PIPETTE FOR USE WITH A PIPETTE TIP AND PIPETTE TIP LINE COMPRISING SEVERAL PIPETTE TIPS OF DIFFERENT TYPES FOR USE WITH A PIPETTE

Abstract

A pipette comprises a pipette housing, a neck configured to clamp on a pipette tip, and a drive apparatus. The drive apparatus comprises a drive element configured to displace a displacement element to draw a liquid sample into the pipette tip and to eject the liquid sample from the pipette tip. A scanning apparatus comprises a scanning element positioned proximate the neck and configured to be displaced relative to the pipette housing by a collar of the pipette tip when clamping the pipette tip onto the neck. A mechanical display apparatus is coupled to the scanning apparatus and comprises a display. When the pipette tip is clamped to the neck the scanning apparatus is configured to adjust the display depending on a height of the collar of the pipette tip relative to the neck, and the neck is configured to accommodate different collar heights.

Claims

1-23. (canceled)

24. A pipette for use with a pipette tip, the pipette comprising: a pipette housing comprising a top end and a bottom end; a neck positioned at the bottom end of the pipette housing and configured to clamp on a pipette tip, wherein the pipette tip includes a collar at an upper end that defines a mounting opening; a drive apparatus comprising, a drive element configured to displace a displacement element to draw a liquid sample into the pipette tip and to eject the liquid sample from the pipette tip, and an operating element projecting from the pipette housing and configured to be displaced relative to the pipette housing; a scanning apparatus comprising a scanning element positioned proximate the neck and configured to be displaced relative to the pipette housing by a collar of the pipette tip when clamping the pipette tip onto the neck; and a mechanical display apparatus coupled to the scanning apparatus and comprising a display, wherein when the pipette tip is clamped to the neck, the scanning apparatus is configured to adjust the display depending on a height of the collar of the pipette tip relative to the neck, and wherein the neck is configured to accommodate different collar heights.

25. The pipette according to claim 24, wherein the mechanical display apparatus is a volume display.

26. The pipette according to claim 24, wherein the scanning apparatus comprises a pusher including a lower pusher end and an upper pusher end, wherein the pusher is configured to be displaced relative to the pipette housing, and wherein the scanning element is positioned at the lower pusher end and the upper pusher end is coupled to the mechanical display apparatus.

27. The pipette according to claim 26, wherein the pusher comprises at least one of nominal volume data and data characterizing a type of pipette tip, and wherein the pipette housing defines an opening through which at least the nominal volume data is visible from an outside of the pipette housing.

28. The pipette according to claim 26, further comprising: a first stop apparatus comprising, a first stop element positioned on the drive apparatus, and a second stop element positioned on the pipette housing, wherein displacement of the drive element in a first direction is configured to bring the first stop element and the second stop element into contact with each other, and a second stop apparatus comprising, a third stop element positioned on the drive apparatus, and a fourth stop element positioned on the pipette housing, wherein displacement of the drive element in a second direction is configured to bring the third stop element and the fourth stop element into contact with each other, wherein the second direction is different from the first direction, wherein contact of the first stop element with the second stop element and contact with the third stop element with the fourth stop element define a measuring stroke of the drive apparatus.

29. The pipette according to claim 28 further comprising: an adjusting apparatus comprising, a first adjusting element mounted on the pipette housing, and a second adjusting element positioned on one of the first stop apparatus and the second stop apparatus, wherein the second adjusting element is configured to adjust the measuring stroke by adjusting the first adjusting element; and a mechanical counter coupled to the adjusting apparatus and comprising a mechanical range adjusting apparatus, wherein the mechanical counter is configured to display an adjustment of the adjusting apparatus, wherein the scanning apparatus is coupled to the mechanical range adjusting apparatus, and wherein the mechanical range adjusting apparatus is configured to adjust a count range of the mechanical counter depending on a position of the scanning element relative to the pipette housing.

30. The pipette according to claim 29, wherein the range adjusting apparatus comprises a mark on the upper pusher end positioned in front of the mechanical counter, wherein the pusher is configured to be displaced upward when clamping pipette tips of varying collar heights in order to position the mark to display different count ranges.

31. The pipette according to claim 30, wherein the scanning element is positioned on the lower pusher end and is configured to be shifted in a vertical direction along the pipette housing.

32. The pipette according to claim 31, wherein the mark is a bar-like graduation mark.

33. The pipette according to claim 24, further comprising a first spring apparatus configure to contact the pipette housing and a the drive apparatus.

34. The pipette according to one of claim 26, further comprising: a third stop apparatus comprising, a fifth stop element positioned on the pusher, and a sixth stop element positioned on the pipette housing; and a second spring apparatus configured to contact the pipette housing and the pusher, wherein the second spring apparatus is configured to stress the pusher downward and place the fifth stop element on the sixth stop element when the pipette tip is not mounted on the neck.

35. The pipette according to claim 26, wherein the pusher is connected to an ejection button projecting from the top end of the pipette housing, wherein actuation of the ejection button is configured to displace the pusher downward, wherein the lower pusher end is configured to eject the pipette tip from the neck.

36. The pipette according to claim 26, further comprising: a fourth stop apparatus comprising, a seventh stop element positioned on an ejection button, and an eighth stop element positioned on the pipette housing, wherein the seventh stop element and the eighth stop element are configured to limit the displacement of the ejection button upward; and a transmission apparatus positioned between the ejection button and the pusher, wherein the transmission apparatus is configured to prevent upward displacement of the ejection button when the pusher is displaced upward, and wherein the transmission apparatus is further configured to displace the pusher downward when the ejection button is displaced downward.

37. The pipette according to claim 36, wherein the transmission apparatus is a fourth spring apparatus that contacts the ejection button and the pusher, wherein an upward displacement of the pusher compresses the fourth spring apparatus, wherein a downward displacement of the ejection button compresses the fourth spring apparatus, and wherein the ejection button entrains the pusher.

38. The pipette according to claim 36, wherein the transmission apparatus is a locking device positioned between the ejection button and the pusher that is configured to permit an upward displacement of the pusher relative to the ejection button, and further configured to inhibit a downward displacement of the ejection button relative to the pusher.

39. The pipette according to claim 34, further comprising an ejection pusher comprising an upper end and a lower end, wherein the ejection pusher is configured to be guided in a vertical direction along the pipette housing, wherein the upper end is connected to an ejection button and the lower end is radially offset to the lower end of the pusher, wherein the lower end of the pusher and the lower end of the ejection pusher are positioned at a same height, wherein clamping a pipette tip including an inner peripheral step and an outer peripheral step onto the neck displaces the pusher via the inner peripheral step, and wherein actuation of the ejection button is configured to press the lower end of the ejection pusher against the outer peripheral step of the pipette tip in order to push the pipette tip off of the neck.

40. The pipette according to claim 34, further comprising an ejection pusher comprising an upper end and a lower end, wherein the ejection pusher is configured to be guided in a vertical direction along the pipette housing, wherein the upper end is connected to an ejection button and the lower end is radially offset to the lower end of the pusher, wherein the lower end of the pusher is positioned lower than the lower end of the ejection pusher, wherein clamping a pipette tip including a flat upper edge onto the neck is configured to upwardly displace the pusher without upwardly displacing the ejection pusher, and wherein actuation of the ejection button is configured to press the ejection pusher against the upper end of the pipette tip so that the pipette tip can be removed from the neck.

41. A pipette tip line for use with a pipette, the pipette tip line comprising: at least two pipette tips of different types, wherein each pipette tip comprises, a tip opening at a lower end, a collar at an upper end defining a mounting opening, wherein a height of the collar varies between the at least two pipette tips of different types, and a seat region defined on an inner circumference of the collar and configured to be clamped onto a neck of the pipette, wherein the seat region matches a contour of a pipette, wherein the at least two pipette tips of different types are configured to be clamped by the seat region onto a same area of the neck, and wherein the collar of each of the at least two pipette tips of different types project upward along the neck at varying heights.

42. The pipette line according to claim 41, wherein the at least two pipette tips of different types differ with respect to one or more of nominal volume, shape, a dimension, material comprising the pipette tips, type of coating, type of surface treatment, whether the tip comprises an inserted filter, whether the tip is electrically conductive, and degree of purity.

43. The pipette line according to claim 41, wherein each of the at least two pipette tips of different types comprises two concentric peripheral steps at the upper end, and wherein one of the concentric peripheral steps projects further upward relative to the lower tip opening than the other concentric peripheral step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The invention will be further explained below with reference to the accompanying drawings of exemplary embodiments of the invention. In the drawings:

[0083] FIG. 1 illustrates a vertical cross-section of an embodiment of a positive displacement pipette in an unactuated state;

[0084] FIG. 2 illustrates a vertical cross-section of the embodiment of the positive displacement pipette of FIG. 1 with a pipette tip that is clamped and coupled to the drive apparatus;

[0085] FIG. 3 illustrates a vertical cross-section of the embodiment of the positive displacement pipette of FIG. 1 when ejecting a pipette tip;

[0086] FIG. 4a illustrates a perspective side view of the embodiment of the positive displacement pipette of FIG. 1 with a mounted 10 μL pipette tip and without a housing;

[0087] FIG. 4b illustrates a perspective side view of the embodiment of the positive displacement pipette of FIG. 4a with a housing and with a housing;

[0088] FIG. 4c illustrates an enlarged view of the embodiment of the positive displacement pipette of FIG. 4a;

[0089] FIG. 5a illustrates a perspective side view of the embodiment of the positive displacement pipette of FIG. 1 with a mounted 100 μL pipette tip and without a housing;

[0090] FIG. 5b illustrates a perspective side view of the embodiment of the positive displacement pipette of FIG. 5b with a housing;

[0091] FIG. 5c illustrates an enlarged perspective side view of the embodiment of FIG. 3a;

[0092] FIG. 6 illustrates a perspective view of an embodiment of the positive displacement pipette with a mounted pipette tip with a nominal volume of 10 mL;

[0093] FIG. 7 illustrates a perspective view of an embodiment of the positive displacement pipette with a mounted pipette tip with a nominal volume of 100 μl;

[0094] FIG. 8 illustrates a perspective view of an embodiment of the positive displacement pipette without a mounted pipette tip;

[0095] FIG. 9 illustrates a cross-sectional view of an embodiment of a shaft of an embodiment of the positive displacement pipette with a mounted pipette tip having a nominal volume of 10 mL;

[0096] FIG. 10 illustrates a cross-sectional view of an embodiment of a shaft of an embodiment of the positive displacement pipette with a mounted pipette tip having a nominal volume of 100 μL;

[0097] FIG. 11 illustrates a schematic representation of an embodiment of a transmission apparatus including a spring positioned between the ejection button and ejection pusher of an embodiment of an air cushion pipette;

[0098] FIG. 12 illustrates a schematic representation of an embodiment of a gearing apparatus including a locking device positioned between the ejection button and pusher of an embodiment of an air cushion pipette;

[0099] FIG. 13 illustrates a schematic representation of the embodiment of FIG. 12;

[0100] FIG. 14 illustrates a schematic representation of an embodiment of an air cushion pipette comprising a separate scanning apparatus and ejection apparatus, and a pipette tip with steps at the upper end;

[0101] FIG. 15 illustrates a front plan view of an embodiment of a positive displacement pipette with an operating lever and switching apparatus for displacing the plunger in both directions;

[0102] FIG. 16 illustrates a side plan view of the embodiment of a positive displacement pipette of FIG. 15; and

[0103] FIG. 17 illustrates a perspective front view of the embodiment of a positive displacement pipette of FIG. 15.

DETAILED DESCRIPTION OF THE INVENTION

[0104] In the present application, the expressions “upper” and “lower” as well as “vertical” and “horizontal” and terms derived therefrom such as “above” and “below” as well as “over each other” refer to an arrangement of the positive displacement pipette in which the neck is oriented vertically, and is located on the downwardly facing end of the pipette housing. With regard to the pipette tip, these expressions refer to a vertical orientation of the middle axis of the pipette tip, wherein the tip opening is arranged at the bottom, and the mounting opening is arranged at the top.

[0105] According to the embodiment shown in FIG. 1, a pipette 1 is configured as a positive displacement pipette comprising a substantially rod-shaped pipette housing 2 whose upper part is shaped as a handle 3 and whose lower part is shaped as a shaft 4. A neck 5 tapering downward in steps projects from the bottom end of the shaft 4. A first shoulder 6 and above that a second shoulder 7 run around the outer circumference of the neck. From the lower end of the neck 5, a through-channel 8 extends vertically into the pipette housing 2.

[0106] An operating element 9 in the form of a sleeve-shaped operating button closed at the top and open at the bottom projects from the upper end of the pipette housing 2. Arranged below the operating element 9 is a first adjusting element 10 in the form of a sleeve-shaped adjusting knob of an adjusting apparatus 11 for adjusting the measuring stroke at the upper end of the pipette housing 2. The operating element 9 can be pressed almost completely vertical into the first adjusting element 10. The lower end of a stroke rod 12 engages from above in the through-channel 8 of the neck 5. The stroke rod extends upward in the pipette housing 2 and is connected to the bottom side of the operating element 9.

[0107] The stroke rod 12 comprises an upper stroke rod part 13 and a lower stroke rod part 14. The upper stroke rod part 13 is inserted from above into a vertical first borehole 15 that extends in a longitudinal direction through the entire lower stroke rod part 14 so that the upper stroke rod part 13 can be displaced in the lower stroke rod part 14.

[0108] A lower section of a tubular cage 16 is fixed in an upper section of a connecting element 17 in the form of a reducing socket (for example by being screwed in). The lower end of the cage 16 lies against a first projection 18 of the connecting element 17 running around the inner circumference. The lower stroke rod part 14 is fixed in the lower section of the connecting element 17 (for example by being pressed in). The upper section of the connecting element 17 has a larger inner and outer diameter than the lower section, and therebetween, the connecting element 17 has a third shoulder 19 on the outer circumference.

[0109] The cage 16 is bordered at the top by a peripheral second projection 20 projecting radially to the inside. The upper stroke rod part 13 is guided through the cage 16 and the connecting element 17. The upper stroke rod part 13 has a peripheral bead 21 that is arranged in the cage 16. A pretensioned first helical spring 22 sits between the bead 21 and the first projection 18 on the upper stroke rod part 13. This presses the bead 21 against the second projection 20.

[0110] The upper side of the cage 16 is a first stop element 23. Arranged above that is a spindle nut 24 that is fixed in the pipette housing 2. A threaded spindle 25 engages in the spindle nut 24 and has a second borehole 26 through which the upper stroke rod part 13 is guided. The lower face of the threaded spindle 25 forms a second stop element 27. The spindle nut 24 and the threaded spindle 25 are a component of a first gearing for adjusting the vertical position of the second stop element 27.

[0111] The first adjusting element 10 is tightly connected to an adjusting sleeve 28. This is coupled for conjoint rotation to the threaded spindle 25 via a catch apparatus 29 with axially running grooves 30 in the inside of the adjusting sleeve 28 and wings 31 that engage therein and project radially outward, and is coupled to the threaded spindle 25 in a displaceable manner relative to each other in a vertical direction. Consequently by rotating the first adjusting element 10, the axial position of the second stop element 27 can be adjusted in the pipette housing 2 without axially displacing the first adjusting element 10. The first stop element 23 and the second stop element 27 together form a first stop apparatus 32 that limits the upward displacement of the stroke rod 12.

[0112] The upper stroke rod part 13 is guided through the spindle nut 24 and is tightly connected to the operating element 9 such that it can be displaced vertically downward by pressing the operating element 9. The adjusting sleeve 28 is coupled at its lower end by a pinion 33 to a mechanical display apparatus in the form of a mechanical counter. Counter rollers 35 of the counter 34 arranged one over the other on a vertical axis of rotation are visible from the outside through a first window 36.1 in a vertical side surface of the pipette housing 2. The lower face of the connecting element 17 is a third stop element 37.

[0113] Held below the connecting element 17 in the pipette housing 2 is a pot-shaped fourth stop element 38 that has a central through-hole 39 in its floor 40 through which extends the lower stroke rod part 14. The fourth stop element 38 is securely held by a compensating spring 41 contacting its upper edge and supported in the pipette housing 2 via a flange 42 running on its outer circumference on a fourth shoulder 43 in the pipette housing 2. The third stop element 37 and the fourth stop element 38 together form a second stop apparatus 44 that limits the downward displacement of the lower stroke rod part 14.

[0114] A first spring apparatus 45 in the form of a conical spring has a first contact point in the pipette housing 2 on the upper side of the floor 40 and a second contact point on the third shoulder 19 of the connecting element 17 in order to displace the cage 16 upward when the operating button 9 is released until contacting the first stop apparatus 32. The stroke rod 12 and the operating button 9 are part of a drive apparatus 46 for a plunger.

[0115] According to FIGS. 4 and 5, a scanning apparatus 47 is mounted on the pipette housing 2. The former has a scanning element 48 that is formed by the lower end of a pusher 49. At the bottom, the pusher 49 has a pusher sleeve 50 guided on the shaft 4 and an aperture 51 at the top. The pusher sleeve 50 and the aperture 51 are connected to each other by a rod 52. The rod 52 is fixed at the bottom in a protrusion 53 projecting at the side from the pusher sleeve 50. A bar-like graduation mark 54 of the aperture 51 forms a mark 55 that can be adjusted after the lowest pre-decimal position and/or in front of the highest post-decimal position of the counter 34.

[0116] On the inside of the pipette housing 2, the aperture 51 is arranged on the outside in front of the counter 34 so that the graduation mark 54 is visible from the outside through the first window 36.1 of the pipette housing 2 that is covered by a transparent pane. At the upper end of the aperture 51 is a tab 56 in which several different nominal volume data 57, 58 are arranged one over the other. A nominal volume datum 57, 58 can be seen from the outside through a second window 36.2 of the pipette housing 2 which is covered by transparent pane. The rod 52 of the pusher 49 bears a radially projecting disk 59 that forms a fifth stop element 60.

[0117] The protrusion 53 is arranged through a duct opening 61 at the lower end of a duct 62 arranged on the side of the pipette housing 2. Within the duct 62, the rod 52 is guided through a hole in a horizontal partition wall 63 of the pipette housing 2. The upper side of the partition wall 63 (also noted in FIG. 4) is a sixth stop element 64 that limits the downward displacement of the pusher 49 by contacting the fifth stop element 60. The fifth stop element 60 and sixth stop element 64 jointly form a third stop apparatus 65.

[0118] A second spring apparatus 66 in the form of a second helical spring 67 is braced at the top against a third contact point on a holder 68 of the pipette housing 2 for the counter 34, and at the bottom against a fourth contact point on a horizontal frame part 69 of the aperture 51. The second helical spring 67 is under pretension in order to keep the fifth stop element 60 in contact with the sixth stop element 64.

[0119] According to FIGS. 2 and 3, a pipette tip 70 has a cylindrical plunger travel region 71. At the lower end of the cylindrical plunger travel region 71, there is a conical initial section 72. The tip opening 73 is arranged centrally in the lower end of the initial section 72. The plunger travel region 71 is connected at the top to a conical transition region 74 which adjoins a cylindrical connecting region 75. The cylindrical connecting region 75 is connected by an expansion 76 to a collar 77. The collar 77 has an upwardly expanding, slightly conical shape. On the inner circumference, it has a peripheral bead 78 that belongs to a seat region 78.1 or forms it.

[0120] A plunger 79 is arranged in the pipette tip 70. The former has a conical plunger section 80 that can be inserted into the cylindrical plunger travel region 71. At the upper end, the plunger section 80 is sealed by a sealing edge 81 against the plunger travel region 71. At the bottom, the plunger section 80 can be inserted into the conical initial section 72 of the pipette tip 70. At the top, the plunger section 80 is connected to a conical connecting section 82 that can be inserted into the transition region 74. A short plunger rod 83 extends upward from the transition region 74.

[0121] Pipette tips 70 with different nominal volumes have cylindrical plunger travel regions 71 and corresponding conical plunger sections 80 with different cross-sections. Moreover, they differ in that the collar 77 has a different height relative to the scat region 78.1. The mounting opening 84 for the pipette tip 70 is located at the upper end of the collar 77.

[0122] According to FIGS. 2 and 4 to 7, a pipette 1 is inserted with the neck 5 into the mounting opening 84 of a pipette tip 70 with an integrated plunger 79. When mounting the pipette tip 70 on the neck 5, an inner step 76.1 within the collar 77 (see FIG. 9) or the upper edge of the collar 77 (see FIG. 10) contacts the second shoulder 7. In both embodiments, the bead 78 lies below the first shoulder 6 under pretension similarly on the collar 77 so that the pipette tip 70 is securely clamped on the neck 5. In this case, the bead 78 and therefore the seat region 78.1 in both embodiments lie sealingly against the same clamping zone 5.1 of the collar 5.

[0123] When the upper edge of the collar 77 contacts the second shoulder 7, the pusher 49 is not moved, and the display of the mechanical counter 34 remains unchanged. This is the case when mounting the 100 mL pipette tip that is shown in FIGS. 2, 5, 7 and 10. The display is the same as in FIG. 8 that shows the pipette without a mounted pipette tip 70. The graduation mark 54 shows the user the lowest pre-decimal position or the highest post-decimal position.

[0124] When the inner step 76.1 contacts the second shoulder 7, the upper edge of the collar 77 projecting beyond the inner step 76.1 contacts the lower end of the pusher 49 and moves it upward counter to the effect of the second helical spring 67. In this case, the aperture 51 is displaced so that the graduation mark 54 is shoved into a different position between two counter rollers 35 of the counter 34. This is the case when mounting the 10 mL pipette tip 1 that is shown in FIGS. 4, 6 and 9. The displacement of the graduation mark 54 depends on the height of the collar 77. Depending on the nominal volume of the pipette tip 70, the graduation mark 54 is therefore adjusted next to a specific position of the counter 34. In addition, the user is shown the particular nominal volume datum 57, 58 of the mounted pipette tip 70 in the second window 36.2.

[0125] In the following, pipetting with the pipette 1 will be explained. The plunger rod 83 is connected to the stroke rod 12 by pressing down the operating element 9 until contacting the second stop apparatus 44. In this case, the plunger rod 83 is clamped in the first borehole 15 in the stroke rod 12. This is shown in FIG. 2.

[0126] Then, when the operating element 9 is pressed down, the lower end of the pipette tip 70 can be immersed in a liquid in a vessel. When the operating element 9 is released, the stroke rod 12, and therefore the plunger 79, is displaced upward by the first spring apparatus 45 until contacting the first stop apparatus 32, and liquid is drawn into the pipette tip 70.

[0127] To discharge the drawn volume of liquid, the lower end of the pipette tip 70 is inserted into another container, and the liquid is discharged by pressing down the operating element 9 until contacting the second stop apparatus 44. In so doing, the plunger 79 is moved into its lowest position in the pipette tip 70, and the liquid volume is displaced through the tip opening 73 into the container.

[0128] According to FIG. 3, the operating element 9 is pressed down further to release the pipette tip 70 so that the first helical spring 22 is compressed, and the upper stroke rod part 13 presses the plunger rod 83 out of the first borehole 15.

[0129] Given a pipette 1 designed as an air cushion pipette, the stroke rod 12 is coupled to a plunger that is displaceable in a cylinder arranged in the pipette housing 2 by actuating the operating element 9. The cylinder is connected via a channel to a hole in the lower end of the neck 5.

[0130] As with the positive displacement pipette, the scanning apparatus 47 can be configured such that it has a scanning element 48 on the lower end of a pusher 49 that has a pusher sleeve 50 guided on the shaft 4. The pusher 49 is coupled at the top to a mark 55 for adjusting on the side next to a counter roller 35 of a counter 34 and, if applicable, to a tab 56 for displaying various nominal volume data 57, 58 in a window.

[0131] The pusher 49 can also be used to eject the pipette tip 70. To accomplish this, the pusher 49 according to FIG. 9 is coupled to an ejection button 85 that projects outwardly out of the pipette housing 2. In principle, the ejection button 85 can be rigidly connected to the pusher 49. However, this has the consequence that the position of the ejection button 85 depends on the height of the collar 77 of the mounted pipette tip 70.

[0132] In the exemplary embodiments in FIGS. 11 to 13, this is prevented by providing a fourth stop apparatus 86 with a seventh stop element 87 on the ejection button 85 and an eight stop element 88 on the pipette housing 2 that limit an upward displacement of the ejection button 85. In addition, there is a transmission apparatus 89 between the ejection button 85 and pusher 49 that, when the pusher 49 is displaced upward, does not displace the ejection button 85 upward and entrains the pusher 49 downward when the ejection button 85 is displaced downward. According to FIG. 11, the transmission apparatus 89 is a fourth spring apparatus 90 between the ejection button 85 and rod 52 of the pusher 49 that is designed as a third helical spring 91.

[0133] The fourth spring apparatus 90 is under pretension so that when the ejection button 85 is not pressed down, the fourth stop apparatus 86 takes effect. When a pipette tip 70 is mounted, the pusher 49 is displaced upward, and the fourth spring apparatus 90 is compressed. The ejection button 85 remains in its upper stop position. When the ejection button 85 is actuated, first the fourth spring apparatus 90 is compressed further. Then the ejection button 85 presses against the rod 52 of the pusher 49, whereby it slips the pipette tip 70 off of the neck 5. According to FIGS. 12 and 13, the transmission apparatus 89 comprises a locking device 92 arranged between the ejection button 85 and pusher 49. In this case, it is a toothed wheel 93 that is rotatably mounted on the ejection button 85 and possesses a freewheel 94. The rod 52 has a toothed rack 95 on one side which engages with the toothed wheel 93.

[0134] When the ejection button 85 is not actuated, the fourth stop apparatus 86 takes effect due to a fifth spring apparatus 96 acting thereupon. When a pipette tip 70 is mounted, the pusher 49 is displaced upward, wherein the toothed wheel 93 rotates freely therewith. Only when the ejection button 85 is actuated, the free rotation of the toothed wheel 93 is stopped, and the rod 52 is moved downward therewith. Consequently, the pusher 49 presses the pipette tip 70 off of the neck 5.

[0135] According to FIG. 14, a displacement of the ejection button 85 when the pipette tip 70 is being mounted is prevented in that there is an ejection pusher 97 in addition to the pusher 49. At the lower end, the pusher 49 has an inner pusher sleeve 98 guided on the shaft, and the ejection pusher 97 has an outer pusher sleeve 99 guided on the inner pusher sleeve 98 on the lower end.

[0136] At the upper edge, the pipette tip 70 has two concentric peripheral steps 100, 101, wherein the inner step 100 projects further upward in a vertical direction than the outer step 101. When mounting the pipette tip 70, the inner step 100 actuates the pusher 49, which adjusts the graduation mark 54 on the mechanical counter 34. The ejection pusher 97 is not actuated by the outer step 101. When pressing down the ejection button 85, the lower end of the ejection pusher 97 contacts the outer step 101 and presses the pipette tip 70 off of the neck 5.

[0137] According to FIGS. 15 to 17, a pipette 1 is a positive displacement pipette and comprises a pipette housing 2 with an operating element 9 on a vertical side surface designed as an operating lever 102 that can be swung vertically upward and downward, and a first adjusting element 10 designed as a knob 103 for adjusting a volume on the upper end. At the bottom, a positive displacement pipette tip 70 can be clamped onto the neck 5.

[0138] By pressing the operating lever 102 downward one or several times, an adjusted volume can be drawn into the pipette tip 70. A spring is arranged in the pipette housing 2 that is compressed downward by pressing the operating lever 102 downward, and swings the operating lever 102 upward after releasing. The length of movement of the operating lever 102 and/or the number of its actuations depend on the adjusted volume. Furthermore the drawn liquid can be dispensed from the pipette tip 70 by swinging the operating lever 102 downward one or more times. The actuation, or respectively the number of actuations also depends on the adjusted volume.

[0139] To control both the drawing in of the liquid into the pipette tip 70 as well as the discharge of the liquid out of the pipette tip 70 by swinging the operating lever 102 downward, the drive apparatus of the pipette 1 has a switching apparatus that reverses the direction of displacement of the plunger 79 by actuating the operating lever 102 after drawing in the adjusted volume into the pipette tip 70. As a consequence, the ejection of the drawn liquid out of the pipette tip 70 is brought about by further actuating the operating lever 102.

LIST OF REFERENCE NUMBERS

[0140] 1 Pipette

[0141] 2 Pipette housing

[0142] 3 Handle

[0143] 4 Shaft

[0144] 5 Neck

[0145] 5.1 Clamping zone

[0146] 6 First shoulder

[0147] 7 Second shoulder

[0148] 8 Through-channel

[0149] 9 Operating element

[0150] 10 First adjusting element

[0151] 11 Adjusting apparatus

[0152] 12 Stroke rod

[0153] 13 Upper stroke rod part

[0154] 14 Lower stroke rod part

[0155] 15 First borehole

[0156] 16 Cage

[0157] 17 Connecting element

[0158] 18 First projection

[0159] 19 Third shoulder

[0160] 20 Second projection

[0161] 21 Bead

[0162] 22 First helical spring

[0163] 23 First stop element

[0164] 24 Spindle nut

[0165] 25 Threaded spindle

[0166] 26 Second borehole

[0167] 27 Second stop element

[0168] 28 Adjusting sleeve

[0169] 29 Catch apparatus

[0170] 30 Groove

[0171] 31 Wing

[0172] 32 First stop apparatus

[0173] 33 Pinion

[0174] 34 Mechanical counter

[0175] 35 Counter roller

[0176] 36.1 First window

[0177] 36.2 Second window

[0178] 37 Third stop element

[0179] 38 Fourth stop element

[0180] 39 Through-hole

[0181] 40 Floor

[0182] 41 Compensation spring

[0183] 42 Flange

[0184] 43 Fourth shoulder

[0185] 44 Second stop apparatus

[0186] 45 First spring apparatus

[0187] 46 Drive apparatus

[0188] 47 Scanning apparatus

[0189] 48 Scanning element

[0190] 49 Pusher

[0191] 50 Pusher sleeve

[0192] 51 Aperture

[0193] 52 Rod

[0194] 53 Protrusion

[0195] 54 Graduation mark

[0196] 55 Mark

[0197] 56 Tab

[0198] 57 Nominal volume datum

[0199] 58 Nominal volume datum

[0200] 59 Pane

[0201] 60 Fifth stop element

[0202] 61 Duct opening

[0203] 62 Duct

[0204] 63 Partition wall

[0205] 64 Sixth stop element

[0206] 65 Third stop apparatus

[0207] 66 Second spring apparatus

[0208] 67 Second helical spring

[0209] 68 Holder

[0210] 69 Frame part

[0211] 70 Pipette tip

[0212] 71 Plunger travel region

[0213] 72 Conical initial section

[0214] 73 Tip opening

[0215] 74 Conical transition region

[0216] 75 Cylindrical connecting region

[0217] 76 Expansion

[0218] 76.1 Inner step

[0219] 77 Collar

[0220] 78 Bead

[0221] 78.1 Seat region

[0222] 79 Plunger

[0223] 80 Conical plunger section

[0224] 81 Sealing edge

[0225] 82 Conical connecting section

[0226] 83 Plunger rod

[0227] 84 Mounting opening

[0228] 85 Ejection button

[0229] 86 Fourth stop apparatus

[0230] 87 Seventh stop element

[0231] 88 Eighth stop element

[0232] 89 Transmission apparatus

[0233] 90 Fourth spring apparatus

[0234] 91 Third helical spring

[0235] 92 Locking device

[0236] 93 Toothed wheel

[0237] 94 Freewheel

[0238] 95 Toothed rack

[0239] 96 Fifth spring apparatus

[0240] 97 Ejection pusher

[0241] 98 Inner pusher sleeve

[0242] 99 Outer pusher sleeve

[0243] 100 Inner step

[0244] 101 Outer step

[0245] 102 Operating lever

[0246] 103 Knob