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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 ‘ '7 Sheets-Sheet 2 E N '2" LL. Q. ~ ‘JOHN c. FISHER 1‘ BY‘ _ KENWAY, 'JENNEY, WITTER & HILDRETH ATTORNEYS March 12, 1963 J. C. FISHER 3,080,822 LIQUID PUMP Filed Feb. 8. 1960 7 Sheets-Sheet 3 Fig. 3 mmvmx. 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 7 Sheets~Sheet 5 // I lv?fy 2%. -“M. I \ \ \\\ > mmvrox. " JOHN c. FISHER‘ BY KENWAY. JENNEY. WITTER & HILDRETH ATTORNEYS March 12, 1963 J. c. Flsl-lzia 3,080,822 LIQUID PUMP Filed Feb. 8. 1960 7 Sheets-Sheet 6 Fig. 7 Fig. 8 Fig. 9 s2 62 eo~ so 48 7| , ’ .~s5 8| 8| ~7I 7 22 43 7 30 5s 52 82 k =1; , - ~46 72 83 E-s2 82 as ~6| ‘ \ 72 83 \, M g ’ % 73 66 63 INVENTOR. JOHN C. FISHER BY KENWAY, ~.IIENNEY, WITTER &' HILDRETH ATTORNEYS March 12, 1963 JQC. FISHER 3,080,822 LIQUID PUMP Filed Feb. 8. 1960 ' ' '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 , '