Liquid transfer pipetting device with a factory adjustable and sealable calibration stop

Claim 1

In a liquid transfer pipetting device that includes a hollow barrel shaped handle member, a piston chamber within said barrel, a piston element within said piston chamber and extending outward through one end of said piston chamber, means extending through one end of said barrel member for imparting reciprocal motion to said piston, resilient means within said barrel for normally urging said piston toward said one end of said piston chamber, and means extending from an opposite end of said barrel for engaging a hollow detachable tip and for providing fluid communication between another end of said piston chamber and an internal portion of said tip, the improvement comprising: a disc termination of the piston at its end removed from the piston chamber, said disc extending across the interior space of said barrel member, said piston motion imparting means includes a plunger extending out of said one end of the barrel member through an aperture therein and engaging at its other end within the barrel member said piston terminating disc without an attachment thereto that prevents movement of the plunger in a direction downward across said hollow barrel width, the cross-sectional shapes of said plunger and said barrel member aperture cooperating to prevent relative rotation therebetween, a calibration stop threadedly attached to said plunger within the barrel member for limiting travel of the piston and plunger toward said one end of the barrel member by engaging an internal surface of said one barrel member end, whereby the piston stroke can be calibrated by turning said calibration stop with respect to said plunger, and means fixing said calibration stop to said plunger for preventing rotation therebetween, whereby the piston stroke is permanently calibrated once the calibration stop has been adjusted and fixed.

Claim 7

A method of accurately calibrating a liquid transfer device that includes a hollow barrel shaped handle member, a piston chamber within said barrel, a piston having one end sealably inserted into said piston chamber with its other end cooperating with an elongated plunger that extends through an opening in one end of said handle member, a spring within said handle member that normally urges said piston and plunger toward said one handle end, said plunger being shaped outside said handle member to have two ledges that may be selected to engage an outside surface of said one handle end by lateral displacement of said plunger, thereby to select the volume of fluid displaced by the piston during one inward stroke of the plunger, said calibrating method comprising the steps of: threadingly attaching a piston stop member to said plunger within said handle member in a manner that the spring normally urges said piston and plunger to an extreme rest position wherein the stop member engages an inside surface of said one handle member end, holding said plunger against the force of said spring with a predetermined distance between the outside surface of said one handle member end and one of said plunger ledges, turning said stop member relative to said plunger until the stop member has advanced therealong to firmly engage the inside surface of said one handle member end, fixing said stop member to said plunger to prevent further rotation therebetween, and releasing said plunger, whereby the amount of fluid displaced in the piston chamber by one stroke of said plunger has been accurately calibrated.

Claim 8

A method of accurately calibrating a liquid transfer device that includes a hollow barrel shaped handle member, a piston chamber within said barrel, a piston having one end sealably inserted into said piston chamber with its other end cooperating with an elongated plunger that extends through an opening in one end of said handle member, a spring within said handle member that normally urges said piston and plunger toward said one handle end, said plunger being shaped outside said handle member to have two ledges that may be selected to engage an outside surface of said one handle end by lateral displacement of said plunger, thereby to select the volume of fluid displaced by the piston during one inward stroke of the plunger, said calibrating method comprising the steps of: threadingly attaching a piston stop member to said plunger within said handle member in a manner that the spring normally urges said piston and plunger to an extreme rest position wherein the stop member engages an inside surface of said one handle member end, holding said plunger against the force of said spring with a predetermined distance between the outside surface of said one handle member end and one of said plunger ledges, turning said stop member relative to said plunger until the stop member has advanced therealong to firmly engage the inside surface of said one handle member end, fixing said stop member to said plunger to prevent further rotation therebetween, and releasing said plunger, whereby the amount of fluid displaced in the piston chamber by one stroke of said plunger has been accurately calibrated.