Automatic control system of plate-and-frame filter press

Abstract

The utility model discloses a plate and frame filter press automatic control system, including control portion, executive portion and sensing portion, control portion includes the control man -machine interface of frame filter press, programmable controller, switch power supply, and programmable controller includes input, output, and control portion passes through programmable controller, receives all from the control man -machine interface of plate and frame filter press's instruction and programmable controller input end signal, sends control command to the output of programmable controller after logic judgment, and executive portion is connected in programmable controller output through cable, is responsible for according to the control command of control portion, and drives the execution element in plate and frame filter press through the conduction intermediate relay or solenoid valve, and sensing portion is connected in programmable controller input through cable, is responsible for the series sensor signal feedback of plate and frame filter press gives programmable controller. The utility model discloses can realize plate and frame filter press operation automation, and then improves the professional health of operating personnel.

Description

Technical Field

[0001] This utility model relates to the field of automatic control, specifically an automatic control system for a plate and frame filter press. Background Technology

[0002] Plate and frame filter presses are machines used for chemical dewatering. They are widely used because of their advantages such as large filtration driving force, high solid content in filter cake, and clear filtrate.

[0003] Currently, most existing plate and frame filter presses are manually controlled, requiring frequent human operation and inspection. This means low efficiency, high cost, and unsuitability for large-scale industrial production. In addition, these types of equipment are often used in hazardous environments, such as chemical sludge treatment, and manual control is detrimental to the occupational health of operators. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this utility model provides an automatic control system for plate and frame filter presses. Based on a programmable control chip, a human-machine interface, a switching power supply, and a series of sensors and switches, the automatic control system for plate and frame filter presses can be built to automate the operation of the plate and frame filter press, avoiding excessive manual operation and inspection, thereby improving the occupational health of operators. Furthermore, automated operation can effectively improve work efficiency and reduce labor costs.

[0005] The technical solution of this utility model is:

[0006] The automatic control system for a plate and frame filter press includes a control unit, an execution unit, and a sensing unit.

[0007] The control unit includes a human-machine interface (HMI) for the plate and frame filter press, a programmable logic controller (PLC), and a switching power supply (SMPS). The PLC includes input terminals and output terminals. The switching power supply converts 220V AC power to 24V DC power to supply power to the HMI and the PLC output terminals of the plate and frame filter press. The HMI is connected to the PLC via a communication cable and displays the status parameters of the automatic control system of the plate and frame filter press, providing an interface for manual input of commands. The control unit receives all commands from the HMI and input signals from the PLC, and after logical judgment, sends control commands to the PLC output terminals.

[0008] The actuator is connected to the output of the programmable logic controller (PLC) in the control unit via a communication cable. It is responsible for driving the actuators in the plate and frame filter press by activating intermediate relays or solenoid valves according to the control commands from the control unit. The actuator includes a first rotary cylinder solenoid valve, a second rotary cylinder solenoid valve, a first lifting cylinder solenoid valve, a second lifting cylinder solenoid valve, an oil level abnormality indicator light, a pneumatic pump abnormality indicator light, a low tank pressure indicator light, an air source abnormality indicator light, an alarm, an intermediate relay, a three-way solenoid valve, a first directional valve, and a second directional valve. The actuators in the plate and frame filter press include a rotary cylinder, a lifting cylinder, and an oil pump motor.

[0009] The sensing unit is connected to the input terminal of the programmable logic controller (PLC) in the control unit via a communication cable, and is responsible for feeding back a series of sensor signals from the plate and frame filter press to the PLC in the control unit. The sensing unit includes a first pressure switch, a second pressure switch, a third pressure switch, a fourth pressure switch, a three-way solenoid valve push-button switch, an upper limit oil level sensor, a lower limit oil level sensor, a thermal relay feedback terminal, a front position oil cylinder, a rear position oil cylinder, a left limit rotary cylinder, a right limit rotary cylinder, an upper limit lifting cylinder, a lower limit lifting cylinder, a first photoelectric sensor, a second photoelectric sensor, a first magnetic sensor, a second magnetic sensor, a front limit plate and frame, and a rear limit plate and frame.

[0010] Furthermore, the control unit also includes a cabinet and a first circuit breaker, a second circuit breaker, a contactor, and a thermal relay installed inside the cabinet; the human-machine interface for the plate and frame filter press is located on the cabinet panel, and the PLC and switching power supply are located inside the cabinet.

[0011] The first circuit breaker is a 4-pole switch, and the second circuit breaker is a 1-pole switch. The cabinet is connected to a 380V AC power supply via the first circuit breaker, and then sequentially connected to a contactor and a thermal relay via cables to form the main control circuit. This main control circuit, after being protected by the first circuit breaker, contactor, and thermal relay, supplies power to the oil pump motor of the plate and frame filter press. An intermediate relay is connected to the contactor to form a secondary control circuit, used to control the connection and disconnection of the oil pump motor's power supply path. The second circuit breaker is connected to one of the live wires from the power supply connected to the first circuit breaker, and sequentially supplies power to the PLC, switching power supply, and secondary control circuit. The switching power supply has a built-in rectifier circuit that converts 220V AC to 24V DC. The output port of the switching power supply is connected to the human-machine interface (HMI) of the plate and frame filter press and the PLC output, supplying power to the components of the HMI and the actuators of the PLC output.

[0012] Below the human-machine interface on the cabinet panel is an operation panel, which includes an automatic / manual switch button, a start button, a stop button, and a reset button. These buttons are connected to the input terminals of the PLC in the control unit via communication cables. The automatic / manual switch button is used to switch control modes, the start button is used to start operation, the stop button is used to stop operation, and the reset button is used to unlock the program after an abnormality is resolved.

[0013] Furthermore, the specific control of the actuator and the sensor in relation to the plate and frame filter press is as follows:

[0014] Plate and frame filter press includes a platform trolley, plate and frame frame, plates and frames, rotary cylinder, and lifting cylinder;

[0015] The platform trolley is driven by a stepper motor. The platform trolley is connected to the plate frame for pulling the plate. The stepper motor is connected to the PLC of the control unit through a driver. The PLC can drive the stepper motor to rotate forward or backward by turning on the forward or reverse port of the stepper motor driver. The forward or reverse rotation of the stepper motor can drive the platform trolley to move forward or backward, thereby pulling the plate frame to the designated position.

[0016] The rotary cylinder and the lifting cylinder act on the plate frame to shake the plate frame for slag discharge; the rotary cylinder rotates to the left by the PLC through the first rotary cylinder solenoid valve of the actuator, and the rotary cylinder rotates to the right by the PLC through the second rotary cylinder solenoid valve of the actuator; the lifting cylinder rises by the PLC through the first lifting cylinder solenoid valve of the actuator, and the lifting cylinder falls by the PLC through the second lifting cylinder solenoid valve of the actuator.

[0017] The left and right limits of the rotating cylinder of the sensing unit are used to detect whether the rotating cylinder has reached the designated position; the upper and lower limits of the lifting cylinder are used to detect whether the lifting cylinder has reached the designated position; the first photoelectric sensor and the second photoelectric sensor are used to sense the position of the plate frame handle; the first magnetic sensor and the second magnetic sensor are used to sense the front and rear limit positions of the platform trolley.

[0018] The power circuit of a plate and frame filter press includes two main power circuits: the air circuit and the oil circuit.

[0019] The air circuit includes a shut-off valve, a filter, a pressure regulating valve, a three-way solenoid valve, and a pneumatic diaphragm pump. The shut-off valve is connected to the filter, pressure regulating valve, three-way solenoid valve, and pneumatic diaphragm pump in sequence via pipelines. The pneumatic diaphragm pump is connected to the sedimentation tank via pipelines. A first pressure switch is located between the filter and the pressure regulating valve to detect whether the inlet air pressure is normal. A second pressure switch is located at the bottom outlet of the sedimentation tank to detect the bottom pressure, serving as a judgment and adjustment for whether the filtration process is complete. The three-way solenoid valve is controlled by the output terminal of the PLC. A third pressure switch is located at the inlet of the filter press to detect the sludge conveying pressure. The air circuit introduces air from the shut-off valve to provide power to the pneumatic diaphragm pump, which pumps the slurry to be filtered from the sedimentation tank into the filter press frame. If the air pressure is insufficient or the sludge conveying pressure is abnormal, the first and third pressure switches will send signals to the PLC. The PLC will then disconnect the three-way solenoid valve to stop the pneumatic diaphragm pump, and the air source abnormality indicator light will illuminate and the alarm will sound.

[0020] The oil circuit includes an oil tank, an oil pump, an electromagnetic hydraulic directional valve, and an oil cylinder. The oil tank is sequentially connected to the oil pump, electromagnetic hydraulic directional valve, check valve, and oil cylinder via pipelines. The oil pump is driven by an oil pump motor and is used to draw oil from the oil tank to the oil circuit and pressurize it. The oil pump motor is powered by the main control circuit and its on / off state is controlled by the PLC through the intermediate relay of the actuator. The feedback terminal of the thermal relay is connected to the input terminal of the PLC of the control unit to detect whether the oil pump motor is overloaded and to provide an oil pump motor overload protection signal to the PLC. If the oil pump motor is overloaded, the equipment stops, the red indicator light flashes, the buzzer sounds an alarm, and the human-machine interface indicates that the oil pump motor is overloaded. The upper limit oil level sensor and the lower limit oil level sensor are located inside the oil tank and are used to detect oil levels. Whether the tank liquid level is within the allowable range; the electromagnetic hydraulic directional valve is controlled by the output of the PLC. The PLC switches the oil circuit direction by changing the energized state of the coils at both ends of this valve, thereby controlling the forward and backward movement of the oil cylinder to achieve "pressing" or "releasing" of the plate and frame assembly; the fourth pressure switch is located at the oil cylinder inlet to detect whether the oil cylinder pressure has reached the set value, thereby determining the operation and stop of the oil pump; the two limit switches for the front and rear positions of the oil cylinder are located at the set positions before and after the oil cylinder, and are used to send the real-time position of the oil cylinder to the PLC, which is the judgment condition for the oil cylinder action limit; the oil circuit introduces high-pressure oil from the oil tank and provides it to the oil cylinder to drive the oil cylinder forward or backward, thereby pressing or releasing the plate and frame assembly of the filter press to filter the slurry to be filtered.

[0021] Furthermore, when using the above-mentioned automatic control system for plate and frame filter presses for automated operation, the specific steps are as follows:

[0022] Step 1: Start-up preparation;

[0023] The default automatic / manual switch button is set to the automatic side. When the operator presses the start button, the equipment enters a self-test, where the PLC checks whether each input condition meets the normal start-up and operation conditions, including inlet air pressure (first pressure switch pressure value) > set pressure value, bottom pressure (second pressure switch pressure value) > set value, sludge conveying pressure (third pressure switch pressure value) > set value, and oil tank level within the allowable range. If the conditions are met, proceed to the next step.

[0024] Step 2: Press the frame and plate together;

[0025] Based on sensor signals and logical judgment, the PLC issues a control command to drive the plate and frame filter press to automatically perform tasks. Specifically: if the cylinder pressure (the pressure value of the fourth pressure switch) is less than or equal to the set value, the PLC starts the oil pump through the contactor. Then, the PLC controls the hydraulic solenoid directional valve to switch to the "pressing" direction of the plate and frame assembly, causing the cylinder to advance and push the plate and frame to close. The PLC detects the fourth pressure switch and the cylinder's forward position signal. When the pressure reaches the set value or the cylinder reaches the forward position, the PLC considers the pressing complete and stops the oil pump.

[0026] Step 3: Feed filtration;

[0027] The PLC controls the three-way solenoid valve of the air circuit to open, and the compressed air drives the pneumatic diaphragm pump to work; the slurry is pumped into the filter press plate and frame to start filtration. The liquid flows out through the filter cloth and the solid forms a filter cake; the PLC monitors the third pressure switch. As the filter cake thickens, the resistance increases. If the sludge conveying pressure exceeds the set high limit or the program set time is reached, the PLC will determine that filtration is complete.

[0028] Step 4: Release the material:

[0029] The PLC controls the electromagnetic hydraulic directional valve to switch to the "release" direction of the plate frame assembly, causing the cylinder to retract and release the plate frame. The PLC detects the cylinder's rear position signal; when the cylinder reaches the rear position, it confirms complete release. The equipment continues until the pressure at the bottom of the pool is less than the set value or the set running time is reached. At this point, the equipment goes into standby mode, the alarm sounds, and the HMI prompts for plate unloading. If no response is received within 30 minutes of the alarm, the equipment automatically starts the plate unloading program. The PLC drives a stepper motor to move the platform trolley, sequentially pulling each plate frame to its designated position. The first and second photoelectric sensors are used to locate the plate frame positions. Then, a rotary cylinder and a lifting cylinder act on the plate frame to vibrate and shake the material. Specifically:

[0030] The PLC activates the forward rotation port of the stepper motor driver, causing the stepper motor to rotate forward and drive the platform trolley forward. When the first photoelectric sensor detects the handle of the frame plate, the PLC disconnects the forward rotation port, and the trolley stops. Next, the PLC activates the first rotary cylinder solenoid valve. The right limit of the rotary cylinder is detected, and the first rotary cylinder solenoid valve closes. The PLC then activates the reverse rotation port of the motor driver, causing the trolley to retreat to a set distance. When the first frame plate reaches the designated position, the PLC disconnects the reverse rotation port, the first lifting cylinder solenoid valve opens, and the lifting cylinder rises. The upper limit of the lifting cylinder is detected, and the first lifting cylinder solenoid valve closes. The second lifting cylinder solenoid valve opens, and the cylinder descends. The lower limit of the lifting cylinder is detected, and the second lifting cylinder solenoid valve closes. The first lifting cylinder solenoid valve opens again. This cycle repeats 3-5 times, and the material residue on the first frame plate is basically shaken off. Then, the PLC turns on the reverse port of the motor driver, the trolley moves backward, the second photoelectric sensor detects the rear position of the board frame, the PLC disconnects the reverse port, the trolley stops, the PLC turns on the second rotary cylinder solenoid valve, the rotary cylinder senses the left limit, the second rotary cylinder solenoid valve closes, the PLC turns on the forward port of the motor driver, the trolley moves forward, the first photoelectric sensor detects the board frame handle, the trolley stops, and the first board frame is thus processed; the above process is repeated until the first magnetic sensor on the trolley senses the front limit of the trolley's travel, that is, the last board frame is processed, the trolley continues to move backward until the second magnetic sensor on the trolley senses the rear limit of the trolley, the trolley stops in position, and one cycle ends;

[0031] Step 5: The PLC checks whether each input condition meets the operating conditions for the next cycle, including inlet air pressure (pressure value of the first pressure switch) > set pressure value, bottom pressure (pressure value of the second pressure switch) > set value, sludge conveying filter pressure (pressure value of the third pressure switch) > set value, and oil tank level within the allowable range; if the conditions are met, proceed to step 2 to start the next filter press cycle.

[0032] Beneficial effects:

[0033] This utility model provides an automatic control system for a plate and frame filter press. Based on a programmable control chip, a human-machine interface, a switching power supply, and a series of sensors and switches, the automatic control system for the plate and frame filter press can automatically realize the operation of the plate and frame filter press, avoid excessive manual operation and inspection, thereby improving the occupational health of operators. Moreover, automated operation can effectively improve work efficiency and reduce labor costs. Attached Figure Description

[0034] Figure 1 This is a circuit schematic diagram of an embodiment of the present utility model;

[0035] Figure 2 This is a schematic diagram of the air circuit and oil circuit of an embodiment of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0037] like Figures 1 to 2 As shown, an automatic control system for a plate and frame filter press includes a control unit, an execution unit, and a sensing unit.

[0038] The control unit includes a human-machine interface (HMI) for the plate and frame filter press, a programmable logic controller (PLC), and a switching power supply (SMPS). The PLC includes input terminals and output terminals. The switching power supply converts 220V AC power to 24V DC power to supply power to the HMI and the PLC output terminals of the plate and frame filter press. The HMI is connected to the PLC via a communication cable and displays the status parameters of the automatic control system of the plate and frame filter press, providing an interface for manual input of commands. The control unit receives all commands from the HMI and input signals from the PLC, and after logical judgment, sends control commands to the PLC output terminals.

[0039] The actuator is connected to the output of the programmable logic controller (PLC) in the control unit via a communication cable. It is responsible for driving the actuators in the plate and frame filter press by activating intermediate relays or solenoid valves according to the control commands from the control unit. Figure 1 As shown, the actuator includes rotary cylinder solenoid valve 1, rotary cylinder solenoid valve 2, lifting cylinder solenoid valve 1, lifting cylinder solenoid valve 2, oil level abnormality indicator, pneumatic pump abnormality indicator, low tank pressure indicator, air source abnormality indicator, alarm, intermediate relay KA1, three-way solenoid valve, and directional valve 1 (i.e., Figure 2 The electromagnetic hydraulic directional valve), directional valve 2 (i.e. Figure 2 The one-way valve in the plate and frame filter press); the actuators in the plate and frame filter press include a rotary cylinder, a lifting cylinder, and an oil pump motor;

[0040] The sensing unit is connected to the input terminal of the programmable logic controller (PLC) in the control unit via a communication cable, and is responsible for feeding back a series of sensor signals from the plate and frame filter press to the PLC in the control unit; such as Figure 1 As shown, the sensing unit includes a pressure switch 1, a pressure switch 2, a pressure switch 3, a pressure switch 4, a three-way solenoid valve push-button switch, an upper limit oil level sensor, a lower limit oil level sensor, a thermal relay feedback terminal, a front position oil cylinder, a rear position oil cylinder, a left limit rotary cylinder, a right limit rotary cylinder, an upper limit lifting cylinder, a lower limit lifting cylinder, a photoelectric sensor 1, a photoelectric sensor 2, a magnetic sensor 1, a magnetic sensor 2, a front limit plate frame, and a rear limit plate frame.

[0041] In this embodiment, the control unit further includes a cabinet and a first circuit breaker QF1, a second circuit breaker QF2, a contactor KM1, and a thermal relay FR1 installed inside the cabinet; the human-machine interface for the plate and frame filter press is located on the cabinet panel, and the PLC and switching power supply are located inside the cabinet.

[0042] The first circuit breaker is a 4-pole switch, and the second circuit breaker is a 1-pole switch. The cabinet is connected to 380V AC power via the first circuit breaker, and then sequentially connected to contactor KM1 and thermal relay FR1 via cables to form the main control circuit. This main control circuit, after being protected by the first circuit breaker QF1, contactor KM1, and thermal relay FR1, supplies power to the oil pump motor of the plate and frame filter press. The intermediate relay KA1 is connected to contactor KM1 to form a secondary control circuit, used to control the connection and disconnection of the oil pump motor's power supply path. The second circuit breaker QF2 is connected to one of the live wires of the power supply connected to the first circuit breaker QF1. The second circuit breaker sequentially supplies power to the PLC, switching power supply, and secondary control circuit. The switching power supply has a built-in rectifier circuit that converts 220V AC to 24V DC. The output port of the switching power supply is connected to the human-machine interface (HMI) of the plate and frame filter press and the PLC output terminal, supplying power to the components of the HMI and the actuators of the PLC output terminal.

[0043] Below the human-machine interface on the cabinet panel is an operation panel, which includes an automatic / manual switch button, a start button, a stop button, and a reset button. These buttons are connected to the input terminals of the PLC in the control unit via communication cables. The automatic / manual switch button is used to switch control modes, the start button is used to start operation, the stop button is used to stop operation, and the reset button is used to unlock the program after an abnormality is resolved.

[0044] In this embodiment, the association control between the actuator and the sensing unit and the plate and frame filter press is specifically as follows:

[0045] Plate and frame filter press includes a platform trolley, plate and frame frame, plates and frames, rotary cylinder, and lifting cylinder;

[0046] The platform trolley is driven by a stepper motor. The platform trolley is connected to the plate frame for pulling the plate. The stepper motor is connected to the PLC of the control unit through a driver. The PLC can drive the stepper motor to rotate forward or backward by turning on the forward or reverse port of the stepper motor driver. The forward or reverse rotation of the stepper motor can drive the platform trolley to move forward or backward, thereby pulling the plate frame to the designated position.

[0047] The rotary cylinder and the lifting cylinder act on the plate frame to shake the plate frame for slag discharge; the rotary cylinder rotates to the left by the PLC through the rotary cylinder solenoid valve 1 of the actuator, and the rotary cylinder rotates to the right by the PLC through the rotary cylinder solenoid valve 2 of the actuator; the lifting cylinder rises by the PLC through the lifting cylinder solenoid valve 1 of the actuator, and the lifting cylinder falls by the PLC through the lifting cylinder solenoid valve 2 of the actuator.

[0048] The left and right limits of the rotating cylinder of the sensing unit are used to detect whether the rotating cylinder has reached the designated position; the upper and lower limits of the lifting cylinder are used to detect whether the lifting cylinder has reached the designated position; photoelectric sensor 1 and photoelectric sensor 2 are used to sense the position of the plate frame handle, and magnetic sensor 1 and magnetic sensor 2 are used to sense the front and rear limit positions of the platform trolley.

[0049] The power circuit of a plate and frame filter press includes two main power circuits: the air circuit and the oil circuit.

[0050] The air circuit includes a shut-off valve, a filter, a pressure regulating valve, a three-way solenoid valve, and a pneumatic diaphragm pump. The shut-off valve is connected to the filter, pressure regulating valve, three-way solenoid valve, and pneumatic diaphragm pump in sequence via pipelines. The pneumatic diaphragm pump is connected to the sedimentation tank via pipelines. Pressure switch 1 is located between the filter and the pressure regulating valve to detect whether the inlet air pressure is normal. Pressure switch 2 is located at the bottom outlet of the sedimentation tank to detect the bottom pressure, serving as a judgment and adjustment for whether the filtration process is complete. The three-way solenoid valve is controlled by the output terminal of the PLC. Pressure switch 3 is located at the inlet of the filter press to detect the sludge conveying pressure. The air circuit introduces air from the shut-off valve to provide power to the pneumatic diaphragm pump, which pumps the slurry to be filtered from the sedimentation tank into the filter press frame. If the air pressure is insufficient or the sludge conveying pressure is abnormal, pressure switches 1 and 3 will send signals to the PLC. The PLC will then disconnect the three-way solenoid valve to stop the pneumatic diaphragm pump, and the air source abnormality indicator light will illuminate and the alarm will sound.

[0051] The oil circuit includes an oil tank, an oil pump, an electromagnetic hydraulic directional valve, and an oil cylinder. The oil tank is sequentially connected to the oil pump, electromagnetic hydraulic directional valve, check valve, and oil cylinder via pipelines. The oil pump is driven by an oil pump motor and is used to draw oil from the oil tank to the oil circuit and pressurize it. The oil pump motor is powered by the main control circuit and its on / off state is controlled by the PLC through the intermediate relay of the actuator. The feedback terminal of the thermal relay is connected to the input terminal of the PLC of the control unit to detect whether the oil pump motor is overloaded and to provide an oil pump motor overload protection signal to the PLC. If the oil pump motor is overloaded, the equipment stops, the red indicator light flashes, the buzzer sounds an alarm, and the human-machine interface indicates that the oil pump motor is overloaded. The upper limit oil level sensor and the lower limit oil level sensor are located inside the oil tank and are used for detection. Whether the oil tank level is within the allowable range; the electromagnetic hydraulic directional valve, controlled by the output of the PLC, switches the oil circuit direction by changing the energized state of the coils at both ends of this valve, thereby controlling the forward and backward movement of the oil cylinder to achieve "pressing" or "releasing" of the plate and frame assembly; pressure switch 4 is located at the oil cylinder inlet to detect whether the oil cylinder pressure reaches the set value, thereby determining the operation and stop of the oil pump; two limit switches, one for the front position and one for the rear position of the oil cylinder, are located at the set positions before and after the oil cylinder, used to send the real-time position of the oil cylinder to the PLC, which is the judgment condition for the oil cylinder's action limit; the oil circuit introduces high-pressure oil from the oil tank and supplies it to the oil cylinder to drive the oil cylinder forward or backward, thereby pressing or releasing the plate and frame assembly of the filter press to filter the slurry to be filtered.

[0052] In this embodiment, the specific steps for automating operations using the aforementioned automatic control system for plate and frame filter presses are as follows:

[0053] Step 1: Start-up preparation;

[0054] The default automatic / manual switch button is set to automatic. When the operator presses the start button, the equipment enters a self-test, where the PLC checks whether each input condition meets the normal start-up and operation conditions, including inlet air pressure (pressure value of pressure switch 1) > set pressure value, bottom pressure (pressure value of pressure switch 2) > set value, sludge conveying pressure (pressure value of pressure switch 3) > set value, and oil tank level within the allowable range. If the conditions are met, proceed to the next step.

[0055] Step 2: Press the frame and plate together;

[0056] Based on sensor signals and logical judgment, the PLC issues a control command to drive the plate and frame filter press to automatically perform tasks. Specifically: if the cylinder pressure (pressure switch 4) is less than or equal to the set value, the PLC starts the oil pump through the contactor. Then, the PLC controls the electromagnetic hydraulic directional valve to switch to the "pressing" direction of the plate and frame assembly, causing the cylinder to advance and push the plate and frame to close. When the PLC detects the pressure switch 4 and the cylinder forward position signal, and the pressure reaches the set value or the cylinder reaches the forward position, the PLC determines that pressurization is complete and stops the oil pump.

[0057] Step 3: Feed filtration;

[0058] The PLC controls the three-way solenoid valve of the air circuit to open, and the compressed air drives the pneumatic diaphragm pump to work; the slurry is pumped into the filter press plate and frame to start filtration. The liquid flows out through the filter cloth and the solid forms a filter cake; the PLC monitors the pressure opening and closing. As the filter cake increases, the resistance increases. If the sludge conveying pressure exceeds the set high limit or the program set time is reached, the PLC determines that filtration is complete.

[0059] Step 4: Release the material:

[0060] The PLC controls the electromagnetic hydraulic directional valve, switching it to the "release" direction of the plate frame assembly. The cylinder retracts, releasing the plate frame. The PLC detects the cylinder's rear position signal; when the cylinder reaches the rear position, it confirms complete release. The equipment continues until the pressure at the bottom of the pool is less than the set value or the set running time is reached. Then, the equipment goes into standby mode, the alarm sounds, and the HMI prompts for plate unloading. If no one responds after 30 minutes of alarm activation, the equipment automatically starts the plate unloading program. The PLC drives the stepper motor, which in turn moves the platform trolley to sequentially pull each plate frame to its designated position. Photoelectric sensors 1 and 2 are used to locate the plate frame position; magnetic sensors 1 and 2 are used to locate the trolley position. Then, a rotary cylinder and a lifting cylinder act on the plate frame to vibrate and shake the material. Specifically:

[0061] The PLC activates the forward rotation port of the stepper motor driver, causing the stepper motor to rotate forward and drive the platform trolley forward. When photoelectric sensor 1 detects the handle of the frame plate, the PLC disconnects the forward rotation port, and the trolley stops. Next, the PLC activates the rotary cylinder solenoid valve 1. The rotary cylinder's right limit is detected, and the rotary cylinder solenoid valve 1 closes. The PLC then activates the reverse rotation port of the motor driver, causing the trolley to retreat to a set distance. When the first frame plate reaches the designated position, the PLC disconnects the reverse rotation port, and the lifting cylinder solenoid valve 1 opens, causing the lifting cylinder to rise. The upper limit of the lifting cylinder is detected, and the lifting cylinder solenoid valve 1 closes. The lifting cylinder solenoid valve 2 opens, causing the cylinder to descend. The lower limit of the lifting cylinder is detected, and the lifting cylinder solenoid valve 2 closes. This cycle repeats 3-5 times, until the material residue on the first frame plate is mostly shaken off. Then, the PLC turns on the reverse port of the stepper motor driver, the trolley moves backward, the photoelectric sensor 2 senses the rear position of the board frame, the PLC disconnects the reverse port, the trolley stops, the PLC turns on the rotary cylinder solenoid valve 1, the rotary cylinder senses the left limit, the rotary cylinder solenoid valve 2 closes, the PLC turns on the forward port of the motor driver, the trolley moves forward, the photoelectric sensor 1 senses the board frame handle, the trolley stops, and the first board frame is thus processed; the above process is repeated until the magnetic sensor 1 on the trolley senses the front limit of the trolley, that is, the last board frame is processed, the trolley continues to move backward until the magnetic sensor 2 on the trolley senses the rear limit of the trolley, the trolley stops in position, and one cycle ends;

[0062] Step 5: The PLC checks whether each input condition meets the operating conditions for the next cycle, including inlet air pressure (pressure value of pressure switch 1) > set pressure value, bottom pressure (pressure value of pressure switch 2) > set value, sludge conveying pressure (pressure value of pressure switch 3) > set value, and oil tank level within the allowable range; if the conditions are met, proceed to step 2 to start the next filter press cycle.

[0063] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An automatic control system for a plate and frame filter press, characterized in that: It includes a control unit, an execution unit, and a sensing unit; The control unit includes a human-machine interface (HMI) for the plate and frame filter press, a programmable logic controller (PLC), and a switching power supply (SMPS). The PLC includes input terminals and output terminals. The switching power supply converts 220V AC power to 24V DC power to supply power to the HMI and the PLC output terminals of the plate and frame filter press. The HMI is connected to the PLC via a communication cable and displays the status parameters of the automatic control system of the plate and frame filter press, providing an interface for manual input of commands. The control unit receives all commands from the HMI and input signals from the PLC, and after logical judgment, sends control commands to the PLC output terminals. The actuator is connected to the output of the programmable logic controller (PLC) in the control unit via a communication cable. It is responsible for driving the actuators in the plate and frame filter press by activating intermediate relays or solenoid valves according to the control commands from the control unit. The actuator includes a first rotary cylinder solenoid valve, a second rotary cylinder solenoid valve, a first lifting cylinder solenoid valve, a second lifting cylinder solenoid valve, an oil level abnormality indicator light, a pneumatic pump abnormality indicator light, a low tank pressure indicator light, an air source abnormality indicator light, an alarm, an intermediate relay, a three-way solenoid valve, a first directional valve, and a second directional valve. The actuators in the plate and frame filter press include a rotary cylinder, a lifting cylinder, and an oil pump motor. The sensing unit is connected to the input terminal of the programmable logic controller (PLC) in the control unit via a communication cable, and is responsible for feeding back a series of sensor signals from the plate and frame filter press to the PLC in the control unit. The sensing unit includes a first pressure switch, a second pressure switch, a third pressure switch, a fourth pressure switch, a three-way solenoid valve push-button switch, an upper limit oil level sensor, a lower limit oil level sensor, a thermal relay feedback terminal, a front position oil cylinder, a rear position oil cylinder, a left limit rotary cylinder, a right limit rotary cylinder, an upper limit lifting cylinder, a lower limit lifting cylinder, a first photoelectric sensor, a second photoelectric sensor, a first magnetic sensor, a second magnetic sensor, a front limit plate and frame, and a rear limit plate and frame.

2. The automatic control system for a plate and frame filter press according to claim 1, characterized in that: The control unit also includes a cabinet and a first circuit breaker, a second circuit breaker, a contactor, and a thermal relay installed inside the cabinet; the human-machine interface for the plate and frame filter press is located on the cabinet panel, and the PLC and switching power supply are located inside the cabinet. The first circuit breaker is a 4-pole switch, and the second circuit breaker is a 1-pole switch. The cabinet is connected to a 380V AC power supply via the first circuit breaker, and then sequentially connected to a contactor and a thermal relay via cables to form the main control circuit. This main control circuit, after being protected by the first circuit breaker, contactor, and thermal relay, supplies power to the oil pump motor of the plate and frame filter press. An intermediate relay is connected to the contactor to form a secondary control circuit, used to control the connection and disconnection of the oil pump motor's power supply path. The second circuit breaker is connected to one of the live wires from the power supply connected to the first circuit breaker, and sequentially supplies power to the PLC, switching power supply, and secondary control circuit. The switching power supply has a built-in rectifier circuit that converts 220V AC to 24V DC. The output port of the switching power supply is connected to the human-machine interface (HMI) of the plate and frame filter press and the PLC output, supplying power to the components of the HMI and the actuators of the PLC output. Below the human-machine interface on the cabinet panel is an operation panel, which includes an automatic / manual switch button, a start button, a stop button, and a reset button. These buttons are connected to the input terminals of the PLC in the control unit via communication cables. The automatic / manual switch button is used to switch control modes, the start button is used to start operation, the stop button is used to stop operation, and the reset button is used to unlock the program after an abnormality is resolved.

3. The automatic control system for a plate and frame filter press according to claim 1, characterized in that: The specific control of the actuator and the sensor in relation to the plate and frame filter press is as follows: Plate and frame filter press includes a platform trolley, plate and frame frame, plates and frames, rotary cylinder, and lifting cylinder; The platform trolley is driven by a stepper motor. The platform trolley is connected to the plate frame for pulling the plate. The stepper motor is connected to the PLC of the control unit through a driver. The PLC can drive the stepper motor to rotate forward or backward by turning on the forward or reverse port of the stepper motor driver. The forward or reverse rotation of the stepper motor can drive the platform trolley to move forward or backward, thereby pulling the plate frame to the designated position. The rotary cylinder and the lifting cylinder act on the plate frame to shake the plate frame for slag discharge; the rotary cylinder rotates to the left by the PLC through the first rotary cylinder solenoid valve of the actuator, and the rotary cylinder rotates to the right by the PLC through the second rotary cylinder solenoid valve of the actuator; the lifting cylinder rises by the PLC through the first lifting cylinder solenoid valve of the actuator, and the lifting cylinder falls by the PLC through the second lifting cylinder solenoid valve of the actuator. The left and right limits of the rotating cylinder of the sensing unit are used to detect whether the rotating cylinder has reached the designated position; the upper and lower limits of the lifting cylinder are used to detect whether the lifting cylinder has reached the designated position; the first photoelectric sensor and the second photoelectric sensor are used to sense the position of the plate frame handle; the first magnetic sensor and the second magnetic sensor are used to sense the front and rear limit positions of the platform trolley. The power circuit of a plate and frame filter press includes two main power circuits: the air circuit and the oil circuit. The air circuit includes a shut-off valve, a filter, a pressure regulating valve, a three-way solenoid valve, and a pneumatic diaphragm pump. The shut-off valve is connected to the filter, pressure regulating valve, three-way solenoid valve, and pneumatic diaphragm pump in sequence via pipelines. The pneumatic diaphragm pump is connected to the sedimentation tank via pipelines. A first pressure switch is located between the filter and the pressure regulating valve to detect whether the inlet air pressure is normal. A second pressure switch is located at the bottom outlet of the sedimentation tank to detect the bottom pressure, serving as a judgment and adjustment to determine whether the filtration process is complete. The three-way solenoid valve is controlled by the output of the PLC. The third pressure switch is located at the inlet of the filter press and is used to detect the sludge conveying pressure. The air circuit introduces air from the shut-off valve to provide power to the pneumatic diaphragm pump, which is used to pump the slurry to be filtered from the sedimentation tank into the filter press plate frame. If the air pressure is insufficient or the sludge conveying pressure is abnormal, the first and third pressure switches will send signals to the PLC. The PLC will control the pneumatic diaphragm pump to stop by disconnecting the three-way solenoid valve, and the air source abnormality indicator light will illuminate and the alarm will sound. The oil circuit includes an oil tank, an oil pump, an electromagnetic hydraulic directional valve, and an oil cylinder; the oil tank is connected to the oil pump, the electromagnetic hydraulic directional valve, the check valve, and the oil cylinder in sequence through pipelines; the oil pump is driven by an oil pump motor and is used to draw oil from the oil tank to the oil circuit and pressurize it; the oil pump motor is powered by the main control circuit and its on / off state is controlled by the PLC through the intermediate relay of the actuator; The thermal relay feedback terminal is connected to the input terminal of the control unit PLC to detect whether the oil pump motor is overloaded and provide an oil pump motor overload protection signal to the PLC. If the oil pump motor is overloaded, the equipment stops, the red indicator light flashes, the buzzer sounds an alarm, and the human-machine interface prompts that the oil pump motor is overloaded. The upper limit oil level sensor and the lower limit oil level sensor are located inside the oil tank to detect whether the oil level in the tank is within the allowable range. The electromagnetic hydraulic directional valve is controlled by the output terminal of the PLC. The PLC switches the oil circuit direction by changing the energized state of the coils at both ends of this valve. This controls the forward and backward movement of the hydraulic cylinder, enabling the plate and frame assembly to be "pressed" or "released." A fourth pressure switch is located at the inlet of the hydraulic cylinder to detect whether the hydraulic cylinder pressure reaches the set value, thereby determining the operation and stop of the oil pump. Two limit switches, one for the front position and one for the rear position of the hydraulic cylinder, are located at the set positions before and after the hydraulic cylinder. These switches are used to send the real-time position of the hydraulic cylinder to the PLC and serve as the judgment condition for the hydraulic cylinder's action limit. The oil circuit introduces high-pressure oil from the oil tank and supplies it to the hydraulic cylinder to drive it forward or backward, thereby pressing or releasing the plate and frame assembly of the filter press to filter the slurry.

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