U.S. patent number 3,645,649 [Application Number 05/016,519] was granted by the patent office on 1972-02-29 for stirling cycle-type thermal device servo pump.
This patent grant is currently assigned to Research Corporation. Invention is credited to William T. Beale.
United States Patent |
3,645,649 |
Beale |
February 29, 1972 |
STIRLING CYCLE-TYPE THERMAL DEVICE SERVO PUMP
Abstract
A servo pump assisting a pulsating primary pump. A Stirling
cycle engine drives an expansible chamber pump in series with the
primary pump. Pulses are transmitted from the primary pump to drive
the displacer piston of the engine to drive the pump in phase with
the primary pump.
Inventors: |
Beale; William T. (Athens,
OH) |
Assignee: |
Research Corporation (New York,
NY)
|
Family
ID: |
21777546 |
Appl.
No.: |
05/016,519 |
Filed: |
March 4, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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812530 |
Mar 5, 1969 |
3552120 |
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Current U.S.
Class: |
417/379; 60/517;
62/6; 128/DIG.3 |
Current CPC
Class: |
A61M
60/871 (20210101); A61M 60/268 (20210101); A61M
60/40 (20210101); A61M 60/00 (20210101); Y10S
128/03 (20130101) |
Current International
Class: |
A61M
1/10 (20060101); A61M 1/12 (20060101); F04b
017/00 (); A61f 001/00 (); F25b 009/00 () |
Field of
Search: |
;417/321,323,329 ;60/24
;62/6 ;3/1,DIG.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Walker; Robert M.
Parent Case Text
This application is a continuation-in-part application of my
copending application Ser. No. 812,530, filed 5 Mar. 1969, now U.S.
Pat. No. 3,552,120.
Claims
What is new and therefore desired to be protected by Letters Patent
of the United States is:
1. A servo pump for assisting a pulsating primary pump
comprising:
a Stirling cycle engine having displacer and power piston
means;
an expansible chamber pump driven by said power piston, means
connecting said expansible chamber pump in series with said primary
pump; and
means for transmitting pulses from said primary pump to initiate
drive of said displacer piston to thereby actuate said engine to
drive said expansible chamber pump in phase with said primary
pump.
2. A servo pump for assisting a pulsating primary pump
comprising:
a Stirling cycle engine having displacer and power piston
means;
an expansible chamber pump driven by said power piston, means
connecting said expansible chamber pump in series with said primary
pump; and
means for transmitting pulses from said primary pump to initiate
drive of said displacer piston to thereby actuate said engine to
drive said expansible chamber pump in phase with said primary pump,
wherein said means for transmitting pulses comprises a fluid column
interconnecting said primary pump and said engine, and means for
translating fluid pressure pulses transmitted through said column
to mechanical movement to actuate said displacer piston.
3. A pump in accordance with claim 2 wherein said means for
translating includes a diaphragm bisecting a chamber with one side
thereof communicating with said fluid column and the other with
ambient pressure.
4. A pump in accordance with claim 3 wherein said means for
translating further includes a drive rod interconnecting said
diaphragm and said displacer piston.
5. A pump in accordance with claim 3 wherein said means for
transmitting pulses further comprises a return fluid column and
valve means provide flow from said primary pump, through said one
side of said chamber and back to said primary pump through said
return column.
6. A pump in accordance with claim 1 wherein said expansible
chamber pump comprises a pump housing, a pump piston reciprocable
in said pump housing, means connecting said pump piston to said
drive piston and inlet and outlet means communicative with said
pump housing.
7. A pump in accordance with claim 6 wherein said pump piston
divides said pump housing into inlet and outlet chambers, said
inlet and outlet means comprising check valve controlled conduits
communicating with said inlet and outlet chambers, respectively,
and check valve means disposed through said pump piston to provide
transfer of fluid from said inlet to said outlet chambers.
Description
This invention relates to an improved Stirling cycle-type thermal
device, of the type disclosed in the above application which is
suitable for use as a servo pump to assist primary cyclical pumps
and particularly a servo pump which is suitable for assisting the
heart in pumping blood.
The principles of the Stirling cycle thermal device are well known
in the art and a relatively comprehensive review of past and recent
developments in Stirling thermal engines and the comparison of such
engines with the Otto, Brayton, Carnot and Ericsson cycle engines
is found in Volume 68 SAE Transactions 1960, pps. 665-684.
The thermal device as disclosed in the above application generally
comprises a displacer cylinder zone; a displacer piston mounted for
reciprocation in the zone; a power cylinder; a power piston mounted
in the cylinder normally mechanically independent of the
reciprocation of the displacer piston; a working fluid in the
displacer cylinder zone; means creating a pressure differential
between the opposite faces of the displacer piston; the last-named
means including means for adding heat to or removing heat from each
end of the displacer cylinder zone; means providing a power
coupling between the displacer piston and the power piston
consisting of fluid communication conductors between one end of the
power cylinder and one end of the displacer cylinder zone.
It is an object of the present invention to provide means to
incorporate the above-described thermal device into a servo pump
for assisting a primary cyclical pump. This is accomplished by
utilizing the power piston of the device as a pump drive in the
fluid circuit of the primary pump and then initiating the cycle of
the displacer piston of the device by a pulse from the pressure
stroke of the primary pump.
Although the thermal device servo pump of this invention can be
used for general application, the invention is described
hereinafter as specifically adapted for use as a heart assist pump
for pumping blood. Such a device is intended for use as a portion
of the circulatory system of a human being to assist a damaged
heart by providing means to reduce resistance to the pumping action
of the heart.
In this invention a blood pump is placed in series with the heart
and is driven by a Stirling cycle engine, the motion of which is
triggered by heart action so that the heart and the pump operate in
synchronization.
The invention will be more particularly described in reference to
the accompanying drawings wherein:
FIG. 1 is a sectional view of a heart assist servo pump and
associated circuit in accordance with the invention; and
FIG. 2 is a fragmentary view similar to FIG. 1 showing a variation
in accordance with the invention.
Referring now to FIG. 1 of the drawings, 10 generally designates a
Stirling cycle-type servo pump in accordance with the invention
connected to the left ventrical of a heart, schematically shown at
12.
The servo pump 10 includes a housing 14 which defines a cylinder in
which a displacer piston 18 is mounted for reciprocation.
A power piston 20 is reciprocally mounted in the housing 14 beneath
the displacer piston 18 and drives a pump 22. The pump is provided
with an inlet 24 controlled by an inwardly opening flapper valve 26
and an outlet 28 controlled by an outwardly opening flapper valve
30.
The pump 22 comprises a housing 32 having a pump piston 34
reciprocally mounted therein to divide the housing into an upper
chamber 36, communicative with the outlet 28 and a lower chamber 38
communicative with the inlet 24. Communication between the chambers
is provided by check valves, shown schematically at 40, through the
piston 34. The power piston 20 drives the pump piston 34 through a
hollow drive shaft 42 which traverses communicating openings in
adjacent portions of the housing 14 and pump housing 32. A bellows
seal 44 is disposed between the shaft 42 and the openings in the
housings to provide a seal between housings.
The heart, the left ventricle of which is schematically shown at
12, communicates through a valved return, with the left auricle at
46 and through the aorta 48 is connected to the pump inlet 24. A
branch duct 50 also connects the heart to a diaphragm chamber 52
disposed beneath the pump 22. The chamber 52 is provided with a
diaphragm 54 which divides that chamber into upper and lower
sections 56 and 58, respectively. A flexible bag 60 communicates
with the upper section 56 for purposes to be described in greater
detail below.
The diaphragm 54 is connected to the displacer piston 18 by means
of a drive rod 62 which traverses the pump 22 coaxially through the
hollow drive shaft 42 and power piston 20. A bellows seal 64
between the lower end of the shaft 62 and the diaphragm chamber
segregates the upper section 56 of that chamber from the lower
chamber 38 of the pump 22. A bellows seal 66, around the rod 62
between the lower wall of the pump 22 and the piston 34, segregates
the lower chamber 38 from the interior of the hollow drive shaft
42.
The displacer rod 62 runs through a close sliding seal 63 serving
to separate the space 76 and its varying pressure from the bounce
space 75 which is relatively large and has approximately constant
pressure, of, for example, 2,000 p.s.i.
The remainder of the hollow drive rod space including the space
within the bellows seals 44, 66, 64, is held at bounce space
pressure by means of a hole 77 in the drive rod between the bounce
space and the interior of the drive rod. Thus the varying pressures
of the gas in space 76 act only on the small area of the displacer
drive rod 62, and do not serve to drive the displacer appreciably.
The displacer is then free to be driven by the blood pressure
acting on diaphragm 54.
The upper end of the housing is provided with heaters, regenerators
and coolers, schematically shown at 68, 70 and 72, respectively, in
the bypass path around the displacer piston 18. The construction,
function and operation of this portion of the thermal device is
more fully set forth in the above-referred-to application,
particularly in the description of FIG. 6 thereof. For the purposes
of this disclosure, it suffices to say that the devices 68, 70 and
72 function, when connected to suitable sources of energy, to cool
gas being circulated downwardly therethrough by upward movement of
the displacer piston 18 and to heat gas being circulated upwardly
therethrough by downward movement of the displacer piston thereby
providing a hot zone 74 in the housing above the piston 18 and a
cold zone 76 below the piston.
The housing is charged with a gas at high pressure, such, for
example, as with helium or hydrogen gas at 2,000 p.s.i. For this
reason the housing 14 is fabricated to withstand high internal
pressures.
In order to provide a substantially neutral system, e.g., one in
which there are no large biasing force acting on the pistons,
spring effects are built into one or more of the bellows seals 44,
64 and 66 to balance the charge gas pressures on the moving parts
so that they may move readily under the influence of fluid pressure
changes.
The upper section 56 of the diaphragm chamber 52 is charged with
air or inert gas at ambient pressure. The bag 60 serves to equalize
the pressure within the upper section with barometric changes of
pressure in the ambient zone.
With the device charged as above, the inlet 24 is connected to the
aorta 48, the outlet 28 to the inlet to the arterial system and the
pump chambers 36 and 38 and connecting lines are flooded with
blood. The branch duct 50 is connected to the heart 12 and the
lower section 58 of the diaphragm chamber is filled with blood so
that pressure pulses from the heart can be transmitted to the
diaphragm 54. The heater 68 and cooler 72 are then energized and
the servo pump 10 operates as follows:
a. The heart muscle contracts and develops a positive pressure in
the left ventricle 12.
b. The positive pressure is communicated through the duct 50 to
displace the diaphragm 54 upwardly.
c. Upward movement of the diaphragm 54, caused by the pressure
difference between section 58 and the ambient section 56, drives
the rod 62 and displacer piston 18 upwardly.
d. The working gas in the hot zone 74 of the thermal device is
displaced through the regenerator 70 and cooler 72 by upward
movement of the piston 18 and is cooled thereby.
e. The reduced pressure in working gas in the cold zone 76 caused
by the cooling process causes the drive piston 20 to be driven
upwardly by the resulting pressure differential between the gas in
the space below the piston 20 and the gas in the cold zone.
f. The piston 34 of the pump 22 is drawn upwardly, closing the
check valves 40 and pumping blood from the upper chamber 36 through
the outlet 28 to the arterial system. Blood is simultaneously drawn
into the lower chamber 38 through the inlet 24.
g. The heart muscle relaxes at the completion of its pump stroke
lowering the pressure in the left ventricle 12 and therefore in the
diaphragm chamber 52.
h. With the lowering of pressure in the chamber 52, the diaphragm
54, rod 62 and displacer piston 18 move downwardly driving gas from
the cold zone 76 through the regenerator 70 and heater 68 heating
the gas as it enters the hot zone 14.
i. With the increase in pressure caused by the heating of the
working gas, the drive piston 20 is driven downwardly.
j. Downward movement of the piston 20 drives the pump piston 34
downwardly through the shaft 42 opening the valves 40 and
transferring blood from the lower chamber 38 to the upper chamber
36. The valves 30 and 26 are, of course, shut during this cycle
thereby isolating the pump from the system to preclude
overpressured return of blood to the heart or return to the pump
from the arterial system.
The above cycle is then repeated on the next beat of the heart.
The device may be altered, if so desired such that the pump
discharges on the downward stroke by reversing the connections of
the upper section 56 and the lower section 58 of the diaphragm
chamber 52 so that the ventricle pressure drives the displacer
downward. The arterial and aorta connections also must be
interchanged so that the blood enters through 28 and leaves through
24. The direction of operation of the valves 26, 30 and 40 must
also be reversed for such operation.
In FIG. 2, a variation of the diaphragm chamber 52 of FIG. 1 is
illustrated. In this embodiment, components thereof corresponding
to like components of the preceding Figure are indicated by the
like numerals only of the next higher order. In this embodiment,
the chamber 152 is provided with inlet and outlet connections 178
and 180 respectively. The connections communicate, through flapper
check valves 182 and 184 respectively, with a lower section 158 of
the chamber 152 below a diaphragm 154. The operation of the
diaphragm and connected drive rod 162 is identical to that of the
embodiment of FIG. 1.
The connections 178 and 180 are connected to the left ventricle 112
of a heart through transmitting and return lines 150 and 151
respectively.
The advantage provided by the above-described variation is that a
net blood circulation takes place in the lower section 158 thereby
avoiding stagnation at that point. Obviously, other methods of
transmitting the pressure pulse to the diaphragm 154, such for
example as, a column of inert fluid communicative with a transducer
actuated by the heart beat, could function for the purposes of this
invention.
What has been set forth above is intended as exemplary to enable
those skilled in the art in the practice of the invention.
Obviously, the device has general application as a servo in any
system in which a small triggering force is required to cause a
large effect in phase with the force.
* * * * *