CN114341429A

CN114341429A - Former for producing a fibrous material web in a paper machine

Info

Publication number: CN114341429A
Application number: CN202080060339.4A
Authority: CN
Inventors: V.施密特-罗尔; T.鲁尔
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2019-08-26
Filing date: 2020-08-11
Publication date: 2022-04-12
Also published as: WO2021037548A1; DE102019122784A1; EP4022126A1

Abstract

The invention relates to a former for a paper machine for producing a fibrous web (1), in particular a paper, cardboard, tissue or packaging paper web, comprising a forming wire (2) forming a loop, on which forming wire (2) the fibrous web (1) is located and is guided together by means of a turning roll (3) located in the loop to a pick-up point (4), at which the fibrous web (1) is received from the forming wire (2) by means of a clothing (6), wherein, immediately before the pick-up point (4) and immediately after the turning roll (3), a suction-capable suction element (7) having an opening (9) facing the forming wire (2) is arranged in the loop. The invention is characterized in that the deflecting roller (3) is non-suction-capable and has at least one helically running groove (10) on the surface in the circumferential direction, and preferably the suction element (7) is designed as a high-vacuum suction.

Description

Former for producing a fibrous material web in a paper machine

The invention relates to a former for a paper machine for producing a fibrous web, in particular paper, cardboard, tissue or packaging paper web. The former includes a forming wire forming a loop on which the fibrous web is positioned and guided together by turning rolls positioned within the loop to a pick-up point where the fibrous web is received from the forming wire by a clothing. Immediately before the pick-up point and immediately after the turning roll, a suction-capable suction element having an opening facing the forming wire is arranged in the loop.

Such devices are known. Document WO2013026597 a1 describes a twin-wire former with a first wire which is guided together with the fibrous web through grooved, drilled or otherwise structured guide rollers which are not directly sucked through a roller housing. This structure in the surface of the guide roller prevents the fibrous web from floating.

Despite these measures, floating cannot be completely prevented in the known devices. Furthermore, the dry weight content of the fibrous web at the pick-up point is too low compared to known formers with screened suction rolls, which leads to expensive and high running costs. This results in a higher load on the downstream press section in terms of dewatering capacity.

The technical problem to be solved by the invention is therefore to improve the known former such that the running performance of the fibrous web is better and the load of the press section is lower.

This object is achieved by the features of claim 1. A former for a paper machine for producing a fibrous web, in particular paper, paperboard, tissue or wrapping paper web, is proposed. The former comprises a forming wire forming a loop, on which the fibrous web is located and guided together by turning rolls located in the loop to a pick-up point, where the fibrous web is received from the forming wire by a clothing, wherein immediately before and immediately after the pick-up point, in the loop, a suction-capable suction element having an opening facing the forming wire is arranged. According to the invention, the deflecting roller is not suction-proof and has at least one helically running groove on the surface in the circumferential direction, and the suction element is preferably designed as a high-vacuum suction.

In order to avoid inefficient energy consumption, the deflecting roller is suction-free, i.e. it is not suction-free both from the inside and from the outside.

The spiral design of the at least one groove improves the holding properties and the discharge of air which is entrained into the winding wedge gap between the forming wire and the turning roll by the boundary layer of air formed on the inner side of the forming wire.

The grooved region of the surface of the deflecting roller preferably corresponds at least to the width of the fibrous web, in particular the entire width of the deflecting roller.

The at least one helically extending slot extends between a drive side and an operator side of the former. The beginning and the end of the groove are open, whereby the air enclosed between the forming wire and the surface of the turning roll can flow in the groove. The accommodation of air into the groove is likewise improved. This prevents the fiber web from floating and improves the traveling performance of the fiber web. Furthermore, the at least one helically running groove suppresses marking in the fibrous web compared to a groove arranged concentrically to the cross section of the deflecting roller. Thereby preventing the quality of the fiber web from being reduced.

These advantages are particularly effective at high speeds and high grammages of the fibrous web. Preferably the speed is greater than 800m/min, especially greater than 1000m/min, preferably greater than 1100 m/min. The gram weight is more than 70g/m 2.

In a possible embodiment, the former is designed as a hybrid former or a gap former.

In an advantageous further development, the deflecting roller has at least two helically running grooves on the surface in the circumferential direction.

The two grooves may start at the edge of the turning roll.

But they may also start at the centre of the turning roll. In this case, the orientations of the spirals are opposite to each other.

It is basically also conceivable to arrange more than two helically running grooves.

In case there are a plurality of helically extending grooves, they may also extend between the drive side and the operator side of the former. The beginning and end of the plurality of grooves are open whereby air enclosed between the forming wire and the surface of the turning roll can flow within the grooves. This applies correspondingly also to the possible case, i.e. the groove starts in the centre of the turning roll. The accommodation of air in the groove is also improved in this case. This prevents the fiber web from floating and improves the traveling performance of the fiber web. Furthermore, the plurality of helically extending grooves suppresses marking in the fibrous web compared to grooves arranged concentrically to the cross section of the deflecting roller. In this possible embodiment, a reduction in the quality of the fibrous web is thus avoided.

It is particularly advantageous if the groove depth is at least 1mm, preferably at least 3 mm. Thereby facilitating the accommodation of air into the slot.

Preferably, the surface of the opening of the turning roll is more than 10% and less than 75%. Thus, the unopened face of the turn roll surface between the grooves is preferably less than 90% and more than 25%. The sum of the surface of the unopened face and the surface of the opening constitutes the surface of the outer circumferential face of the steering roller.

In a practical development that is possible, a further suction element with an opening facing the forming wire is arranged in the ring immediately before the turning roll.

Furthermore, the suction element and/or the further suction element can be designed as a high-vacuum aspirator and can be dimensioned such that a vacuum of greater than or equal to 40kPa, in particular greater than or equal to 52kPa, preferably greater than 60kPa, can be applied. This facilitates a higher dry weight content of the fibrous web before the pick-up point.

Preferably, the opening is designed as a suction slot.

Furthermore, the slot width of the suction slot may be less than or equal to 25mm, preferably less than or equal to 20mm, in particular less than or equal to 17 mm. In combination with the high vacuum, this reduces wear of the forming wire and reduces the driving power of the former.

These openings can also be designed as suction openings. The diameter of the suction apertures may be less than or equal to 27mm, preferably less than or equal to 22mm, in particular less than or equal to 18mm, in particular less than or equal to 16 mm.

The invention also extends explicitly to those embodiments which are not given by the combination of features explicitly cited in the claims, and the features disclosed in the invention can therefore be combined with one another in any desired manner, as far as this is technically possible.

Further features and advantages of the invention will emerge from the following description of a preferred embodiment with reference to the accompanying drawings.

In the attached drawings

FIG. 1 shows a simplified schematic of a cross-sectional portion of a former;

FIG. 2 shows a simplified schematic of an embodiment of a grooved surface of a turning roll;

FIG. 3 shows a simplified schematic of another embodiment of a grooved surface of a turning roll;

fig. 4a shows a simplified schematic cross-sectional view of a part of the outer circumference of a turning roll with a possible embodiment of a groove;

fig. 4b shows a simplified schematic cross-sectional view of a part of the outer circumference of a turning roll with a further possible embodiment of the groove;

fig. 1 shows a simplified cross-sectional view of a part of a former of a paper machine for producing a fibrous web, in particular paper, paperboard, tissue or wrapping paper web, according to the invention. In this example, the shaper is designed as a hybrid shaper. The former comprises a forming wire 2 forming a loop, on which forming wire 2 the fibrous web 1 is located and together are guided in the direction of travel 14 by turning rolls 3 located in the loop to a pick-up point, where the fibrous web 1 is received from the forming wire 2 by a clothing 6. Immediately before the pick-up point 4 and immediately after the turning roll 3, a suction-capable suction element 7 having an opening 9 facing the forming wire 2 is arranged in the loop. The deflecting roller 3 is non-suction-able and has at least one helically running groove 10 on its circumferential surface. The suction element 7 is designed as a high-vacuum aspirator. The grooved area of the outer circumferential surface of the deflecting roller 3 corresponds at least to the width of the fibrous web 1. The grooved region may also extend axially over the entire width of the deflecting roller 3. In this example, a helically extending groove 10 is provided on the outer circumferential surface of the turning roll 3. It extends between the drive side and the operator side of the former, i.e. transversely to the direction of travel 14 of the fibrous web. The beginning and the end of the groove 10 are open, whereby the air enclosed between the forming wire 2 and the surface of the turning roll can flow in the groove 10. The accommodation of air into the tank 10 is likewise improved. This prevents the fiber web 1 from floating and improves the traveling performance of the fiber web 1. Furthermore, marks in the fibrous web are suppressed by the grooves 10 compared to grooves arranged concentrically to the cross section of the deflecting roller. This prevents a deterioration of the quality of the fibrous web 1. The groove depth 11 is 1.5 mm. It may also be at least 3 mm. Thereby facilitating the accommodation of air into the tank 10. The open surface of the turning roll 3 is illustratively 42%, and the open surface of the turning roll 3 between the grooves 10 is 58%. Immediately before the turning roll 3, inside the loop there is also arranged a further suction element 8, which further suction element 8 has an opening 9 facing the forming wire 2. The further suction element 8 is also designed as a high-vacuum aspirator, which is dimensioned to apply a vacuum of greater than or equal to 40 kPa. This facilitates a higher dry weight content of the fibrous web before the pick-up point. The opening 9 is designed as a suction slit and has a slit width of less than 25 mm. The suction element 7 and the further suction element 8 are connected to a suction device 13 for generating a vacuum.

Fig. 2 shows a simplified schematic view of an embodiment of the grooved surface of the turning roll 3. In this example, two helically extending grooves 10 are machined in the surface of the turning roll 3. They each start in the center of the turning roll 3 and extend to the respective edge of the turning roll 3, i.e. in the direction of the drive side or the operator side. The orientation of the spirals are opposite to each other. The unopened face 12 in this example was 58%.

Fig. 3 shows a simplified schematic illustration of a further embodiment of the grooved surface of the deflecting roller 3 with only one groove 10. The grooved area of the surface of the turning roll 3 extends over the entire width of the turning roll 3. The unopened face 12 in this example was 58%. The helically extending slot 10 extends between a drive side and an operator side of the former. The beginning and the end of the groove 10 are open, whereby the air enclosed between the forming wire 2 and the surface of the turning roll can flow in the groove 10. The accommodation of air into the tank 10 is likewise improved.

Fig. 4a and 4b each show a simplified sectional view of a part of the outer circumference of the deflecting roller 3 with a possible embodiment of the groove 10. The cross section of the groove 10 is rectangular in fig. 4a, with a groove depth 11 of 1.5 mm. The unopened surface 12 was also 58% in this example. In contrast fig. 4b shows a circular cross-sectional shape of the groove 10 with a groove depth 11 of 1.3 mm. The unopened surface 12 was also 58% in this example.

The various features described in the embodiments are not limited to the respective embodiments, but may be explicitly combined or interchanged with one another as long as no contradiction arises. Likewise, the examples do not limit the scope of the invention. Any possible combination or partial combination of the features of the invention is considered to be within the scope of the invention.

List of reference numerals:

1 fibrous web

2 Forming wire

3 turning roll

4 pick up point

5 pick-up roller

6-mesh blanket

7 suction element

8 additional suction element

9 opening

10 groove

10.1 second groove

11 groove depth

12 surface not opened

13 suction device

14 direction of travel

Claims

1. A former for a paper machine for producing a fibrous web (1), in particular a paper, paperboard, towel or wrapping paper web, which former comprises a forming wire (2) forming a loop, on which forming wire (2) the fibrous web (1) is located and is guided together to a pick-up point (4) by means of a turning roll (3) located in the loop, receiving the fibrous web (1) from the forming wire (2) by means of a clothing (6) at the pick-up point, wherein immediately before the pick-up point (4) and immediately after the turning roll (3), arranged within the ring is a suction-capable suction element (7) having an opening (9) facing the forming wire (2), characterized in that the deflecting roller (3) is non-suction-able and has at least one helically running groove (10) on the surface in the circumferential direction, and preferably the suction element (7) is designed as a high-vacuum suction.

2. The apparatus of claim 1,

the deflecting roller (3) has at least two helically running grooves (10) on the surface in the circumferential direction.

3. The apparatus of claim 2,

two troughs (10) start at the edge of the turning roll (3) or two troughs (10) start at the centre of the turning roll (3).

4. Device according to one of the preceding claims,

the groove depth (11) is at least 1mm, preferably at least 3 mm.

5. Device according to one of the preceding claims,

the surface of the opening of the turning roll (3) is greater than 10% and less than 75%.

6. Device according to one of the preceding claims,

immediately before the turning roll (3) inside the loop there is also arranged a further suction element (8), which further suction element (8) has an opening (9) facing the forming wire (2).

7. Device according to one of the preceding claims,

the suction element (7) and/or the further suction element (8) is designed as a high-vacuum suction and is dimensioned to be able to apply a vacuum of greater than or equal to 40kPa, in particular greater than or equal to 52kPa, preferably greater than 60 kPa.

8. Device according to one of the preceding claims,

the opening (9) is designed as a suction slot.

9. The apparatus of claim 8,

the suction slot has a slot width of less than or equal to 25mm, preferably less than or equal to 20mm, in particular less than or equal to 17 mm.

10. Device according to one of the preceding claims,

the opening (9) is designed as a suction opening.

11. The apparatus of claim 10,

the diameter of the suction opening is less than or equal to 27mm, preferably less than or equal to 22mm, in particular less than or equal to 18mm, in particular less than or equal to 16 mm.