Patent Publication Number: US-11660863-B2

Title: Droplet ejection head, manifold component therefor, and design method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage entry of international application no. PCT/GB2019/052106, filed Jul. 26, 2019, which is based on and claims the benefit of foreign priority under 35 U.S.C. 119 to GB 1812284.6, filed Jul. 27, 2018. This entire contents of the above-referenced applications are herein expressly incorporated by reference. 
     The present invention relates to a manifold component for a droplet ejection head, and to an associated design method. It may find particularly beneficial application in a printhead, such as an inkjet printhead. 
     Droplet ejection heads are now in widespread usage, whether in more traditional applications, such as inkjet printing, or in 3D printing, or other rapid prototyping techniques. 
     Recently, inkjet printheads have been developed that are capable of depositing ink directly onto ceramic tiles, with high reliability and throughput. This allows the patterns on the tiles to be customized to a customer&#39;s exact specifications, as well as reducing the need for a full range of tiles to be kept in stock. 
     In other applications, droplet ejection heads may be used to form elements such as colour filters in LCD or OLED displays used in flat-screen television manufacturing. 
     Droplet ejection heads and their components continue to evolve and specialise so as to be suitable for new and/or increasingly challenging applications. 
     SUMMARY 
     Aspects of the invention are set out in the appended independent claims, while particular embodiments of the invention are set out in the appended dependent claims. 
     The following disclosure describes, in one aspect, a manifold component for a droplet ejection head, the manifold component comprising:
         a mount for receiving an actuator component that provides one or more rows of fluid chambers, each chamber being provided with a respective at least one actuating element and a respective at least one nozzle, the at least one actuating element for each chamber being actuable to eject a droplet of fluid in an ejection direction through the corresponding at least one nozzle, each row extending in a row direction;   a manifold chamber, which extends from a first end to a second end, and widens from said first end to said second end, the second end providing fluidic connection, in parallel, to at least a group of chambers within said one or more rows and being located adjacent said mount; and   at least one port, each port opening into the manifold chamber at the first end thereof;   wherein at least one portion between the first end and second end of the manifold chamber is shaped as a hyperbolic acoustic horn.       

     The following disclosure describes, in another aspect, a manifold component for a droplet ejection head, the manifold component comprising one or more manifold chambers and at least one port; wherein a transitional portion connects one of said at least one ports to the second portion of said one or more manifold chambers and wherein said transitional portion comprises a change in cross-sectional shape to blend from the cross-sectional area of said one port to that of said second portion of said one or more manifold chambers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the drawings, which are representational only and are not to scale, and in which: 
         FIG.  1 A  is a cross-sectional view of a manifold component according to a first embodiment of the disclosure; 
         FIG.  1 B  is an end view of the manifold component shown in  FIG.  1 A ; 
         FIG.  2 A  is a cross-sectional view of a manifold component according to another embodiment; 
         FIG.  2 B  is an end view of the manifold component shown in  FIG.  2 A ; 
         FIG.  2 C  is a side view of the manifold component shown in  FIGS.  2 A and  2 B ; 
         FIG.  3 A  is a cross-sectional view of a manifold component according to another embodiment which has multiple horn-shaped portions; 
         FIG.  3 B  is an end view of the manifold component shown in  FIG.  3 A ; 
         FIG.  4    is a manifold component according to another embodiment; 
         FIG.  5 A  is a cross-sectional view of a manifold component according to yet another embodiment which has multiple horn-shaped portions; 
         FIG.  5 B  is an end view of the manifold component shown in  FIG.  5 A ; 
         FIG.  5 C  is a side view of the manifold component shown in  FIGS.  5 A and  5 B ; 
         FIG.  6 A  is the fluidic path in a manifold component according to a first test design; 
         FIG.  6 B  is the fluidic path in a manifold component according to another embodiment with multiple horn-shaped portions; 
         FIG.  6 C  compares the calculated performance of the manifold components in  FIGS.  6 A and  6 B ; 
         FIG.  7 A  is a cut-away three-dimensional view of the fluidic path in a through-flow enabled manifold component according to another test design; 
         FIG.  7 B (a) is a cut-away three-dimensional view of the fluidic path in a manifold component according to another embodiment that is through-flow enabled and has multiple horn-shaped portions; 
         FIG.  7 B (b) is a cross-sectional view of the manifold component depicted in  FIG.  7 B (a); 
         FIG.  7 B (c) is a cross-sectional view of the manifold component  750  depicted in  FIG.  7 B (a) and (b); 
         FIG.  7 B (d) is a cut-away three-dimensional view of a detail of the fluidic path depicted in  FIG.  7 B (a); 
         FIG.  7 C  compares the calculated coefficient of reflection across the frequency range for a manifold component as per  FIG.  7 A  and a manifold component as per  FIG.  7 B ; 
         FIG.  8    is an extract from a print sample produced using drop-on-demand inkjet printheads; 
         FIG.  9   (A-C) are graphs comparing drop velocity data produced using a printhead comprising a test manifold component as per  FIG.  7 A  and a printhead comprising a horn-shaped manifold component as per  FIG.  7 B ; and 
         FIG.  10    is a schematic diagram depicting a method of designing a horn-shaped portion for a manifold component according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Embodiments of the disclosure in general relate to a manifold component for a droplet ejection head. 
     Turning now to  FIG.  1   , shown is a manifold component  50  according to a first example embodiment. More particularly,  FIG.  1 A  is a cross-sectional view of a manifold component  50  according to a first embodiment of the disclosure;  FIG.  1 B  is an end view of the manifold component  50  shown in  FIG.  1 A . The example embodiment shown in  FIG.  1 A-B  relates in general to a manifold component  50  for a droplet ejection head. The manifold component  50  has a mount  80  for receiving an actuator component  150  that provides one or more rows of fluid chambers (not shown). Each such chamber is provided with a respective at least one actuating element, for example a piezoelectric actuating element, and a respective at least one nozzle. In operation each actuating element is actuable to eject a droplet of fluid in an ejection direction  505  through the corresponding nozzle. Each of the rows of fluid chambers extends in a row direction  500 , indicated with respective arrows in  FIGS.  1 A and  1 B . In the particular example embodiment of  FIGS.  1 A and  1 B , the mount  80  is a flat receiving surface. 
     As may be seen from  FIG.  1 A , a manifold chamber  55  is provided within the manifold component  50 . The manifold chamber  55  extends from a first end  51  to a second end  52 , widening from the first end  51  to the second end  52 . Fluid flowing within the manifold chamber  55  during operation may be described as “fanning out” as it approaches the second end  52 . The second end  52  provides a fluidic connection, in parallel, to at least a group of chambers within the one or more rows in the actuator component  150 , the second end  52  being located adjacent to said mount  80 . As may also be seen from  FIG.  1 A , the manifold component further includes a port  120  which opens into the manifold chamber  55  at the first end  51  thereof. In operation the port  120  may supply fluid to the first end  51  of the manifold chamber  55  such that the port  120  may be said to be an inlet port and the manifold chamber  55  may be said to be an inlet manifold chamber. In operation the fluid then passes through the inlet manifold chamber  55  from its first end  51  to its second end  52 . For the manifold chamber  55 , the entire portion between the first end  51  and the second end  52  thereof is shaped as a hyperbolic acoustic horn so as to assist in transferring acoustic waves away from the corresponding group of chambers in the actuator component  150 . This may be referred to as the ‘horn-shaped portion’. As shown representationally in  FIG.  1   , the cross-sectional area of the manifold chamber  55  may increase in a hyperbolic fashion from the first end  51  to the second end  52  so as to form a hyperbolic acoustic horn therein. The cross-sectional area of the hyperbolic horn-shaped portion of the manifold chamber  55  increasing in a hyperbolic fashion may, in operation, result in low levels of acoustic cross-talk between the fluid chambers of the actuator component  150 . This may occur because a manifold chamber with a portion shaped as a hyperbolic acoustic horn may assist in transmitting acoustic waves (generated when one or more actuating elements are actuated) out of the manifold chamber  55  and into the fluidic supply. This may in turn improve the drop velocity and volume profile of the droplets of fluid ejected from the nozzles. 
     It has been calculated that when using a manifold component similar to that described in relation to  FIG.  1    an improved acoustic performance may be expected. Furthermore, experiment-based tests for alternative embodiments (described later) have shown that an improved print quality may result. This may be explained as follows. When an actuating element is actuated to eject a droplet of fluid in an ejection direction  505 , acoustic waves pass from the actuator component  150  back into the manifold chamber  55 . Reflected waves may return to the actuator component  150  and influence the behaviour of the fluid in other fluid chambers in the actuator row, leading to non-uniform drop velocity and non-uniform drop volume and causing defects in the appearance of the printed image. Transmitting acoustic waves out of the manifold chamber  55  and into the rest of the fluidic system via the port  120  has now been shown to improve the consistency of the drop velocity and volume of droplets ejected from individual fluid chambers, and hence improve the appearance of the printed image or product. 
     It should be understood that an acoustic horn, similar to that shown in the embodiment of the manifold component  50  depicted in  FIG.  1   , includes a region whose cross-sectional area increases according to a hyperbolic equation connecting two cross-sectional areas A 2  and A 1 , where A 2  is the smaller area and A 1  is the larger area. In the manifold component  50  depicted in  FIG.  1   , A 2  is the cross-sectional area at the first end  51 , proximate the port  120  and A 1  is the cross-sectional area at the second end  52 , proximate the mount  80 . In the manifold component  50  the source of the acoustic waves of interest is one or more of the fluid chambers in the actuator component  150 . In operation therefore acoustic waves would emanate from any fluid chamber where an actuating element is actuated and into the manifold chamber  55 , e.g. travelling through the area A 1  towards the area A 2 . 
     The changing cross-sectional area of the manifold chamber  55 , indicated by arrow  56  in  FIG.  1 A , can be represented by equation (1) where A(x) is the calculated area of area  56  at a given position as x increases along the central path  515  from the area A 2  to towards the area A 1  and where x=0 is at the location of the area A 2 . Such regions of increasing cross-sectional area linking two different cross-sectional areas A 2  and A 1  are generally referred to as hyperbolic horns, also called hyperbolic-exponential or hypex horns. 
     Hypex horns are a general family of horns given by the wavefront area expansion:
 
 A ( x )= A 2[cos  h ( x/x _ T )+ T _ sin  h ( x/x _ T )]{circumflex over ( )}2  (1)
 
where T is a parameter which sets the shape of the horn. For most practical applications 0≤T≤1.
 
x_T is a reference distance given as:
 
 x _ T=c /(2π f _ c )  (2)
 
where c is the speed of sound in the fluid and f c is the cutoff frequency. The cutoff frequency is the frequency below which most of the energy is reflected and above which most of the energy is transmitted.
 
     Such equations may be used to design hypex horns as per any of the embodiments described herein. Depending on the desired operational capabilities of a droplet ejection head, it may be understood that different operating frequency ranges and acceptable cutoff frequencies may be required and may be designed for and chosen accordingly. 
     The manifold component  50  having a cross-sectional area changing in a hyperbolic fashion may therefore be described as follows. The manifold chamber  55  has a central path  515 , which extends centrally through the manifold chamber  55  from the centre of the area A 2  proximate the first end  51  to the centre of the area A 1  proximate the second end  52 . At any given point along the central path  515  the changing cross-sectional area is indicated by arrow  56  and is the area at right-angles to the central path  515 . In the embodiment shown in  FIG.  1    the central path  515  is parallel to the ejection direction  505 , but this is in no way an essential feature. In the portion shaped as a hyperbolic acoustic horn the cross-sectional area of the area  56  varies according to a hyperbolic function of distance from the area A 2  along the central path  515 . In other words, the portion of the manifold chamber  55  which is shaped as a hyperbolic acoustic horn has a central path  515 , which extends centrally through the manifold chamber, from the centre of the first end  51  of the manifold chamber  55  to the centre of the second end  52 , the areas of cross-sections  56  taken perpendicular to the central path  515  vary approximately according to a hyperbolic function of distance from said first end  51  along the central path  515 . 
     In some embodiments the cross-sectional area of the horn-shaped portion of the manifold chamber  55  increases according to an exponential function. As those skilled in the art will appreciate, a cross-sectional area increasing in an exponential fashion is a special case (with T=1) of a cross-sectional area increasing in a hyperbolic or hypex fashion and the manifold chamber  55  operates as an exponential acoustic horn. 
     It may be understood that the constraints of manufacturing an actual product and the imposition of manufacturing tolerances means that the manifold chamber  55  may not have an exactly mathematically true hypex (hyperbolic profile or exponential profile) for the horn-shaped portion. A horn-shaped portion with a profile that is close to or substantially hyperbolic may still provide improvements in ejection performance when used in the manifold chamber  55 . The terms “hyperbolic fashion”, “hyperbolic horn-shaped portion” and the like, including simply “horn-shaped”, may therefore be understood to encompass a profile that is substantially hyperbolic. For example instead of having a smooth wall profile, a stepped horn-shaped portion consisting of multiple stacked cross-sections, each section having a discrete height in the ejection direction  505  may provide improvements in ejection performance when used in the manifold chamber  55 . Such a profile may occur when using 3D printing, for example, to build up the manifold chamber  55  by depositing multiple layers. Moulded components may tolerate a degree of shrinkage and warpage during manufacture that alters the profile of the manifold chamber  55 , for example, whilst still improving ejection performance. In general a certain amount of noise on the equation (1) may be tolerated when generating the profile for the walls of the manifold chamber  55  whilst still providing acceptable droplet ejection performance. 
     It may be understood that in other embodiments the hyperbolic horn-shaped portion may not extend through the entire manifold chamber  55 , in which case the area A 2  will be proximate the first end  51  of the manifold chamber  55 , but not necessarily coincident with it, and the area A 1  will be proximate the second end  52  of the manifold chamber  55 , but not necessarily coincident with it. 
     As may be seen from  FIG.  1 B , in this embodiment the actuator component  150  is elongate such that its length in the row direction  500  is much greater than its depth in the depth direction  510 . In some embodiments it may therefore be desirable that the second end  52  of the manifold chamber  55  is defined by an opening which is elongate parallel to the row direction  500  (for example, such that the opening has a long axis which extends in the row direction  500  and a short axis that extends in the depth direction). This may enable ready fluidic connection from the manifold chamber  55  to the actuator component  150 . In some embodiments, the opening of the manifold chamber  55  at the second end  52  may have a point on each end of the long axis that defines the same angle  53  (see  FIG.  1 A ) between the plane of the opening and the wall of the manifold chamber  55 . 
     Furthermore, as can be also be seen from  FIG.  1   , in this embodiment the manifold component  50  and the manifold chamber  55  are likewise elongate, though this is by no means essential. Such an arrangement may be suitable when, for example, the manifold component  50  is part of an arrangement of multiple manifold components, for example so as to supply different colours for printing onto paper or fabric, or to enable dense printing of a single colour, as this shape enables close packing of multiple manifold components. 
     In the particular embodiment depicted in  FIG.  1   , the actuator component  150  is rectangular and the manifold chamber  55  has an opening that is rectangular in cross-section at its second end  52 . However this is in no way limiting, and other arrangements of fluid chamber rows and shapes of actuator and manifold components are envisaged. 
     It may be readily understood that if the actuator component  150  is very long and slender then it may be expedient to use an array of manifold chambers  55  arranged adjacent to each other in the row direction  500  so that, in operation, each acts as an inlet manifold chamber  55  and supplies fluid to a portion of the actuator component  150 . In such an arrangement each individual manifold chamber  55  would feed at least one group of fluid chambers within the one or more rows of fluid chambers in the actuator component  150 . In some embodiments the second end  52  of the manifold chamber  55  may provide a fluidic connection, in parallel, to a corresponding one of said one or more rows of fluid chambers. 
     Turning now to  FIG.  2   , shown is a manifold component  250  according to another example embodiment. More particularly,  FIG.  2 A  is a cross-sectional view of a manifold component  250 ,  FIG.  2 B  is an end view of the manifold component  250  shown in  FIG.  2 A , and  FIG.  2 C  is a side view of the manifold component  250  shown in  FIGS.  2 A and  2 B . The embodiment shown in  FIG.  2 A-C  is in many respects similar to that seen in  FIG.  1    and thus, where appropriate, like reference numerals have been used. 
     Unlike the embodiment shown in  FIG.  1   , the manifold component  250  depicted in  FIG.  2    does not have a horn-shaped profile over the entire length of the manifold chamber  55 . Instead, as seen in  FIG.  2 A , the manifold chamber  55  includes a horn-shaped portion  30  and an additional (non-horn-shaped) portion  20  located between the first end  51  and the horn-shaped portion  30 . The horn-shaped portion  30  is the portion of the manifold chamber  55  which has a cross-sectional area that increases in a hyperbolic fashion. The horn-shaped portion starts at the area A 2  which is offset from the first end  51  of the manifold chamber  55  by a distance  58 . The horn-shaped portion  30  may be described as commencing at the area A 2  proximate the first end  51  and finishing at the area A 1  proximate the second end  52 . It should be appreciated that in embodiments where the hyperbolic portion starts at the first end  51 , such as that depicted in  FIG.  1   , the area A 2  and the first end  51  coincide, and there is no additional portion  20 . 
     The portion of the manifold chamber  55  that increases in a hyperbolic fashion may in part be limited by the physical constraints of the wider droplet ejection head design, but in some embodiments the cross-sectional area of the at least one manifold chamber  55  may increase in a hyperbolic fashion over a majority of the distance between the first end  51  and the second end  52 , i.e. the hyperbolic horn-shaped portion extends at least the majority of the distance between the first end  51  and the second end  52  of the corresponding manifold chamber  55 . More particularly the cross-sectional area may increase in a hyperbolic fashion over a distance that is a fraction between 0.6 and 0.9 of the distance between the first end  51  and the second end  52 , i.e. the hyperbolic horn-shaped portion may extend between 0.6 and 0.9 times the distance between the first end  51  and the second end  52  of the corresponding manifold chamber  55 . In still other embodiments the cross-sectional area of the manifold chamber  55  may increase in a hyperbolic fashion over the entirety of the distance along the manifold chamber  55  between the first end  51  and the second end  52 , i.e. the entire manifold chamber  55  is a hyperbolic horn (as shown in the embodiment depicted in  FIG.  1   ). It should be understood that the term “distance” in this context refers to the distance between the first end  51  and the second end  52  along the central path  515  of the manifold chamber  55 . It may further be understood that in the embodiments described herein the positions of A 2  and A 1  within the manifold chamber  55  depend on the extent and position relative to the first end  51  of the hyperbolic portion. 
     Like the embodiment illustrated in  FIG.  1   , the manifold component  250  in  FIG.  2    also has an actuator component  150  that is elongate such that its length in the row direction  500  is greater than its depth in the depth direction  510  (see  FIG.  2 B ). The manifold component  250  also has a manifold chamber  55  with an elongate opening parallel to the row direction  500  at the second end  52 . The manifold component  250  differs from the manifold component  50  in  FIG.  1    in that the cross-sectional area is elongate in the row direction  500  over the entire hyperbolic horn-shaped portion  30 . In this case the cross-sectional area may be defined as the area  56  where the area  56  is elongate. As seen in  FIG.  2 A  the angle  53  may be measured at opposing (short) ends of the elongate area  56  in the row direction  500 . The area  56  is a portion of a plane that intersects with the bounding walls of the manifold chamber  55  at any given point between the area A 2  and area A 1  such that the angle  53  between the walls of the manifold chamber  55  and the plane of the cross-section is equal at the point of intersection on opposing ends of the manifold chamber  55 . In other words, the manifold chamber  55  has at least two points on opposing ends of the elongate area  56  at least at the second end  52  that define the same angle  53  to the wall of said manifold chamber  55 . 
     As can be seen from  FIG.  2    the depth in the depth direction  510  of the hyperbolic horn-shaped portion  30  remains generally constant. The depth direction  510  is perpendicular to the row direction  500  and the ejection direction  505 , as seen in  FIGS.  2 A and  2 B . Since the depth of the horn-shaped portion  30  is generally constant, the hyperbolic change in cross-sectional area is largely due to increasing the width  57  in the row direction  500  of the horn-shaped portion  30 . As seen in  FIG.  2 A , the central path  515  has a section, central path  315 , which runs centrally through the horn-shaped portion  30  from the area A 2  to the area A 1 . At each point on the central path  315  the width  57  is measured in a direction that is normal to the central path  315  at that point and that is perpendicular to the depth direction  510 . The widths  57  vary generally according to a hyperbolic function with distance along the central path  315  from the area A 2  to the area A 1 . 
     As can further be seen from  FIG.  2 A , as for the embodiment in  FIG.  1    there is a port  120  located on surface  81  on the opposite side of the manifold component  250  to the mount  80  in the ejection direction  505 . The port  120  in this embodiment has a circular cross-sectional area so as to enable ready connection to a fluidic supply system. The first end  51  of the manifold chamber  55  likewise has a circular cross-sectional area. As previously discussed the second portion  30  of the manifold chamber  55  may have a generally constant depth in the depth direction  510  and hence it may also be elongate along the entire central path  315 . This means that the change in cross-sectional shape from circular to elongate occurs in the portion  20  of the manifold chamber  55  and the portion  20  is not a hyperbolic acoustic horn. In some embodiments the portion  20  may be limited in its extent such that the manifold chamber  55  may, for at least the majority of its extent thereof in the ejection direction  505 , have a generally constant depth in the depth direction  510 , which is perpendicular to the row direction  500  and to the ejection direction  505 . As may be seen from  FIGS.  2 B and  2 C , another significant difference to the embodiment in  FIG.  1    is that the manifold component  250  in  FIG.  2    has two manifold chambers, manifold chambers  55  and  60 , whereas the manifold component  50  in  FIG.  1    has only a single manifold chamber  55 . As may be seen from  FIG.  2 C  manifold chamber  60  is offset from manifold chamber  55  such that the two are adjacent to each other in the depth direction  510 . Furthermore in this embodiment the geometric shape of the manifold chamber  60  is the same as that of the manifold chamber  55 , but these are by no means essential features and other arrangements and geometries of manifold chamber are envisaged. In this implementation therefore, the portion  25  (which may be referred to herein as a “transitional portion”) and the portion  35  of the manifold chamber  60  are the same geometric shape as the portion  20  and the portion  30  respectively of the manifold chamber  55 . Also, the horn-shaped portion  35  starts at the area A 2  which is offset from the first end  61  of the manifold chamber  60  by a distance  58  and ends at the second end  62  of the manifold chamber  60 . 
     As can further be seen from  FIG.  2 C , in contrast to the embodiment shown in  FIG.  1   , the manifold component  250  of  FIGS.  2 A- 2 C  includes two ports  120  and  220 , whereas the manifold component  50  in  FIG.  1    has only a single port  120 . In the particular embodiment shown, these are located on surface  81 , however it should be understood that this location is by no means essential. In operation, when the ports  120 ,  220  are fluidically connected to a suitable fluid supply, the manifold component  250  shown in  FIGS.  2 A- 2 C  may be operated in a so-called “through-flow” mode such that droplet fluid may, in operation, flow continuously from the port  120  via the manifold chamber  55 , the actuator component  150  and the manifold chamber  60  to the port  220 , with port  120 , manifold chamber  55 , actuator component  150 , manifold chamber  60  and port  220  being fluidically connected, in series, in that order. In operation, a portion of the fluid flowing through selected fluid chambers in the actuator component  150  may be ejected from the respective nozzles for those fluid chambers, whilst the remainder of the fluid continues through the individual fluid chambers and via the manifold chamber  60  to the port  220 . In such embodiments the manifold chamber  55  is configured as an inlet manifold chamber where the corresponding port  120  is configured as an inlet port, in operation supplying fluid to the first end  51  of the inlet manifold chamber  55 . The second end  52  of the inlet manifold chamber  55  in operation supplies fluid in parallel to each chamber within the corresponding group of fluid chambers in the actuator component  150 . Furthermore, in such embodiments the manifold chamber  60  is configured as an outlet manifold chamber with the corresponding port  220  being configured as an outlet port that in operation receives fluid from the first end  61  of the outlet manifold chamber  60  in question. The second end  62  of the outlet manifold chamber  60 , in operation, receives fluid in parallel from each chamber within the corresponding group of fluid chambers of the actuator component  150 . 
     In alternative arrangements, in operation, fluid may be supplied to the actuator component  150  from both ports  120  and  220 , whereby the droplet ejection head may be considered to operate in a non through-flow mode and the manifold chambers  55  and  60  are both inlet manifold chambers and the ports  120 ,  200  are both operating as inlet ports. 
     In the embodiment depicted in  FIG.  2   , the central path  515  is a straight line that is parallel to the ejection direction  505  owing to the geometry of the design depicted. In other embodiments, the central path  515  may not be a straight line but may follow a curved or serpentine path or any other path as defined by the shape of the manifold chamber  55 ,  60 . Manifold chambers may be shaped in such a manner as a result of, for example, physical constraints elsewhere in the droplet ejection head, or to enable a ready connection to a fluidic supply. In such cases it may be appropriate, for example, to offset the port  120  and/or the port  220  from the centre of the manifold component  250  in the array direction  500 , or even to locate the ports on one of the sides  82 ,  83  of the manifold component  250 . In these cases, the central path  515  may follow a different route, for example at an angle to the ejection direction  505 , depending on the shape of the manifold chamber  55 ,  60 . In some embodiments the central path  515 , which runs centrally through the manifold chamber in question, from the centre of the first end  51  to the centre of the second end  52 , may not be parallel to the ejection direction  505  along some of its length. It may be desirable to ensure that the central path  515  is running generally parallel to the ejection direction  505  at the second end  52  of the manifold chamber in question, so as to improve fluidic performance by providing fluid flowing in a favourable direction to the actuator component  150 . As may be readily understood, other shapes of manifold chamber  55 ,  60 , and hence central path  515 , are envisaged. 
     Turning now to  FIG.  3   , shown is a manifold component  350  according to another example embodiment. More particularly,  FIG.  3 A  is a cross-sectional view of a manifold component  350  and  FIG.  3 B  is an end view of the manifold component  350  shown in  FIG.  3 A . Considering  FIG.  3 A  it is clear that the manifold component  350  in this embodiment differs from the preceding two embodiments in that it comprises a plurality of hyperbolic horn-shaped portions  30 ( x,y,z ), arranged side-by-side in an array. Such a design may be suitable where the actuator component  150  is long in the row direction  500 , for example, and where a single horn-shaped portion to cover the entire actuator component in the row direction  500  may be too large in the ejection direction  505  to be practical. Using a plurality of hyperbolic horn-shaped portions allows the height of the manifold chamber  55  to be reduced and enables a more compact droplet ejection head to be manufactured. For example, it may be seen from  FIG.  3 A  that the height of the manifold chamber  55  in the ejection direction  505  from its first end  51  to its second end  52  is comparatively equal to but less than the extent of the actuator component  150  in the row direction  500 , giving a desirably compact arrangement. 
     As can be seen from  FIG.  3 A , the hyperbolic horn-shaped portions  30 ( x,y,z ) are arranged side-by-side in an array whereby they are adjacent to each other in the row direction  500 . The horn-shaped portions  30 ( x,y,z ) each have a central path  315 ( x,y,z ) respectively that splits from the central path  515  and respective areas  316 ( x,y,z ) that are perpendicular to the respective central paths  315 ( x,y,z ). It may be understood that the areas  316 ( x,y,z ) of the horn-shaped portions  30 ( x,y,z ) increase in a substantially hyperbolic fashion along the respective central paths  315 ( x,y,z ) from the area A 2 ( x,y,z ) to the areas A 1 ( x,y,z ). As in the embodiment shown in  FIG.  2   , the embodiment in  FIG.  3    includes hyperbolic portions that don&#39;t commence at the first end  51  of the manifold chamber  55 . Suitable spatial offsets  58 ( x,y,z ) allow for the central path  515  splitting and forming the respective central paths  315 ( x,y,z ). It should be understood that, owing to design constraints, the offsets  58 ( x,y,z ) may not be the same as each other but rather may be determined according to the shape, location, orientation, etc. of the horn-shaped portions  30 ( x,y,z ) and/or their respective central paths  315 ( x,y,z ) and/or the path to each of their respective areas A 2 ( x,y,z ) from the first end  51 . It may be understood that in practice the hyperbolic equation for each horn-shaped profile may more readily be determined by setting x=0 individually for each, located in the centre of their respective area A 2 ( x,y,z ). 
     The cross sectional area of each horn-shaped portion  30 ( x,y,z ) may be defined as follows. The hyperbolic acoustic horns may each have a corresponding central path  315 ( x,y,z ), which extends centrally through portions  30 ( x,y,z ), from the centre of the area A 2 ( x,y,z ) to the centre of the area A 1 ( x,y,z ). At each point along the central paths  315 ( x,y,z ) there is defined a corresponding cross-sectional area, area  316 ( x,y,z ), which is the area lying within a plane perpendicular to the central path  315 ( x,y,z ) and bounded by the walls of the hyperbolic acoustic horn, which may be part of the inner surface of the manifold chamber  55  and one side of one of the plurality of walls  70 ( i,ii ) or two sides of two opposing walls amongst the plurality of walls  70 ( i,ii ). The cross-sectional area of the area  316 ( x,y,z ) varies approximately according to a hyperbolic function of distance from the Area A 2 ( x,y,z ) along the central path  315 ( x,y,z ). 
     As may also be seen from  FIG.  3 A , neighbouring horn-shaped portions  30 ( x,y ) are separated by a corresponding wall  70 ( i ) located within the manifold chamber  55 , and likewise neighbouring horn-shaped portions  30 ( y,z ) are separated by a corresponding wall  70 ( ii ) also located within the manifold chamber  55 . As is apparent from  FIG.  3 A , each of the walls  70 ( i,ii ) extends over only part of the distance between the first end  51  and the second end  52  of the manifold chamber  55 . The horn-shaped portions  30 ( x,y,z ) comprise first ( 701 - 703 )( i ) and second ( 701 - 703 )( ii ) side surfaces, which are spaced apart in said row direction  500 , said side surfaces  701 - 703 ( i,ii ) being substantially concave. The first ( 701 - 703 )( i ) and second ( 701 - 703 )( ii ) side surfaces are formed from amongst the edges of the walls  70 ( i ) and  70 ( ii ) and the sides of the manifold chamber  55 ; such that first side surface  701 ( i ) and second side surface  701 ( ii ) bound horn-shaped portion  30 ( x ), first side surface  702 ( i ) and second side surface  702 ( ii ) bound horn-shaped portion  30 ( y ), and first side surface  703 ( i ) and second side surface  703 ( ii ) bound horn-shaped portion  30 ( z ). It may be understood that the constraints of manufacturing an actual product and the imposition of manufacturing tolerances means that the horn-shaped portions  30 ( x,y,z ) may not have a mathematically true hyperbolic or exponential profile. For example, while the walls  70 ( i,ii ) are depicted as having sharp or pointed ends, this is purely representational and it should be understood that, in practice, the ends might, for example, be blunted or chamfered in order to facilitate manufacture. A profile or shape that is close to or substantially hyperbolic or that changes in a hyperbolic fashion may still, for example, provide desirable print performance when used in the horn-shaped portions  30 ( x,y,z ) of a manifold component  350  for a drop-on-demand printhead. For example, for manufacturing reasons a design constraint may be to limit the walls  70 ( i,ii ) such that they may not be less than a certain thickness, for example 400 micrometers, and fillets or other smoothing features may be necessary at the tips of the walls. 
     It should be appreciated that, while the particular embodiment shown in  FIG.  3 A  includes two walls  70 ( i,ii ) and three horn-shaped portions  30 ( x,y,z ) this is by no means essential and alternative embodiments may comprise any suitable number of horn-shaped portions and corresponding dividing walls. In other embodiments it may be desirable for fluidic reasons to have the plurality of horn-shaped portions staggered, by altering the positions of the walls in the ejection direction  505 , or other suitable arrangements to aid smooth fluidic flow from the first portion  20  into the plurality of horn-shaped portions. 
     In the embodiment depicted in  FIG.  3 A  the walls  70 ( i,ii ) are elongate and curved, and shaped appropriately to provide a suitable hyperbolic profile to the horn-shaped-portions  30 ( x,y,z ) between the areas A 2 ( x,y,z ) and A 1 ( x,y,z ). A manifold component  350  featuring such walls  70 ( i,ii ) might, for example, be manufactured using 3D printing techniques since it may be easier to manufacture such slender internal features using this method as compared to conventional casting, molding or machining techniques. A 3D printed component may also be easy to make without seams and fluid-tight, reducing leakage problems in a droplet ejection head. However, while the use of slender walls is described to partition the horn-shaped manifolds  30 ( x,y,z ), other embodiments may instead use much wider walls or other physical features and the manufacturing technique could comprise forming several separate components, for example, and joining them together in any suitable fashion so as to form a single, fluid-tight manifold component  350 . 
     As may be seen from  FIG.  3 A , each of the horn-shaped portions  30 ( x,y,z ) is positioned so as to overlap with a section of the second end  52  of the manifold chamber  55  in the row direction  500 . In operation each horn-shaped portion  30 ( x,y,z ) preferentially provides a fluidic connection, in parallel, to a respective group of chambers within the one or more rows in the actuator component  150 . In this embodiment the horn-shaped portions divide the second end  52  into three equal sections. For example, if there are 300 fluid chambers in the row direction  500 , each of the horn-shaped portions  30 ( x,y,z ) will, in operation, largely supply fluid to a group of 100 fluid chambers most closely adjacent to its position. Since the walls  70 ( i,ii ) do not extend into the slot  201 , there is the possibility of some fluid intermixing therein, so it may be understood that in operation the number of fluid chambers each horn-shaped portion  30 ( x,y,z ) supplies may not be precisely  100  and there may be some overlap near the wall  70 ( i,ii ) positions. It should be further understood that 300 fluid chambers is merely an example; in some embodiments there may be fewer or far greater numbers of fluid chambers. 
     It should be understood that in other embodiments there may be any number of horn-shaped portions. It may further be understood that in a design with a plurality of horn-shaped portions, that these are not necessarily identical. For example the horn-shaped portions could be of different sizes so as to divide the second end  52  into equal or unequal sections and that therefore the horn-shaped portions may supply equal or unequal sized groups of fluid chambers. As another example, a plurality of non-identical horn-shaped portions may be used to account for asymmetry in the manifold chamber  55 . For example, as seen in  FIG.  3 A , the port  120  is located on the surface  81  at a position offset from the centre of the manifold component  350  in the row direction  500  (unlike the embodiments in  FIGS.  1  and  2   ). This is by no means essential, but may be suitable in some embodiments for ease of connection to other components such as a fluidic supply. As a result, as may also be seen in  FIG.  3 A , the manifold chamber  55  connecting the port  120  to the actuator component  150  is asymmetric and the horn-shaped portions  30 ( x,y,z ) are shaped accordingly such that they are not identical. 
     The manifold component  350  in  FIG.  3    is similar to the embodiment depicted in  FIG.  1    in that it includes a single manifold chamber  55 . However, it is similar to the embodiment in  FIG.  2    in that it includes a manifold chamber  55  which is divided into a (non-horn-shaped) portion  20 ( 1 ) proximate the port  120  and a horn-shaped portion  30  proximate the actuator component  150 . As for the manifold component  250  in  FIG.  2   , the embodiment depicted in  FIG.  3    includes a change in cross-sectional shape, from circular to match the port  120 , to elongate to match the actuator component  150  within the portion  20 ( 1 ). Furthermore, as for the embodiment depicted in  FIG.  2   , the manifold component  350  of  FIG.  3    includes horn-shaped portions  30 ( x,y,z ) that have an elongate cross-sectional area in the row direction  500 . 
     It can be further seen in  FIG.  3 A  that the manifold component  350  comprises two parts that have been joined together, first manifold section  100  and second manifold section  200 , with the mount  80  now located on the lower surface of the second manifold section  200  in the ejection direction  505 . The actuator component  150  is mounted on the mount  80 . This is in no way an essential feature, but may be useful in some embodiments to aid in securely connecting the actuator component  150  to the manifold component  350 , or for improving the longevity of the actuator component  150 , or for improving the assembly process. For example, if the first manifold section  100  is made from a material such as a resin or a thermosetting plastic or a plastic/fibre composite material for ease of manufacture or cost reasons, it may have different thermal properties to the actuator component  150  which may be manufactured largely from a silicon or piezoceramic material. The second manifold section  200  may be made of a material such as a ceramic or a metal that more closely matches the thermal properties of the actuator component  150  than the first manifold section  100 , and may reduce stresses induced in the actuator component  150  during assembly or operation. 
       FIG.  3 A  also shows that the second manifold section  200  has a slot  20 ( 2 ) therein, fluidically connecting the horn-shaped portions  30 ( x,y,z ) to the second end  52  of the manifold chamber  55  and hence to the actuator component  150 . It may be understood that such a second manifold section  200  is in no way an essential feature and in many embodiments suitable thermal matching may be encompassed within a single manifold component as depicted in  FIGS.  1  and  2    and/or within the actuator component  150 . 
     As may also be seen from  FIG.  3 A , the areas A 1 ( x,y,z ) and the second end  52  do not coincide. The slot  20 ( 2 ) is a non-hyperbolic portion connecting the horn-shaped portions  30 ( x,y,z ) to the second end  52  of the manifold chamber  55 . In operation the slot may allow for some fluidic mixing between the fluid exiting the horn-shaped portions and entering the actuator component  150  and may also act as a flow straightener, in operation aligning and directing the fluid flow so that it is more closely parallel with the ejection direction  505  at the second end  52 . It may also act to flatten the velocity profile along the row direction  500  such that the fluid supplied to the actuator component  150  is at a more uniform velocity. 
       FIG.  4    shows a manifold component according to another embodiment. Specifically,  FIG.  4    depicts a manifold component  450  with a manifold chamber  55  comprising a hierarchical arrangement of a plurality of hyperbolic horn-shaped portions  30 ( 1 )( i - ii ),  30 ( 2 )( i - vi ) and  30 ( 3 )( i - xii ) which are divided by a plurality of walls  70 ( i - ii ),  71 ( i - iii ) and  72 ( i - vi ); where, unlike the embodiment depicted in  FIG.  3   , not all of the walls extend over the entirety of the portion  30 . Such a design may be suitable, for example, where the actuator component  150  is long in the row direction  500 , and there is a requirement for multiple horn-shaped portions owing to space constraints in the ejection direction  505 . Another reason to have a hierarchical arrangement of a plurality of hyperbolic horn-shaped portions may be when there is insufficient room at the apex of the manifold chamber  55  proximate the first end  51  to fit the plurality of walls owing to manufacturing constraints such as a minimum wall thickness. Introducing increasing numbers of walls as the manifold chamber  55  widens in the ejection direction  505  may overcome this constraint. Another reason to stagger the introduction of the walls may be where, for example, the fluidic design requires a minimum gap in the row direction  500  between the walls proximate the first end  51 . This may be desired in order to ensure that there is smooth unhindered fluidic flow into the horn-shaped portions but where there are space constraints on the length in the array direction  500  of the first end  51 . 
     It can be seen from  FIG.  4    that some of the walls  70 ( i,ii ) extend through all three of the hierarchical portions  30 ( 1 )( i - ii ),  30 ( 2 )( i - vi ) and  30 ( 3 )( i - xii ), some through two of the hierarchical portions (walls  71 ( i - iii )) and the remainder are only in the final hierarchical portion (walls  72 ( i - vi )). Such an arrangement may make design and manufacture easier, but is by no means essential. In some embodiments different arrangements of walls may be used to separate the hierarchical portions, for example an arrangement whereby each wall extends only part of the distance from the first end  51  to the second end  52  of the corresponding manifold chamber  55  is envisaged. 
     A manifold component  450  as depicted in  FIG.  4    comprising a plurality of said arrays of side-by-side horn-shaped portions, may include an initial array of side-by-side horn-shaped portions  30 ( 1 )( i - ii ), which is proximate the first end  51  of the inlet manifold chamber  55 , and a final array of horn-shaped portions  30 ( 3 )( i - xii ), which is proximate the second end  52  of the inlet manifold chamber  55 , said arrays being arranged consecutively from the first end  51  to the second end  52  of the manifold chamber  55 , with the number of horn-shaped portions in each array increasing progressively from said initial array  30 ( 1 ) to said final array  30 ( 3 ). Furthermore the plurality of horn-shaped portions  30 ( 1 )( i - ii ),  30 ( 2 )( i - vi ) and  30 ( 3 )( i - xii ) is arranged hierarchically, such that a horn-shaped passageway in a given one of said arrays is fluidically connected to two or more horn-shaped passageways in the consecutive array nearer the second end  52  of the manifold chamber  55 . At each hierarchical portion  30 ( 1 )( i - ii ),  30 ( 2 )( i - vi ) or  30 ( 3 )( i - xii ) in the manifold chamber  55 , neighbouring (in the row direction  500 ) horn-shaped portions in the plurality of arrays are separated by a corresponding wall, located within the manifold chamber  55  in question. 
     The final stage in the hierarchical arrangement depicted in  FIG.  4   , horn-shaped portion  30 ( 3 )( i - xii ) is divided into twelve portions at the ends of the walls proximate the second end  52 . Furthermore it may be preferable for acoustic reasons not to have the width proximate the second end  52  of any individual horn-shaped portion greater than one twelfth of the overall width at that point in the row direction  500 . In other words, the width, in the row direction  500 , of each horn-shaped portion is less than 1/12 of the width, in the row direction  500 , of the second end  52  of the manifold chamber  55 . This may improve acoustic performance by rejecting the first lateral resonance frequency. It may be understood that twelve horn-shaped portions is due to the length of the actuator component  150  and the speed of sound c in a typical fluid for an droplet ejection head for inkjet printing. The number of horn-shaped portions desired may differ depending on the length of the actuator component  150  in the row direction  500  and the speed of sound in the ejection fluid being used. Furthermore it may be preferable for acoustic reasons that all of the horn-shaped portions  30 ( 3 )( i - xii ) are of equal length in the row direction at the end proximate the second end  52  of the manifold chamber  55 . 
     Turning now to  FIG.  5   , shown is a manifold component  550  according to another example embodiment. More particularly,  FIG.  5 A  is a cross-sectional view of a manifold component  550 ,  FIG.  5 B  is an end view of the manifold component  550  shown in  FIG.  5 A  and  FIG.  5 C  is a side view of the manifold component  550  shown in  FIGS.  5 A and  5 B . It can be seen from  FIG.  5 A  that the manifold component  550  has a manifold chamber  55  similar to the embodiment shown in  FIG.  3   . It can also be seen from  FIG.  5 C  that there are two further manifold chambers  60 ( a,b ), partially overlapping the manifold chamber  55  in the depth direction  510 . It can be seen from  FIG.  5 A  that the manifold chamber  60 ( a ) is a reversed geometrical copy of the manifold chamber  55  and has a plurality of horn-shaped portions  35 ( a )( x,y,z ) arranged side-by-side, or adjacent to each other, in the row direction  500 . Although not shown in  FIG.  5 A , the second manifold chamber  60 ( b ) is identical to the first manifold chamber  60 ( a ) and located on the opposite side of the manifold chamber  55  to it in the depth direction  510 . Throughout the following description like reference numerals are used for the component parts of the two manifold chambers  60 ( a,b ) with (a) or (b) appended accordingly. 
     The embodiment depicted in  FIG.  5    is an arrangement, similar to that shown in  FIG.  2   , which allows so-called “through-flow” of fluid when connected to a suitable fluidic supply. In operation therefore, the port  120  can operate as an inlet port, the manifold chamber  55  can act as an inlet manifold chamber and the manifold chambers  60 ( a,b ) can operate as outlet manifold chambers with the ports  220 ( a,b ) operating as outlet ports. The main difference, as compared to the embodiment depicted in  FIG.  2    which has one inlet manifold chamber  55  and one outlet manifold chamber  60 , is that there is a ratio of two outlet manifold chambers  60 ( a,b ) to one inlet chamber  55  in the embodiment of  FIG.  5   . 
     In the arrangement shown in  FIG.  5   , the actuator component  150  has two rows of fluid chambers (not shown) extending parallel to each other in the row direction  500 . As before each fluid chamber in a row may be provided with at least one respective actuating element and at least one respective nozzle, each actuating element being actuable to eject a droplet of fluid in an ejection direction  505  through the corresponding at least one of the nozzles. This example arrangement would therefore have at least two rows of nozzles, each row corresponding to a particular row of fluid chambers. 
     In operation in through-flow mode the manifold component  550  depicted in  FIG.  5    can allow fluid to pass from the inlet port  120  via the inlet manifold chamber  55  to the actuator component  150  where the fluid path will split such that some of the fluid will pass into the first row of fluid chambers, via individual inlets to each fluid chamber therein, while the other part of the fluid will pass through the second row of fluid chambers, via individual inlets to each fluid chamber in the other row. Part of the fluid passing into the chambers may be ejected in the form of droplets, while the remainder will exit the chambers via respective fluid chamber outlets. The fluid chamber outlets of the first row are fluidically connected to the outlet manifold chamber  60 ( a ) and hence to the outlet port  220 ( a ). The fluid chamber outlets of the second row are fluidically connected to the outlet manifold chamber  60 ( b ) and hence to the outlet port  220 ( b ). When operating the embodiment depicted in  FIG.  5    in through-flow mode it may be preferable that the fluid split is balanced such that half the fluid follows one path through the manifold component  550  and half the fluid follows the other path. 
     In operation, a portion of the fluid passing through any individual fluid chamber may be ejected depending on the drive signals supplied by wiring (not shown) to the actuating element(s). The outlet ports  220 ( a,b ) may be connected in some manner to a single fluidic outlet path to remove the fluid from the manifold component  550 , or they may be separately connected to individual fluidic outlet paths. Since in the example shown in  FIG.  5    there is a single port  120  and a single inlet manifold chamber  55  it is apparent that this arrangement will, in operation, supply a single fluid type to both the rows of fluid chambers and so both rows of nozzles will eject the same fluid type. This arrangement may allow for close packing of nozzle rows within the actuator component  150  and may be appropriate, for example, where there are space constraints and/or where a high nozzle density is required to form a high resolution droplet ejection head. In the embodiment depicted in  FIG.  5   , the second end  52  of the inlet manifold chamber  55  provides a fluidic connection, in parallel, to two rows of fluid chambers, whilst each of the outlet manifold chambers  60 ( a ) and  60 ( b ) provides a fluidic connection, in parallel, to one row of fluid chambers. 
     As can be seen from  FIG.  5 A , like the embodiment depicted in  FIG.  3   , the manifold component  550  comprises first and second manifold sections  100 ,  200 . The second manifold section  200  located between the first manifold section  100  and the actuator component  150 . The second manifold section  200  has three slots, one slot  20 ( 2 ) fluidically connects the horn-shaped portions  30 ( x,y,z ) to the second end  52  of the inlet manifold chamber  55  and then to the actuator component  150 . Two further slots  25 ( 2 )( a ) and  25 ( 2 )( b ), one either side of slot  20 ( 2 ) in the depth direction  510 , fluidically connect the second ends  62 ( a,b ) of the outlet manifold chambers  60 ( a,b ) to the horn-shaped portions  35 ( a,b )( x,y,z ). 
     As previously discussed with regard to the embodiment depicted in  FIG.  3   , each inlet horn-shaped portion  30 ( x,y,z ), is located so as to cover a portion of the second end  52  in the row direction  500  such that each provides a fluidic connection, in parallel, to a respective group of chambers within the one or more rows in the actuator component  150 . Similarly the outlet horn-shaped portions  35 ( a,b )( x,y,z ) are located so as to provide fluidic connection, in parallel, to respective groups of chambers within the one or more rows in the actuator component  150 . In operation each outlet horn-shaped portion  35 ( a,b )( x,y,z ) will largely be receiving fluid from a respective group of fluid chambers adjacent to it in the row direction  500 . However, since the walls  75 ( a,b )( i,ii ) do not extend into the slots  25 ( 2 )( a,b ) there is the possibility of some fluid intermixing therein. 
     In alternative arrangements, fluid may be supplied to the actuator component  150  from all three ports  120  and  220 ( a,b ), such that the droplet ejection head may be considered to operate in a non through-flow mode. 
     Attention is now directed to  FIGS.  6 A-C , in which:  FIG.  6 A  is the inlet-only fluidic path in a manifold component  10  according to a first test design;  FIG.  6 B  is the fluidic path in a manifold component  650  according to a further embodiment; and  FIG.  6 C  is a graph that compares the calculated performance of the manifold components  10  and  650 . As can be seen in  FIG.  6 B , the manifold component  650  is an embodiment similar to that in  FIG.  3    where there the manifold chamber  55  is an inlet manifold chamber  55  and there are a plurality of horn-shaped portions  30 ( s - z ). Such embodiments might be described as including a multicellular acoustic horn, or might be described as multicellular ‘horned’ manifolds. Also, as for the manifold components in  FIGS.  2  and  3   , the embodiment depicted in  FIG.  6 B  comprises a change in cross-sectional shape, from circular to match the port  120 , to elongate to match the actuator component  150  within the portion  20 ( 1 ). 
     As may be seen by comparing  FIGS.  6 A and  6 B , whilst the test design and the horned manifold component differ in that the former is not a hyperbolic acoustic horn and the latter has multiple acoustic horns, both the test design and the horned manifold component were designed to share certain features. The manifold chambers  55 ′ and  55  in the test manifold component  10  and the horned manifold component  650  both have a rectangular second end  52 ′, 52  of the manifold chambers  55 ′,  55  and the inlet port opens at the same location relative to the second ends  52 ′,  52  of the manifold chambers  55 ′,  55 . 
     Attention is now directed to  FIG.  6 C , which is a graph showing the coefficient of reflection for acoustic pressure waves for the manifold components  10 ,  650  illustrated in  FIGS.  6 A and  6 B  as the frequency of ejection is varied. The coefficient of reflection was calculated using Finite Element analysis to investigate the response of a horned manifold as per  FIG.  6 B  and a test manifold as per  FIG.  6 A . The calculations were performed using the rigid piston assumption, to perform a frequency sweep from 0 to 100 kHz. The rigid piston was located at the second ends  52 ,  52 ′ at a position analogous to that of the actuator component  150 . 
     As can be seen in  FIG.  6 C , a coefficient of reflection of 0 corresponds to no reflection, where all acoustic waves are transmitted out of the manifold component through the cross-sectional area A 2 . A coefficient of reflection of 1 means that there is no transmission and all of the acoustic waves are reflected back to the cross-sectional area A 1 . For a droplet ejection head design that utilises one or other of the manifold components  10  (test) and  650  (horned), the frequency range considered is 0 to 100 kHz, where 0-100 kHz is the droplet ejection frequency (100 kHz is the upper frequency limit for the droplet ejection head of the present embodiment). Preferably, a manifold component for a droplet ejection head would have a coefficient of reflection as low as possible over the considered frequency range 0 to 100 kHz. It may be seen from  FIG.  6 C , that for the horned manifold component  650  the coefficient of reflection is reduced across a substantial part of the considered range as compared to the test manifold component  10 . It may be understood that for droplet ejection heads with different frequency conditions/requirements, an improved manifold component may be designed for a different upper frequency limit than 100 kHz. 
     Considering now  FIG.  7   ,  FIG.  7 A  is a cut-away three-dimensional view of the fluidic path in a through-flow enabled manifold component  110  according to a second test design. This may be referred to as a ‘test’ manifold component.  FIG.  7 B (a) is a cut-away three-dimensional view of the fluidic path in a manifold component  750  according to another embodiment that is through-flow enabled and has multiple horn-shaped portions. This may be referred to as a ‘horned’ manifold component.  FIG.  7 B (b) is a cross-sectional view through an inlet manifold chamber  55  in the manifold component  750  depicted in  FIG.  7 B (a), also including the slot  20 ( 2 ).  FIG.  7 B (c) is a cross-sectional view through an outlet manifold chamber  60 ( a ) in the manifold component  750  depicted in  FIG.  7 B (a), also including the slot  25 ( 2 )( a ).  FIG.  7 C  compares the calculated coefficient of reflection across the frequency range for a test manifold component as per  FIG.  7 A  and a horned manifold component as per  FIG.  7 B . The calculations were performed in a similar manner to those described above with regards to  FIG.  6 C . 
     Turning now to  FIG.  7 B (a), the manifold component  750  illustrated therein is similar to the embodiment illustrated in  FIG.  5    in that it has multiple horn-shaped portions and is through-flow enabled. It differs from the embodiment in  FIG.  5    in that for ease of connection to a fluidic supply the outlet manifold chamber  60 ( a ) is not an identical reflection of the inlet manifold chamber  55 . The outlet manifold chambers  60 ( a ) and  60 ( b ) in the manifold component  750  are generally identical to each other. It can further be seen from  FIG.  7 B (a) that the outlet manifold chambers  60 ( a,b ) are connected to a single port  220  and that the transitional portion  25  acts to merge the fluid exiting both outlet manifold chambers  60 ( a,b ) before connecting to the port  220 . The plurality of horn-shaped portions  30 ( x,y,z ) and  35 ( a,b )( x,y,z ) may have a cross-sectional area that increases in a hyperbolic fashion over at least a portion of the distance in the ejection direction  505 . 
     The example embodiment shown in  FIG.  7 B (a) relates in general to a manifold component  750  for a droplet ejection head. The manifold component  750  comprises a mount  80  for receiving an actuator component  150  that provides one or more rows of fluid chambers, each chamber being provided with a respective at least one actuating element and a respective at least one nozzle, the at least one actuating element for each chamber being actuable to eject a droplet of fluid in an ejection direction  505  through the corresponding at least one nozzle, each row extending in a row direction  500 . The manifold component  750  has manifold chambers  55 ,  60 ( a ),  60 ( b ) that extend from respective first ends  51 ,  61 ( a ),  61 ( b ) to respective second ends  52 ,  62 ( a ),  62 ( b ), and widens from said first ends  51 ,  61 ( a ),  61 ( b ) to said second ends  52 ,  62 ( a ),  62 ( b ). The second ends  52 ,  62 ( a ),  62 ( b ) of the manifold chambers  55 ,  60 ( a ),  60 ( b ) provide fluidic connection, in parallel, to at least a group of chambers within said one or more rows and are located adjacent to the mount  80 . There are ports  120 ,  220 , the former of which opens into the manifold chamber  55  at the first end  51  and the latter of which opens into the manifold chambers  60 ( a ),  60 ( b ) at the first ends  61 ( a ),  61 ( b ). The manifold chambers  55 ,  60 ( a ),  60 ( b ) comprise a plurality of horn-shaped passageways  30 ( x,y,z ),  35 ( a,b )( x,y,z ) the cross-sectional area of each of which decreases, at a decreasing rate, with distance from the second ends  52 ,  62 ( a ),  62 ( b ) of the manifold chambers  55 ,  60 ( a ),  60 ( b ). The horn-shaped passageways within each respective manifold chamber  55 ,  60 ( a ),  60 ( b ) are arranged side-by-side in an array which extends generally in the row direction  500 . The ports  120 ,  220  are fluidically connected in parallel with their respective horn-shaped passageways  30 ( x,y,z ) and  35 ( a,b )( x,y,z ). 
     As can be seen from  FIG.  7 B (b) the horn-shaped passageways  30 ( x,y,z ) comprise first ( 701 - 703 )( i ) and second ( 701 - 703 )( ii ) side surfaces, which are spaced apart in said row direction  500 , said side surfaces  701 - 703 ( i,ii ) being substantially concave. As for the manifold component  250  in  FIG.  2   , the manifold chamber  55  depicted in  FIG.  7 B (a) and  7 B(b) includes a change in cross-sectional shape within the portion  20 ( 1 ), in this implementation from circular to match the port  120 , to elongate (in this instance rectangular) to match the actuator component  150  (not shown). The port  120  is also offset from the manifold chamber  55  in the depth direction  510  so the portion  20 ( 1 ) also comprises shaping in the depth direction to connect the two. 
     Likewise as can be seen from  FIG.  7 B (c) the horn-shaped passageways  35 ( a )( x,y,z ) comprise first ( 711 - 713 )( i ) and second ( 711 - 713 )( ii ) side surfaces, which are spaced apart in said row direction  500 , said side surfaces  711 - 713 ( i,ii ) being substantially concave. 
     Although not shown, it may be understood that manifold chamber  60 ( b ) is similarly configured. One or more of the horn-shaped passageways  30 ( x,y,z ),  35 ( a,b )( x,y,z ) may have a hyperbolic profile. In some embodiments all of the horn-shaped passageways  30 ( x,y,z ),  35 ( a,b )( x,y,z ) may be shaped as a hyperbolic acoustic horn, whereby such horn-shaped passageways  30 ( x,y,z ),  35 ( a,b )( x,y,z ) may be described as hyperbolic horn-shaped portions  30 ( x,y,z )  35 ( a,b )( x,y,z ). 
     The manifold chambers  60 ( a ),  60 ( b ) depicted in  FIG.  7 B (a) (and  60 ( a ) depicted in  FIG.  7 B (c)) also include a change in cross-sectional shape from elongate to match the actuator component  150  (not shown), to circular to match the port  220  in the transitional portion  25 . Also, as previously mentioned, the outlet manifold chambers  60 ( a,b ) are connected to a single port  220  and that the transitional portion  25  acts to merge the fluid exiting both outlet manifold chambers  60 ( a,b ) before connecting to the port  220 . 
       FIG.  7 B (d) is a detailed view of the fluidic path depicted in  FIG.  7 B (a) depicting the portions  20  and  25  in greater detail. It can be seen that the inlet port  120  is offset from the portion  20  such that the portion  20  further comprises a blended change in position in the depth direction  510  to connect the inlet port  120  to the rectangular cross-sectional area  4 . 
     Considering  FIG.  7 B (d) further it can be seen that the transitional portion  25  comprises two arms  25 ( a ) and  25 ( b ), one per outlet manifold chamber  60 ( a )( b ) which blend from rectangular cross-sectional areas  1 ( a ) and  1 ( b ) to oval cross-sectional areas  2 ( a ) and  2 ( b ) and then merge to form a single passage  25 ( c ) which connects to outlet port  220  via a circular cross-sectional area  3 . The transitional portion  25  has a blended cowl-like shape which may improve the fluid flow therein and which may also help to reduce acoustic crosstalk by assisting in transmitting acoustic waves out of the manifold chambers  60 ( a ) and  60 ( b ) and into the fluidic supply. It may be understood that this is merely one implementation and other combinations of cross-sectional shapes and areas and blended regions may be combined in any suitable manner to provide the transitional portion  25  with a blended cowl-like form, for example by sweeping a cross-sectional shape or shapes and/or a range of cross-sectional areas along suitable paths or trajectories. In some implementations the manifold chamber may have an elongate cross-sectional area. The transitional portion  25  may connect a number of cross-sectional areas, both at its ends where it is connectable to the port and the manifold chamber, and along the length of the transitional portion  25 . In some implementations the cross-sectional shapes of the blended cowl-like form of the transitional portion  25  are chosen from a list comprising elongate, rectangular, oval, and circular. In some implementations such blended cowl-like forms may be formed from a 3D printed material. Such a transitional portion  25  may suitably be used in implementations with at least two, or more, manifold chambers, where at least two of said manifold chambers are connected to a single port, which may be an outlet port  220 , wherein the transitional portion  25  connects the port  220  to the at least two manifold chambers  60 ( a )( b ). In such an implementation the transitional portion  25  comprises at least one passage  25 ( c ) and further comprises an arm  25 ( a )( b ) per manifold chamber  60 ( a )( b ). Further manifold chambers can be connected using a suitable number of additional arms, one per manifold chamber, where the arms may be merged together using any suitable number of connecting passages. It may be understood that such a transitional portion  25  may be used for two or more inlet manifold chambers or two or more outlet manifold chambers to connect to an inlet or outlet port respectively. Further such a transitional portion  25  may suitably be used in implementations where the two or more manifold chambers comprise one or more horn-shaped passageways, or in other implementations where the two or more manifold chambers do not comprise horn-shaped passageways. 
       FIG.  7 C  compares the calculated coefficient of reflection across the frequency range of 0-100 kHz for a test manifold component as per  FIG.  7 A  and a horned manifold component as per  FIG.  7 B .  FIG.  7 C (a) compares calculated coefficients of reflection across the frequency range for the inlet manifold chambers for the test ( FIG.  7 A ) and horned ( FIG.  7 B ) manifolds.  FIG.  7 C (b) compares calculated coefficients of reflection across the frequency range for an outlet manifold chamber in the test ( FIG.  7 A ) and horned ( FIG.  7 B ) manifolds. It can be seen that the coefficient of reflection is largely reduced for the horned manifold in both the inlet and outlet chambers as compared to the test manifold. 
     Considering now  FIG.  8   , shown are respective print samples produced using a droplet ejection head comprising a test manifold component similar to  FIG.  7 A , and a horned manifold component similar to that in  FIG.  7 B . The print direction is along the vertical. The heads were operating in through-flow mode at a droplet frequency of 110 kHz. The samples were printed using magenta ink. It can be seen that, from top to bottom of the sample, the greyscale was increased successively per printed block. It may clearly be seen that the horned manifold component ( FIG.  8 ( a ) ) produced an improvement in the quality of the print test sample as compared to the test manifold component ( FIG.  8 ( b ) ). It is believed that the defects in the test manifold component print sample are due to acoustic crosstalk. 
       FIG.  9   (A-C) are graphs comparing drop velocity data produced using a printhead comprising a test manifold component as per  FIG.  7 A  and a printhead comprising a horned manifold component as per  FIG.  7 B . The data was collected using a commonly available brand of droplet measurement and analysis tool (a JetXpert™ Dropwatcher by ImageXpert®). The results compare the drop velocity data for droplets ejected from one row of 360 nozzles in the actuator component  150  at droplet ejection frequency (and the drive signal supplied to the actuators in the fluid chambers) of 5 kHz ( FIG.  9 A ), 20 kHz ( FIG.  9 B ) and 40 kHz ( FIG.  9 C ). It can clearly be seen that at the frequencies measured, the drop velocity is more consistent in the row direction  500  for the horned manifold as opposed to the test manifold. At the higher frequencies considerable waviness and variability in the drop velocity profile in the row direction  500  can be seen for the test manifold as compared to the horned manifold. 
       FIG.  10    is a schematic diagram depicting a method of designing a horn-shaped portion for a manifold component according to an embodiment as described herein. As shown in  FIG.  10   , the method involves determining an initial shape for the manifold chamber  55 , according to which the manifold chamber extends, along an initial, straight-line path  515 , from a first end  51  to a second end  52 , with there being a continuum of cross-sections A(x) perpendicular to the initial path  515 , the areas of said cross-sections increasing from A 2  to A 1  with increasing distance from the first end  51 , such that there is at least a portion of the manifold chamber for which the areas of the cross-sections A(x) increase in a hyperbolic fashion between the first end  51  and the second end  52 . The next step involves deforming said initial path  515  to produce a modified path  515 ′, with each cross-section A(x) being moved with a corresponding point on the initial path  515 , thus providing a modified shape, manifold chamber  55 ′ with cross sections A 2 ′, A(x)′ which have the same cross-sectional areas as cross sections A 2  and A(x). It may be seen that cross-section A 1  at the second end  52  remains in its initial position. The deforming step depicted in  FIG.  10    is such that the cross-sections A 2 ′, A(x)′ and A 1  remain substantially parallel, though it should be understood that this may not be essential in all embodiments. Furthermore the modified path  515 ′ may be a straight-line path; and the deforming step may be such that the cross-sections A 2 ′, A(x)′ and A 1  remain substantially parallel to one another and angled with respect to said modified path  515 ′. In other embodiments it may be understood that other deforming steps may be implemented, for example using a non straight-line variant of path  515 ′, or some other form of translation or rotation of the initial path  515 . 
     It should be generally understood that for reasons of space constraint it may be desirable to have a manifold component as per any of the embodiments described herein where the extent of each manifold chamber  55 ,  60  in the ejection direction  505  is less than or equal to 2 times the extent in the row direction  500 ; and in some embodiments the extent of each manifold chamber in the row direction  500  is less than or equal to 2 times the extent in the ejection direction  505 . In some embodiments it may be preferable that the extent of each manifold chamber in the row direction  500  is approximately equal to the extent in the ejection direction  505 , as for those shown in  FIGS.  3  and  4   . It may be understood that where there are space constraints, using a multi-cellular horn with a plurality of horn-shaped portions as depicted in  FIGS.  3  and  4    and elsewhere may enable a suitably compact design. 
     It may be understood that in some embodiments the mount  80  may for example comprise a flat receiving surface as in  FIG.  1 A  to which the actuator component  150  may be attached by glue. Alternatively the mount  80  may have more complex arrangements of mounting surfaces and connecting elements and the use of fixing devices such as screws or pins or push fits or slide fits or glue to enable the actuator component  150  to be securely attached to any of the manifold components as described herein. The fluid chambers have been described as being in a row of fluid chambers; however, it should be understood that the row is not necessarily a straight line, and that fluid chambers can be staggered within the row. 
     In some embodiments the first portion  20  may comprise a hyperbolic acoustic horn as well as a change in cross-sectional shape to blend from the cross-sectional area of the port  120  to one that suits the actuator component  150 . It may therefore be understood that an offset  58  may not be an essential feature in such embodiments. It should further be understood that the offset  58  is not necessarily a distance in a straight line in the ejection direction  500 , it depends on the shape of the manifold chamber  55 , the route that the central path  515  takes and where the portion that forms a hyperbolic acoustic horn occurs. It may be understood that the shape of the first portion  20  may therefore depend on the cross-sectional shape(s) of the port and the actuator component. 
     It may further be understood that manifold components may comprise a plurality of manifold chambers as described herein and arranged in any manner that is suitable for the application in question. The manifold components may comprise a plurality of inlet manifolds and/or a plurality of outlet manifolds. Some or all of the features described herein may be combined in any suitable manner to form a manifold component. 
     It may further be understood that where there are two or more manifold components of the same type (as depicted in  FIGS.  5 A and  7 B ) these may all have their own individual port (as depicted in  FIG.  5 A ) or share a common port (as depicted in  FIG.  7 B ). In the latter case, as depicted in  FIG.  7 B , the transitional portion  25  may divide the fluid path into a suitable number of arms to connect to the respective manifold chambers as well as to blend the cross-sectional shape and/or area of the fluid path from that of the common port to one that suits the actuator components  150 . It should be understood that such an arrangement would work whether the manifold chambers are acting as inlet manifolds or outlet manifolds. 
     It should be understood that manifold components as described herein are suitable for inclusion in a wide variety of droplet ejection heads. In particular, manifold components as described herein are suitable for inclusion in droplet ejection heads having various applications. 
     In this regard, it should be appreciated that, depending on the particular application, a variety of fluids may be ejected by droplet ejection heads. 
     For instance, certain heads may be configured to eject ink, for example onto a sheet of paper or card, or other receiving media, such as ceramic tiles or shaped articles (e.g. cans, bottles etc.) Ink droplets may, for example, be deposited so as to form an image, as is the case in inkjet printing applications (where the droplet ejection head may be termed an inkjet printhead or, in particular examples, a drop-on-demand inkjet printhead). 
     Alternatively, droplet ejection heads may eject droplets of fluid that may be used to build structures, for example electrically active fluids may be deposited onto receiving media such as a circuit board so as to enable prototyping or manufacture of electrical devices. In examples, polymer containing fluids or molten polymer may be deposited in successive layers so as to produce a 3D object (as in 3D printing). In still other applications, droplet ejection heads might be adapted to deposit droplets of solution containing biological or chemical material onto a receiving medium such as a microassay. Droplet ejection heads suitable for such alternative fluids may be generally similar in construction to inkjet printheads—as may the manifold component therein—potentially with some adaptations made to handle the specific fluid in question. 
     Furthermore, it should be noted that droplet ejection heads may be arranged so as to eject droplets onto suitable receiving media, and may therefore be termed droplet deposition heads. 
     For instance, as mentioned above, the receiving media could be sheets of paper or card, ceramic tiles, shaped articles (e.g. cans, bottles etc.), circuit boards, or microassays. 
     Nonetheless, it is by no means essential that droplet ejection heads as described herein are arranged as droplet deposition heads, ejecting droplets onto receiving media. In some applications, it may be relatively unimportant where the ejected droplets land; for instance, in particular examples droplet ejection heads may be utilised to produce a mist of ejected droplets. Moreover, similar head constructions may, in some cases, be used whether or not the ejected droplets land on receiving media. Accordingly, the more general term “droplet ejection head” is (where appropriate) used in the above disclosure. 
     Manifold components as described in the above disclosure may be suitable for drop-on-demand inkjet printheads. In such heads, the pattern of droplets ejected varies in dependence upon the input data provided to the head. 
     A droplet ejection head may comprise a portion for a manifold component as described herein to connect the main portion of the manifold component to a port and an actuator component  150  fixed at the mount  80 . 
     A droplet ejection head may comprise a manifold component as described in any of the above embodiments and an actuator component  150  fixed at the mount  80 . 
     A droplet ejection head may comprise a manifold component as described in any of the above embodiments and an actuator component  150  fixed at the mount  80 , wherein each group of chambers comprises at least 100 chambers.