A milling fixture for precision cutting of large hyperbolic aircraft skin

Abstract

This invention relates to the field of milling fixture technology, specifically a milling fixture for precision cutting of large hyperbolic aircraft skin. It includes a support mechanism and a negative pressure mechanism. The support mechanism comprises a U-shaped box, an elastic membrane, a corrugated tube, a patch, and a support rod. The bottom of the U-shaped box has a circular opening; the corrugated tube is connected to the circular opening; the patch is connected to the top of the corrugated tube; the support rod is located inside the corrugated tube; an air cavity is formed inside the support rod; a rolling groove is formed at the top of the support rod; a hollow sphere is located inside the rolling groove; magnetorheological fluid is stored inside the U-shaped box; the elastic membrane is connected to the top opening of the U-shaped box; the elastic membrane is connected to the patch; the negative pressure mechanism includes a vacuum pump, a hollow plate, and a telescopic hose; the telescopic hose is connected to air hole c; the telescopic hose is connected to the support rod; the vacuum pump is connected to the hollow plate through pipe a; a magnetic component is located inside the hollow plate. This invention can achieve complete contact when dealing with aircraft skins of different curvatures, ensuring the stability of the skin adsorption and clamping.

Description

Technical Field

[0001] This invention relates to the field of milling fixture technology, and specifically to a milling fixture for precision cutting of large hyperbolic aircraft skin. Background Technology

[0002] The core requirements for fixtures used in mirror milling of large hyperbolic aircraft skins are the ability to "flexibly clamp" and "provide local support" to cope with the characteristics of the skins being "large in size, thin in thickness, and easily deformable".

[0003] Chinese patent CN110682124A discloses a milling fixture for precision cutting of large hyperbolic aircraft skin. The fixture places the aircraft skin parts on a positioning and adsorption assembly and an auxiliary clamping plate. A quick-connect fitting on the base platform is connected to a vacuum pump to evacuate the formed cavity to a vacuum level of not less than 0.08 MPa, thereby tightly adsorbing the aircraft skin parts onto the positioning and adsorption assembly and achieving the clamping function of the aircraft skin.

[0004] However, the existing technology has the following drawbacks: the shape of the absorption component is fixed, and its surface curvature can only be adapted to one type of aircraft skin. For aircraft skins with different curvatures, the absorption component cannot fully fit the surface of the aircraft skin, resulting in a significant decrease in the negative pressure suction force generated by the absorption component on the aircraft skin, which in turn leads to a significant decrease in the clamping effect on the aircraft skin. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the background art by proposing a milling fixture for precision cutting of large hyperbolic aircraft skin.

[0006] The technical solution of this invention: A milling fixture for precision cutting of large hyperbolic aircraft skin, comprising:

[0007] A support mechanism includes a U-shaped box, an elastic membrane, a corrugated tube, a patch, and a support rod. The bottom of the U-shaped box has multiple evenly distributed circular openings. The corrugated tube is connected to the inside of the U-shaped box at each of the circular openings. The patch is connected to the top of the corrugated tube and has vent holes a. The support rod is located inside the corrugated tube and has an air cavity inside. A rolling groove is formed at the top of the support rod. A hollow sphere is movably disposed inside the rolling groove. Multiple vent holes b are formed at the bottom of the hollow sphere. The top of the hollow sphere is connected to the patch and communicates with vent holes a. The U-shaped box contains magnetorheological fluid. The elastic membrane is connected to the top opening of the U-shaped box and has multiple connection ports. The patch is connected to the connection ports.

[0008] The limiting mechanism, located at the bottom of the housing, is used to limit the support rod.

[0009] The negative pressure mechanism includes a vacuum pump, a hollow plate, and a telescopic hose; the hollow plate has evenly spaced air holes c; multiple telescopic hoses are provided, with one end connected to the air holes c; a solenoid valve is provided at the air hole c; a sensor is provided inside the air hole c; the other end of the telescopic hose is connected to the bottom end of a support rod; one end of the vacuum pump is connected to the hollow plate through a pipe a; multiple magnetic components are provided inside the hollow plate to provide a magnetic field for the magnetorheological fluid.

[0010] Preferably, the hollow plate is supported by support legs; a recycling port aligned with the center opening of the U-shaped box is provided at the center of the hollow plate.

[0011] Preferably, the U-shaped box is supported by a support plate; the vacuum pump is connected to the support plate.

[0012] Preferably, the limiting mechanism includes a drive unit, an annular box, a slider, and a clamping plate; the annular box is connected to the bottom end of the U-shaped box; the support rod passes through the hole in the center of the annular box; the inner wall of the annular box has aligned clamping openings; two sliders are provided and slidably disposed inside the annular box; the clamping plate is connected to one end of the slider; the other end of the slider is connected to the inner wall of the annular box by a spring; the drive unit is located below the U-shaped box for driving the slider to move.

[0013] Preferably, the drive unit includes a telescopic component, an annular plate, a push plate, and a push rod; a groove is provided at the bottom end of the slider; an inclined block is provided in the groove; a sliding hole is provided at the bottom end of the annular box opposite the groove; the push rod is slidably disposed in the sliding hole; the bottom end of the push rod is connected to the annular plate; the telescopic component is disposed at the bottom end of the U-shaped box and is connected to the push plate; a through-hole for the telescopic hose to pass through is provided on the push plate.

[0014] Preferably, the clamping surface of the clamping plate is provided with a rubber layer; the rubber layer is provided with several protrusions to increase friction.

[0015] Preferably, the top of the push rod is provided with a rolling groove; a ball bearing is provided in the rolling groove to reduce the friction between the push rod and the tilting block.

[0016] Compared with the prior art, the above-mentioned technical solution of the present invention has the following beneficial technical effects:

[0017] Equipped with a support mechanism, a limiting mechanism, and a negative pressure mechanism, when the hoisting equipment places the skin to be milled onto the elastic membrane, the weight of the skin will press down on the elastic membrane, causing it to deform. The liquid magnetorheological fluid, combined with the deformation of the elastic membrane, naturally adapts to the curvature of the skin. At the same time, the patch, made of rubber material, is deformable and can completely adhere to the surface of the skin. This ensures complete contact when dealing with aircraft skins of different curvatures, guaranteeing that the negative pressure mechanism can generate sufficient negative pressure suction for aircraft skins of different curvatures, thereby ensuring the stability of the skin's adsorption and clamping. Simultaneously, it ensures that the negative pressure suction on the skin is evenly distributed, avoiding local stress concentration and workpiece deformation. Attached Figure Description

[0018] Figure 1 A three-dimensional representation of an embodiment of the present invention Figure 1 ;

[0019] Figure 2 A three-dimensional representation of an embodiment of the present invention Figure 2 ;

[0020] Figure 3 for Figure 2 Enlarged structural diagram at point A in the middle;

[0021] Figure 4 This is a schematic diagram of the structure when the elastic membrane separates from the U-shaped box in one embodiment of the present invention;

[0022] Figure 5 This is a cross-sectional structural diagram of the bellows, support rod, and patch in one embodiment of the present invention;

[0023] Figure 6 for Figure 5 Enlarged structural diagram at point B;

[0024] Figure 7 This is a schematic cross-sectional view of a hollow plate in one embodiment of the present invention.

[0025] Figure 8 This is a cross-sectional structural diagram of the limiting mechanism in one embodiment of the present invention;

[0026] Figure 9 This is a schematic diagram of the assembly structure of the limiting mechanism in a cross-sectional state according to an embodiment of the present invention.

[0027] Reference numerals: 1. U-shaped box; 2. Elastic membrane; 3. Support plate; 4. Vacuum pump; 5. Push plate; 6. Hollow plate; 7. Patch; 701. Air hole a; 8. Telescopic component; 9. Annular box; 10. Push rod; 11. Support rod; 12. Telescopic hose; 13. Corrugated pipe; 14. Annular piece; 15. Hollow ball; 1501. Air hole b; 16. Slider; 17. Clamping plate; 18. Spring; 19. Inclined block; 20. Sensor; 21. Solenoid valve; 22. Magnetic component. Detailed Implementation

[0028] Example 1, as Figures 1-7 As shown, the present invention proposes a milling fixture for precision cutting of large hyperbolic aircraft skin, comprising a support mechanism, a limiting mechanism, and a negative pressure mechanism;

[0029] The support mechanism includes a U-shaped box 1, an elastic membrane 2, a bellows 13, a patch 7, and a support rod 11; the U-shaped box 1 is supported by a support plate 3; a vacuum pump 4 is connected to the support plate 3; the bottom of the U-shaped box 1 has multiple evenly distributed circular openings; the bellows 13 are connected to the circular openings inside the U-shaped box 1 (the bellows 13 can act as an insulator to separate the support rod 11 from the magnetorheological fluid, and the bellows 13 is also flexible to perfectly adapt to the internal volume changes of the magnetorheological fluid after solidification; and the high-quality metal bellows 13 is designed to withstand millions or even tens of millions of cycles of expansion and contraction). (It can be circulated without breaking, meeting the requirements of long-term dynamic use); patch 7 is connected to the top of bellows 13 (pattern 7 is made of rubber material and can deform, increasing its adhesion to the skin surface); patch 7 has air holes a701; support rod 11 is located inside bellows 13; air cavity is opened inside support rod 11; rolling groove is opened at the top of support rod 11; hollow ball 15 is movably installed inside the rolling groove (hollow ball 15 can roll freely in the rolling groove, allowing patch 7 to turn flexibly); multiple air holes b1501 are opened at the bottom of hollow ball 15 (air holes b1501 The presence of the hollow sphere 15 ensures that it remains connected to the air cavity inside the support rod 11 after rotation; the top of the hollow sphere 15 is connected to the patch 7 and is connected to the air hole a701; the U-shaped box 1 contains magnetorheological fluid (magnetorheological fluid is a stable suspension formed by suspending micron-sized soft magnetic particles (such as carbonyl iron powder) in a non-magnetic carrier liquid (such as mineral oil, silicone oil, synthetic oil) and adding stabilizers (such as surfactants, thixotropic agents); under the action of an external magnetic field, the suspended magnetic particles are magnetized within milliseconds (usually <10ms) and arranged into chain-like or columnar structures along the direction of the magnetic field lines; these The structure enhances the cohesion of the fluid, making it exhibit solid-like properties and generating a measurable shear yield stress; this process is reversible. The elastic membrane 2 is connected to the top opening of the U-shaped box 1. (The elastic membrane 2 is made of TUP material; TUP (thermoplastic polyurethane) is a high-performance elastomer often used to make flexible, wear-resistant films and coatings. TUP maintains good flexibility over a wide temperature range and can withstand shape changes and internal pressure fluctuations of the magnetorheological fluid under a magnetic field, making it less prone to brittleness.) Multiple connection ports are provided on the elastic membrane 2; the patch 7 connects to these connection ports.

[0030] The limiting mechanism is located at the bottom of the box and is used to limit the support rod 11.

[0031] The negative pressure mechanism includes a vacuum pump 4, a hollow plate 6, and a telescopic hose 12. The hollow plate 6 has evenly spaced air holes c. Multiple telescopic hoses 12 are provided, with one end connected to an air hole c. A solenoid valve 21 is located at each air hole c. A sensor 20 is located inside the air hole c (the sensor 20 includes, but is not limited to, a micro-thermal sensor 20; when there is no airflow, the heat generated by its internal heater is symmetrically distributed, and the upstream and downstream temperatures are equal; when there is airflow, the airflow "blows away" the heat, disrupting the symmetry and creating a temperature difference between the upstream and downstream; the faster the flow rate, the greater the temperature difference; by measuring this temperature difference, the flow rate can be accurately calculated; the micro-thermal sensor 20 is generally small in size, for example, model STS4x / STS4L, with a volume of 1.5 mm × 1.5 mm × 0.55 mm). mm); the other end of the telescopic hose 12 is connected to the bottom end of the support rod 11; one end of the vacuum pump 4 is connected to the hollow plate 6 through pipe a; the hollow plate 6 is provided with multiple magnetic components 22 for providing a magnetic field to the magnetorheological fluid (magnetic components 22 include but are not limited to electromagnets); the hollow plate 6 is supported by legs; a recovery port is provided at the center of the hollow plate 6, which is aligned with the center opening of the U-shaped box 1.

[0032] In this embodiment, the skin to be milled is placed on the elastic membrane 2 using a hoisting device (so that the milling part is aligned with the center opening of the U-shaped box 1). Under the gravity of the skin, the elastic membrane 2 is pressed down and deformed, while the patch 7 and the magnetorheological fluid are pressed down. The liquid magnetorheological fluid, in conjunction with the deformation of the elastic membrane 2, can naturally adapt to the curvature of the skin. At the same time, the patch 7 is made of rubber material and can deform, so as to completely adhere to the surface of the skin, thus achieving complete contact when dealing with aircraft skins with different curvatures. Then, the magnetic component 22 is activated, and the magnetic component 22 generates a magnetic field, which causes the magnetorheological fluid to solidify. At the same time, the limiting mechanism is used to clamp and fix the support rod 11, realizing the limiting function of the support rod 11. The support rod 11 is in the solidified magnetorheological fluid. The part can act as a skeleton, significantly improving the strength and stability of the overall structure of the cured magnetorheological fluid; ensuring its stability in supporting the aircraft skin; then the hoisting equipment is removed, and then the vacuum pump 4 is turned on. The vacuum pump 4 generates suction force, which, together with the hollow plate 6, quickly removes the air from the air chambers inside each support rod 11. At this time, the sensor 20 in the air hole c can sense the airflow velocity. For the air hole c with a continuous airflow velocity, the external controller will control the corresponding solenoid valve 21 to close, ensuring that the air hole a701 at the patch 7 that is attached to the skin has sufficient negative pressure suction force, thereby ensuring the stability of the skin adsorption and clamping; at the same time, it ensures that the negative pressure suction force on the skin is evenly distributed, avoiding local stress concentration and skin deformation.

[0033] It should be noted that for certain parts of some military aircraft, helicopters, or ships, the required aircraft skin can be magnetically attracted. The magnetorheological fluid generates magnetism under the action of an external magnetic field, thereby magnetically attracting the skin, further enhancing the adsorption force on the aircraft skin and further ensuring the stability of the skin clamping.

[0034] Before milling, place the recycling box under the hollow plate 6 to facilitate the recycling of debris generated during the milling process.

[0035] It should be noted that the electrical equipment in this invention is controlled by an external PLC controller.

[0036] Example 2, as Figures 8-9 As shown, this invention proposes a milling fixture for precision cutting of large hyperbolic aircraft skin. Compared to Embodiment 1, this embodiment further details the structure of the limiting mechanism, which includes a drive unit, an annular box 9, sliders 16, and clamping plates 17. The annular box 9 is connected to the bottom end of the circular box 1. A support rod 11 passes through a hole in the center of the annular box. Aligned clamping openings are provided on the inner wall of the annular box. Two sliders 16 are provided and slidably disposed inside the annular box. The clamping plate 17 is connected to one end of the slider 16. The other end of the slider 16 is connected to the inner wall of the annular box 9 via a spring 18. The drive unit is located below the circular box 1 to drive the sliders 16 to move. The drive unit includes a telescopic component 8, an annular plate 14, a push plate 5, and a push rod 10. A groove is provided at the bottom end of the slider 16. An inclined block 19 is provided in the groove. The bottom end of the annular box 9 is directly opposite the groove. A sliding hole is provided; the push rod 10 is slidably disposed in the sliding hole; the bottom end of the push rod 10 is connected to the annular plate 14; the telescopic component 8 is disposed at the bottom end of the U-shaped box 1 and is connected to the push plate 5 (the push plate 5 has a connecting opening aligned with the recycling port and the center port, so that the debris generated during the milling process can fall into the recycling box, facilitating the subsequent recycling of debris); the telescopic component 8 includes, but is not limited to, devices such as cylinders; the push plate 5 has a through-hole for the telescopic hose 12 to pass through; the clamping surface of the clamping plate 17 is provided with a rubber layer; the rubber layer has several protrusions to increase the friction (the outer surface of the support rod 11 is provided with anti-slip texture, which can further increase the friction and ensure the stability of the clamping plate 17 in clamping the support rod 11); the top end of the push rod 10 is provided with a rolling groove; the rolling groove is provided with a ball to reduce the friction between the push rod 10 and the inclined block 19.

[0037] In this embodiment, when it is necessary to clamp the support rod 11, the telescopic component 8 is activated. The telescopic component 8 drives the push plate 5 to move upward. The upward movement of the push plate 5 pushes the annular piece 14 to move upward. The annular piece 14 drives the push rod 10 to move upward and presses the inclined surface of the inclined block 19, thereby realizing the function of laterally pushing the slider 16 (during this process, the spring 18 is stretched), so that the slider 16 drives the clamping plate 17 to move. The clamping plate 17 passes through the clamping port to clamp and fix the support rod 11. When the push rod 10 moves downward, under the action of the spring 18, the slider 16 is reset, thereby driving the clamping plate 17 away from the support plate 3, releasing the clamping and fixing of the support rod 11.

[0038] In summary, the skin to be milled is placed on the elastic membrane 2 using a hoisting device (aligning the milling part with the center opening of the U-shaped box 1). Under the weight of the skin, the elastic membrane 2 is pressed down, deforming it. Simultaneously, the patch 7 and the magnetorheological fluid are pressed down. The liquid magnetorheological fluid, combined with the deformation of the elastic membrane 2, naturally adapts to the curvature of the skin. Meanwhile, the patch 7, made of rubber, is deformable and can completely adhere to the skin surface, thus achieving complete contact when dealing with aircraft skins of different curvatures. Then, the magnetic component 22 is activated, generating a magnetic field that solidifies the magnetorheological fluid. Simultaneously, the telescopic component 8 is activated, causing the push plate 5 to move upwards. The upward movement of the push plate 5 pushes the annular plate 14 upwards, which in turn moves the push rod 10 upwards and presses against the inclined surface of the inclined block 19, thereby achieving the function of laterally pushing the slider 16 (during this process, the spring 18 is stretched), causing the slider... 16 drives the clamping plate 17 to move, and the clamping plate 17 passes through the clamping port to clamp and fix the support rod 11. The support rod 11 can act as a skeleton inside the cured magnetorheological fluid, which significantly improves the strength and stability of the overall structure of the cured magnetorheological fluid and ensures its stability in supporting the aircraft skin. Then the hoisting equipment is removed, and then the vacuum pump 4 is turned on. The vacuum pump 4 generates suction force to work with the hollow plate 6 to quickly remove the air in the air chambers inside each support rod 11. At this time, the sensor 20 in the air hole c can sense the airflow velocity. For the air hole c with a continuous airflow velocity, the external controller will control the corresponding solenoid valve 21 to close, so that the air hole a701 at the patch 7 that is attached to the skin has sufficient negative pressure suction force, thereby ensuring the stability of the skin adsorption and clamping. At the same time, it ensures that the negative pressure suction force on the skin is evenly distributed, avoiding local stress concentration and skin deformation.

[0039] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A milling fixture for precision cutting of large hyperbolic aircraft skin, characterized in that, include: The support mechanism includes a U-shaped box (1), an elastic membrane (2), a bellows (13), a patch (7), and a support rod (11); the bottom of the U-shaped box (1) has multiple evenly distributed circular openings; the bellows (13) is connected to the bellows (13) at the circular openings inside the U-shaped box (1); the patch (7) is connected to the top of the bellows (13); the patch (7) has an air hole a (701); the support rod (11) is located inside the bellows (13); the inside of the support rod (11) An air cavity is provided; a rolling groove is provided at the top of the support rod (11); a hollow ball (15) is movably provided inside the rolling groove; multiple air holes b (1501) are provided at the bottom of the hollow ball (15); the top of the hollow ball (15) is connected to the patch (7) and it communicates with the air hole a (701); magnetorheological fluid is stored in the U-shaped box (1); the elastic membrane (2) is connected to the top opening of the U-shaped box (1); multiple connection ports are provided on the elastic membrane (2); the patch (7) is connected to the connection ports; The limiting mechanism is located at the bottom of the box and is used to limit the support rod (11); The negative pressure mechanism includes a vacuum pump (4), a hollow plate (6), and a telescopic hose (12); the hollow plate (6) is evenly provided with air holes c; the telescopic hose (12) is provided with multiple air holes c and one end of the hose is connected to the air hole c; a solenoid valve (21) is provided at the air hole c; a sensor (20) is provided inside the air hole c; the other end of the telescopic hose (12) is connected to the bottom end of the support rod (11); one end of the vacuum pump (4) is connected to the hollow plate (6) through a pipe a; the hollow plate (6) is provided with multiple magnetic components (22) inside to provide a magnetic field for the magnetorheological fluid.

2. A milling fixture for precision cutting of large hyperbolic aircraft skin according to claim 1, characterized in that, The hollow plate (6) is supported by legs; a recycling port is provided at the center of the hollow plate (6) and aligned with the center opening of the U-shaped box (1).

3. A milling fixture for precision cutting of large hyperbolic aircraft skin according to claim 1, characterized in that, The U-shaped box (1) is supported by the support plate (3); the vacuum pump (4) is connected to the support plate (3).

4. A milling fixture for precision cutting of large hyperbolic aircraft skin according to claim 1, characterized in that, The limiting mechanism includes a drive unit, an annular box (9), a slider (16), and a clamping plate (17); the annular box (9) is connected to the bottom end of the circular box (1); the support rod (11) passes through the hole in the center of the annular box; the inner wall of the annular box has aligned clamping openings; there are two sliders (16) which are slidably disposed inside the annular box; the clamping plate (17) is connected to one end of the slider (16); the other end of the slider (16) is connected to the inner wall of the annular box (9) through a spring (18); The drive unit is located below the circular box (1) and is used to drive the slider (16) to move.

5. A milling fixture for precision cutting of large hyperbolic aircraft skin according to claim 4, characterized in that, The drive unit includes a telescopic component (8), an annular plate (14), a push plate (5), and a push rod (10); the bottom end of the slider (16) is provided with a groove; an inclined block (19) is provided in the groove; the bottom end of the annular box (9) is provided with a sliding hole facing the groove; the push rod (10) is slidably provided in the sliding hole; the bottom end of the push rod (10) is connected to the annular plate (14); the telescopic component (8) is provided at the bottom end of the U-shaped box (1) and is connected to the push plate (5); the push plate (5) is provided with a through-hole for the telescopic hose (12) to pass through.

6. A milling fixture for precision cutting of large hyperbolic aircraft skin according to claim 4, characterized in that, The clamping surface of the clamping plate (17) is provided with a rubber layer; the rubber layer is provided with several protrusions to increase friction.

7. A milling fixture for precision cutting of large hyperbolic aircraft skin according to claim 4, characterized in that, The top of the push rod (10) is provided with a rolling groove; a ball is provided in the rolling groove to reduce the friction between the push rod (10) and the inclined block (19).

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