Pipette controller with graduate reading plunger

Claim 1

A pipette controller comprising: a cylinder having, at its base, a first port provided with a rubber seal and a collet for tightly connecting with the mouthpiece of a pipette inserted therein, and a second port communicating with the atmosphere via a channel; a cap member of substantially U-shaped vertical section coaxially mounted on the upper end of the cylinder; a piston capable of reciprocation inside the cylinder; and a threaded rod having one end connected to the piston and the other end threadedly connected with a plunger assembly extending through an opening on the top of the cap member, said plunger assembly having a radial flange on the lower end thereof and a coiled spring biasing said flange against the inner upper side of said cap member, said spring wound around the threaded rod between said flange and said cylinder for normally maintaining the upper end of the plunger assembly projected outside the cap member and providing restoring force therefor; said plunger assembly including: a hollow tubular member of transparent material; a lid closing the upper end of the tubular member; a nut member fixedly connected to the lower end of the tubular member, a threaded opening extending through the nut member for threadedly engaging and guiding the upper end of the threaded rod such that the upper end of the threaded rod will be caused to ascend or descend with respect to the wall of the tubular member when the plunger is turned in clockwise or counter clockwise direction; a set of graduations spaced on the surface of the wall of the tubular member in cooperation with an indicating means provided on the upper-most end of the threaded rod inside the tubular member to indicate the volume of the liquid being sucked in by the travel of the piston, whereby the volume of the liquid to be pipetted may be preset by turning the plunger to have the indicating means coincide with a selected one of the graduation lines; and an operable lever assembly connected to close said channel for controlling the natural drainage of the liquid from the inserted pipette; and wherein said operable lever assembly includes: a lever arm; a seal pad fixed to one end of said lever arm for selectively sealing said channel; a pair of claws at one end of said lever arm and detachably clamped to the base of said cylinder so as to cause said seal pad to airtightly close said channel; and a projection at the medial portion of said lever arm adjacent the claws, such that said natural drainage can be effected when the other end of the lever arm is biased toward the cylinder with the projection serving as a fulcrum in contact with the wall of the cylinder.