Abstrict A desiccant media containing cartridge for use in a gas drying
apparatus adapted to firstly function in a gas drying cycle in which
a moist gas is permitted to pass upwardly through said desiccant
media whereby at least a portion of the moisture is removed from
said gas, and adapted to secondly function in a desiccant media
purge cycle in which a portion of said dried gas is allowed to pass
back downwardly through said desiccant media to absorb moisture
therefrom thereby at least partially regenerating said desiccant
media, including a means for concentrating the desiccant purge cycle
at the bottom of the desiccant media, which means comprise a purge
tube extending vertically partially through the desiccant media,
and a flapper valve adjacent to an upper end of the purge tube adapted
to close and restrict flow of gas through the purge tube when the
gas is flowing upwardly in during the gas drying cycle and to open
and promote gas flow through the purge tube when the gas is flowing
downwardly during the desiccant purge cycle.
Claims We claim:
1. Gas drying apparatus for use in a compressed gas drying system
comprising:
(a) a cartridge containing a desiccant media and having a pair
of opposed porous wall members, said cartridge adapted to firstly
function in a gas drying cycle in which a moist gas is permitted
to ingress through a first of said porous wall members, pass through
said desiccant media whereby at least a portion of the moisture
is removed from said gas, with the dried gas then egressing through
a second of said porous wall members; said cartridge further adapted
to secondly function in a desiccant purge cycle in which a portion
of said dried gas is allowed to pass back through said desiccant
media to absorb moisture therefrom thereby at least partially regenerating
said desiccant media;
(b) a purge tube extending partially through said desiccant media,
a first end of which is adjacent to said second porous wall member
and a second end spaced from said first porous wall member; and
(c) a one-way valve means adjacent to said first end of said purge
tube adapted to close and restrict flow of gas through said purge
tube when said gas is flowing in said gas drying cycle and to open
and promote gas flow through said purge tube when said gas is flowing
in said desiccant purge cycle.
2. Gas drying apparatus for use in a gas drying system, according
to claim 1 in which said purge tube extends through approximately
a 2/3 length of said desiccant media.
3. Gas drying apparatus for use in a gas drying system, according
to claim 2 in which said purge tube is provided with a plurality
of apertures through a wall thereof adjacent to said second end
of said purge tube.
4. Gas drying apparatus for use in a gas drying system, according
to claim 1 in which said one-way valve means comprises a flat rubber
flapper valve adjacent to said first end of said purge tube and
said second porous wall member, and is adapted to restrict flow
of gas through said purge tube when gas is flowing in said gas drying
cycle, and to overlay and thus block said second porous wall member
and deflect flowing gas into said purge tube when gas is flowing
is said desiccant purge cycle so as to divert at least a majority
of said dried gas through said purge tube during said purge cycle.
5. Gas drying apparatus for use in a gas drying system, according
to claim 4 in which said flat rubber flapper valve is generally
circular in form having a plurality of diametric cuts therethrough
intersecting at an axis of said circular form to provide a plurality
of pie-shaped portion joined at the periphery of said valve, said
plurality of pie-shaped portions adapted to be deflected into said
purge tube when gas is flowing in said desiccant purge cycle.
6. Gas drying apparatus for use in a gas drying system, according
to claim 5 further including a screen member disposed over said
flat rubber flapper valve adapted to maintain the generally flat
configuration of said flapper valve and restrict the flow of gas
through said purge tube when gas is flowing in said gas drying cycle.
7. Gas drying apparatus for use in a gas drying system, according
to claim 6 further including a wave spring disposed over said screen
member adapted to generally maintain said flapper valve and said
screen member biased against said upper porous wall member.
8. Gas drying apparatus for use in a compressed gas drying system
comprising:
(a) a cylindrical cartridge containing a particulate desiccant
media and having a porous wall members at each cylindrical end,
said cartridge adapted to firstly function in a gas drying cycle
in which a moist gas is permitted to ingress through a lower of
said porous wall members, percolate upwardly through said desiccant
media whereby at least a portion of the moisture is removed from
said gas, with the dried gas then egressing through an upper of
said porous wall members; said cartridge further adapted to secondly
function in a purge cycle in which a portion of said dried gas is
allowed to percolate back through said desiccant media to absorb
moisture therefrom thereby at least partially regenerating said
desiccant media;
(b) a purge tube extending partially through said desiccant media,
a first end of which is adjacent to said second porous wall member
and a second end spaced from said first porous wall member; and
(c) a rubber flapper valve adjacent to said upper porous wall member
adapted to restrict flow of gas through said purge tube when gas
is flowing in said gas drying cycle, and further adapted to overlay
said upper porous wall member and open into said purge tube when
gas is flowing is said desiccant purge cycle to thereby divert at
least a majority of said dried gas through said purge tube during
said desiccant purge cycle.
9. A gas drying apparatus for use in a gas drying system, according
to claim 8 in which said purge tube is cylindrical in form and
disposed at the axial center of said drying cartridge.
10. A gas drying apparatus for use in a gas drying system, according
to claim 9 in which said purge tube is provided with a plurality
of apertures through a cylindrical wall thereof adjacent to said
a lower end thereof such that said dried gas can enter radially
into said desiccant media adjacent to the lower end of said purge
tube during said desiccant purge cycle.
11. A gas drying apparatus for use in a gas drying system, according
to claim 9 in which said flapper valve is fabricated of sheet rubber
having a flat annular form adapted to overlay both said second porous
wall member and said first end of said purge tube such that when
gas is flowing is said desiccant purge cycle, said flapper valve
will overlay and block passage of gas directly into said desiccant
through said second porous wall member, and will be deflected into
said purge tube thereby promoting passage of gas into said purge
tube.
12. Gas drying apparatus for use in a gas drying system, according
to claim 11 further including a screen member disposed over said
flat rubber flapper valve adapted to maintain the generally flat
configuration of said flapper valve and restrict the flow of gas
through said purge tube when gas is flowing in said gas drying cycle.
13. Gas drying apparatus for use in a gas drying system, according
to claim 12 further including a wave spring disposed over said
screen member adapted to generally maintain said flapper valve and
said screen member biased against said upper porous wall member.
14. Air cleaning and drying apparatus for use in a compressed air
drying system comprising:
(a) a vertically disposed cylindrical cartridge containing a particulate
desiccant media and having a porous wall members at each cylindrical
end, said cartridge adapted to firstly function in an air cleaning
and drying cycle in which a moist air is permitted to ingress through
a lower of said porous wall members, pass upwardly through said
desiccant media whereby the air is filtered and at least a portion
of the moisture is removed from said air, with the cleaned and dried
air then egressing through an upper of said porous wall members;
said cartridge further adapted to secondly function in a desiccant
purge cycle in which a portion of said dried air is allowed to pass
back through said desiccant media to absorb moisture therefrom thereby
at least partially regenerating said desiccant media;
(b) a cylindrical purge tube extending vertically through an axis
of said desiccant media, the upper end of which is adjacent to said
upper porous wall member and the lower end of which is approximately
2/3 the distance to said lower porous wall member;
(c) a circular flapper valve adapted to overlay said upper porous
wall member and an upper end of said purge tube,
said flapper valve adapted to overlay said second porous wall member
to restrict the flow of air directly into said desiccant media via
said second porous wall member when air is flowing is said desiccant
purge cycle;
said flapper valve having a plurality of diametric cuts therethrough
intersecting at an axis thereof to provide a plurality of pie-shaped
portion joined at the periphery, said pie-shaped portions adapted
to be deflectable into said purge tube to promote the flow of air
through said purge tube when air is flowing is said desiccant purge
cycle;
(d) a circular screen disposed over said circular flapper valve
adapted to maintain the generally flat configuration of said flapper
valve and restrict the flow of air through said purge tube when
air is flowing in said air cleaning and drying cycle; and
(e) a wave spring disposed over said circular screen adapted to
generally maintain said flapper valve and said circular screen biased
against said upper porous wall member.
15. Gas drying apparatus for use in a compressed gas drying system,
according to claim 14 in which said purge tube is provided with
a plurality of apertures through a cylindrical wall adjacent to
said lower end.
16. In a desiccant media containing cartridge for use in a gas
drying apparatus adapted to firstly function in a gas drying cycle
in which a moist gas is permitted to pass upwardly through said
desiccant media whereby at least a portion of the moisture is removed
from said gas, and adapted to secondly function in a desiccant media
purge cycle in which a portion of said dried gas is allowed to pass
back downwardly through said desiccant media to absorb moisture
therefrom thereby at least partially regenerating said desiccant
media; a means for concentrating the desiccant purge cycle at the
bottom of the desiccant media, said means comprising:
(a) a purge tube extending vertically partially through said desiccant
media; and
(b) a flapper valve adjacent to an upper end of said purge tube
adapted to close and restrict flow of gas through said purge tube
when said gas is flowing upwardly in said gas drying cycle and to
open and promote gas flow through said purge tube when said gas
is flowing downwardly in said desiccant purge cycle.
17. A desiccant media containing cartridge, according to claim
16 in which said purge tube extends through approximately a 2/3
length of said desiccant media.
18. A desiccant media containing cartridge, according to claim
17 in which said purge tube is provided with a plurality of apertures
through a wall thereof adjacent to a lower end thereof.
19. A desiccant media containing cartridge, according to claim
16 in which said flapper valve comprises a flat rubber flapper
valve adjacent to an upper end of said purge tube and is adapted
to restrict flow of gas through said purge tube when gas is flowing
in said gas drying cycle, and to overlay and thus block access to
said desiccant media deflecting flowing gas into said purge tube
when gas is flowing is said desiccant purge cycle.
20. A desiccant media containing cartridge, according to claim
19 in which said flat rubber flapper valve is generally circular
in form having a plurality of diametric cuts therethrough intersecting
at an axis of said circular form to provide a plurality of pie-shaped
portion joined at the periphery of said valve, said plurality of
pie-shaped portions adapted to be deflected into said purge tube
when gas is flowing in said desiccant purge cycle.
Description FIELD OF THE INVENTION
The present invention generally relates to a new and improved air
drying apparatus for inclusion within compressed air supply system.
More particularly, the present invention pertains to a new and unique
desiccant containing cartridge having a purge tube and a flapper
valve for inclusion within a desiccant containing drying tower as
utilized within a compressed air cleaning and drying system. The
purge tube and flapper valve function to control ingress of purge
air to concentrate such ingress at a location of highest moisture
content to thereby maximize moisture removal from the desiccant
material during the so-called purge mode of operation.
BACKGROUND OF THE INVENTION
It will be appreciated that a Westinghouse Air Brake Company C-1
air dryer is designed to remove moisture from compressed air for
use in a compressed air system as utilized on railway trains, transit
vehicles and the like, as necessary to operate the air brake system
and air valves. U.S. Pat. No. 5423129 assigned to the assignee
of this invention and cited above, discloses such a system wherein
the compressed air is cleaned and dried by passing it through a
regenerating system containing a desiccant material to absorb the
moisture and filter-out particulate matter. The desiccant is regenerated
by passing a small percentage of the dried air back therethrough
which absorbs at least some of the moisture collected in the desiccant
and is therefore discarded.
In operation, the above noted prior art air drying system (now
referred to as the "single tower" system) receives compressed
air from a conventional air compressor, a supply which typically
contains an unacceptably high amount of moisture and other particulates
suspended therein. This unpurified compressed air is caused to flow
upwardly through a desiccant material usually in the form of a porous
cartridge containing a porous desiccant media. The desiccant plays
the key role within the single tower air drying system in that it
absorbs the moisture and traps various particulates (e.g., dust,
dirt, etc.) as the compressed air moves upwardly through the desiccant
media. Once moisture and particulates are extracted from the air
stream, the cleaned and dried compressed air continues flowing from
the desiccant media through a purge check valve situated near the
top of the tower. This purified compressed air then passes through
a side chamber, a part of which eventually reaches a purge volume.
When the air compressor is cycled off, the system operates in a
purge mode. During the purge mode, the purified pressurized air
contained within the purge volume passes slowly in the reverse direction
through a choke in a purge check valve and then back through the
desiccant media. This slow stream of dried air reabsorbs a portion
of the moisture previously collected within the desiccant media.
Having evaporated into this passing stream of dry air, the evaporated
moisture eventually exhausts through the sump volume to atmosphere.
This gradual purging of dry air back through the system serves to
dry out and thus rejuvenate or regenerate the desiccant media. When
the air compressor is again cycled on, the tower system returns
to operation in a drying mode, with the desiccant media then again
removing moisture from the stream of unpurified compressed air passing
therethrough.
More recently, a twin tower system has been proposed and developed
in which a pair of desiccant containing chambers or towers are provided,
each alternating back and forth between operation in drying mode
and in recycle mode. Accordingly, at any given moment of operation,
one tower is operating in air drying cycle while the other is operating
in recycle mode or purge cycle. A pair of control valves are provided
to automatically switch the flow to reverse these flow directions
so that after a defined time period the cycles are reversed so that
in effect a continuous operation is achieved with each tower alternately
operating in drying mode permitting moisture to collect within the
desiccant media while the other tower is in recycle mode removing
the collected moisture from the desiccant material or media. This
unique system obviously had a greater moisture removing capability
and also avoids the need to have the source of unpurified air cycled-off
in order to purge the desiccant material of the moisture it has
accumulated, and thereby eliminate the need to temporarily deprive
the pneumatic system of a steady supply of clean and dried compressed
air while the compressor is turned off.
In addition to the above advantages, the switching of the two drying
assemblies alternately between the drying and the purging modes
allows the twin tower system to exsiccate the air stream more efficiently
than the prior art single tower system. Two desiccant towers rather
than one are employed in the air drying system with one absorbing
moisture while the other is being purged of it. The switching of
the two drying assemblies alternately between the drying and the
purging modes thus serves to continuously purge moisture from the
twin tower system. More fully desiccated air is thus supplied to
the pneumatic system. The amount, density and overall surface area
of the desiccant can also be selected to suit varying needs.
The twin tower system can be applied to a wide variety of pneumatic
systems. Typical of the types of pneumatic systems to which the
twin tower system could be applied include the pneumatic brake systems
of passenger and freight railroad trains, subway trains and various
other types of rail related transportation systems. Further examples
include the pneumatic brake systems of various truck transport vehicles.
Other types of pneumatic systems to which the twin tower system
could be applied may be found outside the transportation field.
Another disadvantage of the single tower air drying system is that
it is only capable of removing a certain, limited amount of moisture
during the purge mode. Because the volume of unpurified air flowing
into the system to be dried vastly exceeds the volume of purified
air used to purge the desiccant media, the desiccant media never
adequately exsiccates during operation of the single tower system.
Indeed, the desiccant media adequately exsiccates only after the
system has been turned off for a prolonged time sufficient to accomplish
same. While the twin tower system has a greatly increased moisture
removing capacity by permitting a continuous operation of both the
drying cycle and the desiccant purging cycle, even the current twin
tower system is not capable of completely removing the absorbed
moisture from the desiccant media during the purge cycle. Specifically,
it has been found that when the moist air is percolated upwardly
through the desiccant media there is a tendency for the moisture
to be concentrated adjacent to the bottom inlet end so that after
a period of time the moisture is highly concentrated in the lower
1/3 portion of the desiccant media. In subsequently purging the
desiccant media in a reverse directional flow, namely, from the
top downward, moisture removal is commenced at the top of the desiccant
media, so there may be little or no moisture removal from the area
where moisture in most concentrated. Hence, there is a continuing
tendency for the lower one-third of the desiccant body to retain
most of the moisture collected during the drying mode. This tendency
is enhanced by gravitational forces which cause moisture in the
upper 1/3 portion of the media to flow downwardly into the mid-portion,
and the moisture in the mid-portion to flow downwardly into the
lower 1/3 portion. The end result is that during any such purge
cycle moisture is removed primarily from the upper 2/3 portion of
the desiccant media, with very little, or even no, moisture removal
from the lower 1/3 portion. Hence after several cycles of operation,
the lower 1/3 portion of the media virtually becomes saturated with
moisture and remains so saturated, so that only the upper portion
of the desiccant media can function to remove moisture during the
air drying cycle as intended, and of course, the media's water removing
capacity progressively diminishes with a progressive increase in
water saturated desiccant.
SUMMARY OF THE INVENTION
This invention is predicated upon our conception and development
of a new and improved desiccant containing cavity having a purge
tube and a spring biased flapper valve associated therewith which
is designed to control the ingress of dry purge air or gas through
the desiccant media so that its ingress is concentrated at the lower
1/3 portion of the media where it can be more effective in removing
moisture from the media and can in fact reduce the moisture content
throughout the entire body of media thereby preventing the tendency
for the lower 1/3 portion of the media from becoming and staying
saturated throughout a prolonged operation. The net result being
that the entire system is far more effective in removing moisture
during the desiccant purge cycle.
In essence, therefor, the unique and novel apparatus of this invention
includes a cavity or a cartridge containing a desiccant media and
having a pair of opposed porous wall members, the cavity or cartridge,
pursuant to prior art practices, is adapted to firstly function
in a gas drying cycle in which a moist gas or air is permitted to
ingress through a first of the porous wall members, pass through
the desiccant media whereby at least a portion of the moisture is
removed from said air or gas, with the dried air or gas then egressing
through a second of the porous wall members. In addition, the cavity
or cartridge is further adapted to secondly function in a desiccant
purge cycle in which a portion of the dried air or gas is allowed
to pass back through the desiccant media to absorb moisture therefrom
thereby at least partially regenerating the desiccant media. The
inventive feature of the invention includes a purge tube extending
partially through the desiccant media, a first or upper end of which
is adjacent to the second porous wall member and a second or lower
end spaced upwardly from the first porous wall member by a distance
of about 1/3 of the height of the desiccant media, with a one-way
valve means (check valve) provided over the upper end of the purge
tube adapted to close and restrict flow of air through the purge
tube when the air or gas is flowing in the air or gas drying cycle
and to open and promote air or gas flow through the purge tube when
the air or gas is flowing in the desiccant purge cycle. The purge
tube is preferably provided with a plurality of apertures through
a wall thereof adjacent to a lower end thereof. The one-way valve
means, i.e., check valve, is a preferably a flat rubber flapper
valve over the upper end of the purge tube and the second porous
wall member, and is adapted to restrict flow of air through the
purge tube when air is flowing in the air drying cycle, and to overlay
and thus block the second porous wall member and deflect the air
into the purge tube when it is flowing is the desiccant purge cycle
so as to divert at least a majority of the dried air or gas through
the purge tube during the purge cycle.
OBJECTS OF THE INVENTION
It is, therefore, a primary object of the present invention to
provide a new and improved system for removing moisture from a compressed
gas such as compressed air.
It is another object of this invention to provide a new and improved
desiccant cavity or cartridge for use in a desiccant tower type
of air cleaning and drying system, whether a single tower or twin
tower system, which does a superior job of drying moisture from
the desiccant media during the recycle, desiccant purge cycle.
It is still another object of this invention to provide a new and
improved desiccant cavity or cartridge for use in a desiccant tower
type of air cleaning and drying system, whether a single tower or
twin tower system, in which a purge tube is provided to admit the
recycle dried air into the desiccant media at a location where the
moisture content is the greatest, the purge tube provided with a
one-way valve means adapted to close and restrict flow of air through
the purge tube when the air is flowing in the air drying cycle and
to open and promote air flow through the purge tube when the air
is flowing in the desiccant purge cycle.
It is an even further object of this invention to provide a new
and improved desiccant cavity or cartridge for use in a desiccant
tower type of air cleaning and drying system, whether a single tower
or twin tower system, in which the recycle dried air is admitted
into the desiccant media at a location where the moisture content
is the greatest, namely at a level approximately 1/3 of the way
upward from the bottom of the desiccant media.
In addition to the above-described objects and advantages of the
air drying system of this invention, various other objects and advantages
of the present invention will become more readily apparent to those
persons who are skilled in the same and related arts from the following
more detailed description of the invention, particularly, when such
description is taken in conjunction with the attached drawing figures
and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional side view through a twin tower air
drying system incorporating a pair of desiccant containing chambers
each having a purge tube and rubber flapper valve pursuant to a
presently preferred embodiment of this invention.
FIG. 2 is a side view of the purge tubes shown in FIG. 1.
FIG. 3 is a plan view of the rubber flapper valves shown in FIG.
1.
FIG. 4 is a plan view of the wave spring shown if FIG. 1.
FIG. 5 is a side view of the wave spring shown on FIG. 4.
FIG. 6 is an isometric view of a desiccant containing fabric bag
which can function as a preferred embodiment of the desiccant containing
cartridge of this invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENTS OF THE INVENTION
Before describing the present invention in detail, it is noted
that for the sake of clarity and understanding, identical components
having identical functions in each of the accompanying drawings
have been marked with the same reference numerals throughout each
of the several Figures illustrated herein.
Reference to FIGS. 1 will illustrate a presently preferred embodiment
of a desiccant cavity 10 of this invention wherein two such cavities
10 are shown in a side-by-side relationship as is common in the
above-mentioned twin tower system. As shown, the cavities 10 are
cylindrical in form and essentially identical and side-by-side within
a cast housing member 12. Each cavity 10 is provided with a circular,
porous support member 14 such as a screen or the like, resting
on a circular protruding flange 16 near the bottom of the cavity
10 thereby providing an inlet chamber 18 in the lower portion of
the cavity 10 under the support member 14. An inlet ports 20 at
the base of each inlet chamber 18 is connected to a control valve
(not shown) through which compressed air emerging from a centrifugal
separator (not shown) can be admitted into the bottom of the cavity
10 via one of the ports 20 and the inlet chamber 18 connected thereto.
Compressed air from the centrifugal separator (not shown) is routed
past two such control valves (not shown), each one capable of being
opened to admit the compressed air into just ones of the cavities
10 while the other control valve is closed so that the other cavity
10 will be in the desiccant purge cycle.
A desiccant containing cartridge 22 is disposed within each cavity
10 and supported on top of porous support member 14. The top or
each chamber 10 is provided with an outlet chamber 24 above the
upper surface of desiccant containing cartridge 22. Outlet chambers
24 are formed in part by the undersurface of a cover member 26 attached
over the two cavities 10 with the cover member 26 also including
a shuttle valve mechanism 28 adapted to pass the dried compressed
air emerging from that cavity 10 (the one functioning in the air
drying cycle) to the system for further use. At the same time, the
shuttle valve mechanism 28 will permit a small portion of the dried
compressed air to be admitted into the top of the other cavity 10
via its outlet chamber 24 so that this limited volume of dry compressed
air will move downwardly through that other cavity 10 and the desiccant
therein for effecting the desiccant purge cycle within that other
chamber 10. Accordingly, the air from the centrifugal separator
(not shown) is passed upwardly through just one of the desiccant
containing chambers 10 via one of the control valves (not shown)
which is opened for that purpose to effect the air cleaning and
drying cycle within that one desiccant containing chamber 10. Concurrently,
the shuttle valve mechanism 28 will direct a portion of dried air
exiting from that one chamber 10 to the top of other chamber 10
for effecting the desiccant purge cycle whereby the dried air passes
downwardly through that other chamber to remove moisture from the
desiccant therein. The other of the two control valves will then
exhaust that recycle air containing the re-absorbed moisture to
atmosphere. A timer (not shown) is provided to periodically change
the two control valves (not shown) so that the two cycles are reversed
at periodic intervals.
One each cartridge 22 containing a particulate desiccant 23 is
inserted within the two cavities 10 each resting upon a porous
support member 12 and as necessary to providing an outlet chamber
24 within the cavity 10 above the cartridge 22. Accordingly, each
chamber 10 is adapted to function in the air drying cycle whereby
the air to be dried is admitted into inlet chamber 18 pass upwardly
through the desiccant media 23 and exit via outlet chamber 24. Pursuant
to this invention, a purge tube 30 is disposed within the desiccant
media 23 aligned in the direction of air flow therethrough such
that the top of purge tube 30 is level with the upper surface of
the desiccant media 23 and thus open to outlet chamber 24. The lower
end of the purge tube 30 is spaced approximately 2/3 of the distance
downward from the upper surface of the desiccant media 23 with the
base thereof spaced upwardly from support member 12. Accordingly,
purge tube 30 should preferably extend vertically through the upper
2/3 portion of the desiccant media 23 with its upper end open to
the to the outlet chamber 24 and its lower end open to the mass
of desiccant media 23 and spaced the remaining 1/3 distance above
the base or porous support member 12. Preferably, purge tube 30
is provided with a plurality of apertures 32 (6 as shown) equally
spaced around the cylindrical wall spaced just upward from the open
lower end thereof.
While the cartridges 22 can take any of a number of different forms,
a preferred embodiment thereof, as shown in FIG. 6 is the use of
a porous cylindrical fabric bag 22a having a smaller cylindrical
recess 22b at the axis in the upper surface of the fabric bag 22a,
and having a size and configuration adapted to snugly receive the
purge tube 30. Obviously, the particulate desiccant media 23 is
contained within fabric bag 22a. Ideally, the fabric bag 22a should
be completely filled with the desiccant media 23 and of such size
and configuration as to snugly fit within the cavity 10 to avoid
any open spaces therearound through which air could pass without
passing through the desiccant media 23. In a like manner, the purge
tube 30 should snuggle fit within the opening 22b to avoid any open
spaces through which air could by-pass either the desiccant media
23 or the purge tube 30. Accordingly any compressed air entering
into the cavities 10 via either inlet chamber 18 or outlet chamber
24 will be free pass either upwardly of downwardly, depending on
the direction of flow, through the desiccant media 23 as well as
through purge tube 20.
A circular disk shaped flapper valve 40 (FIG. 3) having a diameter
to match that of the desiccant containing cartridge 20 is disposed
onto the upper surface of each cartridge 22 (or bag 22a) As shown
in FIG. 3 flapper valve 40 preferably made of sheet rubber, is
adapted to overlay and cover the annular, porous upper surface of
cartridge 22 (bag 22a) as well as overlay the upper opening into
purge tube 30. Flapper valve 40 is further provided with a plurality
of diametric slots or cuts 42 intersecting at the axis of the circular
form (as shown in FIG. 3), so that a plurality of pie-shaped portions
44 of the flapper valve 40 point to each other across the axis,
with the outer ends of pie-shaped portions 44 joined together at
the circular perimeter of flapper valve 40. Accordingly, the pie-shaped
portions 44 are adapted to deflect inwardly or outwardly at the
axis of flapper valve 40 while the base ends thereof at the perimeter
of flapper valve 40 do not deflect. A circular screen member 46
is disposed on top of flapper valve 40 while a circular wave spring
48 (FIGS. 4 and 5) is disposed thereover.
In operation, compressed air from a conventional compressor (not
shown) is firstly routed through a centrifugal separator (not shown)
wherein a significant amount of moisture is removed from the compressed
air. From the centrifugal separator, the compressed air may be still
rather moist and is routed past the two control valves (not shown),
only one of which will be open to permit the compressed air through
one of the inlet ports 20 where it passes into the associated inlet
chamber 18 and from there is allowed to pass upwardly through the
desiccant media 23 within cartridge 22 (or bag 22a) within one of
the chambers 10. Due to the upward flow forces, the flapper valve
40 will attempt to deflect the flow of compressed air, but cannot
because the screen member 46 is in the way, preventing any significant
deflection of pie-shaped portions 44. Accordingly, the shape of
flapper valve 40 reaming substantially flat, thereby restricting
the flow of compressed air upward through purge tube 30 so that
the greater mass of compressed air is forced to pass through the
desiccant media 23 within cartridge 20 whereby the desiccant media
23 will function as intended to remove moisture therefrom. As should
be apparent, the upward flow of compressed air will readily flow
into outlet chamber 24 as the pressure thereof will be able to lift
and deform flapper valve 40 at least to the extent necessary to
get therepast. While flapper valve 40 will not function to prevent
the flow of any compressed air upwardly through purge tube 30 the
relatively flat nature thereof as maintained by screen member 46
will restrict and limit such upward flow through purge tube 30 from
what might otherwise be normal, so that in essence a majority of
the compressed air is caused to flow upwardly through the desiccant
media 23. The wave spring 48 will function to keep flapper valve
40 biased against the upper surface of cartridge 22 and to help
maintain the flat shape of the flapper valve 40.
When either of the cavities 10 are functioning in the desiccant
purge cycle, however, the flow of compressed air therethrough is
in the reverse direction, so that the dry, purge air is admitted
into outlet chamber 24 (which now becomes an inlet chamber). From
there the dry air is forced downwardly through the desiccant media
23 to remove moisture therefrom. This directional flow will cause
an increase in pressure within outlet cavity 24 thereby biasing
flapper valve 40 downward against the upper surface of desiccant
containing cartridge 22 (or bag 22A) which blocks much of that dry
air from entering directly into the cartridge 22 through the porous
upper surface. The downward flow of compressed, dry air within outlet
chamber 24 however, will force the pie shaped portions 44 of flapper
valve 40 to be deflected into the upper open end of purge tube 30
so that the great majority of the compressed, dry air, instead of
entering into cartridge 22 through the porous upper surface, will
enter into purge tube 30 and move downwardly therethrough. Therefore,
this mass of compressed, dry air will not enter directly into the
mass of desiccant media 23 except as it exits the lower end of purge
tube 30 where the moisture content of the desiccant media 23 is
concentrated. Clearly, the flapper valve 40 does not provide an
air-tight seal to the reverse flow of compressed, dry air, as air
can by-pass the flapper valve 40 through the slots 42 and around
the peripheral edge. Nevertheless, flapper valve 40 will function
to direct a significant majority of the reverse flowing dry air
downwardly through the purge tube 30 as opposed to through the
upper mass of desiccant media 23 to thereby promote and commence
moisture removal from the desiccant media 23 at a location approximately
2/3 of the distance downwardly from the upper surface of the desiccant
media 23 where the water content is concentrated. During the air
drying cycle, on the other hand, when the compressed, moist air
is moving upwardly, hopefully through the desiccant media 23 so
that the desiccant media will extract moisture therefrom, flapper
valve 40 again does not form an air tight seal, but by maintaining
its relatively flat configuration, it does restrict the upward flow
of compressed air through the purge tube 30 so that at least a
majority of it will pass upwardly through the desiccant media 23.
Having disclosed one embodiment of this invention, it should be
apparent that a number of different embodiments and modifications
could be devised and incorporated without departing from the spirit
of the invention. For example, the purge tube could take different
forms or a plurality of purge tubes could be utilized if desired.
Obviously too, the flapper valve could take different forms provided
any such check valve is in essence a one-way valve designed to restrict
or limit the upward flow of air or gas through the purge tube 30
during the gas drying cycle, and to enhance and promote the downward
flow of gas through the purge tube 30 during the desiccant purge
cycle. For example, a floating ball within the cylindrical purge
tube 30 could be designed to function in a similar fashion. That
is, the upward flow of moist gas or air could close the floating
ball against a circular seal at the upper end of the tube, while
the downward flow of dry air or gas could force the ball downward
sufficient to expose lateral apertures in the tube where it is desired
to permit ingress of the dry air or gas for better effecting the
purge cycle. |