MXPA97002953A - A regulatory deposit for a writing instrument containing liquid ink and a writing instrument that includes this deposit - Google Patents

Abstract

The writing instrument (1) includes a reservoir (5) for liquid ink (8) and an opening that opens towards the inside of the reservoir (5) for the feeding tip (3) and a regulating reservoir (4) suitable for absorb the excess ink (8), in case the pressure in the tank (5) varies, and to return it subsequently, the deposit is implemented in the form of a compact block made of an open-pore material based on micro-accounts. According to the invention, the regulating tank (4) is composed of micro-accounts that are hydrophobic with respect to the ink and a small proportion of micro-accounts that are hydrophilic with respect to the ink, the mixture is uniform throughout the volume of the regulating deposit (4) or non-uniform, the proportion of micro-hydrophilic accounts being smaller, in the area that is immediately in contact with the excess ink, and greater in the area furthest away from it. The proportion of hydrophilic microbeads is preferably in the range of 2% to 10% with respect to the total weight of the regulatory deposit (

Description

A REGULATORY DEPOSIT FOR A WRITING INSTRUMENT THAT CONTAINS LIQUID INK AND A WRITING INSTRUMENT THAT INCLUDES THIS DEPOSIT BACKGROUND OF THE INVENTION The present invention relates to writing instruments that use liquid ink, that is, with writing instruments in which the ink is in a "free" state, that is, it is not held captive in a fiber deposit. . This writing instrument includes a reservoir for the ink and a feed tip for feeding the ink by capillarity from the reservoir to the appropriate writing head, which may be constituted by the end of the feeding tip. When the reservoir containing the ink is not isolated from the air, there is a variation in the conditions of use and, in particular, an increase in the pressure of the air contained in the reservoir due to the heating of the air, resulting in an operation Abnormal flow of ink through the feed tip and that can lead to stains or leaks when the top of the instrument is removed. To avoid this phenomenon, measures can be taken to equip this type of instrument with a regulating tank, whose function is to absorb the excess ink that comes from the tank P1181 / 97 X before it reaches the writing head, that is, before it reaches the attack end of the feed tip, whose end serves as a writing tip and, once it has returned to the conditions normal, return to the writing tip the ink it contains. In EP 0 516 538, the applicant had already proposed a writing instrument of this type, whose regulating tank was made of an open-pore hydrophobic material, and was made up of at least one compact block that fits tightly around the feed tip and that is coaxial with it. Preferably, the porous hydrophobic material is based on microbeads or microspheres, made, for example, of polypropylene. The regulating tank provided in EP 0 516 538 is satisfactory from the functional point of view, that is, it technically fulfills the functions of absorbing the excess ink that reaches the feed tip, when the pressure in the ink tank varies. , and subsequently returning the excess ink to the feed tip. Unfortunately, the applicant has observed that the effectiveness of the regulating tank decreases radially going outward from the area in which the regulating tank is in contact with P1181 / 97MX the feed tip. In other words, the ink diffuses easily from the feed tip to the buffer tank, in an area that is relatively close to the feed tip, which zone extends over a distance in the range of 2 mm to 4 mm depending on the case. The greater the distance from the feed tip, the more diffuse the diffusion of ink becomes and it becomes reduced to zero at a distance that is approximately in € 1 interval from 6 mm to 7 m. Since the function of the regulating tank is to be able to absorb the excess ink due to a variation in the pressure of the ink tank, it will be understood that the working volume of the regulating tank is a function of the maximum volume of excess ink that can be result of such variation. The volume of excess ink is a function, in particular, of the volume of air contained in the liquid ink reservoir, since there is generally an increase in the temperature of the air contained in the liquid ink reservoir causing the pressure variation that causes excess ink in the feed tip. The smaller the amount of ink remaining in the tank, the greater the amount of air contained therein and the greater the amount of excess ink for the same temperature increase. P1181 / 97MX The problem that the Applicant has observed, normally leads either to the supply of a regulating tank that is very long, that is, that has a large surface area in contact with the feed tip or that the capacity of the tank Liquid ink is limited.

SUMMARY OF THE INVENTION An objective of the applicant is to provide a regulatory deposit that reduces the aforementioned drawbacks. This objective is achieved very well by means of the regulating reservoir of the invention and which, in the manner described in EP 0 516 538, is a regulating reservoir for a writing instrument containing liquid ink, the writing instrument includes a reservoir for liquid ink and an opening that opens into the reservoir and where the feeding tip is adjusted, the regulating reservoir is suitable for absorbing the excess ink, in case the pressure in the reservoir varies, and to return it subsequently, and is implemented in the form of a compact block made of an open-pore material based on micro-accounts. Characteristically, according to the invention, the buffer tank is made of micro-beads that are hydrophobic with respect to the ink and P1181 / 97MX a small proportion of micro-accounts that are hydrophilic with respect to ink. In the present text, the notions of hydrophilic or hydrophobic are related to the notions that are related to the type of ink, in particular, its viscosity and its surface tension. A porous material through which a given ink diffuses naturally under normal conditions of use is considered to be hydrophilic with respect to the ink - and even when the ink does not have water as a solvent. It is considered that a porous material through which the given ink does not diffuse under normal conditions of use is hydrophobic with respect thereto. A given material can be hydrophobic for a given ink and hydrophilic for another ink. For example, polypropylene is hydrophobic for an aqueous ink without any additive capable of modifying its surface tension and hydrophilic for an ink of the type having alcohol as a solvent. However, the principle of the regulating deposit is that the excess ink can diffuse through the hydrophobic material when the conditions of use are modified, in particular, by an abnormal increase in pressure. Unexpectedly, the presence of a small proportion of hydrophilic micro-accounts between the hydrophobic micro-accounts facilitates the diffusion of the ink through the entire volume of the regulating deposit, P1181 / 97MX well beyond the peripheral zone that is in direct contact with the ink, in particular on the surface of the feed tip. The applicant believes that it is difficult for the ink to diffuse through the mesh constituted by the hydrophobic microbeads of the regulating tank, due to the loss of pressure which increases with increasing radial distance from the periphery of the feed tip. The local arrangement or location of the hydrophilic microbeads on the trajectory followed by the ink through the mesh of hydrophobic microbeads allows the ink to reach hydrophobic sites that would be inaccessible in the case of a regulatory deposit made exclusively of hydrophobic microbeads. The presence of hydrophobic and hydrophilic microbeads can result in a mixture that is uniform throughout the volume of the buffer reservoir. It can also be a non-uniform mixture, the proportion of hydrophilic microbeads in the area being immediately in contact with the excess ink and being greater in the area furthest away from it. On average, the proportion of hydrophilic micro-accounts is in the range of 2% to 10% in relation to the total weight of the regulatory deposit. In a preferred embodiment, the mixture is a P1181 / 97MX uniform mixture, of which 95% is made up of hydrophobic micro-accounts and 5% is made up of hydrophilic micro-accounts.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood with the reading of the following description that refers to a modality of a writing instrument that contains liquid ink and that includes a regulating deposit composed of hydrophobic microbeads and a small proportion of hydrophilic microbeads. . This embodiment is shown in the accompanying drawings, in which: Figure 1 is a diagrammatic section in longitudinal section through a writing instrument; and Figure 2 is a diagrammatic cross-sectional view of line II-II of Figure 1.

DESCRIPTION OF THE PREFERRED MODALITY The writing instrument 1 shown in the Figure 1 complies with the teachings of EP 0 516 538 of the applicant. Includes a body 2, a feed tip 3 and a regulating tank .4. The rear portion of the body 2 constitutes a reservoir 5 for liquid ink, this reservoir is closed by a partition Internal P1181 / 97MX 6; the leading end 3b constitutes the writing tip and extends outwardly from the body 2 through a central hole 7. The regulating tank 4 is suitable for absorbing, by capillarity, € -1 excess ink coming from the feed tip 3 , when the pressure in the tank 5 varies, and to subsequently return the excess ink to the feed tip. The regulating tank is made of a material having open pores and is based on micro-accounts and is in the form of a compact block that fits snugly around the feed tip 3 and is coaxial with it. In this writing instrument 1, the ink 8 coming from the reservoir 5 is consumed in the writing tip 3b as the writing instrument is used and the ink is being replaced by air that can flow freely between the surroundings and the reservoir 5, due to the natural porosity of the feeding tip 3, but also due to a communication hole 9 which is provided in the central hole 7, through which the writing tip 3b passes, because there is an empty space 10 around the regulating tank 4. The regulating tank 4 is a compact and porous block based on micro-accounts of which its quality, grain size, distribution, molecular weight and P1181 / 97MX morphology. As taught in EP 0 516 538, the compact block can be obtained by thermally melting a mixture of micro beads of at least two thermoplastic materials of different qualities, ie two materials having different melting points. Once the microbeads have been uniformly mixed in a suitable mold, they are heated to a given temperature which is higher than the melting point of the material of the first type and lower than the melting point of the second type material. In this way, the material of the microcuentae of the first type melts, thus creating, in the first place, microcavities corresponding to the open pores and, secondly, joining all the micro-accounts of the materials of the second type. This modality is not limitative. In particular, the compact block can be obtained using microbeads of a single thermoplastic material only by sintering, the capillary mesh is constituted by the interstices between the microbeads, after they have been locally melted and bonded. Under normal conditions of use, the ink 8 which is contained in the reservoir 5 and which is in contact with the carrying end 3a of the feeding tip 3, is absorbed and migrates by capillary action towards the feeding tip 3 until it reaches the Attack end 3b P1181 / 97MX the same. The ink consumed by the leading end 3b and serving as a writing head is replaced by ink 8 coming from the reservoir 5 as it is consumed. In the tank 5, the ink that diffuses towards the feed tip 3 is replaced by air coming from the inside of the body 2. The pressure balance is thus established between the air contained in the tank 5 and the air contained in the rest of the body 2. Under abnormal conditions of use, due, in particular, to an increase in pressure in the reservoir 5, for example, when the instrument 1 is heated, the excess ink 8 flows from the reservoir 5 towards the feeding tip 3. Due to the presence of the regulating tank 4, the excess ink does not reach the writing tip 3b. The excess ink is diffused by capillarity towards the regulating tank 4, in contact with the capillary tubes of the feed tip 3, until the balance or pressure equilibrium is restored. Then, when reusing the instrument 1, the ink consumed by the writing head 3b preferably comes from the regulating reservoir 4. The regulating reservoir 4 must be able to accept all the excess ink that can flow from the feed tip 3, in the case of an abnormal increase in pressure inside the tank 5. This storage capacity P1181 / 97MX is a function of the capacity of the liquid ink reservoir 5, the excess is at a maximum when the ink reservoir contains a large proportion of air that tends to expand considerably, in case the temperature increases of the instrument 1. Given the proportion of air in the porous and compact block that constitutes the regulating tank 4, theoretically it is possible to make calculations to define the ideal volume necessary for the regulating deposit of a given writing instrument. Unfortunately, the applicant has observed that, depending on the configuration of the regulating tank 4, the ideal volume is not always sufficient to absorb all the excess ink since the regulating deposit is not always fully saturated because the ink is unable to diffuse radially. beyond a certain distance from the face that is in contact with the feed tip 3. This distance is a function of the type of ink 8, in particular, its surface tension and its viscosity and also the structure of the buffer tank 4. In certain cases, the distance that is genuinely effective, that is, the distance over which the regulating tank is saturated, may be limited to the range of 2 mm to 3 mm. To solve this problem, it could be P1181 / 97MX increase the surface area of the regulating tank 4 which is in immediate contact with the ink. However, it would be necessary to modify the structure of the deposit 4, increasing, for example, its length for a given ideal volume. This modification in the structure would require that, in accordance with this, the configuration of the instrument be modified. The invention solves the problem mentioned above by forming the regulatory deposit 4 from micro-accounts, using hydrophobic micro-accounts and a small proportion of hydrophilic micro-accounts, where the concepts 'hydrophobic' and 'hydrophilic' are understood in accordance with the particular definition provided before. The presence of the small proportion of hydrophilic micro-accounts facilitates the diffusion of the ink throughout the volume of the regulating deposit. The polyethylene microbeads have an average diameter that falls in the range of 25 μm to 250 μm, the proportion of suitable hydrophilic polyethylene to achieve the above technical effect is in the range of 2% to 10% of all the micro-accounts that constitute the regulatory deposit. To manufacture the regulating tank 4, most of the micro accounts that are used are hydrophobic and a P1181 / 97MX small proportion of them are hydrophilic. It causes the micro accounts to be hydrophobic or hydrophilic as a function of the type of ink used, either by appropriately selecting the materials from which they are made or by pretreating them appropriately, for example by treating them with a plasma containing fluorine to make them hydrophobic or by subjecting them to an oxidation treatment to make them hydrophilic or depositing a surfactant agent to bring the surface energy of the material to a determined value as a function of the desired property; that is, the hydrophilic property or the hydrophobic property. In one embodiment, the hydrophobic micro-accounts and the hydrophilic micro-accounts are mixed uniformly throughout the volume of the buffer reservoir. In a particular example, in which an aqueous ink and polyethylene microbeads having an average diameter of about 140 μm were used, the mixture contained 95% hydrophobic microbeads and 5% hydrophilic microbeads. The regulating tank had a cylindrical shape and approximately 12.5 mm, the feed tip located or axially disposed in the regulating tank had a diameter of approximately 5 mm. By cyclically raising, during use, the temperature of the instrument to high temperatures such as those in the range of 50 ° C to P1181 / 97MX 55 ° C, the entire volume of the regulating tank was completely saturated at the end of a cycle, when the ink tank 5 was almost empty. It should be emphasized that if the proportion of hydrophilic micro accounts increases, the regulatory deposit behaves as if it were made of a completely hydrophilic material. In other words, the ink diffuses through the material in question even if the conditions of use are normal conditions. Obviously, this is not the technical function that is desired for the regulatory deposit. The regulating tank must absorb and return the excess ink, which results from abnormal conditions of use, and must not act as a storage medium in which the ink is stored in addition to being stored in the liquid ink tank. For the cases examined by the applicant, the maximum percentage of micro-accounts that allows the desired effect of improving ink migration to be obtained was approximately 10%. This ratio can change as a function of the type of ink and the type and size of the micro accounts. Therefore, it should be allowed for a person skilled in the art to accurately determine, as a function of these parameters, the optimum proportion that will be chosen for hydrophilic micro-accounts in relation to all micro-accounts.

P1181 / 97MX used to form the regulating tank. As previously emphasized, the diffusion of the ink 8 from the face in contact with the feed tip 3 slows down due to the existence of a loss of pressure in the capillary mesh of the buffer reservoir 4. However, the diffusion is very good in the area immediately in contact with the ink. Therefore, in this area, it would be possible to use only hydrophobic micro-accounts or, optionally, an even smaller proportion of hydrophilic micro-accounts. In other words, it would be possible to cause the proportion of hydrophilic microbeads to vary continuously or discontinuously from the area immediately in contact with the ink to the area that is much further away than the area. When this variation is discontinuous, the regulating deposit may then be in the form of annular elements that nest within one another, the outer annular element having the highest proportion of hydrophilic micro-accounts. Figure 2 shows a regulating tank 4 that is made of three successive elements 4 ', 4"and 4" 1 nested one inside the other and where the proportion of hydrophilic microbeads is respectively 2% for more internal element 4', 6 % for intermediate element 4", and 10% for outermost element 4" '. P1181 / 97MX The present invention is not limited to the modality described above by way of non-exhaustive example. In particular, the choice of the micro accounts involved in the composition of the regulatory deposit is determined as a function of the desired properties. These can be made of polyethylene, as in the aforementioned example, or they can be made of other materials such as, in particular, polypropylene. Hydrophilic micro-accounts can be made of a material that is different from the material of the hydrophobic micro-accounts. In addition, it may be advantageous to choose micro-accounts having different dimensions, or even different amounts of hydrophobic micro-accounts and / or hydrophilic micro-accounts may be chosen. These differences in the dimensions and also the differences in the melting point, if the qualities are different, affect the capillary properties of the resulting regulating deposit. The wide variety of parameters that may be involved in the implementation of the regulatory deposit broadens the possibilities offered to a person skilled in the art.

P1181 / 97MX

Claims (8)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A regulatory deposit for a writing instrument containing a liquid ink, the instrument of writing includes a reservoir for liquid ink and an opening for the feed tip that opens into the reservoir, the regulating reservoir is suitable for absorbing the excess ink, in case the pressure in the reservoir varies, and for return it subsequently; the tank is implemented in the form of a compact block made of an open-pore material based on micro-accounts, the buffer tank is characterized in that it is made of micro-accounts that are hydrophobic with respect to the ink and a small proportion of micro-accounts that are hydrophilic with respect to the ink. to the ink.
2. 2. A regulating tank according to claim 1, characterized in that the hydrophobic microbeads and the hydrophilic microbeads are distributed in a mixture that is uniform throughout the volume of the regulating tank.
3. 3. A regulating tank according to claim 1, characterized in that the micro-accounts P1181 / 97 X hydrophobic and hydrophilic microbeads are distributed in a mixture that is not uniform, the proportion of hydrophilic microbeads is smaller in the area that is immediately in contact with the excess ink and is greater in the area that is furthest away Of the same.
4. 4. A regulating tank according to claim 3, characterized in that it is made of annular elements nested together, the proportion of hydrophilic microbeads is smaller in the element that is more immediately in contact with the excess of ink, and is larger in the element that is furthest from it.
5. A regulating tank according to any of claims 1 to 4, characterized in that the proportion of hydrophilic microbeads is in the range of 2% to 10% with respect to the total weight of the regulating deposit.
6. 6. A regulating tank according to claim 2, characterized in that 95% of the uniform mixture consists of hydrophobic microbeads and 5% of the uniform mixture consists of hydrophilic microbeads.
7. 7. A regulating tank according to any of claims 1 to 6, characterized in that the P1181 / 97MX hydrophilic micro-accounts are made of a different material and / or have different dimensions and / or have a different quality than the hydrophobic micro-accounts.
8. 8. A writing instrument including a reservoir for liquid ink, an opening that opens into the feed tip in the reservoir and a regulator reservoir, according to any of claims 1 to 7, the regulating reservoir is adjusted to tightly around the feed tip and is coaxial with it. P11T1 / 97MX