Electronic safety equipment for machines or industrial plants and related safety method

Abstract

To provide electronic safety equipment capable of solving the problem in which an actual resonant frequency of an antenna circuit of known devices may be far from its nominal resonant frequency.SOLUTION: An antenna circuit (10) comprises a resonant electric circuit (6) with a plurality of tuning auxiliary elements (7) arranged in parallel to at least one first inductor (61) and at least one first capacitor (62). Further provided is selection means (3) associated with the tuning auxiliary elements (7) and configured to include or exclude one or more of the tuning auxiliary elements (7) in or from the resonant electric circuit (6) to modify the inductance and / or capacitance of the resonant electric circuit (6) and obtain a desired tuning frequency value of the resonant electric circuit (6).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates generally to electronic safety equipment for industrial machines and plants.

[0002] The invention belongs to the technical field of safety equipment, in particular to safety equipment applied to machines and / or industrial plants.

[0003] In particular, the invention relates to electronic safety switches of the RFID type, in this context a safety switch must at least detect a suitable actuator in its vicinity in order to activate its safety output and, as a consequence, to send a consensus signal for the safe start-up of a machine and / or industrial plant.

[0004] The equipment covered by the present invention can also be applied to safety switches that lock actuators, depending on the requirements and needs, where the safety switch needs to sense the correct actuator (guard closed) in close proximity and lock onto itself (guard closed and locked) in order to activate its safety output. [Background technology]

[0005] In industrial environments, numerous industrial machines of different complexity, size, and difficulty of use are used daily.

[0006] Such industrial machinery, depending on its construction and use, has a variety of hazards and elements that require attention.

[0007] Indeed, systems and devices are used to guard access and danger areas of such industrial machines to protect users and operators.

[0008] Traditionally, access is protected by guards, such as doors, gates, shutters, covers or other elements or devices that, when closed, prevent a user from reaching a hazardous area or potentially accidentally contacting such industrial machinery or equipment.

[0009] To monitor the status of a guard protecting an access, it is known to use electronic security systems which usually comprise a first device attached to a fixed part of the guard and a second device attached to a movable part of the guard, the second device being in close proximity to the first device when the access is closed.

[0010] Typically, the first device includes antenna circuitry for recognizing in a wireless mode that a second device is in proximity to the first device.

[0011] To enable this, the second device includes an RFID transponder that generates a response signal when excited by the signal transmitted by the antenna circuit.

[0012] This response signal is in turn received by the antenna circuitry and processed by the first device, causing the first device to recognise that a second device is in proximity and therefore that the guard is closed.

[0013] A disadvantage of known devices is that the effective values ​​of components in the antenna circuit usually lie within a fairly wide tolerance range from the nominal purchased value. For example, an inductor or capacitor may have a tolerance of ±10% from the nominal value of inductance or capacitance. Therefore, the actual resonant frequency of the antenna circuit of known devices may also be far from the nominal resonant frequency.

[0014] This has a very negative impact on the performance of the device's antenna circuits, e.g. resulting in low accuracy of transponder recognition and high performance variability between different devices.

[0015] These drawbacks are even worse when known devices are installed and used in environments subject to high temperature fluctuations of 90-100° C. or more. Summary of the Invention

[0016] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an electronic safety device that can solve the above-mentioned inconveniences and serious problems.

[0017] Another object of the present invention is to provide an electronic safety system capable of protecting and guarding access and danger areas of industrial machinery.

[0018] A further object of the present invention is to provide an electronic safety equipment for controlling and managing moving guards and other safety elements already known and existing on the market.

[0019] It is another object of the present invention to provide an electronic safety system in which the tolerances of the various components can be controlled.

[0020] It is a further object of the present invention to provide an electronic safety equipment which is able to adapt its characteristics to the temperature of the environment in which it is installed.

[0021] Another object of the present invention is to provide an electronic safety system which is simple and inexpensive to implement.

[0022] It is a further object of the present invention to provide an electronic safety system that is easy to install and use on new or existing industrial machines and systems.

[0023] These and other objects are achieved by an electronic safety system as claimed in the attached independent claims.

[0024] Further detailed technical features are set forth in the attached dependent claims. [Brief description of the drawings]

[0025] The present invention will now be described by way of example only and not by way of limitation in accordance with some of its preferred embodiments with reference to the accompanying drawings. [Figure 1] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Diagram 2] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Diagram 3] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Figure 4] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Diagram 5] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Figure 6] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Figure 7] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Figure 8] 1 is a schematic diagram of components of an electronic safety system according to embodiments of the present invention; [Figure 9] 1 is a schematic top view of a machine protected by a guard employing electronic safety equipment according to the present invention; FIG. [Figure 10] 4 is a flowchart showing the operation of the electronic safety equipment according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] With reference to the above mentioned drawings, preferred embodiments of the electronic safety equipment according to the present invention are shown.

[0027] With reference to the above figure, the electronic safety equipment 1 to which the present invention relates comprises a first electronic safety device (hereinafter safety switch 11) mounted, for example, on a fixed part 41 of a guard 40 of a protective barrier 43 for a machine 50 or an industrial plant, and a second electronic safety device (hereinafter actuator 12) mounted, for example, on a movable part 42 of the guard 40 itself.

[0028] With reference to the accompanying FIG. 9, it can be seen that the safety switch 11 and the actuator 12 are mounted on a guard 40 of a machine 50, for example an industrial machine.

[0029] Referring again to Figure 9, the guard 40 comprises a door with the safety switch 11 fixed to a fixed frame 41 (fixed part) of the door and the actuator 12 fixed to a leaf 42 (movable part) of the door.

[0030] When the door is closed, a safety switch 11 detects the proximity of an actuator 12 which means the door is closed.

[0031] In a first embodiment of the present invention, the actuator 12 comprises a transponder 63 and the safety switch 11 comprises a switching means 30, a control unit 20 and an antenna circuit 10 configured to excite the transponder 63 when the actuator 12 is in the vicinity of the safety switch 11 to detect the presence of the safety switch 11.

[0032] The switching means 30 is controlled by the control unit 20 and can be in a mutually distinguishable active state and inactive state.

[0033] In this example, the switching means 30 includes one or more safety output units 31 of an OSSD (Output Signal Switching Device) type, each of which can take at least an active state and an inactive state that are distinguishable from each other.

[0034] By way of example only, an active secure output unit transmits a signal and has a logic state of "1" or "ON", while an inactive secure output unit does not transmit a signal and has a logic state of "0" or "OFF".

[0035] More preferably, the switching means 30 comprises at least two independent and redundant safety outputs 31 in the form of OSSDs.

[0036] In other possible embodiments, the switching means 30 may be of other known types and may comprise electronic contacts of a mechanical, electromechanical, relay or other electrical, electronic or electromechanical element selectively switchable from an active state allowing transmission of a signal to an inactive state not allowing transmission of a signal.

[0037] The switching means 30 is connected to a communication interface (not shown) configured to transmit one or more signals (associated with the state of the switching means 30) to one or more command devices 51 external to the safety switch 11. In particular, the communication interface is configured to transmit at least one signal encoding the state of the switching means 30.

[0038] By way of example only, the communication interface may comprise one or more connectors or a communication BUS such as an IO-Link, IO-Link Safety, ProfiSafe or ProfiNet type, or may be wireless, or may be implemented in any of the combinations mentioned or known in the state of the art.

[0039] The communication interface may be coupled or connected to a command device 51 arranged, in use, to control a plant or machine 50 based on a signal associated with the state of the switching means 30 .

[0040] The command device 51 may comprise a PLC or a safety module or a contactor connected to the power supply of the plant or machine 50 or any other similar or similar device or any combination of these.

[0041] For example, if the state of the switching means 30 is inactive, the control device will not allow the machine 50 to be started or to be interrupted in operation.

[0042] Alternatively, the communications interface may be directly coupled or connected to the machine 50 .

[0043] The antenna circuit 10 of the safety switch 11 is configured to detect whether the actuator 12 is in close proximity to the safety switch 11, and if close proximity is detected, to transmit a presence signal A directly or indirectly to the control unit 20.

[0044] The control unit 20 activates the switching means 30 based on at least the presence signal A.

[0045] For example, the control unit 20 may activate the switching means 30 when the presence signal A indicates that the actuator 12 is in proximity to the safety switch 11, in other words that the guard 40 is closed.

[0046] In addition, if the safety switch 11 is equipped with a locking mechanism (not shown) that locks the actuator 12 to the safety switch 11 itself mechanically or by magnetic force due to an electromagnetic field, the control unit 20 may be configured to activate the switching means 30 when it detects that the presence signal A indicates that the actuator 12 is in proximity to the safety switch 11 and, at the same time, that the actuator 12 is also locked by the locking mechanism, in other words, that the guard 40 is closed and locked.

[0047] In such a case, the switching means 30 will issue a safety signal B indicating that the machine 50 is in a safe state and can be started.

[0048] To illustrate this, in an embodiment in which the switching means 30 includes two safety outputs 31OSSD, both safety outputs 31OSSD are in the active state to identify the safety signal B. Alternatively, the first safety output 31OSSD is activated when the guard is closed, while the second safety output 31OSSD is activated when the guard is locked.

[0049] In an exemplary and preferred embodiment, the control unit 20 includes at least a first microcontroller 1 and at least a second microcontroller 2 that are connected to each other and communicate redundantly (FIGS. 1 to 4). In another embodiment not shown, the control unit 20 includes one microcontroller that performs the functions of the two microcontrollers 1 and 2.

[0050] Advantageously, the two microcontrollers 1, 2 are connected to switching means 30 and control the switching means 30 to switch it from an active state to an inactive state or from an inactive state to an active state. For example, in an embodiment in which the communication means 30 comprises two secure outputs 31 OSSDs, the first microcontroller 1 is connected to a first secure output and the second microcontroller 2 is connected to a second secure output.

[0051] The antenna circuit 10 comprises a resonant electric circuit 6 having at least one first capacitor 62 , at least one first inductor 61 in parallel with the first capacitor 62 , and a number of tuning assist elements 7 .

[0052] As described in more detail below, when power is supplied to the resonant electrical circuit 6, the transponder 63 of the actuator 12 is excited and modulates the electric field generated by the resonant electrical circuit 6 by changing the shape of the oscillatory wave in the resonant electrical circuit 6 to generate a presence signal A.

[0053] The tuning assist element 7 preferably includes a plurality of assist capacitors arranged in parallel with the first inductor 61 and the first capacitor 62 (FIGS. 1 to 4).

[0054] Alternatively, in an embodiment not shown, the tuning assist element 7 comprises a plurality of auxiliary inductors arranged in parallel with the first inductor 61 and the first capacitor 62 .

[0055] In a further embodiment, as shown diagrammatically in FIGS. 5 and 7, which show only the resonant electric circuit 6 , the tuning assist element 7 comprises at least one auxiliary capacitor arranged in series with said first capacitor 62 .

[0056] In another possible embodiment, as shown diagrammatically in FIGS. 6 and 8 which show only the resonant electric circuit 6, the tuning assist element 7 comprises at least one auxiliary inductor arranged in series with the first inductor 61.

[0057] The safety switch 11 also comprises selection means 3 associated with said tuning assist elements 7 and configured to include or exclude one or more of said tuning assist elements 7 from said resonant electric circuit 6. The selection means 3 thus make it possible to modify the overall inductance and / or capacitance of the resonant electric circuit 6 in order to obtain a desired tuning frequency value of the resonant electric circuit 6.

[0058] Advantageously, in this way, even if the actual values ​​of the inductance and capacitance of the first inductor 61 and the first capacitor 62 do not correspond to their nominal values, a desired frequency, for example 125 kHz or another frequency other than 125 kHz, can be obtained by activating or deactivating one or more tuning assist elements 7. This allows the safety switches 11, whose resonant circuits are always tuned to the desired tuning frequency, to be industrially produced, guaranteeing the desired performance for all produced safety switches 11, minimizing production losses and reducing production time and costs.

[0059] In practice, by varying the capacitance or inductance of the resonant electric circuit 6, the frequency of the resonant electric circuit 6 can be tuned to a desired frequency.

[0060] For example, when tuning the antenna to 125 KHz, a capacitance is added in parallel or series with the first inductor 61 and / or the first capacitor 62 when the excitation frequency of the resonant electric circuit 6 is greater than 125 KHz, and a capacitance is removed in parallel or series with the first inductor 61 and / or the first capacitor 62 when the excitation frequency is less than 125 KHz. In practice, when tuning the antenna circuit 10, the control unit 20 uses the selection means 3 to include or exclude one or more tuning assist elements 7, each having a capacitance, from the resonant electric circuit 6 in order to achieve a desired tuning frequency.

[0061] The selection means 3 is controlled by the control unit 20. The selection means 3 may, for example, comprise one or more switches 14. Each of the one or more switches 14 is electrically associated with at least one of the tuning assist elements 7 and includes or excludes the at least one tuning assist element 7 from the resonant electrical circuit 6.

[0062] For example, in an embodiment in which the tuning assist elements 7 are electrically connected in parallel with the first inductor 61 and the second inductor 62, each switch 14 is electrically placed in series with a respective tuning assist element 7. In this case, when the switch 14 is open, each associated tuning assist element 7 is excluded from the resonant electrical circuit 6. Further, when the switch 14 is closed, each associated tuning assist element 7 is included in the resonant electrical circuit 6.

[0063] Alternatively, in embodiments in which the tuning assist elements 7 are electrically connected in series with the first inductor 61 or the second inductor 62, each switch 14 is electrically disposed in parallel with at least one tuning assist element 7 (FIGS. 5-8). In this case, when the switch 14 is closed, each associated tuning assist element 7 is bypassed, and thereby excluded from the resonant electrical circuit 6. And, when the switch 14 is open, each associated tuning assist element 7 is included in the resonant electrical circuit 6.

[0064] The switch 14 may be of a MOS, MOSFET, transistor, electromechanical or other type.

[0065] It should be noted that the position of the selection means 3 in the drawing is merely an example and is not limiting.

[0066] In one embodiment, the selection means 3 are integrated into the control unit 20, for example into either the first microcontroller 1 or the second microcontroller 2.

[0067] In another embodiment, the selection means 3 are external to the control unit 20 and are controlled by one of the first microcontroller 1 and the second microcontroller 2 (FIGS. 1 and 2).

[0068] In another embodiment, the control unit 20 comprises a third microcontroller 5 (Figures 3 and 4), and the selection means 3 are external to the third microcontroller 5 and are controlled by the third microcontroller 5. In a further embodiment, the third microcontroller 5 comprises the selection means 3. In this case, the third microcontroller 5 is preferably a programmable logic component such as of the FPGA (Field Programmable Gate Array) or CPLD (Complex Programmable Logic Device) type.

[0069] Preferably, the third microcontroller 5 may have an internal memory which stores information encoding the combination of tuning assist elements 7 which are to be excluded or activated to obtain correct tuning at a desired frequency (e.g. 125KHz).

[0070] If electronic safety equipment is used, one of the first and second microcontrollers 1, 2 reads information in the internal memory of the third microcontroller 5 which encodes the combination of tuning auxiliary elements 7 which are to be excluded.

[0071] After taking this reading, the first microcontroller 1 or the second microcontroller 2 which has taken the reading communicates to a third microcontroller 5 which has selection means 3 which operate to exclude or include tuning assistance elements 7 necessary to obtain the desired tuning of the resonant electrical circuit 6.

[0072] The resonant electric circuit 6 can be directly connected to the control unit 20 for receiving power from the control unit 20 and for transmitting a presence signal A to the control unit 20 (FIGS. 1, 3).

[0073] Alternatively, the antenna circuit 10 may include a signal processing unit 4 (FIGS. 2 and 4) that is connected to the resonant electric circuit 6, feeds power to the resonant electric circuit 6, and processes a signal generated by the resonant electric circuit 6. The signal processing unit 4 processes the analog signal output from the resonant electric circuit 6 to obtain a digital presence signal A, which it then transmits to the control unit 20.

[0074] The signal processing section 4 may comprise a control circuit 41, a peak detector 42, a filter stage 43 and a decoder stage Manchester 44.

[0075] The control circuit 41 generates and supplies to the resonant electrical circuit 6 a sinusoidal signal having a response frequency related to the ratio of the inductance and capacitance of the resonant electrical circuit 6 .

[0076] The control circuit 41 is also connected to a control unit 20 which controls the start-up and operating voltages, in other words the peak and valley voltages and the average voltage of the sinusoidal signal.

[0077] As an example, one of the first and second microcontrollers 1, 2 requests the control circuit 41 to be switched on / off and sends a signal encoding the peak and valley voltages and the average voltage at which the oscillator circuit 41 operates to the third microcontroller 5 (FIG. 4). The third microcontroller 5 then controls the activation of the control circuit 41 and sets its operating voltage. In an embodiment without the third microcontroller 5, one of the first and second microcontrollers 1, 2 directly controls the activation of the control circuit 41 (FIG. 2).

[0078] When power is applied to the resonant electrical circuit 6, the transponder 63 of the actuator 12 is excited and modulates the electric field generated by the resonant electrical circuit 6 by changing the shape of the oscillatory wave.

[0079] The peak detector 42 of the signal processing unit 4 is configured to detect the difference between the peaks of the wave modified by the transponder 63 of the actuator 12 and generate an analog signal. The peak detector 42 is connected to the filter stage 43 and transmits said analog signal to the filter stage 43.

[0080] The filter stage 43 is configured to filter the analog signal to remove noise and generate a filtered signal, which is connected to a decoding stage Manchester 44 and transmits the filtered signal to said decoding stage Manchester 44.

[0081] The decoding stage Manchester 44 is configured to digitize the filtered signal. By way of example, the decoding stage Manchester 44 generates a digital binary signal which corresponds to the presence signal A and comprises the identification code of the transponder 63 of the actuator 12. The decoding stage Manchester 44 is connected to the control unit 20 and delivers the presence signal A to the control unit 20.

[0082] Based on at least the presence signal A, the control unit 20 activates or deactivates the switching means 30 and, thereby, the safety output unit 31 OSSD, thereby sending a safety signal B indicating that the machine 50 or industrial plant is in a safe state and can be started.

[0083] Optionally, the safety switch 11 comprises at least one auxiliary sensor (not shown) configured to detect at least one environmental parameter and connected to the control unit 20. For example, the auxiliary sensor may be configured to detect the temperature of the environment in which the safety switch 11 is located.

[0084] In this case, the control unit 20 is also configured to control the selection means 3 depending on an environmental parameter detected by the auxiliary sensor.

[0085] By way of example, the control unit 20 can store a characteristic curve relating the value of the environmental parameter to a capacitance value of the resonant electric circuit 6 suitable for ensuring the desired tuning of the resonant electric circuit 6. In this way, the control unit 20 can control the selection means 3 as the environmental parameter changes, thereby varying the capacitance value of the resonant electric circuit 6 in response to the measured environmental parameter.

[0086] FIG. 10 shows an exemplary block diagram of the working steps of an electronic safety system 1 to which the present invention relates.

[0087] As can be seen from FIG. 10, the following is identified: In a first step 101, the antenna circuit 10 detects the proximity of the actuator 12 to the safety switch 11 when the guard 40 is closed. In a second step 102 , the antenna circuit 10 sends a presence signal A to the control unit 20 . In a third step 103 , the control unit 20 activates the switching means 30 . In a fourth step 104, the switching means 30 emits a safety signal B identifying that the system or machine 50 is in a safe state and can be started up.

[0088] In some embodiments, there is also a step 105 in which the safety switch 11 locks the actuator 12 to itself.

[0089] The invention also relates to a safety system comprising a machine 50 or industrial plant and an electronic safety equipment 1 according to the invention.

[0090] From the above description, the characteristics of the electronic safety system which is the subject of the invention are clear, as well as its advantages.

[0091] Finally, it is clear that numerous other modifications may be made to the device without departing from the principles of novelty inherent in the inventive idea, and it is likewise clear that in the specific implementation of the invention, the materials, shapes and sizes of the details shown may be arbitrarily chosen as required and may be replaced by equivalents.

[0092] Where features and techniques described in any claim are followed by reference signs, such reference signs are provided solely for the purpose of enhancing the clarity of the claim and, therefore, such reference signs shall not have any limiting effect on the interpretation of the respective elements illustratively designated by the reference signs.

Claims

1. An electronic safety equipment (1) comprising a safety switch (11) and an actuator (12) associated with a guard (40) of a machine (50) or an industrial plant and configured to interact when opening or closing said guard (40), said safety switch (11) comprising: - switching means (30) adapted to take an active or inactive state and to emit a safety signal (B) allowing the start-up of the machine (50) or industrial plant; a control unit (20) connected to the switching means (30) and configured to activate the switching means in response to at least a presence signal (A) of the actuator (12) adjacent to the safety switch (11); an antenna circuit (10) that detects whether the actuator (12) is in proximity to the safety switch (11) and transmits the presence signal (A) to the control unit (20); The antenna circuit (10) comprises at least one resonant electric circuit (6) having at least one first inductor (61), at least one first capacitor (62), and a number of tuning assist elements (7); The electronic safety equipment (1) further comprises a selection means (3) associated with the tuning assist elements (7) and configured to include or exclude one or more of the tuning assist elements (7) in the resonant electric circuit (6) to modify the inductance and / or capacitance of the resonant electric circuit (6) and to obtain a desired tuning frequency value of the resonant electric circuit (6).

2. 2. The electronic safety equipment according to claim 1, wherein the actuator (12) comprises a transponder (63), and the antenna circuit (10) is configured to excite the transponder (63) when the actuator (12) is in proximity to the safety switch (11) to detect the presence of the safety switch (11).

3. 3. The electronic safety equipment according to claim 1 or 2, wherein the control unit (20) comprises a first microcontroller (1) and a second microcontroller (2) connected to each other and communicating redundantly with each other and connected to the switching means (30), and the first microcontroller (1) and the second microcontroller (2) control the switching means (30) to switch the switching means (30) from the active state to the inactive state or from the inactive state to the active state.

4. 4. The electronic safety equipment according to claim 1, wherein the tuning auxiliary element (7) comprises at least one auxiliary capacitor or auxiliary inductor arranged in parallel with the first inductor (61) and the first capacitor (62).

5. 5. The electronic safety equipment according to claim 1, wherein the tuning auxiliary element (7) comprises at least one auxiliary inductor or auxiliary capacitor arranged in series with the first inductor (61) or the first capacitor (62), respectively.

6. 6. The electronic safety equipment according to claim 1, wherein the selection means (3) is controlled by the control unit (20) and comprises one or more switches (14), each of which is electrically arranged in parallel or in series with each of the tuning auxiliary elements (7).

7. 7. An electronic safety equipment according to any one of claims 3 to 6, wherein the control unit (20) comprises a third microcontroller (5), and the selection means (3) is controlled by the third microcontroller (5).

8. 8. Electronic safety equipment according to claim 7, characterized in that the third microcontroller (5) comprises the selection means (3) and is preferably of the CPLD or FPGA type.

9. The electronic safety equipment according to at least one of claims 1 to 8, wherein the antenna circuit (10) is provided with a signal processing unit (4) connected to the resonant electric circuit (6) and configured to process an analog signal output from the resonant electric circuit (6) to transmit the presence signal (A) in a digital format to the control unit (20).

10. 10. The electronic safety equipment according to claim 9, wherein the safety switch (11) comprises at least one auxiliary sensor configured to detect at least one environmental parameter and connected to the control unit (20), the control unit (20) controlling the selection means (3) depending on the environmental parameter detected by the auxiliary sensor.

11. A safety system comprising a machine (50) or an industrial plant and an electronic safety equipment (1) according to at least one of claims 1 to 10, wherein the switching means (30) is connected to a communication interface configured to transmit one or more signals associated with a state of the switching means (30) to a command device (51) external to the safety switch (11), and the command device (51) is configured to control the machine (50) or the industrial plant based on the signals associated with the state of the switching means (30).

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