FI129277B

FI129277B - A runnability component for a drying section

Info

Publication number: FI129277B
Application number: FI20206053A
Authority: FI
Inventors: Hannu Koljonen
Original assignee: Valmet Technologies Oy
Priority date: 2020-10-26
Filing date: 2020-10-26
Publication date: 2021-11-15
Also published as: CN114481668B; AT524347B1; CN114481668A; AT524347A1; FI20206053A1; DE102021127366A1

Abstract

The invention relates to a runnability component (1) for a drying section of a paper machine, board machine or the like. The runnability component (1) has an elongated box-like body with a longitudinal axis extending from a first end to a second end through a centroid (5) of the body. The elongated box-like body is formed by an entry side surface (2) and an exit side surface (2’), extending from the first end to the second end, and an upper surface (3) and a lower surface (4), which connect the entry side and the exit side surfaces (2, 2’) and extend from the first end to the second end. The runnability component (1) comprises straightening means (8), which are arranged to create a straightening stress to the elongated box-like body of the runnability component (1).

Description

A RUNNABILITY COMPONENT FOR A DRYING SECTION The present invention relates to a runnability component for a drying section of a paper machine, board machine or the like according to the preamble of the enclosed independent claim.

Runnability components are used in drying sections of paper and board machines.

In a drying section the fibrous web comes into contact with a plurality of heated drying cylinders and their surfaces.

Runnability components are arranged into pocket spaces, which are formed in the drying section between two adjacent drying cylinders and the turning roll at a different level, situated between the drying cylinders.

The runnability components create a suitable underpressure, which helps to keep the web to be dried in contact with a wire and improves the overall runnability of the drying section of the paper or board machine.

Runnability components are usually formed as blow boxes or suction boxes, or they may provide both blowing and suction action for web stabilization.

Usually the runnability components are elongated box-like components, comprising hollow interior spaces or channels for necessary transfer of air.

WO 98/48109 discloses a blow box used in the drying section of a papermaking machine and a method for sealing a pocket space provided with a blow box and a blow nozzle.

N WO 00/50693 discloses a blowing device comprising a blow box which is arranged N 25 at the opening nip between the wire and the cylinder and which is provided with at = least two nozzles arranged close to the wire. : a US 5,074,278 discloses a pocket ventilation system for the dryer section of a 3 papermachine.

S 30 N Runnability components extend over the whole width of the web to be dried and they are supported from their ends, for example to the structures of the drying section.

Nowadays the width of the paper and board machines can be up to, or even over,

12 meters. In practice this may lead bending of the elongated runnability components by forces originating from blowing and/or suction actions which they produce and/or by gravitational force or even by uneven heat elongation of the runnability component. If the runnability component bends, the seal(s) of the runnability component may come into a contact with the surfaces to be sealed. Said contact can cause wear to the seal(s) or open sealing gap, which both lead to the waste of vacuum. Bending of the runnability component may also lead incorrect blowing and/or suction forces directed towards the web to be dried, which may cause unexpected runnability and/or quality problems in the production of paper, board, or the like. Sometimes the problems associated with the bending of the runnability components are counteracted by manufacturing runnability components which are not completely straight, but which are slightly curved or crowned. The goal is that when — the runnability component is installed to its place in the drying section and it is in operation, the slight curvature or crowning counterbalances the bending forces and runnability component appears straight when in use. However, the manufacture of curved or crowned runnability components is time-consuming, and it requires careful tailoring of each runnability component according to its intended location and operational parameters, which is not suitable approach for cost-effective manufacture. An object of this invention is to minimise or even totally eliminate the disadvantages N existing in the prior art. N 25 = An object is to provide a runnability component which appears straight when in 7 operation.

T a 3 A further object of the invention is to provide a runnability component which is easy S 30 and effective to manufacture.

O N

A yet further object of the invention is to provide a runnability component which bending can be corrected while it is installed in a drying section of paper or board machine or the like. These objects are attained with the invention having the characteristics presented below in the characterising parts of the independent claims. The embodiments mentioned in this text relate to all aspects of the invention, even if this is not always separately mentioned. The different embodiments can be freely combined with each other, if not explicitly stated otherwise. A typical runnability component according to the invention for a drying section of a paper machine, board machine or the like, the runnability component having an elongated box-like body with a longitudinal axis extending from a first end to a second end through a centroid of the body, wherein the elongated box-like body is formed by - an entry side surface and an exit side surface, which extend from the first end to the second end, - an upper surface and a lower surface, which connect the entry side and the exit side surfaces and extend from the first end to the second end, wherein the runnability component comprises straightening means, which are arranged to create a straightening stress to the elongated box-like body of the runnability component.

N a 25 In the present context the “natural” bending is understood as the bending of the = body of the runnability component caused by gravity as well as the blowing and/or 7 suction forces during the operation. In the present invention this natural bending can E be corrected by the straightening means arranged in connection with the body of 3 the runnability component. It has been surprisingly found that the bending of the S 30 —runnability component can be effectively counteracted by the straightening means N which create a straightening stress. The straightening stress induced to the body of the runnability component causes the body to bend to the opposite direction than the "natural bending. The straightening means can be used to straighten the runnability component while it is installed to its final location in the drying section. With the help of the present invention, each runnability component can be manufactured as identical, and the correction against the “natural” bending can be provided individually for each runnability component after its installation by using the straightening means. The runnability component according to the present invention has an elongated box- like body, which can be formed of any suitable metal, such as aluminium or steel. The body of the runnability component has a longitudinal axis, which extends from its first end to its second end and which goes through the centroid of the body. The box-like body of the runnability component is a substantially continuous structure from the first end to the second end of the body. This means that the body of the runnability component is a single structure, where the stress created by the straightening means is able to deform the body in its longitudinal direction as desired and cause a carefully controlled bending of the body. The body of the runnability component is essentially free of circumferential gaps in its structure. The runnability component may be a blow box and/or a suction box, and it usually comprises at least one a suction element and/or a blowing element arranged on the entry side surface of the runnability component and preferably at least one sealing member on the entry side surface and/or the exit side surface of the runnability component. The elongated box-like body of the runnability component is formed by an entry side surface and an exit side surface. These surfaces extend from the first N end to the second end of the body. The entry side surface and the exit side surface N 25 are opposite each other in the longitudinal direction of the runnability component, = usually arranged in a small angle there between. In height direction, they can be, 7 for example, mirror image of each other. The interior of the runnability component is E further limited by an upper surface and a lower surface, which connect the entry 3 side and the exit side surfaces and extend also from the first end to the second end. S 30

O N The runnability component comprises straightening means which may be arranged in connection with the body to create the straightening stress. According to one preferable embodiment the straightening means are arranged to create the straightening stress, which is unidirectional with the longitudinal axis of the body.

The straightening stress may thus be unidirectional with the longitudinal axis of the body, and the straightening means are arranged to subject the elongated body of the runnability component to loading force(s) which are unidirectional with the 5 longitudinal axis of the body.

The force(s) created by the straightening means can be directed outwards (tension) or inwards (compression) towards the ends of the body, as seen from the inside of the body.

The straightening means may be arranged in connection with the elongated box- like body of the runnability component in a manner that ensures that the created straightening stress straightens the body as desired.

A person skilled in the art is able, on basis of his experience and simple experiments, as well as common structural calculations for determining bending moments, bending stresses, and bending force loads to determine the proper location of the straightening means in — connection with the body of the runnability component.

According to one embodiment of the invention the straightening means may be arranged above a horizontal level conjoining the longitudinal axis which extends from the first end to the second end through the centroid of the body.

In this case the straightening means may be arranged to create the straightening stress by exerting an outwardly directed tension force parallel with the longitudinal axis.

The straightening means exert a tension force, directed towards the ends of the body, seen from the centroid of the body.

In other words, the straightening means tension N the ends outwards and create the desired straightening stress.

N 25 = Alternatively, according to one preferable embodiment the straightening means may 7 be arranged below the horizontal level conjoining the longitudinal axis which extends E from the first end to the second end through the centroid of the body.

In this case 3 the straightening means may be arranged to create the straightening stress by S 30 exerting a compression force parallel with the longitudinal axis.

The straightening N means exert a compression force, directed towards the centroid of the body from the ends of the body.

According to one embodiment of the present invention the straightening means may be arranged in connection to the upper surface and the lower surface of the elongated box-like body. The straightening means are arranged to create the straightening stress by exerting a drawing force between the upper and lower surface of the body of the runnability component. According to one preferable embodiment the straightening means may comprise a force transfer bar, which may have any suitable diameter, mainly limited by the available space. In one example the force transfer bar may have a diameter of 7 — 50 mm, preferably 10 — 25 mm, more preferably 15 — 20 mm. The force transfer bar may be arranged in connection with the first end and the second end of the elongated box-like body. Alternatively, the force transfer bar may be arranged in connection with the upper surface and the lower surface of the elongated body. In the latter case, the first end of the force transfer bar may be arranged in connection with a fixed structure outside the runnability component, e.g. with a support structure of the drying section, and the second end of the force transfer bar is arranged in fixed connection with the surface of the body of the runnability component. In general, force transfer bar provides uncomplicated and easy way to straighten the elongated body of the runnability component. Simply by arranging the force transfer — barin connection with the body of the runnability component at a suitable location, it is possible to create a straightening stress to the body that is opposite to the “natural” bending forces. N According to one preferable embodiment the straightening means may be arranged N 25 mostly or completely within the body of the runnability component. For example, = when the straightening means is a force transfer bar extending from the first end to 7 the second end of the body, it is preferably arranged within the body of the E runnability component. The arrangement of the straightening means within the body 3 saves space in the limited pocket space and may also protect the straightening S 30 means from environmental impacts.

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N The first end and the second end of the runnability component may comprise end plates. At least one straightening means may be arranged in connection with the end plates, preferably in fixed and/or direct connection with the end plates. For example, when the straightening means is a force transfer bar, the first end of the bar may be fixedly connected to the first end plate of the runnability component, and the second end of the force transfer bar may be arranged in the connection with the second end plate of the runnability component. The end plates may comprise necessary openings, for example for the adjustment means of the straightening means as well as for other elements of the runnability component, e.g. air inlets and/or outlets.

According to one embodiment of the invention the straightening means may comprise a thermal element arranged in connection with the surface of the elongated box-like body for creating the straightening stress to the body by heating or cooling. Preferably the thermal element is arranged in connection with the upper surface of the elongated box-like body and to heat the upper surface at desired location(s). The thermal element may be integrated to the structure of the body, or it may be arranged into a direct contact to the surface of the body. Use of the thermal element as straightening means is advantageous as the adjustment of the temperature, and consequently the adjustment of the straightening stress, is relatively simple.

The straightening means may be arranged at least partly outside the elongated body of the runnability component. For example, when the straightening means is a thermal element, it may be arranged in a direct and immediate contact with the upper N surface of the elongated body of the runnability component, as explained above. N 25 Alternatively, if the end plates are larger than the cross-sectional area of the body, = the straightening means such as force transfer bar may be connected to the end 7 plates outside the elongated body. It is also possible that the straightening means E such as the force transfer bar is connected to the support structures of the drying 3 section. When the straightening means are located outside the elongated body it S 30 may be easier to make any necessary adjustments and/or service to the N straightening means.

According to one embodiment of the invention the runnability component may comprise two or more straightening means. The straightening means may be of different each other, e.g. the first straightening means may be force transfer bar and the second straightening means may be thermal element. It is further possible that the runnability component may comprise two or more straightening means that are force transfer bars. The first force transfer bar may create a drawing force between the first end and the second end of the runnability component, and the second force transfer bar may create a compression force between the first end and the second end of the runnability component. In the latter case, the first and second straightening means are arranged at different locations in the runnability component. According to one embodiment of the present invention the straightening means can be arranged adjustable in order to adjust the straightening stress created to the elongated box-like body. This makes it possible to adjust the straightening stress — while the runnability component is installed in its place in the pocket space of the drying section. The adjustment may even be possible during the operation of the runnability component. The straightening means can comprise or be connected to any suitable adjustment means. For example, if the straightening means is a force transfer bar, it may comprise adjustments means which make it possible to adjust the length of the force transfer bar, and thus the tension/compression force exerted towards the ends of the body of the runnability component. If the strengthening means is a thermal element, the thermal element may be connected to a regulator with which the temperature of the thermal element may be adjusted.

N a 25 In context of the present application the runnability component is arranged in a = pocket space, which is defined by the first and second drying cylinder and a turning 7 roll between them. The drying cylinders are parallel, i.e. their longitudinal axes are E parallel with each other, and they are arranged at a distance from each other. 3 Typically the adjacent drying cylinders are arranged horizontally on the same level S 30 and the turning roll is arranged between the two adjacent drying cylinders so that N the longitudinal axis of the turning roll is substantially parallel with the longitudinal axes of the drying cylinders, but located on a different level in the vertical direction than the axes of the drying cylinders. Turning roll is thus arranged on a higher or lower level than the drying cylinders, typically on a lower level.

Furthermore, the turning roll is placed between the drying cylinders so that its surface does not touch the surfaces of the drying cylinders, i.e. is free from contact with the drying cylinder surfaces.

The box-like runnability component, the drying cylinders and the turning rolls are elongated in the cross direction of the paper machine or the like and extend substantially over the entire width of the web run.

The distance between the first end and the second end of the elongated box-like body of the runnability component may be 5 — 15 m, preferably 8 — 12 m.

The ends of the pocket space are typically sealed, for example by means of end plates of the runnability component.

The vertical end plates are arranged in machine direction, on both ends of the pocket space.

The invention is described in more detail below with reference to the enclosed schematic drawings, in which

Figure 1a shows a schematic view of a pocket space between two drying cylinders and one turning roll, and a runnability component according to an embodiment of the invention arranged in the pocket space, seen in direction of the longitudinal axis of the runnability component,

Figure 1b shows a schematic view of an another embodiment of the runnability component of Figure 1a, and N Figure 2 shows schematic view of a runnability component according to yet N 25 another embodiment of the invention, arranged in the pocket space, seen in = direction of the longitudinal axis of the runnability component. : a Figure 1a shows a schematic view of a pocket space between two drying cylinders 3 A, A’ and one turning roll B.

A runnability component 1 is arranged in the pocket S 30 space C.

The runnability component 1 has an elongated box-like body, which N extends over the machine width, parallel with the drying cylinders A, A’. The box- like body of the runnability component 1 comprises an entry side surface 2 and an exit side surface 2’, as well as an upper surface 3 and a lower surface 4, which are connected to the entry side and the exit side surfaces 2, 2’. The box-like body has a longitudinal axis which extends from its first end to its second end through a centroid 5 of the body. Seal members 6, 6’, 6” may be arranged in connection with the lower part of the entry side surface 2 and/or with the lower surface 4.

The runnability component comprises straightening means 8 which are arranged to create a straightening stress to body of the runnability component 1. In Figure 1a straightening means 8 is a force transfer bar, which have been arranged in connection with the end plates (not shown) of the runnability component 1. The straightening means 8 are arranged below a horizontal level 7 conjoining the longitudinal axis which extends from the first end to the second end through the centroid 5 of the body of the runnability component 1. The straightening means 8 are arranged to create the straightening stress by exerting a compression force parallel with the longitudinal axis. It can be imagined that the straightening means 8 exert a force that “pulls” the ends of the runnability component closer together. This compression force counteracts the forces that cause deformation, i.e. bending, of the runnability component 1 along its longitudinal axis. Figure 1b shows a schematic view of an another embodiment of the runnability component of Figure 1a. The same reference numbers for the same components are used in Figure 1b than in Figure 1a. Also, in Figure 1b straightening means 8’ is a force transfer bar, which have been N arranged in connection with the end plates (not shown) of the runnability component N 25 1. The straightening means 8' are arranged above the horizontal level 7 conjoining = the longitudinal axis which extends from the first end to the second end through the 7 centroid 5 of the body. The straightening means 8 are arranged to create the E straightening stress by exerting a tension force parallel with the longitudinal axis. It 3 can be imagined that the straightening means 8’ exert a force that “pushes” the ends S 30 of the runnability component away from each other. This compression force N counteracts the forces that cause deformation, i.e. bending, of the runnability component 1 along its longitudinal axis.

In some embodiments of the invention it is possible that the runnability component comprises two or more straightening means. For example, it is possible that the runnability component comprises two straightening means, where the first straightening means is located below the horizontal level, as shown in Figure 1a, andthe second straightening means is located above the horizontal level, as shown in Figure 1b. Figure 2 shows another a runnability component 1 according to another embodiment of the invention arranged in the pocket space. The same reference numbers for the same components are used in Figure 2 than in Figures 1a and 1b. In Figure 2 the straightening means 8 is a force transfer bar, and the straightening means 8 are connected to the upper surface 3 and the lower surface 4 of the body of the runnability component 1. The straightening means 8 create a straightening stress by exerting a drawing force, drawing the lower surface 4 of the runnability component 1 upwards. Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.

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Claims

1. A runnability component (1) for a drying section of a paper machine, board machine or the like, the runnability component (1) having an elongated box-like body with a longitudinal axis extending from a first end to a second end through a centroid (5) of the body, wherein the elongated box-like body is formed by - an entry side surface (2) and an exit side surface (2°), which extend from the first end to the second end, - an upper surface (3) and a lower surface (4), which connect the entry side and the — exit side surfaces (2, 2’) and extend from the first end to the second end, characterised in that the runnability component (1) comprises straightening means (8), which are arranged to create a straightening stress to the elongated box-like body of the runnability component (1).

2. The runnability component (1) according to claim 1, characterised in that the straightening means (8) are arranged to create the straightening stress, unidirectional with the longitudinal axis of the body.

3. The runnability component (1) according to claim 1 or 2, characterised in that the straightening means (8) are arranged above a horizontal level (7) conjoining the longitudinal axis of the body and arranged to create the straightening stress by exerting a tension force parallel with the longitudinal axis.

N 4. The runnability component (1) according to claim 1 or 2, characterised in that N 25 — the straightening means (8) are arranged below a horizontal level (7) conjoining the = longitudinal axis of the body and arranged to create the straightening stress by 7 exerting a compression force parallel with the longitudinal axis.

T 3 5. The runnability component (1) according to any of claims 1 — 4, characterised in S 30 that that the first end and the second end of the runnability component (1) comprise N end plates, and that the straightening means (8) are arranged in connection with the end plates.

6. The runnability component (1) according to claim 1, characterised in that the straightening means (8) are connected to the upper surface (3) and the lower surface (4) of the elongated box-like body and arranged to create the straightening stress by exerting a drawing force.

7. The runnability component (1) according to any preceding claim 1 — 6, characterised in that that the straightening means (8) are arranged mostly within the body of the runnability component (1).

8. The runnability component (1) according to any of preceding claims 1 — 7, characterised in that the straightening means (8) comprises a force transfer bar.

9. The runnability component (1) according to any of preceding claims 1 — 8, characterised in that the straightening means (8) comprise a thermal element arranged in connection with the upper surface (3) of the elongated box-like body for thermally creating the straightening stress to the body.

10. The runnability component (1) according to any of the preceding claims 1 — 9, characterised in that the straightening means (8) are adjustable for adjusting the straightening stress created to the elongated box-like body.

11. The runnability component (1) according to any of preceding claims 1 — 10, characterised in that the runnability component (1) is a blow box and/or a suction S box. & 25 =

12. The runnability component (1) according to any of preceding claims 1 — 11, 7 characterised in that the runnability component (1) comprises at least one suction E element and/or a blowing element arranged on the entry side surface (2) of the 3 runnability component (1) and preferably at least one sealing member (6, 6’, 6”) on S 30 the entry side surface (2) and/or the exit side surface (2') of the runnability N component (1).

13. The runnability component (1) according to any of preceding claims 1 — 12, characterised in that the distance between the first end and the second end of the elongated box-like body is 5 — 15 m, preferably 8 — 12 m.

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