Pump

Abstract

A pump that has a cavity ( 13 ) in which is located a non-elastomeric membrane ( 14 ). An inlet ( 24 ) opens into the cavity ( 13 ) and is associated with a valve ( 27 ). A valve ( 28 ) is likewise provided in an outlet ( 25 ). Also opening into cavity ( 13 ) is a port ( 22 ) to which a negative or positive pressure can be applied whereby the membrane ( 14 ) can be moved between its two stable states corresponding to completion of inlet and exhaust of a pumping cycle.

1 . A membrane pump including:
 i. an elongate cavity with opposing surfaces and having a ratio of width to depth in the range 8:1 to 16:1, where the depth is measured from one opposing surface to a mid-point of the cavity;   ii. inlet and outlet passages communicating with the cavity;   iii. a pressure port connected to the cavity; and   iv. a pre-deformed non-elastomeric membrane located within the cavity;   wherein the pre-deformed non-elastomeric membrane:
 a) has a first stable state in contact with one of the opposing surfaces, the first stable state corresponding to completion of an inlet stage of a pumping cycle; 
 b) has a second stable state in contact with the other opposing surface, the second stable state corresponding to completion of an exhaust stage of a pumping cycle; and 
 c) can be caused to invert from one stable state to the other stable state by application of positive or negative pressure to the cavity via the pressure port. 
   
     
     
         2 . A pump as claimed in  claim 1  wherein the ratio of width to depth is in the range 10:1 to 14:1. 
     
     
         3 . A pump as claimed in  claim 1  wherein the ratio of width to depth is around 12:1. 
     
     
         4 . A pump as claimed in  claim 1  wherein the non-elastomeric membrane is formed of a non-elastomeric sheet material. 
     
     
         5 . A pump as claimed in  claim 1  wherein the non-elastomeric membrane is resistant to corrosion by chemicals. 
     
     
         6 . A pump as claimed in  claim 1  wherein the non-elastomeric membrane is formed from a non-elastomeric fluoropolymer. 
     
     
         7 . A pump as claimed in  claim 1  wherein the non-elastomeric membrane is formed from one of: polytetrafluoroethylene, perfluoroalkoxy polymer resin or fluorinated ethylene-propylene. 
     
     
         8 . A pump as claimed in  claim 1  wherein the non-elastomeric membrane is has a thickness in the range 0.002 to 0.025 inches 
     
     
         9 . A pump as claimed in  claim 8  wherein the thickness is in the range 0.005 to 0.020 inches. 
     
     
         10 . A pump as claimed in  claim 8  wherein the thickness is in the range 0.010 to 0.015 inches 
     
     
         11 . A pump as claimed in  claim 1  wherein the depth is less than 5 mm. 
     
     
         12 . A pump as claimed in  claim 1  wherein the depth is less than 3 mm. 
     
     
         13 . A pump as claimed in  claim 1  wherein the depth is in the range 1 to 3 mm. 
     
     
         14 . A pump as claimed in  claim 1  wherein the pressure port is situated adjacent one end of the cavity. 
     
     
         15 . A pump as claimed in  claim 14  wherein the outlet passage is situated adjacent the same end of the cavity as the pressure port. 
     
     
         16 . A pump as claimed in  claim 1  wherein the membrane is clamped between first and second housing sections, each section having a cavity section such that when the housing sections are assembled to form a housing, said cavity is formed. 
     
     
         17 . A pump as claimed in  claim 1  wherein each opposing surface has continuous curvature. 
     
     
         18 . A method of forming a membrane pump membrane, including:
 arranging a non-elastomeric material adjacent a concave surface;   securing the non-elastomeric material at two or more peripheral points; and   permanently deforming the non-elastomeric material by forcing it against the concave surface, such that the permanently deformed non-elastomeric material will conform to a pump surface.