EP2740600B1 - Method for printing an inner surface of an object that is to be printed using a pad printing press - Google Patents

Description

TECHNICAL AREA

The present invention relates to a method for printing an inner surface of an object to be printed by means of a pad printing machine and a pad printing machine for carrying out such a method. By means of this method, in particular inner surfaces of hollow cylindrical objects, such as finger rings, can be printed by means of a pad printing machine.

STATE OF THE ART

Pad printing machines are known in the prior art in numerous designs and are used for printing differently shaped objects. For this purpose, a print image is taken from a cliché by means of a printing pad and then transferred to an object to be printed. By forming the printing pad from an elastic material, it is also possible to print on uneven surfaces.

However, printing on inner surfaces presents a particular challenge for pad printing machines. Such inner surfaces, which are difficult to access for the printing pad, are present in particular in the case of tubular or annular objects.

A method of printing the inner surfaces of hollow cylindrical Items is in the US 4,667,594 described. In this case, a pressure pad is introduced with a cylindrically shaped outer surface in the interior of, for example, a tube. By the printing pad is then pressed together along its longitudinal axis from two opposite sides by means of two pressure plates, a radial expansion of the printing pad is achieved. The outer surface of the printing pad is thereby brought circumferentially in contact with the inner surface of the tube, and transferred the printed image to the inner surface of the tube.

A disadvantage of the in the US 4,667,594 disclosed printing method is that so that only cylindrically shaped inner surfaces can be printed, the inner radius of each is slightly larger than the outer radius of the pressure pad. Inner surfaces with larger inner radii as well as inner surfaces, which deviate strongly from the cylindrical form, can not be printed with this printing process.

PRESENTATION OF THE INVENTION

It is therefore an object of the present invention to provide a method for printing on an inner surface by means of a pad printing machine, which allows printing even if the inner surface has an arbitrarily large inner radius and / or deviates greatly from the cylindrical shape. To solve this problem, a method is proposed, as indicated in claim 1. In addition, a tampon printing machine for carrying out this method is specified in claim 8. Advantageous embodiments of the invention are specified in the dependent claims.

• Aufnahme eines Druckbildes vom Klischee mittels der Aussenfläche des Drucktampons (Farbaufnahme); sowie
• Übertragen des Druckbildes von der Aussenfläche des Drucktampons auf ein zu bedruckendes Objekt (Farbabgabe).

The present invention thus provides a method for printing an inner surface of an object to be printed by means of a pad printing machine, which has at least one cliché and a printing pad with an outer surface. The method has at least the following steps:

• Recording a printed image from the cliché by means of the outer surface of the printing pad (color image); such as
• Transferring the print image from the outer surface of the print pad to an object to be printed (color output).

When transferring the print image onto the object to be printed, that is to say during the ink dispensing, the outer surface of the print pad is unrolled on an inner surface of the object to be printed and / or an inner surface of the object to be printed is unrolled on the outer surface of the print pad.

By unrolling the printing pad on the inner surface or the inner surface on the printing pad, printing is still possible without problems even if the inner surface has a radius that is many times greater than the printing pad. It is also a printing of inner surfaces possible, which differ greatly from the cylindrical shape. The inner surface can have both concave and convex areas, which are both printable by the specified method.

Advantageously, the inner surface of the object to be imprinted is a concavely curved and, in particular, a substantially cylindrical inner surface. In general, the inner surface extends over an angular range of 360 ° and is in particular designed to be circumferentially closed. However, the inner surface does not necessarily have to extend circumferentially over an angular range of 360 °. In general, however, it is then an inner surface, if it extends at least over an angular range of 180 ° or more.

The object to be printed may in particular be a ring-shaped or tubular article. Preferably, it is a finger ring, which is in particular made of a transparent material, such as glass. The finger ring does not have to be closed circumferentially.

When transferring the print image, the object to be printed is advantageously held in an object holder, which has a substantially cylindrical outer side. As a result, in particular the printing of objects is facilitated, which have a non-cylindrical outer surface. The object holder thus serves, in particular, to provide a cylindrical outer side independently of the configuration of the object to be printed, in order to facilitate unrolling or holding the object to be printed in a holding device. Furthermore, the object holder can serve to provide a concentric arrangement of the object to be printed and in particular to ensure its inner surface relative to the cylindrical outer side of the object holder.

In one embodiment of the invention, the object to be printed is rolled laterally guided in a rolling track when transferring the printed image. The printing pad is usually moved relative to the object to be printed in a direction which is substantially perpendicular to a roll axis, which is given by the rolling of the object to be printed in the rolling track.

In another development of the invention, the printing pad has a longitudinal central axis and, when transferring the printed image onto the object to be printed, essentially executes a circular movement about an axis of rotation which extends parallel to but spaced from this longitudinal central axis. The radius of this circular movement is usually chosen such that it is equal to or slightly larger than the radius, which results from a subtraction of the inner radius of the inner surface of the object to be printed minus the outer radius of the pressure pad.

Advantageously, when taking the printed image, the outer surface of the printing pad is unrolled on the plate and / or the plate is unrolled on the outer surface of the printing pad. The length of the roll-off is advantageously chosen so that it corresponds to the circumferential length of the pressure pad. By rolling the outer surface of the printing pad on the cliché and / or the cliché on the outer surface of the printing pad usually a roll axis is defined. During the recording of the printed image relative to the cliche, the printing pad is preferably moved in a first direction along this roll axis, so that the outer surface of the printing pad receives the printed image along a helical line. During the transfer of the print image, the print pad is then moved relative to the object to be printed in a direction opposite to the first direction second direction, so that the print image is transmitted again along a straight line on the object to be printed. In this way, the inner surface of the object to be printed can also be printed with printed images which are formed longer than the circumferential length of the printing pad. It is thus possible in particular a printing of the inner surface with a printed image, which is the same length as the circumferential length of the inner surface.

The present invention also provides a pad printing machine which is adapted to carry out such a method. The pad printing machine has a cliché and a printing pad with an outer surface, which serves to receive a printed image from the cliche and then transferring this print image to an object to be printed.

The pad printing machine also has means to allow a guided unrolling of the outer surface of the printing pad on an inner surface of the object to be printed and / or an inner surface of the object to be printed on the outer surface of the printing pad.

Preferably, the pad printing machine also has a printing pad carrier, with which the printing pad is connected such that the printing pad is freely rotatable relative to the printing pad carrier about an axis of rotation. This axis of rotation can in particular correspond to a longitudinal central axis of the printing pad. Additionally or alternatively, the pad printing machine has a holding device with a base unit and a holding device connected to the base unit, which serves for holding an object to be printed, and which is freely rotatable about an axis of rotation relative to the base unit. The base unit is usually immovable relative to a machine frame of the pad printing machine. The printing pad or the holding device is thus rotatable as smoothly as possible, so that during printing, the printing pad on the inner surface or the inner surface can roll on the printing pad, without in particular mutual sliding movements occur. This ensures a clean unrolling of the printing pad on the inner surface. For this purpose, for example, one or more ball bearings may be present, which are arranged between the printing pad and printing pad carrier or between the holding device and the base unit.

Preferably, the pad printing machine has a linear unit on which either the printing pad or a holding device is mounted for holding an object to be printed, wherein the printing pad is linearly displaceable by means of the linear unit relative to the holding device in a direction which extends substantially parallel to the axis of rotation. The linear unit may in particular be a Act linear motor. But it is also a pneumatic operation of the linear unit conceivable.

The printing pad is advantageously rotationally symmetrical. Even more advantageously, the outer surface of the printing pad is barrel-shaped. It can even be formed substantially cylindrical. In a barrel-shaped configuration, the outer surface may, in deviation from a purely cylindrical configuration, in particular also be curved circumferentially outwards along the longitudinal central axis of the pressure pad. Advantageously, the printing pad has a Shore 00 hardness of 75 to 95, more preferably 80 to 90, and most preferably about 85. In particular, for the printing of conical and / or wavy inner surfaces of the printing pad but can also have a Shore 00 hardness in the range between 70 and 80. The printing pad then adapts better to the inner surface due to its flexibility.

As a means for the guided unwinding, the pad printing machine may have a rolling track, within which an object holder with a substantially cylindrical outer side during the transfer of the print image on an object held in the object holder to be printed object is unrolled. The rolling track is designed in particular as a profile strip with a U-shaped cross-section.

In general, the printing pad has a longitudinal center axis, and the pad printing machine has a pad carrier on which the printing pad is attached. As a means for the guided rolling of the printing pad can then also be rotatable relative to the pad carrier about an axis of rotation which extends substantially parallel, but spaced from the longitudinal center axis of the printing pad. Between tampon carrier and printing pad then advantageously a rotary member, in particular a rotary cylinder, arranged, which is rotatable about an axis of rotation relative to the pad carrier, and on which the printing pad is mounted with respect to its longitudinal central axis eccentric to this axis of rotation.

Preferably, the pad printing machine has a first drive unit for moving the print pad in a substantially horizontal direction and a second drive unit for moving the print pad in a substantially vertical direction move. The first and / or the second drive unit may in particular comprise a servomotor. The first drive unit serves, in particular, to displace the printing pad linearly along a y-axis of the pad printing machine, and the second drive unit serves, in particular, to move the printing pad linearly along a z-axis of the pad printing machine that is substantially perpendicular to the y-axis. As a means for the guided unwinding, the pad printing machine can then also have a motion control unit, which is designed to simultaneously drive the first drive unit and the second drive unit such that the resulting movement of the pressure pad essentially represents a movement along a circular line. The first and the second drive unit are thus preferably controlled by the motion control unit in such a way that the pressure pad is moved along the y or the z axis according to a speed function which corresponds to a sine or a cosine function. If the pad printing machine has a linear unit, this preferably serves to move the printing pad along an x-axis which is substantially perpendicular to the y-axis and the z-axis.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

zeigt eine perspektivische Ansicht einer Tampondruckmaschine gemäss einer ersten erfindungsgemässen Ausführungsform;

Fig. 2

zeigt eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine;

Fig. 3

zeigt eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine während der Aufnahme des Druckbildes vom Klischee;

Fig. 4

zeigt eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine nach Verschieben des Drucktampons in den Bereich des zu bedruckenden Objekts;

Fig. 5

zeigt eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine nach Verschieben des Drucktampons in eine Position zum Übertragen des Druckbildes auf das zu bedruckende Objekt;

Fig. 6

zeigt eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine zu Beginn des Abrollens des Drucktampons auf einer Innenfläche des zu bedruckenden Objekts in einer Abrollbahn;

Fig. 7

zeigt eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine am Ende des Abrollens des Drucktampons auf einer Innenfläche des zu bedruckenden Objekts in einer Abrollbahn;

Fig. 8

zeigt eine perspektivische Teilansicht einer Tampondruckmaschine gemäss einer zweiten erfindungsgemässen Ausführungsform;

Fig. 9

zeigt eine perspektivische Teilansicht der in der Fig. 8 gezeigten Tampondruckmaschine nach Verschieben des Drucktampons in den Bereich des zu bedruckenden Objekts;

Fig. 10

zeigt eine perspektivische Teilansicht der in der Fig. 8 gezeigten Tampondruckmaschine nach Verschieben des zu bedruckenden Objekts in eine Position zum Übertragen des Druckbildes vom Drucktampon auf das zu bedruckende Objekt;

Fig. 11

zeigt eine perspektivische Teilansicht der in der Fig. 8 gezeigten Tampondruckmaschine während des Bedruckens aus einer ersten Blickrichtung;

Fig. 12

zeigt eine perspektivische Teilansicht der in der Fig. 8 gezeigten Tampondruckmaschine während des Bedruckens aus einer zweiten Blickrichtung;

Fig. 13

zeigt eine perspektivische Teilansicht einer Tampondruckmaschine gemäss einer dritten erfindungsgemässen Ausführungsform nach Verschieben des Drucktampons in den Bereich des zu bedruckenden Objekts; sowie

Fig. 14

zeigt eine perspektivische Teilansicht der in der Fig. 13 gezeigten Tampondruckmaschine während des Bedruckens.

Preferred embodiments of the invention will be described below with reference to the drawings, which are given by way of illustration only and are not to be interpreted as limiting. In the drawings show:

Fig. 1

shows a perspective view of a pad printing machine according to a first embodiment of the invention;

Fig. 2

shows a partial perspective view of the in the Fig. 1 shown pad printing machine;

Fig. 3

shows a partial perspective view of the in the Fig. 1 shown pad printing machine during recording of the printed image from the cliché;

Fig. 4

shows a partial perspective view of the in the Fig. 1 shown pad printing machine after moving the printing pad in the area the object to be printed;

Fig. 5

shows a partial perspective view of the in the Fig. 1 shown pad printing machine after moving the printing pad in a position for transferring the printed image on the object to be printed;

Fig. 6

shows a partial perspective view of the in the Fig. 1 shown pad printing machine at the beginning of the rolling of the printing pad on an inner surface of the object to be printed in a rolling track;

Fig. 7

shows a partial perspective view of the in the Fig. 1 shown pad printing machine at the end of the rolling of the printing pad on an inner surface of the object to be printed in a roll-off;

Fig. 8

shows a partial perspective view of a pad printing machine according to a second embodiment of the invention;

Fig. 9

shows a partial perspective view of the in the Fig. 8 shown pad printing machine after moving the printing pad in the area of the object to be printed;

Fig. 10

shows a partial perspective view of the in the Fig. 8 shown pad printing machine after moving the object to be printed in a position for transferring the printed image from the printing pad on the object to be printed;

Fig. 11

shows a partial perspective view of the in the Fig. 8 shown pad printing machine during printing from a first viewing direction;

Fig. 12

shows a partial perspective view of the in the Fig. 8 shown pad printing machine during printing from a second viewing direction;

Fig. 13

shows a partial perspective view of a pad printing machine according to a third embodiment of the invention after moving the printing pad in the area of the object to be printed; such as

Fig. 14

shows a partial perspective view of the in the Fig. 13 shown pad printing machine during printing.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the FIGS. 1 to 7 a tampon printing machine is shown, which is suitable for carrying out the method according to a first embodiment of the invention.

As it is in the FIG. 1 is shown, the pad printing machine on a machine frame 10, which has a substantially U-shape, the opening points in the horizontal direction. The upper leg of this U-shape forms an arm 101. At the end face of this arm 101, a display 11 is arranged, which serves for displaying operating conditions, machine parameters, etc. Below the display 11 a plurality of input elements 12 are provided on the arm 101, which serve for setting and operating the pad printing machine by the user.

In the region of the outer end of the lower leg of the U-shaped form of the machine frame 10, a slide 50 is mounted, which serves to support an object to be printed. The slide 50 is immovable relative to the machine frame 10. As in particular from the Figures 2 and 3 is visible, is on the upper side of the lower leg of the machine frame 10, a plate carrier 20 is arranged with a cliché mounted thereon 21 and on the underside of the upper leg a displaceable in the horizontal direction along the arm 101 tampon carrier 43 is attached. By means of adjusting elements 201, the position of the plate 21 on the plate carrier 20 is manually adjustable. The pad printing machine also has a paint pot 30 arranged in a region close to the printing plate 21.

As it is from the FIG. 2 can be seen, the pad carrier 43, to which a printing pad 46 is attached, via a linear unit 42, a rail 41 and a vertical displacement unit 40 to the arm 101 is connected. The vertical displacement unit 40 is held in a rail formed on the underside of the arm 101, not visible in the drawings, which allows the displacement unit 40 and thus the printing pad 46 to be displaced in the horizontal direction. This horizontal direction, in which the vertical displacement unit 40 is displaceable along the arm 101, is hereinafter referred to as the y-axis 71 of the pad printing machine (see FIG. 1 ). The vertical displacement unit 40 has the shape of a bellows and is in the vertical direction by accordingly provided, the skilled person well known means extender or shortened, so that the vertical displacement unit 40 allows movement of the printing pad 46 in the vertical direction. This vertical direction, which is referred to hereinafter as the z-axis 72 of the pad printing machine, is perpendicular to the y-axis 71. The printing pad 46 is thereby basically linearly displaceable at least in two directions, namely along the arm 101 in the horizontal direction (y-axis 71 ) and substantially perpendicular thereto in the vertical direction (z-axis 72). For the displacement of the printing pad in these two directions, the pad printing machine advantageously has corresponding drives, in particular servomotors.

The rail 41 is fixedly attached to the underside of the vertical adjustment unit 40. At the bottom of the rail 41, a linear unit 42 is movably mounted such that it is manually displaceable relative to the rail 41 in a direction substantially perpendicular to the vertical direction of the z-axis 72 and the through the arm 101 predetermined horizontal direction of the y-axis 71 is. This direction, in which the linear unit 42 is displaceable relative to the rail 41, extends along the x-axis 70 of the pad printing machine defined below. To facilitate the user's correct positioning of the printing pad 46, a scale is attached to the rail 41. It can also be provided locking elements, such as screws, which allow fixing of the linear unit 42 along the x-axis 70 and the underside of the rail 41.

The linear unit 42 has a housing 421 which is displaceably mounted on the rail 41 along the x-axis 70 and has a displacement element 422 held therein (see, for example, US Pat Figures 3 and 5 ) to which the pad carrier 43 and thus the printing pad 46 are attached. The displacement member 422 is movable relative to the housing 421 such that linear displacement of the attached tampon carrier 43 and thus the printing pad 46 in the same horizontal direction is enabled, in which the rail 41 extends. By this direction, in which the pressure pad 46 by means of displacement of the displacement element 422 relative to the housing 421 of the linear unit 42nd is movable, an x-axis 70 of the pad printing machine is defined (see FIG. 1 ).

For the displacement of the displacement element 422 relative to the housing 421, the linear unit 42 has a drive, in particular a linear motor. It could alternatively also be a pneumatic drive. The printing pad 46 is thus in the present embodiment by means of corresponding drives within the three-dimensional space extending between the two legs of the U-shaped configuration of the machine frame 10 anywhere along the x, y, and z axes 70, 71, 72 positionable.

The tampon carrier 43 fixed on the underside of the displacement element 422 serves to hold the pressure pad 46 via a round rod 45. The tampon carrier 43 has a continuous receiving opening extending along the x-axis 70 in a lower region for receiving the round rod 45 serves. At the round rod 45 corresponding locking means may be provided to allow a locking of the round rod 45 in this receiving opening.

From the pad carrier 43, the round rod 45 held therein extends outwardly along the x-axis 70. Spaced apart from the pad carrier 43, a printing pad 46 is attached to the round rod 45, in particular in the area of a free end of the round rod 45. The printing pad 46 generally has the shape of a barrel with a peripheral outer surface curved slightly outwards in the longitudinal direction. The barrel-shaped configuration of the outer surface of the printing pad 46 defines a longitudinal central axis 461 of the printing pad 46, which extends along the x-axis 70 of the pad printing machine.

The printing pad 46 is mounted on the round rod 45 such that it is freely rotatable relative to this about its longitudinal central axis 461. Between printing pad 46 and round rod 45 two not visible in the drawings ball bearings are provided for this purpose. Of course, the printing pad 46 could also be rotationally fixed to the round rod 45, if for the round rod 45 is rotatably connected about its longitudinal axis with the pad carrier 43. One or more ball bearings could then be provided correspondingly between round rod 45 and pad carrier 43.

The printing pad 46 is harder in comparison to the printing pads commonly used in pad printing methods and has a Shore A hardness of 75 or more, especially about 90. In particular, for the printing of conical and / or corrugated inner surfaces of the printing pad 46 may also be formed softer.

From the FIG. 2 it can be seen that the slide 50 here has a flat, horizontal top surface on which a roll-off 51 is mounted. The rolling track 51 is formed as a cross-sectionally U-shaped rail, which extends along the y-axis 71 of the pad printing machine. The two lateral limbs of the U-shaped profile rail serve as lateral guides of the object 61 to be imprinted in an object holder 60 during printing (see FIG FIG. 4 ).

The object holder 60 has in particular a cylindrical outer side, which is slightly shorter in the direction of its longitudinal center axis compared to the inner spacing of the lateral guides of the rolling track 51. The object holder 60 can be guided laterally roll in the roll-off 51. Along a circumferential center line of its outer side, the object holder 60 is separable into two separate shells to allow insertion of the object 61 to be printed in the object holder 60.

The object 61 to be printed is a transparent, in particular made of glass, finger ring. By means of the pad printing machine, the inner surface of the finger ring to be printed in order to cause an optical effect on its outside due to the transparency of the finger ring. The finger ring to be printed has a substantially cylindrical inner surface and an outer surface deviating from a cylindrical shape. The object holder 60 serves to allow a laterally guided rolling of the finger ring in the rolling track 51 around the longitudinal central axis defined by its inner surface.

The method of printing on the inner surface of the object 61 to be printed by the pad printing machine of the present embodiment is particularly understood from FIGS FIGS. 3 to 7 clearly visible. In a first step, ink is usually transferred from the ink pot 30 to the plate 21 by means of a doctor blade (not visible in the figures) in order to form a printed image 22 there.

As it is in the FIG. 3 is shown, the printing pad 46 is lowered by the vertical adjustment unit 40 along the z-axis 72 downwards (arrow a) for ink absorption until it rests with its outer surface on the plate 21. The vertical adjustment unit 40 is then moved forward along the y-axis 71 (arrow b), so that the printing pad 46 rolls on the printed image 22 (arrow c) and this is recorded by means of the outer surface of the printing pad 46. By means of the vertical adjustment unit 40, the printing pad 46 is then raised along the z-axis 72 (arrow d).

The vertical adjustment unit 40 is then displaced along the y-axis 71 (arrow e, FIG. 4 ), that the printing pad 46 occupies a position directly in the region of the longitudinal center axis defined by the inner surface of the object 61 to be printed, or in particular somewhat below it.

From this position, the printing pad 46, as shown in the FIG. 5 is shown by extending the sliding element 422 from the housing 421 of the linear unit 42, along the x-axis 70 in the limited by the inner surface of the object to be printed 61 interior space (arrow f).

In order to print on the inner surface of the object 61 to be printed, the printing pad 46 is finally lowered by the vertical adjustment unit 42 (arrow g, FIG. FIG. 6 ) until it rests on the inner surface of the object 61 to be printed. The vertical adjustment unit 42 is then moved during the actual printing process along the y-axis 71 (arrow h, FIG. 7 ) that the object holder 60 with the object 61 to be imprinted therein is guided laterally in the rolling-down path 51 (arrow i, FIG. FIG. 6 ). The printing pad 46 thereby performs a rotation about its longitudinal central axis 461 and thereby transmits the printed image from its outer surface to the inner surface of the object 61 to be printed. During unrolling, the longitudinal central axis 461 of the printing pad 46 forms the rolling axis of the rolling movement.

A pad printing machine according to a second embodiment of the invention is in the FIGS. 8 to 12 and a pad printing machine according to a third embodiment of the invention is shown in FIGS FIGS. 13 and 14 shown. Equal or similar elements of the tampon printing machines of the second and third embodiments will be denoted below by the same reference numerals as the corresponding elements in the FIGS. 1 to 7 shown first embodiment.

The in the FIGS. 8 to 12 The second embodiment shown differs from the first embodiment, inter alia, in that the pad carrier 43 is attached directly to a carriage 47 connected to the rail 41. There is thus no linear unit between the rail 41 and the pad carrier 43. In order to enable the printing pad 46 to be displaced relative to the object 61 to be printed along the x-axis 70, a holding device provided with a linear unit 53 for holding the object holder 60 with the object 61 to be printed is provided here. The holding device is attached to a housing 531 of the linear unit 53 fixedly mounted on the slide 50. The linear unit 53, which may be operated pneumatically, for example, but is preferably designed as a linear motor, has a relative to the housing 531 linearly displaceable along the x-axis 70 sliding element 532, at the end of a three-point gripper 52 is attached. The three-point gripper 52 has three holding jaws distributed uniformly along a circumferential direction and forms a holding device for holding the object holder 60. By means of the linear unit 53, the object 61 to be imprinted in the object holder 60 is moved along the x-axis 70 relative to the slide 50 and to the Machine frame 10 displaced.

As another difference to that in the FIGS. 1 to 7 shown embodiment, the pad printing machine here on no roll-off, but a rotary cylinder 44 (see FIG. 9 ), which is arranged between the pad carrier 43 and the round rod 45 and is displaceable by means of a corresponding drive in a rotational movement. The rotary cylinder 44 has a cylindrical outer surface and two flat, mutually parallel end surfaces, of which the first is connected to the pad carrier 43. At the second end surface of the round rod 45 is mounted eccentrically, so that a Rotary movement of the rotary cylinder 44 about its longitudinal central axis leads to a circular movement of the printing pad 46 about an axis of rotation, which extends parallel, but spaced from the longitudinal central axis 461 of the printing pad 46.

The recording of the printed image 22 from the plate 21 is analogous to the first embodiment. For transferring the printed image 22 onto the object 61 to be printed, the printing pad is subsequently displaced along the y-axis 71 toward the object 61 to be printed (arrow j, FIG. 9 ). In order to bring the printing pad 46 in the area directly delimited by the inner surface of the object 61 to be printed, the displacement element 532 of the linear unit 53 is then moved along the x-axis 70 in accordance with FIG FIG. 10 shown arrow k out of the housing 531. For the actual, in the FIGS. 11 and 12 shown printing process, the printing pad 46 is first lowered according to arrow 1 until it rests on the inner surface of the object 61 to be printed. The rotary cylinder 44 is then placed in a rotational movement about its longitudinal central axis (arrow m), so that the round rod 45 and thus also the printing pad 46 each perform a circular movement about the longitudinal center axis of the rotary cylinder 44 (arrow n). The outer surface of the printing pad 46 rolls thereby guided on the inner surface of the rotatably fixed object to be printed 61 and transmits the printed image.

The in the FIGS. 13 and 14 The third embodiment shown differs from the second embodiment of FIG FIGS. 8 to 12 in that the round rod 45 is mounted directly on the printing pad carrier 43 and thus the rotary cylinder 44 is omitted in comparison to the second embodiment. The ink absorption takes place analogously to the first and the second embodiment. After taking the ink, the printing pad 46 is displaced along the y-axis 71 toward the object 61 to be printed (arrow o, FIG. 13 ). By means of the linear unit 53, the object 61 to be printed is then displaced along the x-axis 70 so far that it laterally surrounds the printing pad 46 ( FIG. 14 ).

For printing, the printing pad 46 is first lowered onto the inner surface of the object to be printed (61) (arrow p). For the guided rolling on the inner surface of the object to be printed 61, the printing pad 46 is then placed in a circular motion about a roll axis, which is parallel, but spaced from the longitudinal center axis 461 of the Pressure pads 46 extends (arrows q and r). To put the printing pad 46 in this circular motion, the pad printing machine has a not visible in the drawings motion control unit, which drive units for moving the vertical adjustment unit 40 along the y-axis 71 and for extending the vertical adjustment unit 40 along the z-axis 72nd at the same time controls such that a circular movement of the printing pad 46 results around the defined by the inner surface of the object to be printed 61 longitudinal central axis. The two linear movements along the y-axis 71 and the z-axis 72 are thus superimposed by means of the motion control unit such that a rotational movement results. The two drive units for the movements along the y-axis 71 and the z-axis 72 are thereby controlled by the motion control unit in particular such that the linear movements are performed according to a speed function corresponding to a sine or a cosine function.

Of course, the invention described herein is not limited to the mentioned embodiments and a variety of modifications is possible. Thus, in an alternative embodiment, during the transfer of the printed image onto the object to be printed, the printing pad can, for example, also be fixed relative to the machine frame and the object to be printed is set in a circular movement about the longitudinal central axis of the printing pad. Between the object to be printed and the slide could then be arranged a rotary cylinder, to which the object to be printed is mounted eccentrically. In this alternative embodiment, but also in the embodiments described above, the printing pad could even be attached to the machine frame in a rotationally fixed manner if, correspondingly, the object to be imprinted is freely rotatable about an axis extending along the x-axis. A variety of other modifications is conceivable. LIST OF REFERENCE NUMBERS 10 machine frame 46 printing pad 101 poor 461 Longitudinal central axis 11 display 47 carriage 12 input elements 50 slides 20 plate holder 51 rolling path 201 adjusting 52 Three-point gripper 21 cliche 53 linear unit 22 print image 531 casing 532 displacement element 30 paint pot 60 object holder 40 Vertical displacement unit 61 Object to be printed 41 rail 42 linear unit 70 X axis 421 casing 71 y-axis 422 displacement element 72 z-axis 43 pad carrier 44 rotary cylinder a - r arrows 45 round bar

Claims (14)

1. Method for printing a concavely curved inner surface of an object (61) to be printed by means of a pad printing machine which has at least one printing plate (21) and a printing pad (46) with an outer surface, the method having at least the following steps:

   - picking up a printing image (22) from the printing plate (21) by means of the outer surface of the printing pad (46); and

   - transferring the printing image from the outer surface of the printing pad (46) to an object (61) to be printed;

   characterized in that
   when transferring the printing image (22) to the object (61) to be printed, the outer surface of the printing pad (46) is rolled on a concavely curved inner surface of the object (61) to be printed and/or a concavely curved inner surface of the object (61) to be printed is rolled on the outer surface of the printing pad (46).
2. Method according to Claim 1, wherein the inner surface of the object (61) to be printed is a substantially cylindrical inner surface.
3. Method according to one of the preceding claims, wherein, during the transfer of the printing image (22), the object (61) to be printed is held in an object holder (60) which has a substantially cylindrical outer side.
4. Method according to one of the preceding claims, wherein, during the transfer of the printing image (22), the object (61) to be printed is rolled and guided laterally in a rolling track (51).
5. Method according to one of Claims 1 to 3, wherein the printing pad (46) has a longitudinal central axis (461) and, during the transfer of the printing image (22) to the object (61) to be printed, substantially executes a circular movement about an axis of rotation which extends parallel to but at a distance from this longitudinal central axis (461).
6. Method according to one of the preceding claims, wherein, when picking up the printing image (22), the outer surface of the printing pad (46) is rolled on the printing plate (21) and/or the printing plate (21) is rolled on the outer surface of the printing pad (46).
7. Method according to Claim 6, wherein, as a result of rolling the outer surface of the printing pad (46) on the printing plate (21) and/or rolling the printing plate (21) on the outer surface of the printing pad (46), a rolling axis is defined, and wherein, when picking up the printing image (22), the printing pad (46) is moved relative to the printing plate (21) in a first direction along this rolling axis, so that the outer surface of the printing pad (46) picks up the printing image (22) along a helical line, and wherein, during the transfer of the printing image, the printing pad (46) is moved relative to the object (61) to be printed in a second direction pointing counter to the first direction.
8. Pad printing machine for carrying out a method according to one of the preceding claims, having
   a printing plate (21), and
   a printing pad (46) with an outer surface, for picking up a printing image (22) from the printing plate (21) and for subsequently transferring this printing image (22) to an object (61) to be printed,
   characterized in that
   the pad printing machine has means in order to permit guided rolling of the outer surface of the printing pad (46) on a concavely curved inner surface of the object (61) to be printed and/or guided rolling of a concavely curved inner surface of the object (61) to be printed on the outer surface of the printing pad (46).
9. Pad printing machine according to Claim 8, additionally having a printing pad carrier (43) to which the printing pad (46) is connected in such a way that the printing pad (46) is freely rotatable relative to the printing pad carrier (43) about an axis of rotation, and/or wherein the pad printing machine has a holding device with a base unit (50, 53) and a holding device (52) which is connected to the base unit (50, 53) and which is used to hold an object (61) to be printed and which is freely rotatable relative to the base unit (50, 53) about an axis of rotation.
10. Pad printing machine according to Claim 9, additionally having a linear unit (42; 53), to which either the printing pad (46) or a holding device (52) for holding an object (61) to be printed is attached, wherein the printing pad (46) is linearly displaceable relative to the holding device (52) by means of the linear unit (42; 53) in a direction which extends substantially parallel to the axis of rotation.
11. Pad printing machine according to one of Claims 8 to 10, wherein the outer surface of the printing pad (46) is barrel-shaped, in particular substantially cylindrical.
12. Pad printing machine according to one of Claims 8 to 11, wherein the pad printing machine has, as means for the guided rolling action, a rolling track (51), within which, during the transfer of the printing image (22) to an object (61) to be printed that is held in the object holder (60), an object holder (60) having a substantially cylindrical outer side can be rolled.
13. Pad printing machine according to one of Claims 8 to 11, wherein the printing pad (46) has a longitudinal central axis (461) and the pad printing machine has a pad carrier (43), to which the printing pad (46) is attached, and wherein, as means for the guided rolling action, the printing pad (46) can be rotated relative to the pad carrier (43) about an axis of rotation which extends substantially parallel to but at a distance from the longitudinal central axis (461) of the printing pad (46).
14. Pad printing machine according to one of Claims 8 to 11, wherein the pad printing machine has a first drive unit in order to move the printing pad (46) in a substantially horizontal direction, and has a second drive unit in order to move the printing pad (46) in a substantially vertical direction, and wherein, as means for the guided rolling action, the pad printing machine additionally has a movement control unit which is configured so as to activate the first drive unit and the second drive unit simultaneously in such a way that the movement of the printing pad (46) resulting therefrom substantially represents a movement along a circular line.

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