Positioning and sticking device and method for a distributed optical fiber shape sensor

Abstract

The application provides a positioning and pasting device and method of a distributed optical fiber shape sensor, belongs to the field of optical fiber sensors, and can solve the problems of low precision of manual positioning and pasting of the optical fiber and uneven glue coating in the case that the diameter of the sensor base body is small. The device comprises a guide rail with scale lines and a rack; a sensor base body and an optical fiber; a moving glue coating device for converting the horizontal movement of the mechanism along the guide rail into the movement of the piston in the glue pipe, ensuring the uniformity of the glue coating, and controlling the glue output by changing the radius ratio of the gear set, and the flexible glue delivery pipe ensures the accuracy of the glue coating position; a fixed pre-tensioning device for fixing the pre-tensioning sensor base body and the distributed optical fiber, and the friction force of the elastic pressing sheet ensures that each optical fiber has the same pre-tensioning force. The application has the advantages of convenient operation, fast pasting speed, accurate positioning, uniform glue coating and the like.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensors and relates to a positioning and pasting device and method for a distributed fiber optic shape sensor. Background Technology

[0002] Fiber optic shape sensors are a new type of sensor that has emerged with the development of fiber optic sensing technology. Their principle involves measuring the strain of a substrate by attaching optical fibers to its surface, and then calculating the substrate displacement using shape sensing algorithms. Due to their advantages such as distributed operation, high precision, small size, corrosion resistance, and immunity to electromagnetic interference, they are widely used in civil engineering, mechanical engineering, aerospace, and other fields. However, during sensor fabrication, the optical fibers must be attached to specific locations on the substrate surface. Existing research has shown that the positioning and attachment techniques of the optical fibers directly affect the accuracy of strain measurements.

[0003] Currently, there are two common methods for bonding optical fibers. One is to directly bond the fiber to the substrate surface. However, the bonding position of the fiber cannot be precisely positioned, especially when the substrate is cylindrical with a small diameter, which drastically increases the strain measurement error. The other method is to groove the substrate surface to achieve precise fiber positioning. However, when the substrate is made of hard materials such as shape memory alloys, grooving the surface is time-consuming, labor-intensive, and expensive. Furthermore, the length of a single groove is typically only 50 cm, resulting in errors at the junctions of each groove. In addition, both methods involve manual pre-tensioning of the fiber, which cannot guarantee that the fiber has the same pre-tension force, affecting the measurement range of the fiber. Simultaneously, manual adhesive application makes it impossible to control the amount of adhesive applied. Currently, there is no dedicated device for precisely positioning and bonding optical fibers to the substrate surface, requiring manual positioning and manual adhesive application, which suffers from poor positioning accuracy, low efficiency, and uneven adhesive application, significantly impacting the application of fiber optic shape sensors. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a positioning and bonding device and method for a distributed optical fiber shape sensor, which solves problems such as inaccurate optical fiber positioning, uneven adhesive application, low efficiency, and high cost of mechanical grooving when manually bonding optical fibers. This invention offers reliable performance, allows control over the pre-tension of the substrate and optical fiber, and significantly improves optical fiber positioning accuracy and bonding quality, thereby substantially increasing work efficiency.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A positioning and bonding device for a distributed optical fiber shape sensor includes a guide rail 1, a fixed pre-tensioning device 2, a movable adhesive applicator 3, a sensor substrate 4, and an optical fiber 5. Two fixed pre-tensioning devices 2 are arranged on both sides of the guide rail 1, and the movable adhesive applicator 3 is arranged in the middle of the guide rail 1. Both the fixed pre-tensioning devices 2 and the movable adhesive applicator 3 can move horizontally on the guide rail. The sensor substrate 4 passes sequentially through the left fixed pre-tensioning device 2, the movable adhesive applicator 3, and the right fixed pre-tensioning device 2. The sensor substrate 4 is fixed and pre-stretched by the substrate fixing mechanism 2C and the support moving mechanism 2B on the two fixed pre-tensioning devices 2. The optical fiber 5 passes sequentially through the optical fiber pre-tensioning mechanism 2D on the left fixed pre-tensioning device 2, the movable adhesive applicator 3, and the optical fiber pre-tensioning mechanism 2D on the right fixed pre-tensioning device 2. The optical fiber is fixed and pre-stretched by the optical fiber pre-tensioning mechanisms 2D on both sides, ensuring that the pre-stretching force on each optical fiber is the same. The movable adhesive applicator 3 applies adhesive evenly at specific positions on the sensor substrate 4 by moving, thus bonding the optical fiber 5.

[0007] The guide rail 1 is a dual-axis guide rail, with two axes distributed parallel to each other on both sides of the guide rail. A rack is engraved in the middle of the upper surface of the guide rail 1, and a scale is marked along the length of the guide rail next to the rack to help determine the length of the adhesive fiber 5. The adhesive length can be extended by combining guide rails 1. Furthermore, the cross-sectional shape of the two axes on the guide rail 1 is circular.

[0008] The aforementioned fixed pre-tensioning device 2 includes a fixed support 2A, a support moving mechanism 2B, a base fixing mechanism 2C, and an optical fiber pre-tensioning mechanism 2D. Specifically:

[0009] The fixed support 2A is a cuboid, and the shape of its lower front surface matches the upper surface of the guide rail 1. Therefore, the fixed support 2A can only move horizontally along the length of the guide rail 1. The lower surface of the fixed support 2A has a plane at its center, with a cuboid groove 2A3 extending upwards along the plane, but the groove 2A3 does not penetrate the cuboid. The cuboid sidewall of the fixed support 2A has two through-holes 2A2, which pass through the bottom groove 2A3, and the centers of the two holes 2A2 are on a vertical line. A vertical plate 2A4, perpendicular to the upper surface of a cuboid, is fixed near the front. A circular through hole is located near the top of the vertical plate 2A4. A cylinder is horizontally fixed near the bottom of the back of the vertical plate 2A4. A fixing plate 2A5, perpendicular to the upper surface of the cuboid, is located near the back of the fixing support 2A. A rectangular through hole is located at the top of the fixing plate 2A5. A circular hole is located at the center of the top of the fixing plate 2A5. The circular hole passes through the rectangular through hole and has internal threads. Two circular holes are symmetrically distributed on the lower surface of the rectangular through hole.

[0010] The support moving mechanism 2B includes a shaft 2B1 with a rotating handle at one end, and a spring 2B2, a ratchet 2B3 with a pull rod, and a transmission gear 2B4 arranged sequentially on the shaft 2B1. The spring 2B2 is sleeved on the shaft 2B1 and located between the rotating handle and the ratchet 2B3, and can move along the shaft 2B1. The ratchet 2B3 with a pull rod is a common ratchet with a circular through hole in the center, sleeved on the shaft 2B1, and the diameter of the circular through hole is slightly larger than the diameter of the shaft 2B1, and can move along the shaft 2B1. A pull rod with a pull ring is fixed to the back of the ratchet. The transmission gear 2B4 is a combination of a gear and a common ratchet. The transmission gear 2B4 is fixed on the shaft 2B1 and cannot move along the shaft 2B1, but can rotate with the shaft 2B1.

[0011] The following describes the installation position of the support moving mechanism 2B: The shaft 2B1 passes through the lower circular through hole on the side of the fixed support 2A and can rotate. At the bottom groove 2A3 of the fixed support 2A, the spring 2B2, the ratchet 2B3 with a pull rod, and the transmission gear pass through the shaft 2B1 in sequence. The spring 2B2 and the ratchet 2B3 with a pull rod can move along the shaft 2B1, and the pull ring of the ratchet 2B3 with a pull rod faces the same direction as the handle of the shaft 2B1. The transmission gear 2B4 is fixed to the shaft 2B1 and rotates with the shaft 2B1. The ratchet surface of the transmission gear 2B4 meshes with the ratchet surface of the ratchet 2B3 with a pull rod. After installation, the gear on the transmission gear 2B4 can mesh with the rack on the guide rail 1.

[0012] The sensor base fixing mechanism 2C includes a lower positioning block 2C1, an upper positioning block 2C2, a dual-axis pressure rod 2C3, and a screw 2C4 with a rotating handle. The lower positioning block 2C1 is a cuboid with a semi-circular through groove on the top of its front side and two symmetrically distributed through circular holes on its top. The upper positioning block 2C2 is also a cuboid with a semi-circular through groove on the bottom of its front side and two symmetrically distributed through circular holes on its top. The lower positioning block 2C1 and the upper positioning block 2C2 are symmetrical structures, and the two semi-circular through grooves, when joined together, form a circular through hole. The dual-axis pressure rod 2C3 is a cuboid with two symmetrically fixed cylinders at its bottom, which pass through the top circular holes of the lower positioning block 2C1 and the upper positioning block 2C2. The screw 2C4 with a rotating handle has external threads on its rod. As the screw 2C4 moves downward, it presses the top of the two dual-axis pressure rods 2C3, causing them to move downward synchronously. Furthermore, the shape of the semi-circular through grooves on the upper positioning block 2C2 and the lower positioning block 2C1 can be changed according to the shape of the sensor substrate.

[0013] The installation of the sensor base fixing mechanism 2C is described below: The lower positioning block 2C1, the upper positioning block 2C2, and the dual-axis pressure rod 2C3 are placed in the rectangular through hole on the fixing plate 2A5 of the fixing support 2A in sequence; the two cylinders below the dual-axis pressure rod 2C3 pass through the circular through hole at the top of the upper positioning block 2C2, the circular through hole at the top of the lower positioning block 2C1, and the two circular holes at the bottom of the rectangular through hole in sequence; the screw 2C4 with a rotating handle passes through the circular through hole at the top of the fixing plate 2A5, and the external thread of the screw is engaged with the internal thread of the circular through hole.

[0014] The fiber pre-tensioning mechanism 2D includes a limiting plate 2D1, an elastic pressure plate 2D2, and a screw 2D3. The limiting plate 2D1 is primarily a rectangular plate with a circular through-hole near the bottom and a central circular through-hole a near the top. Around the central circular through-hole a, three teardrop-shaped through-holes are evenly distributed. One end of each teardrop-shaped through-hole is arc-shaped, and the width of the other tip is the same as the diameter of the fiber 5, with a smooth transition between the two ends. The tip connects to the central circular through-hole a. The arc-shaped end of the teardrop-shaped through-hole is to increase the through-hole area, facilitating the passage of the fiber 5. The position of the teardrop-shaped through-holes can be changed according to the position of the fiber on the substrate. Around the central circular through-hole a, there are also three evenly distributed peripheral circular through-holes b, and the peripheral circular through-holes b have internal threads. The elastic pressure plate 2D2 has good flexibility, with a circular limiting hole at one end, a V-shaped groove on the lower surface of the other end, and a lever on the upper surface. Furthermore, a rubber gasket is located on the V-shaped groove.

[0015] The installation of the fiber pretensioning mechanism 2D is described below: First, three elastic pressure plates 2D2 are fixed to the outer circular through hole b of the limiting plate 2D1 with screws. All three elastic pressure plates 2D2 are inclined towards the center of the central circular through hole a of the limiting plate 2D1, and the levers of the elastic pressure plates 2D2 are all facing the outer periphery of the central circular through hole a. Then, the limiting plate 2D1 passes through the circular through hole near the bottom of the fixed support 2A and the upright plate 2A4 at the top. Finally, the screw 2D3 passes through the circular through hole near the top of the upright plate 2A4, and the external thread of the screw 2D3 is engaged with the internal thread of the circular through hole on the upright plate 2A4.

[0016] The mobile adhesive applicator includes a fixed support 3A and an adhesive applicator 3B. Specifically:

[0017] The fixed support 3A includes a bottom guide groove 3A1, an internal shaft 3A2, a portal frame 3A3, a limiting piece 3A4, a variable diameter shaft 3A5, and a fixing block 3A6. The base of the fixed support 3A is a cuboid, with a through bottom guide groove 3A1 on the bottom front of the cuboid that fits with the guide rail. The guide groove 3A1 has a flat surface in the middle and a rectangular through hole, with an internal shaft 3A2 parallel to the front of the through hole. The upper surface of the fixed support 3A has a portal frame 3A3. One inner wall of the portal frame 3A3 has a limiting piece 3A4. Below the limiting piece 3A4 is a variable diameter shaft 3A5. The upper surface of the fixed support 3A has a fixing block 3A6 near the front, and one side of the fixing block 3A6 has a U-shaped groove for fixing the rubber tube.

[0018] The adhesive application mechanism 3B includes a gear 3B1, a gear set 3B2, a transmission rack 3B3, an adhesive cylinder 3B4, and a flexible adhesive delivery tube 3B5. The gear set 3B2 is a combination of two coaxial gears of different radii. The transmission rack 3B3 is a rectangular rack with a groove running through its thickness in the middle along its length. The adhesive cylinder 3B4 has a piston inside containing adhesive, and several nozzles on one side. Squeezing the piston on the other side squeezes out the adhesive from the nozzles. The flexible adhesive delivery tube 3B5 is a universal flexible tube that can be arbitrarily changed shape to deliver the adhesive to the location where the optical fiber is to be bonded.

[0019] The following describes the installation of the mobile adhesive applicator 3B: Gear 3B1 is mounted on the inner shaft 3A2; gear set 3B2 is mounted on the variable diameter shaft 3A5; adhesive cylinder 3B4 is fixed in the groove on the side wall of the fixing block 3A5; finally, the transmission rack 3B3 is placed horizontally through the limiting piece 3A4; gear 3B1 meshes with the rack on the guide rail 1; the large gear in gear set 3B2 meshes with gear 3B1; the transmission rack 3B3 meshes with the small gear in gear set 3B2; one end of the transmission rack 3B3 is connected to the piston inside the adhesive cylinder 3B4; the flexible adhesive delivery tube 3B5 is connected to the adhesive outlet at one end of the adhesive cylinder 3B4.

[0020] The sensor substrate 4 is typically circular in cross-section, and its shape and dimensions are the same as the shape and dimensions of the through hole formed after the lower positioning blocks 2C1 and 2C2 are docked. The optical fiber 5 is a distributed optical fiber.

[0021] A method for positioning and attaching a distributed optical fiber sensor, based on the aforementioned positioning and attaching device, specifically includes the following steps:

[0022] The first step is to install the movable glue applicator 3 and the two fixed pre-tensioning devices 2 on the guide rail 1. The movable glue applicator 3 is located in the middle of the guide rail 1, and the two fixed pre-tensioning devices 2 are located on both sides of the guide rail 1. The movable glue applicator 3 and the two fixed pre-tensioning devices 2 can all move along the axis on the guide rail 1.

[0023] The second step involves sequentially passing the sensor substrate 4 through the substrate fixing mechanism 2C, the fiber pre-tensioning mechanism 2D, and the movable adhesive applicator 3 on the left side of the fixed pre-tensioning device 2, as well as the fiber pre-tensioning mechanism 2D and the substrate fixing mechanism 2C on the right side of the fixed pre-tensioning device 2. Rotating the screws 2C4 at the top of the substrate fixing mechanisms 2C on both sides causes the biaxial pressure rod 2C3 to move downwards, thereby firmly fixing the sensor substrate 4 within the central circular hole formed by the upper positioning block 2C2 and the lower fixing block 2C1. The surface of the sensor substrate is polished and cleaned with alcohol to ensure a more secure adhesion of the fiber optic cable 5.

[0024] Thirdly, the shaft 2B1 with a rotating handle in the rotating support moving mechanism 2B drives the fixed pre-tensioning device 2 to move to both sides of the guide rail 1, thereby achieving the pre-tensioning and fixing effect on the sensor base 4. Because the ratchet surface of the ratchet 2B3 with the pull rod meshes with the ratchet surface of the transmission gear 2B4 under the thrust of the spring 2B2, the fixed pre-tensioning device 2 can only move in one direction at this time. Therefore, the fixed pre-tensioning device 2 will not move due to the reaction force of the sensor base 4.

[0025] The fourth step involves threading the three optical fibers 5 through the corresponding teardrop-shaped through holes on the upper part of the optical fiber pre-tensioning mechanisms 2D on both sides, and then pressing the optical fibers 5 firmly onto the surface of the sensor substrate 4 using the V-groove of the elastic pressure plate 2D2. Under the action of the teardrop-shaped through holes, the optical fibers 5 are always kept in a specific position on the sensor substrate 4.

[0026] Fifth, rotate screw 2D3 to push the left and right limiting plates 2D1 to move towards the sides of guide rail 1, causing the elastic pressure plate 2D2 to move. Under the friction of the rubber gasket in the V-groove of the elastic pressure plate 2D2, the optical fiber 5 moves on the surface of the sensor substrate 4, achieving pre-stretching of the optical fiber 5. When the optical fiber 5 is stretched to a certain extent, the internal contraction force of the optical fiber 5 exceeds the frictional force of the rubber gasket on the optical fiber 5, and the optical fiber 5 stops stretching. This ensures that the pre-tension of the optical fiber 5 is the same at different positions and prevents the optical fiber 5 from breaking due to excessive pre-tension. By replacing the rubber gasket with one of different friction coefficients, different degrees of pre-stretching of the optical fiber 5 can be achieved.

[0027] Step 6: Adjust the shape of the flexible adhesive tube 3B5 so that its end is positioned where the optical fiber needs to be bonded. Move the movable adhesive applicator 3 from one side of the guide rail 1 to the other. Since gear 3B1 meshes with the rack on the guide rail 1, the movement causes gear 3B1 to rotate, which in turn rotates gear set 3B2. The rotation of the small gear in gear set 3B2 causes the transmission rack 3B3 to move horizontally, which in turn moves the piston inside the adhesive cartridge 3B4, ensuring the adhesive is evenly applied near the optical fiber 5. The adhesive dispensing speed of the adhesive cartridge 3B4 can be changed by adjusting the radius ratio k = R1:R2 of the large and small gears in gear set 3B2.

[0028] Step 7: Pull the lever on the ratchet 2B3 with the pull rod. The ratchet 2B3 separates from the ratchet on the transmission gear 2B4. Rotate the shaft 2B1 with the rotating handle in the opposite direction to release the pre-tension on the sensor substrate 4. Remove the pasted sensor substrate 4 and optical fiber 5.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention enables precise positioning of the optical fiber using a limiting plate on the optical fiber pre-tensioning mechanism, ensuring accurate strain measurement. The movable adhesive applicator in the device adjusts the adhesive dispensing amount and ensures uniform application by changing the radius of the large and small gears on the gear set, while the flexible adhesive delivery tube ensures accurate adhesive application positioning. The substrate fixing mechanism and optical fiber pre-tensioning mechanism respectively pre-tension the substrate and optical fiber, ensuring alignment during the bonding process. The device can adapt to substrates of different shapes and sizes by changing the shape of the grooves on the upper and lower positioning blocks, offering strong applicability. The combination of elastic pressure plates and rubber gaskets ensures uniform pre-tension force on each optical fiber, expanding the effective measurement range. Using this device and method can improve the manufacturing quality and accuracy of sensors, significantly increasing work efficiency. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 This is a three-dimensional schematic diagram and a side view of the guide rail in this invention;

[0033] Figure 3a This is a schematic diagram of the fixed support structure in this invention;

[0034] Figure 3b This is a schematic diagram of the bottom groove structure of the fixed support structure in this invention;

[0035] Figure 4a This is a schematic diagram of the support moving mechanism in this invention;

[0036] Figure 4b This is a schematic diagram showing the installation position of the support moving mechanism in this invention;

[0037] Figure 5a This is a schematic diagram of the base fixing mechanism in this invention;

[0038] Figure 5b This is a schematic diagram showing the installation position of the base fixing mechanism in this invention;

[0039] Figure 6a This is a schematic diagram of the optical fiber pretensioning mechanism in this invention.

[0040] Figure 6bThis is a schematic diagram of the limiting plate structure in this invention.

[0041] Figure 6c This is a schematic diagram of the elastic compression sheet structure in this invention.

[0042] Figure 6d This is a schematic diagram showing the installation position of the optical fiber pre-tensioning mechanism in this invention.

[0043] Figure 7a This is a schematic diagram of the fixed support structure in this invention.

[0044] Figure 7b This is a schematic diagram of the bottom groove of the fixed support structure in this invention.

[0045] Figure 8a This is a schematic diagram of the adhesive application mechanism in this invention.

[0046] Figure 8b This is a schematic diagram showing the installation position of the adhesive application mechanism in this invention.

[0047] Figure 9 The following are enlarged views and cross-sectional views of the optical fiber and sensor substrate in this invention.

[0048] In the diagram: 1. Guide rail; 2. Fixed pre-tensioning device; 3. Moving adhesive applicator; 4. Sensor substrate; 5. Optical fiber; 2A. Fixed support; 2B. Support moving mechanism; 2C. Substrate fixing mechanism; 2D. Optical fiber pre-tensioning mechanism; 3A. Fixed support; 3B. Adhesive applicator.

[0049] 2A1 Guide groove at the bottom of the fixed support; 2A2 Through hole in the side wall of the fixed support; 2A3 Bottom groove; 2A4 Vertical plate at the top of the fixed support; 2A5 Fixed plate at the top of the fixed support; 2B1 Shaft with rotating handle; 2B2 Spring; 2B3 Ratchet with pull rod; 2B4 Transmission gear; 2C1 Lower positioning block; 2C2 Upper positioning block; 2C3 Dual-axis pressure rod; 2C4 Screw with rotating handle; 2D1 Limiting plate; 2D2 Elastic pressure plate; 2D3 Screw; 3A1 Bottom guide groove; 3A2 Internal shaft; 3A3 Portal frame; 3A4 Limiting piece; 3A5 Variable diameter shaft; 3A6 Fixed block; 3B1 Gear; 3B2 Gear set; 3B3 Transmission rack; 3B4 Glue cylinder; 3B5 Flexible glue delivery tube. Detailed Implementation

[0050] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0051] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] Example 1:

[0053] Reference Figure 1 -8. This invention provides a technical solution: a positioning and bonding device for a distributed optical fiber sensor, comprising a guide rail 1, a fixed pre-tensioning device 2, a movable adhesive applicator 3, a sensor substrate 4, and an optical fiber 5. The fixed pre-tensioning device 2 includes a fixed support 2A, a support moving mechanism 2B, a substrate fixing mechanism 2C, and an optical fiber pre-tensioning mechanism 2D. The movable adhesive applicator includes a fixed support 3A and an adhesive applicator 3B.

[0054] Preferably, the guide rail is a dual-axis guide rail, with a rack engraved in the middle of the upper surface, and a scale marked along the length of the guide rail next to the rack. The two axes of the guide rail are distributed parallel to each other on both sides of the guide rail, and the cross-sectional shape of the axes is circular. Preferably, the bonding length can be extended by combining guide rails.

[0055] Preferably, the main body of the fixed support 2A is a cuboid, and the shape of its lower front surface matches the upper surface of the guide rail 1. Therefore, the fixed support 2A can only move horizontally along the length of the guide rail 1. The lower surface of the fixed support 2A has a plane at its center, with a cuboid groove 2A3 extending upwards along the plane, and the groove 2A3 does not penetrate the cuboid. The sidewall of the fixed support 2A has two through circular holes 2A2, which pass through the bottom groove 2A3, and the centers of the two holes 2A2 are on a vertical line. A vertical plate 2A4, perpendicular to the upper surface of the cuboid, is fixed near the front of the cuboid. A circular through hole is located near the top of the vertical plate 2A4. A cylinder is horizontally fixed near the bottom of the back of the vertical plate 2A4. A fixing plate 2A5, perpendicular to the upper surface of the cuboid, is located near the back of the cuboid. A rectangular through hole is located at the top of the fixing plate 2A5. A circular hole is located at the center of the top of the fixing plate 2A5. The circular hole passes through the rectangular through hole and has internal threads. Two circular holes are symmetrically distributed on the lower surface of the rectangular through hole.

[0056] Preferably, the support moving mechanism 2B includes a shaft 2B1 with a rotating handle at one end, a spring 2B2, a ratchet 2B3 with a pull rod, and a transmission gear 2B4; the spring 2B2 can pass through the shaft 2B1; the ratchet 2B3 with a pull rod is an ordinary ratchet with a circular through hole in the center, and the diameter of the circular through hole is slightly larger than the diameter of the shaft 2B1, and a pull rod with a pull ring is fixed to the back of the ratchet; the transmission gear 2B4 is a combination of a gear and an ordinary ratchet, and the transmission gear 2B4 is fixed on the shaft 2B1.

[0057] The following describes the installation position of the support moving mechanism 2B: Shaft 2B1 passes through the lower circular through hole on the side of the fixed support 2A and can rotate. At the bottom groove 2A32 of the fixed support 2A, spring 2B2, ratchet 2B3 with pull rod, and transmission gear are sequentially passed through shaft 2B1. Spring 2B2 and ratchet 2B3 with pull rod can move along shaft 2B1, and the pull ring of ratchet 2B3 with pull rod faces the same direction as the handle of shaft 2B1. Transmission gear 2B4 is fixed to shaft 2B1 and rotates with shaft 2B1. The ratchet surface of transmission gear 2B4 meshes with the ratchet surface of ratchet 2B3 with pull rod. After installation, the gear on transmission gear 2B4 can mesh with the rack on the guide rail.

[0058] Preferably, the sensor substrate fixing mechanism 2C includes a lower positioning block 2C1, an upper positioning block 2C2, a dual-axis pressure rod 2C3, and a screw 2C4 with a rotating handle. The lower positioning block 2C1 is a cuboid with a semi-circular through groove on the top of its front side and two symmetrically distributed through circular holes on its top. The upper positioning block 2C2 is also a cuboid with a semi-circular through groove on the bottom of its front side and two symmetrically distributed through circular holes on its top. The dual-axis pressure rod 2C3 is a cuboid with two cylinders symmetrically fixed below it. The screw 2C4 with a rotating handle has external threads on its rod. Preferably, the shape of the grooves on the upper positioning block 2C1 and the lower positioning block 2C2 can be changed according to the shape of the sensor substrate.

[0059] The following describes the installation of the sensor base fixing mechanism 2C: The lower positioning block 2C1, the upper positioning block 2C2, and the dual-axis pressure rod 2C3 are placed in the rectangular through hole on the fixing plate 2A5 of the fixing support 2A in sequence; the two cylinders below the dual-axis pressure rod 2C3 pass through the circular through hole at the top of the upper positioning block, the circular through hole at the top of the lower positioning block, and the two circular holes at the bottom of the rectangular through hole in sequence; the screw 2C4 with a rotating handle passes through the circular through hole at the top of the fixing plate 2A5, and the external thread of the screw is engaged with the internal thread of the circular through hole.

[0060] Preferably, the fiber pretensioning mechanism 2D includes a limiting plate 2D1, an elastic pressure plate 2D2, and a screw 2D3. The limiting plate 2D1 is primarily a rectangular plate with a circular through-hole near the bottom and a central circular through-hole a near the top. Around the central circular through-hole a, three teardrop-shaped through-holes are evenly distributed. One end of each teardrop-shaped through-hole is arc-shaped, and the width of the other pointed end is the same as the fiber diameter, with a smooth transition between the two ends. The pointed end connects to the circular through-hole. The arc-shaped end increases the through-hole area, facilitating the passage of the fiber 5. The position of the teardrop-shaped through-holes can be changed according to the fiber's position on the substrate. Around the circular through-hole, there are also three evenly distributed peripheral circular through-holes b, each with internal threads. The elastic pressure plate 2D2 has good flexibility, with a circular limiting hole at one end, a V-shaped groove on the lower surface of the other end, and a lever on the upper surface. Furthermore, a rubber gasket is present on the V-shaped groove.

[0061] The following describes the installation of the fiber pretensioning mechanism 2D: First, fix the three elastic pressure plates to the outer circular through hole b of the limiting plate 2D1 with screws. All three elastic pressure plates are inclined towards the center of the central circular through hole a of the limiting plate 2D1, and the levers of the elastic pressure plates 2D2 are all facing the outer periphery of the central circular through hole a. Then, the limiting plate 2D1 passes through the circular through hole near the bottom of the fixed support 2A to the top of the upright plate 2A4. Finally, the screw 2D3 passes through the circular through hole near the top of the upright plate 2A4, and the external thread of the screw 2D3 matches the internal thread of the circular through hole on the upright plate 2A4.

[0062] Preferably, the fixed support 3A includes a bottom guide groove 3A1, an internal shaft 3A2, a portal frame 3A3, a limiting piece 3A4, a variable diameter shaft 3A5, and a fixing block 3A6; the base of the fixed support 3A is a cuboid, and the bottom of the front of the cuboid has a through bottom guide groove 3A1 that fits with the guide rail; the middle of the guide groove 3A1 is flat and has a rectangular through hole, and there is an internal shaft 3A2 parallel to the front of the through hole; the upper surface of the fixed support 3A has a portal frame 3A3; one side of the inner wall of the portal frame 3A3 has a limiting piece 3A4; there is a variable diameter shaft 3A5 below the limiting piece 3A4; there is a fixing block 3A6 on the upper surface of the fixed support 3A near the front, and one side of the fixing block 3A6 has a U-shaped groove for fixing the rubber tube;

[0063] Preferably, the glue application mechanism 3B includes a gear 3B1, a gear set 3B2, a transmission rack 3B3, a glue cylinder 3B4, and a flexible glue delivery tube 3B5; the gear set 3B2 is a combination of two coaxial gears of different radii; the transmission rack 3B3 is a rectangular rack with a groove running through its thickness in the middle along its length; the glue cylinder 3B4 contains glue and has several glue nozzles on one side, which can squeeze out glue by pressing a piston on the other side; the flexible glue delivery tube is a universal hose that can be arbitrarily changed in shape.

[0064] The following describes the installation of the mobile glue applicator 3B: Mount gear 3B1 on the internal shaft 3A2, mount gear set 3B2 on the variable diameter shaft 3A5, fix glue cylinder 3B4 in the groove on the side wall of the fixing block 3A5, and finally place the transmission rack 3B3 horizontally through the limiting piece 3A4; gear 3B1 meshes with the rack on the guide rail 1, the large gear in gear set 3B2 meshes with gear 3B1, and the transmission rack 3B3 meshes with the small gear in gear set 3B2; one end of the transmission rack 3B3 is connected to the piston inside the glue cylinder 3B4; the flexible glue delivery tube 3B5 is connected to the glue outlet at one end of the glue cylinder 3B4.

[0065] The working principle of this invention is as follows: After the fixed pre-tensioning device 2 and the movable adhesive applicator 3 are fully installed, the movable adhesive applicator is placed in the middle of the guide rail through the guide groove, and the two fixed pre-tensioning devices are placed at both ends of the guide rail through the guide groove. Then, the sensor substrate is passed through the substrate fixing mechanism and the optical fiber pre-tensioning mechanism of the fixed pre-tensioning devices on both sides of the guide rail. The substrate fixing mechanism first fixes both ends of the sensor substrate. The rotating handle in the rotating support mechanism drives the fixed pre-tensioning device to move to the end of the guide rail through the internal gear, thereby straightening and tightening the sensor substrate, which facilitates the subsequent positioning and bonding of the optical fiber. Due to the ratchet structure inside the rotating support mechanism, it can only move in one direction. Only by pulling the pull ring on the rotating support mechanism, compressing the spring, and separating the two ratchets can reverse movement be achieved. Then, the optical fiber is passed through the optical fiber pre-tensioning mechanism and fixed by the elastic pressure plate. Rotating the handle on the optical fiber pre-tensioning mechanism tightens the three optical fibers at different positions. Since the pre-tensioning force is equal to the elastic force of the elastic pressure plate and the friction force provided by the rubber pad on the V-groove, it can be ensured that the pre-tensioning force on each optical fiber is the same. Finally, adjust the position of the end of the flexible glue delivery tube to the fixed position of the optical fiber, and move the mobile glue applicator from one end of the guide rail to the other end. During the movement, the gears are driven to rotate. By changing the radius ratio of the large and small gears on the gear set, the movement distance of the transmission rack can be changed while the mobile glue applicator moves the same distance, thereby changing the glue output of the glue tube and ensuring uniform glue application.

[0066] This device precisely positions the optical fiber using a limiting plate on the fiber pre-tensioning mechanism, ensuring accurate strain measurement. The movable adhesive applicator adjusts the adhesive dispensing amount and ensures uniform application by changing the radius of the large and small gears on the gear set, while the flexible adhesive delivery tube ensures accurate adhesive application. The substrate fixing mechanism and fiber pre-tensioning mechanism respectively pre-tension the substrate and optical fiber, ensuring alignment during bonding. The device can adapt to substrates of different shapes and sizes by changing the shape of the grooves on the upper and lower positioning blocks, offering strong applicability. Using this device and method can improve the manufacturing quality and accuracy of sensors, significantly increasing work efficiency.

[0067] Example 2:

[0068] This embodiment provides a method for positioning and attaching a distributed optical fiber sensor, which can be applied to the distributed optical fiber sensor positioning and attaching device of Embodiment 1. The method includes the following steps:

[0069] The first step is to install the mobile glue applicator 3, the left fixed pre-tensioning device 2, and the right fixed pre-tensioning device 2 on the guide rail 1. The mobile glue applicator is located in the middle of the guide rail, and the two fixed pre-tensioning devices are located on both sides of the guide rail.

[0070] The second step involves sequentially passing the sensor substrate 4 through the substrate fixing mechanism 2C and fiber pre-tensioning mechanism 2D on the left-side fixing pre-tensioning device, and the fiber pre-tensioning mechanism 2D and substrate fixing mechanism 2C on the right-side fixing pre-tensioning device. Rotating the screws 2C4 at the top of both substrate fixing mechanisms causes the biaxial pressure rod 2C3 to move downwards, thus firmly fixing the sensor substrate within the central circular hole formed by the upper positioning block 2C2 and the lower fixing block 2C3. The surface of the sensor substrate is then polished and cleaned with alcohol to ensure a more secure fiber optic bond.

[0071] Thirdly, the shaft 2B1 with a rotating handle in the rotating support moving mechanism 2B drives the fixed pre-tensioning device 2 to move to both sides of the guide rail, thereby achieving the pre-tensioning and fixing effect on the sensor base 4. Because the ratchet surface of the ratchet 2B3 with the pull rod meshes with the ratchet surface of the transmission gear 2B4 under the thrust of the spring 2B2, the fixed pre-tensioning device 2 can only move in one direction at this time. Therefore, the fixed pre-tensioning device 2 will not move due to the reaction force of the base.

[0072] The fourth step involves threading the three optical fibers 5 through the corresponding teardrop-shaped through holes on the upper part of the optical fiber pre-tensioning mechanisms 2D on both sides, and then pressing the optical fibers 5 firmly onto the surface of the sensor substrate 4 using the V-groove of the elastic pressure plate 2D2. Under the action of the teardrop-shaped through holes, the optical fibers 5 are always kept in a specific position on the sensor substrate 4.

[0073] Fifth, rotate screw 2D3 to push the left and right limiting plates 2D1 to move along the guide rails, causing the elastic pressure plate 2D2 to move. Under the friction of the rubber pad in the V-groove of the elastic pressure plate 2D2, the optical fiber 5 moves on the surface of the sensor substrate 4, achieving pre-stretching of the optical fiber. When the optical fiber 5 is stretched to a certain extent, the internal contraction force of the optical fiber 5 exceeds the friction force of the rubber pad on the optical fiber, and the optical fiber stops stretching. This ensures that the pre-tension force of the optical fiber is the same at different positions and prevents the optical fiber from breaking due to excessive pre-tension force. By replacing the rubber pads with different friction coefficients, different degrees of pre-stretching of the optical fiber 5 can be achieved.

[0074] Step 6: Adjust the end of the flexible adhesive delivery tube 3B5 to be positioned at the fiber optic cable 5, and push the movable adhesive applicator 3 from one side of the guide rail to the other. Since gear 3B1 meshes with the rack on guide rail 1, the movement causes gear 3B1 to rotate, which in turn rotates gear set 3B2. The rotation of the small gear in gear set 3B2 causes the transmission rack 3B3 to move horizontally, which in turn moves the piston inside the adhesive cartridge 3B4, ensuring the adhesive is evenly applied near the fiber optic cable 5. By adjusting the radius ratio k = R1:R2 of the large and small gears in gear set 3B2, the moving length of the transmission rack 3B3 can be changed, thus altering the amount of adhesive dispensed per unit length from the adhesive cartridge 3B4.

[0075] Step 7: Pull the lever on ratchet 2B3 with pull rod. Ratchet 2B3 separates from the ratchet on transmission gear 2B4. Rotate shaft 2B1 with rotating handle in the opposite direction to release the pre-tension on the substrate and remove the pasted sensor and optical fiber.

[0076] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A positioning and bonding device for a distributed optical fiber shape sensor, characterized in that, The positioning and pasting device includes a guide rail (1), two fixed pre-tensioning devices (2), a movable adhesive applicator (3), a sensor substrate (4), and an optical fiber (5); The fixed pre-tensioning device (2) is arranged on both sides of the guide rail (1), and the movable adhesive applicator (3) is arranged in the middle of the guide rail (1). All three can move horizontally on the guide rail. The sensor substrate (4) passes through the left fixed pre-tensioning device (2), the movable adhesive applicator (3), and the right fixed pre-tensioning device (2) in sequence. The sensor substrate (4) is fixed and pre-stretched by the substrate fixing mechanism (2C) and the support moving mechanism (2B) on the two fixed pre-tensioning devices (2). The optical fiber (5) passes through the optical fiber pre-tensioning mechanism (2D) on the left fixed pre-tensioning device (2), the movable adhesive applicator (3), and the optical fiber pre-tensioning mechanism (2D) on the right fixed pre-tensioning device (2) in sequence. The optical fiber is fixed and pre-stretched by the optical fiber pre-tensioning mechanism (2D) on both sides, ensuring that the pre-stretching force on each optical fiber (5) is the same. The movable adhesive applicator (3) is moved to apply adhesive evenly at a specific position on the sensor substrate (4) to adhere the optical fiber (5). The fixed pre-tensioning device (2) includes a fixed support (2A), a support moving mechanism (2B), a base fixing mechanism (2C), and an optical fiber pre-tensioning mechanism (2D); specifically: The fixed support (2A) is a cuboid, with its bottom front end fitting into the upper surface of the guide rail (1). The fixed support (2A) moves horizontally only along the length of the guide rail (1). The lower surface of the fixed support (2A) has a plane in the middle, with a cuboid groove (2A3) extending upwards along the plane. The groove (2A3) does not penetrate the cuboid. The cuboid sidewall of the fixed support (2A) has two through-holes (2A2), which pass through the bottom groove (2A3). The centers of the two holes (2A2) are on a vertical line. A vertical plate (2A4) is fixed to the upper surface of a cuboid near the front. The vertical plate (2A4) has a circular through hole near the top. A cylinder is horizontally fixed to the back of the vertical plate (2A4) near the bottom. A fixing plate (2A5) is fixed to the upper surface of the cuboid near the back. The fixing plate (2A5) has a rectangular through hole at the top. A circular hole is located at the top center of the fixing plate (2A5). The circular hole passes through the rectangular through hole and has internal threads. Two circular holes are symmetrically distributed on the lower surface of the rectangular through hole. The support moving mechanism (2B) includes a shaft (2B1) with a rotating handle at one end, and a spring (2B2), a ratchet with a pull rod (2B3), and a transmission gear (2B4) arranged sequentially on the shaft (2B1). The spring (2B2) is sleeved on the shaft (2B1) and located between the rotating handle of the shaft (2B1) and the ratchet with a pull rod (2B3), and can move along the shaft (2B1). The ratchet with a pull rod (2B3) is an ordinary ratchet with a circular through hole in the center, sleeved on the shaft (2B1), and the diameter of the circular through hole is slightly larger than the diameter of the shaft (2B1), and can move along the shaft (2B1). A pull rod with a pull ring is fixed on the back of the ratchet. The transmission gear (2B4) is a combination of a gear and an ordinary ratchet. The transmission gear (2B4) is fixed on the shaft (2B1), cannot move along the shaft (2B1), but can rotate with the shaft (2B1). The base fixing mechanism (2C) includes a lower positioning block (2C1), an upper positioning block (2C2), a dual-axis pressure rod (2C3), and a first screw (2C4) with a rotating handle; the lower positioning block (2C1) is a cuboid with a semi-circular through groove on the top of its front face and two symmetrically distributed through circular holes on the top; the upper positioning block (2C2) is also a cuboid with a semi-circular through groove on the bottom of its front face and two symmetrically distributed through circular holes on the top; the lower positioning block (2C1) The upper positioning block (2C2) has a symmetrical structure, with two semi-circular through grooves joined together to form a circular through hole; the dual-axis pressure rod (2C3) is a cuboid with two cylinders symmetrically fixed at the bottom, passing through the top circular holes of the lower positioning block (2C1) and the upper positioning block (2C2); the first screw (2C4) with a rotating handle has external threads on its rod, and during the downward movement of the first screw (2C4) with the rotating handle, it presses the top of the dual-axis pressure rod (2C3) to make it move downward synchronously; The fiber pre-tensioning mechanism (2D) includes a limiting plate (2D1), an elastic pressure plate (2D2), and a second screw (2D3). The limiting plate (2D1) is a rectangular plate with a circular through hole near the bottom and a central circular through hole a near the top. M teardrop-shaped through holes are evenly distributed around the central circular through hole a. One end of each teardrop-shaped through hole is an arc, and the width of the other tip is the same as the diameter of the fiber (5). The two ends are smoothly connected, and the tip is connected to the central circular through hole a. The position of the teardrop-shaped through hole changes according to the position of the fiber on the substrate. There are also M peripheral circular through holes b evenly distributed around the central circular through hole a, and the peripheral circular through holes b have internal threads. The elastic pressure plate (2D2) is flexible, with a circular limiting hole at one end, a V-shaped groove on the lower surface of the other end, and a lever on the upper surface.

2. The positioning and pasting device for a distributed optical fiber shape sensor according to claim 1, characterized in that, The guide rail (1) is a dual-axis guide rail with two axes distributed parallel to each other on both sides of the guide rail; a rack is provided in the middle of the upper surface of the guide rail (1), and a scale is marked next to the rack along the length of the guide rail to help determine the length of the adhesive fiber (5); the adhesive length can be extended by combining the guide rail (1).

3. The positioning and pasting device for a distributed optical fiber shape sensor according to claim 2, characterized in that, The semi-circular through grooves on the upper positioning block (2C2) and lower positioning block (2C1) are shaped according to the shape of the sensor substrate; the elastic pressure plate (2D2) has a rubber pad on its V-groove; The mobile adhesive applicator includes a fixed support (3A) and an adhesive applicator mechanism (3B); specifically: The fixed support (3A) includes a bottom guide groove (3A1), an internal shaft (3A2), a portal frame (3A3), a limiting piece (3A4), a variable diameter shaft (3A5), and a fixing block (3A6). The base of the fixed support (3A) is a cuboid, with a through bottom guide groove (3A1) on the bottom front of the cuboid that fits with the guide rail. The guide groove (3A1) has a flat surface in the middle and a rectangular through hole, with an internal shaft (3A2) parallel to the front of the through hole. The upper surface of the fixed support (3A) has a portal frame (3A3). One side of the inner wall of the portal frame (3A3) has a limiting piece (3A4). Below the limiting piece (3A4) is a variable diameter shaft (3A5). Near the front of the upper surface of the fixed support (3A), there is a fixing block (3A6), and one side of the fixing block (3A6) has a U-shaped groove for fixing the rubber tube. The adhesive application mechanism (3B) includes a gear (3B1), a gear set (3B2), a transmission rack (3B3), an adhesive cartridge (3B4), and a flexible adhesive delivery tube (3B5). The gear set (3B2) is a combination of two coaxial gears of different radii. The transmission rack (3B3) is a rectangular rack with a groove running through its thickness along its length. The adhesive cartridge (3B4) has a piston inside containing adhesive and several nozzles on one side. Squeezing the piston on the other side squeezes out the adhesive from the nozzles. The flexible adhesive delivery tube (3B5) is a universal flexible tube that can be arbitrarily changed in shape to deliver the adhesive to the location where the optical fiber is to be bonded.

4. The positioning and pasting device for a distributed optical fiber shape sensor according to claim 3, characterized in that, The sensor substrate (4) has a circular cross-section, and its shape and size are the same as the through hole formed after the lower positioning block (2C1) and the upper positioning block (2C2) are docked; the optical fiber (5) is a distributed optical fiber.

5. A method for positioning and attaching a distributed optical fiber sensor, characterized in that, Based on the positioning and pasting device described in claim 4, the specific steps include: The first step is to install the mobile glue applicator (3) and the two fixed pre-tensioning devices (2) on the guide rail (1). The mobile glue applicator (3) is located in the middle of the guide rail (1), and the two fixed pre-tensioning devices (2) are located on both sides of the guide rail (1). The mobile glue applicator (3) and the two fixed pre-tensioning devices (2) can both move along the axis on the guide rail (1). In the second step, the sensor substrate (4) is passed through the substrate fixing mechanism (2C), fiber pre-tensioning mechanism (2D), moving adhesive applicator (3) of the left fixed pre-tensioning device (2) and the fiber pre-tensioning mechanism (2D) and substrate fixing mechanism (2C) on the right fixed pre-tensioning device (2) in sequence; the first screw (2C4) at the top of the substrate fixing mechanisms (2C) on both sides is rotated so that the biaxial pressure rod (2C3) moves downward and firmly fixes the sensor substrate (4) in the middle circular hole formed by the upper positioning block (2C2) and the lower positioning block (2C1); The third step involves using the shaft (2B1) with a rotating handle in the rotating support moving mechanism (2B) to move the fixed pre-tensioning device (2) along both sides of the guide rail (1), thereby achieving the pre-tensioning and fixing effect on the sensor substrate (4). Due to the thrust of the spring (2B2), the ratchet surface of the ratchet with the pull rod (2B3) meshes with the ratchet surface of the transmission gear (2B4). At this time, the fixed pre-tensioning device (2) can only move in one direction, and the fixed pre-tensioning device (2) will not move due to the reaction force of the sensor substrate (4). In the fourth step, M optical fibers (5) are passed through the corresponding teardrop-shaped through holes on the upper part of the optical fiber pre-tensioning mechanism (2D) on both sides, and the optical fibers (5) are pressed onto the surface of the sensor substrate (4) by the V-groove of the elastic pressure plate (2D2); under the action of the teardrop-shaped through holes, the optical fibers (5) are always kept at a specific position on the sensor substrate (4); Fifth step, rotate the second screw (2D3) to push the left and right limit plates (2D1) to move to both sides of the guide rail (1), which in turn moves the elastic pressure plate (2D2). Under the friction of the rubber pad in the V-groove of the elastic pressure plate (2D2), the optical fiber (5) moves on the surface of the sensor substrate (4), thus pre-stretching the optical fiber (5). When the optical fiber (5) is stretched to a certain extent, the internal contraction force of the optical fiber (5) is greater than the friction of the rubber pad on the optical fiber (5), and the optical fiber (5) is no longer stretched, ensuring that the pre-tightening force of the optical fiber (5) is the same at different positions, and that the optical fiber (5) will not break due to excessive pre-tightening force. By replacing the rubber pad with different friction coefficients, different degrees of pre-stretching of the optical fiber (5) can be achieved. Step 6: Adjust the shape of the flexible glue delivery tube (3B5) so that its end is located at the position where the optical fiber needs to be pasted. Push the moving glue applicator (3) from one side of the guide rail (1) to the other side. Since the gear (3B1) and the rack on the guide rail (1) are meshed, the gear (3B1) is rotated while moving, which in turn drives the gear set (3B2) to rotate. Under the rotation of the small gear in the gear set (3B2), the transmission rack (3B3) is driven to move horizontally, which in turn drives the piston in the glue tube (3B4) to move, so that the glue is evenly applied near the optical fiber (5). Step 7: Pull the lever on the ratchet (2B3) with the lever. The ratchet (2B3) with the lever will separate from the ratchet on the transmission gear (2B4). Rotate the shaft (2B1) with the rotating handle in the opposite direction to remove the pre-tension on the sensor substrate (4). Remove the pasted sensor substrate (4) and optical fiber (5).

6. The method for positioning and attaching a distributed optical fiber sensor according to claim 5, characterized in that, In the sixth step, the dispensing speed of the glue cartridge (3B4) is changed by adjusting the radius ratio k = R1:R2 of the large and small gears in the gear set (3B2).

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