Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F23/00—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing
  • B41F23/04—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing by heat drying, by cooling, by applying powders
  • B41F23/044—Drying sheets, e.g. between two printing stations
  • B41F23/0443—Drying sheets, e.g. between two printing stations after printing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F23/00—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing
  • B41F23/04—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing by heat drying, by cooling, by applying powders
  • B41F23/06—Powdering devices, e.g. for preventing set-off
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H29/00—Delivering or advancing articles from machines; Advancing articles to or into piles
  • B65H29/24—Delivering or advancing articles from machines; Advancing articles to or into piles by air blast or suction apparatus
  • B65H29/245—Air blast devices
  • B65H29/246—Air blast devices acting on stacking devices
  • B65H29/247—Air blast devices acting on stacking devices blowing on upperside of the sheet

Definitions

• the invention relates to sheet-fed offset printing processes in which flow conditions in the interior of a housing of a sheet delivery of a sheet-fed offset printing machine are changed in order to prevent uncontrolled spreading of powder in the housing, at least at one point along a
• the invention further relates to a sheet-fed offset printing machine with a sheet delivery, one arranged in a housing of the sheet delivery
• Dusting device for dusting the printed sheets with powder, as well as air supply devices for supplying air from the outside into the housing and / or air suction devices for extracting powder-laden air from the housing, which at least one point along an empty strand
• Sheet conveying device are arranged to prevent uncontrolled spread of powder in the housing by changing the flow conditions inside the housing.
• a printing method and a printing press of this type are described in the German patent application 198 01 949.1 of the two applicants, which was not yet published on the day relevant to the seniority of the present application.
• Air turbulence occurs to a large extent in the sheet deliveries of conventional offset printing machines.
• This air turbulence is caused, among other things, by the fact that air is entrained in the direction of movement of the respective run below and above the delivery run and the empty run of the sheet delivery arm by the suction effect of the moving sheet grippers and chains, that printed sheets carried by the delivery run flutter or when deflected the bevel in the horizontal with its rear edge rocking upwards (so-called whip or flag effect), and in that air is blown out of the so-called bend baffle against the bend to guide it over the baffle without contact, whereby however, some of this air flows between the adjacent arches and upwards past the arches.
• Sheet delivery especially through the sheet exit opening and Air outlet grille on the top of the housing, exits into the environment.
• the printing press gets onto the still moist surface of the printing material or the printing ink.
• the powder which usually consists of starch, absorbs some of the liquid there, for example from the
• the liquid absorbed by the powder does not blow away into the printing material, or does so considerably more slowly, and does not participate in the chemical crosslinking process of the printing ink, the moisture content of the sheet is higher when it is deposited on the sheet stack, which delays drying and the time required for further processing of the printed products Period becomes longer.
• the liquid absorbed by the powder can also cause the abrasion resistance of the printing ink to decrease if powder particles deposited on the damp printing ink become detached during scrubbing, as a result of which incompletely dried punctiform surface areas of the printing ink are exposed.
• the area of the sheet delivery immediately behind the delivery drum could be kept almost powder-free, which not only reduced wear and powder emissions into the environment, but also surprisingly accelerated the drying of the printing material and the printing ink, presumably due to the Mechanism of action described in the previous paragraph.
• Sheet delivery in the direction of movement of the conveyor run behind the powder dusting device the amount of excess powder emerging in the vicinity of the sheet delivery could be reduced again.
• Powder emissions inside and outside the sheet delivery can still be improved.
• the object of the invention is a sheetfed offset printing process and a
• Sheetfed offset printing machine of the type mentioned in the introduction with a view to reducing the spread of powder.
• inventive channeling or control of air flows within the housing can prevent these air flows, which arise in part from the change in the flow conditions in the housing as a result of the supply and / or suction of air along the empty run of the sheet conveying device, from whirling powder up to the impression cylinder of the last printing unit or up to the delivery drum of the printing press.
• the invention is based on the knowledge that the main transport routes for whirled-up powder in the housing of the sheet delivery run along the latter due to the suction effect of the sheet conveying device, the air flow along the empty strand transporting powder in the direction of the printing press.
• Area of the powder dusting device and the conveyor run into the flow path of the empty run and from there to the impression cylinder of the last printing unit or to the delivery drum of the printing machine.
• the air flows within the housing can be in the direction of movement of the empty strand behind the point at which the air is sucked off and / or supplied in order to discharge powder-laden air carried along along the same from the flow path of the empty strand by the suction effect of the empty strand, air not contaminated with powder is fed into the housing.
• This preferably pre-cleaned air replaces the discharged powder-laden air and prevents powder-laden air from flowing in from other areas of the sheet delivery as a result of a negative pressure which can occur if the flow path along the empty strand is interrupted.
• the inflow of powder-laden air from the area of a powder dusting device or a conveying run of the sheet conveying device can additionally or alternatively into the flow path along the
• the air not contaminated with powder can be supplied
• the last-mentioned variant has the advantage that, firstly, the amount of air blown in to interrupt the air flow and / or for flushing purposes can be kept low, and secondly that it is prevented that any powder particles contained in this air are transported in the direction of the printing press.
• air is drawn in through ventilation slots or ventilation grilles in the top of the
• Air that is blown in and / or sucked in is deflected in the direction of the printing press when it enters the housing and then flows (as in conventional sheet deliveries the powder-laden air) through the suction of the sheet conveying device along its empty run to the delivery drum of the printing press. Since the housing of the sheet delivery is closed in this area, the air is there together with the
• the sheet conveying device is deflected and flows below and above the sheets transported by its conveying strand again in the direction of the powder apparatus.
• This air flow forms an air cushion above and below the freshly printed sheets, which can be reinforced if necessary on the underside by supplying air through the sheet guide plate and ensures that the sheets run extremely smoothly.
• Mechanical means for blocking an inflow of powder-contaminated air include in particular a partition arranged between the empty strand and the conveying strand, which expediently extends over the entire width of the sheet delivery and at least over part of the length of the sheet delivery, preferably starting at the latest where the air is sucked off and / or supplied along the empty run or the powder-laden air flow is interrupted, and then runs up to the vicinity of the delivery drum of the printing press.
• Flow-related means for preventing an inflow of powder-laden air into the flow path along the empty run include, in particular, suctioning off powder-laden air, supplying air that is not contaminated with powder, or producing targeted air flows which prevent powder-laden air from entering the flow path of the empty run .
• powder-laden air is sucked off in the vicinity of the powder apparatus, preferably on the rear edge of the air suction and deflection trough which serves for air extraction and air supply and faces the printing press, in order to prevent undesired swirling of powder away from the powder apparatus as a result of
• An air diverter can expediently be arranged above the powder apparatus, which in each case directs a portion of the air supplied past the delivery-side front or the printing machine-side rear of the powder apparatus downwards.
• the part directed to the front is preferably part of the fresh air used to interrupt the air flow and blown in from above through the empty run, while the part directed to the rear Part is part of the air sucked into the housing of the sheet delivery from the outside behind the point of interruption.
• the measures mentioned to prevent the spread of the powder within the housing of the sheet delivery can also extremely reduce powder consumption, i.e. can be reduced to about 10% of the quantities previously required.
• powder consumption i.e. can be reduced to about 10% of the quantities previously required.
• the powder because the powder only gets to where it is needed, namely on the surface of the sheet, and on the other hand, because the previously caused surface drying of the printing ink and the substrate requires considerably less powder to deposit the sheet to prevent.
• less powder consumption also means less powder emissions in the vicinity of the sheet delivery, so that this problem can also be largely eliminated.
• additional air suction devices can be provided in the area of the sheet exit opening, which serve to suck off powder between the edges of the sheet exit opening and the edges of the printed sheet before it is blown downwards by the delivery fans through the sheet exit opening into the vicinity of the sheet delivery to achieve a further reduction in powder emissions to the environment.
• Interrupt the air flow and serve to supply air not contaminated with powder and expediently in the upper one horizontal section of the sheet delivery are arranged.
• These are preferably a nozzle box, possibly equipped with brushes, arranged above the empty run, from which clean air is blown downwards in the direction of the empty run, and an air box, optionally equipped with brushes, arranged below the nozzle box in the space between the empty run and the conveyor run.
• Suction and deflection trough each of which sucks some of the air or deflects it in the direction of the printing press, as well as an air accumulator arranged in the direction of travel of the empty run behind the nozzle box and the trough, from which the vacuum generated sucks clean air into the housing of the sheet delivery through air openings .
• FIG. 1 Facilities, i.e. Nozzle box, tub and air storage, only one air storage to be provided on the top of the housing, so that if necessary, additional air can be sucked into the housing of the sheet delivery by the suction of the empty strand.
• the air storage can be kept under a slight excess pressure, so that the air is always fed into the interior of the sheet delivery.
• the air inside the air accumulator is preferably under atmospheric pressure. According to a further preferred embodiment or alternative of the invention, this enables simple control of the air supply as a function of the printing speed, because higher printing speeds necessitate higher running speeds of the sheet delivery, which in turn means a stronger one
• Suction is caused by the fact that more air is sucked out of the air reservoir.
• FIG. 2 shows an enlarged, partially sectioned side view of the sheet delivery of the printing machine from FIG. 1;
• FIG. 3 a top view of a combined air suction and deflection trough shown in FIG. 2;
• Fig. 4 is a sectional view of the air suction and deflection pan along the line V-V of Fig. 4;
• FIG. 5 an enlarged, partially sectioned side view of a sheet delivery modified compared to the sheet delivery from FIG. 2;
• paper sheets are transferred in succession by means of an automated sheet feeder 4 from a paper stack 8 arranged in a sheet-fed system 6 of the printing machine 2 to a feed drum 10 of a first printing unit 12 and then through the first printing unit 12 and possibly further of the total of eight printing units (only two shown) to be printed on one or both sides in one or more colors.
• the chain boom 20 essentially consists of two parallel chains (not shown) which are guided in opposite lateral guide rails and which are connected at regular intervals by the gripper systems 18, which are also referred to as curved grippers.
• the chain boom 20 has a lower, the sheet transporting conveyor strand (leading system) 30, which moves obliquely upwards from the two sprockets 31 of a delivery drum 32 and is then deflected into the horizontal before two drive sprockets 34 at the free end of the Sheet delivery 22 reached.
• Its upper empty run (return system) 36 moves horizontally in the direction of the printing press 2 from the chain wheels 34 before it is deflected obliquely downwards and returned to the delivery drum 32.
• each sheet is guided in a contactless manner in the direction of movement of the conveying run 30 by sheet guide plates 38 past laterally adjustable guide bar blowers 40 and over a sheet brake 42 arranged behind it, and then reaches a sheet outlet opening 44 on the underside of the horizontal section of the housing 24 of the sheet delivery 22.
• the sheets transferred and braked by the grippers 18 to the sheet brake 42 are blown downward onto the sheet stack 26 by means of a plurality of delivery fans 46 arranged above the outlet opening 44. This rests on a lifting mechanism 48 which lowers the stack 26 synchronously with the speed of the sheet feed.
• a powder apparatus 50 is arranged above the same in the space 52 between the conveyor run 30 and the empty run 36.
• the powder apparatus 52 dustes the top of the pressurized sheets held by the sheet grippers 18 of the conveyor run 30 with a fine powdered starch powder to prevent the sheets from sticking together when they are stacked on top of each other.
• the powder apparatus 50 essentially consists of a tube 54 which runs transversely to the direction of movement of the chain conveyor 20 through the intermediate space 52 and has a plurality of powder outlet slots on its underside.
• the starch powder is supplied by means of a blower (not shown) connected to the pipe 54, the dosage depending on the size and color intensity of the printed areas.
• Lifting mechanism 48 ie in the direction of movement of the conveyor run 30 behind the powder apparatus 50, two rows of brushes 76, 92 are provided, which extend over the entire clear width of the sheet boom and protrude from above or from below into the path of movement of the empty run 36.
• the ends of the bristles of the brushes 76, 92 each bend as the gripper systems 18 pass through, so that they can pass through the brushes 76, 92, but prevent the powder from forming with the powder by forming an air flow running along the empty strand in the direction of the printing press the front part of the delivery 22 can get to the rear in the vicinity of the impression cylinder 16 or the delivery drum 32.
• a nozzle box 58 is arranged there over the empty strand 36, which is provided on its underside with air outlet nozzles through which powder-free air is blown into the housing 24 from above.
• a combined air suction and deflection pan 56 in the intermediate space 52 arranged between the conveyor strand 30 and the empty strand 36, which serves to suck off a portion of the air blown in together with the powder cleaned from the empty strand and to divert the rest of the air in the direction of the printing press.
• the combined blowing and suction of air creates an air flow or air curtain which traverses the flow path of the empty run 36 transversely to its direction of movement and, together with the brushes 76, 92, interrupts the powder-laden air flow running along the empty run 36.
• the air suction and deflection trough 56 essentially consists of a thin-walled flat housing 62.
• the housing 62 extends below the lateral guides of the empty run 36 over the entire clear width of the chain arm 20 and forms a continuous closed partition between a flow path along the conveyor run 30 and a flow path along the empty run 36.
• the housing 62 has an upper housing wall 64 which is bent several times in the direction of movement of the chain conveyor 20, so that two flat troughs 66 are formed, which are arranged between them Survey 68 are separated.
• the upper housing wall 64 is further provided with rows of powder suction slots 70 arranged at a distance from one another.
• suction slots 70 While adjacent middle rows of suction slots 70 are located at the deepest points of the troughs 66, outer rows are arranged in the immediate vicinity of the opposite outer edges of the housing 62. Of the rows of powder suction slots 70, the obliquely downwardly oriented slots 70 are most strongly subjected to negative pressure on the outer edge facing the printing press.
• Each of the rows of slots is connected by a suction channel 72 arranged inside the housing 62 to one of four suction nozzles 74 which protrude beyond the edge of the tub 56 on the printing press side.
• the suction nozzles 74 open into an air suction pipe 75 which is connected to a suction fan (not shown) via a dust separator with cyclone and fine filter.
• adjustable flow control valves 77 are arranged in front of the openings of each suction port 74 in the air suction pipe 75.
• the valves 77 essentially consist of a threaded rod 79 which passes through a threaded hole in the wall of the air suction pipe 75 and is provided on its inner or outer end in a rotationally fixed manner with a disk-shaped plate 81 or an adjusting wheel 83. By turning the adjusting wheel 83, the distance between the plate 81 and the end of the adjacent suction nozzle 74 projecting inward into the air suction pipe and thus the flow cross section of the air flow can be changed.
• One (76) of the two cleaning brushes 76, 92 is also attached to the top of the upper housing wall 64.
• the brush 76 is located in the trough 66 which is first swept by the empty strand 36 of the chain arm 20 which passes over the housing 62.
• the housing 62 further has a lower housing wall 80 which is between the two troughs 66 and below the elevation 68 of the upper housing wall 64 with a recessed upwards
• Bulge 82 is provided, the cross section of which has the shape of an inverted U.
• the housing wall 80 encloses the transverse drive shaft 60, which is arranged between the empty strand 36 and the conveying strand 30 and the upper side of which supports the housing 62.
• the latter is provided with a Teflon coating in the region of the bulge 82.
• the air suction and deflection tray 56 is supported on the drive shaft 60, so that it is only a few fastening screws on opposite side walls of the Chain boom 20 must be attached to hold them in place.
• the nozzle box 58 serving as an air supply device consists of a flat metal housing which is provided on its flat underside facing the empty run 36 with a multiplicity of air outlet nozzles through which the sheet grippers 18 of the chain conveyor 20 passing under the nozzle box 58 can be showered with air.
• On the underside is the brush 92 in the direction of movement
• the nozzle box 58 is controllable by an air line (not shown) via an intermediate
• Throttle valve 102 is connected to a compressor 108, which draws in atmospheric air from the surroundings of the printing press 2 and compresses it to a pressure between 1.5 and 3.5 bar.
• a particle filter 110 is interposed between the compressor 108 and the nozzle box 58 in order to make the air fed into the nozzle box 58 dust-free.
• the amount of air fed into the nozzle box 58 is between 30 and 50 m 3 / h and is dimensioned such that only a part is sucked in through the powder suction slots 70 of the air suction and deflection tub 56, while the remaining air is at the top of the air Suction and deflection tray 56 is deflected in the direction of the printing press 2.
• the air is supplied at a relatively low pressure of 1.5 to 2 bar, while the air pressure is increased to 3 to 3.5 bar during a subsequent cleaning of the sheet delivery 22.
• the controllable throttle valve 102 in the air line allows a clocked air supply in the nozzle box 58.
• the air blown down from the nozzle box 58 flows past the sheet grippers 18 and past the chains of the chain conveyor 20, these being showered off by the air and adhering powder particles being carried downward, so that they do not move any further from the empty run 36 in the direction of the printing press 2 can be transported.
• the chains and guide rails 28 of the chain arm 20 also remain clean and saturated with grease, so that powder-related wear can be prevented.
• the remaining air on the top of the tub 56 is deflected in the direction of movement of the empty strand 36. Part of this air is deflected downward by the air intake at the rear outer edge of the tub 56 and flows partially into the air intake slots 70 arranged there and partially downwards on the front side of the powder apparatus 50 facing away from the printing press. Another part of the deflected air is from the suction of the empty run 36 above the powder apparatus
• the interruption of the air flow along the empty run 36 generates a negative pressure on the printing machine side of the brushes 76, 92, the strength of which depends on the amount of air supplied through the nozzle box 58. If relatively little air is supplied through the nozzle box 58, and consequently the negative pressure is greater, air is drawn into the interior of the housing 24 from the surroundings of the sheet delivery through a ventilation grill 95 arranged at the upper end of the inclined section of the housing 24, as shown in FIG. 2. Most of this air is carried along by the suction of the empty strand 36 in the direction of the printing machine 2, while a smaller part flows past the air suction pipe 75, which acts as an air switch, and along the back of the powder apparatus 50 pointing in the direction of the printing machine. These air currents formed above and on both sides of the powder apparatus 50 help to convey the powder down to the surface of the sheets transported past and to prevent whirling up and spreading of whirled up powder.
• an air accumulator 97 is arranged on the top of the sheet delivery 22 above the ventilation grill 95. Air that is not contaminated with powder is supplied from the particle filter 110, which is then sucked through the ventilation grille 95 instead of ambient air.
• the air in the air reservoir 97 is preferably kept under atmospheric pressure, so that more or less dried air is fed into the interior of the housing 24 depending on the level of the negative pressure generated by the empty run 36 of the sheet delivery 20. Since the level of the negative pressure increases with the running speed of the sheet delivery 20, simple control of the air supply depending on the printing speed can be achieved in this way.
• another air reservoir 97 connected to the particle filter 110 is arranged in the lower horizontal section at two points above a ventilation grille in the top of the housing to ensure that the powder-free air as far as the delivery drum 32 and Impression cylinder 16 of the printing press 2 is transported.
• a partition 99 parallel to the chain conveyor 20 can be arranged between the empty run 36 and the conveying run 30 of the sheet delivery, which divides the air flow before reaching the printing press 2 and creates powder-laden cross flows from the area of the conveying run upwards into the flow path of the empty run 36 prevented.
• the partition 99 can extend to the rear outer edge of the tub 56 in order to prevent powder from entering the blown or sucked-in clean air above the powder apparatus 50 and thus into the flow path of the empty run 36. On the side of the printing press 2, the partition 99 extends almost to the delivery drum 32.
• the extended sheet delivery 22 shown in FIG. 7 also has a further nozzle box 59 in front of the air accumulator 97 and one below the one in the direction of movement of the empty strand 36
• the trough 57 is somewhat flatter than the trough 58 and is supported by the side cheeks of the sheet boom 20.
• two such combinations of tub 57, nozzle box 59 and air reservoir 97 can also be provided.
• the air flow along the empty run 36 is interrupted or deflected downwards towards the delivery run 30, as shown in FIG. 7.
• part of the air blown in through the nozzle box 59 and the air sucked in from the air reservoir 97 pass through the suction effect of the empty run 36 are conveyed in the direction of the printing press 2.
• the air blown in by means of the nozzle box 58, 59 or sucked in from the one or more air stores 97 and transported by the suction effect of the empty run 36 of the sheet delivery 20 along the same to the delivery drum 32 forms an air cushion above and below the sheets, to calm the sheet travel contributes.
• the air cushion generated on the underside of the sheets can be supplemented and reinforced by supplying air from the sheet guide plates 38.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Printing Methods (AREA)
• Delivering By Means Of Belts And Rollers (AREA)
• Separation, Sorting, Adjustment, Or Bending Of Sheets To Be Conveyed (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Manufacture Of Motors, Generators (AREA)
• Discharge Heating (AREA)
• Sheets, Magazines, And Separation Thereof (AREA)
• Feeding Of Articles By Means Other Than Belts Or Rollers (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=7887910

Family Applications (1)

Country Status (5)

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• 1999
  • 1999-11-08 EP EP99955959A patent/EP1091855B1/fr not_active Expired - Lifetime
  • 1999-11-08 DE DE59913083T patent/DE59913083D1/de not_active Expired - Lifetime
  • 1999-11-08 AT AT99955959T patent/ATE316467T1/de not_active IP Right Cessation
  • 1999-11-08 WO PCT/EP1999/008552 patent/WO2000029215A1/fr active IP Right Grant
• 2001
  • 2001-05-23 US US09/863,923 patent/US6606946B2/en not_active Expired - Fee Related

Non-Patent Citations (1)

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