METHOD FOR DETERMINING THE POSITION OF A SLIDING BLOCK OF A DOOR DRIVE, LOCKING DEVICE AND DOOR DRIVE

Description

[0001] The invention relates to a method for determining a position of a sliding block, which is mounted so as to be movable along a slide rail between a closed position and an open position, of a door drive having a locking device for automatically closing a door, as well as to a locking device designed to carry out this method and to a door drive equipped with such a locking device.

[0002] WO2010 / 052012 A1 and EP2957696 A1 disclose such door drives, in particular door closers, with a locking device and a sliding block mounted so as to be movable along a sliding rail between a closed position and an open position.

[0003] The method according to the invention is provided for a locking device comprising a locking element for blocking the movement of a sliding block from the open position toward the closed position, corresponding to a closing movement of the door, and an energizable electromagnet. The locking element is movable between a locking position, in which it is designed to prevent the movement of the sliding block, and a release position, in which it is designed to release the movement of the sliding block. The electromagnet, acting as an actuator, locks the locking element in the locking position when energized with a predetermined current.The locking element can be pushed from the locking position into the release position by the sliding block when the sliding block passes over the locking element. To correctly control the individual components of the locking device, in particular the electromagnet, and / or other devices coupled to the locking device, it is desirable to automatically determine the position of the sliding block in relation to the locking element precisely and reliably. In particular, it is desirable to be able to determine with certainty at any time whether the sliding block is in its closed or open position, or, if applicable, at the level of the locking element.

[0004] Accordingly, it is an object of the present invention to provide a method for accurate and reliable automatic position determination of a sliding block of a door drive.

[0005] This object is achieved by a method having the features of claim 1. Advantageous further developments of the method can be found in the dependent claims. Furthermore, the present invention also relates to a locking device designed to implement this method and to a door drive equipped with such a locking device.

[0006] According to the present invention, the method comprises at least the following steps: applying a current of the predetermined or lower current intensity to a magnetic coil of the electromagnet; monitoring the coil current of the electromagnet; detecting an overtravel of the blocking element by the sliding block based on the temporal profile of the monitored coil current; and determining the position of the sliding block with respect to the blocking element, in particular whether the sliding block is in the open position or in the closed position, using the detection of the overtravel of the blocking element by the sliding block.

[0007] Specifically, the locking element is used here as part of a first sensor device, and the position or attitude of the sliding block relative to the locking element is determined using the coil current of the electromagnet coupled to the locking element. By directly detecting the movement of the locking element over, any incorrect determinations that could occur when providing, in particular, only a separate sensor arranged next to the locking element for position determination are avoided. Furthermore, by directly monitoring and evaluating the coil current of the electromagnet coupled to the locking element and provided anyway, it is not necessary to provide a separate sensor that determines whether the locking element is in the locked position or the released position in order to determine the position or attitude of the sliding block.Consequently, the method according to the invention provides particularly accurate and reliable determination results and is structurally relatively simple to implement.

[0008] Preferably, the detection of the sliding block passing over the blocking element is carried out by detecting the occurrence of current peaks in the monitored coil current when the sliding block passes over the blocking element.

[0009] Such current peaks provide particularly clear and reliable information about the crossing of the blocking element and thus about the position of the sliding block.

[0010] Furthermore, a movement of the blocking element from the locking position to the release position is preferably detected via a current peak of a first polarity and a movement of the blocking element from the release position to the locking position is preferably detected via a current peak of a second polarity opposite to the first polarity.

[0011] Taking polarity into account makes it possible to distinguish between the direction of travel of the sliding block at the beginning and at the end or termination of the sliding block's movement over the locking element.

[0012] Further preferably, when the sliding block completely passes over the blocking element, first a current peak of the first polarity is detected and then a current peak of the second polarity is detected.

[0013] This enables the detection of a complete overrun of the sliding block and thus the determination that the sliding block has passed the locking element.

[0014] The electromagnet preferably comprises an armature slidably arranged within the solenoid coil, which armature is connected to an armature plate arranged outside the solenoid coil. The armature is coupled to the locking element in such a way that the armature plate breaks away from the solenoid coil to cause the current peak of the first polarity when the locking element moves from the locking position to the release position, and strikes the solenoid coil to cause the current peak of the second polarity when the locking element moves from the release position to the locking position. The respective current peak arises because the inductance of the solenoid coil changes abruptly when the armature plate breaks away or strikes.

[0015] This enables a particularly reliable determination of the position of the sliding block.

[0016] The locking device preferably comprises a separate sensor arranged in front of the locking element with respect to a movement of the sliding block from the closed position toward the open position. The separate sensor detects when the sliding block is at the level of the separate sensor. The position of the sliding block is determined using the sequence of detection when the sliding block is at the level of the separate sensor and the detection of the sliding block passing over the locking element, and thus using the direction of travel of the sliding block.

[0017] The inclusion of the separate sensor in the manner described enables an even further improvement of the determination result and the determination and consideration of further information, such as in particular the direction of travel of the sliding block in the control system.

[0018] Preferably, the magnetic coil is supplied with a current of low current intensity when the sliding block approaches the locking element from the closed position in the direction of the open position, and is supplied with a current of the predetermined current intensity when the sliding block approaches the locking element from the open position in the direction of the closed position.

[0019] The low current ensures that, when the sliding block moves from the closed position toward the open position, movement of the locking element can be detected by a current peak in the coil current, without unnecessarily impeding the movement of the sliding block due to excessive current. The specified current locks the locking element and thus blocks the movement of the sliding block from its open position toward the closed position, as is the purpose of a locking device. The specified current serves to (at least partially) generate a holding force on the locking element intended to block the movement of the sliding block.

[0020] Preferably, the predetermined current intensity is at least 1 time, in particular at least 10 times, in particular at least 20 times, greater than the lower current intensity.

[0021] This allows the locking element to be locked sufficiently with the specified current, while the lower current allows detectable current peaks to be generated without locking the locking element.

[0022] Preferably, the lower current is in the range of 1mA to 20mA, in particular 10mA, and / or the predetermined current is in the range of 2mA to 400mA.

[0023] These value ranges have proven to be particularly suitable.

[0024] A locking device according to the invention for locking a sliding block of a door drive for automatically closing a door, which sliding block is mounted so as to be movable along a sliding rail between a closed position and an open position, is designed to carry out the method described above.

[0025] Such a locking device makes it possible to utilize the advantages of the method described above.

[0026] A door drive according to the invention, in particular a door closer according to the invention, comprises the locking device described above as well as a corresponding slide rail and a corresponding slide block.

[0027] Such a door drive benefits from the advantages of the previously described method utilized in the locking device.

[0028] The invention will now be described by way of example with reference to the accompanying drawings, in which FIG. 1 shows a cross-section of an exemplary locking device suitable for carrying out the method according to the invention; FIG. 2 shows a cross-section of the rear (right) area of ​​the FIG. 1 Fig. 3 shows schematically different states of such a locking device in interaction with a corresponding sliding block; and Fig. 4 shows a diagram illustrating a coil current during a movement of a sliding block from position 2 FIG. 3 in position 3 FIG. 3 and back to position 2 FIG. 3 reproduces.

[0029] The FIG. 1 The locking device 1 shown for locking a sliding block of a door drive for automatically closing a door, which sliding block is mounted so as to be movable along a slide rail between a closed position and an open position, is a preferred embodiment of a locking device designed to carry out the method according to the invention. It comprises a housing 3, a locking element 5, an actuator 7, and a control device 9.

[0030] The locking element 5 is movably mounted in the housing 3 via a stationary first pivot joint 6. The locking element 5 is movable between a locking position (in FIG. 1 shown) and a release position. In the locking position of the locking element 5, at least one head section 5a of the locking element 5 protrudes from the housing 3 in order to hinder or block a movement of a sliding block (not shown here) along a slide rail (not shown) positioned on the locking device 1 (in particular below it). In the release position, the head section 5a of the locking element 5 is retracted into the housing 3 in order not to hinder or release a movement of the sliding block along the locking device 1.

[0031] As in FIG. 2 As can be seen, the locking element 5 is connected to a first coupling arm 10a of a coupling rod 10 at a coupling section 5b opposite the head section 5a via a second rotary joint 8. The first coupling arm 10a is connected to a second coupling arm 10b of the coupling rod 10 via a third rotary joint 11. The second coupling arm 10b is rotatably mounted relative to the housing 3 via a stationary fourth rotary joint 13 and is connected to a third coupling arm 10c of the coupling rod 10 via a fifth rotary joint 15. Finally, the third coupling arm 10c is connected via a sixth rotary joint 19 to an armature 21 which is displaceably mounted along the housing 3. The sixth rotary joint 19 is connected by a guide plate 20 (see FIG. 1 ) is mounted so as to be only axially displaceable along the housing 3. The armature 21 is also mounted in the housing in such a way that it is only axially displaceable along the housing 3. The armature 21 is part of an electromagnet 25 and is at least partially surrounded by a magnetic coil 23 of the electromagnet 25, which is arranged within a housing of the electromagnet 25, wherein the electromagnet 25 forms at least part of the actuator 7. In the present case, the electromagnet 25 functions as an actuator 7. At its end opposite the sixth rotary joint 19, the armature 21 is coupled to an armature plate 27 by means of a fixing element 26. The armature plate 27 is arranged outside the magnetic coil 23 and is dimensioned such that it cannot immerse itself in the magnetic coil 23, but rather strikes the magnetic coil 23 or the electromagnet 25.

[0032] In the housing 3, a receiving area 3a is formed, in which the armature plate 27 can be moved axially along the housing 3 between a stop position in which the armature plate 27 abuts the electromagnet 25 or the magnetic coil 23 (cf. FIG. 1 ), and at least one further position in which the armature plate 27 is released from the electromagnet 25 or from the magnetic coil 23 (starting from the position shown further to the left in FIG. 1 ), is mounted so that it can be moved.

[0033] Furthermore, the locking device 1 comprises a prestressing element (not shown), which ensures that the locking element 5 is prestressed into its locking position, so that the locking element 5 always assumes the locking position when the locking element 5 is not pressed into the release position by the sliding block 33. Preferably, the prestressing element acts directly on the locking element 5 or a component of the coupling linkage 10 and is designed in particular as a mechanical prestressing element, for example as a (leg) spring.

[0034] The magnetic coil 23 is coupled to the control device 9 and can be supplied with current by it. For this purpose, the control device 9 can be coupled to a corresponding, in particular external, power supply (not shown), for example via cable 29. The control device 9 is designed to monitor and evaluate the current flowing through the magnetic coil 23 (here also referred to as coil current). The value of the determined current corresponds to a first detection signal, whereby the actuator 7 effectively functions at least as a component of a first sensor device 4 of the locking device 1. Based on the temporal profile of the monitored coil current, overtravel of the locking element 5 by the sliding block is detected.Finally, the control device 9 is designed to determine the position of the sliding block relative to the locking element 5 by detecting the sliding block's passage over the locking element 5. In particular, the control device 9 can determine whether the sliding block is in the open position or the closed position. How this happens in concrete terms is explained below with reference to . FIG. 3 described.

[0035] In addition to the first sensor device 4 just described, the locking device 1 in the embodiment shown comprises a second sensor device 31 or a separate sensor 31, which is coupled to the control device 9. The separate sensor 31 is connected to a movement of the sliding block from the closed position towards the open position (in FIG. 1 from left to right) in front of the blocking element 5. It is designed to detect whether the sliding block is at the level of the separate sensor 31 and to output a corresponding second detection signal to the control device 9.

[0036] In the present case, the separate sensor 31 is designed as an electrical switching element, specifically as a microswitch. However, other configurations are also possible, such as other contact sensors or configurations with contactless sensors, such as optical sensors or magnetic sensors.

[0037] The control device 9 is designed to receive the two detection signals, i.e. the first detection signal from the first sensor device 4, and the second detection signal from the second sensor device 31 or the separate sensor 31. Furthermore, the control device 9 is designed to use these two detection signals to determine the direction of travel of the sliding block when traveling over the blocking element 5 and thus the position of the sliding block with respect to the blocking element 5. In particular, the control device 9 can determine whether the sliding block is in the closed position (left in FIG. 1 ) or in the open position (right in FIG. 1 ). In the embodiment shown, it is also possible for the control device 9 to determine various intermediate positions of the sliding block, which are located between the closed position and the open position.

[0038] A concrete example of determining the position of a sliding block is shown below using the FIG. 3 with reference to FIG. 4 described. FIG. 3 schematically five different positions are shown, which a sliding block 33 of a door drive in relation to the locking element 5 and the second sensor device 31 or the separate sensor 31 of the FIG. 1 shown locking device 1. The FIG. 4 shows a diagram showing a coil current during a movement of the sliding block from position 2 FIG. 3 in position 3 FIG. 3 and back to position 2 FIG. 3 reproduces.

[0039] In position 1, which, in the context of the present invention, corresponds to a closed position of the sliding block 33, the separate sensor 31 is in a "non-actuated" state and thus does not detect the positioning of the sliding block 33 at the level of the separate sensor 31. At the same time, the locking element 5 is in its locking position due to its preload by the preload element. In position 1, the control device 9 does not supply current to the solenoid 23.

[0040] If the sliding block 33 now moves from its closed position (i.e., from position 1) to the illustrated position 2, the separate sensor 31 is "activated" and thus detects the positioning of the sliding block 33 at the level of the separate sensor 31. The locking element 5 is not yet pushed into the release position by the sliding block 33. This enables the control device 9 to detect that the sliding block 33 is in a first intermediate position between the closed position and the open position (position 5, described in more detail later). In anticipation of the sliding block 33 beginning to move over the locking element 5, the control device 9 now applies a first, relatively low current I1 to the solenoid coil 23, preferably between 1 mA and 20 mA, for example, 10 mA.This is necessary in order to be able to detect a movement of the locking element 5 between its locking position and its release position in the embodiment described above, as will become clear below.

[0041] If the sliding block 33 moves from this point back to position 1 or the closed position, the separate sensor 31 returns to the "unactuated" state, or the separate sensor 31 no longer detects that the sliding block 33 is at its height. This allows the control device 9 to detect that the sliding block 33 is back in position 1, i.e., in its closed position. Because the sliding block 33 is no longer expected to immediately overrun the locking element 5, the control device 9 stops supplying current to the solenoid 23.

[0042] If, however, the sliding block 33 moves from position 2 to position 3, the sliding block 33 pushes the locking element 5 against the force of the pre-tensioning element from its locking position into the release position (here upwards). This movement of the locking element 5 is transmitted to the armature 21 by the coupling rod 10 and leads to an axial movement of the armature 21 along the housing 3 (to the left in FIG. 1 ). This leads to a tearing off of the armature plate 27 from the magnetic coil 23 or from the electromagnet 25 and thereby to a current peak (cf. the current peak "Armature tearing off" in FIG. 4 ) of a first polarity within the magnetic coil 23. This current peak is detected by the control device 9 due to the monitoring of the coil current, whereby the control device detects that the sliding block 33 has overrun (i.e., in particular, the beginning of overrun) the blocking element 5. In this case, the separate sensor 31 is still in its "actuated" state and thus indicates to the control device 9 that the sliding block 33 is still at the level of the separate sensor 31. This enables the control device 9 to determine that the sliding block 33 is in position 3. This position 3 corresponds to a second intermediate position of the sliding block 33 between its closed position and its open position.

[0043] If the sliding block 33 moves from here back to position 2, i.e. into the first intermediate position, the sliding block 33 releases the locking element 5 again, whereby the locking element 5 is moved back into its locking position by the pre-tensioning element or the locking element 5 again assumes the locking position. This movement of the locking element 5 is transmitted to the armature 21 by the coupling rod 10 and leads to an axial return movement of the armature 21 along the housing 3 (to the right in FIG. 1 ). This leads to the armature plate 27 striking the magnetic coil 23 or the electromagnet 25 and thereby to a current peak (cf. the current peak "armature striking" in FIG. 4 ) a second polarity, opposite to the first polarity, within the magnetic coil 23. This current peak is again detected by the control device 9 due to the monitoring of the coil current. The separate sensor 31 is still in its "actuated" state and thus indicates to the control device 9 that the sliding block 33 is still at the level of the separate sensor 31. This enables the control device 9 to determine that the sliding block 33 is back in position 2 or back in the first intermediate position. The control device 9 thus also detects an interruption in the sliding block 33's movement over the blocking element 5.

[0044] However, if the sliding block 33 moves from position 3 to position 4, the separate sensor 31 returns to the "unactuated" state, while no further current peak is generated in the solenoid 23. This enables the control device 9 to determine that the sliding block 33 is in position 4 and thus in a third intermediate position. In anticipation of the imminent completion of the sliding block 33's passage over the blocking element 5, the control device 9 now applies a second, predetermined current I2 to the solenoid 23, which is greater than the first current I1. This second current I2 serves to immediately generate the holding force intended to lock the blocking element 5 in its locking position, i.e., to hold the sliding block 33 in the open position as soon as the sliding block 33 has passed the blocking element 5 and arrives in its open position.The second current intensity I2 is preferably at least 1 time, in particular at least 10 times, in particular at least 20 times greater than the first current intensity I1, and is preferably in a range from 2mA to 400mA.

[0045] If the sliding block 33 moves back to position 3 from this point, the separate sensor 31 is "activated" again, while no further current peak is generated in the solenoid coil 23. This enables the control device 9 to determine that the sliding block is back in position 3 and thus in the second intermediate position. As a result, the control device 9 now applies the first current I1 to the solenoid coil 23 again. It is no longer expected that the sliding block 33 will reach the open position for the time being. Consequently, it is also not necessary to apply the second current I2 to the solenoid coil 23 of the actuator 7, which is required to generate the specified holding force.

[0046] However, if the sliding block 3 moves from position 4 to position 5, the sliding block 33 releases the locking element 5 again, whereby the locking element 5 is moved back into its locking position by the pre-tensioning element or the locking element 5 again assumes the locking position. This movement of the locking element 5 is transmitted to the armature 21 by the coupling rod 10 and leads to an axial return movement of the armature 21 along the housing 3 (to the right in FIG. 1 ). This leads to the armature plate 27 striking the magnetic coil 23 or the electromagnet 25 and thereby to a current peak (similar to the current peak "armature strike" in FIG. 4 ) of the second polarity, opposite to the first polarity, within the magnetic coil 23. This current peak is in turn detected by the control device 9 due to the monitoring of the coil current. The separate sensor 31 is still in its "unactuated" state and thus indicates to the control device 9 that the sliding block 33 is no longer at the level of the separate sensor 31, i.e., in front of the locking element 5. This detects the completion of the sliding block 33's movement over the locking element 5 from the closed position toward the open position, and the control device 9 determines that the sliding block 33 is in position 5 and thus in its open position.

[0047] In this case, the magnetic coil 23 is still energized with the second, i.e. the predetermined current intensity I2, whereby the blocking element 5 is locked in its locking position with the predetermined holding force in order to prevent the sliding block 33 from moving from the open position towards the closed position (i.e. from the right back to the left into the Figuren 1 and 3) and thus to "block" the closing movement of a door equipped with the locking device. It is, of course, still possible, with the appropriate amount of force, to move the sliding block 33 back toward the closed position against the predetermined holding force, i.e., to manually push the locking element 5 toward the closed position. In addition, it is also possible, in certain situations, to force the control device 9 to interrupt or reverse the current supply to the magnetic coil 23 in order to allow the sliding block 33 to move back to its closed position. Such functionality is particularly useful as a fire protection measure.

[0048] In addition, it should be noted that the sliding block 33 can be arbitrarily moved between its closed position (compare position 1 from FIG. 3 ) and its open position (compare position 5 from FIG. 3 ) can be moved back and forth.

[0049] For example, the sliding block 33 can be moved from its closed position (see position 1 from FIG. 3 ) only up to the third intermediate position (cf. position 4 in FIG. 3 ) and from here back to its closed position (see position 1 in FIG. 3 ) without changing the open position (see position 5 in FIG. 3 ). This is of course also analogous for a movement of the sliding block 33 from its closed position only to the second intermediate position (cf. position 3 in FIG. 3 ) or even only to the first intermediate position (cf. position 2 in FIG. 3 ) and back. It is also possible that the sliding block moves during a movement from the closed position (see position 1 in FIG. 3 ) into the open position (see position 5 in FIG. 3 ) or from the closed position (see position 1 in FIG. 3 ) back to the closed position (see position 1 in FIG. 3 ) the different intermediate positions (see positions 2 to 4 in FIG. 3 ) as often as desired.

[0050] Conversely, a movement of the sliding block 33 starting from the open position (cf. position 5 in FIG. 3 ) into one of the three intermediate positions (see positions 2 to 4 in FIG. 3 ) and back, or completely into the closed position (see position 1 in FIG. 3 ), is possible. The control device 9 can reliably determine the direction of travel and thus also the specific position or attitude of the sliding block 33. In particular, the control device 9 can clearly determine whether the sliding block 33 is in front of (i.e. in the Figuren 1 and 3 left of) the locking element 5 or behind (i.e. in the Figuren 1 and 3 right of) the locking element 5, and suitably control the components of the locking device 1 and / or other devices coupled to the locking device 1.

[0051] Finally, it should be noted that, in light of the above description, a person skilled in the art will readily conceive a multitude of modifications which are not explicitly described here, but are encompassed by the scope of the appended claims. In particular, the present invention further relates to a locking device designed to implement the method according to the invention, as well as to a door drive (not shown), in particular a door closer equipped with such a locking device 1, and a corresponding slide rail (not shown) and a corresponding slide block 33. Bezugszeichenliste

[0052] 1 Locking device 3 Housing 3a Mounting area 4 First sensor device 5 Locking element 5a Head section 5b Coupling section 6 First swivel joint 7 Actuator 8 Second swivel joint 9 Control device 10 Coupling linkage 10a First coupling arm 10b Second coupling arm 10c Third coupling arm 11 Third swivel joint 13 Fourth swivel joint 15 Fifth swivel joint 19 Sixth swivel joint 20 Guide plate 21 Armature 23 Solenoid coil 25 Electromagnet 26 Fixing element 27 Anchor plate 29 Cable 31 Second sensor device / separate sensor 33 Sliding block I1 First current / lower current I2 Second current / specified current

Claims

1. Method for determining a position of a sliding block (33), which is movably mounted along a sliding rail between a closed position and an open position, of a door drive, which has an arresting device (1), for automatically closing a door, wherein the arresting device (1) comprises a blocking element (5) for blocking a movement, which corresponds to a closing movement of the door, of the sliding block (33) from the open position in the direction of the closed position and an energizable electromagnet (25); wherein the blocking element (5) can be moved between an arresting position, in which it is designed to hamper the movement of the sliding block (33), and a release position, in which it is designed to release the movement of the sliding block (33); wherein the electromagnet (25), in a state in which it is energized with a specified current intensity, arrests the blocking element (5) in the arresting position; and wherein the blocking element (5) can be pushed from the arresting position to the release position by the sliding block (33) when the sliding block (33) passes across the blocking element (5); wherein the method comprises at least the following steps: applying a current of the specified current intensity (I2) or a current intensity (I1) lower than this to a magnet coil (23) of the electromagnet (25); monitoring the coil current of the electromagnet (25); detecting the situation of the sliding block (33) passing across the blocking element (5) on the basis of the time course of the monitored coil current; and determining the position of the sliding block (33) with respect to the blocking element (5), in particular whether the sliding block (33) is in the open position or in the closed position, using the detection of the situation of the sliding block (33) passing across the blocking element (5).

2. Method according to Claim 1, characterized in that the situation of the sliding block (33) passing across the blocking element (5) is detected by way of the occurrence of current peaks in the monitored coil current being detected when the sliding block (33) passes across the blocking element (5).

3. Method according to Claim 2, characterized in that a movement of the blocking element (5) from the arresting position to the release position is detected by means of a current peak of a first polarity and a movement of the blocking element (5) from the release position to the arresting position is detected by means of a current peak of a second polarity, which is opposite to the first polarity.

4. Method according to Claim 3, characterized in that, when the sliding block (33) completely passes across the blocking element (5), a current peak of the first polarity is initially detected and then a current peak of the second polarity is detected.

5. Method according to Claim 3 or 4, characterized in that the electromagnet (25) comprises an armature (21) which is arranged displaceably within the magnet coil (23) and is connected to an armature plate (27) arranged outside the magnet coil (23), wherein the armature (21) is coupled to the blocking element (5) in such a way that the armature plate (27) tears off from the magnet coil (23), in order to cause the current peak of the first polarity when the blocking element (5) moves from the arresting position to the release position, and hits the magnet coil (23), in order to cause the current peak of the second polarity when the blocking element (5) moves from the release position to the arresting position.

6. Method according to any of the preceding claims, characterized in that the arresting device (1) comprises a separate sensor (31), which is arranged in front of the blocking element (5) with respect to a movement of the sliding block (33) from the closed position in the direction of the open position, wherein the separate sensor (31) detects when the sliding block (33) is level with the separate sensor (31), wherein the position of the sliding block (33) is determined using the sequence of detecting when the sliding block (33) is level with the separate sensor (31), and detecting the situation of the sliding block (33) passing across the blocking element (5) and thus using the traversing direction of the sliding block (33).

7. Method according to any of the preceding claims, characterized in that a current of the low current intensity (I1) is applied to the magnet coil (23) when the sliding block (33) approaches the blocking element (5) from the closed position in the direction of the open position, and in that a current of the specified current intensity (I2) is applied to the magnet coil (23) when the sliding block (33) approaches the blocking element (5) from the open position in the direction of the closed position.

8. Method according to any of the preceding claims, characterized in that the specified current intensity (I2) is at least 1 time, in particular at least 10 times, in particular at least 20 times, higher than the relatively low current intensity (I1).

9. Method according to any of the preceding claims, characterized in that the relatively low current intensity (I1) is in the range of from 1 mA to 20 mA, in particular at 10 mA, and / or the specified current intensity (I2) is in the range of from 2 mA to 400 mA.

10. Arresting device (1) for arresting a sliding block (33), which is movably mounted along a sliding rail between a closed position and an open position, of a door drive for automatically closing a door, wherein the arresting device (1) is designed to execute the method according to any of the preceding claims.

11. Door drive, in particular door closer, having an arresting device (1) according to Claim 10, wherein the door drive comprises a corresponding sliding rail and a corresponding sliding block (33).