DE3432328A1 - Structure for varying the air boundary layers of a heat-transmission roller - Google Patents

Abstract

The invention relates to a simple mechanical system, by means of which the composition of the boundary-layer atmosphere connected to the passage of a web around a heat-transmission roller is removed, reduced or varied. The aim of the invention is to eliminate the air layer between the web and the heat-transmission roller or to remove as much air as possible, so that more intimate contact is achieved between the web and the heat-transmission roller, or to vary the pressure and the composition of the atmosphere to the effect that a higher efficiency of the heat transmission from the roller to the web is achieved. For this, the mechanical structure can have a squeezing-off roller which is located between the heat-transmission roller and by which the air boundary layer adhering to the web is stripped off before the contact of the web with the heat-transmission roller. At the same time, a vacuum can also be applied at the squeezing-off roller. Furthermore, the object of the invention is to reduce the temperature of the air boundary layer by cooling the latter and by using fixed boundary-layer air removal rods and/or squeezing-off or stripping-off rollers. The squeezing-off roller is covered with a soft surface, preferably of rubber or a plastic, so that it comes into intimate contact with the heat-transmission roller and is driven as a result of this contact.

Description

The invention relates to the field of heat transfer

support rollers, but is also used in all situations, in which it is desired, an air boundary layer from a web of fabric or ~ top ~ to remove flat, The prior publications listed below are relevant in relation to the general problem raised here, but in most Cases a vacuum system is used on the drive or rotary roller: 2,679,572; 2,826,827; 3,097,933; 3,118,743; 3,122,295; 3,151,796; 3,258,184; 3,286,895; 3 327 916; 3,366,298; 3,405,855; 3,420,424; 3,465,320; 3,561,133; 3,688,336; 3 782 003 and 3,854,222.

The following publications are also mentioned, those for the general operation of the heat transfer rollers and in particular at Cooling rollers are relevant, those for ink setting are important after publishing (1) "An Investigation of Self-Acting Bearings", which appeared in the Journal of Basic Engineering, Dec. 1965 on pages 837-846 is; and after (2) "Fluid Effects associated with Web Handing" by Kenneth L. Knox and thomas L. Sweeney, who graduated from Ohio State College Ind. Eng.

Chem Process Des Development, Volume 10, No. 21971, page 201 and in Graphic Arts Monthly ", June 1980, pages 76-82.

With arch guides, there is a layer of air between the roller and the Train wanted, because the train would then over the reels with a low level of friction between the rotating or the stationary roller (guide) and the web or roller moves. In the case of heat transfer rollers, this is the luminous layer however, undesirable because of the resistance of the insulating properties that trapped between the web and the surface of the heat transfer roll Air layer because it reduces the application or dissipation of heat will. The aim is to reduce this effect if possible.

In the foregoing prior publications, it is indicated that there is a Air layer forms under the web at the nip where the web meets the roll surface touches or, in other words, where the boundary layers that are on the surface of the Heat transfer surface and the web adhere to each other and meet. This thickness h0 is the one enclosed between the nip of the web and the roller Air layer can be calculated. It is less than the sum of each one Boundary layer that meets at the roll gap. The expression of this is the following formula: h0 -65 R (6, uu) 2/3 for a non-rotating roller or drum.

If the roller rotates with a peripheral speed, the same is large as that of the train and runs in the same direction, the factor is 6 in the Replace the above formula with a factor of 12. Appears in all equations for h0 in the prior publication 1 also the factor / u.

u = viscosity of the enclosed air u = film speed (Prior publication 1) r = tension of the web.

The dimensions of the parameters in the above equation are prior publication 1 can be found.

The tests listed on page 841 of the prior publication show a smaller thickness h0 than that calculated above.

It is generally assumed and this is done through calculations and tests confirm that the air layer at the roll gap is much smaller than that Boundary layers carried on by the roller and web that meet at the roller gap will.

The boundary layer then also creates itself quickly when the Web leaves the roller, whereby the web can also swing back and forth (prior publication 1, Fig. 15).

The boundary layer thickness according to prior publication 2, page 202, equation (4), gives the dimension # = 6.37 (/ U X / S) V1 / 2, where X is the distance from the starting point the boundary layer is moving on a continuous flat Forms film in a stagnant infinite fluid and where: S = boundary layer thickness S = liquid density V = speed of the web (see prior publication 2 for dimensions).

Factors such as machine vibration, film flutter, gravity, centrifugal force, that affects the railway, where this changes direction at the roll gap, and dimensional fluctuations were not taken into account here (page 205) of the prior publication 2).

In particular with regard to the use of a cooling roller in one Offset printing, in which the web is heated, can be done with a 150 a (300 ° F) heated web have associated boundary layer above 1590 C (3000 F) because they is supplied from an air dryer at 2600 C (5000 F). The one with the first Boundary layer connected to the cooling roll can, after it leaves the first cooling roll, also lie above the tin temperature. (Your temperature will be between the temperature the cooling roller surface and that of the web). When these two boundary layers meet at the roll gap, the temperature of the air layer at the gap is above that of the surrounding air.

Accordingly, the aim of the invention is to have the effect of To reduce the air layer at the roll gap.

Because the boundary layers in general and the air layer at the gap both have a viscosity / u in the equation with an exponent of 2/3 and 1/2, such an effect can be reduced by lowering the viscosity / u or that other / u influencing factors are changed.

In the Chemical Engineers Handbook Perry 3rd Edition, page 371, Fig. 17 the viscosity is given in centipoise of the gases at 1 atm. So will for example by lowering the temperature of the air layer at the gap from 2050 C (4000 B) 270 C (800 B) the viscosity / u of the air from 0.025 to 0.018 or up a li 0.72 reduced compared to the previous level. The layer of air at the gap and their thermal resistance should be lowered to o.722 / 3 = o.88 or 12 percent. If one assumes in this context an overall thermal resistance between the Web and heat transfer roller from 0.05 to 0.08, it should be 0.12 X (0.05 to 0.08) or by 0.006 to 0.0096. Thus, at a viscosity which is the most influential component in the total heat transfer resistance of approximately 0.07 between the chill roll and the web represents the improvement in the whole Heat transfer can be around 10 percent or above by changing the viscosity or is reduced.

It is therefore the aim of the invention to reduce the air layer to be achieved by creating an enclosure or closed space in front of the roll gap through which most of the boundary layers expelled and through cool Low viscosity air is replaced. After another suggestion the ore in A mechanical "squeeze" roller is used to reduce the thickness of the boundary layer reached, which is covered with a rubber layer and on the heat transfer roller along with the boundary layer holding on the surface of the heat transfer roller is graduated or squeezed while at the same time the web is touched, which approaches the nip of the heat transfer roll where it is against the web rotates, and the greatest effectiveness is exerted by the hot boundary layer thickness the web is reduced as it enters the nip area.

Friction with the web would be minimal because of the sheet guiding effect. Means should also be provided to reduce the contact pressure of the exhaust roller Changing springs, weights, air or hydraulic cylinders, which are used in many workshops usually used to remove more of the boundary layer that is attached to the chill roll sticks when it moves towards the roll gap.

Furthermore, a space is to be provided by the invention, bounded by the squeegee roll, the heat transfer roll and the web, so that it is vented by the air blown in from one side that comes out of the exits the other side, with air also being introduced into the central space through a pipe which could be vented without inclusion on the sides at either end, In addition, the invention provides for cooling of the air boundary layer, only a small amount of cooling is required to adjust the viscosity factor / u to lower. A vacuum could also be applied to lower the factor / u.

The inventive arrangement of the entire structure to increase the performance is not expensive, it can be set up easily and is extremely reliable.

The invention is also intended to create a boundary layer, which consists of other gases - such as air and which have a lower viscosity, how for example propane, these gases to a usable Gas heater drier fed back and burned in the exhaust chimney, so that their heat energy can be recovered.

The invention also provides that the "squeegee roller on the heat transfer roller runs along with it and is driven by it, whereby its temperature through the immediate.contact with the cooling roller (in the case of cooling) or by suitable toothing from Heat transfer mill is reduced.

The foregoing object and objects of the invention are as follows described in more detail. They are achieved by an arrangement by the one Boundary air layer modification for a heat transfer roller is performed, the is used in the structure so that it takes up a path around it, whereby the heat transfer between the web and the roller and which is characterized by: Means for inserting the heat transfer roller in a rotatable bearing guide; Means for wrapping the web around the heat transfer roll located at the point of contact forms a nip with the web; Means for stripping immediately next to the Heat transfer roll and as close as possible to the nip so that the air boundary layer mechanically from the heat transfer roller as it approaches the nip can be squeezed off, whereby by these means the web with her in sliding Contact in the vicinity of the roll gap remains so that the air boundary layer from the Underside of the web is mechanically stripped immediately next to the roll gap.

The features of the invention and its technical advantages emerge from the following description of several exemplary embodiments in conjunction with the claims and the drawings.

1 shows a schematic representation of the general Arrangement that has two "squeegee" rolls with two chill rolls and in which the around them is laid out path; FIG. 2A is a side elevation in section of FIG Squeegee roller and the cooling roller with air inlets and / or vacuum outlets, and especially the play for the side inclusions against the rollers; Fig. 2B a 2A similar view in which the inlet and outlet for atmosphere exchange are shown; Fig. 3 is a front view of the squeegee roller with a resilient rubber or plastic layer is coated, Fig. 3A is a front view the steel-honored squeegee roller, which is only covered with rubber or plastic at its ends is occupied, Fig. 4 a squeegee roll with heat transfer properties, Fig. 5 is a schematic front view of a gear drive for the squeegee roller; 6A and 6B are schematic views of a modified embodiment in FIG the other gases in the space between the squeegee roller, the cooling roller and the Web can be injected or vacuum filled, and Figure 7 is a schematic Side view of a modified embodiment of a fixed washboard type Device located at the nip between the web and the chill roll, which as fixed discharge rod of a boundary layer acts.

It is set out below in accordance with the statutory provisions only the exemplary embodiments according to the invention are described, in which the cooling roller gives printing ink to an offset press during operation. Regardless, the However, the invention also apply to heat transfer rollers, both for such for cooling as well as for heating and is designed so that the Thickness of the air layer decreased and / or the air layer at the gap between the Web and the heat transfer ax is affected that thereby the effectiveness the heat transfer from the roll to the web is increased.

Normally, the web speed in printing presses is tei about 7.6 m (300 ') to 50.8 m (2000') per minute with web tension at 0.45 kg to 4.99 Kg per inch (2.54 cm) width and the web temperature at the base of the chill roll nip is about 1540 C (3000 F). A typical surface temperature the chill roll is about 43.50 C (110 ° F) with a wrap of 2600 and a roll surface supfinition of 16-52, a paper web of 18.14 Kg (40 pounds) per ream that is approximately 900 m2 (3000 square feet) of surface area. in the Normally the specific heat of the web is around -0.35.

As stated in the prior publications, the equations depend for boundary layers, thickness and temperatures of the thickness and temperature of the Air that is sucked in at the gap of the cooling roller, and of the effect on the Heat transfer characteristics from the chill roll to the web.

The invention aims to be represented by the reference numeral 12 of the Fig. 1 to eliminate indicated thickness of the boundary layers and their temperature or to reduce those on the lower surface of the web and the outer surface of the chill roll or role is guided.

According to the preferred procedure of the invention as exemplified by The general arrangement of Figure 1 is identified as a squeegee roll provided, generally indicated by the reference numeral 20 and the with the chill roll 22 at the gap or as close as possible to the gap 24 between the Web 26 and whose contact with the chill roll 22 comes into frictional engagement. Consequently as much of the air boundary layers as possible is squeezed off by the squeegee roller, on the surface of the cooling roller 22 and the lower surface of the Web 26 are carried along, so that only a small fraction of that Grenzachichtdicke can regress before the web hits the gap 24.

In some cases it may be desirable to have a small gap between the squeegee roll 20 and the chill roll 22 and the web 26. If, for example, there is damp paint or the like on the surface of the web 26 no direct contact would be desired because it would change the color would smear. Similarly, in other cases it would be appropriate to use a relative one Countermovement between the roller 20 and either the chill roller 22 or the web 26 with the slight gap (from about 0.00254 to 0.01 cm) to allow for friction and to avoid wear (and also the undesired generation of heat), to provide which would be advantageous over frictional engagement. Accordingly, according to the invention a roller adjustment mechanism, indicated by block 27, is provided and is connected to the roller 20 in a mechanical manner familiar to the person skilled in the art, as indicated by arrow 27a, so that for a suitable adjustment of the roller 22 is taken care of in the selected direction, for example as indicated by the double-ended arrow 276 perpendicular to the web 26 or opposite the roller 22 in the radial direction can, as indicated by the double-ended arrow 27c. Thus can be controlled by a Combination of these movements achieve the optimal setting of the roller 20 in order to to achieve the best boundary layer reduction, which of course by a simple Rules must be carried out by the specialist.

Thus it is easy to see that during the frictional engagement Roller 20 with roller 22 is to be regarded as optimal, in some cases, in particular there, if there is a relative countermovement between the two rollers, a small one Gap or small space may be preferable to that of the mechanism 27 can be regulated, but even then there is frictional engagement between the air boundary layers, however, it may not be between the rollers.

According to FIGS. 2-A and 2-B, the squeegee roller has an outer one Rubber sheath 21 made of relatively soft rubber or plastic provided that it is intended to come into contact with the cooling roller 22 and to run concurrently with it perform this rotary movement. Here is on -den. inner and outer coat 22a and 22b to pay attention to the cooling roller through which the heat transfer medium is passed through in a conventional manner.

To close off the space, which is triangular (from the Side seen), and between the squeegee roll 21, the chill roll 22 and the web 26 are generally triangular shaped inclusion portions according to the invention 25 is used, as best shown in Fig. 2-A.

There is one for each side end of the respective rollers Inclusion part. There is a very small one between the chill roll and the containment part 25 Bridge 27 is provided so that it does not close with the chill roll one Contact and damage comes. A similar gap 27a lies between the squeegee roller 20 and containment member 25, but with web 26 simply on the surface of the inclusion part is carried away. By the fact that the boundary layer from the surfaces the chill roll and the web is squeezed and that the inclusion parts 25 on each Forming a kind of closure or seal at the end is the possibility of new ones Form boundary layers, largely restricted.

The invention also provides that by the inclusion part 25 also an input and output can be provided, one of which in Fig. 2-B by the reference number 29 is indicated and through which a vacuum is filled into the enclosed area or possibly cooler air or another medium can be introduced, which according to the above has a lower / u factor, whereby the Heat transfer characteristics between the chill roll 22 and the web 26 are increased can be. Here, the input and output 29 can have a long Hollow tube communicating the entire length between the inclusion parts 25 covers, leaving a vacuum along the entire length of the enclosed area can be drawn, and the like.

According to Fig. 3, the squeegee roller has a simple cylinder, which are rotatably inserted in the opposite end bearings 20a and 20b is.

The cylinder carries a sheath 21 made of rubber or plastic which it comes into driving frictional engagement with the roller 22 by simply moving by Gravity applies to them and takes a pinch position, creating the air boundary layer is eliminated and squeezed off by the chill roll.

Additional means of making a Application pressure, for example, by springs, air cylinders, counterweights or the like. insert. Fig. 1 shows that the web 26 slightly.

runs on and over the top surface of the roller 20, causing it with you come into intimate contact and in turn squeeze off the air boundary layer, before the web hits the gap 24.

In Fig. DA is a slightly modified embodiment of the Squeegee roller shown, which the rubber or plastic cover only at the end sections 21a and 21b, the basic portion of the roller being steel or chrome plated is and has a very smooth training, so that it is between those covered with rubber End portions 21 a and 21 b comes to be rubbing engagement. With the steel or chrome plated Surface 21c engages with high dimensional accuracy. In this embodiment the web 26 can be more easily faced across the chrome plated surface 21c the area 21 of the enveloping rubber. Fig. 2 lead.

Fig. 4 shows a squeegee roll with heat transfer characteristics, namely with an inlet and an outlet opening 30 and 32, respectively, which are then used can occur if there is a tendency that the squeegee roller heats up too much, so that it has the opportunity to cool off. Although the surface the squeegee roller in Fig. 4 as from made of solid steel or Chrome-plated, it can also be that shown in Figures 3 or 3-A Have design. Of course, the roller shown in FIG is, also be designed in the same way as the cooling roller itself, the heat transfer area only a small section of the concentric wrappings instead of a passageway represented by its entire interior section.

In addition, the invention provides that the squeegee roller after Figures 3 to 4 could have a spiral groove for each end towards the middle, assistance in centering the web, removing the green layer in the squeegee roller assembly as well as when removing the vacuum of the boundary layer or the application of pressure to Can make lowering of the boundary layer temperature.

Fig. 5 shows a modified embodiment according to the invention with a heat transfer roller 40 having a drive pinion 42 which is connected to the Bearing 41 of the heat transfer roller 40 is connected. The pinion 42 drives an intermediate gear 44, which in turn drives a pinion 46, which in turn is attached to the shaft of the squeegee roller 48 lies. In this way, between the heat transfer roller 40 and the squeegee roller 48 causes an inevitable entrainment, sometimes the frictional connection is preferable, and possibly more useful, when a squeegee roller the heat transfer characteristics as shown in FIG. 4 is used owns.

Fig. 6-A shows schematically how either particular gases or a cooling as an entrance through the enclosures in the one between the squeegee roll, the web and the heat transfer roller delimited area can be provided.

In Fig. 6-A, the inclusions are generally referred to as the reference number 50 wear, at opposite ends of the combination of cooling roller, intermediate gear and squeegee roller. Air 52 is fed in through valve 54 on the left-hand side, whereby special gases 56 can also be supplied via another valve 58, if so desired list. The input mixture is passed through a fan 60 Cooling and / or heating system 64, a control valve 66, a pressure gauge 68 in the direction of the arrow 62 passed into the enclosed area. A cooperating with the outlet valve 72 Outlet pressure gauge 70 closes the schematic circuit, with the exhaust gases then connected released into the atmosphere or sent to a dryer for incineration, if the gas fed in is a special combustible gas.

The embodiment of Fig. 6-B also includes the enclosures 50. Here, however, there is also a vacuum pump 80, which has the same valve arrangement 6-A works together, but with the fan 60 and the cooling unit 64 not applicable.

Here the malfunction unfairness runs according to the direction of the arrow 62 a. Otherwise, the same reference numerals have been used on the arrangement shown in Fig. 6-A similar components.

The embodiment according to the invention, which is shown in Fig. 7, is a stationary boundary layer knockout rod 90 with three independent chambers 92, 94 and 96, which are designed to be as far as possible to the intermediate track 10 and the gap 98 lying on the heat transfer roller are sufficient. According to the representation the web 100 is actually passed over the top of the rod 90, wherein very little play between the heat transfer roller 102 and the rod remain. The chamber 92 has an entrance opening 92a through which, as indicated at 2b, eiii vacuum is sucked in, so that air from the boundary layer to the bottom surface the web 100 is discharged. The chamber 94 has an inlet 94b for a cooled Atmosphere or cooling air, which can exit via the outlet 94a, the chamber 96 in turn a vacuum 96 b has to pass through the opening 96 a in the area immediately next to the gap 98 to draw off excess air. The movement of the atmosphere shows the respective arrow 104, so that it can be seen how the fixed rod removes the boundary layer and brings about the lowering of the temperature of its remaining boundary layer, wherein the rod unit performs this operation very effectively. Also here could be each constriction of the fixed rod, similar to Figures 2A and 2B, an containment member be provided so that the entire area is basically included.

In addition, the stripping device can have more than one squeegee roller include, with a smaller diameter roller in closer proximity to the nip arranged can be. In some cases it may be desirable to use one of a self-lubricating Blade with low coefficient of friction wiping wiper to use the comes into direct contact with the chill roll and the web.

Claims (14)

Structure for changing the air boundary layers of a heat transfer roller Claims 1. Device for performing an air boundary layer change for a heat transfer roller designed to revolve around itself can accommodate a web, with heat transfer taking place between the web and the roller, not shown by a device for insertion into a bearing holder a heat transfer roll (22,40), means through which the web (26) is passed around the heat transfer roller, with a roller gap (24, 40, 98) at the point of contact of the web with the heat transfer roller, and by stripping means (20,48,90) immediately adjacent to the heat transfer roller as close as possible to the gap, around the air boundary layer (12) as it approaches at mechanically squeeze the gap, this means being very close to the web and abut the gap to the air boundary layer from the underside of the web directly to be mechanically wiped off next to the gap and designed as a rotating squeegee roller are, which extends parallel over their entire length, a smaller one Diameter and is immediately next to the gap. 2. Apparatus according to claim 1, g e k e n n z e i c n e t d u r c h Enclosures (25,50) or self-contained components for general enclosure of the end openings between the heat transfer roller, the squeegee roller and the Track at both ends and to create an enclosed area. 3. Apparatus according to claim 1, g e k e n n z e i c h -n e t d u r c h means for applying suction to the area passed by the heat transfer roll, the squeegee roll and the web. 4. Apparatus according to claim 1, g e k e n n z e i c h -n e t d u r c h means for changing the physical characteristics of the atmosphere in that by the heat transfer roll, the squeegee roll and the web with the the confinement constituent parts delimited by the pressurized area Air is supplied to lower the overall temperature. 5. The device according to claim 1, g e k e n n z e i c h -n e t d u r-c h means for changing the physical characteristics of the atmosphere in that by the heat transfer roll, the squeegee roll and the web with the die Enclosure-forming components delimited the area by reducing their density will 6. The device according to claim 2, g e k e n n z e i c h -n e t d u r c h a Device for changing the physical characteristics of the atmosphere in that by the heat transfer roller, the squeegee roller and the web with the die Inclusion-forming components delimited the area by increasing their thermal conductivity and viscosity is decreased. 7. Device according to claims 3, 4, 5 or 6, g e -k e n n z e I n e t d u r c h a device for controlling the work steps in the reduction the thickness density, the temperature, the thermal conductivity and the viscosity of the Atmosphere next to the nip. 8. The device according to claim 1, d a d u r c h g e -k e n n z e i c h n e t that the squeegee roller is formed with a surface (21) made of elastomers is carried out by frictional contact with the heat transfer roller the rotary movement of the squeegee roller is driven. 9. The device according to claim 1, d a d u r c h g e -k e n n z e i c It should be noted that the ends of the squeegee roller are made of elastomeric materials (21a) is so that it is driving contact to be frictional by engagement with the heat transfer roller comes, wherein between the squeegee roller and the heat transfer roller a small gap remains. 10. The device according to claim 1, g e k e n n z e i c h -n e t d u r c h separate drive means (42,44,48) for the rotating drive of the squeegee roller, which is in frictional engagement with the heat transfer roller. 11. The device according to claim 1, d a d u r c h g e -k e n n z e i c h n e t that the stripping means are designed as a stationary hollow rod (90), which are used immediately next to the heat transfer roller and the nip and in that means for sequentially applying a vacuum, an air pressure to bring about a drop in temperature and a vacuum in the area that is immediately next to the nip, are provided. 12. The apparatus of claim 11, d a d u r c h g e -k e n n z e i c h n e t that the hollow rod has three separate chambers (92,94,96) with the gap leading away progressively increasing in size and having enclosed spaces in order to to enclose the intermediate laterally open spaces and one of the heat transfer roller, the stripping means and the web to determine the bounded area, each compartment is related to the delimited area. 13. The apparatus of claim 11, d a d u r c h. g e -k e n nz e i c h n e t that the train is with the hollow bar in sliding Intervention is located. 14. The apparatus of claim 1, g e k e n n z e i c h -n e t d u r c h a device for performing a controllable positional movement of the squeegee roller parallel to the web and the heat transfer roller.