A METHOD AND AN APPARATUS FOR COUNTING UNIFORM OBJECTS ON A CONVEYOR

Abstract: A method and an apparatus for counting objects (10) transported by a conveyor. The method ensures correct counting of the objects, no matter how they pass a row of sensors (1-9) placed transversely to the conveyor.

Description: A method and an apparatus for counting uniform objects on a conveyor The invention concerns a method of counting uniform objects passing a counting location on a conveyor, said method being of the type stated in the introductory portion of claim 1. The object may e.g. be beer bottles, which are conveyed in a brewery between various treatment stations, often in several lanes on the conveyor. The counting of bottles at two or more locations on the conveyor may e.g. be used for controlling the belt speed with a view to reducing the noise caused by bottle collisions. The inhibition prevents a passing object from being counted by two or more sensors, and the geometrical arrangement ensures that any passing object will be counted, ir¬ respective of the inhibition. The object of the invention is to provide a method of the present type which eliminates the uncertainty that may arise in those instances where an object passes the row of sensors exactly halfway between two adjacent sensors. This object is achieved in that the method is performed as stated in the characterizing portion of claim 1, since the scanning ensures that it is always the first one of two simultaneously activated sensors which gets the status of central sensor. The feature .defined in claim 6 ensures that it is only the leading flank of the pulses applied by the control circuit which activates the counter, so that there will always be a minimum time interval between two counter activations, corresponding to the time interval between two successive scanning pulses. The invention also concerns an apparatus for performing the stated method, said apparatus being of the type stated in the introductory portion of claim 2 and characterized by the subject matter defined in the characterizing portion 5 of claim 2. In particular when such cylindrical objects as stated in the introductory portion of claim 3 are involved, e.g. beer or mineral water bottles, the certainty of all J O bottles being counted once and just once may be established in that the row of sensors satisfies the condition stated in the characterizing portion of claim 3. When, additionally, the control circuit is arranged as 15 stated in claim 4, any first-time-activated sensor will establish itself either as the central one of a 3-group or ^s_one of a 2-group with the adjacent sensor or sensors inhibited, and each group counts one object. The adjacent groups may overlap, but the overlap must not affect the 20 activated sensors. An unactivated sensor which is a member of a group may be activated later, but does not count because it is inhibited. The feature defined in claim 5 ensures that it is only 25 the leading flank of the pulses applied by the control circuit which activates the counter, so that there will always be a minimum time interval between two counter activations, corresponding to the time interval between two successive scanning pulses. 30 The invention will be described more fully below with reference to the drawing, in which fig. 1 schematically shows how a plurality of sensors are 35 placed over a conveyor on which the objects are packed as densely as possible, fig. 2 shows a preferred embodiment of an apparatus according to the invention, fig. 3 is a block diagram of a display unit according to a preferred embodiment, and fig. 4 shows single wave forms in a signal processing circuit which forms part of the display unit shown in fig. 3. Fig. 1 shows a sensor assembly consisting of sensors 1-9, and this assembly is placed over a conveyor conveying a plurality of objects 10, which are bottles in a typical use of the present invention. In the shown embodiment, the sensors 1-9 are so designed that their detection areas touch each other. This means that an object on the conveyor might be able to activate more than one sensor when passing the sensor assembly. With a view to determining accurately that an object passes the assembly, the sensors are scanned sequentially, When, upon scanning of a sensor, it is recognized that the sensor is activated by an object, then the adjacent sensors are inhibited, or the adjacent sensor if one of the outer sensors 1 and 9 is activated. This makes it certain that a passing object is recognized only once, thereby enabling accurate counting of the passing objects Thus, upon recognition of objects, groups of inhibited sensors are formed, which may consist of two or three sensors and may include sensors common to the groups; however, the sensor initiating the formation of a -group can only be a member of one group. The sensor- groups thus formed are broken down when the situation occurs that no sensor in the group is activated any longer, which means that the activating object is now outside the detection area of the sensors. Fig. 2 shows the part of the apparatus of the invention which performs scanning of the sensors 1-9 and divides these into groups when it is recognized that an object passes the sensor assembly. The function of the circuit shown in fig. 2 will be explained now, it being assumed that only one sensor is activated in a scanning period; * this assumption just serves to simplify the description. The sensors are scanned in that a scanning pulse is applied to the signal inputs 29-31-33 of the circuit in succession. Hereby, a sensor output signal is transmitted from inputs 30-32-34 to gates 16-17-18. If it is assumed that the sensor signal on the input 32 is logic "high", i.e. the sensor has recognized an object, and that the input 31 switches to logic "high" by the scanning signal, the output 39 of the gate 17 will be logic "low". This output signal is transmitted to a gate 23. If the other inputs 41 and 40 of this gate are both logic "low", the output 42 of the gate 23 will switch to logic "high", and the output 37 of a flip-flop 27 will then assume the value logic "high". In this way, the circuit transmits in¬ formation about recognition of an object. Inhibition of the adjacent sensors of the activated sensor takes place in that the "high" output signal on the output 37 is directed to gates 22 and 24, which thus inhibit flip-flops 26 and 28. A group is formed in this way around the sensor connected to the input 32 when its adjacent sensors are connected to the inputs 30 and 34, respectively. A group formed in the manner described above is broken down when all the sensors forming part of the group are no longer activated by the object. This means that the inputs 30, 32, 34 are at the "low" level, and thus all the inputs of the gate 19 are on "low" so that its output 43 will be "high"; this signal resets the flip-flop 27 whose output switches to "low", which removes the inhibition of the flip-flops 26 and 28. All output signals 36, 37, 38, 44, 45, 46, 47, 48, 49 from the sampling and group forming circuit shown in fig. 2 are transmitted to the circuit shown in fig. 3. The circuit shown in fig. 3 comprises an input signal processing circuit 50 and a counting circuit 51. The counting circuit is of a conventional type and will not be described in detail. The purpose of the signal processing circuit 50 is to convert the pulse signals arriving from the signal outputs 36-38, 44-49 to a form of pulse signals which are more distinctly spaced from each other in terms of time. In fig. 4, it is shown with the reference letter a that the input signal to the signal processing circuit 50 is a square signal. Since such a signal would block the counter for other signals, the signal is differentiated with a capacitor 52, resulting in the wave form shown with the reference letter b. This signal is half-wave rectified with a diode 53, resulting in the wave form shown with the reference letter c. It will be seen that this signal processing has the effect that it is only the leading edge of the pulse signal from the s.ampling and group formation circuit which affects the counting circuit 51. This is an important property of the present circuit because it is the group formation moment of time which expresses when an object has been recognized, whereas the breaking down moment of time has no importance for the counting. Further, the signal processing circuit 50 serves to ensure that no signals block others. The sensors described in the foregoing may be of an inductive, optical or any other type where the scanning area is well-defined. Thus, it is possible to use a pattern recognition system to scan the position of the objects on the conveyor. Such a solution would require the presence of a television camera or other optical signal receiver over the conveyor, and processing of the output signal from it in such a manner that the above- mentioned groups may be formed and broken down. It is clear that the shown, preferred embodiment of the scanning and group formation unit, and of the signal processing and counter unit, may be replaced by any form of a logic network capable of performing these functions,

Claims: P a t e n t C l a i m s 1. A method of counting uniform objects (10) passing a counting location on a conveyor by means of a row of sensors (1-9) placed over the conveyor with such mutual spacing that no object can pass the row without activating at least one sensor, wherein an activated sensor inhibits that or those of the other sensors which might otherwise be activated by the same object, c h a r a c t e r i z e d by scanning the sensors (1-9), and by inhibiting the adjacent sensors or the adjacent sensor of that of the two simultaneously activated sensors which is scanned first. 2. An apparatus for performing the method according to claim 1, comprising a row of sensors (1-9) placed over a conveyor with such a mutual spacing that a passing object will always activate at least one sensor, said sensors being connected to an electric control circuit designed to inhibit, upon reception of a signal from an activated sensor, the other sensor or sensors which might otherwise be activated by the same object, and to activate a counter (51), c h a r a c t e r i z e d in that the control circuit is moreover designed to scan the sensors (1-9), and that it is the adjacent sensors or the adjacent sensor of the first scanned one of two simultaneously activated sensors which is inhibited. 3. An apparatus according to claim 2 for counting uniform objects (10) with a detectable central area whose diameter is approximately half the diameter of the objects, c h a r a c t e r i z e d in that the row of sensors is substantially perpendicular to the conveyor and contains N = 2p - 1 sensors (1-9), where p is the number of objects (10) in a densely packed transverse row on the conveyor. 4. An apparatus according to claim 3, c h a r a c ¬ t e r i z e d in that the control circuit is designed to inhibit the two adjacent sensors of an activated sensor or the adjacent sensor if the activated sensor is an outer sensor. 5. An apparatus according to claim 2, 3 or 4, c h a r a c t e r i z e d in that differentiation circuits (52) followed by half-wave rectifiers (53) are interposed between the control circuit and the counter (51).

Inventors: LYNGSIE GORM, LYNGSIE, GORM
Applicants: FORENEDE BRYGGERIER AS, DE FORENEDE BRYGGERIER A/S
Application year: 1986
Main classification: G06M7
IPC codes: G06M3, G06M7