Digital printing machine

Abstract

To provide a digital printing machine having high functional reliability when a print head support is shifted. [Solution] The digital printing press comprises a substrate transport device 2 and an assigned print head support 1. The print head support 1 is supported by a coupling gear so that the height can be adjusted. The coupling gears are arranged offset from one another in the substrate transport direction T. A common motor is provided for driving the coupling gears. The coupling gears each have a first coupling body and a second coupling body and a crank with a first lever arm and a second lever arm.

Description

[Technical field]

[0001] The invention relates to a digital printing press having a printing substrate transport device and an associated print head support, in which the print head support is supported in a height-adjustable manner by a coupling gear device, and in which the coupling gear devices are arranged offset relative to one another in the printing substrate transport direction.

[0002] Such a digital printing machine is shown in U.S. Patent No. 10,081,206. Another prior art is described in Japanese Patent Laid-Open Publication No. 10-202922.

[0003] An object of the present invention is to provide a further digital printing machine.

[0004] The above problem is solved by a digital printing press having a printing material transport device and an associated printing head support, in which the printing head support is supported in a height-adjustable manner by a coupling transmission device, and the coupling transmission devices are arranged offset from one another in the printing material transport direction, characterized in that a common motor is provided for driving the coupling transmission devices, the coupling transmission devices each have a first coupling body and a second coupling body, and the coupling transmission devices each have a crank with a first lever arm and a second lever arm.

[0005] The advantage obtained in the digital printing machine according to the invention is a high degree of functional reliability when shifting the printhead support.

[0006] An additional advantage is that the printhead support can be suitable to accommodate a plurality of printheads which can be arranged in a row parallel to the substrate transport direction.

[0007] The developments listed below can be implemented either individually or in any combination with one another.

[0008] The coupling transmissions are connectable to each other via at least one movable transmission member.

[0009] The transmission member may be a synchronous shaft.

[0010] The printhead support is connectable to the first link via a horizontal linear guide.

[0011] There may be a right angle between the first lever arm and the second lever arm of each crank.

[0012] The printhead support can be assigned a compensation device for compensating for the weight.

[0013] The compensation device may have a number of rocker levers on which the printhead support may be supported.

[0014] The rocker lever may be loaded by a compensation mass.

[0015] Further advantageous functional and structural developments emerge from the following description and the accompanying drawings. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a three-dimensional view of a digital printing press with a printhead support. [Diagram 2] FIG. 2 is a side view showing the printhead support in the active position. [Diagram 3] FIG. 2 is a side view showing the printhead support in an intermediate position. [Figure 4] FIG. 2 is a side view showing the printhead support in a passive position. [Diagram 5] FIG. 1 is a three-dimensional view showing a digital printing press with the printhead support omitted for better clarity.

[0017] The digital printing press comprises a printhead support 1 in which a number of printheads (not shown in the drawings), preferably for inkjet, are arranged in a row parallel to the substrate-transport direction T. The printhead support 1 is configured as a lattice frame with accommodation compartments for the printheads. Below the printhead support 1 is arranged a substrate-transport device 2, for example a conveyor belt or tablet chain, which runs in a circular fashion during the printing operation. The substrate-transport device 2 transports the substrate, preferably in the form of a sheet, in the substrate-transport direction T during printing.

[0018] The print head support 1 is supported on an auxiliary frame 3 so as to be shiftable for height adjustment via two connecting transmissions 4. This allows the print head support 1 to be selectively shifted between an active position (see FIG. 2) close to the substrate transport device 2 during printing and a passive position (see FIG. 4) away from the substrate transport device 2, for example during maintenance, and also to an intermediate position (see FIG. 3) located therebetween. One connecting transmission 4 is arranged upstream of the print head and print head support 1 as viewed in the substrate transport direction T, and the other connecting transmission 4 is arranged downstream of the print head and print head support 1.

[0019] In order to synchronize the two coupling gears 4, the two coupling gears 4 are connected to one another via at least one gear member, in particular a synchronizing shaft 5. The synchronizing shaft 5 is arranged coaxially to a common motor 6 which drives the two coupling gears 4. The motor 6 is an electric motor which rotates when the coupling gears 4 are shifted to the respective required direction of rotation.

[0020] The two coupling transmissions 4 have the same structure and each has a first crank 7, a second crank 8 and a first connector 9 (main connector). Each coupling transmission 4 can in particular be called a parallelogram four-joint transmission or a parallel crank transmission. The first crank 7 and the second crank 8 reciprocate during shifting within an angular range of values ​​of 180° and can therefore also be called oscillating. Preferably, each coupling transmission 4 additionally has a second connector 10 (auxiliary connector).

[0021] Each of the cranks 7, 8 is connected to a first connecting body 9 via a first joint 11, connected to a second connecting body 10 via a second joint 12, and further rotatably supported on the auxiliary frame 3 via a third joint 13. The synchronous shaft 5 is arranged coaxially with the third joint 13 of the two connecting transmissions 4. The second crank 8 of the connecting transmission 4 is fixed to the synchronous shaft 5, which forms a joint pin of the third joint 13 and is connected to the motor 6.

[0022] Each of the first crank 7 and the second crank 8 has a first lever arm a leading from the first joint 11 to the third joint 13, a second lever arm b leading from the second joint 12 to the third joint 13 and an angle α preferably of 90° existing between the two lever arms a, b. With regard to the joint spacing, i.e. the length of the first lever arm a and the length of the second lever arm b and the magnitude of the angle α, the four cranks 7, 8 of the two coupling transmissions 4 are identical.

[0023] Each second link 10 is bent so that it can bend somewhat under a forcing force due to its flexural elasticity. The second link 10 has a concavely extending underside due to the flexure or bending. In FIG. 3 the link 4 is shown in an extended position, in which the first joint 11 and the third joint 13 of the two cranks 7, 8 are located on the same line, so that the two first lever arms a are aligned horizontally on said line. The extended position is not defined with respect to the other directions of movement if the second link 10 is not provided. The task of the second link 10 is to ensure uniqueness with respect to the other directions of movement in the current extended position of the link 4.

[0024] This allows a maximum shift distance, i.e. a difference in height from the active position (see FIG. 2) to the passive position (see FIG. 4), to be twice as large as the second lever arm b. The first lever arm a of the first crank 7 and the first lever arm a of the second crank 8 each start from the third joint 13 and extend vertically downwards when the print head support 1 is at the bottom of all possible positions, i.e. the active position (see FIG. 2). The first lever arm a of the first crank 7 and the first lever arm a of the second crank 8 each start from the third joint 13 and extend vertically upwards when the print head support 1 is at the top of all possible positions, i.e. the passive position (see FIG. 4).

[0025] An additional advantage resulting from the presence of the second coupling body 10 of the two coupling gears 4 is that this allows the respective coupling gear 4 to be overdetermined, so that the first crank 7 is clamped without play to the second crank 8. In this way, tilting of the print head support 1 due to play is avoided.

[0026] The print head support 1 is connected to the auxiliary frame 3 via two vertical linear guides 14 and to the first coupling bodies 9 of the two coupling transmissions 4 via four horizontal linear guides 15. The vertical linear guides 14 and the horizontal linear guides 15 each consist of a roller fixed to the print head support 1 and an elongated hole introduced into the auxiliary frame 3 or into the first coupling body 9, in which the roller engages and runs inside during shifting. The two vertical linear guides 14 are arranged at two opposite ends of the auxiliary frame 3 in the substrate transport direction. A pair of horizontal linear guides 15 is assigned to each first coupling body 9, the two horizontal linear guides 15 of each pair being offset from one another in the transverse direction to the substrate transport direction T.

[0027] A compensating device with compensation masses 16 is used to compensate for the weight of the printhead support 1 and the printhead present therein when shifting into the above-mentioned positions. The compensation masses 16 are arranged on rocker levers 17 which are pivotally supported on the auxiliary frame 3. The rocker levers 17 each have a support arm 18 which bears from below against the printhead support 1 under the action of the compensation masses 16. A roller is arranged at the free end of each support arm 18, on which the printhead support 1 is supported.

[0028] The compensation mass 16 serves to preferably precisely compensate for the weight of the print head unit, i.e. the weight of the print head support 1 and the print head present therein, in such a way that the height of the print head unit changes only when the motor 6 is correspondingly energized and moves, the locking and frictional torques of the motor 6 advantageously preventing movements of the print head unit that are not related to a height adjustment of the print head unit, for example in the event of a power failure.

[0029] Many variations are possible.

[0030] Instead of the compensation mass 16, the compensation device may include a number of springs which engage the rocker lever 17 to move the support arm 18 upwardly.

[0031] The compensation device can be adapted to the locking and friction torques in the case of the above-mentioned variations in the size of the compensation mass 16 or in the size of the spring force, so that in the event of a power failure, the compensation device overcomes the locking and friction torques of the motor 6 while moving the print head unit 1 upwards from the active position, for example to a passive position.

[0032] Instead of the synchronizing shaft 5, a chain combined with sprockets, a belt combined with belt pulleys, or a rack combined with pinions can also be used to synchronize the two linking transmissions 4.

[0033] In order to prevent the print head support 1 from tilting, instead of the second connecting body 10, the vertical linear guides 15 can each have two rollers which are fixed to the print head support 1 with a large vertical distance from each other and engage in the long holes of the vertical linear guides 15. [Explanation of symbols]

[0034] 1 Print head support 2 Print substrate conveyance device 3 Support frame 4. Connecting transmission device 5 Synchronous shaft 6 Motor 7 First Crank 8. Second Crank 9 First Connecting Body 10 Second connector 11 First Joint 12 Second Joint 13 The third joint 14 Vertical linear guide 15 Horizontal linear guide 16 Compensation mass 17 Rocker lever 18 Support Arm a First lever arm b Second lever arm T Printing substrate conveyance direction α angle

Claims

1. A digital printing machine comprising a printing substrate transport device (2) and an associated print head support (1), The print head support (1) is supported by a coupling transmission device (4) so ​​as to be height-adjustable, and the coupling transmission devices (4) are arranged offset from one another in the printing medium transport direction (T). In digital printing machines, A common motor (6) is provided to drive the coupling transmission (4), The coupling transmission device (4) has a first coupling body (9) and a second coupling body (10), The linking transmission (4) has cranks (7, 8) each having a first lever arm (a) and a second lever arm (b). A digital printing machine characterized by:

2. The coupling transmissions (4) are connected to each other via at least one movable transmission member.

2. The digital printing machine of claim 1.

3. The transmission member is a synchronous shaft (5).

3. The digital printing machine according to claim 2.

4. The print head support (1) is connected to the first connector (9) via a horizontal linear guide (15).

4. A digital printing machine according to claim 1.

5. a right angle (α) exists between the first lever arm (a) and the second lever arm (b) of each of the cranks (7, 8); 4. A digital printing machine according to claim 1.

6. a compensation device for compensating for the weight of the print head support (1) is assigned to the print head support (1), 2. The digital printing machine of claim 1.

7. The compensation device comprises a rocker lever (17) which engages with the printhead support (1).

7. The digital printing machine according to claim 6.

8. The rocker lever (17) is loaded by a compensation mass (16).

8. The digital printing machine according to claim 7.

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