A brinell hardness tester

Abstract

This application relates to the field of materials mechanical property testing instruments, and discloses a Brinell hardness tester, including a base and a cantilever fixedly connected to one side of the base. A support module is provided in the middle of the base for supporting the test sample. A hollow main optical path tube is passed through and fixedly connected to the center of the top of the cantilever. The hollow main optical path tube is located above the support module, and the centers of both are on the same axis. An optical measurement channel is formed inside the hollow main optical path tube, running vertically through it. An optical imaging system is provided at the top of the optical measurement channel, and a switching unit is provided at the bottom of the hollow main optical path tube. A pressure head is located at the bottom of the switching unit, and the switching unit drives the pressure head to enter or exit the optical measurement channel. By physically folding the optical measurement channel and the heavy-duty pressure channel along the Z-axis in space, zero Abbe error optical-mechanical coaxial absolute static in-situ measurement is achieved, completely eliminating the guide rail clearance and coordinate cumulative tolerance caused by macroscopic translation.

Description

Technical Field

[0001] This invention relates to the field of instruments for testing the mechanical properties of materials, specifically a Brinell hardness tester. Background Technology

[0002] The Brinell hardness test, a classic physical method for evaluating the macroscopic mechanical properties of metallic materials, relies on the core mechanism of pressing a cemented carbide indenter into the sample surface under a very high vertical load, followed by precise measurement of the geometric dimensions of the indentation left after plastic deformation using a microscopic optical system. This fundamental testing principle introduces an inherent topological interference contradiction in the spatial structure design of the equipment: forcing the indenter to penetrate the sample requires the presence of a solid metal load-bearing structure with extremely high yield strength and shear resistance directly above it; while obtaining a high-resolution, unobstructed, and distortion-free indentation image strictly requires that this coaxial region be a vertically continuous transparent optical corridor.

[0003] To circumvent the physical conflict between mechanical solidity and optical hollowness, traditional Brinell hardness testers generally rely on the spatiotemporal switching of macroscopic mechanical components. In conventional engineering practice, mainstream solutions often employ a top mechanical turret to alternately screw in the indenter and objective lens, or a bottom cross slide to forcibly shift the working base supporting the heavy sample. However, this compromise design, relying on long-stroke physical displacement, inevitably disrupts the static environmental closed loop necessary for high-precision measurement. The dynamic meshing clearance of the gears and the micro-fit tolerance of the guide rails are continuously accumulated and geometrically amplified during repeated alternations at the workstation, directly inducing Abbe error that disrupts the equipment's positioning reference. This error causes unpredictable coordinate misalignment between the physical origin of the indentation action and the center of the microscope's field of view, forcing operators to perform tedious secondary manual focusing after each indentation and introducing a systematic parallax that is difficult to eliminate. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a Brinell hardness tester that solves the problem of Abbe measurement error that is inevitably introduced by traditional equipment due to its reliance on external macroscopic mechanical displacement to switch the optomechanical station.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a Brinell hardness tester includes a base and a cantilever fixedly connected to one side of the base. A support module is provided in the middle of the base for supporting the test sample. A hollow main optical path tube is passed through and fixedly connected to the center of the top of the cantilever. The hollow main optical path tube is located above the support module, and the centers of both are on the same axis. An optical measurement channel is formed inside the hollow main optical path tube, and an optical imaging system is provided at the top of the optical measurement channel. A switching unit is provided at the bottom of the hollow main optical path tube. A pressure head is provided at the bottom, which is driven to enter or exit the optical measurement channel by a switching unit. A splicing load transfer unit is provided in the middle of the hollow main optical path cylinder, which is used to transfer the load provided by the hydraulic cylinder to the switching unit. During the pressing test stage, the switching unit enters the optical measurement channel, and the splicing load transfer unit is spliced ​​at the center above the switching unit to receive and vertically transfer the downward test load to the switching unit. During the optical measurement stage, the splicing load transfer unit separates to both sides, and the switching unit exits the optical measurement channel laterally to ensure that the vertical downward optical path of the optical imaging system is unobstructed.

[0006] Preferably, the switching unit includes a limiting sleeve, which is fitted and slidably connected to the bottom outer wall of the hollow main optical path cylinder, and the top of the limiting sleeve is connected to the top of the cantilever by a return spring. The bottom of the limiting sleeve extends along the X-axis to form a relief cavity. A slide rail is provided at the bottom of the limiting sleeve, and a pressure block is suspended and slidably connected on the slide rail. A first electric push rod is fixedly connected to the side of the limiting sleeve facing the relief cavity. The output end of the first electric push rod is connected to the side wall of the pressure block by a flexible spring. The center of the bottom wall of the pressure block is fixedly connected to the top of the pressure head. After the test load is removed, the elastic force of the return spring drives the limiting sleeve and the pressure block to rise as a whole, so that the pressure head is vertically pulled out of the test sample and suspended in the air, so as to avoid physical scratching of the test sample surface when the pressure head exits the optical measurement channel laterally.

[0007] Preferably, the top of the pressure block has an inverted conical structure facing away from the bottom of the pressure block, and an LED light source array is provided on the side of the inverted conical structure opposite to the relief cavity. The LED light source array is projected onto the surface of the test sample at an oblique angle through the reflector bowl structure, so that the pressure block in the relief state can be reused as a dark field auxiliary illumination base for the optical imaging system.

[0008] Preferably, the assembled load transfer unit includes two symmetrically arranged load blocks. The load blocks are slidably disposed in the middle of the hollow main optical path cylinder. A vertical first T-shaped groove is formed on the side wall of the load block away from the assembly center. Two second electric push rods are correspondingly arranged on the outside of the hollow main optical path cylinder. A semi-circular block is fixedly connected to the output end of the second electric push rod. The semi-circular block is attached to the outer arc surface of the load block. A first T-shaped protrusion is fixedly connected to the inner arc surface of the semi-circular block. The first T-shaped protrusion is inserted into and slidably connected in the first T-shaped groove. The two load blocks are synchronously driven to laterally assemble or disassemble by the two second electric push rods. When the two load blocks are laterally assembled and bear the load force provided by the hydraulic cylinder, the load blocks slide vertically along the optical measurement channel, and the first T-shaped groove slides along the stationary first T-shaped protrusion to eliminate the vertical shear force on the second electric push rod.

[0009] Preferably, the top wall of the pressure block is fixedly connected with three hemispherical positioning buttons arranged in a circular array. On the bottom surface formed after the two load blocks are joined together, three inverted V-shaped grooves are machined, each corresponding to one of the hemispherical positioning buttons. When subjected to test load, the inverted V-shaped grooves press down on the hemispherical positioning buttons, and the tangential component force generated by the inclined plane forces the pressure block to perform spatial attitude fine-tuning and centering, so that the pressure block adaptively locks into a rigid body state with six degrees of freedom constraints to prevent force deflection.

[0010] Preferably, the inner edges of the two load blocks that are joined together are machined into acute-angled cutting edge sections, and the surface of the acute-angled cutting edge sections is sprayed with an anti-light-diffusing coating to suppress diffuse reflection of light. During the optical measurement stage, the two load blocks are controlled to hover at a specific distance of the pull-out stroke to both sides. The acute-angled cutting edge sections of the two load blocks are suspended opposite each other, forming a slit variable aperture in front of the optical imaging system. The effective light-transmitting aperture is controlled by dynamically adjusting the specific distance and the optical depth of focus of the optical imaging system is increased.

[0011] Preferably, the hydraulic cylinder is fixedly connected to the top of the hollow main optical path cylinder by a bracket, and the hydraulic cylinder is located above the optical imaging system. The output end of the hydraulic cylinder passes through the bracket and is fixedly connected to an inverted U-shaped extension frame. The two parallel forked rods of the inverted U-shaped extension frame are distributed on both sides of the optical imaging system and extend downward to the load block. The bottom end of the forked rod is fixedly connected to a second T-shaped protrusion, which is embedded and slidably connected in the second T-shaped groove opened on the top of the load block. At the same time, the rod body of the forked rod is embedded and slidably connected in the annular wall of the optical measurement channel. The hydraulic cylinder outputs load to the load block through the inverted U-shaped extension frame and drives the load block to move axially along the optical measurement channel.

[0012] Preferably, the bearing module includes a trapezoidal lifting screw, the bottom of which is fixedly connected to the base, and a guide sleeve is sleeved and threadedly connected to its output end. The outer wall of the guide sleeve is slidably connected to a through hole in the upper part of the base, and a hardness testing anvil is fixedly connected to the top of the guide sleeve.

[0013] This invention provides a Brinell hardness tester. It has the following beneficial effects: 1. This invention achieves zero Abbe error optical-mechanical coaxial absolute static in-situ measurement by physically folding the optical measurement channel and the heavy-duty pressure channel along the Z-axis in space. It breaks through the conventional architecture of traditional Brinell hardness testers that rely on mechanical turrets or sample translation stages for station switching. Throughout the entire indentation and image acquisition cycle, the optical imaging system and the trapezoidal lifting screw reference supporting the sample at the bottom maintain an absolute static closed loop, completely eliminating guide rail clearance and coordinate accumulation tolerances caused by macroscopic translation. This ensures that the physical origin of the indentation action perfectly coincides with the optical center of the microscopic field of view, eliminating the need for tedious secondary manual focusing.

[0014] 2. Addressing the kinematic challenge of lateral yielding components easily overturning under heavy pressure, this invention takes a reverse approach. A passive constraint interface, consisting of a hemispherical positioning button and an inverted V-groove, is introduced between the pressure block and the load block. At the instant of the vertical hydraulic pressure limit, the extreme downward pressure is forcibly converted into a corrective tangential force through the inclined plane. This forces the pressure block, suspended on the slide rail, to overcome the flexible spring and mechanical clearance, undergoing lateral fine-tuning and instantly locking into a rigid body with six degrees of freedom. This ensures the ideal trajectory of the indenter penetrating the sample vertically and the roundness of the high-pressure mark. Simultaneously, considering the high risk of fatal shear interference between the load block and the drive mechanism during longitudinal downward pressure application and lateral separation, this invention precisely designs mutually perpendicular T-shaped sliding networks on the sidewalls and top of the load block. When the load block, under heavy load, sinks vertically along the optical path, the lateral first T-shaped groove slides smoothly down only along the stationary transverse electric push rod protrusion, completely detaching the devastating vertical pressure from the horizontal actuator and protecting the fragile precision linear drive components from shear breakage. Furthermore, traditional internal translational avoidance schemes often result in direct lateral sliding after unloading, causing the indenter, deeply embedded in the plastic deformation pit of the sample, to tear the material surface. This invention suspends the entire limiting sleeve on a cantilever using a return spring. At the moment the hydraulic cylinder depressurizes and retracts, the accumulated spring potential energy is violently released, vertically lifting the pressure block along with the bottom indenter and suspending it in the air. Then, the first electric push rod smoothly pulls it back to the side retraction cavity, preserving the true three-dimensional morphology of the indentation and eliminating the risk of equipment jamming.

[0015] 3. This invention, through the cooperation of a combined load transfer unit and a switching unit, breaks through the physical limitations of simple load-bearing and realizes the cross-domain reuse of heavy machinery load-bearing entities into precision optical control units. During unloading and separation, the load block suspended at a specific interval utilizes the sharp-angled cutting edge section coated with matte material on its inner side to directly reconstruct a slit variable aperture in front of the optical imaging system, dynamically adjusting the light-transmitting aperture and cutting stray light through physical blocking; while the pressure block retreating into the dark chamber utilizes an LED light source array to obliquely emit LED beams, transforming itself into a coaxial dark field illumination base, completing the closed-loop functional reconstruction of heavy mechanical components in a microscopic optical environment. Attached Figure Description

[0016] Figure 1 This is a perspective view of the present invention; Figure 2 This is a schematic diagram of the internal structure of the hollow main optical path tube in this invention; Figure 3 for Figure 2 Enlarged view of point A in the middle; Figure 4 This is a three-dimensional schematic diagram of the pressure block in this invention; Figure 5 This is a top-view perspective view of the load block in this invention; Figure 6 This is a bottom-view perspective view of the load block in this invention; Figure 7 This is a schematic diagram of the internal structure of the load block in this invention.

[0017] The components include: 1. Base; 2. Cantilever; 3. Load-bearing module; 301. Trapezoidal lifting screw; 302. Guide sleeve; 303. Hardness testing anvil; 4. Hollow main optical path cylinder; 401. Optical measurement channel; 5. Switching unit; 501. Limiting sleeve; 502. Return spring; 503. Slide rail; 504. Pressure block; 505. First electric push rod; 506. Flexible spring; 507. Hemispherical positioning button; 6. Pressure head; 7. Assembled load transfer unit; 701. Load block; 702. First T-shaped groove; 703. Second electric push rod; 704. Semi-arc block; 705. First T-shaped protrusion; 706. Inverted V-shaped groove; 707. Second T-shaped groove; 8. Optical imaging system; 9. Hydraulic cylinder; 10. Bracket; 11. Inverted U-shaped extension frame; 1101. Second T-shaped protrusion. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see the appendix Figure 1 - Appendix Figure 7 This invention provides a Brinell hardness tester, including a base 1 and a cantilever 2 fixedly connected to one side of the base 1. A support module 3 is provided in the middle of the base 1 for supporting the test sample. A hollow main optical path tube 4 is fixedly connected through and to the top center of the cantilever 2. The hollow main optical path tube 4 is located above the support module 3, and the centers of the two are on the same axis. An optical measurement channel 401 is formed inside the hollow main optical path tube 4, which is vertically connected. An optical imaging system 8 is provided at the top of the optical measurement channel 401. A switching unit 5 is provided at the bottom of the hollow main optical path tube 4, and a pressure head 6 is provided at the bottom end of the switching unit 5. The drive head 6 of the element 5 enters or exits the optical measurement channel 401. A splicing load transfer unit 7 is provided in the middle of the hollow main optical path cylinder 4, which is used to transfer the load provided by the hydraulic cylinder 9 to the switching unit 5. During the press-in test stage, the switching unit 5 enters the optical measurement channel 401. The splicing load transfer unit 7 is spliced ​​at the center above the switching unit 5 to receive and vertically transfer the downward test load to the switching unit 5. During the optical measurement stage, the splicing load transfer unit 7 separates to both sides, and the switching unit 5 exits the optical measurement channel 401 laterally so that the vertical downward optical path of the optical imaging system 8 is unobstructed.

[0020] The load-bearing module 3 includes a trapezoidal lifting screw 301. The bottom of the trapezoidal lifting screw 301 is fixedly connected to the base 1. Its output end is fitted with and threadedly connected to a guide sleeve 302. The outer wall of the guide sleeve 302 is slidably connected to the through hole in the upper part of the base 1. The top of the guide sleeve 302 is fixedly connected to a hardness testing anvil 303.

[0021] In this embodiment, the base 1 serves as the ground bearing reference for the entire device, and a sturdy cantilever 2 is vertically and fixedly connected to one side of its top. The top of the cantilever 2 extends horizontally outward and extends directly above the central area of ​​the base 1.

[0022] At the center of the top of the outward-extending cantilever 2, a hollow main optical path tube 4 is rigidly and permanently fixed. The hollow main optical path tube 4 is a high-strength metal cylindrical tube with a large wall thickness, and an optical measurement channel 401 that is completely open from top to bottom is opened inside. The central axis of the hollow main optical path tube 4 is defined as the absolute principal axis of the Benn Brinell hardness tester, i.e., the Z-axis.

[0023] The optical imaging system 8 is mounted on the top end face of the hollow main optical path tube 4. The optical imaging system 8 includes a downward-looking microscope objective lens group and an image sensor, and the optical observation axis of its lens is completely coincident with the absolute principal axis of the hollow main optical path tube 4. Throughout the entire hardness indentation and optical measurement cycle, the hollow main optical path tube 4, together with the optical imaging system 8, remains absolutely physically stationary relative to the base 1, without any macroscopic translation or deflection.

[0024] At the center of the base 1, directly below the hollow main optical path tube 4, a support module 3 is vertically installed upwards. The center of the support module 3 is also strictly aligned with the aforementioned absolute main axis, used to stably support the test sample and provide vertical support reaction force from bottom to top.

[0025] The internal structure of the bearing module 3 includes a trapezoidal lifting screw 301, a guide sleeve 302, and a hardness testing anvil 303. The threaded output end of the trapezoidal lifting screw 301 extends upward, and the guide sleeve 302 is externally sleeved and threadedly connected to it. A handwheel is fixedly connected to the input end of the trapezoidal lifting screw 301, and rotating the handwheel drives the guide sleeve 302 to move up and down. The outer wall of the guide sleeve 302 slides in fit with a vertical through hole opened on the upper part of the base 1 to restrict the guide sleeve 302 from rotating circumferentially, ensuring that it can only move in a pure linear motion along the absolute principal axis. The hardness testing anvil 303 is rigidly fixedly connected to the top of the guide sleeve 302. The hardness testing anvil 303 is a cylindrical, thick alloy steel anvil seat that has been surface hardened and precision ground. Its top surface is an absolutely flat horizontal force-bearing surface, on which the sample to be tested is placed.

[0026] During the test preparation phase, the guide sleeve 302 and the top hardness testing anvil 303 are driven to move vertically along the Z-axis by rotating the trapezoidal lifting screw 301. This lifting action not only accommodates test samples with different geometric thicknesses, but also ensures that the upper surface of the sample can accurately enter the preset depth of focus range of the main optical imaging system 8, which is fixed at the top, thereby completing the initial optical focusing at the bearing reference end.

[0027] The switching unit 5 includes a limiting sleeve 501, which is sleeved and slidably connected to the bottom outer wall of the hollow main optical path cylinder 4. The top end of the limiting sleeve 501 is connected to the top end of the cantilever 2 by a return spring 502. The bottom of the limiting sleeve 501 extends along the X-axis to form a relief cavity. A slide rail 503 is provided at the bottom of the limiting sleeve 501. A pressure block 504 is suspended and slidably connected on the slide rail 503. A first [unclear] is fixedly connected to the side of the limiting sleeve 501 facing the relief cavity. The output end of the electric push rod 505 is connected to the side wall of the pressure block 504 via a flexible spring 506. The bottom center of the pressure block 504 is fixedly connected to the top of the pressure head 6. After the test load is removed, the elastic force of the return spring 502 drives the limiting sleeve 501 and the pressure block 504 to rise as a whole, so that the pressure head 6 is vertically pulled out of the test sample and suspended in the air, so as to avoid physical scratching of the test sample surface when the pressure head 6 exits the optical measurement channel 401 laterally.

[0028] The top of the pressure block 504 is an inverted cone structure facing away from the bottom of the pressure block 504. An LED light source array is provided on the side of the inverted cone structure opposite to the relief cavity. The LED light source array is projected onto the surface of the test sample at an oblique angle through the reflector bowl structure, so that the pressure block 504 in the relief state can be reused as the dark field auxiliary illumination base of the optical imaging system 8.

[0029] The top wall of the pressure block 504 is fixedly connected to three hemispherical positioning buttons 507 arranged in a circular array. On the bottom surface formed by the two load blocks 701 after being assembled, there are three inverted V-shaped grooves 706 that correspond one-to-one with the positions of the hemispherical positioning buttons 507. When subjected to test load, the inverted V-shaped grooves 706 press down on the hemispherical positioning buttons 507. The tangential component force generated by the inclined plane forces the pressure block 504 to perform spatial attitude fine adjustment and centering, so that the pressure block 504 adaptively locks into a rigid body state with six degrees of freedom constraints to prevent force deflection.

[0030] In this embodiment, the implementation details of the switching unit 5, which is arranged at the bottom of the hollow main optical path tube 4 and has a Z-axis flexible avoidance and dark field illumination multiplexing mechanism, are described in detail.

[0031] The limiting sleeve 501 is fitted onto the bottom outer wall of the hollow main optical path cylinder 4 with a precision clearance sliding fit, allowing the limiting sleeve 501 to slide up and down relative to the hollow main optical path cylinder 4 along the vertical Z-axis. The top outer edge of the limiting sleeve 501 is suspended upwards and connected to the top of the cantilever 2 via a return spring 502. In the initial state without external test load, the tension of the return spring 502 holds the limiting sleeve 501 at its highest upper limit.

[0032] The lower half of the limiting sleeve 501 extends outward along the horizontal X-axis, forming a hollow recess. A slide rail 503 is horizontally fixed along the X-axis on the inner wall plane of the bottom of the limiting sleeve 501. One end of the slide rail 503 is located directly below the optical measurement channel 401, and the other end extends outward into the recess.

[0033] The pressure block 504 is a high-strength rigid metal block that is suspended and slidably connected to the slide rail 503 via a slider structure at its bottom. The pressure block 504 can move horizontally along the slide rail 503, thereby cutting in and out back and forth between the optical measurement channel 401 directly below and the side relief cavity.

[0034] The spherical indenter 6, made of hard alloy, is rigidly fixed to the center of the bottom wall of the pressure block 504, and the bottom of the indenter 6 protrudes downward and is exposed to the external space for direct contact and penetration of the test sample below.

[0035] On the top load-bearing plane of the pressure block 504, three hemispherical positioning buttons 507 are protruding upwards and rigidly fixedly connected. These three hemispherical positioning buttons 507 are evenly distributed in a circular array with the center of the top surface of the pressure block 504 as the origin, forming the lower physical support point to bear the extreme load above and achieve microscopic centering.

[0036] To drive the lateral translation of the pressure block 504, a first electric push rod 505 is fixedly installed on the outer wall of the limiting sleeve 501 facing the retraction cavity. The actuation direction of the first electric push rod 505 is parallel to the X-axis. The output end of the first electric push rod 505 extends inward into the retraction cavity and is horizontally connected to the side wall of the pressure block 504 via a flexible spring 506.

[0037] The flexible spring 506 serves as the horizontal force transmission medium between the power source and the load, converting the rigid telescopic displacement of the first electric push rod 505 into a flexible push-pull force that drives the pressure block 504 to slide along the slide rail 503. This flexible connection design allows for compensation of minor lateral backlash that occurs during the pressure positioning process of the pressure block 504, without causing rigid tension on the linear push rod structure.

[0038] In addition to the three hemispherical positioning buttons 507 mentioned above, the top geometry of the pressure block 504 is recessed downwards into an inverted conical structure. An LED light source array is embedded on the inner inclined wall of this inverted conical structure, specifically on the half of the sidewall facing away from the recessed cavity and towards the center of the optical path. This structure has a reflector bowl. When the pressure block 504 slides outwards into the recessed cavity, the inverted conical structure moves to the side and below the optical measurement channel 401. At this time, the LED light source array is illuminated, and the beam, through the geometric refraction of the reflector bowl, is accurately projected from the side at an oblique angle onto the indentation area of ​​the sample surface below, providing a coaxial and shadowless dark-field auxiliary illumination environment for the optical imaging system 8 to extract the edge contour of the indentation.

[0039] The assembled load transfer unit 7 includes two symmetrically arranged load blocks 701. The load blocks 701 are slidably disposed in the middle of the hollow main optical path cylinder 4. A vertical first T-shaped groove 702 is formed on the side wall of the load block 701 away from the assembly center. Two second electric push rods 703 are correspondingly arranged on the outside of the hollow main optical path cylinder 4. A semi-arc block 704 is fixedly connected to the output end of the second electric push rod 703. The semi-arc block 704 is attached to the outer arc surface of the load block 701, and the inner arc surface of the semi-arc block 704 is fixedly connected to... A first T-shaped protrusion 705 is attached, which is inserted into and slidably connected in a first T-shaped groove 702. Two load blocks 701 are driven to laterally assemble or disassemble by two second electric push rods 703. When the two load blocks 701 are laterally assembled and bear the load force provided by the hydraulic cylinder 9, the load blocks 701 slide vertically along the optical measurement channel 401, and the first T-shaped groove 702 slides along the stationary first T-shaped protrusion 705 to eliminate the vertical shear force on the second electric push rods 703.

[0040] The inner edges of the two load blocks 701 that are joined together are machined into acute-angled cutting edge sections, and the surface of the acute-angled cutting edge sections is sprayed with an anti-light-diffusing coating to suppress diffuse reflection of light. During the optical measurement stage, the two load blocks 701 are controlled to hover at a specific distance of the pull-out stroke to both sides. The acute-angled cutting edge sections of the two load blocks 701 are suspended opposite each other, forming a slit variable aperture in front of the optical imaging system 8. The effective light-transmitting aperture is controlled by dynamically adjusting the specific distance and increasing the optical depth of focus of the optical imaging system 8.

[0041] The hydraulic cylinder 9 is fixedly connected to the top of the hollow main optical path cylinder 4 via the bracket 10, and the hydraulic cylinder 9 is located above the optical imaging system 8. The output end of the hydraulic cylinder 9 passes through the bracket 10 and is fixedly connected to an inverted U-shaped extension frame 11. Two parallel forked rods of the inverted U-shaped extension frame 11 are distributed on both sides of the optical imaging system 8 and extend downward to the load block 701. The bottom end of the forked rod is fixedly connected to a second T-shaped protrusion 1101, which is embedded and slidably connected in the second T-shaped groove 707 opened on the top of the load block 701. At the same time, the rod body of the forked rod is embedded and slidably connected in the annular wall of the optical measurement channel 401. The hydraulic cylinder 9 outputs load to the load block 701 through the inverted U-shaped extension frame 11 and drives the load block 701 to move axially along the optical measurement channel 401.

[0042] In this embodiment, the implementation details of the combined load transfer unit 7 and the hydraulic cylinder 9 loading assembly located in the middle and top of the hollow main optical path cylinder 4 are described in detail. This part of the structure realizes the orthogonal decoupling and safe load transmission of the system in the vertical downward pressure and lateral separation states.

[0043] The hydraulic cylinder 9 serves as the power source for outputting large vertical loads. Its outer cylinder body is vertically fixed to the outer top of the hollow main optical path cylinder 4 via a rigid bracket 10. The overall physical position of the hydraulic cylinder 9 is raised and suspended in the space above the top optical imaging system 8, without obstructing the downward field of view of the optical imaging system 8.

[0044] The piston output end of the downward-moving hydraulic cylinder 9 passes through the main body of the bracket 10 and, after avoiding the optical lens assembly, is fixedly connected to an inverted U-shaped extension bracket 11. The upper crossbeam of the inverted U-shaped extension bracket 11 is located outside the optical path, and two parallel bifurcated rods extend vertically downward from its two ends. These two bifurcated rods are respectively distributed on the left and right sides of the optical imaging system 8 and penetrate downward into the interior of the hollow main optical path cylinder 4.

[0045] The longitudinal long rod of the forked rod is embedded and vertically slidably connected in the annular inner wall of the optical measurement channel 401. The guiding effect of the inner wall ensures that the thrust output by the hydraulic cylinder 9 is strictly transmitted vertically downward along the Z-axis, eliminating lateral instability bending moment.

[0046] The modular load transfer unit 7 is located directly below the two forked rods, and its core consists of two absolutely symmetrical thick metal load blocks 701. The two load blocks 701 are in a horizontal orientation and are slidably installed in the side wall guide opening in the middle section of the hollow main optical path cylinder 4.

[0047] The two load blocks 701 can slide towards each other along the horizontal X-axis to the center of the optical path to form a solid metal frustum, or slide away from each other to be removed from the center of the optical path. On the bottom end face of the two downward-extending forked rods, a second T-shaped protrusion 1101 is integrally machined downward.

[0048] On the flat top force-bearing planes of each of the two load blocks 701, a second T-shaped groove 707 is horizontally formed along the lateral sliding direction. The second T-shaped protrusion 1101 is inserted from above and slidably connected to the corresponding second T-shaped groove 707. This top sliding engagement structure transmits the downward vertical thrust of the hydraulic cylinder 9 to the load block 701, while allowing the second T-shaped groove 707 to smoothly move along the second T-shaped protrusion 1101 without lateral displacement when the load blocks 701 are horizontally slid together or separated on the bottom surface, thus achieving upper kinematic decoupling between the vertical power source and the lateral moving part.

[0049] On the bottom surface of the complete solid formed by the relative splicing of the two load blocks 701, three upward-recessed inverted V-shaped grooves 706 are precisely machined. The spatial coordinates of these three inverted V-shaped grooves 706 correspond one-to-one with the geometric array positions of the three hemispherical positioning buttons 507 on the top of the aforementioned pressure block 504, forming a rigid contact interface that accepts heavy loads and induces the bottom pressure block 504 to achieve microscopic orientation alignment.

[0050] To drive the lateral displacement of the two load blocks 701, two second electric push rods 703 are symmetrically fixedly installed on the outside of both sides of the hollow main optical path cylinder 4. The horizontal output end of the second electric push rod 703 is fixedly connected to a concave semi-arc block 704, and the inner arc surface of the semi-arc block 704 is closely attached to the outer arc surface exposed by each load block 701.

[0051] At the center of the inner arc surface of the semi-arc block 704, a first T-shaped protrusion 705 is fixedly connected. Correspondingly, on the outer end wall of each load block 701 away from the assembly center, a first T-shaped groove 702 is formed vertically along the Z-axis. The first T-shaped protrusion 705 is inserted into and slidably connected within the first T-shaped groove 702 from the side.

[0052] The inner edges of the two opposing load blocks 701 are both machined into beveled, acute-angled cutting edges. On the metal surface of this acute-angled cutting edge, a micro-nano level high-absorption matting coating is sprayed using physical vapor deposition or chemical blackening processes. This coating suppresses diffuse reflection and diffraction of light at the beveled edge of the metal surface, forming a solid light-shielding boundary for the variable aperture subsequently used to adjust the light-passing aperture of the optical measurement channel 401.

[0053] In this embodiment, the multi-module collaborative dynamic timing of the Brinell hardness tester during the entire in-situ testing and measurement cycle, as well as the alternating reconstruction process of the mechanical and optical channels, are described in detail.

[0054] In the initial stage of testing, the test sample is placed horizontally on top of the hardness testing anvil 303. The trapezoidal lifting screw 301 is rotated by turning the handwheel to drive the power mechanism inside the base 1. As the trapezoidal lifting screw 301 rotates, the guide sleeve 302 drives the hardness testing anvil 303 and the test sample carried above it to rise vertically along the absolute principal axis.

[0055] During the vertical ascent, the optical imaging system 8, fixed at the top, continuously acquires images of the test sample surface. When the sample surface reaches the preset clear depth of focus range of the optical imaging system 8, the rotation of the trapezoidal lifting screw 301 stops, completing the non-contact macroscopic pre-focusing based on the optical visual focus. The trapezoidal lifting screw 301 is then locked by an external mechanical mechanism, establishing the bottom bearing reference. Throughout the subsequent operation cycle, the Z-axis distance between the test sample and the top optical imaging system 8 is permanently fixed.

[0056] Upon entering the mechanical cutting and preparation phase, the first electric push rod 505 extends, pushing the pressure block 504 along the slide rail 503 out of the retraction cavity and into the center position directly below the optical measurement channel 401. Simultaneously, the second electric push rods 703 on both sides extend synchronously, pushing the outer semi-circular block 704. The first T-shaped protrusion 705 on the semi-circular block 704 abuts against the first T-shaped groove 702, driving the two load blocks 701 to slide towards the center, and completing the solid assembly directly above the pressure block 504.

[0057] During the core heavy-load pressing and fine-tuning alignment stage, the top hydraulic cylinder 9 outputs working hydraulic pressure downwards, driving the inverted U-shaped extension frame 11 to descend vertically along the inner wall of the optical measurement channel 401. The second T-shaped protrusion 1101 at the bottom of the inverted U-shaped extension frame 11 presses down on the second T-shaped groove 707, applying the ultimate vertical test load to the top of the assembled load block 701.

[0058] The load block 701 moves downward under pressure, and the three inverted V-grooves 706 at its bottom contact and press against the three hemispherical positioning buttons 507 on the top of the lower pressure block 504. As the downward pressure increases sharply, a large normal force and tangential force are generated between the inclined surface of the inverted V-grooves 706 and the hemispherical surface. This tangential force forces the pressure block 504, which is suspended on the slide rail 503, to overcome the initial assembly clearance and the slight deformation of the flexible spring 506, resulting in horizontal micro-slippage and tilt self-correction.

[0059] The moment the three hemispherical positioning buttons 507 are absolutely pressed in and engaged at the bottom of the inverted V-groove 706, the pressure block 504 loses all its movement clearance and is forcibly constrained into a rigid body with zero spatial degrees of freedom. Subsequently, the downward heavy load continues to be transmitted through the rigid pressure block 504 to the bottom pressure head 6. The pressure head 6 vertically penetrates the surface of the test sample, while simultaneously causing the limiting sleeve 501 to stretch the top return spring 502, completing the pressing work process.

[0060] During the aforementioned extreme pressing process, due to the vertical downward displacement of the load block 701 within the optical measurement channel 401, the first T-shaped groove 702 on its side slides vertically downward along the stationary first T-shaped protrusion 705. This lateral, vertically open sliding fit ensures that the downwardly transmitted heavy load is completely physically separated from the horizontally distributed second electric actuator 703, thus completely eliminating the risk of the electric actuator system suffering vertical shear failure.

[0061] After the indentation is prepared, the unloading and removal stage begins. The hydraulic cylinder 9 releases pressure and drives the inverted U-shaped extension frame 11 to return to its original position. The downward pressure on the load block 701 disappears, and the extremely stretched return spring 502 quickly releases its elastic potential energy, contracts upward, and strongly pulls the limiting sleeve 501 upward along the outer wall of the hollow main optical path cylinder 4. Since the pressure block 504 is mounted inside the limiting sleeve 501, the pressure block 504, together with the pressure head 6 at the bottom, undergoes an absolutely vertical upward Z-axis lifting action, causing the pressure head 6 to be pulled out of the indentation pit of the test sample and kept in a suspended state.

[0062] After the indenter 6 is completely pulled out of the sample surface, the first electric push rod 505 retracts, pulling the pressure block 504 laterally back into the relief cavity, eliminating the risk of the indenter 6 scraping due to forced lateral movement. At the same time, the second electric push rods 703 on both sides retract, driving the two load blocks 701 to separate outwards.

[0063] Entering the optical measurement stage, the pressure block 504, which has been withdrawn into the retraction cavity, is powered on and illuminated by the LED light source array on its top. The light is refracted by the reflector bowl and projected at a specific low angle from the outer edge of the optical measurement channel 401 onto the residual indentation on the sample, generating a coaxial dark field illumination effect that emphasizes the three-dimensional edge contour of the indentation.

[0064] Meanwhile, during the separation process, the two load blocks 701 receive control commands and hover at specific coordinate points in the middle of the retraction stroke. The two load blocks 701 are relatively stationary, with their inner acute-angled cutting edge sections, coated with matte finish, suspended above the edge of the optical path. By adjusting the hovering distance of the second electric push rod 703, this cutting edge section directly transforms into a physical slit variable aperture in front of the optical imaging system 8, effectively controlling the light-passing aperture and cutting stray diffracted beams that block the periphery of the main optical axis to obtain a high-edge-contrast digital image for subsequent measurement and calculation.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A Brinell hardness tester comprising a base (1) and a cantilever (2) fixedly connected to one side of the base (1), characterized in that, The base (1) has a bearing module (3) in the middle for bearing the test sample. The cantilever (2) has a hollow main optical path tube (4) that is fixedly connected through the center of the top. The hollow main optical path tube (4) is located above the bearing module (3), and the centers of the two are on the same axis. The hollow main optical path tube (4) has an optical measurement channel (401) that runs vertically through it. The top of the optical measurement channel (401) is equipped with an optical imaging system (8). The bottom of the hollow main optical path tube (4) is equipped with a switching unit (5), and the bottom of the switching unit (5) is equipped with a pressure head (6). The pressure head (6) is driven to engage or disengage by the switching unit (5). The optical measurement channel (401) is provided with a splicing load transfer unit (7) in the middle of the hollow main optical path cylinder (4), which is used to transfer the load provided by the hydraulic cylinder (9) to the switching unit (5). During the pressing test stage, the switching unit (5) cuts into the optical measurement channel (401). The splicing load transfer unit (7) is spliced ​​in the center above the switching unit (5) to receive and vertically transfer the downward test load to the switching unit (5). During the optical measurement stage, the splicing load transfer unit (7) separates to both sides, and the switching unit (5) exits the optical measurement channel (401) laterally so that the vertical downward optical path of the optical imaging system (8) is unobstructed.

2. The Brinell hardness tester according to claim 1, characterized in that, The switching unit (5) includes a limiting sleeve (501), which is sleeved and slidably connected to the bottom outer wall of the hollow main optical path cylinder (4). The top end of the limiting sleeve (501) is connected to the top end of the cantilever (2) by a reset spring (502). The bottom of the limiting sleeve (501) extends along the X-axis to form a relief cavity. A slide rail (503) is provided at the bottom of the limiting sleeve (501). A pressure block (504) is suspended and slidably connected on the slide rail (503). The limiting sleeve (501) is fixed towards the relief cavity. A first electric push rod (505) is connected. The output end of the first electric push rod (505) is connected to the side wall of the pressure block (504) through a flexible spring (506). The bottom center of the pressure block (504) is fixedly connected to the top of the pressure head (6). After the test load is removed, the elastic force of the reset spring (502) drives the limiting sleeve (501) and the pressure block (504) to rise as a whole, so that the pressure head (6) is vertically pulled out of the test sample and suspended in the air, so as to avoid physical scratching of the test sample surface when the pressure head (6) exits the optical measurement channel (401) laterally.

3. A Brinell hardness tester according to claim 2, wherein The top of the pressure block (504) facing away from the bottom of the pressure block (504) adopts an inverted conical structure, and an LED light source array is provided on the side of the inverted conical structure opposite to the relief cavity. The LED light source array is projected onto the surface of the test sample at an oblique angle through the reflector bowl structure, so that the pressure block (504) in the relief state can be reused as the dark field auxiliary lighting base of the optical imaging system (8).

4. A Brinell hardness tester according to claim 2, wherein The assembled load transfer unit (7) includes two symmetrically arranged load blocks (701). The load blocks (701) are slidably disposed in the middle of the hollow main optical path cylinder (4). A vertical first T-shaped groove (702) is provided on the side wall of the load block (701) away from the assembly center. Two second electric push rods (703) are correspondingly arranged on the outside of the hollow main optical path cylinder (4). A semi-arc block (704) is fixedly connected to the output end of the second electric push rod (703). The semi-arc block (704) is attached to the outer arc surface of the load block (701). The inner arc surface is fixedly connected to a first T-shaped protrusion (705). The first T-shaped protrusion (705) is inserted into and slidably connected in the first T-shaped groove (702). The two load blocks (701) are driven to laterally assemble or disassemble by two second electric push rods (703). When the two load blocks (701) are laterally assembled and bear the load force provided by the hydraulic cylinder (9), the load blocks (701) slide vertically along the optical measurement channel (401), and the first T-shaped groove (702) slides along the stationary first T-shaped protrusion (705) to eliminate the vertical shear force on the second electric push rod (703).

5. A Brinell hardness tester according to claim 4, characterized in that, The top wall of the pressure block (504) is fixedly connected to three hemispherical positioning buttons (507) arranged in a circular array. On the bottom surface formed by the two load blocks (701) after being assembled, there are three inverted V-shaped grooves (706) that correspond one-to-one with the positions of the hemispherical positioning buttons (507). When subjected to test load, the inverted V-shaped grooves (706) press down on the hemispherical positioning buttons (507). The tangential component force generated by the inclined plane forces the pressure block (504) to perform spatial attitude fine adjustment and centering, so that the pressure block (504) adaptively locks into a rigid body state with six degrees of freedom constraints to prevent force deflection.

6. A Brinell hardness tester according to claim 4, wherein The inner edges of the two load blocks (701) that are joined together are processed into acute-angled cutting edge sections, and the surface of the acute-angled cutting edge sections is sprayed with an anti-light-diffusing coating to suppress diffuse reflection of light. During the optical measurement stage, the two load blocks (701) are controlled to hover at a specific distance of the pull-out stroke to both sides. The acute-angled cutting edge sections of the two load blocks (701) are suspended opposite each other, forming a slit variable aperture in front of the optical imaging system (8). The effective light-transmitting aperture is controlled by dynamically adjusting the specific distance and increasing the optical depth of focus of the optical imaging system (8).

7. A Brinell hardness tester according to claim 4, wherein The hydraulic cylinder (9) is fixedly connected to the top of the hollow main optical path cylinder (4) via the bracket (10), and the hydraulic cylinder (9) is located above the optical imaging system (8). The output end of the hydraulic cylinder (9) passes through the bracket (10) and is fixedly connected to an inverted U-shaped extension frame (11). The two parallel forked rods of the inverted U-shaped extension frame (11) are distributed on both sides of the optical imaging system (8) and extend downward to the load block (701). The bottom end of the forked rod is fixedly connected to a second T-shaped protrusion (1101), which is embedded and slidably connected in the second T-shaped groove (707) opened on the top of the load block (701). At the same time, the rod body of the forked rod is embedded and slidably connected in the annular wall of the optical measurement channel (401). The hydraulic cylinder (9) outputs load to the load block (701) through the inverted U-shaped extension frame (11) and drives the load block (701) to move axially along the optical measurement channel (401).

8. A Brinell hardness tester according to claim 1, wherein The bearing module (3) includes a trapezoidal lifting screw (301). The bottom of the trapezoidal lifting screw (301) is fixedly connected to the base (1). Its output end is fitted with and threaded with a guide sleeve (302). The outer wall of the guide sleeve (302) is slidably connected to the through hole at the top of the base (1). The top of the guide sleeve (302) is fixedly connected with a hardness testing anvil (303).

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