Device and method for printing labels by means of thermal printing

Abstract

A device (1) for printing labels (2) by means of thermal printing using a thermal head (3), which has a thermal strip (4), having a counter-pressure element carrier (5), which has a counter-pressure element (6), wherein an insertion gap (7) is formed between the thermal strip (4) and the counter-pressure element (6), through which the label (2) to be printed in each case can be guided, wherein the thermal head (3) is fastened in a movable manner on a thermal head carrier (8) and wherein the thermal strip (4) is pressed with a predetermined contact pressure against the counter-pressure element (6). To reduce the operating costs, the counter-pressure element (6) is movable relative to the insertion gap (7). A method for printing labels (2) using the device (1) is also disclosed.

Claims

1. A device for printing labels by thermal printing having a thermal head, which has a thermal strip, and a counter-pressure element carrier, which has a counter-pressure element, wherein an insertion gap is formed between the thermal strip and the counter-pressure element, through which said insertion gap the label to be printed in each case is guidable, wherein the thermal head is fastened in a movable manner on a thermal head carrier, wherein the thermal strip is pressed against the counter-pressure element with a predetermined contact pressure, wherein the counter-pressure element is movable relative to the insertion gap, wherein the device further has a control device, and wherein the control device is configured to successively: (a) move the counter-pressure element into a first position relative to the insertion gap, in which a contact pressure is smaller than in an end position defined by a first stop or position sensor or counter, in which at the end position the contact pressure is at a maximum value, (b) detect a degree of blackening or color intensity using an optical sensor, (c) compare a detected degree of blackening or color intensity with a predetermined reference value or reference value range for the degree of blackening or color intensity, and (d) move the counter-pressure element in a direction of the thermal strip into a further position, in which the contact pressure is larger than in the first position, if the detected degree of blackening or colour intensity is smaller than the reference value or reference value range.

2. The device according to claim 1, wherein a section of the counter-pressure element carrier or all of the counter-pressure element carrier is linearly or pivotably movable relative to the insertion gap.

3. The device according to claim 2, wherein the counter-pressure element carrier is pivotable about a pivot axis parallel to the insertion gap.

4. The device according to claim 3, wherein the counter-pressure element carrier has a lever arm, which extends from the pivot axis to the counter-pressure element.

5. The device according to claim 3, wherein the counter-pressure element carrier is connected via a gear mechanism to a motor having a motor shaft.

6. The device according to claim 5, wherein the gear mechanism has at least one wheel or wheel segment, which is connected in a rotationally fixed manner to the counter-pressure element carrier, wherein the rotational axis of the gear wheel or wheel segment runs coaxially to the pivot axis of the counter-pressure element carrier, and a drive pinion, which is driven by the motor and is connected in a rotationally fixed manner to the motor shaft.

7. The device according to claim 5, wherein the motor is a stepper motor.

8. The device according to claim 6, wherein the counter-pressure element or the counter-pressure element carrier interacts via the wheel or wheel segment, with a first stop, which delimits movement of the counter-pressure element in the direction of the insertion gap, and/or interacts with a second stop, which delimits movement of the counter-pressure element in a direction away from the insertion gap.

9. The device according to claim 8, wherein the counter-pressure element carrier or the wheel or wheel segment has a groove or a slot, in which a projection is guided, and which forms the first stop and/or second stop.

10. The device according to claim 8, wherein two or more of the thermal head carrier, pivot axis, motor, first stop and second stop are immovable relative to one another.

11. The device according to claim 5, wherein the device has at least one position sensor or the motor has at least one counter.

12. The device according to claim 11, wherein the device has at least one pressure sensor.

13. The device according to claim 4, wherein the control device controls movement of the counter-pressure element or of the section of the counter-pressure element carrier or of the lever arm of the counter-pressure element carrier in the direction of the insertion gap.

14. The device according to claim 12, wherein the control device is configured in such a manner that it controls movement of the counter-pressure element or of the section of the counter-pressure element carrier or of the lever arm of the counter-pressure element carrier depending on sensor signals of the position sensor and/or counter and/or optical sensor and/or pressure sensor.

15. The device according to claim 1, wherein the control device is configured in such a manner that steps (b) to (d) are repeated in sequence until the further position corresponds to the end position.

16. The device according to claim 1, wherein the thermal head is resiliently connected to the thermal head carrier via at least one spiral spring and/or at least one coil spring, and the predetermined contact pressure is a spring force.

17. The device according to claim 16, wherein the predetermined contact pressure provided by the spring force is adjustable.

18. A method for printing labels using a device according to claim 1, said method comprising successive steps of: (a) moving the counter-pressure element in the direction of the thermal strip into the first position, in which the contact pressure is smaller than in the end position defined by the first stop delimiting the movement of the counter-pressure element in the direction of the insertion gap or a position sensor or a counter, in which end position the contact pressure has the maximum value, (b) detecting the degree of blackening or color intensity using the optical sensor, (c) comparing the detected degree of blackening or color intensity with the predetermined reference value or reference value range for the degree of blackening or colour intensity, and (d) moving the counter-pressure element in the direction of the thermal strip into the further position, in which the contact pressure is larger than in the first position, if the detected degree of blackening or color intensity is smaller than the reference value or reference value range.

19. The method according to claim 18, wherein the steps (b) to (d) are repeated in sequence until the further position corresponds to the end position.

20. The method according to claim 18, wherein, before step (a), the counter-pressure element is moved into its end position defined by the first stop or position sensor or the counter and then the contact pressure of the thermal strip relative to the counter-pressure element arranged in the end position is adjusted to the predetermined value.

21. The method according to claim 18, wherein, prior to step (a), the contact pressure is adjusted to the predetermined value by moving the counter-pressure element in the direction of the insertion gap and pressing the counter-pressure element against the thermal strip.

22. A device for printing labels by thermal printing having a thermal head, which has a thermal strip, and a counter-pressure element carrier, which has a counter-pressure element, wherein an insertion gap is formed between the thermal strip and the counter-pressure element, through which insertion gap the label to be printed in each case is guidable, wherein the thermal head is fastened in a movable manner on a thermal head carrier, wherein the thermal strip is pressed against the counter-pressure element with a predetermined contact pressure, wherein the counter-pressure element is movable relative to the insertion gap, wherein the device further has a control device, and wherein the control device is configured in such a manner that it controls movement of the counter-pressure element or of a section of the counter-pressure element carrier or of a lever arm of the counter-pressure element carrier depending on values of temperature or electrical resistance of individual or all heating resistors of the thermal strip read out from the thermal strip.

23. The device according to claim 22, wherein the device has at least one optical sensor.

24. A method for printing labels using a device according to claim 22, said method comprising successive steps of: (a) moving the counter-pressure element in the direction of the thermal strip into the first position, in which the contact pressure is smaller than in the end position defined by the first stop delimiting the movement of the counter-pressure element in the direction of the insertion gap or a position sensor or a counter, in which end position the contact pressure has the maximum value, (b) reading out the value of the temperature or the electrical resistance of individual or all heating resistors of the thermal strip, (c) comparing the read value of the temperature or the electrical resistance with the predetermined reference value or reference value range for the temperature or the electrical resistance, and (d) moving the counter-pressure element in the direction of the thermal strip into the further position, in which the contact pressure is larger than in the first position, if the read out value of the temperature or the electrical resistance is smaller than the reference value or reference value range.

Description

(1) There is a multiplicity of possibilities for configuring and developing the device according to the invention and the method according to the invention. In this regard, reference may be made to the patent claims dependent on Patent Claims 1 and 21 on the one hand, and to the description of an exemplary embodiment on the other hand in connection with the drawing. In the drawing:

(2) FIG. 1 shows a device for printing labels by means of thermal printing in a first setting,

(3) FIG. 2 shows a device for printing labels by means of thermal printing in a second setting, and

(4) FIG. 3 shows a device for printing labels by means of thermal printing in a third setting.

(5) The device 1 shown in FIGS. 1 to 3 is used for printing labels 2 for example by means of direct thermal printing. The labels 2 are by way of example self-adhesive labels 2 here, which are arranged in a detachable manner on a carrier strip (not illustrated), which is mounted in an unwindable manner as rolled material in the printing device or the printer 1.

(6) The printing device 1 has a thermal head 3 with a thermal strip 4, wherein the thermal strip 4 has a multiplicity of heating resistors (dots) 29, by means of which a printed image of a certain print quality is created on the upper side of the respective label 2, which is guided past the thermal strip 4.

(7) The thermal head 3 is resiliently connected to a thermal head carrier 8 together with the thermal strip 4, here for example by means of a spiral spring 26 constructed as a leaf spring and/or a coil spring 27 constructed as a compression coil spring (here both springs are illustrated for better understanding, although also only one spring or even no spring may be provided). The thermal head carrier 8 is arranged in a fixed manner, that is to say in a non-movable manner, in the device 1.

(8) A counter-pressure element 6 is arranged on the side opposite the thermal strip 4, that is to say here below the label 2, which counter-pressure element is a constituent of a pivotably arranged counter-pressure element carrier 5. The counter-pressure element 6 is here constructed as a strip coated with printing felt, but can fundamentally also be constructed as a print roller.

(9) An insertion gap 7 is formed between the thermal strip 4 and the counter-pressure element 6, through which the label 2 is guided. In this state, the thermal strip 4 presses against the counter-pressure element 6 and thus holds the label 2 or the carrier strip during the printing process in connection with a pulling device (not illustrated), e.g. a winding device for the carrier strip, under tension.

(10) The contact pressure, with which the thermal strip 4 presses against the counter-pressure element 6 during printing operation or in one of the operating positions, is on the one hand determined by the spring force of the springs 26 and 27 and on the other hand by the position of the counter-pressure element carrier 5 or counter-pressure element 6. Thus, the counter-pressure element carrier 5 can be pivoted about a pivot axis 10 running parallel to the insertion gap 7, as a result of which a section 9 or lever arm 11 of the counter-pressure element carrier 5 moves relatively to the insertion gap 7, that is to say in the direction of the insertion gap 7 or counter to the direction of the insertion gap 7. In this case, in the operating position of the counter-pressure element 5 shown in FIG. 1, the contact pressure is still relatively low, whereas in the operating position shown in FIG. 2 (first end position) the contact pressure is at a maximum. In this manner, it is possible, starting with the position shown in FIG. 1, to move the counter-pressure element 6 or the counter-pressure element carrier 5 over time (during the service lift of the thermal strip 4) step-by-step in the direction of the end position illustrated in FIG. 2, specifically whenever the degree of blackening or colour intensity of the printing falls below a predetermined reference value.

(11) As FIG. 3 shows, the counter-pressure element carrier 5 can also be moved into an open position (second end position or maintenance position). In this open position (which is only illustrated in some sections in FIG. 3 for reasons of clarity), the counter-pressure element 6 no longer touches the thermal strip 4, but rather is spaced so far from the thermal strip 4, that the interior of the device 1 is easily accessible through the thus formed opening between the thermal strip 4 and the counter-pressure element 6, for example for maintenance, cleaning or repair purposes or for the exchange of the label roll or thermal strip.

(12) In order to be able to move the counter-pressure element carrier 5 and correspondingly the counter-pressure element 6 between the illustrated positions, the counter-pressure element carrier 5 is connected via a gear mechanism 12 to a motor 13, which has a motor shaft 14. The motor 13 effects the movements of the counter-pressure element carrier 5. Here, the gear mechanism 12 has a gear wheel segment 15 connected to the counter-pressure element carrier 5, the rotational axis 16 of which runs coaxially to the pivot axis 10, and also a drive pinion 17 driven by the motor 13 and connected in a rotationally fixed manner to the motor shaft 14. The drive pinion 17 engages into the gear wheel segment 15 and thus transmits the rotational movement of the motor shaft 14 to the counter-pressure element carrier 5. The motor 13 is a stepper motor, which is connected to a counter 28. The counter 28 is configured to count the individual steps (full steps or partial steps) in the respective rotational direction of the stepper motor and thus to travel to the individual positions of the counter-pressure element carrier 5 in a reproducible manner.

(13) In addition, the counter-pressure element carrier 5, here in a disc-shaped section, which carries the wheel segment 15, is provided with a groove 20. A fixed, bolt-shaped projection 21 is guided in the groove 20 relatively to the pivot axis 10, which projection forms a first stop 18 on its underside illustrated here and a second stop 19 on its upper side. The first stop 18 delimits the movement of the counter-pressure element 6 in the direction of the insertion gap 7, thus upwards here. The second stop 19 delimits the movement of the counter-pressure element 6 in the direction away from the insertion gap 7, thus downwards here.

(14) In the present exemplary embodiment, the thermal head carrier 8, the pivot axis 10, the motor 13 and the bolt 21 and thus the first and second stops 18 and 19 are non-movable relative to one another. It would however also be conceivable that the thermal head carrier 8 is adjustable.

(15) The counter-pressure element carrier 5 is further provided with a position sensor 22, here on the underside thereof, which position sensor is used for detecting the individual positions of the counter-pressure element carrier 5 or counter-pressure element 6, including at least the positions in FIGS. 1 to 3. Fundamentally, the position sensor 22 can also detect each intermediate position, to which it is possible to travel using the stepper motor 13.

(16) The device 1 additionally has an optical sensor 23, which can be camera. The optical sensor 23 is arranged at a location of the device 1, in which it can detect the degree of blackening or colour intensity of the printed image of this label 2 directly during the printing of a label 2.

(17) Furthermore, a pressure sensor 24 is provided in the counter-pressure element 6, which is used for detecting the contact pressure of the thermal strip 4 on the counter-pressure element 6.

(18) The sensors 22, 23 and 24 and also the counter 28 are (electronically) connected to a control device 25, which is likewise part of the device 1. The control device 25 controls the movement of the counter-pressure element carrier and therefore of the counter-pressure element 6 or the section 9 or lever arm 11 relatively to the insertion gap 7 depending on the sensor signals and the information from the counter 28. In addition, the control device 25 can also be (electronically) connected to the thermal strip and read out values of the temperature or the electrical resistance of individual or all heating resistors 29 of the thermal strip 4.

(19) The printing device 1 according to the invention can be operated as follows with the aid of the control device 25:

(20) Thus, the counter-pressure element 6 can initially be moved to its (first) end position defined by the first stop 18, and then the contact pressure of the thermal strip 4 on the counter-pressure element 6 can be adjusted. The adjustment of the contact pressure takes place by changing the spring force, in that the compression coil spring 27 is adjusted here. Alternatively, it is also conceivable to adjust the spring force of the leaf spring 26 or to change the position of the thermal head carrier 8. The contact pressure is for example adjusted to a value in a range from 30 to 55 N, for example to a value of 50 N. The precise adjustment of the contact pressure takes place by means of the pressure sensor 24 in the counter-pressure element 6. A corresponding setting is illustrated in FIG. 2.

(21) Subsequently, from this end position, the counter-pressure element carrier 5 is moved back by means of the stepper motor 13 by a few stepper steps (full steps or partial steps), until it reaches the position illustrated in FIG. 1. In this position, the contact pressure of the thermal strip 4 against the counter-pressure element 6 is reduced compared to the first end position in FIG. 2, particularly to a value in a range from 25 to 45 N, preferably 30 to 35 N. The value 35 N is exemplary here.

(22) In this position, labels 2 are then printed or the thermal strip 4 is actuated until the optical sensor 23 detects a degree of blackening or colour intensity of the printed image, which lies below a reference value saved in the control device 25. The counter-pressure element carrier 5 is then moved into a position, in which the contact pressure is somewhat larger than before, in that the stepper motor 13 is correspondingly controlled by the control device 25. This takes place in that the stepper motor 13 moves the counter-pressure element carrier 5, for example by a single stepper step, in the direction of the position illustrated in FIG. 2.

(23) Over time, the counter-pressure element carrier 5 and the counter-pressure element 6 increasingly approach the end position illustrated in FIG. 2. When the end position is reached and the degree of blackening or colour intensity detected by the optical sensor 23 falls below the predetermined reference value, the thermal strip 4 or the thermal head 3 must be replaced.

(24) In a variant of the previously described method, it is also possible to dispense with first travelling the counter-pressure element carrier 5 into the first end position illustrated in FIG. 2 and then adjusting the thermal head 3 in such a manner that the desired maximum contact pressure is applied, before first operating the thermal strip 4. Instead, it is also conceivable to move the counter-pressure element carrier 5 out of the second end position illustrated in FIG. 3 or a different position, in which the counter-pressure element 6 does not touch the thermal strip 4, in the direction of the insertion gap 7 or the thermal strip 4, until a contact pressure is present in a range from 25 to 45 N, preferably 30 to 35 N. The number of stepper steps (full steps or partial steps) of the stepper motor 13 necessary therefor is saved in particular, for example by means of the counter 28 in connection with the control device 25, and thus allows a reproducible start-up of the optimum thermal strip contact pressure even in the future, once a new thermal strip has been used.

(25) From the last-mentioned setting, which is illustrated in FIG. 1, the counter-pressure element carrier 5, as described already, is then moved step-by-step over time in the direction of the position illustrated in FIG. 2 and, if no stop is provided, if appropriate also beyond, in order to increase the contact pressure always when the degree of blackening or colour intensity lies below the said reference value. In the latter case, if no stop is provided, the contact pressure can be adjusted to virtually any desired level.