WO2009016328A1

WO2009016328A1 - Marking system with integrated linearity synchronisation

Info

Publication number: WO2009016328A1
Application number: PCT/GB2007/002884
Authority: WO
Inventors: Gary David Stamp; Peter Richard Lisher; Ashley Glenister
Original assignee: Quill Coding Solutions Limited
Priority date: 2007-07-27
Filing date: 2007-07-27
Publication date: 2009-02-05
Also published as: GB201002252D0; GB2463847A

Abstract

The system applies marks (i.e. human or machine readable) by a marking device (200) and uses an internal synchronisation system to ensure the quality of the mark is optimum whilst allowing the use of less expensive, wider tolerance components. An encoder system (201) monitors internal marking device movement which is analysed by the common control system (208) to synchronise individual lines of the mark being printed thus compensating for mechanical variations of the marking device (200). Critically, the synchronisation process allows printing to occur earlier within the marking cycle leading to a significant increase in productivity. The marking system enclosure is mounted on a stage (207) and positioned to produce a mark (206) upon items (204) as they are laced (205) at the markin device.

Description

MARKING SYSTEM WITH INTEGRATED LINEAR SYNCHRONISATION

This invention relates to field of marking, and particularly but not exclusively, to machine and human readable codes found on food and pharmaceutical packaging including but not limited to, expiry dates and production batch codes.

Within industry in general, there is a requirement to mark products and product packaging with unique identifying codes and information relating to contents, expiry dates and production codes. It is also important that producing such marks does not slow the capacity of the production line. In the European Union, Directive N° 2000/13/EC on labelling, identifies the rules put in place on the labelling of foodstuffs to enable, amongst other things, European consumers to get comprehensive information on the contents and the composition of food products. Further legislation governs the labelling and marking of pharmaceutical packaging to guarantee product integrity and trace ability.

It is critical that products contain the appropriate mark to identify, but not exclusively, content and expiry dates. This is particularly important with pharmaceuticals but also perishable products, which are required to be traced back to origin of manufacture. In some instances supplying a poorly or inaccurately marked package is likely to incur a fine and possible suspension from supplying such future product.

Prior art marking methods include thermal transfer, laser and inkjet. The mark must be legible, accurate, indelible and machine-readable where appropriate. Many factors affect the quality of the mark and include the accurate positioning of lines and spaces, which together form machine- readable barcodes and character construction for human readable codes. Prior art validation systems, deploying image capture techniques, are added to the production line and operate separately and independently to the marking device to check that products have been correctly marked. The complexity of computer algorithms to analyse human and machine-readable marks, requires a preliminary set up process where the image capture and validation device must first determine character parameters to recognise specific marks. Subsequent printed marks must not greatly deviate from those initially recognised and stored by the validation system.

According to a first aspect of the present invention, there is provided marking system comprising a marking device arranged to apply a mark to products or their packaging, the marking device comprising a print head mounted on a moveable carriage, an encoder system arranged to detect the speed and position of the moveable carriage, and a control system arranged to control the marking device, the control system arranged to control the energy output of the print head according to the speed and position of the moveable carriage.

According to a second aspect of the present invention, there is provided marking method comprising applying a mark to products or their packaging, from a marking device comprising a print head mounted on a moveable carriage, detecting the speed and position of the moveable carriage, and controlling the marking device, thereby controlling the energy output of the print head according to the speed and position of the moveable carriage.

Owing to the invention, it is possible to provide an integrated marking system that uses low cost and low tolerance components where printer instability is compensated and an appropriate mark of the highest quality with reproducible results is produced so that subsequently the marks are capable of tolerating the maximum amount of damage and still remain readable.

Specific implementations of the present invention aim to provide a marking system in which a product is marked and employs an integrated linearity synchronisation system to maintain high quality character shapes, including but not exclusively machine readable barcodes, reducing the need for high tolerance and expensive system components.

In a preferred implementation, marking and linearity synchronisation is carried out under the control of a single machine containing the marking device, a spatial encoder device and a data control system. The marking device, a spatial encoder device and a data control system operate to perform integrated marking, synchronising printed data to compensate for irregular print head movement to deliver a consistent spatially accurate mark. The marking and linear synchronisation is carried out under the control of a common control system. A user interface may be provided, enabling an operator to monitor stages of marking and synchronisation activity to set quality levels below which, items marked would automatically be rejected.

The invention includes an interface display for operating a marking, verification and compensation apparatus for applying at least one mark to at least one packaged item and for monitoring levels of synchronisation for said mark, said interface comprising; A pass/warning/fail indicator for indicating a result of the synchronisation process and a data display for displaying marking data, subject of said applied mark and a stable/warning/unstable indicator for indicating the condition of the production line. The invention includes an interface display for configuration of marking and synchronisation apparatus and diagnostic set up for spatial encoder device.

In the food and pharmaceutical industries it is essential that products be correctly marked to indicate content, manufacture audit trail and expiry date. Manual checking of each package is not practical on high speed manufacturing lines. Present optical validation systems^' in use are added to the process but are very sensitive to the quality and stability of the mark. Expensive, high tolerance components are necessary to produce accurate marks, particularly for computer readable barcodes and vision validation systems, and still satisfy the need for high productivity. More critically, system component set-up and wear degrades the quality of the printed mark over time and the marking device must be frequently maintained. The invention described herein uses considerably cheaper and lower tolerance components without loss of print quality and also significantly improves productivity. In addition, the invention reduces the need for such frequent maintenance. In prior art systems, the print head must be accelerated to a stable speed before printing can begin, and only while this constant speed is maintained can accurate printing be performed. This methodology imparts a very high tolerance demand to the components that are controlling the print head speed. Expensive motor and bearing systems are required, which generally only have a limited life span before degradation of performance will affect the print quality.

By using an encoder system that detects both the speed and position of the moveable carriage that mounts the print head, far lower tolerance is required of the components and greater accuracy is achieved. The control system controls the making device to adjust the energy output of the print head to place a mark at the right position, but also to tailor the energy level to the current speed of the print head. This removes the need for the carriage to be moving at a constant speed as now the interaction of the encoder system and the control system will compensate for any variations in speed. If a pixel is required at a specific position, then when the encoder and control systems detect that the correct position has been reached by the print head, and determine the correct energy output for the present speed of the carriage.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 illustrates schematically a food label mark, comprising a barcode with human readable characters,

Figure 2 illustrates schematically in perspective view a marking system with integrated spatial synchronisation according to a first specific implementation of the present invention, Figure 3 illustrates schematically a surface to be marked and a prior art marking machine, comprising a carriage with print head and fixed guide bar, Figure 4 illustrates schematically a prior art marking machine, comprising a print head and carriage, guide bar and a surface to be marked which contains a plurality of deposited printed pixels,

Figure 5 illustrates schematically a prior art marking machine, comprising a print head and carriage, guide bar and a surface to be marked which contains a plurality of deposited printed pixels and a graph depicting print head displacement verses velocity throughout the print cycle,

Figure 6 illustrates schematically a prior art marking machine, comprising a print head and carriage, guide bar and a surface to be marked which contains a plurality of deposited printed pixels and a graph depicting print head displacement verses velocity throughout a compressed print cycle,

Figure 7 illustrates schematically a marking machine according to best implementation of the present invention, comprising a print head and carriage, and a surface to be marked which contains printed pixels, a graph depicting print head displacement verses velocity throughout a compressed print cycle and signals produced by a spatial encoder,

Figure 8 illustrates schematically in perspective view a prior art marking machine prior to the marking operation, comprising a print head and carriage, a motor device and belt system, and a surface to be marked, Figure 9 illustrates schematically in perspective view a prior art marking machine subsequent to the marking operation, comprising a print head and carriage, a motor device and belt system, and a surface to be marked,

Figure 10 illustrates schematically in perspective view a marking machine, prior to the marking operation, according to best implementation of the present invention, comprising a print head and carriage and spatial encoder, and a solenoid device and spatial encoder, and a surface to be marked,

Figure 11 illustrates schematically in perspective view a marking machine, subsequent to the marking operation, according to best implementation of the present invention, comprising a print head and carriage and spatial encoder, and a solenoid device and spatial encoder, and a surface to be marked, Figure 12 illustrates schematically in perspective view a more detailed section of the marking machine, and

Figures 13 and 14 illustrate schematically in end view the marking machine of Figure 12.

There will now be described, by way of example, the best mode contemplated by the inventors for carrying out the invention. In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details including but not limited to, methods that apply linear motion. In other instances, other well-known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention. Specific implementations according to the present invention provide for an integrated marking system with data synchronisation:- in particular applying human readable and computer readable marks with high spatial accuracy using low cost, low tolerance marking system components. A package is delivered beneath the marking device and a signal passed to the marking system from the packaging system, requesting a mark to be printed. The marking system produces the mark, particularly but not exclusively, using a prior art inkjet printing process.

During the printing process, an encoder system monitors the position and speed of the print head and synchronises the application of data and control signals. The encoder system compensates variations in acceleration and velocity such that data is only printed when the print head is in the correct position. This produces a highly accurate linearity of print whilst utilising low spec components. The energy output by the print head is also adjusted according to the detected speed of the print head. Fluctuations between encoder signals are further used to indicate the stability of the production process aiding users to maximise manufacturing capacity and anticipate when maintenance will be required. There will now be described in detail, a specific marking and synchronisation system and method of operation of the marking and synchronisation system and a marking and synchronisation method, according to a specific implementation of the present invention. Figure 1 shows a food label mark, comprising a barcode with human readable characters (the numbers at the bottom). The barcode is constructed from lines 101 and spaces 100 which are spatially accurately positioned 102 to create specific characters which are recognised by an appropriate scanning system. The food label mark also contains human readable characters. A marking system, for applying a mark such as the barcode of Figure 1, is shown in Figure 2. Here there is illustrated schematically, in perspective view, a marking system with integrated spatial synchronisation according to a first example embodiment of the present invention. The machine comprises a mounting 207 supporting the single print system 203 comprising a marking device 200 and encoder system 201. A marking control system 208 also contains the user interface visual display unit with associated touch screen 202. The print system 203 is mounted above the items 204 to be marked. Each item 204 to be marked is presented under the printer 203 by a conveyor 205 and held stationary whilst the full mark 206 is applied to the item 204. The printer is shown in more detail in Figure 3, wherein, there is illustrated schematically a marking device composing a travelling carriage 301 which traverses back and forth along a fixed bar 303. An inkjet print head 300 which positions a plurality of jet elements (pixels) arranged across the print head 300 and which are rapidly switched to generate drops of ink pigment which bond to the substrate 302 being printed upon. The switching is controlled by an energy supply to the print head 300.

In Figure 4 there is illustrated schematically the marking device with the travelling carriage 301 upon which is placed the inkjet print head 300 where the assembly traverses along the fixed bar 303. Under the control of the central control system, the carriage assembly is accelerated from its home position 406 along the fixed bar 303 and then maintained at a stable velocity. The central control system controls the print head to deliver pixels 405 thus forming the total image 404 to be printed upon the substrate 302.

Similarly, in Figure 5, there is illustrated schematically the marking device, of the prior art type, comprising the travelling carriage 301 upon which is placed the inkjet print head 300 where the assembly traverses along the fixed bar 303. The graph in the lower half of the Figure shows a speed against position relationship for the carriage 301. Under the control of the central control system, the carriage assembly is accelerated from its home position 506 along the fixed bar 303 and then maintained at a stable velocity 508. The central control system controls the print head to deliver pixels 405 thus forming the total image 404 to be printed upon the substrate 302. The carriage assembly requires a settling time before the first line of the image is printed 509 to allow for velocity variations 510 due to the effect of inertia caused by the rapid acceleration of the carriage assembly 301. When the complete image has been printed 507 the carriage assembly is decelerated 511 then returned to home 506 ready for another print operation.

Figure 6 shows a view similar to Figure 5, in which the prior art marking device reduces the print cycle time by printing as soon as possible, but produces unacceptable print quality. The marking device comprising the travelling carriage 301 upon which is placed the inkjet print head 300 where the assembly traverses along the fixed bar 303. Under the control of the central control system, the carriage assembly is accelerated from its home position 506 along the fixed bar 303. The central control system controls the print head to deliver a mark 404 to be printed upon the substrate 302 without waiting for a settling time 510 to pass or achieving a stable velocity 508. The lines of image are poorly spaced and of varying sizes, as shown at 405 and 612. As a result, the poor spatial quality of the printed image will result in barcodes being unreadable by electronic scanners and human readable characters being rejected by on-line image verification systems. In Figure 7 there is illustrated schematically a marking device according to an example embodiment of the present invention, which reduces the print cycle time, but still produces high quality print. The marking device composes a travelling carriage 701 upon which is placed an inkjet print head 700 where the assembly traverses along a fixed bar 703. Under the control of the central control system, the carriage assembly is accelerated from its home position 706 along the fixed bar 703. The central control system controls the print head to deliver a line of image 704 to be printed upon the substrate 702 without waiting for a settling time 710 or achieving a stable velocity 708.

An encoder system (shown in more detail below with reference to Figures 12 to 14) monitors the carriage assembly 701 displacement as the carriage traverses the length of the fixed bar 703 and produces a signal 713 coincident to the start position of each image line to be printed. The central control system uses the encoder signal to synchronise the printing of each line of image irrespective of carriage velocity 708. Lines of printed image remain evenly spaced and of equal size, as shown at 705 and 712. The encoder system is detecting the speed and position of the carriage 701 , and this used to determine the timing and energy output of the print head 700. Therefore, with a reduced print cycle time, the carriage assembly requires less time to complete the print operation 706 consequently increasing overall productivity of the host packaging machine.

Figure 8 shows schematically in perspective view a prior art marking device comprising an inkjet print head 800, fitted to a carriage 801 which positions a plurality of jet elements (pixels) arranged across the print head at a pitch, but not exclusively, in excess of 300dpi and which are rapidly switched to generate droplets of ink. Items to be marked 802 are positioned beneath the print head, a synchronised signal from the host packaging line requests a marking operation. The marking device control system employs a motor 805 and pulley belt 806 to accelerate the carriage assembly 801 comprising pulley belt connection 804 and the print head 800, along the guide bars 803.

Similarly in Figure 9, there is illustrated schematically in perspective view the prior art marking device comprising the inkjet print head 800, carriage assembly 801 and motor device 805. The items to be marked 802 are positioned beneath the print head, a synchronised signal from the host packaging line requests a marking operation. The marking device control system employs the motor 805 and pulley belt 806 to accelerate the carriage assembly 801 along the guide bars 803. When the carriage has stabilised at a velocity, the marking device control system prints individual lines of the image upon the substrate 802. Once the full image 908 has been printed the carriage assembly is decelerated and reversed back to its original position ready to repeat the printing process.

Figure 10 shows schematically a marking device according to an example embodiment of the present invention, and comprises an inkjet print head 1000, fitted to a carriage 1001 which positions a plurality of jet elements (pixels) arranged across the print head at a pitch, but not exclusively, in excess of 300dpi and which are rapidly switched to generate droplets of ink. Items to be marked 1002 are positioned beneath the print head, a synchronised signal from the host packaging line requests a marking operation. The marking device control system employs, particularly but not exclusively, an electrical solenoid 1005 which attracts the rod 1006. The rod contains regular position marks 1006 which are monitored by an encoder 1007. The rod 1006 is coupled to the carriage assembly 1004 and when the solenoid 1005 is energised by the marking device control system, the carriage assembly accelerates towards the solenoid 1005, mounted on further rods 1003. Figure 11 shows illustrated schematically the marking device according to the example embodiment of the present invention, following printing. The device comprises the inkjet print head 1000 fitted to the carriage 1001, electrical solenoid 1005 and an encoder 1007. Items to be marked 1002 are positioned beneath the print head, a synchronised signal from the host packaging line requests a marking operation. The marking device control system employs an electrical solenoid 1005 which attracts the rod 1006. The rod contains regular position marks 1006 which are monitored by an encoder 1007. The rod 1006 is coupled to the carriage assembly 1004 and when the solenoid 1005 is energised by the marking device control system, the carriage assembly accelerates towards the solenoid 1005.

The marking device control system prints individual lines of the image 1108 upon the substrate 1002 synchronised to the marks on the rod 1106 detected by the encoder 1107. Once the full image 1108 has been printed the carriage assembly is decelerated and the solenoid polarity reversed to return the carriage back to its original position ready to repeat the printing process.

Figure 12 shows part of a further embodiment of a marking device 10 according to an example of the invention. The marking device is arranged to apply a mark to products or their packaging. A frame 12 has moveably mounted thereon a carriage 14. The carriage 14 on the opposite side of the frame 12 has a print head mounted thereon. A pneumatic piston 16 drives a carriage 18, which through an arm 20 moves the moveable carriage 14, which therefore moves the print head over packing being marked.

The device 10 also includes an encoder system 22 arranged to detect the speed and position of the moveable carriage 14. The encoder system 22 comprises an encoder strip 24 and an optical device 26 arranged to read the encoder strip 24. The optical device 26 is mounted on the moveable carriage 14. The encoder strip 24 is a pre-printed strip of plastic that has in the order of 10 lines per mm printed thereon, in a regular pattern. As the moveable carriage 14 moves, thereby moving the print head, the optical device 26 is passing over the encoder strip 24. The optical device 26 reads the printed pattern on the strip 24 as it moves, and this is used to calibrate the current movement of the moveable carriage 14, in real time. This is used to calculate the current speed and the current position of the moveable carriage 14.

The device 10 also includes a control system (not shown) that is arranged to control the marking device 10, the control system being arranged to control the energy output of the print head according to the speed and position of the moveable carriage 14. The feedback provided by the encoder system 22 enables the control system to control accurately the energy output of the print head. This means that it is no longer necessary to wait for the moveable carriage 14 to reach a constant speed, and only print when the moveable carriage 14 is moving at that constant speed (as in prior art systems). As soon as the piston 16 operates to drive the movement of the moveable carriage 14, then the control system can operate to generate printing at the print head, as the encoder system 22 is providing the information about the speed and position of the moveable carriage 14.

Many advantages accrue from the system shown in Figure 12. For example, much cheaper components can be used to drive the movement of the moveable carriage 14, because accuracy of that movement is no longer paramount. A very regular graph of the acceleration and speed of the moveable carriage 14 is no longer required, as the actions of the encoder system 22 and the control system compensate for any irregularities.

Degradation of the components of the marking device 10 is also no longer a problem. If the moveable carriage 14 is, over time, taking longer to reach a specific point in its movement (owing to wear of bearings for example) then this is automatically compensated for, because the optical reader 26 is determining very precisely the position of the moveable carriage 14. Indeed the device 10 will be aware of degradation through the feedback, and can provide warnings to a user that the device is no longer working as fast as previously, but crucially this does not affect the quality of the printed mark, as the print head is always placing the elements of the mark in the right place, even if this is taking slightly longer than optimum.

Figures 13 and 14 show end views of the device 10 of Figure 12. In Figure 13, the moveable carriage 14 is in the home position, the same as in Figure 12. The frame 12 mounts the moving parts, and the piston 16 drives, through the carriage 19 and arm 20, the moveable carriage 14. The encoder system 22 comprises the encoder strip 24 (printed with a regular pattern) and optical reader 26, which is mounted on the moveable carriage 14, and moves with the movement of the carriage 14.

In Figure 14, the moveable carriage 14 has been driven by the piston 16 away from its home position and into a printing cycle. The moveable carriage 14 moves the print head over the substrate being printed upon. The encoder system 22 is determining the position and speed of the moveable carriage 14, and this is used by the control system to calculate when to provide energy to the print head for printing. The speed of the moveable carriage 14 is used to determine how much energy to use to achieve the desired result. Therefore the control system is using the position of the moveable carriage 14 to determine when to fire the print head, and the speed of the moveable carriage 14 to determine how much energy to use in the firing.

Claims

1. A marking system comprising

• a marking device arranged to apply a mark to products or their packaging, the marking device comprising a print head mounted on a moveable carriage,

• an encoder system arranged to detect the speed and position of the moveable carriage, and

• a control system arranged to control the marking device, the control system arranged to control the energy output of the print head according to the speed and position of the moveable carriage.

2. A system according to claim 1, wherein the encoder system comprises an encoder strip and an optical device arranged to read the encoder strip.

3. A system according to claim 2, wherein the optical device is mounted on the moveable carriage.

4. A system according to claim 1 , 2 or 3, wherein the control system comprises a user interface.

5. A system according to any preceding claim, wherein the mark comprises machine readable or human readable marks or a combination of machine readable and human readable marks.

6. A system according to any preceding claim, and further comprising a visual display device, the visual display device arranged to display at least one display interface.

7. A system according to any preceding claim, wherein the marking device and encoder system are housed within a single housing.

8. A system according to any one of claims 1 to 6, wherein the marking device and encoder system are separated into marking device and encoder device under the control of the control system.

9. A marking method comprising

• applying a mark to products or their packaging, from a marking device comprising a print head mounted on a moveable carriage,

• detecting the speed and position of the moveable carriage, and • controlling the marking device, thereby controlling the energy output of the print head according to the speed and position of the moveable carriage.

10. A method according to claim 9, wherein the detecting of the speed and position of the moveable carriage is carried out by an encoder system comprising an encoder strip and an optical device arranged to read the encoder strip.

11. A method according to claim 10, wherein the optical device is mounted on the moveable carriage.

12. A method according to claim 9, 10 or 11 , and further comprising receiving input from a user interface.

13. A method according to any one of claims 9 to 12, wherein the mark comprises machine readable or human readable marks or a combination of machine readable and human readable marks.

14. A method according to any one of claims 9 to 13, and further comprising displaying at least one display interface.

15. A method according to any one of claims 9 to 14, and further comprising recording and analysing consecutive compensation parameters to establish the stability of the production process and likely probability of rejected marks.