A machine and method for testing the conductivity of powdered graphite

Abstract

The application discloses a kind of powdered graphite conductivity testing machine and testing method, it is related to graphite resistivity detection technical field, including box, control panel, control component, pressure component, sample cylinder component, probe socket and sliding table component. Box is divided into upper working cavity and lower working cavity by transverse partition, control component is arranged in upper working cavity, sliding table component is arranged at the bottom of lower working cavity, sample cylinder component is clamped at the top of sliding table component, probe socket is arranged at the bottom of lower working cavity and is located at one end of sliding table component sliding direction, pressure component is arranged in lower working cavity and is located at one side of sliding table component long side, the barrel wall of sample cylinder component is provided with multiple probes along the radial direction, for with probe socket plug-in connection.This application eliminates repeated positioning error by fixing probe on the barrel wall of sample cylinder, and uses sliding table component to make the outer end of probe automatically plug-in connection with probe socket after sliding to position, realizes the semi-automatic operation of testing process.

Description

Technical Field

[0001] This invention relates to the field of graphite conductivity testing technology, and in particular to a powdered graphite conductivity testing machine and testing method. Background Technology

[0002] In the quality inspection and scientific analysis of powdered graphite materials, resistivity is a key physical property parameter. Its accurate measurement is crucial for evaluating the conductivity, purity, and batch stability of graphite. Currently, the industry generally refers to the two-pole four-probe method in GB / T 24521-2018 "Methods for Determination of Resistivity of Carbon Raw Materials and Coke". This method involves loading the powder into a sample cylinder, compressing it, and then applying current and measuring the voltage drop using four probes to calculate the resistivity. Compared to the traditional two-probe method, the four-probe method effectively eliminates the influence of contact resistance and lead resistance, resulting in higher measurement accuracy. Therefore, it is widely used for resistivity testing of powdered materials such as graphite and carbon.

[0003] However, existing powdered graphite resistivity testing devices still have significant shortcomings in practical operation. First, the probes of traditional devices typically need to be re-inserted into the powder sample after each loading, which is cumbersome and results in poor positioning consistency. Frequent insertion and removal can also lead to probe bending or wear, directly affecting the repeatability and accuracy of the test results. Second, the sample cylinder is often separated from the press and resistance meter, with sample loading, pressurization, and wiring steps being independent. Operators need to manually connect the test leads, which is not only inefficient but also prone to introducing measurement errors due to poor contact. In addition, in batch testing scenarios, the disassembly and cleaning of the sample cylinder lack convenient positioning and locking mechanisms, making the entire testing process time-consuming and unable to meet the needs of rapid, high-throughput testing.

[0004] Therefore, how to develop a powdered graphite conductivity tester that eliminates repeatability errors by fixing the probe to the sample cylinder wall and automatically connects the probe outer end to the probe socket after sliding into position using a slide assembly, thus realizing semi-automatic operation of the testing process, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a powdered graphite conductivity tester and test method. By fixing the probe to the sample cylinder wall, the repeated positioning error is eliminated, and the slide assembly is used to automatically connect the outer end of the probe to the probe socket after sliding into place, thus realizing semi-automatic operation of the test process.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides a method for testing the electrical conductivity of powdered graphite, comprising the following steps: S1. Load the powdered graphite to be tested into the sample tube assembly; S2. Apply and maintain a constant pressure to the powdered graphite inside the sample cylinder assembly using a pressure assembly to compact and shape it. S3. Make the powdered graphite come into contact with the four probes fixed on the wall of the sample tube assembly. The four probes are divided into two groups, two of which are used as current source probes and the other two are used as voltage measurement probes. S4. Apply a constant current to the powdered graphite sample through the current source probe, and measure the voltage drop on the surface of the powdered graphite sample through the voltage measurement probe. S5. Based on the applied current and the measured voltage drop, the resistivity of the powdered graphite is calculated, and then the conductivity is calculated according to σ=1 / ρ.

[0007] Preferably, in step S2, the constant pressure is set to 3.9 MPa ± 0.03 MPa.

[0008] Preferably, in step S4, the constant current is set to 500mA ± 0.1mA.

[0009] A powdered graphite conductivity testing machine includes a housing, a control panel, a control component, a pressure component, a sample cylinder assembly, a probe socket, and a slide assembly. A transverse partition is horizontally fixed within the housing, dividing the interior of the housing into an upper working chamber and a lower working chamber. The control component is located in the upper working chamber. The slide assembly is located at the bottom of the lower working chamber. The sample cylinder assembly is engaged with the top of the slide assembly. The probe socket is located at the bottom of the lower working chamber, situated at one end of the slide assembly's sliding direction. The pressure component is located in the lower working chamber and positioned on the slide assembly. On one side of the long side of the assembly, the working end of the pressure component is located above the sample cylinder assembly for pressurizing the powdered graphite inside the sample cylinder assembly. Multiple probes are radially arranged through the cylinder wall of the sample cylinder assembly. One end of each probe is flush with or slightly protrudes into the inner wall of the sample cylinder assembly for contacting the powdered graphite. The other end of each probe is located outside the sample cylinder assembly for connecting with the probe socket after the slide assembly has slid into place. The control panel is embedded in the front side of the housing, and the control panel, pressure component, and probe socket are all electrically connected to the control component.

[0010] Preferably, the enclosure further includes a door, which is hinged to the opening side of the lower working chamber, and a transparent observation window is provided on the door.

[0011] Preferably, the control components include a resistance measuring instrument and a PLC controller. The probe socket is electrically connected to the resistance measuring instrument via a wire. The resistance measuring instrument, the control panel, and the pressure component are all electrically connected to the PLC controller.

[0012] Preferably, the control panel includes a display screen and operation buttons. The display screen and operation buttons are both fixedly installed on the front side of the housing and located on the front side of the upper working cavity. The display screen and operation buttons are both electrically connected to the PLC controller.

[0013] Preferably, the pressure assembly includes a guide rail, an L-shaped slider, a pressure head, a threaded rod, a top plate, a servo motor, and a pressure sensor. A vertically mounted mounting plate is fixedly connected to the bottom of the lower working chamber. The guide rail and servo motor are both fixedly connected to the mounting plate. The guide rail is vertically positioned, and the servo motor is located at the top of the guide rail. The threaded rod is rotatably connected to the guide rail via a bearing seat, and the top end of the threaded rod is fixedly connected to the power output end of the servo motor. The vertical section of the L-shaped slider is slidably connected to the guide rail, and the vertical section of the L-shaped slider is threadedly connected to the threaded rod. The pressure sensor is fixedly connected to the bottom of the horizontal section of the L-shaped slider. The top plate is located below the horizontal section of the L-shaped slider. Multiple adjusting screws are arranged above the top plate. The adjusting screws pass through the horizontal section of the L-shaped slider and are fixedly connected to a locking nut. The top of the top plate abuts against the detection end of the pressure sensor. The pressure head is fixedly connected to the bottom of the top plate. The servo motor and pressure sensor are both electrically connected to the PLC controller.

[0014] Preferably, the slide assembly includes a slide groove, a limiting groove, a slider, a limiting block, a slide top plate, a sealing block, and a rotating plunger. The slide groove is formed at the bottom of the lower working chamber. The limiting groove is symmetrically formed on the two long side walls of the slide groove. Two limiting blocks matching the limiting grooves are symmetrically fixedly connected to the left and right sides of the slider. An installation groove for installing the slider is formed at the end of the slide groove away from the probe socket. The width of the installation groove is greater than the width of the slide groove. The sealing block is embedded in the installation groove and fixedly connected to the bottom of the lower working chamber by bolts. The slide top plate is fixedly connected to the top of the slider. The rotating plunger is threaded through the slide top plate, and the two rotating plungers are symmetrically arranged on the left and right sides of the slide top plate. A locking positioning hole matching the telescopic end of the rotating plunger is formed at the bottom of the lower working chamber.

[0015] Preferably, the sample cylinder assembly further includes a sample cylinder body, a sleeve, and sleeve limiting bosses. The sample cylinder body is configured as a tubular structure with open ends. Multiple probes are connected through the cylinder wall of the sample cylinder body, and the test ends of the probes are flush with or slightly protrude into the inner wall of the sample cylinder body. The bottom of the sample cylinder body is provided with external threads. The sleeve is configured as a cup-shaped tube structure with open end, and the outer peripheral wall of the sleeve is provided with anti-slip texture. The sample cylinder body is embedded in the inner cavity of the sleeve, and the sleeve is threadedly connected to the sample cylinder body. Two sleeve limiting bosses are symmetrically fixedly connected to the outer peripheral wall of the sleeve. The top of the slide plate has a mounting groove for mounting the sleeve. A limiting mounting groove is provided on the side wall of the mounting groove. The bottom of the sleeve is embedded in the mounting groove and is fixed to the slide plate by the engagement of the sleeve limiting boss and the limiting mounting groove.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1) This invention directly fixes four probes to the wall of the sample tube body and sets an insulating bushing between each probe and the tube wall, eliminating the tedious operation of repositioning and inserting probes for each test, and avoiding the problem of probe bending or wear caused by frequent insertion and removal. The fixed probes, together with the sliding stage assembly, drive the sample tube assembly to slide smoothly between the sample loading position and the measurement position, so that the outer end of the probe automatically completes the connection with the probe socket after sliding into place, without the need for manual connection of any wires, which significantly improves the testing efficiency and operation convenience in batch testing, and ensures that the relative position of the probe and the powdered graphite sample is consistent, thereby effectively improving the repeatability and accuracy of resistivity measurement results; 2) This invention employs a servo motor in conjunction with a threaded rod and an L-shaped slider to drive the pressure head up and down. A pressure sensor provides real-time feedback of the pressure value to the PLC controller, forming a closed-loop control system. This system can precisely apply and maintain a constant pressure of 3.9 MPa ± 0.03 MPa on the powdered graphite inside the sample cylinder. Simultaneously, the PLC controller, as the control core, coordinates the working sequence of the pressure components and the resistance measuring instrument, achieving semi-automatic operation of automatic pressurization, automatic measurement, and automatic data acquisition and calculation after sample loading. This reduces human error and ensures the consistency and comparability of test results from different batches. 3) This invention designs the sample cylinder assembly as a separate threaded connection structure of the sample cylinder body and the sleeve. The outer peripheral wall of the sleeve is provided with anti-slip texture, which facilitates the unscrewing of the sample cylinder body and the downward push to compact the sample after the test. This makes cleaning convenient and less likely to damage the cylinder body. At the same time, the slide assembly achieves reliable measurement position locking through the cooperation of the rotating plunger and the locking positioning hole, preventing the slide from retracting during pressurization. The sleeve is engaged with the limiting mounting groove on the top plate of the slide through the sleeve limiting boss, which not only ensures the reliable positioning of the sample cylinder assembly in the vertical direction, but also facilitates removal for cleaning or replacement, meeting the practical needs of convenient operation and maintenance in batch testing. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the overall structure of a powdered graphite conductivity testing machine according to the present invention. Figure 2 This is a schematic diagram of the internal structure of a powdered graphite conductivity testing machine according to the present invention; Figure 3 This is a schematic diagram of the pressure component in the present invention. Figure 1 ; Figure 4 This is a schematic diagram of the pressure component in the present invention. Figure 2 ; Figure 5 This is a schematic diagram of the sample tube assembly in this invention; Figure 6 This is a schematic diagram of the slide assembly in this invention; Figure 7 This is a schematic diagram of the connection structure of the sliding groove, the mounting groove and the limiting groove in this invention; Figure 8 This is a schematic diagram of the slider structure in this invention; Figure 9 This is a schematic diagram of the sealing block in this invention; Figure 10 This is a schematic diagram of the probe socket in this invention.

[0019] Explanation of reference numerals in the attached drawings: 1. Box body; 11. Horizontal partition; 12. Box door; 121. Transparent observation window; 13. Upper working chamber; 14. Lower working chamber; 15. Mounting plate; 2. Control panel; 21. Display screen; 22. Operation buttons; 3. Control components; 31. Resistance measuring instrument; 32. PLC controller; 4. Pressure assembly; 41. Guide rail; 42. L-shaped slider; 43. Pressure head; 44. Threaded rod; 45. Top plate; 451. Adjusting screw; 452. Locking nut; 46. Servo motor; 47. Pressure sensor; 5. Sample tube assembly; 51. Probe; 52. Sample tube body; 53. Sleeve; 531. Anti-slip texture; 54. Sleeve limiting boss; 6. Probe socket; 7. Slide assembly; 71. Slide groove; 711. Mounting groove; 72. Limiting groove; 73. Slider; 74. Limiting block; 75. Slide top plate; 751. Mounting groove; 752. Limiting mounting groove; 76. Sealing block; 77. Rotating plunger; 78. Locking positioning hole. Detailed Implementation

[0020] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0021] like Figure 1-10 As shown, a method for testing the electrical conductivity of powdered graphite includes the following steps: S1. Load the powdered graphite to be tested into the sample tube assembly; S2. Apply and maintain a constant pressure to the powdered graphite inside the sample cylinder assembly using a pressure assembly to compact and shape it. S3. Make the powdered graphite come into contact with the four probes fixed on the wall of the sample tube assembly. The four probes are divided into two groups, two of which are used as current source probes and the other two are used as voltage measurement probes. S4. Apply a constant current to the powdered graphite sample through the current source probe, and measure the voltage drop on the surface of the powdered graphite sample through the voltage measurement probe. S5. Based on the applied current and the measured voltage drop, the resistivity of the powdered graphite is calculated, and then the conductivity is calculated according to σ=1 / ρ.

[0022] Specifically, the powdered graphite to be tested can be either natural or artificial graphite. If the original graphite is in block form, it can be pre-ground into powder before testing. The graphite to be tested must be sieved to the specified particle size. This test method references and improves the two-pole four-probe method in GB / T 24521-2018 "Methods for Determination of Resistivity of Carbon Raw Materials and Coke," fixing four probes 51 directly to the wall of the sample cylinder body 52. ​​To prevent electrical conduction between the probes 51 and the metal sample cylinder body 52, an insulating bushing is provided between each probe 51 and the cylinder wall of the sample cylinder body 52. ​​This insulating bushing is made of ceramic or polytetrafluoroethylene material, ensuring that the current flows only through the inner end of the probe 51 through the powdered graphite sample and does not form a short circuit through the cylinder wall. This fixed probe structure eliminates the step of repositioning and inserting the probes each time, thereby improving testing efficiency and data repeatability.

[0023] Specifically, since powdered graphite is loose and granular, its resistivity cannot be directly measured like that of block materials. Therefore, the core of this method is to first press the powdered graphite into a compacted sample with a certain density and shape using the pressure component 4, and then measure the resistivity of the compacted sample to obtain stable and reliable test results.

[0024] Specifically, in S2, the constant pressure is set to 3.9 MPa ± 0.03 MPa.

[0025] Specifically, the pressure parameter is determined according to the standard requirements for measuring the resistivity of carbon raw materials and coke. The pressure component 4 in this invention can stably apply a pressure of 3.9 MPa ± 0.03 MPa to the sample and maintain this pressure constant throughout the entire test. Using this pressure value for compaction enables the powdered graphite to achieve a suitable density, avoiding both insufficient pressure leading to loose samples and inaccurate measurement results, and excessive pressure causing damage to the graphite particles.

[0026] Specifically, the pressure component 4 is controlled in a closed loop by the PLC controller 32, and with the real-time feedback from the pressure sensor 47, the set pressure value can be accurately maintained, with a pressure control accuracy of ±0.03MPa, thereby ensuring the consistency and comparability of test results from different batches.

[0027] Specifically, in S4, the constant current is set to 500mA±0.1mA.

[0028] Specifically, the powder resistance meter can provide a stable DC current of 500mA ± 0.1mA. This current value balances measurement accuracy and safety: too low a current will result in a weak voltage drop signal and increased measurement error; too high a current may cause the graphite sample to heat up, affecting the true resistivity value. The constant 500mA current, combined with the four-probe measurement method, effectively eliminates the influence of contact resistance on the measurement results, improving measurement accuracy.

[0029] A powdered graphite conductivity testing machine includes a housing 1, a control panel 2, a control component 3, a pressure component 4, a sample cylinder assembly 5, a probe socket 6, and a slide assembly 7. A transverse partition 11 is horizontally fixed inside the housing 1, dividing the inner cavity of the housing 1 into an upper working chamber 13 and a lower working chamber 14. The control component 3 is located in the upper working chamber 13. The slide assembly 7 is located at the bottom of the lower working chamber 14. The sample cylinder assembly 5 is snapped onto the top of the slide assembly 7. The probe socket 6 is located at the bottom of the lower working chamber 14 and at one end of the sliding direction of the slide assembly 7. The pressure component 4 is located in the lower working chamber 14. Located on one side of the long side of the slide assembly 7, the working end of the pressure assembly 4 is positioned above the sample cylinder assembly 5 to pressurize the powdered graphite inside the sample cylinder assembly 5. Multiple probes 51 are radially arranged through the cylinder wall of the sample cylinder assembly 5. One end of each probe 51 is flush with or slightly protrudes into the inner wall of the sample cylinder assembly 5 to contact the powdered graphite. The other end of each probe 51 is located outside the sample cylinder assembly 5 and is used to connect with the probe socket 6 after the slide assembly 7 has slid into position. The control panel 2 is embedded in the front side of the housing 1, and the control panel 2, pressure assembly 4, and probe socket 6 are all electrically connected to the control assembly 3. In one specific embodiment, four probes are provided, and the spacing between the probes has been calibrated inside the resistance measuring instrument, and the cylinder size of the sample cylinder assembly 5 is limited.

[0030] Specifically, this invention optimizes and integrates components such as the sample cylinder assembly 5, probe 51, pressure assembly 4, and resistance measuring instrument 31 into a convenient testing device. The housing 1 serves as the supporting frame for the entire device, and its internal partition 11 separates the upper and lower working chambers. The upper working chamber 13 is used to install the control assembly 3 to avoid dust contamination, while the lower working chamber 14 is used to complete pressurization and measurement operations. The structural layout is reasonable and facilitates maintenance and operation.

[0031] Specifically, the slide assembly 7 allows the sample tube assembly 5 to slide smoothly between the sample loading position and the measurement position. When the slide assembly 7 moves the sample tube assembly 5 to the end away from the pressure assembly 4, the operator can easily remove the sample tube assembly 5 from the top of the slide assembly 7 and take it outside the equipment for powdered graphite filling. After filling, the sample tube assembly 5 is snapped back onto the top of the slide assembly 7. Subsequently, the operator pushes the slide assembly 7 inward to the end close to the pressure assembly 4. At this time, the sample tube assembly 5 is directly below the pressure head 43. Simultaneously, the outer end of the probe 51 fixedly connected to the side wall of the sample tube assembly 5 automatically completes the insertion and conduction with the fixed probe socket 6, without the need for manual connection of any wires. This removable sample loading combined with automatic insertion design not only facilitates sample loading and sample tube cleaning but also ensures the reliability of electrical connections, greatly improving the testing efficiency and operational convenience during batch testing.

[0032] Specifically, the housing 1 also includes a door 12, which is hinged to the opening side of the lower working chamber 14, and a transparent observation window 121 is provided on the door 12.

[0033] Specifically, the enclosure door 12 creates a relatively enclosed testing environment in the lower working chamber 14, preventing external dust and impurities from entering and avoiding powder splashing during pressurization. The transparent observation window 121 is made of high-strength transparent material, allowing operators to monitor the operation of the pressure head 43 in real time during equipment operation, facilitating timely detection of abnormalities.

[0034] Specifically, the control component 3 includes a resistance measuring instrument 31 and a PLC controller 32. The probe socket 6 is electrically connected to the resistance measuring instrument 31 via a wire. The resistance measuring instrument 31, the control panel 2, and the pressure component 4 are all electrically connected to the PLC controller 32.

[0035] Specifically, the PLC controller 32, as the control core of the entire equipment, is responsible for coordinating the working sequence of various components. When the operator starts the test program through the control panel 2, the PLC controller 32 first controls the servo motor 46 to move, causing the pressure head 43 to descend and apply the set pressure to the powdered graphite. After the pressure stabilizes, the PLC controller 32 controls the resistance measuring instrument 31 to apply a constant current to the graphite sample through the probe socket 6 and the probe 51 and measure the voltage drop. After the measurement is completed, the PLC controller 32 feeds back the measurement data to the control panel 2 for display or further calculation. The entire testing process achieves automated control, reducing human error.

[0036] Specifically, the control panel 2 includes a display screen 21 and operation buttons 22. The display screen 21 and operation buttons 22 are both fixedly installed on the front side of the housing 1 and located on the front side of the upper working cavity 13. The display screen 21 and operation buttons 22 are both electrically connected to the PLC controller 32.

[0037] Specifically, the display screen 21 can be a touch-screen LCD, which can serve as a parameter setting interface and also display the current pressure value, current value, voltage drop, and calculated resistivity value in real time. The operation buttons 22 include a start button, a stop button, and an emergency stop button, facilitating operator control of the equipment. Furthermore, the control panel 2 is ergonomically designed, allowing operators to complete all settings and operations without bending over.

[0038] Specifically, the pressure assembly 4 includes a guide rail 41, an L-shaped slider 42, a pressure head 43, a threaded rod 44, a top plate 45, a servo motor 46, and a pressure sensor 47. A vertically arranged mounting plate 15 is fixedly connected to the bottom of the lower working chamber 14. Both the guide rail 41 and the servo motor 46 are fixedly connected to the mounting plate 15. The guide rail 41 is vertically arranged, and the servo motor 46 is located at the top of the guide rail 41. The threaded rod 44 is rotatably connected to the guide rail 41 via a bearing seat, and the top end of the threaded rod 44 is fixedly connected to the power output end of the servo motor 46. The vertical section of the L-shaped slider 42 is slidably connected to the guide rail 41. The vertical section of the L-shaped slider 42 is threadedly connected to the threaded rod 44. The pressure sensor 47 is fixedly connected to the bottom of the horizontal section of the L-shaped slider 42. The top plate 45 is located below the horizontal section of the L-shaped slider 42. Multiple adjusting screws 451 are provided above the top plate 45. The adjusting screws 451 pass through the horizontal section of the L-shaped slider 42 and are fixedly connected to the locking nut 452. The top of the top plate 45 abuts against the detection end of the pressure sensor 47. The pressure head 43 is fixedly connected to the bottom of the top plate 45. The servo motor 46 and the pressure sensor 47 are both electrically connected to the PLC controller 32.

[0039] Specifically, the pressure assembly 4 employs a servo motor 46 in conjunction with a threaded rod 44 and an L-shaped slider 42 for transmission, enabling precise control over the descent speed and position of the pressure head 43. When the servo motor 46 rotates forward, the threaded rod 44 drives the L-shaped slider 42 to slide downwards along the guide rail 41, causing the pressure head 43 to descend and apply pressure to the powdered graphite inside the sample cylinder assembly 5. The pressure sensor 47 detects the applied pressure value in real time and feeds it back to the PLC controller 32. When the set pressure of 3.9 MPa is reached, the PLC controller 32 controls the servo motor 46 to stop and maintain the current torque, thereby maintaining constant pressure.

[0040] Specifically, the adjusting screw 451 and locking nut 452 allow for fine-tuning of the relative position between the top plate 45 and the L-shaped slider 42, ensuring precise alignment of the axis of the pressure head 43 with the axis of the sample cylinder assembly 5. Furthermore, when it is necessary to replace the pressure head 43 with a different specification, simply loosen the locking nut 452 and replace the top plate 45 and the pressure head 43, facilitating disassembly and assembly by the operator.

[0041] Specifically, the slide assembly 7 includes a slide groove 71, a limiting groove 72, a slider 73, a limiting block 74, a slide top plate 75, a sealing block 76, and a rotating plunger 77. The slide groove 71 is formed at the bottom of the lower working cavity 14. The limiting grooves 72 are symmetrically formed on the two long side walls of the slide groove 71. Two limiting blocks 74 that match the limiting grooves 72 are symmetrically fixed to the left and right sides of the slider 73. An installation groove 711 for installing the slider 73 is formed at the end of the slide groove 71 away from the probe socket 6. The width of the mounting groove 711 is greater than the width of the sliding groove 71. The sealing block 76 is embedded in the mounting groove 711 and is fixedly connected to the bottom of the lower working cavity 14 by bolts. The top of the slider 73 is fixedly connected to the slide table top plate 75. The rotating plunger 77 is threaded through the slide table top plate 75, and the two rotating plungers 77 are symmetrically arranged on the left and right sides of the slide table top plate 75. The bottom of the lower working cavity 14 is provided with a locking positioning hole 78 that matches the telescopic end of the rotating plunger 77.

[0042] Specifically, the cooperation of the slide groove 71 and the slider 73 constitutes the linear motion guide mechanism of the slide assembly 7. The cooperation of the limiting groove 72 and the limiting block 74 can effectively prevent the slider 73 from shifting laterally or tipping over during sliding, ensuring the smoothness of sliding. The width of the mounting groove 711 is greater than the width of the slide groove 71. In this way, during assembly, the slider 73 can first align the limiting block 74 with the mounting groove 711 and then push it horizontally into the slide groove 71. The structure is simple and easy to disassemble and assemble.

[0043] Specifically, the rotary plunger 77 is a manually operated locking and positioning element. When the operator pushes the slide assembly 7 to the measurement position, the telescopic end of the rotary plunger 77 aligns perfectly with the locking positioning hole 78 at the bottom of the lower working chamber 14. At this point, pressing down and rotating the knob of the rotary plunger 77 allows its telescopic end to insert into the locking positioning hole 78, locking the slide assembly 7 in this position and preventing it from retracting due to pressure reaction during testing. After the test is completed, rotating and lifting the rotary plunger 77 in the opposite direction unlocks and allows the slide assembly 7 to be pulled out. Furthermore, multiple sets of locking positioning holes 78 can be set as needed to further expand its adjustment and positioning range.

[0044] Specifically, the sample tube assembly 5 further includes a sample tube body 52, a sleeve 53, and sleeve limiting bosses 54. The sample tube body 52 is configured as a tubular structure with open ends. Multiple probes 51 are connected through the tube wall of the sample tube body 52, and the test ends of the probes 51 are flush with or slightly protrude into the inner wall of the sample tube body 52. ​​The bottom of the sample tube body 52 is provided with external threads. The sleeve 53 is configured as a cup-shaped tube structure with one open end, and the outer peripheral wall of the sleeve 53 is provided with anti-slip textures 531. The sample tube body 52 is embedded in the inner cavity of the sleeve 53, and the sleeve 53 is threadedly connected to the sample tube body 52. ​​Two sleeve limiting bosses 54 are symmetrically fixedly connected to the outer peripheral wall of the sleeve 53. The top of the slide plate 75 is provided with an installation groove 751 for installing the sleeve 53. A limiting installation groove 752 is provided on the side wall of the installation groove 751. The bottom of the sleeve 53 is embedded in the installation groove 751 and is fixed on the slide plate 75 by the cooperation of the sleeve limiting boss 54 and the limiting installation groove 752.

[0045] Specifically, the sample tube assembly 5 adopts a split structure. The sample tube body 52 and the sleeve 53 are connected by threads, which is convenient for disassembly and cleaning. After the test is completed, the operator can hold the anti-slip texture 531 on the outer peripheral wall of the sleeve 53 and unscrew the sample tube body 52 out of the sleeve 53. Then, the compacted graphite sample is pushed out from the bottom of the sample tube body 52. ​​The operation is convenient and will not damage the sample tube body 52.

[0046] Specifically, four probes 51 are directly fixed to the wall of the sample cylinder body 52, with the test ends of all four probes 51 flush with or slightly protruding into the inner wall of the sample cylinder body 52 to ensure reliable contact with the powdered graphite sample. The four probes 51 are divided into two groups: the two outer probes serve as current source probes, and the two inner probes serve as voltage measurement probes. This arrangement effectively eliminates the influence of contact resistance and lead resistance on the measurement results. In practice, the probes 51 are cylindrical with smoothly rounded ends, effectively improving the flowability and filling properties of the powder during compaction and minimizing low-density voids at the probe root. During the test, continuous uniform pressure is applied while real-time monitoring of resistivity changes is conducted. With continuous pressure, powder particles are forced into the area surrounding the probes until the real-time resistivity stabilizes. This process effectively overcomes the density inhomogeneity in the initial compaction stage, ensuring a tight and stable contact between the probes and the powder, thereby guaranteeing the stability of the contact resistance. Furthermore, the inner wall of the sample tube body 52 and the probe surface are polished, and combined with the rounded corner design of the probe tip, the adhesion of powder to the inner wall and gaps is significantly reduced, making the powder easier to detach after pressure relief and avoiding the formation of dense and impossible-to-clean "permanent conductive bridges". After the test, the sample tube body 52 can be disassembled, and the probe root and gaps can be cleaned with special cleaning tools and anhydrous ethanol to thoroughly remove residual powder and avoid contamination and interference for the next test.

[0047] Specifically, the sleeve 53 is engaged with the limiting mounting groove 752 on the top plate of the slide table via the sleeve limiting boss 54. This engagement method allows the sample tube assembly 5 to be reliably positioned in the vertical direction, while also allowing it to be easily removed from the top plate of the slide table for cleaning or replacement, thus meeting the requirements for ease of operation during batch testing.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for testing the electrical conductivity of powdered graphite, characterized in that, Includes the following steps: S1. Load the powdered graphite to be tested into the sample tube assembly; S2. Apply and maintain a constant pressure to the powdered graphite inside the sample cylinder assembly using a pressure assembly to compact and shape it. S3. Make the powdered graphite come into contact with the four probes fixed on the wall of the sample tube assembly. The four probes are divided into two groups, two of which are used as current source probes and the other two are used as voltage measurement probes. S4. Apply a constant current to the powdered graphite sample through the current source probe, and measure the voltage drop on the surface of the powdered graphite sample through the voltage measurement probe. S5. Based on the applied current and the measured voltage drop, the resistivity of the powdered graphite is calculated, and then the conductivity is calculated according to σ=1 / ρ. The above steps S1-S5 are completed by configuring a powdered graphite conductivity tester, including a housing (1), a control panel (2), a control component (3), a pressure component (4), a sample tube assembly (5), a probe socket (6), and a slide assembly (7). A horizontal partition (11) is fixedly connected inside the housing (1), which divides the inner cavity of the housing (1) into an upper working chamber (13) and a lower working chamber (14). The control component (3) is located in the upper working chamber (13), the slide assembly (7) is located at the bottom of the lower working chamber (14), the sample tube assembly (5) is snapped onto the top of the slide assembly (7), the probe socket (6) is located at the bottom of the lower working chamber (14) and is located at one end of the sliding direction of the slide assembly (7), and the pressure component (4) is located at the bottom of the lower working chamber (14). The working end of the pressure component (4) is located above the sample tube assembly (5) and is positioned within the lower working chamber (14) and on the long side of the slide assembly (7). It is used to pressurize the powdered graphite inside the sample tube assembly (5). Multiple probes (51) are radially arranged on the wall of the sample tube assembly (5). One end of the probe (51) is flush with or slightly protrudes into the inner wall of the sample tube assembly (5) and is used to contact the powdered graphite. The other end of the probe (51) is located outside the sample tube assembly (5) and is used to connect with the probe socket (6) after the slide assembly (7) slides into place. The control panel (2) is embedded in the front side of the housing (1), and the control panel (2), pressure component (4), and probe socket (6) are all electrically connected to the control component (3).

2. The method for testing the electrical conductivity of powdered graphite according to claim 1, characterized in that: In S2, the constant pressure is set to 3.9 MPa ± 0.03 MPa.

3. The method for testing the electrical conductivity of powdered graphite according to claim 1, characterized in that: In S4, the constant current is set to 500mA±0.1mA.

4. The method for testing the electrical conductivity of powdered graphite according to claim 1, characterized in that: The box body (1) also includes a box door (12), which is hinged to the opening side of the lower working chamber (14), and a transparent observation window (121) is provided on the box door (12).

5. The method for testing the electrical conductivity of powdered graphite according to claim 1, characterized in that: The control component (3) includes a resistance meter (31) and a PLC controller (32). The probe socket (6) is electrically connected to the resistance meter (31) via a wire. The resistance meter (31), the control panel (2), and the pressure component (4) are all electrically connected to the PLC controller (32).

6. The method for testing the electrical conductivity of powdered graphite according to claim 5, characterized in that: The control panel (2) includes a display screen (21) and operation buttons (22). The display screen (21) and operation buttons (22) are both fixedly installed on the front side of the housing (1) and located on the front side of the upper working cavity (13). The display screen (21) and operation buttons (22) are both electrically connected to the PLC controller (32).

7. The method for testing the electrical conductivity of powdered graphite according to claim 5, characterized in that: The pressure assembly (4) includes a guide rail (41), an L-shaped slider (42), a pressure head (43), a threaded rod (44), a top plate (45), a servo motor (46), and a pressure sensor (47). A vertically arranged mounting plate (15) is fixedly connected to the bottom of the lower working chamber (14). The guide rail (41) and the servo motor (46) are both fixedly connected to the mounting plate (15). The guide rail (41) is vertically arranged, and the servo motor (46) is located at the top of the guide rail (41). The threaded rod (44) is rotatably connected to the guide rail (41) through a bearing seat, and the top end of the threaded rod (44) is fixedly connected to the power output end of the servo motor (46). The vertical section of the L-shaped slider (42) slides along the guide rail (41). The vertical section of the L-shaped slider (42) is threadedly connected to the threaded rod (44). The pressure sensor (47) is fixedly connected to the bottom of the horizontal section of the L-shaped slider (42). The top plate (45) is located below the horizontal section of the L-shaped slider (42). Multiple adjusting screws (451) are provided above the top plate (45). The adjusting screws (451) pass through the horizontal section of the L-shaped slider (42) and are fixedly connected to the locking nut (452). The top of the top plate (45) abuts against the detection end of the pressure sensor (47). The pressure head (43) is fixedly connected to the bottom of the top plate (45). The servo motor (46) and the pressure sensor (47) are both electrically connected to the PLC controller (32).

8. The method for testing the electrical conductivity of powdered graphite according to claim 1, characterized in that: The slide assembly (7) includes a slide groove (71), a limiting groove (72), a slider (73), a limiting block (74), a slide top plate (75), a sealing block (76), and a rotating plunger (77). The slide groove (71) is provided at the bottom of the lower working chamber (14). The limiting groove (72) is symmetrically provided on the two long side walls of the slide groove (71). Two limiting blocks (74) that match the limiting groove (72) are symmetrically fixedly connected to the left and right sides of the slider (73). An installation groove (74) for installing the slider (73) is provided at the end of the slide groove (71) away from the probe socket (6). 11) The width of the mounting groove (711) is greater than the width of the sliding groove (71). The sealing block (76) is embedded in the mounting groove (711) and fixedly connected to the bottom of the lower working cavity (14) by bolts. The top of the slider (73) is fixedly connected to the slide plate (75). The rotating plunger (77) is threaded through the slide plate (75), and the two rotating plungers (77) are symmetrically arranged on the left and right sides of the slide plate (75). The bottom of the lower working cavity (14) is provided with a locking positioning hole (78) that matches the telescopic end of the rotating plunger (77).

9. The method for testing the electrical conductivity of powdered graphite according to claim 8, characterized in that: The sample tube assembly (5) further includes a sample tube body (52), a sleeve (53), and a sleeve limiting boss (54). The sample tube body (52) is configured as a tubular structure with open ends. Multiple probes (51) are connected through the tube wall of the sample tube body (52), and the test end of the probe (51) is flush with or slightly protrudes into the inner wall of the sample tube body (52). The bottom of the sample tube body (52) is provided with an external thread. The sleeve (53) is configured as a cup-shaped tube structure with one end open, and the outer peripheral wall of the sleeve (53) is provided with anti-slip texture (531). The sample tube body (52) is embedded in the inner cavity of the sleeve (53), and the sleeve (53) is threadedly connected to the sample tube body (52). Two sleeve limiting bosses (54) are symmetrically fixedly connected to the outer peripheral wall of the sleeve (53). The top of the slide plate (75) is provided with an installation groove (751) for installing the sleeve (53). A limiting installation groove (752) is provided on the side wall of the installation groove (751). The bottom of the sleeve (53) is embedded in the installation groove (751) and is fixed on the slide plate (75) by the engagement of the sleeve limiting boss (54) and the limiting installation groove (752).

Images