrusion (180a). The foreign substance prevention cap (180) of FIG. 18 is equipped with an annular pressure sensor (161).

[0109]

[0110] Compression member

[0111] The metal pipe connecting device of the present invention may also include a compression member (170) that compensates for thermal expansion of the metal pipe. The compression member (170) has an elastic structure formed of rubber, silicone, a corrugated pipe, or the like.

[0112] Fig. 14 shows an example in which a compression member (170) is provided between a protrusion (111) and a sealing member (140). When thermally expanded, the protrusion (111) compresses the compression member (170), and the compression member (170) can absorb changes in pipe length due to thermal expansion. In pipes with significant thermal changes, a compression member (170) may also be installed between the protrusion (111) and the locking bolt (130).

[0113]

[0114] (Explanation of symbols)

[0115] 1: First metal pipe

[0116] 2: Second metal pipe

[0117] 110: Insertion part

[0118] 111: Protrusion

[0119] 120: Expansion Unit

[0120] 121: Locking Hole

[0121] 121a: Locking hole extension

[0122] 130: Locking bolt

[0123] 140: Absence of confidentiality

[0124] 141: Sealing washer

[0125] 142: Absence of isolation

[0126] 150: Pressure check space

[0127] 151: Pressure check hole

[0128] 161: Pressure sensor

[0129] 170: Compression member

[0130] 180: Foreign body prevention cap

[0131] 190: Separation space

[0132] 191: First separation space

[0133] 192: Second Separation Space

[0134] 200: Overpressure prevention member

Claims

1. A connecting device for a metal pipe, including an insertion portion (110) provided at one end of a first metal pipe (1), an expansion portion (120) provided at one end of a second metal pipe (2), and a locking bolt (130). The above expansion member (120) is provided with a plurality of locking holes (121) penetrating the wall of the above expansion member (120). A ring-shaped protrusion (111) is provided along the outer surface of the above insertion portion (110), The above insertion part (110) is inserted into the expansion part (120) so that the insertion part (110) and the expansion part (120) are combined into a combined state. In the above-mentioned combined state, there is a separation space (190) between the inner surface of the expansion member (120) and the outer surface of the insertion member (110). The above separation space (190) includes a first separation space (191) on the front side of the insertion part (110) based on the protrusion (111) and a second separation space (192) on the front side of the expansion part (120). The above locking hole (121) includes a locking hole extension portion (121a) protruding from the outer surface of the expansion member (120), The above locking holes (121) are two in number to form a pair. The above locking bolt (130) is inserted so as to penetrate the pair of locking holes (121) and the second separation space (192) to lock the combined state and make it a locked state. In the above locked state, the locking bolt (130) is caught on the protrusion (111), thereby preventing the insertion part (110) from moving backward arbitrarily and the combined state from becoming loose. A connecting device for metal pipes.

2. A connecting device for a metal pipe in the first paragraph, wherein the protrusion height (h1) of the protrusion (111) is greater than or equal to the wall thickness (t1) of the insertion portion (110).

3. In the first paragraph, the locking hole (121) is a metal pipe connecting device formed integrally by cutting the expansion part (120) in the longitudinal direction to a predetermined length and pushing one side of the cut portion toward the outside of the expansion part (120) so that the protruding portion becomes the locking hole extension portion (121a), and the cut portion forms an arch to become the locking hole (121).

4. In the first paragraph, a connecting device of a metal pipe in which the locking bolt (130) is in tangential contact with the inner circumference of the expansion member (120).

5. In the first paragraph, a connecting device of a metal pipe in which the locking bolt (130) is in tangential contact with the outer circumference of the insertion portion (110).

6. In the first paragraph, a metal pipe connection device having a ring-shaped sealing member (140) made of elastic material that is installed in the first separation space (191) and contacts the outer surface of the insertion part (110) and the inner surface of the expansion part (120).

7. In the first paragraph, the protrusion (111) is a metal pipe connecting device in which the protrusion height of the lower section is higher than the protrusion height of the upper section by an additional protrusion (200a), and the additional protrusion (200a) functions as an over-pressure prevention member (200).

8. A metal pipe connecting device having two sealed members (14) isolated from each other in the first paragraph; a pressure check space (150) defined by the two sealed members (140) and the outer surface of the insertion part (110) and the inner surface of the expansion part (120); and a pressure check hole (151) penetrating the wall of the expansion part (120) and communicating with the pressure check space (150).

9. In the first paragraph, a foreign matter prevention cap (180) made of resin is inserted into the annular space between the tip of the expansion portion (120) and the insertion portion (110), and the foreign matter prevention cap (180) includes the over-pressure prevention member (200) made of metal in one of the upper and lower sections. A connecting device for a metal pipe.

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