Positive displacement pump having piston and/or liner with vapor deposited polymer surface
First Claim
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1. A metering pump for dispensing small, precise volumes of fluid, comprising:
- a pump housing;
a chamber within said pump housing, said chamber being bounded by a cylindrical wall within said housing;
a piston having a cylindrical body portion extending within said chamber, said cylindrical body portion of said piston having a cylindrical outer surface and a duct formed therein;
two or more passages extending through said pump housing and communicating with said chamber;
a drive mechanism coupled to said piston for rotating and reciprocating said piston within said chamber;
said outer surface of said cylindrical body portion of said piston including a surface finish exhibiting a roughness average of at least about four microinches and a vapor deposited polymer.
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Abstract
A metering pump for providing relatively small, precise volumes of fluid is provided. The pump piston and/or the interior of the cylinder has a surface finish exhibiting a roughness average within selected limits and a vapor deposited polymer such as polytetrafluoroethylene. A drive mechanism is provided for simultaneously rotating and reciprocating the piston within a cylindrical chamber. Fluid is thereby drawn into the chamber and expelled.
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Citations
24 Claims
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1. A metering pump for dispensing small, precise volumes of fluid, comprising:
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a pump housing;
a chamber within said pump housing, said chamber being bounded by a cylindrical wall within said housing;
a piston having a cylindrical body portion extending within said chamber, said cylindrical body portion of said piston having a cylindrical outer surface and a duct formed therein;
two or more passages extending through said pump housing and communicating with said chamber;
a drive mechanism coupled to said piston for rotating and reciprocating said piston within said chamber;
said outer surface of said cylindrical body portion of said piston including a surface finish exhibiting a roughness average of at least about four microinches and a vapor deposited polymer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A metering pump for dispensing small, precise volumes of fluid, comprising:
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a piston including a substantially cylindrical outer surface having a surface finish exhibiting a roughness average of at least about four microinches and a duct formed within said outer surface;
a housing having an inner surface defining a cylindrical chamber, said piston extending into said cylindrical chamber;
an inlet passage extending through said housing;
an outlet passage extending through said housing;
means for rotating said piston about a longitudinal axis;
means for reciprocating said piston within said chamber such that fluid is drawn into said chamber through said inlet passage and expelled through said outlet passage; and
a vapor deposited polymer on said substantially cylindrical outer surface of said piston. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A piston and cylinder assembly for a metering pump for dispensing small, precise volumes of fluid, comprising:
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a ceramic piston including a substantially cylindrical outer surface having a surface finish exhibiting a roughness average of at least about four microinches and a duct formed within said surface;
a housing having a ceramic inner surface defining a cylindrical chamber and exhibiting a roughness average of at least about four microinches, said piston extending within said chamber;
a vapor deposited polymer comprising polytetrafluoroethylene on at least one of said substantially cylindrical outer surface of said piston and said inner surface of said housing. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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Specification