Note: Descriptions are shown in the official language in which they were submitted.
893
METERI~G VALVE
Background Of The Invention
Many types of gas supplying and gas utilizing
devices require relatively precise metering of the gas
flow volume. When the device is one which utilizes or
supplies a mixture of two or more gases, the flow volume
of each gas must be precisely measured. One example cf
such a device is a medical respirator used to assist or
control the breathing of a patient. ~t is a customary
practice in respirators to mix various amounts of oxygen
and ambient air and to discharge a predetermined volume
of the mixture of gases into the patient at specific in-
tervals. This is known as volume ventilating and is a
procedure which has largely replaced ~he earlier patient
ventilating technique known as pressure ventilating.
Since frequently the same respirato~ is used for many
different patients having different breathing require-
ments, the mixture of oxygen and air supplied thereby
should be controllable within a range from 100~ oxygen
to 100% ambient air. Likewise, the signal wave form
for establishing a breathing pattern should be con-
trollable.
A third patient ventilating technique known
as high frequency positive pressure ventilation
(H.F.P.P.V.) has gained increasingly favorable recog-
nition for patient ventilating in various circumstances.
In the H.F.P.P.V. technique the patient's lungs are
stopped, and low volume jets of air are intr~duced in
rapid succession to the patient, simulating a panting
type of breathing pattern. As many as 60 "breaths"
may be introduced in a one minute interval. It is
believed by many people in the medical field that the
1.
893
H.F.P.P.V. technique can be tolerated more easily by
the patient than volume ventilating is tolerated. An
H.F.P.P.V. ventilator should also have means for con-
trolling the gas mixture output within a range from
100% ambient air to 100% oxygen, and the signal wave
form for the breathing pattern should also be control-
lable to provide a variety of different breathing pat-
terns.
in a device for performing any of the afore-
mentioned patient ventilating techniques, three basic
valving functions are required. First, mixing of the
gases in predetermined proportions must be performed,
usually by a mixing valve. Second, a flow rater is
required to provide a signal for controlling the in-
duced breathing pattern and the rate of breathing,
and third, a throttle valve is required to control the
volume of gas passed in each breath. These three
functions have largely been performed by separate in-
dividual valving apparatus which result in a relatively
large device with numerous operating parts and many po-
tential sources of malfunction. Further, because of the
different volume and flow rate requirements for per-
formance of the volume ventilating technique as com-
pared with the requirements for the performance of the
H.F.P.P.V. technique, and because of the limitations of
the valving apparatus presently used therefor, separate
ventilators are required for the preformance of each
technique. Hence, substantial finan~ial investment by
medical facilities is required for the different types
of ventilators.
A further disadvantage of previous ventilators
is that no precise feedback of the actual ventilator
output is available for controlling the operation of
11538~3
the ventilator. Standard ventilators commonly have
controls for selecting various gas mixture ratios and
inspiration rates as well as for selecting one of
several flow patterns; however, no precise feedback
of the actual output is provided, and the flow pattern
of the output is limited to only those few specific
patterns which are made available on the ventilator.
Very little flexibility in flow pattern and rate is
provided in most ventilators.
Summary of the Invention
An object of the present invention is to
provide a metering valve which is particularly
advantageous for use in ventilating devices for medical
patients, and which can be used for both volume ventllation
and high frequency positive pressure ventilation of a
patient.
A further object of the present invention is
to provide a metering valve which provides a means for
sensing and determining the actual valve output for
reappraisal and adjustment of the output during the
next successive output phase if necessary.
Still another object of the present invention
is to provide a metering valve which can be used individually
to control the volume and frequency of flow of a gas.
It is a preferred feature of the present invention
to provide a metering valve which combines gas mixture
ratio regulating, mixed gas output volume controlling, and
output pattern determining functions in a single compact
valve, and which is capable of producing a corresponding
flow rate for any signal wave form.
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dm~
1153893
In another preferred embodiment it is desired to
provide a metering valve which can be used in combination
with another metering valve to control the flow
frequency and volume and the mixing of two or more gases
in a device.
These and other objects are accomplished in
the present invention by providing a metering valve for
dispensing a selected volume of gas at selected intervals,
comprising a body having an inlet and an outlet opening
therein, a passageway between the inlet and the outlet
openings, valve element means for controlling the flow of
agas through the passageway, a proportional solenoi~ assembly for moying
the element means a selected distance for a selected period of time to
open the passageway, and sensing means, such as a linear
variable differential transformer, for determining the
position of the element means and therefore the flow of
gas through the valve.
In the preferred structure the valve has infinite
operating positions within its operating range, and can
be operatively connected to a micro-processor for controlling
the frequency and the distance which the valve opens,
thereby controlling the volume of gas passing through the
valve and the frequency and pattern of gas output.
The frequency and volume of gas output are
regulated by controlling the electric power input to the
solenoid assembly and the electromagnetic field created
thereby. The shaft may be connected to a linear variable
differential transformer (L.V.D.T.) core and, in such case,
moves the core in relation to movement of the element.
Core movement in the L.V.D.T. causes variations in the
voltage output from the L.V.D.T. which can be analyzed
:
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~lS313~3
by conventional micro-processors for determining the
actual valve output. Diaphragms may be provided within
the valve to balance the pressures on opposite sides of
the valve element so that fluctuations in the inlet and/or
outlet pressures will not cause the element to move. Two
or more of the metering valves may be connected together
for providing variable mixtures at any desirable volume
and fre~uency within the operating ranges of the valves.
In another embodiment, there is provided a metering
valve comprising a body having inlet and outlet openings
therein and a passageway between the openings, a valve
element for controlling fluid flow through the passageway,
a proportional solenoid assembly for creating an electro-
magnetic field, a shaft connected to the element and extending
through the solenoid assembly, the electromagnetic field
causing the shaft to move axially in the solenoid assembly
for moving the element and opening the passageway, a linear
variable differential transformer attached to the solenoid
assembly and having a core connected to the shaft, the axial
movement of the shaft causing axial movement of the core
for varying the voltage output from the transformer to provide
a feedback signal indicative of actual output from the
metering valve.
In yet another embodiment, there is provided
a metering valve assembly for dispensing a selected volume
of gas at selected intervals, the volume and intervals
being regulated in response to the actual flow through the
valve previously, the assembly comprising a body having
an inlet and an outlet opening therein, a passageway between
the inlet and the outletopenings, valve element means for
controlling the flow of a gas through the
dm:\ ~' ~ S ~
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11538'~3
passageway between the inlet and the outlet openings,
a proportional solenoid assembly for moving the element mear-s a
selected distance for a selected period of time to open the passageway, and
sensing means for determining the flow of gas through the
valve and for providing a signal for controlling the means
for moving the element means.
Additional objects and advantages of the present
invention will become apparent from the following detailed
description and the accompanying drawings.
Brief Description of the Drawings
Figure 1 is a perspective view of a mixing and
metering valve assembly for use in a ventilator;
Figure 2 is a perspective view of the mixing
and metering valve assembly with the cover thereof removed,
revealing the two mixing valve units therein;
Figure 3 is a top view of the mixing and metering
valve assembly shown in Figure 1, with some of the con-
cealed parts shown by broken lines;
Figure 4 is a side elevational view of the mixing
and metering valve assembly shown in Figure 1, again with
some of the concealed parts shown by broken lines; and
Figure 5 is an enlarged cross sectional view of
the mixing and metering valve assembly shown in Figure 3,
taken on line 5 - 5 of the latter figure.
Detailed Description of the Preferred Embodiment
Referring now more specifically to the drawings,
and to Figure 1 in particular, numeral 10 designates a
mixing and metering valve assembly suitable for use
in a patient ventilator. The mixing and metering valve
assembly includes a valve body 12 having an oxygen
inlet 14, an air inlet 16, and a mixed gas outlet 18.
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11538~3
Anodized aluminum alloys are suitable materials for body
12, although other suitable materials may also be used.
An oxygen metering valve 20 controls the flow of oxygen
between oxygen inlet 14 and mixed gas outlet 18, and an
air metering valve 22 controls the flow of air between air
inlet 16 and mixed gas outlet 18. An oxygen pressure tap
24 and an air pressure tap 26 axe disposed in body 12, and
a pressure tap outlet 28 is also provided. Oxygen meter-
ing valve 20 and air metering valve 22 are similar in con-
struction and perform similar functions in controlling the
flow of the gases between the inlets thereof and the mixed
gas outlet. It should be understood that one metering
valve may be used individually for providing a predetermined
flow o~ a gas in any selected wave form. Similarly, in an
apparatus having more than two gas inlets, three or more
metering valves may be used to provide a calculated volume
flow of each gas at a predetermined frequency and in any
wave form pattern for providing variable mixtures of the
various gases. The two-metering-valve embodiment shown
in the drawings is merely one example of an advantageous
use of the present metering valve invention.
Metering valves 20 and 22 are connected by wire
harnesses ~0 and 32, respectively, to electrical con-
nectors 34, 3~, 3~ and 40 disposed on a bracket 42. The
bracket may be stainless steel, aluminum, or the like,
and is connected to body 12 by screws 44, 46, 48 and 50.
A housing cover 52 encloses the metering valves and
bracket and includes holes 54, 56, 58 and 60 through which
connectors 34, 36, 38 and 40 extend when the cover is in
place on body 12. The cover can be made of an acrylic
thermoplastic, such as methyl methacrylate, or other
~iS38~3
suitable material, and is held on body 12 by screws 62,
64, 66 and 68. It should be understood that the shapes
of body 12 and cover 52, and the position and orientation
of the various inlets and outlets, as well as the electri-
cal connectors, can be varied, and the arrangement of parts
shown in the drawings is merely one suitable arrangement.
As mentioned previously, oxygen metering valve
20 and air metering valve 22 are similar in construction,
and the description of oxygen metering valve 20 to follow
is similarly descriptive of air metering valve 22. The
oxygen metering valve will be described more fully with
reference particularly to Figure 5, and parts of air
metering valve 22 which correspond to the parts described
for oxygen metering valve 20 are designated with prime
eference numerals similar to the oxygen metering valve
reference numerals.
Oxygen metering valve 20 includes a valve as-
sembly 80 driven by a proportional solenoid, which includes
a valve element or seal assembly 82 operating between pass-
ageways 84 and 86 to control the flow of oxygen between
oxygen inlet 14 and mixed gas outlet 18, and a propor-
tional solenoid assembly 88 for moving element 82 to open
and close the passage. Valve assembly 80 is operatively
connected to a linear variable differential transformer
(L.V.D.T.) assembly 90 which provides a voltage output
signal that can be interpreted by a microprocessor, for
analyzing the position of element 82 and therefore the
volume and frequency of oxygen transmittal between oxygen
inlet 14 and mixed gas outlet 18.
Element 82 includes a sealing member 92 which
engages a seat 94 in passageway 84 to prevent the flow
of oxygen from passageway 84 to passageway 86. The mem-
11S;3~1~3
ber 92 is disposed on a valve element body or retainer
96 connected to a shaft 98 which extends through sole-
noid assembly 88 and is connected to L.V.D.T. assembly
90 as will be described more fully hereinafter. A
stem assembly 100 extends from element 82 in the op-
posite directicn from shaft 98 and includes a stem 102
in an open area generally indicated by numeral 104 be-
tween passageway 84 and passageway 86. The open area
104 in body 12 extends through the outer surface of the
body, and a cap 106 for the opening, of material similar
to that of the body, is connected to the body by bolts
108. A diaphragm 110 is disposed on the end of stem 102
and is held on the end of the stem by a washer 112 and
a screw 114. Synthetic materials such as silicone cr
dacron are suitable for the diaphragm. The diaphragm
is disposed between cap 106 and a shoulder 116 in body
12 and seals the area between the cap and body and also
the end of stem 102. The diaphragm is a rolling friction-
less seal which provides pressure balancing of the valve
element so that variations in outlet pressure will not
affect operation of the element.
Proportional solenoid assembly 88 includes a
housing 130 threadedly connected to body 12 at threads
132 and secured in the housing by a set screw 134. Dis-
posed within housing 130 are a front ring assembly 136,
a rear ring assembly 138 and a magnet 140 between the
aforementioned ring assemblies. A coil assembly 142 is
disposed axially in the solenoid assembly, and an armature
assembly 144 is disposed axially in the coil assembly.
Shaft 98 extends through the armature assembly and has a
9~3
diaphragm 146 disposed thereon which is held against
seal retainer 96 by a nut 148. The diaphragm is si-
milar to diaphragm 110 and is held against a shoulder
150 in housing 130 by a retaining ring 152. The dia-
phragm operates similarly to diaphragm llO in balancing
inlet pressure forces. Thus, diaphragms 146 and llO
equalize the pressure forces on opposite sides of ele-
ment 82 so that the seating and unseating of member 92
on seat 94 is not affected by differences in pressure
forces on opposite sides of the element.
Front ring assembly 136 includes a ring 154 and
a spring 156 disposed between nut 148 and a shoulder 157
of ring 154. Rear ring assembly 138 includes a ring 158
and a spring 160 disposed against a shoulder 161 of ring
158. The springs are flat tempered spring steel which
bend when member 92 is moved away from seat 94, and which
move the shaft axially to return the member to the seated
position when the activating current to the proportional
solenoid assembly is interrupted. The coil assembly 142
includes a bobbin 162 wrapped with magnet wire in the
area indicated by numeral 164. Wires 166 and 168, which
form a part of harness 30, extend from the coil assembly
and can be connected to an electrical power source
through the aforementioned electrical connectors. Armature
assembly 144 includes an armature 170 and an armature
plate 172 disposed on the armature and separated from
spring 156 by a shim 174. Armature 170 is threadedly
engaged on shaft 98 and causes axial movement of the
shaft in response to the field created by the coil as-
sembly and magnet when an electric current is applied
to the coil assembly through wires 166 and 168. Hence,
115389~
by controlling the electrical field created, member 92
can be moved any distance from seat 94 within the oper-
ating range of the valve, and can be held in an opened
or closed position for any duration of time. The valve
can be opened quickly, slowly, or in varying stages, and
can be held in any partially opened or fully opened po~i-
tion for any desirable length of time. Hence, any wave
form of gas flow through the valve can be created.
The linear variable differential transformer
assembly 90 includes a holder 190 connected to the valve
assembly and an L.V.D.T. 192 héld in the holder by a set
screw 194. Voltage input and output leads indicated gen-
erally by the numeral 196, which also form a part of har-
ness 30, extend from the L.V.D.T. to the electrical con-
nectors and can be attached to a microprocessor for com-
parison of the voltage output to the voltage input for
interpretation of the valve output. The holder has a
flange portion 198 which extends from the cylindrically
shaped main body of the holder to housing 130. The flange
is disposed against the end of ring 158, and a wave washer
200 is disposed on the top of flange 198 and has a spacer
202 disposed on top thereof. The entire L.V.D.T. assembly
is held by a retaining ring 204 disposed in a channel in
the inner surface of housing 130.
The L.V.D.T. is a conventional structure from
which the position of an axially moveable core 206 is
detected by comparing the voltage input to the voltage
output of the device. A suitable type is an electro-
mechanical transformer having a ferro-magnetic core and
a primary and two secondary windings on a bobbin. The
core is axially moveable and causes a change in the
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115;~893
voltage induced in the secondary windings when power is
applied to the primary winding. The voltage from the
output terminals is proportional to the displacement of
the axially moveable core. When used in the present
metering valve, the axially moveable core of the L.V.D.T.
is connected by a stud 210 to shaft 98. Hence, axial
movement of the shaft as the valve opens and closes
moves the core of the L.V.D.T., thereby changing the
output voltage from the L.V.D.T. The changes in output
voltage can be interpreted by a microprocessor which con-
trols the operation of the solenoid operated valve as-
sembly, and feedback of the actual output of the valve
is provided. The microprocessor will include knowledge
of the pressure and gas flow characteristics, as well as
knowledge of the position of valve element 82 in inter-
preting the output from the valve. A nut 212 is disposed
on shaft 98 on the opposite side of spring 160 from stud
210. The stud includes a shoulder 214 with a washer 216
disposed thereon. A spring retainer 218 is disposed on
stud 210 and is connected to an inwardly extending portion
220 of holder 190. A spring 222 is disposed between re-
tainer 218 and washer 216. The stud slides axially in
retainer 218 when shaft 98 moves axially; hence, as the
valve opens, with member 92 moving away from seat 94, stud
210 is moved into and toward the L.V.D.T., thereby moving
the core of the L.V.D.T. axially and causing a change in
the voltage output from the L.V.D.T.
Air metering valve 22 is similar to oxygen
metering valve 20; hence, a detailed description thereof
is not required and will not be given. For purposes of
clarity, several of the parts of air metering valve 22
have been shown in Figure 5 and are designated with prime
~153~ 3
numerals similar to the numerals designating the cor-
responding parts in oxygen metering valve 20. A pas-
sageway 230 from the air metering valve intersects with
passageway 86 at mixed gas outlet 18. Hence, the oxygen
passing through oxygen metering valve 20 meets and mixes
with the air passing through air metering valve 22 at
mixed gas outlet 18. Legs 232, 234, 236 and 238 may be
disposed under body 12, and if the legs are threadedly con-
nected to the body, the legs may be adjusted to level
the valve assembly.
In the use and operation of a mixing and
metering valve embodying the present invention, oxygen
inlet 14 and air inlet 16 are connected to supplies of
the gases. Appropriate connections are made between con-
nectors 34, 36, 38 and 40, a microprocessor, and an elec-
tric supply source to provide an electrical input to the
solenoid assembly 88 and voltage inpuL and output con-
nections to L.V.D.T. 192. In the off, or at rest, po-
sition, when no current is being provided to solenoid
assembly 88, springs 156, 160 and 222 hold shaft 98
in a position such that member 92 is engaged on seat 94,
and oxygen entering oxygen inlet 14 is prevented from
passing through area 104 and passageway 86 to outlet 18.
When an electric current is provided to the solenoid
assembly, causing the creation of an electromagnetic
field, shaft 98 is moved axially as a resllt of the axial
movement of armature 170 to which the shaft is connected.
Member 92 is moved away from seat 94, permitting the
passage of oxygen from passageway 84 to passageway 86
through area 104. The strength of the field required
to move the shaft is determined by the strength of springs
156, 160 and 222, and the distance which member 92 is
moved from seat 94 is determined by the strength of the
field created in the solenoid assembly. Thus, the volume
of gas passæng through the valve is controlled in part by
the degree to which the valve is opened, which is con-
trolled by the strength of the electromagnetic field,
and, in part, by the time which the valve is open.
The valve remains open until the current supplied to
the coil assembly is interrupted, and the electromagnetic
field is terminated. When the electromagnetic field is
terminated, springs 156, 160 and 222 move shaft 98
axially until member 92 engages seat 94, effectively
blocking the flow of gas through the valve. It is clear
that any wave form of gas flow can be created in the pre-
sent valve by simply controlling the characteristics of
the electromagnetic field created in the solenoid assembly.
For example, a sudden high voltage input to the coil as-
s embly will rapidly move the valve element to a fully
opened position. Alternatively, the current supplied to
the coil can be moderate at first and steadily increasing,
thus resulting in the valve opening slowly, or the electro-
magnetic field can be moderately established at first and
held at that level, with a subsequent increase crea$ing
a low volume gas flow followed by a higher volume gas flow.
Other variations in the characteristics and volume of gas
flow can likewise be created. Hence, when used in a ven-
tilator, the metering valve can be used to provide a gas
for volume ventilating, as well as high frequency positive
pressure ventilating, and one ventilator can be used for
both techniques, creating virtually any desired inspiration
wave form.
Axial movement of shaft 98 is directly trans-
ferred to axial movement of core 206 in L.V.D.T. 192,
in that stud 210 is connected to the shaft and to the
core. Thus, as valve element 82 is moved away from seat
llS38~33
94, core 206 is moved axially in L~V~D~T~ 192, and the
voltage output from the L~V~D~T~ changes. The changes in
voltage output from the L~VoD~T~ correspond to changes
in the position of valve element 82. Thus, the exact
characteristics of the valve output and the exact wave
form of the valve output are mirrored by changes in the
voltage output from the L~V~D~T~ The microprocessor means
controlling the current to solenoid assembly 88 may also
receive and interpret the voltage signals to and from the
L~V~D~T~ to interpret the valve output and make adjustments
in the current supplied to the solenoid assembly, if re-
quired.
Air metering valve 22 operates similarly to oxygen
metering valve 20, and the air passing therethrough enters
passageway 230 and meets with the oxygen from passageway 86
at mixed gas outlet 18. Thus, by controlling the flow of
gases tnrough each valve, precise ratios of mixtures at
outlet 18 are created. One hundred percent oxygen or air
can be provided simply by sending no electric current to
the solenoid assembly of the valve for the gas which is
not desired, so that the va]ve does not open and only gas
from the other valve reaches outlet 18. Normally in a
respirator the two valves will open for the same time
duration when mixed gas is required. To vary the ratios
of oxygen and air in the mixed gas, the distances which
the valve elements are moved from the seats are controlled
so that a greater volume of the gas desired in a higher
percent will flow through the controlling valve thereof
to outlet 18 than will the other gas.
One metering valve of the present invention can
be used to control the flow of a gas in a device, and can
provide any wave form of flow pattern for the gas in ad-
dition to a feedback signal which can be used to analyze
the exact output from the valve. In devices having more
than two gases flowing therethrough, three or more of the
1153893
metering valves can be used, one metering valve for each
of the gases.
Although one embodiment of a mixing and metering
valve has been shown and described in detail herein, vari-
ous changes may be made without departing from the scope
of the present invention.
15.
