A temperature monitoring and unqualified product rejection system for a rotary wrapper and a control method thereof

Abstract

The application provides a rotating pancake machine temperature monitoring and unqualified product rejection system and a control method thereof, and relates to the technical field of pancake machines. The rotating pancake machine temperature monitoring and unqualified product rejection system comprises a first temperature measurement unit arranged in a post-feeding temperature rising area of a heating pot, the first temperature measurement unit comprises a plurality of microwave-resistant infrared temperature sensors, and is used for synchronously collecting multi-point temperature data of a pancake in a heating pot temperature rising stage; a second temperature measurement unit arranged in a pre-removal high-temperature area of the heating pot, the second temperature measurement unit also comprises a plurality of microwave-resistant infrared temperature sensors, and is used for collecting multi-point temperature data of the pancake before the pancake is separated from the heating pot; and a positioning trigger unit arranged along each production line conveying path. The multi-point temperature measurement accurately determines the sterilization standard, automatically rejects defective products, prevents misoperation through equipment interlocking, and completely stores production records to meet compliance requirements.

Description

Technical Field

[0001] This invention relates to the field of pan-frying machine technology, specifically to a temperature monitoring and defective product rejection system and control method for a rotary pan-frying machine. Background Technology

[0002] The rotary crepe machine is a specialized heating device in the pastry processing industry used for the continuous preparation of crepe cakes and pancake crepes. The main body of the machine is equipped with a ring-shaped rotating support, on which multiple heating pans are evenly mounted along the circumference. The mainstream models on the market are available in 8-pan and 14-pan specifications. During production, the dough adheres to the surface of the uniformly rotating heating pans and is continuously heated. After cooking and sterilization, it rotates with the machine to the discharge position and is then conveyed to downstream processes via a conveyor line. For caramel crepe products, the industry standard requires the crepe to reach 90°C and maintain this temperature for at least 6 seconds to meet the lethal conditions for killing food microorganisms and ensuring the safety of the finished product. Currently, the temperature control methods used in the industry for rotary crepe machines fall into three categories: manual handheld temperature gun sampling, single-point infrared temperature measurement at the discharge port, and contact thermocouple temperature measurement during periodic shutdowns.

[0003] The above three temperature measurement methods can only obtain the single-point temperature value of the dough at the moment of discharge. They cannot completely collect the temperature of the dough during the entire heating process in the heating pot. They cannot quantitatively verify the coupled sterilization condition of 90℃ for 6 seconds. The production line lacks a closed-loop control solution that can simultaneously realize real-time judgment and automatic rejection of unqualified dough. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a temperature monitoring and defective product rejection system and control method for a rotary pancake frying machine, which solves the problems that pancake frying machines cannot verify the sterilization condition of 90°C for 6 seconds, cannot accurately and automatically reject defective products, and have difficulty in tracing production data.

[0005] Technical solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a temperature monitoring and defective product rejection system for a rotary pan-frying machine, wherein the rotary pan-frying machine is equipped with multiple sets of heating pots arranged in a circular pattern along the circumference, the number of heating pots being 8 or 14, comprising:

[0007] The first temperature measuring unit is located in the heating area after the material is fed into the heating pot. The first temperature measuring unit includes multiple microwave-resistant infrared temperature sensors, which are used to synchronously collect multi-point temperature data during the heating stage when the dough adheres to the heating pot.

[0008] The second temperature measuring unit is set in the high-temperature area before the dough leaves the heating pot. The second temperature measuring unit is also equipped with multiple anti-microwave infrared temperature sensors to collect multi-point temperature data before the dough leaves the heating pot.

[0009] A positioning trigger unit is arranged along the conveying path of each production line. The positioning trigger unit includes a color mark sensor, which is used to identify the position boundary of a single piece of dough and output a positioning trigger signal.

[0010] The control unit establishes signal transmission connections with the first temperature measuring unit, the second temperature measuring unit, and the positioning trigger unit respectively, receives temperature acquisition signals and positioning trigger signals, and completes the determination of the lethal conditions for crust sterilization.

[0011] The rejection execution unit is installed in the downstream finished product conveying section of the pancake machine. It is connected to the control unit signal, receives the non-conforming judgment signal issued by the control unit, and performs the pancake rejection operation.

[0012] Preferably, the first temperature measuring unit is equipped with three microwave-resistant infrared temperature sensors. The three sensors are uniformly installed in the annular intervals corresponding to heating pots 1 to 3 or heating pots 2 to 4. The sensors are equipped with adjustable mounting brackets, which can slide and adjust the installation points along the circumference of the heating pot.

[0013] Preferably, the control unit includes a Siemens S7-1200 PLC, a switch, and a host human-machine interface (HMI); the PLC is equipped with a digital input module, a multi-channel analog signal acquisition module, and a digital output module, and the switch enables data communication between the PLC and the HMI; the PLC has a pre-set equivalent time difference calculation program.

[0014] Preferably, the equivalent time difference calculation program built into the PLC is used to record the time node when the dough reaches 90°C and the time node when the dough is taken out of the pot for temperature measurement, calculate the actual duration between the two nodes, and compare the calculated duration with the preset 6-second standard duration for verification.

[0015] Preferably, the PLC is internally programmed with device operation interlock control logic; when the system is in normal temperature measurement operation, the PLC blocks the operation authority of adjusting the frequency of the pan-frying machine host and modifying the conveyor speed, while monitoring abnormal conditions such as color mark sensor obstruction and human intervention in material handling in real time, and outputs a device alarm signal after detecting an abnormality.

[0016] Preferably, the HMI host computer integrates a data storage module, a historical curve retrieval module, and a batch data export module; the system stores the feeding temperature at multiple points, the discharge temperature at multiple points, the corresponding heating pot number, the qualification judgment result, and the rejection action record for each pancake, and all data is stored for no less than 15 days, and the exported file format is CSV.

[0017] Preferably, the rejection execution unit includes a pneumatic solenoid valve, a compressed air pipeline, and a blowing nozzle; the control terminal of the solenoid valve is connected to a PLC digital output module, and the PLC calculates the compensation delay based on the straight-line distance from the temperature measurement point to the rejection mechanism and the real-time running speed of the conveyor line. After the delay ends, the PLC outputs a drive signal to the solenoid valve, and the airflow blows away the unqualified cakes through the nozzle.

[0018] Preferably, all components inside the system that may come into direct or indirect contact with food are made of SUS304 stainless steel, the surface roughness of the components is controlled within 0.4μm, and the splicing positions of the components are treated with full welding and polishing process, with no dead corners for hygiene cleaning.

[0019] Preferably, the system is equipped with a complete electrical control circuit, which includes an AC220V main power supply branch and a 24VDC regulated power supply branch; the digital input module connects to all color mark sensors and heating pot proximity switch signals, the multi-channel analog acquisition module collects infrared temperature measurement signals from the front and back ends of each production line, and the digital output module drives the rejection solenoid valves of each production line in a unified manner.

[0020] A method for temperature monitoring and defective product rejection control in a rotary dough skin making machine includes the following steps:

[0021] S1. During the production line conveying process, the color mark sensor captures the cake mark and transmits a positioning trigger signal to the PLC;

[0022] After receiving the trigger signal, the S2.PLC synchronously reads all the multi-point temperature values ​​collected by the first temperature measuring unit and the second temperature measuring unit according to the preset fixed sampling interval.

[0023] S3.PLC calls the equivalent time difference calculation program to check whether the average temperature of the pancake reaches 90℃ and whether the duration of temperature rise meets the standard is 6 seconds. If both conditions are met, the pancake is deemed qualified; otherwise, it is deemed unqualified.

[0024] S4.PLC calculates the rejection compensation delay based on the real-time operating parameters of the conveyor line, and after the delay ends, it outputs a drive signal to the corresponding pneumatic solenoid valve of the production line to complete the rejection of unqualified cakes.

[0025] The S5.HMI host computer synchronously stores all production data of this batch of pie crusts. Staff can retrieve historical data tables and temperature change curves by production date, and support batch export and archiving.

[0026] The S6.PLC continuously collects operating parameters of the pan-frying machine and conveyor line. After identifying abnormal operating conditions such as equipment speed adjustment or sensor obstruction, it pauses the temperature measurement and acquisition process, simultaneously triggers an audible and visual alarm, and locks and removes the execution unit.

[0027] Beneficial effects

[0028] This invention provides a temperature monitoring and defective product rejection system and control method for a rotary dough-making machine. It has the following beneficial effects:

[0029] 1. This invention deploys multiple sets of microwave-resistant infrared temperature probes at the initial heating station and the high-temperature discharge station of the dough, and uses color mark sensors to lock the timing of data collection for each dough sheet. The PLC is equipped with an equivalent time difference calculation program to calculate the effective high-temperature maintenance time of the dough sheet and verify the sterilization process standard for each sheet. This prevents qualified dough sheets from being mistakenly rejected or substandard sterilized dough sheets from flowing downstream. The entire temperature measurement and rejection mechanism operates online throughout the process, without the need to interrupt the production of the dough sheet making machine for manual shutdown and inspection.

[0030] 2. This invention incorporates interlocking logic for the entire machine's operation into the control program. Adjustments to the frequency of the pan-frying host and the speed of the conveyor line will be locked by the system. Abnormal operating conditions such as sensor obstruction and human handling of materials can be identified in real time and trigger alarms. The accompanying host computer can store no less than 15 days of full production records. Each record is bound to the heating pot number, multi-point temperature measurement values, judgment results, and rejection actions. The stored data supports table export and temperature curve playback, meeting the mandatory requirements of food industry quality traceability regulations. Attached Figure Description

[0031] Figure 1 This is a system electrical network block diagram of the present invention;

[0032] Figure 2 This is the overall power supply circuit diagram of the system of the present invention;

[0033] Figure 3 This is the PLC digital input wiring diagram for the present invention;

[0034] Figure 4 This is the wiring diagram for the digital input of the PLC color mark sensor of the present invention;

[0035] Figure 5 This is the wiring diagram for the digital output of the PLC rejection solenoid valve in production lines 1-4 of this invention;

[0036] Figure 6 This is the wiring diagram for the digital output of the PLC rejection solenoid valve in production lines 5-7 of this invention.

[0037] Figure 7 This is the wiring diagram for PLC analog signal acquisition on production lines 1-4 of this invention;

[0038] Figure 8 This is the wiring diagram for PLC analog signal acquisition on production lines 5-7 of this invention;

[0039] Figure 9 This is a schematic diagram of the HMI (Human Machine Interface) of the present invention;

[0040] Figure 10 This is a diagram of the interface between the host computer data traceability and temperature curve of this invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1: A temperature monitoring and defective product rejection system for a rotary pan-frying machine, such as... Figure 1-10 As shown, the system consists of five parts: a first temperature measuring unit, a second temperature measuring unit, a positioning trigger unit, a control unit, and a rejection execution unit. The first temperature measuring unit is located in the heating zone after the material is loaded into the heating pot and includes three microwave-resistant infrared temperature sensors. The second temperature measuring unit is located in the high-temperature zone before the material is unloaded from the heating pot and is also equipped with three microwave-resistant infrared temperature sensors of the same model. The positioning trigger unit consists of color mark sensors arranged along the production line and installed along the finished product conveying path. The control unit consists of a Siemens S7-1200 PLC, an industrial switch, and a 12-inch HMI upper-level controller. The PLC hardware includes digital input modules, two 8AD analog signal acquisition modules, and multiple digital output modules. The rejection execution unit is installed in the finished product conveying section downstream of the pan-frying machine and consists of a pneumatic solenoid valve, compressed air pipeline, and air blowing nozzle.

[0043] The PLC establishes signal transmission links with the first temperature measuring unit, the second temperature measuring unit, and the positioning trigger unit, respectively, and receives multiple temperature analog signals and crust positioning trigger signals. It uses the internally stored equivalent time difference calculation program to determine the sterilization and lethality conditions of the crust. The PLC digital output module is electrically connected to the rejection execution unit. After determining that the crust is unqualified, it outputs a drive signal to control the air nozzle to complete the crust rejection.

[0044] Specifically, in the above specific embodiments, the selected microwave-resistant infrared temperature sensor can work stably in the microwave heating environment of the frying machine, is not affected by microwave radiation, and continuously outputs a linear analog temperature signal of 0~150℃, which can avoid the problems of reading drift and false alarms of ordinary infrared temperature measuring equipment under microwave conditions.

[0045] It is worth noting that the hardware structure of this system is compatible with both 8-pot and 14-pot rotary frying machines, which are the two mainstream types on the market. Switching between devices only requires modifying the number of pots in the HMI parameter interface, without changing the hardware installation structure such as sensors and electrical control circuits, thus making the equipment more adaptable.

[0046] The three microwave-resistant infrared temperature sensors of the first temperature measurement unit are uniformly assembled in the annular section corresponding to heating pots #1 to #3 or heating pots #2 to #4. Each sensor is equipped with an independent stainless steel adjustable mounting bracket, the bottom of which has a slide rail that slides along the circumference of the heating pot, and the bracket body has a pitch angle adjustment bolt.

[0047] Specifically, in the above-mentioned specific embodiments, the staff can adjust the lateral position of the sensor along the circumferential slide rail according to the actual width of the pancake and the offset of the heating area of ​​the heating pot. By adjusting the bolts, the probe's pitch focusing angle can be changed to ensure that each pancake passing through the heating pot falls completely into the temperature measurement and acquisition field of view, thus eliminating the single-point temperature measurement failure defect caused by pancake position fluctuations.

[0048] It is worth noting that all components in the system, including supports, covers, and air nozzles, that may come into direct or indirect contact with food are made of SUS304 stainless steel. The surface roughness of the components is controlled within 0.4μm, and the joints are made using a full-welding and polishing process. There are no weld grooves or unsanitary corners, which meets the hygiene design standards for food production equipment.

[0049] The entire electrical system uses an AC220V mains power supply. A 20A incoming line is connected to a 6A main circuit breaker, with branch lines connecting to a 240W 24VDC switching power supply. This 24VDC power supply powers the PLC, sensors, solenoid valves, and HMI touchscreen. An industrial switch hub connects to the PLC's Ethernet interface, the GL20-RTU interface module, and the 12-inch HMI touchscreen via network cables, enabling data exchange across the entire system.

[0050] The PLC digital input module DI connects to the metal proximity switches of heating pots 1-14 and the color mark sensors at the front and rear ends of each production line. The E-STOP safety circuit for the entire machine is connected in series at the front end of the digital input circuit. Two 8AD analog acquisition modules acquire the infrared temperature analog signals of the first and second temperature measurement units of line 14 and lines 5-7, respectively. The multi-channel digital output module DO drives the left and right rejection solenoid valves of the seven production lines in two groups.

[0051] Specifically, in the above specific embodiments, each branch of the power supply circuit is equipped with an independent fuse and a whole machine PE grounding protection terminal. The emergency stop circuit has the highest priority. When the equipment malfunctions and triggers an emergency stop, it directly cuts off all rejection and temperature control outputs, meeting the LOTO safety specifications for industrial equipment.

[0052] It should be noted that the PLC analog signal acquisition channel supports free switching between 100ms and 200ms temperature measurement sampling intervals. The factory preset parameters for each production line are shown in the table below. These parameters can be found at [link to table]. Figure 9 Manually modify the HMI parameter settings interface shown:

[0053] Line 1 200ms 50ms 400ms Lines 2-7 100ms 50ms 400ms

[0054] The PLC has a pre-stored equivalent time difference calculation program for determining the lethal conditions of microorganisms. The determination logic uses a dual-condition simultaneous determination formula:

[0055]

[0056] In the formula: This represents the average temperature of three temperature measurement points in the area after a single dough sheet is fed. The system timestamp for the first time the average temperature of the crust reached 90℃; The system timestamp for when the dough moves to the pre-cooking area and when the second temperature measurement unit completes temperature acquisition.

[0057] The PLC determines that the current dough is qualified only if both the average temperature and the duration of the temperature are met; if either indicator fails to reach the preset threshold, the dough is deemed to be substandard and unqualified.

[0058] Specifically, in the above specific embodiments, the algorithm abandons the existing mode of judging the finished product by relying solely on a single instantaneous temperature, and incorporates two dimensions, the average temperature and the duration of high temperature, into the judgment criteria, which can offset the misjudgment caused by small fluctuations in single-channel temperature measurement data.

[0059] It is worth noting that existing single-point temperature measurement devices can only collect the instantaneous temperature of the dough when it comes out of the pot, and cannot obtain complete heating time sequence data of the dough, nor can they quantify the duration of high temperature maintenance. This algorithm incorporates the time dimension into the sterilization condition verification, which is the core technological innovation that distinguishes it from existing temperature measurement devices.

[0060] The PLC continuously collects data on the driving frequency of the pan-frying machine and the operating speed of the conveyor line, while simultaneously monitoring the signal output status of the color mark sensor. When the system is in normal temperature measurement mode, the HMI interface locks the parameter modification buttons for the pan-frying frequency and conveyor line speed. If the conveyor line speed fluctuation exceeds ±5% or the color mark sensor is blocked and has no signal for more than 300ms, the PLC immediately pauses all temperature measurement sampling processes, simultaneously outputs an audible and visual alarm signal, and locks the drive output of all rejection solenoid valves.

[0061] Specifically, in the above specific embodiments, the interlock logic is a PLC-based program that cannot be shielded by manual operation. This can prevent production losses caused by misalignment of temperature measurement timing and rejection action when production line parameters are adjusted or sensors are blocked, resulting in the wrong rejection of qualified pancakes and the leakage of unqualified pancakes from the production line.

[0062] It is worth noting that conventional temperature measurement and rejection equipment on the market lacks underlying hardware interlocking logic. After the production line speed is adjusted, the timing of temperature measurement and rejection becomes completely disordered, which can easily lead to a large amount of raw material waste. This interlocking logic avoids this defect from the control layer.

[0063] PLC built-in dynamic rejection delay calculation formula:

[0064]

[0065] In the formula: To eliminate the compensation delay time; This is the fixed delivery distance from the second temperature measuring unit to the air blowing nozzle; This refers to the real-time operating line speed fed back by the encoder of the conveyor line.

[0066] The PLC reads the conveyor speed value in real time and updates the delay parameters in real time by substituting it into the formula; when the dough is judged to be unqualified, the PLC waits. Once the allotted time is up, a 400ms drive signal is sent to the corresponding production line solenoid valve, and compressed air is ejected through the nozzle to remove the defective cake.

[0067] Specifically, in the above specific embodiments, the delay time is synchronously corrected in real time according to the conveyor speed, so that there will be no missed rejection faults such as premature air jetting or air jetting after the cake has passed the rejection point. It should be noted that the traditional rejection mechanism uses fixed delay parameters and is only suitable for a single conveyor speed. After the production line speed is adjusted, the rejection accuracy drops significantly. This dynamic delay solution is suitable for all conventional speed adjustment ranges of the production line.

[0068] The host computer human-computer interaction interface is as follows Figure 9 As shown, the host computer is equipped with a local hard drive, and all production data is stored for no less than 15 days. Each storage record fully includes: production time, production line number, heating pot number, three-point temperature at the loading point, three-point temperature at the unloading point, average temperature, effective high-temperature duration, pass / fail judgment result, rejection action status, and rejection delay value. The host computer supports three data retrieval methods: querying the complete production record table by a specified date, replaying the real-time temperature change curve, and batch exporting raw data files in CSV format.

[0069] Specifically, in the above specific embodiments, the original production records stored in the system have an unalterable system timestamp, and staff cannot manually delete or modify historical data. During food supervision and inspection, complete production files can be directly exported, meeting the mandatory requirements of food industry quality traceability regulations.

[0070] It should be noted that the existing temperature measuring equipment for frying dough does not have long-term local storage capabilities and does not have the ability to record time-series temperature curves, thus making it impossible to complete food safety compliance traceability reviews.

[0071] Example 2 is a method for temperature monitoring and defective product rejection control of a rotary skin-making machine based on the system of Example 1. This example is a complete control process adapted to the above system, and the steps are as follows:

[0072] S1. The color mark sensor continuously scans the moving dough on the conveyor line, identifies the color mark on the surface of the dough, and sends a dough positioning trigger signal to the PLC digital input channel after identifying the color mark.

[0073] After receiving the trigger signal, the S2.PLC synchronously collects the three temperatures from the first temperature measuring unit and the three temperatures from the second temperature measuring unit according to the preset sampling interval of the corresponding production line.

[0074] S3.PLC calculates the average temperature measured at three points in the feeding area and records the timestamp when the average temperature first reaches 90℃. Read the timestamp corresponding to the temperature measurement after the pot is removed. Substitute the equivalent judgment formula to complete the crust qualification verification;

[0075] S4. If the dough is determined to be substandard, the PLC reads the real-time operating speed of the conveyor line and substitutes it into the delay calculation formula to calculate the compensation delay. After the waiting delay ends, a 400ms continuous drive signal is output to the rejection solenoid valve of the corresponding production line, and compressed air nozzles spray air to reject the cake; if the cake is determined to be qualified, no rejection drive signal is output, and the cake flows normally to the downstream process along the conveyor line.

[0076] S5. The host computer captures all temperature measurement, judgment, and rejection data for this batch of pancakes in real time and writes them to the local storage medium for permanent storage.

[0077] The S6 PLC continuously collects the operating frequency of the pan-frying machine, the conveyor speed, and the signal status of the color mark sensor. Once it detects a large fluctuation in equipment parameters or continuous sensor obstruction, it immediately pauses the temperature measurement and acquisition process in step two, outputs an audible and visual alarm, and locks all rejection output signals.

[0078] Specifically, in the above specific embodiments, the entire control process is executed continuously in a closed loop. Signal acquisition, algorithm judgment, elimination action, data storage, and abnormal interlocking operate synchronously, without the need for real-time human intervention.

[0079] It is worth noting that the entire control method relies on the PLC's underlying loop program for execution. The response delay from signal acquisition to judgment completion in a single round does not exceed 50ms, which can match the continuous high-speed production cycle of the rotating pancake machine and will not cause problems such as missed acquisition or judgment of pancakes.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A temperature monitoring and defective product rejection system for a rotary pan-frying machine, wherein the rotary pan-frying machine is equipped with multiple sets of heating pots arranged in a circular pattern along the circumference, the number of heating pots being 8 or 14, characterized in that, include: The first temperature measuring unit is located in the heating area after the material is fed into the heating pot. The first temperature measuring unit includes multiple microwave-resistant infrared temperature sensors, which are used to synchronously collect multi-point temperature data during the heating stage when the dough adheres to the heating pot. The second temperature measuring unit is set in the high-temperature area before the dough leaves the heating pot. The second temperature measuring unit is also equipped with multiple anti-microwave infrared temperature sensors to collect multi-point temperature data before the dough leaves the heating pot. A positioning trigger unit is arranged along the conveying path of each production line. The positioning trigger unit includes a color mark sensor, which is used to identify the position boundary of a single piece of dough and output a positioning trigger signal. The control unit establishes signal transmission connections with the first temperature measuring unit, the second temperature measuring unit, and the positioning trigger unit respectively, receives temperature acquisition signals and positioning trigger signals, and completes the determination of the lethal conditions for crust sterilization. The rejection execution unit is installed in the downstream finished product conveying section of the pancake machine. It is connected to the control unit signal, receives the non-conforming judgment signal issued by the control unit, and performs the pancake rejection operation.

2. The system according to claim 1, characterized in that, The first temperature measuring unit is equipped with three microwave-resistant infrared temperature sensors. The three sensors are uniformly installed in the annular intervals corresponding to heating pots 1 to 3 or heating pots 2 to 4. The sensors are equipped with adjustable mounting brackets, which can slide and adjust the installation points along the circumference of the heating pot.

3. The system according to claim 1, characterized in that, The control unit includes a Siemens S7-1200 PLC, a switch, and a host human-machine interface (HMI). The PLC is equipped with a digital input module, a multi-channel analog acquisition module, and a digital output module. The switch enables data communication between the PLC and the HMI. The PLC has a pre-set equivalent time difference calculation program.

4. The system according to claim 3, characterized in that, The PLC's built-in equivalent time difference calculation program is used to record the time node when the dough reaches 90°C and the time node when the dough is taken out of the pot for temperature measurement. It calculates the actual duration between the two nodes and compares the calculated duration with the preset 6-second standard duration for verification.

5. The system according to claim 3, characterized in that, The PLC is internally programmed with device operation interlock control logic. When the system is in normal temperature measurement mode, the PLC blocks the operation permissions of adjusting the frequency of the pan-frying machine host and modifying the conveyor speed. At the same time, it monitors abnormal conditions such as color mark sensor obstruction and human intervention in material handling in real time. After detecting the abnormality, it outputs an equipment alarm signal.

6. The system according to claim 3, characterized in that, The HMI host computer integrates a data storage module, a historical curve retrieval module, and a batch data export module. The system stores the feeding temperature at multiple points, the discharge temperature at multiple points, the corresponding heating pot number, the pass / fail judgment result, and the rejection action record for each pancake. All data is stored for no less than 15 days, and the exported file format is CSV.

7. The system according to claim 1, characterized in that, The rejection execution unit includes a pneumatic solenoid valve, a compressed air pipeline, and a blowing nozzle; the solenoid valve control terminal is connected to a PLC digital output module. The PLC calculates the compensation delay based on the straight-line distance from the temperature measurement point to the rejection mechanism and the real-time running speed of the conveyor line. After the delay ends, it outputs a drive signal to the solenoid valve, and the airflow blows away the unqualified cakes through the nozzle.

8. The system according to claim 1, characterized in that, All components inside the system that may come into direct or indirect contact with food are made of SUS304 stainless steel. The surface roughness of the components is controlled within 0.4μm. The splicing points of the components are treated with full welding and polishing process, leaving no dead corners for hygiene cleaning.

9. The system according to claim 1, characterized in that, The system is equipped with a complete electrical control circuit, which includes an AC220V main power supply branch and a 24VDC regulated power supply branch; the digital input module connects to all color mark sensors and heating pot proximity switch signals, the multi-channel analog acquisition module collects infrared temperature measurement signals from the front and back ends of each production line, and the digital output module drives the rejection solenoid valves of each production line in a unified manner.

10. A method for temperature monitoring and defective product rejection control of a rotary frying machine based on the system described in any one of claims 1 to 9, characterized in that, It includes the following steps: S1. During the production line conveying process, the color mark sensor captures the cake mark and transmits a positioning trigger signal to the PLC; After receiving the trigger signal, the S2.PLC synchronously reads all the multi-point temperature values ​​collected by the first temperature measuring unit and the second temperature measuring unit according to the preset fixed sampling interval. S3.PLC calls the equivalent time difference calculation program to check whether the average temperature of the pancake reaches 90℃ and whether the duration of temperature rise meets the standard is 6 seconds. If both conditions are met, the pancake is deemed qualified; otherwise, it is deemed unqualified. S4.PLC calculates the rejection compensation delay based on the real-time operating parameters of the conveyor line, and after the delay ends, it outputs a drive signal to the corresponding pneumatic solenoid valve of the production line to complete the rejection of unqualified cakes. The S5.HMI host computer synchronously stores all production data of this batch of pie crusts. Staff can retrieve historical data tables and temperature change curves by production date, and support batch export and archiving. The S6.PLC continuously collects operating parameters of the pan-frying machine and conveyor line. After identifying abnormal operating conditions such as equipment speed adjustment or sensor obstruction, it pauses the temperature measurement and acquisition process, simultaneously triggers an audible and visual alarm, and locks and removes the execution unit.

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