Patent Application
20080184823
1. Field of Invention
The present invention generally relates to pipettes, and more particularly to an improved multichannel pipette.
2. Description of Related Art
A known multichannel pipette, for example, as described in U.S. Pat. No. 5,021,217, is designed as a hand-held unit, and is actuated by hand. Multichannel pipettes that are handheld, but that are actuated by a motor have also been disclosed, for example, as described in U.S. Pat. No. 4,779,467.
A multichannel pipette generally includes a plurality of cylinder/piston arrangements, for example, in order to dose quantities simultaneously into the wells of microtiter plates. Multichannel pipettes with eight channels or twelve channels are particularly common, because the most common microtiter plates are ones with 96 (8×12) wells.
The cylinder/piston arrangements are disposed alongside one another in the displacement part. The cylinders of the cylinder/piston arrangements are joined as a block. The pistons of the cylinder/piston arrangements are also joined, namely with a common piston drive.
Multichannel pipettes are mostly designed as air displacement pipettes. Columns of air are displaced by the cylinder/piston arrangements in such a way that specimen liquid can be suctioned into and discharged from exchangeable pipette tips, which can be fitted onto shafts of the cylinders and which are generally made of plastic and designed as disposable parts. Only the pipette tips come into contact with the liquid.
In principle, however, direct-displacement multichannel pipettes are also known.
Multichannel pipettes can have non-adjustable or adjustable dosing volumes in the cylinder/piston arrangements. A change in the dosing volumes is obtained by adjusting the travel of the piston-driving device in the grip part.
Many functions can be integrated in motor-driven multichannel pipettes, for example, as described in U.S. Pat. No. 4,779,467, including repeated dispensing of small amounts of the liquid.
The displacement part of a multichannel pipette, in which part the several cylinder/piston arrangements are located alongside one another, and to a considerable extent transverse to the longitudinal axis of the grip part. The displacement part basically acts as a broad plate from which the pipette tips disposed alongside one another protrude downward. Depending on how a user holds the grip part during the pipetting operation, the user's view of the microtiter plate may be obstructed by the orientation of the displacement part. It is therefore advantageous to mount the displacement part such that it can rotate relative to the grip part about the longitudinal axis of the grip part. However, to ensure that the displacement part does not undesirably move too easily relative to the grip part, it is advantageous that the rotation be braked in some way, either by friction or notching.
The displacement part must also be able to be removed from the grip part. A connection device serves for the detachable connection of the displacement part to the grip part. A magnetic connection between grip part and displacement part is described in German Patent Application DE-A-198 26 065. However, a screw connection, for example, as described in U.S. Pat. Nos. 4,779,467 and 5,021,217, is more common.
In known multichannel pipettes, the displacement part can rotate relative to the grip part steplessly with friction braking. The engaging threaded elements have a friction that is greater than the friction in the rotary bearing of the displacement part. In this way, the threaded elements normally remain in engagement with one another, even upon rotation of the displacement part relative to the grip part.
To unscrew the displacement part from the grip part, the rotary bearing is blocked by a manual release action, such that a rotation of the displacement part is then transmitted to the connection part. The manual release action is executed by actuation of an axially movable ejection mechanism for the pipette tips. By depressing an ejection button of the ejection mechanism, the blocking of the rotary bearing is freed.
Modern multichannel pipettes should be able to be completely autoclaved in the assembled state. In this process, they are exposed to temperatures of over 120° C., wherein the threads formed in plastic parts lose some of their pretensioning. A threaded connection that is loosened by the autoclaving may come undone upon subsequent orientation of the displacement part relative to the grip part, because the friction suitable for the thread has become less than the friction in the rotary bearing.
If a threaded connection has been loosened by autoclaving or by other means, stroke and measuring errors arise even in the event of very slight rotary movements, for example, when lifting the pipette tips from a rack. This often goes unnoticed by the user. Even a warning in the operating instructions cannot normally always help.
The object of the invention is therefore to improve the known multichannel pipette with regard to its susceptibility to error during operation, taking particularly into account the circumstances that arise during autoclaving.
Accordingly, the above and other objects are met by the features of the exemplary multichannel pipette, wherein the threaded elements of the threaded connection between the support part of the grip part and the connection part are supplemented by a form-fit blocking provided by matching form-fit configurations, which engage with one another in the end position of the thread, so that the displacement part is secured in the intended position on the grip part. With this feature, a reverse rotation of the connection part relative to the support part is definitively prevented. The thread thus remains in stable engagement independently of the friction that exists between the threaded elements and that may possibly have been reduced by repeated autoclaving. This positive form-fit blocking of the threaded connection of grip part and displacement part can be released by a manual release action, such that the displacement part can be rotated about the longitudinal axis relative to the grip part even against a comparatively high braking force, without affecting the engagement of the threaded elements. The position of the piston-driving device relative to the coupled pistons of the cylinder/piston arrangements thus also remains unchanged, and the piston stroke does not change.
Some of the terms used within the context of the teachings of the present invention, include:
The longitudinal axis, which the grip part forms in its orientation relative to the displacement part, hereinafter defines the “axial” direction of the multichannel pipette.
The piston-driving device in the grip part can be a hand-actuated device or a motor-actuated device, as previously described.
In the displacement part, the several cylinder/piston arrangements disposed alongside one another can also be disposed not just in one direction, that is to say along a tranverse axis, but also in two directions, in further embodiments of the invention.
The rotatable bearing of the displacement part on the connection part will already have a certain inherent friction. This can be strengthened and adjusted to a defined value by an integrated friction brake, by a ratchet brake, for example, with an adjustability in mostly equidistant notching steps, or by a combination of both brake types.
The support part of the grip part, which carries the threaded connection element of the connection device, can also be an integral component of a body of the grip part and does not have to be a separate structural part.
The connection part with the coupled cylinders of the cylinder/piston arrangement forms the abutment for the pistons driven by the piston-driving device in the grip part. Here, an axially precise connection is employed in order to minimize the error in the stroke of the piston-driving device. However, the term “axially fixed connection” does not exclude the possibility of a slight axial play being present in the rotary bearing.
The form-fit configurations can have any suitable shape. They will be in engagement with one another when the threaded elements are completely engaged, so that in this definitive end position, a reverse rotation of the connection part relative to the support part is prevented. However, the engagement of the form-fit configurations will generally occur shortly before the end position of the threaded elements is reached, so that threaded elements are “substantially completely engaged.”
In the novel multichannel pipette, the rotary bearing of the displacement part is designed such that it can be blocked. Specifically, it can be blocked by the manual release action, which disengages the form-fit configurations from one another. Then, by gripping the displacement part, it is possible to rotate the connection part and thus release its threaded connection to the grip part.
In further embodiments of the form-fit configurations, an asymmetrical, sawtooth-shaped design of the form-fit configurations is provided, which together then form a kind of asymmetrical wedge mechanism, leading to what may also be an acoustically perceptible ratchet effect, which signals to the user that the end position of the threaded elements has been safely reached. In this case, it is not necessary that the shapes of the form-fit configurations, which engage one another, are identical. For example, different numbers of form-fit configurations can be arranged on the two involved parts of the multichannel pipette.
In further embodiments of the manual release action for the form-fit configurations, the additional catch element, which is assigned in particular to the connection part, but can be moved relative to the latter between two positions, forms an advantageous means of implementing the release action.
It is also advantageous, in the multichannel pipette, for an axially movable ejection mechanism to be provided on the grip part. The axially movable ejection mechanism forms a well-tried means of also achieving the manual release action desired according to the invention for the form-fit configurations. In particular, the catch element can be moved axially by means of the ejection mechanism.
Further embodiments provide the interaction of the ejection mechanism with an outer housing of the displacement part of the multichannel pipette, wherein the outer housing is pretensioned against the grip part by a spring force. The outer housing itself is thus part of the force chain running from the ejection mechanism to the pipette tips at the bottom of the displacement part. In this way, the outer housing can also be used as part of the force chain running from the ejection mechanism to the catch element.
A particularly advantageous embodiment of the catch element is further realized by rotation-transmission ribs and rotation-transmission grooves with radially inward or radially outward orientations, depending on the construction.
Thermoplastic can be employed for most parts of the multichannel pipette. Polypropylene reinforced by minerals can be used. However, ABS, polycarbonates, or the like, also can be used. In the final analysis, chemical resistance, injection-moldability and temperature resistance play the decisive role in the choice of suitable plastics. As noted above, the multichannel pipette can be autoclaved in an assembled state.
The invention is explained in more detail below, with reference to drawings that show preferred and nonlimiting illustrative embodiments.
At the lower end of the displacement part 7,
The grip part 2 is connected releasably to the displacement part 7. This is effected by a connection device, which leads to an axially rigid connection of the parts, but permits a rotation of the displacement part 7 relative to the grip part 2 about the longitudinal axis 1.
To permit the detachability of grip part 2 and displacement part 7, the connection device includes a threaded connection element 16, arranged on a support part 15 of the grip part 2, and also a connection part 17 with a matching threaded element 18 in engagement with the threaded connection element 16. The threaded elements 16, 18 are indicated in
The rotatability of the displacement part 7 relative to the grip part 2 about the longitudinal axis 1 is achieved by the displacement part 7 being mounted on the connection part 17, so as to rotate about the longitudinal axis 1. Except for clearance that is needed for this rotary bearing 19, the connection part 17 is connected in an axially fixed manner to the coupled cylinders 12 of the cylinder/piston arrangements 8, and therefore to the cylinder bar 12′.
When the displacement part 7 is mounted securely on the grip part 2 and is located in its end position, the threaded elements 16, 18 are completely in engagement with each other. When the displacement part 7 is rotated in the direction of screwing relative to the grip part 2, nothing changes in the threaded connection of the parts. Thus, the effective stroke of the piston-driving device 3 also remains unchanged. However, if the displacement part 7 is turned in the opposite direction relative to the grip part 2, then, in the event of a threaded connection having come loose, it may happen that the displacement part 7 is not turned relative to the connection part 17 in the rotary bearing 19, but instead the displacement part 7 takes along the connection part 17, and the connection part 17 is then unscrewed from the support part 15 of the grip part 2 or at least loosened.
The threaded elements 16, 18 are locked in a form-fit manner in the state when substantially completely screwed in. For this purpose, form-fit configurations 20 matching one another are provided, on the one hand, on the support part 15 and, on the other hand, on the connection part 17, and, when the threaded elements 16, 18 are substantially completely engaged, the form-fit configurations 20 engage with one another in such a way that they prevent a reverse rotation of the connection part 17 relative to the support part 15. However, the form-fit configurations 20 can be disengaged from one another by a manual release action, such that a reverse rotation of the connection part 17 relative to the support part 15 is possible. Although not depicted here, a manual release action can, for example, be effected by an additional manual release element on the grip part 2, for example, a slide, or a button that acts on the support part 15 or the connection part 17.
The rotary bearing 19 can also be blocked by the manual release action. The form-fit configurations 20 are disengaged from one another, indicated at the top of the connection part 17 in
The form-fit configurations 20 have an asymmetrical design in a sawtooth shape. In this way, an asymmetrical wedge mechanism is created. During the rotation of the threaded elements 16, 18 in the direction of complete engagement on the last section of the travel, the wedge mechanism acts like a ratchet. In the same way, the mechanism prevents a reverse rotation shortly before the end position of the threaded elements 16, 18, but allows further rotation until the end position is reached.
The form-fit configurations 20 can be oriented axially. Accordingly, the movement of the form-fit configurations 20 with respect to one another also takes place in the axial direction when the manual release action is performed. This, advantageously, permits ergonomic handling of the multichannel pipette.
In principle, especially when using an independent actuation part, the form-fit configurations 20 can also be oriented radially or at a defined angle to the longitudinal axis 1. Corresponding structural solutions can be employed, as will be appreciated by those skilled in the relvant art(s).
The form-fit configurations 20, assigned to the support part 15, not shown separately in the view in
The catch element 21 is the transmission means for moving the form-fit configurations 20 relative to one another. By the manual release action, the catch element 21 can be moved into its second position, as a result of which the form-fit configurations 20 disengage. Thus, the catch element 21 can be moved axially and counter to a spring force into the second position.
As previously noted, the pipette tips 14 are intended to be ejected from the shafts 13 of the cylinders 12 by a manual action. This is normally done using an axially adjustable ejection mechanism 22 on the grip part 2. An actuation button 23 can be seen in
The desired manual release action for the form-fit configurations 20 can now also take place by means of the ejection mechanism 22, wherein the catch element 21 can be moved axially by means of the ejection mechanism 22, and explained in more detail below with reference to
In principle, the axial movement of the ejection mechanism 22 is optimally suited for the preferred axial movement of the catch element 21 as drive movement. The nature of the force transmission can be modified within wide limits and can be achieved using a different construction.
The outer housing 24 is part of the force transmission path from the actuation button 23 of the ejection mechanism 22 to the pipette tips 14 at the bottom of the displacement part 7 that surrounds the cylinder/piston arrangements 8 of the displacement part 7. The outer housing 24 is axially movable relative to the cylinder/piston arrangements 8, more specifically relative to their cylinders 12, which are held together by the cylinder bar 12′.
An outer housing 24 axially movable counter to a spring force with use as an ejector for the pipette tips 14, can be employed, as known in the prior art. The outer housing 24, closed by a housing lid 25, can be moved by means of the ejection mechanism 22, counter to the spring force, over a defined ejection stroke A, as shown in in
If the actuation button 23 of the ejection mechanism 22 has been pressed down sufficiently, the form-fit configurations 20 disengage from one another, as a result of the function of the catch element 21. If the user holds the actuation button 23 in this position, the user can turn the outer housing 24 of the displacement part 7 in the release direction. In this state, the rotary bearing 19 is blocked and the connection part 17 is taken along, so that the matching threaded element 18 on the connection part 17 detaches itself from the threaded connection element 16 on the support part 15. The displacement part 7 can be removed from the grip part 2.
The construction explained above also allows the unscrewing to be done by continuous pulling of the outer housing 24 of the displacement part 7 in the direction away from the grip part 2. Then, the actuation button 23 of the ejection mechanism 22 does not have to be kept permanently pressed down.
The jacket 27 is integrally formed on and protruding upward from the housing lid 25 of the outer housing 24 and carries the radially inwardly protruding carriers 28. The outwardly curved ends of the carrier arms 26 formed integrally on the catch element 21 engage under these carriers 28. Starting from the position in
The inwardly protruding carriers 28 on the jacket 27 are also used for blocking the rotary bearing 19 during the manual release action. For this purpose, inwardly protruding rotation-transmission ribs 30 are formed on the carriers 28, and opposite these, outwardly protruding rotation-transmission grooves 31 are formed on the connection part 17 at a considerable axial distance from the form-fit configurations 20. In
Rotation-transmission ribs 30 and rotation-transmission grooves 31 can be realized, for example, in the form of matching outer and inner teeth, and visa versa.
The catch element 21 is coupled to the connection part 17 fixedly in the direction of rotation, otherwise the form-fit configurations 20 could not come into action.
In
Most parts of the pipette are expediently produced from an injection-moldable theromoplastic, for example, from polypropylene reinforced with minerals, from ABS or polycarbonate. The spring elements can be made of other materials, in order to permanently retain the necessary spring forces, even under the conditions of frequent autoclaving. The improved multichannel pipette is particularly advantageous by virtue of the fact that it can be autoclaved in the assembled state.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 006 076.0 | Feb 2007 | DE | national |
