Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2000-09-01
2001-07-24
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C356S004010, C356S141400, C356S622000
Reexamination Certificate
active
06265725
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an optoelectronic device for detecting objects in a monitoring range with a distance sensor, the device including a transmitter for transmitting light rays; a deflection unit on which the transmitted light rays are reflected for periodically sweeping the transmitted rays over the monitoring range; a receiver for receiving light rays; and an evaluation unit for evaluating the signals received at the receiver.
A device of this type is disclosed in German Patent 39 32 844 C2. The device has a distance sensor that operates according to the triangulation principle and comprises a transmitter for transmitting light rays as well as a receiver which receives light rays and is connected to an evaluation unit. The transmitted light rays are deflected by a deflection unit with a deflection mirror, so that these rays periodically sweep over a monitoring range. The position of the objects is detected by determining the actual angular position of the deflection unit and the range values determined with the aid of the distance sensor.
The dimensions of the monitoring range are stored in the evaluation unit in the shape or outline contour of the monitoring range, in sequential pairs of range and angle values.
In order to detect an object, its position is detected by recording the associated range and angle values. These range and angle values are compared to the stored outline contour of the monitoring range. If it turns out that the object is located inside of the monitoring range, then a signal transmission is triggered.
A disadvantage of this method is that only one monitoring range is stored in the evaluation unit. In practical applications, however, objects frequently must be detected with the aid of an optoelectronic device in different monitoring ranges having different dimensions. For example, if an optoelectronic device is mounted on the front of an unmanned transport vehicle for monitoring the area in front of the vehicle, the dimensions of the monitoring range can depend on whether the vehicle moves in a corridor along a predetermined track or whether it moves freely inside a hall.
For applications of this type, the optoelectronic device is used in particular in the area of protection of persons, so that the optoelectronic device must meet technological safety standards. It is essential that the selection of suitable monitoring ranges also ensures a correspondingly high protection against errors.
German Patent 197 21 105 A1 relates to an optoelectronic sensor, comprising a light transmitter for transmitting a light beam into a monitoring range, as well as a receiver for receiving a light beam formed by the transmitted light that is reflected by an object in the monitoring range. In this case, the angle of the received light beam changes relative to the transmitted light beam, in dependence on the distance between the object and the sensor. The sensor also comprises a control and evaluation unit for processing the output signal from the light receiver. The light receiver is provided with a multi-element light sensor, comprising at least four individual sensor elements, which are arranged next to each other, such that the light beam is admitted to different sensor elements depending on the beam angle. The signal outputs for the sensor elements are connected to switches, wherein the sensor can be adjusted to different reference distances for an object by actuating the switch.
SUMMARY OF THE INVENTION
It is an object of the invention to create an error-free selection of various monitoring ranges for an optoelectronic device of the aforementioned type.
The above and other objects are accomplished according to the invention by the provisions of an optoelectronic device for detecting objects in a monitoring range with a distance sensor, comprising: a transmitter for transmitting light rays; a deflection unit on which the transmitted light rays are reflected for periodically sweeping the transmitted rays over the monitoring range; a receiver for receiving light rays; an evaluation unit for evaluating the signals received at the receiver, the evaluation unit including means for storing dimensions of different monitoring ranges and several inputs each of which is operatively associated with a respective one of the stored dimensions of the different monitoring ranges, the evaluation unit further including a test output for emitting a test signal having a predetermined signal value; several feed lines each of which is connected to a respective one of the several inputs; and several switches each of which is connected via a respective one of the feed lines to a respective one of the inputs of the evaluation unit, wherein upon activation of one of the switches a predetermined signal value is transmitted to the respective input for activating the input thereby activating the respective stored monitoring range so that objects in the activated monitoring range are detected; and wherein the test output of the evaluation unit is coupled to each of the feed lines, and for test purposes the test signal is transmitted via the test output to each of the feed lines, whereby an error-free operation is signified if the predetermined signal value of the test signal is present at the respective inputs of the evaluation unit.
Thus, in accordance with the invention, the dimensions of different monitoring ranges are stored in the evaluation unit of the optoelectronic device. For the selection of one or several of these monitoring ranges, several switches are connected via separate feed lines to an input of the evaluation unit, wherein one stored monitoring range is assigned to each input. As a result of activating a switch, a predetermined signal value is present at the associated input, which corresponds to an activation of this input. By activating this input, the monitoring range assigned to this input is also activated and the objects inside the monitoring range are detected. For test purposes, respectively one signal value is emitted via an output of the evaluation unit to the feed lines. With an error-free operation, this signal value is present at the respective inputs of the evaluation unit.
One essential advantage of the device according to the invention is that an error-free selection of a specific monitoring range can occur by way of a single input of the evaluation unit. The error protection is ensured in that the signal values, issued at the output of the evaluation unit, are fed via the evaluation unit inputs back into this unit and are checked there. This results in a considerable reduction in the switching expenditure as compared to traditional error-free switching arrangements, for which the inputs normally must have a redundant design.
Another advantage of the optoelectronic device according to the invention is that a nearly optional use of switches is possible for selecting the individual monitoring ranges. In particular, the switches can be designed as relays and control outputs, for example SPS controls. Controls of this type permit a central selection of the monitoring ranges. The switches can also be designed as binary sensors, for example formed by light barriers or proximity switches. These sensors can be located on machines, for example, and can serve to determine the actual position of a processing center that can be moved back and forth on the machine. The optoelectronic device is installed on the machine so that it is possible to monitor the area in front of the machine. Depending on the position of the processing center on the machine, one of the switches is activated, whereupon a suitable monitoring range is selected in the optoelectronic device.
Advantageously, the switch between monitoring ranges occurs in that a second switch is activated while a first switch is still activated, thereby allowing objects in two different monitoring ranges to be detected during a transitional period. The first switch is not reset to the starting position until this transitional period is completed, so that only the monitoring range selected wit
Brunner Rolf
Moll George
Allen Stephone B.
Kinberg Robert
Leuze Electronic GmbH & Co.
Venable
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