U.S. patent number 3,827,828 [Application Number 05/318,520] was granted by the patent office on 1974-08-06 for fluid pump control system.
Invention is credited to Miles Lowell Edwards.
United States Patent |
3,827,828 |
Edwards |
August 6, 1974 |
FLUID PUMP CONTROL SYSTEM
Abstract
This device controls the amount of blood flow in an
extracorporeal blood circuit of a patient requiring long term
profusion to prevent the excessive blood damage as is likely to
occur in the usual heart-lung machines employed during surgery if
it were to be used for an extended time. The device regulates the
speed of the blood pump in accordance with rate of flow of blood
from the body so that the pump does not impose a back pressure on
the blood supply by running too slowly and does not create suction
pressure on the body by running too fast. The speed of the blood
pump is controlled by a potentiometer having a slider contract
driven in opposite directions by a reversible motor. A constant
speed rotating cam intermittently actuates one or the other, or
both, of a pair of switches on opposite sides of the cam. One
switch energizes the potentiometer motor for rotation in one
direction and the other switch energizes the potentiometer motor
for rotation in the opposite direction. The switches are shifted
relative to the cam by a platen bearing against a tubular bladder
in the blood inlet to the pump. As the bladder expands, the pump is
speeded up and as the bladder contracts, the pump is slowed down.
In addition to normal adjustment of pump speed to comply with
normal small variations in blood flow, an emergency safeguard is
provided which causes the pump to stop immediately in case the
blood supply is abruptly interrupted such as would occur if the
blood supply tubing were suddenly closed by a kink or by an
attendant stepping on it. If the blood pump were to continue to
operate when the bladder is empty, the pump could draw fatal air
bubbles into the blood stream.
Inventors: |
Edwards; Miles Lowell (Santa
Ana, CA) |
Family
ID: |
23238522 |
Appl.
No.: |
05/318,520 |
Filed: |
December 26, 1972 |
Current U.S.
Class: |
417/43; 200/83B;
417/45; 200/81.4; 600/16 |
Current CPC
Class: |
A61M
60/109 (20210101); A61M 60/50 (20210101); F04B
49/20 (20130101); A61M 60/546 (20210101); A61M
60/508 (20210101); A61M 60/38 (20210101); A61M
1/3666 (20130101); A61M 60/268 (20210101); A61M
60/00 (20210101); A61M 60/40 (20210101); A61M
2205/3334 (20130101) |
Current International
Class: |
A61M
1/10 (20060101); F04B 49/20 (20060101); F04b
049/06 () |
Field of
Search: |
;417/43,20,25,26,300,38,45 ;200/83B,81.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Sher; Richard
Attorney, Agent or Firm: Schermerhorn; Lee R.
Claims
Having now described my invention and in what manner the same may
be used, what I claim as new and desire to protect by Letters
Patent is:
1. A fluid pump control system comprising a flexible tubular
bladder connected in the fluid supply line to said pump, a platen
bearing on said bladder and movable in response to the expansion
and contraction of the bladder with variations in the rate of inlet
flow to the pump, a continuously rotating cam, a pair of switches
on opposite sides of said cam movable in unison by said platen in a
diametral direction relative to the axis of the cam, a reversible
motor energized for rotation in opposite directions by said
switches, a potentiometer having a sliding contact movable in
opposite directions by said reversible motor, and a variable speed
motor driving said pump under the control of said potentiometer,
whereby the speed of said pump varies in accordance with said inlet
flow.
2. A system as defined in claim 1 including a switch operable by
said platen to stop said pump motor in response to cessation of
said inlet flow.
3. A control unit as defined in claim 1, said switches and platen
being mounted on a pivotal rocker plate.
4. A control unit as defined in claim 3 including an arm on said
rocker plate, and a switch mounted for actuation by said arm when
said bladder is substantially fully contracted.
Description
BACKGROUND OF THE INVENTION
This invention relates to a fluid pump control system for
regulating the speed of a pump in accordance with the fluid supply
so that the pump does not impose a back pressure on the source of
supply by running too slowly and does not create suction pressure
on the source of supply by running too fast. The invention is of
general application for the specified purpose but it is disclosed
herein with particular reference to an extracorporeal blood circuit
for a patient.
Open heart practices are today very well established as applied to
surgical procedures where the normal blood supply to the muscles of
the heart and to the brain must not be interrupted during repair of
critical organs.
With the advancement of the art of fabricating membrane
oxygenators, which are notably low in damage to the blood, there
has been a need for developing new procedures to permit long time
profusion of a patient during periods of crisis. Patients suffering
from heart attack, emphysema, asthma, or the like, may over a
period of days with supplementary profusion with well oxygenated
blood develop sufficient recovery of natural organ functions to
carry on without the need of the extracorporeal blood supply.
To do this it is desirable to make connection through catheterized
connections to more peripheral blood vessels of the body. This
avoids the necessity of opening the patient's chest for access to
the larger vessels near the heart.
It is also important to provide the equipment which will permit
carrying on the longer period of a procedure in an intensive care
area of the hospital without usurping a surgical area for the
extended period.
The present system makes it possible to operate an extracorporeal
blood circuit without the close attention of a skilled pump
attendant as is usually employed in cases where a short term
profusion is indicated as is usual during heart surgery.
During heart surgery, a pump and oxygenator take over the normal
functions of the heart and lungs to circulate and oxygenate the
blood in order to keep those organs of the patient alive which
require a continuous supply of fresh blood. An array of mechanical
equipment attended by a team of specialists is necessary to do this
in addition to the team of surgeons who perform the operation. One
of the functions which demands constant attention is to maintain a
proper speed of the blood pump so as not to let the extracorporeal
circuit become too out of phase with blood supply and demands of
the profused organs. The purpose of the present device is to
regulate the pump automatically so that manual supervision is not
required.
Objects of the invention are, therefore, to provide an improved
fluid pump control system, to provide a pump control system which
regulates the speed of the pump according to the rate of flow of
its source of supply, to control a pump so that it does not impose
a back pressure on its source of supply by running too slowly and
does not create suction pressure in its source of supply by running
too fast, to provide an electric control system for the purpose
described which is operable on standard 120 volt alternating
current house wiring, and to provide a control system of the type
described which is suitable for use in connection with the flow of
blood in an extracorporeal blood circuit.
SUMMARY OF THE INVENTION
In the present pump system the speed of the pump is controlled by a
potentiometer having a slider contact driven in opposite directions
by a reversible motor. A constant speed rotating cam intermittently
actuates one or the other, or both, of a pair of switches on
opposite sides of the cam. One switch energizes the potentiometer
motor for rotation in one direction and the other switch energizes
the potentiometer motor for rotation in the opposite direction. The
switches are shifted relative to the cam by a platen bearing
against a tubular bladder which conveys the fluid input to the
pump.
As the bladder expands, the pump is speeded up and as the bladder
contracts, the pump is slowed down. Thus, the speed of the pump is
regulated to correspond to its input flow so that the pump does not
impose a back pressure on the input flow by running too slowly and
does not create suction pressure in the source of supply by running
too fast.
In addition to normal adjustment of pump speed to comply with
normal small variations in blood flow, an emergency safeguard is
provided which causes the pump to stop immediately in case the
blood supply is abruptly interrupted such as would occur if the
blood supply tubing were suddenly closed by a kink or by an
attendant stepping on it. If the blood pump were to continue to
operate when the bladder is empty, the pump could draw fatal air
bubbles into the blood stream.
The invention will be better understood and the foregoing and other
objects and advantages will become apparent from the following
description of the preferred embodiment illustrated in the
accompanying drawings. Various changes may be made, however, in the
details of construction and arrangement of parts and certain
features may be used without others. All such modifications within
the scope of the appended claims are included in the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of a fluid pump control system embodying
the invention;
FIG. 2 is a side elevation view;
FIG. 3 is a view on the line 3--3 in FIG. 1;
FIG. 4 is a view on the line 4--4 in FIG. 1;
FIG. 5 is a schematic wiring diagram of the control circuit;
and
FIG. 6 is a schematic diagram of the fluid circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As best shown in FIGS. 3 and 4, a vertical front plate 10 is
mounted on a horizontal base plate 11. A stationary horizontal
table 12 is mounted on the front side of vertical plate 10 to
support a flexible tubular bladder 15. Bladder 15 conveys the fluid
input to the pump P in FIG. 6 which is to be controlled.
One end of bladder 15 is provided on its underside with an inlet
ell connection 16 which is received in a slot 17 in one end of
table 12. The opposite end of the bladder is provided on its upper
side with an outlet ell connection 18 which is inserted in a slot
19 in a bracket 20 on vertical plate 10 a short distance above the
table 12. The ends of tubular bladder 15 are sealed at 21.
A horizontal platen 25 rests on the upper side of bladder 15 and is
vertically movable in response to volumetric expansion and
contraction of the bladder. Platen 25 has a vertical flange 26
connected by thumbscrews 27 to a pair of arms 28 on a rocker plate
30 on the back side of vertical plate 10. Arms 28 project through
openings 31 in plate 10. Rocker plate 30 is mounted for oscillation
on a pair of horizontal stub shafts 32 mounted in a pair of
transverse vertical plates 33 and 34 which are attached to the back
side of vertical plate 10. The vertical movements of platen 25 in
response to expansion and contraction of bladder 15 oscillate
rocker plate 30 on its stub shafts 32.
As best shown in FIG. 1, a constant speed motor 35 is mounted on
plate 33 with its horizontal shaft 36 extending through the plate.
Shaft 36 supports a cam 40 having four lobes 41 as shown in FIG. 3.
Cam 40 rotates continuously about a fixed horizontal axis. The
direction of rotation is immaterial.
Mounted on opposite sides of cam 40 is a pair of micro switches,
one being a fast switch S.sub.F and the other being a slow switch
S.sub.S. Each of these switches is mounted on the upright arm of an
L-shaped mounting bracket 45. The horizontal arm of each bracket 45
contains a pair of slots 46 which receive screws 47 in rocker plate
30. Slots 46 permit adjustment of the switches toward and away from
cam 40. Since the adjustments of the switch brackets 45 involve
very minute movements, the positioning of the brackets is
accurately adjusted by means of adjusting screws 48 before the
screws 47 are tightened. Screws 48 form stops which bear against
brackets 45 to hold the adjustment.
Each bracket 45 also carries a pin 49 for pivotally mounting a cam
follower arm 50 having a roller 51 bearing against the cam 40. The
roller is pressed against the cam by a switch actuating button 52
which bears against arm 50. Button 42 is biased outward from the
switch body to switch open position by an internal spring within
the switch body.
The oscillation of rocker plate 30 is limited by an L-shaped arm 55
having a lower horizontal leg provided with slots 46 receiving
screws 47 in the plate 30 for adjustment purposes. Adjustment is
facilitated and maintained by a stop screw 48. The movements of the
upper end of arm 55, and hence the movements of rocker plate 30,
are limited by a pair of stop screws 56 in a U-shaped bracket 57
mounted on vertical plate 34, as shown in FIG. 4. An emergency low
level control single pole double throw micro switch S.sub.E is
mounted on a block 58 on vertical plate 34 adjacent the arm 55. A
pivotal switch arm 50 has a roller 51 normally spaced away from arm
55. An internal spring in switch S.sub.E presses the switch
actuating button 52 outward, holding the switch in one closed
position in normal operation.
It will be observed in FIGS. 3 and 4 that the weight of platen 25
and its supporting arms 28 unbalances the rocker plate 30 whereby
platen 25 tends to rotate downward by gravity so as to bear lightly
against the top of bladder 15. The switch spring forces applied by
switches S.sub.F and S.sub.S are relatively insignificant in
comparison with the weight of platen 25 and its supporting arms 28
acting on a relatively long lever arm with respect to the
supporting stub shafts 32.
FIG. 5 illustrates the electrical system for energizing the present
control device from a 120 volt alternating current supply source
65. The pump motor M is a direct current motor having a constant
potential field winding 66 energized directly from alternating
current supply wires 65 through rectifier 67. The motor armature 68
is energized through a rectifier 69. One input terminal of
rectifier 69 is connected by a wire 70 to one wire of the supply
source 65. The other input terminal of rectifier 69 is connected by
a wire 71 with a sliding contact 72 on a potentiometer 73 which is
connected across the supply wires 65.
Slider contact 72 is mounted on a non-rotatable nut 74 on a screw
75 which may be rotated in opposite directions by a reversible
capacitor-type, single phase, alternating current motor 76. One
terminal of motor 76 is connected directly to a line wire of supply
source 65 by means of a wire 77. A second wire 78 from motor 76 is
connected to fast switch S.sub.F and a third wire 79 is connected
to slow switch S.sub.S. Both of these switches are connected
through a common wire 80 to the opposite line of supply source
65.
With reference to FIG. 3, as the bladder 15 expands it raises
platen 25 moving fast switch S.sub.F toward cam 40 and moving slow
switch S.sub.S away from the cam. When switch S.sub.F is thus
closed repeatedly by the cam and switch S.sub.S remains open, motor
76 rotates screw 75 repeatedly in one direction to shift slider
contact 72 to the left in FIG. 5, increasing the voltage applied to
motor armature 68 to cause the pump P in FIG. 6 to run faster.
When bladder 15 contracts, platen 25 drops to a lower position,
causing slow switch S.sub.S to move toward cam 40 while fast switch
S.sub.F moves away from the cam. In this position of rocker plate
30, slow switch S.sub.S is closed repeatedly and fast switch
S.sub.F remains open. This causes potentiometer motor 76 to rotate
screw 75 to reverse direction, moving slider contact 72 to the
right in FIG. 5. This decreases the potential applied to motor
armature 68, causing the pump to slow down.
When bladder 15 is expanding or contracting, switch S.sub.F or
S.sub.S is actuated about 128 times per minute by cam 40, which is
about two actuations per second. Thus, the bladder 15 is monitored
about twice per second and the pump speed adjusted, if necessary,
every one-half second. This affords much closer control of the pump
speed than can be accomplished manually over a long period of time
in conventional practice.
When fluid flows through bladder 15 at a uniform rate, platen 25
and rocker plate 30 become stabilizEd in a neutral position which
does not actuate either one of switches S.sub.F. or S.sub.S. In
such condition both wires 78 and 79 remain deenergized, preventing
rotation of potentiometer motor 76, and slider contact 72 remains
stationary in equilibrium position maintaining a constant speed of
pump motor armature 68.
If the fluid supply should stop, bladder 15 would collapse
completely allowing platen 25 to drop until arm 55 engages the
right stop screw 56 in FIG. 4. This condition would actuate
emergency low level control switch S.sub.E, opening the circuit to
armature 68 at wire 81 and stopping the pump motor. In this
actuation the switch arm at S.sub.E leaves contact 82 and engages
contact 83, short circuiting the armature 68 through wires 81 and
84 for rapid dynamic braking to stop the pump quickly.
Resumption of fluid flow through bladder 15 moves arm 55, shifting
switch arm S.sub.E back to contact 82 to energize motor armature 68
and re-start the pump. In the meantime, the collapsed bladder has
caused potentiometer slider 72 to move to the extreme right for
slow pump speed. Thus, the pump re-starts at slow speed and
accelerates as bladder 15 fills and expands.
Arm 55 is adjusted on rocker plate 30 so that the normal up and
down movements of platen 25 while fluid is flowing through bladder
15 do not actuate switch S.sub.E.
The extracorporeal blood circuit is shown in FIG. 6. Blood from the
patient's body B passes through bladder tube 15 to the inlet of
blood pump P. Pump P returns the blood to the body through
oxygenator O. In order to purge air from the system when it is
initially primed with blood, the inlet 16 to the bladder 15 is on
the underside and outlet 18 is on the upper side.
* * * * *