EP0082268A1 - Apparatus for electroplating printing rollers - Google Patents

Abstract

1. Apparatus for galvanizing a rotary printing cylinder (1) comprising a current-carrying rotary drive mechanism (3) coupled to a power source (41) through carbon brushes (6) and a slip ring (5) and to which the printing cylinder (1) is joined by means of an axial clamping element (9), with the printing cylinder, while rotating, being at least partially immersed in a galvanizing bath (25) as the cathode, characterized in that a current-carrying cylindrical sleeve (40) is positioned concentrically to the clamping element (9, 42) in front of the printing cylinder (1), which sleeve has its rear portion (40') provided with the slip ring (5), and that the sleeve (40) has its front side (45) contacting an annular contact member (43) under elastic tension exerted by the clamping element (9, 42), which contact member, in turn, contacts the front side (21) of the printing cylinder (1) directly, or, in order to compensate for different diameters of the sleeve (40) and of the printing cylinder (1), through a rotationally symmetrical intermediate member (60) and a further annular contact member (43').

Description

The invention relates to a device for electroplating a rotary printing cylinder, which has a current-carrying rotary drive which is connected to a power source and to which the printing cylinder is connected via an axial tensioning element, the latter being at least partially immersed in a galvanizing bath as a cathode while rotating.

Such a device for electroplating a rotary printing cylinder is known from the relevant practice. It is common for the rotary drive to be equipped with an output shaft which is provided with a conically tapering, cylindrical bore at the end receiving the stub shaft of the pressure cylinder, similar to a drilling or milling spindle, the conical outlet of the bore for receiving an annular cone provided with an outer cone is used, the inner bore with a snug fit on the stub axle of the pressure cylinder is pushed on. The conical ring tensioning element is elastically tensioned by an axial tensioning element which is passed through a central bore of the shaft and screwed to the axle stub, so that it forms a tight fit with the axle stub.

The shaft of the rotary drive is otherwise provided at the opposite end with a slip ring which is connected to the negative pole of a direct current source via carbon brushes. The flow of current from the shaft into the pressure cylinder takes place to a lesser extent via the metallic tensioning element, and to a greater extent via the ring tensioning element onto the stub shaft of the pressure cylinder.

The disadvantage of this is that there are relatively high resistances for the current flowing with a low voltage and a relatively high current density. In particular, when moving from the shaft via the ring tensioning element into the axle stub there are high resistances, since the conical flank of the ring tensioning element is slightly convex to compensate for a not exactly axially aligned fit system between shaft and axle stub, and consequently there is more or less a line contact, which significantly reduces the conductive cross section. In practice, these conditions often led to resistance heating, which resulted in questionable changes in the material structure at this point, as well as considerable losses in electrical feed energy.

In the known arrangement, it was also necessary to protect the connection and power transition point between the shaft and the stub shaft by means of an overlapping protective tube, preferably made of plastic, before wetting to protect the electrolyte, for which purpose, in addition to the protective tube, a clamping ring screw connection in the axial direction and centering by radial spacers were required. This, as well as a possibly required radial locking disk, together with the unsatisfactory current transfer conditions, also resulted in a relatively high outlay both on parts and on assembly work.

The object of the invention is a significant improvement in the current transfer conditions from the current-carrying rotary drive to the pressure cylinder, in particular to save energy and prevent local heating at the stub axle of the pressure cylinder, and also drastically simplify the device by eliminating parts and assembly work.

The object is achieved in a device for electroplating of the type mentioned in that a cylindrical sleeve is arranged between the clamping element and the pressure cylinder and is connected directly to the power source by means of sliding contacts, and in that the end face of the sleeve by means of elastic tension with the interposition of a annular contact element rests on the pressure cylinder.

With the invention, there is the advantage that the cylindrical sleeve results in a current conductor with a relatively high current cross section, which, due to the interposition of the special ring-shaped contact element, feeds the current directly into the pressure cylinder with the least possible resistance, thereby avoiding resistance losses and harmful heating. In the end, the invention saves up to 30% electrical energy or significantly better performance in the galvanization aims.

In order to limit the inevitable resistances during the current transfer from the sleeve to the pressure cylinder to the lowest possible extent, it is further proposed that the contact element be made of an elastic and / or plastically deformable metal with as low an electrical resistance value as possible, such as pure copper, silver or silver alloy, Lead or the like is made. As a result, the line resistances at the transition point are advantageously minimized as far as possible.

It is also provided that the sleeve rests on the end face of the printing cylinder.

This has the further advantage that the current is introduced from the sleeve into the pressure cylinder bypassing the stub shaft via a large ring-shaped contact cross section directly into the body of the cylinder. This has another advantage. While the production-related alignment of the material structure in the intergranular region with central current introduction through the stub shaft results in small resistance differences and thus current densities in different planes perpendicular to the axis of rotation, which affect the uniformity of the electroplating process on the circumference of the pressure cylinder when the current is fed in centrally, this disadvantageous phenomenon is caused by the current introduction according to the invention advantageously avoided on the end face of the cylinder and in a ring cross section far outside the axis of rotation.

A full and even surface pressure that is elastic under all operating conditions between the end face of the sleeve, the contact element and the pressure To achieve cylinders, it is further proposed that the clamping element is designed as a spring element or is equipped with such.

An uncomplicated mechanical integration of the sleeve directly connected to the power source with the rotary drive results from the fact that, according to a further proposal, the sleeve is received by and firmly connected to a hollow shaft, which in turn has a rotatable bearing and the rotary drive.

An uncomplicated centering between the pressure cylinder and the rotary drive is achieved in a pressure cylinder with a stub axle on the end face in that annular centering bodies are fitted between the latter and the sleeve surrounding the stub shaft.

Because these centering bodies, in contrast to the ring tensioning element, are arranged outside of the current supply, they can be equipped with much more generous tolerances and therefore require a significantly lower amount of work both in manufacture and in assembly.

In the event that there is a considerable difference in diameter between the sleeve and the end face of the printing cylinder, as can be the case, for example, in a printing cylinder with a very small diameter, a further proposal provides that a rotationally symmetrical between the sleeve and the end face of the printing cylinder Shaped body is arranged to compensate for different diameters, and that a contact element is arranged between the sleeve and the shaped body and between the shaped body and the pressure cylinder.

To further improve the current transfer conditions and reduce the contact resistance, it is further proposed that the sleeve on the end face receiving the contact element has an annular groove with obliquely converging flanks, and that the contact element has a hemispherical bead in cross section.

This results in a further advantage in cross-section a cone / ball fit, which results in excellent metallic double line contact in a circular cross-section, in particular due to the elastic and / or plastic deformability of the contact element, and thus a relatively large current carrying cross-section with a small one Contact resistance results.

For a further embodiment of the device it is provided that the current transfer area of the sleeve and the pressure cylinder is covered with a sleeve made of elastic material. Finally, it can further be provided that the sleeve is equipped with a radial sealing lip made of elastic material at the point of passage through the container wall of the galvanizing bath.

• Figur 1 eine Vorrichtung zum Galvanisieren eines Rotations-Druckzylinders nach dem Stand der Technik, im Schnitt,
• Figur 2 eine andere Ausführung einer Galvanisierungsvorrichtung nach dem Stand der Technik, mit einem im Verhältnis zum Drehantrieb kleinen Durchmesser des Druckzylinders, ebenfalls im Schnitt,
• Figur 3 eine Ausführung der Vorrichtung zum Galvanisieren eines Rotations-Druckzylinders nach der Erfindung, im Schnitt,
• Figur 4 eine andere Ausführung der Vorrichtung gemäß Figur 3 mit einem im Verhältnis zur Hülse kleinen Durchmesser des Druckzylinders, im Schnitt,
• Figur 5 eine vergrößerte Detaildarstellung der Hülse mit einer ringförmigen Nut mit schräg zusammenlaufenden Flanken und einem Kontaktelement mit im Querschnitt halbkugelförmigem Wulst, ebenfalls im Schnitt,
• Figur 6 ein als Federelement ausgebildetes Spannelement, ebenfalls im Schnitt,
• Figur 7,eine am Stromübergangsbereich von Hülse und Druckzylinder angeordnete Manschette aus elastischem Material mit einer radialen Dichtlippe, ebenfalls im Schnitt.

The invention is explained in more detail below with reference to exemplary embodiments in the drawing. Show it:

• 1 shows a device for galvanizing a rotary printing cylinder according to the prior art, in section,
• Figure 2 shows another embodiment of a galvanizing device according to the prior art, with a small diameter of the pressure cylinder in relation to the rotary drive on average,
• FIG. 3 shows an embodiment of the device for electroplating a rotary printing cylinder according to the invention, in section,
• FIG. 4 shows another embodiment of the device according to FIG. 3 with a diameter of the printing cylinder that is small in relation to the sleeve, in section,
• FIG. 5 shows an enlarged detailed illustration of the sleeve with an annular groove with obliquely converging flanks and a contact element with a bead that is hemispherical in cross section, likewise in section,
• FIG. 6 shows a tensioning element designed as a spring element, likewise in section,
• FIG. 7, a sleeve made of elastic material with a radial sealing lip arranged at the current transition area of the sleeve and pressure cylinder, likewise in section.

A device from the prior art for electroplating a rotary printing cylinder according to FIG. 1 shows the printing cylinder 1 with the front axle stub 2. The rotary drive 3, which receives the printing cylinder 1, comprises the shaft 4, at the rear end of which the slip ring 5 is pressed on. which makes the conductive connection to the shaft 4 via the spring-loaded carbon brushes 6 with the negative pole of a DC power source, not shown. As is known, the slip ring 5 is made of copper, while the shaft 4 is usually made of steel. This has a central bore 8, which receives a bolt 9 as a clamping element, the threaded end 10 is firmly screwed to the stub shaft 2 of the pressure cylinder 1. The bore 8 is widened in the direction of the stub axle to a larger bore 11 which widens against the pressure cylinder 1 with a conical outlet 12. Between the conical outlet 12 of the shaft 4 and the bearing seat 26 of the stub axle 2, the ring clamping element 13 is arranged, which is initially pushed over the bearing seat 26 with a slight snug fit and is contracted as a result of tensioning with the conical outlet 12 of the shaft 4 by the clamping element 9 such that it connects between the bearing seat 26 and the conical outlet 12 with a tight fit. However, because an absolutely aligned alignment between the axis of rotation 27 of the printing cylinder 1 and the axis of rotation 28 of the shaft 4 is not always given, the conical outer jacket of the ring tensioning element 13 usually has to be spherical. This has the consequence that basically only a line contact takes place between the conical outlet 12 and the outer jacket of the ring clamping element 13, which considerably reduces the electrically conductive cross section at this point. It should be taken into account here that a galvanization current of low voltage, for example 12 V, with a high current density flows from the direct current source via the carbon brushes 6 and the slip ring 5 through the shaft 4 into the stub shaft 2. Of these, a partial flow passes through the bolt 9 of the tensioning element into the stub axle, while the major part of the current flow through the shaft 4 flows through the ring tensioning element 13 into the bearing seat 26 of the stub axle 2.

From there, the current flows into the body of the pressure cylinder 1, which is partially immersed as the cathode in the electroplating bath 25. In order to prevent galvanic precipitation of metal from reaching the stub shaft 2, this, as well as part of the shaft 4, is removed from a protective tube 18 made of plastic covered, which is pressed by a clamping ring 20 in the axial direction against the end face 21 of the printing cylinder 1 and with the help of the annular soft seal 19 sealingly abuts the end face 21 of the printing cylinder 1. Radial centering bodies 22 and 23, which are preferably also made of plastic, hold the protective tube 18 in a concentric position. A radial locking disk 24, also made of plastic, prevents further flow of an electrolyte film on the shaft 4 in the direction of the slip ring 5. In addition to the shaft 4, the rotary drive 3 includes the sleeve 14, which is firmly connected to the shaft 4 by means of shear bolts 17, and which in turn carries the bearing 15 and the drive wheel 16. The electroplating bath 25 is located in the trough 29.

In the device for electroplating the rotary printing cylinder 1 according to the prior art, as shown in FIG. 1, the disadvantage is a high resistance to the current flow, in particular at the line contact between the inner flank of the conical outlet 12 and the crowned one Outer flank of the ring tensioning element 13, which, after constant operating experience, results in considerable heating from the electrical resistance, which in some cases even leads to harmful structural changes in the stub axle 2. This also resulted in a considerable power loss when feeding the electrical energy, which adversely affected the economy of the electroplating process. It was also found that slightly different order results were achieved on the circumference of the printing cylinder 1 when the current was fed in via the front-side central stub 2, which is due to slight differences in the conductivity of the material structure of the printing cylinder 1.

A similar arrangement from the prior art, which has become known from practice, is shown in FIG. 2. Here, the printing cylinder 1 is not equipped on its end face 21 with an axle stub, but with a welded-in head piece 20, which is used for clamping onto a working shaft of a rotary printing press has conical bore 31. In such a configuration of the pressure cylinder 1, it was customary in the prior art to use an intermediate piece 32 with ends 33 and 34 which are conical on both sides between the shaft 4 of the rotary drive 3 and the pressure cylinder 1, and this together with the shaft 4 by means of a continuous tensioning element 9 in the form of a long threaded rod. Because the two conical ends 33 and 34 had to be spherical to compensate for inaccurate alignments, there were two conical ends 33 and 34 with respect to the overlapping conical bores, namely the conical bore 12 of the shaft 4 and the conical receptacle 31 of the Head piece 30, essentially a line contact with a relatively small line cross-section for the current flow and correspondingly high resistances, which in the end resulted in the disadvantageous consequences in particular of heating and energy loss. The devices for electroplating a rotary printing cylinder which have been further developed and improved according to the invention can be seen by way of example from FIGS. 3 and 4 and in detail from FIGS. 5 to 7.

According to the invention, the device according to FIG. 3 has the sleeve 40 for receiving the printing cylinder 1 and for introducing the current, which sleeve is provided on its rear area 40 'with the copper slip ring 5, which is in conductive contact with the carbon brushes 6 shown purely schematically with a hint current symbolized by arrow 41 source is connected. The sleeve 40, which accordingly represents a current conductor of a relatively large line cross section, is connected at its other end 44 with its end face 45 via a contact element 43 directly to the end face 21 of the pressure cylinder 1 and is clamped against it by the tensioning element 42 under relatively high elastic tension Printing cylinder 1 clamped. This arrangement is not only considerably less complicated than the embodiment according to FIGS. 1 and 2 with the conical endings 12, 13, and 33 and 34 used there, but also ensures an unimpeded flow of the electrical current to be introduced without any reduction in the conductive cross section from the current source 41 via the sleeve 40 right up to the end face 21 of the printing cylinder 1.

The contact element 43 in the form of a relatively large-caliber ring made of a highly conductive metallic material, firmly clamped between the end face 45 of the sleeve 40 and the end face 21 of the pressure cylinder 1, ensures optimal contact and accordingly low contact resistance between the sleeve due to its elastic and / or plastic deformability 40 and impression cylinder 1.

The significant improvement achieved in this way of an unimpeded power supply with low resistance avoids the damaging heating of the material, as well as the energy losses caused thereby. It has been shown in practice that with the arrangement according to the invention, in addition to avoiding the disadvantages described, energy savings in the order of 30% could be achieved, or, with the same energy supply, a similar amount higher precipitation results on the pressure cylinder 1 used as the cathode.

In order to achieve a consistently rich, elastic contact force between the sleeve 40 and the end face 21 of the pressure cylinder 1 in the arrangement according to the invention, the tensioning element 42 is either, as in the example shown in FIG. 3, designed as an expansion bolt which has the effect of a spring element with a high level Progression achieved, or even better equipped with a spring arrangement, as shown in Figure 6, wherein an arrangement of disc springs 47 is provided between the clamping element 42 and the clamping plate 46 which provides the counterhold. It is at the skilled person's discretion to provide two clamping plates with an elastic intermediate layer made of rubber or an elastic plastic instead, etc.

As can also be seen from FIG. 3, the sleeve 40 is guided concentrically about the axis of rotation 28 by two centering bodies 48 and 49. Furthermore, the sleeve 40 is inserted into the hollow shaft 50, which forms part of the rotary drive 3, and is connected to the bearing 51 and the drive wheel 52.

FIG. 4 shows the sleeve 40 in connection with a printing cylinder 1, which is considerably smaller in diameter, on average. In this case, a reducing intermediate piece 60, which is, for example, a rotationally symmetrical molded part made of copper, is arranged between the sleeve 40 and the pressure cylinder 1. Contact elements 43, 43 'are clamped between the sleeve 40 and the intermediate piece 60, as well as between the intermediate piece 60 and the pressure cylinder 1, and are held together under elastic tension by the purely schematically indicated tensioning element 9. So that the pressure cylinder 1, which is shown in section in this case seen from the side, into the electrolyte of the electroplating bath can dive, the intermediate piece 60 is provided with an annular circumferential groove 61 which engages over the edge 62 of the trough 29.

The direct power supply with large wire cross-sections and low wire resistance in the end face 21 of the printing cylinder 1 in a circular cross-section near the periphery of the printing cylinder 1 results in an optimal current flow and a very even current distribution over the circumference of the printing cylinder 1, which results in the galvanization, as is has shown in practice with the invention is achieved with much higher specific performance and more uniform result. This proves that the object is fully achieved with the invention.

The transition area between the end face 45 of the sleeve 40 and the end face 21 of the pressure cylinder 1, which is important for the current supply, is shown on an enlarged scale and in section in FIG. 5. The end face 45 of the sleeve 40 receiving the contact element 43 has a groove 53 with obliquely converging flanks 54, while the contact element 43 has a hemispherical bead 55 in cross section. This and the selection of an elastically and / or plastically deformable, highly conductive material for the contact element 43 results in an excellent centering of the contact element 43 by the flanks 54, as well as a very strong double line contact, similar to a ball / cone seal between the bead 55 and the flanks 54. In this way, an excellent current transfer with minimized resistances is created. In terms of manufacturing technology, the corresponding parts can be produced easily and inexpensively and can be used repeatedly.

Finally, FIG. 7 shows the transition area between the sleeve 40 and the end face 21 of the pressure cylinder 1 with an elastic protective sleeve 56 pulled over it, which is equipped with a radial lip seal 58 to seal the rotary drive 3 inserted horizontally into the galvanizing trough 29 through a lateral opening 57.

Claims (10)

1. Device for electroplating a rotary printing cylinder, which has a current-carrying rotary drive which is connected to a power source and to which the printing cylinder is connected via an axial tensioning element, the latter being at least partially immersed in a galvanizing bath as a cathode while rotating,
characterized in that a cylindrical sleeve (4) is arranged between the tensioning element (9, 42) and the pressure cylinder (1) and is connected directly to the power source (41) by means of sliding contacts (6), and in that the sleeve (40) with its Front side (45) by means of elastic tension by the tensioning element (9, 42) with the interposition of an annular contact element (43) on the pressure cylinder (1). 2. Device according to claim 1, characterized in that the contact element (43) is made of an elastically and / or plastically deformable, as low as possible electrical resistance metal such as pure copper, silver or silver alloy, lead or the like. 3. Device according to one of claims 1 or 2, characterized in that the sleeve (40) bears on the end face (21) of the printing cylinder. 4. Device according to one of claims 1 to 3, characterized in that the clamping element (9, 42) is designed as a spring element or is equipped with such (47). 5. Device according to one of claims 1 to 4, characterized in that the sleeve (40) is received by a hollow shaft (50) and is fixedly connected thereto, which in turn has a rotatable bearing (51) and a drive wheel (52). 6. Device according to one of claims 1 to 5, characterized in that in a pressure cylinder (1) with front stub axle (2) between this and the stub axle (2) surrounding sleeve (40) annular centering body (48, 49) are fitted . 7. The device according to claim 6, characterized in that between the sleeve (40) and the end face (21) of the pressure cylinder (1) a rotationally symmetrical shaped body (60) is arranged to compensate for different diameters, and that between the sleeve (40) and a contact element (43, 43 ') is arranged between the shaped body (60) and between the shaped body (60) and the pressure cylinder (1). 8. Device according to one of claims 1 to 7, characterized in that the sleeve (40) on the end face (45) receiving the contact element (43, 43 ') has an annular groove (53) with obliquely converging flanks (54), and that the contact element (43) has a hemispherical bead (55) in cross section. 9. Device according to one of claims 1 to 8, characterized in that the current transition region of the sleeve (40) and pressure cylinder (1) is covered with a sleeve (56) made of elastic material. o. Device according to claim 9, characterized in that the sleeve (40) at the passage point (57) through the container wall (29) of the galvanizing bath (25) is equipped with a radial sealing lip (58) made of elastic material.

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