Communications – electrical: acoustic wave systems and devices – Echo systems – Presence or movement only detection
Reexamination Certificate
2000-05-05
2001-11-06
Mullen, Thomas (Department: 2632)
Communications, electrical: acoustic wave systems and devices
Echo systems
Presence or movement only detection
C271S263000, C340S511000, C340S674000
Reexamination Certificate
active
06314054
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Priority is claimed with respect to application No. 199 21 217.1 filed in Germany on May 7, 1999, and application No. 199 27 865.2-27 filed in Germany on Jun. 18, 1999, the disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for detecting objects formed by labels on a carrier material, and sheets, particularly sheets of paper.
An apparatus of this type is known from German Patent DE-PS 195 21 129. This apparatus includes a capacitive sensor having two adjacent capacitor elements, which are spaced from one another opposite a capacitor plate. The carrier material with the labels is guided in the air gap between the capacitor plate and the capacitor elements.
For detecting the labels on the carrier material, a timing element that generates a pulse sequence and a low-pass filter are disposed downstream of each capacitor element. The outputs of the low-pass filters are guided to the inputs of a differential amplifier. This circuit can detect labels on the carrier material, even if the labels and the carrier material comprise transparent materials.
A disadvantage, however, is that such apparatuses are extremely sensitive to temperature influences, and humidity in particular. They also encounter difficulties in detecting metallized materials. Furthermore, the two capacitor elements can only detect the signal flanks occurring in the detection of a label edge. A prerequisite of this is that the labels and the carrier material be moved past the capacitor elements at a predetermined speed. Static detection with a stationary carrier material is not possible. A further drawback is that a reliable label detection is only possible if the label edges travel along a straight line transverse to the transport direction of the carrier material, so that an at least approximately constant spacing between adjacent labels must be maintained over the label width.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an apparatus of the type mentioned at the outset to assure the reliable detection of labels on carrier materials, and sheets, for the broadest material spectrum.
The above and other objects are accomplished in accordance with a first embodiment of the invention by the provision of an apparatus for detecting objects each of which is composed of a label applied to a carrier, the apparatus comprising: a transmitter for emitting ultrasonic waves; a receiver for receiving ultrasonic waves spaced apart from the transmitter so that the objects can be passed between the transmitter and the receiver, the receiver producing an output signal representing an attenuation of ultrasonic waves when one of the objects is between the transmitter and receiver; means for comparing the receiver output signal with a threshold value in order to detect the label; and balancing means for automatically determining the threshold value as a function of a received signal registered during a balancing procedure when a segment including at least one of the carrier material and the label is located between the transmitter and the receiver.
Thus, according to the first embodiment of the invention, the apparatus is used to detect labels on a carrier material, and has a transmitter that emits ultrasonic waves and a receiver that receives ultrasonic waves. The carrier material is guided, with the labels, in the space between the transmitter and the receiver. The ultrasonic waves are attenuated in various ways, depending on whether they detect the carrier material alone, or a label applied to the carrier material, between the transmitter and the receiver. The corresponding differences in the received signal are detected at the receiver output through the comparison of the received signal to a threshold value. This threshold value is adapted to the occurring level of the received signals in the balancing procedure. In the balancing procedure, which is performed prior to the detection of the labels, the magnitude of the threshold value is determined automatically as a function of the received signal registered when the carrier material and/or a label is or are located between the transmitter and the receiver.
The ultrasonic waves can be used to detect labels on the carrier material, virtually independently of the nature of the label material. In particular, labels on carrier materials can even be recognized if the labels are transparent or have metallized surfaces. The apparatus of the invention can reliably detect even very thin labels. A notable advantage is that the apparatus of the invention is not susceptible to environmental influences, such as humidity or temperature fluctuations.
A further advantage is that the apparatus of the invention can recognize labels on the carrier material regardless of whether the carrier material is moved relative to the apparatus. Finally, the apparatus of the invention advantageously recognizes the entire surface of the labels, not merely their edges. Hence, labels having virtually arbitrary edge contours can be recognized.
According to another embodiment of the invention there is provided an apparatus for detecting sheets and to distinguish between single and multiple sheets, the apparatus comprising: a transmitter for emitting ultrasonic waves; a receiver for receiving ultrasonic waves spaced apart from the transmitter so that sheets can be passed between the transmitter and the receiver, the receiver producing an output signal representing an attenuation of ultrasonic waves when one or more sheets is between the transmitter and receiver; means for comparing the receiver output signal with a threshold value at an output of the receiver in order to distinguish between single and multiple sheets; and balancing means for automatically determining the threshold value as a function of a received signal registered during a balancing procedure when at least one of the sheets is located between the transmitter and the receiver.
According to the second embodiment of the invention, the apparatus is used to detect sheets, particularly paper sheets, and distinguishes between single sheets and multiple sheets formed from a plurality of superposed sheets.
The apparatus according to the invention thus serves to distinguish between different sheet layer thickness, and, in an especially advantageous embodiment of the invention, is used for checking sheets in printing presses.
A problem in the printing-press application is that sheets must be drawn individually from a stack at the entrance of the press so that they can be supplied individually and consecutively to the printing group of the press. If a double sheet or multiple sheets are fed into the press, as opposed to a single sheet, this can damage the press.
The apparatus of the invention employs a transmitter that emits ultrasonic waves to distinguish such multiple sheets from single sheets with high detection reliability, regardless of the nature of the sheet material.
A significant advantage of the apparatus of the invention is that a frequency modulation of the ultrasonic waves prevents the formation of standing waves of the ultrasonic waves between the transmitter and the receiver, thus avoiding interferences that would skew the measured values.
REFERENCES:
patent: 4066969 (1978-01-01), Pearce et al.
patent: 4368438 (1983-01-01), Stienstra
patent: 5348286 (1994-09-01), Buck
patent: 5458728 (1995-10-01), Galchefski
patent: 5823693 (1998-10-01), Henderson
patent: 5978004 (1999-11-01), Ehrhardt
patent: 3620042 (1987-01-01), None
patent: 195 21 129 (1996-10-01), None
Kinberg Robert
Leuze Electronic GmbH & Co.
Mullen Thomas
Venable
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