Patent Publication Number: US-10780704-B2

Title: Ink-jet print head assemblies with a spacer surrounding an ink fill port and method of manufacturing

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. § 371, this application is a United States National Stage Application of International Patent Application No. PCT/EP2016/001125, filed on Jul. 1, 2016, the contents of which are incorporated by reference as if set forth in their entirety herein. 
     BACKGROUND 
     Continuous ink supply systems are used in some ink-jet printers to ensure a steady and or uninterrupted availability of ink for printing jobs. A reservoir, such as an external ink supply, may contain a volume of ink, which is generally larger than the volume of ink an ink compartment of the print head assembly and can be supplied to the print head assembly and the ink compartment. Thereby, the risk of running out of ink may be reduced. The printing capacity may be increased. Moreover, a steady level of ink in the print head may facilitate reproducible print quality. 
     The ink fed from the external supply for temporary storage in the print head before printing may be filled into the ink compartment of the print head assembly via an ink fill port. The ink may be stored in the ink comportment of the print head assembly in a foam insert, which takes up the ink during storage and releases the ink to be discharged in a printing process by the print head assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various examples will be described below by referring to the following Figures. 
         FIG. 1  shows a cross-section of a print head assembly for an ink-jet printer operable with a continuous ink supply system; 
         FIG. 2  shows an expanded detail of the cross-section of the print head assembly of  FIG. 1 ; 
         FIG. 3  shows a bottom view of a lid of a print head assembly for an ink-jet printer operable with a continuous ink supply system; 
         FIG. 4A  shows a cross-section of a lid of a print head assembly for an ink-jet printer operable with a continuous ink supply system; 
         FIG. 4B  shows an expanded detail of the cross-section of the lid of  FIG. 4A ; 
         FIG. 5A  shows a bottom view of a lid of a print head assembly for an ink-jet printer operable with a continuous ink supply system; 
         FIG. 5B  shows an expanded detail of the bottom view of the lid of  FIG. 5A ; 
         FIG. 6  schematically shows an ink-jet printer with a continuous ink supply system and a print head assembly; and 
         FIG. 7  schematically shows flow diagram of a method of manufacturing a print head assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a print head assembly  110  for an ink-jet printer operable with a continuous ink supply system according to one example. 
     However, before proceeding further with a detailed description of  FIG. 1 , further aspects will be discussed. 
     An aspect provides a print head assembly for an ink-jet printer operable with a continuous ink supply system. The print head assembly comprises an ink compartment, a foam insert, an ink fill port, and a spacer. The ink fill port is for receiving ink fed from an external supply and to be printed by the print head assembly. The ink compartment is for storing the ink to be printed. The foam insert is in the ink compartment and for taking up the ink to be stored. The spacer extends into the ink compartment, provides for the formation of a clearance between the foam insert and the ink fill port surrounds the ink fill port either completely or with one or more gaps having a gap width, wherein the gap width of none of the gaps presents an aperture angle of more than 25% of 360° with respect to a center of the ink fill port. 
     In some examples, the ink compartment may be an essentially hollow space in the print head assembly adapted to keep a certain volume of ink available in vicinity to the print head such that the print head can draw from said volume of ink to fulfill active print jobs. 
     In some examples, the foam insert may be a capillary media adapted to of take up the ink to be stored. For instance, sponge-like materials may be used, such as a polyurethane sponge and a fibrous sponge. 
     In some examples, the ink fill port may be an opening in the print head assembly for (direct or indirect) coupling to an external supply of ink and to receive ink fed from said supply. For instance, an ink fill port may be used during manufacturing of a print head assembly to receive the initial fill of ink from an external supply. Such ink fill ports may be referred to as “initial fill ports”. 
     Additionally or alternatively, an ink fill port may be used during operation of a print head assembly in an ink-jet printer with a continuous ink supply system to continuously, quasi-continuously, regularly or at least repeatedly receive ink from an external supply to maintain a given level of ink in the ink compartment. The “continuous” supply of ink may occur with or without interruptions. For instance, during phases of high printing volume, ink may be supplied in larger quantities than during phases of low printing volume. The quantity of ink to be supplied may be controlled by a variety of variables, such as pressure. A pressure difference between the external supply and the ink compartment of the print head assembly may drive ink from the external supply into the ink compartment. In such cases, an essentially constant level of ink in the ink compartment may be envisioned. In some examples, the continuous ink supply may be actively driven, such as by a pump. 
     In some examples, the spacer may be a distance piece for the ink fill port, adapted to physically contact the foam and thereby form a clearance between the foam and the ink fill port. In general, the spacer may be physically and rigidly coupled to the ink fill port in order to provide for a durable protection from influences such as from contact with the foam insert. 
     In some examples, the clearance between the foam insert and the ink fill port may be a space which is capable of comprising a volume of air. The volume of air may change, e.g. in shape or size, depending on ambient conditions. For instance, a change in temperature or in pressure may lead to a change in size of the volume of air. The clearance formed between the foam insert and the ink fill port by the spacer may be adapted to comprise this volume of air for at least a certain range in ambient conditions. 
     In some examples, the spacer may surround the ink fill port completely. In particular, it may be continuous and not comprise any gaps. In some examples, the spacer may surround the ink fill port with one, two or more gaps having a gap width. In general, no gap has a gap width, which presents an aperture angle of more than 25% of 360° with respect to a center of the ink fill port. Examples of gap width include aperture angles of 1%, 5%, 10%, 20% or 25% of 360° with respect to a center of the ink fill port. In cases of multiple gaps, the gaps may or may not have a same gap width. 
     Gaps with an aperture angle of no more than 25% of 360° may provide for the formation of air paths between the ink fill port and an area surrounding the spacer above the foam insert, while hindering contact between the foam insert and the ink fill port. This may prevent the gaps from being sealed by a portion of the foam insert protruding into the gap, whereby an air path between the ink fill port and an area surrounding the spacer above the foam insert may be sealed. Additionally or alternatively, this may prevent a foam insert from contacting and potentially sealing the ink fill port. 
     In some examples, the spacer may be discontinuous to provide for at least one air path between the ink fill port and an area surrounding the spacer above the foam insert. 
     In some examples, the discontinuity may be due to gaps or discrepancies. In particular, the spacer may comprises multiple spacer members, which are separated by discontinuities or gaps. In such cases, the gaps may provide for the spacer being discontinuous and for formation of an air path. 
     In some examples, the air path may be an area, which does not preclude fluid communication, in particular gas communication, between two ends of said air path. However, the size, shape or form of an “air path” is not restricted. In particular, an air path may or may not be elongate in shape. 
     In some examples, the area surrounding the spacer above the foam insert may be an area or space located between the foam insert and the upper boundary of the print head assembly, while the spacer and the area adjacent to the ink fill port and surrounded by the spacer may be excluded from such area or space. Such area may in some cases, at least partially form part of the ink compartment. 
     Here, if not otherwise specified, terms such as “above”, “below”, “upward”, “downward” may refer to the physical orientation when used in a printer, in particular in view of acting gravity forces. These orientations may or may not coincide with the views illustrated in the drawings. 
     In some examples, the ink fill port and the spacer may be located essentially above the ink compartment and the foam insert. In such cases, the ink to be printed may be discharged in an essentially downward direction from the ink compartment. 
     In some examples, the print head assembly may comprise a lid, which comprises the ink fill port and the spacer. The lid may be an upper closure of the print head assembly. In particular, the lid may cap and seal the ink compartment of the print head assembly. In cases of a pressure-driven continuous ink supply system, the lid mounted on the print head assembly may reliably seal the print head assembly to withstand and uphold the pressure difference driving the continuous ink supply. 
     In some examples, the print head assembly may comprise an ink supply channel for feeding ink from the external ink supply to the ink fill port. 
     In some examples, the print head assembly may comprise at least one of a manifold and a tubing, for connection to the external ink supply. A manifold may be equipped with connectors for facilitated connection, removal and replacement of the external ink supply. In some examples, the manifold may be equipped for connection, removal and replacement of the external ink supply during operation. In such cases, the manifold may for instance comprise a sealing septum to uphold the pressure in the ink compartment despite removal of the external supply. 
     In some examples, the print head assembly may comprise the external ink supply. 
     In some examples, the spacer may be a standoff. The standoff may be a spacer, which is formed of the same material as the material surrounding the opening of the ink fill port. For instance, in cases of the print head assembly comprising a lid, and an ink fill port formed in the lid, the material of both the lid and the standoff may comprise polyethylene terephthalate (PET). Additionally or alternatively, the material may comprises glass gibers, e.g. for increased rigidity. In some examples, the material may be glass-filled PET, such as PET with 15% glass fibers. 
     In cases of the print head assembly comprising a lid with a standoff, the lid and the standoff may be produced by injection molding. 
     In general, the properties (such as dimensions, materials, rigidity) of the spacer may be chosen dependent on the materials used. For instance, dependent on an elasticity of a foam insert to be used, the height and/or the aspect ratio of the spacer may be chosen. As mentioned above, the foam insert may for instance be a polyurethane sponge. The standoff may be at least 2.2 mm in height. Additionally or alternatively, the standoff may have an aspect ratio (height:width) of about 1:3. 
     In some examples, the print head assembly may be movable and may be for use in a swath-type printer. In a swath-type printer, the print head assembly may be movable with respect to the substrate to be printed. In such cases, printing quality or reproducibility may be influenced by the mass and inertia of the print head assembly. In continuous ink supply systems, in cases where the external supply of ink is not moved along with the print head assembly, the mass and inertia of the print head assembly may be reduced as compared to a print head assembly containing a comparable volume of ink. 
     Another aspect provides a method of manufacturing a print head assembly for an ink-jet printer operable with a continuous ink supply system. The method may comprise building an ink compartment, filling a foam insert into the ink compartment, building an ink fill port, and building a spacer. The ink fill port may be built for receiving ink fed from an external supply and to be ink-jet printed by the print head assembly. The ink compartment may be built for storing the ink to be printed. The foam insert may be filled into the ink compartment for taking up the ink to be stored. The spacer may be built to extend into the ink compartment, to provide for the formation of a clearance between the foam insert and the ink fill port and to surround the ink fill port either completely or with one or more gaps having a gap width, wherein the gap width of none of the gaps presents an aperture angle of more than 25% of 360° with respect to a center of the ink fill port. 
     In some examples, the spacer may be built to be discontinuous in order to provide for at least one air path between the ink fill port and an area surrounding the spacer. 
     In some examples, the method may comprise building a lid for the print head assembly, wherein the ink fill port and the least one spacer are built at the lid. In such cases, the building of the lid with the ink fill port and the spacer may be carried out by injection molding. The lid may be mounted onto the print head assembly by one of a variety of processes, such as by ultrasonic welding. Ultrasonic welding may ensure a tight sealing of the print head assembly, e.g. to uphold the pressure inside the ink compartment in the case of pressure-driven continuous ink supply systems. 
     Returning to  FIG. 1 , the print head assembly  110  according to  FIG. 1  has an ink compartment  112 , a foam insert  114 , an ink fill port  116  and a spacer  118 . 
     In addition, the print head assembly  110  has a manifold  132  for connection to an external ink supply (not shown) and an ink supply channel  134  for feeding ink from the external ink supply to the ink fill port  116 . 
     The ink fill port  116  receives ink fed from the external supply via the manifold  132  and the ink supply channel  134 . The ink is to be printed by the print head assembly  110 . 
     The ink compartment  112  stores the ink to be printed. The foam insert  114  is in the ink compartment  112  and takes up the ink to be stored. 
     The spacer  118  extends into the ink compartment  112 , provides for the formation of a clearance  122  between the foam insert  114  and the ink fill port  116  and surrounds the ink fill port  116  with a gap having a gap width, which does not present an aperture angle of more than 25% of 360° with respect to a center of the ink fill port. 
     The ink fill port  116  and spacer  118  are part of a lid  120  of the print head assembly. They are located essentially above the ink compartment and the foam insert. 
     The ink to be printed may be discharged from the foam insert and form the ink compartment. The ink to be printed is received by a print head (not shown), which may be located in the lower portion of the print head assembly  110 . The print head contains nozzle(s) to emit or eject the ink onto a substrate to be printed on. Ink discharge from the foam insert, e.g. by ejection through print head nozzles, gives rise to ink refilling from the external supply through the ink fill port to uphold the previous level of ink in the ink compartment. In particular, ink discharge results in a drop in pressure in the ink compartment. In a pressure-driven continuous ink supply system, the drop in pressure may lead to novel ink to be drawn into the ink compartment. 
       FIG. 2  schematically illustrates an enlarged detail of the print head assembly  110  according to the example of  FIG. 1 , as indicated by a circle at ink fill port  116  of  FIG. 1 . 
     In particular,  FIG. 2  shows the portion of ink fill port  216 , which opens into ink compartment  212  filled with a foam insert  214 . 
     The ink fill port  216  is surrounded by a spacer  218  with a gap having a gap width, which does not present an aperture angle of more than 25% of 360° with respect to a center of the ink fill port  216 . The spacer  218  is essentially circular when viewed from below. As a result, the cross-section shown in  FIG. 2  shows spacer  218  as two elements, extending into ink compartment  212 . Spacer  218  is in contact with foam insert  214  and acts as a distance piece pressing the insert down into the ink compartment and hindering contact between the foam insert  214  and ink fill port  216 . The lack of contact between the foam insert  214  and the ink fill port  216  allows for the formation of a clearance  222  between the foam insert  214  and the ink fill port  216 . Ink taken up by the foam insert  214  is hindered from contacting and potentially sealing the underside of ink fill port  216 . In the case of contact between the foam insert  214  and the ink fill port  216 , ink from the foam insert  214  may migrate upwards through ink fill port  216 . Such migration is suppressed by avoiding contact between the foam insert  214  and the ink fill port  216  and in particular by formation of the clearance  222 . 
     The clearance  222  may change in size upon changing ambient conditions. For instance, a decrease in ambient temperature may give rise to a decrease in size of the clearance  222  by isobaric compression of the gas contained therein. In case of a relatively small spacer  218  (or complete lack thereof), the clearance  222  (if existent at all) may not be sufficiently proportioned to hinder contact between ink fill port  216  and ink from the foam insert  214  over a range of ambient temperatures common for ink-jet printer uses. Similarly, upon an ambient temperature increase, a volume of air in the clearance  222  may expand. Based on its location underneath the ink fill port, the air may expand through the ink fill port into the tubing of channel above. In the absence of a way of liberating expanding gas, ink drool may occur. 
       FIG. 3  schematically illustrates a lid  320  of a print head assembly for an ink-jet printer operable with a continuous ink supply system according to one example. The lid  320  is depicted in bottom view in  FIG. 3 . 
     The lid  320  has an ink fill port  316  for continuously receiving ink fed from an external supply (not shown). Further, lid  320  has four ports  317  for an initial filling of an ink compartment of a print head assembly (not shown) onto which the lid may be mounted. Ports  317  are not for continuously receiving ink. Ink fill port  316  is surrounded by a spacer  318  with two gaps having a gap width, wherein the gap width of none of the gaps presents an aperture angle of more than 25% of 360° with respect to a center of the ink fill port. 
     Ports  317  are partially surrounded with spacers. In particular, the spacers surrounding ports  317  are essentially quadrant-shaped with additional straight portions for increased stability. In the case of “initial ink fill” ports  317 , a contact between a foam insert and ink fill port opening may in general be considered as not as critical as in the case of a “continuous” ink fill port, e.g. ink fill port  316 . Each one of ink fill port  317  is surrounded by a spacer with a gap, whose gap width presents an aperture angle of 75% of 360° with respect to the center of the respective one of ports  317 . A sealing of one or more of ports  317  after initial filling can be considered to not influence the functioning of the print head, since the ports  317  have served to initially fill the ink compartment. 
     In particular, the “continuous” ink fill port  316  (for continuously receiving ink) shall be protected from sealing or other detrimental influences (such as those mentioned above) by the ink contained in the foam insert or by air trapped between the foam insert and the lid. 
     Spacer  318  of the lid  320  as shown in  FIG. 3  is of a generally circular shape (in bottom view as depicted) with two straight appendices extending radially outwards (at 12 o&#39;clock and 6 o&#39;clock positions of the circumference, when viewed as depicted in  FIG. 3 ) for increased stability and with two discontinuities or gaps (at 3 o&#39;clock and 9 o&#39;clock positions in  FIG. 3 ). Based on the two discontinuities  324 , the spacer is considered to comprise two symmetrical spacer members. 
     The discontinuities  324  may also be referred to as gaps and provide for the formation of one or more air paths between the ink fill port  316  and an area  326  surrounding the spacer  316  above the foam insert. The air path serves as a way of fluid communication between the ink fill port  316  and the area  326 . In particular, any air bubbles trapped in area  326  above the foam insert may escape through one of air paths provided by discontinuities  324  into the ink fill port and migrate upwards from the port (e.g. into a manifold or tubing). Additionally or alternatively, said air paths provide for a smooth filling of ink through ink fill port  316 . Each of the two gaps has a gap width presenting an aperture angle of about 5% of 360° with respect to a center of the ink fill port. In some examples, the gap width of each gap may be smaller, such as presenting an aperture angle of about 1%, or greater, such as presenting an aperture angle of about 10% or 20% of 360°. Gap widths presenting aperture angles of no more than 25% of 360° may be capable of providing for the formation of air paths. 
       FIG. 4A  shows a cross-section of a lid  420  of a print head assembly for an ink-jet printer operable with a continuous ink supply system.  FIG. 4B  shows an expanded detail of the cross-section of the lid of  FIG. 4A . Lid  420  of  FIGS. 4A and 4B  may essentially correspond to lid  320  according to the example of  FIG. 3 , wherein the cross-section is taken along the axis of symmetry of lid  320  from top to bottom of  FIG. 3 . 
     In  FIGS. 4A and 4B , lid  420  comprises an ink fill port has an ink fill port  416  for continuously receiving ink fed from an external supply (not shown). Ink fill port  416  is surrounded with a spacer  418  with one or more gaps having a gap width, wherein the gap width of none of the gaps presents an aperture angle of more than 25% of 360° with respect to a center of the ink fill port  416 . The spacer is formed of the same material as lid  420  and may be referred to as standoff  418 . The spacer  418  has a height of 2.53 mm and an aspect ratio (height:width) of about 1:3, wherein the diameter of the essentially circular spacer  418  is taken as its width. 
     A discontinuity  424  of spacer  418  is provided in form of a gap in the circumference of spacer  418 . The gap has a gap width presenting an aperture angle of about 10% of 360° with respect to the center of the ink fill port. The discontinuity  424  provides for the formation of at least one air path between the ink fill port  416  and an area  426  surrounding the spacer  416  above an foam insert of an ink compartment of a print head assembly onto which lid  420  may be mounted. 
       FIG. 5A  shows a bottom view of a lid  520  of a print head assembly for an ink-jet printer operable with a continuous ink supply system according to another example. Lid  520  has three ink fill ports  518 . In particular, each ink fill port may serve to fill ink of another color into a respective one of three ink compartments (not shown) of a print head assembly onto which the lid  520  may be mounted. For instance, each one of the three ink fill ports  518  may serve fill cyan, yellow, and magenta (CYM) color ink, respectively. 
     Each one of ink fill ports  518  is partially surrounded by a respective spacer  516  with two gaps having a gap width, wherein the gap width of none of the gaps presents an aperture angle of more than 25% of 360° with respect to a center of the ink fill port. Each one of spacers  516  has a partially arcuate form and is discontinuous with two gaps providing for an air path between the respective ink fill port  518  and an area  526  surrounding, or at least adjacent to, the respective spacer  516  above a foam insert in a respective one of the three ink compartments. One of the ink fill ports  518  with spacer  516  according to  FIG. 5A  is shown in expanded view in  FIG. 5B . A first gap of spacer  516  has gap width presenting an aperture angle  517   a  of about 5% of 360° with respect to the center of the ink fill port  518 . A second gap of spacer  516  has gap width presenting an aperture angle  517   b  of about 25% of 360° with respect to the center of the ink fill port  518 . Neither the first nor the second gap has a gap width presenting an aperture angle of more than 25% of 360° with respect to the center of the ink fill port  518 . 
       FIG. 6  schematically shows an ink-jet printer  600  with a print head assembly  610  according to one example The printer  600  is equipped with an external ink supply  630  and the print head assembly  610 . 
     The ink supply  630  is connected via tubing  631  to the print head assembly  610 . The print head assembly comprises a manifold  632  for connection to the tubing  631 . The manifold  632  is further connected to an ink fill port  616  of the print head assembly  610  feeds ink from the external ink supply  630  via ink fill port  616  into an ink compartment  612  of print head assembly  610 . The ink fill port  616  is surrounded by a spacer  618  completely, i.e. without gaps. The spacer extends into the ink compartment  618 . The ink compartment  612  is partially filled with a foam insert  614  for taking up the ink fed in via the ink fill port  616  and to be printed. 
     The foam insert  614  is in contact with spacer  618 . The spacer provides for a clearance between the foam insert and the ink fill port. In the depicted case, the foam insert is not deformed or compressed by the spacer  618 . In some examples, the foam insert may be deformed or compressed by the spacer  618 . 
     The print head assembly also has a print head  636  which receives ink discharged from the foam insert  614  and form the ink compartment  612 . The print head  636  is located in the lower portion of the print head assembly  610 . The print head contains nozzles to emit the ink onto a substrate  640  to be printed on, such as a piece of paper or a three-dimensional printing substrate. 
     The printer  600  is a swath-type printer, wherein the print head assembly  610  is movable relative to the substrate  640  and to other components of the printer  600 , as indicated by arrows R and L in  FIG. 6 . In this case, the external ink supply  630  is stationary with respect to the printer  600 . Thus, the print head assembly  610  may be movable with respect to the ink supply  630 . The tubing  631  and its properties may be chosen to ensure repeated and unobstructed mobility of the print head assembly. The set of external ink supply  630 , the print head assembly  610  as well as the tubing  631  linking both can be referred to as a continuous ink supply system. 
       FIG. 7  schematically shows flow diagram of a method  700  of manufacturing a print head assembly for an ink-jet printer operable with a continuous ink supply system according to one example. The method comprises building an ink compartment ( 710 ), filling a foam insert into the ink compartment ( 720 ), building an ink fill port ( 730 ), and building a spacer ( 740 ). 
     The ink compartment is built for storing the ink to be printed. The foam insert is filled in the ink compartment for taking up the ink to be stored. The ink fill port is built for receiving ink fed from an external supply and to be ink-jet printed by the print head assembly. The spacer is built to extend into the ink compartment to provide for the formation of a clearance between the foam insert and the ink fill port and to surround the ink fill port either completely or with one or more gaps having a gap width, wherein the gap width of none of the gaps presents an aperture angle of more than 25% of 360° with respect to a center of the ink fill port.