METHOD AND DEVICE AT A SHEET OFFSET MACHINE

Abstract: The invention relates to a method and an arrangement in a sheet offset press. The method is characterised by a combination of measures taken in the following steps: A space (1) is created through which printed sheets are allowed to pass. The space (1) is sealed off so that the admission of air to the space (1) is at least restricted without significantly affecting the passage of the sheets through the space (1). Powder is sprayed over the sheets in the space in order to prevent smearing of the ink on succeeding sheets during subsequent stacking. By extracting air from the space (1) a negative pressure is created therein and any excess powder occurring is removed from the space (1) by extraction of the air. The arrangement comprises a combination of the following: A space (1), which has a feed and an outlet opening (2, 3). A conveyor arrangement (4) designed to convey printed sheets through the space (1) by way of the said openings (2, 3). Sealing elements (8) arranged at the openings and designed to restrict the admission of air to the space (1) without significantly impeding the conveying of the printed sheets through the space (1). A powder source (9) arranged in the space and designed to spread an excess amount of powder with the aim of providing each sheet with a powder coating, in order to prevent printing ink from one sheet smearing off on to the following sheet during subsequent stacking of the sheets after passing through the space, and a pipe (10) connected to the space (1) and communicating with a suction fan (12) for extracting the excess powder from the space (1).

Description: METHOD AND DEVICE AT A SHEET OFFSET MACHINE The present invention relates to a method and an arrangement in a sheet offset press. In such a press the printing ink, at the printing speeds now prevalent, does not have time to dry during conveying of the sheet from the press to a sheet stacker. Arranging an IR radiation source immediately adjacent to the sheet conveyor track in order to speed up the drying of the printing ink, with a view to thereby preventing the printing ink on a sheet from smearing by the following sheet, is known, for example, from Swedish patent No. 501057. Dispersing a special starch powder with a very small particle size against the newly printed sheet, in order to produce a smear-resistant coating on the sheet, is also known in the art. Even if endeavours are made to ensure that as little powder as possible gets out into the air, it has become apparent that after a certain operating time both the press and the premises, in which the press is installed, will be covered with powder. The powder is moreover unhealthy to inhale and gives rise to mechanical wear on machine parts in motion. The object of the present invention is to limit the effect of the above-mentioned disadvantages and to improve the powder handling. This object is achieved by the method according to the invention as set out by the characterising part of claim 1. The characteristics of an arrangement according to the invention are specified in the characterising part of claim 3. Modifications of the invention may have one or more of the characteristics specified in the subordinate claims. By means of the invention a cleaner and healthier environment is achieved in the immediate surroundings of the sheet offset press, together with less wear of moving machine parts due to the powder. The invention will be explained in more detail with reference to the attached drawing, which shows a diagram of an arrangement according to the invention. In the drawing 1 denotes a space defined by a casing 1 A with a feed opening 2 and an outlet opening 3. A conveyor arrangement 4 comprising a chain 5 of gripping carriers runs through the space 1. The gripping carriers, controlled by rails 6, run through the space 1 and over two split rollers 7, only one of which is visible on the drawing. Each of the gripping carriers is designed to grip hold of the edges of a newly printed sheet coming from a printing machine (not shown), to convey the sheet into the space via the feed opening 2 and out of the space 1 via the outlet opening 3 in order there to stack the sheets one on top of another. The gripping carriers run in empty through the opening 3 and out through the opening 2. Sealing elements 8, designed to restrict the admission of air into the space 1 essentially without impeding the passage of the carriers through the openings 2, 3, are arranged at the openings 2, 3. In the embodiment shown the chain 5 of gripping carriers runs, as stated, both in and out through the openings 2, 3, and the sealing elements here consist of sealing sheets 8a with opposing rows of brushes 8b directed towards the respective part of the chain. In the space 1 there is a powder source 9, shown on the drawing. This is designed to produce a thin coating of powder on each printed sheet passing through the space 1, the function of the powder being to prevent smearing of the printing ink. Connected to the casing 1 A is a pipe 10, which is connected to a suction fan 12 by way of a filter unit 11. Also connected to the filter unit 1 1 is a collecting vessel 13, whilst a silencer 14 is connected to the pressure side of the fan 12. The function of the suction fan 12 is to produce a negative pressure in the space 1. Finally the drawing shows a suction hose 15, which can be coupled to an outlet 1 la on the filter unit or alternatively to a corresponding outlet 10a on the pipe 10. With the suction hose 15 connected to either of the outlets 10a or 1 la powder can be easily and effectively removed where ever it occurs, in the space 1 or outside the latter. The arrangement according to the invention functions as follows: During the movement of the gripping carriers through the space 1 an air flow is generated in the latter that entrains with it any excess powder from the powder source 9. The air flow is arrested by the sealing elements 8, and by means of the negative pressure produced by the suction fan 12 the powder-laden air is conveyed by way of the pipe 10 to the filter 11. This is designed to separate the powder out of the air and allow this to fall down into the collecting vessel 13. The air, freed of powder, is released into the open air. The silencer 14 produces a sound level, which means that the equipment, comprising the filter 11, the collecting vessel 13 and the fan 12, can be located in the same room as the sheet offset press without creating a nuisance. When this and the sheet conveyor are shut down the facility exists, with the suction hose 15 connected to either of the outlets 10a, 1 la, for achieving an effective cleaning of the press and the space 1. The arrangement according to the invention means that there is also room in the space 1 for so-called IR lighting 16, in order to accelerate the drying of the printed sheet. The person skilled in the art will perceive that the method and the arrangement according to the invention can be modified in many ways within the framework of the idea of the invention, as manifested in the claims attached.

Claims: Claims 1. Method in a sheet offset press, characterised by a combination of measures taken in the following steps: a space (1) is created through which printed sheets are allowed to pass and the space (1) is sealed off so that the admission of air to the space (1) is at least restricted without significantly affecting the passage of the sheets through the space (1), powder is sprayed over the sheets in the space in order to prevent smearing of the ink on succeeding sheets during subsequent stacking, by extracting air from the space (1) a negative pressure is created therein and any excess powder occurring is removed from the space (1) by extraction of the air. 2. Method according to claim 1 , characterised in that the sheets in the space (1) are exposed to IR radiation. 3. Arrangement in a sheet offset press, characterised in that the arrangement comprises a combination of the following: a space (1), which has a feed and an outlet opening (2, 3), a conveyor arrangement (4) designed to convey printed sheets through the space (1) by way of the said openings (2, 3) sealing elements (8) arranged at the openings and designed to restrict the admission of air to the space (1) without significantly impeding the conveying of the printed sheets through the space (1), a powder source (9) arranged in the space and designed to spread an excess amount of powder with the aim of providing each sheet with a powder coating, in order to prevent printing ink from one sheet smearing off on to the following sheet during subsequent stacking of the sheets after passing through the space, and a pipe (10) connected to the space (1) and communicating with a suction fan (12) for extracting the excess powder from the space (1). 4. Arrangement according to claim 3, characterised in that the arrangement comprises an IR radiation source (16) located in the space (1) and close to the sheet conveyor track. 5. Arrangement according to either of claims 3 or 4, characterised in that the arrangement comprises a filter (1 1) interacting with the suction fan (12) and designed to separate the powder out of the air. 6. Arrangement according to any of claims 3 to 5, characterised in that the arrangement comprises a suction hose (15), that can be coupled to the pipe (10) or the filter (1 1) in order to permit suction cleaning of the space (1) when the sheet conveyor is not in operation. 7. Arrangement according to any of claims 3 to 6, characterised in that the sealing elements (8) comprise opposing rows of brushes (8b) arranged transversely to the sheet conveying direction. AMENDED CLAIMS [received by the International Bureau on 19 May 2000 (19.05.00); original claims 1 -7 replaced by new claims 1-4 (1 page)] 1. Arrangement in a sheet offset press, comprising: a space (1), which has a feed and an outlet opening (2, 3), a conveyor arrangement (4) designed to convey printed sheets through the space (1) by way of the said openings (2, 3) sealing elements (8) arranged at the openings and designed to restrict the admission of air to the space (1) without significantly impeding the conveying of the printed sheets through the space (1), a powder source (9) arranged in the space and designed to spread an excess amount of powder with the aim of providing each sheet with a powder coating, in order to prevent printing ink from one sheet smearing off on to the following sheet during subsequent stacking of the sheets after passing through the space, and a pipe (10) connected to the space (1) and communicating with a suction fan (12) for extracting the excess powder from the space (1), characterised in that the arrangement also comprises a suction hose (15), that can be coupled to the pipe (10) or the filter (1 1) in order to permit suction cleaning of the space (1) when the sheet conveyor is not in operation or outside said space (1). 2. Arrangement according to claim 1, characterised in that the arrangement comprises an IR radiation source ( 16) located in the space ( 1 ) and close to the sheet conveyor track. 3. Arrangement according to either of claims 1 or 2, characterised in that the arrangement comprises a filter (1 1) interacting with the suction fan (12) and designed to separate the powder out of the air. 4. Arrangement according to any of claims 1 to 3, characterised in that the sealing elements (8) comprise opposing rows of brushes (8b) arranged transversely to the sheet conveying direction.

Inventors: LARSSON JAN-OLOV, LARSSON, JAN-OLOV
Applicants: BALDWIN IVT AB, LARSSON JAN OLOV, LARSSON, JAN-OLOV
Application year: 1999
Main classification: B41F23
IPC codes: B41F13, B41F23, B41F35