Patent Application
20110209639
The present invention relates to a rotary printing machine with a printing cylinder and an ink delivery system for supplying the printing cylinder with ink with an ink chamber, which is connectable with an ink source.
Rotary printing machines, in particular letterpress printing machines, mainly have a rotatably mounted printing cylinder, a correspondingly rotatably mounted impression cylinder, a printing screen, a doctor blade and a print material feed device. The print material to be printed is transferred to the rotating impression cylinder via the feed device. The impression cylinder rotates in the opposite direction in the rotational direction of the printing cylinder so that the print material is fed between both cylinders. During this movement, the ink located in the printing cylinder is applied to the print material. For this, a non-rotating doctor blade presses the screen meshes of the printing screen filled with ink, which at least in part forms the casing of the printing cylinder, onto the print material, which is located between the oppositely rotating cylinders. After the imprint, the print material is advanced further through the impression cylinder and is then transferred to a storage area.
A screen printing machine of the aforementioned type can process different types of paper depending on the requirement. In particular, both paper in continuous webs as well as individual pages can be printed. For individual webs, a grab retainer is provided in particular, which holds the paper during guidance along the impression cylinder. A corresponding doctor blade retainer and a linearly moveable doctor blade guide, which is drawn away from the grab retainer during printing, is described in DE 199 49 099 C2.
DE 102 32 254 B4 shows an ink delivery system arranged near the doctor blade, with an ink duct and a plurality of ink release openings, wherein the ink delivery system extends parallel to the doctor blade. On the basis of DE 199 49 099 C2, the printing ink is released via a control valve depending on a respective rotational position of the printing screen.
However, these known devices are unsuitable or at least impractical for applying an even inking to a printing screen of a rotary printing machine. Rather, according to the known method, considerably more ink than necessary is applied to the inside of the rotary printing screen, wherein the relatively high excess is cleared with the doctor blade.
The object of DE 102 32 254 B4 also addresses this problem statement in that an ink delivery system connected with the ink duct and extending parallel to the doctor blade with a plurality of ink dispending openings is arranged almost and in the rotational direction in front of the doctor blade. However, the printing ink is released in a controlled manner via at least one control valve depending on the respective rotational position of the printing screen, but only punctiform via a plurality of ink release openings.
The object of the present invention is to provide an ink delivery system for rotary printing machines that take into consideration both the circumferential as well as the axial requirements of an even and economical ink supply.
This object is solved through a rotary printing machine with the characteristics of claim 1. Preferred embodiments of the invention are specified in the dependent claims.
According to the invention, a rotary screen printing machine, in particular a rotary screen printing machine, with a printing cylinder and an ink delivery system with an ink chamber is provided. The ink delivery system serves to supply ink to the printing cylinder. The ink chamber can be connected with an ink source. The invention also provides that the ink chamber has an ink discharge opening in the form of a slit, which extends mainly parallel to the printing cylinder axis and is aligned with the printing cylinder such that the ink can be discharged into it.
Ink, in particular ink for rotary printing machines, can have a plurality of processing properties. One of the important properties is the viscosity, the density and the particle size distribution of the ink pigments. Among other things, it can thus be wise to want to change the shape and size of the ink discharge opening. Thus, in an advantageous embodiment, the shape and size of the slit of the ink chamber can be changed by means of a cover plate. The cover plate can preferably be controlled and/or regulated by means of a quick tensioning means for example by means of a spindle. In particular, the cover plate can be moved into or respectively out of the ink discharge opening through the translatory movement of the spindle and thus reduce the cross-section of the ink discharge opening. Cover plates with a special design are also possible, for example with a sinusoidal or serrated contour over the length of the cover plate for a periodically changing ink distribution.
In order in particular to enable an even ink discharge over the length of the slit, the ink chamber can have flow guides. Suitable for this are for example webs or fins, which at least partially separate the ink flow in the ink chamber and/or guide or respectively steer the ink flow to areas of the ink chamber, which would be hardly or only slightly passed through without the flow guides.
In another advantageous embodiment, the ink chambers can be releasably fastened on an element of the remaining ink delivery system. For this, the ink delivery system can have at least one receptacle, which receive/s the ink chambers in the manner of an insert. A seal, in particular a silicone seal, can also be arranged between the receptacle and the insert. It is also possible that several ink chambers are also releasably fastened on one and/or if applicable several elements of the remaining ink delivery system. In another advantageous embodiment, at least one or more ink chambers can be fastened separately or in groups releasably on one and/or more elements of the remaining ink delivery system. A fastening can be designed such that the at least one ink chamber is fastened on an element of the remaining ink delivery system through quick tensioning means. In order to enable a correct or respectively a clear positioning of the releasable ink chamber, a guide, for example in the form of a tongue and groove, can be provided, which enables the exact positioning of the ink chamber relative to the remaining ink receptacle.
Furthermore, the rotary printing machine can have a pressure supply, from which the ink chambers, individually or together, are supplied. Thus, for example, each chamber can be supplied with pressure by one individual pressure supply or a pressure supply can supply several ink chambers mainly with the same pressure together by means of a supply chamber. For this, the pressure supply can also have a pump, in particular a spiral pump or a pump with a cylinder/piston arrangement. In an advantageous embodiment, the pressure supply is regulated depending on the pressures in the chambers. If the rotary printing machine has for example several same ink chambers, it can be enabled through the regulation of the pressure supply that the ink chambers are supplied with the same pressure. This is wise in particular when the boundary conditions of the ink chamber, in particular the settings of the cover plates, change over time. Thus, the regulation could for example guarantee a constant pressure demand in the chambers and/or in the pressure supply as such, even when the cover plates change the shape and/or size of the slit during the printing operation.
Moreover, it is possible that the rotary printing machine has different ink chambers, which preferably have the same pressure requirements, but in comparison to each other have different volume flow requirements. It is also possible here through a corresponding regulation to guide the pressure supply such that the pressures in the ink chambers meet the requirements, namely for example a constant pressure supply. Input parameters of a regulation of the aforementioned type can be signals of pressure, temperature and/or flow speed sensors. Output parameters of the regulation can be variables for operating devices, such as controllable valves, pressure reducers and/or the electrical voltage of motors, in particular for motors of the drive unit of the pressure supply.
The pressure supply can be controlled in another advantageous embodiment depending on the rotational position of the printing cylinder. Furthermore, a volume flow can be controlled and/or regulated from the slit depending on the rotational position of the printing cylinder preferably via at least one valve and/or cover plate. A possible input parameter of a control or a regulation can be for example the radial contour of a control disk connected with the printing cylinder and thus also rotating. The radial contour can be transferred to a controller and/or regulator through a non-rotating, radially moveable acceptor, preferably following the radial contour with rollers.
Besides the cover plate, which can change for example the shape and size of the slit, it is also possible that a volume flow to an ink chamber and thus also from the slit and/or the ink volume flow to several chambers can each be controlled or regulated by a valve.
According to the invention, a rotary printing machine, in particular a rotary screen printing machine, with a printing cylinder, its cylinder casing is made at least partially of a metallic printing screen.
These and other characteristics and advantages of the present invention are described in greater detail with reference to the attached drawings of exemplary embodiments of the present invention.
Flow guides 20, in particular webs and/or fins, are shown in
Furthermore, at least one side wall 22 of the ink chamber 3 is formed by an element of the remaining ink delivery system 2. It is also possible that both the rear side wall 22 and the front side wall 24, as also shown in
As also shown in
So that the printing screen 28 of the circumferential and axial contour of the cylinder casing surface 26 can take place in a bridging manner, it is advantageous that the printing screen 28 is braided out of metallic threads 30. The braiding of these threads 30 can take place for example crosswise in the axial and circumferential direction. Alternative and/or supplementary metal threads can for example also run diagonally or at any other angle and/or be arranged with respect to each other such that low frictional resistance results between doctor blade 5 and printing screen 28 during printing. In order to be able to resist the mechanical stress of the printing screen 28, in particular by the doctor blade 5, the printing screen is produced at least partially galvanically. In another advantageous embodiment, the printing screen 28 can be equipped with for example hexagonal holes as a type of perforated sheet.
In order to fasten in particular indirectly the printing screen 28 in a simple manner on the casing surface 26 of the printing cylinder 1, the printing screen 28 is fastened on a screen frame 32. The screen frame 32 can in turn be releasably fastened on the printing cylinder 26. In particular, the screen 28 and/or the screen frame 32 are mainly even before their fastening on the printing cylinder 26.
Furthermore, the printing screen frame 32 is preferably only bendable in the circumferential direction so that the screen frame 32 and the printing screen 28 connected with it can be adjusted to the rounding contour 34 as also shown in
In contrast to conventional printing screens, which are made of plastic for example, the preferably metallic printing screen 28 according to the invention has a considerably higher stability, in particular inherent stability. The overall stability of the printing screen 28 is also increased in that the printing screen 28 is permanently connected with the screen frame 32. Printing screens that can be fastened by means of a resistance welding process or adhesion to the screen frame 32 are particularly well suited for this. This has the particular advantage that a power transmission from the printing screen 28 to the screen frame 32, for example in the case of a load by the doctor blade 5, can take place via the mainly entire contact surface of the frame. Furthermore, the printing screen 28 is fastened on the printing cylinder 26 and/or on the screen frame 32 in a mainly stressfree manner. The screen frame 32 or respectively the printing cylinder 26 thus predetermine rather only the form of the printing screen. If the printing screen 28 is fastened on the screen frame 32, it is advantageous if the printing cylinder 26 and the screen frame 32 have position guides, for example in the manner of a tongue and groove so that the screen frame 32 is positioned as exactly as possible on the printing cylinder 26. A screw connection for positioning with the smallest possible tolerance measures is also possible. In order to generally avoid an undesired waviness of the screen, which can be brought about in particular by uneven preloading on the screen, the printing screen 28 is fastened on the printing cylinder 26 and/or on the screen frame 32 mainly without axial and/or tangential forces.
The mounting of the two ink chamber surfaces is realized through a joint 36. The use of free-moving needle or ball bearings is suggested for a preferred mounting. For one, such bearings can be purchased economically as individual parts and secondly this purchase eliminates the need for a separate production effort. Production- and manufacturing-related errors can hereby be avoided.
The opening of the ink chamber is normally controlled via the setting of the system pressure, i.e. the pressure with which the printing ink is pressurized within the ink chamber. The closing process is preferably realized in this case via at least one spring, which in the moment of unpressurized material delivery exerts a higher force and presses the two ink chamber halves against each other and thus closes them. The at least one spring is preferably designed such that the spring force is adjustable. Excess pressure is first necessary to set a preload force for the opening of the ink chamber. This causes the ink chamber to close immediately after the pressure in the material supply or respectively the ink chamber is reduced to a value below a closing pressure. The closing process already begins at the time of pressure reduction and can thus be performed comparatively quickly.
In an alternative embodiment of the ink chamber, electrically, pneumatically or hydraulically driven setting means are provided instead of the at least one spring, with which the opening and closing of the ink chamber, thus in particular the ink discharge opening, are systematically controllable. An opening and closing of the ink discharge opening is realized with a high level of accuracy in this manner.
The opening angle α of the ink chamber is decisive for the ink volume flow besides the system pressure at which the printing ink is pressurized. The opening angle determines how much ink is transferred onto the screen.
In order to exclude unfavorable printing results to the greatest extent possible, the opening angle α should be limited in the case of the constructive design of the ink chamber for the rotary screen printing. If only a discrete opening angle is possible during the opening of the ink chamber 3, the ink volume flow is still only determined by an adjustable variable, namely the system pressure in the ink chamber and/or the material storage container. It is thereby possible to change the ink volume flow without difficulty and to dose exactly the ink amount necessary for the printing process through the use of suitable, finely adjustable pressure regulating valves. In order to be able to realize a consumption-dependent, exact ink dosing, it is necessary to ensure a homogenous ink flow on the ink discharge side 4 from the ink chamber 3. To achieve this, a special design of the ink chamber 3 provides the two ink chamber inner surfaces with fins. For one, the dimensional stability of the ink chamber 3 is considerably increased through this constructive measure and, secondly, a guided and controllable ink outflow is ensured through the use of fins.
In the known technical solutions, the opening process of the ink chamber and thus the opening angle and inevitably the ink volume flow are determined via the material pressure in the storage container and/or the ink chamber. In a constructive further development of the ink chamber of a rotary screen printing machine designed according to the invention, only the ink volume flow is set via the system pressure in the ink chamber and/or in the storage container. Besides a mechanical restriction of the opening angle of the ink chamber, it is thus suggested to uncouple the opening and closing process from the ink volume flow technically with the help of electrically, pneumatically or hydraulically adjustable setting means. The opening and closing of the ink chamber is hereby designed such that the setting unit fulfills this task independently of the regulation of the ink volume flow.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 025 927.6 | May 2008 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/002784 | 4/16/2009 | WO | 00 | 2/24/2011 |
