Pressure difference compensation membrane

Abstract

A compensation membrane and a pen or the equivalent including a compensation membrane. The compensation membrane being configured for compensating a pressure difference between the outside and the inside of a free ink reservoir of a pen or the equivalent. The membrane including a first portion having a first rigidity and a second portion having a second rigidity, the first rigidity being less than the second rigidity.

Claims

1. A pen comprising: a barrel forming a reservoir and a compensation membrane; the barrel having a writing tip disposed at a first axial end of the barrel and the compensation membrane disposed at an opposing second axial end of the barrel; the compensation membrane including a first portion having a first rigidity and a second portion having a second rigidity that is greater than the first rigidity where the first portion deforms when an inside pressure of the reservoir increases or an outside pressure of the reservoir decreases while the second portion retains its shape and the second portion deforms upon the inside pressure of the reservoir increasing or the outside pressure of the reservoir decreasing an additional amount.

2. The pen according to claim 1, further comprising a third portion having a third rigidity greater than the first rigidity and less than the second rigidity where the first portion and third portions deform when the inside pressure of the reservoir increases or the outside pressure of the reservoir decreases while the second portion retains its shape and the second portion deforms upon the inside pressure of the reservoir increasing or the outside pressure of the reservoir decreasing an additional amount.

3. The pen according to claim 2, wherein the first, second and third portions are made from the same material.

4. The pen according to claim 2, wherein the first, second and third portions are each made from different materials.

5. The pen according to claim 2, wherein the first, second and third portions each have different thicknesses.

6. The pen according to claim 2, wherein the second portion is arranged between the first and third portions.

7. The pen according to claim 6, wherein the first, second and third portions are concentric and radially symmetric about an axis.

8. The pen according to claim 2, wherein the first, second and third portions are configured to deform and deploy towards an outside of the reservoir upon the inside pressure of the reservoir increasing or the outside pressure of the reservoir decreasing an additional amount.

9. The pen according to claim 8, wherein the compensation membrane is configured to return to its original shape in the absence of the inside pressure of the reservoir increasing or the outside pressure of the reservoir decreasing.

10. The pen according to claim 1, wherein a flyweight is disposed between the first portion and the second portion.

11. The pen according to claim 10, wherein the flyweight is annular in shape and is positioned axially symmetric with respect to the first and second portions, the flyweight is configured to increase an inertia of the compensation membrane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages can be better understood on reading the following detailed description of embodiments given as non-limiting examples. The description refers to the accompanying sheets of drawings, in which:

(2) FIG. 1 shows a first embodiment of a pen, seen in cross-section, fitted with a compensation membrane and a portion that is porous and hydrophobic;

(3) FIG. 2 shows a detail of the FIG. 1 compensation membrane in its rest state;

(4) FIGS. 3A, 3B and 3C show the successive steps in deploying the FIG. 2 compensation membrane during a relative increase of pressure in the reservoir of the pen; and

(5) FIG. 4 shows a second embodiment of a pen seen in cross-section, fitted with a compensation membrane and with a baffle device.

DETAILED DESCRIPTION

(6) FIG. 1 is a cross-section view of a free ink pen 10 (referred to below, for short, as a “pen”) in a first embodiment. The pen 10 comprises a barrel 12 forming a reservoir 14 in which the ink (not shown) is free to flow. The barrel 12 may have raised portions or internal or external shapes, e.g. to enable it to be assembled with other parts of the pen. The shapes or raised portions of the barrel 12 may also be merely for an appearance effect.

(7) As shown in FIG. 1, the reservoir 14 extends in a substantially axial direction X. The pen 10 has a writing tip 16 in fluid flow communication with the reservoir 14. The writing tip 16 may be any kind of tip, in particular a ballpoint, a felt tip, a pen nib, or any otherwise known type of tip. The connection between the writing tip 16 and the reservoir 14 is adapted to the type of tip in ways that are known in the prior art. In FIG. 1, there can be seen a writing tip 16 comprising a ballpoint with a fiber connector directly connected to the reservoir 14.

(8) The pen 10 has a compensation membrane 20, a portion 30 that is porous and hydrophobic, and a breathing membrane 40. The compensation membrane 20 closes a first opening of the reservoir 14 arranged in the vicinity of a first axial end 14a. Specifically, the first axial end 14a is the end of the reservoir 14 opposed to the writing tip 16. The structure and the operation of the compensation membrane 20 are described below.

(9) The porous and hydrophobic portion 30 closes a second opening situated at a second axial end 14b of the reservoir 14. The second axial end 14b is opposed to the first axial end 14a. The second axial end 14b is situated beside the writing tip 16.

(10) The breathing membrane 40 also closes the second opening. More precisely, it is adjacent to the porous and hydrophobic portion 30, the porous and hydrophobic portion 30 being arranged on the inside of the reservoir 14 relative to the breathing membrane 40. The breathing membrane 40 and the porous and hydrophobic portion 30 may be adjacent directly or indirectly, i.e. there might be one or more elements between them.

(11) The compensation membrane 20 has an actuation threshold. In other words, it is designed to be deformed only from a predetermined pressure difference between the inside and the outside of the reservoir 14. This makes it possible in particular for the reservoir 14 to be at slightly reduced pressure. In particular, when the pen 10 is held with its tip at the bottom, the porous and hydrophobic portion 30 absorbs some of the ink, thereby creating a small amount of suction in the reservoir 14. This suction is small enough not to be compensated by a movement of the compensation membrane 20, it serves to compensate the weight of the ink on the writing tip 16, and thus serves to avoid ink dripping from the writing tip 16. In addition, the breathing membrane 40 prevents the reservoir 14 from leaking in the event of the porous and hydrophobic portion 30 being saturated with ink.

(12) Because of its impermeability to liquids and permeability to gases, the breathing membrane 40 allows air to penetrate into the reservoir 14. Air can also pass without difficulty through the porous and hydrophobic portion 30. This assembly of the breathing membrane 40 and the porous and hydrophobic portion 30 thus operates like a vent, allowing air to enter or leave the reservoir 14, and this, in combination with the compensation membrane 20, enables the pressure inside the reservoir 14 to be controlled as a function of the outside pressure.

(13) In the present embodiment, the compensation membrane 20 is configured to be stressed solely in its elastic deformation range. The compensation membrane 20 is thus configured to return to its reference position (its shape) in the absence of external stress. As mentioned above, the compensation membrane 20 serves to absorb large and/or rapid variations of pressure. For this purpose, the compensation membrane 20 deforms, thereby creating stresses internal to the compensation membrane 20, said stresses seeking to return the compensation membrane 20 to its reference position as soon as that is compatible with balancing pressures inside and outside the reservoir 14.

(14) The structure of the compensation membrane 20 is described in detail below with reference to FIG. 2. In FIG. 2, the compensation membrane 20 is shown in axial cross-section and in a rest position, i.e. a position in which the difference between the inside pressure Pi (pressure inside the reservoir 14), and the outside pressure Po (pressure outside the reservoir 14) is less than the actuation threshold of the compensation membrane 20.

(15) The compensation membrane 20 has a first portion 22 having first stiffness K1, a second portion 24 having second stiffness K2, and a third portion 26 having third stiffness K3. In the example shown, the first stiffness is less than the third stiffness, which is in turn less than the second stiffness (i.e. K1<K3<K2). The greater the rigidity of a portion, the greater the forces needed to deform that portion. Furthermore, as shown in FIG. 2, each portion has an undulating or equivalent shape when the pressure difference on either side of the compensation membrane is less than the actuation threshold of the compensation membrane. The presence of undulations or convolutions serves to release a larger volume when the portion is deployed.

(16) Furthermore, the radial order of the portions 22, 24, and 26 of different rigidities may be modified relative to the order shown in FIG. 2.

(17) The portions 22, 24, and 26 of the compensation membrane 20 may be made of different materials or they may be made of the same material. In particular, when they are made of the same material, in order to obtain different rigidities, the portions may have different thicknesses.

(18) As shown in FIG. 2, in this example, each portion has rigidity that increases with increasing thickness of the portion. Specifically, the first portion 22 is thinner than the third portion 26, which is in turn thinner than the second portion 24. For example, at least one portion may be made of polymer material, in particular of silicone or of thermoplastic elastomer.

(19) When the compensation membrane is made of a plurality of materials, it may be made by bi-injection, by tri-injection, or by putting inserts into place.

(20) In the present embodiment, the portions 22, 24, and 26 of the compensation membrane are concentric about an axis X. Furthermore, they are substantially axially symmetric about the axis X.

(21) In FIG. 2, it can be seen that the compensation membrane 20 is fastened to the barrel 12 by a radially outer portion 20a. Nevertheless, the compensation membrane could be directly injected or co-injected when injecting the barrel 12, thereby further improving the leaktightness of the reservoir 14.

(22) The compensation membrane 20 also has a flyweight 28. Specifically, the flyweight is annular and has an axially symmetric shape, so as to avoid disturbing the general symmetry of the compensation membrane 20. The flyweight 28 is arranged between the first portion 22 and the second portion 24. The flyweight 28 increases the inertia of the compensation membrane 20.

(23) The operation of the compensation membrane 20 is described in detail below with reference to FIGS. 3A-3C, which show a plurality of successive states of deformation of the compensation membrane 20. The succession of states in FIGS. 3A-3C occurs when the difference between the inside pressure and the outside pressure (Pi−Po) is positive and increasing. Naturally, opposite deformation (towards the inside of the reservoir), as obtained when the pressure difference Pi−Po is negative and decreasing, is analogous and is not described in detail.

(24) An initial state is shown in FIG. 2. In FIG. 2, all three portions 22, 24, and 26 are in the rest state (where they have a substantially undulating shape), which means that the pressure difference Pi−Po is of absolute value smaller than the actuation threshold of the compensation membrane 20.

(25) When the inside pressure increases or the outside pressure decreases, e.g. under the effect of high temperature or altitude, the difference Pi−Po increases. When it crosses the actuation threshold of the compensation membrane 20, the compensation membrane begins to deform. The first portion 22, having the lowest rigidity K1, begins to deform towards the outside of the reservoir 14 in order to increase the volume of the reservoir 14, and thus cause the inside pressure Pi to decrease. This state is shown in FIG. 3A. The second and third portions 24 and 26, of respective rigidities K2 and K3 that are greater than the first rigidity K1, substantially retain their original shapes. This state defines a first regime in which variations in the pressure difference are accommodated mainly by deformation of the first portion 22.

(26) The three respective rigidities K1, K2, and K3 of the portions 22, 24, and 26 define three successive regimes for variation in the deformation of the compensation membrane 20 as the pressure difference Pi−Po increases.

(27) In each regime, variations of the pressure difference are accommodated mainly by deformation of a given portion; the portions that are less rigid than the given portion are stretched (i.e. they are already deformed towards the outside), while the portions that are more rigid than this given portion are substantially relaxed (i.e. deformed little or not yet). shown in FIG. 3B. For example, an intermediate state is In this intermediate state, the pressure difference is accommodated mainly by the third portion 26. The first and third portions 22 and 26 are deformed towards the outside, while the portion 24 having the greatest rigidity is deformed little or not at all.

(28) In other words, the pressure forces are sufficient to deform the first and third portions 22 and 26, but not to deform the second portion 24.

(29) If the difference Pi−Po increases further, the various portions of the compensation membrane 20 continue to deform on the same principle, in the order of their increasing rigidities and in the successive regimes, until reaching a state in which all of the portions 22, 24, and 26 are deployed towards the outside. This is the state shown in FIG. 3C.

(30) Because of the various rigidities and shapes of the various portions 22, 24, and 26, the compensation membrane 20 may be said to be a controlled deployment membrane.

(31) Furthermore, the respective rigidities K1, K2, and K3 of the portions 22, 24, and 26 are preferably dimensioned in such a manner that the deformations of the compensation membrane 20 remain in the elastic ranges of the portions 22, 24, and 26. Thus, when the pressure difference Pi−Po becomes once more less than the actuation threshold of a portion, said portion returns substantially to its reference position. Consequently, in this sense, the compensation membrane 20 can be said to be a shape memory membrane. In other words, and in general manner, the membrane is thus configured to remain in or to return to its rest position in the absence of external stress, there being only one such position.

(32) More precisely, starting from the state of FIG. 3C, if the pressure difference Pi−Po decreases, then the compensation membrane 20 returns to the rest state in the reverse order to the steps described above. Starting from the rest state shown in FIG. 2, if the pressure difference Pi−Po decreases further, then the compensation membrane 20 deforms towards the inside of the reservoir 14; the portions 22, 24, and 26 then deform in the order of their respective increasing rigidities.

(33) FIG. 4 shows a free ink pen in another embodiment. The pen 110 of FIG. 4 is identical to the pen 10 of FIG. 1, except that the porous and hydrophobic portion 30 is replaced by a baffle device 130. The baffle device 130 has an air passage and the baffles are suitable for storing a quantity of ink that is a function of the pressure difference across the baffle device 130. Thus, the baffle device 130 can perform the same functions as the porous and hydrophobic portion 30. Nevertheless, its reliability is guaranteed only because of its co-operation with the breathing membrane 40 and the compensation membrane 20, which remain unchanged in this embodiment. In a variant, the pen 110 could also have a porous and hydrophobic portion arranged in series with the baffle device 130.

(34) Although the present invention is described with reference to specific embodiments, modifications may be applied to those embodiments without going beyond the general ambit of the invention, as defined by the claims. In particular, the individual characteristics of the various embodiments that are shown and/or mentioned may be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive.