Recorders – Markers and/or driving means therefor – With ink supply to marker
Patent
1984-06-07
1986-03-11
Goldberg, E. A.
Recorders
Markers and/or driving means therefor
With ink supply to marker
G01D 1516
Patent
active
045757372
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Phase Application corresponding to the PCT/CH83/00110 filed Oct. 5, 1983 and based, in turn, upon Swiss National Application No. 5914/82-83 filed Oct. 8, 1982, the priority of which has been claimed under the International Convention.
FIELD OF THE INVENTION
This invention relates to a device for projecting droplets of an electrically conducting liquid.
BACKGROUND OF THE INVENTION
There are two types of devices for projecting droplets of a liquid, in particular, ink in ink-jet printing systems. One of these types consists in fractionates a pressurized jet into droplets and requires a source of liquid under pressure, a nozzle designed to form a jet, means which can induce high frequency pressure variations in the flow in order to fractionate it, means for directing the droplets and means for recovering and recycling the unused ink. These devices are designed preferably for large plants because they use relatively numerous and complex means and because of the substantial throughput of ink. They are designed for machines such as large computers or very high frequency text processing printers, the cost of which is in line with this type of ink jet device.
The other of these types makes it possible to project droplets at will and generally comprises means for creating an overpressure within an enclosure containing the liquid to be projected and having an opening through which the liquid is expelled whenever the pressure exceeds the force of cohesion of the meniscus formed by the liquid in that opening. Such a device is described, in particular, in U.S. Pat. No. 3,832,579.
This device has a frequency or period of droplet formation which is limited by the speed at which the meniscus can form again after the expulsion of a drop, said period of formation being of the order of 100.times.10.sup.-6 s.
All known ink jet devices use an orifice connected to a reservoir in order to project the droplets. Such devices require droplet tubes in the case of a printer permitting the simultaneous formation of a multiplicity of droplets. A matrix of tubes which can produce this simultaneous projection raises obvious practical problems. In addition, the nozzles through which the ink is projected may clog up, in particular, after a period of nonuse.
OBJECT OF THE INVENTION
The object of this invention is to eliminate, at least partially, the above-mentioned drawbacks.
SUMMARY OF THE INVENTION
To this effect, this invention provides a device for projecting drops of an electrically conducting liquid, characterized by the fact that it comprises at least one electrode the diameter of which is of the same order of magnitude as that of the drops to be projected, flush with a surface of an electrically insulating support, a source of intermittent current one pole of which is connected to that electrode, means for forming a layer of said liquid having a specified thickness, covering at least the surface of the support at which the electrode is flush and a second electrode in contact with said layer and connected to the other pole of the source of intermittent current so as to form an electric field through said liquid, concentrating on that part of the electrode flush with the surface of said support.
The advantages of the device, which is the object of the invention, are numerous. The droplets are no longer projected through a hole but are detached from the surface of a layer of liquid. As a result, the speed of reformation of the layer is less critical. The formation of a matrix for the simultaneous projection of droplets can be obtained, for example, by means of a printed circuit technique, the distance between the droplet generating electrodes being reduced with respect to a matrix of tubes. It is possible to implement the invention in the form of a very planar structure. Transducers are no longer necessary to create the force necessary to project the droplets. The cost of production of such a device is substantially reduced. As a result, the possible ap
REFERENCES:
patent: 3834301 (1974-09-01), Croquelois et al.
patent: 4275290 (1981-06-01), Cielo et al.
patent: 4383265 (1983-05-01), Kohashi
Genequand Pierre
Vermot-Gaud Jacques
Battelle (Memorial Institute)
Dubno Herbert
Goldberg E. A.
Kampe Fred L.
Ross Karl F.
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