EP0993957B1 - Automatic device for adjusting the height of a printing device comprising a sensor - Google Patents

Abstract

A device for automatically adjusting the height of a printer arranged above a conveyor comprises a spring-supported print head mounting which is movable at least at right angles to the conveyance direction of the surface to be printed. The printer is provided with a print head holder with an attached scanner device. Preferred Features: The weight of the print head mounting is at least partly balanced by an adjustable tension spring arranged above the mounting. The printing device is preferably an ink jet, laser or digital printer which is linked to a control device. The control device is also linked to both the conveyor and a print-impression memory device.

Description

The invention relates to a device for automatically adjusting the height of a printer device (D) arranged above a conveyor with a movably mounted, resilient print head suspension (DA) and a print head holder (DH) for the printer device (D) connected to the print head suspension (DA).

The design of printing systems for the direct labeling of products has become increasingly important in recent years. In particular, inkjet technology has proven to be a reliable, convenient and cost-effective way of signing and labeling products. High reliability, low cost, excellent ease of use and high print quality characterize this technique.

For example, from DE 24 52 393 C2 discloses a printing system for applying figures and characters on packages that are brought on a conveyor known. The printing system has u.a. a, adjacent to a conveyor frame on which a print head is arranged, which is adjustable in a direction parallel to the Packgutoberfläche level in two mutually perpendicular directions, and in a third, perpendicular to this parallel plane direction and forth guided and forth which is provided with a drive device for this reciprocation.

In order to make it possible to automatically determine a region which is suitable for applying the imprint and to ensure that the imprint is easy to read, even in the case of certain unevenness of the surface to be printed, it is provided in detail that the ink jet printer Printhead is arranged on a carriage which is movably guided in the two mutually perpendicular and parallel to the Packgutoberfläche directions and connected for each of these directions of movement with a drive motor. Furthermore, the print head is associated with a surface element that is responsive to surface irregularities of the packaged product surface, which is in communication with 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 suitable for printing on the packaged goods. The scanning element, by controlling the drive means for moving the print head in the third direction, maintains a preselected distance of the print head from a package surface having surface irregularities.

The protruding on the bumper probe element is loaded by a spring which is arranged on a guide shaft. A switch responsive to the load of the spring engages a motor when the set load limits of the spring are reached. If the sensing element does not feel resistance, the minimum spring load is achieved and the motor rotates in the direction in which the printhead is extended. If the probe then encounters resistance, the spring is loaded and the switch shuts off the motor. If the load on the spring rises 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 again until the switch switches off the motor. The spring thus controls the fine region and the motor controls the coarse region of the probe element. The switch may be load or motion dependent, and the probe may include a ferromagnetic head that generates a signal as it strikes a steel band.

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

Furthermore, from DE 38 36 142 A1 a device for printing thin-shelled objects by the pad printing method, with at least one clamping device for the objects and at least one pad printing station known. In order to print raw or boiled eggs in the shell multicolored on the front and back of the egg after the pad printing process, the device has a clamping devices with two opposing jaws, which are each equipped with a pressure ring, each of which can be placed on a pole portion of an egg is.

In order to bring the captured in the jig eggs, which are not exactly aligned to bring in an exact alignment, so that a perfect multi-color printing on the front and back of an egg is possible, in addition to this, one of the jaws in a slightly loosened clamping position be brought, wherein the clamped egg is rotatable relative to the other jaw. It is also possible that with the help of a clamped, slightly loosened egg contacting straightening jaw, from which the egg is centered when turning and advancing, the egg straighten. The directional jaw consists for example of a slightly concave curved surface, which is designed with a rubber-elastic mass. When rolling along the straightening jaw, which is preferably located above the direction of movement of the egg is by rolling and pressing of the egg aligned in an aligned position between the pressure rings of the clamping jaws.

The tensioning position, which is slightly loosened for alignment, is generated by means of a pulling device acting on the clamping jaw. In this case, the pulling device may preferably be a fixed Gleitkulisse, slide along the parts of the clamping jaw so that this clamping jaw is pulled over the other slightly outwards, so that the clamping position is relaxed.

In order to process larger quantities, several of the jigs are mounted on a linear conveyor which passes through several stations in succession, wherein at the beginning of the run an egg feeder and at least one, preferably up to eight tampon printing stations are arranged in the conveyor.

Since an egg breaks up again and again during printing and clamping, a sensor which senses the non-occupation or the presence of a broken egg is arranged in the region through which the clamping device passes after the delivery device and the first tampon printing station. In the event that the proximity sensor signals a broken egg, the printing stations are activated via a control device so that they pass the non-existent or damaged eggs provided jigs without printing.

Furthermore, from DE 195 32 724 A1 discloses a multi-color printing device with a print head containing the printhead, which is arranged in a printing unit known, the print head via a separate drive translationally above the object to be printed is moved, and wherein a Guiding device is provided for the object to be printed. In order to provide a multi-color printing device, with significantly higher objects are printable, the guide means on a receiving surface for the object to be printed, wherein the object via the guide means in a direction orthogonal to the direction of movement of the printing unit under the printing unit is movable and wherein the distance of the printing unit is adjustable to the receiving surface of the guide device.

Specifically, it is provided that the drive for the object and the drive for the printing unit are controlled by a common control. This corresponds essentially to the control in a conventional printer, where the transport rollers are controlled there. In this case, the drive of the printing unit is controlled via signals of the drive of the object. The printing unit is thus controlled depending on the presence of an object or depending on the position of the object.

Finally, a height sensor is provided for the sensor. This sensor automatically detects the height of the object and adjusts the distance of the printing unit to the recording surface. This can be done immediately before the printing process and / or during the printing process. In this way, successively different height objects can be printed, which may also change the height of an object or the printing process can take place in two different levels.

Finally, from DE 34 17 381 A1 discloses a device for automatically adjusting the height of a printer head over a supplied paper web in dependence on the thickness of the supplied paper known. In addition to the automatic adjustment of the height of the print head over the paper web, the paper entry does not hinder, the device in the conveying direction of the paper in front of the printer head a feeler roller rests on the supplied paper web on. The sensor roller is resiliently mounted in the direction perpendicular to the conveying direction of the paper web and the sensor roller is connected to a linearly perpendicular to the conveying direction movable holder for the printer head.

In particular, the feeler roller is pivotable about a pivot point arranged in the direction of extent of the paper web at a relatively great distance from it, in that the connection point between the feeler roller and holder is arranged substantially perpendicularly above the axis of rotation of the feeler roller and as a joint between a pivot arm for the feeler roller and the holder is trained. It is thereby achieved that the amount of movement perpendicular to the conveying direction of the paper is approximately the same at the sensing point determined by the feeler roller and in the pressure range.

According to a further embodiment, it is provided that the feeler roller is pressed elastically against the paper web, wherein the elastic attachment is preferably effected by a spring. As a result, the feeler roller presses the paper web firmly against a support pad located below the paper web, preferably a support roller. When this back-up roll is driven, a reliable and easy delivery is achieved by the pressure. In particular, the threading of a new paper web to the printer head is easy, since this only has to be pushed under the feeler roller, which is thereby raised.

In order to set different distances in the printing area, without changing the height or the distance in Hubbewegungsrichtung at the Abfühlstelle the feeler roller, it is finally provided that the printer head is adjustable relative to a by the sensing roller to the respective paper thickness in height above the paper web adjustable holder , The height adjustment can be achieved in that the printer head is adjustable relative to the holder via a slot in the direction perpendicular to the paper web. It can also be provided here appropriate eccentric means.

Furthermore, for the maintenance-free printing of eggs with food coloring at the PACK IT '95 in Basel by the company Francis Bühler AG, a system with four print cartridges was presented in which the different inscription surface heights are compensated by scanning and a parallelogram tilting. This approach has also been taken in the subject matter of EP 0 908 313 A2, which is not prepublished.

As the above assessment of the prior art shows, printing on non-flat objects - e.g. B. paper webs, CD o. The like. - But significantly higher items, such. As technical items, such as housing parts, toys, eg cubes o. The like. (Objects with a non-negligible thickness), a lot 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 for this application printing system - as in the subject of DE 34 17 381 A1 - could be of great benefit, on the other hand, a printing device separates with a scanner, which resiliently presses against the surface to be printed on fragile goods and to carry out a large height adjustment. This is particularly important because the printing industry is a highly advanced, development-friendly industry that is quick to pick up and put into effect any improvements or simplifications.

Finally, from DE 34 173 81 A1 a device for automatically adjusting the position of the printer head to the thickness of paper, which is present as a roll, known. The in the ground state vertically arranged holder for the printer head is guided at the top by a likewise vertically aligned slot. In the lower area is connected to the holder via a joint with a lever. The lever applied to the hinge point is supported at the bottom by the sensor roller resting on the paper, the sensor roller being rotatably connected to the lever by the point of articulation, and the lever being displaced on a radial curved path when the sensor roller displaces on thick paper, the printhead forcibly displacing it vertical position with respect to the object to be printed loses.

The invention is compared to the known printing systems on the object to design this of such that the printing of curved and irregular -. B. convex surfaces - is possible, the image should be largely undistorted and perfectly legible.

The object is achieved by a device which is characterized in that at least the resilient print head suspension (DA) is aligned perpendicular to the conveyor of the surface to be printed, and the print head holder (DH) for the printer device (D) with an integrally formed scanner (A). is configured, and the printing device (D) extends into the scanner (A).

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 costly effort is low by eliminating a drive means for moving the print head and corresponding distance and position detectors. By the print head suspension ensures that the contact force on the surface to be printed is low, so that even against shock-sensitive surfaces can be printed. Farther It is advantageous that the distance between the surface to be printed and the print head is small and is also constant, so that the printed image remains largely undistorted even at the transition to the curved surface. Depending on the height difference, it is possible to print exactly over material overlays.

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

This embodiment of the invention has the advantage that the attenuation of the transient process of the print head suspension is adjustable over a wide range when the scanner abuts the surface to be printed. Damage to the surface to be printed or overshoot of the print head suspension is thereby reliably avoided.

According to claim 3, the weight of the print head suspension is at least partially offset by a laterally arranged on the print head suspension rocker with associated adjustable compression or tension spring or by a counterweight.

An extension of the oscillating arm ensures that, with regard to inevitably existing tolerances in the print head guide, the distortions of the printed image caused by the pivoting remain small and, moreover, are not significant due to the extremely short distance between the print head and the surface to be printed.

In a further development of the invention, according to claim 5, the scanner has a spherical shape and has a recess for the printing area and a Winkeleinstelleinrichtung on. This is adjustable so that the scanner slides at an acute angle to the surface to be printed.

This development of the invention has the advantage that a "smooth sliding" is achieved on the surface to be printed by the rounded on all sides scanner. In addition, a direct contact after the printing process, regardless of the direction of printing, practically can not take place through a slot beyond the curves.

If at least two print heads are arranged on the print head suspension, it is preferably provided according to claim 15 that the control device keeps the filling quantity in the print head cartridge of both print heads at the same fill level.

By this configuration, a misalignment of the print head suspension is reliably avoided during operation.

FIG. 1a

eine erste Ausführungsform der erfindungsgemäßen Druckkopfaufhängung in der Ansicht und

FIG. 1b

in der Seitenansicht und

FIG. 2a

eine zweite Ausführungsform der erfindungsgemäßen Druckkopfaufhängung in der Ansicht und.

FIG. 2b

in der Seitenansicht.

Further advantages and details can be taken from the following description of preferred embodiments of the invention shown in the drawing. In the drawing shows:

FIG. 1a

a first embodiment of the printhead suspension according to the invention in the view and

FIG. 1b

in the side view and

FIG. 2a

a second embodiment of the printhead suspension according to the invention in the view and.

FIG. 2 B

in the side view.

FIG. 1a shows a first embodiment of the print head suspension DA according to the invention in the view, wherein 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 DA which exerts a counterforce.

FIG. 2a shows a second embodiment of the print head suspension DA according to the invention, in which the weight of the print head suspension DA is at least partially compensated 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.

Common to both embodiments that the printhead holder DH is designed as a movable printhead suspension DA with a molded-on scanner A, wherein the distance between the surface to be printed and the print head DK is low and also constant. As a guide for the print head suspension DA a parallelogram or triangular or roller or gear guide can be provided with or without pneumatic drive of the print head suspension DA.

The scanner A may be spherically shaped and have a recess AS for the printing area. Furthermore, an angle adjusting device can be provided, which is preferably adjustable such that the scanner A in acute angle slips on the surface to be printed. When impinging on the surface to be printed, the scanner A triggers a switching function for the printing process. The printing device D itself may be an ink jet printer or a laser printer or a digital printer which is in communication with a control device. The control device is connected both to the conveyor and to a storage device containing the imprint (not shown in the drawing).

In the event that the print head suspension DA carries at least two print heads DK, they will be kept at the same height. For this purpose, it may be provided that the control device keeps the filling quantity in the printhead 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 in each case print in the product direction or perpendicular to the transport direction. For printing on the side and / or bottom surface of the product on the conveyor, printhead holders DH are or are arranged laterally and / or underneath.

The printing system according to the invention is suitable for the direct printing of fragile goods, such as eggs, glass surfaces, and also goods with flat and uneven surface such as cardboard, food, pipes, film wraps, tarpaulins, Produktumwüllungen, pharmaceutical preparations, furniture and similar wood products, tubes, bottles, Balloons, CD-s, data carriers such as floppy disks, chip cards and other suitable. If, for example, a film roll is to be printed during the wrapping process, preferably the printing device is followed by an infrared or UV lamp or a blower. At the Umwickelvorgang holds the controller, the transport speed of the conveyor and the printing speed to each other synchronously. For this purpose, a rotary encoder / frequency co-ordinator can be provided. Furthermore, at least one air nozzle can be arranged on the scanner A in such a way that an air cushion can be generated between the scanner A and the product surface by overpressure or by suction to the product surface. Finally, special inks can be used, which indicate, for example by color change, the state raw or cooked eggs.

• ➢ Verzerrungen des Druckbilds sind praktisch nicht wahrnehmbar.
• ➢ Durch Hintereinanderschaltung mehrerer Druckköpfe ist die Druckgeschwindigkeit in weitem Bereich zu steigern.
• ➢ Die Auflagekraft kann je nach Anwendungsfall in weitem Bereich variiert werden.
• ➢ Der zusätzliche Kostenaufwand für die bewegliche Druckkopfaufhängung und dem Abtaster ist sehr gering.

The device according to the invention for automatically adjusting the height has the advantage that in a surprisingly simple manner it is possible to inscribe any flat or uneven surfaces-with or without a surface structure-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 over a wide range.
• ➢ The contact force can be varied over a wide range depending on the application.
• ➢ The additional cost of moving the print head suspension and scanner is very low.

All illustrated and described embodiments, as well as all disclosed in the description and / or the drawings new individual features and their combination with each other, are essential to the invention. For example, the application of a tube to be printed on a mandrel (frictional engagement) can be omitted since no pressure force is applied during the printing process, the printing system is also for printing under difficult environmental conditions (dust), e.g. suitable for printing on cement sacks, etc.

Claims (17)

1. Device for automatically adapting the height of a printer device (D) arranged above a conveying device, comprising a movably mounted, resilient elastic printing head suspension (DA), and

   - a printing head holder (DH), which is connected to the printing head suspension, for the printing device (D),
   wherein

   - at least the resilient printing head suspension (DA) is aligned perpendicular to the conveying device of the surface to be printed, and
   characterised in that

   - the printing head holder (DH) for the printing device (D) is designed with a fitted-on scanner (A), and

   - the printing device (D) extends into the scanner (A).
2. Device according to claim 1, characterized in that the weight of the printing head suspension (DA) is at least partly compensated by an adjustable tension spring (ZF), which is arranged above the printing head suspension and exerts a counter force.
3. Device according to claim 1, characterized in that the weight of the printing head suspension (DA) is at least partly compensated by means of an hinged arm (S), which is arranged laterally on the printing head suspension and has assigned to it an adjustable compression or tension spring (F), or by means of a counterweight.
4. Device according to claim 1, characterised in that a parallelogramshaped or triangular or roller or toothed-wheel guide,. comprising a vibration damper for the printing head suspension (DA) is provided.
5. Device according to claim 1, characterised in that the scanner (A) is spherically shaped, has a recess (AS) for the print region and an angular setting device that is adjustable such that the scanner (A) slides at an acute angle on the surface to be printed.
6. Device according to claim 1, characterised in that when the scanner (A) encounters the surface to be printed, it triggers a switching function for the printing operation.
7. Device according to claim 1, characterised in that the printing head suspension (DA) bears at least two printing heads (DK), which are kept at the same height by the printing head suspension (DA)..
8. Device according to claim 1, characterised in that the printing device (D) is an ink-jet printer or a laser printer or a digital printer, which is in connection with a control device, and that the control device is connected both to the conveying device and to a storage device containing the imprint.
9. Device according to claim 7 or 8, characterised in that to obtain a high printing speed and/or resolution, a plurality of printing heads (DK) are connected in series and are actuated in parallel by the control device, and print in the product direction or perpendicular to the conveying direction.
10. Device according to claim 1 or 8, characterised in that, for printing the side or base surface of the product located on the conveying device, a printing head holder or holders (DH) is/are located laterally or below.
11. Device according to claim 1, characterised in that an infrared or UV lamp or a fan is arranged downstream of the printing device (D).
12. Device according to claim 1, characterised in that at least one air nozzle is arranged on the scanner (A) such that an air cushion between the scanner (A) and product surface can be generated by overpressure, or suction on the product surface can be generated by underpressure.
13. Device according to claim 1, characterised in that the underside of the scanner (A) has a depression.
14. Device according to claim 1, characterised in that the printing head holder (DH) is arranged such that it is suspended on an hinged arm (S).
15. Method for using a device according to claim 7 or 8, characterised in that the control device keeps the filling amount in the printing head cartridge of both printing heads (DK) at the same filling level.
16. Method for use of a device according to one of the preceding claims 1 to 14, characterised in that the control device keeps the transport speed of the conveying device and the printing speed synchronous with one another.
17. Method for use of a device according to the preceding claims 1 to 14, characterised by the use of an ink that displays the raw or cooked state of the eggs by means of a colour change..

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