DE9203395U1 - Pressing device - Google Patents

Description

Attorney file: P 4900

J.M. Voith GmbH

Keyword: "Floating Shoe Bed"

Pressing device

The invention relates to a pressing device with a shoe-pressing unit which, together with a counter roll, forms a press nip and which serves to treat a running web of material, preferably for smoothing or dewatering a paper web, e.g. in a papermaking machine.

The invention is based on a pressing device with the features specified in the preamble of claim 1. Regarding the state of the art, reference is made to US 44 04 724; in it, Figures 1 to 10 show a shoe pressing unit whose roller shell is designed as a metal roller tube; the figure, on the other hand, shows a pressing device with two shoe pressing units whose circumferential shells are designed as band-shaped, flexible pressing shells. Figures 7 and 8 reveal a shoe that extends parallel to the main axis of the shoe pressing unit and serves to transfer the pressing force from the yoke to the roller shell. For this purpose, a pressure chamber is formed between the shoe and a complementary bar supported on the yoke. The complementary bar extends into the interior of the shoe like a piston.

DE 41 13 623 (file: P 4824) discloses a pressing device in which a shoe pressing unit and a counter roll together form an extended press nip. The shoe pressing unit has an endless, flexible press jacket, which can be tubular (i.e. with closed ends) or band-shaped (with open ends). Again, a pressure chamber is provided between a shoe, which extends transversely to the direction of web travel, and a complementary bar supported on the yoke.

In this case, the complementary bar is designed in the manner of a pressure cylinder as a so-called shoe bed into which the shoe protrudes like a piston.

DE-GM 91 14 699 (file: P 4865) discloses a shoe press unit, the shoe of which is attached to a piston (e.g. "hat piston"), which together with the yoke defines the pressure chamber.

These known pressing devices have in common that the deflection of the yoke resulting from the pressing force and/or gravity occurs essentially parallel to the pressing plane, which is always arranged vertically. The complementary bar also follows this deflection, because it is rigidly attached to the yoke. In contrast, the shoe always adapts its lengthwise extension - under the pressure prevailing in the pressure chamber - to the current shape of the shell and/or the counter roller. Pressing devices of this type have proven themselves in practice for many years. Problems arise, however, when different deflections occur transversely to the pressing plane, on the one hand of the yoke and on the other hand of the shell and/or the counter roller. There can be various reasons for this:

1. The direction of the pressing plane can deviate from the vertical direction, for example it can be horizontal. In this case, the bending lines resulting from gravity on the one hand of the yoke (plus the complementary strip attached to it) and on the other hand of the shell and/or the counter roller are different. This difference in deflection, which is effective transversely to the pressing plane, results in a fitting error occurring either between the outer surface of the shoe and the inner surface of the metal roller tube -

or between the outer surface of the shoe and the outer surface of the counter roll if the pressing device has a flexible press cover.

This results in the risk of increased frictional forces and premature wear. There is also the risk that the pressing force becomes uneven over the length of the pressing device (and thus over the width of the web) and/or that the pressure chamber becomes leaky (e.g. due to failure of the seal located at the "border" between the shoe and the complementary strip).

2. The yoke can suffer thermally induced bending in which the metal roller tube or (if a flexible press sleeve is present) the counter roller does not participate. The consequences are the same as described above under 1.

3. A pressing device can have several, for example two, press gaps, which are formed by more than two rollers or shoe press units. It can be desirable, for example, that two press planes are not in the same plane, i.e. that they form an angle other than 180° with each other, and that a middle shoe press unit has a shoe for each press zone, i.e. two shoes in total. In this case, the press force acting in one press zone causes the yoke (plus the two complementary strips) to bend transversely to the press plane of the other press zone. This results in the same problems as described above under 1.

4. In contrast to the case described under 3, the middle shoe press unit in a double press can have a metal roller tube and only a single shoe that transmits the pressing force in one pressing zone. In this case, the pressing force exerted in the other pressing zone can bend the metal roller tube transversely to the shoe press plane. Consequently, different deflections of the yoke and roller tube occur in this transverse direction, which in turn results in the same disadvantages that have already been described above.

The invention is based on the object of further developing a pressing device of the generic type in such a way that under all operating conditions occurring, a fitting error between the shoe on the one hand and the metallic roller tube and/or the counter roller is avoided.

This task is solved by the features specified in claim 1. For the preferred design (according to claim 2) with a complementary bar, the essential idea of the invention can be described as follows: The complementary bar that guides the shoe in the radial direction is no longer rigid as before, but is now connected to the yoke in an articulated manner. The complementary bar is still supported on the yoke under the effect of the pressing force; however, it no longer follows a bending of the yoke that takes place transversely to the pressing plane; instead, together with the shoe - transversely to the pressing plane - it always follows the current shape of either the metal roller tube of the shoe pressing unit or (if the shoe pressing unit has a flexible pressing jacket) the counter roller. If, for example, the bending line of the metal roller tube or, if applicable, the counter roller is in the pressing plane, then the bending line of the complementary strip (and, of course, the bending line of the shoe) also remains in the

Press plane, regardless of whether the yoke bends across the press plane or not. However, if the metal roller tube or the counter roller itself bends across the press plane for some reason, in which the yoke does not participate or does not participate to the same extent, the shoe and complementary bar follow this bend. In all cases, increased friction and wear on the parts sliding against one another are avoided. In addition, the distribution of the pressing force across the width of the web is more even than before, and the risk of the pressure chamber becoming leaky is eliminated.

Claims 3 to 8 specify advantageous structural embodiments of the invention which can be used individually or in combination with one another to implement the basic inventive concept specified in claim 1.

In the simplest case, the pressing device according to the invention can, according to claim 9, have only a single pressing gap and a pressing plane inclined against the vertical direction (e.g. running horizontally). In this case, the invention mainly eliminates those disadvantages which result from gravity-related deflection differences between the yoke and the roller tube or counter roller.

However, the invention is mainly applicable in a multiple press, e.g. double press (claims 10 to 13).

For the design in which the pressure chamber is arranged between the yoke and the piston (e.g. "hat piston"), the solution features specified in claims 1 and 14 or 15 apply.

Embodiments of the invention are explained below with reference to the drawing.

Figure 1 is a schematic cross-section through a pressing device.

Figure 2 is a partial longitudinal section along line II of Fig. 1.

Figures 3 to 6 are schematic cross-sections through different pressing devices, all of which differ from Figure 1.

Figure 7 shows a detail from Fig. 5 on an enlarged scale, also as a cross-section.

The pressing device shown in Figures 1 and 2 comprises a shoe pressing unit, designated overall by 10, and two counter rollers 21 and 22. The pressing device is used to treat a running web of material 9. The shoe pressing unit 10 has a metal roller tube 11 as a roller shell. This forms a first press gap with one counter roller 21, which lies in the first press plane E x, and also a second press gap with the other counter roller 22, which lies in the second press plane E2. A stationary yoke 12 extends through the metal roller tube 11. In the area of each press gap, this carries a complementary strip 13 designed as a shoe bed. In each shoe bed there is a press shoe 14 with a convex sliding surface; it is used to transfer a pressing force from the yoke 12 to the metal roller tube 10. Each shoe bed 13 and each shoe 14 extend largely over the entire length of the roller tube, i.e. transversely to the direction of web travel. In order to press the press shoe 14 against the inside of the roller tube 11, a pressure chamber 15 is formed between the shoe bed and the shoe in the usual way, which is sealed off from the rest of the roller interior by means of sealing strips 16. The shoe press unit 10 is therefore a type of deflection compensation roller; i.e. the roller tube 11 remains largely deflection-free during operation; but the yoke 12 bends, as described below.

The individual shoe bed 13 is connected to the yoke 12 in an articulated manner transversely to the pressing plane E x or E2. For this purpose, a pivot bearing 17 is provided in the area of the ends of the shoe bed, but at a certain distance a from each shoe bed end. This preferably has the shape of a pin, the longitudinal axis of which lies essentially in the relevant pressing plane Ei or E2. The distance a of the individual pivot bearing from the shoe bed end is approximately a quarter to a third of the total length b of the shoe bed 13. In its longitudinal direction, the individual shoe bed 13 is fixed by only one of the two pivot bearings 17; because the pin of the other pivot bearing engages in a longitudinal groove 18 in the shoe bed 13.

In Fig. 1 it is also schematically indicated that between the individual shoe bed 13 and the yoke 12 there is a hydrostatic relief pocket 19, which is sealed against the rest of the roller interior by means of sealing strips 20.

From Fig. 2 it can also be seen that the roller tube 11 is rotatably mounted on the yoke 12 at both ends (only one of which is visible) with the aid of a bearing ring 11a and with the aid of a self-adjusting roller bearing 11b. The stationary yoke 12 rests in support brackets (not shown). Other known designs can also be used, for example the roller tube bearings can be arranged directly in the support brackets mentioned, whereby the distance between the two roller tube bearings is preferably made the same as the distance between the support points of the yoke.

The effect of the construction shown can be seen from Fig. 2. Under the effect of the pressing force which the roller tube exerts on the first counter roller 21 in the first pressing plane E ₁ (and which is generated by the pressure in the relevant pressure chamber 15), the yoke 12 bends transversely to the other pressing plane E 2, as is shown exaggeratedly in Fig. 2.

Thanks to the articulated connection (by means of the pins 17) between the yoke 12 and the (in Fig. 1) upper shoe bed 13,
the latter is at least approximately straight; ie it does not participate in the deflection of the yoke 12. This prevents the formation of a gap between the inner surface of the roller tube 11 and the
curved outer surface of the pressing plane E 2
Press shoe 14 a fitting error occurs. In other words: The
resulting from such a passport error
Frictional forces and signs of wear are avoided.
The same effect is also observed in the pressing plane E^
lying press shoe 14; because the in the pressing plane E2
acting pressing force causes an additional deflection of the yoke 12 transverse to the pressing plane E^.

The following differences exist between the arrangement according to Fig. 3 and that according to Fig. 1: In Fig. 3 it is assumed that
the pressing force exerted in the first pressing plane E^ is
considerably smaller than the pressing force exerted in the second pressing plane E2. Therefore, the shoe pressing unit 10 only has
second press level E2 a press shoe 14A. This could be exactly
be designed identically to the press shoe 14 of Fig. 1.
However, Fig. 3 shows a hat-shaped shoe 14A in cross section and a complementary strip 13A, which is
of a piston into the interior of the shoe 14A. The yoke 12, according to Fig. 3, suffers essentially only in the vertical
direction (namely in the second pressing plane E2) a
Deflection. Under the force acting in the first pressing plane E^
However, due to the pressing force, the roller tube 11 can suffer a deflection transverse to the second pressing plane E2. The yoke 12 does not participate in this deflection. Thanks to the articulated connection between the yoke 12 and the complementary bar 13A, this and
in particular the shoe 14A to the deformation state of the
Adjust the roller tube 11.

Fig. 4 shows a long-nip press whose pressing plane E is arranged approximately horizontally. The shoe press unit 1OB comprises a flexible roller shell HB, a press shoe 14B with a concave sliding surface, and a stationary yoke 12B with side parts 12a and 12b, between which a piston 24 is located. The yoke, the side parts, the piston and sealing strips 25 arranged between them delimit a pressure chamber 15B. The connection between the press shoe 14B and the piston 24 is designed to be articulated, as is the connection (according to Figures 1 and 2) between the shoe bed 13 and the yoke 12.

The counter roll 2IB is designed as a shoeless deflection compensation roll with a rotating roll shell 26 and a stationary yoke 27, between which the usual longitudinal seals 28 are provided, which delimit a pressure chamber 29. During operation, the roll shell 26 remains largely deflection-free in the press plane E, while the yoke 27 deflects in the press plane E. This corresponds to the conventional technology. In addition, the following is now achieved: The arrangement makes it possible for the counter roll 21B (in particular its roll shell 26) and the yoke 12B with the piston 24 (hat-shaped in cross section) to suffer different deflections transversely to the press plane E under gravity. In this case, the press shoe 14A adapts to the respective shape of the roll shell 26 independently of the piston 24.

The embodiment according to Fig. 5 differs from Fig. 4 essentially only in that the press shoe 14C interacts in a known manner in the manner of a piston with a complementary strip designed as a shoe bed 13C. Between these two components there is again a pressure chamber 15C. Between the shoe bed 13C and the stationary yoke 12C of the shoe press unit IOC there is again a hydrostatic relief pocket 19C. Due to the

A dewatering felt 8 runs through the extended press nip (between the flexible press cover HC and the counter roll 21C) and together with this a paper web (not shown) to be dewatered.

The pressing device shown in Fig. 6 has - similar to that shown in Fig. 1 - two pressing planes ε and E2, which, however, form an angle between 90° and 180°. The pressing device comprises a central shoe pressing unit IOD, which has a metal roller tube 11, and two counter rollers, both of which are designed as shoe pressing units IOC. Each of these shoe pressing units IOC is constructed in exactly the same way as the shoe pressing unit IOC in Fig. 5. The central shoe pressing unit IOD is constructed essentially in exactly the same way as the shoe pressing unit 10 in Fig. 1. A first press felt 8 guides the paper web to be dewatered through the first press nip. The paper web then runs through the second press nip together with a second press felt 8'. The paper web visible at 9 then runs from the roller tube 11 to a support belt 7 and together with this into a drying section (not shown).

Fig. 7 shows further details of the shoe press unit IOC, which is only roughly sketched in Figs. 5 and 6. The essential details of Fig. 7 are also applicable to the shoe press units 10 or 1OA of Figs. 1 and 3 respectively. In Fig. 7 one can see again the stationary yoke 12C, the shoe bed 13C and the press shoe 14C arranged therein in the manner of a piston. Other elements already mentioned are the pressure chamber 15C (limited by the sealing strips 16) and the hydrostatic relief pocket 19C, limited by the sealing strips 20. The pressure area D of the pressure chamber 15C acting on the press shoe 14C is larger than the effective area F of the relief pocket 19C. In this case, essentially the same

Pressures assumed. Pressure oil passes through the channel 30 first into the relief pocket 19C and from here through an opening 31 into the pressure chamber 15C.

The shoe bed 13C is kept in constant contact with the seals 20 by means of disc springs 32 and flexible screws 33. However, the flexible screws 33 allow the shoe bed 13C to move transversely to the press plane E relative to the yoke 12C, so that the shoe 14C always remains in the correct position relative to the counter roll 21C (or IOD, Fig. 6).

Fig. 7 also shows that the press shoe 14C is coupled to the shoe bed 13C by means of a flexible bolt 35 and a compression spring 36. This coupling allows the shoe to be displaced along the pressing plane E x relative to the shoe bed and also to be tilted. It also prevents the press shoe from escaping from the shoe bed.

Instead of the hydrostatic relief pocket 19C, a magnetic plain bearing could be provided.

Heidenheim, 12.03.92
O615k/DSh/SrÖ/5-15

Claims (15)

Attorney file: P 4900 J.M. Voith GmbH Keyword: "Floating shoe bed11 Claims 1. Pressing device with a shoe press unit (10) which forms a press nip with at least one counter roller (21, 22) for the purpose of treating a running web of material (9), e.g. for the purpose of dewatering a paper web in a papermaking machine, with the following features: a) the main axes of the shoe press unit (10) and the counter roll (22) lie in a pressing plane (E2); b) the shoe press unit (10) has a circumferential casing which can be designed either as a metallic roller tube (11) or is designed as an endless flexible press cover, furthermore a stationary yoke (12) extending through the cover and, in the region of the press nip, at least one shoe (14) which extends transversely to the web running direction and serves to transfer the pressing force from the yoke via the cover to the counter roll; c) at least one pressure chamber (15) that can be filled with pressure medium is provided for pressing the shoe (14) onto the casing (11); d) characterized in that the shoe (14) is movable transversely to the pressing plane (E2) relative to the yoke (12) in such a way that the shoe remains independent of a deflection of the yoke occurring transversely to the pressing plane (E2) (12) relative to the shell (11) or the counter roll. 2. Pressing device according to claim 1, wherein the pressure chamber (15) is located between the shoe (14) and a complementary strip (e.g. shoe bed 13) supported on the yoke, characterized in that the complementary strip (13) is connected to the yoke (12) in an articulated manner such that it remains independent of a deflection of the yoke occurring transversely to the pressing plane (E2). 3. Pressing device according to claim 2, characterized in that a pivot bearing (17) is provided on the complementary bar (13) for connection to the yoke (12) in the region of each end of the complementary bar (13), but at a certain distance (a) therefrom. 4. Pressing device according to claim 3, characterized in that the distance (a) is approximately one quarter to one third of the length (b) of the complementary bar (13). 5. Pressing device according to claim 3 or 4, characterized in that the complementary bar (13) is fixed in the longitudinal direction by only one of the two pivot bearings (17). 6. Pressing device according to one of claims 2 to 5, characterized in that a hydrostatic relief pocket (19) is provided between the complementary bar (13) and the yoke (12) (Fig. 1, 3, 4, 7). 7. Pressing device according to claim 6, characterized in that the pressure surface (D) of the pressure chamber (15C) acting on the shoe (14C) is larger than the effective surface (F) of the relief pocket (19C), wherein a pressure of substantially the same level prevails in the latter as in the pressure chamber (Fig. 7). 8. Pressing device according to one of claims 2 to 5, characterized in that a magnetic sliding bearing is provided between the complementary bar and the yoke. 9. Pressing device according to one of claims 2 to 8, characterized in that only a single pressing zone is present, wherein the pressing plane (E) is inclined against the vertical direction, e.g. runs horizontally (Fig. 4, 5). 10. Pressing device according to one of claims 2 to 8, characterized in that the shoe press unit (10) forms a second press gap in a second press plane (Ei) with an additional counter roller (21), and that the two press planes (εx, E2) form an angle with one another that differs from 180° (Fig. 1, 3, 6). 11. Pressing device according to claim 10, characterized in that the shoe pressing unit (10) has a shoe (14) in each pressing plane (E^ and E2) (Fig. 1, 6). 12. Pressing device according to claim 10, characterized in that the shoe pressing unit (10A) has a shoe (14A) in only one of the two pressing planes (�E x or E ₂ ) (Fig. 3). 13. Pressing device according to one of claims 2 to 12, characterized in that the counter roll or at least one of the counter rolls (10C) is also designed as a shoe press unit with the features specified in claim 1 (Fig. 6). 14. Press device according to claim 1, wherein the shoe (14B) is supported on a piston (24) which forms a pressure chamber (15B) with the yoke (12B), characterized in that the shoe (14B) is articulated with the piston (24) in such a way is connected in such a way that it remains independent of any deflection of the yoke (12B) and the piston (Fig. 4) occurring transversely to the pressing plane (E). 15. Press device according to claim 14, characterized in that a hydrostatic relief pocket (19B) is provided between the shoe (14B) and the piston (24). Heidenheim, 12.03.92
O615k/DSh/Srö/l-4