WO1990005067A1

WO1990005067A1 - An arrangement in fluid jet printers

Info

Publication number: WO1990005067A1
Application number: PCT/SE1989/000649
Authority: WO
Inventors: Lars Uddgren; Ulf Mielke
Original assignee: Scandot System Ab
Priority date: 1988-11-11
Filing date: 1989-11-13
Publication date: 1990-05-17
Also published as: SE8804081D0

Abstract

An arrangement in fluid jet printers for ejection of a fluid in the form of droplets on a recording medium so as to generate characters thereon, such as bar codes (2), comprises a housing wall in which are formed a number of holes for reception in each one thereof of a valve body, a valve plate connected to the housing wall and formed with fluid passageway apertures in front of and in alignment with the valve bodies, said valve bodies sealingly cooperating with valve seats surrounding the apertures, and a nozzle plate (10) connected to the valve plate and provided with fluid channels the ends of which are positioned in front of the fluid passageway apertures, some of said fluid channels being branched off so as to form branch channels, the free ends of which are connected to jet nozzles directed towards the recording medium.

Description

AN ARRANGEMENT IN FLUID JET PRINTERS

This invention concerns an arrangement in fluid jet printers for ejection of a fluid in the form of droplets on a recording medium to generate characters thereon, said printer comprising a housing with a wall . 5 in which are formed a plurality of through holes in each one of which is received a preferably electro-magne- tically operated valve body, a valve plate which is connected to the housing wall and which is formed with fluid passage-way apertures positioned in front of

10 and in alignment with the respective valve bodies, each aperture having a valve seat sealingly cooperating with its associated valve body, and a nozzle plate intercon¬ nected with the valve plate on the valve plate face turned away from the housing wall, said nozzle plate

15 formed with fluid channels having one of their ends positioned in alignment with the fluid passageway aper¬ tures whereas their opposite ends communicate with jet nozzles, said nozzles being directed towards the recording medium.

20 In using fluid jet printers of this type to generate large characters, i.e. characters having a height of approximately 30 mm and more, on a recording medium the vertical spacing between the dots formed by the fluid droplets into the characters will be so large

25. that the gaps between the dots become very obvious.

In some applications this is of no great signific¬ ance but in other applications it constitutes a serious drawback.

For instance, in printing e.g. bar codes consisting

30 of straight lines or bars of different widths enclosed by a rectangular frame and having the character height indicated above, the gaps between the dots forming the bars and the frame may result in coding errors in the equipment designed to read and/or record/convert the code, with obvious consequential risks.

In some cases, large letters and numbers are dis- advantegous because of the difficulties that they present both to the eye and to the reading equipment as regards reading and interpret action, which is due precisely to the obvious gaps between the dots.

The purpose of the subject invention is to indicate an arrangement in fluid jet printers of the kind out¬ lined initially, by means of which it becomes possible to generate characters, i.e. letters, numbers, bar codes and the like, having a higher degree of homogeneity and without disturbing gaps between the dots, resulting in a considerably safer and clearer reading and/or de¬ coding of the characters. This purpose is achieved in accordance with the invention in that at least some of the fluid channels are branched off so as to form branch channels, each one of which communicates with its respective jet nozzle. Consequently, fluid supplied to each such branched off fluid channel will be discharged simultaneously from all jet nozzles connected thereto. Preferably, these jet nozzles are positioned in a row in a closely juxta¬ posed relationship.

Owing to this arrangement the gaps between the dots in each character will be greatly reduced or non¬ existent, with the result that the characters will appear as completely homogeneous.

The invention will be described in the following with reference to the accompanying drawings which to- gether illustrate a presently particularly preferred embodiment. In the drawings:

Fig. 1 shows in a laterally perspective view a fluid jet printer of the type referred to, wherein the components incorporated in the printer are shown in a disassembled position and in some case only partially. Fig. 2 is a view from above, the left part of which illustrates a nozzle plate incorporated in the fluid jet printer in accordance with Fig. 1 and the right hand part of which shows a bar code printed by means of the printer.

Fig. 3 illustrates the nozzle plate in accordance with Fig. 2 on an enlarged scale.

The fluid jet printer illustrated in Fig. 1 and generally indicated by numeral reference 1 is designed . to eject a liquid, for instance ink, in droplet form onto a recording medium, not shown, so as to form charac- ters, for instance the bar code 2 illustrated in Fig. 2, on that medium.

In accordance with the embodiment shown the fluid jet printer comprises a housing, not illustrated in any detail, incorporating a bottom wall 3. In the bottom wall 3 are provided a plurality of through holes 4, in the embodiment shown 17 holes, for reception in each one of said holes of a valve body 5 in the shape of a piston. The valve bodies 5 are electro-magnetically operated in a manner known per se to open and close fluid passage way apertures 6. These apertures 6 are positioned in alignment opposite their respective one of the valve bodies and they are formed in a valve plate 7 which is fastened to the housing wall 3, for instance by means of screws. A coating 8 of rubber or similar material is applied on the valve plate 7 and around the fluid passageway apertures 6 it is formed with valve seats 9 which sealingly cooperates with their respective one of the valve bodies 5.

A nozzle plate 10 is joined to the valve plate 7, for instance by means of screws, on the valve plate face which is turned away from the housing wall 3, a packing seal 11 being sandwiched between the plate 7 and the plate 10. As appears also from Figs. 2 and 3 there are provided in the nozzle plate 10, in the side thereof facing the valve plate 7, a number of compara¬ tively shallow fluid channels 13, the first ends 12 of which are positioned in alignment with the fluid passage- way apertures 6. The fluid channels 13 consequently extend in parallel with the plane of the nozzle plate 10. The opposite channel ends 14 are connected to jet nozzles 15 which are directed towards the recording medium.

More precisely, at least some of the fluid channels 13, in accordance with the shown embodiment 10 out of a total of 17, are branched off into four branch channels 16, each one of which communicates with its respective one of the jet nozzles 15.

The jet nozzles 15 associated with the branch chan¬ nels 16 are placed very close together in one single row 17 with a spacing in accordance with the embodiment illustrated of approximately 1 mm. The row 17 of branch channels 16 extends transversely to the direction of movement in relation to the recording medium.

Also the branch channels 16 are formed in the side of the nozzle plate 10 that faces the valve plate 7 but are shallower than the branched off fluid channels 13 before the branching off points of the latter. The opposite ends 14 of the branch channels 16 as well as those of the remaining seven fluid channels 13 debouch into fluid discharge apertures 18 which extend through the nozzle plate 10 and in which are mounted the jet nozzles 15.

In accordance with the embodiment illustrated and described the ten branched off fluid channels 13 serve to produce homogeneous, comparatively tall characters 2 as shown in Fig. 2, by way of their branch channels 16 and jet nozzles 15 associated therewith, whereas the remaining seven fluid channels 13 serve to produce the lower characters 19 shown in Fig. 2 by way of their associated jet nozzles 15.

Claims

1. An arrangement in fluid jet printers (1) for ejection of a fluid in the form of droplets on a record¬ ing medium to generate characters (2, 19) thereon, said printer (1) comprising a housing with a wall (3) in which are formed a plurality of through holes (4) in each one of which is received a preferably electro-magne- tically operated valve body (5), a valve plate (7) which is connected to the housing wall (3) and which is formed with fluid passageway apertures (6) positioned in front of and in alignment v/ith the respective valve bodies (5), each aperture having a valve seat (9) sealingly cooperating with its associated valve body (5), and a nozzle plate (10) interconnected with the valve plate (7) on the valve plate face turned away from the housing wall (3) said nozzle plate (10) formed with fluid channels (13) having one of their ends (12) positioned in alignment with the fluid passageway apertures (6) whereas their opposite ends (14) communicate with jet nozzles (15), said nozzles being directed towards the recording medium, c h a r a c t e r i z e d in that at least some of the fluid channels (13) are branched off so as to form branch channels (16) each one of which communicates with its respective jet nozzle (15).

2. An arrangement as claimed in claim 1, c h a - r a c t e r i z e d in that the jet nozzles (15) asso¬ ciated with the branch channels (16) are placed closely ^•together in a row (17).

3. An arrangement as claimed in claim 2, c h a ¬ r a c t e r i z e d in that the fluid channels (13) and the branch channels (16) are formed in the side of the nozzle plate ( 10) facing the valve plate (7), and in that the opposite ends ( 14) of the channels (13, 16) open into fluid discharge apertures (18) extending through the nozzle plate, said jet nozzles (15) being mounted in said fluid discharge apertures (18).

4. An arrangement as claimed in claim 3 c h a - r a c t e r i z e d in that the branched off fluid channels (13) are deeper upstream of their branching off points into the branch channels (16).

5. An arrangement as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that the nozzle plate (10) comprises at least seventeen fluid channels (13), at least ten of which are branched .off into at least four branch channels (16) each.