Note: Descriptions are shown in the official language in which they were submitted.
~L~6~39~
The present invention relates to hot air dryin~ apparatus, with
simultaneous support, for continous webs of flewible material coming from
a prev;ous treatment requiring evaporation and removal of liquid substances
which can be vaporised, especially drying webs of printed paper coming from
an offset press line and from which the solvents of the deposited ink are
to be eliminated (only solvents consisting of light oils when greasy inks
are used, fixed by the application of heat).
The invention relates more particularly to apparatus of the kind
comprising a housing within which are disposed, between two web inlet and
outlet openings, two rows of nozzles disposed one above and one below the
plane of movements of the web, these nozzles presenting air ejection slits
extending transversing relative to the direction of movement of the web,
the slits opening towards the web to de dried, said nozzles being connected
to at least one recycling fan and a source of heat, the housing connecting
also with an extractor fan.
Due to this arrangement, the substances to be evaporated, for
example, the solvents of the printing inks, are removed in a short lapse of
time, due to the intensive thermal exchange, while the jets of hot air
emitted by the slits of the nozzles ensure continous support of the web
between the nlet and outl~t o~enings, av iding any cont3rt of the weh w~th
the components of the apparatus, which might prejudice conservation of the
result obtained on the web by the preceding treatment in question, producing,
for example, swearing of the still wet i-nk in the case of printed paper. In
the same particular case, the webs coming from the offset rotors run at
speeds which are frequently 5 to 10 m/s and the hot air is blown at a tempe-
rature of 150C to 300C, consequently the web of paper is heated to 120C
to 160C and it is desirable to cool it before cutting and folding it. The
nozzles of the upper set are offset relative to those of the lower set,
which creates undulations in the longitudinal direction which cancel out
the transverse undulations which tend to be produced under the effect of
the web tension.
.~ ~
~i~7~2
2.
Apparatus of this kind is already known~ for example from U.S.A.
Patent n 3 739 491, in which the housing is in a single piece over the
whole length of the apparatus and incorporates the source of hot air, which
is a single source for the whole apparatus and is disposed asymmetrically.
However, certain disadvantages appear when drying apparatus of
this kind is to be adapted to treatment lines operating at high speeds,
such as high speed printing rotors (speed reaching 10 m/s).
Thus, for example, the input of substances (for example so1vents
bearing other components of the ink? becomes high and their dew point rises
(40C, up to 70C) so that condensation occurs at the drying air inlets,
which can produce spotting of the web, or even blocking of certain openings,
producing a loss of support which can require stoppage of the apparatus and
of the whole line. Essentially, it is the cold air from outside entering
through the web inlet and outlet openings which forms a source of condensa-
lS tion like a mist as it needs the hot air loaded with solvent rising fromthe web.
It should also be noted that, in the case of printing, on a given
apparatus, the quantity of solvent varies to a very considerable extent,
and can reach over a ratio of 1 to 100, depending on the substance, so that
in some cases the concentration of solvent is too high and produces an
undesirable condensation, even if on certain apparatus one tries to maintain
a constant pressure drop by controlling the flow rate of extraction of used
air as a function of this pressure drop, this regulation of the pressure
drop being quite insufficient in the case of maximum concentrations of solYent.
Moreover, in certain applications to treatment lines, the increase
of runningspeeds of the webs requires the des;gn of drying apparatus of
greater and greater length, because then they are more economical, and consume
less energy than short drying tunnels, but then there is a limit because the
structure of the support for the nozzles at the operatins temperatures used,
which can reach 300C, then has mechanical strength defects, twisting and
curving under the effect of the thermal stresses.
34Z 3-
In certain other apparatus, the fan and burner are disposed
beneath and above the drying zone itself (which comprises the nozzles),
with the ran downstream of the burner, and connected to the nozzles by a
wedge-shaped chamber, which has the disadvantage that, if the flame blows
through (because of a drop in air pressure or an ;ncrease in gaz pressure),
i~ reaches the fan, which damages the fan and can even destroy it, besides
which with such an arrangement, the fan pressure being related to air
density, thus to its temperature which can vary from 120C to 33~C,sign;-
ficant pressure variations can occur which are also unfavourable to the
required uniformity of blowing and adequate support of the web. -
Finally, the thermal energy consumption of these known appara-
tus is very high, because of the high flow rates of used air (extracted),
which moreover also requires the use of large upstream cleaners which also
consume a lot of energy. This flow rate is due particularly to the entry
of quantities of cold air through the inlet and outlet openings in the
housing which cannot be reduced without risk of blocking the recycled
air, loaded with solvents.
As for the side structure of the system, some known apparatus
have a main hou6ing which only contains the nozzles and the means extrac-
t,ng used air, whereas the .an and burr,er, wnich constitute the means for
- reheating the air supply, are placed in a separate housing disposed on
the side of the first ho~sing and connected to it by sleeves. It follows
that this arrangement is difficult to adapt to the available space
offered for the installation of the apparatus, and moreover prevents any
extension of the apparatus required by an increase of speed.
In general, the installation of two drying tunnels "in lin ",
even touching, has the disadvantage of not ensuring equal spacing of the
nozzles at the interface zone, and consequent reliable web support.
Accordingly, the present invention has as object to avoid the
various disadvantages of the known drying apparatus.
3L~ 7t;~3~ 4.
Thus, the invention provides an apparatus of the kind referred
to, characterised in that, in the direction of movement of the web, the
housing comprises at least two separate sections which are fixed together
each section comprising a set of nozzles which comprises two rows of nozzles
and a recycling fan whose input communicates with the inside volume of the
housing and whose output is connected to said rows of nozzles through ducts
provided with heat addition means connected to the source of heat.
Due to this arrangement, the complete housing of the apparatus
which, for the high running speeds now required, especially on offset prin-
ting rotors, has to have a considerable length, for example 7 m approxima-
tely, is subdivided into a plurality of sections,for example two or three,
or more if required, and they can even be juxtaposed indefinitely, since
these sections are practically identical, except for those which also bear
the common source of heat or the common extractor fan, thus making the
structure perfectly modular and adaptable. If follow that the length of
each section can be limited to a suitable value, for example of the order
of 2,5 m for normal web sizes, or 3 m for small web widths (given that the
wider the apparatus has to be because of the web widths to be treated, the
more the number of sections in line can be increased, so as to reduce the
flow rite to be produced on each recycling fan). Th;s subdivis;on of the
housi~g thus enables each of its sect;ons to be guaranteed a su;table
mechanical strength at the nozzles. The subdivision also, by enabling a
regular spacing of the nozzles connected to the recycling fan of each
section, improves the uniformity of blowing and the temperature distribution.
In particularly advantageous fashion, the distance between the
last nozzle of one sect;on and the f;rst one of the next can be equal to
the d;stance between the nozzles of a given section, which thus ensures
a constant spacing of the nozzles from one end to the other of the hous-
ing and avoids any interruption in the support of the web, so that no
flapping of the web will appear on passing from one section to the next.
4A
~ qore particularly, the present invention relates
to an apparatus for simultaneously drying in hot air and
supporting a continuous web of flexible material. The
apparatus comprises a casing defining a web inlet opening
and a web outlet opening for the web which travels through
the inlet opening and the outlet opening in a general path
longitudinally through the casing. Each supply means and
exhausting means for exhausting used air from inside the
casing are provided. The casing comprises at least two
sections defining chambers in adjacent relation longitudinally
of the casing, each section having an upper set of nozzles
and a lower set of nozzles disposed respectively above and
below the general path. Each section includes air recycling
means having input means communicating with the inside of
the casing and output means, duct means putting the output
means in communication with the upper set of nozzles and the
lower set of nozzles of the respective section and heat
adding means for putting the heat supply means in communication
with the duct means for adding heat from the heat supply means
to the air recycled to the sets of nozzles by the output means
of the recycling means.
"~
3L~'~t~ 5.
In a preferred embodiment of the invention,at least one end
section of the housing can contain a burner which is associated with a
combustion chamber.
In a particularly preferred embodiment of the invention, the
source of heat can be provided by at least one burner disposed at the end
of a combustion chamber presenting an inlet for recycled air connected
to the output of a recycling fan, the inlet being situated upstream of
the heat addition means for said ducts. This arrangement enables a mixture
to be obtained in two stages, firstly dilution of the burner gas with air
coming directly from the recycling fan associated with this burner, and
secondly dilution with air sent by the same fan directly to the blower
ducts, which gives greater flexibility in regulating the temperature and
the pressure, and a more uniform temperature. Moreover, the positioning
of the passages inputting heat to the blower ducts downstream of the
recycling fan avoids any damage to or destruction of the fan.
Preferably the heat source can be common to at least two
sections, the temperature of the air arriving at the nozzles of each sec-
tion being regulable independently by dosing the heat input to each of the
sections; in this way, for example, variable angle flaps can be disposed
in the passages inputting heat to the blower ducts of at least one of the
sections of the housing which enables the flow of burnt gas from the
combustion chamber going to the different sections to be regulated, so as
to obtain different temperatures in the sections and thus provide pro-
gressive evolution of the heating of the moving web. These flaps can be
controlled normally or automatically and, in the latter case, the flaps
of one section can be connected to an automatic regulator device, itself
connected to temperature pick-ups disposed in that section and in a
juxtaposed section.
.
6.
In an embodiment, it can be arranged that the nozzles of a
given sect;on of the housing are split into at least two groups which
are connected to the supply means of combustion gas recycled air mixture
by two temperature regulating means, which are separately controllable.
The section can be separated, by means of partitions, into at least two
parts, a control flap being formed by the same number of separately con-
trollable members, which enables blower temperatures which are different
and controllable to be obtained in the same section.
Preferably the extractor fan can be situated inside the hous-
10 ing of the apparatus, in which case only its drive motor is disposedoutside, which avoids having to provide a special frame disposed on the
envelope, eliminates the connecting ducts which would be heat insulated,
and above all deadens the noise of the fan.
In particularly advantageous fashion, each of the web inlet
and outlet openings in the envelope is provided with two nozzles placed
one above and one below, and which each present at least one air ejec-
tion slit extending transversely relative to the direction of web move-
ment and across the whole width of the web, these nozzles being connected
to a source of a;r external to the envelope Gf the appara~us and which
is associated with pre-heating means. In this way, these nozzles form
curtains of air which obstruct the entry of outside air through the inlet
and outlet openings, the air blown in the form of a curtain being taken
from outside the housing and pre-heated, which eliminates the risk of
condensation within the housing and also reduces the required extraction
flQw. Preferably, the upper and lower nozzles of each of the inlet and
outlet openings can each present two slits spaced apart in the direction
of web movement, the space between the upper slits being offset and par-
tially overlapping relative to the space between the lower slits.
This arrangement creates an additional node on the path of the
web, at the inlet or outlet of the housing thus stabilising further
3l1'7~j~3~2
the web movement, particularly at its entry into the housing where it
elilninates flapping which would lead to harmful contacts. Moreover, the
creation of this additional node, adjacent the inlet or outlet opening,
reduces practically to zero the play of the web in the opening, such that
the height of the opening can be made minimal and reduce practically to
zero the inflow of external air which might enter the housing through
this opening (the flow being a function of the cross-sectional area of
the passage presented and of the speed of flow, therefore of the diffe-
rence in air pressure between the inside and the outside).
Conveniently, the external air source can comprise a fan for
combustion air associated, as well, with the heat source, which avoids
having to instal an additional air source and enables a reduction in
energy consumption since, in normal operation, the burner only works at
approximately one third of its power, the maximum power only being used
during warm-up of the apparatus, while moreover there is no disadvantage
in having a lower air pressure in the inlet and outlet nozzles during
warm-up since there is not yet, in this phase any solvent passing through
the apparatus which might produce condensation.
; Preferablyj again, the pre-heat.ng means can cnmprise a he~t
exchanger situated in the combustion chamber of the burner of the appa-
ratus which avoids using any additional source of pre-heat.
Thus the pre-heating means can be arra-nged to comprise a
system for recovering heat from one of the two heat bearing elements
consisting of the dried web and the air coming out of the extractor fan
(with or without filtering of this air).
In a particular embodiment the external air source and the
heat recovery system can be associated with a web cooler disposed at
the output of the drying apparatus (the fan for burner combustion air
can, for example, take air in from the hood of the web cooler).
3Ll'~t~ Z 8.
Preferably the control of the extractor fan flow can be connec-
ted to an automatic regulat;on device, itself servo-ed both to an element
measuring the pressure difference between the inside and the outside of
the housing and an element for measuring a second parameter relating to
the concentration of solvent occurring in the apparatus. This enables
extraction to be reduced when the solvent concentration is low and to in-
crease it when the concentration is high, this regulat;on being essential
to avoid the undesirable condensation referred to above. The second para-
meter used can comprise, for example, the rotor speed in the case of a
press line, the power of the burner or again the concentration of oxygen
in the housing or the solvent concentration itself in the extracted air.
Preferably, the longitudinal members bearing the nozzles com-
prise tubes presenting air flow orifices which communicate with said
nozzles and are open at their ends, so that a small part of the blown air
penetrates these longitudinal members and ensures a uniform temperature.
Other features and advantages of the invention will appear
from the following description, by way of non-limiting example, with
reference to the acoompa~ying drawings in which :
: Fig. 1 represents an external perspective veiw of an apparatus
according to a particular embodiment, in accordance with the invention,
and comprising two sections;
Fig. 2 represents a diagrammatic view of this apparatus in
vertical section in a vertical longitudinal plane of the apparatus;
Fig. 3 represents a perspective view of a blower according to
a particular embodiment of the invention and including a saparation wall,
Fig. 4 represents a.transverse section of the part of the
apparatus through which passes the web;
Fig. 5 represents a detail from Fig. 4 according to a parti-
cular embodiment of the invention.
.
~L1'~tj~4 ~ 9
The apparatus represented in the drawings is an apparatus for
drying webs of printed paper coming from an offset printing line.
The apparatus comprises, mounted on a support consisting of
feet 1, a closed envelope 2 which has a generally parallelopiped shape,
comprising two vertical end faces 2a and 2b in each of which is formed
an inlet ~3a) or outlet (3b) opening, in front of which is disposed a
pair of nozzles 4a or 4b fixed outs;de on the end faces 2a and 2b, the
two openings 3a and 3b defining a horizontal plane for movement of the
web to be dried, the movement following a direction D extending horizon-
tally from the inlet opening 3a towards the outlet opening 3b.
In succession in the longitudinal direction of the apparatus
which forms the direction of movement D, thehousing comprises two
separate sections comprising parallelopiped chambers 5a and 5b which
are joined in a vertical plane 6 and are fixed together in this plane.
In the vertical direction, each of these sections 5a and 5b
comprises two superposed chamber elements 7a and 7b, the lower chamber
7a forming the blower chamber, while the upper chamber 7b forms a
reheating chamber, the elements being joined in a horizontal plane 8.
In each of the blower chambers 7a and 7b of the two sections
5a and 5b, are disposed two sets of nozzles 9c and 9d, disposed in two
horizontal planes parallel to the average plane of the web B and placed
at a small distance from this plane, for example 3 to 4 mm away. Each
of the nozzles 9c or 9d comprises an elonsate bar extending transversely
relative to the direction D, this bar being hollow and comprising, on
its face towards the web B two parallel slits, transverse relative to
the direction D and extending right across the width of the web B, these
slits 10 being separated by a solid part which enables an air cushion
to be created ensuring the support of the web B upwards or downwards.
The air bars 9c above the band B are disposed in alternation in the
iongitudinal direction D with the lower bars 9d, of equal number,
6~2 lo.
so as to ensure equal spacing between the alternate bars with a pitch p.
The different nozzles 9c or 9d, disposed above or below the
web are fixed to a collector or plenum llc or 11d which extends horizon-
tally in the direction D along the whole set of associated elements,
each collector communicating both with the air bars 9c and 9d and with
a communication duct 12c or 12d, these ducts outputting into the collec-
tors llc and 11d in the middle of the collectors lengthwise (although
for clarity, the junction of the lower duct 12d has been displaced in
the diagram to one end of the collector).
The same arrangement exactly is provided in the second section
5b of the envelope. The two upper collectors llc and the two lower col-
lectors lld are positioned lengthwise, moreover, so that the same pitch p
which separates the different nozzles of a given collector also separates
the last nozzle 9d of the lower collector of the first section from the
first nozzle of the upper collector of the second section thus ensuring
perfect alternation of the air cushions fr~m one end of the housing
to the other.
The lower collectors 11d are mounted in two parts telescopically
sliding relative tQ each other in the vertical direction, with elastic
seals 13 interposed between the shaped facing edges of the two component
parts. The lower part of the lower collectors being fixed, their upper
part which carries the air bars 9d can therefore be displaced vertically
by a push rodard linka~e shown schematically at 14 and reacting against
the housin~ itself. The mechanism 14 is controlled by a jack 15 which
itself is supplied with compressed air 16 though a distributor 17. This
enables the lower set of nozzles to be lowered either when the apparatus
is shut down, for example for washing the plates, or during operation
to avoid damage to the paper which, over-heated, would break and require
the apparatus to be re-started, with a consequent considerable waste
of time. The mechanism 14 supports the two longitudinal hollow tubular
~7~
members 18 which are disposed laterally, on opposite sides of the
collectors 11d, and on which the nozzles 9d are fixed.
As shown more precisely in Fig. 4 and 5, each of the air
bars 9c which communicates in its central part and by its its upper face
with the upper collector or plenum llc, is also fixed and suspended at
each of its two ends beneath one of the two hollow tubular members 18,
which itself is suspended permanently from the envelope 2. Holes 19 are
formed between these members 18 and the air bars 9c, so as to ensure
that hot air penetrates inside the members 18 which are also open at
their ends, this circulation of air ensuring, in this way, a uniform
temperature. The same applies to the lower air bars 9d, which are fixed
and carried in an exactly symmetrical fashion above other hollow tubu-
lar members 18, fixed to a part 18a which can be displaced vertically
using the mechanism 14. Holes 19 are also provided between the bars 9d
and these members 18 to ensure a similar circulation.
Each pair of nozzles at the inlet 4a and outlet 4b presents
a horizontal passage for the web B at the height of the inlet (3a) and
outlet (3b) openings these horizontal passages 20 comprising nozzles
consisting of slits transverse to the direction D, of which two are
provided on each of the upper and lower faces of this passage, the two
upper slits 21c being disposed alternately with the two lower slits
along the hor;zontal direction D. These slits 21c and 21d are disposed
at practically the same distance from the web B as the slits of the air
bars 9c and 9d, and the slit 21d or 21c of each nozzle closest to the
end wall 2a or 2b of the envelope is positioned as close as possible to
the inlet opening 3a or to the opening 3a or 3b, this same slit 21c or
21d being also disposed at the same distance p from the closest air bar
9c or 9d inside. The air coming out of each of the slits 21c, 21d forms
à curtain of air which separates the gases within the housing 2 from the
external air. Moreover, the slits being disposed in pairs on opposite
. ~
ti~4 ~
12.
sides of the hand, air cushions are formed which also maintain rodes of
undulations in the path of the web B.
In each of the upper elements 7b of the two sections 5a and
5b, is a recycling chamber 22a or 22b, each of these chamberscommunica-
ting with the outlet of a blower or recycling fan 23a or 23b which isfixed under the upper surface of the housing 2, so that only the drive
motor 24 of each fan is disposed above the hous}~g. The two side ends
of each of the chambers 22a or 22b are connected to vertical ducts 12c
and 12b which output into the collectors llc and 11d.
In the outlet wall 2b of the hou~ing and at the level of the
upper element 7b, a burner 24 is fixed which can be a mixed burner
operating either on gaz or on fuel oil. Within the housing the torch
of the burner which emits the flame 24a is surrounded with a certain
gap 25, by a cylindrical combustion chamber, which extends from this
burner as far as the front end of the blower chamber 22a. This combus-
tion chamber 26 presents enlargedparts, at the level of the two blower
chambers 22a and 22b, in the shape of hoods directed downwards and
; communicating through passages 27 with the vertical ducts 12c and 12d.
At the edges cf these pass~ges ?' are piv~cd control fa'ps 28 which
enable the proportion between the recycled air coming from the fan 23a
or 23b and the burnt gas coming from the combustion chamber to be
varied.
In a particular embodiment, the control flaps 28 of the first
section 5a are connected mechanically to a servo motor 29 which itself
is connected electrically to a control device 30 receiving values given
by two temperature pick-ups 31a and 31b disposed respectively in the two
upper collectors llc. The control of the burner 24 is connected on one
hand to a second temperature pick-up 32 disposed in the second section
5b or else to an infrared temperature detector 33 disposed downstream
of the outlet block 4b. The input of combustionair for the burner 24
3L~ 7 6 ~3~2 13.
is connected to the output of a fan 34 which itself is fed from the hood
of a cooler 44, disposed downstream ofthe drying apparatus, and through
which the web B passes subse~uently.
On the p;p;ng supply;ng combust;on a;r to th;s burner, a
second pipe 36 is connected which enters the combustion chamber 26, at
the le~el of the chamber 22b and passes through this chamber to the
other side so as to form a heat exchanger with this chamber, the pipe
then subdividing to join the two inlet (4a) and outlet (4b) blocks in
both their upper and lower parts.
The blower chamber 22b of the second section also communicates
w;th a th;rd duct 37 wh;ch is bent round so as to house the combus-
tion chamber in the vicinity of the burner and to communicate with the
gap 25 left free round the burner so as to bring in recycled air at
this po;nt.
Finally, between the two blower chambers 22a and 22b, there
is provided an extractor fan 38 which ;s fixed under the upper wall of
the housing 2 ;n similar fash;on to the fans 23a and 23b and which
communicates w;th a chimney 39 venting to air. In the chimney ;s ;nter-
posed a flap 40 for controlling the flow of air extracted which is con-
trolled by a jack 41 receiving on one hand a signal com;ng from a regu-
lation device 42 fed with air sensitive to the pressure drop within
the housing and on the other hand a transm;tter 43 sensitive to the
solvent concentration within the housing.
As shown m~re precisely ;n Fig. 3, the upper collector or
plenum llc has the shape of an elongate parallelopiped chamber w;th a
wedge-shaped end, that is to say a chamber whose cross-section ;n a
vertical plane parallel to the direction of web movement D is a trapeze.
The alr bars 9c are fixed underneath and across the whole width of this
chamber. Above this chamber, and across a part only of ;ts width, is
disposed the duct 12c which, conversely, extends along the whole lensth
~ 4 ~ 14.
of the upper face of the plenum llc. At its upper end, this duct 12c com-
municates with another feed chamber 22a, which extends over the same
length as the duct in the direction D, which projects from it transver-
sely (in the direction of the air bars 9c) and within which is disposed
the recycling fan 23a. Within the blower duct 12c, is disposed a vertical
partition 44 extending transversely, this partition being extended by a
further partition 44a which also extends transversely over the whole
w;dth of the collector 11_~ but is inclined generally parallel to one of
the duct 12c are mounted, pivoting about a horizontal axis X-X, parallel
to the direction of web movement D, two control flaps 28, 28' disposed
on opposite sides of the partition 44 in this section of this duct 12c.
There are thus two air currents which pass on opposite sides of the
partitions 44 and 44a to reach the group of air bars 9c positioned in
front of the partition 44a and to reach the group behind it.
It should be noted lastly that it can be arranged for each
section of the housing to contain two housing elements disposed in
relation to each other above, below or beside, in any case transversely
rel~tive to the direction of web movement, these elements comprising
one the blower zone and the other the reheating zone, which presents
a great flexibility of adaptation as a function of the space available
or of any desired lateral extension of the apparatus. The reheating
element of each section can be positioned remote from the blower
element, in which case a third element establishes the connection
between these two.
