A front-support hanging basket retraction device and its retraction method

Abstract

This application relates to a front-support hanging basket retraction device and its retraction method, comprising two retraction tracks, each connected to a traveling track and forming a horizontal straight line with the traveling track; a traveling trolley anchored to the bottom of a cast-in-place beam segment, connected to the retraction tracks and capable of traveling on both tracks; and a through-type jack mounted on the hanging basket body and located at the front end of a thrust block, used to push the thrust block on the hanging basket body to gradually retract the hanging basket body. This application allows for the rapid and safe dismantling of the front-support hanging basket when it is impossible to directly lower it.

Description

Technical Field

[0001] This application relates to the field of front-support hanging baskets, and more particularly to a front-support hanging basket retraction device and retraction method thereof. Background Technology

[0002] The front support formwork is a crucial structure for the cantilever construction of the main girder of a cable-stayed bridge. It comprises the formwork body, anchoring system, template system, traveling system, traction system, and thrust structure. The template system is installed at the front end of the formwork body. The traveling system includes a traveling track installed at the rear end of the formwork body, a traveling trolley anchored to the bottom of the already cast girder segment and capable of moving along the track, a guide structure positioned on the top surface of the cast girder segment, and a traction structure connecting the guide structure to the front end of the formwork body.

[0003] After the construction of a cable-stayed bridge is completed, the front support formwork needs to be dismantled, at which point it is suspended below the middle section of the bridge. The conventional method is to directly dismantle the front support formwork and gradually lower it. If there is open ground below, the formwork is lowered directly to the open ground and then transported away by truck. If there is a river below, workers use a motorboat to lower the formwork onto the boat and transport it away. However, if there is a building below the formwork, or if the river is rapid, this direct lowering method is not feasible.

[0004] Therefore, the inventors believe that how to quickly and safely dismantle the front support basket when it is impossible to lower it directly is an urgent problem to be solved. Summary of the Invention

[0005] In order to quickly and safely dismantle the front fulcrum hanging basket when it is impossible to lower it directly, this application provides a front fulcrum hanging basket retraction device and retraction method.

[0006] Firstly, the front-support basket retraction device provided in this application adopts the following technical solution:

[0007] A front-support hanging basket retraction device, comprising:

[0008] Two backward tracks are provided, and the two backward tracks are respectively connected to the travel tracks, and are in a horizontal straight line with the travel tracks they are connected to;

[0009] The traveling trolley is anchored to the bottom of the cast beam segment. The traveling trolley is connected to the retracting track and can travel on the retracting track and the traveling track.

[0010] A through-type jack is installed on the hanging basket body and located at the front end of the thrust structure. It is used to push the thrust block on the hanging basket body to push the hanging basket body to gradually move backward.

[0011] By adopting the above technical solution, two retraction tracks connected to the original travel track are added, forming two tracks running the length of the hanging basket body. Adding a traveling trolley connected to the retraction track facilitates cooperation with the existing traveling trolleys connected to the travel track on the hanging basket body, allowing for stable lifting of the hanging basket body. When the hanging basket body is pushed backward by the through-type jack, the traveling trolley can move stably along both the travel track and the retraction track, ensuring stable retraction of the hanging basket body. When the hanging basket body retracts until the traveling trolley at the front of the retraction reaches the end of the retraction track, a traveling trolley connected to the travel track is installed at the front of the traveling basket body to facilitate further retraction until the hanging basket body is pushed back to the initial lifting position of block 0. Then, the front support hanging basket is lowered and dismantled, allowing for quick and safe dismantling of the hanging basket body.

[0012] Preferably, the end of the reversing track away from the traveling track protrudes from the end of the hanging basket body.

[0013] By adopting the above technical solution, as the hanging basket body gradually retreats, when the traveling trolley at the front end of the retreating movement reaches the part of the retreating track that protrudes from the end of the hanging basket body, the construction personnel inside the hanging basket body, while maintaining the temporary suspension of the hanging basket body by the traveling trolley, install a new traveling trolley at the rearward end of the hanging basket body and connect the new traveling trolley to the traveling track. The installation of the new traveling trolley ensures the stability of the hanging basket body and guarantees construction safety. Afterwards, the traveling trolley at the front end of the retreating movement is removed, and then the through-type jack pushes the hanging basket body to continue retreating, repeating the above steps until the hanging basket body is retreated to the initial lifting position of block 0.

[0014] Preferably, at least three traveling trolleys are provided on each side, and the at least three traveling trolleys are respectively located at the rear end, middle and front end of the hanging basket body.

[0015] By adopting the above technical solution, at least three traveling trolleys on each side can stably lift the hanging basket body, so as to ensure that the hanging basket body is evenly stressed at all positions, thus ensuring the stability of the hanging basket body during movement and ensuring construction safety.

[0016] Preferably, the two traveling trolleys suspended at both ends of the hanging basket body are positioned at a point where the distance between the traveling trolley in the middle of the hanging basket body and the end of the hanging basket body is bisected.

[0017] By adopting the above technical solution, the longest backward travel of the basket body each time is 1 / 4 of the total length of the basket body. While ensuring the walking stability of the basket body, the backward travel of the basket body each time is extended, thereby improving the backward travel efficiency of the basket body.

[0018] Preferably, the traveling trolley includes a trolley body for connecting to the retracting track and the traveling track, and an anchor plate anchored to one side of the cast-in-place beam segment, with the top of the trolley body hinged to the anchor plate.

[0019] By adopting the above technical solution, the trolley body is connected to the traveling track and the reversing track to travel along them. The anchor plate is used to anchor the traveling trolley and the cast-in-place beam segment. The traveling trolley acts as a suspender for the hanging basket body, allowing the hanging basket body to gradually retract without the need for a traction structure. By using a hinged connection between the trolley body and the anchor plate, the traveling trolley has better flexibility and adaptability when the hanging basket body retracts, reducing the probability of the trolley body suffering rigid damage and extending the service life of the traveling trolley.

[0020] Preferably, the anchor plate includes a main anchor plate fixed to one side of the cast beam segment by bolts and a secondary anchor plate vertically fixed to one side of the main anchor plate. The secondary anchor plate and the cast beam segment are anchored together by a first fine-rolled threaded steel bar.

[0021] By adopting the above technical solution, since the anchoring stability between the anchor plate and the cast-in-place beam segment has a significant impact on the backward stability of the formwork body when it retracts, the double fixing method of bolt anchoring between the main anchor plate and the cast-in-place beam segment and hanging anchoring between the secondary anchor plate and the cast-in-place beam segment with precision-rolled threaded steel is adopted to increase the anchoring stability between the traveling trolley and the cast-in-place beam segment and improve the backward stability of the formwork body.

[0022] Preferably, both the traveling track and the reversing track are I-beams fixed to the hanging basket body. The trolley body includes a connecting part, a main frame, and two sets of tank wheels rotatably connected within the main frame. An installation space is formed inside the main frame for the I-beams to extend into and engage with the vertical plate of the I-beams. The two tank wheels are located on both sides of the I-beams.

[0023] By adopting the above technical solution, the end of the traveling track passes through the installation space to connect the trolley body and the traveling track. When the through-type jack pushes the hanging basket body backward, as the I-beam gradually moves backward, the tank wheel rotates, reducing the frictional resistance between the traveling trolley and the I-beam, which facilitates the movement of the hanging basket body.

[0024] Secondly, this application provides a method for retracting a front-support hanging basket, employing the following technical solution:

[0025] A method for retreating while hanging from a front pivot point includes the following steps:

[0026] S1: Anchoring structure before construction to lift the front end of the hanging basket body;

[0027] S2: Installation of the retraction device: Construct retraction tracks and traveling trolleys on both sides of the hanging basket body; install a through-type jack at the front end of the hanging basket body;

[0028] S3: Release the connection between the traction structure and the guide structure, and release the front anchoring structure and other anchoring structures that anchor the hanging basket body;

[0029] S4: The through-hole jack pushes the hanging basket body backward, so that the traveling trolley travels along the backward track and the traveling track;

[0030] S5: As the hanging basket body moves backward, the traveling trolley at the front end of the backward movement is gradually removed, and a traveling trolley connected to the traveling track is installed at the front end of the traveling movement of the hanging basket body. This process is repeated until the hanging basket body moves backward to the lifting position.

[0031] By adopting the above technical solution, the front anchoring structure temporarily lifts the front end of the hanging basket body, which facilitates the dismantling of the traction structure and the installation of the traveling track and traveling trolley. After the retraction track and traveling trolley are installed, the weight of the hanging basket body is shared by the traveling trolley and the anchoring structure of the cast beam segment. At this time, the front anchoring structure can be removed, and the through-hole jack can be started to push the hanging basket body to gradually move backward.

[0032] Preferably, the front anchoring structure in step 1 is located on both sides of the hanging basket body. During construction, the anchoring distribution plate is first fixed on one side of the hanging basket body, and the anchoring seat is installed on the top surface of the cast beam segment. Several second fine-rolled threaded steel bars are used to pass through the cast beam segment to pull the second fine-rolled threaded steel bars between the anchoring distribution plate and the anchoring seat.

[0033] By adopting the above technical solution, the anchoring installation of the front anchoring structure is facilitated.

[0034] Preferably, in step 2, the end of the retracting track away from the traveling track extends out of the basket body;

[0035] In step 5, when the traveling trolley located at the front of the reversing path travels to the end of the reversing track, a new traveling trolley is first installed at the front of the traveling path, and then the traveling trolley located at the front of the reversing path is removed.

[0036] By adopting the above technical solution, the stability of the hanging basket body is improved when installing the new traveling trolley.

[0037] In summary, this application includes at least one of the following beneficial technical effects:

[0038] 1. This application suspends the basket body by adding a retractable track connected to the traveling track and a traveling trolley connected to the retractable track. Due to the pushing action of the through-type jack and the jacking block, the basket body is pushed to gradually retract. When the basket body retracts, the traveling trolley and the retractable track are relatively displaced. When the basket body retracts, the traveling trolley is gradually installed at the retractable end and the traveling trolley at the retractable front end is gradually removed until the basket body is retracted to the initial lifting position. Under the premise that the front support basket cannot be directly lowered, the front support basket is quickly and safely dismantled.

[0039] 2. By protruding the end of the retracting track away from the traveling track from the end of the hanging basket body, the construction personnel inside the hanging basket body can install the newly added traveling trolley at the retracting end of the hanging basket body while maintaining the temporary suspension of the hanging basket body by the traveling trolley, thus ensuring the stability of the hanging basket body and ensuring construction safety.

[0040] 3. At least three traveling trolleys are set on each side to ensure that the force is evenly distributed on all parts of the hanging basket body, to ensure the stability of the hanging basket body when moving, and to ensure construction safety. Attached Figure Description

[0041] Figure 1 This is a schematic diagram showing the state of the hanging basket body when it is lifted by the front anchoring structure.

[0042] Figure 2 This is a schematic diagram showing the state of the hanging basket body after the traveling trolley is installed before it moves.

[0043] Figure 3 This is a schematic diagram showing the state when the hanging basket body retracts to its maximum retraction distance, with the newly added traveling trolley installed at the end of the retraction.

[0044] Figure 4 This is a side view of the main body of the car.

[0045] Explanation of reference numerals in the attached drawings: 1. Reverse track; 2. Traveling trolley; 21. Trolley body; 211. Connecting part; 2111. Clamping steel plate; 2112. Pin shaft; 212. Main frame; 2121. Installation space; 213. Tank wheel; 22. Anchor plate; 221. Main anchor plate; 222. Secondary anchor plate; 23. Bolt; 24. First fine-rolled threaded steel bar; 3. Hanging basket body; 31. Thrust block; 4. Traveling track; 5. Cast-in-place beam segment; 6. Front anchoring structure; 61. Anchoring distribution plate; 62. Anchoring seat; 63. Second fine-rolled threaded steel bar. Detailed Implementation

[0046] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0047] This application discloses a front-support hanging basket retraction device and its retraction method. (Refer to...) Figure 1 and Figure 2 The front support hanging basket retraction device includes a retraction track 1, a traveling trolley 2, and a through-type jack (not shown in the figure).

[0048] Reference Figure 2 The retraction rails 1 are installed on both sides of the hanging basket body 3. The two retraction rails 1 are connected to the existing travel rails 4 on the hanging basket body 3. The traveling trolley 2 is anchored to both sides of the bottom of the cast-in-place beam segment 5, allowing it to connect to the retraction rails 1 on both sides of the hanging basket body 3. The traveling trolley 2 can travel on both the retraction rails 1 and the travel rails 4. A through-type jack is installed on the hanging basket body 3 and located at the front end of the thrust structure, used to push the thrust block 31 on the hanging basket body 3 to gradually retract the hanging basket body 3. As the through-type jack pushes the hanging basket body 3 backward, the traveling trolley 2 travels along the retraction rails 1 and gradually retreats to behind the travel rails 4. Then, construction workers on the hanging basket body 3 install the traveling trolley 2 sequentially at the front end of the hanging basket body 3 in the direction of travel, allowing the hanging basket body 3 to continue retracting until it returns to its initial lifting position.

[0049] Reference Figure 2 and Figure 3 Furthermore, the end of the retracting track 1 furthest from the traveling track 4 protrudes from the end of the hanging basket body 3. When the traveling trolley 2 located at the retracting front end of the hanging basket body 3 reaches the end of the retracting track 1, a new traveling trolley 2 is installed at the traveling front end of the hanging basket body 3, and the traveling trolley 2 located at the retracting front end is removed. This facilitates the installation of the traveling trolley 2 at the traveling front end while maintaining the suspending effect of the traveling trolley 2 at the retracting front end on the hanging basket body 3, thereby maintaining the balance and stability of the hanging basket body 3 and ensuring the safety of construction personnel inside the hanging basket body 3.

[0050] At least three traveling trolleys 2 are provided on each side of the retraction track 1, and these at least three traveling trolleys 2 are distributed at the rear, middle, and front of the basket body 3. The at least three traveling trolleys 2 are evenly spaced along the length of the basket body 3 to ensure uniform force distribution on the basket body 3 and improve its stability during retraction. This application only illustrates the example of three traveling trolleys 2 located on one side of the basket body 3.

[0051] Generally, when the basket body 3 is stationary, the closer the two traveling trolleys 2 at both ends are to the ends, the better the stability of the basket body 3. However, when the basket body 3 is in motion, if the two traveling trolleys 2 are installed close to the ends of the basket body 3 during installation, the basket body 3 will need to retract a short distance before needing to add another traveling trolley 2 at the end of the retraction. Further retraction will cause the front end of the basket body 3 to become unbalanced, compromising its stability during retraction. Furthermore, among the three traveling trolleys 2 on the same side, the two traveling trolleys at both ends of the basket body 3 are positioned at the bisection of the distance between the middle traveling trolley 2 and the end of the basket body 3. It can be calculated that the longest retraction distance of the basket body 3 each time is 1 / 4 of its total length. This extends the retraction distance of the basket body 3 each time while ensuring its stability, thus improving its retraction efficiency.

[0052] Reference Figure 2 and Figure 4 The traveling trolley 2 includes a trolley body 21 for traveling along the retracting track 1 and the traveling track 4, and an anchor plate 22 anchored to one side of the cast-in-place beam segment 5. The top of the trolley body 21 is hinged to the anchor plate 22. By using a movable hinge connection between the trolley body 21 and the anchor plate 22, the traveling trolley 2 has better flexibility and adaptability when the hanging basket body 3 retracts, reducing the probability of the trolley body being subjected to rigid damage and extending the service life of the traveling trolley 2.

[0053] Reference Figure 2 Since the hanging basket body 3 is only fixed to the bottom of the cast beam segment 5 by the anchor plate 22, in order to increase the connection stability between the hanging basket body 3 and the cast beam segment 5, the anchor plate 22 includes a main anchor plate 221 fixed to one side of the cast beam segment 5 by bolts 23 and a secondary anchor plate 222 vertically fixed to one side of the main anchor plate 221. The secondary anchor plate 222 is also anchored to the cast beam segment 5 by a first fine-rolled threaded steel bar 24.

[0054] Reference Figure 2 and Figure 4Both the traveling track 4 and the reversing track 1 are I-beams fixed to the hanging basket body 3. The trolley body 21 includes a connecting part 211 for connecting with the main anchor plate 221, a main frame 212, and two sets of tank wheels 213 rotatably connected inside the main frame 212. The main frame 212 is composed of two symmetrical C-shaped frames spliced ​​together, so that the interior of the main frame 212 forms an installation space 2121 for the I-beams to extend into and engage with the vertical plate of the I-beams. The two sets of tank wheels 213 are located on both sides of the I-beams, and the top surface of each set of tank wheels 213 abuts against the bottom surface of the top plate of the I-beam. Each set of tank wheels 213 includes two, and the two tank wheels 213 are arranged along the length of the I-beam. During installation, the trolley 2 is inserted through the end of the I-beam and slid along the length of the I-beam to the corresponding position of the main anchor plate 221 via the tank wheel 213. The connecting part 211 and the main anchor plate 221 are then hinged together via the pin 2112.

[0055] Reference Figure 4 The connecting part 211 includes two opposing clamping steel plates 2111, forming a clamping space between the two clamping steel plates 2111 for the bottom of the main anchoring plate 221 to extend into. Both the two clamping steel plates 2111 and the main anchoring plate 221 have hinge holes for the pin 2112 to pass through. During installation, the main anchoring plate 221 is inserted into the clamping space formed by the two clamping steel plates 2111, aligning the hinge holes on the clamping steel plates 2111 with the hinge holes on the main anchoring plate 221, and the pin 2112 is then inserted sequentially into the hinge holes of the clamping steel plates 2111 and the main anchoring plate 221.

[0056] This application also discloses a method for retracting a front-support hanging basket, comprising the following steps:

[0057] S1: Before construction, the anchoring structure 6 is used to lift the front end of the hanging basket body 3;

[0058] S2: Installation of the retraction device: Construct retraction tracks 1 and traveling trolleys 2 on both sides of the hanging basket body 3; install a through-type jack at the front end of the hanging basket body 3.

[0059] S3: Release the connection between the traction structure and the guide structure, and release the front anchoring structure 6 and other anchoring structures that anchor the hanging basket body 3.

[0060] S4: The through-hole jack pushes the hanging basket body 3 backward, so that the traveling trolley 2 travels along the backward track 1 and the traveling track 4;

[0061] S5: As the hanging basket body 3 moves backward, the traveling trolley 2 at the front end of the backward movement is gradually removed, and a traveling trolley 2 connected to the traveling track 4 is installed at the front end of the traveling movement of the hanging basket body 3. This process is repeated until the hanging basket body 3 moves backward to the lifting position.

[0062] In order to maintain the stability of the hanging basket body 3 when installing the retracting track 1 and the traveling trolley 2, the front end of the hanging basket body 3 is lifted by the front anchoring structure 6 before installing the retracting track 1, so that the hanging basket body 3 is stably suspended below the poured beam segment 5, which facilitates the removal of the traction structure and the installation of the retracting track 1, the traveling trolley 2 and the through-hole jack.

[0063] In step 1, the front anchoring structure 6 is located on both sides of the hanging basket body 3. The front anchoring structure 6 includes an anchoring distribution plate 61 installed on one side of the hanging basket body 3, an anchoring seat 62 set on the top surface of the cast-in-place beam segment 5, and several second fine-rolled threaded steel bars 63 pulled in front of the anchoring distribution plate 61 and the anchoring seat 62. By using the second fine-rolled threaded steel bars 63 to pass between the anchoring distribution plate 61 and the anchoring seat 62, the front end of the hanging basket body 3 can be quickly lifted.

[0064] In step 2, during installation, the retraction track 1 is connected to the existing travel track 4 on the hanging basket body 3, ensuring that the retraction track 1 and travel track 4 are in a horizontal straight line. Both the travel track 4 and the retraction track 1 use I-beams. When cutting the I-beams for the retraction track 1, first measure the distance between the end of the travel track 4 and the other end of the hanging basket body 3 to obtain the usable distance of the retraction track 1. Then, based on this usable distance, add a temporary suspension distance of 50-100cm to allow the traveling trolley 2 at the front of the retraction to temporarily suspend the hanging basket body 3, ensuring the stability of the hanging basket body 3 and facilitating the installation of the new traveling trolley 2 at the front of the hanging basket body 3 by the construction personnel inside the hanging basket body 3. After the traveling trolley 2 at the front of the traveling body 3 is installed, the through-hole jack pushes the hanging basket body 3 to continue retraction, and the above operation is repeated until the hanging basket body 3 is retracted to the initial lifting position at block 0. Then, the hanging basket body 3 is lowered, facilitating the quick and safe dismantling of the hanging basket body 3 when it cannot be directly lowered.

[0065] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A front-support hanging basket retraction device, characterized in that: include: Two backward tracks (1) are provided, and the two backward tracks (1) are respectively connected to the walking track (4), and are in a horizontal straight line with the walking track (4) they are connected to. The traveling trolley (2) is anchored to the bottom of the cast beam segment (5). The traveling trolley (2) is connected to the retracting track (1) and can travel on the retracting track (1) and the traveling track (4). A through-type jack is set on the hanging basket body (3) and located at the front end of the thrust structure. It is used to push the thrust block (31) on the hanging basket body (3) to push the hanging basket body (3) to gradually move backward. The end of the retracting track (1) away from the walking track (4) protrudes from the end of the hanging basket body (3); at least three walking trolleys (2) are provided on each side, and at least three walking trolleys (2) are located at the rear end, middle and front end of the hanging basket body (3) respectively; The traveling trolley (2) includes a trolley body (21) for connecting with the retracting track (1) and the traveling track (4) and an anchor plate (22) anchored to one side of the cast beam segment (5), the top of the trolley body (21) being hinged to the anchor plate (22).

2. The front fulcrum hanging basket retraction device according to claim 1, characterized in that: The two traveling trolleys (2) suspended at both ends of the hanging basket body (3) are both located at the bisection of the distance between the traveling trolley (2) in the middle of the hanging basket body (3) and the end of the hanging basket body (3).

3. The front fulcrum hanging basket retraction device according to claim 1, characterized in that: The anchor plate (22) includes a main anchor plate (221) fixed to one side of the cast beam segment (5) by bolts (23) and a secondary anchor plate (222) vertically fixed to one side of the main anchor plate (221). The secondary anchor plate (222) and the cast beam segment are suspended and anchored by a number of first fine-rolled threaded steel bars (24).

4. The front fulcrum hanging basket retraction device according to claim 3, characterized in that: The walking track (4) and the reversing track (1) are both I-beams fixed on the hanging basket body (3). The trolley body (21) includes a connecting part (211), a main frame (212), and two sets of tank wheels (213) rotatably connected in the main frame (212). The main frame (212) forms an installation space (2121) for the I-beam to extend into so as to engage with the vertical plate of the I-beam. The two tank wheels (213) are located on both sides of the I-beam.

5. A method for retracting a front-support hanging basket, comprising using the front-support hanging basket retraction device as described in any one of claims 1-4, characterized in that: Includes the following steps: S1: Before construction, the anchoring structure (6) is used to lift the front end of the hanging basket body (3); S2: Installation of the retraction device: Construct retraction tracks (1) and traveling trolleys (2) on both sides of the hanging basket body (3); Install a through-hole jack at the front end of the hanging basket body (3); S3: Release the connection between the traction structure and the guide structure, and release the front anchoring structure (6) and other anchoring structures that anchor the hanging basket body (3); S4: The through-hole jack pushes the hanging basket body (3) backward, so that the traveling trolley (2) travels along the backward track (1) and the traveling track (4); S5: As the basket body (3) moves backward, the traveling trolley (2) at the front end of the backward movement is gradually removed, and a traveling trolley (2) connected to the traveling track (4) is installed at the front end of the traveling movement of the basket body (3). This process is repeated until the basket body (3) moves backward to the lifting position.

6. The method for retracting a front-support hanging basket according to claim 5, characterized in that: In step 1, the front anchoring structure (6) is located on both sides of the hanging basket body (3). During construction, the anchoring distribution plate (61) is fixed on one side of the hanging basket body (3), and the anchoring seat (62) is installed on the top surface of the cast beam segment (5). Several second fine-rolled threaded steel bars (63) are used to pass through the cast beam segment (5) to pull the second fine-rolled threaded steel bars (63) between the anchoring distribution plate (61) and the anchoring seat (62).

7. The method for retracting the front fulcrum hanging basket according to claim 5, characterized in that: In step 2, the end of the retracting track (1) that is away from the traveling track (4) extends out of the hanging basket body (3); In step 5, when the traveling trolley (2) located at the front of the backward movement reaches the end of the backward track (1), a new traveling trolley (2) is first installed at the front of the movement, and then the traveling trolley (2) located at the front of the backward movement is removed.

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