DE29818055U1 - Device for automatically adjusting the height of a printing device by means of a printhead suspension - Google Patents

Description

Werner Dreykdrn-Lindner ste.nlachstrasse 2

DlPL.-lNB. D-9D571 SCHWAIG Patent Attorney

European Patent Attorney Tel: 091 i- 5O5B99

European Trademark Attorney fax: ogi i- 5D5B99 DSP-PRINT-TEC GmbH

Ludwigstrasse 19
D-97276 Margetshöchheim

Dipl.-Ing. Karl-Heinz Pröstler Tuesday, 13 October 1998

Rossstrasse 46 DSP G05

D-97261 Güntersleben

Description

"Device for automatically adjusting the height of a printing device by means of print head suspension"

State of the art

The invention relates primarily to a device for automatically adjusting the height of a printing device arranged above a conveyor device with a scanner which presses elastically against the surface to be printed, which is pivotable and mounted perpendicular to the conveying direction of the surface to be printed and which is connected in an articulated manner to a print head holder, wherein the print head holder is movable perpendicular to the conveying direction (preamble of claim 1).

The design of printing systems for direct labeling of products has become increasingly important in recent years. Inkjet technology in particular has proven to be a reliable, convenient and cost-effective option for signing and labeling products. This technology is characterized by high reliability, low costs, very good ease of use and high print quality.

For example, DE 24 52 393 C2 discloses a printing system for applying figures and characters to packages that are fed on a conveyor device. The printing system has, among other things, a frame arranged adjacent to a conveyor device, on which a print head is arranged, which is arranged in a plane parallel to the packaged goods surface in

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is adjustable in two directions lying at right angles to each other, and is guided to be moved back and forth in a third direction perpendicular to this parallel plane and which is provided with a drive device for this reciprocating movement.
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In order to enable automatic determination of an area suitable for applying the print and to ensure that the print is clearly legible even if the surface to be printed is uneven, the print head, designed as an inkjet printer, is arranged on a carriage which is guided so that it can move in the two directions that are perpendicular to each other and parallel to the surface of the packaged goods and is connected to a drive motor for each of these directions of movement. In addition, the print head is assigned a sensing element that responds to surface irregularities on the surface of the packaged goods and is connected to a control device. The control device controls the drive motors for the carriage in such a way that the print head is automatically adjusted to an area on the packaged goods that is suitable for the print. The sensing element maintains a preselected distance of the print head from a surface of the packaged goods that has surface irregularities by controlling the drive device for moving the print head in the third direction.

The pushbutton element protruding from the bumper is loaded by a spring that is arranged on a guide shaft. A switch that responds to the load on the spring switches on a motor when the set load limits of the spring are reached. If the pushbutton element does not feel any resistance, the minimum spring load has been reached and the motor rotates in the direction in which the print head is extended. If the pushbutton element then encounters resistance, the spring is loaded and the switch switches the motor off.

If the load on the spring increases to the set maximum value, the switch responds again and causes the motor to rotate in the opposite direction, so that the spring is relieved of load again until the switch switches the motor off. The spring thus controls the fine range and the motor the coarse range of the sensing element. The switch can work depending on the load or movement and the sensing element can have a ferromagnetic-sensitive head that generates a signal when it hits a steel strip.

The printing system also detects protruding frame strips and strapping bands made of steel or plastic and prevents them from falling into the labeling area. It is also possible to print on curved and irregular surfaces - e.g. convex surfaces - whereby the print image is perfectly legible by keeping the distance between the print head and the surface to be printed on constant.

Furthermore, DE 38 36 142 A1 discloses a device for printing thin-shelled objects using the pad printing process, with at least one clamping device for the objects and at least one pad printing station. In order to print raw or boiled eggs in the shell in multiple colors on the front and back of the egg using the pad printing process, the device has a clamping device with two opposing clamping jaws, each equipped with a pressure ring that can be placed on a pole area of an egg.

In order to bring the eggs held in the clamping device, which are not exactly aligned, into an exact alignment so that perfect multi-color printing on the front and back of an egg is possible, one of the clamping jaws can be brought into a slightly loosened clamping position, whereby the clamped egg can be rotated relative to the other clamping jaw. It is also possible to straighten the egg with the help of a straightening jaw that contacts the clamped, slightly loosened egg and that aligns the egg centrally as it rotates and moves further. The straightening jaw consists, for example, of a slightly concave surface that is covered with a rubber-elastic mass. When rolling along the straightening jaw, which is preferably arranged above the direction of movement of the egg, the egg is aligned by rolling and pressing into an aligned position between the pressure rings of the clamping jaws.

The slightly loosened clamping position for alignment is created with the help of a pulling device that engages the clamping jaw. The pulling device can preferably be a fixed sliding guide along which parts of the clamping jaw slide in such a way that this clamping jaw is pulled slightly outwards compared to the other one, so that the clamping position is loosened.

In order to be able to process larger quantities, several of the clamping devices are attached to a linear conveyor, which runs through several stations one after the other, with an egg feed device at the beginning of the run and at least one, preferably up to eight pad printing stations in the conveyor's run.

Since an egg always breaks during printing and clamping, a sensor is arranged in the area that the clamping device passes through after the feed device and the first pad printing station, which senses the absence or presence of a broken egg. In the event that the proximity sensor signals a broken egg, the printing stations are activated via a control device in such a way that they

existing clamping devices or those with damaged eggs pass through without any pressure being applied.

Furthermore, from DE 195 32 724 A1, a multi-color printing device with a print head containing the printing ink, which is arranged in a printing unit, is known, wherein the print head can be moved in translation above the object to be printed via its own drive, and wherein a guide device is provided for the object to be printed. In order to provide a multi-color printing device with which significantly higher objects can be printed, the guide device has a receiving surface for the object to be printed, wherein the object can be moved under the printing unit via the guide device in a direction orthogonal to the direction of movement of the printing unit, and wherein the distance between the printing unit and the receiving surface of the guide device is adjustable.

In detail, it is intended that the drive for the object and the drive for the printing unit are controlled via a common control system. This essentially corresponds to the control system in a conventional printer, where the transport rollers are controlled. The drive of the printing unit is controlled via signals from the drive of the object. The printing unit is therefore controlled depending on the presence of an object or depending on the position of the object.

Finally, a sensor is provided to detect the height of the object. This sensor automatically detects the height of the object and sets the distance between the printing unit and the receiving surface. This can be done immediately before the printing process and/or during the printing process. In this way, objects of different heights can be printed one after the other, whereby the height of an object can also change if necessary or the printing process can take place on two levels of different heights.

Finally, DE 34 17 381 A1 discloses a device for automatically adjusting the height of a printer head above a fed paper web depending on the thickness of the fed paper. In order not to hinder the paper feed in addition to the automatic adjustment of the height of the printer head above the paper web, the device has a sensor roller in front of the printer head in the direction of paper conveyance, which rests on the fed paper web. The sensor roller is flexibly mounted in a direction perpendicular to the direction of paper conveyance, and a holder for the printer head that can be moved linearly perpendicular to the direction of conveyance is connected to the sensor roller.

In detail, the sensor roller can be pivoted about a pivot point arranged at a relatively large distance from the paper web in the direction of extension, in that the connection point between the sensor roller and the holder is arranged essentially vertically above the axis of rotation of the sensor roller and is designed as a joint between a pivot arm for the sensor roller and the holder. This ensures that the amount of movement perpendicular to the conveying direction of the paper at the sensing point determined by the sensor roller and in the printing area is approximately the same.

According to a further embodiment, the sensor roller is pressed elastically against the paper web, the elastic contact preferably being achieved by a spring. As a result, the sensor roller presses the paper web firmly against a support base located underneath the paper web, preferably a support roller. If this support roller is driven, the pressure ensures reliable and simple conveying. In particular, threading a new paper web to the printer head is easy, since it only has to be pushed under the sensor roller, which is then raised.

In order to set different distances in the printing area without changing the height or the distance in the stroke movement direction at the sensing point of the sensor roller, it is finally provided that the printer head is adjustable relative to a holder whose height above the paper web can be adjusted by the sensor roller to the respective paper thickness. The height adjustment can be achieved by adjusting the printer head relative to the holder via a slot in a vertical direction to the paper web. Suitable eccentric pulleys can also be provided here.

As the above assessment of the state of the art shows, printing on objects that are not flat - e.g. paper webs, CDs or the like - but rather significantly taller objects, e.g. technical objects such as housing parts, toys, e.g. dice or the like (objects with a non-negligible thickness) requires a great deal of effort for height adjustment. For example, a height-adjustable platform for the object, as in an embodiment described in DE 195 32 724 A1, or a drive device for moving the print head, as in the printing system according to DE 24 52 393 C2. A simpler printing system for this application - as in the subject of DE 34 17 381 Al - could be of great use, but on the other hand a printing device with a scanner that presses against the surface to be printed with elastic springs is not suitable for fragile goods and for carrying out a large height adjustment. This is particularly important because the printing industry is an extremely progressive, development-oriented industry.

which very quickly picks up on any improvements and simplifications and puts them into practice.

problem

Compared to the known printing systems, the invention is based on the task of designing them in such a way that printing on curved and irregular surfaces - e.g. convex surfaces - is also possible, whereby the printed image should be largely undistorted and perfectly legible.

invention

These problems are solved, starting from a device with the features in the preamble of claim 1, in that the print head holder is designed as a movable print head suspension with a molded-on scanner.

Advantageous effects of the invention

The device according to the invention has the advantage that a continuous transition between flat and uneven surfaces to be printed is created in a surprisingly simple manner. Compared to the prior art, the cost is low due to the elimination of a drive device for moving the print head and corresponding distance and position detectors. The print head suspension ensures that the contact force on the surface to be printed is low, so that even surfaces sensitive to impact can be printed. Another advantage is that the distance between the surface to be printed and the print head is small and also constant, so that the print image remains largely undistorted even at the transition to the curved surface. Depending on the height difference, printing can be carried out precisely across material overlaps.

Further embodiments of the invention

In a preferred embodiment of the invention according to claim 2, the weight of the print head suspension is at least partially balanced by an adjustable tension spring arranged above the print suspension, which exerts a counterforce.

This embodiment of the invention has the advantage that the damping of the transient response of the print head suspension when the scanner hits the surface to be printed can be adjusted over a wide range. Damage to the surface to be printed or overshoot of the print head suspension is thus reliably avoided.

According to protection claim 3, the weight of the print head suspension is at least partially balanced by a swing arm arranged on the side of the print head suspension with an associated adjustable compression or tension spring or by a counterweight.

By extending the swing arm, it is ensured that, in view of the inevitable tolerances in the print head guide, the distortions of the print image caused by the pivoting remain low, and are also not significant due to the extremely small distance between the print head and the surface to be printed.

In a further development of the invention, according to claim 5, the scanner is spherically shaped and has a recess for the printing area and an angle adjustment device. This can be adjusted in such a way that the scanner slides at an acute angle onto the surface to be printed.

This development of the invention has the advantage that the scanner, which is rounded on all sides, achieves a "soft glide" on the surface to be printed. In addition, a long hole beyond the rounded edges means that direct contact after the printing process, regardless of the printing direction, is practically impossible.

If at least two print heads are arranged on the print head suspension, it is preferably provided according to claim 9 that the control device keeps the filling quantity in the print head cartridge of both print heads at the same filling level. This design reliably prevents the print head suspension from becoming skewed during operation.

Description of the invention

Further advantages and details can be found in the following description of preferred embodiments of the invention shown in the drawing. The drawing shows:

FIG. 1 a first embodiment of the print head suspension according to the invention in the view and

FIG. Ib in side view and

FIG. 2a shows a second embodiment of the print head suspension according to the invention in the view and
FIG. 2b in side view.

FIG. la shows a first embodiment of the print head suspension DA according to the invention in the view, wherein the weight of the

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Print head suspension DA is at least partially balanced by an adjustable tension spring ZF arranged above the print head suspension DA, which exerts a counterforce. FIG. 2a shows a second embodiment of the print head suspension DA according to the invention in view, wherein the weight of the print head suspension DA is at least partially balanced by a rocker S arranged laterally on the print head suspension DA with an associated adjustable compression or tension spring F or by a counterweight. What both embodiments have in common is that the print head holder DH is designed as a movable print head suspension DA with a molded-on scanner A, wherein the distance between the surface to be printed and the print head DK is small and also constant. A parallelogram or triangular or roller or gear guide with or without a pneumatic drive of the print head suspension DA can be provided as a guide for the print head suspension DA.

The scanner A can be spherical and have a recess AS for the printing area. Furthermore, an angle adjustment device can be provided, which is preferably adjustable in such a way that the scanner A slides onto the surface to be printed at an acute angle. When it hits the surface to be printed, the scanner A triggers a switching function for the printing process. The printing device D itself can be an inkjet printer or a laser printer or a digital printer which is connected to a control device. The control device is connected both to the conveyor device and to a storage device containing the print (not shown in the drawing).

If the print head suspension DA carries at least two print heads DK, these will be kept at the same height. For this purpose, the control device can be provided to keep the fill level in the print head cartridge of both print heads DK at the same level.

To achieve a high printing speed and/or resolution, several print heads DK are connected in series, which are controlled in parallel by the control device and which each print in the product direction or perpendicular to the transport direction. To print on the side and/or bottom surface of the product on the conveyor, print head holder DH is or are arranged on the side and/or below.

The printing system according to the invention is suitable for the direct printing of fragile goods, such as eggs, glass surfaces, etc., as well as goods with flat and uneven surfaces such as cardboard boxes, pipes, film wraps, tarpaulins, product wrappings, furniture and similar wooden products, tubes, bottles, balloons, candles (see DE 85 00 482.0 Ul), CDs (see DE 44 38 246 Cl),

Labels (see DE 31 53 380 C2), data carriers such as diskettes, chip cards, etc. are ideally suited to this without the need for complex and specially designed printing devices as in the state of the art. Cosmetics such as DE 197 07 254 Al or foodstuffs such as DE 195 10 232 Al or pharmaceutical products such as DE 28 49 495 Bl can also be printed directly. If, for example, a film roll is to be printed during the wrapping process, an infrared or UV lamp or a blower is preferably arranged downstream of the printing device. During the wrapping process, the control device keeps the transport speed of the conveyor and the printing speed synchronized with each other. A rotary pulse generator/frequency converter can be provided for this purpose.

Finally, special inks can also be used which, for example, indicate whether the eggs are raw or cooked by a color change. In practical operation, for this application, the cycle time of the conveyor system (conveyor belt) is approx. lsec, the printing speed is ¹ A to lm/sec, the printing field for the freely defined text, consecutive number, date and/or time, logos (graphics) and &Egr;&Agr;&Ngr; code is 5mm high and 25mm long, the printing resolution is between 75 and 300 pixels / inch and the printing output is between 10,000 and 40,000 eggs / hour.

The device according to the invention for automatically adjusting the height has the advantage that it enables the labeling of any flat or uneven surface - with or without a surface structure - in a surprisingly simple manner, which has the following advantages:

> Distortions of the printed image are practically imperceptible.

> By connecting several print heads in series, the printing speed can be increased significantly.

> The tracking force can be varied widely depending on the application.

> The additional costs for the movable print head suspension and the scanner are very low.

All of the possible designs shown and described, as well as all of the new individual features disclosed in the description and/or the drawing and their combination with one another, are essential to the invention. For example, the application of a tube to be printed onto a mandrel (frictional engagement) can be omitted, since no pressure force is exerted during the printing process, the printing system is also suitable for printing under difficult environmental conditions (dust), e.g. for printing on cement bags, the scanner can be designed in a tunnel shape, the printing process can also be triggered by a light barrier, etc.

Claims (13)

Werner DREYKaRN-LiNDNER steinlachstrasse &zgr; Dipl.-Ing. D-9D57 1 Schwaib Patent holder European Patent Attorney Tel: 091 &igr;- 5&Ogr;5899 European Trademark Attorney fax: ag! i- 505399 DSP-PREVT-TEC GmbH Ludwigstrasse 19
D-97276 Margetshöchheim Dipl.-Ing. Karl-Heinz Pröstler Tuesday, 13 October 1998 Rossstrasse 46 DSP G05 D-97261 Güntersleben " Device for automatically adjusting the height of a printing device
by means of print head suspension " Protection claims 1. Device for automatically adjusting the height of a printing device (D) arranged above a conveyor device with a scanner (A) which presses elastically against the surface to be printed, which is pivotable and mounted in a direction perpendicular to the conveying direction of the surface to be printed and which is connected in an articulated manner to a Print head holder (DH) is connected, wherein the print head holder (DH) is movable perpendicular to the conveying direction, characterized in that the print head holder is designed as a movable print head suspension (DA) with a molded-on scanner (A).
10 2. Device according to claim 1, characterized in that the weight of the print head suspension (DA) is at least partially compensated by an adjustable tension spring (ZF) arranged above the print head suspension, which exerts a counterforce. 3. Device according to claim 1, characterized in that the weight of the print head suspension (DA) is at least partially compensated by a rocker (S) arranged laterally on the print head suspension with an associated adjustable compression or tension spring (F) or by a counterweight. 4. Device according to claim 1, characterized in that a parallelogram or triangular or roller or gear guide with or without pneumatic drive of the print head suspension (DA) is provided. 5. Device according to claim 1, characterized in that the scanner (A) is spherically shaped, has a recess (AS) for the printing area and an angle adjustment device, which is preferably adjustable in such a way that the scanner (A) slides at an acute angle onto the surface to be printed. , 6. Device according to claim 1, characterized in that the scanner (A) triggers a switching function for the printing process when it hits the surface to be printed. 7. Device according to claim 1, characterized in that the print head suspension (DA) carries at least two print heads (DK) which are held at the same height by the print head suspension (DA). 8. Device according to claim 1, characterized in that the printing device (D) is an inkjet printer or a laser printer or a digital printer which is connected to a control device and that the control device is connected both to the conveying device and to a storage device containing the print. 9. Device according to claim 7 or 8, characterized in that the control device keeps the filling quantity in the print head cartridge of both print heads (DK) at the same filling level. 10. Device according to claim 7 or 8, characterized in that in order to achieve a high printing speed and/or resolution, several print heads (DK) are connected in series, which are controlled in parallel by the control device and which each print in the product direction or perpendicular to the transport direction. 11. Device according to claim 1 or 8, characterized in that for printing the side and/or bottom surface of the product located on the conveyor device, the print head holder (DH) is or are arranged laterally and/or underneath. 12. Device according to claim 1, characterized in that an infrared or UV lamp or a fan is arranged downstream of the printing device (D). 13. Device according to claim 1, characterized in that the control device keeps the transport speed of the conveyor device and the printing speed synchronized with each other.