GB2520745A

GB2520745A - An improved support bar for a printhead

Info

Publication number: GB2520745A
Application number: GB1321106.5A
Authority: GB
Inventors: Gian Mario Guidotti; Giovanni Barbanti; Marco Faretra
Original assignee: INGEGNERIA CERAMICA Srl
Current assignee: INGEGNERIA CERAMICA Srl
Priority date: 2013-11-29
Filing date: 2013-11-29
Publication date: 2015-06-03
Also published as: EP3092127A1; WO2015079422A1; GB201321106D0; EP3092127B1

Abstract

A printhead 1 includes a support element 3 which supports individual heads 2; each individual head 2 comprises a fluid chamber 21 having a nozzle associated therewith and the support element 3 includes an internal cavity 31 formed therein, through which fluid can flow to the heads 2, and, wherein the individual heads 2 are arranged on the support element 3 and retained thereon; the cavity 31 preferably the pressure of fluid in the chamber of each head 2 is equal; the support element 3 preferably provides fluid delivery 311 and fluid return 312 portions which are in fluid communication at one end. A head 2 for a printhead 1 including coupling apertures is also disclosed.

Description

DESCRIPTION

An improved support bar for a printhead The present invention relates to a printhead, particularly, but not exclusively to a printhead with at least two heads assembled on a support bar.

Conventional ink jet printers generally comprise a plurality of printheads, each of which is designed to discharge drops of a printing liquid towards a printing surface or support.

An obturator is designed for opening and closing the nozzle in a controlled manner to allow the liquid to be discharged at precise positions on the surface of a substrate. The functionality of printheads is well known in the art, for example as described in EP1972450B.

The heads have to be positioned with respect to one another in such a way that the discharged drops fall on the printing support in predetermined positions.

To obtain an optimum and uniform print quality and control of each individual printed drop on a substrate, the individual heads in a printhead are operated independently of each other. Furthermore, all the heads are required to operate under the same conditions; in particular, ideally, all the heads have to be supplied individually with fluid for printing uniformly e.g. using individual supply conduits, so that the same pressure conditions are present upstream and downstream of each printing nozzle.

The printing liquid is required to circulate continuously to avoid local compositional variations and/or sedimentation.

These requirements have the effect that each head is supplied independently of the others, whereby, for example, each head is connected to its own individual liquid feed and return circuit for feeding and recirculating the printing liquid. Such a configuration significantly complicates the structure of the head, as each circuit will have complex pressure control associated therewith to ensure optimum functionality of the printhead, which increases the overall cost and complexity e.g. of control/assembly of the printheads.

For example, in some printers it is required to connect individual heads to a supply conduit using individual conduits, which require the provision of complex dynamic tuning of each individual supply conduit to obtain the desired operating pressure.

It will be appreciated that the cost and complexity increases for each additional head required to be added to the printhead.

It is an object of the present invention to provide a printhead for an ink jet printer which addresses the abovementioned disadvantages of conventional printheads.

Accordingly, in a first aspect, there is provided a printhead having at least two individual heads, wherein each head comprises a fluid chamber having a nozzle associated therewith for printing a fluid onto a substrate, characterised in that the printhead further comprises a support element having an internal manifold formed therein, through which fluid can flow to the heads, and, wherein the individual heads are arranged on the support element and retained thereon.

Preferably, the printhead is adapted such that, in use, the pressure of fluid in the fluid chambers is substantially equal across all fluid chambers of the printhead.

Preferably, the internal manifold is in fluid communication with the fluid chambers of the individual heads via at least one opening formed in the support element.

Preferably, the support element is a longitudinal support element.

Preferably, the internal manifold comprises a longitudinal duct having a fluid delivery portion and a fluid return portion, wherein the fluid delivery portion and the fluid return portion are separated by a dividing portion extending along the longitudinal duct, and wherein the delivery portion is in fluid communication with the return portion towards a first end of the duct.

Preferably, the profile of the fluid delivery portion and/or the fluid return portion varies along the length of the duct.

Preferably, the profile of the fluid delivery portion and/or the fluid return portion varies linearly.

Preferably, the profile of the fluid delivery portion and/or the fluid return portion varies non-linearly.

Preferably, the internal manifold is provided in the support element as a removable insert.

Preferably, the internal manifold is fabricated integral to the support element.

Accordingly, in a second aspect, there is provided a support element, for a printhead, wherein the support element comprises an internal fluid manifold, and wherein the support element is operable to receive at least one head having a fluid chamber thereon, and wherein, in use, the support element is operable to supply fluid to the fluid chamber of the at least one head.

Preferably, the support element is adapted such that, in use, the pressure of fluid in the fluid chambers is substantially constant across all fluid chambers of the at least one head.

Preferably, in use, the internal manifold is in fluid communication with the fluid chamber of the at least one head via at least one opening formed thereon.

Preferably, the support element is a longitudinal support element.

Accordingly, in a third aspect, there is provided a head, for a printhead, comprising a body having a fluid chamber formed therein, wherein the fluid chamber is in fluid communication with a nozzle, and wherein the body further comprises a coupling aperture formed therein, wherein the coupling aperture comprises a coupling surface, and wherein the body further comprises at least one fluid channel formed therein having a first opening at the coupling surface and a second opening in the fluid chamber, wherein the head is operable to be assembled on a support element and retained thereon.

Preferably, the at least one fluid channel is in fluid communication with an internal manifold provided in the support element when the head is assembled thereon.

Accordingly, in a fourth aspect, there is provided a printhead comprising: at least two heads, each of which is provided with at least one fluid chamber having a nozzle associated therewith for printing a liquid onto a substrate, wherein each head comprises a main body, in which at least one feeding duct and at least one return duct are formed, each duct providing fluid communication between the fluid chamber and a coupling surface of the body; and wherein a support element having an internal duct is provided with a feeding opening, configured to align with a feeding duct of a head, and with a return opening, configured to align with a return duct of a head; and wherein the support element is connected to the heads at the coupling surfaces when the head is assembled on the support element.

Preferably, the internal duct is shaped in such a way that the pressure of the printing liquid is substantially constant at all of the feeding openings.

Preferably, the internal duct is shaped in such a way that the pressure of the printing liquid is substantially constant at all of the return openings.

Preferably, the internal duct is divided into two portions, a delivery portion positioned in communication with the feeding openings and a return portion positioned in communication with the return openings.

Preferably, the delivery portion and the return portion are in reciprocal communication.

Preferably, the internal duct comprises a longitudinal partition, which separates the delivery portion and the return portion.

Preferably, the longitudinal partition defines at least two communication openings between the delivery portion and the return portion, said communication openings being arranged in end zones of the internal duct.

One advantage of the printhead according to the present invention is that it has an overall design which is significantly simpler than the printheads currently available.

Another advantage of the printhead according to the present invention is that it requires a substantially reduced number of conduits than the printheads currently available.

A further advantage of the printhead is that it provides for reduced pressure regulation requirements than the printheads currently available.

Figure 1 shows, in perspective, a cross section view of a printhead and support bar having a plurality of individual heads assembled thereon, showing the direction of fluid flow into the printhead via a fluid supply duct, according to a first embodiment of the present invention; Figure 2 shows, in perspective, a cross section view of the printhead and support bar of Figure 1, showing the direction of fluid flow out of the printhead via a fluid return duct; Figure 3 shows, in perspective, an exploded view of the printhead of Figure 1; Figure 4 shows a section view of the printhead and support bar through the longitudinal axis of the support bar of Figure 1 and the fluid return duct of the individual head; Figure 5 shows a section view of the printhead and support bar through the longitudinal axis of the support bar of Figure 1 and the fluid supply duct of the individual head; Figure 6 shows a top down section view through print chambers of two individual heads of Figure 1; Figure 7a shows, in perspective, a delivery portion of an insert according to a first embodiment of the present invention; Figure 7b shows a section view through the longitudinal axis of a first end of the insert of Figure 7a along the line A-A; Figure 7c shows a section view through the longitudinal axis of a second end of the insert of Figure 7a along the line B-B; and Figure 7d shows, in perspective, a return portion of the insert of Figure 7a.

Figure 1 shows, in perspective, a cross section view of a printhead 1 and support bar 3 having a plurality of individual heads 2 thereon. Figure 2 shows, in perspective, a cross section view of the printhead 1 and support bar 3; Figure 3 shows, in perspective, an exploded view of the printhead 1; Figure 4 shows a section view of the printhead 1 and support bar 3 through the longitudinal axis of the support bar 3 and a fluid return duct 25 of the individual head 2; Figure 5 shows a section view of the printhead 1 and support bar 3 through the longitudinal axis of the support bar 3 and a fluid supply duct 24 of the individual head 2; Figure 6 shows top down section view through fluid chambers 21 of two individual heads 2; Figure 7a shows, in perspective, a delivery portion 311 of an insert 310; Figure 7b shows, a section view through the longitudinal axis of a first end of the insert 310 the line A-A; Figure 7c shows a section view through the longitudinal axis of a second end of the insert 310 along the line B-B; and Figure 7d shows, in perspective, a return portion 312 of the insert 310.

The printhead 1 according to the present invention comprises at least two individual heads 2, each of which is provided with at least one fluid chamber 21 (e.g. as shown in Figures 4-6) and a nozzle 22 (e.g. as shown in Figures 3-6) positioned in fluid communication with the fluid chamber 21.

An obturator (not shown), as known to a person skilled in the art of inkjet printing, is provided in the fluid chamber 21 for opening and closing the nozzle 22 in a controlled manner to allow the liquid to be discharged/printed at precise positions onto a surface of a substrate to be decorated.

The figures 1-3 of the present embodiment show a printhead 1 having five individual heads 2, although it will be appreciated that a printhead 1 is not limited to having five individual heads 2, and may have as many heads as required for a specific application, as will be appreciated by a skilled

person having taken account of this specification.

Whilst the operation of the printhead 1 is described hereinafter using glaze as the printing liquid, it will be appreciated that any suitable fluid could be used depending on the specific application e.g. methyl ethyl ketone or acetone based ink for printing on cardboard/paper/food packaging or polymer/metallic based ink for 3D-printing.

The glaze itself may contain pigment to provide colour after firing, and have other additives such as clay to provide different finishes such as glossy, matt, opaque finishes that may be combined on the same surface, as well as special effects such as metallic tones and lustre. Texture or relief structures can be provided by printing a solution containing predominantly engobe. An exemplary digital glaze composition is disclosed in ES2386267. Particle sizes within the glaze are generally in the range of between O.lpm -SOpm, and preferably up to 30 pm, but will vary dependent on the specific formulation required for a particular application.

Alternatively engobe may be used in the printhead, whereby engobe is used for priming of ceramic tiles, to make the tile water permeable after pressing; or for printing raised features on the tile for wood, stone effects.

Engobe is a clay particle suspension, whilst glaze generally comprises an aqueous or solvent based glass frit suspension, or a suspension within a solution, made up of a liquid part having a quantity of mineral particulates/powders dispersed therein, whereby the specific glaze formulation is dependent on the requirements of the end user. A matt glaze may also contain engobe.

Each head 2 comprises a main body 23, through which at least one internal feeding duct (channel) 24 (e.g. as shown in Figures 1, 5 and 6) and at least one internal return duct (channel) 25 (e.g. as shown in Figures 2, 4 and 6) are formed, wherein both the feeding duct 24 and the return duct 25 each have an opening into the fluid chamber 21 and a second opening at a coupling surface 26 of the head 2 (as shown in Figures 4 and 5).

The body 23 of an individual head 2 is formed of a robust material which has mechanical and chemical resistance to the specific fluids used for a particular printing application. For example, when using glaze, one suitable material is polyether ether ketone (PEEK) e.g. Victrex PEEK, which has suitable mechanical and chemical resistance properties for both organic and aqueous fluids including aqueous based glaze.

The printhead 1 further comprises a support element 3, formed in the present embodiment as a cylindrical structure having an outer surface on which the individual heads 2 are assembled, and having a hollow internal duct 31, through which glaze can flow.

The bodies 23 of the individual heads 2 further comprise an aperture 29 formed therethrough (e.g. as shown at Figures 3, 4 and 5), whereby the internal surface of the aperture 29 i.e. a coupling surface 26 is such that when a head 2 is assembled on the support bar 3, the coupling surface 26 is in contact with the support bar 3, such that the head 2 is maintained substantially in position thereon and relative thereto.

Retention and alignment of the heads 2 relative to the support bar 3 is provided by any suitable means, for example by way of a frictional fit between the support element 3 and the coupling surfaces 26, and/or by complementary/keyed locating formations 305 provided on the support element 3 and the coupling surface 26 of the heads 2.

The apertures 29 have a shape which is substantially complementary to the support element 3, and, for the present embodiment, are cylindrical in shape. As can be seen in Figure 3. the coupling surface 26 of each head 2 is defined substantially by the internal surface of an aperture 29 formed through the main body 23 of said head 2.

The heads 2 can therefore be assembled on the support element 3 alongside one another, and aligned along a longitudinal axis (Y) of the support element 3.

The angular position of the heads 2 can be defined by means of the cylindrical coupling between the support element 3 and coupling surfaces 26 by reference means e.g. the locating formations 305 which can be provided to define the angular position of the heads 2 around the longitudinal axis (Y).

The position of each head 2 along the longitudinal axis (Y) can be defined by means of appropriate references or spacers distributed along the support element 3. In the embodiment shown, the position of each head 2 along the longitudinal axis (Y) is defined by placing the heads 2 in contact with one another.

For this purpose, the main bodies 23 of the heads 2 are shaped so as to allow direct contact between the heads 2. In particular, the main bodies 23 of the heads 2 are provided with opposing lateral surfaces 23a and 23b intended to be positioned in contact with the lateral surfaces 23a and 23b of adjacent heads 2, as shown in Figure 3.

It is preferable that at least one of the lateral surfaces of the heads 2 is provided with a first coupling zone 23c and that the other lateral surface is provided with a second coupling zone 23d. The first coupling zone 23c of a head 2 is intended to be positioned in contact with the second coupling zone 23d of an adjacent head 2, and vice versa. It is preferable that the coupling zones 23c, 23d are structured so as to prevent relative rotation between two adjacent heads around the longitudinal axis (Y), e.g. the surfaces may be keyed by providing cooperating structures on the lateral surfaces 23a and/or 23b at the coupling zones 23c and/or 23d.

The overall position of the two or more heads 2 with which the printhead is provided along the longitudinal axis (Y) can be defined by fixing means. In the present embodiment, a first end locating element 41 and a second end locating element 42 are provided as fixing means to retain the heads in position on the support element 3.

Each of the end locating elements 41, 42 are designed to be fixed to the support element 3 using any suitable means e.g. screws, grub screws, adhesive etc. The two or more heads 2 are inserted substantially between the two end locating elements 41, 42 such that they cannot slide/move along the longitudinal axis (Y). The locating elements 41/42 may also be provided with internal conduits formed integral thereto to provide for flow of glaze therein/therethrough.

Furthermore, as shown in Figure 3, various leakage prevention/reduction means 27 e.g. 0-rings/flanges/formations are provided on the lateral surfaces 23a and/or 23b of adjacent heads 2, to prevent/reduce the leakage of glaze from the heads 2 whilst printing, which would otherwise cause pressure and/or printing issues.

The heads 2 are therefore aligned in succession along the support element 3, whereby, as described above, the fluid chambers 21 of the heads 2 are further connected in fluid communication with the internal duct 31 of the support element 3 by means of their own feeding ducts 24 and return ducts 25.

The support element 3 is provided with a feeding opening 32 through the surface thereof into the internal duct 31 (e.g. as shown at Figures 1, 3 and 5). The feed opening 32 is designed to be aligned with the opening of the feeding duct 24 on the coupling surface 26, when the individual head 2 is assembled in position on the support element 3.

The support element 3 is further provided with a return opening 33 through the surface thereof into the internal duct 31 (as shown at Figures 2, 3 and 4). The return opening 33 is designed to be aligned with the opening of the return duct 25 on the coupling surface 26, when the individual head 2 is assembled in position on the support element 3.

When a head 2 is assembled in position on the support bar 3 each feeding opening 32 is aligned with the feeding duct 24 of a head 2 and each return opening 33 into the internal duct 31 is aligned with the return duct 25 of a head 2.

It will be seen therefore, that as the internal duct 31 is in fluid communication with the feeding ducts 24 and return ducts 25 of individual heads assembled on the support element 3, the internal duct 31 is in fluid communication with the fluid chamber 21 of the individual heads 2 assembled on the support element 3 via the respective feed and return ducts 24 and 25 of the respective heads.

In general, the support element 3 is provided with as many feeding openings 32 and as many return openings 33 as there are heads 2 provided in the printhead 1. Therefore, in the present embodiment, the internal duct 31 is provided with five feeding openings 32 and five return openings 33. In alternate embodiments a printhead having ten (10) or more individual heads 2, and preferably sixteen (16) heads 2 is provided.

Advantageously, a first end locating element 41 is provided with a feed conduit (channel) 34 provided in fluid communication with the internal duct 31 of the support element 3 when assembled thereon, whereby glaze is fed to the internal duct 31 from a system ink reservoir via the feeding conduit 34.

The first end locating element 41 is further provided with a return conduit (channel) 35 in fluid communication with the internal duct 31, when assembled on the support element 3, whereby unprinted glaze is returned to the system ink reservoir via the return conduit 35.

It will be appreciated that additionally or alternatively to the first end locating element 41, the second end locating element 42 may be provided with an internal conduit(s) in communication with the internal duct 31.

In this way, the support element 3 having the internal duct 31 therein performs both the task of a fluid supply and return manifold for the heads 2 and the task of support element for the heads 2.

In the present embodiment, the internal duct 31 comprises two portions: a delivery portion 311 and a return portion 312 extending along a portion thereof.

The delivery portion 311 is positioned in fluid communication with the feeding openings 32, each of which is in fluid communication with the ink chamber 21 via the feeding duct 24 of a head 2 as described above.

Furthermore, the return portion 312 of the internal duct 31 is positioned in fluid communication with the return openings 33, each of which is in fluid communication with the ink chamber 21 via the return duct 25 of a head 2 as described above.

A longitudinal sealing partition 313 extends substantially along the length of the internal duct 31 from an area located towards the first end 331 of the body 330 to an area located towards a second end 331 of the body 330, whereby the sealing partition is operable, in use, to provide a seal between the fluid delivery portion 311 and the return portion 312. The sealing partition 313 opens at an end 315 of the internal duct 31, whereby the delivery portion 311 is in fluid communication with the return portion 312, such that glaze can flow from the delivery portion 311 to the return portion 312 at the end 315.

The sealing partition 313 opens towards an end 315, such that, in use, the delivery portion 311 is in fluid communication with the return portion 312, whereby glaze can flow from the delivery portion 311 to the return portion 312 at the opening.

In the present embodiment, an insert 310 (e.g. as shown at Figures 7a-7d) is provided within the internal duct 31. The insert 310 comprises a longitudinal body 330, having a first end 331 and a second end 332, whereby the body 330 comprises a substantially cylindrical cross-section.

The body further comprises an outer surface 318, whereby the outer surface is formed to locate e.g. frictionally fit inside the internal duct 31.

The body 330 further comprises at least two formations provided therein to define the delivery portion 311 and the return portion 312 and the sealing portion 313.

A central wall 313 extends longitudinally from an area located towards the first end 331 to an area located towards the second end 332, whereby the central wall 313 is a sealing partition 313 between the delivery portion 311 and the return potion 312, whereby the sealing partition 313 comprises an upper surface 338, whereby, the width of the upper surface 338 is preferably less than the width of the top surface 318 of the sealing partition 313 below the upper surface 338.

The delivery portion 311 and the return portions comprise flow surfaces 321, which extend a distance (L) transverse to the sealing partition 313.

In the present embodiment, the top surface 338 of the sealing partition 313 frictionally locates against an inner surface of the internal duct 31 to provide a sealing functionality between the delivery portions 311 and return portions 312 when the insert 310 is inserted into the internal duct of the support element 3 (e.g. as shown in Figures 1, 2, 4 and 5), whilst as described above, a portion of the sealing partition 313 opens towards the end 315.

In an alternative embodiment, the internal duct 31 of the support element 3 is provided with formations formed integral thereto, to define the delivery portion 311 and return portion 312 i.e. whereby no insert is required.

As shown schematically for example at Figures 1, 2, 4 and 5, the glaze is fed, under pressure e.g. iBar, to the internal duct 31 through the feed conduit 34 and flows into the delivery portion 311 towards a first end 325 thereof, and flows within the delivery portion 311 towards a second end 326 thereof, whereby the glaze flows, under pressure, into the feeding ducts 24 through the feeding openings 32 located along the surface of the internal duct 31 between the first end 325 and second end 326 of the delivery portion 311.

The quantity of glaze which is not fed to the heads 2 flows from the delivery portion 311 into the return portion 312, through the sealing partition 313 at the opening towards the end 315. The glaze then flows within the return portion 312 to a return conduit 35 via a channel 327 (Figure 7d) located towards a second end of the return portion 312, such that the excess glaze is recirculated in the system.

In the present embodiment the openings 32 are provided along a horizontal plane located substantially vertically above a horizontal plane on which the openings 33 are provided. Such a configuration results in the delivery portion 311 being located above the return portion 312, which minimises or negates sedimentation of particles in the printhead.

Furthermore, it will be seen that the openings 32 and 33 are provided on different vertical planes i.e. they are offset. However, it will be appreciated that, in alternative embodiments, the openings 32 and 33 may be located on the same vertical plane.

Of the total quantity of glaze fed to the individual heads 2 through the feeding ducts 24, a quantity is discharged from the nozzles 22 during a printing cycle, whilst the remaining glaze flows through the return ducts 25 and the openings 33 into the return portion 312, whereby the glaze then flows, under pressure, into the return conduit 35 via the channel 327 (Figure 7d) such that substantially all glaze which is not printed is recirculated in the system (as shown in Figures 1 and 2).

Advantageously, the recirculation of the glaze at pressure e.g. 1 Bar reduces/prevents sedimentation of particulates and/or obstructions in any part of the internal duct 31 and of the heads 2.

Furthermore, the internal duct 31 of the support element 3 is structured in such a way that the pressure of the glaze is substantially constant across all of the feeding openings 32 and fluid chambers 21 in the head. This ensures that the fluid chambers 21 in the heads 2 of the printhead 1 are fed substantially with the same quantity of glaze at a substantially constant pressure e.g. 1 Bar, which provides for controlled fluid feed to the chamber, controlled droplet formation and controlled droplet ejection. The internal duct 31 is further shaped in such a way that the pressure of the glaze is substantially constant at all of the return openings 33 to provide for controlled fluid return from the chamber 21.

In the present embodiment, in order to provide for a substantially equal pressure across all feeding openings 32, return openings 33, and within the fluid chambers 21, the cross section profile of the portions 311 and/or 312 varies between each end of the portions 311 and/or 312, thereby effecting a corresponding controlled variation in the pressure drop per length between each end of the delivery and return portions 311 and 312, when glaze is flowing therethrough.

As an example of the variation in the cross section profile, Figure 7a shows, in perspective, a delivery portion 311 of an insert 310; Figure 7b shows, a sectional view of the insert 310 along the line A-A; Figure 7c shows a sectional view of the insert 310 along the line B-B; and Figure 7d shows, in perspective, a return portion 312 of the insert 310.

Specifically, Figure 7a shows a delivery portion 311, whilst Figure 7d shows a return portion 312, whereby each portion comprises a curved flow surface 321 extending curvedly downwards from an area towards the first end 331 of the body 330 in the direction of the second end 332.

At a point 340 located between the first and second ends of the body 330, the flow surface 321 extends upwards in the direction of the second end 332 of the body 330. This upward extension may be linear or non-linear.

As can be seen in Figures 7b and 7c, the distance L is larger at the section through A-A which is located closer to point 340, than at the section through B-B, which is located closer to the second end 332.

By varying the angle at which the surfaces 321 of the respective portions 311 and/or 312 extend upwards or downwards, the pressure drop per length of glaze flowing through the portions 311 and/or 312 can be easily controlled and optimised such that, in use, the pressure is maintained substantially constant across all the feed openings 32.

In an alternative embodiment, the delivery portion 311 may be fabricated such that the profile of the portion 311 varies linearly between a first end and second end of the portion 311, to cause a flow rate in the delivery portion to decrease dependent on the taper, as described in FF1140513, such that a substantially constant pressure is provided across all the feed openings 32 along the delivery portion 311.

Alternatively or additionally, the cross-section profile of the return portion 312 may be fabricated to vary linearly or non-linearly such that a substantially constant pressure is provided across all the return openings 33.

In a further alternative embodiment, the profiles of the delivery and/or return portion 311 and/or 312 may remain constant between each end, but further pressure regulation will be required for the heads 2. For example, the profiles of the feed ducts 24 and/or the return ducts 25 may vary to ensure the glaze flows into and/or out of the fluid chamber 21 at a constant pressure.

In the present embodiment, the insert is formed of a thermoplastic material having high stiffness, low friction and excellent dimensional stability e.g. Polyoxymethylene (POM), and which is resistant to glaze. The insert may be fabricated using any suitable technique for example 3d-printing, injection molding.

In an alternative embodiment, the internal duct 31 is not provided with an insert but, instead, the support element 3 is provided with formations formed integral thereto at the internal duct 31, to define the delivery portion 311 and return portion 312. On account of the support element 3 having the internal duct 31 having substantially sealed delivery and return portions 311 and 312 provided therein, there is, therefore, no need for separate feed circuits for each of the individual heads 2, nor is there a requirement for individual feed and supply circuits and/or complex pressure regulation for each individual head.

The variation in the profile of the delivery portion 311 and return portion 312 can be obtained by means of the flow surface 321, which is structured to define the internal profile of the portions 311 and/or 312, and therefore the specific shape, volume and pressure drop per length of the portions 311 and/or 312.

The printhead according to the present invention achieves important advantages.

For example, the structures of the support element 3 and of the heads 2 make it possible to form a supply circuit for feeding fluid to multiple heads substantially without the need for individual complex pressure control circuits or controls.

The circuit for supplying and recirculating the glaze is defined essentially by the support element 3 and by the main bodies 23 of the heads 2, without the need for further conduits with the exception of a conduit for supplying the glaze to the support element 3.

The support element 3 further provides a support and a simple and precise reference for positioning the heads 2 thereon.

Claims

CLAIMS1) A printhead (1) having at least two individual heads (2), wherein each head (2) comprises a fluid chamber (21) having a nozzle associated therewith for printing a fluid onto a substrate, characterised in that the printhead (1) further comprises a support element (3) having an internal cavity (31) formed therein, through which fluid can flow to the heads, and, wherein the individual heads (2) are arranged on the support element (3) and retained thereon.
2) The printhead (1) of Claim 1, wherein the printhead (1) is adapted such that, in use, the pressure of fluid in the fluid chambers (21) is substantially equal across all fluid chambers (21) of the printhead (1).
3) The printhead (1) of Claim 1 or Claim 2, wherein the internal cavity (31) is in fluid communication with the fluid chambers (21) of the individual heads (2) via at least one opening (32, 33) formed in the support element (3) and at least one channel (24, 25) formed in the heads (2).
4) The printhead (1) of any preceding claim, wherein the support element (3) is a longitudinal support element (3).
5) The printhead (1) of any preceding claim, wherein, the internal cavity (31) comprises a longitudinal duct (31) having a fluid delivery portion (311) and a fluid return portion (312), wherein the fluid delivery portion (311) and the fluid return portion (312) are separated by a dividing portion (313) extending along the longitudinal duct (31), and wherein the delivery portion (311) is in fluid communication with the return portion (312) towards a first end of the duct (31).
6) The printhead (1) according to Claim 5, wherein the cross section profileofthefluid delivery portion (311)and/orthefluid return portion (312) varies along the length of the duct (31).
7) The printhead (1) according to Claim 6, wherein the profile of the fluid delivery portion (311) and/or the fluid return portion (312) varies linearly.
8) The printhead (1) according to Claim 6, wherein the profile of the fluid delivery portion (311) and/or the fluid return portion (312) varies non-linearly.
9) The printhead (1) according to any preceding claim wherein the internal cavity (31) is provided in the support element (1) as a removable insert (310).
10) The printhead (1) according to any of claims 1 to 8, wherein the internal cavity (31) is fabricated integral to the support element (3).
11) A support element (3), for a printhead (1), wherein the support element (3) comprises an internal fluid cavity (31), and wherein the support element is operable to receive at least one head (2) having a fluid chamber thereon, and wherein, in use, the support element is operable to supply fluid to the fluid chamber of the at least one head (2).
12) The support element (3) of Claim 11, wherein the support element (3) is adapted such that, in use, the pressure of fluid in the fluid chambers (21) is substantially constant across all fluid chambers (21) of the at least one head (2).
13) The support element (3) of Claims 11 or Claim 12, wherein, in use, the internal cavity (31) is in fluid communication with the fluid chamber (21) of the at least one head (2) via at least one opening (32, 33) formed thereon.
14) The support element (3) of Claim 11, wherein the support element (3) is a longitudinal support element (3).
15) The support element (3) according to any of Claims 11 to 14, wherein, the internal cavity (31) comprises a longitudinal duct (31) having a fluid delivery portion (311) and a fluid return portion (312), wherein the fluid delivery portion (311)and the fluid return portion (312) are separated by a dividing portion (313) extending along the longitudinal duct (31), and wherein the delivery portion (311) is in fluid communication with the return portion (312) towards a first end of the duct (31).
16) The support element (3) according to Claim 15, wherein the profile of the fluid delivery portion (311) and/or the fluid return portion (312) varies along the length of the duct (31).
17) The support element (3) according to Claim 16, wherein the profile of the fluid delivery portion (311) and/or the fluid return portion (312) varies linearly.
18) The support element (3) according to Claim 16, wherein the profile of the fluid delivery portion (311) and/or the fluid return portion (312) varies non-linearly.
19) The support element (3) according to any of claims 11 to 18 wherein the internal cavity (31) is provided in the support element (1) as a removable insert (310).
20) The support element (3) according to any of claims 11 to 18, wherein the internal cavity (31) is fabricated integral to the support element (3).
21) A head (2), for a printhead (1), comprising a body (23) having a fluid chamber (21) formed therein, wherein the fluid chamber (21) is in fluid communication with a nozzle (22), and wherein the body (23) further comprises a coupling aperture formed therein, wherein the coupling aperture comprises a coupling surface (26), and wherein the body further comprises at least one fluid channel (24, 25) formed therein having a first opening at the coupling surface (26) and a second opening in the fluid chamber (21), wherein the head (2) is operable to be assembled on a support element (3) and retained thereon.
22) The head (2) according to claim 1, wherein the at least one fluid channel (24, 25) is in fluid communication with an internal cavity (31) provided in the support element (3) when the head is assembled thereon.
23) A printer having a printhead (1) of any of claims 1 to 10.
24) A printer having a support element (3) of any of claims 11 to 20.
25) A printer having a head (2) of any of claims 21 or 22.
26) A printhead having at least two individual heads substantially as hereinbefore described, with reference to figures 1 to 6 of the accompanying drawings.
27) A support element, substantially as hereinbefore described, with reference to figures 1 to 5 of the accompanying drawings.
28) A head substantially as hereinbefore described, with reference to figures 1-6 of the accompanying drawings.
29) An insert substantially as hereinbefore described, with reference to figures 1-5 of the accompanying drawings.