Pipette with a single channel bottom, and pipette with a top and a single channel bottom.

Abstract

It provides a single-channel lower section for pipettes, enabling more reliable and accurate pipetting. [Solution] The pipette has a rod-shaped housing comprising a hollow cylindrical lower housing 3 and an elongated hollow upper housing. The lower housing has a hollow cylindrical upper housing portion 5 having a spring space 6 and a hollow cylindrical lower housing portion 7 having a housing space 8. The spring space and the housing space together form the internal space 9 of the lower housing. The lower housing portion has a larger inner diameter than the upper housing portion. The upper housing portion has a cylindrical upper wall 10 that defines the spring space laterally. The upper housing portion has a circular opening 11 to the spring space defined by the upper edge of the upper wall at its top and a shoulder-shaped limit 12 that extends along the inner circumference of the upper wall and protrudes radially inward at its bottom, defining the bottom of the spring space 6. A circular through-opening 14 is formed in the center of the shoulder.

Description

Technical Field

[0001] The present invention relates to a single-channel pipette lower part, and a pipette provided with an upper part and the single-channel lower part.

[0002] Pipettes are used in scientific industrial laboratories, especially for medical, molecular biological, and pharmaceutical applications, to measure a selected volume of liquid. This liquid may especially be a homogeneous (single-phase) liquid consisting of a single liquid component, or a homogeneous mixture of a plurality of liquid components (solution). Further, this liquid may be a heterogeneous (multiphase) liquid mixture (emulsion) of one liquid and another liquid, or a heterogeneous (multiphase) liquid mixture (suspension) of one liquid and a solid.

[0003] Known pipettes have an elongated hollow pipette housing with a spigot (attachment) at the lower end for clamping a pipette tip. The spigot is usually a conical, cylindrical, or partially conical or cylindrical protrusion, also called the "working cone part". The pipette tip is a hollow tube having a tip opening at the lower end and a mounting opening at the upper end, and the pipette tip can be clamped to the spigot by the mounting opening. Liquid is inhaled into the pipette tip and discharged therefrom. The inhalation and discharge of the liquid are controlled by the pipette. A pipette with a fixed volume serves to pipette a certain volume. In a variable pipette, the volume to be measured can be adjusted. The set volume is displayed using a mechanical counter. To set the volume, the stroke of the drive device can be adjusted by a setting device connected to the counter. After use, this pipette tip is removed from the attachment and can be replaced with a new pipette tip. In this way, cross-contamination during subsequent pipetting operations can be prevented.

[0004] An air-cushion pipette has a plunger / cylinder or other displacement device within the pipette housing, which is connected by a through-channel to a hole at the lower end of the spigot. The air cushion moves to draw liquid into the pipette tip, which is clamped to the spigot, by displacing the plunger within the cylinder using the drive device, and then to discharge the liquid from there. Disposable or reusable pipette tips are typically made of plastic. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In air-cushion pipettes, the displacement mechanism can become contaminated. This can be caused by improper handling resulting in liquid contamination, or by vapors or very fine droplets of the liquid being pipetted entering the displacement mechanism.

[0006] A positive displacement pipette is used with a pipette tip that has an integrated plunger. This type of pipette has a spigot to which the pipette tip is attached, and a drive device for displacing the plunger, which can be connected to the integrated plunger (tip plunger). Since the plunger comes into direct contact with the liquid, the adverse effects of air cushions are eliminated. Positive displacement pipettes are particularly suitable for applications in molecular biology where it is important to measure high vapor pressure, high viscosity, or high density liquids, and where the absence of aerosols to avoid contamination is crucial.

[0007] An air-cushion pipette in which the lower section, equipped with a displacement device and attachment for mounting pipette tips, is detachable from the upper section, which is equipped with a drive device for driving the displacement device. This simplifies the assembly and disassembly of the displacement and drive devices, as well as cleaning, maintenance, and repair, and allows connection to various single-channel and / or multi-channel lower sections using the same upper section.

[0008] European Patent No. 1 559 480 B1 describes a pipette in which a displacement device and a drive device can be connected to and disconnected from each other more easily and quickly. The pipette has a displacement device comprising a displacement chamber having a displaceable limit, which corresponds to a preferred embodiment and is hereinafter referred to as a plunger. Furthermore, the pipette has an attachment for connecting to a pipette tip and a connection channel between the displacement chamber and the free end of the attachment. In addition, the pipette comprises a drive device for driving the plunger of the displacement device by a drive member having a removable and operable connection to the plunger. Furthermore, the pipette has a bayonet connection between the drive device and the displacement device, which can be established by operably connecting the drive member and the plunger and is removable by disconnecting the operable connection between the drive member and the plunger.

[0009] The drive member is a stroke rod of a drive device that is displaceable parallel to the longitudinal axis of the bayonet connection. The displacement member is connected to the plunger via a plunger rod, is oriented laterally to the stroke rod, and has a contact surface that is pressed against the lower end of the stroke rod by a stroke spring. The stroke spring is a helical spring surrounding the plunger rod. The actuariable connection between the drive member and the plunger is established by establishing the bayonet connection and disengaged by releasing the bayonet connection.

[0010] Therefore, the objective of this invention is to provide a single-channel lower section for pipettes that enables more reliable and accurate pipetting operations. [Means for solving the problem]

[0011] This objective is achieved by the single-channel lower section of the present invention for pipettes as described in claim 1. Advantageous embodiments of the present invention are specified in the dependent claims and the following description.

[0012] The lower part of the single channel for pipette according to this invention is • The lower part of the hollow cylindrical housing, Interior space and, The upper end has an opening, At the bottom end is the housing floor, An attachment for mounting pipette tips, the attachment having a through channel that protrudes downward from the housing floor and extends from the lower end of the attachment into the internal space, A lower part of the housing comprises a spring space that forms an internal space or part thereof, having an opening at the top and a through opening at the bottom, and having at least one limit projecting radially inward, A rod-shaped plunger actuator for displacing a plunger within a cylinder, wherein the plunger actuator is at least partially located within a spring space, extends axially from the lower part of a hollow cylindrical housing, and is aligned with a through-opening. • Contact surface for the stroke rod of the drive device located at the upper end of the plunger actuator, • A spring support portion that is connected to the plunger actuator beyond its limit and protrudes radially outward from the plunger actuator, • A coil spring positioned in the spring space, with its top supported on the underside of the spring support and its bottom supported by the limit, through which the plunger actuator extends. A first guide for axially guiding a plunger actuator at the bottom of a hollow cylindrical housing, comprising: a first guide having at least one first guide surface provided on the inner circumferential surface of a spring space; and a first guide having at least one second guide surface provided on the outer circumferential surface of a guide element that is guided by the first guide surface, protrudes radially outward from the plunger actuator, and is connected to the plunger actuator.

[0013] The applicant has determined that, in particular, in high-capacity pipettes designed for use with pipette tips of nominal capacities of 2 ml, 5 ml, or 10 ml, the plunger of the displacement device may tilt within the cylinder under unfavorable conditions. This can occur, for example, when the lower part and the displacement device located therein are connected to the upper part and the drive device located therein in an air-cushion pipette. According to the applicant's findings, the tilting of the plunger can create a gap between the seal and the cylinder wall, resulting in slight to significant leakage between the plunger and the cylinder. This can lead to inaccurate pipetting results, and may even make pipetting impossible. Furthermore, the tilting of the plunger within the cylinder can increase wear and repair costs.

[0014] According to this invention, the plunger actuator is aligned in the spring space of the lower housing to displace the plunger within the cylinder, thereby preventing unfavorable tilting of the plunger within the cylinder. Therefore, the plunger is not only guided within the cylinder, but is also aligned in the spring space away from the cylinder by the plunger actuator. As a result, tilting of the plunger within the cylinder and the resulting drawbacks are avoided. This improves the accuracy of pipetting, reduces pipette wear, and lowers the costs of calibration and repair. Expansion of the guide surface, friction generated during plunger displacement, and the manufacturing costs of the guide surface can be kept low.

[0015] Because the plungers of large-capacity pipettes tend to tilt particularly strongly due to their large cross-section, the advantageous effect of this invention is especially pronounced in large-capacity pipettes with a nominal volume of at least 2 ml. However, the advantageous effect of this invention can also be used in pipettes with smaller nominal volumes. This invention can be used in both air-cushion pipettes and positive displacement pipettes. It is suitable for use in fixed-volume pipettes and variable-volume pipettes. This invention is particularly suitable for manual and electric pipettes, and preferably for manual pipettes that can be held and operated with one hand. This invention can also be advantageously used in laboratory and weighing machines that use the single-channel lower section described in claim 1.

[0016] According to one embodiment of the present invention, the contact surface is the upper surface of the plunger actuator and / or the upper surface of the spring support. In this way, the contact surface is integrated into an existing component, reducing design and structural complexity.

[0017] In another embodiment, the contact surface is the upper surface of a plunger head connected to the upper end of the plunger actuator and having a larger cross-section than the adjacent area of ​​the plunger actuator. This allows for a particularly large contact surface, which facilitates connecting the lower part of the housing to the upper part of the housing and positioning the lower end of the stroke rod in the center of the contact surface. In another embodiment, the plunger head is either detachably fixed to the upper end of the plunger actuator or integrally connected to the upper end of the plunger actuator.

[0018] According to another embodiment, the contact surface is cup-shaped. The cup-shaped contact surface allows the stroke rod, with its lower end resting on it, to be centrally positioned, thereby avoiding lateral forces acting on the plunger actuator that would increase friction in the first guide.

[0019] In another embodiment, the spring support comprises a spring seat held by a plunger actuator and a spring retainer that secures the spring seat to the plunger actuator. This simplifies the assembly of the plunger actuator, spring seat, and spring retainer. In another embodiment, the spring retainer is detachably fixed to the plunger actuator. This allows for disassembly, for example, for maintenance or repair. In another embodiment, the spring seat and spring retainer are separate parts. Alternatively, the spring seat and spring retainer are integrally formed. Integral-formed parts reduce manufacturing and assembly costs. In another embodiment, the spring seat is a lower part, and the sole function of the spring retainer is to secure the spring seat to the plunger actuator. In another embodiment, the contact surface is formed on the upper surface of the spring retainer. As a result, a particularly large contact surface can be provided, thereby simplifying the assembly of the lower part to the upper part and the central positioning of the lower end of the stroke rod.

[0020] According to another embodiment, the guide element is a plunger head and / or spring support. In this way, the first guide can be positioned at a particularly large distance from the cylinder, and the plunger can be aligned particularly well. In addition, structural costs can be reduced. According to another embodiment, the plunger head and / or spring support has a second guide surface on its outer circumference.

[0021] According to another embodiment, the first and second guide surfaces are cylindrical. This is particularly advantageous for easily and accurately manufacturing the guide surfaces.

[0022] According to another embodiment, the spring space preferably has two first guide surfaces that are diametrically opposed, and these first guide surfaces are symmetrically distributed around its central axis, each of which extends only over a part of the entire circumference and the guide element abuts thereon. The guide element has a single second guide surface that extends over the entire circumference, or preferably two second guide surfaces that are diametrically opposed, and these second guide surfaces are symmetrically distributed around the plunger actuator, each of which extends only over a part of the entire circumference. This makes it possible to guide the plunger actuator particularly uniformly with low friction.

[0023] According to an alternative embodiment, the spring space has only a single first guide surface against which the guide element abuts and which extends over the entire circumference, preferably symmetrically distributed around the plunger actuator, and each of which has two diametrically opposed second guide surfaces that extend only over a part of the entire circumference. This makes it possible to guide the plunger actuator particularly uniformly with low friction.

[0024] According to another embodiment, the guide element has a hollow cylindrical part, and has at least one second guide surface on the outer circumference of the hollow cylindrical part, and the hollow cylindrical part accommodates the upper end part of the plunger rod. In this way, it is possible to realize a structurally simple embodiment of the guide element that can be easily assembled and disassembled as required.

[0025] According to another embodiment, the second guide surface is present on the outside of a wing that protrudes outward from the outer circumference of the hollow cylindrical part. In this way, a structurally simple embodiment of the elastically deformable guide element is achieved, and as a result, the frictional force can be reduced.

[0026] According to an embodiment, the wing has a cavity that extends parallel to the plunger actuator and has an arcuate cross-section. In this way, accumulation of material can be avoided, which is particularly advantageous for dimensionally stable injection molding of a plastic guide element. Furthermore, the arcuate hollow cross-section increases elasticity.

[0027] According to one embodiment, the guide element has at least one corrugated portion on its outer circumference, preferably two corrugated portions facing each other in the diametrical direction. These corrugated portions facilitate the assembly of the guide element and, if necessary, its disassembly.

[0028] According to another embodiment, the guide element has a snap-on connection to the plunger actuator, and / or a form-fit connection to the plunger actuator, and / or a press-fit connection to the plunger actuator, and / or a connection to the plunger actuator by another part. This simplifies the assembly and, if necessary, disassembly of the guide element. For disassembly, the snap-on connection and / or form-fit connection and / or press-fit connection and / or connection by another part are configured as removable connections.

[0029] According to another embodiment, the guide element and the plunger actuator each include at least one connecting element, which is configured to form a snap-on connection, a form-fit connection, or a press-fit connection. According to another embodiment, at least one connecting element of the guide element is integrally connected to the guide element, and at least one connecting element of the plunger actuator is integrally connected to the plunger actuator. According to another embodiment, a further component is a lower component whose sole function is to secure the guide element to the plunger actuator.

[0030] According to another embodiment, the hollow cylindrical portion has at least one connecting element on its inner circumference that connects to a plunger actuator. According to another embodiment, the hollow cylindrical portion and the plunger actuator have connecting elements that fit together and connect to each other. According to another embodiment, the fitting connecting elements are elements of a snap-on connector and / or a form-fit connector and / or a press-fit connector. According to another embodiment, the hollow cylindrical portion has four inwardly projecting parallel pins on its inner circumference, the ends of which engage with grooves on the outer circumference of the plunger actuator.

[0031] According to another embodiment, the limit is a shoulder that extends around the entire or partial circumference of the inner circumference of the internal space at the lower end of the spring space.

[0032] According to another embodiment, the pipette is an air-cushioned pipette. According to another embodiment, the lower part of the housing has a hollow cylindrical upper housing portion having a spring space that forms part of the internal space, and the lower part of the housing has a hollow cylindrical lower housing portion having a housing space that is defined at the bottom by the housing floor and forms a further part of the internal space, a cylinder is placed in the housing space, the cylinder is connected at the bottom to a through channel of the attachment, a plunger is placed inside the cylinder, the plunger abuts on the outer surface to seal the inner surface of the cylinder, the plunger is displaceable in the axial direction of the cylinder, a plunger actuator in the form of a plunger rod is connected to the plunger, the plunger rod extends upward from the plunger through a through opening into the upper housing portion. In this air-cushioned pipette, the plunger, guided within the cylinder placed in the housing space, is further aligned by a first guide of the plunger actuator, preventing the plunger from tilting.

[0033] According to another embodiment, the housing space of the lower housing has a larger diameter than the spring space of the upper housing. In this way, it is possible to provide a housing space for a cylinder in which a plunger having a predetermined stroke and volume is displaceable, in a structurally relatively simple manner.

[0034] According to another embodiment, the connecting portion connects the lower edge of the upper housing portion to the upper edge of the lower housing portion. The connecting portion can bridge upper and lower housing portions of different diameters. Since upper and lower housing portions of various diameters are connected to each other by the connecting portion, the structural complexity can be kept relatively low.

[0035] According to another embodiment, the connecting portion comprises an annular disc-shaped cover and a hollow cylindrical collar projecting downward from the outer edge of the cover, the upper housing portion being connected to the upper surface of the cover, the collar being connected to the upper edge of the lower housing portion, and the cover covering the occupant space at the top. The connecting portion simultaneously forms a cover for the occupant space and the cylinder placed therein. The cover can be manufactured integrally with the upper housing portion. This is advantageous for manufacturing the upper and lower housing portions by injection molding, as undercuts can be avoided. After injection molding, the upper housing portion can be connected to the upper edge of the lower housing portion by the collar of the cover.

[0036] According to another embodiment, the collar is connected to the upper edge of the lower housing via a screw connection, a bayonet connection, a removable snap-on connection, or other removable connection. This allows the housing to be opened for cleaning, maintenance, or repair without damaging the lower part of the housing, and then closed again, for example, when replacing the plunger seal inside the cylinder.

[0037] Alternatively, the collar is connected to the upper edge of the lower housing by heat fusion or adhesive, using a non-removable connector, such as a snap-on connector that cannot be removed without destruction.

[0038] According to another embodiment, the pipette is a positive displacement pipette. In a positive displacement pipette as well, it is useful to be composed of a top and bottom to simplify assembly, disassembly, cleaning, maintenance, and repair, and to allow the same top to be used to connect to various single-channel and / or multi-channel bottoms.

[0039] According to another embodiment, the lower end of the plunger actuator has a device for connecting to the upper end of a tip plunger that is inserted into a pipette tip that can be clamped to an attachment. In this embodiment, the plunger actuator is formed to connect to the tip plunger of a pipette tip that incorporates the tip plunger and can be clamped to an attachment. By aligning the plunger actuator with a first guide, the tip plunger is prevented from tilting within the pipette tip.

[0040] According to another embodiment, a second guide for the plunger actuator is located axially at the bottom of the hollow cylindrical housing, and this guide has at least one third guide surface on the through-opening and at least one fourth guide surface on the outer circumference of the plunger actuator. The second guide further improves the alignment of the plunger within the cylinder and cancels out any tilt.

[0041] According to one embodiment, the through-opening of the limit has a circular cross-section. According to another embodiment, the through-opening has two guide grooves facing each other in the diametrical direction, and the plunger rod has at least two guide ribs on its outer circumference that engage with the guide grooves and project outward in the diametrical direction. By guiding the guide ribs within the guide grooves, rotation is prevented. This ensures that the first guide surface and the second guide surface of the first guide are aligned with each other, and thus the plunger can be positioned as desired.

[0042] According to another embodiment, the cylinder has a volume of at least 2 ml, preferably 2 ml, 5 ml, or 10 ml. Improving measuring accuracy and avoiding breakage is particularly effective in large-capacity pipettes where the nominal capacity is within the previously defined range or the aforementioned values.

[0043] Furthermore, this invention relates to claim 1 ~ A pipette comprising an upper and a single-channel lower according to one of the embodiments specified in paragraph 24 or the specification, wherein the upper comprises a housing upper, an operating button provided on the outside of the housing upper, a drive device located on the housing upper and operably connected to the operating button, and a displaceable stroke rod of the drive device, the lower end of which is accessible from the outside through a further opening in the housing upper, the upper and the single-channel lower are formed such that the lower end of the stroke rod is brought to a connection position in contact with the contact surface of a plunger actuator, and there exists a connecting device that connects the upper and the lower to each other in the connection position.

[0044] The present invention will be described in more detail below based on the accompanying drawings of exemplary embodiments. [Brief explanation of the drawing]

[0045] [Figure 1] A vertical cross-sectional view of a manual air-cushion pipette having a single-channel lower section according to the present invention. [Figure 2] A magnified vertical cross-sectional view of the same lower section. [Figure 3] The same lower section, top view. [Figure 4] A horizontal cross-sectional view of the same lower section, seen from above. [Figure 5] Figure 5a shows a perspective view of the plunger actuator with a spring support before assembly, viewed from diagonally above (Figure 5a) and diagonally below (Figure 5b). Figure 5c shows the pre-assembly state viewed from diagonally above (Figure 5c) and a top view of the pre-assembly state (Figure 5d), and a top view of the assembled state (Figure 5e). [Modes for carrying out the invention]

[0046] In this application, demonstrative terms such as “top” and “bottom,” “up” and “down,” as well as derived terms such as “bottom” and “top,” and “horizontal” and “vertical,” refer to the orientation of a pipette in which the sheet is positioned at the lower end of the pipette and directed vertically downward. In this orientation, the pipette tip attached to the sheet can be directed toward a container positioned below in order to draw liquid into the pipette tip and dispense liquid from the pipette tip.

[0047] According to Figure 1, the pipette 1 has a rod-shaped housing 2 comprising a hollow cylindrical lower housing 3 and an elongated hollow upper housing 4.

[0048] According to Figures 2 to 5, the lower housing 3 has a hollow cylindrical upper housing portion 5 with a spring space 6 and a hollow cylindrical lower housing portion 7 with a housing space 8. The spring space 6 and the housing space 8 together form the internal space 9 of the lower housing 3. The lower housing portion 7 has a larger inner diameter than the upper housing portion 5.

[0049] The upper housing portion 5 has a cylindrical upper wall 10 that defines the spring space 6 laterally. The upper housing portion 5 has a circular opening 11 to the spring space 6 defined by the upper edge of the upper wall 10 at its top, and a shoulder-shaped limit 12 projecting radially inward at its bottom, which extends along the inner circumference of the upper wall and defines the bottom of the spring space 6. A circular through-opening 14 is formed in the center of the shoulder 13. The through-opening 14 has two guide grooves 15 on its inner circumference that are diametrically opposed and extend axially.

[0050] The upper wall 10 has two inwardly projecting pedestal-shaped regions 16 on its inner circumference, extending axially along the spring space 6 and circumferentially only over a portion of the inner circumference, and facing each other in the diametrical direction. The pedestal-shaped regions 16 are located at the front and rear of the plane in the drawings of Figures 1 and 2, and are shown in Figure 3. The inner surfaces of the pedestal-shaped regions 16 each form a first cylindrical guide surface 17 having a radius of curvature centered on the central axis of the spring space 6.

[0051] The lower housing section 7 has a cylindrical lower wall 18 that laterally defines the housing space 8. The lower housing section 7 has a further opening 19 at its top. At its bottom, the lower housing section 7 has a conical housing floor 20 that defines the bottom of the housing space 8. A narrow, annular, slightly conical attachment 21 protrudes downward from the housing floor 20 and has a seat 22 with a peripheral groove for an O-ring for attaching a pipette tip 23. The attachment 21 has a circular cross-section and a through channel 24 that extends from the lower end of the attachment into the housing space 8.

[0052] The upper housing portion 5 is connected to the lower housing portion 7 via a connecting portion 25. The connecting portion 25 has an annular disc-shaped cover 26 that is integrally connected to the lower edge of the upper wall 10. A cylindrical collar 27 of the connecting portion 25 protrudes downward and is integrally connected to the outer edge of the cover 26. The collar 27 has a female thread 28, and the upper edge of the lower wall 18 has a male thread 29 that engages with the female thread 28. The female thread 28 of the connecting portion 25 is screwed into the male thread 29 of the lower wall 18, and in this way the upper housing portion 5 is connected to the lower housing portion 7. The disc-shaped cover 26 covers a further opening 19 of the lower housing portion 7.

[0053] A displacement chamber 30 shaped like a cylinder 31 is positioned in the lower housing 7. This cylinder has a conical base 32 that defines the bottom of the cylinder 31. A further attachment 33 protrudes downward from the conical base 32. A further through channel 34 extends from the lower end of the further attachment 33 and enters the cylinder 31. The cylinder 31 is inserted so as to fit snugly into the lower housing 7. The outer shape of the cylinder 31 corresponds to the inner shape of the lower housing 7. The outer circumference of the further attachment 33 is sealed via an O-ring 35 provided on the inner circumference of the attachment 21. The top of the cylinder 31 is fixed to the lower housing 7 by a connecting portion 25.

[0054] A roughly disc-shaped plunger 36, having a flat top surface and a frustoconical bottom surface, is positioned within the cylinder 31. A conical spigot 37 protrudes downward from the center of the bottom surface and can slide into the further attachment 33 to seal the further attachment 33. The plunger 36 has a seal lip 38 extending around its outer circumference. A rod-shaped plunger actuator 39, also called a plunger rod 39, protrudes vertically upward from the center of the top surface of the plunger 36. The plunger actuator 39 is positioned on the central axis of the lower part 3 of the hollow cylindrical housing. The plunger actuator 39 extends through a through-opening 14 into the spring space 6 and protrudes from the opening 11 at its top.

[0055] The plunger actuator 39 has four radially outward projecting guide ribs 41 extending longitudinally on its outer circumference, of which two guide ribs 41.1 project further outward, while two guide ribs 41.2 do not project as far outward. Both of the guide ribs 41.1 that project further outward are guided into guide grooves 15 that extend axially through the through opening 14. The two guide ribs 41.2 that do not project as far outward are guided to the inner circumference of the through opening 14 and each has a radially outward projecting stepped portion 41.3 at its leg (see Figures 5a and 5c).

[0056] At the uppermost position of the plunger 36 shown in Figure 2, the stepped portion 41.3 abuts against the lower surface of the cover 26.

[0057] The spring support portion 42 is fixed to the upper end of the plunger actuator 39. The plunger actuator 39 and the spring support portion 42 are shown in their pre-assembly state in Figures 5a and 5b. The spring support portion 42 protrudes radially outward from the plunger actuator 39. The spring support portion 42 has a hollow cylindrical portion 43 and four parallel pins 44 that extend inward from its inner circumference and are supported by the plunger actuator 39. The outer circumference of the plunger actuator 39 has a groove 45, which has an axial groove portion 45.1 extending axially downward from its upper end, and each of these groove portions 45.2 extending in part around the axial groove portion, starting from the lower end of the axial groove portion. The inner ends of the pins 44 slide into the axial groove portion 45.1 (see Figures 5c and 5d), and the pins 44 rotate into the groove portions 45.2 extending in part thereto (see Figure 5e). The groove 45 and the pin 44 form a bayonet connection portion 46, which holds the spring support portion 41 in a fixed position on the plunger actuator 39.

[0058] The spring support portion 42 is also a guide element 47.

[0059] As shown in Figure 3, two wings 48, formed by two arc-shaped regions 49, protrude outward from the outer circumference of the hollow cylindrical portion 43. These wings are positioned on sides of the hollow cylindrical portion 43 that are opposite each other in the diametrical direction and extend across the entire height of the hollow cylindrical portion 43. Each arc-shaped region 49 has a curved region 50 with an arc-shaped cross-section and outwardly angled legs 51 that originate from both ends of this region and connect to the hollow cylindrical portion 43. The curved region 50 forms a second circular cylindrical guide surface 52. On the outside, the curved region 50 has a radius of curvature corresponding to the radius of curvature of the first guide surface 17. The two curved regions 50 and the hollow cylindrical portion 43 define two cavities 53 that extend axially from the lower part 3 of the hollow cylindrical housing.

[0060] The first guide surface 17 and the second guide surface 52 together form the first guide 54.

[0061] The guide groove 15 forms a third guide surface 55, and the guide rib 41 forms a fourth guide surface 56. The third guide surface 55 and the fourth guide surface 56 together form a second guide 57.

[0062] Between the two arc-shaped regions 49, the hollow cylindrical portion 47 has two corrugated portions 58 on its outer circumference that extend axially and face each other in the diametrical direction.

[0063] The spring support section 42 also includes a spring seat 59 and a spring retainer 60 that fixes the spring seat 59 to the plunger actuator 39.

[0064] The upper end of the plunger actuator 39 is cup-shaped and forms a contact surface 61 with the lower end of the stroke rod of the drive device.

[0065] The coil spring 62 is positioned in the spring space 6, with its bottom supported by the limit 12 and its top supported by the lower surface of the spring support 42. The coil spring 62 is preloaded so as to press the plunger actuator 39 upward until the plunger 36 contacts the lower surface 64 of the cover 26 with the stepped portion 41.3 of its upper plunger surface 63 (see Figure 2, 5c).

[0066] The lower part of the housing 3 has a pot-shaped discharge sleeve 65 on its exterior. The upper housing section 5 and the lower housing section 7 are inserted into the discharge sleeve 65. The attachment 21 protrudes downward through a circular lower hole 66 and exits the conical housing floor 67 of the discharge sleeve 65. At the top, the discharge sleeve 65 is closed by a lid-shaped discharge transmission element 68, which has a circular upper hole 69 through which the cylindrical upper side wall 10 of the upper housing section 5 protrudes upward. On the top surface, the discharge transmission element 68 has a small hole (eye) 70 for accommodating the lower end of the discharge rod.

[0067] According to Figure 1, the upper part 4 of the housing includes a stroke rod 71, which abuts against the upper surface of the contact surface 61. The lower end of the stroke rod 71 engages with a cup-shaped recess in the contact surface 61. An operating button 72, which protrudes outward from the upper end of the housing 2, is fixed to the top of the stroke rod 71.

[0068] The stroke rod 71 is guided through the central spindle bore 73 of a threaded spindle 74 located in the upper housing 4. On the outside, the threaded spindle 74 has a male thread 75, which can be screwed into a female thread 76 of a stroke body 77, which is held at its bottom by a carrier 78 in the upper housing 4. The stroke body 77 forms a spindle nut 79.

[0069] The lower end face of the threaded spindle 74 is an upper stop portion 80 for a stop element 81 in the shape of an annular bead 82 on the outer circumference of the stroke rod 71.

[0070] The threaded spindle 74 is connected at its upper end to a catch 83 and rotates with it, the catch engaging with an axial groove 85 of a catch sleeve 86 by a radially outward projecting rib 84. The catch sleeve 86 is positioned concentrically with respect to the threaded spindle 74 and is rotatably mounted on the outer circumference of the stroke body 77. The catch sleeve 86 has a pair of teeth 87 extending around the lower edge of its outer circumference.

[0071] The adjustment sleeve 88 is pressed against the catch sleeve 86. The adjustment sleeve 88 is connected to the catch sleeve 86 so as to rotate together with it. The upper end of the adjustment sleeve 88 protrudes outward from the upper end of the housing 2. Here, the adjustment sleeve 88 has an adjustment ring 89 on its outer circumference, which in turn carries an additional corrugated portion 90 on its outer circumference.

[0072] A counter 91, in the form of a roller counter with a drive gear 92, is held on a first carrier 78. The numeral rollers of the counter 91 are visible from the outside of the housing 2 through a window in the upper part 4 of the housing.

[0073] A pot-shaped holder 93 is positioned on the upper part 4 of the housing below the stroke body 77. The holder 93 includes a lower stop 94, which is supported by an overstroke spring 95 in the form of a coil spring supported in the base of the holder 93. The stroke rod 71 is guided through the central passage of the lower stop 94, through the overstroke spring 95, and through the central passage in the base of the holder 93.

[0074] As the adjustment sleeve 88 rotates, the catch sleeve 86 also rotates. Using the catch sleeve 86, the threaded spindle 74 is screwed into the female thread 76 fixed to the housing, and the upper stop 80 moves upward or downward depending on the direction of rotation. This adjusts the distance between the upper stop 80 and the lower stop 94, and determines the measuring volume. Each set measuring volume is readable by a counter 91 driven by the drive gear 92 of the catch sleeve 86.

[0075] The discharge button 96 rests on a discharge rod 97 adjacent to the adjustment sleeve 88 in the upper edge region of the upper part 4 of the housing. The discharge rod 97 extends parallel to the stroke rod 71, passing through the upper part 4 of the housing. The lower end of this rod is firmly pressed into a small hole 70 of a discharge transmission element 68 of a discharge sleeve 65, which is displaceably positioned in the lower part 3 of the housing.

[0076] A discharge spring 98, designed as a coil spring, is positioned in the upper part 4 of the housing, with one end of the discharge spring supported within the housing 2 and the other end supported by the discharge rod 97. The discharge spring 98 presses the discharge rod 87 upward, causing the discharge floor 67 to come into contact with the housing floor 20.

[0077] The lower housing 3 and the upper housing 4 are connected to each other by a snap-on connector 99. According to Figure 1, the snap-on connector 99 preferably includes two spring-loaded hooks 100 defined by slots from the lower housing 3 on the circular cylindrical upper wall 10 of the upper housing 5. The hooks 100 are not shown in Figure 2 because Figure 2 shows a vertical cross-section rotated 90° relative to Figure 1 around the central axis of the lower housing. Furthermore, the snap-on connector 99 includes an inner step 101 that encircles the inner circumference of an axially oriented receiving portion 102 provided at the lower end of the upper housing 4 for insertion of the upper housing 5 into the lower housing 3. The lower housing 3 and the upper housing 4 are connected to each other by snapping the spring-loaded hooks 100 behind the upper surface of the inner step 101.

[0078] Before pipetting, the user can set the desired volume to be measured. For this purpose, the user rotates the adjustment ring 33 until the desired volume is displayed by the counter 91.

[0079] The user can secure the pipette tip 23 to the pipette 1 by pressing the seat 7 of the pipette 1 against the upper opening of the pipette tip 23. For pipetting, the user first presses down the operating button 72 so that the stop element 81 is displaced relative to the lower stop 94 by the upper stop 80. At this time, the stroke rod 67 pushes the plunger 36 downward, preloading the coil spring 62. Then, the user immerses the lower opening of the pipette tip 23 in the sample liquid and releases the operating button 72. As a result, the coil spring 62 pushes the plunger 31 and stroke rod 71 upward until the stop element 81 contacts the upper stop 80. At this time, an amount of liquid corresponding to the set measuring volume is drawn into the pipette tip 23.

[0080] To dispense a volume of liquid, the user holds the lower opening of the pipette tip 23 over another container and presses the operating button 72 downwards again. Once the lower stop 94 is reached, the user can push the operating button 72 further in, overcoming the resistance of the overstroke spring 95, to discharge the remaining liquid from the pipette tip 23 through an overstroke.

[0081] As the stroke rod 71 is displaced downward and upward, the plunger actuator 38 is guided by the first guide 54 and the second guide 57, thereby preventing the plunger 36 from tilting within the cylinder 31. [Explanation of Symbols]

[0082] 1 pipette 2 Housing 3. Hollow cylindrical housing lower part 4. Top of the housing 5. Upper housing section 6 Spring space 7 Lower housing section 8. Containment space 9 Interior space 10 Upper wall 11 Circular opening 12 Limit 13 Shoulder 14 Through-opening 15 Guide grooves 16. Base-shaped area 17 Guide surface 18 Lower wall 19 Further openings 20 Conical housing floor 21 Conical attachments 22 seats 23 Pipette Tips 24 through-channels 25 Connection part 26. Annular disc-shaped cover 27 Colors 28 Female thread 29 Male screw 30 Displacement Chamber 31 cylinders 32 Conical floor 33 Further attachments 34 Further through-channels 35 O-rings 36 Disc-shaped plungers 37. Conical spigot 38 Seal Lip 39 Plunger Actuator 40 Plunger Rods 41, 41.1, 41.2 Guide Ribs 41.3 Stepped section 42 Spring support section 43 Hollow cylindrical section 44 pins 45 Groove 45.1 Axial groove 45.2 Peripheral groove 46 Bayonet connector 47 Guide Elements 48 Wing 49 Arc-shaped region 50. Arc-shaped curved region 51 Legs 52 Second guide surface 53 Cavity 54 The First Guide 55 Third guide surface 56. Fourth guide surface 57 The Second Guide 58 Waveform section 59 Spring Seat 60 Spring retainer 61 Contact surface 62 Coil springs 63 Top surface of plunger 64 Cover bottom 65 Discharge sleeve 66 Lower hole 67 Conical discharge bed 68 Discharge transmission element 69 Upper hole 70 Small hole 71 Stroke Rod 72 Operation Buttons 73 Spindle Bore 74 Threaded spindle 75 Male screw 76 Female thread 77 Stroke Body 78 Carriers 79 Spindle nut 80 Upper stop 81 Stopping elements 82 Ring Bead 83 Catch 84 Protruding ribs 85 Axial groove 86 Catch Sleeve 87 A pair of teeth 88 Adjustable Sleeves 89 Adjustment Ring 90 Further waveform section 91 counter 92 Drive Gear 93 Pot-shaped holder 94 Lower stop 95 Overstroke spring 96 Dispensing button 97 Discharge Rod 98 Discharge spring 99 Snap-on connector 100 hooks 101 Inner step 102 Receiving part

Claims

1. Lower part of a single channel pipette, - The lower part (3) of the hollow cylindrical housing, Interior space (9) and, The upper end has an opening (11), The lower end has a housing floor (20) and An attachment (21) for attaching a pipette tip (23), the attachment (21) having a through channel (24) that protrudes downward from the housing floor (20) and extends from the lower end of the attachment (21) into the internal space (9), The lower part of the housing (3) comprises a spring space (6) that forms the internal space (9) or a part thereof, having the opening (11) at the top and the through opening (14) at the bottom and having at least one limit (12) that protrudes radially inward, - A rod-shaped plunger actuator (39) for displacing a plunger (36) in a cylinder (31), wherein the plunger actuator (39) is at least partially located within the spring space (6), extends axially in the lower part (3) of the hollow cylindrical housing, and is aligned with the through opening (14), - The contact surface (61) for the stroke rod (71) of the drive device located at the upper end of the plunger actuator (39), - A spring support portion (41) is connected to the plunger actuator beyond the limit (12) and protrudes radially outward from the plunger actuator, - A coil spring (62) is positioned in the spring space (6), with its top supported by the lower surface of the spring support portion (42) and its bottom supported by the limit (12), through which the plunger actuator (39) extends, - A single-channel lower section for a pipette, comprising: a first guide (54) for axially guiding the plunger actuator (39) in the lower section (3) of the hollow cylindrical housing, the first guide (54) having at least one first guide surface (17) provided on the inner circumferential surface of the spring space (6); and at least one second guide surface (52) provided on the outer circumferential surface of a guide element (47) that is guided by the first guide surface (17), protrudes radially outward from the plunger actuator (39), and is connected to the plunger actuator (39).

2. The lower part according to claim 1, wherein the contact surface (61) is the upper surface of the plunger actuator (39) and / or the upper surface of the spring support portion (42).

3. The lower part according to claim 2, wherein the contact surface (61) is the upper surface of the plunger head (39) which is connected to the upper end of the plunger actuator (39) and has a larger cross-section than the adjacent area of ​​the plunger actuator (39).

4. The lower part according to claim 1, wherein the contact surface (61) is cup-shaped.

5. The lower part according to claim 1, wherein the spring support portion (41) comprises a spring seat (59) held by the plunger actuator (39) and a spring retainer (60) that fixes the spring seat (59) to the plunger actuator.

6. The lower part according to claim 1, wherein the plunger head and / or the spring support portion (41) is the guide element (47) and has the second guide surface (52) on its outer circumference.

7. The lower part according to claim 1, wherein the first guide surface (17) and the second guide surface (52) are cylindrical.

8. (i) The spring space (6) has two preferably diametrically opposed first guide surfaces (17), the first guide surfaces (17) being distributed symmetrically around its central axis, each extending only to a portion of the entire circumference, with the guide element in contact with a single second guide surface extending over the entire circumference, or preferably having two diametrically opposed second guide surfaces (52), the second guide surfaces (52) being distributed symmetrically around the plunger actuator (39), each extending only to a portion of the entire circumference, or (ii) The spring space (6) has only a single diametrically opposed first guide surface (17) with the guide element (47) in contact with it and extending over the entire circumference, and preferably having two diametrically opposed second guide surfaces (52) being distributed symmetrically around the plunger actuator (39), each extending only to a portion of the entire circumference.

9. The lower part according to claim 1, wherein the guide element (47) has a hollow cylindrical portion (42) and at least one second guide surface (52) on the outer circumference of the hollow cylindrical portion (42), and the hollow cylindrical portion houses the plunger actuator (39).

10. The lower part according to claim 9, wherein the second guide surface (52) is located on the outside of the wing (48) that protrudes outward from the outer circumference of the hollow cylindrical portion (43).

11. The lower part according to claim 10, wherein the wing (48) has a cavity (53) that extends parallel to the plunger actuator (39).

12. The lower part according to claim 1, wherein the guide element (47) has at least one corrugated portion (58), preferably two corrugated portions facing each other in the diametrical direction, on its outer circumference.

13. The lower part according to claim 1, wherein the guide element (47) has a snap-on connection portion to the plunger actuator (39) and / or a form-fit connection portion.

14. The lower part according to claim 1, wherein the limit (12) is a shoulder (13) that fully or partially extends the inner circumference of the lower part (3) of the housing.

15. The lower part according to claim 1, wherein the lower housing (3) has a hollow cylindrical upper housing portion (5) having the spring space (6) which forms part of the internal space (9), the lower housing has a hollow cylindrical lower housing portion (7) which is defined at the bottom by the housing floor (20) and has a housing space (8) which forms a further part of the internal space (9), a cylinder (31) is disposed in the housing space (8), the cylinder is connected at the bottom to the through channel (24) of the attachment (21), a plunger (36) is disposed inside the cylinder (31), the plunger abuts against the outer surface so as to seal the inner surface of the cylinder (31) and is displaceable in the axial direction of the cylinder, a plunger actuator (39) in the form of a plunger rod (40) is connected to the plunger (36), the plunger rod extends upward from the plunger through the through opening (14) into the upper housing portion (5).

16. The lower part according to claim 15, wherein the housing space (8) of the lower housing portion (7) has a larger diameter than the spring space (6) of the upper housing portion (5).

17. The lower part according to claim 15, wherein the connecting portion (25) connects the lower edge of the upper housing portion (5) and the upper edge of the lower housing portion (7).

18. The lower part according to claim 17, wherein the connecting portion (25) comprises an annular disc-shaped cover (26) and a hollow cylindrical collar (27) protruding downward from the outer edge of the cover, the upper housing portion (5) is connected to the upper surface of the cover (26), the collar (27) is connected to the upper edge of the lower housing portion (7), and the cover (26) covers the housing space (8) at its top.

19. The lower part according to claim 18, wherein the collar (27) is connected to the upper edge of the lower housing (8) via a screw connection, a bayonet connection, a snap-on connection that can be removed without destruction, or another connection that can be removed without destruction.

20. The lower part according to claim 1, wherein the lower end of the plunger actuator (39) has a device for connecting to the upper end of a tip plunger that is inserted into a pipette tip (23) that can be secured to the attachment (21).

21. The lower part according to claim 1, wherein the second guide (57) of the plunger actuator (39) is located in the axial direction of the lower part (3) of the hollow cylindrical housing, and the guide has at least one third guide surface (55) on the through opening (14) and at least one fourth guide surface (56) on the outer circumference of the plunger actuator (39).

22. The lower part according to claim 1, wherein the through-opening (14) has a circular cross-section.

23. The lower part according to claim 1, wherein the through opening (14) has two guide grooves (15) facing each other in the diametrical direction, and the plunger actuator (39) has at least two guide ribs (41) on its outer circumference that engage with the guide grooves and project outward in the diametrical direction.

24. The lower part according to claim 1, wherein the cylinder (31) has a volume of at least 2 ml, preferably 2 ml, 5 ml, or 10 ml.

25. Upper part and Claim 1 ～ A pipette comprising a single-channel lower section as described in one of 24, wherein the upper section comprises a housing upper section (4), an operating button (72) provided on the outside of the housing upper section (4), a drive device disposed on the housing upper section (4) and operably connected to the operating button (82), and a displaceable stroke rod (71) of the drive device, the lower end of which is accessible from the outside through a further opening in the housing upper section (4), the upper section and the single-channel lower section are formed such that the lower end of the stroke rod (71) is brought to a connection position in contact with the contact surface (61) of the plunger actuator (39), and a connecting device exists that connects the upper section and the lower section to each other at the connection position.

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