Device for transporting bows

Abstract

A device for transporting sheets (1) comprises at least one circulating belt (3, 4) and at least one suction chamber (5) for pneumatically holding the sheets (1) on the at least one circulating belt (3, 4), wherein a series of parallel belts (3, 4) together form a sheet transport plane (13) under a pressure unit (14), of which at least one belt (4) runs upstream of the other belts (3) and is deflected downwards from the sheet transport plane (13).

Description

[0001] The present invention relates to a device for transporting sheets, comprising at least one circumferential belt and at least one suction chamber for pneumatically holding the sheets on the at least one circumferential belt.

[0002] Such devices are used, for example, in inkjet printing machines.

[0003] For example, a device corresponding to the aforementioned type is described in DE 10 2018 216 029 B3.

[0004] The object of the invention is to create a further device for transporting bows.

[0005] The problem is solved by a device for transporting sheets, comprising at least one circulating belt and at least one suction chamber for pneumatically holding the sheets on the at least one circulating belt, characterized in that a series of parallel belts together form a sheet transport plane under a pressure unit, of which at least one belt runs upstream of the other belts and is deflected downwards from the sheet transport plane.

[0006] An advantage of the device according to the invention is that, in this device, there are structurally favorable conditions for the arrangement of one or more separating elements for separating or detaching the sheets from the tapes.

[0007] The following training courses can be taken individually or, provided they are not technically mutually exclusive, in any combination: In a further development advantageous for a staggered downward deflection of the belts in the belt row, a deflection point for at least one belt and deflections for the other belts are arranged at positions offset from each other in the direction of the arc travel. The deflection point for the at least one belt and the deflections for the other belts can be designed as deflection rollers.

[0008] In a further development that is advantageous with regard to fixing the sheets and ensuring they lie flat during printing, several suction chambers are provided to hold the sheets on the series of parallel belts, together forming a rotating tray chain. The tray chain can be driven by the series of parallel belts.

[0009] In a further development that is advantageous with regard to high operational reliability when dispensing the sheets from the device, at least one belt leaves a gap between the other belts as it dips down. A separating element is arranged to engage in this gap and serves to separate the sheets from the other belts. This separating element can be a conveyor belt.

[0010] In a further development that is advantageous with regard to the removal of paper dust and / or smeared ink stains, a cleaning station is provided for cleaning the series of parallel belts.

[0011] In a further development that is advantageous with regard to cost-effective manufacturing, a common drive shaft is provided for driving the series of parallel belts. Thus, a single motor can advantageously drive all parallel belts of the belt series synchronously via the common drive shaft.

[0012] In a further development that simplifies spare parts inventory, at least one belt is the same length as the other belts and runs on a track with a different path than the tracks of the other belts. Because the belts are the same length, it is possible to use identical spare belts for both the at least one belt and the other belts; there is no need to stock spare belts of different types.

[0013] Further information can also be obtained from the following description of an exemplary embodiment and the associated drawing.

[0014] It shows: Fig. 1. The diagram of a sheet transport device in a digital printing machine in side view and Fig. 2 the bow transport device from Fig. 1. Top view.

[0015] In Fig. 1 and Fig. Figure 2 shows a sheet transport device from various perspectives, which transports sheets 1 past printheads 2, which print the sheets 1, e.g., using inkjet technology. During transport, the sheets 1 lie on endless belts 3, 4, which are made, for example, of welded steel. The belts 3, 4 run over suction chambers 5, which apply a vacuum to the belts 3, 4 and guide them in a plane 6.

[0016] The bands 3, 4 are designed as suction bands and have perforations 7, e.g., bores, through which a negative pressure from the suction chambers 5 located beneath the respective band 3, 4 acts on the sheet 1. This suction effect on the sheet 1 holds the sheet 1 in place on the band 3, 4.

[0017] Belts 3 and 4 are driven by a common drive shaft 8, so that all belts 3 and 4 rotate synchronously. The drive shaft 8 is formed by a drive roller which deflects the belts 3 and 4.

[0018] In the example shown in the drawing, the suction chambers 5 are mobile and together form an endless tray chain 9. The tray chain 9 performs a circular motion 10 and is driven by the belts 3, 4, which in turn perform a circular motion 11. The tray chain 9 is driven by the belts 3, 4 by force or friction, whereby the suction chambers 5 exert a suction effect on the closed surface areas of the belts 3, 4 located between the perforations 7 and thus adhere to them temporarily.

[0019] Each belt 3, 4 is deflected by several deflection rollers 12. For each belt 3, 4, one of the deflection rollers 12 is designed as a convex centering roller for centering the belt 3, 4. A small lateral gap A of preferably about 0.5 mm to 0.9 mm exists between the parallel belts 3, 4.

[0020] The belts 3 and 4 form a sheet transport plane 13, the so-called printing section, beneath a printing unit 14 in which the printheads 2 are arranged. In the area of ​​the sheet transport plane 13, all belts 3 and 4 run on the suction chambers 5. The tray chain 9 supports the series of parallel belts 3 and 4 from below.

[0021] At a first position I of the sheet transport plane 13, the suction chambers 5 are deflected downwards. The suction chambers 5 move along an orbit which has the shape of an elongated ring. This orbit is defined, for example, by a rail system on which the interconnected suction chambers 5 rotate. At the first position I, said orbit causes the suction chambers 5 to successively detach from the belts 3, 4 and descend downwards from the sheet transport plane 13, after the suction chambers 5 have passed the pressure unit 14 and transported the respective sheet 1 past the pressure unit 4 in the sheet travel direction BLR.

[0022] Further downstream along the arc 1, there is first a second position II and then a third position III of the arc transport plane 13. At the second position II, a first row 15 of belt deflectors is arranged, and at the third position III, a second row 16 of belt deflectors. The belt deflectors of both rows 15, 16 can be designed as deflection rollers. At the second position II, a portion of the belts 3, 4, preferably every second belt 3, 4, dips downwards, while the other portion of the belts 3, 4 continues horizontally to the third position III, where it also dips downwards. The belts 3, 4 are deflected downwards out of the horizontal at positions II, III, which are offset from each other in the arc travel direction BLR. The belt deflections of the first row 15 deflect the belts 4 downwards from the sheet transport plane 13 and the belt deflections of the second row 16 deflect the remaining belts 3 downwards from the sheet transport plane 13.

[0023] In the area between the second and third positions II, III, there are gaps between the belts 3, the width B of which corresponds to the width of a belt 4 already immersed there, plus twice the distance A. Separating elements 17 engage in these gaps, assisting in the separation of the sheets 1 from the belts 3, which is advantageous for the discharge of the sheets 1 from the sheet transport device. Each separating element 17 is aligned with a respective belt 4 in the sheet travel direction BLR. The separating elements 17 can be designed as guide brackets or, preferably, as in Fig. 1 shown - designed as conveyor belts, in particular suction belts. In Fig. For the sake of simplicity, the separating elements 17 are not shown in Figure 2.

[0024] The arrangement of the deflection rollers in the sheet transport plane 13, offset from each other in the direction of the sheet travel BLR, which prevents the belts 4 from diving in front of the belts 3 and the comb shape (cf. Fig. 2) The effect of the end of the device is particularly important at the sheet discharge end of the device, which is located on the left in the drawing. However, this arrangement can also be transferred to the sheet receiving end of the device, as shown in the drawing, whereby the deflection rollers 12 are offset from each other such that the belts 3 emerge first and reach the sheet transport plane 13, and only then do the belts 4 emerge and reach the sheet transport plane 13. The comb-shaped design of both device ends ensures that the belts 3 and the belts 4 are exactly the same length.

[0025] At least one belt tensioning mechanism is provided for tensioning the belts 3, 4; preferably, each belt 3, 4 is assigned its own tensioning mechanism 18 for tensioning the respective belt 3, 4. The belts 3 are each of the same length as the belts 4, although the belts 3 travel on a track that has a different path shape than the track on which the belts 4 travel.

[0026] A cleaning station 20 for cleaning the belts 3, 4 is arranged on a belt return section 19 of the belts 3, 4 that is antiparallel to the sheet transport plane 13. The cleaning station 20 is designed for wet cleaning (washing) of the belts 3, 4 and may have a cleaning cloth soaked with a cleaning fluid - e.g. an aqueous solution - or - as in Fig.1 indicated - wiping rollers. The cleaning station 20 can be deactivated during printing to ensure that belts 3 and 4 are completely dry when sheets 1 are placed on them. This is particularly advantageous for high printing speeds. In this case, cleaning takes place during printing interruptions. At low printing speeds, cleaning station 20 can even perform a cleaning process during printing. In this case, a belt drying station (not shown in the drawing) can be connected downstream of cleaning station 20. The belt drying station can, for example, include one or more rubber squeegees for removing residual cleaning fluid from belts 3 and 4. The following modifications are possible:

[0027] Instead of the mobile suction chambers 5, stationary suction chambers can be used, e.g. in the form of one or more fixed suction boxes. In this case, the belts 3, 4 are guided slidingly on the upper surface of the stationary suction chambers, which is preferably equipped with a friction-reducing surface.

[0028] A length compensation arrangement may be provided, in particular an offset between deflection rollers of belts 3 that are not located in the sheet transport plane 13 and deflection rollers of belts 4 that are not located in the sheet transport plane 13. This offset may exist in the belt return section 19 and preferably between spring-loaded deflection rollers that are components of the tensioning mechanisms 18 of belts 3 and 4. The length compensation arrangement is particularly advantageous with regard to ensuring that all belts 3 and 4 are of equal length in the case where only the sheet discharge end of the device is comb-shaped and not the sheet receiving end.

[0029] In this special case, instead of several bands 4 – in the example shown, every second band 3, 4 in the band row – only a single band 4 can dip in front of the other bands 3, so that the resulting comb shape of the device end has only a single gap. In this case, only a single separating element can be present, and this can engage in the single gap. Reference symbol list 1 sheet 2 Printhead Volume 3 Volume 4 5 Suction chamber Level 6 7 Perforation 8 Drive shaft 9 tray chain 10 Orbital motion 11. Circular motion 12 Pulley 13. Bow transport level 14 printing units 15 first row 16 second row 17 Separating element 18 clamping mechanism 19 Tape return section 20 cleaning stations I first position II second position III third position A distance B Width BLR arc direction

Claims

[1] Device for transporting sheets (1), comprising at least one circulating belt (3, 4) and at least one suction chamber (5) for pneumatically holding the sheets (1) on the at least one circulating belt (3, 4), characterized by , that a series of parallel belts (3, 4) together form an arc transport plane (13) under a pressure unit (14), of which at least one belt (4) runs upstream of the other belts (3) and is deflected downwards from the arc transport plane (13). [2] Device according to claim 1, characterized by , that a deflection of at least one belt (4) and deflections of the remaining belts (3) are arranged at positions (II, III) offset from each other in the direction of arc travel (BLR). [3] Device according to claim 2, characterized by , that the deflection of at least one belt (4) and the deflections of the other belts (3) are designed as deflection rollers (12). [4] Device according to claim 1, characterized by, that several suction chambers (5) are provided for holding the sheets (1) on the series of parallel belts (3, 4) and together form a tray chain (5) that circulates. [5] Device according to claim 4, characterized by , that the tray chain (5) is driven by the series of parallel belts (3, 4). [6] Device according to claim 1, characterized by , that at least one band (4) leaves a gap between the other bands (3) when diving, into which a separating element (17) engages to separate the arcs (1) from the other bands (3). [7] Device according to claim 6, characterized by , that the separating element (17) is a conveyor belt. [8] Device according to claim 1, characterized by , that a cleaning station (20) is available for cleaning the series of parallel belts (3, 4). [9] Device according to claim 1, characterized by, that a common drive shaft (8) is provided to drive the series of parallel belts (3, 4). [10] Device according to any one of claims 1 to 9, characterized by , that at least one band (4) is of the same length as the other bands (3) and orbits on a path which has a different orbital shape than the orbits of the other bands (3).

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