DOSAGE PIPETTE

Abstract: A pipette which is provided with a piston, with a toothed rack connected with the piston, with a striking pin resting against the toothed rack, and with a dosage lever mounted on the striking pin. By depressing the lever, the filled pipette can be emptied as successive doses of specified magnitude. The pipette is additionally provided with a lifting lever (20) placed at the side of the toothing, the distance of the said lever from the end of the toothed rack being adjustable (24) as desired and the said lever permitting the striking pin to push the toothed rack over a specified distance only. In this way, it is possible to adjust the magnitude of the emptying step as desired. Moreover, the toothed rack is provided with a second toothing (5), a cogwheel (7) resting against it and, at the other side, resting against a second toothed rack (11), whose top end is provided with a press knob (12). By pressing this knob downwards, the toothed dosage rack with its piston is shifted to its upper position, and the pipette is filled.

Description: Dosage pipette The invention described herein is concerned with a pipette which is provided with a piston and a cylinder and with two operating knobs, whereat, by means of one of the said knobs, the cylinder can be filled with liquid by depressing the knob once, and by means of the other one of the knobs, the cylinder can be emptied stepwise by means of successive depressions of the piston, of desired magnitude. There may be one or several piston-cylinder assemblies. Several types of such so-called step pipettes are known in prior art, e.g., a pipette in accordance with the published Finnish Patent Application FI 802,403 or the pipette as per the German published Patent Application DE ' 2,926,691 (= GB 2,057,581) . The said prior-art pipettes, however, often involve the drawback that the filling lever must be operated by lifting, whereby two hands are usually required. Moreover, when the prior-art apparatuses are used, an error is often produced when, by mistake, the last dose is also dosed, in which case the piston can no longer be displaced over a sufficiently long distance. Now, a dosage pipette has been invented in which, in a way in itself known, the piston has been connected with a toothed rack, which can be pushed out¬ wards from the pipette by steps of specified magnitude by means of the dosage lever and a striking pin mounted on same. A novelty of the pipette is a resilient lifting lever placed at the side of the toothing, the distance of the said lifting lever from the end of the toothed rack being adjustable to the desired level and the said lever being provided with a cam which lifts the striking pin apart from the toothing for the time of the rising stage of the striking pin. The top end of the toothed rack should preferably be provided with a cam which, when the toothed rack approaches the bottom position, raises the lifting lever by the height of the toothing. Thereby the cam of the lifting lever raises the striking pin to such an extent that the striking pin no longer reaches the toothing when the lever is depressed. Moreover, the toothed rack is provided with a second toothing, with a cogwheel which rests against the said second toothing and which, at the other side, rests against a second toothed rack, which is provided with a press knob. The pipette is easy to operate, because it can be filled by one hand, while the other hand remains free, e.g., for the handling of test tubes. Moreover, the lifting-lever system described here is of simple construction and reliable in operation. By means- of the cam provided at the top end of the toothed rack, it is, moreover, possible to avoid the pipetting of the last, too little dose. The invention will be illustrated in more detail by means of the attached drawings. Figure I is a sectional side view of an embodiment, and Figure II is a certain sectional view of same as viewed from the top. Figure III shows a detail of the tip portion of a multi-tip pipette. The pipette comprises an oblong handle 1 , at whose lower end there is a cylinder 2, and in the cylinder a piston 3. The cylinder may be attached to the handle, e.g., by means of a bayonet socket. To the top end of the piston, a -toothed rack 4 parallel to the handle is attached, which rack is provided with two toothings 5 and 6. A striking pin 8 is pressed against the toothing 6 by the force of a spring 16, and the striking pin is mounted on a lever 9. The lever 9 is mounted on a shaft 15 located in the handle. Moreover, the lever is connected with a spring 19, which attempts to keep the lever in its upper position. The movement of the striking pin 8 is stopped at the lower position by a limiter 18. OMPI A cogwheel 7 operates in contact with the toothing 5 on the toothed rack 4 , which cogwheel is mounted on a shaft 10. At the other side, the cogwheel 7 operates in contact with a toothed rack 11 , whose top rΛ 5 end is provided with a press knob 12. At the side of the toothing 6 on the toothed rack 4, there is a resilient lifting lever 20 and, on the lever, a cam 21, which raises the striking pin 8 apart from the toothing 6 during the stage of upward 10 movement of the lever 9. The top end of the lifting lever is provided with a guide pin 23, which is fitted into a guide groove 25 provided in the adjusting wheel 24. The adjusting wheel is mounted on a shaft 26. The top end of the toothed rack 4 is addi- 15 tionally provided with a cam 22, which, as the toothed rack approaches its lower position, shifts the lifting lever 20 towards the striking pin 8. The pipette operates so that, when the lever 9 is in its upper position and when the striking pin 8 20 is, consequently, apart from the toothing 6 and when the piston 3 is in the cylinder 2 in its lower position, the press knob 12 is depressed, whereat the cogwheel 7 starts revolving and lifts the toothed rack 4 and, along with the rack, the piston 3 in the cylinder 2 upwards. 25 In this way, suction is generated in the cylinder 2, whereby the cylinder is filled with liquid 13. After the cylinder 2 has been filled com¬ pletely and the press knob 12 is in its lower position 14, the dosage can be started by means of the lever 9. 30 When the dosage lever 9 is depressed, the spring 16 presses the striking pin 8 into the toothing 6, whereat the striking pin 8 starts pushing the toothed rack 4 and the piston 3 downwards until the striking pin 8 meets the limiter 18 , against which the movement stops. 35 The spring 19 restores the dosage lever 9 back to its upper position upon completion of the depressing. Thereat, the striking pin 8 must jump over the toothing 6 until, near the upper position of the striking pin 8, the cam 21 of the resilient lifting lever 20 raises the striking pin 8 apart from the toothing 6. The dosage can be repeated until the toothed rack 4 and the piston 3 approach their lower position. Thereat, the cam 22 at the top end of the toothed rack 4 meets the lifting lever 20 and raises it by the height of the toothing 6. Thereat, on the other han , the cam 21 of the lifting lever 20 raises the striking pin 8 to such an extent that the striking pin no longer reaches the toothing 6 when the lever 9 is depressed again for dosage. Thereby, striking of the piston 3 against the bottom of the cylinder 2 is prevented, which striking might make the last dose inaccurate. When the adjusting wheel 24 is turned, the guide groove 25 shifts the lifting lever 20 upwards or downwards by the intermediate of the pin 23, whereat, correspondingly, at the bottom end of the lifting lever, the cam 21 is shifted and permits the striking pin 8 to move over the desired distance on the toothing 6, e.g. over 1, 2, 3, 4 or more teeth, per each depression of the dosage lever 9. In this way, a 1-, 2-, 3- or 4-fold dose is obtained. In Figures I and II, the toothings 5 and 6 are shown as located one after the other, but, if • desired, they may also be very well placed side by side on the toothed rack 4.

Claims: WHAT IS CLAIMED IS: 1. Dosage pipette, which is provided with a handle (1), with a cylinder (2) attached to the handle, with a piston (3) inside the cylinder, with a toothed dosage rack (4) attached to the piston, with a striking pin (8) resting against the dosage toothing (6) of the said rack, the said striking pin being mounted on a dosage lever (9) so that, when the dosage lever is depressed, the striking pin pushes the toothed rack outwards, c h a r a c t e r i z e d in that, at the side of the dosage toothing, there is a resilient lifting lever (20) , whose distance from the end of the toothed rack can be adjusted as desired by means of an adjusting device (24) and which lever is provided with a cam (21) , which raises the striking pin apart from the dosage toothing during the stage of upward movement, and that the toothed dosage rack is additionally pro¬ vided with a second toothing (5)ι, with a cogwheel (7) resting against the said toothing and, at the opposite side, resting against a second toothed rack (11), which is provided with a filling press knob (12) . 2. Pipette as claimed in claim 1, c h a r ¬ a c t e r i z e d in that the top end of the toothed dosage rack is provided with a cam (22) , which, when the toothed dosage rack approaches its lower position, pushes the lifting lever towards the striking pin so that the lifting lever, prevents the striking pin from reaching contact with the toothing. 3. Pipette as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the toothings on the toothed dosage rack are placed side by side. 4. Pipette as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the toothings on the toothed dosage rack are placed one after the other. OMPI 5. Pipette as claimed in any of claims 1 to 4, c h a r a c t e r i z e d in that the filling press knob is placed at the side of the handle. OMPI

Inventors: FAGERSTEDT MIKAEL, KASKI ERKKI, TERVAMAEKI JUKKA, FAGERSTEDT, MIKAEL, KASKI, ERKKI, TERVAMAEKI, JUKKA
Applicants: LABSYSTEMS OY
Application year: 1984
Main classification: B01L3
IPC codes: B01L3