Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1997-10-20
2001-04-03
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S085000, C347S084000
Reexamination Certificate
active
06209997
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a drop-on-demand or impulse fluid jets which eject a droplet of fluid such as ink in response to the energization of a transducer.
BACKGROUND OF THE INVENTION
Impulse fluid or ink jets are designed and driven so as to eject a droplet of fluid such as ink on demand from a chamber through an orifice in the chamber. Where impulse jets are utilized in many applications including industrial applications, it is important that the impulse ink jets operate reliably. Such reliability can be jeopardized where the impulse jets can be deprimed due to fluid disturbances in the supply of ink to and through the impulse jet. Such depriming can occur as a result of brief disturbances to the fluid supply as well large, longer disturbances caused by, for example, bumping the apparatus.
SUMMARY OF THE INVENTION
In accordance with this invention, an apparatus is provided for preventing depriming of an impulse jet.
In still further accordance with the invention, an apparatus is provided for preventing depriming of an impulse jet in response to small and/or brief disturbances in the ink or fluid supply line to the impulse ink jet or elsewhere.
In still further accordance with the invention, an apparatus is provided for preventing depriming of an impulse jet in response to large and/or longer disturbances in fluid supply line or elsewhere.
In accordance with a preferred embodiment of the invention, an impulse ink fluid apparatus comprises a transducer, and a fluid jet chamber coupled to the transducer, the chamber having an orifice through which droplets of fluid are ejected in response to the energization of the transducer. A fluid supply is coupled to the fluid jet chamber through a compliant chamber which forms at least part of a low pass filter substantially attenuating fluid disturbances having a duration substantially less than time constant of the low pass filter formed by the compliant chamber.
In the preferred embodiment, the time constant represented by the product of the fluidic capacitance of the compliant chamber and at least a portion of the fluidic resistance of the fluid supply substantially attenuates pressure disturbances having a duration less than 0.01 the value of the time constant. In the preferred embodiment, disturbances of less than 0.01 and preferably less than 0.05 seconds will be attenuated.
In the preferred embodiment, the compliant chamber comprises a compliant member for absorbing pressure waves. The compliant chamber comprises a flexible diaphragm which is nonplanar in the undisturbed state such that deformation is nonlinear with respect to changes in pressure. Preferably, pressure waves are absorbed without pressure increases in the compliant chamber. In the preferred embodiment, the compliant chamber comprises an air passage allowing ambient air pressure to flow through and reach the compliant member.
The compliant chamber may also include a filter permitting the flow of ink through the filter from the ink supply to the fluid jet chamber.
In one preferred embodiment, the apparatus further comprises at least one check valve located between the fluid jet or a manifold serving a plurality of fluid jets and the compliant chamber for preventing the reverse flow of ink from the ink jet chambers to the compliant chamber while permitting ink to flow from the compliant chamber to the ink jets. Each check valve includes passageways permitting the passage of air through the check valves. In this regard, the check valve comprises a valve seat, a valve member, a valve support comprising at least one passage permitting fluid flow between the valve seat and the valve member and through the fluid passage toward the fluid chamber. The check valve includes a valve body forming the valve seat and containing the valve member and the valve support such that the fluid passage in the valve support is located adjacent to the valve body. Preferably, the valve support comprises a plurality of passages located adjacent to the valve body.
In another preferred embodiment, the check valve, which acts as a rectifier to maintain positive pressure at the orifice(s), is coupled between the fluid supply and the compliant chamber. Moreover, in this embodiment the compliant chamber holds negative pressure between −0.1 and −10 in-H
2
O created by orifice jetting and the static height of the ink supply. Further, the check valve is characterized by a cracking pressure of between 0.1 and 3 in-H
2
O, whereby excessive buildup of negative pressure at the orifice during jetting is prevented.
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Cahill Cliff John
Duong Ha Van
Ky Bopta
Barlow John
Croll Mark W.
Do An H.
Illinois Tool Works Inc.
O'Brien John P.
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