AU6431894A

AU6431894A - Piston pipette

Info

Publication number: AU6431894A
Application number: AU64318/94A
Authority: AU
Inventors: Jukka Tervamaki
Original assignee: Labsystems Oy
Current assignee: Thermo Fisher Scientific Oy
Priority date: 1993-04-21
Filing date: 1994-04-20
Publication date: 1994-11-08
Also published as: FI931806A0; WO1994023838A1; DE69413021D1; EP0695220B1; EP0695220A1; JPH08510158A; DE69413021T2; JP3697527B2

Description

PISTON PIPETTE

FIELD OF TECHNOLOGY

The invention relates to the handling of liquids and it concerns a hand-held piston pipette.

TECHNICAL BACKGROUND

Manually operated piston pipettes are usually provided with a knob at the piston rod by which the piston is moved by pressing with the thumb. Such a pipette is known, for example, from publication FI-C-47461 (corresponds, for example, to publication US-3810391) .

In a so-called step pipette the liquid volume drawn into the pipette cylinder is metered out in several smaller doses. In the step pipette the piston rod usually has teeth and the body has a matching striker always pushing the piston downward over the desired distance during a dosing stroke. One such pipette is known, for example, from publication US- 4099548 wherein the top end of the body has a thumb-operated push knob. Publication GB-A-2048712 again presents a similar step pipette, wherein in the side of the top part of the body there is a forefinger-operated dosing push button.

In some step pipettes the striker actuator is a lever journalled in the body in its top part above the striker point. The lever is operated with the thumb. One such step pipette is known, for example, from publication DE-A-2926691 (corresponds, for example, to publication GB-A-2057581) . This pipette also has a volume control device having a lon¬ gitudinally moving covering plate above the teeth. The striker always moves over a standard distance, but part of the movement is along the covering plate off the teeth. Thus the distance covered by the piston is dependent on the location of the plate.

In conventional pipettes the pipette is gripped by the hand, so that the pipette must by necessity be made quite long. Dosing liquid to a very small place is difficult with such a pipette and in any case requires a very steady hand and great carefulness. Known electrically operatig pipettes are also gripped with the hand and the operating button is located in the upper part of the body. Such pipettes are described, for example, in publications FI-A-742083 (corresponds, for example, to publication US-4058370) and FI-A-932942 (corresponds, for example, to publication EP-A-576967) .

DESCRIPTION OF THE INVENTION General description A pipette as defined in claim 1 has now been invented. Its advantageous applications are presented in the other claims.

The pipette according to the invention is designed to be gripped like a pencil. Thus liquid can be dosed very precisely with the pipette even to very small places. The pipette is particularly suitable for use in certain laboratory work and in assembly glueing. The pipette may be a step pipette or a one-dose pipette. It may be manually operated or electrically operating. Description in detail In a manually operated pipette according to the invention there is a gripping means attaching to a piston for moving the piston downward, but also allowing the piston to be pulled upward. The pipette has a transfer means extending below the gripping means and joined to this and preferably also associated with a separate push button. The pipette body may have a longitudinal gap partly open at least on one side for the cylinder and the piston.

The transfer means is preferably spring-operated so that it will always return to its original position after the transfer movement.

The transfer means is preferably movable in the lon¬ gitudinal body direction so that the top position of the transfer means also corresponds with the top position of the gripping means. The transfer means is preferably on one side of the body. Hereby the opposite side of the body may have an open gap through which an exchangeable cylinder and piston can be mounted. The transfer means is also preferably joined to an operating lever articulated to the body and articulated to the transfer means.

The pipette may also have a stroke length control means. A point vessel into which liquid is drawn can be used at the cylinder end. However, the cylinder may function at the same time also as a liquid container and both the cylinder and the piston can be exchangeable.

The pipette can be provided, for example, with a spring means for pulling the piston upward. However, a step pipette is preferably only provided with a piston knob for pulling the piston upward by hand. Then the body is preferably provided with a stop to prevent the piston from escaping from the cylinder. In addition, the pipette may have equipment for controlling the liquid volume to be drawn into the pipette.

In a step pipette one transfer movement of the transfer means transfers the piston downward only by a stroke of a certain length out of the entire distance of the piston movement. Thus, the liquid volume drawn into the pipette is discharged from the pipette in several smaller doses. The stroke length control means may have, for example, a stop which moves in the body direction and which limits the upper position of the striker.

In a step pipette a spring is preferably connected to the gripping means for pressing down the moving gripping means against the piston rod. The device is also preferably provided with a releaser automatically to release the grip¬ ping means from the piston when the gripping means is in its top position in relation to the piston, whereby the piston can be easily pulled up to its top position.

Some applications of the invention are described in the following as examples. In the drawings of the description

- Figure 1 is a side view of a step pipette in accordance with the invention, - Figure 2 is a view from above of the pipette in Figure

1,

- Figure 3 shows a pipette in accordance with the inven¬ tion in use, - Figure 4 is a side view of another step pipette in accordance with the invention,

- Figure 5 is a top view of the pipette in Figure 4,

- Figure 6 shows a third step pipette according to the invention in the initial dosing position,

- Figure 7 shows the pipette of Figure 6 in the end position,

- Figure 8 shows a fourth step pipette,

- Figure 9 is a top view of the control equipment of the pipettes in Figures 6 - 8,

- Figure 10 shows a one-dose pipette according to the invention in the initial position,

- Figure 11 is a partially blown-up view of the pipette of Figure 10 in the initial drawing-in stage, and - Figure 12 is a partially blown-up view of the pipette in

Figure 10 in the emptying stage.

The main parts of the pipettes given as examples are body 1, cylinder 2 and therein piston 3 as well as striker 4, which functions as a transfer means, and connected to this gripping means 5 and operating lever 6.

The body has a longitudinal gap 7. At the lower body end the gap is open only to one side of the body, but at the upper end the gap extends through the body forming a sliding slot for the rod of piston 3. At the lower body end hole 8 forms an extension to the gap. At the upper end an end stop

9 closes the gap.

The cylinder and piston 3 are placed in gap 7 so that the cylinder head extends out of hole 8 at the lower body end. At the top end of the cylinder there is a peak-like flange 10, which at the mid-point of the body is pushed into a transverse groove 11 opening to the open side of the gap. In this way the cylinder is prevented from moving in a lon¬ gitudinal direction. The piston has a rod emerging at the upper cylinder end which at its end in a sliding slot has a pulling knob 12 with edges extending from the gap to the sides of the body. Liquid is drawn into the cylinder by pulling the piston upward at the knob. Stop 9 at the top end of the sliding slot prevents the piston from being pulled out of the cylinder by mistake. The figures show the piston both in its top and lower positions.

The striker is located in the body on the opposite side of gap 7 to slide longitudinally in a groove. The top end of the striker has a sliding slot containing gripping means 5, which co-operates with the rod of piston 3 and which when moving downward will grip the piston rod and move it downward, but which when moving upward is free of the piston rod, thus not moving the piston. In the pipette shown in Figures 1 and 2 gripping means 5 is a sharp link pressing onto the surface of the rod of piston 3 obliquely from above, thus biting into the piston rod. This gives the advantage that the stroke length can be controlled steplessly by limiting the striker's movement in some suitable way.

In the pipette according to Figures 4 and 5 and 6 and 7 the rod of piston 3 is provided on the striker side with teeth 13 and the gripping means is a sharp cam pressing obliquely from above into these teeth. In this way the grip- ping means is made to operate more reliably, but control can only be arranged stepwise. The teeth are made easily at the same time as the piston.

The striker is connected together with a spring 14, which forces the striker upward against stop 15 in the sliding slot. The lower stop end is camfered at the top and thus it lifts gripping means 5 off the rod of piston 3 when the gripping means is forced to its top position.

In the pipette according to Figures 1 and 2 spring 14 is a bent wire spring having its lower end attached to the body and its top end to the striker. The spring pushes the striker against stop 15.

In the pipette according to Figures 3 and 4 spring 14 is a helical spring having its lower end supported against a support in the body and its top end against the striker. Here too the spring pushes the striker against stop 15. The helical spring is covered by plate 16.

In the pipette according to Figures 6 and 7 spring 14 is a draw-spring having one end attached to the striker and the other end to a control rod 20 located at the top body end. At the lower end of the striker there is also a striker operating lever 6 articulated at point 17 with its other end articulated at a lower point 18 in the body. The free lever end is bent downward. The turning point of the lever in the striker is closer to the body than the support point of the lower end of spring 14. In this way the spring pushes the striker both upward against stop 15 and inward against the rod of piston 3. By pressing at operating lever 6 the piston is made to move a step at a time downward. The pipettes are also provided with a device for control¬ ling the stroke length of the striker. In the pipette accor¬ ding to Figures 1 - 5 it is a bushing 19 at the lower body end moving longitudinally of the body and the free end of operating lever 6 is pressed against it when dosing liquid. The upper the location of the bushing the shorter naturally is the stroke. The bushing and the body may have suitable friction means to prevent the bushing from sliding inadver¬ tently. In the pipette according to Figures 4 and 5 the bushing also has a transparent plate with a reading line. The body has a corresponding scale from which the volume to be dosed can be read.

In the pipette according to Figures 6 and 7 the top body end has a control rod 20 movable lengthwise of the body. Its lower end 21 works as a cam to lift the top end 22 of the striker off the teeth 13 when the striker is in its top position. Gripping means 5 is located in the striker at an interval from its top end. Thus, the position of the control rod determines at which point the gripping means will engage with the teeth. At the top end of the control rod a transverse pin 23 is fitted to move in a cam groove rotating eccentrically in control disc 24. The rod position can thus be controlled - by rotating the disc. The body and control disc are provided with a scale from which the volume cor¬ responding to a dosing stroke can be read. Plate 16 also covers the control rod.

Figures 6 and 7 also show the shape of piston 3 which corresponds to the cylinder 2 shape narrowing conically from below sealing point 25. Groove 7 here extends all the way to the lower body end. In the pipette according to Figure 8 the lower end 21* of control rod 20 functions as a stop for the top position of striker 4. In its top position the striker rises to disengage from teeth 13 with the aid of cam 26 located on one side of the teeth. This gives the advantage that there is no idle motion during the early stroke, because gripping means 5 engages with the teeth at once as the striker leaves its top position. In addition, the position of lever 6 gives a clear picture and feel of the volume to be dosed. In the pipette according to Figures 6 - 8 spring 14 pulls control rod 20 downward. In the groove in control disc 24 there is a recess at each place corresponding to a volume to be set and pin 23 comes to rest in this recess.

Figures 10 - 12 show a one-dose pipette according to the invention having a replaceable point container 26. The equip¬ ment for volume control is similar to that in Figures 5 - 8. Here gripping means 5* is a push button located transversely at the top end of striker 4'and corresponding to flange 12* at the top end of piston 3* . Push button 5' is free of flange 12' . A calibrating screw

27 is threaded through the push button against flange 12 • to allow exact control of the piston position in relation to the push button.

The top end of cylinder 2' has a sealing ring 25' on top of which is a compression flange 28. Located between the compression flange and flange 12• at the top end of the rod of piston 3' is a primary spring 29 pressing the piston against push button 5' .

Cylinder 2' has a broader top part 30 with a narrower bottom part 31 attached to an enlarged bore in its bottom end so that an annular hollow space is left between them. In this space there is a secondary support formed like a disc and between this and the top end of the bottom part of the cylinder there is a spring 33 pressing the secondary support upward. Piston 3' too has a broader top part 34 and a nar¬ rower bottom part 35. With the piston in its top position the bottom end of top part 34 is above secondary support 32 (Figure 10) . When taking liquid into the pipette the piston is pressed downward against the force of spring 29 until the bottom end of the piston top part 34 meets secondary support 28 (Figure 11) , whereby one feels when secondary spring 33 begins resis- ting the movement. The head end of container 26 is brought into the liquid to be dosed and the primary spring is allowed to return the piston to its top position. When discharging liquid from the pipette the piston is pushed further downward, that is, also against the force of the secondary spring (Figure 12) , whereby the container is emptied as completely as possible.

The pipette according to the invention is gripped like a pencil and operating lever 6 is pushed with the forefinger. The pipette can thus be brought very precisely even to a small object. Dosing too is easy.

The pipette is especially suitable for use, for example, in certain immunofluorescence determinations performed with glass plates (Figure 3) , where liquid must be dosed onto very small areas. When dosing, the hand may also be supported against the table, which is not possible when using conven¬ tional pipettes.

The pipette is also very suitable for glueing requiring high precision, for example, in assembly jobs. Nowadays glue is usually dosed from a co pressable bottle in such jobs. Using a pipette according to the invention is much easier and the doses are essentially more exact. Nor will the glue dry in the cylinder so easily as in a bottle.

It is understandable that within the scope of the inven¬ tion many kinds of different pipettes can be constructed and that the purpose of the pipette also affects the construction possibilities. Decisive factors are in particular the pipette size, the desired draw-in volume, the required dosing precision, the special nature of the liquid (for example, viscosity) and on what kind of object and in what doses the liquid will be dosed. Many different construction pos¬ sibilities exist especially as regards the gripping means and its transfer means as well as possible springs, the operating lever and the volume control equipment.

Claims

1. Piston pipette having a longitudinal body (1) provided with a cylinder space and functioning as a handle and having a top end and a lower end, in the cylinder space a cylinder (2/2¹), where there is a point emerging from the lower body end and provided with a liquid opening, a top end and a piston (3/3') having a rod emerging from the top end of the cylinder and pulling equipment for moving the piston upward in the cylinder and pushing equipment for moving the piston downward in the cylinder, characterized in that the pipette body is designed to be gripped like a pencil.

2. Pipette as defined in claim 1, characterized in that the pushing equipment has a gripping means (5/5') moving in the longitudinal direction of piston (3/3') rod between a top and a bottom position, which when moving downward transfers the piston, and in the body there is a transfer means (4/4') extending below the gripping means and joined to this and movable between initial and end positions for moving the gripping means so that when the gripping means is in the top position the transfer means is in the initial position and when the gripping means is in the bottom position the transfer means is in the end position.

3. Pipette as defined in claim 1 or 2, characterized in that the transfer means (4/4') is attached directly to the gripping means and it is movable longitudinally of the body.

4. Pipette as defined in claim 1 or 2, characterized in that it has a spring (14/29) for forcing the transfer means to its initial position.

5. Pipette as defined in any claim 1 - 4, characterized in that when moving downward the gripping means (5) is attached to the piston rod at its side and moves the piston downward, but when moving upward it is free of the piston rod.

6. Pipette as defined in claim 5, characterized in that a spring (14) is connected to the gripping means (5) for pushing the gripping means against the piston rod when the gripping means is moving downward.

7. Pipette as defined in claim 5 or 6, characterized in that it has a stop (15/21/21'/26) for lifting the gripping means off the piston rod in the top position so that the piston can be pulled freely to the top position.

8. Pipette as defined in any claim 5 - 7 characterized in that the gripping means is a link pressing upon the piston rod.

9. Pipette as defined in any claim 5 - 7 characterized in that the piston rod has teeth and that the gripping means is a blade matching with the teeth.

10. Pipette as defined in any claim 1 - 9, characterized in that a movement of the gripping means (5) downward pushes the piston downward only over a part of the entire distance available to the piston.

11. Pipette as defined in claim 10 characterized in that the body has a stop (9) for limiting the top position of the piston movement.

12. Pipette as defined in any claim 1 - 11, characterized in that the cylinder (2) and preferably also the piston (3) are exchangeable.

13. Pipette as defined in claim 12, characterized in that there is a longitudinal gap (7) in the pipette side where the cylinder is attached and wherein the piston rod moves.

14. Pipette as defined in claim 13, characterized in that the gap (7) is on the body side opposite to the transfer means.

15. Pipette as defined in claim 13 or 14, characterized in that the cylinder top end has a flange (10) and the body has a corresponding transverse groove (11) into which the flange is pushed.

16. Pipette as defined in any claim 1 - 15, characterized in that the piston rod end is provided with a pulling knob (12) .

17. Pipette as defined in claim 1 - 4, characterized in that when moving downward the gripping means (5¹) presses on the piston from its top end.

18. Pipette as defined in claim 17, characterized in that the piston is connected to a spring (29) for pressing the piston against the gripping means.

19. Pipette as defined in claim 18, characterized in that the piston is connected to another spring (33) , against the force of which the piston can be pressed downward to empty the pipette as completely as possible.

20. Pipette as defined in any claim 17 - 19 characterized in that the a calibrating means (27) is connected to the gripping means for controlling the clearance between the gripping means and the piston.

21. Pipette as defined in any claim 1 - 20, characterized in that the transfer means is connected to a lever (6) ar¬ ticulated to the body for actuating the transfer means.

22. Pipette as defined in claim 21, characterized in that the lever (6) can be turned downward.

23. Pipette as defined in claim 21 or 22, characterized in that the lever (6) is articulated directly to the transfer means (4) .

24. Pipette as defined in any claim 21 - 23 characterized in that the lever is in the lower body (1) part.

25. Pipette as defined in any claim 1 - 23, characterized in that it has equipment (19/20) for controlling the distance of movement between the top and lower positions of the grip- ping means.

26. Pipette as defined in claim 25, characterized in that the control equipment (19/20) is a stop which is movable in the longitudinal direction of the body.

27. Pipette as defined in claim 26, characterized in that the gripping means is connected to a spring for pressing the gripping means against the piston rod when the gripping means is moving downward and that the pipette contains a control rod (20) the end (21/21') of which functions as a stop for lifting the gripping means free of the piston rod in the top position and to which control rod a spring is attached to pull the control rod downward.

28. Method of dosing liquid, characterized in that a pipette as defined in any claim 1 - 27 is used in it.

29. Method as defined in claim 28 for dosing liquid in immunofluorescence determinations using a glass plate or for dosing glue onto a point to be glued.