Patent ID: 7690274

Claim:
A pipette comprising: a housing defining a pipette axis; a tip removably fitted onto a distal end of the housing for receiving a liquid therein; and a tip removal mechanism for removing the tip from the housing, wherein the tip removal mechanism comprises, (i) an operating rod which is reciprocally movable relative to the housing axis between retracted and extended positions; (ii) a ramp member which is rotatable about a rotation axis that is parallel to the pipette axis; (iii) a ramp abutment member fixed to an upper end of the operating rod and defining a response surface in opposition to and in contact with the ramp surface; wherein (iv) each of the ramp and response surfaces define an opposed circular spiral surface having a high point, a low point and a substantially vertical step between the high and low points such that rotation of the ramp member causes the ramp surface to rotatably move against the response surface to thereby responsively displace the operating rod from the retracted position to the extended position thereof and thereby remove the tip from the housing.