Patent Publication Number: US-11396761-B2

Title: Safety switch

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of EP 17197166.6 filed on 2017 Oct. 18 and the priority of EP 17202141.2 filed on 2017 Nov. 16; all applications are incorporated by reference herein in their entirety. 
     BACKGROUND 
     Such a safety switch comprises, with an associated actuator, a safety switch arrangement used in the area of safety technology. For use in the area of safety technology, especially in the area of personal protection, the safety switch arrangement must meet standards-compliance requirements with regard to fault reliability, such that it is ensured that an appropriately safe monitoring function can be executed using the safety switch arrangement. Such a safety switch arrangement can typically be used to secure access to a hazard area. For example, a safety switch arrangement can be used as a lock for a barrier protective element, such as a safety door providing access to a hazard area. In this case, a hazardous system inside the hazard area can only be released for operation if the safety door is locked using the safety switch arrangement. The release of the system can be performed using a safety control unit to which safety-related control signals are supplied. 
     For latching the safety door when the safety door is in its closed position, the actuator, in the form of a bar or similar, is brought into engagement with the safety switch by, for example, inserting the actuator into a recess of the safety switch. This latching process is controlled by means of an RFID reader in the safety switch which detects a transponder in the actuator. 
     In addition to this latching process, locking of the safety door may be provided. Such a locking device is known, for example, from WO 2016/058718 A1. In this locking device, a locking bolt is provided that is actuated by means of an electric motor having a planetary gear train. With the electric drive, the locking bolt can be moved into a blocking position in which the actuator is locked by the locking bolt. 
     SUMMARY 
     The invention concerns a safety switch ( 2 ) with a latching unit ( 12 ), by means of which an associated actuator ( 3 ) is held in a latched position. The latching unit ( 12 ) has an opening ( 9 ) and a blocking element. In a latched position, the blocking element projects into the opening ( 9 ) and rear-engages an actuator head ( 8 ) of the actuator ( 3 ), which is in the latched position. The blocking element is held in the latched position by means of a positioning element with a setting force. When the actuator head ( 8 ) is inserted into or removed from the opening ( 9 ), the actuator head ( 8 ) pivots the blocking element out against the setting force. 
     DETAILED DESCRIPTION 
     The invention seeks to solve the problem of providing a compact safety switch that enables a reliable safety function. 
     For solving this problem, the features of claim  1  are provided. Advantageous embodiments and useful further developments of the inventions are described in the dependent claims. 
     The invention concerns a safety switch with a latching unit by means of which an associated actuator is held in a latched position. The latching unit has an opening and a blocking element. In a latched position, the blocking element projects into the opening and rear-engages an actuator head of the actuator, which is in the latched position. The blocking element is held in the latched position by means of a positioning element under a setting force. When the actuator head is inserted into or removed from the opening, the actuator head pivots the blocking element out against the setting force. 
     The small and compact design of the safety switch represents an essential advantage. 
     The safety switch is easy to install and can be used flexibly in combination with an actuator to create a safety switch arrangement. The safety switch arrangement formed in this manner can generally be used in the area of safety technology, especially for securing access to a hazard area. 
     The functional principle of the latching unit of the safety switch according to the invention is such that the blocking element in its latched position projects into the opening of the latching unit so that a reduced opening results. The front end of the actuator has a cross-sectional area that is larger than this reduced opening but smaller than the opening itself. If therefore the actuator is inserted with its front free end through the reduced opening of the latching unit, the blocking element is pivoted out against the setting force and can thus pass through the opening. Once the actuator is moved into its latched position, the blocking element is again returned to the latched position by means of the setting force and projects into the opening, by which means the blocking element rear-engages the front end of the actuator, which ensures a form-locked latching and locking of the actuator. 
     It is especially advantageous if the actuator is matched to the latching unit of the safety switch such that the latter has an actuator head that is connected to a core body of the actuator by a connecting element. The longitudinal axis of the connecting element is advantageously oriented in a stable base position perpendicular to the surface of the core body and has high rigidity in its axial direction. Thus, the actuator head can be moved with touch pressure against the blocking element projecting into the opening, which causes the blocking element to be pivoted out against the setting force and the actuator to be moved into the latched position. In the latched position of the actuator, the blocking element is then moved into the latched position by the setting force and rear-engages the actuator such that it is held and locked in the latched position. 
     According to an advantageous embodiment, the blocking element is realized as a latch. 
     In this regard the latch, with its lower end, is engaged with the positioning element. In the latched position, the upper end of the latch projects into the opening; the upper end has a circular edge the curvature radius of which corresponds to the radius of the opening. 
     The latch forms a cost-effective mechanical component with compact dimensions. 
     By means of the circular edge of the upper end of the latch, it is ensured that, when the actuator head is pushed into the opening and the latch is thereby pivoted out of the latched position, the edge of the latch approximately or exactly coincides with an edge region of the opening such that the latch fully exposes the opening and the actuator head can be pushed into the opening without hindrance. 
     In general, the opening is not restricted to a circular contour, but rather can have any kind of contours. Accordingly, the edge of the latch is generally adapted to the contour of the opening. 
     Adapted to the form of the blocking element, the positioning element is formed by a rocker. 
     The rocker has a bar-shaped end of the rocker element. A pivot bearing is provided at a first longitudinal end of the rocker element. A spring that generates the setting force for the blocking element abuts the underside of the rocker element. 
     The rocker has a simple structure with just a few separate parts. The positioning element formed in this manner can be realized in compact designs. The setting force is realized by very straightforward means by the spring acting on the rocker element. 
     In this embodiment, the blocking element is moved into the latched position by a pivot motion. In general, positioning elements that move the blocking element into the latched position by pushing movements or the like are also conceivable. 
     To ensure effective transmission of the setting force to the blocking element, it is expedient that the spring abuts a central region of the rocker element on the latter&#39;s underside. In this region, the lower end of the latch rests on the upper side of the rocker element. 
     An additional advantage is that the setting force can be adjusted by pre-tensioning the spring. 
     This enables straightforward adjustment to various applications, especially various actuators. 
     According to an advantageous embodiment of the invention, the latching unit is associated with a locking unit. The blocking element is locked in its latched position by means of the locking unit. 
     An additional safety function of the safety switch is provided by means of this locking. 
     It is advantageous if the locking unit has a hinged armature solenoid that has an electromagnet and an armature that can be pivoted using the electromagnet. The armature can be brought into a locked position. In the locked position, the armature latches the rocker. 
     The hinged armature solenoid forms a compact unit by means of which reliable locking can be effected. The locking is implemented in a straightforward manner in that the armature of the hinged armature solenoid is brought into engagement with the rocker. 
     This can be realized in an especially straightforward manner in that the rocker has a detent at its second free end. In the locked position, the armature is engaged with this detent. 
     It is especially advantageous for the armature to be pivotable about a swivel axis. A pivoting arm forms a lever that can be brought into engagement with the rocker. A second pivoting arm forms a counterweight. Improved shock stability is achieved by means of the counterweight. 
     Due to the improved shock stability, the functionality of the hinged armature solenoid remains largely unaffected by external forces. 
     The safety switch according to the invention together with the actuator forms a safety switch arrangement for use in the area of safety technology. 
     It is advantageous for the actuator head to be ball-shaped. 
     The actuator has a base body that is connected to the actuator head by a connecting element, wherein the cross-sectional surface of the connecting element is smaller than the cross-sectional surface of the actuator head. 
     The respective designs of the safety switch and of the actuator are adapted to one another in order to ensure optimal functioning. In particular, the geometry of the opening is adapted to the shape of the actuator head. 
     Furthermore, the latched position of the actuator is monitored by recording signals from a transponder in the actuator with a reader unit of the safety switch. 
     This monitoring function can be used to identify errors in the locking of the actuator. This represents an essential measure to meet the required safety level for the use of the safety switch arrangement in the area of safety technology. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained below based on the drawings. The following is shown in: 
         FIG. 1  Exemplary embodiment of the safety switch arrangement in accordance with the invention with a safety switch and an actuator. 
         FIG. 2A  One state of the latching unit and locking unit of the safety switch arrangement from  FIG. 1 , upon insertion of the actuator into a latched position. 
         FIG. 2B  Another state of the latching unit and locking unit of the safety switch arrangement from  FIG. 1 , upon insertion of the actuator into a latched position. 
         FIG. 2C  A further state of the latching unit and locking unit of the safety switch arrangement from  FIG. 1 , upon insertion of the actuator into a latched position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows schematically an exemplary embodiment of a safety switch arrangement  1  with a safety switch  2  and actuator  3 . 
     This safety switch arrangement  1  can be used, for example, to secure a protected door that serves as access to a hazard area. The actuator  3  can be arranged at the safety door; the safety switch  2  can be arranged on a frame surrounding the door opening that is closed off by means of the safety door. 
     The components of the safety switch  2  are integrated into a housing  4  from which a cable connector  5  protrudes for connection to external units. 
     As is evident from  FIG. 1 , the actuator  3  has a core body  6  in which a connecting element  7  is mounted. The connecting element  7  is formed by an elongated body, the cross-section of which is at least approximately constant over its entire length. 
     The connecting element  7  is mounted in the core body  6  with its first free end such that the longitudinal axis of the connecting element  7  is oriented perpendicular to the surface of the core body  6 . At the other end of the connecting element  7 , an actuator head  8  is mounted. In the present case, the actuator head  8  is sphere-shaped. In principle, the actuator head  8  can also be formed by another body with rotational symmetry. In principle, the actuator head  8  can also have an oval or polygonal cross-section. In any case the actuator head  8  has a larger cross-sectional area than the connecting element  7 , such that the actuator head  8  projects across its entire cross-sectional plane beyond the connecting element  7 . 
     In general, the connecting element  7  is made of a material that ensures high rigidity of the connecting element  7  in the axial direction and which maintains the connecting element  7  in its base position shown in  FIG. 1 , especially when the effects of gravity are present. 
     On a sidewall of the safety switch  2 , an opening  9  is provided into which a cavity in the safety switch  2  opens out into which cavity the actuator head  8  can be inserted such that the actuator  3  is then in its latched position. 
     The opening  9  is circular in form. A reading coil  10  is provided in the edge region of the sidewall that delimits the opening  9 . The reading coil  10  is mounted on a separate circuit board (not shown) and forms a reader unit, specifically an RFID reader unit. Corresponding to this, a transponder  11  is mounted in the actuator head  8 . In general, the transponder  11  can also be provided in the base body  6  of the actuator  3 . 
     By means of the reading coil  10 , signals from the transponder  11  can be detected in the actuator head  8  when the actuator  3  is moved into the latched position in the safety switch  2 , by which means it can be verified that the actuator  3  is actually in the latched position. 
     For secure latching and locking of the actuator  3  in its latched position, the safety switch  2  has a latching unit  12 . The latching unit  12  has a blocking element in the form of a latch  13  that can, with its upper end, be moved into the region of the opening  9 . 
     The latch  13  is composed of a planar component that is closed-off at its upper end by a circular-shaped edge  13   a . At the lower edge, a convex support element  13   b  is provided which forms a mechanical coupling to a positioning element. The latch  13  is displaceably mounted in the axial direction, i.e., in the vertical direction. Preferably, guide elements (not shown) are additionally provided. 
     The positioning element is realized in the form of a rocker  14  that has a bar-shaped rocker element  15 . A swivel bearing  16  is provided at a first longitudinal end of the rocker element  15  such that the rocker element  15  is pivotable about a swivel axis extending through the swivel bearing  16 . A detent  15   a  is provided at the second longitudinal end of the rocker element  15 . 
     The rocker  14  formed in this manner is associated with a spring  17 , the longitudinal axis of which extends in the vertical direction and the lower end of which is mounted on a stationary support. The upper end of the spring  17  abuts a central region of the rocker element  15  on the underside of the latter. The support element  13   b  of the latch  13  abuts the rocker element  15  on the latter&#39;s upper side in the same region. As evident in  FIG. 1 , the support element  13   b  is arranged along the longitudinal axis of the spring  17 . The spring force of the spring  17  effects a setting force that is transmitted from the rocker element  15  to the latch  13  such that the latch  13  is pushed upwards and with its upper edge  13   a  projects into the opening  9 . This position shown in  FIG. 1  is the locked and latched position of the latch  13 . 
     The setting force can be adjusted by appropriately pre-tensioning the spring  17 . 
     This latching unit  12  is associated with a locking unit  18  by means of which the latch  13  can be locked in place. 
     The locking unit  18  has a hinged armature solenoid  19  that has an electromagnet  20  and an armature  21 . The armature  21  is realized in the form of a lever that forms a pivoting arm  21   a  which is pivoted about a swivel bearing  22 . The arrangement can be expanded by a second pivoting arm  21   b  that forms a counterweight to the lever, thereby resulting in improved shock stability of the hinged armature solenoid  19 . The hinged armature solenoid  19  furthermore has a spring element  24  mounted on a guide segment  23  of the electromagnet  20 . As a result, the armature  21  is pivoted out when current is supplied to the electromagnet  20 . Locking of the latching unit  12  is effected insofar as the armature  21  is pivoted out such that it clicks into the detent  15   a  of the rocker element  15 . In general, the hinged armature solenoid  19  can be shaped differently in various embodiments and works according to the normally de-energized circuit (i.e., open circuit) principle or normally energized circuit principle. It can also be implemented as a bistable magnet. 
     The functioning of the latching and locking of the safety switch arrangement  1  is explained based on  FIGS. 2A to 2C . 
     In the starting position, for example, with an open protective door, the actuator  3  lies at a distance from the protective door. When the protective door is closed, the actuator  3  is moved into a latching unit  12  inside the safety switch  2 . 
     To this end, the actuator  3  with the actuator head  8  is moved against the opening  9  in the safety switch  2 , wherein in this starting position the latch  13  is in the latched position and projects into the opening  9 . 
     When the actuator head  8  is inserted into the opening  9  of the safety switch  2 , the latch  13  is pushed down and out of the latched position due to the pressing force of the actuator head  8  since the diameter of the actuator head  8  is adapted to the inner diameter of the opening  9  and fills it virtually completely. This situation is depicted in  FIG. 2A . The actuator head  8  lies in the opening  9 , and the latch  13  is pushed down and out of the latched position against the spring force of the spring  17  such that the upper circular curved edge  13   a  lies in the edge region of the opening  9 . Here it is advantageous for the curvature radius of the upper edge  13   a  of the latch  13  to correspond to the radius of the opening  9  such that the edge contour of the latch  13  corresponds approximately or exactly to the edge contour of the opening  9 . In general, the opening can also have a non-circular contour, wherein also the edge  13   a  is then adapted to this contour. 
     The actuator  3  is then pushed farther into a latched position such that the actuator head  8  lies completely in the cavity adjacent to the opening  9 . Then, as shown in  FIG. 2B , the connecting element  7  lies in the region of the opening  9 . Since the diameter of the connecting element  7  is smaller than the diameter of the actuator head  8 , the latch  13  is pushed up and into the latched position ( FIG. 2B ) by the spring force from the spring  17  and secures and locks the actuator head  8  in the latched position. The locked and latched position of the actuator  3  is monitored by reading the signals from the transponder  11  in the reader unit. In the locked and latched position, the latch  13  rear-engages the actuator head  8 , thereby holding the actuator  3  in the latched position. 
     In the situation shown in  FIG. 2B , the locking has not yet been activated, i.e., the armature  21  of the hinged armature solenoid  19  is not engaged with the detent  15   a  of the rocker element  15  of the rocker  14 . Therefore, it is still possible to unlatch the actuator  3 , i.e., the actuator  3  can be pulled out of the locked and latched position when exposed to forces, wherein then, when the actuator head  8  passes through the opening  9  of the safety switch  2 , the latch  13  is pushed down and out of the latched position against the spring force. 
     Finally,  FIG. 2C  shows the situation when the actuator  3  is inserted into the latched position and locking is activated. In the latched position, the latch  13  in the latched position rear-engages the actuator head  8  and holds the actuator  3  in the latched position. 
     The locking is activated such that the armature  21  is pivoted out by means of the electromagnet  20  and engages in the detent  15   a  of the rocker  14 . The rocker  14  is therefore secured in place. Due to the secured rocker  14 , the actuator  3  can no longer move out of the latched position since the rocker  14  secures the latch  13  from moving out of the latched position. Therefore, the actuator  3  can only be released again when locking is deactivated, i.e., when the armature  21  is no longer engaged in the detent  15   a.    
     When the safety switch arrangement  1  according to the invention is used to secure a protective door serving as access to a hazard area, the safety switch  2  can, when the actuator  3  is latched and locked, emit a switching signal that can be used to release a hazardous system within the hazard area for operation. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
             ( 1 ) Safety switch arrangement 
             ( 2 ) Safety switch 
             ( 3 ) Actuator 
             ( 4 ) Housing 
             ( 5 ) Cable connection 
             ( 6 ) Core body 
             ( 7 ) Connecting element 
             ( 8 ) Actuator head 
             ( 9 ) Opening 
             ( 10 ) Reading coil 
             ( 11 ) Transponder 
             ( 12 ) Latching unit 
             ( 13 ) Latch 
             ( 13   a ) Edge 
             ( 13   b ) Support element 
             ( 14 ) Rocker 
             ( 15 ) Rocker element 
             ( 15   a ) Detent 
             ( 16 ) Swivel bearing 
             ( 17 ) Spring 
             ( 18 ) Locking unit 
             ( 19 ) Hinged armature solenoid 
             ( 20 ) Electromagnet 
             ( 21 ) Armature 
             ( 21   a ) Pivoting arm 
             ( 21   b ) Second pivoting arm/counterweight 
             ( 22 ) Swivel bearing 
             ( 23 ) Guide segment 
             ( 24 ) Spring element