Closed inner form suitable for small box girder

Abstract

The application discloses a closed inner mold suitable for small box girders, which comprises a first side mold assembly, a second side mold assembly, a track control mechanism and a telescopic assembly. The track control mechanism is used for connecting the first side mold assembly and the second side mold assembly into a whole, and can make the two relatively close or open along a set track. The telescopic assembly is used for driving the first side mold assembly and the second side mold assembly to close into a closed inner mold shape when being opened, and realizing that the whole cross section is smaller than the beam end outlet when the inner mold is contracted and closed. The application has the advantages of stable structure, large inner cavity operation space, simple construction, economy and practicality and the like, solves the problem that the existing small box girder inner mold cannot install a formwork in some areas, further solves the problem that manual pouring and troweling are needed after demolding, and significantly improves the construction efficiency of the box girder.

Description

Technical Field

[0001] This invention belongs to the technical field of box girder internal molds for bridges, specifically relating to a closed internal mold suitable for small box girders. Background Technology

[0002] The box girder has a hollow cavity inside. During prefabrication, an inner mold needs to be embedded inside the box girder, and the mold is removed after the concrete is poured. The end outlet of the girder has a smaller cross-section than the inner cavity, so the formwork needs to be shrunk significantly before demolding.

[0003] Existing technology assembles the template into single segments. The top two templates are demolded by two vertical hydraulic cylinders pulling the top and bottom templates, while the left and right side templates are demolded by horizontally positioned retraction hydraulic cylinders. A lifting hydraulic cylinder and a sliding block are located in the center of the bottom. After demolding, the template is lifted and then removed via the sliding block. This solution has the following problems:

[0004] 1. Due to the presence of the sliding block, the template cannot be fully enclosed, and personnel still need to enter the base plate for finishing.

[0005] 2. The internal space of the small box girder is small, especially the bottom plate space, which is very narrow. The bottom width of the exit at the end of the beam is usually less than 500mm. After deducting the space occupied by the formwork, the setting of the lifting cylinder and slide will make the internal space even narrower during actual operation. When the formwork shrinks, it is easy to cause interference, resulting in inconvenience in demolding.

[0006] 3. The sliding block occupies the space of the base plate, which greatly limits the lateral movement of the templates on both sides. In many beam types with small end outlet sections, it is impossible to achieve the purpose of demolding.

[0007] In addition, existing technologies also mention a solution to remove the middle lifting cylinder to increase the inner mold's movement space, but the template still cannot be installed in some areas of the inner cavity bottom plate, and the empty parts still need to be manually poured and plastered.

[0008] To address the issue of needing to separately pour and finish the bottom of the inner formwork for small box girders, existing technologies have mentioned assembling the inner formwork by connecting two templates at both ends. However, because the bottoms of the two templates support each other, demolding requires first demolding one side of the inner formwork and removing it with a winch, followed by demolding the other side. While this method solves the problem of a fully enclosed inner formwork, the separate demolding of the left and right sides means that each inner formwork is relatively independent. Each time it is installed, the two sides must be connected and fixed with bolts or other connectors, and then the connectors must be removed during demolding. This results in a very large workload for workers, and the extremely confined space within the inner formwork makes operation very difficult. Summary of the Invention

[0009] This invention provides a closed inner mold suitable for small box girders, which is simple in structure, easy to install and disassemble, economical and practical, has a large internal operating space, and is easy to construct. It solves the problems of the bottom plate mold requiring manual finishing and the inability of the two side templates of the inner mold to be demolded at the same time in the prior art.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] A closed inner mold suitable for small box girders includes: a first side mold assembly, a second side mold assembly, a trajectory control mechanism, and a telescopic assembly; the trajectory control mechanism is used to connect the first side mold assembly and the second side mold assembly into a whole, and can make the two close or open relative to each other along a set trajectory; the telescopic assembly is used to drive the first side mold assembly and the second side mold assembly to open and close; when the inner mold is open, it forms a closed inner mold shape, and when it is contracted and closed, the entire cross-section is smaller than the beam end outlet.

[0012] As a further improvement of the present invention, the trajectory control mechanism includes a connecting rod, a first hinge seat mounted on the first side mold assembly, and a second hinge seat mounted on the second side mold assembly. Both the first hinge seat and the second hinge seat are double-hole hinge seats. The first hinge seat, the second hinge seat, and the two connecting rods cooperate with each other to form a four-bar linkage, so as to realize that the first side mold assembly and the second side mold assembly can close or open according to the set trajectory.

[0013] As a further improvement of the present invention, the first side mold assembly includes a first side upper mold and a first side lower mold that are hinged to each other, and a telescopic component for shrinking or opening the first side upper mold is provided between them; the second side mold assembly includes a second side upper mold and a second side lower mold that are hinged to each other, and a telescopic component for shrinking or opening the second side upper mold is provided between them; a telescopic component is connected between the first side lower mold and the second side lower mold to realize the closing or opening of the first side lower mold and the second side lower mold.

[0014] As a further improvement of the present invention, the telescopic assembly includes a first telescopic element, a second telescopic element, and a third telescopic element; the two ends of the first telescopic element are respectively hinged to a first side upper mold and a first side lower mold, for realizing the contraction or opening of the first side upper mold; the two ends of the second telescopic element are respectively hinged to a second side upper mold and a second side lower mold, for realizing the contraction or opening of the second side upper mold; the two ends of the third telescopic element are respectively connected to a first side lower mold and a second side lower mold, for realizing the closing or opening of the first side lower mold and the second side lower mold.

[0015] As a further improvement of the present invention, the upper end of the first side mold assembly is obliquely cut and fitted with the upper end of the second side mold assembly, and the lower end of the first side mold assembly is obliquely cut and fitted with the lower end of the second side mold assembly.

[0016] As a further improvement of the present invention, the second lower side mold includes a side mold and a bottom plate mold, and the side mold and the bottom plate mold can move relative to each other.

[0017] As a further improvement of the present invention, a second hinge seat is installed on the side mold, and the first hinge seat, the second hinge seat and the two connecting rods cooperate with each other to form a first four-bar linkage.

[0018] As a further improvement of the present invention, a third hinge seat is also installed on the base plate mold, and a fourth hinge seat is installed on the side mold. Both the third and fourth hinge seats are double-hole hinge seats. The third and fourth hinge seats and two connecting rods cooperate with each other to form a second four-bar linkage. The four-bar linkage is used to realize the closing or opening of the base plate mold and the side mold according to a preset motion trajectory.

[0019] As a further improvement of the present invention, the motion trajectory of the first four-bar linkage is symmetrical to that of the second four-bar linkage.

[0020] As a further improvement of the present invention, the telescopic component is a hydraulic cylinder, a pneumatic cylinder, an electric push rod, or a folding rod.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] 1. The closed inner mold of the present invention, applicable to small box girders, is structurally stable and easy to construct, composed of a first side mold assembly, a second side mold assembly, a trajectory control mechanism, and telescopic components. The trajectory control mechanism connects the first and second side mold assemblies into an integral structure, allowing them to close or open relative to each other along a set trajectory. By connecting multiple sets of telescopic components to the first and second side mold assemblies, the first and second side mold assemblies, driven by the telescopic components, form a closed inner mold with a large internal operating space when they open. When they close, the entire cross-section of the inner mold is smaller than the beam end outlet, achieving automatic demolding. This solves the problem in the prior art where templates cannot be installed in certain areas of the inner mold of small box girders, and further solves the problem of needing to manually pour and plaster after demolding. This greatly reduces the labor intensity of on-site construction, saves labor hours, ensures the appearance and internal quality of the product, and significantly improves construction efficiency.

[0023] 2. The closed inner mold for small box girders in the preferred embodiment of the present invention avoids interference between the two molds during demolding by setting the connecting end faces of both molds to be obliquely fitted. Furthermore, by setting double-hole hinge seats on both the first and second side mold assemblies, the two double-hole hinge seats are connected to two connecting rods to form a four-bar linkage. The four-bar linkage allows the first and second side mold assemblies to translate along a preset trajectory. When the third telescopic element retracts, it drives the first and second lower molds to translate and close along the preset trajectory of the four-bar linkage. After the mold is closed, the first lower mold retracts to above the second lower mold, avoiding conflict when the two lower molds close. This significantly improves the stability of the inner mold when it is closed. Moreover, the overlapping of the two lower molds greatly saves the cavity space and improves the convenience of subsequent mold moving operations.

[0024] 3. The closed inner mold for small box girders in the preferred embodiment of the present invention is achieved by splitting the second lower mold into a side mold and a bottom plate mold. The bottom plate mold and the side mold can be hinged or obliquely fitted. A double-hole hinge seat is provided on the side mold, and two double-hole hinge seats are provided on the bottom plate mold. A first four-bar linkage is formed between the first lower mold and the bottom plate mold, and a second four-bar linkage is formed between the bottom plate mold and the second lower mold. This enables two sets of four-bar connections between the first lower mold and the second lower mold, ensuring that the first lower mold and the second lower mold retract and close upward along the preset trajectory of the four-bar linkage. This not only helps to avoid positional conflicts when the two lower molds close, but also significantly improves the stability of the inner mold when closing. Furthermore, it provides a larger internal operating space, making it easier for the power traction device to pull out the inner mold as a whole, reducing construction time and improving the overall quality of the box girder. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structural principle of the inner mold in the tension state in Embodiment 1 of the present invention.

[0026] Figure 2 This is a schematic diagram of the structural principle of the first side upper mold in the mold-retracting state in Embodiment 1 of the present invention.

[0027] Figure 3 This is a schematic diagram of the structural principle of the second side upper mold in the mold-retracting state in Embodiment 1 of the present invention.

[0028] Figure 4 This is a schematic diagram of the structural principle of the inner mold in the mold-shrinking state in Embodiment 1 of the present invention.

[0029] Figure 5 This is a schematic diagram of the structural principle of the inner mold in the mold-shrinking state in Embodiment 2 of the present invention.

[0030] Figure 6This is a schematic diagram illustrating the structural principle of the inner mold of the present invention in a stretched state.

[0031] Legend:

[0032] 1. First side mold assembly; 11. First side upper mold; 12. First side lower mold; 2. Second side mold assembly; 21. Second side upper mold; 22. Second side lower mold; 221. Side mold; 222. Base plate mold; 3. Track control mechanism; 31. First hinge seat; 32. Second hinge seat; 33. Connecting rod; 34. Third hinge seat; 35. Fourth hinge seat; 4. Telescopic assembly; 41. First telescopic element; 42. Second telescopic element; 43. Third telescopic element. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0034] Example 1

[0035] like Figures 1 to 4 As shown, this invention is applicable to closed inner molds for box girders with small cross-sectional dimensions, including a first side mold assembly 1, a second side mold assembly 2, a trajectory control mechanism 3, and a telescopic assembly 4. The trajectory control mechanism 3 connects the first side mold assembly 1 and the second side mold assembly 2 into a whole, and allows them to translate relative to each other along a set trajectory to close or open. Multiple sets of telescopic assemblies 4 are respectively arranged above and below the first side mold assembly 1 and the second side mold assembly 2. The telescopic assemblies 4 are used to drive the first side mold assembly 1 and the second side mold assembly 2 to open and close. When the inner mold is open, it forms a closed inner mold shape; when it is closed, the entire cross-section is smaller than the beam end outlet. It should be noted that in this embodiment, the height of the inner mold used for the small box girder is generally no more than 1.5m, the width of the top of the inner mold is about 1m, and the width of the bottom of the inner mold is about 0.5m. Therefore, the operating space provided inside the small box girder is relatively small, making it inconvenient for operators to work inside the small box girder.

[0036] In this embodiment, the first side mold assembly 1, the second side mold assembly 2, the trajectory control mechanism 3, and the telescopic assembly 4 together form a stable and simple inner mold. The trajectory control mechanism 3 connects the first side mold assembly 1 and the second side mold assembly 2 into an integral structure, allowing them to close or open relative to each other along a set trajectory. By connecting multiple sets of telescopic assemblies 4 to the first side mold assembly 1 and the second side mold assembly 2, the first side mold assembly 1 and the second side mold assembly 2, driven by the telescopic assemblies, form a closed inner mold with a large internal operating space when they open. When they close, the entire cross-section of the inner mold is smaller than the beam end outlet, achieving automatic demolding. This solves the problem that some areas of the inner mold of small box girders cannot be installed with templates in the prior art, and further solves the problem that manual pouring and finishing are required after demolding. This greatly reduces the labor intensity of on-site construction, saves labor hours, and ensures the appearance and internal quality of the product, significantly improving the construction efficiency of the box girder.

[0037] like Figure 1 As shown, in this embodiment, the trajectory control mechanism includes a connecting rod 33, a first hinge seat 31 mounted on the first side mold assembly 1, and a second hinge seat 32 mounted on the second side mold assembly 2. Both the first hinge seat 31 and the second hinge seat 32 are double-hole hinge seats. The first hinge seat 31, the second hinge seat 32, and the two connecting rods 33 are hinged together to form a four-bar linkage, enabling the first side mold assembly 1 and the second side mold assembly 2 to close or open according to the trajectory set by the four-bar linkage. It can be understood that in other embodiments, the first hinge seat 31, the second hinge seat 32, and the two connecting rods 33 can also be connected by a sliding groove to form a four-bar linkage.

[0038] In this embodiment, the first side mold assembly 1 includes a first side upper mold 11 and a first side lower mold 12 that are hinged to each other, and a telescopic component 4 for shrinking or opening the first side upper mold 11 is provided between them; the second side mold assembly 2 includes a second side upper mold 21 and a second side lower mold 22 that are hinged to each other, and a telescopic component 4 for shrinking or opening the second side upper mold 21 is provided between them; the lower part of the first side lower mold 12 and the lower part of the second side lower mold 22 are connected by the telescopic component 4 to realize the closing or opening of the first side lower mold 12 and the second side lower mold 22.

[0039] Furthermore, the telescopic assembly 4 includes a first telescopic element 41, a second telescopic element 42, and a third telescopic element 43. The two ends of the first telescopic element 41 are hinged to the first upper mold 11 and the first lower mold 12, respectively, to realize the contraction or opening of the first upper mold 11, thereby completing the demolding and erection of the first upper mold 11. Figure 1As shown, when the first telescopic element 41 drives the first side upper mold 11 to be in the open state, a stable triangular support structure is formed between the first telescopic element 41, the first side upper mold 11 and the first side lower mold 12, which helps to ensure the stability of the inner mold during concrete pouring.

[0040] The two ends of the second telescopic element 42 are hinged to the second upper mold 21 and the second lower mold 22 respectively, to realize the contraction or opening of the second upper mold 21, thereby completing the demolding and erection of the second upper mold 21. Figure 1 As shown, when the second telescopic element 42 drives the second side upper mold 21 to be in the open state, a stable triangular support structure is formed between the second telescopic element 42, the second side upper mold 21, and the second side lower mold 22, which helps to ensure the stability of the inner mold during concrete pouring.

[0041] The two ends of the third telescopic element 43 are hinged to the lower parts of the first lower mold 12 and the second lower mold 22, respectively, to realize the closing or opening of the first lower mold 12 and the second lower mold 22. Figure 1 As shown, when the third telescopic element 43 is in the extended state, a stable triangular support structure is formed between the third telescopic element 43, the first side lower mold 12, and the second side lower mold 22, which helps to ensure the stability of the inner mold during concrete pouring.

[0042] In this embodiment, the first telescopic element 41, the second telescopic element 42, and the third telescopic element 43 are all hydraulic cylinders, which have the advantages of convenient installation and stable transmission. In other embodiments, the first telescopic element 41, the second telescopic element 42, and the third telescopic element 43 can also be in the form of a cylinder, an electric push rod, or a folding rod, as long as it can realize the smooth opening and closing of the first side mold assembly 1 and the second side mold assembly 2.

[0043] like Figure 1 As shown, in this embodiment, the upper end of the first side mold assembly 1 is obliquely fitted to the upper end of the second side mold assembly 2, and the lower end of the first side mold assembly 1 is obliquely fitted to the lower end of the second side mold assembly 2. Specifically, the lower end of the first side upper mold 11 is hinged to the upper end of the first side lower mold 12, the upper end of the first side upper mold 11 is obliquely fitted to the upper end of the second side upper mold 21, the lower end of the second side upper mold 21 is hinged to the upper end of the second side lower mold 22, and the lower end of the first side lower mold 12 is obliquely fitted to the lower end of the second side lower mold 22. Using an obliquely fitted end design helps ensure that there is no interference between the two molds during demolding.

[0044] Furthermore, in this embodiment, a first hinge seat 31 is provided on the inner bottom side of the first lower mold 12, and a second hinge seat 32 is provided on the inner bottom side of the second lower mold 22. The first hinge seat 31 and the second hinge seat 32 are hinged together by a connecting rod 33. Through the transmission action of the connecting rod 33, the first lower mold 12 and the second lower mold 22 can be closed or opened according to a preset trajectory, thereby avoiding mutual interference between the bottom of the first lower mold 12 and the bottom of the second lower mold 22. Furthermore, both the first hinge seat 31 and the second hinge seat 32 are double-hole hinge seats, and the first hinge seat 31, the second hinge seat 32, and the connecting rod 33 form a four-bar linkage.

[0045] In this embodiment, by setting the connecting end faces of both molds to be obliquely fitted, interference between the two molds during demolding is avoided. Furthermore, by providing double-hole hinge seats on the inner bottom sides of both the first lower mold 12 and the second lower mold 22, and hinged to two connecting rods to form a four-bar linkage, the four-bar linkage allows the first lower mold 12 and the second lower mold 22 to translate along a preset trajectory. When the third telescopic element 43 retracts, it drives the first lower mold 12 and the second lower mold 22 to translate and close along the preset trajectory of the four-bar linkage. This also achieves the first lower mold 12 retracting above the second lower mold 22 after mold closing, avoiding conflict during mold closing and significantly improving the stability of the inner mold during closing. Furthermore, the overlapping of the two lower molds greatly saves internal space and improves the convenience of subsequent mold transfer operations.

[0046] The workflow for demolding the closed automatic inner mold in this embodiment is as follows:

[0047] Step S1: The first telescopic element 41 retracts, thereby causing the first side upper mold 11 to contract to... Figure 2 The state shown.

[0048] Step S2: The second telescopic element 42 retracts, thereby causing the second side upper mold 21 to shrink to... Figure 3 The state shown.

[0049] Step S3: The third telescopic element 43 retracts, thereby causing the first lower mold 12 and the second lower mold 22 to move relative to each other. Under the action of the four-bar linkage, the first lower mold 12 slides upward toward the second lower mold 22, eventually closing together as shown. Figure 4 As shown, the overall structure of the inner mold after mold closing is smaller than the beam end outlet. After mold closing, the first side lower mold 12 is located above the second side lower mold 22, which solves the problem of conflict between the two lower molds. Furthermore, the lower molds on both sides overlap, so that when the inner mold shrinks and closes, the entire cross-section is smaller than the beam end outlet, which greatly saves the internal space and makes subsequent mold moving more convenient.

[0050] Step S4: The power traction device (such as a winch) pulls the inner mold out as a whole, completing the demolding of the box girder inner mold.

[0051] Example 2

[0052] like Figure 5 As shown, this invention is applicable to closed inner molds for box girders with small cross-sectional dimensions. It has a similar structural configuration to the inner mold in Embodiment 1, with the main difference being that the second lower side mold 22 includes a side mold 221 and a bottom plate mold 222, which can move relative to each other. Furthermore, the side mold 221 and the bottom plate mold 222 can be hinged or obliquely fitted, and the bottom plate mold 222 and the second lower side mold 22 are obliquely fitted. It can be understood that in other embodiments, the upper and lower molds of the first side mold assembly 1 and the upper and lower molds of the second side mold assembly 2 can be further disassembled into multiple interconnected templates, so that the inner mold after demolding has a smaller volume, while also providing a larger operating space for the inner cavity of the small box girder.

[0053] like Figure 5 As shown, a second hinge seat 32 is installed on the base plate mold 222. The first hinge seat 31, the second hinge seat 32, and the two connecting rods 33 cooperate to form a first four-bar linkage. Further, a third hinge seat 34 is also installed on the base plate mold 222, and a fourth hinge seat 35 is installed on the side mold 221. Both the third hinge seat 34 and the fourth hinge seat 35 are double-hole hinge seats. The third hinge seat 34, the fourth hinge seat 35, and the two connecting rods 33 cooperate to form a second four-bar linkage. The four-bar linkage is used to realize the closing or opening of the base plate mold 222 and the side mold 221 according to a preset motion trajectory. It can be understood that the four-bar linkage can also be formed by using a sliding groove connection between each hinge seat and the connecting rod.

[0054] In this embodiment, the motion trajectories of the first four-bar linkage and the second four-bar linkage are symmetrical. With the cooperation of the first and second four-bar linkages, the first side lower mold 12 and the base plate mold 222 are closed or opened according to a preset motion trajectory, as are the base plate mold 222 and the side mold 221. These two sets of four-bar linkages further improve the stability of the inner mold during mold closing and erection. Furthermore, driven by the third telescopic element 43, relative movement is achieved between the first side lower mold 12 and the base plate mold 222, and between the base plate mold 222 and the side mold 221, further ensuring that the entire cross-section is smaller than the beam end outlet when the inner mold contracts and closes.

[0055] It is understood that in other embodiments, the second hinge seat 32 may also be configured as follows: Figure 6 The three-hole hinge seat shown has a first hinge seat 31 and a fourth hinge seat 35 that are hinged to the three-hole hinge seat via a connecting rod 33 to form a four-bar linkage.

[0056] The workflow for demolding the closed automatic inner mold in this embodiment is as follows:

[0057] Step S1: The first telescopic element 41 retracts, thereby causing the first side upper mold 11 to shrink.

[0058] Step S2: The second telescopic element 42 retracts, thereby causing the second side upper mold 21 to shrink.

[0059] Step S3: The third telescopic element 43 retracts, thereby causing the first lower die 12 and the second lower die 22 to move towards each other, and the first lower die 12 and the second lower die 22 close upwards along the preset trajectory of the four-bar linkage until... Figure 5 As shown, the overall structure of the inner mold after demolding is smaller than the beam end outlet. After demolding, the first side lower mold 12 and the second side lower mold 22 achieve convergence and close proximity, resolving the problem of conflict between the two lower molds.

[0060] Step S4: The power traction device (such as a winch) pulls the inner mold as a whole, and the bottom plate mold 222 slides longitudinally on the poured concrete surface to realize the inner mold as a whole is removed from the inner cavity of the beam, thereby completing the demolding of the box girder inner mold.

[0061] In this embodiment, the second lower mold 22 is divided into a side mold 221 and a bottom plate mold 222. The bottom plate mold 222 and the side mold 221 can be hinged or obliquely fitted. A double-hole hinge seat is provided on the side mold 221, and two double-hole hinge seats are provided on the bottom plate mold 222. A first four-bar linkage is formed between the first lower mold 12 and the bottom plate mold 222, and a second four-bar linkage is formed between the bottom plate mold 222 and the side mold 221. This enables two sets of four-bar connections between the first lower mold 12 and the second lower mold 22, ensuring that the first lower mold 12 and the second lower mold 22 retract and close upward along the preset trajectory of the four-bar linkage. This not only helps to avoid positional conflicts when the lower molds on both sides close, but also significantly improves the stability of the inner mold when it closes. It also provides a larger internal operating space, making it easier for the power traction device to pull out the inner mold as a whole, reducing construction time and improving the overall quality of the box girder.

[0062] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A closed form inner form suitable for use with a small box girder, characterised in that, The end outlet of the beam body is smaller than the section of the inner cavity of the beam, and the closed inner mold comprises a first side mold assembly (1), a second side mold assembly (2), a track control mechanism (3) and a telescopic assembly (4); the track control mechanism (3) is used for connecting the first side mold assembly (1) and the second side mold assembly (2) into a whole, and can make the two relatively close or open along a set track; the telescopic assembly (4) is used for driving the first side mold assembly (1) and the second side mold assembly (2) to open and close; the inner mold is closed when it is opened to form a closed outer shape of the inner mold, and the whole cross section is smaller than the beam end outlet when it is closed; the first side mold assembly (1) comprises a first side upper mold (11) and a first side lower mold (12) which are hingedly connected, and the second side mold assembly (2) comprises a second side upper mold (21) and a second side lower mold (22) which are hingedly connected; the telescopic assembly (4) is connected between the first side lower mold (12) and the second side lower mold (22) to realize the closing or opening of the first side lower mold (12) and the second side lower mold (22); when the first side lower mold (12) and the second side lower mold (22) are translated and closed along a preset arc-shaped track, the first side lower mold (12) is retracted above the second side lower mold (22); The track control mechanism comprises connecting rods (33), a first hinged seat (31) mounted on the first side mold assembly (1) and a second hinged seat (32) mounted on the second side mold assembly (2), and the first hinged seat (31), the second hinged seat (32) and the two connecting rods (33) cooperatively form a four-bar mechanism to realize the closing or opening of the first side mold assembly (1) and the second side mold assembly (2) according to a set track.

2. The enclosed form for small box girders according to claim 1, wherein, The first hinged seat (31) and the second hinged seat (32) are both double-hole hinged seats.

3. The enclosed form for small box girders according to claim 1, wherein, The telescopic assembly (4) is arranged between the first side upper mold (11) and the first side lower mold (12) to realize the retraction or opening of the first side upper mold (11); and the telescopic assembly (4) is arranged between the second side lower mold (22) and the second side upper mold (21) to realize the retraction or opening of the second side upper mold (21).

4. The enclosed form for small box girders according to claim 3, wherein, The telescopic assembly (4) comprises a first telescopic element (41), a second telescopic element (42) and a third telescopic element (43); the two ends of the first telescopic element (41) are hingedly connected with the first side upper mold (11) and the first side lower mold (12) respectively to realize the retraction or opening of the first side upper mold (11); the two ends of the second telescopic element (42) are hingedly connected with the second side upper mold (21) and the second side lower mold (22) respectively to realize the retraction or opening of the second side upper mold (21); and the two ends of the third telescopic element (43) are connected with the first side lower mold (12) and the second side lower mold (22) respectively to realize the closing or opening of the first side lower mold (12) and the second side lower mold (22).

5. The enclosed form for small box girders according to any one of claims 1 to 4, characterized in that, The upper end of the first side mold assembly (1) is obliquely cut and attached to the upper end of the second side mold assembly (2), and the lower end of the first side mold assembly (1) is obliquely cut and attached to the lower end of the second side mold assembly (2).

6. The enclosed form for small box girders according to claim 3, wherein, The second side lower die (22) comprises a side edge die (221) and a bottom plate die (222), and the side edge die (221) and the bottom plate die (222) are capable of relative movement.

7. The enclosed form for small box girders according to claim 6, wherein, The second hinge seat (32) is installed on the bottom plate die (222), the first hinge seat (31), the second hinge seat (32) and the two connecting rods (33) form a first four-bar linkage.

8. The enclosed form for small box girders according to claim 7, wherein, The bottom plate die (222) is further provided with a third hinge seat (34), the side edge die (221) is provided with a fourth hinge seat (35), the third hinge seat (34) and the fourth hinge seat (35) are both double-hole hinge seats, the third hinge seat (34), the fourth hinge seat (35) and the two connecting rods (33) form a second four-bar linkage, and the four-bar linkages are used for realizing folding or unfolding of the bottom plate die (222) and the side edge die (221) according to a preset movement track.

9. The enclosed form for small box girders according to claim 8, characterized in that, The movement track of the first four-bar linkage is symmetrical to the movement track of the second four-bar linkage.

10. The closed form inner form suitable for use with a small box girder according to any one of claims 1 to 4 or 6 to 9, wherein, The telescopic assembly (4) is a hydraulic oil cylinder, a gas cylinder, an electric push rod or a folding rod.

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