A clamp-type joint and a lever loading system employing the same

Abstract

The application discloses a clamp type joint and a lever loading system adopting the joint. The joint comprises a double-ear connecting piece, a clamp, a first connecting bolt and a second connecting bolt. The double-ear connecting piece has an internal thread part, and the clamp has an external thread part, which are screwed to form a thread pair. An upper lever is hinged to the double-ear connecting piece through the first connecting bolt, and a lower lever is fastened to the clamp through the second connecting bolt. The application is characterized in that when the two-stage levers change the relative pose due to external deformation, the clamp can slightly tilt relative to the double-ear connecting piece, and the change is adapted through the redistribution of the contact pressure of the thread pair, so that the harmful concentrated constraint bending moment is converted into distributed pressure, and the jamming, high stress and instability risk of the traditional rigid joint are fundamentally eliminated. The joint has a height adjustment function at the same time, can compensate for installation errors, significantly improves the force transmission accuracy and system reliability, and is particularly suitable for the lever loading system under large deformation conditions such as aerospace tests.

Description

Technical Field

[0001] This invention relates to the field of aircraft structural strength testing technology, specifically to a clamp-type joint for an aircraft tension-compression pad-lever loading system and a lever loading system including the joint. Background Technology

[0002] In ground strength verification tests of aircraft structures, a tension / compression pad-lever loading system is often used to simulate aerodynamic and inertial loads during flight. This system uses a series of multiple levers to proportionally amplify the concentrated load output from the actuator and precisely apply it to specific parts of the test component, such as the wing or tail. Each lever level needs to be reliably connected via joints to transmit the tension and compression loads.

[0003] Currently, this field commonly uses integrated rigid joints to connect adjacent levers, such as... Figure 1-2 As shown. This type of joint is usually a single integral component, using one or more bolts to directly clamp and fix the lugs of the upper and lower levers, forming a near-fixed constraint. In tests in large deformation areas such as aircraft wings, the inherent defects of this connection method are fully exposed. Under load, the aircraft wing will undergo significant elastic bending and torsional deformation, resulting in complex relative linear and angular displacements (i.e., relative attitude changes) between the mounting points of the various levers fixed to the wing surface. Traditional one-piece rigid joints, because their structure itself does not have the degree of freedom to adapt to such changes, force the lever system to deform accordingly, thereby generating huge, non-design path secondary constraint bending moments and shear stresses at the connection root between the joint and the lever.

[0004] This situation has led to a series of serious problems: First, the additional bending moment severely disrupts the load transfer path, causing an unacceptable deviation between the actual load distribution applied to the structure and the theoretical design value, directly affecting the accuracy and validity of the test data. Second, extremely high local stress can easily lead to plastic deformation and fatigue crack propagation in the joint itself, and even instantaneous buckling instability failure in extreme cases, posing a serious safety hazard to personnel and equipment at the test site. Third, in cyclic loading fatigue tests, this rigid constraint can easily cause interference and jamming of the kinematic pairs, resulting in uneven load application, abnormal data, and even forcing the test to be interrupted.

[0005] Despite the aforementioned long-standing unresolved engineering challenges, existing technical solutions primarily focus on improving connection strength, reducing weight, or refining assembly processes, such as using special bushings to facilitate alignment during installation. However, these solutions do not fundamentally change the rigid connection nature of the joint and cannot resolve the core contradiction of the joint being forced to bear enormous additional internal forces due to large deformations of the supporting structure. Therefore, developing a new type of lever joint that can proactively adapt to and mitigate relative positional changes from a structural perspective, fundamentally eliminate the risks of jamming and instability, and simultaneously ensure accurate force transmission has become an urgent technical requirement in the field of aircraft structural strength testing.

[0006] Therefore, there is an urgent need to develop a new type of lever system connector that can adapt to relative pose changes, reduce additional internal forces, avoid jamming, and maintain accurate force transmission. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a clamp-type joint and a lever loading system using the joint. This joint can effectively adapt to relative positional changes at the connection point, transforming the concentrated constraint bending moment generated by traditional rigid connections into favorable distributed contact pressure, thereby significantly reducing stress concentration, jamming risk, and instability at the connection point, and can compensate for installation errors to a certain extent, improving force transmission accuracy and system reliability.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a clamp-type connector suitable for connecting two levers with relative positional changes, comprising: A double-ear connector, which has ear plates for connecting to an upper lever and is provided with an internal thread; A clamp having a clamp body for connecting to a lower lever and an external thread portion that mates with the internal thread portion; The first connecting bolt is used to connect the upper lever to the double-ear connector; The second connecting bolt is used to connect the lower lever and the clamp; The clamp engages with the internal thread on the double-ear connector via its external thread to form a threaded pair, and the connection is configured to adapt to the relative positional changes.

[0010] Furthermore, the lugs of the double-ear connector are provided with through holes for the first connecting bolt to pass through, and the clamp body is provided with through holes or U-shaped grooves for the second connecting bolt to pass through. The design of the through holes or U-shaped grooves facilitates the insertion and fixing of bolts, achieving a reliable hinge connection.

[0011] Furthermore, the threaded pair is a fine-pitch thread with a pitch of 1-3 mm. The use of fine-pitch threads provides more precise height adjustment capabilities, while its smaller helix angle results in better self-locking properties and load-bearing stability under axial loads.

[0012] Furthermore, the clamp body is a ring-shaped or C-shaped structure, and its inner hole shape matches the end shape of the lower lever. The ring-shaped structure provides uniform clamping force, while the C-shaped structure facilitates quick installation and disassembly. The matching inner diameter ensures that the clamp body fits tightly against the lever cylinder surface, effectively transmitting radial force and frictional force.

[0013] Furthermore, it also includes an anti-loosening structure, which is disposed on the first connecting bolt and / or the second connecting bolt and / or the threaded pair, and is selected from at least one of cotter pins, lock nuts, and thread-locking adhesive. The anti-loosening structure is used to prevent the bolted connection or threaded pair from loosening under vibration or alternating loads, ensuring long-term reliability.

[0014] Furthermore, the tensile strength of the materials used for the double-ear connector and the clamp is not less than 800 MPa. The use of high-strength materials ensures that the core load-bearing components of the joint do not undergo plastic deformation or fracture under complex loads, meeting the high requirements of aerospace applications.

[0015] Furthermore, the material is 30CrMnSiA alloy steel, which has undergone quenching and tempering heat treatment. 30CrMnSiA is a classic high-strength structural steel for aerospace applications. Through quenching and tempering (quenching + high-temperature tempering), it can obtain excellent comprehensive mechanical properties (high strength, high toughness, and good fatigue performance), making it very suitable for manufacturing the key load-bearing components of this invention.

[0016] In a second aspect, the present invention provides a lever loading system, including at least one clamp-type joint as described above, for connecting two adjacent levers.

[0017] Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention decomposes the overall rigid connection into a series semi-flexible connection of double ears, clamps, and threaded pairs. When the two levers undergo relative deflection or displacement due to external structural deformation, the threaded pair between the clamps and double ears allows for minute relative rotation (typically ±1° to ±5°) and axial micro-movement at the connection interface. This adaptive process cleverly transforms the harmful concentrated constraint moment, which cannot be released in traditional rigid joints, into distributed normal pressure on the threaded pair contact surface. This fundamental change reduces the maximum stress level at the joint root by more than 50%, completely eliminating the risks of yielding, fatigue, and buckling instability caused by stress concentration, and eradicating motion jamming.

[0018] 2. This invention clarifies an optimized force transmission path where shear force is primarily transmitted through the first and second connecting bolts, while a portion of the bending moment is transmitted as pressure through the contact surface of the threaded pair. This path better aligns with the mechanical principles of lever transmission, reducing unnecessary internal force coupling. Actual tests show that, under simulated large deformation conditions, the lever system using this joint achieves a 10%-20% higher accuracy in applying the final load compared to systems using traditional rigid joints, and reduces load fluctuation by over 50%.

[0019] 3. The threaded joint of this invention is itself a precision height adjustment mechanism. By rotating the clamp, the overall assembly height of the joint can be continuously and precisely adjusted. This function can effectively absorb and compensate for the cumulative height error caused by part machining tolerances, unevenness of the structural mounting surface, and wear during long-term use (typical compensation capability can reach 3-5mm), which not only simplifies the installation and debugging process, but also ensures optimal alignment during long-term system operation.

[0020] 4. The entire connector of this invention consists of only a few core parts, such as a double-ear connector, a clamp, and two bolts, resulting in an extremely simple structure and a low failure rate. Through standardized design (such as unified thread specifications and interface dimensions), this connector can be easily integrated into various lever transmission or loading systems of different specifications and load levels as a universal module, facilitating serialization and mass production.

[0021] 5. This invention, through its modular design, makes installation, disassembly, and maintenance extremely convenient, requiring no special tools. Replacement can be completed quickly even in harsh testing environments. Its inherent stress-relieving characteristics also provide the system with a higher safety margin in the event of overload or accidental impact. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a traditional tension / compression pad-lever loading system. Figure 2 This is a schematic diagram of a traditional integrated rigid joint. Figure 3 This is a schematic diagram of the overall structure of the clamp-type connector according to an embodiment of the present invention; Figure 4 This is an exploded view of the structure of the double-ear connector and the clamp in an embodiment of the present invention; Figure 5 This is a schematic diagram showing the connection state between the clamp-type connector and the upper and lower levers in an embodiment of the present invention.

[0023] In the diagram: 1-Double-ear connector, 2-Clamp, 3-1-First connecting bolt, 3-2-Second connecting bolt, 4-Upper lever, 5-Lower lever, 6-Internal thread, 7-External thread, 8-Anti-loosening structure. Detailed Implementation

[0024] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0025] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar words used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components.

[0027] Example 1 like Figures 3-5 As shown, the clamp-type connector of the present invention mainly consists of the following parts: a double-ear connector 1, a clamp 2, a first connecting bolt 3-1, a second connecting bolt 3-2, a threaded pair, and an anti-loosening structure 8. Specifically: Dual-ear connector 1: such as Figure 3-5 As shown, in this embodiment, this component is located below the connector and is also the part connected to the upper force transmission mechanism (i.e., the upper lever 4). Its main body is typically U-shaped or fork-shaped, with two parallel lugs. Through holes are machined on the lugs for hinged connection with the corresponding lugs on the upper lever 4 via the first connecting bolt 3-1. An internal thread 6 is machined at the center of the top of the U-shape, typically a blind hole or through hole with internal threads. The core function of this double-lug connector 1 is to provide a stable lower hinge point and to transmit the load from the upper lever upward to the threaded connection area.

[0028] Clamp 2: such as Figure 3-5As shown, in this embodiment, the component is located above the connector and is used to clamp and connect the lower lever 5. The clamp 2 is an integral ring structure (or a C-shaped opening structure), and its inner hole cross-section is preferably rectangular; an external thread is machined at the center of its bottom, forming an external threaded part 7, which is used to engage with the internal threaded part 6 of the double-ear connector 1. The shape of its inner hole matches the end shape of the lower lever 5, using a clearance fit or a transition fit. Two through holes or U-shaped grooves are symmetrically machined on the middle of both sides of the clamp 2 for inserting the second connecting bolt 3-2 to fasten the clamp to the lower lever 5. The core function of the clamp 2 is to form an integral part with the lower lever through clamping force. Its external threaded part 7 engages with the internal threaded part 6 of the double-ear connector 1 to jointly form a threaded pair that transmits axial load and adapts to relative positional changes. At the same time, its structure allows it to adjust its posture within a certain range.

[0029] The first connecting bolt 3-1 and the second connecting bolt 3-2: The first connecting bolt 3-1 is used to achieve a rotatable hinge between the double-ear connector 1 and the upper lever 4. The second connecting bolt 3-2 is used to achieve a tight connection between the clamp 2 and the lower lever 5. Both are typically made of high-strength standard bolts and equipped with washers. The function of the two bolts is to provide the main shear force transmission path and allow the joint to have rotational freedom in the lever plane.

[0030] Threaded pair: Formed by the interlocking of the internal threaded portion 6 of the double-ear connector 1 and the external threaded portion 7 of the clamp 2. The core function and effect of this threaded pair are: a) Bearing and force transmission: This threaded pair bears the main axial tensile and compressive forces connecting the upper and lower parts, and transmits the load from the clamp to the double-ear connector in the form of contact pressure.

[0031] b) Adaptation to Deformation: When the upper and lower levers undergo non-collinear relative deflection (i.e., relative orientation change), a traditional rigid joint would form a fixed constraint at this point, generating a large root bending moment. However, in this embodiment of the invention, the clamp 2 can tilt slightly relative to the double-ear connector 1 about the thread axis. This tilt alters the contact pressure distribution of the threaded pair, but the resultant force still passes through the axis. This process is essentially a static equivalent process of decomposing the concentrated bending moment into an asymmetrically distributed pressure on the thread surface. It is this mechanism that allows the joint to adapt to deformation without generating destructive internal constraint stress.

[0032] c) Height adjustment: By rotating the clamp 2, the depth to which it is screwed into the double-ear connector 1 can be changed, thereby achieving stepless and fine adjustment of the total height of the entire connector.

[0033] Anti-loosening structure 8: Installed on the first connecting bolt 3-1 and / or the second connecting bolt 3-2 and / or the threaded pair. Anti-loosening structure 8 can be selected from at least one of cotter pins, lock nuts, and thread-locking adhesive. Specifically, a cotter pin can be installed at the end of the second connecting bolt 3-2, which is a classic and reliable method to prevent bolt loosening. Alternatively, double nuts can be used to lock the first connecting bolt 3-1, or a medium-strength thread-locking adhesive can be applied when assembling the threaded pair to prevent loosening during use. Anti-loosening structure 8 ensures that all critical connection parts remain pre-tightened under long-term vibration, impact, or alternating loads, maintaining the long-term stability of the joint performance.

[0034] The following example, using the above-mentioned joint in a lever loading system for a static test of an aircraft wing, illustrates the specific design parameters of the clamp-type joint described in this invention: Specifically, both the double-ear connector 1 and the clamp 2 are forged from aerospace-grade 30CrMnSiA alloy steel bars, machined, and then subjected to quenching and tempering heat treatment: oil quenching at 850-880℃, followed by tempering at 520-560℃. The treated material achieves a hardness of HRC32-38 and a tensile strength of... ≥800MPa.

[0035] The threaded pair uses fine-pitch threads with a pitch of 1-3 mm. In a preferred embodiment, the threaded pair uses metric fine-pitch threads with a specification of M30×2 (i.e., nominal diameter 30 mm, pitch 2 mm); the thread machining accuracy is 6H / 6g, and the depth is 15 mm; selecting a fine-pitch thread with a 2 mm pitch provides sufficient strength while ensuring good adjustment precision (height changes by 2 mm per revolution) and self-locking properties.

[0036] The thickness of the ear piece of the double-ear connector 1 is 25mm, and the diameter of the through hole is Φ38mm. The first connecting bolt 3-1 and the second connecting bolt 3-2 are 12.9 grade high-strength bolts with a diameter of M30, and are equipped with corresponding anti-loosening washers.

[0037] The installation and adjustment process is as follows: First, insert the lug of the upper lever 4 into the U-shaped opening of the double-ear connector 1, align the holes, insert the first connecting bolt 3-1, and tighten the nut. Then, place the end of the lower lever 5 into the inner hole of the clamp 2, align the holes, insert the second connecting bolt 3-2, and initially tighten it.

[0038] Then, screw the external thread of clamp 2 into the internal thread of the double-ear connector 1. Use a large wrench to rotate clamp 2 and observe the total height of the joint until it meets the design size requirements.

[0039] Finally, fully tighten the nut of the second connecting bolt 3-2 and install the cotter pin 6. Add a lock nut to the nut side of the first connecting bolt 3-1 and tighten it to prevent loosening.

[0040] In this test, the maximum wing deflection resulted in a relative rotation angle of approximately 2.5° at adjacent lever mounting points. Using a conventional joint, sensors detected stress at the joint root reaching 85% of the material's yield strength, accompanied by abnormal noise (signs of jamming) during loading. After replacing the joint with the one described in this embodiment, the maximum stress at the joint decreased to below 35% of the yield strength under the same operating conditions, the loading process was smooth and stable, and the final load distribution applied to the wing surface matched the theoretical value by more than 98%.

[0041] For extra-large lever loading systems, the joint size can be increased accordingly. For example, the thickness of the lug of the double-ear connector can be increased to 30mm, the thread specification can be increased to M48×3, and the connecting bolts can be increased to M48 accordingly.

[0042] To verify the effectiveness of the clamp-type connector described in the embodiments of the present invention, the following comparative tests were conducted: Large deformation adaptability test: On the test bench simulating 30° deformation of the airfoil, the traditional integrated joint showed obvious jamming when loaded to 80% of the design load, with load fluctuation reaching ±15%; while the joint of the present invention operated smoothly under 100% design load, with load fluctuation of only ±3%.

[0043] Fatigue durability test: Under alternating tensile and compressive loads of R=0.1 and frequency of 5Hz, the traditional joint loosened after 500,000 cycles and the threads wore out severely after 1 million cycles; the joint of the present invention remained intact after 2 million cycles with no obvious wear.

[0044] Error compensation test: When the simulated installation surface height error is 3.5mm, traditional joints cannot be installed normally; the present invention can successfully compensate for the error by rotating the clamp 2.5 turns, and the force transmission accuracy deviation after installation is <1%.

[0045] This invention has been successfully applied to the wing surface loading system during the static test of a certain type of passenger aircraft. During the six-month test, 86 sets of this type of connector were used, with a cumulative loading of over 5000 cycles, and no reports of jamming or failure were received. Compared to the original integrated connector, the test preparation time was reduced by 40%, load control accuracy was improved by 15%, and safety was significantly enhanced.

[0046] The clamp-type joint provided by this invention is not limited to the aerospace testing field in terms of its principle and advantages. This joint can be used to improve performance in any lever transmission, linkage mechanism, or loading device where there is foundation deformation, thermal deformation, or the need to compensate for installation errors. Examples include: health monitoring loading systems for large civil engineering structures (bridges, stadiums); connections of some force transmission links in heavy engineering machinery (such as excavators and cranes); and leveling and connection mechanisms for optical platforms and experimental equipment requiring high-precision alignment. In summary, this invention, through its ingenious structural design, solves the inherent defects of rigid joints under non-ideal working conditions, and provides a reliable, precise, and adaptive high-performance connection solution.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments of 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 clamp-type connector, characterized in that, Suitable for connections between two levers with relative pose changes, including: The double-ear connector (1) has an ear for connecting to the upper lever (4) and is provided with an internal thread (6). The clamp (2) has a clamp body for connecting to the lower lever (5) and an external thread (7) that mates with the internal thread. The first connecting bolt (3-1) is used to connect the upper lever (4) to the double-ear connector (1). The second connecting bolt (3-2) is used to connect the lower lever (5) to the clamp (2); The clamp (2) is screwed into the internal thread (6) on the double-ear connector (1) through the external thread (7) to form a threaded pair. The connection is configured to adapt to the relative positional changes.

2. The clamp-type connector according to claim 1, characterized in that, The ear piece of the double-ear connector (1) is provided with a through hole for the first connecting bolt (3-1) to pass through, and the clamp (2) is provided with a through hole or U-shaped groove for the second connecting bolt (3-2) to pass through.

3. The clamp-type connector according to claim 1, characterized in that, The threaded pair is a fine thread with a pitch of 1-3 mm.

4. The clamp-type connector according to claim 3, characterized in that, The threaded pair is an M30×2 metric fine thread.

5. The clamp-type connector according to claim 1, characterized in that, The clamp (2) has a ring or C-shaped structure, and its inner hole shape matches the end shape of the lower lever (5).

6. The clamp-type connector according to claim 1, characterized in that, It also includes an anti-loosening structure (8), which is disposed on the first connecting bolt (3-1) and / or the second connecting bolt (3-2) and / or the threaded pair, and the anti-loosening structure is selected from at least one of cotter pin, lock nut, and thread sealant.

7. The clamp-type connector according to claim 1, characterized in that, The tensile strength of the materials of the double-ear connector (1) and the clamp (2) is not less than 800 MPa.

8. The clamp-type connector according to claim 7, characterized in that, The material is 30CrMnSiA alloy steel, which has undergone quenching and tempering heat treatment.

9. A lever loading system, characterized in that, Includes at least one clamp-type connector as described in any one of claims 1-8, for connecting two adjacent lever stages.

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