SCRAPER HOLDER AND SCRAPING DEVICE

Abstract

A scraper holder for a scraping device of a machine for producing or processing a fibrous web has a base plate and a cover plate. The base plate and the cover plate are tiltable relative to one another about an axis of rotation which extends transversely to the machine direction. The cover plate includes a holding device to accommodate a scraper blade. The scraper holder has at least one application tube which is arranged in an interior space of the scraper holder which is delimited by the base plate and the cover plate. One or more cleaning openings are provided in the base plate, in order to allow liquid and/or dirt particles to be removed from the interior space to the outside.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of International Patent Application No. PCT/EP2023/066984 entitled “SCRAPER HOLDER AND SCRAPING DEVICE,” filed Jun. 22, 2023, which is incorporated in its entirety herein by reference. International Patent Application No. PCT/EP2023/066984 claims priority to German Patent Application No. 10 2022 116 963.4 filed on Jul. 7, 2022, which is incorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to scraper holder and a scraping device for a machine for producing or processing a fibrous web and to an associated scraping device.

2. Description of the Related Art

During production and processing of fibrous webs, such as paper or cardboard webs, the fibrous web is guided over a multitude of rolls and cylinders.

In order to keep the surfaces of said rolls and cylinders free of deposits during operation it is known to provide suitable scraping devices which mechanically remove possible deposits from respective surfaces.

The scraping devices generally include a scraper blade which is in contact with the surface and which—as a wear material—is replaced regularly, and a scraper holder on which the scraper blade is mounted. The scraping device can then have suitable tube devices for applying and lifting the scraper blade. Such scraping devices are known, for example from WO 2013 019 989. DE 102019117901 A1 also presents such a scraping device.

During operation, these scraping devices are usually exposed to very high levels of moisture and various types of dirt particles. Over time, this leads to contamination of these scraping devices, which can result in the scraping device having to be removed from the machine in order to be cleaned. However, this is only possible when the machine is shut down. In addition, the effort required for this generates costs for the operator.

What is needed in the art is a scraping device that can be operated reliably, even under difficult operating conditions. What is also needed in the art is a scraping device that has to be removed from the production line less frequently for service and maintenance.

SUMMARY OF THE INVENTION

A scraper holder for a scraping device of a machine for producing or processing a fibrous web is provided. The scraper holder has a base plate and a cover plate. The base plate and the cover plate are tiltable relative to one another about an axis of rotation, extending transversely to the machine direction. The cover plate has a holding device to accommodate a scraper blade. In addition, the scraper holder has at least one application tube which is arranged in an interior space of the scraper holder which is delimited by the base plate and the cover plate.

According to the invention it is provided that one or more cleaning openings are provided in the base plate, in order to allow liquid and/or dirt particles to be removed from the interior space to the outside.

Moreover, a scraping device of a machine for producing or processing a fibrous web is provided. The scraping device includes a scraper blade and a scraper holder provided according to the invention.

The inventors have recognized that a large proportion of malfunctions in the operation of the scraping device result from liquid and particles penetrating the interior space of the scraper holder. These dirt particles can then accumulate, for example on the rotary axis or the tubes, and can, for example, impair the functionality of the scraping device.

In addition, the liquids occurring in a paper machine are, for example, often loaded with an excessive amount of dissolved or dispersed substances, for example mineral fillers as used in paper production, such as CaCO₃. If such a liquid (generally water) penetrates into the interior space of the scraper holder, these substances can precipitate and can also deposit on moving or stationary elements. This often occurs in the form of incrustations (“calcifications”).

The inventors' idea for addressing the needs in the prior art is based on the recognition that prevention of penetration of dirt and moisture by completely sealing the scraper holder is not possible with a justifiable effort.

Instead, one or more cleaning openings are provided in scraper holders according to the invention. These cleaning openings in fact favor penetration of liquid and particles into the scraper holder, which at first glance seems to run counter to the problem to be solved. However, the contaminated water also quickly drains out of the interior space of the scraper holder through these cleaning openings, so that dissolved substances do not have sufficient time to deposit themselves on parts of the scraper holder. Thus, the contaminated water no longer contributes significantly to the contamination of the interior space of the scraper holder. On the contrary, the interior is flushed with this water and thus cleaned. If, for any reason dirt particles such as fiber fragments accumulate in the interior space, they will be flushed out through the cleaning openings by the process water that is present anyway.

In this way, an at least partially self-cleaning scraping device is created. The service life of the scraping device is thus considerably extended before maintenance and possibly replacement becomes necessary.

Moreover, a scraper holder provided according to aspects of the invention is also useful in applications in which no, or only small amounts of process water occur, as is the case for example, in the dryer section of a paper machine. Automatic flushing with process water is emitted in this section, and there is a risk that only part of the dry dirt particles that penetrate through the cleaning openings get back to the outside. It is however possible that—when the machine is at a standstill—to easily clean the scraper holder from the outside with a hose or a high pressure cleaner without having to remove it. The water will penetrate into the interior space through the cleaning openings. From there it will pick up the particles and will, again flush them to the outside through the cleaning openings. With the scraper holders provided according to aspects of the invention, the period of time before maintenance and, if necessary, removal become necessary can also be significantly increased in this application.

The design, geometry, and number of cleaning openings can vary according to the particular design.

Thus, it may for example be provided that at least some, in particular all cleaning openings are designed as bores, and have a diameter of more than 3 mm, in particular more than 5 mm, optionally more than 8 mm.

Alternatively, or in addition, it may be provided that at least some, in particular all cleaning openings are designed as slots, wherein the slots have a width of at least 3 mm, such as at least 5 mm, optionally 8 mm or more, and/or a length of at least 10 mm, such as at least 15 mm or at least 30 mm. Longer slots are also possible. In particular, longer slots can be oriented in longitudinal direction of the scraper holder, that is, installed in transverse machine direction.

Exemplary slot dimensions may be 2 mm×15 mm, 5 mm×30 mm, 8 mm×50 mm or 7 mm×40 mm.

When selecting the size of the cleaning openings, the type of raw materials used in production can also play a role. For example, softwood-sulphate pulp has long, strong fibers that have an average length of 3.3 mm. In contrast, hardwood pulp has shorter fibers that have an approximate length of 1 mm. In order to avoid the risk of a blockage of the openings with fibers, smaller opening cross sections are sufficient when using hardwood pulp (for example from 3 mm), whereas larger opening cross section of, for example 5 mm or greater may be advantageous. Since however, other factors in addition to the fiber length are to be considered in regard to blockage, even larger openings may also be helpful.

The open area, which is the proportion of the cleaning openings over the entire surface of the base plate can be at least 5%, optionally between 5% and 20%, optionally between 6% and 13%, for example 7%. A compromise can always be found here. A larger open area allows the water to drain quickly, leads however to a destabilization of the base plate and also poses the risk that the application tube is damaged by mechanical influences. The specified ranges have proven to be a good compromise.

In some embodiments, the base plate can be manufactured entirely or partially from a perforated sheet metal. Perforated sheet metals of this type are commercially available in various materials and various hole patterns. These perforated sheet metals can then be formed into the desired shape to be further processed.

Alternatively, or in addition, the cleaning openings can also be introduced after production of the scraper holder or the base plate. In terms of production technology, this is more complex than the use of a perforated sheet metal. However, the cleaning openings can be positioned precisely at the desired locations.

One example for this is the common situation where the base plate is designed as a trough. In this case, it can be advantageous if at least some of the cleaning openings, in particular all cleaning openings are arranged in the region of at least one of the bending radii of the trough. Experience has shown that there is a great tendency for deposits to form in the region of these bending radii. In addition, these regions are the lowest region of the scraper holder in many installation positions, so that—due to gravity—the liquids flow to these regions where they can reliably drain through the cleaning openings located there. For cleaning openings that are provided at such bending radii it can be particularly advantageous if these cleaning openings are designed as slots. In terms of production technology, such slots can be placed easily at the right locations. A cleaning opening is also “in the region of a bending radii” if only one part of the cleaning opening protrudes into the curved section of the trough

In particular with a small bending radius it may occur that some or all cleaning openings do not protrude directly into the curved section of the trough. Such openings should, however, still be considered as being “in the region of the bending radius” if the distance to the curved section of the trough is less than 5 mm, in particular less than 3 mm.

In some embodiments of the scraper holder it can be provided that the scraper holder includes a flushing device which is designed to apply liquid or gaseous flushing medium to the interior space of the scraper holder. Suitable flushing media for this application is water, which is possibly mixed with suitable cleaning agents (for example tensides or acids to dissolve lime).

With these arrangements, highly targeted cleaning of the scraper holder is possible, even in installation situations where direct flushing with process water does not occur or is not implemented to a sufficient extent. The flushing devices can also be targeted at areas that either tend to heavy dirt accumulation or which—in the case of dirt accumulation—rapidly impair the functionality of the scraper device.

Such flushing devices can be implemented in various ways. In principle, it is possible in addition, to also run lines for compressed air or water in the interior space of the scraper holder.

Since the installation space is limited in many installation positions of the scraper device, it is desirable that an increase in size of the scraper device is avoided whenever possible. It can therefore be advantageous if the flushing device is designed as a spray tube which is arranged along the axis of rotation. The flushing device can perform a dual function in addition to the cleaning function, the spray tube can serve as a rotary hub for rotating the cover plate. In many cases, this rotary hub is already designed as a tube and can be converted into a suitable rinsing device with little effort. Suitable spray tubes have an inside diameter between 6 mm and 10 mm, with an outside diameter between 8 mm and 13 mm. With smaller (inside) diameters it is often not possible to move enough flushing medium, while larger (outside) diameters can only be fitted into available installation spaces with difficulty.

For the supply of flushing medium, it can be provided that the scraper holder has at least one feed for a flushing medium which is arranged at the base plate. Providing a feed on the base plate is very easily accomplished.

Alternatively, it may be provided that the scraper holder has a feed for a flushing medium which is arranged on at least one end face of the scraper holder. This can be advantageous since the supply lines with pressure medium for the application tube and the lift-off tube are already provided at the end face.

Depending on the application and, for example, also depending on the length of the scraping device, several feeds can also be provided in order to ensure a uniform supply of flushing medium to the scraping device.

In some embodiments it can be provided that the scraper holder has a plurality of scraper holder segments which are arranged adjacent to one another in longitudinal direction (L). Each scraper holder segment includes a base plate segment and a cover plate segment. In this way, the scraper holder can be of modular construction.

Such a scraper holder is no longer produced in one piece but consists of several standardized short segments. This can offer several advantages. In the event of damage, the entire scraper holder does not have to be replaced. Instead, thanks to the segmentation, replacement of individual segments—either scraper holder segments or also base plate segments or cover plate segments—is sufficient in order to restore the functionality of the scraper holder.

The scraper holder can be designed to be segmented into standardized individual segments of the same size. These segments can be designed, for example in a length range of 60 cm to 130 cm, optionally 60 to 120 cm. This facilitates simplification of logistic, for example when shipping, since standard packaging units (for example standard pallets) can be used, whereas in contrast a non-segmented scraper holder having a length of 10 m usually has to be transported as special freight.

In the case of segmented scraper holders, the tubes that are used, that is the application tube, and the lift-off tube are designed as continuous tubes, which extend in one piece along the entire length of the scraper holder. However, this is not a problem, since these tubes can still be rolled up and transported very easily, even at greater length.

Due to this type of standardization, the user needs to keep a small amount of segments in stock, instead of one or several entire scraper holders in order to be able to conduct repairs in the event of damage.

At best, the first and the last segment (the outer segments) are generally “special components” because of the varying overall lengths of the rolls to be scraped and the tube guides that are to be mounted and which are not consistent with the specified standard dimensions but must instead be adapted to a specific installation situation. These special components can, however, also be easily shipped.

Connection of adjacent scraper holder segments occurs on the one hand by the scraper blade, which is optionally designed as a continuous blade. Advantageously, each cover plate segment also can have a holding device for accommodating the scraper blade. In addition, the individual segments of the scraper holder are mounted on a frame, thus also providing a connection.

Moreover, additional ways may possibly be provided for connecting and adjusting adjacent scraper holder segments. For example, dowel pins or guide grooves and springs can be provided to connect adjacent segments with one another.

In principle, it is possible that the axis of rotation is also segmented. Rotary axis segments of adjacent scraper holder segments can then be connected to one another, where applicable.

In some embodiments, however, a continuous axis of rotation may be provided. This offers the advantage that the connection of the scraper holder segments to each other occurs at least partially also via the axis of rotation. This is moreover advantageous in arrangements where a flushing device is provided and wherein the axis of rotation is, in particular, designed as a flushing device. In this case, a continuous spray tube can be utilized. This saves the effort of having to connect individual spray tube segments tightly with one another, in order to prevent leakage of the pressurized flushing medium at the connection points.

This does require a spray tube of the entire length of the scraper holder. However, such comparatively simple components can generally be sourced locally and do not have to be purchased from specialized workshops that may be far away. This disadvantage is therefore of little consequence.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in further detail below, with reference to schematic drawings. The invention is thereby not limited to the arrangements illustrated in the drawings:

FIG. 1 illustrates a side view of an exemplary embodiment of a scraping device provided according to the current invention;

FIG. 2 illustrates a perspective view of another exemplary embodiment of a scraping device provided according to the current invention;

FIG. 3 illustrates a side view of another exemplary embodiment of a scraping device provided according to the current invention;

FIG. 4 illustrates a section from a base place for a scraper holder provided according to one aspect of the current invention; and

FIG. 5 illustrates a perspective view of another exemplary embodiment of a scraping device provided according to the current invention.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, the scraping device in FIG. 1 comprises a base plate 2 and a cover plate 3 which form an interior space 9 in scraper holder 1. A holding device 6 is provided on cover plate 3 to accommodate scraper blade 7. Scraper blade 7 may be a conventional scraper blade 7 known from the current state of the art. Base plate 2 and cover plate 3 are designed to be tiltable relative to one another, about an axis of rotation 5, extending transversely to the machine direction. An application tube 4 and a lift-off tube 8 are provided in interior space 9 of scraper holder 1. If application tube 4 is pressurized, cover plate 2 is tilted about axis of rotation 5. This causes scraper blade 7 to make contact with a running surface 20. Running surface 20 may, for example, be the surface of a dryer cylinder in a machine for producing or processing a fibrous web. In order to ensure reliable lifting of scraper blade 7 off from running surface 20, a lift-off tube 8 can be pressurized, while the pressure on application tube 4 is relieved. As a result, cover plate 3 is tilted again about axis of rotation 5 in the opposite direction and the contact of scraper blade 7 with running surface 20 is released.

Base plate 2 is provided with a number of cleaning openings 10. Said cleaning openings 10 allow liquid and/or dirt particles to be removed from interior space 9 to the outside. In the scraping device illustrated in FIG. 1, base plate 2 is manufactured from a perforated sheet metal. In this case, in particular, cleaning openings 10 can be evenly distributed over entire base plate 2. The types of perforated sheet metal generally have round bores for cleaning openings 10. The bores can have a diameter of more than 3 mm, such as more than 5 mm.

The scraping device in FIG. 2 differs from the device in FIG. 1 in that no perforated plate was used for the production of base plate 2, but instead cleaning openings 10 were introduced in a targeted manner at specific locations in base plate 2. Base plate 2 is designed in the form of a trough. At the transition between floor and wall, this trough has a bending radius 12. In the example in FIG. 2, cleaning openings 10 are arranged in the region of at least one of the bending radii 12 of trough 2. It can be advantageously provided that cleaning openings 10 are designed as slots, wherein the slots can have a width, in particular of at least 3 mm, optionally at least 4 mm and/or a length of at least 10 mm, such as at least 15 mm.

The scraping device illustrated in FIG. 3 shows an arrangement where a flushing device 11 is provided in interior space 9 of scraper holder 1. Flushing device 11 is designed as a spray tube 11 which is arranged along axis of rotation 5. The flushing device 11 can perform a dual function. In addition to the cleaning function, spray tube 11 can serve as a rotary hub for rotating cover plate 3. Flushing device 11 has an outlet for flushing medium 11a. This outlet can be arranged in such a way that flushing medium 11a is targeted specifically onto locations where the risk of contamination is greatest. Several outlets can also be provided which are located at different positions. The position of cleaning openings 10 can also be adapted to the direction of flushing device 11.

In order to supply flushing device 11 with required flushing medium 11a, a feed 13 is provided. A suitable media line, for example, a water hose or a compressed air line, can then be connected to feed 13. Feed 13 is provided on base plate 3 as an example in FIG. 3. In particular, with long scraping devices several feeds 13, which are spaced apart from each other, can be provided. Alternatively, it may be provided that scraper holder 1 has one feed 13 for a flushing medium 11a which is arranged on at least one end face of scraper holder 1.

Such a flushing device 11 can, in particular, also be provided in the arrangements illustrated in FIGS. 1 and 2.

FIG. 4 is a schematic top view onto a base plate 2 for a scraper holder 1 provided according to one aspect of the invention. Base plate 2 is designed as a perforated sheet, or more specifically, as a slotted sheet. Slots 10 serve as cleaning openings 10 in scraper holder 1. The slots are therein oriented in longitudinal direction L of scraper holder 1, that is, installed in transverse machine direction.

In the arrangement in FIG. 1, cleaning openings 10 are arranged in two rows. These rows respectively, are located at the position of bending radius 12. By bending base plate 2 at the locations of bending radii 12, the front and back of scraper holder 1 are created. This type of production is advantageous because it allows cleaning openings 10 to be positioned very precisely and accurately at the critical locations of bending radii 12. This also means that comparatively large openings 10 can be provided at the locations of bending radii 12—which increases the cleaning effect—while at the same time the total open area of base plate 2 remains small. The latter has an advantageous effect on the stability of the base plate and ensures good protection of application hose 4, and also of lift-off hose 8 from mechanical damage. Advantageous dimensions for slots 10 are a width of 4 mm-6 mm and a length of between 30 mm and 60 mm and open surface areas of between 6% and 13%.

FIG. 5 shows a scraper holder 1 provided according to an additional aspect of the invention. Scraper holder 1 is constructed of scraper holder segments la which are arranged adjacent to one another in longitudinal direction L. Each scraper holder element la has a base plate segment 2a and a cover plate segment 3a. In addition, each scraper holder segment la includes a holding device 6 for accommodating scraper blade 7. Scraper blade 7 is designed as a continuous non-segmented scraper blade 7. Whereas an entire scraper holder 1 can have a length of 10 m or more, the scraper holder elements are significantly shorter and generally have a length of only between 60 and 130 cm.

Application tube 4 and lift-off tube 8 are both continuous, in other words, non-segmented. Each scraper holder segment la has one or more cleaning openings 10 in base plate segment 2a in order to allow liquid and/or dirt particles to be removed from the interior space to the outside. In the arrangement in FIG. 5, slots are provided for this purpose which are arranged along bending radius 12. Moreover, the scraper holder includes a flushing device 11 which is designed as spray tube 11 and which is arranged along axis of rotation 5. Spray tube 11 is also optionally continuous, in other words, non-segmented. This not only avoids problems with tightness at connection points of adjacent spray tube segments. Continuous spray tube 11 can also at least partially assume the function of connecting and adjusting of adjacent scraper holder segments 1a.

While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

COMPONENT IDENTIFICATION LISTING

• • 1 scraper holder
  • 1a scraper holder segment
  • 2 base plate
  • 2a base plate segment
  • 3 cover plate
  • 3a cover plate segment
  • 4 application tube
  • 5 axis of rotation
  • 6 holding device
  • 7 scraper blade
  • 8 lift-off tube
  • 9 interior space
  • 10 opening
  • 11 flushing device
  • 11a flushing medium
  • 12 bending radius
  • 13 feed
  • 20 moving surface
  • L longitudinal direction (=CD)

Claims

1. A scraper holder for a scraping device of a machine for producing or processing a fibrous web, the scraper holder comprising:

a base plate;

a cover plate comprising a holding device configured to accommodate a scraper blade, wherein the base plate and the cover plate are tiltable relative to one another about an axis of rotation which extends transversely to a machine direction;

at least one application tube which is arranged in an interior space of the scraper holder and which is delimited by the base plate and the cover plate; and

one or more cleaning openings provided in the base plate in order to allow liquid and/or dirt particles to be removed from the interior space to the outside.

2. The scraper holder of claim 1, wherein at least some of the one or more cleaning openings are designed as bores and have a diameter of more than 3 mm.

3. The scraper holder of claim 2, wherein all of the one or more cleaning openings are designed as bores.

4. The scraper holder of claim 2, wherein the one or more cleaning openings have a diameter of more than 5 mm.

5. The scraper holder of claim 1, wherein at least some of the one or more cleaning openings are designed as slots, wherein the slots have a width of at least 3 mm and/or a length of at least 10 mm.

6. The scraper holder of claim 5, wherein the slots have a width of at least 5 mm and/or a length of at least 15 mm.

7. The scraper holder of claim 1, wherein the base plate is designed as a trough.

8. The scraper holder of claim 7, wherein at least some of the one or more cleaning openings are arranged in a region of at least one bending radius of the trough.

9. The scraper holder of claim 8, wherein all of the one or more cleaning openings are arranged in the region of at least one bending radius of the trough.

10. The scraper holder of claim 1, further comprising a flushing device which is designed to apply liquid or gaseous flushing medium to the interior space of the scraper holder.

11. The scraper holder of claim 10, wherein the flushing device is designed as a spray tube which is arranged along the axis of rotation.

12. The scraper holder of claim 10, further comprising at least one feed for a flushing medium which is arranged on the base plate.

13. The scraper holder of claim 10, further comprising a feed for a flushing medium which is arranged on at least one end face of the scraper holder.

14. The scraper holder of claim 1, comprising a plurality of scraper holder segments which are arranged adjacent to one another in a longitudinal direction, wherein each of the scraper holder segments includes a base plate segment and a cover plate segment.

15. The scraper holder of claim 14, wherein connection of the scraper holder segments to each other occurs at least partially also via a continuous axis of rotation, wherein the axis of rotation is designed as a flushing device.

16. A scraping device for a machine for producing or processing a fibrous web, the scraping device comprising:

a scraper blade; and

a scraper holder comprising: a base plate; a cover plate comprising a holding device accommodating the scraper blade, wherein the base plate and the cover plate are tiltable relative to one another about an axis of rotation which extends transversely to a machine direction; at least one application tube which is arranged in an interior space of the scraper holder and which is delimited by the base plate and the cover plate; and one or more cleaning openings provided in the base plate in order to allow liquid and/or dirt particles to be removed from the interior space to the outside.

17. The scraping device of claim 16, wherein at least some of the one or more cleaning openings are designed as bores and have a diameter of more than 3 mm.

18. The scraping device of claim 17, wherein all of the one or more cleaning openings are designed as bores.

19. The scraping device of claim 17, wherein the one or more cleaning openings have a diameter of more than 5 mm.

20. The scraping device of claim 16, wherein at least some of the one or more cleaning openings are designed as slots, wherein the slots have a width of at least 3 mm and/or a length of at least 10 mm.