US3792932A

US3792932A - Ink feed for ball point pens

Info

Publication number: US3792932A
Application number: US00253769A
Authority: US
Inventors: E Henriksen
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-05-16
Filing date: 1972-05-16
Publication date: 1974-02-19
Anticipated expiration: 1991-02-19
Also published as: AU7712575A; FR2251444A1; NL7314258A; GB1475076A; DE2352165A1; DE2352165C2; FR2251444B1; AU494043B2; CH574826A5

Abstract

The writing tip of a ball point pen is mounted to an ink reservoir by a resiliently deformable member defining part of an ink passageway from the reservoir to the writing tip and supporting the tip for axial movement of the tip relative to the reservoir. A check valve prevents flow of ink from the passageway to the reservoir and writing pressure on the tip distorts the resilient member in a manner to apply pressure to the ink trapped in the passageway. In some forms an air bubble or equivalent pressure accumulator is incorporated in the device and in some forms the check valve is normally open and is closed by initial movement of the writing tip upon applying writing pressure thereto.

Description

United States Patent [1 1 Henrik sen [451 Feb. 19, 1974 INK FEED FOR BALL POINT PENS [22] Filed: May 16, 1972 211 Appl. No.: 253,769

[52] U.S. Cl. 401/148, 401/188 [51] Int. Cl B43k 7/10 [58], Field of Search 401/148, 187, 188

[56] 4 References Cited UNITED STATES PATENTS 2,762,337 9/1956 Eeckwith 401/148 3,457,019 7/1969 Blanchard 401/187 FOREIGN PATENTS OR APPLICATIONS 926,054 4/1955 Germany 401/187 Primary ExaminerLawrence Charles Attorney, Agent, or FirmBacon & Thomas [57] ABSTRACT The writing tip of a ball point pen is mounted to an ink reservoir by a resiliently deformable member defining part of an ink passageway from the reservoir to the writing tip and supporting the tip for axial movement of the tip relative to the reservoir. A check valve prevents flow of ink from the passageway to the reservoir and writing pressure on the tip distorts the resilient member in a manner to apply pressure to the ink trapped in the passageway. In some forms an air bubble or equivalent pressure accumulator is incorporated in the device and in some forms the check valve is normally open and is closed by initial movement of the writing tip upon applying writing pressure thereto.

11 Claims, 27 Drawing Figures PATENTEDFEB 19 m4 3 792 932 saw 10E 4 INK FEED FOR BALL POINT PENS This application is a continuation-in-part of my prior application Ser. No. 162,200 filed July 13, 1971 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to ball point pens having rotatable writing balls, and particularly to means for ensuring a supply of ink at the writing tip.

A conventional gravity feed ball point pen will not write when the tip is raised to a level substantially higher than the reservoir because gravity tends to cause rearward flow of the ink when ink in the narrow gap around the ball is used up. Air is then drawn into the ball point through that gap and into the reservoir, sometimes causing permanent damage to the pen since air bubbles in ducts leading to the ball point usually prevent the flow of ink when the pen is again used in normal writing position. This failing of conventional ball point pens is true whether the reservoir or ink flow passages are of capillary dimensions or larger.

Attempts have been made to solve this problem heretofore, some of which involved means for temporarily or permanently compressing the air or other gas in the reservoir behind the supply of ink. Such constructions, however, are not satisfactory since the air pressure is not uniform at all times and is usually either too high, causing bleeding of the ink at the ball point, or too low so that the pen stops writing unless some manual operation is performed to adjust the air pressure. Devices for performing such manual operations are relatively complicated and expensive.

Devices have alsobeen suggested whereby mechanical pressure is applied to the ink column in the reser-' voir by a pump means responsive to pressure on the writing tip. Examples of such proposals are the patent to Barlow et al. U.S. Pat. No. 2,106,046 and the patent to Beckwitt U.S. Pat. No. 2,762,337. The Barlow patent employs a slidable piston-type pump but is not applied to a conventional ball point pen having a rollable writing tip. The Beckwitt patent employs a slidable writing tip and a relatively complicated and expensive pumping structure actuated thereby. This proposal likewise is relatively expensive and complicated to manufacture.

SUMMARY OF THE INVENTION In its broader aspects the present invention comprises a writing tip, including a rollable ball, and an ink reservoir with means for conducting ink from the reservoir to the ball tip. At least a portion of that means, which can be referred to as a passageway, is formed of resiliently flexible material sealingly joined to both the writing tip and the reservoir and normally holding the same in assembled relationship. The resilient material is deformable, however, so that when writing pressure is applied to the ball tip, the material deforms to reduce the volume of at least a portion of that passageway and a one-way valve adjacent the reservoir prevents reverse flow of ink whereby writing pressure enforces maintenance of a supply of ink at the writing tip irrespective of the attitude of the pen.

In certain forms of the invention pressure accumulator means are provided to at least temporarily maintain pressure on the ink near the writing tip even during periods of reduction or relief of writing pressure at the tip.

Before describing specific structual embodiments of the invention, applicant will define certain terms employed herein.

As used in this application, the term ball point or ball point pen refers to a pen having a suitable hard spherical ball rotatably mounted in Upon suitable housing in such manner that part of the ball protrudes from the housing, which part is adapted to be engaged with a surface on which writing is to be placed, the ball being adapted to be rotated by being moved over and in contact with that writing surface. dUpon rotating the ball, a film of ink passes through a gap between the ball and its housing, which film is deposited as a trace on the writing surface. The ball is mounted in the housing with very little clearance, the gap between the ball and its side seat through which the ink is carried past the ball is preferably between 0001mm and 0.0lmm, limiting axial movement of the ball to a maximum of 1/10 the ball diameter, and it rests on a part spherical bottom seat which is provided with grooves or other passages permitting the passage of ink past that bottom seat when the ball is pressed against it during writing. The side seat preferably extends at least to the equator of the ball. Due to the minute dimensions of the gap, capillary forces are created which prevent flow of ink past the ball when it does not rotate even when a relatively high pressure is applied to the ink.

The term reservoir refers to a structure for containing a supply of ink and from which ink is permitted to be fed to the ball point by gravity when the pen is in normal writing position. The reservoir is provided with a vent permitting the admission of air thereto to replace ink as the latter is used and further, it is provided with means to prevent the air from being mixed with the ink even when the reservoir is tilted to a normally nonwriting position, so that the ink will remain in a continuous column extending from its rear surface toward the ball point. Examples of such means are slidable followers in the reservoir, such as described in the patent to Henriksen U.S. Pat. No. 3,424,537. Also, a capillary tube reservoir inherently has such characteristics.

A capillary tube or passageway of capillary dimensions is referred to herein to define a tube or bore of such small diameter that ink contained therein will form a meniscus which is stable enough to withstand the forces of gravity acting upon the ink, including forces created by normal shocks. The actual dimensions of a capillary passage or tube varies with the properties of the ink, including the viscosity thereof, the surface tension and the degree to which the ink wets the materials of the wallssurrounding it. Writing ink is referred to herein as an ink suitable for use in ball point pens, preferably having a viscosity of between 1500 and 20,000 centipoises at 25C, and at least sufficiently fluid to be able to flow to the ball point by its own weight when the pen tip is down.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary sectional view through the tip portion of a ball point pen embodying the present invention and showing the structure embodying the invention housed in a conventional holder;

FIG. 2 is a similar fragmentary section of a modified form of the invention;

FIG. 3 is a transverse sectional view on the line 3-3 of FIG. 4;

FIG. 4 illustrates a further modified form of the invention;

FIG. 5, 6, 7 and 7a illustrate further modified forms;

FIG. 8 is a transverse sectional view on the line 8-8 of FIG. 7;

FIGS. 9, 10 and 11 illustrate additional modifications;

FIG. 12 is a transverse sectional view, taken on the line 12-12 of FIG. 11;

FIGS. 13 and 14 illustrate still further modifications of the invention;

FIGS. 15 and 16 are fragmentary sectional views of modifications usable with the embodiments of FIGS. 13 and 14;

FIG. 17 is a transverse sectional view taken on the line 17-l7 of FIG. 16;

FIG. 18 is a longitudinal sectional view of a further modification;

FIG. 19 is a transverse section on line 1919 of FIG.

FIG. 20 is a longitudinal sectional view of a still further modification; and

FIGS. 21-26 illustrate additional embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a highly schematic viewof a structure embodying the basic principles of the invention. As shown, assembly 2, which embodies the principles of the invention, is shown housed in a conventional hand case or holder 4, often referred to as the barrel of the pen. It is to be understood that all forms of the invention are intended to be placed in a holder or barrel. The assembly 2 includes a tubular reservoir 6 having a reduced forwardly extending tubular portion 8 terminating in a tapered valve seat 10. Engageable with the valve seat 10 is a ball 11 adapted to close the tubular member 8 against rearward flow ofink. A writing tip 12 includes a housing portion 14 containing a rotatable ball point 16 supplying the ink through passageways l8 and 20. Even though not specifically described in each case, the Writing tip of every form of the invention is provided with a rotatable ball point and ink conducting passageway equivalent to that shown at 18-20 in FIG. 1. The writing tip 12 extends rearwardly and terminates short of the ball 11, its rearward edge being provided with suitable notches 22, or equivalent passageways, whereby the ball 11 cannot seal against the writing tip. A tubular body 24 of elastomeric material, comprising a connecting means, tightly surrounds the rear portion of the writing tip and the forward portion of the tube 8 and is sealingly engaged with both while holding them in the illustrated axial alignment. The material of the tubular element 24 may be any suitable flexible resilient materials, such as soft polyvinyl, soft polyethylene, silicone rubber, or similar materials. While the drawings do not illustrate the ink itself; it is to be assumed that the reservoir 6, tube 8 and passageways l8 and 20 are filled with ink. When the pen illustrated is used in a normal writing attitude, with the writing tip pointing downwardly, the ball 11 can move free of seat 10 to provide free unrestricted flow of ink therepast to the writing tip. If the pen is used in an inverted attitude, that is, with the writing tip pointing upwardly, gravity will tend to cause the ball 11 to engage seat 10 to prevent rearward flow of ink. As writing pressure is applied to the writing tip, the tubular element 24 will be compressed slightly and will obviously tend to reduce the volume of the ink passageway forwardly of the valve seat 10 to thus apply some pressure to the ink and maintain a constant supply of ink at the writing tip. Even if the ball 11 does not seat firmly on the seat 10 under the influence of gravity, the initial application of writing pressure to the ball tip will tend to cause ink to flow rearwardly to the reservoir and such tendency, resulting from pressure on the ink in the writing tip will itself force the ball 11 into firm seating engagement with seat 10. Thus, the pen illustrated will write even in an inverted position or under conditions of zero gravity or high vacuum. Obviously, relief of pressure on the writing tip or removal of the same from the writing surface will relieve all pressure from the tubular member 24 and the latter will then expand axially, pushing the writing tip forwardly and drawing more ink from the reservoir 6, into the passageway between valve seat 10 and ball point 16.

The modification of FIG. 2 comprises a tubular reservoir 26, a writing tip 28 and a connecting means 30. The connecting means 30 has a skirt 32 tightly fitted in the reservoir 26 and a cylindrical portion 34 defining a chamber 36. The structure 30 also includes a smaller diameter tubular portion 38 extending into the chamber 36 and sealingly joined thereto by a flexible resilient transverse wall or diaphragm 40. The innermost end of tubular member 38 is closed, as at 42, and defines a transverse surface 44. An integral rod-like extension 46 extends rearwardly from the surface 44. A plug 48 is tightly fitted in the skirt 32 and is provided with a bore 50 loosely receiving the element 46. It is also provided with a counterbore seat receiving a body 52 of elastomeric material having an enlarged opening 54 therein through which element 46 passes very loosely. The tubular element 38 is also provided with an opening 56 providing communication between the chamber 36 and the interior of tubular member 38. It is to be understood that the interior or tubular member 38 communicates with a suitable passageway in writing tip 28 for conducting ink to the ball tip 16. It is to be noted that the opening 56 is a substantial distance forwardly of the transverse surface 44. Ball point pens are conventionally charged with ink by centrifuging into the reservoir and writing tip. This is done by arranging the pen or refill with its writing tip pointing radially outwardly, then rotating the same at high speed while depositing ink in the rear end of the reservoir. Due to the position of the opening 56, ink centrifuged into the pen described will pass through the openings 50 and 54 into the chamber 36 and from there through opening 56 to the writing tip, but the space within tubular member 38 rearwardly of the opening 56 will have a body of air 58 trapped therein, and the interior of tubular member 38 is preferably of capillary dimensions so that a stable meniscus 60 is formed as shown.

The parts are so dimensioned that the normal space between the transverse surface 44 and the body 52 is quite small, although of sufficient extent to permit free flow of the ink therebetween when no pressure is applied to the tip.

In this form of the invention and in all other modifications to be described later, it is to be understood that the pen can be used in a normal writing attitude, that is, with the writing tip pointing downwardly. However, writing pressure applied to the writing tip will normally cause the pen to function in a manner to be described even when the pen is employed with the writing tip uppermost. Assume the pin to be charged with ink and the user applies the tip to a writing surface with the writing tip pointing upwardly. Initial pressure applied to the writing tip first causes the writing tip and tubular member 38 to move rearwardly slightly due to the flexure of the transverse wall or diaphragm 40. After a very minute rearward movement, the surface 44 engages resilient body 52 to in effect close a valve to prevent rearward flow of ink. Continued pressure on the writing tip causes additional flexure of the wall 40 and results in some axial compression of the body 52. This results in a decrease in volume of the chamber 36 and thus applies pressure to the ink, ensuring a continuous supply of ink to the writing tip.'The body of air 58 previously described, functions as a pressure accumulator. When pressure is applied to the ink in chamber 36, that pressure is also transmitted through opening 56 and somewhat compresses the air 58 whereby temporary or momentary reduction or removal of pressure at the writing tip, premitting the chamber 36 to expand somewhat, will result in the air pressure maintaining sufficient pressure on the ink at the writing tip to ensure maintenance of an adequate supply of ink thereto until writing pressure is again applied. In the form of FIG. 2, initial writing pressure need overcome only the resilience of the transverse wall 40 to bring surface 44 into valveclosing engagement with body 52. Thereafter, writing pressure must overcome the resistance of both the wall 50 and body 52 to apply pressure to the ink. The material of connecting means 30 may be polypropylene or other material having about the same rigidity and/or flexibility. Body 52 must obviously be softer than plug 48.

As will be discussed further in greater detail later, the initial movement of the writing tip to effect closing of the valve 44-52 is very small.

In FIG. 4, a reservoir 62, is formed of suitable resilient material, such as polyethylene or polypropylene or the like, by way of example only, and is provided with a valve plug 64 therein having a ball valve 66 engageable with a seat 68 and caged in the plug 64 by suitable projections 67 (see also FIG. 3). At its forward end the reservoir tube 62 telescopically receives a writing tip 70 having a cllar.72 fixed thereon and against which the tube 62 abuts. As illustrated herein, the tube 62 is what would he referred to as a capillary tube although it may be of larger dimensions. Between the ball valve 64-68 and the writing tip 70, the tube 62 is cut, molded or otherwise formed to define a thin wall bellows section 74, which is preferably readily deformable in an axial direction. The bellows section could be molded by heat softening the material of the reservoir and forming by a blowing or other operation. Any suitable form of plastic, for example, polyethylene of the hard type or polypropylene, may be employed to form the bellows section 74 and it will be obvious that the same is resiliently deformable in an axial direction by writing pressure applied to the writing tip 70 and upon release of such pressure, the bellows will axially expand to draw more ink past the ball 66 into the chamber 74. Initial writing pressure seats the ball 66 on seat 68 and applies pressure to the ink in chamber 76 for the purpose and with the results already described.

FIG. is similar to FIG. 4 but in this form a reservoir 78 is joined to a writing tip 80 by a connecting means comprising a flexibly resilient bellows section 82 and

tubular extensions

84 and 86 tightly fitting adjacent portions of the writing tip and reservoir 78, respectively. The tubular portion 86 is open at its inner end 88 and defines a tapered ball seat 90 against which a ball 92 can sealingly seat. The ball 92 is retained adjacent the seat 90 for only minute movement relative thereto by an inwardly struck tab 94. The clearance between the ball 92 and tubular portion 86 is very small but sufficient to permit forward flow of ink therearound. The manner of functioning of this form of the invention will not be described in detail since it is similar to those already described. The connecting member having the bellows section 82 may be made of any suitable material and is adapted to be constructed of metal, such as copper alloys, stainless steel, or the like, although plastics may also be employed.

In FIG. 6, a writing tip 96 slidably fits in a tubular end portion 98 of a reservoir 100 and at its inner end the writing tip tightly receives a tubular portion 102 of a connector means having a cylindrical portion 104 tightly fitting the inside of reservoir 100 and joined to the tubular portion 102 by a resiliently flexible transverse wall or diaphragm 106. Thus, the writing tip is axially movable relative to the reservoir by resilient flexure of the wall 106 under writing pressure. Rearwardly of the cylindrical portion 104 is a valve carrier 108, shown as made of metal but not limited thereto, tightly fitted in the reservoir 100 and carrying a valve ball 110 engageable with a valve seat 112. The ball 110 is retained in close proximity to the seat 112 by suitable spaced imperforate indentations 114. Here again, the clearance between ball 110 and its surrounding structure is small but sufficient to permit forward flow of ink therepast. The function and operation of the modification of FIG. 6 is essentially the same as that already described and need not be repeated here.

In FIGS. 78, a writing tip 116 is connected to a reservoir 118 by connecting means having

tubular portions

120 and 122 tightly and sealingly fitting in the adjacent ends of the writing tip and reservoir, respectively. The connecting means also includes a single-fold bellows section 124, as shown. Within the reservoir 118 immediately rearwardly of the connecting means is a check valve structure comprising a tightly fitted plug 126 having a bore 128 nearly therethrough and a closed inner end 130, see FIG. 7a which is an enlarged view of the check valve showing the end 30 in open position by dotted lines. This plug may be hard or soft polyethylene, soft polyvinyl or similar materials. The closed end 130 is separated from the plug body 126 by a slit 132 extending almost completely through the body but leaving enough material connecting end 130, at 131, to the body to serve as a resilient flexible hinge. The body 126 is ofa suitable plastic or similar material of resilient characteristics so that the end 130 constitutes a flap valve normally held in closed position but responsive to minute pressure differences to open sufficiently to permit forward flow of ink. In this form also, the operation of the devices is essentially the same as that previously described and will not be repeated in detail. If desired, a plug member 134, of polyethylene or polypropylene, may be tightly fitted in the rearward tubular portion 136 of the writing tip and provided with a passageway 138 through which ink may flow. The plug 134 is provided with a forwardly facing bore or chamber 140 of capillary dimensions and in which a bubble of air is trapped by meniscus 142 when the pen is centrifugally charged with ink in a manner already described. The bubble of air in chamber 140 functions as a pressure accumulator operating in the same manner as already described with reference to FIG. 2. Clearly, such a plug may be provided in any of the other forms of the invention shown herein and may be in addition to or in place of other pressure accumulators shown.

The embodiment of FIG. 9 is shown as comprising a tubular reservoir 144, the forward end of which telescopically engages a tubular portion 146 of a resiliently flexible, preferably elastomeric, connector means 148, which may be of any suitable material, such as those described with reference to the FIG. 1 embodiment. The means 148 is provided with an enlarged cylindrical portion 150 integral with the tubular portion 146 and abutting the end of the reservoir 144 and also abutting a shoulder 152 on writing tip 154. The shoulder 152 being defined by the juncture between the main body portion of the writing tip and a rearward tubular extension 156 tightly fitting a central bore 158 in the connecting means 148. Rearwardly of the inner end of the tubular extension 156 is a check valve indicated generally by the numeral 160, having a ball 161 engageable with a valve seat 163. The check valve is of a general construction already described with reference to previous embodiments. In this form of the invention, writing pressure applied to the writing tip will produce compression in the cylindrical portion 150 of the connector and the tubular portion 146 thereof is sufficiently distortable so that the writing tip and its tubular portion can move rearwardly to reduce the volume of chamber 162 between the writing tip and valve 160. The tubular portion 146 of the connector functions in the nature of a transverse resilient wall, but due to its axial length, it also maintains the writing tip and reservoir in axial alignment. The function and operation of this embodiment is essentially the same as those already described, as will be obvious to those skilled in the art.

The embodiment of FIG. comprises a writing tip 164 and a reservoir 166 sealingly joined together by a connector means 168. The connector means comprises a cylindrical portion 170 having an extended skirt 172 tightly fitting the end of reservoir 166 and having therein a tight fitting plug 174 provided with an ink passageway 176 and a ball seat 178. A ball 180 is held adjacent the seat 178 by inwardly struck lips 182 while premitting small movement away from the seat. The connector means also includes a smaller diameter tubular portion 184 tightly fitting within the rear tubular portion of the writing tip 164 and having a bore 186 therethrough. A transverse resiliently flexible wall or diaphragm 188 integrally joins the tubular portion 184 and cylindrical portion 170, similar to the diaphragm described in connection with FIGS. 2 and 6. A compression spring 190 is positioned between the wall 188 and plug 174 and serves to ensure that the writing tip return to a forward position after release or relief of axial pressure applied thereto during writing. As will be obvious, writing pressure applied to the tip will cause the wall 188 to flex and will result in a reduction in the volume of chamber 192 and closure of valve 180 in the manner already described and for the purposes described. The spring 190 must be strong enough to return the wall 188 to its normal position yet weak enough to compress under normal writing pressure, usually from 100-400 grams. The material of connector means 168 may be the same as described for FIG. 2.

FIGS. 11 and 12 illustrate a possible form of check valve usable with any of the embodiments of the invention. This form of valve comprises a tubular plug 194 tightly fitted in a tubular reservoir 196 of a tubular portion of the connector means. The plug 194 defines a passageway completely therethrough for the flow of ink and includes a shoulder portion defining a valve seat 198, and a ball valve 200 thereadjacent. The ball is held in close proximity to its seat 198 by a shoulder 202 at the end of a smaller diameter tubular passageway 204 having grooves or the like 206 extending therealong to permit free flow ofink therethrough even when the ball 200 engages the shoulder 202. As stated, FIGS. 11 and 12 merely illustrates one form of valve that may be employed in any of the forms of the invention to which a valve of this type is adapted. Such a valve may be conveniently made by the same machinery used in making ball point pen writing tips.

In the form of FIG. 13, a large diameter tubular reservoir 208 is provided with a follower plug 210 of the type and for the purpose referred to earlier herein. The forward end of the reservoir 208 is reversely configured to define a forwardly facing pocket or tubular portion having a first cylindrical surface 212 and a rearwardly extending but smaller cylindrical surface 214 defining a chamber 216. A unitary body of resiliently flexible material, preferably elastomeric, has a cylindrical portion 218 tightly fitted in the cylindrical pocket 212 and a second smaller cylindrical portion 220 extending into chamber 216, spaced from the sides thereof, and having a closed inner end 222 defining a substantially flat transverse surface 224 normally spaced a short distance from the periphery of an opening 226 in the inner end wall of the chamber 216. The material of the connector means may be the same as described with reference to FIG. 1. A writing tip 226 has a rearwardly extending tubular portion 228 tightly received in the larger cylindrical portion of connector means 218 and the interior of which communicates with a blind bore 230 in the connector portion 220. A transverse opening 232 in the side wall of connector portion 220 provides communication between the chamber 216 and the writing tip, similar to that described in connection with FIG. 2. Thus, there is formed a forwardly facing capillary pocket 234 to trap a bubble of air to be held therein by meniscus 236 when ink is centrifiged into the pen.

In operation, writing pressure applied to the writing tip 226 will produce axial distortion of the connector means particularly a transverse wall portion thereof joining

cylindrical portions

218 and 220, permitting rearward movement of the writing tip relative to the reservoir 208. Initial rearward movement engages surface 224 with the rear wall of the chamber 216 outwardly of the opening 226 to thus, in effect, close a valve. Further rearward movement of the writing tip results in axial compression of the connector portion 220 and reduction in the volume of chamber 216 to apply pressure to ink at the writing tip for the purpose and with the results already described. The air bubble in 234 functions as a pressure accumulator, as already described.

FIG. 14 is very similar to FIG. 13 but is applied to a reservoir 238 of capillary dimensions and in which a body of ink forms a stable meniscus 240. The reservoir 238 includes an adaptor 242 tightly fitted thereon and defining a forwardly facing cylindrical pocket or chamber 244 communicating with the reservoir through a passageway 246. The passageway 246 terminates in the bottom wall of the chamber 244. A writing tip 248 has a tubular portion 250 extending rearwardly and sealingly engaging the surface of a tubular connector means 252 of resiliently flexible, preferably elastomeric material of the type previously described. The connector means 252 is provided with a blind bore 254 therein and an end surface 256 facing the bottom of the chamber 244. The rearward portion of the connector means is of lesser diameter than the chamber 244 and has an opening 258 therethrough corresponding to the opening 232 of FIG. 13. Thus, the connector defines a capillary pocket 260 similar to the pocket 234 of FIG. 13

i and functioning in the same manner. It will be obvious to those skilled in the art how this embodiment operates in a manner similar to those already described.

FIGS. 15 and 17 are enlarged fragmentary sectional 4 views through portions of elements of the invention which may in all other respects be identical to either FIGS. 13 or 14. In each case, a portion of the reservoir or adaptor defines a chamber 262 in which a reduced diameter portion of a connector means 264 extends. The bottom wall of the chamber is provided with an opening 266 which may be identical to the corresponding

openings

226 or 246 of FIGS. 13 or 14 and having substantially flat transverse surfaces 224 and 256, respectively, on the end of the connector means. FIG. 15 shows the corresponding transverse surface 268 as being in an obliquely arranged plane. Thus, only an initial portion 270 will engage the end wall of the chamber 262- and compression or distortion of the elastomeric material is necessary before the valve opening 266 can be closed. This ensures that, upon release of writing pressure from the writing tip, the valve will open and ensure a passageway for flow of ink from the reservoir into chamber 262 even though the material of member 264' may have assumed some permanent setting or for other reason adhere to the bottom wall of the chamber 262. In FIG. 16, instead of providing an oblique surface, such as the surface 258 of FIG. 15, the transverse surface 272 is provided with a plurality of spaced rearward pointed projections 274 formed integrally thereon. It will be obvious that these portions must be compressed before the valve can be closed and their natural resilience will ensure opening of the valve when writing pressure is released.

In the form shown in FIG. 18 a tip member 280 is secured to the forward end of tubular reservoir 282. The member 280 is provided with a bore 284 therein and a counterbore 286 defining a shoulder 288. Within the bore 284, adjacent the end of the reservoir 282, there is fixedly positioned a solid plug member 289, shown in section in FIG. 19. The member 289 is provided with a flat forward surface 290 and a plurality of grooves or passages 292 spaced around its periphery. Thus, the passages 292 provide communication between the reservoir 282 and the bore 284. A writing tip 294 is provided with a short rearwardly extending tubular portion 296, the cylindrical portion 298 of the writing tip being longitudinally slidable in the counterbore 286. A shoulder 300 on the writing tip cooperates with the shoulder 288 to limit rearward movement of the writing tip. A general cylindrical body 302 of elastomeric material is provided with a central opening 304 communicating with a larger axial opening 306 therein. The tubular portion 296 fits tightly and sealingly within the bore 306, the forward end of the body 302 abutting the writing tip 294. The opening 304 extends through the rearward surface of the body 302, which is provided with a circular rib or rim 308 around that opening. The body 302 is also provided with a peripheral flange 310 engageable with the forward end of the plug member 289. The body 302 fits snugly within the bore 284 at the rearward end but is reduced in diameter forwardly thereof, as shown at 312, for a purpose to be explained.

When writing, pressure is applied to the tip 294, the writing tip is caused to move rearwardly in the bore 286 and thus distort the body 302 until the rib 308 engages surface 290 to thus, in effect, close a valve in the flow path between the reservoir and the writing tip and continued writing pressure further distorts or compresses the body 302 to apply pressure to the ink at the writing tip. As shown, the peripheral flange 310 is of greater axial height than the rib 308 and, thus, the natural resilience of the body 302 will tend to hold the valve member in open position until writing pressure is applied.

The reduced diameter portion 312 of the body 302 reduces frictional resistance to inward movement of the writing tip 294 and the

shoulders

288 and 300 provide positive stop means so as to prevent damage to the body 302 if excessive pressure is applied to the writing tip. As will be apparent, this form of the invention is relatively simple to construct, particularly with regard to molding of the elastomeric body 302.

In the embodiment of FIG. 20, a tubular reservoir 314 is provided at its forward end with a fitting 316 having a first bore 318 therein and a counterbore 320. The counterbore supports a tip member 322 having a bore 324 therein slidably guiding a tubular member 326 to which a writing tip (not shown) is attached. The slidable tubular member 326 extends rearwardly into the bore 318 and has fixed thereon a generally cupshaped body 328 of elastomeric material, which in turn sealingly engages within the bore 318. The innermost end of tubular member 326 abuts a shoulder 330 in member 328, the shoulder surrounding a forwardly extending bore 332 in the member 328. The innermost or rearward end of the body 328 is formed as a flat surface 334 on the inner end of a reduced diameter portion 336. When the body 328 is relaxed or in its normal unstressed condition, the surface 334 is spaced slightly from the inner surface of a transverse wall 338 at the inner end of fitting 316. The wall 338 is provided with an opening 340 therethrough axially opposite a portion of the surface 334. The elastomeric body 328 is further provided with a passageway or opening 342 providing communication between the chamber defined by bore 318 and the chamber within body 328 defined by bore 332. As is apparent from the drawings, when the parts are in the relative positions shown, a continuous flow passage for ink is provided from the reservoir, through opening 340, the space between 338 and 334, the chamber within bore 318, the opening 342 and the interior of tubular member 326, to the writing tip.

When writing pressure is applied to the writing tip, the tubular member 326 slides rearwardly and distorts the elastomeric body 328 sufficiently to engage its surface 334 with the inner surface of wall 338 and thus in effect close a valve to prevent rearward flow of ink to the reservoir. Continued writing pressure further distorts or compresses the body 328 to apply pressure to the ink at the writing tip, all in the manner and for the purpose set forth with reference to previous modifications. As shown, the fitting 322 is provided with a rear surface 344 spaced from a shoulder 346 forming the transition between

bores

318 and 320. An annular ring 348 is secured to the tubular member 326 and extends radially outwardly therefrom into the space between

shoulders

344 and 346. This ring serves as stop means to limit inward movement of tubular member 326 and thus prevent damage to the body 328 if excessive pressure is applied to the writing tip.

As shown in FIG. 21, a reservoir 350 is secured to a tip member 352 having a bore 354 at its forward end in which a writing tip 356 slides. The writing tip 356 has the usual ink passage 358 therein extending through a rearward extension 360 of smaller diameter. The tip member 352 is provided with a counterbore 362 smaller than the bore 354 and a second counterbore 364 communicating with a passageway 366 providing communication with the interior of the reservoir 350. In the counterbore 364 is a part-spherical seat 368 and a ball check valve 370 fitting loosely within the counterbore 364. A washer 372, of any suitable substantially rigid material, is seated in the bottom of counterbore 362 and is provided with a square opening 374 therethrough (see FIG. 22). A body of elastomeric material 376 butts against the washer 372 to align its passageway 378 with the square opening 374. A larger bore 380 sealingly embraces the writing tip extension 360 while the inner end portion of the body 376 snugly and sealingly fits the bore 362. The forward portion of the elastomeric body 376 is of reduced diameter, thus providing an annular space 382 between that smaller portion and the bore 362.

In operation, the space 382 provides room for the elastomeric body to expand somewhat radially when pressure is put on the writing tip and thus eliminate frictional drag resisting inward movement of the writing tip. The square opening 374 in washer 372 ensures that there will always be a flow path for ink passing around the ball 370 into the passage 378. The manner of operation of this form will be obvious since writing pressure on the writing tip 356 will put the ink in passageway 378 under pressure and thus firmly seat ball 370 against valve seat 368 to prevent flow of ink back to the reservoir and the pressure thus applied to the ink will force the same forwardly to the writing ball tip 384 regardless of the attitude of the pen.

In FIG. 23, parts bearing the same numerals as in FIG. 21 are similar parts and will not be described in further detail. In this form of the invention, the washer 372 of FIG. 21 is replaced by a washer 386, see also FIG. 24, having a round opening 388 therethrough, but the face of the washer facing the reservoir is provided with radial grooves 390 to ensure flow of ink forwardly from the reservoir even when the flat disc valve 392 is seated against the washer 386. The flat disc valve 392 of FIG. 23 may be of any suitable material and replaces the ball valve 370 of FIG. 21. It will be apparent that the operation of this form of the invention is essentially the same as that of FIG. 21, the disc valve 392 seating against the forwardly facing surface 394 of tip member 352 when the writing tip applies pressure to the ink by compressing elastomeric member 376.

In the form shown in FIG. 25, all parts are the same as in FIGS. 21 and 22 except the check valve arrangement. In this form, the elastomeric body 376 butts directly against a partition member 396 in the tip member 352 and its passageway 378 is aligned with an opening 398 in that partition member. A check valve member 400 of elastomeric material is tightly fitted in the bore 42 of tip member 352 and is provided with a blind bore 404 therein, terminating in a forward integral wall 406. The valve member is provided with a transverse slit 408 extending most of the way therethrough but leaving a portion 410 serving as a hinge by which the end wall 406 may flex forwardly, as shown in FIG. 26, to open the valve and permit flow of ink from the reservoir into the passageway '378. The check valve member 400 is of elastomeric material and the end wall 406 normally assumes the closed position shown in FIG. 25. Here again, the operation of the writing instrument will be obvious from the foregoing description, the check valve 400 operating in a manner already described with reference to FIGS. 7 and 7a.

As indicated heretofore, the operation of all forms of the invention described herein are essentially the same, that is, upon initial application of any writing pressure to the writing tip of the pen, the valve near the reservoir is closed after very slight movement thereof and continued writing pressure results in the application of feeding pressure to the ink forwardly of that valve. Thus, while writing a constant supply of ink is supplied to the ball point even though the pen is in an inverted position, that is, with the writing tip pointing upwardly. In each case, the writing tip is connected to the reservoir by a connector means that is resiliently deformable and which defines at least a portion of an ink passageway so that the deformation decreases the volume of a portion of the passageway to apply the described pressure.

The various forms of valve illustrated and described for preventing flow of ink rearwardly to the reservoir are merely illustrative. Any of the forms of valves may be used with any of the embodiments to which they are adapted and even other forms of valve may be employed. However, it is important that the total movement of that valve between open and closed position be very small so that the valve will immediately close upon initial application of writing pressure to the writing tip without substantial movement thereof. Preferably, the movement of the writing tip required to close the check valve is kept within about 0.1mm. This is desirable since too great an axial movement of the tip would be objectionable. Even after the check valve is closed, it is desirable to limit movement of the writing tip to about 0.5mm since many users would object to greater movement than that. In each of the forms illustrated, there are inherent stop means or the structure of such nature and position that total movement of the writing tip is very limited.

In certain of the forms described, a small capillary chamber was provided to serve to trap a bubble of air which functions as a pressure accumulator. Such small chambers must face in the direction of the writing tip if the pen is charged with ink by centrifuging. However, in a pen where the centrifugal step is not employed, such air chamber could face in any direction. Further, multiple bores of capillary dimensions may be used to increase the volume of trapped air. A further modification could be employed wherein at least a portion of the resiliently deformable connector means, or even a separate element, would respond to pressure and stretch to an expanded shape, to thereby function as a pressure accumulator. In those forms of the invention employing an elastomeric material, certain sections thereof could be made sufficiently thin to function as a stretchable diaphragm for pressure accumulation. For example, in FIG. 7, the flap valve 130 could be constructed in such a manner. Since no air can escape from the chambers the volume of trapped air therein will remain substantially uniform throughout the life of the pen regardless of the decrease in the volume of ink in the reservoir due to consumption during writing.

The ink consumption in a ball point is very small, at the most milligrams per meters of written line. Therefore, the velocity with which the ink column moves in the ducts leading to the ball seat is very small, for example, if the writing speed is 10 meters per minute the velocity of the ink in a 0.5 milimeter bore,

which is normal in a ball point having a l milimeter ball, will only be about 0.025 milimeter per minute Thus it can be seen that almost no axial movement of the writing instrument relative the writing point is required for continuous feed of ink during writing.

As is apparent, when the supply of ink in the reservoir has all passed the check valve of any of the forms disclosed, the pen is depleted as the remaining ink can be used only with the pen in the normal attitude, with the writing point down. It is, therefore, desirable that the features of this invention be designed, configured and dimensioned so that the check valve is as close to the writing point as possible.

In those forms of the invention employing a bellows structure, if the pen is to be charged with ink by centrifuging, the bellows folds should be of the tapered configuration of FIGS. 4 and 7, to avoid trapping air in the outer portions, which might possibly occur with the form shown in FIG. 5. However, the latter form could be used where filling is done in other ways.

In this invention the check valves described must be so constructed that there is a minimum clearance for flow of ink and a minimum movement of the valve member to effect closing thereof. In general, such valves, when in the form of a ball, are of a diameter of the order of 1 mm to 4 mm.-This general dimension should be maintained for any free sliding valve even though it may not be a spherical ball. Furthermore, the radial clearance between such a free sliding valve member and its confining housing or plug should be held as small as is consistent with satisfactory ink flow, depending upon the type of ink used. In general, the radial clearance around the free sliding valve member is preferably about 0.1mm but can be as large as 0.2mm. Clearances of even lessthan .1 mm are contemplated where the type of ink will permit. The axial movement ofa free sliding valve member between closed and fully open position should also be held at a minimum and, here again, it is preferable that such movement not exceed about 0.1mm, although movement up to .3mm is permissible. As with the radial clearance, the axial movement of the valve member may even be less than .lmm if the particular ink will flow through such a minutely open valve. As is obvious, it is desirable that axial movement and radial clearance be held to a minimum to ensure closure of the valve almost instantly upon contact of the writing tip with the paper or other surface on which it is desired to write.

It is to be further pointed out that applicants invention as described herein contemplates a ball point pen assembly wherein the writing tip, the connecting means and the reservoir are permanently assembled as a unitary assembly and wherein the connecting means is permanently attached or sealed to the writing tip and reservoir. Thus, the invention is embodied in a unitary member that may be in the form of a refill for a ball point pen or as a complete pen in itself wherein the claimed parts are permanetly and sealingly connected, not being capable of separate replacement or ready separation.

Preferably the resilient flexible means are of such construction that axial movement of the tip toward the reservoir starts as soon as writing pressure is applied. It has been found that the best results are obtained when a force as small as 30 grams will cause an axial movement of at least 0.05mm in a completely assembled pen but having no ink therein, but that a unit will be operable even if the resulting movement is only 0.0lmm under the same load. If the load is'50 grams the movement will be approximately doubled. An example of a meterial which has been found to permit a movement of at least .05 mm by a force of 30 grams is a composition of polyvinyl chloride having a hardness on the Durometer A scale of about 40 when used in an assembly as illustrated in FIG. 20 whereby the o.d. of the body 328 is 4.5mm. One such composition is sold by Mattel Inc. of California under the name of Clear Plastigoop. In order to facilitate the insertion of the body 328 in the bore 318 a vacuum may be applied to the rear end of the reservoir 414 during the assembling operation. The size of the vacuum may be adjusted to obtain the ideal size of the gap between the

faces

334 and 338.

I claim: 1. In a ball point pen having a writing tip and an ink reservoir:

flexible resilient connecting means sealingly fixed to and connecting said writing tip and said reservoir for limited relative axial movement therebetween by flexure of said connecting means, said connecting means defining at least a portion of a passageway for conducting ink from said reservoir to said writing tip and being deformable by writing pressure applied to said writing tip to decrease the volume of said portion of said passageway; and

check valve means, between said portion of said passageway and said reservoir, which valve closes upon initial relative axial movement by said writing pressure for preventing flow of ink from said passageway to said reservoir whereby writing pressure on said writing tip causes sufficient pressure to be applied to ink in said passageway to maintain a supply of ink at said writing tip irrespective of the attitude of said pen and which check valve means permits free flow of ink from said reservoir to said passageway in the absence of such pressure.

2. A ball point pen as defined in claim 1 including means defining a small air-containing chamber communicating with said passageway and serving as a pressure accumulator to maintain pressure on ink in said passageway during brief period of reduction of writing pressure on said writing tip.

3. A ball point pen as described in claim 1 wherein said resilient connecting means comprises a resiliently flexible wall means extending transverse to the length of said pen.

4. A ball point pen as defined in claim 3 wherein said resiliently flexible wall means is in the form of an annular bellows.

5. A ball point pen as defined in claim 1 wherein said connecting means comprises an annular body of elastomeric material.

6. A ball point pen as defined in claim 5 wherein said writing tip and ink reservoir are provided with gener ally cylindrical, concentric radially spaced portions defining an annular space therebetween; said annular body of elastomeric material radially spanning said annular space.

7. A ball point pen as defined in claim 1 wherein said valve means comprises a valve member movable with said writing tip and having a transverse surface, and a valve seat fixed relative to said reservoir and engageable by said surface of said valve member, one of valve member and valve seat comprising a body of elastomeric material.

8. A ball point pen as defined in claim 7 wherein said valve member is of said elastomeric material and is provided with at least one projection engageable with said valve seat prior to valve-closing engagement of said transverse surface with said valve seat.

9. A ball point pen as defined in claim 1 including means restraining said writing tip against substantial lateral tilting relative to said reservoir.

10. A ball point pen as defined in claim 1 wherein said valve means comprises a portion of said flexible resilient means, movable with said writing tip, and cooperating means fixed relative to said reservoir, said valve means being closed by initial rearward movement of said writing tip.

11. A ball point pen as defined in claim 1 wherein said valve means is responsive to rearward movement of said writing tip to be closed thereby, said resilient means providing for relative movement between said writing tip and reservoir of at least .0} mm in response to writing pressure of about

Claims

1. In a ball point pen having a writing tip and an ink reservoir: flexible resilient connecting means sealingly fixed to and connecting said writing tip and said reservoir for limited relative axial movement therebetween by flexure of said connecting means, said connecting means defining at least a portion of a passageway for conducting ink from said reservoir to said writing tip and being deformable by writing pressure applied to said writing tip to decrease the volume of said portion of said passageway; and check valve means, between said portion of said passageway and said reservoir, which valve closes upon initial relative axial movement by said writing pressure for preventing flow of ink from said passageway to said reservoir whereby writing pressure on said writing tip causes sufficient pressure to be applied to ink in said passageway to maintain a supply of ink at said writing tip irrespective of the attitude of said pen and which check valve means permits free flow of ink from said reservoir to said passageway in the absence of such pressure.

6. A ball point pen as defined in claim 5 wherein said writing tip and ink reservoir are provided with generally cylindrical, concentric radially spaced portions defining an annular space therebetween; said annular body of elastomeric material radially spanning said annular space.

11. A ball point pen as defined in claim 1 wherein said valve means is responsive to rearward movement of said writing tip to be closed thereby, said resilient means providing for relative movement between said writing tip and reservoir of at least .01mm in response to writing pressurE of about 30 grams.