In the automation industry, tape is often applied automatically by a tape applicator machine to closed boxes traveling along a conveyor system. Since the tape is applied automatically and given that the tape is essential to retain the integrity of the goods within the shipper box, it is important for the manufacturer shipping the goods to ensure that the box did get tape applied, and was not missed.
To sense the presence of the tape on the box, the factory needs to decide if seeing the tape anywhere on the shipper box is sufficient to conclude it is taped, or whether they need to verify that the tape must be on the shipper box over its entire length.
The first situation is easy, using two sensors, one as an Interrogate Sensor, the other as the Inspect Sensor. The Interrogate Sensor, by sensing the leading-edge of the shipper box, simply verifies that the shipper box is in position for the Inspection Sensor to be viewing the tape somewhere along the length of the box, to verify that it sees tape at the instant the Interrogate Sensor first sees the leading edge of the shipper box. The Interrogate Sensor and the Inspection Sensor outputs are fed to the corresponding inputs of a Tri-Tronics’ Product Inspection Module so that if the tape is not present at this instant of time, the Tri-Tronics Product Inspection Module can either stop the conveyor, or merely reject the box without tape, while allowing the conveyor to proceed without interruption.
The second situation is more difficult to explain, but it requires two Interrogate sensors; e.g., a and b, which are mounted very close together in the horizontal plane, whose outputs are connected together in AND logic, so that they only have an unique output when both see the shipper box during its passage. The third sensor is an Inspection Sensor looking for the presence of the tape the entire duration of the combined output of sensors a and b. The combination of a AND b outputs, along with the appropriate output from the Inspection sensor, can provide a resulting unique output level for a box with no tape, allowing rejection of such defect.
The typical behavior of sealing tape, whether clear or brown versus the shipper box that it is applied to, is that the tape is usually significantly more reflective than the shipper box surface, so the difference in contrast is relatively easy to detect.
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