Writing instruments having a selectively permeable barrier and methods of use thereof

Abstract

Writing instruments with a selectively permeable barrier and methods of use thereof are provided that enable a user to use the writing instrument in environments having low ambient air pressure, such as at high altitudes or in environments that have high ambient temperatures. The selectively permeable barrier is located such that at least a portion of the selectively permeable barrier is exposed to the ambient environment. The selectively permeable barrier allows flow of air from the ambient environment into the ink tank of the writing instrument but prevents the flow of ink from the ink tank to the outside of the writing instrument via the selectively permeable barrier. The selectively permeable barrier acts as the sole ink flow control mechanism and the writing instrument does not have any other ink flow control mechanism.

Description

34757-2905WRITING INSTRUMENTS HAVING A SELECTIVELY PERMEABLE BARRIERAND METHODS OF USE THEREOFCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Indian Patent Application No. 202411060290, filed August 9, 2024, which is incorporated by reference herein.TECHNICAL FIELD

[0002] The present disclosure relates generally to writing instruments, and more specifically, to writing instruments having a selectively permeable barrier that is used for ink flow control.BACKGROUND

[0003] Writing instruments, and specifically pens, have been in widespread use for hundreds of years, with the modem ballpoint pen dating to the 1940s. Pens are typically writing instruments with an internal ink reservoir that dispenses ink on a writing surface as the pen makes contact with a substrate. Pens use various dispensing designs and inks to create a controlled ink output that does not leak ink when the pen is not in use. Ballpoint pens are commonly used, combining the internal reservoir with a dispensing tip that includes a roller ball to dispense the ink on a writing medium.

[0004] To further prevent the inadvertent dispensing of ink, pens routinely come with a cap or cover to protect the dispensing tip and prevent inadvertent activation of the roller ball. Alternatively, some pens utilize a retractable tip that withdraws the dispensing tip into the body of the pen w hen the pen is not in use. The conventional pens often use an airflow control system, commonly known as a lamella, to ensure flow of air into the ink reservoir to replace the ink being dispensed onto the paper. However, such pens are prone to ink leakage at higher altitudes and / or environments with high ambient temperatures. Accordingly, a need exists for a pen that will perform reliably even at high altitudes and in high ambient temperatures for a variety of ink types and configurations.SUMMARY

[0005] The present invention provides systems and methods for writing which comprise a selectively permeable barrier system that addresses the limitations of prior art34757-2905 systems. The instruments of the present invention comprise a barrier coupled to an end of an ink tank opposite to a tip adaptor, wherein the barrier is configured to selectively allow entry of ambient air into the ink tank and prevent ink from passing through it. In some embodiments, the barrier is permeable to air at ambient air pressures below 0.7 bar.Typically, the writing system does not include other ink flow control mechanisms, and in particular the system typically does not include a lamellar air flow channel. In some embodiments, the barrier is minimally flexible and does not allow a bellows-like flex. In some embodiments, the membrane is comprised of ePTFE material.

[0006] Embodiments of the present disclosure provide writing instruments that overcome the above disadvantages of the conventional writing instruments and perform optimally in environments with low pressure and / or environments having a high ambient temperature. An embodiment of the present disclosure provides a writing instrument that eliminates the use of the traditional ink flow controller and replaces that with a minimally flexible, selectively permeable barrier that allows the flow of air into the ink tank but prevents ink from leaking out of the ink tank in low pressure and high temperature environments.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 A illustrates an exploded view of a conventional writing instrument in accordance with the principles of the present disclosure.

[0008] FIG. IB illustrates a close-up view of a conventional ink flow control component in accordance w ith the principles of the present disclosure.

[0009] FIG. 2 show s a graph illustrating operation of a writing instrument in accordance with the principles of the present disclosure.

[0010] FIG. 3 illustrates a selectively permeable barrier in accordance with the principles of the present disclosure.

[0011] FIG. 4 illustrates a structure of the selectively permeable barrier in accordance with the principles of the present disclosure.

[0012] FIG. 5 illustrates an exploded view of a w riting instrument in accordance with the principles of the present disclosure.

[0013] FIG. 6A is a perspective view of a barrier plug for a writing instrument in accordance with the principles of the present disclosure.34757-2905

[0014] FIG. 6B is a top view of the barrier plug for a writing instrument in accordance with the principles of the present disclosure.

[0015] FIG. 7 illustrates a portion of a writing instrument including the selectively permeable barrier in accordance with the principles of the present disclosure.

[0016] FIG. 8 illustrates an exploded view of another writing instrument having the selectively permeable barrier in accordance with the principles of the present disclosure.

[0017] FIG. 9 illustrates yet another writing instrument with the selectively permeable barrier in accordance with the principles of the present disclosure.

[0018] FIG. 10. illustrates an exploded view of another writing instrument having the selectively permeable barrier in accordance with the principles of the present disclosure.

[0019] FIG. 11 illustrates portion of a writing instrument having a selectively permeable barrier in accordance with the principles of the present disclosure.

[0020] FIG. 12 illustrates the operation of a writing instrument in accordance with the principles of the present disclosure.

[0021] The drawings are provided for purposes of illustration only and merely depict example embodiments of the disclosure. The drawings are provided to facilitate understanding of the disclosure and shall not be deemed to limit the breadth, scope, or applicability of the disclosure. The use of the same reference numerals indicates similar, but not necessarily the same or identical components. Different reference numerals may be used to identify similar components. Various embodiments may utilize elements or components other than those illustrated in the drawings, and some elements and / or components may not be present in various embodiments. The use of singular terminology to describe a component or element may, depending on the context, encompass a plural number of such components or elements and vice versa.DETAILED DESCRIPTION

[0022] The various writing instruments described herein advantageously can accommodate various inks and writing mediums. The present disclosure includes nonlimiting embodiments of writing instruments having a selectively permeable barrier or a semi-permeable barrier, referred to generally herein as “writing instruments." The embodiments are described in detail herein to enable one of ordinary skill in the art to practice the writing instruments having a selectively permeable barrier, although it is to be understood that other embodiments may be utilized and that logical changes may be made34757-2905 without departing from the scope of the disclosure. Reference is made herein to the accompanying drawings illustrating some embodiments of the disclosure, in which use of the same reference numerals indicates similar or identical items. Throughout the disclosure, depending on the context, singular and plural terminology may be used interchangeably.

[0023] The meanings of the terms used herein will be apparent to one of ordinary skill in the art or will become apparent to one of ordinary skill in the art upon review of the detailed description when taken in conjunction with the several drawings and the appended claims.

[0024] Embodiments of the present disclosure include a writing instrument that comprises an ink tank that has a first end and an opposing second end. The writing instrument includes an adaptor that is coupled to the first end of the ink tank. The writing instrument further includes a tip adapter that is coupled to the adapter and a tip that is coupled to the tip adapter. The writing instrument further includes a selectively permeable barrier that may be coupled to the second end of the ink tank. In an embodiment, at least a portion of the selectively permeable barrier may be exposed to an external environment of the writing instrument. Further, the selectively permeable barrier may be configured to selectively allow entry of ambient air into the ink tank and prevent ink from passing through it. In an embodiment, the selectively permeable barrier may be made from a fluoropolymer material such as enhanced polytetrafluroethylene (ePTFE) material. In an embodiment, the selectively permeable barrier may be air permeable at ambient air pressures below 0.7 bar and the writing instrument does not include any other ink flow control mechanism other than the selectively permeable barrier. In some embodiments, the writing system does not include an air slit or lamella in line with the ink. In certain embodiments, the selectively permeable material does not flex in response to air pressure changes at atmospheric pressure. In an embodiment, the selectively permeable barrier may have a density of between 0.2 to 2.2 grams / cc and may be impermeable to liquids having a viscosity of 1 cps or more. In another embodiment, the selectively permeable barrier may be further impermeable to the liquids at an ambient air pressure of at or below 0.7 bar. In a further embodiment, the first end of the ink tank has a first diameter and the second end of the ink tank has a second diameter, wherein the second diameter is smaller than the first diameter.34757-2905

[0025] Other embodiments of the present disclosure provide a writing instrument that includes an ink tank that has a first end and an opposing second end. The second end of the ink tank is closed. The writing instrument also includes a writing tip that is coupled to the first end and a selectively permeable barrier coupled to a portion of a surface of the ink tank. At least a portion of the selectively permeable barrier is exposed to an ambient environment outside the writing instrument and the selectively permeable barrier is configured to allow ambient air to enter the ink tank and prevent flow of ink from the ink tank through the selectively permeable barrier. In an embodiment, the selectively permeable barrier may be disposed in a barrier housing and the barrier housing is integrated into the ink tank. In another embodiment, the writing instrument does not include any other ink flow control mechanism. The selectively permeable barrier is air permeable at or below an ambient air pressure of 0.7 bar and may be located closer to the second end of the writing instrument. In an embodiment, the selectively permeable barrier may be made using an enhanced polytetrafluroethylene (ePTFE) material.

[0026] In yet another embodiment, a writing instrument is provided that has an ink tank enclosure. An ink tank is partially disposed within the ink tank enclosure and a first portion of the ink tank is located outside the ink tank enclosure. The first portion of the ink tank has a first end. An adapter coupled to the first end of the ink tank and a tip is coupled to the adapter. The writing instrument also includes a selectively permeable barrier that is coupled to the ink tank. At least a portion of the selectively permeable barrier is exposed to ambient environment outside the writing instrument and the selectively permeable barrier is configured to allow ambient air to enter the ink tank via the selectively permeable barrier and prevent ink from the ink tank from flowing out through the selectively permeable barrier. In an embodiment, the selectively permeable barrier is coupled to an end of the ink tank enclosure. In another embodiment, the selectively permeable barrier is coupled to a surface of the first portion of the ink tank. The selectively permeable barrier may have a density of betw een 0.2 grams / cc to 2.2 grams / cc and may be made from an enhanced polytetrafluroethylene (ePTFE) material. In certain embodiments, a viscosity of ink in the ink tank may be betw een leps and 10 cps.

[0027] The present disclosure provides details on a few types of writing instruments, but one skilled in the art will realize that other types of writing instruments may also be manufactured using the systems and methods provided in this disclosure.34757-2905

[0028] FTG. 1 A illustrates one type of a conventional writing instrument 100. The writing instrument 100 includes an ink tank 102. The ink tank 102 acts as a reservoir for storing ink associated with the writing instrument 100. The ink used in writing instrument 100 can be of various types. For example, ink used in a ballpoint pen may be a low- viscosity, oil-based ink that flows easily and dries quickly. Fountain pens on the other hand may either use dye-based or pigment-based ink. Dye-based inks are highly water soluble and flow easily, but are prone to spills. Pigment-based inks may be water resistant or waterproof, but they need more frequent cleaning to prevent the ink from drying out or clogging the feed. Another type of ink in common use is a water-based gel ink that flows freely and is resistant to smudging. Writing instruments like marker pens may use pigment, water, oil, or alcohol-based inks depending on the medium (paper vs non-paper media) on which the pen is being used. The writing instrument 100 may use a low viscosity ink in the range of 1 to 10 centipoise (cps). Writing instruments that use such low viscosity inks are generally referred to a free flow ink writing systems.

[0029] The writing instrument 100 also includes a candle filter 104 suspended in the ink tank 102. The candle filter 104 is a rigid, porous barrier made of fibers such as Nylon. The candle filter 104 removes fine particulate matter from the ink by trapping contaminants and allows clean ink to flow to the other parts of the writing instrument 100 for depositing on a writing medium such as paper. The candle filter 104 is attached to an ink flow controller 106. The ink flow controller 106 is commonly referred to as a lamella in the art. In operation, the ink flow controller 106 allows air to enter the ink tank 102 as the ink from the ink tank 106 is dispensed onto a writing medium. The ink flow controller 106 ensures constant flow" of ink to a w riting tip of the w riting instrument 100 while maintaining the pressure inside the ink tank 102. The ink flow controller 106 is usually made of plastic or other synthetic material. The ink flow controller 106 usually occupies a significant portion of the writing instrument 100 and is a major cost component of the writing system 100.

[0030] The waiting instrument 100 further includes a tip adapter 108. The tip adapter 108 acts as a conduit betw een the ink flow controller 106 and a writing tip 110. The ink flow controller 106 is designed to balance the flow of air into the ink tank 102 and is usually larger in size and diameter than the w riting tip 110. In order for the writing tip 110 to receive a constant flow' and the right amount of ink, the flow of ink needs to be controlled precisely. The tip adapter 108 helps to control the flow of ink from the ink flow34757-2905 controller 106. In addition, the physical design of the tip adapter 108 is such that it bridges the difference in the sizes of the ink flow controller 106 and the writing tip 110. In one instance, the tip adapter 108 may reduce the available diameter between the ink flow controller 106 and the writing tip 110 thereby controlling or reducing the flow of ink as well as providing a robust physical connection between the writing tip 1 10 and the ink flow controller 106. The tip adapter 108 may be made of any suitable material such as plastic or metal. The writing tip 110 is connected to the tip adapter 108. The writing tip 110 is usually the portion of the writing instrument 100 that makes contact with the writing medium, such as a paper. The writing tip 110 may include a ball bearing that rolls along the surface of the writing medium as ink is dispensed onto the writing medium. The writing tip 100 is usually made of metal, but can also be made from non-metallic materials, such as in dry erase markers. The writing instrument 100 may also include a cap (not shown) that protects the writing tip 110 when the writing instrument 100 is not in use such as when being stored or transported.

[0031] FIG. IB illustrates a close-up view of the ink flow controller 106. The ink flow controller 106 includes an opening 116 that runs along the entire length of the length of the ink flow controller 106. In operation, the ink from the ink tank 102 flows through the opening 116 and towards the wnting tip 110. The ink flow controller 106 includes a channel 112 that may run for at least a portion along the length of the ink flow controller. The channel 112 keeps the ink tank 102 in fluid communication with an external environment of the writing instrument 100. In operation, as ink is dispensed from the ink tank 102, air enters the ink tank 102 via the channel 112 in the ink flow controller 106. The air replaces the ink being displaced so as to maintain the pressure inside the ink tank 102.

[0032] FIG. 2 illustrates a graph showing the pressure change within the ink tank 102 over time as ink is dispensed via the writing tip 110. As a user starts writing with the writing instrument 100, ink is dispensed on the writing medium. As the ink is dispensed from the ink tank 102 to the writing tip 110, the pressure inside the ink tank drops gradually over time as the ink tank 102 acts as a closed system. This drop in pressure is illustrated between t=0 and t=l 0 seconds in FIG. 2. As the pressure drops in the ink tank 102. the flow of ink can be restricted. In order to maintain the flow of ink. air from the ambient environment outside of the writing instrument 100 enters the ink tank 102 via the channel 112 of the ink flow controller 106. As the air enters the ink tank 102, the pressure34757-2905 inside the ink tank 102 rises to about the atmospheric pressure, such as 1 bar, thereby continuing the flow of ink to the writing tip 110. This cycle of pressure drop and pressure increase continues until the user keeps writing or until all the ink in the ink tank 102 is dispensed.

[0033] The writing instrument 100 thus allows free flow of ink to the writing tip 110 ensuring an uninterrupted writing experience for the user. While the writing instrument 100 works well in most conditions, its performance is affected in environments where the ambient pressure is low or in environments where the ambient temperature is high. For example, in environments where the ambient pressure is lower, such at altitudes of 9000 feet or higher, ink from the ink tank 102 can leak outside the writing instrument 100 even when the writing instrument 100 is not being used. In this instance, the ink flows out of the ink tank 102 into the ink flow controller 106 but does not reach the writing tip 110. This causes the ink flow controller 106 to get saturated with the ink and the ink then eventually leaks out of the ink flow controller 106, via the channel 112, to the outside of the writing instrument 100. This reduces the life span of the writing instrument 100 and may also affect the writing quality7.

[0034] In another instance, when the ambient temperature of the environment is high, such as 45 °C or higher, the ink in the ink tank 102 expands since the ink has low viscosity. Since the ink tank 102 has limited volume, the expanded ink in the ink tank 102 has nowhere to go. The ink then leaks into the ink flow controller 106. Over time, as the ink flow controller 106 gets saturated by the ink, the ink eventually leaks out of the ink flow controller 106. via the channel 112, out of the writing instrument 100 and into the external environment. This may cause premature failure of the writing instrument 100 as the ink present in the ink flow controller dries and blocks free flow of ink through the opening 116 of the ink flow controller 106. Thus it is desirable to create a writing instrument that overcomes the above disadvantages of the conventional writing instrument 100.

[0035] Some alternatives for writing instruments have been proposed to prevent such leakage of ink in high altitude, low pressure and / or high temperature environments. One solution is to use a reservoir based system without the use of an ink flow controller. In such a writing instrument, the ink is stored in a foam-based reservoir instead of an ink tank. Since this writing instrument does not need an ink flow controller, the possibility of the ink leaking out of the reservoir is eliminated or reduced significantly. However, such34757-2905 reservoir-based writing instruments usually leave a lot of the ink unused reducing the lifespan of the writing instrument and increasing the costs for the consumers. In some instances, upwards of 50% of the ink may go unused if the writing instrument is left unused for long periods of time as the ink in the reservoir may dry and / or evaporate depending on the ambient temperature and pressure. Thus, such a reservoir-based writing instrument is not an ideal solution.

[0036] Another alternative would be to increase the viscosity' of the ink to avoid the ink leaking out and / or expanding based on the ambient temperature and / or the pressure. For example, the viscosity of the ink can be increased by adding gels or gums into the ink formulation. While this may reduce the likelihood of the ink leaking and / or expanding, a higher viscosity' gel -based ink usually needs a high laydown for an optimal writing performance. Laydown refers to the amount of ink needed for 100 meters of writing distance. For example, a water-based free flowing roller ball ink writing instrument may operate for up to 2000 meters of writing distance while a similar gel-ink based writing instrument may struggle to cross 400 meters of writing distance. Thus increasing the viscosity' of the ink greatly affects the lifespan of the w riting instrument and consequently results in higher costs for users. Thus, even a writing instrument having a gel-based ink is not an ideal solution for high altitude and / or high temperature environments.

[0037] Another method that has been proposed to avoid the use of a lamella-based ink flow control is use of a flexible barrier that adjusts for the pressure difference in the ink tank by flexing. However, the flexing of the barrier creates a “bellows” effect that impedes constant flow of ink. In most instances, the flexing of the barrier is not fast enough resulting in an inconsistent flow of ink to the w riting tip. This results in a “start and stop” effect where ink will suddenly stop flowing for a time period and restart flowing, depending on the flexing speed of the barrier. This is highly undesirable since it results in an inconsistent writing performance. Moreover, the bellows effect is more pronounced at higher altitudes further degrading the w riting performance of such a writing instrument.

[0038] Embodiments of the present disclosure provide w riting instruments that overcome the above disadvantages of the conventional w riting instruments and perform optimally in environments with low pressure and / or environments having a high ambient temperature. An embodiment of the present disclosure provides a writing instrument that eliminates the use of the traditional ink flow controller 106 and replaces that with a minimally flexible, selectively permeable barrier that allow s the flow' of air into the ink34757-2905 tank but prevents ink from leaking out of the ink tank in low pressure and high temperature environments.

[0039] FIG. 3 illustrates a selectively permeable barrier 300 that can be used in a writing instrument. In an embodiment, the selectively permeable barrier 300 can be made from a fluoropolymer material like enhanced polytetrafluroethylene (ePTFE).. The, ePTFE material is microporous and air-permeable. The ePTFE material is also chemical resistant to most chemicals and repels liquids such as water, ink and the like. Further, the ePTFE material has a low dielectric constant (e.g., in the range of 2.00 to 2. 10). Moreover, the density and porosity of the selectively permeable barrier 300 can be customized based on the application. Fig. 4 illustrates a close-up view of the structure of the selectively permeable barrier 300. The selectively permeable barrier has a porous structure having a plurality of pores 302. The size and amount of pores 302 can be customized based on the application. In addition, the distribution of the pores 302 over the surface area of the selectively permeable barrier 300 can be controlled. In an embodiment, the pores 302 are distributed unevenly throughout the selectively permeable barrier 300. In an embodiment of the present disclosure, the selectively permeable barrier 300 may have the following characteristics. a. Air flow at dp=12mbar - 0.3 liters / hour to 0.5 liters / hour b. Water entry pressure (WEP) - > 0.3 bar. WEP is the minimum amount of pressure needed to force water through the largest opening of the selectively permeable barrier 300.

[0040] FIG. 5 illustrates an exploded view of a writing instrument 400 according to an embodiment of the present disclosure. The writing instrument 400 includes an ink tank 402 having a first end and a second end. The first end of the ink tank 402 is closer to a front portion or the writing tip end of the writing instrument 400 and the second end of the ink tank is towards the back portion of the writing instrument 400. The ink tank 402 is configured to hold one or more types of ink described above and can be made using a suitable material such as plastic, metal, or the like. The writing instrument 400 also includes a flow adapter 408. The flow adapter 408 connects at the first end of the ink tank 402. The function of the flow adapter is to regulate the flow of ink from the ink tank 402 to the writing tip of the writing instrument 400. In some embodiments, the flow adapter 408 may be made of plastic, rubber, or other similar material. The writing instrument 400 further includes a tip adapter 404. The tip adapter can be made from any suitable material34757-2905 like metal or the like. The tip adapter 404 is located inside the flow adapter 408 and is designed to be attached to a writing tip 406. The tip adapter further channels the ink received from the flow adapter 408 to the writing tip 406. The writing tip 406 is the portion of the writing instrument 400 that makes contact with the writing medium when the writing instrument 400 is being used by a user. The writing tip 406 can be made of plastic, foam, metal, or the like depending on the nature and usage of the writing instrument 400.

[0041] The writing instrument 400 also includes a cap 410. The cap 410 is used to protect the writing tip 406, the tip adapter 404. and the flow adapter 408 when the writing instrument 400 is not in use, such as when being stored or transported. When the writing instrument 400 is not being used, the cap 410 covers the writing tip 406, the tip adapter 404, and the flow adapter 408 and protects them from exposure to the outside environment. In some embodiments, the writing instrument 400 may also include a tip spring (not shown). When the writing instmment 400 is being used, pressure from the paper and a metallic ball inside the writing tip 406 pushes the tip spring. The tip spring then rotates the ball in the writing tip 406 that results in ink being dispensed on to the paper. In some embodiments, the tip spring may be made of metal or any other suitable material.

[0042] The writing instrument 400 may further include a barrier plug 414. The barrier plug 414 includes a housing structure and a selectively permeable barrier disposed in the housing structure. Details of the construction and function of the barrier plug 414 is described below. In one embodiment, the barrier plug 414 may be attached to the second end of the ink tank 402. In this instance, the barrier plug 414 may define the back-end of the writing instmment 400. There are several ways of attaching the barrier plug 414 to the ink tank 402, some of which are described below. In one embodiment, the housing of the barrier plug 414 can be made from the same material as the ink tank 402 to ensure proper fit and design continuity. In other embodiments, the material for the housing of the barrier plug 414 may be different than the material of the ink tank 402. It is to be noted that use of barrier plug 414 eliminates the need for an ink flow controller or lamella that is used in conventional writing instruments. The writing instrument 400 eliminates the biggest source of ink leakage in environments having a low pressure and / or high temperature.

[0043] When using the writing instrument 400 in high altitude, low ambient pressure environments, there is no place for the ink to escape as there is no path for the ink from the34757-2905 ink tank 402 to the external environment of the writing instrument 400. The ink can only flow from the ink tank 402 to the writing tip 406. The flow adapter 408 has a water-tight connection to the ink tank 402 and does not allow any ink to escape at the connection point between the ink tank 402 and the flow adapter 408. Since the barrier inside the barrier plug 414 is selectively permeable, it allows the air from outside to enter the ink tank 402 but prevents ink from within the ink tank 402 to pass through the selectively permeable barrier, even when the writing instrument is stored horizontally or when the writing instrument 400 is resting on the barrier plug 414. The barrier plug 414 helps to maintain the same pressure inside of the writing instrument 400 as the pressure of the external environment so as to prevent any ink leakage from the writing instrument 400. During operation, as the ink from the ink tank 402 is dispensed via the writing tip 406, the barrier plug 414 allows the ambient air to enter the ink tank 402 thereby raising the pressure inside the ink tank 402 and ensuring constant and smooth flow of ink from the ink tank 402 to the writing tip 406.

[0044] When the writing instrument 400 is used in a high temperature environment (e.g., >45 °C) the ink in the ink tank 402 may expand and increase in volume. However, since the selectively permeable barrier in the barrier plug 414 is not permeable to the ink, it prevents the ink from leaking out of the writing instrument. In order to ensure that the volume of ink after the expansion is less than the volume of the ink tank 402, the amount of ink included in the ink tank 402 at the time of the manufacture of the writing instrument 400 may be precisely determined since the chemical and physical properties of the ink are known. Based on the properties of the ink, the amount of potential expansion of the ink can be calculated for any given temperature. Based on that determination and the volume of the ink tank 402, the initial amount of ink to be included in the writing instrument can be determined. Over time as the ink is used, the amount of available space in the ink tank 402 will increase and the expansion of the remaining ink can be easily accommodated within the ink tank 402.

[0045] FIGS. 6A and 6B illustrate the structure of the barrier plug 414 according to an embodiment of the present disclosure. The barrier plug 414 can include a barrier housing having a first portion 420 and a second portion 422. The first portion 420 of the barrier housing includes a selectively permeable barrier 424 that defines a surface of the first portion 420. In an embodiment, selectively permeable barrier 424 is similar to the selectively permeable barrier 300 described above and has similar properties. The34757-2905 selectively permeable barrier 424 may be attached to the first portion 420 of the barrier housing using some form of a suitable adhesive. Other suitable methods of attachment may also be used to attach the selectively permeable barrier 424 to the first portion 420 of the barrier housing. As shown in FIG. 6B the top portion of the barrier plug 414 is exposed to the ambient environment. Looking from the top side of the barrier plug 414, a portion of the selectively permeable barrier 424 is visible. This ensures that the selectively permeable barrier 424 is exposed to the ambient environment so that air may enter the ink tank 402 via the selectively permeable barrier 424. The size and shape of the first portion 420 and the second portion 422 is designed based on the size and shape of the ink tank 402. The barrier plug 414 forms a water tight connection with the second end of the ink tank 402 such that ink from the ink tank cannot leak out via the connection between the barrier plug 414 and the ink tank 402. In addition, since the selectively permeable barrier 424 is impermeable to the ink. the ink cannot out leak out via the selectively permeable barrier 424 either. Thus, the ink is contained within the ink tank 402 at all times. While the barrier plug 414 is shown as having two portions 420 and 422, this is not needed. One skilled in the art will realize that the barrier plug 414 may have a single housing structure with a barrier or the selectively permeable barrier 424 may be directly integrated into the ink tank 402. For instance, the diameter of the end of the ink tank 402 closer to the back end of the writing instrument 400 can be adjusted as needed and the selectively permeable barrier 424 may be integrated into the ink tank 420 at that end. In an embodiment, the diameter of the ink tank 402 at the back end of the writing instrument 400 is smaller than the diameter of the ink tank 402 at the end where it connects to the flow adapter 408. Further, while the barrier plug 414 is shown as being located at an end of the ink tank 402, this is merely exemplary'. The selectively permeable barrier 424 and / or the barrier plug 414 may be located at other locations of the w riting instrument 400.

[0046] FIG. 7 illustrates a writing instrument 500 according to another embodiment of the present disclosure. Writing instrument 500 includes an ink tank 502. The ink tank 502 may be similar to the ink tank 402 described above. The w riting instrument further includes a cap 504. The cap 504 may be similar to the cap 410 descried above. The writing instrument 500 may include other components such as a flow adapter, a tip adapter, a writing tip, etc. These components are not shown in FIG. 7 for sake of brevity. The writing instrument 500 includes a barrier plug 506. The barrier plug 506 may be similar to the barrier plug 414 described above. The barrier plug 506 may be integrated into the ink34757-2905 tank 502 and may be located at any place along the surface of the ink tank 502. A first end 510 of the barrier plug 506 is exposed to the ambient environment and second end 512 of the barrier plug 506 may be located at least partially inside the ink tank 502. A selectively permeable barrier, such as the selectively permeable barrier 424 above, may be disposed within the barrier plug 506 and at least a portion of the selectively permeable barrier is exposed to the ambient environment via the first end of the barrier plug 506. Air enters the ink tank 502 via the first end 510, through the selectively permeable barrier, and the second end 512. However, since the selectively permeable barrier is impermeable to the ink, the ink cannot and does not flow out from the ink tank 502 through the barrier plug 506. One skilled in the art will realize that the location for the barrier plug 506 is not limited to what is described in this disclosure. The barrier plug 506 can be located anywhere on the writing instrument that allows ambient air to enter the ink tank, at least when the writing instrument 500 is in use. Thus, it is advisable to ensure that the barrier plug 506 and / or the selectively permeable barrier be located such that the opening of the barrier plug 506 or the selectively permeable barrier itself is not blocked from receiving the ambient air, at least when the writing instrument is in use.

[0047] FIG. 8 shows another writing instrument 600 according to an embodiment of the present disclosure. The writing instrument 600 may be a retractable roller ball pen. The writing instrument 600 includes a refill tube 602 that holds the ink. The writing instrument 600 further includes a tip adapter 604, a writing tip 606, and a barrier plug 610. The tip adapter 604 may be perform a similar function and made of similar materials as the tip adapter 404 described above. The writing tip 606 may perform a similar function and be made of similar materials like the writing tip 406 described above.. The refill tube 602 has a first end 612 that is connected to the tip adapter 604 and second end 614 that is distal to the first end 614. The barrier plug 610 may be connected at the second end 614 of the refill tube 602. In an embodiment, the barrier plug 610 may be similar to the barrier plug 414 described above. The barrier plug 610 allows ambient air to enter the refill tube 602 but prevents the ink from the refill tube from escaping out of the barrier plug 610. The first end 612 of the refill tube 602 has a water-tight connection with the tip adapter 604, hence there is no path for the ink to leak through that connection either. Thus, the ink is contained within the refill tube 602, even when the ambient pressure is low and / or the ambient temperature is high. Similar to the writing instrument 400, the amount of ink in34757-2905 the refill tube 602 can be adjusted to account for any expansion of the ink in high ambient temperatures.

[0048] FIG. 9 illustrates yet another writing instrument 700 according to an embodiment of the present disclosure. The writing instrument 700 may be a retractable type roller ball based writing instrument. The writing instrument 700 may be similar in many ways to the writing instrument 600 described above in relation to FIG. 7. The writing instrument 700 may include a refill tube 702 that may be similar to the refill tube 602 above. The writing instrument 700 may further include a tip adapter 706 that may be similar to the tip adapter 604 above and connected to the refill tube 702. A tip 708 may be connected to the tip adapter 706. The tip 708 may be similar to the writing tip 606 above. Writing instrument 700 may include other components not specifically described herein for sake of brevity. The refill tube 702 may include a barrier plug 704. Barrier plug 704 may be similar to the barrier plug 506 or 414 described above and may be located almost anywhere along the surface of the refill tube 702. The barrier plug 704 may include a selectively permeable barrier, such as the selectively permeable barrier 300 or 424 described above. The barrier plug 704 allows ambient air to enter the refill tube 702 via the selectively permeable barrier but prevents the ink from the refill tube 702 from escaping to the outside of the writing instrument 700. The barrier plug 704 is placed in a location where it will not be blocked, for example by a user’s fingers, when the writing instrument 700 is in use. Similar to what is described above, the amount of ink the refill tube 702 (and 602) can be adjusted to account for the ink expansion in high temperature environments.

[0049] FIG. 10 illustrates another writing instrument 800 according to an embodiment of the present disclosure. The writing instrument 800 can be an acrylic-based marker pen in one embodiment. The writing instrument 800 may include an ink tank enclosure 802. The ink tank enclosure 802 may house an ink tank 804. The ink tank 804 is at least partially disposed within the ink tank enclosure 802. A first end 820 of the ink tank 804 is disposed outside of the ink tank enclosure 802. A second end 822 of the ink tank 804 is aligned with an end of the ink tank enclosure 802. In some embodiments, the ink tank 804 is inseparable from the ink tank enclosure 802. In other embodiments, the ink tank 804 may be removed from the ink tank enclosure 802 and replaced with a new ink tank. The writing instrument 800 may further include a first cap portion 808, a second cap portion 812, and a tip protector 810. In practice, the first cap portion 808, the tip protector 810,34757-2905 and the second cap portion 812 are a single unit and inseparable from each other. The first cap portion 808, the tip protector 810, and the second cap portion 812 help to protect the tip of the writing instrument 800 when the writing instrument 800 is not in use.

[0050] The writing instrument 800 further includes an ink tank adapter 806. The construction and function of the ink tank adapter 806 may be similar to the ink tank adapter 408 described above. The writing instrument 800 may also include a writing tip 814. The writing tip 814 may be similar in function and construction to the writing tip 406 and / or the writing tip 606 described above. The writing tip 814 is attached to the ink tank adapter 806. The writing instrument 800 may further include a ball 816. The ball 816 may be a ball bearing that is used to mix up the ink to prevent the chemicals and the pigment from separating. The writing instrument 800 also includes a barrier plug 818. The barrier plug 818 may be similar in construction and function to the barrier plug 414 described above.

[0051] FIG. 11 illustrates an ink tank 902 that includes a barrier plug 904 according to yet another embodiment of the present disclosure. The ink tank 902 and the barrier plug 904 can be part of a writing instrument similar to the writing instrument 800 described above. Only the portions of the writing instrument germane to the disclosure are shown in FIG. 11. In an embodiment, the ink tank 902 is similar in construction and function to the ink tank 804 described above. Thus, only a portion of the ink tank 902 may be exposed outside its ink tank enclosure (not shown). The barrier plug 904 may be placed along the surface of the exposed portion of the ink tank 902. The barrier plug 904 may be similar to the barrier plug 506 described above. The placement of the barrier plug 904 is chosen such that the barrier plug is not blocked, for example by a user’s fingers, when the writing instrument is being used. Ambient air enters the ink tank 902 via the barrier plug 904, however, the presence of a selectively permeable barrier within the barrier plug 904 prevents the ink from the ink tank 904 from leaking outside of the writing instrument.

[0052] FIG. 12 illustrates an operation 1000 of a writing instrument according to an embodiment of the present disclosure. At step 1002, a writing instrument is provided. This writing instrument includes a selectively permeable barrier. At least a portion of this selectively permeable barrier is exposed to the ambient environment outside the writing instrument. When a user is writing on a writing medium, such as a paper, air from the ambient environment enters the ink tank of the writing instrument via the selectively permeable barrier (step 1004). This increases the pressure inside the ink tank. The increase34757-2905 in pressure causes the ink from the ink tank to be dispensed to the writing tip of the writing instrument (step 1006). In the instance where the wri ting instrument is being used at altitudes where the ambient air pressure is 0.7 bar or lower, the selectively permeable barrier prevents the ink inside the ink tank of the writing instrument from leaking out of the writing instrument (step 1008). In instances where the writing instrument is used in ambient environments having a temperature of 45 °C or greater, the selectively permeable barrier ensures that the ink that has expanded due to the high ambient temperature stays within the ink tank and does not leak outside the ink tank via the selectively permeable barrier (step 1010). In this manner, the writing instruments according the various embodiments of the present disclosure allow for a smooth and optimal writing experience even in environments having low ambient air pressure (e.g., at high altitudes) and high ambient temperatures.

[0053] The writing performance of any of the writing instruments described above can be adjusted by choosing a selectively permeable barrier with the right characteristics. For example, the amount of ink dispensed by the writing instrument is linearly proportional to the amount of air entering the ink tank. So, by controlling the amount of air that can enter the ink tank, the flow of the ink can be controlled. In other w ords, the ‘laydown ’ performance of the writing instrument can be adjusted based on the amount of air allowed into the ink tank. One way to control the amount of air entering the ink tank of the writing instrument is by manipulating the density7of the selectively permeable barrier. The higher the density of the selectively permeable barrier, the less the amount of air entering the ink tank resulting in a slower dispensation of the ink on the writing medium. Conversely, a lower density selectively permeable barrier will allow a higher amount of air to enter the ink tank resulting in faster or higher dispensation of the ink. It is to be noted that the above assumes that ink being used in both instances is the same ty pe. A change in the ink type, for example from water-based to pigment-based, can significantly change the performance of the writing instrument when the density of the selectively permeable barrier is also varied at the same time.

[0054] Since the tip size, ink tank size, and the expected writing performance of an existing writing instrument are known, the optimal type of the selectively permeable barrier for that writing instrument can be determined. The mesh density of the selectively permeable barrier for a particular writing instrument can be determined by understanding how much the pressure varies inside the ink tank of a particular writing instrument. For34757-2905 example, the graph illustrated in FIG. 2 can be used for this purpose. From the pressure data from inside the ink tank, an amount of suction force needed for the air to enter into the ink tank is determined. Based on the amount of suction force needed, the density' of the selectively permeable barrier can be determined and the selectively permeable barrier can be accordingly manufactured to have that density'. Thus, each type of writing instrument can have a customized selectively permeable barrier that has a thickness and density' that is optimal for operation of that particular writing instrument. Thus a roller ball based free flowing ink writing instrument may have a selectively permeable barrier of different thickness and / or density' than a pigment-ink based marker pen. In an embodiment the selectively permeable barrier can have a thickness in the range of 0.3 mm to 0.4 mm. As noted above, introduction of the selectively permeable barrier obviates the need to have a traditional ink flow controller or lamella thereby eliminating the biggest source of ink leakage in the writing instrument.

[0055] In conventional writing instruments, a significant portion of the writing instrument is occupied by the lamella. Since the writing instruments according to the embodiments of the present disclosure do not include a lamella, the writing instruments can accommodate a bigger ink tank thus increasing the ink holding capacity of the writing instrument. A bigger ink tank results in the increase in the writing lifespan of the writing instrument thereby providing more value to the consumer.

[0056] Most conventional writing instruments regardless of the ty pe are not well suited to be used at higher altitudes where the ambient atmospheric pressure can fall below 1 bar. The conventional writing instruments experience ink leakage when the ambient pressure falls to 0.7 bar or lower. The writing instruments according to embodiments of the present disclosure described above have no ink leakage even at ambient pressures as low as 0.3 bar. This represents a 55%+ performance improvement over the conventional writing instruments.

[0057] One or more illustrative embodiments of the disclosure have been described above. The above-described embodiments are merely illustrative of the scope of this disclosure and are not intended to be limiting in any way. Accordingly, variations, modifications, and equivalents of the embodiments disclosed herein are also within the scope of this disclosure.

[0058] While the present disclosure has been described with reference to a number of embodiments, it will be understood by those skilled in the art that the invention is not34757-2905 limited to such disclosed embodiments. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not described herein, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described embodiments. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

34757-2905CLAIMSWhat is claimed is:

1. A writing instrument comprising: an ink tank having a first end and an opposing second end; a tip adapted to be coupled to the first end of the ink tank; a barrier coupled to the second end of the ink tank, wherein at least a portion of the barrier is exposed to an external environment of the writing instrument and wherein the barrier is configured to selectively allow entry of ambient air into the ink tank and prevent ink from passing through it.

2. The writing instrument of claim 1, wherein the barrier comprises enhanced polytetrafluroethylene (ePTFE) material.

3. The writing instrument of claim 1, wherein the barrier is air permeable at ambient air pressures below 0.7 bar.

4. The writing instrument of claim 1, wherein the writing instrument does not include any other ink flow control mechanism.

5. The writing instrument of claim 1, wherein the barrier is located at the second end of the writing instrument.

6. The writing instrument of claim 1 , wherein the barrier is impermeable to liquids having a viscosity of 1 cps or more.

7. The writing instrument of claim 6, wherein the barrier is further impermeable to the liquids at an ambient air pressure of at or below 0.7 bar.

8. The writing instrument of claim 1, wherein the first end of the ink tank has a first diameter and the second end of the ink tank has a second diameter, wherein the second diameter is smaller than the first diameter.34757-29059. A writing instrument comprising: an ink tank having a first end and an opposing second end, wherein the second end is closed; a barrier coupled to a portion of a surface of the ink tank, wherein at least a portion of the barrier is exposed to an ambient environment outside the writing instrument and the barrier is configured to allow ambient air to enter the ink tank and prevent flow of ink from the ink tank through the barrier.

10. The writing instrument of claim 9, wherein the barrier is disposed in a barrier housing and barrier housing is integrated into the ink tank.

11. The writing instrument of claim 9, wherein the writing instrument does not include any other ink flow control mechanism.

12. The writing instrument of claim 9, wherein the barrier is air permeable below an ambient air pressure of 0.7 bar.

13. The writing instrument of claim 9, wherein the barrier is located closer to the second end of the writing instrument.

14. The writing instrument of claim 9, wherein the barrier comprises enhanced polytetrafl uroethylene (ePTFE) material.

15. A writing instrument comprising an ink tank enclosure; an ink tank partially disposed within the ink tank enclosure, wherein a first portion of the ink tank is located outside the ink tank enclosure, the first portion of the ink tank having a first end; an adapter coupled to the first end of the ink tank; a tip coupled to the adapter; and a barrier coupled to the ink tank, wherein at least a portion of the barrier is exposed to ambient environment outside the writing instrument and the barrier is configured to34757-2905 allow ambient air to enter the ink tank via the barrier and prevent ink from the ink tank from flowing out through the barrier.

16. The writing instrument of claim 15. wherein the barrier is coupled to an end of the ink tank enclosure.

17. The writing instrument of claim 15, wherein the barrier is coupled to a surface of the first portion of the ink tank.

18. The writing instrument of claim 15, wherein the barrier is located closer to the tip of the writing instrument.

19. The writing instrument of claim 15. wherein the barrier comprises enhanced polytetrafluroethylene (ePTFE) material.

20. The writing instrument of claim 15, wherein a viscosity' of ink in the ink tank is between 1 cps and 10 cps.

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