DD228494A1 - OVERPRESSURE DEVICE FOR INK JET PRINTS - Google Patents

Abstract

It is the object of the invention to provide an overpressure device which can be produced with little technical outlay, which can be actuated by machine, the effect of which can be exactly defined, and thus protects the inkjet printhead against damage. Geloest this task is essentially characterized in that the Tintenvorratsbehaelter and the ink jet print head an elastic ink tube bubble is interposed, which is housed in a housing and acts on a forming die, which, in the program-controlled print carriage movement outside of the write line area, defined aufläue on a frame-fixed pressure pin - or in that the ink supply system arranged in the channel body has a gewoelbte membrane which can be acted upon by a wagengestellfesten rocker arm, which is in operative connection with a machine frame fixed pivot lever. Fig. 1

Description

VEB Robotron Optima - 670 -

D. Moller / J. Michel

Title of the invention

"Overprinting device for inkjet printing units"

Field of application of the invention

The invention relates to a top pressure device for ink jet printing units, which operate in the negative pressure process with discontinuous droplet generation and whose ink supply systems have an elastically deformable chamber.

Characteristic of the known technical solutions

Top pressure devices of the above-mentioned type have become generally known through their printed publications, in particular in the patent literature, and by their obvious use in products of modern writing technology. They exist in different technical versions and with differentiated functionality and have in common that their operation must be done manually.

Thus, in the "Siemens magazine * Year 51, Issue 4/1977 pp 219-221 an overpressure device is described, the ink reservoir consists of a pot-like body, which is enclosed by an elastic plastic skin and in which a molding is arranged, the Upon actuation of this device, the pressure in the ink supply system is increased, thereby effecting the flushing of the ink jet nozzles.

In principle, similar solutions in which the pressure in the ink supply system is temporarily increased by means of manually operated plunger or punch, are described in the invention descriptions DE-OS 2 460 573, DE-AS 2 543 452 and DE-AS 2 610 518 and z. B. in the product PT 80 of the Fa. Siemens obviously used.

With the invention description WP B41Ü / 2 622 497 another, also manually operated solution has been proposed. In this description, the possibility of mechanical actuation of the upper pressure device is pointed out, but without providing the necessary instructions for action.

All these known top pressure devices have the disadvantage that their manual operation is dependent on the subjective behavior of the respective operating force and thus dysfunctional misbehavior en can not be excluded.

Object of the invention

The invention has the aim of counteracting the mentioned disadvantages of the known solutions and to provide an overhead printing device for inkjet printing units which can be produced with low technological expenditure, which can be actuated by a machine and whose effect can be exactly defined.

Being the invention

The invention has therefore been based on the object / to provide a .Oberdruckeinrichtung available that can be actuated by taking advantage of the pressure carriage movement, the actuation time and the intensity of which is controllable and can be produced by simple means.

This object has been achieved with the technical means described in the characterizing part of the invention claim and explained in more detail in two embodiments.

Execution at play

Two embodiments of the invention will be explained in more detail with reference to the drawing, which is limited to the perspective view of the fiction, essential parts of the upper printing device

 It means:

1 is a perspective view of the Überdruckeinricht un g,

Fig. 2 is a perspective sectional view of a housing in which four tube bubbles with different

store colored writing fluid,

Fig. 3 is a diagrammatic side view of the second embodiment of the invention.

In the machine frame (1) rotatably supports the platen (2) and on the frame-fixed guide shaft (3) of the print carriage (4) ν parallel to the platen (2) displaceable, arranged. The movement of the print carriage (4) is carried out, key-operated or program-controlled, by the drive (5), which is preferably a stepping motor.

On the carriage (4) of the inkjet print head (6) is attached ,, which is supplied from the ink reservoir (7) out of the puncture cannula (8) and the elastic tube bladder (9) with writing fluid. The tube bladder (9) is mounted in the housing (10), at the lower end of the ink return check valve (11) is arranged and on the bladder shell, a receptacle (10.1) is formed, in which the forming die (12) by the return spring (12.1) is slightly biased, is slidably arranged. Achsengleich with the forming die (12) into the machine frame (1) a pressure pin (13) is arranged, which is slidably mounted, an adjustable stop (13.1) for 3ustage the "start of printing and an adjustable spring biasing plate (13.1), with which the compression spring With the defined pretension of the compression spring (13.2), a maximum overpressure is generated in the transition region (B) and in the pressure region (C) independently of the carriage speed in the entire channel system of the printhead Furthermore, a limit switch (14) is arranged on the machine frame (1), which can be designed as a microswitch or as a light barrier and which is connected to the one on the printing carriage (4). attached actuation

member (15) cooperates. ^e

The mode of operation of the overpressure device according to the invention is the following

In the writing line area A, the switching step-controlled printing carriage advance and the drawing carriage return are motor-driven in a known manner. By the operation of the switch (16), which can be done manually or programmatically, a subroutine is called in the machine control (17), according to which the drive (5) the print carriage (4) over the limitation of the write line area (A) out, away - and speed-controlled, by the over-

passage area (B) into the printing area (C) and back to the boundary of the write line area (A) is transported back. In the transition region (B), the neck of the mold tem pe Is (12) runs as far as the pressure pin (13) · until all bearing clearances are eliminated. The forming punch (12) / which is now supported on the one hand on the hose bladder (9) pushes with the carriage movement on the other hand, the pressure pin (13) so that the stop disc (13.1) from the machine frame (1) stands out. Thereby, the bias of the compression spring (13.2) on the pressure pin (13) and the forming die (12) for overpressure generation on the tube bladder (9) transmitted.

In the pressure range (C), the compression spring (13.2) is further biased so that a spring travel reserve to realize a max. There is a flow rate for rinsing and cleaning the ink channels and ink jet nozzles. With the beginning of the overpressure in the hose bladder and thus also in the ink channels at the end of the transition region (B), the return valve (11) is closed against the ink reservoir (7).

The flow rate in the ink channels and nozzles and the associated amount of ink discharge from the ink jet nozzles depend on the difference between the pressure in the bladder (9) and the atmospheric pressure and the mold resistances in the ink channels and nozzles.

When partially added nozzles of the form of resistance is large, so that sets a small ink flow. In contrast, with clean nozzles, a large flow of ink is present. Therefore, it is advantageous to open in a manner not described here either only one or two pairs of nozzles in succession.

Corresponding to the amount of ink flowing out of the inkjet nozzles, the shaping punch (12) is tracked upon deformation of the elastic tube bladder (9).

> With the switching of the carriage movement and the carriage return to the beginning of the write line area (A) takes place the discharge of the elastic tube bladder (9) and their reversion by the subsequent flow of ink ejected during the flushing process from the ink reservoir (7). However, the reshaping of the elastic tube bladder (9) may only take place in such a way that the negative pressure which arises in the ink supply system is not greater than the capillary forces of the inkjet nozzles. For this reason, the pressure carriage movement from the pressure range (C) in the transition region (B) in the subroutine, the machine control (17) is gradually set slowly so that the recovery of the elastic tube bladder (9) can be made gradually.

For multi-color printing, z. B. four colors, the entire ink supply system (7, 8, 9, 11) is applied four times and deflected into four different inkjet nozzles or nozzle groups. The generation of the overpressure required for the rinsing process takes place in the same manner already described by the pressure of a forming punch (12) on the elastic tube bubbles (9.1-4) (Fig. 2).

In another embodiment of the invention shown in Fig. 3, the ink supply system (8, 9, 11) following the ink reservoir (7) is inserted in the ink jet print head (6) and has an outwardly bulging elastic membrane (19) forming a protective membrane (20) is upstream. As a pressure piece in the sense of the forming punch (12), the upper end of a rocker arm (21) which bears on the print carriage (4) and rests with its lower end on the wedge or curved active surface (22.1) of the pivot lever (22). The pivot lever (22) is rotatably mounted on the machine frame (1) and is held by a frame-fixed helical tension spring (23) against an adjustable stop (24).

Claims (2)

trf in training claim 1. Überdruckei nric heht for an ink jet printing unit, which operates in the negative pressure method with discontinuous droplet generation and whose on the printing car angeeangeordnetes ink supply system comprises an elastically deformable chamber and an ink Rückflußsperre, characterized - That the ink reservoir (7) and the ink jet print head (6) is interposed an elastic ink hose bladder (9) in a housing (10) superimposed, in which a tubular bladder mold adapted forming punch (12) is axially slidably inserted, - That for multi-color printing, z. B. with four colors, the four elastic tube bubbles (9) in a housing (10) store and by a forming die (12) · are deformed together, - That with the forming die (12) the same axis in the machine frame (1) a displaceable pressure pin (13) is arranged, which has an adjustable stop (13.1), an adjustable spring biasing plate (13.3) and a compression spring (13.2), - that switch-actuated a subroutine of the machine control (17) is retrievable, according to which the print carriage (4) through the carriage drive (5) over the scream bzeilen area (A) addition, by a transition region (B) through, for the defined feed of the forming punch (12 ) against the pressure pin (13) into the pressure area (C) and back to the limit of the write line area (A) fixed by the limit switch (14). 0 is portable. 2. overpressure device according to part 1 of the invention claim, characterized in that the ink supply system introduced into an inkjet print head (6) has a curved membrane (19) which can be acted upon by a carriage-mounted rocker arm (21) which is connected to the oblique active surface (22.1) of a machine frame-fixed pivoting lever (22) which can be moved against an adjustable stop (22). 24) is biased defined by a tension spring (23), is operatively connected. hl
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