A verticality measurement and adjustment structure for steel pipe columns in reverse construction of foundation pit

Abstract

The present invention relates to a verticality measurement and adjustment structure for a steel pipe column in a foundation pit reverse construction method, which solves the problem of limited verticality measurement accuracy of a steel pipe column in the existing foundation pit reverse construction method. The structure includes a pile hole opened on the ground, a steel pipe column is arranged in the pile hole, and an adjustment bracket is arranged around the top of the pile hole. A photosensitive sensor is arranged on the upper end of the side wall of the steel pipe column through an automatic leveling pan-tilt. The photosensitive sensor includes a downward-facing flat photosensitive plate, and a vertically downward laser is arranged at the center of the flat photosensitive plate. A reflector is fixedly arranged on the side wall of the steel pipe column below the photosensitive sensor. The reflector is an upward-facing convex mirror, and the line connecting the swing center point of the laser on the pan-tilt and the center of the mirror surface of the reflector is located on the axial plane of the steel pipe column. The present invention uses optical measurement to accurately measure the deflection direction and deflection amount, and performs secondary deflection on the reflected signal to amplify the reflected signal, thereby further improving the verticality measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of underground structure construction of buildings, relates to a reverse construction technology, and particularly to a steel pipe column verticality measurement and adjustment structure for reverse construction of foundation pits. Background Art

[0002] With the rapid development of urban construction in my country, buildings are constantly developing into the sky. At the same time, underground spaces and facilities for various purposes have also been unprecedentedly developed, including high-rise building basements, underground commercial streets and other types. To build these underground facilities, deep foundation pits must be excavated. The traditional foundation pit adopts the sequential method, which is to excavate the deep foundation pit all day according to the depth requirements of the foundation pit, and then build the underground structure layer by layer from bottom to top. The sequential method has a large construction volume, a large amount of earthwork excavated at one time, a long construction period for the underground structure, and a large depth of foundation pit excavated at one time has an impact on the surrounding plots. Therefore, it is necessary to leave a large safety distance around the construction project and spend a high amount of support costs to ensure construction safety. According to statistics, the cost of underground deep foundation engineering is 20% to 30% of the total price of the entire high-rise building, of which the support cost of the foundation pit accounts for about 10% of the total project price. Secondly, some enclosure structures are only used as temporary structures during the entire basement construction process, which also occupies part of the project cost.

[0003] There is also a reverse construction method for foundation pits, such as the Chinese patent published on March 16, 2018, with the publication number CN107806112A, and the name is reverse steel lattice columns and construction methods for supporting foundation pits. In the reverse construction method, the pile holes are manually drilled at the design points of the foundation pit steel pipe columns, and the steel cage is lowered. The support platform is cast around the top of the pile hole and the adjustment bracket is installed. After the steel pipe column is lowered to the design elevation by a crane, the support plates on both sides of the top of the steel pipe column are supported by the adjustment bracket, and the verticality of the steel pipe column is adjusted by the adjustment device on the adjustment bracket. After the adjustment is completed, cement grouting is performed to cast and fix the bottom end of the steel pipe column to the steel cage. In the reverse construction process, the verticality adjustment of the steel pipe column is a key process, which has a very important impact on the overall structure of the building. The verticality of the steel pipe column in the construction project basically meets the requirements of less than 1 / 500 or even one thousandth. The existing verticality measurement device is generally implemented by a total station, but because the main structure of the steel pipe column is below the ground elevation, a 2-3 meter guide column is generally welded on the upper end of the steel pipe column for verticality measurement and adjustment. The total station measures the verticality of the guide tube and then infers the verticality of the steel pipe column. The measurement accuracy is difficult to meet the high-precision verticality measurement requirements. There is also a method of setting an inclinometer tube parallel to the axis of the steel pipe column on the side wall of the steel pipe column, and then measuring the verticality by moving the inclinometer along the inclinometer tube. The inclinometer tube can penetrate below the ground elevation, but due to the long length of the inclinometer tube, the pipe itself will be partially bent during installation, which will affect the inclinometer moving along the inclinometer tube, and the measurement accuracy is limited. Summary of the invention

[0004] The present invention mainly solves the problem of limited verticality measurement accuracy of steel pipe columns in the existing foundation pit reverse construction method, and provides a steel pipe column verticality measurement and adjustment structure for foundation pit reverse construction method, which can measure the verticality of the steel pipe column with high precision and adjust the verticality in multiple directions through a jack.

[0005] The purpose of the present invention is mainly achieved through the following scheme: a verticality measurement and adjustment structure of a steel pipe column for reverse construction of a foundation pit, comprising a pile hole opened on the ground, a steel pipe column is arranged in the pile hole, an adjustment bracket is arranged around the top of the pile hole, the upper end of the steel pipe column is mounted on the adjustment bracket, and a jack for adjusting the verticality of the steel pipe column is arranged on the adjustment bracket, wherein the characteristic is that a photosensitive sensor is arranged on the upper end of the side wall of the steel pipe column through an automatic leveling platform, the photosensitive sensor includes a downward plane photosensitive plate, the center of the plane photosensitive plate is provided with a vertically downward laser, a reflector is fixedly arranged on the side wall of the steel pipe column below the photosensitive sensor, the reflector is an upward convex mirror, and the line connecting the swing center point of the laser on the platform and the center of the mirror surface of the reflector is located on the axial plane of the steel pipe column. Traditional verticality measurement uses a mechanical inclinometer traveling along the inclinometer tube, and the accuracy is affected by the bending of the inclinometer tube itself, and the height of the steel pipe column exposed above the ground is insufficient, and the verticality accuracy measured by the total station is also insufficient. This device adopts laser measurement method. The light can maintain good direct radiation in a uniform air medium. The photosensor always keeps emitting light signals vertically downward through the pan / tilt. The reflector tilts with the steel pipe column. The laser is reflected by the reflector to the photosensitive plate. The distance between the reflected signal received by the photosensitive plate and the transmitted signal can accurately measure the deflection direction and deflection amount. The photosensitive plate can display the signal on an external display screen through signal export to guide the vertical adjustment. This scheme further sets the reflector to be an arc surface. The photosensitive sensor and the reflector are precisely aligned up and down, so that the reflected signal and the transmitted signal have good coincidence. When the photosensitive sensor and the reflector are misaligned up and down, the arc reflector further deflects the angle of the reflected light, so that the reflected signal received by the photosensitive plate can be further increased, thereby improving the sensitivity of the sensor. For example, the photosensitive sensor and the reflector are 10 meters apart from each other. If there is a vertical deviation in the steel pipe column, the tilt angle is α, and the angle between the reflected signal light reflected by the plane mirror and the vertical line is 2α. If a curved mirror with a radius of 10 meters is used, the angle between the reflected signal light and the vertical line is 4α, and the sensor sensitivity is doubled. The photosensitive sensor is limited by the area of ​​the photosensitive plate and has a small measurable range. Therefore, a total station can be used to perform a rough vertical measurement and make preliminary adjustments. When the vertical deviation is reduced to a small enough size, the photosensitive sensor of this device can be used for fine adjustment. The photosensitive sensor and other high-precision components of this device are set at the upper end of the steel pipe column. After the adjustment is completed and the steel pipe column is grouted and fixed, it can be disassembled for secondary use. The reflector is located below the ground elevation and can be selected not to be recycled.

[0006] Preferably, the outer wall of the steel pipe column is provided with an inclinometer tube parallel to the axis of the steel pipe column, the photosensitive sensor is arranged at the upper end of the inclinometer tube, and the reflector is arranged at the lower end of the inclinometer tube. The inclinometer tube protects the photosensitive sensor and the reflectivity, and as long as the optical path is kept unobstructed, the installation coaxiality requirement is reduced.

[0007] Preferably, avoidance grooves are provided at the upper and lower ends of the inclinometer tube on the sides of the steel pipe column, and the inclinometer tube is fixed to the steel pipe column by a plurality of clamps.

[0008] Preferably, two groups of photosensitive sensors and reflectors are arranged on the side wall of the steel pipe column, and the two groups of photosensitive sensors and reflectors are arranged at an interval of 90 degrees in the circumferential direction of the steel pipe column. The mirror surface of the reflector is a cylindrical surface, and the axis of the cylindrical surface is arranged along the radial direction of the steel pipe column. The emission outlet of the laser is in the shape of a point, a line or a cross. The cylindrical reflector can only detect the deviation in one direction, so two groups of photosensitive sensors and reflectors are arranged at an interval of 90 degrees for verticality detection in two vertical directions. Linear or cross-shaped signals are easier to identify.

[0009] As another preferred solution, the photosensitive sensor and the reflector are arranged in a group on the side wall of the steel pipe column, the reflector surface is a spherical surface, and the laser emission port is a dot or cross shape. When the spherical reflector is used, it is difficult to align and calibrate with the photosensitive sensor, but a group of photosensitive sensors and reflectors can be used to detect verticality in all directions. Such detection signals are more intuitive when guiding adjustments, and the direction in which the verticality has deviations can be directly selected for correction and adjustment.

[0010] Preferably, the distance between the photosensor and the reflector is L, the arc radius of the reflector is R, R=L, and further L=10m.

[0011] Preferably, the pan head comprises an outer ring frame, a middle ring frame and an inner ring frame. The outer ring frame is fixed to the side wall of the steel pipe column by a connecting rod. A transverse hinge axis is provided between the outer ring frame and the middle ring frame, a longitudinal hinge axis is provided between the middle ring frame and the inner ring frame, and the inner ring frame is provided with a photosensor.

[0012] Preferably, the adjustment bracket is provided with a lower adjustment device and an upper adjustment device, the lower adjustment device comprises four lower jacks radially mounted on the steel pipe column and four lower adjustment screws radially mounted on the steel pipe column, the four lower jacks and the four lower adjustment screws are alternately and evenly arranged around the steel pipe column, the lower jacks and the lower adjustment screws are fixedly arranged on the adjustment bracket, the upper end of the steel pipe column is coaxially welded and extended with a guide column, the upper adjustment device comprises four upper jacks that can be radially ejected inward to the guide column and four upper adjustment screws that can be radially ejected inward to the guide column, the upper adjustment screws and the lower adjustment screws are aligned and fixedly arranged up and down, an annular track is arranged below the upper jack, the four upper jacks are arranged at equal intervals on the annular track and rotate synchronously, and a ring seat is arranged around the outer ring of the four upper jacks to abut against the outer ends of the upper jacks. The upper adjustment device acts on the guide column, and the lower adjustment device acts on the steel pipe column. The weld between the guide column and the steel pipe column is between the upper adjustment device and the lower adjustment device. During adjustment, the lower adjustment device is used to clamp and position the steel pipe column, and then the upper adjustment device is used to adjust and calibrate, so that the steel pipe column is adjusted with the clamping position of the lower adjustment device as the rotation fulcrum. During adjustment, according to the result of the verticality deviation detection, the verticality deviation direction and deviation amount of the steel pipe column are obtained, and the four lower jacks are first ejected inward for positioning, and the four upper jacks can be synchronously rotated on the circular track to the direction corresponding to the verticality deviation. The two upper jacks perpendicular to the deviation direction are ejected inward, and then the two upper jacks along the deviation direction are adjusted and calibrated. After the calibration is completed, the upper adjustment screw and the lower adjustment screw are ejected inward for positioning. The ring seat serves as the rear end abutment seat of the upper jack, and a sliding seat that can slide along the sliding rail is provided between the upper jack and the slide rail. The upper jack can slide radially along the sliding seat so that the reaction force of the upper jack will not act on the slide rail.

[0013] Preferably, the annular track is formed by welding and assembling two semicircular tracks, and the ring seat is formed by welding and assembling two semicircular rings.

[0014] Preferably, a plurality of inclined cables are evenly arranged around the top circumference of the guide column and between the adjustment bracket, and an adjustment rod is arranged in the middle of the inclined cables.

[0015] Preferably, a grouting hole is provided on the side wall of the upper end of the steel pipe column, and the grouting hole is higher than the ground elevation and lower than the lower regulating device.

[0016] Preferably, the top end of the steel pipe column extends outward to both sides to provide a support plate, which is mounted on an adjustment bracket.

[0017] Preferably, a support platform is cast on the ground around the top of the pile hole, and the adjusting support is fixed on the support platform.

[0018] The present invention adopts a photosensitive sensor, which can accurately measure the deflection direction and deflection amount. The photosensitive plate can display on an external display screen through signal export to guide the verticality adjustment; the reflector is set to an arc surface, which can perform secondary deflection on the reflected signal, amplify the reflected signal, and further improve the sensitivity of the photosensitive sensor; the upper jack used for adjusting the verticality is provided with a circular track, and the adjustment direction can be accurately selected according to the result of the verticality detection, thereby simplifying the adjustment process and improving the adjustment accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] Attached Figure 1 It is a structural schematic diagram of the present invention.

[0021] Attached Figure 2 The present invention Figure 1 Schematic diagram of the lower adjustment device structure at section AA of the structure.

[0022] Attached Figure 3 The present invention Figure 1 Schematic diagram of the upper adjustment device structure at section BB of the structure.

[0023] Attached Figure 4 It is a schematic diagram of the installation structure of the upper jack of the present invention.

[0024] Attached Figure 5 It is a schematic diagram of the structure of a photosensor and a reflector of the present invention.

[0025] Attached Figure 6 It is a schematic diagram of a pan / tilt structure of the present invention.

[0026] Attached Figure 7 It is a schematic diagram of a reflector signal amplification structure of the present invention.

[0027] Illustrations: 1. Adjusting bracket, 2. Steel pipe column, 3. Guide column, 4. Weld, 5. Bracket, 6. Upper jack, 7. Lower jack, 8. Adjusting rod, 9. Inclinometer tube, 10. Grouting hole, 11. Pile hole, 12. Bracket platform, 13. Lower adjusting screw, 14. Upper adjusting screw, 15. Ring seat, 16. Ring track, 17. Sliding seat, 18. Pan-tilt head, 19. Photosensitive plate, 20. Laser, 21. Reflector, 22 Avoidance groove, 23. Outer ring frame, 24. Middle ring frame, 25. Inner ring frame, 26. Transverse articulated shaft, 27. Longitudinal articulated shaft, 28. Connecting rod. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0029] Embodiment: A verticality measurement and adjustment structure for a steel pipe column in a foundation pit reverse construction method, such as Figure 1 , 2 , 3. The device includes a pile hole 11 opened on the ground, a steel cage below the bottom of the pile hole, a support platform 12 cast around the top of the pile hole, and a 1.8-meter-high adjustment support 1 welded and assembled on the support platform. A steel pipe column 2 is arranged in the pile hole 11, and the upper end of the steel pipe column is mounted on the adjustment support 1 through brackets 5 extending from both sides. The upper end of the steel pipe column is coaxially welded with a guide column, which is 2 meters high. Four inclined cables are evenly arranged around the upper end of the guide column and the upper surface of the adjustment support 1. An adjustment rod 8 is connected in series in the middle section of the inclined cable. A bolt hole is arranged at each end of the adjustment rod, and an adjustment bolt is arranged in the bolt hole. The two adjustment bolts are connected to the upper end of the guide column and the upper surface of the adjustment support through the steel cable. By twisting the adjustment rod, the tightness of the two bolts can be adjusted synchronously to achieve the purpose of adjusting the tension of the inclined cable. A grouting hole is arranged on the side wall of the upper end of the steel pipe column 2, and the grouting hole is higher than the ground elevation and lower than the bracket 5.

[0030] The adjusting bracket 1 is provided with a lower adjusting device and an upper adjusting device, and the weld 4 between the guide column 2 and the steel pipe column 3 is between the upper adjusting device and the lower adjusting device. The lower adjusting device includes four lower jacks 5 radially mounted on the steel pipe columns 2 and four lower adjusting screws 13 radially mounted on the steel pipe columns. The four lower jacks and the four lower adjusting screws are alternately and evenly arranged around the steel pipe columns 2. The lower jacks 5 and the lower adjusting screws 13 are arranged at fixed points on the adjusting bracket 1, that is, the lower jacks 5 are arranged in the east, south, west and north directions, and one lower adjusting screw 13 is arranged in the southeast, southwest, northeast and northwest directions respectively.

[0031] like Figure 3 , 4 As shown, the upper adjustment device includes four upper jacks 6 that are radially protruded inward and four upper adjustment screws 14 that are radially protruded inward. The upper adjustment screws and the lower adjustment screws are aligned and set at fixed points. A circular track 16 is provided below the upper jack 6. The four upper jacks 6 are arranged at equal intervals on the circular track and rotate synchronously. A ring seat 15 that abuts against the outer end of the upper jack 6 is provided around the outer ring of the four upper jacks. The circular track 16 is formed by welding and assembling two semicircular tracks, and the ring seat 15 is formed by welding and assembling two semicircular rings. A slide seat 17 that can slide along the slide rail is provided between the upper jack and the slide rail. The upper jack can slide radially along the slide seat, and adjacent slide seats are positioned by arc or linear connecting rods to keep synchronous rotation. The upper jack can slide radially along the slide seat to avoid deformation of the slide rail during jacking.

[0032] like Figure 1 , 5As shown, the outer wall of the steel pipe column 2 is provided with an inclinometer tube 9 parallel to the vertical axis of the steel pipe column, and a photosensitive sensor is mounted on the upper end of the steel pipe column side wall at the upper end of the inclinometer tube 9 through an automatically leveling pan / tilt 18, the photosensitive sensor includes a downward and horizontal flat photosensitive plate 19, a vertically downward laser 20 is arranged at the center of the flat photosensitive plate, a reflector 21 is fixedly arranged on the steel pipe column side wall at the lower end of the inclinometer tube 9, and avoidance grooves 22 are provided on the upper and lower ends of the inclinometer tube 9 close to the side of the steel pipe column, and the inclinometer tube is fixed to the steel pipe column through a plurality of clamps.

[0033] like Figure 6 As shown, the pan / tilt head 18 includes an outer ring frame 23, a middle ring frame 24, and an inner ring frame 25. The outer ring frame is fixed to the side wall of the steel pipe column 2 by a connecting rod 28. A transverse hinge axis 26 is provided between the outer ring frame 23 and the middle ring frame 24, a longitudinal hinge axis 27 is provided between the middle ring frame 24 and the inner ring frame 25, and a photosensor is mounted on the inner ring frame 25.

[0034] The reflector is an upward convex mirror, and the line connecting the swing center point of the laser on the pan / tilt 18 and the center of the mirror surface of the reflector 21 is located on the axial plane of the steel pipe column 2. There are two settings here, one: two inclinometer tubes 9 are set at an interval of 90 degrees on the side wall of the steel pipe column 2, that is, two groups of photosensitive sensors and reflectors are set at an interval of 90 degrees on the side wall of the steel pipe column, and the two groups of photosensitive sensors and reflectors are set at an interval of 90 degrees on the side wall of the steel pipe column. The arc surface of the reflector 21 is a cylindrical surface, and the axis of the cylindrical surface is set along the radial direction of the steel pipe column. The laser's emission port is linear, forming a linear projection on the reflector, and the projected light is along the normal of the cylindrical surface of the reflector. In this way, each inclinometer tube is responsible for the verticality measurement in one direction, that is, the north-south measurement and the east-west measurement are carried out separately, and each group of photosensitive sensors and reflectors only needs to be calibrated in one direction. Second: an inclinometer tube is set up, that is, a group of photosensitive sensors and reflectors are set up on the side wall of the steel pipe column, the mirror surface of the reflector 21 is spherical, and the emission outlet of the laser is cross-shaped. In this setting method, the photosensitive sensor and reflector need to be calibrated in two directions, and the position offset position of the intersection of the cross projection lines indicates the direction and amount of verticality deviation.

[0035] like Figure 5 , 7 As shown, the distance between the photosensitive sensor and the reflector 21 is L, and the arc radius of the reflector 21 is R, R=L=10m. The steel pipe column 2 has a vertical deviation and an inclination angle of α. A curved mirror 21 with a radius of 10 meters is used, and the angle between the reflected signal light and the vertical line is 4α, which can increase the sensitivity of the photosensitive sensor. The photosensitive sensor is limited by the area of ​​the photosensitive plate and has a small measurable range. Therefore, a total station can be used to perform a rough vertical measurement and make preliminary adjustments. When the vertical deviation is reduced to a small enough size, the photosensitive sensor of the device can be used for fine adjustment.

Claims

1. A verticality measurement and adjustment structure for a steel pipe column in a foundation pit reverse construction method, comprising a pile hole opened on the ground, a steel pipe column arranged in the pile hole, an adjustment bracket arranged around the top of the pile hole, the upper end of the steel pipe column mounted on the adjustment bracket, and a jack for adjusting the verticality of the steel pipe column arranged on the adjustment bracket, wherein the characteristics are: A photosensitive sensor is arranged on the upper end of the side wall of the steel pipe column through an automatically leveling platform. The photosensitive sensor includes a downward-facing flat photosensitive plate, and a vertically downward-facing laser is arranged at the center of the flat photosensitive plate. A reflector is fixedly arranged on the side wall of the steel pipe column below the photosensitive sensor. The reflector is an upward-facing convex mirror. The line connecting the swing center point of the laser on the platform and the center of the mirror surface of the reflector is located on the axial plane of the steel pipe column. The pan / tilt head comprises an outer ring frame, a middle ring frame and an inner ring frame, wherein the outer ring frame is fixed to the side wall of the steel pipe column by a connecting rod, a transverse hinge axis is arranged between the outer ring frame and the middle ring frame, a longitudinal hinge axis is arranged between the middle ring frame and the inner ring frame, and a photosensitive sensor is arranged on the inner ring frame; The adjusting bracket is provided with a lower adjusting device and an upper adjusting device, the lower adjusting device comprises four lower jacks with four radially mounted steel pipe columns and four lower adjusting screws with four radially mounted steel pipe columns, the four lower jacks and the four lower adjusting screws are alternately and evenly arranged around the steel pipe columns, the lower jacks and the lower adjusting screws are fixedly arranged on the adjusting bracket, a guide column is coaxially welded and extended at the upper end of the steel pipe column, the upper adjusting device comprises four upper jacks which can be radially ejected inward to the guide column and four upper adjusting screws which can be radially ejected inward to the guide column, the upper adjusting screw and the lower adjusting screw are aligned and fixedly arranged up and down, an annular track is provided below the upper jack, the four upper jacks are equally spaced on the annular track and rotate synchronously, a ring seat is provided around the outer ring of the four upper jacks, which abuts against the outer ends of the upper jacks.

2. The verticality measurement and adjustment structure of a steel pipe column for foundation pit reverse construction according to claim 1 is characterized by: The outer side wall of the steel pipe column is provided with an inclinometer tube parallel to the axis of the steel pipe column, the photosensitive sensor is arranged at the upper end of the inclinometer tube, and the reflector is arranged at the lower end of the inclinometer tube.

3. The verticality measurement and adjustment structure of a steel pipe column for foundation pit reverse construction according to claim 2 is characterized in that: The upper end and the lower end of the inclinometer tube are provided with avoidance grooves close to the side of the steel pipe column, and the inclinometer tube is fixed to the steel pipe column through a plurality of clamps.

4. A steel pipe column verticality measurement and adjustment structure for foundation pit reverse construction according to claim 1, 2 or 3, characterized in that: The photosensitive sensors and reflectors are arranged in two groups on the side wall of the steel pipe column, and the two groups of photosensitive sensors and reflectors are arranged on the side wall of the steel pipe column at an circumferential interval of 90 degrees. The mirror surface of the reflector is a cylindrical surface, and the axis of the cylindrical surface is arranged along the radial direction of the steel pipe column. The emission outlet of the laser is point-shaped, line-shaped or cross-shaped.

5. A steel pipe column verticality measurement and adjustment structure for foundation pit reverse construction according to claim 1, 2 or 3, characterized in that: The photosensitive sensor and the reflector are arranged in a group on the side wall of the steel pipe column, the mirror surface of the reflector is a spherical surface, and the emission outlet of the laser is in a point shape or a cross shape.

6. A steel pipe column verticality measurement and adjustment structure for foundation pit reverse construction according to claim 1, 2 or 3, characterized in that: The distance between the photosensitive sensor and the reflector is L, the arc radius of the reflector is R, and R=L.

7. The verticality measurement and adjustment structure of a steel pipe column in a foundation pit reverse construction method according to claim 1 is characterized by: The annular track is formed by welding and assembling two semicircular tracks, and the ring seat is formed by welding and assembling two semicircular rings.

8. The verticality measurement and adjustment structure of a steel pipe column in a foundation pit reverse construction method according to claim 1 is characterized by: A plurality of inclined cables are evenly arranged around the top of the guide column and between the adjusting bracket, and an adjusting rod is arranged in the middle of the inclined cables.

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