Apparatus for drying sheets in a sheet-fed printing press and sheet-fed printing press having the apparatus

Abstract

An apparatus for drying sheets in a sheet-fed printing press includes a hot air dryer having a hot-air outflow temperature which is at least 300° C. A sheet-fed printing press having the apparatus is also provided.

Description

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE of the drawing is a fragmentary, highly diagrammatic, side-elevational view of a sheet-fed printing press.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in detail to the single FIGURE of the drawing, there is seen a sheet-fed printing press 1 which includes a hot air dryer 2 having nozzles 3 that are disposed in a pattern. A sheet 4 or the printing ink disposed thereon is dried by hot air ejected from the nozzles 3, and the respective sheet 4 is transported past the hot air dryer 2 by a suitable transport apparatus 5.

The transport apparatus 5 is a transport belt but may, instead, be a cylinder, for example an impression cylinder, of the printing press 1. The transport apparatus 5 transports the sheet 4 in a sheet travel direction which is indicated symbolically in the FIGURE by an arrow.

The nozzles 3 are connected to a hot air feeder 6, and the hot air which is ejected from the nozzles 3 is extracted again by an extraction device 7, after the hot air has impinged on the sheet 4 and has imparted part of the warmth thereof to the sheet 4. The nozzles 3 are configured as so-called round nozzles having circular nozzle openings which, respectively, define an outflow diameter D.

A nozzle effective spacing H is to be measured between outlet mouths or nozzle openings of the nozzles 3 and the sheet 4, toward or onto which the nozzles 3 are directed. The transport device 5 and the hot air dryer 2 are positioned adjacent one another in such a manner that the nozzle effective spacing H is ensured.

A further parameter important for functioning or operation is a nozzle center spacing L, at which respective adjacent nozzles 3 are situated with respect to one another in longitudinal rows and within transverse rows of the nozzle pattern. The nozzle center spacing L is to be measured between the respective nozzles 3 following one another in the longitudinal row in a direction which is parallel to the sheet travel direction, and is to be measured between nozzles 3 following one another in the respective transverse row in a direction which is perpendicular to the sheet travel direction. The nozzle center spacing L can vary slightly within the nozzle pattern and can, for example, be slightly different within the longitudinal rows than within the transverse rows.

The nozzle effective spacing H can also be slightly different from nozzle 3 to nozzle 3. In every case, the nozzle effective spacing H is smaller than 20 millimeters and preferably smaller than 10 millimeters.

The outflow diameter D measured at the nozzle openings is greater than one tenth of the nozzle effective spacing H and is smaller than half of this nozzle effective spacing H. The nozzle center spacing L is greater than the nozzle effective spacing H and smaller than three times the nozzle effective spacing H.

It is decisive that the hot air which is ejected from the nozzles 3 for drying the sheet 4 has an outflow temperature which is greater than 300° C. and is preferably greater than 350° C.

Claims

1. An apparatus for drying sheets in a sheet-fed printing press, the apparatus comprising: a hot air dryer ejecting hot air onto the sheets with a hot-air outflow temperature;said outflow temperature being at least 300° C.

2. The apparatus according to claim 1, wherein said outflow temperature is at least 350° C.

3. The apparatus according to claim 1, wherein said hot air dryer further comprises: nozzles from which the hot air flows;said nozzles having a nozzle-effective spacing of less than 20 millimeters from the respective sheets to be dried.

4. The apparatus according to claim 3, wherein said nozzle-effective spacing is less than 10 millimeters.

5. The apparatus according to claim 3, wherein each of said nozzles has a respective outflow diameter which is greater than one tenth of said nozzle-effective spacing and smaller than one-half of said nozzle-effective spacing.

6. The apparatus according to claim 5, further comprising: a nozzle center spacing provided between respectively adjacent nozzles;said nozzle center spacing being greater than said nozzle effective spacing and smaller than three times said nozzle effective spacing.

7. A sheet-fed printing press, comprising an apparatus according to claim 1.