Patent Publication Number: US-2006018770-A1

Title: Valve

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a valve. More specifically, the present invention relates to a valve for use in implantable infusion pumps.  
      2. Discussion of Related Art  
      Valves of various embodiments are known for a long time. Valves have an inlet, a valve body interacting with a valve seat, an actuating element acting upon the valve body and on outlet. An example of a prior art valve is disclosed in “Brockhaus, Naturwissenschaften und Technik”, 1983, Bd. 5, S. 192.  
      It is an object of the present invention to create a compact and reliable valve, which is suitable for the conveyance of very small quantities of liquid. It is also an object of the present invention to provide a valve that if it fails, will do so in a safe state. It is a further object to provide a valve that has a compact design, which would be well suited for an implantable medical device. It is a further object of the present invention to provide a valve that has a minimal displacement, thereby allowing for minimal energy consumption. It is a further object of the present invention to provide a valve that has a minimal dead volume.  
     SUMMARY OF THE INVENTION  
      According to the present invention these and other objects are solved in an exemplary embodiment of a valve having a housing, an inlet, an outlet and a ram receiving chamber. A ram has a first end and a second end and is slidably supported in the ram receiving chamber. The ram has a central pin on the second end of the ram. An actuating element is connected to the ram. A plate is fixedly connected to the housing. The plate has a central bore. The ram and plate selectively abut to form a valve seat. The inlet is in fluid communication with the ram receiving chamber. The ram has an outer wall. Fluid communicates between a portion of the ram receiving chamber adjacent to the first end of the ram and a portion of the ram receiving chamber adjacent to the second end of the ram. In the closed position, the ram abuts with the plate. The pin protrudes through the central bore in the plate. In the open position, the actuating element displaces the ram such that the ram is spaced from the plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       FIG. 1  is a sectional view of a valve in accordance with an exemplary embodiment of the present invention, shown in the closed position; and  
       FIG. 2  is a sectional view of the valve of  FIG. 1 , shown in the open position. 
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION  
      Referring now to  FIGS. 1 and 2 , the valve includes a cylindrical ram  12  forming the valve body. Ram  12  is axially slidably supported within a cylindrical ram receiver  20 , which is in the form of a bore in a valve housing  11 . An inlet  10  is in fluid communication with one axial end  22 , sometimes referred to as the lower face, of ram  12 . The other axial end  26  of ram  12  is sometimes referred to as the upper face.  
      A groove  28  is formed in the outer wall of ram  12 . Groove  28  provides fluid communication between the chamber adjacent to the lower face  22  within the housing  11  and the chamber adjacent to the upper face  26 . Groove  28  is in a currently preferred exemplary embodiment a spiral groove. But groove  28  could be axial. Additionally, ram  12  could have multiple grooves, such as two, three or even more grooves. Alternatively, ram  12  could have no grooves, but a relatively small annular gap would exist between the outer circumferential wall of ram  12  and the inner cylindrical wall of cam receiving chamber  20 . In another alternative design, the groove or grooves could be formed in the inner cylindrical wall of the cam receiving chamber  20  and not in the outer surface of the ram. In addition, the groove or grooves could be formed in the inner cylindrical wall of the cam receiving chamber  20  and in the outer surface of ram  12 . Thus, in any embodiment, liquid entering via inlet  10  flows to the area of the cam receiving chamber adjacent to lower face  22  of the ram  12  and is conveyed from this area to the area of the cam receiving chamber adjacent to upper face  26  of the ram  12  via groove(s)  28  or via the annular gap between the outer circumferential wall of ram  12  and the inner cylindrical wall of cam receiving chamber  20 .  
      A gasket  29  is formed in the upper face  26  of ram  12 . In a currently preferred exemplary embodiment, gasket  29  is made of an elastically yielding plastic material, preferably silicone. But gasket  29  could be made of any biocompatible deformable plastic or soft metal. A plate  23  is fixedly connected to housing  11 . Plate  23  includes a downwardly depending annular projection  14  that forms a valve seat for gasket  29  of ram  12 . As illustrated in  FIG. 1 , the valve is in the closed position. Thus, gasket  29  abuts against projection  14  to prevent fluid from travelling past the valve seat to an outlet  18  of the valve. Plate  23  has a central recess or bore  24 , thereby forming an annular channel between bore  24  and an upwardly projecting pin  30  of ram  12 . Pin  30  protrudes through bore  24  of plate  23 . In the open position illustrated in  FIG. 2 , ram  12  is displaced downwards such that the gasket  29  is spaced from the projection  14 . Thus, the liquid can flow past the valve seat from the outer area above front face  26  to the inner area above front face  26  and through the annular channel between bore  24  and pin  30 . The fluid then flows through a gap  34  between a plate  23  and a membrane  32  to the outlet  18  and out of the valve housing  11 .  
      In a currently preferred exemplary embodiment, projection  14  has a trapezoidically shape in cross-section as illustrated. But projection  14  could have different shapes, such as, for example, hemispherical. In another embodiment projection  14  could be formed on the front face  26  or ram  12  and gasket  29  could be formed in plate  23 .  
      Central pin  30  is provided on the front face  26  and is directed towards plate  23 . An actuating element  16 , preferably in the form of a bending plate, acts upon the central pin  30 . Actuating element  16  has a downwardly projecting projection  38 , which is aligned with pin  30 . A flexible membrane  32  is disposed between the free end of the pin  30  and the free end of the projection  38  of actuating element  16 . Membrane  32  forms a hermetic seal within the housing. Thus, the fluid within the valve housing  11  doesn&#39;t contact projection  38  or actuating element  16 . In a currently preferred exemplary embodiment, actuating element  16  is a piezoelectric element, which requires very little energy to move from the position illustrated in the drawing Figure to the downward position, thereby opening the valve. In addition, in a currently preferred exemplary embodiment, membrane  32  is made of titanium. But membrane  32  could be made of stainless steel. In addition, membrane  32  could have a bellows shape.  
      A coil spring  36  rests within the ram receiver  20  and acts upon the lower face  22  of ram  12 . Thus, spring  36  biases ram  12  in the upper direction to the position illustrated in the drawing, thereby closing the valve.  
      Even if the valve were to fail, the valve would be brought to the illustrated closed position due to the coil spring  36  acting on ram  12 . Additionally, the fluid flowing into the valve will apply a pressure on the entire lower face  22  of ram  12 , but only on an outer annular portion of upper face  26 . The fluid will naturally bias ram  12  upwardly against projection  14  of plate  23 . Thus, if the valve in accordance with the present invention fails, it will do so in a safe state. This is especially important to prevent unwanted volume of fluids from being infused into the body.  
      The valve in accordance with the present invention has a compact design, which is well suited for an implantable medical device, such as, for example, an implantable infusion pump. Within such a pump, the pump inlet is in fluid communication with the valve inlet, and the pump outlet is in fluid communication with the valve outlet. The valve has a minimal displacement, thereby allowing for minimal energy consumption. The valve also has a minimal dead volume.  
      In the specification, terms, such as, for example, “upper”, “lower”, “upwardly” and “downwardly”, etc. are used with reference to the drawing figures to ease the description of the present invention. However, these terms are not to be so limited as the valve could be oriented in virtually any direction. Thus, for example, the term “upwardly” may not necessarily be upward when the valve is used.