Claims
- 1. A pipette for obtaining a precise measured dose of a liquid, said pipette comprising a first and second piston mounted for reciprocal movement in a chamber,
- first resilient means for permitting first movement in a first direction of said first and second pistons to displace a defined volume of a material contained in said chamber,
- second resilient means for permitting further movement in said first direction of said second piston in said chamber while said first piston has stopped movement,
- whereby said first movement can define said precise measured dose,
- said first and second pistons being axially aligned and of different diameter to define a desired said precise dose,
- said first resilient means comprises a spring capable of being resiliently compressed by a first force,
- said second resilient means comprises a second spring capable of being compressed by a second force greater than said first force,
- and said further movement can provide an air blowout.
- 2. A pipette for obtaining a precise measured dose of a liquid, said pipette comprising a first and second piston mounted for reciprocal movement in a chamber,
- first resilient means for permitting first movement in a first direction of said first and second pistons to displace a defined volume of a material contained in said chamber,
- second resilient means for permitting further movement in said first direction of said second piston in said chamber while said first piston has stopped movement,
- whereby said first movement can define said precise measured dose,
- said first and second pistons being axially aligned and of different diameter to define a desired said precise dose,
- said first piston is of smaller diameter than the diameter of said second piston,
- said pistons being mounted so that as said first and second pistons move in said first direction, a portion of said first piston leaves said chamber and another portion of said second piston enters said chamber.
- 3. A pipette for obtaining a precise measured dose of a liquid, said pipette comprising a first and second piston mounted for reciprocal movement in a chamber,
- first resilient means for permitting first movement in a first direction of said first and second pistons to displace a defined volume of a material contained in said chamber,
- second resilient means for permitting further movement in said first direction of said second piston in said chamber while said first piston has stopped movement,
- whereby said first movement can define said precise measured dose,
- said first and second pistons being axially aligned and of different diameter to define a desired said precise dose,
- said first piston is of larger diameter than the diameter of said second piston,
- said pistons being mounted so that as said first and second pistons move in said first direction, a portion of said first piston leaves said chamber and another portion of said second piston enters said chamber.
- 4. A pipette for obtaining a precise measured dose of a liquid, which dose is no greater than 10 microliters,
- said pipette comprising first and second axially aligned cylindrical different diameter pistons mounted for reciprocal movement in a chamber along a central axis,
- a first spring mounting the first piston at least partially within said chamber, for movement into and out of said chamber,
- a second spring mounting said second piston at least partially within said chamber, for movement into and out of said chamber,
- and an actuating means for applying pressure to one of said springs, whereby both of said pistons move axially in a first direction and whereby only said second piston moves upon further actuation of said means to cause a gas expelling effect in said chamber upon movement of said second piston,
- said first and second pistons being axially aligned and of different diameter to define a desired said precise dose.
- 5. A pipette in accordance with claim 4, wherein said second piston has a greater diameter than said first piston.
- 6. A pipette in accordance with claim 4, wherein said springs are helical springs axially aligned with said pistons and mounted within a cylindrical chamber of a housing, whereby a first axial force can move both of said pistons axially to cause a portion of said second piston to move into said chamber and a portion of said first piston to move out of said chamber and further axial movement can cause said second piston to move towards said first piston and all movements being reciprocal, due to spring action of said helical springs.
- 7. A method of pipetting fluids, said method comprising,
- providing a chamber with first and second axially aligned pistons of different diameters mounted in said chamber in an at rest position with said first piston diameter being larger than said second piston diameter,
- moving said first piston out of said chamber while moving said second piston into said chamber to define a first volume of negative space within said chamber, said movement being carried out with said chamber having a orifice exposed to a liquid, so that air pressure acting on said liquid can aspirate said liquid into said negative space and fill a portion of said chamber with a measured dose of said liquid,
- removing said pipette from said liquid,
- moving said second piston in said chamber to disburse said liquid dose and provide an air blast to clear said orifice.
Parent Case Info
This application is a continuation, division, of application Ser. No. 07/956906, filed Oct. 2, 1992, which is a continuation of 07/571081, filed Aug. 22, 1990 and both now abandoned.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2323997 |
Apr 1977 |
FRX |
Continuations (2)
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Number |
Date |
Country |
Parent |
956906 |
Oct 1992 |
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Parent |
571081 |
Aug 1990 |
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