Writing instrument including a device for venting the chamber

ES 2 339 890 T3

DESCRIPTION

Writing instrument comprising a reservoir ventilation device.

Technical sector

The present invention relates to a writing instrument comprising an ink tank, a writing tip and an ink tank vent device.

State of the art

The ink tank venting device has an ink buffer function. It allows absorbing a possible spillage of a part of the ink contained in the tank, which would otherwise be poured out of the instrument through the writing tip. Such an ink spill can be caused, for example, by a temperature variation caused by prolonged contact with a user's hand. It can also be caused by an overpressure in the ink reservoir caused by a collision with the writing instrument.

Furthermore, during use of the writing instrument, the ink flows from the reservoir towards the nib, and exits the nib when the nib is moved against a writing medium, such as a sheet of paper. The ink reservoir is then progressively emptied, and it is necessary to allow a volume of air equivalent to that of the ink consumed to enter the reservoir, to avoid a stoppage of the ink flow. Another function of the reservoir ventilation device is therefore to balance the pressure in the reservoir with respect to the pressure of the air present outside the writing instrument, so that the ink continues to flow by capillarity from the reservoir to the tip. of writing.

Various embodiments of an ink tank ventilation device are known. There are known, specifically from documents US 4,556,336 and US 6,474,894, ventilation devices of the ink tank comprising a set of zigzag passages. The set of zigzag steps forms a labyrinth connecting the ink reservoir with an open hole on the outside of the instrument. It is made up of a piece of plastic material, which is usually molded. The absorption of an ink spill is obtained by fine adjustment of the ink capillarity in the zigzag passages. Ink can penetrate the zigzag conduits, but this penetration is limited by capillary forces exerted on the ink by the walls of the zigzag conduits. A drawback of such devices results from the complex shape of the piece that defines the zigzag ducts. The molding of this part is difficult to carry out, and generates a significant increase in the manufacturing cost for the writing instrument.

Document US-A-2003/0231921 discloses another embodiment of an ink tank ventilation device. The device comprises a cavity that is filled with a porous element, with open porosity. Like the set of zigzag conduits in the previous case, the cavity is in communication on the one hand with the ink reservoir, and on the other hand with a hole that opens on the outside of the instrument. The operation of such a device is based on the capillarity of the ink and the porosity of the element. But a porous element exhibiting a certain open porosity is difficult to reproduce in large series in a reproducible manner. Their manufacture then contributes to an increase in the cost price of the writing instrument.

Document US-A-4588319 discloses a writing instrument comprising an ink reservoir, a writing tip with fluid connection to this reservoir and through which the ink comes out during use of the instrument, as well as a device for ink tank vent.

Object of the invention

An object of the present invention is to provide an ink tank ventilation device of a writing instrument, which can be realized simply and inexpensively.

This ink tank ventilation device comprises a cavity which is in communication with the tank, which communicates directly with the outside through an open hole on the outside of the instrument, and which is adapted to absorb an ink spill. For this, the cavity is filled with separate grains that have sharp angles and edges of dimensions of the same order of magnitude with respect to an apparent dimension characteristic of the granulometry of said grains.

During the absorption of an ink spill, a part of the ink contained in the reservoir of the writing instrument enters the cavity of the reservoir ventilation device, and is distributed among the grains, in interstices formed by neighboring grains.

Considering that the grains which are contained in the cavity of the venting device of the ink tank are separate grains, these can be poured into the cavity in a simple manner. Such a manufacturing step is quick and inexpensive, and contributes to obtaining a low-cost writing instrument.

ES 2 339 890 T3

Furthermore, the use of an ink tank ventilation device according to the invention enables the design and production of writing instruments with complex or original shapes. In particular, when the reservoir ventilation device is located at the level of a gripping area of ​​the instrument, this area can have an ergonomic shape, in order to facilitate or make use of the writing instrument more pleasant.

These angles and edges of the grains modify the capillary power of the material with respect to the ink in the cavity, so that the ink can penetrate into the cavity between the grains under the effect of an overpressure inside the tank, however, does not flow freely through the cavity to the vent hole. The ink spill absorbing function obtained in this way is particularly effective, and prevents ink leakage from appearing at the vent hole or at the level of the writing nib. These sharp angles and edges are the result of the outer shape of the grains. They are therefore reliefs that have dimensions of the same order of magnitude as the apparent dimension d, or the grain size, of a grain in question, that is, a few tenths to several hundredths of its apparent dimension d.

In various embodiments of the invention, one and / or the other of the following provisions, which constitute improvements of the invention, may also be used:

- the grains are essentially non-porous;

- at least some of the grains can be constituted by a mineral material;

- the mineral material of some of the grains may comprise sand, calcium carbonate, corundum or crushed glass;

the grains can have an average dimension between 40 pm and 550 pm, this average dimension being determined by laser granulometry in all the grains contained in the cavity of the tank ventilation device;

- 95% of the grains contained in the cavity of the tank ventilation device can have at least one dimension less than 800 pm;

- 95% of the grains contained in the cavity can have at least one dimension greater than 0.5 pm;

- 95% of the grains contained in the cavity can have at least one dimension greater than 150 pm;

- the individual dimension of the grains can vary by a proportion of less than 10 for 95% of the grains contained in the cavity;

- the grains can have a granulometric distribution depending on their individual dimension that presents a single maximum; Y

- the ink can be a liquid ink, and preferably an aqueous type ink.

- the grains have not undergone any treatment that modifies their capillarity with respect to the ink, apart from simple washing operations, and preferably they are of natural origin.

In order that the venting device of the ink reservoir can contain an overflow of ink even more efficiently, the grains are preferably immobile in the cavity. In this way, the ink is fully retained between the grains by capillarity, and no relative movement of the grains with respect to each other disturbs this retention.

The cavity of the reservoir ventilation device can have a peripheral wall that is at least partly transparent. It is then possible to see a progression of the ink in the cavity, and thus avoid a possible leakage of ink through the ventilation hole.

On the other hand, the cavity of the reservoir ventilation device is delimited by a chamber other than the reservoir and provided with the hole, which can be in reduced communication with the ink reservoir in different ways. In particular, it can be directly in communication with the ink reservoir through at least one calibrated hole, or be in communication with the latter by means of a connector arranged to lead the ink from the reservoir towards the writing tip.

The inventors have found that a writing instrument whose center of gravity is located in the area for gripping and / or holding the instrument in the hand of a user for writing is particularly easy and pleasant to use. Indeed, a secure and well controlled holding and movement of the instrument is then obtained, so that writing is facilitated. In particular, the center of gravity of the writing instrument may be located at a distance from the writing tip that is less than half the total length of the instrument.

ES 2 339 890 T3

Preferably, the center of gravity of the writing instrument is located at a distance from the writing tip of between one sixth and one half of the length of the writing instrument.

When a reservoir ventilation device according to the invention is located at the front of the writing instrument, the weight of the grains, particularly when the grains are made of a mineral material, helps to shift the instrument's center of gravity towards the tip of the instrument. writing.

Finally, the invention can be applied to writing instruments of different types. Specifically, the writing nib can be a porous capillary nib, for example for a marker or felt-tip pen, a ball nib, or an ink roller nib.

Description of the figures

Other particularities and advantages of the present invention will be apparent from the following description of two non-limiting embodiments, with reference to the attached drawings, in which:

Figures 1a and 1b are respective sectional views of a writing instrument according to two variant embodiments of the invention;

figure 2 schematically illustrates grains of sand used for the invention; Y

FIG. 3 is a diagram of the particle size distribution of the grains contained in the ventilation device of the ink tank of a writing instrument according to the invention.

Detailed description of the invention

It is understood that the dimensions of the different parts of the writing instruments that are represented in figures 1a and 1b do not correspond to the dimensions, nor to the proportions of actual dimensions. Specifically, these dimensions can be adapted to obtain a writing instrument having a greater ink capacity, or to make a writing instrument having a pocket format.

By way of example, the writing instrument represented in FIG. La is of the "rollerpen" type. It comprises an ink tank (1), a connector (2) and an inking roller (3) that constitutes the writing tip. The ink reservoir (1) is limited by an external peripheral wall (10), which is substantially cylindrical. The reservoir (1) can be of the free ink type, that is, the ink (11) can circulate freely in the reservoir. The inking roller (3) is held, while remaining free to rotate, by a mount (4) that is fixed on a front end of the reservoir (1). The connector (2) allows the ink (11) that is contained in the reservoir (1) to flow towards the inking roller (3). It can be made up of a set of fibers aligned longitudinally and intended to be impregnated with the ink (11). These fibers are selected as a function of the capillarity of the ink (11), and are brought together with a controlled density in a substantially cylindrical bundle to form the connector (2). Eventually, one end of the connector (2) can enter the reservoir (1) to obtain a suitable impregnation of the connector (2) along its entire length.

A reservoir (1) ventilation device (5) is inserted between the mount (4) that forms the conical tip of the instrument and the reservoir (1). It comprises a cavity (50) which is arranged around the connector (2), and which is limited by an external peripheral wall (53). The wall (53) of the cavity (50) may be substantially in the extension of the wall (10) of the reservoir (1). Furthermore, according to the longitudinal direction of the writing instrument, the cavity (50) is limited by the mount (4) on the side of the writing tip, and by a partition (54) on the side of the reservoir (1) . On the other hand, the cavity (50) communicates with the free air through a hole (51), and with the reservoir through one or more holes (55 through the partition (54). Preferably, the hole (51) is located on one side of the cavity (50) opposite the hole (s) (55).

The wall (53), the frame (4) and the partition (54) form a chamber (60), that is to say, an essentially closed space except for the hole (51) and the hole (s) (55), which is different of the tank (1) and delimiting the cavity (50) of the ventilation device. As can be seen in figure 1a, the holes (55) are calibrated in such a way as to guarantee a reduced communication between the reservoir (1) and the cavity (50).

The cavity (50) is filled with separate grains (52) of a solid material. Preferably, the grains (52) completely fill the volume of the cavity (50), so that they are immobilized against each other. However, the cavity (50) can be filled leaving a small free volume of grains (52), that is to say it is not completely filled, leaving a sufficiently reduced mobility of the grains so that the agitation of the instrument does not displace the stained grains by the ink in the vicinity of the hole (51) that communicates with the open air. It is also conceivable to reduce the mobility of the grains (52) with an elastically deformable or fibrous element placed in the cavity (50). The separate grains (52) allow a quick and inexpensive realization of the ventilation device (5). To do this, they are simply poured into the cavity (50), before the assembly of the frame (4) on the front end of the tank (1).

An impact applied to the writing instrument or a dilation of the air present in the reservoir (1) causes the ink (11) contained in the reservoir (1) to spill. The amount of ink corresponding to this spill passes through the

ES 2 339 890 T3 or the holes (55) and penetrates into the cavity (50). It is distributed among the grains (52), in the interstices formed by adjacent grains. It is therefore retained in the cavity (50) under the effect of the capillary power that results specifically from the shape of the grains (52). The inventors have found that the angles and ridges on the surface of the grains (52) make it possible to obtain a spill-absorbing capacity that is particularly efficient, so that the ink does not reach the hole (51). Therefore, no ink leakage is observed, neither through the hole (51), nor at the level of the inking roller (3).

Advantageously, the external wall (53) of the cavity (50) can be transparent, or have a transparent window, to visualize the penetration of the ink (11) into the cavity (50). In this way an ink leakage from the hole (51) can be prevented. On the other hand, the hole (51) makes it possible to compensate for a depression in the reservoir (1) that appears when the ink (11) comes out of the writing tip, in the course of normal use of the writing instrument.

The ink (11) preferably has a low viscosity. In other words, ink (11) is liquid, as opposed to greasy inks whose viscosity is high. It may be an aqueous solvent ink, in particular, although the use of an alcoholic or other solvent ink is perfectly conceivable.

Figure 1b illustrates another possible embodiment of the invention, in which the cavity (50) is in communication with the reservoir (1) through the connector (2). In this other embodiment, the partition (54) separating the cavity (50) and the reservoir (1) is watertight, and the cavity (50) is open towards the connector (2), towards the center of the measuring instrument. writing. This opening may extend over the entire length of the cavity (50), parallel to the longitudinal direction of the writing instrument, or only for a part of this length. The cavity (50) is therefore limited, towards the center of the writing instrument, by the lateral surface (56) of the connector (2). This surface (56) is defined by the outer circumference of the fiber bundle of the connector (2), or by a film surrounding this bundle. In the latter case, the film is permeable to ink (11).

As in the previous embodiment, the cavity (50) is therefore delimited by a chamber (60) different from the reservoir (1) and in reduced communication with it due to the presence of the connector (2).

When the grains (52) are mineral grains, a capillary behavior of these grains with respect to the ink (11) in the cavity (50) is observed, which is even more favorable to obtain an efficient absorption of an ink spill. The material of the grains can be of the oxide or carbonate type. Alumina, particularly corundum type, silica, crushed glass, or calcium carbonate are grain materials for which satisfactory performance of the tank vent device has been observed. Furthermore, these materials are chemically inert with respect to the inks used.

Remarkable ink spill absorption performances have also been obtained with sand grains placed in the cavity (50). Sand is understood to be a powder essentially based on silica or calcium carbonate of natural origin. Various origins of sand have been tested, corresponding to various quarries. Satisfactory ink absorption performances have been obtained for controlled spillage, with natural sands of different origins. It appears, however, that for a given ink certain sand origins provide better results.

Figure 2 schematically reproduces a micrograph of such grains of sand (52). This micrograph has been made by means of scanning electron microscopy, with a magnification of x 100. The sharp edges are very visible, as are the angles between these edges. They are therefore angles and sharp edges of significant dimensions with respect to the apparent dimension (d) of the grain. These macroscopic sharp edges and angles are supposed to significantly and beneficially modify the fluid dynamics of the ink between the grains, including the physicochemical interactions between the ink and the grains.

The interstices between the grains (52) therefore constitute capillary spaces of volume and of highly variable shape due to the irregular shape of each of the grains. It seems that this improves the retention of eventual ink spills that may come from the reservoir (1), the narrow gaps slow down the spills and the larger gaps serve as a buffer reservoir.

It will be understood that it is the interstices between the grains (52) that constitute the volume of the cavity (50) capable of retaining the ink, since the grains (52) of sand have almost zero porosity with respect to the ink. However, it is not excluded to use grains that have sufficient porosity to contain a not negligible amount of ink in their pores. However, the penetration of the ink into these pores must be low due to their reduced dimensions with respect to the interstices. Non-porous grains are therefore preferred.

It will be observed that even in the case of porous grains, these must externally present sharp angles and edges of significant dimensions so that the capillary spaces between the grains fulfill their function, it being understood that the pore openings cannot constitute in themselves such angles and sharp edges. Likewise, microscopic defects or reliefs on the surface of rounded grains, or pearls, would not make it possible to obtain the same capillary effects of the grains and interstices with respect to the ink. Figure 3 is a typical sand grain size distribution diagram. This granulometric analysis has been carried out by means of a laser, using a commercially available apparatus. The horizontal axis indicates, in microns, the apparent dimension (d) of each grain, and the vertical axis indicates the fraction of the total volume of sand analyzed whose grains have the dimension indicated by the horizontal axis. The surface area between the curve and the horizontal axis therefore corresponds

ES 2 339 890 T3 at 100%. 95% of the grains of the sand sample corresponding to figure 3 have at least one dimension greater than 150pm. Simultaneously, 95% of the grains have at least one dimension less than 750 pm. The curve shows a maximum for the grain size of approximately 320 pm. This dimension, indicated as (d_m), is also approximately equal to the mean size of the grains, calculated for the whole sample of sand analyzed. Such dimensions are adapted so that a large number of grains are simultaneously contained in the cavity (50), which statistically guarantees an ink absorption and retention efficiency by the grains (52) that is reproducible. Furthermore, these grain dimensions are large enough to prevent some grains (52) from coming out through the hole (51). Likewise, these dimensions prevent some grains (52) from passing into the tank (1) through the hole (s) (55), or from entering the connector (2) through the lateral surface (56) thereof. In this way a possible obstruction of the connector (2) is avoided.

Sand grains having dimensions other than those indicated by Figure 3 have also given satisfactory ink spill absorption characteristics. However, the inventors have found that better characteristics are obtained when the mean dimension of the grains (d_m) is between 40 pm and 550 pm, and / or when 95% of the grains have a dimension (d) less than 800 pm, and / or when 95% of the grains have a dimension (d) greater than 0 , 5 pm, preferably greater than 150 pm.

On the other hand, it is preferable that the grains (52) that are contained in the cavity (50) have limited variations in dimension. Specifically, the individual dimension of the grains (d) varies preferably in a proportion lower than (10), for 95% of the grains. Such a granulometric characteristic makes it possible to prevent a large number of interstices between the larger grains from being filled by smaller grains. The ink capacity of the cavity (50), and therefore the absorption capacity of the reservoir ventilation device (5), is therefore higher. This also makes it possible to avoid stagnation or segregation of the grains (52) depending on their size, which will occur in the cavity (50) after a long period of immobility of the writing instrument. The device (5) therefore maintains constant efficiency as an ink buffer in the event of spillage, even in the event of a resumption of use of the writing instrument. Likewise, a granulometric distribution of the grains as a function of their respective dimensions that presents only a maximum threshold constitutes another criterion to ensure that the interstices between the grains form a sufficient free volume to accommodate the ink.

It will be appreciated that the natural sand that constitutes the grains (52) can be subjected to washing, for example to prevent dust or dirt particles from the grains from altering their capillary properties. However, treatments that modify the surface of the grains, such as chemical attacks or depositions, will preferably be excluded, given the satisfactory results obtained by the shape of the grains and the cost that such treatments could entail.

In the preferred embodiment described above, the cavity (50) contains only grains of the same nature and preferably of mineral material. However, it is not excluded that the cavity contains a fraction of grains of a different nature, for example of polymeric or metallic material, or even that it contains a fibrous element in particular to immobilize the grains.

The fact of filling the cavity (50) of the ventilation device (5) with a mineral material such as sand, which has a density higher than that of plastic materials, can significantly increase the weight of the instrument. This higher weight, compared to comparable instruments comprising a zigzag duct ventilation device, provides, in the opinion of some users, a better feel during handling. Furthermore, the inventors have found that with the annular cavity (50) located between the mount (4) and the ink tank (1), and when this cavity is filled with a heavy material, that is, the grains (52), the center of gravity of the writing instrument is located closer to the writing tip (3) than in the case of comparable previous writing instruments.

Greater comfort in handling and writing has been found when choosing the position and volume of the cavity (50), as well as the density of the material that fills it, so that the center of gravity is located in the area grip of the writing instrument, and more particularly when the center of gravity is located at a distance from the writing tip between 1/6 and 2/5 of the total length of the instrument in writing configuration, and specifically at approximately 1/3 of this length.

Obviously, it is possible to obtain this advantage, which is an advantage other than that provided by the use of grains with sharp edges for the tank ventilation device, using any type of heavy material, that is, whose density is significantly higher than those of the materials. plastic commonly used to make writing instruments. However, the fact of using a mineral granular material allows not only to obtain these two advantages, but this also facilitates the manufacture due to its fluid character, does not increase the cost excessively and does not pose any particular problem of pollution of the environment or recycled due to its inert nature. Therefore, it is more advantageous to obtain this positioning of the center of gravity with the help of a mineral granular material, such as sand, than with a metallic mass, for example of lead.

It is understood that the writing instrument described in detail above can be modified as long as it retains at least some of the advantages of the invention. In particular, the invention is not limited to its application to a writing instrument of the "rollerpen" type, and can be applied to other types of pens or markers.

ES 2 339 890 T3

References cited in memory

This list of references cited by the applicant is only intended to aid the reader and is not part of the European patent document. Even if the greatest care has been taken in its design, errors or omissions cannot be excluded and the OEB declines all responsibility in this regard.

Patent documents mentioned in the specification • US 4556336 A (0004) · US 20030231921 A (0005) • US 6474894 B (0004) · US 4588319 A (0007)