A kind of auxiliary demoulding equipment for well lid casting with protection function

Abstract

The present application relates to the technical field of well lid casting, and particularly relates to a well lid casting auxiliary demolding equipment with a protection function. In view of the technical problem that the traditional demolding method is prone to cause deformation or bump damage of the well lid. The equipment comprises a frame body, a plurality of electric conveying rollers are rotationally connected in the frame body, the electric conveying rollers are used for conveying a lower mold, a fixing device for fixing the lower mold is arranged at the middle part of the frame body, the lower mold is provided with a plurality of mold grooves for casting the well lid, a top plate is slidably connected to the bottom of the mold groove, an electric push rod is fixedly connected to the position corresponding to each mold groove at the lower part of the frame body, a first connecting shell is fixedly connected to the extension end of the electric push rod, a first piston rod is slidably connected in the first connecting shell, and a buffer protection mechanism is arranged at the upper end of the first piston rod. The rigid ejection force is converted into the elastic ejection force through the buffer protection mechanism, and the deformation of the well lid or the damage of the inner wall of the lower mold (mold groove) caused by the rigid ejection is avoided.

Description

Technical Field

[0001] This invention relates to the field of manhole cover casting technology, and in particular to an auxiliary demolding device for manhole cover casting with protective function. Background Technology

[0002] As an infrastructure that ensures urban public safety, manhole covers need to have sufficient structural strength and durability. Currently, most manhole covers are produced using metal casting technology.

[0003] In the casting process of manhole covers, molten metal is usually poured into a cavity formed by the upper and lower molds. After it cools and solidifies, the mold is opened. However, when the manhole cover cools in the mold, it is easy to adhere or mechanically engage with the surface of the mold cavity. Traditional demolding methods often rely on workers to pry, knock or vibrate with tools. This is not only labor-intensive and inefficient, but also difficult to control the demolding force and the position of force application. This can easily lead to local stress concentration in the manhole cover, resulting in micro-cracks, deformation or impact damage inside or on the surface, affecting the strength and appearance integrity of the finished product, and even creating safety hazards. Summary of the Invention

[0004] In view of the shortcomings mentioned in the background art, the present invention provides an auxiliary demolding device for casting manhole covers with protective function.

[0005] The technical implementation of this invention is as follows: an auxiliary demolding device for casting manhole covers with protective function, comprising a frame, multiple electric conveying rollers rotatably connected within the frame for conveying a lower mold, a fixing device for fixing the lower mold in the middle of the frame, the lower mold having multiple mold slots for casting manhole covers, a top plate slidably connected to the bottom of the mold slots, an electric push rod fixedly connected to the lower part of the frame corresponding to the position of each mold slot, a first connecting shell fixedly connected to the telescopic end of the electric push rod, a first piston rod slidably connected within the first connecting shell, a buffer protection mechanism provided at the upper end of the first piston rod for protecting the manhole cover and the lower mold, a first fixing plate fixedly connected to the buffer protection mechanism, a fixing rod fixedly connected to the center of the upper side of the first fixing plate, a fixing sleeve fixedly connected to the lower side of the top plate, the fixing rod being insertable into adjacent upper and lower fixing sleeves, a vibration demolding mechanism provided on the upper side of the first fixing plate for vibratingly separating the manhole cover and the lower mold, and an overload protection mechanism provided within the first connecting shell for preventing the manhole cover from being crushed and damaged.

[0006] Furthermore, the buffer protection mechanism includes a second connecting shell, which is fixedly connected to the upper end of the adjacent first piston rod. The second piston rod is slidably connected inside the second connecting shell, and a first spring is connected between the two adjacent piston rods. The top end of the second piston rod is fixedly connected to the adjacent first fixing plate.

[0007] Furthermore, the vibration demolding mechanism includes an electric rotating shaft mounted on a fixed rod. The electric rotating shaft is splined to a rotating sleeve. A third connecting shell, circumferentially distributed, is fixedly connected to the upper side of the first fixed plate. A third piston rod is slidably connected to the third connecting shell, and a second spring connects adjacent shells. A connecting rod is fixedly connected to the outer side of the third piston rod. A circumferentially distributed arc-shaped triangular plate is fixedly connected to the lower side of the rotating sleeve. The arc-shaped triangular plate and the connecting rod are pressed together. A vibration adjustment component is provided on the first connecting shell, which is used to adjust the vibration amplitude.

[0008] Furthermore, a limiting ring is fixedly connected to the outer side of the third piston rod, a second fixing plate is fixedly connected to the upper part of the fixing rod, the third piston rod is slidably connected to the adjacent second fixing plate, and the limiting ring is located on the lower side of the second fixing plate.

[0009] Furthermore, the length of the third piston rod located on the upper part of the second fixed plate is greater than the length of the fixed rod located on the upper part of the second fixed plate.

[0010] Furthermore, the vibration adjustment assembly includes a connecting sleeve, which is rotatably connected to an adjacent rotating sleeve. A first rack is fixedly connected to the lower side of the connecting sleeve. The first rack passes through and is slidably connected to an adjacent first fixed plate. A gear is rotatably connected to the lower side of the first fixed plate. A second rack is fixedly connected to a second connecting shell. Both the first rack and the second rack mesh with the adjacent gear.

[0011] Furthermore, the overload protection mechanism includes a slide rod, which is fixedly connected to the lower end of an adjacent second piston rod. The slide rod passes through the adjacent second connecting shell and the first piston rod in sequence, and both the second connecting shell and the first piston rod are slidably connected to the adjacent slide rod. A pressing block is fixedly connected to the lower end of the slide rod. Symmetrically distributed limiting frames are slidably connected inside the first connecting shell. A third spring is fixedly connected between the limiting frames and the first connecting shell. Both limiting frames are pressed and engaged with the pressing block, and both limiting frames are limited and engaged with the first piston rod.

[0012] Furthermore, the second connecting shell and the second piston rod are fitted with a sliding fit that has a set frictional resistance.

[0013] Furthermore, the distance the first piston rod slides within the first connecting housing is greater than the distance the second piston rod slides within the second connecting housing.

[0014] The present invention has the following advantages: The present invention converts the rigid ejection force into an elastic ejection force through the first spring, avoiding deformation of the manhole cover or damage to the inner wall of the lower mold (mold groove) caused by rigid ejection, ensuring a smooth demolding process and protecting the integrity of the product and the mold.

[0015] This invention uses an arc-shaped triangular plate to drive multiple third piston rods to perform high-frequency, short-stroke reciprocating vibration in the vertical direction, which loosens and breaks the adhesion between the manhole cover and the side wall of the mold groove, assisting the manhole cover to separate smoothly, thereby avoiding scratches and damage to the surface texture or edges of the manhole cover that may be caused by forced static ejection.

[0016] This invention uses a vibration adjustment component to adjust the position of the interaction between the arc-shaped triangular plate and the connecting rod, thereby flexibly adjusting the vibration amplitude according to the adhesion degree or specifications of the manhole cover, significantly improving the equipment's adaptability to different working conditions and demolding efficiency.

[0017] This invention utilizes an overload protection mechanism that automatically triggers mechanical disengagement when the ejection resistance increases abnormally. In extreme cases such as severe jamming of the casting, the ejection force is immediately cut off, preventing irreversible hard extrusion and collision damage to the mold and manhole cover, thus achieving active safety protection. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0019] Figure 2 This is a left view of the three-dimensional structure of the present invention.

[0020] Figure 3 This is a three-dimensional structural diagram of the top plate, electric push rod, and first connecting shell of the present invention.

[0021] Figure 4 This is a three-dimensional structural diagram of the second connecting shell, the second piston rod, and the first spring of the present invention.

[0022] Figure 5 This is a three-dimensional structural diagram of the rotating sleeve, the third connecting shell, and the third piston rod of the present invention.

[0023] Figure 6 This is a three-dimensional structural diagram of the limiting ring, the second fixing plate, and the connecting sleeve of the present invention.

[0024] In the attached diagrams: 1-Frame, 2-Electric conveyor roller, 3-Lower mold, 4-Fixing device, 5-Mold groove, 6-Top plate, 7-Electric push rod, 8-First connecting shell, 9-First piston rod, 10-First fixing plate, 11-Fixing rod, 12-Fixing sleeve, 13-Second connecting shell, 14-Second piston rod, 15-First spring, 16-Electric rotating shaft, 17-Rotating sleeve, 18-Third connecting shell, 19-Third piston rod, 20-Second spring, 21-Connecting rod, 22-Arc-shaped triangular plate, 23-Limiting ring, 24-Second fixing plate, 25-Connecting sleeve, 26-First rack, 27-Gear, 28-Second rack, 29-Slide rod, 30-Extrusion block, 31-Limiting frame, 32-Third spring. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The following detailed description, with reference to the accompanying drawings, illustrates a specific embodiment of a demolding device with anti-deformation function for manhole cover casting according to the present invention. This device is mainly used to automatically and smoothly demold manhole cover castings from the lower mold without damage. Figures 1-3 As shown, an auxiliary demolding device for casting manhole covers with protective functions includes a frame 1. Multiple electric conveying rollers 2 are rotatably connected to the front and rear parts of the upper side of the frame 1. The electric conveying rollers 2 are used to convey the lower mold 3. A fixing device 4 for fixing the lower mold 3 is provided in the middle of the frame 1. The fixing device 4 is located at an electric pin. The frame 1 is provided with insertion holes that cooperate with the fixing device 4 to lock the lower mold 3 after it reaches the position, preventing it from moving during ejection. The lower mold 3 is provided with four mold grooves 5 for casting manhole covers. A top plate 6 is slidably connected to the bottom of the mold grooves 5. The top plate 6 is pre-embedded in the lower mold 3 and undergoes special treatment (such as nitriding, physical vapor deposition (PVD) coating, and surface polishing). Before casting the manhole cover, a special demolding agent needs to be sprayed onto the inner wall of the mold grooves 5 and the upper side of the top plate 6 to prevent the manhole cover from being cast... The components are bonded together. At the lower part of the frame 1, corresponding to the center of each mold groove 5, an electric push rod 7, which serves as the main lifting power source, is fixedly connected. The telescopic end of the electric push rod 7 is fixedly connected to a first connecting shell 8. A first piston rod 9 is slidably connected inside the first connecting shell 8. A buffer protection mechanism is provided at the upper end of the first piston rod 9. The buffer protection mechanism is used to protect the manhole cover and the lower mold 3. A first fixing plate 10 is fixedly connected to the buffer protection mechanism. A fixing rod 11 is fixedly connected at the center of the upper side of the first fixing plate 10. A fixing sleeve 12 is fixedly connected to the lower side of the top plate 6. The fixing rod 11 can be inserted into the upper and lower adjacent fixing sleeves 12. A vibration demolding mechanism is provided on the upper side of the first fixing plate 10. The vibration demolding mechanism is used to vibrate and separate the manhole cover and the lower mold 3. An overload protection mechanism is provided inside the first connecting shell 8. The overload protection mechanism is used to prevent the manhole cover from being squeezed and damaged.

[0027] like Figure 3 and Figure 4As shown, the buffer protection mechanism includes a second connecting shell 13, which is fixedly connected to the upper end of the adjacent first piston rod 9. A second piston rod 14 is slidably connected inside the second connecting shell 13, and a first spring 15 is connected between the two adjacent piston rods. The top end of the second piston rod 14 is fixedly connected to the adjacent first fixing plate 10. The second connecting shell 13 and the second piston rod 14 are in a sliding fit with a set frictional resistance. At the same time, the elastic force of the first spring 15 is sufficient to overcome the resistance between the second connecting shell 13 and the second piston rod 14 to prevent the manhole cover from being quickly pushed out and separated from the top plate 6 due to the elastic force of the first spring 15 when it is about to separate from the lower mold 3, thus preventing damage to the manhole cover.

[0028] like Figure 5 and Figure 6 As shown, the vibration demolding mechanism includes an electric rotating shaft 16, which is mounted on a fixed rod 11 and can rotate on the fixed rod 11. The electric rotating shaft 16 is splined to a rotating sleeve 17. A third connecting shell 18 with circumferential distribution is fixedly connected to the upper side of the first fixed plate 10. A third piston rod 19 is slidably connected to the third connecting shell 18, and a second spring 20 is connected between adjacent piston rods 19. A connecting rod 21 is fixedly connected to the outer side of the third piston rod 19. A circumferentially distributed arc-shaped triangular plate 22 is fixedly connected to the lower side of the rotating sleeve 17. The arc-shaped triangular plate 22 and the connecting rod 21 are pressed together. When the circumferentially distributed arc-shaped triangular plate 22 rotates, it presses the connecting rod 21, causing the third piston rod 19 to move up and down reciprocally. A vibration adjustment component is provided on the first connecting shell 8 to adjust the vibration amplitude.

[0029] like Figure 5 and Figure 6 As shown, a limiting ring 23 is fixedly connected to the outer side of the third piston rod 19, and a second fixing plate 24 is fixedly connected to the upper part of the fixing rod 11. The third piston rod 19 is slidably connected to the adjacent second fixing plate 24. The limiting ring 23 is located on the lower side of the second fixing plate 24 and is used to limit the maximum upward position of the third piston rod 19. The length of the third piston rod 19 located on the upper side of the second fixing plate 24 is greater than the length of the fixing rod 11 located on the upper side of the second fixing plate 24, ensuring that the second spring 20 is in a compressed state after the fixing rod 11 is inserted into the adjacent fixing sleeve 12.

[0030] like Figure 5 and Figure 6As shown, the vibration adjustment assembly includes a connecting sleeve 25, which is rotatably connected to an adjacent rotating sleeve 17. A first rack 26 is fixedly connected to the lower side of the connecting sleeve 25. The first rack 26 passes through and is slidably connected to an adjacent first fixed plate 10. A gear 27 is rotatably connected to the lower side of the first fixed plate 10. A second rack 28 is fixedly connected to a second connecting shell 13. Both the first rack 26 and the second rack 28 mesh with the adjacent gear 27.

[0031] like Figure 4 As shown, the overload protection mechanism includes a slide rod 29, which is fixedly connected to the lower end of an adjacent second piston rod 14. The slide rod 29 passes sequentially through an adjacent second connecting shell 13 and a first piston rod 9, and both the second connecting shell 13 and the first piston rod 9 are slidably connected to the adjacent slide rod 29. A pressing block 30 is fixedly connected to the lower end of the slide rod 29. Symmetrically distributed limiting frames 31 are slidably connected inside the first connecting shell 8. A third spring 32 is fixedly connected between the limiting frame 31 and the first connecting shell 8. Both limiting frames 31 are pressed and engaged with the pressing block 30, and both limiting frames 31 are limited and engaged with the first piston rod 9. The distance that the first piston rod 9 slides inside the first connecting shell 8 is greater than the distance that the second piston rod 14 slides inside the second connecting shell 13, ensuring that after the two limiting frames 31 lose their limiting effect on the first piston rod 9, the distance that the first piston rod 9 slides inside the first connecting shell 8 is sufficient to allow the fixed rod 11 to be pulled out from the fixed sleeve 12.

[0032] When it is necessary to separate the manhole cover from the lower mold 3, the upper mold has been removed and the lower mold 3 is located on the upper side of the electric conveyor roller 2. The operator starts multiple electric conveyor rollers 2 inside the frame 1. The electric conveyor rollers 2 drive the lower mold 3, which carries multiple manhole cover castings, to move horizontally until it reaches the preset working position in the middle of the frame 1. Then, the operator starts the fixing device 4 to firmly lock the lower mold 3 in the current position to prevent it from shifting during subsequent ejection operations.

[0033] After the preparations are complete, the staff simultaneously start all the electric push rods 7. The telescopic ends of the electric push rods 7 drive the first connecting shell 8 to move upward. The first connecting shell 8 pushes the first piston rod 9 to rise through the two limit brackets 31, thereby driving the parts on the first piston rod 9 to rise as a whole until the fixing rod 11 is inserted into the fixing sleeve 12.

[0034] When the fixing rod 11 is inserted into the fixing sleeve 12, as the telescopic end of the electric push rod 7 continues to extend, the fixing rod 11 drives the top plate 6 to rise steadily along the bottom of the mold groove 5 through the fixing sleeve 12, and begins to push the manhole cover casting. At this time, the upper end of the third piston rod 19 remains in contact with the lower side of the top plate 6, but the second spring 20 is in a compressed state.

[0035] During the ejection process, if the ejection resistance increases abnormally due to excessive adhesion between the manhole cover and the side wall of the mold groove 5, this resistance will be transmitted to the second piston rod 14 through the fixed rod 11 and the first fixed plate 10, forcing the second piston rod 14 to overcome the elastic force of the first spring 15 and tend to move downward. However, in reality, the second connecting shell 13 continues to move upward, while the second piston rod 14 and its upper parts remain stationary, thus avoiding structural damage to the mold or casting caused by continuous rigid ejection force.

[0036] While the manhole cover casting is being pushed, to assist in separation, the workers start the electric rotating shaft 16. The electric rotating shaft 16 drives the rotating sleeve 17 to rotate, and the rotating sleeve 17 drives multiple arc-shaped triangular plates 22 to rotate synchronously. During the rotation of the arc-shaped triangular plates 22, their inclined surfaces periodically contact and squeeze the end of the connecting rod 21, thereby pushing the third piston rod 19 to slide downward against the elastic force of the second spring 20. When the inclined surface of the arc-shaped triangular plate 22 rotates away, the second spring 20 pushes the third piston rod 19 and the connecting rod 21 to return to their original position and strike the lower side of the top plate 6 to generate vibration. This cycle repeats, converting the continuous rotation of the rotating sleeve 17 into high-frequency, small-amplitude reciprocating movement of multiple third piston rods 19 in the vertical direction, thereby loosening the adhesion between the manhole cover and the side wall of the mold groove 5, assisting in their complete separation, and avoiding damage to the appearance of the manhole cover caused by forced peeling.

[0037] During the ejection process, when the second piston rod 14 and its upper part are stationary, as the second connecting shell 13 continues to move upward, the second rack 28 moves upward synchronously, and through the gear 27, the first rack 26 moves downward. The first rack 26 drives the connecting sleeve 25 and the rotating sleeve 17 to move downward, thereby changing the initial relative position between the arc-shaped triangular plate 22 and the connecting rod 21. In this way, the stroke of the reciprocating movement of the third piston rod 19 is adjusted, thereby achieving the adjustment of the vibration amplitude.

[0038] During the reciprocating movement of the third piston rod 19, the limiting ring 23 and the second fixed plate 24 work together to limit the final position of the third piston rod 19 in a single movement. This prevents the inconsistent elastic coefficient of the second spring 20 from causing inconsistent movement stroke of the third piston rod 19, which could lead to unstable vibration amplitude, reduced demolding effect, or even mechanical interference or collision due to excessive stroke.

[0039] After demolding is completed, the staff controls the electric push rod 7 to retract, driving the entire ejection mechanism to descend and reset. Then, the fixing device 4 is unlocked, the electric conveying roller 2 is started again, and the emptied lower mold 3 is transported away from the working position and prepared to connect to the next mold to be demolded, and the cycle repeats.

[0040] As the second connecting shell 13 continues to move upward, when the second piston rod 14 and its upper parts are stationary, the slide rod 29 drives the pressing block 30 at its lower end to move downward synchronously (relative to the second connecting shell 13). If the resistance continues to increase until the inclined surface of the pressing block 30 contacts the two limiting frames 31, the pressing block 30 presses the two limiting frames 31, forcing them to overcome the elastic force of the third spring 32 and move away from each other until the two limiting frames 31 release the locking limit on the first piston rod 9. At this time, under the action of gravity, the first piston rod 9 and its upper parts fall downward, the fixing rod 11 is pulled out from the fixing sleeve 12 and no longer presses the top plate 6, so that in extreme cases (such as when the casting is stuck), the ejection force is immediately interrupted, and hard collision and squeezing damage to the mold and the well cover are absolutely prevented.

[0041] When the staff finds that the fixing rod 11 has been pulled out of the fixing sleeve 12, they immediately shut down all electric push rods 7 and electric rotating shafts 16. Then, the staff first investigates and resolves the root cause of the ejection overload, such as removing stuck foreign objects, confirming the alignment of the mold and the top plate 6, or manually loosening abnormally adhered castings. After confirming that the problem has been resolved, the staff gently pushes the first fixing plate 10 and its upper components upward, causing the second piston rod 14 to move upward relative to the second connecting shell 13. The slide rod 29 and the extrusion block 30 rise accordingly, and the two limit frames 31 automatically reset under the action of the third spring 32 until the two limit frames 31 re-engage under the lower side of the first piston rod 9, restoring the normal locking of the first piston rod 9. At this time, the staff can restart the automatic process, and the equipment will start from the initial state to execute the next demolding cycle.

[0042] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An auxiliary demolding device for casting manhole covers with protective functions, characterized in that: The frame includes a frame (1), with multiple electric conveying rollers (2) rotatably connected inside the frame (1). The electric conveying rollers (2) are used to convey the lower mold (3). A fixing device (4) for fixing the lower mold (3) is provided in the middle of the frame (1). The lower mold (3) is provided with multiple mold grooves (5) for casting manhole covers. A top plate (6) is slidably connected to the bottom of the mold groove (5). An electric push rod (7) is fixedly connected to the lower part of the frame (1) at the position corresponding to each mold groove (5). A first connecting shell (8) is fixedly connected to the telescopic end of the electric push rod (7). A first piston rod (9) is slidably connected inside the first connecting shell (8). The upper end of 9) is provided with a buffer protection mechanism, which is used to protect the manhole cover and the lower mold (3). The buffer protection mechanism is fixedly connected to the first fixed plate (10). The center of the upper side of the first fixed plate (10) is fixedly connected to the fixed rod (11). The lower side of the top plate (6) is fixedly connected to the fixed sleeve (12). The fixed rod (11) can be inserted into the upper and lower adjacent fixed sleeves (12). The upper side of the first fixed plate (10) is provided with a vibration demolding mechanism, which is used to vibrate and separate the manhole cover and the lower mold (3). The first connecting shell (8) is provided with an overload protection mechanism, which is used to prevent the manhole cover from being squeezed and damaged.

2. The auxiliary demolding device for casting manhole covers with protective function as described in claim 1, characterized in that: The buffer protection mechanism includes a second connecting shell (13), which is fixedly connected to the upper end of the adjacent first piston rod (9). A second piston rod (14) is slidably connected inside the second connecting shell (13), and a first spring (15) is connected between the two adjacent piston rods. The top end of the second piston rod (14) is fixedly connected to the adjacent first fixing plate (10).

3. The auxiliary demolding device for casting manhole covers with protective function according to claim 2, characterized in that: The vibration demolding mechanism includes an electric rotating shaft (16), which is mounted on a fixed rod (11). The electric rotating shaft (16) is splined to a rotating sleeve (17). A third connecting shell (18) is fixedly connected to the upper side of the first fixed plate (10). A third piston rod (19) is slidably connected to the third connecting shell (18), and a second spring (20) is connected between adjacent piston rods. A connecting rod (21) is fixedly connected to the outer side of the third piston rod (19). A circumferentially distributed arc-shaped triangular plate (22) is fixedly connected to the lower side of the rotating sleeve (17). The arc-shaped triangular plate (22) and the connecting rod (21) are pressed together. A vibration adjustment component is provided on the first connecting shell (8). The vibration adjustment component is used to adjust the vibration amplitude.

4. An auxiliary demolding device for casting manhole covers with protective function as described in claim 3, characterized in that: A limiting ring (23) is fixedly connected to the outer side of the third piston rod (19), and a second fixing plate (24) is fixedly connected to the upper part of the fixing rod (11). The third piston rod (19) is slidably connected to the adjacent second fixing plate (24), and the limiting ring (23) is located on the lower side of the second fixing plate (24).

5. An auxiliary demolding device for casting manhole covers with protective function as described in claim 4, characterized in that: The length of the third piston rod (19) located on the upper part of the second fixing plate (24) is greater than the length of the fixing rod (11) located on the upper part of the second fixing plate (24).

6. An auxiliary demolding device for casting manhole covers with protective function as described in claim 3, characterized in that: The vibration adjustment assembly includes a connecting sleeve (25), which is rotatably connected to an adjacent rotating sleeve (17). A first rack (26) is fixedly connected to the lower side of the connecting sleeve (25). The first rack (26) passes through an adjacent first fixed plate (10) and is slidably connected to it. A gear (27) is rotatably connected to the lower side of the first fixed plate (10). A second rack (28) is fixedly connected to the second connecting shell (13). Both the first rack (26) and the second rack (28) mesh with the adjacent gear (27).

7. An auxiliary demolding device for casting manhole covers with protective function as described in claim 6, characterized in that: overload The protective mechanism includes a slide rod (29), which is fixedly connected to the lower end of the adjacent second piston rod (14). The slide rod (29) passes through the adjacent second connecting shell (13) and the first piston rod (9) in sequence. The second connecting shell (13) and the first piston rod (9) are slidably connected to the adjacent slide rod (29). The lower end of the slide rod (29) is fixedly connected to a pressing block (30). The first connecting shell (8) is slidably connected to symmetrically distributed limiting frames (31). The limiting frames (31) and the first connecting shell (8) are fixedly connected to a third spring (32). Both limiting frames (31) are pressed and engaged with the pressing block (30), and both limiting frames (31) are limited and engaged with the first piston rod (9).

8. The auxiliary demolding device for casting manhole covers with protective function according to claim 7, wherein the second connecting shell (13) and the second piston rod (14) adopt a sliding fit with a set frictional resistance.

9. An auxiliary demolding device for casting manhole covers with protective function as described in claim 7, characterized in that: The distance that the first piston rod (9) slides within the first connecting shell (8) is greater than the distance that the second piston rod (14) slides within the second connecting shell (13).

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