Printers

Abstract

A printer (5) operable to print a message in strokes on a substrate (7) passing in a print direction (8) along a moving line (6), wherein the printer is operable (15) to receive an indication of an allowable increase in length in the print direction of a message due to an increase in length in the print direction of gaps between successive strokes printed by the printer, to receive (14) an indication (9) of a speed of movement in the print direction of a moving line, to determine from the indication of the speed of movement of the moving line whether an increase in length in the print direction of a message printed by the printer is greater than the allowable increase in length and, if so, to generate an alert.

Claims

1. A method of regulating the operation of a printer printing in strokes on a substrate passing along a moving production line in a print direction, said method being characterised in that it includes a user of said printer defining an allowable amount of stretch in said print direction of a message to be printed by said printer.

2. A method as claimed in claim 1 wherein a speed sensing facility is provided giving an output representative of the speed of said moving production line, said method comprising defining, in units corresponding to the output of said speed sensing facility, target gaps between strokes in said print direction; defining an allowable stretch in said message; and comparing the outputs of said speed sensing facility with said target gaps.

3. A method as claimed in claim 2 wherein the output of said speed sensing facility is provided as encoder pulses and wherein said target gaps are defined in terms of pulses, said method comprising comparing the counts of encoder pulses with the counts representing said target gaps.

4. A method as claimed in claim 3 wherein said printer is provided with a print system into which a message to be printed is loaded, said method comprising programming said print system to determine said target count measures.

5. A method as claimed in claim 2 further including determining and storing a maximum difference between the outputs of said speed sensing facility and said target gaps.

6. A method as claimed in claim 1 further including generating an alert in the event said allowable amount of stretch exceeds a defined limit.

7. A printer operable to print in strokes on a substrate passing along a moving production line, wherein said printer is configured to apply the method claimed in claim 1.

8. A printer operable to print a message in strokes on a substrate passing in a print direction along a moving production line, wherein the printer is operable to receive an indication of an allowable increase in length in the print direction of a message due to an increase in length in the print direction of gaps between successive strokes printed by the printer, to receive an indication of a speed of movement in the print direction of a moving production line, to determine from the indication of the speed of movement of the moving line whether an increase in length in the print direction of a message printed by the printer is greater than the allowable increase in length and, if so, to generate an alert.

9. A printer as claimed in claim 8 comprising a continuous inkjet printer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One embodiment of the invention will now be described with reference to the accompanying drawings in which:

(2) FIG. 1: shows a schematic view of a printer installation to which the invention might be applied;

(3) FIG. 2: shows a block diagram of the method steps used to perform the invention; and

(4) FIGS. 3A to 3C: show examples of acceptable, barely acceptable, and unacceptable stretch of a message.

DETAILED DESCRIPTION OF WORKING EMBODIMENT

(5) The embodiment described herein is directed to a continuous (CIJ) printer but it will be appreciated, by those skilled in the art, that the invention may be applied to any printer that prints in strokes.

(6) Referring to FIG. 1, a CIJ printer 5 is shown alongside a moving line 6 on which articles 7, constituting a substrate, are conveyed in the direction of arrow 8. A speed sensing facility such as encoder 9 is provided to output a sequence of pulses representative of the speed of the line 6.

(7) In the conventional manner the CIJ printer 5 comprises a cabinet 10 and a printhead 11 positioned over the line 6 and connected to the cabinet 10 by an umbilical 12. The cabinet 10 contains the usual mechanical system 13 and electronics system 14 that enables the CIJ printer to operate in the known manner, the umbilical 12 circulating ink and make-up between the cabinet and the printhead in the known manner.

(8) A user interface 15, conventionally comprising a screen and a keyboard, is provided to allow data and instructions to be entered into the printer and line speed data is also entered into the electronics system 14 from the encoder 9.

(9) Turning now to FIG. 2, the invention provides a method which gives a more meaningful alert to a user that print quality has been affected by over-speed situations. In essence the method allows the user to specify an amount of allowable elongation or stretching of a printed message before an alert is raised. Furthermore the user may also be informed of the amount of stretching that has actually been detected to assist with decision-making on how to deal with the alert.

(10) As a first step, the user inputs an amount of allowable elongation or stretch via the user interface 15; this may be in units of distance or encoder-related counts and the value is stored in a register 20 in the electronics system 14 of the printer.

(11) The output signal from encoder 9 is entered and processed at 21, a step which may involve multiplication or division of the encoder frequency, and the resultant signal is then used to increment a counter 22 which represents the distance along the substrate.

(12) The message 23 to be printed on the substrate is loaded into print system 24, the print system analysing the message and establishing a series of charge or voltage values which constitute the vertical drop placements required for each stroke, along with target encoder count values for the horizontal positions of the starts of the strokes which are stored at 25. It will be appreciated that the spacing between strokes may not be constant but may vary according to the message which may contain segments at different pitches.

(13) The encoder counter 22 and the stroke target count 25 are continually compared/subtracted at step 26 and the result is presented to a comparator 27. If the encoder counter 22 is larger than the stroke target 25 by an amount greater than the allowable stretch entered at 20, then an alert is raised at step 28.

(14) The output of the subtract step 26 may also be fed into a peak detector 29 which records the maximum level of stretch observed since the value was last read by the electronics system 14. The value of peak detection may be used alongside the alert notification to give the user an indication of the actual stretch amount seen.

(15) Referring to FIG. 3, the stretch referred to may be better understood by observing the line showing “SELL BY DATE” and the Date “APRIL 17”. In FIG. 3A, the date is shown at the correct spacing while in FIG. 3B the spacing, though still acceptable, is stretched toward the edge of the label. FIG. 3C indicates a print that has been stretched beyond an acceptable level and which would incur an alert as described herein.

(16) Having been alerted, a user may then implement a solution. This solution may involve the use of a faster raster or possibly slowing the line speed, the method chosen depending on the nature of compromise that the user is willing to accept.