Double interlocking safety control system for electric equipment

Abstract

The invention provides a double-interlocking safety control system for electric equipment. The system comprises a position detection module, a first switch module, a second switch module and a control module. The first switch module is an electromechanical switch, the control end is connected with the position detection module, and the main loop is connected in series with the motor power supply loop; the second switch module is a semiconductor switch, the main loop is connected in series with the downstream of the first switch module, and the control end is connected with the control module; the input end of the control module is connected with the position detection module. The electromechanical switch and the semiconductor switch are connected in series to form two independent hardware breakpoints, position signals are fed back to the control module for arbitration, and a safety structure with hardware redundancy interlocking and state monitoring feedback is formed. The structure effectively overcomes the defects that a traditional single mechanical switch is poor in reliability and has no state feedback, and the safety and reliability of equipment in the aspect of preventing accidental contact with a high-speed rotating component are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of electrical safety structure technology, and in particular to a dual interlock safety control system for electric equipment. Background Technology

[0002] Currently, in electric appliances with high-speed rotating components (such as grinders and blades), a common safety measure to ensure user safety is to install a mechanical microswitch on the appliance's movable protective cover or casing. When the casing is opened, the switch contacts directly disconnect, thus cutting off the motor's main power supply circuit. However, this traditional single-switch structure has significant drawbacks: First, the switch contacts directly interrupt the motor's inductive load current, which can easily generate arcs. Long-term use may lead to contact erosion and adhesion, causing the safety function to fail and posing a safety hazard. Second, this structure is merely a simple on / off circuit; the appliance's control unit cannot obtain the switch's status (such as whether it is faulty or whether the contact is good) or the actual position of the casing. The system is in an open-loop state without feedback and lacks fault detection capabilities. Finally, the entire safety circuit relies on only one physical break point. Once this switch fails (such as contact adhesion), the appliance will completely lose its safety protection and may operate in a dangerous state.

[0003] In summary, the problems existing in the current technology urgently need to be solved. Summary of the Invention

[0004] This invention provides a dual interlock safety control system for electric equipment, which overcomes the shortcomings of the prior art and comprehensively improves the safety and reliability of the equipment.

[0005] This invention provides a dual interlock safety control system for electric equipment, comprising: A position detection module is installed on the moving part of the electric device to sense whether the moving part is in a safe position and output a corresponding position signal; The first switch module has its control terminal electrically connected to the position detection module so as to be directly driven by the position signal; the first switch module is connected in series in the power supply circuit of the electric device and is used to cut off the power supply circuit at the first node by physically disconnecting its main contacts when the position signal indicates an unsafe position. The second switch module is connected in series in the power supply circuit of the electric equipment and is located downstream of the first switch module. The control terminal of the second switch module is connected to the control module and is used to turn on or off the power supply circuit at the second node under the control of the control module. The control module has its input terminal connected to the position detection module and its output terminal connected to the control terminal of the second switch module. It is used to receive the position signal and to output a trigger signal to the second switch module to turn off the second node when the position signal indicates an unsafe position. The main circuits of the first switch module and the second switch module are connected in series to form two independent breakpoints arranged in sequence on the power supply circuit. Both must be in the conducting state at the same time for the drive motor to be powered and run.

[0006] According to the present invention, a dual interlocking safety control system for electric equipment is provided, wherein the position detection module includes a micro switch, a Hall sensor, or a proximity switch.

[0007] According to the present invention, a dual interlocking safety control system for electric equipment is provided, wherein the first switch module is an electromagnetic relay and its main contacts are normally open contacts.

[0008] According to the present invention, a dual interlock safety control system for electric equipment is provided, wherein the first switching module further includes a drive circuit, the drive circuit including a switching element connected in series in the coil circuit of the electromagnetic relay and a freewheeling diode connected in reverse parallel, and the control terminal of the switching element is connected to the position detection module as the control terminal of the first switching module.

[0009] According to the present invention, a dual interlock safety control system for electric equipment is provided, wherein the second switching module includes a trigger circuit and a MOSFET, the trigger circuit includes an optocoupler or a transformer, the input terminal of the optocoupler or transformer is connected to the control module, and the output terminal is connected to the control electrode of the MOSFET.

[0010] According to the present invention, a dual interlock safety control system for electric equipment is provided, wherein the trigger circuit further includes a current-limiting resistor connected in series at the output terminal of the optocoupler and an RC buffer circuit connected in parallel between the control electrode and the main terminal of the bidirectional thyristor.

[0011] According to the present invention, a dual interlock safety control system for electric equipment is provided, the system further comprising an alarm module connected to the control module, for issuing acoustic or optical alarm signals according to the instructions of the control module.

[0012] According to the present invention, a dual interlock safety control system for electric equipment is provided, wherein the control module includes a microcontroller unit or a programmable logic device.

[0013] According to the present invention, a dual interlock safety control system for electric equipment is provided, wherein the input terminal of the control module further includes a Schmitt trigger shaping circuit for shaping the received position signal to eliminate jitter.

[0014] According to the present invention, a dual interlock safety control system for electric equipment is provided, wherein the electric equipment is a coffee machine, a food processor, a juicer, or a power tool.

[0015] This invention provides a dual interlocking safety control system for electric equipment. The system connects an electromechanical first switch module, directly controlled by mechanical position signals, and a semiconductor-type second switch module, intelligently controlled by a control module, in series within the motor power supply circuit, forming two independent hardware breakpoints. This structural redundancy interlocking ensures that the motor power supply can be forcibly cut off in the event of a failure in either switch, fundamentally eliminating the risk of single-point failure and conforming to the "fail-safe" design principle. Simultaneously, the control module receives feedback signals from the position detection module in real time, not only controlling the triggering of the second switch module but also continuously monitoring the safety link status. This enables diagnosis and early warning of the casing position and switch response, giving the system closed-loop monitoring and fault identification capabilities. Furthermore, this architecture fully leverages the advantages of two types of switching devices: relays enable rapid physical power-off, while thyristors support millisecond-level precise shutdown and smooth control. Together, they ensure safety while also supporting soft-start and speed regulation functions, improving safety levels while optimizing equipment performance and lifespan. Overall, this invention constructs a rapid-response, status-aware, and redundantly reliable safety protection system without excessively increasing costs, which can be widely applied to various electric devices with moving parts. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a module of the dual interlock safety control system for electric equipment provided by the present invention; Figure 2 This is a circuit diagram of the dual interlock safety control system for electric equipment provided by the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] To address the problems in existing technologies, this invention proposes a dual interlock safety control system for electric equipment, thereby comprehensively improving the safety and reliability of the equipment. The dual interlock safety control system for electric equipment is described below, as follows: Figure 1 As shown, including but not limited to the following modules: A position detection module is installed on the moving part of the electric device to sense whether the moving part is in a safe position and output a corresponding position signal; The first switch module has its control terminal electrically connected to the position detection module so as to be directly driven by the position signal; the first switch module is connected in series in the power supply circuit of the electric device and is used to cut off the power supply circuit at the first node by physically disconnecting its main contacts when the position signal indicates an unsafe position. The second switch module is connected in series in the power supply circuit of the electric equipment and is located downstream of the first switch module. The control terminal of the second switch module is connected to the control module and is used to turn on or off the power supply circuit at the second node under the control of the control module. The control module has its input terminal connected to the position detection module and its output terminal connected to the control terminal of the second switch module. It is used to receive the position signal and to output a trigger signal to the second switch module to turn off the second node when the position signal indicates an unsafe position. The main circuits of the first switch module and the second switch module are connected in series to form two independent breakpoints arranged in sequence on the power supply circuit. Both must be in the conducting state at the same time for the drive motor to be powered and run.

[0020] like Figure 2As shown, the position detection module is physically installed on the moving part of the device that needs to be monitored, such as the top cover or protective cover of a grinder. Its core function is to sense whether the moving part is in a defined "safe position" such as closed or locked. In a preferred embodiment, the module can be a normally open micro switch. When the top cover is closed, it is pressed by a mechanical structure, and the contacts close; when the top cover is opened, the contacts reset and open. Its implementation is not limited to this; it can also be a combination of a Hall sensor and a magnet, or a proximity switch, etc. The module outputs a level signal (i.e., a position signal), for example, a high level represents a "safe position," and a low level represents a "non-safe position." This position signal is simultaneously output to the control terminal of the first switch module and the input terminal of the control module.

[0021] First Switching Module: This module is an electromechanical switching device, preferably an electromagnetic relay K1. The coil (i.e., the control terminal) of relay K1 is directly electrically connected to the output terminal of the position detection module. When the position signal indicates a "safe position" (e.g., outputting a drive voltage), the coil of relay K1 is energized and engaged; when the position signal indicates a "non-safe position" (e.g., the drive voltage disappears), the coil is de-energized and released. The normally open main contacts of relay K1 are connected in series to the AC or DC power supply circuit (L / N) of the drive motor M, forming the first physical break point (first node). Its function is to provide a hardware power-off mechanism directly and quickly driven by mechanical position, with fast response speed, and physical separation of contacts upon disconnection, high insulation resistance, and absolute shutdown.

[0022] The second switching module is a semiconductor switching device that can be triggered by an electrical signal, preferably a bidirectional TRIAC (Triac). Its two main terminals are connected in series in the aforementioned power supply circuit and are located downstream of the main contacts of relay K1. Its control electrode (i.e., the control terminal) is connected to an output port of the control module through an isolation drive circuit (such as an optocoupler). The conduction and cutoff of the TRIAC are completely controlled by the trigger signal output by the control module, forming a second controllable breakpoint (second node). Its advantages lie in its extremely fast switching speed (microsecond level) and ease of implementation of zero-crossing triggering, phase control, etc., making it suitable for soft starting or speed regulation of motors.

[0023] Control Module: This module serves as the system's logic arbitration and monitoring center, typically implemented by a microcontroller unit. One of its input / output (I / O) ports acts as an input, connected to the position detection module to continuously read and determine the position signal's status. The other I / O port acts as an output, connected to the control terminal of the second switching module via the aforementioned isolation drive circuit. The control module is programmed to execute core safety logic: it only sends a trigger signal to the TRIAC (Semiconductor Triac) from its output to turn it on when it continuously detects a position signal indicating a "safe position"; at any time, if the position signal changes to indicate a "non-safe position," it immediately (typically within microseconds) stops outputting the trigger signal, forcibly turning off the TRIAC.

[0024] The system works as follows: Safe Standby State: When the equipment cover is open, the position detection module outputs a "non-safe" signal. At this time, the coil of the first switch module (relay K1) is de-energized, and its main contacts open; simultaneously, the control module detects the "non-safe" signal and does not output a trigger signal, and the second switch module (thyristor) is turned off. The power supply circuit is cut off at both nodes, the motor M cannot be energized, and the system is in a safe state.

[0025] Normal startup process: a. When the user closes the cover, the position detection module is triggered and outputs a "safe" signal.

[0026] b. The "safety" signal directly drives the coil of relay K1 to engage, its main contacts close, the first node of the power supply circuit is connected, and power is supplied to the anode of the thyristor TRIAC.

[0027] c. Simultaneously, the control module's input receives a "safe" signal. The MCU's internal program then determines whether to send a trigger signal. Only after confirming that the "safe" signal remains stable (e.g., after software debouncing) will the MCU output a trigger signal.

[0028] d. The trigger signal, via the isolation drive circuit, turns on the TRIAC, connecting the second node of the power supply circuit. Motor M is then energized and begins controlled operation (e.g., smoothly accelerating to the set speed via soft start). At this point, the system enters normal operating mode.

[0029] Emergency shutdown and interlock protection: a. Active cover opening protection: If the user accidentally opens the cover during equipment operation, the position detection module 1 will immediately output an "unsafe" signal.

[0030] b. First-level rapid shutdown: The "unsafe" signal is captured in real time by the control module 4. The MCU cancels the trigger signal output in a very short time (within the program loop cycle, usually <1ms). The TRIAC turns off rapidly when the current crosses zero, and the motor immediately stops.

[0031] c. Second complete shutdown: Almost simultaneously, the "unsafe" signal causes the relay K1 coil to lose power, and its main contacts open under the action of mechanical spring force (with a mechanical release delay of a few milliseconds), thus achieving physical isolation of the power supply circuit.

[0032] d. Fail-safety: This process highlights the core value of dual interlocking. Even if the control module fails to turn off the SCR in time due to program malfunction (a low-probability event), the contacts of relay K1, directly driven by the position signal and belonging to an independent hardware link, will still physically disconnect upon opening the cover, ensuring ultimate safety. Conversely, if the relay contacts cannot disconnect due to sticking, the control module can still stop the motor by turning off the SCR. The two serve as redundant backups for each other.

[0033] As a further optional embodiment, the position detection module includes a micro switch, a Hall sensor, or a proximity switch.

[0034] Specifically, a micro switch is a low-cost, simple, and reliable mechanical position sensor. In this embodiment, the micro switch is fixedly mounted on the device housing, and its button or lever mechanism contacts the inner surface of the moving part (such as the top cover of a grinder) or the linkage mechanism. When the moving part is closed to the safe position, the button of the micro switch is pressed, changing the state of its internal contacts (e.g., from normally open to closed), thereby outputting a level signal indicating a "safe position" (e.g., from a high-impedance state to a low-impedance state). The advantage of this scheme is its simple and direct circuit and clear signal. Its disadvantage is that it is a contact-based detection method, and long-term use may lead to mechanical wear.

[0035] A Hall sensor is a non-contact magnetic sensing element. In this embodiment, the Hall sensor chip is fixedly mounted on the device housing, while a permanent magnet is correspondingly mounted on the moving part. When the moving part moves to a safe position, the permanent magnet approaches the Hall sensor, causing it to sense a sufficient magnetic field strength. The output pin state of the Hall sensor then flips (e.g., from high to low), outputting a "safe position" signal. This solution has no physical contact, a long lifespan, and good environmental resistance, but its cost is slightly higher than that of a microswitch, and it requires ensuring the alignment of the magnet and the sensor.

[0036] Proximity switches (such as inductive or capacitive types) are also a type of non-contact sensor. In this embodiment, the sensing surface of the proximity switch faces the movement path of the moving part. When the moving part (usually a metal part) enters its preset sensing distance and stops at a safe position, the internal circuit state of the proximity switch changes, and its output terminal generates a jump, thereby emitting a "safe position" signal. This solution is particularly suitable for detecting metal moving parts and has high reliability, but it is usually slightly more expensive and larger than the former two methods.

[0037] As a further optional embodiment, the first switch module is an electromagnetic relay, and its main contacts are normally open contacts.

[0038] In this embodiment, the core component of the first switching module is an electromagnetic relay. Its coil forms the control terminal, directly driven by the position signal output by the position detection module: the coil is energized when the position signal indicates a safe position; otherwise, it is de-energized. The normally open main contact of this relay serves as the actuating component and is connected in series to the power supply circuit of the drive motor.

[0039] Its working logic and advantages are as follows: When the moving parts are in an unsafe position, the relay coil is de-energized, and its normally open main contacts remain in their inherent open state, physically disconnecting the first node. The power supply circuit cannot be connected, and the system is in a safe state. This design essentially conforms to the "fail-safe" principle, meaning that in the event of a power outage, wire breakage, or signal abnormality, the system defaults to a safe disconnection. Simultaneously, the physical isolation provided by the mechanical contacts ensures complete shutdown. Furthermore, the relay is directly driven by the position signal, forming a hardware safety redundancy link independent of the control module. Even if the control system fails, basic safety can still be guaranteed through mechanical action.

[0040] As a further optional embodiment, the first switching module further includes a driving circuit, which includes a switching element connected in series in the coil circuit of the electromagnetic relay and a freewheeling diode connected in reverse parallel. The control terminal of the switching element is connected to the position detection module as the control terminal of the first switching module.

[0041] Specifically, the driving circuit is integrated inside the first switching module, and its main components include a switching element and a freewheeling diode. The switching element (e.g., an NPN bipolar transistor or an N-channel MOSFET) is connected in series between the coil of the electromagnetic relay and the power supply. Its control terminal (e.g., the base of the transistor or the gate of the MOSFET) is the overall control terminal of the first switching module, which is directly electrically connected to the output of the position detection module to receive and respond to the position signal.

[0042] The freewheeling diode is connected in reverse parallel across the two ends of the electromagnetic relay coil, with its anode connected to the negative end of the coil (or the switching element side) and its cathode connected to the positive end of the coil (or the power supply side).

[0043] Its working process and beneficial effects are as follows: When the position detection module outputs a valid signal indicating a "safe position," this signal drives the switching element to conduct, thereby forming a complete current path and energizing the relay coil. When the position signal changes to indicate a "non-safe position," the switching element is turned off, and the coil circuit is broken.

[0044] The freewheeling diode plays a crucial protective role at this moment: The relay coil is an inductive load, and a high reverse induced electromotive force (voltage spike) is generated when the current is suddenly interrupted. The freewheeling diode provides a discharge path for this reverse electromotive force, allowing it to decay through the diode cycle, thereby effectively clamping the voltage and preventing high-voltage spikes from breaking down or damaging the switching elements and the output circuit of the position detection module. This greatly improves the reliability and lifespan of the drive circuit.

[0045] This drive circuit is a preferred and classic implementation designed to enable safe and reliable control of a high-power relay coil by a small current signal (from the position detection module).

[0046] As a further optional embodiment, the second switching module includes a trigger circuit and a MOSFET. The trigger circuit includes an optocoupler or a transformer. The input terminal of the optocoupler or transformer is connected to the control module, and the output terminal is connected to the control electrode of the MOSFET.

[0047] In this embodiment, the core switching device of the second switching module is a power metal-oxide-semiconductor field-effect transistor. Its two main terminals (source and drain) are connected in series to the power supply circuit of the drive motor and are located at the second node downstream of the first switching module (such as a relay).

[0048] To ensure safe and reliable control of the power MOSFET by the control module and to achieve electrical isolation between high and low voltages, this embodiment is equipped with a dedicated trigger circuit. The core of this trigger circuit is an isolation device, which can be an optocoupler or a pulse transformer.

[0049] When an optocoupler is used: its input terminal (usually a light-emitting diode) is connected to a designated output pin of the control module, and is driven to emit light by a trigger signal output by the MCU. Its output terminal (phototransistor) is connected to the gate (i.e., the control electrode) of the power MOSFET. When the MCU outputs a valid trigger signal to turn on the optocoupler, it provides a driving voltage to the gate of the MOSFET, turning it on; otherwise, it turns it off.

[0050] When a pulse transformer is used: its primary winding receives a pulse-type trigger signal from the control module, and the isolation voltage induced in the secondary winding is used to drive the gate of the MOSFET.

[0051] As a further optional embodiment, the trigger circuit also includes a current-limiting resistor connected in series at the output of the optocoupler and an RC buffer circuit connected in parallel between the control electrode and the main terminal of the bidirectional thyristor.

[0052] Specifically, this current-limiting resistor is connected in series between the output of the optocoupler (i.e., the collector or emitter of the phototransistor) and the power supply (used to provide gate / trigger current). Its main function is to limit the maximum current flowing into the control electrode of the second switching module. When the optocoupler is turned on, without this resistor, the instantaneous current may be too large, potentially exceeding the rated current of the optocoupler output and also impacting the gate of the second switching module (such as the gate of a MOSFET or the gate of a thyristor). Adding a suitable current-limiting resistor ensures that the drive current is stable within a safe and effective range, protecting both the driving and driven devices, and is a fundamental design feature to ensure stable and reliable triggering operation.

[0053] This RC snubber circuit consists of a resistor and a capacitor connected in series, and then connected in parallel between the main terminals (usually T1 and T2) of the second switching module (taking a triac as an example) and its control electrode (gate). (A more common connection is direct parallel connection between the T1 and T2 main terminals, but connection to the gate is used for specific protection.) Its main function is to suppress the rate of change of voltage (dv / dt) and possible voltage spikes. When semiconductor devices such as triacs are turned off, or when transient voltage changes occur in the circuit, excessively high dv / dt may cause the device to turn on falsely. The RC snubber circuit absorbs transient energy through the capacitor and dampens oscillations through the resistor, effectively reducing the dv / dt between the main terminals and absorbing surge voltages generated during switching. This prevents the second switching module from being falsely triggered or damaged due to electrical stress, significantly enhancing its durability and reliability under inductive loads (such as motors).

[0054] As a further optional embodiment, the system also includes an alarm module connected to the control module, for issuing acoustic or optical alarm signals according to instructions from the control module.

[0055] In this embodiment, the alarm module is an important extension of the system's human-computer interaction and the visualization and audibility of its safety status. Its core function is to receive and execute instructions from the control module, conveying specific system status, especially safety anomalies or fault information, to users or maintenance personnel through sound and light.

[0056] Acoustic alarm unit: typically an active or passive buzzer (requiring a drive circuit to generate a specific frequency). Active buzzers integrate an oscillation source, producing sound upon power-up, and are simple to control; passive buzzers require a control module to output a PWM signal of a specific frequency to drive them, enabling tone changes.

[0057] Optical alarm unit: Typically consists of one or more light-emitting diodes (LEDs), which can be designed with different colors (e.g., green for normal operation, red for fault) to visually distinguish the status. Multi-color LEDs or small displays can also be used to display richer information.

[0058] The drive input terminals of the alarm module (such as the power control terminal of the buzzer, the anode drive terminal of the LED) are connected to one or more general purpose input / output (GPIO) pins of the control module. The internal program of the control module is configured to activate the corresponding alarm unit by setting the corresponding GPIO port level high / low or outputting a PWM signal when a specific event is detected.

[0059] During equipment operation, if the control module detects in real time that the position signal suddenly becomes "unsafe" (such as the casing being accidentally opened), in addition to immediately executing the shutdown procedure, it can simultaneously trigger the alarm module (for example, drive the red LED to flash rapidly and make the buzzer sound urgently), to immediately warn the user of dangerous operation or state, thereby improving the timeliness and effectiveness of safety warnings.

[0060] Under normal and safe conditions, the control module can also drive the green LED in the alarm module to remain constantly lit, serving as a visual confirmation that the system is ready and in a safe locked state, thereby improving the user experience and interactivity of the product.

[0061] As a further optional embodiment, the control module includes a microcontroller unit or a programmable logic device.

[0062] Specifically, a microcontroller unit (MCU) is a single-chip microcomputer that integrates a processor core, memory, timers, and various input / output interfaces. In this embodiment, a general-purpose MCU (such as products from ST, Microchip, NXP, etc.) with sufficient I / O ports and program storage space is selected. One I / O port is configured as an input mode, connected to the position detection module, for continuously sampling position signals; another I / O port is configured as an output mode, connected to the control electrode of the second switch module through an isolation drive circuit, for outputting trigger signals; additional I / O ports can also be allocated for connecting peripheral devices such as alarm modules.

[0063] Its advantages lie in the high flexibility and powerful programmability of MCUs. Developers can write complex control, diagnostic, and communication programs using high-level languages ​​such as C, such as implementing software debouncing, fault diagnosis algorithms, delayed startup logic, and communication protocols with higher-level systems. MCUs offer a high degree of intelligence, convenient function expansion, and relatively low overall cost, making them ideal for mass-produced consumer electronics products.

[0064] A programmable logic device (PLD) is a semiconductor device, such as a CPLD or FPGA, whose internal logic gates and interconnections can be configured by the user as needed. In this embodiment, a PLD is used to implement the core interlocking logic of the control module.

[0065] Its advantages lie in the following: the hardware parallel processing characteristics of PLDs enable extremely fast response speeds, with logic decision and signal output delays as low as nanoseconds, providing the highest level of real-time performance. Its internal logic is defined by a hardware description language (such as VHDL), ensuring deterministic and reliable execution, eliminating the risk of software malfunctions, and exhibiting strong anti-interference capabilities. It is particularly suitable for industrial or special applications with extremely stringent requirements for safety response time. Once its logic is programmed and solidified, its operation is highly stable.

[0066] As a further optional embodiment, the input of the control module also includes a Schmitt trigger shaping circuit for shaping the received position signal to eliminate jitter.

[0067] In this embodiment, the Schmitt trigger shaping circuit, as a pre-conditioning stage, is located in the path between the output of the position detection module and the core logic processing unit of the control module (such as the GPIO port of the MCU). Its core function is to "clean" the raw position signal, which may be accompanied by jitter, glitches, or slow edges.

[0068] When moving parts (such as the top cover) close or open, their mechanical movement can cause physical bounce in the contacts of mechanical position sensors such as microswitches, resulting in multiple rapid transitions in the output signal within a short period (i.e., "jitter"). Schmitt triggers have a hysteresis voltage characteristic, meaning they have two distinct threshold voltages (positive and negative). The output flips high only when the input signal level exceeds the higher positive threshold; and only when the input signal level falls below the lower negative threshold. Input changes between the two thresholds do not cause output changes. This characteristic effectively "absorbs" the limited voltage fluctuations caused by contact bounce, converting them into clean, stable single-level transitions, thus preventing the control module from misinterpreting a valid operation as multiple invalid triggers.

[0069] Electrical noise in the power supply line or environment may couple onto the position signal line, creating glitches. The hysteresis characteristic of the Schmitt trigger can also effectively filter out small noise spikes, improve the signal's anti-interference capability, and ensure that the signal input to the control module remains reliable and clear even in complex electromagnetic environments.

[0070] For sensor signals with slow response or skewed edges, Schmitt triggers can convert them into digital signals with steep edges and clear logic, which is beneficial for control modules to perform fast and accurate sampling and identification.

[0071] This circuit can directly use an integrated Schmitt trigger logic gate chip (such as 74HC14) to connect the raw output signal of the position detection module to its input terminal, and then connect its output terminal to the input pin of the MCU. Alternatively, a similar function can be achieved in the MCU software by configuring the pull-up / pull-down resistors inside the input pins in conjunction with a software debouncing algorithm. However, the hardware Schmitt trigger solution provides a more deterministic guarantee at the pure hardware level, does not consume MCU processing resources, and has a more immediate and reliable response.

[0072] As a further optional embodiment, the electric device is a coffee machine, food processor, juicer, or power tool.

[0073] This system is not limited to any specific device; its generalized architecture allows it to be widely adapted to various household appliances, kitchen equipment, and power tools. The following are some typical application examples: Coffee machine: In this application, the "moving part" specifically refers to the grinder cover or bean hopper cover of the coffee machine. The position detection module is installed near the cover opening to detect whether the cover is fully closed and sealed. The drive motor is a grinding motor that drives the grinding disc. The system ensures that the grinding motor can only start when the cover is fully closed, preventing the user from touching the high-speed rotating blades.

[0074] Food processors / food processors: In such devices, the "moving part" is typically the lid of the container or the cover of the blade assembly. A position detection module detects whether it is properly installed. The drive motor is a high-speed motor that drives the mixing or grinding blades. This system effectively prevents the blades from activating when the container is not properly sealed, avoiding food splashing or user contact with hazardous areas.

[0075] Juicer: The operating principle is similar to that of a food processor. By detecting the position of the feed tube cover or the protective cover of the pressing head, the power supply of the motor that drives the extrusion screw or blade is controlled to ensure safe operation.

[0076] Power tools (such as angle grinders and chainsaws): In such industrial or household hand tools, the "moving part" may be a tool guard or a safety catch. The system is used to ensure that the guard is in the correct position to block flying debris, or that the safety catch is released, before the tool motor driving the spindle or saw chain can be turned on, preventing serious personal injury caused by accidental start-up.

[0077] The above application examples demonstrate that the system architecture of this invention possesses high flexibility and versatility. Its core value lies in providing a standardized, highly reliable safety interlock solution for any device that requires a strong correlation between physical location and motor power supply, effectively improving the inherent safety level of various electric devices.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual interlock safety control system for electric equipment, characterized in that, include: A position detection module is installed on the moving part of the electric device to sense whether the moving part is in a safe position and output a corresponding position signal; The first switch module has its control terminal electrically connected to the position detection module so as to be directly driven by the position signal; the first switch module is connected in series in the power supply circuit of the electric device and is used to cut off the power supply circuit at the first node by physically disconnecting its main contacts when the position signal indicates an unsafe position. The second switch module is connected in series in the power supply circuit of the electric equipment and is located downstream of the first switch module. The control terminal of the second switch module is connected to the control module and is used to turn on or off the power supply circuit at the second node under the control of the control module. The control module has its input terminal connected to the position detection module and its output terminal connected to the control terminal of the second switch module. It is used to receive the position signal and to output a trigger signal to the second switch module to turn off the second node when the position signal indicates an unsafe position. The main circuits of the first switch module and the second switch module are connected in series to form two independent breakpoints arranged in sequence on the power supply circuit. Both must be in the conducting state at the same time for the drive motor to be powered and run.

2. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The position detection module includes a micro switch, a Hall sensor, or a proximity switch.

3. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The first switch module is an electromagnetic relay, and its main contacts are normally open contacts.

4. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The first switching module further includes a driving circuit, which includes a switching element connected in series in the coil circuit of the electromagnetic relay and a freewheeling diode connected in reverse parallel. The control terminal of the switching element is connected to the position detection module as the control terminal of the first switching module.

5. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The second switching module includes a trigger circuit and a MOSFET. The trigger circuit includes an optocoupler or a transformer. The input terminal of the optocoupler or transformer is connected to the control module, and the output terminal is connected to the control electrode of the MOSFET.

6. The dual interlock safety control system for electric equipment according to claim 5, characterized in that, The trigger circuit also includes a current-limiting resistor connected in series at the output of the optocoupler and an RC buffer circuit connected in parallel between the control electrode and the main terminal of the bidirectional thyristor.

7. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The system also includes an alarm module connected to the control module, used to issue acoustic or optical alarm signals according to the instructions of the control module.

8. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The control module includes a microcontroller unit or a programmable logic device.

9. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The input terminal of the control module also includes a Schmitt trigger shaping circuit, which is used to shape the received position signal and eliminate jitter.

10. The dual interlock safety control system for electric equipment according to claim 1, characterized in that, The electric equipment is a coffee machine, food processor, juicer, or power tool.

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