Method and device for high-precision boring of fixed structure in narrow space

Abstract

The invention discloses a high-precision boring method and device for a fixed structure in a narrow and small space in the technical field of anchor box anchor hole machining, is suitable for machining an anchor hole of an anchor box in a steel box girder box, and comprises the following steps that S1, the size of an operation space around the anchor box is determined, and a positioning datum line is drawn on the surface of an anchor backing plate; s2, a first fixing device and a second fixing device are installed, and stable preliminary constraint is formed on the side of the bottom plate; s3, the connecting base is installed on a gear speed reducer, and a cutterhead and a high-alloy turning tool are installed on the gear speed reducer; s4, the connecting base is clamped into the two fixing devices, and a third fixing device on the top plate side is installed; s5, an adjustable carrying pole beam system is installed on the block web and connected to a lifting lug of a gear reducer; and S6, boring machining of the anchor hole is executed. The problems that the operation space is extremely limited, equipment positioning is difficult, and the precision is affected by the dead weight and vibration of equipment in the machining process can be solved, and finally it is ensured that the anchor hole machining precision meets the requirement within + / -0.5 mm.

Description

Technical Field

[0001] This invention relates to the field of steel box girder internal anchor box anchor hole processing technology, and in particular to a method and apparatus for high-precision boring of fixed structures in confined spaces. Background Technology

[0002] The accuracy of the anchor plates and anchor holes in the anchor box structure of a steel box girder is crucial, even decisive, for bridges, especially long-span cable-stayed or suspension bridges. The cables of a cable-stayed bridge or the suspenders of a suspension bridge are the main load-bearing components, comparable to the bridge's "lifeline." The force of this "lifeline" is ultimately transferred safely and smoothly to the steel box girder, and then to the entire bridge structure, through the anchor box, a key force-transmitting component. The anchor plates and anchor holes are the "final interface" and "choke point" of the force transmission path. Their accuracy directly determines the stress state of the cables (or suspenders) and the installation and normal operation of the anchorages.

[0003] Insufficient precision can directly lead to the following serious engineering problems: First, it poses a structural safety hazard. Under long-term eccentric loads and fatigue, brittle fracture may occur in the anchor box structure or at the connection welds, leading to cable anchorage failure. Second, the completed bridge alignment and internal force state may deviate from the design. The cable force of each cable is precisely calculated to ensure that the bridge achieves the designed alignment and ideal internal force state. The additional bending moment and cable force loss caused by anchor hole deviation will make the actual cable force inconsistent with the design value. Finally, it will also cause construction delays due to construction difficulties. Repair work such as "hole enlargement" and "grinding" at the bridge site is time-consuming and labor-intensive, and will damage the already applied anti-corrosion coating.

[0004] Traditional construction methods involve machining anchor plates, load-bearing plates, and other structural components before incorporating them into block fabrication and segment assembly. The drawback of this method is that while machining ensures the accuracy of the anchor holes, uncontrollable factors such as welding deformation in subsequent processes can affect the accuracy of the anchor holes and the coordinates of the anchor points. Furthermore, if the design changes the hole diameter after the anchor holes have been machined and incorporated into the segment assembly, secondary machining of the anchor holes must be considered. Machining the anchor holes after the anchor blocks have been welded together with the web, diaphragms, and other structures significantly reduces accuracy deviations caused by welding deformation. However, the internal space of a steel box girder is extremely confined and enclosed, making it impossible for large precision machine tools to access the structure, and conventional hand tools cannot guarantee the required accuracy. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and apparatus for high-precision boring of fixed structures in confined spaces. This method overcomes challenges such as extremely limited operating space, difficulty in equipment positioning, and the impact of equipment weight and vibration on accuracy during processing. Ultimately, it ensures that the anchor hole processing accuracy meets the extremely high requirement of ±0.5mm.

[0006] The objective of this invention is achieved as follows: a method for high-precision boring of fixed structures in confined spaces, applicable to the machining of anchor holes in anchor boxes inside steel box girders, comprising the following steps:

[0007] S1: Measure the operating space dimensions around the anchor box inside the welded steel box girder block; draw the positioning reference line on the surface of the anchor plate according to the theoretical coordinates of the anchor point and the center of the foundation hole measured on site.

[0008] S2: Using the center of the basic hole determined in step S1 as a reference, install the first fixing device and the second fixing device on the bottom plate side of the anchor plate. The angle between the two devices and the line connecting them to the center is 100°~140°, and they are arranged symmetrically on the left and right sides to form a stable preliminary constraint on the bottom plate side.

[0009] S3: Install the connecting seat onto the gear reducer, and install the cutter head and high-alloy turning tool on the drive shaft of the gear reducer; the rated output torque of the gear reducer is calculated and selected based on the anchor plate material, hole diameter and cutting parameters, and usually needs to be more than 1.5 times the maximum working torque, and its reduction ratio needs to be adapted to the cutting requirements of low speed and high torque in a confined space; the turning tool is made of cemented carbide, and its rake angle and clearance angle are optimized for the intermittent cutting conditions of steel;

[0010] S4: Hoist the assembly into place, so that the non-perforated flange of the connecting seat is against the anchor plate and snapped into the two fixing devices on the bottom plate side. Then install the third fixing device on the top plate side, so that the three fixing devices are distributed in an approximately equilateral triangle, with the center of the anchor hole located at the center of this triangle. Tighten the bolts of all fixing devices to make the connecting seat flange and the anchor plate fit tightly. This three-point asymmetric constraint method, compared with the four-point symmetric constraint, can better adapt to the non-uniformity of the welded structure and form a statically determinate constraint, passively offsetting the micro-deformation caused by the release of residual stress.

[0011] S5: An adjustable spreader beam system is installed on the web of the block and connected to the lifting lug of the gear reducer by a sling to bear its entire weight; this system can fully bear the weight of the reducer and couple the equipment-tooling-workpiece into a rigid whole, effectively isolating external disturbances;

[0012] S6: Start the gear reducer to bore the hole, and monitor the cutting status through the observation window on the connecting seat web tube, clean the debris or spray cooling, and finally complete the boring of the anchor hole.

[0013] As a further improvement of the present invention, in step S1, the step of drawing the positioning line includes: drawing the positioning line with the center of the anchor hole base hole as the reference and the outer radius of the connecting seat flange as the reference, to ensure that the installation position of the fixing device accurately corresponds to the theoretical coordinates of the anchor point.

[0014] As a further improvement of the present invention, in step S2, the angle between the line connecting the first fixing device and the second fixing device and the center of the circle is 120°.

[0015] As a further improvement of the present invention, in step S3, the material of the connecting seat is not lower than Q235B, and the thickness of its flange plate is not less than 20mm.

[0016] As a further improvement of the present invention, in step S3, the high-alloy turning tool is made of cemented carbide YG8 or YW1.

[0017] As a further improvement of the present invention, in step S5, the adjustable spreader beam system achieves longitudinal position adjustment through the slot, lateral position adjustment through the sliding of the spreader beam in the sleeve, and vertical position adjustment through adjusting the length of the sling.

[0018] This invention also proposes a boring device for implementing the above method, comprising: a gear reducer with lifting lugs on the body; a connecting seat, including a web tube and flange one and flange two welded to both ends of the web tube respectively; flange one is a smooth surface without holes for tightly fitting the anchor plate; flange two has multiple bolt holes for connecting the gear reducer; a portion of the web tube is cut off to form an observation hole; three fixing devices for applying a constraint force distributed in an equilateral triangle to the connecting seat; each fixing device includes an L-shaped connecting block and a tightening bolt, one side of the L-shaped connecting block has a drilling and tapping structure for pressing the flange of the connecting seat by tightening the bolt; an adjustable spreader beam system, including a spreader beam, a sleeve, a support with a slot and a sling; both ends of the spreader beam extend into their respective sleeves for fixing; the bottom of the sleeve is fixedly connected to the upper side of the support, and the slot of the support engages with the edge of the anchor box web plate; and a cutting unit, including a cutter head and a high-alloy turning tool mounted on the drive shaft of the gear reducer.

[0019] As a further improvement of the present invention, the gear reducer has a built-in precision lead screw feed mechanism, which is used to control the axial feed speed of the cutting tool.

[0020] As a further improvement of the present invention, the cutter head is fixed to the drive shaft by a flat key and a shaft end baffle.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Through the systematic integration of "three-point statically determinate constraint fixing", "external adjustable rigid support vibration reduction" and "modular small power head", micron-level precision boring is achieved in an immovable and narrow space; (2) With this method, the accuracy of the anchor hole center position can be stably controlled within ±1mm, the hole diameter accuracy within ±0.5, and the surface roughness can reach Ra≤6.3μm, which fully meets the highest standard of bridge anchoring system; (3) Compared with the manual on-site grinding after the failure of traditional process (a single hole often requires 1-2 working days), the average processing time of a single hole can be shortened to 3-4 hours by using this device for systematic boring, the efficiency is increased by more than 100%, and the original anti-corrosion coating is not damaged; (4) The supporting equipment selected by the present invention is convenient to purchase and process and is inexpensive. The method is not affected by design changes and can perform high-precision hole processing or correction at any stage after final assembly, which is flexible in application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a three-dimensional structural diagram of the fixing device in this invention.

[0024] Figure 2 This is a schematic diagram showing the positioning and installation of the fixing device on the anchor plate.

[0025] Figure 3 This is a three-dimensional structural diagram of the connector in this invention.

[0026] Figure 4 This is a schematic diagram of the assembly of the gear reducer and the connecting seat in this invention.

[0027] Figure 5 for Figure 4 Detailed diagram of the connection between the drive shaft, the tool head, and the cutting tool.

[0028] Figure 6 This is a three-dimensional structural diagram of the adjustable spreader beam system in this invention.

[0029] Figure 7 This is a schematic diagram of the overall construction process for anchor hole processing within the confined space of a steel box girder, according to the present invention.

[0030] Among them, 1 gear reducer, 101 lifting lug, 102 drive shaft, 103 flat key, 2 connecting seat, 201 web tube, 202 flange one, 203 flange two, 204 observation hole, 3 fixing device, 301 tightening bolt, 302 L-shaped connecting block, 4 adjustable spreader beam system, 401 spreader beam, 402 sleeve, 403 slot, 404 support, 405 lifting strap, 5 cutting unit, 501 high alloy turning tool, 502 cutter head, 503 shaft end baffle, 504 bolt, 6 anchor box, 7 steel box girder block, 8 web plate, 9 anchor plate, 10 positioning line. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1-7 As shown, the boring method and boring device provided by this invention are mainly used for the precision machining of anchor holes on the anchor plate 9 of the anchor box 6 inside a steel box girder. The internal space of the steel box girder block 7 is small, and its bottom plate and adjacent partitions form a three-sided closed structure.

[0033] The boring device includes:

[0034] The gear reducer 1 has a lifting lug 101 on its body and a built-in precision lead screw feed mechanism for controlling the axial feed speed of the cutting tool.

[0035] The connecting seat 2 includes a web tube 201 and flange 1 202 and flange 2 203 welded to both ends of the web tube 201 respectively; flange 1 202 is a smooth surface without holes and is used to tightly attach to the anchor plate 9; flange 2 203 is provided with multiple bolt holes 504 for connecting the gear reducer 1; a portion of the web tube 201 is cut off to form an observation hole 204;

[0036] Three fixing devices 3 are used to apply a constraint force distributed in an equilateral triangle to the connecting seat 2; each fixing device 3 includes an L-shaped connecting block 302 and a tightening bolt 301. The L-shaped connecting block 302 has a drilling and tapping structure on one side for pressing the flange of the connecting seat 2 by tightening the bolt 301.

[0037] The adjustable spreader beam system 4 includes a spreader beam 401, a sleeve 402, a support 404 with a slot 403, and a sling 405; both ends of the spreader beam 401 extend into their respective sleeves 402 and are fixed; the bottom of the sleeve 402 is fixedly connected to the upper side of the support 404, and the slot 403 of the support 404 is engaged with the upper edge of the web plate 8 of the anchor box 6;

[0038] The cutting unit 5 includes a cutter head 502 and a high-alloy turning tool 501 mounted on the drive shaft 102 of the gear reducer 1.

[0039] The steps for implementing the method of the present invention are as follows:

[0040] S1: First, assess the internal space of the welded box girder block. Within this space, operator movement is difficult, and large equipment cannot enter. Then, perform precise positioning. Using the existing blanking hole center O of the anchor plate 9 as a reference point, use a high-precision scribing tool to draw a circle with the radius R of the non-perforated flange of the connecting seat 2 as the radius. This circle is the installation positioning line 10 for the three fixing devices 3.

[0041] S2: As Figure 2 As shown, the first and second fixing devices 35a and 5b are installed on the bottom plate side of the anchor plate 9, and the angle α between the two and the line connecting them to the center O is controlled at 120° to obtain the best bottom plate side support stability.

[0042] S3: Assemble the power unit. Select a gear reducer 1 with a rated output torque of not less than 500 N·m and a reduction ratio of approximately 50:1 to meet the boring requirements of low speed (approximately 10-30 rpm) and high torque. Secure the flange 203 of the connecting seat 2 to the flange of the reducer using high-strength bolts 504. The connecting seat 2 is made of Q345B steel plate with a flange thickness of 25 mm. Finite element analysis has verified that its deformation is less than 0.01 mm under maximum cutting resistance. Install a flat key 103 on the drive shaft 102 of the reducer, then install the cutter head 502 equipped with a high-alloy turning tool 501 (grade YG8, rake angle 8°, clearance angle 6°), and finally fix it with the shaft end plate 503 and bolts 504.

[0043] S4: Perform core fixing and leveling. Use a crane (not shown in the figure) to lift the assembly into the box, so that the flange 202 of the connecting seat 2 is close to the anchor plate 9 and snaps into the two already installed bottom plate side fixing devices 35a and 5b. Then install the third fixing device 35c on the top plate side. The L-shaped blocks of the three fixing devices 35 are pressed by the strong bolts 504 to firmly "clamp" the connecting seat 24 onto the anchor plate 93. This "two-on-one-on-one" equilateral triangular constraint layout constitutes a statically determinate system, which is superior to the over-constraint that may occur with four or more points, can better adapt to the unevenness of the structural surface, and ensure a tight fit without gaps.

[0044] S5: Install the vibration damping system. Initially fix the support 404 of the adjustable spreader beam 401 to the web plate 8 via the slot 403. Insert the spreader beam 401 into the sleeve 402 to allow for lateral movement. Connect the reducer lifting lug 101 and the spreader beam 401 using a sling 405. By adjusting the length of the sling 405 (vertical), moving the position of the spreader beam 401 in the sleeve 402 (lateral), and adjusting the position of the slot 403 on the support 404 (longitudinal), the support force can be precisely adjusted, ensuring that the reducer's weight is entirely borne by the spreader beam 401. The machining point is in a "weightless" state, greatly eliminating the impact of self-weight deflection and vibration on accuracy.

[0045] S6: Perform boring. Start gear reducer 1, the cutting tool rotates, and simultaneously the leadscrew (not shown in the figure) drives the drive shaft 102 axially for feed at a speed of approximately 5-10 mm / min. The operator can observe the cutting process through the observation window on the web tube 201 of the connecting seat 2, and use compressed air to clean the chips or spray coolant if necessary. After boring is completed, disassemble the device.

[0046] The method provided by this invention achieves a level of superiority comparable to traditional processes (referring to the "machining before welding" process using large fixed machine tools in an open workshop environment) in terms of key processing quality indicators. Specifically, the anchor hole position accuracy can be controlled within ±1 mm; the hole diameter accuracy can reach ±0.5 mm; and the surface roughness can reach Ra6.3.

[0047] This demonstrates one of the core values ​​of this invention: under extremely unfavorable construction conditions (the narrow, enclosed space formed after the steel box girder assembly), this invention, through systematic tooling design and process methods, successfully achieved high-precision machining quality comparable to that under ideal factory conditions. This fundamentally overcomes the limitations of on-site conditions on machining accuracy, ensuring the critical performance of the anchor holes.

[0048] The most significant technological advantage lies in construction efficiency. Using the method of this invention, construction efficiency is nearly doubled compared to traditional methods. This remarkable efficiency improvement is primarily due to:

[0049] (1) In the traditional “processing before welding” process, the anchor holes are easily deformed during subsequent welding, often requiring expensive on-site corrections or even scrapping and remaking. The present invention processes the entire assembly in one go, eliminating secondary operations caused by welding deformation and avoiding rework and correction.

[0050] (2) The dedicated fixing device and adjustable support system greatly shorten the time for equipment positioning, installation and adjustment in a narrow space, and achieve rapid positioning.

[0051] (3) This method can be implemented simultaneously in multiple box girder segments or different anchor box positions without relying on the scheduling of large fixed machine tools, thus accelerating the overall project progress.

[0052] In summary, this invention not only successfully solves the technical challenge of high-precision hole machining in immovable, extremely confined spaces, ensuring processing quality equivalent to traditional processes, but also brings a significant benefit of nearly doubling construction efficiency. This comprehensively resolves the contradictions between quality, feasibility, and economy, and has outstanding practical value for ensuring the manufacturing precision and construction period of large bridge steel structures.

[0053] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for high-precision boring of fixed structures in confined spaces, applicable to the machining of anchor holes in anchor boxes inside steel box girders, characterized in that, Includes the following steps: S1: Measure the operating space dimensions around the anchor box inside the welded steel box girder block; draw the positioning reference line on the surface of the anchor plate according to the theoretical coordinates of the anchor point and the center of the foundation hole measured on site; S2: Using the center of the basic hole determined in step S1 as a reference, install the first fixing device and the second fixing device on the bottom plate side of the anchor plate. The angle between the two devices and the line connecting them to the center is 100°~140°, and they are arranged symmetrically on the left and right sides to form a stable preliminary constraint on the bottom plate side. S3: Install the connecting seat onto the gear reducer, and install the cutter head and high-alloy turning tool on the drive shaft of the gear reducer; the rated output torque of the gear reducer is greater than the actual maximum working torque; S4: Hoist the assembly into place, so that the non-perforated flange of the connecting seat is against the anchor plate and snapped into the two fixing devices on the bottom plate side. Then install the third fixing device on the top plate side, so that the three fixing devices are distributed in an approximately equilateral triangle, with the center of the anchor hole located at the center of this triangle. Tighten the bolts of all fixing devices to make the connecting seat flange and the anchor plate fit tightly together. S5: An adjustable spreader beam system is installed on the web of the block and connected to the lifting lugs of the gear reducer by slings to bear its entire weight; S6: Start the gear reducer to bore the hole, and monitor the machining process through the observation window on the connecting seat web tube to complete the boring of the anchor hole.

2. The method for high-precision boring of a fixed structure in a confined space according to claim 1, characterized in that, In step S1, the step of drawing the positioning line includes: drawing the positioning line with the center of the anchor hole as the reference and the outer radius of the connecting seat flange as the reference, to ensure that the installation position of the fixing device accurately corresponds to the theoretical coordinates of the anchor point.

3. The method for high-precision boring of a fixed structure in a confined space according to claim 1, characterized in that, In step S2, the angle between the line connecting the first fixing device and the second fixing device and the center of the circle is 120°.

4. The method for high-precision boring of a fixed structure in a confined space according to claim 1, characterized in that, In step S3, the material of the connecting seat is not lower than Q235B, and its flange plate thickness is not less than 20mm.

5. The method for high-precision boring of a fixed structure in a confined space according to claim 1, characterized in that, In step S3, the high-alloy turning tool is made of cemented carbide YG8 or YW1.

6. The method for high-precision boring of a fixed structure in a confined space according to claim 1, characterized in that, In step S5, the adjustable spreader beam system achieves longitudinal position adjustment through the slot, lateral position adjustment through the sliding of the spreader beam within the sleeve, and vertical position adjustment through adjusting the length of the sling.

7. A boring apparatus for implementing the method according to any one of claims 1-6, characterized in that, include: The gear reducer has lifting lugs on its body; The connecting seat includes a web tube and flange one and flange two welded to both ends of the web tube respectively; flange one is a smooth surface without holes and is used to fit tightly against the anchor plate; flange two is provided with multiple bolt holes for connecting a gear reducer; a portion of the web tube is cut off to form an observation hole; Three fixing devices are used to apply constraint forces distributed in an equilateral triangle to the connecting seat; each fixing device includes an L-shaped connecting block and a tightening bolt, and one side of the L-shaped connecting block is provided with a drilling and tapping structure for tightening the flange of the connecting seat by tightening the bolt; An adjustable spreader beam system includes a spreader beam, sleeves, a support with a slot, and a sling; both ends of the spreader beam extend into their respective sleeves and are fixed; the bottom of the sleeve is fixedly connected to the upper side of the support, and the slot of the support is engaged with the edge of the web of the anchor box. The cutting unit includes a cutter head and a high-alloy turning tool mounted on the transmission shaft of the gear reducer.

8. The boring device according to claim 7, characterized in that, The gear reducer has a built-in precision lead screw feed mechanism, which is used to control the axial feed speed of the cutting tool.

9. The apparatus according to claim 6, characterized in that, The cutter head is fixed to the drive shaft by a flat key and a shaft end baffle.

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