DE2915629A1 - Ink jet recorder bar - with piezoceramic transducers arranged side by side - Google Patents

Abstract

A recorder bar for ink jet printers, consists of lines of piezoceramic transducers which are connected to partly common supply lines and produce the ink jets by volumetric changes, caused by the piezoelectric effect when an electric field is applied to them. The transducers are pref. arranged side-by-side in one or several lines and can be connected in turn to a black and to a red ink supply. A wiper, coated with rubber sponge and impregnated by a capillary system with polyethylene glycol is fitted above the nozzle plate. Such a recorder bar saves space compared with the conventional recording heads.

Description

Writing strip for non-contact workers

Ink printer The invention relates to a writing strip for non-contact ink printers in which a number of so-called

Piezoceramic conveying elements arranged side by side in a narrow space can be.

On the basis of piezoceramic conveying elements (transducers) working, contact-free working ink printers are already known (see Siemens-Zeitschrift 51 (4), Pp. 219-221). The piezoceramic transducers used here are around tubes made of polarized ceramic material, in which one in a ditse ending delivery line made of insulating material (glass, plastic) is embedded. If now an electrical one is briefly applied to the piezoceramic transducer at certain intervals When the field is applied, volume fluctuations are caused by the piezoelectric effect generated, which are transferred to the delivery line and so to shoot out the smallest lead discrete liquid particles.

The previously known ink printer working on this principle bundle (focus) the from the supply bottle or

an intermediate distribution board outgoing delivery lines the piezoceramic transducer (micropump) in the write head, in which the delivery lines converge in rays. However, this has the disadvantage that only one single digit can be printed from. This means that the entire Print head can be moved; in addition, the production is relatively expensive.

It has now been found that these disadvantages are avoided and at the same time a number of other advantages (described later) can be achieved if the individual piezoceramic conveying elements (micropumps) are not in a write head but bundles them separately, e.g. horizontally next to each other (possibly also at an angle offset at the top or as separate strands lying horizontally next to each other vertically arranged, each connected to a common supply line Tubes) in a writing strip summarizes. where is it possible similar to the teleprinter, only the upward movement of the paper is made without having to move the writing strip yourself.

However, a slight transverse movement is advisable provided, which corresponds at most to the distance of one tube from the other (approx. 5 mm) and, if desired, can be subdivided into several (5-10) sub-steps. on in this way, an overlap of the individual write operations is achieved, resulting in a particularly sharp appearance of the print (similar to so-called needle printing) leads. This is also the case with multicolor printing that is easily possible with this Lateral shift of a maximum of one letter required when changing color he follows.

The writing bar essentially consists of one for the power supply or the computer control necessary (expediently rectangular-elongated) board, which represents the back wall. There are numerous different ones in it adjacent openings (bores) which, for example, are made by means of a metal mandrel plate can be produced. The piezoceramic The tubes and the internal delivery line are pushed in so that they protrude to the front and then, e.g. with. Epoxy resin, cemented in1 ?. The various Glass capillaries open into a common line which leads to the storage container. If several colors are to be printed, you can see (as already described above) several adjacent strands of mutually vertically arranged conveyor elements which are each supplied from different storage tanks.

The front of the writing bar is formed by a nozzle plate, i.e. one of the mouths (nozzles) of the individual piezoceramic tubes (approx. 80 » wide) uncovered cover plate (e.g. made of sheet metal), which has the task, for one rectilinear; to ensure sharp exit of the liquid jet the Movements of the writing bar (it can be next to the previously mentioned slight sideways movement an outward movement can also be provided) are expediently steplessly working electric motor controlled.

Since the drying properties of the ink are high, partly contradicting requirements have to be made (smudge-proof on the paper, but not drying up in the nozzles), according to the state of the art, it becomes a wetting one hygroscopic antifreeze, e.g. polyethylene glycol, added (see Siemens magazine loc. cit.).

If you stand for a long time, however, there is still a risk of constipation.

It has therefore proven to be useful preventive on chemical Ways to make an easily removable fastener that uses thixotropic properties A gel can be used, for example, by adding the ink easily coagulable agent such as pectin is added and this if necessary (by means of Acid) coagulates as soon as the ink printer is no longer needed. As a coagulating Acid can e.g.

Fumaric acid can be used, which can be obtained by heating (e.g. 3.

by means of a heating coil) can be easily sublimated, then off a storage vessel expediently used below the writing bar and is blown along the writing strip by means of a fan. The first Contraction "opens" the chemical lock.

Another way to remove the excess (because of the addition of Solvents (usually very light) ink are harmless when the printer is switched off to do is to make a (e.g. in a quarter turn) above the nozzle plate Provide swiveling wiper, which is covered with fine-pored foam rubber and immediately after swiveling down the nozzle plate and so that the writing nozzle applies. The wiper has the shape of a (with the Foam rubber-lined) channel, but it can also be simply one with foam rubber, for example be occupied disk.

The foam rubber is produced by a capillary oil system distributed in it, which through a small storage container (ampoule or similar) by means of the capillary force is constantly refilled, soaked with polyethylene glycol. This is to create a To prevent crust formation on the print heads.

It is also possible to have the wiper in its lower half with felt and only to be covered with foam rubber in the upper part. In this case you will see one Two-phase swivel movement (e.g. executable by a small electric motor) before: In the first phase - e.g. for a brief standstill of the device - only the felt strip is pushed in front of the writing nozzle, during longer periods of standstill the foam rubber section is placed in front of it.

The writing strip according to the invention has the particular advantage that overall fewer piezoceramic conveying elements are required, i.e. the otherwise Ample space is considerably reduced.

The invention is described in more detail below with reference to FIGS. 1 to 3, without restricting it: FIG. 1 shows (highly schematized) a writing strip from the beginning. You can see the juxtaposed nozzles of the individual piezoceramic Tubes that are alternately supplied by different strands of wire. 1 means "black ink supply 1 ?, 2" red ink supply ".

Figure 2 shows adjacent "strands" of nozzle openings, which in turn lie vertically one above the other.

1 and 2 have the meaning given above.

Figure 3 shows a cross section through a writing strip.

3 means the (pierced) board, 4 the "walled in" in the openings piezoceramic tubes and 5 the common delivery line that supplies them with ink (Glass capillary). 6 is the cover (nozzle) plate.

Claims (11)

Patent claims 1. Writing strip for non-contact ink printers, characterized in that numerous piezoceramic conveying elements in a plate (W.randler) are embedded, which through - partially common - feed lines to one or more storage containers connected and their nozzles if desired are covered with a plate. 2. Writing strip according to claim 1, characterized in that the pi ezokerami rule conveyor elements are arranged side by side. 3. writing strip according to claim 2, characterized in that the Conveying elements alternating common feed lines to a common storage container own. 4. writing strip according to claim 1, characterized in that several Strands of conveyor elements arranged vertically to one another, horizontally next to one another lie. 5. writing strip according to claim 4, characterized in that the Strands in each case alternating common feed lines to a common storage container to have. 6. writing strip according to claim 1, characterized in that it a transverse movement up to approx. the simple distance between the piezoceramic conveying elements can do from each other. 7. writing strip according to claim 1, characterized in that their Movement is controlled by an infinitely variable electric motor. 8. writing strip according to claim 1, characterized in that on their underside a storage container is arranged in which there is a suitable Acid that forms a sublimate when heated. 9. Writing strip according to one of the preceding claims, thereby characterized in that they have a pivotable, with foam rubber above the nozzle plate has occupied wiper. 10. writing strip according to claim 9, characterized in that the Foam rubber of the wiper soaked in polyethylene glycol by means of a capillary system will. 11. writing strip according to one of claims 9 and 10, characterized in that that the wiper is in its lower half with felt and the upper half with foam rubber is occupied and can be swiveled down in a two-step movement.