Freely retractable box beam prefabricated formwork skeleton structure and construction method thereof

Abstract

The present invention belongs to the technical field of box girder prefabricated formwork, and in particular relates to a freely retractable box girder prefabricated formwork skeleton structure and a construction method thereof. The present invention arranges a hydraulic cylinder, a vertical support frame, an inner lining plate unit, a fixed rod unit, a telescopic rod unit, and a screw-connected sleeve unit on an adjustable slide unit, thereby: 1. The overall length of the vertical support frame is flexibly adjustable, and an inner lining plate unit of the same adjustable length is adapted thereto, ensuring that the formwork skeleton structure can be constructed to obtain small box girders of different length specifications; 2. The adjustable slide unit can adjust the slide rail angle and fine-tune the inclination angle of the vertical support frame, making the box girder prefabricated formwork more applicable.

Description

Technical Field

[0001] The invention belongs to the technical field of box beam prefabricated formwork, and in particular relates to a freely retractable box beam prefabricated formwork skeleton structure and a construction method thereof. Background Art

[0002] The span range of small box girder structure is generally 20-40m, so the construction method of prefabricated formwork is very suitable for it. This method has the advantages of relatively simple construction and relatively low cost.

[0003] Existing prefabrication methods for small box girders typically incorporate automated hydraulic support devices in addition to traditional steel formwork, enabling the assembly and disassembly of the formwork. This process not only effectively controls the formwork assembly and disassembly processes, shortening construction time and reducing labor intensity, but also improves the overall quality of the prefabricated small box girders. The steel formwork combined with the automated hydraulic support devices constitutes the main structure of the prefabricated formwork, which can be referred to as the prefabricated formwork skeleton.

[0004] The Chinese utility model patent with patent announcement number CN217318472U and announcement date 2022.08.30 discloses a tie-rod-free prefabricated hydraulic box girder formwork for highways, including two groups of outer frames and a base, each group of outer frames includes multiple outer frames arranged in parallel, the two groups of outer frames are arranged opposite to each other, and the base is arranged between the two outer frames; side linings are respectively provided on the opposite sides of the two groups of outer frames, and a bottom lining is provided on the top of the base, and the side linings and the bottom linings form a cavity with an isosceles trapezoidal cross-section that is larger at the top and smaller at the bottom; the side linings are fixed on multiple sliders, and the sliders are arranged on the slide, and the slide is arranged perpendicular to the cavity. Each slider is connected to the corresponding slide through a hydraulic cylinder, one end of the hydraulic cylinder is hinged to the slider, and the other end of the hydraulic cylinder is hinged to the slide.

[0005] The general structural principle of the hydraulic box beam formwork in this utility model patent is as follows:

[0006] Side lining plates are respectively provided on the opposite sides of the two sets of outer frames, and a bottom lining plate is provided on the top of the base. The side lining plates and the bottom lining plate enclose a cavity with an isosceles trapezoidal cross section that is larger at the top and smaller at the bottom.

[0007] The side linings are fixed on multiple sliders, which are arranged on slides. The slides are arranged perpendicular to the cavity. Each slider is connected to the corresponding slide through a hydraulic cylinder. One end of the hydraulic cylinder is hinged to the slider, and the other end of the hydraulic cylinder is hinged to the slide. Multiple support rods are respectively connected to the opposite surfaces of the two side linings.

[0008] Finally, the closing and opening of the liner can be carried out stably, and the support stability of the template is sufficient.

[0009] However, the hydraulic box girder template has at least the following two deficiencies during actual construction and use, which are, in other words, the technical problems to be solved by the present invention.

[0010] 1. Its lining structure lacks a suitable longitudinal length adjustment function. When the size of the cast beam changes, the original formwork cannot be reused, and the hydraulic system needs to be re-arranged, resulting in low utilization rate of the hydraulic formwork, high cost, and long reassembly time.

[0011] 2. The sliding seat structure cannot adjust the tilt angle, which reduces the application range of the template and greatly reduces its flexibility of use.

[0012] Therefore, in summary, there is an urgent need for a new formwork skeleton structure in which the longitudinal length of the lining plate can be freely telescopically adjusted and the inclination angle of the slide seat can also be adjusted for prefabricated box girders. Summary of the Invention

[0013] The present invention provides a freely retractable box girder prefabricated formwork skeleton structure, which can achieve the following by arranging a hydraulic cylinder, a vertical support frame, an inner lining plate unit, a fixed rod unit, a telescopic rod unit, and a screw-connected sleeve unit on an adjustable slide unit: 1. The overall length of the vertical support frame is flexibly adjustable, and an inner lining plate unit with the same adjustable length is adapted thereto, thereby ensuring that the formwork skeleton structure can be constructed to obtain small box girders of different length specifications; 2. The adjustable slide unit can adjust the slide rail angle and fine-tune the inclination angle of the vertical support frame, thereby making the application range of the box girder prefabricated formwork wider.

[0014] In addition, the present invention also provides a construction method for the above-mentioned box beam prefabricated formwork skeleton structure, which includes the following steps in sequence: design and selection of the longitudinal length of the skeleton structure, installation of the vertical support frame, installation of the adjustable slide unit, and adjustment of the lateral width of the skeleton structure.

[0015] The technical solution adopted by the present invention to solve the above problems is: a freely retractable box beam prefabricated formwork skeleton structure, including a hydraulic cylinder and a vertical support frame, and also including an inner lining plate unit arranged on all the vertical support frames, a fixed rod unit or a telescopic rod unit arranged on two pairs of the vertical support frames, an adjustable slide unit arranged on the fixed rod unit and equipped with the hydraulic cylinder, and a threaded sleeve unit arranged on the adjustable slide unit and used to lift and fix the vertical support frame.

[0016] A further preferred technical solution is that the inner lining plate unit includes a bent main plate arranged on a pair of the vertical support frames, and a bent sub-plate arranged between the bent main plates.

[0017] A further preferred technical solution is that the inner lining plate unit also includes longitudinal stiffening plates arranged on the bent main plate and the bent sub-plate, openings arranged on the longitudinal stiffening plates and used to snap into the vertical support frame, and connecting blocks arranged at the end positions of the two longitudinal stiffening plates.

[0018] A further preferred technical solution is that the longitudinal length of the bent main plate is 3.5, 4.0 or 5.0 m; and the longitudinal length of the bent sub-plate is 0.3, 0.5 or 1.0 m.

[0019] A further preferred technical solution is that the fixed rod unit includes an inner round rod and an outer rod arranged on two pairs of vertical support frames and used to connect the adjustable slide unit, and an upper connecting rod arranged on the two pairs of vertical support frames, and the inner round rod is hinged to the hydraulic cylinder.

[0020] A further preferred technical solution is that the telescopic rod unit includes an X-shaped double rod provided on the two vertical support frames in a pair and hinged in the middle thereof, and a lower sleeve provided on the two vertical support frames in a pair.

[0021] A further preferred technical solution is that the adjustable slide unit includes a U-shaped base plate, two slide rails hingedly arranged at one end on the U-shaped base plate, a slider arranged on the slide rail, a fixing ring arranged on the inner end of the slider and sleeved with the inner round rod, a vertical support column arranged on the outer end of the slider, an open hole fine-tuning plate arranged on the outer rod and sleeved with the vertical support column, and an adjusting nut arranged on the vertical support column and used to support the open hole fine-tuning plate.

[0022] A further preferred technical solution is that the threaded sleeve unit includes an internally threaded rotating cylinder arranged on the side of the U-shaped base plate, a movable ring sleeved on the inner round rod, a second internally threaded cylinder arranged on the movable ring, and supporting studs arranged on the internally threaded rotating cylinder and the second internally threaded cylinder.

[0023] A further preferred technical solution is that: the adjustable slide unit further includes a side groove provided on the U-shaped bottom plate; the threaded sleeve unit further includes a transverse rod provided on the internally threaded rotating cylinder and used for inserting into the side groove.

[0024] A further preferred technical solution is that the adjustable slide unit also includes an upper opening arranged on the side groove; the threaded sleeve unit also includes a vertical screw hole arranged on the transverse rod, and a lifting stud arranged on the vertical screw hole and the upper opening and used to support the slide rail.

[0025] The construction method of the freely retractable box beam prefabricated formwork skeleton structure comprises the following steps in sequence:

[0026] S1. Design and selection of the longitudinal length of the skeleton structure: Determine the number of vertical support frames, fixed rod units, and telescopic rod units, as well as the number and length specifications of the inner lining plate units, based on the actual length of the prefabricated small box beam;

[0027] S2. Installation of vertical support frames: Install the fixed rod units or telescopic rod units on the two paired vertical support frames, and lay the inner lining plate units, ultimately forming two bilaterally symmetrical prefabricated formwork groups;

[0028] S3. Installation of the adjustable slide unit: The adjustable slide unit is first adjusted to its own tilt angle by the threaded sleeve unit, and then the fixed rod unit and the hydraulic cylinder are installed on the adjustable slide unit;

[0029] S4. Adjust the lateral width of the skeleton structure; push the hydraulic cylinder inward until the distance between the two prefabricated template groups reaches the required width for mold closing. At this time, the vertical support frame is fixed with the threaded sleeve unit, and the hydraulic cylinder can be withdrawn, and the entire construction operation of the prefabricated template skeleton structure is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the present invention.

[0031] Figure 2 Schematic diagram of the position structure of the fixed rod unit in the present invention.

[0032] Figure 3 Schematic diagram of the positions of the fixed rod unit and the telescopic rod unit in the present invention.

[0033] Figure 4 Schematic diagram of the position structure of the telescopic rod unit in the present invention.

[0034] Figure 5 This is a schematic diagram of the position structure of the lining plate unit in the present invention.

[0035] Figure 6 This is a schematic diagram of the position structure of the opening and the connecting block in the present invention.

[0036] Figure 7 Schematic diagram of the position structure of the adjustable slide unit in the present invention.

[0037] Figure 8 Schematic diagram of the position and shape of the fixed ring and the movable ring in the present invention from a top view.

[0038] Figure 9 Schematic diagram of the position and shape of the U-shaped bottom plate in the present invention from a top view.

[0039] Figure 10 It is a schematic diagram of the position structure of the threaded sleeve unit in the present invention from a top view.

[0040] Figure 11 Schematic diagram of the position and shape of the lifting stud in the present invention.

[0041] Figure 12 Schematic diagram of the use of the support plate in the present invention.

[0042] In the figure, the meanings of the marks are as follows:

[0043] Support plate a, small box beam b;

[0044] Hydraulic cylinder 1, vertical support frame 2;

[0045] Inner lining plate unit 3, fixed rod unit 4, telescopic rod unit 5, adjustable slide unit 6, threaded sleeve unit 7;

[0046] Bending main plate 301, bending sub-plate 302, longitudinal stiffening plate 303, opening 304, connecting block 305, inner round rod 401, outer rod 402, upper connecting rod 403, X-shaped double rod 501, lower sleeve 502, U-shaped bottom plate 601, slide rail 602, slider 603, fixing ring 604, vertical support column 605, opening fine-tuning plate 606, adjusting nut 607, internal threaded rotating cylinder 701, movable ring 702, second internal threaded cylinder 703, support stud 704, side groove 608, transverse rod 705, upper opening 609, vertical screw hole 706, lifting stud 707. DETAILED DESCRIPTION

[0047] The following description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention.

[0048] As attached Figure 1-12 As shown, the freely retractable box girder prefabricated formwork skeleton structure includes a hydraulic cylinder 1 and a vertical support frame 2, and also includes an inner lining plate unit 3 arranged on all the vertical support frames 2, a fixed rod unit 4 or a telescopic rod unit 5 arranged on two pairs of the vertical support frames 2, an adjustable slide unit 6 arranged on the fixed rod unit 4 and provided with the hydraulic cylinder 1, and a threaded sleeve unit 7 arranged on the adjustable slide unit 6 and used to lift and fix the vertical support frame 2.

[0049] In this embodiment, the installation structure and use method of the hydraulic cylinder 1 and the vertical support frame 2 are all carried out in accordance with the existing technology, namely:

[0050] Both ends of the hydraulic cylinder 1 are hinged, and the vertical support frame 2 is on one side of the small box beam b in an inverted trapezoidal shape, forming a stable lateral support structure, that is, serving as the outer support structure of the inner lining plate unit 3 and as the force application object of the hydraulic cylinder 1.

[0051] In addition, the main body material of the inner lining plate unit 3 is thin steel plate, and is divided into multiple specifications according to different longitudinal lengths, ensuring that the skeleton structure with freely retractable and adjustable longitudinal length is always fully covered by the inner lining plate unit 3. In this process, it is only necessary to select the inner lining plate unit 3 of the appropriate number and specifications.

[0052] In addition, the adjustable slide unit 6 provides a stable and adjustable "slope" for the skeleton structure, ensuring that the inner lining plate unit 3 has the advantage of flexible selection of multi-angle styles when the mold is finally closed.

[0053] Finally, there is the threaded sleeve unit 7, which is stuck in the inclined downward retracting direction of the vertical support frame 2. Therefore, as long as the structure of the threaded sleeve unit 7 is not broken, the mold closing state of the skeleton structure is stable, and the hydraulic cylinder 1 can also be completely withdrawn during this period, which is very efficient and economical.

[0054] The inner lining plate unit 3 includes a bent main plate 301 arranged on the pair of vertical support frames 2 and a bent sub-plate 302 arranged between the bent main plates 301 .

[0055] In this embodiment, the vertical cross-sectional shapes of the bent main plate 301 and the bent sub-plate 302 are exactly the same, and the only difference between the two is the longitudinal length. The longitudinal length of the skeleton structure can be freely extended and retracted, which corresponds to the specific design and selection of the respective quantities of the bent main plate 301 and the bent sub-plate 302.

[0056] In addition, the bent main plate 301 and the bent sub-plate 302 include at least one side edge with an inwardly inclined lower end and a bottom edge. The "inside" here refers to the direction in which the two templates approach each other, that is, the direction close to the small box beam b.

[0057] The inner lining plate unit 3 also includes a longitudinal stiffening plate 303 arranged on the bent main plate 301 and the bent sub-plate 302, an opening 304 arranged on the longitudinal stiffening plate 303 and used to be inserted into the vertical support frame 2, and a connecting block 305 arranged at the end position of each pair of the longitudinal stiffening plates 303.

[0058] In this embodiment, the longitudinal stiffening plate 303 is made of channel steel, which is welded to a thin steel plate and then engaged with the vertical support frame 2 through the opening 304 and then welded or screwed to ensure that the bent main board 301 can be stably installed on the vertical support frame 2.

[0059] There is no supporting structure below the bending sub-plate 302 , so the opening 304 may not be provided on the longitudinal stiffening plate 303 of the bending sub-plate 302 . However, the connecting block 305 is particularly important, and its functions include at least the following two points.

[0060] First, the bent sub-plate 302 is indirectly mounted on the vertical support frame 2 , otherwise it does not have sufficient lateral inward supporting strength.

[0061] Second, the vertical support frame 2 provided with the telescopic rod unit 5 may not be provided with the adjustable slide unit 6. Therefore, the connection relationship between the longitudinal stiffening plates 303 can also be connected to the entire vertical support frame 2 without the adjustable slide unit 6, so that all the vertical support frames 2 can be "integrated into one".

[0062] In addition, the connecting block 305 can be a welding block, or a channel steel of the same shape that is welded, snap-fitted, or screwed to the longitudinal stiffening plate 303 .

[0063] The longitudinal length of the bent main plate 301 is 3.5, 4.0 or 5.0 m; the longitudinal length of the bent sub-plate 302 is 0.3, 0.5 or 1.0 m.

[0064] In this embodiment, the two vertical support frames 2 are matched with the fixed rod unit 4, and the total longitudinal length is 3.0m. The two vertical support frames 2 are matched with the telescopic rod unit 5, and the total longitudinal length is 3.0-4.5m, ensuring that the length of the bent main board 301 is not too large on the support structure of the former and the latter. When matched with the bent sub-board 302 of appropriate length, it can be ensured that the skeleton structure can provide template styles with a variety of total length specifications.

[0065] Among them, at most one bending sub-plate 302 is arranged between the two bending main plates 301 to avoid an unstable installation structure of the bending sub-plate 302 , since there is no supporting structure on the bending sub-plate 302 .

[0066] The fixed rod unit 4 includes an inner round rod 401 and an outer rod 402 arranged on the two paired vertical support frames 2 and used to connect the adjustable slide unit 6, and an upper connecting rod 403 arranged on the two paired vertical support frames 2, and the inner round rod 401 is hinged to the hydraulic cylinder 1.

[0067] In this embodiment, the cross-sectional shapes of the outer rods 402 and the upper connecting rods 403 can be round or square, and no hinge relationship is required. The number of the upper connecting rods 403 is 4-8 to ensure sufficient longitudinal connection strength.

[0068] The ends of the fixed rod unit 4 and the telescopic rod unit 5 may all be welded or screwed.

[0069] The telescopic rod unit 5 includes an X-shaped double rod 501 which is arranged on the two vertical support frames 2 in a pair and hinged at the middle part thereof, and a lower sleeve 502 which is arranged on the two vertical support frames 2 in a pair.

[0070] In this embodiment, the X-shaped double rod 501 is a rectangular plate with two center holes, which are plugged together with a fixed axis to provide an adjustable longitudinal support size. The lower sleeve 502 includes an internal threaded barrel, a screw, and a limit nut to ensure that the above-mentioned adjustable longitudinal support structure is limited and fixed.

[0071] The adjustable slide unit 6 includes a U-shaped base plate 601, two slide rails 602 hinged at one end on the U-shaped base plate 601, a slider 603 arranged on the slide rail 602, a fixing ring 604 arranged on the inner end of the slider 603 and sleeved with the inner round rod 401, a vertical support column 605 arranged on the outer end of the slider 603, an opening fine-tuning plate 606 arranged on the outer rod 402 and sleeved with the vertical support column 605, and an adjusting nut 607 arranged on the vertical support column 605 and used to support the opening fine-tuning plate 606.

[0072] In this embodiment, the longitudinal dimension of the adjustable slide unit 6 is smaller than the inner round rod 401 , and a single inner round rod 401 corresponds to two hydraulic cylinders 1 , that is, two slide rails 602 .

[0073] In addition, the cross-section of the slider 603 is an inverted U-shape, and the slider 603 is connected to the inner round rod 401 and even the entire vertical support frame 2 as a whole through the fixing ring 604.

[0074] Finally, the vertical support column 605, the perforated fine-tuning plate 606, and the adjusting nut 607 serve as the mechanism for fine-tuning the tilt angle of the vertical support frame 2. Specifically, when the adjusting nut 607 is properly lowered, the outer side of the vertical support frame 2 can tilt slightly downward. Of course, the vertical support frame 2 is not, and cannot be, absolutely rigid at this point, so the above-mentioned fine-tuning function is effective.

[0075] The threaded sleeve unit 7 includes an internally threaded rotating cylinder 701 arranged on the side of the U-shaped base plate 601, a movable ring 702 sleeved on the inner round rod 401, a second internally threaded cylinder 703 arranged on the movable ring 702, and a supporting stud 704 arranged on the internally threaded rotating cylinder 701 and the second internally threaded cylinder 703.

[0076] In this embodiment, the threaded sleeve unit 7 is pushed in the inclined downward retracting direction of the vertical support frame 2. Therefore, as long as the threaded structure at both ends of the support stud 704 is effective, the threaded sleeve unit 7 can replace the hydraulic cylinder 1 to support the vertical support frame 2, so that the hydraulic cylinder 1 does not need to be maintained for a long time after being lifted up, which is very efficient and economical.

[0077] Among them, after the vertical support frame 2 is lifted up to the preset position, the internal threaded rotating cylinder 701 is first aligned with the second internal threaded cylinder 703, and the support stud 704 is then screwed out on the internal threaded rotating cylinder 701, and then partially screwed into the second internal threaded cylinder 703, ensuring that the entire inclined support structure is stable and immobile.

[0078] The adjustable slide unit 6 further includes a side groove 608 provided on the U-shaped bottom plate 601 ; the threaded sleeve unit 7 further includes a transverse rod 705 provided on the internally threaded rotating cylinder 701 and used for inserting into the side groove 608 .

[0079] In this embodiment, the transverse rod 705 is fixed to the side of the internal thread rotating cylinder 701 and then plugged into the side groove 608 to ensure that the internal thread rotating cylinder 701 can rotate to align with the second internal thread cylinder 703 which can also rotate.

[0080] The adjustable slide unit 6 also includes an upper opening 609 arranged on the side groove 608; the threaded sleeve unit 7 also includes a vertical screw hole 706 arranged on the transverse rod 705, and a lifting stud 707 arranged on the vertical screw hole 706 and the upper opening 609 and used to support the slide rail 602.

[0081] In this embodiment, the lifting studs 707 can both support the slide rails 602 and prevent the transverse rods 705 from accidentally sliding out or falling off.

[0082] In addition, there is a vertically aligned slot below the upper opening 609, so that the lifting adjustment range of the lifting stud 707 is larger, that is, the optional tilt range of the slide rail 602 is larger.

[0083] The construction method of the freely retractable box beam prefabricated formwork skeleton structure comprises the following steps in sequence:

[0084] S1. Design and selection of the longitudinal length of the skeleton structure: Determine the number of the vertical support frames 2, fixed rod units 4 and telescopic rod units 5, as well as the number and length specifications of the inner lining plate units 3 based on the actual length of the prefabricated small box beam;

[0085] S2. Installation of vertical support frames: Install the fixed rod unit 4 or the telescopic rod unit 5 on the two paired vertical support frames 2, and lay the inner lining plate unit 3, finally forming two bilaterally symmetrical prefabricated template groups;

[0086] S3. Installation of the adjustable slide unit: The adjustable slide unit 6 is first adjusted to its own tilt angle through the threaded sleeve unit 7, and then the fixed rod unit 4 and the hydraulic cylinder 1 are installed on the adjustable slide unit 6;

[0087] S4. Adjust the lateral width of the skeleton structure; push the hydraulic cylinder 1 inward until the distance between the two prefabricated template groups reaches the required width for mold closing. At this time, use the threaded sleeve unit 7 to fix the vertical support frame 2, and the hydraulic cylinder 1 can be withdrawn, and the entire construction operation of the prefabricated template skeleton structure is completed.

[0088] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the aforementioned embodiments. Various modifications are possible within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. These modifications are non-inventive and are protected by patent law as long as they fall within the scope of the claims of the present invention.

Claims

1. A freely retractable box beam prefabricated formwork skeleton structure, comprising a hydraulic cylinder (1) and a vertical support frame (2), characterized in that: It also includes an inner lining plate unit (3) provided on all the vertical support frames (2), a fixed rod unit (4) or a telescopic rod unit (5) provided on two of the paired vertical support frames (2), an adjustable slide unit (6) provided on the fixed rod unit (4) and equipped with the hydraulic cylinder (1), and a threaded sleeve unit (7) provided on the adjustable slide unit (6) and used for lifting and fixing the vertical support frames (2). The fixed rod unit (4) comprises an inner round rod (401) and an outer rod (402) provided on the two paired vertical support frames (2) and used to connect the adjustable slide unit (6), and an upper connecting rod (403) provided on the two paired vertical support frames (2), wherein the inner round rod (401) is hinged to the hydraulic cylinder (1). The adjustable slide unit (6) comprises a U-shaped base plate (601), two slide rails (602) hingedly arranged at one end on the U-shaped base plate (601), a slider (603) arranged on the slide rail (602), a fixing ring (604) arranged on the inner end of the slider (603) and sleeved with the inner round rod (401), a vertical support column (605) arranged on the outer end of the slider (603), an opening fine-tuning plate (606) arranged on the outer rod (402) and sleeved with the vertical support column (605), and an adjusting nut (607) arranged on the vertical support column (605) and used to support the opening fine-tuning plate (606).

2. The freely retractable box beam prefabricated formwork skeleton structure according to claim 1 is characterized in that: The inner lining plate unit (3) comprises a bent main plate (301) arranged on a pair of the vertical support frames (2), and a bent sub-plate (302) arranged between the bent main plates (301).

3. The freely retractable box beam prefabricated formwork skeleton structure according to claim 2 is characterized in that: The inner lining plate unit (3) further comprises longitudinal stiffening plates (303) arranged on the bent main plate (301) and the bent auxiliary plate (302), openings (304) arranged on the longitudinal stiffening plates (303) and used for snapping into the vertical support frame (2), and connecting blocks (305) arranged at the ends of the longitudinal stiffening plates (303).

4. The freely retractable box beam prefabricated formwork skeleton structure according to claim 2 is characterized in that: The longitudinal length of the bent main plate (301) is 3.5 m, 4.0 m, or 5.0 m; the longitudinal length of the bent secondary plate (302) is 0.3 m, 0.5 m, or 1.0 m.

5. The freely retractable box beam prefabricated formwork skeleton structure according to claim 1 is characterized in that: The telescopic rod unit (5) comprises an X-shaped double rod (501) which is arranged on the two vertical support frames (2) in a pair and hinged at its middle portion, and a lower sleeve (502) which is arranged on the two vertical support frames (2) in a pair.

6. The freely retractable box beam prefabricated formwork skeleton structure according to claim 1 is characterized in that: The threaded sleeve unit (7) comprises an internally threaded rotating cylinder (701) arranged on the side of the U-shaped bottom plate (601), a movable ring (702) sleeved on the inner round rod (401), a second internally threaded cylinder (703) arranged on the movable ring (702), and supporting studs (704) arranged on the internally threaded rotating cylinder (701) and the second internally threaded cylinder (703).

7. The freely retractable box beam prefabricated formwork skeleton structure according to claim 6 is characterized in that: The adjustable slide unit (6) further includes a side groove (608) provided on the U-shaped bottom plate (601); the threaded sleeve unit (7) further includes a transverse rod (705) provided on the internally threaded rotating cylinder (701) and used for inserting into the side groove (608).

8. The freely retractable box beam prefabricated formwork skeleton structure according to claim 7 is characterized in that: The adjustable slide unit (6) further includes an upper opening (609) provided on the side groove (608); the threaded sleeve unit (7) further includes a vertical screw hole (706) provided on the transverse rod (705), and a lifting screw (707) provided on the vertical screw hole (706) and the upper opening (609) and used to support the slide rail (602).

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