DE19955810A1 - Web pick-up point for the paper/cardboard web between the former and press sections has structured movement paths reducing overpressure - Google Patents

Abstract

Web pick-up point for the paper/cardboard web between the former and press sections has structured movement paths for the fourdriniers and pick-up blanket to deflect the carried air streams and reduce overpressure. At the web (W) pick-up point (N0), between the web former and press sections, the shortest gap (d) between the outer surface (30a) of the pick-up blanket (30) and the outer circumference of the leading guide roller (12') of the outer fourdrinier (10) is <= 300 mm. The rising angle ( alpha ) between the tangent plane (T1) from the circumferences of the guide rollers (12'.32') and the horizontal plane (VT) is <= 80 deg . The extension (C1) of the path (C) of the pick-up blanket (30), between two guide rollers (32',32), intersects (P1) a vertical plane (PT) through the center (M12') of the axis of the guide roller (12') for the outer fourdrinier (10), at a point over the intersection (P0) of the vertical plane (PT) and the circumference of the fourdrinier guide roller (12'). The air stream (I1), carried by the pick-up blanket (30), is not directed at the pick-up point (N0), but is detached from the blanket surface by the centrifugal forces where the blanket (30) is deflected round the first guide roller (32') and the normal overpressure at the pick-up point can be reduced. The outer fourdrinier (10) pumps air (I2) from the zone (50) in front of the pick-up point N0), defined by the inner fourdrinier (20) and the pick-up blanket (30). The rising angle ( alpha ) is pref. <= 60 deg . The loop angle ( beta ) of the pick-up blanket (30) at the leading guide roller (32') is \-45 deg or \-90 deg . The extension (C1) of the pick-up blanket path (C) intersects the path (D) of the outer fourdrinier (10) between its guide rollers (12',12) at a point (P2) at a gap from the intersection (P0) of the vertical plane (PT) with the circumference of the first guide roller (12'). The leading guide roller (32'), for the pick-up blanket (30), is a guide roller in front of the pick-up roller (31) in the direction (S30) of the blanket movement. One or more intermediate rollers can be between the pick-up roller (31) and the leading guide roller (32') of the blanket (30).

Description

The invention relates to one in the preamble of the patent Proverb 1 defined arrangement for reducing the over pressure at the pick-up point of the web between the former and the press section of a paper or board machine.

In the state-of-the-art solutions in which the formed web from the inner wire of the former to the pick-up cloth the press section is transferred occurs in the pick-up presses gap between the pick-up roller and the inner wire strong Blowing on the area around the pick-up area and the Edge syringes dirty and at the same time the running sheep paper or board machine. This Blowing is mainly due to that of the pick-up cloth and air carried into the pick-up gap.

The essential features of the arrangement according to the invention are defi in the labeling part of claim 1 kidney.  

The invention is based on the fact that on the two-wire part of the former following guide roller of the outer wire and the Guide roller of the pick-up cloth of the press section preferably be placed close together. For the pick-up cloth is a sufficient loop angle around the guide roller of the Pick-up wipes are provided so that the ones from the pick-up wipe entrained air due to the centrifugal force of the Pick-up cloth on the guide roller of the pick-up cloth peels off where due to the air carried by the pick-up cloth not into the Pick-up point reached. In addition, by appropriate arrangement the run of the pick-up cloth and the run of the outside siebs created a situation in which the outer screen air pumps away from the pick-up point, which increases the excess pressure in the pick-up point and that of the inner strainer Air volume transported to the pick-up point reduced. There this keeps the pick-up point and the edge syringes clean As a result, business interruptions are reduced like and the efficiency of the machine improves. The Reducing the overpressure at the pick-up point affects also favorable for the transfer of the web from the wire section to the press section. The web can do the pick-up cloth better consequences.

In the constructions of the prior art, the air quantity I coming into the pick-up gap is obtained assuming a machine width of 10 m and a machine speed of 2,000 m / min as well as one carried by the inner screen and the pick-up cloth Air layer of 100 mm as follows:

I = 0.1 m × 10 m × 33 m / s × 2 = 66 m ³ / s.

It is therefore quite considerable air amount due to the environment of the pick-up point and the Contaminate edge syringes.

In the following the invention with reference to the Figures of the accompanying drawing described on the However, the details of the invention are not limited should.

In Fig. 1 a schematic representation is shown of the arrangement according to the invention forming section-applying solution.

Fig. 2 shows an enlargement of the apparent from Fig. 1 transition between the former and the press section.

A variant of the solution according to FIG. 2 is shown in FIG. 3.

FIG. 4 shows a second variant of the solution according to FIG. 2.

In Fig. 5 a third variant of the solution according to Fig. 2 is shown.

In Fig. 6, an embodiment of the invention is shown ge, in which the pick-up cloth is a band.

In Fig. 7, an alternative embodiment of the invention is shown.

In Fig. 1, a two-wire former is shown on the left, which consists of an outer wire 10 guided by guide rollers 12 and an inner wire 20 guided by guide rollers 22 , from which the web W formed is removed with the pick-up cloth 30 of the press section. The former has a formation gap G, into which the stock suspension jet J is fed from the lip opening of the headbox. Formation of the gap G is within the roller by the existing Außensiebschleife 10 with a negative pressure zone 11 equipped formation roller 11 and the breast located within the Innensiebschleife 20 21 determined. An upward-running two-wire zone A is formed between the outer wire 10 and the inner wire 20 behind the formation gap G. The two-wire zone A ends at the suction zone 23 a which prevails within the inner wire loop 20 and which is the deflection suction roller 23 .

On the outlet side of the suction zone 23 a of the Umlenksaug roller away the outer wire 10 guided from the inner wire 20 and runs from the the guide suction roll 23 following guide roll 12 'of the outer wire 10 and the other guide rolls 12' ', 12 of the outer wire 10 23 back to the formation roll 11 , whereby it forms a closed outer sieve loop.

Behind the outlet side of the vacuum zone 23 a of the deflection suction roller 23 , the web W follows the inner wire 20 , from which the web W is removed at the pick-up point N ₀ between the inner wire 20 and the pick-up roller 31 . The web W is removed from the inner wire 20 with the aid of the vacuum zone 31 a of the pick-up roller 31 , with which the web W is also attached to the pick-up cloth 30 . The pick-up point N _{0 is} located on the between the deflection suction roller 23 of the inner screen 20 and the following guide roller 22 'of the inner screen 20 on a downward inclined train B near the guide roller 22 ' of the inner wire 20th Behind the guide roller 22 'of said inner wire 20 , the inner wire 20 is guided by guide rollers 22 back to the breast roller 21 . The direction of rotation of the outer wire 10 is identified in the figure by the reference number S ₁₀ and the direction of rotation of the inner wire 20 accordingly by the reference character S ₂₀ .

The pick-up cloth 30 of the press section runs after the pick-up roller 31 in the first press nip N ₁ formed from a press roller 33 and a counter roller 43 , after which the pick-up cloth 30 is guided into the return line by guide rollers 32 . After the web in the suction zone 31a of the pick-up Wal ze 31 is attached to the pick-up fabric 30 W, the web W from the pick-up fabric 30 is supported in the first press nip _N1 transferred, which the web W runs between the pick-up cloth 30 on the top and the press cloth 40 on the bottom. The direction of rotation of the pick-up cloth 30 is identified in the figure by the reference symbol S ₃₀ and the direction of rotation of the press cloth 40 accordingly by the reference symbol S ₄₀ .

In Fig. 1, a solution from the prior art is also drawn in the chain line, in which the pick-up cloth 30 'directly from the guide roll 32 ''preceding the pick-up roll 32 ' of the aforementioned pick-up cloth 30 Pick-up cloth 30 runs to pick-up roller 31 . In a solution of this type, the air carried by the pick-up cloth 30 'and the lower sieve 20 flows directly into the pick-up press nip N ₀ , which creates overpressure in the pick-up press nip N ₀ and the environment Pick-up press nips N ₀ and the edge syringes get dirty.

FIG. 2 shows the arrangement between the former and the press section according to FIG. 1 as an enlargement, from which the solution according to the invention can be seen more clearly. The solution according to the invention is based on the fact that the penetration of the air flow I ₁ carried by the pick-up cloth 30 into the pick-up point N _{0 is} prevented and that air is removed before the pick-up point N ₀ . This can be achieved if the solution meets the following three conditions:
Due to the first condition, the shortest distance d between the outer surface 30 a of the pick-up cloth 30 and the outer circumference of the first guide roller 12 ′ of the outer sieve 10 following the deflection suction roller 23 in the direction of rotation S ₁₀ of the outer sieve 10 is less than 300 mm.

Due to the second condition, the rise angle α lies between the first guide roller 12 'of the outer screen 10 which follows the deflection suction roller 23 in the direction of rotation S ₁₀ of the outer wire 10 and the upper outer peripheral half of the first guide roller preceding the pick-up roller 31 32 'of the pick-up cloth 30 located tangent plane T ₁ and the horizontal plane VT in the range α = 0 ° -80 °, preferably in the range α = 0 ° -6 °.

Due to the third condition, the lengthening C ₁ of the first guide roller 32 'of the pick-up towel 30 preceding the one in the direction of rotation S _{30 of} the pick-up towel 30 of the pick-up roller 31 and the guide roller 32 preceding this 'of the pick-up fabric 30 running train C of the pick-up fabric 30 passing through the center M _12' of the axis of the outer wire 10 to the guide suction roll 23 following in the rotational direction S ₁₀ first guide roll 12 'of the outer wire 10 Drawn designated in the axial direction lying vertical plane PT at point P ₁ , which lies above the intersection P _{0 of} the vertical plane PT with the upper outer circumferential half of the outer circumference of the first guide roller 12 'of the outer wire 10 or coincides with this.

It is also advantageous in the invention that the loop angle β of the pick-up cloth 30 on the first guide roller 32 ′ of the pick-up cloth 30 preceding the pick-up roller 31 is greater than 45 ° and preferably greater than 90 ° is.

With the help of the free distance d between the Außenflä surface 30 a of the pick-up cloth 30 and the outer circumference of the following guide roller 23 following the first guide roller 12 'of the sens sieve 10 , a channel of suitable width is achieved through which the outer sieve 10 air I ₂ from the triangular space in front of the pick-up gap N ₀ from the inner screen 20 and the pick-up cloth 30 can be limited. In this way, the excess pressure which arises in the space 50 mentioned can be reduced, the inner screen 20 also not carrying any appreciable amount of air into the pick-up gap N ₀ .

By the angle of rise α of the between the upper surfaces of the outer circumferences of the first guide roller 32 'of the pick-up cloth 30 and the first guide roller 12 ' of the outer screen 10 ge placed tangent plane T ₁ ensures that the ge mutual position of said first guide roller 32 'of the pick-up cloth 30 and the first guide roller 12 ' of the outer wire 10 is suitable. The highest point of the outer circumference of the first guide roller 32 'of the pick-up cloth 30 should be at least on the same horizontal plane as the highest point of the outer circumference of the first guide roller 12 ' of the outer screen 10 , so that the one carried by the pick-up cloth 30 Air flow I _{2 is} not guided too far down to the outer circumference of the first guide roller 12 'of the outer wire 10 , where it could prevent the outer wire 10 from pumping air from the space 50 in front of the pick-up nip N ₀ . The first guide roller 32 'of the pick-up cloth 30 , on the other hand, must not be too high with respect to the first guide roller 12 ' of the outer wire 30 , so that the pick-up cloth 30 runs between the first guide roller 32 'of the pick -up cloth 30 and the first guide roller 12 'of the outer wire 10 does not collect air again.

Due to the location of the point of intersection P ₁ between the lengthening C ₁ of the first guide roller 32 'between the pick-up roller 31 of the pick-up cloth 30 ' and the train C of the pick-up which runs before the second guide roller 32 ' -Tuch 30 and the center line M ₁₂ 'of the axis of the following the deflection suction roller 23 following the first guide roller 12 ' of the outer wire 10 drawn in the axial direction lying vertical plane PT ensures that the Rich direction of said train C of the pick-up cloth 30 is such that the carried by the pick-up fabric 30 air flow I ₂ not too far roll down to the outer circumference of the first Leit 12 'of the outer wire 10 is guided, where they sieve the outer 10 could prevent air to be pumped out of the space 50 located in front of the pick-up gap N ₀ .

With the sufficiently large loop angle β, it is seen that the air flow I ₁ carried by the pick-up cloth 30 is detached by the centrifugal force from the surface of the pick-up cloth 30 while the direction of travel of the pick-up cloth 30 Cloth 30 is changed on the first guide roller 32 '. This ensures that the air flow I ₁ carried by the pick-up cloth 30 cannot flow into the pick-up gap N ₀ .

In the situation according to FIG. 2, the extension C ₁ of the train C of the pick-up running between the first guide roll 32 ′ of the pick-up cloth 30 preceding the pick-up roll 31 and the preceding second guide roll 32 ′ hits the train C of the pick-up -Tuch 30 on the train D of the outer wire 10 running between the first guide roller 12 'of the outer wire 10 following the deflection suction roller 23 and the second guide roller 12 ' following this at the point P ₂ , which lies at a distance from the point at which the outer wire 10 detaches from the first of the guide rollers 12 'of the outer wire which follows the deflection suction roller 23 . In this way, an advantageous situa tion is achieved, in which the 30 th mitgeführ air flow from the pick-up fabric of the outer wire 10 is steered I ₁ on said train D, from where the outer wire 10, they are transported away.

In Fig. 3, a situation is shown, the situation of Fig. 2 corresponds to the direction of the inter mediate in the direction of rotation S _{30 of} the pick-up cloth 30 of the pick-up roller 31 preceding the first guide roller 32 'and this preceding second guide roller 32 ″ running train C of the pick-up cloth 30 . In the situation according to FIG. 2, the direction of the train C in question of the pick-up cloth 30 is such that the extension C _{1 of} the train in question intersects the outer sieve 10 at point P ₂ , which is between the direction of circulation S ₁₀ the guide suction roll 23 following the first guide roll 12 'of the outer wire 10 and the second guide roll following this 12' 'extending train D of the outer wire 10. In the situation according to FIG. 3, the lengthening C _{1 of} the relevant train C of the pick-up cloth 30 does not affect the train D of the outer sieve 10 at all. However, the invention works well in this situation. The entrained by the pick-up cloth air flow I ₁ is guided to above the outer wire 10 and the outer wire 10 pumps air I ₂ in front of the pick-up point N _0, and continues to run it in front of the pick-up point N ₀ off.

In FIG. 4 illustrates a situation in which the in the direction of rotation S ₃₀ of the pick-up fabric 30 of the pick-up roller 31 preceding first guide roll 32 'of the pick-up fabric 30 compared with the situation according to Fig. 2 with respect to the first guide roller 12 'of the outer wire 10 following the deflection suction roller 23 is located lower. In the situation according to FIG. 4, the extension C ₁ of the train C of the pick-up cloth 30 running between the first guide roll 32 'of the pick-up cloth 30 and the preceding second guide roll 32 ' meets the through the center of the axis of the guide suction roll 23 following the first guide roll 12 'of the outer wire 10 drawn kalebene in the axial direction lying Verti PT in the point P ₁ with the intersection point P ₀ Zvi said vertical plane PT and the upper half rule of the outer periphery of the first guide roll 12' of the Outer sieve 10 coincides. The air flow I ₁ carried by the pick-up cloth 30 is directed onto the outer screen, where it mixes with the air flow I ₂ pumped out of the outer screen 10 in front of the pick-up point N ₀ and as air flow I ₃ with the outer screen 10 moved away from the pick-up point N ₀ . If the extension C _{1 of} the mentioned train C of the pick-up cloth 30 would hit the said vertical plane PT below the point P ₀ , the air flow I _{1 carried} by the pick-up cloth 30 would be too far below the circumference He guide roller 12 'of the outer wire 10 are guided, whereby the pumping out of the air I _{2 of} the outer wire from the space 50 located in front of the pick-up gap N ₀ would be disturbed.

In FIG. 5, one extreme case is shown, wherein the uppermost point of the outer periphery of the guide suction roll 23 following the first guide roll 12 'fangs of the outer wire 10 on the same horizontal plane as the uppermost point of the Außenum of the pick-up roller 31 preceding the first Leitwal ze 32 'of the pick-up cloth 30 is. The angle α between the tangent plane T1 located between the upper halves of the outer circumferences of the first guide roller 12 'of the outer wire 10 and the first guide roller 32 ' of the pick-up cloth 30 and the horizontal plane VT is 0 ° in this embodiment. The between the pick-up roller 31 preceding the first guide roller 32 'of the pick-up cloth 30 and this preceding second guide roller 32 ' running train C of the pick-up cloth 30 is also in the horizontal plane, with the extension C _{1 of} the said train C of the pick-up cloth 30 on the vertical plane PT drawn at the point P ₁ by the center point M ₁₂ 'of the axis of the first guide roller 12 ' of the outer wire 10 following the deflection suction roll 23 , which meets the point of intersection P ₀ of said vertical plane PT and the upper half of the outer circumference of the first guide roller 12 'of the outer wire 10 coincide. The air flow I ₁ carried by the pick-up cloth 30 is guided to the outer sieve 10 , where it combines with the air flow I ₂ pumped out of the outer sieve 10 in front of the pick-up gap N ₀ and as the air flow I ₃ with the Outer screen 10 moved away from pick-up point N ₀ . If the first guide roller 32 'of the pick-up cloth 30 is lowered further with respect to the first guide roller 12 ' of the outer wire 10 , the air flow I ₁ carried by the pick-up cloth 30 interferes with the pumping out of the air I ₃ des Outer screen 10 from in front of the pick-up point N ₀ .

In FIG. 6 illustrates a situation in which the pick-up fabric 30, a so-called. Strap that is, a substantially non-water receiving transfer belt is. The pick-up nip N ₀ is here between the inside of the inner wire loop 20 at the end of the two-wire zone A of the former deflection suction roll 23 and the pick-up roll 31 is formed. The diameter of the deflection suction roll 23 is relatively large compared to the diameter of the pick-up roll 31 and the pick-up nip N _{0 also} works as a so-called pre-press nip, in which the web W through the inner wire 10 into the suction zone 23 a of the deflection suction roll 23 is dewatered. The pick-up roller 31 is preferably a roller with a closed jacket and a smooth surface. The invention can also be applied well to a construction of this type, in that the mutual position of the first guide roller 12 'of the outer wire 10 and that of the pick-up roller 31 ' preceding the first guide roller 32 'of the pick-up cloth 30 in a suitable manner Way is arranged. A shoe press nip serves as the first press nip N _{1 of} the press section.

In Fig. 7, a situation is shown in which between the pick-up roller 31 and the first guide roller 32 'of the pick-up cloth 30, an intermediate roller 34 is arranged. The function of the invention is not affected per se by an intermediate roller of this type and, if desired, a plurality of intermediate rollers 34 can be arranged between the pick-up roller 31 and the most guide roller 32 'of the pick-up cloth 30 if necessary is held. Placing an intermediate roller 34 or more intermediate rollers in a confined space can cause problems, but of course the invention also works in such a situation. The first guide roller 32 'of the pick-up cloth 30 is also in this situation that guide roller of the pick-up cloth 30 , the position of which with respect to the first guide roller 12 ' of the outer wire 10 has to meet the requirements of the above-mentioned invention.

With the above-described arrangements according to the invention, a situation is achieved in which the air flow I ₁ carried by the pick-up cloth 30 cannot get into the pick-up position N ₀ . The air flow I ₁ in question is at the first guide roll 32 'of the pick-up fabric 30 on the outer surface of the outer wire 10 to the between the in order directional S ₁₀ of the outer wire 10 to the guide suction roll 23 following the first guide roll 12' of the outer wire 10 and the subsequent D guide roller 12 'of the outer wire 10 running D of the outer wire 10 or above the relevant train D of the outer wire. The outer screen 10 also pumps air I ₂ out of the space in front of the pick-up point N ₀ delimited by the pick-up cloth 30 and the inner screen 20 . The overpressure in front of the relevant pick-up point N ₀ can thus be reduced and under the most favorable circumstances, negative pressure can be generated in front of the pick-up point N ₀ .

In Figs. 1 to 7, the first guide roll 32 'of the pick-up fabric 30 and the first guide roll 12' of the outer wire 10 are substantially drawn equally large, but the invention is not limited to an embodiment of this kind, but the diameter of the rolls 12 'and 32 ' can also be different sizes.

The invention is also in no way limited to the Darge presented type of the former and in Fig. 1 or 6 Darge presented type of press section.

The pick-up cloth 30 can consist of a press felt, an essentially no water-absorbing transfer belt, ie a so-called belt or the like.

Claims (7)

1. Arrangement for reducing the overpressure at the pick-up point (N ₀ ) of a web (W) between the former and the press section of a paper or board machine, the former looping an outer wire ( 10 ) and an inner wire ( 20 ) has, which form a two-wire zone (A) in which the web is dewatered, the outer wire ( 10 ) being detached from the web (W) at the end of the two-wire zone (A) and leading to the first guide roller ( 12 ') of the outer wire ( 10 ) is guided and the web (W) formed is made to follow the inner wire ( 20 ), from which the web (W) is then nipped in the pick-up press (N ₀ ) between the pick-up roller ( 31 ) and the inner wire ( 20 ) or a roller ( 23 ) located inside the inner wire loop ( 20 ) is transferred to the pick-up cloth ( 30 ) of the press section, characterized in that in the arrangement:

• - The shortest distance (d) between the outer surface ( 30 a) of the pick-up cloth ( 30 ) and the outer circumference of the first guide roller ( 12 ') of the outer screen ( 10 ) is less than 300 mm,
• - The angle of rise (α) between the between the upper outer circumferential half of the first guide roller ( 12 ') of the outer sieve ( 10 ) and the upper outer circumferential half of the most guide roller ( 32 ') of the pick-up cloth ( 30 ) located tangent plane (T ₁ ) and the horizontal plane (VT) is smaller than 80 °, and
• - The extension (C ₁ ) of the train (C) extending between the first guide roller ( 32 ') of the pick-up cloth ( 30 ) and the preceding guide roller ( 32 ') of the pick-up cloth ( 30 ) of the pick-up cloth ( 30 ) drawn through the center point (M ₁₂ ') of the axis of the guide roller ( 12 ') of the outer wire ( 10 ) in the axial direction lying de vertical plane (PT) at point (P ₁ ) which intersects above the intersection (P ₀ ) of the vertical plane (PT) and the upper outer circumferential half of the first guide roller ( 12 ') of the outer wire ( 10 ) or coincides with it, whereby
  the air flow (I ₁ ) carried by the pick-up cloth ( 30 ) does not reach the pick-up point (N ₀ ), but instead moves away from the surface of the pick-up cloth ( 30 ) due to the centrifugal force the first guide roller ( 32 ') when the pick-up cloth ( 30 ) turns and the overpressure normally occurring at the pick-up point can be reduced by the outside screen ( 10 ) air (I ₂ ) before the pick-up pumps up point (N ₀ ) from the space ( 50 ) delimited by the inner sieve ( 20 ) and the pick-up cloth ( 30 ).

2. Arrangement according to claim 1, characterized in that the said angle of rise (α) is below 60 °. 3. Arrangement according to claim 1 or 2, characterized in that the loop angle (β) of the pick-up cloth ( 30 ) on the first guide roller ( 32 ') of the pick-up cloth ( 30 ) is greater than 45 ° . 4. Arrangement according to claim 1 or 2, characterized in that the loop angle (β) of the pick-up cloth ( 30 ) on the first guide roller ( 32 ') of the pick-up cloth ( 30 ) is greater than 90 ° . 5. Arrangement according to one of claims 1 to 4, characterized in that the extension (C ₁ ) between the first guide roller ( 32 ') of the pick-up cloth ( 30 ) and the two guide roller ( 32 '') of Pull-up cloth ( 30 ) running pull (C) of the pick-up cloth ( 30 ) the outer wire ( 10 ) on the between the first guide roller ( 12 ') of the outer wire ( 10 ) and the second guide roller following this ( 12 '') of the outer screen ( 10 ) running train (D) at point (P ₂ ), which at a distance from the intersection (P ₀ ) through the center (M ₁₂ ') of the axis of the first guide roller ( 12 ' is located) of the outer wire (10) vertical plane drawn (PT) and the obe ren outer peripheral half of the first guide roller (12 ') of the outer sieve (10). 6. Arrangement according to one of claims 1 to 5, characterized in that the first guide roller ( 32 ') of the pick-up Tu ( 30 ) in the circumferential direction (S ₃₀ ) of the pick-up cloth ( 30 ) one of the pick -up roller ( 31 ) preceding guide roller ( 32 '). 7. Arrangement according to one of claims 1 to 5, characterized in that between the pick-up roller ( 31 ) and the first guide roller ( 32 ') of the pick-up cloth ( 30 ) one or more intermediate rollers ( 34 ) installed are.