Note: Descriptions are shown in the official language in which they were submitted.
z:~
The present invention relates to a method o~ and apparatus for
electrochemically processing metallic surfaces of ~orkpieces arrangecl in a
contact-ree manner with regard to the ca~hode and anode, by means of an elec-
trolyte which, for purposes of transferring an electric charge to the surface
to be processed, cvntains electrically conductive bodies which are suspended
in the electrolyte and wh;ch are charged in an electrolytic cell on ~he elec-
trode which determines the processing of said surface, and which are protected
against a dischar~e on the coun~er elec~Tode of ~he electroly~ic cell by a
s ~ . lJ;r~
. ~~ diaphragm skiol~ivg or an ion exchange membranelsaid counter electrode, said
electrolyte being positively conveyed between ~he elec~rode charging said
; electrically conduct;ve bodies on one hand and the surface of the workpieces
to be processed on the other hand.
Printed circuits are produced in conformity with thîs method. To
this end, one or both sides of plates of electrically non-conductive syn~hetic
material are copper coated. Those metal surfaces which are intended to ~orm
the desired circuit are covered by a protective layer while the remaining
portion of ~he copper coating is removed from said plates of synthetic material.
The electrically conductive bodies whi~h are suspended in the electrolyte are
positively charged on the anode of an electrolytic cell, and subsequently are
brought into contact with the sur~ace of the copper layer. Metal ions enter
into solution ~Ihich ions are deposited on the cathode of the electrolykic cell.
This method is also employed for making metallic form parts with which parti-
cular precision and contour sharpness is a foremost requirement, as is also
the case with flow conducting elements such as turbine blades or nozzles. The
; direct recovery of the remo~ed metals as it is possible in this method -- which
metals deposit on the counter electrode -- leads to an econo~ic and at the
same time ecologically favorable method. This ad~antage of the method is in
particular also used when recovering metals from so-called cable scrap.
From this method described in United States Patent 3,97~,0so l)ioisok
et al issued August 10, 1976 it is known to fced thc clectrolytc containing
-- 1 --
the electrically conductive bodies, between the electrode which charges sald
bodies on one hand and the surface of the workpieces to be processed on the
other hand, and to do this by rotating the electrode, or by the employment of
circulating pumps. The electrolyte passes from the interior of the electro-
lytic cell in which the electrically conductive bodies are charged on the
electrode determining the processing of said surface, through the diaphragm
into the region of the counter electrode. ~ drawback of this method is
that in the course of the operation electrically conductive bodies are
deposited on the diaphragm so that consequently the exchange of electrolyte
between cathode chamber and anode chamber (which exchange is necessary for
the electrolytic processing operation) is gradually reduced. When removing
metal from metallic surfaces, due to the reduction in metal ions within the
region of the cathode, there exists the danger that undesired hydrogen gener-
ation will occur in the cathode chamber. A further disadvantage of this
method is that during the operation, the cell voltage and thus the energy
consumption required for the processing operation gradually increases, and at
the same time a reduction occurs on the electrically conductive bodies in the
electrolyte which transfer the charge sn that the processing time necessary
for the partial removal of the surface increases.
The present invention provides a method of electrochemically pro-
cessing metallic surfaces of workpieces arranged in a contact-free manner
relative to the electrodes of an electrolytic cell by means of an electrolyte
containing electrically conductive bodies suspended in said electrolyte,
which method includes the steps of: charging said electrically conductive
bodies in said electrolytic cell on one electrode, which determines the
polarity of the workpiece surface to be processed, while shielding the other
electrode against discharge thereon of said electrically conductive bodies,
and while positively circulating said electrolyte in a circuit between the
said one electrode and the workpiece to be processed, withdrawing electrolyte
from said circuit outside sald electrolytlc cell after separ~tLon of sald
electrically conductive bodies suspended in the electrolyte, and lntrocluclng
electrolyte from outside sald electro]ytlc cell into the shlelded reg:Lon con-
.
s
taining said other electrode of said electrolytic cell.
From another aspect, the invention provides an installation for
electrochemically processing metallic surfaces of workpieces, including:
; an electrolytic cell provided with a diaphragm inserted between
anode and cathode electrodes, the diaphragm being adapted to divide the cell
into first and second chambers; said first chamber, which includes a first
of said electrodes the polarity of which determines the polarity of the work-
piece, containing conductive bodies suspended in an electrolyte so that said
bodies are charged by contact with said electrode; and said second chamber
including the other electrode and containing electrolyte free of said ~ ;
suspended conductive bodies;
a treatment chamber wherein to dispose, free from contact with
anode and cathode, workpieces the surfaces of which are to be contacted with
the electrolyte containing the electrically conductive bodies after charging
of said bodies at said first electrode;
a conveying path for the electrolyte containing the bodies being
provided between the treatment chamber and said first chamber, one part of
the conveying path being provided with a porous wall which is permeable to
the electrolyte but retains the electrically conductive bodies; and
means for conducting electrolyte, permeating without said bodies
through said porous wall, into said second chamber of the electrolytic cell
for exchanging electrolyte therewith.
Objects and advantages of the invention will appear more clearly
from the following specification in connection with the accompanying drawing,
in which: ;
Figure 1 diagrammatically shows by way of example one installation
for practicing the method of the invention.
Figure 2 is a diagrammatical vertical section of the installation
according to Figure 1, said section being taken along the llne II-II of
Figure 1.
According to the method of the present inventlon for electrochemic-
?q,~
ally processing metallic surfaces o~ workpieces arranged in a contact-free
manner with regard to the cathode and anode, the elec~rolyte is pos:itively cir-
culated in a circult between the electrode charging said workpieces and the
sur~ace of the workpieces to be processed, and electrolyte pro~ided outside
the electr~ly~ic C911 after s~paration o the el~ctrically conductive bodies
suspended in the ~lectrolyte, is withdrawn from said circuit and is in~roduced
in~o the electrolytic cell within ~he region of the counter electrode shielded
by the diaphragm.
Referring now to the drawing in detail, the apparatus according to
the invention includes an electrolytic cell 1 with an anode 2 and a cathode 3.
Interposed between these electrodes o the elec~rolytic cell 1 is a diaphragm
or an ion exchange membrane 4 which divides the electrolytic cell into two
chambers 5 and 6. In the chamber 5 which houses the anode 2, there are elec-
trically conductive bodies which are suspended in ~he electrolyte and which
are electrically charged on the anode 2. The electrically conductive bodies
are prevented from passing from chamber 5 into chamber 6 of the electrolytic
cell 1 in which ~he cathode 3 is arranged by means of said inser~ed diaphragm
4.
~rom the chamber 5 of the electrolytic cell 1 electrolyte with ano-
dically charged electrically conductive bodies is passes into a conveying
i` line 8 by a conveying means 7, in the speciic example by a Y~ *~ pump P.
The conveying line 8 leads in~o a processing chamber 9. At the end of ~he
conveying line 8, nozzle spray heads 10 are arranged, through which the elec-
trolyte is sprayed onto the sur~ace of a workpiece 11 to be processed> ~he
workpiece being transported for the electrolytic treatment from the position
shown in Figure 1 on the left hand side of the nozzle spray heads 10 to be-
tween the nozzle spray heads, Instead of spraying the electrolyte containing
the charged bodies onto the surface of the workpieces to be processed, it is
also possible to immerse the workpieces into an olectrolytic bath. ~xpodiently,
this is done for instance when recovering metals from so~called cable scrap.
~?,,~
In the p~ocessing or treatment chamber 9, ~he anodically charged el0ctrically
conductive bodies give off their charge to the surface ~o be processed while
ions corresponding to the electrochemical charge equivalent en~er in~o solution
in the electrolyte. With the processing of workpieces having a copper surface
as is assumed in the paFticular embodiment shown, copper cations en~er into
solution.
From ~he processing chamber 9, ~he electrolyte containing ~he dis-
~) qve ~ o ~ ~
B charged electrically conductive bodies and the cations which w4*~ into solution,flows hack into ~he chamber 5 of the electrolytic cell 1, where the elec~ric-
ally conductive bodies suspended in the electroly~e are charged again on the
anode 2. 'rhe electroly~e is re-circulated and conveyed ~o the processing
chamber 9.
Qn the pressure side of the pump 7, in the conveying line 8 there
is a saction 12 ~hich has a porous wall. In ~he specific embodiment shown,
the section 12 of the conveying line 8 consists of a grzphite pipe 13 through
which the electroly~e solution passes which contains ~he electrically conduc-
tive bodies, The graphite pipe 13 is surrou~lded by a mantle 14 so that be-
tween the graphite pipe 13 and the mantle 14 there is an annular chamber into
which electrolyte free from electrically conductive bcdies can pass ~hrough
the porous wall of the section 12. This annular chamber communicates through
a pipeline 15 with the chamber 6 of the electrolytic cell 1 in wh;ch the
cathode 3 is arranged~ In this way, on the cathode 3 a uni~orm metal ion
concentration is assured, and the development of hydrogen on ths cathode is
prevented. At the same time, the cell voltage in the electrolytic cell 1
remains constant.
Due to the feed in o electrolyte into the chamber 6 of the cathode
3, an o~erpressure is created so that electroly~e ~lows through the diaphragm
4 into the chamber 5 o~ the e~ectrolytic cell 1. In this way, the diaphragm
is rinsed, and electrically conductive bodies which mlght have deposited there-
on ~ill be ~a~hed o~ the diaphragm. When an ion exchange membrane is used
- 5 ~
(instead of a diaphragm) the electrolyte flows hack into the chamber S ~hrough
a connection tube 20 or through a conveying line 16.
To the space surrounding the section 12 with a porous wall there is
connected a further conveying line 16 which leads in~o a r~nsing chamber 17
for the workpieces to be ~reated in the processing chamber 9. In the drawing,
the workpieces present in the rinisng chamber 17 are designated with the
reference nu~eral lla. During the rinsing operation with the electrolyte,
the processed surfaces of ~he workpieces are cleaned of adherlng electrically
conductive bodies. From the rinsing chamber 17, ~he electrolyte flows back
directly into the chamber 5 o~ the electrolytic cell 1.
In the specific embodiment shown in the drawing, the rinsing chamber
17 is followed by a further rinsing chamber 18 in which the ~reated workpieces
which in Figure 1 are designated with the reference ~u~eral llb are freed
from the residual still adhering electrolyte by means of clear water. The
water is conveyed into the rinsing chamber 18 by a pump 19.
Exa~ple:
Por processing copper covered plates, graphite powder particles of
a size of up ~o 0.1 mm were added to an ammoniacal electrolyte which contained
a coppar salt contalning up to 100 grams copper per liter. As graphite pipe
of commerc~ally available por~us graphite ~here was installed a pipa with an
inner diameter of 40 mm, a wall thickness of 5 mm and a length of 1000 mm.
In the apparatus, approximately S0 liters per minute of electrolyte was cir-
culated. Of this quantity of electrolyte, per minute approximately from 400
to 500 cubic centimeters of electrolyte free from electrically conductive
bodies were withdrawn from the annular space surrounding the graphite pipe
13 while of this quanti~y about 60% were introduced into the cathode space
whereas the rest was employed ~or rinsing the processed or treated surface
of the workpieces, In the apparatus during the period of operation, the
necessary cell voltage remained constant in the electrolytic cell at 1.8 V
3Q ~ith20 A current ~low~ Also the diaphragm 4 romalned well pormoable.
S
It is, of course, to be und~rstood tha~ ~he present invention is,
by no means, limited to the specific showing in the drawing or the specific
example set orth above, but also comprises any modifica~ions within the scope
of the appended claims.
