U.S. patent number 3,868,973 [Application Number 05/341,915] was granted by the patent office on 1975-03-04 for flow controlling or metering device.
Invention is credited to Howard R. Bierman, John G. Mast.
United States Patent |
3,868,973 |
Bierman , et al. |
March 4, 1975 |
FLOW CONTROLLING OR METERING DEVICE
Abstract
A device for controlling or metering a relatively small flow of
liquid which may be a gravity flow such as in intravenous
introduction of liquids into human veins. The controller, referred
to as a flow rater in one form is a cylindrical ceramic filter
element of a predetermined length capable of maintaining a uniform,
metered flow without monitoring. Adjustable forms of the flow rater
are provided in which two resistance materials are provided in
series, one of which is adjustable by compressing it to provide
rates between zero and a very small flow. In another form, the
effective length of the cylindrical ceramic filter element is
adjustable.
Inventors: |
Bierman; Howard R. (Beverly
Hills, CA), Mast; John G. (Cincinnati, OH) |
Family
ID: |
23339550 |
Appl.
No.: |
05/341,915 |
Filed: |
March 16, 1973 |
Current U.S.
Class: |
138/43; 138/46;
604/246; 210/448 |
Current CPC
Class: |
F16L
55/027 (20130101); A61M 5/165 (20130101); A61M
5/16877 (20130101) |
Current International
Class: |
A61M
5/165 (20060101); F16L 55/027 (20060101); A61M
5/168 (20060101); F16L 55/02 (20060101); F15d
001/00 () |
Field of
Search: |
;138/41,42,43,46 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Ruehl; Charles A.
Attorney, Agent or Firm: Herzig & Walsh
Claims
What is claimed is:
1. A flow controller for controlling a small, slow flow of liquid
comprising in combination: structure means forming a tubular body,
said tubular body defining a longitudinal tubular cavity and having
an inlet formed in one end and an outlet formed in its other end; a
first flow resistance member tubularly shaped to fit within said
tubular cavity in a spaced apart relationship from its inner
peripheral wall, said first tubularly shaped flow resistance member
being mounted at one end within said tubular cavity with one of its
ends in communication with said inlet and its other end closed
whereby liquid flowing into said inlet flows into said tubular
cavity by passing through the flow restriction defined by the
portion of the tubular wall of said first flow resistance member
extending into said tubular cavity, said first flow resistance
member being made of a material having a fixed resistance to flow
characteristic; a second flow resistance member mounted within said
tubular cavity across said outlet so that liquid flowing into said
tubular cavity through said first flow resistance member must pass
through said second flow resistance member to flow out said outlet,
said second flow resistance member being made of a resilient
compressible material having a resistance to flow characteristic
which varies directly with its compression; and means for
selectively compressing said second flow resistance member for
selectively controlling and adjusting the flow of liquid through
said flow controller.
2. A flow controller as in claim 1, wherein the density of the
material making up said second flow resistance member is
substantially less even when compressed than the material making up
said first flow resistance member whereby selective compression of
said second flow resistance member operates to make a fine
adjustment in the flow rate through said flow controller.
3. A flow controller as in claim 1, wherein said means for
selectively compressing said second flow resistance member is
formed by making said body a threaded adjustable member which is
movable axially to compress said second flow resistance member.
4. a flow controller as in claim 1, wherein said means for
selectively compressing said second flow resistance member
comprises means positioned to be radially adjustable with respect
to said body for compressing the material making up said second
flow resistance member.
5. A flow controller for controlling a small, slow flow of liquid
and having the capability of making fine adjustments in the
resistance to flow comprising, in combination: a body defining a
channel therethrough, a first flow resistance material having
uniform flow resistance characteristics positioned within said
channel so that liquid flowing therein passes through said first
flow resistance material; a second flow resistance material in said
body arranged and positioned in said channel for a series flow
through the two resistance materials, said second resistance
material having an adjustable flow resistance characteristic; and
means for selectively adjusting the resistance characteristic of
said second flow resistance material for selectively controlling
and adjusting the flow of liquid through said flow controller, the
density of said second flow resistance material being substantially
less than said first flow resistance material even when adjusted to
provide greatest flow resistance whereby selective adjustment of
the resistance characteristic of said second resistance material
operates to make a fine adjustment in the flow rate through said
flow controller.
6. A flow controller for controlling a small, slow flow of liquid
and having the capability of making fine adjustments in the
resistance to flow comprising, in combination: a body defining a
channel therethrough, a first flow resistance material having
uniform flow resistance characteristics positioned within said
channel so that liquid flowing therein passes through said first
flow resistance material; a second flow resistance material in said
body arranged and positioned in said channel for a series flow
through the two resistance materials, said second resistance
material having an adjustable flow resistance characteristic; and
means for selectively adjusting the resistance characteristic of
said second flow resistance material for selectively controlling
and adjusting the flow of liquid through said flow controller, said
second flow resistance material being a resilient compressible
material and having a resistance to flow characteristic which
varies directly with its compression and said means for selectively
adjusting the resistance characteristic of said second flow
resistance material being operable to apply compressive force to
said second material for the purpose of making fine adjustments in
its resistance characteristic, the density of said second flow
resistance material being substantially less even when compressed
than said first flow resistance material whereby selective
compression of said second flow resistance material operates to
make a fine adjustment in the flow rate through said flow
controller.
7. A flow controller as in claim 6, wherein said means for
selectively adjusting the resistance characteristic of said second
flow resistance material comprises axial adjustable threaded means
capable of being rotated relatively for applying axial compressive
force to said second material.
8. A flow controller as in claim 6, wherein said means for
selectively adjusting the resistance characteristic of said second
flow resistance material comprises means within said body
positioned to be movable radially for applying pressure to said
second material and means for adjusting said radially movable means
to make fine adjustments in the flow resistance of said second
material.
Description
SUMMARY OF THE INVENTION
The invention relates to a liquid flow controller or metering
device typically referred to as a flow rater. The device is
particularly adapted for use in the medical field for control of
the supply of liquids other than orally with respect to the body of
a patient.
For example, in intravenous feeding, liquids are administered
through a needle introduced into a vein. Further at times, in the
treatment of diseases, solutions are introduced in concentrated
form locally at the site of the diseased condition. other
situations may call for the infusion or introduction of liquids in
the body of a patient such as well known to the medical profession.
Such infusion is necessary or desirable flow rate of the liquid is
known and prescribed by the doctor must be held at the desired rate
and controlled or regulated for a substantial period of time.
Typically, the flow is a relatively small one at a pressure rate
which usually would be quite low as described more in detail
hereinafter.
Typically, the problem exists of giving a patient a certain volume
of fluid over a period of six, eight, twelve, or twenty four hours
in the usual amount of about 1,000 cc's of fluid. The rate must be
monitored, since the body reserve over a prescribed amount is only
about twenty percent. That is to say, twenty percent more than the
prescribed amount might prove seriously injurious or even fatal to
the patient. Therefore, a ten percent change is extreme over the
prescribed rate. As the rate or amount of fluid injected increases,
the venous pressure tends to rise and so does the diastolic
pressure.
Experience indicates that approximately one-third of the nurse's
time is expended in adjusting the flow rate of the flow controller.
Since this occurs on each shift, a considerable amount of the
nurse's time is thereby saved if the flow rate does not vary
sufficiently to require constant attention and adjustment. In
practice, the intravenous bottle is suspended a sufficient distance
above a patient so that the difference in pressure drop due to the
lowering level of the fluid in the bottle during the transfusion or
injection is inconsequential. It is noted that the distance the
fluid level lowers is generally only a distance of about five
inches. The resulting drop in pressure head is generally less than
a ten percent drop. For example at 180 cc's of fluid in a bottle
and the bottle 6 feet about the patient's heart, a drop of as much
as 6 inches would amount to less than a ten percent drop in the
head of pressure.
With conventional commercial installations, the drop varies from
manufacturer to manufacturer; and whereas some equipment yields 15
drops per cubic centimeter of fluid, others yield 22 drops per
cubic centimeter. Also, the fluid level varies depending upon the
amount of fluid remaining in the bottle.
With respect to the fibrous or porous flow controller as described
herein, the higher the column, the lower degree of pressure
difference between the delivery when the bottle is full and when
the bottle is empty. That is, if the bottle can be raised to eight
feet above the heart level of the patient, it is so much the
better. It is desirable to keep the difference in pressure from
full to empty bottle to approximately one to two percent.
A primary object of the invention is to realize and make available
a flow controller which will meet and solve the problem described
in the foregoing paragraphs, and more specifically, one which will
not require monitoring by the nurse, but rather one which will
dependably deliver the fluid consistently at a rate within
specifications as set out. Realization of this objective
contemplates provision of a controller which is not adjustable that
will provide dependably a set flow rate and does not require
monitoring by the nurse.
A further object is to provide a controller as described taking the
form of a member having a through bore and made of an appropriate
material, such as ceramic having the required characteristics.
A further object of the invention is to provide and make available
a control device or flow rater as described having the necessary
characteristics to adapt it to the service described above and
particularly, that it will be capable of metering a controlled,
uniform flow of liquid at a low rate for a long period of time.
A further object is to provide a simple, nonadjustable flow rater
for conventional intravenous systems which will permit flow of for
example 42, 83, or 125 cc per hour.
Another object is to provide and make available a flow rater which
enables the user to make adjustments in flow rates in the area of
42, 83, and 125 cc per hour of flow. More specifically, an object
is to provide such a flow rater using a tubular ceramic filter
element as a resistance means, the device providing mechanism to be
able to vary the effective length of the tubular element. A more
specific object is to provide such a flow rater wherein two
resistance materials are provided in a flow rater in series, one of
them having a very uniform characteristic and the other being
variable by being subjected to pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and additional advantages of the invention will
become apparent from the following detailed description and annexed
drawings, wherein:
FIG. 1 is a sectional view of a nonadjustable flow controller;
FIG. 2 is a schematic view of a test set up for the flow
controllers;
FIG. 3 is a chart of flow rate versus length of filter, i.e., flow
resistance element;
FIG. 4 is a sectional view of an adjustable form of flow
controller;
FIG. 5 is a perspective view illustrating utilization of the flow
controller of the invention in association with gravity feed from a
bottled liquid;
FIG. 6 is a cross sectional view of a perferred form of adjustable
flow controller of the invention;
FIG. 7 is a perspective view of two of the components of the
assembly of FIG. 6;
FIG. 8 is a sectional view taken along the line 8--3 of FIG. 6;
FIG. 9 is a sectional view of a modified form of adjustable flow
controller;
FIG. 10 is a sectional view taken along the line 10--10 of FIG.
9;
FIG. 11 is a sectional view of another modified form of adjustable
flow controller; and
FIG. 12 is a sectional view taken along line 12--12 of FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a 0.12 micron ceramic filter 14 in a plastic holder
10. Ceramic filters as manufactured by Flowtronics are made in
cylindrical shape as shown in various lengths for product
uniformity reasons. In the flow rater shown, one end of the filter
is plugged at 16 by a plug of suitable material, and the
drug-carrying solution is forced to flow into open end 17 of the
filter and through the side walls. Thus, the filter area becomes
the inside circumference of the cylinder times the filter length, A
= c1. However, c is fixed by the manufacturer. Thus, the flow rate
is determined by the filter length only. The tubular filter
material is fitted within an assembly of molded polyethylene or
similar material comprising tube 20 and standard medical male and
female luer fittings 22 and 24 fitted together as shown.
The incoming fluid containing the desired drug comes in at high
pressure (530 to 600 mm hg) and drops to a lower arterial blood
pressure (90 mm hg) through the filter material. Since the filter
material is linear, that is, the flow rate through the filter is
linearly proportional to the pressure differential between the two
sides of the filter, the flow rate permitted by the flow rater is
proportional only to the filter area available to transmit flow.
Mathematically, F = KA (Pin - Pout). Since Pin - out is fixed and k
is fixed by filter material choice (in this case, 0.12 micro
ceramic filters manufactured by Flowtronics, Inc.), it is left only
to adjust the filter area to get the desired flow rate.
To choose appropriate lengths and filter porosities, a test set up
as in FIG. 2 may be used. Balloon 30, valve 32, and flow rater 10
are set in their usual configuration, but instead of connecting to
a catheter or needle, it connects to a tube 34 leading to a column
of water 36. The water column height is chosen to be 48.2 in (1,224
mm) which produces a pressure of 1,224 mm water (90 mm hg) or
arterial pressure. To the pressure generator and flow rater, the
column of water is equivalent to a human venous system. The feed
tube (0.035 I.D. polyethylene tubing) and graduated bottle (10 cc
syringe barrel) were used and were large enough to not restrict
flows or cause a considerable pressure drop at these low flow
rates. Using this system, the data generated is shown in FIG.
3.
FIG. 2 also illustrates a typical installation or set-up including
infusion means 33 adapted for insertion into the human body.
Since a 0.40 length is long enough to be manufacturable easily and
that 0.01 in manufacturing length errors do not cause a significant
error in flow rate (only 0.01/0.40 = 2.5 percent), this material
was chosen. If a low standard porosity filter material manufactured
by Flowtronics, such as 0.10 micron is used, then the filter would
be lengthened and thus lengthen the overall product making it more
cumbersome to the user and more fragile (although this might be a
reasonable second choice material). If a 0.27 micron or 0.8 micron
filter material were chosen, the filter element would become
extremely short (about 1/5 and 1/50 as long, respectively)
resulting in flow raters which were shorter but extremely sensitive
to manufacturing error.
Once the desired filter material is chosen and kc (material
constant times inside circumference) is fixed, it becomes an easy
matter to use the curve as shown in FIG. 3 to choose the desired
curve to choose the desired filter length.
Running a horizontal line at the desired flow rate (1 cc per hour)
until it intersects the flow line and then read downward, it is
found that the 0.12 micron filter should be 0.40 inch long. Once
this dimension is found, the remainder of the flow rater's
dimensions are chosen simply to allow adequate flow in and out of
the filter to avoid interferring with or damaging the filter and to
fit standard luer (medical connector) dimensions into which the
rater must fit.
With a standard intravenous bottle hung at 72 inches above the
patient's heart and assuming that the flow rater's back pressure is
neglectible (venous pressure is very low relative to a pressure of
72 inches of water), a test stand using a standard McGaw 500 ml
intravenous bottle and McGaw No. V140 I.V. set can be arranged
similar to FIGS. 2 and 5.
Using the graduations on the bottle and a watch to measure flow
rate, filter elements of various lengths can be tested for flow
rates they permit. Using this data, a flow rate curve similar to
the one appearing in FIG. 3 for the balloon and 0.12 micron filter
element can be generated.
When the desired flow rates are known, the desired lengths are
easily found. The 0.8 micron filter material was selected because
it is the highest porosity of Flowtronics standard filter material.
If the lower porosity, 0.27 micron filter material were chosen, the
resulting filter element would be roughly ten times longer which
would result in an undesirably long flow rater. If a slightly lower
porosity filter material were developed by Flowtronics, a new
slightly longer filter element length could be found. This might be
desirable because the 0.19 length is slightly short but acceptable.
If a higher porosity material became available, the filter lengths
could be adjusted shorter accordingly.
Once the filter length is selected including the plug length, the
remainder of the flow rater dimensions are designed to house the
filter and allow unrestricted flow in and out of the filter.
The following describes the approaches undertaken to give some
adjustability to the flow as described. The primary advantage of
ceramic materials as made by Flowtronics is uniformity. However,
this property negates adjustability of the ceramic material short
of filters with adjustable effective element lengths which can be
done as illustrated in FIG. 4. Body 40 has extending nozzle part or
luer 42. It has bore 44 and bore 46 in the nozzle part. It has
external threads 45 to receive internally threaded knob 50 having
bore 52 and threaded counterbore 54. Numeral 60 indicates the
tubular ceramic filter element. Body 40 has internal flange 64
which seals to element 60, the end of which is closed by plug 68.
Only the part of element 60 beyond the sealing flange is effective
to control flow, which is adjustable by turning knob 50.
As pointed out in the foregoing, a primary objective is to make
available a flow controller for controlled rates of flow which is
readily capable of having fine adjustments made in the flow rate.
Basically, the controller of the preferred form of the invention
embraces the concept of having two flow resistances in series so
that an advantage can be taken of the desirable positive qualities
of each. The first resistance is in the form of a ceramic filter,
fixed length and density. This element may be one which is readily
commercially available. Specifically, the material of this
resistance is chosen for its high resistance, chemical stability,
large pore size, and its filter-to-filter batch-to-batch
uniformity. In typically available commercial materials, uniformity
can be expected to be no worse than .+-.5 percent of the flow
rate.
The desired filter element lengths may be determined experimentally
by supplying known pressure to a filter element of known length and
then measuring the flow rate through the filter. It was found that
in the case of the 0.010 micron ceramic material pressure of 47
inches of water produced a flow rate of 299 cc/hour for every inch
of element. Thus, for any specific flow rate in cc's per hour taken
pressure the length of the filter can be readily calculated.
It can be pointed out that for the first resistance, any filter
material can be used, although materials as described have
preferred characteristics. Filters made of uniform ceramic material
are preferred so that advantage can be taken of the uniformity.
The second element in the series is a low density pressure drop
unit. Low density material is necessary because it is to be
expected that there will be considerable uniformity in acceptable
materials for this element. If this material were twice its desired
density, the element supplies only 5 percent of the total pressure
drop through the flow controller and only 5 percent will be
introduced into the overall system. Thus, a 100 percent
nonuniformity produces a 5 percent error in the flow controller
acceptable level.
The preferred material in the second element is polyurethane foam,
although it could be polyethylene or other comparable material. Any
relatively uniform, non-wettable, chemically inert, compressible
material may be used. Some further examples of materials which can
be used include plastic, rubber, paper (cellulose), of chemical
fibers, electrostatically charged or chargable particles, or
possibly fragments of any inert, slightly compressible material
such as plastic spheres. However, for handling convenience, foam
type material is preferred.
Properties of plastic foams and fibrous material include typically
low pressure drop flow rate constants; hence, it takes a great
thickness of fiberous material to get the same properties as the
ceramic and extreme sensitivity to changing through flow rate
properties with compression as well as manufacturing variations.
Thus, it is practical to use the ceramic filter for gross fixed
flow rating and fibrous material for fine adjustments.
Polyethylene foam is preferred because it is easy to handle,
inexpensive, and can be made in a desired thickness. A particular
foam density will give a 5 to 10 percent change in flow rate with
varying compression on the foam. The ceramic filter length is the
same as nonadjustable units except it is roughly two percent longer
to make up for the pressure drop through the polyethylene foam.
The series resistances can be set up in various ways. The preferred
embodiment or set up is shown in FIGS. 6 through 8, and modified
forms are shown in FIGS. 9, 10, 11, and 12. In the typical
preferred embodiment, only one of the resistances in series has
adjustable flow resistance. That is the low density nonuniform one.
In each form of the invention, means are provided to slowly or
variably compress the foam material to variably control its
resistance.
In FIG. 6, there is provided a cylindrical or tubular body 74
having internal threads as shown at 76. At one end, there is formed
nozzle fitting for male luer 77. Fitting into the opposite end of
body 74 is a cylindrical plug 78 having an end knob 80. The plug
has a part 82 of smaller diameter which fits into the end of
cylindrical body 74. Part 82 does not have internal screw threads.
The cylindrical part of the plug is sealed by an O-ring 84 which
fits into complementary annular grooves in the end of body 74 and
in part 82 of plug 78. Plug 78 has a bore 86 and a larger
counterbore 88 which forms a female luer to receive a connecting
tube 90.
The bore within body 74 has an end taper 92 adjacent to luer 77. In
this end part of body 74, there is provided one of the flow
resistance materials which may preferably be a polyurethane foam as
designated at 96. Adjacent to this resistance material is a
threaded disc 98 as may be seen in FIG. 7 which has a plurality of
axial ports 100 in it and a square center bore 102. Numeeral 104
designates the filter element which is not adjustable and which
preferably is in the form of a ceramic tube as shown, one end of
which fits into a counterbore 106 in the end part of plug 78. At
the other end of tubular filter element 104 is a disc 108 having an
extending square stem 110 which fits into square bore 102 into
threaded disc 98.
As may be seen from the foregoing, the two filter element
resistance elements are in series in the same sense that electrical
resistances may be in series, one of them being adjustable. Knob 80
of plug 78 may be turned, and this may be done by the nurse. This
rotates the threaded disc 98, causing it to move axially to thus
adjust the pressure on foam 96 to thereby adjust and control its
resistance to flow. FIG. 5 illustrates a typical utilization of the
flow controller or the flow rater. Typically, it attaches to a
needle 120 adapted for insertion into a patient's vein, and the
flow controller is connected by tube 122 to a suspended bottle 124
of intravenous feeding liquid for example which feeds by gravity.
In use, the rate of flow is prescribed by the doctor, and this rate
can readily be reduced to a rate in terms of drops per minute, for
example. A nurse, using a watch, can readily check the drops per
minute which will feed through the flow rater. Then, she can easily
adjust knob 80 on plug 78 to provide for the prescribed flow rate.
Therefore as may be seen, the device provides a flow controller
which is readily adjustable by the nurse and takes full advantages
of the capabilities of the extremely uniform, ceramic filter
material while providing for fine adjustments in flow by the
capability of adjusting the pressure on the polyurethane filter
material. Because of the linear flow characteristic of this
material, the adjustment can readily be made to achieve the desired
flow rate.
FIGS. 9 and 10 show a modified form of the invention using two flow
resistance materials which are identified by the same reference
numerals as FIG. 6. In these figures, there is a cylindrical body
120 having a nozzle end 122 forming a male luer. Body 120 has bore
124 with a taper 126 at the end. Luer 122 has a bore 128. At the
end of body 120, there is a flange 132. Numeral 134 designates a
cap member having an inturned flange 136 forming a bore of a size
to be fitted over body 120 and to come flush against flange 132 on
the body. Cap member 134 has a threaded bore 140 which receives a
threaded end plug 142, the end part of which forms a knob 144. At
the inner end of plug 142, there is a flange 150 which fits inside
cap 134. It has external threads as shown which thread into
threaded bore 140. Plug 142 has a bore 152 and a larger counterbore
154 adapted to receive a tubular connection. At the inner end of
plug 142, it has a counterbore 156. Received in this counterbore is
tubular filter or flow resistance member 104. Interposed between
flange 132, body 120, and flange 150 on plug 142, there is a
compressible sealing ring member 160.
At the end of flow resistance member 104 is a disc 162 having
apertures in it as shown at 164. This disc presses against the
compressible flow resistance material 96 which engages against
taper 126. As may be seen from FIGS. 9 and 10, when the knob of
threaded plug 142 is rotated, flange 150 pushes against the sealing
ring, compressing it, and a flow resistance element 104 pushes
against disc 162 which in turn pushes on the compressible material
96 causing its resistance to be varied, making it possible to make
fine adjustments in the flow rate of the unit as a whole.
FIGS. 11 and 12 show another modified form of the invention. In
these figures, numeral 170 designates a tubular barrel having a
bore 172 and a nozzle or luer end 174 with bore 176. Numeral 180
designates a knob part having a bore 182 which is shown
schematically associated with the barrel part 170. This association
may be like that of FIGS. 6 or 9. The tubular flow resistance
element seats in a counterbore 184 in knob part 180 which has an
annular groove or depression 186 at the bottom thereof. The end of
the flow resistance, element 104 is closed by disc 190. Variable
resistance material 96 is between this disc and taper 171 at the
end of bore 172. Numeral 192 designates a circular element having
holes 195 through it and bevel or slanting wedge surface 193, its
flat end positioned against resistance material 96. Numeral 194
designates a threaded element or screw having a head 196 and an end
part 198 of smaller diameter which engages the top of a wedge
member 199 having wedge surface 200 engaging surface 193. The wedge
member is between element 192 and disc 190. Thus, by turning screw
194, wedge 199 can be caused to push down against surface 200 to
urge element 192 against resistance material 96 to change its flow
resistance characteristic by compression to thus change the overall
resistance to flow through the unit as in the previous embodiments.
Screw 194 makes it possible to make very fine adjustments in the
flow resistance.
From the foregoing disclosure, those skilled in the art will
readily understand the nature and the characteristics of the
invention and the manner in which it achieves and realizes all of
the objects as set forth in the foregoing.
The foregoing disclosure is representative of preferred forms of
the invention and it is to be interpreted in an illustrative rather
than a limiting sense, the invention to be accorded the full scope
of the claims appended hereto.
* * * * *