Laminated Liquid Pump And Method Of Making Same

Abstract

A liquid pump is formed by superposing several sheets of thin flexible material which may be fused together, for example, polyvinyl chloride. The flexible sheets form a displacement chamber, an air pressure operated pumping chamber inlet and outlet passages and check valve flaps in the passages. The valve flaps are formed from the flexible sheets by slitting in appropriate places or are provided by separate flexible sheets. The several sheets are laminated by applying heat and pressure in a predetermined pattern to provide the essential pump elements. The pumping air chamber may be omitted.

Description

This invention relates to a liquid pump and a method of making the same. More specifically, the invention relates to a blood pump suitable for use during open heart surgery or for use in implantable hearts in animals or humans and a method of making such a pump from sheet material.

It has previously been proposed to provide extracorporeal blood pumps for use during heart surgery to bypass the heart and give the surgeons a dry field free of blood so that they can see what they are doing. The presently available pumps of this type are expensive, require an inordinate amount of service before, during and after the operation and tend to cause serious damage to the blood. In addition, intrathoracic blood pumps have been proposed to be used as artificial hearts. However, these designs have been extremely complex and also have a record of damaging blood. It is now recognized that the design of a blood pump should include the following features: (1 ) the pumping action should simulate the natural heart's action and be hemodynamically accurate, (2 ) the valve action should allow for free flow and low turbulence in the open position and should be hydraulically active to match the pumping action of the chambers, (3 ) the construction materials should be sterile and non-thrombogenic, (4 ) the fabrication should be simple and of reasonable cost.

It is therefore an object of this invention to provide a simple inexpensive hemodynamically accurate blood pump.

Another object of this invention is to provide a liquid pump formed of laminated flat flexible sheets.

A further object is to provide a method of making a liquid pump by laminating several flexible sheets.

Yet another object of the invention is to provide a method of making a liquid pump by slitting the walls of an existing passage formed of flexible sheets and laminating thereto additional flexible sheets.

The invention is carried out by securing together thin sheets of a fusible flexible material to form a displacement chamber, inlet and outlet passages and check valves in the passages. The invention further contemplates forming an air pumping chamber within or adjacent the displacement chamber.

More specifically, the invention is carried out by laminating several layers of thin flexible sheet material to define a displacement chamber and air pumping chamber and inlet and outlet passages and providing slits in certain of the flexible sheets to provide cooperating flaps to form a check valve in each passage.

The invention is also carried out by providing a liquid pump having walls and valves formed of thin flexible sheet-like material defining displacement, inlet and outlet passages and check valves in each passage. The invention further contemplates one or more air pumping chambers adjacent or within the displacement chamber also formed of thin flexible sheet material.

The above and other advantages will be made more apparent from the following specification taken in conjunction with the accompanying drawings wherein like reference numerals refer to like parts and wherein:

FIG. 1 is a plan view of a liquid pump according to the invention;

FIG. 2 is an elevational cross-section view of the pump of FIG. 1 taken along lines 2--2 thereof and illustrating an intermediate step in the formation of the blood pump;

FIG. 3 is a cross-sectional view of the pump of FIG. 1 taken along lines 2--2 illustrating the pump in its filling mode;

FIG. 4 is a cross-sectional view of the pump of FIG. 1 taken along lines 2--2 illustrating the pump in its pumping mode;

FIG. 5 is an elevational view of a second embodiment of a liquid pump;

FIG. 6 is a cross-sectional elevational view of the pump of FIG. 5 taken along lines 6--6;

FIG. 7 is a cross-sectional view of the pump of FIG. 6 taken along the lines 7--7;

FIG. 8 is a plan view of a third embodiment of a liquid pump according to the invention;

FIG. 9 is an exploded cross-sectional side view of the pump of FIG. 8 taken along lines 9--9 thereof illustrating an intermediate step in the process of making it; and,

FIG. 10 is a schematic view of the blood pump of FIG. 8 and an apparatus for operating the pump.

The fabrication of the preferred embodiment is best explained with reference to FIGS. 1 and 2. The pump is formed entirely of thin sheets of non-thrombogenic flexible material such as a medical grade of polyvinyl chloride. Two sheets 10 of this material, preferable 0.008 inch thick are laid together and spaced slits 12 and 14 at the desired position of the valves are cut transversely of the desired pumping channel to the width of the channel. Then sheets of stop-off material 16 are laid outside the sheets 10 between the slits 12 and 14 and extending at either end through the slits and finally between the sheets 10 outboard of the slits 12 and 14. The width of the stop-off material 16 conforms to the width of the desired channel. The stop-off material may be any dielectric sheet material having a melting point substantially higher than the material to be laminated. Where polyvinyl chloride is used to form the pump, Teflon (tetrafluoroethylene) is a suitable stop-off material. An outer pair of flexible sheets 18 are placed on either side of the assembly, these sheets being preferably of 0.016 inches thickness. Another small sheet of stop-off material 20 is placed somewhere between the slits 12 and 14 and between the sheets 10 and extends beyond the side of the channel. Then the sheets are simultaneously laminated according to a predetermined pattern under heat and pressure sufficient to fuse together the four sheets of flexible material in the area of that pattern except in those regions where the sheets are separated by stop-off material.

As shown in FIG. 1 the lamination pattern 22 as defined by a dielectric embossing die 23 extends fully along either side of the stop-off material 16 to define the pumping channel. The pattern further extends transversely of the channel to the left of the slits 12 and again to the right of the slits 12 to define semi-elliptical valve flaps 24 adjacent the slits 12. The area around the slits 14 is laminated in the same pattern to define a valve flap 26 in each sheet 10 opening in the same direction as the flaps 24. As best seen in FIGS. 2, 3 and 4, the flaps 24 are fused together at their upstream end as at 28 whereas the flaps 26 are each fused at their upstream ends as at 30 to an adjacent sheet 18. The sheets 10 are fused together along the side of the pumping channel as well as transversely as at 28 and 32 to form a completely enclosed air pumping chamber 34 except in the area defined by the stop-off material 20 which provides an inlet to the pumping chamber 34. An additional fused area extends from the edge of the pumping channel adjacent the inlet and forms a finger 36 extending parallel to the pumping chamber to define an air supply channel 37.

The lamination of the several sheets is preferably carried out by the well-known method of dielectric embossing using a die 23 or dies having the shape of the desired pattern 22 as described. By reason of the stop-off material 16 and 20 selective lamination of the several sheets is accomplished. After the lamination step the sheets 16 and 20 of stop-off material are pulled out of the pump. The completed pump then includes an inlet passage 38, and an outlet passage 40 containing valve flaps 26 and 24, respectively. The volume between the valve flaps 24 and 26 and between the sheets 18 exclusive of the pumping chamber 34 comprises a displacement chamber 42.

In operation, the air supply channel 37 is connected by a tube 44 to a pulsating air source 46 thereby causing the air pumping chamber 34 to alternately expand and contract. The inlet and outlet passages 38 and 40 are connected by any suitable means to a blood circulation system and the pump is primed by filling it with blood. As the air pumping chamber 34 is deflated, blood is drawn in through the inlet 38 and through the valve flaps 26 to fill the displacement chamber 42. Blood flow in the opposite direction from the outlet passage 40 is prevented by the valve flaps 24 which seat against the walls of the outlet passage 40. Then when the pumping chamber 34 is inflated, the valve flaps 26 close together and the flaps 24 fold together to permit blood flow through the outlet passage 40. Thus the valve flaps 24 and 26 serve as check valves on either side of the displacement chamber 42 to permit blood flow in only one direction as the pumping chamber 34 pulsates.

There are several advantages of the pump as described when used as an extracorporeal pump during surgery: (1 ) The pumping action is pulsatile (that is, similar to the normal heart), (2 ) physiologically accurate pressure pulses are applied to the blood, (3 ) pumping volume and pulse rate can be adjusted to meet the needs of the body, (4 ) pumping can be synchronized with the bodies own electrical pulse, (5 ) the priming volume of the pump is small, (6 ) the pump is completely disposable and sterile so that extensive servicing before, during and after the operation is not required as with conventional blood pumps, (7 ) the valve action allows free flow and low turbulence in the open position and is hydraulically active to match the pumping action of the chambers, and (8 ) blood damage is minimal.

Another embodiment of a blood pump having these same advantages is fabricated as shown in FIGS. 5, 6 and 7. The first step of fabricating this pump is to laminate two sheets 50 of thin flexible material which may be thermally fused such as polyvinyl chloride along straight spaced lines 52 to form a channel 54. Alternatively, this pump may be formed in a previously formed channel of thin flexible material such as is found in a commercial blood oxygenator. The sheets 50 are then slit as at 56 and 58 transversely of the channel 54 to form the free ends of valve flaps 60 and 62. Stop-off material, not shown, is inserted in the channel between the sheets 50. Then a pair of sheets 64 are laid against the outer surfaces of the sheets 50 and the assembly is laminated according to a pattern defined by an embossing die 66 which is very much like that described for the previous embodiment except that an outer opening is allowed to form inlets to the pumping chambers as will appear. In this manner, each sheet 50 is fused to its adjacent sheet 64 according to the pattern 66 to provide the attachments as shown at 68 in FIG. 6. Finally, the stop-off material is removed.

There is thus formed a completely enclosed channel having an inlet portion 70, an outlet portion 72 and containing the valve flaps 60 and 62 each of which is secured at its upstream end to an outer sheet 64. A displacement chamber 74 lies between the two pairs of valve flaps and a pair of separate air pumping chambers 76 are formed on either side of the displacement chamber 74 and confined between sheets 50 and 64. Each air pumping chamber 76 is connected with an air inlet channel 78 adapted to be connected to a pulsating air source. The cross-sectional view of FIG. 7 illustrates the pumping chamber 74 bounded on either side by an air pumping chamber 76 which is connected to the inlet channels 78, all formed from the initially flat sheets 50 and 64. In operation, as the pumping chambers 76 are inflated and deflated, the displacement chamber 74 is compressed and expanded respectively. Since the valve flaps 60 and 62 and cooperate to form check valves operable to permit flow in the same direction, pumping is effected much as in the embodiment of FIGS. 1 -4.

FIGS. 8, 9 and 10 illustrate a further embodiment of the invention which is formed without an attached air pumping chamber but which is particularly well-suited for use as an intrathoracic blood pump 80 or artificial heart ventricle. This pump 80 is preferably formed of a medical grade of silicone rubber since its non-thromobogenic qualities are superior to those of polyvinyl chloride and therefore better suited to long term use. The silicon rubber sheets used for fabrication are initially non-vulcanized and thus may be fused together upon application of heat. The pump 80 comprises a pair of outer sheets 82 of silicone rubber 0.030 inches thick reinforced with dacron. A sheet of stop-off material 84, preferably aluminum foil 0.001 inches thick, is inserted between the rubber sheets 82. This stop-off material 84 is generally circular in shape with a pair of upwardly extending neck portions 86 which extend at least to the upper edge of the rubber sheets 82. Adjacent each neck portion 86 are small rectangular flaps 88 of silicone rubber 0.01 inches thick which are placed on either side of the stop-off material 84 and are of sufficient width to extend beyond the sides of the neck portion 86. Additional sheets of aluminum stop-off material 90 are placed partially between the flaps 88 and the sheets 82. The stop-off material 90 is elliptically shaped along its lower edge which is spaced above the lower edge of the flaps 88 in the case of the outlet valve which is depicted in FIG. 9. The inlet valve is the same as the outlet valve but is inserted so that the flap 88 and the stop-off material 90 for the outlet valve are somewhat differently placed than for the inlet valve. To laminate the pump the sandwich of material is heated under sufficient pressure to hold the sheets together until the rubber sheets, to the extent they are not separated by the stop-off material, are fused or vulcanized together. Then the aluminum foil stop-off material is dissolved by hydrochloric acid.

Thus there is formed a generally circular displacement chamber 92 between the sheets 82, and inlet and outlet passages 94 each containing a pair of flaps 88 defining a check valve. As indicated schematically in FIG. 9 at 96 at least the lower portion of the flaps 88 of the outlet valve will be secured to its adjacent wall 82 while the upper ends of the flaps will be free to open or close according to the hydraulic action of the displacement chamber 84. In the case of the inlet valve in the left passage 94 of FIG. 8, the free end of the flaps 88 will be the lower ends.

In operation, external pulsing must be applied to alternately compress and relieve the displacement chamber 92 to effect pumping. FIG. 10 diagrammatically illustrates a device for actuating the pump 80. This device includes a bracket 100 having a reaction plate 102 on one side of the pump 80 and a pressure plate 104 on the other side of the portion 80, the pressure plate being reciprocally driven by an electromagnetic motor or solenoid 106. The solenoid 106 is electrically connected to a pulsating electrical power supply 108. This arrangement is intended to be merely suggestive of one means for actuating the pump 80. Where it is desired to simulate a natural heart, two pumps 80 may be used to represent the two heart ventricles. The two pumps 80 would be juxtaposed for simultaneous operation by a pressure actuator and if desired, may share a common wall so that only three sheets 82 and four pairs of valve flaps 88 would be required.

Claims

The embodiment of the invention described herein is for purposes of illustration and the scope of the invention is intended to be limited only by the following claims:

1. A liquid pump operable by pulsed air pressure having a displacement chamber with walls formed of two flat sheets of flexible material joined at their sides, inlet and outlet passages communicating with the displacement chamber and having walls formed of the same sheets, an inflatable pumping chamber within the displacement chamber and formed of two flat sheets of flexible material joined at their periphery, inlet means for supplying air to the pumping chamber for varying the volume of the displacement chamber, and inlet and outlet valves in the inlet and outlet passages respectively, the valves comprising pairs of flexible flaps each secured to one of the sheets and cooperating to provide unidirectional fluid flow.

2. A liquid pump operably by pulsed air pressure having a displacement chamber with walls formed of flat sheets of flexible material joined at their sides, inlet and outlet passages communicating with the displacement chamber and having walls formed of the same sheets, at least a portion of each displacement chamber wall being double layered to define an air chamber between the two wall layers, an inlet means for supplying pulsed air pressure to the air chambers for varying the volume of the displacement chamber, and inlet and outlet valves in the inlet and outlet passages respectively, each valve comprising a pair of flexible flaps each secured to one of the sheets and cooperating to provide unidirectional fluid flow.