EP2280779B1

EP2280779B1 - Pipette with a knob

Info

Publication number: EP2280779B1
Application number: EP09725898A
Authority: EP
Inventors: Mikael Lind; Vesa Salo; Kari Järvimäki; Tapani Pullinen
Original assignee: Thermo Fisher Scientific Oy
Current assignee: Thermo Fisher Scientific Oy
Priority date: 2008-03-28
Filing date: 2009-03-26
Publication date: 2012-05-09
Anticipated expiration: 2029-03-26
Also published as: CN101980786A; WO2009118456A1; ATE556777T1; EP2280779A1; FI20080247L; CN101980786B; FI120672B; FI20080247A0

Abstract

The invention relates to a pipette comprising a volume adjustment mechanism, with which the stroke of piston may changed by turning the rod. The rod (10) comprises a knob (11) having a lower position and an upper position so that when the knob is rotated, in the lower position the rod does not rotate with the knob but in the upper position it rotates. So the change of volume setting by accident is prevented.

Description

Field of technology

The invention relates to liquid dispensing and concerns a pipette, in which the volume to be dispensed is set by turning the knob of piston rod.

Background of the technology

For instance in laboratories, piston pipettes are used for dispensing liquids, the pipettes comprising a piston rod extending above the handle and having a knob at the end. The piston can thus be moved by the knob. Also such pipettes are used, in which the length of the piston's suction stroke, and thus the volume to be dispensed, may be set by turning the knob. Such a pipette is known e.g. from publication FI 64752 (corresponds e.g. to EP 112887 ). There have also been on the market these kinds of pipettes, in which the top part of the knobs turns freely (Socorex Acura® manual, Socorerx Isba S.A., Switzerland, and Finnpipette® F3, Thermo Fisher Scientific Oy, Finland). Hereby, when the knob is pressed, the volume setting is not easily changed by accident. When the volume is adjusted, the lower part of the knob must be turned.

General description of the invention

A pipette according to claim 1 has now been invented. The other claims describe some preferable embodiments thereof.
In the pipette according to the invention, the dispensing volume is adjusted by turning the piston rod. On the rod, preferably at its end, there is a knob, which has a lower position in which the knob turns freely around the rod. The dispensing volume can thus not be changed in this position. The knob can however be moved from the lower position to an upper position, in which the knob turns together with the rod and the volume can thus be adjusted by turning the knob. The invention provides first of all the advantage that the volume may not be changed by accident when pipetting. And when adjusting the volume, one can hold the knob easily and firmly in the way that suits best. In the pipettes of this art, the piston rod is usually provided with some kind of a friction locking so that the rod could not turn by accident. Now the force used for the locking may be decreased, whereby a simpler and less wearing structure is achieved. Because of the smaller friction also the adjustment is easier. Also the turning knob increases the ergonomics of the pipette.
The structure according to the invention may be realized e.g. with indentations. For instance such that the rod comprises a circumferential indentation and the knob comprises a counterindentation, which, in the lower position of the knob, is located below the indentation of the rod, and, in the upper position, attached to the indentation of the rod thus preventing the turning of the knob in relation to the rod.
In practice the knob must further comprise some kind of a holding mechanism, which prevents the knob from coming off the end of the rod. The locking mechanism may be especially preventing by form. It may e.g. comprise flanges of different size in the knob and rod, which flanges prevent the knob from coming off.
The knob may comprise a locking mechanism of the upper position, which mechanism prevents the knob from transferring by itself to the lower position. The transfer requires a force of at least a certain size, by which the knob has to be pressed. This increases the convenience of the volume adjustment. In the lower position there may be a locking mechanism, which prevents the knob from transferring accidentally to the upper position. The locking mechanisms may be realized e.g. with the help of magnets or springs. A magnet mechanism may have a magnet especially in the knob. Then, even if the both mechanisms were realized, only one magnet is needed. The magnet may be especially a ring magnet.
Volume control may be arranged so that on the piston rod there is a thread and a nut fitted upon it, which nut has been arranged as nonrotatable in relation to the housing but as gliding in the lengthwide direction of the housing. The housing has a stoppage, which together with nut determines the upper position of the piston. One such pipette is known from the publication FI-64752 mentioned above. Therein the set volume is displayed by means of a series of digit wheels. It comprises coaxially with the piston a disc, which rotates in a stepwise manner with the piston and which in turn in a stepwise manner rotates the first digit wheel in the series of digit wheels, which digit wheel in turn always after a certain amount steps by the connection of a transmission wheel rotates the next wheel and so on. This kind of mechanism has been presented also e.g. in WO 2005/050554 .

Drawings

The accompanying drawings form a part of the written description of the invention and relate to the detailed description of some embodiments of the invention presented below. In the drawings, Figure 1 shows a pipette in accordance with the invention as a sectional view, the knob of the rod being in the lower position, Figures 2a and 2b show the upper end of the piston rod and the knob as an enlarged view, the knob being respectively in the lower position and in the upper position, Figure 3 shows the upper part of the knob from below as a perspective view, and Figure 4 shows the lower part of the knob and the end of the rod from above as a perspective view.

Detailed description of some embodiments of the invention

The pipette according to Figure 1 comprises a housing 1 with a tip portion 2 at its lower end, a tip container, i.e. a tip, being fixed to the lower end of the tip portion. A sliding tip ejector sleeve 3 surrounds the tip portion. It is extended by a tip ejector button 4, which, for reducing the necessary driving force, is urged to move relative to the handle by means of a wheel 5 (cf. FI 92374 corresponding e.g. to publication EP 566939 ). A return spring 6 for the tip ejector is disposed on the side of the housing. A handle portion 7 shaped so as to fit the user's hand is disposed on the housing. The body comprises a finger support 8 at its top part.
The tip portion 2 is perforated with a circular hole, which continues as a hole passing through the body 1, too. In the tip portion there is a piston 9 extended by a piston rod 10. The lower part of the rod is sleeve-like and disposed around the upper part of the piston. The upper part of the rod is narrower, extending through the housing. A knob 11 is provided at the upper end of the rod. At the upper part of the tip portion, the hole has an expansion, and at its bottom an O-ring 12 for sealing the piston against the tip portion. The O-ring is pressed from above by an O-ring spring 13 disposed between the housing and the tip portion.
The piston rod 10 comprises an adjustment thread equipped with an adjustment nut 14, whose rotation relative to the body is prevented by means of longitudinal guides and grooves. When the rod is rotated, the nut is consequently moved in the longitudinal direction of the rod. The body comprises a stopper 15, against which the adjustment nut and hence the piston are pressed from below by a primary spring 16. In other words, the adjustment nut and the stopper determine the upper limit of the piston stroke. A sleeve-like secondary support 17 has been slidingly disposed around the upper part of the rod, the secondary support having an internal flange at its lower end. Above the secondary support, a calibration nut 18 is fitted with a thread into the bore of the housing, the secondary support being pressed against the calibration nut from below by means of a secondary spring 19, which has greater force than the primary spring. The upper end of the rod comprises fixedly a thicker upper sleeve 20, which has been arranged to move within the calibration nut and the secondary support. However, the sleeve has a larger diameter than the diameter of the hole formed by the lower flange of the secondary support. Together with the flange of the secondary support, the lower end of the sleeve thus determines the lower limit of the piston stroke. When liquid is aspirated into the tip, the piston is pressed against this lower limit and is then allowed to return towards the upper limit. When liquid is removed from the tip, the piston is pressed further against the force of the secondary spring so as to pass by the lower limit in order to eject the liquid as completely as possible. (Similar arrangements have been explained e.g. in publications FI 64752 , corresponding to EP 112887 , and in EP 737515 ).
A first digit wheel 21 is fitted around the piston rod 10 so as to rotate along with this. The upper end surface of the first digital ring comprises a stop notch matching each reading on the ring, the stop notch mating with a boss on a non-rotary ring spring 22 (cf. FI 92374 ). In this manner, the piston rod will rotate and get locked step-wise. The first digit wheel is connected over a first sprocket wheel 23 to a second digit wheel 24 located below, so that, after each revolution, the first digit wheel rotates the second digit wheel by one step. Similarly, the second digit wheel is connected with a third digit wheel 26 over a second sprocket wheel 25.
The upper end of the upper sleeve 20 comprises a broader cup 27 (Fig. 2a), the upper edge of which further comprises a broader edge flange 28. The inner wall of the cup has the shape of a slightly opening cone. The bottom of the cup comprises a hole in its middle. The end of the piston rod 10 comprises a pin 29, which is thinner than the rod itself and which extends through the hole into the cup. The outer side of the edge flange is surrounded by an indentation 30. Around the cup, there is a fitted cap 31 above and a holding ring 32 below, the holding ring being fixed to the cap. At the lower edge of the holding ring there is a holding flange 33, the inner diameter of which is smaller than the outer diameter of the edge flange of the cup but large enough so that the holding ring is able to slide on the enlargement of the upper sleeve. At the lower edge of the cap, there are symmetrically four downward protrusions 34 so that the cap is able to slide on the cup. In the holding ring there are correspondingly four upward protrusions 35 (Fig. 4), which fit the spaces between the protrusion in the cap. Outside the protrusions, there is a circumferential groove and a ring 36 fitted in it. The protrusions have on the outer circumference a circumferential groove, and the ring respectively on the inner circumference a ridge fitting to the groove. The indentation of the edge flange of the cup has interruptions, so that the protrusions of the holding ring can be fitted between the protrusions of the cap. On the inner circumference of the holding ring there is a holding indentation 37 mating the indentation of the edge flange in the cup. The upper edge of the holding indentation is wedge-shaped, so that the indentations settle comfortably interlocked, when the holding ring is lifted.
When the knob 11 is in its lower position, it rotates freely relative to the upper sleeve 20 and thus also relative to the piston rod 10, and the volume setting is consequently not changed. When the knob is lifted to the upper position, the indentations 30 and 37 settle interlocked, whereby, when the knob is rotated, the upper sleeve and the rod rotate with, and thus the volume setting can be changed.
On the bottom of the cup there is a ferromagnetic concave lower ring 38, which is attached between the edges of the cup and the pin 29. The cap has in its middle a downward claw pin 39, to which a ring magnet 40 is attached. Above this, on the upper edge of the cup, there is further attached a ferromagnetic upper ring 41. When the knob 11 is in its lower position, the magnet is attached to the lower ring, and the knob may be lifted only by using a sufficient force. In the upper position of the knob, the magnet is correspondingly attached to the upper ring, and the knob may be pressed down only by using a sufficient force.
The protrusion 35 of the holding ring 32 comprises a sideways dent 42 and in the inner side of the ring 36 there is a counterindentation 43 (Figs. 3 and 4). Thus the rotation of the ring has been prevented.

Claims

A pipette comprising
- a housing (1) with an upper end and a lower end,

- in the housing, a cylinder (2) with an upper end and an open lower end,

- in the cylinder, a piston (9) having a rod on the upper end side of the cylinder,

- a mechanism, with which the stroke of the piston may changed by turning the rod,
characterised in that
- the rod (10) comprises a knob (11) having a lower position and an upper position relative to the rod so that, when the knob is rotated, in the lower position the rod does not rotate with the knob but in the upper position the rod rotates with the knob.
A pipette according to claim 1, wherein the rod comprises an indentation (30) and the knob comprises a counterindentation (37) so that in the upper position the indentations are interlocked preventing the knob rotating relative to the rod.
A pipette according to claim 1 or 2, wherein there is a locking mechanism so that the knob may be transferred from the upper position to the lower position only by using a sufficiently big force.
A pipette according to any of claims 1 to 3, wherein there is a locking mechanism so that the knob may be transferred from the lower position to the upper position only by using a sufficiently big force.
A pipette according to claim 3 or 4, wherein the locking mechanism comprises a magnet (40).