WO2008060171A2

WO2008060171A2 - An exchangeable pipette tip ejection device

Info

Publication number: WO2008060171A2
Application number: PCT/PL2007/000077
Authority: WO
Inventors: Romuald Andrzej Rylski; Andrzej Jankowski; Wojciech Wyszogrodzki
Original assignee: Pz Htl Spolka Akcyjna
Priority date: 2006-11-16
Filing date: 2007-11-16
Publication date: 2008-05-22
Also published as: PL211691B1; WO2008060171A3; PL381071A1

Abstract

The exchangeable tip ejection device in the pipette built of the handle (1), the nozzle (2) and of, coupled with them, the pipetting push-button and the drawing up and discharging mechanism, said ejection device comprises the ejector push-button (3) seated in the upper part of the pipette handle (1), the ejector (4) by its lower end seated onto the pipette nozzle (2) and the assembly for continuous adjustment of the ejector length, said assembly for continuous adjustment of the ejector length is arranged between the ejector push-button (3) and the ejector (4), characterised in that the assembly for continuous adjustment of the ejector length is the connection of a 'turnbuckle' type, and the ejector (4) comprises the ejector rod (6) and the ejector arm (9), whereas the ejector rod (6) is coupled with the ejector push-button (3), the ejector arm (9) is seated by its lower end onto the pipette nozzle (2), and the ejector rod (6) and the ejector arm (9) are coupled with each other with formation the cylindrical joint of the axis of rotation perpendicular to the longitudinal axis X of the pipette nozzle (2).

Description

An exchangeable pipette tip ejection device

Technical Field

The invention relates to an exchangeable tip ejection device in a pipette assigned for transferring and dispensing a liquid.

Background Art

From the United States Patent Specification No US 3,991,617 is known a device for ejection an exchangeable pipette tip, whereas a lower end of a pipette nozzle has a conical shape for attaching the exchangeable pipette tip to it. The device incorporates a rod placed in a passage disposed in a pipette body, which slides therein parallel to a pipette axis, a member facilitating upward and downward movements of the rod, and a spring forcing the rod upwards. Moreover, the device comprises a detachable ejector which has its upper portion, middle portion, and lower portion, whereas the upper portion is connected to the rod lower part, the middle portion is placed in the proximity to the pipette, while the lower portion is guide-shaped and has an ejecting member which encloses at least the cylindrical lower end of the pipette in the vicinity of its conical portion, whereas the lower end of the ejecting member does not reach the upper edge of the exchangeable tip when it is seated on the pipette lower end. The rod has in its upper part a push button which slidably moves the ejecting member downwards to eject the exchangeable pipette tip. In this solution of the exchangeable pipette tip ejection device, the ejector, though detachable, is rigidly connected with the ejector pushbutton and is slidably mounted onto the pipette nozzle, and possible lateral compensation of dimension or shape variations of mating structure elements is feasible only over a range of clearances between the rod and the passage in the pipette body as well as between the ejector push-button and the pipette body.

In turn, in the United States Patent Specification No US 5,435,197 a pipette is disclosed with a tip ejector, which pipette has an elongated body. The pipette has an ejector on its body, being slidable along the body to eject therefrom a tip mounted on the lower end of the body; as the extension of the ejector upper end, an arm is provided to slide the ejector along the body, and a manual lever mechanism extending from the side of the body and linked to the arm with elements by which the arm and said ejector mechanism can be manually pressed downward to reject the tip from the body so that the force required to press is lower than the force required to eject the tip of the body. In this solution of the exchangeable pipette tip ejection device, the ejector is essentially rigidly connected with the lever mechanism and with the pipette nozzle, and possible lateral compensation of dimension or shape variations of mating structure elements is feasible over a range of assembling clearances between mating structure elements only.

A pipette for transferring liquids, known from the United States Patent Specification No US 6,833,114, comprises at least one piston-nozzle arrangement, in which the nozzle can be provided with a replaceable tip for containing the liquid to be transferred, a piston actuating device for drawing up and discharging the liquid and a tip ejector device. The ejector device comprises an ejection mechanism which can be displaced along the nozzle in order to eject the tip from the end of the nozzle. The pipette also comprises a device for actuating the ejection mechanism. The ejector device comprises a sub-assembly for adjusting a limit position of an ejection end of the ejector device at the end of a stroke. In this solution of the renewable pipette tip ejection device, the ejector is tubular, is detachable from the pipette body by means of a sleeve and has a discrete length regulation that is realised by means of another sleeve or a nut coupled with the ejector at its ejection end of renewable tips. In this solution of the exchangeable pipette tip ejection device, the ejector is slidably connected with the pipette nozzle, and possible lateral compensation of dimension and shape of the ejector and the nozzle is feasible over a range of assembling clearances between these structure elements only.

From the United States Patent Application Specification No US 2004/0028564 Al is known a sampling pipette including an ejector arm for separating from the pipette a tip that is fixed to the pipette, whereas the pipette includes adjustment means enabling the length of the arm to be varied continuously over a range of values. The ejector arm consists of two portions connected to each other by a screw-and-nut connection in such a way that a lower portion of the ejector arm, which is suitable for coming into a contact with the tip, can be separated from the pipette starting from an operating position by displacement of the ejector arm lower portion in a direction perpendicular to the longitudinal direction of the pipette. The nut is prevented from sliding relative to one of the arm portions and is connected by the screw to the other arm portion. The nut can be knurled and is accessible directly from outside of the pipette. In this solution of the exchangeable tip ejection device, the ejector is segmented, detachable from the pipette due to a side snap fastener, it enables a desired ejecting force to be decreased due to a lever arrangement of an ejector push-button and it has a continuous length adjustment by the nut being accessible from outside of the pipette. Lateral compensation of dimension and shape variations of the ejector and the nozzle is feasible only over a range of lateral clearance between structure elements of the ejection device and the nozzle and a pipette handle. However, a desired comfort of a routine maintenance of the pipette with this tip ejection device is not guaranteed due to a presence, between mentioned structure elements, of clearances in two lateral directions relative to a nozzle longitudinal axis.

Disclosure of Invention

One aim of this invention is to provide an exchangeable pipette tip ejection device of a structure enabling its cooperation with tips of different types by providing a continuous adjustment of ejector length and, simultaneously, the structure enabling easy and precise correction of a pre-set longitudinal setting of an ejector relative to a pipette nozzle for a given type of the tip, whereas this correction is indispensable to be performed because of length and shape variations of the ejector and the pipette nozzle in result of autoclaving.

The next aim of the invention is to provide the exchangeable pipette tip ejection device having the structure which assures a reliable fastening of a plastic nut onto a metallic threaded nozzle at dimensions' changes of the nut in consequence of periodic pipette autoclaving.

The aim of the invention is also to provide the exchangeable pipette tip ejection device of the structure enabling easy accommodation of possible misalignment of the pipette nozzle and an ejector opening as well as a compensation, in a direction perpendicular to the longitudinal axis of the pipette nozzle, of unintentional shape changes of the ejector and the pipette nozzle after autoclaving.

The next aim of the invention is to provide the exchangeable pipette tip ejection device of the structure enabling easy detachment and attachment of the ejector from/into the pipette, for example, for dismantling the pipette nozzle to be cleaned or autoclaved. Moreover, the structure of the ejection device according to the invention should facilitate disassembly and assembly of the ejector without a necessity of performing a readjustment of the ejector length that is pre-set for the given type of the tips, after consecutive re-assembly of the ejector.

Another aim of the invention is also to provide the ejection device having the structure guaranteeing improved operation ergonomics of the pipette with the tip ejection device according to the present invention.

The aimed objects have been achieved in the ejection device according to the present invention the essence of which is presented below. The essence of the first variation of the invention that is an exchangeable tip ejection device in a pipette built of a handle and a nozzle and of, coupled with them, a pipetting pushbutton and a drawing up and discharging mechanism, comprising an ejector push-button seated in an upper part of the pipette handle, an ejector with its lower end seated onto the pipette nozzle and an assembly for continuous adjustment of the ejector length, whereas said assembly for continuous adjustment of the ejector length being arranged between the ejector push-button and the ejector, is that said assembly for continuous adjustment of the ejector length is a connection of a ,,turnbuckle" type.

Preferably, the assembly for continuous adjustment of the ejector length constitutes the connection of a ,,turnbuckle" type between, threaded on ends with opposite directions, a rod of the ejector push-button, which is rigidly fixed in the ejector push-button, and an ejector rod.

Preferably, the rod of the ejector push-button and the ejector rod are coupled by a longitudinal nut provided with an easily accessible from outside adjustment segment of a grip improving outer surface.

The essence of the second variation of the invention that is an exchangeable tip ejection device in a pipette built of a handle and a nozzle and of, coupled with them, a pipetting push-button and a drawing up and discharging mechanism, comprising an ejector push-button seated in an upper part of the pipette handle and an ejector consisting of an ejector rod coupled with the ejector push-button and of an ejector arm seated by its lower end onto the pipette nozzle, is that said ejector rod and an upper end of said ejector arm are coupled with each other forming a cylindrical joint of an axis of rotation perpendicular to a longitudinal axis of the pipette nozzle.

Preferably, the ejector rod and the upper end of the ejector arm are coupled with each other in a snap-fastener manner in accordance with the direction of the longitudinal axis of the pipette nozzle.

Preferably, a cylindrical socket of the cylindrical joint between the ejector rod and the ejector arm has elastic profiled guiding arms which extend parallel to the longitudinal axis of the pipette nozzle. Preferably, a cylindrical socket of the cylindrical joint is situated in the lower end of the ejector rod, and a cylindrical pin of the cylindrical joint is situated in the upper end of the ejector arm.

Preferably, the ejector rod and the upper end of the ejector arm are coupled with each other by a fastening member which is rigidly fixed onto the ejector rod, whereas on the lower end of the fastening member a cylindrical socket of the cylindrical joint is situated, and in the upper end of the ejector arm a cylindrical pin of the cylindrical joint is situated.

The essence of the third variation of the invention that is an exchangeable tip ejection device in a pipette built of a handle and a nozzle and of, coupled with them, a pipetting push- button and a drawing up and discharging mechanism, comprising an ejector push-button seated in an upper part of the pipette handle, an ejector seated by its lower end onto the pipette nozzle and an assembly for continuous adjustment of the ejector length, said assembly for continuous adjustment of the ejector length being arranged between the ejector push-button and the ejector, is that said assembly for continuous adjustment of the ejector length is a connection of a ,,turnbuckle" type, and the ejector is comprised of an ejector rod which is coupled with the ejector push-button and of an ejector arm which is seated by its lower end onto the pipette nozzle, whereas the ejector rod and the ejector arm are coupled with each other forming a cylindrical joint of an axis of rotation perpendicular to a longitudinal axis of the pipette nozzle. Preferably, the assembly for continuous adjustment of the ejector length constitutes a connection of a ,,turnbuckle" type arranged between, threaded on ends with opposite directions, the ejector push-button rod which is rigidly fixed in the ejector push-button and the ejector rod.

Preferably, the ejector push-button rod and the ejector rod are coupled by a longitudinal nut provided with an easily accessible from outside adjustment segment of a grip improving outer surface and constituting a hollow casing for a cylindrical joint between the ejector rod and the ejector arm.

Preferably, a cylindrical socket of the cylindrical joint between the ejector rod and the ejector arm has elastic profiled guiding arms which protrude parallel to the longitudinal axis of the pipette nozzle.

Preferably, a cylindrical socket of the cylindrical joint is situated in the lower end of the ejector rod, and a cylindrical pin of the cylindrical joint is situated in the upper end of the ejector arm.

The advantage of the solution, following the invention, is that it can mate with the tips of different types, and that the applied therein connection of a ,,turnbuckle" type provides an easy, continuous and precise adjustment of the ejector length with an available wider adjustment range at a correspondingly narrower range of values of turning the nut than it is in the ejection devices of exchangeable pipette tips known form the art.

What is next advantageous in the said device, following the invention, is that it provides the reliable connection of its plastic structure elements with metallic structure elements, for example, the nut and the ejector rod made of plastic with the metallic pushbutton rod.

The next advantage of the solution, following the invention, is that it provides after every disassembly and assembly or autoclaving the possibility of caring out a compensation of dimension and shape variations of mating structure elements, namely the pipette nozzle and the ejector, in the single and the most important direction transverse to the longitudinal axis of the pipette nozzle. Simultaneously, the ejection device structure limits clearances in the second transverse direction and in the longitudinal direction, which clearances are disadvantageous because they decrease operational ergonomics and utility comfort of the pipette. Another advantage of the present invention is simplicity of its disassembly and reassembly at, simultaneous, maintaining repeatability of the longitudinal setting of the ejector relative to the pipette nozzle, which longitudinal setting is pre-set for each given type of tips. This eliminates the necessity of performing the re-adjustment of the ejector length after consecutive re-assembly of the ejector. The exchangeable pipette tip ejection device according to the present invention has the simple structure of small number of structure elements.

Brief description of drawings

The invention embodiments are presented by way of drawing documentation, in which, Figure 1 presents the pipette with the exchangeable pipette tip ejection device according to the first variation of the invention, in its partial longitudinal section, Fig. 2 — presents the pipette with the exchangeable pipette tip ejection device according to the second variation of the invention, in its partial longitudinal section, Fig. 3 - presents the pipette with the exchangeable pipette tip ejection device according to the third variation of the invention, in the general view, Fig. 4 - presents the pipette with the exchangeable pipette tip ejection device from Fig. 3, in the partial longitudinal section, Fig. 5 - presents the enlarged fragment A from Fig. 4 of the longitudinal section of the exchangeable pipette tip ejection device, which depicts the assembly for continuous adjustment of the ejector length and the snap- fastener cylindrical joint, Fig. 6 - presents the enlarged fragment of the longitudinal section of the exchangeable pipette tip ejection device from Fig. 4, in the view from W direction, this fragment depicts the snap-fastener cylindrical joint, and Fig. 7 - is the pipette with the exchangeable pipette tip ejection device from Fig. 3 and 4, according to the third variation of the invention, in the perspective view with the partial longitudinal section.

Best Mode of Carrying Out the Invention

The exchangeable pipette tip ejection device according to the first variation of the invention, as it is shown in fig. 1, is seated in a body of a pipette built of a handle 1 in an upper part and of a nozzle 2 in a lower part and of, coupled with them, a pipetting push-button and a drawing up and discharging mechanism. Onto the lower end of the nozzle 2, exchangeable tips of different types (not shown) are mounted. The exchangeable pipette tip ejection device according to the first variation of the invention comprises a push-button 3 of a ejector 4, which push-button 3 is seated in the upper part of the pipette handle 1, the ejector 4 by its lower end seated onto the nozzle 2 of the pipette and the assembly for continuous adjustment of the length of the ejector 4, which is arranged between the ejector push-button 3 and the ejector 4. The push-button 3 of the ejector 4 is shapely seated in the upper part of the handle 1. Shape fastening of the push-button 3 of the ejector 4 in the upper part of the handle 1 aims at assuring the reliable guidance of the push-button 3 in the handle 1 during ejection of the tip. A rod 5 of the ejector push-button 3 is rigidly fixed, preferably, by means of interference connection, in the ejector push-button 3. The rod 5 of the push-button 3 of the ejector 4 is guided in a bore of a sleeve of the handle 1. The rod 5 is guided in the bore of the sleeve of the handle 1 and is pushed upwards by a spring. The spring abuts by its one end against a shoulder in the bore of the sleeve of the handle 1, and by the other end against a spring retainer assembly which is rigidly fixed onto the rod 5 at the upper end of the rod 5. The spring pushes upwards protrusions of the rod 5 to the bottom edge of the sleeve bore in the handle 1 thereby holding the push-button 3 of the ejector 4 in its upper position. The lower end of the rod 5 of the push-button 3 is threaded and is coupled by a screwed connection with an upper segment of a longitudinal nut 7, which constitutes a sleeve with the threaded bore, suitably, for mating with the threaded lower end of the rod 5 of push-button 3. Moreover, the nut 7 has the middle segment constituting a sleeve with the threaded bore, suitably, for mating with the threaded upper end of a rod 6 of the ejector 4 and has the lower segment being an adjustment segment 8 of the nut 7. The rod 6 of the ejector 4 is in its upper end threaded with the opposite direction to the rod 5 of the push-button 3 and is coupled by a screwed connection with the middle segment of the longitudinal nut 7. The adjustment segment 8 of the nut 7 is easily accessible from outside and has a knurled outer surface for improving the grip reliability by user fingers during caring out the adjustment of the length of the ejector 4 in the course of usage of the pipette.

The rod 6 of the ejector 4 extends downwards along the nozzle 2 of the pipette and is firmly connected to a profiled ejector arm 9 which, by its lower end, is seated onto the nozzle 2 of the pipette. The rod 6 of the ejector 4 together with the profiled arm 9 of the ejector 4, preferably, constitutes a single integral structure element. The lower end of the ejector arm 9 encloses at least partially the cylindrical or conical lower end of the pipette nozzle 2. An ejection edge 13 of the lower end of the arm 9 of the ejector 4 is disposed above the upper edge of the replaceable tip (not shown).

Firm fixing between the rod 5 of the push-button 3 and the push-button 3 enables the change of screwing in, that is the change of the position, of the nut 7 relative to the rod 5 and, simultaneously, guidance of the arm 9 of the ejector 4 longwise the nozzle 2 enables the change of screwing in, that is the change of the position, of the upper end of the rod 6 relative to the nut 7 during rotation of the nut 7 in the course of the adjustment of the length of the ejector 4. The shape fastening of the push-button 3 of the ejector 4 in the upper part of the handle 1, besides a function of reliable guidance of the push-button 3 in the handle 1 during the tip ejection, also prevents the rod 5 of the ejector push-button 3 from rotation during the adjustment of the length of the ejector 4 when the adjustment segment 8 of the nut 7 is turned. The rod 5 of the push-button 3 of the ejector 4, the longitudinal nut 7 and the rod 6 of the ejector 4 constitute the assembly for continuous adjustment of the length of the ejector 4 arranged between the ejector push-button 3 and the ejector 4 and form the connection of a ,,turnbuckle" type.

The connection of a ,,turnbuckle" type enables an easy, continuous and precise adjustment of the length of the ejector 4. It enables the length of the ejector 4 to be varied over a wider range of adjustment values at a correspondingly narrower range of values of turning the nut 7 than in the known ejection devices of exchangeable pipette tips of this type. Turning with the adjustment segment 8 of the nut 7 causes mutual displacement, that is approaching or moving away from each other, simultaneously two ends of this coupling, namely, the rod 5 of the ejector push-button 3 and the rod 6 of the ejector 4. Thus, with the smaller turning of the nut 7 the bigger change of the length of the ejector 4 is obtained, that is the bigger shortening or lengthening of the ejector 4, than it is in the solutions known from the art. This feature of the ejection device of the present invention is very advantageous as far as usability of the exchangeable pipette tip ejection device of this type is concerned. The nut 7 and the rod 6 of the ejector 4, in the preferred embodiment of the present invention, are made of plastic, and the rod 5 of the push-button 3 of the ejector 4 is metallic. Screwed connections between, made of different materials, structure elements of the connection of a ,,turnbuckle" type are reliable, especially at presence of dimension and shape changes of the plastic structure elements, here, the nut 7 and the rod 6 of the ejector 4, which dimension and shape changes can emerge after autoclaving.

In order to aspirate a liquid by the pipette with the exchangeable pipette tip ejection device according to the first variation of the invention, onto the lower end of the pipette nozzle 2 the exchangeable tip should be mounted, whereas the liquid is drawn up into the tip by pushing down and releasing the pipetting push-button which is operatively coupled with the drawing up and discharging mechanism arranged in the handle 1 and the nozzle 2. When the liquid is drawn up and discharged, then the dirty tip should be removed from the nozzle 2. In this order, the ejector push-button 3 is pressed down. The push-button 3 of the ejector 4 is coupled via the assembly for continuous adjustment of the length of the ejector 4 with the arm 9 of the ejector 4. In effect, the arm 9 of the ejector 4 moves downwards along the nozzle 2 of the pipette till the ejection edge 13 of the lower end of the ejector arm 9 contacts the upper edge of the exchangeable tip, thereupon further downward movement of the ejector arm 9 causes the ejection of the tip from the pipette nozzle 2.

The adjustment of the length of the ejector 4 for harmonisation with the type of the exchangeable tip used, that is the pre-set setting of the position of the ejection edge 13 of the ejector arm 9 relative to the lower end of the nozzle 2 of the pipette, is performed by turning the adjustment segment 8 of the nut 7.

The exchangeable pipette tip ejection device according to the second variation of the invention, as it is shown in fig. 2, is seated in a body of a pipette built of a handle 1 in an upper part and a nozzle 2 in a lower part and of, coupled with them, a pipetting push-button and a drawing up and discharging mechanism. On the lower end of the nozzle 2 exchangeable tips of different types (not shown) are mounted. The exchangeable pipette tip ejection device according to the second variation of the invention further comprises a push-button 3 of an ejector 4, which is seated in the upper part of the pipette handle 1, and the ejector 4. The ejector 4 comprises a rod 6, a fastening member 16 and an arm 9 which is by its lower end seated on the nozzle 2 of the pipette. The rod 6 of the ejector 4 is rigidly fixed, preferably, by the interference connection, in the push-button 3 of the ejector 4 and, further, is guided in a bore of a sleeve of the handle 1. The rod 6 is guided in the bore of the handle sleeve and is pushed upwards by a spring. The spring abuts by its one end against a shoulder in the bore of the sleeve of the handle 1, and by the other end against a spring retainer assembly that is rigidly fixed onto the rod 6. The spring pushes upwards protrusions of the rod 6 to the bottom edge of the sleeve bore in the handle 1 thereby holding the push-button 3 of the ejector 4 in its upper position. The lower end of the rod 6 of the ejector 4 is rigidly fixed, preferably, by an interference connection, in the bore of the sleeve of an upper segment of a fastening member 16 of the ejector 4. A lower segment of the fastening member 16 is, in accordance with the direction of the longitudinal axis X of the pipette nozzle 2 and in a snap-fastener manner, connected with the upper end of a profiled arm 9 of the ejector 4 with formation of a cylindrical joint of an axis of rotation perpendicular to the longitudinal axis X of the pipette nozzle 2. The lower segment of the fastening member 16 of the ejector 4 has a cylindrical socket 10 which performs a function of a socket in the connection of the cylindrical joint type, and the upper end of the ejector arm 9 has a cylindrical pin 12 which performs a function of a pin in the connection of the cylindrical joint type. The lower segment of the fastening member 16 of the ejector 4 has elastic profiled guiding arms 11 which extend downwards, essentially parallel to the longitudinal axis X of the nozzle 2 of the pipette. The elastic profiled guiding arms 11 facilitate disengagement and engagement of the arm 9 of the ejector 4 from and into the lower segment of the fastening member 16. Disengagement and engagement of the ejector arm 9 from or into the lower segment of the fastening member 16 is performed by pulling downwards or by moving upwards, in accordance with the direction of the longitudinal axis X of the pipette nozzle 2, the ejector arm 9 along the pipette nozzle 2. The ejector arm 9 has, in this order bent outwards, an upper portion which is provided with a shape surface 15 to facilitate gripping the arm 9. In turn, the guiding arms 11 are elastic and have profiled inner surfaces 14. The guiding arms 11 deflect suitably and guide the cylindrical pin 12 which is situated in the upper end of the ejector arm 9 thereby releasing it from or snapping it into the cylindrical socket 10 situated in the lower end of the lower segment of the fastening member 16. This enables snap disengagement from, in accordance with the direction of the longitudinal axis X of the pipette nozzle 2, or engagement of the ejector arm 9 with the rod 6 of the ejector 4 with formation of the connection of the cylindrical joint type. The lower segment of the fastening member 16 has, preferably, a circumferential outer surface constituting the casing of the snap cylindrical joint between the rod 6 and the ejector arm 9. The arm 9 of the ejector 4 extends downwards longwise the nozzle 2 of the pipette and is by its lower end seated onto the pipette nozzle 2. The lower end of the arm 9 encloses at least partially the cylindrical or conical lower end of the pipette nozzle 2. The ejection edge 13 of the lower end of the arm 9 of the ejector 4 is disposed above the upper edge of the replaceable tip (not shown).

The connection between the arm 9 of the ejector 4 with the rod 6 of the ejector 4 by the fastening member 16, which constitutes the cylindrical joint type connection enables accommodation of misalignment of an orifice in the lower end of the ejector arm 9 with the longitudinal axis X of the pipette nozzle 2 as well as compensation of dimension and shape changes of the ejector arm 9 in one the most important rotation plane of the ejector arm 9 with simultaneous limitation of disadvantageous clearances in the transverse plane, as well as limitation of disadvantageous stresses arising in the nozzle-arm system of the ejector in consequence of the pipette thermal stresses originating in the course of autoclaving.

The snap connection of the arm 9 of the ejector 4 by the fastening member 16 with the rod 6 of the ejector 4 enables simple disengagement and re-engagement of these structure elements, whereas the repeatability of the pre-set longitudinal setting of the ejector 4 relative to the pipette nozzle 2 for each given type of tips is maintained. In order to aspirate a liquid by the pipette with the exchangeable pipette tip ejection device according to the second variation of the invention, the exchangeable tip should be mounted onto the lower end of the pipette nozzle 2, whereas the liquid is drawn up into the tip by pushing down and releasing the pipetting push-button. The pipetting push-button is coupled in operation with the drawing up and discharging mechanism arranged in the handle 1 and in the nozzle 2. When the liquid is drawn up and discharged, then the contaminated tip should be removed from the nozzle 2. In this order, the push-button 3 of the ejector 4 is pressed down. The push-button 3 is coupled by the rod 6 of the ejector 4 and by the fastening member 16 with the arm 9 of the ejector 4: In effect, the arm 9 of the ejector 4 moves downwards along the pipette nozzle 2 till the ejection edge 13 in the lower end of the ejector arm 9 is in a contact with the upper edge of the exchangeable tip, thereupon further downward movement of the arm 9 of the ejector 4 causes the ejection of the tip from the nozzle 2 of the pipette.

For disengagement of the arm 9 of the ejector 4 from the pipette in order to remove the nozzle 2 away for its purification or autoclaving, the arm 9 should be pulled down along the nozzle 2 by holding the bent outwards shape surface 15 of the upper portion of the ejector arm 9. For re-engagement of the ejector arm 9 to the pipette, the inverse actions should be carried out by moving the arm 9 upwards along the nozzle 2.

The exchangeable pipette tip ejection device according to the third variation of the invention, as it is shown in fig. 3-7, is seated in a pipette body having in an upper part a handle 1, and in a lower part a nozzle 2 onto which exchangeable tips of different types are mounted accordingly to the user need. In the upper part of the handle 1, a pipetting pushbutton is disposed. The pipetting push-button is coupled with a drawing up and discharging mechanism which is arranged inside the handle 1 and the nozzle 2. In the handle 1 and the pipette body nozzle 2, the exchangeable tip ejection device in the pipette according to the third variation of the invention is seated.

The exchangeable tip ejection device in the pipette comprises a push-button 3 of an ejector 4, the ejector 4 and an assembly for continuous adjustment of the ejector length which is arranged between the ejector push-button 3 and the ejector 4. The ejector push-button 3 is shapely seated in the upper part of the handle 1. Shape fastening of the push-button 3 of the ejector 4 in the upper part of the handle 1 is aimed at assuring reliable guidance of the ejector push-button 3 in the handle 1 during ejection of the tip. A rod 5 of the ejector push-button 3 is rigidly fixed, preferably, by an interference connection, in the ejector push-button 3. The rod

5 of the push-button 3 of the ejector 4 is guided in a bore of a sleeve of the handle 1. The rod 5 is guided in the bore of the sleeve of the handle 1 and is pushed upwards by a spring. The spring abuts by its one end against a shoulder in the bore of the sleeve of the handle 1, and by the other end against a spring retainer assembly which is rigidly fixed on the rod 5. The spring pushes upwards protrusions of the rod 5 to the bottom edge of the sleeve bore in the handle 1 thereby holding the push-button 3 of the ejector 4 in its upper position. The lower end of the rod 5 of the push-button 3 is threaded and is coupled by a screwed connection with an upper segment of a longitudinal nut 7. The upper segment of the longitudinal nut 7 constitutes a sleeve with a threaded bore, suitably, for engagement with the threaded lower end of the rod 5 of the push-button 3. Moreover, the nut 7 has a middle segment constituting a sleeve with a threaded bore, suitably, for engagement with the threaded upper end of the rod 6 of the ejector 4 and further has a lower segment constituting an adjustment segment 8 of the nut 7. The rod

6 of the ejector 4 is on its upper end threaded in the opposite direction to the rod 5 of the push-button 3 and is coupled by a screwed connection with the middle segment of the longitudinal nut 7. The adjustment segment 8 of the nut 7 is easily accessible from outside and has a knurled outer surface for improving reliability of grip by user fingers during performing the adjustment of the length of the ejector 4 in the course of the pipette usage.

The lower end of the rod 6 of the ejector 4 is coupled in a snap-fastener manner, in accordance with the direction of the longitudinal axis X of the pipette nozzle 2, with the upper end of a profiled arm 9 of the ejector 4. This connection forms a cylindrical joint of an axis of rotation perpendicular to a longitudinal axis X of the pipette nozzle 2, whereas the lower end of the rod 6 of the ejector 4 has a cylindrical socket 10 performing a function of a socket in the connection of the cylindrical joint type, and the upper end of the arm 9 of the ejector 4 has a cylindrical pin 12 performing the function of a pin in the connection of the cylindrical joint type. The lower end of the rod 6 of the ejector 4 has elastic profiled guiding arms 11 which extend downwards, essentially parallel to the longitudinal axis X of the pipette nozzle 2. The elastic profiled guiding arms 11 facilitate disengagement and engagement, in a snap-fastener manner and in accordance with the direction of the longitudinal axis X of the pipette nozzle 2, of the arm 9 the ejector 4 from and into the whole assembly for continuous adjustment of the ejector length. Disengagement and engagement of the arm 9 of the ejector 4 from or into the whole assembly for continuous adjustment of the ejector length is performed by pulling downwards or moving upwards, in accordance with the direction of the longitudinal axis X of the pipette nozzle 2, of the arm 9 of the ejector 4 along the pipette nozzle 2. The arm 9 of the ejector 4 has, in this order bent outwards, an upper portion provided with a shape surface 15 which facilitates gripping the arm 9. In turn, the guiding arms 11 are elastic and have profiled inner surfaces 14, due to which the guiding arms 11 suitably deflect and guide the cylindrical pin 12 situated in the upper end of the arm 9 of the ejector 4 releasing it or snapping it in the cylindrical socket 10 situated in the lower end of the rod 6 of the ejector 4 for the snap disengagement or engagement, in accordance with the direction of the longitudinal axis X of the pipette nozzle 2, of the arm 9 of the ejector 4 from or into the whole assembly for continuous adjustment of the ejector length thereby the connection of the cylindrical joint type is formed.

The arm 9 of the ejector 4 extends downwards along the pipette nozzle 2 and is by its lower end seated onto the pipette nozzle 2. The lower end of the arm 9 encloses at least partially the cylindrical or conical lower end of the pipette nozzle 2. An ejection edge 13 of the lower end of the ejector arm 9 is situated above the upper edge of the replaceable tip (not shown).

Firm fixing of the rod 5 of the push-button 3 in the push-button 3 enables the change of screwing in, that is the change of the position, of the nut 7 relative to the rod 5 and, simultaneously, guidance of the arm 9 of the ejector 4 longwise the nozzle 2 enables the change of screwing in, that is the change of the position, of the upper end of the rod 6 relative to the nut 7 during turning the nut 7 in the course of the adjustment of the length of the ejector 4. Shape fastening of the push-button 3 of the ejector 4 in the upper part of the handle 1, besides the function of reliable guidance of the push-button 3 in the handle 1 during tip ejection, also prevents the rod 5 of the push-button 3 of the ejector 4 from rotation during the adjustment of the length of the ejector 4 by turning the adjustment segment 8 of the nut 7.

The rod 5 of the ejector push-button 3, the longitudinal nut 7 and the rod 6 of the ejector 4 constitute the assembly for continuous adjustment of the ejector length, which is arranged between the push-button 3 of the ejector 4 and the ejector 4 and form a connection of a ,,turnbuckle" type.

The connection of a ,,turnbuckle" type enables easy, continuous and precise adjustment of the length of the ejector 4. It enables the length of the ejector 4 to be varied over a wider range of adjustment values at a correspondingly narrower range of values of turning of the nut 7 than in the known ejection devices of exchangeable pipette tips of this type. Turning with the adjustment segment 8 of the nut 7 causes mutual, that is approaching or moving away from each other, simultaneously two ends of this coupling, namely, the rod 5 of the push-button 3 of the ejector 4 and the rod 6 of the ejector 4. Thus, in the ejection device according to the present invention, with the smaller turning of the nut 7 the bigger change of the length of the ejector 4 that is the bigger shortening or lengthening of the ejector 4 is obtained than it is in the known ejection devices. This feature of the device of the present invention is very advantageous as far as usability of the exchangeable tip ejection device in the pipette of this type is concerned.

The nut 7 and the rod 6 of the ejector 4 are made of plastic, and the rod 5 of the push- button 3 of the ejector 4 is metallic. Screwed connections between structure elements of the connection of a ,,turnbuckle" type made of different materials are reliable, especially at dimension and shape changes of the plastic elements, here, the nut 7 and the rod 6 of the ejector 4, which dimension and shape changes can emerge after autoclaving.

The connection between the arm 9 of the ejector 4 with the rod 6 of the ejector 4 with formation of the cylindrical joint type connection enables accommodation of misalignment of an orifice in the lower end of the arm 9 of the ejector 4 with the longitudinal axis X of the pipette nozzle 2 as well as compensation of dimension and shape changes of the arm 9 of the ejector 4 in one the most important rotation plane of the ejector arm 9. Simultaneously, disadvantageous clearances in the lateral plane as well as disadvantageous stresses arising in the nozzle-arm system of the ejector in consequence of the pipette thermal stresses originating in the course of autoclaving are significantly limited.

The connection of the arm 9 of the ejector 4 with the rod 6 of the ejector 4 in a snap- fastener manner and in accordance with the direction of the longitudinal axis X of the pipette nozzle 2 enables simple disengagement and re-engagement, of these structure elements, whereas the repeatability of the pre-set longitudinal setting of the ejector 4 relative to the pipette nozzle 2 for each given type of tips is maintained. This eliminates the necessity to readjust the length of the ejector 4 after every subsequent re-assembly of the ejector 4.

In order to aspirate a liquid by the pipette with the exchangeable pipette tip ejection device according to the third variation of the invention, the exchangeable tip should be mounted onto the lower end of the pipette nozzle 2, whereas the liquid is drawn up into the tip by pushing down and releasing the pipetting push-button which is operationally coupled with the drawing up and discharging mechanism arranged in the handle 1 and in the nozzle 2. When the liquid is drawn up and discharged then the contaminated tip should be removed from the nozzle 2. In this order, the push-button 3 of the ejector 4 is pressed down. The pushbutton 3 is coupled by the assembly for continuous adjustment of the ejector length with the arm 9 of the ejector 4. In effect, the arm 9 of the ejector 4 moves downwards along the pipette nozzle 2 till the ejection edge 13 of the lower end of the ejector arm 9 contacts the upper edge of the exchangeable tip, thereupon further downward movement of the arm 9 of the ejector 4 causes the ejection of the tip from the pipette nozzle 2.

The regulation of the length of the ejector 4 for adjustment the ejector length to the type of the exchangeable tip, that is the pre-set setting of the position of the ejection edge 13 of the ejector arm 9 relative to the lower end of the pipette nozzle 2 is performed by turning the adjustment segment 8 of the nut 7. For disengagement of the arm 9 of the ejector 4 from the pipette for removing the pipette nozzle 2 and its purification or autoclaving, the arm 9 should be pulled downward along the nozzle 2 by holding the bent outwards upper portion of the ejector arm 9 by the shape surface 15 of the upper portion of the arm 9. The inverse actions of upward moving the arm 9 along the nozzle 2 should be carried out for engagement of the ejector arm 9 to the pipette.

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

Claims

We claim:

1. An exchangeable tip ejection device in a pipette built of a handle and a nozzle and of, coupled with them, a pipetting push-button and a drawing up and discharging mechanism, said ejection device comprising an ejector push-button seated in an upper part of the pipette handle, an ejector by its lower end seated onto the pipette nozzle and an assembly for continuous adjustment of an ejector length, said assembly for continuous adjustment of the ejector length being arranged between said ejector push-button and said ejector, characterised in that said assembly for continuous adjustment of the ejector length is a connection of a ,,turnbuckle" type.

2. The exchangeable tip ejection device in the pipette according to claim 1, characterised in that said assembly for continuous adjustment of the ejector length is the connection of the ,,turnbuckle" type arranged between, threaded on ends with opposite directions, a rod (5) of said push-button (3) of said ejector (4) and a rod (6) of said ejector (4), whereas said rod (5) is rigidly fixed in said push-button (3) of said ejector (4),

3. The exchangeable tip ejection device in the pipette according to claim 2, characterised in that said rod (5) of said push-button (3) of the ejector (4) and said rod (6) of the ejector (4) are coupled by means of a longitudinal nut (7) provided with an easily accessible from outside adjustment segment (8) of a grip improving outer surface.

4. An exchangeable tip ejection device in a pipette built of a handle and a nozzle and of, coupled with them, a pipetting push-button and a drawing up and discharging mechanism, said ejection device comprising an ejector push-button seated in an upper part of said pipette handle and an ejector including an ejector rod coupled with said ejector push-button and an ejector arm seated by its lower end onto said pipette nozzle, characterised in that said rod (6) of said ejector (4) and the upper end of said arm (9) of said ejector (4) are coupled with each other with formation of a cylindrical joint of an axis of rotation perpendicular to the longitudinal axis (X) of said pipette nozzle (2).

5. The exchangeable tip ejection device in the pipette according to claim 4, characterised in that said rod (6) of said ejector (4) and the upper end of said arm (9) of said ejector (4) are coupled with each other in a snap-fastener manner in accordance with the direction of the longitudinal axis (X) of said pipette nozzle (2).

6. The exchangeable tip ejection device in the pipette according to claim 5, characterised in that a cylindrical socket (10) of said cylindrical joint arranged between said rod (6) of said ejector (4) and said arm (9) of said ejector (4) has elastic profiled guiding arms (11) which protrude parallel to the longitudinal axis (X) of said pipette nozzle (2).

7. The exchangeable tip ejection device in the pipette according to claim 6, characterised in that said cylindrical socket (10) of said cylindrical joint is situated in the lower end of said rod (6) of said ejector (4), and a cylindrical pin (12) of said cylindrical joint is situated in the upper end of said arm (9) of said ejector (4).

8. The exchangeable tip ejection device in the pipette according to claim 6, characterised in that said rod (6) of said ejector (4) and the upper end of said arm (9) of said ejector (4) are coupled with each other by a fastening member (16) which is rigidly fixed onto said rod (6), whereas in the lower end of said fastening member (16) said cylindrical socket (10) of said cylindrical joint is situated, and in the upper end of said arm (9) of said ejector (4) said cylindrical pin (12) of said cylindrical joint is situated.

9. An exchangeable tip ejection device in a pipette built of a handle and a nozzle and of, coupled with them, a pipetting push-button and a drawing up and discharging mechanism, said ejection device comprising an ejector push-button seated in an upper part of said pipette handle, an ejector by its lower end seated onto said pipette nozzle and an assembly for continuous adjustment of an ejector length, said assembly for continuous adjustment of the ejector length being arranged between said ejector push-button and said ejector, characterised in that said assembly for continuous adjustment of the ejector length is a connection of a ,,turnbuckle" type, and said ejector (4) comprises of a rod (6) of said ejector (4) and an arm (9) of said ejector (4), whereas said rod (6) of said ejector (4) is coupled with said push-button (3) of said ejector (4), said arm (9) of said ejector (4) is seated by its lower end onto said pipette nozzle (2), and said rod (6) of said ejector (4) and said arm (9) of said ejector (4) are coupled with each other with formation of a cylindrical joint of an axis of rotation perpendicular to the longitudinal axis (X) of the pipette nozzle (2).

10. The exchangeable tip ejection device in the pipette according to claim 9, characterised in that said assembly for continuous adjustment of the ejector length is the connection of a ,,turnbuckle" type arranged between, threaded on ends with opposite directions, a rod (5) of said push-button (3) of said ejector (4) and a rod (6) of said ejector (4), whereas said rod (5) is rigidly fixed in said push-button (3) of said ejector (4),

11. The exchangeable tip ejection device in the pipette according to claim 9, characterised in that said rod (5) of said push-button (3) of said ejector (4) and said rod (6) of said ejector (4) are coupled by a longitudinal nut (7) which is provided with an easily accessible from outside adjustment segment (8) of a grip improving outer surface, whereas said adjustment segment (8) constitutes a hollow casing for said cylindrical joint arranged between said rod (6) of said ejector (4) and said arm (9) of said ejector (4).

12. The exchangeable tip ejection device in the pipette according to claim 10, characterised in that said rod (6) of said ejector (4) and the upper end of said arm (9) of said ejector (4) are coupled with each other in a snap-fastener manner with accordance with the direction of the longitudinal axis (X) of said pipette nozzle (2).

13. The exchangeable tip ejection device in the pipette according to claim 11, characterised in that a cylindrical socket (10) of said cylindrical joint arranged between said rod (6) of said ejector (4) and said arm (9) of said ejector (4) has elastic profiled guiding arms (11) which extend parallel to the longitudinal axis (X) of said pipette nozzle (2).

14. The exchangeable tip ejection device in the pipette according to claim 12, characterised in that said cylindrical socket (10) of said cylindrical joint is situated in the lower end of said rod (6) of said ejector (4), and a cylindrical pin (12) of said cylindrical joint is situated in the upper end of said arm (9) of said ejector (4).