JP3615337B2 - Folding pipe propulsion machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a front cylinder having a cutter head, a middle cylinder connected so that the front cylinder can be tilted by a direction-correcting jack, and a rear cylinder connected so that the middle cylinder can be freely tilted via a bent portion. And a middle-folding type pipe propulsion machine constituted by a leading conductor that regulates the maximum folding angle at the middle-folded portion and a main pushing jack that propels a subsequent pipe connected to the rear trunk.
[0002]
[Prior art]
As a method for embedding a small-diameter pipe having a diameter of 800 mm or less in the ground, a method called a pipe propulsion method is generally known. In this pipe propulsion method, a succeeding pipe made of a fume pipe or the like is sequentially connected behind a leading conductor having a cutter head, and the following ground pipe is propelled by a main jack installed in a start shaft. This is a method of excavating with a leading conductor and burying each succeeding pipe by pushing it into the ground sequentially. A pipe propulsion device is an apparatus composed of a leading conductor and a main pushing jack in order to implement such a pipe propulsion method. Among these pipe propulsion machines, the pipe propulsion machine to be improved by the present invention is a half-folder that can perform so-called curved construction in which the subsequent pipe is embedded in the ground while operating the direction correcting jack. Type pipe propulsion machine.
[0003]
Therefore, the basic technical contents of the related art related to the present invention will be described with reference to FIGS. FIG. 3 is a horizontal sectional view schematically showing a portion of a leading conductor in a conventional middle-folded pipe propulsion device, and FIG. 4 is an enlarged view of a middle-folding portion of the leading conductor in a conventional middle-folding type pipe propulsion device. FIG.
[0004]
3 and 4, 1 is a front cylinder having a cutter head 4, 2 is a middle cylinder to which the rear end portion of the front cylinder 1 is connected, and 3 is a rear cylinder to which the rear end portion of the middle cylinder 2 is connected. 4 is a cutter head provided at the front of the front cylinder 1 for excavating natural ground, 5 is a direction correcting jack for connecting and tilting the front cylinder 1 with respect to the middle cylinder 2, and 6 is an intermediate cylinder 2 and a rear cylinder 3. Are formed between the adjacent ends of the front cylinder 1 and the middle cylinder 2, and are formed between the adjacent ends of the front cylinder 1 and the middle cylinder 2. The direction correcting portion is a portion for connecting the two, 8 is a fixing fitting to be described in detail later, 9 is an adapter pipe connected to the rear end portion of the rear barrel 3, and 10 is a bent seal. Although not clearly shown in FIG. 3, the cutter head 4 is capable of excavating a hole having a slightly larger diameter than each of the cylinders 1, 2, 3 and the subsequent pipe. A plurality of direction correcting jacks 5 are installed so as to connect the front cylinder 1 and the middle cylinder 2 with a predetermined interval in the circumferential direction, and the front cylinder 1 is placed in the middle by the stroke difference of the plurality of direction correcting jacks 5. It can be tilted with respect to the barrel 2. In this example, a pair of direction correction jacks 5 are provided symmetrically, and the front barrel 1 can be tilted in the horizontal direction.
[0005]
Next, a specific structure of the folded portion 6 directly related to the present invention will be described in detail. A flange 2a and a flange 3a are formed at the rear end portion of the middle cylinder 2 and the front end portion of the rear cylinder 3 by forming notches on the inner peripheral side and the outer peripheral side, respectively. The flange 2a of the middle barrel 2 and the flange 3a of the rear barrel 3 are fitted to each other so as to be tiltable so as to be fitted to each other, and the contact portions of both are sealed with the middle-fold seal 10. A pin-shaped fixture 8 is symmetrically projected on the inner peripheral portion of the flange 2a of the middle barrel 2 in the left and right directions, and is arranged in the axial direction of the rear barrel 3 on the outer peripheral portion of the flange 3a of the rear barrel 3. A long long groove 3 b is formed at a position corresponding to the fixing bracket 8. The end of the fixing metal fitting 8 is fitted into the long groove 3b of the rear cylinder 3, and when the middle cylinder 2 is tilted with respect to the rear cylinder 3, it slides along the longitudinal direction of the long groove 3b. Therefore, the middle barrel 2 can freely tilt within a range in which the fixing metal member 8 can slide in the long groove 3b, and the middle bending angle θ that is a tilt angle with respect to the rear barrel 3 can be arbitrarily changed. As described above, the middle bent portion 6 is roughly divided into a flange 2a of the middle barrel 2 on which the fixing bracket 8 is projected and a flange 3a of the rear barrel 3 on which the long groove 3b is formed. Thus, the maximum bending angle, which is the maximum value of the angle at which the middle cylinder can tilt with respect to the rear cylinder, is regulated. Since the middle-folded pipe propulsion machine is used at construction sites under various underground conditions and may be curved with large and small curvature radii R, the maximum half-turn angle is the radius of curvature R It is designed so that it can be adapted to curve construction with a minimum radius of curvature. That is, the maximum bend angle is set as large as possible so that the curve construction with the largest curve among the curve constructions with various possibilities of actual construction can be performed.
[0006]
As is apparent from the above description, the leading conductor of the folding pipe propulsion machine includes a front cylinder 1 having a cutter head 4 and a middle cylinder to which the front cylinder 1 is connected to be tilted by a direction correcting jack 5. 2 and a rear cylinder 3 connected so that the middle cylinder 2 can be freely tilted through the middle folding part, and the maximum middle folding which is the maximum angle at which the middle cylinder 2 can tilt with respect to the rear cylinder 3 The corners are regulated at the middle break. Although not shown, a buried pipe such as a fume pipe is connected to the rear end of the adapter pipe 9, and forms a subsequent pipe together with the adapter pipe 9. At the position corresponding to the last part of this succeeding pipe, a start shaft is built as a starting point for pipe burial, and a leading jack and a jack jack for propelling the succeeding pipe are installed in the start shaft. ing. The center-folded type pipe propulsion machine is roughly composed of the main pushing jack and the leading conductor. By operating the direction correcting jack 5, the front cylinder 1 is tilted with respect to the middle cylinder 2 and the succeeding pipe. You can bury it by pushing it into the ground while curving it.
[0007]
When carrying out the pipe propulsion method with a half-folded type pipe propulsion machine, the main jack in the start shaft is brought into contact with the rear end surface of the rearmost succeeding pipe, and then the main jack is extended to propel the succeeding pipe. . This propulsive force is transmitted to the leading conductor, and the leading conductor excavates the natural ground with the cutter head 4 while applying the propulsive force. In addition, a drainage pipe (not shown) is laid in the succeeding pipe, and the excavated soil is discharged to the ground through the drainage pipe. In this way, the pipe propulsion device embeds the ground behind the leading conductor with a leading jack while excavating the front ground with the leading conductor and sequentially pushes it into the ground and embeds it. In the case of curve construction, the front cylinder 1 is tilted with respect to the middle cylinder 2 by expanding and contracting the right and left direction correcting jacks 5. Then, as shown in FIG. 3, the front cylinder 1 is excavated and bent while tilting with respect to the middle cylinder 2, and then the front cylinder 1 while the middle cylinder 2 is tilted with respect to the rear cylinder 3. The rear body 3 also bends so as to follow the middle body 2. In this case, as shown in FIG. 4, the propulsive force transmitted to the rear cylinder 3 is transmitted to the rear end surface of the middle cylinder 2 through one side 3 c of the front end surface of the rear cylinder 3 and applied to the front cylinder 1. In the middle folding type pipe propulsion machine, since the curved path is formed in advance by the front cylinder 1, the middle cylinder 2 and the rear cylinder 3, the underground pipe is bent so as to bend while guiding the subsequent pipe along this curved path. Can be pushed into.
[0008]
[Problems to be solved by the invention]
By the way, in the conventional middle folding type pipe propulsion machine, as described above, the middle cylinder 2 can be freely tilted by the middle folding part 6 with respect to the rear trunk 3, and the middle folding angle θ is autonomous. The intermediate bending angle θ fluctuates depending on external conditions such as the strength of the passing ground of the leading conductor. Moreover, the maximum in the bending angle, as can be adapted to practice are possible construction curve construction of the largest curve of the curve construction in various curves, since it is designed to maximize, The change in the bending angle θ is also significant. Therefore, in areas where the ground is soft and the reaction force is difficult to take, when performing straight construction or curving construction with a gentle curve with a large radius of curvature, the middle bending angle θ becomes larger than necessary and the leading conductor becomes There was a problem that the propulsion direction could not be determined due to deviation from the planned construction trajectory, or the tip conductor's posture fluctuated. Conventionally, when such a problem is about to occur, the operator senses this quickly and copes with the operator's maneuvering technique, for example, by reducing the direction correction angle. However, this method that relies on the operator's maneuvering technique not only requires a high level of skill supported by the operator's intuition and experience, but also cannot reliably prevent such problems.
[0009]
The present invention is intended to solve such a problem seen in the conventional middle-pipe type pipe propulsion machine, and its technical problem is that the curve construction can be performed without requiring a high degree of skill as compared with the conventional one. It is an object of the present invention to provide a folding type pipe propulsion machine that can accurately and reliably perform the above-described operation.
[0010]
[Means for Solving the Problems]
Such a technical problem of the present invention is that "a front cylinder having a cutter head, a middle cylinder connected so that the front cylinder can be tilted by a direction-correcting jack, and the middle cylinder can be freely tilted via a folding part. A rear cylinder having a rear cylinder that is formed at the front end of the rear cylinder and having a long groove formed therein, and a fixing bracket that is slidably fitted into the long groove, and a rear end of the middle cylinder The leading conductor is configured so that the flanges of the middle barrel formed in the above are fitted together so that both flanges can tilt relative to each other to form a folded portion, and the maximum folded angle is regulated by the length of the long groove of the folded portion. And a push jack for propelling the succeeding pipe connected to the rear trunk. By operating the direction correcting jack, the front trunk is tilted to push the underground pipe into the ground while being curved. Can be used as a The bending angle is achieved by selectively limiting provided limiting means during a maximal bending angle that can be "able to be smaller than the angle which is regulated by the long groove length of the center-folding unit.
[0011]
Since the middle folding type pipe propulsion device of the present invention employs such technical means, when performing straight construction or curve construction with a gentle curve, the maximum middle folding angle is set to the middle using the maximum middle folding angle limiting means. By limiting the angle to be smaller than the angle regulated by the length of the long groove in the fold, even if the construction is performed in an area where the ground is soft and the reaction force is difficult to take, the construction trace planned by the tip conductor It is possible to prevent the position of the lead conductor from being deviated from or from being staggered. As a result, curve construction can be performed accurately and reliably without requiring a high degree of skill as compared with a conventional middle-folded pipe propulsion device.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be clarified by describing a concrete example showing how the present invention is actually embodied based on FIG. 1 and FIG. 2. FIG. 1 is a horizontal sectional view showing an essential part of a middle folding type pipe propulsion device according to a first embodiment of the present invention, and FIG. 2 shows a middle folding type pipe thruster according to a second embodiment of the present invention. It is sectional drawing which shows the principal part, (A) is a cross-sectional view, (B) is a horizontal cross-sectional view. In FIG. 1 and FIG. 2, the part which attached | subjected the same code | symbol as FIG.3 and FIG.4 represents the part equivalent to these figures, and is not explained in full detail in order to avoid duplication of description. Each of the embodiments of the present invention includes a front folding cylinder 1 having a cutter head 4, a middle cylinder 2 that is connected so that the front cylinder 1 can be tilted by a direction-correcting jack 5, and the middle cylinder. 2 is provided with a rear cylinder 3 that is connected so as to be freely tiltable through a bent portion 6, and a flange 3a of the rear cylinder 3 formed at a front end portion of the rear cylinder 3 and formed with a long groove 3b, and the long groove 3b. A fixing metal fitting 8 that is slidably inserted into the inner cylinder 2 protrudes and is fitted to the flange 2a of the inner cylinder 2 so that both flanges 2a and 3a can be tilted with respect to each other. A leading conductor which constitutes the middle folding portion 6 and regulates the maximum middle folding angle, which is the maximum angle at which the middle barrel 2 can tilt with respect to the rear barrel 3, by the length of the long groove 3 b of the middle folding portion 6 ; And a push jack for propelling a succeeding pipe connected to the rear barrel 3 and operating a direction correcting jack 5 3 and FIG. 4, the conventional middle-folded pipe propulsion device shown in FIGS. 3 and 4 can be embedded in the ground while tilting the front barrel 1 and curving the subsequent pipe. And no different.
[0013]
Therefore, the characteristic technical contents of the middle folding type pipe propulsion device according to the first embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 11 denotes a half-restricted bar-like metal fitting such as a bolt having a male screw part 11 a and a shaft part 11 b on the distal end side and a base part side, and a head part 11 c on the base part, and 12 a male screw part 11 a to be screwed. An internal thread cylinder having an internal thread portion on the inner peripheral portion, and 13 is a cylindrical member having an insertion hole into which the shaft portion 11b of the folding restriction rod-shaped metal fitting 11 is inserted. A plurality of female screw cylinders 12 and cylindrical members 13 are provided, and are fixed so as to face the inner periphery of the flange 3a of the rear cylinder 3 and the inner periphery of the rear end of the middle cylinder 2, respectively. The insertion hole of the cylindrical member 13 has such a diameter that the shaft portion 11b and the cylindrical member 13 can be relatively tilted within a certain angle range when the shaft portion 11b of the folding restriction rod-shaped metal fitting 11 is inserted. Designed. When the head portion 11c of the middle-fold limiting rod-shaped metal fitting 11 is screwed into the male screw portion 11a to reduce the distance from the end surface of the tubular member 13, the shaft portion 11b and the tubular member 13 are thus tilted relatively. At this time, it abuts against the end surface of the tubular member 13 and the tilt angle is limited to an appropriate angle according to the distance from the end surface of the tubular member 13. In the present embodiment, the maximum folding angle is selected to be smaller than the angle regulated by the long groove 3b of the folding portion 6 by the folding-restricting rod-shaped metal fitting 11, the female screw cylinder 12, and the cylindrical member 13. The maximum bending angle limiting means that can be limited automatically is configured.
[0014]
When such a means for limiting the maximum bending angle is used, the male threaded portion 11a of the middle folding restriction rod-shaped metal fitting 11 is screwed to the female screw cylinder 12, and the head 11c of the middle folding restriction rod-shaped metal fitting 11 and the end surface of the cylindrical member 13 are used. , And the shaft portion 11 b of the middle-fold limiting rod-shaped metal fitting 11 is inserted into the tubular member 13. In this state, when the pipe propulsion method is carried out by the pipe propulsion apparatus of this embodiment, the middle cylinder 2 and the rear cylinder 3 are about to bend at the middle folding part 6 at a larger folding angle than necessary. When the shaft portion 11b and the cylindrical member 13 are relatively close to each other and tilted by a predetermined angle, the head portion 11c of the folding restriction rod-shaped metal fitting 11 comes into contact with the end surface of the cylindrical member 13 which is a contacted member. The maximum folding angle is limited to be smaller than the folding angle regulated by the long groove 3b of the folding portion. Further, in the case where straight folding does not require any middle folding at the middle folding part 6, if the middle folding restriction rod-shaped metal fitting 11 is sufficiently tightened and the head 11 c is pressed against the end surface of the tubular member 13, the middle folding restriction is achieved. The rod-shaped metal fitting 11 and the tubular member 13 cannot be tilted relatively. Furthermore, when the middle folding restriction rod-shaped metal fitting 11 is extracted from the cylindrical member 13, the maximum middle folding angle set by the length of the long groove 3b of the middle folding part 6 is not restricted. Can be folded at the designed maximum bend angle. As described above, in this embodiment, the maximum folding angle is set to be larger than the angle regulated by the long groove 3b of the middle folding portion 6 by enabling the middle folding restriction rod-shaped metal fitting 11 to be attached to and detached from the tubular member 13. It can be selectively limited to be small.
[0015]
In this embodiment, by adjusting the distance between the head portion 11c of the folding restriction rod-shaped fitting 11 and the end surface of the tubular member 13, the relative relationship between the shaft portion 11b of the folding restriction rod fitting 11 and the tubular member 13 is achieved. Since the tilt angle can be limited to a desired value, the maximum bend angle of the bendable portion 6 is adjusted by rotating the head portion 11c and adjusting the screwing allowance of the external thread portion 11a into the internal thread cylinder 12. It can be adjusted stepwise so as to be smaller than the middle turning angle regulated by the long groove 3b. Further, by rotating the head portion 11c and moving the head portion 11 so as to be separated from the end surface of the tubular member 13, the folded portion 6 can be obtained without removing the folded-restricting rod-shaped metal fitting 11 from the tubular member 13. The middle trunk 2 and the rear trunk 3 can be folded at the maximum middle folding angle set by the length of the long groove 3b. In this embodiment, the internal thread cylinder 12 and the tubular member 13 are fixed to the flange 3a of the rear cylinder 3 and the rear end of the middle cylinder 2, respectively, but these are replaced and fixed to the opposite side. Also good.
[0016]
Next, the technical contents characteristic of the second embodiment of the second embodiment of the present invention will be described with reference to FIG. In FIG. 2, reference numeral 14 denotes a half-restricted plate-like metal fitting such as a spacer that is detachably attached to the inner peripheral edge of the flange 3 a of the rear trunk, and is attachable / detachable by a bolt 16 via a washer 15 having an L-shaped cross section. It is attached. The folding restriction plate-shaped metal fitting 14 forms an arc-shaped block formed by dividing an annular member. In this embodiment, a large number of such folding-restricting plate-like metal fittings 14 are arranged so as to form an annular shape at the inner peripheral edge of the flange 3a, and are attached via a washer 15 so as to slightly protrude from the front end surface of the flange 3a. It is done. When the middle-fold limiting plate-like metal fitting 14 is attached to the rear barrel flange 3a in this way, the gap between the front end surface of the rear barrel flange 3a and the rear end surface of the middle barrel 2 facing this in the middle folded portion 6 is: It is slightly narrowed by the middle-fold limiting plate-like metal fitting 14.
[0017]
Therefore, in the case where the pipe propelling machine of this embodiment is used in such a state, when the middle cylinder 2 and the rear cylinder 3 are about to bend at the middle folding part 6 at a large middle folding angle, the middle folding restriction is performed. When the plate-shaped metal fitting 14 and the rear end surface of the inner cylinder 2 are relatively tilted and tilted by a predetermined angle, the middle-folding limiting plate-shaped metal fitting 14 as the contact member is the rear end surface of the inner cylinder 2 as the contacted member. The maximum bend angle is limited to be smaller than the bend angle restricted by the long groove 3b of the bend portion. Further, when the bolt 16 is loosened and the middle folding restriction plate-shaped metal fitting 14 is removed from the flange 3a of the rear trunk, the maximum middle folding angle set by the length of the long groove 3b is not restricted, so the middle trunk 2 and the rear trunk 3 Can be folded at the designed maximum bend angle. As described above, in this embodiment, the maximum folding angle is regulated by the long groove 3b of the folding portion 6 by allowing the folding-limiting plate-shaped metal fitting 14 to be attached to and detached from the flange 3a of the rear trunk. Can be selectively limited to be smaller. If several sets of those having different thicknesses are prepared in advance, the maximum folding angle is adjusted stepwise to a desired angle by selecting and using them. be able to. In this specific example, the middle folding restriction plate-shaped metal fitting 14 is attached to the inner peripheral edge of the flange 3a of the rear barrel, and the middle folding restriction plate-like metal fitting 14 is attached to the rear end surface of the middle cylinder 2 when the middle folding portion 6 is folded. However, the middle-fold limiting plate-shaped metal fitting 14 is attached to the inner peripheral edge of the middle barrel 2 so that the middle-fold limiting plate-shaped metal fitting 14 is brought into contact with the rear end surface of the flange 3a of the rear trunk. In short, when the middle cylinder 2 tilts with respect to the rear cylinder 3, the middle folding limit plate-shaped metal fitting 14 is detachably attached to the inner peripheral edge of one of the middle cylinder 2 and the rear cylinder 3. The tilt angle may be limited by bringing the folding restriction plate-shaped metal fitting 14 into contact with the end surface of the other body.
[0018]
In each embodiment described above, the middle-folded pipe propulsion machine has a maximum folding angle that is regulated by the long groove 3b of the middle-folded part when performing straight construction or curving with a gentle curve. For example, the propulsion method can be used in areas where the ground is soft and the reaction force is difficult to remove. Even when it is carried out, it is possible to prevent the leading conductor from deviating from the planned construction trajectory and the leading conductor's posture from being fluctuated. As a result, curve construction can be performed accurately and reliably without requiring a high degree of skill as compared with a conventional middle-folded pipe propulsion machine. Thus, although it is comprised so that the effect superior to the conventional one may be exhibited, a complicated mechanism is not required and the internal space in the machine is not substantially impaired. The means for limiting the maximum bending angle in each embodiment is different in specific structure, but both are provided on the abutting member provided on one side of the middle cylinder 2 and the rear cylinder 3 and on the other side. The contact member can contact the contact member, and when the middle cylinder 2 is tilted with respect to the rear cylinder 3, the contact member is brought into contact with the contact member and the maximum bending is achieved. In the point which made it possible to restrict | limit an angle | corner, it is the same, and the basic technique of this invention exists in this point. Therefore, when implementing such a means for limiting the maximum bend angle, a contacted member for contacting the fixing member 8 on the side of the middle cylinder 2 as a contact member is attached to and detached from the end of the long groove 3b of the rear cylinder 3. You may make it embed | buy possible.
[0019]
【The invention's effect】
As is clear from the above description, according to the present invention, in the folding type pipe propulsion device, in particular, the maximum middle folding angle is selectively limited to be smaller than the angle regulated by the middle folding portion. By providing a means for limiting the maximum bend angle that can be performed, it is possible to obtain a bend-type pipe propulsion machine that can perform curve construction accurately and reliably without requiring a high degree of skill compared to the conventional one. .
[Brief description of the drawings]
FIG. 1 is a horizontal cross-sectional view showing a main part of a half-folded pipe propulsion device according to a first embodiment of the present invention.
FIGS. 2A and 2B are cross-sectional views showing the main part of a second embodiment of the second embodiment of the present invention, where FIG. 2A is a cross-sectional view and FIG. 2B is a horizontal cross-sectional view.
FIG. 3 is a horizontal cross-sectional view schematically showing a portion of a leading conductor in a conventional middle-folded pipe propulsion device.
FIG. 4 is an enlarged horizontal cross-sectional view showing a bent portion of a leading conductor in a conventional bent tube propulsion machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Front cylinder 2 Middle cylinder 2a Middle cylinder flange 3 Rear cylinder 3a Rear cylinder flange 3b Long groove 4 Cutter head 5 Direction correction jack 6 Middle folding part 7 Direction correction part 8 Fixing metal fitting 11 Middle folding restriction rod-shaped metal fitting 12 Female thread cylinder 13 Cylinder Shaped member 14 Folding restricting plate-shaped bracket 15 Washer 16 Bolt

Claims (4)

A front cylinder having a cutter head, a middle cylinder connected so that the front cylinder can be tilted by a direction-correcting jack, and a rear cylinder connected so that the middle cylinder can be freely tilted via a folding part, A flange of the rear cylinder formed at the front end portion of the rear cylinder and having a long groove, and a flange of the intermediate cylinder formed at the rear end portion of the middle cylinder by protruding a fixing metal fitting slidably inserted into the long groove, The flanges are fitted to each other in such a way that they can be tilted with each other to form a bent portion , and the leading conductor that regulates the maximum bent angle by the length of the long groove of the bent portion and the subsequent connected to the rear cylinder It is composed of a main push jack that propels the pipe, and by operating the direction correcting jack, it can be pushed into the ground while tilting the front trunk to curve the subsequent pipe and embed it into the ground. in machine, a bending angle in the maximum, in the long groove length of the center-folding unit Pipe propulsion type folding in, characterized in that a limiting means during a maximal bending angle that can be selectively restricted to less than the angle that is braking. The limiting means for the maximum bending angle is composed of a contact member provided on one side of the middle and rear cylinders and a contacted member provided on the other side and capable of contacting the contact member. 2. The mid-folding type tube according to claim 1, wherein when the middle barrel is tilted with respect to the rear barrel, the abutting member is brought into abutment with the abutted member so that the maximum folding angle can be limited. Propulsion machine. Abutting member is a limit bracket bending in the rod-contacted member is in foldable according to claim 2, characterized in that the cylindrical member is Ru can be inserted to limit metal bending in the bar-like Tube propulsion machine. A limit bracket break in the contact member is mountable is a plate-like detachable from the inner peripheral edge portion of one cylinder of a medium cylinder and a rear cylinder, and wherein the contacted member is their other cylinder The middle folding pipe propulsion device according to claim 2.

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