EP0334899B1

EP0334899B1 - Apparatus for sequentially drying both sides of a paper web

Info

Publication number: EP0334899B1
Application number: EP88901398A
Authority: EP
Inventors: O. Mihara Works Mitsubishi Heavy Ind.Coltd Sankoda; I. Mihara Works Ohnishi
Original assignee: Beloit Corp
Current assignee: Beloit Technologies Inc
Priority date: 1986-12-02
Filing date: 1987-11-12
Publication date: 1991-12-27
Anticipated expiration: 2007-11-12
Also published as: AR246571A1; ATE70868T1; PL158253B1; BR8707946A; KR890700180A; PH30381A; JPS6389996U; EP0334899B2; EP0334899A1; KR940005201B1; PL269182A1; CN1013598B; IN168979B; ZA879009B; DE334899T1; CA1340582C; FI892657A; CN87107232A; WO1988004206A3; FI892657A0

Abstract

An apparatus (10) for sequentially drying both sides (8A, 9) of a paper web (1A). The apparatus includes a first drying roller (2A'') and a first felt (4A) extends around the first drying roller (2A'') for heating a first side (8A) of the web (1A). The first felt (4A) and the web (1A) extend around a first downstream suction roller (3A'''). A first guide roll (5A) guides the first felt (4A) away from the first suction roller (3A''') and a second suction roller (7A) is disposed adjacent to the first suction roller (3A'''). A second felt (4A') extends around the second suction roller (7A) and a second guide roll (12) guides the second felt (4A') towards the second suction roller (7A) such that the first and second felts (4A, 4A') define therebetween a web transfer section (14) so that the web (1A) is sandwiched between the felts (4A, 4A') during passage through the transfer section (14). A downstream second drying roller (6A) is disposed such that the web (1A) is sandwiched between the second felt (4A') and the second drying roller (6A) for heating a second side (9) of the web (1A).

Description

This invention relates to an apparatus for and a method of drying a web.
DE-A-2 355 397 discloses an apparatus for sequentially drying both sides of a paper web, said apparatus comprising a plurality of groups of dryer drums, a plurality of guide rolls each being disposed between a respective pair of adjacent dryer drums, and a plurality of single dryer felts each being associated with a respective group of dryer drums and defining a continuous loop which extends in a sinusoidal configuration past altemate dryerdrums of the respective group and guide rolls with the web being sandwiched between the dryer felt and each dryer drum for heating a respective side of the web and with the dryer felt being sandwiched between the web and each guide roll. The known apparatus includes a web transfer section between two consecutive groups of dryer drums, said web transfer section comprising the downstream dryer felt associated with the downstream group of dryer drums and the upstream dryer felt associated with the upstream group of dryer drums and guide rolls for guiding said upstream dryer felt towards said downstream dryer felt with the web being supported and guided by the upstream dryer felt from the upstream group of dryer drums to the downstream group of dryer drums. The embodiments shown in figures 5, 6, 8 and 9 of the above-mentioned document do not include means for holding the web against the respective dryer felt while the dryer felt passes around the guide rolls. Thus there is a danger for the web to become separated from the respective dryer felt. Moreover the above-mentioned embodiments do not include means for completely avoiding an open draw in the web transfer sections. As a result the web in the web transfer sections is susceptible to breaks.
US-A-4 359 827 discloses an apparatus for drying a web, said apparatus comprising a series of upper dryer drums and a series of lower grooved dryer drums each being disposed between a pair of adjacent upper dryer drums, and a fabric which passes alternately around upper and lower dryer drums in a sinusoidal configuration with the web being sandwiched between the fabric and each upper drums and with the fabric being sandwiched between the web and each lower drum. Since there is no direct contact between the lower dryer drums and the web any drying of the web during passage around the lower dryer drums is greatly reduced. In order to hold the web against thefabric vacuum boxes are provided between the upper and lower dryer drums. Moreover, it is suggested that the lower drums are replaced with cylinders having foraminous major surfaces and that a vacuum is applied on the cylinder interiour so that the vacuum evacuates the grooves, thereby holding the web and fabric combination together onto the cylinder outer surface. There is no suggestion that the foraminous cylinders should have a diameter smaller than the dryer drums. Thus the foraminous cylinders cannot be placed sufficiently close to the dryer drums to avoid a long fabric draw between consecutive dryer drums. As a result of the vacuum boxes between the upperdrums and the lowerdrums or lowerforaminous cylinders fabric wear will occur whenever the fabric comes into contact with the vacuum boxes because they have a stationary rigid surface.
Another conventional drying apparatus for sequentially drying both sides of a paper web is known in practice as a BEL RUN type drying section in which a first drying section dries one side of the web and then a subsequent drying section dries the opposite side of the web. In the BEL RUN type drying section, the single felt section may be made up of four groups of rollers. Typically, these groups indude drying rollers and suction rollers which provide no open draw in their configuration because the paper web is always supported by a dryer felt. As the web progresses from one group of dryers to the next, the same side of the web is always presented to the successive drying rollers. However, in order to present the opposite side of the web to a successive drying roller, it is necessary to transfer an unsupported web to a subsequent dryer felt.
A further conventional drying apparatus is the so-called single-felted dryer section in which a joint run of the web and felt successively passes around upper and lower dryer drums in a sinusoidal configuration. Although this arrangement provides felt support for the web between successive upper and lower dryer drums, the lower dryer drums are virtually redundant in that the felt is sandwiched between the web and the drying roller thereby greatly reducing any drying of the web during passage around the lower drying rollers. Furthermore, such a single-felted dryer section still does not dry from both sides.
In the aforementioned BEL RUN configurations and single-felted dryers, problems exist in that only one side of the web is dried during passage of the web through the first few groups of dryers. Consequently, such arrangement results in differences in surface strength and properties. Additionally, the smoothness of the respective surfaces of the web differ which is a problem when sheet paper is required in which both sides of the sheet must have similar characteristics. Also, curi and non-uniform response to change in humidity have been problems with the aforementioned dryer sections.
An object of the present invention is to provide an apparatus and a method that overcome the aforementioned inadequacies of the prior art drying apparatuses and which permit a positive transfer of the web between successive groups of dryers in a no-open-draw-configuration such that alternate sides of the web can be dried thereby providing a paper product having uniform surface characteristics, surface strength and smoothness, and no tendency to curl.
According to one aspect of the invention, there is provided an apparatus for drying a web, said apparatus comprising a first single tier dryer section having a first plurality of dryer drums rotating in a first direction for drying a first side of the web, said first dryer section including a first plurality of suction rolls rotating in a second direction opposite to said first direction, said suction rolls being disposed between adjacent dryer drums of said first plurality of dryer drums, first dryer felt means for conveying the web in a serpentine path along said dryer drums and said suction rolls, a second single tier dryer section disposed downstream relative to said first dryer section and having a second plurality of dryer drums rotating in said second direction for drying a second side of the web, said second dryer section including a second plurality of suction rolls rotating in said first direction and disposed between adjacent dryer drums of said second plurality of dryer drums, second dryer felt means for conveying the web in a serpentine path along said second plurality of dryer drums and said second plurality of suction rolls, and means for guiding said first and second felt means in close proximity to each other between said first and said second dryer sections so as to sandwich the web between said first and said second felt means to effect a controlled transfer of the web from said first felt means to said second felt means.
According to another aspect of the invention there is provided a method of drying a web, said method including the steps of:

guiding the web through a first single tier dryer section having a first plurality of dryer drums rotating in a first direction for drying a first side of the web, said first dryer section including a first plurality of suction rolls which rotate in a second direction opposite to said first direction, said suction rolls being disposed between adjacent dryer drums of said first plurality of dryer drums;
conveying the web contiguously with a first dryer felt means such that the web and said first dryer felt means follow a serpentine path along said dryer drums and said suction rolls,
guiding the web through a second single tier dryer section disposed downstream relative to said first dryer section and having a second plurality of dryer drums rotating in said second direction for drying a second side of the web, said second dryer section including a second plurality of suction rolls rotating in said first direction and disposed between adjacent dryer drums of said second plurality of dryer drums;
conveying the web contiguously with a second dryer felt means such that the web and said second dryer felt means follow a serpentine path along said second plurality of dryer drums and said second plurality of suction rolls; and
guiding said first and second felt means in close proximity to each other between said first and second dryer sections so as to sandwich the web between said first and second felt means to effect a controlled transfer of the web from said first felt means to said second felt means.

Although the present invention is desribed with a certain degree of particularity in the detailed description contained hereinafter, it will be apparent to those skilled in the art that many modifications and variations of the concept of the present invention can be carried out without departing the spirit and scope of the present invention. In the drawing,

Figure 1 is a side-elevational view of a prior art BEL RUN type drying section showing the first four groups of dryer drums drying a first side of a paper web,
Figure 2 is a side-elevational view of a drying apparatus according to the present invention showing the means for transferring the web without open draw from a first to a second felt means, and
Figure 3 is an enlarged side-elevational view of Figure 2 particularly showing, in detail, the web transfer section enabling the opposite side of the web to come into physical contact with a subsequent group of dryer drums.

Similar reference characters refer to similar parts throughout the various Figures of the drawing.
Figure 1 is a side-elevational view of a conventional BEL RUN type drying section including groups A,B,C and D for drying a web of paper 1. As shown in Figure 1, the web 1 is guided in sinusoidal configuration around a plurality of dryer drums 2, 2' and 2" and suction transfer rolls 3, 3' and 3". A first felt 4 loops around a plurality of guide rolls 5, 5', 5", 5"' and 5"" and supports the web 1 as the web moves alternatively past dryer drums and suction rolls 3, 2, 3', 2', 3" and 2". A second group B of dryer drums 6, 6', and 6" has suction rolls 7, T and 7" disposed altemately therebetween such that a second felt 4' loops around the suction rolls and dryer drums 7, 6, 7', 6', 7" and 6" in sinusoidal configuration. The web 1 is unsupported by the felt 4 as the web 1 supported by the dryer drum 2" rotates adjacent to the second felt 4' so that the web 1 is transferred to the second felt 4' and around the suction roll 7. However, as seen in Figure 1, the same side 8 of the web 1 is brought into contact with the heating surfaces of the dryer rolls 2, 2', 2", 6, 6' and 6" so that the same side 8 is dried.
The present invention, as shown in Figure 2, enables the web 1A to be reversed from a first single tier dryer section A1 to a second single tier dryer section B1 so that during passage of the web 1A through the first section A1, a first side 8A of the web 1A comes into physical contact with the dryer drums 2A, 2A' and 2A" rotating in a first direction 20. In the second section B1, a second side 9 of the web 1A comes into physical contact with the heating surface of dryer drums 6A, 6A' and 6A" rotating in a second direction 22 opposite to said firt direction 20.
Figure 3 is an enlarged, fragmentary view of the transfer section shown in Figure 2 to show how the web 1A is reversed. More particularly, with reference to Figure 3, the apparatus generally designated 10 for reversing the paper web 1A includes the last dryer drum 2A" of the first section A1 with the web extending around a portion of the circumference of the dryer drum 2A". A first felt 4A extends ar.ound a portion of the dryer drum 2A" such that the web 1A is sandwiched between the first felt 4A and the dryer drum 2A" for heating a first side 8A of the web 1A. A first suction roll 3A"' rotating in said second direction 22 is diposed downstream relative to the dryer drum 2A". The first suction roll 3A"' has an axis of rotation which is disposed parallel and spaced relative to the rotational axis of the dryer drum 2A". The first felt 4A and the web 1A extend around a portion of the circumference of the first suction roll 3A"' such that the first felt 4A is sandwiched between the web 1A and the first suction roll 3A"'. First guiding means 5A, as shown in Figure 2, guide the first felt 4A away from the first suction roll 3A"'. A second suction roll 7A rotating in said first direction 20 is disposed adjacent to the first suction roll 3A"', the second suction roll 7A having an axis of rotation parallel and spaced relative to the axis of rotation of the first suction roll 3A"'. A second felt 4A' extends around the second suction roll 7A, and a second guiding means 12 shown in Figure 2 guides the second felt 4A' towards the second suction roll 7A such that the first and second felts 4A and 4A' respectively define therebetween a web transfer section generally designated 14 so that the web 1A is sandwiched between the felts 4A and 4A' during passage through the transfer section 14. The first dryer drum 6A of the second section B1 is disposed downstream relative to the second suction roll 7A with the dryer drum 6A having an axis of rotation parallel to the axis of rotation of the second suction roll 7A such that the web 1A is sandwiched between the second felt4A' and the dryer drum 6A for heating the second side 9 of the web 1 A.
As shown in Figure 2, the first felt 4A is a continuous loop which extends in sinusoidal configuration past alternate dryer drums and suction rolls 3A, 2A, 3A', 2A' 3A", 2A" and 3A"' of the first section A1 such that the dryer drums 2A, 2A', 2A" physically contact the first side 8A of the web 1 A and the second plurality of dryer drums 6A, 6A' and 6A" physically contact the second side 9 of the web 1A so that alternate sides of the web 1A are sequentially dried.
More specifically, the first guiding means includes a first guide roll 5A for guiding the first felt 4A and the second guiding means includes the second guide roll 12 for guiding the second felt 4A'.
In operation of the apparatus according to the present invention, alternate sides 8A and 9 of the paper web 1A are sequentially dried by the following method steps:

1. The joint run of the web 1A and the first felt 4A are guided around the dryer drums 2A, 2A', 2A" and suction rolls 3A', 3A" Figure 2 such that the web 1A is sandwiched between the first felt 4A and the dryer drums 2A, 2A', 2A" for heating the first side 8A of the web 1A.
2. Thereafter, the joint run of the web 1A and the first felt 4A are guided around a first suction roll 3A'" such that the first felt 4A is sandwiched between the web 1A and the first suction roll 3A"'.
3. The first felt 4A is guided around a first guide roll 5A, and a second felt 4A' is guided from a second guide roll 12 around a second suction roll 7A such that the first and second felts 4A and 4A' respectively define therebetween a web transfer section 14 so that the web 1A supported by the first felt 4A is guided into the web transfer section 14 with the web 1A being disposed between the first and second felts 4A and 4A' respectively.
4. The web 1A emerging from the web transfer section 14 is drawn around the second suction roll 7A such that the second felt 4A' is disposed between the web 1A and the second suction roll 7A.
5. Thereafter, the joint run of the web 1 A and second felt4A' is directed around the dryerdrums 6A, 6A', 6A" and suction rolls 7A', 7A" such that the web 1A is sandwiched between the second felt 4A' and the dryer drums 6A, 6A', 6A" for heating the second side 9 of the web 1A.

In the first dryer section A1, the suction rolls are disposed below the dryer drums whereas in the second dryer section B1, the suction rolls are disposed above the dryer drums. This configuration enables the provision of the aforementioned simple web transfer section such that the web may be transferred from the first to the second felt.
A third single tier dryer section C1 is disposed downstream relative to the second single tier dryer section B1 for further drying the first side 8A of the web 1A, and a fourth single tier dryer section D1 is disposed downstream relative to the third single tier dryer section C1 for further drying the second side 9 of the web 1A. A further web transfer section is disposed between the second and third dryer sections B1 and C1, and yet another web transfer section is disposed between the third and fourth dryer sections C1 and D1.

Claims

1. An apparatus for drying a web (1A), said apparatus comprising a first single tier dryer section (A1) having a first plurality of dryer drums (2A, 2A', 2A") rotating in a first direction (20) for drying a first side (8A) of the web (1A), said first dryer section (A1 ) including a first plurality of suction rolls (3A', 3A") rotating in a second direction (22) opposite to said first direction (20), said suction rolls (3A', 3A") being disposed between adjacent dryer drums of said first plurality of dryer drums (2A, 2A', 2A"), first dryer felt means (4A) for conveying the web (1A) in a serpentine path along said dryer drums (2A, 2A', 2A") and said suction rolls (3A', 3A"), a second single tier dryer section (B1) disposed downstream relative to said first dryer section (A1) and having a second plurality of dryer drums (6A, 6A', 6A") rotating in said second direction (22) for drying a second side (9) of the web (1A), said second dryer section (B1) including a second plurality of suction rolls (7A', 7A") rotating in said first direction (20) and disposed between adjacent dryer drums of said second plurality of dryer drums (6A, 6A', 6A"), second dryer felt means (4A') for conveying the web (1A) in a serpentine path along said second plurality of dryer drums (6A. 6A', 6A") and said second plurality of suction rolls (7A', 7A"), and means (3A"', 5A, 7A, 12) for guiding said first and second felt means (4A, 4A') in close proximity to each other between said first and said second dryer sections (A1, B1) so as to sandwich the web (1A) between said first and said second felt means (4A, 4A') to effect a controlled transfer of the web (1A) from said first felt means (4A) to said second felt means (4A').

2. An apparatus as set forth in claim 1 wherein said means for guiding said first and said second felt means in close proximity to each other include a first suction roll (3A"') disposed downstream relative to said first plurality of dryer drums (2A, 2A', 2A"), and a second suction roll (7A) disposed downstream relative to said first suction roll (3A"'), said first suction roll (3A"') being operable to apply a vacuum to said web (1A) through said first felt means (4A) to hold said web (1A) against said first felt means (4A) while said web and said first felt means pass jointly around said first suction roll (3A"'), said second suction roll (7A) being operable to apply a vacuum to said web (1A) through said second felt means (4A') to hold said web (1A) against said second felt means (4A') when said first felt means (4A) separates from the web (1A), so that the web (1A) is transferred without open draw from said first felt means (4A) to said second felt means (4A'), and when said second felt means (4A') and said web (1A) pass jointly around said second suction roll (7a).

3. An apparatus as set forth in claim 2, said apparatus including a third single tier dryer section (C1) disposed downstream relative to said second dryer section (B1) and having a third plurality of dryer drums rotating in said first direction (20) for further drying said first side (8A) of the web (1A), said third dryer section (C1) including a third plurality of suction rolls rotating in said second direction (22) and disposed between adjacent dryer drums of said third plurality of dryer drums, third dryerfelt means for conveying the web (1A) in a serpentine path along said third plurality of dryer drums and said third plurality of suction rolls, a fourth single tier dryersection (D1) disposed downstream relative to said third dryer section (C1) and having a fourth plurality of dryer drums rotating in said second direction (22) forfurther drying said second side (9) of the web (1A), said fourth single tier dryer section (D1) including a fourth plurality of suction rolls rotating in said first direction (20) and disposed between adjacent dryer drums of said fourth plurality of dryer drums, fourth dryer felt means for conveying the web (1A) in a serpentine path along said fourth plurality of dryer drums and said fourth plurality of suction rolls, further means (7A"') for guiding said second and third felt means (4A') in close proximity to each other between said second and third dryer sections (B1, C1) so as to sandwich the web (1A) between said second (4A') and said third felt means to effect a further controlled transfer of the web (1A) from said second felt means (4A') to said third felt means, and additional means for guiding said third and fourth felt means in close proximity to each other between said third and fourth dryer sections (C1, D1) so as to sandwich the web (1A) between said third and said fourth felt means to effect yet another controlled transfer of the web (1A) from said third felt means to said fourth felt means, wherein each of said further means for guiding said second and third felt means (4A') in close proximity to each other and said additional means for guiding said third and fourth felt means in close proximity to each other include a respective pair of suction rolls disposed adjacent to each other.

4. An apparatus as set forth in claim 2 or claim 3 wherein said first felt means (4A) and the web (1A) extend around a portion of each dryer drum of said first plurality of dryer drums (2A, 2A', 2A") such that the web (1A) is sandwiched between said first felt means (4A) and each dryer drum of said first plurality of dryer drums (2A, 2A', 2A") for heating said first side (8A) of the web (1A); said means for guiding said first and second felt means (4A, 4A') in close proximity to each other include first guiding means (5A) for guiding said first felt means (4A) away from said first suction roll (3A"'), and second guiding means (12) for guiding said second felt means (4A) towards said second suction roll (7A) such that said first and second felt means (4A, 4A') define therebetween a web transfer section (14) with the web (1A) being disposed between said first and second felt means (4A, 4A') during passage through said transfersection (14); said first felt means (4A) and the web (1A) extend around a portion of the circumference of said first suction roll (3A"') such that said first felt means (4A) is sandwiched between the web (1A) and said first suction roll (3A"'); said second felt means (4A') and the web (1A) extend around said second suction roll (7A) such that said second felt means (4A') is sandwiched between the web (1A) and said second suction roll (7A); and said second plurality of dryer drums (6A, 6A', 6A") is disposed downstream relative to said second suction roll (7A), each dryer drum of said second plurality of dryer drums (6A, 6A', 6A") having a respective axis of rotation parallel to the axis of rotation of said second suction roll (7A) such that the web (1A) is sandwiched between said second felt means (4A') and each dryer drum of said second plurality of dryer drums (6A, 6A', 6A") for heating said second side (9) of the web (1A).

5. An apparatus as setforth in anyone of the preceding claims wherein said first felt means comprise a single felt (4A) defining a continuous loop which extends in sinusoidal configuration past alternate dryer drums of said first plurality of dryer drums (2A, 2A', 2A") and suction rolls of said first plurality of suction rolls (3A', 3A") such that each dryer drum of said first plurality of dryer drums (2A, 2A', 2A") physically contacts said first side (8A) of the web (1A), and said second felt means comprise a singlefelt (4A') defining a continuous loop which extends in sinusoidal configuration past alternate dryer drums of said second pluralityofdryerdrums (6A, 6A', 6A") and suction rolls of said second plurality of suction rolls (7A', 7A") such that each dryer drum of said second plurality of dryer drums (6A, 6A', 6A") physically contacts said second side (9) of the web (1A) so that alternate sides of the web (1A) are sequentially dried.

6. An apparatus as set forth in claim 4 or claim 5 when dependent on claim 4 wherein said first guiding means include a first guide roll (5A) for guiding said first felt means (4A); and said second guiding means include a second guide roll (12) for guiding said second felt means (4A').

7. An apparatus as set forth in any one of the preceding claims wherein said pluralities of suction rolls (3A', 3A"; 7A', 7A") are disposed altemately below and above said pluralities of dryer drums (2A, 2A', 2A"; 6A, 6A', 6A").

8. A method of drying a web (1A), said method including the steps of: guiding the web (1A) through a first single tier dryer section (A1) having a first plurality of dryer drums (2A, 2A', 2A") rotating in a first direction (20) for drying a first side (8A) of the web (1A), said first dryer section (A1) including a first plurality of suction rolls (3A', 3A") which rotate in a second direction (22) opposite to said first direction (20), said suction rolls (3A', 3A") being disposed between adjacent dryer drums of said first plurality of dryer drums (2A, 2A', 2A"); conveying the web (1A) contiguously with a first dryerfelt means (4A) such that the web (1A) and said first dryer felt means (4A) follow a serpentine path along said dryer drums (2A, 2A', 2A") and said suction rolls (3A', 3A"), guiding the web (1A) through a second single tier-dryer section (B1) disposed downstream relative to said first dryer section (A1) and having a second plurality of dryer drums (6A, 6A', 6A") rotating in said second direction (22) for drying a second side (9) of the web (1A), said second dryer section (B1) including a second plurality of suction rolls (7A', 7A") rotating in said first direction (20) and disposed between adjacent dryer drums of said second plurality of dryer drums (6A, 6A', 6A"); conveying the web (1A) contiguously with a second dryer felt means (4A') such that the web (1A) and said second dryer felt means (4A') follow a serpentine path along said second plurality of dryer drums (6A, 6A', 6A") and said second plurality of suction rolls (7A', 7A"); and guiding said first and second felt means (4A, 4A') in close proximity to each other between said first and second dryer sections (A1, B1) so as to sandwich the web (1A) between said first and second felt means (4A, 4A') to effect a controlled transfer of the web (1A) from said first felt means (4A) to said second felt means (4A').

9. A method of drying a web (1A) as set forth in claim 8, said method including the steps of: guiding a joint run of the web (1A) and said first felt means (4A) around each dryer drum of said first plurality of dryer drums (2A, 2A', 2A") such that the web (1A) is sandwiched between said first felt means (4A) and each dryer drum of said first plurality of dryer drums (2A, 2A', 2A") for heating a first side (8A) of the web (1A); guiding the joint run of the web (1A) and said first felt means (4A) around a first suction roll (3A"') such that said first felt means (4A) is sandwiched between the web (1A) and said first suction roll (3A'''); guiding said first felt means (4A) around a first guide roll (5A); guiding said second felt means (4A') from a second guide roll (12) around a second suction roll (7A) such that said first felt means (4A) and said second felt means (4A') define therebetween a web transfer section (14) so that the web (1A) supported by said first felt means (4A) is guided into the web transfer section (14) with the web (1A) being disposed between said first and second felt means (4A, 4A');(drawing the web (1A) emerging from the web transfer section (14) around the second suction roll (7A) such thatsaid second felt means (4A') is sandwiched between the web (1A) and the second suction roll (7A); and thereafter directing a joint run of the web (1A) and said second felt means (4A') around each dryer drum of said second plurality of dryer drums (6A, 6A', 6A") such that the web (1A) is sandwiched between said second felt means (4A') and each dryer drum of said second plurality of dryer drums (6A, 6A', 6A") for heating the second side (9) of the web (1A).

10. A method of drying a web (1A) as set forth in claim 8 or claim 9, said method including the step of guiding the web (1A) through additional single tier dryer sections (C1, D1) for further drying the first and second sides (8A, 9) of the web (1A) respectively.