High-precision scissor lift platform and control method thereof

Abstract

The application discloses a high-precision scissor-type lifting platform and a control method thereof. The lifting process of the lifting platform comprises the following steps: S1: setting the corresponding relationship between the pulse signal sent by a PLC and the rotating frequency of a stepping motor, and setting the initial height, the set height and the displacement speed through a touch screen; S2: the PLC sends a pulse to control the starting of the stepping motor according to the setting of the touch screen, and the stepping motor changes the included angle of a scissor assembly through synchronous transmission of a synchronous belt, so that the lifting platform starts to lift; S3: during the lifting process of the lifting platform, a height measuring instrument on the lifting platform scans a height analog signal and transmits the signal to the PLC, the PLC adjusts the frequency and the number of the sent pulses according to the received height analog signal, and then adjusts the speed of the stepping motor until the lifting platform reaches the set height. The application utilizes the stepping motor driving and the synchronous belt transmission, can overcome the shortcomings of the hydraulic system, and improves the positioning accuracy of the lifting platform.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of conveying mechanical equipment, in particular to a high-precision scissor-type lifting platform and a control method thereof. BACKGROUND

[0002] On various automatic production lines, the lifting work platform is a commonly used workpiece conveying equipment, which is used to drive the workpiece to move to realize automatic feeding and discharging. The most commonly used and widely used driving form of the lifting work platform today is hydraulic driving, which has the advantages of compact structure, large carrying capacity, and stepless speed regulation in a large range. However, it also inevitably has some disadvantages. First, due to the leakage in the hydraulic transmission and the compressibility of the liquid, the transmission ratio of this transmission cannot be strictly guaranteed. In order to reduce leakage and meet certain performance requirements, the matching parts of the hydraulic components require high manufacturing precision and complex processing technology, and it is not easy to check and eliminate faults. Secondly, the hydraulic transmission is sensitive to changes in oil temperature. When the temperature changes, the viscosity of the liquid changes, causing changes in the motion characteristics, which affects the stability of the work and cannot accurately control the lifting height. Therefore, it is not suitable to work in an environment with large temperature changes. In addition, hydraulic transmission requires a separate energy source, which is not as convenient as power supply.

[0003] In recent years, with the continuous progress of science and technology and the continuous improvement of production process level, automatic equipment has been widely applied in various industries. Mechatronics is an inevitable trend to realize factory automation. Flexible production and intelligent manufacturing are two aspects of production automation application. Through precise and flexible production, the on-site needs of enterprises at various stages and the increasingly detailed production division of various industries are met.

[0004] On some modern production lines, the lifting work platform can be used as a connecting device for different height conveying lines between two processes to automatically lift and transfer components. In some special cases, it is necessary to accurately position the height to intelligently control the lifting and landing. The height error is even less than 5mm. Obviously, the traditional hydraulic driving work platform cannot meet this requirement. SUMMARY

[0005] The present application provides a high-precision scissor-type lifting platform and a control method thereof, which can accurately control the lifting height, has good stability, uses a stepping motor for driving, uses a synchronous belt for transmission, and simultaneously applies force to the inner and outer forks. It can meet the production load, ensure the positioning accuracy, overcome the shortcomings of the hydraulic system, and has the advantage of labor saving.

[0006] Technical solution: To achieve the above-mentioned purpose, a high-precision scissor type lifting platform of the application comprises an upper platform, a lower platform and an open loop synchronous belt; a scissor assembly is arranged between the upper platform and the lower platform, the scissor assembly comprises inner forks and outer forks with variable included angles, a pull beam assembly is movably arranged in the transverse shear opening of the inner forks and the outer forks, a synchronous pulley is arranged on the inner forks or the outer forks, and the synchronous pulley is located on the back side of the opening direction of the shear opening with the pull beam assembly; the power mechanism of the scissor assembly is a stepping motor, the stepping motor is controlled by a PLC, the stepping motor can drive one end of the synchronous belt to move, the other end of the synchronous belt is connected to the pull beam assembly after passing through the synchronous pulley; the inner forks and the outer forks are combined in an X shape and are hingedly connected through a pin shaft assembly; the oblique upper end of the inner forks is hingedly connected to the upper platform through an upper fixed hinge support, and the oblique lower end of the inner forks is in rolling contact with the lower platform through a lower running wheel; the oblique lower end of the outer forks is hingedly connected to the lower platform through a lower fixed hinge support, and the oblique upper end of the outer forks is in rolling contact with the upper platform through an upper running wheel; the pull beam assembly comprises a connecting shaft and guide wheels at both ends of the connecting shaft; a linear guide rail is mounted below the oblique upper end of the inner forks, and a sliding block is slidably arranged on the linear guide rail; a rotating hole is arranged on the sliding block, and the guide wheels are rotatably mounted in the rotating hole, so that the guide wheels are slidably connected with the linear guide rail through the sliding block; the guide wheels are in rolling contact with the upper profile surface of the oblique lower end of the outer forks, and the guide wheels can move along the oblique upper end of the inner forks and the oblique lower end of the outer forks simultaneously; a belt buckle is arranged on the connecting shaft, and the other end of the synchronous belt is fixed on the connecting shaft through the belt buckle.

[0007] Further, the synchronous pulley is fixedly installed on a transmission shaft, the transmission shaft is rotatably installed on the oblique lower end of the inner forks; the synchronous pulley is in meshing transmission with the synchronous belt.

[0008] Further, the rotation of the stepping motor is positively correlated with the lifting of the upper platform; the upper profile surface of the oblique lower end of the outer forks is a trajectory adjusting curved surface, the trajectory adjusting curved surface is an outer arc curved surface, the slope of the trajectory adjusting curved surface gradually decreases from the oblique lower end to the oblique upper end of the outer forks; the guide wheels are in rolling contact with the trajectory adjusting curved surface, so that the positive correlation between the stepping motor and the upper platform approaches to linearity.

[0009] Further, a control method of a high-precision scissor type lifting platform, the lifting execution mechanism of the lifting platform is a scissor assembly, the included angle of the scissor assembly is variable, and the power mechanism for changing the included angle of the scissor assembly is a stepping motor; the stepping motor is controlled by a PLC, and the stepping motor and the scissor assembly are synchronously driven in a synchronous belt transmission mode.

[0010] Further, the lifting process of the lifting platform comprises the following steps: S1: setting the corresponding relationship between the pulse signal emitted by the PLC and the rotation frequency of the stepping motor, and setting the initial height, the set height and the displacement speed through the touch screen;

[0011] S2: The PLC sends pulses to control the stepper motor to start according to the settings on the touch screen. The stepper motor changes the included angle of the scissor lift assembly through the synchronous transmission of the synchronous belt, so that the lifting platform starts to rise and fall. S3: During the lifting process, the height measuring instrument on the lifting platform scans the height analog signal and transmits the signal to the PLC. The PLC adjusts the frequency and number of pulses sent according to the received height analog signal, so as to adjust the speed of the stepper motor until the lifting platform reaches the set height.

[0012] Furthermore, in step S1, the variable speed height is set via the touchscreen; in step S3, the lifting process of the upper platform is divided into a first stage and a second stage performed sequentially; in the first stage, the PLC controls the upper platform to quickly move from the initial height to the variable speed height; in the second stage, the PLC controls the upper platform to slowly move from the variable speed height to the set height.

[0013] Furthermore, in step S1, a delay protection time is set via the touchscreen; in step S3, after the lifting platform moves to the set height, protection is performed according to the set delay protection time, so that the lifting platform stays at the set height for the corresponding time.

[0014] Furthermore, step S4 is added after step S3; Step S4: After the delay protection time ends, the PLC controls the stepper motor to start again, so that the upper platform returns to the initial height.

[0015] Beneficial Effects: The high-precision scissor lift platform and its control method of the present invention have the following beneficial effects:

[0016] 1) Since this invention uses synchronous belt drive instead of hydraulic drive, it takes advantage of the accurate transmission ratio of synchronous belt drive, which can accurately position the device, while the stepper motor has good self-locking performance.

[0017] 2) Since there is no hydraulic transmission, there is no need for a hydraulic pump station or oil circuit system, which greatly reduces production costs; it can be used in various occasions that require cleanliness and low noise.

[0018] 3) When the stepper motor drives the synchronous belt, the inner fork can be displaced by pulling the lower end of the inner fork through the synchronous belt pulley, and the shearing can be opened by the pull beam assembly. It has the advantage of saving effort and makes the force on the inner and outer forks more even during the lifting process, and the operation is more stable during the lifting process.

[0019] 4) The upper contour surface of the lower end of the outer fork is a trajectory adjustment surface. The guide wheel structure in the tie beam assembly rolls in contact with the trajectory adjustment surface, so that the movement of the stepper motor and the upper platform is positively correlated to a near-linear relationship. When the stepper motor rotates at a constant speed, the upper platform tends to rise and fall at a constant speed, which makes the upper platform more stable during the lifting process and is conducive to the precise positioning of the lifting platform.

[0020] 5) Employing PLC control combined with a height measuring instrument and touchscreen control, the system enables the lifting and conveying of different items at varying heights. It features high accuracy and stable operation, reducing labor intensity and increasing productivity. Furthermore, the system's open and compatible architecture allows for different production needs to be met through various hardware combinations and program modifications, demonstrating broad application prospects. Attached Figure Description

[0021] Appendix Figure 1 This is a schematic diagram illustrating the working principle of a lifting platform.

[0022] Appendix Figure 2 This is the wiring diagram for a photoelectric switch;

[0023] Appendix Figure 3 A table showing the input and output points of the PLC;

[0024] Appendix Figure 4 PLC I / O address allocation table;

[0025] Appendix Figure 5 Wiring diagram for the driver;

[0026] Appendix Figure 6 Design a flowchart for the control program of the lifting platform;

[0027] Appendix Figure 7 This is a front view of the scissor lift platform of the present invention;

[0028] Appendix Figure 8 This is a top view of the scissor lift platform of the present invention;

[0029] Appendix Figure 9 This is a side view of the scissor lift platform of the present invention;

[0030] Appendix Figure 10 This is a three-dimensional structural schematic diagram of the scissor lift platform of the present invention;

[0031] Appendix Figure 11 for Figure 10 A magnified view of region A in the middle. Detailed Implementation

[0032] The invention will now be further described with reference to the accompanying drawings.

[0033] As attached Figures 1 to 11The aforementioned control method for a high-precision scissor lift platform utilizes a scissor assembly as its lifting actuator. The included angle of the scissor assembly is variable, and changes in this angle correspondingly alter the height of the lifting platform. A stepper motor 1, controlled by a PLC, powers the scissor assembly via a synchronous belt 2. This combination of stepper motor 1 and synchronous belt 2, controlled by a PLC, significantly improves the lifting accuracy and stability of the system.

[0034] The PLC is connected to the touchscreen, the stepper motor 1 driver, and the height measuring instrument. The PLC connected to the touchscreen is used to set the initial height, set height, and fast / slow traverse speed of the lifting platform. The stepper motor 1 driver is connected to stepper motor 1, which is connected to the synchronous belt 2, thereby precisely controlling the displacement of the lifting platform. The speed and displacement of stepper motor 1 can be precisely controlled based on the frequency and number of pulses emitted by the PLC.

[0035] The lifting platform has height displacement, and the height measuring instrument is installed at the screw hole on the side of the lifting platform. The height measuring instrument generally uses a photodiode, also known as a photoelectric sensor, which converts changes in light intensity between the transmitting and receiving ends into changes in current, and then uses the signal for detection. It typically uses a cold light source, such as blue light, red light, or infrared light. Active photoelectric detection is achieved through pulse modulation. The detection method is non-contact, and this sensor has advantages such as high accuracy, long lifespan, fast response, adjustable detection distance, and strong resistance to optical and electromagnetic interference.

[0036] This system uses Jiazhun's slotted photoelectric switch FC-SPX303P. Wiring principle is shown below. Figure 2 .

[0037] The PLC module uses a Mitsubishi Fx2N-48MT PLC. The Mitsubishi Fx2N-48MT PLC features excellent design and reliable performance. The CPU module is available in standard and economy models. The standard model is used in complex industrial applications, while the economy model is used in simple industrial applications. The standard CPU module is scalable, expandable up to 188 points, meeting the needs of multiple I / O control tasks and satisfying the control requirements of most small-scale automation equipment. The economy CPU module meets control requirements with a single unit. The CPU module itself can provide up to three channels of 100kHz high-speed pulse output, and simultaneously supports Pulse Train Output, PTO pulse control mode / Pulse Width Modulation, PWM analog control mode, and various motion modes, including a customizable motion envelope.

[0038] See the appendix for input / output point statistics.Figure 3 The appendix in the appendix, by Appendix Figure 3 It is known that this system involves 4 digital input points, 4 digital output points, and 1 motion axis. Therefore, the Fx2N-48MR PLC is sufficient. Specific technical specifications of this model: integrated cabinet structure; its basic unit integrates the CPU, memory, input / output interfaces, and power supply into a single module, resulting in a compact structure, small size, low cost, and easy installation. The FX2N's user memory capacity can be expanded to 16K, and its I / O points can be expanded to a maximum of 256. The FX2N has various special function modules, such as analog input / output modules, high-speed counter modules, pulse output modules, position control modules, RS-232C / RS-422 / RS-485 serial communication modules or function expansion boards, analog timer expansion boards, etc. The FX2N features over 3000 auxiliary relays, 1000 status relays, over 200 timers, 200 16-bit up counters, 35 32-bit up / down counters, over 8000 16-bit data registers, 128 jump pointers, and 15 interrupt pointers. It also has 128 function instructions and a power supply capability of 24VDC 5mA. Address allocation is detailed in the appendix. Figure 4 Appendix to the document.

[0039] The PLC needs to monitor the vertical displacement in real time. An expansion module, an analog input module (A / D converter), is added to the PLC to receive signals from the process control sensors, convert them into standard input signals, and transmit them to the PLC main controller.

[0040] The touchscreen used is an MCGS TPC series touchscreen.

[0041] The stepper motor driver is selected from Beijing Shidai Chaoqun's ZD-2HA860WL.

[0042] This system mainly consists of an Fx2N-48MT PLC, stepper motor 1, and a driver. The PLC is powered by 24V DC, while the driver's coils are powered by 48V DC. A+, A-, B+, and B- are connected to the A and B coils of stepper motor 1, respectively. The motor brake is powered by a separate 24V DC power supply. The driver's direction signal DIR- is connected to the PLC's Y002 terminal, and the pulse signal PUL- is connected to the PLC's Y000 terminal. DIR-, PUL-, and ENA- are connected to 0V, and the remaining terminals are left floating. See [link to driver wiring diagram] for details. Figure 5 .

[0043] The lifting process of the lifting platform includes the following steps: S1: Set the correspondence between the pulse signal sent by the PLC and the rotation frequency of the stepper motor 1, and set the initial height, set height, and displacement speed through the touch screen; S2: The PLC sends pulses to control the stepper motor 1 to start according to the settings on the touch screen. The stepper motor 1 changes the included angle of the scissor lift assembly through the synchronous transmission of the synchronous belt 2, so that the lifting platform starts to lift; S3: During the lifting process, the height measuring instrument on the lifting platform scans the height analog signal and transmits the signal to the PLC. The PLC adjusts the frequency and number of pulses sent according to the received height analog signal, thereby adjusting the speed of the stepper motor 1 until the lifting platform reaches the set height.

[0044] In a scissor lift platform, the platform's height is adjusted by changing the angle between the scissor tips. The stability of the platform during lifting depends on the stability of the scissor tips. Slow scissor movement, while providing relatively stable lifting, results in slow and inefficient operation. Conversely, fast scissor movement, while increasing lifting speed, leads to instability and affects positioning accuracy. Therefore, in step S1, a variable-speed height is set via a touchscreen. In step S3, the lifting process of the upper platform 4 is divided into two stages: the first stage, where the PLC controls the upper platform 4 to rapidly move from its initial height to the variable-speed height to improve productivity; and the second stage, where the PLC controls the upper platform 4 to slowly move from the variable-speed height to the set height to improve positioning accuracy. This requirement can be easily achieved by controlling the frequency and pulse count of the synchronous motor via PLC.

[0045] In step S1, a delay protection time is set via the touchscreen; in step S3, after the lifting platform moves to the set height, protection is performed according to the set delay protection time, so that the lifting platform stays at the set height for the corresponding time.

[0046] Step S4 is added after step S3; Step S4: After the delay protection time ends, the PLC controls the stepper motor 1 to start again, so that the upper platform 4 returns to the initial height.

[0047] In terms of program design, this system uses GXWORKS programming software for ladder diagram design. This software mainly completes functions such as initialization, lifting command triggering, brake control, and PLSY instructions. The design flow is shown below. Figure 6 During initialization, the lifting platform must rise to the set initial height before other motion controls can be activated. In the PLSY command, controlling the pulse frequency controls the motor's speed; the motor's forward and reverse rotation is controlled by the positive and negative values ​​of the pulse frequency and the Y002 direction. To improve efficiency while maintaining precise control, the first 80% of the travel from the initial height to the working height is fast forward, and the last 20% is slow forward.

[0048] In summary, this system uses a PLC as the controller to apply pulses of a certain frequency to the driver, driving stepper motor 1 to drive synchronous belt 2 to move the lifting platform up and down, thereby achieving lifting control. This system is simple and reliable in design and has achieved the expected results.

[0049] The drive mechanism of this invention uses a stepper motor 1, which is an open-loop control element that converts electrical pulse signals into angular or linear displacement. Under non-overload conditions, the motor's speed and stopping position depend only on the frequency and number of pulse signals, and are unaffected by load changes. When the stepper driver receives a pulse signal, it drives the stepper motor 1 to rotate a fixed angle in a set direction, called the "step angle." Its rotation occurs step by step at fixed angles. The angular displacement can be controlled by controlling the number of pulses, thus achieving accurate positioning; simultaneously, the speed and acceleration of the stepper motor 1 can be controlled by controlling the pulse frequency, thus achieving speed regulation. The performance of the drive circuit greatly affects the overall system performance. Through on-site debugging, the equipment can meet design requirements, accurately transporting items to a precise height. The required height can be reached by manually inputting precise values ​​on the human-machine interface, and peripheral devices can function normally after receiving the data. This system exhibits stable performance, simple structure, and convenient application, meeting control requirements.

[0050] A stepper motor 1 is a type of motor controlled by electrical pulses, converting these pulse signals into corresponding angular displacements. Each input electrical pulse propels the stepper motor 1 forward one step, and its output angular displacement is proportional to the number of input pulses. Therefore, controlling the number or frequency of pulses input to its coil windings controls both the angular displacement and speed of the stepper motor 1. However, the pulses input to the various coil windings of the stepper motor 1 require distribution by a pulse distributor. When controlling the stepper motor 1 using a PLC, the pulse distribution can be designed in software or implemented in hardware.

[0051] This invention employs PLC control combined with a height sensor to achieve flexible control of different conveying heights through a scissor lift system in the mechanical part. Furthermore, the system's open and compatible structure allows for different production needs to be met through various hardware combinations and program modifications, demonstrating broad application prospects.

[0052] This invention employs a stepper motor 1 and a synchronous belt 2 for transmission, controlled by a PLC, which greatly improves the accuracy and stability of the system's lifting and lowering. Furthermore, a touchscreen is used as the human-machine interface to receive input signals and display device status, significantly enhancing convenience and operability.

[0053] The PLC-controlled lifting work platform can seamlessly integrate with other logistics equipment, enabling centralized management and real-time allocation of both physical and informational material flows. Furthermore, its system design employs a standardized and modular assembly approach. Additionally, by slightly modifying the system to meet different production requirements, it significantly enhances the flexibility of the production line.

[0054] A high-precision scissor lift platform implementing the method of claim 1 includes an upper platform 4, a lower platform 11, and a synchronous belt 2; a scissor assembly is provided between the upper platform 4 and the lower platform 11, the scissor assembly including an inner fork 5 and an outer fork 7 with variable included angle, a pull beam assembly 3 is movably arranged in the transverse scissor opening of the inner fork 5 and the outer fork 7, a synchronous pulley 16 is provided on the inner fork 5 or the outer fork 7, and the synchronous pulley 16 is located on the back side of the opening direction of the scissor opening with the pull beam assembly 3; the power mechanism of the scissor assembly is a stepper motor 1, the stepper motor 1 is controlled by a PLC, the stepper motor 1 can drive one end of the synchronous belt 2 to move, and the other end of the synchronous belt 2 passes around the synchronous pulley 16 and is connected to the pull beam assembly 3. The opening and closing action of the shear can change the included angle between the inner fork 5 and the outer fork 7, thereby changing the distance between the upper platform 4 and the lower platform 11. The movable displacement of the pull beam assembly 3 within the shear can change the degree of opening and closing of the shear. Therefore, when the stepper motor 1 causes the pull beam assembly 3 to move through the synchronous belt 2, the upper platform 4 can be raised and lowered accordingly.

[0055] The lifting platform of this invention is achieved by using a stepper motor 1, a synchronous belt 2, a synchronous pulley 16, and a tie beam assembly 3. Compared with traditional hydraulic drive, the transmission ratio of the synchronous belt 2 is more accurate, the lifting platform is more precisely positioned, and there is no need for a hydraulic pump station or oil circuit system, which greatly reduces production costs. It can be used in various occasions that require cleanliness and low noise.

[0056] Furthermore, the synchronous pulley 16 is located on the movable end of the inner fork 5 or the outer fork 7. When the stepper motor 1 pulls the pull beam assembly 3 via the synchronous belt 2, the synchronous pulley 16 is also subjected to tension. The synchronous pulley 16 subjected to tension can pull the movable end of the inner fork 5 or the outer fork 7 to move. Therefore, during the lifting process, not only does the pull beam assembly 3 act on both the inner fork 5 and the outer fork 7 simultaneously, but the movable end of the inner fork 5 or the outer fork 7 is also subjected to force. As a result, the force on the inner fork 5 and the outer fork 7 is more even during the lifting process, making the lifting platform more stable. Moreover, the transmission structure formed by the stepper motor 1, the synchronous belt 2, the synchronous pulley 16, and the pull beam assembly 3 is similar to a movable pulley, which has the advantage of saving effort.

[0057] The inner fork 5 and the outer fork 7 are combined in an X shape and hinged together by a pin assembly 6 to form a rotating pair. The upper end of the inner fork 5 is hinged to the upper platform 4 via an upper fixed hinge support 24, and the lower end of the inner fork 5 is in rolling contact with the lower platform 11 via a lower wheel 10. The lower end of the outer fork 7 is hinged to the lower platform 11 via a lower fixed hinge support 23, and the upper end of the outer fork 7 is in rolling contact with the upper platform 4 via an upper wheel 8.

[0058] The synchronous pulley 16 is fixedly mounted on the drive shaft 9, which is rotatably mounted on the lower end of the inner fork 5. Both ends of the drive shaft 9 are rotatably connected to the inner fork 5. The synchronous pulley 16 meshes with the synchronous belt 2 for transmission. The synchronous belt 2 transmission consists of an open-loop rubber belt with equally spaced teeth on its inner circumferential surface and a synchronous pulley 16 with corresponding tooth grooves. During operation, the belt teeth mesh with the tooth grooves of the synchronous pulley 16 to transmit motion and power. Firstly, the synchronous belt 2 transmission is a meshing transmission. Although the base material of the synchronous belt 2 is polyurethane or neoprene rubber, which is elastic, its load-bearing reinforcing layer is die-cast from steel wire or glass fiber material with very low elongation. Under working tension and alternating stress, the elongation is extremely small, and the pitch of the synchronous belt 2 remains constant, ensuring correct meshing between the belt teeth and the tooth grooves of the synchronous pulley 16 without missing steps, achieving slip-free synchronous transmission and obtaining an accurate transmission ratio. Because the synchronous belt 2 has a more accurate transmission ratio than conventional hydraulic transmission, the positioning accuracy of the lifting platform is higher. In addition, the synchronous belt 2 has a transmission efficiency of up to 98%, and the transmission is smooth. It has a buffering and vibration reduction effect, low noise, and no need for lubrication.

[0059] The tie beam assembly 3 includes a connecting shaft 26 and guide wheels 27 at both ends of the connecting shaft 26. A linear guide rail 22 is installed below the upper inclined end of the inner fork 5. A slider 28 is slidably mounted on the linear guide rail 22. The slider 28 has a rotating hole, and the guide wheel 27 is rotatably mounted in the rotating hole, allowing the guide wheel 27 to slide and engage with the linear guide rail 22 through the slider 28. The guide wheel 27 rolls in contact with the upper contour surface of the lower inclined end of the outer fork 7 to reduce friction and allow the guide wheel 27 to move simultaneously along the upper inclined end of the inner fork 5 and the lower inclined end of the outer fork 7. The linear guide rail 22 is a standard part, used to support and guide the moving parts to perform reciprocating linear motion in a given direction. Its working principle can be understood as a rolling guide, where steel balls roll infinitely between the slider 28 and the linear guide rail 22, reducing the coefficient of friction to one-fiftieth of that of traditional sliding guides, easily achieving high positioning accuracy.

[0060] A stepper motor 1 is mounted on the lower platform 11 and connected to a worm gear reducer 17. The output shaft of the worm gear reducer 17 is connected to a drive shaft 19 via a coupling 18. The drive shaft 19 is supported by a bearing 20 mounted on the lower platform 11. Two pulleys 21 are symmetrically arranged on the drive shaft 19. One end of each of the two synchronous belts 2 is fixed to the pulleys 21, allowing them to wind around as the drive shaft 19 rotates. A buckle 12 is provided on the connecting shaft 26, and the other end of each synchronous belt 2 is fixed to the connecting shaft 26 via the buckle 12.

[0061] A conveyor roller assembly 13 is installed on the upper platform 4. The conveyor roller assembly 13 consists of a frame 15 and several parallel rollers 14. The conveyor roller assembly 13 can meet the rolling conveying of items.

[0062] The rotation of the stepper motor 1 is positively correlated with the lifting and lowering of the upper platform 4. When the stepper motor 1 rotates, the upper platform 4 rises and falls accordingly. If the upper contour surface of the lower inclined end of the outer fork 7 is a plane, the lifting and lowering of the upper platform 4 will not be uniform if the stepper motor 1 rotates at a constant speed. Therefore, the upper contour surface of the lower inclined end of the outer fork 7 is made into a trajectory adjustment surface 25. The guide wheel 27 rolls in contact with the trajectory adjustment surface 25, making the positive correlation between the movement of the stepper motor 1 and the upper platform 4 approach linearity. That is, when the stepper motor 1 rotates at a constant speed, the upper platform 4 tends to rise or fall at a constant speed. This allows the rotation angle of the stepper motor 1 to be more accurately converted into the lifting and lowering height of the upper platform 4, thereby enabling accurate positioning of the lifting platform.

[0063] As attached Figure 7 As shown, the trajectory adjustment surface 25 is an outer arc surface. The trajectory adjustment surface 25 can be integrally formed on the upper contour surface of the lower inclined end of the outer fork 7, or it can be a separate curved guide rail connected to the lower inclined end of the outer fork 7. In this case, the trajectory adjustment surface 25 is the upper contour surface of the curved guide rail. From the lower inclined end to the upper inclined end of the outer fork 7, the slope of the trajectory adjustment surface 25 gradually decreases to adjust the movement trajectory of the guide wheel 27, so that when the stepper motor 1 rotates at a constant speed, the upper platform 4 approaches a constant speed of lifting and lowering.

[0064] The specific application of this invention is as follows: Initially, the upper platform 4 is in a low position, the movable ends of the outer fork 7 and the inner fork 5 are at their farthest points, the pull beam assembly 3 is at the uppermost point of the linear guide rail 22, and the synchronous belt 2 is in its maximum extension state. The stepper motor 1 and the worm gear reducer 17 start working, driving the drive shaft 19 to rotate. The synchronous belt 2 is stretched accordingly, and the synchronous pulley 16 is stressed, driving the inner fork 5 to move inward. At the same time, the upper end of the synchronous belt 2 is stressed, driving the guide wheel 27 on the pull beam assembly 3 to move on the linear guide rail 22 of the inner fork 5. The guide wheel 27 on the pull beam assembly 3 also moves on the trajectory adjustment surface 25 of the outer fork 7. Under the action of these forces, the angle between the inner fork 5 and the outer fork 7 is widened, and the upper platform 4 rises. Conversely, when the upper platform 4 is descending from a high position, the stepper motor 1 and the worm gear reducer 17 work in opposite directions, the drive shaft 19 rotates, the synchronous belt 2 loosens, the inner fork 5 moves outward, the guide wheel 27 on the pull beam assembly 3 slides towards the upper end of the linear guide rail 22, and the guide wheel 27 on the pull beam assembly 3 simultaneously moves on the trajectory adjustment surface 25 of the outer fork 7. Under the action of gravity, the angle between the inner fork 5 and the outer fork 7 decreases, and the upper platform 4 descends.

[0065] The stepper motor 1 is controlled and driven by a PLC, and the upper platform 4 is equipped with a height measuring instrument connected to the PLC signal. The PLC can achieve flexible control of different conveying heights through the scissor lift system of the mechanical part. At the same time, the openness and compatibility of the system structure allow for different production needs to be met through different hardware combinations and program modifications, thus having broad application prospects.

[0066] During the lifting process, the upper platform 4 is raised and lowered by changing the angle between the inner fork 5 and the outer fork 7. The stability of the upper platform 4 during the lifting process depends on the stability of the inner fork 5 and the outer fork 7. When the inner fork 5 and the outer fork 7 move slowly, although the lifting of the upper platform 4 is relatively stable, the slow movement affects work efficiency. When the inner fork 5 and the outer fork 7 move quickly, although the lifting of the upper platform 4 is faster, the platform 4 becomes unstable during the lifting process, affecting positioning accuracy. Therefore, the working stroke is divided into two stages: the first stage is fast operation to improve productivity, and the second stage is slow operation to improve positioning accuracy. This requirement can be easily achieved by controlling the frequency and pulse count of the stepper motor 1 using a PLC.

[0067] The specific working process is as follows: First, a height measuring instrument is used to set a reference point. The initial position of the lifting platform is measured using the height measuring instrument, which can be achieved through a photoelectric sensor. The working height, i.e., the lifting distance, is determined according to the usage requirements; for example, if the initial position is 50 cm and the working height is 100 cm, this is displayed on the screen. Control is performed via touch; the control process is divided into fast forward and slow forward. That is, fast forward from 50 cm to 80 cm aims to improve efficiency; slow forward from 80 cm to 100 cm aims to improve accuracy. The height error is ±1-2 mm. The same principle can be used to control the descent of the lifting platform.

[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-precision scissor lift platform, characterized in that: The system includes an upper platform (4), a lower platform (11), and an open-loop synchronous belt (2). A scissor lift assembly is provided between the upper platform (4) and the lower platform (11). The scissor lift assembly includes an inner fork (5) and an outer fork (7) with a variable included angle. A tie beam assembly (3) is movably arranged in the transverse scissor opening of the inner fork (5) and the outer fork (7). A synchronous pulley (16) is provided on the inner fork (5) or the outer fork (7), and the synchronous pulley (16) is located on the back side of the opening direction of the scissor opening with the tie beam assembly (3). The power mechanism of the scissor lift assembly is a stepper motor (1). The stepper motor (1) is controlled by a PLC. The stepper motor (1) can drive one end of the synchronous belt (2) to move. The other end of the synchronous belt (2) passes around the synchronous pulley (16) and is connected to the tie beam assembly (3). The inner fork (5) and the outer fork (7) are combined in an X shape and are hinged together by a pin assembly (6); the upper end of the inner fork (5) is hinged to the upper platform (4) through an upper fixed hinge support (24), and the lower end of the inner fork (5) is in rolling contact with the lower platform (11) through a lower wheel (10); the lower end of the outer fork (7) is hinged to the lower platform (11) through a lower fixed hinge support (23), and the upper end of the outer fork (7) is in rolling contact with the upper platform (4) through an upper wheel (8); The tie beam assembly (3) includes a connecting shaft (26) and guide wheels (27) at both ends of the connecting shaft (26); a linear guide rail (22) is installed below the upper inclined end of the inner fork (5), and a slider (28) is slidably mounted on the linear guide rail (22); a rotating hole is provided on the slider (28), and the guide wheel (27) is rotatably installed in the rotating hole, so that the guide wheel (27) slides and cooperates with the linear guide rail (22) through the slider (28); the guide wheel (27) rolls in contact with the upper contour surface of the lower inclined end of the outer fork (7), and the guide wheel (27) can move simultaneously along the upper inclined end of the inner fork (5) and the lower inclined end of the outer fork (7); a buckle (12) is provided on the connecting shaft (26), and the other end of the synchronous belt (2) is fixed on the connecting shaft (26) through the buckle (12).

2. The high-precision scissor lift platform according to claim 1, characterized in that: The synchronous pulley (16) is fixedly mounted on the drive shaft (9), which is rotatably mounted on the lower end of the inner fork (5); the synchronous pulley (16) meshes with the synchronous belt (2) for transmission.

3. The high-precision scissor lift platform according to claim 1, characterized in that: The rotation of the stepper motor (1) is positively correlated with the lifting and lowering of the upper platform (4); the upper contour surface of the lower end of the outer fork (7) is a trajectory adjustment surface (25), which is an outer arc surface. From the lower end to the upper end of the outer fork (7), the slope of the trajectory adjustment surface (25) gradually decreases; the guide wheel (27) rolls in contact with the trajectory adjustment surface (25), making the positive correlation between the movement of the stepper motor (1) and the upper platform (4) approach linear.

4. A high-precision scissor lift platform according to claim 1, characterized in that: The lifting mechanism of the lifting platform is a scissor lift assembly. The included angle of the scissor lift assembly is variable. The power mechanism used to change the included angle of the scissor lift assembly is a stepper motor (1). The stepper motor (1) is controlled by a PLC, and the stepper motor (1) and the scissor lift assembly are synchronously driven by a synchronous belt (2).

5. The control method for a high-precision scissor lift platform according to claim 4, characterized in that: The lifting process of the lifting platform includes the following steps: S1: Set the correspondence between the pulse signal sent by the PLC and the rotation frequency of the stepper motor (1), and set the initial height, set height and displacement speed through the touch screen; S2: The PLC sends pulses to control the stepper motor (1) to start according to the settings of the touch screen. The stepper motor (1) changes the angle of the scissor lift assembly through the synchronous transmission of the synchronous belt (2), so that the lifting platform starts to rise and fall. S3: During the lifting process of the lifting platform, the height measuring instrument on the lifting platform scans the height analog signal and transmits the signal to the PLC. The PLC adjusts the frequency and number of pulses issued according to the received height analog signal, so as to adjust the speed of the stepper motor (1) until the lifting platform reaches the set height.

6. The control method for a high-precision scissor lift platform according to claim 5, characterized in that: In step S1, the variable speed height is also set via the touch screen; in step S3, the lifting process of the upper platform (4) is divided into a first stage and a second stage, which are carried out sequentially; in the first stage, the PLC controls the upper platform (4) to move quickly from the initial height to the variable speed height; in the second stage, the PLC controls the upper platform (4) to move slowly from the variable speed height to the set height.

7. The control method for a high-precision scissor lift platform according to claim 5, characterized in that: In step S1, a delay protection time is set via the touchscreen; in step S3, after the lifting platform moves to the set height, protection is performed according to the set delay protection time, so that the lifting platform stays at the set height for the corresponding time.

8. The control method for a high-precision scissor lift platform according to claim 7, characterized in that: Step S4 is added after step S3; Step S4: After the delay protection time ends, the PLC controls the stepper motor (1) to start again, so that the upper platform (4) returns to the initial height.

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