An apparatus for regulating pressure of treatment fluid during ophthalmic procedures is described. Flow sensing and pressure regulating diaphragms are used to modulate a flow control valve. The pressure regulating diaphragm is connected to the flow control valve to urge the valve to an open position due to pressure being applied to the diaphragm by bias means such as a spring. The flow sensing diaphragm is mechanically connected to the flow control valve and urges it to an opened position because of the differential pressure on the diaphragm generated by a flow of incoming treatment fluid through an orifice in the diaphragm. A bypass connection with a variable restriction is connected in parallel relationship to the orifice to provide for adjusting the sensitivity of the flow sensing diaphragm. A multiple lever linkage system is utilized between the center of the second diaphragm and the flow control valve to multiply the force applied to the valve by the other diaphragm and reverse the direction of the force

Baehr, E. F.

English

NASA Technical Reports Server

United States Patent [19] [111 4,084,612 
Baehr [45] Apr. 18, 1978 
[54] FLOW COMPENSATING PRESSURE 
[75] Inventor: Edward F. Baehr, Berea, Ohio 
[73] Assignee: The United States of America as 
REGULATOR 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 779,428 
[22] Filed: Mar. 21,1977 
[51] Int. c1.z .............................................. F16K 17/34 
[52] U.S. c1. ................................. 137/484.2; 137/501; 
137/505.16 
[58] Field of Search ............... 137/484.2, 484.4, 484.6, 
137/484.8, 505.14, 505.16, 501 
[561 References Cited 
U.S. PATENT DOCUMENTS 
2,182,873 12/1939 King .................................. 137/484.2 
3,433,254 3/1969 Frascati ........................... 137/505.16 
Primary Examiner-Harold W. Weakley 
Attorney, Agent, or Finn-N. T. Musial; J. R. Manning; 
J. A. M a c h  
PI ABSTRACT 
Apparatus for regulating pressure of treatment fluid 
being supplied to a human or animal eye during oph- 
thalmic procedures such as cataract surgery is dis- 
closed. 
Flow sensing and pressure regulating diaphragms are 
provided in a body to modulate a flow control valve. 
The pressure regulating diaphragm is connected to the 
flow control valve to urge the valve to an open position 
due to pressure being applied to the diaphragm by bias 
means such as a spring. The flow sensing diaphragm is 
mechanically connected to the flow control valve and 
urges it to an opened position because of the differential 
pressure on the diaphragm generated by a flow of in- 
coming treatment fluid through an orifice in the dia- 
phragm. A bypass connection with a variable restriction 
is connected in parallel relationship to the orifice to 
provide for adjusting the sensitivity of the flow sensing 
diaphragm. 
A multiple lever linkage system is utilized between the 
center of the second diaphragm and the flow control 
valve to multiply the force applied to the valve by the 
other diaphragm and reverse the direction of the force. 
A vertically extending tube communicates with the 
upper side of the pressure regulating diaphragm which 
also communicates with an auxiliary outlet port. 
17 claims, 1 Drawing Figure 
I i I d 4 9  (46 A' 
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U.S. Patent April 18, 1978 4,084,6 12 
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4,084,612 
1 
FLOW COMPENSATING PRESSURE 
REGULATOR 
ORIGIN OF THE INVENTION 
This invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured or used by or for the Government with- 
out the payment of any royalties thereon or therefor. 
BACKGROUND OF THE INVENTION 
In many ophthalmic procedures, as for example cata- 
ract surgery, fluid under pressure is often supplied to 
the operative site to maintain a desired pressure in the 
eye. In recent years there have been a number of ad- 
vances in cataract surgery techniques wherein instru- 
ments are inserted through the cornea of an eye to 
mascerate the lens material. Treatment fluid is supplied 
to the operative site through the surgical instrument and 
mascerated material and treatment fluid are withdrawn 
either through the surgical instrument or by an ancillary 
conduit. 
In some cases the pressure of the treatment fluid 
delivered to the operative site is controlled simply by 
elevating or lowering a reservoir containing the treat- 
ment fluid. Obviously, this procedure cannot compen- 
sate for variations in pressure caused by changes in the 
rate of fluid flow or other conditions which vary the 
pressure. 
In one cataract surgical procedure a computer is used 
to control pressure and also to monitor fluid flow rate 
so that surges will not cause a pressure rise great enough 
to damage the eye. Such apparatus is both complex and 
expensive. 
Pressure regulators of the type utilizing a spring bi- 
ased diaphragm are well-known. Such regulators are 
generally restricted to a limited range of flow rate and 
rapidly lose their regulating effect outside of that range. 
OBJECTS AND SUMMARY OF THE 
INVENTION 
It is an object of the invention to provide a new and 
novel apparatus for regulating the pressure of a fluid at 
a site away from a source of pressurized fluid. 
It is another object of the invention to provide a 
pressure regulator which maintains an accurate pressure 
regulation over a relatively wide range of change in the 
flow rate of fluid through the regulator. 
Another object of the invention is to provide a pres- 
sure regulator which can be adjusted to alter the per- 
missible variation in pressure resulting from any given 
change in fluid flow rate. 
Still another object of the invention is to provide a 
pressure regulator which is compact and relatively 
inexpensive. 
Yet another object of the invention is to provide a 
pressure regulator which utilizes the weight of a liquid 
to modify a pressure regulating characteristics of the 
regulator for use in certain types of ophthalmic proce- 
dures wherein pressure in the eye can be reduced at a 
predetermined rate. 
BRIEF DESCRIPTION OF THE DRAWING 
The single FIGURE shows an oblique longitudinal 
sectional view of a pressure regulator embodying the 
invention together with schematically illustrated oph- 
thalmic surgical equipment. 
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2 
DESCRIPTION OF A PREFERRED 
EMBODIMENT 
Referring now to the single FIGURE, there is shown 
a pressure regulator comprising a body 10 having 
therein an inlet port 11, an outlet port 12, an ambient 
port 13, a first chamber 14 and a second chamber 15. A 
flow sensing diaphragm 16 divides the first chamber 
into an inlet subchamber 17 and a flow control sub- 
chamber 18. Similarly, a diaphragm 19 divides chamber 
15 into a regulated outlet subchamber 20 and an ambient 
pressure subchamber 21. A valve means 22 which 
serves as a flow control valve means is disposed be- 
tween chamber 14 and chamber 15 and may comprise a 
poppet member 23 which seats against the rim of an 
orifice 24. 
Diaphragm 19 has attached thereto a backing plate 25 
which engages a stem 26 of poppet 23. Consequently, 
any movement of the diaphragm 19 toward the regu- 
lated outlet subchamber 20 will move poppet 23 off its 
seat to permit fluid flow through the orifice 24. To this 
end, a coil spring 27 is disposed between the backing 
plate 25 of diaphragm 19 and a threaded plug 28 having 
an orifice 29 therein. The threaded plug 28 may be 
rotated to increase or decrease the pressure exerted on 
diaphragm 19 by the spring 27 which serves as a bias 
means. 
The flow sensing diaphragm 16 is supported on a 
backing plate 30 having an upwardly extending stem 31 
with a sensing orifice 32. A spacer 33 is disposed around 
stem 31 and with a pivot nut 38 is free to move verti- 
cally through a pivot support plate 34 to engage a multi- 
ple linkage system as will now be described. 
The multiple lever linkage system is interposed be- 
tween the stem 31 of diaphragm 16 and the poppet 23 of 
valve means 22 and serves to multiply the pressure of 
diaphragm 16 resulting from fluid flow through the 
orifice 32. The multiple lever linkage comprises a lever 
arm 35 and a lever arm 36. 
Lever arm 35 pivots about a fixed pivot 37 intermedi- 
ate its ends and mounted on pivot support plate 34. One 
end of lever 35 is pivotally connected by pivot nut 38 to 
stem 31 of diaphragm 16 while the other end is pivotally 
connected by a link 39 to one end of lever arm 36. The 
other end of lever arm 36 is attached to a fixed pivot 
point provided by the pivot link 40 mounted on pivot 
support plate 34. A point intermediate the ends of lever 
arm 36 is pivotally connected by link 41 to the poppet 
23. 
With this arrangement, it will be seen that upward 
movement of diaphragm 16 and stem 31 produces 
downward movement of pivot 41. The poppet 23 is 
consequently pulled off its seat opening valve 22. 
The use of the multiple lever linkage system multi- 
plies the effect of sensing diaphragm 16 on poppet 23. 
This advantageously allows diaphragms 16 and 19 to be 
approximately the same size. However, the multiplica- 
tion effect can be achieved by making diaphragm 16 
much larger in area than diaphragm 19 as, for example, 
60 two to fifteen times as large. 
As will be seen from the figure, the multiplication 
factor of the multiple lever of linkage is determined by 
the positioning of fixed pivot 37 and intermediate pivot 
41. The positioning of fixed pivot 37 alone is sufficient 
The pressure on the diaphragm 16 due to fluid flow 
through orifice 32 together with the multiplication fac- 
tor of the multiple lever system and the bias exerted by 
65 to give a wide range of multiplication factors. 
4,084.6 12 
3 
spring 27 on poppet 23 by way of diaphragm 18 are all 
factors in the determination of the pressure which ap- 
pears at the outlet port 12. The sensitivity of the pres- 
sure regulator to changes in the rate of fluid flow is 
closely related to the pressure drop caused by fluid flow 
through orifice 32. To the end that the sensitivity may 
be adjusted, a conduit 41 is connected between a bypass 
outlet port 42 communicating with inlet subchamber 17 
and a bypass inlet port 43 communicating with regulat- 
ing subchamber 18. The sensitivity is adjusted by means 
of a pinch valve 44 disposed around the bypass conduit 
41. It will be obvious that any suitable valve may be 
inserted in the bypass conduit 41. 
The outlet port 12 of pressure regulator 10 is con- 
nected through a conduit 45 to the ophthalmic lens 
mascerating tool 46 from which it flows to the operative 
site such as lens 47 of eye 48. The fluid is obtained from 
a treatment fluid reservoir 49 from which it flows 
through a passageway 50, a filter 51 and a passageway 
52 to the inlet port 11 of the pressure regulator 10. The 
pressure of the fluid at inlet port 11 is determined by the 
height of reservoir 49 and should be substantially 
greater than the desired regulated pressure at outlet 
port 12. 
In certain types of operations where it may be desir- 
able to gradually reduce the pressure in an eye, a verti- 
cal tube 53 may extend vertically upward from ambient 
port 13, and an auxiliary port 54 in communication with 
the ambient subchamber 21 may be provided. The verti- 
cal tube 53 may be filled with a liquid, the weight of 
which is impressed through plug 28 onto diaphragm 19 
to alter the pressure regulating characteristics of the 
regulator 10. A bleed line, valve or conduit (not shown) 
may be attached to auxiliary port 54 to gradually reduce 
the liquid level in the tube 53. 
In operation, treatment fluid from reservoir 49 enters 
the inlet port 11 and then flows through the orifice 32 
into subchamber 18. The pressure drop developed 
across orifice 32 causes the diaphragm 16 and stem 31 to 
move upwardly as viewed in the drawing. This causes 
the pivot 41 to exert a downward force on poppet 23 
tending to open the flow control valve 22. The down- 
ward force on poppet 23 is added to the downward 
force already applied thereto by spring 27 through 
backing plate 25 and diaphragm 19. The fluid passing 
through orifice 32 then passes through the flow control 
valve 22 into the regulating subchamber 20 and outlet 
port 12 to the ophthalmic instrument 46. From the fore- 
going explanation, it will be seen that as additional fluid 
is required at the operative site in lens 47, the pressure 
drop across orifice 32 will increase adding additional 
downward force through the poppet 23. This allows 
additional fluid to flow through the valve 22 while at 
the same time reducing the pressure drop at that point 
so that the desired pressure may be maintained at the 
operative site. 
As discussed previously, some of the fluids entering 
inlet port 11 may be diverted through the bypass outlet 
42, the conduit 41 and the bypass inlet 43. This parallel 
flow of treatment fluid reduces the pressure drop across 
the orifice 32 to alter those pressure regulating charac- 
teristics of the pressure regulator which are responsive 
to changes in the fluid flow rate. This sensitivity is 
adjustable by means of the pinch valve 44 disposed 
around the conduit 41. 
Under conditions in which no fluid flow is being 
delivered to the operative site in eye 48 there is, of 
course, no pressure drop across orifice 32. Under these 
4 
conditions, the pressure at outlet 12 is regulated by the 
pressure of spring 27 on the backing plate 25 of dia- 
phragm 19. This pressure is adjustable by means of the 
threaded plug 28. 
It will be understood that changes and alterations 
may be made to the above-described pressure regulator 
without departing from the spirit and scope of the in- 
vention as set forth in the claims appended hereto. 
5 
What is claimed is: 
1. A pressure regulator comprising: 
a body having an inlet port, an oulet port, an ambient 
port, and including a first chamber and a second 
chamber; 
a flow sensing diaphragm disposed in said first cham- 
ber and forming an inlet subchamber and a flow 
control subchamber, said diaphragm having 
therein a signal generating orifice, said inlet sub- 
chamber being in communication with said inlet 
port; 
a pressure regulating diaphragm disposed in said sec- 
ond chamber and forming a regulated outlet sub- 
chamber and an ambient pressure subchamber, said 
regulated outlet subchamber being in communica- 
tion with said outlet port; 
flow control valve means disposed between said flow 
control subchamber and said regulated outlet sub- 
chamber; 
means operatively connecting said pressure regula- 
tion diaphragm to said valve means; 
bias means urging said pressure regulating diaphragm 
into said regulated outlet subchamber and thereby 
urging said valve means to an open position; and 
means operatively connecting said flow sensing dia- 
phragm to said valve means, said flow sensing dia- 
phragm urging said valve means to an open posi- 
tion due to pressure drop across said orifice when 
fluid flows therethrough. 
2. The pressure regulator of claim 1 and including 
bypass means for directing fluid from said inlet sub- 
chamber to said flow control chamber to modify the 
pressure drop across said orifice. 
3. The pressure regulator of claim 2 wherein said 
bypass means includes a variable flow restrictor. 
4. The pressure regulator of claim 1 wherein said 
flow sensing diaphragm is substantially larger in area 
than said pressure regulating diaphragm. 
5. The pressure regulator of claim 4 wherein said 
flow sensing diaphragm is at least two times greater in 
6. The pressure regulator of claim 1 wherein said bias 
means is a coil spring. 
7. The pressure regulator of claim 1 wherein said 
means operatively connecting said flow sensing dia- 
55 phragm to said valve means is a multiple lever linkage. 
8. The pressure regulator of claim 7 wherein said 
multiple lever linkage multiplies the force applied to the 
valve means by at least a factor of two times the force 
at the center of said flow sensing diaphragm. 
9. The pressure regulator of claim 7 wherein said 
multiple lever linkage comprises first and second lever 
arms, said first lever arm being shorter than said second 
lever arm and pivoting on a fixed pivot intermediate its 
ends, one end being pivotally connected to the center of 
65 said flow sensing diaphragm and the other end being 
pivotally connected to one end of said second lever 
arm, the other end of said second lever arm being pivot- 
ally connected to a fixed pivot, a point intermediate the 
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4,084,612 
5 6 
ends of said second lever arm being pivotally connected 14. The pressure regulator of claim 1 wherein said 
to said flow control valve means. orifice is at the center of said flow sensing diaphragm. 
10. The pressure regulator of claim 9 wherein said 15. In a pressure regulator of the type comprising a 
pivot points are positioned such that the force exerted body including a chamber and a biased diaphragm with 
on said valve means is at least twice as great as that 5 a fluid inlet and a fluid outlet communicating with one 
applied to said one end of said first lever arm by said side of the diaphragm, and a flow valve controlled by 
flow sensing diaphragm. the diaphragm, the improvement comprising a verti- 
11. The pressure regulator of claim 9 wherein said cally extending fluid tube communicating with the 
pivot points are positioned such that the force exerted other side of the diaphragm and with an auxiliary port 
on said valve means is about five times as great as that 10 in the body, and bleed means communicating with the 
applied to said one end of said first lever arm by said auxiliary port whereby the weight of a fluid disposed in 
flow sensing diaphragm. said fluid tube adds to the normal bias on the diaphragm 
12. The pressure regulator of claim 1 wherein the and whereby the bias may be reduced to normal as the 
centers of said flow sensing and pressure regulating height of fluid in said tube is reduced by the bleed 
diaphragms lie on a common axis perpendicular to said 15 means. 
diaphragms. 16. The regulator of claim 1 wherein said bleed means 
13. The pressure regulator of claim 1 and further 
including an auxiliary outlet port in communication 17. The regulator of claim 16 wherein said tubing has 
with said ambient chamber and a tube extending gener- 
is a length of tubing. 
an inside diameter ofD.031 inch. * * * * *  ally vertically from said ambient port. 20 
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Flow compensating pressure regulator

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