EP0783972B1 - Ink tank integrated with franking head - Google Patents

Description

Field of technique and prior art

The present invention relates exclusively to the field of mail processing and concerns an ink tank for a module integrated in a removable machine head franking and particularly suitable for the transport of this head, this ink tank being defined in the preamble of claim 1.

Proper operation of a machine printing module to frank, in particular inkjet, supposes a total absence of any trace of air inside the ink supply duct of this module, during or outside an operating phase, and that the head whether or not mounted on the base of the franking machine.

Definition and object of the invention

An object of the invention is to provide an ink tank which can be handled and transported without having the aforementioned drawbacks. A another goal is to provide a relatively simple tank structure and can be easily integrated into a print head.

These aims are achieved by an ink tank intended to supply a printing module of a franking machine print head, the tank being integrated into this print head and comprising a means of intermediate storage to store a main volume of ink determined having a central area of symmetry S, a means for bringing ink to the intermediate storage means from an ink reserve located in a base of the franking machine, and a suction means to collect the ink from the intermediate storage medium and bring it up to the printing module, characterized in that it further comprises a means for defining a free surface of the ink remote from said zone of symmetry and in that the suction means enters the means of intermediate storage up to the vicinity of said central area of symmetry, so that the suction medium remains constantly immersed in the ink volume regardless of the position of the reservoir in space.

By this structure, it is possible to handle and transport the tank without risk of seeing the print module unusable for the impression of monetary values due to the presence of air bubbles in the ink. Indeed, the intermediate storage means is constantly filled to a minimum level and the ink suction area which is located closest to a central area of symmetry of this storage means can stay submerged regardless of the tank position.

The means for defining the free surface of the ink may consist of a overflow line which drains excess ink from the supply in an overflow cavity of this tank or even simply in a means intended to ensure at all times a minimum level of ink in the intermediate storage medium independently of the ink taken by the printing module.

The integrated ink tank according to the invention further comprises a vent pipe to selectively maintain pressure atmospheric means of intermediate storage.

Preferably, the intermediate storage means has a general cylindrical shape in the axis of revolution of which are arranged two opposite re-entrant and non-adjoining parts defining between they said central area of symmetry. One of these re-entrant parts includes the suction means. Advantageously, these re-entrant parts have external frustoconical or spherical shapes to avoid the attachment of micro-air bubbles.

The suction means can be selectively closed by a device shutter, preferably disc, which guarantees a cut optimal ink supply. It also includes a strainer for prevent any foreign objects from being sucked into the print module.

The present invention also relates to any print head of franking machine comprising an integrated ink tank as described previously.

Brief description of the drawings

• la figure 1 est une vue schématique d'un réservoir d'encre selon l'invention associé à un module d'impression à jet d'encre,
• les figures 2, 3 et 4 sont des vues en perspective selon trois orientations différentes du réservoir de la figure 1 avec des parties arrachées, - la figure 5 est une vue en perspective du réservoir avec son conduit d'alimentation obturé, et
• les figures 6, 7, 8 et 9 représentent schématiquement le réservoir selon quatre inclinaisons différentes.

Other characteristics and advantages of the present invention will emerge more clearly from the following description, given for information, with reference to the appended drawings, in which:

• FIG. 1 is a schematic view of an ink tank according to the invention associated with an inkjet printing module,
• FIGS. 2, 3 and 4 are perspective views according to three different orientations of the reservoir of FIG. 1 with parts cut away, - FIG. 5 is a perspective view of the reservoir with its supply conduit closed, and
• Figures 6, 7, 8 and 9 schematically represent the tank according to four different inclinations.

Detailed description of a preferred embodiment

Figure 1 shows part of a removable jet print head 1 ink from a franking machine incorporating an ink tank 2 according to the invention and a printing module 3 connected to this reservoir by a flexible ink supply 4. The reservoir is itself supplied from a ink reserve 5 located in a base 6 of the franking machine and which ink can be pumped continuously or on demand by control means 7.

The structure of this tank is shown in more detail in the figures 2 to 5 which present this reservoir in perspective according to several orientations different and with parts torn off to reveal its structure internal.

The ink tank 2 essentially comprises a tank 10 forming a means of intermediate storage of the ink between the reserve and the module printing, containing a determined main volume of ink 12, and closed by a cover 14. A means formed by an inlet duct 16 for bring the ink from the reserve and a suction means formed by a outlet conduit 18 to which the hose 4 is connected to power the print module are connected to this tank (this conduit can be single or multiple depending on the number of nozzles to be supplied). The conduit of outlet is provided at its entrance with a wall pierced with holes, such as a strainer 20, to prevent the suction of foreign bodies to the ejection nozzles. A overflow conduit 22 is further provided for discharging excess ink in an overflow cavity 24. The residual volume of the tank above ink level is maintained at atmospheric pressure through a conduit 26 venting. Each of the preceding conduits is provided with a sealing device: the device 28 for sealing the inlet duct, the device 30 for closing the outlet duct, device 32 for closing of the overflow pipe, and the device 34 for closing the delivery pipe outdoors. Of course, each of these shutter devices is controlled by a specific control mechanism, for example the control mechanism 36 for closing the shutter device print module supply duct. For reasons of simplification of the drawings, the other shutter mechanisms are not represented but those skilled in the art can easily determine the means allowing their realization.

Figures 2 and 5 illustrate the two positions of the device obturation 26 of the supply duct 18. This device which must provide optimal shutdown of the ink supply to the print module is preferably consisting of a disc shutter.

The positions of the shutter devices, open or closed, which vary depending on whether or not the print head is mounted in the base of the franking machine, cause a different operation of the tank. When the head 1 is in place on the base 6, and in an ejection mode ink through the nozzles, ink 38 is pumped from reserve 5 by means 7 and reaches tank 10 of tank 2 through the conduit inlet 16, the shutter device 28 is in an open state. She floods the internal volume 12 of this tank to a corresponding level to the overflow pipe 22, the closure device 32 of this pipe being in an open state (note that the definition of a minimum level ink into the tank through the overflow conduit-cavity assembly can also be achieved by judicious control of the control means 7). The closure device 34 of the vent pipe is also placed in an open state to keep the tank under pressure atmospheric. The shutter device 30 being of course open, the ink is then sucked through the outlet conduit 18 to be supplied to the different ejection nozzles. Apart from this ejection mode, the different shutter devices are closed by their respective control, the control mechanism 36 of the starting duct 18, however, being engaged before the others.

During the transport phase of the print head, after its removal from the base of the franking machine, the configuration of the tank is such that the strainer 20 at the inlet of the outlet conduit 18 for the supply of ink from the print module remains constantly submerged, and what whatever the position of the head during this transport. Figures 6 to 9 which show the tank with four different slopes, respectively 15 °, 45 °, 75 ° and 90 ° relative to an initial vertical position illustrate indeed this essential feature of the invention. So it can be noted that the free surface of the ink 40 is always above the suction zone of the ink that is located closest to a central area of volume symmetry main ink 12. To do this, the tank has a bottom in the form of dome or "bottleneck" 42 and the outlet conduit 18 enters the interior of this tank over a sufficient distance to reach the near the central area of symmetry, facing the top of the dome. Of more, the overflow conduit 22 which defines the free surface of the ink is placed sufficiently above this central area.

Advantageously, the closure device 30 and the dome 42 have frustoconical or spherical external shapes to avoid the attachment of any micro air bubbles.

Claims (10)

1. An ink reservoir for feeding a print module of a print head of a postage meter, the reservoir being integrated in said print head (1) and including intermediate storage means (10) for containing a determined main volume of ink (12) having a central zone of symmetry (S), means (16) for bringing the ink to the intermediate storage means from an ink supply (5) situated in a base (6) of the postage meter, and suction means (18) for taking ink from the intermediate storage means and feeding it to the print module (3), characterized in that it further comprises means (22, 24) for defining a free surface of the ink (40) at a distance from said zone of symmetry, and in that the suction means (18) penetrates into the intermediate storage means (10) in the vicinity of said central zone of symmetry in such a manner that the suction means remains continuously immersed in the volume of ink whatever the inclination of the reservoir.
2. An integrated ink reservoir according to claim 1, characterized in that said means for defining the free surface of the ink includes an overflow duct (22) that conveys excess ink feed from the reservoir (5) to an overflow cavity (24) of said reservoir.
3. An integrated ink reservoir according to claim 1, characterized in that said means for defining the free surface of the ink includes means (7) designed to guarantee at all times a minimum level of ink within the intermediate storage means (10) independently of the ink taken by the print module.
4. An integrated ink reservoir according to claim 1, characterized in that it further includes a duct (26) for connection to the atmosphere to selectively maintain the intermediate storage means (10) at atmospheric pressure.
5. An integrated ink reservoir according to claim 1, characterized in that said intermediate storage means is generally cylindrical in shape and has two opposite and non-touching reentrant portions disposed on its axis of revolution, defining between them said central zone of symmetry.
6. An integrated ink reservoir according to claim 5, characterized in that one of said reentrant portions includes the suction means (18).
7. An integrated ink reservoir according to claim 5, characterized in that said reentrant portions include spherical or frustoconical outside shapes to avoid catching microbubbles of air.
8. An integrated ink reservoir according to claim 1, characterized in that said suction means may be selectively closed by a shutter device, preferably including a disk (30).
9. An integrated ink reservoir according to claim 1, characterized in that said suction means further includes a strainer (20) for preventing any foreign bodies being sucked towards the print module (3).
10. A print head for a postage meter including an integrated ink reservoir according to any one of claims 1 to 9.

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