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EP-4533506-B1 - SAFETY SWITCH FOR ACCESS CONTROL

EP4533506B1EP 4533506 B1EP4533506 B1EP 4533506B1EP-4533506-B1

Inventors

  • PIZZATO, MARCO
  • ZONTA, SIMONE

Dates

Publication Date
20260506
Application Date
20230526

Claims (13)

  1. A safety switch for controlling the access to industrial machines or plants, comprising: - a switching device (2) housing switching means for controlling one or more command and/or service circuits of the machine or plant; - an actuator device (3) adapted to interact with said switching means upon the opening/closing of the access for opening/closing one or more of said circuits; - a locking/unlocking mechanism (14) housed in said switching device (2) and provided with a locking pin (15) movable in said switching device (2) between at least one locking position of the access and at least one unlocking position thereof; - an operating pin (8) associated with said actuator device (3) and adapted to interact with said locking pin (15) to hold said actuator device (3) fastened to said switching device (2); characterized in that said switching device houses at least one locking element with controlled deformation, mechanically connected to said locking pin (15) and sized to deform plastically upon the application on said locking pin (15) by said operating pin (8), of a first deformation stress higher than a predetermined threshold value.
  2. Safety switch as claimed in claim 1, characterized in that said locking element with controlled deformation is a portion of said locking pin (15).
  3. Safety switch as claimed in claim 2, characterized in that said locking pin (15) comprises a locking end (16) adapted to engage said operating pin (8) and defining said locking element with controlled deformation.
  4. Safety switch as claimed in claim 3, characterized in that said locking pin (15) is movable in said switching device (2) along a predetermined longitudinal movement direction (X) and comprises a body (18) which extends along a main development axis (A) substantially parallel to said movement direction (X) and is connected to said locking end (16) by a weakening zone (19).
  5. Safety switch as claimed in claim 4, characterized in that said weakening zone (19) is defined by a portion of said locking pin (15) having a cross-section smaller than that of said body (18).
  6. Safety switch as claimed in claim 4 or 5, characterized in that said weakening zone (19) is defined by one or more areas with section reduction and/or notches made in said locking end (16) of said locking pin (15).
  7. Safety switch as claimed in any claim 4 to 6, characterized in that said switching device (2) has a longitudinal passage (20) wherein said body (18) of said locking pin (15) is housed slidingly and in an axially aligned position.
  8. Safety switch as claimed in claim 7, characterized in that said locking end (16) of said locking pin (15) is substantially cylindrical- or disc-shaped and is sized to move, upon the application of said first deformation stress, from an undeformed condition axially aligned with said longitudinal passage (20) to a deformed and misaligned position with respect to the axis (A) of said longitudinal passage (20) and such as to bring said locking end (16) into at least partial interference with the inner surface of said longitudinal passage (20).
  9. Safety switch as claimed in any preceding claim, characterized in that said switching device (2) houses sensor means thereinside for detecting the position of said locking pin (15) and detecting, upon the sending of a locking or unlocking signal of the access, the movement of said locking pin (15) to send an error signal in absence of detection of the correct stroke towards the corresponding locking and unlocking positions of the access.
  10. Safety switch as claimed in any preceding claim, characterized in that said locking element with controlled deformation of said locking pin (15) is sized to deform in such a manner to prevent the extraction of said operating pin (8) outside said switching device (2).
  11. Safety switch as claimed in any preceding claim, characterized in that said actuator device (3) comprises an anchoring body (7) for anchoring to the access and from which said operating pin (8) project along a transverse direction (Y).
  12. Safety switch as claimed in any claim 3 to 11, characterized in that said switching device (4) comprises a casing (5) housing said switching means and a head (6) provided with at least one slot (11) for the insertion of said operating pin (8), said locking pin (15) being sized to move said locking end (16) between said locking position wherein said locking end (16) is completely inserted in said head (6) and said unlocking position wherein said locking end (16) is not inserted in said head (6) or is inserted only partially.
  13. Safety switch as claimed in any preceding claim, characterized in that said actuator device (3) is provided with a first remote communication element of the receiving or transmitting type and wherein said switching device (2) is provided with a second remote communication element of the transmitting or receiving type adapted to communicate with said first remote communication element by sending or receiving a presence signal.

Description

Technical Field The present invention finds application in the field of industrial electrical devices and particularly relates to a safety switch for controlling access to safety barriers or perimeters for industrial machines and plants. State of the art As known, safety switches for controlling accesses to safety barriers and perimeters for industrial machines or plants generally comprise a switching device suitable for being anchored to the fixed part of the access and an actuator device suitable for being anchored to the movable part. The two devices are adapted to interact with each other when the access is opened and closed to signal the opening/closing condition, as well as locking/unlocking, to the control system of the machine or plant, and allow the control of the machine or plant according to methods that vary according to the adopted configuration. The interaction between the switching device and the actuator device may be of the mechanical or electromechanical type, wherein the actuator device is provided with a mechanical actuator, for example a key actuator, suitable to be inserted inside the switching device to interact mechanically with the switching means, and of the completely electronic type. In this second case, the interaction between the two devices occurs through the exchange of a presence signal through which it is possible to discriminate the proximity between the two devices, so as to distinguish the opening and closing conditions of the access. In both embodiments, the actuator device may also be provided with a pin which has the function of centering and retaining the actuator device on the switching device, so to prevent access from being opened without prior consent from the central system or from opening following the release thereof due to vibrations or other minimal solicitations not related to an opening attempt. The pin of the actuator device is usually designed to engage the locking pin of a locking/unlocking mechanism housed in the switching device. Generally, in electromechanical switches the action is carried out by the key or mechanical actuator itself. Some solutions also make it possible to detect any breakage of the locking/unlocking mechanism pin in order to prevent the switch from operating even if this event occurs. However, the breakage condition of the locking/unlocking mechanism pin should always be avoided since, in this case, it would still be possible for the integral part of the same locking pin to descend, which could therefore be erroneously detected as correct operation. JP2002216591 and JP2004079204 discloses a switch which, in a first configuration, has the purpose of avoiding the pin to break by providing a mechanism which prevents to apply thereto, through the traction exerted on the actuating pin, an excessive stress, by means of a series of referral mechanism which allow the applied stress to be dispersed. However, the constructive complexity of the locking mechanism makes this solution relatively expensive and unreliable. A safety switch solution which provides that there is no deformation or breakage of the locking pin even in case of excessive stress is also disclosed in JP2007257973. In a second embodiment of JP2002216591, on the other hand, the access always occurs also in the event of pin breakage. However, the above risk that the system may not detect such an opening condition due to the downward translation of the pin is not prevented. JP2002216591 and JP200345294 show further solutions which provide that the actuator pin may be released even in the event of deformation or breakage of the locking pin; however, no actions are provided to prevent the descent of the broken or deformed locking pin. JP2004079190 discloses a safety switch wherein a cam mechanism is provided to intervenes upon detection of an extraction force applied to the actuator having a value greater than a limit value to operate on a locking element acting in turn on the locking pin and producing the opening of the switching means, avoiding damage to the locking pin. The value of the limit force at which the cam mechanism intervene is established arbitrarily by means of a control element present in the locking element. The publication US2019/316381 describes a safety switch according to the preamble of claim 1. Other examples of switches provided with a locking mechanism are described in US 2011/127147 and US2020/165839. Scope of the invention The object of the present invention is to overcome the above drawbacks, by providing a safety switch for access control for industrial machines and plants which has features of high efficiency and relative cost effectiveness. A particular object is to provide an access control safety switch which provides evidence of the application of excessive stresses imparted to the pin of the locking/unlocking mechanism and exceeding a threshold value and which could cause damage to the actuator device itself and/or to the locking/unlocking mech