Measuring and testing – Sheet – woven fabric or fiber
Reexamination Certificate
1998-12-28
2001-09-18
Kwok, Helen (Department: 2856)
Measuring and testing
Sheet, woven fabric or fiber
C073S599000
Reexamination Certificate
active
06289729
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
Ultrasonic sensors having a transmitter disposed on one side of a web and a receiver disposed on the other side of the web for locating the position of an edge of the web therebetween, are known in the art. Such ultrasonic sensors are mounted perpendicular to the web direction of travel and suffer from problems due to the reflection of sound between the transmitter, the web, and the receiver. Noise is thereby introduced into the signal produced by the receiver, and reduces the accuracy of the prior art ultrasonic sensors.
Previously, people in the art attempted to solve this problem by changing the angle of the ultrasonic sensor with respect to the web (away from the perpendicular orientation discussed above), as well as designing sensor housing to maintain non-parallelism between transmit and receive sides, so that the sound reflections would be reflected away from the receiver. Although the prior art method reduced the problem of sound reflection somewhat, it is less desirable to have the prior art ultrasonic sensor mounted angularly with respect to the direction of web travel. In addition, this angular mounting limits the effective sensing gap and allows less web plane change than that of perpendicular mounting.
Thus, there is a need for an ultrasonic sensor which does not suffer from the aforementioned problems caused by the reflection of the sound waves as described hereinabove. It is to such an improved ultrasonic sensor that the present invention is directed.
SUMMARY OF THE INVENTION
The present invention relates to a sensor system for determining the position of at least one edge of a web of material. Broadly, the sensor system comprises a transmitter, a receiver, and a sensor drive circuit.
The transmitter is capable of selectively transmitting ultrasonic signals. The receiver is positioned to receive at least a portion of the ultrasonic signals transmitted by the transmitter. In response thereto, the receiver generates receiver output signals indicative of the position of the web.
The sensor drive circuit periodically transmits to the transmitter a transmitter drive signal to cause the transmitter to transmit periodic ultrasonic signals. In one aspect of the present invention, each of the transmitter drive signals may be representative of substantially one cycle of a sinusoidal waveform.
The sensor drive circuit receives receiver output signals generated by the receiver responsive to the reception by the receiver of the ultrasonic signals generated by the transmitter. Each receiver output signal indicates the position of at least a portion of the web. The receiver output signals are then utilized to generate a sensor output signal indicative of the position of at least a portion of the web.
In one aspect of the present invention, the sensor drive circuit outputs receiver cutoff signals to selectively toggle the receiver in between a first mode wherein the receiver is permitted to form the receiver output signal responsive to the receiver sensing ultrasonic signals, and a second mode wherein the receiver is restricted from providing the receiver output signal.
The transmission of the periodic signals, and the selective toggling of the receiver cooperate to substantially eliminate the problems associated with the reflection of the sound waves in between the receiver, the transmitter or the web.
In one aspect, the present invention may include a temperature sensor for sensing the environmental temperature surrounding at least a portion of the sensor system and a microcontroller having access to a plurality of temperature compensation values. The microcontroller utilizes: (1) a temperature signal generated by the temperature sensor; (2) the receiver output signal; and (3) at least one of the temperature compensation values to generate a sensor output signal. In the sensor output signal, changes in the environmental temperature no longer have a substantial effect on the nature of the sensor output signal thereby improving the accuracy of the sensor system.
Other advantages and features will become apparent to those skilled in the art when the following description is read in conjunction with the attached drawings and the appended claims.
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Haque Md M.
Hueppelsheuser Dale
Newton John P.
Storie Greg A.
Winter Darcy
Dunlap Codding & Rogers P.C.
Fife Corporation
Kwok Helen
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