Sheet feeding or delivering – Feeding – With means to interrupt feeding
Reexamination Certificate
2002-06-17
2004-05-25
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
With means to interrupt feeding
C271S263000, C271S265040, C073S001810
Reexamination Certificate
active
06739591
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a double sheet feeding detector, a method for detecting double feeding of sheets and a computer program for controlling such a detector, and in particular, concerns a double sheet feeding detector which can more positively detect double feeding of sheets and such a method and a program.
2. Description of the Related Art
When a sheet of paper is fed in a printer, double feeding occurs in the case where two or more sheets are simultaneously fed with at least one portion of one sheet being partially superimposed on another. When such double feeding occurs, it is not possible to carry out a proper printing process. Therefore, in the case where two or more sheets are simultaneously fed, it is necessary to detect this as a double feeding and to temporarily suspend the feeding process.
Conventionally, methods in which ultrasonic waves are used to detect double feeding have been disclosed in Japanese Patent No. 1725105 and JP-A-52-40379.
In Japanese Patent No. 1725105, ultrasonic waves that have been transmitted through sheets are received, and the receiving level is detected. Since there is a difference in the level of the received ultrasonic waves between one sheet of paper and two or more sheets that have been fed, double feeding is detected based upon the difference.
Moreover, as disclosed by JP-A-52-40379, the phase of an ultrasonic wave that has been transmitted through sheets is detected. Since there is a difference in the phase thereof between one sheet of paper and two or more sheets that have been fed, double feeding is detected based upon the phase.
Here, the applicant of the present application has proposed a detecting method in Japanese Patent Application No. 11-13257, in which double feeding is detected by comparing the phases of the receiving signal of an ultrasonic wave and a reference signal, and further comparing a signal corresponding to the phase difference with a reference level.
However, in Japanese Patent No. 1725105, double feeding is detected based upon the receiving level of ultrasonic waves; therefore, in the case when a sheet of paper is thin, there is not much difference in the levels of the received ultrasonic wave signals between one sheet of paper and two or more sheets that have been fed, and it is not possible to detect double feeding correctly.
Moreover, in JP-A-52-40379, in which double feeding is detected based upon the phase of a received ultrasonic signal, when a number of sheets of paper are fed at once, the level of the receiving signal is extremely attenuated, making it impossible to accurately detect the phase of a received signal, and resulting in a failure to accurately detect double feeding.
Furthermore, in the method disclosed in Japanese Patent Application No. 11-13257, since it is necessary to generate a reference signal, a complex process is required in cases when determining conditions, etc. are altered.
SUMMARY OF THE INVENTION
The present invention has been devised to solve the above-mentioned problems and to positively detect double feeding independent of the thickness of sheets, and also to easily set determination conditions.
A first double sheet feeding detector of the present invention is provided with: ultrasonic wave generation means for generating ultrasonic waves to be applied to a feeding path for sheets; ultrasonic wave receiving means for receiving ultrasonic waves generated by said ultrasonic wave generation means; phase-difference detection means which detects a phase difference between a phase of the ultrasonic waves received by the ultrasonic wave receiving means and a predetermined reference phase; comparison means which compares the phase difference detected by the phase-difference detection means with a predetermined first reference value that has been preliminarily set; counting means which counts the number of times of cases in which the phase difference, as detected by the phase-difference detection means, exceeds the first reference value based upon the results of comparison of the comparison means; and double feeding detection means which compares the calculated value counted by the counting means with a second reference value that has been preliminarily set, and detects a double feeding of the sheet based upon the results of this comparison.
In this double sheet feeding detector, the number of times of cases in which the phase difference of the received ultrasonic waves from a predetermined reference phase exceeds the first reference value is counted, and a double feeding of sheets is detected based upon the results of comparison between the counted value and the second reference value. Therefore, it is possible to positively detect double feeding independent of the thickness of sheets. Here, the reference phase refers to a phase of a preliminarily set receiving waves that corresponds to the receiving waves obtained when one sheet is being fed.
In particular, since it is not necessary to generate a reference signal to be compared with the received ultrasonic waves, it is not necessary to set and adjust a reference signal so as to detect a double feeding, thereby making it possible to improve the operability.
For example, sheets are made of paper. The ultrasonic wave generating means is provided as an ultrasonic wave transmitter, and the ultrasonic wave receiving means is provided as an ultrasonic wave receiver.
The preliminarily set reference phase of a received ultrasonic wave is digitized as a phase difference with the peak timing of the transmission waves being set as a base point (phase=0). Moreover, the phase of the receiving waves is also measured with the peak timing of the transmission waves being set as a base point (phase=0).
The phase difference detection means may be provided as a CPU.
The counting means may be provided as a determining counter.
The double feeding detection means may be provided as a CPU.
With respect to the first reference value, the comparison means may have at least either a third reference value serving as a reference with respect to the deviation of the phase difference in the positive direction or a fourth reference value having an absolute value different from the third reference value and serving as a reference with respect to the deviation of the phase difference in the negative direction.
The third reference value is formed by, for example, &Dgr;Z
2
shown in
FIG. 9
, and the fourth reference value is formed by &Dgr;Z
1
.
In this manner, by setting the reference values in the positive direction and negative direction as different values, it is impossible to more positively detect double feeding of sheets in response to inherent conditions of respective devices for feeding sheets.
The double feeding detection means may alter the second reference value in accordance with the feeding speed or the size (length) of the sheets.
The second reference value may be set as a small value when the feeding speed of sheets is great, and also set as a great value when the size of sheets is great (the length thereof is long).
In this manner, by altering the second reference value dynamically in accordance with the feeding speed and the size of the sheets, it becomes possible to more positively detect double feeding.
The count number per unit time by the above-mentioned counting means may be altered in accordance with the feeding speed or the size of the sheets.
Thus, it becomes possible to positively detect double feeding.
A feeding means for feeding sheets onto a feeding path may be further placed so that the phase-difference detection means is allowed to detect a phase difference from the reference phase of ultrasonic waves received by the ultrasonic wave receiving means, in synchronism with a motor driving signal.
The feeding means for feeding sheets may be formed by, for example, a motor driver for driving a motor. The signal synchronizing to the feeding amount is formed by, for example, a motor clock synchronous signal.
Thus, even in the case when the feeding speed of sheets is ch
Chujo Hideki
Inoue Tomohiro
Taniguchi Keitaro
Bower Kenneth W
Omron Corporation
Walsh Donald P.
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