Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1995-02-21
2000-09-05
Mullen, Thomas
Communications: electrical
Condition responsive indicating system
Specific condition
340554, 342 28, 343767, 343771, 343772, 367 93, G08B 1318
Patent
active
06114956&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to electronic devices for sensing and/or protection of persons or objects in the immediate environment of automatic devices, such as automatic doors or potentially dangerous automatic devices, so as to avoid any motion or movement of the latter which may bring about dangerous contact with these persons or objects.
PRIOR ART
Electronic sensors are known which comprise a transmitter for transmitting waves or radiations, such as UHF waves or infrared radiations, and a receiver for detecting the reflected waves or the scattered radiation reflected by an obstacle situated in the spatial field covered, so as to produce a sensing signal depending on the characteristics of the reflected radiation. In this regard, Doppler effect UHF motion sensors, which conventionally installed on the upper part of an automatic door cover a spatial sensing field whose shape and dimensions are determined by the antenna used and which have the function of controlling the opening of the door following the sensing of the motion of a person or object in the sensing field, are known.
Generally, it is desired that the sensing lobe thus developed by the sensor should be relatively broad and that the sensor should sense any motion with equal sensitivity, irrespective of the direction of motion of the person or object with respect to the door.
In certain cases it is desirable, however, for the depth of the sensing lobe projected in front of the door to be further reduced. The case presents itself in particular when the sensor is to control the opening of a door situated in proximity to a sidewalk or in a shopping arcade. It is clearly appreciated, in this case, that the incessant traffic of pedestrians strolling along the sidewalk or in the arcade, without intending to pass through the door, should not cause the untimely opening of the latter.
The same is true when the sensor is to ensure the protection of persons or objects in the immediate approaches to a revolving door, to a pivoting door, or to a slatted or roller shutter door. In this case, the sensor is fixed on the door itself and accompanies it in its motion, whilst monitoring the dangerous environment, that is to say, the space situated in front of the moving leaf for a revolving door or a pivoting door, or the space surrounding the horizontal leading edge of a roller shutter door. In these cases of application, the depth of the sensing lobe should be reduced so as to avoid, during the motion of the door, and hence of the sensor, sensing persons or objects situated outside the danger zones.
Solutions known heretofore and based on the use of special horn antennas, enable Doppler effect UHF motion sensors to develop a relatively shallow sensing lobe. A limit exists, however, to this technology, which does not make it possible to achieve a depth of lobe substantially less than a meter.
What was described above applies also to UHF presence sensors, whose function, contrary to the sensors mentioned earlier, is to sense the presence of a person or object stationary in their sensing field, so as to prevent the door performing a dangerous motion. In these application cases, the zone to be protected should also be of very reduced depth and situated in proximity to the door so as to cover only the danger zone and avoid untimely disabling through the sensing of too far-off a presence.
Other types of sensors, such as active infrared sensors, make it possible, by virtue of an optic consisting for example of cylindrical Fresnel lenses, to sense the presence--and a fortiori the motion--of any being or object in a sensing field of very reduced depth constituting a sensing or protection curtain.
However, it is well known that optoelectronic presence sensors are particularly sensitive to the nature, color and reflective power of the background which they cover and of the target to be sensed. Depending on the fixed triggering threshold, the least unforeseen disturbance brings about unwanted sensing, and thus the untimely opening or di
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Belgian Electronic Research S.A.
Mullen Thomas
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