Pipe joint, method for connecting pipe, and preliminary processing jig

Abstract

To provide a pipe joint and a method for connecting a pipe.SOLUTION: A pipe joint includes a stop ring 3 including a claw part 36 and a pressure-contact inclined surface 32. In a preliminary connection process, the claw part 36 is preliminarily and slightly locked to a pipe P. In the main connection process thereafter, the stop ring 3 is pressed-in strongly.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for connecting a pipe to a pipe joint, and a preliminary processing jig used therefor. [Background technology]

[0002] The pipe joint in Figs. 10 to 12 is a pipe joint previously proposed by the present applicant, and its configuration is as follows. That is, (as shown in Figs. 10 to 12) a flare joint body 1 having a male thread portion 9 and a tip reduced diameter tapered portion 5; a cap nut 2 having a female thread portion 12 screwed into the male thread portion 9 at the base end of a hole portion 11 and forming a storage space E having a uniform diameter portion 14 and a tip reduced diameter tapered portion 17 in the middle of the hole portion 11; a cap nut 2 which is fitted inside the storage space E and has a pressure-contact gradient surface 32 which is in pressure contact with the tip reduced diameter tapered portion 5, and has a plastically deformable thin-walled cylindrical portion 35 on the tip side and a claw portion 36 at the tip of the cap nut for biting into the outer circumferential surface of a pipe; We have previously proposed a pipe fitting comprising: a stop ring 3 having a seal groove recessed in the middle of its inner circumference; and a seal 4 fitted into the seal groove of the stop ring 3, wherein the claw portions 36 of the stop ring 3 bite into the outer peripheral surface 10A of the straight tip portion 10 of the connected pipe P as the cap nut 2 is screwed on, generating a pipe pull-out resistance force Z, and further wherein the cap nut 2 has an annular insulating ring 40 at the tip portion of the cap nut that corresponds to the outer peripheral surface of the connecting pipe P (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5091191 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it has recently become clear that when the pipe connection work site is dark and narrow, or when the workers are inexperienced, accidents involving fluid leakage to the outside can occur. One of the reasons for this is that the cross-sectional areas of the thin-walled cylindrical portion 35 and the claw portion 36 are extremely small compared to the overall cross-sectional area of ​​the stop ring 3, and the press-fitting slope surface 32 of the stop ring 3, which has a large cross-sectional area, is pressed against the end of the reduced diameter tapered portion 5 of the flare joint body 1 in the direction of the arrow F in FIG. 5 The inventors have found that when applying pressure as described above, it is extremely difficult to delicately deform the thin-walled cylindrical portion 35 and the claw portion 36, which have an extremely small cross-sectional area (as shown from the solid line to the imaginary line in FIG. 13).

[0005] Therefore, the present invention aims to solve such problems and provide a method of connecting a pipe fitting and a pipe, which can always maintain stable fluid-tightness without causing external leakage of fluid, even when the work site where the pipe fitting and the pipe are connected is dark and narrow, or when the worker is not very skilled, and a preliminary processing jig for use in said connection. [Means for solving the problem]

[0006] Therefore, a method of connecting a pipe joint and a pipe according to the present invention comprises: a flare joint body having a male thread portion and a tip reduced diameter tapered portion; a cap nut having a female thread portion at a base end of a hole portion which is screwed into the male thread portion and which forms a storage space portion having a constant diameter portion and a tip reduced diameter tapered portion in the middle of the hole portion; and a stop ring which is fitted inside the storage space portion and has a pressure-welding gradient surface which is in pressure contact with the tip reduced diameter tapered portion, and which has a plastically deformable thin-walled cylindrical portion on the tip side and a claw portion at the tip of the stop ring for biting into the outer circumferential surface of the pipe. The method comprises the steps of: providing a pipe joint having a stop ring and configured so that the claw portions of the stop ring bite into the outer peripheral surface of the straight tip of a pipe to be connected, thereby generating a predetermined pipe pull-out resistance; and prior to an actual connection step of connecting to the pipe, adding a preliminary connection step; and in the preliminary connection step, pressing a circular annular portion of the stop ring radially outward from the pressure welding gradient surface with a preliminary processing jig, so that the biting claw portions at the tip of the stop ring preliminarily bite into the straight tip of the pipe.

[0007] In addition, the preliminary processing jig according to the present invention has a male threaded portion that can be screwed into the female threaded portion of the cap nut, and further has a conical pressing contact surface with an apex angle of 120° to 175° to press the circular annular portion while avoiding contact with the pressing gradient surface of the stop ring.

[0008] In addition, the preliminary machining jig of the present invention has a hexagonal head at an intermediate position in the axial direction which is clamped by a tightening work tool; further, two male threaded portions, one large and one small, which can be screwed into the female threaded portion of the cap nut, protrude in both axial directions from the hexagonal head; and in order to press the circular annular portion while avoiding contact with the pressure contact gradient surface of the stop ring, a conical pressing contact surface with an apex angle of 120° to 175° is formed on the tip side of the male threaded portion.

[0009] The nut further has a base having a hexagonal cross section at an intermediate portion in the axial direction which is held by a tightening work tool; and two male threaded protrusions, one large and one small, which can be screwed into the female threaded portion of the cap nut, are provided at both ends from the base; and in order to press the circular annular portion while avoiding contact with the pressure contact gradient surface of the stop ring, two pressure rings having different outer diameters and each having a conical pressure contact surface with an apex angle of 120° to 175° are connected by a connecting rod inserted into a hole in the base; the pressure ring with the larger outer diameter corresponds to the large diameter male threaded protrusion, and the pressure ring with the smaller outer diameter corresponds to the small diameter male threaded protrusion. Effect of the Invention

[0010] According to the method for connecting a pipe joint and a pipe of the present invention, the preliminary connection process can be performed in a bright and spacious work space, and the claws of the stop ring can be preliminarily and reliably bit into the outer circumferential surface of the pipe with high precision. Then, in the actual connection process, the claws are pushed in slightly to the normal depth (so as to generate a predetermined pipe pull-out resistance), so that the piping is always connected normally. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a pipe joint and a pipe in a connected state by a connecting method according to the present invention. [Diagram 2] 1 is a cross-sectional view showing an example of a pipe joint which can be a target of a connecting method according to the present invention. [Diagram 3] FIG. 1 is an enlarged explanatory diagram of an essential portion of the base end portion of a stop ring, where (A) is an enlarged explanatory diagram of an essential portion showing the pressure-welded slope surface and the circular annular portion radially outward from it, (B) is an enlarged explanatory diagram of an essential portion showing the state in which the circular annular portion is pressed by the pressure contact surface, and (C) is an enlarged explanatory diagram of an essential portion showing the state in which the pressure-welded slope surface is pressed by the tip reduced diameter tapered portion of the flare fitting body. [Figure 4] 1A and 1B are diagrams showing an embodiment of a preliminary machining jig, in which (A) is a front view and (B) is a left side view. [Diagram 5]11 is a cross-sectional view showing a state in which a large male thread portion of a preliminary machining jig is screwed together to perform preliminary machining. FIG. [Figure 6] 11 is a cross-sectional view showing a state in which a small male thread portion of a preliminary machining jig is screwed together to perform preliminary machining. FIG. [Figure 7] 13 is a cross-sectional view illustrating an inspection step in the latter half of the preliminary connection step. FIG. [Figure 8] FIG. 11 is a cross-sectional view showing another embodiment of the preliminary machining jig. [Figure 9] 8 is a cross-sectional view showing a state in which the large male thread portion of the preliminary machining jig shown in FIG. 7 is screwed together to perform preliminary machining. FIG. [Figure 10] 8 is a cross-sectional view showing a state in which a small male thread portion of the preliminary machining jig shown in FIG. 7 is screwed in to perform preliminary machining. FIG. [Figure 11] FIG. 11 is a cross-sectional view showing a conventional connection method. [Figure 12] FIG. 11 is a cross-sectional view of a conventional example showing a connection completed state. [Figure 13] FIG. 13 is an enlarged cross-sectional view for explaining problems with the conventional example shown in FIGS. 11 and 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below based on the illustrated embodiments. 1 and 2, the pipe joint according to the present invention has a structure generally similar to that of the conventional pipe joint explained in FIGS. 11 to 13, but the structure will be explained again.

[0013] The pipe joint according to the present invention has a flare joint body 1 and a cap nut 2. The flare joint body 1 has a male thread portion 9 and a tip reduced diameter tapered portion 5. The cap nut 2 has a female thread portion 12 that is screwed onto the male thread portion 9 at the base end of a hole portion 11. In addition, a storage space E having a uniform diameter portion 14 and a tapered portion 17 having a reduced diameter at the tip is formed in the middle of the hole 11 . Also, there is a stop ring 3 that is fitted inside the storage space E. This stop ring 3 has a pressure-contact inclined surface 32 that is in pressure contact with the tip diameter-reducing tapered portion 5 (see FIG. 3). Furthermore, the stop ring 3 has a plastically deformable thin-walled cylindrical portion 35 on the tip side, and a claw portion 36 at the tip for biting into the outer circumferential surface of the pipe.

[0014] Other attached parts include a seal 4 that provides a seal between the inner circumferential surface of the stop ring 3 and the pipe P, and further, an annular insulating ring 40 is attached to the tip of the cap nut 2. Also, a seal (O-ring) 46 is attached to prevent the stop ring 3 from accidentally coming out of the cap nut 2 before it is assembled to the flare joint body 1 (see FIG. 2).

[0015] In the method of connecting a pipe fitting and a pipe P according to the present invention, a "preliminary connection process" shown in Figures 5, 6, and 7, or Figures 9 and 10 is added prior to the actual connection process of connecting the above-mentioned pipe fitting to the pipe P - that is, the actual connection work process shown in Figures 11 and 12. The preliminary connection step will be described below.

[0016] The preliminary connection process is a process in which the pressure-welding gradient surface 32 (shown in Figs. 1, 2 and 3) of the stop ring 3 is pressed against the radially outward R 0 This is a process in which the circular annular portion 33 is pressed with a preliminary processing jig 50 such as that shown in Figures 4 to 6 or Figures 8 to 10, so that the biting claw portion 36 at the tip of the stop ring 3 is pre-bite into the outer peripheral surface 10A of the straight tip portion 10 of the pipe P. It is preferable to further add an "inspection process" to this preliminary connection process, as shown in Fig. 7. This "inspection process" will be described later.

[0017] First, a preliminary machining jig 50 used in the method of connecting a pipe joint to a pipe will be described. 4(A), 5 and 6, the preliminary machining jig 50 has a large diameter male thread portion 51A and a small diameter male thread portion 51B so as to be able to screw into the female thread portions 12 of the cap nuts 2, 2 having different large and small dimensions. Specifically, the preliminary machining jig 50 has a hexagonal head portion 52 at a central portion in the axial direction that is gripped (held) by a tightening work tool such as a wrench. The preliminary machining jig 50 is an integral block shape that includes the hexagonal head portion 52 and the male thread portions 51A, 51B protruding on the left and right sides thereof.

[0018] FIG. 5 shows a case where a large diameter male thread portion 51A is used for a large (large diameter) cap nut 2, and FIG. 6 shows a case where a small diameter male thread portion 51B is used for a small (small diameter) cap nut 2. 4(A), 5 and 6 has male threads 51A, 51B (two types, large and small) that can be screwed into the female thread 12 of the cap nut 2. Furthermore, it has a conical pressing contact surface 53 with an apex angle θ (see FIG. 4) of 120° to 175° to press the circular annular portion 33 on the radially outer side while avoiding contact with the pressing gradient surface 32 (see FIG. 3) of the stop ring 3.

[0019] In the specific example shown in FIG. 4(A) and in FIG. 5 and FIG. 6, small-diameter disk portions 54, 55 are connected to the axially outer end faces of the screw portions 51A, 51B, and a pressing contact surface 53 having an apex angle θ of 120° to 175° is formed at the outer end (corner) of each of the disk portions 54, 55. If θ<120°, the inclined press-contact surface 32 shown in Fig. 3 may be pressed and damaged. Conversely, if θ>175°, the circular annular portion 33 may be damaged, and the base end of the stop ring 3 may become eccentric. As shown in FIG. 4(B), the preliminary machining jig 50 may be freely shaped to have only one of the large diameter male thread portion 51A and the small diameter male thread portion 51B.

[0020] Next, FIGS. 8 to 10 show another embodiment of the preliminary processing jig 50. As shown in FIG. The base 57 is a base portion having a hexagonal cross-sectional outer shape provided at the axial center portion, and is clamped by a fastening tool. It has circular outer flanges 57A, 57A at both ends. Male threaded protrusions 51C, 51D protrude from both end faces of the base 57. The large diameter male threaded protrusion 51C, base 57, and small diameter male threaded protrusion 51D are integral and share a common axial center L. 50 .

[0021] Circular recesses 64, 65 are formed in the large diameter male thread protrusion 51C and the small diameter male thread protrusion 51D, and thrust bearings 66, 67 are fitted in them. Furthermore, as shown in Figures 9, 10 and 3, in order to press the circular annular portion 33 while avoiding contact with the pressure contact gradient surface 32 of the stop ring 3, two pressing wheels 21, 22, one large and one small, having conical pressing contact surfaces 53, 53 with an apex angle θ of 120° to 175° are connected by a connecting rod 23 inserted into the hole 63 of the base 57.

[0022] The connecting rod 23 (the large diameter rod and the small diameter rod) is integrally connected by a screw connection 24 . The pressure wheel 21 having a larger outer diameter is fitted to the large diameter male thread protrusion 51C, and the pressure wheel 22 having a smaller outer diameter is fitted to the small diameter male thread protrusion 51D, and then used.

[0023] As shown in FIGS. 9 and 10, the base portion 57 is rotated in the direction of the arrow M by a power tool (not shown). 57 2, the male screw convex portions 51C and 51D are screwed into the female screw portion 12 of the cap nut 2, and the preliminary machining jig 50 rotates in the direction indicated by the arrow F. 50 The pressure wheels 21 and 22 are pivotally mounted on the thrust bearings 66 and 67 so that they can rotate freely. 50 When moving forward, (single axis L 50 That is, there is absolutely no rotational sliding between the pressure contact surfaces 53 of the pressure wheels 21 and 22 and the stop ring 3. Therefore, there is an advantage that the circular annular portion 33 of the stop ring 3 can be prevented from being scratched or the like.

[0024] Arrow F in Figure 5, Figure 6, or Figure 9, Figure 10 50 As shown in FIG. 1, when the stop ring 3 is pushed into the inner part (front) of the cap nut 2 by the preliminary machining jig 50, the biting claw portion 36 at the tip of the stop ring 3 forms a preliminary biting V with the outer peripheral surface 10A of the straight tip portion 10 of the pipe P. 36 (See FIG. 7) can be applied.

[0025] As shown in the conventional method of FIG. 11 and FIG. 12, or as shown in FIG. 1, before the actual connection step, the circular annular portion 33 of the stop ring 3 is pressed by a preliminary processing jig 50 to form a preliminary bite V. 36 However, this preliminary bite V 36 As the next step, it is desirable to add the inspection step shown in FIG. The above-mentioned preliminary bite V 36 After this step, when the preliminary processing jig 50 is removed from the cap nut 2, the rear end side of the cap nut 2 becomes open as shown in Fig. 7. The worker (inspector) uses the naked eye 26 or an inspection device such as a fiberscope and an image display means to check the position of the cap nut 2 at the position indicated by the arrow X in Fig. 7. 1 ,X 2 As shown above, the following two points (i) and (ii) can be inspected.

[0026] That is, (i) whether or not the tip 27 of the pipe P abuts against the step portion 28 of the hole of the stop ring 3, and (ii) whether or not the protruding portion 30 is formed on the inner peripheral surface of the pipe P (with the claw portion 36 sufficiently biting in). That is, in the conventional connection method, as shown in Figures 11 and 12, there was only a main connection process (without a preliminary connection process), and therefore it was not possible to inspect the above (i) and (ii). Therefore, in the conventional method, there was a risk of an accident at the piping connection site in which the pipe P was pulled out of the pipe joint, causing a fluid leak. According to the present invention, the above two points (i) and (ii) can be easily, quickly and reliably inspected, thereby solving the problems that exist in connection structures that are connected only through the conventional production connection process.

[0027] By the way, the pipe pull-out resistance force by the claw portion 36 when the preliminary connection process is completed is F 1 and the pipe pull-out resistance force by the claw portion 36 when the actual connection process is completed is F 0 In this case, the following formula is set: 0.2 F 0 ≦F 1 ≦ 0.6 F 0 (Number 1) Preferably, 0.3 F 0 ≦F 1 ≦ 0.5 F 0 (Number 2) More preferably, 0.33 F 0 ≦F 1 ≦ 0.4 F 0 (Number 3)

[0028] Pipe pull-out resistance F of the claw portion 36 when the preliminary connection process is completed 1 However, if the value is below the lower limit, the benefits of the spare connection are hardly realized, and the same problems as before remain. That is, the pressing inclined surface 32 of the stop ring 3 having a large cross-sectional area is pressed against the stop ring 3 in the direction of the arrow F in FIG. 5 When applying pressure as described above, the thin-walled cylindrical portion 35 with an extremely large cross-sectional area and the small claw portion 36 must be delicately deformed, and this is still largely required in the actual connection process. Conversely, the pipe pull-out resistance force F of the claw portion 36 when the preliminary connection process is completed 1 However, if the upper limit of the above formula is exceeded, the burden on the preliminary processing jig 50 used in the preliminary connection step increases, causing a sudden shortening of its life. Also, there is a risk that part of the pressure contact gradient surface 32 of the stop ring 3 may be damaged.

[0029] As described above, the present invention comprises a flare joint body 1 having a male thread portion 9 and a tip reduced diameter tapered portion 5; a cap nut 2 having a female thread portion 12 screwed into the male thread portion 9 at the base end of a hole portion 11 and a storage space E having a constant diameter portion 14 and a tip reduced diameter tapered portion 17 at the middle of the hole portion 11; and a cap nut 2 which is fitted into the storage space E and has a pressure-contact gradient surface 32 which is in pressure contact with the tip reduced diameter tapered portion 5 and has a plastically deformable thin-walled cylindrical portion 35 and and a stop ring 3 having claw portions 36 for biting into the outer circumferential surface of a pipe at its tip, the claw portions 36 of the stop ring 3 biting into the outer circumferential surface 10A of a straight tip portion 10 of a connected pipe P to generate a predetermined pipe pull-out resistance Z. A preliminary connection step is added before a real connection step of connecting the pipe P, and in the preliminary connection step, a radially outward R 0 The circular annular portion 33 is pressed by a preliminary machining jig 50, and the biting claw portion 36 at the tip of the stop ring 3 is fitted to the straight tip portion 10 of the pipe P, forming a preliminary biting V. 36 Since this is a method of connecting a pipe fitting and a pipe by precisely and delicately deforming the small biting claw portion 36 at the tip of the stop ring 3 to bite into (the pipe P) in the preliminary connection step, and then the pressing gradient surface 32 at the base end of the stop ring 3, which has a large cross-sectional area, is pressed by the tip reduced diameter tapered portion 5, so that the actual connection step can be performed easily and reliably. This allows the pipe connection work to be performed highly accurately and efficiently. In particular, even if the pipe connection site is dark and narrow, or if the worker is inexperienced and inexperienced, the occurrence of external leakage accidents as in the past can be reliably reduced.

[0030] In addition, the preliminary machining jig of the present invention has a male thread portion 51 that can be screwed into the female thread portion 12 of the cap nut 2, and further has a conical pressing contact surface 53 with an apex angle θ of 120° to 175° in order to press the circular annular portion 33 while avoiding contact with the pressure contact gradient surface 32 of the stop ring 3. Therefore, the circular annular portion 33 can be reliably pressed without damaging the pressure contact gradient surface 32 of the stop ring 3, and it is also possible to make the jig into a block body with a simple overall structure, which has excellent durability.

[0031] In addition, the hexagonal head 52 is located at the axial center and is held by a tightening tool; two large and small male threads 51A, 51B that can be screwed into the female thread 12 of the cap nut 2 are protruded from the hexagonal head 52 in both axial directions; and conical pressing contact surfaces 53, 53 with an apex angle θ of 120° to 175° are formed on the tip side of the male threads 51A, 51B to press the circular annular portion 33 while avoiding contact with the press-fitting slope surface 32 of the stop ring 3, so that it can be used conveniently with two types of pipe joints of large and small diameter cap nuts 2 as shown in Figures 5 and 6. Moreover, the circular annular portion 33 can be reliably pressed without damaging the press-fitting slope surface 32 of the stop ring 3, and it is possible to form a block body with a simple overall structure, which is excellent in durability.

[0032] In addition, the nut has a base 57 having a hexagonal cross section at an intermediate portion in the axial direction, which is clamped by a tightening tool; and two male thread protrusions 51C, 51D, one large and one small, which can be screwed into the female thread portion 12 of the cap nut 2, are provided at both ends from the base 57; and further, in order to press the circular annular portion 33 while avoiding contact with the pressure contact gradient surface 32 of the stop ring 3, an apex angle θ is set to 120° or Two pressure wheels 21, 22 having 175° conical pressing contact surfaces 53, 53 and different outer diameters are connected by a connecting rod 23 inserted into a hole 63 of the base 57; the pressure wheel 21 having a larger outer diameter corresponds to the large diameter male thread protrusion 51C, and the pressure wheel 22 having a smaller outer diameter corresponds to the small diameter male thread protrusion 51D, so that it can be used conveniently as both a pipe joint for a large diameter cap nut 2 and a pipe joint for a small diameter cap nut 2 (as shown in Figures 9 and 10). In particular, when the base 57 is rotated by a work tool and the male thread protrusions 51C, 51D are screwed in to press the pressure wheels 21, 22 into the cap nut 2, the pressure wheels 21, 22 are aligned along a single axis L. 50 The stop ring 3 can be pushed in while remaining "non-rotating" around the base 57. This prevents the circular annular portion 33 of the stop ring 3 from being scratched by friction. Furthermore, the rotational torque applied to the base 57 by the power tool can be small because the base 57 is "non-rotating" as described above. In other words, work can be easily performed with a small rotational torque of the power tool. [Explanation of symbols]

[0033] 1 Flare joint body 2 Cap nuts 3 Stop ring 5. Tapered tip 9 Male thread 10 Straight tip 10A outer surface 11 Hole 12 Female thread 14 Same diameter part 17 Tip tapered section 21 Pressure wheel 22 Pressure wheel 23 Connecting rod 32 Pressure-welded slope surface 33 Circular ring section 35 Thin-walled cylindrical section 36 Claw part 50 Spare machining jig 51 Male thread 51A Large diameter male thread 51B Small diameter male thread 51C Large diameter male thread convex part 51D Small diameter male thread convex part 52 Hexagon head 53 Pressurized contact surface 57 Base 63 Hole E Storage space P Pipe R 0 Radial Outer V 36 Preliminary bite Z Pipe pull-out resistance θ vertical angle

Claims

1. A flare joint body (1) having a male thread portion (9) and a tip reduced diameter tapered portion (5); a cap nut (2) having a female threaded portion (12) at a base end of a hole (11) to be screwed into the male threaded portion (9), and having a storage space portion (E) formed in the middle of the hole (11) and having a constant diameter portion (14) and a tip reduced diameter tapered portion (17); a stop ring (3) that is fitted in the storage space (E) and has a pressure-contact inclined surface (32) that is in pressure contact with the tip diameter-reducing tapered portion (5), and has a plastically deformable thin-walled cylindrical portion (35) at its tip and a claw portion (36) at its tip for biting into the outer circumferential surface of the pipe; a pipe joint configured so that the claw portion (36) of the stop ring (3) bites into the outer peripheral surface (10A) of the straight tip portion (10) of the connected pipe (P) to generate a predetermined pipe pull-out resistance force (Z), Before the actual connection process of connecting to the above pipe (P), A preliminary connection step is added. In the preliminary connection step, the pressure contact gradient surface (32) of the stop ring (3) is located radially outward (R 0 The circular annular portion (33) of the stop ring (3) is pressed by a preliminary machining jig (50), and the biting claw portion (36) at the tip of the stop ring (3) is fitted to the straight tip portion (10) of the pipe (P) by a preliminary biting (V 36 ) A method for connecting a pipe to a pipe fitting.

2. 2. A preliminary machining jig used in the method of connecting a pipe joint to a pipe according to claim 1, comprising: a male thread portion (51) that can be screwed into the female thread portion (12) of the cap nut (2); and further comprising a conical pressing contact surface (53) having an apex angle (θ) of 120° to 175° in order to press the circular annular portion (33) while avoiding contact with the pressure contact gradient surface (32) of the stop ring (3).

3. A hexagonal head (52) is provided at an axially intermediate portion thereof for clamping by a fastening tool; Furthermore, two male threaded portions (51A) and (51B), one large and one small, which can be screwed into the female threaded portion (12) of the cap nut (2), are provided protruding from the hexagonal head (52) in both axial directions, 2. A preliminary machining jig used in the method of connecting a pipe joint to a pipe as set forth in claim 1, wherein a conical pressing contact surface (53) (53) having an apex angle (θ) of 120° to 175° is formed on the tip side of the male thread portion (51A) (51B) in order to press the circular annular portion (33) while avoiding contact with the pressing inclined surface (32) of the stop ring (3).

4. A base (57) having a hexagonal cross section that is clamped by a fastening tool is provided at an axially intermediate position, Furthermore, two large and small male thread convex portions (51C) (51D) that can be screwed into the female thread portion (12) of the cap nut (2) are provided protruding from both ends of the base portion (57), Furthermore, in order to press the circular annular portion (33) while avoiding contact with the pressure contact gradient surface (32) of the stop ring (3), two pressing rings (21) and (22) having conical pressing contact surfaces (53) with an apex angle (θ) of 120° to 175° and different outer diameters are connected by a connecting rod (23) inserted into a hole (63) of the base portion (57); 2. A preliminary machining jig used in the method of connecting a pipe joint to a pipe according to claim 1, wherein a pressure ring (21) having a larger outer diameter corresponds to the large-diameter male thread convex portion (51C), and a pressure ring (22) having a smaller outer diameter corresponds to the small-diameter male thread convex portion (51D).

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