EP1389693A2 - Heated roller and operating process - Google Patents

Abstract

The heated calender roll for paper and cardboard has an inlet (9) for heating medium which passes through one bearing (7), a central channel (6) and an outlet (10) which passes through the second bearing (8). A flow guide (17) with radial spokes adjusts the peripheral speed of flow of the medium to correspond to that of the roll.

Description

The invention relates to a roll with a temperature control Roll body and one roll neck on each axial end of the roller body, with a flow path provided for a heat transfer medium by the roller is that in a first section radially from the inside outwards, in a second section axially through the Roller body radially below its peripheral surface and in a third section radially from the outside runs inside. The invention further relates to a method for operating a temperature-controlled roller, at which a heat transfer medium through the roller radially below guided by its peripheral surface and through one Roll neck is led out.

Such a temperature-controlled roller is used, for example used in calenders to make a web of material, in particular a paper or cardboard web. The Tempering can mean that the roller is heated, in order to be able to apply heat to the material web. The Temperature control can also mean that the roller is cooled becomes. For example, you can by cooling dissipate heat from the elastic covering of the roller, which heats up during operation.

In order to be able to effect this temperature control, the heat transfer medium, usually a liquid through initiated a roll neck. The initiation takes place usually concentric to the roller axis. The heat transfer medium then flows radially outward until it comes on the desired position. If the roller body is designed as a tube, then this position is the Inner wall of the pipe. The heat transfer medium then flows axially along the inner wall of the tube. On the other roll neck the heat transfer medium has to radially follow again flow inside to be led out through the other roll neck to become. If the flow path is controlled differently it can also be the inflow and the outflow of the heat transfer medium through the same Cause roll neck.

A roller that flows through in the manner described first is known from WO 02/29267 A1. Tried here one, with the help of mixer devices in the hollow Interior of the roller swirling the heat transfer fluid to reach. This is to ensure that the tube wall is always acted on with heat transfer fluid can be a predetermined temperature Has. There should be no flow paths if possible form for the heat transfer fluid, where not emitted enough heat to the pipe wall or from there is recorded.

Around the heat transfer medium, in particular a heat transfer liquid, to drive through the roller needed one with rolls, the roll body is designed as a tube is, sometimes considerable pressures. These pressures are conditional a relatively large effort in operation.

The invention has for its object the heat transfer medium with as little effort as possible through the roller to drive.

This task is carried out with a temperature-controlled roller type mentioned solved in that in the area a guide device is arranged in the third section which is the local velocity of the heat transfer medium in the circumferential direction at any radial distance from the roller axis to the local speed adapts the roller in the direction of rotation.

The local orbital velocity of a point on one rotating body decreases with increasing approach to the axis of rotation. The management facility provides now that the heat transfer medium in the direction of circulation is braked when it is radial from the outside in flows. The circulation speed of the heat transfer medium the rotational speed of the roller customized. This adjustment does not have to be an exact match mean. If the heat transfer medium is in the area the roller axis has arrived, where it comes from the roller can be removed, then theoretically it has no rotational speed more, in practice is the speed of circulation tiny. This causes pressure drops kept small. The heat transfer medium can therefore drive through the roller at a reduced pressure. One avoids the formation of a swirling fluid swirl (Potential vortex) when using a Heat transfer fluid. Because a significant portion of the Pressure, which is used to drive the heat transfer fluid required by the roller to compensate for pressure losses serves in the outlet of the roller means the reduction such a pressure loss at the outlet a clear one Reduction of the effort with which the heat transfer medium drives through the roller.

The roller body is preferably designed as a tube and the guide device ends in a predetermined one Distance radially in front of the inner wall of the pipe. In order to there is a gap between the guide device and the inner wall of the tube, which ultimately the Thickness of a liquid film determined by the Roller flows through. Radially within the limit that defined by this gap may change under certain circumstances result in a dead water area inside the roller, so that essentially the freshly incoming heat transfer medium flows around the inner wall of the tube. It results so there is a displacement effect. With a suitable choice of The gap height, i.e. the distance, becomes the flow velocity of the heat transfer medium on the inner wall of the pipe higher, whereby the Nusselt number and thus the Heat transfer increases.

The guide device preferably has a plurality of webs that extend radially from the inside out. The webs form a propeller, so to speak, but not the heat transfer medium at the exit accelerates, but on its way from the radially outside brakes radially inward in the direction of rotation. The usage of such webs is a relatively simple one Embodiment to the heat transfer medium in the desired Way to lead.

The guide device preferably has a plate at a predetermined distance from the roll neck, the webs between the roll neck and the plate are arranged. Between the plate and the roll neck a space is clearly delimited by which the Heat transfer medium flows from the outside to the inside. In this The heat transfer medium is guided through the webs, so slowed down. So you are no longer on it instructed the heat transfer medium in the entire hollow Brake the interior of the roller. That too will Losses kept low.

The webs preferably fill a space between the plate and the roll neck in the axial direction out. This means that the entire heat transfer medium in the space between the plate and the roll neck occurs, slowed down on its way from the outside in. Vortex formation is avoided.

The webs preferably run on radial beams to the roller axis. This is a particularly simple embodiment, but which has a sufficient effect.

In a preferred embodiment it is provided that the webs at each of their radially outer ends Bracket are attached, which is between the roll neck and the plate extends. The radially outer end. the dock is basically the most heavily loaded Place of the webs. If you have an additional bracket here provides the mechanical stability of the guide device significantly increased.

It is preferred that the holder is designed as a tube is. A pipe represents a sufficiently large one Attack surface available so that the webs are reliable can be attached. The pipe can one Have a diameter that is larger than the thickness of a web, based on the circumferential direction of the Roller. However, this plays for the management of the heat transfer medium none on its way from the outside in Role. The tube can thus in the direction of rotation of the roller seen quite one-sided or even on both sides survive the respectively assigned web.

A fastening bolt is preferably through at least one tube led the plate with the roll neck combines. You can then add the pipe for fastening the guide device to the roll neck use. A bracket that also with the roll neck is a particularly stable abutment for the dock.

The webs preferably leave at their radially inner End of an outflow space. It is theoretical possible, the webs together at their radially inner end connect to. However, this requires an increased Manufacturing effort. One can without any noteworthy Losses a discharge space on the radially inner one Release the end of the webs, leaving this space then is dimensioned such that it is the cross section of an outflow channel through the roll neck. If that Heat transfer medium first up to this position has flowed, then another braking is no longer required.

The webs are preferably at their radially inner end attached to a pipe. This tube is coaxial with arranged the drain channel through the roll neck. This Pipe can enclose the outflow space, for example, although this is not necessary. In this Case it may be appropriate in the wall of the pipe Drill holes through which the heat transfer medium can flow in. But you can also provide that Tube is shorter than the webs in the axial direction, so that An outflow cross-section is kept free on one end becomes.

The webs preferably have at their radially inner End a beveled corner. This beveled Ekke then allows the formation of an outflow space.

The webs are preferably provided with a centering device connected, which is axially in one in the roll neck extending channel extends into it. With the centering device will be a centering of the guide device relative to the roll, more precisely the roll neck, reached. The centering device must not necessarily be connected to all of the webs. If the centering device as a plate with a trapezoidal shape Is formed, then it is sufficient if you have the Centering device, for example, with two each other opposite webs connects.

A guide device is preferably at both axial ends arranged. This training has several Benefits. On the one hand, you are at one Design no longer depends on the fact that Roll installed with a predetermined orientation becomes. The roller is largely based on its axial center symmetrical. On the other hand, through the management facility also when the heat transfer medium flows in achieved an advantageous effect. The heat transfer medium is then by the guide at Flow accelerated from the inside to the outside in the circumferential direction.

A compressed gas connection preferably opens into the interior of the roller body. It is with the compressed gas connection possible, a gas, such as air, with a predetermined Feed pressure into the interior of the roller. This gas can then turn the liquid up to a certain level Displace dimension so that the roller behaves so as if a displacer was installed. The heat transfer fluid then flows helically from the Inlet to outlet. The thickness of the liquid film can by the gap width between the guide device and predetermined the inner wall of the roller body become. If you get the liquid from the interior displaced, then the rotating mass is reduced.

Alternatively or in addition, the interior of the A displacer body can be arranged, whose specific weight is not greater than the specific one Weight of the heat transfer medium is. This displacement body no longer has to be fixed in the roller body become. It centers itself when the roller is on a predetermined speed is brought. requirement is just that the specific weight of the displacer is smaller than that of the heat transfer medium. For example, one can be used for the displacement body Use cylindrical sponge or polystyrene bodies.

The task is in a method of the aforementioned Kind of solved by looking at the local speed of the heat transfer medium in the direction of circulation at any radial distance from the roll axis to the adjusts the local speed of the roller in the direction of rotation.

At the outlet, you brake the liquid on hers Path from radially outside to radially inside in the direction of rotation from, so that pressure losses in the outlet of the roller be kept small. One prevents the emergence of one non-rotating fluid vortex.

Preferably, the roller is first accelerated to one predetermined speed and then feeds the heat transfer medium on. The speed of the roller is chosen so that the heat transfer medium due to the Centrifugal force is applied to the inside wall of the roller and there forms a liquid film. So you are no longer relied on the roller completely with the heat transfer medium to fill.

Additionally or alternatively, you can use a gas a predetermined pressure in the hollow interior of the Feed roller. This gas can then be the liquid oust as far as desired. The rotating one This reduces mass.

In an alternative preferred embodiment can the roller is completely filled with a liquid heat transfer medium to fill. The management organization responsible for this ensures that the movements of the liquid heat transfer medium and the roller when flowing from the inside out and agree from the outside in, ensures at the same time that the roller even at lower speeds and simultaneous inflow of heat transfer medium completely filled with the heat transfer medium can be. This is without the guidance facility not the case because after reaching a liquid level the remaining volume of the Air above the liquid level no longer escapes can. It then comes through the rotation of the roller due to the dynamics of the liquid filling to undesirable Unbalances. Through the guide device however, the residual air after a few revolutions of the roller removed so that the roller completely with liquid is filled and then shows no more unbalance. It so there is always a reproducible stable Fill state.

Fig. 1

eine schematische Ansicht einer temperierbaren Walze im Schnitt,

Fig. 2

eine Schnittansicht durch eine Führungseinrichtung und

Fig. 3

eine Draufsicht auf die Führungseinrichtung.

The invention is described below with reference to a preferred embodiment in connection with the drawing. Show here:

Fig. 1

1 shows a schematic view of a temperature-controlled roller in section,

Fig. 2

a sectional view through a guide device and

Fig. 3

a plan view of the guide device.

Fig. 1 shows schematically a roller 1 with an as Tube-formed roller body 2, which has an elastic Rubber 3 wears. The elastic covering 3 can for example be formed from a plastic.

At both axial ends of the roller body 2 is a roll neck 4, 5 arranged. The roll neck 4, 5 and the roller body 2 together enclose a hollow Interior 6.

The roller journals 4, 5 have shaft ends 7, 8, with which the roller 1 rotatably in a not shown Rack can be stored. The stub of the waves 7 is penetrated by an inflow channel 9 which opens into the interior 6. The other stub 8 is penetrated by an outflow channel 10, which also opens into the interior 6. Through the inflow channel 9 can, as indicated by an arrow 11 is a heat transfer fluid into the interior 6 be fed. Through the outflow channel 10, as indicated by another arrow 12, the heat transfer fluid flow out of the interior 6.

When the roller 1 rotates, the heat transfer fluid settles in a film 13 on the inner wall 14 of the roller body 2 and under the action of Centrifugal force.

In addition, a compressed air connection 15 is provided is only shown schematically. Via the compressed air connection 15 it is possible to get compressed air into the interior 6 feed the roller 1. Since the roller 1 can rotate, the compressed air connection 15 is in a rotating union shown only schematically 16th

In front of the outflow channel 10 is a guide device 17 arranged in connection with FIGS. 2 and 3 should be explained in more detail. An identical guiding device 18 is arranged behind the inflow channel 9.

The guide device 17 is in the area of the outflow side Roller pin 5 arranged and concentric on it attached so that between the guide device 17 and the inner wall 14 of the roller body 2 a gap 19 results. This gap 19 essentially determines the thickness of the film 13.

The guide device 17 has a plate 20, the at a predetermined distance from the roll neck 5 is arranged. A fastening ring lies on the roll neck 5 21 on. Between the plate 20 and the mounting ring 21 several extend in the radial direction Crosspieces 22. As can be seen from FIG. 3, it acts are a total of eight webs that extend in the circumferential direction are 45 ° apart.

In principle, the webs are rectangular. However, they have a beveled corner 23. The chamfered corners 23 together form an outflow space 24. This outflow space 24 extends into Radial direction about as far as the diameter the outflow channel 10.

A tube 25 is connected to the plate 20. The inner ones The ends of the webs 22 are also connected to the tube 25 connected. The tube 25 thus forms a holder for the radially inner ends of the webs 22.

The radially outer ends of the webs 22 are also each connected to a tube 26. The tube 26 has a diameter that is greater than the thickness the bridges. In the circumferential direction of the roller 1 are Pipes 26 left and right over the webs 22. The tubes 26 connect the plate 20 to the mounting ring 21. You can do this with plate 20 as well as welded to the mounting ring 21. The webs 22 can also be welded to the tubes 26 his.

The tubes 26 also serve to receive fastening bolts 27 with which the guide device 17 is screwed onto the roll neck 5. This will ensured that the webs 22 on their radially outer End up being held very reliably. You can so take up relatively high loads.

As can be seen from Fig. 3, the webs 22 are like this led how radial rays run.

The webs 22 fill the space between the roll neck 5 or the mounting ring 21 and the plate 20 in Axial direction completely, i.e. act upon them a liquid that is in the space between the Plate 20 and the mounting ring 21 moves completely. This avoids eddies.

A centering device 28 has the cross section Shape of a trapezoid, i.e. the centering device 28 is a plate with tapered sides 29 which in the outflow channel 10 is inserted. If the management facility 17 applied to the roll neck 5 centering takes place automatically.

The guide device 18 is basically constructed the same way. A more detailed explanation can therefore be omitted.

The operation of the guide device 17 can be briefly describe as follows:

The heat transfer fluid from the film 13 is through the gap 19 between the guide device 17 and the inner wall 14 of the roller body 2 in an intermediate space 30 fed between two in the circumferential direction adjacent webs 22 is formed. If the Then liquid is pushed radially further inwards is braked by the webs 22, i.e. your Speed in the direction of rotation decreases so that it when reaching the outflow chamber 24 is so small that the Liquid without significant pressure loss through the Outflow channel 10 can flow out. You avoid on this way the emergence of a non-rotating fluid vortex (Potential vortex).

As a corresponding guide device on the inlet side 18 is arranged, the feeding takes place the heat transfer fluid through the guide device 18 directly to the roll shell 2, i.e. to the inner wall 14, which ensures better temperature control of the roller body 2 is achieved. Through the management facility 17, 18 a larger dead water area forms in the interior 6, so that essentially the freshly tapered one Heat transfer fluid flows around the inner wall 14. The Flow rate of the heat transfer fluid becomes higher on the inner wall 14, causing the Nusselt number and so the heat transfer increases.

For the tempering of an elastic middle roller modern calenders can at low flow speeds and flooded roller such a completely sufficient Heat dissipation or supply can be achieved.

You can now take further measures to heat transfer to improve. One can, for example, first raise the empty roller 1 to operating speed and only then feed in heat transfer fluid. This will make the film 13 described above on the inner wall 14 formed. The roller 1 is not complete flooded. The roller behaves as if a displacer installed. The liquid film 13 flows helically from the inlet to the outlet.

The thickness of the liquid film 13 can be determined by the width of the gap 19 can be predetermined with a good approximation.

In addition, you can 15 Compressed air or another compressed gas into the interior 6 feed. The compressed air can then be the heat transfer fluid displace. This also works if the roller has been completely filled beforehand. But even if the roller only at operating speed the compressed air can be supportive Act.

You can also, as shown in dashed lines, Arrange a displacer 31 in the interior 6. The Displacer 31 only has to be rough in the axial direction be fixed. There is an attachment in the radial direction not required, i.e. the displacer 31 must not be centered. The only requirement is that its specific weight is smaller than the specific one Weight of the heat transfer fluid. This leaves can be achieved, for example, by the displacement body 31 as a cylindrical body made of a sponge or polystyrene is formed. The outside diameter of the Displacer 31 must be smaller than the inside diameter of the roller body. This will make the convection with the freshly flowing heat transfer fluid most of the inside of the roller 1 Avoided liquid, so that the displacement effect takes effect.

You can also with the help of the guide device 17, 18 ensure that the roller is completely filled with a liquid Heat transfer medium can be filled without unbalance occurs.

Without a guide device 17 would after reaching a Liquid level that is above the height of the outlet, the remaining volume of air above the liquid level can no longer escape. If the roller then turns, it comes through the dynamics of the Liquid filling to undesirable unbalance.

The residual air is removed by the guide device 17 a few revolutions of the roller against it, so that the roller is completely filled with liquid and then shows no more unbalance. So it happens always reproducible stable filling condition.

Claims (21)

Temperable roll with a roll body and a roll pin at each axial end of the roll body, a flow path for a heat transfer medium through the roll being provided, which in a first section radially from the inside out, in a second section axially through the roll body radially below whose circumferential surface and in a third section runs radially from the outside inwards, characterized in that a guide device (17) is arranged in the region of the third section, which guides the local speed of the heat transfer medium in the circumferential direction at every radial distance from the roller axis to the local speed adapts the roller in the direction of rotation. Roller according to claim 1, characterized in that the roller body (2) is designed as a tube and the guide device (17) ends at a predetermined distance radially in front of the inner wall (14) of the tube. Roll according to claim 1 or 2, characterized in that the guide device (17) has a plurality of webs (22) which extend radially from the inside to the outside. Roll according to Claim 3, characterized in that the guide device has a plate (20) at a predetermined distance from the roll neck (5), the webs (22) being arranged between the roll neck (5) and the plate (20). Roll according to claim 4, characterized in that the webs (22) fill an intermediate space between the plate (20) and the roll neck (5) in the axial direction. Roll according to one of claims 3 to 5, characterized in that the webs (22) run on radial jets to the roll axis. Roll according to one of Claims 3 to 6, characterized in that the webs (22) are each fastened at their radially outer end to a holder (26) which extends between the roll neck (5) and the plate (20). Roller according to claim 7, characterized in that the holder (26) is designed as a tube. Roller according to Claim 8, characterized in that a fastening bolt (27) is guided through at least one tube and connects the plate (20) to the roller journal (5). Roller according to one of Claims 3 to 9, characterized in that a fastening ring (21) is arranged between the roller journal (5) and the webs (22) on the side of the webs (22) which faces the roller journal (5) , Roll according to one of claims 3 to 10, characterized in that the webs (22) leave an outflow space (24) at their radially inner end. Roller according to claim 11, characterized in that the webs (22) are fastened to a tube (25) at their radially inner end. Roll according to claim 11 or 12, characterized in that the webs (22) have a chamfered corner (23) at their radially inner end. Roll according to one of Claims 3 to 13, characterized in that the webs (22) are connected to a centering device (28) which extends into a channel (10) which runs axially in the roll neck (5). Roll according to one of claims 1 to 14, characterized in that a guide device (17, 18) is arranged at both axial ends. Roller according to one of claims 1 to 15, characterized in that a compressed gas connection (15) opens into the interior (6) of the roller body (2). Roller according to one of claims 1 to 16, characterized in that a displacement body (31) is arranged in the interior (6) of the roller body (2), the specific weight of which is not greater than the specific weight of the heat transfer medium. Method for operating a temperature-controlled roller, in which a heat transfer medium is passed through the roller radially below its circumferential surface and is led out through a roll neck, characterized in that the local speed of the heat transfer medium in the circumferential direction at any radial distance from the roll axis to the local speed adapts the roller in the direction of rotation. A method according to claim 18, characterized in that the roller is first accelerated to a predetermined speed and then the heat transfer medium is fed. A method according to claim 18 or 19, characterized in that a gas with a predetermined pressure is fed into the hollow interior of the roller. A method according to claim 18 or 19, characterized in that the roller is completely filled with a liquid heat transfer medium.

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