Pipette for Use with a Pipette Tip

Abstract

A pipette for use with a pipette tip includes a housing, a pin on the bottom end of the housing holding a pipette tip having first means for form-fit connection and a second means for form-fit connection which can be shoved onto the pin, constricting the pin, and/or expanding the tip before form-fit connection with the pin, a drive apparatus, at least one locking sleeve arranged concentric to the pin which is guided toward the pin in the housing, wherein the locking sleeve has a locked position having a pin in the inside constricted by shoving on a pipette tip, and/or is bordered on the outside by a tip shoved onto the pin, preventing a release from the pin, and the locking sleeve is upwardly displaceable out of the locked position so that the pin, and/or the tip is released, and the tip is removable from the pin.

Claims

1. A pipette for use with a pipette tip comprising: a rod-shaped pipette housing (2), a pin (4) on the bottom end of the pipette housing (2) for holding a pipette tip (57) that has first means for the form-fit connection (9) to a pipette tip (57) so that a pipette tip (57), that has second means for the form-fit connection (66) to the first means for the form-fit connection (9), can be shoved onto the pin (4) while elastically constricting the pin (4), and/or while elastically expanding the pipette tip (57) before its form-fit connection with the pin (4), a drive apparatus (12) for displacing a displacement element (69) for aspirating a liquid specimen into a pipette tip (57) held on the pin (4), and ejecting the specimen from the pipette tip (57), at least one locking sleeve (46) arranged concentric to the pin (4) which is displaceably guided toward the pin (4) in the pipette housing (2), wherein the at least one locking sleeve (46) is displaceable into a locked position in which it is bordered on the inside by a pin (4) which can be constricted by shoving on a pipette tip (57), and/or is bordered on the outside by a pipette tip (57) that is expandable by being shoved onto the pin (4), whereby the locking sleeve (46) prevents a release from the pin (4) of a pipette tip (57) that is connected in a form-fit to the pin (4), and the locking sleeve (46) is upwardly displaceable out of the locked position so that the pin (4), and/or the pipette tip (57), is at least partially released, and the pipette tip (57) is removable from the pin (4).

2. The pipette according to claim 1, wherein the pin (4) has at least one slot (10, 11) running in the longitudinal direction, and the locking sleeve (46) in the locked position borders the pin (4) on the inside, and/or wherein the locking sleeve (46), in locked position, is designed to border a pipette tip (57) on the outside having at least one slot running in the longitudinal direction at the upper end and connected in a form-fit to the pin (4).

3. The pipette according to claim 1, wherein the locking sleeve (46) is connected to a first operating element (83) projecting from the pipette housing (2) and displaceable relative to the pipette housing (2) in order to displace the locking sleeve (46) downward into the locked position, and upward out of the locked position, by actuating the first operating element (83).

4. The pipette according to claim 1, having an ejection apparatus (26) that comprises an ejection rod (39) which is displaceably guided in the pipette housing (2) in the longitudinal direction of the pin (4), and comprises a second operating element (84) connected to the ejection rod (39) in order to displace the ejection rod (39), wherein the ejection apparatus (26) is designed to press a pipette tip (57) held on the pin (4) off of the pin (4) by displacing the ejection rod (39) downward when the locking sleeve (46) at least partially releases the pin (4) and/or the pipette tip (57).

5. The pipette according to claim 4, wherein as a positive displacement pipette, the ejection rod (39) is arranged within an axial bore in a stroke rod (17) for displacing a tip plunger (69) in the pipette tip (57), and is arranged with the lower end above a seat (25) of the stroke rod (17) for the upper end of the tip plunger (69) of a pipette tip (57) held on the pin (4) and engaging with the tip plunger (69) in a through bore (5) in the pin (4).

6. The pipette according to claim 4, wherein as an air cushion pipette, a displacement apparatus with a displacement element that can be displaced by a drive element (16) of the drive apparatus (12) is present in the pipette housing (2) and is connected to a through bore (5) in the pin (4), and the lower end of the ejection rod (39) is arranged on the side next to the pin (4).

7. The pipette according to claim 4, wherein the locking sleeve (46) and the ejection rod (39) are connected to a gear apparatus (73) that comprises the first operating element (83) and the second operating element (84), and is designed to control the displacement of the locking sleeve (46) and the ejection rod (39) in opposite directions when at least one operating element (83, 84) is actuated so that a pipette tip (57) held on the pin (4) prevents the plunger from being removed from the pin (4) by displacing the ejection rod (39) upward and the locking sleeve (46) downward, and the pipette tip (57) can be removed from the pin (4) by displacing the locking sleeve (46) upward and the ejection rod (39) downward.

8. The pipette according to claim 5, wherein the locking sleeve (46) and the ejection rod (39) are connected to a gear apparatus (73) that comprises the first operating element (83) and the second operating element (84), and is designed to control the displacement of the locking sleeve (46) and the ejection rod (39) in opposite directions when at least one operating element (83, 84) is actuated so that a pipette tip (57) held on the pin (4) prevents the plunger from being removed from the pin (4) by displacing the ejection rod (39) upward and the locking sleeve (46) downward, and the pipette tip (57) can be removed from the pin (4) by displacing the locking sleeve (46) upward and the ejection rod (39) downward.

9. The pipette according to claim 7, wherein when pressing off a pipette tip (57), the gear apparatus (73) is designed to first displace the locking sleeve (46) upward, and then the pipette tip (57) is pressed off of the attachment (4) by displacing the ejection rod (39) downward.

10. The pipette according to claim 7, wherein the same operating element (83, 84) controls the displacement of the locking sleeve and the displacement of the ejection rod (39).

11. The pipette according claim 1, wherein the other operating element controls the drive apparatus (12).

12. The pipette according to claim 7, wherein the gear apparatus (73) is a gear train (74) that has two outputs (75, 76) with a first and a second output-side rack (77, 78) which is connected to the ejection rod and the locking sleeve, and that has a first drive (79) with a first drive-side rack (81) that is connected to a first actuating element (83), wherein the first drive-side rack (81) is connected to the second output-side rack (78) via a drive pinion (85) and a first output pinion (86) rigidly connected to the drive pinion (85), and is connected to the first output-side rack (77) via the drive pinion (85), an intermediate gear (88) and a second output pinion (87) rigidly connected rigidly to the intermediate gear (88).

13. The pipette according to claim 12, wherein the gear apparatus (73) has a second drive (80) with a second drive-side rack (82) that has a second operating element (84) on the end distant from the first operating element (83), wherein the two drive-side racks (81, 82) mesh with the same drive pinion (85) on different sides in order to control the movement of the locking sleeve (46) and the ejection rod (39) by optionally actuating the different operating elements (83, 84) on different sides of the pipette housing (2).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention is explained below based on the accompanying drawings of an exemplary embodiment. In the drawings:

[0041] FIG. 1 shows a perspective view of a partially cut away positive displacement pipette with a pipette tip mounted on the pin;

[0042] FIG. 2 shows an enlarged perspective view of a slotted pin with an inner adjacent locking sleeve of the same positive displacement pipette with a mounted pipette tip;

[0043] FIG. 3 shows the same arrangement in a side view;

[0044] FIG. 4 shows the same arrangement in a longitudinal view;

[0045] FIG. 5 shows positive displacement pipette from FIG. 1 in an exploded view;

[0046] FIG. 6 shows positive displacement pipette from FIG. 1 in an exploded view without pipette housing;

[0047] FIG. 7 shows a perspective view of a rotating sleeve with the ejection rod and the locking sleeve of the same positive displacement pipette in the start position;

[0048] FIG. 8 shows a partial cutaway of the same positive displacement pipette in the start position in a side view;

[0049] FIG. 9 shows a partial cutaway of the same positive displacement pipette while pipetting in a side view;

[0050] FIG. 10 shows a partial cutaway of the same positive displacement pipette in the start position when ejecting in a side view;

[0051] FIG. 11 shows a slotted pipette tip on a pin of another positive displacement pipette with a locking sleeve lying on the outside of the pipette tip in a longitudinal section;

[0052] FIG. 12 shows a gear train for displacing the locking sleeve and the ejection rod of a positive displacement pipette in a perspective view obliquely from the front;

[0053] FIG. 13 shows the gear train in a perspective view obliquely from below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] In the present application, the expressions upper and lower as well as vertical and horizontal and terms derived therefrom such as above and below, standing upright and upside down as well as over each other refer to an arrangement of the pipette in which the pin 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.

[0055] According to FIG. 1, a pipette 1 designed as a positive displacement pipette has a rod shaped (e.g. cylindrical) pipette housing 2. From the bottom end of the pipette housing 2, a hollow cylindrical shaft 3 projects downward. A pin 4 projects downward from the bottom end of the shaft 3 that, according to FIGS. 1 and 4, has a through bore 5 with a through-hole in the bottom end. The inner diameter of the through bore 5 is smaller than the inner diameter of the shaft 3.

[0056] The pin 4 has a top pin section 6 in the shape of a hollow cylinder, and underneath, a lower pin section 7 in the shape of a hollow cone. An annular groove 8 runs around the outer circumference of the pin 4 between the upper pin section 6 and the lower pin section 7.

[0057] The upper pin section 6, the annular groove 8 and the lower pin section 7 form first means for the form-fit connection 9 of the pipette to a pipette tip. Furthermore, the pin 4 has two slots 10, 11 running in its longitudinal direction that lie diametrically opposed to each other. The slots 10, 11 extend from the lower end over the entire length of the pin 4.

[0058] According to FIGS. 1, 5 and 6, there is a drive apparatus 12 in the pipette housing 2 that comprises a transmission element 13 in the form of a transmission rod 14, a transmission mechanism 15 and a drive element 16 in the form of a stroke rod 17. Furthermore, the drive apparatus 12 comprises an operating element 18 in the form of an operating lever 19 that is securely connected via a bar 20 to a support plate 21.

[0059] According to FIG. 6, the support plate 21 has an oval shape with a wide, rounded end and a narrow rounded end, wherein the operating lever 19 projects from the edge of the narrow rounded end. In addition to this edge, the support plate 21 has a first curved slot 22 that runs approximately parallel to the contour of the narrow rounded end. Furthermore, the support plate 21 has a rectangular, first edge cutout 23 in the middle of the first curved slot 22 on the side of the narrow rounded end.

[0060] According to FIGS. 1 and 5, the stroke rod 17 is inserted from above into the shaft 3 and the pin 4. According to FIG. 4, it is hollow and provided with a longitudinal slot 24 running in a longitudinal direction starting from the lower end. Because of the longitudinal slot 24, the stroke rod 17 has a C-shaped cross-section. Its lower end forms a seat 25 for the upper end of a plunger rod.

[0061] The transmission mechanism 15 is designed so that the stroke rod 17 is alternatingly displaced downward and upward during sequential downward displacements of the operating lever 19 between which the operating lever 19 is displaced upward. Consequently, by pressing the operating lever 19 downward, the stroke rod 17 can be displaced out of an upper position into a lower position, the stroke rod 17 retains the lower position during the subsequent upward displacement of the operating lever 19, and the stroke rod 17 is again displaced upward by subsequently pressing the operating lever 19. This can be repeated as frequently as desired.

[0062] According to FIGS. 1, 5 and 6, the pipette 1 is provided with an ejection apparatus 26. This comprises a curved support 27 that is rotatably mounted in the pipette housing 2 and is designed as a hollow cylindrical rotating sleeve 28. The rotating sleeve 28 is for example rotatably mounted by its outer circumference on the inner circumference of the pipette housing 2, and the upper and lower ends are braced against ledges of steps on the inner circumference of the pipette housing 2 so that they cannot be displaced in an axial direction in the pipette housing 2. The rotational axis of the rotating sleeve 28 coincides with the longitudinal axis of the pipette housing 2 and the longitudinal axis of the pin 4.

[0063] The rotating sleeve 28 has parallel cutouts 29, 30 on two diametrically opposite sides parallel to its rotational axis which extend from the upper edge of the rotating sleeve 28 and terminate at a distance from their lower edge. Below the cutouts, the rotating sleeve 28 accordingly consists of an annular base 31, and it also consists of two diametrically opposing sectors 32, 33 of an annulus that border the two cutouts 29, 30 on the side.

[0064] A first curve 34 and a second curve 35 are arranged on the outer circumference of the circular base 31 of the rotating sleeve 28. The first curve 34 is designed as a first groove 36 in the form of an inverted (upside down) Y. The vertical part 37 of the Y extends far upward to a sector 32 just short of the top edge of the sector 32. The second curve 35 is a second groove 38 in the outer circumference of the base 31 of the rotating sleeve 28 in the form of an upright V. The first curve 34 and the second curve 35 are arranged offset 90 relative to each other on the circumference of the rotating sleeve. The first curve 34 and the second curve 35 each extend over an angular range of less than 90 over the circumference of the rotating sleeve 28.

[0065] According to FIGS. 1, 5 and 6, the ejection apparatus 26 comprises an ejection rod 39 that comprises a strip-shaped upper ejection rod part 40 and a cylindrical lower ejection rod part 41. The upper and the lower ejection rod part 40, 41 are parallel to each other and arranged laterally offset to each other. The lower end of the upper ejection rod part 40 is connected to the upper end of the lower ejection rod part 41 by a strip-shaped connecting rod part 42 angled obliquely relative to the two ejection rod parts. A first sensing element 43 in the form of a first guide pin 44 extends at a right angle from the inside of the upper ejection rod part 40. The ejection rod 39 is preferably designed as a single part, for example from a rigid plastic.

[0066] According to FIGS. 1, 4 and 7, the ejection rod 39 is guided by the guide pin 44 into the first groove 36, the connecting rod part 42 penetrates the longitudinal slot 24 of the stroke rod 17, and the lower ejection rod part 41 extends within the stroke rod 17 almost up to the lower bottom end thereof.

[0067] According to FIGS. 1, 4, 5 and 6, the pipette 1 comprises a locking apparatus 45 that comprises a locking sleeve 46 and a strip-shaped control rod 47 parallel thereto. The upper end of the locking sleeve 46 and the lower end of the control rod 47 are connected to each other by a second connecting rod part 48 that is angled obliquely to the locking sleeve 46 and to the control rod 47. A second sensing element 49 in the form of a second guide pin 49.1 extends from the inside of the control rod 47.

[0068] According to FIGS. 1 and 7, the second guide pin 49.1 is guided in the second groove 38. According to FIGS. 1 and 4, the locking sleeve 46 is inserted from above into the shaft 3 and lies against the inner side of the pin 4. The stroke rod 17 and the ejection rod 39 are inserted from above into the locking sleeve 46.

[0069] With the first curved slot 22, the operating element 19 is shoved onto the sector 32 of the rotating sleeve 28 on which the first groove 36 extends. According to FIGS. 1, 6 and 7, the rotating sleeve 28 is connected at the top to a support ring 50 that bridges the two sectors 32, 33 and stabilizes the rotating sleeve 28. On the outer edge, the support ring 50 has a downwardly projecting casing 51 that laterally surrounds the outer edges of the two sectors 32, 33. Furthermore, it has a second curved slot 52 that accommodates the upper edge of the sector 33 which is not provided with a groove 36, 38. On the diametrically opposite side, there is a rectangular second edge cutout 52.1 in the casing 51 that is open at the bottom and is designed to accommodate the web 20 between operating lever 19 and support plate 21.

[0070] The support ring 50 is for example connected to the rotating sleeve 28 by adhesion.

[0071] The rotating sleeve 28 and the locking sleeve 46 as well as the operating element 18 are for example made of one or more rigid plastics and/or metal. The rotating sleeve 28, the support ring 50, the operating element 18 and/or the locking sleeve 46 are preferably each designed as a single part. An operating button of the operating element 18 can also be produced from an elastic or soft elastic plastic or rubber.

[0072] So that it can be operated from the outside, the operating lever 19 extends out of the pipette housing 2 through a first housing slot running transverse to the longitudinal axis of the pipette housing 2 and extending over a part of the circumference of the pipette housing 2. The first housing slot is connected in the middle to a second housing slot running in the longitudinal direction of the pipette housing 2.

[0073] Opposite the effect of a spring apparatus, the operating lever 19 can be displaced downward, starting from the support ring 50, along the second housing slot, wherein it slides with the first curve slot 22 on the sector 32 of the rotating sleeve 28. After being relieved, the spring apparatus independently displaces the operating lever 19 upward.

[0074] A sleeve-shaped third sensing element 53 is guided on the outside of the shaft 3. A spring apparatus in the form of a helical spring 54 guided on the shaft abuts the bottom side of the pipette housing 2 and the top side of the third sensing element 53. By means of the helical spring 54, the third sensing element 53 is pressed from above against a stop element on the shaft 3 or the pin 4.

[0075] An adjusting knob 55 for adjusting a metering volume is adjusted on the top side of the pipette housing 2. The metering volume can be adjusted by turning the adjusting knob 55. A counter 56 arranged thereunder in the pipette housing 2 indicates the respectively adjusted metering volume. The adjusting knob 55 and/or the counter 56 is coupled to the transmission mechanism 15. The transmission mechanism 15 is designed to change the stroke of the stroke rod 17 corresponding to the respectively adjusted metering volume, which stroke is executed by the downward displacement of the operating element 18.

[0076] According to FIGS. 1 and 4, a pipette tip 57 is mounted on the pin 4. The pipette tip 57 comprises a tubular body 58 that has a tip opening 59 in the bottom end, a collar 61 having a mounting opening 60 on the top end, and a seat region 62 on the inner circumference of the collar 61 for clamping onto the pin 4. The seat region 62 has a contour complementary to the pin 4 that has a conical, lower seat section 63 at the bottom for accommodating the conical lower pin section 7, above which is a peripheral bead 64 for engaging in the annular groove 8 of the pin 4, and above which is a cylindrical upper seat section 65 for accommodating the cylindrical upper pin section 6. The lower seat section 63, the bead 64, and the upper seat section 65 form second means for the form-fit connection 66 of the pipette tip 57 with the pipette 1.

[0077] Below the seat region, 62, the tubular body 58 has a cylindrical plunger travel region 67. Thereunder, the tubular body 58 has a downwardly tapering tip section 68 with the shape of a conical frustum. The tip section 68 is shown in FIG. 4 and is omitted in the other drawings for reasons of simplification. A tip plunger 69 is inserted into the tubular body 58. This comprises a plunger 70 that is guided in the plunger travel region 67. A plunger rod 71 projects upward from the plunger 70 and has a smaller diameter than the plunger 70. At the top end, the plunger rod 71 has a plunger head 72. According to FIG. 4, the plunger head 72 is pressed downward into the seat 25 of the stroke plunger 17.

[0078] The pipette 1 can be used as follows:

[0079] According to FIGS. 1 and 8, a pipette tip 57 is held on the pipette 1 in a starting state. The seat region 62 is in particular connected to the pin 4 in a form-fit by the bead 64 engaging in the annular groove 8. The actuating element 18 is located in the starting position at the top end of the second housing slot and can be screwed into the first housing slot in both directions. The maximum angle of rotation is limited by the extent of the first and second grooves 36, 38 in the circumferential direction, or the first housing slot depending on which extent is smaller.

[0080] The locking sleeve 46 is arranged in the lowest position according to FIG. 4 so that it prevents the pipette tip 57 from unintentionally releasing from the pin 4. For the form-fit connection to be released, a radial constriction of the pin 4 would in fact be necessary that the locking sleeve 46 does not permit in this position. In deviation from FIG. 4, the tip plunger 69 in the starting position does not yet press into the seat 25 of the stroke rod 17 with the plunger head 72.

[0081] To connect the tip plunger 69 to the stroke rod 17, the operating element 18 is pressed downward. The movement is transmitted by the transmission mechanism 15 to the stroke rod 17 so that it is pressed with the seat 25 onto the plunger head 72. This is shown in FIG. 4.

[0082] After being released, the operating element 18 is displaced back into it starting position by a spring apparatus according to FIG. 8. The stroke rod 17 and the tip plunger 69 maintain the positions according to FIG. 4.

[0083] To draw liquid, the pipette 1 is immersed in a liquid by the bottom end of the pipette tip 57 held thereon. Then the operating element 18 is again pressed downward. This movement is converted by the transmission apparatus 15 into a stroke movement of the stroke rod 17. As a result, the tip plunger 69 is displaced upward. In so doing, the plunger head 72 entrains the ejection rod 39 so that the first guide pin 44 slides upward in the vertical part 37 of the Y-shaped first groove 36. During this, the locking sleeve 46 retains its position. This is shown in FIG. 9.

[0084] Once the operating element 18 has executed the set stroke, the pipette tip 57 is filled with a certain amount of liquid. Then the operating element 18 is relieved and is displaced back upwards by the spring apparatus up to the stop on the support ring 50. To discharge this amount of liquid, the pipette tip 57 of the pipette 1 can be oriented over another vessel. By again pressing the operating element 18 downward, the stroke rod 17 is displaced downward, and the amount of liquid is discharged. In so doing, the first guide pin 44 slides downward to the node of the first groove 36.

[0085] The stroke executed by the operating element 18 while drawing and discharging liquid depends on the set amount of liquid.

[0086] Drawing and discharging liquid can occur several times.

[0087] To eject the pipette tip 57, the operating lever 18 in the starting position is swung to the right or to the left. This rotates the rotating sleeve 28 so that the second groove 38 displaces the second guide pin 49.1, and therefore the locking sleeve 46, upward until the locking sleeve 46 has released the pin 4 until it deforms radially inward. To accomplish this, preferably the locking sleeve 46 is pulled out of the through bore 5. Furthermore by rotating the rotating sleeve 28, the first guide pin 44 is displaced downward in one of the two lateral sections of the bottom part of the first groove 36 so that the ejection rod 39 presses against the tip plunger 69 that abuts the tip section 68 at the bottom. In so doing, the bead 64 exerts a radial force on the pin to constrict it, and the form-fit connection between pipette tip 57 and pin 4 is released. This releases the pipette tip 57 from the pin 4. This is shown in FIG. 10. The scraping of the pipette tip 57 off the pin 4 can be assisted by the sensing element 53 that is pressed by the pretensioned helical spring 54 against the top edge of the pipette tip 57.

[0088] Once the used pipette tip 57 is released from the pin 4, a new pipette tip 57 can be connected to the pin 4. To accomplish this, the pipette 1 can be inserted with the pin 4 into the drawing opening 68 of a pipette tip 57 provided in a support. In so doing, the sensing element 53 is displaced upward and pretensions the helical spring 54. Furthermore, the plunger head 72 presses against the bottom side of the ejection rod 39 so that the first guide pin 44 slides up to the first branching point of the first groove 36. In so doing, the rotating sleeve 28 is rotated in the pipette housing 2 until the operating element 18 is located in the starting position. At the same time, the second guide pin 49.1 slides in the second groove 38 to the low point. This displaces the locking sleeve 46 in the locked position in FIG. 4 in which it prevents the pipette tip 57 from releasing from the pin 4.

[0089] Connecting the tip plunger 69 to the stroke rod 17 and pipetting can be carried out in the above-described manner.

[0090] The exemplary embodiment in FIG. 1 differs from that described above in that the locking sleeve 46 is shoved into the locked position beyond the outer circumference of the collar 61 of the pipette tip 57. With this positive displacement pipette, pipette tips 57 are used that have at least one longitudinal slot proceeding from the upper end. The longitudinal slot enables a radial expansion of the pipette tip 57 in order to establish a form-fit connection of the pipette tip 57 with the pin 4. The form-fit connection is prevented from releasing when the locking sleeve 57 is located in the locked position as shown in FIG. 11. To release the pipette tip 57 from the pin 4, the locking sleeve 46 is displaced upward by means of the rotating sleeve 28 as in the above-described exemplary embodiment, and then the pipette tip 57 is released from the pin 4 by pressing against the top side of the tip plunger 69.

[0091] According to FIGS. 12 and 13, a gear apparatus 73 is designed as a gear train 74 to displace the locking sleeve 46 and the ejection rod 39. The gear train 74 has two outputs 75, 76 in the form of a first and a second output-side rack 77, 78. The first output-side rack 77 is connected via the control rod 47 to the locking sleeve (46), and the second output-side rack 78 is connected to the ejection rod 39. Furthermore, the gear apparatus 73 has two drives 79, 80 in the form of a first and a second drive-side rack 81, 82. The first drive-side rack 81 is connected at one end to a first operating element 83, and the second drive-side rack 82 is connected at the end remote from the first operating element 83 to a second operating element 84. The two drive-side racks 81, 82 mesh on different sides with the same drive pinion 85. The first and the second drive-side track 81, 82 are connected to the second output-side rack 78 via the drive pinion 85 and a first output pinion 86 rigidly connected to the drive pinion 85, and are connected to the first output-side rack 77 via the drive pinion 85, an intermediate gear 88 and a second output pinion 87 rigidly connected to the intermediate tooth wheel.

[0092] The first and the second operating element 83, 84 are arranged on different sides of the pipette housing 2.

[0093] By optionally actuating the first operating element 83 or the second operating element 84, the movement of the locking sleeve 46 and the ejection rod 39 can be controlled in different directions.

[0094] The gear apparatus 73 with the gear train 74 can be arranged in the pipette housing 2 instead of the gear apparatus with the rotating sleeve 28. The drive apparatus 12 can be separate from the gear apparatus 73, wherein there can be a separate operating element for driving the drive apparatus 12 that is separate from the two operating elements 83, 84 of the gear apparatus 73. This can be an operating element 18 that projects from the pipette housing 2 through a longitudinal slot running in the longitudinal direction of the pipette housing 2 and can be displaced in the direction of the pin 4. The operating element 18 can displace a drive element 16 of the drive apparatus 12 alternatingly downward and upward by means of a transmission mechanism 15 that is designed therefor when the operating element 18 is sequentially displace downward, between which the operating element 18 is displaced upward.

REFERENCE SIGN LIST

[0095] 1 Pipette [0096] 2 Pipette housing [0097] 3 Shaft [0098] 4 Pin [0099] 5 Through bore [0100] 6 Upper pin section [0101] 7 Lower pin section [0102] 8 Annular groove [0103] 9 First means for a form-fit connection [0104] 10 Slot [0105] 11 Slot [0106] 12 Drive direction [0107] 13 Transmission element [0108] 14 Transmission rod [0109] 15 Transmission mechanism [0110] 16 Drive element [0111] 17 Stroke rod [0112] 18 Operating element [0113] 19 Operating lever [0114] 20 Web [0115] 21 Support plate [0116] 22 First curved slot [0117] 23 First edge cutout [0118] 24 Longitudinal slot [0119] 25 Seat [0120] 26 Ejection apparatus [0121] 27 Curved support [0122] 28 Rotating sleeve [0123] 29 Cut-out [0124] 30 Cut-out [0125] 31 Base [0126] 32 Sector [0127] 33 Sector [0128] 34 First curve [0129] 35 Second curve [0130] 36 First groove [0131] 37 Vertical part [0132] 38 Second groove [0133] 39 Ejection rod [0134] 40 Upper ejection rod part [0135] 41 Lower ejection rod part [0136] 42 Connecting rod part [0137] 43 First sensing element [0138] 44 Guide pin [0139] 45 Locking apparatus [0140] 46 Locking sleeve [0141] 47 Control rod [0142] 48 Second connecting rod part [0143] 49 Second sensing element [0144] 49.1 Second guide pin [0145] 50 Support ring [0146] 51 Casing [0147] 52 Second curved slot [0148] 52.1 Second edge cutout [0149] 53 Third sensing element [0150] 54 Helical spring [0151] 55 Adjusting knob [0152] 56 Counter [0153] 57 Pipette tip [0154] 58 Body [0155] 59 Tip opening [0156] 60 Mounting opening [0157] 61 Collar [0158] 62 Seat region [0159] 63 Lower seat section [0160] 64 Bead [0161] 65 Upper seat section [0162] 66 Second means for a form-fit connection [0163] 67 Plunger travel region [0164] 68 Tip section [0165] 69 Tip plunger [0166] 70 Plunger [0167] 71 Plunger rod [0168] 72 Plunger head [0169] 73 Gear apparatus [0170] 74 Gear train [0171] 75 Output [0172] 76 Output [0173] 77 First output-side rack [0174] 78 Second output-side rack [0175] 79 Drive [0176] 80 Drive [0177] 81 First drive-side rack [0178] 82 Second drive-side rack [0179] 83 First operating element [0180] 84 Second operating element [0181] 85 Drive pinion [0182] 86 First output pinion [0183] 87 Second output pinion [0184] 88 Intermediate gear