A printing apparatus and method of operating a printing apparatus

Abstract

A printing apparatus and a method of operating a printing apparatus including a controller and a print head having a plurality of heating elements for selective heating to melt ink from a tape onto a substrate, the controller controlling the heating elements, including the steps of: obtaining a print speed of the printing apparatus, determining optimised signal characteristics for controlling one or more of the plurality of heating elements, wherein the optimised signal characteristics includes a supply voltage, and performing a printing operation using the optimised signal characteristics.

Description

[0001] A printing apparatus and method of operating a printing apparatus

[0002] FIELD

[0003] Embodiments of the present invention relate to a printing apparatus and method of operating a printing apparatus.

[0004] BACKGROUND

[0005] In the field of thermal transfer printing, a reel of inked ribbon (hereinafter “tape”) is typically mounted onto a spool support. The spool support is rotatable to transfer tape from the first (supply) spool to a second (take up) spool into which tape may be wound after / during use. The second spool support is also rotatable. Various methods of operation of such a reel to reel tape drive are known in the art. Tape is typically transferrable between the pair of spools in both directions, but generally speaking, as ink is removed from the tape during successive printing operations, the used tape is wound onto the second “take-up” spool, such that the diameter of the supply spool decreases and the diameter of the take-up spool increases.

[0006] A print head is provided which includes multiple heating elements. As the inked ribbon is moved through the printing apparatus (between the spool supports), it is passed under the print head (and the heating elements). The inked ribbon is sandwiched between the print head and a substrate on which an image is to be printed. One or more heating elements are heated to melt a portion of ink on the ribbon and it is transferred to the substrate to print.

[0007] The heating elements are small resistors (typically of the order of 83|jm x 62pm) - thus, the print head includes an array of small resistors. The resistors are typically arranged in a line across the print line of a print head. This line of energised resistors generates heat, which is used to melt ink on the ribbon. The melted ink is used to produce a line of a printed image (which may be around 1 / 12mm for example).

[0008] BRIEF DESCRIPTION OF THE INVENTION

[0009] According to a first aspect of the invention we provide a method of operating a printing apparatus including a controller and a print head having a plurality of heating elements for selective heating to melt ink from a tape onto a substrate, the controller controlling the heating elements, including the steps of: obtaining a print speed of the printing apparatus, determining optimised signal characteristics for controlling one or more of the plurality of heating elements, wherein the optimised signal characteristics includes a supply voltage, and performing a printing operation using the optimised signal characteristics.

[0010] The supply voltage may be related to the print speed (i.e. the supply voltage chosen may depend predominantly or entirely on the print speed required by the printing apparatus). As such, a lower supply voltage may be set for a lower print speed and a higher supply voltage may be set for a faster print speed.

[0011] The optimised signal characteristics may further include one or more of: a supply signal duration, and a signal modulation.

[0012] The supply signal duration may be related to the print speed (i.e. the supply signal duration chosen may depend predominantly or entirely on the print speed required by the printing apparatus). As such, a longer supply signal duration may be set for a lower print speed and a shorter supply signal duration may be set for a higher print speed.

[0013] The signal modulation may include switching the supply voltage at a predetermined rate between two or more values. Alternatively or additionally the signal modulation may include switching the supply signal duration at a predetermined rate between two or more values. In other words, the signal modulation may include two parts - one dictating the rate of switching of the supply voltage and one dictating the rate of switching of the supply signal duration. The signal modulation may be a frequency with which the supply voltage or the supply signal duration changes.

[0014] The signal modulation may alter the supply voltage and / or the supply signal duration on the basis of at least one of: line-by-line printing action, a print-by-print printing action, and a predetermined time interval.

[0015] The signal modulation may be between around 8 Hz and 1 kHz. This may be for one or both of the supply voltage and supply signal duration.

[0016] The print speed may be below around 10mm / s or up to around 1 m / s. A single print line may be around 1 / 12mm wide.

[0017] The step of determining optimised signal characteristics may further include using one or more of: materials being printed on which may include one or more of: a substrate material, a type of printing tape, and what is being printed (i.e. the pattern / image being transferred from the tape to the substrate).

[0018] According to a second aspect of the invention we provide a printing apparatus including a print head and a controller operable according to the first aspect of the invention.

[0019] The print head may include a plurality of heating elements. Optionally, each heating element may include a resistor. The plurality of heating elements may be formed in a single line. Optionally, each heating element may be around 83pm x 62pm in size.

[0020] DESCRIPTION OF THE DISCLOSURE

[0021] The present invention is particularly useful in so called continuous printing. In this type of transfer printing the ribbon and substrate continually move past the print head, so that the next line can be printed (i.e. fresh ribbon and substrate are presented to the print head for the next line print).

[0022] The active resistors are turned on by a signal called the strobe. The duration of the strobe and the voltage supplied to the print head, dictates the resistor’s peak temperature and the speed at which it reaches that temperature.

[0023] The time between any two printed lines is dictated by the speed of the ribbon and substrate, and the print resolution. At a ribbon / substrate speed of 1m / s, the time is 83ps. Thus, the strobe duration can be a maximum of 83ps before the next line needs to be printed.

[0024] Essentially, the disclosure relates to a method of operating a printing apparatus (which has a controller and a print head). The print head includes a plurality of heating elements - during printing the heating elements are selectively heated (which melts ink from a tape onto a substrate). The heating elements may be resistors arranged in a predetermined configuration on the print head - this may be a linear array across the width of the print head.

[0025] The controller controls the operation of the heating elements. In other words, the controller determines and applies the operating signals to ensure the heating elements heat (and cool) as desired to obtain the predetermined printing patterns on the substrate.

[0026] The controller obtains a print speed of the printing apparatus (i.e. the speed at which the next printing operation will occur). In some embodiments, the controller assesses the print speed by monitoring a speed of the substrate past the print head (or another sensor device). However, it should be appreciated that the print speed could be entered by an operator and / or the print speed could come from a network connection or memory. The print speed may be constant for multiple printing operations (i.e. an entire print run) or it may change on a schedule. Thus, the controller may obtain a print speed that will occur for an extended time period (e.g. a print run) or the print speed may fluctuate according to a predetermined schedule.

[0027] The controller determines optimised signal characteristics for controlling one or more of the plurality of heating elements. In other words, the controller uses the print speed information to determine how to control the heating elements. The optimised signal characteristics includes a supply voltage (i.e. the voltage that is applied to the heating elements to cause the required heating for printing).

[0028] In embodiments, the optimised signal characteristics further includes one or more of a supply signal duration (also known as the strobe length), and a signal modulation. In other words, the controller / control system operates a dynamic supply voltage and strobe signal control to the print head (and more specifically, to the heating elements on the print head).

[0029] In some embodiments, the optimised signal characteristics are configured for each individual (i.e. a single) heating element or a group of heating elements (i.e. the elements could be grouped by location) or according to knowledge of the printing that will occur (i.e. it may be advantageous to control a group of elements that the controller knows will be used in a certain manner in the printing operation).

[0030] In some embodiments, the controller determines the optimised signal characteristics from additional information about the next printing operation. The step of determining optimised signal characteristics may include one or more of: materials being printed on (e.g. a substrate material or the type of inked tape being used) and what is being printed (e.g. the characteristics of the image being printed on the substrate). In other words, the control system could use knowledge of what is being printed (i.e. the configuration of the printed image), and materials on which printing is being performed (i.e. whether the substrate requires a specific maximum printing temperature or its relative ease of printing, etc.) to determine an ideal supply voltage and strobe.

[0031] It should be appreciated that modern print heads are capable of receiving more energy / power than previous print heads. This allows the print heads to generate more heat and print onto increasingly difficult ribbons and substrates. The amount of energy that can be supplied to the resistors is still limited by the length of the strobe if the print head supply voltage is a constant.

[0032] Thus, embodiments of the present method alters the strobe and / or voltage provided to improve printing (this could make it possible to print at a faster rate or with better quality or on more difficult mediums). Print speed is limited by the ability to receive and process (known as ability to “clock”) print line data. As the clock rate increase, the print speed will put further pressure on the strobe and voltage (faster print speeds will reduce the maximum strobe time). While a higher supply voltage can improve this situation (since the heating elements heat up quicker) it can be at the expense of the slower speeds - making the printing apparatus less able to cope with slower printing.

[0033] The present disclosure provides a printing apparatus that can operate in a manner that can allow the printing apparatus to print slow and / or fast depending on what is desired. The controller essentially alters the supply voltage / strobe length according to the predetermined print speed.

[0034] In some embodiments, the supply voltage is related to the print speed. As such, a lower print speed will result in a lower supply voltage. Likewise, a higher / faster print speed will result in a higher supply voltage.

[0035] In some embodiments, the controller will also set a strobe length / supply signal duration. As such, a longer supply signal duration may be set for a lower print speed and a shorter supply signal duration may be set for a higher print speed.

[0036] In some embodiments, the controller combines the supply voltage and the supply signal duration to output a balanced / optimised combination of the two. For example, a slower print speed will mean that the supply signal duration may be longer because the heating elements have more time between printing operations (meaning that there is more time for the heating elements to reach a required temperature) - as such the controller can extend the strobe length and lower the supply voltage. Thus, the heating elements heat to a printing temperature over a longer period of time (the heating rate is lower).

[0037] Conversely, for a higher print speed the controller may alter the supply voltage and supply signal duration in an opposing manner. Since the print speed is higher, the heating elements have less time between printing operations (and, thus, less time to heat to the required temperature). As such, the controller may shorten the supply signal duration and increase the supply voltage. Thus, the heating elements heat to the printing temperature over a shorter period of time (and heating rate is higher).

[0038] The target speed of the substrate is determined at the point the printing apparatus receives the “print go” signal. For example, this can range from speeds less than 10mm / s to more than 1m / s. The printing apparatus (i.e. the controller) makes the decision to alter the print head supply voltage to allow the resistor(s) to receive the most suitable strobe duration. In more detail, at high speeds, the voltage can be increased to allow energy to be applied to the resistor(s) quicker. The strobe must be shortened to allow fast printing so the increase in voltage allows the resistors to heat quicker and allows printing within the limited strobe duration. This results in higher resistor temperatures but a shorter period of heated resistors, so that the next line can be printed.

[0039] At slower speeds, a higher voltage would mean the resistor(s) heat up too fast and are therefore forced to cool down long before the end of their printing area (as discussed above, around 1 / 12mm). This would result in a smaller area of ink being melted, which may not be long enough for the printed line.

[0040] Thus, instead of a higher voltage, the printing apparatus will lower the voltage. However, the strobe will have an extended duration. The lower voltage over a longer period of time allows the resistors to heat up slower. Thus, they are heated for a prolonged time, which results in the ability to melt a full 1 / 12mm worth of ink.

[0041] In some embodiments, the controller implements a signal modulation. In embodiments, the signal modulation includes switching the supply voltage and / or the supply signal duration at a predetermined rate between two or more values. The signal modulation is related to changes in print speed and, thus, the supply voltage and / or the supply signal duration is alternated / switched between different values. As such, the signal modulation provides one or more frequencies with which the supply voltage and / or the supply signal duration may be changed.

[0042] For example, an option could be to modulate the strobes during the 1 / 12mm printed line. Thus, the resistor(s) temperature may be balanced by modulating the strobes and / or the supply voltage depending on the speed of printing desired, etc.

[0043] The modulation of the supply voltage and / or the supply signal duration can be performed on a print-by-print or potentially line-by-line basis or any other time domain. Care will be required developing a suitable power supply for a line-by-line modulation due to the high switching frequency required (> 1 KHz). Print-by-print modulation may be advantageous from this point of view since the frequency of switching required for that is relatively low (< 8 Hz) - this is easier to implement in power supply components.

[0044] When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The invention may also broadly consist in the parts, elements, steps, examples and / or features referred to or indicated in the specification individually or collectively in any and all combinations of two or more said parts, elements, steps, examples and / or features. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein.

[0045] Protection may be sought for any features disclosed in any one or more published documents referenced herein in combination with the present disclosure. Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and / or to encompass equivalents.

Claims

CLAIMS1 . A method of operating a printing apparatus including a controller and a print head having a plurality of heating elements for selective heating to melt ink from a tape onto a substrate, the controller controlling the heating elements, including the steps of: obtaining a print speed of the printing apparatus, determining optimised signal characteristics for controlling one or more of the plurality of heating elements, wherein the optimised signal characteristics includes a supply voltage, and performing a printing operation using the optimised signal characteristics.

2. A method of operating a print head according to claim 1 wherein the supply voltage is related to the print speed such that a lower supply voltage is set for a lower print speed and a higher supply voltage for a faster print speed.

3. A method of operating a print head according to any of claims 1 or 2 wherein the optimised signal characteristics further includes one or more of: a supply signal duration, and a signal modulation.

4. A method of operating a print head according to claim 3 wherein the supply signal duration is related to the print speed such that a longer supply signal duration is set for a lower print speed and a shorter supply signal duration is set for a higher print speed.

5. A method of operating a print head according to any one of claims 3 or 4 wherein the signal modulation includes switching the supply voltage or the supply signal duration at a predetermined rate between two or more values.

6. A method of operating a print head according to claim 5 wherein the signal modulation is a frequency with which the supply voltage or the supply signal duration changes.

7. A method of operating a print head according to any of claims 5 to 6 wherein the signal modulation alters the supply voltage or the supply signal duration on the basis of at least one of: line-by-line printing action, a print-by-print printing action, and a predetermined time interval.

8. A method of operating a print head according to any one of claims 5 to 7 wherein the signal modulation is between around 8 Hz and 1 kHz9. A method of operating a print head according to any one of the preceding claims wherein the print speed is below 10mm / s or up to 1m / s.

10. A method of operating a print head according to any one of the preceding claims wherein a single print line is around 1 / 12mm wide.

11. A method of operating a print head according to any one of the preceding claims wherein the step of determining optimised signal characteristics further includes using one or more of: materials being printed on which includes one or more of: a substrate material, a type of printing tape, what is being printed.

12. A printing apparatus including a print head and a controller operable according to the method of operating a print head according to any one of the preceding claims.

13. A printing apparatus according to claim 12 wherein the print head includes a plurality of heating elements, and optionally each heating element includes a resistor.

14. A printing apparatus according to claim 13 wherein the plurality of heating elements are formed in a single line, and optionally each heating element is around 83pm x 62pm in size.