Air recycling apparatus for drying a textile web

An apparatus and method for removing moisture from a porous textile web. The web is passed sequentially through a plurality of drying regions, dividing each of the drying regions into an upper drying zone and a lower drying zone. Air is drawn through the traveling web by variable speed fans disposed in the drying regions, the air forced by each of the fans into an air passageway having fluid communication with all of the upper drying zones and separated into air channels by divider panels. The fans are operable to maintain differential fluid pressure across the web in each of the drying zones, with the differential fluid pressure being greatest in the drying region last traversed by the web and decreasing at each of the drying regions upstream thereof so that the lowest differential fluid pressure is maintained in the first drying region, a portion of the air from each fan being caused to be recirculated to the upper drying zone above the respective fan and a portion of the air being passed to the upper drying zone of the respective adjacent upstream drying zone.

BACKGROUND OF INVENTION 
1. Field of Invention 
The present invention relates to the field of textile manufacturing, and 
more particularly but not by way of limitation, to equipment for the 
removal of moisture from textile products. 
2. Discussion 
In the manufacture of textile products, which are usually processed in long 
webs of varying widths, the textile material must be passed through a wash 
cycle to remove excess dye products and other accumulated substances, and 
following the wash cycle, the textile product must be dried. Numerous 
prior art devices have been operated with varying degrees of 
effectiveness, most of which have become near obsolete as the cost of 
energy has increased traumatically worldwide during the last few years. As 
energy has become more determinative of equipment function, different 
approaches to dryer designs have attempted to increase the operating 
efficiency while maintaining a reasonable balance of equipment investment. 
Examples of recent prior art dryer designs may be found in the following 
patents: U.S. No. 3,955,287 subjects a carpet web to an initial high 
temperature air stream as the web enters the initial drying region, after 
which the carpet passes through another drying region that is maintained 
at a lower temperature; U.S. No. 3,743,474 subjects the entering carpet 
web to a high velocity of exhausting air, and as the web continues through 
the machine, low velocity heated air is recirculated through the web; and 
U.S. No. 3,849,904 passes a carpet web through a series of four chambers, 
paired such that the first and third chambers, and the second and fourth 
chambers, operate to force air down through the traveling web, and 
independent heat recovery systems operate to extract energy from the 
exhausted air. 
SUMMARY OF INVENTION 
The present invention provides an apparatus and method for removing 
entrained moisture from a porous carpet web wherein the web is passed 
through a plurality of housing assemblies defining an equal number of 
drying regions. The carpet web initially passes through a first drying 
region and then through each of the other drying regions in sequence, 
dividing each of the drying regions into an upper drying zone and into a 
lower drying zone. A plurality of air fans, one for each drying region, 
maintain differential fluid pressure across the traveling web between the 
upper and lower zones of each region to establish air flow through the 
web. Plural conduits interconnect the drying regions so that the air drawn 
from the lower zone of each drying zone is passed in part to the upper 
zone above said lower zone and in part to the upper zone of the respective 
adjacent upstream drying region by the maintenance of a lower differential 
fluid pressure in said adjacent upstream drying region. Plural heater 
units are disposed in selected ones of the drying zones for heating the 
air passing therethrough; an air inlet conduit permits external air entry 
only to the upper zone of the drying region last traversed by the 
traveling web; and an exhaust conduit withdraws air only from the first 
drying region traversed. 
The exhausted air, in the preferred embodiment of the invention, is passed 
through a condenser apparatus in heat exchange relationship to a coolant 
fluid to cool the exhaust air and to remove moisture. The cooled and 
partially dried exhaust air is then passed as inlet air to the air inlet 
conduit; a portion of the exhaust air can be discharged to the atmosphere 
as required. 
It is an object of the present invention to provide an apparatus and method 
for drying a porous textile product wherein maximum hot air contact is 
made with the textile product utilizing a minimum of equipment hardware. 
Another object of the present invention, while achieving the above stated 
object, is to provide a dryer apparatus that maximizes the utilization of 
heating energy consumed by the apparatus. 
Yet another object of the present invention, while achieving the above 
stated objects, is to provide a dryer apparatus of compact design that 
facilitates manufacturing, and minimizes operating and maintenance 
expense. 
Other objects, features and advantages of the present invention will become 
apparent from a reading of the following detailed description of the 
preferred embodiment when considered with the included drawings and 
appended claims.

DESCRIPTION OF INVENTION 
Referring to the figures generally, and particularly to FIGS. 1 and 2, 
shown therein and designated by the numeral 10 is a dryer apparatus 
constructed in accordance with the present invention. In FIG. 1, the dryer 
apparatus 10 is shown in semi-detail, side elevational view, and in FIG. 
2, a sectional view of the dryer apparatus 10 is shown as taken along the 
line 2--2 in FIG. 1. 
The dryer assembly 10 comprises a housing 11 that is in turn subdivided 
into a plurality of housing assemblies through which a web 12, 
representing a porous carpet or the like, passes sequentially. Each of the 
housing assemblies serves as an individual drying region, and for purposes 
of the present disclosure, the dryer apparatus 10 is depicted having a 
first housing assembly 14, a second housing assembly 16, a third housing 
assembly 18, and a fourth housing assembly 20. These drying assemblies 
will also be referred to hereinbelow as the first drying region 14, the 
second drying region 16, the third drying region 18 and the fourth drying 
region 20. 
The drying apparatus 10 is constructed generally in the shape of an 
elongated, box-like housing member having a front wall 24 and a back wall 
26; a top wall 28 and a bottom wall 30; and a first side wall 32 and a 
second side wall 34 (the side walls viewable in FIG. 2), all of which 
interconnect to form a generally sealed internal compartment 34. The 
bottom wall 30 is supported on a series of longitudinally extending I-beam 
members 36 which in turn are supported on a floor 38. 
Internally, the internal compartment 34 is divided into the above-mentioned 
drying regions by a series of inner wall partitions. That is, a first wall 
partition 40 attaches to, and extends normal from, the second wall 34, and 
the wall partition 40 extends generally normal between, and attaches to, 
the top wall 28 and the bottom wall 30. Various means may be utilized for 
attaching the first wall partition 40 to the top, bottom and side walls 
28, 34 and 30, respectively, such as by welding, and such attachment 
should provide a substantially airtight seal. 
In like manner to that described for the first wall partition 40, a second 
wall partition 42 and a third wall partition 44 are attached to, and 
extend generally normal from, each of the top wall 28, the bottom wall 30 
and the second side wall 34 in spaced apart, parallel relationship to each 
other and to the first wall partition 40. The partitions 40, 42 and 44 
attach to a longitutinally extending internal wall member 48 that is 
supported by the housing 11 and disposed to extend from the front wall 24 
to the back wall 26 between, and substantially parallel to, the first and 
second side walls 32, 34. The wall partitions 40, 42 and 44 are sealingly 
attached to the internal wall 48 (as by welding), and the ends of the 
internal wall 48 are sealingly attached to the front and back walls 24, 
26. The internal wall 48 attaches to the bottom wall 30, and an air 
passageway 50 is formed between the top edge 52 of the internal wall 
member 48 and the top wall 28 of the housing 11. 
Between the first wall partition 40 and the front wall 24, a baffle member 
46 attaches to, and extends generally normal from, the bottom wall 30 in a 
generally parallel, spaced-apart relation to the first wall partition 40 
and the front wall 24. The baffle member 46 extends between, and attaches 
to, the second side wall 34 and the internal wall member 48. The top edge 
47 of the baffle member 46 is disposed just below the lower surface of the 
carpet 12 such that the carpet 12 passes closely to, but does not touch, 
the baffle member 46. Also, the internal wall member 48 has an extension 
portion 54 that extends to, and attaches to, the top wall 28 in the manner 
illustrated in the isometric, partially phantomized view of FIG. 3. 
The above described arrangement of internal wall partitions in the housing 
11 provides for the division of the internal compartment 34 into several 
compartments as follows: the internal wall member 48 divides the internal 
compartment 34 into an air passing compartment 55 on one side of the wall 
member 48 and into a drying chamber 56 on the other side of the wall 
member 48. The partitions 40, 42 and 44 serve to divide the drying chamber 
55 into a first drying region 60, a second drying region 62, a third 
drying region 64 and a fourth drying region 66. The web 12, traveling in 
the direction indicated by the arrow 70, passes through a slot provided in 
each of the front and back walls 24, 26 and through slots provided in the 
inner wall partitions 40, 42 and 44. That is, the web 12 enters the 
housing 11 through a slot or web entry opening 72 provided in the front 
wall 24; the web 12 passes through the first drying region 60, and exits 
this drying region via a web opening 74 in the first wall partition 40; 
the web 12 passes through the second drying chamber 62 and exits this 
drying region via a web opening 76 in the second wall partition 42; the 
web 12 passes through the third drying region 64 and exits via a web 
opening 78 in the third wall partition 44; finally, the web 12 passes 
through the fourth drying chamber 66 and exits this drying chamber via a 
web exit opening 80 in the back wall 26. 
The baffle member 46 is disposed to partition off the drying chamber 56 
beneath the textile web 12 in the first drying chamber 60 to form an 
exhaust region 84 from which the dryer air finally exits from the drying 
chamber 56, as will be made clear below. 
The web openings 74, 76 and 78, disposed respectively in the first wall 
partition 40, the second wall partition 42 and the third wall partition 
44, are sized to freely pass a textile web, and conventional sealing 
curtains (not shown) may be disposed at these openings to minimize air 
passage therethrough. Also, conventional air curtain assemblies 86 and 88 
(shown diagrammatically in FIG. 1) may be provided to minimize air 
escapement from the web entry opening 72 and the web exit opening 80 
disposed respectively in the front wall 24 and the back wall 26. 
The carpet web 12, in its passage through the housing 11, divides each of 
the drying regions into an upper (or first) zone and into a lower (or 
second) zone on opposing sides of the web 12. That is, the traveling web 
12 divides the first dryer region 60 into an upper zone 90 on a first side 
92 of the web 12, and into a lower zone 94 on a second side 96 of the web 
12. Similarly, the web 12 divides the second dryer region 62 into an upper 
zone 100 and into a lower zone 102 on opposite sides of the web 12, the 
web 12 divides the third dryer region 64 into an upper zone 110 and into a 
lower zone 112 on opposite sides of the web 12; and the web 12 divides the 
fourth dryer region 66 into an upper zone 120 and into a lower zone 122 on 
opposite sides of the web 12. A discussion of the air flow in the dryer 10 
is provided hereinbelow, and the reason for considering these upper and 
lower zones will be made clear. 
Returning to the air passing compartment 55 mentioned hereinabove, and with 
reference especially to FIGS. 1 and 3, it will be noted that a plurality 
of divider panels are disposed within the compartment 55 in the following 
manner. A first divider panel 130, a second divider panel 132 and a third 
divider panel 134 are disposed to divide the air passing compartment 55 
into a first air channel 136, a second air channel 138, a third air 
channel 140 and a fourth air channel 142. Each of the divider panels 
extends angularly from the bottom wall 30 to the top of the internal wall 
member 48 at which point each panel extends generally vertically to the 
top wall 28, and each divider panel extends between the internal wall 
member 48 and the first side wall 32; further, each wall panel is attached 
at points of contact with the bottom wall 30, the top wall 28, the 
internal wall 48 and the first side wall 32 via welding or the like to 
seal air flow except as directed in the above described air channels 136, 
138, 140 and 142 in the manner described below. 
The structure of the divider panels is as follows: the divider panel 130 
has an angled portion 144 and a vertically extending member 146; the 
second divider panel 132 has an angled portion 148 and a vertical member 
150; the third divider panel 134 has an angled portion 152 and a vertical 
portion 154. Additionally, an exhaust divider panel 160, similar to the 
other divider panels described, is disposed to form an exhaust conduit 162 
near the front wall 24 as shown, and has an angled portion 164 and a 
vertical member 166. The vertical member 166 is connected to the 
vertically extending portion 54 of the internal wall member 48, and a hole 
168 is provided in the top wall 28 for air escapement. Finally, a divider 
panel 170, having an angled portion 172 and a vertical member 174, is 
provided near the back wall 26 as shown. 
The above described arrangement of the divider panels, as mentioned, 
divides the air passing compartment 55 into several flow channels that 
have been enumerated as the air channels 136, 138, 140 and 142. These flow 
channels, respectively, communicate with the lower zone 94 of the first 
dryer region 60; the lower zone 102 of the second dryer region 62; the 
lower zone 112 of the third dryer region 64; and the lower region 122 of 
the fourth dryer region 66. It will be clear from FIGS. 1 and 3 that each 
of the air channels communicates with two of the upper zones of the drying 
regions, with the exception of the first air channel 136 that communicates 
with the upper zone 90, a space above the web 12 in the first dryer region 
60 and above the exhaust region 84. As for the remaining air channels, the 
second air channel 138 communicates with the upper zone 90 (of the first 
drying region 60) and the upper zone 100 (of the second drying region 62); 
the third air channel 140 communicates with the upper zone 100 (of the 
second drying region 162) and with the upper zone 110 (of the third drying 
region 64); and the fourth air channel 142 communicates with the upper 
zone 110 (of the third drying region 64) and the upper zone 120 (of the 
fourth drying region 66). 
The dryer apparatus 10 has a plurality of variable speed air blowers or 
fans equal in number to the number of drying regions. That is, each drying 
region has an air blower disposed to draw air through the web 12 passing 
therethrough and to discharge the air into its respective air channel. As 
shown in FIGS. 1 and 3, a first air blower 180 is supported by the 
internal wall member 48, having a nozzle portion 182 projecting through an 
aperture (not shown) in the wall 48 into the lower zone 94 of the first 
drying region 60. The blower 180 also has a discharge portion 184 disposed 
in the first air channel 136 of the air passing compartment 55. As for the 
other blower units mentioned hereinbelow, the air blower 180 is of the 
centrifical cage type in which air is drawn through the nozzle 182 and 
discharged peripherally from the discharge portion or rotating fan member 
184. 
In like manner to that which has been described for the first air blower 
180, a second air blower 186 is disposed to draw air from the lower 
portion 102 (of the second drying region 62) and to discharge the air into 
the second air channel 138; a third air blower 188 is disposed to draw air 
from the lower portion 112 (of the third drying region 64) and to 
discharge the air into the third air channel 140; and a fourth air blower 
190 is disposed to draw air from the lower portion 122 (of the fourth 
drying region 66) and to discharge the air into the fourth air channel 
142. Another air blower 192, similar to the other air blowers described, 
is supported by the internal wall member 48 and positioned to draw air 
from the exhaust region 84 and to discharge the air into the exhaust 
conduits 162. The passage of air effected by the air blowers 180, 186, 
188, 190 and 192 through the dryer apparatus 10 will be discussed 
hereinbelow. 
As the air passes through the dryer 10, the air is heated by a plurality of 
heaters located in the lower zones of the drying regions. While any of 
several modes of heating may be employed, the dryer 10 is depicted with 
fuel burners as shown in FIG. 2, which shows a heater assembly 200 having 
a burner unit 202 extending through the second side wall 34 into the lower 
zone 112 of the third drying region 64. A blower unit 204 is located 
outside of the housing 11 and supported on the floor 38. Fuel supply lines 
are not shown. Similarly, heaters 210, 212 and 214 are disposed 
respectively in the lower zones of the first drying region 60, the second 
drying region 62 and the fourth drying region 66. 
The dryer structure depicted as the dryer apparatus 10 shown in the Figures 
has been abbreviated in the interest of maintaining brevity and clarity of 
description herein. It will be understood that there are several features, 
such as electrical conduits, that need not be described, as such are 
conventional. It will be pointed out that certain structural details that 
have not been discussed hereinabove are shown in the drawings, such as the 
rollers 220 that are disposed at intervals along the path of the carpet 
web 12 in its passage through the housing 11; the rollers 220 may support 
an endless conveyor belt (not shown), the rollers 220 may be powered or 
free wheeling. The rollers 220 are conventional and are supported on 
structural members that connect to traversing I-beam members 222 that 
extend between and connect to the second side wall 34 and the internal 
wall member 48. Other structural members, such as stiffening members, may 
be employed as required in a conventional manner. 
Another structural feature that has not been discussed is the air inlet 
conduit, which is represented in FIG. 3 as the hole 224 disposed in the 
top wall 28. The purpose of the hole 224 is to provide means for entering 
air to be admitted to the upper zone 120 of the fourth drying region 66. 
The passage of air through the housing 11 is depicted by the boldly marked 
arrow line 230, which represents the major path of air movement through 
the housing 11. The entering air is admitted to the drying housing through 
the hole 224 and passes fourth drying region 66. The air blower 190 
maintains differential fluid pressure across the traveling carpet web 12 
that divides the upper zone 120 from the lower zone 122, causing the 
entering air to be drawn through the carpet web 12 into the nozzle of the 
air blower 190 to be discharged into the fourth air channel 142 where the 
air is passed in a generally upward direction. A portion of the air 
discharged by the air blower 190 passes along the main air path 230 and 
enters the upper zone 100 of the third drying region 64. As the air 
reaches the top of the fourth air channel 142, it will be recognized that 
this air channel serves as a conduit means that interconnects between 
adjacent drying regions (in this case, the third and fourth drying regions 
64 and 66) so that fluid communication is provided therebetween and air is 
passable from the lower zone of the upstream drying zone to the upper zone 
of the downstream drying zone that is adjacent thereto. However, it will 
also be recognized that the air channel 142 communicates with the upper 
zone above the fourth drying region from which the air has been taken, so 
that a portion of the air that is being discharged into the fourth air 
channel passes back to the upper zone 120 as depicted by the small arrow 
line 120A. As will become clear with the discussion of the operaton of the 
dryer apparatus 10 that is provided hereinbelow, the air blowers 180, 186, 
188 and 190 are operated in a manner that causes the bulk air flow to 
follow the mass flow path indicated by the bold arrow line 230, but a 
considerable amount of recirculating air is created in each of the drying 
regions 60, 62, 64 and 66. 
Continuing with a description of the air flow through the housing 11, the 
portion of air flowing from the fourth air channel 142 to the upper zone 
110 is drawn through the carpet 12 by the third air blower 188 and 
discharged into the third air channel 140. A portion of the air flowing 
through the third air channel 140 follows the path indicated by the bold 
arrow line 230, while another portion of the air flows back to the upper 
zone 64 as indicated by the small arrow line 110A which represents air 
from the third air channel 140 recirculated through the traveling carpet 
web 12 in the third drying region 64. The air portion traveling from the 
third air channel 140 via the bold arrow line 240 is drawn through the 
carpet web 12 in the second drying region 62 via the second air blower 186 
which discharges the air into the second air channel 138. Again, the air 
traveling through the second air channel 138 is divided into a portion 
that follows the bold arrow line 230 and into a portion that recirculates 
as depicted by the small arrow line 100A to be drawn through the carpet 
web 12 in the second drying region 62. The portion that travels along the 
bold arrow line 230 enters the upper zone 90 of the first dryer region 60 
and is drawn through the carpet web 12 via the first air blower 180 which 
discharges the air into the first air channel 136. 
A portion of the air passing through the first air channel 136 follows the 
bold arrow line 230 and discharges into the upper zone 90 at a point 
somewhat upstream to that of the discharge air stream coming to the upper 
zone 90 from the second air channel 136, and as denoted by the small arrow 
line 90A, another portion recirculates through the carpet web 12 to the 
lower zone 44 of the first drying region 60. The exhaust blower 192 draws 
the air along the bold arrow line 230 through the traveling carpet web and 
into the exhaust region 84 to discharge the air into the exhaust conduit 
162 where the air is discharged from the housing 11 through the hole 168 
in the top wall 28. 
From the above description, it will be clear that the bold arrow line 230 
represents the overall air flow through the dryer housing 11, while the 
recirculating air flow loops created in each drying region are depicted by 
the small arrow lines 120A, 110A, 100A and 90A. As the air passes through 
the housing 11, the air is heated via the heating assemblies 214, 200, 212 
and 210 in order, and the moisture content of the air will increase as the 
air is passed through the dryer housing 11. Turning to FIG. 4, depicted 
therein is what happens to the air once it has been discharged from the 
housing 11. 
FIG. 4 is a diagrammatical representation of the dryer apparatus 10 and its 
associated moisture removal equipment. An exhaust conduit 240 connects to 
the dryer housing 11 to receive air from the hole 168 in the top wall 28, 
the exhaust conduit 240 passing the air to a condenser 242. The condenser 
242 has an outer jacket 244 and a heat exchanger coil 245 contained within 
the jacket 244. The air from the exhaust conduit 240 passes through the 
jacket 244 in heat exchange relationship to the heat exchanger 245 and 
enters an air inlet conduit 246. An air bleed valve 248 is provided to 
reduce the amount of air flowing in the air inlet conduit 246 that returns 
to the housing 11 to enter the hole 224 in the top wall 28 of the housing 
11. The amount of air that is bled from the air inlet conduit 246 via the 
air bleed valve 248 will depend upon the type of heaters provided in the 
bottom of each of the drying regions 60, 62, 64 and 66. That is, in the 
case of fuel combustion in which combustion air is introduced into the 
drying regions, a build up in gas volume because of the products of 
combustion and the excess air introduced by the heater assemblies will 
occur, and the total volume of air and gas products recirculated through 
the dryer will remain constant in equilibrium conditions only by removing 
the excess of the air build up. Of course, there will be some leakage in 
the system, and this will mean that the air bleed valve 248 need remove 
only an amount necessary to maintain the proper air flow rate. In the 
event that steam or electrical heaters are used, it is possible that the 
air bleed valve will serve as an air make up valve to provide make up air 
equal to the amount of air lost by leakage. Additionally, it may be 
necessary under certain circumstances to provide air bleed off while at 
the same time providing fresh air make up to the heater 11 in those cases 
in which stoichiometric balances must be maintained when such factors as 
the products of combustion that are introduced in the system must be 
maintained below certain limits. For example, in an oil burner in which 
trace quantities of sulphur are present, a build up of detrimental acid in 
the air must be prevented, and it may be necessary to constantly remove a 
portion of the air and to make up a portion of the inlet air with fresh 
air. 
Continuing with the diagrammatical representation of FIG. 4, a storage tank 
250 is connected to a conduit 252 which connects to one end of the heat 
exchanger 245, and a return conduit 254 is connected between the other end 
of the heat exchanger 245 and the storage tank 250. A pump 256 is 
interposed in the conduit 252. The storage tank 252 holds a coolant fluid, 
such as a process water supply, and the coolant fluid is circulated via 
the pump 256 through the heat exchanger 245 so as to pass in heat exchange 
relationship with the air passing through the condenser jacket 244. The 
coolant fluid is thus heated and returned via the return conduit 254 to 
the storage tank 250. This arrangement serves to extract energy from the 
exhaust air exiting the housing 11 while cooling the exhaust air to 
condensate moisture therefrom in the condenser jacket, the moisture being 
removed therefrom as condensate via a moisture removal conduit 260. The 
cooled and dried air exiting the condenser jacket 244 is available for 
return to the housing assembly 11. In the event that air having less 
moisture is desired for return to the housing 11, conventional drying 
means, such as commercially available adsorbent units, may be employed. 
The temperature of the air exhausted from the dryer housing 11 is measured 
by a conventional temperature measurement and indicating device 270 
disposed in the exhaust conduit 240. The purpose of measuring and 
indicating the temperature of the exhaust air will become clear below when 
the method of operating the dryer 10 is discussed. Basically, although the 
speed or velocity control apparatus that controls the variable speed air 
blowers of the dryer 10 is not shown, the speed of the air blower 190 is 
determined in accordance with the information provided by an exhaust 
temperature measuring and indicating device 270, as the speed of this air 
blower is varied according to whether the temperature of the exhaust air 
from the dryer is at, or deviates from, a set point temperature determined 
by equilibrium conditions within the exhaust region 84. The exhaust 
temperature measuring and indicating device 270 may be a simple 
thermometer disposed in a thermometer well, or it may be a more elaborate 
device featuring multipen readout and recording. 
In like manner to the exhaust temperature measuring and indicating device 
270, similar devices are provided to measure and indicate the temperature 
of the air exiting each of the drying regions 60, 62, 64 and 66. That is, 
a first temperature measuring and indicating device 272 is disposed to 
measure and indicate the temperature of the air removed from the first 
drying region 60 via the first air blower 182; a second temperature 
measuring and indicating device 274 measures and indicates the temperature 
of the air removed from the second drying region 62 via the second air 
blower 186; a third temperature measuring and indicating device 276 
measures and indicates the temperature of the air removed from the third 
drying region 64 via the third air blower 188; and a fourth temperature 
measuring and indicating device 278 measures and indicates the temperature 
of the air removed from the fourth drying region 66 via the fourth air 
blower 190. 
For the purpose of discussing the operation of the dryer apparatus 10, 
reference will be made to "upstream" and "downstream" positions in the 
dryer apparatus. These terms refer to portions of the structure that are 
located relative to the entering and exiting locations of the carpet web 
12. The carpet web 12 enters the dryer apparatus 10 via the web entry 
opening 72 disposed in the front wall 24, and the structure in FIG. 1 
located to the reader's right of the opening 72 will be referred to as 
being downstream. In contrast, structure in FIG. 1 located to the reader's 
left of the web exit opening 80 will be referred to as being upstream. 
Accordingly, air enters the dryer apparatus 10 downstream to the web entry 
opening 72 and bears a sinuous path from the fourth (or last) drying 
region 66 to the first drying region 60 before exhausting from the housing 
11. The carpet web 12, on the other hand, enters the housing 11 at an 
upstream position via the web opening 78 in the front wall 24 and moves 
along a linear, countercurrent path relative to the air flow, the web 
supported by a conveyor or the like supported by the plural rollers 220. 
The path of the web 12 extends from the first drying region 60 to the 
fourth (or last) drying region 66 where the web exits the housing 11 via 
the web exit opening 80 in the back wall 26. 
In this manner, the carpet web 12, passing through the several sequentially 
positioned drying regions in the dryer apparatus 10, divides each of the 
drying regions 60, 62, 64 and 66 into upper and lower drying zones on 
opposing sides of the web 12. The air enters upstream in the dryer 
apparatus 10 and moves downstream, passing through the carpet web 12 in 
each of the drying regions and becoming more saturated with moisture as it 
moves toward the downstream end of the dryer 10. The sinuous movement of 
the air through each of the drying regions 60, 62, 64 and 66 has been 
discussed, and mention need only be made that the air is heated in 
passing, in turn, through the lower zones 122, 112, 102 and 94 via the 
heaters 214, 200, 212 and 210, respectively, in the drying regions 66, 64, 
62 and 60 as the air progresses downstream relative to the web 12. 
In order to assure vigorous recirculation of the air in each of the drying 
regions, the air blower units 190, 188, 186 and 180 are operated at 
different fan velocities as follows. Referring to the differential 
pressure across the dynamic web in each drying region by its respective 
numerical designation, the pressure differential across the web 12 in the 
first drying region 60 will be designated the first differential fluid 
pressure; the pressure differential across the web 12 in the second drying 
region 62 will be designated the second differential fluid pressure; the 
pressure differential across the web 12 in the third drying region 64 wil 
be designated the third differential fluid pressure; and the pressure 
differential across the web 12 in the fourth drying region 66 will be 
designated the fourth differential fluid pressure. 
In the operation of the dryer apparatus 10, the controls of the air blowers 
or fans 190, 188, 186 and 180 are set so as to establish a greater 
differential fluid pressure in the fourth (or last) drying region 66, with 
the value of the differential fluid pressure progressively becoming less 
with the drying regions located upstream relative to the fourth drying 
region 66. That is, the pressure drop effectuated in the drying regions 
increases with the drying regions located downstream (relative to the web 
12) and decreases with the drying regions upstream (relative to the web 
12); this progressively changing pressure drop across the web 12 is 
effected by operating the fourth air blower 190 at a faster air rate than 
the third air blower 188, which in turn is operated faster than the second 
air blower 186, and the second air blower 186 is operated faster than the 
first air blower 180, which is operated somewhat faster than the exhaust 
fan 192. Another way of considering this method of operation is to 
designate the ratio of the fan velocity of the fourth air blower 190 to 
the fan velocity of the third air blower 188 as F.sub. 4 :F.sub.3, the fan 
velocity of the third air blower 188 to the fan velocity of the second air 
blower 186 as F.sub.3 :F.sub.2, and the fan velocity of the second air 
blower 186 to the fan velocity of the first air blower 180 as F.sub.2 
:F.sub.1. The velocities of the air blowers are established to make each 
of these ratios (F.sub.4 :F.sub.3 ; F.sub.3 :F.sub.2 ; and F.sub.2 
:F.sub.1) greater than one, which assures that a portion of air at each 
drying region will be recirculated along the air paths indicated by the 
arrow lines 120A, 110A and 100A. The operation of the exhaust air blower 
192 is established such that the ratio F.sub.1 :F.sub.E is also slightly 
greater than one, thereby assuring recirculation along the air path 
indicated by the arrow line 90A. 
As indicated above, the temperature measuring and indicating devices 270, 
272, 274, 276 and 278 measure and indicate the temperatures, respectively, 
of the exhaust gasses leaving the housing 11, the air drawn from the first 
drying region 60, the air drawn from the second drying region 62, the air 
drawn from the third drying region 64 and the air drawn from the fourth 
drying region 66. In practice, each drying region will have a different 
temperature of air leaving that region because of the varying moisture 
content of the air and the effect of the heating of the air in each 
region. It is contemplated that a computer will receive signals indicating 
the conditions in each drying region, and that the conditions in each 
drying region will be independently monitored and varied, within the 
bounds, of course, of the fan velocity ratio restraints discussed above. 
The determination of the ratio of fan velocities between two adjacent 
drying regions will determine the quantity of air recirculated to the 
downstream (relative to the web 12) drying region. Whether by computer or 
by manual control, the following order is observed in operating the 
sequentially spaced drying regions comprising the dryer apparatus 10. 
With experience on a particular type of carpet web, the equilibrium 
conditions existing in each drying zone can be calculated by performing 
heat and mass balance calculations on the dryer 10. From these 
calculations, conditions are set for each of the drying zones, and a known 
temperature and fan speed ratio is set. For a particular drying region, 
the temperature of the air leaving that region is compared to the 
established or set temperature, and if a variation is observed, the heater 
in that particular drying region is adjusted within the range of the 
heater capability to effect a change in the temperature of the leaving 
air. If the air temperature yet deviates from the set temperature after 
changing the heater to the limits of its capability, the air flow rate in 
the drying region is adjusted within determined ranges of fan velocities 
acceptable within the restraints of establishing the fan velocity ratios 
as discussed above. If, after the fan velocity has been adjusted within 
the limits of the fan capability, there is still a deviation between the 
leaving air temperature and the set temperature, the linear speed of the 
carpet is changed to a carpet speed that brings the temperature back to 
the set point. 
This process of monitoring the temperature of the air is performed for each 
of the drying regions 60, 62, 64 and 66, and it will be recognized that 
the changes effected in one drying region will have a bearing on the 
conditions in the other drying region. Accordingly, it is recommended that 
monitoring of the air temperatures and varying the conditions of the 
drying regions be performed in a sequential manner. That is, it is 
suggested that the changes be performed as necessary for the conditions in 
the fourth drying region 66, immediately following which the conditions 
are monitored in the third drying region 64 and the necessary changes are 
accomplished; immediately following this, the conditions prevailing in the 
second drying region 62 should be monitored and necessary changes made 
accordingly; and immediately following these changes, the conditions in 
the first drying region 60 should be monitored and changes made 
accordingly. Finally, the conditions should be monitored in the exhaust 
region 84 and changes made accordingly in this region. Having performed 
this monitoring process for each of the drying regions 60, 62, 64 and 66, 
and for the exhaust region 84, in sequence, attention once again is 
directed to the fourth drying region 66 and the monitoring process is 
again performed in sequence. Once equilibrium conditions are established, 
little or no changes will be required. With computer monitoring, the 
changes will be made more rapidly and in continuous sequence. 
Once the air exits the housing assembly 11 the air is passed via the 
exhaust conduit 240 to the moisture removal assembly represented by the 
condenser 242 and associated equipment. The exhausted air is passed 
through the condenser jacket 244 in heat exchange relationship to the heat 
exchanger 245. The coolant contained in the storage tank 250 is circulated 
via the pump 256 through the heat exchanger 245 and back to the storage 
tank 250 via the conduit 254. This arrangement serves to collect and 
accumulate a substantial portion of the heat energy contained in the 
exhaust gas leaving the housing assembly 11, and the storage tank 250 
represents a source of energy available for other unit operations of a 
carpet mill or the like. As the exhaust air is passed in heat exchange 
relationship to the heat exchanger 245, moisture is condensed from the air 
and is removed from the condenser jacket 244 via the moisture removal 
conduit 260. The cooled air exits the condenser jacket 244 via the conduit 
246, and the air bleed valve 248 removes a selected portion of the air 
before the air is passed back to the housing assembly 11 to enter the hole 
224. As mentioned above, the air bleed valve 248 may not be necessary when 
products of combustion are not added to the air flowing through the 
housing assembly 11. 
It is clear that the present invention is well adapted to carry out the 
objects and attain the ends and advantages mentioned as well as those 
inherent therein. While a presently preferred embodiment of the invention 
has been described for purposes of this disclosure, numerous changes may 
be made which will readily suggest themselves to those skilled in the art 
and which are encompassed within the spirit of the invention disclosed and 
as defined in the appended claims.