Patent Application
20220024199
The invention relates to a printing press having at least one electric motor.
Printing presses with electric motors serving for the drive unit are known. In these printing presses, solvent-containing ink is normally used, so that there is a danger of the air becoming enriched with solvent vapor and being ignited by a spark in the electric motor.
In order to prevent such an explosion, it is known in the prior art how to employ special electric motors with explosion protection, so that there are no ignition sparks which might come into contact with the surrounding air. Furthermore, it is known how to evacuate the solvent-containing air at the emission source of the solvent vapors, so that no ignitable composition can be formed in the air. The drawback of these designs is that they are very expensive in their construction and therefore they are costly.
The problem which the invention proposes to solve is to provide a printing press which has an economical explosion protection.
As the solution of the problem, a printing press is provided with at least one electric motor, which is arranged at a distance of less than 0.5 m from an emission source. Moreover, the printing press comprises at least one explosion protection wall, which is configured such that the minimum thread measure between the emission source and the electric motor is greater than 0.5 m.
In the sense of the invention, an emission source will mean a location at which solvent vapor is emitted, especially during the operation of the printing press, especially from fluid solvent-containing ink which is not yet fully dried. The location is formed in particular by a part of the printing press itself, where operating means such as material webs and printing ink are viewed in this context as being part of the printing press. For example, the emission source may be an anilox roller, a pressure cylinder, a chambered doctor blade bar, an ink tray or an imprinted web of material.
In the sense of the invention, the thread measure is the length of a thread stretched between two points, i.e., the shortest free path connecting two points to each other, skirting obstacles. By contrast, obstacles lying between two points are not considered in the case of their distance.
Thanks to the explosion protection wall, the minimum thread measure between the emission source and the electric motor is extended to at least 0.5 m. In this way, the minimum thread measure amounts to more than 0.5 m, which needs to be observed according to the safety regulations in order to safely rule out an explosion hazard. Thanks to the explosion protection wall, the printing press can have a very compact and economical design, since no expensive features are required for the explosion protection.
In one embodiment, the explosion protection wall is part of a labyrinth structure, which ensures that the minimum thread measure is greater than 0.5 m, even when the electric motor is arranged closer than 0.5 m to the emission source.
In another embodiment, the explosion protection wall is part of a housing open at one end. In this way, the thread measure from the electric motor can be determined, which is not the case with a fully enclosed housing, since the thread cannot be pulled through a fully enclosed housing. The open housing has the advantage that heat can be more easily dissipated from the electric motor in this way, which can prevent an overheating of the electric motor with less expense.
It is advantageous here for the housing to have an opening on the side with the electric motor, which is arranged opposite to the emission source. In this way, the thread measure is especially greatly lengthened through the housing, so that the electric motor can be arranged especially close to the emission source.
According to another embodiment, the printing press comprises a receptacle which is designed to hold solvent-containing ink up to a maximum level. The electric motor is arranged relative to the receptacle such that the minimum thread measure between the maximum level and the electric motor without the explosion protection wall is less than 0.5 m. At the same time, the explosion protection wall is designed such that the minimum thread measure between the maximum level and the electric motor with the explosion protection wall is greater than 0.5 m. The maximum level in particular forms the emission source here. Moreover, the maximum level takes account of any machine parts dipping into the ink, such as ink rolls, so that the required safety distance of 0.5 m is assured in the operation of the printing press.
In one embodiment, the receptacle is an ink box or an ink tray, which usually has a rather large amount of fluid solvent-containing ink and thus forms a major emission source during operation.
Preferably, the electric motor itself does not have an explosion-protected design, so that the printing press can have an especially economical design.
Further benefits and features will emerge from the following description, as well as the enclosed drawings. These show:
In an alternative embodiment, the printing press 10 need not have an ink box 12.
The printing press 10 for example is a flexographic printing press or a gravure printing machine.
The ink box 12 is filled with fluid solvent-containing ink 16 up to a maximum level 18.
The electric motor 14 is fastened to a beam 20 of the printing press 10.
In the present embodiment, the electric motor 14 constitutes an adjustment drive unit of the printing press 10.
The distance A between the ink box 12 and the electric motor 14 is 0.25 m.
The thread measure F1 between the maximum level 18 and the electric motor 14 is 0.4 m.
The distance between the maximum level 18 and the electric motor 14, disregarding the wall thickness of the ink box 12, is 0.25 m, similar to the distance A between the ink box 12 and the electric motor 14.
In order to make sure that the thread measure between the emission source, constituted here by the maximum level 18, and the electric motor 14 is at least the required 0.5 m, an explosion protection wall 22 is provided (see
In an alternative embodiment, the emission source may be formed by any given location, especially one in or on the printing press 10, which has solvent-containing ink 16 which gives off solvent vapors to the surroundings during the operation of the printing press 10.
The explosion protection wall 22 is part of a housing 24 which encloses the electric motor 14.
The electric motor 14 here is arranged in the housing 24 and fastened along with it to the beam 20.
The housing 24 is cuboidal and has an opening 26, arranged opposite to the ink box 12 and thus opposite to the maximum level 18. Hence, the housing 24 has the shape of an open shoe box.
In particular, the housing 24 is entirely closed, apart from the opening 26, so that no solvent or solvent-containing air can pass through the housing 24. In other words, the housing 24 is tight.
The explosion protection wall 22 here is collar shaped and runs in the circumferential direction, enclosing the electric motor 14.
With the explosion protection wall 22, the minimum thread measure F2 between the maximum level 18 and the electric motor 14 is 0.6 m.
In an alternative embodiment, the housing 24 and/or the explosion protection wall 22 can have basically any desired form, the geometry of the housing 24 and/or the explosion protection wall 22 ensuring that a sufficiently large thread measure F is ensured between the emission source and the electric motor 14.
In addition or alternatively, the explosion protection wall 22 may be part of a labyrinth structure which ensures that the thread measure F between the emission source and the electric motor 14 is greater than 0.5 m.
Of course, the printing press 10 is not confined to the exemplary embodiment shown in the figures. In particular, the distance A between the electric motor and the emission source may have any value between 0 and 0.5 m. Moreover, the minimum thread measure F2 can have any value above 0.5 m.
Furthermore, the concept may be applied accordingly for protection distances other than 0.5 m.
In this way, the thread measure F1 is extended by the explosion protection wall 22 to the thread measure F2, which ensures that the electric motor 14 is located outside a range where an ignitable air mixture can form during the operation of the printing press. Thus, an explosion of the solvent can be safely ruled out.
This provides an economical printing press with an effective explosion protection.
The invention is not confined to the embodiment shown. In particular, individual features of one embodiment may be combined at will with features of other embodiments, in particular independently of the other features of the corresponding embodiments.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/025381 | 11/5/2019 | WO | 00 |
