WO1993002869A1

WO1993002869A1 - Plotter

Info

Publication number: WO1993002869A1
Application number: PCT/BE1992/000030
Authority: WO
Inventors: Louis-Philippe Mascart
Original assignee: Mascart Louis Philippe
Priority date: 1991-07-30
Filing date: 1992-07-24
Publication date: 1993-02-18
Also published as: BE1005081A3; EP0600907A1; AU2311092A

Abstract

A plotter (1) for depositing an amount of liquid on a medium (3), said amount being determined by a unit of length. Said plotter includes a tubular pen (5) mounted on a pen holder (6) which is provided with a first device (4) for moving the pen relative to the medium. The first device is arranged to effect writing in a first direction (43) by the pen on the medium, and the end of the pen that engages the medium comprises a notch (2) forming an interstice between said end and the medium which gets progressively larger in the direction opposite the writing direction.

Description

"Tracer"

The invention relates to a tracer intended to deposit a quantity, predetermined per unit of length, of liquid on a support, said tracer comprising a tubular nib mounted on a nib holder which is provided with first means arranged to move one relative to the other the pen and the support.

Such a tracer is known from an advertisement which appeared in "Industry" of April 1990. The known tracer is used for medical purposes, in particular for the production of test strips. The liquid is poured into a reservoir that is part of the pen holder and is then deposited using the pen on a support, preferably a chromatographic support. After the liquid has been deposited, the support is cut into a series of strips on the basis of which the analysis will be carried out. To facilitate the deposition of the drops on the support, the pen holder is moved along the lines where the liquid is to be deposited.

A disadvantage of the known tracer is that the feathers used have a tendency to damage the support which is generally fragile and thus to make it unusable. This is in particular the case when using feathers whose outlet of the liquid is managed by a valve actuated for example by means of a needle in contact with the support. These feathers, although excellent for drawing ink lines, are less suitable for depositing a liquid on a fragile support. Indeed, the support used is significantly more fragile than the paper normally used for making drawings. The needle will damage the support and make it unusable. In addition, such feathers do not allow very fine adjustment of the amount of liquid to be deposited. The object of the invention is to produce a tracer whose pen deteriorates the support on which the liquid is to be deposited to be substantially less and whose quantity of liquid deposited is better controllable. To this end a tracer according to the invention is characterized in that the first means are arranged to carry out a writing in a unidirectional direction of the pen on the support and in that the end of the pen intended to be placed on the support comprises a notch arranged so as to release between said end and said support an interstice which is increasing in the opposite direction to that of writing. The indentation and the unidirectional writing direction allow that the quantity of liquid deposited is, apart from the speed of movement of the pen or the support, determined by the gap, which can be machined with precision. This gap allows the liquid to exit without having to use a needle.

The risk of damaging the support is thus significantly reduced. Since the interstice is increasing in the opposite direction to that of writing, the choice of the size of the interstice also makes it possible to calibrate the outlet of the liquid in a very precise manner. A variant of a plotter according to the invention, where the pen has a substantially planar writing end, is characterized in that the plotter comprises second means arranged to place the pen in a first position where an axis of the pen is substantially perpendicular to the support and in a second position where said axis forms with respect to the writing direction of the pen an oblique angle. The gap can also be created by tilting the pen facing the support and will therefore offer the same advantages as those described above.

A first preferred embodiment of a tracer according to the invention is characterized in that said notch is formed by an obliquity of said end. This allows easy and precise machining of the pen.

A second preferred embodiment of a tracer according to the invention is characterized in that said notch is formed by cutting obliquely at an angle located between 1 and 2 °, in particular 5 °, from the tip of the pen. By using a relatively small angle it is possible to obtain very low flow rates, necessary in medical applications.

A third preferred embodiment of a tracer according to the invention is characterized in that said end comprises a first cut part substantially parallel to the support and a second part arranged obliquely to the first. The first part thus determines the width of the line applied while the second determines the quantity deposited. A fourth preferred embodiment of a tracer according to the invention is characterized in that the pen holder comprises a reservoir in which is housed a shutter arranged to close inside the reservoir the passage of the liquid towards the pen. This avoids an untimely exit of the liquid when the pen is not used, for example.

Preferably said shutter has one end which extends outside the tank, said end being provided with a cover arranged to close said tank, said plotter being provided with a first stop intended to retain said cover when the pen is on the support and to release said access. A mechanically simple and reliable control of the opening of the pen is thus obtained.

Preferably the plotter comprises a second stop placed at a distance, greater than the thickness of the cover, from the first stop and arranged to retain said cover when the pen is recessed with respect to the support and to close said access. This prevents the shutter from being ejected by inertia when the pen is removed.

Preferably said shutter is formed by a rod whose outer wall is provided with longitudinal notches.

The notches facilitate the passage of the liquid towards the pen and the ascent of the air in the tank.

The invention will now be described in more detail with the aid of an embodiment shown in the drawings in which: - * -

Figure 1 shows a general view of a tracer; Figure 2 illustrates a section through a pen holder provided with a feather according to the invention; Figure 3, respectively shows a detail of a first, respectively second embodiment of the pen according to the invention; Figure 5 shows a section along line IV-IV through the shutter; FIG. 6 illustrates a first example of the means for moving the pen holder; Figure 7 shows a detail of these displacement means; Figure 8 illustrates other means of movement of the pen holder.

In the drawings, the same reference has been assigned to the same element or to an analogous element.

The tracer 1, illustrated in FIG. 1, comprises a base plane 2 intended to carry a support 3. The tracer is intended to deposit a liquid on the support 3. The tracer is in particular intended for the purposes of medical analyzes. The liquid deposited is for example a reactive or crystallizing liquid such as a solution containing antibodies. The support used for this purpose is preferably a chromatographic support. Such supports are more vulnerable than normal paper, which requires the use of special nibs as will be described below.

The pen 5 is mounted on a pen holder 6 which itself is mounted on first displacement means, which allow the displacement in three directions of the pen holder and of its pen relative to the support. The plotter also includes a magazine 7 where other pen holders are stored. By moving the pen on the support, the liquid is deposited in different places, preferably in the form of parallel lines. When the deposited liquid has dried, the support is, for example, cut into thin strips perpendicular to the parallel lines. The strips are used then for review.

It goes without saying that the tracer according to the invention is not limited solely for the purposes of medical analysis and that other applications can be envisaged such as for example the application of dyes. The displacement means can also be arranged to move the support relative to the pen.

Figure 2 illustrates a section through a pen holder according to the invention. The pen holder 6 comprises an envelope 8, preferably made of transparent material such as Plexiglas for example. The upper opening of this envelope 8 is closed by a cover 9 provided with two perforations 10 eτ 11 intended inter alia for the introduction of the liquid. A shutter 12 passes through the cover 9 along its central axis 15. The feather 5 is a tubular feather of cylindrical or rectangular section, one end 13 of which is pressed into the pen holder. The lower end 1 of the shutter comes in the closed position to close the inlet of the pen, thus preventing the leakage of the liquid when the pen is not used. The shutter 12 passes through the reservoir 0 of the pen holder and is formed by a rod preferably made of stainless steel and the outer wall of which is provided with longitudinal notches 19, as illustrated in FIG. 5. The sections 42 of the rod between the notches scrape the inner wall of the tank. The sections 45 and 46 of the shutter are rounded so that neither air bubbles nor drops of liquid remain attached to the interior wall. The sections 42 also serve to guide the rod in the tank. The notches also allow a better circulation of the liquid, for example introduced by the perforation 10, towards the pen as well as a release of the air present in the tank for example by the perforation 11. The notches also make it possible to avoid, during a movement of the rod, pressure variations in the part of the tank located above the end of the pen, inside the tank. In order to ensure proper sealing of the pen, the end 14 of the rod is provided with a flexible material, for example a rubber seal. Preferably the seal has a diameter slightly greater than that of the end of the rod in order to avoid the entrapment of air bubbles around the seal. In another embodiment, this end 14 is for example formed of a ball which comes to rest on the end 13 of the pen.

As illustrated in Figure 2 the tank thins about halfway up while the rod grows in about the same place. This allows better control of the dosage of liquid to the pen. By increasing the size of the rod in the lower part of the tank, the volume of liquid in this part is reduced. A larger column of liquid is thus obtained in the upper part, which makes it possible to increase, without modifying the volume of the liquid, the hydrostatic pressure exerted on the feather. This increase in hydrostatic pressure allows better circulation of the liquid towards the pen.

The vulnerability of the support imposes a very specific geometry at the end of the pen intended to come into contact with the support. It has indeed been found that the usual feathers, which include a shutter needle, damage the aforementioned particular support and make it unusable for the purposes of medical analysis. The use of a tracer for medical purposes, in particular for the deposition of reactive liquids therefore requires special feathers. A first embodiment of the pen 5 according to the invention is shown on an enlarged scale in FIG. 3. This pen is arranged to write in a unidirectional writing direction indicated by the arrow 43. The outlet end of the pen comprises a first part 16 substantially parallel to the plane of the support 3, when the pen rests on the support. A second part 17 of the outlet end is placed obliquely to the first part. Preferably, the second part extends over half of the exit surface of the pen and forms an angle e with respect to the plane 18 in which the first part is located. This angle is located between 1 ° and 20 °, depending on the size of the ejector and the viscosity of the liquid to be deposited. When the liquid to be deposited is for example a solution containing anti-bodies, the angle f- has 5 °. The angle of inclination of the pen is proportional to the viscosity of the liquid to be deposited. Due to the fact that the second part is oblique to the first end of the pen has a notch arranged so as to release a gap between the support and the exit end of the pen. This gap is growing in the opposite direction to that of writing. When the pen is placed on the support, the first part is in contact with the latter. Due to the small aperture diameter, about 0.7 mm, of the pen and the fact that the first part is in contact with the support, little liquid can escape through the first part and most of the liquid will come out through the gap formed by the second part. The first part being in direct contact with the support, the pen will be rigorously aligned with respect to the support. Thanks to this good alignment, the flow rate up to the gap is rigorously controlled, since it is practically invariable for a given feather. This alignment also causes the pen to follow the irregularities of the support, and therefore its irregularities will have little or no influence on the flow. Since it is the first part, which is smooth and which is placed on the support, its friction will not damage the support. In addition, since we no longer use needles to adjust the flow, there are no longer sharp objects that come into contact with the support and therefore these objects can no longer damage the support. In addition, good control of the liquid flow also significantly limits losses of the precious liquid to be deposited.

FIG. 4 illustrates a second embodiment of a feather according to the invention. This pen is also unidirectional. In this second embodiment, the notch is formed by an obliquity of the end of the feather which extends over the entire thickness of the feather. This end is cut at an angle / _> between 1 and 20 °, in particular 5 °. In this example, the interstice created also increases in a direction opposite to that of writing. The gap between the support and the end of the pen can also be obtained by tilting the pen holder and its pen relative to the support. This embodiment is shown in Figure 8. The pen holder 6 is also connected to second displacement means 44 arranged to tilt the pen holder relative to the support. In the rest position, shown in dotted line in Figure 8, the pen holder is held substantially perpendicular to the support. In the writing position the second means 44 tilt the pen holder so that the axis forms an angle V ", preferably located between 80 and 88 ° with the support, relative to the direction of writing 43 There is thus also obtained an interstice at the end of the pen.

Due to the special geometry of the tip of the pen, it can only write in one direction. This implies a correct positioning of the pen relative to the direction of writing. To allow this correct positioning, the envelope of the pen holder comprises for example two notches (not shown in the drawings) different from each other. One notch is used to fit a first lug of the pen holder, while the other notch is used to fit a second lug of the pen holder located approximately 180 ° from the first lug. The first and second lugs have different dimensions. The lugs are for example made by a small vertical screw whose head is tangent to the pen.

To facilitate the explanation of the movement of the pen holder, the ascent and descent mechanism to the support will be described first. This mechanism is illustrated in FIG. 6 and comprises a lever 20 mounted in articulation around a point 21. The pen holder 6 is mounted on one end of the lever while at the other end displacement means are provided. The articulation point 21 is located on a mobile carriage 27 allowing the lever to move along the support.

The displacement means, which allow the movement of raising and lowering of the pen holder, comprise in the present embodiment a solenoid 22 inside which is housed a plunger core 23 provided with a head 24. A spring main 25 is housed in a housing 26 located under the solenoid. When the pen holder has to write, an electric current is sent to the solenoid, which has the effect of attracting the plunger core 23 inside the solenoid. The head 24 of the core will then exert a force against the housing 26 and thus compress the main spring 25 thus releasing the lever 20 which will tilt on the support 3 as illustrated in FIG. 5. A space is left between the housing 26 and the lever 20 when the feather is in contact with the support. This space allows the pen to follow a movement imposed by irregularities in the support and therefore not to damage the support during its movement.

To raise the pen holder relative to the support, it suffices to interrupt the current flowing in the solenoid, which will cause the plunger core 23 to fall. This will release the housing 26 from the force exerted on it by the core and therefore allow the main spring 25 to relax. The relaxation of the spring will cause the housing 26 to exert a force on the lever 20. Under the effect of this force the lever will rock around the point of articulation and will raise the feather. In this way, the solenoid is not energized in the rest state.

The up and down movement of the pen holder will also cause the pen to close and open. The cover 9 is fixed with two nuts 38 and 39 to the shutter 12. Part of the cover is housed between two stops 34 and 35, each fixed with a screw 36, 37 to the carriage . The space between the lower stop 35 and the upper stop is greater than the thickness of the cover 9 and can be adjusted for example using screws. The position of the cover 9 is also adjustable using the nuts 38 and 39 referred to on the screw 40. When the pen descends, the cover 9 abuts against the lower stop 35. This stops the movement of the shutter, while that of the pen continues. The end 14 of the rod will thus remain immobile and access to the feather will be freed when the feather lands on the support. Preferably a dead time, for example of the order of one second, is observed before writing begins when the pen has landed on the support, in order to allow the liquid to flow into the pen. The lower stop or first stop is arranged so that the opening of the pen is a fraction of a second before it lands on the support. Thus the pen remains closed during the descent of the pen holder which will prevent leakage of liquid during this descent.

When the pen holder goes up the access to the pen will be quickly closed, due to the short distance between the end

14 and the pen. In its upward movement the pen holder also drives the shutter since the latter is housed in the tank. The cover will therefore move in the space between the lower stop 35 and the upper stop 34. The upper stop serves to hold the shutter in its upward movement and at the same time to keep the access closed towards the pen when the latter is not placed on the support. The upper stop also serves to prevent the shutter from being ejected from the tank when the pen is raised. The force with which the pen holder is raised could cause the shutter to be ejected. By abutting the cover against this upper stop, the shutter is retained and its ejection is prevented.

The presence of the two perforations 10 and 11 in the cover also makes it possible to combat the piston effect of the shutter when the feather rises. Indeed, air can escape through these perforations and thus destroy the piston effect.

To allow correct descent of the body of the pen holder, an auxiliary spring 32 is provided as illustrated in FIG. 7. The auxiliary spring is mounted offset from the main spring. The auxiliary spring is fixed between the lever arm

20 and the end 33 of a screw 22 fixed by two nuts 29 and 30 to the upper cover 31 of the solenoid. This auxiliary spring slows the upward movement of the pen holder. When reassembling the extension of the auxiliary spring will require a force which will be taken from the energy supplied by the fall of the core. The counter force exerted by the auxiliary spring is adjusted by moving the screw 22 relative to the nuts 29 and 30.

Claims

1. Tracer intended to deposit a quantity, predetermined per unit of length, of liquid on a support, said tracer comprising a tubular nib mounted on a nib holder which is provided with first means arranged to move one relative to the other the pen and the support, characterized in that the first means are arranged to write in a unidirectional direction of the pen on the support and in that the end of the pen intended to be placed on the support comprises a notch arranged so as to release between said end and said support an interstice which is increasing in the opposite direction to that of writing.

2. Tracer intended to deposit a quantity, predetermined per unit of length, of liquid on a support, said tracer comprising a tubular nib having a substantially planar writing end, said nib being mounted on a nib holder, said tracer also being provided with first means arranged to move the pen and the support relative to each other, characterized in that the tracer comprises second means arranged to place the pen in a first position where an axis of the pen is substantially perpendicular to the support and in a second position where said axis forms with respect to the writing direction of the pen an oblique angle.

3. Tracer according to claim 1, characterized in that said notch is formed by an obliquity of said end.

4. Plotter according to claim 3, characterized in that said notch is formed by cutting obliquely at an angle between 1 and 20 °, in particular 5 °, of the end of the pen.

5. Tracer according to claim 3, characterized in that said end comprises a first cut part substantially parallel to the support and a second part arranged obliquely to the first.

6. Tracer according to one of claims 1 to 5, characterized in that the pen holder comprises a tank in which is housed a shutter arranged to close inside the tank the passage of the liquid to the pen.

7. Tracer according to claim 6, characterized in that the other end of the pen is located inside said tank, said shutter being arranged to close said other end.

8. Tracer according to claim 6 or 7, characterized in that said shutter has one end which extends outside the tank, said end being provided with a cover arranged to close said tank, said tracer being provided with a first stop intended to retain said cover when the feather is on the support and to release said access.

9. Tracer according to claim 8, characterized in that it comprises a second stop placed at a distance, greater than the thickness of the cover, from the first stop and arranged to retain said cover when the pen is in retreat from the support and to close said access.

10. Tracer according to one of claims 6, 7,

8 or 9, characterized in that said shutter is formed by a rod whose outer wall is provided with longitudinal notches.

11. Pen holder for a plotter according to one of claims 1 to 10, characterized in that it comprises a shutter.

12. Pen intended for a plotter according to one of claims 1 to 1 1, characterized in that it comprises a writing end of which at least a part is oblique.