Mechanical pipette with adjustable volume value of aspirated liquid

Abstract

Mechanical pipette with adjustable volume value of aspirated liquid is built of a handle (1) and a nozzle (3) and coupled with them: an ejection mechanism of a pipette exchangeable tip (8), a drawing up and discharging mechanism with a plunger (33) mounted in said pipette nozzle (3), a plunger working stroke adjustment mechanism, a manually actuated lock mechanism of a drive assembly of an adjustment screw of the plunger working stroke, a mechanical counter, a drive mechanism of a mechanical counter and a calibration mechanism for correction of the pipette accuracy deviation. The calibration mechanism comprises, mounted in the mechanical counter, releasable coupling means for complete disengagement of a revolvers assembly from the mechanical counter drive mechanism in CALIBRATION MODE, further, engaged with them, changeover means for changing over the pipette into CALIBRATION MODE and resetting means of the indication of the liquid volume value on the counter in CALIBRATION MODE.

Claims

1. A mechanical pipette with an adjustable volume value of aspirated liquid, comprising a handle and a nozzle, and coupled with said handle and said nozzle: a pipetting button connected with a plunger disposed in said pipette, a plunger working stroke adjustment mechanism screw, a mechanical counter responsive through a mechanical counter drive mechanism to rotation of the adjustment screw configured to indicate a volume value of liquid drawn-up by the pipette depending on an adjusted plunger working stroke, and a calibration mechanism configured to correct pipette deviation between the actual volume value of dispensed liquid and the liquid volume value indicated on said mechanical counter, said calibration mechanism comprising a releasable coupling which disengages said mechanical counter from said drive mechanism, and a manually operated reset element coupled with said mechanical counter configured to reset a liquid volume value indication on said mechanical counter while said mechanical counter is disengaged from said drive mechanism.

2. The pipette according to claim 1, wherein said releasable coupling is slidably and rotatably arranged on a counter axis.

3. The pipette according to claim 1, wherein said releasable coupling comprises a clutch gear-wheel and a counter clutch.

4. The pipette according to claim 1, wherein said releasable coupling comprises a two-stage torque value differentiator configured to induce a change of an angle position of said releasable coupling around a counter axis.

5. The pipette according to claim 4, wherein said torque value differentiator comprises a shape portion comprising an upper part having protrusions and a lower part having protrusions, the protrusions of the lower part being larger than the protrusions of the upper part.

6. The pipette according to claim 1, wherein said releasable coupling is engaged with said mechanical counter via a revolver sleeve, the revolver sleeve comprising longitudinal notches configured to receive longitudinal protrusions of said releasable coupling and the revolver sleeve further comprising a protrusion configured to engage a first revolver of said mechanical counter.

7. The pipette according to claim 1, further comprising a slider which is accessible from outside of the pipette and is engaged with said releasable coupling for selective disengagement and engagement of said releasable coupling.

8. The pipette according to claim 1, wherein said reset element comprises a shape end of a counter clutch for cooperation with a shaped end of a calibration wrench having a cross tongue.

9. The pipette according to claim 1, wherein said mechanical counter comprises an elastic element for continuous mutual pressing of mechanical counter structure elements along a counter axis.

10. The pipette according to claim 9, wherein said elastic element of said mechanical counter comprises a counter spring disposed under a clutch gear-wheel.

11. The pipette according to claim 1, wherein said drive mechanism comprises an adjustment sleeve with a toothed-wheel rim, a toothed gear with a double gear, and a clutch gear-wheel mounted rotatably and slidably on a counter axis, wherein said clutch gear-wheel includes a shape clutch that cooperates with a releasable counter clutch.

12. The pipette according to claim 1, further comprising a lock mechanism comprising a ratchet mechanism configured to prevent adjustment of an adjustment knob of the pipette.

13. The pipette according to claim 12, wherein said ratchet mechanism comprises ratchets which are formed on said adjustment knob.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention preferred embodiment, given as a non-restrictive example, is presented with reference to the attached drawings, wherein

(2) FIG. 1 presents the mechanical pipette with the adjustable drawn-up liquid volume value in the general view, in PIPETTING MODE with the plunger working stroke adjustment mechanism in LOCKED POSITION that is with the adjustment knob in its extreme lower position,

(3) FIG. 2presents the pipette from FIG. 1 in the longitudinal section with the enlarged cut fragment showing fastening of the revolvers axis with the counter spring and with the enlarged cut fragment showing the counter ratchet mechanism,

(4) FIG. 3presents the pipette in the longitudinal section in ADJUSTMENT MODE with the plunger working stroke adjustment mechanism in UNLOCKED POSITION that is with the adjustment knob in its extreme upper position,

(5) FIG. 4presents the pipette in the general view in CALIBRATION MODE with the depicted partial longitudinal section through the mechanical counter with the calibration wrench resting against the counter axis face and with the enlarged cut fragment of this area,

(6) FIG. 5presents in the exploded perspective view seen from the top the internal structure elements of the pipette handle,

(7) FIG. 6presents in the exploded perspective view seen from the bottom the internal structure elements of the pipette handle,

(8) FIG. 7presents in the perspective view the adjustment knob,

(9) FIG. 8presents the counter clutch in the perspective views and in the longitudinal section,

(10) FIG. 9presents the revolvers sleeve in the perspective view,

(11) FIG. 10presents the slider in the perspective view,

(12) FIG. 11presents the brake sleeve in the perspective view and in the longitudinal section,

(13) FIG. 12presents the main assemblies of the mechanical pipette handle in the exploded perspective view,

(14) FIG. 13presents the enlarged fragment of the handle, which cooperates with the slider,

(15) FIG. 14presents the enlarged fragment of the handle, which cooperates with the ejector push button, seen from the bottom, and

(16) FIG. 15presents the enlarged general view and the longitudinal section A-A of the ejector push button and its fragment showing the contact surface of the canopy notch which cooperates with the respectively canopy end of the ejector frame arm.

BEST MODE OF CARRYING OUT THE INVENTION

(17) The pipette with the adjustable volume of the aspirated liquid according to the invention in the preferred but non-limiting embodiment is presented in FIG. 1-15. Generally, this pipette is built of a handle 1 and a nozzle 3 and of coupled with them and cooperating with each other mechanisms which perform different functions of the mechanical pipette.

(18) In the pipette according to the invention, an improved ejection mechanism of an exchangeable tip 8 is applied, which provides the present pipette with important operational and structure advantages. The ejection mechanism constitutes a second-class lever and comprises a push button 4 of an ejector 2, which is rotatably mounted in the upper part of the pipette handle 1 and the ejector 2 which surrounds the pipette nozzle assembly and, between them, intermediate means for transferring the force from the push button 4 to the ejector 2. The rotation axis of the push button 4 of the ejector 2 is perpendicular to the pipette axis and is situated on the side of the pipette axis opposite to the point of the application by the user to the push button 4 of the force actuating the ejection mechanism. The intermediate means of the ejection mechanism comprise a frame 37 which cooperates with a sleeve 38 connected with the ejector 2. The push button 4 presses onto two parallel arms 37a of the frame 37 which is movable along the mechanical pipette axis. The frame 37, in turn, presses onto the sleeve 38 which is connected by a screw connection with the ejector 2 movable along the mechanical pipette axis, as shown in FIGS. 2 and 4. The arms 37a of the frame 37 are symmetrically arranged in relation to the pipette axis and are longitudinally guided in the handle 1 for improving symmetry of guidance of the exchangeable tip 8 along the ejector 2 during the ejection movement in TIP EJECTION MODE.

(19) A drawing up and discharging mechanism comprises a pipetting button 7 connected via a pipetting rod 11 with a plunger 33 mounted inside the pipette nozzle 3. On the nozzle 3, for performing PIPETTING MODE, the exchangeable tips 8 are seated with interference, as shown in FIGS. 1 and 2.

(20) A plunger working stroke adjustment mechanism is provided with a adjustment knob 5 coupled via an adjustment screw 12 with an upper stop 13 of the working stroke of the plunger 33 that is placed in a nozzle assembly. The plunger working stroke adjustment mechanism has two positions, namely, LOCKED POSITION for realization of PIPETTING MODE as shown in FIGS. 1 and 2 and UNLOCKED POSITION for realization of ADJUSTMENT MODE as shown in FIGS. 3 and 4.

(21) For the change of the position of the plunger working stroke adjustment mechanism, the pipette has a lock mechanism of the plunger working stroke adjustment mechanism, which is manually activated by displacement of the adjustment knob 5 along the pipette axis and between its extreme lower position in LOCKED POSITION of the plunger working stroke adjustment mechanism and its extreme upper position in UNLOCKED POSITION of the plunger working stroke adjustment mechanism. The lock mechanism comprises a brake assembly of the adjustment screw 12, which cooperates with the adjustment knob 5 and which comprises a brake sleeve 34 having a guiding arm 34c with a groove 34d for cooperation with rib 35a of a cover 35 of the handle 1 to precludes the rotation of the brake sleeve 34 and an adjustment sleeve 14 coupled with the adjustment screw 12, as shown in FIGS. 5 and 6. Such a rotational movement, which is eliminated in the present pipette, would cause the disadvantageous change of the setting of the drawn-up liquid volume value. The lock mechanism applied in the present pipette constitutes the releasable friction brake, which after its actuation provides the large braking moment exerted onto the plunger working stroke adjustment mechanism and prevents against an incidental changeover in PIPETTING MODE and in CALIBRATION MODE and, simultaneously, after its release enables the change of the setting of the plunger working stroke, which is necessary for the adjustment of the desired drawn-up liquid volume value.

(22) The plunger working stroke adjustment mechanism is in all pipette operational modes continuously engaged and coupled via the toothed gear of the drive mechanism with the clutch gear-wheel, and a revolvers assembly of the mechanical counter, in CALIBRATION MODE of the pipette, is disengaged from a clutch gear-wheel 17 which drives the revolvers assembly in ADJUSTMENT MODE of the pipette.

(23) A drive mechanism of the mechanical counter for indication of the volume value of the liquid drawn-up by the pipette in dependency on the plunger working stroke pre-set in ADJUSTMENT MODE, which is applied in the present pipette, comprises an adjustment sleeve 14 with a toothed-wheel rim 14a, the toothed gear with a double gear 16 as well as the clutch gear-wheel 17. The clutch gear-wheel 17 is mounted rotatably and slidably on a counter axis 24 and has in its upper part a shape clutch 17a that cooperates with the respectively formed lower part of a releasable counter clutch 18, which, in turn, by means of its protrusions 18e cooperates with respective notches 21b of a revolver sleeve 21, as shown in FIGS. 5, 6 and 8.

(24) A calibration mechanism which is applied in the present pipette for correction of the pipette accuracy deviation which constitutes the difference between the actual volume value of the dispensed liquid and the volume value of the liquid indicated on the counter, eliminates the above described disadvantageous phenomena present in the known pipettes in CALIBRATION MODE. This is due to the structure which enables disengagement of the drive of the counter revolvers assembly from the adjustment knob 5 without disengagement of the drive of the upper stop 13 from the adjustment knob 5 of the adjustment mechanism. For this purpose, in the mechanical counter the releasable coupling means are disposed. The releasable coupling means serve the complete disengagement, in CALIBRATION MODE, of the revolvers assembly from the drive mechanism of the mechanical counter and the plunger working stroke adjustment mechanism for the change of the indication of the drawn-up liquid volume value at the given setting of the plunger working stroke by means of resetting the angle location of the revolvers in the revolvers assembly. The releasable coupling means comprise the clutch gear-wheel 17 and the counter clutch 18 which is being disengaged from the clutch gear-wheel 17 and the toothed gear of the drive mechanism before the counter indication correction.

(25) The nozzle assembly with the nozzle 3 is screwed down to the lower part of the handle 1, and on the conical lower part of the nozzle 3 the exchangeable tip 8 is mounted.

(26) All mechanisms of the pipette according to the present invention will be described in detail together with the presentation of the subsequent operational modes of the pipette.

(27) The mechanical pipette with the adjustable volume of the drawn-up liquid according to the invention has the following operational modes, namely ADJUSTMENT MODE, PIPETTING MODE, CALIBRATION MODE and TIP EJECTION MODE.

(28) Adjustment Mode

(29) In the mechanical pipette according to the present invention, the drawn-up liquid volume value is indicated on the three- or four-position mechanical counter which is driven by the means of the toothed gear of the mechanical counter drive mechanism. The toothed gear via the adjustment sleeve 14 with the toothed-wheel rim 14a receives rotational movement from the adjustment screw 12 coupled with the adjustment knob 5 of the plunger working stroke adjustment mechanism. The toothed gear via the double gear 16 and the clutch gear-wheel 17 with the shape clutch 17a transfers this rotational movement and, simultaneously, multiplies this rotational movement onto three or four revolvers of the counter. The revolver of the revolvers assembly is also named in the technical field as the counter wheel or the number wheel of the mechanical counter. These revolvers of the counter are driven by means of pinions 23, 26, and possibly 28. In the drawings, there is presented the embodiment of the pipette according to the invention with four-position counter which four revolvers 22, 25, 27, 29 are driven by the three pinions 23, 26, 28.

(30) In order to change the setting of the volume value of the liquid drawn-up by the pipette, the pipette has to be changed over into ADJUSTMENT MODE i.e. the working stroke adjustment mechanism into UNLOCKED POSITION, and thus the lock mechanism of the plunger working stroke adjustment mechanism needs to be released by release of the friction brake.

(31) The adjustment of the drawn-up liquid volume value is realized in the pipette ADJUSTMENT MODE, shown in FIG. 3 and FIG. 4. To changeover the pipette from PIPETTING MODE, shown in FIG. 1 and FIG. 2, to ADJUSTMENT MODE the adjustment knob 5, shown in enlargement in FIG. 7, has to be moved from its lower extreme position into its upper extreme positionuntil the ratchets 5b of the adjustment knob 5 jump into grooves 12c of the adjustment screw 12, see FIGS. 5 and 6. This displacement of the adjustment knob 5 causes the upward movement of the brake sleeve 34 of the brake assembly of the adjustment screw 12 of the lock mechanism of the plunger working stroke adjustment mechanism. The brake sleeve 34, shown as enlarged in FIG. 11, is engaged with the adjustment knob 5 by means of a yoke 34a which is located in a circumferential groove 5a of the adjustment knob 5, what enables free rotating the adjustment knob 5. The brake sleeve 34 is protected against the rotation in relation to the pipette axis by means of a guiding arm 34c which groove 34d cooperates with a rib 35a of a cover 35 od the handle 1, see FIG. 12.

(32) The displacement of the adjustment knob 5 to its upper extreme position causes that two braking cones: a cone 34b of the brake sleeve 34, shown in FIG. 11, and a cone 14d of the adjustment sleeve 14, shown in FIG. 5, move away from each other, which results in the decay of friction forces between these two conic surfaces. This enables to change the setting of the volume value of the liquid drawn-up by the pipette. The plunger working stroke adjustment mechanism is in UNLOCKED POSITION in which the pipette ADJUSTMENT MODE is being performed.

(33) When the adjustment knob 5 is moved into its lower extreme position, the friction forces between the cone 34b of the brake sleeve 34 and the cone 14d of the adjustment sleeve 14 are induced and the possibility of the rotation of the adjustment sleeve 14 in relation to the pipette axis is locked. The plunger working stroke adjustment mechanism is in LOCKED POSITION in which the pipette PIPETTING MODE is being performed.

(34) The blockade of the setting of the desired drawn-up liquid volume value is particularly required feature of the mechanical pipette because it prevents against the incidental change of the setting and thereby guarantees the required reliability of the liquid drawn-ups taken. The high value of the force necessary to be applied by the user to the adjustment knob 5 and needed to the pipette changeover from PIPETTING MODE into ADJUSTMENT MODE prevents against an unintended changeover.

(35) Additionally, due to application in the present pipette the ratchet mechanism, the possibility of the location by the user of the adjustment knob 5 in the position between two operational modes of the pipette, namely between ADJUSTMENT MODE and PIPETTING MODE, was eliminated. The ratchet mechanism applied in the lock mechanism of the present pipette comprises the ratchets 5B formed on the adjustment knob 5, which ratchets 5b in the pipette ADJUSTMENT MODE cooperate with the grooves 12c of the adjustment screw 12.

(36) ADJUSTMENT MODE in the mechanical pipette according to the present invention is performed in UNLOCKED POSITION of the plunger working stroke adjustment mechanism and consists in that the desired volume value of the liquid drawn-up by the pipette is manually set by turning the adjustment knob 5 which is in its upper extreme position. The adjustment knob 5 is coupled with the adjustment screw 12, the rotational movement of which induces linear movement of the upper stop 13. The upper stop 13 determines the working stroke of the plunger 33 and constitutes a nut cooperating with the adjustment screw 12, as shown in FIGS. 5 and 6. In ADJUSTMENT MODE, by means of the adjustment knob 5 and the adjustment screw 12 of the plunger working stroke adjustment mechanism, the position of the upper stop 13 is being changed.

(37) The upper stop 13 is protected against the rotation by means of its longitudinal ribs 13a cooperating with guiding grooves 15a on the inner surface of a bearing sleeve 15, as shown in FIGS. 4 and 5. The screw 12 is axially fixed in the bearing sleeve 15 by means of a lock 32. The lock 32 is seated in a circumferential groove 12a of the adjustment screw 12 and in rectangular openings 15b of the bearing sleeve 15. The upper stop 13 is a limiter of the upper position of the pipetting rod 11 which abuts with the upper surface 11c of the circumferential tongue 11b on the lower surface 13b of the upper stop 13. The spherical lower end 11a of the pipetting rod 11 contacts with and affects the pipette plunger 33, which executes the axial movement for aspiration and discharge of the desired volume value of the liquid drawn-up by the pipette, as shown in FIG. 4. Rotating with the adjustment knob 5, which is engaged with the adjustment screw 12 by means of notches 5c cooperating with ribs 12d of the adjustment screw 12, causes the rotation of the adjustment sleeve 14 of the drive mechanism. The adjustment sleeve 14 is mounted on the adjustment screw 12 by means of notches 14b cooperating with the ribs 12d of the adjustment screw 12, see FIGS. 5 and 6. The adjustment sleeve 14 has in its lower part the toothed-wheel rim 14a coupled with the double gear 16, which, in turn, drives the clutch gear-wheel 17. The clutch gear-wheel 17 has in its upper part a shape clutch 17a which, in ADJUSTMENT MODE, cooperates with the respectively shaped lower portion 18a of the counter clutch 18, shown in enlargement in FIG. 8. The counter clutch 18 is a structure element of the releasable coupling means of the calibration mechanism, which serve to complete disengagement in CALIBRATION MODE of the revolvers assembly from the drive mechanism of the mechanical counter. The counter clutch 18 is continuously engaged by means of the longitudinal protrusions 18e with the notches 21b of the revolver sleeve 21. The revolver sleeve 21, which is shown in enlargement in FIG. 9, causes by means of the protrusion 21a driving of the first revolver from the revolvers assembly, namely the counter revolver 22. The counter revolver 22, in turn, drives by means of the pinion 23 the counter revolver 25. The counter revolver 25, in turn, drives by means of the next pinions 26, 28 the next revolvers 27, 29 of the revolver assembly, which are mounted ratatably on the revolver sleeve 21.

(38) The plunger working stroke adjustment mechanism is in all pipette operational modes continuously actuated and continuously engaged via the toothed gear of the drive mechanism with the clutch gear-wheel 17. The mechanical counter assembly comprises the clutch gear-wheel 17, the counter clutch 18, the revolvers sleeve 21, the revolvers 22, 25, 27, 29 and the pinions 23, 26, 28. The mechanical counter assembly is continuously pressed to the counter cover 30 in results of application of a counter spring 19 which via a washer 20 exerts the axial force onto the lower surface of the clutch gear-wheel 17. Due to such a construction, all clearances between the structure elements of the mechanical counter assembly are continuously compensated. Further, also dimensional changes of the structure elements, which appear in results of the thermal expansion of materials during the process of autoclaving, are compensated. The application of the counter spring 19 guarantees the operational reliability of the counter assembly due to elimination of possible indication errors which arise in consequence of the positions change of the structure elements of the counter assembly in results of the clearances appearing in the course of the pipette operating and in the course of the autoclaving process.

(39) For discretisation of the counter indications, in the mechanical counter assembly in the pipette according to the present invention, the ratchet mechanism is applied. The ratchet mechanism comprises an elastic click 30a of the counter cover 30, as shown in FIGS. 2 and 5, and the shape portion 18c which is respectively shaped and is formed on the counter clutch 18, as shown in FIG. 8. The elastic click 30a is pressed to the shape portion 18c of the counter clutch 18 due to operation of the spring 31 acting, as shown in FIG. 2. The structure of the shape portion 18c of the counter clutch 18 enables the torque value differentiation, which torque is necessary for the change of the angle position of the counter clutch 18 in relation to the counter axis 24 and in dependence on the current operational mode of the pipette. The technical means for two-stage differentiation of a torque value, with which the present pipette is provided, comprise the shape portion 18c which has in its upper part the smaller protrusions 18f for cooperation with the elastic click 30a of the counter cover 30 in ADJUSTMENT MODE and has in its lower part the larger protrusions 18g for cooperation with the elastic click 30a of the counter cover 30 in the pipette CALIBRATION MODE.

(40) And thus, in ADJUSTMENT MODE, the counter clutch 18 is driven via the toothed gear which comprises the adjustment sleeve 14 which has in its lower part the toothed-wheel rim 14a coupled with the pinion 16a of the double gear 16. The gear 16b of the double gear 16, in turn, further drives the clutch gear-wheel 17, as shown in FIG. 5. The overall gear ratio of this toothed gear is equal of, for example, 10:1, and thus the complete single rotation of the adjustment knob 5 around the pipette axis causes ten, 10, complete rotations of the counter clutch 18 around the counter axis 24.

(41) The effect of application between the adjustment knob 5 and the counter clutch 18 the toothed gear with gear ratio of 10:1, is the necessity to exert by the user onto the adjustment knob 5 the torque which is 10 times larger than the torque transferred by the counter clutch 18 and which is indispensable for the change of the angle position of the counter clutch 18 around the counter axis 24. For decrease the torque on the counter clutch 18 and in consequence on the adjustment knob 5, in the upper part of the shape portion 18c, the smaller protrusions 18f were formed on the counter clutch 18. The smaller protrusions 18f are different form the larger protrusions 18g in the lower part of the shape portion 18c. In such a way, the resistance moment caused by the deflection of the elastic click 30a of the counter cover 30 during rotation of the counter clutch 18 has been decreased. Thus, in pipette ADJUSTMENT MODE, the elastic click 30a of the counter cover 30 cooperates with the upper part of the shape portion 18c of the counter clutch 18, which has the smaller protrusions 18f which provide the less value of the torque necessary to induce the change of the angle position of the counter clutch 18. Due to such a structure, the change of the mechanical counter indication in result of the change of the setting of the volume value of the drawn-up liquid is easier in ADJUSTMENT MODE of the pipette.

(42) Pipetting Mode

(43) In PIPETTING MODE of the pipette, the plunger working stroke adjustment mechanism has to be in LOCKED POSITION and the lock mechanism has to be actuated i.e. the friction brake in the described preferred embodiment of the pipette is in the actuated position as shown in FIGS. 1 and 2.

(44) After adjustment of the desired volume value of the drawn-up liquid, the pipette is being changed over from ADJUSTMENT MODE into PIPETTING MODE via the displacement of the adjustment knob 5 to its lower extreme position and the plunger working stroke adjustment mechanism is being entered into LOCKED POSITION. In this position, between the cone 34b of the brake sleeve 34 and the cone 14d of the adjustment sleeve 14 of the brake assembly of the adjustment screw 12 of the lock mechanism of the plunger working stroke adjustment mechanism, the friction forces are induced.

(45) For the execution of PIPETTING MODE, the pipette has the drawing up and discharging mechanism which is mounted inside the handle 1 and the nozzle 3. The drawing up and discharging mechanism comprises the pipetting button 7 on the pipette upper end above the handle 1, which is connected via the pipetting rod 11 with the plunger 33 disposed in the pipette nozzle 3.

(46) The user, by the pipetting button 7, pushes the pipetting rod 11 downwards and then this movement is via a spherical lower end 11a of the pipetting rod 11 transferred onto the plunger 33 inside the nozzle 3 and against the force of the pipetting spring. In the pipette PIPETTING MODE, during downward movement the plunger 33 push out an air from the nozzle 3 outside the end 8. When the pipetting rod 11 is pushed home, the plunger 33 stops in its lower position. When the tip 8 is dipped in the liquid and the pipetting button 7 is released, the plunger 33 under action of the pipetting spring returns to its upper position and simultaneously aspirates the liquid to the tip 8. For tip evacuation, the pipetting button 7 has to be again pressed down so that the plunger 33 moves to its lower position.

(47) In the pipette PIPETTING MODE, there is also being controlled how much the actual volume value of the liquid drawn-up by the pipette differs from that indicated by the counter. This difference between the actual volume value of the liquid drawn-up by the pipette and the liquid volume value indicated by the counter is called the pipette accuracy deviation. For this purpose, the series of the liquid drawn-ups is carried out, and then their weight measures and on this basis the actual pipette drawn-up liquid volume value is being determined at the given adjustment of the plunger working stroke i.e. at the given counter indication. In the case when the difference between the desired pipette drawn-up liquid volume value and the actual volume value is ascertained, these different volume values are being brought into conformity with each other by correction of the pipette accuracy deviation i.e. by the change of the mechanical counter indication into the actual volume value of the liquid drawn-up by the pipette. The change of the mechanical counter indication is carried out in CALIBRATION MODE.

(48) Calibration Mode

(49) In the case when the discrepancy between the aspirated liquid volume value and the volume value indicated on the counter is observed, the pipette should be calibrated. The calibration in the presented pipette is based on resetting of the mechanical counter indication to the actual volume value of the drawn-up liquid.

(50) During CALIBRATION MODE, in the calibration mechanism, the drive of the mechanical counter revolvers assembly is completely disengaged from the toothed gear of the mechanical counter drive mechanism, wherein the adjustment knob 5 of the plunger working stroke adjustment mechanism remains in the continuous coupling with the upper stop 13 of the plunger working stroke in LOCKED POSITION of the plunger working stroke adjustment mechanism.

(51) The disengagement is in the present pipette possible due to application in the calibration mechanism and exactly in the mechanical counter the releasable coupling means. The releasable coupling means are engaged with changeover means changing over the pipette into CALIBRATION MODE and are also engaged with resetting means for resetting the indication of the liquid volume value on the counter in CALIBRATION MODE.

(52) The releasable coupling means are slidably and rotatably mounted on the counter axis 24. The releasable coupling means comprise the clutch gear-wheel 17 and the counter clutch 18 and are coupled with the revolvers assembly via the revolver sleeve 21 which is provided with the longitudinal notches 21b for receiving the longitudinal protrusions 18e of the coupling means and with the notch 21b for engagement with the first revolver 22 of the counter revolvers assembly.

(53) The changeover means for changing over the pipette into CALIBRATION MODE enable the disengagement of the coupling means, together with the revolvers assembly coupled with them, from the drive mechanism. The changeover means comprise a slider 9 which is accessible from outside, and, preferably, a flat end 39a of the calibration wrench 39.

(54) The resetting means, in the preferred embodiment here described, comprise the shape end 18d of the counter clutch 18 for cooperation with the respectively shaped the second end of the calibration wrench 39, which is provided with the cross tongue 39b.

(55) In order to carry out the pipette calibration, the adjustment knob 5 should be placed in its lower extreme position i.e. the same way like in PIPETTING MODE in LOCKED POSITION of the plunger working stroke adjustment mechanism with the lock mechanism activated. Then, the plug 6 should be taken out from the opening 4b of the ejector push button 4 with the assistance of the calibration wrench 39 which flat end 39a should be entered in a caving 4a of the push button 4 of the ejector 2 in order to lever the plug 6, see FIGS. 2 and 5.

(56) In the next step, the flat end 39a of the calibration wrench 39 provided with the pipette should be introduced into a longitudinal socket 9a of the slider 9, which is shown in enlargement in FIG. 10, and should be moved from its lower extreme position to its upper extreme position until catch pawls 9b skip from lower grooves 1a of the handle 1 into upper grooves 1b of the handle 1. The lower grooves 1a and the upper grooves 1b are shown in enlargement in FIG. 13. In such a way, by means of the changeover means the pipette is changed over into CALIBRATION MODE. The upward displacement of the slider 9 coupled with the counter clutch 18 by means of the slider yoke 9d, which yoke 9d is placed in the circumferential groove 18b of the counter clutch 18, causes the axial displacement of the counter clutch 18 along the counter axis 24. The axial displacement of the counter clutch 18 causes disengagement of the counter clutch 18 from the shape clutch 17a, see FIG. 5.

(57) Further, the calibration wrench 39 should be inserted with its end with the cross tongue 39b into the opening 4b of the push button 4 of the ejector 2 so that its end with the cross tongue 39b hits the respectively formed shape end 18d of the counter clutch 18, which is shown in enlargement in FIG. 8. After engaging the cross tongue 39b with the counter clutch 18, the change of the indication in the pipette counter is possible due to turning with the calibration wrench 39 and without the change of the position of the upper stop 13 which is mounted in the plunger working stroke adjustment mechanism. Thereby the change of the indication in the pipette counter is possible without the change of the setting of the volume value of the liquid drawn-up by the pipette. In such a way, by the resetting means the respective change of the liquid volume value indication is being performed on the counter.

(58) For performing CALIBRATION MODE, the disengagement of the mechanical counter revolvers assembly of the shape clutch 17a of the clutch gear-wheel 17 from the toothed gear of the drive mechanism has to be carried out, wherein the toothed gear remains in continuous engagement with the plunger working stroke adjustment mechanism.

(59) In order to prevent the pipette from the incidental changeover from CALIBRATION MODE to PIPETTING MODE by an unintentional and incidental downwards pressing the counter clutch 18 due to the non-competent or careless introducing of the calibration wrench 39 into the shape end 18d of the counter clutch 18, the counter axis 24 has the respective length. This counter axis length is chosen such that the end of the calibration wrench 39, which has the cross tongue 39b formed, in the course of turning in CALIBRATION MODE with the counter clutch 18 for the change of the counter indication is continuously abutted against the face 24a of the counter axis 24 and simultaneously does not exert the pressure on the face 18h of the shape end 18d of the counter clutch 18, as shown in FIG. 4 and FIG. 8. In such a way, it is not possible for the user to move axially the counter clutch 18 downwards by accident that is incidental changeover of the pipette into PIPETTING MODE by unintentional exertion of the pressure on the counter clutch 18 has been eliminated.

(60) In CALIBRATION MODE, during the upward displacement of the slider 9 coupled by means of the circumferential groove 18b with the counter clutch 18, the displacement of the counter clutch 18 takes place. This is such a displacement that the elastic click 30a of the counter cover 30 starts to cooperate with the lower part of the shape portion 18c of the counter clutch 18. The shape portion 18c forms technical means for two-stage differentiation of the torque value which is indispensable to induce the change of the angle position of the coupling means around the counter axis 24. The shape portion 18c is in its lower part provided with the larger protrusions 18g for cooperation with the elastic click 30a of the counter cover 30, respectively, in the pipette CALIBRATION MODE.

(61) In this system, the resistance moment caused by deflection of the elastic click 30a during the rotation of the counter clutch 18 by means of the calibration wrench 39 is larger then the torque on the counter clutch 18 in ADJUSTMENT MODE. However, in CALIBRATION MODE, the torque which is exerted by the user during the rotation with the calibration wrench 39 is still significantly less than the torque which is exerted on the adjustment knob 5 in ADJUSTMENT MODE because of the lack of any gear ratio. However, in order to increase the calibration accuracy, the discrete leap of the mechanical counter indication has to be well recognized by the user. Therefore, in CALIBRATION MODE, the elastic click 30a cooperates with the larger protrusions 18g formed on the lower part of the shape portion 18c of the counter clutch 18, which increases the resistance moment caused by the deflection of the elastic click 30a during the rotation of the counter clutch 18 by means of the calibration wrench 39. Thus, the torque value, which has to be overcome and has to be exerted by the user during turning with the calibration wrench 39, increases.

(62) The discretization of the change of the counter indication is, thus, in CALIBRATION MODE better perceptible by the user od the mechanical pipette according to the present invention. The larger value of the torque necessary to change of the angle position of the counter clutch 18 in CALIBRATION MODE enables to control the change of the angle position of the counter clutch 18 around the counter axis 24 and makes the correct adjustment on the counter of the volume value indication of the drawn-up liquid easier.

(63) After completion of the calibration, that is when the counter indication is harmonised with the actual drawn-up liquid volume value, the above mentioned activities should be performed in the inverse sequence. The calibration wrench 39 has to be withdrawn from the opening 4b in the push button 4 of the ejector 2, then the slider 9 has to be movedby inserting the flat end 39a of the calibration wrench 39 in the longitudinal socket 9a of the slider 9to its lower extreme position until the catch pawl 9b skips with the upper grooves 1b of the handle 1 into the lower grooves 1a of the handle 1, and simultaneously engaging the counter clutch 18 with the clutch gear-wheel 17, and thereby changing over the pipette from CALIBRATION MODE to PIPETTING MODE. Finally, the plug 6 should be placed in the opening 4b of the push button 4 of the ejector 2.

(64) Moreover, for preventing the pipette according to the present invention from the incidental miscalibration, the slider 9 of the calibration mechanism is protected against the incidental displacement in all pipette operational modes. For this purpose, in the slider 9, on the ribs with the semicircular notches 9c additional technical elastic means were mounted, which constitute the elastic element 36 in the form of O-ring, see FIGS. 5, 10, 12 and 13.

(65) Tip Ejection Mode

(66) For exchange of the tip 8 in the pipette, in the case when the tip 8 is worn or damaged or when there is a need of the change of the working values of liquid volume, and to avoid the contact of the user pipette with the aspirated liquids, the pipette according to the present invention is provided with the improved ejection mechanism of the exchangeable tip 8 from the pipette nozzle 3.

(67) In the pipette according to the present invention, the technical solution is applied, which decreases the value of the force necessary to eject the tip 8 from the nozzle 3. Due to application of the mechanism of the second-class lever, the force necessary to remove the tip 8 has been reduced by the value which results from the distance ratio between the place where the force is applied by the user, which distance has the variable value dependent on the way of the operation with the push button 4 by the user, and the rotation axis of the push button 4 and the distance from the rotation axis of the push button 4 to contact points of the push button 4 with the arms 37a of the frame 37 of the intermediate means for transferring the force from the push button 4 to the ejector 2, which distance has the variable value dependent on the rotation angle of the push button 4.

(68) In the presented preferable embodiment of the present invention, as the intermediate means between the push button 4 and the ejector 2 of the ejection mechanism, which serve to transfer the force from the push button 4 onto the ejector 2, the frame 37 cooperating with the sleeve 38 connected with the ejector 2 are applied.

(69) The principle of functioning of the applied ejection mechanism is as following: when the pipette user wants to eject the tip 8 from the pipette nozzle 3 presses the ejector push button 4 in the place where the plug 6 is pushed into the opening 4b of the push button 4. In consequence, the angle movement of the push button 4 around the rotation axis of the push button 4 of the ejector 2 is caused. The rotation axis is created by bearing of cylindrical side pins 4d of the push button 4 of the ejector 2 in respectively formed cylindrical cavings 1c of the handle 1, which are shown in FIGS. 5 and 12 and in enlargement in FIG. 14 as well as in cylindrical cavings 35b of the cover 35 of the handle 1, which are shown in FIG. 12. The angle movement of the push button 4 causes the longitudinal movement of the frame 37 of the intermediate means of the ejection mechanism due to sliding of the arms 37a of the frame 37 along the rectilinear contact surfaces 4c of the push button 4, which are shown in enlargement in FIG. 15.

(70) For elimination of lateral skid of the arms 37a of the frame 37 from the rectilinear contact surfaces 4c of the push button 4, ends 37b of the arms 37a of the frame 37 are formed with the canopy shape and, similarly, the cooperating with them, in TIP EJECTION MODE, the rectilinear contact surfaces 4c of the push button 4 are formed with the notches of the corresponding canopy profile.

(71) The frame 37 of the intermediate means is longitudinally guided between the guiding ribs 1d and 1e of the handle 1, which are shown in FIG. 12, and the abutting tongues 15c of the bearing sleeve 15, see FIG. 5. Due to such an arrangement, the frame 37 is guided in the handle 1 in reliable way and without any disadvantageous friction. The angle movement of the push button 4 of the ejector 2 causes the longitudinal movement of the frame 37 of the ejector 2, which then is transferred onto the abutting surface 38a of the sleeve 38 of the ejector 2. The sleeve 38 is screwed in via a screwed connection with the ejector 2, as shown in FIG. 2. Further, the lower end of the ejector 2 during its downward movement pushes the tip 8 with its ejection edge away from the nozzle 3.

(72) The ejector 2 return to the initial position is assured due to the return spring of the ejection mechanism, which acts onto the sleeve 38 of the ejector 2 in the direction opposite to the direction of the force exerted by the user onto the push button 4 of the ejector 2.

(73) Due to such a constructional solution of the ejection mechanism, it is possible to obtain the large working stroke of the pipette ejector 2 and, simultaneously, the large reduction of the force indispensable to eject the tips 8 in result of the respective proper choice of geometry of the cooperating component elements.

(74) The structure of the ejection mechanism enables to obtain a non-linear characteristic of the longitudinal movement of the frame 37 of the intermediate means versus the rotation angle of the push button 4 of the ejector 2. In the initial phase, the angle movement of the ejector push button 4 results in the small longitudinal movement of the frame 37 and the sleeve 38 thereby causing the substantial decrease of the value of the force which is necessary to eject the tip 8 from the pipette nozzle 3. Then, due to the displacement of the contact point of the ends 37b of the arms 37a of the frame 37 of the ejector 2 with the rectilinear contact surfaces 4c of the push button 4 towards the point of the application of the force by the pipette user, the leverage of the second-class lever decreases at simultaneous increase of the route of the longitudinal movement of the frame 37 of the ejector 2. Thus, in the terminal phase of TIP EJECTION MODE, in the pipette according to the present invention, the accelerated removal of the tip 8 from the nozzle 3 takes place in comparison with the known pipettes.

(75) The ejection mechanism applied in the pipette according to the present invention, the construction of which provides the long working stroke of the ejector 2, enables that the pipette is able to the cooperation with the wide portfolio of the tips 8 of different geometries for the given volume value of the drawn-up liquid.

(76) Moreover, from the perspective of the necessity to provide the high accuracy and repeatability of the volume values aspirated by the pipette in PIPETTING MODE, the temperature of the pipette interior should be constant. However, during long operation with the pipette, the pipette, which is held in the user hand, is heated and together with it also the air contained inside the pipette is heated. This has disadvantageous impact onto the change of the pipette accuracy deviation during the pipette operational use and forces the correction of the pipette accuracy deviation in CALIBRATION MODE. In the present pipette, due to the improved structure of the ejection mechanism performing the angle movement of the push button 4 of the ejector 2, the forced air circulation takes place inside the pipette in TIP EJECTION MODE. This induces the exchange of the heated air into the cool one and significantly increases the metrological pipette accuracy.

(77) The ejection mechanism disclosed in the present description may be applied in the mechanical pipettes of different structures than hereby disclosed, and especially in the pipettes provided with different plunger working stroke adjustment mechanisms, different engaging mechanisms, different counter drive mechanism and with different calibration mechanisms, as well as in the electronic pipettes.

(78) On the basis of the above example embodiments of the invention, it is possible to provide its different changes, modifications and improvements, while such changes, modifications and improvements are obvious in the light of the idea of the invention and the attached hereto patent claims.

(79) TABLE-US-00001 List of structure elements 1. Handle 1a. Lower groove 1b. Upper groove 1c. Cylindrical caving 1d. Guiding rib 1e. Guiding rib 2. Ejector 3. Pipette nozzle 4. Push button (of the ejector 2) 4a. Caving 4b. Opening 4c. Contact surface 4d. Side pin 5. Adjustment knob 5a. Groove 5b. Ratchet 5c. Notch 6. Plug 7. Pipetting button 8. Tip 9. Slider 9a. Socket 9b. Catch pawl 9c. Notch 9d. Yoke 10. Counter cover 11. Pipetting rod 11a. Spherical lower end 11b. Tongue 11c. Upper surface 12. Adjustment screw 12a. Circumferential groove 12b. Groove 12c. Groove 12d. Rib 12e. Cavings 13. Upper stop 13a. Rib 13b. Lower surface 14. Adjustment sleeve 14a. Toothed-wheel rim 14b. Notch 14c. Catches 14d. Cone 15. Bearing sleeve 15a. Guiding groove 15b. Rectangular opening 15c. Abutting tongue 16. Double gear 16a. Pinion 16b. Gear 17. Clutch gear-wheel 17a. Shape clutch 18. Counter clutch 18a. Lower portion 18b. Groove 18c. Shape portion 18d. Shape end 18e. Protrusion 18f. Smaller protrusion 18g. Larger protrusion 18h. Face (of the shape end 18d) 19. Counter spring 20. Washer 21. Revolvers sleeve 21a. Protrusion 21b. Notch 22. Revolver 23. Pinion 24. Counter axis 24a. Face (of the counter axis 24) 25. Revolver 26. Pinion 27. Revolver 28. Pinion 29. Revolver 30. Counter cover 30a. Elastic click 31. Spring (of the elastic click 30a) 32. Lock 33. Plunger 34. Brake sleeve 34a. Yoke 34b. Cone 34c. Guiding arm 34d. Groove 35. Cover (of the handle 1) 35a. Rib 35b. Cylindrical caving 36. Elastic element 37. Frame (of the ejector 2) 37a. Arm 37b. End 38. Sleeve (of the ejector 2) 38a. Abutting surface 39. Calibration wrench 39a. Flat end 39b. Cross tongue