CN115142290A

CN115142290A - Doctor blade for a fiber web machine and doctor arrangement in a fiber web machine

Info

Publication number: CN115142290A
Application number: CN202110338152.2A
Authority: CN
Inventors: 孙庆园
Original assignee: Valmet Technologies Oy
Current assignee: Valmet Technologies Oy
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2022-10-04

Abstract

The invention relates to a doctor blade for a fiber web machine. The doctor blade (11) comprises a foil portion (14) having a sharp point (21). In the foil portion (14), there are a plurality of through-holes (22) distributed over substantially the entire length (L) of the doctor blade (11). The invention also relates to a doctor device in a fiber web machine.

Description

Doctor blade for a fiber web machine and doctor arrangement in a fiber web machine

Technical Field

The invention relates to a doctor blade for a fiber web machine, which doctor blade comprises a foil portion with a sharp tip. The invention also relates to a doctor device in a fiber web machine.

Background

Us patent No. 6491791B1 discloses a doctor blade for cleaning the surface of a roll in a fiber web machine, in particular a grooved or drilled roll surface. The doctor blade has a chamber opening located near the tip of the doctor blade. The compressed air supplied to the chamber is flushed out through the openings and creates a vacuum in the slots or bores, thereby improving drainage. However, the doctor blade is complicated and thus difficult to manufacture. In addition, the doctor blade has poor wear resistance and compressed air results in high operating costs.

Another known doctor blade arrangement comprises two successive doctor blades. In particular, the first blade is a foil blade that removes water from the roller housing slots or perforations by means of a vacuum created between the foil blade and the roller. The second blade is a standard doctor blade that removes water sucked by the foil blade and cleans the roll surface. Two doctor blades require a lot of space and the doctor blades must be oriented in a specific manner. The known doctor device is therefore suitable only for a few positions.

Disclosure of Invention

It is an object of the invention to provide a new doctor blade for a fiber web machine, which has a more versatile function and positioning than before. Another object of the invention is to provide a new doctor blade arrangement in a fiber web machine, which doctor blade arrangement can be adapted in a completely new position. The characteristic features of the doctor blade and the doctor apparatus according to the invention are set forth in the examples of this specification. The blade will create a vacuum as before, but the sucked water is easier to drain than before without additional structure. At the same time, the doctor blade may be positioned more freely than known doctor blades. With the new doctor blade the doctor device remains simple and easy to place even in narrow (light) positions or in otherwise critical positions.

Drawings

The present invention is described in detail below with reference to the attached drawing figures, which show some embodiments of the invention, wherein

Fig. 1 shows a known scraper device adapted to be positioned in the vicinity of a surface to be scraped (cleaned);

figure 2 shows a doctor apparatus according to the invention, adapted to be located in the vicinity of a surface to be doctored;

fig. 3a shows a cross-section of a first doctor blade according to the invention;

fig. 3b shows a cross-section of a second doctor blade according to the invention;

fig. 3c shows a cross-section of a third doctor blade according to the invention;

figure 4a shows a close-up view of a doctor apparatus according to the invention; and

fig. 4b shows an isometric cross-sectional view of a blank for a doctor blade according to the invention.

Detailed Description

Fig. 1 shows a known doctor device, which is adapted to be located in the vicinity of an opening surface 10 to be doctored. The doctor apparatus is particularly suitable for fibre-web machines such as paper, board and tissue machines. Here two doctor blades 11 are provided one after the other. The first doctor blade 11 is a foil blade 12, which is used in particular for removing water and fine substances from the open surface 10 to be doctored. The opening surface 10 is here rotated clockwise. In particular, such doctor blade devices are suitable for use in scraping polymer coated rolls, belts and transfer belts, and open-faced rolls. In fiber web machines, such as paper, board or tissue machines, open-faced rolls are used for several different reasons. For example, in a suction roll, the shell is perforated to direct the vacuum effect from the inside of the roll to the outside of the roll. The hole opens the housing surface. On the other hand, grooved rolls are also used, wherein the surface of the shell is grooved mainly to improve dewatering. There are also suction rolls with grooved surfaces, the shell of which is provided with both holes and grooves. In addition to or instead of slots, blind holes, for example, can also be used. Soft coatings are also used in the rollers, while belts and transfer belts have soft surfaces due to their nature. In addition, grooves may be formed on the surface of the belt, for example.

There is a narrow gap between the foil blade 12 and the opening surface 10 to be scraped. When the roller 16 rotates, a vacuum is created in the gap due to the mutual movement of the opening surface 10 and the foil blade 12. The vacuum absorbs water and fine matter from the open surfaces, which is advantageous for the operation of the fiber web machine. The removed water falls by gravity into a lower water tank (trough) 13. The optional second doctor blade 11 removes the remaining water and impurities from the opening surface. The positioning of the doctor blade has its limitations due to gravity assisted water removal.

The doctor blade 11 has a length extending in the cross-machine direction of several meters (1 to 11 meters) and a width extending in the machine direction of 5 to 20 centimeters. Further, the doctor blade 11 includes a foil portion 14 and a fastening portion 15. In the embodiment shown in fig. 2, the foil portion 14 is adapted to make light contact with the open surface 10 of the roller 16. The doctor blade 11 is supported by a blade holder 17 comprising a fastening plate 18 and a jaw portion (jaw part) 19. The jaw portion 19 includes two jaws between which the doctor blade 11 is assembled, the first jaw being located on the side of the open surface to be doctored, and the second jaw being opposite to the first jaw. In the design of fig. 1 and 2, the second jaw is shorter than the first jaw, but is provided with a separate pressure plate 29. The fastening plate 18 is supported to the structure of the fiber web machine and a loading hose 20 is arranged between the fastening plate 18 and the jaw part 19. Here, the doctor blade 11 is loaded by pressurizing the loading hose 20. Accordingly, for example, in order to replace the scraper blade, the scraper blade can be detached from the opening surface to be scraped by introducing a vacuum into the loading hose. The supporting and loading effect of the blade holder 17 can be extended far enough by the blade holder design of fig. 1 and 2 using the hold down plate 29. In addition, the characteristics of the blade holder can be changed by changing the pressure plate. However, it should be understood that conventionally designed holders in which the jaws are of the same length or the second jaw is longer than the first jaw are well suited for holding the scraper blade of the present invention.

Figure 2 shows a doctor apparatus according to the invention. Here, similarly to fig. 1, in the vicinity of the opening surface 10 to be scraped, a doctor blade 11 including a sheet portion 14 having a sharp tip 21 is arranged. However, according to the present invention, there are a plurality of through holes 22 distributed over substantially the entire length L of the doctor blade 11 in the foil portion 14, and the tip 21 is arranged to point downward. The through-holes extend from one planar surface of the doctor blade to the opposite planar surface. First of all, the doctor blade itself is and can be positioned in a completely new manner. The doctor blade may now be arranged with its tip facing downwards on the rising side of the roll. The tip may be located between 6. In this position, the doctor blade creates a vacuum and water drips under gravity onto the top of the doctor blade. The water then flows through the through-holes into the underlying water tank 13. The flow of water is indicated by dashed arrows. By means of the new doctor blade, water can be removed efficiently even with only one blade. More generally, the doctor blade 11 may be the only doctor blade in the doctor arrangement. This can reduce operating costs while maintaining continuous water removal.

Fig. 3 a-3 c show three doctor blades 11 for a fiber web machine. As previously mentioned, these doctor blades are foil blades. Each doctor blade 11 includes: a fastening portion 15 held in a jaw portion 19 of the blade holder 17; and a thin sheet portion 14 for removing water and dirt from the opening surface 10. The fastening portion 15, which is thinner than the tab portion 14, may have a completely flat profile, or preferably a substantially flat profile, with a thicker portion as the stop member 30 and a thinner fastening neck 31 adapted to abut against the second jaw of the jaw portion 19 of the blade holder 17. The foil portion 14 comprises a foil 25 starting from a sharp point 21 and a foil neck 32 at the opposite end of the foil portion 14. In other words, the tab portion 14 has a relatively thin tab neck 32 between the fastening portion 15 and the tab 25. The thickness of the tab neck 32 is greater than the thickness of the fastening neck 31 and may be less than or equal to the thickness of the stop member 30. In fig. 3a and 3b, the lamella portion 14 comprises a wedge-shaped portion 33 with a large head (bulk head) 26, which tapers towards the sharp point 21. More generally, the wedge 33 has a large head 26 and two opposing surfaces that are flat but not parallel and meet at the sharp point 21. Thus, the wedge portion 33 tapers from the large end portion 26 toward the sharp tip 21. According to the invention, there are a plurality of through-holes 22 distributed over substantially the entire length L of the doctor blade 11 in the foil portion 14. In the illustrated embodiment, the through-hole 22 extends through the thickness of the wedge 33 from one planar surface to the opposite planar surface of the wedge. In this way, water can flow past the doctor blade even when the blade is mounted with the tip down.

Advantageously, each through hole 22 is a circular hole 23 having a diameter D greater than the thickness T of the sheet neck 32. First, cylindrical or round holes are easy to machine. Secondly, the large pores remain open even if the water is contaminated with impurities. Also, a tapered hole that opens in the flow direction of water may be utilized. This further promotes drainage. Regardless of the configuration, the through-holes 22 are oriented vertically or slightly inclined with respect to the doctor blade 11. Such a hole is easy to machine. Also, the length of the bore is minimized.

Here, the foil 25 of the foil portion 14 has a wedge 33 which may be asymmetric, have a bevel on the side of the blade near the tip 21 (as shown in fig. 3 a), or more symmetric (as shown in fig. 3 b). The through-hole 22 is located in the region of the head 26 of the wedge 33. The head is the thicker end of the wedge 33 and is located adjacent the thinner foil neck 32. Similar to fig. 2, the sheet surface 25 is arranged toward the opening surface 10. Here, when the roller 16 rotates, the doctor blade 11 creates a vacuum which draws water out of the open surface 10. After the wedge 33, the water flows through the through-hole 22. Here, the through-holes do not change the strength of the doctor blade.

Advantageously, the head 26 of the wedge 33 is inclined downwards towards the sheet neck 32, such that there is an angle α between the head 26 and the sheet neck 32, which is 100-160 degrees, preferably 120-140 degrees. In this way, the wedge-shaped portion prevents water from flowing back between the doctor blade and the opening surface. Also, the wedge collects and directs water into the bore. In addition, in order to collect water, grooves 27 are provided in the head 26 extending over substantially the entire length L of the doctor blade 11. The size and shape of the slot may vary and there may be more than one slot. In the illustrated embodiment, the grooves are continuous and of uniform depth. Alternatively, the depth as well as the width may vary. For example, there may be a semicircular slot at the location of the through hole for collecting water. Regardless of the embodiment, the through-hole 22 is arranged to open on the groove 27. This facilitates drainage. Fig. 4b shows a blank for a doctor blade according to the invention. Here the groove 27 has been machined and the position of the through hole is shown by two dot-dash lines.

Fig. 3c shows a third embodiment of a doctor blade 11 according to the invention. Here, the wedge 33 is formed with wings 28 and thus has the shape of the letter V, opening between the V-shaped prongs. The partially open structure reduces the amount of raw material and the design is also suitable for manufacturing by pultrusion. The groove 27 may then have been integrated into the shape of the lamella 25 during moulding, or the groove 27 may be machined deep to form a V-shaped design. On the other hand, doctor blades may be manufactured by combining several components. For example, a key-like member may be secured to a wedge-shaped blade blank. At the same time, the capacity for removing water is large. Thus, any overflow will be avoided. In addition, water may flow laterally in the deep grooves towards the end of the doctor blade. This helps to drain water.

The doctor blade according to the invention is so versatile in design that it can be adapted to almost all known blade holders. Furthermore, the surprising drainage function makes most scraping locations and requirements possible. Moreover, the new doctor blade can be put into use without major equipment changes or investments. When the water is properly discharged, the foil effect of the doctor blade is maintained, thereby effectively absorbing the water. In addition, a doctor apparatus with a single doctor blade can be installed even in a narrow position. Despite the through-holes and grooves, the doctor blade according to the invention may also be used in the doctor apparatus shown in fig. 1.

Claims

1. A doctor blade for a fiber web machine, which doctor blade (11) comprises a foil portion (14) with a sharp tip (21), characterized in that a plurality of through-holes (22) are present in the foil portion (14) distributed over substantially the entire length (L) of the doctor blade (11).

2. A doctor blade as claimed in claim 1, characterized in that the foil portion (14) comprises foils (25) starting from the sharp point (21) and foil necks (32) at opposite ends of the foil portion (14).

3. A doctor blade as claimed in claim 2, characterized in that each through-hole (22) is a round hole (23) having a diameter (D) which is larger than the thickness (T) of the foil neck (32).

4. A doctor blade as claimed in any one of claims 1 to 3, characterized in that the through-holes (22) are oriented perpendicularly or slightly obliquely with respect to the doctor blade (11).

5. A doctor blade as claimed in any one of claims 1 to 4, characterized in that the foil portion (14) comprises a wedge-shaped portion (33) with a large head (26), which tapers towards the sharp point (21), and the through-hole (22) is located in the region of the head (26).

6. A doctor blade as claimed in claim 5, characterized in that there is an angle (α) between the head (26) and the foil neck (32), which angle (α) is 100-160 degrees, preferably 120-140 degrees.

7. A doctor blade as claimed in claim 6, characterized in that the head (26) is provided with a groove (27) extending substantially over the entire length (L) of the doctor blade (11), and that the through-hole (22) is arranged to open onto the groove (27).

8. A doctor arrangement in a fiber web machine, in which, in the vicinity of an open surface (10) to be doctored, a doctor blade (11) is arranged, which doctor blade comprises a foil portion (14) with a sharp tip (21), characterized in that, in the foil portion (14), there are a number of through holes (22) distributed over substantially the entire length (L) of the doctor blade (11), and that the tip (21) is arranged to point downwards.

9. Doctor arrangement according to claim 8, characterized in that the doctor blade (11) included in the doctor arrangement is a doctor blade according to any of claims 2-7.

10. A blade arrangement according to claim 8 or 9, characterized in that the open surface (10) belongs to a roll (16), advantageously a couch roll.