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Патент USA US3054310

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Sept. 18, 1962
E. L. BURNER
3,054,295
METHOD AND APPARATUS FOR DETERMINING RATE OF PRESSURE CHANGE
Filed June 26, 1958
5 . 'Fmer
HP
Pressure Impulse
m/0
LP
Pressure impulse
/27
/8/ Timer
25
26
Fig. 2.
m3w ‘I
I!’
TIME
Fig. 3.
INVEN TOR.
Eugene L. Burner
A
IVE)’ I
Free
1
,
3,054,295
Patented Sept. 18, 1962
2
7 of a dilferential pressure cell separated by ?exible dia
phragm 8. A conventional recorder 9’ is operatively con
nected to diaphragm ‘8, the trace 10' of the pressure ap
pearing on chart 11. Assuming the pressure to be de
3,054,295
METHOD AND APPARATUS FOR DETERMINING
RATE OF PRESSURE CHANGE
Eugene L. Burner, Morgantown, W. Va., assignor to
creasing, then chamber 6 is the high pressure chamber
and chamber 7 the low pressure. Solenoid valve 4 oper
ated by timer 5 is in line 2 to control the transmission of
pressure impulse into high pressure chamber 6. With
United States of America as represented by the Secre
tary of the Interior
Filed June 26, 1958, Ser. No. 744,881
6 Claims. ((31. 73-391)
(Granted under Title 35, US. Code (1952), sec. 266)
valve 4- open, the pressure is the same on both sides of
10 the diaphragm. The resulting trace on the pressure chart
The invention herein described and claimed may be
manufactured and used by or for the Government of the
United States of America for governmental purposes with
out the payment of royalties thereon or therefor.
This invention relates to a method and apparatus for 15
is the datum pressure. Valve 4 is then closed, trapping
the pressure in high pressure chamber 6. Line 3 is open,
and the pressure impulse enters low pressure chamber 7.
As the pressure falls, the diaphragm becomes de?ected,
and this is recorded as a change of pressure on recorder 9.
determining minute changes of pressure and for deter
mining the rate of change of a varying pressure.
In many chemical and manufacturing processes it is
Timer 5 is connected to solenoid valve 4 to close off
line 2 at predetermined intervals.‘ When the valve 4 is
rate of change of the pressure.
falling, the diaphragm again is de?ected because of the
open, the pressure equalizes on both sides of the dia
necessary to determine the variation of some quantity in
phragm, and the recorder returns to the datum. Subse
a system with respect to time and more particularly, the 20 quently, as the valve 4 closes with the originating pressure
For example, the rate
of feed of a ?uidized solid to or from a reaction or stor
age vessel can be measured by supporting the vessel on
difference in force on its opposite surfaces, and this is
recorded in the pressure recorder as a change in pressure.
a weighing cell, the weight being represented by a pres
Volume chamber 12 is connected to chamber 6 by line
sure impulse, to which it is directly proportional. By 25 13 to increase the accuracy of the device by minimizing
taking pressure readings at various time intervals the rate
the percentage changes of volume due to movement of
of ?ow of the powdered solid into or out of the vessel
diaphragm 8.
may be readily determined. Manual timing and reading,
The modi?cation of FIGURE 2 shows the differential
besides being subject to human error, gives no permanent
pressure device adapted to measure pressures that may
record of the pressure changes. A pressure recorder 30 vary above a datum value as well as below. The process
obviates the latter defect, but may not give accurate re
pressure impulse is led via lines 14, 15, and 16 into the
sults with small pressure changes,
hight pressure and low pressure chambers 19‘ and 20‘ of a
It is an object of this invention to provide a method
differential pressure cell, which are separated by dia
phragm
21. Solenoid valve 17 and timer 18 are similar to
sure.
35 valve and timer 4 and 5 of FIGURE 1. Volume chamber
It is a further object of this invention to provide a
22, similar to chamber 12 of FIGURE 1, is connected to
means for introducing a constant time interval into a
chamber
20 by line 23 having therein a valve 24, which
pressure recording.
may be a solenoid valve like valve 4 of FIGURE 1.
Other objects of this invention will appear from a con
Chamber 22 is connected to the atmosphere by a line
sideration of the speci?cation and claims.
40 25 having therein a valve 26. Recorder 27, similar to
In brief, my invention comprises a conventional differ
recorder 9 of FIGURE 1, is operatively connected to
ential pressure cell having a high pressure and low pres
diaphragm 21. The portion of the apparatus within the
sure chamber separated by a ?exible, movable diaphragm.
dotted line 28 can be kept at a constant temperature, as
Unequal pressure impulses are transmitted to these cham
by thermostatically controlled heating, to reduce or elimi
bers and the amount of resulting displacement of the 45 nate any errors due to changes in temperature.
diaphragm is a measure of the pressure difference. A
With valve 24 closed, and 17 and 26 open, process
valve in the pressure inlet line to one of the chambers
pressure is fed to chambers 19 and 20 via lines 14, 15,
opening and closing periodically at predetermined inter
and 16. Valves 17 and 26 are then closed,v thereby trap
vals introduces a time factor. This data may be recorded
ping air in volume ‘chamber 22 at atmosphere pressure,
automatically and rate of change of pressure may be 50 and pressure in chamber 20‘ at process pressure level. At
readily calculated from the resultant pressure versus time
this moment, the pressure indication is zero since there is
and apparatus for determining the rate of change of pres
chart, wherein the time between pressure impulses is
no diaphragm de?ection. Valve 24 is then opened, join
ing chamber 22 to 20‘. This lowers the trapped pressure
clearly de?ned.
The pressure impulse employed can come from a proc
ess as such, or from a pneumatic transmitter.
By con~ 55
verting variables such as temperature, ?ow, weight, etc.,
into pressure impulses, small changes in these variables,
or their time rate of changes may be measured, or em
ployed for control purposes.
In the drawing:
FIGURE 1 is a schematic drawing of one form of this
apparatus.
FIGURE 2 is a schematic drawing of a form of the
invention adapted to pressures which vary above and
below a reference pressure.
FIGURE 3 shows one form of a recording chart ob
tained from the apparatus shown in FIGURE 1.
Referring to FIGURE 1, a pressure impulse, which
may come from a process as such, or from a pneumatic
by an amount depending on the ratio of volumes of the
two chambers, thereby causing an unbalance of forces in
the diaphragm. With chamber 22 about the same volume
as 20, the pressure in the latter is reduced to roughly
one-half. The reading on the recorder now obtained is
the datum pressure, and pressure readings can be taken
60 both above and below this value.
.
A portion of a typical pressure graph produced by the
apparatus of FIGURE 1, where the pressure is decreas
ing, is shown in FIGURE 3. The datum line is O—-O,
t is the time cycle between the closing and opening of
65 valve 4, A1, A2—-A4 are the peak pressure readings ob
tained. The rate of change may be readily calculated by
subtracting A2 from A1, and dividing by t.
I claim:
1. Apparatus vfor determining the rate of change of a
line connected to some instrument, is conducted through 70 varying pressure, including a differential pressure cell
line 1 into lines 2 and ;3 which lead into chambers 6 and
having a pair of chambers separated by a diaphragm, said
3,054,295
‘
3
diaphragm being capable of movement in response to
pressure thereon, conduit means for conducting a ?uid
pressure impulse, inlets in said chambers connected to
said conduit means, operative valve means in only one
of said inlets, means adapted to open and close said
valve means at predetermined time intervals, means for
sensing the movement of the diaphragm to obtain re
4
conduit means, means adapted to open and close the latter
valve means at predetermined time intervals, means for
sensing the movement of the diaphragm to obtain an indi
cation representative of a datum pressure when the second
and said latter mentioned valve means is opened, and to
thereafter obtain repeatedly in sequence indications repre
sentative of the pressure of the impulse when after an
aforesaid predetermined time interval the said latter men
peatedly in sequence indications representative of a datum
tioned valve means is opened, followed by indications
pressure when the valve means is open, followed by indi
representative of the dataum pressure when after the said
cations representative of the pressure of the impulse when 10 time interval the said latter mentioned valve means is
the valve means is closed, whereby a rate of change in
pressure during a time interval between impulse pressure
indications, each such interval being substantially equal
closed, whereby a rate of change in pressure during a time
interval between impulse pressure indications, each such
interval being substantially equal to the said time interval,
to a said predetermined time interval, may be determined
may be determined from the difference of two consecutive
from the difference of two consecutive impulse pressures 15 impulse pressure indications divided by the said time
divided by the aforesaid time interval.
interval.
2. Apparatus for determining the rate of change of a
5. Apparatus for determining the rate of change of a
decreasing pressure which comprises, a differential pres
varying pressure, including a differential pressure cell
sure cell having a high pressure and a low pressure cham
having a pair of chambers separated by a diaphragm, said
ber separated by a diaphragm, said diaphragm being 20 diaphragm being capable of movement in response to pres
capable of movement in response to pressure thereon, a
sure thereon, conduit means for conducting a ?uid pres~
?rst conduit means for transmitting a ?uid pressure im
sure impulse, inlets in said chambers connected to said
pulse, second and third conduit means connecting said
conduit means, operative valve means in one of the inlets,
?rst conduit means to said high and low pressure cham
the other being unobstructed for the passage of the fluid
bers, respectively, operative valve means in said second 25 impulse, means adapted to open and close said valve means
conduit means only, means adapted to open and close
at predetermined intervals, means for sensing the move
said valve means at predetermined time intervals, means
ment of the diaphragm to obtain repeatedly in sequence
for sensing the movements of the diaphragm to obtain
indications representative of a datum pressure when the
repeatedly in sequence indications representative of a
valve means is open, followed by indications representa
datum pressure when the valve means is open, followed 30 tive of the pressure of the impulse when the valve means
by indications representative of the pressure of the im
is closed, whereby a rate of change in pressure during a
pulse when the valve means is closed, whereby a rate of . time interval between impulse pressure indications, each
change in pressure during a time interval between impulse
such interval being substantially equal to a said predeter
pressure indications, each such interval being substantially
mined time interval, may be determined from the dif
35
equal to a said predetermined time interval, may be de
ference of two consecutive impulse pressures divided by
termined from the difference of two consecutive impulse
the aforesaid time interval.
pressures divided by the aforesaid time interval.
6. Apparatus for determining the rate of change of a
3. Apparatus for determining the rate of change of an
varying pressure, including a differential pressure cell hav
increasing pressure which comprises, a differential pres
ing a pair of chambers separated by a diaphragm, said
sure cell having a high pressure and a low pressure cham 40 diaphragm being capable of movement in response to
ber separated by a diaphragm, said diaphragm being capa
pressure thereon, conduit means for conducting a ?uid
ble of movement in response to pressure thereon, a ?rst
pressure impulse, inlets in said chambers connected to said
conduit means for transmitting a ?uid pressure impulse, " conduit means, operative valve means in one of the inlets,
second and third conduit means connecting said ?rst con
the other being unobstructed at all times for the passage
duit means to said high and low pressure chambers, re
of the ?uid impulse, means adapted to open and close
spectively, operative valve means in said third conduit
said valve means at predetermined intervals, means for
means only, means adapted to open and close said valve
sensing the movement of the diaphragm to obtain re
means at predetermined time intervals, means for sensing
peatedly in sequence indications representative of a datum
the movements of the diaphragm to obtain repeatedly in
pressure when the valve means is open, followed by indi
sequence indications representative of a datum pressure 50 cations representative of the pressure of the impulse when
when the valve means is open, followed by indications
the valve means is closed, whereby a rate of change in
representative of the pressure of the impulse when the -, pressure during a time interval between pressure indica
valve means is closed, whereby a rate of change in pres
tions, each such interval being substantially equal to a
sure during a time interval between impulse pressure in
said predetermined time interval, may be determined from
dications, each such interval being substantially equal to 55 the difference of two consecutive impulse pressures divided
a said predetermined time interval, may be determined
by the aforesaid time interval.
.
from the difference of two consecutive impulse pressures
divided by the aforesaid time interval.
References Cited in the ?le of this patent
4. Apparatus for measuring the rate of change of vary
UNITED STATES PATENTS
ing pressure which comprises, a differential pressure cell 60'
1,098,931
Akimo? _______________ __ June 2, 1914
having a high pressure and a low pressure chamber sepa
rated by a diaphragm, said diaphragm being capable of
1,381,139
Smoot _______________ __ June 14, 1921
movement in response to pressure thereon, a third cham
ber having about the same volume as one of said pressure
1,997,412 _
Fischel , ____ -7 _________ __ Apr. 9, 1935
2,648,041
Perkins _______________ __ Aug. 4, 1953
cell chambers, ?rst conduit means, including valve means, 65
connecting said third chambers to said one pressure cell
chambers, means including valve means for venting said
third chamber to the atmosphere, second conduit means
for transmitting a ?uid pressure impulse, third and fourth
conduit means for connecting said second conduit means 70
to said one pressure cell chamber and to the other pres
sure cell chamber, respectively, valve means in the third
2,681,563 A
Golden ______________ __ June 22, 1954
2,735,368
2,775,122
2,819,615
Antonazzi ____________ .__ Feb. 21, 1956
Smith et al ____________ __ Dec. 25, 1956
Colt _________________ __ Jan. 14, 1958
_
FOREIGN PATENTS
952,846
Germany ____________ __ Nov. 22, 1956
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