WO1993011870A1

WO1993011870A1 - Pipetter

Info

Publication number: WO1993011870A1
Application number: PCT/GB1992/002304
Authority: WO
Inventors: Ronald William Cowley
Original assignee: John Poulten Limited
Priority date: 1991-12-13
Filing date: 1992-12-11
Publication date: 1993-06-24
Also published as: AU3092592A

Abstract

A hand-held pipetter (1) having a body (2), a piston and cylinder device (3, 4) in the body, a manually actuable plunger (5) projecting from the body and by which the piston is moved in the cylinder, a piston rod (6) connected to the piston, screw-threaded means (21) connecting the piston rod to the plunger whereby rotation of the plunger relative to the body adjusts the effective stroke of the piston in the cylinder, means (13, 14, 15, 16) providing a visual indication of the effective stroke of the piston, and a tube (8) communicating with the cylinder and having a free end (9) carrying a pipetter tip (22), the arrangement being such that movement of the piston causes liquid to be drawn into the pipetter tip or dispensed therefrom, characterised in that the stroke indicating means comprises a first visual indicating set (13, 14) provided by an indicator (13) on or formed by the piston rod (6) co-operating with a corresponding first indicator (14) on the plunger (5), and a second visual indicating set (15, 16) provided by a second indicator (15) on the plunger (5) co-operating with a corresponding indicator (16) on the body (2).

Description

TITLE: PIPETTER DESCRIPTION

TECHNICAL FIELD

The invention relates to a pipette or pipetter. More particularly the invention relates to a pipette or pipetter of the nature of a hand-held utensil and having a body, a piston and cylinder within the body, a manually actuable plunger projecting from the body and by which the piston is moved within the cylinder, piston rod means connecting the piston and the plunger whereby rotation of the plunger in the body adjusts the effective stroke of the piston in the cylinder, means providing a visual indication of the effective stroke of the piston and a tube communicating with the cylinder and through which liquid can be drawn into the tip of the pipetter or dispensed therefrom on movement of the piston.

BACKGROUND ART

Such devices, hereinafter referred to as pipetters, are commonly used in laboratories for handling small liquid samples, and can be made to be accurate to a fraction of a microlitre. It is common for such pipetters to include a digital display which provides an accurate indication of the working volume of the pipetter to 0.2/xl, which working volume is adjusted by rotation of the plunger.

It is known from GB 1428375 of POULTEN to provide a piston and cylinder device for filling and emptying pipettes.

It is known from GB 1522669 of MARTEAU D'AUTRY to provide a pipetter having a pipette tip ejector.

There exists an unfulfilled demand for a simple and relatively inexpensive version of such a pipetter but it is difficult to achieve this in practice given the current manner in which such devices are made and calibrated.

It is an object of the invention to provide a relatively simple and inexpensive pipetter.

DISCLOSURE OF INVENTION According to the invention there is provided a hand¬ held pipetter having a body, a piston and cylinder device in the body, a manually actuable plunger projecting from the body and by which the piston is moved in the cylinder, a piston rod connected to the piston, screw-threaded means connecting the piston rod to the plunger whereby rotation of the plunger relative to the body adjusts the effective stroke of the piston in the cylinder, means providing a visual indication of the effective stroke of the piston, and a tube communicating with the cylinder and having a free end carrying a pipetter tip, the arrangement being such that movement of the piston causes liquid to be drawn into the pipetter tip or dispensed therefrom, characterised in that the stroke indicating means comprises a first visual indicating set provided by an indicator on or formed by the piston rod co-operating with a corresponding first indicator on the plunger and a second visual indicating set provided by a second indicator on the plunger co-operating with a corresponding indicator on the body. Preferably the first indicator on the plunger comprises an axially arranged series of graduations or scale.

The indicator on the body may comprise a series of graduations disposed radially around the plunger. Preferably the graduations on the body are formed by pointed projections. Advantageously one of the projections is larger in size than other of the projections.

The free end of the piston rod may be visible through the plunger to form the indicator. Thus the plunger may be of a transparent plastics.

Preferably the tube is in the form of a one-piece extruded plastics member. The pipetter may comprise a tip ejector surrounding the tube and axially movable relative thereto, and an actuating rod operatively connected to the tip ejector by clip means and extending to a position adjacent to the plunger whereby the pipetter is capable of one-handed operation both as regards the depression of the plunger and as regards tip ejection.

The tip ejector is preferably formed at its inner end with a flange against which the actuating rod abuts.

The actuating rod may be formed with a forked portion at one end which forms the clip means which is resiliently engagable about the inner end of the tip ejector.

The end of the actuating rod remote from the clip means may be formed with a manually actuable knob or button.

Preferably the actuating rod is made in one piece from a plastics material. BRIEF DESCRIPTION OF DRAWINGS The invention is diagrammatically illustrated, by way of example, in the accompanying drawings in which:-

Figure 1 is a sectional side view of a pipetter; Figure 2 is a scrap view of the pipetter of Figure 1, and

Figure 3 is a perspective view of a detachable tip ejector actuating rod for the pipetter of Figures 1 and 2. BEST MODE FOR CARRYING OUT THE INVENTION In the drawings there is shown a pipetter 1 of the kind comprising a body 2 adapted to be grasped and held by a user's hand and by means of which small liquid samples can be sucked up and dispensed. A piston 3 and cylinder 4 device is housed within the body and the piston is moved in the cylinder by means of a manually actuable plunger 5 projecting from the body and in screw-threaded engagement at 21 with a piston rod 6 attached to the piston 3. Means (not shown) is provided for preventing rotation of the piston in the cylinder. The screw-threaded engagement 21 between the piston rod and the plunger has the effect that rotation of the plunger relative to the body alters the position of the piston within the cylinder and thus adjusts its effective working stroke. A coil spring 7 is provided within the body and surrounding the piston rod and arranged whereby the plunger is biased into a rest position as shown in Figure 1 the drawings in which the plunger is fully extended from the body.

A hollow tube 8 is mounted in the body 2 and extends from the lower end of the body. The tube 8 is connected to the cylinder so as to communicate with its interior and a pipetter tip 22 is adapted to be a push fit on the free end 9 of the hollow tube in conventional fashion. A sleeve 10 is mounted on the body to surround the tube and is capable of movement along the tube against the action of a coil spring 11 which urges the sleeve into the rest position shown in Figure 1. When the sleeve is depressed by means of a flange 12 at the upper or inner end 23 of the sleeve as seen in Figure 1, it acts to contact and eject the tip 22 from the free end 9 of the tube.

The plunger 5 is made of a transparent plastics material whereby the end 13 of the piston rod 6 is visible through the plunger and forms an indicator or cursor which can be viewed against a series of graduations or scale 14 provided axially along the plunger. This provides a first indicating set by which the effective working stroke of the piston in the cylinder can be set. In addition the plunger 5 is formed with one or more dots 15 about its periphery at a position near to the body and which may be aligned with corresponding markings 16 provided on the body radially around the plunger at spaced intervals as shown in Figure 2. These markings 16 are in the orm of pointed projections 24, one 25 of which is larger than the rest so that it is easily possible to count a full rotation of the plunger. The markings 16 and the dot or dots 15 provide the second indicating set for accurately determining the working stroke of the piston within the cylinder. The first and second indicating sets thus generally resemble the linear and radial graduations of a micrometer and adjustment is carried out in the same way. In the present case, however, it is preferred to arrange the plunger as described above so that the length of the pipetter does not vary with adjustment of the volume since this can adversely effect one-handed operation.

It is envisaged however that it might be possible to construct a pipetter in which the first, i.e. axial, indicating set is provided externally in similar manner to that of a conventional micrometer.

By these means the working volume of the pipetter can be adjusted as desired by the user. Since the adjustment means is simple the pipetter can be manufactured relatively inexpensively e.g. using plastics and the like. This in turn allows the pipetter to be autoclavable. Preferably the tube 8 on which the pipetter tip is mounted is formed as a one-piece plastics extrusion in the interest of economy. The cylinder 4 is preferably also of plastics and is secured to the tube 8 by means of an adhesive.

As shown in Figure 1, an actuating rod 17 is clipped onto the sleeve 10 adjacent to the flange 12 whereby the tip ejector sleeve can be operated with one hand rather than requiring two handed manipulation as might be the case with the arrangement of Figure 1.

The actuating rod is shown more particularly in Figure 3 of the drawings and comprises a one piece plastics moulding of polypropylene or the like having a first end formed with an operating knob or button 18, an elongate stem 19 and at its other end a clip portion 20 in the form of a fork member defining a part circular cut-out which can be engaged with snap action about the sleeve 10. Due to the shape of the clip portion, the actuating rod can be rotated about the sleeve to assume any position convenient to the user. In this connection it will be appreciated that the position of the tip ejector actuating mechanism with conventional pipetters is fixed and cannot be adjusted to suit both left and right handed users.

INDUSTRIAL APPLICABILITY The invention thus provides a simple and inexpensive hand-held pipetter for use in dispensing liquid samples e.g. in a laboratory or classroom or the like.

Claims

CLAIMS 1. A hand-held pipetter (1) having a body (2) , a piston and cylinder device (3,4) in the body, a manually actuable plunger (5) projecting from the body and by which the piston is moved in the cylinder, a piston rod (6) connected to the piston, screw-threaded means (21) connecting the piston rod to the plunger whereby rotation of the plunger relative to the body adjusts the effective stroke of the piston in the cylinder, means (13,14,15,16) providing a visual indication of the effective stroke of the piston, and a tube (8) communicating with the cylinder and having a free end (9) carrying a pipetter tip (22) , the arrangement being such that movement of the piston causes liquid to be drawn into the pipetter tip or dispensed therefrom, characterised in that the stroke indicating means comprises a first visual indicating set (13,14) provided by an indicator (13) on or formed by the piston rod (6) co-operating with a corresponding first indicator (14) on the plunger (5) , and a second visual indicating set (15,16) provided by a second indicator (15) on the plunger (5) co-operating with a corresponding indicator (16) on the body (2) .

2. A hand-held pipetter according to claim 1, characterised in that the first indicator (14) on the plunger comprises an axially arranged series of graduations.

3. A hand-held pipetter according to claim 1 or claim 2, characterised in that the indicator (16) on the body (2) comprises a series of graduations disposed radially around the plunger (5) .

4. A hand-held pipetter according to claim 3, characterised in that the graduations (16) on the body are formed by pointed projections (24,25).

5. A hand-held pipetter according to claim 4, characterised in that one (25) of the projections (24,25) is larger in size than other of the projections.

6. A hand-held pipetter according to any preceding claim characterised in that the free end (13) of the piston rod (6) is visible through the plunger (5) and forms the indicator (13) .

7. A hand-held pipetter according to any preceding claim, characterised in that the tube (8) is in the form of a one- piece extruded plastics member.

8. A hand-held pipetter according to any preceding claim, characterised by a tip ejector (10) surrounding the tube (8) and axially movable relative thereto, and an actuating rod (17) operatively connected to the tip ejector by clip means (20) and extending to a position adjacent to the plunger (5) whereby the pipetter is capable of one-handed operation both as regards the depression of the plunger and as regards tip ejection.

9. A hand-held pipetter according to claim 8, characterised in that the tip ejector (10) is formed at its inner end (23) with a flange (12) against which the actuating rod (17) abuts.

10. A hand-held pipetter according to claim 8 or claim 9, characterised in that the actuating rod (17) is formed with a forked portion (20) at one end which forms the clip means (20) which is resiliently engagable about the inner end (23) of the tip ejector (10) .

11. A hand-held pipetter according to claim 10, characterised in that the end of the actuating rod (17) remote from the clip means (20) is formed with a manually actuable knob or button (18) .

12. A hand-held pipetter according to any one of claims 8 to 11, characterised in that the actuating rod (17) is made in one piece from a plastics material.