Clamping device for gravure printing cylinders to be processed in an electroplating plant

The invention is directed to a clamping device for gravure printing cylinders to be processed in an electroplating plant. The clamping device for gravure printing cylinders to be processed in an electroplating plant is equipped, in accordance with a first basic solution, with an interchange holder (1) for a plurality of cone sleeves (2) which have an inside diameter adapted to different spindle ends of various gravure printing cylinders, so that adaptation to a respective identical receiving cone quill (8) is made possible and in the same electroplating plant a plurality of different printing cylinders can be continuously successively processed without the complicated fitting and removal of different collet chucks. According to a second basic solution the interchange holder and the different cone sleeves are not required for the clamping device. Instead, a hardened cone sleeve (21) is used as essential clamping element and clamping is effected with very high contact pressure. Because of the practically gastight connection between the cylinder spindle end and the wall of the hollow cone, very high currents can surprisingly be transmitted.

FIELD OF THE INVENTION 
The present invention relates to a clamping device for gravure printing 
cylinders to be processed in an electroplating plant, which have different 
spindle diameters, and more particularly to where the current is 
transmitted from a current supply system to the outer ends of the gravure 
printing cylinders introduced into the plant. 
BACKGROUND OF THE INVENTION 
For electroplating treatment, for example, the electroplating of gravure 
printing cylinders, there are basically two possible ways of transmitting 
current to the cylinder introduced into the electroplating plant; namely, 
on the one hand, to the end face of the cylinder body and, on the other 
hand, through the spindle ends of the cylinder. In the case of current 
transmission to the spindle end, which is of primary concern here, collet 
chuck systems are generally used; in which case, adequately large contact 
transmission areas and a high contact pressure must be ensured because of 
the high current densities required. 
In an electroplating plant for the purpose in question, a number of 
cylinder types usually have to be processed. The problem then recurs that, 
when different spindle ends exist, it is not possible for all the 
cylinders in a printing works to be clamped in the same collet chuck. In 
the subsequent electroplating processing of cylinders having different 
spindle ends, it is, therefore, necessary to have available different 
collet chucks for manual interchange. 
SUMMARY OF THE INVENTION 
The problem underlying the invention is, therefore, that of providing a 
clamping device of the kind indicated with which a simple, preferably 
automatic change is made possible for adaptation to different cylinder 
spindle ends. 
Other objects, advantages and features of the present invention will be 
more readily appreciated and understood when considered in conjunction 
with the following detailed description and drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
All the disclosed embodiments can be made using conventional compounds and 
procedures without undue experimentation. All the disclosed embodiments 
are useful. 
In a clamping device of the type first mentioned above, according to a 
first embodiment the invention is characterized by: 
a plurality of cone sleeves having an external cone, the same outside 
diameter and an inside diameter adapted in each case to a determined 
spindle end diameter of different gravure printing cylinders, 
in each case, an intermediate sliding member mounted in each cone sleeve 
for axial sliding, 
a movably mounted interchange holder receiving the plurality of cone 
sleeves, provided with the appertaining intermediate sliding member, in 
bores adapted to their outside diameter, 
a quill cone sleeve which serves to transmit current to a respective 
spindle end by way of an appertaining external cone sleeve and whose 
internal cone is adapted to the respective identical external cone of the 
cone sleeves, and by 
an ejector device mounted concentrically to the quill cone sleeve for the 
axial displacement of a respective intermediate sliding member and the 
respective cone sleeve to the released position inside the appertaining 
bore in the interchange holder. 
According to a second basic solution to the problem posed, in a clamping 
device for gravure printing cylinders to be processed in an electroplating 
plant, which have different spindle diameters, wherein the current is 
transmitted from a current supply system to the outer ends of the gravure 
printing cylinders introduced into the plant, the invention is 
characterized by a hardened hollow cone serving as holding and centering 
element for gravure printing cylinders which are to be clamped at the 
spindle ends and which have different spindle diameters, and serving as 
current transmission element between the current supply system and the 
spindle end of a clamped gravure printing cylinder. 
The gravure printing cylinder is clamped axially tinder high pressure by 
means of hardened hollow cones. In a preferred embodiment, pointed cones 
having an angle of inclination of less than 60.degree. are used, and in a 
particularly preferred embodiment, an angle of inclination of 
approximately in the region of 45.degree., to the axis of the cone. 
Through the use of high pressure, both the torque and high currents, 
(i.e., high current densities), can be transmitted. 
The second embodiment of the invention simplifies the problem of adaptation 
of the clamping device to different spindle ends to a very considerable 
extent, because with this solution, not only the constructionally 
expensive collets, which are complicated to manipulate, but also, the 
interchange holder according to the first embodiment can be dispensed 
with. 
The functional capability of the second embodiment is surprising for the 
following reason: 
A critical point with this kind of clamping by way of a hollow cone is 
current transition. The literature takes as its starting point 
transmissible current densities of 2 amperes per square millimeter. This 
would conflict with a high current transmission through the linear contact 
in a hollow cone. However, trials have surprisingly shown that with a high 
contact pressure, for example of about 3000 kp, a practically gastight 
connection is made between the cone and the spindle end of the cylinder. 
Far higher current densities can thus be transmitted than was hitherto 
assumed. In a tested exemplary embodiment of the invention a current of 
3000 A was transmitted through a spindle journal of a diameter of 70 mm, 
with an estimated line width of 0.5 mm of the contact pressure between the 
hollow cone and the end face edge of the spindle journal, in continuous 
operation. In a tested plant there can even be transmitted up to 9000 A 
can with current transmission at both ends. Despite this high current, no 
noteworthy signs of wear are found on the cone or on the spindle end. Even 
heat losses are surprisingly extremely low; that is to say, the current 
transmission region is not excessively heated. This is attributed to the 
fact that the resistance path between the cone and the spindle end has 
only a minimal contact resistance. 
The current transmission principle according to the second basic embodiment 
of the invention very substantially simplifies the constructional design 
of electroplating plants for the purpose indicated, particularly when 
different types of cylinders have to be processed. In this case, different 
adapter sleeves can in addition be dispensed with. 
Advantageous further developments of and additions to the clamping device 
according to the invention are the objects of each of the various 
dependent patent claims. 
As the result of the first embodiment according to the invention, the 
automatic provision of the spindle end of printing cylinders to be treated 
by electroplating with a sleeve which compensates for differences in 
diameter and/or length and, therefore, adaptation to the respective 
identical receiving quill in the same electroplating plant are possible, 
so that all printing cylinders of a client can be processed in a 
continuous working process, irrespective of their various individual 
dimensions. 
The invention and advantageous details are explained more fully below with 
reference to exemplary embodiments and with the aid of the drawings. 
EXAMPLES 
Specific embodiments of the invention will now be further described by the 
following, non-limiting examples. 
At one end of an electroplating vessel (not shown) for printing cylinders 
there are cylinder spindle 3 being shown in each case in FIGS. 1 and 
2-disposed a drive 11, which is housed in a casing 10 and is of no further 
interest here since it is known, and a current supply system 12 which 
transmits the necessary electroplating current to the cylinder spindle end 
3 by way of a collector sleeve 13, a quill cone sleeve 8 and a cone sleeve 
2 provided with an external cone adapted to the quill cone sleeve. The 
cone sleeve 2 is held for axial sliding in a bore 14, adapted to the 
outside diameter of said cone sleeve, in an interchange holder, which in 
the exemplary embodiment illustrated is an interchange disc 1. The 
interchange disc 1 can be turned about an axis 15. The inside diameter of 
the cone sleeve 2 is adapted to the diameter of the spindle end of the 
printing cylinder; that is to say, the cone sleeve 2 serves as an adapter 
for different spindle end diameters of the various types of printing 
cylinders. A rotationally symmetrical intermediate sliding member 4, whose 
axial length expediently corresponds to that of the cone sleeve 2, is 
provided at each of its two end faces with flange-like outwardly 
projecting annular shoulders 16 and 17, respectively. The annular shoulder 
16 serves to limit the possible movement path of the intermediate sliding 
member 4 to the left in FIGS. 1 and 2, by cooperating with an annular stop 
surface 18 inside the cone sleeve 2. At the other end, the flange-like 
annular shoulder 17 limits the possible movement path of the intermediate 
sliding member 4 when the latter is pressed into the cone sleeve 2 by the 
piston or ram 6 of an ejector device 7 (see FIG. 2). The ejector device 7 
is a gas compression spring in the example illustrated. 
As can be seen in FIG. 3, in the exemplary embodiment illustrated, the 
interchange holder, that is to say the interchange disc 1, is equipped 
with three different cone sleeves 2. These different cone sleeves 2 are 
inserted into annular flange bore 18 disposed with approximately the same 
angular spacing around the periphery, the respective axes of which bores 
are disposed on a circle 20 around the axis of rotation 15 of the 
interchange disc 1. 
When the gas compression spring 7 is operated, so that the ram 6 is pushed 
out to the right for ejection purposes, the intermediate sliding member 4 
is first moved to the right, driving the cone sleeve 2 with it by means of 
its annular shoulder 17 until said cone sleeve, encountering a stop 5, has 
reached its position of rest inside the appertaining bore 18. 
The operating cycle for clamping or changing a printing cylinder, which is 
to be electroplated, with the aid of the clamping device according to the 
invention is as follows: 
A cone sleeve 2 fitting a determined cylinder end is first prepositioned by 
turning the interchange disc 1. The cylinder spindle 3 is then engaged and 
clamped, where the cylinder spindle end pushes the intermediate sliding 
member 4 in. The intermediate sliding member 4 then carries with it the 
cone sleeve 2 by means of the flange like external shoulder 16 until the 
cone sleeve 2 reaches the quill cone sleeve 8, so that the cone sleeve 2 
is then pressed onto the cylinder spindle end. The electroplating 
treatment of the printing cylinder then follows. 
On completion of the treatment, the gas compression spring 7 pushes the ram 
6 to the right in order to release the clamping, while the cone sleeve 2 
is pushed back into the associated receiving bore 18 by means of the 
intermediate sliding member 4, until it lies against the stop 5. At the 
same time, the end stroke, that is to say the engagement movement path of 
the gas compression spring, is limited by an annular shoulder stop 19 in 
cooperation with the quill cone sleeve 8. The spindle end 3 of the gravure 
printing cylinder is now completely disengaged; it rests on the stop 5, 
which at the same time serves as a half-shell-shaped support, and the 
completely processed printing cylinder can be lifted out of the 
electroplating plant. 
The interchange holder 1 according to the invention for the various cone 
sleeves 2 need not necessarily be in the form of an interchange disc, 
although for reasons of space and for automated changing of the cone 
sleeves this appears at the present time to be the optimum solution. A 
plate-like interchange holder slidable horizontally or vertically in 
appropriate guides would for example also be possible. 
One exemplary embodiment for the second basic type of a clamping device 
according to the invention will be explained below with reference to FIGS. 
4 and 5. The parts and subassemblies already explained with reference to 
FIGS. 1 to 3 will not be described again. 
As FIG. 4 shows, in this second type of a clamping device according to the 
invention, the interchange disc provided with different cone sleeves is 
dispensed with. Instead, as the sole essential adapter element for 
adaptation to different spindle diameters of gravure printing cylinders 
use is made of a hardened hollow cone 21, which is screwed in place by 
means of an annular flange 22, which is inserted into the wall of the 
casing 10 and screwed to the end face of the sleeve of the gas compression 
spring 7, in order to transmit high axial forces. The front region of the 
ram 6 of the gas compression spring 7 slides through the correspondingly 
adapted inside diameter of the hollow cone 21 when the printing cylinder 
is ejected. The angle of inclination or slope of the hollow cone 21, which 
preferably slopes to a point, is about 45.degree. relative to its axis. 
This angle of inclination should be smaller than 60.degree. and, depending 
on the application and the current density to be transmitted, could be 
between 30.degree. and 45.degree.. 
The most suitable hardenable material for the hollow cone 21 is the steel 
alloy 100 Cr 6. Despite the high contact pressures mentioned and the 
extremely high current densities, this material permits long service 
lives, so that the replacement of the cone sleeve 21 becomes necessary 
only very occasionally. 
While there is shown and described herein certain specific structures 
embodying this invention for the purpose of clarity of understanding, the 
same is to be considered as illustrative in character, it being understood 
that only preferred embodiments have been shown and described. It will be 
manifest to those skilled in the art that certain changes, various 
modifications and rearrangements of the parts may be made without 
departing from the spirit and scope of the underlying inventive concept 
and that the same is not limited to the particular forms herein shown and 
described except insofar as indicated in the scope of the appended claims. 
The entirety of everything cited above or below is expressly incorporated 
herein by reference.