Many different apparatuses are known for measuring the rate of erythrosedimentation of blood (Katz factor).

One known method in the determination of the rate of erythrosedimentation (E.S.R.) is the Westerg- ren method.

The blood obtained from venopuncture is immediately mixed in the proportion of 4 volumes of blood to 1 of Sodium Citrate. The blood is introduced in a calibrated tube which is placed in a vertical position in a suitable support. After the first and the second hour, the height of the formed plasmatic column is read.

In Italian Patent Nr. 721.410, compare parent USA Patent Nr. 3.373.601 and G.B. Patent Nr. 2.048.836, the oral aspiration of the blood is obviated by manufacturing the test tube with an internal sealing rim which cooperates in the manner of a piston gasket with the blood of the graduated tube. The graduated tube receives blood from the test tube leaving an air space in such a way that, by adjusting the volume of the air space, it is possible to bring the blood level to zero (0), (having made the tube touch the bottom of the test tube).

The known apparatus comprises accordingly

• - a test tube with a cylindrical portion (PC¹) closed at its bottom and to be filled with a blood sample,
• - and a calibrated pipette to be introduced into the test tube to displace the blood inside said test tube and to cause the blood to rise inside of the hole of the pipette until the top of the blood column at least will reach a reference mark or zero level (0),

It will be understood that such a method has different inconveniences both in the moulding and in function, for the stated reason that adjusting operations are necessary in order for the level of the blood to reach, with its meniscus, the zero (0) reference graduation.

The object of the invention is to reduce or obviate in a practical way the above mentioned inconveniences by proposing an apparatus for measuring the rate of erythrosedimentation (E.S.R) of the blood.

This object is achieved by an apparatus of the kind mentioned which is characterised in that said pipette, is dimensioned to have a sliding and sealing fit into the cylindrical portion, and that the upper end of said pipette is provided with an overflow sleeve, for receiving excess blood from the inside of the pipette through an overflow canal, of the entrance cone which at one lower end presents an entrance) for receiving blood from the pipette, but prevents reflux into the pipette,

• and which on the other end projects into an excess blood reception tank
• said overflow sleeve, ensuring an automatic filling and zero levelling of the pipette at the one lower end of the canal, when the pipette is arrested at the bottom of the test tube.

An embodiment of apparatus according to the invention will now be described by way of example with reference to the accompanying drawings, in which:

• Figure 1 represents in a detailed longitudinal section the various elements of the apparatus according to the invention;
• Figure 2 represents the part A of Figure 1;
• Figure 3 represents an enlarged, sectional view of the sleeve of Figure 1;
• Figure 4 represents a variation of the overflow sleeve embodying the cap;
• Figure 5 represents in section the stopper of the test tube;
• Figures 6 and 7 represent in longitudinal and transverse section (VII-VII of Figure 6) a base for the support of the measuring apparatus.

With reference to the drawings, PR indicates a test tube of transparent plastic material having a per- fectlycylindrical portion PC¹ which prolongs itselfwith another cylindrical part PC² of greater diameter. The two portions adjoin in correspondence of a conical trunk part TK with a knurled border ZR which in one way acts as a reference line Aand in another way permits to obviate the blood surface tension so as to facilitate the mixing of blood/anticoagulant.

TC indicates a graduated and calibrated tube hereinafter mentioned as "pipette" also made of transparent plastic material, the external diameter of which is such that it will slide and seal along the cylindrical portion PC¹.

The pipette is, preferably, perfectly, transparent, without visible defects or internal striations.

The graduated scale in mm extends for 150±0.35 mm from one extremity to the other of the vertical axis.

Generally, the test tube PR is filled in advance with an anticoagulant AC and closed with a stopper TP of flexible material in such a way to permit a hermetic sealing of the test tube.

According to a very important characteristic of the invention, a sleeve BS is provided which is mounted and sealed in correspondance of the top end ES of the pipette and presents a small canal CN which projects out in respect to a diaphragm DF in such a way that it extends on one side in the hole KA of the pipette and on the other in a chamber CMforming an excess overflow tank.

The apparatus functions as follows:

First of all the stopper TP is removed (or pierced) and then the test tube PR is filled with blood up to the knurled zone ZR; the filling is executed with some approximation in excess for reasons which will emerge further on. The calibrated tube (pipette) TC is then introduced in the portion PC¹ and consequently the blood will rise up inside said pipette.

Supposing, as is verified in the majority of the cases, that the volume of the blood is greater than the internal volume of the pipette, the excess blood will flow through the canal CN and it will be deposited in the chamber CM assuring, for this reason, a constant level of blood independently of the care taken in filling with the blood the test tube PR. In fact, after the simple operation of introducing the pipette TC all the way down until it is arrested by the bottom FO of the test tube, an operator does not have to execute any other operation or adjustment and this is positively reflected not only in the exactness of the measurement of the rate of erythrosedimentation, but also in the rapidity of the measure itself.

It is observed that the test tube does not have any sealing rim. Therefore, the manufacturing or moulding requirements are remarkably simplified and every moulding tolerance (pipette calibration) is practically compensated by the excess overflow sleeve BS.

It is also observed that the filling of the test tube with blood is not critical.

In the case of a great excess of blood, the bell mouthed part PC² of the test tube serves as an excess blood tank without affecting the accuracy of the measurement in as much that the blood which flows into the calibrated tuba (pipette) is always the same volume es the internal portion PC¹ thanks to the continuous seal of the pipette along the portion PC¹.

The overflow sleeve will be manufactured in a plastic material so as to be mounted on the calibrated tuba (pipette) and will be constituted of materials not necessarily transparent.

In order to prevent excess blood from being sprayed externally with the risk of contaminating the room, the overflow sleeve can be provided with a cap TA which has a hole FR so as to prevent the "cap" function from negatively affecting the value of the measure.

The cap TA can be connected to the overflow sleeve by means of an isthmus so as to form a single unit.

According to an important characteristic, the diameter of the entrance cone CE of the sleeve is proportioned in such a way that it may intercept the flow of the erythrocytes and function as a barrier for the same, that cannot longer influence the value of the measure.

As seen from Figure 6, a stand ST in a transparent plastic material is provided in which the test tubes PR are received and kept in a vertical position, and touching the work bench top when inserted in the stand.

The concept of the invention can also be expressed according to the variation of Figure 4. In this realization the overflow sleeve aS¹ presents an obturator OTwhich cooperates with the hole KA of the pipette, said obturator being completed with a milling CN¹ equivalent to the canal CN and proportioned in such a way as to prevent the reflux of the blood. The sleeve presents a vent hole FR¹ and its bottom TA¹ functions as a cap (anti-spray). The sleeve presents some arrest counter shoulders SP in a rib formation.

The test tube may be filled with blood without removing the cap TP: in effect as provided in Italian Patent Application Nr. 30952 A/76, the bottom BT of the cap TP may be of perforable kind and the end of the calibrated tube opposite to the "zero" location may be tapered TT in order to secure a prompt perforation. The bottom portion FO of the test tube may be provided with a internal conical projection CP in order to secure a tight obturation of the end of the calibrated tube with the cylindrical portion PC¹ of the test tube, thus obviating possible moulding deficiencies.