Digital printing machine with capping element

Abstract

A digital printing press comprises a printing substrate transport device (2), a print head (3) with nozzles, which is mounted so as to be vertically adjustable towards the printing substrate transport device (2) into a first print head position and away from the printing substrate transport device (2) into a second print head position (6), and a capping element (7) which is adjustable into an active position (8), in which the capping element (7) covers the nozzles, and into a passive position, in which the capping element (7) does not cover the nozzles. A mechanism (10) is provided which automatically adjusts the capping element (7) to the passive position when the print head (3) is vertically adjusted to the first print head position and automatically adjusts it to the active position (8) when the print head (3) is vertically adjusted to the second print head position (6).

Description

[0001] The present invention relates to a digital printing machine, comprising a printing material transport device, a print head with nozzles, which is mounted so as to be vertically adjustable towards the printing material transport device into a first print head position and away from the printing material transport device into a second print head position, and a capping element which is adjustable into an active position in which the capping element covers the nozzles, and into a passive position in which the capping element does not cover the nozzles.

[0002] Capping elements are used to cover nozzle plates in inkjet printing machines to protect the nozzles in the nozzle plates from drying out and clogging during a printing interruption.

[0003] DE 10 2016 222 960 A1 describes a digital printing press in which the print heads are mounted vertically adjustable and the capping elements are mounted pivotably. Automatic adjustment of these capping elements is not provided. Manual adjustment of the capping elements increases maintenance time. Furthermore, the operating personnel may forget to adjust one of the capping elements, which can lead to complications. These complications could include, for example, a fault indication on the control panel if the positioning of the capping element is monitored by sensors. This delays the machine start-up.

[0004] Furthermore, US 5 677 715 A, US 2007 / 0 146 414 A1 and JP 2001 - 277 529 A describe non-generic digital printing machines in which the print head is mounted in a horizontally adjustable manner.

[0005] The object of the invention is to create a further digital printing machine of the type mentioned above.

[0006] The object is achieved by a digital printing machine, comprising a printing material transport device, a print head with nozzles, which is mounted so as to be vertically adjustable towards the printing material transport device into a first print head position and away from the printing material transport device into a second print head position, and a capping element which is adjustable into an active position in which the capping element covers the nozzles, and into a passive position in which the capping element does not cover the nozzles, characterized in that a mechanism is provided which automatically adjusts the capping element to the passive position when the print head is vertically adjusted to the first print head position and automatically adjusts it to the active position when the print head is vertically adjusted to the second print head position.

[0007] One advantage of the digital printing press according to the invention is that the capping element does not need to be manually adjusted to the active and passive positions. This shortens maintenance time. The digital printing press according to the invention is not only easier to maintain but also safer to operate. A delay in machine start-up caused by incorrect positioning of the capping element is eliminated.

[0008] The following further training courses are possible: The mechanism may include a coupling gear. The coupling mechanism can be a four-bar mechanism. The coupling mechanism may comprise a first rocker, a second rocker and a coupling which connects the first rocker and the second rocker to each other in an articulated manner, and the capping element can form the coupling. There may be a spring that secures the capping element in the active position and in the passive position. The spring can be part of a multiple detent. The mechanism may include a cam gear. The cam mechanism can have a first control cam for adjusting the capping element to the passive position and a second control cam for adjusting the capping element to the active position. The first control curve and the second control curve may be concave at least in sections. The first control curve and the second control curve can face each other. The cam mechanism may have a cam follower element that cooperates with both the first control cam and the second control cam. There may be a rocker having a first lever arm and a second lever arm, and the cam follower element may be arranged on the first lever arm, and the capping element may be arranged on the second lever arm. Components of the mechanism and the print head can be connected to each other, so that when the print head is moved to the first print head position and when the print head is moved to the second print head position, the components of the mechanism are also adjusted. The mechanism and the print head may be connected to each other via a support which is adjustable towards and away from the substrate transport device and which carries the components of the mechanism and the print head. Said components may include gear elements of the coupling mechanism (e.g. the first rocker arm and the second rocker arm) and / or gear elements of the cam mechanism (e.g. the cam follower element).

[0009] Further developments also arise from the following description of an embodiment and the associated drawing.

[0010] Showing: Fig. 1a - 6b show a print head with a capping mechanism in different positions, viewed from different directions, Fig. 7 a digital printing machine with multiple print heads and associated capping mechanisms that Fig. 1a - 6b are trained accordingly, and Fig. 8 shows an enlarged view of a modification of the capping mechanism.

[0011] In Fig. Figure 7 shows a digital printing press 1 with an annular substrate transport device 2 and a row of print heads 3 for different colors in multi-color printing, running in the substrate transport direction 28. Each print head 3 comprises a row of segments running transversely to the substrate transport direction 28, each segment having a nozzle plate. The substrate transport device 2, e.g., a conveyor belt or a chain of transport tables (trays), rotates and transports the substrate, specifically printed sheets, past the print heads 3, which print the substrate using the inkjet printing process. The print heads 3 or their ink-ejecting nozzles 4 (cf. Fig. 1a) are directed downwards toward a linear section of the annular orbit. Nozzles 4 are incorporated into the nozzle plates of said segments.

[0012] The respective print head 3 is mounted so as to be vertically adjustable in various positions relative to the printing material transport device 2 or the said linear section and is arranged in a support 26 which can be moved up and down. The positions are shown in the Fig. 1a - 6b; in the figures labelled "a" seen from a first viewing direction and in the figures labelled "b" seen from an opposite, second viewing direction.

[0013] The print head 3 is in the Fig. 3a and Fig. 3b in a first print head position 5 for printing and in the Fig. 6a and Fig. 6b in a second print head position 6, in which the print head 3 is not printing (e.g. maintenance position). The first print head position 5 and the second print head position 6 are end positions of the print head 3. Between the first print head position 5 and the second print head position 6 there are intermediate positions, which are shown in the Fig. 2a - 5b. The print head 3 assumes the intermediate positions during its adjustment from the first print head position 5 to the second print head position 6 and back.

[0014] In the second printhead position 6, a capping element 7 (e.g., a tray) filled with a fluid absorber (e.g., a plastic sponge) impregnated with a humectant is located in an active position 8 in front of the nozzles 4 to protect them from drying out and / or damage. A pump supplies the humectant to the capping element 7 and, if the capping element 7 is integrated into a circuit, can be removed again.

[0015] In the first printhead position 5, the capping element 7 is in a passive position 9, in which the capping element 7 exposes the nozzles 4. In the active position 8, the capping element 7 is horizontally aligned below the printhead 3 and, in the passive position 9, vertically aligned to the side of the printhead 3. Consequently, the two end positions 8, 9 of the capping element 7 are essentially orthogonal to each other.

[0016] A mechanism 10 is provided that positively pivots the capping element 7 from the passive position 9 to the active position 8 when the print head 3, together with the capping element 7 and components of the mechanism 10 carried by the carrier 26, is raised from the first print head position 5 to the second print head position 6. The mechanism 10 positively pivots the capping element 7 from the active position 8 to the passive position 9 when the print head 3, together with the capping element 7 and said components of the mechanism 10, is lowered from the second print head position 6 to the first print head position 5.

[0017] The mechanism 10 comprises a coupling gear 11, which determines the movement path of the capping element 7, and a cam gear 19, which drives the movement of the capping element 7. The coupling gear 11 and the cam gear 19 are arranged on opposite sides of the print head 3.

[0018] The coupling mechanism 11 comprises a first rocker arm 12 and a second rocker arm 13, each pivotably connected at one end to a coupling 14 formed by the capping element 7. The first rocker arm 12 and the second rocker arm 13 are each pivotably connected at their other end to the carrier 26. This results in the coupling mechanism 11 being of the four-bar type.

[0019] The cam mechanism 19 comprises a first control cam 20 and a second control cam 21, which are arranged in a fixed position separately from the support 26, e.g., on a frame, and are thus not adjusted when the support 26 is adjusted upwards and downwards. The first control cam 20 or its cam track points upwards, and the second control cam 20 or its cam track points downwards. Furthermore, the cam mechanism 19 comprises a cam follower element 22, specifically a cam roller, which is arranged on the support 26 and cooperates with the first control cam 20 when the support 26 is adjusted downwards, and comes into contact with the second control cam 21 when the support 26 is adjusted upwards.

[0020] The cam follower element 22 is arranged on a first lever arm 24 of a rocker 23, which is pivotally mounted in the support 26. A second lever arm 25 of the rocker 23 is hinged to the capping element 7.

[0021] The cam mechanism 19 and the coupling mechanism 11 are connected to each other by a shaft 27, which transmits torque from the cam mechanism 19 to the coupling mechanism 11. The rocker 23 of the cam mechanism 19 and the second rocker 13 of the coupling mechanism 11 are each fixedly mounted on the shaft 27, which is rotatably mounted in the carrier 26. Thus, the pivoting movement of the rocker 23 is transmitted via the shaft 27 to the second rocker 13, which is the driving rocker of the coupling mechanism 11.

[0022] To secure the capping element 7 in its two end positions, a multiple detent 16 is provided. The multiple detent 16 is arranged on the side of the print head 3 on which the coupling gear 11 is also arranged. The multiple detent 16 comprises a detent projection 16, which enters a first detent recess 18.1 to secure the capping element 7 in the passive position 9 and enters a second detent recess 18.2 to secure the capping element 7 in the active position 8. The two detent recesses 18.1, 18.2 are depressions and are formed in a circumferential surface that is formed on the second rocker 13 and runs essentially concentrically with the shaft 27. The detent projection 16 is held in the respective detent recess 18.1, 18.2 by a spring 15, specifically a leaf spring. The locking projection 16 is designed as a roller and emerges from the respective locking recess 18.1, 18 by overcoming the friction and against the action of the spring 15.2 again when said circumferential surface or the second rocker 13, on which the circumferential surface is formed, is rotated with sufficient force.

[0023] The system shown works as follows: The Fig. 1a to 3b show the automatic release of the nozzles 4 by the capping element 7 when the print head 3 moves downwards.

[0024] In the Fig. 1a, Fig. 1b shows a first release phase in which the cam follower element 22 comes into contact with the first control cam 20. The first control cam 20 is designed in a stepped manner with an upper section and a lower section. The lower section of the first control cam 20 has a (with respect to the Fig. 1a, Fig. 1b (open upwards and to the left) concave L-shape with a horizontal flank and a vertical flank. The cam follower element 22 strikes the upper section in the first phase. At this point, the locking projection 16 is still located in the second locking recess 18.2 and the capping element 7 is still horizontally aligned in its active position 8.

[0025] In the Fig. 2a, Fig. 2b shows a second release phase in which the cam follower element 22 is deflected by the upper section so that the rocker 23 with the capping element 7 with respect to Fig. 2a begins to pivot counterclockwise around its geometric axis of rotation. The torque is transmitted from the rocker 23 to the second rocker 13 via the shaft 27, which is coaxial with the geometric axis of rotation of the rocker 23. The locking projection 16 has protruded from the second locking recess 18.2, and the capping element 7 is in an inclined position.

[0026] In the Fig. 3a, Fig. Figure 3b shows a third release phase in which the cam follower element 22 has reached the lower section of the first control cam 20. The capping element 7 is vertically aligned in its passive position 9, and the locking projection 16 is seated in the first locking recess 18.1. This corresponds to printing operation, with the print head 3 in the first print head position 5 being as close as possible to the printing substrate transport device 2.

[0027] The multiple detent 16 only secures the capping element 7 in the passive position 9 by frictional engagement. However, in the first print head position 5, the frictional engagement is not sufficient because, during printing, an unintentional release of the capping element 7 from the passive position 9 could result in a collision with the printing material transport device 2 and damage. Therefore, the capping element 7 is additionally secured by positive engagement. The positive engagement is achieved by a lateral curved area 29 of the first control cam 20, which has a Fig. 3a would block the clockwise pivoting movement of the rocker 23 in the first print head position 5. The cam region 29 is formed by the aforementioned vertical flank of the L-shape and is located to the side of the cam follower element 22 in its blocked pivoting path.

[0028] If printing is interrupted, the carrier 26 is raised. The carrier 26 is constructed in several parts, with a skeleton structure, and all print heads 3 are housed within it, so that all print heads 3 rise together with the carrier 26.

[0029] The Fig. 4a to 6b show the automatic covering of the nozzles 4 by the capping element 7 when the print head 3 moves upwards in the carrier 26.

[0030] The Fig. 4a, Fig. 4b shows a first capping phase, in which the cam follower element 22 comes into contact with the second control cam 21. The second control cam 22 has a cam track with a concave V- or U-shape (open downwards). The cam follower element 22 abuts against a section of the cam track that slopes upwards. At this point, the locking projection 16 is still seated in the first locking recess 18.1, and the capping element 7 is still vertically aligned in its passive position 9.

[0031] In the Fig. 5a, Fig. Figure 5b shows a second capping phase, in which the cam follower element 22 continues to move upwards along the curved path of the second control cam 21 and is deflected by the said curved path section, which rises diagonally upwards. As a result, the rocker 23 with the capping element 7 pivots with respect to Fig. 5a clockwise (and accordingly with respect to Fig. 5b (counterclockwise). The torque is transmitted from the rocker 23 to the second rocker 13 via the shaft 27, causing the locking projection 16 to emerge from the first locking recess 18.1. The locking projection 16 then runs on the circumferential region of the outer circumference of the eye of the second rocker 13, located between the first locking recess 18.1 and the second locking recess 18.2. The capping element 7 is in an inclined position.

[0032] The Fig. 6a, Fig. 6b shows a third capping phase, in which the cam follower element 22 has reached an upper section of the cam track of the second control cam 21. The capping element 7 is aligned horizontally in its active position 8 and covers the nozzles 4 from below. The locking projection 16 has reached the second locking recess 18.2 and has engaged therein. The system state shown corresponds to a maintenance mode in which the print head 3 is in the second print head position 6, at its maximum distance from the printing substrate transport device 2.

[0033] Fig. Figure 8 shows a modification in which the first rocker arm 12 has been omitted. A cam follower element 30, e.g., a pin, is attached to the capping element 22. A grooved cam 32, into which the cam follower element 30 engages, is introduced into a stationary plate 31. When the capping element 7 is moved from the passive position 9 shown to the active position 8, the cam follower element 30 runs along the grooved cam 32, the geometry of which determines the shape of the movement of the capping element 7. In the modification according to Fig. 8, the capping element 7 moves in the same way as with respect to the Fig. 1 to 7. The modification differs from this embodiment in terms of construction and function only in the differences explained. List of reference symbols 1 digital printing machine 2 Printing material transport device 3 Print head 4 nozzle 5 first print head position 6 second print head position 7 Capping element 8 Active Position 9 Passive position 10 Mechanism 11 coupling gear 12 first wings 13 second swing 14 paddocks 15 spring 16 multiple detent 17 Rast-Vorsprung 18.1 first rest recess 18.2 second locking recess 19 cam gear 20 first control curve 21 second control curve 22 Curve follower element 23 Seesaw 24 first lever arm 25 second lever arm 26 carriers 27 Wave 28 Substrate feed direction 29 Curve area 30 Curve follower element 31 plate 32 Groove curve QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2016 222 960 A1

[0003] US 5 677 715 A

[0004] US 2007 / 0 146 414 A1

[0004] JP 2001 - 277 529 A

[0004]

Claims

[1] Digital printing machine (1), comprising - a substrate transport device (2), - a print head (3) with nozzles (4) which is mounted so as to be vertically adjustable towards the printing material transport device (2) into a first print head position (5) and away from the printing material transport device (2) into a second print head position (6), and - a capping element (7) which is adjustable into an active position (8), in which the capping element (7) covers the nozzles (4), and into a passive position (9), in which the capping element (7) does not cover the nozzles (4), characterized by that a mechanism (10) is present which automatically moves the capping element (7) into the passive position (9) when the print head (3) is moved vertically into the first print head position (5) and automatically moves it into the active position (8) when the print head (3) is moved vertically into the second print head position (6). [2] Digital printing machine according to claim 1, characterized by that the mechanism (10) has a coupling gear (11). [3] Digital printing machine according to claim 2, characterized by that the coupling mechanism (11) is a four-bar mechanism. [4] Digital printing machine according to claim 2 or 3, characterized by that the coupling mechanism (11) has a first rocker (12), a second rocker (13) and a coupling (14) which connects the first rocker (12) and the second rocker (13) to one another in an articulated manner, and that the capping element (7) forms the coupling (14). [5] Digital printing machine according to one of claims 1 to 4, characterized by that a spring (15) is present which secures the capping element (7) in the active position (8) and in the passive position (9). [6] Digital printing machine according to claim 5, characterized by that the spring (15) belongs to a multiple detent (16). [7] Digital printing machine according to one of claims 1 to 6, characterized by that the mechanism (10) has a cam gear (19). [8] Digital printing machine according to claim 7, characterized by that the cam mechanism (19) has a first control cam (20) for adjusting the capping element (7) into the passive position (9) and a second control cam (21) for adjusting the capping element (7) into the active position (8). [9] Digital printing machine according to claim 8, characterized by that the first control curve (20) and the second control curve (21) are at least partially concave. [10] Digital printing machine according to claim 8 or 9, characterized by that the first control cam (20) and the second control cam (21) face each other [11] Digital printing machine according to one of claims 8 to 10, characterized by that the cam mechanism (19) has a cam follower element (22) which cooperates with both the first control cam (20) and the second control cam (21). [12] Digital printing machine according to claim 11, characterized by that a rocker (23) with a first lever arm (24) and a second lever arm (25) is provided, and that the cam follower element (22) is arranged on the first lever arm (24) and the capping element (7) is arranged on the second lever arm (25). [13] Digital printing machine according to one of claims 1 to 12, characterized by that components of the mechanism (10) and the print head (3) are connected to one another, so that when the print head (3) is adjusted to the first print head position (5) and the print head (3) is adjusted to the second print head position (6), the components of the mechanism (10) are also adjusted. [14] Digital printing machine according to claim 13, characterized bythat the mechanism (10) and the print head (3) are connected to one another via a support (26) which is adjustable towards and away from the printing material transport device (2) and which carries the components of the mechanism (10) and the print head (3).

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