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Патент USA US3080825

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March 12,1963
3,080,822
J. C. FISHER
LIQUID PUMP
Filed Feb. 8. 1960
'7 Sheets-Sheet 1
l
Fig.
INVENTOR.
JOHN C; FISHER
BY
'uzmww. JENNEY, WITTER & HILDRETH
ATTORNEYS
March 12, 1963 ' ' >
J. c. FISHEFQ
3,080,822
LIQUID PUMP
Filed Feb. 8. 1960
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~ ‘JOHN c. FISHER 1‘
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KENWAY, 'JENNEY, WITTER & HILDRETH
ATTORNEYS
March 12, 1963
J. C. FISHER
3,080,822
LIQUID PUMP
Filed Feb. 8. 1960
7 Sheets-Sheet 3
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JOHN c. FISHER
BY KENWAY. 'JENNEY, WITTER &' HILDRE'H
ATTORNEYS
March 12,’ 1963
‘J. c. FISHER
3,080,822
LIQUID PUMP
Filed Feb. 8. 1960
7 Sheets-Sheet 4
I Fig. 4
INVENTOR.
JOHN C. FISHER
KENWAY, JENNEY, WlTl'ER & HILDRETH
ATTORNEYS
March _12, 1963
3,080,822
J. c. FISHER
LIQUID PUMP
Filed Feb. 8. 1960
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March 12, 1963
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INVENTOR.
JOHN C. FISHER
BY KENWAY, ~.IIENNEY, WITTER &' HILDRETH
ATTORNEYS
March 12, 1963
JQC. FISHER
3,080,822
LIQUID PUMP
Filed Feb. 8. 1960
'
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'7 Sheets-Sheet '7
Fig.
l0
INVENTOR.
JOHN C. FISHER
BY
KENWAY, 'JENNEY, WETTER & HILDRETH
ATTORNEYS
Unite States Patent'O "
1
acsaszz
LIQUID PUMI’
John C. Fisher, Cambridge, ‘Mass, assignor to Am Dyue
Trust, a trust of Massachusetts
Filed Feb. 8, 1960, Ser. No. 9,156
12 Claims. (Cl. 103-53)
3,980,822
Patented Mar. 12, 1963
2
The piston is oscillated at a frequency between 20 and
300. cycles per second and to this end any suitable means
may be employed, depending on the particular support
ing structure and the size or capacity of the pump. For
example, where the piston is slidably supported on or by
means entirely within the con?nes of the housing, a
. magnetornotive member such as a coil surrounding the
This invention relates to liquid pumps of the double
housing maybe employed, but if the piston is rigidly sup
acting piston type and particularly to an improved type
ported on a piston rod extending beyond the con?nes of
which is capable of pumping corrosive, toxic, explosive, or 10 the housing then either an electrodynamic vibrator or
otherwise dangerous liquids, without the leakage associat
other reciprocating motor may be employed.
ed with conventional piston pumps which operate at low
The preferred construction of my pump comprises a
frequencies of reciprocation. Such pumps require com
cylindrical piston rigidly mounted on a straight, coax
paratively long strokes in order to provide the requisite
ial rod, the piston being located concentrically in a cyl
discharge; they'require piston rings or packings in order 15 inder of the same shape but of slightly larger cross-sec
to minimize leakage around the piston; and they must
tional area, so that there is no point at which the piston
have sliding-contact shaft seals where the shaft emerges
touches the bore of the cylinder. The transverse cross
from the body of the pump. These features make the
section of the piston and cylinder may be circular, tri
ordinary piston pump unsuitable for use with corrosive
angular, square, rectangular, or any regular polygon. The
liquids or highly active solvents, which, respectively, ruin 20 cylinder is formed within a block and communicates at
precise ring-to-cylinder ?ts by erosion ‘of the carefully
each end with a somewhat enlarged chamber. In order
machined mating surfaces, and leak through even the
to avoid the rapid corrosion which occurs between piston
most ingenious seals and pack-ings now available. Be
rings and cylinder wall'when a conventional piston pump
cause of the long stroke, a pump of this sort cannot em
is used with corrosive liquids, the piston must be mounted
ploy a shaft seal of the continuous-enclosure type, and 25 so that it cannot touch the cylinder bore at any point, as
because of the low frequency of operation, it is not feas
has been mentioned above. However, this construction
ible to employ a piston without rings or packing because
has the disadvantage that it creates a leakage space be
the volumetric e?iciency would be low.
tween the piston and cylinder walls, through which liquid
This application is a continuation-in-part of my prior
will ?owfrom the chamber which is momentarily at high
copending application Serial No. 707,531, ?led January 30 pressure to the chamber which is momentarily at low pres
7, 1958, now abandoned.
The principal object of my present invention is to pro
sure. This internal leakage flow is undesirable, because
it reduces the external discharge from the pump. Several
vide a double-acting piston pump which can pump cor
methods have been employed in the past to reduce this
rosive, toxic, explosive, or otherwise dangerous liquids
leakage ?ow to tolerable levels.
Without external leakage and with high volumetric ef 35 , One‘prior technique employed by L. S. Barengueras in
ficiency, which requires no piston rings or packings, and
United States Patent No. 1,233,438 comprises the use of
which permits the discharge to be varied without the use
perforations, or undulous grooves and ridges, in the sur
of external control valves.
faces of the piston and cylinder wall. The high cost of
Further objects relate to certain structural and func
manufacturing such surfaces limits this method to very
tional features which will be better understood from a 40 specialized applications Where cost is of little importance
consideration of the following disclosure.
and has undoubtedly contributed to the lack of commer
In accordance with the present invention I provide a
cial use of this method. The essential feature of the
pump which comprises a housing in which is slidably
Barengueras device is that it causes added turbulence and
mounted a piston with at least substantially all its side
energy losses in the liquid ?owing through the clearance
,walls or wall being smooth and being in closely
space. These energy losses are functions of the velocity of
spaced out-cf-contact relation to the adjacent smooth side
the liquid in the clearance space as well as of the viscosity
,wall or walls of the housing. The piston may be sup
of the liquid. The Barengueras method becomes less ef~
‘ported by spaced longitudinally extending ribs projecting
fective as the viscosity of the liquid decreases and would
from its side wall or walls so as to provide the desired 50 be completely ineffectual with a ?uid having zero vis
clearance, which need merely be such as to prevent con
cosity. No such ?uid exists, of course, but most gases
tact between the adjacent surfaces. If desired, resilient
approximate this condition.
supporting ?ngers may be secured to the ends of the pis- _
ton, or it may be slidable on a ?xed rod within the hous
ing, or it may be rigidly secured to a rod slidably mounted
at or adjacent to the ends of the housing. In any event,
Another technique is that employed by E. T. Booth,
lit, in United States Patent No. 2,668,656, namely the
use of a piston and cylinder wall which have cooperating
surfaces forming a convoluted leakage path around the
the piston divides the housing into two chambers each
having an inlet port and an outlet port.
piston so that the leakage flow through the clearance
7 The inlet ports are connected with an inlet manifold or
changes in direction. The surfaces of piston and cylinder
space must undergo one or more rather abrupt or severe
header and are provided with suitable rectifying valve 60 wall in the vicinity of these bends in the passage are
means operative to permit a liquid flow only from the in—
essentially smooth, being cylindrical or conical in their
let manifold into the respective chambers. Similarly the
geometry. Suchv surfaces, while being cheaper to manu
outlet ports are connected with an outlet manifold or
header and are provided with rectifying valve means op
facture than those used by Barengueras, and while being
reasonably effective in limiting the leakage, also impose
erative to permit a liquid flow only from the respective 65 an undesirable restriction on the stroke which the piston
chambers into the outlet manifold. An outlet or dis
can undergo without ‘striking any portion of the cylin
charge duct is connected to the ‘outlet manifold and an
der; The essential feature of the method of the Booth
patent is the same as that of the Barengueras patent,
inlet duct or intake is connected with the inlet manifold,
the discharge and intake being connected with an ex
namely the increase of energy losses in the leakage stream
terior circuit as in my copending application’ Serial No. 70. because of velocity-dependent e?ects. It is, of course,
553,015, ?led December 14, 1955, now Patent No.
2,936,713.
a well known principle of ?uid mechanics that loss of
head from a ?owing ?uid stream because of friction is
3,080,822
3
dependent upon the geometry of the flow passageway,
the kinematic viscosity of the liquid, and the velocity of
the liquid.
The preferred construction of my pump utilizes only
the simplest and most economical geometry for the piston
and cylinder bore, namely a straight, circular cylinder
with smooth, unconvoluted surfaces spaced from a'smooth
walled piston of smaller diameter. Since the annular un
convoluted leakage space so created is inherently low in
its resistance to leakage ?ow, something else must be 10
but will be invariant with axial distance along the leakage
space.
Since this is a two-dimensional situation of un
steady ?ow with one moving‘ boundary, the velocity pro
?le will not be like that encountered in more conventional
situations (for example, the parabolic velocity pro?le
encountered in steady laminar flow in a rigid, stationary
pipe).
if only viscous shearing forces (i.e. frictional forces)
were acting on the liquid, the ‘shear stress in the liquid
would be expressible as
done to minimize leakage. In order to understand how
this leakage flow can be controlled, we must examine the
( l)
basic differential equation of the flow, under certain sim
where
plifying assumptions, which are fairly well ful?lled in
practice. The assumptions are as follows:
15 lys=the shear stress along any cylindrical surface within
(1) The motion of the piston is a regular, periodic
the liquid and coaxial with the piston;
function of time (sinusoidal, for example).
'
',u=the absolute viscosity of the liquid,
(2) The cylinder block is stationary.
Vs=velocity of the liquid in the axial direction;
(3) The liquid is incompressible.
n=distance measured normal to the piston axis (radi
(4) The variation of absolute pressure in each cham 20
ally).
ber at the ends of the piston is a regular, periodic function
It may be shown that the resulting pressure gradient
of time.
is given by
(5) The piston and bore are coaxial, and their common
axis is horizontal, or nearly so. (It does not matter if
the piston be vertical, as long as the maximum pressure 25
( 2)
as“ or?“ on?
head in each chamber is large by comparison with the
‘where
length of the clearance space in the axial direction.)
P=the absolute pressure in the liquid;
(6) The change in elevation from top to bottom of
S=distance measured parallel to the piston axis.
the piston (assumed horizontal) is negligible by com
parison with the maximum pressure head in each pump 30, On the other hand, if only inertia forces were acting
chamber.
on the liquid, the pressure gradient would be
(7) The clearance space is of constant cross-section in
oP__ w 5V,
planes normal to the common axis, its bounding surfaces
are smooth, and its radial dimension is small by com
m“ 5 6t
<3>
35 where
parison with its axial length.
(8) The liquid is Newtonian ‘(i.e., the shear stress with
w=the speci?c weight of the liquid;
in the liquid is proportional to the rate of shear), and its
g=the acceleration due ‘to the earth’s gravity;
temperature is constant.
t=time, measured from any convenient reference instant.
Under the influence of the instantaneous pressure differ
ence between the chambers at the ends of the piston, 40 Note that the pressure gradient given by Equation 3 is
liquid will flow through the clearance space from the
in such a direction as to oppose the acceleration of the
high-pressure chamber to the low-pressure chamber. Be
liquid (i.e. the pressure falls in the direction of positive
cause the geometry of the clearance annulus is constant,
and because the pressure difference and piston velocity are
acceleration, so that a pressure difference or drop is re
quired to accelerate a liquid column over any ?nite dis
periodic functions of time, the leakage flow will itself be 45 tance parallel to the acceleration).
a regular, periodic function of time. It will have a zero
When both frictional (viscous) and inertial forces act
average value over any whole number of cycles of piston
simultaneously, as they do in this case, the net pressure
motion. Therefore, the leakage flow is a purely alter
gradign; must be the sum of those given by Equations
nating motion of liquid through the clearance space, and
an
:
it will have both an alternating velocity and an alter 50
nating acceleration. It will become apparent from the
subsequent discussion that this acceleration is the factor
es“”’o7“5 6t
which is used in my pump to limit the leakage flow to a
This is the basic differential equation of the leakage flow
through the annulus between a cylindrical piston with
(4)
tolerable level.
During any half cycle of the leakage flow, the pressure 55 smooth wall and a coaxial cylindrical bore with smooth
wall. In general, it is very di?icult to solve this equation,
gradient in the axial direction through the leakage an
but a qualitative study of the equation, and laboratory
nulus must have two components: (1) a component due
experiments on the physical situation, reveal certain
to the acceleration of the liquid, and (2) a component due
pertinent facts:
to the viscous shearing of the liquid. Under our fore
going assumptions, the pressure gradient at any instant 60
must be constant over the whole axial span of the clear
ance space, and each plane normal to the piston axis must
be a surface of constant pressure at any instant. Since
both frictional and inertial forces act on the liquid, the
(1) Since the piston velocity and the pressure differ
ence are regular, periodic functions of time, the leakage
?ow must be a regular, periodic function of time, de
scribable by a Fourier series of time-harmonic functions
having a fundamental (base) frequency equal to that of
velocity pro?le across the radial dimension of the leak 65 the piston velocity.
age space will not be ?at, but rather the velocity of the
(2) If other parameters are held constant, the crest
liquid at any instant will be zero at the cylinder wall,
value and root-means-square value of the alternating leak
rise to some maximum value in a direction opposite to
age ?ow will diminish as the fundamental frequency of
the piston velocity is increased. Therefore, the total
the piston velocity near the center of the annulus, and
fall through zero velocity down to the value of piston 70 volume of liquid which passes through the leakage an
nulus on each discharge stroke of the piston, and thus
velocity at the piston surface. It must be remembered
diminishes both the outflow from the discharge valve on
that the piston forms one boundary of the leakage space,
the high-pressure side and the inflow through the intake
and this is a boundary which, in general, moves with a
valve on the low-pressure side, must also be diminished.
velocity opposite to that of the bulk of the leakage ?ow.
‘This velocity pro?le will change from instant to instant, 75 This decrease of leakage flow with frequency is due to
5
8,080,822
the fact that, for a given maximum liquid velocity, the
maximum liquid acceleration increases with frequency,
while the available pressure difference which causes the
leakage does not increase correspondingly.
(3) In view of item (2) above, it is evident that the
leakage ?ow through the annular clearance space can
6
tern-a1 to the rod is a space into which the liquid within
the pump may ?ow through the small annular clearance
space around the rod in the rod hole, but from which it
cannot escape. to the outside environment.
A further extension of the rod at each end beyond the
sealing boot or bellows providesv means for attachment
ofthe rod to special springs or “?exures,” which serve to.
restrain the. rod against all‘ motions other than those
be decerased to any desired level merely by making the
piston frequency high enough, and this method is effec
tive even for liquids having negligible viscosity, provided
parallel to its axis. These flexures support the weight
only that they have a speci?c weight greater than zero. 10 of the rod. and piston, thereby preventing it and the piston
The heavier the liquid, the more effective is this method
from touching their respective bores during operation so
of limiting the leakage ?ow, but it is effective. even for
that no rubbing of solid surfaces against each other takes
the lightest liquids which are pumped in industry.
place.
Experiment-s conducted upon actual pumps of the type
Each of the two discharge valves communicates on its
described herein have shown that, at a piston frequency .15 downstream side with the interior space of a discharge
60 cycles per second, with a piston 5 inches long, 3 inches
header or manifold which is attached to the cylinder
in diameter, and having a radial clearance in. the bore
block. Emerging from this discharge header is an outlet
of 0.010 inch, the equivalent lost external discharge due
duct or nipple to which may be clamped a suitable ?ex
to the leakage how is 2.90 gallons of water per minute
ible hose or tube, this tube serving to carry the emerging
at an equivalent average pressure difference of 40 pounds 20 liquid flow to an external circuit or apparatus. Such a
per square inch, gage. The equivalence between average
tube is preferably elastic so as to eliminate ‘for the most
leakage ?ows and pressure differences, and their corre
part the pulsations inherent in the output, stream. The
sponding peak values was based upon the sinusoidal varia
tube performs this latter function by virtue. of its elas
tions of these parameters which were used in conducting
ticity, i.e., its ability toexpand and contract slightly in
the tests:
25 the radial direction in response to changes of internal
pressure. For the frequencies of operation and ampli
Equivalent average value‘=:2>< (peak value of parameter)
tudes encountered in conventional piston pumps, this
1r
means of pulsation removal would not be so effective; but
By comparison with this leakage ?ow through the clear
ance space under dynamic conditions at 60 cycles per
second, the steady leakage flow through the same annular
for higher frequencies, the distributed compliance of the
tube will permit substantial velocity differences for the
flow along its length with only a moderate ?uctuation of
space under constant pressure difference (i.e. zero fre—
internal pressure. Thus, as the frequency of operation
quency) is 2.90 gallons per minute at only 3.50 pounds
increases, a ?exible hose or tube becomes a progressively
per square inch, gage. Conversely, at 40 p.s.i.g. the steady
better pulsation eliminator, up to the point at which the
leakage would be 16.2 gallons per minute.
35 length of the tube becomes an appreciable fraction of the
Furthermore, experiments of this same type show that i
wave length of sound in the enclosed liquid. The pre
when the piston frequency is below 20 cycles, the leakage
ferred frequency of operation of my pump is 60‘ cycles
?ow past the piston becomes undesirably large, even if
per second, the practical range of operating frequency
the radial dimension of the clearance’ space is reduced
being from 20 to 300 cycles per second.
to the point where it is difficult to maintain the out-of 40
Each of the two intake valves communicates on its
contact relation between piston and bore. On the other
upstream side with the interior space of an intake manifold
hand, if the piston frequency is made very high, the axial
or header which is attached to the cylinder block. Con
length of the clearance space becomes an appreciable frac
nected to the intake header is an intake duct or nipple
tion of the wavelength of sound in the enclosed liquid,
which serves as a connection point for another length
and resonance phenomena can occur which actually mag
nify the leakage ?o-w. Therefore, the preferred range of
operation of ‘my pump is 20 to 300 cycles per second.
This operating frequency permits the use of the simplest
possible geometry for both‘ piston and bore: coaxial cylin
tiers whose cross sections are regular polygons of the same
number of sides (preferably the circle, which is a regular
polygon with an infinite number of sides) and whose
surfaces are smooth and unconvoluted.
Each of the pump chambers at the ends of the piston is
preferably provided wtih a pair of reed-type ?uid recti?ers
of the type described in my copending application Serial
No. 636,597, ?led January 28, 1957, now abandoned; one
r of suitable ?exible tubing or hose.
This tubing carries
the entering flow from the external apparatus and may
also serve to introduce into the steady ?ow from this
apparatus the pulsations which were eliminated by the
hose on the discharge side. Were these pulsations not in
troduced, cavitation would occur in each pump chamber
on the intake. stroke. However, the intake tubing pre
vents cavitation by means of slight radial expansions and
contractions as the internal pressure ?uctuations cyclically
below the atmospheric pressure which surrounds the outer
surface of the hose. If the operating dischage pressure is
too high for the hose to resist wtihout reinforcement, it
may be made with a woven fabric molded into the elas
valve permitting liquid to enter the chamber but not to
tomer of the wall, or it may be made with the wall of
leave it, and the other valve permitting liquid to leave
pure elastomer and covered externally with a close-?tting
but not to enter. Within each. chamber, directly opposite 6,0 woven metal braid.
,
the respective end of the cylinder bore, there is provided
One end of the shaft of my pump isconneoted through
an opening through which the rod passes. This rod open
a drive link to the armature of an electrodynarnic vibra
ing has the same cross-sectional shape (circular being the
tion motor, which produces a reciprocating motion, the
preferred shape) and a slightly larger cross-sectional area
double amplitude of which does not exceed 0.75 inch.
than the rod 'so that the shaft does not touch the bore 65 ‘This motion is customarily sinusoidal in its time variation,
of the shaft-hole at any point.
1
but other wave forms (such as triangular, trapezoidal, or
At each end of the structure, where the rod emerges
rectangular) are possible. The technology of such vibra
:from the housing, there is provided a solid, but longi
tion'motors-is well known and need not be discussed here,
tudinally ?exible, rod seal which is securely clamped at
other than to say that the amplitude and the frequency
its ?xed end to the pump housing or a suitable extension 70 of the vibration are readily controllable by electrical
‘thereof, and at its moving end to the rod or a suitable
means, so that theoutput of the pump which is connected
extension theerof. This seal, which might be described in
other types of machinery as a “boot,” is tubular in shape
but, if desired, it may be in the form. of a bellows which
is open at each end. Within. the boot or bellows and ex
to this motor may be varied without the use of control
valves. Other driving means may be employed,‘ such as
a conventional rotary motor coupled to a crankshaft
75 ‘whose. connecting rod actuates a crosshead attached to
3,080,825
8
the pump shaft. However, the function of the pump is
not dependent upon the speci?c details of the drive system.
In operation, the pump causes the liquid to ?ow because
on each stroke of the piston the volume of the chamber
at the trailing end is increased while that of the chamber
at the leading end is decreased; on the succeeding stroke
these events are interchanged for the two chambers.
Hence, in each complete cycle, each chamber alternately
mover M are mounted on a channel-shaped base or sup
port 1, to which are bolted four upright posts 2 (FIGS.
1 and 3) and channel-section girders 3‘ (FlGS. 3 to 5)
which are in the form of an inverted U. The upper ends
of posts 2 are bolted by cap screws 4 to horizontal angle
‘brackets 5, one bracket being located on each side of the
pump unit. Each angle bracket 5 is secured by screws 6
10 its respective side of a cylinder block 7 (FIGS. 1
and 6).
receives an in?ux of liquid from the intake header and
Each of the girders 3 supports the upper end of one
then discharges this excess liquid to the discharge header. 10
?exure assembly comprising two short, ?at leaf springs
The action of the valves prevents any signi?cant back
of high transverse stiffness 8 and 9 which are bolted in a
?ow through the valve ports. Because the clearance space
horizontal position to the underside of channel 3 by cap
around the piston is small in area compared with the
screws 11} (FIG. 1), these springs 8 and 9 being separated
cross-sectional area of the piston itself, and because the
period of each stroke is short, the leakage flow around the 15 by a solid metal spacer block 11 and extending in parallel
overlying spaced relation. At their outer ends the springs
piston is effectively restricted. Both frictional forces due
8 and 9 are bolted to a similar spacer block 12 (FIG. 1)
to viscous shearing of the liquid and inertial forces due to
by cap screws 13, which ?t into tapped holes in nut plate
high acceleration of the liquid act to limit the leakage
14. Secured to the outer vertical surface of spacer block
?ow to a small fraction of the external discharge. Thus,
the pump does not need the piston rings of conventional 20 12 is the upper end of a main ?exure (leaf spring) 15,
piston pumps in order to atain high volumetric efficiency.
The leakage ?ow is further reducedlby making the axial
length of the piston as long as is feasible.
the general plane of which extends at right angles to the
general plane of the springs 8 and 9. The ?exure 15 is
?ow (leakage only in the sense of reducing the volumetric
e?iciency) is effectively limited by the following factors:
(1) the small clearance space around the shaft, (2) the
special elongated plug 18 extending at right angles to the
general plane of the spring 15. Between the hexagonal
clamped to the block 12 by a single cap screw 16 which
passes through washer plate 17 and ?exure 15 into a
Although the space within the seal boot or bellows at
each side of the cylinder block is open to liquid ?ow to 25 tapped hole in block 12. At the center of ?exure 15 there
is a hole through which passes the threaded shank of a
and from the corresponding pump chamber, this leakage
shoulder of plug 18 and a narrow hex nut 19 are two
fact that the change in internal volume of the space within 30 square washer plates 20 and 21 which con?ne ?exure 15
and de?ne the upper and lower horizontal lines along
the boot is much less than the change in volume of the
which bending of ?exure 15 may occur. Nut 19 is
pump chamber, and (3) the fact that the intra-boot space
tightened securely so as to clamp the parts in place during
may be reduced by placing a set of close-?tting elastomer
vibration. The lower end of each ?exure 15 is clamped
washers on the portion of the shaft inside the boot.
In practice the piston, shaft, cylinder block, valve 35 to a set of parts identical to those at its upper end, with
the exception that the lower assembly of short ?exures
blocks, and headers are preferably made of a suitable
metal, such as stainless steel. The intake and discharge
ducts, together with the seals, may be made of a variety
of elastomers such as polyvinylchlorides (Tygon), chlo
rinated polyethylenes (Hypalon), neoprenes, rubbers,
silicone rubbers, plasticized tri?uoro-monochloroethylene
(Kel-F), etc., the exact material being chosen according
to the requirements of the particular pumping problem.
is secured directly to base 1 vertically below the place of
attachment of the upper parts to channel 3.
Each ?exure assembly is so designed that the stiffness
against vertical displacements in the plane of the ?exure
115 is very high, being in the order of 50,000‘ to 100,000
pounds per inch. The stiffness against horizontal dis
placements in the plane of ?exure 15 is several orders of
magnitude higher. Because of the two short ?exures 8
The ?exures are best made of a high-carbon spring steel
and 9 used at each end, the blocks 12 can undergo no
covered with a corrosion resistant paint or plastic, or of
hard-tempered stainless steel. The seals may also be 45 rotation, but only a vertical translation, so that when
plug 18 undergoes a horizontal displacement of up to 14
made of stainless steel or other metal, provided that they
inch from rest position, the concomitant shortening of the
are formed with convolutions to give them ?exibility in the
vertical length of ?exure 15 (which amounts to no more
axial direction.
than 0.020 inch in most cases) can occur without any
The foregoing and other important aspects and features
change in the direction of ?exure 15 at its ends. Further
of my invention will be apparent from a consideration of
more, this shortening induces only minor tensile stresses
the accompanying drawings, wherein:
in ?exure 15 by comparison with the bending stresses
FIG. 1 is a side view of a high-frequency, double-acting
piston pump mounted on a base with an electrodynamic
caused by the transverse horizontal de?ection at the cen~
ter of the ?exure 15. The advantage of this spring sus
vibration motor as prime mover, with one of the ?exure
55
pension is that it permits a true rectilinear motion of the
supports shown cut away for clarity;
FIG. 2 is a top view substantially along the line 2—2 of
members which are suspended between the centers of
?exures 15, but without the severe changes of stiffness
FIG. 1;
FIG. 3 is a sectional view substantially along the line
with increasing de?ection which would occur if the upper
and lower ends of ?exures 15' were rigidly clamped.
3—3 of FIG. 1;
FIG. 4 is a sectional view substantially along the line 60
The stiffness of the ?exure system against horizontal
motions on an axis passing through the centers of ?exures
4—4 of FIG. 1;
FIG. 5 is a sectional view substantially along the line
15 is readily and accurately computed from theory, and
it is chosen so that the natural frequency of the moving
5—~5 of FIG. 4;
FIG. 6 is a median sectional view substantially along the
system of the pump is equal or nearly to the frequency of
line 6--6 of FIG. 3, the ?exure supports being shown cut 65 operation. This removes the inertia-force load from the
away for clarity;
prime mover M which is itself designed so that its own
FIG. 7 is a sectional View substantially along the line
natural frequency coincides with the operating frequency.
7—7 of FIG. 6;
The prime mover M is of the electrodynamic type having
FIG. 8 is a sectional view substantially along the line
70 an armature shaft 25, such as shown in my copending
8-8 of FIG. 6;
_
FIG. 9 is a sectional view substantially along the line
9-9 of FIG. 6; and
FIG. 10 is a median sectional view of a bellows-type
application Serial No. 553,015, ?led December 14, 1955,
now Patent No. 2,936,713, to which reference may be
had for a more complete disclosure.
Between the inner ?anges of channels 3, at their upper
portions,
is fastened a stiffening rod 22 (FIGS. 1 and 2)
75
With reference to FIGS. 1 to 6, the pump P and prime
seal boot.
.
10
which adds rigidity to the flexure-supporting structure.
Supported between plugs 18, with its outer ends threaded
and screwed tightly into blind tapped holes in plugs 18,
same thickness) above it, the whole assembly being
clamped between pressure plates at its ?xed end by screws
is a straight rod or shaft 30 (FIGS. 3, 6 and 7 to 9‘), hav
ing a circular cross section. Near each of its outer ends
rod 30 passes through a long circular bushing 31 (FIGS.
3 ‘and 6) which is coaxial with rod 30 and which has an
such rectifying valves is fully described in my co-pending
application Serial No. 636,597, ?led January 28, I957,
inside diameter slightly larger than the outside diameter
The advantage of this construction is that for a given
stress level in all the reeds at maximum deflection the
of rod 30, so that no contact occurs between rod and
bushing.
The bushing 31 is press-?tted or otherwise secured co
axially within a larger sleeve 32, having three distinct
diameters. The largest of these diameters, at the inner
set into tapped holes in. the valve block. The theory of
now abandoned.
However, one re?nement is added
her, namely, the use of several reeds of different lengths.
10 natural frequency of the composite valve is higher than
for a single reed or a stack of several reeds all of the
same length. The projection of each valve seat above
the valve block is designed so that when closed each valve
end of sleeve 32, ?ts freely into a mating hole at either
stack is under a slight preload, and this causes, the base
end of cylinder block 7. The adjacent diameter, some 15 reed to. close the port against static back?ow, while in
what smaller, is either press-?tted or welded into a mating
suring that all the reeds remain in contact with one
hole in a rectangular end plate 33, which is fastened to the
another at all times.
end of cylinder block 7 by screws 34, which serve to
The intake-valve block 49 is formed with internal
compress a thin gasket 35 between plate 33 and block 7.
passages having sloping surfaces, so that there is no
The screws 34 are set into blind tapped holes in block 7, 20 where a horizontal surface or dome ‘which can trap air
so that no leakage via the screw _threads can occur.
The
smallest diameter of sleeve 32, at its'outer end, is the same
_or gas bubbles.
’has no horizontalSimilarly,
surfaces or
thedomes
discharge-valve
in its internal
blockpas
as the inside diameter of an elastomer sealboot 36, which
sages. Interposed between valve block 48 and cylinder
is tightly clamped around sleeve 32 by a screw-and-band
block 7 is a thin, ?at gasket 71 which ‘prevents leakage
clamp 37. The other end of boot 36 is similarly clamped 25 across the interface. Similarly, a gasket 72 is interposed
by another clamp 38 to a smooth circular portion at the
inner end of plug 18. Because there are no openings to
between valve block 49 and cylinder block 7.
the outside, no leakage of the liquid being pumped can
connect intake nipple’ 63 with valve ports 46 and 47.
take place from the space within boot 36 to the outside
environment.
During the reciprocating motion of shaft 30, the boots
36 are alternately elongated and compressed, the deforma
tion, as a fraction of the normal length, being chosen so
that the internal stresses in the elastomer are low, and the
Fastened
below block 49 is an intake header 61, which serves to
Nipple 63 is either press-?tted, screwed (via pipe threads),
or welded into header 61.
Between header 6i and
block 49‘ is ‘another thin, ?at gasket 73 to prevent lea-k
age across this interface. Connected securely to nipple
63 by means of a suitable clamp 76 is a flexible hose or
tube 77 which carries the entering ?ow of liquid to the
operating life correspondingly long. Because the space 35 pump.
within each boot is essentially exposed to the. average
Directly above discharge-valve'block 48 is fastened a
pressure within the pump chambers 40 and '41, the boot
is subjected to radial deformation outward on this ac
count.
'
Secured to the. center of rod 30 by setscrews 42 is a
cylindrical smooth walled piston 43 (FIGS. 6 to 9) having
a circular cross section. Piston 43 is coaxial with shaft
30.and with the smooth walled cylinder bore in block 7,
there being a small annular clearance space around piston
43 so that no contact occurs between piston and bore.
The clearance area is chosen so that it is one per cent or
less of the piston area, and the bore length made as great
as practical, in order to minimize leakage ?ow past the
piston. It will be noted that the cylinder bore, piston and
enlarged pump chambers 40 and ‘41, which as shown in
FIG. 6 are at the oposite ends of the piston, are con
structed and arranged so that the leakage path between
the chambers 40, 41 is' unconvoluted or in other words
the leakage path between the chambers at the opposite
‘ends of the piston is‘ formed entirely by the radial spac
ing of the piston and bore, and the annular space between
the piston and bore opens into and communicates directly
with the chambers at the opposite ends of the piston.
In this connection, it will be noted that the piston is pro
vided with a rectangular longitudinal cross section in any
plane passing through the piston axis.
'
As mentioned above, t each end of the cylinder bore,
there is a somewhat enlarged liquid chamber '40 or 41
(FIG. 6), the chamber '40 communicating with an intake
_valve port 46, and a discharge valve port 44, while cham
ber 41 communicates with intake port 47 and discharge
>
discharge header 60‘ which serves to collect the pulsating
flow which emerges alternately from valve ports 44 and
45, and to guide this ?ow to discharge nipple 62. Nipple
62,,which is securely fastened into header 60, has clamped
to it by means .of clamp 74 a flexible discharge hose 75
which carries the emergent flow to the external apparatus
(not shown). Between header 6t)‘ and valve block 48
is a gasket 70 to prevent leakage across the interface.
Note that the interior space of header Gtl‘need not be
45
provided with a sloping roof, since the accumulation of
-air or gas bubbles therein does no harm, and may in fact
help to veliminate the pulsations from the liquid ?ow
through hose 75.
As shown in FIGS. 7, 8 and 9, the header 6% and valve
50
block 48 are secured to each other and to cylinder block
7 by long screws ‘80, which are regularly spaced near
and around the periphery of members 7, 48 and 6t).
These screws pass through clearance holes in parts 48,
‘60, 7.0 and 71 into tapped holes in cylinder block 7.
Note that wherever these tapped holes might emerge into
any of the liquid chambers if carried through, the holes
are blind. so as to prevent leakage to the outside. The
central portion of block 48 is compressed against gasket
71 and block 7 by shorter screws 81 which pass through
clearancev holes in parts 48. and 71 into tapped holes in
block 7. If desired, these holes can run through into
the cylinder bore, since the negligible leakage which might
occur throughout them cannot escape to the outside en
vironment. (Of course, the screws must not project
into the bore.) In an exactly similar fashion, intake
fheader 61 and valve block 49' are fastened to each other
port 45. Each valve port is a circular opening in a sleeve
type valve seat 50 to 53, preferably made of a'suitable
and to cylinderblock 7 by long screws 82, while screws
plastic in order to suppress valve noise and insure wear
783 secure the center of 49 to block 7.
These valve seats are lightly press-?tted into
resistance.
corresponding holes in the intake-valve block 49 and the‘ .70 ' Into a blind tapped hole in the outer end of the plug
18 which. is opposite prime mover M there is screwed
discharge-valve block 48.
the threaded end of a slender drive link ‘85 (FIGS. 1, 2
Each valve port is closed against downward liquid flow
and 6) which carries a locknut 86 preventing this threaded
by means of a stack of flat leaf springs or reeds 54 to
shank from working loose when in motion. The other
57, each stack being composed of one long base reed
with several reeds of progressively shorter length, (but the." '75. end. of link 85 is similarly fastened into the end of the
8,080,82'32
12
11
armature shaft 25 of prime mover M by means of an
means including a piston rod to dispose said piston with
other threaded shank and locknut 87. The purpose of
this drive link is to provide a mechanical connection be
tween pump and driver that is su?iciently rigid against
axial compression and tension to transmit the requisite
in said bore, said piston dividing the housing into two
chamber 41 back to chamber 40 via the clearance space
piston rod extending coaxially from the piston and sup
chambers located respectively at the opposite ends of the
piston, the circumferential wall of said piston being ra
dially inwardly spaced relative to the wall of said bore
to provide a liquid leakage path past said piston and from
driving force, but su?iciently ?exible against transverse
one chamber to the other chamber, said leakage path
bending to permit small misalignments between the
formed by the radial spacing of the piston and bore
armature shaft of the driver and rod 39 of the pump,
opening at its opposite ends directly into said chambers,
without inducing large bending stresses in either shaft.
In operation of the pump, the sequence of events is as 10 means for introducing liquid into each of said chambers
including means for impeding liquid flow out of the
follows: Assuming that piston 43 is instantaneously mov
chambers, means for conducting liquid out of said cham
ing to the right in FIG. 6, the volume of chamber 40‘ is
bers including means for impeding back flow of liquid
then being increased, and hence the pressure therein is
into said chambers, and means for reciprocating said
decreasing. Valve 56 permits liquid to enter chamber 40
piston longitudinally of said bore at a frequency of be
from chamber 66 via valve port 46, and simultaneously
tween 20 and 300 cycles per second.
valve 54 prevents any liquid from entering 49 from cham
2. In a liquid pump of the class described, a housing
ber 65 via port 44. At the same time, the volume of
having a smooth walled bore, a smooth walled piston
chamber 41 is being reduced, and hence some of the
disposed within said bore and dividing the housing into
liquid therein is forced out into chamber 65 via valve port
45. While this takes place, no liquid is allowed to escape 20 a pair of chambers, the piston being cross sectionally
smaller than said here to provide a substantial space be
from chamber 41 via port 47, because valve 57 closes
tween the circumferential walls of the piston and bore, a
this port. A small amount of liquid will leak from
ported in spaced out-of-contact relation to the housing,
around piston 43 in the cylinder bore, but, as has been
previously explained, this is an insigni?cant fraction of 25 deformable sealing means between the rod and housing
to prevent liquid ?ow externally of the housing around
the total piston displacement per stroke. Also, a neg
said piston rod, means for introducing liquid into each
ligible amount of liquid may escape from 41 into the
of said chambers including means for impeding liquid
space within seal boot 36 on the same side as chamber 41.
?ow out of the chambers, means for conducting liquid
On the return stroke (to the left), the events in cham
bers 4t} and 41 will be interchanged, with liquid entering 30 out of said chambers including means for impeding back
flow of liquid into said chambers, and means for recipro
chamber 41 via port 47 and leaving chamber 40 via port
cating said piston longitudinally of said bore at 21 fre
44. Thus, there is a pulsating ?ow of liquid from intake
quency of between 20 and 300 cycles per second.
nipple 63 to discharge nipple 62, with two pulsations of
3. In a liquid pump of the class described, a housing
the ?ow per cycle of piston displacement. To those who
are familiar with electrical technology, it will be ap 35 having a smooth walled bore, a smooth walled piston dis
posed within said bore and dividing the housing into a
parent that valves 54, 55, 56 and 57 are connected in the
pair of chambers, the piston being cross sectionally
form of a single-phase, full-wave bridge, so as to rectify
smaller than said bore to provide a substantial space be
the alternating motion of the liquid which occurs in
tween the circumferential walls of the piston and bore
chambers 40 and 41.
The modi?cation shown in FIG. 10 is a variation of 40 and provide a liquid leakage path between said chambers
which is formed entirely by the radial spacing of said
the seal boot wherein a bellows 95) is used in place of
piston and bore and which opens directly into said cham
the cylindrical elastomer tube previously illustrated. If
bers, a piston rod extending coaxially from the piston
this bellows is made of an elastomer, then it may be
and supported in spaced out-of-contact relation to the
clamped at its ends by clamps 91 and 92, but if the bel
lows is of metal, then the clamping means must consist 45 housing, deformable sealing means between the rod and
housing to prevent liquid flow externally of the housing
of suitable end ?anges and gaskets such as are customarily
around said piston rod, means for introducing liquid into
used with metal bellows. In either case, the volume of
each
of said chambers including means for impeding
the space within the seal boot or bellows may be almost
liquid ?ow out of the chambers, means for conducting
entirely ?lled with a stack of elastomer washers 93
mounted about the rod 30. The free length of this stack 50 liquid out of said chambers including means for impeding
back ?ow of liquid into said chambers, and means for
is chosen so that when the stack is installed it is com~
reciprocating said piston longitudinally of said bore at a
pressed statically by an amount which exceeds the single
frequency of between 20 and 300 cycles per second.
amplitude of the motion of the shaft. Thus, the stack
4. In a liquid pump of the class described, a housing
of washers is never entirely relieved of compression,
having
a smooth walled bore, a smooth walled piston,
and the washers always remain in contact with one an 55
means including a piston rod to dispose said piston within
other and with the pump members at each end of the
said bore, said piston dividing the housing into two cham
stack. If the static compression of the stack is a suitably
bers located respectively at the opposite ends of the piston,
small fraction of the free length, then the compressive
the circumferential wall of said piston being radially in
stresses in the stack during operation are kept low enough
wardly spaced relative to the wall of said bore to provide
to insure long service life.
60
a liquid leakage path past said piston and from one cham
In summary, the advantages of my invention are as
her
to the other chamber, the piston having a substan
follows: ?rst, the pump is constructed in such a way that
tially rectangular longitudinal cross section in any plane
no leakage of the liquid being pumped can occur between
taken through the piston axis to provide that the leakage
‘the interior of the pump and the outside environment;
second, because theentire moving system is elastically 65 path formed by the radial spacing of the piston and bore
communicates directly with said chambers, means for in
‘suspended, without sliding contact between the moving
troducing liquid into each of said chambers including
and stationary parts, wear on the moving parts due to
means for impeding liquid ?ow out of the chambers,
friction is eliminated; and third, because the external
means for conducting liquid out of said chambers includ
discharge is governed by the frequency and amplitude of
the piston motion, the discharge may be controlled by 70 ing means for impeding back ?ow of liquid into said
chambers, and means for reciprocating said piston longi
electrical means acting on the prime mover, rather than
tudinally of said bore at a frequency of between 20 and
by expensive ?ow-control valves.
I
claim:
1 Y
'
300 cycles per second.
5. ‘A liquid pump of the class described comprising a
1. In a liquid pump of the class described, a housing
having a smooth walled bore, a smooth walled piston, 75 housing having a smooth, walled bore, a piston rod ex
3,080,822
13
14
tending coaxially of and within said bore and mounted
for oscillatory movement longitudinally of the bore, said
10. A liquid pump of the class described comprising a
?xed housing, a support for the housing, a reciprocable
rod extending through said housing, elastic means support
ing the ends of said rod for substantially purely axial
movement of said rod including a pair of vertically dis
posed ?at leaf springs each having a general plane extend
ing at right angles to the axis of said rod, said springs
being respectively clamped to the ends of said rod for
movement therewith and being clamped to said support
at points spaced from said rod, a piston supported by
said rod intermediate its ends within said housing with
its side wall portions in closely spaced out-of-contact rela
tion to the adjacent inner walls of said housing, said piston
dividing said housing into two chambers, each chamber
rod being spaced in out-of-contact relation to said hous
ing, at least one end of said rod projecting outwardly
of said housing, a smooth walled piston secured to said
rod within said bore, said piston’ dividing said housing
into two chambers, the circumferential wall of the piston
being spaced radially inwardly of the wall of’ said bore
to provide a liquid leakage path past said piston and be
tween said chambers, said leakage path opening directly
into said chambers, each of said chambers having an in
let port and an outlet port, inlet manifold means con
necting the inlet ports, outlet manifold means connecting
the outlet ports, rectifying valve means in said inlet ports
operative to permit a liquid to ?ow only into the re 15 having an inlet port and an outlet port, means forming an
spective chambers, rectifying valve means in said outlet
inlet manifold secured to said housing and connecting
ports operative to permit a liquid to ?ow only from the
the inlet ports, means forming an outlet manifold secured
respective chambers, a tubular member enveloping the
to said housing and connecting the outlet ports, an inlet
projecting end of said rod and providing a fluid-tight seal
duct connected with the inlet manifold, an outlet duct
between said projecting end of said rod and the housing, 20 connected with the outlet manifold, rectifying valve means
and means acting on said projecting end for oscillating
in said inlet ports operative to permit a liquid ?ow only
said piston at a frequency of between 20 and 300 cycles
per second.
‘
,
into the respective chambers, rectifying valve means in
said outlet ports operative to permit a liquid flow only
,
6. A liquid pump of the class described comprising a
from the respective chambers, and means acting on one
‘ housing having between its ends a cylindrical bore, sleeves 25 end of said rod for oscillating said piston.
at the opposite ends of said‘ho'using and coaxial with said
11. A liquid pump as set forth in claim 10 wherein the
bore, a piston rod extending in radially spaced coaxial
opposite ends of said rod are secured to the centers of the
vertically disposed leaf springs, a pluralityjof relatively
short horizontally extending leaf springs each having a
general plane extending at right angles to the general
plane of the vertically disposed leaf springs, the upper
' relation relative to said bore and said sleeves, one end
of said rod extending outwardly beyond the adjacent end
of said housing, a piston ‘secured to said rod within said
bore, said piston dividing said housing into two chambers,
the side wall of said piston being in out-of-contact rela
tion to the wall of said bore, each of said chambers hav
and lower ends of each of said vertically disposed leaf
springs being supported by said horizontally extending
ing an inlet port and an outlet port, means forming an
leaf springs, one end of each of said horizontally extend
inlet manifold secured to said housing and connecting the 35 ing leaf springs being connected to one of said vertically
inlet ports, means forming an outlet manifold connecting
disposed leaf springs and the other end of each of said
the outlet ports, an inlet duct connected with the inlet
manifold, an outlet duct connected with the outlet mani
' fold, rectifying valve means in said inlet ports operative
, to permit a liquid to ?ow only into the respective cham
horizontally extending leaf springs being ?xed relative to
the housing.
12. In a pump of the type having the housing provided
40 with a horizontally extending bore, a piston reciprocably
bers, rectifying valve means in said outlet ports operative
to permit a liquid to ?ow only from the respective cham
bers, sealing'means providing a ?uid-tight seal for said '
one end of the rod' including a tubular member having
‘expandable and contracti‘ole side walls telescopically sur 45
rounding the outwardly projecting one end of said rod,
means connecting one end of said tubular member to the
received in said bore in radially spaced relation to said
bore, a piston rod extending from the piston and co
axially of said bore, and means to support the piston rod
from movement coaxialy of said bore including a verti~
cally arranged ?at leaf spring extending at right angles to
the axis of said rod adjacent one end thereof, means con~ .
necting ‘the center of said, leaf spring to said onerend of
the rod for movement therewith, and means supporting
the leaf spring with its center aligned with the axis of
housing, means connecting the other end of the tubular
member to said rod for movement therewith, and means
acting on said one end of the rod for oscillating said 50 said bore including a pair of relatively short horizontally
piston at a frequency between 20 and 300 cycles per
arranged ?at leaf springs disposed in parallel overlying
spaced relation adjacent each of opposite ends of said
vertically arranged leaf spring, means anchoring one end
of the springs of each pair of said horizontally arranged
a tubular elastomer clamped ‘at one end to the outer end 55 springs in ?xed relation to said housing, and means rigidly
of one of said sleeves, and a metallic plug carried for
connecting the other ends of the springs of each pair of
movement by said one end of the rod and connected to
said horizontally arranged leaf springs to each other and
second.
‘
e
V
7. .A liquid pump as set forth’in claim 6 wherein the
sealing means for the projecting end of said rod comprises
the other end of said tubular elastomer to seal said other
to said vertically arranged leaf spring.
'
end of the elastomer and connect the same to said one'
end of the rod for movement therewith.
,
60
8. A liquid pump, as set forth in claim 6 wherein the
References Cited in the ?le of this patent
UNITED STATES PATENTS -
' sealing means for the ‘projecting end of said rod com
prises a corrugated bellows clamped at one end to the
outer end of one of said sleeves and a metallic plug car
ried for movement by said one end of the rod‘and con 65
i ' nected to the other end of said bellows to close said other
L end' of the bellows and connect the same for movement
with said rod.
.
9. A liquid pump as set forth in claim 8, wherein a .
Restored patent ,
(No number)
342,696
1,085,963
1,233,438
Smallman _.._..j_‘._____AUg. 29, 1815
'
'
Hood‘ ______________ _.. May 25, 1886
Bresnahan _.._;. ____ _.._...._ .Feb. 3, 1914
Barengueras __________ __ July 17, 1917
1,555,192
' Dennedy ___________ __'_'Sep_t.>29, 1925
1,978,866
Konig ______________ .._ Oct. 30, 1934
2,668,656 .
Booth et a1 _____________ .. Feb. 9, 1954
plurality of resilient elastomeric washers are circumposed 70
2,690,128
about the projecting end of said rod within the con?nes
2,833,220
of the bellows,.the Washers normally being under a com
pressive stress.
Basilewsky __________ __ Sept. 28, 1954
Robinson et al _________ __ May, 6, 1958
,
'
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