Measuring and testing – Sampler – sample handling – etc. – Capture device
Reexamination Certificate
1999-04-29
2001-05-22
Williams, Hezron (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Capture device
C422S065000, C422S105000
Reexamination Certificate
active
06234033
ABSTRACT:
The invention relates to an automatic pipetting apparatus, having a drive for moving a pipetting instrument from a source site to a target site, which apparatus is used, for example, for mass screening in order to discover new lead structures in particular for pharmacology and crop protection.
At the moment, it is generally customary for the substances to be tested to be presented to an automatic testing apparatus in the Mikrotiter Format (with 96 to 1536 wells per plate). From this presentation arrangement, the substances have to be transferred separately to the individual analysis sites using an automatic pipetting apparatus. Also, as the tests progress, further pipetting steps are required although in general these may be carried out together rather than separately for each analysis site. The pipetting of individual substances when carrying out mass screening tests is particularly time-consuming. Screening with so-called spot arrays also requires an enormous number of individual pipetting steps.
The automatic pipetting apparatus which are currently customary guide the pipetting instrument over a work surface with one drive each for the x-, y- and generally also the z-axes. According to the prior art, it is possible, in principle, to establish various types of drive. For example, one drive used is a stepper motor which transmits a linear movement via a recirculating ball screw. The advantage of this type of drive is the very high level of accuracy combined with relatively low costs. The main drawback is the fact that the linear movement is extremely slow, even if a speed ramp with different speeds is passed through during the actual adjustment operation.
In addition, DC motor drives with a resistive, inductive or capacitive sensor or with an optical linear guide are used for position feedback. These drives are significantly quicker than stepper motors, but are complex and therefore expensive.
In principle, the same advantages and disadvantages also apply to linear motors used as an alternative to rotating motors.
The invention relates to an automatic pipetting apparatus which avoids the drawbacks of previous arrangements while achieving high pipetting speeds.
According to the invention, it is possible to divide the linear movement into a rapid movement over a relatively long distance between source site and target site, end stops, which can be finely adjusted automatically, being arranged with a high level of accuracy at both the source site and the target site. The adjustable end stops, which normally only have to be adjusted by a few millimeters or a few hundred micrometers, combined with the rapid movement result in an enormous increase in the transfer rate.
Arranging shock-absorbing means on the end stops decelerates the rapid movement before the stop is reached. It is thus possible to avoid impacts.
Preferably, the drive is designed as a hydraulic or pneumatic linear drive and is therefore inexpensive when moving rapidly.
In order to feed back information concerning arrival at the end stops, sensors for position detection may be arranged in the area of the end stops, which sensors register the arrival of the pipetting instrument at the end stops and, if appropriate, feed this information to a control unit or memory unit. To counteract having to wait for the end of the transient mechanical effect caused by the stop, the speed is increased again.
Finally, it is possible to use end stops with different adjustment accuracies, allowing the costs to be reduced further, since hitherto the highest adjustment accuracy of one individual direction of movement was decisive for the entire system.
The invention also relates to a method with which the pipetting speeds are increased significantly, which is achieved by means of the mutually independent adjustment within short distances of the end stop and the relatively long distances.
In a refinement of the method, the rapid movement is decelerated before the end stop is reached, it being possible, furthermore, to measure the position of the pipetting instrument after the end stop has been reached and, if appropriate, to carry out a correction in the event of positional inaccuracies.
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patent: 4812392 (1989-03-01), Miyake et al.
patent: 5306510 (1994-04-01), Meltzer
patent: 5443791 (1995-08-01), Cathcart et al.
patent: 5897837 (1999-04-01), Mizuno
patent: 5906795 (1999-05-01), Nakashima et al.
patent: 5985214 (1999-11-01), Stylli et al.
patent: 6132582 (2000-10-01), King et al.
BASF - Aktiengesellschaft
Garber C. D.
Keil & Weinakuf
Williams Hezron
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