CA2099008A1 - Arrangement in an installation for electrolytic treatment of workpieces - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The invention relates to an arrangement for an installation used for the electrolytic treatment of workpieces comprising two anode bars (2) with series-mounted anodes (A) and one cathode bar (3) with series-mounted workpieces (W). In order to ensure in a simple manner and without major power losses that the individual workpieces are each subjected to the same cell voltage, thereby producing the desired material deposit of approximately the same thickness of each workpiece, different cross sectional ratios of the anode (2) to the cathode bar (3) and/or changes in the electrical resistance of these bars per unit of length and/or resistors (R) between the individual anode bars (2) and the respective associated anode (A) are used in order to supply defined current levels to the anode bars (2) and give a defined current output from the cathode (3).

Description

20'~9~

~1--2 AR}~NGENENl~ IN AN IN~ A~A~ION FOR E~ECq!ROLYq!:tC

3 T~EATMEN'r OF WORX~IECE8 The invention relate~ to an ar~angement 6 aa~o~ding to thq preamble of clalm 1. It i9 7 intended chie~ly for the eield o~ galvanization, but 8 al~o for other in~tallations ~or elec~rolytia g treatment of workpiece~, e.g. olectrophoresl~. ~he parts o~ workpiece~ to be treated no~mally ~orm the 11 oathode and are in a conductive connection with the 12 aathode rall. ~he cathode rall conventionally forms 13 . the 50~a~1 led goods carrler. The anodes are 14 connected to ~he two anode rails which are ~ituated ln the bath along wlth the workpiece~. ~he 16 workpieces ~an be lowered into and removed from the ~7 bath via good~ carrier~. The anode rails and the 18 cathode rail lie outside the bath li~uid, whlle the 19 Ano~e~ ccnnected with the anode ralls and the wo~kpleces connectod with the cathode rall are 2~ loaa~ed in the bath liquid. The anode rail~ and the 22 ~a~hode rall have a dual function in that they must 23 ha~e a ~u~lcient meahanic~l ~tability for 24 supporting the anodes a~ well a~ the workpieces on the one hand. They should also have su~flci~ntly 26 lArge cro~s seations with hlgh conductivity ~or 27 ~eedln~ and drawlng of~ the electrolytl¢ ~reatment 28 current~ which ar~ generally very high. Although 29 copper, a~ a work material, has very high electric aonductlvity, it i~ generally not suitable ~or the 31 production o~ rails of this type in view of its 32 susceptlbil~ty to ao~rosion and its poor mechanlcal 33 stren~th. Therefore, in practice, spe~ial ~teel is 34 preferred for this purpo~e for reliability of . .

:
' , 209~

1 contact and mechanical strength. Its sub~tantlally 2 low~r conductivity compared wlth cepper must be 3 taken into the bargain.

4 A ~erie~ o~ so-called parallel-connected cell~
ar~ located ln ~he bath along with the workpieces 6 which are to receive electrolytic treatment. It ~
7 endeavored to achleve a uniform ~hlokne~ o~ the 8 electrolytlo coating on all wor~pieceR, i.e. in all 9 cells. ~his can only bs accomp}ished i~ the electrolytic current 1~ approximately identical in 11 all cells, which ln turn require~ a corresponding 12 equalization o~ the galvanizing Yoltages (aell 13 voltages) for all workpieces. As a result of 14 voltage drope which o~ou~ in ~he anode rail~ a~ well a~ in ~he cathode rall, there i~ a change alon~ th~
16 length of the rails in the galvanioally active oell 17 voltage on every workplece. Consequently, the 18 thlckncss of the eleatrolytlcally applied layer 1~ varies Prom one workpiece to the other. In newer ln~tallations, thi~ e~fect i~ aggravated because o~
21 the de~ire to maintain a very low cell volt~ge Uz, 22 e.g. in the order of magnitude of 1 V, so as to 23 economize on energy in the electrolytic bath.
24 Accordingly, di~ferences ln cell voltage in the millivolt range cAussd by the v41tage drop ln the 26 rail~ have a negatlve lmpaat.
27 Formerly, the aforementioned disadvantage wa~
28 tolerated or el~e Various attempts were made to 29 remedy the situation. For exampls, the cros~
seotions of the anode rall~ and cathode rail wore 31 lnoreased in order to reduce unwAnted voltage drops 32 ~U. In other ca~e~, the rails were manufactured 33 ~rom aopper instead o~ special steel with it~
34 mechanical advantage. ~hi~ was subiect to very 2 0 ~ 8 l ~trict economic limits due ~o the increa~ed weight 2 Oe the rails and the re~ultiny expense. When copper 3 was used, its suscepti~ ty to corrosion relative 4 to the aggre~sive electrolyte~, e.g. o~ a galvanlc bath, al~o came in~o play. Thus, only lnslgni~icant 6 l~provement~, if any, were achieved in practlce, An 7 at~empt wa~ al~o made to supply or remo~e the 8 ~urrents at both ends o~ the rails. This g presuppose~ a constan~ transition resi~tance of contact at both end~, which could not be achieved in 11 practice. Moreover, this doe~ not eliminate the 12 voltage drop generated by the respective required 13 eurrent along the rail, but reducss it by half, l.e.
14 defectq caused by voltage drops are only eliminated to a limited extent. A balancing o~ the indlvidual 16 voltages of all cells and accordingly an 17 equalization o~ all cell currents wh~¢h would 18 substantially or even entirely eliminate the~e 19 de~ects could not be achleved.
~ proces~ for balancing the partial currents ln 21 an electrolytic bath is known from DE-OS 37 32 22 476.4. In thi~ proces~, pa~ive dropplng re~i~tor~
23 were inserted into the technologically conditioned 24 partial circuit~ (aells) of the 2S overall eleatrolytic alrcuit to improve the layer 26 thickness dl~tribution, 50 that the magnitude o~ the 27 partial currents in the series connection ~ormed ~n 28 this way is determined by the dropping re~is~or~.
29 DE-OS 37 32 476.4 provides no detailed in~ormatlon aoncernlng the number and arrangement of anode and 31 cathode rails. In partlaular, no technlcal teaching 32 i~ pro~ided a~ to where the r~spectlve ourrents are 33 ~ed into the rails or where they exit from the 34 ralls. ~he technical di~closure of thi~ pu~lication 20~9~

1 1~ thu~ limitsd to the u~e o~ the a~orementioned 2 dropping resistors. These dropping re~i~tor~ are to 3 be substantially greater than the technologically 4 conditloned unstable ele¢trolytl¢ partlal resi~tance, the intent~on being to achleve equallty 6 of ~he lndivldual partial ourrents, i.e. the cell 7 currents, by a ~uffiaien~ly high dropplng resistance a ln reliance ~n Kirchho~f'~ law. The u~e of ~uah 9 hic3h ~esi~tance value~ With correspondingly high el~ctroly~e partial currents causes aorresponding 11 energy losse~ and hlgh voltage drops. Both o~ these 12 re~ults conPlict with the above-mentioned demands 13 for energy savlng and worklng wlth voltages in the 14 range of 1 V. ~he re~lstors have very large dimension~ due ~o the hlgh ourrent~ and are 16 therefore very d~Pficult to employ with resp~ct to 17 de~ign. By the same token, the costs are 18 considerable. DE-OS 29 51 708, which addresse~ the 19 same problem, ls mu¢h too costly ln term~ of apparatuq.
21 The present invention propose~ ~o en~ure, even 22 with the use o~ anode and cathode rails having a 23 poorer electrical conductivity than copper, e.g.
24 produced from the above-mentioned ~peaiaI ~teel, that ~dentical cell voltage i9 applied to the 26 individual workpieces o~ the cells o~ ~uch a bath in 2~ a simple manner and without sub~tantial energy 28 los~es. This is one of the precondition~ ~or the 2g de~ired depoa$tion o~ material of approxlmately equal ~hlckness on eve~y workpiece.
31 ~ir~t, proceeding from the preamble of claim 1, 3a the combinat~on of feature~ a) and b1) o~ the 33 cbaraateriz$ng part o~ claim 1 i~ pro~lded ~n order 34 tc meet this ob~ect. ~he fea~ur~s of part a) cause 2 E~ 9 ~

a rRduction in the current 10wing throucJh the anod~
2 ralls in the feed ~irectlon ~rom one anode to the 3 other, slnce a portlon o~ th1s current is drawn of 4 lnto the bath with each anode. In the cathode rail, on th~ other hand, the cu~rent increa~ee in the same 6 direction ~rom workpiece to workpiece until exiting 7 at the other ~ide o~ the bath, since a corre~pond$ng 8 partial current f low8 into every workpleae 9 tcathode). When this arranyemen~ 18 ob~erved from one sid~ o~ the bath where current is fed into the 11 anode rails toward th~ other ~ide of the bath where 12 the curren~ exits from the cathode rall, then, ~3 assuminq a cons~ant cro~ 6eo~10n of each of the 14 a~orementioned rails, the~e re~ults ln thl~
direction a reductlon in the voltage drop per rail 16 length at the anode rails and an increase in the 17 ~oltage drop at the cathode rall. These ~oltage 18 drops compensate ~or one another at least in part.
19 ~he e~ects Oe feature bl) also come into play in ao thl~ respect. ~his ratio o~ the oathode rail cross 21 section ~QK) to the cross section of the anode rall3 22 (QA) takes in~o account the fact that the cathod~
23 rail must absorb and transmlt the electrolyte 24 currents of the two anode rail~. The anode rail~
and the cathode rail can accordingly be produced 26 ~rom a material such a6 ~peclal ~teel which, in 27 comparlson to copper, 19 ~esi6tan~ to corroslon and 28 ha~ poor conductlvity.
29 An alternative solution to the object and problem posed ~y the present invention i~ provlded 31 ln the ~ub~ect matter o~ the a~sociated claim 2.
32 T~e proamble and feature a) of thls claim are 33 identlcal to the corresponding parts of claim 1.
34 Part b2) contalns an increa~e and rQd~ction, 2:~99~

1 re~pectively, in the cross sec~ion o~ the ra~ls 2 which ro~ghly aorre~pond~ to the ahanging value~ o~
3 the current in the rails and accordingly lead~ to - 4 approximately equal cell voltage in each cell o~ the bath as a result of ~he vol~aye drops caused in the 6 individual partial lengths o~ the rails acaording to 1 Ohm'~ law.
8 The subj~ct matter o~ claim 3 contains another 9 assooiated alterna~lve ~ol~ltion to the ob~eçt an~
problem proposed ab~ve. In thls :ln~tanae, al~, the 11 prea~ble and featu~e a) are Ldentical to tho~e o~
12 cla$m 1 and clalm 2. The difPerence between these 13 alaims consists in ~eature b3~, which likewie~
14 aahleve~ an equalizatlon Oe the olectrclyte partlal currents of the indivldual cells and accordlngly 16 meet~ the ob~eat of ~he lnvention, whlle 17 n~vertheless avoiding the disadv~ntages disau~sed 18 with ref~rence to ~OS P 37 32 476.4. In addl~io~, 19 DE-OS P 37 32 476.4 contains neither the arrangement o~ features of the preamble nor that o~ part a) o~
21 claims 1, 2 and 3. Howeve~, in the caee of featu~e 22 b3~, the magnitude of resi~tanoe i~ by no meane 23 optionally high as ie lndicatcd in ~E-OS P 37 32 24 476.4. On the contrary, the ~lue ~f the~e resl~tors must be adapted, according to Ohm's law, 26 to the other ele¢trlcal specifications, particularly 27 the voltage drop~, Q~ the overall arrangement so 28 that the desired ~ualization of partial currents 29 takes place.
~he ~eature~ indicated in the a6sociated clalm~
31 1, 2 and 3 in parte bl), b2) and b3) can al~o be 32 aombined in an advantageous manner, including the 33 ~eatures of the preamble and of part a). ~h~s is 34 th~ sub~ect m~tter of claims 4 to 7 and r~sult~ in 20~9~

1 a co~re~pondlng combined effect of the ~eatures oP
2 part~ bl), b2) and b3).
3 Further developments, advan~aga~ and ~eature~
4 of ~he inven~ion eollow from th~ add~tlonal subclalm~, a~ well a~ from the following descrlption 6 and relevant, ~ubstantially sch~matic drawlng~, The 7 drawlng~ ~how only thos~ ~eature~ neces~ary ~or an 8 under~tanding of the lnvention:
g Fig. 1 ~how9 an arrangement ~ccording to the prior 11 art;

13 Flgs. ~ and 3 ~how arrangements accordiny ~o tho 14 lnvention;
16 Fig. 4 ~how~ a bas~c illu~tratlon o~ the voltago 17 drops and voltages in a flow o~ aurrent a~ ~hown in 18 Figs. 2 and 3, in whlch the effec~s o~ features b), 19 b2) an~ b3) o~ the clalms are not ta~en into accountJ
22 Fig. 5 shows a baslc vlow of the invention in wh~ch 23 number~ have been provided for the current~ and 24 voltage drops ln an embodlment form of ~he invention accordlng to Fig. 2 21 Fig. 6 show~ a chart de~cribing the embodiment form 28 a¢aordlng to Figs. 2 and 5;
as Flg. 7 ~hows the current~ ~nd voltage drop~ in an 31 arrangement aacordlng to Flg. 3 ~chematlaally;

33 Flg. 8 ls another chart showing the rail re~istance 34 along the length of the rall~

, ~- , .
' . ,~
. , , 20990~8 1 ~lgs. 8a to ~d show d~fferent constructions of 2 re~l~tors pertainlng ln principle to the chart 3 accordln~ to Fig. 6;

~ig. ~ shows another embodiment ~orm of the 6 lnvention.

8Fig. 1 shows an arrangement accordlng to ~he 9prior art wlth a rectl~ler 1 ~upplyin~ dc voltage, lOtwo anode rail~ ~, and a aathode xall 3. A~
11mentioned in the begin"lng, the anode rails and the 12cathode rail are slt~ated outside the bath llquld, 13whereas the anodes oonneated wlth the anode rail~
1~and the workpieaes connected with the aathode rail 15~re placed in the bath llquid. For ~he ~ake of 16~lmpliclty, however, the anodes Al-An and workpieces 17Wl-Wm are only $nd1cated in a ba~ic way in ~ig~. l 18and 4. Otherwise, the anode6 and woxkpieco~ are 19~ymboliaally aomprehended or subfitituted fo~ by the 20anede ra11s and aathode rall shown ln the dxawing.
alThe ~low dlrection~ of the current in ~he rail~ and 22in the bath 4 are lndicated schematically. It can 23be seen that the aurrent feed~ 5 into the anode 24rall~ and the current outlet 6 ~rom the cathode rall 25are eaah locatcd on tho ~ame side o~ the bath in 26~ig. l. For the above-mQntionod, ~athematiaally 27demonstrable reason~, the volta~e drops occurr~ng 28al~ng the rail~ 2, 3 cau~e unequal voltages at the 29~ndividu~l aells containlng the workpieaes W, which 30are only indicated schematic~lly. Di~ferent ccll 31currents (parti~l aurrent~) occur corresponding to 32the dlf~erent cell vol~ages, re~ulting in 33dlfference~ in the thicknes~ of the layer~ depo~lted 34on the ~oods (workpiece~) W. Simllar di~advantage~

20sslao~

l resulted ln a construction according to the prlor 2 art, not shown in particular, ln which curren~ was 3 fed from the recti~ier voltage ~ource l into the 4 anode rail~ and cathode rall from both sides.
The 1nvention i~ shown ~ir~t, also 6 ~chematiaally, with reference ~o Fi~ures 2 and 3.
7 Fig. 4 is a basic illustratlon of ~he voltage 8 ratio~.
9 Aacord1ng to ~igs. 2 and 3, the current 1s fed fxom ~he dc power sourae l into the ends of the ll anode rail~ 2 proceeding ~rom one ~ide 4' o~ the 12 ba~h 4 ~ltuated on ~he right ~re~erenae nu~ber ~).
13 ~he current then ~low~ from the anode rail~ 2 14 through the bath to the ca~hode rail 3, according to lS re~erence number 9, and exits ~rom the latt~r at a 16 side 4" oP the bath ~s~e reference numb~r lO~
17 oppo~ e to ~he ~eed ~ of ~he anode currants. In 18 other word~, th~ current lnlet ends o~ the anode lg rails an~ ~urrent outlet end oP the cathode rail are located opposlte one anothsr.
21 In the embodiment example of ~ig. ~, the 22 reSpectiVQ cro~ ~ections of ~ails 2 and 3 are a3 ~haded. q`he drawing shows that ths cro~s section QK
24 o~ the cathode ra`il 3 ls greater than the oros~
2~ ~ection QA of the respective anode rails 2. ~he 26 ratio QK:4A ~hould be no le6s than l.7~l, but can be 27 greater than 1.7:1 optionally as eoonomically aB feaslble. A cro~s-sectlonal ratio of 2;1 has proven 29 par~lc~larly advantageous. In thi~ re~pect, the chart according to F~g. 6 shows, by way of example, 31 that the relative uni~orml~y a~ the cross-seatlonal 32 ra~io af QK:QA - 2:1, which will be di6cu~sed at 33 greater length in th~ following, is ~oQt ~avorable, 34 while a very poor value i9 as6umed below this ratio, ::. '. : ~ - , - ~: - ' -, ~ ~

20~9008 1 although values whl¢h are stlll acceptable are 2 malntalned above it, as is shown by the contlnued 3 curve on the abscissa.
4 In the exa~ple ~hown ln ~ig. 3, the circuit arrangement is the ~ame as that in the example shown 6 ln Flg. 2, the di~ference belng that the cro 7 ~e~tion of the anode rail~ 2 deareases p~oceedin~
8 from the feed locations ~ oontinuing in the aurrent 9 flow directlon 12 " ,e. the speclfi~ electxical re~istance o~ ths aross ~ection of the anode rail~
11 increases in direction 12. The cathode rall 3 i8 12 arranged in ~uah a way that the cross section~ of ~3 thi~ rall increase ln the aurrent ~low directlon 13, 14 i.e. ~he specific electrical re~istanc~ o~ the a~o~
lS sections decrea~es in dlrection 13. Thi~ inventive 16 ldea is not 1 imited to the steplike change in the 17 cro3s sectlons of the rall~ 2, 3 shown ln Fig. 3 a~
18 will become more apparent in the following from 19 Figures 8 to 8d and their descrlptlon.
Fig. 4 shows schematically the anode rail~ 2 21 and the cathode rall 3 with the current ~eed~ 8, the 22 current outlet 10 and the anodes Al to An, as well 23 a~ the woxkpiece~ Wl to Wm. The letter~ "n" and "m"
24 are intentionally dif~erent to ~how that the number 2S of anodes need no longer coincide with the number of 26 workpieces. The correspondlng voltage drop~ at the 27 anodes are de~ignated by ~UlV to ~UnV and ~UlR to 28 ~UnR, respeatlvely. ~he voltage drops at the 29 cathode rail from one workpiece to the next are designated by ~Ul to ~Um. The voltages in the ba~h 31 at each cell ~re designatqd by UzlV to UzmV and Uzl~
32 to Uzm~, re~pec~ively. Thi~ arrangement corre~pond~
33 ~o the circuit or current feed and aurrent feed-out 34 aacording to the preamble and ~eature a) of the ', ~ '' ' ' -. ' .
.

2~99~

1 claims. However, the construct:ions according to 2 feature~ bl), b~) and b3) are not yet taken into 3 account. A theoretical calculat~on of the 4 arrangement according to Fig. 4 shows that while a partial compen~ation of de~ecte cau~ed by voltage 6 drops ls already achieved, th~ compensation ls ~till 7 no~ ~ufflclen~. Slnce only ~he differenc~s between 8 the aell voltagei necessAry Eor galvanizatlon ar~ to 9 be con~ldered in this instance, all volta~e drop~
~U~ prlor to the flr~t workpieae at the cathode rail 11 (point A) and ~UlV or ~UlR aEt~r the first anode at 12 the anode rail (point ~) are omitted. The sf~eative 13 bath voltage Uba~h V ~or the front side V and the 14 rear side R o~ the workpiece i5 accord~ngly applied between point A and points B. Each o f the f our 16 ~urrent paths from A to 8 shown in Fig. 4 ha~
17 di~ferent voltage drops on the ralls. The sum of 18 the voltage drop~ of every current path plu9 the 19 respective cell voltaye Uz i~ identlcal Eor the dlstance Erom A to B under consideratlon. ~y 21 de~inition, ~hls is Ubath V for the ~ront ~ide of' 22 th~ workpiece and Uba~h ~ for ~he rear ~ide. Thi~
23 ie eX~ressed mathematically in the ~ollowing manner:

-: , .

, 2~9~

a UzmV ' Ubath V - ~ U2V ~ ~ U3v ~ ~ UnV;
3 Uz3v = U~ath V ~ ~ U2V ~ ~ U3v ~ ~ U3J
4 ~t~ ~ Ubath V ~ ~ Ul - ~ U2 ~ U3;
~ Unyc ~ U3 and 6 ~ U3v~ U2 (symmetrical ~pecial case) 7 and 8 ~ U2v~ Q U
~o $t ~ollows that: UZmv ~ UZ3v ~ UælV;
11 ~1hi~ is proven by a numeri~al example wlth 12 re~erenc~ to the voltage~ entered in Fig. 5. When 13 Ubath ~ 1.4 volt~ the ~ollowing eq~ations re~ult:

Ubath ~ 1.4 V ~ Uzlv ~ 285 mV;
16 1.4 V ~ ~5 mV + Ux2v ~ 266 mV:
17 1.~ V ~ 171 mV ~ UZ3V ~ 228 mvt 18 1.4 V ~ 228 mV ~ UZ4V ~ 171 mVJ
19 1.4 V - 266 mV + UZ5V ~ 95 mV~
1.~ V ~ 285 mV ~ Uz6;

22acaoxdlngly:

a4 Uzlv ~ 1.4 V - 0.285 V ~ 1.115 Y ~ Uz max.
2~ Uz2v ~ V - 0.361 V ~ 1.039 Y
26 UZ3V ~ V - 0.399 V = 1.001 Y = Uz min.
27 UZ4v ~ V - 0.399 V = 1.001 v 28 UZ5V ~ 1.4 V ~ 0.361 V = 1.033 ~
29 Uz~V = 1.4 V - 0.285 V = 1.115 Y
31 that 1~, 32 Uzlv ~ UZ~V ~ Uz3y 33 UZ4V ~ UZ5V ~ Uz6Y;
Uzlv 3 UZ6V

20~9a~

UZ2V ~ Uz5V
2 Uz3V ~ Uz4v 4 ~he ~ame i~ ~rue for the cell voltage~ of the rear side o~ the workpieces:
6 Wlth a cross-sectlonal ratio o~ the cathode 7 rail to the anode rail~ according to Fig. 2 and 8 feature bl) oE th~ claims, Fig. 5 i8 a schematic 9 view (without the individual current feed~) of the anode rails 2 and the cathode rail 3 with the 11 current feed~ 8 of ~he anode current~ IA on the 12 rlght slde o~ the bath and the current outlet 10 of 13 the cathode rall current ~K on the left s~de o~ the 14 bath. A ratio QK:QA o~ 2:1 is assumed. The numbers employed ~or the respective current~ and voltage 16 drop~ are glven wlth re~rence to an example ~7 oalculated by simpli~ication~ permi~sible in a ~lrst 18 approximation. The guantity of voltage drop5 at an 19 anode rail is 14 and the quantity of voltage drops at the cathode rall i~ 15.
21 Tho comparative value y 18 introducQd ~or 22 evalua~ing ~he effectiveness o~ the various rail 23 arrang~ment~ he value y ls cnlculated ~rom the 24 maximum difference of the cell voltage~ with reference to the minimum cell voltage.

27 y = Uz max ~ Uz min ~ 100~;

29 Uz mln 32 y ls the relative nonuniformity. When aurrent 33 i~ ~ed in on one side accordlng to the prior art 34 ~Fig. 1), e.g. in rail~ which are prcferably produced ~rom special steel and have equal cro~

2 ~

1 section~, l.e. the cros~ section QK of the cathode 2 rail i9 equal to the croaa ~ec~ion QA of each of the 3 anode rails, r = 85%.
4 With the same parameter~, but with feature bl, in whiah the croas-seational ratio QK : QA of the 6 raila ~ 2 : 1, and wlth oppositely located feed 7 according to ~ig. 2, y l~ reduced to 11.4~ a~cordlng 8 ~o ~he following calculation:
~ ~ Uzmax - Uzmin . 100% - 1.115V - l.OOlV . 100% - 11.4%
11 _ ~2 U2min l.OOlV---14 ~hus, this embodiment ~orm o~ the invention already com~e aub~antially ¢lo~er to the ideal ~al~e o~ y 16 ~ 0 ~han was po~ible in the prlor art.
17 In ~he above respeat, Fig. 6 ~hows a ohart ~or 18 the latter example, where the ordinate shows the 19 nonuni~rmity y according to the formula glven above. The ~ro~a-seational ratio QX:QA is plotted 21 on the abacls~a. ~he curve shows that although the 22 ideal value o~ y - 0 i~ not yet reached with a 23 cro~6-5ectional ratio QK:RA of 2:1, there are al~o 24 acceptable value~ oP ~ above thl~ value of the curve 16, while t-he other curve branch takes an 26 unfavorable a~urse at values oP approximately 1.7:1 27 and lower.
28 Fig. 7 showa a view, similar to Fig. 5, of the 2g volt~ge drop~ and currenta of a numerical example in a construction oP the arrangement, according to the . . :

209~ JS8 1 lnventlon, according to Figs. 2 and 3. That i~, the 2 cros~-~ectlonal ra~io QK:QA = 2:1 is selec~ed ~Fig.
3 2) as w~ll as a change in the re~i~tanc~ values of 4 the rails ln theix lon~i~ud~n~l direction according to Flg. 3.
7 The followlng equations result when Ubath ~ 1.4V:

9 Ubath ~ 1.4V = Uzlv + 400mV~
1.4V - g5mV ~ Uz2v ~ 304mV;
ll 1~4V a 171mV + Uz3y ~ 22amv, 12 1.4V - 228mV + UZ4V ~ 171mVt 13 1.4V - 304mV ~ UZ5v ~ 95mV:
14 1.4V D 400mV ~ Uz6v S
~5 16 so ~ha~:

18 Uzlv ~ 1.4V - 0.400V ~ l.OOOV = Uz min.
19 Uz2v - 1.4V - 0.3~V - l.OOlV = Zz max U~3V ' 1.4V - 0.399V - l.OOlV
21 Uz~V ~ 1.4V ~ o,39gV ~ l.OOlV
22 UZ5V a l . 4V - 0.399V ~ l.OOlV
23 Uz6v ~ 1-4V - 0-400V 5 1 ~ OOOV

tha~

27 U~lV Uz2V U~3v Uz~V U25V Uz6V;

-~6-1 The same i~ true Eor the oRll voltage~ of the rear 2 ~ide o~ the workpiece~.
3 The relative nonun~formity amount~ to ~ ~ Uzmax ~ U2min . 100% ~ l.oolV - l.OooV loo~ ~ o%
Uzmin ~ ov l~D_ 11 ~hus Fiy. 7 ~how~ that the combinatlon o~ the 12 cxoss-~eational ratlo~ of the ralls acaording to 13 ~lg. 2 wlth the change in resistance along the 14 length oE the ralls accordlng to Flg. 3 combined with the aurrent di~ection~ or current ~eed~ and 16 aurrent outlet~ accordlng to feature a of the claim~
17 result~ in an optimal balanclng o~ the cell 18 voltage~.
19 Al60, the preceding ~a~ement~ ehow that substantially better values result co~pared with the 21 prior art already with the use of the features of 22 clalm 1 or those of clalm 2, since ln both ca~e~ ~he 23 voltage drop~ ~U at the anode rails and a~ the 24 cathode rail are changed ln A defined manner relatlve to the prior art, resultin~ in an 26 approxlmation o the amount~ of all cell voltages 27 VzlV to Uzmv, and Uzl~ to UzmR. Although i~ the 28 ideal oase of such an approximation the rela~ive 29 nonuni~ormlty y = 0%, the invention al~o lnclude~
arrangement~ wlth dif~erent values as alre~dy 31 mentloned, e.g. as was shown by way of example with ~\

2 ~

1 re~erence to Flg~ 2 and 5. For the re~t, there is 2 al~o a substantial improv~ment o~ the value y in the 3 ~xample of Figures 3 and ~ in ltsel~ ~alaim 2).
4 This is brought abou~ ln that the ¢hange in resistance at th~ anode rail~ cau~e~ an lncrease in 6 t~e voltage drop~ at the ends o~ the rail remote of 7 the ~ed, ~ituated at left in the drawings, wherea~
8 at the aa~hode rail an inarea~e in the voltage drops 9 re~ults at the end of the XA i l ~emote of the outlet situated on the right-hand side in the drawings.
11 This Pollows from ~he inarea~e in the rail 12 rasistance in the lndlcated regions. Fig. 8 shows 13 a basla chart o~ the change in the rail re~i~tance 14 R along the rall length L, where the direation of the ab~ai~sa ~ollows from the ~tatement~ made above 16 with re~erence to Fig~. 3 and 7 and particularly 17 from th~ schematic resl~tance d~agram in Fig. 3.
18 A~ already mentioned, the anode rail~ 2 and the cathode rail 3 can be produ~ed from special ~teel, ~0 e.y. V2~ steel. Tn this aase it is recomm~nd~d that 21 the part of the installation e~tabllsh~ng aontact 22 with th~ anode rall has a contact surfaoe made from 23 the same 6peoisl ~teel or i6 produced in its 24 entlrety from the same pecial ~teel.
2S Fig~. 8a to ~d eontaln e~odimen~ ~orm~ of the 26 construation of the rails 2, 3 whl~h are possible 27 and advantageous in praotlae for achievlng dl~ferent 2~9~

-18~
1 r~si~tance values over the leng~h of the rail as 2 disaussed above. Fig. 8a shows that the rail ls 3 provided in the reylon o~ high resistance with a 4 greater number o~ bo~e holes or other rece~ses 16 than in the portions of lower resis~ance. Fig. 8b 6 ~hows a rail whose cro~ ~ection chan~e~
7 continuously in the ~ongitudinal direction o~ the 8 rail, while Figs. ~c and 8d ~how rall con~truc~lons 9 who~e ~peciflc reslstanoe value ls reduced by steps ~17) in the longitudinal d~re~tion of the rails.
~1 Fig. 8c shows a rail which i~ ~a~hioned ln one plece 12 and Flg. 8d ~hows a rail composed o~ corresponding 13 laminatlons 18, 19. In particula~, the con~tructlon 14 a~aor~ing ~o F~g. 8a is dlstinguished by hlgh mechanical ~abllity~ ~he sandwich-type 1~ aonstruction aacerdlng to Fig. 8d can be 17 advantag~ou~ly constructed in such a way ~hat the 18 longest layer or laminatlon 18, at bottom in the 19 drawing, i~ made ~rom a -~pecial ~teel of very great mecnanlcal ~t~ength, while the ~hor~er layers or 21 laminat~ons 1~ locatQd above the latter are produaed 22 ~rom copper, i.e. from a very highly conductive 23 material. ~urther, it can be seen that the deslxed 24 resistance aurve tCour~e of resi~ta~ae along the as length of ~he rail) according to Flg. 8 aan be 26 achieved ~y changlng the design o~ tho 27 a~oxementioned rail examples according to Figs. 8a .
., .

. . ~
'' . ~

., :
.

"

2~9~

1 to 8d.
2The detailed view in ~ig. 9 ~howa only ene ~f ~~he rall~ 2 or 3 wlth ~eed llnes 20 to the 4workpieces 7 and the anodes ~1 to An~ Provlded 5along the course oE the~e eeed line~ are ohmlc 6resis~ors Rl, R2, ~3, eta. whose resi~tance valuos 7are xelatively low, 90 that voltage drop~ at those 8resistors at the occurring curxent~ lie only in the 9millivolt ran~e. The~ resi~tor~ are ~elected ln 10such ~ way ~hat, while aoaounting ~or the voltage 11drop~ ln the anode rail~, the cathode rail and ~t 12the anode~ and workpleces thqmselves, the re~pective 13cell ~oltages are equal to one another, or at lea~t 14achieve values which come very close to one another.
15Thus, on the on~ hand by effectlng expedient changes 16in the~e resistor~ R1, e~c., the desired ahange in 17the cell voltage~ in tha sense o~ a balance between 18them can be achie~d, but becau~e of the very low 19~e~istance values no critical losses need be 20 tolerated.
21AB was already mentioned, an arrangement 22aacording to Fiy. 9 which corxesponds to ~eature b3) 23of cla~m 3 can also be comblned with ~ature~ bl~
24(Figs. 2 and 5) and~or b2) ~igs. 3 and 7~, while 25still retalning the ba~c arrangement aocording to 26Fig. 4 (preamble and E~ature a of the claim~).
27Inso~ar a~ th~ de~ir~d approx1mat1on or 2 ~

1 equalization o~ the ~alues of the cell vol~age~ 18 2 achieved, it al~o lie~ within the scope o~ the 3 invention to overcompensate for the defect~ caused 4 by voltage drops mentioned with re~erenae to the prior art within the aforementioned limit~, .

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Claims (14)

Patent Claims:

1. Arrangement in an installation serving for electrolytic treatment of workpieces, whose bath has two anode rails, each of which is electrically connected with a series of anodes arranged one after the other in the longitudinal direction of the anode rails, a cathode rail also being provided which is electrically connected with workpieces which are arranged one after the other in the longitudinal direction of the cathode rail and are to receive electrolytic treatment, measures being provided which aim at a uniformity of the layer thickness distribution on the workpieces of the individual cells of such a bath, characterized by the combination of the following features:

a) a connection of the anode rails (2) and the cathode rail (3) to the do power source (1) which is effected in such a way that the currents (IA) are fed (8) into the two anode rails (2) at the same side (4') of the bath (4) so that these currents are rectified relative to one another in the anode rails and exit (9) into the bath, that the current is fed into the cathode rail (3) from the bath and exits (10) from the cathode rail at the side (4") of the bath lying opposite to the first side (4') of the anode current feeds (8), and b1) that the cross sections (QA) of the anode rails (2) are identical to one another, and that the ratio of the cross section (QK) of the cathode rail (3) to the cross section (QA) of each anode rail is at least 1.7 : 1.0 or more.

2. Arrangement in an installation serving for electrolytic treatment of workpieces, whose bath has two anode rails, each of which is electrically connected with a series of anodes arranged one after the other in the longitudinal direction of the anode rails, a cathode rail also being provided which is electrically connected with workpieces which are arranged one after the other in the longitudinal direction of the cathode rail and are to receive electrolytic treatment, measures being provided which aim at a uniformity of the layer thickness distribution on the workpieces of the individual cells of such a bath, characterized by the combination of the following features:
a) a connection of the anode rails (2) and the cathode rail (3) to the dc power source (1) which is effected in such a way that the currents (IA) are fed (8) into the two anode rails (2) at the same side (4') of the bath (4) so that these currents are rectified relative to one another in the anode rails and exit (9) into the bath, that the current is fed into the cathode rail (3) from the bath and exits (10) from the cathode rail at the side (4") of the bath lying opposite to the first side (4') of the anode current feeds (8), and b2) that the ohmic resistance per unit of length of the anode rails (2) increases in the direction (12) of the current feed (8) and the ohmic resistance per unit of length of the cathode rail (3) decreases in the direction (13) of the current outlet (10).

3. Arrangement in an installation serving for electrolytic treatment of workpieces, whose bath has two anode rails, each of which is electrically connected with a series of anodes arranged one after the other in the longitudinal direction of the anode rails, a cathode rail also being provided which is electrically connected with workpieces which are arranged one after the other in the longitudinal direction of the cathode rail and are to receive electrolytic treatment, measures being provided which aim at a uniformity of the layer thickness distribution on the workpieces of the individual cells of such a bath, characterized by the combination of the following features:
a) a connection of the anode rails (2) and the cathode rail (3) to the dc power source (1) which is effected in such a way that the currents (IA) are fed (8) into the two anode rails (2) at the same side (4') of the bath (4) so that these currents are rectified relative to one another in the anode rails and exit (9) into the bath, that the current is fed into the cathode rail (3) from the bath and exits (10) from the cathode rail at the side (4") of the bath lying opposite to the first side (4') of the anode current feeds (8), and b3) that ohmic resistors (R1-Rn) are installed between the respective anode rail (2) and the anodes (A1-An) which are electrically connected to the latter, the value of the ohmic resistors (R1-Rn) being such that approximately equal cell voltage is applied to each cell accompanied by a balancing of the currents passing over the anodes.

4. Arrangements according to claims 1 and 2, characterized by the combination of the groups of features a, b1) and b2).

5. Arrangement according to claims 1 and 3, characterized by the combination of the groups of features a, b1) and b3).

6. Arrangement according to claims 2 and 3, characterized by the combination of the groups of features a, b2) and b3).

7. Arrangement according to one of claims 1 to 3, characterized by the combination of the groups of features a, b1), b2) and b3.

8. Arrangement according to one of claims 1, 4, 5 and 7, characterized in that the ratio of the cathode rail cross section (QK) to the cross section (QA) of each anode rail is 2:1.

9. Arrangement according to one of claims 2, 4, 6 to 8, characterized in that the cross section of the anode rails (2) decreases in the direction (12) of the current feed (8) by means of recesses, such as bore holes, of different dimensions.

10. Arrangement according to one of claims 2, 4, 6 to 8, characterized in that the cross section of the cathode rail (3) increases in the direction (13) of the current outlet (10) by means of recesses, such as bore holes, of different dimensions.

11. Arrangement according to one of claims 2, 4, 6 to 8, characterized in that the cross section of the respective rail (2, 3) decreases and increases, respectively, in steps (17) in the respective indicated direction.

12. Arrangement according to claim 11, characterized in that the number and position of the steps coincide with the number and position of the anodes.

13. Arrangement according to claim 11 or 12, characterized in that the steps (17) are achieved by means of individual layers (18, 19) which form rails when connected with one another.

14. Arrangement according to claim 13, characterized in that the longest layer (18) is produced from a mechanically strong special steel, while the remaining, relatively shorter layers (19) are produced from a material with high electrical conductivity such as copper.