FR2639430A1 - METHOD AND DEVICE FOR DETECTING AND COUNTING AN INSTANTANEOUS PROFILE VARIATION AND THEIR APPLICATIONS - Google Patents

Abstract

The invention consists in reproducing, in particular using a light emitter 23, in the plane of an optical detector 24 the profile of an object or of a set of objects in contact or overlapping on a strip. 21, for example newspapers 20, in the form of a function Y = f (X), then to explore the profile by two receivers 27, 28 delimited by two slots 30, 31, ensuring that the intersections of the Y function and the lines representing the two receivers are reduced to approximately two points and that the distance between the two lines is as small as possible, and finally to permanently determine the derivative Y '(X) and to actuate an associated electronic circuit to the detector 24 generating an output signal proportional to the value of the derivative Y '(X). In the case of detection and counting, the output signal is compared with a predetermined value, representative of an instantaneous variation 22 of the profile and a pulse is emitted when the output signal becomes greater than the predetermined value. The invention also applies to the detection of breaks in threads.

Description

METHOD AND DEVICE FOR DETECTING AND COUNTING ANY VARIATION

  SNAPSHOT OF PROFILE, AND THEIR APPLICATIONS

  The present invention relates to a method and a device for detecting and counting any instantaneous variation of the profile of an object in continuous scrolling or of a set of overlapping objects on a conveyor belt, said profile being represented by a function Y = f (X). An instantaneous variation is called any variation of the profile characterized by a very large variation of the slope between two points of the function Y = f (X) whose distance tends towards O. The known methods for detecting and counting an instantaneous variation concern the detection and counting of dislocations caused by the overlap of two consecutive flat objects on the conveyor belt. They are, therefore, related and limited to flat object counting applications.

  continuous scrolling, overlapping on a conveyor belt.

  In the field of counting flat objects in continuous scrolling, overlapping on a conveyor belt, several methods and devices based on different principles of operation are known. For example, there are known mechanical or electromechanical counters still requiring physical contact with scrolling items and meters

  optoelectronic remote operating without physical contact.

  US Patents 3,969,993 - US 4,091,269 and US 4,139,765 describe several methods and devices for counting flat objects in continuous scrolling by physical contact. The reliability and accuracy of these depend, among other things, on the thickness of the objects and consequently on the importance of the dislocation, the distance separating two dislocations, the speed of the scrolling and the amplitude of the vibration of the conveyor belt. Experience shows that these methods and devices, even under optimum operating conditions, are unsatisfactory when the thickness of the objects is low and the speed of scrolling is very large. In addition these devices

  are subject to inherent wear in mechanical systems.

  Optoelectronic detection and counting without physical contact has been the subject of several patents. For exemple

  JP N 770, GB 841094 and US 4,450,352 may be cited.

  The methods and devices described in these patents have in common the fact of exploiting the light reflected by the surface of the objects in continuous scrolling to detect the passage of a dislocation and cause counting thereof. Despite the great effort to improve the reliability of processes and devices by introducing microprocessors to ensure safer processing of reflected light, the results are not entirely satisfactory. The main parameters disturbing these processes and devices are the surface condition of the object (matt or glossy), its color reflecting more or less the radiation and the vibrations of the conveyor belt, whose amplitude can

  sometimes be greater than that of the thickness of the object.

  All of these parameters can affect the results of the

  detection and according to the principle retained be source of errors.

  o All the processes and devices mentioned above provide an output signal directly proportional to the variations of the function Y = f (X). Since the value of Y corresponds to the thickness of the object or set of objects, the output signal is therefore directly proportional to the thickness of the objects in continuous scrolling. a change in the production range, in order to take into account the difference between the parameters of the new production range and that of the

previous production range.

  It is the object of the invention to provide a method and a device for detecting and counting instantaneous variations and only these by exploring the profile of an object in continuous scrolling or a set of overlapping objects on a conveyor belt. The method and the device, which provide an output signal directly proportional to the value of the derivative Y 'and not that of the function Y, overcomes the disadvantages noted, in that its operation is independent of the thickness of the scrolling objects, their surface state, their speed of movement, the amplitude of the possible vibrations to which they are subjected during their scrolling and the distance between them

  two consecutive instantaneous variations.

  It is therefore the object of the invention to provide a method and a device making it possible to detect o instantaneous verifications and only these with very high reliability thus ensuring a very low or even zero error rate. The method of the invention consists in: a) reproducing said profile in the plane of an optical detector in the form of a function Y = f (X), the axis of the abscisses / 5 corresponding to the direction of the scrolling and the y-axis corresponding to the direction in which the object or set of objects presents or may have instantaneous variations of the profile, b) to explore the profile by two receivers delimited by two slits so that the intersections of the function Y = f (X) defined by the profile and the lines representing the two receivers are reduced to approximately two points, and the distance between the two points is as small as possible, c) to permanently determine the derivative Y '(X) and actuating an electronic circuit associated with the optical detector generating an output signal proportional to the value of the derivative Y' (X), d) operating the output signal, e) and giving an instruction based on of the exploitation of

output signal.

  According to a first version of the method of the invention, applied to detection and counting, the exploitation of the output signal consists in comparing it to a predetermined value representative of an instantaneous variation of the profile and the instruction consists of a part.to emit a pulse when the output signal becomes greater than the predetermined value and

  on the other hand to exploit the pulse emitted.

  According to a second version of the method of the invention, the object is a textile yarn having fibers, hairs or pilous on the surface and the method exploits the stochastic distribution of said pilous; in this case, the instruction consists in transmitting a pulse when the output signal is uniform,

  indicating the breaking of the thread or stopping the scrolling.

  The invention also relates to a device specially designed for the implementation of the aforementioned method, that is to say that it allows the realization of the mathematical conditions to obtain an output signal that is directly proportional to the value of the derivative Y '(X) and not that of the function Y = f (X) which is defined by the profile of the object or set of objects in contact, or overlapping on a conveyor belt, in t5 scrolling continued. According to the invention the device comprises: a) means for reproducing in the plane of an optical detector, the profile of the object or of the set of contact objects or overlapping on a conveyor belt in continuous scrolling , b) two receivers delimited by two slots so that the intersections of the Y = f (X) function defined by the profile and the lines representing the two receivers are reduced to approximately two points and the distance between the two points is the smallest possible, c) and an electronic circuit associated with the receivers comprising two converters connected to a differential amplifier and providing a signal directly proportional to the derivative Y '(X)

  the function Y = f (X) defined by the profile.

  According to a first version of the device of the invention, applied to detection and counting, the electronic circuit also comprises a comparator, able to compare the output signal with a predetermined value, a pulse generator, able to generate a pulse when the output signal becomes greater than the predetermined value, and an output member

exploiting the transmitted pulse.

  According to a second version of the device of the invention, applied to the detection of yarn breaks on a textile machine, the electronic circuit also comprises a high-pass filter amplifier, a releasable monostable, changing state and generating a pulse when the amplified and filtered signal remains uniformly constant and means controlled by said pulse

  and triggering an alarm or stopping the machine.

  The method and apparatus of the invention have many advantages over existing methods and devices. The detection and counting of all instantaneous variations are obtained with a very high reliability and a very low or even zero error rate. The device is not subjected to any mechanical wear; after installation, it does not require any adjustment. The detection and the counting are independent of the thickness of the scrolling object, the spacing of two / 5 successive objects if it is a set of overlapping objects, of the surface state , the coloring, the speed of scrolling, and the amplitude of the possible vibrations to which the object or set of objects is subjected during its scrolling. The applications of the method and of the device of the invention relate to the detection and counting of objects in contact and in continuous scrolling, in particular of cigarettes, or objects

  riding on a conveyor belt, including newspapers.

  They also relate to the detection of knots on textile yarn, 1 5 as well as the detection of breakages of yarn or stopping the running of thread on textile machine. Other characteristics and advantages of the invention will appear more clearly on reading the

  description that will be made, as non-limiting examples,

  two embodiments of the object of the invention: a first embodiment of the detection device is applied to the counting of newspapers and a second is applied to the detection of the knots of textile threads. The description is illustrated by the appended drawings in which: FIG. 1 shows the curve of the functions Y = f (X) defined by the profiles of continuously moving objects presenting instantaneous variations, respectively an object (FIG. set of objects in contact (Fig. lb) and a set of objects

  overlapping on a conveyor belt (Fig. Ic).

  Fig. 2 shows the curves corresponding to the function Y = f (X) (Fig. 2a) and its derivative Y '(Y) (Fig. 2b), said function Y being defined by a profile having variations

  continuous and regular and an instantaneous variation.

  FIG. 3 is a schematic perspective view of a portion of the device placed at the exit of a folding installation of

  packaging or newspaper products.

  Figure 4 shows the detector in perspective and reproduction

  instant of a part of a profile.

  Figure 5 shows the detection plane with both receivers

and the scrolling plan.

  Figure 6 shows the intersection of the curve defined by the

profile and the two receivers.

  Figure 7 shows the detector plane, the two receivers and

the two slots.

  Figure 8 shows the behavior of the derivative (fig.8b) when the function representing the profile moves in the direction of Y (fig.8a). Figure 9 shows the projection of the profile of overlapping products on a conveyor belt stopped in front of

  receivers at the instant ti (FIG 3a) and at the moment ta. (Figure 9b).

  Fig. 10 shows respectively the function (Fig. 10a) defined by the products overlapping on the conveyor belt and its

derivative (Fig. lob).

  Figure 11 shows a diagram of different components of the device. FIG. 1 shows three examples of what in the present text is understood to mean instantaneous variation of a profile. The profile of an object, that is to say the projection in the plane of this marker of the outer surface of the object, has been taken as a function Y = f (X) in an orthonormal coordinate system. In FIG. 1a, the two curves I and 2 correspond to the upper and lower profiles of a filiform object 3 having an instantaneous variation 4, for example a node. In FIG. 1b, the two curves 5 and 7 correspond to the upper and lower profiles of a set of objects 7 in contact, for example cigarettes; the instantaneous variations 8 of profile correspond to the passage from one object to another. In Fig. Ic, it is a set of flat objects 9, for example newspapers or wrapping products folded and overlapping on a conveyor belt; the curve II corresponding to the lower part / o of the conveyor belt 10 is rectilinear; the curve 12 corresponding to the upper part of the objects 9 has

instantaneous variations 13.

  The instantaneous variation of profile is a sudden variation, compared to a continuous and regular variation. FIG. 2a shows a curve 14 Y f (X) representing the profile of an object, presenting on the one hand continuous and regular variations, approximately sinusoidal in shape with two maxima 15 and 16, and on the other hand, an instantaneous variation 17, having the shape of a small peak. All the known methods for detecting and counting thicknesses, that is, quantities directly proportional to the thickness, are not able to detect the instantaneous variation 17, without also detecting the maxima 15 and 16; indeed they detect and count the values of the function Y exceeding a certain threshold 2 y proportional to the thickness of the object; however, in the case illustrated by FIG. 2a, the thicknesses corresponding to the maxima 15 and 16 are larger than the extra thickness due to the presence of

the instantaneous variation 17.

  The method of the invention is based not on the function 3o Y-f (X) but on the derivative Y '(X) of this function. In FIG. 2b, opposite curve 14, curve 18 corresponding to the derivative Y '(X) of function Y is represented. The continuous and regular variations of curve 14 correspond to small and regular variations of the curve. 18, with the cancellation of the derivative Y 'for the maxima 15 and 16. At the internal variation 17 of the curve 14 corresponds a short and very important variation 19 of the curve 18. Thus according to the method of the invention, the output signal, being proportional to the derivative Y ', will have a low value when it comes to continuous and regular variations of the profile and a very low value.

  important when it comes to instant variation.

  The method of the invention will ignore continuous and regular variations such as those represented in the intervals (O, XI) and (X3, X4) (FIG. 2a), which provide only a very small value of the derivative ( Fig. 2b) and will instead detect and count the instantaneous variation represented in the interval (X2, X3) (Fig. 2a) which provides a very high value

of the derivative (Figure 2b).

  In the first example described now, the device of the invention is mounted at the output of a folding installation of flat objects, for example newspapers. After being printed, the folded newspapers 20 are arranged on a conveyor belt 2]. Due to the speed of travel of the conveyor belt 21 and the rate of removal, the newspaper 20 deposited at a given instant 2 is superimposed in part with the newspaper deposited at the instant

  previous. It is this overlap that creates the dislocations 22.

  The value of this dislocation 22 is generally equal to the thickness of a newspaper. It is understood that such a dislocation 22 corresponds to an instantaneous variation of the upper profile of the

Z 5 newspapers 20.

  The object or set of objects is scrolled, here the newspapers 20 resting on the conveyor belt 21, between a transmitter 23 and a detector 24 placed transversely with respect to the conveyor belt 21. The emitter 23 is constituted a Jo source electromagnetic radiation, preferably bright in the range of visible or invisible, where the radiation can be modulated or not. The detector 24 consists of two receivers 27 and 28 and a diaphragm. The two receivers 27,28 are of rectangular shape, with a very small width by length, they are identical in their geometry and in their physical characteristics, they are parallel and arranged perpendicularly to the plane 29 of scrolling (FIG. 5). they are placed one after the other in the direction of scrolling. The diaphragm consists of two slots 30, 31 arranged respectively in front of the receivers 27, 28. The spacing between the two slots, 31 is the lowest possible. The width of each slot

, 31 is the smallest possible.

  The radiation flux, cut off by the object or objects, reproduces on the detector the profile of the object or objects, which is characterized by an irradiated zone 25 and a non-irradiated zone 26, eclipsed by the object or objects. objects. By scrolling the object or objects between the transmitter 23 and the detector 24, the profile is scanned by the detector 24 as the radiation flux is cut off. The transmitter 23 and the detector 24 being placed just at the transport plane of the band 21, the length of the receivers 27,28 must be sufficient for the radiation flux emitted by the transmitter 23 to never be completely stopped by the section of newspapers 20 based on the band 21. The profile of scrolling newspapers is thus explored

  continuously by the receptors 27,28.

  It is also possible to reproduce an actual image of the profile in the plane of the detector by arranging the emitter 23 and the detector 24 on the same side with respect to the moving object or objects, but by implementing a complementary optical device . FIG. 6 shows the reproduction of a curve 32 in the plane of the detector 24, equipped with two receivers 27, 28 without slots (FIG. 6a) and with two slots 30, 31 (FIG. 6b). Because the slots 30, 31 have a very small width, the intersection of the curve 32 representing the profile and the slots 30, 31 is reduced to two points 33, 34 (FIG. 6b), whereas it corresponded to two lines in the case where the receivers 27,28 were not provided with the two slots 30,31 (Figure 6a). Moreover, because of the small spacing between the points 33 and 34 of intersection of the curve 32 with the slots 30, 31, the conditions are met so that the output signal emitted by the detector 24 is proportional to the derivative Y '( X) of the function Y = f (X). Indeed the spacing between the slots 30, 31dX is constant and tends to zero, and the signal had proportional to dY,

  difference between the two values of Y in points 33 and 34.

  Figure 9a schematically shows the tape 21 supporting newspapers 20 stopped in front of the two slots 30,31 at a given time ti. FIG. 9b represents the same band 21 stopped in front of the two slots 30, 31 at a given instant tu .. Let / O Yf (X) be the function representing the profile of the logs (FIG 10A), the derivative of Y is Y ' = dY / dX when dX tends to O

  The ideal function of Y 'is represented in FIG.

  Approximately Y 'can be determined: ## EQU1 ## at time ti by Y'ti = (Y2ti-Ylti) / (X2-X1) and at time t by Y't2 = (Y2ti-Ylt2) / (X2- Xl) The signal transmitted by each receiver 30,31 is proportional

  to the amount of radiation it receives over the entire surface.

  When an object cuts the flow, the emitted signal will decrease in 2-o depending on the section of the product cutting the flow. Since the width of the slots 30, 31 is very small, it can be considered that the transmitted signal is proportional to the difference between the length of the receiver L and the thickness of the product 1 cutting the flux, that is to say Y = C (Lt). In the case of two receivers according to FIG. 9, of identical dimensions and having the same

  physical characteristics we have two signals Yl.i and Y2w1.

  YIli = C (L-11) Y2t = C (L-12> in which 11 is the thickness of the strip 21 and the newspapers 20 3 o facing the first receiver 30 and 12 the thickness of the strip 21 and journals 20 facing the second receiver 31. The value dY at time tI is: dY = Y2wi - YlI = = C (11-12) dX is here a constant defined by the distance separating the two slots: l} dX = X2-X1 By dividing dY / dX we obtain an approximate value of the derivative Y't this value differs very little from the theoretical value

  (Fig. 10b) when the difference X2-XI is very small.

  At the instant t; we obtain in the same way Y'tz (fig.lOb). It is understood that the value of the derivative Y '(X) is independent of the position of the curve Y = f (X) with respect to the origin. This is illustrated by FIG. 8 showing that the curve Y '(X) is the same for two curves Y = f (X) shifted on the ordinate. This explains why the process is independent of any vibrations to which the object or assembly is subjected.

objects when scrolling.

  An electronic circuit is associated with the receivers and first provides preprocessing of the signals to provide a signal directly proportional to the derivative of the function defined by the profile, then a continual comparison of the value of the derivative to a predetermined value. . This predetermined value of the derivative defines a safety threshold during operation. 2o the receivers 27, 28 are, for example, photodiodes with

  silicon, especially sensitive in the infra-red.

  Each photodiode 27, 28 is coupled to a converter transforming the signals into voltage. The two converters 35, 36 are connected to a differential amplifier 37 itself being connected to a comparator 38. The comparator 38 is connected to a pulse generator 39 which emits a pulse whenever the value of the derivative reaches a maximum as shown in FIG. 10. This maximum corresponds to an instantaneous variation according to the 30th morphology of the profile 35; but it is always much greater than the value of the derivative of the curve not representing an instantaneous variation. The generator 39 is connected to a sensor 40 which displays the number of pulses emitted, that is to say the number of instantaneous variations which have passed between the emitter 23 and the detector 24 and therefore the number of newspapers 20. In the second example of application of the device, intended for the detection of the nodes on a textile, the emitter 23 and the detector 24 are placed on either side of the path of the wire for example on a winder or a paddle machine. Although the profile of a node is more complicated than that of overlapping objects, they have in common the instantaneous variations of the function representing the profile; these are detected and evaluated in the same way as described above. The diagram of FIG. 10 with comparator 28, the generator

  pulses 39 and the sensor 40 remains valid.

  In the context of detection on textile machine, it is possible to have the same device fill a function of detection of breakages of thread, which can be complementary to that of the detection of the nodes. For this, we exploit the stochastic distribution of the pilous existing on the surface of the wire, which provide impulse noise. The output signal, corresponding to this impulse noise, is negligible compared to the signal provided by the passage of an instantaneous variation such as a node. As a result, this impulse noise is filtered and amplified, then feeds a releasable monostable. The latter changes state When the pulses stop,

  that is to say either at the stop of the scrolling or with the breaks of wire.

  For this purpose the device comprises (FIG. 11), connected to the differential amplifier 37, an amplifier and high-pass filter 41, itself connected to a releasable monostable 42,

  providing the necessary signal for an actuator 43.

  The invention is not limited to the embodiments which have been described as non-limiting examples but covers all variants thereof. In particular one can use without leaving

  of the invention of other types of transmitters and receivers.

13 2639430

Claims (9)

  An optoelectronic process based on the instantaneous variations of the profile of an object or set of objects in continuous scrolling, characterized in that it consists in: a) reproducing said profile in the plane of a detector (24) The optical axis in the form of a function Y = f (X), the abscissa axis corresponding to the scroll direction and the ordinate axis corresponding to the direction in which the object or set of objects present or can present instantaneous variations of the profile, ob) to explore the profile by two receivers (27, 28) delimited by two slots (30, 31) so that the intersections of the function Y = f (X) defined by the profile and the lines representing the two receivers are reduced to approximately two points, and the distance between two points is the smallest possible, c) to permanently determine the derivative Y '(X) and to operate an electronic circuit associated with the optical detector generated an output signal proportional to the value of the derivative Y '(X), d) to exploit the output signal, C, eJ) and to give an instruction according to the operation of the output signal.   2. Method according to claim 1 characterized in that the exploitation of the output signal consists of comparing it to a predetermined value representative of an instantaneous variation of the 2.5 profile and in that the instruction consists on the one hand to emitting a pulse when the output signal becomes greater than the predetermined value and on the other hand exploiting the transmitted pulse. 3. Method according to claim 2 based on the instantaneous variations of the profile of a textile thread having pilous on the surface, and exploiting the stochastic distribution of said pilous, characterized in that the instruction consists in emitting a pulse when the output signal. is uniform, indicating the   breaks the thread or stops scrolling.   4. Mechanical and optoelectronic detection device for achieving the mathematical conditions so that the output signal according to the method of claim 1 is directly proportional to the value of the derivative Y '(X) and not that of the function Y = f (X) defined by the profile of the object or of all the objects in contact or overlapping on a continuously moving transport belt, characterized in that it comprises: a) means (23) enabling reproducing, in the plane of an optical detector (24), the profile of the object or set of objects in contact or overlapping on a continuously moving conveyor belt; b) two receivers (27); , 28) delimited by two slots (30, 31) so that the intersections of the function Y = f (X) defined by the profile and the lines representing the two receivers are reduced to approximately two points (33, 34) and that the distance between the two points is the us small possible, c) and an electronic circuit associated with receivers (27,28) 2oc comprising two converters (35,36) connected to a differential amplifier (37) and providing a signal directly proportional to the derivative Y '(X) of the function Y = f (X) defined by the profile.   5. Device according to claim 4 for the detection of instantaneous variations of the profile of an object or a set of objects in continuous scrolling characterized in that the electronic circuit also comprises a comparator (38) adapted to compare the signal of output to a predetermined value, a pulse generator (39), adapted to generate a pulse when the output signal becomes greater than the predetermined value, and a   output member (40) exploiting the transmitted pulse.   6. Device according to claim 4 for the detection of yarn breaks on a textile machine, characterized in that the electronic circuit also comprises a high-pass filter amplifier (41), a releasable monostable (42), changing state and generating a pulse when the amplified and filtered signal remains uniformly constant and means (43) controlled by said pulse and triggering an alarm or stopping the machine.   7. Application of the process according to claims 1 and 2 and the   device according to claims 4 and 5 to the detections and   counting of objects in contact, including cigarettes (7) or overlapping cigarettes, including newspapers (20) on a strip of transport (21).   / C 8. Application of the process according to claims 1 and 2 and   device according to claims 4 and 5 for the detection of knots (4) on textile thread (3).   9. Application of the process according to claims I and 3 and   device according to claims 4 and 6 to the detection of   / 5 breakages of textile thread or stop scrolling.