Diaphragm valve for medication infusion pump
This is a continuation of co-pending application Ser. No. 731,307, filed on May 7, 1985, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an improved valve particularly suited for application in small medical devices, particularly in infusion pumps, which are used to inject fluids into a patient. Such a valve is easily manufactured and operates reliably over a long period of life. 
     In medical devices, only medical grade materials may be used because of the contact with the medicine or other fluids which are administered. The device of the invention is readily manufactured of such materials and, also, does not introduce or foster contamination. 
     Infusion pumps, sometimes referred to as i.v. pumps, are utilized to pump fluids intravenously (and occasionally, intra-arterially,) into a patient. Some of the most common uses of such devices are to inject electrolytes, antibiotics, insulin and plasma into a patient. Other fluids, including but not limited to other drugs, may also be injected by such devices. 
     The valve of the invention may be made very small and yet operate effectively as required in the control of fluid flow. It is a unidirectional, passive valve; that is, it opens or closes under pressure (or flow) in the conduit in which it is disposed and permits flow in one direction only. It provides a positive seal against flow in the backward direction and yet opens readily for flow in the forward direction. Further, it may be constructed so as not to restrict forward flow significantly, and allow only a small pressure drop. In prior valves, constructed of rubber, silicone rubber or the like, the material would tend to wrinkle, elongate and creep into voids, causing several problems. The valve of this invention is substantially superior in that such undesirable results are minimized. 
     The valve will operate under a low pressure and in small channels. 
     It is, therefore, an object of this invention to provide a valve that may be easily manufactured in small sizes. 
     It is another object of this invention to provide a valve that may be manufactured entirely of medical grade materials. 
     Another object of this invention is to provide a valve that is reliable and operates effectively over a long period of time. 
     Still another object of this invention is to provide a valve which is suitable for use in a medical device. 
     Further objects and features will become apparent to those skilled in the art, from the description set forth below. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates an infusion system which may utilize the valve of the invention. 
     FIG. 2 is a cross-section of a double-acting pump showing how the valve may be used both for output and intake. 
     FIG. 3 is an exploded view of the parts of two valves disposed in opposite directions. 
     FIG. 4 is a cross-section of two valves disposed in opposite directions. 
     FIG. 5 is a cross-section which shows the flow of fluid through the valve. 
     FIG. 6 is a cross-section which shows the valve sealing against the backward flow of fluid. 
     FIG. 7 illustrates an embodiment in which the diaphragm is self-adjusting as the valve is assembled. 
     FIG. 8 illustrates another means of holding the diaphragm in place which seals against leakage. 
     FIG. 9 shows an &#34;O&#34; ring used to hold the diaphragm in place and to seal against leakage. 
     FIG. 10 illustrates another method of stretching the diaphragm between the parts of the valve. 
     FIG. 11 illustrates a circular diaphragm having the holes therein asymmetrically located. 
     FIG. 12 shows a diaphragm having a flange portion both above and below the web of the diaphragm. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates an infusion system 1, which in this case might be, for example, an insulin infusion pump, having a controller 2 and various other microelectronic components 3 and 4. Prime mover 5 is contained within the body 6 of the infusion system 1 and receives power from battery 7, to drive pump 8. The prime mover 5 may be, for example, a rotating motor, step motor or a solenoid. In addition, prime mover 5 may be a hydraulic motor. Dotted lines 9 are intended to portray the different possibilities of driving the pump 8, whether it be by direct drive or fluid or otherwise. The term &#34;prime mover&#34;, or &#34;driver&#34; is intended to cover all suitable devices. If the drive system is hydraulic, the valve of the invention may be used in the drive system, if desired, although it is most suitable for flow control in or in association with, the pump 8. In FIG. 1 fluid enters the pump through intake conduit 10 and exits through output conduit 11. 
     In FIG. 2 is shown a cross-section of a double-acting cylindrical pump 8 in which piston 12 moves within a cylinder 14, driven by drive means 9 connected to eccentric 13 and rotating motor 5. When piston 12 moves to the right, on the intake stroke, fluid is drawn in through intake conduit 10 and its associated intake valve 15. When piston 12 moves to the left, on the pump stroke, the fluid is pumped from the cylinder 12 through the output valve 16 and the output conduit 11. On the intake stroke, output valve 16 shuts tightly and on the output stroke, intake valve 15 shuts tightly. A diaphragm such as diaphragm 18 in FIG. 3 would be required to be disposed between body elements 17 and 19 so as to be a part of valves 15 and 16. 
     FIG. 3 is an exploded view of the essentials of the valve. Two body elements 17 and 19 hold a flexible diaphragm 18 tightly between them. The elements may be made of any rigid plastic, or even hard rubber, so long the material used is biologically compatible and suitable for medical use. The plastics include the acrylics, polysulfins, polyethylenes, polycarbonates and others. The diaphragm may be made of any medical grade silicone rubber, natural rubber or other suitable flexible, elastic, or resilient, material. The thickness of the diaphragm may be on the order of from 3 to 10 mils for conduits which are 1/16&#34; to 1/8&#34; in diameter. Other size conduits and thickness of valves may, of course, be utilized. Pressure on said valve, as an input valve or an output valve, may be on the order of from -4 to +20 psi. Of course, the &#34;break&#34; pressure, the pressure at which the valve opens, varies with the thickness of the diaphragm material, its elasticity, and the tension placed upon it. In FIG. 3 two valves are shown, one for each direction of flow. Each of the elements 17 and 19 has a raised or protruding portion, 20 and 21, respectively, which may be a portion of a sphere, frusto-conical, convex or other protruding surface. Mating with such raised portions 20 and 21 are corresponding recesses 23 and 22, respectively, which form chambers in the portion of the opposing element opposite the raised portions 20 and 21. Such recesses 22 and 23 may be constructed generally to fit the protruding surfaces 21 and 20, respectively, but preferably are right circular cylinders if the protruding surfaces 20 and 21 are spherical in shape. Thus, it is evident that the protruding surfaces 20 and 21 and the recesses 22 and 23 need not necessarily be curved. The recesses 22 and 23 are preferably not curved and the protruding surfaces 20 and 21, preferably, are curved. At any rate, the protruding surfaces 20 and 21 must fit at least partially into the recesses 23 and 22, respectively. A line of contact is sufficient, but a wider area of contact may be utilized. The line or area of contact, grips the elastic diaphragm 18 and seals the valve assembly from leakage from the fluid path to the outside. Also, suitable preloading of the diaphragm 18 can be obtained by the areas of contact between the protruding surfaces 20 and 21 and the recesses 22 and 23. Each recessed surface 22, 23 as well as each protruding surface 20, 21 has a conduit 10, 11, 24, 25 therethrough. Preferably, each conduit 10, 11, 24, 25 is disposed to emerge in the center of the surface 20, 21, 22, 23 with which it is associated. Each conduit 10, 11, 24, 25 may, however, be located to emerge at a point other than the center of the recess 22, 23 or the protruding surface 20, 21. Also, the holes 26 and 27 need not entirely encompass the conduits 10, 11, 24, 25, but may be disposed only on one side of the conduits 10, 11, 24, 25. The preferred construction, however, is as shown in FIGS. 3 and 4. 
     FIG. 4 is a cross-section of the dual valve arrangement, in which the valves are oppositely directed, such as one for intake and one for output. The mating between the two pump body parts 17 and 19 is illustrated. As can be seen in FIG. 4, the conduit 10 permits fluid flow out the apex of protruding surface 20 (where the elastic diaphragm 18 is flexed greatest) and through the holes 26 (FIG. 3). The fluid flows into chamber 23 and through conduit 24. Similarly, a conduit 25 emerges at the apex of protruding surface 21 and fluid flows from conduit 25 through the holes 27 (FIG. 3) in diaphragm 18 on into chamber 22 and out through conduit 11. The holes 26 and the holes 27 are shown as disposed concentrically with the conduits 10 and 25. As previously indicated, they need not be so disposed and may be eccentrically located with respect to the chambers 22, 23 and the protruding surfaces 20, 21 and the conduits 10, 11, 24, 25 need not emerge through such surfaces 20, 21, 22, 23 at a central location. However, having the conduits 10, 11, 24, 25 centrally located and the holes 26, 27 concentrically around the conduits 10, 11, 24, 25 is preferred. 
     FIG. 5 illustrates how element 17 fits to element 19 and how a portion of the diaphragm 18 is held between them. In the embodiment shown, there is an edge, or line, contact, inasmuch as chamber 22 is cylindrical in shape. The edges of the chamber 22 could, of course, be beveled or sloped to provide a wider contact area, or a beveled edge, to hold the diaphragm 18 against protruding surface 21. Thus, the diaphragm 18 may be held between a portion of the wall of the chamber 22 and the protruding surface 21. When fluid is flowing with a forward bias, the diaphragm 18 is pushed away from the protruding surface 21 and fluid flows out the holes on into chamber 22. As the elements are fitted together diaphragm 18 may be stretched or caused to be stretched. 
     FIG. 6 illustrates how the valve seals against backward flow. The pressure in the reverse direction of the valve causes the diaphragm 18 to seal shut against the entrance to conduit 25. 
     FIG. 7 illustrates the mounting of a circular diaphragm 18 between body elements 17 and 19. A flange on diaphragm 18 fits into a circular recess 26. As body element 19 is forced against body element 17, the web of diaphragm 18 is evenly and uniformly stretched over raised portion 20. By &#34;evenly&#34; it is meant that the diaphragm is stretched the same in one direction as another. By &#34;uniformly&#34; is meant that from pump to pump, all the diaphragms will have substantially the same amount of stretch, thereby causing the valves to exhibit a uniform break pressure which varied by changing the thickness of the diaphragm. The device of the invention works best when the diaphragm 18 is stretched evenly over the protrusion 20. 
     FIG. 8 illustrates another method of tensioning and holding the diaphragm 18 in place. Body element 19 has a circular ridge which presses the diaphragm 18 into circular recess 26 of body element 17, as the valve parts are assembled. Sealing against leakage is also of concern and such structure effectively seals against leakage of the valve. 
     FIG. 9 illustrates still another means for tensioning and holding the diaphragm 18 in place. &#34;O&#34; ring 28 (which may be a Quad ring or other sealing ring of rubber, silicone rubber, or even metal,) acts to press diaphragm 18 into recess 26 and, also, to seal the valve against leaking to the outside between the body elements 17 and 19. 
     FIG. 10 illustrates still another method of stretching elastic diaphragm 18 over protrusion 20. Diaphragm 18 in this illustration is manufactured with a flange, or lip, around its edge which is forced downwardly by the body element 17 to evenly stretch the web of the diaphragm 18 over protrusion 20. 
     FIG. 11 shows diaphragm 18 with holes therethrough which are asymmetrically located and not of circular shape. It is possible that the diaphragm 18 be so constructed, depending on what is desired. The holes in the diaphragm 18 may be molded in or punched after the diaphragm 18 is manufactured. 
     It may be understood that the diaphragm 18 need not be constructed of uniform thickness. It may, for example, be thicker in a band in which the holes are located or at the location where it fits against the apex of the raised portion 20 or around the outside of the web. Further, the thickness of the diaphragm may vary from a central location to an outer location. 
     FIG. 12 illustrates a configuration of the diaphragm 18 of FIG. 7 in which a flange is also included below the diaphragm to aid in sealing the valve against leakage. 
     Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.