BUCKLE FOLDING UNIT AND SHEET-FED FOLDING MACHINE INCLUDING THE BUCKLE FOLDING UNIT

Abstract

A buckle folding unit for sheets includes a buckle plate, three rollers that form a transport roller pair and a folding roller pair, and a blown-air nozzle for guiding the sheets. The at least one blown-air nozzle emits a blown-air jet in a direction radial to a common roller of the transport roller pair and the folding roller pair. The air jet places the sheet against the surface of the common roller and guides it into a nip of the folding roller pair in a defined way, advantageously resulting in an improved quality of the fold. A sheet-fed folding machine including a buckle folding unit is also provided.

Claims

1. A buckle folding unit for sheet-shaped elements, the buckle folding unit comprising: a buckle plate; three rollers forming a transport roller pair for feeding the sheet-shaped elements and a folding roller pair for folding the sheet-shaped elements, one of said three rollers being a common roller of said transport roller pair and said folding roller pair; and at least one blown-air nozzle for guiding the sheet-shaped elements, said at least one blown-air nozzle delivering an air jet oriented in a radial direction relative to said common roller.

2. The buckle folding unit according to claim 1, which further comprises a control unit associated with said blown-air nozzle for activating said blown-air nozzle in a timed manner.

3. The buckle folding unit according to claim 1, which further comprises a nozzle bar, said at least one blown-air nozzle including a plurality of blown-air nozzles disposed in a row in said nozzle bar.

4. The buckle folding unit according to claim 1, wherein the sheet-shaped elements are introduced to said buckle plate along a plane of introduction, and said buckle plate is disposed at an angle of introduction of approximately 20 to 40 relative to said plane of introduction.

5. The buckle folding unit according to claim 1, wherein at least a further roller of said folding roller pair not being said common roller has a surface and at least one channel formed in said surface.

6. The buckle folding unit according to claim 5, wherein said surface of said further roller is a lateral surface, and said at least one channel is an endless circumferential channel formed in said lateral surface.

7. A sheet-fed folding machine, comprising: at least one buckle folding unit according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a diagrammatic, longitudinal-sectional view of a sheet-fed folding machine in accordance with the invention;

[0024] FIGS. 2A and 2B are front-elevational views of prior art buckle folding units;

[0025] FIG. 3 is a front-elevational view of a buckle folding unit in accordance with the invention; and

[0026] FIGS. 4A and 4B are respective front-elevational and top-plan views of another embodiment of a buckle folding unit in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Referring now in detail to the figures of the drawings which are not drawn to scale and in which components that correspond to one another have the same reference symbol, and first, particularly, to FIG. 1 thereof, there is seen a sheet-fed folding machine 100 including a sheet feeder 10, a feed unit 20 with an alignment table, a buckle folder 30 having two buckle folding units 30.1, 30.2, and a signature delivery 50. In the region of the sheet feeder 10, a respective sheet 1000 is separated from a sheet stack 1001 and transferred to the feed unit 20 having the alignment table. A respective sheet 1000 is fed from the feed unit 20 to the buckle folder 30 in a direction of sheet transport T. Upstream knife shafts 31 treating the sheets 1000 may be provided to prepare the folds. The actual treatment of the sheets 1000 is carried out in the buckle folding unit 30, i.e. the sheets 1000 are folded by a buckle plate 33 in cooperation with folding rollers 32. The construction of the buckle folding unit 30 will be described in more detail based on the further figures. A sheet 1000 that has been folded in the buckle folding unit 30 is delivered to the signature delivery 50 as a signature 1002.

[0028] FIGS. 2A and 2b illustrate a buckle folding unit 30.1 in accordance with the prior art. Two rollers 32.1 and 32.2, which form a transport roller pair, transport a respective sheet 1000 in a direction of transport T into the buckle plate 33 until the leading edge of the sheet 1000 is in contact with a leading edge stop 34. As shown in FIG. 2B, the sheet 1000 then buckles in a folding space 36 and is gripped by a folding nip formed between the rollers 32.2 and 32.3, which form a folding roller pair. This is the actual folding process. The buckling process is dependent on a number of factors, for instance the traveling speed of the sheet, the weight of the sheet, the configuration of an entrance 35 to the buckle plate, the width of the sheets 1000, the surface of the rollers 32, etc.

[0029] In order to improve the quality of the fold, a nozzle bar 41 with a number of blown-air nozzles 40 is provided in the entrance or entry region 35 of the buckle plate 33, i.e. in the region of an upper plate edge. The blown-air nozzles 40 are aligned in such a way that they provide an air jet 42 that is oriented in a radial direction relative to the second roller 32.2, i.e. that is directed towards the central axis of the second roller 32.2. This air jet 42 causes a sheet 1000 to be reliably placed flatly against the second roller 32.2 and to be introduced into the nip of the folding roller pair 32.2, 32.3 in a defined way. In contrast, an air jet directed directly into the nip would not cause any increase in the accuracy of the fold. The initiation of the folding process in that case would be dominated by the air jet and the formation of the fold would not be precisely reproducible because a sheet would flutter into the nip of the folding roller pair more or less by chance. Due to the radial direction of the air jet 42 in accordance with the invention, the initiation of the folding process is very accurate and reproducible for every sheet 1000. In this case, the formation of the fold is substantially determined by the geometric dimensions of the folding unit 30.1, namely by the position of the stop 34.

[0030] In the embodiment shown in FIG. 3, the buckle plate 33 is oriented at an angle of introduction of approximately 25 relative to a plane E of introduction. In contrast to the angles of introduction common in the prior art of approximately 45, a sheet 1000 may enter the buckle plate 33 more easily and disruptions to the introduction process may be avoided.

[0031] The blown-air nozzles 40 may be integrated in the illustrated position into the nozzle bar 41 extending over the respective widths of the buckle plate 33 and of the folding rollers 32, as shown in FIG. 4B. As is additionally indicated in FIG. 4B, the nozzle bar 41 is connected to a blown-air source 44 and may be supplied with blown air in a timed way by a control unit 45 of the machine. For this purpose, a sensor with a data connection to the control unit of the machine may be integrated into the buckle folding unit 30.1 to monitor contact between the leading edge of a respective sheet 1000 and the buckle plate stop 34 and to provide a signal for the provision of blown air.

[0032] In the embodiment shown in FIG. 4A, at least one channel 37, also referred to as a groove, is formed in the surface of the buckle-side folding roller 32.3. The groove 37 is formed as a depression in the lateral surface of the folding roller 32.3 and is in particular an endless circumferential groove formed in the lateral surface of the roller 32.3. The groove 37 forms an air channel that helps the air that is present underneath a sheet 1000, i.e. between the sheet 1000 and the folding roller pair 32.2, 32.3, to escape. The presence of air is undesired in this location during the initiation of the folding process because it hinders close contact between the sheet 1000 and the folding rollers 32.2 and 32.3. Therefore, the air is allowed to escape not only on the bearing-side ends of the folding rollers 32.2, 32.3, but also through the channel 37. As is shown in the top view of FIG. 4B, a number of channels 37 are formed in the lateral surface of the folding roller 32.3.