Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
(Case No. 8447)
ARRANGEMENT FOR CONTROLLING THE REMOVAL OF MOISTURE
_ FROM A TWO--CYLINDER TYPE MOSITURE REMOVER
FIELD OF THE INVFNTION
This invention relates to an arrangement for
controlling the removal of moisture from a dual-cylinder
drying apparatus of a compressed air supply system for
air brake equipment carried by railway vehicles.
BACKGROUND OF THE INVENTION
Several examples of air drying arrangements are
shown and disclosed in Japanese Utility Model
Re,gistration No. 55-23621, in Japanese Utility Model
Registration No. 59-86231, and in Japanese Patent No. 53-
34664, as well as in our United States Patent Application
Serial No. 932,121, filed November 19, 1986, now Patent
No. 4,721,515, issued on January 26, 198~, entitled
"Control System of a Dual-Cylinder Type Dehumidifier."
One control method of switching a pair of drying
cylinders into either a drying mode or a regeneration
mode is illustrated in FIG. 4 of the present application.
In this first control method, a pair of electromagnetic
valves, represented by characters MVl and MV2, are
switched "ON" and "OFF" at each,preset time period T
determined by a suitable timer (not indicated). In other
words, the drying and regeneration cycles of one pair of
drying cylinders, represented by the characters DR1 and
DR2, are equally and alternatively repeated during the
'~1- ~
~3~ 3
operation. The second control method of a prior art
arrangement is illustrated in FIG. 5 of the present
application. The time chart of FIG. 5 is taken from the
Table in FIG. 3 of Japanese Patent NoO 53-34664. As
shown, the operational relationship o-f the ON-OFF periods
o~ the governor GO is used to sense or detect the
pressure level P in the air reservoir MR. That is, the
cycling, namely, the startup and shtudown of the air
compressor CO is controlled by the pressure. It will be
noted that both of the electromagnetic valves MVl and MV2
are in an "ON" state when the air compressor CO stops or
shuts down, so that both of the drying cylinders DRl and
DR2 switch to a regenerating phase. When the air
compressor CO again switches "ON", the electromagnetic
valves MV1 and MV2 are switched to opposite states so
that the driers DR1 and DR2 are switched.
In the first control method, illustrated in FIG. 4,
the drying and regenerating cycles of the driers DRl and
DR2 are alternately repeated. Each of the recurring
periods of time T is predetermined by a timer, which is
independent of the operation and shutdown of the air
compressor CO. Thus, the driers may be switched while
the air compressor is stopped, so that the frequency
increases. Therefore, the switching mechanism, including
the electromagnetic valves MV1, MV2 and their control
portions, tend to wear out and the chance of failures
increases proportionally which represents a disadvantage
and causes problems.
- 2 -
. .
' '
~3~
In the second control method, illustrated in FIG. 5,
the pressure in the air reservoir MR is raised from
atmospheric air to the upper pressure regulating limit
value P2 by the governor GO during time tlO in FIG. 5,
: when the air in the air reservoir MR :is consumed while it
is compressed from the lower pressure regulati.ng limit
value P1 to the upper pressure regulating limit value P2
by the governor GO. It will be seen that the pressure
increase or buildup is slow during time tll. ~t the same
time, the drying cylinder DR~ continues the same drying
operation during the entire period. This causes the
drying cylinder to go beyond the drying limit and the
drying performance to greatly decrease, which poses
another problem.
QBJECTS AND SUMMARY OF THE INVENTION
Therefore, it is an object of this invention to
solve the problems of the prior art arrangement,
described above, as far as the limit of the drying time
. of the drying cylinder is concerned. Thus, the switching
of the drying and regeneration cycles of the drying
cylinder are arranged at each preset time only when the
~,,
air compressor is in continuous operation that is longer
~O than the preset time. When the air compressor shuts
down, it maintains the drying cylinder in the same
condition that it was in just hefore its shutdown. After
the air compressor has shut down and after the pressure
in the discharge side decreases to a certain pressure and
- 3 -
~3~5~3
after the passage of a predetermined period of time, both
the drying cylinders are put into the drying state or the
regeneration state. When the air compressor goes into
operation, each of the drying cylinders is switched to
the status opposite to that of the previous operated
condition. Thus, the subject invention employs a method
to control a two-cylinder type moisture remover in which
the moisture in the air compressor is fed from the inlet
to the outlet direction of one drying cylinder, one pair
of drying cylinders containing the absorbent to be dried
by the absorbent in the drying cylinder. A portion of
the dried air is counterflowed from the outlet to the
inlet direction of the other drying cylinder to
regenerate the absorbent in the drying cylinder. ~he
drying and regeneration cycles are alternatively
repeated.
Another object of this invention is to provide a
system for controlling a two-cylinder type of moisture
remover in which the drying time limit of the drying
cylinders is preset; means for switching each of the
drying cylinders to a drying and regenerating state at
the preset time only when an air compressor continuously
operates for a time longer than the preset time; means
; for maintaining each of the drying cylinders in the
condition it was in just prior to the stopping of the air
compressor; means for causing both of the drying
cylinders to assume the drying state or the regenerating
-- 4 --
..~
A~ ~
~3~ 3
state together when the outlet pressure decreases to a
certain pressure after the air compressor has stopped and
when a predetermined length of time has passed after
stoppage of the air compressor; means for causing the
drying cylinders to be switched to a state opposite that
of previous operation when the air compressor is again
placed in operation; means for ~eeding moist air from the
air compressor from the inlet to the outlet direction of
the one drying cylinder to the other clrying cylinder;
each of the drying cylinders includes absorbent; means
for causing a portion of the dried air of one drying
cylinder to circulate in counterflow from the outlet to
the inlet direction to regenerate the absorbent in the
other drying cylinder; and means for alternately
repeating the drying and regeneration states of the
: drying cylinders.
A further object of this invention is to provide a
system for removing moisture from compressed air in
pneumatic brake equipment comprising, an air compressor
having an outlet pneumatically connected to an inlet of a
cooler, said cooler having an outlet pneumatically
.~ connected to a pair of electromagnetic multi-way valves,
each of which includes supply section and an exhaust
section, a pair of drying cylinders having inlets
selectively pneumatically connectable to said supply and
exhaust sections of the respective pair of
electromagnetic multi-way valves; an air reservoir having
_ 4~A -
its inlet pneumatically connected to the outlets of said
drying cylinders via a respective check valve; a governor
pneumatically connected to said air reservoir for sensing
t.he pressure level in said air reservoir; and a control
circuit electrically connected to said pair of
electromagnetic multi-way valves and said governor for
causing the drying cylinders to switch to the drying and
regen~rating state at a preset time only when the air
compressor is continuously operating for a time longer
than the preset time and to remain in the same positions
that they were in ~ust prior to the stoping of the air
compressor and for causing the drying cylinders to be
placed in the drying state or the regenerating state
together when the pressure level drops to a certain level
after the air compressor has stopped and when a
predetermined length of time has elapsed.
~ BRIEF DESCRIPTION QF THE DRAWINGS
:~ The subject invention will be explained below on the
basis of several embodiments which are illustrated in the
: 20 drawings, wherein:
FIG. 1 is a timing chart showing a plurality of
operating characteristic curves of a first embodiment of
the present invention;
~IG. 2 is a chart showing a plurality of operating
characteristic curves of a second embodiment of the
present invention;
:: FIG. 3 shows a schematic view of a typical two-
cylinder moisture removing system, which may be employed
_ 4-B -
~3~15;7~3
in practicing the first and second embodiments as
illustrated in FIGS. 1 and 2; and
FIGS. 4 and 5 show a graphical illustration of the
operating curves of two prior art moisture-removing
systems.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and in particular to
FIG. 3, there is shown a typical two-c:ylinder type
moisture
~,
~' :
~'
:, ~
;~:
_ ~C --
'.~4
~3~5~
removal system which includes an air compressor C0 and a
cooler CL. The inlet of cooler CL is connec-ted to the
outlet of the air compressor C0, while the outlet of cooler
CL is connected to a pair of electromagnetic valves MVl and
MV2. The two drying cylinders DRl and DR2 have their
inlets connected to the outlets of the spring biased
electromagnetic valve MVl, MV2, respectively. The dryers
DRl and DR2 contain suitable absorbent or desiccant. A
pair of check valves CVl and CV2 are connected to the
outlets of the pair of drying cylinders DRl, DR2. The
check valves CV1 and CV2 prevent flow back to the outlets
of the dryers DRl and DR2. A throttle valve NV is
connected to the outlets of the drying cylinders DRl and
DR2 on the upatream side of the check valves CVl and CV2.
An air reservoir MR i8 connected to the check valves CVl
and CV2 on the downstream side thereof. The outlet of the
air reservoir MR feeds the compressed air to the air brake
system, such as, the brake cylinders (not shown). A
governor G0 is connected to the air reservoir MR. The
governor GO senses and detects the upper pressure
regulating limit value P2, and the lower pressure
~ regulating limit value Pl controls the operation of the air
; compressor CO to supply or stop air pressure to the air
reservoir MR.
The two-position electromagnetic valves MV1 and MV2
each have an exhaust position "a" in which the f low inlet
i8 closed and the flow outlet is opened to the atmosphere
~3~ L3
when the respective electromagnetic valve is energized to an
"ON" condition. Conversely, each electromagnetic valve has
a feed position "b" in ~hich the exh~ust outlet is closed
and air flows from the inlet to the outlet when the
respective electromagnetic valve is deenergi~ed to an "OFF"
condition.
When the electromagnetic valve MV1 is in the "OFF"
condition while the electromagnetic valve MV2 in in the "ON"
condition, the moist air from the air compressor CO passes
from the cooler CL to the feed position "b" of the
electromagnetic valve MVl. Thus, the air is fed to the
drying cylinder DRl and is dried by the absorbent in the
drying cylinder DRl. The dry air then travels to the ~ir
reservoir MR via the check valve CVl. At the same time, a
eortion of the dried air from the drying cylinder DRl is
~ counterflowed from the outlet of the drying cylinder DR2 via
`~; the throttle valve NV. This diverted portion of the dried
air regenerates the absorbent in the drying cylinder DR2.
This air picks up moisture and the moist air is expelled to
the atmosphere through the exhaust connection, since the
electromagnetic valve MV2 is "ON" and in position "a".
`::
~ When the electromagnetic valve MV1 is switched "ON" and
:
: the electromagnetic valve MV2 is sw.itched "OFF", the moist
::
air is dried in the drying cylinder DR2 while, at the ~ame
time, the absorbent in the drying cylinder DRl is
regenerated. Now, when the pressure P in the air reservoir
MR reaches the upper pressure regulating limit value P2,
.
~3~t5~7~3
the governor GO shuts "OFF" the ~ir compressor CO and, when
the pressure P in the air reservoir MR de~creases to the
lower pressure regulating limit value Pl, the governor GO
tur~s "ON" the air compressor CO.
It will be assumed that the continuous operating time
of the air compressor is less than the specified drying
limit time and that the air comeressor switches from "ON"
to "OFF", but the drying and regeneration are not
switched. Thus, it will be seen that unnecessary switching
is eliminated and that the frequency of switching is
decreased. In addition, when the air compressor switches
from "OFF" to "ON", it i9 switched to the status opposite
that of the final stage in the previous operation and, at
the same time, when the continuous operating time passes
the specified ti~e limit, the drying and regeneration
phases are switched at each specified time limit in order
~: to pre~ent deterioration of the drying performance or
operation. In addition, after the air compressor CO
switches from "ON" to "OFF", and when the length of the
ZO shutdown exceeds the specified time limit, or when the
outlet ~ide pre~sure in the air compressor CO is reduced to
the ~pecified pressure, both of the two drying cylinders
are switched to the drying status or the regeneration
3tatus, so that the drastic decrease of air pressure in the
2~ piping from the air compressor CO to the driers is
prevented. Thus, the delay in the supply of pressure to
the drying cylinder outlet side ia ~ninimized when the air
compre~aor resumes operation.
~ 3~ L3
First, the operating curves of the first embodiment,
:~ shown in FIG. 1, will be explained in conjunction with the
operation of the system illustrated in FIG. 3. Now, when
the electrical power from source V is initially supplied to
the electrical control circuit CC by closing switch SW, the
~; control circuit CC turns "ON'I electromagnetic valve MVl.
This switches the electromagnetic valve MVl to the exhaust
position "a". However, the electromagnetic valve MV2 will
remain in an "OFF" condition and will remain in its feed
position "b". It will be appreciated that, at this time,
the pressure P in the air reservoir MR is at atmosphere.
The electrical power is also suppIied to the governor
GO via control circuit CC when the switch SW is closed.
The governor GO turns i'oN" and detects the atmospheric
~` 15 pressure P in the air reservoir MR. This switches "ON" the
.~ air co~pressor CO so that it begins to run. The dried
compressed air is conveyed to air reservoir MR via cylinder
DR2, which performs the drying function. At the ~ame time,
~; the drying cylinder DRl performs the regeneration function
on the absorbent material contained in dryer DRl. In this
~: :
state, when the preset time Tl (which i8 set to the optimum
drying time limit of the drying cylinders DRl and DR2) has
expired, the electromagnetic valve MVl i3 turned "OFF".
The turning "OFF" of electromagnetic valve MVl causes the
valve to shift to th~e supply position "b" while the
electromagnetic v~lve MV2 torns "ON" and ~oves to the
exhaust position "a". The drying cylinder DRl performs
~3~ 7~3
the drying operation, and the drying cylinder DR2 performs
the regeneration operation. This switchin~ of the drying
and regeneration operations continues at the preset time Tl
until the air compressor CO is deenergized and stops
operating.
Now, when the preset drying time Tl expires and when
the pressure P in the air reservoir MR reaches the upper
pressure regulating limit value P2, the governor GO detects
this condition and switches "OFF". The turning "OFF" of
governor GO causes the air compressor CO to stop
operating. However, the electromagnetic multi-way valves
MVl and MV2 maintain the same positions that they were in
just before the compressor shutdown. After the air
compressor CO shuts down, the compressed air retained in
the piping including the cooler CL is discharged to the
at~osphere by passing through the feed position "b" of the
electromagnetic valve MV2, the drying cylinder DR2, the
throttle valve NV, the drying cylinder DRl, and the exhaust
position "a" of the electromagnetic valve MVl, so that the
pre~sure drops as shown by the dotted line PD in FIG. 1.
However, when the specified time T2 has passed after
the air compresæor CO shuts down, the electromagnetic valve
MVl i~ cut "OFF" and ~hifts to the feed position "b".
~ Under this condition, both drying cylinders DRl and DR2
~5 move into the drying positions, and the air pressure in the
piping stops dropping. Therefore, when the air ~ompres~rr
CO goe3 back into operation, there is undue delay in
S7~
feeding compressed air into the air reservoir MR. After the
e~piration of the preset time t2, and after the shutdown of
the air compressor COr the pressure P in the air reservoir
MR decreases and approaches the lower pressure regulatlng
limit value Pl. When the pressure reaches the lower
pressure regulatin~ limit value Pl, the governor GO switches
"ON" and the electromagnetic valve MV2 moves to the exhaust
position "a". At this time, the electromagnetic valve MVl
is still "OFF" and remains in the feed position "b", so that
the drying cylinder DRI performs the drying function and the
drying cylinder DR2 performs the regeneration function. In
other words, electromagnetic valve MV2 is switched to its
opposite position in relation to the position it occupied
during operation tl.
Since the continuous operating time t3 of the air
compres~or C'O is less than the specified time Tl, the
electromagnetic valves MVl and MV2 do not shift positions,
and the drying cylinders DRl and DR2 remain in their
respective positions. After the expiration of the time t3,
and when the governor GO switches "OFF", the air compressor
CO stops running. However, the electromagnetic valves MYl
and MV2 do not shift their positions, and the drying
cylinders DRl and DR2 maintain their given tunctions. Then,
when the specified time T2 has expired, the electromagnetic
valve MV2 is turned "OFF" and returns to the feed position
"b". Therefore, in the same manner as described above, both
drying cylinders DRl and DR2 are in their drying positions.
~3~5~
.,
The operation during the passage of time periods t4,
t5, and t6 is substantially the sa~e as described above, so
that no further detailed description appears to be
necessary.
In the first embodiment described above, when the air
com~ressor CO shuts down, the drying cylinders DRl and ~R2
function in the same manner as they did just before
shutdown for a certain length of time T2. After the
passage of this specified time T2, both drying cylinders
; 10 DRl and DR2 assume the drying positions. In other words,
both electromagnetic valves MVl and MV2 are switched "OFF",
~o that both electromagnetic valves MVl and MV2 move into
the feed position "b". If the electro~agnetic valves MVl
and MV2 are temporarily frozen while the air compressor CO
is shut down and does not operate, the electromagnetic
valves MVl and M~2 are kept in the feed position "b".
Thus, when the air compressor CO resumes operation, the
discharged compressed air will not leak from the exhaust
outlet of the electromagnetic valves MVl and MV2 to the
atmosphere, since the valves are in feed position "a".
Referring now to the second embodiment, which is
functionally illustrated by the curves of FIG. 2, it will
be seen that when the pressure P in the air reservoir MR
reaches the upper pressure regula~ing limit value P2, the
air compressor CO stops. The air pressure in the piping,
including the cooler CL, starts to decrease toward a
specified pre~sure, namely, lower pressure regulating
1 1
~311~i7~3
limit value Pl. The drying cylinders DRl and DR2 remain
in the positions they occupied just before shutdown, and
when the pressure reacheæ this specified pressure
regulating limit value Pl, both electromagnetic valve~ MV1
and MV2 are switched "ON" and are shiftecl to the exhaust
position "a". In other words, both dryiny cylinders DRl
and DR2 assume the regeneration positionæ.
In this embodiment, a presYure sensitive switch may be
suitably located in the outlet of the cooler CL for
detecting the air pressure in the piping to determine a
decrease to a specified pressure.
Since the other partæ of this second embodiment are
the ~ame as those in the first embodiment, no add1tional
explanation appears necessary at this point since those
skilled in the art will readily underætand the function
and operation of the invention.
It will be seen that in the invention, as illustrated in
both of the embodiments, when the air compres30r CO shuts
; down, the system will stay in the same state that it
occupied just prior to shutdown, if the continuous operating
time of the air compressor CO is less than the specified
drying limit time. Thus, the drying and regenerating phases
~re not switched. Therefore, unnecessary switching
operations can be eliminated 80 that the switching mechanism
is not subjected to needless wear, and the problemæ caused
by such wear can be correspondingly decreased.
.
~ 12
~3~
In addition, when the air compressor CO begins to
operate, the drying and regenerating conditions are switched
to the sta~e which is the reverse of the f inal state of the
previous operating time. When the operating time becomes
S longer than the preset drying limit time, the drying and
regenerating states are switched at each preset time so that
a decrease in drying performance is prevented, and more
efficient drying is possible without any need to increase
the amount of the absorbent.
In addition, when the outlet pressure decreases to a
specified pressure after the shutdown of the air compressor
C0, or when a specified time has passed after the shutdown
of the air compressor CO, both drying cylinders DRl and DR2
move into either the dryiny condition or the regenerating
condition. Thus, no further decrease in the pressure in the
piping from the air compressor CO to the drying cylinder
occurs, so that undue delay of the dried air supply to the
outlet of the drying cylinder is minimized upon resumption
of opera-tion of the air compressor CO.
The following is a listing of the components shown in
the dra~ing~ and described in the specification:
; C0 air compressor
CL cooler
MVl, MV2 electromagnetic valves (switch valves)
DRl, DR2 drying cylinders
MR air reservoir
Pl lower pressure regulating limit value (specified pressure)
P2 upper pressure regulating limit value (3pecified pressure)
13
.
~3~5~
P pressure in the air reservoir MR
Tl preset time
T2 specified time
V power supply voltage
SW switch
CC control circult
CVl~ CV2 check valves
NV throttle valve
G0 governor
"a" e~haust position
"b" feed position
Thus, the present invention has been described in such
full, clear~ concise, and exact terms as to enable any
person skilled in the art to which it pertains to make and
use the same, and having set forth the best mode
contemplated of carrying out this invention. We state
that the subject matter, which we regard as being our
invention, is particularly pointed out and distinctly
asserted in what is claimed. It will be understood that
a~ variations, modifications, equivalents, and sub3titutions
for components of the above specifically-described
embodiments of the invention may be made by those persons
skilled in the art without departing from the spirit and
scope of the invention as set forth in the appended
2B claims,
14
