EP1747147B2 - Method and device for printing on the surface of a strip-type medium - Google Patents

Abstract

A method and device for improving the handling, in a label printer, of labels without a carrier strip operates by reversing the direction of transport of the label medium for a short distance before transporting the medium in the printing direction, allowing the label strip to reliably detach from a transport roller (10) that is used to guide the label strip through the printer.

Description

The invention relates to a method for printing on a surface of a strip-shaped medium whose other surface is self-adhesive coated, according to the preamble of claim 1 and to a device suitable for carrying out the method according to the preamble of claim 8.

Such methods and devices are used in particular for the production of printed labels, which are glued in sales shops on goods. In particular, weight data, for example from a self-service scale, price information and / or bar codes are printed on the surface to be printed, which are important for the settlement of the sales transactions. The fact that the self-adhesive coated surface is passed through the printing process offers the advantage over other conventional methods in which the self-adhesive coated surface is provided with a cover tape from which the finished printed labels are withdrawn for use The printing usually supplied in roll form medium requires less space and at the same time the costs associated with the masking tape costs are saved. However, handling the media exposed with its self-adhesive coated surface during the printing process requires special measures to prevent the medium from sticking during printing. In particular, the strip-shaped medium, which is usually a paper designed for thermal printing, tends to run after the transport roller with which it is engaged for its transport on its self-adhesive coated surface, d. H. to wrap around the roller.

In a known method and a known device ( DE 101 11 228 A1 ) is imprinted on the strip-shaped medium a shape behavior, the effect of which is to force the strip-shaped medium into a shape which deflects it away from the transport roller as soon as it emerges from the passage gap delimited between the print head and the transport roller. For a safe operation of this device under all circumstances must be taken to ensure that caused by the inherent rigidity and the embossed shape behavior of the strip-shaped medium separation effect is always greater than the adhesion between the transport roller and the emerging from the passage gap medium. It must be taken into account in particular that wear off the surface of the transport roller with increasing mileage and therefore the adhesion between the roller surface and the strip-shaped medium can increase. Also, after longer periods of use, for example, overnight or on weekends, the medium at the first start of its transport may be more prone to run after the transport roller.

Other known methods and devices ( EP 0 758 979 B1 and EP 0 758 955 B1 ) encounter this problem in that the transport roller and also other surfaces which come into contact with the self-adhesive coated surface during the printing process are provided with an adhesive-repellent coating. However, this is not enough to safely detach the medium from the transport roller. Therefore, in these known methods and devices as a particularly important element in the transport direction behind the transport roller and the latter immediately adjacent a detaching blade or a small diameter detaching roller arranged whose surface is coated adhesive repellent and passes over the strip-shaped medium and is thereby deflected by the transport roller.

US 5,993,093 discloses a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 8.

The invention has for its object to provide a method and an apparatus of the type mentioned are available, which are characterized by maintaining increased simplicity by maintaining increased reliability.

With regard to the method, this object is achieved by the characterizing part of claim 1.

It has been found that, on the one hand, the inclination to adhere to the transport roller in the subsequent transport interval is reduced by the return transport of the strip-shaped medium which is opposite to the transport direction. In this subsequent transport interval, then the medium dissolves more reliably after its passage through the passage gap from the transport roller and reaches the removal point at which a the length of the transport interval corresponding and possibly printed with desired print data section separated from the strip-shaped medium and, for example as Stick-on label can be used. Since the separation of the portion occurs at a distance from the passage gap and the length of the return transport does not exceed this distance, the medium is permanently clamped in the passage gap between the transport roller and the print head and thereby stands for the next transport interval, in which it by the attack the transport roller is transported, ready. In practice, a return transport of a few millimeters in length is sufficient. On the other hand, an additional security is provided that the medium leaves the transport roller substantially tangentially during its short return transport.

The intended return transport is expedient in particular before the first transport interval, which is carried out after a longer service life. In an advantageous embodiment of the method according to the invention, however, it is provided that the reverse transport to the transport direction is carried out before each of the transport intervals. This will in particular increases the reliability in cases in which the surface of the transport roller is worn after a long mileage.

For a particularly high degree of effectiveness of the measure according to the invention, it is furthermore advantageous that the return transport opposite to the transport direction and the transport taking place in the transport direction are carried out directly in succession. There is no time gap between the return transport and the transport in the subsequent transport interval. Rather, the two transport processes connect directly to each other.

Further, according to an advantageous embodiment, it is particularly effective that the length in which the medium is transported back opposite to the transport direction, at least as large as the arc length over which the medium touches the transport roller. In this case, therefore, the medium is offset by the return transport to the transport roller to the entire area where it has been in engagement with the transport roller before the return transport.

A particularly important embodiment of the method according to the invention is characterized in that the medium is impressed by a shape behavior by which it separates from the transport roller. In this embodiment, the inventive method with the in DE 101 11 228 A1 revealed separation of the medium from the transport roller combined, thereby achieving a particularly high reliability. Conveniently, the shape behavior is thereby brought about in that the medium is impressed in its longitudinal direction, a curvature whose center of curvature of the surface to be printed opposite to the medium during its transport in front of the transport roller.

The basic principle of a device according to the invention suitable for carrying out the method according to the invention is specified in claim 8. According to the invention, viewed in the transport direction, arranged in front of the printing unit, a self-adhesive coated surface of the medium opposite support member. According to the invention, the support element is designed as a rotatably mounted roller.

The support member is arranged near the transport path of the strip-shaped medium such that the latter comes to rest on the support element, if the strip-shaped medium at its opposite to the transport direction return transport does not dissolve tangentially from the transport roller and thereby of the transport path, it in its transport in the transport direction assumes, would differ in the direction of the support element. The support element thereby provides additional security for the medium to leave the transport roller substantially tangentially during its short return transport.

In the context of the invention it is also provided that with the self-adhesive coated surface of the strip-shaped medium coming into contact Surface regions of the device are designed adhesive repellent, which can be achieved in particular by suitable coatings. In particular, this adhesive-repellent design is provided for the lateral surfaces of the transport roller and the lateral surface of a support roller forming the support element.

Further features, details and advantages of the invention will become apparent from the following description and the single drawing figure, wherein the invention is explained and illustrated by means of an embodiment.

The embodiment shown in the drawing has a base plate 1 on which all components of the device are mounted. A to-print, strip-shaped medium is wound in the form of a supply roll 2, which is rotatably supported on a lower region 1a of the base plate 1 in the drawing. The medium consists, for example, of thermal printing paper whose surface 3 to be printed on the other side 4 is self-adhesive coated. Such media are known in the art as "linerless label material" or "linerless label web". The supply roll 2 is wound in such a way that the self-adhesive coated surface 4 faces the center of the supply roll 2.

At a distance from the supply roll 2, a guide roller 5 is rotatably mounted coaxially to this at a central region 1 b of the base plate 1. Coaxially to the guide roller 5 and set back relative to this in the direction of the supply roll 2, a stamping cylinder 7 is fixedly or rotatably supported on a carrier 6 connected to the base plate 1. In a top in the drawing area 1c of the base plate, a printing unit is arranged. This has a strip-shaped thermal print head 8, which extends in a direction perpendicular to the base plate 1, ie parallel to the axes of the guide roller 5 and the embossing cylinder 7 level.

The print head 8 extends tangentially to the casing 9 of a transport roller 10, which is rotatably mounted in comparison to the print head 8 on a bearing plate 11 connected to the base plate 1. The transport roller 10 is driven by a drive not visible in the illustration, which is arranged on the base plate 1 and has a gear transmission and an electric motor. Further, a guide roller 14 is rotatably mounted on the bearing plate 11 at a location between the transport roller 10 and the embossing cylinder 7 position. In addition, a support roller 12 is rotatably mounted on the bearing plate 11 at a location located between the transport roller 10 and the guide roller 14 whose coat 13 comes close to one of the jacket 9 of the transport roller 10 and the jacket 14 a of the guide roller 14 common tangent.

The supplied from the supply roll 2 strip-shaped medium extends from the supply roll 2 to the guide roller 5, over which it passes with its self-adhesive coated surface 4, and further to Embossing cylinder 7, over which it is carried away with its surface to be printed 3. From the embossing cylinder 7, the medium passes to the guide roller 14, passes over with its self-adhesive coated surface 4, then continue with its self-adhesive coated surface 4 close to the jacket 13 of the support roller 12 over and on to the transport roller 10, on which it self-adhesive coated surface 4 is held by the voltage applied to the surface 3 to be printed printhead 8 in engagement. As a result of this engagement in the passage gap formed in this way, the rotational movement introduced by the drive into the roller 10 is transferred to the medium, as a result of which it is withdrawn from the supply roll 2 and transported in its longitudinal direction. The transport movement and the operation of the thermal print head 8 (not shown) in such a manner coordinated by an electronic control device that by the print head 8 on the surface to be printed 3 of the medium during its passage through the passage gap between the print head 8 and the transport roller 10 desired contents are printed. In particular, labels serving for product labeling are printed, which are torn off the strip-shaped medium after it has passed through the device. In order to assist in the tearing off, a tearing strip 16 pointing to the printing surface 13 is provided at the outlet 15 of the device, which extends over the width of the strip-shaped medium, as a result of which the printed labels can be torn off.

The mutual relative position of the two deflection rollers 5, 14 and the embossing cylinder 7 determine the wrap angle with which the medium is guided around the embossing cylinder 7. The radius of the embossing cylinder 7 is relatively small, whereby the medium undergoes a stretching on its surface 3 to be printed with respect to its self-adhesive coated surface 4. As a result, a permanent curvature is impressed on the medium in its longitudinal direction, whose center of curvature is opposite to the surface 3 to be printed. Although the medium is against this curvature by the transport roller 10 in the longitudinal direction of the medium, d. H. its transport direction, train exerted straight during its transport between the embossing cylinder 7 and the guide roller 14 and between the guide roller 14 and the transport roller 10 again, but takes after its passage between the transport roller 10 and the thermal print head 8 released from the Transportzug medium embossed Curvature again. As a result, the medium is detached from the roller 10, since the force with which the embossed curvature is assumed sufficient to overcome the adhesive force between the jacket 9 of the transport roller 10 and the self-adhesive coated surface 4 of the medium.

Notwithstanding the spaced arrangement of the guide roller 5 and the embossing cylinder 7 shown in the drawing, the guide roller 5 could be arranged such that it forms in its operating position with the embossing cylinder 7 a roll clamping gap through which the medium passes. In this case, two axial generatrices of the deflection roller 5 and the embossing cylinder 7 face each other on both sides of the medium and determine the point at which the wrap angle begins. So that the medium can be inserted without difficulty when replacing the roller 2, an adjusting device (not shown) may be provided with which the guide roller and the embossing cylinder can be moved relative to each other in a release position in which they are mutually spaced and the insertion of the enable strip-shaped medium.

In this embodiment, therefore, the mutually facing generatrices of the embossing cylinder 7 and the upstream in the transport direction arranged deflection roller determine the beginning of the wrap angle. Additionally or alternatively, such a deflection roller could also be arranged downstream of the embossing cylinder 7 (not shown) in order to fix the end of the wrap angle in the same way.

The lateral surfaces of the deflection rollers 5 and 14 and the transport roller 10, over which the medium with its self-adhesive coated surface 4 passes, and also the lateral surface 13 of the support roller 12 are designed adhesive repellent, for example by suitable coatings.

The arrangement of the transportation of the medium serving transport roller 10 in juxtaposition to the print head 8 corresponds to the known prior art in the field of label printers. Therefore, the transport roller 10 is often referred to as a "pressure roller". But it is also conceivable to arrange the transportation of the medium serving transport roller 10 in the transport direction behind the print head 8 and provide a non-driven counter element for the print head 8, which holds the medium for the printing operation on the print head 8.

If the medium by its wrap of the embossing cylinder 7 still should not take sufficient curvature, a cascade of several embossing cylinders 7 may be provided, which are circulated in succession by the medium during its transport.

In the foregoing description, it has been assumed by way of example that in roll 2 the self-adhesive coated surface 4 of the medium faces the roll center. In this case, as shown in the drawing, the roller 2 rotates in unwinding the medium in the counterclockwise direction. Alternatively, however, the roll 2 may be wound in such a way that the surface 3 to be printed faces the center of the roll. In this case, the roller 2 is inserted into the device so that they are in the unwinding clockwise rotates. By this type of winding the medium is already impressed on the roller 2 a pre-curvature, which is opposite to the curvature of the transport roller 10. This shape behavior can already be sufficient with a suitable material to separate the medium from the transport roller 10, without the need for further imprinting. In this case, the embossing cylinder 7 and the guide roller 5 having embossing device can be completely eliminated and the medium can be transported directly from the roller 2 between the transport roller 10 and the print head 8.

By the electronic control device, the drive of the transport roller 10 is operated in a known manner such that the latter deducts by their engagement with the strip-shaped medium the transport intervals corresponding lengths of the strip-shaped medium of the supply roll 2 and under the print head 8 through the tear bar 16 from the device also promotes. Meanwhile, these lengths of the strip-shaped medium are printed by the print head 8 with the respective desired print contents. These printed lengths can be separated with the help of the tear bar 16 and used for example as adhesive labels.

In addition, this control device has a device which operates as follows: Before the control device causes the drive to drive the transport roller 10 to carry out a transport interval in the counterclockwise direction, causes the said device briefly in the opposite direction of rotation, ie clockwise, taking place the drive Transport roller 10. As a result, the medium is transported back opposite to the transport direction. This return transport takes place over a length which is smaller than the distance between the tear strip 16 and the passage gap formed between the transport roller 10 and the print head 8, so that the medium remains clamped in the passage gap even after this return transport has been carried out. As a result of the adhesion occurring between the self-adhesive coated surface 4 of the strip-shaped medium and the jacket 9 of the transport roller 10, it may happen that the strip-shaped medium with respect to the jacket 9 is not exactly tangential, but rests on it over a small arc length. The return transport of the medium takes place over a length which is at least as large as this arc length. If the medium does not readily detach tangentially from the transport roller 10 in this return transport, but is slightly taken along in the clockwise direction of rotation of the transport roller 10, the medium is deflected in the direction of the support roller 12, the jacket 13 close to a common tangent the transport roller 10 and the guide roller 14 comes up. Even after a very short deflection, the medium reaches the jacket 13 of the support roller 12 in abutment, whereby the tangential separation of the medium is supported by the transport roller 10. After the return transport, the drive direction reverses; This starts the transpuning interval by driving the transport roller 10 counterclockwise and causing a corresponding feed of the medium. The return transport and the subsequent transport in the transport direction can connect directly to each other. However, it is also possible to provide a short time interval therebetween. Furthermore, the device may be designed so that it carries out the return transport before each transport interval. However, it is also possible to carry out the return transport only before such transport intervals, which has been preceded by a prolonged shutdown. The device could also be designed to cause the return transport when a predetermined number of transport intervals greater than one has been performed.

List of reference numbers

1

baseplate

1a

lower area

1b

middle area

1c

upper area

2

supply roll

3

to be printed surface

4

self-adhesive coated surface

5

idler pulley

6

carrier

7

embossing cylinders

8th

printhead

9

coat

10

transport roller

11

bearing plate

12

supporting role

13

coat

14

idler pulley

14a

coat

15

output

16

floating toolbar

Claims (22)

1. A method for printing on one surface (3) of a strip-type medium, the other surface (4) of which has a self-adhesive coating, and which during conveyance intervals is conveyed in its longitudinal direction from a supply position where a supply (2) of the medium is kept available, through a printing unit in which the medium is passed past a passage gap (8, 10) with its surface with a self-adhesive coating, over a driven conveyance roller (10), and with its surface to be printed past a print head (8) disposed opposite the conveyance roller (10) to a removal point where a section running ahead in the direction of conveyance a distance away from the passage gap (8, 10) is separated from the medium, before at least one of the conveyance intervals the medium being conveyed back over a length not exceeding the distance from the passage gap (8,10) in a direction opposite to the direction of conveyance, wherein the medium, with its surface (4) with a self-adhesive coating, comes to rest on a support element (12) disposed before the printing unit, as viewed in the direction of conveyance, in case it would not be released tangentially from the conveyance roller (10) upon its return conveyance and would in this way deviate from the path of conveyance that it follows upon conveyance in the direction of conveyance towards the support element (12), characterized in that the support element is formed by a rotatably mounted roller (12).
2. The method according to Claim 1, characterised in that the return conveyance in the direction opposite to the direction of conveyance is implemented before each of the conveyance intervals.
3. The method according to Claim 1 or 2, characterised in that the return conveyance in the direction opposite to the direction of conveyance and the conveyance implemented in the direction of conveyance are implemented directly one after the other.
4. The method according to any of Claims 1 to 3, characterised in that the length over which the medium is conveyed back in the direction opposite to the direction of conveyance is at least as great as the arc length over which the medium is in contact with the conveyance roller (10).
5. The method according to any of Claims 1 to 4, characterised in that a form characteristic is impressed into the medium by means of which it separates itself from the conveyance roller (10).
6. The method according to Claim 5, characterised in that impressed into the medium in its longitudinal direction upon its conveyance before the conveyance roller (10) is a curvature, the curvature centre point of which lies opposite the surface (3) to be printed.
7. The method according to Claim 6, characterised in that the medium is conveyed on its surface (3) to be printed with a wrap angle (17) suitable for impressing over an impressing cylinder (7) having a radius suitable for this purpose.
8. An apparatus for printing on one surface (3) of a strip-type medium, the other surface (4) of which has a self-adhesive coating, with a printing unit which has a conveyance roller (10) provided with a drive and over which the medium, with its surface (4) with a self-adhesive coating, is guided for its conveyance in its longitudinal direction, and a print head (8) disposed opposite the conveyance roller (10) such as to form a passage gap past which the medium, with its surface to be printed (3), is conveyed, and with a control device by means of which the drive for conveyance of the medium from a supply position, where a supply (2) of the medium is kept available, through the printing unit to a removal point where a section running ahead in the direction of conveyance can be separated from the medium by means of a separation apparatus (16) spaced apart from the passage gap, can be controlled in conveyance intervals, the control device having a device used for inverting the direction of the drive direction by means of which before at least one of the conveyance intervals the medium can be conveyed back in the direction opposite to the direction of conveyance over a length not exceeding the distance between the passage gap (8, 10) and the separation device (16), wherein a support element (12) facing towards the surface (4) of the medium with a self-adhesive coating is disposed before the printing unit, as viewed in the direction of conveyance, with which the medium comes to rest in case it would not be released tangentially from the conveyance roller (10) upon its return conveyance and would in this way deviate from the path of conveyance that it follows upon conveyance in the direction of conveyance towards the support element (12), characterized in that the support element (12) is formed by a rotatably mounted roller (12).
9. The apparatus according to Claim 8, characterised in that the device serving to invert the direction of the drive device implements the conveyance back in the direction opposite to the direction of conveyance before each of the conveyance intervals.
10. The apparatus according to Claim 8 or 9, characterised in that the device serving to invert the direction of the drive device implements the conveyance back in the direction opposite to the direction of conveyance and the conveyance implemented in the direction of conveyance in immediate succession.
11. The apparatus according to any of Claims 8 to 10, characterised in that the length over which the device serving to invert the direction controls the conveyance back of the medium in the direction opposite to the direction of conveyance is at least as great as the arc length over which the medium is in contact with the conveyance roller.
12. The apparatus according to any of Claims 8 to 11, characterised in that the support element (12) has anti-adhesion coating.
13. The apparatus according to any of Claims 8 to 12, characterised by a device for impressing a form characteristic separating the medium from the conveyance roller (10).
14. The apparatus according to Claim 13, characterised in that the device serving to impress the form characteristic is formed by an impressing unit (5, 7) disposed before the conveyance roller (10) in the direction of conveyance in order to impress a curvature extending in the longitudinal direction of the medium the curvature centre point of which lies opposite the surface (3) to be printed.
15. The apparatus according to Claim 14, characterised in that the impressing unit has an impressing cylinder (7) with a radius suitable for the impressing of the curvature about which the medium is passed with an appropriate wrap angle on its surface to be printed (3).
16. The apparatus according to Claim 15, characterised in that the impressing cylinder (7) is in a fixed position.
17. The apparatus according to Claim 15, characterised in that the impressing cylinder (7) is disposed rotatably about the cylinder axis.
18. The apparatus according to any of Claims 15 to 17, characterised in that a deflection roller (5) serving to set the wrap angle is provided by means of which the medium is guided on its surface (4) with a self-adhesive coating.
19. The apparatus according to Claim 18, characterised in that the deflection roller (5) is disposed a distance away from the impressing cylinder (7).
20. The apparatus according to any of Claims 8 to 19, characterised in that the medium to be delivered is wound into a roll (2) in which the surface (4) with the self-adhesive coating faces towards the centre point of the roll.
21. The apparatus according to any of Claims 8 to 19, characterised in that the medium to be delivered is wound into a roll (2) in which the surface (3) to be printed faces towards the centre point of the roll.
22. The apparatus according to any of Claims 8 to 21, characterised in that surface regions of the apparatus coming into contact with the surface (4) with the self-adhesive coating (4) are designed to repel adhesive.

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