EP0202369B1

EP0202369B1 - Printing head

Info

Publication number: EP0202369B1
Application number: EP19850303544
Authority: EP
Inventors: Keiichi Hori
Original assignee: Toshiba Corp; Fujitsu Ltd; Mitsubishi Electric Corp; Elm Co Ltd
Current assignee: Toshiba Corp; Fujitsu Ltd; Mitsubishi Electric Corp; Elm Co Ltd
Priority date: 1985-05-20
Filing date: 1985-05-20
Publication date: 1990-05-16
Also published as: DE3577673D1; EP0202369A1

Description

The present invention relates to a printing head.
In the conventional ink jet printer, a plurality of ink jet nozzles are used, and ink is jetted onto a printing paper by a piezoelectric drive means. In such a conventional printer, however, it is very difficult to eliminate nozzle stoppage which, in effect, causes a white point to be printed on the printing paper.
On the other hand, in the case of an ink ribbon type printer, the ink is used in the course of time and consequently the printing density gradually becomes paler.
Further, in the case of a thermal transfer printer or the hammer type printer, a coated tape has to be thrown away after one printing operation. Therefore, a printer or typewriter or wordprocessor which can print with a continuous supply of ink has scarcely been previously developed. Japanese Patent JP-A-59 142 158 shows an ink jet printer in which an ink supply roller supplies ink to the orifices of a multihole ink ribbon. US Patent 4,387,384 describes a device including an endless multi-hole ink ribbon which enters an ink bath and is immersed in the ink in order to transfer ink to the ribbon.
According to the present invention, there is provided a printing head for transferring ink from at least one ink reservoir in at least one housing to at least one film member having a plurality of holes or recesses therein, for application to a record medium by the action of associated dot elements of a printing head, characterised in that the housing is formed integrally with or secured to a thermal printing element, to constitute a replaceable printing head cassette, and in that an ink transfer member is provided for transferring ink from the reservoir to the film and into the holes or recesses therein, the said ink transfer member being in physical contact with the ink in the reservoir.
The or each film member may slidably engage a respective ink transfer member.
The or a said housing may have a film supporting member mounted thereon, the film supporting member having recess portions for guiding the, or the respective, film member.
A cap member may be detachably mounted on the or each film supporting member so as to cover the outer surface thereof, the cap member having a slit portion for guiding the film member.
The or each housing may be provided with a pair of ink transfer members which are disposed on opposite sides of the film member, each ink transfer member having a curved portion to guide the film member towards a contact portion of the ink transfer member.
The or each housing may be provided with a detachable valve member for introducing ink into the housing.
The or each housing may also be provided externally with a mounting recess portion for detachably securing the housing to another member.
The thermal printing element may be disposed between two said housings.
Each thermal printing element may be provided with a plurality of heating dot elements.
There may be a plurality of film members and respective thermal printing elements for printing a plurality of different colours.
The or each film member may pass through a sealed space which is supplied with ink by a said ink transfer member.
The sealed space may be disposed between the housing and a member which is resiliently urged towards the housing, the sealed space being sealed by sealing members which engage opposite sides of the film member.
The or each ink transfer member may be connected to an ink reservoir by way of a frangible member, means being provided for breaking the frangible member to enable ink to pass from the ink reservoir to the ink transfer member.
The invention is illustrated, merely by way of example, in the accompanying drawings, in which:

Figures 1 to 7 illustrate a first embodiment of a printing head according to the present invention,
Figure 1 is a cross-sectional view, of a cassette body forming part of the printing head,
Figure 2 is a plan view of the cassette body shown in Figure 1,
Figure 3 is a side view of the said cassette body and shows a cap member thereon,
Figure 4 is a plan view of part of the structure shown in Figure 3,
Figure 5 is a perspective view of a serial printer provided with a printing head according to the present invention,
Figures 6 and 7 are respectively a plan view and a front view of a part of the structure shown in Figure 5 to illustrate the position of the parts during printing,
Figures 8 to 10 illustrate a second embodiment of a printing head according to the present invention,
Figure 8 is a perspective view of the basic construction of the said second embodiment,
Figure 9 is a side view of the structure shown in Figure 8,
Figure 10 is a perspective view of the basic construction of a colour printer incorporating a printer head as shown in Figures 8 and 9,
Figures 11 to 14 illustrate a third embodiment of the present invention,
Figure 11 is a perspective view of a printing head according to the present invention,
Figure 12 is a vertical sectional view of the printing head shown in Figure 11, and
Figures 13 and 14 are plan views of alternative constructions of sealing members which may be used in the said third embodiment.

In Figures 1-7 there is shown a first embodiment of a cassette type printing head according to the present invention. As shown in Figure 1, within a housing or cassette body 1 of elongated box shape there is housed a liquid ink or a sintered liquid ink material 2, the latter being housed in the hollow interior 1a of the cassette body 1. A hollow cylindrical film supporting member 3, which is formed integrally with the cassette body 1, protrudes from one surface of the cassette body 1. The supporting member 3 is provided on opposite sides thereof with a pair of recessed portions 5, (Figure 2) for guiding a film 4 so that the film 4 can pass through the supporting member 3 at right angles to the length of the cassette body 1a in what will be described as an axial direction. Further, a pair of ink guiding and supplying members 6, 6, which are made of a felt or fibrous material, are mounted respectively in two recessed portions 3b, 3b of the inner walls 3a, 3a, of the supporting member 3, the ink supplying members 6 being mounted centrally of the supporting member 3. The end portions of the ink supplying members 6, 6 contact each other. The ink supplying members 6, 6 are provided with curved portions 6a, 6a for easy insertion of the film 4 therebetween. The film 4 can thus both contact and slide with respect to the ink supplying members 6, 6 at contact portions 6b thereof. Thus the ink supplying members 6 are disposed on opposite sides of the film 4, the curved portions 6a guiding the film 4 towards the contact portions 6b. The lower sides of the ink supplying members 6, 6 are immersed in or in contact with the ink 2 in the cassette body 1. A valve or bulb member 7, having an O-ring 7a for filling or changing ink, is detachably mounted in an opening 16 in the cassette body 1.
A cap member 8 (Figures 3 and 4) of cylindrical shape, is detachably mounted on the outside of the supporting member 3. The cap member 8 has a pair of slit portions 8a, 8a, on substantially opposite sides of the cap member 8 for guiding the film 4 substantially in the said axial direction. When the cap member 8 is mounted on the supporting member 3, the film 4 is able to slide between the ink guiding members 6, 6 and through the slits 8a, 8a and the recessed portions 5, 5. Drying out of the ink in holes or recesses 4a (Figures 6 and 7) of the film 4 and in the ink supplying members 6, 6 is prevented by the cap member 8.
Recessed portions 11 for detachably mounting the cassette body 1 on a carriage member9 (Figure 5) are provided at the sides of the cassette body 1. In the embodiment of serial printer illustrated in Figure 5, a pair of cassette bodies 1,1 are mounted on the carriage member 9 which is movable in the directions indicated by the double headed arrow A. The carriage member 9 is slidably mounted for this purpose on a pair of guide shafts 12, 12 along which they may be moved by a pair of cassette levers 10,10. Athermal printing element 13, which is mounted on the carriage member 9, is located between the cassette bodies 1, 1. The supporting members 3, 3 are disposed on opposite sides of thermal printing element 13 so that ink is supplied to the film 4 from different directions. The thermal printing element 13 and the cassette bodies 1 are integral with or secured to each other so as to constitute a replaceable cassette for use in a printer.
The film 4 which is guided by and is in contact with the supporting members 3, 3 and with the thermal printing element 13, has a large number of small holes or recesses 4a as indicated in Figures 6 and 7. Ink 2, which is supplied from the ink supplying members 6, 6, fills each of the small holes or recesses 4a. When a signal current is applied to a heating surface 13a (Figure 6) of the thermal printing element 13, ink in the small holes or recesses 4a is jetted onto a recording paper sheet 15 so as to effect printing on the latter. In this case, a plurality of the small holes or recesses 4a correspond to one dot element of the heating surface 13a. Normally, the heating surface 13a is composed of a plurality of dot elements, the said one dot element corresponding to one picture element. Therefore even if one or two holes or recesses 4a are stopped up, the picture element can still be printed.
The film 4 is entrained around a pair of pulleys 16,16 and can be extended by means of pins 16a which engage the film 4.
In the above described first embodiment of the present invention, the thermal printing element 13 is disposed between a pair of cassette bodies. However, the same effect can be obtained if the thermal printing element 13 is mounted in a recess formed between cassette bodies constituting an integral structure. Furthermore, it is possible to use a single ink supply member 6 instead of the pair of members 6 described above.
In Figures 8-10 there is shown a second embodiment of a printing head according to the present invention.
In the construction shown in Figure 8, a film 4 is made of a thin metallic film of aluminium or an organic film of polyimide and has a large number of holes 4a. The film 4 may be of any desired length and width. Both ends of the film 4 are rolled up so that if a hole or holes 4a become blocked up, a new portion of the film 4 may be brought into use by suitably unrolling the film. A thermal printing element 13 has a plurality of thermal head dot elements 13a and there is an ink supplying member which comprises a cassette body 1 of box like shape which has an inkfilling inlet (not shown) so that ink may be introduced into the interior thereof. Ink is supplied to the holes 4a by way of an ink supplying member 6 which is made of sponge material and contacts one surface ofthefiim4. The thermal printing element 13 and ink supplying member 6 are arranged side by side so as collectively to be of cassette shape and to contact a surface of the film 4 and move serially when printing or recording is performed. Ink 2, which is disposed in the holes 4a of the film 1, is jetted onto recording paper 18 by bubble pressure caused by heating the ink in a group of holes 4a by means of a thermal dot element 13a.
Figure 9 illustrates the operation of the film 4 and the thermal printing element 13. When ink 2 has been introduced into the holes 4a, only the ink 2 in holes 4a aligned with the thermal dot element 13a of the thermal printing element 13will be heated. A flexible cable 17 is used to supply a drive signal to the thermal printing element 13 from a drive circuit (not shown).
Figure 10 illustrates a basic construction for producing a colour print. The recording paper 18 is mounted on a drum 19.
Alternatively, instead of mounting the paper 18 on the drum 19 as shown in Figure 10, one can use paper of the "one pass" type. Films 4a, 4b, 4c and 4d are employed for the printing of the Y (yellow), M (magenta), C (cyan) and B (black) colours respectively. The thermal printing element 13 and ink supplying member 6 are used in the manner shown in Figures 8 and 9. A supporting base 20 supports the element 13, the latter being slidably mounted on a pair of supporting bars 21. Colour printing is performed in the line direction by moving the supporting base 20 longitudinally of the drum 19 for each colour. That is to say, in Figure 10 a single thermal printing element 13 is shown as aligned with the film 4a for printing the colour Y. In practice, however, each of the other films 4b, 4c, 4d would also have its respective thermal head.
The second embodiment of the present invention which is shown in Figures 8-10 makes it possible to effect mono and colour printing by a means of a simple mechanism. Moreover, if the nozzle constituted by a group of holes 4a becomes blocked, all that is necessary is to unroll a fresh length of film 4. Thus the construction is applicable to a copying machine or electronic typewriter.
In Figures 11-14 there is shown a third embodiment of the present invention.
A recording ink cassette or cassette body 1 is employed in a printing head in which a recording ink 2 is housed in a plurality of small holes or recesses 4a of a thin film 4 made of a metal or organic material. The recording ink 2 is jetted towards a recording paper (not shown) by contacting the film 4 with a thermal printing element 13 which causes expansion of the ink in the holes or recesses 4a so as to effect printing by bubble pressure.
The recording ink cassette 1 is composed of a recording ink housing member 1b, a recording ink supplying member 6 which is arranged to be connected, as described below, to said housing member 16 so as to supply ink to the holes or recesses 4a, first sealing members 22 for sealing said housing member 1b, and a pressure member 24 having second sealing members 23 which are disposed opposite first sealing members 22. The sealing members 22, 23 engage opposite sides of the film 4 which passes through a space 26 which is sealed by the sealing members 22, 23. The pressure member 24 is pressed by a spring member 25 towards the ink cassette 1.
Recording ink 2 fills the sealed space 26 which is sealed by the sealing members 22 and 23 and thus passes into the small holes or recesses 4a of the film 4 which passes through the recording ink 2. The recording ink 2 is supplied to the sealed space 26 by the ink supplying member 6 and, if desired, it may be arranged that the ink supplying member 6 contacts the film 4. The sealing members 22 and 23 prevent the recording ink from leaking out and enable a uniform amount of recording ink to be contained in the small holes or recesses 4a of the film 4. The sealing members 22, 23 may be made of plastics, rubber, a silicone resin or a fluorine resin which has a good low friction characteristic. The sealing members 22, 23 are also preferably 0-ring shape.
The width of the sealing members 22 and 23 may be greater than the width of the film 4, as shown in Figure 13. However, it is possible to prevent the leakage of the recording ink if the material of the sealing member has a substantial elasticity. Further it is possible to make the width of the sealing members 22 and 23 less than the width of the film 4, a shown in Figure 14.
A very thin sealing film 28 is interposed between a porous or other connecting member 27 which extends between the reservoir of ink within the housing member 1b and the recording ink supplying member 6. The sealing film 28 can easily be broken by pushing a protruding member 29 downwardly when required, whereby the recording ink 2 is supplied to the connecting member 27 and thus to the recording ink supplying member 6.
The connecting member 27 is preferably constituted by a cylindrical member containing a porous or fibrous material. It is also preferable to use an ink-retaining member made of porous material, sponge or felt as the recording ink guiding member 6. The porous or fibrous material operates as an absorbing material to prevent outflow of the ink. It is also possible to provide a filter (not shown) for filtering out dust or debris in the ink or a broken piece of the sealing film 28.
In the preferred embodiment of the ink jet printing system, the film 4 is fixed while the recording ink cassette 1 and thermal printing element 13 are in sliding contact with the film 4. It is possible to mount recording ink cassettes 1 on opposite sides of the thermal printing element 13 so as to permit a reciprocating record therebetween.
In the constructions described above, ink is constantly applied to a film, and it is possible to print at a constant print density without density irregularity by changing the cassette body when the ink is exhausted or the ink supplying member is damaged.

Claims

1. A printing head for transferring ink from at least one ink reservoir (2) in at least one housing (1) to at least one film member (4) having a plurality of holes or recesses (4a) therein, for application to a record medium by the action of associated dot elements of the printing head, characterised in that the housing (1) is formed integrally with or secured to a thermal printing element (13), to constitute a replaceable printing head cassette, and in that an ink transfer member (6, 27) is provided for transferring ink from the reservoir (2) to the film (4) and into the holes or recesses therein, the said ink transfer member (6, 27) being in physical contact with the ink in the reservoir (2).

2. A printing head cassette as claimed in Claim 1 characterised in that the or each film member (4) slidably engages the respective ink transfer member (6).

3. A printing head cassette as claimed in Claim 1 or 2 characterised in that the or a said housing (1) has a film supporting member (3) mounted thereon, the film supporting member (3) having recess portions (5) for guiding the, or the respective, film member (4).

4. A printing head cassette as claimed in Claim 3, characterised in that a cap member (8) is detachably mounted on the or the respective film supporting member (3) so as to cover the outer surface thereof, the cap member (8) having a slit portion (8a) for guiding the film member (4).

5. A printing head cassette as claimed in any preceding claim, characterised in that the or each housing (1) is provided with a pair of ink transfer members (6) which are disposed on opposite sides of the film member (4), each ink transfer member (6) having a curved portion (6a) to guide the film member (4) towards a contact portion (6b) of the ink transfer member (6).

6. A printing head cassette as claimed in any preceding Claim characterised in that the or each housing (1) is provided with a detachable valve member (7) for introducing ink into the housing (1).

7. A printing head cassette as claimed in any preceding Claim characterised in that the or each housing (1) is provided externally with a mounting recess portion (11) for detachably securing the housing (1) to another member (9).

8. A printing head cassette as claimed in any preceding Claim, characterised in that the thermal printing element (13) is disposed between two said housings (1).

9. A printing head cassette as claimed in any preceding Claim, characterised in that the or each thermal printing element (13) is provided with a plurality of heating dot elements (13a).

10. A printing head cassette as claimed in any preceding Claim, characterised in that there are a plurality of film members (4a, 4b, 4c, 4_d) and respective thermal printing elements (13) for printing a plurality of different colours.

11. A printing head cassette as claimed in any of Claims 1-9 characterised in that the or each film member (4) passes through a sealed space (26) which is supplied with ink by a said ink transfer member (6).

12. A printing head cassette as claimed in Claim 11, characterised in that the sealed space (26) is disposed between the housing (1) and a member (24) which is resiliently urged towards the housing (1), the sealed space (26) being sealed by sealing members (22, 23) which engage opposite sides of the film member (4).

13. A printing head cassette as claimed in any preceding Claim, characterised in that the or each ink transfer member (6) is connected to an ink reservoir by way of a frangible member (28), means (29) being provided for breaking the frangible member (28) to enable ink to pass from the ink reservoir to the ink transfer member (6).