Diaphragm Metering Pump Device for Medical Use

Abstract

This pump comprises a chamber and an annular pumping diaphragm secured to the said chamber and the inner edge of which is secured to a central drive part. This diaphragm has a convex domed profile so that its expulsion stroke results essentially in the energy-generating flexing of the intake stroke. The rigidity of the diaphragm is chosen so that the absolute pressure of the chamber lies within the following range: P atm −(|Δ P valve — in |+|ΔP Δh — in |+|ΔP pd |)≧ P>P vap where: P atm =atmospheric pressure, P vap =vapour pressure of the pumped fluid, ΔP valve — in =pressure difference between the upstream and downstream side of the inlet valve for opening it, ΔP Δh — in =pressure difference in the upstream pipe between its distal end and the upstream side of the inlet valve as a result of the weight of the column of fluid, ΔP pd =pressure drop in the upstream pipe for the desired flow rate.

1 . Metering pump device for medical use comprising a pumping chamber, an annular pumping diaphragm the outer edge of which is secured to the said pumping chamber and the inner edge of which is secured to a central drive part that is more rigid than the said diaphragm, able to be displaced parallel to itself between an extreme return position and an extreme displacement position in its expulsion stroke and its intake stroke, respectively, these two positions lying one on each side of the plane containing the outer edge of the said annular diaphragm, the said pumping chamber comprising an inlet valve and an outlet valve which are respectively opened by a reduced pressure and by a raised pressure in the pumping chamber as a result of the movements of the said annular pumping diaphragm, the intake stroke of the said diaphragm resulting from the energy accumulated by the elastic deformation of the diaphragm during its expulsion stroke, characterized in that the said annular pumping diaphragm has, in the said extreme return position, a convex annular profile domed towards the outside of the said pumping chamber so that its expulsion stroke results essentially in the energy-generating flexural deformation of the intake stroke and in the annular compression/relaxation of compression of the said convex annular profile upon each outward stroke of the said diaphragm, the rigidity of the diaphragm being chosen so that the absolute pressure in the pumping chamber in the range of operation of the diaphragm situated between the extreme displacement position and the extreme return position lies within the following range:
     P   atm −(|Δ P   valve     —     in   |+|ΔP   Δh     —     in   |+|ΔP   pd |)≧ P>P   vap  
   where:
 P atm =atmospheric pressure 
 P vap =vapour pressure of the pumped fluid 
 ΔP valve     —     in =pressure difference between the upstream and downstream side of the inlet valve for opening it 
 ΔP Δh     —     in =pressure difference in the upstream pipe between its distal end and the upstream side of the inlet valve as a result of the weight of the column of fluid 
 ΔP pd =pressure drop in the upstream pipe for the desired flow rate. 
   
     
     
         2 . Pumping device according to  claim 1 , in which the said diaphragm is made of silicone. 
     
     
         3 . Device according to  claim 1 , in which the ratio between the radial width ΔR of the annular part of the pumping diaphragm and the exterior radius thereof lies within the range: 
       
         
           
             
               0.1 
               ≤ 
               
                 
                   Δ 
                    
                   
                       
                   
                    
                   R 
                 
                 
                   R 
                   ext 
                 
               
               ≤ 
               0.9 
             
           
         
       
     
     
         4 . Device according to  claim 1 , in which the ratio between the radial width ΔR of the annular part of the annular pumping diaphragm and the length of the stroke of the diaphragm between its extreme return position and its extreme displacement position lies within the range: 
       
         
           
             
               0.05 
               ≤ 
               
                 
                   Δ 
                    
                   
                       
                   
                    
                   R 
                 
                 
                   d 
                   max 
                 
               
               ≤ 
               5 
             
           
         
       
     
     
         5 . Device according to  claim 1 , in which the ratio between the thickness e of the annular pumping diaphragm and the radial width ΔR of the annular part thereof lies within the range: 
       
         
           
             
               0.01 
               ≤ 
               
                 e 
                 
                   Δ 
                    
                   
                       
                   
                    
                   R 
                 
               
               ≤ 
               1 
             
           
         
       
     
     
         6 . Device according to  claim 1 , in which the ratio between the maximum distance between the chord subtended by the concave side of the annular part of the diaphragm and the thickness e of this diaphragm lies within the range: 
       
         
           
             
               0 
               < 
               
                 b 
                 e 
               
               < 
               10 
             
           
         
         for an elastic material the elastic modulus E of which ranges between 0.1 MPa≦E≦100 MPa. 
       
     
     
         7 . Device according to  claim 1 , in which said range of operation lies between 0.7 and 1.2 mm, with a rigidity of the diaphragm having a gradient of typically 1.10 4  Pa/0.2 mm. 
     
     
         8 . Device according to  claim 1 , in which the pumping chamber is made of polycarbonate. 
     
     
         9 . Device according to  claim 1 , in which the annular pumping diaphragm is an element overmoulded on the pumping chamber.