CN110775671A

CN110775671A - Digital printing machine

Info

Publication number: CN110775671A
Application number: CN201910674986.3A
Authority: CN
Inventors: A·米勒
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 2018-07-25
Filing date: 2019-07-25
Publication date: 2020-02-11
Anticipated expiration: 2039-07-25
Also published as: CN110775671B; DE102019209125A1

Abstract

The invention relates to a digital printing machine comprising a tray (3) which jointly supports printed sheets (2) and rotates along an annular rail (4), wherein a gap (6) is present between the side surfaces (15) of the tray (3). An element (7) for narrowing, sealing or bridging the gap (6) is arranged on the side face (15).

Description

Digital printing machine

Technical Field

The invention relates to a digital printing machine comprising trays (Tablett) which together carry the sheets to be printed and which rotate along an endless track, wherein a gap is present between the sides of the trays.

Background

DE 102015204514 a1 and DE 102016204215 a1 each describe a printing press in which each printed sheet is carried by only one tray.

In WO 2012/108870 a1, a printing press is described in which a single sheet is simultaneously supported by a plurality of trays. That is, in this closest prior art, there are a plurality of trays that collectively carry one substrate sheet.

There are the following problems here: there is a gap between the trays that is filled with ambient air. The thermal characteristics of these gaps are different from those of the trays. Since the supported sheet covers these gaps, these gaps locally thermally influence the sheet. Thereby possibly affecting the print quality.

Disclosure of Invention

The object of the invention is to provide a digital printing press with a pallet, in which thermally induced effects on the printing quality are avoided.

This object is achieved by a digital printing machine comprising trays which together carry the sheets to be printed and which rotate along an endless track, wherein gaps are present between the sides of the trays, characterized in that elements are arranged on the sides for narrowing, sealing or bridging the gaps.

There are many possible improvements:

these elements may be formed or fastened to these trays.

The side faces may each have an outer half with reference to the annular rail, and the elements may extend in the outer halves of the side faces. These elements may extend only in the outer halves or may extend beyond the outer halves.

These elements can extend over the format width (format) of the printed sheet. In this case, the elements can form an arrangement which is at least as long as the format width, or each element can be at least as long as the format width.

These elements may be or may comprise rubber elastic elements.

The trays can have a support surface for the printed sheets, and the elements can be arranged flush with the support surface.

These elements may have lamellae (Lamellen).

The sheets may be arranged as leaves for each tray

In the form of (1).

These sheets may constitute a hinge (Leporello) for each tray.

These elements may form a comb-like structure embedded in one another.

Drawings

Further developments emerge from the following description of embodiments and the accompanying drawings, in which:

FIG. 1: a schematic overall view of a digital printer with a tray;

fig. 2a and 2 b: a first embodiment in which the elements according to the invention are each mounted on only one of two adjacent trays;

FIG. 3: a second embodiment, wherein the elements are mounted on two adjacent trays;

fig. 4a and 4 b: a third embodiment wherein the elements are accordion-like;

FIG. 5: a fourth embodiment, wherein the elements are formed by a combination of sheets and elastic blocks; and

FIG. 6: a fifth embodiment, wherein these elements constitute a labyrinth seal.

In fig. 1 to 6, members whose functions correspond to each other are denoted by the same reference numerals, so that a repeated description is not necessary.

Detailed Description

A digital printer with an inkjet print head 1 is shown in fig. 1. The transport device transports the sheets 2, wherein the sheets 2 are printed by the printing heads 1. The conveyor device comprises a pallet 3 revolving on an endless track 4. These trays 3 are connected to each other by a drive chain and guided by a rail system. The endless track 4 has sections which are curved about a central point 5 in the front and in the rear with reference to the transport direction T of the printed sheets 2, in which the trays 3 are deflected. The curved sections are interconnected by straight, horizontally oriented sections. In the straight upper section, the printed sheets 2 are transported in the transport direction T on the trays 3, while in the straight lower section the trays 3 are returned empty. The print heads 1 are directed with their nozzles towards a straight upper section.

The trays 3 each have a support surface 8, and the support surfaces 8 are designed as suction surfaces, which have vacuum openings for holding the printed sheets 2 in a stationary manner. Between each two adjacent trays 3 there is a gap 6 in the form of a gap. When the trays 3 run through the straight section of the annular rail 4, the sides 15 of the two trays 3 delimiting the gap 6 are parallel to one another, and the gap 6 has a constant gap width, as can be seen in fig. 2 a. The gap width is less than 1mm and is for example 0.4 mm. These lateral surfaces 15 each have an outer half 17, referred to the annular rail 4, which outer half 17 engages the support surface 8. As the trays 3 travel through the curved section of the annular rail 4, the gap width of the gap 6 increases from the inside to the outside with reference to the annular rail 4, wherein the two sides 15 are distanced from one another, as can be seen in fig. 2b to 5.

Since each printed sheet 2 is simultaneously supported by at least two or more trays 3 during its transport, the printed sheet 2 covers at least one or more of the gaps 6 between the trays 3 supporting the printed sheet 2. The number of gaps 6 covered by the printing sheet 2 is dependent on the respective format length of the printing sheet 2.

If no countermeasures according to the invention are taken in the form of elements 7, there is a risk of impaired printing quality due to these gaps 6, said elements 7 being described next on the basis of different embodiments. This risk is present in particular when there is a large temperature difference between the trays 3 and the sheets 2. The sheets 2 can be precoated in a digital printing machine with a primer and then dried by a thermal dryer directly before the sheets 2 are printed by the printing head 1. When the sheets 2 heated by the dryer are transported on the trays 3 to the printing heads 1, the gaps 6 located below the sheets 2 can cause thermal disturbances which are then visible as stripes in the printed image if they are not suppressed or at least reduced by the elements 7.

The elements 7 are arranged on the trays 3 in the region of the gaps 6. The elements 7 can be formed on the trays 3 (as in the exemplary embodiment according to fig. 6) or fastened to the trays 3 (as in the other exemplary embodiments). These elements 7 comprise elastic elements in addition to the embodiment according to fig. 6. These elements 7 may be bridges between adjacent trays 3, may be seals in the gaps 6, may be extensions of the receiving surface 8, or may be a combination of the above. For example, the elements 7 can be seals which prevent or partially limit the contact between the cooler ambient air in the gaps 6 and the hotter printing sheet 2 above the gaps 6. Likewise, the elements 7 can be, for example, bridges between adjacent trays 3, or can be extensions of the receiving surfaces 8 of the trays 3, wherein the temperature of the elements 7 is higher than the temperature of the ambient air in the gaps 6 and can be comparable to or close to the temperature of the trays 3.

Fig. 2a to 6 show various exemplary embodiments of detail a shown in fig. 1 in an enlarged manner.

Fig. 2a and 2b show a first exemplary embodiment, in which the element 7 is designed as a strip or block made of rubber-elastic plastic. Said element 7 is fastened to one of the two trays 3 delimiting the gap 6 on the tray 3 in the upper corner region of the tray 3. Where said element 7 can be glued to the side wall 15 of the tray 3. The elements 7 are arranged flush with the support surface 8 in the first exemplary embodiment, as in all other exemplary embodiments. Such a flush is advantageous if the element 7 forms an extension of the receiving surface 8 (as in fig. 6, for example). If the element 7 forms a seal (as in fig. 2a to 3, for example), such a flush is not necessary and the element 7 can be located slightly below the support surface 8. During the travel of the two trays 3 over the straight upper section of the annular rail 4, the element 7 constitutes a bridge bridging the gap 6 and rests briefly on the tray 3 to which the element 7 is not fastened. Here, the element 7 is compressed, as can be seen in fig. 2 a. In fig. 2b, it can be seen that the element 7 is loose (entspan) when the element 7 is released from the side wall of the one pallet 3 while running over the curved front section of the endless track 4. Since all the trays 3 of the transport device are of identical construction, the description given by way of example of one gap 6 with regard to the arrangement and the construction of the elements represents the elements 7 of all the gaps 6.

Fig. 3 shows the second exemplary embodiment in a movement phase corresponding to fig. 2 b. Here, on each of the two trays 3, in the region of its upper corners, an element 7 is arranged. These two elements 7 projecting in the gap 6 do not contact each other during the movement phase of the illustrated tray 3, but contact each other under stress (corresponding to fig. 2a) during the movement phase not illustrated. In addition, a further element 7 can be arranged on each of the two pallets 3 in the lower corner region thereof, wherein the two lower further elements 7 are in contact with one another in both of the above-described two phases of movement of the pallets 3 (i.e. in the case of straight travel and in the case of curved travel). In the second exemplary embodiment, these elements 7 are arranged not only in the outer half 17 of the side 15 with reference to the annular rail 4, but also in the inner half. In the second embodiment, each element 7 is also configured as a strip or block of rubber-elastic plastic.

A third embodiment is shown in fig. 4a and 4B, wherein fig. 4B shows detail B in fig. 4a in an enlarged manner. The element 7 is arranged here as in the first exemplary embodiment. As in the other exemplary embodiments, the element 7 extends over the entire width of the conveyed printing sheet 2, which is to be measured orthogonally to the drawing plane of fig. 4 a. The element 7 is profiled in a zigzag shape and has the form of a hinge 9. The lamellae or lamellae 16 of the element 7 are connected to each other by a bent hinge, so that the element 7 springs in the direction given by the arrow (feeder). In the side 15 of the tray 3, pins 10 are provided for fastening and guiding the elements 7. The element 7 has holes by means of which the element 7 is plugged onto pins 10, which pins 10 are arranged in a row along the element 7.

A fourth embodiment is shown in fig. 5, in which the element 7 is made up of sheets 16, which sheets 16 together form a leaf 11. Between the sheet layers 16, elastic strips or blocks 19 (for example made of foam) can be arranged, which strips or blocks 19 are each fastened (for example glued) to only one sheet layer 16 in the upper end region of the sheet layer 16. The sheets 16 are swingable about hinges 12, in which hinges 12 each sheet 16 is supported at a lower end of the sheet 16.

Fig. 6 shows a fifth exemplary embodiment in a view based on the viewing direction VI shown in fig. 1, wherein for the sake of greater clarity the sheets 2 are not shown together, which sheets 2 cover the gaps 6 on the two aforementioned trays 3 and on the vacuum openings of the trays 3 in the support surface 8. The mutually facing sides 15 of the trays 3 each have a comb structure 18, wherein the comb structures 18 engage into each other during the transport of the printing sheet 2. The comb-shaped structures 18 have tines 13 projecting into the gap 6, the tines 13 being molded onto the trays 3 and constituting the elements 7. These sharp teeth 13 constitute an extension of the support surface 8 and are flush or coplanar therewith. These elements 7 together form a labyrinth seal 14, in which labyrinth seal 14 a narrow, meandering air gap remains free relative to gap 6. The amount of ambient air reaching the printing sheet 2 via the air gap is so small that it does not cause appreciable thermal disturbances and visible impairment of the printing quality.

List of reference numerals

1 printing head

2 printing sheet

3 tray

4 annular rail

5 center point

6 gap

7 element

8 bearing surface

9 hinge

10 pin

11 leaf

12 hinge part

13 tine

14 labyrinth seal

15 side surface

16 sheets

17 outer half

18 comb structure

19 pieces

Details A

Details of B

T direction of conveyance

Claims

1. A digital printing machine comprises trays (3) which jointly carry the sheets (2) to be printed and which revolve along an endless track (4),

wherein a gap (6) is present between the side faces (15) of the tray (3),

it is characterized in that the preparation method is characterized in that,

an element (7) for narrowing, sealing or bridging the gap (6) is arranged on the side face (15).

2. The digital printer according to claim 1, wherein,

it is characterized in that the preparation method is characterized in that,

the side surfaces (15) each have a half (17) that is external with respect to the annular rail (4) and

the element (7) extends in the outer half (17) of the side (15).

3. The digital printer according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the element (7) protrudes beyond the side face (15).

4. The digital printer according to any one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the element (7) extends over the format width of the printing sheet (2).

5. The digital printer according to any one of claims 1 to 4,

it is characterized in that the preparation method is characterized in that,

the element (7) is or comprises a rubber-elastic element.

6. The digital printer according to any one of claims 1 to 5,

it is characterized in that the preparation method is characterized in that,

the tray (3) has a receiving surface (8) for the printed sheets (2), and

the elements (7) are arranged flush with the support surface (8).

7. The digital printer according to any one of claims 1 to 6,

it is characterized in that the preparation method is characterized in that,

the element (7) has a sheet (16).

8. The digital printer according to claim 7, wherein,

it is characterized in that the preparation method is characterized in that,

the sheet (16) is arranged in the form of a leaf (9) for each tray (3).

9. The digital printer according to claim 7, wherein,

it is characterized in that the preparation method is characterized in that,

the lamellae (16) form a hinge (8) for each tray (3).

10. The digital printer according to any one of claims 1 to 6,

it is characterized in that the preparation method is characterized in that,

the elements (7) form comb structures (18) that are embedded in one another.