US0059l7527A
`
`United States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,917,527
`
`Boyd et al.
`
`[45] Date of Patent:
`
`*Jun. 29, 1999
`
`[54]
`
`INK-JET PEN WITH NEAR NET SIZE
`POROUS MEMBER
`
`[75]
`
`Inventors: Patrick V. Boyd, Albany; Mark C.
`Huth, Corvallis; John M. Altendorf,
`Corvallis; Joseph R. Elliot, Corvallis,
`all of Oreg.
`
`Hewlett-Packard Company, Palo Alto,
`Calif.
`
`This patent issued on a continued pros-
`ecution application filed under 37 CFR
`l.53(d), and is subject to the twenty year
`patent
`term provisions of 35 U.S.C.
`154(a)(2).
`
`Appl. No.: 08/747,135
`
`Filed:
`
`NOV. 12, 1996
`
`Related U.S. Application Data
`
`Continuation of application No. 08/331,848, Oct. 31, 1994,
`abandoned.
`
`Int. Cl.6 .................................................... .. B41] 2/175
`U.S. Cl. .................................... .. 347/87; 347/85
`Field of Search .......... ..
`347/85, 86, 87
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,025,271
`5,213,751
`5,440,333
`5,448,275
`5,450,112
`FOREIGN PATENT DOCUMENTS
`
`......................... .. 347/87
`Baker et al.
`Terry .......... ..
`. 264/321
`Sykora et al.
`.. 347/87
`Fong
`.. 347/87
`Seheffelin
`
`0424133
`0520695
`520695
`0603515
`603515
`4121962
`
`4/1991
`12/1992
`12/1992
`6/1994
`6/1994
`1/1993
`
`....... .. B41J 2/175
`European Pat. Off.
`.. B411 2/175
`European Pat. Off.
`........ .. 347/86
`European Pat. Off.
`B411 2/175
`European Pat. Off.
`.... .. 347/86
`European Pat. Off.
`Germany ........................... B41J 2/17
`
`Primary Extzmz'rzer—Valerie Lund
`Attorney, Agent, or Fir/n—Kevi11 B. Sullivan; H. Brian
`Davis
`
`[57]
`
`ABSTRACT
`
`Disclosed is a novel inkjet print cartridge (pen) in which a
`body of polyurethane foam is inserted into an ink chamber
`of the pen for ink containment and backpressure. The ink
`chamber has a tall narrow aspect ratio. The body of poly-
`urethane foam is felted in the width direction of the pen to
`have a Width less than 20% of its pre-felted Width. After
`felting, the body of foam is cut to have a “near net size” as
`the interior volume of the ink chamber. Specifically, the
`pre—insertion volume is less than about 130% of the interior
`volume of the ink chamber. The substantial felting in the
`Width direction provides su icient stiffness to the foam that
`it can be inserted into the tall, narrow aspect ratio ink
`chamber.
`
`4,929,969
`
`5/1990 Morris.
`
`13 Claims, 6 Drawing Sheets
`
`HP 1012
`Page 1 of 14
`
`

`
`725,719,5
`
`HP 1012
`Page 2 of 14
`
`

`
`Jun. 29, 1999
`
`Sheet 2 of 6
`
`HP 1012
`Page 3 of 14
`
`

`
`Jun. 29, 1999
`
`Sheet 3 of 6
`
`5,917,527
`
`HP 1012
`Page 4 of 14
`
`

`
`U.S. Patent
`
`Jun. 29, 1999
`
`Sheet 4 of 6
`
`F|G 5
`
`462..n7
`
`m?////////////4m.,‘E.§.“--\‘--‘-~§::\“Mmy///¢V/VA.v////////Mum..
`
`LE‘I‘in_“_'!“'"‘!““““I,“‘iJV‘..
`
`.435war
`Amlk.
`
`4'
`
`4|
`
`2
`
`
`2%?/9/a7//////,9,‘
`l~.:~L‘~:§“‘-~§V:‘~‘~.~.:-.
`
`VEEE‘Ii“l'.‘.".‘.“‘.“‘.“_“‘I1'17‘7‘rI
`
`HP 1012
`Page 5 of 14
`
`

`
`HP 1012
`Page 6 of 14
`
`

`
`U.S. Patent
`
`Jun. 29, 1999
`
`Sheet 6 of 6
`
`.____..___.._......_._L
`
`HP 1012
`Page 7 of 14
`
`

`
`5,917,527
`
`1
`INK-J ET PEN WITH NEAR NET SIZE
`POROUS MEMBER
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`This is a continuation of application Ser. No. 08/331,848
`filed on Oct. 31, 1994, now abandoned.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention is directed to device and method for
`storing ink in a reticulated foam for use in ink—jet printing,
`and is particularly directed to reticulated foam that has a
`Volume, before being inserted in the ink chamber, that is
`close to its net volume after insertion.
`
`2. Description of the Related Art
`Ink-jet printers commonly employ ink—jet print cartridges,
`or “pens,” which include a sophisticated printhead and an
`attached ink chamber filled with a supply of ink. The "
`printhe ad is a micromeehanical part that contains an array of
`miniature tl1ern1al resistors or piezoelectric transducers that
`are energized to eject small droplets of ink out of an
`associated array of nozzles. In some cases the printhead is
`permanently attached to the ink supply, and in others the ink
`supply can be separately replaced. The pen is mounted in a
`carriage in the printer where the pen electrically interfaces
`with the printer. The printer scans the pen back and forth
`across the print medium (e.g., paper) as the pen ejects small
`droplets from the nozzles in selected matrix patterns,
`to
`thereby print a swath of the desired alphanumeric characters
`or graphics. After each swath of printing,
`the printer
`advances the medium incrementally to begin a new swath.
`Successive swaths are printed in this manner to complete the
`desired alphanumeric characters or graphics on the medium.
`The ink in the pen must be held in the ink chamber at less
`than atmospheric pressure, so that the ink does not drool out
`of the nozzles when the nozzles are not firing. However, this
`negative relative pressure, or backpressure, must not be so
`great
`that air
`is gulped into the interior of the firing
`chambers, thereby causing them to “deprime” and no longer
`function. Various mechanisms have been devised to provide
`the appropriate backpressure, such as resilient bladders and
`combinations of springs and flexible bags.
`One of the most reliable backpressure systems uses a
`porous material, such as synthetic foam, in the ink tank. Ink
`is injected into the foam and the foam retains the ink at the
`appropriate backpressure by capillary action. U.S. Pat. No.
`4,771,295 (Baker
`’295), which is assigned to Hewlett-
`Packard Company (the assignee of the present invention),
`discloses an ink—jet pen that uses synthetic foam for ink
`retention and backpressure. A key feature of the pen dis-
`closed in Baker ’295 is an ink pipe that extends upward from
`a bottom wall of the pen body and into compressive contact
`with the foam. The ink pipe is the fluid conduit for the ink
`from the foam to the printhead. The ink pipe locally com-
`presses the foam to thereby increase its capillarity in the
`region of the ink pipe. As ink is depleted from the foam, the
`increased capillarity near the ink pipe tends to draw ink from
`all other portions of the foam toward the ink pipe, so that the
`maximum amount of ink can be drawn from the foam for
`printing.
`It is important in foam-based pens to keep the foam in
`secure contact with the ink pipe to maintain the compressive
`capillarity and the ink seal between the pipe and the ink-
`filled foam. If this compressive contact is broken an air path
`
`_
`
`,
`
`2
`forms from the ambient air around the sides of the foam and
`into the interior of the ink pipe, resulting in a catastrop 11C
`deprime of the pen. To ensure adequate compressive contact
`between the ink pipe and the foam, prior art pens have
`employed bodies of foam that are larger in volume than he
`ink chamber they are to fill. The foam body must therefore
`be compressed by some mechanism during insertion. Once
`inserted, the compression is released so that the sides of
`foam can expand into resilient contact with the walls of
`ink chamber. This compressive contact with the walls of
`ink chamber keeps the foam in place and in contact with
`ink pipe. In many cases, such foam bodies have pre-insertion
`volumes that can be 50% or more greater than the interior
`volume of the ink chamber.
`
`It is very important to minimize or avoid wrinkling he
`foam or causing other compression anomalies in the foam
`during the process of inserting the foam into the ink cham-
`ber. Such localized wrinkles and anomalies introduce unin-
`tended regions of higher compression. These regions of
`increased compression will have a higher capillarity than the
`surrounding foam, and ink will be stranded at these loca-
`tions. Ink thus stranded is wasted and will not be available
`for printing.
`The mechanisms needed to insert foam members that
`have large volumes relative to the internal volume of the ink
`chamber add complexity and expense to the assembly of the
`pen. One such mechanism, for example, involves parallel
`plates that squeeze the foam to a width smaller than the ink
`chamber. After the plates and the foam are lowered into the
`ink chamber, a separate mechanism pushes the back of the
`foam while the plates are removed from the pen body in a
`shuffling or ratcheting motion.
`The complexity of foam insertion mechanisms is com-
`pounded as ink chambers become taller and more narrow. It
`has become increasingly important to make ink—jet pens as
`narrow as possible. The overall width of the pen influences
`the width of the printer and the amount of desk space the
`printer takes up. In addition, when printing with multiple
`pens, such as in color printing, print quality can be enhanced
`by making the pens narrower. Narrower pens allow the
`printheads of the pens to be more closely spaced so that
`during printing, as the pen is scanned across the print
`medium, less time goes by between ejection of the different
`colored droplets. On the other hand, users of printers desire
`that ink—jet pens last longer, in other words, that they hold
`more ink. Often the best way of increasing the volume of ink
`while maintaining a narrow profile is to make the pen taller.
`However, the taller and more narrow the pen is, the more
`difficult it is to properly insert foam into the ink chamber.
`Particularly with pens that load the foam from the top down
`into the pen, the taller the pen is, the more likely it will be
`that undesirable wrinkles or other anomalies will form in the
`foam as the foam is loaded into the pen. Also, the taller the
`pen is, the n1ore chance there is that friction between the
`foam and the interior walls of the pen body during insertion
`will impede the desired compressive force between the foam
`and the ink pipe. The mechanisms needed to insert foam
`bodies that have a substantially greater pre-insertion volume
`than the ink chamber where the ink chamber is tall and
`narrow may be prohibitively complex.
`There remains a need for a foam-based ink containment
`device that avoids the problems associated with insertion of
`large foam bodies, and which at the same time provides
`adequate sealing between the foam and the ink pipe. This
`solution would preferably allow for top-down insertion into
`ink—jet pens having tall, narrow aspect ratios.
`
`y
`
`HP 1012
`Page 8 of 14
`
`

`
`5,917,527
`
`3
`SUMMARY OF THE INVENTION
`
`The present invention provides an ink containment device
`and method for an ink—jet printing system that includes an
`ink chamber having an internal volume. Abody of synthetic
`reticulated foam is inserted into the ink chamber. The foam
`body has a volume before insertion into the ink chamber less
`than about 130% of the internal volume of the ink chamber.
`
`The invention provides a solution to the problems asso-
`ciated with the insertion of foam bodies into ink chambers,
`particularly ink chambers with narrow aspect ratios. Since
`the volume of the foam and/or its width is close to the
`volume and/or width of the ink chamber, problems relating
`to foam insertion into narrow aspect-ratios pens are mini-
`mized. It would be very difficult, if not impossible, to insert
`foam members into tall, narrow aspect—ratio chambers, such
`as the center chamber of the illustrated embodiment, without
`using foam members made according to the present inven-
`tion.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective, partial cut-away, view of a printer
`employing an ink—jet pen of the invention.
`FIG. 2 is a perspective view of a pen of the invention.
`FIG. 3 is a side view of the pen of FIG. 2.
`FIG. 4 is an exploded perspective view of a pen of the
`invention.
`
`FIG. 5 is a sectional view of a portion of an assembled
`pen, also taken along section line 5—5 of FIG. 3 as viewed
`to the left in FIG. 3.
`
`FIGS. 6 and 7 are side views of a felting mechanism.
`FIG. 8 illustrates sequential steps for forming a low-
`friction cover sheet 158 for the center foam member 130.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`FIG. 1 illustrates an ink—jet printer that uses a pen of the
`invention. The printer is illustrated only schematically, and
`paper input trays, paper output trays and other options are
`not
`illustrated. The printer, generally indicated at 10,
`includes a housing 12, carriage 14, controller 16, carriage
`drive motor 18 and paper drive motor 20. A monochrome
`black pen 22 and a multi—chamber three-color pen 24 are
`mounted in carriage 14 as shown. A print medium 26 is
`shown in printer 10 to be printed on by pens 22 and 24. Print
`medium 26 may be, for example, paper, transparency film,
`envelopes, or other print media.
`Printer 10 activates pens 22 and 24 to print upon print
`medium 26 in a manner well known in the art, but briefly
`described as follows. Carriage advance motor 18 is linked to
`carriage 14 by means of belt 28. Controller 16 activates
`carriage advance motor 18 to drive carriage 14 to the right
`or to the left in the scanning direction as indicated by the H
`arrow marked X. Each time carriage 14 moves to the right
`or to the left, the printer prints a “swath” on medium 26.
`Media advance motor 20 is connected to gearing mechanism
`30 (schematically illustrated). Gearing mechanism 30 is
`connected to drive rollers and pinch rollers (not shown),
`which in t11rn directly interface with the medium 26 in a
`manner well known in the art.
`
`_
`
`After carriage 14 has completed one swath of printing,
`controller 16 activates media advance motor 20 to move the
`medium 26 one swath width in the direction marked Y,
`which is the media-advance direction. After another swath is
`completed, the medium 26 is advanced another swath width
`
`4
`in direction Y so that another swath may be printed. In this
`manner, successive swaths are printed until all of the desired
`alphanumeric characters and/or graphics are printed on
`medium 26.
`The area of medium 26 that is being printed upon may be
`referred to as the print zone, markedA. The print zone Amay
`be considered to be the current swath width area that is being
`printed upon as carriage 14 scans across medium 26. The
`width of various components of pens 22 and 24 are mea-
`sured in the scanning direction X. The length of components
`of pens 22 and 24 are measured in the media-advance
`direction Y. The height of pens 22 and 24 is measured in the
`direction marked Z, which is normal to the print medium 26
`at the print zone A.
`As shown in FIGS. 2 and 3, multi—chamber pen 24
`includes a main body member 110, side cover members 112
`and 114, center cover member 116, finger tab 118, and a flex
`strip 120 containing contact pads 122. The finger tab 118 is
`included to allow the user to more easily insert the pen 24
`into the printer carriage 14 as shown in FIG. 1. The main
`body member 110 of pen 24 is divided mainly into two parts,
`the main ink cavity portion 124 and the nose portion 126.
`As shown in FIG. 4,
`the multi—chamber pen 24 also
`includes center porous member 130, side porous member
`132, side porous member 134, center filter 136, side filters
`138 and 140, and printhead 142. Printhead 142 is attached to
`main body member 110 by means of a heat curable epoxy
`layer 144. Flex strip 120 is heat staked to main body member
`110. Flex strip 120 is a custom-made tape automated bond-
`ing (TAB) circuit formed of a polymer film with custom
`designed copper traces that connect to contact pads on the
`printhead. An adhesive layer 146 of thermoplastic bonding
`film is laminated to flex strip 120 before it is heat staked to
`the main body member. Adhesive layer 146 melts and aids
`the bonding of flex strip 120 to the main body member and
`helps provide electrical insulation for the conductors on the
`flex strip. Custom-made TAB circuits are commonly avail-
`able and widely used in the electronics industry. The printer
`into which the pen 24 is inserted interfaces with contact pads
`on flex strip 120 to provide the appropriate driving signals
`to cause the resistors on the printhead to fire at the appro-
`priate time.
`Filters 136, 138 and 140 are attached to n1ain body
`member 110. A threaded nylon plug 146 is pressed into hole
`148 formed in center cap 116. Likewise,
`threaded nylon
`plugs 150 and 152 are pressed into holes 154 and 156
`formed in main body member 110. The helical thread pattern
`on these plugs provides an air path to allow the pen to
`breathe in air as ink is depleted from the foam members 130,
`132, and 134. The long narrow channel of this helical pattern
`acts as barrier to vapor dilfusion from the inside of the pen
`to the ambient environment.
`
`A low friction cover sheet 158 is provided to cover the
`sides of foam member 130. Foam member 130 is inserted
`into center chamber 160 of main body member 110. Foam
`member 132 is inserted into side chamber 162, and foam
`member 134 is fitted into side chamber 164. Foam members
`130, 132, and 134 are preferably formed of a polyether based
`polyurethane open cell foam without anti-oxidant. Other
`porous materials may also be used, such as innately reticu-
`late thermoset melamine condensate. After the foam mem-
`bers are inserted into the main body member, cover members
`114, 112, and center cover member 116 are ultrasonically
`bonded to the main body member [10 to enclose the foam
`members 130, 132, and 134 within the pen. Once the step of
`bonding cover members 112, 114, and 116 is complete, ink
`is injected into foam members 130, 132, and 134.
`
`HP 1012
`Page 9 of 14
`
`

`
`5,917,527
`
`5
`As shown in FIG. 5, main body member 110 is formed as
`a single unitary part to include the previously described
`center chamber 160, and side chambers 162 and 164. Main
`body member 110 includes a manifold section 166, which
`channels the ink from the ink chambers [60, 162, and 164
`toward the printhead. Main body member 110, as with other
`portions of the pen body,
`is made of glass filled PET
`(polyester) witl1 a 15% glass fill.
`Manifold 166 includes a center ink pipe 168 and two side
`ink pipes 170 and 172. Ink pipe 168 extends upward from
`bottom wall 174 and ink pipes 170 and 172 extend outward
`from sidewalls 176 and 178. Ink pipes 168, 170 and 172
`form ink inlets to receive ink from their respective ink
`chambers. These ink pipes have rectangular cross sections
`with dimensions of 9.6 mm by 4.5 mm, and thus have
`internal cross-sectional areas of 43.2 mmz. Filter 136, which
`is formed of stainless steel wire mesh is heat staked to center
`ink pipe 168, as shown. Similarly, stainless steel wire mesh
`filters 138 and 140 are heat staked to side ink pipes 170 and
`172, as shown. These filters have the same e ective filtering "
`area as the ink pipes to which they are attached, i.e., 43.2
`mmz. They have a nominal filtration cajability of 15
`microns, and a typical thickness of about 0.15 mm.
`
`These filters preclude debris and air bubbles from passing
`from the foam into the ink pipes. They a so provide an
`important function in preventing spiked surges of ink
`through the filter. The spaces between the wire strands act as
`fluid restrictors, which resist fluid flow based on an expo-
`nential relationship to the velocity of fluid passing through
`the filter. Thus, if ink is traveling slowly through the filters,
`for example during printing, nominal resistance is met at the
`filter. Without the filter, if the pen were to be jarred, for
`example, by being dropped, any surges in the ink could
`easily cause air to be gulped into the firing chambers of the
`printhead, causing these chambers to deprime. However,
`with the filter in place, rapid fluid flow through the filters is
`largely prohibited, so that gulping does not occur.
`Center foam member 130 is inserted into center chamber
`160 from the Z direction to be compressed by center ink pipe
`168 and filter 136. Center foam member 130 compresses
`down over and extends around the perimeter of ink pipe 168
`and filter 136, as shown. This compression and overlap of
`foam member 130 around the perimeter of ink pipe 168 and
`filter 136, because of frictional engagement, greatly inhibits
`any motion of foam member 130 in any direction normal to
`the Z direction. Similarly, foam member 132 is inserted into
`side ink chamber 162 from the X direction shown in FIG. 5
`to be compressed by and to conform around the perimeter of
`side ink pipe 170 and filter 138. Foam member 134 is 5
`inserted into ink chamber 164 from the X direction to be
`compressed by and to conform around the perimeter of ink
`pipe 172 and filter 140, as shown. The compression of foam
`members 132 and 134 by their respective ink pipes and
`filters and their frictional engagement of the perimeter of the ’
`ink pipes and filters greatly inhibits any motion of foam
`members 132 and 134 in any direction normal to the X
`direction.
`
`’
`
`The compression of foam members 130, 132, and 134 by
`their respective ink pipes and filter increases the capillarity
`of the foam members in the region of their respective ink
`pipes and filters. This capillarity increase causes ink to be
`attracted toward the ink pipes [68, 170, and 172. From these
`conduits, the ink is fed to the back side of printhead 142
`from which it can be jetted onto the print medium according
`to signals received from the printer.
`
`6
`Printhead 142 is based on a substrate formed from an
`electronics grade silicon wafer. The resistors, conductors,
`ink channel architecture, and other printhead components
`are formed on the substrate using photolithographic tech-
`niques similar to those used in making integrated circuits.
`Printhead 142 is a face—shooter design, which means that the
`ink is fed to the substrate from a position behind the
`substrate, and the droplets are ejected normal to the substrate
`surface. Because the ink is fed to the back side of the
`printhead, the natural orientation of the ink pipe in face-
`shooter printheads is normal to and pointing away from the
`print medium and orthogonal to the scanning direction. One
`advantage of bringing the ink to the printhead surface from
`the back side is that the ink contact with the printhead can
`act as a heat sink to remove heat from the printhead as
`printing progresses.
`As can be seen, the width W1 of the printhead 142 is
`significantly smaller than the width W2 of the entire pen. As
`has been stated, minimizing the size of the printhead is
`important in minimizing the overall cost of the pen because
`of the relatively expensive components in the printhead. It is
`also apparent that the only ink-to-ink interface between inks
`of different colors occurs at the back side of the printhead
`142. Specifically, adhesive layer 144 keeps the inks of
`different colors apart. Thus, even though pen 24 carries a
`relatively large volume of ink and has a relatively small
`printhead, the manifold feature 166 allows the printhead to
`have only one ink-to-ink interface. In other words, there are
`no seams or other connections at other positions in the
`printhead where ink of one color might leak into a chamber
`dedicated to another color. This beneficial feature of having
`only one ink-to-ink interface is accomplished because of the
`novel manifold 166 being formed as part of the main body
`member 110. And because the outer chambers are loaded
`from the sides, no ink-to-ink interface occurs at the point of
`attachment of the cover members 112, 114, and 116 to main
`body member 110. Thus, an ink-to-ink interface is elimi-
`nated as compared to previous-generation multi-color I-II’
`pens, in which the region of attachment of the ink chamber
`cover member provided an additional ink-to-ink interface,
`with the inherent risk of ink mixing.
`The center chamber 160 is defined by the space between
`sidewalls 176 and 178 and extending upwardly from bottom
`wall 174. The side chambers 162 and 164 are defined to be
`on the outside of sidewalls 176 and 178 respectively. Ink
`pipe 168 extends upwardly from bottom wall 174 and into
`compressive contact with the center foam member 130.
`Inward walls 176 and 178 extend upwardly from bottom
`wall 174. Ink pipes 170 and 172 extend outwardly from
`inward walls 176 and 178, respectively, and into compres-
`sive contact with the respective foam members 132 and 134,
`as shown. Manifold 166 has three ink outlets, 183, 184, and
`185. Printhead 142 has three groups of nozzles, 186, 187,
`and 188. As can be seen, center ink pipe 168 fluidically
`communicates with center ink outlet 184, and thus with the
`center group of nozzles 187. Side ink pipe 170 fluidically
`communicates with ink outlet 183 and hence with nozzle
`group 186. Side ink pipe 172 fluidically communicates with
`outlet 185 and hence with nozzle group 188.
`It is important that ink pipes 168, 170, 172 extend into
`compressive contact with the foam to increase the capillarity
`of the foam in the region of the ink pipes. The filters 136,
`138, and 140 also serve an important role in assisting in this
`compression. In the previous-generation pens produced by
`the assignee of the present invention, discussed above, these
`ink pipes extend upwardly, all in the same direction, from a
`bottom wall of the pen. These ink pipes are all oriented in the
`
`HP 1012
`Page 10 of 14
`
`

`
`5,917,527
`
`7
`same direction, upwardly and away from the bottom wall of
`the pen. However,
`in the illustrated pen of the present
`invention, only one of the ink pipes, ink pipe 168, extends
`upwardly away from the bottom wall 174. The other two ink
`pipes, 170 and 172 extend outwardly into their respective
`ink chambers.
`
`The dimensions of the pen 24 are given in Table 1, below.
`These dimensions are given for the main ink cavity portion
`124 and ignoring the nose portion 126 (FIG. 3). For the
`portions of pen 24 described, the width is taken along X axis,
`length is taken along the Y axis, and height is taken along the
`Z axis. As shown in FIG. 5, center chamber 160 has a bottom
`width W3 and a top width W4. Chambers 162, 164 have
`bottom widths W5, VV7 and top widths VV6, W8 respectively.
`All dimensions are given in millimeters except where indi-
`cated.
`
`TABLE 1
`
`
`
`8
`
`TABLE 3
`
`Previous-Genera lion HP Pens
`
`Pen Type
`51606A Paintlet black)
`51606A Paintlet color)
`51608A DeskJet black)
`51625A DeskJet color)
`
`width
`22.6
`6.8
`25.3
`14.2
`
`height
`32.8
`33.0
`41.2
`42.0
`
`length
`31.4
`32.8
`34.3
`25.6
`
`ht/wid
`1.45
`4.89
`1.66
`2.96
`
`In/wid
`1.39
`4.86
`1.36
`1.80
`
`As indicated in Table 3, DeskJet 51608A color pens have
`a height/width ratio 2.96 and the length/width ratio is 1.80.
`A question that must be resolved, however, is what is the
`“width” of the chambers in the 51625A DeskJet color pen.
`For the purposes of the above tables,
`the narrowest
`dimension, which is in the media—advance direction,
`is
`selected as the width dimension. If the dimension along the
`scanning direction (when the pen is installed in the printer)
`is chosen as the width, then the width and length measure-
`ments would be interchanged in the above tables. The
`chambers in the 51625A color pens are narrower in the
`paper-advance direction because they are transversely
`oriented, or arranged side by side in the paper-advance
`direction, rather than in the scanning direction. This trans-
`verse orientation creates the need for a complicated mani-
`fold to duct the ink from the ink chambers to the printhead.
`This manifold must be formed as a separate part and
`attached, e.g., by adhesive or ultrasonic weld to the bottom
`of the pen. The manifold thereby introduces undesirable
`additional ink-to-ink interfaces between inks of different
`colors at locations where pen parts are attached to each
`other.
`
`PainIJet 51606A color pens have a height/width ratio of
`4.89 and a length/width ratio of 4.86. Thus, the Paintlet
`color pcn chambers have close to a square cross section as
`viewed from the side, and may be considered as having a
`narrow aspect ratio. PaintJet color pens avoid the problem of
`multiple ink-to-ink interfaces between pen body parts.
`However, these pens have the undesirable trait of having a
`very wide printhead. This wide printhead is expensive and
`also places the nozzles groups corresponding to the three
`colors farther apart
`than is desirable for improved print
`quality.
`It is significant to note that the height/width ratio of the
`pen 24 chambers are between 35 to 73% greater than the
`height/width ratio of the Paintjet color chambers. In terms of
`absolute height, the height of the pen 24 chambers is about
`70 mm (excluding the nose portion 126); whereas the height
`of the PaintJet color chambers is just 33 mm. Therefore, the
`pen 24 chambers are more than twice as tall as the Paintlet
`color pen chambers.
`Previous HP foam-based pens have the ink pipe extending
`upward into the foam from a bottom interior wall of the pen.
`This upward orientation, normal to the printhead surface and
`to the print medium is the natural orientation for the ink pipe
`in face-shooter pens. However, because of the absolute
`height of pen 24 and its height/width aspect ratio, loading
`the foam into the ink chambers from the top would be
`difficult without introducing wrinkling or other anomalies in
`the foam that cause stranding of ink.
`Pen 24 also has narrow aspect ratio ink chambers, since
`it has both a height/width or length/width ratios of 4 or more.
`Even though the ink chambers in pen 24 have narrow aspect
`ratio ranges as indicated in Table 2, the foam members are
`
`Bottom Top
`Width Width
`8.05
`10.29
`
`Bottom Top
`Length Length Height
`56.64
`57.73
`68.07
`
`8.64
`
`5 .75
`
`55.75
`
`70.01
`
`Center
`Chamber 160
`Side Chambers 9.83
`162 and 164
`
`The following Table 2 compares the height of the three
`ink chambers 160, 162, 164 against their respective widths.
`Since the three chambers each have diifering widths along
`their height, the height/width comparisons are made for the
`bottom width, top width, and average width of each cham-
`ber.
`
`TABLE 2
`
`Pen 24 Dimension Ratios
`
`hei ht’width ratios
`
`len th’width ratios
`
`bottom top
`8.46
`6.62
`7.12
`8.10
`
`average
`7.42
`7.58
`
`bottom top
`7.03
`5.61
`5.67
`6.45
`
`average
`6.24
`6.04
`
`Center chamber 160
`Side Chambers
`162 and 164
`
`Thus the height/width ratios are all at least 6, with most
`of them at least 7. They range from about 6-1/2 to about 8-1/2.
`The height/width ratios using the average widths of the
`chambers are all at least 7, and are close to about 7-1/2. The ..
`length/width ratios are all at least 5. They range from about
`5-1/2 to about 7. The length/width ratios using the average
`widths of the chambers are all in about the 6 to 6-1/4 range.
`
`The dimensions and dimension ratios of the chambers of
`pens 24 can be compared to corresponding values of
`previous-generation pens produced by Hewlett-Packard
`Company, the assignee of the present invention. The fol-
`lowing Table 3 gives the dimensions and key dimension
`ratios of previous-generation HP pens, as identified by their
`commonly known and widely used model numbers.
`
`HP 1012
`Page 11 of 14
`
`

`
`5,917,527
`
`9
`loaded into their respective chambers 160, 162, and 164
`without introducing the above-mentioned problems associ-
`ated with narrow aspect ratio ink chambers. This is true
`because of various factors. First,
`the foam members are
`highly felted, which provides these foam members enhanced
`stiffness. In addition, the foam members are felted to have
`final dimensions close to the interior cavity dimensions of
`their respective chambers. (Felting is discussed more com-
`pletely in reference to FIGS. 6 and 7.) In center chamber
`160, which must be loaded top down, the chamber l1as a
`greater width near its top than near its bottom, so that the
`walls of the chamber increasingly compress the foam as it is
`loaded.
`
`Finally, the outer chambers 162 and 164 of pen 24 open
`o the side, rather than from the top, and the foam members
`132 and 134 are loaded from the outward side. This produces
`he result that foam members 132 and 134 only need to be
`loaded over a very small distance (about 9 mm) into the pen
`3ody before they in compressive contact with their ink pipes.
`Therefore, problems related to foam insertion, such as ink H
`stranding and uncertain contact with the ink pipe, are
`minimized. In addition, assembly costs are reduced, because
`here is no need for specialized tools to insert the foam into
`he pen body. The foam can be fairly simply inserted into the
`outer chambers.
`
`An important issue that must be considered is the molding
`process that must be used to form the pen body parts. Ink-jet
`3611 bodies are typically formed of injection molded plastic.
`The chambers of the previous generation I-IP foam-based
`pens have their ink pipes extending upward from the bottom
`of the chambers and are formed to have the foam inserted
`from openings from the top of the chambers. These cham-
`bers are therefore formed as deep interior cavities. To form
`such a deep cavity, a molding part must extend deeply into
`tie plastic part being molded. In the case of three —chambered
`pens, there must be three such mold parts closely spaced side
`by side.After the plastic is injected into the mold and around
`he molcing parts to form the pen body,
`the deep mold
`sections must be removed from the ink chambers. The
`greater the height/width and/or length/width ratios are, the
`more di ‘icult it is to remove these mold sections Without
`amaging the molded part. If all three ofthe chambers in pen
`