Technical Field
[0001] The present invention relates to continuous ink jet printers and, more particularly,
to a droplet generator for a continuous ink jet printer, the drop generator having
an integral fluid cavity.
Background Art
[0002] Ink jet printing systems are known in which a print head defines one or more rows
of orifices which receive an electrically conductive recording fluid, such as for
instance a water base ink, from a pressurized fluid supply manifold and eject the
fluid in rows of parallel streams. Printers using such print heads accomplish graphic
reproduction by selectively charging and deflecting the drops in each of the streams
and depositing at least some of the drops on a print receiving medium, while others
of the drops strike a drop catcher device.
[0003] Droplet generators are one of the major components in a continuous ink jet printhead.
Droplet generators often uses a nozzle plate attached to a resonant body to stimulate
the jets. Several different methods are currently in practice to supply fluid to the
nozzle plate. One known method includes fluid passages originating at the nodal line
of the resonant body, with internal cavities leading to the nozzle plate. Another
known method teaches that the fluid ingress can be achieved by feeding ink toward
the same end of the nozzle plate, thus eliminating the longer internal cavities required
with a nodal line feed droplet generator. This latter method is referred to as a bottom
front feed droplet generator. As a variation of that concept, it is known that fluid
can be fed from the side, as opposed to the front.
[0004] In all cases, additional space is required to provide a means to get the fluid to
those inlet and outlet points. In the case of the side feed, this is especially undesirable
because this increases the amount of space required perpendicular to the typical flow
of the print media relative to a jet array printhead. A second drawback of current
methods is that, in some cases, asymmetric modes of vibration may occur very near
the desired mode. In particular, a shear type mode can exist across the narrow dimension
of the body, parallel to the nozzle array. The damaging effect can be that each side
of nozzle will experience out of phase excitation, thus destroying the desired uniform
oscillations. These asymmetric modes generally will not occur unless the body is unsymmetrical
or it is driven unsymmetrically. In particular, the front feed design could provide
the means to excite the unwanted asymmetric mode.
[0005] It is seen then that there is a need for a droplet generator and the associated fluid
cavity which reduces the space requirement while overcoming the problems associated
with prior art drop generator designs.
Summary of the Invention
[0006] This need is met by the droplet generator according to the present invention, wherein
the droplet generator utilizes a resonant body configuration that minimizes space
requirements for an ink jet printhead.
[0007] In accordance with one aspect of the present invention, a droplet generator is provided
for use with an ink jet printhead of a continuous ink jet printer. The droplet generator
assembly has a nozzle plate with associated nozzles to stimulate jets. The droplet
generator assembly has a fluid ingress location and a fluid egress location, on a
side of the resonator body opposite the nozzle plate. A fluid trench redirects flow
in-line with the nozzles. A fluid passage extends from the fluid ingress location
to the fluid trench.
[0008] The droplet generator assembly according to the present invention provides a variety
of advantages. First, the droplet generator utilizes a resonant body configuration.
In addition, the droplet generator provides fluid ingress and egress on the side opposite
the nozzle plate. This, in turn, provides the advantage of minimizing space requirements
for an ink jet printhead.
[0009] Other objects and advantages of the invention will be apparent from the following
description, the accompanying drawings and the appended claims.
Brief Description of the Drawings
[0010]
Fig. 1A is an exploded view of the components of the droplet generator assembly of
the present invention; and
Fig. 1B is a view along line B-B of Fig. 1A.
Detailed Description of the Preferred Embodiments
[0011] The present invention provides a droplet generator for an ink jet printhead. The
droplet generator according to the present invention has an integral fluid cavity
wherein fluid ingress and egress to and from the resonator body is on a second side
of the resonator body opposite the nozzle plate which is on a first side of the resonator
body, i.e., a top feed resonator. Of course, with ink jet printing systems, the goal
is to get fluid into the resonator body and down to the nozzle plate. Existing top
and front feed resonators do this very efficiently, but require external fluid tubing
to the ingress and egress points. The external tubing is required by prior art systems
because fluid tubing is typically routed to a point above the drop generator, as opposed
to its sides, for space economy reasons. In accordance with the present invention,
the top feed resonator has incorporated prior external fluid tubing into the fluid
passages internal to the resonator body. This has the desirable effect of minimizing
space requirements for an ink jet printhead.
[0012] Referring now to the drawings, in Figs. 1A and 1B there are illustrated the components
of the droplet generator assembly according to the present invention. A droplet generator
1 comprises fluid ingress and egress on a surface 7 opposite nozzle plate 2. A counterbore
3 feature permits an effective means to secure fittings 6 to the droplet generator
1. A fluid passage 4 allows fluid to travel from an ingress point 8 down to the nozzle
plate 2 and fluid trench 5. Narrow fluid trench 5 redirects fluid flow from the fluid
passage 4 to an in-line direction with the nozzles associated with nozzle plate 2.
The fluid passage 4 is located substantially along a centerline of the resonator body.
Since the fluid passage 4 from the ingress point 8 to fluid trench 5 is not directly
above fluid trench 5, this avoids fluid resonances directly between the nozzle plate
2 and the fluid passage 4.
[0013] The fluid passage 4 follows a 'U' shaped path through the resonator, as best illustrated
in Fig. 1B. The narrow fluid trench 5 intersects the fluid passage 4 perpendicular
to the flow. Fluid flow in passage 4 is in the direction of arrows 10; whereas fluid
flow in the trench 5 is in the perpendicular direction, as indicated by arrows 11.
Hence, trench 5 redirects fluid flow from the fluid passage 4 in the direction of
arrows 10, to a direction 11 in-line with the nozzles, as indicated by arrows 12.
[0014] There are two modes of operation which can allow two different egress points. The
first is what is referred to as crossflush mode, where fluid enters the resonator
at the ingress point 8, follows the entire fluid passage 4, and exits at the egress
point 9. In this mode, some fluid may flow into the narrow fluid trench 5 and weep
out of the nozzles. The second mode is where a valve external to the resonator and
downstream from the egress point may be selectively closed and substantially halt
fluid flow from the egress point 9. In this mode, the nozzle plate is the only other
passage for fluid to flow and have a much greater resistance to flow than the egress
point. Also, greater fluid pressure is established within the resonator and jets are
established through the nozzles.
Industrial Applicability and Advantages
[0015] The droplet generator assembly according to the present invention is useful in continuous
ink jet printers. The droplet generator utilizes a resonant body configuration. In
addition, the droplet generator provides fluid ingress and egress on the side opposite
the nozzle plate. This, in turn, provides the advantage of minimizing space requirements
for an ink jet printhead.
[0016] Having described the invention in detail and by reference to the preferred embodiment
thereof, it will be apparent that other modifications and variations are possible
without departing from the scope of the invention defined in the appended claims.
1. A droplet generator assembly for an ink jet printhead of a continuous ink jet printer,
the droplet generator assembly having a resonator body, the assembly comprising:
a nozzle plate on a first side of the resonator body, the nozzle plate having associated
nozzles to stimulate jets;
a fluid ingress location on a second side of the resonator body, opposite the first
side of the resonator body;
a fluid egress location;
a fluid passage extending from the fluid ingress location to the fluid egress location;
a fluid trench to redirect flow from the fluid passage to a direction in-line with
the nozzles.
2. A droplet generator assembly as claimed in claim 1 wherein the fluid passage from
the ingress point to the fluid trench is not located directly above the fluid trench.
3. A droplet generator assembly as claimed in claim 1 wherein the fluid passage comprises
a U-shaped fluid passage.
4. A droplet generator assembly as claimed in claim 1 wherein the fluid egress location
comprises a location on a second side of the resonator body, opposite the first side
of the resonator body.
5. A droplet generator assembly as claimed in claim 1 wherein the fluid passage is located
substantially along a centerline of the resonator body.