Technical field

[0001 ] The present invention relates generally to a system for screening off an area. The system comprises panels and posts, where the panels are attached to the posts in order to screen off a certain area, such as a protected area. The certain area may be an area where machines such as robots work. In this case, the system may be called a machine guarding system. The certain area may be an area in an automated warehouse where autonomous machines, i.e. vehicles such as fork-lift trucks, work.

Background art

[0002] In industry, machines that may constitute a hazard are common. Such machines may be robots, automated fork-lifts etc. In order to protect people, and in some cases also objects or other machines, in the environment around the machines, there are various types of arrangements for screening off an area in which such machines are situated. The screening off may be such that people are prevented from entering into the area of the machine when the machine is in operation, the screening off may arrest objects that are thrown out from the area by mistake, the screening off may prevent spattering of liquid, and/or impede troublesome light, such as welding light etc.

[0003] Regardless of what the screening off arrangement is meant to protect against, there are a number of common safety requirements. One safety requirement is that the screening off arrangement should not be passable without the consequences thereof first being considered. Another safety requirement is that it should not be possible to leave the screening off arrangement in an open state unintentionally.

[0004] International patent application WO03/106788 describes an example of such a screening off arrangement. This screening off arrangement comprises a number of carrier elements in the form of posts and a number of partitioning elements in the form of panels to be positioned in between the posts. For interconnecting the panels to the posts, the posts have lower and upper anchorage devices and the panels have lower and upper recesses, wherein the lower anchorage devices are arranged to cooperate with the lower recesses and the upper anchorage devices are arranged to cooperate with the upper recesses. The upper anchorage devices include locking means which are disposed to retain the panel in a locked position to its post. Such a screening off arrangement is easy to mount and dismount but at the same time it prevents unintentional access to the screened off area.

[0005] For different reasons, someone may have to remove a panel of such a screening off arrangement, or at least open an interconnection between post and panel so that it becomes possible to enter the screened off area through the screening off arrangement. One such reason may be that a machine operator needs access to the screened off area in order to do some kind of maintenance of the machine. The machine operator then, after shutting off the machine inside the screened off area, removes a panel in order to come into the screened-off area and perform the necessary maintenance. After completing the maintenance, the operator leaves the screened off area. If the operator then forgets to connect the panel to the post of an arrangement as in WO03/106788 and/or to lock a locking means so that the panel is locked to its post, there is a risk that the machine is started again without the area being correctly screened off. As a result, someone may accidentally enter the screened off area and get hurt from the working machine. Consequently, there is a need of an improved arrangement for screening off an area that avoids such scenarios or at least makes such scenarios very unlikely.

Summary of invention

[0006] An object of embodiments of the present invention is to provide a system for screening off an area that lowers the risk of accidents occurring due to a panel not being correctly locked to any of its posts when a machine inside the area is working. Another object of embodiments is to provide a system for screening off an area that monitors that the panels are correctly locked to their posts. Another object of embodiments is to provide a system that can issue a warning in case any of the panels is not correctly locked to any of its posts.

[0007] It is possible to achieve at least one of these objects and possibly others by using a system for screening off an area as defined in the attached independent claim.

[0008] According to one aspect, a system for screening off an area is provided. The system comprises at least one panel and a plurality of posts. The plurality of posts are arranged for connection to a panel of the at least one panel and the at least one panel is arranged for connection to a post of the plurality of posts. Further, at least one of the plurality of posts has a locking support, and at least one of the at least one panel has a locking means. Each locking support can be in a locked state, in which one of the locking means is locked to the locking support, and in an open state in which none of the locking means is locked to the locking support. Further, each of the at least one post further has a sensor arranged in connection with the locking support of the same post for detecting whether the locking support of the same post is in the locked state or the open state. Also, the system is arranged for communicatively connecting the sensor(s) to a control unit, whereby the system can inform the control unit when any of the sensor(s) detects that its locking support is in the open state.

[0009] By each locking support having a sensor that is able to detect whether the locking support is in the locked or open state, it can automatically be determined whether any of the panels are not correctly arranged to a post. Further, by arranging the system so that each sensor is arranged to be communicatively connected to a control unit, which is connected to the system when the system is in use, the system can inform the control unit when any of the sensors detects that its locking support is in the open state. The control unit can then take an action on the information on locking support open state, such as issuing an alarm, audible and/or visible, or automatically shut off the machine inside the screened-off area. Another action that the control unit can take is to prevent the machine inside the screened-off area to be restarted as long as any of the sensors detects that the locking support is in the open state. Hereby, the risk of accidents occurring due to a panel not being correctly locked to any of its posts is eliminated or at least lowered compared to an arrangement as in prior art.

[0010] According to an embodiment, the system further comprises the control unit. Then the at least one sensor is communicatively connected to the control unit. The system may comprise the control unit when sold, as described in this embodiment, or the system may be arranged for connection to a control unit which is a part of another system, for example a control system for controlling operation of a machine inside the screened off area. The control unit can then be the control unit of the control system of the machine. That the at least one sensor is communicatively connected to the control unit means that the at least one sensor is able to communicate to the control unit when it detects that its locking support is in the open state.

[0011 ] According to an embodiment, each of the at least one sensor comprises a mechanical switch that can be in either a closed position indicating the locked state of its locking support or an open position indicating the open state of its locking support. Also, the locking support is arranged for closing the mechanical switch when in the locked state. As the locking support itself closes the mechanical switch when going from open state to locked state, a failsafe detection of whether the locking support is in the open or closed state is achieved. Also, the locking support itself opens the mechanical switch when going from closed to open state, or at least when no pressure is applied to the mechanical switch it returns to the open position.

[0012] According to another embodiment, each of the at least one sensor is arranged to be communicatively connected to the control unit via a wireline connection, over which wireline connection the system is arranged to inform the control unit when any of the sensors detects that its locking support is in the open state. By connecting the control unit to the at least one sensor via wireline, a more stable system is provided compared to if a wireless connection would have been used. Also, by arranging the sensors at the posts instead of at the panels, electrical conductors of the wireline connection do not risk being in the way of any user trying to enter into a correctly opened passageway between a post and a panel, or between two posts in case a panel is opened at its opposite sides and taken away.

[0013] According to another embodiment, the at least one sensor comprises a plurality of sensors. Also, the wireline connection comprises a first electrical conductor. Further, when the system is set up and the plurality of sensors are connected via the wireline connection to the control unit, a first set of the plurality of sensors are connected via the first electrical conductor to the control unit. In other words, the first set of sensors are connected to the control unit via one and the same first electrical conductor. The first set of sensors may be all sensors that are to be connected to the control unit or the first set of sensors may be some of the sensors. Then the other sensors that are to be connected to the control unit are connected via a second electrical conductor separate from the first conductor. By using one electrical conductor for connection to more than one sensor, length of electrical conductors is saved. Also, as the most important is to know whether any of the locking supports is in the open state, it is enough that one signal can be sent for one set of sensors, i.e. locking supports.

[0014] According to anther embodiment, the first set of sensors are connected to the control unit via the first electrical conductor in such a way that when one of the first set of sensors detects that its locking support is in the open state, this open-state information overrides on the first electrical conductor any locked-state information of other of the first set of sensors. Hereby, the control unit is informed that any of the locking supports connected to any of the first set of sensors is in the open state.

[0015] According to yet another embodiment, the wireline connection comprises a cable arranged to lead from the control unit via each of the at least one of the plurality of posts to an outermost of the plurality of posts. Further, the cable comprising the first electrical conductor and a second electrical conductor leading unbroken from the control unit to the outermost post. The first electrical conductor is electrically connected to the second electrical conductor at the outermost post. Hereby, the first electrical conductor can be used as signal provider from the first set of sensors to the control unit, starting from the outermost post towards the control unit, and the first electrical conductor can be provided with an electrical potential from the second electrical conductor, which electrical potential is set by the control unit.

[0016] According to yet another embodiment, the cable comprises a third electrical conductor that is electrically connected to the second electrical conductor at the outermost post. Further, the plurality of sensors comprises a second set of sensors connected via the third electrical conductor to the control unit. Hereby it is possible to arrange the system with two separate detection loops even though the same cable is used.

[0017] According to another embodiment, each of the at least one of the posts has a local control unit electrically connected to the sensor of the post. The local control unit is arranged to receive information from the sensor, information whether the sensor detects that the locking support is in the closed state or the open state. By having such a local control unit at each post that receives information whether the sensor detects that the locking support is in the closed or open state, it is possible to determine locally at each post whether the locking support of this post is in closed or open state. In other words, the local control unit can determine whether the sensor detection revealed that the locking support is in closed or open state and, the local control unit can inform accordingly whether “it's” locking support is closed or open. Hereby, the system can easily inform the surrounding environment, for example an operator, at which post a locking support is in open state. According to an embodiment, the local control unit may be electrically connected to one or more visual indicator situated at or on the post, and the local control unit may be arranged to trigger the one or more visual indicator to indicate by visual indication whether the locking support is in closed or open state, hereby informing the surrounding environment at which post a locking support is in open state.

[0018] Further possible features and benefits of this solution will become apparent from the detailed description below. Brief description of drawings

[0019] The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

[0020] Fig. 1 is a perspective view of a system for screening off an area in which a machine is situated.

[0021 ] Fig. 2 is a schematic side view of a part of a system for screening off an area connected to a control unit, according to an embodiment.

[0022] Fig. 3 is a schematic perspective view of a part of a system for screening off an area according to an embodiment.

[0023] Fig. 4A is a close-up view of a locking arrangement of a post according to an embodiment, wherein the locking support is in an open state.

[0024] Fig. 4B is a close-up view of the locking arrangement of fig. 4A in which the locking support is in a closed state.

[0025] Fig. 5 is a schematic side view of a part of a system for screening off an area connected to a control unit, according to another embodiment.

[0026] Fig. 6 is an electrical circuit diagram of a wireline connection according to an embodiment.

Description of embodiments

[0027] Fig. 1 describes a system for screening off an area, which system in the shown example is used for screening off an area in which there is a robot 10 situated, which is controlled by a robot control unit (not shown). The system comprises a plurality of panels 110a, 110b, 110c, 110d, 110e and a plurality of posts 120a, 120b, 120c, 120d, 120e, 120f. In this example, the panels 110a-110e are essentially flat panels of rectangular shape, however, the panels may have many other geometrical shapes. The panels 110a-110e may be of e.g. , metal or plastics. The panels may be of sheet material or a mesh of wires. The panels 110a-110e are connected at opposite sides to the posts 120a-120f via fixings 140 on panels and posts. According to another embodiment, at least one of the panels may be a door that is connected to a post at one side, such as hingely connected, and has a locking means according to any of the embodiments disclosed at its other side for connection to a locking arrangement of a post.

[0028] Fig. 2 shows part of a system for screening off an area according to an exemplary embodiment. This system comprises panels 110a, 110b and posts 120a, 120b, 120c. Further, each post has a locking arrangement 121. The locking arrangement 121 has a locking support 122 and a sensor 124, which are shown and described in connection with figs. 3, 4A and 4B. Further, the panels 110a, 110b each has a locking means 112 (fig. 3 and 4A, 4B) arranged for connection to one of the locking supports 122. Further, the locking arrangements 121 and especially the sensors are connected via a wireline connection 140 to a control unit 130, which may also be called a central control unit. The control unit 130 may be a part of the system for screening off an area, or the control unit 130 may be a separate control unit to which the system for screening off an area is to be connected when it is installed and used for screening off an area. The control unit 130 may then for example be a control unit responsible for control of the machine 10 (fig. 1 ) that is inside the screened off area.

[0029] Fig. 3 shows the locking arrangement 121 of one post 120 and the locking means 112 of one panel 110 in more detail, according to an embodiment. The panel 110 here comprises a pole 111 onto which the locking means 112 is arranged. However, the pole is optional, and the locking means 112 may in another embodiment be arranged directly to the edge of the panel 110. The locking means 112 protrudes away from the panel 110 in approximately the same plane as the panel extends. The locking means 112 has a first part 112a and a second part 112b, the second part 112b having a diameter that is larger than the first part 112a. The first part 112a is arranged closer to the panel 110 than the second part 112b. According to an embodiment, the first part 112a is firmly attached to the pole 111 and the first part extends into the second part 112b. Further, the locking arrangement 121 of the post 120 has a slit 125 with a diameter slightly larger than the diameter of the second part 112b of the locking means 112, in order to be able to receive the second part 112b of the locking means. Also, the locking arrangement 121 has a recess 123 that extends from an outer surface of the locking arrangement and into the slit 125. The recess 123 has a smaller diameter than the slit 125. Preferably, the recess 123 has a diameter slightly larger than the first part 112a of the locking means 112 for receiving the first part of the locking means. In fig. 3, the panel 110 is in an open state, i.e. the panel 110 is not locked to the post 120. When the panel is to be locked, the panel 110 is moved towards the post 120 in the direction of the arrow at the top of the pole 111 of fig.

3. The second part 112b of the locking means 112 is then led into the slit 125 of the locking arrangement 121 , and the first part 112a of the locking means 112 is simultaneously led into the recess 123.

[0030] Further, in figs. 4A and 4B, the locking arrangement 121 is shown in more detail. Especially, inner parts of the locking arrangement 121 is shown in more detail in order to describe the function of the locking arrangement 121 according to embodiments. The locking arrangement 121 comprises a locking support 122. The locking support 122 can be in a locked state, in which a locking means, such as the locking means 112 of fig. 3, is locked to the locking support 122, and in an open state in which there is no locking means locked to the locking support. Fig. 4A shows the locking support 122 in its open state when the locking means 112 of the panel 110, i.e., its second part 112b, is not inserted into the slit 125 of the locking arrangement 121. Fig. 4B shows the locking support 122 in its closed state when the locking means 112 has been inserted into the slit 125.

[0031] In the shown embodiment of fig. 4A and 4B, the locking support 122 is rotatably attached to the post 120 via a rotation shaft 122a. The rotation shaft 122a passes through a hole (not shown) of the locking support 122. The hole may be situated centrally in the locking support 122. The locking support 122 may be formed as a flat plate. The locking support 122 has a main part in which the hole is arranged and two protruding portions 122b, 122c that in between them forms a recess. The locking support 122 is arranged so that when the locking means 112 is inserted into the slit 125, when the locking support is in the open state as in fig. 4A, the locking means 112 is also inserted into the recess that is formed between the two protruding portions 122b, 122c of the locking support 122. The locking means 112 then starts to push on one of the protruding portions 122b so that, as the locking means 112 is inserted further into the slit 125, the locking support 122 rotates around the rotation shaft 122a and into its locked state shown in fig. 4B.

[0032] As mentioned in relation to fig. 2, the locking arrangement 121 further has a sensor 124 arranged in connection with the locking support 122 for detecting whether the locking support 122 is in the open state or in the locked state. In the embodiment shown in figs. 4A and 4B, the sensor 124 comprises a switch 124a that is mechanically actuated by the locking support 122. In more detail, the switch 124a is arranged so that when the locking support 122 is in its open state, the locking support is not in contact with the switch 124a, and the switch is in an open position. When the locking support 122 is moved from its open state to its locked state by the insertion of the locking means 112 into the slit 125, the locking means 122 mechanically closes the switch 124a, i.e. , changes the switch 124a from its open position (fig. 4A) to its closed position (fig. 4B). In the same way, when the locking support 122 is moved from its locked state to its open state, the switch 124a is automatically moved from its closed position to its open position. The switch 124a may be pre-tensioned so that its resting position is its open position, i.e., if the switch is not actuated it takes its open position. When the switch 124a is in its closed position, two electrical conductors 124b, 124c are made to contact each other. When the switch 124a is in its open position, the two electrical conductors 124b, 124c do not contact each other. The sensor 124 is communicatively connected to the control unit 130 via its electrical conductors 124b, 124c, whereby the control unit 130 can be informed when the sensor 124 detects that its locking support 122 is in the open state. The control unit 130 can also be informed via the electrical conductors 124b, 124c whether the locking support 122 is in the locked state, but this can also be made optional in case there are many locking supports 122 in the system and in case it is decided to prioritize signaling to the control unit 130 whether any of the many locking supports of the system is in the open state. Fig. 6, which will be described later, shows a possible implementation of how to inform the control unit 130 via wireline when the locking support 122 is in the open state. [0033] In the above-described embodiment, the sensor 124 comprises a mechanically actuated switch. In another embodiment, the sensor has a magnet arranged to sense whether the locking support 122 is close to itself. Still alternatively, the sensor may be a metal detector that is arranged to detect whether the locking support 122 is within close distance to it. In those alternatives, the sensor may also comprise a switch that is connected to the magnet or metal detector, which switch may be closed in case the locking support is detected to be nearby, indicating locked state. When the switch is in the closed state it keeps an electric circuit closed and the closed electric circuit may be signaled to the control unit, and vice versa: when the electric circuit is open it may be signaled to the control unit. In another embodiment, the sensor 124 may be any kind of proximity sensor that senses whether the locking support 122 is in its locked state or its open state, and via a communicative connection to the control unit signals information indicating whether locked state or open state was detected, for example by sending a 0 or a 1 over the communicative connection.

[0034] According to an embodiment shown in fig. 4A and 4B, the locking arrangement 121 further comprises a locking support stop 126. The locking support stop 126 is rotatably secured to the post 120 via a stop rotation shaft 126a that protrudes through a hole extending through the locking support stop 126. The rotation support stop 126 has a first end 126b and a second end 126c and the hole may be situated centrally in the locking support stop 126. The locking support 122 and the locking support stop 126 are positioned so that when the locking support 122 is rotated into its locked state, a shoulder 122d of the locking support 122 starts cooperating with the first end 126b of the locking support stop 126 so that the first end 126b of the locking support stop 126 prevents the locking support 122 from being rotated back into its open state. More specifically, when in the locked state, the first end 126b of the locking support stop 126 bears against the shoulder 122d of the locking support 122 whereby the locking support 122 is prevented from being rotated back to its open state. In order to make it possible to move the locking support 122 into its open state, which is necessary for an operator to separate a panel 120 from its post 110 and thereby be able to enter the screened off area for e.g., maintenance of the machine inside the screened off area, there is a grip at the stop rotation shaft 126a. The grip is formed so that a tool specially adapted for this purpose would be fit to the grip, which tool should be available for an authorized operator. When using such a tool and positioning it into the grip, the locking support stop 126 can be rotated so that the first end 126b of the locking support stop 126 gets out of the position where it bears against the shoulder 122d of the locking support 122. Then the locking support 122 is free to rotate back to its open state.

[0035] The locking arrangement 121 may further have a first spring 128b that is arranged to cooperate with the one of the protruding portions 122b of the locking support 122 on which the locking means 112 starts to push when it is inserted into the slit 125 and starts to rotate the locking support 122 from its open state into its locked state. The first spring 128b is biased so that it pushes the locking support 122 back in its open state. This means that when an operator uses the tool for rotating the locking support stop 126 out of the contact with the shoulder 122d of the locking support 122, and there is no locking means 112 in the slit 125, the first spring 128b pushes the locking support 122 back into its open state. The locking arrangement 121 may further have a second spring 128a arranged for keeping the locking support stop 126 in position bearing at the shoulder 122d of the locking support 122. In other words, the second spring 128a is arranged to push the second end 126c of the locking support stop 126 so that its first end 126b has its resting position in the position where it bears against the shoulder 122d of the locking means 122 when the locking means 122 is in the locked state. In one embodiment, which is the one shown in figs. 4A and 4B, the first and second springs 128a, 128b are opposite ends of one and the same locking spring 128.

[0036] Fig. 5 shows an embodiment of the system for screening off an area in which the control unit 130 is communicatively connected to the sensors 124 of the locking arrangements 121 via a cable 240. The cable 240 leads from the control unit 130 via each of a plurality of posts 120a, 120b of the system that has a locking arrangement 121 to an outermost 120x of the plurality of posts. "Outermost post" 120x here means outermost when following the cable 240 from the control unit 130. The outermost post 120x may be situated geographically quite close to the control unit 130 in case the posts and panels are arranged to form a ring, but also geographically furthest away from the control unit 130.

[0037] The cable 240 comprises a first electrical conductor 141 to which a first set of sensors 124 are communicatively connected. The first set of sensors may be all sensors in the system, i.e. sensors of the posts 120a, 120b, 120x in the exemplary system of fig. 5. In another alternative, the first set of sensors may be a subset of all sensors and there may also be a second set of sensors that are communicatively connected via a third electrical conductor 143 of the cable 240. The third electrical conductor 143 is shown in the right part of fig. 6, which shows an example of a cable 240 having up to five electrical conductors 141-145. The cable 240 further comprises a second electrical conductor 142 (fig. 6) that leads unbroken from the control unit 130 to the outermost post 120x. That the second electrical conductor 142 leads unbroken from the control unit 130 to the outermost post 120x signifies that it has no electrical connection to any electrical circuits at any of the posts it passes before it reaches the outermost post 120x. When the second electrical conductor 142 reaches the outermost post 120x, it is electrically connected to the first electrical conductor 141 , as shown in fig 6. Hereby, the first electrical conductor 141 can be used as signal provider in a direction from the first set of sensors to the control unit 130, starting from the sensor of the outermost post 120x. Also, the first electrical conductor 141 can be provided with a potential from the second electrical conductor 142, which potential is set by the control unit 130. According to an embodiment, in case a first potential, which is higher than a second potential, is set on the second electrical conductor 142, sensors 124 of the first set of sensors that detects a closed state of its locking support 122 will not change the first potential. But in case any of the first set of sensors detects an open state of its locking support 122, that sensor triggers a change to the lower second potential on the first electrical conductor 141 and the control unit 130 will receive the second potential instead of the first potential and consequently determine an open state in the system. Hereby, only one electrical conductor can be used per some or even all sensors in the system in order to detect an open state on any of the locking supports 122, as a detected open state overrides detected closed states. Hereby, electrical conductor length is saved. Also, a failsafe detection of open state locking support in the system achieved.

[0038] As mentioned, and as shown in the right part of fig. 6, the cable 240 may comprise a third electrical conductor 143 that is electrically connected to the second electrical conductor 142 at the outermost post 120x. The electrical connection between the first and second electrical conductor 141 , 142 and this optional third electrical conductor 143 can be performed at a connection block situated at the outermost post 120x. Further, the plurality of sensors 124 comprises, apart from the first set of sensors also a second set of sensors connected via the third electrical conductor 143 to the control unit 130. Thus, it is possible to arrange the system with two separate detection loops, one via the first electrical conductor 141 and the first set of sensors and one via the third electrical conductor 143 and the second set of sensors, even though the same cable 240 is used. The first set of sensors may for example be arranged to the same posts as the second set of the sensors but then the first set of sensors are for detecting whether the locking support of one side of each post is in the locked state or the open state and the second set of sensors are for detecting whether the locking support of a second side of each post is in the locked state or the open state.

[0039] According to another embodiment shown in fig. 6, the cable 240 further comprises a fourth conductor 144 for providing a local control unit 170 arranged at each post that has a locking arrangement 121 with power. The cable 240 may further comprise a ground conductor 145 that is connected to ground.

[0040] The wireline connection 140 between a sensor 124 and the control unit 130 can be realized for example with an electrical circuitry as shown in fig. 6. The electrical circuitry is provided with power from the fourth conductor 144 (see Vied). According to an embodiment, the electrical circuitry comprises a transistor, which may be a field effect transistor (FET) 180 connected with its gate to the switch 124a, its drain to ground and its source to the first electrical conductor 141. When the switch 124a is closed, the power and thereby current provided to the electrical circuitry via the fourth electrical conductor 144 goes through the switch 124a to ground. Consequently, there is no or at least low current at the gate of the FET 180, whereby the electrical potential of the first electrical conductor 141 is not affected. However, when the switch 124a is opened, based on a detection that the locking support 122 of this switch is moved to its open state, the voltage on the gate of the FET 180 is increased, whereby current flows through the FET 180 and sets the drain of the FET at low voltage, as its source is connected to ground. As the drain is set to low voltage, i.e. , connected to ground over the FET 180, also the first electrical conductor will get a low voltage, i.e. a low potential, which is detected at the control unit 130. There may also be a diode connected from source to drain. This implementation uses a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) as transistor 180. However, other transistors or other electrical circuitry can be used as long as the result of a detection of open state overrides on the first electrical conductor any locked-state information of other of the sensors switches in the system connected to the first electrical conductor.

[0041] According to another embodiment, some of the posts 120 may have a local control unit 170 electrically connected to the sensor 124 of the post 120. This local control unit 170 is arranged for receiving information from the sensor 124 whether the sensor detects that the locking support 122 is in the closed state or the open state. Hereby it can be detected locally at each post whether the locking support 122 of this certain sensor 124 is in the open state or locked state.

[0042] According to another embodiment, the local control unit 170 is electrically connected to one or more visual indicator 171 , 172. Further, the local control unit 170 is arranged to trigger the one or more visual indicator 171 , 172 to indicate a first signal signifying that the locking support 122 is in the closed state and to trigger the one or more visual indicator 171 , 172 to indicate a second signal signifying that the locking support 122 is in the open state, e.g., based on the position of the switch 124a. In the implementation shown in fig. 6, the one or more visual indicators 171 , 172 comprises a first visual indicator 171 in the shape of a first Light Emitting Diode (LED) that indicates when the switch 124a is closed. The first LED 171 may emit green light when the switch is closed. For this reason, when the switch 124a is closed, current provided through the fourth conductor 144 will flow through the first LED 171 thanks to the arrangement of transistors 173, 177, diodes 175, 179a and resistors 174, 176, 179b of the electrical circuitry of the local control unit 170 connected between the switch 124a and the fourth conductor (Vied). Also, the one or more visual indicators 171 , 172 may comprise a second visual indicator 172 in shape of a LED that indicates when the switch 124a is open. The second LED 172 may emit red light when the switch is open. For this reason, when the switch 124a is open, current provided through the fourth conductor 144 will flow through the second LED 172 thanks to the arrangement of transistors 173, 177, diodes 175, 179a and resistors 174, 176, 179b of the electrical circuitry of the local control unit 170. A person skilled in the art would understand the coupling and use of the components of the electrical circuitry, as well as that such electrical circuitry may take many different realizations, for which reasons the realization of the electrical circuitry of fig. 6 is not elaborated on any further here.

[0043] According to another embodiment, the local control unit(s) 170 of the at least one of the posts 120 is/are electrically connected to the control unit 130 via a second wireline connection electrically separated from the wireline connection 140 by which the sensors 124 are connected to the control unit 130. This second wireline connection may be realized as the fourth electrical conductor 144 mentioned above.

[0044] According to another embodiment, one or more of the posts 120 that has a locking support 122 may also have a second locking support and a second sensor arranged in connection with the second locking support of the same post 120. Those second locking supports may be arranged similarly as the locking supports 122 and the second sensors may look like the sensors 124. As for the locking supports 122, the second locking support can be in a locked state in which one of the locking means is locked to the second locking support, and in an open state in which none of the locking means is locked to the second locking support. Further, the second sensor is arranged for detecting whether the second locking support of the same post is in the locked state or the open state. The locking support 122 and the second locking support may be arranged on opposite sides of the same post for detecting any opening of panels that are on both opposite sides of the post. According to an embodiment, some of the second locking arrangements may not have any sensor connected to it.

[0045] According to yet another embodiment, the control unit 130 is arranged to issue an indication when being informed that any of the sensors 124 has detected or detects that its locking support 122 is in the open state. The indication may be an audible or visual alarm sounding or lighting in the environment of the screened off area, at a display of an operator computer etc. Alternatively, the indication may be a control signal shutting of a machine residing in the screened off area, or a control signaling preventing turning on a machine that is in shut-off state.

[0046] Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. It will be appreciated that the scope of the presently described concept fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the abovedescribed embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for an apparatus to address each and every problem sought to be solved by the presently described concept, for it to be encompassed hereby.