HK1021839B - Device for sampling and/or injecting inside a plugged sample tube - Google Patents

Description

The present invention relates to a device for sampling and/or injection into closed containers, such as sample tubes closed with plastic caps.

It is generally known that, for reasons of safety and precision, in many analysis processes, especially biological analyses, sample tubes are used which are covered with rubber or, more generally, elastomer caps, so that all the manipulations involved in these processes can be carried out without having to remove the cap and thus without direct access to the sample.

The sampling and/or injection operations in these tubes then involve the use of devices each comprising a hollow needle connected to an aspiration and/or repulsion line and specially designed to pierce the plugs in order to penetrate the inside of the tube. If it is equipped with an automatic analysis device, the sampling device is carried by a pipette head equipped with means to ensure vertical movement of the needle, and possibly mobile over a pipette area containing a plurality of tubes.

In practice, the development of such a device and the design of such sampling needles present many problems.

Thus, the use of conventional hollow needles with sharp, considerably conical tips is not well suited in automatic or semi-automatic analysers for the following reasons: When the needle is pierced, these needles act as part-carriers, cutting out a circular piece of section roughly equal to the section of the needle channel in the stopper. This circular piece enters the channel and causes it to be at least partially closed.During the punching action, the cap undergoes a deformation which causes a change in pressure (overpressure) inside the container, which is a second source of error in the quantities taken. Similarly, during the needle extraction, the reverse deformation of the cap causes a depression causing a suction effect which tends to suck up the liquid taken. The imprecision resulting from these two phenomena is amplified by the fact that the sample level inside the tube is variable from one tube to another and, consequently, the values of the overpressure and the overpressure cannot be predetermined.The needle-pull effect leads to the formation of holes which close poorly after the needle is removed so that the tightness of the stopper can no longer be guaranteed.

To solve the problems of the coin-carrying effect, it has already been proposed, by patents DE195 12 607 and US 5 220 947, to use needles with the channels blocked at their pointed ends and with lateral perforations made in the needle bodies.

To solve the problems of imprecise sampling, it has been proposed to use sampling devices using sets of electrical valves to perform complex sampling sequences taking into account the parameters mentioned above, but this solution is expensive, unreliable and does not solve all the problems mentioned above.

The invention is therefore intended to provide a simple, inexpensive and yet effective solution to these problems.

It proposes a sampling device using a hollow needle which moves axially so that a stopper sealing the container containing the sample can be pierced.

This device consists of a hollow needle which moves axially so as to pierce the stopper, the pointed end of the needle comprising at least one sharp edge tangent to a generator of the cylindrical body of the needle, an oblique shape connecting the edge to the cylindrical body and a lateral channel outlet centered on the said generator at a distance from the edge, this opening being oriented perpendicular to the longitudinal axis of the needle.

According to the invention, this device is characterised by the fact that the end of the needle body is elongated and machined to comprise a machining face tangent to the said generator, perpendicular to the plane of symmetry of the end of the elongation and into which the needle channel opens through the said orifice, the end of this machining face constituting the bore of the sharp edge.

The advantage is that the above-mentioned edge and the above-mentioned orifice extend in the same plane tangent to the above-mentioned generator.

According to a preferred embodiment of the invention, the oblique shape is a cylinder end coupling while the tangent plane is a machining plane perpendicular to the symmetry plane of the coupling.

According to another feature of the invention, the cylindrical body of the needle has at least one axial neck at its outer cylindrical surface, terminating at a predetermined distance from the tip of the needle, preferably a square or rectangular section, which is intended to ensure that the inner volume of the sample is brought into the atmosphere during sampling.

A method of execution of the invention will be described below, by way of example but not limited to, with reference to the attached drawings in which: Figure 1 is a schematic representation of a conventional sampling device;Figures 2 and 3 are partial views illustrating the deformation of the sample tube during the drilling of the cap (Figure 2) and during the needle extraction (Figure 3);Figure 4 is a side view of the needle used in accordance with the invention, in a plane parallel to the longitudinal plane of symmetry of the needle;Figure 5 is a side view of the needle at 90° from the view in Figure 4;Figure 6 is an axial cut of the end of the needle;Figures 7 and 8 are cuts according to A/A and B/B respectively, using the principle of Figure 6 9;The schematic representation is a diagram allowing the perpendicularity of the needle to be represented in Figure 8

In the example shown in Figure 1, the container containing the sample to be analysed consists of a conventional glass tube of type 1 closed by a rubber stopper 2 comprising a cylindrical body 3 of slightly greater diameter than the inner diameter of tube 1 and a cap 4, also cylindrical in diameter than the outer diameter of tube 1. The upper face of the cap 4 includes a clearly spherical cap 5 designed to reduce the thickness of the central region where the drilling is carried out. Of course, the 3 is sealed in tube 1 while the cap 4 forms with the 3 a shoulder which comes over the top edge of tube 1 in a cap.

The tube 1 axis shows a pipette head 6 moving perpendicular to the tube axis and incorporating a mechanism for operating a needle 7 oriented parallel to the tube axis.

This mechanism consists of a needle-bound rack 8 on which a gear 9 is driven by a DC electric motor M powered by an electric current source S, the intensity and/or voltage characteristics of which are measured by a detector D before being transmitted to a processor P which controls the device.

The operation of this device is then as follows: during a sampling and/or injection phase, pipette head 6 is placed above tube 1 and needle 7 is located in the longitudinal axis of tube 1.

The processor P then commands the rotation of the M engine in such a way as to cause the rack 8 and therefore the needle 7 to which it is attached to be displaced.

The needle 7 therefore undergoes a translational displacement until it reaches the stopper 2. When the needle tip on the stopper 2 comes into contact with it, the resulting resistant torque at the level of the motor M changes the characteristics of the supply current. These changes are detected by the detector D which transmits corresponding information to the processor P. During the perforation of the stopper 2, the needle 7 exerts a stress on the rubber body 3 causing a downward deformation (pumping) of the rubber body and, at the same time, an increase in the volume of the cavity (Figure 2). This deformation therefore causes an increase in pressure inside the tube 1. Even if this is done in the case of an accelerated pressure caused by a circulation of gas inside the tube 7, the amount of pressure will remain uncompensated.

When needle 7 is removed, the body 3 of cap 2 is subjected to the opposite stress: the lower side of the body of cap 2 is deformed to a concave shape, creating a depression inside the tube (Figure 3). This depression will create a suction of the liquid taken by the needle so that a new imprecision is added to the sample quantity taken.

Of course, in addition to these causes of imprecision, there is the fact that a conventional needle acts like a coin-operated carrier and cuts through a piece of rubber that may at least partially block the needle 7.

As shown in Figures 4 to 8, the needle of the invention avoids these inconveniences.

This needle 7 comprises a hollow cylindrical body 10 whose pointed end 11 is obtained by bending the body 10 end and then machining the cubic end to a face 13 tangent to a generator of the body 10 and perpendicular to the plane of symmetry of the said cubic part C.

This gives a flat 13 machine face with the ovoid end forming the beginning of the cutting edge, A1 and A2 being sharpened by grinding two side faces 14, 15 which give it a pointed V shape as shown in Figure 5.

In addition, the outer surface of body 7 comprises four longitudinal gorges 16 diametrically opposed by two, each having a square section.

These longitudinal 16 throats, which are made over a large part of the length of the needle 7, terminate at a predetermined distance from the tip 11 so as never to come into contact with the liquid to be removed.

The cutting edge of the A1, A2 of the tip 11 makes a straight cut of the rubber, thus avoiding any part-winding phenomenon. This F-slit is then stretched out elastically on one side by the elongated part until it reaches the body 10 and gradually takes on a circular shape. During this cutting, the machining face 13 into which the O-hole of the AC channel exit of the needle opens slides over the rest of the F-slit on which the weakest and only very slightly deformed (plane) slit is applied.

Once the tip of the needle 7 has passed through the stopper 2 and the 16 throats have emerged from the inside of tube 1, the pressure in tube 1 at the time of sampling is reduced to a constant value (atmospheric pressure).

When needle 7 is removed, the needle tip that has been in contact with the sample is wiped away, especially since no rubber has been removed and the gap closes gradually as the needle section decreases.

When the needle is removed, the slit is completely closed and the pressure exerted by the tube on the body ensures perfect sealing.

Claims (7)

1. Device for the sampling and/or injecting of liquid into a receptacle (1) sealed by a stopper (2), this device using a hollow needle (7) that is axially mobile so as to be capable of perforating the stopper (12), the pointed tip (11) of the needle (7) comprising at least one cutting edge (A₁, A₂) at a tangent to a generating line of the cylindrical body (10) of the needle (7), an oblique shape (C) connecting the edge (A₁, A₂) to said cylindrical body (10) and a lateral outlet hole (O) of the channel (CA) centered on said generating line at a location distant from the edge (A₁, A₂), this hole (O) being angled perpendicularly to the longitudinal axis of the needle (7) characterized in that the said tip of the body of the needle is cranked and machined so as to comprise a machined face (3) at a tangent to said generating line, perpendicular to the plane of symmetry to said cranked tip and into which the channel (CA) of the needle (7) opens by the said hole (O), the extremity of this machined face (13) constituting the start of the cutting edge (A₁, A₂).
2. Device according to claim 1, characterized in that the said hole (O) and said edge (A₁, A₂) extend in a same plane at a tangent to said generating line.
3. Device according to claim 1, characterized in that the cylindrical body (10) of the needle (7) comprises, in its outer cylindrical surface, at least one axial groove (16) ending at a predetermined distance from the tip (11) of the needle.
4. Device according to claim 3, characterized in that the said groove (16) is of square or rectangular cross-section.
5. Device according to one of the claims 3 and 4, characterized in that the said body (10) comprises four longitudinal grooves (16) diametrically opposed two by two.
6. Device according to one of the preceding claims, characterized in that the cutting edge (A₁, A₂) has a pointed shape thanks to the grinding of two lateral faces (14, 15).
7. Device according to one of the preceding claims, characterized in that the motion in translation of the needle (7) is controlled by an electric motor (M) supplied by a circuit including a detector (D) capable of detecting a parameter representative of the load moment generated when the tip of the needle (7) enters into contact with the stopper (2).