Bridge expansion joint measuring device and measuring method thereof

Abstract

This invention relates to the technical field of bridge expansion joint measuring devices, and discloses a bridge expansion joint measuring device and its measuring method, comprising: a fixed main handle, which is arranged in a hollow cylindrical shape; and an external probe measuring head, which is mirror-symmetrically arranged on both sides of the fixed main handle and movably arranged on both sides of the fixed main handle through a combined telescopic mechanism. Each external probe measuring head includes: a measuring base, which is coaxially arranged with the fixed main handle and has a diameter smaller than that of the fixed main handle. This device uses a first telescopic part and a second telescopic part in the combined telescopic mechanism to form a two-stage telescopic structure. The first telescopic part can automatically push the external probe measuring head outward after unlocking, which can meet the needs of rapid measurement of expansion joints of conventional width. When the width of the expansion joint exceeds the maximum stroke of the first telescopic part, the second telescopic part can be unlocked at the same time, and the fixed positioning plate and the entire external probe measuring head can be driven to further expand outward through the outer telescopic cylinder and the radial connecting rod, so that the measuring range is multiplied.

Description

Technical Field

[0001] This invention relates to the field of bridge expansion joint measuring device technology, specifically a bridge expansion joint measuring device and its measuring method. Background Technology

[0002] Bridge expansion joints are crucial structural components installed between bridge beams or between beams and abutments. Their primary function is to accommodate the expansion and contraction of the bridge under conditions such as temperature changes, concrete shrinkage and creep, and vehicle loads, while ensuring a smooth and continuous bridge deck for safe and comfortable driving. Common types of expansion joints include modular expansion joints, toothed expansion joints, and rubber expansion joints. In the daily maintenance and periodic inspection of bridges, the width of the expansion joints is one of the key parameters that needs to be monitored. Changes in joint width directly reflect the bridge's expansion and contraction status; abnormal widening or narrowing may indicate problems such as damage to the expansion device, restricted beam displacement, or bearing defects. Therefore, regular and accurate measurement of the expansion joint width is of great significance.

[0003] Currently, the commonly used tools for measuring expansion joints at bridge inspection sites mainly include vernier calipers, steel rulers, and handheld laser rangefinders. Vernier calipers offer high accuracy, but their measuring range is typically limited to 150mm to 300mm, making it difficult to measure wider expansion joints. Furthermore, the calipers are relatively long, and the two measuring jaws need to be pressed against the two sides of the joint, often requiring inspectors to bend over or even lie prone on the bridge surface to take readings, making operation extremely inconvenient. While steel rulers or steel tape measures have a larger measuring range, they require manual visual alignment of both ends, and the rulers themselves are prone to bending and deformation, resulting in significant measurement errors and poor repeatability. Handheld laser rangefinders are relatively quick to operate, but require personnel to set up reflective targets on both sides of the joint or rely on experience for alignment, which is difficult for a single person to complete, and they cannot continuously record data during dynamic scanning.

[0004] Furthermore, existing measuring tools have significant shortcomings in terms of portability and storage. Vernier calipers, with their slender scales and sharp measuring jaws, are difficult to fit into regular tool bags and often require specialized boxes, taking up considerable space. Long-range steel rulers can exceed one meter in length, making them unsuitable for ordinary toolboxes and prone to bending or scratching operators during transport. Even handheld laser rangefinders, while compact in size, still require additional accessories such as centering supports and reflective targets, making overall storage inconvenient. Inspectors typically need to travel between multiple bridge piers; carrying various measuring tools undoubtedly increases workload and increases the risk of missing or losing accessories.

[0005] In summary, existing bridge expansion joint measuring devices have certain shortcomings in terms of portability, flexible storage, and adaptability to different joint widths, and need further improvement. Summary of the Invention

[0006] The purpose of this invention is to provide a bridge expansion joint measuring device to solve the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a bridge expansion joint measuring device, comprising: The main handle is fixed and is designed in a hollow cylindrical shape. External probe measuring heads are symmetrically arranged on both sides of the fixed main handle and are movably mounted on both sides of the fixed main handle via a combined telescopic mechanism. Each external probe measuring head includes: The measuring base is coaxially arranged with the fixed main handle and its diameter is smaller than that of the fixed main handle. The edge rolling balls are evenly distributed circumferentially on the side of the measuring base away from the fixed main handle, and are used to abut against the side walls of the expansion joint and facilitate sliding. A laser rangefinder is embedded in the measuring base on one side adjacent to the fixed main handle; A high-precision double-sided reference target plate is fixedly installed in the center of the fixed main handle. It consists of a left target plate and a right target plate that are mirror-symmetrical. The left side of the left target plate forms a high-reflectivity diffuse reflection surface facing the left external probe measuring head, and the right side of the right target plate forms a high-reflectivity diffuse reflection surface facing the right external probe measuring head. The combined telescopic mechanism has an unobstructed ranging channel connecting the laser rangefinder and the high-precision double-sided reference target plate. The laser beam emitted by the laser rangefinder is directed through the unobstructed ranging channel to the high-reflectivity diffuse reflection surface on the corresponding side of the high-precision double-sided reference target plate and then reflected back. A level is also embedded in the side wall of the fixed main handle to indicate the horizontal state of the fixed main handle.

[0008] According to the above technical solution, the combined telescopic mechanism includes a first telescopic part and a second telescopic part, wherein the first telescopic part includes: A fixed positioning plate is set inside one side of the fixed main handle, and is coaxially corresponding to the external probe measuring head, with a central channel through the center. A nested telescopic rod, coaxially positioned between the fixed positioning plate and the external probe measuring head, includes: The main nested telescopic rod is fixedly installed at one end on one side of the fixed positioning plate; The secondary nested telescopic rod has one end nested and movable inside the main nested telescopic rod, and the other end fixedly installed on the side wall of the measuring base; A telescopic spring is fixedly installed inside the main nested telescopic rod, and its telescopic end is fixedly connected to one side of the secondary nested telescopic rod; The main nested telescopic rod and the secondary nested telescopic rod are both hollow, and the main nested telescopic rod, the secondary nested telescopic rod and the central channel are connected to form the unobstructed distance measuring channel.

[0009] According to the above technical solution, the second telescopic part includes: The outer telescopic cylinder is composed of a hollow movable cylinder and a side wing fixing plate. The hollow movable cylinder is slidably installed in the sliding groove of the outer wall of the fixed main handle, and the hollow movable cylinder and the outer wall of the fixed main handle are flush. The hollow movable cylinder is fixedly installed at the end of the side wing fixing plate away from the fixed main handle. The secondary nested telescopic rod is movably installed through the side wing fixing plate. A radial connecting rod is arranged along the radial direction of the hollow movable cylinder and is movably installed through the guide grooves evenly distributed around the circumference of the fixed main handle. One end of the radial connecting rod is fixedly connected to the inner wall of the hollow movable cylinder and the other end is fixedly connected to the outer wall of the fixed positioning plate.

[0010] According to the above technical solution, the outer telescopic cylinder is disposed outside the fixed main handle by a fixed-point limiting component, the fixed-point limiting component comprising: The fixed-point limiting rod is movably installed in the arc-shaped moving groove of the side wall of the fixed main handle, and its two ends penetrate through the side wall of the fixed main handle and extend into the corresponding hollow moving cylinder; A fixed-point limiting block is fixedly installed at the end of the fixed-point limiting rod and is engaged in the fixed-point limiting groove on the side wall of the hollow movable cylinder. A fixed-point limiting groove is opened near the top and bottom surfaces of the hollow movable cylinder, respectively. A tension spring is fixedly installed in the arc-shaped moving groove, and its telescopic end is fixedly connected to the fixed-point limiting rod. An external actuating block is embedded in the fixed-point limiting rod, with its top protruding from the outer wall of the fixed main handle and having anti-slip texture.

[0011] According to the above technical solution, when the first and second telescopic parts are fully retracted, the external probe measuring head is locked at its extreme position by a limit locking mechanism, the limit locking mechanism comprising: A central protruding column is fixedly installed on the side wall of the side wing fixing plate. The secondary nested telescopic rod is movably installed inside the central protruding column. An embedded groove is provided on the side of the central protruding column near the measuring base. The screw ring is movably fitted onto the outer wall of the central protruding column; Radial locking blocks are arranged along the radial direction of the embedded groove and are evenly distributed in the reset groove within the embedded groove. The side wall of the measuring base is provided with radial locking grooves that correspond one-to-one with the radial locking blocks. A reset spring is fixedly installed in the reset groove, and its telescopic end is fixedly connected to the side wall of the radial locking block; The flexible connecting rope is fixedly connected to the radial locking block at one end and to the inner wall of the screw ring at the other end.

[0012] According to the above technical solution, sealing mechanisms are provided on both sides of the fixed main handle to seal and protect the fully retracted external probe measuring head. The sealing mechanisms include: The sealing cover is detachably installed on the side wall of the side wing fixing plate. The detachable installation method is set as threaded connection, magnetic connection or snap-on connection.

[0013] According to the above technical solution, a cleaning mechanism with an edge rolling ball is provided on the outer side of the sealing cover, the cleaning mechanism comprising: An external fixing cap is fixedly installed on the outside of the sealing cover; A cleaning brush is evenly distributed in a ring on the outside of the sealing cover, corresponding to the edge rolling ball; An inner rotating docking cap is movably mounted on the side wall of the side wing fixing plate; The outer fixed docking cap can be movably fitted onto the outside of the inner rotating docking cap, and both the outer fixed docking cap and the inner rotating docking cap have a regular octagonal cross-section.

[0014] According to the above technical solution, a coaxial optical path constraint component is provided in the unobstructed ranging channel, and the coaxial optical path constraint component includes: The first matte finish guide tube is fixedly installed on the inner wall of the main nested telescopic rod; The second matte guide tube is fixedly installed on the inner wall of the secondary nested telescopic rod; The first and second matting guide tubes are nested together in the expansion and contraction overlap area, the inner diameter of the first matting guide tube is smaller than the outer diameter of the second matting guide tube, and the two have an overlapping area in the axial direction.

[0015] According to the above technical solution, the inner walls of both the first and second matting conduits are provided with a composite functional layer, the composite functional layer comprising: A light-absorbing substrate is applied to the inner wall matrix of the first and second extinction conduits. The surface microstructure layer, integrally formed on the light-absorbing substrate, consists of microgrooves, pyramidal arrays, or villous protrusions extending along the axial or spiral direction.

[0016] A measurement method for a bridge expansion joint measuring device includes the following steps: Step S1: Remove the sealing cover and select the stroke level of the unlocking combination telescopic mechanism according to the width of the expansion joint. When the width of the expansion joint is less than or equal to the maximum stroke of the first telescopic part, only the first telescopic part is unlocked. When the width of the expansion joint is greater than the maximum stroke of the first telescopic part, both the first and second telescopic parts are unlocked at the same time, so that the two external probe measuring heads extend outward under the action of the telescopic spring. Step S2: Place the edge rolling balls of the two external probe measuring heads against the two side walls of the expansion joint respectively, and adjust the posture of the fixed main handle by observing the level until it is horizontal; Step S3: Move the device back and forth along the axis of the fixed main handle, and simultaneously collect the dynamic reading sequence of the laser rangefinders on both sides; if the change in the reading sequence on both sides exceeds the preset threshold at the same time, a fault alarm signal for the measuring device will be issued. Step S4: Fix the device to the point to be measured, and obtain the left distance value measured by the left laser rangefinder and the right distance value measured by the right laser rangefinder respectively. After calculation by the built-in processor, the final value of the expansion joint width is directly displayed on the data display screen. Step S5: After the measurement is completed, press the two external probe measuring heads along the axial direction to fully retract the first and second telescopic parts, and automatically lock the retracted state through the limit snapping mechanism. Finally, install the sealing cover.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) The two-stage telescopic mechanism enables wide-range adaptive measurement and compact storage. This device employs a two-stage telescopic structure consisting of a first telescopic section and a second telescopic section in a combined telescopic mechanism. The first telescopic section contains a telescopic spring that automatically extends the external probe measuring head outward upon unlocking, facilitating rapid measurement of expansion joints of standard widths. When the expansion joint width exceeds the maximum stroke of the first telescopic section, the second telescopic section can be unlocked simultaneously. This, via the outer telescopic cylinder and radial connecting rod, drives the fixed positioning plate and the entire external probe measuring head to further extend outward, multiplying the measurement range. After measurement, pressing the external probe measuring head axially completely retracts the two-stage telescopic mechanism, which is then automatically locked by a limit-locking mechanism. This design makes the device compact and portable when folded, and allows for flexible selection of the telescopic stroke based on the joint width during use, achieving a balance between small size and a large measurement range.

[0018] (2) A high-precision double-sided reference target plate enables absolute measurement and eliminates system calibration errors. A high-precision double-sided reference target plate is fixedly installed at the center of the fixed main handle. This high-precision double-sided reference target plate is composed of a left target plate and a right target plate that are attached to each other. The left side of the left target plate and the right side of the right target plate form high-reflectivity diffuse reflection surfaces facing the outward-protruding measuring heads on both sides. The laser rangefinders on both sides measure the distance to their respective diffuse reflection surfaces. The slit width is finally obtained by adding the known outward convexity of the edge rolling ball and the thickness of the high-precision double-sided reference target plate to the distance measured on both sides. Since the high-precision double-sided reference target plate is fixed at the geometric center of the fixed main handle and there is no reference transformation between it and the laser rangefinders on both sides, the entire measurement process does not depend on the absolute size of the fixed main handle or on-site calibration, eliminating the systematic errors caused by reference drift or inaccurate calibration in traditional measuring devices.

[0019] (3) The edge rolling ball achieves low-friction rolling contact, improving positioning accuracy and ease of operation. Each external probe measuring head has evenly distributed edge rolling balls on the circumferential side of its measuring base away from the fixed main handle. These balls directly abut against the side walls of the expansion joint. This multi-point circumferential arrangement ensures rolling contact rather than sliding contact between the measuring base and the side walls. This significantly reduces frictional resistance as the device moves along the joint length, facilitating continuous scanning measurements. Furthermore, the spherical structure automatically adapts to the microscopic unevenness of the side walls, avoiding single-point contact errors caused by local protrusions or depressions. This improves the positioning stability and repeatability of the measuring base.

[0020] (4) The unobstructed ranging channel, in conjunction with the coaxial optical path constraint component, ensures the stability of the optical path during telescopic motion. The central channel connecting the main nested telescopic rod, the secondary nested telescopic rod, and the fixed positioning plate forms an unobstructed ranging channel. This channel runs through the entire combined telescopic mechanism, providing an unobstructed propagation path for the laser beam. Furthermore, a coaxial optical path constraint assembly is installed within this unobstructed ranging channel. This assembly includes a first extinction guide tube fixed to the inner wall of the main nested telescopic rod and a second extinction guide tube fixed to the inner wall of the secondary nested telescopic rod. The two are interlocked in the telescopic overlap area, with the inner diameter of the first extinction guide tube being larger than the outer diameter of the second extinction guide tube, and they overlap axially. This structure ensures that when the main and secondary nested telescopic rods move relative to each other or shift radially, the two extinction guide tubes always form a continuous, straight, rigid optical tube, forcing the laser beam to propagate along the axis. This avoids beam deflection, contact with steps, or multipath reflection caused by gaps or eccentricity in the telescopic rods, thus guaranteeing the straightness and stability of the ranging optical path throughout the entire telescopic stroke.

[0021] (5) The dynamic self-testing method effectively identifies device faults and avoids erroneous data output. In the measurement method based on this device, step S3 requires reciprocating the device along the axis of the fixed main handle while simultaneously acquiring dynamic reading sequences from both laser rangefinders. If the changes in the reading sequences on both sides simultaneously exceed a preset threshold, a fault alarm signal for the measurement device is issued. This self-checking mechanism utilizes the physical law that the measured values ​​on both sides should maintain a linked change during continuous movement (an increase on one side results in a decrease on the other side, with the sum remaining essentially constant). This mechanism can quickly detect faults such as telescopic rod jamming, optical path contamination, and laser rangefinder malfunctions before formal measurement, thereby avoiding the use of erroneous data and improving the reliability of on-site measurements.

[0022] (6) The unobstructed ranging channel, together with the coaxial optical path constraint component and the composite functional layer, ensures optical path stability and signal purity. The central channel connecting the main nested telescopic rod, the secondary nested telescopic rod, and the fixed positioning plate forms an unobstructed ranging channel. This channel runs through the entire combined telescopic mechanism, providing an unobstructed propagation path for the laser beam. Furthermore, a coaxial optical path constraint assembly is installed within this unobstructed ranging channel. This assembly includes a first extinction guide tube fixed to the inner wall of the main nested telescopic rod and a second extinction guide tube fixed to the inner wall of the secondary nested telescopic rod. The two are interlocked in the telescopic overlap area, with the inner diameter of the first extinction guide tube being larger than the outer diameter of the second extinction guide tube, and they overlap axially. This structure ensures that when the main and secondary nested telescopic rods move relative to each other or shift radially, the two extinction guide tubes always form a continuous, straight, rigid optical tube, forcing the laser beam to propagate along the axis and preventing beam deflection, contact with steps, or multipath reflection caused by gaps or eccentricity in the telescopic rods. Simultaneously, the inner walls of both the first and second extinction guide tubes are provided with a composite functional layer. This composite functional layer consists of a light-absorbing substrate covering the inner wall matrix and a surface microstructure layer integrally formed on top of the light-absorbing substrate. The light-absorbing bottom layer uses a low-reflectivity black material to absorb the energy of incident light. The surface microstructure layer causes stray light that deviates from the axis to undergo multiple diffuse reflections and be captured, while the direct laser light propagating along the axis is almost unimpeded. The synergistic effect of these two elements ensures the straightness and stability of the ranging optical path throughout its entire extension and retraction, while effectively suppressing stray light interference within the channel, thus improving the signal-to-noise ratio of the laser rangefinder's received signal and its resistance to ambient light interference. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a first perspective view of the present invention; Figure 2 This is a second perspective view of the present invention; Figure 3 This is a third perspective view of the present invention; Figure 4 This is a first partial three-dimensional schematic diagram of the present invention; Figure 5 This is a second partial perspective view of the present invention; Figure 6 This is a third partial perspective view of the present invention; Figure 7 This is a fourth partial perspective view of the present invention; Figure 8 This is a fifth partial perspective view of the present invention; Figure 9 This is a sixth partial perspective view of the present invention; Figure 10 This is a third-dimensional schematic diagram of the seventh part of the present invention; Figure 11 This is the present invention. Figure 9 A magnified view of a portion of point A in the middle; Figure 12 This is the present invention. Figure 10 A magnified view of a portion of point B in the middle; In the diagram: 1-Fixed main handle, 2-Level, 3-External probe measuring head, 31-Measuring base, 32-Edge rolling ball, 33-Laser rangefinder, 4-Combined telescopic mechanism, 41-First telescopic part, 411-Fixed positioning plate, 412-Nested telescopic rod, 4121-Main nested telescopic rod, 4122-Secondary nested telescopic rod, 4123-Telescopic spring, 42-Second telescopic part, 421-Outer edge telescopic cylinder, 4211-Hollow movable cylinder, 4212-Side wing fixing plate, 422-Radial connecting rod, 43-Fixed point limiting assembly, 431-Fixed point limiting rod, 432-Fixed point limiting block, 433-Fixed point limiting groove, 434-Tension spring, 435 - External actuating block, 44- Limit locking mechanism, 441- Central outward protruding post, 442- Twisting ring, 443- Radial locking block, 444- Reset groove, 445- Radial locking groove, 446- Reset spring, 447- Flexible connecting rope, 5- High-precision double-sided reference target plate, 51- Left target plate, 52- Right target plate, 6- Unobstructed ranging channel, 7- Sealing mechanism, 71- Sealing cover, 8- Cleaning mechanism, 81- External fixed docking cap, 82- Cleaning brush, 83- Internal rotating docking cap, 9- Coaxial optical path constraint assembly, 91- First glare-extinguishing guide tube, 92- Second glare-extinguishing guide tube, 10- Composite functional layer, 101- Light absorption bottom layer, 102- Surface microstructure layer. Detailed Implementation

[0024] 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.

[0025] Please see Figure 1-12 The present invention provides a technical solution: a bridge expansion joint measuring device, comprising: The main handle 1 is fixed and is arranged in a hollow cylindrical shape; External probe measuring heads 3 are mirror-symmetrically arranged on both sides of the fixed main handle 1, and are movably mounted on both sides of the fixed main handle 1 via a combined telescopic mechanism 4. Each external probe measuring head 3 includes: The measuring base 31 is coaxially arranged with the fixed main handle 1 and its diameter is smaller than that of the fixed main handle 1. The edge rolling ball 32 is evenly distributed circumferentially on the side of the measuring base 31 away from the fixed main handle 1, and is used to abut against the two side walls of the expansion joint and facilitate sliding. A laser rangefinder 33 is embedded in the measuring base 31 on one side adjacent to the fixed main handle 1; A high-precision double-sided reference target plate 5 is fixedly installed in the center of the fixed main handle 1. It consists of a left target plate 51 and a right target plate 52 that are mirror-symmetrical. The left side of the left target plate 51 forms a high reflectivity diffuse reflection surface facing the left external probe measuring head 3, and the right side of the right target plate 52 forms a high reflectivity diffuse reflection surface facing the right external probe measuring head 3. The combined telescopic mechanism 4 has an unobstructed ranging channel 6 inside, connecting the laser rangefinder 33 and the high-precision double-sided reference target plate 5. The laser beam emitted by the laser rangefinder 33 is directed through the unobstructed ranging channel 6 to the high reflectivity diffuse reflection surface on the corresponding side of the high-precision double-sided reference target plate 5 and reflected back. A level 2 is also embedded in the side wall of the fixed main handle 1 to indicate the horizontal state of the fixed main handle 1; Specifically, the combined telescopic mechanism 4 includes a first telescopic part 41 and a second telescopic part 42, wherein the first telescopic part 41 includes: The fixed positioning plate 411 is set inside one side of the fixed main handle 1 and is coaxially corresponding to the external probe measuring head 3, and a central channel is opened through the center position; A nested telescopic rod 412, coaxially disposed between the fixed positioning plate 411 and the external probe measuring head 3, includes: The main nested telescopic rod 4121 is fixedly installed at one end on one side of the fixed positioning plate 411; The secondary nested telescopic rod 4122 has one end nested and movable inside the main nested telescopic rod 4121, and the other end fixedly installed on the side wall of the measuring base 31; The telescopic spring 413 is fixedly installed inside the main nested telescopic rod 4121, and its telescopic end is fixedly connected to one side of the secondary nested telescopic rod 4122; The main nested telescopic rod 4121 and the secondary nested telescopic rod 4122 are both hollow, and the main nested telescopic rod 4121, the secondary nested telescopic rod 4122 and the central channel are connected to form the unobstructed distance measuring channel 6; Specifically, the second telescopic portion 42 includes: The outer telescopic cylinder 421 is composed of a hollow movable cylinder 4211 and a side wing fixing plate 4212. The hollow movable cylinder 4211 is slidably installed in the sliding groove of the outer wall of the fixed main handle 1, and the hollow movable cylinder 4211 and the outer wall of the fixed main handle 1 are flush. The hollow movable cylinder 4211 is fixedly installed at the end of the side wing fixing plate 4212 away from the fixed main handle 1. The secondary nested telescopic rod 4122 is movably installed through the side wing fixing plate 4212. A radial connecting rod 422 is arranged along the radial direction of the hollow movable cylinder 4211 and is movably installed through the guide grooves evenly distributed around the fixed main handle 1. One end of the radial connecting rod 422 is fixedly connected to the inner wall of the hollow movable cylinder 4211 and the other end is fixedly connected to the outer wall of the fixed positioning plate 411. Specifically, the outer telescopic cylinder 421 is disposed outside the fixed main handle 1 by a fixed-point limiting component 43, the fixed-point limiting component 43 comprising: The fixed-point limiting rod 431 is movably disposed in the arc-shaped moving groove of the side wall of the fixed main handle 1, and its two ends penetrate through the side wall of the fixed main handle 1 and extend into the corresponding hollow moving cylinder 4211. A fixed-point limiting block 432 is fixedly installed at the end of the fixed-point limiting rod 431 and is engaged in the fixed-point limiting groove 433 on the side wall of the hollow movable cylinder 4211. A fixed-point limiting groove 433 is respectively opened near the top and bottom surfaces of the hollow movable cylinder 4211. A tension spring 434 is fixedly installed in the arc-shaped moving groove, and its telescopic end is fixedly connected to the fixed-point limiting rod 431. An external actuating block 435 is embedded in the fixed-point limiting rod 431, with its top protruding from the outer wall of the fixed main handle 1 and having anti-slip texture. Specifically, when the first telescopic part 41 and the second telescopic part 42 are fully retracted, the external probe measuring head 3 is locked at its extreme position by a limit locking mechanism 44, which includes: The central protruding column 441 is fixedly installed on the side wall of the side wing fixing plate 4212. The secondary nested telescopic rod 4122 is movably installed inside the central protruding column 441. The central protruding column 441 has an embedded groove on the side near the measuring base 31. The screw ring 442 is movably sleeved on the outer wall of the central protruding post 441; Radial locking blocks 443 are arranged along the radial direction of the embedded groove and are evenly distributed in the reset grooves 444 within the embedded groove. The sidewall of the measuring base 31 is provided with radial locking grooves 445 that correspond one-to-one with the radial locking blocks 443. The reset spring 446 is fixedly installed in the reset groove 444, and its telescopic end is fixedly connected to the side wall of the radial locking block 443. The flexible connecting rope 447 is fixedly connected to the radial locking block 443 at one end and fixedly connected to the inner wall of the screw ring 442 at the other end. Specifically, sealing mechanisms 7 are provided on both sides of the fixed main handle 1 to seal and protect the fully retracted external probe measuring head 3. The sealing mechanism 7 includes: The sealing cover 71 is detachably installed on the side wall of the side wing fixing plate 4212. The detachable installation method is set as threaded connection, magnetic connection or snap-on connection. Specifically, a cleaning mechanism 8 with an edge rolling ball 32 is provided on the outer side of the sealing cover 71, and the cleaning mechanism 8 includes: An external fixing cap 81 is fixedly installed on the outside of the sealing cover 71; Cleaning brush 82 is evenly distributed in a ring on the outside of the sealing cover 71, corresponding to the edge rolling ball 32; The inner rotating docking cap 83 is movably mounted on the side wall of the side wing fixing plate 4212; The outer fixed docking cap 81 is movably sleeved on the outside of the inner rotating docking cap 83, and both the outer fixed docking cap 81 and the inner rotating docking cap 83 have a regular octagonal cross-section. Specifically, a coaxial optical path constraint component 9 is provided within the unobstructed ranging channel 6, and the coaxial optical path constraint component 9 includes: The first matte finish guide tube 91 is fixedly installed on the inner wall of the main nested telescopic rod 4121; The second matte guide tube 92 is fixedly installed on the inner wall of the secondary nested telescopic rod 4122; The first matting guide tube 91 and the second matting guide tube 92 are interlocked in the expansion and contraction overlap area. The inner diameter of the first matting guide tube 91 is smaller than the outer diameter of the second matting guide tube 92, and the two have an overlapping area in the axial direction. Specifically, the inner walls of both the first matting conduit 91 and the second matting conduit 92 are provided with a composite functional layer 10, the composite functional layer 10 comprising: A light-absorbing substrate 101 covers the inner wall substrate of the first and second light-absorbing guide tubes 91 and 92. The surface microstructure layer 102 is integrally formed on the light-absorbing bottom layer 101 and is composed of microgrooves, pyramidal arrays or villous protrusions extending along the axial or spiral direction. A measurement method for a bridge expansion joint measuring device includes the following steps: Step S1: Remove the sealing cover 71, select the stroke level of the unlocking combination telescopic mechanism 4 according to the width of the expansion joint. When the width of the expansion joint is less than or equal to the maximum stroke of the first telescopic part 41, only the first telescopic part 41 is unlocked. When the width of the expansion joint is greater than the maximum stroke of the first telescopic part 41, both the first telescopic part 41 and the second telescopic part 42 are unlocked at the same time, so that the two external probe measuring heads 3 extend outward under the action of the telescopic spring 413. Step S2: Place the edge rolling balls 32 on the two outer probe measuring heads 3 against the two side walls of the expansion joint respectively, and adjust the posture of the fixed main handle 1 by observing the level 2 until it is horizontal; Step S3: Move the device back and forth along the axis of the fixed main handle 1, and simultaneously collect the dynamic reading sequence of the laser rangefinders 33 on both sides; if the change in the reading sequence on both sides exceeds the preset threshold at the same time, a fault alarm signal for the measuring device will be issued. Step S4: Fix the device to the point to be measured, and obtain the left distance value measured by the left laser rangefinder 33 and the right distance value measured by the right laser rangefinder 33 respectively. After calculation by the built-in processor, the final value of the expansion joint width is directly displayed on the data display screen. Step S5: After the measurement is completed, press the two outer probe measuring heads 3 along the axial direction to fully retract the first telescopic part 41 and the second telescopic part 42, and automatically lock the retracted state through the limit locking mechanism 44. Finally, install the sealing cover 71.

[0026] This device is based on the principle of dual-sided laser ranging and absolute reference calibration, combined with mechanical graded expansion mechanism and precision optical path constraint technology, to achieve non-contact, high-precision, and self-calibrating measurement of the width of bridge expansion joints.

[0027] 1. Mechanical self-adaptive principle Two-stage telescopic mechanism: The core mechanical structure of the device includes the first telescopic part 41 and the second telescopic part 42 in the combined telescopic mechanism 4.

[0028] The first telescopic section 41 consists of a fixed positioning plate 411, nested telescopic rods 412 (including a main nested telescopic rod 4121 and a secondary nested telescopic rod 4122), and a built-in telescopic spring 413. This section is the primary telescopic stage, which can automatically extend within a small range under the action of spring force.

[0029] The second telescopic section 42 consists of an outer telescopic cylinder 421 (including a hollow movable cylinder 4211 and a side wing fixing plate 4212) and a radial connecting rod 422. This part is a secondary telescopic stage, which is fixedly connected to the outer wall of the fixing positioning plate 411 of the first telescopic section through the radial connecting rod 422. When unlocked, it moves outward together with the first telescopic section to achieve a larger extension stroke.

[0030] Travel selection: The first telescopic part 41 and the second telescopic part 42 can be locked or unlocked separately by means of the fixed-point limit component 43. For narrow gaps, only the first telescopic part 41 needs to be unlocked; for wide gaps, both telescopic mechanisms can be unlocked at the same time, thus multiplying the measurement range.

[0031] Rolling contact: The measuring base 31 has rolling balls 32 evenly distributed around its end face. The spherical surface of the ball forms rolling contact with the side wall of the expansion joint. On the one hand, this reduces frictional resistance and makes it easier for the device to slide along the length of the joint. On the other hand, the multi-point spherical contact can automatically adapt to the micro-unevenness of the side wall and avoid positioning errors caused by point contact.

[0032] 2. Principle of Optical Measurement and Absolute Reference Laser ranging path: The laser rangefinder 33 on each side emits a laser beam, which passes through the unobstructed ranging channel 6 formed by the central channel of the main nested telescopic rod 4121, the secondary nested telescopic rod 4122 and the fixed positioning plate 411, and is directed toward the high reflectivity diffuse reflection surface of the high precision double-sided reference target plate 5 fixed in the center of the fixed main handle 1. After reflection, it returns along the original path and is received by the laser rangefinder 33.

[0033] Absolute reference: The high-precision double-sided reference target plate 5 is formed by bonding a left target plate 51 and a right target plate 52. The left side of the left target plate 51 forms a high-reflectivity diffuse reflection surface facing the left-side outward-probing measuring head 3, and the right side of the right target plate 52 forms a high-reflectivity diffuse reflection surface facing the right-side outward-probing measuring head 3. This target plate is fixed at the geometric center of the fixed main handle 1, serving as a common absolute reference for distance measurement on both sides.

[0034] Seam width calculation formula: W = L_left + L_right + D_ball + T_target in: L left: The distance value on the left side measured by the left laser rangefinder 33 (distance to the reflective surface of the left target plate 51); L Right: The distance value on the right side measured by the right laser rangefinder 33 (distance to the reflective surface of the right target plate 52); D-ball: The fixed outward convexity value from the outermost end point of the edge rolling ball 32 to the end face of the measuring base 31; T-target: The thickness of the high-precision double-sided reference target plate 5 (the total thickness between the outer walls of the left target plate 51 and the right target plate 52).

[0035] Since the D-ball and T-target are known constants, the change in slit width is entirely reflected by Lleft + Lright, achieving absolute measurement without the need for on-site calibration. Furthermore, the data display screen can be either externally connected to the fixed main handle 1 or embedded in the outer wall of the fixed main handle 1. The algorithm used is a common technique in this field and will not be elaborated upon further here.

[0036] Level 2: Embedded in the side wall of the fixed main handle 1, used to indicate the horizontal state of the fixed main handle 1. The operator can adjust the grip angle accordingly to eliminate the cosine error caused by tilting.

[0037] 3. Principles of Optical Path Fidelity and Anti-interference Unobstructed ranging channel 6: The hollow structure of the main nested telescopic rod 4121 and the secondary nested telescopic rod 4122 is connected to the central channel of the fixed positioning plate 411, ensuring that the laser beam can pass freely in the telescopic mechanism without being blocked by springs, connectors, etc.

[0038] The coaxial optical path constraint assembly 9 includes a first extinction guide tube 91 fixed to the inner wall of the main nested telescopic rod 4121 and a second extinction guide tube 92 fixed to the inner wall of the secondary nested telescopic rod 4122. The two are interlocked in the telescopic overlap area: the inner diameter of the first extinction guide tube 91 is larger than the outer diameter of the second extinction guide tube 92, and they overlap axially. During mechanical telescopic movement, this structure maintains the axial alignment of the optical path. Both the first and second extinction guide tubes 91 and 92 are made of black rigid engineering plastic (such as polyoxymethylene (POM) or polyetheretherketone (PEEK)) or black anodized aluminum alloy. This interlocked structure ensures that regardless of the relative movement of the telescopic rods, the two guide tubes always form a continuous, straight, rigid optical tube. The laser beam emitted by the laser rangefinder 33 propagates within this optical tube, unaffected by radial offset or angular deflection of the telescopic rods, preventing the beam from impacting the channel steps or inner wall, thereby eliminating multipath reflections and optical axis deflection, and ensuring the straightness and stability of the ranging optical path.

[0039] Composite functional layer 10: The inner walls of both the first and second extinction guide tubes 91 and 92 are provided with a composite functional layer 10, including a light-absorbing bottom layer 101 and a surface microstructure layer 102 (composed of microgrooves, pyramidal arrays, or villous protrusions extending along the axial or helical direction). The light-absorbing bottom layer 101 is made of a low-reflectivity material to absorb the energy of incident light. The surface microstructure layer 102 consists of microgrooves, pyramidal arrays, or villous protrusions extending along the axial or helical direction, causing oblique stray light to undergo multiple diffuse reflections and be captured by the light-absorbing bottom layer, while the direct laser propagating along the axial direction is almost unimpeded. This achieves efficient suppression of stray light, improves the signal-to-noise ratio of the received signal, and ensures the accuracy of laser ranging.

[0040] 4. Self-testing and fault alarm principle Dynamic scanning self-test: Before the formal measurement, move the device back and forth along the axis of the fixed main handle 1. Since the rolling balls 32 on both sides are in close contact with the slit wall, when the device moves, the readings of the laser rangefinders 33 on both sides should change in tandem (one side increases, the other side decreases, and the sum is basically constant). If the reading sequence on both sides jumps violently at the same time and exceeds the preset threshold, it indicates that there may be mechanical jamming, optical path contamination or electrical fault inside the device, and an alarm signal will be issued immediately.

[0041] 5. Storage and Protection Principles Limit locking mechanism 44: When the first telescopic part 41 and the second telescopic part 42 are fully retracted, the radial locking block 443, under the action of the return spring 446, engages with the radial locking groove 445 on the side wall of the measuring base 31, locking the external probe measuring head 3 in the retracted position. The rotating screw ring 442 can pull the locking block away through the flexible connecting rope 447 to unlock it.

[0042] Sealing mechanism 7: The sealing cover 71 is detachably installed on the side wall of the side wing fixing plate 4212 to seal and protect the fully retracted external probe measuring head 3, preventing dust and moisture from entering. The detachable installation method is threaded connection, magnetic connection or snap-fit ​​connection.

[0043] Cleaning mechanism 8: A cleaning brush 82 is provided on the outside of the sealing cover 71. When the sealing cover 71 is rotated, the cleaning brush 82 rotates stably relative to the edge rolling ball 32 through the docking transmission between the outer fixed docking cap 81 and the inner rotating docking cap 83 (both of which have a regular octagonal cross section), thereby achieving automatic cleaning.

[0044] Based on the measurement method described in claim 10, and in accordance with the above principles, the specific operation procedure of this device is as follows: Step S1: Preparation and Selection of Expansion / Extension Amount Remove the sealing cover 71 to expose the fully retracted external probe measuring head 3.

[0045] Visually estimate or predict the width of the expansion joint: If the seam width is less than the maximum stroke of the first telescopic part 41, the first telescopic part 41 is unlocked only by the fixed-point limiting component 43, while the second telescopic part 42 remains locked.

[0046] If the seam width is greater than the maximum stroke of the first telescopic part 41, then the first telescopic part 41 and the second telescopic part 42 are unlocked simultaneously.

[0047] The two protruding measuring heads 3 extend outward automatically under the elastic force of the telescopic spring 413 until the edge rolling ball 32 contacts or approaches the side wall of the expansion joint.

[0048] Step S2: Contact and Leveling Place the device into the expansion joint, ensuring that the rolling balls 32 on both sides are pressed firmly against the side walls. Since the rolling balls 32 are circumferentially distributed, the operator can gently shake the device to allow the spherical surfaces to automatically adapt to the flatness of the side walls, ensuring multi-point contact.

[0049] Observe the level 2 on the side wall of the fixed handle 1, and adjust the holding angle until the bubble is centered, ensuring that the axis of the fixed handle 1 is horizontal. This step can eliminate measurement errors caused by tilting.

[0050] Step S3: Dynamic Self-Test The device moves back and forth at a constant speed for about 50-100mm along the axial direction of the fixed main handle 1 (i.e., the length direction of the expansion joint).

[0051] Simultaneously record the real-time readings of the laser rangefinders 33 on both sides. During the movement, the readings on both sides should show a regular change (if one side increases, the other side decreases, and the sum remains basically unchanged).

[0052] If the changes in the reading sequences on both sides simultaneously exceed the system's preset threshold (e.g., a single change > 0.5 mm), a malfunction is detected in the device (e.g., telescopic rod jamming, optical path contamination, or rangefinder abnormality), and an alarm signal is immediately issued via buzzer or indicator light. Measurement should be stopped at this time, and the device should be inspected and cleaned.

[0053] If the self-test passes, proceed to the next step.

[0054] Step S4: Fixed-point measurement and reading Fix the device at the point to be measured and keep it stationary.

[0055] The device's built-in processor reads the left distance value measured by the left laser rangefinder 33 and the right distance value measured by the right laser rangefinder 33, respectively.

[0056] The processor automatically calculates the expansion joint width according to the stored constants (the convex value of the edge rolling ball 32 and the thickness of the high-precision double-sided reference target plate 5) and the built-in formula.

[0057] The calculated final width value is displayed directly on the data display screen. The operator does not need to perform any manual calculations or understand the formula details.

[0058] Step S5: Storage and Locking After the measurement is completed, press the measuring bases 31 on both sides along the axial direction with your hand to make the external probe measuring head 3 retract completely against the elastic force of the telescopic spring 413.

[0059] When the measuring head reaches the limit retraction position, the radial locking block 443 of the limit locking mechanism 44 automatically engages with the radial locking groove 445 on the measuring base 31 under the action of the return spring 446, locking the external probe measuring head 3 in the retracted state.

[0060] Finally, reinstall the sealing cap 71 onto the side wing fixing plate 4212, locking it using a threaded, magnetic, or snap-fit ​​method according to the design (the appropriate method can be selected according to the actual situation; the attached drawings of this invention use a threaded connection). During installation, if it is necessary to clean the edge rolling ball 32, the sealing cap 71 can be rotated, and the cleaning brush 82 will be driven by the octagonal mating cap to clean the surface of the rolling ball.

[0061] At this point, the device is back to its compact and portable storage state, and can be safely placed in a toolbox or storage cabinet.

[0062] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0063] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bridge expansion joint measuring device, characterized in that, include: The fixed main handle (1) is arranged in a hollow cylindrical shape; External probe measuring heads (3) are arranged symmetrically on both sides of the fixed main handle (1) and are movably mounted on both sides of the fixed main handle (1) via a combined telescopic mechanism (4). Each external probe measuring head (3) includes: The measuring base (31) is coaxially arranged with the fixed main handle (1) and its diameter is smaller than that of the fixed main handle (1); The edge rolling ball (32) is evenly distributed circumferentially on the side of the measuring base (31) away from the fixed main handle (1) to abut against the two side walls of the expansion joint and facilitate sliding; A laser rangefinder (33) is embedded in the measuring base (31) on one side adjacent to the fixed main handle (1); A high-precision double-sided reference target plate (5) is fixedly installed in the center of the fixed main handle (1). It consists of a left target plate (51) and a right target plate (52) that are mirror-symmetrical. The left side of the left target plate (51) forms a high reflectivity diffuse reflection surface facing the left external probe measuring head (3), and the right side of the right target plate (52) forms a high reflectivity diffuse reflection surface facing the right external probe measuring head (3). The combined telescopic mechanism (4) has an unobstructed ranging channel (6) inside that connects the laser rangefinder (33) and the high-precision double-sided reference target plate (5). The laser beam emitted by the laser rangefinder (33) is directed through the unobstructed ranging channel (6) to the high reflectivity diffuse reflection surface on the corresponding side of the high-precision double-sided reference target plate (5) and reflected back. A level (2) is also embedded in the side wall of the fixed main handle (1) to indicate the horizontal state of the fixed main handle (1).

2. The bridge expansion joint measuring device according to claim 1, characterized in that, The combined telescopic mechanism (4) includes a first telescopic part (41) and a second telescopic part (42), wherein the first telescopic part (41) includes: The fixed positioning plate (411) is set inside one side of the fixed main handle (1), and is coaxially corresponding to the external probe measuring head (3), and a central channel is opened through the center position; A nested telescopic rod (412), coaxially disposed between the fixed positioning plate (411) and the external probe measuring head (3), includes: The main nested telescopic rod (4121) is fixedly installed at one end on one side of the fixed positioning plate (411); The secondary nested telescopic rod (4122) has one end nested and movable inside the main nested telescopic rod (4121), and the other end is fixedly installed on the side wall of the measuring base (31); A telescopic spring (413) is fixedly installed inside the main nested telescopic rod (4121), and its telescopic end is fixedly connected to one side of the secondary nested telescopic rod (4122). The main nested telescopic rod (4121) and the secondary nested telescopic rod (4122) are both hollow. The main nested telescopic rod (4121), the secondary nested telescopic rod (4122) and the central channel are connected to form the unobstructed distance measuring channel (6).

3. The bridge expansion joint measuring device according to claim 2, characterized in that, The second telescopic part (42) includes: The outer telescopic cylinder (421) is composed of a hollow movable cylinder (4211) and a side wing fixing plate (4212). The hollow movable cylinder (4211) is slidably installed in the sliding groove of the outer wall of the fixed main handle (1), and the hollow movable cylinder (4211) and the outer wall of the fixed main handle (1) are flush. The hollow movable cylinder (4211) is fixedly installed at the end of the side wing fixing plate (4212) away from the fixed main handle (1). The secondary nested telescopic rod (4122) is movably installed through the side wing fixing plate (4212). A radial connecting rod (422) is arranged along the radial direction of the hollow movable cylinder (4211) and is installed through the guide grooves evenly distributed around the fixed main handle (1). One end of the radial connecting rod (422) is fixedly connected to the inner wall of the hollow movable cylinder (4211) and the other end is fixedly connected to the outer wall of the fixed positioning plate (411).

4. A bridge expansion joint measuring device according to claim 3, characterized in that, The outer telescopic cylinder (421) is disposed outside the fixed main handle (1) by a fixed-point limiting component (43), the fixed-point limiting component (43) comprising: The fixed-point limiting rod (431) is movably set in the arc-shaped moving groove of the side wall of the fixed main handle (1), and its two ends penetrate through the side wall of the fixed main handle (1) and extend into the corresponding hollow moving cylinder (4211). A fixed-point limiting block (432) is fixedly installed at the end of the fixed-point limiting rod (431) and is snapped into the fixed-point limiting groove (433) on the side wall of the hollow movable cylinder (4211). A fixed-point limiting groove (433) is opened near the top and bottom surfaces of the hollow movable cylinder (4211). A tension spring (434) is fixedly installed in the arc-shaped moving groove, and its telescopic end is fixedly connected to the fixed-point limiting rod (431); An external actuating block (435) is embedded in the fixed-point limiting rod (431), with its top protruding from the outer wall of the fixed main handle (1) and having anti-slip texture.

5. A bridge expansion joint measuring device according to claim 4, characterized in that, When the first telescopic part (41) and the second telescopic part (42) are fully retracted, the external probe measuring head (3) is locked at its limit position by a limit locking mechanism (44), which includes: The central protruding column (441) is fixedly installed on the side wall of the side wing fixing plate (4212), and the secondary nested telescopic rod (4122) is movably installed inside the central protruding column (441). The central protruding column (441) has an embedded groove on the side near the measuring base (31). The screw ring (442) is movably sleeved on the outer wall of the central protruding column (441); Radial locking blocks (443) are arranged along the radial direction of the embedded groove and are evenly distributed in the reset groove (444) within the embedded groove. The side wall of the measuring base (31) is provided with radial locking grooves (445) that correspond one-to-one with the radial locking blocks (443). The reset spring (446) is fixedly installed in the reset groove (444), and the telescopic end is fixedly connected to the side wall of the radial locking block (443); The flexible connecting rope (447) is fixedly connected to the radial locking block (443) at one end and fixedly connected to the inner wall of the screw ring (442) at the other end.

6. A bridge expansion joint measuring device according to claim 5, characterized in that, The fixed main handle (1) is provided with sealing mechanisms (7) on both sides to seal and protect the fully retracted external probe measuring head (3). The sealing mechanism (7) includes: The sealing cover (71) is detachably installed on the side wall of the side wing fixing plate (4212), and the detachable installation method is set as threaded connection, magnetic connection or snap-on connection.

7. A bridge expansion joint measuring device according to claim 6, characterized in that, The outer side of the sealing cap (71) is provided with a cleaning mechanism (8) with an edge rolling ball (32), the cleaning mechanism (8) including: An external fixing cap (81) is fixedly installed on the outside of the sealing cover (71); A cleaning brush (82) is evenly distributed in a ring on the outside of the sealing cover (71) and corresponds to the edge rolling ball (32); The inner rotating docking cap (83) is movably mounted on the side wall of the side wing fixing plate (4212); The outer fixed docking cap (81) can be movably sleeved on the outside of the inner rotating docking cap (83), and both the outer fixed docking cap (81) and the inner rotating docking cap (83) have a regular octagonal cross-section.

8. A bridge expansion joint measuring device according to claim 1, characterized in that, The unobstructed ranging channel (6) is provided with a coaxial optical path constraint component (9), which includes: The first matting guide tube (91) is fixedly installed on the inner wall of the main nested telescopic rod (4121); The second matting guide tube (92) is fixedly installed on the inner wall of the secondary nested telescopic rod (4122); The first matting guide tube (91) and the second matting guide tube (92) are nested in a gap in the expansion and contraction overlap area. The inner diameter of the first matting guide tube (91) is smaller than the outer diameter of the second matting guide tube (92), and the two have an overlapping area in the axial direction.

9. A bridge expansion joint measuring device according to claim 8, characterized in that, The inner walls of both the first matting conduit (91) and the second matting conduit (92) are provided with a composite functional layer (10), the composite functional layer (10) comprising: A light-absorbing substrate (101) is applied to the inner wall substrate of the first and second extinction conduits (91) and the second extinction conduits (92); The surface microstructure layer (102) is integrally formed on the light-absorbing bottom layer (101) and consists of microgrooves, pyramidal arrays or villous protrusions extending along the axial or spiral direction.

10. The measurement method of the bridge expansion joint measuring device according to claim 9, characterized in that, Includes the following steps: Step S1: Remove the sealing cover (71), select the stroke level of the unlocking combination telescopic mechanism (4) according to the width of the expansion joint. When the width of the expansion joint is less than or equal to the maximum stroke of the first telescopic part (41), only the first telescopic part (41) is unlocked. When the width of the expansion joint is greater than the maximum stroke of the first telescopic part (41), both the first telescopic part (41) and the second telescopic part (42) are unlocked at the same time, so that the two external probe measuring heads (3) extend outward under the action of the telescopic spring (413). Step S2: Place the edge rolling balls (32) on the two external probe measuring heads (3) against the two side walls of the expansion joint respectively, and adjust the posture of the fixed main handle (1) until it is horizontal by observing the level (2); Step S3: Move the device back and forth along the axis of the fixed main handle (1) while collecting the dynamic reading sequence of the laser rangefinders (33) on both sides; if the change in the reading sequence on both sides exceeds the preset threshold at the same time, a fault alarm signal for the measuring device will be issued. Step S4: Fix the device to the point to be measured, and obtain the left distance value measured by the left laser rangefinder (33) and the right distance value measured by the right laser rangefinder (33). After calculation by the built-in processor, the final value of the expansion joint width is directly displayed on the data display screen. Step S5: After the measurement is completed, press the two external probe measuring heads (3) along the axial direction to make the first telescopic part (41) and the second telescopic part (42) fully retract, and automatically lock the retracted state through the limit snapping mechanism (44), and finally install the sealing cover (71).

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