Self cleaning reciprocating and/or rotating device

A fluid metering device for pumping a fluid from a fluid source to a fluid outlet comprising:

• a substantially hollow sleeve, said sleeve comprising a pumping portion and a journal portion, said pumping portion comprising at least one inlet and at least one outlet;
• a piston comprising a pumping portion and a journal portion, wherein said piston is movably supported at least partially within said sleeve such that said journal portion of said sleeve overlaps said journal portion of said piston forming a contact area, and wherein said pumping portion of said piston displaces a fluid within said pumping portion of said sleeve, said journal portion of said piston comprising a generally cylindrical cross-section with an outer diameter dimensioned to provide a clearance of less than 0.0005 inches between said journal portion of said piston and said journal portion of said sleeve;
• wherein at least one of said piston or said sleeve comprises a ceramic comprising a leachable substance which migrates out of said ceramic and coagulates in said clearance upon sustained contact with said fluid thereby forming a coagulum and tending to bind said piston to said sleeve;
• at least one of said piston or said sleeve further comprising a scraping edge which moves across a portion of said contact area to scrape said coagulum from said gap , said journal portion not comprising rinse ports for the removal of said coagulum .

A cylinder-sleeve combination operating in the presence of a reactive fluid comprising:

• a reactive fluid;
• a substantially hollow sleeve;
• a cylinder movably supported at least partially within said sleeve such that said sleeve overlaps at least a portion of said cylinder to define a contact area, said cylinder having an outer diameter dimensioned to provide a gap having a clearance of less than 0.0005 inches between said cylinder and said sleeve in said contact area;
• wherein at least one of said cylinder or said sleeve is formed of a material comprising a leachable substance which migrates out of said cylinder or said sleeve and coagulates in said gap upon sustained contact with said reactive fluid thereby forming a coagulum and decreasing said clearance between said sleeve and said cylinder and tending to bind said cylinder to said sleeve;
• at least one of said cylinder or said sleeve further comprising a scraping edge which move across a portion of said contact area to scrape said coagulum from said gap , said journal portion not comprising rinse ports for the removal of said coagulum .

A valveless, positive displacement pump for controlling the movement of a fluid from a fluid source to a fluid outlet comprising:

• a substantially hollow sleeve;
• a piston movably supported at least partially within said sleeve such that said sleeve overlaps at least a portion of said piston, said piston having an outer diameter dimensioned to provide a gap having a clearance of less than 0.0005 inches between said piston and said sleeve in said overlap area;
• means for supplying fluid, said fluid comprising at least one component which will coagulate on the surface of at least one of said sleeve or said piston and decrease said clearance between said sleeve and said piston and tending to bind said piston to said sleeve;
• said sleeve comprising a control portion and a journal portion, said control portion comprising at least one inlet and at least one outlet, wherein said inlet is in fluidic communication with said supplying means;
• said piston further comprising at least one groove which extends entirely around the circumference of said piston forming a scraping edge which moves across a portion of said contact area to scrape said coagulum from said gap.