DE29718986U1 - Device for direct or indirect application of a liquid or pasty application medium to a running material web, in particular made of paper or cardboard - Google Patents

Description

PATENT ATTORNEYS

jtjr« JH.
D.PL..1NG. FA WEICKMANN

DlPL-CHEM B. HUBER

DR-IMC. H. LISKA

DlPLPHYS DR J. PRECHTEL

DIPL-CHEM. DR. B. BÖHM

D1PL.<HEM. DR. W. WEISS

D1PL.-PHYS. DR. J. TIESMEYER

D.PL.-PHYS.DR. M. HERZOG

.JTOSTFACH 860 820

81635 MUNICH

KOPERMKUSSTRASSE 9 81679 MUNICH

TELEPHONE (089) 4 55 63-0 TELEX 5 22 621 FAX (089) 4 70 50 eMail weickmannOcompuserve.com

Our sign:

17291G DE/HGsi Applicant:

Voith Sulzer Paper Technology Patent GmbH
St. Pöltener Street 43

89522 Heidenheim

Device for direct or indirect application

a liquid or pasty application medium onto a moving material web, especially made of paper or cardboard

Device for direct or indirect application

a liquid or pasty application medium on a moving web of material, especially paper or cardboard

Description

The invention relates to a device for the direct or indirect application of a liquid or pasty medium to a fully formed but still wet material web, in particular made of paper or cardboard.

For example, US Pat. No. 4,793,899 discloses a device for indirectly applying an application medium to a still wet material web.

In order to ensure that the application medium penetrates sufficiently into the wet material web, the known device has the following structure: A first press roller forms a first application gap with the application roller, in which the application medium applied by an application unit to the surface of the application roller is pressed into the material web. After the first application gap, the material web continues to run against the application roller until it reaches a second application gap, which is formed by the application roller with a second pressure roller. In the second application gap, the application medium, which has still not been absorbed into the material web despite the long exposure path, is pressed into the material web again. Overall, the material web is guided around about half the circumference of the application roller.

As can be seen from the above, the application device known from US-PS 4,793,899 has a structurally complex design with a high installation space requirement. It is therefore the object of the present invention to provide an application device that works in the wet area of a plant for the production of paper or cardboard, which requires little space and is simple to configure.

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structure that can ensure the penetration of the application medium into the material web.

This object is achieved according to the invention by a device for the direct or indirect application of a liquid or pasty medium to a fully formed but still wet material web, in particular made of paper or cardboard, comprising at least one screen belt carrying the material web, a counter element with a convexly curved surface section around which the material web is guided, the counter element being an application element in the case of indirect application and a support element in the case of direct application, an application unit for the direct application of the liquid or pasty medium directly to the material web or for the indirect application of the liquid or pasty medium to the material web using the application element, and a press shoe with a concavely curved surface section, the concavely curved surface section of the press shoe facing the convexly curved surface section of the counter element and forming a gap with it through which the material web and the at least one screen belt are guided.

Due to the interaction of the convexly curved surface section of the counter element and the concavely curved surface section of the press shoe, the application gap has a length that considerably exceeds the length of a gap formed between two rollers. Due to the correspondingly long exposure time provided by the arrangement according to the invention, the application medium can form a reliable bond with the material web. Multiple pressure applications, as had to be provided for in the prior art in order to compensate for the low absorbency and thus low receptivity of the material web in the wet area of the machine for producing paper or cardboard due to the high moisture content of the material web, are not required when using a press shoe according to the invention.

In order to be able to bring the application medium into contact with the material web as gently as possible, it is proposed that the convexly curved surface section of the counter element and the concavely curved surface section of the press shoe are designed to be coordinated with one another in such a way that the gap tapers in the running direction of the material web over at least part of its length.

The counter element can - as in the prior art - be an application roller or a support roller; however, it is also conceivable in principle that the counter element is formed by another press shoe, i.e. a press shoe with a convexly curved surface section. The first-mentioned design variant has the advantage that when converting an existing machine for producing paper or cardboard, existing parts can be used to a large extent, for example an existing application roller with application unit. The latter design variant has the advantage that the profile of the application gap in the running direction of the material web can be varied not only by the design of the concave surface section of one press shoe, but that the design of the convex surface section of the other press shoe is also available to influence this profile.

In order to reduce the sliding friction between the concave or convex surface section of the press shoe and the material web or the screen belt, it is proposed that a flexible endless belt be provided which runs around the surface section of the press shoe in direct contact with the latter.

The material web can be guided in direct contact with the convexly curved surface section. If the convexly curved surface section is provided on an application element, for example an application roller, the medium applied to the application element can be transferred directly to the material web. In principle, however, it is also possible for the material web to be guided on the convexly curved surface section.

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at least with the intermediate arrangement of a sieve belt in indirect system. If the convex surface section is provided on an application element in this case, the transfer of application medium takes place through the openings of the sieve belt.

Particularly in the case of application to a very sensitive, for example still very wet, material web, it can be provided that the material web is held between two screen belts.

To adjust the pressure with which the application medium is pressed into the material web, it is suggested that the press shoe and the counter element can be adjusted against each other. For example, only the adjustability of the press shoe relative to a machine frame supporting the counter element can be used, or only the corresponding adjustability of the counter element. However, it is also possible to adjust both elements, the press shoe and the counter element, relative to the machine frame. The adjustment relative to the machine frame can be carried out using any known actuator. For example, pneumatic, hydraulic or electric motor drives can be used.

In principle, any type of applicator can be used. However, free-jet nozzle applicators or applicators with a short dwell time of the application medium between application and leveling, so-called "short dwell time" applicators, have proven to be particularly suitable.

For applying a liquid or pasty medium to both sides of a fully formed but still wet material web, a device according to the invention can be used, for example, to apply the liquid or pasty medium to a first side of the material web, and a further application device according to the invention can be arranged downstream of this application device for application to a second side of the material web opposite the first side.

In order to be able to provide the preferred type of application in both cases, i.e. application through the openings of the screen belt or directly from the application device or the surface of the application element onto the material web, it is proposed that between the two application devices the material web is transferred from a screen belt carrying the material web from the second side to a screen belt carrying the material web from the first side.

The invention will be explained in more detail below using exemplary embodiments in the accompanying drawing. It shows:

Fig. 1 shows a first embodiment of a device according to the invention

for applying an application medium to a moving material web;

Fig. 2 to 6 further embodiments of application devices according to the invention; and

Fig. 7 shows a series arrangement of two application devices according to the invention

devices for coating the material web on both sides.

Fig. 1 shows a rough diagram of a device designated 10 for indirectly applying a liquid or pasty medium 12 to a material web 14 moving in the running direction L. The application device 10 according to the invention is arranged in the wet part of a machine for producing paper or cardboard, i.e. in the forming and pressing section of this machine.

As the term "wet part" already suggests, the material web 14 in this area of the paper or cardboard production machine is already fully formed, but still has a very high moisture content. As a result, the fiber structure of the material web has not yet solidified to the point that it has the tear resistance required for the web running speed of modern machines. The material web 14 is therefore carried by a screen belt 16, which is preferably a continuously rotating endless belt. Of course, the screen belt 16 moves at the same running speed as the material

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material web 14, so that there is no relative movement between the material web and the screen belt.

In the area of the application device 10, the material web 14 is guided around an application roller 18, onto the surface 18a of which an application device 20 applies liquid or pasty medium. The application roller 18 is driven to rotate about its axis A in the direction of arrow P in such a way that it is in essentially slip-free contact with the moving material web 14. By rotating the application roller 18, the liquid or pasty medium 12 is conveyed to the surface 14a of the material web 14 and brought into contact with it. So that the application medium 12 does not simply remain on the surface 14a of the material web 14 due to the wetness of the material web 14, but can penetrate into the material web 14, an application gap 24 is formed between the application roller 18 and a press shoe 22, in which the application medium is pressed into the material web 14 under the influence of the hydrodynamic pressure of the application medium 12 present.

The press shoe 22 has a concavely curved surface section 22a on its side facing the material web 14, which forms the application gap 24 in conjunction with the convex surface 18a of the application roller 18. On both the inlet side and the outlet side, the concavely curved surface section 22a is adjoined by convexly curved surface sections 22b and 22c, the purpose of which is to enable the material web to enter or exit the application gap 24 as gently as possible. The course of the concave surface section 22a is preferably selected such that the application gap 24 tapers in the running direction L of the material web 14, i.e. that the gap width d1 on the inlet side is larger than the gap width d2 on the outlet side. As a result, the hydrodynamic pressure, which is important for the penetration of the application medium 12 into the material web 14, gradually increases from the inlet side to the outlet side of the application gap 24. This allows a better application result to be achieved.

Due to the interaction of the concave surface 22a of the press shoe 22 with the convex surface 18a of the application roller 18, the application gap 24 has a length I that is considerably greater than the length of an application gap formed by two interacting rollers. The length of the application gap increases the length of time the material web spends in the application gap and thus also the amount of application medium penetrating it in the application gap.

Fig. 2 shows a further embodiment of the application device according to the invention, whose structure and function essentially correspond to those of the embodiment according to Fig. 1. Analogous parts in Fig. 2 are therefore provided with the same reference numerals as in Fig. 1, but increased by the number 100. The application device 110 according to Fig. 2 will only be described below insofar as it differs from the application device 10 according to Fig. 1, to the description of which reference is otherwise expressly made hereby.

In contrast to the application device 10 according to Fig. 1, the screen web 116 carrying the material web 114 does not slide directly on the concave surface section 122a of the press shoe 122, but is in essentially non-slip engagement with an endless belt 126 that runs around the press shoe 122 in the direction of the arrow P'. The inner surface 126a of the endless belt 126 facing the concave surface section 122a can be provided with a friction-reducing surface coating. However, it is also possible for the entire endless belt 126 to be made of a material that slides with little friction on the material of the press shoe 122. By designing the application device 110 with the endless belt 126 circulating around the press shoe 122, the wear on the press shoe 122 and the screen belt 116 can be reduced.

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As far as the application roller 118, the application mechanism 120 for the application medium 112, the application gap 124 and the like are concerned, the embodiment according to Fig. 2 corresponds to that according to Fig. 1.

Fig. 3 shows a further embodiment of an application device according to the invention, which essentially corresponds to the embodiment according to Fig. 2. Therefore, analogous parts are provided with the same reference numerals below as in Fig. 2, but increased by the number 100, i.e. increased by the number 200 compared to Fig. 1. The embodiment according to Fig. 3 will be described below only insofar as it differs from the embodiment according to Fig. 2, to the description of which reference is hereby made, including the reference to the description of the embodiment according to Fig. 1.

In the application device 210, the liquid or pasty application medium 212 applied by the application unit 220 to the surface 218a of the application roller 218 is applied through the screen belt 216 to the application side 214a of the material web 214. For this purpose, in the embodiment according to Fig. 3, the arrangement of the material web 214 and the screen belt 216 is swapped over with the embodiment according to Fig. 2, i.e. the screen belt 216 rests on the application roller 218, while the material web 216 rests on the endless belt 226 circulating around the press shoe 222. Due to the pressure forces prevailing in the application gap 224, the provision of the endless belt 226 is advisable in the embodiment according to Fig. 3 in order to avoid excessive stress or tearing of the material web 214.

A further embodiment of the application device according to the invention is shown in Fig. 4. It corresponds in structure and function essentially to the embodiments according to Fig. 1 and 3. Analogous parts are therefore provided with the same reference numerals in Fig. 4 as in Fig. 1, but increased by the number 300. The application device 310 will be described below only insofar as it differs from the application device 10 according to Fig. 1 or the application

device 210 according to Fig. 3, to the description of which express reference is hereby made.

The application device 310 is characterized in particular by the fact that the material web 314 is held between two screen belts 316a and 316b and is thus reliably protected from excessive stress, in particular in the application gap 324. Of course, to reduce the frictional resistance between the concave surface 222a of the press shoe 222 and the screen belt 316b, an endless belt running around the press shoe can also be provided. With regard to the application of the liquid or pasty medium 312 from the application device 320 via the surface 318a of the application roller 318 and through the screen belt 316a onto the material web 314, the embodiment according to Fig. 4 corresponds to that according to Fig. 3.

The application device 410 according to Fig. 5 serves for the direct application of a liquid or pasty medium 412 by means of an application device 420 through a screen belt 416 onto a moving material web 414 which is guided around a support roller 428. The support roller 428 is driven to rotate about its axis A in the direction of arrow P, so that it is in essentially slip-free engagement with the material web 414 moving in the running direction L. The convex surface 428a of the support roller 428, together with the concave surface 422a of the press shoe 422, forms an application gap 424 that preferably tapers in the running direction L, in which the application medium 412, supported by the hydrodynamic pressure forces acting in the application gap 424, is in contact with the material web 414 for such a long time that it forms a reliable bond with it.

In Fig. 6, a further embodiment of the application device according to the invention is shown, whose structure and function essentially correspond to those of the embodiment according to Fig. 1. Analogous parts in Fig. 6 are therefore provided with the same reference numerals as in Fig. 1, but increased by the number 500. The application device 510 according to Fig. 6 is only described in the following insofar as

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be described as it differs from the application device 10 according to Fig. 1, to whose description reference is otherwise expressly made herewith.

The application device 510 according to Fig. 6 differs from the application device 10 according to Fig. 1 only in that instead of the application roller 18, a further press shoe 530 with an endless application belt 532 running around it is provided, onto the surface 532a of which the application device 520 applies the liquid or pasty medium 512. The further press shoe 530 has a convex surface section 530a opposite the press shoe 522, which gives the application belt 532 a correspondingly convex course in the area of the application gap 524. In the application gap 524 formed between the convex section 532b of the path of the endless belt 532 and the concave surface section 522a of the press shoe 522, the application medium 512 is brought into contact with the material web 514 carried by the screen belt 516 - as in the embodiment according to Fig. 1 - for such a long time that it reliably bonds to the material web 514 despite the wetness of the material web 514.

Fig. 7 shows a device for applying a liquid or pasty medium to both sides of a material web 614, which is constructed by arranging two application devices 610 and 610' one behind the other. In the embodiment shown in Fig. 7, both the application device 610 and the application device 610' are constructed according to the embodiment shown in Fig. 1. The structure and function of these application devices will therefore not be explained below. In principle, however, it is also possible to replace one or both application devices 610 or 610' with another application device, as explained above with reference to Figs. 2 to 6.

In order to enable the application of application medium directly onto the material web 614, i.e. not through the openings of a screen belt, the material web 614 is placed between the two application devices 610 and

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610' at 638 from a screen belt 616 to a screen belt 616'. It is understood that a corresponding transfer of the material web 614 can also take place if the application of the liquid or pasty medium to the material web in both application stations 610 and 610' is to take place through the openings of a screen belt. Such a transfer can be dispensed with if the application takes place directly on the material web in one of the application devices, while in the other application device it takes place through the openings of the screen belt.

It should also be noted that the applicator 20, 120, etc. is a free-jet nozzle applicator. So-called "short dwell time" applicators can also be used.

It should also be added that the press shoe 22 can be adjusted against the roller 18 (or 118 or 218 or 318 or 428) or the further press shoe 530 by means of an adjusting device 40, of which only the drive tappet 40a is shown in the figures, in particular Fig. 1. This allows the width of the application gap 24 and thus the hydrodynamic pressure acting on the application medium to be varied. The adjusting device 40 can be a pneumatic, hydraulic or electric motor drive.

Claims (13)

&bull; * - 12- Protection claims 1. Device (10) for the direct or indirect application of a liquid or pasty medium (12) to a fully formed but still wet material web (14), in particular made of paper or cardboard, comprising: at least one screen belt (16) carrying the material web (14),
a counter element (18) with a convexly curved surface section (18a) around which the material web (14) is guided, the counter element (14) being an application element in the case of indirect application and a support element in the case of direct application, an application unit (20) for directly applying the liquid or pasty medium directly to the material web or for indirectly applying the liquid or pasty medium (12) to the material web (14) by means of the application element (18), and a press shoe (22) with a concavely curved surface section (22a), wherein the concavely curved surface section (22a) of the press shoe (22) faces the convexly curved surface section (18a) of the counter element (18) and forms with it a gap (24) through which the material web (14) and the at least one screen belt (16) are guided. 2. Device according to claim 1, characterized in that the convexly curved surface section (18a) of the counter element (18) and the concavely curved surface section (22a) of the press shoe (22) are designed to be coordinated with one another in such a way that the gap (24) tapers in the running direction (L) of the material web (14) over at least part of its length (I). 3. Device according to claim 1 or 2, characterized in that the counter element is an application roller (18) or a support roller (428). 4. Device according to claim 1 or 2, characterized in that the counter element is formed by a further press shoe (530). 5. Device according to one of claims 1 to 4, characterized in that a flexible endless belt (126) is provided which runs around the press shoe (122) in direct contact with the surface section (122a) of the latter. 6. Device according to one of claims 1 to 5, characterized in that the material web (14) is guided in direct contact with the convexly curved surface section (18a). 7. Device according to one of claims 1 to 5, characterized in that the material web (214) is guided in indirect contact with the convexly curved surface section (218a) at least with the interposition of a screen belt (216). 8. Device according to one of claims 1 to 7, characterized in that the material web (314) is carried between two screen belts (316a, 316b). 9. Device according to one of claims 1 to 8, characterized in that the press shoe (22) and the counter element (18) can be pressed against each other. 10. Device according to one of claims 1 to 9, characterized in that the application unit is a free-jet nozzle application unit. - 14- 11. Device according to one of claims 1 to 9, characterized in that the application unit is an application unit with a short residence time of the application medium between application and equalization. 12. Device according to one of claims 1 to 11, characterized in that it (610) serves to apply the liquid or pasty medium to a first side of the material web (614) and that it has a further device (610') according to one of the preceding claims is arranged downstream. 13. Device according to claim 12, characterized in that between the two application devices (610, 610') a transfer (at 638) of the material web (614) takes place from a screen belt (616) carrying the material web (614) from the second side to a screen belt (616') carrying the material web (614) from the first side. 17291GDE-anm / 08.09.97 10:11