The present invention relates to continuous ink jet printers, and more specifically to the fabrication of an orifice plate and a charge plate for such printers.
This invention relates to continuous-type ink jet printing systems, which create printed matter by selective charging, deflecting, and catching drops produced by one or more rows of continuously flowing ink jets. The jets themselves are produced by forcing ink under pressure through an array of orifices in an orifice plate. The jets are stimulated to break up into a stream of uniformly sized and regularly spaced droplets. The approach for printing with these droplet streams is to selectively charge and deflect certain drops from their normal trajectories.
A charge plate accomplishes droplet charging. The charge plate has a series of charging electrodes located equidistantly along one or more straight lines. Each charging electrodes is formed with an electrically conductive material so as to define a cylindrical charging electrode. Electrical leads are connected to each such charge electrode, and the electrical leads in turn are activated selectively by an appropriate data processing system.
U.S. Pat. No. 4,636,808, which issued to Herron, describes a simple arrangement of the drop generator and the charge plate, but the orifice plate attached to the drop generator and the charge electrodes require careful mechanical alignment and fixation so that the charge electrodes align exactly with corresponding jets issuing from the orifice plate. If the jets are misaligned or become misaligned in use, the quality of printing is adversely affected. Misalignment of as little as 10 micrometers can cause rejection of the print head and require it to be refurbished. Matching of the dimensions of the ink jet array and the charge electrode array becomes problematic, especially for page-wide arrays where there are thousands of ink jets and charge electrodes.
Conventional and well-known processes for making the orifice plate and charge plate separately consist of photolithography and nickel electroforming. Orifice plate fabrication methods are disclosed in U.S. Pat. No. 4,374,707; No. 4,678,680; and No. 4,184,925. The commonality of these and other patents is in the deposition of a nonconductive thin disk onto a substrate, which is followed by partial coverage of this with nickel to form an orifice. In the prior art process, a conductive substrate of solid metal is used to hold the thin disk and the plating. After formation of the orifice, the metal substrate is selectively etched away leaving the orifice plate electroform as a single component. Charge plate electroforming is described in U.S. Pat. No. 4,560,991 and No. 5,512,117. These charge plates are made by depositing nonconductive traces on a metal substrate followed by deposition of nickel in a similar fashion to orifice plate fabrication, except that parallel lines of metal are formed instead of orifices.
Accordingly, it is an object of the present invention to provide a simplified and more accurate method for fabrication of the orifice plate and charge plate. It is another object of the present invention to provide such an aligned orifice plate and charge plate as one, self-aligned component.
According to a feature of the present invention, fabrication of the orifice plate and charge plate are carried out on opposite sides of the same substrate platform such that the one is optically aligned to the other in sequential steps that ensure self-alignment of the two components. That is, the orifice plate and charge plate are made in a single piece.
According to another feature of the present invention, an orifice array plate and a charge plate for a continuous ink jet printer print head are integrally fabricated by providing an electrically non-conductive substrate; forming, on one side of the substrate, an orifice plate with an array of orifices; forming, on the other side of the substrate, a charge plate comprising a plurality of charge leads aligned with respective ones of the orifices; and removing at least that portion of the substrate that is between the orifices and the charge leads.
According to yet another feature of the present invention, an integrally fabricated orifice array plate and charge plate for a continuous ink jet printer print head includes an electrically non-conductive substrate; an orifice plate, including an array of orifices, on one side of the substrate; a charge plate, including a plurality of charge leads, on the other side of the substrate such that the charge leads are aligned with respective ones of the orifices; and a plurality of passages through the substrate, said passages extending between the orifices and the charge leads.
In a preferred embodiment of the present invention, the substrate is a smooth sheet of flexible dielectric material. A layer of conductive metal is between the substrate and each of the plates. At least that portion of the metal coatings that is between the orifices and the charge leads has been removed. The dielectric material is polyimide.
It will be understood that the orifice array plate and the charge plate of the present invention are intended to cooperate with otherwise conventional components of ink jet printers that function to produce the desired streams of uniformly sized and spaced drops in a highly synchronous condition. Other continuous ink jet printer components, e.g. drop ejection devices, deflection electrodes, drop catcher, media feed system, and data input and machine control electronics (not shown) cooperate to effect continuous ink jet printing. Such devices may be constructed to provide synchronous drop streams in a long array printer, and are comprised in general of a resonator/manifold body to which the orifice plate is bonded, a plurality of piezoelectric transducer strips, and transducer energizing circuitry.
After the orifice plate 28 has been formed on one side of the substrate, a charge plate is formed on the opposite side of the substrate, as shown in
Because the substrate is electrically non-conductive, the substrate can remain as part of the orifice plate/charge plate structure. This would not be possible with the conventional methods because the charge electrodes are held at about 100 volts with respect to the orifice plate/drop generator. The old methods used conductive, solid metal sheets as substrates, and if so used in the present invention would cause electrical shorting of orifice plate 28 and charge leads 34.
In order for ink to issue from the orifices, a portion of dielectric substrate 10 must be removed from between orifice plate 28 and charge plate 34.
After the thin metallization layer 18 is removed from between the charge electrodes, it is desirable to fill the space between the charge leads with a non-conductive material. This non-conductive material prevents conductive ink from filling the space between charging leads where it can produce lead-to-lead electrical shorts. This non-conductive material may be an epoxy or other appropriate material that won't break down due to exposure to the ink or due to the electrical fields produced between charging leads.
A schematic perspective view of the completed orifice plate/charge plate integrated structure is shown in
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
Reference is made to commonly assigned, co-pending U.S. patent applications Ser. No. ______ (D. 89661) CHARGE PLATE AND ORIFICE PLATE FOR CONTINUOUS INK JET PRINTERS to Richard W. Sexton, Ser. No. ______ (D. 89584) entitled ELECTROFORMED INTEGRAL CHARGE PLATE AND ORIFICE PLATE FOR CONTINUOUS INK JET PRINTERS to Shan Guan et al. and Ser. No. ______ (D. 89619) entitled INTEGRATED CHARGE AND ORIFICE PLATES FOR CONTINUOUS INK JET PRINTERS to Shan Guan et al. filed concurrently herewith.