EP1219439A1 - Ink jet print head - Google Patents

Abstract

Inkjet print head (1) has an ink chamber (4) with outlet holes (14) that are closed using moving closing bodies (20). The closing bodies are lifted axially from their outlet openings using a traction element (22). The latter is sealed by a seal (36) where it enters the ink chamber. The seal completely encloses the traction element and forms the closing body for the opening in its shut position.

Description

a) einer in einem Gehäuse angeordneten, mit Tinte unter Überdruck befüllbaren Tintenkammer, in der in einer Frontwand Austrittsöffnungen angeordnet sind,

b) jeweils an einer Innenseite der Frontwand anliegenden und jeweils eine Austrittsöffnung verschliessende, in einer Längsrichtung der zugehörigen Austrittsöffnungen bewegbaren Schliesskörpern,

c) Zugelementen, die jeweils mit einem Schliesskörper verbunden sind und sich koaxial zur Längsrichtung der jeweils zugeordneten Austrittsöffnung und jeweils durch eine in einer Rückwand der Tintenkammer angeordnete Betätigungsöffnung hindurch erstrecken,

d) Führungsrohren, in denen die Zugelemente zumindest teilweise geführt sind,

e) Zugvorrichtungen, die jeweils mit einem der Zugelemente an seinem der Tintenkammer abgewandten Ende verbunden sind, und

f) Dichtungselementen, die jeweils eine Zugvorrichtung gegenüber der Tintenkammer derart abdichten, dass ein Kontakt der Tinte mit der Zugvorrichtung verhindert wird,

   wobei die Zugelemente derart axial bewegbar sind, dass bei einer kurzzeitigen Betätigung der Zugvorrichtung der zugehörige Schliesskörper von seiner Austrittsöffnung abgehoben wird und Tinte durch die Austrittsöffnung nach aussen gelangt.The invention relates to an inkjet write head

a) an ink chamber which is arranged in a housing and can be filled with ink under excess pressure and in which outlet openings are arranged in a front wall,

b) in each case on an inner side of the front wall and each closing an outlet opening, movable in a longitudinal direction of the associated outlet openings,

c) tension elements which are each connected to a closing body and extend coaxially to the longitudinal direction of the respectively assigned outlet opening and in each case through an actuating opening arranged in a rear wall of the ink chamber,

d) guide tubes in which the tension elements are at least partially guided,

e) traction devices, each connected to one of the traction elements at its end facing away from the ink chamber, and

f) sealing elements, each of which seals a pulling device from the ink chamber in such a way that contact of the ink with the pulling device is prevented,

the traction elements being axially movable in such a way that when the pulling device is briefly actuated, the associated closing body is lifted from its outlet opening and ink reaches the outside through the outlet opening.

Such inkjet printheads are used in particular in matrix printers used and are for example from EP 0 445 137 B1 and DE 36 25 067 A1 known.

A print head of a matrix printer is characterized in that it has a Large number of closely located, movable locking bodies has closed expression openings or outlet openings. Under a matrix becomes a two-dimensional or a one-dimensional arrangement understood by several outlet openings.

The aforementioned ink jet printheads are used in particular as printheads used for marking devices with which labeling on objects, for example packs is applied. The outlet openings the printhead by lifting the closing body briefly released so that ink under pressure on the printable Surface can be brought. For this every closing body assigned pulling elements by means of the controllable pulling device actuates that the desired labeling on the surface to be printed arises.

For an appealing or exact print image it is a prerequisite that the individual outlet openings with a minimum distance from each other are. This is complicated by the fact that the pulling devices, usually Electromagnets have dimensions such that these not as close together as the outlet openings can. Therefore, between the closing bodies and the associated Traction devices arranged traction elements of such a length that the Traction devices can be arranged fanned out side by side. The Drive movements of the pulling devices are based on the pulling elements transmit the closing body, the tension elements for example as Pull ropes or wires or can also be designed as pull rods.

Since the ink in the ink chamber is under pressure, it is imperative necessary pressure-tight between the pulling devices and the ink chamber Provide seals.

In EP 0 445 137 B1 there are sealing elements to protect the pulling devices disclosed, each outside the ink chamber, between one Actuating opening and the associated tie rod are arranged. As Actuating opening are those openings through which the Pulling element is led out of the housing of the ink chamber. This So-called tie rod seals are in the axial direction of as tie rods executed tension elements deformable and both with the actuation opening as well as firmly connected to the pull rod. The tie rod seals are frustoconical, with the further end at Edge of the actuating opening is attached sealingly and the narrower end of the Grips tightly around the tie rod. Ink can thus pass through the actuation openings through into the spaces defined by the tie rod seals reach. The ink is thus in contact with moving parts (Pull bar). This is disadvantageous because ink often crystallizes out over time or components of the ink are excreted or deposited.

If it is not used temporarily, it can also dry out the Ink come. Mechanical movements can be caused by such deposits or influenced by the dried ink and possibly be affected. In addition, there is an exchange of the tie rod seals is only possible with relatively great effort.

The sealing element disclosed in DE 36 25 067 A1 are also outside of the ink chamber, in which oppose the ink chamber End area of guide tubes for the tension elements, here wire ropes, arranged. The sealing elements are preferably in the vicinity of the respective one Traction devices arranged and for example as opposite the traction device tight bellows. Thus, the pressure increases standing ink from the ink chamber through the guide tubes to designed as a bellows seal. Even with this construction the traction rope to be moved is surrounded by ink, which is why here too caused by crystallization or other types of deposits May result in impairments for the mechanically movable parts. The maintenance and repair, especially the exchange of Seals are also difficult and time consuming.

The object of the present invention is a generic Improve inkjet printhead to be an impairment of the mechanical movements, especially in the area the traction elements and / or the traction device is minimized as far as possible. The inkjet print head should have the longest possible technical service life have and the manufacture and maintenance as simple and be inexpensive to carry out.

According to the invention, this is achieved in that one sealing element in each case the area of a tension element protruding into the ink chamber completely encloses and the associated actuation opening seals against the ink chamber, the sealing element is designed such that it has the closing body with its free end forms for the outlet opening.

Because the sealing elements are arranged within the ink chamber and the areas of the tension elements protruding into the ink chamber enclose tightly, prevents ink with moving Sharing comes into contact. The described, by crystallization or other deposits related problems or limitations moving parts are thus effectively avoided.

The arrangement of the sealing elements within the ink chamber causes advantageously that the ink pressure or that with about 1 bar under pressure standing ink, has a sealing effect on the sealing elements, since these pressed against the guide tubes or in the direction of the actuation openings become. Thus, in contrast to the known embodiments the pressure inside the ink chamber with constant or even increasing sealing effect of the sealing elements also increased significantly be (for example up to 10 bar). A high pressure is among other things also preferred because it is in the types of inks used often highly viscous liquids.

In an advantageous embodiment, the sealing elements can that are already built into the inkjet print head, as pull rods executed traction elements are plugged on, so that an exchange defective Sealing elements can be done quickly and easily. This is special then advantageous if the front wall of the ink chamber from the outside is removable.

To ensure a simplified seal, extend in one particularly advantageous embodiment, the guide tubes for the Pull rods through the actuation openings into the ink chamber, so that the sealing elements both on the tie rods and on the guide tubes can be pushed on. This also guarantees a complete sealing if the sealing elements are not on the inside the wall of the ink chamber having the actuating openings issue.

The sealing elements can advantageously on their inner sides at least one, preferably two annular, transverse to the longitudinal axis of the Sealing elements have running beads (O-rings) on the guide tubes or tie rods. The sealing effect of the sealing elements is thereby further improved.

The sealing elements can also constrictions or formations have, each to an annular, opposite the inner surfaces of the Protruding sealing elements that run transversely to the longitudinal axis Lead to narrowing. On the one hand, the sealing elements are on the Tension rods are better held, on the other hand, when pressing the Drawbars a defined expansion of the sealing elements. These wide itself between the constriction and the the end facing the actuation opening crowned.

In principle, the sealing elements fulfill two independent of each other Tasks. The section facing the associated actuation opening effects the sealing of the ink chamber and that of the associated one Section facing outlet opening effects the closing function. Characterized in that the closing body itself formed by the sealing elements and because the sealing elements are made of an elastic, rubber-like Material, the sealing of the outlet openings is guaranteed and it can be higher in terms of the length of the sealing elements Manufacturing tolerances are accepted. For a complete Sealing the ink chamber from the actuation openings is sufficient due to the bag-like design of the sealing elements only the sealing sections enclosing the guide tube. Moreover the closing bodies are firmly attached to the tension elements due to the one-piece production held and are still quick and easy to assemble or disassemble.

In a particularly advantageous embodiment variant, the sealing elements have starting from the outlet openings a truncated cone Section that merges into an approximately cylindrical section, wherein the narrower end faces of the frustoconical section each have the outlet openings closure. The conical design of the sealing elements causes the ink to flow better towards the outlet openings, which in turn results in less swirling of the ink Has. Thus, a higher possible printing speed and a more precise one Print image can be achieved.

Furthermore, it has been shown that it is advantageous if the guide tubes protrude outside the ink chamber opposite the outer wall of the housing. The above section has the advantage that the inevitably outside dirt and deposits arising in the ink chamber, that preferentially deposit on the outer wall of the housing, only difficult can penetrate into the actuation openings.

The seal of the ink chamber against penetrating from the outside Soiling can also be improved if the outside sections of the guide tubes arranged in the ink chamber additional sealants are closed. For example, as Capillary hoses made sealing elements on the above sections of the guide tubes are pushed on so that they also tightly enclose the drawbar.

Lubrication of the tension elements can also be achieved by that the openings of the guide tubes arranged outside the ink chamber also be charged with an oil.

The ink jet print head according to the invention has an extremely small Susceptibility to faults because, on the one hand, the ink chamber completely against the outside Dirt is sealed and secondly the ink is not in can reach the area of the moving parts. The inkjet print head also builds very small and can be maintained and repaired quickly and efficiently, since the sealing elements after opening the ink chamber can be easily exchanged.

Further advantageous design features of the object according to the invention are in the description of the figures and in the dependent claims contain.

Figur 1:

eine Ausschnittsvergrösserung eines erfindungsgemässen Tintenstrahl-Schreibkopfes im Schnitt, wobei der Übersicht halber die Systemkomponenten Zugstange, Führungsrohr und Dichtungselement nur einmal dargestellt sind,

Figur 2:

eine Ausschnittsvergrösserung einer weiteren Ausführungsvariante des erfindungsgemässen Tintenstrahl-Schreibkopfes im Schnitt gemäß Fig. 1.

Figur 3:

eine Ausschnittsvergrösserung einer weiteren Ausführungsvariante eines erfindungsgemässen Dichtungselementes

The invention is explained in more detail with reference to the following figures. The exemplary embodiments shown are not to be understood as restrictive. Show it:

Figure 1:

2 shows an enlarged detail of an ink jet write head according to the invention, with the system components pull rod, guide tube and sealing element being shown only once for the sake of clarity,

Figure 2:

2 shows an enlarged detail of a further embodiment variant of the inkjet write head according to the invention in section according to FIG. 1.

Figure 3:

an enlarged detail of a further embodiment of a sealing element according to the invention

An inkjet write head 1 according to the invention has one in a housing 2 arranged ink chamber 4. The essentially cubic Ink chamber 4 is through a front wall 6, side walls 8 and a rear wall 10 limited. The front wall 6 is preferably detachable from the housing 2 connected and via a preferably designed as an O-ring 12 Sealed gasket. Outlet openings 14 are arranged in the front wall 6, the nozzle 16 for ink emerging during the printing process Act. The term ink 16 means all for labeling and marking suitable substances such as lacquers, acids, etc. The Area surrounding outlet openings 14 is in the direction of the ink chamber 4 curved, the outlet openings 14 in the center of the curvature 18 are arranged. The curvature 18 has two advantageous advantages Effect. On the one hand, the outlet openings 14 are in the direction of their Longitudinal axes X-X lengthened, which ensures better guidance of the exiting Ink drop is reached, which in turn requires a more precise print image. On the other hand, they are directed towards the ink chamber 4 Arches 18 for better sealing of the outlet openings 14 by closing bodies 20 resting on the outlet openings 14 are the surfaces of the closing bodies 20 which abut the outlet openings 14 essentially executed plan. Basically, the at the outlet openings 14 adjacent surfaces of the closing body 20 are also curved be executed. It is also possible to have both contact surfaces Closing body 20 and the area around the outlet openings 14), plan to execute.

Each closing body 20 is a pull element 22, preferably a pull rod assigned, the coaxial to the longitudinal axis X-X of the respective outlet opening 14 runs. Instead of pull rods, it is also possible to pull cables or to use similar tension elements. The tension elements 22 extend through actuating openings 24 arranged in the rear wall 10 and are connected to pulling devices, not shown. advantageously, can the tension elements 22 have a diameter of, for example Have 1 to 1.2 mm and be designed as a hollow pull tube to to achieve a material and thus a weight reduction. As Traction devices are particularly suitable for electromagnets Achieve stroke of the closing body 20 of, for example, about 0.2 mm.

According to the invention are in the actuating openings 24 coaxial with the tension elements 22 extending guide tubes 26 arranged, both a ink chamber portion 28 protruding into the ink chamber 4 and one projecting outside the ink chamber 4 relative to the housing 2 Have outer section 30. The tension elements 22 are in the guide tubes 26 out. The ink 16 passes through a bore 32 from a Ink container, not shown, the connection end 34 with the in one of the side walls 8 arranged bore 32 is connected under Overpressure in the ink chamber 4.

According to the invention, the actuation openings 24 are opposite those in FIG Ink chamber 4 located ink 16 each through a sealing element 36 sealed. The sealing elements 36 advantageously enclose them the areas of the tension elements 22 projecting into the ink chamber 4 the embodiment shown enclose the sealing elements 36 not only the tension elements 22, but also the ink chamber sections 28 of the guide tubes 26, and thus seal the actuation openings 24 off safely.

Advantageously, the sealing elements 36 can easily on the tension elements 22 and guide tubes 26 or their ink chamber sections 28 be postponed. To ensure a secure fit on the tension elements 22 or to ensure the guide tubes 26, the tension elements 22 one in each of their end regions facing the outlet openings 14 annular groove 38 which extends transversely to the longitudinal axis X-X and in which the respective Sealing element 36 comes to rest.

A particular advantage of the sealing elements according to the invention 36 lies in the fact that it itself acts directly as a closing body 20 act, since they consist of an elastic rubber-like material Sealing elements 36 bear against the outlet openings 14. additional Closing body elements are omitted.

Due to the different requirements for the ink 16 are also for the manufacture of the sealing elements 36 possible types of material adjust accordingly.

Figure 1 shows a first embodiment of the sealing element according to the invention 36. This is essentially cylindrical and has a thinned wall section 40 in the middle. This section of wall 40 facilitates the deformation of the sealing element 36 when the pulling device is actuated or when the Closing body 20 from the outlet opening 14. The wall section 40 can then preferably deform inwards.

Figure 2 shows an advantageous further embodiment of the inventive Sealing element 36. This indicates on the basis of the area adjacent to the outlet opening 14 has a frustoconical section 42, which in a substantially cylindrical portion 44th transforms. The design of the frustoconical section 44 has Consequence that the pressurized ink towards the outlet opening 14 is steered. This enables high printing speeds and realize an exact print image. The overpressure in the ink chamber is, for example, 1 bar, which also minimizes swirling of the ink 16 become.

Furthermore, it has also proven to be advantageous if the sealing element 36 in the area between the outlet opening 14 and near the end of the ink chamber portion 28 of the guide tube 26 is a constriction 46 instead of the thinned wall section 40 shown in FIG. 1 having. The constriction 46 has the effect that when the pulling elements are actuated 22 a defined expansion of the constriction 46 and that end of the sealing element 36 which faces the actuating opening 24 limited area results. Through this relatively long section, a gentle deformation of the sealing element 36 is achieved, which in turn the durability of the sealing element 36 is significantly extended.

The technical life of the inkjet write head 1 can be additional be prolonged by the penetration of dirt particles or deposits through the actuating openings 24 in the area of Tension elements 22 is avoided by closing means. This can essentially be can be achieved in that the outer sections 30 of the guide tubes 26 can also be closed with sealants 50. This are advantageously tubular and consist of an elastic Material, preferably the material from which the sealing elements 36 are made. The sealing means 50, in particular capillary tubes, are on the tension elements 22 or on the outer sections of the guide tubes 26 pushed on and enclose them. Because of their elasticity the sealing means 50 hinder the movement of the tension elements 22 Not.

Furthermore, the actuation openings 24 or the corresponding ends the guide tubes 26 are charged with an oil 48 for lubrication to reach the tension elements 20.

As shown in Fig. 3, the protrude into the ink chamber 4 Ends of the guide tubes 26 in a further embodiment variant according to the invention flared ends 52. These are in the postponed Sealing elements 36 in areas of the thinned wall sections 40 and expand them accordingly. This variant too ensures a defined, directed in the direction of expansion Deformation of the sealing elements 36 when the tension elements 22 are actuated. In addition, the sealing elements 36 on the guide tubes 26 are better held. Furthermore, the sealing elements 36 can likewise, as in FIG. 3 shown, at least one, preferably two, on the inside have annular webs 54 (O-rings) running transversely to the longitudinal axis X-X, which abut the guide tubes 26 or the tension elements 22. The sealing effect of the sealing elements is due to the small surface area 36 or the sealant 50 additionally increased. Such ridges 54 can also have the sealing means 50.

The invention is not based on the illustrated and described exemplary embodiments limited, but also includes all within the meaning of the invention equivalent designs.

Are preferably between the outer sections of the guide tubes and the traction elements each arranged sealing means, both the outer sections as well as enclose the tie rod.

Preferred are at the ends of the actuating openings facing away from the ink chamber Locking means arranged.

Claims (10)

Inkjet print head (1) with a) an ink chamber (4) which is arranged in a housing (2) and can be filled with ink (16) under excess pressure and in which outlet openings (14) are arranged in a front wall (6), b) in each case on an inside of the front wall (6) and each closing an outlet opening (14), closing bodies (20) movable in a longitudinal direction (XX) of the associated outlet openings (14), g) tension elements (22), which are each connected to a closing body (20) and are coaxial to the longitudinal direction (XX) of the respectively assigned outlet opening (14) and each through an actuating opening arranged in a rear wall (10) of the ink chamber (4) 24) extend through h) guide tubes (26) in which the tension elements (22) are at least partially guided, i) traction devices, each connected to one of the traction elements (22) at its end facing away from the ink chamber (4), and j) sealing elements (36), each sealing a pulling device with respect to the ink chamber (4) in such a way that contact of the ink (16) with the pulling device is prevented, wherein the pulling elements (22) are axially movable in such a way that when the pulling device is briefly actuated, the associated closing body (20) is lifted from its outlet opening (14) and ink (16) passes outside through the outlet opening (14),
characterized in that in each case one sealing element (36) completely surrounds the area of a pulling element (22) projecting into the ink chamber (4) and seals the associated actuating opening (24) with respect to the ink chamber (4), the sealing element (36) being such It is designed that it forms the closing body (20) for the outlet opening (14) with its free end. The ink jet write head (1) according to claim 1, characterized in that the guide tubes (26) have an ink chamber section (28) projecting into the ink chamber (4) and other end have an outer section (30) projecting out of the housing (2). Inkjet write head (1) according to claim 2, characterized in that in each case one sealing element (36) in each case sealingly encloses an ink chamber section (28) of a guide tube (26). Inkjet write head (1) according to one of Claims 1 to 3, characterized in that the sealing elements (36) have a frustoconical section (42), the narrower end of which seals the outlet opening (14) respectively associated with the sealing element (36) and the other End merges into an approximately circular-cylindrical section (44). Inkjet write head (1) according to one of Claims 1 to 4, characterized in that the tension elements (22) are designed as hollow tension tubes. Inkjet write head (1) according to one of Claims 1 to 5, characterized in that the pull rod (23) has a groove (38) running transversely to the longitudinal axis (XX) in its end region facing the respective outlet opening (14). Inkjet write head (1) according to one of Claims 1 to 6, characterized in that the sealing elements (36) between the ends of the respectively assigned ink chamber sections (28) of the guide tubes (26) and the respectively assigned outlet openings (14) have at least one constriction ( 46) which is arranged such that the sealing elements (36) deform into a spherical shape between their constriction (46) and their end facing the actuating opening (14) when the pulling elements (22) are actuated. Inkjet write head (1) according to one of claims 1 to 7, characterized in that the front wall (6) is detachably connected to the housing (2). Inkjet write head (1) according to one of Claims 1 to 8, characterized in that within the ink chamber (4) the respective area surrounding an outlet opening (14) is designed as a curvature (18) curved in the direction of the ink chamber (4), wherein the associated outlet opening (14) is arranged in the center of the arch (18) and the surface of the associated closing body (20) closing the outlet opening (14) is made flat. Inkjet write head (1) according to one of Claims 1 to 9, characterized in that the sealing elements (36) have on their inner sides at least one annular bead which extends transversely to the longitudinal axis (XX) and projects from the inner surface and which is attached to the associated ink chamber section (28 ) of the guide tube (26).

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