Special nut for overlapping edge of foam interlayer of unit piece of X-band large-scale radar radome

Abstract

The invention discloses a special nut for a foam interlayer overlap edge of an X-band large radar radome unit, which comprises a circular truncated cone, a cylinder and a plurality of needle-shaped bulges, the cylinder is coaxially arranged on the bottom surface of the circular truncated cone, and the outer diameter of the cylinder is smaller than that of the circular truncated cone, so that the bottom surface of the circular truncated cone forms an annular plane; the needle-shaped protrusions are vertically and evenly distributed on the annular plane in the circumferential direction and located on the outer side of the cylinder, threads are arranged on the inner ring of the cylinder, grooves are formed in the outer ring of the cylinder at intervals in the axial direction, and a plurality of open grooves are formed in the tail end of the cylinder wall at intervals in the axial direction. The special nut overcomes the defects of connection of overlapping edges of foam interlayers of traditional unit pieces, locking torque of the nut is effectively improved, looseness and torsion of the nut and damage of the overlapping edges of the unit pieces are avoided, and reliability of connection of the unit pieces is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of radar radome manufacturing, and particularly to a special nut for the foam sandwich lap joint of a large X-band radar radome unit component. Background Art

[0002] Most large radar radomes are formed by splicing multiple unit components through lap joints. The lap joints of conventional unit components adopt a solid glass fiber structure. Drill holes in the lap joints, and then use an adhesive to bond and fix the nuts on the lap joints. Pass a bolt through the through hole and screw it onto the nut to achieve the connection and fixation of adjacent lap joints.

[0003] Large X-band radar radomes have high requirements for electrical performance, and the lap joints of their unit components adopt a sandwich structure of skin and foam. Drill holes in the lap joints, apply glue to the nuts and fix them on the lap joints. The cylindrical section of the nut is bonded to the foam and the skin together to jointly bear the tightening torque of the nut. However, since the strength of the foam is much worse than that of the solid glass fiber, the foam is easily damaged during the nut tightening process, resulting in the nut being prone to loosening and twisting, and the tightening torque of the nut not meeting the design requirements.

[0004] Chinese patent document CN110802668 A discloses a foam sandwich composite part with an internally threaded positioning metal insert and a preparation method thereof. The metal insert is embedded through a counterbore pre-opened in the foam core, and black foaming glue is used to bond the insert and the upper and lower skins to improve the overall pull-out strength and positioning accuracy. However, relying only on the adhesive force of the adhesive and the foaming material, it is difficult to avoid the damage of the foam layer and the loosening of the nut under high torque.

[0005] Another example is US patent document US3621557 A, titled Insert for Sandwich Panels and Method of Installation, which discloses an insert with a flange and a detent means. After positioning in the hole of the sandwich panel, a potting compound is injected from the hole of the insert to prevent backflow to achieve fixation. However, it uses epoxy injection or potting compound locking, mainly to solve the positioning and bonding during the insertion process, lacking a mechanical structure to enhance anti-torque and protect the foam core from damage.

[0006] For another example, European Patent Document EP 2980420B1, titled "Panel-Insert Assembly and Method", discloses a threaded insert with multiple flanges or protrusions in a sandwich panel. By combining the flanges with the panel or through mechanical biting / clamping methods, the pull-out resistance is improved, and the pouring material is reduced or eliminated. However, it focuses on the flange straddling the panel and the clamping process, and does not design an integrated structure for the foam sandwich edge of the X-band radar radome unit to improve the locking torque and prevent loosening. Summary of the Invention The technical problem to be solved by the present invention is to provide a special nut for the foam sandwich lap joint of the X-band large radar radome unit. This special nut overcomes the defects of the traditional connection of the foam sandwich lap joint of the unit, effectively improves the locking torque of the nut, avoids the loosening and torsion of the nut and the damage of the lap joint of the unit, and ensures the reliability of the connection of the unit.

[0007] To solve the above technical problems, the special nut for the foam sandwich lap joint of the X-band large radar radome unit of the present invention includes a frustum, a cylinder and a number of needle-like protrusions. The cylinder is coaxially arranged at the bottom surface of the frustum, and the outer diameter of the cylinder is smaller than the outer diameter of the frustum, so that the bottom surface of the frustum forms an annular plane. The number of needle-like protrusions is vertically and evenly distributed along the circumferential direction on the annular plane and is located outside the cylinder. The inner ring of the cylinder is provided with threads, the outer ring is provided with grooves at intervals along the axial direction, and a number of opening grooves are opened at intervals at the end of the cylinder wall.

[0008] Further, a number of counterbores are pressed at intervals on the annular plane, and the number of needle-like protrusions are arranged in the number of counterbores and have an interference fit.

[0009] Further, the annular plane includes a concentric inner ring plane and an outer ring plane. The inner ring plane and the outer ring plane are respectively provided with a number of first needle-like protrusions and a number of second needle-like protrusions at intervals along the circumferential direction, and the height of the number of first needle-like protrusions on the inner ring plane is smaller than the height of the number of second needle-like protrusions on the outer ring plane.

[0010] Further, the width of the inner ring plane is 1.5 mm, and the width of the outer ring plane is 2.0 mm.

[0011] Further, a number of counterbores with a diameter of 0.8 mm and a depth of 2.2 mm are pressed at equal intervals on the inner ring plane, and a number of counterbores with a diameter of 1.2 mm and a depth of 2.5 mm are pressed at equal intervals on the outer ring plane. First needle-like protrusions with a height of 1.5 mm are implanted in the counterbores of the inner ring plane, and the bottom cylinder diameter of the first needle-like protrusion is 0.7 mm and the top cone angle is 32°. Second needle-like protrusions with a height of 2.2 mm are implanted in the counterbores of the outer ring plane, and the bottom cylinder diameter of the second needle-like protrusion is 0.9 mm and the top cone angle is 34°.

[0012] Further, the total height of the needle-shaped protrusions exposed on the annular plane is 1.5 - 2.2 mm, and the bottom of the needle-shaped protrusions is cylindrical and the top is conical. The diameter of the cylindrical section is 0.7 - 1.0 mm, the cone angle of the conical shape is 30 - 35°, and the hardness of the needle-shaped protrusions is HRC58 - 62.

[0013] Further, a plurality of opening grooves at the end of the cylindrical wall are obliquely arranged at an angle of 5° along the axial direction.

[0014] Further, the outer groove of the cylinder is formed by cold heading process. Since the special nut for the foam sandwich lap joint of the X-band large radar radome unit of the present invention adopts the above technical solution, that is, the special nut includes a frustum, a cylinder and a plurality of needle-shaped protrusions. The cylinder is coaxially arranged at the bottom surface of the frustum, and the outer diameter of the cylinder is smaller than the outer diameter of the frustum, so that the bottom surface of the frustum forms an annular plane. A plurality of needle-shaped protrusions are vertically and evenly distributed along the circumferential direction on the annular plane and are located outside the cylinder. The inner ring of the cylinder is provided with threads, the outer ring is provided with grooves at intervals along the axial direction, and a plurality of opening grooves are arranged at intervals at the end of the cylinder wall. This special nut overcomes the defects of the traditional connection of the foam sandwich lap joint of the unit, effectively improves the locking torque of the nut, avoids the loosening and torsion of the nut and the damage of the lap joint of the unit, and ensures the reliability of the connection of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The following further elaborates on the present invention in conjunction with the drawings and embodiments: Figure 1 is a schematic structural diagram of this special nut; Figure 2 is a schematic diagram of the arrangement of the inner and outer ring planes and the first and second needle-shaped protrusions in this special nut; Figure 3 is an application schematic diagram of this special nut. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] For example, as Figure 1 shown, the special nut for the foam sandwich lap joint of the X-band large radar radome unit of the present invention includes a frustum 1, a cylinder 2 and a plurality of needle-shaped protrusions 3. The cylinder 2 is coaxially arranged at the bottom surface of the frustum 1, and the outer diameter of the cylinder 2 is smaller than the outer diameter of the frustum 1, so that the bottom surface of the frustum 1 forms an annular plane 11. The plurality of needle-shaped protrusions 3 are vertically and evenly distributed along the circumferential direction on the annular plane 11 and are located outside the cylinder 2. The inner ring of the cylinder 2 is provided with threads, the outer ring is provided with grooves 21 at intervals along the axial direction, and a plurality of opening grooves 22 are arranged at intervals at the end of the cylinder 2 wall.

[0017] Preferably, a plurality of counterbores are pressed at intervals on the annular plane 11, and the plurality of needle-shaped protrusions 3 are arranged in the plurality of counterbores and are in interference fit.

[0018] Preferably, as Figure 2As shown, the annular plane 11 includes an inner ring plane 111 and an outer ring plane 112 that are concentrically arranged. The inner ring plane 111 and the outer ring plane 112 are respectively provided with a plurality of first needle-like protrusions 31 and a plurality of second needle-like protrusions 32 at intervals along the circumferential direction, and the heights of the plurality of first needle-like protrusions 31 on the inner ring plane 111 are less than the heights of the plurality of second needle-like protrusions 32 on the outer ring plane 112.

[0019] The double-layer needle-like protrusions can be first penetrated by the high needles at the initial stage of locking, and then gradually engaged by the low needles to achieve progressive mechanical engagement, better dispersing and bearing the torque step by step.

[0020] Preferably, the width of the inner ring plane 111 is 1.5 mm, and the width of the outer ring plane 112 is 2.0 mm.

[0021] Preferably, a plurality of counterbores with a diameter of 0.8 mm and a depth of 2.2 mm are pressed equidistantly on the inner ring plane 111, and a plurality of counterbores with a diameter of 1.2 mm and a depth of 2.5 mm are pressed equidistantly on the outer ring plane 112. The first needle-like protrusions 31 with a height of 1.5 mm are implanted in the counterbores of the inner ring plane 111, and the bottom cylindrical diameter of the first needle-like protrusions 31 is 0.7 mm, and the top conical angle is 32°. The second needle-like protrusions 32 with a height of 2.2 mm are implanted in the counterbores of the outer ring plane 112, and the bottom cylindrical diameter of the second needle-like protrusions 32 is 0.9 mm, and the top conical angle is 34°.

[0022] Preferably, the total height of the needle-like protrusions 3 exposed on the annular plane 11 is 1.5 - 2.2 mm, and the bottom of the needle-like protrusions 3 is cylindrical and the top is conical. The diameter of the cylindrical section is 0.7 - 1.0 mm, the conical angle of the conical shape is 30 - 35°, and the hardness of the needle-like protrusions 3 is HRC58 - 62.

[0023] Preferably, a plurality of opening grooves 22 at the end of the wall of the cylinder 2 are obliquely opened at an angle of 5° along the axial direction.

[0024] The opening grooves 22 are set as obliquely opening grooves with a 5° slope along the axial direction to facilitate the generation of a spiral pressing effect during flaring; when using a flaring tool to rotate one circle along the outside of the cylinder, the metal wall at the end of the cylinder can form a spiral clamping force while the flange edge of the unit part overlaps and turns, further improving the locking reliability.

[0025] Preferably, the outer groove 21 of the cylinder 2 is formed by cold forging.

[0026] As Figure 3As shown in the figure, when the special nut is actually applied, drill holes at the overlapping edges of the single-component foam sandwich 4. Apply adhesive evenly to several grooves 21 on the outer ring of the cylinder 2, and vertically pass through the drilled holes at the overlapping edges of the foam sandwich 4. Press several needle-shaped protrusions 3 on the annular plane into and pierce the skin 41 of the overlapping edge to reach the foam core layer 42. Then, use a bolt 5 to screw into the internal thread of the inner ring of the cylinder 2 to lock the special nut, realizing the connection of the overlapping edges of the single-component foam sandwich 4.

[0027] If the single-component has overlapping flange edges, after the cylinder vertically passes through the drilled holes at the overlapping edges of the foam sandwich, use a flaring tool to expand and turn the end wall of the cylinder through several opening slots to the overlapping flange edge, further improving the connection reliability between the special nut and the overlapping edge of the single-component.

[0028] The special nut realizes the triple cooperative locking of point-line-surface through the double-layer needle-piercing and groove gluing of point and surface, combined with the linear locking of spiral flaring.

[0029] Its beneficial effects are as follows: Progressive needle biting: The needle-shaped protrusions of double layers with different heights pierce the foam, which can gradually transmit the locking force, further reducing the local stress concentration of the foam and increasing the upper limit of the locking torque.

[0030] Spiral flaring: The inclined slots of the inclined opening slots and the radial pressing force generated by spiral turning make the overlapping flange edges of the single-component fit more tightly, with stronger anti-vibration and anti-thermal cycling capabilities.

[0031] Through the triple locking of "point-line-surface", the connection firmness and reliability of the overlapping edges are significantly improved.

[0032] The special nut realizes multi-point piercing and biting through the cooperation of an annular counterbore and needle-shaped protrusions to achieve point-type mechanical locking; the multi-point dispersed locking torque avoids the local stress concentration and damage of the foam material, greatly improving the anti-loosening performance and connection stability under high torque conditions. The dual bonding cooperation of cold-heading grooves + adhesive increases the contact surface with the skin and foam on the one hand, and provides a glue storage space for the adhesive on the other hand. In addition to point-type piercing and biting, surface-type adhesive locking is supplemented to achieve "point + surface" dual bonding, effectively increasing the overall locking torque and anti-disassembly ability, avoiding the damage of the overlapping edges of the single-component during the connection operation, and ensuring the connection reliability of the single-component. The "opening slot + flaring and turning" flange-type clamping forms a mechanical locking similar to a circlip; the all-metal clamping structure does not rely on the curing of the adhesive, further enhancing the anti-loosening reliability under severe vibration or thermal cycling. The overall process adopts a four-step in-line process of "counterbore stamping → cold-heading forming grooves → opening slot punching → interference fitting of needle-shaped protrusions", without secondary pouring and curing or additional forming processes, so as to simplify the process and control costs.

Claims

1. A special nut for the foam sandwich lap joint of a large X-band radar radome unit, characterized in that: It includes a frustum of a cone, a cylinder, and several needle-shaped protrusions. The cylinder is coaxially arranged on the bottom surface of the frustum of the cone, and the outer diameter of the cylinder is smaller than that of the frustum of the cone, so that the bottom surface of the frustum of the cone forms an annular plane. The several needle-shaped protrusions are vertically and evenly distributed along the circumferential direction on the annular plane and are located outside the cylinder. The inner ring of the cylinder is provided with threads, the outer ring is provided with grooves at intervals along the axial direction, and several opening grooves are spacedly opened at the end of the cylinder wall.

2. The special nut for the foam sandwich lap joint of the X-band large radar radome unit according to claim 1, characterized in that: Several counterbores are pressed at intervals on the annular plane, and the several needle-shaped protrusions are arranged in the several counterbores and are in interference fit.

3. The special nut for the foam sandwich lap joint edge of the X-band large radar radome unit part according to claim 1 or 2, characterized in that: The annular plane includes a concentrically arranged inner ring plane and an outer ring plane. The inner ring plane and the outer ring plane are respectively provided with several first needle-shaped protrusions and several second needle-shaped protrusions at intervals along the circumferential direction, and the height of the several first needle-shaped protrusions on the inner ring plane is smaller than the height of the several second needle-shaped protrusions on the outer ring plane.

4. The special nut for the foam sandwich lap joint edge of the X-band large radar radome unit according to claim 3, characterized in that: The width of the inner ring plane is 1.5 mm, and the width of the outer ring plane is 2.0 mm.

5. The special nut for the foam sandwich lap joint edge of the X-band large radar radome unit according to claim 3, characterized in that: Several counterbores with a diameter of 0.8 mm and a depth of 2.2 mm are pressed equidistantly on the inner ring plane, and several counterbores with a diameter of 1.2 mm and a depth of 2.5 mm are pressed equidistantly on the outer ring plane. First needle-shaped protrusions with a height of 1.5 mm are implanted in the counterbores of the inner ring plane, and the bottom cylinder diameter of the first needle-shaped protrusions is 0.7 mm and the top cone angle is 32°. Second needle-shaped protrusions with a height of 2.2 mm are implanted in the counterbores of the outer ring plane, and the bottom cylinder diameter of the second needle-shaped protrusions is 0.9 mm and the top cone angle is 34°.

6. The special nut for the foam sandwich lapping edge of the X-band large radar radome unit part according to claim 1, characterized in that: The total height of the needle-shaped protrusions exposed on the annular plane is 1.5 - 2.2 mm, and the bottom of the needle-shaped protrusions is cylindrical and the top is conical. The diameter of the cylindrical section is 0.7 - 1.0 mm, the cone angle of the conical shape is 30 - 35°, and the hardness of the needle-shaped protrusions is HRC58 - 62.

7. The special nut for the foam sandwich lap joint edge of the X-band large radar radome unit according to claim 1, characterized in that: The several opening grooves at the end of the cylinder wall are obliquely opened at an angle of 5° along the axial direction.

8. The special nut for the foam sandwich lapping edge of the X-band large radar radome unit according to claim 1, characterized in that: The grooves on the outer ring of the cylinder are pressed by a cold heading process.

Images