DE102006027146B4 - A method for reducing the required cooling capacity in a cooling roll stand of a web-fed rotary printing press and a device in a cooling roll stand with cooling rolls - Google Patents

Abstract

A method for reducing the required cooling capacity in a chill roll stand (06) of a web-fed rotary printing machine, wherein one or more in the chill roll stand (06) incoming material webs (01) before impinging on a first chill roll (07-I) is acted upon by an air flow, the Running direction of the web (01) is opposite and extending over the entire width of the material web (01), wherein the air flow at an angle of attack (β) of 15 ° to 60 ° on the web (01) impinges, wherein the flow velocity of the air stream 0 , 2 to 2 m / s, and wherein the air flow is directed under a pressure of 3 to 10 bar on the web (01), so that the "COANDA" effect is used.

Description

method to reduce the required cooling capacity in a chill roll stand one Web-fed rotary printing press and a device in a chill roll stand with chill rolls

The The invention relates to a method for reducing the required cooling capacity in a chill roll stand one Web-fed rotary printing press and a device in a chill roll stand with chill rolls according to the claim 1 or 6.

in the Web offset printing is the double-sided printed paper web after hot air drying a chill roll group fed. It should be at about 110 ° C up to 140 ° C heated web can be brought to a temperature below 30 ° C. This cooling has the task after hot air drying make even very sticky paint film virtually tack-free, so the printed image of the mechanical influences and loads on the former, the folder and the rod boom has grown. The chill roll group Depending on the arrangement of two to five large-sized, highly polished Steel cylinders of different arrangement. With as possible great Wrap angle of 140 ° to 240 ° the hot one Track for removal against the flowed through with coolant cylinders guided.

at higher Web speeds occur on the chill rolls increasingly problems with the railway cooling and the mineral oil condensate precipitate on. Therefore There are different causes. On the one hand, when leaving the Paper web from the dryer more or less surrounded by mineral oil vapors partially come out of the dryer and by evaporation due to the web temperature arise. The hot web continues to adhere an air boundary layer with which the mineral oil vapors to the cooling rolls get there and there on the surface can condense. The can smear and soiling of the printed image or a Deposition of ink on the chill roll result. there it can lead to a so-called chill roll plucking come.

A other cause for the problems occurring at higher Web speed is the formation of a speed-dependent air cushion between the cooling cylinder and the above running material web. This heat insulating Air layer leads to a hindrance of heat dissipation the surface the cooling cylinder, so that the heat transfer at the individual cooling cylinders decreases with increasing web speed. The bigger that Air cushion between paper web and cylinder becomes, the bigger also the amount of condensates that can settle on the cooling cylinder and the lower the transferable to the material web Cooling capacity.

in the State of the art are for the reduction of the air cushion various ways known. This is on the one hand the pressing of the web with a pressure roller, this But method is for not suitable for web offset printing. Furthermore, it is known by an air press with impact jet nozzles the material web to the chill roll to press. It is also known to have smaller roll radii in a simultaneous increase the number of chill rolls to choose, for the cooling to optimize the material web.

A another possibility for reducing the air cushion between the material web and the cooling roller consists in the application of electrostatic effects. It will be specifically charge carriers Applied to the webs, in this state of the grounded chill roll surface are tightened. This results in an improved application of the material web to the Chill roll.

From the EP 10 46 874 B1 is a dryer with an integrated cooling unit known. In order to avoid air layers between the chill roll surface and the material web, it is proposed to accommodate the chiller unit in the same housing in which the dryer is located. Since the web between dryer and chill roll stand are no longer exposed to the conditions of the surrounding atmosphere, the adhesion of boundary layers of cold air on both sides of the web can be prevented. In this way, the sooting at the dryer outlet can be avoided because the dryer outlet is not connected to the surrounding atmosphere. In the cooling unit, the material web assumes a substantially vertically oriented path. Details of the cooling unit are not described.

From the EP 08 12 685 A1 is a suction device for air extraction in the region of the inlet gap between a web and cooling roller of a web offset printing known. With a suction device, the boundary layer adhering here to the web is sucked off. According to a preferred embodiment, means may be provided for peeling off the air entrained by the material web on the housing wall of the suction device and thus for better suction. These means may be Abschälbleche or blow-off nozzles. Blow-off nozzles are arranged so that they blow air against the running direction of the material web. By these Abblasdüsen the laminar flow of the air is torn open at the web surface and swirled, so that an closing suction can be done. The blow-off nozzle is designed as a slot nozzle whose slot extends over the entire length of the cooling roller.

From the US 42 65 384 A , of the US 43 84 666 A as well as the US 47 18 178 A Various nozzle arrangements or air rails are known, which are arranged in a hot-air dryer for sheet material. The nozzles are designed to apply the Coanda effect of streaming air to the web.

The US 53 95 029 A describes a nozzle chamber assembly for use in a web transport apparatus in which the webs are to be transported horizontally. Here, nozzles are proposed in which the flow characteristics of the individual nozzles can be changed in order to use the transport device for different material webs under the same conditions.

The DE 94 19 702 U1 relates to a device for reducing the corrugation of webs after drying. For this purpose, a device is provided before entering the web in a chill roll stand or in front of the first chill roll, which deflects the material web with a smaller diameter twice over blow rods. It is also proposed here to arrange a Coanda plate parallel to the material web, whereby air can be blown into the gap between it and the web by means of a nozzle, whereby the web is attracted to the Coanda plate without touching it.

Farther It is known Abrakelsysteme in the dryer and at the exit of the dryer to arrange, which should avoid that the paper web an air layer travels with exhaust gases and high humidity.

All Systems known from the prior art do not provide sufficient Protection against the problems occurring at high web speeds in a chill roll stand, the on at the railway surface entrained Air and condensate layers are due.

The JP 05-330019 A and the DE 36 14 742 C2 disclose blowing air nozzles between dryer and cooling rollers, which are directed opposite to the web running direction.

Of the Invention is based on the object, a method for reduction the needed cooling capacity in a chill roll stand one Web-fed rotary printing press and a device in a chill roll stand with chill rolls to create, with simple means better heat transfer possible is.

The The object is achieved by the Characteristics of claim 1 or 6 solved.

The particular advantages of the invention are that the required cooling capacity in a chill roll stand in Compared with the prior art can be greatly reduced, which leads to greater energy savings. Farther The smoke at the dryer outlet can be minimized. One Another advantage results in the longer life of the cooling rollers by a reduced condensate deposit on the surface of this. There are advantageously webs of material at web speeds from above 15 m / s effectively coolable.

there is prior to hitting a coming of a hot air dryer web on a first chill roll in a chill roll stand the material web, z. B. paper web with one of their transport direction opposite Blow air flow cold air. The cold air flow moves along the surface the web in the direction of the exit of the hot air dryer. As a result, the hot air layer flowing from the dryer is torn off, so they no longer act as an insulator between the paper web and the chill roll can work. The opposite Air flow causes a flow directly above the web and in the closer Environment in the direction of dryer, thereby the exhaust fumes with the high humidity and temperature with this airflow over the disposed of dryer-specific output. This is no extra Extraction above the chill roll group required.

Of the opposing Air flow, which preferably has ambient temperature has already a first cooling the web before the entry into the first chill roll result, so that through the chill rolls provided cooling capacity can be designed smaller.

In a preferred embodiment becomes the airflow both on the top and on the bottom of the web inflated. Due to resulting under- and overpressure areas in addition to Tear off the laminar boundary layer applying the material web to the first Chill roll.

A Device has a nozzle tube on, which runs across the web and on the entire width of this extends. The nozzle tube is in the web run the first chill roll arranged the chill roller stand.

The nozzle tube advantageously has nozzle bores, which are distributed uniformly over the length of the nozzle tube. The nozzle tube has a connection for the purpose of flowing through with a suitable cooling medium. A suitable cooling medium is for example air, which passes under pressure the nozzle tube.

The Nozzles of the nozzle tube are opposite to the direction of the web. That is, if a compressed air at the nozzle tube is applied through the nozzles of the nozzle tube caused an air flow on the paper web, which is the direction of travel the material web is directed opposite.

Preferably is arranged on both sides of the web in each case a nozzle tube.

In Advantageously, the nozzle tube or the nozzle pipes arranged so that the "COANDA" effect is used.

One embodiment is shown in the drawings and will be described in more detail below.

It demonstrate:

1 a schematic representation of an output of a hot air dryer and a subsequent chill roll stand;

2 a schematic diagram of a device for reducing the cooling capacity in a cooling roll stand;

3 a detailed representation of the device according to 2 ;

4 a schematic representation of in 3 illustrated device components;

5 a representation of the pressure and air flow distribution on a material web before entering a first cooling roll of a cooling roll stand.

In 1 is a device for cooling a web without the device for reducing the cooling capacity in a chill roll stand 06 shown. The material web 01 leaves after printing a hot air dryer 02 through a so-called flue gas tunnel 03 in the direction of an indicated movement arrow 04 , The material web 01 is then placed in a chill roll stand 06 weiterführgeführt, in which cooling rollers 07 are arranged. The material web 01 goes through the numbered with the Roman reference numerals I to IV cooling rollers 07 with as large a wrap angle as possible in order to achieve a high cooling capacity.

The temperature with which the material web 01 the hot air dryer 02 leaves, increases for technological reasons with increasing web speed. While, for example, a material web 01 achieved with a web speed of 13 m / s at the dryer output about 110 ° C, due to the faster web transport at, for example, 15 m / s at the dryer exit a web temperature of 120 ° C and at 17 m / s a web temperature of 130 ° C can be measured.

Furthermore, at elevated web speeds from 15 m / s a strong smoke formation at the exit of the flue gas tunnel 03 observed. In the 1 are exemplified by hatched arrows emanating flue gas vortex 08 shown. It can be seen that parts of the flue vortex 08 above the chill roll stand 06 escape into the environment, which usually requires an extraction system in this area (not shown).

With the material web 01 a laminar boundary layer is created, which is formed by hot condensate-containing air. In the vicinity of the smokehouse tunnel 03 a laminar suction flow forms 09 in the direction of the smoke gas tunnel 03 , which is symbolized by non-hatched flow arrows, with the clean, dry ambient air against the material web running direction in the flue gas tunnel 03 is sucked.

2 shows a chill roll stand 06 with a device. The device for minimizing the cooling capacity comprises at least one nozzle tube 11 ; 12 , In a preferred embodiment, an upper nozzle tube 11 and a lower nozzle tube 12 , which in the web run in front of the first cooling roller 07 -I are arranged. The at least one nozzle tube 11 ; 12 indicates a distance of one to two meters to the exit of a hot air dryer 02 on.

The nozzle pipes 11 and 12 generate a flow of air at the surface of the web 01 along, but opposite to the direction of transport runs. This one from the nozzle pipes 11 and 12 generates counterflowing air flow causes a flow 13 (represented by blackened arrows) directly above the web 01 and in the immediate vicinity, which in the flue gas tunnel 03 is directed.

As a result, the exhaust gases with high humidity and temperature on the dryer-specific output or the flue gas tunnel 03 disposed of or pushed back into these. An additional suction device, which normally above the chill roll stand 06 can be arranged, can advantageously be omitted. Furthermore, the coming of the nozzle air flow, which approximately with room or ambient temperature over the web 01 blows away, already one first cooling of the material web 01 before their entry into the first chill roll 07 -I.

It can also be seen in this illustration that the flue-gas vortices 08 a much smaller extent than in the embodiment according to 1 and do not or only to a minimum escape into the environment.

3 is a detailed view of the device according to 2 in perspective view. The nozzle pipes 11 respectively. 12 extend over the entire width of the material web 01 and have nozzle bores to create the countercurrent airflow 14 on. The nozzle holes 14 have a diameter between 0.8 and 2 mm. Preferably, the size of the nozzle holes is 14 in the range of 1 to 1.5 mm.

The nozzle holes 14 can each have a distance of 30 to 150 mm. This distance is preferably 70 up to 120 mm.

Based 4 become advantageous dimensions or arrangements of the device in a cooling roll stand 06 explained. The nozzle pipes 11 respectively. 12 are in a z. B. vertical distance y ₁ ; y ₂ from the material web 01 spaced apart, this distance y ₁ ; y _{2 is} in the range of 10 to 300 mm, preferably between 50 and 130 mm. The distance y ₁ ; y _{2 of} the nozzle tubes 11 ; 12 from the material web 01 does not have to be the same size on top and bottom.

The upper nozzle tube 11 is preferably in the web running direction of the material web 01 approximately in a vertical plane with the longitudinal axis of the first cooling roller 07 -I arranged. The distance x _{1 of} the upper nozzle tube 11 to the vertical plane may be arranged in the web running direction to about 100 mm in front of or behind the vertical plane. Preferably, the distance x ₁ -20 to +20 mm.

The lower nozzle tube 12 is preferably in the web running direction of the material web 01 approximately in a vertical plane with the longitudinal axis of the first cooling roller 07 -I arranged. The distance x _{2 of} the lower nozzle tube 12 to the vertical plane can be arranged in the direction of web travel 200 mm to about 400 mm in front of the vertical plane. Preferably, the distance x _{2 is} 250 mm to 350 mm.

The distance x _{3 of} the nozzle tubes 11 ; 12 to one another, measured on a horizontal plane, in an advantageous embodiment is 100 to 300 mm, preferably 150 to 200 mm.

The nozzle holes 14 are at an angle of incidence β in the opposite direction to the web 01 directed. The angle of incidence β can be varied from 15 ° to 60 °, it is preferably in a range between 30 ° and 40 °.

The through the nozzle holes 14 outflowing air is preferably applied to a pressure of 3 to 10 bar.

Of the Air flow preferably has a temperature of 20 ° C to 40 ° C.

Based 5 the self-adjusting flow and pressure conditions are displayed on a device. Hatched indicates a zone of turbulent invisible cold flow 16 , z. B. compressed air 16 , Outside the area 16 is an area of clean, flowing laminar airflow 17 , On the edge of the current 16 form negative pressure areas 18 , which exerts a force on the material web 01 have as a consequence. The resulting force vectors are with the force arrows 19 characterized. As a result, a wave formation of the material web 01 and a better concern of the material web 01 at the first cooling roll 07 -I reached.

The flow 16 reaches a flow velocity counter to the web running direction of 0.2 to 2 m / s. Through this flow 16 In fact, a tearing off of the laminar boundary layer of condensate-containing air can be achieved.

The introduced at the bottom of the rail air flow of the nozzle tube 12 creates a vacuum wedge 21 at the inlet between the first cooling roller 07 -I and the material web 01 , so that in addition the overpressure acting on the upper side of the web causes an application of the material web 01 on the first chill roll 07 -I effects. If the upper nozzle tube is not available 11 the ambient pressure acts on the material web 01 ,

The location of the chill roll 07 -II is chosen according to the air flow at the bottom of the track such that also at the inlet between the web 01 and the second cooling roll 07 -II a negative pressure is created, so that in addition a pressing of the material web to the second cooling roller 07 -II can be achieved.

01

web

02

Hot air dryer

03

Flue gas tunnel

04

movement arrow

05

06

Chill roller stand

07

chill roll

08

Flue gas vortex

09

intake flow

10

11

Nozzle tube, upper

12

Nozzle tube, lower

13

flow

14

nozzle bore

15

16

Flow, compressed air

17

Flow, laminar

18

Under pressure area

19

force arrow

20

21

Under pressure wedge

x ₁

Distance nozzle tube ( 11 ) to the chill roll ( 07 )

x ₂

Distance nozzle tube ( 12 ) to the chill roll ( 07 )

x ₃

Distance between the nozzle tube ( 11 ; 12 )

y ₁

Distance between nozzle tube ( 11 ) and material web ( 01 )

^y 2

Distance between nozzle tube ( 12 ) and material web ( 01 )

β

angle of attack

Claims (14)

Method for reducing the required cooling capacity in a cooling roll stand ( 06 ) of a web-fed rotary printing press, one or more of which is fed into the chill roll stand ( 06 ) incoming material webs ( 01 ) before hitting a first chill roll ( 07 -I) is acted upon by an air flow, the running direction of the web ( 01 ) is opposite and over the entire width of the web ( 01 ), wherein the air flow at an angle of attack (β) of 15 ° to 60 ° to the material web ( 01 ), wherein the flow velocity of the air flow is 0.2 to 2 m / s, and wherein the air flow under a pressure of 3 to 10 bar on the web ( 01 ), so that the "COANDA" effect is used. A method according to claim 1, characterized in that the air flow on both sides of the material web ( 01 ). A method according to claim 1 or 2, characterized that the air flow has a temperature of 20 ° C to 40 ° C. A method according to claim 1, characterized in that the upper nozzle tube ( 11 ) at a distance (x ₁ ) to a vertical plane with the longitudinal axis of the first cooling roll ( 07 -I) of less than 100 mm in front of or behind this plane. A method according to claim 1, characterized in that the upper nozzle tube ( 11 ) at a distance (x1) to a vertical plane with the longitudinal axis of the first cooling roll ( 07 -I) of less than 20 mm in front of or behind this plane. Device in a chill roll stand ( 06 ) with cooling rollers ( 07 ), wherein a nozzle tube ( 11 ; 12 ) in the web run in front of a first cooling roll ( 07 I) is arranged and over the entire width of the chill roll stand ( 06 ) fed material web ( 01 ), wherein the nozzle tube ( 11 ; 12 ) for the flow of a gaseous cooling medium nozzle bores ( 14 ), which essentially counter to the running direction of the material web ( 01 ) are aligned so that the cooling medium against the direction of the web ( 01 ) is inflated to this, wherein on each Bedruckseite the web ( 01 ) a nozzle tube ( 11 ; 12 ), wherein the upper nozzle tube ( 11 ) at a distance (x1) to a vertical plane with the longitudinal axis of the first cooling roll ( 07 -I) of less than 100 mm in front of or behind this plane, the distance (x3) of the nozzle tubes ( 11 ; 12 ) in the horizontal direction to each other 100 to 300 mm, wherein the nozzle bores ( 14 ) at an angle of attack (β) of 15 ° to 60 ° on the material web ( 01 ) are directed. Apparatus according to claim 6, characterized in that the nozzle tubes ( 11 ; 12 ) at a vertical distance (y ₁ , y ₂ ) of 10 to 300 mm to the material web ( 01 ) are arranged. Apparatus according to claim 7, characterized in that the vertical distance (y ₁ ; y ₂ ) between the nozzle tubes ( 11 ; 12 ) and material web ( 01 ) Is 50 to 130 mm. Apparatus according to claim 6, characterized in that the horizontal distance (x ₃ ) between the nozzle tubes ( 11 ; 12 ) Is 150 to 200 mm. Device according to one of claims 6 to 9, characterized in that the nozzle tubes ( 11 ; 12 ) a distance of one to two meters to the exit of a hot-air dryer ( 02 ) exhibit. Device according to one of claims 6 to 10, characterized in that the nozzle bores ( 14 ) in the nozzle tube ( 11 ; 12 ) have a distance from each other of 30 to 150 mm. Apparatus according to claim 11, characterized in that the nozzle bores ( 14 ) have a distance of 70 to 120 mm from each other. Device according to one of claims 6 to 12, characterized in that the nozzle bores ( 14 ) have a diameter of 0.8 to 2 mm. Apparatus according to claim 13, characterized in that the nozzle bores ( 14 ) have a diameter of 1 to 1.5 mm.