U.S. patent number 3,923,610 [Application Number 05/500,861] was granted by the patent office on 1975-12-02 for method of copper plating gravure cylinders.
This patent grant is currently assigned to Intaglio Service Corporation. Invention is credited to Michael J. Bergin, Richard Flaig.
United States Patent |
3,923,610 |
Bergin , et al. |
December 2, 1975 |
Method of copper plating gravure cylinders
Abstract
Used gravure cylinders are reconditioned by electrolytic methods
using a conventional electroplating machine. During a first stage
of the method, copper is alternately and repeatedly removed from
and applied to the cylinder by repeatedly reversing the direction
of flow of current, with the predominant flow being in a direction
to remove copper. In a second stage of the method, copper is also
alternately and repeatedly removed from and applied to the cylinder
by repeatedly reversing the direction of flow of current, but with
the predominant flow being in a direction to apply copper. In a
third stage, repeated reversal of flow of current may be
discontinued, and sustained flow of current in a direction to apply
copper to the cylinder may be continued until a layer of the
desired thickness is reached.
Inventors: |
Bergin; Michael J. (Bayside,
NY), Flaig; Richard (Danbury, CT) |
Assignee: |
Intaglio Service Corporation
(Stamford, CT)
|
Family
ID: |
23991244 |
Appl.
No.: |
05/500,861 |
Filed: |
August 27, 1974 |
Current U.S.
Class: |
205/103; 156/59;
205/115; 205/151; 205/215; 205/651; 101/170; 204/DIG.9;
205/127 |
Current CPC
Class: |
C25D
5/617 (20200801); C25D 5/18 (20130101); Y10S
204/09 (20130101) |
Current International
Class: |
C25D
5/18 (20060101); C25D 5/00 (20060101); C25D
005/18 (); C25D 007/04 (); B41N 003/00 () |
Field of
Search: |
;204/6,17,25,32R,52R,52Y,129.43,DIG.9 ;156/59 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mack; John H.
Assistant Examiner: Weisstuch; Aaron
Attorney, Agent or Firm: Sandoe; Nichol M.
Claims
What is claimed is:
1. A method of reconditioning used gravure cylinders consisting of
a cylindrical substrate having a layer of copper deposited thereon
and having an ink carrying intaglio image consisting of a
multiplicity of cells etched into the surface of said layer of
copper, which said method comprises the steps of:
a. exposing the surface of said cylinder to an electrolyte,
b. passing direct current through said electrolyte and
cylinder,
c. removing copper from said layer during a first stage of
operation in which the direction of flow of direct current through
said electrolyte is reversed repeatedly so that forward flow of
current through said electrolyte is alternated with reverse flow
and in which the duration of reverse flow of current exceeds the
duration of forward flow, and
d. applying copper to said layer during a second stage of operation
in which the direction of flow of direct current through said
electrolyte is reversed repeatedly so that forward flow of current
through said electrolyte is alternated with reverse flow and in
which the duration of forward flow of current exceeds the duration
of reverse flow.
2. The method claimed in claim 1 in which the flow of current
during said second stage of operation is terminated while the flow
of current is in the forward direction.
3. The method claimed in claim 1 which includes applying copper
during a third stage of operation in which the direction of flow of
direct current through said electrolyte is continuously in the
forward direction.
4. The method claimed in claim 1 in which, during said first stage
of operation, the ratio of duration of reverse flow to forward flow
is approximately 6 to 1.
5. The method claimed in claim 1 in which, during the said second
stage of operation, the ratio of duration of forward flow to
reverse flow is approximately 8 to 1.
6. The method claimed in claim 1 in which, during the said first
stage of operation, the ratio of duration of reverse flow to
forward flow is approximately 6 to 1, and in which, during said
second stage of operation the ratio of duration of forward flow to
reverse flow is approximately 8 to 1.
7. The method claimed in claim 1 in which, during the said second
stage of operation, the ratio of duration of forward flow to
reverse flow exceeds the ratio of reverse flow to forward flow
during the said first stage of operation.
Description
This invention relates to methods of reconditioning used gravure
cylinders having an intaglio image etched into the cylindrical
surface thereof.
Gravure cylinders that are commonly used in roto-gravure printing
processes usually consist of steel or aluminum tubing of a wide
range of lengths and diameters. Some cylinders are solid throughout
rather than tubing for greater strength to resist bending. In some
cylinders, the tubing is permanently mounted on a shaft on which
the cylinder may be rotated. Other types of cylinders are provided
with a removable shaft which may be inserted into the tubing and
locked in place.
In all such gravure cylinders, the steel or aluminum cylinder forms
a substrate which provides a support for a layer of copper which is
usually electroplated onto the outside cylindrical surface of the
substrate by conventional methods of electrolytic deposition. After
a layer of the desired thickness has been deposited, the surface is
leveled by grinding or by cutting with a lathe, and is then
polished to a very smooth finish. The thickness of the layer of
copper is usually approximately twenty thousandths of an inch, buy
may vary between fifteen and thirty thousandths.
In the use of such cylinders in rotogravure printing, an
ink-carrying intaglio image consisting of a multiplicity of small
cells is etched into the smooth, polished surface of the cylinder
by conventional methods. After the cylinder has served its purpose,
as by completion of the printing job for which it had been etched,
it is usually reconditioned for use in another job. Heretofore,
this has usually been done by placing the cylinder in a precision
lathe or grinding machine and either cutting or grinding off copper
to a depth slightly exceeding the depth of the deepest cells which
had been formed in the copper. Then the cylinder has been replaced
by usual methods of electrolytic deposition to restore the copper
layer to the desired thickness. Thereafter, the surface is leveled
by grinding or cutting, after which it is again polished to a very
smooth finish adapted to receive a new intaglio image. Cylinders
may be thus reconditioned an unlimited number of times. Such
methods, however, are time consuming and expensive, and require the
use of a precision lathe or grinding machine. They also result in
waste of considerable quantities of copper.
It is an object of the present invention to provide a method of
reconditioning used gravure cylinders which is entirely
electrolytic in nature, except for a final polishing step.
In performing the method of the present invention a conventional
copper plating machine may be used, consisting of a vat containing
an electrolyte and means for mounting a cylinder therein with its
cylindrical surface exposed to the electrolyte, usually consisting
essentially of a solution of copper sulphate and sulphuric acid in
water. If desired, one or more known reagents may be added to
regulate the formation of the desired copper crystalline structure
and composition as known in the art. During the practice of the
invention the cylinder is rotated in the conventional manner to
expose all portions of the surface uniformly to the
electrolyte.
The method of the invention comprises three stages of operation,
(1) a stage during which copper is alternately and repeatedly
removed from and applied to the cylinder electrolytically, but in
which the removal of copper predominates, and (2) a stage during
which copper is alternately and repeatedly removed from and applied
to the cylinder electrolytically, but in which the application of
copper predominates and (3) a stage during which copper is applied
continuously to the cylinder electrolytically until a layer of
copper of the desired thickness has been deposited.
It is well understood in the art that direct current is used in
electrolytic plating processes and that whether copper is removed
from or applied to the surface of the cylinder depends on the
direction of flow of the current through the electrolyte. When the
polarity of the current is so arranged that the immersed surface of
the cylinder is cathodic and the solid copper immersed in the
electrolyte in the conventional manner is anodic, the flow of
current will cause electro-deposition of metallic copper onto the
surface of the cylinder. For convenience, flow of current in this
manner will be referred to hereinafter as forward flow. On the
contrary, when the polarity of the current is reversed so that the
immersed surface of the cylinder is anodic and the immersed solid
copper is cathodic, the flow of current will cause removal of
metallic copper from the surface of the cylinder. For convenience,
flow of current in this manner will be referred to hereinafter as
reverse flow.
During the progress of the first stage of the method of the
invention, reverse flow of current predominates but relatively long
periods of reverse flow are alternated with relatively short
periods of forward flow. Preferably the ratio of the duration of
reverse flow to the duration of forward flow during this stage is
approximately 6 to 1. During the second stage of the method forward
flow of current predominates, but relatively long periods of
forward flow are alternated with relatively short periods of
reverse flow. Preferably the ratio of forward flow to the duration
of reverse flow during this stage is approximately 8 to 1. Thus,
during the first stage, more copper is removed by reverse flow than
is added by forward flow, while during the second stage, more
copper is added by forward flow than is removed by reverse flow.
However, for reasons which are not completely understood, the
repeated and frequent reversal of the direction of flow of current
during both the first stage and the second stage causes the
intaglio cells to fill with copper until, during the second stage,
they disappear almost entirely. When this occurs, and as a third
stage of the method, repeated reversal of the direction of flow of
current may be discontinued, and forward flow may be continued
until the copper layer reaches the desired thickness.
It has been found that the intaglio cells cannot be eliminated
merely by subjecting the cylinder to reverse flow of current to
remove copper, followed by a single reversal of the direction of
flow to forward flow to apply copper to the cylinder. The success
of the method depends on the frequent reversal of the direction of
flow of current during both stages.
The single FIGURE of the drawing is a schematic diagram showing the
electrical circuit and the essential components of the
apparatus.
EXAMPLE
A specific example of the practice of the method for the
reconditioning of a used cylinder 68 inches in length, having an
outside circumference of 223/4 inches, follows:
Prior to placing a used cylinder bearing an intaglio image into the
plating machine, the cylinder should be thoroughly cleaned to
remove all traces of residual ink, oil, grease and dirt. The
cleaning is done by first washing the surface with a suitable
solvent, and then by scrubbing the surface with a detergent soap
solution. Cleaning should be continued until, after rinsing with
water, there are no breaks in the water film covering the
surface.
The cleaned cylinder is then placed in the plating machine with
approximately one third of its cylindrical surface area immersed in
the electrolyte. The electrolyte preferably consists of a solution
of copper sulphate and sulphuric acid in water in the proportions
of 30 ounces of copper sulphate and 10 ounces of sulphuric acid to
a gallon of water. The electrolyte should preferably be maintained
at a temperature of from 90.degree. to 110.degree.F. and filtered
and agitated continuously in accordance with conventional practice
during the operation of the machine. The cylinder should preferably
be rotated at a peripheral speed of approximately 150 feet per
minute. Solid copper, preferably phosphorized copper, should be
immersed in the electrolyte and electrically connected to a source
of current. The cylinder is also electrically connected to a source
of current. A rectifier and reversing switch are interposed in the
circuit between the line source of alternating current and the
electrodes (cylinder and copper) in order to provide direct current
and to facilitate the reversal of the direction of flow of current
during the operation. Also, to further facilitate the operation,
two timers may be provided to control the operation of the
reversing switch, one to regulate the duration of forward flow, and
the other to regulate the duration of reverse flow. The rectifier
is set to provide direct current at 6 to 12 volts and to supply a
current density of about 225 amperes per square foot of immersed
cylinder surface area.
At the start of the operation, the reversing switch is set for
reverse flow of current and the timers are set to provide periods
of 30 seconds of reverse flow, then 5 seconds of forward flow, then
30 seconds of reverse flow and so on. This mode of operation should
be continued for a period of 30 minutes, at which time
approximately 0.0015 inch of copper will have been removed from the
cylinder. The current is then switched off and the cylinder should
be brushed and inspected. Inspection should show that the intaglio
cells have virtually disappeared.
The current is then switched on again after resetting the timers to
provide 40 seconds of forward flow, then 5 seconds of reverse flow,
then 40 seconds of forward flow and so on. This mode of operation
is continued for a period of approximately 30 minutes, after which
the current may be switched off, preferably during a period of
forward flow. Inspection of the cylinder should show that the
intaglio cells have completely disappeared.
The diameter or circumference of the cylinder is then measured, and
the timers should then be set for continuous forward flow. The
current is then again switched on and allowed to continue until a
copper layer of the desired thickness had been deposited.
The cylinder may then be removed from the plating machine and
placed in a polishing machine to remove any excess copper and to
polish the surface. Grinding or cutting to remove excess copper are
usually unnecessary.
Referring to the drawing, the apparatus comprises a rectifier 1 for
converting alternating current such as may be available from any
convenient power source 2, preferably three phase, 60 cycle current
at 220 volts. Such current may be converted by the rectifier into
direct current of low voltage and high amperage. The rectifier 1 is
electrically connected by leads 3 and 4 to a reversing switch 5
capable of reversing the polarity of the current exiting from the
reversing switch so that current passing through leads 6 and 7 may
be plus and minus or minus and plus, respectively, as desired.
Preferably, a pair of automatic timers 8 and 9 may be connected to
the reversing switch, which said timers may be set to actuate the
reversing switch to reverse the current at desired intervals.
The cylinder 10 which is to be reconditioned is mounted on a shaft
11 by means of which the cylinder may be supported in conventional
manner for rotation in the electrolyte 12 contained in the vat 13.
As shown, the cylinder is only partially immersed in the
electrolyte, but rotation of the roller exposes all portions of the
surface of the cylinder to the electrolyte. If desired, of course,
the cylinder may be completely immersed in the electrolyte.
The lead 7 is in electrical contact with the cylinder shaft 11 and
the lead 6 is electrically connected to a member 10 which is
supported in the electrolyte in any suitable manner and which may
either be made of copper of may serve as a basket or pan containing
solid copper. It will be understood that all of the components of
the apparatus above described, including the rectifier, the
reversing switch, the timers and the plating machine are
conventional and well known in the art.
* * * * *