Note: Descriptions are shown in the official language in which they were submitted.
Express Mail #TB88805738X US
zi47i~.3
Docket No. 11836.950294
OPTIMAL PNEUMATIC PRESSURE REGULATOR
WITH ELECTRONIC COMPENSATION
Background of the Invention
The invention presented herein relates to the regulation of fluid in a
particularly reliable
and precise fashion.
Pressure regulation devices have been known for a long time. - The majority of
pressure
regulation devices are pneumatic and electronic. A number of patents relating
to pressure
regulation devices exist, including regulators that release pressure in beer
barrels dating from the
previous century. These pneumatic pressure regulation devices are reliable
because they utilize
proven technologies and do not require an electrical energy source for their
operation. Their
precision is limited and their rigging is difficult and expensive.
Electronic pressure regulation devices are equally well known; they are
comprised of, at
minimum, a pressure sensor and an actuator which opens or closes as a function
of the command
signal issued by the pressure sensor. These electronic regulation systems are
not reliable because
they require an electrical source which can fail. On the other hand, precision
electronic systems
are very expensive. These systems are sensitive to exterior conditions such as
temperature and
must be compensated, which increases their complexity.
The present invention aims notably to furnish a regulation system which
responds much
better than those previously known in practice, most notably, it permits the
regulation of a fluid
in a precise and reliable manner and for a reasonable cost.
214'~11~
Summary of the Invention
This invention proposes notably an electronically compensated pneumatic
regulator with
a programmable correction system, on the one hand, after testing, all the
imprecisions due to
fabrication tolerances of pneumatic regulators, and on the other hand, to
modify the regulated
outlet pressure in order to obtain in a precise fashion the outl~ regulation
law that may be precise,
complex and nonlinear, then the electronic compensation systems can be non-
precise and
consequently less cosily in the measure where the compensation force F~ is
reliable. For example,
if the force F represents just '10 ~ of the force in play of the equilibrium
of the obturator, then an
error of 5 ~, for example, of the force F will drive an error of E=0.10x0.05
=0.005 or .5 ~ only
on the accuracy of the outlet pressure. The other errors attributed to
pneumatic regulation are
naturally corrected by a programmable method. The following terms are employed
in the overall
sense and have principally the following significance:
Pneumatic pressure regulator: a system that regulates the pressure of a fluid
whether it is liquid or gaseous.
SE: Pressure sensing area. This area forms a boundary between the volume VS
where the pressure is to be regulated and the volume VR where the pressure is
the
reference pressure.
~ PE: Regulator inlet pressure
PS: Regulator outlet pressure
PR: Reference pressure
One goal of this invention is to propose a pneumatic pressure regulator
comprised of at
least an obturator actuated by at least an elastic membrane with a pressure
sensing area SE which
forms a boundary between the volume VS where the pressure is regulated and the
volume VR
2
2147113
where the pressure is the reference pressure, this regulator is comprised of
at least an inlet orifice
which permits entry of a fluid under pressure and comprised of at least an
outlet orifice which
permits the exit of the fluid at the regulated pressure.
These goals are achieved by a system according to this invention which is
essentially
characterized by a programmable means which creates a force F on an obturator,
this force F being
defined at the end of a test and varying as a function of at least one
parameter P relating to the
operation of the regulator in a manner that the outlet pressure PS = f(P) of
the regulator is exactly
equal to the value of the predefined pressure PD = f(P) for each value of the
parameter P measured
during operation of the regulator.
According to one advantageous embodiment, the command parameter P is the
pressure PE
of the fluid at the regulator inlet, this pressure being measured by a
pressure sensor, the information
furnished by this command pressure sensor is sent to a programmable controller
which commands
a means to create a force on the obturator, and is programmed in the course of
a preliminary test
of the regulator in order that the value of the force F applied to the
obturator is such that the outlet
pressure PS = f(PE) is equal to the value of the desired pressure PD = f(PE)
whatever the value
of the pressure PE.
According to another advantageous embodiment, the command parameter P is the
flow D
of the fluid flowing through the regulator, this flow D is measured by a flow
sensor, the
information supplied by the flow command sensor is sent to a programmable
controller which
commands a means to create a force on the obturator, and is programmed in the
course of a
preliminary test of the regulator in order that the value of the force F
applied to the obturator is
3
2147113
such that the outlet pressure PS = f(D) is equal to the value of the outlet
pressure desired
PD = f(D) whatever the value of the flow D.
According to another advantageous embodiment, the command parameter P is the
value of
the reference pressure PR, this value PR being measured by a pressure sensor,
the information
of this command sensor is sent to a programmable controller which commands the
means to create
a force on the obturator, and is programmed in the course of a preliminary
test of the regulator. in
order that the value of the force F applied to the obturator is such that the
outlet pressure
PS = f(PR) is equal to the value of the desired outlet pressure PD = f(PR)
whatever the value of
the reference pressure PR.
According to another advantageous embodiment, the average command creating a
force on
the obturator is a pneumatic chamber containing a fluid under pressure PV and
having an effective
sensing area such that F = PV x SE.
According to another advantageous embodiment, the average command creates a
force F
which is relatively small such that the regulator performance is still
acceptable even though there
is a failure of the programmable electronic systems.
This invention is better understood in view of the detailed description which
follows in
conjunction with a preferred embodiment illustrated in the attached drawings.
Brief Description of the Drawings
Figure 1 illustrates a pneumatic regulator 1 which is comprised of an
obturator 2 and an
elastic membrane 3;
Figure 2 is a graph which illustrates the value of the parameter P on the
abscissa and the
value of the regulated pressure at the regulator outlet PS on the ordinate;
4
2147113
Figure 3 is a graph illustrating the value of the parameter P on the abscissa
and the force F
on the ordinate.
Detailed Description of a Preferred Embodiment
The detailed description that follows refers to a preferred embodiment, as
shown in Figure
1. The embodiment is comprised of an electronic correction based on a
parameter P which has been
chosen here to be equal to the value of the reference pressure PR. The reader
should understand
that the invention applies equally if one identifies the parameter P at a
value of flow D or the value
of the inlet pressure PE for example. The invention applies equally if one
identifies the parameter
as a combination of values of several operational parameters of the regulator.
In this case, the
controller integrates the different factors to define the force F to apply to
the obturator, and F will
then be a function of the different parameters.
A pneumatic regulator regulates the outlet pressure of a fluid . that flows
through it. This
regulated pressure varies as a function of a number of parameters such as
temperature, flow, inlet
pressure, reference pressure, etc. An example of such a regulator is presented
in Figure 1. Shown
in Figure 1, pneumatic regulator 1 is comprised of obturator 2 and elastic
membrane 3. This
membrane separates the fluid under regulated pressure occupying the volume VS
in regulation
chamber 19 from the fluid at reference pressure occupying the volume VR in
reference chamber 18.
Spring 11 holds the obturator to open or close and permits regulation of an
equilibrium value.
Obturator 2 separates the volumes VS and VE, the volume VE being the volume in
inlet chamber 17
where the fluid under pressure is introduced. The fluid under pressure enters
at the inlet 4 and
exists at a regulated pressure at the outlet 5. A pressure sensor 7 is located
within inlet 4. A
pressure sensor 10 is located in reference chamber 18 containing volume VR. A
flow meter 9 is
located at the outlet 5, for example, and measures the flow through regulator
1. The
5
2147113
n~~asurements by sensor 7, 9 and 10 are sent to controller 8 which makes up
part of the
regulator. A means 6 creates a force F applied to the obturator 2 which
permits a correction to
the operation of the regulator to obtain the desired regulated pressure with
great precision as the
function of the parameters measured by the .sensor 7, 9 and 10. Bench and
controller 12, which
is not an integral part of the regulator, measures the performance of the
regulator over the entire
operating range of the regulator, sweeps the parameters and compares the
desired perforniance
with the measured performance and deducts the corrections supplied and
consequently the force
F to be applied to the obturator 2. In a preferred embodiment, the regulator
contains springs and
adjustments which were not fabricated with precise tolerances and therefore
with a reduced
fabrication cost. In this case, the regulator contains a pressure sensor 10
which measures the
reference pressure. The information supplied by this pressure sensor is sent
to the controller 8.
A test is performed on this regulator with the aid of the control bank 12. The
regulated pressure
PR by the regulator is precisely measured by the control bank such that the
reference pressure
supplied by the control bank varies. For example, ten measurements are
performed for ten values
of the stabilized reference pressure.
The value corresponding to the regulated pressure is recorded. Taking into
account the
characteristics of the regulator, the controller 8 deducts the corresponding
values of the force F
to be applied for each value of the reference pressure parameter. This
collection of points can be
smoothed by the controller to obtain a continuous curve representing a
continuous function
defining the value of F for each value of the reference pressure PR measured
by the pressure
sensor 10. This operation can be restarted many times to augment the precision
of the system.
6
f
..
2147113
1 , force F is produced by a lower power actuator 6 which reacts to the
commands issued by the
controller according to the following relationship:
F=f(PSD-PSR)
where PSD is the desired regulation pressure and PSR is the regulated pressure
measured at the time
of the preliminary tests.
The force F is small such that in the case of a failure of the electronic
systems, the regulation
values are close to the desired ones. Here the actuator is comprised of a
piston moved by the fluid
pressure. A simple electronic regulation system that is low in cost and not
very accurate is
utilized to regulate the pressure supplied to the actuator. In order to be
able to utilize standard,
low cost components, the force F never exceeds one fifth of the force exerted
by spring 11.
In other words, F < R/5 where R is the force exerted by spring 11.
Figure 2 is a graph illustrating the value of the parameter P on the abscissa
and the value
of the regulated pressure at the regulator outlet PS on the ordinate. The
curve 13 represents the
development of the value of the outlet pressure without electronic correction
PSR as the parameter
P varies. Curve 14 represents the development of the desired value of the
outlet pressure PSD.
The algebraic difference between the curves 14 and 13 is equal to the
correction C as follows:
C=PSD-PSR (arrows 15).
Figure 3 is a graph illustrating the value of the parameter P on the abscissa
and the force
F on the ordinate. The curve 16 presents the algebraic development of the
force F applied to the
obturator to correct the operation of the regulator in such a manner that the
value of the pressure
correction is equal to C.
7
2147113
The applications of this invention are numerous. The invention has
applications in the
regulation of fluids, either liquid or gaseous, where the required regulation
precision is very high
and where safety criteria are very important and where it is necessary to
conceive a product at
reduced cost.
8
