GB2048712A - A Micropipette for Repetitive Delivering of small Constant Amounts of Liquid and/or Multiples Thereof - Google Patents

Abstract

A micropipette for repetitive delivering of small constant amounts of liquid e.g. 10 mu l or multiples thereof, comprises a handle body (1) enclosing a rod-shaped element (4) provided with equally spaced engageable formations and carrying a plunger (6) at its lower end for cooperation with a syringe (46) clamped to the body. Means for stepwise advancement of the rod-like element are actuated by a pushbutton and comprise, e.g. a link element (21) for engaging successive projections on the rod-like element, and a pawl (12) rockingly driven by the pushbutton (7) between first and second positions and carrying the link element. Adjustment members (24) are provided for adjusting the stroke of the pushbutton in dependence on the desired quantity of liquid to be dispensed, by varying the range of movement of the pawl and link element, so that the latter moves the element (4) down one or more than one step each time the pushbutton is operated. <IMAGE>

Description

SPECIFICATION A Micropipette for Repetitive Delivering of Small Constant Amounts of Liquid and/or Multiplies Thereof This invention relates to a micropipette for repetitive delivering of constant small amounts of liquid and/or multiples thereof.

Micropipettes for delivering constant small amounts of liquid are already known, but such conventional pipettes have the disadvantage of requiring a repeated actuation of a pushbutton for the repetitive delivery of such constant small amounts of liquid. Moreover, such conventional micropipettes are of a complicated structure and proportionally high cost.

According to the present invention, there is provided a micropipette for repetitive delivery of constant small amounts of liquid and/or multiples thereof, comprising a handle body, a rod-like element provided with equally spaced engageable formations and arranged internally in the body, a syringe which can be clamped on the body, and means actuated by a pushbutton for axially feeding the rod-like element stepwise, wherein the rod-like element passes longitudinally through the body and carries at one end a plunger for cooperation with the syringe, and wherein the push-button actuated means comprises a link element for engaging successive formations of the rod-like element, a pawl reciprocable between first and second positions, the pawl carrying the link element and being adapted to be rocked by actuation of the pushbutton between these two positions and adjustment means for adjusting the stroke or travel of the pushbutton to cause the pawl to move the link element over one or more than one of the engageable formations when moving from its first to its second position and to move the rod-like element axially when moving from its second to its first position.

Such a micropipette can deliver, on a single actuation of the pushbutton, either a given small amount of liquid or a multiple of such amount. The micropipette of the invention may be constructed in structurally simple fashion and cost accordingly be reduced relative to conventional micropipettes.

A preferred embodiment of the invention is shown, by way of example, in the Figures of the accompanying drawings, in which: Figure 1 is a side view showing a micropipette according to the invention; Figure 2 is a fragmentary sectional view taken along line Il-Il of Figure 1; Figure 3 is an enlarged view showing the portion indicated by A in Figure 2; Figure 4 is an enlarged sectional view taken along line IV--IV of Figure 2; and Figure 5 is an enlarged sectional view taken along line V-V of Figure 2.

Referring to the above Figures of the accompanying drawings, a micropipette comprises a box-like body, generally denoted at 1, of suitable material, formed of two shell halves 2 and 3 which can be coupled to each other in any suitable fashion. The configuration and dimensions of body 1 are such that the latter can be easily firmly gripped by the hand. The shell half 2 constitutes the portion for accommodating the various operating mechanisms, described in the following, whereas the shell half 3 essentially merely performs, in the embodiment shown, the function of a lid or cover.

Shell half 2 is axially traversed by a rod-like element 4, suitably guided by bushes 4' and 4", projecting from both end portions of shell half 2, and at one end provided with a threaded knob 5 and on the opposite end with a plunger 6', of rubber or other suitable material. The intermediate portion of this element 4 (shown in Figure 3) has a plurality of equally spaced projections 6, each shaped as a frustum of a cone with the minor or short side towards the end of element 4 carrying the plunger 6'.

Laterally of shell half 2 at suitable position for actuation by the forefinger of the hand gripping the body 1, a pushbutton 7 is provided, which button has an integral extension 8 having a depressed portion defining a cavity 9, the cavity being defined at the bottom by a portion provided with longitudinal slit 10 (Figure 4) and at its sides by walls 11 and 11' extending transversely of the longitudinal axis of extension 8.The end 8' of extension 8 opposite to pushbutton 7 bears on the upper end 12' of a pawl 12 pivoted at 13 on shell half 2, the opposite end 12" of pawl 12 accommodating one end of a spring 14, the other end of which acts on a small block 1 5 of plastics or other material having a high coefficient of friction, which block is freely housed in a seat 1 6 on a thicker portion 17 of shell half 2 and provided with a bore 1 8 through which the rodlike element 4 passes.

Pawl 12 has a lug or projection 19, having a link element 21 pivoted thereon at 20, the end 21' of which is of the shape shown in Figure 5 in order to cooperate with the projections 6 on the median portion of the rod-like piston 4. A spring 22 bears with one end of the link element 21 and has its other end accommodated within a seat 23 provided on pawl 1 2 below pivot as seen in Figure 2. At one side, link element 21 also has a lug or projecting part 21", the function of which is described below.

At the top of shell half 2, arranged with axis parallel with the axis of said rod-like element 4, an adjustment member is provided, as generally shown at 24 and comprising a top portion 25 which is axially slidable within a seat 26, formed in shell half 2 and which is provided with a plurality of notches 27 (of which three are shown in this case) intended to receive an extension 28 mounted on a clamping member 29, the latter being arranged transversely to member 24 and temporarily removable (in the direction of arrow F) from a threaded seat 30. Members 24 and 29 are provided with gripping knobs 31 and 32, respectively.

A median portion 33 of adjustment member 24 has a plurality of steps 34 (of which three are shown in this embodiment) of a pitch corresponding to the distance or spacing between the notches 27.

The bottom portion 35 of adjustment member 24 essentially comprises a pin, passing through slit 10 in extension 8, and freely axially slidable within a seat 36 formed in the thicker portion 1 7 of the shell half 2.

A seat 37 is provided on the end portion of shell half 2 opposite to the adjustment member 24 for axially slidably accommodating a cylindrical element 38, the latter being restrained against rotation by a pin 39 integral with shell half 2 and located in an elongated cavity 40 laterally formed on element 38. Element 38 is provided with an axial bore 41 for the passage of the rodlike element 4 and is urged axially downward by a spring 42 arranged within that portion of seat 37 between bush 4" and a seat 38" provided on the top of cylindrical element 38. Two opposite recesses 43 are formed both on shell half 2 and on shell half 3, such recesses 43 forming with an axial aperture 44 on a T-shaped seat for receiving the finned portion 45 of a conventional syringe 46.

As shown in Figures 1 and 5, a button 47 is provided on shell half 3 and mounted on a slider 48 which is slidable in the direction of arrow F' in a cavity 49 formed internally of shell half 3. An end portion 48' of slider 48 is aligned with the lug or projecting part 21" provided on link element 21.

As described above, the micropipette according to the invention may be used for repetitive delivery of a constant small amount of liquid and/or of multiples of that small amount.

The small amounts are determined by the pitch of projections 6 and the cross-section of plunger 6', the latter corresponding of course to the inner cross-section of syringe 46, and may be, for instance, 10 yl amounts.

In the use of the micropipette of the invention, a syringe 46 is first clamped in place on body 1.

To do this the finned portion 45 is introduced into aperture 44 to raise, against the resisting action of spring 42, the cylindrical element 38, and then the syringe is rotated through 900 until the finned portion 45 is introduced into recesses 43. The pressure action exerted by spring 42 ensures perfect clamping of syringe 46 to body 1 and plunger 6' will be correctly aligned with the axis of the syringe.

In order to fill up the syringe with the desired liquid, plunger 6' is moved to the bottom by acting upon knob 5 in the direction of arrow F" (at this step, link element 21 will not prevent rod-iike element 4 from sliding, due to its particular arrangement with respect to the rod-like element) and then the liquid is drawn from a conventional vial (not shown) by causing element 4 to slide in the direction of arrow F" after disconnecting the link element 21 from projections 6. Such a disconnection is effected by sliding button 47 in the direction of arrow F' with resulting engagement of end portion 48' with lug or projecting part 21'.

For repetitive delivery of individual amounts, e.g. 10 ul, the adjustment and clamping members 24 and 29 are positioned as shown, that is with extension 28 in engagement with the uppermost notch 27, the active or operating position of the uppermost step 34 corresponding thereto.

Upon actuation thereof, the stroke or travel of pushbutton 7 (arrow H) is limited by contact of wall 11 against the uppermost step 34, with a resulting movement (in the direction of arrow H') of pawl 12 to such an extent that end 21' of link element 21 engages the next upwards projection 6. In the course of this stage, through the action of spring 14 compressed by the movement of pawl 12, the small block 1 5 causes a braking effect on the rod-like element 4 by pressure of the inner surface of bore 18 against element 4. On releasing the pushbutton 7, the spring 14 will move pawl 12 back to its initial position, with a resulting return of pushbutton 7 to its initial position, and downward movement of link element 21.Because end 21' is now engaged with the next upwards projection 6, the plunger 6' is displaced downwardly by one step (arrow F") and 10 ,ul of liquid will emerge from the end of the syringe. Such a delivery of 10,ul will be repeated on each actuation and release of pushbutton 7.

For delivery of, for example, 20 ul, on each individual actuation and release of pushbutton 7, it is necessary to bring the extension 28 into engagement with the second notch 27, by unscrewing clamping member 29, lifting of adjustment member 24, to displace the second step 34 into the active or operating position, and re-engaging clamping member 29. Then the forward stroke of pushbutton 7 moves pawl 12 sufficiently to bring the end 21' of link element 21 into engagement with the next but one upper projection 6. Upon release of pushbutton 7, the stroke or travel of plunger 6' is now double what it was with a consequent delivery of 20 yl of liquid each time pushbutton 7 is actuated and released.

For a repetitive delivery of 30 ,ul, the same procedure is followed, bringing the extension 28 into engagement with the third notch 27 with resulting displacement of the third step 34 to the active or operating position and displacement of end 21' of the link element 21 by engagement with the next but two upper projection 6.

For repetitive delivery of amounts different from 10 ,ul, or multiples thereof, rod-like element 4 may be replaced with another similar element having a different pitch for the projections 6, or the plunger' can be replaced by another suitable plunger of different cross-sectional area and fitting another syringe clampable on said body 1, if necessary with a suitable adaptor of appropriate shape.

Rod-like element 4 can be readily replaced by unthreading it from the bottom after unscrewing knob 5, or also by unthreading it from the top after releasing link element 21, by actuating button 47 and removing plunger 6'.

Claims (9)

Claims

1. A micropipette for repetitive delivery of constant small amounts of liquid and/or multiples thereof comprising a handle body, a rod-like element provided with equally spaced engageable formations and arranged internally in the body, a syringe which can be clamped on the body, and means actuated by a pushbutton for axially feeding the rod-like element stepwise, wherein the rod-like element passes longitudinally through the body and carries at one end a plunger for coperation with the syringe, and wherein the pushbutton-actuated means comprises a link element for engaging successive formations of the rod-like element, a pawl reciprocable between first and second positions, the pawl carrying the link element and being adapted to be rocked by actuation of the pushbutton between these two positions and adjustment means for adjusting the stroke or travel of the pushbutton to cause the pawl to move the link element over one or more than one of the engageable formations when moving from its first to its second position and to move the rod-like element axially when moving from its second to its first position.

2. A micropipette according to claim 1 and including a block freely slidable within a seat formed in the body and provided with a bore through which the rod-like element passes, the block being resiliently connected to the pawl whereby to act as a brake on axial movement of the rod-like element when the pawl is moved from its first to its second position.

3. A micropipette according to claim 1 or 2, wherein the adjustment means comprise a member having surfaces what can be positioned at different spacings along the path of the pushbutton so as to act as stop elements limiting the stroke or travel of the pushbutton.

4. A micropipette according to any one of claims 1 to 3 wherein the plunger on the end of the rod-like element is interchangeable to enable different sized plungers to be used with differently dimensioned syringes.

5. A micropipette according to any one of claims 1 to 4 wherein the pushbutton is laterally positioned in the body and has an extension, the end of which engages an end of the pawl, and wherein the pawl is pivoted in the body for rotational movement upon actuation of the pushbutton in a plane including the longitudinal axis of the rod-like element.

6. A micropipette according to any one of claims 1 to 5 and including means for disconnecting the link element from the engageable formations comprising a slider operable by means of a button accessible from outside the body and adapted to act upon the link element to move its active or operating portion away from the engageable formations.

7. A micropipette according to any one of claims 1 to 6 wherein the rod-like element may be removed from the body and replaced with another similar rod-like element having engageable formations with a different pitch.

8. A micropipette according to any one of claims 1 to 7 wherein the syringe can be clamped on the body by a bayonet joint, resilient means being provided within the body to clamp the syringe under pressure when positioned.

9. A micropipette substantially as hereinbefore described with reference to the accompanying drawings.