Measuring and testing – Sampler – sample handling – etc. – Capture device
Reexamination Certificate
1999-08-18
2001-03-13
Raevis, Robert (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Capture device
Reexamination Certificate
active
06199435
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a pipetting system with a pipetting device and at least one pipette tip releasably fastened thereto.
Such pipetting systems are above all used in the laboratory for metering fluid quantities. These fluids are suctioned into pipette tips and ejected therefrom. For this mostly pistons are displacably arranged in a cylinder. With air cushion systems the piston and cylinder are integrated into the pipetting device and communicate with the pipette tip so that the metering of the fluid is evaluated via an air cushion. With direct displacement systems the piston and the cylinder are integrated into the tip and act directly on the suctioned-in fluid. Such pipetting systems are also called syringes. Pistonless systems may in particular comprise a pipette tip with a balloon-like end section which expands for suctioning in fluid, and for expulsion is compressed.
The pipette tip is detachably connected to the pipetting device so that after usage it may be exchanged for a fresh pipette tip, by which means with subsequent meterings contaminations may be avoided. Pipette tips for one-off use are available inexpensively of plastic.
The pipetting devices have a fastening attachment for fastening pipette tips. Mostly this is a conical projection onto which is squeezed the pipette tip with a conical receiver. This may be effected without gripping the pipette tip by sticking the fastening attachment onto a pipette tip which is ready and waiting in a holder.
For avoiding contamination of the operating personnel it is furthermore desirable to release the pipette tip from the fastening attachment without grasping it. For this many pipetting devices are equipped with an ejection means which with an ejection sleeve is allocated to the upper edge region of the pipette tip and may be actuated on an ejection knob. With pipette tips which are stuck on particularly strongly or even “rammed on”, for the ejection of the tips however a high force effort is required which already with one-channel systems compromises the use or even makes it impossible. A particularly high force effort may result by way of the multiplied tip ejection forces with multi-channel pipetting systems which have several parallel pipette tips to be ejected.
From EP 0 566 039 B1 there is known a pipette with a tip remover which for simplifying the use by way of reduction of the ejection force comprises a lever mechanism. This lever mechanism projects laterally from a pipette housing and is to be pressed manually. It may have a toothed wheel which on an actuation arm for the pipette tip is rotatably coupled in a vertical plane. Further the inner flank of the toothed wheel meshes with a rack on the side of the elongate housing. On the outer side of the actuation arm on the side of the housing there is arranged a hollow push-rod which with a thread on its inner side meshes with the outer side of the gearwheel. If the push-rod is pressed down, the toothed wheel moves downwards and simultaneously takes with it the actuation arm and an ejection sleeve, by which means a pipette tip is pushed back from a fastening cone. With this the push-rod covers exactly double the distance as the actuation arm and the force exerted on the push-rod is half as large as the force used for pushing back the pipette tip. This system is expensive in its design and permits only a single transmission ratio of 1:2 so that it is limited in its usability.
BRIEF SUMMARY OF THE INVENTION
Proceeding from this it is the object of the invention to provide a pipetting system with an ejection means which apart from those mentioned previously also permits other transmission ratios and design simplifications.
This object is achieved by a pipetting system with the features of claim
1
. Advantageous formations of the pipetting system are specified in the dependent claims.
The pipetting system according to the invention has
a pipetting device and at least one pipette tip releasably fastenable thereon,
at least one fastening element on the pipetting device, on which the pipette tip is fastened,
an ejection means on the pipetting device, which has an axially movable ejection element for releasing the pipette tip from the fastening element with an axial movement of the ejection element and a drive means for driving the axial movement of the ejection element, and
a pull-means gear, push-means gear or linkage gear which transmits an essentially axial drive movement of the drive means into an axial movement of the ejection element and with which the ejection element at least on releasing the pipette tip from the fastening element is axially movable over a smaller distance than the essentially axial drive movement covers and a force exceeding the force for the essentially axial drive movement can be exerted onto the pipette tip.
The pipetting system according to the invention is an alternative to the known pipette with tip remover, which on account of the pull-means gear, push-means gear or linkage gear permits the known transmission ratio as well as other transmission ratios and thus an increased freedom of design and expanded application possibilities. With a pipetting system according to the invention also transmission ratios are possible which vary during the tip ejection. Furthermore the pipetting system permits the possibility of constructional variations.
With a pull-means gear embodiment the drive means and the ejection element may have end sections which engage over one another and the gear may have a deflection roller rotatably mounted on the end section of the ejection element and a cable which at one end is fixed with respect to the fastening element and at the other end is fastened to the end section of the drive means. With this is it preferred that the drive rod and the ejection element are aligned parallel to one another. With the essentially axial drive movement over a certain distance the ejection element moves only over half this distance. At the same time however on the ejection element there is available a force for releasing the pipette tip, which is roughly double as large as the force exerted for the drive movement. Other transmission ratios may be achieved when several deflection rollers are mounted on the ejection element. This gear permits solutions which are particularly simple with respect to design.
With a push-means gear embodiment the gear has a first piston which is connected to the drive means and is displaceable in a first cylinder, and a second piston which is connected to the ejection element and is displaceable in a second cylinder, wherein the two cylinders communicate with one another, this communicating cylinder system is sealed to the surroundings and is filled with hydraulic fluid and the first piston has a smaller cross sectional surface than the second piston.
With these hydraulic transmission systems there is effected a displacement of the first piston over a certain distance, a displacement of the second piston over a smaller distance, wherein the ratio of the distances is inversely proportional to the ratio of the cross sectional surfaces of the two pistons. However the force exerted by the second piston on the ejection element and thus onto the pipette tip is larger that the force exerted by the drive rod onto the first piston, wherein the ratio of these forces is proportional to the ratio of the cross sectional surface of the two pistons.
With a further push-means gear embodiment the gear has a first bellows connected to the drive means and a second bellows connected to the ejection element, wherein the bellows are connected to one another in a communicating manner, this communicating bellows system being filled with hydraulic fluid and the smaller bellows having a smaller cross section than the second bellows.
With this system by way of the bellows of different diameters there is achieved a result corresponding to the pistons of different diameters. However here a sealing of the pistons or piston rods is done away with.
With both push-means gear designs there exists a large freedom in
Tennstedt Ernst
Wilmer Jens
Brown & Wood LLP
Eppendorf-Netheler-Hinz GmbH
Raevis Robert
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