U.S. patent number 3,814,542 [Application Number 05/267,769] was granted by the patent office on 1974-06-04 for automatic pump shutdown circuit.
This patent grant is currently assigned to Sun Oil Company of Pennsylvania. Invention is credited to Edmundo J. Iglesias, Robert Mayer.
United States Patent |
3,814,542 |
Iglesias , et al. |
June 4, 1974 |
AUTOMATIC PUMP SHUTDOWN CIRCUIT
Abstract
In response to a sustained drop in the vacuum in a pneumatic
line, a circuit automatically shuts down the vacuum pump (which is
coupled to the line) for a short interval, and then restarts the
pump.
Inventors: |
Iglesias; Edmundo J. (Lindwood,
PA), Mayer; Robert (Ardmore, PA) |
Assignee: |
Sun Oil Company of Pennsylvania
(Philadelphia, PA)
|
Family
ID: |
23020048 |
Appl.
No.: |
05/267,769 |
Filed: |
June 30, 1972 |
Current U.S.
Class: |
417/12;
406/15 |
Current CPC
Class: |
F04B
49/02 (20130101); B65G 51/08 (20130101) |
Current International
Class: |
F04B
49/02 (20060101); B65G 51/00 (20060101); B65G
51/08 (20060101); F04b 049/00 () |
Field of
Search: |
;243/4 ;417/12,42
;302/35 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Freeh; William L.
Attorney, Agent or Firm: Church; G. L. Johnson; D. R.
Rechif; Frank A.
Claims
We claim:
1. In combination, a vacuum pump normally operating to produce a
partial vacuum in a line, a vacuum switch operated to the closed
position in response to a decrease in the vacuum in said line to
below a preset value, a first time delay relay connected in series
with said switch and operating its contacts at the end of a first
time interval, said relay having a pair of contacts which when
operated act to shut down said pump; and a second time delay relay
connected in series with said switch and operating its contacts at
the end of a second time interval, said second relay having a pair
of contacts which when operated act to start said pump.
2. Combination of claim 1, wherein said second time interval
exceeds said first time interval.
3. Combination of claim 1, wherein said second time interval is on
the order of 60 seconds, and said first time interval is on the
order of thirty seconds.
4. Combination set forth in claim 1, including also electrically
energized counter means, said first relay having another pair of
contacts which when operated cause energization of said counter
means.
Description
This invention relates to a relay circuit, and more particularly to
a relay circuit useful for automatically shutting down a pump.
This invention is particularly applicable to shutdown of a vacuum
pump (air pump, or blower) which is operating to provide a partial
vacuum in a pneumatic tube system used for the transporting from
one place to another of individual carrier units.
A typical pneumatic tube transporting system is described in the
copending but now abandoned application, Ser. No. 276,625, filed
July 31, 1972. The system so described may be utilized for
transporting small samples of plant streams or tanks to a
laboratory for analysis. The system operates as a vacuum system, a
pump being used to draw air from the remote end of the tube to the
end at the laboratory.
Longer systems, such as the one described in the above application,
utilize several pumps, to provide a more even air flow in the tube
and overcome the greater frictional effect of the long tube. Such
multipump systems are divided into sections by normally closed
valves, each pump having its own section of tubing. As disclosed in
the above-identified application, these valves may be spring-loaded
flapper valves, each valve being held shut (closed) by a
combination of pressures from the spring and the vacuum in the
tube.
Normally, the moving carrier (which contains the sample bottle, and
is used to transport the sample through the tube) strikes the valve
flap and kicks it open, being carried past the valve flap by its
momentum. The valve then closes automatically. Occasionally,
however, a carrier becomes lodged in a flapper valve, creating a
blockage in the pneumatic tube. For minimizing maintenance, it is
desirable to clear such blockages automatically.
An object of this invention is to provide an automatic
valve-unblocking arrangement for pneumatic tubes.
Another object is to provide an automatic shutdown circuit for
vacuum pumps.
A further object is to provide a shutdown circuit for vacuum pumps
which operates in response to a pressure change.
An additional object is to provide an automatic pump shutdown
circuit which functions to first shut down the pump for a short
interval, and then to restart the pump.
A detailed description of the invention follows, taken in
conjunction with the accompanying drawing, wherein:
FIG. 1 is a diagrammatic illustration of a portion of a pneumatic
tube transporting system, with an automatic valve-unblocking
arrangement according to this invention; and
FIG. 2 is a simplified circuit diagram of an automatic pump
shutdown circuit.
Refer first to FIG. 1. A portion of a pneumatic tube 1 is
illustrated, this tube being mounted mostly overhead but dipping
down by means of a vertically extending leg 1' to near ground
level, to provide, for example, for a sample drop indicated at 2. A
carrier being transported moves through the line 1 as indicated by
the solid-line arrows 3.
A spring-loaded flapper valve 4, which is mounted in the vertical
leg 1' and which preferably has the construction described in the
above-mentioned copending application, divides the tube 1 into an
upstream section and a downstream section. Air is drawn from the
remote end of the upstream section of tube 1 by means of the
adjacent vacuum pump 5 (centrifugal blower), as indicated by the
dotted-line arrows 6, and passes through an air take-off 7 (coupled
to the main tube leg 1' just upstream of valve 4) to the intake of
pump 5. The exhaust of pump 5 is to the atmosphere, as indicated at
8. Pump 5 is driven by an electric motor 9, to be described more in
detail later.
In the downstream section of tube 1, air is drawn by a remote
vacuum pump (not shown) through an atmospheric intake 10 (coupled
to tube leg 1' just downstream of valve 4), and flows in the
direction of the dotted-line arrows 11 to the remote pump (located
at the downstream end of the downstream section of tube 1).
The pressure drop in the tube 1, and the flow of air (described)
through the tube 1, propels the carriers in the direction 3. The
moving carriers normally strike the valve flap 4 and kick it open,
the valve closing automatically after the carriers have passed by
the valve flap.
The valve 4 is spring-loaded, as described in the copending
application above mentioned, and is held shut by a combination of
spring pressure and the pressure differential (across its upper and
lower faces) due to the air flows previously described.
When a carrier becomes lodged in a flapper valve such as 4 (that
is, when the valve becomes blocked with a carrier), it can usually
be removed (thus unblocking the valve) simply by shutting down the
adjacent pump 5 (which is to say, the vacuum pump on that section
of the line). The shutting down of the vacuum pump 5 relieves the
differential pressure on the valve flap 4 (which pressure usually
has theretofore been holding the carrier in the valve). Since all
the flapper valves 4 are in a vertical position, once the pressure
on the valve flap has been relieved or released the carrier drops
through the valve with the aid of gravity, and proceeds down the
tube 1. The valve 4 then closes, and the line is ready to be
evacuated.
According to this invention, a relay circuit 12 (shown in detail in
FIG. 2, to be described) is triggered by a sustained drop in line
vacuum (which results when a carrier becomes lodged in the flapper
valve 4), to automatically shut down the vacuum pump 5 for a short
interval, and then restart the pump. It should be realized that
when a carrier becomes lodged in a flapper valve such as 4, the
valve is blocked open, causing the atmospheric pressure in intake
10 to be effective on the take-off 7. A vacuum switch 13 is coupled
at 14 to the air take-off 7 to sense the pressure therein, this
switch operating the relay circuit 12 (as will be described) to
turn off the vacuum pump motor 9 (in response to a drop in the
vacuum in line 7) for a short interval, and then to turn this motor
back on.
Refer now to FIG. 2. The two buses 15 and 16 are connected across
an alternating current source (115 volts) indicated at 17. When the
manually-operated start switch 18 is depressed, an energization
circuit is completed through the winding 19 of a relay 20,
energizing this relay to close its normally open pair of contacts
21. When contacts 21 close, an energization circuit is completed
through the winding 22 of a relay 23, by way of a normally closed,
manually operated stop switch 24. When relay 23 is energized, its
normally open contacts 25 close, to provide a holding circuit
(around contacts 21) which keeps relay 23 energized after relay 20
is deenergized (when the start button 18 is released).
When start switch 18 is depressed to energize relay 20, the
normally open relay contacts 26 of the latter close, energizing the
motor starter coil 27 (through closed switch 24) to turn the pump
motor 9 (FIG. 1) on. When starter coil 27 is energized, the
start-hold contacts 28 (illustrated as a switch) close, keeping the
starter coil 27 energized through these (now closed) contacts 28
and the normally closed contacts 29 of a time delay relay 30 (the
stop switch 24 being closed). Time delay relay 30 has a time delay
of 30 seconds, which means that its contacts are operated 30
seconds after its winding 35 is energized. When the start button 18
is released, relay 20 is deenergized, opening its contacts 21 and
26.
Whenever it is desired to manually turn the pump motor 9 off, the
starter coil 27 is deenergized by depressing the stop switch 24,
which breaks the keep-on circuit previously established for coil
27. When coil 27 is deenergized, the start-hold contacts 28 open.
When stop switch 24 is depressed, the holding circuit previously
established (by way of contacts 25) for relay 23 is opened,
deenergizing this latter relay; the deenergization of relay 23
returns its contacts 25 and 40 to the open position
illustrated.
The vacuum switch 13 is a commercially-available pressure switch
having a C contact 31 (connected to bus 15) and an NC contact 32
(which is connected through the normally closed contacts 33 of a
time delay relay 34 and the winding 35 of relay 30 to bus 16), as
well as another contact (not shown, and not used). Time delay relay
34 has a time delay of 60 seconds, which means that its contacts
are operated 60 seconds after its winding 36 is energized.
When the pneumatic tube 1 is operating normally, there will be a
vacuum of two to four inches of mercury in the air take-off 7. When
the flapper valve 4 becomes blocked, as by a carrier becoming
lodged therein, the vacuum will decrease drastically in the
take-off 7, to which the vacuum switch 13 is pneumatically coupled,
at 14. When this vacuum decreases below three-fourth inch of
mercury, the vacuum switch contacts 31-32 will close, energizing
the winding 35 of time delay relay 30 through the normally closed
contacts 33. Thirty seconds thereafter, the contacts of relay 30
will operate. Contacts 29 of relay 30 open, removing power from the
motor starter coil 27, which deenergizes blower motor 9 (FIG. 1)
and shuts down the vacuum pump 5 which is adjacent the blocked
valve 4.
The normally open contacts 37 of relay 30 are connected in series
with a counter 38, between buses 15 and 16. Therefore, each time
that relay 30 operates, counter 38 is energized, to add one count.
Preventive maintenance of the pneumatic tube requires a weekly
check of this counter, and the keeping of a log of counter
readings. An excessive number of pump shutdowns may indicate: (1)
insufficient suction (the pump setting and the pump intake screen
should be checked); (2) badly worn flap in the valve such as 4 (the
flap surface should be checked); (3) a dry tube (bulk oil should be
added upstream); (4) a defective vacuum switch.
The winding 36 of relay 34 is energized when switch contacts 31-32
close, but this relay has a time delay of 60 seconds. Therefore, 30
seconds after the contacts of relay 30 operate, the contacts of
relay 34 will operate. The contacts 33 of relay 34 open, breaking
the circuit to winding 35 and causing relay 30 to release, closing
its contacts 29. When relay 34 operates, its normally open contacts
39 close, and since relay 23 is always energized (locked in by its
contacts 25) unless the stop switch 24 is depressed, thus
maintaining its contacts 40 closed, the starter coil 27 is
energized through relay contacts 39 and 40. This reenergizes the
motor 9, turning the pump 5 back on.
When the pump 5 is thus restarted, the vacuum in the line should
build up, thus opening the vacuum switch contacts 31-32 and
removing all power from relays 34 and 30 (winding 35 of relay 30
having been previously deenergized by opening of contacts 33, as
previously stated). The pump 5 will stay on because the start-hold
contacts 28 are closed (by energization of starter coil 27) and the
normally closed relay contacts 29 are now closed.
The pump 5 may be shut down for maintenance, repairs, etc. by
depressing the stop button switch 24. This opens the holding
circuit for the relay winding 22, deenergizing relay 23. In
addition, since the normal energization circuit (including
start-hold contacts 28 and the normally closed relay contacts 29)
for the motor starter coil 27 is connected to power bus 15 through
stop switch 24, opening of this latter switch deenergizes starter
coil 27 and thus turns off the pump 5 (due to deenergization of
blower motor 9). It may be here noted that the alternate or
parallel energization circuits for motor starter coil 27 (these
being, on the one hand, relay contacts 26, and, on the other hand,
the series combination of relay contacts 40 and relay contacts 39)
are both connected to power bus 15 through stop switch 24.
* * * * *