JP2013049964A - Backing prevention device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent backing without executing work such as an anchor to a propulsion tube.SOLUTION: In a gap formed between an inclined surface 12bs of a receiving base 12b of a backing prevention device 12 and an outer periphery of a propulsion tube 8, a wedge-shaped stopper 12c integrally connected with the receiving base 12b by a bolt 12bb and a nut 12bn is arranged. When extending the propulsion tube 8, the stopper 12c is pushed into the gap between the receiving base 12b and the propulsion tube 8 by fastening the nut 12bn, and the stopper 12c is moved to the side of the propulsion tube 8 to press the propulsion tube 8. When performing propulsion construction, by loosening the nut 12bn to separate the stopper 12c from the propulsion tube 8, the propulsion construction is performed without hindrance.

Description

  The present invention relates to a backing prevention device for preventing a phenomenon (backing) in which a propulsion pipe is pushed back to a start shaft when a propulsion pipe is added in a propulsion method in which the propulsion pipe is buried in the ground.

  In the propulsion method, a start shaft and a reach shaft are provided at both ends of the planned pipeline line, and the excavator is excavated from the start shaft side with the excavator, while the propulsion pipe is added to the rear end of the excavator in order to create the start shaft. This is a method of constructing a pipe line by pushing the rear end of a propulsion pipe line with an installed propulsion jack to cause the excavator to reach a reaching shaft.

  Because this propulsion method requires less excavation of the road surface than the open-cut method, it is excellent for urban environmental measures such as reduction of construction area, reduction of noise, vibration and dust, and suppression of impacts on traffic and civic life. ing.

  However, in this propulsion method, when the succeeding propulsion pipe is added to the rear end of the existing propulsion pipe, the propulsion jack is separated from the existing propulsion pipe, so that the existing propulsion pipe is caused by earth pressure or water pressure on the ground side. There is a problem that a so-called backing is pushed back into the start shaft, and a subsequent propulsion pipe cannot be installed.

  Therefore, as an example of preventing this backing, post-installed anchors are drilled in the outer peripheral surface of the propulsion pipe, the metal fitting is embedded in the hole, the metal fitting and the propelling pipe are fixed with bolts, and the metal fitting is then supported on the reaction force side. It is designed to resist the backing force by stretching it with a craft.

  However, when drilling an anchor or the like in the propulsion pipe, the propulsion pipe may be damaged and may not be permitted.

  In addition, since the drilling work is manual, it takes time and labor, but the work must be performed for each of a plurality of propulsion pipes. Moreover, the number of anchors always requires the number of the maximum backing force that can be assumed and cannot be reduced. For this reason, there is a problem that the work efficiency of the construction of the pipeline is remarkably lowered.

  In addition to the above-described backing prevention example, the outer periphery of the propulsion pipe is provided with an annular body having a cross-sectional wedge shape having a diameter larger than the outer diameter of the propulsion pipe and the inner surface being reduced in diameter toward the rear. In the gap, a wedge-shaped body having a wedge-shaped cross section whose upper surface is inclined rearward is inserted from the front of the annular body to prevent backing (see, for example, Patent Document 1).

  In addition, a wedge-shaped stopper is movably provided in the gap between the opposing surfaces of the bracket and the propelling pipe fixed to the shaft wall. When propelling the propelling pipe, the wedge-shaped stopper is separated from the gap, while when preventing backing, There is disclosed a type stopper that allows the mold stopper to enter the gap (see, for example, Patent Document 2).

  In addition, a presser fitting that holds the propulsion pipe is provided inside a pair of support bodies provided to face both side surfaces of the propulsion pipe, and a tension member that can tighten the pair of support bodies is provided. In this case, the propulsion pipe is prevented from backing by tightening the support body with a tension material and sandwiching the propulsion pipe with a pressing metal fitting provided inside each of the pair of support bodies (see, for example, Patent Document 3). .

JP 2003-176688 A JP2003-293686A Japanese Patent No. 3751222

  The present invention has been made from the above technical background, and an object of the present invention is to provide a backing prevention device capable of preventing backing without subjecting the propulsion pipe to processing such as an anchor. With the goal.

  In order to solve the above-mentioned problems, the backing prevention device of the present invention according to claim 1 is a backing prevention device for preventing the backing of the propulsion pipe being pushed back into the start shaft when the propulsion pipe is added during the propulsion work. And disposed on the outer periphery of the propulsion pipe in a state of being connected to the support body between the support body and a conduit forming wellhead, and disposed on the outer periphery of the propulsion pipe. A pedestal formed with an inclined portion inclined in a direction away from the outer periphery of the propulsion tube along the propulsion direction of the propulsion tube on the side facing the propulsion tube, and disposed in a gap between the cradle and the propulsion tube, A wedge-shaped deterrent body in which an inclined portion that is inclined along the inclined portion of the cradle is formed on the side facing the cradle, and intersects with the inclined portion of each of the cradle and the deterrent body So that along the propulsion direction of the propulsion pipe And a bolt provided so as to pass through a hole formed in the restraining body, and the restraining body is formed between the cradle and the propelling pipe by the bolt penetrating the hole. It is attached to the cradle so as to be movable in both insertion and removal directions with respect to the gap.

  According to a second aspect of the present invention, there is provided the backing preventing apparatus according to the first aspect, wherein a sheet-like anti-slip member is provided on a surface of the deterrencer that faces the outer periphery of the propelling pipe. Features.

  According to a third aspect of the present invention, the backing preventing device according to the first or second aspect is characterized in that it is formed in a curved shape along the outer periphery of the propulsion body.

  According to a fourth aspect of the present invention, in the invention according to the first, second, or third aspect, when the hole is inserted into the gap between the cradle and the propulsion pipe, The deterrent body is formed to allow movement toward the propelling pipe.

  According to the first aspect of the present invention, when the propulsion pipe is added, the nut is tightened to push the deterrent body into the gap between the cradle and the propulsion pipe, and the outer periphery of the propulsion pipe is pressed by the deterrent body. Therefore, backing can be prevented without processing the propelling pipe such as an anchor.

  According to the second aspect of the present invention, when the deterrence body is inserted into the gap between the cradle and the propulsion pipe to prevent backing, and the bottom surface of the deterrence body is pressed against the outer periphery of the propulsion pipe, Because the frictional force can increase the frictional resistance against the propulsion pipe, the propulsion pipe can be pressed down firmly. For this reason, it becomes possible to improve the backing prevention capability of a propulsion pipe.

  According to the invention described in claim 3, the contact area between the deterrent body and the propulsion pipe can be increased, and the frictional resistance of the deterrent body against the propulsion pipe can be increased, so that the propulsion pipe can be pressed firmly. be able to. For this reason, it becomes possible to improve the backing prevention capability of a propulsion pipe.

  According to the invention described in claim 4, when the deterrence member is inserted into the gap between the cradle and the propulsion tube, the propulsion tube can be firmly pressed by moving the deterrence member toward the propulsion tube. It becomes possible to improve the backing prevention ability of the propulsion pipe.

It is explanatory drawing of the installation position of the backing prevention apparatus of one embodiment of this invention. It is a whole front view of the backing prevention apparatus of FIG. It is a side view of the backing prevention apparatus of FIG. It is a principal part expanded sectional view of the backing prevention apparatus of FIG. It is a front view of the block of the upper left cradle of FIG. FIG. 6 is a plan view of the cradle viewed from the direction A in FIG. 5. It is a fragmentary sectional view of the II line of FIG. FIG. 6 is a side view of the cradle as viewed from the direction B in FIG. 5. FIG. 6 is a side view of the cradle viewed from the direction C in FIG. 5. It is a front view of the stopper of the backing prevention apparatus of FIG. It is a top view of the stopper seen from the D direction of FIG. It is sectional drawing of the II-II line | wire of FIG. It is principal part sectional drawing of the backing prevention apparatus at the time of the extension of a propulsion pipe. It is principal part sectional drawing of the backing prevention apparatus at the time of the propulsion construction of a propulsion pipe.

  Hereinafter, an embodiment as an example of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 1 is an explanatory view of an installation position of a backing preventing apparatus according to an embodiment of the present invention.

  A propulsion stand 4 is installed at the bottom of the start shaft 2 dug in the ground 1 via a foundation stone 3. A hydraulic jack (propulsion jack) 5 is installed on the propulsion table 4. The hydraulic jack 5 is a device for pushing the propulsion pipe 8 through the strut 6 and the push wheel 7 arranged in order on the pressing surface side and pushing the pushing pipe 8 in the pipe line forming direction. A pressure bearing wall 10 that receives a reaction force from the propulsion pipe 8 side is installed on the back side of the hydraulic jack 5 via a steel material 9.

  For example, a reinforced concrete fume pipe is adopted as the propulsion pipe 8. An excavator 11 is connected to the tip of the leading propulsion pipe 8 in the row of the propulsion pipes 8. This excavator 11 is a device that excavates the ground 1 to form a pipe line in the ground. For example, a center shaft type shield excavator is employed.

  Here, when the new propulsion pipe 8 is added to the rear end of the existing propulsion pipe 8, the strut 6 of the hydraulic jack 5 pressing the rear end of the existing propulsion pipe 8 is contracted. The problem that the load on the rear end is lost and the existing propulsion pipe 8 is pushed back into the start shaft 2 due to earth pressure or water pressure on the ground side, so-called backing occurs, and a new propulsion pipe 8 cannot be installed. There is.

  Therefore, in the present embodiment, a backing prevention device 12 is installed in the vicinity of the pipe formation pit H and on the rear end side of the existing propulsion pipe 8. Hereinafter, the backing prevention device 12 will be described.

  2 is an overall front view of the backing preventing device 12 of FIG. 1, FIG. 3 is a side view of the backing preventing device 12 of FIG. 2, and FIG. 4 is an enlarged cross-sectional view of a main part of the backing preventing device 12 of FIG. 2 and 3 are provided with a center line CL for easy understanding of the positional relationship between the drawings.

  The backing prevention device 12 includes a gate-type support (support) 12a, a cradle 12b, a stopper (suppression body) 12c, and a strip 12d.

  The portal support 12a is formed by assembling a plurality of steel materials, for example, and is installed on the outer periphery of the propulsion pipe 8 so as to surround the circular propulsion pipe 8 as shown in FIG. As shown in FIGS. 2 and 3, both leg portions of the portal support 12 a are firmly fixed to the propulsion base 4 through support bases 15 a and 15 b. The support bases 15a and 15b are formed of a steel material such as H-shaped steel, for example.

  As shown in FIG. 4, a collar 16 having a T-shaped cross section is installed along the outer periphery of the propulsion tube 8 at the rear end of the propulsion tube 8. The collar 16 is made of, for example, a steel material, and a seal member 17 made of, for example, rubber is provided on the inner periphery thereof. A small-diameter portion 8 a is formed on the outer periphery of the tip of the subsequent propulsion tube 8, and the small-diameter portion 8 a is fitted into the inner periphery of the collar 16 at the rear end of the previous propulsion tube 8. As a result, the front-stage propulsion pipe 8 and the rear-stage propulsion pipe 8 are sealed by the seal member 17 to provide waterproofness.

  The cradle 12b is distributed on the outer periphery of the propulsion tube 8 so as to surround the propulsion tube 8 when viewed from the front as shown in FIG. Here, the cradle 12b is arrange | positioned left-right symmetrically, for example in three places, the upper side of the propulsion pipe 8, and both right and left sides. The front shape of the cradle 12 b is formed in a curved shape along the outer periphery of the propulsion pipe 8.

  Further, when viewed from the side as shown in FIG. 3, the cradle 12 b is disposed between the pipe formation pit H and the portal support 12 a, and as shown in FIGS. 3 and 4, the connecting portions 18 a, It is firmly connected to the gate-type supporter 12a through 18b. The connecting portions 18a and 18b are made of steel, for example.

  Here, the cradle 12b will be described with reference to FIGS. 5 is a front view of a block of the upper left cradle 12b in FIG. 2, FIG. 6 is a plan view of the cradle 12b as viewed from the direction A in FIG. 5, and FIG. 7 is a partial cross-sectional view taken along the line II in FIG. 8 and 9 are side views of the cradle 12b viewed from the B and C directions in FIG. 5, respectively.

  As shown in FIGS. 3, 4, 6, and 7, the cradle 12b is formed, for example, by assembling a steel plate into a box shape. Further, as shown in FIGS. 3, 4, and 7 to 9, in this cradle 12 b, the propulsion pipe is disposed on the side (surface) facing the outer periphery of the propulsion pipe 8 along the propulsion direction of the propulsion pipe 8. An inclined surface (inclined portion) 12bs is formed that is inclined in a direction away from the outer periphery of 8.

  Moreover, as shown in FIGS. 2 to 5 and 7, a bolt 12 bb is fixed to the inclined portion 12 bs of the cradle 12 b by welding. The bolt 12bb is, for example, a stud bolt without a head, and is provided in a state extending along the propulsion direction of the propulsion pipe 8 from the inclined surface 12bs so as to intersect the inclined surface 12bs. Yes. A nut 12bn is screwed into the male thread at the tip of the bolt 12bb.

  As shown in FIGS. 2 to 7, the reinforcing plate 12br is in the longitudinal direction of the cradle 12b at a position where the bolt 12bb is sandwiched in the cradle 12b (a position corresponding to a position where the stopper 12c is in contact with the inclined surface 12bs). And the strength of the cradle 12b is ensured.

  The stoppers 12c are distributed on the outer periphery of the propulsion tube 8 so as to surround the propulsion tube 8 when viewed from the front as shown in FIG. Here, the stoppers 12c are arranged symmetrically in 10 places in total, for example, 4 places on the upper side of the propulsion pipe 8 and 3 places on the left and right sides of the propulsion pipe 8. By arranging the stoppers 12c symmetrically in this way, the pressure applied from the stopper 12c side to the outer periphery of the propulsion pipe 8 can be equalized when backing is prevented.

  Moreover, the stopper 12c is arrange | positioned in the clearance gap between the receiving stand 12b and the propulsion pipe 8, as shown in FIG.3 and FIG.4. Thereby, since the outer periphery of the propulsion pipe 8 is pressed by the stopper 12c, it is possible to counter the backing force. In FIG. 3, a part of the stopper 12c is shown in a transparent manner for easy understanding, and one of the stoppers 12c is hatched to make the drawing easy to see.

  Here, the stopper 12 c will be described with reference to FIGS. 2 to 4 and FIGS. 10 to 12. 10 is a front view of the stopper 12c, FIG. 11 is a plan view of the stopper 12c viewed from the direction D in FIG. 10, and FIG. 12 is a cross-sectional view taken along the line II-II in FIG.

  As shown in FIGS. 3, 4 and 12, the stopper 12c is made of, for example, a steel material, and its outer shape is formed in, for example, a wedge shape. That is, the stopper 12c includes a front plate 12cf, a bottom plate 12cb orthogonal to the front plate 12c, a side plate 12cs orthogonal to these, and a reinforcing plate 12cr provided so as to delimit the width direction, and of these, the side plate 12cs. In the reinforcing plate 12cr, the side facing the cradle 12b is formed to be inclined along the inclined surface 12bs of the cradle 12b.

  Further, as shown in FIGS. 4, 10, and 12, a hole 12ch is formed in the front plate 12cf of the stopper 12c. This hole 12ch is a hole through which the above-described bolt 12bb passes. That is, as shown in FIGS. 3 and 4, the above-described bolt 12bb extends so as to intersect the inclined surface of the stopper 12c, passes through the hole 12ch, and protrudes from the front plate 12cf of the stopper 12c. Then, when the nut 12bn is screwed into the male screw portion at the tip of the bolt 12bb protruding from the front plate 12cf, the stopper 12c is inserted and removed in both directions with respect to the gap between the cradle 12b and the propulsion pipe 8. It is attached to the cradle 12b in a movable state. As described above, the backing 12b and the stopper 12c are integrated with the bolt 12bb and the nut 12bn, so that the handling of the backing prevention device 12 can be facilitated. Further, the stopper 12c can always be easily disposed at the same appropriate position.

  The hole 12ch of the stopper 12c is formed to allow the stopper 12c to move toward the propulsion pipe 8 when the stopper 12c is inserted into the gap between the cradle 12b and the propulsion pipe 8. Here, as shown in FIG. 10, the hole 12ch is formed in a vertically long shape. That is, the length of the hole 12ch in the vertical direction is longer than the length in the width direction perpendicular to the hole 12ch. The length in the width direction of the hole 12ch is slightly larger than the diameter of the bolt 12bb. Thereby, since the precision of the arrangement position of the stopper 12c in the outer peripheral direction of the propulsion pipe 8 can be improved, the stopper 12c can be quickly arranged at an appropriate position.

  Thus, the hole 12ch is preferably vertically long from the viewpoint of the arrangement position accuracy of the stopper 12c, but is not limited to this, and the stopper 12c is inserted into the gap between the cradle 12b and the propulsion pipe 8. In this case, a circular shape may be used as long as the stopper 12c is allowed to move toward the propulsion pipe 8 side.

  As shown in FIGS. 2 and 10, the surface of the stopper 12 c that faces the outer periphery of the propulsion tube 8 (the back surface of the bottom plate 12 cb of the stopper 12 c) is formed in a curved shape along the outer periphery of the propulsion tube 8. ing. As a result, the contact area between the stopper 12c and the propulsion pipe 8 can be increased, and the frictional resistance of the stopper 12c against the propulsion pipe 8 can be increased, so that the propulsion pipe 8 can be firmly pressed, and the propulsion pipe 8, the ability to prevent backing can be improved.

  As shown in FIGS. 2 and 3, the belt-like body 12 d is formed in a state of extending continuously along the circumference of the propulsion tube 8 so as to surround, for example, about 80% thereof. As shown in FIG. 4, the belt-like body 12d has a two-layer structure of a metal plate 12dm and a sheet-like anti-slip member 12ds.

  A part of the belt-like body 12 d is interposed between the plurality of stoppers 12 c around the propulsion pipe 8 and the propulsion pipe 8. The metal plate 12dm of the strip 12d is connected to the bottom surface of the stopper 12c (the back surface of the bottom plate 12cb) by welding.

  The metal plate 12dm is made of, for example, steel and has a function as a leaf spring that constantly biases the stopper 12c toward the inclined surface 12bs of the cradle 12b in addition to the function of connecting the stopper 12c and the anti-slip member 12ds. Have.

  The anti-slip member 12ds is made of, for example, hard rubber having a friction coefficient larger than that of metal. As a result, when the stopper 12c is inserted into the gap between the cradle 12b and the propulsion pipe 8 to prevent backing and the bottom surface of the stopper 12c is pressed against the outer periphery of the propulsion pipe 8, the propulsion is caused by the frictional force of the anti-slip member 12ds. The frictional resistance against the pipe 8 can be increased, and the repulsive force generated by the elastic deformation of the anti-slip member 12ds acts in the direction of pressing the propulsion pipe 8, so that the propulsion pipe 8 can be firmly pressed. In addition, since hard rubber is higher in elasticity and flexibility than metal, the outer periphery of the propulsion tube 8 is not damaged just because the propulsion tube 8 is pressed by the stopper 12c. Therefore, the ability to prevent backing can be improved without causing damage to the outer periphery of the propulsion pipe 8.

  Next, the operation of the backing prevention apparatus 12 according to the present embodiment when backing is prevented and when backing prevention is released will be described with reference to FIGS. 13 and 14. FIG.

  13 is a cross-sectional view of the main part of the backing prevention device 12 when the propulsion pipe 8 is added, and FIG. 14 is a cross-sectional view of the main part of the backing prevention device 12 when the propulsion pipe 8 is propelled.

  As shown in FIG. 13, when a new propulsion pipe 8 is added after propulsion of the propulsion pipe 8 by a predetermined amount, before the hydraulic jack 5 (see FIG. 1) is pulled back, the backing prevention device 12 has a nut 12 bn. When tightened, the stopper 12c slides along the inclined surface 12bs of the cradle 12b and is pushed into the gap between the cradle 12b and the propulsion tube 8 while moving in the direction of pressing the propulsion tube 8. Then, the force by which the stopper 12c is pushed in is transmitted from the stopper 12c to the metal plate 12dm and the anti-slip member 12ds, and friction is generated between the propulsion pipe 8 and the stopper 12c. This frictional force can counter the backing force and prevent the backing.

  Here, when the backing force increases, the frictional force of the metal plate 12dm and the anti-slip member 12ds is transmitted to the stopper 12c, and further transmitted to the portal support 12a via the cradle 12b, thereby resisting the backing force. it can. Therefore, by increasing the stopper 12c in a wedge shape, it is possible to easily cope with an increase in the backing force.

  Further, in the case of the backing prevention device 12 of the present embodiment, since it is not necessary to perform processing such as anchoring for each propulsion pipe 8, labor in the construction work of the propulsion pipe 8 can be greatly reduced and work efficiency can be reduced. It can be greatly improved. In addition, since the propulsion pipe 8 is not processed, the propulsion pipe 8 is not damaged.

  Further, since the stopper 12c can be pushed in by simply tightening the nut 12bn, the stopper 12c can be pushed in with a relatively small force, and the amount of pushing the stopper 12c can be adjusted by the amount of tightening the nut 12bn. No excessive pressing force is applied to the propulsion pipe 8, and the propulsion pipe 8 is not damaged.

  Subsequently, with the stopper 12c being pushed into the gap between the cradle 12b and the propulsion pipe 8, the hydraulic jack 5 (see FIG. 1) is separated from the existing propulsion pipe 8 and newly introduced through the start shaft 2 (see FIG. 1). After the propulsion pipe 8 is added, the rear end of the propulsion pipe 8 added by the hydraulic jack 5 is pressed.

  Then, as shown in FIG. 14, the nut 12bn of the backing prevention device 12 is loosened. Then, the stopper 12c moves away from the cradle 12b in a state where the inclined surface of the reinforcing plate 12cr of the stopper 12c is pressed against the inclined surface 12bs of the cradle 12b by the action of the leaf spring of the metal plate 12dm of the strip 12d. fall back. Here, since the anti-slip member 12ds on the back surface of the stopper 12c is separated from the outer periphery of the propulsion pipe 8, there is no friction with the propulsion pipe 8, and the resistance force becomes zero. Therefore, when the new propulsion pipe 8 is propelled, the backing prevention device 1 can proceed with work without any hindrance to the propulsion force of the propulsion pipe 8.

  Although the invention made by the present inventor has been specifically described based on the embodiment, the embodiment disclosed in this specification is an example in all respects and is limited to the disclosed technology. Should not be considered. That is, the technical scope of the present invention should not be construed restrictively based on the description in the above-described embodiment, but should be construed according to the description of the scope of claims. All modifications are included without departing from the technical scope equivalent to the described technique and the gist of the claims.

  For example, in the above-described embodiment, the case where the stopper is attached to the cradle with the stud bolt and nut being detachable is described. However, the present invention is not limited to this, and the stopper is inserted with, for example, a hexagon bolt. It may be attached to the cradle in a detachable state. That is, by inserting the hexagon bolt from the front side of the stopper into the hole of the stopper from the male screw part side, and screwing the male screw part of the hexagon bolt into the female screw part formed in advance on the inclined surface of the cradle. The stopper may be attached to the cradle so that it can be inserted and removed. Thus, the bolt for attaching the stopper to the cradle is not limited to the stud bolt, and various types of bolts can be used.

  Further, the propulsion pipe is not limited to reinforced concrete but can be variously changed. For example, a synthetic steel material or a steel material may be used.

  Further, the anti-slip member is not limited to rubber and can be variously changed. For example, a fiber such as carbon fiber or synthetic fiber may be used.

  In the above description, the case where the present invention is applied to a backing prevention device when using a center shaft type shield machine is shown, but other types of shield machines such as an intermediate support type shield machine are used. The present invention can also be applied to a backing prevention device when used.

5 Hydraulic jack (propulsion jack)
8 Propulsion pipe 11 Excavator 12 Backing prevention device 12a Portal support (support)
12b Receiving base 12bb Bolt 12bn Nut 12br Reinforcement plate 12bs Inclined surface (inclined part)
12c Stopper (deterrent body)
12ch Hole 12cr Reinforcement plate 12cs Side plate 12d Strip body 12dm Metal plate 12ds Anti-slip member H Pipeline formation wellhead

Claims (4)

When the propulsion pipe is added during propulsion construction, the propulsion pipe prevents the backing pipe from being pushed back into the start shaft,
A support installed on the outer periphery of the propulsion tube;
Between the support and the pipe-forming wellhead, it is disposed on the outer periphery of the propulsion pipe in a state of being connected to the support, and on the side facing the outer periphery of the propulsion pipe, along the propulsion direction of the propulsion pipe A cradle formed with an inclined portion inclined in a direction away from the outer periphery of the propulsion tube;
A wedge-shaped deterrent body that is disposed in a gap between the cradle and the propelling pipe, and that has an inclined portion that is inclined along the inclined portion of the cradle on the side facing the cradle;
Provided so as to extend along the propulsion direction of the propulsion pipe so as to intersect with the inclined portions of the cradle and the deterrence body, and is provided so as to penetrate a hole formed in the deterrence body. With a bolt
The backing body is attached to the cradle in a state of being movable in both insertion and removal directions with respect to a gap between the cradle and the propelling pipe by the bolt passing through the hole. Prevention device.   The anti-backing device according to claim 1, wherein a sheet-like anti-slip member is provided on a surface of the restraining body facing the outer periphery of the propulsion pipe.   The backing prevention device according to claim 1 or 2, wherein a surface of the restraining body facing the outer periphery of the propulsion pipe is formed in a curved shape so as to follow the outer periphery of the propulsion body.   The hole is formed to allow the deterrence body to move toward the propulsion pipe when the deterrence body is inserted into a gap between the cradle and the propulsion pipe. Item 4. An anti-backing device according to item 1, 2 or 3.

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