US3233594A - Fluid container - Google Patents

Description

Feb. 8, 1966 N. A. ZEPELL 3,

FLUID CONTAINER Original Filed April 28, 1961 2 Sheets-Sheet 1 6 58 6: i i 54 g 72 [W 4 50 F/G 2 K E h 24 32 as 34 INVENTOR. F/G. NATHA/V ALTER ZEPELL N. A. ZEPELL Feb. 8, 1966 l-LUID CONTAINER Sheets-Sheet 2 Original Fihul April 38, 1961 INVENTOR. ,ll'. 7":H ZEPELL of a user.

3,233,594 FLUID CONTAINER "Nathan Alter Zepell, Chicago, 111., assignor to w. A.

Sheaifer' Pen Company, Fort Madison, Iowa, a corporation of Delaware Continuation of application Ser. No. 106,312, Apr. 28, 1961. This appiication Apr. 24, 1964, Ser. No. 363,678

3 Claims. (Cl. 120--45.4)

This application is a continuation of application Serial Number 106,312, filed April 28, 1961, now abandoned. The invention relates to a container for liquids, and more particularly to a fluid reservoir having a wall member which is displaceable to reduce the capacity of the reservoir in response to the withdrawal of fluid there body portion to reduce the volumetric capacity of the reservoir in response to the withdrawal of fluid therefrom.

The reservoir of the usual fountain pen or similar implement remains unchanged as to capacity during normal .useair entering the reservoir to rep-lace fluid as it is withdrawn during writing. Because of the difference in density between air and liquid, the air entering the reservoir rises above-the writing fluid and remains thereabove regardless of the position in which the fountain pen sub-, sequently may be held.

The air thus present in the reservoir of a writing implement will expand or contract if subjected to changes in temperature and/ or atmospheric pressure.

A decrease in atmospheric pressure or an increase in- -temperature easily may cause an undesirable condition in the usual pen should it be positioned point downwardly,

. as in writing; Under these conditions, a quantity of fluid,

equal to the increase in air volume, will be forced from the reservoir and into the expansion chambers of the feed. If such expansion chambers are not of suflicient capacity, a portion of this fluid may drip from the implement into the cap-or blot the writing surface or soil the users hands or clothing. This problem of expansion is encountered particularly during air travel, in which great extremes of temperature and pressure are encountered in relatively short periods of time. However, if a pen is positioned point upwardly when the above described expansion of air occurs, the excess air in the reservoir will escape readily through the feeding passageways without causing leakage.

In addition, as is well understood in the art, present day fountain pens are limited as to capacity because of the above described problem of expansion of air which may be trapped above the fluid. This factor requires relatively frequent refilling of the pen on the part of the user.

These problems long have been recognized in the art, and a number of proposals have been made for their solution. For example, it has been proposed to use valves to prevent leakage and flooding while still allowing'for a large capacity. However, such proposals have not been manufactured commercially because of complications in manufacture and subsequent operation while in the hands Capillary storage cuts have been used in the feed of a fountain pen to partially compensate for expansion of air in the reservoir, but such an arrangement does not eliminate the problem of expansion nor does it provide for a large controlled fluid capacity.

Accordingly, it is a principal object of this invention to provide a fluid reservoir for a fountain pen or the like,

United States Patent C 3, 33,594 7 Patented Feb. 8, 1966 which reservoir is not subject to leaking and flooding as a result of temperature or barometric pressure changes.

' Another object of this invention is to provide a fluid reservoir which has a large capacity but which is not affected by temperature or barometric pressure fluctuations.

A further object of this invention is to provide a fluid reservoir which has a flexible wall member adapted to follow the fluid and reduce the volumetric capacity of the reservoir as the fluid is withdrawn therefrom.

A still further object of this invention is the formationof a reservoir having a'body portion releasably engaging a flexible wall member of the above described character, which wall member may be formed directly within the body portion, thereby eliminating the necessity of any assembly thereof.

Yet another object of this invention is the provision of a fountain pen reservoir of the above character which is furnished in the form of a cartridge unit.

Further and additional objects of this invention will be apparent from the following description when taken with the accompanying drawings.

In accordance with one embodiment of the invention the fountain pen comprises a fluid container and a writing unit assembly mounted forwardly thereof, the fluid container having a vented hollow body portion and a filmlike layer of flexible material forming a flaccid sack engaging and releasably adhering to the interior surface of the body portion. The interior surface of said sack defines a Writing fluid reservoir, and the unit assembly has conduit means providing the sole fluid lead or leads from said writing fluid reservoir. The conduit means is small enough in cross-section to prevent rearward movement of air therethrough into the reservoir while there is writing fluid within the conduit;.tha-t is, air will not bubble through to the reservoir as it does in the usual fountain pen. T he adherent attachment of the sack to the interior surface of the body portion is suflicient to resist separation thereof and the consequent free discharge of writing fluid through the conduit under the influence of the normal weight of said column. However, the sack is separable from and displaceable within the body portion to reduce the volumetric capacity of the reservoir in response to forcible withdrawal of writing from the conduit by capillary action as during writing.

In the drawings:

FIGURE 1 is a greatly enlarged broken longitudinal sectional view of a cartridge barrel unit embodying a preferred form of the present invention; 1

FIG. 2 is a reduced longitudinal sectional view similar to FIG. 1 of the cartridge barrelunitthereof, assembled with the writing unit of a fountain pen, with the fluid supply being partially depleted;

FIG. 3 is a longitudinal sectional view of another embodiment of the present invention, showing a cartridge unit partially assembled with a fountain pen;

FIG. 4 is a fragmentary sectional view of the rearward portion of FIG. 3, showing the venting of the cartridge unit;

FIG. 5 is a sectional view along the line 5-5 of FIG. 3;

FIGS. 6, 7 and 8 are views in longitudinal cross section, showing steps in the manufacture of the cartridge barrel unit of FIG. 1; and

FIG. 9 is a fragmentary sectional view of the rearward portion of the cartridge unit of the embodiment of FIG. 3, showing the holder or carrier utilized during formation of the flexible wall member.

Referring now to the drawings and particularly to FIGS. 1 and 2 thereof, there is provided a fountain pen cartridge unit 10 having a body or support portion 12 molded or otherwise formed of a durable, relatively .anaperture "18 defining a vent passage between the exterior and the interior of the body portion '12.

Disposed within and releasably supported by the body portion 12 is a -flexible orflaccid wall member 20 which ,may beformed ofany one of anumber of materials, as

will be'indicated in more detail herebelow. The wall member 20 is slightly adherent to the body portion .12, and preferably relatively thin. It is shown in the drawings as being proportionately thicker than it normally would be in actual practice, in order to clearly disclose the character thereof. Generally, the wall member may range between .001" to .010" in thickness, although it is understood that the thickness thereof is not to be limited to this range as it may be varied depending upon the material from which it is formed and the fluid feeding characteristics desired.

In this embodiment of the invention, the flexible or flaccid wall member 20 is shown in the general shape of the usual cylindrical ink reservoir sac, having a closed end 22 and an open end 24. The closed end 22 is positioned at the closed end 16of the body portion 12, with its .open end '24 beingpositioned at the open end 14 of thebody portion. Accordingly, the flexible wall member 2%, in effect, forms a liner .within the body portion to provide a laminated reservoir section. Disposed within the body portion 12 adjacent its forward end 14 is a thinjband of adhesive or primer 26 which forms a permanent'bond between the body portion 12 and wall portion '20 adjacent their forward ends 14 and 24, respectively.

The reservoir thus defined by the interior surface of the flexible wall member 20 is intended to be filled with aliquid, such ,as an ink of the type used in pens. Therefore, in order to close the forward end of the body portion 12 and .wall portion 20, there is provided means comprising a closure disc28 having a flange 30 and a rearwardly extending center portion 32. The flange 30 is bonded to the forward end 14 of the body portion 12 as by heat sealing. The closure disc 28 is provided with a centrally disposed circular recess or discharge 34 which defines a thin diaphragm '36 pierceable readily by a pointed tubular member such as those used in present day cartridge type fountain pens.

The outer surface of the flexible wall member 20 is engaged in intimate contact with the interior surface of the body portion .12 throughout the entire surface area thereof. When thus engaged, the flexible wall member 20 is in an unstressed or neutral condition andexerts no appreciable pressure on the liquid disposed therein. Ac-

cordingly, at no time, does .it have a tendency to force fluid from .the reservoir even when the reservoir .is open and in use in a fountain pen or similar implement. In fact, because of theslight adherent attraction between the wall member 20 and the body portion 12, the wall member, as outlined in more detail hereinbelow, will tend to create a slightnegative pressure in the reservoir (2. pressure below normal air pressure) as fluid is withdrawn through the capillary feed channels of a fountain pen or similar implement.

The embodiment of FIG. 1 is shown as being included in a cartridge barrel unit intended for assembly with a fountain :pen Writing unit .38 as illustrated in FIG. 2.

For this reason, the exterior surface of the body portion .1 2,is.pr0vided witha threadedarea ,40, or similar'means, adjacent ,its forward end toallow direct attachment to the fountain pen writing unit 38. Thus, the cartridge barrel unit 10 serves as the exterior barrel as well as the fluidreservoir.

The writing unit 38 includes a generally cylindrical gripping portion 42 which is formed preferably of an attractive and durable material matching or complement- .52 of the writing element or pen point 54. And, as indicated in FIG. 2, the pen point 54 is frictionally maintained within the gripping portion 42 by the feed ba rt48.

To provide communication between the capillary fissure 5t and the reservoir, there is provided an insert 56 positioned in an axial feed aperture 58 which extends from the fissure 50 through the rearward end of the feed bar 48. This insert extends rearwardly beyondthe feedbar 4'8 and terminates within 'a generally cylindrical pierce tube 64 having a pierce point '62 defined by a tapered upper end. Provided by the insert 56 is a capillary passage 64 arranged for the movement of fluid from the reservoir to the feed fissure 50, from where such fluid subsequently is transferred to the slit 5 2 of-the penpoint 54 for deposit during writing.

One of the features of the present invention is the elimination of'the necessity of providing the usual comb cuts in order to retain fluid which might be-forced from the reservoir of a pen as a result of atmospheric pressure or temperature changes.

In addition, there is no need to provide any type of passage for the exchange of air between the feed and reservoir since the flexible wall member 20 is displaced within the body portion 12 to-followthe ink as it is withdrawn during writing and thereby reduce the volumetric capacity of the reservoir. These features eliminate the possibility of the entry of air into the reservoir, and the difliculties attendant thereto, as well as greatly reducing the complexity and cost of manufacturing the feed bar and its associated parts.

The heretofore described fountain pen construction is used by an individual in the same manner as any other fountain pen. Thus, it does not require any special handling or attention on the part ofthe owner. When the implement is in writing use, *fluid is withdrawn'from the reservoir, as defined by the interior surface of the-flexible wall member 2%, through the capillary passage 64 and the feed fissureStl, whereafter'it is transferred to the feed slit 52 of the pen point 54, and then-deposited on a writing surface, such as paper. As the flexible wall member 20 follows the diminishing supply of ink, it gradually is disengaged from the interior surface of the bodyportion 12, air pressure being exerted on its exterior surface through the vent 18 of the body portion 12.

The attraction between the flexible wall member 20 and the body portion 12 prevents separation of-the wall member and body portion except as a resultof a slight negativepressure created in the reservoir upon the withdrawal of fluid through the capillary passage edof the insert 56 and the feed fissure 50 of the feed bar 43. While these capillary channels are capable of producing only limited amounts of force, such force is sufficient, in combination with air pressure, to draw the flexible wall member away from the body portion 12 as represented in FIG. 2 of the drawings.

Since only the substantially empty displaced portion of the wall member .20 is unsupported within the body portion 12,, the weight of theremaining column of fluid doesnot cause any kinking orcreasing of the still-filled portion of the wall member 20, therebypreventingentrapment of part of the fluid behind a crease, or premature stoppage of the flow of fluid.

In the present invention, it is preferred to form the flexible wall member 2%! directly in the'body portion .12 thereby eliminating the expense of subsequent assembly of the individual parts.

The amount of attraction between the wall member and body portion may be controlled in several ways, such as by the selection of materials to be used in the body portion and wall member, by providing slight irregularities such as grooves or a pebble surface on the interior of the body portion, or by using a release agent between the body portion and Wall member should the materials used therein exhibit a greater amount of attraction than is necessary.

Formation of the flexible wall member within the body portion 12 may be accomplished by any one of several methods, such as by spraying the material of the Wall member within the body portion, or by a procedure known as slush molding, which involves filling the body portion with a liquid plastic or rubber compound which is subsequently emptied except for a thin layer adhering to the interior wall of the body portion. The particular process chosen depends somewhat upon the material used in forming the flexible wall member 26 as certain materials lend themselves best to certain processes of handling, as is recognized readily by those in the plastic and rubber fabricating field.

The embodiment of FIG. 1 may be formed by a threestep process such as that shown in FIGS. 6, 7 and 8 of the drawings. This is a process by which the materials are sprayed within the body portion 12 as it is carried from station to station on an automated indexing machine. The body portion 12 is first inserted into a holder or carrier 68 which is provided with a centrally disposed plug 70 adapted to extend into and close the vent 18, thus providing a substantially unbroken interior wall on the closed end 16 of the body portion 12.

The body portion 12 is moved to the first station on the indexing machine as represented in FIG. 6, where a thin layer of a liquefied adhesive or primer is sprayed on the interior surface of the body portion 12 to coat an annular recess 72 formed adjacent its open forward end 14. Thespraying is accomplished by forcing the adhesive or primer through a plurality of small apertures disposed around the periphery of a dispensing nozzle 74.

The body portion 12 is then moved to the next station, as illustrated by FIG. 7, at which time an elongated disspensing nozzle 76 is inserted therein. The nozzle 76 is provided with a plurality of minute apertures spaced over its entire surface so that a liquid material may be forced therethrough to provide an even coating of material on the interior surface of the body portion 12. For this particular step, a liquified silicon rubber has been found to give good results not only from the standpoint of ease of application but of subsequent performance as the flexible wall member 20 in the completed reservoir. Following the second step, it may be desirable to rotate the carrier 68 for a short time in order to insure retention of an even thickness of material as it takes its initial set. Thus, the finished flexible wall member 211 will exhibit a uniform thickness throughout its length.

The third step in the procedure as represented by FIG.

I 8, involves the application of a catalyst to the thin layer of silicon rubber as formed during the second step, in order to complete its vulcanization. As in the case of step 2, the catalyst is sprayed evenly over the layer of silicon rubber through a plurality of apertures spaced over the surface of an elongated dispensing nozzle '78. After application of the catalyst, the body portion 12 may be removed from the carrier 68 and prepared for further handling by the manufacturer.

' It is to be understood that various materials other than silicon rubber are useful in this invention, such as relatively resilient or elastic materials dissolved in a volatile vehicle, as well as materials such as latex dispersed in water. Such materials, of course, may require a different method of application than that hereinabove described, as will be understood readily by those in the art.

After the formation of the flexible wall member 20 has been completed the cartridge unit may then be filled with ink or a similar liquid substance, and the open end '6 thereof sealed with the closure disc 28 as described here'- tofore.

After the complete supply of Writing fluid has been depleted from the cartridge barrel unit 10, and the flexible wall member 20 completely collapsed, it may be discarded and replaced by a fresh, factory filled unit. However, under certain circumstances, it may be desirable to refill the reservoir, which refilling may be done merely by forcing fluid under a light pressure through the above described fluid passages 50 and 64. The pressure used in forcing the fluid through these channels is suflicient to cause distention of the flexible wall member 20 into its original intimate contact with the interior surface of the body portion 12.

It is understood that the term distention, as used herein, does not indicate any stretching or inflation of the flexible wall portion 20 but merely the positioning thereof in its unstressed, neutral position.

The embodiment of FIG. 3, similar basically to the embodiment of FIG. 1 is shown as being disposed in and partially assembled with a fountain pen having a writ ing unit assembly identical to that described hereinabove. This modification includes a body portion or support 186 which is formed preferably of a semi-rigid material such as polyethylene. Formed within the body portion 100, in the manner described heretofore with respect to the embodiment of FIGS. 1 and 2, is a flexible or flaccid wall portion 162. As will be understood from the foregoing discussion of the embodiment of FIG. 1, the flexible wall member is releasable from and displaceable within the body portion 1011 to follow the ink and reduce the volumetric capacity of the reservoir as fluid is withdrawn therefrom during writing.

The forward ends 1114 and 1116 of the body portion and wall member 1612, respectively, are closed by a seal disc 1% molded of polyethylene or similar material and provided with a flange bonded to the body portion 100 at its open forward end 104. The seal disc 1% is provided with an annular recess 112 defining a fluid discharge which is closed by a thin diaphragm member 114 which is readily pierceable by the pierce tube 116 of the writing unit assembly 118. The insert 120 disposed within the pierce tube 116 provides a fluid passage 122 for communication between the interior of the cartridge unit and a fluid feed path 124 formed in the forward portion of the feed bar 126. Thus, after completing assembly of the pen illustrated in FIG. 3 and during writinguse thereof, fluid will be drawn from the reservior,

through the insert passage 122 and into the feed path 124, for transfer to the pen point and subsequent deposit on a writing surface.

As clearly shown in FIG. 5 of the drawing, the body portion 100 is provided with a plurality of longitudinally extending grooves 1125 around its interior surface, in order to provide a larger area or" contact and a greater amount of adhesive attraction between the body portion 100 and the flexible wall member 102.

In order to allow displacement of the flexible wall portion 102 within the body portion 101 as fluid is with drawn from the reservoir during writing, air vent passages 126 and 128 are provided through the rearward end of the pen barrel 120 and the body portion 100, respectively. The vent 126 through the pen barrel 120 is defined by a tubular element 138 provided on its forward end with a pierce point 132. The pierce point is adapted to break a diaphragm 134 which is formed in a second seal disc 136 to close the vent 128 except upon assembly of the cartridge unit with the fountain pen. One of the purposes of providing the diaphragm 134 is to prevent inadvertent damage to the flexible wall member 102 as by the insertion of a pin or other sharp instrument through the vent 128 prior to use of the cartridge unit.

In order to eliminate any possibility of rupture of the flexible wall member 102 by the pierce point 132, the rearward end of the barrel 129 is provided with an internally disposed forwardly facing shoulder 140 which surrounds the tubular element 133 and which abuts the rearward or outwardly facing surface of the second seal disc 136 thereby limiting the amount of movement of the pierce point 132 through the vent 128 during assembly of the barrel with the writing point assembly. This feature is best shown in FIG. 4 of the drawings.

During formation of the flexible wall member 162 within the body portion 1%, it is necessary to provide temporarily a closure member 142, see FIG. 9, which conveniently may comprise a part of the holder or carrier 144. The closure member 142 is sized so as to fit snugly within the rearward end of the body portion ltiii and includes a generally semi-spherical concave surface 146 in its lower end thereby forming a wall portion against which the material of the flexible member 132 is sprayed.

Prior to insertion of the closure member 1412, the lower end 146 preferably is coated with a release agent so that it will readily separate from the rearward end of the flexible wall member 162 after formation thereof. For the purpose of ejecting the body portion Mitt after completion of the wall member 102, the carrier or holder 144 is provided with a ring 148 which is reciprocally movable relative to the closure member 142 and sized to act against the rearward edge of the body portion 1%.

The steps of formation of the wall member 102 within the body portion 108 may be accomplished in substantialiy the same manner as that described previously with respect to the emobdiment of FIG. 1. Accordingly, a discussion of the steps involved will not be repeated at this time.

it is to be understood that although only two embodiments of a fluid reservoir are illustrated and described herein for use with a fountain pen, this invention is not to be limited thereto as modifications thereof may be provided and, likewise, the invention may be utilized in connection with devices such as liquid adhesive dispensers and the like. Also, it is apparent that the flexible wall portion may be formed by methods other than the one specifically described herein.

Accordingly, this invention is not to be limited to the embodiments described hereinabove, and it is contemplated, by the appended claims, to cover any such modifications as fall within the true spirit and scope of this invention.

I claim:

1. A fountain pen comprising a fluid container and a writing unit assembly mounted forwardly of said fluid container, said fluid container having a vented hollow body portion and a film-like layer of flexible material forming a flaccid sack engaging the interior surface of said body portion, the interior surface of said sack defining a writing fluid reservoir, the exterior surface of said sac having an adhesive quality causing it to releasably stick to the interior surface of said body portion, said writing unit assembly having conduit means providing the sole means for fluid passage from said writing fluid reservoir, said conduit means being small enough in cross-section to prevent passage of air therethrough into said reservoir while writing fluid is disposed within said conduit means, the adherent attachment of said sack to the interior surface of said body portion being sufficient to resist separation thereof and the consequent free discharge of writing fluid through said conduit means under the influence of the normal weight of the fluid in the reservoir, and said sack being separable from and displaceable within said body portion to reduce the volumetric capacity of said reservoir in response to withdrawal of writing fluid from said conduit by capillary action.

2. In a fountain pen, a writing fluid container comprising a hollow body member and a flexible wall member formed as a continuous film within and substantially covering the interior surface of said hollow body member, the interior surface of said wall member defining a reservoir for receiving a column of writing fluid, the exterior surface of said wall member having an adhesive quality causing it to releasably stick to the interior surface of said body member, and capillary means for forcibly withdrawing writing fluid from said reservoir while preventing the entry of air thereinto, said container having a means providing atmospheric Venting to the exterior surface of said wall member, the adherent attachment of said wall member to the interior surface of said body member being suflicient to resist separation thereof and the consequent free discharge of writing fluid through said capillary means under the influence of the normal weight of the column of writing fluid in the reservoir, the exterior surface of said wall member being progressively detached from the interior surface of said body member to reduce the volumetric capacity of said reservoir in response to the Withdrawal of writing fluid from said reservoir by said capillary means.

3. In a fountain pen, a writing fluid container comprising a hollow body member and a flexible wall mem ber formed as a continuous film within and substantially covering the interior surface of said hollow body member, the interior surface of said wall member defining a reservoir for receiving a column of Writing fluid, the exterior surface of said Wall member having an adhesive quality causing it to releasably stick to the interior surface of said body member, and capillary means for forcibly withdrawing writing fluid from said reservoir while preventing the entry of air thereinto, said container having a means providing atmospheric venting to the exterior surface of said wall member, the interior of said body member being provided with a surface conformation and finish which will cause said Wall member to be adherently attached thereto suflicient to resist separation therefrom and the consequent free discharge of writing fluid through said capillary means under the influence of the normal weight of the column of writing fluid in the reservoir, but which will nevertheless permit the exterior surface of said wall member to be progressively etached therefrom against the resistance of the force of adhesion between said exterior surface and the interior surface of said hollow body member to reduce the volumetric capacity of said reservoir in response to the'forcible withdrawal of writing fluid from the reservoir by said capillary means.

References Cited by the Examiner UNITED STATES PATENTS 2,492,058 12/1949 OConnor 45.4 2,499,771 3/1950 OCOnnor l2045.4 2,846,103 8/1958 Maxwell 215-l1 2,876,113 3/1959 Barton 2l5 l1 X 2,987,209 6/ 1961 Leonard 215-11 EUGENE R. CAPOZIO, Primary Examiner.

LAWRENCE CHARLES, JEROME SCHNALL,

Examiners.

Claims (1)

1. A FOUNTAIN PEN COMPRISING A FLUID CONTAINER AND A WRITING UNIT ASSEMBLY MOUNTED FORWARDLY OF SAID FLUID CONTAINER, SAID FLUID CONTAINER HAVING A VENTED HOLLOW BODY PORTION AND A FILM-LIKE LAYER OF FLEXIBLE MATERIAL FORMING A FLACCID SACK ENGAGING THE INTERIOR SURFACE OF SAID BODY PORTION, THE INTERIOR SURFACE OF SAID SACK DEFINING A WRITING FLUID RESERVOIR, THE EXTERIOR SURFACE OF SAID SAC HAVING AN ADHESIVE QUALITY CAUSING IT TO RELEASABLY STICK TO THE INTERIOR SURFACE OF SAID BODY PORTION, SAID WRITING UNIT ASSEMBLY HAVING CONDUIT MEANS PROVIDING THE SOLE MEANS FOR FLUID PASSAGE FROM SAID WRITING FLUID RESERVOIR, SAID CONDUIT MEANS BEING SMALL ENOUGH IN CROSS-SECTION TO PREVENT PASSAGE OF AIR THERETHROUGH INTO SAID RESERVOIR WHILE WRITING FLUID IS DISPOSED WITHIN SAID CONDUIT MEANS, THE ADHERENT ATTACHMENT OF SAID SACK TO THE INTERIOR SURFACE OF SAID BODY PORTION BEING SUFFICIENT TO RESIST SEPARATION THEREOF AND THE CONSEQUENT FREE DISCHARGE OF WRITING FLUID THROUGH SAID CONDUIT MEANS UNDER THE INFLUENCE OF THE NORMAL WEIGHT OF THE FLUID IN THE RESERVOIR, AND SAID SACK BEING SEPARABLE FROM AND DISPLACEABLE WITHIN SAID BODY PORTION TO REDUCE THE VOLUMETRIC CAPACITY OF SAID RESERVOIR IN RESPONSE TO WITHDRAWAL OF WRITING FLUID FROM SAID CONDUIT BY CAPILLARY ACTION.

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