GB2126117A

GB2126117A - A self-priming volumetric diluter

Info

Publication number: GB2126117A
Application number: GB08323032A
Authority: GB
Inventors: Claudio Calzi
Original assignee: Instrumentation Laboratory SpA
Current assignee: Instrumentation Laboratory SpA
Priority date: 1982-09-06
Filing date: 1983-08-26
Publication date: 1984-03-21
Also published as: JPS5960359A; FR2532755A1; FR2532755B1; IT1157318B; DE3332502A1; IT8223125A0; GB2126117B; GB8323032D0; JPH0422224B2

Abstract

The device consists of a preferably transparent vessel (40), incorporating chambers (12, 14) for receiving diluent and sample volumes respectively, two pistons (16, 18) being axially reciprocable therein by means of a driven cam mechanism (42). The diluent chamber (12) has an opening (20) which is connected either with a diluent supply (26) or the sample chamber (14) by a solenoid valve (24). The sample chamber (14) has a diluent inlet (22') and a sample inlet (22) through which the diluted sample is also discharged. The device operates as follows. In a filling phase (Figure 1), solenoid (24) connects chamber (12) with the supply (26), the sample chamber (14) is placed in communication with a sample supply (not shown) and the pistons (16; 18) move downwards to allow filing of the respective chambers (12, 14). Then in a diluter phase (Figure 2) solenoid (24) interconnects the chambers (12, 14) and the pistons move upwards to introduce the diluent into the sample chamber (14) and expel the resultant mixture therefrom. Coordination of the solenoid (24) with the piston movement is achieved by means of an exuder (60, 68) mounted on the cam assembly drive (62, Figure 5).

Description

SPECIFICATION Volumetric diluter especially suitable for use with clinical-chemical analyzer apparatus This invention relates to a volumetric diluter, which can be used with most clinical-chemical analyzers, but more especially with flame photometers.

Automatic apparatus of the above kind are old in the art. Among these are some which already comprise two pistons for the reagent volume and for the sample volume respectively as well as an undefined number of one or more valves using commercial type syringes and specific devices.

The devices with two or more valves are in fact very expensive and liable to numerous failures.

The devices already known in the art with just one valve, like the one in accordance with the present invention, are liable to entrap air, thereby falsifying the dilution ratio; moreover they are affected by the viscosity of the sample.

Hence in these cases, the operator must normally fill the two chambers of the diluter carefully by hand with the air of microsyringes, until the bubbles are completely eliminated, this not being obtainable otherwise. The volumetric diluter in accordance with the present invention is totally unique in its own particular industrial field.

Above all it is novel because it is self-priming and has the advantage of being able automatically to vent any air bubbles entrapped at the outlet.

Secondly, it is novel because for all practical purposes it is unaffected by the viscosity of the fluid being analyzed.

The above has been accomplished as a result of certain design features of the diluter, the most important one of which consists of a transparent acrylic resin vessel and therefore easy to inspect incorporating the chambers for the two pistons serving for the diluent volume and the sample volume respectively, these chambers having dimensions such that the pistons never touch the walls of their respective chambers during their stroke, apart from the seals.

The second feature of the invention is that the gap between the pistons and their respective walls is such as to permit discharge of air bubbles to the top.

The third feature of the invention is that chamber of the piston determining the volume of the sample to be analyzed has a hemispherical dome at the top.

The fourth feature of the invention is that the two reagent liquid inlet and outlet tubes converge at the mid point of the aforesaid dome.

The fifth feature of the invention is that those two tubes have equal sections and the junction of the tubes has a section practically identical to that of each of them.

The sixth feature of the invention is that the seal rings of the two pistons are fitted in the lower section of the two chambers accommodating the pistions.

The seventh feature of the invention is that the two pistons have maximum freedom of movement in an horizontal plane, and practically zero freedom in a vertical plane.

These design features, and others of lesser importance, should become apparent from the following description with reference to the accompanying drawings which illustrate by way of example, and without limitation, a preferred embodiment of the invention. In these drawings: Fig. 1 is a diagrammatic view of the apparatus in the suction phase; Fig. 2 is analogous to the preceding figure, but shows the apparatus in the dilution phase; Fig. 3 is an exploded view of the apparatus, with partially sectional front view and without the sheet metal covering the cam with eccentric.The pistons, relative chambers and seals are shown detached for clearer understanding; Fig. 4 is a front assembly view of the apparatus with the sheet metal cover suitably sectioned and partially omitted; Fig. 5 is a sectional view on line V-V of Fig. 4; Fig. 6 is a sectional view on line VI--VI of Fig.

4; and Fig. 7 is a sectional view on line VIl-VIl of Fig.

5.

As can be seen from the drawing, the volumetric diluter apparatus in accordance with the invention (see Figs. 1 and 2) possesses design features which make it self priming, to enable it automatically to vent any air bubbles entrapped at the outset and to render its operation unaffected for all practical purposes by the viscosity of the fluid sample being analyzed.

The apparatus mainly comprises, as shown in Figs. 3 and 4, an upper transparent section 40 preferably of acrylic resin, which is of fundamental importance from the invention point of view, and a lower base section 44 with provision for covering by a metal sheet 54, which is also necessary for the operation of the apparatus, but is less significant from the inventive point of view.

The two sections 40 and 44 are joined together by bolts 28 and 30 threaded in their lower section and engaging in special suitable recesses.

The lower or base section 44 of the apparatus (Fig. 3) is of C-section and it accommodates a cam assembly 42 which slides up and down two shafts 36 and 38: the lower section has recesses for seating the bases 17, 19 of pistons 16, 18.

The rods 16' and 18' of the pistons slide obviously together with the cam assembly 42 with which they are integral in bushings or sleeves 32 and 34 fitted at their lower end with sealing rings 70' and 66'.

The most significant part from the operational point of view is that the heads of the pistons 16, 18, can also slide upwards into special chambers 12 and 14 designed to accommodate the diluent and sample aspirated therein or expelled from the pistons.

As can be clearly seen in Figs. 3 and 4, the chamber 12 has dimensions such that the head of the piston 1 6 never touches the walls of the chamber during its reciprocating movement, apart from seal 70; the same can also be said of the chamber 14 in regard to the piston 18 in which only touches the seal 66 during its recriprocating stroke movement.

These chambers 12 and 14 adjoin at their bottom to parts of different section 1 3 and 1 5 (Fig. 3) which form seats for the aforementioned bushings 32 and 34.

There is at the top and to one side of the transparent section 40' of the diluter, a recess 11' intended to accommodate a block 11 in which is incorporated the typical upper dome shaped part 14' of the chamber 14 at whose mid point there converge the two reagent inlet and outlet tubes 22, 22' respectively.

The tubes 22 and 22' are of identical crosssection and the same applies to their crosssection at their junction.

When comparison is made between the crosssections of the chamber 12 and of the head of the piston 1 6, and between those of the chamber 14 and the head of the piston 18, it can be clearly seen how the gaps between the respective walls are such as to permit easy discharge of the air bubbles towards the top.

Seals 70 and 66, as stated previously, are located (see Fig. 3) in the middle sections of the chambers 12, 13 and 14, 1 5 which have dimensions practically identical to theirs.

The scheme of operation of the diluter in accordance with the invention is clearly shown in Figs. 1 and 2.

In the first suction phase, the diluent contained in a vessel 26 is drawn into the chamber 12 when the piston 1 6 is lowered, and at the same time the sample to be diluted is aspirated from a suitable containing vessel into the chamber 14 by means of a needle 10 when the piston 18 is lowered.

Materially the diluent touches outlet points 26' from the vessel 26 and the inlet tube 20 into the chamber 12. While the sample to be diluted can flow through the dome shaped top 14' of the chamber 14 through the tube 22. Usually the sample remains in the tube 22.

The downward strokes of the pistons 1 6 and 18, by contrast with their upward strokes which take place in the second or dilution phase, occur simultaneously with the actuation of the solenoid valve 24.

During the above described suction phase the solenoid valve 24, through its terminals, interconnects the points 24' and 24", that is in practice the vessel 26 and the diluent chamber 12.

In the second dilution phase, the pistons 16 and 1 8 are raised again due to the movement of the eccentric 50 in the chambers 12 and 14; at the same time the solenoid valve 24 disconnects the vessel 26 and connects, through its terminals, the points 24" and 24"', thereby interconnecting the chambers 12 and 14; in this way the diluent flows from the chamber 12 into the chamber 14 through the inlet tube 22' where it mixes with the sample contained therein and, subsequently- thanks to the quite different sections of the two rods of the pistons 1 6 and 1 8-the diluted sample is expelled from the chamber 14 through the outlet tube 22 and is introduced through the needle 10 into the special vessel provided therein.

Figures 3 and 4 show a front view of the base 44 of the apparatus with the cam assembly 42, provided at its top with recesses 41 and 43 for the bases 17 and 19 of the pistons 16 and 18. 8.

Moreover in its central part it has another recess having curved shorter sides 46 in which the shaft 48 can rotate.

The shaft pin 48 is fixed (see Fig. 5) through an eccentric 50 with the cam 60 and its shaft 62, 62' to which it is fastened by means of a screw 58.

With the aid of a microcomputer or similar means (not shown) a solenoid valve 24 and optical position encoder 68 can be controlled by a geared motor 64 integral with the cam 60 together with the eccentric 50.

Figure 5 also shows for the sake of completeness mounting screws 52 and 52' for the sheet metal cover 54 of the cam assembly 44.

It should be apparent to those skilled in the art that many variations can be made upon the preferred embodiment which has been described within the ambit of the appended claims.

Claims

1. A volumetric diluter, comprising a solenoid valve and optical encoder controllable by means of a microcomputer or similar means, a geared motor integral with a cam and provided with an eccentric to determine the movement of two pistons in respective chambers; said solenoid valve being adapted to connect automatically, during lowering of the pistons in a suction phase, a chamber accommodating the diluent volume with a vessel containing said substance, by disconnecting said chamber from a chamber accommodating the sample to be analyzed which can be aspirated simultaneously from the latter f said chamber, during lowering of a respective piston by means of a needle from another special vessel, said solenoid valve being also capable of automatically disconnecting instead when said pistons are raised, in the dilution phase, the chamber accommodating the volume of diluent from the vessel containing said substance by connecting said diluent volume chamber instead with the sample chamber which can hence be perfectly mixed with said diluent and which can be expelled with said diluent by means of a needle into another suitable container; the whole system being self priming.

2. A volumetric diluter, as claimed in claim 1, and further comprising a transparent vessel in which are incorporated the said chambers for the said two pistons respectively for the diluent volume and for the sample volume to be analyzed which is joined to and supported at the bottom by a C-section base which serves as a support for suitable driving means for said pistons, the transparency of the upper vessel permitting constant inspection of said vessel and enabling the presence or absence of the reagent in the apparatus to be continuously checked.

3. A volumetric diluter as claimed in claims 1 and 2, characterized in that chambers for the diluent volume and for the sample volume to be diluted respectively, have dimensions appreciably greater than those of the rods of pistons moving up and down inside said chambers, whereby the walls of said pistons can never touch the walls of said chambers except for lower sealing means therein.

4. A volumetric diluter as claimed in claim 3, characterized in that the gaps between the walls of the chambers serving for the diluent volume and the sample volume respectively and the walls of the pistons moving in said chambers are such as to permit automatic expulsion of any air bubbles or other gaseous medium if formed inside said chambers.

5. A volumetric diluter as claimed in any of claims 1 to 4, characterized in that the chamber accommodating the piston of the sample to be analyzed has a dome shaped top section and that at the mid point thereof where two tubes converge the cross-section thereof is substantially identical to that of each one of said tubes, so as to favour the discharge of any air bubbles.

6. A volumetric diluter as claimed in any of the preceding claims characterized in that by varying the position of a cam driven by a geared motor with respect to an optical position codifier-with which the cam itself forms an assembly supported by a base section of the apparatus-the position of the solenoid valve is varied and at the same time an eccentric integral with said cam also varies the position of pistons with which said assembly is integral, the latter sliding in both directions along two shafts which together join an upper transparent section and a lower metallic section.

7. A volumetric diluter as claimed in claim 5, characterized in that the pistons are integral with the cam assembly which has upper recesses in which enlarged base sections of said pistons are engageable and because their movement in the two directions is determined by rotation of a shaft in a recess in the middle of the cam assembly, said shaft being fixed through an eccentric with the actual cam.

8. A volumetric diluter as claimed in any of the preceding claims, characterized in that it permits use of sample and reagent in a ratio of 1 to 100, that is to say 20,ul of sample per 2 ml of reagent.

9. A volumetric diluter as claimed in any of claims 1 to 8, characterized in that seal rings of the two pistons are fitted in a lower part of the two chambers accommodating the pistons whose cross-section is substantially identical to that of said seal rings.

10. A volumetric diluter as claimed in any of the preceding claims characterized in that the rods of the two pistons have maximum ease of movement, in an horizontal plane, but almost zero ease of movement in a vertical plane.

11. A volumetric diluter substantially as hereinbefore described with reference to and as illustrated in, the accompanying drawings.