JPS6249130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flexible pipe obtained by continuously bending a relatively long straight steel pipe or stainless steel pipe using a pipe bender (hereinafter referred to as a bender).

It has been conventional practice to manufacture so-called serpentine pipes by continuously bending metal straight pipes using a bender. , are planar and curved alternately by about 180 degrees, the tangent of the tip of each curved part on at least one side of the flexible pipe is about 90 degrees with respect to the straight pipe part, and the curved part is curved so that r = inner radius of bending, When d = outer diameter of the pipe, and L = the axial distance between adjacent straight pipe parts of the pipe, it is a pipe that is curved so that 2r≒L-d, and the pitch of the curved part is particularly small. It belongs to a very special type of so-called snake pipes.

Below, the shape of the flexible pipe to which the present invention is applied will be explained in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing the shape of an example of a flexible pipe to which the present invention is applied, in which A is a plan view of a portion of the flexible pipe, and B is a plan view A to
It is a side view seen from A', and FIG. 2 is an enlarged plan view of the curved part of the flexible pipe.

As shown in FIG. 1A, the flexible pipe to which the present invention is applied is a flexible pipe in which one curved portion 2 to 12 and the other curved portion 1 to 13 are each bent at approximately 180 degrees, and at least one The tangent line 14 of the tip of the curved portions 2 to 12 is approximately 90 degrees to the straight pipe portion 15, and as shown in FIG. 13 are planar flexible pipes that are bent alternately by approximately 180 degrees so that they overlap the straight pipe portions 15.

Furthermore, the present invention is directed to a flexible pipe in which the shortest distance between the outer peripheries of adjacent straight pipe portions of the flexible pipe and the outer diameter of the pipe have a relationship as described below. That is, in FIG. 2, which is an enlarged plan view of the curved portion of the flexible pipe, the radius r of the bending inner side of the curved portion, the outer diameter d of the pipe, and the straight pipe portions 1 adjacent to each other of the flexible pipe are shown.
If the distance between the axes 16 of 5 is L, then 2r≒L−
It is a convoluted pipe in which the relationship d holds true. In other words, if the shortest distance between the outer peripheries of mutually adjacent straight pipe portions 15 of the flexible pipe is K, then the flexible pipe is such that K≈d. Note that the shape of the flexible tube to which the present invention is applied is not limited to that shown in FIG. 1, but also includes flexible tubes having shapes such as A, A, U, and E shown in FIG. 3, for example.

When manufacturing the flexible pipe as described above using a bender, since the inside radius of the curved part of the flexible pipe is extremely small as described above, continuous bending is impossible with a conventional bender. It was necessary to manufacture partial components of the flexible pipe using a bender, and then weld these components individually to create the completed flexible pipe.

The reason for this will be explained below. Fig. 4 is an explanatory diagram showing the main parts of a conventional bender and the state when the pipe to be bent is attached to the bender, and A in the figure is a plan view; A and C are side views seen from A to A' and B to B', respectively, of the plan view A.
When bending a pipe with a conventional bender, one side of the pipe 17 to be bent is sandwiched between a bending die (hereinafter referred to as the die) 18 and a clamp 19 that are fixed concentrically to the rotation axis 29 of the rotating arm 20. , the clamp 19 is pressed against the mold 18 with a pressure sufficient to withstand the repulsive force of the tube generated during the operation of bending the tube. The clamp 19 is fixed to the pressing fitting 21 of the rotary arm 20 with a bolt 22 and a metal plate 23, and the clamp 19 is also fixed to the press fitting 21 of the rotating arm 20.
The pressure to press against is transmitted by the rod 24 via the pressing fitting 21. Note that the pressing fitting 21 can be moved left and right on the rotating arm 20. Pipe 1 that is about to be bent again
7 is supported by a support mechanism 25 so as to withstand the repulsive force of the tube that occurs during the operation of bending the tube.
The support mechanism 25 has a groove 2 in a support fitting 28 that can move left and right on the fixed arm 26.
7 so that when the tube 17 is bent, the support mechanism 25 moves forward along the groove 27. Furthermore, the supporting force to the support mechanism 25 is applied to the rod 2 through the support fitting 28.
4'. After attaching the tube 17 to be bent in this way to each element of the bender, the arrow 30
By rotating the rotating arm 20 in the direction, the clamp 19 and the mold 18 are similarly rotated about the axis 29, and as a result, the tube 17 is bent approximately 180 degrees.

In this way, when a pipe is bent approximately 180 degrees with a conventional bender, the outer diameter d of the pipe is equal to the shortest distance K between the outer circumferences of adjacent straight pipe parts of the flexible pipe.
It is possible to manufacture pipes with a 180 degree bend. In such a case, it goes without saying that the dimensions of the mold 18, clamp 19, and support mechanism 25 must be appropriate for this purpose.

However, when a conventional bender is used to create a planar shape such as the one illustrated in Figs. 180 degrees alternately, and K≒d
It is impossible to manufacture such a flexible pipe. For example, when manufacturing a flat flexible pipe with alternating 180 degree bends using a conventional bender,
Once the tube has been bent at 180 degrees, it must be pulled out of the mold and bent at 180 degrees in the opposite direction again.If we explain this process using a diagram, the pipe will be bent at 180 degrees as shown in Figure 5A. Clamp 1 on tube 31
9, pull it out forward as shown in Figure 5A, and then turn it 180 degrees around the axis of the tube 17 to be bent. However, when inverting this tube, in the conventional bender, the bent tube 31 must be pulled forward to the extent that one tip 32 of the tube does not come into contact with the clamp 19 and the pressing fitting 21 that have been returned to their original positions. Next, from the state shown in FIG. 5A, the rotary arm 20 is rotated again to curve the pipe, resulting in a flexible pipe as shown in FIG. 5C. Furthermore, in the same way, the curved tube 31' shown in Fig. 5C must be pulled forward and turned 180 degrees again.
At this time as well, as shown in FIG. 5D, the curved tube must be pulled forward to the extent that the tip 33 of the curved portion does not come into contact with the clamp 19 and the pressing fitting 21 which have been returned to their original positions. In this way, when a straight pipe is bent 180 degrees with a conventional bender,
It is not impossible to manufacture a flexible pipe that is planar and alternately curved at 180 degrees with K≒d, but the shape of the flexible pipe inevitably becomes a flexible pipe that widens at the end as shown in Figure 6.

Therefore, using conventional vendors,
The flexible pipe shown in the figure cannot be manufactured by continuous bending, and in the past, it was necessary to manufacture partial structural parts of the flexible pipe at a bender and then weld these parts individually to make the finished product. I didn't get it. That is, to explain this with reference to FIG. 7, which shows an example of the shape of the flexible pipe manufactured by a conventional bender, each of the partial components 34 to 36 of the flexible pipe shown in the same figure is individually manufactured by a bender, and these parts are individually assembled. The welding is performed at the welding section 37 to form a completed flexible pipe.

By the way, the above-mentioned corrugated tubes to which the present invention is applied are generally used in heat exchange equipment, but for example, many rows of the corrugated tubes are inserted into sludge slurry in a tank, and cold brine and hot brine are stored in the corrugated tubes. When used in a freeze-thaw tank in which the sludge slurry in the tank is frozen and re-thawed by passing liquid alternately through the tank, a conventional flexible pipe, that is, a flexible pipe having a large number of welded parts 37 as shown in Fig. 7, is used. It is not preferable to use In other words, by alternately passing cold brine and warm brine into the corrugated tube, the tube repeatedly contracts and expands, and the welded portion 37 is particularly susceptible to this, and in some cases, the welded portion 37 of the corrugated tube may Defects may also occur.

Therefore, when a flexible pipe is used under the harsh conditions mentioned above, the current situation is that a flexible pipe is required to have as few welded parts as possible, or in other words, a flexible pipe manufactured by continuous bending as much as possible. be.

The present invention satisfies these demands, and is a flexible pipe in which the steel or stainless steel pipes are planar and alternately curved by about 180 degrees, and the tangent line of the tip of each curved portion on at least one side of the flexible pipe is a straight pipe of the flexible pipe. Furthermore, when the curved part is r = the bending inner radius, d = the outside diameter of the pipe, and L = the axial distance between adjacent straight pipe parts of the serpentine pipe, 2r≒ When manufacturing a flexible pipe curved to form L-d, (1)
The thickness of the shortest part of the clamp in contact with the pipe and the thickness of the shortest part of the support mechanism in contact with the pipe are each less than 2r, (2) the clamp is removable, and (3) the clamp is The points of force for pressing with the pressing fitting and the points of force for supporting the supporting mechanism with the supporting fitting are set at the lower part of the clamp and the lower part of the supporting mechanism so as not to obstruct the already curved pipe, (1), ( In addition to using a bender that meets the requirements of 2) and (3), a pressurizing mechanism consisting of a cylinder and a piston is used to bend S = the thick section of the straight pipe. Area (cm ² ), P = Gauge pressure in cylinder (Kg/
cm ² ), a = piston area of the pressurizing mechanism (cm ² ), then push the pipe to be bent in the direction of curvature so that P x a/S = 700 to 1300 (Kg/cm ² ), Further, as the tube bends, the extrusion pressure is sequentially reduced to bend the tube at approximately 180 degrees.Then, the curved tube is extruded from the mold,
This method includes a second step of inverting the tube by about 180 degrees around the axis of the tube to be bent, and this method involves repeating these steps in sequence to manufacture the above-mentioned flexible tube.

The present invention will be explained in detail below using the drawings.

FIG. 8 shows a bender, which is an embodiment of the present invention having the requirements (1) to (3), used to convert a straight pipe into a flexible pipe as described above, which is an object of the present invention. FIGS. 9 and 10 are plan views showing the process of manufacturing a flexible pipe as exemplified in FIGS.
They are a side view of A' and a side view of B to B'. Also the first
Figure 1 shows the process of manufacturing a flexible pipe using the bender. When manufacturing a flexible pipe using this bender, one side of the pipe 17 to be bent is sandwiched between a mold 18 and a clamp 19 in the same way as with a conventional bender, and the pipe is made to withstand the repulsive force generated during the bending operation. The clamp 19 is pressed against the mold 18 by the pressure from the rod 24 via the pressing fitting 21, and the other side of the tube 17 is pressed against the roller 38 by the pressure from the rod 24' via the supporting fitting 28. and a slide plate 39. However, the structure of the main parts of this bender is different from that of conventional bender, and as shown in Figures 8 to 10, the clamp 1
Thickness E of the shortest part of the part where the tube is pressed in 9, and 3
The thickness F of the shortest part of the tube-supporting part of the support mechanism composed of rollers 38 and slide plate 39 is
The value should be twice the radius r of the inside of the bend when the pipe is bent at 180 degrees, in other words, it should be smaller than the shortest distance K between adjacent straight pipe parts of the flexible pipe, and the clamp 19 should be removable. , and the force point G at which the clamp 19 is pressed with the metal fitting 21
The points of effort H for supporting the support mechanism with the support fittings 28 are set at the clamp 19 and the lower part of the support mechanism, respectively, at positions that do not interfere with the already curved pipe 31. When manufacturing a flexible pipe from a straight pipe using the bender, the first step is to bend the pipe by about 180 degrees according to the steps shown in FIG.
Approximately 180 degrees centering on the axis of the tube 17 to be bent
The second step consists of reversing the degree, and by repeating these steps sequentially, the results of Figures 1 to 3 are
A flexible pipe as illustrated in the figure can be easily manufactured by continuous bending. That is, in the bender, for example, the process from C to E in FIG. 11, that is, the tube 31 bent at 180 degrees in C in FIG. When the tube 17 to be bent is turned 180 degrees around its axis as shown in FIG.
Since it can be inserted freely between the adjacent straight pipe parts of the flexible pipe, the pipe 17 to be bent can be reversed 180 degrees at any position.

In addition, in the process from A to G in FIG. 11, the tube 31 bent at 180 degrees in F of FIG. 11 is similarly extruded from the mold 18 by loosening the clamp 19. When the pipe 17 to be bent is turned 180 degrees around its axis as shown above, the clamp 19 can be removed, so the clamp 19 can be bent to any desired position without hitting the curved part 40 of the pipe. The curved tube 31 can be pushed out, and the tube 17 can be easily turned over 180 degrees. Further, as shown in FIGS. 9 and 10, the force point G at which the clamp 19 is pressed by the metal fitting 21 and the force point H at which the support mechanism composed of the roller 38 and the slide plate 39 is supported by the support metal fitting 28 have already been curved. Since the pipe 17 is located below the bent pipe 31, the pipe 17 to be bent can be easily pressed with the clamp 19 and supported by the support mechanism without being obstructed by the already curved pipe 31.

Note that the bender used in the present invention shown in FIGS. 8 to 10 is an example of an embodiment, and the shape of the clamp may be, for example, a clamp 19' as shown in FIG. 12. In this case, the thickness of the shortest part of the clamp where the tube is pushed is E' as shown in FIG. Further, the support mechanism may be formed by a single roller 38' as shown in FIG. In this case, the thickness of the shortest part of the tube-supporting portion of the support mechanism is F' as shown in FIG.

As explained above, according to the present invention, a flexible pipe as illustrated in Figs. 1 to 3 can be easily and continuously bent. It becomes possible to manufacture a flexible pipe that does not get wet.

Next, when bending a pipe using a bender, the pipe is pulled in the bending direction by the mold and clamp, so the wall thickness of the pipe facing the outside of the bend becomes thinner; The wall thickness of the tube facing inward tends to be thicker, and the cross section of the curved portion tends to be elliptical. Note that the numerical value representing the rate at which the wall thickness of the tube becomes thinner is usually called the thinning rate, and the numerical value representing the ratio of the elliptical shape is called the ovalization rate.
This thinning rate and ovalization rate tend to increase as the inner radius of the curved part becomes smaller, and especially when the inner radius of the curved part is extremely small, such as in the case of the corrugated pipe that is the object of the present invention. In some cases, wrinkles may appear on the inside of the curved portion. In this way, if there is a difference in the cross-sectional wall thickness of the pipe outside and inside the curved part of the curved part, if the curved part becomes elliptical, or if there are wrinkles on the inside of the curved part, the strength of the curved part will be reduced. and unfavorable in terms of corrosion resistance. Therefore, a flexible pipe is required that has as small a rate of thinning of the curved portion as possible and a rate of ovalization as small as possible.

Conventionally, when bending a pipe using a bender, heat is applied, or the straight part of the pipe to be bent is pushed out in the direction of the bend, thereby reducing the rate of thinning and ovalization as described above. However, the concept of extrusion was very vague, and it was never made clear what kind of mechanism should be used, how much pressure should be used, and how it should be extruded.

The inventors of the present invention have conducted further studies on a method of manufacturing a flexible pipe, which is the subject of the present invention, by minimizing the thinning rate and ovalization rate of this curved portion, and have found that ) or (3)
When manufacturing a flexible pipe as illustrated in Figures 1 to 3 by sequentially repeating the two processes using a bender with the following requirements, when bending approximately 180 degrees with the bender , using a pressurizing mechanism consisting of a cylinder and a piston at the initial stage of bending the pipe, S = cross-sectional area of the thick part of the straight pipe (cm ² ), P = gauge pressure in the cylinder (Kg/cm ² ) ,
When a = the area of the piston of the pressure mechanism (cm ² ), the pipe to be bent is pushed out in the bending direction so that P x a/S = 700 to 1300 (Kg/cm ² ), and the pipe is further It has been found that by sequentially decreasing the extrusion pressure as the curved portion is bent, the thinning rate and ovalization rate of the curved portion can be made smaller than in the conventional case.

This will be explained below using drawings.

FIG. 14 is an explanatory diagram showing a state in which a pipe is bent while pushing the pipe to be bent in the bending direction using a pressurizing mechanism according to an example of an embodiment consisting of a cylinder and a piston.

In the figure, 41 is a cylinder, and the cylinder 41 is filled with oil 42, 42'. As described above, the pipe 17 to be bent is held down by the mold 18 and the clamp 19, and the pipe 17 is bent by rotating the rotary arm 20. At this time, the hydraulic pump (see Fig. When oil 42 is further injected by a pump (not shown), the piston 44 is pushed by the pressure, and pressure is applied to the piston shaft 45 connected to the piston 44 in the direction of the arrow 46. One side of a piston arm 47 is fixed to the piston shaft 45, and a fixing fitting 48 is attached to the other side of the piston arm 47.
is fixed. Therefore, when pressure is applied to the piston 44, pressure is also applied to the tube 17 to be bent via the piston shaft 45, piston arm 47, etc. in the direction of the arrow 46', that is, in the bending direction. Note that 49 is a guide that supports the piston shaft 45, and 50 is the pipe 17 that is to be bent.
It is a guide that supports you. Also, 51 is cylinder 4
This is an outflow pipe for excess oil 42' to be discharged from 1.

Here, if the gauge pressure inside the cylinder is P (Kg/cm ² ) and the area of the piston 44 is a (cm ² ), then the pressure in the 46' direction applied to the pipe 17 to be actually bent is P×a (Kg). By the way, when bending a pipe with a bender, the pressure applied to the pipe 17 in order to reduce the rate of thinning and ovalization is largely influenced by the cross-sectional area S of the thick part of the pipe. The larger the cross-sectional area S, the greater the pressure needs to be applied.

When bending a straight steel or stainless steel pipe approximately 180 degrees using a bender, the cross-sectional area S (cm ² ), gauge pressure P in the cylinder
(Kg/cm ² ) and piston area a (cm ² ) of the pressurizing mechanism are closely related to each other, and as a result of thorough examination of this relationship, we found that P x a /S=700 to 1300 (Kg/ ^cm2 )
The direction of bending the pipe is 46'.
We have found that it is optimal to extrude the
Also, as the pipe bends, the extrusion pressure,
In other words, it has also been found that it is an important requirement to sequentially reduce the gauge pressure P within the cylinder.

For example, if the cross-sectional area of the thick wall part of the steel or stainless steel pipe to be bent is 2.2 cm ² and the piston area of the pressure mechanism is 30 cm ² , then the pressure P in the cylinder is set to 51.3 at the beginning of bending the pipe with the bender. Kg/ ^cm2
95.3Kg/ ^cm2 , and as the pipe bends, the pressure P
It is sufficient to sequentially decrease the . Note that when the pressure P is gradually decreased as the pipe bends, the pipe becomes
It is preferable that the pressure P remains slightly applied to the tube even after the 180 degree bending process is completed.

In addition, the value of the pressure P x a / S applied to the pipe 17 to be bent at the beginning of bending the pipe with a bender has a certain range of 700 to 1300, taking into account the difference in the materials of steel pipes and stainless steel pipes. In general, in carbon steel, the smaller the carbon content, the closer to the lower limit value, and the larger the carbon content, the closer to the upper limit value. However, since ordinary steel pipes and stainless steel pipes fall well within this range, it is best to select the optimum value within this range. However, the value of P×a/S is
If the pressure is smaller than or greater than 700 to 1300, or the pressure is not reduced sequentially as the tube bends, e.g. at a constant pressure, the intended purpose cannot be achieved and the result is a reduction. As the thickness and ovalization rate increase,
The semicircular shape of the curved portion is not symmetrical between the left and right sides, resulting in an misshapen curved portion.

When the pipe is bent 180 degrees, the curved part is 2r≒L−
When cold bending a pipe to 180 degrees using a bender so that Approximately 15%
and about 20%, and the value of P×a/S is 950
If the tube is bent while being extruded under a constant pressure, the semicircular shape of the curved portion will not be symmetrical, resulting in a curved portion that is misshapen.

On the other hand, if the tube is extruded at P×a/S=950 at the initial stage of bending as in the present invention, and the pressure is gradually decreased as the tube is bent, the thickness reduction rate and Curved tubes with ovalization rates of about 6% and about 10% are obtained, respectively.

In addition, when a pipe is bent 180 degrees with a bender, the curved part is generally embedded in the mold, and in particular, as in the case of the flexible pipe which is the object of the present invention, the outside diameter of the pipe and the shortest distance between the adjacent straight pipe parts of the flexible pipe are If they are similar to each other, it will be embedded even more firmly. Therefore, it is relatively difficult to remove the curved tube embedded in the mold from the mold, and the conventional method is to strike the tip of the tube with a hammer or the like to remove it.

However, when manufacturing a flexible tube, which is the object of the present invention, a relatively long tube is used for continuous bending, so the tip of the tube to be bent is quite far from the mold, and therefore Hitting the pointed end with a hammer or the like is complicated to operate, and since one of the pointed ends is too far apart, the force is dispersed, making it ineffective. Also, it is not preferable to hit a curved part that has already curved 180 degrees with a hammer, as it may damage the pipe or deform the curved part.

In such a case, the curved portion embedded in the mold can be easily removed by using the pressurizing mechanism consisting of the cylinder and piston described above. That is, in FIG. 14, the tube is bent by 180 degrees by rotating the mold 18 and the clamp 19, and then the clamp 19 is loosened and the cylinder 41 is bent.
Oil 42 is further flowed into the piston 44 using a hydraulic pump or the like to move the piston 44 in the direction of the arrow 46. As a result, the tube 17 moves to the left via the piston shaft 45 and the piston arm 47, so that the tube bent at 180 degrees can be easily inserted into the mold 18.
It can be easily removed and does not damage the tube.

As described above, the present invention provides a flexible pipe in which the steel pipe or the stainless steel pipe is planar and is bent alternately by about 180 degrees, and the tangent line of the tip of each curved part of at least one of the flexible pipes is the straight pipe part of the flexible pipe. about 90 against
2r≈L-d, where r = the radius of the inside bend, d = the outside diameter of the pipe, and L = the axial distance between adjacent straight pipe parts of the curved part. A curved serpentine pipe can be manufactured by continuous bending from a straight pipe using a bender, and in this case, a pressure mechanism consisting of a cylinder and a piston is used to bend the pipe under a predetermined pressure in the initial stage of bending the pipe. By extruding the pipe in the bending direction and gradually reducing the extrusion pressure as the pipe bends, the thinning rate and ovalization rate of the curved part of the helical pipe can be kept small even during cold bending. It becomes possible to do so.

Therefore, by using a long pipe of the required length according to the present invention, it is possible to provide the above-mentioned flexible pipe with no welding points at a relatively low cost, thereby eliminating the need for freezing and thawing treatment of the flexible pipe. The benefits to industry are enormous.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing the shape of an example of a flexible tube to which the present invention is applied, and FIG. 2 is an enlarged plan view of a curved portion of the flexible tube. Further, FIG. 3 is an explanatory diagram showing another shape of the flexible pipe to which the present invention is applied. Fourth
The figure is an explanatory view showing the main parts of a conventional bender and a state in which a pipe to be bent is attached to the bender. A is a plan view, and A and C are side views. Figure 5 is an explanatory diagram of the manufacturing process when manufacturing a flat flexible pipe with alternate 180 degree bends using a conventional bender, and Figure 6 shows the shape of a flexible pipe manufactured using a conventional bender. FIG. FIG. 7 is an explanatory diagram showing the shape of a flexible pipe manufactured by welding using a conventional bender. 8th
The figure is one embodiment of the present invention, and is a plan view showing the process of manufacturing a flexible pipe, which is an object of the present invention, using a bender used in the present invention, and FIGS. 9 and 10. are respective side views of FIG. FIG. 11 is an explanatory diagram showing the steps in manufacturing a flexible pipe, which is a subject of the present invention, using a bender used in the present invention. FIGS. 12 and 13 are explanatory diagrams showing a clamp and support mechanism that are other embodiments of the bender used in the present invention. FIG. 14 is an explanatory view showing a state in which a pipe is bent while pushing the pipe to be bent in the bending direction using a pressure mechanism consisting of a cylinder and a piston, which is an example of an embodiment of the present invention. 1 to 13...Curved section, 14...Tangential line, 15...
Straight pipe section, 16... Axis center, 17... Pipe to be bent, 18... Bending mold, 19... Clamp, 21
...Pushing metal fitting, 25...Support mechanism, 28...
Supporting metal fittings, 31... Curved pipe, 32... Tip of pipe, 34, 35, 36... Partial component of corrugated pipe, 37... Welded portion, 38... Roller, 39...
Slide plate, 41...Cylinder, 42...Oil, 44...Piston, 45...Piston shaft, 4
7... Piston arm, 49, 50... Guide,
r...Inner radius of bending, d...Outer diameter of pipe, L...
Distance between axes, K: Shortest distance between the outer peripheries of adjacent straight pipe parts of the flexible pipe, E: Thickness of the shortest part of the clamp where the pipe is pushed, F: Shortest length of the support mechanism that supports the pipe Part thickness, G, H...emphasis.

Claims (1)

[Claims] 1 Steel pipes or stainless steel pipes are planar and alternately
The tube is curved by 180 degrees, and the tangent of the tip of each curved portion on at least one side of the tube is approximately 90 degrees with respect to the straight portion of the tube, and the curved portion is such that r = inner radius of bending, d = outer diameter of the pipe, L = axial distance between adjacent straight pipe parts of the flexible pipe, 2r≒L
In manufacturing a flexible pipe curved so that -d, (1) the thickness of the shortest part of the clamp in contact with the pipe and the thickness of the shortest part of the support mechanism in contact with the pipe should be less than 2r. (2) the clamp is removable, and (3) the lower part of the clamp is designed so that the point of force for pressing the clamp with the metal fitting and the point of force for supporting the support mechanism with the support metal fitting do not obstruct the already curved pipe. and these (1), (2), below the support mechanism.
In addition to using a pipe bender that meets the requirements in (3), a pressure mechanism consisting of a cylinder and a piston is used to bend the pipe. cm ² ), P = gauge pressure in the cylinder (Kg/cm ² ), a = piston area of the pressure mechanism (cm ² ), P x a/S = 700 to 1300
(Kg/cm ² ), the first step is to push out the pipe in the bending direction, and as the pipe bends, the extruding pressure is gradually reduced to bend the pipe to about 180 degrees. A method for manufacturing the above-mentioned flexible pipe, which consists of a second step of extruding the curved part from a bending die and inverting it approximately 180 degrees around the axis of the pipe to be bent, and repeating these steps in sequence. 2. Regarding bending a pipe, a patent characterized in that a pressure mechanism consisting of a cylinder and a piston is used to release a pipe bent approximately 180 degrees embedded in a bending mold from the bending mold. A method for manufacturing a flexible pipe according to claim 1.