US2961965A - Control arrangement in a pump having a pump chamber of periodically variable volume - Google Patents

Description

NOV. 29, 1960 A SENMNG ETAL 2,961,965

CONTROL ARRANGEMENT IN A PUMP HAVING A PUMP CHAMBER OF PERIODICALLY VARIABLE VOLUME Filed Oct. 4, 1955 2 Sheets-Sheetl g1 INVENTOR5 BY fizz M 71/ ATTO EYS Nov; 29, 1960 AKE SENNING ETAL CONTROL ARRANGEMENT IN A PUMP HAVING A PUMP CHAMBER OF PERIODICALLY VARIABLE VOLUME Filed Oct. 4, 1955 2 Sheets-Sheet 2 United States Patent CONTROL ARRANGEIVIENT IN A PUMP HAVING A PUMP CHAMBER OF PERIODICALLY VARI- ABLE VOLUIVIE Alte Senning and Per Anton Astradsson, Stockholm, Sweden, assignors to Svenska Aktiebolaget Gasaccumulator, Lidingo, Sweden, a corporation of Sweden Filed Oct. 4, 1955, Ser. No. 538,478

Claims priority, application Sweden Oct. 6, 1954 6 Claims. (Cl. 103-37) The present invention refers to an arrangement in a pump which has a pump chamber of periodically variable volume serving for the control of the pump output by means of a pressure medium. The arrangement makes possible a continuous and easily adjustable regulation of the pump output, for instance in response to the level of a liquid in a container connected to the pump intake.

The arrangement is characterized in that a pressure chamber with a resilient wall responsive to the pressure of the pressure medium is adapted to operate on the wall of the pump chamber in such a way that the magnitude of the periodic volume variation of the pump chamher and thus of the pump output increases with an increase in the pressure of the pressure medium.

The control arrangement according to the present invention is particularly suitable for use in connection with a pump adapted for pumping blood, i.e. in a pump which is able to serve as an artificial heart. The invention will be further described with reference to the drawings, in which: Figure 1 is a schematic drawing of an arrangement according to the present invention, and Figure 2 shows another embodiment of an arrangement according to the present invention.

The pump shown in the drawing is provided with two pump chambers 1 and 2 connected in parallel and further connected via inlet valves 3 and 4 and outlet valves 5 and 6 to an intake conduit 7 and an outlet conduit 8, respectively, for the liquid. In the present instance, the liquid is assumed to be blood, which is to be supplied to a patient after a treatment such as an oxygenation or the like. Each of the pump chambers is constructed with a wall of resilient material, which is exposed to periodic pressure from without in order to vary the pump chamber volume. In the embodiment shown, the pump chambers are constructed of rubber, plastic or a similar soft material, and a wall of each pump chamber is acted upon by a crosspiece 10 attached to one end of a rod 9. The other end of the rod is connected with an eccentric device 11, whereby upon rotation of the eccentric device the crosspiece 10 is given a reciprocating motion. The crosspiece 10 then subjects the resilient wall of the pump chambers 1 and 2 to periodic inward pressures. The elasticity of the wall is chosen so as to make it adapt itself to the crosspiece during the return movement of the latter subsequent to the pressure period. If no counterpressure member is arranged so as to limit the movements of the opposite wall, it will take part in the oscillations of the resilient wall. The pump chamber volume will therefore remain constant over the whole period of the oscillations of the crosspiece and the pump output will thus be at a minimum. On the other hand, if a fixed counterpressure member is arranged for the opposite wall, the greatest possible variation in the vol ume of the pump chamber will be obtained during the oscillations of the crosspiece 10, so that in this case a maximum of pump output will be obtained.

A counterpressure member is arranged to provide a control of the effective pump volume discharged for each stroke, the effectiveness of this member being controllable in dependence upon the desired pump output. The counterpressure member is in the form of a pressure chamber having a resilient wall facing the pump chamber. The pressure chamber contains a pressure medium, the pressure of which depends on the desired pump output. In the embodiment of the invention shown in Figure 1, the pressure chamber comprises a rubber tube 12, 13, which is disposed between the pump chamber 1, 2 and a fixed support 14, 15. Each of the chambers 12 and 13 is connected via conduits 16 to 18 to a valve device 19, which in its turn is provided with an inlet conduit 20 for the pressure medium and an outlet conduit 21 for the same. The pressure medium may, for instance, consist of a gas, preferably oxygen under increased pressure, and the gas can then also be used for the oxygenation of the blood pumped through the arrangement.

The valve device comprises a needle valve 23-, which is inserted between the conduits 20 and 18. The needle valve is of such construction that its needle is free to move in its boring even after the valve has closed. The purpose of this arrangement will be apparent from the following. A second needle valve belonging to the valve device is inserted between the conduits 18 and 21 and can be adjusted manually by means of a knob 25 to a position permitting a suitable amount of gas to flow out through the conduit 21. Finally, the valve device comprises a valve 26, which, when opened, allows gas in the pressure chambers 12 and 13 and in the conduits 1618 to flow directly out into the surrounding air.

The valve 23 in the connection between the conduits 20 and 18 is provided with a spring 27 urging the valve towards its open position. The spring operates on a flange 28 on the needle and this flange also serves to limit the opening movement of the valve. The other end of the needle is shaped as a control button 29, which is adapted to be actuated by one end of a lever 31 of first order fulcrumed at a point 30. This end of the lever is additionally acted on by a spring 32. The other end of the lever is connected by means of a rod 33 with a member which is responsive to the level of the liquid in a container 34. This member comprises, in the embodiment of Figure 1, a movable membrane 35 arranged at the bottom of the container 34, the membrane being, in accordance with the above, connected with the lever 33 such as by means of a disc 36 attached thereto. Upon a decrease in the volume of the liquid, which corresponds to a lowered level in the container 34, the membrane 35 is raised under the influence of the spring 32, whereby the needle valve 23 is actuated towards its closed position. The needle valve is again opened when the amount of liquid in the container 34 increases.

The valve 26 is arranged to prevent the amount of liquid in the container 34 to decrease below a predetermined value. To this end, the valve 26 is responsive to the right-hand part of the lever 3-1 so as to open when the membrane 35 is raised a predetermined amount into the container 34 by the spring 32. This occurs when the valve 23 has been closed completely, but it is still possible at this stage for its needle to be brought further down into the boring. The pressure medium in the containers 12 and 13 and in the conduits 1618 is then free to flow out in the surrounding air. The valve 26, as is apparent from the figure, is provided with a pair of pistons, between which the pressure medium flows, which provides a balanced action for the valve in such a way that the pressure medium does not impart a tendency to the valve to be displaced in either direction, thus obviating a back action on the membrane 35.

In the explanation of the operation of the arrangement, it may be assumed to begin with that the inlet conduit leading to the container 34 as well as the inlet 7 to the pump chambers 1 and 2 and the chambers themselves and also the outlet conduit 8 are completely filled with blood, and also that the amount of the blood in the container 34 reaches a predetermined level. This level may be assumed to be chosen such that the needle valve 23 is held in an intermediate position, at which the pressure medium flows in from the conduit 28 through the conduits 18, 16 and 17 to the pressure chambers 12 and 13. Furthermore, it is assumed that the needle valve 24 allows a portion of the pressure medium to flow out through the conduit 21. Thus, the pressure in the conduits 16--18 is held constant and the pressure chambers 12 and 13 are inflated to an intermediate position. When the eccentric 11 is made to rotate, thereby making the crosspiece perform an oscillating motion, a certain amount of bloodis pumped along through the pump chambers 1 and 2. The chambers operate alternately, so that a comparatively even flow of blood is obtained through the conduits 7 and 8. With the pump operating in this fashion, the level of the liquid in the container 34 goes down and causes the membrane 35 to rise. The membrane then actuates the needle valve 23 via the rod 33 and the lever 31, which causes a decreased amount of pressure medium to be supplied to the conduit system 1618. This decreases the inflation of the pressure chambers 12 and 13 and makes the walls thereof more resilient. This in turn diminishes the output of the pump and counteracts, on the assumption of a constant inflow, the lowering of the liquid level in the container 34. The arrangement is therefore self-adjusting to a constant level of the liquid in the container 34. This level can be preadjusted manually by varying the tension of the spring 32, the level in the container 34 being made to rise upon an increase in the spring tension.

In the embodiment of the invention shown, the pump chambers 1 and 2 as well as the pressure chambers 12 and 13 were constructed in the form of tubes or sleeves, but the same effect can be obtained also if one of these members contains a fixed or rigid wall.

Figure 2 shows another embodiment of the present invention, wherein the pressure chambers 12 and 13 are arranged between the crosspiece 10 and the pump chambers 1 and 2. Furthermore, the level-responsive member in container 34, instead of being in a form of a membrane, consists of a float 37 which controls the valve device 19 by means of levers 3 1 and 38 and rods 39 and 40.

What is claimed is:

1. Control arrangement in a pump having a fixed member and a reciprocating member comprising a pump chamber having an inlet and an outlet, said pump chamber having walls of a resilient material and being disposed between the reciprocating member and the fixed member, a flexible pressure chamber disposed between the reciprocating member and the fixed member and abutting said pump chamber, a source of fluid medium connected to said pressure chamber, a container connected to the inlet of said pump chamber, and means connected to said source of fluid medium and responsive to the liquid level within said container for controlling the supply of fluid to said pressure chamber.

2. Control arrangement according to claim 1 wherein said pressure chamber is disposed between the reciprocating member and said pump chamber.

3. Control arrangement according to claim 1 wherein said pressure chamber is disposed between the fixed member and said pump chamber.

4. Control arrangement according to claim 1, wherein the said liquid responsive means includes a membrane disposed in the bottom surface of said container.

5. Control arrangement according to claim 1, wherein said liquid responsive means includes a float disposed in said container.

6. Control arrangement according to claim 1, wherein said liquid responsive means includes a normally closed valve which is adapted to be opened when a predetermined level is present in the container.

References Cited in the file of this patent UNITED STATES PATENTS

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