Square optical fiber preform extrusion die

Abstract

The utility model provides a square optical fiber preform extrusion die which comprises a sleeve internally divided into a filling cavity, a clamping groove and a fixing groove in sequence; the piston is arranged in the filler cavity; the nozzle is arranged in the clamping groove; the fixing ring is arranged in the fixing groove and detachably connected with the fixing groove; wherein a funnel-shaped through hole is formed in the nozzle, the upper end of the through hole is a feed port, and the lower end of the through hole is a discharge port; the section of the feeding hole is circular; the cross section of the discharge port is in the shape of an approximate square of which four sides are concave arcs; therefore, when the softened glass is discharged from the nozzle, the softened glass can be extruded into a cylinder of which the cross section is in the shape of an approximate square with four concave arc edges by the discharge port, so that when the glass expands outwards in the radial direction due to the surface tension problem, the concave part of the concave arc can be filled with the glass, and when the glass is cooled and solidified, the glass is not prone to falling off. An optical fiber preform rod closer to a square shape can be formed; therefore, the problem that the filling coefficient of the glass optical fiber image transmitting bundle is not high is effectively solved.

Description

Technical Field

[0001] This utility model relates to the field of optical fiber preform preparation technology, and in particular to a square optical fiber preform extrusion die. Background Technology

[0002] An optical fiber image bundle is a flexible, passive imaging device composed of many thin optical fiber filaments of a certain length arranged in a regular pattern. Each fiber filament acts as an independent pixel, transmitting images without interference. A sufficient number of pixels allows the image to be transmitted from one end of the fiber bundle to the other. The main performance characteristics of an optical fiber image bundle include resolution and transmittance. Transmittance is related to single-filament loss and fill factor. The fill factor refers to the ratio of the area occupied by the fiber core to the total cross-sectional area of ​​the fiber bundle. Increasing the ratio of the fiber core to the cladding (core-to-cladding ratio) and reducing the gaps between fibers can effectively increase the transmittance of the fiber bundle.

[0003] However, traditional circular optical fibers inevitably have gaps during arrangement, which causes the fill factor of fiber bundles, even those made with circular fibers of high core-to-cladding ratio, to decrease due to these gaps. Using square-section fibers, on the other hand, reduces the gaps between fibers, thus eliminating the impact of these gaps on the fill factor and enabling the fabrication of high-fill-factor fiber imaging bundles. Typically, square-section fiber preforms of high core-to-cladding ratio are fabricated using a lamination and extrusion process.

[0004] Currently, there is an existing Chinese patent with publication number CN108751694B entitled "A Method for Preparing a High-Fill-Coefficient Infrared Chalcogenide Glass Fiber Image Bundle". This patent first uses a lamination extrusion method to prepare a three-layer coaxial composite material rod with a square cross-section. From the inside out, the composite material rod consists of a core of chalcogenide glass, an inner cladding of chalcogenide glass, and an outer cladding of thermoplastic polymer. Then, four composite material rods of equal length are bundled and heat-treated to form a 2×2 array fiber preform, which is then drawn into a 2×2 array fiber. Next, the 2×2 array fibers are stacked in a square arrangement and heat-treated to form an array fiber bundle, which is then drawn into an array fiber multifilament. Finally, the array fiber multifilaments are stacked in a square arrangement to form an array fiber multifilament bundle, and their ends are thermally bonded and wax-sealed to obtain a high-fill-coefficient infrared chalcogenide glass fiber image bundle.

[0005] However, during the fabrication process, to prevent the extruded glass from shattering, it needs to be annealed to near its glass transition temperature. Before reaching the annealing temperature, the glass is still in a softened state. Due to factors such as surface tension, the square cross-section of the optical fiber preform tends to change towards a circular shape, ultimately forming a circular arc shape with slightly protruding sides. This results in optical fiber bundles fabricated using this method still having fiber gaps during fabrication and arrangement, affecting the improvement of the fill factor. Utility Model Content

[0006] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a square optical fiber preform extrusion mold. By inserting a nozzle into the end of a sleeve, when the piston extrudes the filling cavity inside the sleeve, softened glass enters through the nozzle's inlet and exits through the outlet. At this time, the outlet, with its four concave arc sides, extrudes the softened glass into a prism with a cross-sectional shape approximately square. As the glass expands radially outward due to surface tension, it fills the concave arc depressions. When it cools and solidifies, it forms an optical fiber preform that is closer to a square shape. Therefore, this application effectively solves the problem of low filling coefficient in glass optical fiber image bundles.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0008] A square optical fiber preform extrusion die includes:

[0009] The sleeve is divided into three parts from top to bottom: a packing cavity, a groove, and a fixing groove.

[0010] The piston is located inside the packing cavity and slides up and down along the central axis of the sleeve;

[0011] The nozzle is located inside the slot;

[0012] A retaining ring is disposed inside the retaining groove, and its sidewall is detachably connected to the retaining groove by a thread.

[0013] The nozzle has a funnel-shaped through hole inside, with the upper end being the feed inlet and the lower end being the discharge outlet.

[0014] The feed inlet has a circular cross-sectional shape, and its diameter is the same as the inner diameter of the packing cavity;

[0015] The cross-sectional shape of the discharge port is an approximate square with four concave circular arcs on its four sides, and the arc length and radius of curvature of the four concave circular arcs are the same.

[0016] Preferably, the inner diameters of the packing cavity, the slot, and the fixing slot increase sequentially.

[0017] Preferably, the lower part of the nozzle extends out of the slot into the fixing groove.

[0018] Preferably, the diameter of the fixing ring is larger than the diagonal length of the discharge port.

[0019] Preferably, the outer diameter of the piston matches the inner diameter of the packing cavity, and the upper part of the piston is provided with an internal threaded hole for connecting to the output end of the extruder pushing device.

[0020] Preferably, the sleeve, piston, nozzle, and retaining ring are all made of stainless steel.

[0021] This utility model has the following beneficial effects:

[0022] First, the square optical fiber preform extrusion mold provided by this utility model, by inserting the nozzle into the end of the sleeve, allows the softened glass to enter from the nozzle inlet and exit from the outlet when the piston extrudes the filling cavity inside the sleeve. At this time, the outlet with four concave arc sides will extrude the softened glass into a prism with a cross-sectional shape of approximately a square with four concave arc sides. Thus, when the glass expands outward along the radial direction due to surface tension, it will fill the concave arc depression. When it cools and solidifies, it can form an optical fiber preform that is closer to a square shape. In this way, this application effectively solves the problem of low filling coefficient of glass optical fiber image bundle.

[0023] Secondly, the square optical fiber preform extrusion die provided by this utility model sets the nozzle in the slot inside the sleeve, and the diameter of the nozzle inlet is the same as the diameter of the filling cavity inside the sleeve used for pressurizing the glass. This makes the extrusion space formed by the filling cavity and the nozzle continuous and smooth, avoiding the problem that the nozzle is difficult to remove after extrusion due to glass residue entering the gap between the nozzle and the sleeve. It also reduces extrusion resistance, improves extrusion efficiency, and ensures the uniformity of the extruded glass. Attached Figure Description

[0024] Figure 1 A cross-sectional view of the square optical fiber preform extrusion die provided by this utility model;

[0025] Figure 2 A schematic diagram of the nozzle structure of the square optical fiber preform extrusion die provided by this utility model;

[0026] Figure 3 A cross-sectional view of the optical fiber preform provided for the control experimental group of this utility model;

[0027] Figure 4 A cross-sectional view of the nozzle outlet of the square optical fiber preform extrusion die provided by this utility model. Attached image description:

[0029] 1. Sleeve; 2. Piston; 3. Nozzle; 4. Retaining ring; 5. Core glass block; 6. Cladding glass block;

[0030] 11. Packing cavity; 12. Slot; 13. Fixing slot;

[0031] 31. Feed inlet; 32. Discharge outlet. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0033] In the description of this utility model, it should be understood that the terms "upper part," "lower part," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model 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. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this utility model. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the protection scope of this utility model.

[0034] Reference Figure 1 This application provides a square optical fiber preform extrusion die, comprising: a sleeve 1, the sleeve 1 being divided into three parts from top to bottom: a filling cavity 11, a slot 12, and a fixing groove 13, the inner diameters of the filling cavity 11, the slot 12, and the fixing groove 13 increasing sequentially; a piston 2 disposed inside the filling cavity 11 and sliding up and down along the central axis of the sleeve 1; a nozzle 3 disposed inside the slot 12; and a fixing ring 4 disposed inside the fixing groove 13, its sidewall being detachably connected to the fixing groove 13 by threads; wherein, the nozzle 3 has a funnel-shaped through hole inside, the upper end of which is a feed port 31 and the lower end is a discharge port 32; the cross-sectional shape of the feed port 31 is circular, and its diameter is the same as the inner diameter of the filling cavity 11; the cross-sectional shape of the discharge port 32 is an approximately square with four concave arcs on its four sides, and the arc length and radius of curvature of the four concave arcs are the same.

[0035] Furthermore, when using the extrusion die provided in this application to produce optical fiber preforms, by inserting the nozzle 3 into the end of the sleeve 1, when the piston 2 extrudes the filling cavity 11 inside the sleeve 1, the softened glass can enter from the feed port of the nozzle 3 and be discharged from the discharge port 32. At this time, the discharge port 32, with its four concave arc sides, will extrude the softened glass into a prism with a cross-sectional shape that is approximately square with four concave arc sides. Thus, when the glass expands outward along the radial direction due to surface tension, it will fill the concave arc depression. When it cools down and solidifies, it can form an optical fiber preform that is closer to a square shape. In this way, this application effectively solves the problem of low filling coefficient of glass optical fiber image bundle.

[0036] In one embodiment of this application, the inner diameters of the three parts—the packing cavity 11, the slot 12, and the fixing slot 13—are 30mm, 32mm, and 34mm, respectively; the diameter of the piston 2 is 29.8mm; the outer diameter of the nozzle 3 is 31.8mm, and the height is 12mm, with the height of the slot 12 of the nozzle 3 being 10mm; the aperture of the fixing ring 4 is 18mm; the diameter of the inlet 31 of the nozzle 3 is 30mm, and the side length of the square formed by the four vertices of the outlet 32 ​​is 10mm.

[0037] like Figure 3 As shown, this application uses an optical fiber preform extruded through a square discharge port with a side length of L as a control experiment. The distance between adjacent vertices of the quadrilateral is L′, the distance between opposite protrusions is X, the height of a single circular arc protrusion is a, the radius of curvature of the arc is r1, and the center of the upper arc is at position o1.

[0038] Therefore, it can be concluded that:

[0039] r1=(L′ 2 +4a 2 ) / 8a

[0040] and

[0041] a=(XL′) / 2

[0042] In the control experiment with L = 10 mm, L′≈9.48 mm and X≈10.38 mm were measured, and a = 0.45 mm and r1 = 25.19 mm were calculated. Furthermore, under the same conditions as the control experiment, r2 = r1 was set to compensate for the deformation caused by surface tension during glass extrusion. That is, in the mold designed in this application, the radius of curvature of the four concave arcs at nozzle 3 is equal to r1.

[0043] like Figure 1 As shown, the lower part of the nozzle 3 extends from the slot 12 into the fixing slot 13, thereby ensuring that the nozzle 3 is fixed by the fixing ring 4 and improving the stability of the assembly mold.

[0044] like Figure 1 As shown, the diameter of the retaining ring 4 is larger than the diagonal length of the outlet 32, which ensures that the glass passing through the nozzle 3 will not be blocked by the retaining ring 4 and can be smoothly squeezed out from the nozzle 3, thus improving the stability of the molded product.

[0045] like Figure 1 As shown, the outer diameter of piston 2 matches the inner diameter of packing cavity 11, and the upper part of piston 2 is provided with an internal threaded hole for connecting to the output end of extruder push device.

[0046] To improve the service life of the mold provided in this application, the sleeve 1, piston 2, nozzle 3 and retaining ring 4 are all made of stainless steel.

[0047] Working principle:

[0048] First, insert the nozzle 3 into the slot 12 from the fixing groove 13 of the sleeve 1, so that the upper edge of the feed port 31 of the nozzle 3 is tightly fitted with the lower edge of the packing cavity 11 of the sleeve 1; then, screw the fixing ring 4 into the fixing groove 13, so that the fixing ring 4 squeezes the nozzle 3, thus completing the fixing of the nozzle 3.

[0049] Next, prepare the core glass block 5 and the cladding glass block 6. Insert the cladding glass block 6 and the core glass block 5 into the filling cavity 11 inside the sleeve 1 from the top of the sleeve 1. At this time, the cladding glass block is at the bottom and the core glass block is at the top.

[0050] Next, the assembled sleeve 1 is fixed in the corresponding pushing position of the extrusion pushing device, and the piston 2 is connected to the output shaft of the extrusion pushing device. The extrusion pushing device extrudes the piston 2, causing it to slowly push into the sleeve 1 until it contacts the upper surface of the fiber core glass.

[0051] At this time, the internal temperature of the sleeve 1 rises, softening the cladding glass block 6 and the core glass block 5; at the same time, pressure is applied to the top of the piston 2, causing the softened cladding glass to wrap around the core glass and be extruded from the outlet 32 ​​of the nozzle 3, ultimately obtaining a glass fiber preform with a square cross section.

[0052] This application also provides a mold installation method:

[0053] a. Insert the nozzle into the slot from the fixing groove of the sleeve;

[0054] b. First, set up a control experiment using a control nozzle with a square outlet, where the side length of the square is set to L; after producing a set of control optical fiber preforms, measure the parameters of the control optical fiber, and then, according to r1=(L′ 2 +4a 2 The radius of curvature of the reference optical fiber preform is calculated using the formulas ) / 8a and a=(XL′) / 2.

[0055] c. Determine the nozzle type; the radius of curvature of the concave arc at the nozzle outlet should be the same as the radius of curvature of the reference optical fiber preform.

[0056] d. Screw the retaining ring into the retaining groove so that the retaining ring squeezes the nozzle.

[0057] The embodiments of this utility model have been described in detail above with reference to the accompanying drawings, but this utility model is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of this utility model, and these variations still fall within the protection scope of this utility model.

Claims

1. A square optical fiber preform extrusion die, characterized in that, include: The sleeve (1) is divided into three parts from top to bottom: a filling cavity (11), a slot (12), and a fixing slot (13). The piston (2) is located inside the packing cavity (11) and slides up and down along the central axis of the sleeve (1); The nozzle (3) is located inside the slot (12); A fixing ring (4) is provided inside the fixing groove (13), and its sidewall is detachably connected to the fixing groove (13) by threads; The nozzle (3) has a funnel-shaped through hole inside, with the upper end being the feed inlet (31) and the lower end being the discharge outlet (32). The feed inlet (31) has a circular cross-sectional shape, and its diameter is the same as the inner diameter of the packing cavity (11); The cross-sectional shape of the discharge port (32) is an approximately square with four concave arcs on its four sides, and the arc length and radius of curvature of the four concave arcs are the same.

2. The square optical fiber preform extrusion die according to claim 1, characterized in that, The inner diameters of the filling cavity (11), the slot (12), and the fixing slot (13) increase sequentially.

3. The square optical fiber preform extrusion die according to claim 1, characterized in that, The lower part of the nozzle (3) extends from the slot (12) into the interior of the fixing slot (13).

4. The square optical fiber preform extrusion die according to claim 1, characterized in that, The diameter of the fixing ring (4) is larger than the diagonal length of the discharge port (32).

5. The square optical fiber preform extrusion die according to claim 1, characterized in that, The outer diameter of the piston (2) matches the inner diameter of the packing cavity (11), and the upper part of the piston (2) is provided with an internal threaded hole for connecting to the output end of the extruder push device.

6. The square optical fiber preform extrusion die according to claim 1, characterized in that, The sleeve (1), piston (2), nozzle (3) and retaining ring (4) are all made of stainless steel.

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