Safety switching mechanism comprising dual sensors

Abstract

The invention relates to a safety switching mechanism (1) comprising a tactile sensor in the form of a switching strip (2) or a switching pad having electrical contact elements (7), at least one contact element (7) being connected as an electrode (E) of a capacitive proximity sensor in such a way that a capacitive coupling with respect to an obstacle (5) located in the environment is measured, according to the invention, the electrical contact elements (7) of the tactile sensor are connected as a normally closed device and are connected to one another in an electrically conductive manner, individual contact elements or a series of contact elements of the contact elements (7) which are electrically conductively connected to one another form an electrode (E) of the proximity sensor. A shield electrode (8) may optionally be provided.

Description

Technical Field

[0001] This invention relates to a safety switching mechanism having a tactile sensor in the form of a switching strip or switching pad, wherein such switching strip or switching pad has an electrical contact element. For simplicity, the invention will be explained several times from the perspective of an elongated switching strip as an example for a safety switching mechanism, but is not limited to such a switching strip. Background Technology

[0002] The switching bar designed as a normally closed device includes a contact chain formed by multiple electrical contact elements connected in series and, more precisely, theoretically movable away from each other, yet spring-loaded and tightly held in conductive contact. The contact chain can, for example, be disposed within a cavity of a hollow elastomer profile. Upon contact with an obstacle and corresponding deformation of the hollow rubber profile, adjacent contact elements separate against the spring force, thereby interrupting the current and thus initiating the sensor switching process.

[0003] A normally open switching strip, for example, has two electrical contact elements extending at a distance from each other within a cavity of an elastomer hollow profile. These contact elements typically extend linearly and practically along the entire length of the profile. When the switching strip contacts an obstacle, the elastomer profile deforms, and the two contact elements come into contact with each other, closing a current loop and thus initiating a switching process for the sensor.

[0004] A switching element, particularly in the form of a switching bar or switching pad, is known from EP1612822A1, wherein the switching element is designed as a normally open device. Of the two electrodes, i.e., the two contact elements, one electrode also serves as an electrode for a capacitive proximity sensor, thereby allowing capacitive detection of obstacles before the switching element is tactilely triggered by contact between the two electrodes.

[0005] Safety switching mechanisms are also known from DE102008005783A1, EP3287585A1 and WO2010 / 012492A1, which are designed as normally open devices and function as capacitive proximity sensors for tactile detection of obstacles.

[0006] A capacitive sensor device is known from DE102019132508A1, which is capable of triggering a function during a specified operation, for example by extending a finger onto the operating element; however, moist contaminants or wiping the sensor with a damp cloth should not trigger the sensor's response.

[0007] Unlike safety switching mechanisms designed as normally open devices, safety switching mechanisms designed as normally closed devices are inherently safe because, for example, they also generate a sensor switching process in the event of an interruption caused by other reasons for the current, and correspondingly, the connected equipment to be monitored, such as movable machine parts, will automatically switch autonomously movable vehicles or the like to a safe state.

[0008] A one-dimensional switching strip that deviates from a linear shape can operate on a similar principle in a two-dimensional switching pad. Here, electrical contacts can be laid out in different directions within the switching pad, such as multiple parallel contacts, which requires multiple electrical connectors but also allows for a certain degree of positional resolution. Alternatively, the electrical contacts can extend in a corrugated or serpentine manner, thereby enabling inductive coverage of the entire surface with a minimal number of electrical connectors.

[0009] The switching strips and switching pads designed as explained above are "tactile" sensors that respond to contact and, in the event of deformation of the corresponding elastic bracket or housing, induce a switching process by opening or closing the contact elements. Summary of the Invention

[0010] The objective of this invention is to expand the detection range of the sensor so that it can also detect approaching objects and, in addition, achieve a particularly high level of security.

[0011] This task is solved by the safety switching mechanism according to claim 1. Advantageous designs are described in the dependent claims.

[0012] In other words, this invention proposes neither using a sensor with a completely different construction nor supplementing the tactile sensor by adding a separate second sensor, but rather utilizing the existing contact elements of the contact chain as the tactile sensor. However, a second function is additionally assigned to these contact elements, namely, to provide a capacitive proximity sensor, and one or more contact elements of the tactile sensor are used as electrodes of the proximity sensor. According to the invention, a safety switching mechanism operating based on the normally closed principle is used. The function of the capacitive sensor can also be implemented in the safety switching mechanism, which, based on the normally closed principle, has only a single electrode, namely the contact chain.

[0013] To implement the capacitive measurement principle, the safety switching mechanism includes an electrical signal generator connected to the electrodes via a resistor. One or a series of contact elements of the tactile sensor form these electrodes, for example, one, several, or—i.e., all the contact elements before the contact chain is broken—forming the contact chain of the normally closed device. Correspondingly, according to the invention, by using these inherent contact elements, not only a tactile sensor but also a proximity sensor is provided.

[0014] Because the safety switching mechanism is designed as a normally closed device, the proximity sensor function is maintained even when the tactile sensor is triggered—that is, when the contact element of the normally closed device is interrupted and a switching process is initiated. When the contact chain of the normally closed device is interrupted, two segments of the previously uninterrupted contact chain are created, one of which is always connected to the signal generator. Because the tactile sensor has been triggered, the typically movable object to be protected, connected to the safety switching mechanism, is now in a safe state, in which the object is, for example, moving at a reduced speed or has come to a stop. However, it may be important and advantageous for specific use cases that the proximity sensor signal can also be evaluated in this safe state.

[0015] Partially or fully conductive obstacles—such as a human body—are grounded via impedance. This impedance can include ohmic resistors, capacitors, inductors, or combinations thereof, and constitutes an electrical coupling from the obstacle to the ground. Therefore, when the obstacle enters the detection range of the proximity sensor, it interacts with the electrodes, such as a capacitor, which changes the voltage drop across the measuring resistor. From these changes in resistance, firstly, the presence of an obstacle within the detection range can be qualitatively identified (by its presence within the detection range), and secondly, with limited accuracy, it can also be quantitatively determined (by its distance from the electrodes), i.e., at least assessed, for the presence of the obstacle within the detection range.

[0016] The safety switching mechanism, by extending the tactile sensor with additional functionality to the proximity sensor, offers several advantages for this further improvement:

[0017] First, the safety switching mechanism offers improved technical safety because it effectively uses two sensors, i.e., two different operating principles. It is also possible to determine the obstacle's position within the detection range using only a proximity sensor based on a qualitative report, making it easy to abandon the tactile sensor. Compared to such a solution, the safety switching mechanism according to the invention has the advantage that it compensates for the uncertainty of capacitive proximity measurement with secure tactile measurement. That is, capacitive proximity measurement is uncertain as long as proximity measurement depends on obstacle size. When two obstacles of different sizes are at the same distance from the capacitive proximity sensor, the larger obstacle is determined to be closer. Or, when a large obstacle is very close to the capacitive proximity sensor, a smaller obstacle may not be detected by the capacitive proximity sensor. Even though these phenomena should occur in the proximity sensor of the switching mechanism according to the invention, the ever-present function of the tactile sensor ensures the safety functions required by the safety switching mechanism.

[0018] Secondly, compared to installing two completely separate sensors, it enables a particularly simple installation of two different sensor types because the safety switching mechanism according to the invention requires less cabling.

[0019] Third, compared to sensor mounting, the safety switching mechanism according to the invention can be designed to save structural space, in which two completely separate sensor types are installed, such as a tactile sensor and an attached proximity sensor, which operates completely independently of the tactile sensor. For example, there is no need to install an additional ultrasonic sensor or similar proximity sensor that is oriented transversely to the longitudinal direction of the switching bar and would amplify the minimum structural depth required for the switching bar.

[0020] Fourth, compared to conventional safety switching mechanisms, such as switching bars, the safety switching mechanism according to the invention can also be designed to save structural space: the deformation path of a conventional switching bar must typically be so long that it is technically unnecessary for the function of the switching bar itself. The purpose of this unnecessarily large structural depth is to ensure that, after the tactile triggering of the switching bar, when the drive mechanism of the movable object is disengaged, the movable object can continue to move such a distance that it does not collide with the obstacle that triggered the switching process of the switching bar. For example, the metal shell of a ground transport vehicle can be used as a typical example for such a use case, the shell having a switching bar, wherein the foot should not be injured when the switching bar has been triggered by the aforementioned obstacle. The deformation space or structural depth of the switching bar must be approximately related to the braking stroke of the movable object. By using the switching bar as an additional function of the invention as a proximity sensor, an alarm can be triggered before the switching bar deforms, thus the speed of the movable object is reduced in advance, i.e., before the tactile sensor is triggered, and the braking stroke until stopping is correspondingly smaller. Correspondingly, a small structural depth of the switching bar can be maintained.

[0021] Space-saving design of the safety switching mechanism is important because, depending on the application, the outward-protruding switching bar should be kept as small as possible. This should be avoided, for example, in use on ground transport vehicles, where the switching bar may tear or shear during harsh operation, such as when a ground transport vehicle scrapes along the side panels of the loading compartment or adjacent pallets during the loading or unloading of a truck, where the pallets are placed close together. Where necessary, smaller structural dimensions also constitute a key reason for purchasing the appropriate switching bar, based on design advantages.

[0022] Fifth, the design of the safety switching mechanism based on the principle of normally closed devices makes it possible to continue using a portion of the contact chain as a capacitive proximity sensor even after the tactile sensor electrode, i.e., the contact chain formed by multiple individual contact elements, is interrupted.

[0023] In a design that is technically very simple to implement, this involves a single series of interconnected contact elements, namely the share of the contact chain that is always connected to the signal generator and the measuring resistance of the electrodes. In another design, two series of interconnected contact elements, namely the two shares of the contact chain on either side of the break point—that is, the contact chain that is always completely interrupted—can be used as two capacitive proximity sensors.

[0024] One or more contact elements of the tactile sensor thus form electrodes for a capacitive proximity sensor in both indicated designs, including reduced capacitance compared to an uninterrupted contact chain. Although the tactile sensor has been triggered in the event of a contact chain interruption and the moving object is automatically placed in a safe state accordingly, the continued functionality of the capacitive sensor can be advantageously utilized when designing the corresponding control:

[0025] When a vehicle, for example, autonomously movable, automatically reverses direction after contacting an obstacle, the direction of travel can be chosen such that, for example, the vehicle does not simply travel backward along the same trajectory in the opposite direction of its initial travel, but rather moves away from the obstacle in an arc along a different trajectory, having been detected by a capacitive sensor. This allows for the avoidance of obstacles, such as misplaced objects protruding into the vehicle's lane, in a very short time.

[0026] If, after a collision with the first obstacle, a person arrives at the collision site and thus constitutes an additional second obstacle in the movement space of the movable object, the presence of the person can be detected by a capacitive sensor that is always active before the movable object automatically reverses its movement. During the reverse movement, the contact chain closes again and allows the movable object to resume movement in the original direction. Early detection of additional obstacles that were not detected before the tactile sensor is triggered provides additional safety in this situation, thereby providing a particularly high level of safety according to the safety switching mechanism of the invention.

[0027] Finally, sixthly, the safety switching mechanism, designed based on the normally closed principle, provides the possibility of automatically determining the interruption location along the longitudinal direction of the electrode after an electrode interruption. The interruption location can be approximated based on changes in electrode capacitance. This can be advantageous, for example, for statistical evaluation. When it is shown that contact with an obstacle occurs primarily within the area defined by the safety switching mechanism, measures can be taken to alter the safety switching mechanism itself, or the moving object or its environment monitored by the safety switching mechanism, so that collisions with the obstacle are avoided or occur with minimal damage.

[0028] Minimizing damage to the safety switching mechanism extends its service life, thereby reducing the need for corresponding maintenance or repair work during downtime of the moving object. This constitutes an economic advantage provided by the safety switching mechanism according to the invention. The possibility of altering the environment of the moving object when necessary also provides an overall improved or enhanced level of safety, as this reduces the likelihood of future collisions.

[0029] In one design, the safety switching mechanism has a shield. The shield can influence the operation of the proximity sensor. When the switching bar is mounted on a movable component, it is preferable to mount the shield such that it is positioned between the component and the contact element of the switching bar. The shield reduces or completely eliminates interference that may act on the switching bar from the component.

[0030] The shielding portion can be provided by a flat sheet strip, by a strip made of conductive textile material or metal fiber, or, in the case of a co-extruded profile, by a corresponding region made of a material different from the substrate, i.e., an elastomer material with higher electrical conductivity.

[0031] In one design, the safety switching mechanism includes a control device with an input for a measurement signal from at least one additional sensor. The control device can be physically integrated into the safety switching mechanism as an internal control unit, for example, disposed within a cavity of an elastomer hollow profile, where the contact element is also disposed. Alternatively, the control device can be disposed externally, but as part of the safety switching mechanism, effectively wirelessly or wiredly connected to the contact element of the safety switching mechanism for signal transmission, thus allowing for a multi-piece design of the safety switching mechanism.

[0032] The safety switching mechanism may, in another design, be part of a safety switching arrangement structure that includes other components, and more specifically, includes at least one control device, such as an equipment-, vehicle-, or engine control device, which is originally intended for operating the movable object, and which further evaluates the signals of the safety switching mechanism and / or influences the electrical power supply of the safety switching mechanism as an external control device.

[0033] Because the functionality of contactless proximity sensors can be affected by environmental influences experienced by the safety switching mechanism, additional sensors that provide information about these environmental influences can be utilized. For example, air humidity and / or air temperature can be detected to compensate for changes in the capacitive sensor's measurement characteristics that depend on these influences, using appropriate correction factors. Perhaps such additional sensors already exist on a moving object, in which case the signals from these sensors can be processed by internal or external controls of the safety switching mechanism. In another design, the safety switching mechanism itself has one or more additional sensors, which can be mounted, for example, in the area of ​​the control device or integrated as additional elements into the switching bar or pad.

[0034] The safety switching mechanism according to the present invention, operating on the principle of a normally closed element, requires only a single electrode, namely the contact chain formed by the various contact elements. In one design, the safety switching mechanism has another electrode as a so-called reference electrode. In the absence of an optional shielding electrode, the reference electrode constitutes the second electrode of the safety switching mechanism. The aforementioned additional sensor can be called a special sensor because it detects specific parameters and correspondingly provides measured values, such as values ​​for air humidity and / or air temperature. Instead of a special sensor, or additionally, the reference electrode can compensate for changes in the measurement characteristics of the capacitive sensor, which here can be called a general sensor or universal sensor to distinguish it from a special sensor. All effects acting on the contact chain, which is the first electrode, also act on the reference electrode until an obstacle, i.e., the presence of an obstacle, is encountered. The reference electrode is not used to determine whether an obstacle is within or outside the detection range, thus it is a reference electrode distinct from external influences not experienced by the contact chain. This additionally mounted electrode of the capacitive sensor therefore provides a reference measured value.

[0035] The reference electrode can therefore be positioned outside the detection range or within the detection range at a location where the presence of obstacles is not expected. For example, it can be positioned behind the first electrode of the safety switching mechanism or behind a shield, along the direction of movement of the moving object, or between the first electrode of the safety switching mechanism and the moving object. Because the reference electrode, such as the first electrode of a capacitive sensor formed by a contact chain, is also subject to environmental influences, the reference measurement value changes depending on all these influences and not just on a specific, particular influence. The measurement value obtained using the remaining first electrodes can be calibrated using the corresponding reference measurement value.

[0036] Using the switching signal of the safety switching mechanism, the drive mechanism of the monitored moving object can be automatically acted upon by internal or external control devices, for example, automatically slowing down or completely disengaging the drive mechanism. A reference electrode can also be located outside the safety switching mechanism and connected to the control device; for example, one application could be that the safety switching mechanism is designed as a switching bar and located at the front end of an autonomous ground transport vehicle. Here, the reference electrode can be located, for example, under the vehicle or on the vehicle body, in any case outside the switching bar. The control device connects not only the switching bar along with the first electrode therein but also the reference electrode, thereby allowing the value of the reference electrode to be automatically evaluated and used to calibrate the value of the first electrode.

[0037] In one design, the control device of the safety circuit enables the movable object to automatically move backward to a small extent after the tactile sensor is triggered; that is, the movable object travels in the opposite direction. This backward movement, essentially opposite to the direction of movement before the trigger, is carried out only over a limited and narrow distance to avoid creating new accident hazards. Through this reverse movement, the duration of contact with an obstacle is minimized if contact between the object and an obstacle is still possible. Attached Figure Description

[0038] The invention will now be further explained with the aid of purely illustrative diagrams. Here:

[0039] Figure 1 and 2 The schematic diagram illustrates the working principles of a safety switching mechanism designed as a normally closed device and a safety switching mechanism designed as a normally open device, which is not part of this invention.

[0040] Figure 3 A schematic diagram illustrating the capacitive measurement principle is shown; and

[0041] Figure 4 and 5 Two examples of structural implementations for a safety switching mechanism designed as a normally closed device are shown. Detailed Implementation

[0042] exist Figure 1 and 2 The basic functions of the corresponding safety switching mechanism 1 are first shown in the diagram. Figure 1 The switching bar 2, designed as a normally closed circuit, is shown. Figure 2 The switch bar 3, designed as a normally open switch, is shown and is not part of this invention. Each switch bar 2, 3 has two electrical terminals, referred to as the transmitter "Tx" and the contact terminal "Ct".

[0043] Second, when the switching bar has been extended to function as a proximity sensor, then by means of... Figure 1 and 2 Explain how the two toggle bars 2 and 3 work. This applies not only to... Figure 1 The normally closed device shown in the figure, and for in Figure 2 The normally open switch shown is symbolically illustrated in four steps a) to d), with the detection range 4 extending along the elongated switching bars 2 and 3, and the proximity sensor covering the detection range. The switching bars 2 and 3 do not extend centrally through the detection range 4, as explained in more detail later.

[0044] In the first step a) of approaching the obstacle, the obstacle is not yet within the detection range. Therefore, the obstacle is not shown in this step a). The safety device allows unimpeded movement of the movable object, and the safety switching mechanism 1 is configured to and, for example, secured to the object.

[0045] In the second step b), obstacle 5 intrudes into detection range 4. Obstacle 5 is shown as a symbolic hand representing a human body part. Obstacle 5 intruding into detection range 4 triggers an alert: a control device is configured for safety switching mechanism 1, the control device itself being connected to the drive device or drive control device of the movable object, thereby automatically limiting the speed of the movable object based on the alert, for example.

[0046] In the third step c), the obstacle 5 intrudes into the detection range 4 and even reaches the switching bars 2 and 3, but does not trigger the tactile sensing mechanism of the switching bars 2 and 3. However, in this step c), the control device configured for the safety switching mechanism 1 can automatically trigger the safety switching process, for example by automatically cutting off the drive device of the movable object.

[0047] In step d), the obstacle 5 further intrudes into the detection range 4 and triggers the switching process of the tactile sensing mechanisms of the corresponding switching bars 2 and 3. In this case, the same safety switching process is also automatically triggered, set in a known manner when the switching bars are triggered, typically in the form of automatic disconnection of the drive mechanism of a movable object. The different operating principles of the two switching bars 2 and 3 become apparent through the triggering of the tactile sensing mechanisms:

[0048] Figure 1 The design of the normally closed switching bar 2 includes a contact chain 6 composed of multiple electrical contact elements 7, which are held in conductive contact with each other by spring pressure. Figure 1 In the simplified symbolic diagram, contact elements 7 are shown as multiple conductive, for example, metallic, hollow cylinders passing through an elastic, stressed tension element. Contact chains 6 are exemplarily arranged within the cavity of a hollow profile (not shown) made of an elastomeric material. Upon contact with the obstacle 5 and the deformation caused by the hollow profile, adjacent contact elements 7 of the contact chains 6 separate from each other, thereby interrupting the steady current flow and thus initiating the switching process of the switching bar 2. Here, contact end Ct represents the position where the separation of the contact chains 6 is detected.

[0049] Based on the principle of normally closed circuit, the interruption of the steady current of switching bar 2 is triggered by different reasons, such as the damage to the electrical input line leading to the two electrical terminals "Tx" and "Ct" triggering the same switching process as the interruption of contact chain 6, so that the movable object is automatically placed in a safe state, for example by cutting off its drive device.

[0050] exist Figure 2 The switching strip 3 shown is designed as a normally open switch with two linearly extending electrical contact elements 7 spaced apart from each other. The contact elements 7 can be designed, for example, as metallic lines or wires inserted into the cavity of an elastomer hollow profile. When the elastomer hollow profile is manufactured in a co-extrusion process, the contact elements 7 can be made of a material different from the substrate of the hollow profile, i.e., a more conductive material. When an obstacle 5 impacts the switching strip 3, the two contact elements 7 come into contact with each other and close the current loop. Here, contact end Ct represents the position where the two contact elements 7 enter into contact.

[0051] Damage to the electrical input line leading to one of the two electrical connectors "Tx" and "Ct" does not cause the switching process, but rather causes the switching bar 3, which operates according to the normally open principle, to fail.

[0052] exist Figure 1 and 2In the two schematically illustrated switching strips 2 and 3, the conductive contact elements 7 of the normally closed and normally open devices can each realize a variety of conceivable variations, such as one variation in the contact connection of the conductive element or the wiring. This can, for example, replace the detection of the separation of the contact chain 6 or the contact of the two contact elements 7 on the corresponding contact terminal Ct, on the corresponding emitter terminal Tx, or on another element, such as an electrode, with a correspondingly adapted evaluation circuit.

[0053] exist Figure 1 and 2 The detection range extends from different distances from the contact elements 7 of the switching strips 2 and 3, that is, the detection range is within... Figure 1 and 2 Compared to the middle, it extends further upward. This is achieved by the schematically represented shielding portion 8, which in... Figure 1 and 2 These are shown below switching bars 2 and 3, respectively. The shield 8 is schematically simplified and illustrated by a single line and characterized as a "shield electrode" (SdTx), although it actually has at least one, and typically two or more, separate shield electrodes. The design of the shield 8 influences or defines the measurement range in all three dimensions around the contact element 7. The design of the shield 8 involves, for example, the size of the shield, its orientation or shape, the material of the shield, and / or its distance from the contact element 7.

[0054] Figure 3 This illustrates the capacitive measurement principle when the switching bar 2—especially before the corresponding tactile sensor is triggered—operates as a proximity sensor. The safety switching mechanism 1 has a current source or voltage source that generates an AC voltage and is settable regarding amplitude, phase, and frequency. Thus, the current source or voltage source can, for example, generate a sine wave, sawtooth wave, or rectangular wave; therefore, the current source or voltage source can also be referred to as a signal generator. Figure 3 The symbol S represents the signal generator S. The signal generator S is connected to the electrode E via a resistor R. In the normally closed switching bar 2, multiple or all of the contact elements 7 of the contact chain 6 of the tactile sensor form the electrode E. In this way, a safety switching mechanism 1 is provided using the pre-existing contact elements 7, which has both a tactile sensor and a proximity sensor.

[0055] The partially or fully conductive obstacle 5 is grounded via an impedance Z, which constitutes an electrical coupling between the obstacle 5 and the ground. When the obstacle enters the detection range 4 of the proximity sensor, the obstacle 5, together with the electrode E, acts like a capacitor C(d), which... Figure 3The capacitor is represented by a dashed box, and the capacitance C of the capacitor depends on the distance d between the obstacle 5 and the electrode E.

[0056] Tx represents the transmitting end and indicates that the capacitance (capacitive coupling) is detected in the "transmit" or "emit" mode. Instead, and deviating from the illustrated embodiment, the capacitance can be detected in the "receive" or "receive" mode, thus the illustrated embodiment constitutes only one of many possibilities for using the contacts of the tactile sensor of the switching mechanism as electrodes of the capacitive proximity sensor.

[0057] The capacitor C(d) influences and changes the voltage drop U(R, C), which depends on the resistance value R and, secondly, the capacitance of the capacitor C(d). This voltage drop U(R, C) and its change generate a true sensor signal, which is output as a signal by the switching bar 2 and can be automatically evaluated, thereby enabling the switching bar 2 to function as a proximity sensor. The proximity sensor allows for the qualitative identification of the presence of obstacle 5 within the detection range 4. Additionally, with limited accuracy, the presence of obstacle 5 can also be quantitatively determined as its distance from electrode E, thus allowing a safety switching signal to be generated based on the proximity sensor signal before the tactile sensor of the safety switching mechanism 1 is triggered by contact between obstacle 5 and the switching bar 2.

[0058] exist Figure 4 The safety switching mechanism 1 is shown in mid-perspective, and is designed as a normally closed switching bar 2. The housing 9 has a back side 10, which allows it to be directly fastened to a movable object or to a support, which itself is fixed to the movable object. Correspondingly, the opposing front side 11 of the housing 9 is oriented such that it faces away from the movable component and forms the side of the switching bar 2 that is expected to make contact with an obstacle. The contact element 7 shown is part of the contact chain 6. The shield 8 is formed by four shielding electrodes 12, two of which have straight cross-sections and two have curved cross-sections, and the shielding electrodes generally extend in a U-shape around the contact chain 6. Through the shield 8, the detection range 4 of the proximity sensor is substantially directed towards the front side 11 – that is, in… Figure 4 Upward-oriented.

[0059] The housing 9 is shown schematically only. The housing can be made of a solid material, such as a deformable foam material with longitudinal pores in which the contact chain 6 is received. However, the housing 9 can also be designed as a deformable hollow profile, for example, made of an elastomeric material. Both designs allow for easy assembly of the switching bar onto a curved surface. However, the housing 9 can also be designed in two parts, for example, including a rigid profile track forming a back side 10 and a deformable cover forming a front side 11 that allows for the interruption of the contact chain 6.

[0060] exist Figure 5 In, similar to in Figure 4 The safety switching mechanism 1 is shown in mid-perspective and the housing 9 is shown purely schematically as in Figure 4 As shown in the diagram, in this embodiment, the switching bar 2 has a single shielding electrode 12, which forms a shielding portion 8 for proximity sensors. Because the shielding electrode 12 extends in a U-shape, it is similar to... Figure 4 In the switching bar 2, a U-shaped shielding portion 8 is provided, which shields the contact chain 6 towards the back side 10 and thus towards the movable component, thereby approaching the sensor's detection range 4, which is also essentially in the direction of the front side 11 - that is, in Figure 5 Extend upwards from the middle.

[0061] Under shielding part 8 Figure 5 The diagram shows a reference electrode 13, which, based on the shielding portion 8, facilitates capacitive detection of the approach of the switching bar 2 to an obstacle located in front of the front side 11. Because the reference electrode 13 is subjected to all environmental parameters in other cases, such as the first electrode in the form of the contact chain 6, it is used to detect capacitance changes that may occur based on fluctuating environmental parameters. The reference electrode 13, serving not only as the first electrode of the safety switching mechanism 1 (the contact chain 6) but also as the other electrode, is connected to a control device configured for the safety switching mechanism, allowing for automatic evaluation of the value of the reference electrode 13 and its use in calibrating the value of the contact chain 6. The reference electrode 13 may be integrated into the safety switching mechanism 1 as shown in the illustrated embodiment or may be disposed externally to the safety switching mechanism 1.

[0062] List of reference numerals

[0063] 1. Safety switching mechanism

[0064] 2. Designed as a switching bar for normally closed circuit breakers

[0065] 3. Designed as a switching strip for normally open circuits

[0066] 4 Detection range

[0067] 5 obstacles

[0068] 6 contact chains

[0069] 7 contact elements

[0070] 8 shielding sections

[0071] 9 shells

[0072] 10 dorsal side

[0073] 11 Front

[0074] 12 shielding electrodes

[0075] 13 Reference Electrodes

[0076] Tx transmitter

[0077] Ct contact terminal

[0078] SdTx shielding electrode

[0079] S-signal generator

[0080] R resistor

[0081] E electrode

[0082] Z-impedance

[0083] C(d) capacitor

[0084] d distance

[0085] U(R,C) voltage drop

Claims

1. Safety switching mechanism (1), The safety switching mechanism has a tactile sensor in the form of a switching strip (2) or a switching pad. The switching strip or switching pad has an electrical contact element (7), wherein... At least one contact element (7) is connected as an electrode (E) of a capacitive proximity sensor in such a way that the capacitive coupling (C(d)) relative to an obstacle in the environment is measured, the capacitive coupling being particularly dependent on the distance between the obstacle and the capacitive proximity sensor. Its features are, The electrical contact elements (7) of the tactile sensor are connected as normally closed devices and are electrically connected to each other. In this context, the individual contact element or a series of contact elements in the mutually electrically connected contact elements (7) form the electrode (E) of the proximity sensor.

2. The safety switching mechanism according to claim 1, characterized in that, The electrical signal generator (S) is connected to the electrode (E) via a resistor (R), and the safety switching mechanism (1) has a detector for detecting the voltage drop (U(R, C)) across the resistor (R).

3. The safety switching mechanism according to claim 1 or 2, characterized in that, The proximity sensor is provided with a shield (8) such that the contact element (7) connected as the electrode (E) of the capacitive proximity sensor is partially surrounded by the shield electrode (12).

4. The safety switching mechanism according to any one of the preceding claims, characterized in that... A control device having a signal input for a measurement signal from at least one additional sensor, wherein the control device is designed such that a correction factor is determined using the measurement signal from the additional sensor and the measurement value of the capacitive proximity sensor is corrected using the correction factor.

5. The safety switching mechanism according to claim 4, characterized in that... At least one additional sensor, said additional sensor being designed to detect environmental data that affects the function of said capacitive proximity sensor.

6. The safety switching mechanism according to claim 5, characterized in that... The other electrode of the capacitive proximity sensor, which forms the additional sensor, is configured as a reference electrode (13) in such a way that, except in the presence of an obstacle, the other electrode is subjected to the same environmental influences as the first electrode (E) of the capacitive proximity sensor.

7. The safety switching mechanism according to any one of the preceding claims, characterized in that... A control device is designed such that, after triggering a switching process, the control device outputs a reverse driving signal to the drive device of the movable object.

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