Overcoat printing and servicing

1. An apparatus comprising:

a depositing mechanism to perform an overcoat depositing operation, the depositing mechanism comprising a plurality of print head arrays each being arrangeable in a deposit position to deposit an overcoat layer onto a substrate and a service position to enable servicing to be performed; and

an array controller to cause a first print head array of the plurality of print head arrays to be moved periodically from the deposit position to the service position according to a predefined servicing sequence during an ongoing overcoat depositing operation performed by the depositing mechanism;

wherein the array controller moves the first print head array from the deposit position to the service position based on a predefined service interval over which the first print head array is able to deposit an overcoat fluid to form the overcoat layer without clogging occurring; and

wherein the predefined servicing sequence has the first print head array active at the deposit position for twice as long a period of time as the first print head is being serviced at the service position.

2. The apparatus of claim 1 , wherein the predefined service interval is determined by at least one characteristic of the overcoat layer.

3. The apparatus of claim 1 , wherein the array controller causes a second further print head array of the plurality of print head arrays to be moved from the deposit position to the service position when the first print head array is in the deposit position.

4. The apparatus of claim 1 , comprising a service module to perform servicing on the first print head array when the first print head array is in the service position, wherein the service module is moveable between different print head arrays of the plurality of print head arrays.

5. The apparatus of claim 1 , wherein the predefined servicing sequence is determined by the number of print head arrays in the plurality of print head arrays.

6. The apparatus of claim 1 , the apparatus being arranged to deposit the overcoat layer over an ink layer printed upon the substrate.

7. The apparatus of claim 1 , wherein the array controller moves at least two of the plurality of print head arrays to the service position for simultaneous servicing.

8. The apparatus of claim 1 , wherein the array controller moves the at least one print head array vertically away from the substrate to the service position.

9. The apparatus of claim 1 , further comprising a supply of a different fluid from the overcoat fluid, the at least one print head array being supplied with the different fluid for spitting to clean the at least one print head array whilst in the service position.

10. A non-transitory computer-readable storage medium comprising a set of computer-readable instructions stored thereon, which, when executed by a processor, cause the processor to perform a method of controlling a plurality of print head arrays each being arrangeable in a deposit position to deposit an overcoat fluid onto a substrate and a service position to enable servicing to be performed, the method comprising:

causing the first print head array to be moved from the deposit position to the service position according to a periodic servicing sequence, the periodic servicing sequence determined by a period of time at which the first print head array deposits the overcoat fluid without becoming clogged;

causing the second print head array to be moved from the service position to the print position to deposit the overcoat fluid whilst a servicing operation is performed on the first print head array; and

wherein the first print head array is active at the print position and inactive at the service position for equal amounts of time.

11. The non-transitory computer-readable storage medium of claim 10 , the method further comprising moving at least two of the plurality of print head arrays to the service position for simultaneous servicing.

12. A method of operating a plurality of print head arrays including at least a first print head array and a second print head array, each of the plurality of print head arrays being arrangeable independently in a print position to print an overcoat fluid onto a print medium and in a service position to enable servicing to be performed, the method comprising:

moving the first print head array from the print position to the service position according to a periodic servicing sequence;

moving the second print head array from the service position to the print position to print the overcoat fluid whilst a servicing operation is performed on the first print head array; and

and

wherein one from the set of “A” and “B” occurs, where “A” is that the first print head array is active at the print position and inactive at the service position for equal amounts of time, and “B” is that the first print head array active at the print position for twice as long a period of time as the first print head is being serviced at the service position.

13. The method of claim 12 , wherein the periodic servicing sequence has a predefined service period between servicing operations for each of the plurality of print head arrays, the predefined service period determined by a time interval over which the first print head array is able to reliably deposit the overcoat fluid without becoming clogged.

14. The method of claim 13 , wherein the predefined service period is determined by at least one property of the overcoat fluid.

15. The method of claim 12 , comprising:

moving the first print head array from the service position to the print position; and

moving the second print head array from the print position to the service position when the first print head array is in the print position.

16. The method of claim 12 , wherein the predefined servicing sequence is determined by the number of print head arrays in the plurality of print head arrays.

17. The method of claim 12 , comprising printing the overcoat fluid on top of a coloured ink.

18. The method of claim 12 , further comprising moving at least two of the plurality of print head arrays to the service position for simultaneous servicing.