IE45502B1 - Diluting and pipetting apparatus - Google Patents

Description

The invention relates to a diluting and pipetting apparatus for the additive mixing of a preselectable volume of a sample with a preselectable volume of a reagent, particularly for analyses, with a reagent pipetting device including a cylinder in which a piston is slidable with an adjustable stroke for drawing-in a predetermined volume of fluid, and with an inlet valve and an outlet valve, a sample pipetting device being connected to the outlet valve of the reagent pipetting device.

For the removal of predetermined amounts of a liquid, for example a reagent, from a bottle, dispensing apparatuses are known, so-called bottle dispensers, in which the predetermined amount of liquid is drawn in with the aid of a suction piston against the action of an inlet valve, and then discharged again through an outlet opening against the action of an outlet valve.

In a known bottle dispenser a glass cylinder is mounted on a valve head which can be screwed on a bottle, a cylindrical jacket fits displaceably and rotatably over the glass cylinder, ancL-is connected-with a piston sliding in the glass cylinder; in addition, means are provided for adjusting the piston stroke and for indicating the suction volume. 55 02.

By using such bottle dispensers, as mentioned hereinabove, it is possible to draw in or dispense in a precisely reproducible manner very exactly adjustable volumes of a liquid.

In addition, pipetting devices are known which operate in a 5 similar fashion, whereby a piston, adjustable relative to a cylinder serves to draw in an adjustable volume of liquid. The liquid volume is retained in the cylinder as long as the piston remains raised. When tne piston is lowered, the volume of liquid is discharged once more through the intake channel or the intake tube.

In laboratories or, for example, clinics or the like, it is often necessary to dilute or mix a predetermined volume of a liquid with another predetermined volume. This can be accomplished by using the oipetting apparatus described hereinabove in sequential steps. However, devices are already known wherein the two pipetting devices are structurally combined. Thus, a glass device is known with a piston displaceable in a cylinder, the stroke of the piston being limitable in order to set a predetermined liquid volume, whereby the outlet valve of this pipetting device is connected directly to a pipetting device tar withdrawing the second adjustable volume of liquid from another container. The stroke of the second pipetting device is also adjustable, so that, to a certain extent, any mixing ratio can be produced.

However, in operating this apparatus, the two pipetting devices must be operated individually and in sequence, entailing considerable difficulty.

It is also disadvantageous that this known apparatus is made almost entirely in one piece from glass, so that its manufacture involves considerable expense.

In another known apparatus, a piston can be raised and lowered in a 39 sample collector, the piston being raised and lowered by means of a rotatable threaded spindle. Here again it is necessary to operate the two dispensing devices separately, in addition, the sample volume is not variable in this apparatus. in still another known apparatus, the piston of the reagent pipetting device drives the piston of the sample pipetting device through a connection. This allows limited one-hand operation. However, the stroke-length of the reagent piston must always be greater than or equal to the stroke length of the sample piston.

The present invention seeks to provide a diluting and pipetting apparatus by which faultless one-hand operation is possible and any volume can be preset independently for the re-agent and for the sample, the apparatus being structurally simple and preventing any possible operating error. , According to the invention there is provided a diluting and pipetting apparatus for additive mixing of preselected volume of a sample with a preselected volume of a reagent, comprising a reagent pipetting device including a cylinder in which a piston is slidable with an adjustable stroke for drawing-in a predetermined volume of liquid, and inlet and outlet valves, and a sample pipetting device connected to the outlet valve of the reagent pipetting device, wherein a driving element is provided vzhich co-operates with each of the two pipetting devices independently of one another in order to draw in the respectively .,. predetermined volumes of reagent and sample in each particular case and to lb expel the volumes drawn in.

The reagent pipetting device and the sample pipetting device are preferably of similar design and are each provided with a glass cylinder while a cylindrical jacket is displaceably fitted around the glass cylinder and connected to a piston sliding with the glass cylinder, and means are provided for'·adjusting the piston stroke and for indicating the suction volume.

The means for adjusting the piston stroke advantageously consists of a set screw, and the driving element is provided with recesses to engage the set screw bolts of the set screws.

In an especially advantageous manner, the driving element is mounted displaceably parallel to the lengthwise axes of the cylindrical jackets on a guide.

The driving element is advantageously guided on at least one rod, the rod serving simultaneously to guide reset arms connnected to the cylinder jackets.

In a preferred ambodiment of the invention, two parallel round rods are provided as a guide.

However, it is also possible to provide a triangular, rectangular, or polygonal guide rod for the driving element.

To facilitate assembly and/or disassembly of the device, the reset 45802 arms are advantageously made fork-shaped and fit around the guide rod(s). The cylinder axes and the guide axis can be located generally in the same plane; however, they can also be disposed triangularly.

The driving element is expediently provided with a holding part.

The latter can consist eitherof grooves for the fingers or of special handles or holders. It is particularly advantageous if the holding part projects through a slot in a jacket which surrounds the reagent pipetting device. in a modified anbodimsnt, a handle is provided in the form of an iO extension of the axis cf the guide, in the form of a handle mounted on the rod connected with the driving element.

In yet another embodiment of the invention, a mechanically driven displacement device for the driving element is provided. A servo motor acting on a threaded spindle is expediently used as the drive for the driving element.

Instead of the mechanical drive, according to a modification of the invention, an electromagnetic lifting device can be used for the driving element. Instead of the mechanical or electromagnetic drive, a hydraulic (pneumatic) cylinder-piston drive can be provided in an equally advantageous manner for displacing the driving element.

According to a modified embodiment, the scales for the reagent pipetting device and the sample pipetting device are provided on a jacket. The stop means for limiting the piston stroke of the reagent pipetting device and the sample pipetting device are then provided in slots in the jacket.

According to yet another embodiment, the driving element is advantageously made in the form of a jacket part which fits around the reagent pipetting device and sample pipetting device and serves as a handle.

It is particularly advantageous if, according to another feature of this preferred embodiment of the invention, adjustable and lockable set SLew5 in slots ir, ths jacket are provided for independent driving of the pistons and adjustment of the piston stroke.

According to another embodiment, the jacket part is at least Dartially •35 closet! at the upper end and the closing part serves as a reset device for the pistons. 4SS°a According to yet another embodiment, the jacket part is provided at its lower end with guide sleeves fitting around the associated cylinders of the reagent pipetting device and the sample pipetting device.

According, to a preferred embodiment of the invention, the jacket 5 hart is provided with parallel cylindrical chambers, whose walls serve to guide an end piece or stop ring connected with each of the pistons.

Advantageously, the cylindrical chambers of the jacket parts are covered by sealing caps.

Embodiments of the invention will now be described in greater detail 13 by way of example and'with reference to the drawings, which show preferred embodiments in schematic form, and in which:Figure 1 is a device according to the invention partly in section; Figure 2 is a modified embodiment.

Figure 3 is still another embodiment.

IS Figure 4 is an end view of another embodiment of a device according to the invention with the jacket part partially broken away; and Figure 5 is a side view partly in section of the device according to Figure 4.

A diluting and pipetting apparatus according to the invention as shown 20 in Figure 1, consists essentially of a reagent pipetting device 1 and of a sample pipetting device 2, which can be operated with one hand by a driving element 3, while the individual volumes can be adjusted independently of one another as desired. Reagent pipetting device 1 is provided with a valve head 16, to whose upper end a tubular glass cylinder -is attached in a press fit, with the aid of adhesives or the like as desired. Glass cyTindep 15 is surrounded by a cylindrical jacket 14 which is slidable lengthwise along glass.cylinder 15.-A piston 12 is disposed coaxially in cylindrical jacket 14 and held in place by a piston bearing 11 For this purpose, the piston has one end (at the top in the drawing) pressed into and held firmly in a corresponding recess in the cover-shaped piston bearing 11, likewise with the aid of adhesives if desired. Piston bearing 11, thus attached to piston 12, is then attached to the upper end of cylindrical jacket 14, for example by a screw connection.

•Piston 12 is provided with a plastic coating, preferably made of 33 Teflon (Registered Trade Mark). This coating can be applied as a coat, as a shrink film, or in another fashion to piston 12. Finally, it is also possible to manufacture piston 12 directly out of an appropriate plastic. 5 0 2 A stop ring 13, made for example of plastic pressed on when warm, is provided at the upper end of glass cylinder 15. Stop ring 13 has an outside diameter slightly less than the inside diameter of cylindrical jacket 14, so that its lengthwise displacement is not impeded.

Cylindrical jacket 14 is provided with a lengthwise slot 24, in which an adjustable stop is mounted. This step consists of a stop segment 21 which grips laterally next to lengthwise slot 24, behind the wall of cylindrical jacket 14, and consists of backing element 22 whicn rests laterally outside next to lengthwise slot 24 against the outside wail θ of cylindrical jacket 14 and of a set screw 23, by means of which stop element 21 and backing element 22 can be screwed together, so that the device can be locked at any desired level within lengthwise slot 24. Advantageously, backing element 22 is made in the form of a pointer.

Cylindrical jacket 14 can be pulled upward together with piston 12 15 in glass cylinder 15 only until stop segment 21 strikes stop ring 13 from below. In this manner, the fluio volume which can be drawn into glass cylinder 15 can be set.

Cylindrical jacket U is provided with a scale 27, preferably on one or both sides of slot 24. To indicate the volume determined by stop 21, and 23, a pointer 22 is provided, mounted on the backing element or made integral with the latter. This pointer 22 can be made for example in the form of an annular band or the like which fits around the outside of cylindrical jacket 14.

An intake valve 17', 18', 19' and an outlet valve 17, 18, and 19 are located in valve head 16.

The intake valve connects the interior of a bottle 49 or a glass container to which reagent pipetting device 1 is screwed, with glass cylinder 15.

During intake, i.e. when piston 12 is raised, a valve ball 17' lifts off a valve seat bushing 18' with a conical seat for valve ball 17' and allows liquid to flow through a tube or pipe 26, a sealing cap 19', and valve seat bushing 18' into the interior of glass cylinder 15. A sealing cap 19', which holds valve seat bushing 18' which is made of a hard material, is held in place in a matching recess in valve head 16 by an appropriate press fit.

As soon as tne intake stroke is ended, ball 17' falls under the 35 influence of its own weight on to the conical valve seat of valve seat bushing 18’» whereby the return flow of the liquid drawn into glass cylinder 15 is immediately ended. 4SS02 The outlet valve is disposed approximately horizontally relative to valve head 16, in a connecting element 10 which is provided with a connection channel 40.‘ The outlet valve likewise consists of a valve seat bushing 18, with a conical seat for valve ball 17 and a sealing cap 19. The valve seat bushing 18'·' is located in the corresponding recess in valve head 16, and is prevented from falling out by a sealing cap 19 which is secured from outside ahead of it in valve head 16. In addition, a valve compression spring is provided, which rests on one side against sealing cap 19 and on the other side against valve ball 17, so that in the unstressed state valve ball 17 is constantly pressed against the conical valve seat of valve seat bushing 18. When piston 12 is depressed, the pressure of the fluid causes valve ball 17 to rise off the valve seat in valve seat bushing 18 against the action of spring 20, thus allowing the liquid to flow to connecting channel 40. At the moment that the depression of piston 2 is complete, valve ball 17 is pressed against the valve seat again by spring 20, so. that even when another suction stroke follows immediately, the liquid cannot drip through valve 17, 18 and 19.

Reagent pipetting device 1 described above serves to draw in an adjustable volume of a reagent from a reagent bottle 49. An essentially similarly constructed sample pipetting device 2 is provided on connecting element 10, but no inlet or outlet valves are provided therein. Instead, sample pipetting device 2 co-operates through a connecting head 36, to which an intake or outlet tube 46 is attached for example,'with a corresponding sample· .centainer. The suction devices consist essentially of a piston 32 which can be raised and lowered and is guided in a piston bearing 31 and can be moved up and down in a cylinder 35 in a cylindrical jacket 34. A stop ring 33 co-operates, with a set screw 43 provided with a pointer 42, the screw being displaceable in a slot 44 in cylindrical jacket 34. By an appropriate adjustment of set screw 43, any desired volume can be selected and set permanently. Set screw 43 and/or a corresponding set screw bolt 45 are provided with a pointer 42, which shows readings on a scale 47 to indicate the set volume.

Reagent pipetting device 1 and sample pipetting device 2 are advantageously mounted on a supporting plate 5, connected with valve head 16 or connecting element 10. Nuts 6 and 7 are used for attachment. A guide S 5 Ο 2 4, for example in the form of two parallel guide rods, 37',37 for a driving element 3 is provided in the centre between ids two pipetting devices 1 and 2. The two guide rods 37' and 37 can be kept at a set distance at the upper end by a connecting element 38, while connecting 5 element 38 can simultaneously serve as a supporting element for the entire device. Driving element 3 is slidably mounted on guide rod or rods 37. Tnis driving element 3 is provided with slots 28 and 29 open at the top, each of which co-operates with a set device for reagent pipetting device i, namely a set screw bolt 25 for set screw 23 and set screw :0 bolt 45 for set screw 43 of sample pipetting device 2.

The guide rod of guide 4, as shown in Fig. 1, can be screwed for example into supporting plate 5 by means of a fastening screw 39.

In operation, the volume of reagent to be drawn in is set with the aid of set device 23, 24 with the aid of pointer 22 and scale 27. Similarly, the volume cf the sample is preselected with the aid of set device 43, 45, pointer 4?, and scale 47.

To operate the device, it is merely necessary to move driving element 3 upward along guide 4, Depending upon the position of the set devices of reagent pipetting device 1 and sample pipetting device 2, depending on the set volumes of each, the set device of the reagent pipetting device 1, i.e., set screw bolt 25, will engage slot 28 and then set screw bolt 45 of the sample pipetting device 2 will engage slot 29. With corresponding different volumes, the sequence of the operation can be reversed. As driving element 3 continues moving upward, corresponding pistons 12 and 32 are raised until set devices 25 and 45 strike stop rings 13 and 33 by their corresponding stop segments. This assumes that the zero position of both pipetting devices is set at the same level. This means that the stroke of driving element 3 is limited by the height of stop rings 13 and 33.

The upward movement of piston 12 draws the set volume of reagent out of bottle 49. Valve 17' and 18' prevents the reagent from running out.

At the same time, or shortly before or afterwards, a· set volume of sample is drawn out of a sample bottle (not shown) through tube 46 by raising piston 32. 3s If the operator then releases handle 3 or moves it downward, pistons and 32 can slide downward under their own weight. This allows the sample volume to flow out through tube 46. At the same time or later, depending on the ratio between the volumes selected, the reagent volume 45302 will likewise be expelled through outlet valve 17, 18 and connecting channel 40.

In order to return the pistons safely, reset arms 8 and 9 are connected with cylindrical'jackets 14 and 34 respectively, the arms extending into the path of movement of driving element 3. As driving-element 3 moves downward, the reset arms are driven sequentially or simultaneously until they reach their resting position above nuts 6 and 7. In this resting position the two volumes are completely expelled from reagent pipetting device 1 and the sample'pipetting device 2, while the desired dilution of mixing ratio is achieved.

It is immediately clear from the above description that the two voliimes can be set independently of one another, since only the chronological sequence of the engagment of the set devices or set screw bolts in the correspondingly formed bearings or slots in driving element 3 aee changed.

A further advantage of the device according to the invention consists in the fact that reagent pipetting device 1 and the similarly designed sample pipetting device 2 can be made of largely identical parts, aside from their volume independence. The individual pipetting devices can also be removed independently from the common device, so that any defects or malfunctions can be corrected by exchanging only the individual part affected, without having to destroy or take apart the apparatus completely.

Guide rod 37 for guide 4 is preferably made circular, in which case two parallel guide rods 37' and 37 are advantageously provided to prevent driving element 3 from tipping.

Rotation or tipping can also be prevented by using a guide rod·’ with a triangular, rectangular, or polygonal cross section.

In the embodiment shown, the three axes, namely those of the reagent pipetting device 1, sample pipetting device 2, and guide 4, are in a single plane. However, it is also possible for example to raise guide 4 out of the plane (of the drawing), resulting in a triangular arrangement of the three axes. In this case, set screw bolts 25 or 45 form an angle with one another, while slots 28 and 29 in driving element 3 are at the same angle.

An additionally modified embodiment is shown in Fig. 2. In this drawing, a jacket 30 is provided, surrounding reagent pipetting device 1 and sample pipetting device 2, the jacket being provided with a slot 41, in which a handle 43 for driving element 3 is displaceable. Jacket 30, which preferably rests on only one corresponding edge part, is very 5 0 2 easily removable, so that volume adjustment is made possible in the same simple fashion as in the embodiment according to Fig. 1. In order to prevent an undesired or deliberate change in the volumes, jacket 30 is applied, while the material constituting jacket 30 can be transparent or transclucent.

Reset arms 8 and 9 are expediently made fork-shaped, and at least partially surround the guide rods, while a left-right displacement relative to the line connecting the axes of cylinders 15 and 35 is expediently provided, so that one of reset arms 8 or 9 fits around a guide rod 37' or 37“ respectively.

In the modified embodiment shown in Fig. 3, driving element 3 is completely enclosed in a jacket 50 and is actuated with the aid of a rod 56 and a handle 55.

The volumes are adjusted with the aid of set devices displaceable in 15 slots 51 and 52 of a jacket 50. Pointers 22 and 42 are also provided, co-operating with a jacket scale 53 and a jacket scale 54 respectively.

The mutual driving of the pistons of the reagent pipetting device 1 and sample pipetting device 2 is again accomplished with the aid of a driving element 3, which as described can be raised and lowered via rod 56 by means of handle 55.

A device according to the embodiment in Fig. 4 and 5, like the devices in Fig. 1 to 3, essentially consists of a reagent pipetting device 61 and a sample pipetting device 62, which can be operated with one hand by means of a driving element 63 made in the form of a jacket part, while the corresponding volumes can be adjusted independently of one another as desired.

Reagent pipetting device 61 is provided with a valve head 76, to whose upper side a tubular glass cylinder 75 is fastened by a press fit or in another expedient manner. This glass cylinder 75 accepts a coaxial lengthwise-displaceable piston 72, provided with a stop ring 73. Piston 72 is provided with a plastic coating, preferably of Teflon (Registered Trade Mark). This coating car, be applied as a coating, as a shrink film, or in another fashion to piston 72.

Tne device is provided with a valve head 76, with an internal thread with which it can be screwed on to the external thread of a bottle 109.

An intake valve is provided inside valve head 76, the valve corresponding to the intake valve in Fig. ]. A connecting head 96 is connected to valve head 76 by connecting channel 100, with an intake-exhaust tube 106 being fastened to the valve head, and with the valve head being provided with an outlet valve.

The intake valve connects the interior of bottle 109 on which reagent pipetting device 61 is screwed with glass cylinder 75.

A cylinder 95 is located in connecting head 96, the cylinder containing a piston 92 slidable therein, the piston being connected at its upper end with a stop ring 93, Jacket part 63 of the device is provided v/ith slots 84 and 101. Set screws 83 and 103 with corresponding pointers 82 and 102 and set screw bolts 85 and 105 are disposed displaceably and lockably in these slots. Unilateral or bilateral scales 87 and 107 are provided on the edges of slots 84 and 101, respectively, from which scales the adjustable stroke and the volume of liquid which can be drawn in can be read in scale divisions.

The driving element of jacket part 53 is closed at its upper end at least partially by a cover part 68 and is provided at its lower end with respective, guide sleeves 55 or 67, by which jacket part 53 is fitted to cylinders 75 and 95 respectively.

In the preferred embodiment, driving element 63 is made with a relatively massive structure and is provided with two parallel cylindrical chambers 74 and 94, wherein cylinders 75 and 95 respectively and stop rings 73 and 93 of pistons 72 and 92 are slidably mounted.

In the embodiment shown, cylinder chambers 74 and 94 are open at the top, thereby considerably facilitating assembly and especially insertion of pistons 72 and 92. Following assembly, the upper openings of cylinder chambers 74 and 94 are sealed with sealing caps 69 and 70.

To carry out a mixing procedure, a certain volume is set for the reagent with the aid of set screw 83, displaceable in slot 84. Then set screw 83 is tightened onto set screw bolt 85.

The volume of the amount of sample to be drawn up is set similarly with the aid of set screw 103 and set screw bolt 105 in slot 101 using scale 107. To carry out the mixing procedure, jacket part 63 is slid upward. Thus, set screw bolts 85 and 105 co-operate successively and independently of one another with stop ring 73 and stop ring 93. The stop rings and thus simultaneously the corresponding pistons are carried upward by the set screws 83, 103 and set screw bolts 85, 105 until the bottom part of jacket part 63 strikes the stop rings 80 and 90 of cylinders 75 and 85 respectively.

The downward movement of jacket part 63 carries the two pistons downward away from cover part 68s whereby the reagent volume previously drawn up from the reagent bottle and a sample volume drawn from a sample container/through cannula 106 are expelled conjointly in mixed form through outlet cannula 106. The reagent is forced through the outlet valve because the intake valve has been automatically closed by a heavier intake valve ball.

It is clear from th-. above description that the reagent volume and sample volume can be set independently of one another, since only the chronological sequence of the engagement of the set devices or set screw bolts with the corresponding structured stop rings of the pistons are changed.

A spring-loaded valve is provided in connecting channel 100.

Jacket part 63 is preferably made in one piece from plastic. A onepiece cover can also be provided over sealing caps 69 and 70 or instead of them.

The upward and downward movement of the driving element can also be effected by a mechanical dri^e, for example with the aid of a threaded spindle or a servo motor, or with the aid of a selectively energizable lifting magnet or of a hydraulic or pneumatic cylinder and piston drive.

Claims (5)

1. A diluting and pipetting apparatus for additive mixing of a preselected volume of a sample with a pre-selected volume of a reagent, comprising a reagent pipetting device including a cylinder in which a piston is slidable with an adjustable stroke for drawing-in a predetermined volume of liquid and inlet and outlet valves, and a sample pipetting device connected to the outlet valve of the reagent pipetting device, wherein a driving element is provided which co-operates with each of the two pipetting devices independently of one another in order to draw in the respectively predetermined volumes of. reagent and sample in e ach particular case and to expel the volumes drawn in.

2. An apparatus according to Claim 1, wherein the reagent pipetting device and sample pipetting device each comprise a glass cylinder, a cylindrical jacket fitting displaceably and rotatably over the associated glass cylinder and being connected to a respective piston sliding in the respective glass cylinder, and means are provided for adjusting the stroke of each piston and for indicating the volume drawn in.

3. An apparatus according to Claim 1 or Claim 2, wherein the means for adjusting the piston stroke are formed by a set screw and the driving element is provided with recesses for engaging set screw bolts of the set screws. 4. 5 5 0 2 10. An apparatus according to any one of Claims 1 to 9, wherein the driving element has a handle part. 11. An apparatus according to Claim 10, wherein the handle part projects through a slot in a jacket fitting around the reagent pipetting 5 device and in the sample pipetting device. 12. An apparatus according to Claim 10, wherein a handle part is formed as a handle disposed in the extension of the axis of the guide on a rod connection to the driving element. 13. An apparatus according to any one of the preceding Claims, and *' J including a mechanically driven displacing device for the driving element. 14. An apparatus according to Claim 13, wherein the displacing device comprises a servo motor acting on a screw spindle to drive the driving element. 15. An apparatus according to any one of Claims 1 to 12, wherein an 15 electromagnetic lifting device is provided for tne driving element. 16. An apparatus according to any one of Claims 1 to 12, wherein a hydraulic or pneumatic cylinder-piston drive is provided for the displacement of the driving element. 17. An apparatus according to any one of Claims 12 to 16, wherein 20 scales for the reagent pipetting device and the sample pipetting device are provided on a jacket. 18. An apparatus according to any one of Claims 12 to 17, wherein the set means for limiting the piston stroke of the reagent pipetting device and of the sample pipetting device are disposed in slots in the jacket. 19. An apparatus according to Claim 1, wherein the driving element is in the form of a displaceable jacket part serving as a handle part and fitting around the reagent pipetting device and the sample pipetting device. 20. An apparatus according to Claim 19, wherein the set screws 30 disposed adjustably and lockably in slots in the jacket part are provided for the independent driving of the pistons and for adjusting the piston stroke. 21. An apparatus according to Claim 19 or Claim 20, wherein the jacket part is at least partly closed at the top end and that the closing part serves as resetting means for the pistons. 22. An apparatus according to any one of Claims 19 to 21, wherein the jacket part is provided at one end with respective guide sleeves fitting around the appertaining cylinders of the reagent pipetting device and of the sample pipetting device. 23. An apparatus according to any one of Claims 19 to 22, wherein the jacket part has parallel cylindrical chambers whose walls serve both to guide an end piece connected to the respective cylinder and to guide a stop ring connected to the respective piston. 24. An apparatus according to Claim 23, wherein the cylindrical chambers of the jacket part are covered by closure caps. 25. An apparatus according to Claim 23, and comprising a one-piece cover covering the jacket part. 26. A diluting and pipetting apparatus substantially as hereinbefore described with reference to Figure 1 or Figure 1 modified as shown in Figure 2, Figure 3 or Figures 4 and 5 of the accompanying drawings. Dated this 3rd day of June 1977 (signed)

4. An apparatus according to Claim 2 or Claim 3, wherein the driving element is mounted on a guide for displacement parallel to the longitudinal axes of the cylindrical jackets, 5. An apparatus according to Claim 4, wherein the driving element is guided on at least one rod which at the same time serves to guide reset arms connected to the cylinder jackets. 5. An apparatus according to Claim 5, wherein two parallel guide rods are provided. 7. An apparatus according to any one of Claims 4 to 6, wherein the or each guide for the driving element comprises a triangular, quadrangular, or polygonal guide rod. 8. An apparatus according to any one of Claims 5 to 7, wherein the reset arms are fork-shaped and fit round the or each guide rod. 9. Ah apparatus according to any one of Claims 4 to 8, wherein the cylinder axes and the axis of the guide lie substantially in one plane.

5. , Dartmouth Road, DUBLIN, 6 RUDOLF BRAND.