FR2837406A1 - Plastic tube for liquid micro-dosing, has constricted tip with smooth internal transition from tube internal diameter - Google Patents

Abstract

The liquid delivery end of the tube, which carries out the transfer and/or dosing, has a constriction (8) with an internal diameter no greater than 1.5 mm. There is no discontinuity in the internal surface of the section connecting the constriction to the tube (1). During manufacture, a plastic tube (1) of nominal diameter, is gripped (2, 4) firmly on either side of the zone (3) to be constricted. A rod or piano wire (5) is inserted into the tube. Its melting point is much higher than that of the plastic. Its external diameter corresponds with the final internal diameter required in the constriction. The constriction zone is heated to soften it. The tube is drawn, until its internal diameter contacts the insert. The tube is then cut off at this location. An Independent claim is included for the method of manufacture.

Description

- primary to neighboring microcuvettes (1S) concerned.

  PLASTIQ MICRO-DOSING TUBE, AND

PRO SELLS FOR ITS REALIZATION.

  The invention relates to a tube made of plastic, more particularly s intended for dosing and micro-dosing of liquids. The invention therefore relates more particularly to the field of the pharmaceutical industry, medical analysis,

  agrifood, and related activities.

  It also relates to a method for producing such a tube.

  In the context of the implementation of a certain number of equipment for metering and pumping fluid, and in particular liquid, use is traditionally made of pipes made, most often, of stainless steel, and one end of which is in the form of a needle, the diameter of which is chosen in order to be able to

  deliver a dose as close as possible to the desired optimal dose.

  If current techniques make it possible to produce tubes of determined diameter, including very small dimensions, and typically between 2 and 0.1 mm in relation to this material, on the other hand, the phenomena inherent in the tension of surface induce the wetting of the liquid on the stainless steel, and leading to the total non-delivery of the determined quantity of metered liquid, and to the formation of a drop at the end of said needle, drop likely to generate

  soiling at the places where these assays are carried out.

  2s In order to achieve outlet diameters of such dimensions, it is known to make a constriction at the level of the liquid delivery end. This also makes it possible to favor the connection of the other end of the tube at the outlet of a pump.

  metering or other tubular, for example made of plastic.

  However, the length of such a constriction must be adapted to reduce the pressure drops and have a maximum kinetic energy of the liquid at the outlet, and thus make it possible to achieve direct dosing, this adaptation also taking into account the

  above-mentioned surface tension phenomena.

  3s Finally, these terminal needles are traditionally connected to other tubing, in particular of plastic material, thus generating at the very least an interface between the end of the needle and the end of the plastic tubule, requiring ensuring sealing, and further inducing an additional step of fitting the needle fitting at said end as well as a

  increase in the number of parts to be cleaned and sterilized.

  s The object and the invention is to get rid of all of these different. mconvéments. It offers a tube made of plastic, with no length limit taking into account the process obtained, one of the ends of which has a constriction, the internal diameter of which is less than or equal to 1.5 mm, the area connecting the constricted to

  tube showing no discontinuity, especially of its internal surface.

  Advantageously, the plastic material used consists of polytetrafluoroctethylene (TEFLON - trademark), or polyamide, and in particular polyamide 6 (NYLON - registered trademark), or even PVDF (polyvinylidene fluoride), polypropylene or polyethylene. These rigid plastics have a hydrophobic character, thus making it possible to avoid the wetting phenomena inherent in the surface tension, and therefore consequently, the formation of the drop of

terminal liquid.

  The invention also relates to a method for producing this tube. This process consists: - of ensuring the tightening of a plastic tube, and in particular of polytetrafluoroethylene or polyamide, of nominal diameter on either side of the zone at which it is desired to make a constriction, - to insert inside the tube a rod or a piano cord made of a material, the melting point of which is much higher than that of the plastic material of which the tube is made, and whose external diameter corresponds to the internal diameter of the desired final color ; - to provide heating for the constricted area, until the area under consideration is softened; - perform a kaction of the tube until it comes into contact with the internal surface of the tube at the level of the rod or the piano wire;

  - then to ensure the cutting of the tube at this level.

  In an advanced version, a matrix is positioned after heating and before cutting, at the level of the outside area of the shrinkage formation area, clean

  to give the tube a particular shape at the level of its outside diameter.

  s Advantageously, the constituent material of the piano rod or string is not

  polluting (typically AINSI 31 6L stainless steel).

  The manner in which the invention can be carried out and the advantages which result therefrom will emerge more clearly from the two examples of embodiment which follow, given by way of

  o indicative and not limiting in support of the attached figures.

  Figures 1 to 3 show a schematic representation in longitudinal section of a tube during its formation according to a first embodiment of the invention, of which Figure 4 is a representation of the tube obtained with necking. Figures 5 to 8 are views similar to Figures 1 to 4, in another form

for carrying out the invention.

  The example of embodiment which follows is more particularly directed in relation to

  a micro-dosing tube for the pharmaceutical industry.

  This tube (1) is made of polytetrafluoroethylene, and has a constriction (8), the internal diameter of which is close to 0.1 mm. The nominal internal diameter of the tube (1)

  is in the order of 0.5 mm.

  2s Figures 1 to 3 show a first embodiment of this tube. This one is mounted at two fixing jaws, respectively (2) to (4), located on either side of a zone (3), where the constriction will actually take place. At this zone (3), an annular chamfering system is installed, making it possible to reach the melting temperature of the plastic material constituting the tube (1). 5 As a corollary, a piano rod or string (5), the melting point of which is much higher than the melting point of polytetrafluoroethylene, is inserted inside this tube (1). The external diameter of this rod or rope to

  piano (5) corresponds to the desired internal diameter of the neck (8).

  When the melting temperature is reached, and the tube begins to soften, a traction is exerted on the jaw (2), leading to the elongation of the tube at the level of the zone (3) for making the constriction and as a corollary to the thinning of the tube until the internal wall of the tube comes into contact with said piano string (5). The heating is then stopped and a clean cut is made at the

constriction formation (8).

  lo Taking into account the plastic material used, no chips or burrs appear, and there is a tube whose necking has a very short length, making it possible to significantly reduce the pressure drops, and - p artant, during dosing operations, to communicate to the liqui

  measured maximum kinetic energy at the output.

  With such a table, it is possible to carry out dosages in very small quantities,

  typically between 1 and 20,111.

  At the same time and as already specified, the choice of plastic, namely polytetrafluoroethylene, taking into account its hydrophobic nature, makes it possible to avoid the phenomena of wetting, and consequently, the formation of the drop.

  liquid, traditionally obtained with traditional dosing devices.

  In another form of the invention shown in connection with FIGS. 4 to 8, 2s the principle of embodiment of the tube remains substantially equivalent, with the difference however that the constriction (8) is conformed at its external surface to the

  by means of an external matrix (9), depending on the desired shape of the neck.

  The external forming of the perrnet tube also provides a precise and defined shape which can be inserted into a support made of rigid material (typically stainless steel, in particular AINSI 304 L and 316 L) to ensure coaxiality between the

  semi-rigid shrunk tube and the container intended to receive the said microdose.

  The external forming of the tube also makes it possible to obtain a larger diameter ratio before and after shrinking by forcing the material of the tube.

  the state of fusion, to be pressed against the rod or piano wire.

  s It is easy to understand the advantage of the tube and of the production method according to the invention, insofar as it makes it possible to overcome the drawbacks of the metering devices known from the prior art, in particular when the

_work of stainless steel.

  s In addition, such a tube makes it possible to end up with a single piece, thus limiting the number of pieces or elements in contact with the liquid to be dosed, and by way of

  Consequently, reducing the risks of pollution of said liquid.

  Finally, by the implementation of such a monoblock metering tube, the number of interfaces is also limited, and therefore the number of manipulations for the

  production of more complex dosing systems.

Claims (6)

  1. Tube (1), and in particular liquid metering tube made of plastic, characterized in that its delivery end of the liquid which it is intended to transfer and / or to measure has a constriction (8), the internal diameter is s less than or equal to 1.5 mm, the zone connecting the constriction (8) to the tube (1) not having   no discontinuity, especially of its internal surface.   2. Tube according to claim 1, characterized in that the plastic material constituting the tube is chosen from the group comprising 0 polytetrafluoroethylene, polyamide 6, polyvinylidene fluoride,   polypropylene and polyethylene.   3. Method for producing a tube, and in particular a liquid metering tube, characterized in that it consists in: - ensuring the tightening of a tube (1) made of plastic of nominal diameter, of on either side of an area (3) at which it is desired to make a rekeint (8), - to insert inside the tube (1) a rod or a piano cord (5) made in a material, the melting point of which is much higher than that of the plastic material of which the tab is made, and the external diameter of which corresponds to the internal diameter of the desired final neck (8); - to provide heating for the constricted area, until the area under consideration is softened; - perform a kaction of the tube until it comes into contact with the internal surface 2s of the tube at the level of the rod or the piano wire;   - then to ensure the cutting of the tube at this level.   4. Method for producing a tube according to claim 3, characterized in that the plastic material constituting the cloth is chosen from the group comprising polytekafluoroethylene, polyamide 6, polyfluoride   vinylidene, polypropylene and polyethylene.   5. Method for producing a tube according to one of claims 3 and 4,   characterized in that, after heating and before cutting, a matrix (9) is positioned at the outside area of the necking formation area, capable of giving the tube a particular shape at its outside diameter.   6. Method for producing a tube according to one of claims 3 to 5,   characterized in that the material of the piano rod or string (5) is   non-polluting, and for example made of stainless steel AINSI 31 6L).