CN109996922B

CN109996922B - Squeezing device

Info

Publication number: CN109996922B
Application number: CN201780072914.0A
Authority: CN
Inventors: J.莫瑟
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2016-12-05
Filing date: 2017-11-28
Publication date: 2020-12-25
Anticipated expiration: 2037-11-28
Also published as: EP3548664A1; EP3548664B1; CN109996922A; FI3548664T3; DE102016123433A1; DE102016123433B4; WO2018104110A1

Abstract

The invention relates to a press device for dewatering a paper, cardboard, tissue or other fibrous web (1) in a machine for producing and/or refining the paper, cardboard, tissue or other fibrous web (1), the press device comprises a suction roll (2) surrounded by a continuously surrounding, water-absorbing and air-permeable dewatering belt (4) and an outer fibrous web (1), and a cylindrical central roller (3) which is wound by a smooth and continuously-wound conveyor belt (6) and follows along the web running direction (5), the central roll and press rolls (17, 18) form at least one press nip (13, 14) and are surrounded by a continuously circulating, water-absorbing dewatering belt (15, 16), wherein the conveyor belt (6) is guided over the fibrous web (1) from the dewatering belt (4) of the suction roll (2). The dewatering without loss of volume is to be achieved while the web is as smooth as possible by the suction roll (2) and the transfer press roll (7) forming a transfer press nip (12) through which the dewatering belt (4) and the transfer belt (6) of the suction roll (2) run together with the fibrous web (1) located therebetween.

Description

Squeezing device

Technical Field

The invention relates to a press device for dewatering a paper, cardboard, tissue or other fibrous web in a machine for producing and/or refining the paper, cardboard, tissue or other fibrous web, having a suction roll surrounded by a continuously surrounding, water-absorbing and air-permeable dewatering belt and an outer fibrous web, and a subsequent cylindrical central roll surrounded in the web running direction by a smooth, continuously surrounding conveyor belt, which central roll forms at least one press nip with a press roll, which press roll is surrounded by a continuously surrounding, water-absorbing dewatering belt, wherein the conveyor belt passes over the fibrous web from the dewatering belt of the suction roll.

Background

Such a press device is known and offers, due to its compactness, advantages in terms of cost in addition to advantages in terms of space.

However, the problem here is the transfer of the fibrous web onto the conveyor belt.

Furthermore, subsequent offset printing (offset pressure) is often necessary to remove the felt marks in the fibrous web, which is associated with a loss in volume and rigidity.

Disclosure of Invention

The object of the invention is therefore to ensure effective dewatering when reliably guiding a web.

According to the invention, the object is achieved in that the suction roll and the transfer press roll form a transfer press nip, through which the dewatering belt and the conveyor belt of the suction roll run together with the fibrous web located between the dewatering belt and the conveyor belt.

The construction of the press is significantly simplified by the spacing between the suction roll and the central roll and the decoupling associated with said spacing. The transfer press gap ensures a reliable transfer of the web from the dewatering belt to the significantly smoother, impermeable transfer belt. The dewatering belt should accordingly also be guided away from the fibrous web directly after the transfer press nip in order to prevent the fibrous web from getting wet, so that the fibrous web is guided from the transfer press nip to the central roll only by the conveyor belt.

In order to ensure that the fibrous web is securely attached to the transport belt, it is advantageous if the transport belt extends vertically between the transfer press nip and the central roll or extends in the web running direction at an inclination of at most 35 ° to the vertical.

Furthermore, dewatering can also be assisted by the increased viscosity due to heating of the fibrous web. For this purpose, the fibrous web should be steamed by a steam jet box or steam bubble box between the transfer press nip and the central roll.

In order to make full use of the central roll, it is advantageous if the central roll forms a press nip with at least two press rolls, which are each surrounded by a separate, continuously surrounding and water-absorbing dewatering belt.

In order to dewater deeply, but nevertheless without loss of volume, at least one press nip of the cylindrical central roll should be constructed to be lengthened. The extended press nip is generally constituted in a known manner by a shoe press roll having a flexible sleeve which runs over a press shoe (anspressschuh) having a concave press surface in the region of the press nip.

To limit the expenditure, it is generally sufficient to design only the last press nip of the central roll to be lengthened. However, if both press nips of the central roll are constructed to be lengthened, the dewatering efficiency can be optimized.

In order for the central roll to also provide sufficient space for the location to achieve multiple press nips, the central roll should have a diameter of at least 100cm, preferably at least 160 cm.

In order to make full use of the suction roll, it should form a press nip, preferably the first press nip of the press, with a press roll surrounded by a continuously circulating, water-absorbing dewatering belt. Since the moisture content of the fibrous web is still relatively high, a low pressing force is sufficient here.

Furthermore, it may be advantageous for the heating of the fibrous web to provide the fibrous web with a steam bubble box in the wrap region of the suction roll before the press nip is handed over.

In order to guide the web reliably, the dewatering belt of the suction roll should take over the fibrous web from a continuously surrounding belt, preferably from a forming screen of a former for forming the web, and/or transfer the fibrous web after the central roll from a conveyor belt onto a continuously surrounding belt, preferably onto an air-permeable drying screen of a following drying unit of the machine.

At high machine speeds and/or high weights per unit area, it is advantageous here if the fibrous web is guided between the former and the drying unit by at least one belt at all times.

Dewatering can also be assisted by the fact that, before the transfer of the fibrous web, the forming screen is guided together with the continuously surrounding, water-absorbing dewatering belt and the fibrous web located between the forming screen and the dewatering belt through the pre-press gap.

Drawings

The invention is illustrated in detail in the examples below. In the drawings a schematic view of a press device according to the invention is illustrated.

Detailed Description

The press device is used for dewatering a fibrous web 1, in particular a cardboard web, in a paper machine in order to produce the fibrous web, in particular the cardboard web.

A high rigidity of the cardboard should be achieved here by effective, but nevertheless volume-free dewatering of the fibrous web 1. In addition, a smooth transfer belt produces a good cardboard surface, so that offset printing, which is usually subsequent, can be dispensed with.

After the web has been formed in the former, the fibrous web 1 is transferred from the water-permeable forming screen 22 to the water-permeable and air-permeable first dewatering belt 4 of the subsequent press device.

However, a pre-dewatering of the fibrous web 1 is also carried out before the transfer. For this purpose, the forming screen 22 and the water-absorbing fifth dewatering belt 23 and the fibrous web 1 located between them are guided together through the pre-press nip 10 formed by the fourth press roll 24 and the fifth press roll 25.

A first dewatering belt 4, which takes over the fibrous web 1 from the forming screen 22, is arranged above the fibrous web and the fibrous web 1 is guided through the first press nip 11 together with a fourth dewatering belt 19 running below the fibrous web 1. The first press nip 11 is formed here by a lower cylindrical third press roll 20 and a suction roll 2 above said third press roll. However, the third press roll 20 may also be a shoe press roll.

Since the moisture content or moisture content of the fibrous web 1 is high, a relatively low pressing force is sufficient here, wherein the water produced is drained off via the first dewatering belt 4, the fourth dewatering belt 19 and the suction roll 2.

After the first press nip 11, the fiber web 1 is heated in the wrap region of the suction roll 2 by the application of steam by means of the second steam bubble box 9, which promotes dewatering of the fiber web 1.

The fibrous web 1 is then transferred from the upper first dewatering belt 4 onto a water-impermeable and smooth conveyor belt 6 arranged below the fibrous web 1. For this purpose, the first dewatering belt 4, the conveyor belt 6 and the fibrous web 1 located between them are guided through a transfer press nip 12 formed by a suction roll 2 and a cylindrical transfer press roll 7.

The belt 6 guides the upper fibrous web 1 around a central roller 3 rotating below the belt 6 and after passing around the central roller 3 transfers it to an upper, continuously surrounding and air-permeable drying screen 21 of the next drying unit of the paper machine.

The subsequent drying unit is formed by a dryer group in which the fibrous web 1 is guided alternately, supported by a drying screen 21, past a heated drying drum 26 and a first guide roller 27 for drying.

The fibrous web 1 is thus guided between the former and the drying unit at all times by at least one of the first dewatering belt 4 and the conveyor belt 6, which makes the guidance of the web very stable even at high machine speeds and high weights per unit area of the fibrous web 1.

The clear distance between the suction roll 2 and the central roll 3 is between 250 and 2000 mm. The construction of the press is significantly simplified by decoupling the suction roll 2 and the central roll 3. This distance is also necessary in particular because the contact of the central roll 3 with the suction roll 2 cannot be achieved due to the handover of the pressure roll 7.

In order to reliably guide the fibrous web 1 on the conveyor belt 6 between the suction roller 2 and the central roller 3, the conveyor belt 6 extends vertically in this section or, as shown in the drawing, slightly obliquely to the vertical in the machine running direction.

Furthermore, the fibrous web 1 is again steamed by the first steam bubble box 8 between the handover press gap 12 and the central roll 3. The cylindrical central roll 3 with a diameter of more than 160cm is relatively large, so that the second press nip 13 and the third press nip 14 can be formed in the wrap area of the conveyor belt 6 with the fibrous web 1 located outside.

A second press nip 13 in the web running direction 5 is formed here between the central roll 3 and a cylindrical first press roll 17 surrounded by a separate second dewatering belt 15.

The next third press nip 14 is of elongated design. Here, a second press roll 18 of the shoe type, which is likewise wrapped continuously around the third dewatering belt 16, presses against the central roll 3.

The second press roll 18 of the shoe type is usually constituted by a flexible roll jacket running over the press shoe with a concave press surface in the region of the elongated third press nip 14.

The first, second, third, fourth and

fifth dewatering belts

4, 15, 16, 19 and 23, which are continuously surrounding, are used to absorb and transport away the water pressed out of the fibrous web 1 in the respective pre-press gap 10, first press gap 11, transfer press gap 12, second press gap 13 and third press gap 14, and are mostly designed as press felts.

The reception of the fibrous web 1 is usually assisted by a second and third

suction guide roller

28, 29, which

guide rollers

28, 29 are enclosed by the first dewatering belt 4 or the drying screen 21 for reception.

The second and third

suction guide rollers

28, 29 have for this purpose perforated roller sleeves, the inner space of which is connected to a source of underpressure.

Claims

1. A press device for dewatering a fibrous web (1) having a suction roll (2) surrounded by a continuously surrounding, water-absorbing and air-permeable first dewatering belt (4) and an outer fibrous web (1) and a subsequent, cylindrical central roll (3) surrounded in the web running direction (5) by a smooth, continuously surrounding transfer belt (6), which central roll forms a second press nip (13) or a third press nip (14) with a first press roll (17) or a second press roll (18), which first press roll (17) or second press roll (18) is surrounded by a continuously surrounding, water-absorbing second dewatering belt (15) or third dewatering belt (16), wherein the transfer belt (6) passes the fibrous web (1) from the first dewatering belt (4) of the suction roll (2), the suction roll (2) and the transfer press roll (7) form a transfer press nip (12) through which a first dewatering belt (4) and a conveyor belt (6) of the suction roll (2) run together with a fibrous web (1) located therebetween, characterized in that the central roll (3) and at least a first press roll (17) and a second press roll (18) form a second press nip (13) and a third press nip (14), respectively, the first press roll (17) and the second press roll (18) being surrounded by a continuously surrounding, water-absorbing second dewatering belt (15) and a third dewatering belt (16), respectively.

2. Press device according to claim 1, characterized in that the suction roll (2) and the central roll (3) are spaced apart from each other and the fibrous web (1) is guided from the handover press nip (12) to the central roll (3) only by the conveyor belt (6).

3. Press device according to claim 1 or 2, characterized in that the transfer belt (6) extends vertically between the handover press nip (12) and the central roll (3) or in the web running direction (5) at an inclination of not more than 35 ° to the vertical.

4. Press device according to claim 1, wherein the fibrous web (1) is steam-loaded by the first steam bubble box (8) between the handover press nip (12) and the central roll (3).

5. A press device as claimed in claim 1, characterized in that at least one of the second press nip (13) and the third press nip (14) of the central roll (3) is designed to be elongated.

6. A press device as claimed in claim 1, characterized in that the second press nip (13) and the third press nip (14) of the central roll (3) are designed to be elongated.

7. Press device according to claim 1, characterised in that the central roll (3) has a diameter of at least 100 cm.

8. Press device according to claim 7, wherein the central roll (3) has a diameter of at least 160 cm.

9. A press device according to claim 1, characterised in that the suction roll (2) forms the first press nip (11) of the press device with a third press roll (20) surrounded by a continuously surrounding, water-absorbing fourth dewatering belt (19).

10. Press device according to claim 1, wherein the fibrous web (1) is provided with a second steam bubble box (9) in the wrap area of the suction roll (2) before the press gap (12) is handed over.

11. Press device according to claim 1, characterized in that the fibrous web (1) is handed over from the conveyor belt (6) to a continuously surrounding belt after the central roll (3).

12. Press device according to claim 11, characterized in that the fibrous web (1) is handed over from the conveyor belt (6) after the central roll (3) to the air-permeable drying screen (21) of the immediately following drying unit of the machine.

13. Press device according to claim 1, characterised in that the first dewatering belt (4) of the suction roll (2) takes over the fibrous web (1) from a continuously encircling belt.

14. Press device according to claim 13, characterised in that the first dewatering belt (4) of the suction roll (2) is passed over the fibrous web (1) from the forming screen (22) of the former for web formation.

15. A press device according to claim 14, characterized in that the fibrous web (1) is guided between the former and the drying unit at all times by at least one of the first dewatering belt (4) and the transfer belt (6).

16. Press device according to claim 15, wherein the forming screen (22) is guided through the pre-press nip (10) together with the continuously surrounding, water-absorbing fifth dewatering belt (23) and the fibrous web (1) located between the forming screen and the fifth dewatering belt before the fibrous web (1) is delivered.