US 5,467,194 AGranted

Method and device for photoelectric identification of a material web

AssigneeValmet Paper Machinery Inc.

InventorsKari Pellinen, Jukka Koiranen, Kari Erkkila, Juhani Ahola, Harri Vahatalo

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Abstract

A method and apparatus for identifying a moving web in a paper making machine are disclosed. The method includes of the steps of illuminating the web with the light from a transmitter, reflecting the transmitted light off the web, receiving the reflected light with a light transducer to produce an electrical signal corresponding to the intensity of the received light, and identifying the moving web based on the received signal. The intensity of the transmitted light is adjusted so that the received light signal from the transducer is normalized with respect to an optimum value. The apparatus includes a light transmitter, a light receiver, and a control and identification circuit which identifies the web based on a signal from the light receiver, and which adjusts the intensity of the light transmitter to optimize the reception of the signal from the light receiver in order to minimize the effects of environmental interference.

Claims16

Dependent claims

A method of identifying a state of presence of a web moving on and supported by a wire or felt in a paper making machine, comprising the steps of:

illuminating a portion of the web with a pulse-modulated transmitted beam of light from a light transmitter to produce a reflected beam of light, said modulated beam of light modulating in intensity from an on state to an off state, said reflected beam of light having a first pattern when said web supported by the wire or felt is present and a second pattern when said web is not present and the wire or felt is present, said first and second patterns being different from one another;
detecting said reflected beam of light with a light receiver to produce an electric signal corresponding to the intensity of said reflected beam of light received by said light receiver;
obtaining a background light level from said electric signal corresponding to when said modulated transmitted beam of light is in an off state and said web supported by the wire or felt is present;
obtaining an illuminated light level from said electric signal corresponding to when said modulated transmitted beam of light is in an on state and said web supported by the wire or felt is present and is illuminated by said modulated transmitted beam of light;
processing said electric signals corresponding to said background light level and said illuminated light level by subtracting said electric signal corresponding to said background light level from said electric signal corresponding to said illuminated light level to obtain a calibration signal;
adjusting the intensity of said transmitted beam of light when said web supported by the wire or felt is present so that said calibration signal is normalized;
and
analyzing said electric signal produced by said light receiver and determining whether the web supported by the wire or felt is present or whether the web is not present and the wire or felt is present.

5 more elements

A photoelectric device for identifying a state of presence of a web moving on and supported by a wire or felt in a paper making machine, comprising:

an adjustable light intensity transmitter for illuminating a portion of the web with a pulse-modulated transmitted beam of light to produce a reflected beam of light, said modulated beam of light modulating in intensity from an on state to an off state, said reflected beam of light having a first pattern when said web supported by the wire or felt is present and a second pattern when said web is not present and the wire or felt is present, said first and second patterns being different from one another;
a light receiver for detecting said reflected beam of light to produce an electric signal corresponding to the intensity of said reflected beam of light received by said light receiver;
control means for adjusting the intensity of light transmitted by said transmitter comprising:
means for obtaining a background light level from said electric signal generated by said light receiver corresponding to when said transmitter is in an off state and said web supported by the wire or felt is present;
means for obtaining an illuminated light level from said electric signal generated by said light receiver corresponding to when said transmitter is in an on state and said web supported by the wire or felt is present and is illuminated by said modulated transmitted beam of light;
calibration means for processing said electric signals generated by said light receiver corresponding to said background light level and said illuminated light level by subtracting said electric signal corresponding to said background light level from said electric signal corresponding to said illuminated light level to obtain a calibration signal;
adjusting means for adjusting the intensity of light transmitted by said transmitter so that said calibration signal is normalized;
and
signal processing means for analyzing said electric signal generated by said light receiver and determining whether the web supported by the wire or felt is present or whether the web is not present and the wire or felt is present.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/135,315Filed 12 Oct 1993 · continuation
Priority: FI 9105716 Feb 1991
Granted: 14 Nov 1995
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

B65H 23/0216
Sensing transverse register of web: with an element utilising photoelectric effect
B65H 26/025
Responsive to presence of irregularities in running webs: responsive to web breakage
B65H 2557/10
Means for control not provided for in groups B65H2551/00 - B65H2555/00: for signal transmission
B65H
Handling thin or filamentary material