Composite bearing type casing centralizer

Abstract

The invention relates to the technical field of casing running equipment, and discloses a composite bearing type casing centralizer which comprises an upper lantern ring and a lower lantern ring, the upper lantern ring is arranged on the surface of a casing in a sliding and sleeving mode, the lower lantern ring is fixedly connected to the surface of the casing, the surfaces of the two corresponding sides of the lower lantern ring and the upper lantern ring are jointly connected with an alignment piece, and the alignment piece is fixedly connected to the surface of the lower lantern ring. A plurality of groups of alignment pieces are arranged, and are circumferentially arranged along the surface of the sleeve; the alignment piece comprises a connecting block, an upper connecting rod and a lower connecting rod, wherein the upper connecting rod and the lower connecting rod are symmetrically arranged up and down. The ends, away from each other, of the upper connecting rod and the lower connecting rod are rotationally connected with the upper lantern ring and the lower lantern ring correspondingly. The combined bearing design of the plate spring and the parallel connecting rods is adopted, the two ends of the plate spring are hinged to the upper connecting rod and the lower connecting rod which are symmetrically arranged respectively, compared with a traditional single elastic piece structure, the plate spring can provide higher radial elastic force, the overall structure is simple and practical, and compared with a traditional centralizer, the centralizer is more stable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of casing lowering equipment, and particularly relates to a composite bearing type casing centralizer. BACKGROUND

[0002] In the field of energy exploration and development of oil, natural gas and the like, casing lowering operation is a key process in wellbore construction, and its quality directly affects the stability of subsequent drilling, cementing and oil and gas production. The operation process needs to be completed gradually by the drilling platform elevator to connect and lower the casing: first, a single casing is clamped below the elevator, then another casing is lowered into the elevator, the connection of the two casings is realized by rotating and fastening the casing thread, then the elevator is loosened to continue lowering the casing, and the cycle is repeated until the casing is lowered to the designed layer to form a wellbore channel that meets the production requirements.

[0003] During the casing lowering process, the casing is prone to eccentricity, inclination or direct friction with the inner wall of the wellbore due to factors such as irregular wellbore inner wall, differences in formation lithology and gravity distribution of the casing itself. If the casing cannot maintain a central position, it will lead to uneven cement ring thickness in subsequent cementing operations, reduce the sealing performance of the wellbore and increase the risk of oil and gas channeling. Therefore, casing lowering operations need to rely on various downhole tools for assistance, and the centralizer is one of the core tools, which ensures that drilling tools, casings and the like always maintain a central position in the wellbore or pipe trench. The elastic components of traditional centralizers are mostly fixed structures, which are difficult to adjust the support range according to different wellbore diameters, and have poor versatility. Therefore, a centralizer is provided to solve this problem. SUMMARY

[0004] The purpose of the present application is to provide a casing centralizer with simple structure and reasonable design to solve the above problems

[0005] The present application achieves the above-mentioned purposes through the following technical solutions:

[0006] The present application provides a composite bearing type casing centralizer, which comprises an upper sleeve ring and a lower sleeve ring, the upper sleeve ring is slidably sleeved on the surface of the casing, the lower sleeve ring is fixedly connected to the surface of the casing, the two side surfaces of the lower sleeve ring and the upper sleeve ring correspondingly are jointly connected with alignment pieces, the alignment pieces are provided in multiple groups, and the multiple groups of alignment pieces are circumferentially arranged along the surface of the casing;

[0007] The alignment piece comprises a connecting block and upper and lower connecting rods symmetrically arranged above and below, the ends of the upper and lower connecting rods away from each other are rotatably connected with the upper sleeve ring and the lower sleeve ring respectively, the ends of the upper and lower connecting rods close to each other are rotatably connected with the connecting block, the side surface of the connecting block away from the casing is provided with a roller, the surface of the casing is provided with a leaf spring, the upper and lower connecting rods are provided in two groups and are arranged in parallel, and the two ends of the leaf spring are hingedly connected with a group of symmetrically arranged upper and lower connecting rods respectively.

[0008] When the plate spring releases elastic force, the upper sleeve ring is driven to move downward, and the roller is abutted against the inner wall of the wellbore, the upper sleeve ring is provided with a locking assembly, and the locking assembly is used for controlling the release of the elastic force of the plate spring.

[0009] As a further optimization scheme of the present application, the lower surface of the upper sleeve ring is connected with an upper mounting block, the upper surface of the lower sleeve ring is connected with a lower mounting block, one end of each of the two groups of upper connecting rods close to the upper sleeve ring is connected with the upper mounting block through a rotating shaft one, one end of each of the two groups of lower connecting rods close to the lower sleeve ring is connected with the lower mounting block through a rotating shaft two, and the outer sides of the rotating shaft one and the rotating shaft two are sleeved with torsion springs.

[0010] As a further optimization scheme of the present application, one end of each of the two groups of upper connecting rods away from the upper sleeve ring is connected with the connecting block through a rotating shaft three, one end of each of the two groups of lower connecting rods away from the lower sleeve ring is connected with the connecting block through a rotating shaft four, the surfaces of the rotating shaft three and the rotating shaft four close to the sleeve one side are fixedly sleeved with gears, and the two groups of gears are meshed.

[0011] As a further optimization scheme of the present application, the surface of the sleeve is fixedly sleeved with a mounting cylinder, the upper sleeve ring is slidably sleeved on the outer surface of the mounting cylinder, and the locking assembly is arranged on the mounting cylinder.

[0012] The locking assembly comprises a top ring and a bottom ring fixedly sleeved on the outer surface of the mounting cylinder, a rotating ring sleeved on the outer surface of the mounting cylinder, the rotating ring being located between the bottom ring and the top ring, a plurality of slide rods connected with the upper surface of the upper sleeve ring, the upper ends of the slide rods penetrating through the bottom ring, the plurality of slide rods being circumferentially arranged, each of the surfaces of the slide rods being provided with a ratchet groove, a ratchet block corresponding to the slide rod being fixedly connected to the outer surface of the rotating ring, the ratchet groove being meshed with the corresponding ratchet block, and a control assembly arranged on the bottom ring and limiting the rotation of the rotating ring along the surface of the mounting cylinder.

[0013] As a further optimization scheme of the present application, the control assembly comprises a mounting plate, a fixed plate and a return spring, the mounting plate being fixedly connected to the upper surface of the bottom ring, the fixed plate being fixedly connected to the outer surface of the rotating ring, the two ends of the return spring being respectively connected to the surfaces of the fixed plate and the mounting plate, a limiting pin being slidably connected to the top ring, and the lower end of the limiting pin being abutted against the surface of one group of ratchet blocks away from the ratchet groove.

[0014] As a further optimization scheme of the present application, the surface of the mounting cylinder is fixedly sleeved with a limiting ring, the lower surface of the rotating ring is abutted against the upper surface of the bottom ring, and the upper surface of the rotating ring is abutted against the lower surface of the limiting ring.

[0015] As a further optimization scheme of the present application, the top ring is slidably connected with an unlocking bolt and a control bolt, the lower end of the unlocking bolt is connected with an inclined block one, the upper surface of the bottom ring is connected with an inclined block two, the inclined block one and the inclined block two are arranged in cooperation, and the lower end of the control bolt is connected with a group of slide rods.

[0016] As a further optimization scheme of the present application, the upper surface of the bottom ring is fixedly connected with a limiting rod, and the limiting rod is located on the side of the inclined block two away from the inclined block one.

[0017] As a further optimization scheme of the present application, the two side surfaces of the top ring and the bottom ring are jointly connected with an upper sleeve, the upper sleeve is sleeved on the side of the plurality of slide rods away from the mounting cylinder, the two side surfaces of the bottom ring and the upper sleeve are jointly connected with a lower sleeve, the lower sleeve is arranged in an extendable manner, and the lower sleeve is sleeved on the side of the plurality of slide rods away from the mounting cylinder.

[0018] As a further optimization scheme of the present application, the upper ends of the limiting bolt, the unlocking bolt and the control bolt are connected with steel wires, and the steel wires are connected with a hoisting device at the ends away from the top ring.

[0019] The present application has the advantages that: the present application adopts a composite bearing design of a leaf spring and parallel connecting rods, the two ends of the leaf spring are hingedly connected with symmetrically arranged upper connecting rods and lower connecting rods, compared with a traditional single spring structure, the leaf spring can provide stronger radial elastic force, the overall structure is simple and practical, and compared with a traditional centralizer, the present application is more stable. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of the overall structure of the present application;

[0021] Figure 2 is a schematic diagram of the alignment part structure of the present application;

[0022] Figure 3 is a schematic diagram of the gear structure position of the present application;

[0023] Figure 4 is a schematic diagram of the locking assembly structure of the present application;

[0024] Figure 5 is a schematic diagram of the control assembly structure of the present application.

[0025] In the figure: 1, the upper sleeve ring; 2, the lower sleeve ring; 3, the alignment piece; 31, the connecting block; 32, the upper connecting rod; 33, the lower connecting rod; 34, the roller; 35, the leaf spring; 4, the locking assembly; 41, the top ring; 42, the bottom ring; 43, the rotating ring; 44, the slide bar; 45, the ratchet groove; 46, the ratchet block; 5, the upper mounting block; 6, the lower mounting block; 7, the control assembly; 71, the mounting plate; 72, the fixed plate; 73, the return spring; 74, the limiting pin; 8, the rotating shaft one; 9, the rotating shaft two; 10, the torsion spring; 11, the rotating shaft three; 12, the rotating shaft four; 13, the gear; 14, the mounting cylinder; 15, the limiting ring; 16, the unlocking pin; 17, the control pin; 18, the inclined block one; 19, the inclined block two; 20, the limiting rod; 21, the upper sleeve; 22, the lower sleeve. DETAILED DESCRIPTION

[0026] It is necessary to point out here that the following detailed description is only used to further illustrate the application and cannot be understood as limiting the scope of protection of the application. Those skilled in the art can make some non-essential improvements and adjustments to the application according to the above application content.

[0027] Example one

[0028] Reference Figure 1 And Figure 2 As shown in part of the structure, a composite bearing type casing centralizer comprises an upper sleeve ring 1 and a lower sleeve ring 2, the upper sleeve ring 1 is slidably sleeved on the surface of the casing, and the lower sleeve ring 2 is fixedly connected to the surface of the casing. The two side surfaces of the lower sleeve ring 2 and the upper sleeve ring 1 correspondingly are jointly connected with alignment pieces 3, and the alignment pieces 3 are provided in multiple groups. The multiple groups of alignment pieces 3 are circumferentially arranged along the surface of the casing.

[0029] The alignment piece 3 comprises a connecting block 31 and an upper connecting rod 32 and a lower connecting rod 33 symmetrically arranged above and below. The ends of the upper connecting rod 32 and the lower connecting rod 33 away from each other are respectively rotatably connected with the upper sleeve ring 1 and the lower sleeve ring 2. The ends of the upper connecting rod 32 and the lower connecting rod 33 close to each other are rotatably connected with the connecting block 31. The side surface of the connecting block 31 away from the casing is provided with a roller 34. The surface of the casing is provided with a leaf spring 35. The upper connecting rod 32 and the lower connecting rod 33 are provided in two groups and are arranged in parallel. The two ends of the leaf spring 35 are respectively hingedly connected with one group of symmetrically arranged upper connecting rods 32 and lower connecting rods 33.

[0030] When the leaf spring 35 releases the elastic force, the upper sleeve ring 1 is driven to move downward, and the roller 34 abuts against the inner wall of the wellbore. The upper sleeve ring 1 is provided with a locking assembly 4 for controlling the release of the elastic force of the leaf spring 35.

[0031] It should be noted that the leaf spring 35 is in the initial state when it stores the force.

[0032] In actual use, in the initial state, the locking assembly 4 is in the locked state, limiting the downward movement of the upper collar 1, when the casing is lowered into the wellbore, the locking state of the locking assembly 4 is released,

[0033] In this embodiment, the locking assembly 4 can include a hoisting device and a wire rope, the hoisting device is connected with the upper collar 1 through the wire rope, before the casing is lowered into the wellbore, the hoisting device always applies a pulling force to the upper collar 1 through the wire rope, when the casing enters the wellbore, the pulling force applied to the upper collar 1 is cancelled, at this time, the plate spring 35 releases the elastic force, under the cooperation of the upper connecting rod 32 and the lower connecting rod 33, the rollers 34 on the connecting blocks 31 in multiple groups are simultaneously abutted against the inner wall of the wellbore, further making the casing always keep the centered state in the wellbore and enter the designated position, wherein the hoisting device is a prior art mechanism, therefore, in this embodiment, it is not described in detail.

[0034] It should be noted that the rollers 34 on a group of connecting blocks 31 can be provided in multiple groups, which are arranged in a straight line in the vertical direction.

[0035] Reference Figure 3 As shown in part of the structure, the lower surface of the upper collar 1 is connected with the upper mounting block 5, the upper surface of the lower collar 2 is connected with the lower mounting block 6, one end of the two groups of upper connecting rods 32 close to the upper collar 1 is connected with the upper mounting block 5 through the rotating shaft one 8, one end of the two groups of lower connecting rods 33 close to the lower collar 2 is connected with the lower mounting block 6 through the rotating shaft two 9, the outer side of the rotating shaft one 8 and the rotating shaft two 9 is sleeved with the torsion spring 10.

[0036] It should be noted that the torsion spring 10 is provided to assist the rotation of the rotating shaft one 8 and the rotating shaft two 9.

[0037] Further, one end of the two groups of upper connecting rods 32 away from the upper collar 1 is connected with the connecting block 31 through the rotating shaft three 11, one end of the two groups of lower connecting rods 33 away from the lower collar 2 is connected with the connecting block 31 through the rotating shaft four 12, the surface of the rotating shaft three 11 and the rotating shaft four 12 close to the casing side is fixedly sleeved with the gear 13, the two groups of gears 13 are meshed.

[0038] It should be noted that the meshing of the two gears 13 is provided to make the upper connecting rod 32 and the lower connecting rod 33 rotate synchronously along the rotating shaft one 8 and the rotating shaft two 9, respectively.

[0039] Embodiment two

[0040] This embodiment is further improved on the basis of embodiment one, and provides a locking assembly 4 with simple structure, the locking assembly 4 in this embodiment can improve the stability of the alignment member 3, and prevent the upper collar 1 from continuously moving up and down on the surface of the casing when the plate spring 35 releases the elastic potential energy (elastic force).

[0041] Reference Figure 4As shown in part of the structure, the surface of the sleeve is fixedly sleeved with the mounting cylinder 14, the upper sleeve 1 is slidingly sleeved on the outer surface of the mounting cylinder 14, and the locking assembly 4 is arranged on the mounting cylinder 14.

[0042] The locking assembly 4 comprises a top ring 41 and a bottom ring 42 which are fixedly sleeved on the outer surface of the mounting cylinder 14, the outer surface of the mounting cylinder 14 is sleeved with a rotating ring 43, the rotating ring 43 is located between the bottom ring 42 and the top ring 41, the upper surface of the upper sleeve 1 is connected with a plurality of slide rods 44, the upper ends of the slide rods 44 penetrate through the bottom ring 42, the plurality of slide rods 44 are circumferentially arranged, each slide rod 44 is provided with a ratchet groove 45 on the surface, the outer surface of the rotating ring 43 is fixedly connected with a ratchet block 46 corresponding to the slide rod 44, the ratchet groove 45 is engaged with the ratchet block 46 corresponding to the slide rod 44, and the bottom ring 42 is provided with a control assembly 7.

[0043] It should be noted that the cooperation of the ratchet block 46 and the ratchet groove 45 makes the leaf spring 35 unable to move upward under the action of the elastic force, and further makes the roller 34 stably abut against the inner wall of the wellbore.

[0044] Reference Figure 5 As shown in part of the structure, the control assembly 7 comprises a mounting plate 71, a fixed plate 72 and a reset spring 73, the mounting plate 71 is fixedly connected to the upper surface of the bottom ring 42, the fixed plate 72 is fixedly connected to the outer surface of the rotating ring 43, the two ends of the reset spring 73 are connected to the surfaces of the fixed plate 72 and the mounting plate 71 respectively, the top ring 41 is slidingly connected with a limiting pin 74, and the lower end of the limiting pin 74 abuts against one side surface of a group of ratchet blocks 46 away from the ratchet groove 45.

[0045] Specifically, the surface of the limiting pin 74 is fixedly connected with a baffle, and the baffle is located below the top ring 41. The baffle can prevent the limiting pin 74 from being completely pulled out of the top ring 41.

[0046] In actual use, when the limiting pin 74 abuts against one side surface of the ratchet block 46, the rotating ring 43 cannot rotate, and when the leaf spring 35 releases the elastic force, the upper sleeve 1 will drive the slide rod 44 to move downward. In the process of moving downward of the slide rod 44, under the action of the reset spring 73, the ratchet block 46 will always abut against the ratchet groove 45, thereby preventing the slide rod 44 from moving upward.

[0047] Further, the surface of the mounting cylinder 14 is fixedly sleeved with a limiting ring 15, the lower surface of the rotating ring 43 abuts against the upper surface of the bottom ring 42, and the upper surface of the rotating ring 43 abuts against the lower surface of the limiting ring 15.

[0048] It should be noted that the cooperation of the limiting ring 15 and the bottom ring 42 prevents the rotating ring 43 from moving up and down along the mounting cylinder 14.

[0049] Further, the top ring 41 is slidably connected with an unlocking bolt 16 and a control bolt 17, the lower end of the unlocking bolt 16 is connected with an inclined block one 18, the upper surface of the bottom ring 42 is connected with an inclined block two 19, the inclined block one 18 and the inclined block two 19 are matched, and the lower end of the control bolt 17 is connected with a group of slide rods 44.

[0050] In actual use, when the unlocking bolt 16 is pulled, under the cooperation of the inclined block one 18 and the inclined block two 19, the rotating ring 43 rotates, so that the ratchet block 46 is away from the ratchet groove 45, at this time, the control bolt 17 can be pulled to drive the upper sleeve ring 1 to move upwards, so that the leaf spring 35 returns to the initial state.

[0051] Further, the upper surface of the bottom ring 42 is fixedly connected with a limiting rod 20, and the limiting rod 20 is located on the side of the inclined block two 19 away from the inclined block one 18.

[0052] It should be noted that the limiting rod 20 can prevent the inclined block one 18 from moving above the inclined block two 19.

[0053] Reference Figure 2 As shown in the partial structure, the two side surfaces of the top ring 41 and the bottom ring 42 are jointly connected with an upper sleeve 21, the upper sleeve 21 is sleeved on the side of the plurality of slide rods 44 away from the mounting cylinder 14, the two side surfaces of the bottom ring 42 and the upper sleeve ring 1 are jointly connected with a lower sleeve 22, the lower sleeve 22 is arranged to be telescopic, and the lower sleeve 22 is sleeved on the side of the plurality of slide rods 44 away from the mounting cylinder 14.

[0054] It should be noted that the telescopic lower sleeve 22 can also be a corrugated tube arrangement, and the arrangement of the upper sleeve 21 and the lower sleeve 22 can protect the locking assembly 4 and the control assembly 7.

[0055] Further, the upper ends of the limiting bolt 74, the unlocking bolt 16 and the control bolt 17 are connected with a steel wire rope, and the end of the steel wire rope away from the top ring 41 is connected with a hoisting device.

[0056] In actual use, the hoisting device and the steel wire rope can be matched to exert a pulling force on the control limiting bolt 74, the unlocking bolt 16 and the control bolt 17.

[0057] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A composite load-bearing type casing centralizer, characterized by, The upper sleeve ring and the lower sleeve ring are provided, the upper sleeve ring is sleeved on the surface of the sleeve, the lower sleeve ring is fixedly connected to the surface of the sleeve, and the two side surfaces of the lower sleeve ring and the upper sleeve ring are connected with alignment members; the alignment members are provided in multiple groups, and the multiple groups of alignment members are arranged in a circle along the surface of the sleeve. The alignment member comprises a connecting block and upper and lower connecting rods symmetrically arranged above and below, the upper and lower connecting rods are rotatably connected to the upper sleeve ring and the lower sleeve ring at the ends away from each other, the upper and lower connecting rods are rotatably connected to the connecting block at the ends close to each other, a roller is mounted on the side surface of the connecting block away from the sleeve, a leaf spring is arranged on the surface of the sleeve, the upper and lower connecting rods are provided in two groups and arranged in parallel, and the two ends of the leaf spring are hingedly connected to one group of symmetrically arranged upper and lower connecting rods. When the leaf spring releases the elastic force, the upper sleeve ring is driven to move downward, and the roller abuts against the inner wall of the wellbore; the upper sleeve ring is provided with a locking assembly for controlling the release of the elastic force of the leaf spring.

2. A composite load-bearing type casing centralizer according to claim 1, characterized in that: The lower surface of the upper sleeve ring is connected with an upper mounting block, the upper surface of the lower sleeve ring is connected with a lower mounting block, the ends of the two groups of upper connecting rods close to the upper sleeve ring are connected to the upper mounting block through a rotating shaft one, the ends of the two groups of lower connecting rods close to the lower sleeve ring are connected to the lower mounting block through a rotating shaft two, and the outer sides of the rotating shaft one and the rotating shaft two are sleeved with torsion springs.

3. A composite load-bearing type casing centralizer according to claim 2, characterized in that: The ends of the two groups of upper connecting rods away from the upper sleeve ring are connected to the connecting block through a rotating shaft three, the ends of the two groups of lower connecting rods away from the lower sleeve ring are connected to the connecting block through a rotating shaft four, the surfaces of the rotating shaft three and the rotating shaft four close to the sleeve are fixedly sleeved with gears, and the two gears are meshed.

4. The composite load-bearing type casing centralizer according to claim 1, characterized in that: The surface of the sleeve is fixedly sleeved with a mounting cylinder, the upper sleeve ring is sleeved on the outer surface of the mounting cylinder, and the locking assembly is arranged on the mounting cylinder. The locking assembly comprises a top ring and a bottom ring fixedly sleeved on the outer surface of the mounting cylinder, the outer surface of the mounting cylinder is sleeved with a rotating ring between the bottom ring and the top ring, the upper surface of the upper sleeve ring is connected with a plurality of slide rods, the upper ends of the slide rods penetrate through the bottom ring, the plurality of slide rods are arranged in a circle, the surfaces of the slide rods are provided with ratchet grooves, the outer surface of the rotating ring is fixedly connected with ratchet blocks corresponding to the slide rods, the ratchet grooves are meshed with the corresponding ratchet blocks, and the bottom ring is provided with a control assembly.

5. A composite load-bearing type casing centralizer according to claim 4, characterized in that: The control assembly comprises a mounting plate, a fixed plate and a return spring, the mounting plate is fixedly connected to the upper surface of the bottom ring, the fixed plate is fixedly connected to the outer surface of the rotating ring, the two ends of the return spring are connected to the surfaces of the fixed plate and the mounting plate, the top ring is slidably connected with a limiting pin, and the lower end of the limiting pin abuts against one side surface of the ratchet block away from the ratchet groove.

6. A composite load-bearing type casing centralizer according to claim 4, characterized in that: The surface of the mounting cylinder is fixedly sleeved with a limiting ring, the lower surface of the rotating ring abuts against the upper surface of the bottom ring, and the upper surface of the rotating ring abuts against the lower surface of the limiting ring.

7. A composite load-bearing type casing centralizer according to claim 5, characterized in that: The top ring is slidably connected with an unlocking bolt and a control bolt, the lower end of the unlocking bolt is connected with an inclined block one, the upper surface of the bottom ring is connected with an inclined block two, the inclined block one and the inclined block two are matched, and the lower end of the control bolt is connected with a group of slide rods.

8. A composite load-bearing type casing centralizer according to claim 7, characterized in that: The upper surface of the bottom ring is fixedly connected with a limiting rod, and the limiting rod is located on the side of the inclined block two away from the inclined block one.

9. A composite load-bearing type casing centralizer according to claim 4, characterized in that: The corresponding two side surfaces of the top ring and the bottom ring are jointly connected with an upper sleeve, the upper sleeve is sleeved on the side of the groups of slide rods away from the mounting cylinder, the corresponding two side surfaces of the bottom ring and the upper sleeve are jointly connected with a lower sleeve, the lower sleeve is telescopically arranged, and the lower sleeve is sleeved on the side of the groups of slide rods away from the mounting cylinder.

10. The composite load-bearing type casing centralizer according to claim 7, characterized in that: The upper ends of the limiting bolt, the unlocking bolt and the control bolt are connected with steel wires, and the ends of the steel wires away from the top ring are connected with lifting equipment.

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