EP1130160B1 - Calender - Google Patents

Description

The invention relates to a calender with a stand, an upper roll, a lower roll and in between at least two middle rolls, which are supported on the stand by cylinders.

Such a calender is known from DE 37 02 245 A1. US 4,736,678 and US 5,806,415 also show such calenders.

The invention is described below using the example of a calender in which the center rolls are mounted on the stand by levers. In principle, however, the invention can also be used if the rollers are mounted in linear guides.

The cylinders, which can also be called compensation cylinders, are supported directly or indirectly on the stand or frame of the calender. They have different tasks. They compensate during operation, in which a material web is satinized overhanging loads on the rolls, for example guide rolls or scrapers, or part of the roll load itself. In the case of the calender according to US Pat. No. 5,806,415, even the complete roll weight is absorbed by these cylinders. The advantages that result from this driving style are, on the one hand, more even line loads across the width and, on the other hand, possible higher line loads in the upper nips with the same line load in the bottom nip.

The second task of these cylinders is to enable the rolls to be separated quickly, i.e. opening the nips as suddenly as possible. Such opening is necessary in certain error situations in order to avoid damage to the rollers, for example in the event of a web break.

The quick disconnect itself is known. For this purpose, the lower roller is lowered and the cylinders of the middle rollers are relieved. In order to prevent the rollers from hitting hard, end position damping is provided, i.e. at the end of the piston movement of the cylinders, the outflow cross section for the hydraulic fluid is reduced, so that the roller is braked somewhat more gently at the end of its movement.

The invention has for its object to improve the quick separation of the calender.

This object is achieved in a calender of the type mentioned at the outset in that the cylinder has an outflow path which is controlled by more than Kolben of the piston stroke required to lower the center roll.

This means that the control options are no longer limited to braking the roller at the end of its movement, which ultimately has the effect of preventing the roller from abruptly touching down and the associated vibration. Rather, you are able to control the roller over most of its movement. It is now possible to increase the speed at which the rollers are lowered and the nips are opened. At the beginning of the movement in particular, relatively high movement speeds can then be permitted. In addition, it is now possible to coordinate the movements of adjacent rollers with one another, so that a collision of adjacent rollers can practically be ruled out during the opening movement.

The outflow path is preferably controlled by a movement of the piston relative to the cylinder housing. Control results from the movement of the roller itself. External intervention is not necessary, so that additional control means can be dispensed with.

The resistance of the outflow path preferably increases the further the piston is inserted into the cylinder housing. This applies to the usual procedure in which the nips are closed when the piston is extended. In cases where the nips are closed with a cylinder operated in reverse, the resistance of the outflow path decreases accordingly. With this configuration, the speed of movement of the center rollers can be controlled so that they initiate the opening movement relatively quickly, but then become increasingly slower. The entire opening movement may therefore take the same length as in the known ones Cases. However, the enlargement of the nip opening at the start of the movement is faster.

When the nips are closed, the cylinders of different center rolls preferably have different outflow path resistances, the resistances increasing from bottom to top. This takes into account the fact that the top middle roll has to travel a shorter total distance than the bottom middle roll. Basically, the top middle roller only has to cover the path that corresponds to the desired nip opening. The next center roll must already travel twice as long, namely the path to open the nip between the top and the next center roll by the predetermined amount plus the opening width of the top nip. In order to avoid a collision of the "falling" rollers, the resistance in the outflow paths is therefore chosen so that the top roller falls the slowest and the initial speeds of the rollers when opening are increased from top to bottom. This can be achieved relatively simply in that different resistances are present in the outflow paths before the start of the roller movement. The roller with the least resistance in the outflow path is the quickest to displace the hydraulic fluid from the cylinder and accordingly to travel a greater distance in the same time.

The cylinders are preferably of identical design to one another, but have closed pistons with different extensions when the nips are closed. If the resistance in the outflow paths is dependent on the position of the piston, this results in a relatively simple possibility, in spite of the same cylinders being different Provide flow resistances for different roller positions. If the piston is retracted further, the outflow path already has a greater resistance. Such a retracted piston will be found on a roller located higher up. The bottom center roll has the most extended piston and therefore the lowest flow resistance in the outflow path.

A tube is advantageously arranged in the cylinder housing, which has openings in its wall and projects into a bore in the piston. This tube then forms the variable resistances in the outflow path of the cylinder. The more openings are exposed in the wall of the pipe, the lower the resistance in the outflow path. When the piston is retracted, it gradually covers more and more openings in the wall of the tube and thus automatically increases the resistance in the outflow path.

The tube preferably projects into the piston over the entire piston stroke. This enables speed control over the entire piston stroke. The tube is guided in the piston over the entire piston stroke and is thus fixed so that the possibility of errors is kept to a minimum.

A seal is preferably arranged between the piston and the tube. This creates clearly defined flow conditions. It prevents hydraulic fluid from penetrating through the gap between the piston and the tube and resulting in uncontrolled flow conditions.

The tube is preferably open at the end. This only plays a subordinate role for the lowering movement, i.e. for opening the nips. However, the opening can be advantageous when closing the nips. This is because the hydraulic fluid inside the piston can have a supportive effect, so that the piston can be extended more quickly.

The tube is advantageously arranged centrally in the cylinder housing and centrally to the piston. As a result, asymmetrical loads are avoided.

In one embodiment it is preferred that the openings are evenly distributed over the length of the tube. This can be achieved, for example, in that the openings are all of the same size and are arranged at equal intervals in the longitudinal direction. Of course, it is also possible to distribute several openings at the same "altitude" around the circumference of the pipe. If the piston is now moved into the cylinder housing, it covers a quasi linearly increasing opening area and thus reduces the outflow cross-section. Due to the discrete distribution of the openings, this will of course be done discontinuously, but this is of minor importance. Such a linear behavior can also be generated by distributing openings of different sizes with different distances over the length of the tube. With such a linear behavior, a quasi-linear decrease in speed is achieved.

In an alternative preferred embodiment it is provided that the openings are distributed according to a predetermined non-linear function over the length of the tube, in which the outflow cross section decreases disproportionately at the end of the lifting movement. The outflow cross-section is therefore still the smallest at the end of the lifting movement. However, the increase in the cross section when the piston is extended or vice versa, the decrease in the cross section when the piston is retracted is not linear, but according to another function, preferably a quadratic function. This makes it possible to provide a much larger outflow cross-section at the beginning of the piston movement, which permits faster piston movement, while the piston is braked more strongly towards the end of the movement.

The outflow path is preferably connected to a control device which prevents a drop in the pressure in the cylinder housing. When all nips are closed, the middle rollers are at least partially supported by the rollers underneath. The cylinders take on part of the load, which is reflected in a corresponding pressure in the cylinder. If the support from the lower rollers is no longer available, the pressure in the cylinder increases accordingly. The control device now ensures that hydraulic fluid can escape from the cylinders. At the same time, however, it ensures that the pressure in the cylinder does not drop, so that the roller is still held by a certain force. The lowering movement can thus be controlled well, so that a collision of rollers can be avoided.

In a preferred embodiment it is even provided that the control device slightly increases the pressure in the cylinder when the piston is retracted. This improves the "braking behavior" at the end of the movement. The pressure is only released when the roller has reached its "end position" at which the corresponding nips are fully open. In this case, the roller or the lever can, for example, rest on an end stop.

Fig. 1

eine schematische Darstellung eines Kalanders,

Fig. 2

einen Zylinder mit ausgefahrenem Kolben,

Fig. 3

einen Zylinder mit eingefahrenem Kolben,

Fig. 4

zwei Kurven zur Abhängigkeit der Geschwindigkeit vom Weg,

Fig. 5

eine Kurve zur Darstellung der Abhängigkeit der Geschwindigkeit von der Zeit und

Fig. 6

eine Kurve zur Darstellung des Druckverlaufs über der Zeit.

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

Fig. 1

a schematic representation of a calender,

Fig. 2

a cylinder with the piston extended,

Fig. 3

a cylinder with the piston retracted,

Fig. 4

two curves on the dependence of the speed on the path,

Fig. 5

a curve to show the dependence of speed on time and

Fig. 6

a curve to show the pressure curve over time.

1 shows a calender 1 with a stand 2, on which an upper roller 3 with a jacket stroke 4 and a lower roller 5 are arranged on an adjusting cylinder 6. Between the upper roller 3 and the lower roller 5 there are several middle rollers 7-10, which are mounted on levers 11-14 are. The levers can be pivoted about support points 15-18 on stand 2.

In the working position shown, the positioning cylinder 6 has raised the lower roller 5, which then also raises the rollers 10, 9, 8, 7 above it, so that nips 19-23 in which a material web 24, for example a paper web, is satinized, are closed become. The material web 24 is guided over auxiliary and guiding devices, for example deflection rollers 25, which are shown only for the levers 11 and 12 for reasons of clarity. Furthermore, scraper blades or other additional devices can be arranged on the levers 11-14.

In order to compensate for the weights of these so-called overhanging loads, each lever 11-14 is supported on the stand 2 via a compensation cylinder 26-29. The compensation cylinders 26-29 are hereinafter referred to as "cylinders". The cylinders 26-29 are all identical in construction. The only difference lies in the attachment to the stand, more precisely in the distance of an attachment point 30-33 from the lever 11-14 in the operating position shown. Accordingly, the piston rods 34-37 of the cylinders 26-29 are extended to different extents.

The reason for this measure is as follows: in the event of a malfunction or for the introduction of a new material web 24, it is necessary to move the rollers 3, 5, 7-10 apart in order to open the nips 19-23. Here, the top middle roller 7 has to be lowered so far that the nip 19 has a predetermined height, for example 100 mm. The next lower center roll must then be lowered twice as much, so that too the nip 20 can maintain this opening height. The same applies to the other nips 21-23. On the one hand, the opening movement must be possible as quickly as possible, it being sufficient if the first millimeter of the nip height is reached relatively quickly. On the other hand, one must avoid a collision of the rollers 5, 7-10 during the opening movement. Finally, one also wants to prevent the roller movement from ending abruptly. If the levers 11-14 were suddenly placed on an end stop of any kind, the rollers 7-10 could vibrate and be destroyed by adjacent components, for example doctor blades or finger protection angles.

In order to implement such a controlled movement, the cylinders 26-29 have a special structure, which will be explained with reference to FIGS. The cylinder 29 is shown, the explanations correspondingly applying to the cylinders 26-28 because they are identical in construction. 2 shows the cylinder 29 with the piston rod 37 extended, while FIG. 3 shows the cylinder 29 with the piston rod 37 retracted.

The piston rod 37 is arranged on a piston 38 which is movable in a cylinder housing 39. The piston 38 passes through a cover plate 40 of the cylinder housing 39 and is guided relative to the peripheral wall of the cylinder housing with an end plate 41 which is fastened to the piston 38 with the aid of bolts 42. The piston 38 has a central bore 43 which extends over almost the entire length of the piston 38 and is in any case at least as long as the stroke H of the piston 38.

A tube 44 protrudes into the bore 43 and is fastened to the cylinder housing 39, more precisely to a base plate 45. The tube 44 has an end opening 46 which opens into the bore 43. The tube 44 is surrounded by a seal 47 which is arranged at the front end of the piston 38 in the bore 43 in such a way that it lies sealingly against the tube 44. The end plate 41 surrounds the tube 44 at a predetermined distance, so that an annular space 48 is formed between the end plate 41 and the tube 44.

The tube 44 has a plurality of openings 49 in its wall, which extend from a channel 50 formed in the interior of the tube to the pressure chamber 51 when the piston 38 is extended. The channel 50 is connected to a drain connection 52. The pressure chamber 51 has a further connection 53. Through this connection 53, the pressure of the hydraulic fluid in the pressure chamber 51 can be determined, for example. However, it is also possible to supply hydraulic fluid here for faster closing of the nips 19-23. Furthermore, the cylinder housing 39 also has a leakage oil connection 54, through which hydraulic fluid which has passed a sealing arrangement 55 of the end plate 41 can be removed.

In the position shown in Fig. 2, the piston 38 is most extended. Accordingly, most of the openings 49 are free, ie the channel 50 and thus the drain connection 52 are connected to the pressure chamber 51 via the openings 49. If the adjusting cylinder 6 is now relieved and the lower roller 5 is lowered, then the central rollers 7-10 are no longer supported by the lower roller 5, so that the entire weight of the central roller 7-10 is supported by the corresponding cylinder 26-29 must be caught. The pressure in the pressure chamber 51 rises accordingly. A control device (not shown in any more detail) now enables hydraulic fluid to flow through the drain connection 52. The control device ensures that the pressure in the pressure chamber 51 does not drop, but possibly even increases to a small extent.

If the hydraulic fluid can flow out of the pressure chamber 51, then the piston 38 is moved into the cylinder housing 39 due to the weight forces. The hydraulic fluid is displaced into the channel 50 through the openings 49. With increasing entry movement but more and more openings 49 are closed, so that the flow resistance for the outflowing hydraulic fluid increases. This increase in outflow resistance occurs practically from the beginning of the movement of the piston 38. In the end position shown in FIG. 3, in which the face plate 41 bears against the base plate 45, only one opening 49 is free for the outflow of the hydraulic fluid from the pressure chamber 51.

With this distribution of the openings 49 over the axial length of the tube, a speed profile for the piston movement can now be achieved, which is shown schematically in FIG. 4. 4 presents two different alternatives. The course is marked with circles, which results when the openings 49 are evenly distributed in the axial direction over the length of the tube 44. In this case the piston reaches its maximum speed relatively quickly. This speed then drops linearly to about 100 mm until the end position is reached. In an alternative embodiment (marked with X) the openings 49 are distributed according to a quadratic function over the length of the tube 44, ie in the most extended position of the piston 38 a disproportionately large outflow area is released through the openings 49, which becomes very strong at the end of the stroke (FIG. 3) reduced. In this case, a higher speed is reached over a longer drive-in path.

Fig. 5 shows the speed distribution over time. After about half a second, the maximum falling speed of the levers 11-14 is reached. This then decreases almost linearly. The small increments result from the fact that the openings 49 do not provide a continuously reducing outflow surface, but rather a gradual reduction.

6 shows the pressure conditions in the pressure chamber 51. The pressure rises slightly. The serrations in the curve are due to the fact that a short pressure surge occurs when an opening 49 is covered by the seal 47.

As can be seen from FIG. 1, the piston rods 34-37 of the individual center rollers 7-10 are extended to different extents, ie the piston rod 37 and the piston 38 connected to it are extended further in the cylinder 29 than in the cylinder 26. Accordingly, at the beginning an opening movement in the cylinder 29, significantly more openings 49 are available for the outflow of the hydraulic fluid than in the cylinder 26. This has the consequence that the lever 14 can move much faster than the lever 11. Thus, the central roller 7 moves during an opening movement slower than the center roll 10. The opening speed is sufficient, however, to achieve the desired nip opening of the nip 19.

All middle rollers 7-10 move at the respective maximum speed, this speed being greater at the beginning of the opening movement than at the end. The speed distribution is graded from bottom to top so that the lower roller moves faster than the one above it. This prevents a collision between adjacent rollers when opening the nips 19-23.

Claims (15)

1. Calender comprising a stand, a top roll, a bottom roll and at least two intermediate rolls in between, which are supported on the stand by cylinders, characterized in that the cylinder (26-29) has a discharge path which is controlled over more than ¾ of the piston displacement needed to lower the intermediate roll.
2. Calender according to Claim 1, characterized in that the discharge path is controlled by a movement of the piston (38) relative to the cylinder housing (39).
3. Calender according to Claim 1 or 2, characterized in that the resistance of the discharge path increases the further the piston (38) is retracted into the cylinder housing (39).
4. Calender according to one of Claims 1 to 3, characterized in that the cylinders (26-29) of different intermediate rolls (7-10) have different resistances of the discharge path when the nips (19-23) are closed, the resistances increasing from bottom to top.
5. Calender according to Claim 4, characterized in that the cylinders (26-29) are designed identically to one another but, when the nips (19-23) are closed, have pistons (38) extended by different amounts.
6. Calender according to one of Claims 1 to 5, characterized in that in the cylinder housing (39) there is arranged a pipe (44) which has openings (49) in its wall and projects into a bore (43) in the piston (38).
7. Calender according to Claim 6, characterized in that the pipe (44) projects into the piston (38) over the entire piston displacement (H).
8. Calender according to Claim 6 or 7, characterized in that a seal (47) is arranged between piston (38) and pipe (44).
9. Calender according to one of Claims 6 to 8, characterized in that the pipe (44) is open at the end.
10. Calender according to one of Claims 6 to 9, characterized in that the pipe (44) is arranged centrally in the cylinder housing (39) and centrally with respect to the piston (38).
11. Calender according to one of Claims 6 to 10, characterized in that the openings (49) are distributed uniformly over the length of the pipe (44).
12. Calender according to one of Claims 6 to 10, characterized in that the openings (49) are distributed over the length of the pipe (44) in accordance with a predetermined non-linear function, in which the discharge cross section decreases disproportionately towards the end of the displacement movement.
13. Calender according to Claim 12, characterized in that the function is a quadratic function.
14. Calender according to one of Claims 1 to 13, characterized in that the discharge path is connected to a control device which prevents a decrease in the pressure in the cylinder housing (39).
15. Calender according to Claim 14, characterized in that the control device raises the pressure in the cylinder (39) slightly as the piston (38) retracts.