JP7792292B2 - Pipe fittings - Google Patents

Description

The present invention relates to pipe fittings, particularly those with multiple start threads.

A "multiple-start thread" refers to a thread with two or more spirally connected threads. Compared to a single-start thread, a multiple-start thread has a longer axial distance (lead) traveled per rotation, assuming the same axial spacing (pitch) between the threads. Therefore, a multiple-start thread can more easily reduce the number of rotations required to move from the make-up start position to the make-up completion position than a single-start thread. Here, the "make-up start position" refers to the relative position of the two threads when the male thread begins to enter the female thread groove, i.e., when the two threads begin to mesh. Meanwhile, the "make-up completion position" refers to the axial length of the range within the female thread groove when the two threads are meshed, i.e., the relative position of the two threads when the required engagement length is reached. When both threads are coaxially arranged, their relative positions are generally determined by a combination of the circumferential angle of one thread relative to the other and the axial distance (if the two threads are interlocked, this distance may be expressed as a negative value).

Due to these advantages, multiple-start threads are often used to shorten the work time required for fastening (see, for example, Patent Document 1). In particular, when multiple-start threads are used in pipe fittings, the work of connecting pipes using the fittings is expedited. Therefore, pipe fittings with multiple-start threads are useful, for example, in piping equipment used in the manufacture of semiconductors, medical products, pharmaceuticals, or food, particularly in areas where pipes are frequently connected and disconnected. This is because reducing the time required to connect and disconnect pipes effectively reduces the burden on workers performing maintenance such as cleaning. Pipe fittings with multiple-start threads are also useful in piping equipment installed in automobiles that carries gasoline, coolant, exhaust gas, etc. Such piping equipment requires particularly high reliability to ensure the safety of automobiles. To meet this demand while maintaining high workability in assembling piping equipment, using multiple-start threads in pipe fittings is effective in quickly and reliably connecting pipes.

JP 2016-169581 A

In a multiple-start thread, the male thread's threads can generally enter any of the female thread's grooves. Therefore, there are as many fastening start positions as there are threads. Different fastening start positions result in different fastening completion positions, so the number of fastening completion positions is equal to the number of threads. However, having multiple fastening completion positions is not desirable depending on the application of the multiple-start thread. For example, the multiple-start thread disclosed in Patent Document 1 is provided at each open end of two steel pipes to be fastened. These open ends are also provided with a pair of marks that align the threads when they reach the fastening completion position. During the steel pipe fastening operation, aligning these marks confirms that the threads have reached the fastening completion position. In this case, to enable similar confirmation of the arrival of each fastening completion position, a different pair of marks must be provided on both steel pipes for each fastening completion position. However, such marking is cumbersome. Furthermore, when a multiple-start thread is used to fasten two parts that are both rotationally asymmetric, the shapes of the two parts may only align at a specific fastening completion position.

For these applications, it is desirable to pre-select a specific one from multiple make-up completion positions (hereinafter referred to as the "correct make-up completion position") and reduce the possibility of the screw reaching a position other than that (hereinafter referred to as the "incorrect make-up completion position"). For example, in the technique disclosed in Patent Document 1, in addition to a pair of marks that align the positions of the screws when they reach the correct make-up completion position, the two steel pipes to be made-up are also marked with a pair of marks that align the positions of the screws when they are engaged at the correct make-up start position. The "correct make-up start position" refers to the one of multiple make-up start positions from which the screw can reach the correct make-up completion position. Therefore, in the make-up operation of steel pipes, it is already possible to determine whether the make-up completion position that the screw will subsequently reach is correct when the screw is engaged at the make-up start position.

However, it is physically possible to engage the multiple-start thread disclosed in Patent Document 1 at a make-up start position other than the correct make-up start position (hereinafter referred to as the "incorrect make-up start position"), or to move it from the incorrect make-up start position to an incorrect make-up completion position. Therefore, there is a possibility that an operator may accidentally overlook the misalignment of the mark pairs, engage the screw at the incorrect make-up start position, and then move it to the incorrect make-up completion position. This could result in impaired make-up workability, and the device disclosed in Patent Document 1 may not be sufficient in some cases.

The object of the present invention is to solve the above problems, and in particular to provide a pipe fitting that improves the workability of connecting pipes by more reliably preventing multiple-start threads from reaching an incorrect tightening completion position.

A pipe fitting according to one aspect of the present invention comprises a first part and a second part. Both parts are cylindrical, with one axial end including a connection portion for connecting to a pipe and the other end including a multiple-start thread. The two parts can be fastened to each other via these threads. The outer peripheral surface of the first part includes a first protrusion extending outward from a portion of the circumferential direction. The outer peripheral surface of the second part includes a second protrusion extending outward from a portion of the circumferential direction, and a protrusion projecting outward from a portion of the circumferential direction different from the second protrusion and protruding axially. The first protrusion and the second protrusion are configured to align the circumferential positions of the two parts when the screws reach the correct fastening completion position. The protrusion is configured as follows: When the screws are brought coaxially closer to each other during the fastening operation of the two parts, if the circumferential angle between the threads is the value at the correct fastening start position, the protrusion passes through the outer peripheral side of the outer peripheral surface of the first part other than the first protrusion, avoiding collision with the first protrusion, until the screws reach the correct fastening completion position. On the other hand, if the circumferential angle between the threads is the wrong value at the tightening start position, the protrusion will collide with the first protruding portion before the screw reaches the wrong tightening completion position.

This pipe fitting may satisfy all of the following conditions (A), (B), (C), and (D): (A) The rotation angle (hereinafter referred to as the "fit angle") required for the threads to move from the correct fastening start position to the correct fastening completion position is 180° or less. (B) The length of the protrusion is equal to or greater than the distance between the thread bearing surfaces when the threads are engaged at the correct fastening start position. (C) When the threads are arranged coaxially with each other, if the circumferential angle between the threads is the value at the correct fastening start position, the protrusion is separated from the first protrusion in the circumferential direction of the first and second parts by equal to or greater than the fit angle. (D) When the threads are arranged coaxially with each other, if the circumferential angle between the threads is the value at the incorrect fastening start position, the protrusion is located within the range of the first protrusion in the circumferential direction of both parts.

When the threads of this pipe fitting are brought closer to each other coaxially during the tightening operation of the two parts, if the circumferential angle between the threads is the value at the correct tightening start position, the protrusion passes through the outer peripheral surface of the first part other than the first protrusion, avoiding collision with the first protrusion, until the thread reaches the correct tightening completion position. In other words, before the screw reaches the correct tightening completion position, the protrusion deviates from the first part toward the outer peripheral side and moves further outward than the first part without being blocked by the first protrusion. This allows the screw to reach the correct tightening completion position. On the other hand, if the circumferential angle between the threads is the value at the incorrect tightening start position, the protrusion collides with the first protrusion before the screw reaches the incorrect tightening completion position. This prevents the threads from approaching each other further, making it physically impossible for the screw to reach the incorrect tightening completion position. This more reliably prevents the screw from reaching the incorrect tightening completion position, making this pipe fitting even easier to connect piping.

When this pipe fitting satisfies all of the above conditions (A)-(D), it is physically impossible to even engage the threads at an incorrect fastening start position. In fact, when the threads are engaged, if the circumferential angle between the threads is the value for the correct fastening start position, the protrusion is separated from the first protruding portion in the circumferential direction between the first and second parts, and the threads reach the correct fastening start position. The protrusion then moves further outward than the first part without colliding with the first protruding portion, and the threads reach the correct fastening completion position. On the other hand, if the circumferential angle between the threads is the value for the incorrect fastening start position, the protrusion will collide with the first protruding portion before or simultaneously with the threads reaching the incorrect fastening start position. This makes it physically impossible to engage the threads at an incorrect fastening start position. Naturally, it is also physically impossible for the threads to reach the incorrect fastening completion position, making this pipe fitting even easier to connect piping.

The first and second protrusions make the shapes of both the first and second parts rotationally asymmetric. Therefore, by seeing that the circumferential positions of both protrusions are aligned, the worker can visually confirm that the screw has reached the correct tightening completion position. Therefore, the pipe fitting of the present invention further improves the workability of connecting piping.

The first protrusion and the second protrusion may have the same outline when viewed from the axial direction of the first and second parts. Because the outlines of both protrusions appear to overlap perfectly, the worker can confirm at a glance that the screw has reached the correct tightening completion position. Therefore, the pipe fitting of the present invention further improves the workability of connecting piping.

The first protrusion and the second protrusion may be configured to engage with each other in a snap-fit manner when the screw reaches the correct tightening position. This generates at least one of sound and vibration when the two protrusions engage with each other. By hearing the sound or feeling the vibration, the worker can confirm by ear or by hand that the screw has reached the correct tightening position. Therefore, the pipe fitting of the present invention further improves the workability of connecting piping.

The first and second protrusions may be configured to engage with each other when the screw reaches the correct tightening position, preventing the screw from reversing, i.e., rotating in the loosening direction. This prevents the screw from loosening due to external vibration or shock or changes in shape over time.

1 is a perspective view showing the appearance of a pipe joint according to an embodiment of the present invention. FIG. 2 is an exploded view of the pipe joint shown in FIG. 3 is a cross-sectional view taken along the line III-III shown in FIG. 1. 3A and 3B are a plan view and a side view, respectively, showing the appearances of the male part and the female part shown in FIG. 2 when the male part and the female part are arranged coaxially and the circumferential angle between the male thread and the female thread is at the correct fastening start position. 3A and 3B are a plan view and a side view showing the appearance of the pipe joint when the male thread and the female thread shown in FIG. 2 have reached a correct fastening completion position. 3A and 3B are a plan view and a side view, respectively, showing the appearances of the male part and the female part shown in FIG. 2 when the male part and the female part are arranged coaxially and the circumferential angle between the male thread and the female thread is a value at an incorrect fastening start position.

Figure 1 is a perspective view showing the appearance of a pipe fitting 100 according to an embodiment of the present invention, Figure 2 is an exploded view of the pipe fitting 100, and Figure 3 is a cross-sectional view taken along line III-III in Figure 1. The pipe fitting 100 is preferably used to connect a first hose 510 to a second hose 520 inside an automobile (see Figure 3). The first hose 510 and the second hose 520 are made of a resin such as high-density polyethylene (HDPE), and are preferably included in the cooling line of a battery pack in an electric vehicle (EV), and are used as piping for carrying coolant (LLC).

The pipe fitting 100 is a combination of a male part 200 and a female part 300. Both parts 200, 300 are cylindrical parts made of resin such as polyamide (PA) or glass fiber reinforced polyamide (PA-GF). In a cross section perpendicular to their respective central axes 201, 301, their inner circumferential surfaces are circular (see FIG. 2) and their inner diameters are equal (see FIG. 3). As shown in FIG. 3, the male part 200 is connected to a first hose 510, and the female part 300 is connected to a second hose 520. Furthermore, when the two parts 200, 300 are coaxially fastened to each other, the internal space of the first hose 510 communicates with the internal space of the second hose 520 through their internal spaces. In other words, the internal spaces of the two parts 200, 300 function as a flow path for the LLC connecting the two hoses 510, 520.
[Structure of male part]

One axial end 210 of the male component 200 (the left end in Figures 2 and 3; hereafter referred to as the "first end") is the connection point with the first hose 510 and is arranged coaxially within the first hose 510 (see Figure 3). Because the outer diameter of the first end 210 is larger than the inner diameter of the first hose 510, when the first end 210 is press-fitted into the first hose 510, the open end of the first hose 510 is pushed open. The resulting restoring force of the open end tightens the first end 210 inward, securing the first hose 510 to the first end 210 and creating a seal between the inner surface of the first hose 510 and the outer surface of the first end 210.

The other axial end 220 of the male part 200 (the right end in FIGS. 2 and 3 ; hereinafter referred to as the "second end") is the connection portion with the female part 300 and includes an opening 221, an annular groove 230, a male flange 240, and a male thread 250. The opening 221 is a cylindrical wall separating the entrance and exit of the internal space of the male part 200. The annular groove 230 is a ring-shaped groove coaxially surrounding the opening 221 and preferably extending to near the boundary between the first end 210 and the second end 220 in the axial direction of the male part 200 (see FIG. 3 ). The depth of the annular groove 230 in the axial direction is sufficiently greater than the wall thickness of the opening 221. The male flange 240 is a ring-shaped portion of the outer periphery of the second end 220 that is coaxially adjacent to the first end 210 in the axial direction of the male part 200 (the right side in FIGS. 2 and 3 ). The male thread 250 is provided on the outer periphery of the second end 220 on the side opposite to the male flange 240 (the right side in FIGS. 2 and 3 ), and coaxially surrounds the annular groove 230 .
[Structure of female part]

One axial end 310 of the female part 300 (the left end in Figures 2 and 3; hereafter referred to as the "first end") is the connection point with the male part 200 and includes an opening 311, an annular protrusion 330, a female flange 340, and an internal thread 350. The opening 311 is a cylindrical wall separating the entrance and exit to the internal space of the female part 300, and has the same inner diameter as the opening 221 of the male part 200. The annular protrusion 330 protrudes coaxially from the periphery of the opening 311 (to the left in Figures 2 and 3), and its cross section perpendicular to its axial direction is annular. Furthermore, the inner and outer diameters of the annular protrusion 330 are designed so that it can be press-fit into the annular groove 230 of the male part 200 (see below for details). The female flange 340 is a circular member that coaxially surrounds the annular protrusion 330, with one end in the axial direction of the female part 300 (the right end in Figures 2 and 3) coaxially connected to the opening 311, and the opposite end face 341 in the axial direction (the left end face in Figures 2 and 3) extending beyond the tip 331 (the left end in Figures 2 and 3) of the annular protrusion 330. The female thread 350 is provided on the inner surface of the female flange 340 and coaxially surrounds the annular protrusion 330.

The other axial end 320 of the female component 300 (the right end in FIGS. 2 and 3; hereinafter referred to as the "second end") is the connection part with the second hose 520 and is disposed coaxially within the second hose 520 (see FIG. 3). Because the outer diameter of the second end 320 is larger than the inner diameter of the second hose 520, when the second end 320 is press-fitted into the second hose 520, the open end of the second hose 520 is forced open. The resulting restoring force of the open end tightens the second end 320 in the inward circumferential direction, so that the second hose 520 is fixed to the second end 320 and a seal is formed between the inner circumferential surface of the second hose 520 and the outer circumferential surface of the second end 320.
[Male and female threads]

The male thread 250 is a multiple-start thread, for example a double-start right-hand thread, and includes a first thread 251 and a second thread 252 (see Figures 2 and 3). These threads 251, 252 have, for example, a trapezoidal cross section, and form right-handed spirals of the same shape and size around the central axis 201 of the male part 200, with the same shape and size except for the ends of each spiral. The tips of these spirals, i.e., tip 253 of first thread 251 and tip 254 of second thread 252, differ from each other in their circumferential positions around the male thread 250 by 360° divided by the number of threads "2" on the male thread 250, or 180°.

The female thread 350 is a multiple-start thread, such as a double-start right-hand thread, that can mesh with the male thread 250, and includes a first thread groove 351 and a second thread groove 352 (see Figures 2 and 3). These thread grooves 351, 352 have, for example, a trapezoidal cross section, and describe right-handed spirals of the same shape and size around the central axis 301 of the female part 300, with the shape and size being equal except for the ends of each spiral. The ends of these spirals, i.e., the end 353 of the first thread groove 351 and the end of the second thread groove 352 (not shown), differ from each other in their circumferential positions around the female thread 350 by 360° divided by the number of threads on the female thread 350, i.e., 180°.

Since both the male thread 250 and the female thread 350 are right-handed threads, when they are coaxially meshed with each other, clockwise rotation relative to the direction toward the other thread along their respective central axes 201, 301 is the forward direction, i.e., the direction in which the thread tightens, and counterclockwise rotation is the reverse direction, i.e., the direction in which the thread loosens. In Figure 2, for the male thread 250, clockwise MCL is the forward direction relative to the right along its central axis 201, and counterclockwise MCC is the reverse direction. For the female thread 350, clockwise FCL is the forward direction relative to the left along its central axis 301, and counterclockwise FCC is the reverse direction.

Since both the male thread 250 and the female thread 350 have two threads, there are two possible fastening start positions. One (hereinafter referred to as the "correct fastening start position") is the relative position of the two threads 250, 350 when the tip 253 of the first thread 251 begins to enter the tip 353 of the first thread groove 351, and the tip 254 of the second thread 252 begins to enter the tip 354 of the second thread groove 352. The other (hereinafter referred to as the "incorrect fastening start position") is the relative position of the two threads 250, 350 when the tip 253 of the first thread 251 begins to enter the tip 354 of the second thread groove 352, and the tip 254 of the second thread 252 begins to enter the tip 353 of the first thread groove 351.

Like the make-up start position, there are also two make-up completion positions. Hereinafter, the make-up completion position that can be reached from the correct make-up start position will be referred to as the "correct make-up completion position," and the make-up completion position that can be reached from the incorrect make-up start position will be referred to as the "incorrect make-up completion position." At the make-up completion position, the engagement length between the male thread 250 and the female thread 350 reaches a target value. This target value is designed so that the connection between the male part 200 and the female part 300 can sufficiently withstand external forces and the annular protrusion 330 of the female part 300 is press-fitted to the required depth into the annular groove 230 of the male part 200 (see below for details). Furthermore, the leads of the two threads 250, 350 are designed so that the rotation angle required for the two threads 250, 350 to move from the make-up start position to the make-up completion position, i.e., the engagement angle, is preferably 180° or less, and more preferably 90°.
[Flange]

4 to 6 are a plan view (a) and a side view (b) showing the appearance of the coaxially arranged male part 200 and female part 300 when viewed from the first end 210 side of the male part 200. In particular, FIG. 4 shows the appearance when the circumferential angle between the male thread 250 and the female thread 350 is the value at the correct fastening start position. FIG. 5 shows the appearance when both threads 250, 350 have reached the correct fastening completion position. FIG. 6 shows the appearance when the circumferential angle between both threads 250, 350 is the value at the incorrect fastening start position.
-Screw bearing surface-

As shown in Figures 2 and 4 to 6, the axial end face 241 of the male flange 240 that is closest to the male thread 250 (the right end face in Figures 2, 4 to 6(b)) and the axial end face 341 of the female flange 340 (the left end face in Figures 2, 4 to 6(b)) are both toric surfaces perpendicular to the axial direction. As shown in Figure 5(b), the end faces 241, 341 come into contact with each other when the male thread 250 and the female thread 350 reach their correct fastening completion positions, and are pressed against each other by the axial forces of the two threads 250, 350. In this sense, hereinafter, each end face 241, 341 will be referred to as the "bearing surface" of each thread 250, 350.
-Protruding part-

As shown in Figures 1-6, a male protrusion 243 extends from a portion of the circumference of the male flange 240 in the outer circumferential direction (upward in Figures 1-3 and 5, leftward in Figure 4(a), and rightward in Figure 6(a)), and a female protrusion 343 extends from a portion of the circumference of the female flange 340 (upward in Figures 1-6) in the outer circumferential direction. Both flanges 240, 340 have a rotationally asymmetric shape due to the presence of the protrusions 243, 343. Preferably, as shown in Figures 1, 2, and 4-6(a), the outline of each flange 240, 340 as viewed from the axial direction is teardrop-shaped. More preferably, these outlines are the same shape and size as each other, as shown in Figure 5(a). As shown in particular in Figures 4-6(a), both flanges 240, 340 have the same constant outer diameter RF, excluding protrusions 243, 343. Protrusions 243, 343 extend outward beyond this outer diameter RF. Preferably, as shown in Figure 4(a), the width of protrusions 243, 343 in the circumferential direction of each flange 240, 340, particularly the width WF of the portion of flange 240, 340 extending outward beyond outer diameter RF, is approximately 90° when converted into a rotation angle around each central axis 201, 301.

As shown in Figures 2 and 6(b), the tip 253 of the first thread 251 is located within the range of the male protrusion 243 in the circumferential direction of the male flange 240. Preferably, the tip 244 of the male protrusion 243 in the outer circumferential direction of the male flange 240 (the upper end in Figure 2, the front end in Figure 6(b)) is located in the same circumferential location as the tip 253.

A step 248 extends from the tip 244 (top end in Figure 2) of the male protrusion 243 in the forward rotation direction MCL of the male thread 250 (clockwise to the right in Figure 2, downward in Figure 6(b)). The step 248 is a raised portion from the end face 247 (hereinafter referred to as the "blocking surface") of the male protrusion 243, which is located on the same side as the bearing surface 241 of the male thread 250 (the right side in Figures 2, 3, and 6(b)). The tip face 249 (right end face in Figures 2 and 6(b)) of the step 248 in the axial direction of the male flange 240 (the right side in Figures 2 and 6(b)) is perpendicular to that axial direction and is located at the same location as the bearing surface 241 of the male thread 250 or further outward (to the right in Figures 2 and 6(b)).

As shown in Figure 2, the tip 344 (upper end in Figure 2) of the female protrusion 343 in the outer circumferential direction of the female flange 340 is located at a position rotated from the tip 353 of the first thread groove 351 in the reverse direction FCC of the female thread 350 (counterclockwise relative to the left in Figure 2) by an engagement angle of 90° between the male thread 250 and the female thread 350. The tip 353 of the first thread groove 351 and the tip 354 of the second thread groove 352 differ in circumferential position of the female thread 350 by 360°/number of threads "2" = 180°, so the tip 344 of the female protrusion 343 is located 180° - 90° = 90° rotated in the forward rotation direction FCL of the female thread 350 (clockwise relative to the left in Figure 2, upward in Figures 4 - 6(b)) from the tip 354 of the second thread groove 352, as shown in Figures 4-6(b).

As shown in Figures 1-3 and 4-6(b), the female protrusion 343 includes a thin plate portion 345 and a thick plate portion 346. The plate surfaces of both the thin plate portion 345 and the thick plate portion 346 are perpendicular to the axial direction of the female flange 340 (the left-right direction in Figures 1-3 and 4-6(b)), and they face each other with a gap GP between them. In the axial direction, the thin plate portion 345 is thinner than the thick plate portion 346. The plate surface 347 of the thin plate portion 345 farthest from the thick plate portion 346 (the left plate surface in Figures 2, 3, 4-6(b)) is located in the same location as the bearing surface 341 of the female thread 350 in the axial direction of the female flange 340.

As shown in Figures 2 to 4 and 6, a step 348 extends from the tip 344 (the upper end in Figures 2 to 4 and 6) of the female protrusion 343 in the forward rotation direction FCL of the female thread 350 (clockwise relative to the left in Figure 2, and leftward in Figures 4(a) and 6(a)). The step 348 is a portion that protrudes from the plate surface 347 of the thin plate portion 345 (the plate surface on the left side in Figures 2, 3, 4(b) and 6(b)). The range of the step 348 in the radial direction of the female flange 340 (see Figures 2 to 4) at least partially overlaps with the range of the step 248 in the radial direction of the male flange 240 (see Figures 2 and 5(b)). Preferably, a tip end surface 349 (the left end surface in Figures 2, 3, 4(b) and 6(b)) of the step portion 348 in the axial direction of the female flange 340 is inclined with respect to both the axial direction and the circumferential direction of the female flange 340, and the further away from the tip 344 (the upper end in Figures 2 to 4 and 6) of the female protrusion 343 in the forward rotation direction FCL of the female thread 350 (clockwise relative to the left in Figure 2, and leftward in Figures 4(a) and 6(a)), the closer to the plate surface 347 of the thin plate portion 345 it is.
-protrusion-

As shown in Figures 1, 2, and 4-6, the female flange 340 includes a protrusion 360 on its outer peripheral surface (highlighted by hatching in Figures 4-6). The protrusion 360 protrudes outward from a circumferential portion of the outer peripheral surface of the female flange 340 that is different from the female protrusion 343 (the front side in Figures 1-3 and 4-6(b), and the right side in Figures 4-6(a)), and also protrudes in the axial direction (the left side in Figures 1-3 and 4-6(b), and the front side in Figures 4-6(a)). In particular, the protrusion 360 extends axially outward by a distance LP (the left side in Figures 4-6(b)) beyond the bearing surface 341 of the female thread 350.

As shown in Figure 4(a), the width WP of the protrusion 360 in the circumferential direction of the female flange 340 is less than the common width WF of the protrusions 243, 343, and is preferably slightly less than 30°: WP ≈ 30° ≦ WF. Furthermore, as shown in Figures 4(b) and 6(b), the tip 354 of the second thread groove 352 is located within the range of the protrusion 360 in the circumferential direction of the female flange 340. Preferably, the circumferential center of the protrusion 360 is located at the same location in the circumferential direction as the tip 354. Therefore, there is a gap WG of approximately 30° between the female protrusion 343 and the protrusion 360: WG ≈ 30°.

As shown in Figures 4-6(b), the tip surface 361 of the protrusion 360 is perpendicular to the axial direction of the female flange 340, and preferably has an arc shape that follows the outer periphery of the female flange 340, as shown in Figures 4-6(a). In the range from the seat surface 341 of the female thread 350 to the tip surface 361 in the axial direction, i.e., the portion of the protrusion 360 located outside the seat surface 341 (on the left side in Figures 4-6(b)), the inner diameter RP is equal to or greater than the outer diameter RF of the female flange 340 and equal to or less than the maximum outer diameter of the female protrusion 343, i.e., the outer diameter RT of its tip 344: RF≦RP≦RT.

As shown in Figures 2 and 4(b), the tip 353 of the first thread groove 351 of the female thread 350 and the tip 354 of the second thread groove 352 are both located axially further back (to the right in Figures 2 and 4(b)) than the bearing surface 341 of the female thread 350. Therefore, as shown by the two-dot chain line in Figure 4(b), the distance LS between the bearing surfaces 241, 341 when the two threads 250, 350 are engaged in the correct fastening start position is shorter than the length LM of the male thread 250: LS < LM. The distance LP between the bearing surface 341 of the female thread 350 and the tip surface 361 of the protrusion 360 is designed to be preferably equal to or greater than this distance LS: LP ≥ LS.
[Connecting hoses using pipe joints]

The operation of connecting the second hose 520 to the first hose 510 using the pipe coupling 100 is preferably performed in the following procedure: First, the first end 210 of the male part 200 is press-fitted into the open end of the first hose 510, and the second end 320 of the female part 300 is press-fitted into the open end of the second hose 520. In other words, the parts 200, 300 are connected to the hoses 510, 520. Next, the second end 220 of the male part 200 and the first end 310 of the female part 300 are coaxially butted together, and the position at which the male thread 250 and the female thread 350 begin to fasten is found.
- When the screw is close to the correct tightening start position -

In the arrangement of the male part 200 and female part 300 shown in Figure 4, the circumferential angle between the male thread 250 and the female thread 350 is the value at the correct fastening start position. That is, in the circumferential direction of both threads 250, 350, the tip 253 of the first thread 251 is located in the same location as the tip 353 of the first thread groove 351, and the tip 254 of the second thread 252 is located in the same location as the tip 354 of the second thread groove 352. At this time, the protrusion 360 of the female flange 340 is outside the range of the male protrusion 243 in the circumferential direction, and in particular, its circumferential center is located 180° rotated around the central axis 201=301 of both parts 200, 300 from the tip 244 of the male protrusion 243 (the left end in Figure 4(a)). Because the inner diameter RP of the protrusion 360 is equal to or greater than the outer diameter RF of the male flange 240 (RP ≥ RF), when the two screws 250, 350 are brought closer together, the protrusion 360 deviates toward the outer periphery of the male flange 240 and does not collide with the male flange 240. Therefore, the two screws 250, 350 reach the correct fastening start position. That is, the tip 253 of the first thread 251 reaches the tip 353 of the first thread groove 351, and the tip 254 of the second thread 252 reaches the tip 354 of the second thread groove 352. At this time, as shown in Figure 4(a), there is a circumferential gap of approximately 120° (WF + WG ≈ 90° + 30°) between the male protrusion 243 and the protrusion 360.

After the male thread 250 and the female thread 350 reach the correct fastening start position, the male part 200 is rotated in the forward rotation direction MCL of the male thread 250 (clockwise in FIG. 4A), and the female part 300 is rotated in the forward rotation direction FCL of the female thread 350 (counterclockwise in FIG. 4A). Because the inner diameter RP of the protrusion 360 is equal to or greater than the outer diameter RF of the male flange 240 (RP≧RF), the protrusion 360 rotates along the outer periphery of the male flange 240 without colliding with it. Therefore, the first thread 251 enters the first thread groove 351, and the second thread 252 enters the second thread groove 352. In other words, the two threads 250, 350 begin to mesh with each other. When both screws 250, 350 reach the correct fastening start position, the circumferential distance of approximately 120° between male protrusion 243 and protrusion 360 is equal to or greater than the fit angle of both screws 250, 350 of 90°, so both screws 250, 350 reach the correct fastening completion position before protrusion 360 collides with male protrusion 243. In this way, fastening of male component 200 and female component 300 is completed.
- When the screw is close to the incorrect tightening start position -

In the arrangement of the male part 200 and the female part 300 shown in Figure 6, the circumferential angle between the male thread 250 and the female thread 350 is a value at an incorrect fastening start position. That is, in the circumferential direction of both threads 250, 350, the tip 253 of the first thread 251 is located at the same location as the tip 354 of the second thread groove 352, and the tip 254 of the second thread 252 is located at the same location as the tip 353 of the first thread groove 351. At this time, the protrusion 360 of the female flange 340 is located within the range of the male protrusion 243 in the circumferential direction, and in particular, its circumferential center coincides with the circumferential position of the tip 244 of the male protrusion 243 (the right end in Figure 4(a)). On the other hand, the inner diameter RP of the protrusion 360 is equal to or greater than the outer diameter RF of the male flange 240 and equal to or less than the maximum outer diameter RT of the male protrusion 243 (RF≦RP≦RT), and the distance LP between the bearing surface 341 of the female thread 350 and the tip surface 361 of the protrusion 360 is equal to or greater than the distance LS between the bearing surfaces 241, 341 of the two screws 250, 350 that are engaged at the correct fastening start position (LP≧LS). Therefore, when the two screws 250, 350 are brought closer to each other, the protrusion 360 collides with the blocking surface 247 of the male protrusion 243 before the tips 253, 254 of the threads 251, 252 reach the tips 353, 354 of the thread grooves 351, 352, or simultaneously with their arrival. Since the two screws 250, 350 are thus prevented from moving further closer to each other, it is physically impossible to mesh the two screws 250, 350 at the incorrect fastening start position, i.e., to have the tip 253 of the first thread 251 enter the tip 354 of the second thread groove 352, and the tip 254 of the second thread 252 enter the tip 353 of the first thread groove 351.
[The significance of the fit angle being 180° or less]

In the male part 200, the first end 210 and the second end 220 are integrated, and in the female part 300, the first end 310 and the second end 320 are integrated. Therefore, to engage the male thread 250 and the female thread 350, the entire male part 200 and the entire female part 300 must be rotated relative to each other. In the operation of connecting the hoses 510 and 520, the parts 200 and 300 are connected to the hoses 510 and 520 before engaging the threads 250 and 350. Therefore, when engaging the threads 250 and 350, the relative rotation of the parts 200 and 300 inevitably twists at least one of the hoses 510 and 520. Therefore, it is preferable to previously apply a twist in the opposite direction to the twist that will occur at that time to one of the hoses 510 and 520. This ensures that when both screws 250, 350 reach the complete fastening position, no twist remains in either hose 510, 520. When the fit angle of both screws 250, 350 is 180° or less, the twist in the opposite direction that must be applied in advance to either hose 510, 520 is also 180° or less. Therefore, the rotation of male part 200 or female part 300 required to apply this twist in the opposite direction can be performed by an operator with one hand.
[Press-fitting of annular protrusion into annular groove]

The annular protrusion 330 of the female part 300 has a wall thickness slightly larger than the radial width of the annular groove 230 of the male part 200, an inner diameter equal to or slightly smaller than the diameter of the inner peripheral surface of the annular groove 230, and an outer diameter equal to or slightly larger than the diameter of the outer peripheral surface of the annular groove 230. Therefore, when the male thread 250 and the female thread 350 move from the correct fastening start position to the correct fastening completion position, the axial force of the two threads 250, 350 presses the annular protrusion 330 into the annular groove 230, causing the inner peripheral surface of the annular protrusion 330 to tightly contact the inner peripheral surface of the annular groove 230 and the outer peripheral surface of the annular protrusion 330 to tightly contact the outer peripheral surface of the annular groove 230 (see Figure 3). These tight contact areas, i.e., the seal area SR, seal the gap between the opening 221 of the male part 200 and the opening 311 of the female part 300. To ensure a sufficiently high seal for this gap, the width of the sealing region SR in the axial direction of both parts 200, 300, i.e., the length of the portion of the annular protrusion 330 that is to be press-fitted into the annular groove 230, is designed. Furthermore, the target value for the fit length of both screws 250, 350 is designed based on this length, and the complete fastening position is determined.

Because the axial force of the male thread 250 and the female thread 350 is used to press-fit the annular protrusion 330 into the annular groove 230, the force required for press-fitting must be reduced to keep the tightening torque of the two threads 250, 350 to a level that can be applied by bare hands. Therefore, the wall thickness of the opening 221, the width and depth of the annular groove 230, and the thickness and length of the annular protrusion 330 are designed so that distortion of the wall of the opening 221 due to press-fitting is sufficiently small. Specifically, the depth of the annular groove 230 is designed to be sufficiently large relative to the wall thickness of the opening 221, preferably three times or more, and the axial distance from the seal region SR to the bottom 231 of the annular groove 230 is designed to be sufficiently large, preferably more than ten times, the increase in the width of the annular groove 230 due to press-fitting.
[Role of the protrusion]

As shown in Figures 3 and 5, the length LM of the male thread 250 is preferably designed so that the bearing surfaces 241, 341 of the male thread 250 and female thread 350 come into contact with each other when they reach the correct fastening position. However, in reality, it is difficult to confirm that the two threads 250, 350 have reached the correct fastening position just by the contact between the bearing surfaces 241, 341. Furthermore, each time the male part 200 and female part 300 are fastened together, there is likely to be a large deviation between the final relative positions of the two threads 250, 350 and the correct fastening position.

As explained below, the male protrusion 243 and the female protrusion 343 allow the operator to easily confirm that the male thread 250 and the female thread 350 have reached the correct fastening position. This allows the pipe fitting 100 to easily connect the hoses 510, 520. Furthermore, any deviation between the final relative positions of the two threads 250, 350 and the correct fastening position is reliably kept within an acceptable range. This prevents a lack of area in the seal region SR due to an insufficient engagement length of the two threads 250, 350, and prevents excessive creep deformation of the two parts 200, 300 due to excessive tightening torque of the two threads 250, 350. As a result, the pipe fitting 100 is highly reliable due to its high sealing performance.

In the circumferential direction of the male flange 240, the tip 244 of the male protrusion 243 is located at the same location as the tip 253 of the first thread 251. In the circumferential direction of the female flange 340, the tip 344 of the female protrusion 343 is located at a position rotated 90° from the tip 353 of the first thread groove 351 in the reverse direction FCC of the female thread 350, corresponding to the engagement angle between the male thread 250 and the female thread 350 (see Figure 2). When both threads 250, 350 are in the correct fastening start position, the tip 253 of the first thread 251 is located at the tip 353 of the first thread groove 351, and therefore the tip 244 of the male protrusion 243 is located at a position rotated 90° from the tip 344 of the female protrusion 343 in the forward direction FCL of the female thread 350 (see Figure 4(a)). Therefore, only when both screws 250, 350 reach the correct tightening completion position does the protrusions 243, 343 align the circumferential positions of the tips 244, 344, and their outlines appear to completely overlap from the axial direction (see Figure 5(a)). This allows the operator to confirm at a glance that both screws 250, 350 have reached the correct tightening completion position. Furthermore, because even slight misalignment between the tips 244, 344 of the protrusions 243, 343 and misalignment in the outlines between the protrusions 243, 343 are noticeable, it is easy to minimize these misalignments to an unnoticeable level. As a result, the misalignment between the final relative positions of both screws 250, 350 and the correct tightening completion position is reliably kept within an acceptable range.

In the male protrusion 243, the tip surface 249 of the step 248 is located at the same location as the seat surface 241 of the male thread 250 in the axial direction of the male flange 240, or further outward (to the right in Figure 2). In the female protrusion 343, the tip surface 349 of the step 348 is located further outward (to the left in Figure 2) than the seat surface 341 of the female thread 350 in the axial direction of the female flange 340. Therefore, when the two screws 250, 350 reach the correct tightening completion position, the step portions 248, 348 engage with each other in a snap-fit manner, as described below.

Just before the two screws 250, 350 reach the correct tightening completion position, the tip surface 249 of the step 248 of the male protrusion 243 collides with the tip surface 349 of the step 348 of the female protrusion 343. Due to its inclination, the tip surface 349 of the female protrusion 343 receives axial pressure from the tip surface 249 of the male protrusion 343. This causes the thin plate portion 345 of the female protrusion 343 to bend toward the thick plate portion 346. As a result, as the two screws 250, 350 continue to rotate forward, the step portions 248, 348 overcome each other, and the two screws 250, 350 reach the correct tightening completion position. At the same time, the thin plate portion 345 returns to its original bending state, causing the tip surface 349 of the female protrusion 343 to strike the surface of the male protrusion 243. The sound produced at this time reverberates in the gap GP between the thin plate portion 345 and the thick plate portion 346. By hearing this reverberation, the worker can confirm by ear that both screws 250, 350 have reached the correct tightening completion position. Furthermore, by feeling the vibration caused by the inclined surface 349 of the female protrusion 343 striking, the worker can also confirm by hand that both screws 250, 350 have reached the correct tightening completion position.

In addition to the above functions, the protrusions 243, 343 make it easier to rotate the male part 200 and the female part 300 with bare hands. This makes it easier to connect the hoses 510, 520 using the pipe fitting 100. In fact, when rotating the two parts 200, 300 relative to each other, the worker can hook their fingers on the protrusions 243, 343, making it easier to apply circumferential force to the two parts 200, 300. Furthermore, because the protrusions 243, 343 are farther from the central axes 201, 301 of the same parts 200, 300 than other parts of the same parts 200, 300, even when the same amount of circumferential force is applied, a larger torque is applied to each part 200, 300. Therefore, by applying a circumferential force to each protrusion 243, 343, the worker can easily apply a sufficiently large torque to each part 200, 300.

Furthermore, the protrusions 243, 343 prevent the male thread 250 and the female thread 350 from loosening after they reach the correct fastening position. This makes the pipe fitting 100 highly reliable against external vibration shocks or changes in shape over time. In fact, as described above, when the two threads 250, 350 reach the correct fastening position, the steps 248, 348 of the two parts 200, 300 engage with each other. Even if the two threads 250, 350 are subsequently subjected to torque that encourages reverse rotation due to external vibration shocks or the like, the steps 248, 348 will contact each other's circumferential side surfaces, preventing the two threads 250, 350 from reversing. In this way, the protrusions 243, 343 can prevent the two threads 250, 350 from loosening. In particular, because the step portions 248, 348 are adjacent to the tips 244, 344 (upper ends in Figures 2 and 3) of the protrusions 243, 343, they are farther from the central axes 201, 301 of the same parts 200, 300 than other parts of the same parts 200, 300. Therefore, even if the torque that encourages the screws 250, 350 to rotate in the reverse direction is large, the force that presses the step portions 248, 348 against each other is sufficiently weak, and the effect of preventing the screws 250, 350 from loosening due to the mutual engagement of the step portions 248, 348 is sufficiently high.
Advantages of the embodiment

The pipe fitting 100 satisfies all of the following conditions (A), (B), (C), and (D). (A) The fit angle between the male thread 250 and the female thread 350 = 90° is less than or equal to 180°. (B) The distance LP between the seat surface 341 of the female thread 350 and the tip surface 361 of the protrusion 360 of the female flange 340 is greater than or equal to the distance LS between the seat surfaces 241, 341 of the two threads 250, 350 when the two threads 250, 350 are engaged in the correct fastening start position: LP ≥ LS. (C) When the two threads 250, 350 are arranged coaxially with each other, if the circumferential angle between the two threads 250, 350 is the value at the correct fastening start position, the protrusion 360 is separated from the male protrusion 243 by a fit angle of 90° or more in the circumferential direction of the male part 200 and the female part 300. (D) When the two screws 250, 350 are arranged coaxially with each other, if the circumferential angle between the two screws 250, 350 is an incorrect value at the fastening start position, the protrusion 360 will be located within the range of the male protrusion 243 in the circumferential direction of the two parts 200, 300.

Because the pipe fitting 100 satisfies all of the above conditions (A)-(D), it is physically impossible for the male thread 250 and the female thread 350 to mesh at an incorrect fastening start position. In fact, when the two threads 250, 350 mesh, if the circumferential angle between the two threads 250, 350 is the value at the correct fastening start position, the protrusion 360 is spaced from the male protrusion 243 in the circumferential direction of the male part 200 and the female part 300, and the two threads 250, 350 reach the correct fastening start position. Since the protrusion 360 continues to move further outward than the male flange 240 without colliding with the male protrusion 243, the two threads 250, 350 reach the correct fastening completion position. On the other hand, if the circumferential angle between the two threads 250, 350 is the value at the incorrect fastening start position, the protrusion 360 will collide with the male protrusion 243 before or simultaneously with the two threads 250, 350 reaching the incorrect fastening start position. This makes it physically impossible to mate the two threads 250, 350 at an incorrect fastening start position. Naturally, therefore, it is also physically impossible for the two threads 250, 350 to reach an incorrect fastening completion position, so the pipe fitting 100 further improves the workability of connecting piping.
[Modification]

(1) The resin material of the pipe fitting 100 is not limited to PA or PA-GF. Various other resins can be used, including low-density polyethylene, polypropylene, polycarbonate, polyamide, polyacetal, polyether ether ketone, polyphenylene sulfide, and polyimide. These may be selected appropriately depending on the field or application of the pipe fitting 100, the material of the hoses 510 and 520, etc.

(2) In the pipe fitting 100, the male part 200 includes an annular groove 230 into which the annular protrusion 330 of the female part 300 is press-fit. Conversely, the female part 300 may include an annular groove into which the annular protrusion of the male part 200 is press-fit.

(3) In the circumferential direction of the male flange 240, the tip 244 of the male protrusion 243 is located at the same location as the tip 253 of the first thread 251, and in the circumferential direction of the female flange 340, the center of the protrusion 360 is located at the same location as the tip 354 of the second thread groove 352. However, the present invention is not limited to these arrangements. Whether the protrusion 360 collides with the male protrusion 243 before the two screws 250, 350 reach the fastening completion position is determined by the relative positions of the male protrusion 243 and the protrusion 360 when the two screws 250, 350 are engaged, and does not directly depend on the relative positions of the male protrusion 243 and the tip 253 of the first thread 251, or the relative positions of the protrusion 360 and the tip 354 of the second thread groove 352.

(4) The threads 251, 252 of the male thread 250 and the grooves 351, 352 of the female thread 350 both have a trapezoidal cross section, but may have other polygonal shapes such as a triangle, rectangle, or sawtooth, or may have rounded peaks or valleys. Furthermore, while the number of threads on both threads 250, 350 is two, it may also have three or more. In this case, since there are the same number of fastening start positions as the number of threads, i.e., three or more, two or more correct fastening start positions may be selected. Accordingly, protrusions 360 are added up to the same number as the incorrect fastening start positions, and are positioned so as to satisfy the following conditions [a] and [b].

[a] When the two screws 250, 350 are engaged, if the circumferential angle between the two screws 250, 350 is the value at any of the incorrect fastening start positions, one of the protrusions 360 in the circumferential direction of the two screws 250, 350 will be located within the range of the male protrusion 243. If condition [a] is met, no matter which of the incorrect fastening start positions the two screws 250, 350 approach, one of the protrusions 360 will collide with the male protrusion 243, making it physically impossible to engage the two screws 250, 350 at any of the incorrect fastening start positions.

[b] When the two threads 250, 350 are meshed, if the circumferential angle between the two threads 250, 350 is the value at either of the correct fastening start positions, then both protrusions 360 are spaced from the male protrusion 243 in the forward rotation direction MCL of the male thread 250 by an amount equal to or greater than the mesh angle of the two threads 250, 350. To satisfy condition [b], the width WP of the protrusion 360 or the width WF of the male protrusion 243 can be adjusted. If condition [b] is satisfied, it is possible to mesh the two threads 250, 350 at either of the correct fastening start positions, and to reach the correct fastening completion position from there.

(5) In the pipe fitting 100, the female part 300 includes the protrusion 360. Conversely, the male part 200 may include the protrusion. The cross section of the protrusion 360 is arc-shaped, but may be other shapes such as polygonal or circular. The outline of the flanges 240, 340 including the protrusions 243, 343 is teardrop-shaped, but may be other rotationally asymmetric shapes. In this case, the inner diameter of the protrusion 360 should be designed to be equal to or greater than the outer diameter RF of the flanges 240, 340 and equal to or less than the maximum outer diameter RT of the protrusions 243, 343.

(6) Because the pipe fitting 100 satisfies all of the above conditions (A)-(D), it is physically impossible for the male thread 250 and the female thread 350 to mesh at an incorrect fastening start position. However, satisfying all of conditions (A)-(D) is not essential for the present invention. If any of the conditions is relaxed, it may be physically possible for the two threads 250, 350 to mesh at either the correct or incorrect fastening start position. However, for the present invention, it is sufficient that it is physically impossible for the two threads 250, 350 to reach an incorrect fastening completion position. Specifically, when the two threads 250, 350 are brought closer to each other coaxially during the fastening operation of the male part 200 and the female part 300, if the circumferential angle between the two threads 250, 350 is the value at the incorrect fastening start position, the protrusion 360 should collide with the male protrusion 243 before the two threads 250, 350 reach the incorrect fastening completion position. On the other hand, if the circumferential angle between the two screws 250, 350 is the value at the correct fastening start position, the protrusion 360 simply passes through the outer peripheral side of the male flange 240 other than the male protrusion 243 until the two screws 250, 350 reach the correct fastening completion position, thereby avoiding collision with the male protrusion 243.

For example, the distance LP between the bearing surface 341 of the female thread 350 and the tip surface 361 of the protrusion 360 of the female flange 340 may be shorter than the lower limit LS specified in condition (B) (LP < LS). In this case, it is physically possible for the male thread 250 and the female thread 350 to mesh at an incorrect make-up start position. However, if the position of the male protrusion 243 in the circumferential direction of the male flange 240 is appropriately shifted in the forward rotation direction MCL of the male thread 250, or if the width WF of the male protrusion 243 is sufficiently wide, it is possible to cause the protrusion 360 to collide with the male protrusion 243 before the two screws 250, 350 reach an incorrect make-up completion position. This makes it physically impossible for the two screws 250, 350 to reach an incorrect make-up completion position.

When condition (D) is relaxed and the male thread 250 and female thread 350 are coaxially aligned, the protrusion 360 may be positioned outside the range of the male protrusion 243 in the circumferential direction, even if the circumferential angle between them is the value at the incorrect fastening start position. In this case, even if condition (B) is met, the protrusion 360 will not collide with the male protrusion 243, so it is physically possible for the two threads 250, 350 to mesh at the incorrect fastening start position. However, if the protrusion 360 is located away from the male protrusion 243 in the forward rotation direction MCL of the male thread 250 by less than the mesh angle of the two threads 250, 350, the protrusion 360 will soon collide with the male protrusion 243 as the two threads 250, 350 rotate forward. Therefore, it is physically impossible for the two threads 250, 350 to reach the incorrect fastening completion position.

Condition (A) may be relaxed, and the engagement angle between the male thread 250 and the female thread 350 may exceed 180° or even 360° (1 rotation). In this case, if the distance LP between the bearing surface 341 of the female thread 350 and the tip surface 361 of the protrusion 360 is sufficiently shorter than the lower limit LS specified by condition (B), the two threads 250, 350 can be engaged in either the correct or incorrect fastening start position. Furthermore, since condition (C) cannot be satisfied, the protrusion 360 and the male protrusion 243 may instead be designed as follows: When the two threads 250, 350 rotate forward from the incorrect fastening start position and the remaining rotation angle to the incorrect fastening completion position is reduced to a predetermined value less than 360°/number of threads, for example, a predetermined value less than 360°/2 = 180°, the tip surface 361 of the protrusion 360 will reach the same location as the bearing surface 241 of the male thread 250 in the axial direction of the two threads 250, 350. At this time, the tip surface 361 is less than the predetermined distance from the male protrusion 243 in the forward rotation direction MCL of the male thread 250. As a result, the male protrusion 243 collides with the protrusion 360 before the screws 250, 350 reach the incorrect fastening completion position. Therefore, it is physically impossible for the screws 250, 350 to reach the incorrect fastening completion position. On the other hand, when the screws 250, 350 rotate forward from the correct fastening start position and the remaining rotation angle to the correct fastening completion position is reduced to the predetermined value, the tip surface 361 of the protrusion 360 reaches the outer periphery of the bearing surface 241 of the male thread 250 at a location more than the predetermined distance from the male protrusion 243 in the forward rotation direction MCL of the male thread 250. Therefore, the screws 250, 350 reach the correct fastening completion position before the male protrusion 243 collides with the protrusion 360.

(7) In the pipe fitting 100, the male protrusion 243 pushes aside the thin plate portion 345 of the female protrusion 343, causing the step portions 248, 348 to climb over each other and engage. In addition to the step portions 248, 348, various other snap-fit engagement structures are possible. For example, one of the protrusions 243, 343 may have a claw portion and the other a claw receiver. The claw portion protrudes axially from one of the protrusions 243, 343 and can bend radially outward. When the male thread 250 and the female thread 350 reach the correct tightening position, the claw portion bends and its tip engages the claw receiver. The operator can easily confirm that the two threads 250, 350 have reached the correct tightening position by visually confirming that the claw portion is engaged in the claw receiver and by hearing or manually hearing the sound or vibration of the claw tip striking the claw receiver. Furthermore, the mutual engagement between the claw portion and the claw receiver prevents the screws 250, 350 from rotating in reverse. This prevents the screws 250, 350 from loosening due to external vibrations or shocks or changes in shape over time.

(8) In the pipe fitting 100, the male part 200 and the female part 300 have rotationally asymmetric shapes due to the presence of the protrusions 243, 343. This makes it easy to confirm that the male thread 250 and the female thread 350 have reached the tightening completion position during the tightening operation of the two parts 200, 300, and ensures that the deviation between the final relative positions of the two threads 250, 350 and the tightening completion position is within an acceptable range. However, because the two threads 250, 350 are multiple-start threads, it is necessary to select at least one of the multiple tightening completion positions as the correct one, as the circumferential position of the protrusions 243, 343 matches. This is why the tightening completion positions of the two threads 250, 350 can be correct or incorrect. However, this reason is not a necessary premise for the present invention. For whatever reason, the present invention is effective when the correct tightening completion position is selected from the multiple tightening completion positions of the multiple-start thread and it is necessary to prevent the multiple-start thread from reaching any other tightening completion positions.

100 Pipe fitting 200 Male part 201 Central axis of male part 210 First end of male part 220 Second end of male part 221 Opening of male part 230 Annular groove 231 Bottom of annular groove 240 Male flange 241 Bearing surface of male thread 243 Male protrusion 244 Tip of male protrusion 247 Blocking surface of male protrusion 248 Step of male protrusion 249 Tip surface of step of male protrusion 250 Male thread 251, 252 Thread of male thread 253, 254 Tip of thread of male thread 300 Female part 301 Central axis of female part 310 First end of female part 311 Opening of female part 320 Second end of female part 330 Annular protrusion 331 Tip of annular protrusion 340 Female flange 341 Bearing surface of female thread 343 Female protrusion 344 Tip of female protrusion 345 Thin plate portion 346 Thick plate portion 347 Outer plate surface of thin plate portion 348 Step portion of female protrusion 349 Tip surface of step portion of female protrusion 350 Female thread 351, 352 Thread groove of female thread 353 Tip of thread groove of female thread 360 Protrusion of female flange 361 Tip surface of protrusion of female flange 510 First hose 520 Second hose

Claims (5)

A pipe fitting is provided with a first part and a second part, both of which are cylindrical, and which include a connection portion for connection with a pipe at one axial end and a multiple-start thread at the other axial end, and which can be fastened to each other by the threads,
an outer peripheral surface of the first component includes a first protruding portion extending in the outer peripheral direction from a part in the circumferential direction;
The outer peripheral surface of the second component is
a second protruding portion extending from a portion in the circumferential direction toward the outer periphery;
a projection that projects outward from a circumferential portion different from the second protruding portion and also projects in the axial direction,
the first protrusion and the second protrusion are configured to align the first component and the second component in circumferential positions when the screw reaches a correct fastening completion position,
When the screws are brought closer to each other coaxially during the fastening operation of the first part and the second part,
When the circumferential angle between the threads is a value at a correct fastening start position, the protrusion passes through an outer peripheral side of the outer peripheral surface of the first component other than the first protruding portion until the screw reaches a correct fastening completion position, thereby avoiding collision with the first protruding portion,
a pipe fitting, characterized in that the protrusion is configured so that, if the circumferential angle between the threads is a value at an incorrect make-up start position, the protrusion will collide with the first protruding portion before the threads reach an incorrect make-up completion position. The fit angle, which is the rotation angle required for the screw to move from the correct fastening start position to the correct fastening completion position, is 180° or less,
the length of the projection is equal to or greater than the distance between the bearing surfaces of the screws when the screws are engaged at the correct fastening start position,
When the screws are arranged coaxially with each other,
When the angle between the threads in the circumferential direction is a value at a correct fastening start position, the protrusion is spaced apart from the first protruding portion in the circumferential direction of the first component and the second component by the fit angle or more,
When the circumferential angle between the threads is a value at an incorrect fastening start position, the protrusion is located within the range of the first protruding portion in the circumferential direction.
2. The pipe fitting of claim 1. The pipe fitting described in claim 1, wherein the first protrusion and the second protrusion have the same outline when viewed from the axial direction of the first part and the second part. The pipe fitting described in claim 1, wherein the first protrusion and the second protrusion are configured to engage with each other in a snap-fit manner when the screw reaches the correct tightening position. A pipe fitting as described in claim 1, wherein the first protrusion and the second protrusion are configured to engage with each other when the screw reaches the correct tightening position, thereby preventing the screw from being reversed.