WO1985005206A1

WO1985005206A1 - Object counting apparatus

Info

Publication number: WO1985005206A1
Application number: PCT/GB1985/000180
Authority: WO
Inventors: Kenneth Ralph Rickwood; David Roy Winterbottom
Original assignee: Quantity and Time Management Systems Ltd
Current assignee: Quantity and Time Management Systems Ltd
Priority date: 1984-04-28
Filing date: 1985-04-26
Publication date: 1985-11-21
Anticipated expiration: 1986-10-28
Also published as: EP0182802A1; GB8410943D0

Abstract

Apparatus particularly suitable for the counting of folded printed matter being advanced along a line in an overlapping manner has two radiation sources (11 and 12) directing radiation on to the matter from opposite directions but at similar angles to the line of advancement. The radiations may be electromagnetic or sonar, but are distinguishable in time, or in frequency, or in polarisation. Reflected radiation is received by a receiver (16) the output of which is suitably processed to allow discrimination of whether radiation from both sources (11 and 12) is being received, or radiation from only one source, which will happen when the leading edge of an advancing object arrives at the zone at which radiation reflection takes place. Such discrimination then allows a count of the number of objects advanced to be obtained.

Description

OBJECT COUNTIN6 APPARATUS

This invention relates to apparatus for counting objects passing a given point, over a period of time. In particular - but not exclusively - the apparatus of this invention is especially suitable for counting relatively thin, sheet-like objects which are advanced past the counting point in an overlapping manner.

Using modern technology, the counting of objects passing a given point presents no particular problems if those objects a r e spaced apart. For example, the counting can be performed mechanically, optically, or magnetically, depending upon the nature of the objects. Even in the case of essentially flat, sheet-like objects which a re advanced in an overlapping state, relatively simple counters can produce exact results, provided that the thickness of the objects and their overlap a r e substantially constant. Unfortunately, for a case where the thickness of the objects is variable, or where the extent of the overlap varies, the problem of accurately counting the objects is much increased. Depending upon the method employed, the accuracy may be worsened by the objects having variable surface finishes, faults and - for optical counters - colour variations.

A particular problem arises in the case of printed matter leaving a printing press. Such printed matter may be of variable thickness, with different extents of overlap and with light and dark printed areas as well as with torn or damaged portions. If the printed matter is folded, the problems are greatly exacerbated and much effort has been expended on finding satisfactory counters for this kind of printed matter. Whilst mechanical or electromechanical counters can sense the forward folded edge on each printed copy which passes the counting point, very thin copies cannot be sensed reliably in this way and moreover miscounts can easily occur due to creases, bulges or the like. Experience also shows that closely spaced copies cannot reliably be counted, even if the mechanical sensors a r e set and adjusted with great care.

Optical photoelectric counters also have been tried, where a beam of light is directed obliquely on to the printed matter, in the direction of advancement of the product. However, reliable results still are not obtained, either because the photoelectric counter can erroneously react to areas of dark print or because the copy is too thin for a reliable output to be obtained.

The present invention stems from research into apparatus for counting printed matter passing a given point in an overlapping state, in an attempt at least to reduce the difficulties of known counters, as outlined above.

Accordingly, this invention provides apparatus for counting objects advanced in an overlapping manner, comprising a first source adapted to direct radiation to an area in the path of advancement of the objects to be counted, a second source adapted to direct radiation to the same area, the radiation from the second source being similar to but distinguishable from that of the first source, a receiver for radiation emanating from said sources and reflected by objects advancing along the path and passing through said area, the receiver providing an electrical signal dependent upon the received radiation, and discriminator circuit means arranged to act on the receiver signal and to provide an object count signal when radiation from only one of the sources is received by the receiver.

In the apparatus of this invention, the radiation emitted by the two sources may be distinguishable in frequency, in time, or in polarisation or in a combination of two or all three of these. In the most preferred arrangement, the radiation sources are adapted each to emi t electromagneti c radi ation in the visible region of the spectrum, or in a region adjacent the visible region - for instance, infra-red radiation. For such a case, the sources each may radiate substantially the same f requency or f requenci es, and then the radiation from the sources preferably is distinguishable in time. This may be achieved by alternately keying the two sources on and of f, such that when one source is on, the other i s of f and vi ce versa. Each source may thus be energised by square waves, at precisely 180º out of phase with each other. Si mi lar results may be obtained using electromagneti c radiation of other frequencies, for example in the microwave region of the spectrum, or using high f requency sound radi ation, for example in the ultra-sonic region.

With any one σf the arrangements as described above, it wi l l be appreciated that so long as the receiver receives ref lected radiation emanating f rom both sources, the output f rom the recei ver wi l l be substantia lly constant or smooth ly varying in ti me. When however the edge of an object passes the sai d area, the edge may shield the said area f rom radiation f rom one source, so that the receiver detects only radiation from the other source. With the preferred arrangement, the output signal from the receiver wi ll thus be pulsing on and off at the f requency of keying of the source the radiation from which is sti ll being received, and the discriminator circuit means may be configured to provide an output indi cative σf object to be counted when such a pulsed signal is fed thereto. The discriminator circuit means should serve to ignore smoothly varying receiver output signa ls, caused for example by variations in the object surface f inishes, and to react only to a receiver output signal which is keyed on and off at the f requency of keying of the sources, so enhancing the reliability of operation.

As an alternative to having the radiations emitted from the two sources distinguishable in time, the radiations may be of di fferent f requencies. For example, in the case of electromagnetic radiation in the visible region of the spectrum, the radiations from the two sources may accurately be controlled to be of different colours, the receiver and discriminator circuit means combination being suitably configured to detect whether ei ther colour is separately being received, or a colour comprising the combination of the two radiated colours. Microwaves and sonic radiation may be treated similarly.

A further possibi lity is for the radiation from the two sources to be differently polarised, with the receiver able to detect the plane of polarisation of received radiation. Thus, the radiation from each source may be planar polarised, the sources being arranged so that the radiation from one source is, after reflection, polarised in a plane lying at substantially 90º to the plane of polarisation of the radiation from the other source, again after the ref lection of that radiation. The two sources may in this case emit radiation which is indistinguishable in both time and frequency.

The two sources must direct radiation to the said area from different angles, in order that the radiation f rom one source may be shielded or masked by an advancing edge of an object. It is therefore preferred for both sources to direct radiation obliquely on to the objects being advanced, but from mutually opposed directions, though at the same angle with respect to the surface of the objects. Most preferably, both sources direct radiation parallel to the line of movement of the objects. Moreover, the said area to which the radiations are directed must be sufficiently small for an edge to shield the radiation from one of the sources, having regard to the thickness of the objects, the shape of an edge, and so on. Despite this, to accommodate possible variations in the thicknesses of the objects being advanced, it is preferred for the area of overlap of the two beams of directed radiation to be eliptical, with the major axis thereof parallel to the direction of movement of the objects.

By way of example only, one specific embodiment of this invention wi l l now be described in detai l, reference being made to the accompanying drawings, in whi ch :- Figure 1 is a di agrammati c view of the genera l configuration of object counting apparatus of this invention, arranged to count printed matter; Figure 2 is a block diagram of the circuitry for use with the apparatus of Figure 1; and Figure 3 shows three wave-forms for the signals present at various points in the apparatus of Figures 1 and 2; This embodi ment of apparatus of the invention is intended for counting printed and folded matter, advancing in an overlapping state past a particular point at which counting is to be performed; such printed matter is shown in Figure 1 at 10. Two light emitting diode array sources 11 and 12 are provided with suitable lens arrangements 13 and 14, so as to direct focussed beams of radiation on to an eliptical area at the point 15 at which counting is to be performed. The two sources direct radiation at substantially the same oblique angle on to the printed matter 10 but from opposite directions parallel to the line of advancement of the printed matter. Directly over the area on to wh i ch l i ght i s di rected there i s provi ded a photoelectric detector 16 and lens 17, to collect radiation reflected from the area and to focus it on to the detector 16.

Referring to Figure 2, it can be seen that each light emitting diode array 11 and 12 is provided with an individual drive ci rcuit 18 and 19 respectively, these drive circuits receiving square wave clock signals from a generator 20 configured to provided two clock signals 180º out of phase. In this way, when one light emitting diode 11 is turned on, the light emitting diode 12 is turned off, and vice versa. The photoelectric detector 16 provides a n electrical output to an a.c. amplifier 21, the output of which is fed to a gating circuit 22. The other input to this gating circuit is derived from a gating control circuit 23, driven by one of the square wave clock outputs from the generator 20. The gating circuit output is amplified and supplied to a d.c. level comparator 24, and the output of that comparator is used to control an output pulse circuit, which provides an electrical pulse every time another object is counted. Figure 3a shows the detector 16 output when only radiation from diode array 11 is received, whereas Figure 3b shows the detector output when only radiation from array 12 is received: these outputs correspond to the keying of the arrays themselves and are exactly 180º out of phase.

As will be appreciated from Figure 3c, the total detector output is a uniform d.c. level so long as reflected radiation from both arrays is received. That d.c. signal may vary with time, for example as portions of white and black print pass through the said area 15, as shown in the left hand and central portions of Figure

3c, but such variations will not be at precisely the same frequency as that at which the two diode arrays are driven, and so such changes will be rejected by the gating circuit 22. When however the edge between two pieces of overlapping printing matter is a t the said area 15, much of the radiation from array 12 will be masked and so the detector 16 wi ll mostly see radiation emanating from array 11. This is illustrated in the right hand side of Figure 3c, and. the gating circuit 22 passes this output to the level comparator

24, to permit the output pulse circuit to produce a count signal. It is preferred for the area 15 to be eliptical, with the major axis extending generally parallel to the Line of advancement of the printed matter 10. This is conveniently achieved by arranging the light emitting diodes in a Linear array, or by using cylindrical Lenses, appropriately positioned, to give an elongate but narrow Light beam. Then, provided the thickness of an object to be counted falls in a predetermined range, the beams wi ll be overlapping at the point at which reflection is occuring.

Claims

1. Apparatus for counting objects advanced in an overlapping manner comprising a first source adapted to direct radiation to an area in the path of advancement of the objects to be counted, a second source adapted to direct radiation to the same area, the radiation from the second source being simi lar to but distinguishable from that of the first source, a receiver for radiation emanating from said sources and ref lected by objects advancing along the path and passing through said area, the receiver providing an electrical signal dependent upon the received radiation, and discriminator circuit means arranged to act on the receiver signal and to provide an object count signal when radiation from only one of the sources is received by the receiver.

2. Apparatus according to c lai m 1, wherein the radiation emitted by the two sources is distinguishable in frequency, or in time, or in polarisation or in a combination of any two or all three of these.

3. Apparatus according to c lai m 1 or clai m 2, wherein the radiation sources are adapted to emit radiation selected from the group consisting of: ultraviolet electromagneti c radi ation; electromagneti c radi at i on i n the vi s i b le regi on; i nf ra-red electromagnetic radiation; microwave electromagnetic radiation; and ultra-sound sonic radiation.

4. Apparatus according to any of the preceding claims, wherein the sources radiate at substantially the same frequency or frequencies, the radiation from the sources being distinguishable in time.

5. Apparatus according to claim 4, wherein the two sources are alternately keyed on and off, such that when one source is on, the other is off and vice versa.

6. Apparatus according to claim 5, wherein each source is energised by square waves, at precisely 180° out of phase with each other.

7. Apparatus according to any of claims 1 to 3, wherein the radiations emitted from the two sources are at different frequencies.

8. Apparatus according to claim 7, wherein the two sources emit electromagnetic radiation in the visible region of the spectrum, the radiations from the two sources being accurately controlled to be of different colours and the receiver and discriminator circuit means combination being suitably configured to detect whether either colour is separately being received, or a colour comprising the combination of the two radiated colours.

9. Apparatus according to any of claims 1 to 3, wherein the radiation emitted f rom each source i s planar polarised, the sources being arranged so that the radi ation f rom one source is, after ref lection, polarised in a plane, lying at substantially 90º to the plane of polarisation of the radiation from the other source, also after the ref lection thereof, and the receiver being adapted to detect the plane of polarisation of received radiation.

10. Apparatus according to any of the preceding claims, wherein both sources direct radiation obliquely on to the objects being advanced from mutually opposed directions, though at the same angle with respect to the surface of the objects, and preferably, in a direction parallel to the line of movement of the objects.