JP6803514B2 - Metal bellows tube - Google Patents

Description

The present invention relates to metal bellows tubes, such as metal bellows tubes used for water supply in sprinkler systems.

A metal bellows pipe through which a fluid flows inside is used, for example, at a bent portion of a pipe line. This type of metal bellows tube is made by, for example, plastic working a straight metal tube. Therefore, in general, the wall thickness of the tube wall of the metal bellows tube is uniform. Then, in order to impart flexibility to the pipe, pleated large-diameter portions and small-diameter portions are alternately formed in the axial direction of the pipe as at least a part of the pipe wall. As such a metal bellows tube, for example, there is one described in Patent Document 1 below. In this metal bellows tube, the inclined portion from the small diameter portion to the large diameter portion along the flow direction of the fluid formed as a part of the tube wall and flowing inside is set as the first inclined portion, and the fluid flow direction is also the same. When the inclined portion from the large diameter portion to the small diameter portion is defined as the second inclined portion, the first inclined angle with respect to the pipe axis of the first inclined portion is larger than the second inclined angle with respect to the pipe axis of the second inclined portion. Is also small. With this configuration, the metal bellows tube can reduce noise and vibration during internal fluid flow.

Japanese Unexamined Patent Publication No. 2009-150458

By the way, when this kind of metal bellows pipe is used as a water supply pipe of a sprinkler system, for example, it is necessary to reduce the resistance of the fluid flowing inside the metal bellows pipe, specifically, the resistance of water, specifically, the friction loss. If this is possible, it will be possible to reduce the capacity of the pump that discharges water. Since the pump is usually electric, if the capacity of the pump can be reduced, the cost such as electricity cost can be reduced. However, in the metal bellows tube described in Patent Document 1 described above, there is room for further reduction in friction loss.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a metal bellows tube capable of further reducing friction loss.

In order to achieve the above object, in the invention according to claim 1, the large diameter portion and the small diameter portion forming folds are alternately formed in the axial direction as at least a part of the pipe wall, and the wall thickness of the pipe wall is uniform. In a metal bellows tube, which is formed as a part of the tube wall and is inclined from the small diameter portion to the large diameter portion along the flow direction of the fluid flowing inside, the inclination angle with respect to the axial direction is A first inclined portion, which is a preset first inclined angle, and a first inclined portion, which is formed as a part of the pipe wall and is inclined from the large diameter portion toward the small diameter portion along the flow direction of the fluid, said. It is characterized by including a second inclined portion which is a second inclined angle whose inclination angle with respect to the axial direction is smaller than the first inclined angle.

According to this configuration, the second inclination is inclined from the large diameter portion to the small diameter portion than the first inclination angle of the first inclined portion that is inclined from the small diameter portion to the large diameter portion along the flow direction of the fluid. Since the second inclination angle of the portion is smaller, the flow resistance when the fluid is sent from the large diameter portion to the small diameter portion in the pipe becomes small. Therefore, the entire flow resistance when passing through the fold portion including the small diameter portion and the large diameter portion is reduced, and the pressure loss of the fluid flowing in the pipe, that is, the friction loss is reduced.

The invention according to claim 2 is characterized in that, in the metal bellows tube according to claim 1, the second inclined portion is provided only in the vicinity of the small diameter portion.

According to this configuration, it is possible to suppress an increase in the pitch of the folds composed of the large diameter portion and the small diameter portion.

The invention according to claim 3 is characterized in that, in the metal bellows tube according to claim 1 or 2, the fluid is the water supply of the sprinkler system.

According to this configuration, it is possible to reduce the capacity of the water discharge pump (water supply pump) in the sprinkler system.

As described above, according to the present invention, the flow resistance when the fluid is sent from the large diameter portion to the small diameter portion in the pipe becomes small, and thereby the entire flow resistance when passing through the fold portion composed of the small diameter portion and the large diameter portion. Is reduced, so that the friction loss of the fluid flowing in the pipe can be reduced.

It is a partial cross-sectional front view which shows one Embodiment of the metal bellows tube of this invention. It is a detailed view of the part A of the metal bellows tube of FIG. It is a detailed view of the large diameter part and the small diameter part of the metal bellows tube of FIG. It is a detailed view of the large diameter part and the small diameter part of the conventional metal bellows tube. It is explanatory drawing of the straight line piping in a fluid flow test. It is explanatory drawing of the U-shaped pipe in a fluid flow test.

Hereinafter, embodiments of the metal bellows tube of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional front view showing the overall configuration of the metal bellows tube of this embodiment, and FIG. 2 is a detailed view of part A of FIG. The metal bellows pipe 10 of this embodiment is used as a part of the water supply pipe portion of the sprinkler system. Therefore, the fluid circulated inside is the water supply for the sprinkler system. The metal bellows tube 10 can be used not only in this application but also in all fields, and the fluid circulated inside is not limited to this.

The metal bellows tube 10 of this embodiment is made by, for example, plastic working a straight metal tube, so that the wall thickness of the tube wall 12 is uniform and the entire tube wall 12 is pleated. The large-diameter portion 14 having a large diameter and the small-diameter portion 16 having a small diameter are alternately formed in the L direction of the axis of the pipe. Both the large diameter portion 14 and the small diameter portion 16 of this embodiment are formed of an arc curved surface having a preset curvature in order to avoid stress concentration and the like. By the way, the curvature of the small diameter portion 16 of this embodiment is set to be slightly larger than the curvature of the large diameter portion 14. In the metal bellows tube 10 of this embodiment, the fluid flow direction is set in the direction indicated by the arrow in the figure, that is, in the direction from the right to the left in the figure. Further, in the metal bellows tube 10 of this embodiment, folds composed of a large diameter portion 14 and a small diameter portion 16 are formed over the entire length in the L direction of the tube axis, but in the metal bellows tube of the present invention, at least the tube wall is formed. It suffices that a fold composed of a large diameter portion 14 and a small diameter portion 16 is formed as a part of 12.

FIG. 3 shows further details of the large diameter portion 14 and the small diameter portion 16 of the metal bellows tube 10. In the figure, hatching of the cross section is omitted in order to avoid complication. In the metal bellows tube 10 of this embodiment, the large-diameter portion 14 and the small-diameter portion 16 forming folds are connected to each other by inclined portions (tapered portions) 18 and 20 formed of conical surfaces. Here, the inclined portion from the small diameter portion 16 to the large diameter portion 14 is the first inclined portion 18, and the inclined portion from the large diameter portion 14 to the small diameter portion 16 is the second inclined portion 20 along the internal flow direction of the fluid. In this embodiment, from the first inclination angle θ1 formed by the first inclined portion 18 as the pipe axis L (the pipe axis in FIG. 3 is a virtual pipe axis parallel to the actual pipe axis). However, the second inclination angle θ2 formed by the second inclined portion 20 with the pipe axis L is smaller. By the way, in this embodiment, the first inclined portion 18 is directly connected to the large diameter portion 14 along the internal flow direction of the fluid, but the second inclined portion 20 is a connecting curved surface portion having a small curvature. It is connected to the large diameter portion 14 via 22.

FIG. 4 shows details of the large diameter portion 14 and the small diameter portion 16 of the conventional metal bellows tube 10. The conventional metal bellows tube 10 also uses the same reference numerals as the metal bellows tube 10 of the embodiment of the present invention. As is clear from the figure, for example, when the direction from right to left in FIG. 4 is set to the internal flow direction of the fluid, the first direction from the small diameter portion 16 to the large diameter portion 14 is set along the internal flow direction of the fluid. A first inclination angle θ1 formed by the inclined portion 18 as a pipe axis L (the pipe axis in the figure is a virtual pipe axis parallel to the actual pipe axis) and a second inclined portion from the large diameter portion 14 to the small diameter portion 16. The second inclination angle θ2 formed by 20 with the pipe axis L is the same. That is, in this conventional metal bellows tube 10, the internal flow direction of the fluid is not substantially defined.

This conventional metal bellows tube 10 is a conventional example, the metal bellows tube 10 of FIGS. 1 to 3 is an example, and an example of flowing a fluid through the metal bellows tube 10 of FIGS. 1 to 3 from the opposite direction. As a comparative example, a fluid flow test was performed on each test piece. Therefore, in the examples and the comparative examples, the first inclined portion 18 and the second inclined portion 20 defined as described above are reversed. The inner diameter of the test piece (inner diameter of the small diameter portion 16) is 21 mm, the outer diameter (outer diameter of the large diameter portion 14) is 25 mm, and the length is 1400 mm. In the test, each test piece was formed in the straight pipe shown in FIG. 5 and the U-shaped pipe shown in FIG. 6, and the fluid was circulated in the flow direction shown in the figure to carry out the test. There are virtually no restrictions on distribution directions). The fluid flow direction entry side (hereinafter, also referred to as the primary side) of each test piece is connected to the water discharge pump (water supply pump) via a run-up pipe (not shown), and the fluid flow direction exit side (hereinafter, also referred to as the secondary side). ) Was connected to the flow meter by attaching a guide pipe (not shown).

The approach pipe and the guide pipe are straight pipes, respectively, and are provided with pressure measuring holes for measuring pressure. A pressure gauge was attached to each of the pressure measuring holes of the approach pipe and the guide pipe. Further, a primary side valve is provided on the approach pipe and a secondary side valve is provided on the guide pipe. After the water supply pump is started, the flow rate on the secondary side is approximately 80 liters per minute or 50 liters per minute and is on the secondary side. Adjust the primary and secondary valves so that the pressure is 0.1 to 0.2 MPa. In that state, adjust the secondary valve so that the flow rate on the secondary side stabilizes at 80 liters per minute or 50 liters per minute. Then, water is sent in two ways, the secondary side flow rate is 80 liters per minute and 50 liters per minute, the pressures on the primary side and the secondary side are measured, and the differential pressure, that is, the pressure loss is calculated from the difference between the two. The magnitude of the pressure loss corresponds to the friction loss of each test piece, that is, the metal bellows tube 10. In the above-mentioned secondary side pressure adjustment and secondary side flow rate adjustment, the pressure on the primary side varies. The test results are shown in Table 1 below.

As is clear from Table 1, the metal bellows tube 10 of the example has a small differential pressure, that is, friction loss in all the tests. Since it is necessary to secure the flow rate of the sprinkler head at the end of the water pump of the sprinkler system, if the friction loss in the middle of the piping can be reduced, the capacity of the water pump can be reduced. Therefore, by using the metal bellows pipe 10 of this embodiment for the piping, it is possible to reduce the capacity of the water supply pump. If the capacity of the water pump of the sprinkler system can be reduced, it is possible to reduce the cost such as electricity bill.

For example, when water is sent to a metal bellows pipe having a small diameter portion 16 having an inner diameter of 21 mm at a secondary flow rate of 50 liters per minute or 80 liters per minute, the flow velocity in the pipe is correspondingly large. When water (fluid) flows through the metal bellows tube 10 at such a high speed, the flow of the fluid flowing inside the small diameter portion 16 becomes the mainstream due to the viscosity and inertia of the fluid. At this time, for example, paying attention to the first inclination angle θ1 of the first inclined portion 18 from the small diameter portion 16 to the large diameter portion 14 along the flow direction of the fluid, the larger the first inclination angle θ1, the more from the mainstream. The peeling becomes large. If the peeling is large, the fluid stagnates in the peeling area with a vortex. Therefore, in the metal bellows tube of the embodiment in which the first inclination angle θ1 is large, the main flow of the fluid is stable inside the first inclined portion 18 and the large diameter portion 14 from the small diameter portion 16 to the large diameter portion 14. If the mainstream of the fluid is stabilized in this way, it is easy to send the fluid from the large diameter portion 14 to the small diameter portion 16, and it is considered that the friction loss of the entire fold portion is reduced.

As a result, it has been confirmed that the flow velocity of the internal fluid is large in the metal bellows tube of the example. On the other hand, in the metal bellows tube of the embodiment, focusing on the second inclination angle θ2 of the second inclined portion 20 from the large diameter portion 14 to the small diameter portion 16 along the flow direction, the second inclination angle θ2 is large. As a result, peeling and vortex flow occur in the small diameter portion 16, and as a result, it becomes difficult to send the fluid from the large diameter portion 14 to the small diameter portion 16. Therefore, it is considered that the friction loss is large in the metal bellows tubes of the conventional example and the comparative example in which the second inclination angle θ2 is large. Further, the first inclination angle θ1 of the first inclined portion 18 from the small diameter portion 16 to the large diameter portion 14 along the flow direction (note that the first and second are reversed in the comparative example) is small. In the metal bellows tube of the comparative example, the fluid expands in diameter along the first inclined portion 18, and the expanded fluid collides with the second inclined portion 20 from the large diameter portion 14 to the small diameter portion 16. It is considered that the friction loss will be further increased.

As described above, in the metal bellows tube 10 of this embodiment, the diameter portion larger than the first inclination angle θ1 of the first inclined portion 18 from the small diameter portion 16 to the large diameter portion 14 along the fluid flow direction. Since the second inclination angle θ2 of the second inclined portion 20 from 14 to the small diameter portion 16 is smaller, the flow resistance when the fluid is sent from the large diameter portion 14 to the small diameter portion 16 in the pipe becomes small, whereby the small diameter portion 16 is formed. The entire flow resistance when passing through the fold portion including the portion 16 and the large diameter portion 14 is reduced, and the pressure loss of the fluid flowing in the pipe, that is, the friction loss is reduced.

Further, by providing the second inclined portion 20 only in the vicinity of the small diameter portion 16, it is possible to suppress an increase in the pitch of the folds composed of the large diameter portion 14 and the small diameter portion 16.

Further, by using it for water supply of the sprinkler system, it is possible to reduce the capacity of the water supply pump in the sprinkler system.

It goes without saying that the present invention includes various embodiments not described above. Therefore, the technical scope of the present invention is defined only by the matters specifying the invention described in the claims that are valid from the above description.

10 Metal bellows tube 12 Tube wall 14 Large diameter part 16 Small diameter part 18 1st inclined part 20 2nd inclined part L Axis line θ1 1st inclined angle θ2 2nd inclined angle

Claims (2)

In a metal bellows tube used for water supply of a sprinkler system, in which large diameter parts and small diameter parts forming folds are alternately formed in the axial direction as at least a part of the pipe wall, and the wall thickness of the pipe wall is uniform.
The large-diameter portion and the small-diameter portion are composed of an arc curved surface having a preset curvature.
It is composed of a conical surface formed as a part of the pipe wall and inclined from the small diameter portion to the large diameter portion along the flow direction of the fluid flowing inside, and the inclination angle with respect to the axial direction is preset. The first inclined portion, which is the first inclined angle,
It is composed of a conical surface formed as a part of the pipe wall and inclined from the large diameter portion to the small diameter portion along the flow direction of the fluid, and the inclination angle with respect to the axial direction is the first inclination angle. With a second tilted portion, which is a smaller second tilt angle ,
A metal bellows tube characterized in that the first inclined portion and the second inclined portion are connected to both sides of the small diameter portion in the fluid flow direction . The first aspect of the present invention is characterized in that the second inclined portion is provided only in the vicinity of the small diameter portion, and the second inclined portion and the large diameter portion are connected via a connecting curved surface portion having a small curvature. The metal bellows tube described.

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