WO1999051812A1

WO1999051812A1 - Seal construction for a suction box in a suction roll

Info

Publication number: WO1999051812A1
Application number: PCT/FI1999/000256
Authority: WO
Inventors: Jorma Laapotti
Original assignee: Valmet Corporation
Priority date: 1998-04-02
Filing date: 1999-03-29
Publication date: 1999-10-14
Also published as: AU3038399A; DE19983088T1; FI103593B1; FI980759A0; FI103593B

Abstract

The invention concerns a seal construction for a suction box (11) in a suction roll (10). The suction roll comprises a suction box (11) and therein axial seals (12a1, 12a2), which have been fitted in grooves (U1, U2) in a holder part (14). The holder part (14) has been fitted to be non-stationary in relation to the suction box (11) and has been fitted to be displaceable in an opening (O) at the top of the suction box (11), in which connection the deflection of the holder part (14) is not changed to a substantialy extent when the vacuum varies in the interior of the suction box (11).

Description

Seal construction for a suction box in a suction roll

The invention concerns a seal construction for a suction box in a suction roll.

The object is a suction roll construction in which the seal ribs do not require water lubrication. Such a suction roll is needed in particular in such applications in a press section or dryer section in which water lubrication of the seals lowers the dry solids content that has been achieved to a significant extent. A typical application of this sort is a transfer suction roll by whose means the web is transferred as a closed draw from a press fabric onto a drying fabric.

In the suction roll construction that is suggested herein, the requirement of water lubrication for the seal ribs is avoided so that the holder part of the seals in the suction roll is not bent by the effect of the vacuum load. Thus, the seals can be locked in the holder part right from the beginning so that a little gap (e.g. , 0.1...1 mm) is fitted between the seals and the roll mantle. As a second alternative, the seals have been dimensioned and fixed in their holders so that they are radially slightly mobile, so that initially they rub against the roll mantle, but after a certain little wear their movement towards the roll mantle is prevented, and the pressure of contact against the roll mantle is lowered to zero.

Bending of the holder part of the seals in the suction roll against the roll mantle has been prevented so that the relatively rigid holder part of the seals, which is supported by means of ribs, has been separated from the suction box proper of the suction roll. The holder part of the seals has been fitted in an opening of the suction box placed at the side of the suction sector as sealed, so that bending of the suction box does not bend the holder part of the seals. The holder part of the seals has been dimensioned so that the width (Bl) of the "effective" suction opening between the seals in the machine direction is equal to the width (B2) of the holder part of the 2 seals in the machine direction in the opening of the suction box. In such a case, the forces arising from differences in pressure are balanced, and the holder part of the seals is not bent when the vacuum is regulated.

The sealing between the suction box and the holder part of the seals can be accomplished, for example, by means of gliding seals or by means of bending or rolling seals of lower friction.

In order that the "effective" dimension of width of the suction sector could be defined as precisely as possible and in order that the vacuum acting through the suction holes should not apply a bending force to the holder part by the intermediate of the seal ribs, it is preferable to use rather narrow seals or to chamfer the seals.

The attaching of the seals to the holder part can be accomplished, for example, by means of cotter pins, screws or shoulders, and it is preferable to attach the seal ribs so that a movement against the roll mantle is restricted, but a movement towards the suction box is permitted (for example, oval holes for cotter pins in the seals). In this way an intensive rubbing against the roll mantle is avoided if, for example, thermal expansion should bend the holder part, in some situation, at the middle towards the roll mantle. In such a case, underneath the seals, it is possible to use, for example, springs, by whose means it is guaranteed that the seals move to their outer position when the vacuum is switched on in the roll.

The holder part of the seals has been attached by means of fastening parts in the end areas of the roll to the suction box (bending of the suction box is substantially zero in those areas), and to the fastening point it is also possible to fit means of regulation of the gap between the seal ribs and the roll mantle also in view of regulation taking place from outside.

If a suction roll with two or three suction sectors is needed, in the interior of the roll mantle a suction box with two or three blocks is fitted, and said blocks are provided with seal holder parts of their own with the principle described above. 3

Thus, in the construction in accordance with the present invention, a separate holder part is used, which has been fitted to move in the suction box construction and which is preferably also sealed in relation to said construction. The seals are placed in a stationary position in seal grooves provided in the holder part, and the seals may have been attached in the desired position, for example, by means of a cotter pin. In the construction in accordance with the invention, the bending of the suction box itself is approximately of the same magnitude as in a prior-art construction, and the holder part of the axial seals, to which holder both of the axial seals that define the suction sector have been attached, is substantially non-bending irrespective of changes in the vacuum and can be positioned separately in relation to the roll construction.

According to a preferred embodiment of the invention, the suction box can be provided with a separate cylinder device, by whose means the holder part of the axial seals, which holder part is mobile in relation to the suction box, is pressed into contact with the inner face of the roll mantle so that the seals provided in the holder part are placed against the inner face of the roll mantle or are at a very short distance from said face, in which case no wear of the seals takes place.

The suction roll construction in accordance with the invention is characterized in what is stated in the patent claims.

The invention will be described in the following with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying draw- ings, the invention being, yet, not supposed to be confined to said embodiments alone.

Figure 1A shows a prior-art construction of axial seals in a suction roll. The roll is shown as a sectional view.

Figure IB shows the construction of Fig. 1A as a side view and in a running situation. 4

Figure 1C shows a stage of the prior-art solution in which there is no suction, in which case the suction box is in the original position and, as is shown in the figure, wear of the seals has taken place; the maximal wear has occurred in the area of the highest bending, i.e. in the middle area of the roll.

Figure 2A shows a construction of axial seals in a suction roll in accordance with the invention as a sectional view of the roll.

Figure 2B shows the construction in accordance with the invention as a longitudinal sectional view of the roll.

Figure 2C is a sectional view taken along the line I— I in Fig. 2A, illustrating one end of the roll.

Figure 2D is an illustration in part of one end of a roll. What is shown is a preferred embodiment of an equipment of regulation.

Figure 2E shows the holder part and the suction box as an illustration in part and as a separate illustration.

Figure 2F shows an embodiment of regulation of the position of the holder part.

Figure 3A is a longitudinal sectional view of a roll in accordance with the invention, of an embodiment of the roll in which an actuator, favourably a cylinder device, has been added between the seal holder part and the suction box, by means of which actuator the distance of the holder part and, thus, of the seals from the inner face of the roll mantle can be regulated actively.

Figure 3B is a sectional view taken along the line II— II in Fig. 3A.

Fig. 1A illustrates the commonest present-day prior art. The suction box and the holder part of the seals have been attached to each other rigidly. The seals 1 are 5 loaded against the roll mantle 2 by means of loading hoses 3, in which connection the seals can be made to be pressed against the roll mantle with a substantially invariable pressure also when the suction box is bent. Owing to the pressure applied to the seals, water lubrication W is necessary to reduce the wear of the seals and of the inner face of the roll mantle. Water lubrication can, however, not be used, or use of water lubrication is uneconomical in those applications of a suction roll in which the paper or board web has already been dewatered or dried (by pressing or by drying) to a high dry solids content (approximately higher than 35 %).

Fig. IB is a longitudinal sectional view of a prior-art suction roll in which the seals 1 have been attached fixedly to the suction box 4. When a vacuum p₂ is switched on in the suction box, an outside higher pressure p_j bends the suction box towards its suction opening, and the seals are pressed with force against the roll mantle in particular in the middle area of the roll. In such a situation, the seals are worn to a higher extent in the middle area than in the lateral areas.

Fig. 1C shows a situation in which there is no vacuum in said roll shown in Fig. IB. In the case of worn seals, there is a gap d between the seals and the roll mantle, and when a vacuum is applied to the roll again, the seal gap in the middle area and the leakage of air through said gap may prevent formation of an adequate vacuum.

Fig. 2 A is a sectional view of a suction roll construction 10 in accordance with the present invention. The vacuum present in the interior of the roll 10 does not bend the holder part 14 of the axial seals yi^ Yl^ in the suction roll 11, and no pressure that wears the seals and arises from bending of the suction roll is formed between the seals 12a_j,12a₂ and the roll mantle 10b. A vacuum is produced in the space D in the interior of the suction box 11 , and the vacuum is passed into the interior of the suction roll through a central suction opening in the axle of the suction box and through a connected suction pipe, and further from the interior of the suction box, within a certain sector, to the interior of the holder part 14. The holder part 14 is a circumferential structural part, into whose space placed between the axial seals 12a_{1 ;} 12a₂ the vacuum is passed from the suction box 11 through a central through opening O^ In such a case, by means of the vacuum, suction can be applied through the perforations in the roll mantle to a press felt and to a paper or board web. The suction box 11 is supported in the interior by means of transverse ribs m. The holder part 14 has been fitted as freely mobile in the radial direction in an opening O provided on the top of the suction box 11. Thus, the holder part 14 has been fitted non-stationarily in relation to the suction box 11. A seal S has been fitted between the holder part and the suction box 11. The regulation of the position of the holder part 14 takes place from its ends by means of regulation devices Rι,R₂, preferably screw devices. As is shown in Fig. 2A, the measures B_j and B₂ have been chosen as equally large. The area defined by the seal S is equal to the area that remains between the axial seals 12a₁, 12a₂. In such a case, no bending of the holder part 14 arising from a difference in pressure occurs.

Fig. 2B is a longitudinal sectional view of the suction roll construction in accordance with the invention. As is shown in the figure, the suction roll 10 comprises axial seals 12a₁,12a₂ placed in a holder part 14, which has been inserted into the suction box 11 of the suction roll 10 through an oblong through opening O.

As is shown in the figure, the suction box 11 has been attached to fastening bearing housings Gι,G₂, and, by means of the bearing means G₃,G₄ of the axles a_j and a₂ connected with the suction box 11, the roll 10 mantle 10a has been mounted revolving. The axial seals 12a_{1 ;}12a₂ extend over the entire length of the suction box, so that they seal the whole suction sector both from the sides and also from the ends by means of separate seals 12b provided at the ends. The vacuum is passed into the interior of the suction box 11 into the space D_j through a hollow axle a₂ at one end of the suction box 11.

Fig. 2C is a sectional view taken along the line I— I in Fig. 2 A illustrating an end of the roll. The perforations passing through the mantle 10a of the roll 10 are denoted with lOb^lOb^ .. The inner face of the roll 10 mantle 10a is denoted with lOa^ 7

As is shown in Fig. 2C, the holder part 14 is an oblong box-like structural part. It comprises side walls 14a_j , 14a₂, 14a₃ and 14a and end walls 14a₅ and 14a₆ for the axial seals 12aτ , 12a₂. Said walls define longitudinal grooves U_j and U₂ for the axial seals 12a_{l 5}12a₂. The suction sector is formed between the seals 12a_{1 ;}12a₂. Further, end seals 12b have been fitted at the ends. The walls 14a₂, 14a₃,14a₆ define the suction area O₂ passing through the holder part 14.

Fig. 2D is a longitudinal sectional view and an illustration in part of the suction roll 10 and of the fastening of the holder part 14 of the seals 12a_{l 5} 12a₂ and 12b to the suction box 11. As is shown in Fig. 2D, the separate holder part 14 in accordance with the invention of the axial seals 12a₁,12a₂ and of the end seals 12b has been fitted in such a way in the suction box construction 11 that it can be adjusted by means of screw devices R_j,R₂ in the vicinity of the roll 10 ends. The screw devices R_j and R₂ are placed between the ends of the holder part 14 and the suction box 11. By means of the screw devices R_j and R₂, a desired distance of the holder part 14 and, thus, of the seals 12∑L^ , 12a₂ and 12b from the inner face lOa_j of the roll mantle 10a can be regulated. Thus, e.g. , the holder part can be regulated by means of the screw devices R and R₂ so that the seals 12a_} and 12a₂ and 12b placed in the holder part are placed at a short distance from the inner face lOai_^ of the roll mantle 10a.

The height position of the holder part 14 of the seals and, at the same time, the gap of the seals Ha^ , 12a₂ and 12b in relation to the roll mantle 10a can be regulated in connection with installation (or possibly also later) by means of the regulation screws Rι ,R₂- In stead of, or in addition to, the regulation screws, it is also possible to use shims between the projection on the holder part of the seals and the suction box. Regulation from outside the roll is also possible if, for example, the roll mantle 10a is provided with holes J at said screws Rι ,R₂.

Fig. 2E is a separate illustration of the holder part 14. 8

Fig. 2F illustrates the positioning of the holder part 14 in relation to the suction box 11 or to a construction connected with same. The regulation device comprises the screws R and R₂. Favourably, the number of each of the screws is two. The screws R_j are engaged by means of their threading N_j in the threading N₂ in the threaded hole 63 provided in the suction box 11. The screw R_j has been passed through a free hole 61 provided in an extension part 60 connected with the holder part 14. The screw Rι has been connected with the part 60 as freely revolving, and the coupling between the part 60 and the screw R_j is secured, e.g., by a spring washer 65. When the screw R₂ is rotated, the part 60 is raised/lowered. The screw R₂ revolves in the threaded hole 64 in the part 60. The end of the screw R₂ is fitted against the face f of the suction box 11. By means of the screws R_j , which are rotated in the threading N_j in the threaded hole 63 in the part 11, the part 60 is tightened against the suction box 11. The coupling construction of the holder part 14 can be similar at both ends of the holder part 14. In Fig. 2F, just one embodiment of the regulation of the holder part is illustrated.

Fig. 3 A is a longitudinal sectional view of an embodiment of a suction roll in which an actuator 15 has been added between the holder part 14 of the seals 12a_{1 ;}12a₂ and 12b and the suction box 11 , by means of which actuator it is possible to regulate the distance of the seals 12a_{1 ;} 12a₂ from the roll mantle 10a actively. The holder part 14 has been attached from its ends stationarily to the suction box 11. In respect of the other portions, the holder part 14 is freely connected with the suction box 11, as is the case also in the embodiment described above. By means of the actuator 15, the bending and the position of the holder part 14 in relation to the inner face lOai_^ of the roll mantle 10a are regulated. Between the suction box 11 and the holder part 14, there may also be screw devices R^,R₂ similar to those employed in the embodiment described above.

Fig. 3B is a sectional view taken along the line II— II in Fig. 3A. the position of the holder part 14 can be regulated by means of a separate actuator 15, preferably a cylinder device, of which cylinder devices there can be one or several, preferably in the interior space D_j in the suction box 11. A suitable distance of the axial seals 12a_j , 12a₂ is obtained, for example, by monitoring the distance of the holder part 14 from the cylinder face by means of an inductive detector 100.

The distance of the holder part 14 of the seals 12a_{1 ;} 12a₂ from the roll mantle 10a is measured, for example, by means of an inductive detector 100. By means of the actuator 15 (e.g. , hydraulic cylinder, pneumatic cylinder, screw jack, etc.), a suitable force or distance is produced between the holder part 14 of the seals and the suction box 11, and at the same time, the holder part 14 of the seals 12a_{l 5}12a₂ and 12b is bent so that the desired distance between the seals 12a_{1 ;} 12a₂ and the mantle 100 is provided all the time. The actuator 15 is preferably placed in the middle area of the roll 10. One actuator is enough, but there can also be several actuators.

Claims

10 Claims

1. A seal construction for a suction box (11) in a suction roll (10), which suction roll comprises a suction box (11) and therein axial seals (12a₁, 12a₂), which have been fitted in grooves (U₁,U₂) in a holder part (14), characterized in that the holder part (14) has been fitted to be non-stationary in relation to the suction box (11) and has been fitted to be displaceable in an opening (O) at the top of the suction box (11), in which connection the deflection of the holder part (14) is not changed to a substantial extent when the vacuum varies in the interior of the suction box (11).

2. A seal construction for a suction box in a suction roll as claimed in claim 1, characterized in that there is a separate seal (S) between the suction box (11) and the holder part (14) of the axial seals (12a₁,12a₂).

3. A seal construction for a suction box in a suction roll as claimed in claim 2, characterized in that the area (B₂) defined by the seal (S) is equally large as the area (B_j) that remains between the axial seals (12a_{l 5}12a₂).

4. An equipment as claimed in any of the preceding claims, characterized in that means of regulation (R₁ ,R₂) have been provided in view of displacing the holder part

(14) in relation to the suction box (11).

5. An equipment as claimed in any of the preceding claims, characterized in that the means of regulation (R^,R₂) between the suction box (11) and the holder part (14) consist of screw devices by whose means the position of the holder part (14) in relation to the suction box (11) can be regulated.

6. A seal construction for a suction box in a suction roll as claimed in any of the preceding claims, characterized in that, at the regulation device, preferably regula- tion screws (R₁,R₂), there are holes (g) in the roll mantle (10a), in which case regulation of the screws (R_{1 ;}R₂) can take place from outside the roll. 11

7. A seal construction for a suction box in a suction roll as claimed in any of the preceding claims, characterized in that, between the suction box (11) and the holder part (14), there is an actuator (15), preferably a cylinder actuator, by whose means it is possible to regulate the form of deflection of the holder part (14) and, thus, the distance of the axial seals (12a╬╣ , 12a₂) provided in the holder part from the inner face (lOa^ of the roll mantle (10a) of the roll (10).

8. A seal construction for a suction box in a suction roll as claimed in the preceding claim, characterized in that the actuator (15) has been fitted in the interior of the suction box (11) or to aid the holder part (14), the holder part (14) being supported on the suction box (11) from its longitudinal ends.