Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-01-27
2001-11-06
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S065000
Reexamination Certificate
active
06312097
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for delivering ink, more particularly on a print head for an ink jet printer, provided with a series of ink delivery nozzles which can be actuated selectively in the printing of a sheet of paper or the like.
The present invention also relates to an ink jet printer provided with such a print head device.
The present invention also relates to a method of making such a print head device.
A device of this kind is known inter alia from U.S. Pat. No. 4,364,067. In one embodiment, the print head comprises a base member or plate, which is substantially triangular in cross-section, and which is disposed with the apex towards the paper for printing. The device has two ink inlets situated at the top ends of the oblique sides and connected to an ink reservoir, with each leading into an ink distribution chamber, to which are connected a number of ducts formed in the associated oblique side. In the plane of the associated oblique side these ducts converge in an arc towards a number of obliquely extending ink delivery nozzles. Thus the head surface of the base plate is provided with two rows of obliquely directed ink delivery nozzles which are offset from each other.
The ducts are each provided with a constriction and a pressure chamber situated directly downstream thereof. The ducts are covered by a vibrating plate on which an electrode is disposed. At the pressure chambers, piezo-electric elements provided with an electrode are mounted on the first-mentioned electrode. By selective actuation of the piezo-electric elements the vibrating plate is pressed in locally and the volume of the pressure chamber in the required duct is reduced so that a specific quantity of ink is propelled through said duct to the associated ink delivery nozzle.
The mutually offset arrangement of the two rows of ink delivery nozzles requires a high accuracy of adjustment and operation of the known print head, particularly the height with respect to the paper. Moreover, the designing and making of the ducts in the two sides is complicated, particularly if the print head is to be very wide, for example to be able to cover a page width.
SUMMARY OF THE INVENTION
One object of the present invention is to provide an improvement in this respect by providing an improved a device for delivering ink to a sheet of paper or the like, which comprises a body with sides and a head surface disposed at an angle relative to the sides, and provided with an inlet for the ink originating from a reservoir and one or more ink distribution chambers. A number of ink delivery nozzles are situated at the head surface, and the body is provided with a number of ink passages extending between the ink distribution chambers and the ink delivery nozzles along both sides THEREOF. Ink propulsion means are disposed on the sides of the body at the ink passages for selectively propelling ink therethrough to the ink delivery nozzles. The ink passages are situated at each associated side and extend parallel to one another over the path from at least the ink propulsion means to their delivery end at the ink delivery nozzles. The center-lines of the delivery ends of the ink passages of both sides each intersect the head surface at an angle at the location of points situated in line with one another and the delivery ends are covered by a nozzle plate provided with a series of parallel ink delivery nozzles which are situated in line.
A print head constructed in such manner can be easily designed, even for large print widths, such as A4 paper, and can be easily and accurately controlled, it being possible to achieve the same pressure conditions in the mutually identical ink passages and deliver a straight line of ink with one operation.
It should be noted that U.S. Pat. No. 4,364,067 also shows an alternative construction of a print head, wherein the base plate is provided on either side with the above-described convergent ducts which terminate in a sharp point and wherein the ink delivery nozzles are defined by the vibrating plates which are extended downwardly on both sides. In this case it is intended to obtain a series of ink delivery nozzles situated in one line and delivering the ink perpendicularly. However, the accuracy of this construction leaves much to be desired.
The same patent specification shows a construction in which the base plate has parallel sides and the ducts formed in said sides connect with passages in a nozzle plate fixed on the head surface, the passages themselves having a Y-shape so that finally one in-line series of ink delivery nozzles is obtained. However, because it is complicated, it is difficult to manufacture such a nozzle plate. In addition, ink ducts connected to the same Y-shaped passage may affect one another.
It should also be noted that U.S. Pat. No. 3,988,745 discloses a print head with a base plate having parallel sides and convergent ducts form therein, the ducts being made so deep in one embodiment that their base is situated past the plane of symmetry of the base plate. The ducts end shortly before the head wall. In the head wall, or in the end wall of the ducts, holes are made to define ink delivery nozzles which are situated on a relatively straight line. However, because of the large quantity of material removed, this printer head is vulnerable. In addition, it is difficult to prevent the clogging of an ink delivery nozzle.
Where this application refers to a body or base body, this is considered to include a base body provided with a plate fixed thereon and containing the ink ducts, or a duct plate.
In producing a printer attachment with a relatively wide base plate with ink passages which may or may not be made on a separate duct plate, a wide nozzle plate and a wide piezo-electric propulsion means, the accuracy of the arrangement and the operation may be jeopardized as a result of the increased sensitivity to deviations in the alignment and the dimensioning of the various parts. This problem may be further increased if such parts are made from materials having different coefficients of expansion.
In another development of the device according to the present invention, a far-reaching solution is achieved in that the ink propulsion means are divided into a number of groups each acting on a number of ink passages situated on one and the same side and situated successively on opposite sides from each other.
In this way, the width of each group of propulsion means can be restricted and hence the sensitivity to dimensional deviations and differences in expansion with respect to the base plate and/or the passage plate can be limited. Also, this staggered arrangement can provide sufficient space for the first and last propulsion means, which would otherwise be lacking in a group-wise arrangement on one side of the duct plate or base plate.
Preferably, the ink passages subjected to the action of a group of ink propulsion means are situated directly next to one another and also situated group-wise alternately on one side and the other side, and this may be advantageous from the aspect of convenience of production.
In a further development of the device according to the present invention, the ink passages at the level of the ink propulsion means are formed as ducts and downstream thereof extend in the form of tunnels through the body to their delivery ends at the head surface. Preferably, the tunnels are straight and extend at an angle to the head surface, preferably at an angle of approximately 45° with respect to the head surface, for optimal flow conditions and production conditions.
To obviate the above-mentioned problems as a result of differences in material and considerable length, according to another feature of the present invention, the nozzle plate is provided with expansion means. In this way a long nozzle plate is divided up into smaller parts, so that the expansion length is restricted and the passages in the nozzle plate stay in front of the delivery ends.
Preferably, the expansion means are formed by interruptions in the nozzle plate o
Birch & Stewart Kolasch & Birch, LLP
Nguyen Thinh
Océ Technologies B.V.
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