Automatic pipette detipping

Details Automatic pipette detipping Automatic pipette detipping

2001-06-04

2004-06-15

Warden, Jill (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Control element responsive to a sensed operating condition

C422S105000, C436S180000, 87, 87, 87, 87, 87

Reexamination Certificate

active

06749812

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to pipettes, and more particularly to pipettes having automatic mechanisms for identifying and/or removing tips.
BACKGROUND OF THE INVENTION
Pipettes are commonly utilized to aspirate a fluid from one container or other source and to dispense the fluid to a second container or other receptacle. Since the fluid being aspirated and dispensed is frequently analyzed or otherwise tested after being dispensed, and in order for such testing or analysis to be accurate, it is important that a sample not be contaminated by fluid from a prior aspirated sample. While it is possible to wash a pipette tip between aspirations in order to reduce or eliminate such contamination, and for some pipette systems, particularly those utilizing fluid displacement, this is frequently done, washing the tips is expensive and time-consuming, and it is frequently difficult to remove all contaminants. Therefore, for many pipettes, particularly air displacement pipettes, it is cheaper and easier to replace the pipette tip after each use.
However, when a pipette tip is mounted to the nozzle, it is important that the tip be mounted with sufficient force to seal the nozzle so that fluid being aspirated and dispensed does not leak around the tip-nozzle junction, thereby preventing accurate quantities of fluid from being aspirated and dispensed, and the tip must be mounted with sufficient force to prevent the tip from falling off. However, if the tip is mounted with too much force, it can become difficult to remove the tip from the nozzle after use, resulting in significant strain on the operator's hand. For this and other reasons, an operator working in a laboratory or other facility where large numbers of tips are replaced each day may experience repetitive stress injuries with current pipette designs as a result of repeated tip removals.
Heretofore, control on the force applied in mounting a tip to a nozzle has generally relied on the skill of the person doing the mounting. Thus, while for an illustrative embodiment, only two pounds of force may be required to properly mount a tip to the nozzle, operators may inadvertently be applying 10 to 15 pounds of force in mounting the nozzle, making nozzle removal far more difficult than necessary. However, without tactile guidance, an operator might overcompensate for this problem and not properly mount a nozzle. Further, while some tip removal mechanisms have existed for pipettes in the past, these have generally been manually operated and, since they have generally not controlled tip mounting force, they have frequently required that substantial force be applied by, for example, the operator's thumb to successfully effect tip removal. This operation is therefore another potential cause of repetitive stress injuries. Alternatively, such tip removal schemes have been motor driven, increasing the size, cost and complexity of the pipette.
A related problem is that there are a variety of tips available for use with a given pipette and the pipette volume settings, particularly where these settings are automatically performed, need to be slightly adjusted for some tips to obtain the desired volumes of aspirated and/or dispensed fluid. The tips may for example have different length, volume, orifice diameter/size, shape and/or surface treatment (for example a low liquid retention coating). The tips may also be filtered or unfiltered, and if filtered, may have various special filtering elements, the presence and nature of filtering elements being a major factor in requiring volume adjustments for the pipette. While provision may be made for the user to input information on the tip being used either on the pipette or on a processor used therewith, this can be burdensome for the operator where a large number of pipetting operations are being performed. It also provides a source of pipetting error where the operator either forgets to identify a special tip used for a given operation or makes an erroneous entry, either because the operator doesn't know the tip used or enters tip information incorrectly. It is also possible that the operator may select the wrong tip for a particular pipetting operation. It would therefore be preferable if the pipette could easily and quickly identify the tip being mounted as part of the tip mounting process without requiring any operator input, and could provide some type of feedback to the operator, for example when there is a change in tip used, to minimize inadvertent use of the wrong tip.
A need therefore exists for improved pipettes which overcome the various tip mounting, tip removal and tip identification problems identified above.
SUMMARY OF THE INVENTION
The tip mounting and removal problems indicated above are generally overcome in accordance with the teachings of this invention by storing part of the force used by the operator to mount the tip to a nozzle, actively limiting the force with which the tip is mounted to the nozzle, providing a sensory feedback to the operator when the tip is properly positioned on the nozzle and releasing the mechanical energy stored during the mounting of the tip in response to operator activation to facilitate the automatic removal of the tip. An overforce capability may be provided to supplement the stored energy for the removal of a stuck tip. Mechanisms used for the above may also be utilized in solving the tip identification problem.
More specifically, the invention provides a mechanism for facilitating the removal of a tip from a pipette nozzle which includes a spring loaded ejector sleeve through which the nozzle passes, the sleeve terminating near the end of the nozzle to which the tip is mounted when the sleeve is in a normal position, the sleeve being moved away from the end of the nozzle against the spring load when the tip is mounted to the nozzle. The sleeve includes a first latch portion which mates with a second latch portion of the pipette when the sleeve is in a retracted position to which it is moved when a tip is properly mounted to the nozzle to hold the sleeve in the retracted position against the spring load, a third latch portion being provided which is operable to unmate the first and second latch portions, freeing the sleeve to return in response to the spring load to its normal position. The sleeve engages the tip before reaching the normal position to facilitate removal of the tip. The tip removal mechanism may include an overforce mechanism operable to supplement the spring load in moving the sleeve to its normal position against a stuck tip to further facilitate removal of the tip. For one embodiment, the first latch portion is a keyhole slot formed in the sleeve, the second latch portion is a detent having a large portion which fits in an enlarged portion of the slot when the sleeve is in its retracted position and a small portion sized to fit in a narrow portion of the slot, the narrow portion being adjacent to the detent except when the sleeve is in the retracted position. For this embodiment, the third latch portion is a button operable for moving the small portion of the detent into the slot to unlatch the sleeve. For this embodiment, the detent may be spring-biased to move the large portion of the detent into the slot. For another embodiment, the first latch portion is a projection at a proximal end of the sleeve, the second latch portion is a mating lip on a latch plate biased to have the lip engage the projection when the sleeve is in its retracted position and the third latch portion is a portion of the latch plate which is manually operable to move the plate against its bias to move the lip away from the projection, permitting the sleeve to return to its normal position. For this embodiment, an angled surface on the plate may be provided which is positioned to engage an angled surface associated with the sleeve when the latch plate is moved beyond the point where the lip no longer engages the projection, the interaction of the two angled surfaces supplementing the spring load in moving the sleeve to its norm

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