Through-air dryer assembly
View Patent ↗A through-air dryer is disclosed. The through-air dryer includes a cylindrical deck made from a plurality of deck plates that support a throughdrying fabric. The deck plates are supported by opposing hubs. Each of the hubs is in communication with a bearing that is mounted to a stationary shaft for allowing the cylindrical deck and the hubs to rotate. The bearings are positioned so as to create a through-air dryer structure that remains stable during operation and allows for easy calculation of loads on the dryer.
1. An apparatus for through-air drying webs comprising:
a cylindrical deck having sufficient open space to permit air flow therethrough;
a stationary support shaft concentrically positioned with respect to the cylindrical deck;
a support structure positioned between the cylindrical deck and the support shaft for supporting the cylindrical deck, the support structure being configured to rotate on the support shaft, the support structure comprising a first hub spaced from a second hub, each hub engaging an opposite end of the cylindrical deck, the support structure further comprising a rotating tube surrounding the support shaft, the rotating tube being connected at a first end to the first hub and at a second end to the second hub; and
a gas source in communication with the cylindrical deck and being configured to supply a gaseous stream through the cylindrical deck for drying webs thereon.
2. An apparatus as defined in claim 1 , wherein the support structure further comprises at least one internal deck support extending between the rotating tube and the cylindrical deck, and a deck support ring supporting the cylindrical deck in between the first end of the cylindrical deck and the second end of the cylindrical deck, the support ring being connected to the at least one internal deck support.
3. An apparatus as defined in claim 2 , wherein the support structure includes a first internal deck support and a second internal deck support extending between the rotating tube and the cylindrical deck, each of the deck supports being connected to the deck support ring.
4. An apparatus as defined in claim 1 , wherein the apparatus further comprises a first bearing and a second bearing, the first bearing being positioned between the first hub and the support shaft and the second bearing being positioned between the second hub and the support shaft, each bearing being substantially in alignment with each end of the cylindrical deck.
5. An apparatus as defined in claim 4 , wherein the first and second bearings are located so that there is substantially no moment transfer between the cylindrical deck and the support structure.
6. An apparatus as defined in claim 1 , further comprising a hood surrounding the cylindrical deck for directing a hot gaseous stream through the cylindrical deck or away from the cylindrical deck.
7. An apparatus as defined in claim 1 , further comprising a throughdrying fabric wrapped around the cylindrical deck, the throughdrying fabric being configured to carry a web over a portion of the surface of the deck.
8. An apparatus as defined in claim 7 , wherein the throughdrying fabric is wrapped around the cylindrical deck from an upstream point to a downstream point leaving an open free end, and wherein the apparatus further comprises an external baffle positioned over the open free end of the cylindrical deck, the external baffle shielding the open free end of the drying cylinder from external air.
9. An apparatus as defined in claim 1 , wherein the cylindrical deck comprises a plurality of individual deck plates that are attached to the support structure.
10. An apparatus as defined in claim 9 , wherein the individual deck plates are attached to the support structure using a pin attachment structure.
11. An apparatus as defined in claim 9 , wherein the deck plates have a cross sectional profile that tapers in a direction opposite the direction of gas flow through the cylindrical deck.
12. An apparatus as defined in claim 9 , wherein a load supported by the deck plates of the cylindrical deck is the sum of the following forces:
ω
=
w
·
t
·
l
·
δ
where
:
ω
=
weight
per
unit
length
of
a
deck
plate
w
=
width
t
=
thickness
l
=
unit
length
δ
=
density
of
material
F
p
=
2
·
Δ
P
·
r
o
·
l
·
sin
(
θ
2
)
where
:
θ
=
Change
in
angle
between
deck
plates
r
o
=
Outside
radius
of
cylindrical
deck
F
p
=
Force
from
differential
pressure
l
=
Unit
length
of
plate
F
n
=
l
·
t
·
δ
·
V
i
2
2
·
r
i
2
(
r
o
2
-
r
i
2
)
where
:
F
n
=
Normal
force
on
bar
from
rotation
t
=
thickness
l
=
unit
length
δ
=
density
of
material
V
i
=
Velocity
at
“
r
i
”
r
i
=
radius
on
inside
of
support
bar
r
=
distance
from
center
of
TAD
;
and
F
t
=
2
·
T
·
sin
(
θ
2
)
where
:
F
t
=
Force
per
unit
length
from
tension
T
=
Fabric
tension
per
unit
length
θ
=
Change
in
angle
between
deck
plates
.
13. An apparatus as defined in claim 3 , wherein the first deck support and the second deck support have a conical shape for directing gas flow between the cylindrical deck and the first and second hubs and wherein the rotating tube shields the first bearing and the second bearing from the gas flow.
14. An apparatus as defined in claim 1 , wherein the cylindrical deck and the support structure are configured to be disassembled, the apparatus having a disassembled volume when being shipped, the disassembled volume having a maximum dimension that is less than one-half the diameter of the cylindrical deck.