Pipette device with tip ejector utilizing stored energy

1. A pipette for use with a pipette tip to aspirate and dispense a quantity of liquid, comprising:

a housing;

a pipette tip mounting shaft extending from the housing to receive a pipette tip;

a pipette tip ejector mechanism for ejecting the pipette tip from the mounting shaft;

energy storage means;

means responsive to the insertion of the pipette tip onto the mounting shaft for storing energy in the energy storage means; and

means for releasing energy from the energy storage means to assist the tip ejector mechanism in the ejecting of the pipette tip from the mounting shaft.

2. A mechanism for facilitating the removal of a pipette tip from a pipette nozzle comprising a mechanism which stores energy as said pipette tip is mounted on said nozzle and which releases the stored energy when said pipette tip is to be removed to facilitate the removal thereof.

3. The pipette of claim 1 wherein the tip ejector mechanism includes a tip ejection member for ejecting the pipette tip from the mounting shaft and wherein the means for releasing energy releases energy from the energy storage means to move the tip ejection member.

4. The pipette of claim 3 wherein the ejector mechanism is carried by the housing and the tip ejection member is movable from a first position which permits the pipette tip to be inserted onto the mounting shaft and a second position wherein the pipette tip is ejected by the tip ejection member engaging and ejecting the pipette tip from the mounting shaft.

5. The pipette of claim 3 wherein the energy storage means comprising a spring means for storing energy.

6. The pipette of claim 5 wherein:

the spring means for storing energy in the energy storage means comprises

means responsive to the insertion of the pipette tip onto the mounting shaft for compressing the spring means to store energy in the energy storage means and

holding means for retaining the spring means in a compressed condition; and

the means for releasing energy from the energy storage means comprises means for releasing the holding means to drive the tip ejection member against the pipette tip and the tip off of the mounting shaft.

7. The pipette of claim 5 wherein:

the spring means for storing energy in the energy storage means comprises

means responsive to movement of the tip ejection member in a first direction for compressing the spring means to store energy in the energy storage means and

holding means for retaining the spring means in a compressed condition; and

the means for releasing energy from the energy storage means comprises means for releasing the holding means to drive the tip ejection member in a second direction to eject the tip from the mounting shaft.

8. The pipette of claim 6 wherein the

holding means comprises a brake mechanism characterized by (i) a locked condition in which the spring means may be compressed by movement of the pipette tip onto the mounting shaft while blocking movement in an opposite direction relative to the mounting shaft and (ii) an unlocked condition in which the spring means is released to drive the tip ejection member in a direction which ejects the tip from the mounting shaft.

9. The pipette of claim 1 wherein the housing is hand holdable by a user of the pipette and the means for releasing energy from the energy storage means is operable by the user.

10. The pipette of claim 6 wherein the means for compressing the spring means includes the tip ejection member, the spring means having a first end portion fixed relative to the housing and a second end portion moveable with the tip ejection member.

11. The pipette of claim 5 wherein the tip ejection member includes an impact surface and wherein the pipette further includes a piston responsive to energy released by the energy storage means for striking the impact surface to assist in driving the pipette tip from the mounting shaft.

12. The pipette of claim 6 wherein the tip ejection member includes an impact surface and wherein the pipette further includes a piston responsive to energy released by the energy storage means for striking the impact surface to assist in driving the pipette tip from the mounting shaft.

13. The pipette of claim 7 wherein the tip ejection member includes an impact surface and wherein the pipette further includes a piston responsive to energy released by the energy storage means for striking the impact surface to assist in driving the pipette tip from the mounting shaft.

14. In a pipette having a nozzle to which a pipette tip may be mounted, a mechanism for facilitating removal of a pipette tip from the nozzle, comprising:

a spring loaded tip ejection member terminating near an end of the nozzle to which a pipette tip may be mounted when the ejection member is in a normal position, the ejection member being moveable away from said end of the nozzle to a retracted position against said spring load when the pipette tip is mounted on said nozzle;

holding means for holding the ejection member in the retracted position against said spring load; and

means for releasing the holding means to permit the ejection member to return to the normal position in response to said spring load to assist in ejection of the pipette tip from the nozzle.

15. The mechanism of claim 14 wherein the ejection member is moved away from said end of the nozzle by said pipette tip.

16. A mechanism for facilitating the removal of a pipette tip from a pipette nozzle including

an ejector member normally biased to a first position near an end of said nozzle to which said tip is to be mounted, and movable as said tip is mounted to said nozzle against the bias, the ejector member reaching a retracted position when the tip is fully mounted on said nozzle;

holding means for holding the ejector member in the retracted position against said bias; and

means for releasing the holding means to permit the ejector member to return to the first position in response to said bias to assist in ejection of the pipette tip from the nozzle.

17. The pipette of claim 5 wherein the spring means comprises opposing magnetic fields generated by magnets oriented to repel each other.

18. The pipette of claim 5 wherein the spring means comprises an air spring.

19. The pipette of claim 5 wherein the spring means comprises a rubber spring.