A dual spring tandem piston assembly structure for an aircraft wheel

Abstract

The application relates to a double-spring series piston assembly structure for an aviation wheel, belonging to the field of airplane brake braking, and comprising a bushing, a piston, a screw cover, a force transmission plate, a large spring pipe, a large spring, a small spring pipe and a small spring. The piston is slidably arranged in the bushing, and the annular screw cover is arranged at the open end of the piston; the disc part of the force transmission plate is in contact with the end face of the bushing, and the rod part of the force transmission plate penetrates through the central hole of the screw cover and enters the inner cavity of the piston; the large spring pipe is sleeved on the rod part of the force transmission plate in the piston, and the large spring is sleeved on the outer diameter of the large spring pipe; the small spring pipe is fixed to the end of the rod part of the force transmission plate, and the small spring is sleeved on the outer diameter of the rod part of the force transmission plate and the small spring pipe. When braking, the hydraulic oil pushes the piston to extend to exert brake pressure on the brake disc, and when releasing the brake, the elastic force of the two springs makes the piston reset. The problems of abnormal extension and retraction caused by unstable friction in the existing spring pipe type piston assembly structure, the limited use space of the expansion pipe type piston assembly structure and the inconvenience of expansion pipe replacement are solved.

Description

Technical Field

[0001] This invention relates to the field of aircraft braking, and more specifically to a dual-spring tandem piston assembly structure for aircraft wheels. Background Technology

[0002] The cylinder block assembly in an aircraft brake wheel is a crucial component that converts the pressure supplied by the aircraft into piston thrust for braking. The piston assembly is a vital part of the cylinder block assembly. Under braking pressure, the piston in the piston assembly extends smoothly without jamming, allowing the braking system to convert braking pressure into thrust and press against the brake disc to achieve the braking function. After the aircraft depressurizes, the piston assembly retracts smoothly without the piston failing to return to its original position, thus preventing the risk of tire drag. The proper extension and retraction of the piston assembly plays a critical role in aircraft braking and is essential for ensuring smooth braking.

[0003] In existing technologies, there are two commonly used piston assembly structures: the Bourdon tube type and the expander tube type. The Bourdon tube type piston assembly primarily utilizes the friction between the Bourdon tube and the connecting rod to extend and retract the piston. However, due to unstable friction and stress relaxation inherent in the Bourdon tube itself, this structure carries the risk of abnormal extension and retraction. The expander tube type piston assembly, due to its large expander tube size, suffers from space limitations and is only suitable for large brake wheel structures (wheels with tire outer diameters exceeding 800mm). Furthermore, the expander tube in the expander tube type piston assembly is installed inside the piston to maintain a set gap between the piston and the brake disc. When the gap needs adjustment (e.g., replacing the brake disc due to severe wear or adding an adjusting shim), the corresponding expander tube needs to be replaced. This structure cannot replace the expander tube without disassembling the piston assembly, making it inconvenient to use.

[0004] Therefore, there is a need to provide a dual-spring tandem piston assembly structure for aircraft wheels to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved: To avoid the shortcomings of the prior art, the present invention provides a double-spring tandem piston assembly structure for aircraft wheels. By using a double-spring tandem configuration, the piston extension and retraction functions are realized, thereby solving the problems of abnormal extension and retraction caused by unstable friction in the existing spring tube piston assembly structure, limited space in the expansion tube piston assembly structure, and inconvenience in replacing the expansion tube.

[0006] The technical solution of this invention is: a double-spring tandem piston assembly structure for aircraft wheels, comprising: The bushing is a rotary cylindrical structure with open ends, and its outer diameter wall is provided with a first external thread for fixed connection with the cylinder seat in the brake wheel; The piston is a rotary cylindrical structure with one end open and the other end sealed. The piston is coaxially and slidably installed in the bushing, and its outer diameter wall is in contact with the inner diameter wall of the bushing. The screw cap, a ring-shaped structure, is fixedly installed on the open end of the piston; The force transmission plate includes a coaxially arranged disc portion and a columnar rod portion. The rod portion is vertically disposed on one side of the disc portion. The rod portion passes through the inner hole of the screw cap and extends into the inner cavity of the piston. The end face of the disc portion facing the rod portion contacts the end face of the bushing. The disc portion is evenly distributed with multiple oil passage holes for hydraulic oil to enter and exit. The large spring tube is a cylindrical structure with a through hole at one end and an open end with a first outward flange at the open end. The large spring tube is located in the piston cavity, and its through hole end faces the screw cap and is coaxially fitted onto the rod of the force transmission plate. The outer diameter wall of its cylinder can pass through the inner hole of the screw cap. The large spring is fitted onto the outer diameter of the large spring tube, with one end in contact with the screw cap and the other end in contact with the first outer flange of the large spring tube; The small spring tube is coaxially mounted on the end of the rod of the force transmission plate away from the disk. The end of the small spring tube away from the disk is provided with a second outward flange. And a small spring, fitted onto the rod of the force transmission plate and the outer diameter of the small spring tube, and located in the inner cavity of the large spring tube. One end of the small spring contacts the inner wall of the through hole end of the large spring tube, and the other end contacts the second outer flange of the small spring tube. The inner cavity formed by the disc part of the force transmission plate, the bushing, and the piston is the hydraulic oil chamber of the piston assembly. The oil passage hole of the disc part of the force transmission plate and the inner hole of the screw cap are connected to the hydraulic oil chamber. The piston is pushed out by the hydraulic oil, and the large spring and the small spring are used for the piston to return to its original position.

[0007] A further technical solution of the present invention is: the inner diameter wall of the bushing is provided with a sealing ring mounting groove for installing a first sealing ring, the first sealing ring being used for sealing between the piston and the bushing; the outer diameter wall of the bushing is provided with a limiting flange and a sealing ring mounting platform, the sealing ring mounting platform being used for installing a second sealing ring, the second sealing ring being used for sealing between the bushing and the cylinder seat, and the limiting flange being used for axial limiting of the bushing installed in the piston cavity of the cylinder seat.

[0008] A further technical solution of the present invention is: the open end of the piston is provided with an internal thread, the outer diameter of the screw cap is provided with a second external thread, the screw cap is embedded in the open end of the piston and is flush with the end face of the piston, and the second external thread of the screw cap and the internal thread of the piston are engaged and connected.

[0009] A further technical solution of the present invention is: the end of the rod of the force transmission plate away from the disk is provided with a threaded inner hole along the central axis, and the small spring tube is provided with a countersunk screw hole along its central axis that matches the threaded inner hole of the rod, and the small spring tube and the rod of the force transmission plate are fixedly connected by the countersunk screw.

[0010] A further technical solution of the present invention is that the outer diameter of the small spring tube is the same as the outer diameter of the force transmission plate rod.

[0011] A further technical solution of the present invention is: a boss is provided at the center of the end face of the disk portion of the force transmission plate facing the rod portion, the boss is embedded in the bushing, and the outer diameter wall of the boss is in contact with the inner diameter wall of the bushing.

[0012] A further technical solution of the present invention is that both the small spring and the large spring are right-handed springs, and both have a certain amount of compression in their initial state.

[0013] A further technical solution of the present invention is that the outer diameter wall of the piston and the inner diameter wall of the bushing are coated with grease or lubricating oil.

[0014] A further technical solution of the present invention is that the outer diameter of the piston is in the range of Φ32mm-Φ48mm.

[0015] The beneficial effects of this invention are as follows: This invention provides a dual-spring tandem piston assembly structure for aircraft wheels. By inserting the rod of the force transmission plate into the inner hole of the screw cap, a large and a small spring are installed on the rod. The open end of the piston, facing the disc portion of the force transmission plate, is fitted over the large spring and fixed with the screw cap via a threaded connection. A bushing is fitted onto the outer diameter of the piston so that the end face of the bushing abuts against the inner side of the disc portion of the force transmission plate, achieving linkage between the dual springs and the piston. When braking, the cylinder is pushed out under the action of hydraulic oil to apply braking pressure to the brake disc. When the brake is released, the piston is returned to its initial position by the rebound force of the dual springs.

[0016] Compared with existing spring tube piston assembly structures and expander tube piston assembly structures, the double-spring tandem piston assembly structure of the present invention for aircraft wheels has the following advantages: 1. Compared to the Bourdon tube piston assembly structure: The structure of this invention uses a series of return springs to achieve piston extension and retraction. This avoids the malfunction of the piston caused by unstable friction between the Bourdon tube and the connecting rod, resulting in higher reliability of the piston assembly's extension and retraction.

[0017] 2. Compared to the expander tube type piston assembly mechanism: The structure of this invention achieves a spatial leap from small pistons (Φ32mm) to large pistons (Φ48mm), offering greater flexibility in size design. Due to limitations in the diameter of the expander tube and ball head, the smallest piston structure in the expander tube type automatic gap adjusting piston assembly is currently Φ42mm, and it is also quite heavy, making it unsuitable for use in small aircraft brake wheels.

[0018] 3. Compared with the existing spring tube piston assembly structure and expansion tube piston assembly structure, the structure of the present invention requires no additional operation when replacing the brake disc or adding an adjustment shim in the brake device, making it more convenient to use and improving the maintenance efficiency of the brake device.

[0019] Specifically, when replacing the brake disc or adding an adjustment shim in a brake system, the piston assembly structure of the Bourdon tube type requires the use of tools to press the piston assembly back to reset it; otherwise, the brake disc cannot be replaced or the adjustment shim can not be added.

[0020] When replacing brake discs or adding adjusting shims in a brake system, the expansion tube of the expander-type piston assembly requires tools to be replaced; otherwise, the brake disc cannot be replaced or the adjusting shim added. The expander-type piston assembly has an automatic clearance adjustment function. As the brake disc gradually wears down, the expander-type automatic clearance adjustment piston mechanism uses the expansion tube to maintain the same brake clearance between the piston assembly and the brake disc. When the brake disc wears to its limit, the brake system needs to be replaced with a completely new brake disc or an adjusting shim needs to be added. At this point, due to the change in thickness of the new brake disc, it cannot be adapted to the current piston mechanism position, so the expander tube needs to be replaced; otherwise, the brake system cannot continue to be used. Replacing the expander tube requires maintenance personnel to disassemble the expander-type piston assembly structure with special tools, replace the tube, and then reassemble it, which is inconvenient.

[0021] The dual-spring series piston assembly structure of the present invention enables the piston to automatically reset after each braking action and pressure release. Therefore, it is possible to directly replace the brake disc or add an adjustment shim to the braking device, thus improving the efficiency of field use and maintenance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a cross-sectional schematic diagram of a double-spring tandem piston assembly structure for aircraft wheels according to the present invention. Figure 1 (Piston retracted); Figure 2 This is an exploded view of a double-spring tandem piston assembly for an aircraft wheel according to the present invention. Figure 3 This is a cross-sectional schematic diagram of a double-spring tandem piston assembly structure for aircraft wheels according to the present invention. Figure 2 (Piston extended); Figure 4 This is a three-dimensional view of the bushing in this invention; Figure 5 This is a two-dimensional cross-sectional view of the bushing in this invention; Figure 6 This is a two-dimensional cross-sectional view of the piston in this invention; Figure 7 This is a three-dimensional view of the force transmission plate in this invention; Figure 8 This is a two-dimensional cross-sectional view of the force transmission plate in this invention; Figure 9 This is a two-dimensional cross-sectional view of the screw cap in this invention; Figure 10 This is a two-dimensional cross-sectional view of the large spring tube in this invention; Figure 11 This is a two-dimensional cross-sectional view of the small spring tube in this invention; Figure 12 This is a schematic diagram of the installation of the dual-spring tandem piston assembly structure and cylinder seat of the present invention; Figure 13 This is a schematic diagram of the extended state of the dual-spring series piston assembly structure of the present invention during operation; Figure 14 This is a schematic diagram of the retracted state of the dual-spring series piston assembly structure of the present invention during operation.

[0024] In the diagram: 1. Bushing, 1-1. First external thread, 1-2. Sealing ring mounting groove, 1-3. Limiting flange, 1-4. Sealing ring mounting platform, 2. Piston, 2-1. Internal thread, 3. Force transmission plate, 3-1. Disc part, 3-2. Rod part, 3-3. Oil passage hole, 3-4. Threaded inner hole, 3-5. Boss, 4. Threaded cap, 4-1. Second external thread, 4-2. Inner hole of threaded cap, 5. Large spring, 6. Small spring, 7. Large spring tube, 7-1. Through hole, 7-2. First outward flange, 8. Small spring tube, 8-1. Second outward flange, 8-2. Countersunk screw hole, 9. Countersunk screw, 10. First sealing ring, 11. Double spring tandem piston assembly, 12. Cylinder seat, 12-1. Piston chamber of cylinder seat, 13. Brake disc, 14. Brake housing, 15. Second sealing ring. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides an embodiment of a double-spring tandem piston assembly structure for aircraft wheels. This structure is integrally installed in the piston chamber of the brake wheel cylinder seat. Driven by hydraulic oil in the cylinder seat's hydraulic circuit, the piston in the structure is pushed out to apply braking pressure to the brake disc. Figures 1-3 As shown, the dual-spring tandem piston assembly structure includes a bushing 1, a piston 2, a force transmission plate 3, a screw cap 4, a large spring 5, a small spring 6, a large spring tube 7, a small spring tube 8, a countersunk screw 9, and a first sealing ring 10.

[0027] like Figure 1 , Figure 4 , Figure 5 , Figure 12 As shown, bushing 1 is a rotary cylindrical structure with open ends. Its outer diameter wall is provided with a first external thread 1-1 for threaded connection with the cylinder seat 12 in the brake wheel. The outer diameter wall of bushing 1 on one side of the first external thread 1-1 is provided with a radially protruding limiting flange 1-3 and a sealing ring mounting platform 1-4. The sealing ring mounting platform 1-4 is located between the first external thread 1-1 and the limiting flange 1-3. The limiting flange 1-3 is used for axial limiting of bushing 1 in piston cavity 12-1 of cylinder seat. The sealing ring mounting platform 1-4 is used to install second sealing ring 15. The second sealing ring 15 is used for sealing between bushing 1 and cylinder seat 12 to prevent hydraulic oil in piston cavity 12-1 of cylinder seat from flowing out. The inner wall of the bushing 1 is provided with a sealing ring mounting groove 1-2. The sealing ring mounting groove 1-2 is used to install the first sealing ring 10. The first sealing ring 10 is a dynamic sealing ring used to seal between the piston 2 and the bushing 1, preventing hydraulic oil from flowing out from the gap between the piston 2 and the bushing 1 when the piston 2 moves.

[0028] In this embodiment, the bushing 1 is made of 2A14 aluminum alloy with an inner diameter of (Φ38+0.05) mm, and the sealing ring mounting groove 1-2 has a size of 3.5 mm × 2.4 mm. The first sealing ring 10 is a standard part with the code HB4-56 J3F-132 H.

[0029] like Figure 1 , Figure 6As shown, piston 2 is a rotary cylindrical structure with one end open and the other end sealed. Piston 2 is coaxially and slidably installed inside bushing 1. The outer diameter wall of piston 2 contacts the inner diameter wall of bushing 1. Under the hydraulic oil drive of the wheel brake, piston 2 will slide out relative to bushing 1. To ensure smooth sliding, grease or lubricating oil is applied to the outer diameter wall of piston 2 and the inner diameter wall of bushing 1, and the first sealing ring 10 prevents the hydraulic oil in the piston assembly from flowing out when piston 2 moves. The open end of piston 2 has an internal thread 2-1 for installing the screw cap 4. A relief groove is machined on the inner side of the internal thread 2-1 of piston 2 to facilitate the machining of the internal thread 2-1.

[0030] In this embodiment, piston 2 is made of 2A14 aluminum alloy, with an outer diameter of (Φ38-0.05) mm, an inner diameter of Φ30 mm, a piston cavity depth of 36 mm, a sealing end thickness of 4.5 mm, an internal thread 2-1 of M32 mm × 1 mm with a thread depth of 5.5 mm, and a relief groove of Φ32.2 mm × 2 mm. The outer diameter of piston 2 should be the same as the inner diameter of bushing 1, but with different tolerances. The dimensional tolerance of bushing 1 is an added tolerance, while the dimensional tolerance of piston 2 is a subtracted tolerance, to achieve a proper fit between the two.

[0031] like Figure 1 , Figure 9 As shown, the screw cap 4 is an overall ring-shaped structure. The outer diameter of the screw cap 4 is provided with a second external thread 4-1, and the center is the inner hole 4-2 of the screw cap. The screw cap 4 is embedded into the open end of the piston 2 and is flush with the end face of the open end of the piston 2. The second external thread 4-1 of the screw cap 4 and the internal thread 2-1 of the piston 2 are threadedly engaged to fix the two together.

[0032] In this embodiment, the screw cap 4 is made of 2A10 material. The screw cap 4 has an outer diameter of Φ32mm and is designed with a full M29mm×1mm thread, i.e., the second external thread 4-1. The total axial height of the screw cap 4 is 7mm, the thickness at the inner hole 4-2 is 3mm, the inner diameter at the external thread is Φ26mm, and the size of the middle inner hole 4-2 is Φ18mm. The external thread of the screw cap 4 is the same as the internal thread of the piston 2, and the inner diameter at the external thread of the screw cap is the same as the inner diameter of the piston 2. The total axial height of the screw cap 4 is shorter than the depth of the internal thread 2-1 of the piston 2 plus the depth of the relief groove, ensuring that the screw cap 4 does not protrude from the open end face of the piston 2, so as not to affect the stroke of the piston 2.

[0033] like Figure 1 , Figure 7 , Figure 8As shown, the force transmission plate 3 is a T-shaped rotating structure, comprising a coaxially arranged disc portion 3-1 and a cylindrical rod portion 3-2. The rod portion 3-2 is vertically positioned on one side of the disc portion 3-1, passing through the inner hole 4-2 of the screw cap 4 and extending into the inner cavity of the piston 2. The end face of the disc portion 3-1 facing the rod portion 3-2 contacts the end face of the bushing 1 near the open end of the piston 2. To ensure the stability of the fit, a boss 3-5 is provided at the center of the end face of the disc portion 3-1 facing the rod portion 3-2. The boss 3-5 is embedded in the bushing 1, and the outer diameter wall of the boss 3-4 contacts the inner diameter wall of the bushing 1. Four waist-shaped oil passage holes 3-3 are evenly distributed around the disc portion 3-1 for hydraulic oil to enter and exit. The end of the rod portion 3-2 of the force transmission plate 3 away from the disc portion 3-1 has a threaded inner hole 3-4 along the central axis for mounting the small spring tube 8.

[0034] In this embodiment, the force transmission plate 3 is an integral structure made of 30CrMnSiA material. The outer diameter of its disc portion 3-1 is Φ46mm, the thickness of the disc portion 3-1 outside the boss 3-5 is 1.5mm, the outer diameter of the boss 3-5 is Φ38mm, and the protruding thickness of the boss 3-5 is 1.5mm. The center dimension of the four waist-shaped oil passage holes 3-3 is Φ23mm, the hole length is 12mm, the hole width is 4mm, the two ends of the hole are rounded, and the center distance of the hole from the axis of the force transmission plate 3 is 11mm. The rod portion 3-2 has dimensions of Φ8mm×29mm, and the threaded inner hole 3-4 is a 120° tapered threaded hole with a thread size of M5mm×1mm, a thread depth of 10mm, and a hole depth of 12mm. The outer diameter of the disc portion 3-1 is the same as the outer diameter of the bushing 1, and the outer diameter of the boss 3-5 is the same as the inner diameter of the bushing 1. The four oil passages 3-3 need to expose the internal thread 2-1 of the piston 2 so that the piston 2 and the screw cap 4 can be threaded together and then punched to prevent loosening.

[0035] like Figure 1 , Figure 10 As shown, the large spring tube 7 is used to install the large spring 5. The large spring tube 7 is a cylindrical structure with a through hole 7-1 at one end and an open end with a first outward flange 7-2 at the open end. The large spring tube 7 is located inside the piston 2. The through hole 7-1 end of the large spring tube 7 faces the screw cap 4 and is coaxially fitted onto the rod 3-2 of the force transmission plate 3. The outer diameter wall of the large spring tube 7 can pass through the inner hole 4-2 of the screw cap 4 to ensure that the screw cap 4 moves with the piston 2. The first outward flange 7-2 is used to cooperate with the large spring 5. The large spring 5 is fitted onto the outer diameter of the large spring tube 7, with one end contacting the inner wall of the screw cap 4 and the other end contacting the first outward flange 7-2 of the large spring tube 7. The large spring 5 is a right-hand spring and has a certain preload in the initial installation state to ensure stable installation. The large spring 5 is designed according to the elastic force requirements, the inner cavity size of the piston 2, and the outer diameter size of the large spring tube 7.

[0036] In this embodiment, the large spring tube 7 is made of 30CrMnSiA material, with a total height of 32mm, an inner cavity depth of 30mm, an outer diameter of Φ16mm, an inner diameter of Φ14.5mm, a first outer flange 7-2 with dimensions of Φ24mm × 1.5mm, and a through hole 7-1 with dimensions of Φ9mm. The through hole 7-1 is larger than the outer diameter of the rod 3-2, and the outer diameter of the first outer flange 7-2 is smaller than the inner diameter of the piston 2 but larger than the outer diameter of the large spring 5. The large spring 5 is made of 65Si2MnWA material, with a wire diameter of Φ3mm, a spring outer diameter of Φ24mm, a spring free height of 34mm, a maximum spring compression height of 16mm, and a maximum spring force of 400N. The outer diameter of the large spring 5 is smaller than the inner diameter of the piston 2, and in the initial position, the large spring 5 is in a compressed state. This compression is small and does not affect the continued compression of the large spring 5 when the piston 2 extends.

[0037] like Figure 1 and Figure 11 As shown, the small spring tube 8, together with the rod part 3-2 of the force transmission plate 3 and the large spring tube 7, enables the installation of the small spring 6. The small spring tube 8 is a cylindrical structure with a second outward flange 8-1 at one end, and a countersunk screw hole 8-2 along its central axis that matches the threaded inner hole 3-4 of the rod part 3-2. The countersunk end of the countersunk screw hole 8-2 is on the same side as the second outward flange 8-1. The small spring tube 8 is coaxially mounted on the end of the rod 3-2 away from the disc 3-1. During installation, the countersunk screw hole 8-2 and the threaded inner hole 3-4 of the rod 3-2 of the force transmission rod 3 are aligned, and the second outer flange 8-1 of the small spring tube 8 is located on the side away from the force transmission rod 3. The countersunk screw 9 is inserted into the countersunk screw hole 8-2 and the threaded inner hole 3-4 in sequence to achieve a fixed connection between the small spring tube 8 and the rod 3-2 of the force transmission plate 3. The head of the countersunk screw 9 is embedded in the countersunk screw hole 8-2, without occupying additional space in the piston 2 cavity, and without affecting the stroke of the piston 2. The outer diameter of the small spring tube 8 is the same as the outer diameter of the force transmission plate rod 3-2. The small spring 6 is fitted into the rod 3-2 of the force transmission plate 3 and the outer diameter of the small spring tube 8, and is located in the inner cavity of the large spring tube 7. One end of the small spring 6 contacts the inner wall of the through hole end of the large spring tube 8, and the other end contacts the second outer flange 8-1 of the small spring tube 8. The small spring 6 has a certain preload in the initial installation state to ensure stable installation. The small spring 6 is designed according to the elastic force requirements, the inner cavity size of the large spring tube 7, and the diameter of the rod 3-2 of the force transmission plate 3.

[0038] In this embodiment, the small spring tube 8 is made of 30CrMnSiA material, with a total axial height of 5mm. The outer diameter of the second outer flange 8-1 is Φ13.5mm, and the thickness is 1.5mm. The outer diameter of the rod of the small spring tube 8 is Φ8mm. The countersunk screw hole 8-2 is a 90° countersunk screw hole with a head size of Φ8.6mm and a hole size of Φ5.2mm. The small spring 6 is made of 65Si2MnWA material, with a wire diameter of Φ2.5mm, a spring outer diameter of Φ13.5mm, a spring free height of 31mm, a maximum spring compression height of 10mm, and a maximum spring force of 400N. The outer diameter of the small spring 6 is smaller than the inner diameter of the large spring tube 7, and the small spring 6 is in a compressed state in the initial position with a small amount of compression, which does not affect the continued compression of the small spring 6 when the piston 2 extends. The countersunk screw 9 is a standard part, designated A101-M5×12.

[0039] When assembling this dual-spring tandem piston assembly, as follows: Figure 1 , Figure 3 As shown, first, the screw cap 4 is fitted onto the rod portion 3-2 of the force transmission rod 3. Then, the large spring 5 is fitted onto the rod portion 3-2. Next, the through hole 7-1 end of the large spring tube 7 faces the disc portion 3-1 of the force transmission rod 3, and the large spring tube 7 is inserted into the interior of the large spring 5, so that one end of the large spring 5 presses against the inside of the screw cap 4, and the other end presses against the first outer flange 7-2 of the large spring tube 7. Then, the small spring 6 is placed into the inner cavity of the large spring tube 7 and fitted onto the outer diameter of the rod portion 3-2. After aligning the countersunk screw hole of the small spring tube 8 with the threaded inner hole 3-4 of the rod portion 3-2, the small spring tube 8 and the rod portion 3-2 are fixedly connected by the countersunk screw 9. At this time, one end of the small spring 6 presses against the inner wall of the end where the through hole 7-1 of the large spring tube 7 is located, and the other end presses against the second outer flange 8-1 of the small spring tube 8. Insert the assembled assembly into piston 2 from the open end of piston 2. Tighten the internal thread 2-1 of piston 2 and the second external thread 4-1 of screw cap 4. After tightening, use a tool to punch the threads of piston 2 and screw cap 4 through the four oil holes 3-3 of the disc part 3-1 of force transmission plate 3 to prevent loosening. (During the use of the double-spring tandem piston assembly, this structure will not be opened again until the parts are disassembled for inspection. When reassembling after disassembly, punch the threads of piston 2 and screw cap 4 at other locations to prevent loosening again.) Punching the threads to prevent loosening is a mature technology. Then, install the first sealing ring 10 inside bushing 1. Fit bushing 1 onto the outer ring of piston 2 from the closed end to the open end, so that the end face of bushing 1 contacts the disc part 3-1 of force transmission plate 3. This completes the assembly of the double-spring tandem piston assembly.

[0040] When using, such as Figure 1 , Figure 3 , Figure 12 , Figure 13 , Figure 14 As shown, Figure 1When the piston assembly is not subjected to pressure from the brake control system, piston 2 is in the retracted state. Figure 3 When the piston assembly is subjected to pressure from the brake control system, piston 2 is in the extended state. Figures 12-14 This demonstrates the installation and application scenarios of the piston assembly. For example... Figure 12 As shown, the dual-spring tandem piston assembly 11 of the present invention is installed in the piston chamber 12-1 of the brake wheel cylinder seat. The force transmission plate 3 is located at the bottom of the piston chamber 12-1 of the cylinder seat. The external thread of the bushing 1 is connected to the internal thread of the piston chamber 12-1 of the cylinder seat. The gap between the bushing 1 and the cylinder seat is sealed by the second sealing ring 15. After installation, the structure of the present invention and the cylinder seat 12 form a cylinder seat assembly. Figure 13 The brake disc, brake housing, and other components shown together constitute the braking device. In the structure of this invention, the inner cavity formed by the disc portion 3-1 of the force transmission plate 3, the bushing 1, and the piston 2 is the hydraulic oil chamber of the piston assembly. The oil passage hole 3-3 of the disc portion 3-1 of the force transmission plate 3, the inner hole of the screw cap 4, and the through hole 7-1 of the large spring tube 7 are all connected to the hydraulic oil chamber. Figure 1 As shown, in the initial state, piston 2 and disc 3-1 are in contact. When the aircraft brakes, hydraulic oil enters the piston chamber 12-1 of the cylinder seat through the oil passage, and then enters the hydraulic oil chamber through the four oil passages 3-3 of the disc 3-1. At this time, bushing 1 is connected to cylinder seat 12, the disc 3-1 of force transmission plate 3 abuts against the end face of bushing 1, and small spring tube 8 is fixedly connected to force transmission plate 3 by countersunk screw 9. Therefore, bushing 1, force transmission plate 3, and small spring tube 8 are all stationary. Under the pressure of hydraulic oil, piston 2 and screw cap 4 move outward to the outside of piston chamber 12-1 of cylinder seat. At this time, screw cap 4 pushes large spring 5, which is compressed. At the same time, large spring 5 pushes large spring tube 7, which is compressed, until piston 2 presses against brake disc 13. A schematic diagram of the double-spring tandem piston assembly 11 extending to press against brake disc 13 during operation is shown below. Figure 13 As shown in the diagram. When the aircraft releases the brakes, the brake pressure is released, the hydraulic oil is depressurized, and piston 2 retracts under the restoring force of the large spring 5 and the small spring 6. The brake disc 13 is released, the aircraft is released from the brakes, and the double-spring tandem piston assembly 11 retracts during operation. Figure 14 As shown.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A double-spring tandem piston assembly structure for aircraft wheels, characterized in that, include: The bushing is a rotary cylindrical structure with open ends, and its outer diameter wall is provided with a first external thread for fixed connection with the cylinder seat in the brake wheel; The piston is a rotary cylindrical structure with one end open and the other end sealed. The piston is coaxially and slidably installed in the bushing, and its outer diameter wall is in contact with the inner diameter wall of the bushing. The outer diameter of the piston is in the range of Φ32mm-Φ48mm. The screw cap, a ring-shaped structure, is fixedly installed on the open end of the piston; The force transmission plate includes a coaxially arranged disc portion and a columnar rod portion. The rod portion is vertically disposed on one side of the disc portion. The rod portion passes through the inner hole of the screw cap and extends into the inner cavity of the piston. The end face of the disc portion facing the rod portion contacts the end face of the bushing. The disc portion is evenly distributed with multiple oil passage holes for hydraulic oil to enter and exit. The large spring tube is a cylindrical structure with a through hole at one end and an open end with a first outward flange at the open end. The large spring tube is located in the piston cavity, with its through hole end facing the screw cap and coaxially fitted onto the rod of the force transmission plate, and its outer diameter wall can pass through the inner hole of the screw cap. The large spring is fitted onto the outer diameter of the large spring tube, with one end in contact with the screw cap and the other end in contact with the first outer flange of the large spring tube; A small spring tube is coaxially mounted on the end of the rod of the force transmission plate away from the disk. The end of the small spring tube away from the disk is provided with a second outward flange. The end of the rod of the force transmission plate away from the disk is provided with a threaded inner hole along the central axis. The small spring tube is provided with a countersunk screw hole along its central axis that matches the threaded inner hole of the rod. The small spring tube and the rod of the force transmission plate are fixedly connected by countersunk screws. And a small spring, fitted onto the rod of the force transmission plate and the outer diameter of the small spring tube, and located in the inner cavity of the large spring tube. One end of the small spring contacts the inner wall of the through hole end of the large spring tube, and the other end contacts the second outer flange of the small spring tube. The disk portion of the force transmission plate, the bushing, and the inner cavity formed by the piston constitute the hydraulic oil chamber of the piston assembly. The oil passage hole of the disk portion of the force transmission plate and the inner hole of the screw cap are all connected to the hydraulic oil chamber. The piston is pushed out by the hydraulic oil, and the large spring and the small spring are used for the piston to return to its original position. The small spring and the large spring are both right-hand springs, and both have a certain amount of compression in their initial state.

2. The dual-spring tandem piston assembly structure for aircraft wheels according to claim 1, characterized in that, The inner diameter wall of the bushing is provided with a sealing ring mounting groove for installing a first sealing ring, which is used for sealing between the piston and the bushing; the outer diameter wall of the bushing is provided with a limiting flange and a sealing ring mounting platform, which is used for installing a second sealing ring, which is used for sealing between the bushing and the cylinder seat, and the limiting flange is used for axial limiting of the bushing installed in the piston cavity of the cylinder seat.

3. The dual-spring tandem piston assembly structure for aircraft wheels according to claim 1, characterized in that, The piston has an internal thread at its open end, and the screw cap has a second external thread on its outer diameter. The screw cap is embedded in the open end of the piston and is flush with the end face of the piston. The second external thread of the screw cap and the internal thread of the piston are engaged and connected.

4. The dual-spring tandem piston assembly structure for aircraft wheels according to claim 1, characterized in that, The outer diameter of the small spring tube is the same as the outer diameter of the force transmission plate rod.

5. The dual-spring tandem piston assembly structure for aircraft wheels according to claim 1, characterized in that, The disk portion of the force transmission plate has a boss at the center of its end face facing the rod portion. The boss is embedded in the bushing, and the outer diameter wall of the boss is in contact with the inner diameter wall of the bushing.

6. The dual-spring tandem piston assembly structure for aircraft wheels according to claim 1, characterized in that, The outer diameter wall of the piston and the inner diameter wall of the bushing are coated with grease or lubricating oil.

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