Pipe coupling

Abstract

The purpose of the present invention is to provide a pipe coupling capable of preventing a pipe from being cut even if a crushing amount due to a caulking machine is increased.　Provided is a pipe coupling in which a pipe body is inserted along an outer peripheral surface of a nipple and is pressed by a pipe from the outside thereof to bring an inner peripheral surface of the pipe body into close contact with the outer peripheral surface of the nipple. The pipe coupling is characterized in that: the nipple has an uneven section formed on the outer peripheral surface thereof, and a line connecting maximum-height portions of the uneven section shows approximately the same diameter over a range from a nipple tip on a front side in the pipe-body insertion direction to a far side in the pipe-body insertion direction; and the pipe has the minimum diameter at a far-side position farther than a position where a part of the pipe on the front side in the pipe-body insertion direction faces the nipple tip, has the same diameter over a predetermined range from the far-side position, where the pipe has the minimum diameter, to the far side in the pipe-body insertion direction, and has a first tapered part that gradually expands in diameter at a further far side beyond the predetermined range. The pipe coupling solves the problem.

Description

Pipe fittings

[0001] The present invention relates to a pipe fitting used for connecting hoses made of tear-resistant materials such as thermoplastic resins or thermosetting resins, etc. More specifically, the invention relates to a pipe fitting in which a pipe is inserted along the outer periphery of a nipple and a pipe is pressed from the outside to bring the inner periphery of the pipe into tight contact with the outer periphery of the nipple.

[0002] Conventionally, as shown in Patent Document 1, for example, this type of pipe fitting is composed of two parts, a nipple and a pipe, and after the pipe is placed over the pipe to be fitted and the nipple is inserted into the pipe, the pipe is crushed with a crimping machine to prevent the pipe from coming loose or leaking, etc. Patent Document 2 also shows an example of a laminated pipe that can be used as a pipe fitting.

[0003] JP 2006-220186 A Japanese Patent No. 6814485 A

[0004] 8, the pipe fitting of Patent Document 1 is configured so that a pipe H is connected by clamping the pipe P between the inner peripheral surface of the pipe P and the outer peripheral surface of the nipple N, and then the pipe P is crimped. The structure of the connection is such that the inner peripheral surface of the pipe P is horizontal, while the outer peripheral surface of the nipple N is narrow at the nipple tip N1 and tapered at the back side N2.

[0005] However, when the pipe P is crimped with a crimping machine, if the pipe H is tightened from the narrow gap between the nipple N and the pipe P, the pipe H moves to the right in the figure due to the tapered portion N2 toward the nipple tip N1. In pipe H behaving in this manner, stress concentration occurs at the nipple tip N1 and the pipe tip P1, which can cause the pipe H as a hose to break. In particular, laminated pipes such as those shown in Patent Document 2 are prone to breakage because they use silicone rubber, which is weak against tearing. To prevent breakage, it is necessary to adjust the amount of crushing by the crimping machine to reduce the amount of crushing. However, if the amount of crushing is too small, liquid can seep into the inside of the pipe H at the nipple tip N1, causing unnecessary liquid accumulation in this area.

[0006] The present invention addresses these problems and aims to provide a pipe joint that will not break the pipe even if the amount of crushing by the crimping machine is increased.

[0007] In order to achieve this object, the present invention provides a pipe fitting in which a pipe is inserted along the outer peripheral surface of a nipple and pressed from the outside with a pipe to tightly fit the inner peripheral surface of the pipe to the outer peripheral surface of the nipple, wherein the nipple has unevenness formed on its outer peripheral surface, and a line connecting its greatest height parts has approximately the same diameter from the tip of the nipple on the front side in the pipe insertion direction to the rear side in the pipe insertion direction, and the pipe has a minimum diameter at a part on the front side in the pipe insertion direction further rearward than the position opposite the nipple tip, and the pipe has a constant diameter over a predetermined range from the rearward position where it is minimum diameter to the rearward side in the pipe insertion direction, and has a first tapered section which gradually increases in diameter further rearward beyond the predetermined range.

[0008]

[0023] Figure 1(a) is a front view, Figure 1(b) is a cross-sectional view taken along line A-A in Figure 1(a), and Figure 1(c) is a perspective view, showing the overall configuration of a pipe fitting according to an embodiment of the present invention, illustrating a state before a pipe body is inserted and crimped. Figure 2(a) is a front view, Figure 2(b) is a cross-sectional view taken along line A-A in Figure 2(a), and Figure 2(c) is a perspective view, showing the overall configuration of a pipe fitting according to an embodiment of the present invention, illustrating a state after a pipe body is inserted and crimped. Figure 3(a) is a front view, Figure 3(b) is a cross-sectional view taken along line A-A in Figure 3(a).

[0024] Figure 4(a) is a front view, Figure 4(b) is a cross-sectional view taken along line A-A in Figure 4(a), Figure 4(c) is a front view after crimping, and Figure 4(d) is a cross-sectional view taken along line A-A in Figure 4(c). 6(a) and 6(b) are explanatory views showing a pipe fitting according to an embodiment of the present invention, with Fig. 5(a) being a front view before crimping, Fig. 5(b) being a cross-sectional view taken along line A-A in Fig. 5(a), Fig. 5(c) being a front view after crimping, and Fig. 5(d) being a cross-sectional view taken along line A-A in Fig. 5(c). 6(a) and 6(b) are diagrams for explaining a crimping machine, with Fig. 6(a) being a front view, Fig. 6(b) being a left side view, Fig. 6(c) being a right side view, and Fig. 6(d) being a perspective view. 6(b) and 6(d) are comparative explanatory views showing the difference between a conventional example and an embodiment of the present invention in the manner in which a pipe body moves when a pipe fitting is crimped. 6(c) are front views showing a conventional pipe fitting.

[0009] Fig. 1 is an explanatory diagram showing the overall configuration of a pipe fitting according to an embodiment of the present invention, illustrating a state before a pipe body is inserted and crimped, with Fig. 1(a) being a front view, Fig. 1(b) being a cross-sectional view taken along line A-A in Fig. 1(a), and Fig. 1(c) being a perspective view. Fig. 2 is an explanatory diagram showing the overall configuration of a pipe fitting according to an embodiment of the present invention, illustrating a state after a pipe body is inserted and crimped, with Fig. 2(a) being a front view, Fig. 2(b) being a cross-sectional view taken along line A-A in Fig. 2(a), and Fig. 2(c) being a perspective view.

[0010] As shown in Figures 1 and 2, the pipe fitting 100 of an embodiment of the present invention is configured such that the connection side end of a pipe H, with a pipe 2 placed over it, is inserted along the outer peripheral surface of a nipple 1 and crimped, thereby radially clamping the connection side end of the pipe H between the outer peripheral surface of the nipple 1 and the inner peripheral surface of the pipe 2, thereby tightly connecting the inner peripheral surface of the pipe H to the outer peripheral surface of the nipple 1.

[0011] 3A and 3B are explanatory views showing a nipple of a pipe joint according to an embodiment of the present invention, in which FIG. 3A is a front view and FIG. 3B is a cross-sectional view taken along line AA of FIG. 3A.

[0012] As shown in Figure 3, the outer peripheral surface of the nipple 1 is provided with multiple convex and concave portions 11, either continuously in the axial direction or at appropriate intervals. A line connecting the maximum heights of the convex and concave portions has a substantially uniform diameter from the nipple tip 12 on the near side in the pipe insertion direction to the far side in the pipe insertion direction. The portion farther in the pipe insertion direction than the multiple convex and concave portions 11, which have a substantially uniform diameter, may be smooth and slightly smaller in diameter than the outer diameter of the convex and concave portions 11, which makes it easier to insert the hose. Furthermore, while the convex and concave portions 11 are shown in the figure as having a symmetrical shape repeated in sequence, they may also have a bamboo-like shape, with multiple protrusions forming a sharp-angled apex with a locking surface that rises at or near a right angle to the axis and an inclined surface that gradually decreases in diameter toward the tip.

[0013] The nipple does not have the taper that is provided in the conventional example to make it easier to insert a hose, i.e., a tapered shape that is narrow at the tip end and becomes thicker toward the back. Also, a connecting portion 13 for connecting to another device is integrally provided on the axial base end of the nipple 1, but its shape is not limited to that shown in the figure.

[0014] 4A and 4B are explanatory diagrams showing a pipe of a pipe fitting according to an embodiment of the present invention, in which FIG. 4A is a front view before crimping, FIG. 4B is a cross-sectional view taken along line A-A in FIG. 4A, FIG. 4C is a front view after crimping, and FIG. 4D is a cross-sectional view taken along line A-A in FIG. 4C.

[0015] As shown in Figures 4(b) and 4(d), the inner circumferential surface of the pipe 2 has a minimum diameter at a position on the front side in the pipe insertion direction that is further back than the position facing the nipple tip 12 (see also Figures 5(b) and 5(d)). From this minimum diameter position to the rear side in the pipe insertion direction, the diameter is the same over a predetermined range 21, i.e., the minimum diameter.

[0016] Further back beyond the predetermined range 21, a first tapered section 22 is provided, the diameter of which increases toward the back. The first tapered section 22 has a plurality of axially continuous irregularities or a plurality of irregularities at appropriate intervals. Furthermore, a second tapered section 23 is provided from the back position where the diameter is minimum toward the front side, the second tapered section 23 increasing in diameter toward the front side. However, it is also possible to form a stepped shape in which the diameter increases all at once from the back position where the diameter is minimum. To prevent the tube from breaking, it is more important that a portion of the inner circumferential surface of the pipe 2 on the front side in the tube insertion direction has the smallest diameter at a position further back than the position facing the nipple tip 12.

[0017] The pipe 2 is made of a rigid material, such as stainless steel or aluminum, that undergoes compressive deformation when pressure is applied radially by a crimping machine but does not recover its original shape when subjected to the repulsive force of the pipe H. As shown in Figure 2, which is an explanatory diagram showing the state after the pipe body has been inserted and crimped, when the outer periphery of the pipe 2 is pressed from the outside toward the center, the position of the tip where the diameter is smallest is extended and becomes aligned with the position of the nipple tip. Furthermore, the multiple continuous irregularities on the first tapered portion 22 on the inner circumferential surface of the pipe 2 and the multiple continuous irregularities 11 on the outer circumferential surface of the nipple 1 are arranged so that the positions of the respective irregularities alternately intermesh, thereby sandwiching the pipe H and maintaining a high pull-out force.

[0018] The pipe H is made of a thermoplastic resin or a thermosetting resin. Examples of thermoplastic resins include general-purpose plastics such as polyvinyl chloride, polyolefin, polyurethane, and polyamide; engineering plastics with a heat resistance of 100°C or higher; and super-engineering plastics with a heat resistance of approximately 150°C or higher. Examples of thermosetting resins include silicone rubber and other rubbers, as appropriate for the intended application. Furthermore, as described in Patent Document 2, the pipe H can be constructed as a laminated pipe, in which different materials, such as an inner layer of fluororesin and an outer layer of silicone rubber, are bonded together via reinforcing threads made of synthetic resin fibers such as polyester. In this case, silicone rubber is a material that is weak against tearing, while fluororesin, being flexible, requires a thin wall thickness, resulting in poor tear resistance. However, by combining this pipe fitting with the pipe H, it is possible to prevent breakage of the pipe H.

[0019] Next, the assembly procedure for connecting a pipe H using the pipe fitting 100 will be described. First, the pipe 2 shown in Figure 4 is placed over the outer periphery of the pipe H. Next, the nipple 1 shown in Figure 3 is inserted into the pipe H with the pipe 2 covering it. Of course, depending on the operator's preference, the nipple 1 shown in Figure 3 may be inserted into the pipe H first, and then the pipe 2 shown in Figure 4 may be placed over the pipe H with the nipple 1 inserted. Because there is a certain amount of clearance between the pipe 1 before it is crimped, the operator can perform the steps in an order that is easiest for them to handle.

[0020] After the nipple 1, pipe H, and pipe 2 are arranged in this order from the inside to the outside, the pipe 2 is pressed by a crimping machine. In Figure 6, the crimping machine S is an eight-way crimping machine, and is configured to crimp eight points on the outer surface of the pipe 2 with the same pressure using eight claws S1 called dies. By radially sandwiching the connection side end of the pipe H between the outer surface of the nipple 1 and the inner surface of the pipe 2, the inner surface of the pipe H is brought into close contact with the outer surface of the nipple 1, completing the connection.

[0021] The reason why the pipe fitting 100 according to the embodiment of the present invention is less likely to break than conventional pipe fittings will be explained using Figure 7. Figure 7(a) shows a conventional example, and Figure 7(b) shows the pipe fitting 100 according to the embodiment of the present invention, both of which are enlarged views showing the upper part where the nipple, hose, and pipe overlap.

[0022] As shown in Figure 7(a), nipples in conventional pipe fittings are tapered to facilitate hose insertion. However, due to this taper, when a pipe P is crimped with a crimping machine, if the pipe H is tightened from the narrow gap between the nipple N and the pipe P, the pipe H moves to the right, as indicated by the thick arrow in the figure. When the pipe H behaves in this way, the thickened wall of the pipe H is pressed firmly against the nipple tip N1 and the pipe tip P1, causing stress concentration that can cause the pipe H to break as a hose.

[0023] On the other hand, in the pipe fitting 100 according to the embodiment of the present invention, the nipple 1 is not tapered, but the pipe 2 is tapered. As shown in FIG. 7( b), the pipe 2 has a minimum diameter at a position farther back than the position facing the nipple tip 12, and has a constant diameter over a predetermined range 21 from the minimum diameter position toward the rear in the pipe insertion direction. The pipe 2 is configured to have a first tapered portion that gradually increases in diameter further back beyond the predetermined range 21. The pipe 2 also has a second tapered portion that gradually increases in diameter from the minimum diameter position toward the front, as shown in the figure. As a result, the pipe H is pushed outward and moves from the predetermined range 21 toward both the left and right. Therefore, the wall thickness of the pipe H pressed against the nipple tip 12 is smaller than in the conventional example. Furthermore, the second tapered portion causes the moving pipe H to escape upward in the figure, preventing stress concentration at the nipple tip 12. Furthermore, the stress concentration occurring at the tip of the pipe 2 can be kept small enough to not cause any problems.

[0024] Examples of the present invention are described below. [Examples 1 and 2 and Comparative Examples 1 and 2] Examples 1 and 2 and Comparative Examples 1 and 2 shown in Table 1 have a three-layer structure using the materials listed therein: an inner layer (the innermost layer), a reinforcing layer made of braided reinforcing yarn, and an outer layer. Evaluation samples of the same size were then prepared for each example. Pipe H, which is the subject of Example 1 and Comparative Example 1, has an inner layer made of silicone rubber, a reinforcing layer made of polyester reinforcing yarn, and an outer layer made of silicone rubber. Pipe H, which is the subject of Example 2 and Comparative Example 2, has an inner layer made of the fluororesin ETFE, a reinforcing layer made of polyester reinforcing yarn, and an outer layer made of silicone rubber. The pipe fittings used in Comparative Examples 1 and 2 are conventional pipe fittings tapered toward the nipple tip, while the pipe fittings used in Examples 1 and 2 are pipe fittings according to an embodiment of the present invention.

[0025] [Evaluation Criteria] The evaluation results shown in Table 1, including the "Water Pressure Resistance Test," "Bending Test," "Liquid Pooling Test," and "Overall Evaluation," are based on the following indices. The "Water Pressure Resistance Test" involved connecting Examples 1 and 2 and Comparative Examples 1 and 2 to a water pressure resistance tester, applying a water pressure equal to a multiple of the normal pressure (water temperature 23°C: 0.5 MPa) to each evaluation sample for a fixed period of time (3 minutes), and measuring the water pressure at which each evaluation sample burst. The test results were evaluated on a three-point scale. The evaluation results of the "Water Pressure Resistance Test" were evaluated as follows: ◎: No burst or water leakage even at three times the normal pressure or more; ○: Burst or water leakage at twice the normal pressure; ×: Burst or water leakage at (single) the normal pressure. The "Bending Test" involved a continuous bending test with metal fittings performed on Examples 1 and 2 and Comparative Examples 1 and 2 to determine whether or not a tear occurred in either the inner layer or the outer layer. The test results were evaluated on a three-point scale. The evaluation results of this "bending test" were evaluated as follows: ○: no breakage, △: signs of breakage, ×: breakage. Here, the continuous bending test with metal fittings is a test to compare the bending performance and pressure resistance performance of each evaluation sample. Specifically, a metal fitting (pressure-resistant nipple) was inserted into and closed off one end opening of each evaluation sample, and the other end opening of each evaluation sample was closed and a load (2 kg) was attached to support it in a substantially vertical position. Air at a predetermined pressure was intermittently supplied to the inside of each evaluation sample to create an air hammer state, and the metal fitting (pressure-resistant nipple) side was bent approximately 90 degrees left and right from the vertical position at regular intervals, repeatedly swinging (20,000 times), and the changes in the state of each evaluation sample were observed. Here, the test results were evaluated on a three-point scale using Examples 1 and 2 and Comparative Examples 1 and 2. The "liquid accumulation test" was carried out by blocking the pipe fittings of each evaluation sample using Examples 1 and 2 and Comparative Examples 1 and 2, pouring colored ink into the other end opening of each evaluation sample, blocking the other end opening, and intermittently supplying air at normal pressure for 24 hours. After that, the ink was removed and the sample was dried. After that, the sample was cut and disassembled, and changes in the state of ink penetration into the pinched portions of the pipe fitting were observed. The test results were evaluated on a three-point scale: ○: no ink penetration, △: signs of ink penetration, and ×: ink penetration occurred.The "overall evaluation" was a comprehensive evaluation based on the results of the aforementioned "water pressure resistance test," "bending test," and "liquid accumulation test," and was rated on a three-point scale. The results of this "overall evaluation" were rated as follows: ◎: best, ○: good, ×: unsuitable.

[0026]

[0027] In this way, by adopting a shape such as that of the pipe fitting 100 according to the embodiment of the present invention, it is possible to suppress the elongation of the pipe H within the pipe 2, and reduce the amount of hose discharge from the tip of the pipe 2. Therefore, stress concentration does not occur, and even if the amount of crimping is increased, breakage of the pipe H can be effectively prevented. Furthermore, since the amount of crimping can be increased, it is also possible to prevent liquid from entering the inside of the pipe H at the nipple tip N1 and forming a pool.

[0028] The above detailed description of the pipe with wear detection function according to an embodiment of the present invention has been provided with reference to the drawings, and its structure has been explained. However, the specific configuration is not limited to these embodiments, and the present invention includes design changes within the scope of the present invention. For example, to prevent the pipe from breaking, it is important that a portion of the inner circumferential surface of the pipe 2 on the front side in the pipe insertion direction has a minimum diameter at a position further back than the position facing the nipple tip 12. In other words, even if a step is formed instead of the second tapered portion, the pipe fitting can be expected to perform its intended function. However, a tapered portion is advantageous in that it allows the hose to move smoothly.

[0029] REFERENCE SIGNS LIST 1 nipple 11 unevenness 12 nipple tip 13 connection portion 2 pipe 21 predetermined range 22 first tapered portion 23 second tapered portion 100 pipe joint H pipe S crimping machine S1 jaws (die)

Claims

1. A pipe fitting in which a tube is inserted along the outer peripheral surface of a nipple and then pressed from the outside with a pipe to bring the inner peripheral surface of the tube into close contact with the outer peripheral surface of the nipple, wherein the nipple has an uneven outer peripheral surface and a line connecting its maximum height parts has approximately the same diameter from the tip of the nipple on the front side in the tube insertion direction to the rear side in the tube insertion direction, and the pipe has a minimum diameter at a part on the front side in the tube insertion direction further rearward than a position facing the tip of the nipple, and the pipe has a constant diameter over a predetermined range from the rearward position where the minimum diameter is reached to the rear side in the tube insertion direction, and has a first tapered section which gradually increases in diameter further rearward beyond the predetermined range.

2. A pipe fitting as claimed in claim 1, characterized in that the pipe has a second tapered section which gradually expands in diameter from the rear position, at which the diameter is smallest, towards the front.

3. A pipe fitting as described in claim 2, characterized in that when the outer periphery of the pipe is pressed from the outside toward the center, the position of the tip where the pipe has the smallest diameter coincides with the position of the nipple tip.

4. A pipe joint as claimed in claim 1 or 2, characterized in that said pipe has unevenness formed on said first tapered portion.

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