Chain hoist and control method thereof

Abstract

The present application relates to the technical field of hoist, in particular to a chain type hoist and a control method thereof, which comprises vertically symmetrical channel steel frames, a fixed plate is vertically arranged on one side of the upper part of the channel steel frame, a control box is arranged on the side of the lower part of the channel steel frame away from the fixed plate, a partition frame is arranged on the side of the fixed plate close to the control box, a fork frame is arranged on the side of the fixed plate away from the partition frame, fork legs are horizontally arranged on both sides of the fork frame, lifting pull rods are vertically and symmetrically inserted into the top of the partition frame, the same fixed sleeve seats are slidably arranged on the lower part of the lifting pull rods, the fixed sleeve seats are fixed to the outer wall of the fixed plate at the position inside the partition frame, and inclined support protrusions are arranged on both vertical sides of the lifting pull rods. The present application can prevent goods from falling, improve the safety in use, meet the lifting demand of heavy load, and facilitate the splicing, lengthening, disassembling and shortening of the chain, so as to facilitate the expansion of equipment of various heights, and has great advantages in the expansion of super-high equipment.

Description

Technical Field

[0001] This invention relates to the field of hoisting technology, and in particular to a chain hoist and its control method. Background Technology

[0002] A hoist is a mechanical device that transports materials by changing their potential energy. It meets production needs by lifting the bucket to a designated position on the equipment. It typically includes a column, a lifting device, and a fork. The lifting device is located at the bottom of the column, and the fork moves vertically along the column and is raised and lowered under the drive of the lifting device. A fork is located in front of the fork to lift the bucket.

[0003] Existing hoist structures are often inconvenient for height expansion and have low applicability. While wire rope hoists offer convenient expansion, the wire rope is prone to getting stuck and tangled in the middle of the drum during lifting and winding. For example, a simple lifting device disclosed in utility model patent CN211619332U uses wire rope for lifting. During lifting and winding, the wire rope is easily stuck and tangled, affecting its service life. Furthermore, it requires a large drum diameter, long axial winding distance, and low strength. Therefore, there is an urgent need for a hoist structure that is high-strength, stable in use, and has good height expansion capabilities. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a chain-type hoist and its control method to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides a chain hoist and its control method.

[0006] A chain-type hoist includes a vertically symmetrical channel steel frame. A fixed plate is vertically mounted on one side of the upper part of the channel steel frame. A control box is located on the lower part of the channel steel frame away from the fixed plate. An isolation frame is located on the side of the fixed plate near the control box. A fork is located on the side of the fixed plate away from the isolation frame. Fork feet are laterally mounted on both sides of the fork. Lifting rods are vertically symmetrically inserted into the top of the isolation frame. A fixed sleeve is slidably fitted onto the lower part of each lifting rod. The fixed sleeve is fixed to the outer wall of the fixed plate located inside the isolation frame. Diagonal bracing protrusions are provided on both vertical sides of the lifting rods, and the tops of the diagonal bracing protrusions are connected to the fixed plate. The bottom of the fixed sleeve base abuts against each other. The top of the lifting rod is provided with the same chain, and the tail end of the chain is connected to the bottom of the fixed plate. The upper and lower ends of the channel steel frame are respectively provided with a first driven sprocket and a second driven sprocket. The control box is provided with a drive motor. The top output shaft of the drive motor is provided with a reducer. The output end of the reducer is coaxially provided with a drive sprocket. The drive sprocket, the first driven sprocket and the second driven sprocket are fitted with the same chain. The isolation frame is symmetrically provided with rollers on both sides near the channel steel frame. The rollers are all inserted into the channel steel frame. The bottom of the lifting rod is provided with an anti-fall component to prevent the fixed plate from falling off.

[0007] Furthermore, the fall arrestor includes a guide rail horizontally disposed inside the isolation frame. Wedges are symmetrically slidably fitted onto the guide rail. The inclined surfaces of the wedges all slide against the same symmetrical pressure seat. A sliding rod is vertically disposed at the center of the symmetrical pressure seat. A telescopic rod is horizontally disposed on the side of the wedges away from the sliding rod. The fall arrestor also includes multiple slots vertically and equidistantly opened in the channel steel frame. The opening diameter of the slots is larger than the diameter of the telescopic rod. A horizontal plate is fitted onto the upper part of the sliding rod. The two ends of the horizontal plate are fixed to the outer wall of the lifting rod. The top of the sliding rod slides through the top of the fixed sleeve.

[0008] Through the above technical solution: When lifting, the lifting rod drives the horizontal plate and slide rod to rise as a whole. The slide rod drives the symmetrical pressure seats to apply pressure to the wedges on both sides. The wedges are pressed and slide along the guide rail, causing the telescopic rod to slide. At this time, the telescopic rod and the slot are in a separated state. Regardless of whether the fixed plate rises or falls, the telescopic rod will not enter the slot. When the chain breaks, the fixed plate falls as a whole. At this time, the second compression spring releases its elasticity, causing the lifting rod and slide rod to fall as a whole. At this time, the wedges lose their compression. With the cooperation of the retaining ring and the first compression spring, the wedges slide and simultaneously drive the telescopic rod to slide outward. When the telescopic rod passes through the slot, it will continue to expand outward by one end. When the telescopic rod falls to the bottom of the slot, the isolation frame as a whole is resisted and stops falling.

[0009] Furthermore, reinforcing sleeves are slidably fitted on the outer circumference of the telescopic rods, and each reinforcing sleeve is inserted into one vertical side of the isolation frame. Each reinforcing sleeve has a symmetrical support frame at its bottom, and the support frame is fixed to the outer wall of the fixed plate.

[0010] The above technical solution utilizes a reinforced sleeve and support frame to provide enhanced support for the telescopic rod under pressure, preventing it from undergoing significant deformation.

[0011] Furthermore, a retaining ring is fitted on the outer circumference of the telescopic rod at the end away from the wedge, and a first compression spring is fitted on the outer circumference of the telescopic rod near the position between the retaining ring and the reinforcing sleeve.

[0012] The above technical solution utilizes the combination of the retaining ring and the first compression spring to allow the telescopic rod to extend outward with greater elastic force, thereby increasing the success rate of docking with the slot.

[0013] Furthermore, a second compression spring is fitted onto the slide rod near the top of the cross plate and the bottom of the fixed sleeve.

[0014] The above technical solution utilizes the second compression spring to store elastic potential energy, so that when the chain breaks, the descent speed of the lifting rod can be greater than the speed of the fixed plate.

[0015] Furthermore, an electronic pressure switch is vertically installed on the inner wall of the top of the isolation frame, and the detection end of the electronic pressure switch is located on the same axis as the slide rod.

[0016] The above technical solution utilizes an electronic pressure switch to detect whether the chain has broken.

[0017] Furthermore, tension sprockets are symmetrically provided at the lower part of the chain.

[0018] The above technical solution uses a tension sprocket to restrict the movement of the chain, making the drive sprocket more efficient.

[0019] Furthermore, an alarm light is installed on the top of the control box.

[0020] The above technical solution utilizes alarm lights to warn workers that the chain has broken, preventing them from performing dangerous operations.

[0021] Furthermore, the top of the channel steel frame is provided with the same top support frame, and the bottom of the channel steel frame is provided with the same rotating chassis.

[0022] The above technical solution allows the hoist to rotate as a whole by using the support frame and the top support frame together.

[0023] The beneficial effects of this invention are:

[0024] 1. The present invention uses a fall-prevention component. When the chain breaks, the fixed plate descends as a whole. At this time, the second compression spring releases its elasticity, causing the lifting rod and slide rod to descend as a whole. At this time, the wedge block loses its compression. With the cooperation of the retaining ring and the first compression spring, the wedge block slides and simultaneously drives the telescopic rod to slide outward. When the telescopic rod passes through the slot, it will continue to expand outward by one end. When the telescopic rod descends to the bottom of the slot, the isolation frame as a whole is resisted and stops descending.

[0025] 2. In this invention, when the electronic pressure switch loses pressure, its switching state changes. The internal control system of the control box detects the signal and outputs a signal to the alarm light to control its operation, thereby serving as a warning and preventing operators from performing dangerous operations.

[0026] 3. The present invention features a high-strength chain that can meet the lifting requirements of heavy loads. At the same time, the chain can be easily spliced ​​to be lengthened or disassembled to be shortened, making it convenient to expand equipment of various heights. It is especially advantageous for ultra-high equipment, as it is easy to expand.

[0027] 4. Chain structure equipment has low installation and fastening requirements, is easy to process and install, and has strong applicability. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a three-dimensional structural diagram of an embodiment of the present invention;

[0030] Figure 2 This is a side cross-sectional view of an embodiment of the present invention.

[0031] Figure 3 This is a top view of the structure according to an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the fall arrestor component structure according to an embodiment of the present invention;

[0033] Figure 5 Embodiments of the present invention Figure 4 A magnified schematic diagram of the local structure at point A;

[0034] Figure 6 Embodiments of the present invention Figure 4 A magnified schematic diagram of the local structure at point B;

[0035] Figure 7Embodiments of the present invention Figure 4 A magnified schematic diagram of the local structure at point C;

[0036] Figure 8 Embodiments of the present invention Figure 4 A magnified schematic diagram of the local structure at point D.

[0037] The diagram is marked as follows:

[0038] 1. Rotating chassis; 2. Channel steel frame; 201. Slot; 3. Control box; 4. Top support frame; 5. Fixing plate; 6. Fork frame; 7. Fork feet; 8. Isolation frame; 9. Roller; 10. Drive sprocket; 11. Tensioning sprocket; 12. First driven sprocket; 13. Second driven sprocket; 14. Reducer; 15. Drive motor; 16. Lifting rod; 1601. Diagonal brace protrusion; 17. Fixing sleeve; 18. Horizontal plate; 19. Slide rod; 20. Symmetrical pressure seat; 21. Wedge block; 22. Telescopic rod; 23. Reinforcing sleeve; 24. Support frame; 25. First compression spring; 26. Retaining ring; 27. Electronic pressure switch; 28. Alarm light; 29. ​​Chain; 30. Second compression spring; 31. Guide rail. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0040] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0041] like Figures 1 to 8As shown, a chain hoist and its control method include a vertically symmetrical channel steel frame 2. A fixed plate 5 is vertically mounted on one side of the upper part of the channel steel frame 2. A control box 3 is located on the lower part of the channel steel frame 2 away from the fixed plate 5. An isolation frame 8 is located on the side of the fixed plate 5 near the control box 3. A fork 6 is located on the side of the fixed plate 5 away from the isolation frame 8. Fork feet 7 are horizontally mounted on both sides of the fork 6. Lifting rods 16 are vertically symmetrically inserted into the top of the isolation frame 8. A fixed sleeve 17 is slidably fitted onto the lower part of the lifting rods 16. The fixed sleeve 17 is fixed to the outer wall of the fixed plate 5 located inside the isolation frame 8. Diagonal bracing protrusions 1601 are provided on both vertical sides of the lifting rods 16. The top of the diagonal bracing protrusions 1601... The top of the lifting rod 16 is equipped with the same chain 29, which abuts against the bottom of the fixed sleeve 17. The tail end of the chain 29 is connected to the bottom of the fixed plate 5. The upper and lower ends of the channel steel frame 2 are respectively equipped with a first driven sprocket 12 and a second driven sprocket 13. The control box 3 is equipped with a drive motor 15. The top output shaft of the drive motor 15 is equipped with a reducer 14. The output end of the reducer 14 is coaxially equipped with a drive sprocket 10. The drive sprocket 10, the first driven sprocket 12 and the second driven sprocket 13 are fitted with the same chain 29. The isolation frame 8 is symmetrically equipped with rollers 9 on both sides near the channel steel frame 2. The rollers 9 are all inserted into the channel steel frame 2. The bottom of the lifting rod 16 is equipped with an anti-fall component to prevent the fixed plate 5 from falling off.

[0042] For details, please refer to Figure 4The fall arrestor includes a guide rail 31 horizontally disposed inside the isolation frame 8. Wedges 21 are symmetrically slidably fitted on the guide rail 31. The inclined surfaces of the wedges 21 slide against the same symmetrical pressure seat 20. A sliding rod 19 is vertically disposed at the center of the symmetrical pressure seat 20. A telescopic rod 22 is horizontally disposed on the side of the wedges 21 away from the sliding rod 19. The fall arrestor also includes multiple slots 201 vertically and equidistantly disposed on the channel steel frame 2. The opening diameter of the slots 201 is larger than the diameter of the telescopic rod 22. A horizontal plate 18 is fitted on the upper part of the sliding rod 19. The two ends of the horizontal plate 18 are fixed to the outer wall of the lifting rod 16. The top of the sliding rod 19 slides through the top of the fixed sleeve 17. When lifting, the lifting rod 16 drives the horizontal plate 18 and the sliding rod 19 to rise as a whole. The sliding rod 19 drives the symmetrical pressure seat 20 to apply pressure to the wedges 21 on both sides. The wedges 21 slide along the guide rail 31 under pressure and drive the telescopic rod 22 to slide. At this time, the telescopic rod 22 and the slot 201 are engaged. When in the separated state, regardless of whether the fixed plate 5 rises or falls, the telescopic rod 22 will not enter the slot 201. When the chain 29 is disconnected, the fixed plate 5 falls as a whole. At this time, the second compression spring 30 releases its elasticity, causing the lifting rod 16 and the slide rod 19 to fall as a whole. At this time, the wedge block 21 loses its compression. With the cooperation of the retaining ring 26 and the first compression spring 25, the wedge block 21 slides and simultaneously drives the telescopic rod 22 to slide outward. When the telescopic rod 22 passes through the slot 201, it will continue to expand outward by one end. When the telescopic rod 22 falls to the bottom of the slot 201, the isolation frame 8 is resisted as a whole and stops falling.

[0043] For details, please refer to Figure 7 The outer circumference of the telescopic rod 22 is slidably fitted with a reinforcing sleeve 23. The reinforcing sleeve 23 is inserted into the vertical side of the isolation frame 8. The bottom of the reinforcing sleeve 23 is symmetrically provided with a support frame 24. The support frame 24 is fixed to the outer wall of the fixing plate 5. The reinforcing sleeve 23 and the support frame 24 provide reinforcement support for the telescopic rod 22 when it is compressed, preventing it from undergoing large deformation.

[0044] For details, please refer to Figure 8 Each end of the telescopic rod 22 away from the wedge 21 is fitted with a retaining ring 26 on its outer circumference. Each end of the telescopic rod 22 near the position between the retaining ring 26 and the reinforcing sleeve 23 is fitted with a first compression spring 25. By using the retaining ring 26 and the first compression spring 25 in cooperation, the telescopic rod 22 can extend outward with greater elasticity, thereby improving the success rate of docking with the slot 201.

[0045] For details, please refer to Figure 6 A second compression spring 30 is fitted on the slide bar 19 near the top of the horizontal plate 18 and the bottom of the fixed sleeve 17. The second compression spring 30 stores elastic potential energy, so that when the chain 29 is broken, the descent speed of the lifting rod 16 can be greater than the speed of the fixed plate 5.

[0046] For details, please refer to Figure 5 An electronic pressure switch 27 is vertically installed on the inner wall of the top of the isolation frame 8. The detection end of the electronic pressure switch 27 is located on the same axis as the slide bar 19. The electronic pressure switch 27 is used to detect whether the chain 29 is broken.

[0047] For details, please refer to Figure 2 The lower part of the chain 29 is symmetrically provided with tension sprockets 11. The movement of the chain 29 is restricted by the tension sprockets 11, making the drive sprocket 10 more efficient.

[0048] For details, please refer to Figure 1 The top of the control box 3 is equipped with an alarm light 28, which is used to warn of chain breakage and prevent workers from performing dangerous operations.

[0049] For details, please refer to Figure 1 The top of the channel steel frame 2 is provided with the same top support frame 4, and the bottom of the channel steel frame 2 is provided with the same rotating base 1. The hoist can be rotated as a whole by using the support frame 4 and the top support frame 4 in conjunction.

[0050] Working principle: First, the drive motor 15 is started and drives the drive sprocket 10 to rotate through the output of the reducer 14. Through the tension sprocket 11, the first driven sprocket 12 and the second driven sprocket 13 drive the lifting rod 16 to rise. When the lifting rod 16 rises, the inclined support protrusion 1601 abuts against the bottom of the fixed sleeve 17, thereby driving the fixed plate 5 and the isolation frame 8 to rise as a whole. Then, the fork 6 and the fork feet 7 rise synchronously to complete the lifting operation. When lifting, the lifting rod 16 drives the horizontal plate 18 and the slide rod 19 to rise as a whole. The slide rod 19 drives the symmetrical pressure seat 20 to apply pressure to the wedges 21 on both sides. The wedges 21 are pressed and slide along the guide rail 31 and drive the telescopic rod 22 to slide. At this time, the telescopic rod 22 and the slot 201 are engaged. In the separated state, regardless of whether the fixed plate 5 rises or falls, the telescopic rod 22 will not enter the slot 201. When the chain 29 is disconnected, the fixed plate 5 descends as a whole. At this time, the second compression spring 30 releases its elasticity, causing the lifting rod 16 and the slide rod 19 to descend as a whole. At this time, the wedge block 21 loses its compression, and with the cooperation of the retaining ring 26 and the first compression spring 25, the wedge block 21 slides, and simultaneously drives the telescopic rod 22 to slide outward. When the telescopic rod 22 passes through the slot 201, it will continue to expand outward by one end. When the telescopic rod 22 descends to abut against the bottom of the slot 201, the isolation frame 8 is resisted and stops descending. When the chain 29 is disconnected, the fixed plate 5 descends as a whole. As the slide bar descends, the second compression spring 30 releases its elastic force, causing the lifting rod 16 and slide bar 19 to descend as a whole. At this time, the wedge block 21 loses its compression, and with the cooperation of the retaining ring 26 and the first compression spring 25, the wedge block 21 slides, and simultaneously drives the telescopic rod 22 to slide outward. When the telescopic rod 22 passes through the slot 201, it will continue to expand outward by one end. When the telescopic rod 22 descends to abut against the bottom of the slot 201, the isolation frame 8 as a whole is resisted and stops descending. When the slide bar 19 descends, the electronic pressure switch 27 loses pressure, and its switching state changes. The internal control system of the control box 3 detects the signal and outputs a signal to the alarm light 28 to control it to work and play a warning role.

[0051] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A chain-type hoist, comprising vertically symmetrically arranged channel steel frames (2), characterized in that, A fixed plate (5) is vertically mounted on one side of the upper part of the channel steel frame (2). A control box (3) is mounted on the lower part of the channel steel frame (2) away from the fixed plate (5). An isolation frame (8) is mounted on the side of the fixed plate (5) near the control box (3). A fork (6) is mounted on the side of the fixed plate (5) away from the isolation frame (8). Fork feet (7) are horizontally mounted on both sides of the fork (6). Lifting rods (16) are vertically and symmetrically inserted at the top of the isolation frame (8). The same fixed sleeve (17) is slidably mounted on the lower part of the lifting rod (16). The fixed sleeve (17) is fixed to the outer wall of the fixed plate (5) at the position inside the isolation frame (8). Diagonal bracing protrusions (1601) are provided on both sides of the vertical lifting rod (16). The top of the diagonal bracing protrusions (1601) abuts against the bottom of the fixed sleeve (17). The top of the pull rod (16) is provided with the same chain (29), the tail end of the chain (29) is connected to the bottom of the fixed plate (5), the upper and lower ends of the channel steel frame (2) are respectively provided with a first driven sprocket (12) and a second driven sprocket (13), the control box (3) is provided with a drive motor (15), the top output shaft of the drive motor (15) is provided with a reducer (14), the output end of the reducer (14) is coaxially provided with a drive sprocket (10), the drive sprocket (10), the first driven sprocket (12) and the second driven sprocket (13) are fitted with the same chain (29), the isolation frame (8) is symmetrically provided with rollers (9) on both sides near the channel steel frame (2), the rollers (9) are all inserted into the channel steel frame (2), and the bottom of the lifting pull rod (16) is provided with an anti-fall component to prevent the fixed plate (5) from falling off; The fall protection assembly includes a guide rail (31) horizontally disposed inside the isolation frame (8). The guide rail (31) is symmetrically fitted with wedges (21). The inclined surfaces of the wedges (21) slide against the same symmetrical pressure seat (20). The center of the symmetrical pressure seat (20) is vertically provided with a sliding rod (19). The wedges (21) on the side away from the sliding rod (19) are all provided with telescopic rods (22). The fall protection assembly also includes multiple slots (201) vertically and equidistantly opened in the channel steel frame (2). The opening diameter of the slots (201) is larger than the diameter of the telescopic rods (22). A horizontal plate (18) is fitted on the upper part of the sliding rod (19). The two ends of the horizontal plate (18) are fixed to the outer wall of the lifting rod (16). The top of the sliding rod (19) slides through the top of the fixed sleeve (17). The outer circumferential surface of the telescopic rod (22) is slidably fitted with a reinforcing sleeve (23). The reinforcing sleeve (23) is inserted into the vertical side of the isolation frame (8). The bottom of the reinforcing sleeve (23) is symmetrically provided with a support frame (24). The support frame (24) is fixed to the outer wall of the fixing plate (5). A retaining ring (26) is fitted on the outer circumference of the telescopic rod (22) away from the wedge (21), and a first compression spring (25) is fitted on the outer circumference of the telescopic rod (22) near the position between the retaining ring (26) and the reinforcing sleeve (23). A second compression spring (30) is fitted on the slide bar (19) near the top of the cross plate (18) and the bottom of the fixed sleeve (17).

2. The chain-type elevator according to claim 1, characterized in that, The top inner wall of the isolation frame (8) is vertically provided with an electronic pressure switch (27), and the detection end of the electronic pressure switch (27) and the slide rod (19) are located on the same axis.

3. A chain-type elevator according to claim 2, characterized in that, The lower part of the chain (29) is symmetrically provided with tension sprockets (11).

4. A chain-type elevator according to claim 3, characterized in that, An alarm light (28) is provided on the top of the control box (3).

5. A chain-type elevator according to claim 4, characterized in that, The top of the channel steel frame (2) is provided with the same top support frame (4), and the bottom of the channel steel frame (2) is provided with the same rotating base (1).

6. The control method for a chain hoist according to claim 5, characterized in that, Includes the following steps: Step 1: Start the drive motor (15) and drive the drive sprocket (10) to rotate through the reducer (14). Through the tension sprocket (11), the first driven sprocket (12) and the second driven sprocket (13) work together to drive the lifting rod (16) to rise. When the lifting rod (16) rises, the inclined support protrusion (1601) abuts against the bottom of the fixed sleeve (17), thereby driving the fixed plate (5) and the isolation frame (8) to rise as a whole, and then driving the fork (6) and fork feet (7) to rise synchronously to complete the lifting operation. Step 2: When the chain (29) breaks, the fixed plate (5) descends as a whole. At this time, the second compression spring (30) releases its elastic force, causing the lifting rod (16) and slide rod (19) to descend as a whole. At this time, the wedge (21) loses its compression. With the cooperation of the retaining ring (26) and the first compression spring (25), the wedge (21) slides and simultaneously drives the telescopic rod (22) to slide outward. When the telescopic rod (22) passes through the slot (201), it will continue to expand outward by one end. When the telescopic rod (22) descends to the bottom of the slot (201), the isolation frame (8) is resisted as a whole and stops descending. Step 3: When the slide bar (19) descends, the electronic pressure switch (27) loses pressure and its switch state changes. The internal control system of the control box (3) detects the signal and outputs a signal to the alarm light (28) to control it to work and play a warning role.

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