GB2299412A

GB2299412A - Method of controlling articles conveyed through a work station

Info

Publication number: GB2299412A
Application number: GB9506132A
Authority: GB
Inventors: Steven Buckby
Original assignee: Prestek Ltd
Current assignee: Markem Imaje Industries Ltd
Priority date: 1995-03-25
Filing date: 1995-03-25
Publication date: 1996-10-02
Also published as: GB9506132D0

Abstract

A system for controlling articles (A, B, C) which are successively conveyed through a work station (13) comprises sensor means (22, 24) to sense the distance between a first article (A) and a second article (B) and to provide a signal (23, 25) to a control means (18). The control means provides a signal (20) to the operating means to cause the operating means to carry out a work operation on the first article (A) when at the work station, when the control means (18) determines from the input signal that there is a distance greater than a minimum distance between the first article (A) at the work station and the second article. Where the sensed distance is less than the predetermined distance, the control means (18) permits the first article to be conveyed downstream from the work station without the work operation being performed thereon. The application is to printing and attaching of labels.

Description

Title: Method of Controlling a System Description of the Invention This invention relates to a method of controlling a system and more particularly but not exclusively to a method of controlling a labelling or printing system in which either labels are applied to the front or the back surface of each of a plurality of articles e.g. packages which are being conveyed through a labelling station, or in which a printing operation is carried out on the front or the back surface of each of a plurality of articles being conveyed through a printing station.

It will be appreciated that packages on a conveyor tend not to be equally spaced from one another. Hence conventionallv, at or near a labelling or printing station there is provided a sensor which senses the presence of a package at the printing or labelling station and sends an appropriate signal to a control means which responds hy operating the labelling or printing means.

If however the distance between the package at the labelling/printing station and the preceding package in the case of a front of package labelling/printing method, or the next following package in the case of a back of package labelling/printing method. is too small there is a risk that the labelling/printing operation will be interfered with by the preceding or next package.

Although steps may be taken to ensure adequate spacing between successive packages and/or to speed up the printing:labelling operation, these solutions however are not always satisfactory from a practical or financial point of view.

In a front of package labelling/printing situation, if a sensor is provided downstream of the labelling/printing station, it is possible to sense that the preceding package is sufficiently clear of the labeller/printer to ensure that the preceding package does not interfere with the labelling/printing operation.

However in these circumstances it might be that the package at the labelling/printing station is too far advanced with the result that the labelling/printing operation is incorrectly performed. In this case it is no longer possible to apply a label correctly to the package or the printing operation may be inadequate. Furthermore, more serious consequences may arise, e.g. there may be a jam resulting in the packaging line being halted, and/or the articles and/or the labelling/printing apparatus may be damaged.

According to the invention we provide a method of controlling a system in which articles are successively conveyed through a work station where a work operation is carried out thereon by an operating means there being sensor means to sense the distance between a first article and a second article preceding or next being conveyed, and to provide a signal to a control means, wherein the method includes providing a signal to the operating means to cause the operating means to carry out a work operation on the first article when at the work station when the control means determines from the input signal that there is a distance greater than a minimum distance between the first article at the work station and the second article, and where the sensed distance is less than the predetermined distance the control means permitting the first article to be conveyed downstream from the work station without the work operation being performed thereon.

Hence by performing the method of the invention although it is preferred for every article to have the work operation carried out on it such as labelling, in circumstances where it is calculated that it is unlikely a label can be properly applied, or that to attempt to apply the label or perform another work operation on the article would present a risk of malfunction, such risks are avoided.

Thus it may be considered from a pragmatic point of view, that it is better not to attempt to apply a label or perform another work operation, in such circumstances this would present a risk of malfunction, this risk is avoided as the work operation is not performed on the article at the work station.

In some systems it may be acceptable for an article on which a work operation has not been performed, to proceed with other articles on the conveyor, but in other systems the method may include diverting or otherwise removing any article on which the work operation has not been performed, from the conveyor, for remedial action to be taken.

Preferably there is a first sensor to sense the presence of a first article at the work station and to provide a first input signal to the control means, and a second sensor spaced upstream or downstream from the first sensor to sense the presence or absence of the second next upstream or downstream article of the first article at the work station, and to provide a second input signal to the control means, the control means determining from the first and second input signals the distance between the first and second articles.

The first and/or second sensor may be an optical sensor for example, or any other kind of sensor appropriate to the article being sensed.

The articles may be continuously conveyed through the work station or may momentarily be halted at the work station.

The operating means may in one example comprise a labelling means which moves a label from a printing means where information is printed on the label, into the path of the articles, to apply the label to the front or rear surface of an article.

Hence there may be provided a third sensor upstream of the work station to determine parameters such as weight, colour or size, of the articles so that a label unique to each article is printed by the printing means. The operating means may thus be a printing and labelling machine of the kind shown in our previous patent number GB 2248051. In this case in the event that it is determined that a particular article should not be labelled because the article is too close to preceding or next article, either the printing means can be inhibited from printing a label, or means may be provided to discard a printed label, depending upon the relative positions of the sensors.

In the case where a printing operation is carried out directly on the article by a printing means at the work station, such a third sensor may also be provided but of course simply a printing operation would not be carried out on the first article where it is determined that article is too close to the second article, so that there is no risk either that the second article will interfere with the printing operation, or that there will be a malfunction as a result of the first article not being appropriately positioned at the work station.

In the case where the work operation is carried out on a front surface of an article at the work station, the second sensor would be downstream of the first sensor to ensure that the preceding article is sufficiently distant from the first article at the work station, for a work operation to be carried out on the first article at the work station without presenting any risk.

Where a work operation is carried out on a rear surface of the article at the work station, the second sensor would be arranged upstream of the first sensor so as to determine whether the next successive (second) article is too close to the first article at the work station for a work operation to be carried out without risk on the rear surface of the first article.

According to a second aspect of the invention we provide a control apparatus for a system in which articles are successively conveyed through a work station where a work operation is carried out thereon by an operating means, there being sensor means to sense the distance between a first article and a second article preceding or next being conveyed, and to provide a signal to a control means, the control means being adapted to provide a signal to the operating means to cause the operating means to carry out a work operation on the first article when at the work station when the control means determines from the input signal that there is a distance greater than a minimum distance between the first article at the work station and the second article, and where the sensed distance is less than the predetermined distance the control means permitting the first article to be conveyed downstream from the work station without the work operation being performed thereon.

The invention will now be described with reference to the accompanying drawing which is a purely illustrative view of a system which may be controlled by the method of the first aspect of the invention.

Referring to the drawing there is shown a system 10 comprising a conveying means 11 which is adapted to convey a plurality of articles indicated at A in full lines, and B and C in dotted lines, in the direction of arrow 12, the articles A, B and C being adapted to be conveyed to and through a work station indicated in dotted lines at 13.

In this example, each of the articles A, B and C comprises a package containing for example a plurality of items. When a first article i.e. article A is at the work station 13, a work operation can be carried out in this example on a front surface 14 of the article A. The work station 13 includes in this example, a printing means 15 which is adapted to print information on a label 16, and a labelling means 17 which is adapted to move the label 16 away from the printing means 15 and to apply it to the front surface 14 of the first article A at the work station 13.

The work operation is carried out under the control of a control means 18 which provides a first signal 19 to the printing means 15 to cause the label 16 to have the information printed on it, and a second signal 20 to the label applying means 17 to cause the label 16 to be applied to the front surface of the article A.

In order to determine when an article A is at the work station 13, there is provided a first sensor 22 which provides a first input signal 23 to the control means 18. Hence the labelling means 17 at least is only operated to apply the label 16 to the front surface 14 of the article A when the control means 18 determines from the first input signal 23 that there is an article A at the work station 13.

In accordance with the invention there is provided a second sensor 24 which is adapted to provide a second input signal 25 to the control means 18.

The sensor 24 is spaced from the work station 13 or at least first sensor 22, a predetermined amount and provides a signal 25 to the control means 18 to indicate when a preceding article to the article A at the work station 13 i.e. article B, has moved past the sensor 24. Alternatively the sensor 24 may provide a signal to the control means 18 to indicate that the article B has not yet moved past the sensor 24. In either event, the control means 18 is able to determine whether the distance d between the first article A at the work station 13 and the preceding article B is greater than a minimum distance admin. If d is greater than distance admin, the control means 18 is then operative to provide a signal 20 to the labelling means 17 to cause a label 16 to be applied to the front surface 14 of the article A.However in the event that distance d is determined to be less than distance d the control means 1X does not provide the signal 20 to the labelling means 17 and as a result, the article A at the work station would be conveyed through the work station downstream thereof without a label 16 being applied to the front surface 14 thereof. Hence the risk of article B interfering with the correct operation of the labelling means 17 if distance d is too small, is avoided, as is the risk of the labelling means 17 malfunctioning if article A is inappropriately positioned at the work station 13.

Distance d min is determined in accordance with the speed at which the articles A, B and C are conveyed by the conveyor 11, the size of the articles A, B and C, and the time it takes for the label 16 to be applied to the front surface 14 of the article at the work station. d,ll"l is chosen so as to be sufficiently great for a label 16 to be applied without there being any risk of the preceding article B interfering with the labelling operation by virtue of being too close to article A or of article A being inappropriately positioned at the work station 13.

In this example a third sensor indicated at 26 is provided upstream of the work station 13, and in this example upstream of the second sensor 24.

The third sensor 26 provides a third input signal 27 to the control means 18 which depends upon a parameter of the article passing sensor 26. For example the parameter may be a measure of the weight, size or type of the article sensed by the sensor 26.

The control means 18 can thus cause a label to be printed by the printing means 15 unique to the next article to which a label 16 is to be applied by the labelling means 17, even before the label is applied to the preceding article.

In the event that the control means 18 determines that distance d is less than distance admin either the control means 18 can inhibit the printing means 15 from printing a label in the first place, where appropriate, or else some means may be provided to discard a printed label without the label being applied to the article A at the work station, depending upon the spacing of the third sensor 26 from the work station 13, the speed and configuration of the printing means 15 and labelling means 17, and the manner in which distance d is measured.

In another example, instead of the operating means at the work station 13 being adapted to apply a label 16 to a front surface 14 of an article A at the work station 13, the operating means may be arranged to apply a label 16 to a rear surface 28 of the article A at the work station. In this event, it would be necessary for the second sensor 24 to be positioned upstream of the work station 13 or at least sensor 22, rather than downstream as shown, so as to determine the distance d' between the article A at the work station 13, and the next successive article C.Again the control means would be arranged to determine whether d' is greater than a minimum distance dmiii and in the event that d' was determined to be less than distance dm"" the labelling means 17 would not be operated and the operating means would thus not attempt to apply a label 16 to the rear surface 28 of the article A, so as to avoid all risks of doing so.

The first and second sensors 22 and 24 may be simple optical sensors which optically sense the presence of articles A and B, or any other kind of sensor appropriate to articles A and B being sensed.

If desired, the control means 18 may he adapted to provide a warning at least, in the event that more than a predetermined number of articles are not labelled, due to being too close to the next successive, or preceding article, so that remedial steps can be taken, and if required may be arranged to provide a signal to some means downstream which cause an article not labelled or printed, to be diverted or removed from conveyor 13, for reworking.

Although the invention has been described with relation to a system in which labels 16 are applied to the articles A, B, C the control method described may be applied to an arrangement in which a printing operation is directly carried out on the front 14 or rear 28 surface of an article A at the work station 13. In this event, such a printing operation would not be carried out on the article A in the event that the distance from the article A to the preceding article B or the next successive article C as appropriate, is determined to be less than a minimum distance needed for the printing operation to be carried out without there being any risk of interference with the printing operation from the previous article B or the next successive article C respectively, or any risk of malfunction of the printing apparatus if article A is inappropriately positioned at the work station 13.

The invention may be applied to a labelling or printing system in which a labelling or printing operation is carried out other than on a front or rear surface of the article, e.g. on a side surface, where the spacing between successive articles is essential to proper operation, or generally to any other work operation to be carried out on articles which are conveyed through a work station 13 where a work operation requires a minimum spacing between successive articles e.g. to avoid any risk of interference by a preceding or next successive article, as appropriate or any risk of the work operation being malperformed due to inappropriate positioning of the article at the work station because the distance between two successive articles is inadequate. Any alternative desired means for determining the distances between successive articles could be employed. For example it is not essential for the sensor 22 to be provided at the work station to determine distances between successive articles. If desired the control means 18 may calculate the distance by knowing the speed of the conveyor 12 and receiving a single input signal from sensor 26.

If desired each article may be tracked so that the control means 18 is able to identify each article uniquely, and operate the system 10 appropriately.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A method of controlling a system in which articles are successively conveyed through a work station where a work operation is carried out thereon by an operating means there being sensor means to sense the distance between a first article and a second article preceding or next being conveyed, and to provide a signal to a control means, wherein the method includes providing a signal to the operating means to cause the operating means to carry out a work operation on the first article when at the work station when the control means determines from the input signal that there is a distance greater than a minimum distance between the first article at the work station and the second article, and where the sensed distance is less than the predetermined distance the control means permitting the first article to be conveyed downstream from the work station without the work operation being performed thereon.

2. A method according to claim 1 wherein a first sensor senses the presence of a first article at the work station and provides a first input signal to the control means, and a second sensor spaced upstream or downstream from the first sensor senses the presence or absence of the second next upstream or downstream article of the first article at the work station, and provides a second input signal to the control means, the control means determining from the first and second input signals the distance between the first and second articles.

3. A method according to claim 2 wherein the first and/or second sensor is an optical sensor.

4. A method according to any preceding claim wherein the articles are continuously conveyed through the work station or are momentarily be halted at the work station.

5. A method according to any preceding claim wherein the operating means comprises a labelling means which moves a label from a printing means where information is printed on the label, into the path of the articles, to apply the label to the front or rear surface of an article.

6. A method according to claim 5 wherein a third sensor upstream of the work station determines parameters such as weight, colour or size, of the articles so that a label unique to each article is printed by the printing means.

7. A method according to claim 6 wherein in the event that it is determined that a particular article should not be labelled because the article is too close to preceding or next article, either the printing means is inhibited from printing a label, or means are provided to discard a printed label, depending upon the relative positions of the sensors.

8. A method according to any one of claims 1 to 4 wherein the operating means comprises a printing means where a printing operation is carried out directly on the article at the work station.

9. A method according to claim 8 wherein a third sensor upstream of the work station determines parameters such as weight, colour or size, of the articles so that a label unique to each article is printed by the printing means.

10. A method according to any preceding claim wherein where the work operation is carried out on a front surface of an article at the work station, the second sensor is downstream of the first sensor to ensure that the preceding article is sufficiently distant from the first article at the work station, for a work operation to be carried out on the first article at the work station.

11. A method according to any one of claims 1 to 9 wherein where a work operation is carried out on a rear surface of the article at the work station, the second sensor is arranged upstream of the first sensor so as to determine whether the next successive (second) article is too close to the first article at the work station for a work operation to be carried out without risk on the rear surface of the first article.

12. A control apparatus for a system in which articles are successively conveyed through a work station where a work operation is carried out thereon by an operating means, there being sensor means to sense the distance between a first article and a second article preceding or next being conveyed, and to provide a signal to a control means, the control means being adapted to provide a signal to the operating means to cause the operating means to carry out a work operation on the first article when at the work station when the control means determines from the input signal that there is a distance greater than a minimum distance between the first article at the work station and the second article, and where the sensed distance is less than the predetermined distance the control means permitting the first article to be conveyed downstream from the work station without the work operation being performed thereon.

13. A control apparatus substantially as hereinbefore described with reference to the drawing.

14. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings.