EP0232517A2 - Pipette - Google Patents

Abstract

The invention relates to a pipette with an elastic bellows. For the purpose of designing such a pipette for holding liquid in self-absorbing microcapillaries in such a way that it is easy and reliable to handle at the same time, a pressure equalization opening is provided in the bellows and the pipette has a holder in which a microcapillary is held in a frictionally engaged manner .

Description

The invention relates to a pipette according to the preamble of patent claim 1.

Such a pipette is known from DE-PS 28 51 532. The known pipette has an elastic bellows. The bellows stroke is limited by predetermined stops.

In the known pipette, the liquid to be sucked up is first sucked through a suction stroke into the suction tip attached to the housing of the pipette. The liquid is then expelled from the pipette by means of a pressure stroke. The known pipette is therefore not suitable for taking up liquid in self-absorbing microcapillaries in which, due to the capillary action of liquids, the liquid to be sucked up is taken up by a microcapillary, without an internal pressure being reduced compared to the external pressure, for example by a suction stroke got to. One would namely during the absorption of the liquid into a self-absorbing microcapillary in the known pipette, the position of the bellows and thus the volume inside the pipette remain unchanged, the suction process would come to a standstill after a short time, since the volume penetrating through the microcapillary would decrease inside the pipette and consequently a pressure would build up, which prevents further penetration of the liquid into the microcapillary. If, on the other hand, one were to carry out a pressure stroke through the microcapillary before the start of the suction process in order to be able to carry out a suction stroke during the suction process, the handling of the known pipette would be too complicated. In addition, the bellows would then have to be held exactly in its position after the completion of the suction process in order to prevent the liquid thread in the microcapillary from being torn off.

The object of the invention is therefore to provide a pipette of the type specified at the outset which is suitable for holding liquid in self-absorbing microcapillaries and which is simple and reliable to use.

According to the invention, this object is achieved in that a pressure compensation opening is provided in the bellows. A pressure equalization can therefore take place during the suction process. As a result, no excess pressure can build up in the interior of the capillary, which would hinder further liquid absorption in the microcapillary. During the liquid intake, the operator can limit himself to observing the intake process; further measures on your part are not required. Even after completion of the liquid intake, the amount of liquid once taken up remains reliably in the microcapillary without the operator having to do anything. The liquid can be removed from the microcapillary by the operator closing the pressure compensation opening and executes a pressure stroke. The liquid is then pressed out by the excess pressure in the capillary.

In a further embodiment of the invention, the pipette has a holder in which a microcapillary is held in a frictionally engaged manner. This enables the microcapillary to be replaced quickly and easily. The receptacle can consist of a rubber grommet, which gives the microcapillary a secure and tight hold in a particularly simple manner. If the receptacle consists of two support surfaces arranged at a distance from one another, a particularly secure holding of the capillary is ensured.

Because part of the outer sleeve of the pipette is formed by an adapter for the microcapillary, it is possible to adapt the pipette according to the invention to microcapillaries of different dimensions, in particular different diameters, in a quick and simple manner by changing the adapter.

If the capillary is transparent, the level of the liquid in the capillary can be observed. By dimensioning the capillary, predetermined amounts of the liquid to be sucked up can be measured simply and precisely. Because the outer sleeve or the adapter is transparent in the area of the capillary, the liquid to be sucked up can be observed and / or measured over a greater or possibly over the entire length of the capillary.

If the bellows is connected to a push pin protruding from the outer sleeve of the pipette, it can be actuated in a simple manner by the operator. If the pressure equalization opening is on the pressure surface of the pressure pin, which is hollow and airtightly connected to the bellows, this pressure equalization opening can be easily made by placing a Fingers, in particular the operator's finger actuating the pressure pin, are closed.

Because the bellows in an advantageous embodiment of the invention has a spring action in the direction of its position with a larger volume, the pipette is automatically moved back into its initial position after the liquid has been ejected. This effect can be enhanced by providing the bellows with a compression spring.

If bactericidal substances or toxic reagents are to be treated with a pipette, it must be ensured that the operator does not come into contact with such substances. In many cases, however, liquid sensors, in particular microcapillaries, are used for such work, which have to be inserted manually into the pipette.

It is therefore a further object of the invention to provide a pipette which is simple and reliable to handle and in which the liquid receiver, in particular a microcapillary, can be removed from the pipette or separated from the pipette without the aid of the hand.

This object is achieved in a pipette with a liquid pickup in that the liquid ice pickup is frictionally and sealingly held in a receptacle, that a piston in a cylinder is guided in a longitudinally displaceable manner and that the piston can be moved beyond the end of the pressure stroke to the liquid pickup to move out of his admission. Because the liquid receiver is held in a receptacle by friction, it can be moved out of the receptacle by a pressure in the longitudinal direction. Characterized in that a piston is guided longitudinally in a cylinder and can be moved beyond the end of the pressure stroke to the To move the liquid receiver out of its holder, the liquid holder can be removed from the holder without touching it and separated from the pipette. Characterized in that the liquid receiver is held sealingly in a receptacle, the overpressure required to eject the liquid in the liquid receiver can form during the pressure stroke.

In an advantageous development of the invention, the receptacle consists of a rubber grommet, which ensures a particularly simple and secure frictional holding of the liquid receiver and seals the liquid receiver to the piston. If the receptacle consists of two support surfaces arranged at a distance from one another, the liquid receiver is held particularly tightly and firmly by this two-point support. An adapter for accommodating the liquid receiver creates a possibility of adaptation to liquid receivers of different external dimensions.

The connection of the piston with a pressure pin protruding from the outer sleeve of the pipette enables the pipette to be actuated easily.

Limiting the piston stroke by means of stops provides a simple and precisely reproducible possibility of measuring the liquid. If the piston is supported on the outer sleeve by a compression spring, the suction stroke of the piston is effected by spring force, which makes handling easier.

In a particularly advantageous development of the invention, a compression spring is provided which is supported on the one hand on the piston and on the other hand on a stop ring which bears against a stop of the piston during the pressure stroke and subsequently against a stop of the outer sleeve. Thereby After the end of the pressure stroke, the force of the compression spring must be overcome like a pressure point when the piston is further depressed, as a result of which the operator can feel the end of the pressure stroke and the start of the ejection phase of the liquid sensor in a reliable manner. This advantage can be increased in that the compression spring is pre-tensioned and / or harder than the compression spring which triggers the automatic execution of the suction stroke.

In an advantageous development of the invention, a cylinder part is provided which bears on a shoulder of the outer sleeve and has stops for the compression spring and for the stop ring. This cylinder part can be easily inserted into the outer sleeve of the pipette, which makes assembly easier.

If the pressure pin connected to the piston has a stop for the compression spring and stop surfaces for limiting the piston stroke, this stop and these stop surfaces can be formed in a simple manner by pushing the pressure pin onto the piston, which also facilitates assembly. An end cap carried by the outer sleeve with a stop for limiting the piston stroke also makes assembly easier.

In an advantageous development of the invention, the liquid receiver consists of a microcapillary and a pressure compensation opening is provided in the cylinder. The pipette is therefore suitable for use with self-aspirating microcapillaries. The advantages which result from the fact that the microcapillary is transparent, that the microcapillary is dimensioned and that the outer sleeve in the area of the microcapillary is transparent have already been explained.

If the pressure equalization opening in the work area is at a Where it is closed immediately after the start of the pressure stroke, the pressure stroke can be used over its greatest possible length when using a microcapillary. This is also possible if the cylinder part described above is used.

• Fig. 1 eine erste Ausführungsform der Erfindung,
• Fig. 2 eine zweite Ausführungsform der Erfindung vor Beginn des Druckhubes,
• Fig. 3 die Ausführungsform nach Fig. 2 am Ende des Druckhubes und
• Fig. 4 die Ausführungsform der Erfindung nach den Fig. 2 und 3 nach Ausführung der den Flüssigkeitsaufnehmer aus der Aufnahme herausbewegenden Bewegung.

Embodiments of the invention are described below with reference to the accompanying drawings. Show in these

• 1 shows a first embodiment of the invention,
• 2 shows a second embodiment of the invention before the start of the pressure stroke,
• Fig. 3 shows the embodiment of FIG. 2 at the end of the pressure stroke and
• Fig. 4 shows the embodiment of the invention according to FIGS. 2 and 3 after execution of the movement moving the liquid receiver out of the receptacle.

The first embodiment of the invention shown in FIG. 1 shows an all-plastic outer body 1, 2, 7 which is precisely adapted to the shape of the hand and posture from an ergonomic point of view. With the outer sleeve 1, an adapter 7 is firmly connected. The adapter 7 is transparent and allows the filling process and the emptying process to be observed. It carries a rubber grommet 8 in which the microcapillary 9 is guided. The microcapillary 9 is still held by the socket 6. The secure holding of the capillary 9 is ensured with the two contact surfaces in the socket 6 and in the rubber grommet 8. The microcapillary 9 is transparent and provided with markings in order to observe the filling process and the liquid to be absorbed to be able to measure exactly. The bellows 5 is connected airtight to the edge of the bush 6. The bellows 5 is also welded to the outer sleeve 1. The pressure pin 3 protrudes from the outer sleeve 1 of the pipette. It has a cavity 10 which is connected to the outside air via the bore 11. The pressure pin 3 is connected to the bellows 5 firmly and airtight. The inner volume of the bellows 5 is connected to the cavity 10 of the pressure pin 3 via the opening 12. With the outer sleeve 1, an end cap 2 is connected, in which the pressure pin 3 is guided. A spacer ring 4 adjoins the end cap 2 inside the outer sleeve 1.

The pressure pin 3 has a shoulder 13 which carries two stop surfaces. In the position shown in FIG. 1, one of the stop surfaces of the stop ring 13 acts with the stop surface. the spacer ring 4 together. The other stop surface of the stop ring 13 cooperates with the stop 14 of the outer sleeve 1 formed by a shoulder in the outer sleeve 1 after the pressure stroke has been carried out. The pressure stroke is limited by these two stops.

The bellows 5 is preloaded in the state shown in FIG. 1 and therefore presses the stop ring 13 against the spacer ring 4. The restoring force of the bellows 5 can be increased by means of a compression spring, not shown, located in the bellows 5.

The pipette consists exclusively of individual parts that are plugged into one another. With this plug-in technique, the pipette can be easily assembled and, for cleaning purposes, just as easily and completely disassembled without tools.

The length of the pressure stroke can be adjusted using spacer rings 4 of different lengths.

When working with the pipette shown in Fig. 1, the microcapillary 9 is first inserted through the very small opening cross section of the rubber grommet 8 into the socket 6 until it stops. In this position, the capillary is ventilated through the bore 15 of the bushing 6, the opening 12 of the bellows 5 and the bore 11 of the pressure pin 3, so that no internal pressure which hinders the capillary action can build up in the pipette. Depending on the geometry of the capillary 9, the entire pipette 1, 2, 7, 9 is brought to the liquid to be sucked up in a certain inclined position. When the capillary tip is immersed in the liquid, the filling process begins by capillary action. After removing the filled capillary from the liquid, liquid residues on the outer circumference of the capillary or the tip of the capillary can be dabbed off. If necessary, the liquid level in the capillary 9 can be adjusted by carefully dabbing on a printed mark on the capillary 9. To transfer the liquid to a part for further investigation, the bore 11 at the end of the pressure pin 3 is closed with the finger and then the pressure pin 3 is pressed through evenly until the second stop surface of the stop ring 13 of the pressure pin 3 on the stop 14 inside the outer sleeve 1 is present. In this completely depressed state, the capillary 9 is pulled out of the pipette.

After releasing the pressure pin 3, the pipette automatically returns to its starting position due to the restoring force of the bellows 5 which may be increased by a compression spring.

By placing the operator's finger on the end of the pressure pin 3, both the bore 11 of the pressure pin 3 and the pressure pin 3 and so that the bellows 5 moves in the direction of the pressure stroke. By closing the bore 11, no air can escape from the inside of the pipette during the pressure stroke, as a result of which the excess pressure required to push out the liquid in the capillary is generated by a single movement.

2 to 4, a second embodiment of the invention is shown. The outer body of the pipette consists of an outer sleeve 101, an end cap 102 attached to the rear end thereof and an adapter 111 attached to the front end of the outer sleeve 101. A microcapillary 120 is frictionally engaged in a rubber grommet 110 which is connected to the outer sleeve 101 kept sealed. The microcapillary 120 protrudes through an opening 121 of the adapter 111. The rubber grommet 110 is inserted into the outer sleeve 1 and has an area of larger diameter at its end, which is delimited by two stop surfaces. One of these stop surfaces lies against the end face of the outer sleeve 1, the second stop surface lies against a stop surface of the adapter 111 formed by a shoulder. The rubber grommet 110 is held firmly by these two stop surfaces when the adapter 111 is connected to the outer sleeve 101.

In the outer sleeve 101 there is a cylinder part 105, which rests with a shoulder 126 in the interior of the outer sleeve 101. The outer sleeve 101 also has a stop 123 on its inner surface.

A piston 104 is guided in a longitudinally displaceable manner in the interior of the cylinder part 105. In a groove of the piston 104 there is a sealing ring 109 for sealing the piston against the cylinder part 105. The piston 104 has a collar 127 with a larger diameter, on which a compression spring 108 is supported. The other The end of the compression spring 108 is supported on a stop 128 on the inner surface of the cylinder part 105. The compression spring 108 causes the pipette to perform the suction stroke independently.

The piston 104 has at its end a smaller-diameter part, on which a pressure pin 103 is pushed up to a stop. The pressure pin 3 passes through a bore in the end cap 102 and has on its outer surface a stop ring 122 with two stop surfaces 124, 125. In the position shown in FIG. 2, the stop surface 125 of the pressure pin 103 bears against the stop surface 126 formed by the end face of the end cap 102. The stop 125, 126 is reached independently by the pipette through the action of the compression spring 108. The stop formed by the stop surfaces 125, 126 thus limits the suction stroke of the pipette. In the embodiment of the invention shown in FIG. 2, the compression spring 108 is also biased in the position shown in FIG. 2.

The end face of the pressure pin 103 forms the stop face 128 against which the compression spring 107 rests. The other end of the compression spring 107 rests on the stop ring 106 which is guided in a longitudinally displaceable manner on the piston and which in turn rests on the larger-diameter collar 127 of the piston 104. The compression spring 107 is biased in the embodiment of the invention shown in FIG. 2.

In the cylinder part 105 there is the vent hole 105a, which creates a connection to the outside air. The vent hole 105a is located in the area of the working volume 132 of the cylinder directly next to the sealing ring 109 of the piston 104, which delimits the working volume 132. A smaller-diameter part 130 of the piston 104 extends into the working volume 132 and terminates with the stop surface 131. The diameter of the part 130 of the piston 104 is chosen so that that it can penetrate the bore 133 passing through the cylinder part 105. The microcapillary 120 rests on the outer end face of the cylinder part 105. Furthermore, the rubber grommet 110 lies in a ring-shaped manner on the outer end face of the cylinder part 105.

When using the pipette, the capillary 120 is pushed manually through the opening of the adapter 111 and further through the rubber grommet 110 up to the stop on the front end of the cylinder part 105. In this two-point support, the capillary 120 is tight and tight. In the unactuated state shown in FIG. 2, the piston 104 is struck all the way back with the stop surface 125 of the stop ring 122 against the stop surface 126 formed by the end face of the end cap 102 by the force of the compression spring 108. The piston 104 clears the vent hole 105a so that the capillary 120 can now be guided to the liquid with the pipette. The capillary 120 is filled by the capillary action. The pressure equalization takes place via the vent hole 105a. If the adapter 111 is transparent, it can be easily observed at which fill level the suction process has to be ended. This can be supported in that the - transparent - capillary carries 120 markings.

After the suction process has ended, the sucked-in liquid can be transferred to another vessel in that the piston 104 is pressed down against the force of the compression spring 108 via the pressure pin 103. The sealing ring 109 moves at the front end of the piston 104 over the vent hole 105a and builds up a slight overpressure on its further path in the working space 132 between the piston 104 or sealing ring 109 and the liquid, which leads to the discharge of the liquid. The volume of the work space and the volume of the sucked up Liquid must be in a certain relationship to each other so that the liquid column located in the capillary 120 is completely "blown out" when the capillary 120 is emptied, without air jumping back into the capillary 120.

At the end of the first stroke, the piston 104 abuts with its stop ring 106 against the stop 134 formed by the end face of the cylinder part 105, as shown in FIG. 3. The front end 131 of the smaller-diameter part 130 of the piston 104 is now almost at the rear end of the capillary 120. The smaller-diameter part 130 of the piston 104 partially penetrates the bore 133 at the end of the cylinder part 105.

When the piston 104 is depressed further, the relatively high pretensioning force of the compression spring 107 must be overcome like a pressure point. This begins the ejection phase of the capillary 120. The movable stop ring 106 runs up to the block length of the compression spring 108 against the front of the pressure pin 103.

The stroke is ended when the stop surface 124 of the stop ring 122 of the pressure pin 103 strikes the stop surface 123 in the interior of the outer sleeve 101, as shown in FIG. 4. In this state, the piston 104 sits with the end face 131 of the smaller-diameter part 130 in the exemplary embodiment shown, about 2 mm in front of the constriction of the rubber nozzle 110, and the capillary 120 falls out of its own accord when the pipette is held vertically.

The exemplary embodiment of the invention shown in FIGS. 2 to 4 shows a pipette which holds the capillary tightly and axially, so that it fills itself when a liquid surface is touched.

When the pressure pin is pressed down, the liquid that is sucked in is first released evenly slowly and without tearing off the liquid thread. The capillary is then ejected from the pipette by pressing the pressure pin down further without the aid of the hand.

Claims (14)

1. Pipette with elastic bellows, characterized in that a pressure compensation opening (12) is provided in the bellows (5) and that the pipette has a receptacle (8) in which a microcapillary (9) is held in a frictional manner. 2. Pipette according to claim 1, characterized in that the receptacle (8) consists of a rubber grommet, that the capillary receptacle consists of two spaced apart support surfaces (6, 8) and that part of the outer sleeve (1) of the pipette by one Adapter (7) for the microcapillary (9) is formed. 3. Pipette according to one of the preceding claims, characterized in that the microcapillary (9) is transparent, that the microcapillary (9) is dimensioned and / or marked with volume marks and that the outer sleeve (1) and / or the adapter (7) is transparent in the area of the microcapillary (9). 4. Pipette according to one of the preceding claims, characterized in that the bellows (5) with a from the outer sleeve (1, 2) projecting, hollow and with the bellows (5) air-tightly connected pressure pin (3) that the Pressure equalization opening (11) on the pressure surface of the pressure pin (3), that the bellows (5) has a spring effect mediated by a compression spring in the direction of its position with a larger volume, that the stroke of the bellows (5) by stops (13, 4th , 14) is limited, and that the bellows (5) in the area in which it has a sufficiently large restoring force is biased between the stops (13, 4, 14) so that it is without external aids in one of the stops (4) predefined rest position returns. 5. Pipette with a liquid receiver, characterized in that the liquid receiver (120) in a receptacle (110) is frictionally and sealingly held, that a piston (104) in a cylinder (105, 105 a) is guided in a longitudinally displaceable manner and that the piston ( 104) can be moved beyond the end of the pressure stroke in order to move the liquid receiver (120) out of its receptacle (110). 6. Pipette according to claim 5, characterized in that the receptacle consists of a sealing rubber grommet (110) and that the receptacle (110) consists of two spaced apart support surfaces (110, 121) and that part of the outer sleeve (101) the pipette is formed by an adapter (111) for the liquid receiver (120). 7. Pipette according to one of claims 5 or 6, characterized in that the piston (104) with a from the outer sleeve (101) of the pipette projecting pressure pin (103) is connected, that the stroke of the piston (104) by stops (122 , 124, 125, 123) and that the piston (104) is supported by a compression spring (108) on the outer sleeve (101). 8. Pipette according to one of claims 5 to 7, characterized in that a compression spring (107) is provided which is supported on the one hand on the piston (104) and on the other hand on a stop ring (106) which during the pressure stroke on a stop ( 127) of the piston (104) and then against a stop of the outer sleeve (134), the compression spring (107) being pretensioned and / or harder than the compression spring (108). 9. Pipette according to claim 7 or 8, characterized in that a cylinder part (105) is provided which rests on a shoulder (126) of the outer sleeve (101) and stops (129, 134) for the compression spring (108) and for the Has stop ring (106). 10. Pipette according to one of claims 7 to 9, characterized in that the pressure pin (103) connected to the piston (104) has a stop (128) for the compression spring (107) and stop surfaces (124, 125) for limiting the piston stroke having. 11. Pipette according to one of claims 5 to 10, characterized in that the outer sleeve (101) carries an end cap (102) with a stop (126) for limiting the piston stroke. 12. Pipette according to one of claims 5 to 11, characterized in that the liquid receiver (120) consists of a microcapillary and that a pressure compensation opening (105a) is provided in the cylinder (105). 13. Pipette according to claim 12, characterized in that the microcapillary (120) is transparent, that the microcapillary (120) is dimensioned and / or marked with volume marks and that the outer sleeve (101) and / or the adapter (111) in the area the microcapillary (120) is transparent. 14. Pipette according to one of claims 12 or 13, characterized in that the pressure equalization opening (105a) is in the working space (132) at a point at which it is closed immediately after the start of the pressure stroke and that the cylinder part (105) the pressure equalization opening (105a).

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