Patent Publication Number: US-9418522-B2

Title: Electronic hinged safety switch

Description:
FIELD OF THE INVENTION 
     The present invention generally finds application in the field of electric safety devices and particularly relates to an electronic hinged safety device. 
     BACKGROUND ART 
     Hinged safety switches are known to be used in plants or machines having areas or rooms bounded by protection barriers, and containing mechanical moving members or hazardous devices. 
     Particularly, these safety switches are mounted to a protection barrier having a fixed part integral with the machine or plant, and a movable panel designed to be opened by an operator. 
     Hinged safety switches have casing designed to be secured to the fixed part of the barrier and a movable part, which can pivot relative to the enclosure, and is designed to be secured to the panel. 
     Furthermore, the switch comprises an electrical commutator and an actuator, which is adapted to interact with such commutator upon pivotal movement of the movable part. 
     As the panel is opened and/or closed, the movable part of the switch is caused to pivot relative to the casing and the actuator is triggered. 
     This latter will thus actuate the commutator to cause one or more electric safety circuits associated with the barrier to open and/or close. 
     A very common type of hinged safety switches uses mechanical commutators. 
     IT1362135, filed by the applicant hereof, discloses a safety switch with a mechanical commutator housed within the casing. This commutator comprises one or more movable contacts, moving along a longitudinal axis, whose displacement is driven by an actuator which is adapted to convert the rotary motion of the movable part into an axial translational motion. 
     Furthermore, this prior art switch may comprise LED-type optical signaling means, for confirming proper operation of the contacts and indicating where actuation occurs. 
     A first drawback of this prior art arrangement is that the use of mechanical commutators does not easily allow generation of electric signals with additional information concerning the position of the barrier or the state of the switch. 
     This is because mechanical commutators only allow switching of electrical contacts associated with safety circuits and cannot determine any inconsistent switching states of the contacts or wiring or contact unit failures. 
     A further drawback of this arrangement is that switches with mechanical commutators cannot be easily installed in safety plants that use a data bus or a field bus connected to an electronic control unit. 
     The installation of hinged safety devices with analog contact units requires an appropriate analog-to-digital conversion interface, such as AS-i or the like, to be interposed between the bus and the contacts, which will increase installation costs and circuit complexity of the electrical system. 
     DISCLOSURE OF THE INVENTION 
     The object of the present invention is to overcome the above drawbacks, by providing an electronic hinged safety switch that is highly efficient and relatively cost-effective. 
     A particular object of the present invention is to provide an electronic hinged safety switch that allows generation of one or more additional electric signals concerning switch operation. 
     Another object of the present invention is to provide an electronic hinged safety switch designed for connection to a digital communication system of the bus type or the like. 
     A further object of the present invention is to provide an electronic hinged safety switch that affords very quick and fully automatic enabling and/or disabling thereof by the plant during maintenance. 
     These and other objects, as better explained hereafter, are fulfilled by an electronic hinged safety switch as defined in claim  1 . 
     Advantageous embodiments of the invention are obtained in accordance with the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will be more apparent upon reading of the detailed description of a preferred, non-exclusive embodiment of an electronic hinged safety switch according to the invention, which is described as a non-limiting example with the help of the annexed drawings, in which: 
         FIG. 1  is a perspective view of a protection barrier comprising a hinged switch of the invention; 
         FIG. 2  is a perspective view of the switch of  FIG. 1 ; 
         FIG. 3  is a wiring block diagram of the switch of  FIG. 1 ; 
         FIG. 4  is a perspective view of a first detail of the switch of  FIG. 1 ; 
         FIG. 5  is a top view of the detail of  FIG. 4 ; 
         FIG. 6  is a first side view of the detail of  FIG. 4 ; 
         FIG. 7  is a second side view of the detail of  FIG. 4 ; 
         FIG. 8  is an exploded perspective view of the switch of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring to the above mentioned figures, a multifunctional electronic hinged safety switch, generally designated by numeral  1 , is adapted for use in a protection barrier B which is designed to bound a hazardous area of a machine or a plant. 
     Particularly, as best shown in  FIG. 1 , the protection barrier B may comprise a stationary part M which is designed to be secured to the ground or the frame of the machine or plant, and a pivotal part P, such as a door or over hinged to the stationary part M. 
     Furthermore, the barrier B is equipped with one or more electric safety circuits S for signaling that the door D has been opened and/or closed, by varying an appropriate electric signal. 
     The multifunctional hinged switch  1  of the invention comprises, as best shown in  FIG. 2 , a substantially box-like fixed member  2  designed to be secured to a stationary part M of the protection barrier B and a movable member  3  designed to be secured to a pivotal part P of the barrier B and to be coupled to the fixed member  2  through hinge means  4 . 
     The switch  1  further comprises sensing means  5  located in the fixed member  2  and interacting with the hinge means  4  to send an electric control signal S C  to one or more electric safety circuits S at an adjustable switching angle α. 
     The switch  1  may comprise a pair of electric inputs and a pair of electric outputs, not shown, for connection of at least one safety circuit S. 
     According to a peculiar feature of the invention, the sensing means  5  comprise at least one sensor  6  for generating a corresponding actuation signal S A  at the switching angle α. 
     Furthermore, the sensing means  5  comprise an electronic control unit  8  operatively connected to a sensor  6  and having at least one input  9  electrically connected to the sensor  6  for receiving the actuation signal S A  and at least one output  10  connected to the electric safety circuits S for generating the electric control signal S C  in response to such actuation signal S A . 
     Conveniently, the actuation signal may have electric parameters, such as voltage, current or frequency, that are selectively variable according to the number of switching commutations by the sensor  6 . 
     Particularly, the electronic control unit  8  may be designed to cause the sensor  6  to be switched upon detection of a voltage applied to the input and/or an electric current circulating through the contacts. 
     Furthermore, the sensor  6  may generate a single actuation signal S A . 
     Alternatively, the sensor  6  may comprise a plurality of electric and/or electronic contact units associated with the door P of the barrier B, each adapted to generate a corresponding assessment signal s a . 
     In this case, the actuation signal S A  comprises the plurality of assessment signals s a  generated by respective electric and/or electronic contact units in the sensor  6 . 
     Furthermore, the actuation signals s A  may have first and second levels, associated with the open and closed states of the door P of the protection barrier B respectively. 
     Conveniently, the sensor  6  may be selected from the group comprising mechanical commutators and/or electronic sensors. 
     The electronic control unit  8 , as best shown in the diagram of  FIG. 3 , may comprise first microprocessor means  11  for receiving the actuation signal S A  at the input  9 . 
     The first microprocessor means  11  may be designed to process the actuation signal S A  and generate the control signal S C  to be provided at the output  10 . 
     The control signal S C  generated by the first microprocessor means  11  may be of analog or digital type, according to the type of electric safety circuits S associated with the barrier B. 
     Particularly, the electric safety circuits S may comprise a central unit, not shown, for detecting the open and/or closed states of the doors P of a plurality of protection barriers B by detecting a control signal S C  of digital type. 
     Conveniently, the control signal S C  may be null when an actuation signal S A  corresponding to the open state of the door P of the barrier B is present at the input  9 . 
     Otherwise, the control signal S C  may be other than zero when an actuation signal S A  corresponding to the closed state of the door P of the barrier B is present at the input  9 . 
     Advantageously, the control signal may be other than zero, when the totality of the assessment signals s A  perform a passage from the first level to the second level. 
     Conveniently, as best schematically shown in  FIG. 3 , the sensor may comprise electric contacts  7 . 
     Particularly, the electronic control unit  8  may be adapted to generate a control signal other than zero, when the contacts  7  are switched from a state in which they are all open to a state in which they are all closed. 
     Conveniently, the electronic control unit  8  may be designed to generate an alarm signal S X  for indicating the presence of assessment signals s A  at different levels. 
     In this case the alarm signal S X  allows simultaneous signaling of the electric inconsistency state associated with a sensor  6  in the switch  1 . 
     Conveniently, the electronic control unit  8  may comprise interface means  12  connected to the first microprocessor means  11  and to an external communication line  13  associated with one or more additional electric devices, not shown. 
     The external communication line  13  may be as used in common communication systems for electric safety plants and may comprise, for instance, a data bus or a field bus of the AS-i or AS-i Safe type. 
     Conveniently, the interface means  12  may transmit first data D 1  associated with the actuation signal S A  and/or the control signal S C  into the external communication line. 
     Furthermore, the interface means  12  may be designed to receive second data D 2  associated with the additional electric safety devices from the external communication line  13 . 
     Particularly, the first microprocessor means  11  may be designed to generate the control signal S C  in response both to the activation signal S A  and to the second data D 2  received from the interface means  12 . 
     Thus, the switch  1  may be installed in a cascade of interconnected safety devices, and the control signal S C  generated thereby may be influenced by the electric state of the contacts in the additional safety devices. 
     The first microprocessor means  11  may comprise a non-volatile memory medium (ROM), not shown, in which permanent data are stored, and a volatile memory medium (RAM), also not shown, in which temporary data are stored. 
     The first microprocessor means  11  may be designed to perform periodic operation checks on the non-volatile memory medium (ROM) and the volatile memory medium (RAM). 
     Such configuration of the first microprocessor means  11  allows the provision of a switch  1  that can meet current standards concerning totally or partially electronic safety devices. 
     Conveniently, the first microprocessor means  11  may be programmed for periodically starting a check-up on the sensors  6 , the input  9  and the output  10 . 
     Particularly, as best shown in the diagram of  FIG. 3 , the electronic control unit  8  may comprise one or more transistors  14  controlled by the first microprocessor means  11  and operatively connected to the output  10 . 
     Each transistor  14  may comprise a biasing circuit, not shown, which is designed to allow it to operate as a switch by the action of the first microprocessor means  11 , in ON/OFF mode. 
     The on/off operation of the transistor  14  will modify the control signal S C  sent to the electric safety circuit S and generated by the first processing means  11 . 
     Conveniently, the first microprocessor means  11  may be designed for periodically checking proper ON/OFF transition of each transistor  14  and, as a result, proper electrical operation of the output  10 . 
     Furthermore, the first microprocessor means  11  may be adapted to generate an auxiliary electric signal S aux  corresponding to the number of switching instances of the sensor  6 . 
     Particularly, the first microprocessor means  11  may be adapted to detect the overall number of switching instances by the sensor  6  within a predetermined time interval. 
     For example, the first microprocessor means  11  may be adapted to generate an auxiliary signal S aux , when the switch  1  reaches a total operating time equal to a predetermined factory-preset value. 
     Advantageously, the electrical control unit  8  may comprise second microprocessor means  15  which interact with the first microprocessor means  11  to process the actuation signal S A  and generate the control signal S C . 
     Furthermore, the second microprocessor means  15  may be substantially symmetrical to the first microprocessor means  11  for redundant processing of the actuation signal S A . 
     Thus, the second microprocessor means  15  may be designed to only actuate the generation of the control signal S C  by the first microprocessor means  11  when such redundant processing provides results consistent with those obtained from processing by the first microprocessor means  11 . 
     The electronic control unit  8  may comprise power supply means, not shown, for supplying power to the first  11  and second  15  microprocessor means  15 , the interface means  12  and the transistors  14 . 
     Conveniently, as best shown in  FIGS. 4 to 7 , the electronic control unit  8  may comprise a pair of rigid supports  16 ,  17  for supporting and connecting together at least the first  11  and second  15  microprocessor means, the interface means  12  and the transistors  14 . 
     For example, each rigid support  16 ,  17  may be a printed circuit board PCB or the like. 
     Furthermore, as best shown in the illustrated configuration of the invention, the sensor  6  may be interposed between the rigid supports  16 ,  17  and may comprise a pair of substantially flat side walls  18 ,  19 , which are adapted to contact respective bottom walls  20 ,  21  of the rigid supports  16 ,  17 . 
     Conveniently, the sensor  6  may have output terminals  22  connected to the inputs  9  of the electronic processing unit  8  via corresponding interconnection cables  23 . 
     The fixed member  2 , as best shown in  FIG. 8 , comprises a compartment  24 , which is adapted to accommodate therein the sensor  6  and the electronic control unit  8 . 
     Furthermore, the hinge means  4  may comprise a pair of pins  25 ,  26  associated with the movable member  3  and pivoted to the fixed member  2 . 
     The pins  25 ,  26  allow the movable member  3  to pivot relative to the fixed member  2  about a common axis of rotation R. 
     According to a particular configuration of the invention, as shown in the figures, the sensor  6  may be a microswitch  6 ′ with mechanical contacts, and may comprise electric contacts  7  for generating respective assessment signals s a . 
     The number of the electric contacts  7  of the microswitch  6 ′ may depend on the number of connections in the safety circuits S. 
     Also, the microswitch  6 ′ may be designed to cause switching of the contacts  7  either at the same switching angle α or at different switching angles α. 
     The microswitch  6 ′ may be designed to interact with at least one of the pins  25 ,  26 . 
     Furthermore, the microswitch  6 ′ may comprise a slider  27 , which is designed for translation in a direction X parallel to the common axis of rotation R, and is adapted to cause the contacts  7  to open and/or close. 
     Conveniently, the microswitch  6 ′ may comprise at least one actuator element  28 , operatively connected to one of the pins  25 ,  26 , and interacting with the slider  27 . 
     The actuator element  28  may be designed to provide conversion of the rotary motion of the pin  25 ,  26 , into an axial motion of the slider  27 . 
     Furthermore, the switch  1  may comprise adjustment means  29  for adjusting the switching angle α of the contacts  7  associated with at least one of the pins  25 ,  26 . 
     For example the adjustment means  29  may be as disclosed in the Italian patent IT1362135, issued to the applicant hereof. 
     Conveniently, the switch  1  may comprise LED signaling means  30 , as shown in  FIGS. 2 and 8 , associated with the fixed member  2 . 
     The first microprocessor means  11  may be adapted to selectively power the signaling means  30  for generating differentiated light signals according to the actuation signal S A  and/or the control signal S C . 
     Particularly, the signaling means  30  may comprise three or more LEDs for emitting a light signal associated with the electrical function of the input  9 , the output  10  and the sensor  6 . 
     Thus, an operator may easily monitor the operating state of the switch  1  by watching at the differentiated light signals emitted by the signaling means  30 . 
     The above disclosure clearly shows that the invention fulfills the intended objects and particularly provides a remarkably safe and versatile multifunctional hinged switch. 
     The multifunctional hinged switch of this invention is susceptible to a number of changes and variants, within the inventive principle disclosed in the appended claims. All the details thereof may be replaced by other technically equivalent parts, and the materials may vary depending on different needs, without departure from the scope of the invention. 
     While the multifunctional hinged switch has been described with particular reference to the accompanying figures, the numerals are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.