US3148624A - Hydraulic pump - Google Patents

Description

p 1964 A. w. BALDWIN HYDRAULIC PUMP 2 Sheets-Sheet 1 Filed June 21, 1961 LEI-L INVENTOR ALAN W. BALDWIN IX /////l ATTORNEY P 15, 1964 A. w. BALDWIN 1 3,148,624

HYDRAULIC PUMP Filed June 21, 1961 2 Sheets-Sheet 2 INVENTOR ALAN W. BALDW l N ATTORNEY United States Patent Office 3,148,624 Patented Sept. 15, 1964 3,148,624 HYDRAULIC PUMP Alan W. Baldwin, 4406 S. Panorama Drive, Oxon Hill, Md. Filed June 21, 1961, Ser. No. 118,746 1 Claim. (Cl. 103--44) (Granted under Title 35, U.S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to a hydraulic pump, and more particularly, to a pump having a flexible pump chamber which is compressed by hydraulic means to provide a uniform and gentle pumping action. Such a pump is well adapted for use in connection with surgical techniques to provide an extracorporeal blood circulation in open-heart operations.

Recent advances in the medical sciences have demonstrated the effective use of the artificial heart-lung for oxygenating and maintaining continued blood flow into the aorta of a patient, while the surgeon has a bloodless field and direct vision in performing open-heart surgery. The blood in such operations is pumped by extracorporeal means, that is, a pump which is located outside the body undertakes the function of the heart to maintain blood circulation within the body without turbulence, foaming or damage to blood cells. A blood pump should utilize a minimum amount of blood for priming, and the parts thereof should be easily assembled and disassambled to faciltate cleaning, repairing and replacement thereof.

It is therefore a particular object of the invention to provide a novel pump of the above-mentioned character in which the pumping action is considerably more uniform and gentle, and which overcomes previous objections to pumping devices that cause turbulence, foaming and uneven distribution of pressure on fluids.

It is another object of the present invention to provide a simple and eflicient pumping device in which the fluid passing therethrough is isolated from the pumping mechanism thus preventing contamination of said fluid and also safeguarding said device from possible corrosive or fouling action of liquids and gases.

It is a further object of the present invention to provide a pump which is suitable for pumping fragile type liquids, such as, whole blood or algae cultures that are easily bruised by conventional pumping actions.

It is a still further object of the invention to provide a novel pumping device with a flexible pump chamber that experiences a uniform surface contraction and an even distribution of action. I

It is also an object of the invention to provide a pump which may be readily assembled and disassembled-for replacement or cleaning of contaminated parts.

It is yet another object of the present invention to provide a pump which is characterized by a highpumping capacity and/or pressure in which a large volume of liquid may be pumped at each piston stroke.

Further objects and advantages of the invention 'will become apparent in the course of the following detailed description, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a vertical longitudinal section' of one embodiment of the invention showing a double action hydraulic P p; Y

FIG. 2 is a vertical longitudinal section -of another embodiment showing flapper type inlet and outlet valves;

FIG. 3 is a vertical longitudinal section of another embodiment showing flexible tube inlet and outlet valves the applied force during the pumping with which are associated individual hydraulic means for operating said valves.

In general, the hydraulic pump of the present invention comprises a flexible, spherical chamber, for example, a resilient rubber bulb, immersed in a hydraulic medium within a sealed container or housing. The application of pressure on said medium by means of a piston or by the depression of a flexible diaphragm causes an equal distribution of pressure to be exerted on the entire surface area of the flexible, spherical chamber; the pressure applied by the hydraulic medium causes said chamber to contact evenly in its entire surface area, and with subsequent release of hydraulic pressure, said chamber again resumes its normal size. Unlike previous compressible bodies in which the original shape is distorted by a mechanically applied compression stroke, the hydraulic pump of the present invention provides a uniformly applied pressure on all portions of the spherical chamber resulting in a uniform contraction of volume and, consequently, in a much smoother internal pressure. By incorporating a system of valves with said chamber whereby an inlet valve will close as an outlet valve is opened when slight hydraulic pressure is exerted upon the chamber wall, and alternately, whereby said inlet valve will open as the outlet valve thereof closes upon release of said pressure, a uniform and smooth flow of liquid is obtained from the inlet connection to the outlet connection of the pump. 7

Referring now in detail to the drawings, in which like reference numerals designate like parts throughout the figures thereof, the embodiment illustrated in FIG. 1 is a hydraulic pump which comprises an air-tight housing 11, shown as a matter of simplicity in the form of a rectangular container, said housing being divided internally into compartments 12 and 13 by means of a piston member 14. The piston member 14, shown in the drawing as an H-shaped structure, is slidably mounted within said housing and reciprocably driven into each of said fluid compartments, as shown by the direction arrow. In each of said compartments is a flexible pump chamber 16 suspended in a hydraulic medium 15; said flexible chamwill contract on the piston stroke and the applied hydraulic pressure and will expand again on the piston return and release from hydraulic pressure. The chambers, which are designated in the drawing as A and B for quick reference, have a flexible and resilient wall of such thickness that after contraction and expansion of the Wall surface the chamber will return to its normal size.

A pair of oppositely disposed openings 17 in each of said chambers communicate with valve housings 18 and 18a, which are illustrated conveniently as external mountings on the chamber wall and which represent the inlet and outlet valve structures that control the flow of fluid through said chambers. It willbe appreciated that the valve structures illustrated in the present embodiment are examplary and that the valves associated with said chambers may be of any conventional design which are capable of providing a unidirectional fluid flow in said chambers. In an alternate arrangement, valve housings may be inserted and retained within opening 17, thus'providing a chamber with a smooth, external wall. The valvestructures illustrated in FIG. 1 have cylindrical walls made of plastic or other rigid type material, the base surfaces of said structures have abore -20 to which a conduit is connected for conveying liquids and gases therethrough.

A fluted retainer 17a (shown simply=as curved dashes in the drawing) extends=across the housing and provides a barrier for the ball member to limit its movement in a direction away from its seat while allowing fluid to escape through a fluted opening in its center. Valve housings 18 and 18a are similar in structure, but they are mounted in opposite directions on the spherical chamber and their valve seats are formed on different surfaces: valves 18, through which the liquid or gas to be pumped is introduced into the pump chamber, have a valve seat formed on the surface surrounding bore 20, while valves 18a, through which the liquid or gas is passed out of the chamber, have a valve seat formed on the surface surrounding opening 17.

Flexible connections or conduits 21 join inlet valves 18 with rigid connections 22 inside the housing Wall 11, and said rigid connections then pass outside the housing and are coupled to an inlet manifold 22a. Flexible connections or conduits 21 join the outlet valves 18a to rigid connections 23 inside the housing wall 11; said rigid connections then pass outside the housing and merge into an outlet manifold 23a.

The hydraulic pump of the present embodiment has a double action whereby the reciprocating action of the piston creates a compression cycle in one compartment and a decompression cycle in the other. As shown in FIG. 1, when the piston shifts in the direction of chamber A, the pressure exerted on the hydraulic medium in compartment 12 forces chamber A to contract in volume; the outlet valve 18a opens, at the start of said compression cycle, and allows liquid or gas from said chamber to pass out (as shown by arrows) through the flexible connection 21 into rigid connection 23 and into the outlet manifold 23a. During the compression cycle in chamber A, chamber B is going through a decompression cycle: the inlet valve 18 opens and the outlet valve 18a closes at the start of the decompression cycle, and fluid enters chamber B by passing through the inlet manifold 22a (as shown by arrows) into the rigid connection 22 and then into the flexible connection 21 that connects with chamber B. Chamber A will expand upon release of hydraulic pressure, and its inlet valve18 will open at the start of the cycle to allow liquid to refill said chamber.

The reciprocating hydraulic action of the pump, shown in FIG. 1, provides an eflicient pumping device for pumping fluids under sustained pressure as a result of the hydraulic system; in addition, said device has a high pumping capacity, as measured by the volume of fluid delivered per piston stroke. For example, a rubber bulb of 3 diameter when hydraulically compressed to 50% of its volume will pump approximately fluid ounces of fluid for every piston stroke or cycle of the pump. The pump of the present invention may be utilized to supply gases or liquids under high or low pressure by regulating the hydraulic pressure thereof. The rate of flow of the present pump may be varied by operating the Piston mechanism at different rates of speed. The pump is particularly desirable for use with corrosive and fouling type fluids since the pumping mechanism does not come into contact with fluids passing therethrough.

Instead of a pump with ball check valves as indicated in the embodiment described above, the pump may also be constructed in the manner shown in FIG. 2, wherein a smooth and gentle flow of liquid is obtained at low pressures to provide a device which is suitable for use as a blood pump. In the present embodiment, the pump comprises a sealed container 11 filled with hydraulic medium, and immersed therein is a flexible, spherical chamber 16, said chamber having oppositely disposed openings 17 which connect to tubular extensions which are provided with flapper type valves for improved'pumping action in accordance with the intended use.=. A flapper valve in accordance with the embodiment comprises a-uconduit or'rigid tubing in which apair of flexible bands or projections are attached by one of their ends to the inner wall'of said conduit, while the free ends thereof meet to form a loose closure. The flapper valves are arranged to remain normally in the closed position, as shown in the inlet valve 24 wherein the ends of said projections 25 extend within the conduit and contact one another. Outlet flapper valve 26 shows the pair of flexible bands or projections 27 with the free ends thereof in the open position, and fluid flowing through said valve. Fluid flow on the converging side of said projections causes them to open, but when the flow is interrupted, the projections immediately close, and any reverse flow against their diverging sides will retain them closed. Thus fluid flow across flapper valves is essentially in a single direction, as shown by the arrows.

The top of the container 11 is closed by means of a flexible diaphragm 28 which forms an air-tight seal. A flat contact plate 29 is attached to the center of said diaphragm, and said plate is engaged by a cam 31 which is rotatably mounted over said contact plate. When the cam is rotated by a driving means (not shown), the high position of the cam presses the contact plate 29 and causes the diaphragm 28 to be depressed into the hydraulic medium and to transmit hydraulic pressure to the entire surface area of flexible pump member 16. The pump chamber contracts uniformly, causing the fluid within to pass through flapper valve 26 at the outlet or discharge end thereof.

When the low portion of the cam meets the contact plate 29, the diaphragm 28 and said plate are raised to their normal horizontal position; the chamber expands to its normal size and the flapper valve 26 returns to its normally closed position as fluid flow is interrupted. At the beginning of the intake or decompression cycle the partial vacuum created within the chamber will draw fluid from a fluid source through flapper valve 24 into said chamber.

Any suitable driving means may be provided for rotating the cam, but it is desirable to include means for adjusting the cam rotations which may be conveniently employed for regulating fluid flow. The pump may be operated with any suitable hydraulic pressure by employing a cam of such arcuate length and diameter that the compression and suction strokes of the pump may be of any desired duration and intensity.

The flapper valves of the present embodiment close with a wiping action which cleanses the valve seat, or by way of further explanation, said wiping action repels the fluid away from the closure and prevents any abrupt squeezing or area of high pressure contact. The hydraulic pump in accordance with the present invention experiences no distortion or any uneven distribution of forces which are apt to occur in mechanically compressed flexible tubing pumps of the prior art. A tubing which is collapsed or distorted by a directionally applied force creates turbulent flow and eddy currents within the conveyed fluid. Since the desired application of the present pump is in the circulation of whole blood in a patient, the hydraulic system embodied in the present invention has overcome many of the difficulties heretofore encountered by mechanically compressed tubular elements.

In an alternate embodiment, the flexible chamber and its flapper type valve system described herein may be conveniently mounted to a lid by passing the ends of inlet and outlet tubing through openings in said lid; said lid is then adapted to. be attached by any convenient means to a hydraulic chamber to provide a pumping action. Such an arrangement of parts allows for the flexible chamber, tubing and valves to be readily exchanged With clean, sterile units for immediate reuse of the blood pump.

The hydraulic pump may be constructed and operated with separate hydraulic means for compressing various sections of flexible tubing to obtain both pumping and valve action. The hydraulic pump, shown in FIG. 3, illustrates another specific embodiment in which separate hydraulic means are utilized to bring about a pumping action through hydraulic operation of the valves as well as the pump chamber. FIG. 3 shows an inletvalve in .5 compartment C and an outlet valve in compartment E formed of flexible tubing which can be compressed by hydraulic means to form a constriction sufficient to impede fluid flow therein but which has the quality of re turning to the original contour upon release of hydraulic pressure. The pump structure comprises a housing 32 which is divided internally into compartments C, D and E. Tubular conduit 35 which passes through the housing wall 32 and through compartment walls 33 and 34 are made of rigid or thick walled material to resist hydraulic pressure, while the center sections 36 are formed of flexible type tubing. Said flexible tubing is shown under hydraulic pressure in chamber C wherein the tubing has formed a narrow constriction sufficient to impede fluid flow. The outlet valve in compartment E is shown in the open position (save for a slight constriction which is normally retained). The flexible pump chamber D is connected to flexible tubing 37 which flexes during the pumping operation in overcoming dimensional changes in the pressured pump chamber.

Compartments C, D and E are provided with individual cylinders 38 and pistons 39 for applying hydraulic pressures individually on the pump chamber and on the valves. The pistons are connected with piston rods 41 which come into engagement with cams 42, which are rotatably mounted on a single shaft 43 and actuated by motor means 44. The cams have an elliptical high and an elliptical low portion and are so related to the piston rods which move up and down in the hydraulic cylinders and operate in proper sequence to compress or to retract the pistons in said cylinders to exert pressure or to relieve the same from the enclosed hydraulic medium 15.

The piston in compartment C pressures the hydraulic fluid therein to close the inlet valve before the piston in compartment D has applied suflicient pressure to compress the pump chamber therein and pass fluid through the outlet valve in compartment B. After the pump chamber has been compressed, the piston in E descends in the cylinder and applies pressure to constrict the outlet valve before the pistons in C and D ascend in the cylinders to relieve the hydraulic pressure and open the inlet valve. The upward movement of the piston in D, which begins after the inlet valve has been partially opened, expands the pump chamber and draws fluid through the inlet valve from a liquid source.

The separate piston arrangements allow for greater control of the valve action. Movement of the conveyed 6 fluid is considerably more uniform and gentle, and it can also be regulated to a pulsating flow similar to the blood flow in the human body.

The tubing and pump member may be conveniently arranged as a single unit that can be readily disconnected and replaced. Since the inlet and outlet valves in the present embodiment are identical in structure, the replacement unit may be connected to the pump without danger of reversing valve positions.

While the invention has been disclosed in accordance with certain preferred embodiments thereof, such are to be considered as illustrative only, and not restrictive, the scope of the invention being defined in the adjoining claim.

What is claimed is:

A hydraulic pump comprising in combination a sealed contained having therein a hydraulic medium, a pair of compressible, spherical chambers immersed in said medium, each of said chambers having openings at opposite sides thereof defining an inlet and an outlet, valve housings on said chambers associated with said inlet and said outlet, a ball member in each of said housings forming a ball check valve, first conduits sealed through said container and connected to said inlets, second conduits sealed through said container and connected to said outlets, and a piston slidably mounted in said container between said chambers, said piston being adapted to move with reciprocating action to act on diiferent portions of said medium for alternately compressing each of said chambers to force fluid through said chambers from said first conduit to said second conduit.

References Cited in the file of this patent UNITED STATES PATENTS 1,282,145 Tobler Oct. 22, 1918 1,782,144 Jensen Nov. 18, 1930 1,832,257 Stephens Nov. 17, 1931 1,832,258 Stephens Nov. 17, 1931 2,752,854 Prior et al. July 3, 1956 2,807,215 Hawxhurst Sept. 24, 1957 2,871,789 Kiifer et al. Feb. 3, 1959 2,915,016 Weaver et al Dec. 1, 1959 FOREIGN PATENTS 147,826 Sweden Nov. 23, 1954 688,346 France May 12, 1930

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