EP1389693B1 - Heated roller and operating process - Google Patents

Description

The invention relates to a heatable roller with a roller body and a roll neck at each axial end of the roller body, wherein a flow path for a heat transfer medium is provided by the roller, in a first portion radially from the inside to the outside, in a second portion axially through the Roll body radially below its peripheral surface and in a third portion radially from outside to inside and in the region of the third portion, a guide means is arranged, the local velocity of the heat transfer medium in the circumferential direction at each radial distance from the roll axis to the local speed of the roll in Adjusting the direction of rotation and has a plurality of webs extending radially from the inside to the outside. Furthermore, the invention relates to a method for operating a temperature-controlled roller, in which a heat transfer medium is passed through the roller radially below its peripheral surface and led out through a roll neck, wherein one adjusts the local speed of the heat transfer medium in the circumferential direction in each radial distance from the roll axis to the local speed of the roll in the circumferential direction.

Such a roller is out JP 57 120 720 A known. Here, a cooled roller is shown with a tube in the interior of which a second tube is coaxially installed, at both ends of which a guide unit is attached. The guide units are rotationally symmetrical and have four webs, which are perpendicular to each other. The inner tube and the inner wall of the outer tube form an annular gap through which the heat transfer medium can flow.

Such a temperable roller is used for example in calenders to treat a material web, in particular a paper or board web. The tempering may mean that the roller is heated in order to register heat in the material web. However, the temperature control can also mean that the roller is cooled. For example, one can dissipate heat from an elastic coating by the cooling of the roller, which heats up during operation.

In order to effect this tempering, the heat transfer medium, usually a liquid, is introduced through a roll neck. The introduction is usually concentric to the roll axis. The heat transfer medium then flows radially outwards until it reaches the desired position. If the roller body is formed 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. At the other roll neck, the heat transfer medium must again flow radially inwards to be led out through the other roll neck. If the flow path can be controlled differently, it is also possible to effect the inflow and outflow of the heat transfer medium through the same roll neck.

Another roller is out WO 02/29267 A1 known. Here one tries to achieve a swirling of the heat transfer fluid with the help of mixer devices in the hollow interior of the roller. This is to ensure that the pipe wall can always be acted upon by heat transfer fluid, which has a predetermined temperature. As far as possible, no flow paths should be formed for the heat transfer fluid in which not enough heat is given off or taken up from the tube wall.

In order to drive the heat transfer medium, in particular a heat transfer fluid through the roller, one needs in some cases considerable pressures in rolls whose roller body is formed as a tube. These pressures require a relatively large effort in operation.

US 2,531,988 shows a glass plate forming roll, which is formed as a cooling roller. In the interior of a roller body coaxially arranged as a tube core is arranged, which together with the roller body forms an annular gap. At the ends of the roll body there are roll neck, which protrude over a certain distance in the roll body. The core tapers off conical at both ends. On the outer surfaces of the cone four webs are attached via a weld, the webs are perpendicular to each other.

DE 199 50 645 A1 describes a heated calender roll, which is easy to manufacture and should have a low weight. In a hollow cylindrical roller body, a displacement body is arranged, which is held at both ends by supporting flange pin. The displacement body is made of solid plastic, such as foam plastic, and has closed pores, wherein it is held by a press fit in the central bore of the roll body.

US Pat. No. 1,837,562 shows a roller for paper coating machines and the like, in which a roller body, a conical inner body is arranged, which forms with the roller body on the inside of a gap which increasingly narrows with increasing distance from the inlet of a heat transfer medium into the roller body. Behind the narrowest point a guide is arranged, which has a plurality of arcuate radially inwardly curved blades.

DE 41 11 911 A1 shows a roller with a hollow rotatable roller body having a roll shell and at least one of its two ends a hollow roll neck. In the interior of the roller body, a guide body is arranged, which forms a channel system with the roll shell, which can be flowed through by a heat transfer medium.

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

This object is achieved in a temperable roller of the type mentioned above in that the guide means comprises a plate having a predetermined distance from the roll neck, wherein the webs between the roll neck and the plate are arranged and that the webs at their radially outer end in each case at a Holder and are fastened at its radially inner end in each case to a holder which extends between the roll neck and the plate.

The local orbital speed of a point on a rotating body decreases as it approaches the axis of rotation. The guide means now ensures that the heat transfer medium is braked in the direction of rotation when it flows radially from outside to inside. The rotational speed of the heat transfer medium is adapted to the rotational speed of the roller. This adaptation does not necessarily mean exact match. If the heat transfer medium has arrived in the region of the roll axis, where it can be removed from the roll, then theoretically it has no circulation speed, in practice, the rotational speed is very small. As a result, pressure losses are kept small. The heat transfer medium can thus drive with a reduced pressure through the roller. One avoids the emergence of a spin-free fluid vortex (potential vortex) when using a heat transfer fluid. Since a significant proportion of the pressure required to drive the heat transfer fluid through the roller is used to compensate for pressure losses in the outlet of the roller, the reduction of such pressure losses at the outlet means a significant Reduction of the effort with which you drive the heat transfer medium through the roller. The webs thus form a propeller, so to speak, which does not accelerate the heat transfer medium at the exit, but slows down in the direction of rotation on its way from radially outward to radially inward. The use of such webs is a relatively simple embodiment to guide the heat transfer medium in the desired manner. The radially outer end of the webs is basically the most heavily loaded point of the webs. If one provides an additional holder here, the mechanical stability of the guide device is substantially increased.

Preferably, the roller body is formed as a tube and the guide means ends at a predetermined distance radially in front of the inner wall of the tube. This results in a gap between the guide means and the inner wall of the tube, which ultimately determines the thickness of a liquid film which flows through the roller. Radially within the boundary, which is defined by this gap, under certain circumstances, a dead water area inside the roll can result, so that essentially flows around the freshly flowing heat transfer medium, the inner wall of the tube. This results in a displacement effect. With a suitable choice of the gap height, ie the distance, the flow velocity of the heat transfer medium on the inner wall of the tube is higher, whereby the Nußelt number and thus the heat transfer is greater.

Between the plate and the roll neck so a space is clearly defined, through which the heat transfer medium flows from outside to inside. In this room, the heat transfer medium is guided through the webs, so slowed down. It is therefore no longer dependent on decelerating the heat transfer medium in the entire hollow interior of the roller. This also keeps losses low.

Preferably, the webs fill a gap between the plate and the roll neck in the axial direction. Thus, the entire heat transfer medium, which enters the space between the plate and roll neck, braked on its way from outside to inside. A vortex formation is avoided.

Preferably, the webs extend to radial rays to the roll axis. This is a particularly simple embodiment, but achieves a sufficient effect.

It is preferred that the holder is designed as a tube. A tube provides a sufficiently large attack surface available, so that the webs can be reliably attached. Although the tube may have a diameter which is greater than the thickness of a web, based on the circumferential direction of the roller. However, this plays no role in the management of the heat transfer medium in its path from the outside to the inside. The tube can thus seen seen in the direction of rotation of the roller quite one-sided or even on both sides over the respective associated web.

Preferably, a fastening bolt is guided through at least one tube, which connects the plate with the roll neck. You can then use the pipe in addition to the attachment of the guide device on the roll neck. A bracket, which is additionally connected to the roll neck, is a particularly stable abutment for the web.

Preferably, the webs leave at its radially inner end a discharge space. Although it is theoretically possible to connect the webs at their radially inner end with each other. However, this requires an increased effort in the production. It is possible to leave a discharge space at the radially inner end of the webs without significant losses, this space then is approximately sized so that it corresponds to the cross section of a discharge channel through the roll neck. Once the heat transfer medium has flowed to this position, then further braking is no longer required.

Preferably, the webs are attached at their radially inner end to a pipe. This tube is arranged coaxially with the drainage channel through the roll neck. This tube may, for example, enclose the outflow space, although this is not necessary. In this case, it may be appropriate to introduce holes in the wall of the tube, through which the heat transfer medium can flow. But you can also provide that the tube is shorter than the webs in the axial direction, so that an outflow cross section is kept free at one end face.

The webs preferably have a bevelled corner at their radially inner end. This beveled Ekke then allows the formation of a discharge space.

Preferably, the webs are connected to a centering device which extends into a groove in the journal axially extending channel. The centering device thus achieves centering of the guide device relative to the roller, more precisely the roll neck. The centering must not necessarily be connected to all webs. If the centering device is designed as a plate with a trapezoidal shape, then it is sufficient if you connect the centering device, for example, with two opposing webs.

Preferably, a guide device is arranged at both axial ends. This training has several advantages. Firstly, it is no longer necessary in such an embodiment that the roller is installed with a predetermined orientation. The roller is largely symmetrical with respect to its axial center. On the other hand, an advantageous effect is achieved by the guide device even when flowing the heat transfer medium. The heat transfer medium is then accelerated by the guide means when flowing from the inside to the outside in the circumferential direction.

Preferably, a compressed gas connection opens into the interior of the roller body. With the compressed gas connection, it is possible to feed a gas, for example air, with a predetermined pressure into the interior of the roller. This gas can then displace the liquid to a certain extent, so that the roll behaves as if a displacer were installed. The heat transfer fluid then flows helically from the inlet to the outlet. The thickness of the liquid film can be predetermined by the gap width between the guide means and the inner wall of the roll body. If you displace the liquid from the interior, then the rotating mass is reduced.

Alternatively or additionally, a displacement body may be arranged in the interior of the roller body whose specific weight is not greater than the specific weight of the heat transfer medium. This displacer no longer needs to be fixed in the roll body become. It centers itself when the roller is brought to a predetermined speed. The only prerequisite is that the specific gravity of the displacement body is smaller than that of the heat transfer medium. For example, one can use a cylindrical body of sponge or polystyrene for the displacer.

The object is achieved in a method of the type mentioned above in that in addition to the heat transfer medium, a gas at a predetermined pressure in the hollow interior of the roller feeds.

When you run out so slows down the liquid on its way from radially outward to radially inward in the direction of rotation, so that pressure losses in the outlet of the roller are kept small. It prevents the emergence of a rotation-free fluid vortex. The gas can displace the fluid as far as desired. The rotating mass is thereby reduced.

Preferably, the roller is first accelerated to a predetermined speed and then feeds the heat transfer medium. The speed of the roller is chosen so that the heat transfer medium due to the centrifugal force to the inner wall of the roller applies and forms a liquid film there. It is therefore no longer dependent on filling the roller completely with the heat transfer medium.

In an alternative preferred embodiment, the roll can be completely filled with a liquid heat transfer medium. The leadership facility for that ensures that the movements of the liquid heat transfer medium and the roller when flowing from inside to outside and from outside to inside, at the same time ensures that the roller can be completely filled with the heat transfer medium even at low rotational speeds and simultaneous inflow of heat transfer medium. This is not the case without the guide means, since after reaching a liquid level above the height of the outlet, the residual volume of air above the liquid level can no longer escape. Due to the rotation of the roller, the dynamics of the liquid filling result in undesired imbalances. By the guide means, however, the residual air is removed after a few revolutions of the roller, so that the roller is completely filled with liquid and then shows no imbalance. Thus, an always reproducible stable filling state is established.

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 will be described below with reference to a preferred embodiment in conjunction with the drawings. Herein show:

Fig. 1

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 schematically shows a roller 1 with a tube formed as a roller body 2, which carries an elastic coating 3. The elastic covering 3 may for example be formed from a plastic.

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

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

When the roller 1 rotates, then the heat transfer fluid is applied in a film 13 to the inner wall 14 of the roller body 2 under the action of the centrifugal force.

In addition, a compressed air connection 15 is provided, which is shown only schematically. About the compressed air connection 15, it is possible to feed compressed air into the interior 6 of the roller 1. Since the roller 1 can rotate, the compressed air connection 15 is in a rotary feedthrough 16 shown only schematically.

In front of the outflow channel 10, a guide device 17 is arranged, which in connection with the FIGS. 2 and 3 will be explained in more detail. A structurally identical guide device 18 is arranged behind the inflow channel 9.

The guide device 17 is arranged in the region of the outflow-side roll neck 5 and concentrically attached to it, so that there is a gap 19 between the guide means 17 and the inner wall 14 of the roll body 2. This gap 19 substantially determines the thickness of the film 13.

The guide device 17 has a plate 20 which is arranged at a predetermined distance from the roll neck 5. At the roll neck 5 is a mounting ring 21 at. Between the plate 20 and the mounting ring 21 extending in the radial direction a plurality of webs 22. As out Fig. 3 This results in a total of eight webs, which are circumferentially spaced by 45 ° from each other.

The webs are formed rectangular in principle. However, they have a bevelled corner 23. The chamfered corners 23 together form a discharge space 24. This outflow space 24 extends in the radial direction about as far as the diameter of the outflow 10th

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

The radially outer ends of the webs 22 are also connected to a respective tube 26. The tube 26 has a diameter which is greater than the thickness of the webs. In the circumferential direction of the roller 1, the tubes 26 are thus on the left and right over the webs 22 via. The tubes 26 connect the plate 20 with the mounting ring 21. You can be welded to both the plate 20 and with the mounting ring 21. Also, the webs 22 may be welded to the tubes 26.

The tubes 26 also serve to receive fastening bolts 27, with which the guide device 17 is screwed to the roll neck 5. This ensures that the webs 22 are held very reliable at its radially outer end. So you can record relatively high loads.

How out Fig. 3 can be seen, the webs 22 are guided as radial rays run.

The webs 22 fill the space between the roll neck 5 and the mounting ring 21 and the plate 20 in the axial direction completely, ie they act upon a liquid that moves into the space between the plate 20 and the fixing ring 21 completely. Vortexes are avoided.

A centering device 28 has the shape of a trapezoid in cross-section, i. the centering device 28 is a plate with bevelled sides 29, which is inserted into the outflow channel 10. When the guide device 17 is applied to the roll neck 5, this is done automatically centering.

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

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

The heat transfer fluid from the film 13 is fed through the gap 19 between the guide device 17 and the inner wall 14 of the roller body 2 in a gap 30 which is formed between two circumferentially adjacent webs 22. If the liquid is then pressed radially further inward, it is decelerated by the webs 22, i. their speed in the direction of rotation decreases, so that it is so small on reaching the outflow space 24 that the liquid can flow out without any significant pressure losses through the discharge channel 10. In this way one avoids the emergence of a spin-free fluid vortex (potential vortex).

Since a corresponding guide device 18 is arranged on the inlet side, the feeding takes place the heat transfer fluid through the guide device 18 directly to the roll shell 2, ie the inner wall 14, whereby a better temperature control of the roll body 2 is achieved. By the guide means 17, 18 is formed in the interior 6, a larger Totwassergebiet so that substantially the freshly flowing heat transfer fluid flows around the inner wall 14. The flow rate of the heat transfer fluid is higher on the inner wall 14, whereby the Nußelt number and thus the heat transfer is greater.

For the tempering of an elastic center roll on modern calenders, a completely sufficient heat removal or supply can be achieved at low flow velocities and flooded roll.

One can now take further measures to improve the heat transfer. For example, you can first raise the empty roller 1 to operating speed and only then feed heat transfer fluid. Thereby, the above-described film 13 is formed on the inner wall 14. The roller 1 is not completely flooded. The roller behaves as if a displacer was installed. The liquid film 13 flows helically from the inlet to the outlet.

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

In addition, it is possible to feed compressed air or another compressed gas into the interior 6 via the compressed air connection 15. The compressed air can then displace the heat transfer fluid. This also works, when the roller has been completely filled previously. But even if the roller is filled only at operating speed, the compressed air can have a supporting effect.

One can also, as shown in dashed lines, arrange a displacer 31 in the interior 6. The displacer 31 only needs to be roughly fixed in the axial direction. In the radial direction attachment is not required, i. the displacer 31 does not have to be centered. The only requirement is that its specific gravity is less than the specific gravity of the heat transfer fluid. This can be achieved, for example, in that the displacement body 31 is formed as a cylindrical body made of a sponge or polystyrene. The outer diameter of the displacement body 31 must be smaller than the inner diameter of the roller body. As a result, the convection of the freshly flowing heat transfer fluid is avoided with most of the liquid contained in the interior of the roller 1, so that the displacer effect is effective.

It is also possible with the aid of the guide device 17, 18 to ensure that the roller can be completely filled with a liquid heat transfer medium without causing imbalance.

Without guide device 17, the residual volume of air above the liquid level would not be able to escape after reaching a liquid level which is above the height of the outlet. If the roller then rotates, it comes through the dynamics of the liquid filling to unwanted imbalances.

By the guide means 17, however, the residual air after a few revolutions of the roller is removed, so that the roller is completely filled with liquid and then shows no imbalance. Thus, an always reproducible stable filling state is established.

Claims (17)

1. Temperature-controlled roll (1) having a roll body (2) and in each case one roll journal (4, 5) at each axial end of the roll body (2), a flow path for a heat exchange medium being provided through the roll (1), which flow path runs radially from the inside to the outside in a first section, axially through the roll body radially below its circumferential face in a second section and radially from the outside to the inside in a third section, and a guide device (17) being arranged in the region of the third section, which guide device (17) adapts the local speed of the heat exchange medium in the circumferential direction at each radial spacing from the roll axis to the local speed of the roll in the circumferential direction and has a plurality of webs (22) which extend radially from the inside to the outside, characterized in that the guide device has a plate (20) at a predefined spacing from the roll journal (5), the webs (22) being arranged between the roll journal (5) and the plate (20), and in that the webs (22) are fastened at their radially outer end in each case to a holding device (26) and at their radially inner end in each case to a holding device (25) which extends between the roll journal (5) and the plate (20).
2. Roll according to Claim 1, characterized in that the roll body (2) is configured as a tube and the guide device (17) ends at a predefined spacing radially in front of the inner wall (14) of the tube.
3. Roll according to Claim 2, characterized in that the webs (22) fill an intermediate space between the plate (20) and the roll journal (5) in the axial direction.
4. Roll according to one of Claims 1 to 3, characterized in that the webs (22) extend on radial half lines with respect to the roll axis.
5. Roll according to one of Claims 1 to 4, characterized in that the holding device (26) is configured as a tube.
6. Roll according to Claim 5, characterized in that a fastening bolt (27) which connects the plate (20) to the roll journal (5) is guided through at least one tube.
7. Roll according to one of Claims 1 to 6, characterized in that a fastening ring (21) is arranged between the roll journal (5) and the webs (22) on that side of the webs (22) which faces the roll journal (5).
8. Roll according to one of Claims 1 to 7, characterized in that the webs (22) leave an outflow space (24) open at their radially inner end.
9. Roll according to Claim 8, characterized in that the webs (22) are fastened to a tube (25) at their radially inner end.
10. Roll according to Claim 8 or 9, characterized in that the webs (22) have a bevelled corner (23) at their radially inner end.
11. Roll according to one of Claims 1 to 10, characterized in that the webs (22) are connected to a centring device (28) which extends into a channel (10) which runs axially in the roll journal (5).
12. Roll according to one of Claims 1 to 11, characterized in that a guide device (17, 18) is arranged at both axial ends.
13. Roll according to one of Claims 1 to 12, characterized in that a compressed-gas connection (15) opens into the inner space (6) of the roll body (2).
14. Roll according to one of Claims 1 to 13, characterized in that a displacer body (31), the specific weight of which is not greater than the specific weight of the heat exchange medium, is arranged in the inner space (6) of the roll body (2).
15. Method for operating a temperature-controlled roll (1) according to one of Claims 1 to 14, in which method a heat exchange medium is routed through the roll (1) radially below its circumferential face and is guided out through a roll journal (4, 5), the local speed of the heat exchange medium in the circumferential direction at each radial spacing from the roll axis being adapted to the local speed of the roll in the circumferential direction, characterized in that, in addition to the heat exchange medium, a gas is fed into the hollow inner space of the roll at a predefined pressure.
16. Method according to Claim 15, characterized in that the roll (1) is first of all accelerated to a predefined rotational speed and the heat exchange medium is then fed in.
17. Method according to Claim 15 or 16, characterized in that the roll (1) is filled completely with a liquid heat exchange medium.

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