Coating implements with material supply – Material flows through porous tool – Wick feed from within reservoir to tool
Reexamination Certificate
2002-10-03
2003-11-11
Walczak, David J. (Department: 3751)
Coating implements with material supply
Material flows through porous tool
Wick feed from within reservoir to tool
C401S198000, C401S196000
Reexamination Certificate
active
06644880
ABSTRACT:
This invention concerns the field of writing articles, more particularly articles with a capillary writing tip which allows ink to be transferred from a reservoir, fibrous or otherwise, to the end of said tip which acts as a writing head.
The end of the writing tip, acting as a writing head, necessarily protrudes with respect to the body of the article which the user holds when writing. The ink used up on the writing medium is replaced by ink from the reservoir and transferred by capillary action to the writing tip. When the article is not used, a cap is screwed onto the body of the article such that it covers the writing tip in order to protect it against impact and to prevent it drying out. If the protruding end of the writing tip is left exposed to air, the ink solvent evaporates while the various constituents contained in the ink remain there. As a result of this, the writing tip can become clogged by ink constituents, causing problems when the article is reused, and may even render reuse impossible because of the insolubility of the constituents having caused clogging in the ink solvent, and this even if a substantial amount of ink remains in the reservoir.
To avoid this problem, manufacturers of writing articles attempt to increase the “cap-off time”, a term used to describe the length of time a writing article can be left with the cap off the tip without this leading to problems when the article is reused.
One solution has already been proposed. This consists in modifying the composition of the ink by adding an additive to delay drying, notably of the film-forming type. When the writing tip, saturated with ink, is exposed to air for a long period of time, the ink solvent evaporates and a skin or film forms over the surface of said tip as a result of the presence of this additive. This skin or film has very low mechanical resistance such that it is eliminated once the user applies the writing tip to the writing medium.
This solution substantially improves the length of time the tip can be left exposed to air. However, its application is somewhat problematic. The tip-drying phenomenon is, in fact, very important for articles where an alcohol-based solvent is used in the ink. Suitable film-forming substances are either not very soluble or not very dispersible in these solvents, such that when the article is assembled, it is generally necessary to heat the ink in order to dissolve or disperse the additive in an adequate manner.
The purpose of this application is therefore to propose a writing article which circumvents the aforesaid disadvantage by significantly increasing the length of time the writing tip can be exposed to air, without this having a negative effect on use of the article and without the need to alter the composition of the ink and/or usual operating conditions for assembling the article.
This objective is completely attained by the writing article of the invention which consists of ink in a reservoir, fibrous or otherwise, a drying retardant soluble or dispersible in the ink and a writing tip capable of transferring ink from the reservoir to the writing medium. Characteristically, a drying retardant is included in the writing tip and is carried along by the ink in the course of the latter's transfer through said tip. The term “drying retardant” as used in this application is not limited to a single agent as it also covers a mixture of several drying retardants.
When ink is being transferred to the writing tip, the drying retardant in the writing tip is carried along by the ink such that when said ink reaches the end of the tip acting as a writing head, the ink contains a sufficient amount of retardant to form, in the event of drying out by evaporation of the ink solvent, a skin or film at the surface of said writing tip, thus limiting further evaporation.
Preferably, the amount of drying retardant included in the writing tip depends on the ink's capacity to carry along said retardant, on the amount of ink in the reservoir and, possibly, the amount of drying retardant in the ink such that some drying retardant remains in the writing tip when the reservoir is empty. The aim of this is to obtain the desired result for the duration of the writing article's functional life. The ink contained in the reservoir can be completely devoid of drying retardant or it could contain a small amount of retardant, depending on the solubility of this retardant in the ink solvent at room temperature. The need to heat the ink during production of the article is thus avoided. Advantageously, this also avoids the need to incorporate too much retardant and makes it possible to use different retardants, for example a retardant that can be dispersed in the ink solvent in the ink reservoir or a retardant soluble in said solvent in the writing tip.
The choice of drying retardant is evidently dependent on the type of solvent used for the ink. Some agents are only compatible with water-based inks while others are only compatible with alcohol-based inks, and yet others are compatible with both types of solvent. An ink is called “water-based” (or alcohol based) when water (or alcohol) is the principal solvent, which does not exclude the use of smaller amounts of other solvents.
Drying retardants compatible with water-based inks include: N-phenyiurea, N-ethylurea, thiourea, ethylene thiourea, diethyleneglycol, propyleneglycol, polypropyleneglycol, a mixture of propylene glycol and polyglycol, sorbitol and glycerine.
Drying retardants compatible with inks based on alcohol solvents include: paraffin wax, carnauba wax, polyethylene wax, ethylene glycol, cetyl stearate, cetyl palmitate, stearyl stearate, Myristile myristate and, preferably, sorbitan esters (sorbitan monostearate).
Drying retardants compatible with both water-based and alcohol-based inks include beeswax and carnauba wax.
Another aim of the invention is to propose a process for the manufacture of the above-described writing article. This process consists of the following steps:
a) Continuous impregnation of a cylindrical element with high capillarity in a bath containing a specific amount of drying retardant such that uniform distribution in the transverse section of the element is obtained,
b) Drying the impregnated cylindrical element,
c) Sawing and machining.
Preferably, the bath consists of a concentrated solution of the drying retardant whereas the ink used in the writing article is an ink based on a solvent in which the drying retardant is only slightly soluble. It is thus possible, by using a concentrated impregnation bath, to incorporate a large amount of drying retardant in the cylindrical element which forms the writing tip. In the course of ink transfer in the writing tip, the ink carries along only a small amount of the drying retardant, as a function of the limit of solubility of this agent in the ink solvent.
In some cases, a high concentration of the drying retardant can increase the viscosity of the impregnation bath to such a degree that diffusion of the bath into the cylindrical element is particularly slow, if not limited, and it becomes difficult, under industrial conditions, to obtain uniform distribution of the bath throughout the transverse section of said element. If this is the case, the process according to the invention allows for a less concentrated bath to be used and the impregnation (a) and drying (b) steps are carried out until the desired amount of drying retardant is incorporated into the cylindrical element.
In a preferred embodiment, the drying agent incorporated into the writing tip is situated mainly at the edges of said tip. It has in fact been found that it is possible, in some cases, to considerably reduce the total amount of drying retardant used and still obtain the same efficacy.
A process is proposed for the manufacture of a writing tip which is specially designed to such that the drying retardant accumulates at the edges. This process consists of the following steps:
a) Impregnation of a previously machined writing tip in an impregnation bath containing a specific amou
Bedhome Vincent
Duez Jose
Conte
Walczak David J.
Weingarten Schurgin, Gagnebin & Lebovici LLP
LandOfFree
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