Safety switch for access control

Abstract

A safety switch for controlling access to an industrial machine or plant comprises a switching device (2) accommodating a switching means and an actuator device (3), the switching device (2) having an operating pin (8) that interacts with the switching means when opening and closing the access; a locking / unlocking mechanism (14) accommodated within the switching device (2) and provided with a locking pin (15) movable between a locked position and an unlocked position of the access; and an operating pin (8) associated with the actuator device (3) and interacting with the locking pin (15) to hold the actuator device (3) in a state fixed to the switching device (2). The operating pin (8) further houses a locking element with controlled deformation mechanically connected to the locking pin (15), and the locking element with controlled deformation is sized to plastically deform when a deformation stress higher than a predetermined threshold value is applied to the locking pin (15).

Description

Technical Field

[0001] The present invention finds application in the field of industrial electrical devices, and in particular relates to a safety switch for controlling access to safety barriers or boundaries of industrial machines and plants.

Background Art

[0002] As is known, a safety switch for controlling access to safety barriers and boundaries of industrial machines or plants generally comprises a switching device suitable for being installed on a fixed part of the access, and an actuator device suitable for being installed on a movable part.

[0003] These two devices interact with each other when the access is opened or closed, and are adapted to notify the control system of the machine or plant of the open / closed state and locking / unlocking, enabling control of the machine or plant in different ways depending on the adopted configuration.

[0004] The interaction between the switching device and the actuator device may be of a mechanical or electromechanical type, and a mechanical actuator such as a key actuator, suitable for being inserted into the switching device and interacting mechanically with the switching means, may be provided in the actuator device, or it may be of a completely electronic type.

[0005] In this second case, the interaction between the two devices is effected through the exchange of presence signals, whereby the proximity between the two devices can be distinguished and the open / closed state of the access can be determined.

[0006] In both embodiments, the actuator device may be provided with pins having a function of centering and holding the actuator device on the switching device, thereby preventing access from being opened without prior consent from the central system, or being opened by minimal excitation such as vibration unrelated to an attempt to release access after the access has been released.

[0007] The pins of the actuator device are typically designed to engage with the locking pins of the locking / unlocking mechanism housed in the switching device.

[0008] Generally, in an electromechanical switch, an action is performed by a key or the mechanical actuator itself.

[0009] In some solutions, it is also possible to detect the breakage of the locking / unlocking mechanism pin and prevent the switch from operating even if this event occurs.

[0010] However, the broken state of the locking / unlocking mechanism pin must always be avoided. This is because there may remain a possibility that an integral part of the same locking pin drops and is erroneously detected as a correct operation.

[0011] Japanese Patent Application Laid-Open No. 2002-216591 and Japanese Patent Application Laid-Open No. 2004-079204 disclose a switch having an object of avoiding breakage of a pin by providing a mechanism for preventing excessive stress from being applied to an operating pin by a traction force exerted thereon, using a series of transfer mechanisms for dispersing the applied stress, in a first configuration.

[0012] However, since the structure of the locking mechanism is complex, this solution is relatively expensive and has low reliability.

[0013] A safety switch solution in which the locking pin does not deform or break even when excessive stress is applied is also disclosed in Japanese Patent Application Laid-Open No. 2007-257973.

[0014] On the other hand, in the second embodiment of Japanese Patent Application Laid-Open No. 2002-216591, access is always performed even when the pin is damaged. However, the above risk that the system cannot detect such an open state due to the fact that the translation of the pin downward is not hindered is not avoided.

[0015] Japanese Patent Application Laid-Open No. 2002-216591 and Japanese Patent Application Laid-Open No. 2003-45294 disclose a further solution that the actuator pin can be released even when the locking pin is deformed or damaged, but no measures are provided to prevent the damaged or deformed locking pin from descending.

[0016] Japanese Patent Application Laid-Open No. 2004-079190 discloses a safety switch provided with a cam mechanism, which intervenes when it detects that the pulling force applied to the actuator has a value greater than a limit value, operates a locking element to act on the locking pin to release a switching means, and avoids damage to the locking pin.

[0017] The value of the limit force at which the cam mechanism intervenes is arbitrarily set by a control element existing in the locking element.

[0018] Other examples of switches provided with a locking mechanism are described in U.S. Patent Application Publication No. 2019 / 316381, U.S. Patent Application Publication No. 2011 / 127147, and U.S. Patent Application Publication No. 2020 / 165839. Scope of the Invention

[0019] An object of the present invention is to overcome the above-mentioned drawbacks by providing a safety switch for access control of industrial machines and plants, which has the characteristics of high efficiency and cost-effectiveness.

[0020] A specific object is to provide an access control safety switch that provides evidence that excessive stress exceeding a threshold value applied to the pin of the locking / unlocking mechanism has been applied, which may cause damage to the actuator device itself and / or the locking / unlocking mechanism.

[0021] Yet another specific object is to provide a safety switch for access control that prevents the pin of the locking / unlocking mechanism from moving to the access unlocking position even in a damaged state.

[0022] These objects, and other objects that will become more apparent hereinafter, are achieved by the safety switch for access control according to claim 1, which is a switching device that houses switching means for controlling one or more control circuits and / or service circuits of a machine or a plant, a switching device, an actuator device that is suitable for interacting with the switching means to open and close one or more of the circuits when accessing is opened and closed, an actuator device, a locking / unlocking mechanism that is housed in the switching device and is provided with a locking pin that is movable between at least one locking position of the access and at least one unlocking position of the access, a locking / unlocking mechanism, and an operating pin that is associated with the actuator device and is suitable for interacting with the locking pin to hold the actuator device in a fixed state with respect to the switching device.

[0023] The switching device houses at least one limiting deformation locking element that is mechanically connected to the locking pin and is sized to plastically deform without breaking after a first deformation stress higher than a predetermined threshold value is applied to the locking pin via the operating pin.

[0024] In this way, even if excessive stress is applied to the locking pin, the locking pin itself or the appropriate control deformation locking element will not deform and break.

[0025] Therefore, the locking pin remains fixed in the switching device, and in no case will the downstream portion of the deformed end drop to send an access unlocking signal.

[0026] In this situation, there is a possibility that the actuator pin cannot be pulled out and becomes stuck, resulting in an error, which may prevent the restart of the machine in an unsafe state or the release of access while the machine is running.

[0027] Depending on the position of the control-deformed locking element, it may be possible to lock the locking pin either in the lowered position or in the intermediate position.

[0028] Also in this case, when the access is closed, the actuator pin cannot be locked by the locking pin, the locking pin becomes stuck and an error occurs, preventing the restart of the machine or plant, so a safe access state within the protection boundary is guaranteed.

[0029] Advantageous embodiments of the present invention are obtained according to the dependent claims.

Brief Description of the Drawings

[0030] Further features and advantages of the present invention will become more apparent in light of the detailed description of the preferred but non-exclusive embodiments of the safety switch according to the present invention, shown by way of non-limiting example with the aid of the accompanying drawings.

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0032] Referring to the accompanying drawings, a preferred but non-exclusive embodiment of the safety switch according to the present invention is shown, which is generally designed to control at least one access to an industrial machine or plant.

[0033] Generally, the safety switch, generally designated 1 in FIG. 1, is preferably but not exclusively attached to or otherwise arranged in a barrier or movable panel type of protective access which is known per se and not shown, and is designed to control access to and from a safety perimeter or other work area in which the machine or industrial plant in operation is located, and is suitable for preventing dangerous passage.

[0034] In a known manner, the main role of the safety switch 1 is also to interrupt the operation of the machine or plant, or one or more selected parts of the machine or plant, immediately or with a time delay, when access is released or even when there is only a request for access to be released.

[0035] The access may be, for example, hinged or sliding, opening to the right or left, and may be of any type without particular limitation.

[0036] In the illustrated configuration, the safety switch 1 is of an electronically actuated type, i.e., a remote communication system is provided between the switching part and the actuating part, as will be more clearly explained below.

[0037] However, according to an alternative configuration not shown, the switch 1 can be mechanically or electromechanically operated by a key actuator in a manner technically equivalent or similar to that performed by the above-mentioned switch.

[0038] In its most basic form, the safety switch 1 comprises a switching device 2 adapted to be mounted on a fixed part of the access to be normally controlled, and an actuator device 3 adapted to be mounted on a movable part of the access.

[0039] The method of fixing the switching device 2 and the actuator device 3 to their respective parts of access is of a known type and does not form part of the present invention, and will not be described or illustrated in detail.

[0040] In a preferred but non-limiting illustrated configuration, the switching device 2 comprises a housing 4 provided with a case 5 that houses switching means of a known configuration, although not shown in the drawings, and is suitable for being operably connected in a known manner at all times to one or more electrical and / or electronic circuits for power supply and / or control of the main circuit and / or service circuit and / or emergency circuit of a machine or plant.

[0041] The switching means can be selected from among those commonly used in this field without particular limitation, and can also be changed according to the function of the safety switch 1.

[0042] The method of connecting the switching means can be selected from among those typical of this type of product, but they will not be described in detail below either.

[0043] The case 5 may also house control means, such as a microprocessor or a CPU (not shown), for example, which is suitable for receiving input signals from the control circuit and / or service circuit via respective communication channels such as a data transmission bus, transistors, electromechanical contacts, etc., and for verifying their correct operation.

[0044] In this way, the control means may instruct the switching means to send an error signal and / or shut down the plant when there is no communication signal from one of the communication channels, or when an internal or external failure of the device is detected.

[0045] Case 5 is related to head 6, which interacts with actuator device 3 and is designed to enable the interaction between actuator device 3 and the switching means according to the method described below.

[0046] The head 6 may be integral with the case 5 or may represent a separate module that can be applied to the case 5 in a directionable and / or removable manner depending on two or more positions rotated with respect to the main extension axis of the case 5.

[0047] Next, the actuator device 3 is the mounting body 7, which is provided with its own mounting means for installation, and is associated with the operating pin 8 having a first end 9 fixed to the mounting body 7 and a second end 10 protruding transversely from the mounting body 7 to interact with the switching means. The mounting body 7 will be provided.

[0048] For this purpose, the head 6 is provided with one or more slots 11 formed in at least one of its front surfaces 12, 13 or in one of the upper and / or lower axial surfaces. As a result of inserting the operating pin 8 into these, it is possible to interact with the switching means.

[0049] In the preferred but non-exclusive embodiment of the figure, the head 6 is provided with two or more slots 11 formed in the corresponding front surfaces 12, 13, and the switching device 2 is always installed in the same orientation. However, the interaction with the actuator device 3 will be possible regardless of the approaching direction of the actuator device 3 and will instead depend on the closed type of access.

[0050] However, it is understood that it is also possible to provide a single slot 11 associated with the fixed or rotating head 6.

[0051] As can be seen more clearly from the cross-sections of FIGS. 2 to 4, the case 5 also houses the locking / unlocking mechanism 14 of the operating pin 8, which is adapted to engage with the operating pin 8 to maintain the second end 10 in a locked state when the operating pin 8 is fully inserted into the head 6.

[0052] In this document, the expression "fully inserted" refers to the position of the operating pin 8 within the head 6 such that access can be considered to be properly closed.

[0053] In particular, the locking / unlocking mechanism 14 is provided with a locking pin 15 that is translatable or rotationally translatable within the housing 4 along a predetermined longitudinal movement direction X (substantially parallel to the main elongation direction L of the case 5 and orthogonal to the insertion direction Y of the operating pin 8 within the head 6).

[0054] In the unlocked access state, in both the opening and closing stages of the access, as shown in FIG. 2, the operating pin 8 actuates the locking end 16, which represents the upper end of the locking pin 15 in the figure, to cause a downward translation.

[0055] In particular, the locking pin 15 is movable within the housing 4 between at least one unlocking position of the access (where the locking end 16 is not inserted into the head 6 or is only partially inserted) and a locking position as shown in FIG. 3 (where the locking end 16 is fully inserted into the head 6 and engages with the operating pin 8 to prevent the withdrawal of the operating pin 8).

[0056] In the unlocking position, the locking end 16 may be fully retracted so as not to interact with the operating pin 8, or in a preferred manner, it is sufficient to prevent the opening of the access after pulling by the operator, and at the same time, it exerts a minimum holding force sufficient to avoid accidental opening that may be caused by vibrations or impacts applied to the access. In any case, it may partially protrude into the head 6 so as to engage with the operating pin 8.

[0057] In a preferred but non-exclusive configuration of the figure, the locking pin 15 is designed to move between an upward access locking position (where the locking pin engages with the operating pin 8 and is held within the head 6) and a downward unlocking position (when a transverse stress greater than the holding force exerted by the locking pin 15 is applied, the operating pin 8 is pulled out of the head 6, and correspondingly, the switching means may be released).

[0058] Preferably, the operating pin 8 is provided with a seat portion 17 into which the locking end 16 of the locking pin 15 is inserted, and this seat portion 17 is arranged at a position such that it is axially aligned with the locking pin 15 when the operating pin 8 is fully inserted into the head 6.

[0059] The seat portion 17 may be defined by a recess or hole on the lower surface of the second end 10 of the operating pin 8 with an appropriate inlet diameter or other geometric shape for shape coupling, thereby enabling at least partial insertion of the upper locking end 16 of the locking pin 15 and preventing access from being opened, for example, when the locking / unlocking mechanism 14 is in the locked configuration.

[0060] According to a first particular aspect of the present invention, the switching device 2 will accommodate a control deformation block element sized such that a first deformation stress higher than a predetermined threshold is plastically deformed and applied to the locking pin 15 via the operating pin 8.

[0061] In the first embodiment, the locking element with control deformation is sized to plastically deform without breaking.

[0062] According to a further variant, the locking element with control deformation is sized to plastically deform, but there may be a possibility of local damage, that is, damage such that none of the components are separated in any case.

[0063] The control-deformation locking element is mechanically connected to the locking pin 15, for example, by a more or less complex kinematic chain that enables the stress acting on the locking pin 15 to be transmitted to the locking element, or it may be part of the locking pin 15.

[0064] In some cases, there may be a plurality of control-deformation locking elements, and if respective deformation stresses that are not necessarily equal to each other are applied to the locking pin 15, it may be adapted to deform.

[0065] For example, according to the configuration of FIG. 4, the portion of the locking pin 15 suitable for deforming in a controlled manner may be its locking end 16.

[0066] The locking pin 15 comprises a body 18, the body 18 extends along a main elongation axis A parallel to its movement direction X and will be connected to the locking end 16 by a control deformation or weakening zone 19.

[0067] Furthermore, the switching device 2 comprises a longitudinal passage 20, in which the body 18 of the locking pin 15 will be slidably received in an axially aligned position.

[0068] The weakening zone 19 is defined, for example, by a cross-sectional reduction of a part of the locking pin 15, for example a cross-sectional reduction with respect to the cross-section of the body 18, and may define a constriction that enables the locking end 16 to be movable from an undeformed position when a deformation stress is applied.

[0069] Alternatively, the weakening zone 19 may be obtained by providing one or more notches, or by providing other local structural weakening parts on the locking pin 15, and these also correspond to a plurality of deformation sections.

[0070] The locking end 16 of the locking pin 15 is preferably substantially cylindrical or disc-shaped and may, in some cases, have a chamfered edge with an inclined surface to facilitate the interaction with the second end 10 of the operating pin 8 during the insertion and withdrawal steps.

[0071] The transverse dimension of the locking end 16 does not necessarily have to match the transverse dimension of the main body 18.

[0072] Furthermore, when a first deformation stress is applied, the locking end 16 of the locking pin 15 shifts from an undeformed state aligned axially with the longitudinal passage to a deformed position misaligned with respect to the axis A of the longitudinal passage 20, and will be sized such that the locking end 16 at least partially interferes with the inner surface of the longitudinal passage 20.

[0073] Interference means that there is contact between the deformed portion of the locking pin 15 and the inner surface of the longitudinal passage 20 that can prevent mutual sliding.

[0074] In this way, after the deformation of the locking end 16, the locking pin 15 may remain pushed into the longitudinal passage 20 and thus may not move toward the unlocking position.

[0075] According to an embodiment which is possible but not limited thereto, there is a gap of several tenths of a millimeter over the entire circumference of the locking end 16 between the outer side surface of the locking end 16 and the inner surface of the longitudinal passage 20, and the longitudinal passage 20 will also function as a guide for the sliding of the locking pin 15.

[0076] The switching device 2 will suitably be provided internally with sensor means suitable for detecting the position of the locking pin 15.

[0077] The type employed for the sensor means does not limit the present invention, and sensors of any shape, technology, or type may be used.

[0078] By way of example, these sensor means can comprise one or more photocells or other optical-type sensors suitable for detecting the start of movement of the locking pin 15 and / or the main body 18 and, optionally, the end of movement or the reaching of an intermediate position.

[0079] As an alternative to the optical type means, different types of sensors such as magnetic sensors, for example magnetic, RFID, electrical sensors, or sensors based on other technologies may be used.

[0080] The sensor means is designed to detect the movement of the locking pin 15 and / or the body 18 following the door opening signal and, if it does not detect the correct downward stroke (which can be correlated with an error situation causing the plant to stop), will send an error signal.

[0081] In this configuration, the operating pin 8 has the function of an actuator in addition to the function of holding and centering the element with respect to the switching device 2.

[0082] In particular, the operating pin 8 will be provided with a first remote communication element of the transmitting or receiving type (not shown as it is known per se) that is suitable for communicating with a second communication element of the receiving or transmitting type (also not shown) present within the switching device 2 by transmitting or receiving a presence signal.

[0083] For example, the first communication element may be arranged around the seat 17 and, in some cases, incorporated into the second end 10 of the operating pin 8, while the second communication element may be arranged within the head 6 so as to communicate with the first communication element when the operating pin 8 is fully inserted into the head 6.

[0084] Alternatively, the first remote communication element may be inserted into the mounting body 7, and the second remote communication element may instead be within the head 6 or the case 5, and their respective positions will at least partially face each other in a closed access state.

[0085] According to an alternative variant, the first remote communication element may be of the receiving type that receives the presence signal transmitted by the second remote communication element, and thus the second remote communication element will be of the transmitting type.

[0086] The receiving element may be an RFID (Radio Frequency Identification) type antenna configured to receive a remote control signal transmitted by the transmitting element. When the transmitting element is at the minimum detection distance from the antenna, the transmitting element may alternatively be a transponder.

[0087] In particular, the transponder may be equipped with an RFID tag, and the RFID tag has an identification code, which is received by the receiving element and needs to be recognized by the control means of a safety assembly appropriately equipped with a CPU in order to enable the startup of the machine or plant.

[0088] The recognition of the code may be unique or general-purpose, depending on whether a switch with high-level coding or a switch with low-level coding is created.

[0089] Advantageously, the RFID tag will be encoded so as to be clearly recognized by the receiving element and prevent the use of actuator devices other than the actuator device connected to the access, thereby avoiding the risk of the access being opened in an unsafe state.

[0090] The recognition of the tag by the antenna will enable the operation of the locking / unlocking mechanism 14.

[0091] For example, an electromagnet 22 or other actuator means of an electromechanical, electrical, hydraulic or pneumatic type housed in the case 5 can be powered on or off to promote the translation of the locking pin 15 upward or downward according to the type of operation, in a manner known in the art and not described in detail here. Thereby, the locking pin 15 enters the seat 17 of the operating pin 8 and is locked in the head 6, or promotes the downward translation, and the access is unlocked.

[0092] However, it is understood that the transmitting element may be of another type involving electromechanical action, such as a key actuator, or of another type operated by a magnetic or electromagnetic, optical, mechanical, inductive, pressure, or other type of sensor, and as a result, the receiving element will be adapted to the nature of the transmitting element.

Claims

1. A safety switch for controlling access to an industrial machine or plant, comprising: - A switching device (2) accommodating switching means for controlling one or more command circuits and / or service circuits of the industrial machine or plant; - An actuator device (3) adapted to interact with the switching means to open and close one or more of the circuits when opening and closing the access; - A locking / unlocking mechanism (14) housed in the switching device (2) and provided with a locking pin (15) movable between at least one locking position and at least one unlocking position of the access within the switching device (2); - An operating pin (8) associated with the actuator device (3) and adapted to interact with the locking pin (15) to hold the actuator device (3) in a fixed state relative to the switching device (2); characterized in that the switching device (2) houses at least one locking element with controlled deformation, mechanically connected to the locking pin (15) and dimensioned to plastically deform when a first deformation stress higher than a predetermined threshold is applied to the locking pin (15) by the operating pin (8).

2. The safety switch according to claim 1, wherein the locking element with controlled deformation is part of the locking pin (15).

3. The safety switch according to claim 2, wherein the locking pin (15) comprises a locking end (16) adapted to engage with the operating pin (8) and defining the locking element with controlled deformation.

4. The safety switch according to claim 3, wherein the locking pin (15) is movable along a predetermined longitudinal movement direction (X) within the switching device (2) and comprises a body (18) extending along a main elongation axis (A) substantially parallel to the longitudinal movement direction (X) and connected to the locking end (16) by a weakening zone (19).

5. The safety switch according to claim 4, wherein the weakening zone (19) is defined by a part of the locking pin (15) having a cross-sectional area smaller than the cross-sectional area of the main body (18).

6. The safety switch according to claim 4 or claim 5, wherein the weakening zone (19) is defined by one or more regions having a notch and / or a cross-sectional reduction formed in the locking end (16) of the locking pin (15).

7. The safety switch according to any one of claims 4 to 6, wherein the switching device (2) has a longitudinal passage (20) in which the main body (18) of the locking pin (15) is slidably received in an axially aligned position.

8. The locking end (16) of the locking pin (15) is substantially cylindrical or disc-shaped, and when the first deformation stress is applied, it moves from an undeformed state axially aligned with the longitudinal passage (20) to a deformed position not aligned with the axis (A) of the longitudinal passage (20), and the locking end (16) is sized to at least partially interfere with the inner surface of the longitudinal passage (20). The safety switch according to claim 7.

9. The switching device (2) is sensor means for detecting the position of the locking pin (15), and when the locking signal or unlocking signal of the access is transmitted, it detects the movement of the locking pin (15) and transmits an error signal if the correct stroke to the corresponding locking position and unlocking position of the access is not detected. The safety switch according to any one of claims 1 to 8, which houses the sensor means inside.

10. The controlled-deformation locking element of the locking pin (15) is sized to deform in such a manner as to prevent the pulling out of the operating pin (8) to the outside of the switching device (2). The safety switch according to any one of claims 1 to 9.

11. The actuator device (3) is a mounting body (7) for mounting the access, and the mounting body (7) has the operating pin (8) protruding along the transverse direction (Y) from the mounting body (7). The safety switch according to any one of claims 1 to 10.

12. The switching device (4) includes a case (5) that houses the switching means, and a head (6) provided with at least one slot (11) for inserting the operating pin (8), and the locking pin (15) has a locking position where the locking end (16) is fully inserted into the head (6), and a unlocking position where the locking end (16) is not inserted into the head (6) or is only partially inserted, and is sized to move the locking end (16) between them. The safety switch according to any one of claims 3 to 11.

13. The actuator device (3) is provided with a first remote communication element of a reception type or a transmission type, and the switching device (2) is provided with a second remote communication element of a transmission type or a reception type that is adapted to communicate with the first remote communication element by transmitting or receiving a presence signal. The safety switch according to any one of claims 1 to 12.

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