A convenient end structure and method for installing and disassembling dexterous hand fiber tendon cord

Abstract

This invention relates to a convenient installation and disassembly method for the termination structure of a dexterous hand fiber tendon cord, belonging to the field of high-performance fiber applications. The termination structure includes a fiber tendon cord and a shell. The end of the fiber tendon cord is located inside the shell, and the end of the fiber tendon cord and the shell are connected as a single unit via an adhesive curing section. The adhesive curing section is formed by filling the shell with adhesive and completely impregnating and wrapping the end of the fiber tendon cord; after the adhesive cures, the curing section is formed. This invention offers convenient installation and disassembly, strong compatibility, environmentally friendly and efficient processing, and effectively solves the core pain point of high-performance fiber tendon cord termination treatment. In particular, it improves the bonding strength between the fiber tendon cord made of ultra-high molecular weight polyethylene fiber and the cured adhesive, significantly improving long-term high-frequency fatigue resistance.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber application technology, specifically to a termination structure and method for a dexterous hand fiber tendon cord that is easy to install and disassemble. Background Technology

[0002] As a key transmission component of robotic dexterous hands, fiber tendon ties directly affect the grasping accuracy, maneuvering force, and response speed of the dexterous hand. High-performance fibers such as ultra-high molecular weight polyethylene fiber and polyarylate have become the preferred materials for manufacturing tendon ties for dexterous hands due to their excellent properties such as high strength, light weight, high flexibility, and fatigue resistance.

[0003] However, the smooth surface and weak shear resistance of fibrous materials, especially ultra-high molecular weight polyethylene fibers, make end-treatment a persistent technical challenge. Traditional end-treatment methods have significant drawbacks:

[0004] Hot melt method: This method melts the fibers into spheres at high temperatures. This method severely damages the crystal structure of the fibers, causing a sharp drop in the tensile strength of the tendon cord near the molten sphere, making it prone to breakage and resulting in extremely low tensile strength utilization.

[0005] Knotting method: Tie a knot at the end of the tendon cord. The knot creates severe stress concentration in the fiber, causing the breakage to usually occur at the knot, and its strength is usually only about 30% of the breaking strength of the fiber tendon cord itself.

[0006] Metal clamp crimping method: This method uses metal clamps to press the fibers together. For smooth, high-strength fibers, the friction provided by crimping is limited, and slippage is very likely to occur under high-frequency, high-load conditions, resulting in poor reliability.

[0007] Therefore, there is an urgent need in this field for an end-closing structure that can fully utilize the inherent strength of the fiber tendon rope, provide reliable connections, facilitate assembly and disassembly, and prevent damage to the rope. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a convenient and easy-to-install and disassemble end structure and method for a dexterous hand fiber tendon cord, the technical solution of which is as follows:

[0009] In a first aspect, there is an end structure for a dexterous hand fiber tendon cord that is easy to install and disassemble, comprising a fiber tendon cord and a housing, wherein the end of the fiber tendon cord is located inside the housing, and the end of the fiber tendon cord and the housing are connected as one unit by an adhesive curing part; the adhesive curing part is formed by filling the housing with adhesive and completely impregnating and wrapping the end of the fiber tendon cord, and the adhesive curing after curing.

[0010] As a further embodiment of the present invention, the outer shell is a cylindrical shell, a cylindrical conical shell, or a hollow ellipsoidal bead.

[0011] As a further aspect of the present invention, the adhesive is cyanoacrylate adhesive or epoxy resin adhesive.

[0012] As a further embodiment of the present invention, the fiber tendon rope is woven from one or more fibers selected from ultra-high molecular weight polyethylene fiber, aramid fiber, carbon fiber, and polyarylate fiber.

[0013] Secondly, a conveniently installed and disassembled end structure for a dexterous hand fiber tendon cord includes the following steps:

[0014] Step 1: Insert the end of the fiber tendon rope into the outer shell, and loosen the fibers at the end of the fiber tendon rope to obtain a fluffy, open section; use a plasma treatment machine to process the open section.

[0015] Step 2: Immerse the fibers of the spread-out part in glue, and then insert the glue-immersed spread-out part back into the outer shell. The glue cures to form a glue-cured part.

[0016] Step 3: Trim the cured glue section and clean the outer shell to obtain the end structure of the dexterity hand fiber tendon rope that is easy to install and disassemble as described in any one of claims 1 to 4.

[0017] As a further aspect of the present invention, in step 1, the plasma treatment machine uses pure oxygen, with a power of 50~100W, a gas pressure of 30~50Pa, and a treatment time of 50~70s.

[0018] As a further aspect of the present invention, in step 1, the dispersed portion is first frozen in liquid nitrogen before being treated with a plasma treatment machine, and then restored to room temperature.

[0019] As a further aspect of the present invention, in step 1, the liquid nitrogen freezing time is 16~18s.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. Easy installation and disassembly: The fiber tendon rope, shell and glue-filled terminals are matched with the slot of the dexterous hand drive unit to achieve quick assembly and replacement without complicated tools, thus improving maintenance efficiency.

[0022] 2. Strong compatibility: It is compatible with a variety of high-performance fibers such as UHMWPE, aramid, and carbon fiber, and can be adapted to different strength requirements by adjusting the type of adhesive (cyanoacrylate / epoxy resin).

[0023] 3. Environmentally friendly and efficient process: There is no high-temperature melting step, the whole process is room temperature / low temperature treatment, the energy consumption is low, and no harmful gases are generated, which is in line with the trend of green production.

[0024] 4. Effectively solves the core pain point of high-performance fiber tendon rope end treatment, especially improves the bonding strength between fiber tendon rope made of ultra-high molecular weight polyethylene fiber and cured adhesive, and significantly improves long-term high-frequency fatigue resistance.

[0025] This invention is specifically designed for the end treatment of fiber tendon ropes in robot dexterity hands. It can be directly applied to industrial robots, rehabilitation robots, special operation robots and other fields. It can also be extended to fiber rope end connection scenarios that require high strength, fatigue resistance and easy assembly and disassembly (such as small precision machinery, medical devices, etc.). Attached Figure Description

[0026] Figure 1 A photograph of the outer casing described in Example 1;

[0027] Figure 2 A photograph of the ending structure described in Example 1;

[0028] Figure 3 A photograph of the outer casing described in Example 2;

[0029] Figure 4 A photograph of the ending structure described in Example 2;

[0030] Figure 5 A photograph of the casing described in Example 3;

[0031] Figure 6 This is a photograph of the ending structure described in Example 3. Detailed Implementation

[0032] The present invention will be described in detail below with reference to specific embodiments. These embodiments are merely some, not all, implementations of the present invention. All other implementations obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] In this embodiment, the fiber tendon tether is made of 12 strands of ultra-high molecular weight polyethylene fiber, with a diameter of 1.0 mm and a breaking force of 1410 N. Figure 1 As shown, the cylindrical shell is precision machined from stainless steel. The cylindrical shell has a height of 4.5mm, an outer diameter of 3.5mm, an inner diameter of 2.5mm, a wall thickness of 0.5mm, and a small hole at the bottom of the cylindrical shell with a diameter of 1.0mm.

[0035] The manufacturing process of the final structure is as follows:

[0036] 1. Pretreatment: After passing the end of the fiber tendon rope through the small hole at the bottom of the cylindrical shell, use a tool to loosen the ultra-high molecular weight polyethylene fibers at the end of the fiber tendon rope to make them uniform and fluffy, thus obtaining the loose part; first, immerse the loose part in liquid nitrogen to freeze for 17 seconds, then immediately take it out and restore it to room temperature, and then use a plasma treatment machine to treat the loose part. The specific parameters of the plasma treatment machine are: pure oxygen, power 75W, air pressure 45Pa, and treatment time 60s.

[0037] 2. Applying adhesive: Evenly soak the prepared cyanoacrylate adhesive (instant glue or strong glue, such as 502 glue) onto the loose fibers in the spread-out part, ensuring that each fiber monofilament is coated with adhesive.

[0038] 3. Inserting into the mold: Insert the spread-out part coated with cyanoacrylate glue into the cylindrical shell, which acts as a mold in this step.

[0039] 4. Curing: Allow the cyanoacrylate adhesive to fully cure at room temperature. After curing, the cyanoacrylate adhesive, ultra-high molecular weight polyethylene fiber, and cylindrical shell combine to form a cylindrical terminal. The ends of the fiber tendons are securely and mechanically locked within the cylindrical cavity inside the cylindrical shell. Figure 2 As shown.

[0040] 5. Trimming: Trim excess fibers from the outside of the terminal, clean the surface, and polish again if necessary to form a complete termination structure. The terminal's ultimate withstand force reaches 772N. This termination structure can be directly inserted into the corresponding slot of the dexterous hand drive unit to complete the installation.

[0041] When the fiber tendon cord needs to be replaced, simply remove the terminal with the cylindrical housing from the slot on the drive unit and replace it with a new fiber tendon cord. The operation is simple and quick.

[0042] Example 2

[0043] In this example, the outer shell is a cylindrical-conical shell made of stainless steel (one section is cylindrical and the other is conical, such as...). Figure 3 As shown), the total height of the conical shell is 5mm, the height of the cylindrical section is 2.5mm, the outer diameter of the cylindrical section is 3.5mm, the inner diameter of the cylindrical section is 2.5mm, the wall thickness is 0.5mm, the inner diameter of the small end of the conical tube section is 1.0mm, the adhesive is a high-performance epoxy resin adhesive that cures at room temperature (24℃, overlap shear strength greater than 30MPa), and the ultimate bearing capacity of the terminals reaches 833N.

[0044] High-performance epoxy resin adhesives, such as room temperature structural adhesive formulations:

[0045] 100g of E-51 epoxy resin, 100g of TDE-85 (4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester), 18g of CTBN (carboxyl-terminated nitrile butadiene rubber), and 28g of polyurethane prepolymer (CAS No.: 103837-45-2). The curing process is: cure at room temperature for 24 hours or at 80℃ for 2 hours.

[0046] The manufacturing process of the final structure is the same as in Example 1.

[0047] The ends of the fibrous tendon ropes are securely and mechanically locked within the cavity of the conical shell, such as... Figure 4 As shown.

[0048] Example 3

[0049] In this example, the outer shell is a hollow ellipsoidal bead made of stainless steel, such as Figure 5 As shown, the hollow ellipsoidal bead has a total height of 4mm, a maximum outer diameter of 3.5mm, a minimum outer diameter of 3.0mm, a wall thickness of 0.25mm, and an inner diameter of 1.0mm at the port. The adhesive used is the same as in Example 2, and the terminal's ultimate withstand force reaches 811N.

[0050] The manufacturing process of the final structure is the same as in Example 1.

[0051] The ends of the fibrous tendon ligaments are securely and mechanically locked within the cavity of the hollow ellipsoidal bead, as... Figure 6 As shown.

[0052] Characterization experiment

[0053] I. Static Ultimate Tensile Capacity Test

[0054] 1. Testing equipment

[0055] Electronic universal testing machine: measuring range 0-2000N, with displacement control mode (speed adjustable range 0.5-50mm / min) and automatic recording function of tensile force-displacement data.

[0056] Custom-designed clamps can be used to clamp the outer shell and the ends of the fiber tendon rope separately.

[0057] The corresponding fiber tendon cord and its termination structure were selected as samples, with the fiber tendon cord length being 300mm.

[0058] Before testing, the tensile sensor and fixture positioning accuracy were calibrated according to the calibration procedure of the electronic universal testing machine to ensure the normal operation of the equipment.

[0059] The test mode was set to displacement control mode, the tensile speed was 5 mm / min (which meets the conventional standards for tensile testing of precision components), and the tensile data sampling frequency was 10 Hz.

[0060] Start-up test: Start the electronic universal testing machine, stretch the sample at a constant speed, and record the tensile force value in real time until the sample fails (manifested as separation of the terminal / shell from the fiber tendon, or breakage of the glue-cured part), then stop the test.

[0061] Repeat test: Each group of samples is tested three times according to the above steps, and the maximum tensile force value (i.e. the ultimate bearing capacity of the terminal) is recorded for each test.

[0062] Calculate the average value: Take the arithmetic mean of the maximum tensile force value from the three valid test data of each group of samples, and use it as the final ultimate bearing capacity of the group of samples.

[0063] II. High-frequency dynamic tension withstand cycle test

[0064] Perform the test according to the above "Static Ultimate Tensile Strength Test", but repeat the test each time by "first tightening to 80% of the ultimate tensile strength, then holding the tension for 2 seconds, and finally reducing the tension to zero instantly" until the final sample fails. Record the number of repeated tests, which is the ultimate tensile strength test number.

[0065] For example, a limit of 3358 cycles means that the sample failed after being tightened 3358 times using the method of "first tightening to 80% of the limit (618N of tension), then holding the tension for 2 seconds, and finally reducing the tension to zero".

[0066] Comparative Example 1

[0067] Compared to Example 1, the pretreatment process in this example only uses a plasma treatment machine to treat the dispersed parts, and does not involve freezing in liquid nitrogen; all other aspects are the same.

[0068] Comparative Example 2

[0069] Compared with Example 1, in this example, liquid nitrogen is replaced with liquid carbon dioxide during the pretreatment process, while the rest are the same.

[0070] Comparative Example 3

[0071] Compared with Example 1, in this example, the pretreatment process involves first using a plasma treatment machine to treat the dispersed part, then immersing the dispersed part in liquid nitrogen for 17 seconds and immediately removing it to restore it to room temperature. The rest is the same.

[0072] Comparative Example 4

[0073] Compared to Example 1, the fiber tendon cord in this example is woven from ordinary polyethylene fiber (number average molecular weight of 30,000-300,000, which is different from the million-level molecular weight of UHMWPE fiber), and the diameter of the fiber tendon cord is 1.0 mm. All other aspects are the same.

[0074] This case differs from the other test results. For example, the corresponding ultimate tensile strength test result was 263N, but the fracture occurred at the fiber tendon cord, not due to separation between the fiber tendon cord and the cured adhesive (the cured adhesive), or breakage of the cured adhesive, or separation of the shell from the fiber tendon cord. Therefore, it cannot be said that the termination structure failed. Further testing with the "high-frequency dynamic tension bearing capacity test" also showed that the fiber tendon cord broke, which cannot characterize the termination structure as failing.

[0075] Comparative Example 5

[0076] Compared with Example 1, the fiber tendon cord in this example is woven from aramid fibers and has a diameter of 1.0 mm. All other aspects are the same.

[0077] Table 1

[0078]

[0079] As can be seen from the above, the present invention characterizes the mechanical properties of the termination structure. As can be seen from the comparison between Comparative Example 5 and Example 1, the main focus is on the tightness of the bond between the fiber tendon rope, the cured adhesive, and the shell.

[0080] Ultra-high molecular weight polyethylene fiber (UHMWPE) has extremely low surface energy and strong chemical inertness. This results in poor compatibility with most resin matrices and weak interfacial bonding, which is a major technical bottleneck in its application in composite materials.

[0081] Aramids have high surface energy and strong polarity, which allows them to form good physical adsorption and chemical compatibility with polar resin matrices such as epoxy resin and phenolic resin, thereby achieving high interfacial bonding strength.

[0082] In other words, although the bonding force between aramid fibers and the glue-cured part is theoretically stronger, due to the special termination structure of this invention, the glue-cured part will eventually crack in most cases. This is because the glue-cured part itself has a limited strength limit and an upper limit to its ultimate bearing capacity.

[0083] For the final structure of this invention, ultra-high molecular weight polyethylene fibers undergo ultra-low temperature thermal stress under liquid nitrogen freezing, resulting in micro-roughening of the fiber surface, removal of weak interface layers, and exposure of active sites. Further refinement of the microstructure and grafting of polar active groups via plasma high-energy particle deep etching result in a fiber surface with high roughness, high surface energy, and multiple polar groups. This allows the adhesive to fully wet and deeply penetrate the fiber surface, achieving chemical bonding and mechanical interlocking (numerous physical anchor points of varying levels on the fiber surface form an interlocking structure with the cured adhesive). Ultimately, this significantly improves the interfacial bonding strength and mechanical interlocking degree between the fiber and the cured adhesive. Under high-frequency dynamic tension tests, its ultimate withstand cycle is significantly increased; this indicator is a core characteristic of the fiber tendon rope's "long-term high-load service reliability."

[0084] Because the freezing process takes place in liquid nitrogen for an extremely short time, it is a surface modification process that does not damage the high strength and high toughness of the UHMWPE fiber itself. It only optimizes the interfacial properties. To a certain extent, the fiber becomes more deformable, but its strength and durability can still be maintained to a certain extent.

[0085] Aramids naturally have a strong bond with epoxy resins, while liquid nitrogen freezing + plasma is a solution designed to address the "unbonded and surface inert" nature of UHMWPE. For aramids, liquid nitrogen causes low-temperature structural damage, and plasma amplifies the damage and destroys the core bonding groups, resulting in no positive synergistic effect. In addition, the amplification effect of long-term high-frequency fatigue testing will amplify the above defects, thus weakening the bond between aramids and the cured adhesive.

[0086] Experimental Example 1

[0087] In Example 1, the freezing time of the spread-out part immersed in liquid nitrogen was designed according to Table 2, and the corresponding changes in the maximum number of cycles to withstand freezing are shown in Table 2.

[0088] Table 2

[0089]

[0090] Therefore, it can be concluded that, preferably, the freezing time of the dispersed part in liquid nitrogen is 17 seconds.

[0091] Prolonged liquid nitrogen freezing can actually lead to a decrease in performance. It should be noted that a limit of 0 cycles means it will break after just one pull.

[0092] Furthermore, it should be understood that those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. An easy-to-install and easy-to-disassemble end structure for a dexterous hand fiber tendon cord, comprising a fiber tendon cord and a housing, characterized in that: The end of the fiber tendon is located inside the outer shell, and the end of the fiber tendon is connected to the outer shell as one unit by an adhesive curing part; the adhesive curing part is formed by filling the inside of the outer shell with adhesive and completely immersing and wrapping the end of the fiber tendon, and the adhesive curing after the adhesive is cured.

2. The termination structure of the dexterous hand fiber tendon cord for easy installation and disassembly according to claim 1, characterized in that: The outer shell is a cylindrical shell, a conical shell, or a hollow ellipsoidal bead.

3. The termination structure of the dexterous hand fiber tendon cord for easy installation and disassembly according to claim 1, characterized in that: The adhesive is either cyanoacrylate adhesive or epoxy resin adhesive.

4. The termination structure of the dexterous hand fiber tendon cord for easy installation and disassembly according to claim 1, characterized in that: The fiber tendon cord is woven from one or more fibers selected from ultra-high molecular weight polyethylene fiber, aramid fiber, carbon fiber, and polyarylate fiber.

5. An end structure for a dexterous hand fiber tendon cord that is easy to install and disassemble, characterized in that, Includes the following steps: Step 1: Insert the end of the fiber tendon rope into the outer shell, and loosen the fibers at the end of the fiber tendon rope to obtain a fluffy, open section; use a plasma treatment machine to process the open section. Step 2: Immerse the fibers of the spread-out part in glue, and then insert the glue-immersed spread-out part back into the outer shell. The glue cures to form a glue-cured part. Step 3: Trim the cured glue section and clean the outer shell to obtain the end structure of the dexterity hand fiber tendon rope that is easy to install and disassemble as described in any one of claims 1 to 4.

6. The termination method for a dexterous hand fiber tendon cord that is easy to install and disassemble according to claim 5, characterized in that: In step 1, the plasma treatment machine uses pure oxygen, with a power of 50~100W, a gas pressure of 30~50Pa, and a treatment time of 50~70s.

7. The termination method for a dexterous hand fiber tendon cord that is easy to install and disassemble according to claim 5, characterized in that: In step 1, the dispersed portion is first frozen in liquid nitrogen before being treated with a plasma treatment machine, and then restored to room temperature.

8. The termination method for a dexterous hand fiber tendon cord that is easy to install and disassemble according to claim 5, characterized in that: In step 1, the liquid nitrogen freezing time is 16~18s.

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