DE29901664U1 - Lift gate with light curtain monitoring device - Google Patents

Description

PATENT AND LAW FIRM Patent Attorney Dipl.-Ing. H. Schmitt

SCHMITT, MAUCHER & BÖRJES Sponsorship

Samaco GmbH Dreikönigstrasse 13

Rheinstrasse 49 D-79102 Freiburg i. Br.

77694 Kehl

Telephone (07 61) 70 67 73
Fax (07 61) 70 67 76

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Lift gate with light grid monitoring device

The invention relates to a lifting gate which can be moved in a passage area limited to the sides and the top to close and to open this passage area, whereby a light grid monitoring device is provided for controlling the passage area and for detecting objects or the like located in the gate lifting area, optionally fed in from one of the two access sides, whereby on one side of the gate there are height-offset light transmitters for emitting light beams running transversely to the lifting movement of the gate and on the other side of the gate there are light receivers for these light beams, whereby during one of the continuously repeating measuring cycles the light transmitters with associated light receivers are activated one after the other and whereby the light transmitters and the light receivers are connected to an evaluation device.

Lifting gates are a specific type of gate that is typically used on truck garages or loading ramps. The gate is guided in approximately vertical guide rails and can be moved up and down accordingly. A top-side bearing is usually provided so that the passage area can be opened by pulling up the gate. The gate is usually made of slats

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which are rolled up when opened.

To monitor these gates and in addition to other accident prevention measures and also for better operating comfort, such gates are equipped with light grids that prevent or reverse a closing movement if obstacles enter the gate area.

In order to achieve a protective function for traffic coming from both directions, it is necessary to install a light grid on both sides of the gate, each of which is arranged approximately one decimetre apart in front of the gate.

The disadvantage here is that a comparatively high expenditure

" in terms of the technical equipment and therefore also the costs. In addition, the installation of the light grids often encounters difficulties on site and the installation requires a lot of effort. Finally, functional problems can arise because the modulated light beams of the two light grids can interfere with each other.

The object of the present invention is to create a lifting gate with a light grid monitoring device that enables safe monitoring of the gate even when the gate area is accessed from both sides.

penetrating objects, while avoiding the disadvantages of the state of the art. In particular,

the effort can be reduced and yet a high level of functional reliability can be achieved.

To solve this problem, it is proposed that the monitoring device has a single light grid that is arranged within the door stroke area limited by the door's outer surfaces 0 and that the evaluation device has an algorithm generator that uses the door's stroke speed, a stored signal pattern of one or more previous measuring cycles, the time interval between two consecutive measuring cycles and the distance between adjacent light beams to distinguish between an interruption by the door itself or by an object, by then

an object located in the door stroke area is closed if, starting from the door closing edge, the number of continuously interrupted light beams between the stored signal pattern and the current signal pattern differs by more than the number of interrupted light beams that can be changed by a door stroke movement or if there is no continuous coverage of light beams from the door closing edge.

By using only one light grid, the effort is halved compared to the current state of the art. In addition, the system-related problems that occur with multiple light grids

™ Difficulties caused by mutual interference between the light beams are avoided. The arrangement of a single light grid within the gate level simplifies installation considerably, whereby it is advisable if support strips equipped with light transmitters and light receivers are recessed in opposing guide rails for the lifting gate. This allows the light grid components to be housed completely concealed, so that damage is practically impossible. When the gate is closed, the light transmitters and light receivers are also covered and inaccessible from the outside, so that these elements of the light grid are also housed in a vandal-proof manner.

^ The arrangement of the light grid in the plane of the gate creates the problem that the light beams can be interrupted by the gate itself. This problem is solved by an algorithm that, taking into account the gate lifting speed and the measurement cycle period, can distinguish whether the light beams are interrupted by the gate itself or by an object. For a given gate lifting speed, the gate itself can only cover or release a certain number of light beams within the period of a measurement cycle. An object entering the detection area causes the signal pattern to change much more quickly than could be done with the gate itself. Accordingly, this object is then also detected and a signal is sent to stop the

Closing movement of the gate or reversing the lifting movement. Even if an object enters flush with the edge of the gate, this is reliably detected, since although there is continuous, gapless coverage from the gate side, the change in the number of covered light beams occurs much faster due to the object than would be possible with the gate at a given lifting speed.

It is advantageous if the evaluation device is designed to evaluate the signal intensity supplied by the light receivers

This enables self-monitoring of the light grid ", whereby contamination of the light transmitters

and/or the light receiver can be detected. A threshold value can be specified, which leads to a signal if it is undershot. In addition to contamination, it can also detect misalignment or a setting that is too insensitive.

Additional embodiments of the invention are set out in the further subclaims. The invention and its essential details are explained in more detail below with reference to the drawings.

It shows:
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Fig. 1 a somewhat schematic representation of a lifting gate with a light grid monitoring device and

Fig. 2 is a flow chart explaining the function.

Fig. 1 shows a schematic of a lifting gate, designated as a whole by 1, whose gate 2 can itself be moved from top to bottom into the closed position. The gate 2 is guided laterally in opposing, U-shaped guide rails 3, which are only indicated in sections and by dashed lines here. Within these guide rails 3

To create a light grid 4, light transmitters 5 are arranged on one side of the gate and light receivers 6 on the other side of the gate. It is possible to arrange only light receivers on one side of the gate and only light transmitters on the other side, which simplifies the effort, particularly for control. However, it is also possible to arrange light transmitters and light receivers one above the other on one side of the gate, for example alternately, and to provide an identical arrangement of light transmitters and light receivers on the other side, offset by one light row in height.

The light transmitters 5 and the light receivers 6 are preferably installed in ™ support strips 7, which are recessed in the opposite guide rails 3. This promotes a compact structure and easier assembly.

The light grid 4 with its light transmitters 5 and the light receivers 6 is arranged in the plane of the gate 2, so that the gate can cover one or more of the light beams 8 depending on the lifting position. An object 9 located in the area of the light grid 4 also covers light beams 8, so that the measurement result that one or more light beams 8 of the light grid 4 are covered alone does not allow a reliable conclusion that an object is located in the lifting area of the gate 2. In order to be certain

^ In order to distinguish whether the obscuration of light rays 8 originates from the gate itself or an object 9, a monitoring device 10 connected to the light transmitters 5 and the light receivers 6 is provided, which has an algorithm generator which enables a reliable distinction to be made from the available measured variables and characteristic data.
The measurement data are supplied by the light receivers 6 and the 0 characteristic data are given by the specified lifting speed of the gate 2, the distances or grid of the light beams 8 from each other and the measuring cycle. The measuring cycle is formed by the sum of the scanning processes of all light transmitter/light receiver pairs. During each scanning process, a light beam is emitted by a 5 light transmitter 5 and received by an opposite

Light receivers are evaluated. Each light transmitter/light receiver pair belongs to a channel, which are operated in time multiplex, i.e. they are activated and evaluated one after the other. For example, a time grid of 664 microseconds from channel to channel can be provided. Once all channels have been run through, the signal pattern can be evaluated and, if necessary, a control output of the monitoring device can be activated. The sampling cycle of all channels repeats itself continuously and cyclically with a period of, for example, 2 8.5 milliseconds.

According to one possible embodiment, the spatial sequence of the evaluation of the channels can be such that it begins with the lowest channel, closest to the floor, and then the channels are evaluated in their geometric sequence, ending with the highest channel, closest to the gate.

To form the light grid, the light transmitters 5 and the light receivers 6 can be arranged at a uniform distance, for example of 60 millimeters, in the support strips 7, so that the grid dimension, i.e. the distance between adjacent light beams 8, is 60 millimeters.

0 As can be seen in Fig. 1, the gate 2 is in a partially lowered position, whereby the top four light beams 8 are interrupted. In order to be able to detect an object 9 introduced into the area of the light grid 4 in this position of the gate 2, the signal pattern resulting from the output signals of the light receivers 5 6 is stored before the object 9 is introduced and this signal pattern is compared with the signal pattern after the object 9 is introduced. If it turns out that, starting from the gate closing edge 11, the number of continuously interrupted light beams 8 between the stored signal pattern and the current signal pattern differs by more than the number of interrupted light beams that can be changed by a gate lifting movement, it is concluded that an object 9 is located in the gate lifting area. This means that when the gate 2 is stationary or when the gate 5 is moving, an object 9 entering the area of the light grid 4

be recorded.

This also applies if an object 9 enters flush with the door closing edge 11 and thus there is a gapless coverage of a number of upper light beams by the door itself and the adjoining object 9. The detection of an object 9 also occurs if there is no gapless coverage from the door closing edge 11.
In order to achieve a higher resolution for a given distance between the light beams 8, a cross-beam method can be provided. In this case, in two additional scanning cycles, instead of the horizontally assigned light receivers,

" the adjacent light receivers above and below are evaluated. These three scanning cycles together result in a switching cycle and a grid-like beam pattern with up to three times the spatial resolution, depending on the location.

Fig. 2 shows a flow chart to illustrate the function of the light grid monitoring device in different operating situations. The flow chart represents a measuring cycle or scanning cycle. In such a scanning cycle, as indicated in the top field 12, 5 light beams are emitted by the light transmitters, whereby this occurs one after the other, in the present case

^ case from bottom to top. The signal pattern resulting from the output signals of the oppositely assigned light receivers 6 is stored as the result of the scanning cycle together with the signal pattern of a previous measuring cycle or scanning cycle. This storage of at least two signal patterns is represented by field 13. In the direction of travel, this field 13 is followed by a branching diamond 15, where it is queried 0 whether all beam paths were free during the last scanning cycle. If this was the case, the output is switched on (field 19) so that the door can also be moved into the closed position because there is no obstacle. However, if the query according to branching diamond 15 results in the result that not all beam paths were free, the next query is made in the

Branching diamond 16, whether there were free beam paths over interrupted beam paths. If this is the case, it is concluded that there is an object in the light grid and the output is switched off.

In the event that there were no more free beam paths above the interrupted beam paths (by an object), the entire beam coverage can either come from the gate or from an object that is flush with the gate closing edge 11 and the gate itself. In this case, the query is whether, starting from the gate closing edge, the number of continuously interrupted light beams between the stored signal pattern

" of a previous scanning cycle and the current signal pattern by more than the number of interrupted light beams that can be changed by a gate stroke movement.

In the exemplary embodiment, characteristics are provided which, when the gate is moving, result in a maximum of two light beams 8 being covered per measuring cycle. If the number of light beams covered between two measuring cycles differs by less than 2, this is due to a movement of the gate 2. There is therefore no obstacle in the gate area and the output is switched on. However, if more than two light beams 8 have been covered between the stored measuring cycle and the current measuring cycle, then there is an obstacle in the gate area and the output is switched off.

The signal pattern of the current measuring or sampling cycle is then saved and a new measuring cycle begins, the signal pattern of which is then again compared with the saved signal pattern as described above.

/Expectations

Claims (9)

9 Claims 1. Lifting gate (1) which is movable in a passage area limited at the sides and at the top to close and to open this passage area, wherein a light grid monitoring device (10) is provided for monitoring the passage area and for detecting objects or the like located in the gate lifting area, optionally fed in from one of the two access sides, wherein height-offset light transmitters (5) are provided on one side of the gate for emitting light beams (8) running transversely to the lifting movement of the gate (2). and on the other side of the door, light receivers (6) are provided for these light beams (8), wherein during one of the continuously repeating measuring cycles, the light transmitters (5) with associated light receivers (6) are activated one after the other and wherein the light transmitters (5) and the light receivers (6) are connected to an evaluation device, characterized in that the monitoring device (10) has a single light grid (4) which is arranged within the door stroke area delimited by the outer surfaces of the door and that the evaluation device has an algorithm generator which uses the stroke speed of the door (2), a stored signal pattern of one or more previous measuring cycles, the time interval between two successive measuring cycles and the distance between adjacent light beams (8) to differentiate between an interruption by the door (2) itself or by an object (9), in that an object (9) is then concluded to be in the door stroke area if, starting from the door closing edge, 0 the number of gapless interrupted light beams (8) between the stored signal pattern and the current signal pattern differs by more than the number of interrupted light beams (8) that can be changed by a door lifting movement or if there is no complete coverage of the 5 light beams (8) from the door closing edge (11). 2. Lift gate (1) according to claim 1, characterized in that support strips (7) equipped with light transmitters (5) and light receivers (6) are arranged recessed in opposite guide rails (3) for the lift gate (1). 3. Lift gate (1) according to claim 1 or 2, characterized in that the light grid (4) is formed by pairs of approximately horizontally opposite light transmitters (5) and light receivers (6) arranged one above the other. 4. Lift gate (1) according to one of claims 1 to 3, characterized in that a scanning process is formed by the emission of a light beam from a light transmitter (5) and the detection of this light beam by a light receiver (6) which is in particular approximately horizontally opposite and that the sum of the scanning processes of all light transmitter/light receiver pairs forms a measuring cycle. 5. Lift gate (1) according to one of claims 1 to 4, characterized in that a cross-beam method is provided, that Each light transmitter (5) successively emits a light beam and the respective light beam is detected both by the approximately horizontally opposite light receiver (6) and by the light receivers (6) adjacent to it on both sides. 6. Lift gate (1) according to one of claims 1 to 5, characterized in that the light transmitters (5) and the light receivers (6) and the light grid (4) generated by them are arranged in a uniform height grid and that the distance between light transmitters (5) arranged one above the other or between light transmitters (5) and light receivers (6) arranged one above the other is a few centimeters, preferably about 60 mm. 5 7. Lift gate (1) according to one of claims 1 to 6, characterized characterized in that, in a gate (2) moving from top to bottom in the closing direction, the lowest light transmitter/light receiver pair is provided for emitting and receiving the start light beam within a measuring cycle.
5 8. Lift gate (1) according to one of claims 1 to 7, characterized in that the evaluation device is designed to evaluate the signal intensity supplied by the light receivers (6). 9. Lift gate (1) according to one of claims 1 to 8, characterized in that the period duration is in the range of milliseconds and is preferably less than 30 milliseconds with a lifting speed of the gate (2) of less than approximately 1 m/second. Patent Attorney .-rich Börjes- -en- and recissrf (&EEgr;&egr;-I