US2970950A

US2970950A - Method and apparatus for the continuous galvanization of the inner surface of tubes

Info

Publication number: US2970950A
Application number: US787036A
Authority: US
Inventors: Bahmann Hans-Joachim
Original assignee: Benteler Corp
Current assignee: Benteler Corp
Priority date: 1958-01-22
Filing date: 1959-01-15
Publication date: 1961-02-07
Anticipated expiration: 1978-02-07
Also published as: FR1221041A; DE1197719B; NL124779C; GB870352A; NL235329A

Description

1961 HANS--JOACH|M BAHMANN 2,970,950

METHOD AND APPARATUS FOR THE CONTINUOUS GALVANIZATION OF THE INNER SURFACE OF TUBES 5 Sheets-Sheet 1 Filed Jan. 15, 1959 8 8 8 2 8 8 2 Q2 5 A A 1961 HANS--JOACHIM BAHMANN 2,970,950

METHOD AND APPARATUS'FOR THE CONTINUOUS GALVANIZATION OF THE INNER SURFACE OF TUBES Filed Jan. 15, 1959 3 Sheets-Sheet 2 Feb. 1961 HANS--JOACHIM BAHMANN 2,970,950

METHOD AND APPARATUS FOR THE CONTINUOUS GALVANIZATION OF THE INNER SURFACE OF TUBES United States Patenti O METHOD AND APPARATUS FOR THE CONTINU- OUS GALVANIZATION OF THE INNER SUR- FACE OF TUBES Hans-Joachim Bahmann, Paderhorn, Germany, assignor 1 This invention relates to galvanizing, and more specifically to a method and apparatus for the continuous galvanization of the inner surface of tubes.

For galvanizing the inner surface of tubes it has already been proposed to employ anodes arranged coaxially within the tubes while the tubes themselves serve for accommodating the different treatment liquids, especially the electrolyte, which act successively and which are maintained in constant motion. Contrary to the galvanizing of the outer surface of tubes, it has hitherto not been possible to employ a continuous run-through process for galvanizing theinner surface of tubes. This has been hitherto carriedout by using dipping tanks in which the tubes are placed, preferably in groups. Apart,

from the fact that this process is complicated and timewasting owing to the relatively long time the preparation requires, other disadvantages are that these dipping tanks can only be employed for tubes of limited length and that, as a rule, it is not possible to galvanize tubes of different lengths in one and the same plant. Moreover, in the case of these known processes and apparatus, it is extremely difficult, owing to the danger of the electrolyte becoming weaker, to obtain uniform galvanizing of the inner surface in the case of tubes of very small internal diameter.

The object of the present invention is to devise a method and apparatus which enable the carrying out of a continuous galvanization of the inner surface of tubes, even when these have a very small internal diameter, for example down to 3 mm., in a run-through process, but at the same time avoid the disadvantages inherent in the known methods and apparatus While also attaining a considerable improvement from an economical point of view.

'This object is attained by passing the tubes, which are cathode-connected, continuously one after another through bath tanks filled with treatment liquids and at the same time feeding them along an axially arranged stationary anode which they surround, supplying uninterrupted current to the anode by at least a first and a second contact-maker arranged at a distance apart, and,

during the movement of the tubes through the plant in longitudinal direction, automatically sucking the. treatment liquids of the individual bath tanks into the interior of the tubes, pressmg it therethrough and, as soon as the rear end of a tube is free, pumping the liquid back into the respective bath tank by means of stoppers.

fixed on the anode in front of the inlet apertures and following the outlet apertures provided for the tubes in.

i opened at the same time.

escaping through gaps are provided preferably both in 2 suction and pumping efiects automatically produced by the stoppers during the run-through movement of the tubes, the necessary flushing of the inner surface of the tubes to be treated by the different treatment liquids contained in the individual bath tanks is ensured, without these liquids becoming intermixed.

So as to also ensure that the anode is continually supplied with anode current when fresh tubes are continuously fed, each time a tube is slipped on to the introduction end of the anode, the first contact-maker in the run-through direction is broken and at the same time the second contact-maker arranged at a distance from the first contact-maker is closed, preferably automatically, whereas, as the tube continues to run through, the first contact-maker is closed and the second contact-maker The current feed to the tubes is effected preferably by cathode-connected driving rolls which at the same time effect the movement of the tubes, arranged in substantially horizontal position, over the anode extending along the entire length of the galvanizing plant. The method proposed by the invention can obviously be carried out in such a manner that several rows of tubes are passed simultaneously on anodes arranged preferably side by side and at a distance apart in a substantially horizontal plane through the bath tanks serving for the pretreatment and finishing treatment as well as the galvanizing.

An arrangement particularly suitable for carrying out the method according to the invention comprises a plurality of bath tanks connected up in series and filled respectively with treatment liquids for the pretreatment, galvanizing and subsequent treatment of the tubes, at least one anode connected up with contact-makers and extending through all the said tanks, piston-like stoppers mounted on said anode one in front of the tube inlet aperture and one following the outlet aperture of each of said tanks, and of a diameter corresponding approximately to the internal diameter of the tubes to be treated, said stoppers being arranged at a distance apart exceeding the actual length of its associated tanks, and a plurality of rolls serving for transporting and guiding the tubes distributed in the longitudinal direction of the anode. At the same time the tubes are guided preferably only in the run-through region of the electrolyte tank by centering elements arranged on the anode and acting as insulation in relation to the tube wall, these elements being provided with through-flow passages extending parallel to the longitudinal axis of the anode. In this manner the tubes are automatically held in the necessary uniform distance from the surface of the anode, which is absolutely necessary for obtaining a uniform metal coating. The suction and pumping effect produced by the stoppers is not hampered by the centering elements owing to the provision of through-flow passages in these elements. On the other hand the through-flow passages effect an advantageous, continuous thorough mixing of the treatment liquid, so that a reduction in strength or a dissociation of the liquid is avoided.

To ensure a uniform feed of the tubes and a sufliciently reliable guiding, cathode-connected driving rolls front of and following theelectrolyte tank, while the supporting of the tubes in the remaining longitudinal region of the galvanizing plant is effected by idle guide rolls preferably arranged inside the bath tanks. So as to catch the treatment liquid between the inlet and outlet apertures in the bath tanks the plant is in operation,

collecting troughs are provided in front of the apertures,

from which troughs the treattinuously or periodically. of treatment liquid is prevented while on the other hand for the passage of the tubes when e emopso r p it is ensured that the actually necessary 'liquid level'in the tank is maintained. Moreover the constant circulation of the treatment liquid prevents it from separating into parts in the tanks.

The fact that both the driving rolls on a roll stand arranged in front of the electrolyte tank and also those of the set of rolls following the electrolyte tank are connected to the cathode circuit, ensures that, while a tube running ahead is still gripped by the driving rolls of the set of rolls following the electrolyte bath, the next, following tube is already switched into the current circuit and consequently subjected to electrolytic treatment.

The diameter of the anode is chosen so that under all circumstances there is a sufficient through-flow of electrolyte between the anode and inner wall of the tube and, a sufiiciently high current density. It has been found that, even in the case of tubes with small internal diameters, the stoppers coordinated to the bath tanks suffice for sucking the quantity of electrolyte liquid necessary for ensuring a sufliciently thick deposition. Even in the case of low runthrough speeds the filling volume of the tubes increases to such an extent that sufficient cooling and recuperation of the electrolyte liquid are attained.

The method proposed by the invention covers all types of galvanic treatment, such as zinc plating, copper plating, chroming, nickel plating, polishing and so forth.

The anode is preferably provided along a considerable part of its length with an electric insulating coating which is interrupted by electricity conducting surface sections in the run-through region of the electrolytetank. A parti ularly practical solution consists in arranging tubular sections composed of electric insulating and electric conductive material fixed in alternating succession on the wireshaped anode in the runthrough region of the electrolyte tank. The electric insulating tubular sections preferably consist of an elastic moldable plastic proof against the electrolyte and are slipped under elastic expansion on to theWire-shaped anode, The electric conductive tubular sectionsconsist of the metal to be deposited on the surface of the tubes and have an internal. diameter corresponding to the external diameter of the wire-shaped anode, so that theycan be slipped on to the anode and renewed when necessary or can be exchanged for tubular sections composed of another metal, but on the otherv hand are conductively connected with the outer surface of the anode over their entire inner wall. The length ofthetubular sections composed. of. electric insulating and electric con-' ductive materials depends upon the internal diameter of the tubes to be galvanized. and the run-through speedgof;

the tubes. As a rule the total length of the sections oomposed. of electric conductive material amounts to only aboutj fit to /2 the total length of the anode in the region ofthe electrolyte tank,

By the tubular sections composed of the metal to be electrolytically deposited on the inner wall of.the tubes and slipped on the anode, it is possible to effect a continuous regeneration of the electrolyte. that the anode within the electrolyte tank is in'contact with the electrolyte only on a portion of its length through an electricity conductive surface, the hydrogen formation in the electrolyte is reduced in an advantageous manner, An intensive formation of hydrogen would, particularly in the case of tubes with small internal diameter, prevent uniform galvanizing owing tothe formation of bubbles and liberation of hydrogen on the cathode-connected inner wall of the tubes.

Between the tubularsections of electric insulating and electric conductive materials arranged on the wire-shaped, anode, centering elements are provided preferably at uni-' form'distances apart, which elementsare principallyof cortical shape and are also slipped on to the wire-Shaped anode.

"The stoppers and the centering elements are soconstructed that they'insulate thetubewall from theanode T Owing to the fact.

ca'rrbe achieved most simply by'rnaking the stoppers and centering elements from an electric insulating material, particularly synthetic substance.

It is evident that there is no reason why further anodes, for example zinc plates, should not be additionally arranged within the electrolyte tanks outside the tubes, so as to coat also the outer surfaces of the tubes electrolytically with a metal layer.

A'preferred embodiment of the invention is hereinafterdescribed'by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a longitudinal section through a galvanizing plant;

Fig. 2 is a longitudinal section through an anode provided with centering means;

Fig. 3 is a cross section taken on lineIII lIIof Fig. 2;

Fig. 4 illustrates a set of driving rolls, and

Fig. 5 shows a contact-maker for the anode current.

Fig. 1 shows steel tubes 1 which have an internal diameter of about '3 mm. and are slipped. on a horizontally arranged anode 2.

The anode 2 consists, of. a. copper wire 3 which isencased on a considerable part of its length, in an. electric insulating material 4, such as e.g, rubber or plastic. The. anode 2 is stationary, and arranged axially, extendingv through bath tanks, 5, 6, 7 and 8 arranged. one, behind the other, Whereas the copper wire 3 outside the tank 7,. which servesaselectrolyte bath, is providedwiththeelecs' tricinsulating material 4 along its entire lengthwiththe. exception of

sections

3 a and 3b, within the electrolyte. tank 7 tubular sections of electric insulating material 4 andv tubular sections 4a of electric conductive material; are slipped on the copper wire 3 of theanodel in alterw nating succession as shown in Fig. 2. The tubular sectionsv of the electric insulating material 4 tightly surrounding the. anode 2 are preferablymade from plasticwith rubber-,- like characteristics which is not attacked bytreatment, liquids and especially the electrolyte. The tubular sec: tions 4g, likewise firmly seated on the copper wire 3, of, the anode 2 consist, in the example illustrated in the drawn ings, of zinc tubesiwhich are made from a 99.9% ,clectrw, lytic zinc.

Thelevel of the treatment liquids in the bath tanks.5 to. 8 is maintained, preferably automatically, at a height. which ensures complete flooding of the anode 2 and the wheel. On the ranges of length directly in front of and following the bath tanksS, to8, the anode Zis provided; with piston-

like stoppers

9a and 9b which, in the examplej. illustrated in thedrawings, are made froma rubber-like, electric insulating plastic which shows no signs of swelling. inthe presence of oil and acids The

stoppers

9a and, 9b are also'firmly seatedon the copper wire. 3 and their; greatestcross section corresponds to the internal diameter of the tubes 1 to be treated, so that they bear tightly" against the inner wall of the tubes. The stoppers. 9a and 9,b"taper like' ja circular cone arranged coaxiallyvto thel anode 2 in the opposite direction .to the run-through direc-i: tion of the tubesl indicated by arrow x. On the range of length located within the electrolyte tank 7 the anode is, provided with centering cones 10, the greatest cross'sec tion ofwhich also correspondsto the internal diameter of thetubes 1. The'centering cones 10 are made from an electric insulating plastic possessing high wear-resisting, and low deformation properties, for example from polyvinylchloride, which is also not attacked by the electrolyte. As can beseen from Fig. 2, the centering cones 10 are arranged between the'tubular sections of the electric insulating material 4 and the tubular sections 4a mountedon the wire 3 of the anode 2. The centering cones haveconcentric radial apertures constructed as through; fl'ow passages 10a for the electrolyte and extending pa a -j lel to the axis of the anode, see Fig. 3. Thecente'ring cones- 10. are preferably arranged at about uniform dis tances apart one behind the other on the copper'wire' 3.

For the current feed, the ;copper wire 3 outside the electrqlyte tank ,7 lies exposed merely on the two sections" 3a and 3b at a distance apart, the section 3b being of greater length than the section 3a. The exposed copper wire sections 3:: and 3b are, as can be seen from Fig. 5, limited by holding cones ll of insulating material. The length of the exposed copper wire section 3b is preferably so chosen that tubes of practically any lengths coming into question can be galvanized in a continuous operation.

For feeding anode current two contact-

makers

12a and 12b are provided which are coordinated to the

sections

3a and 3b of the copper wire 3 which are not insulated. The contact-

makers

12a and 12b are provided with a slot open in upward direction and of a width corresponding substantially to the diameter of the copper wire 3, and are arranged in a roller bed 13 so that they can be lowered in such a'manner that uninterrupted current is always fed to the copper wire 3 of the anode 2 by one of the two contact-

makers

12a and 12b. Thereby the alternating contact-making can be regulated for example photo-electrically in accordance with the position of a tube to be treated or by a mechanical feeling device. To adapt the spacing of the

contact makers

12a and 12b to an actual tube length, the contact-maker 12b is, in the example illustrated in Fig. 1, arranged to slide to and fro in the run-through direction indicated by the arrow x. For this purpose the contact-maker 12b can be mounted longitudinally shiftable within the roller bed 13 parallel to the anode 2. But it is also possible to build the roller bed 13 itself in such a manner that the part of the roller bed carrying the contact-maker 12b can be shifted to and fro in the run-through direction.

The roller bed 13 is provided with a plurality of transport rollers 14 arranged below and transversely to the anode 2 and which run freely. It is, however, also possible to construct the rollers 14 so that at least some of them can be mechanically driven. The rollers 14 are arranged with their periphery at such distance from the anode 2 that the tubes I slipped on to the anode 2 can be moved on the transport rollers 14 substantially coaxially to the anode in the run-through direction indicated by the arrow x. For this purpose the rollers are preferably provided with a groove conforming approximately to the external diameter of the tubes 1.

Roll stands 15 and 16 arranged respectively in front of and following the electrolyte bath 7 each comprise two driving

rolls

15a, 15b and 16a, 16b respectively which are driven at the same speed and connected to the cathode circuit. The driving rolls 15a, 15b and 16a, 16b respec- V tively are each adjustable in a vertical plane extending in the run-through direction in such a manner that their relative'spacing can be adapted to the different external diameters of the tubes to be treated. Each of the driving rolls 15a, 15b and 16a, 16b respectively is provided with a

groove

15c and 16c, which corresponds approximately to the external peripheryof the tubes to be treated, see Fig. 4. A particularly practical form of construction for the roll stands comprises two cathode-connected rolls, provided for supporting the tubes to be treated and arranged one behind the other at a distance apart, whereas a roll engaging the tubes from above and arranged in the length section located between the two lower rolls is constructed as driving roll. The driving roll can for this purpose be provided with a groove of plastic with transverse ribs.

The tank 7 contains electrolyte liquid 17 which, in the example illustrated in the drawings, consists primarily of a zinc sulphate solution. The level of the electrolyte liquid 17 is slightly above a tube inlet aperture 18a provided on the front end of the tank 7 and a tube outlet aperture 18b provided on the rear end of the tank 7. The

apertures

18a and 18b can with advantage by provided on their circumference with packing sleeves of flexible material to offer a certain amount of resistance to the flowing out of the electrolyte liquid. Below the tube inlet aperture 18a and the tube outlet aperture

18b collecting troughs

19a and 19b respectively are provided for catching the electrolyte escaping through the end apertures in the tank. For pumping back the electrolyte liquid which is caught in the collecting

troughs

19a and 19b a pump (not shown in the drawings) is coordinated to the tank 7 so that a continuous circulation of electrolyte liquid and the maintenance of the necessary level of treatment liquid are ensured. In addition, a circulating pump (also not shown in the drawings) is provided for preventing impoverishment in metal, which would detrimentally affect the uniform separation and also heating of the electrolyte liquid to an excessive extent. Loose guide rollers 20 are provided in the tank 7 for supporting and guiding the tubes.

The bath tanks 5 and 6 connected up in front of the electrolyte tank 7 as well as the bath tank 8 connected up behind it are of substantially the same construction as the tank 7. Each of these tanks is also provided with a tube inlet aperture 18a on its front side and a tube outlet aperture 18b on its rear side and the anode 2 passes substantially coaxially through these apertures. Collecting

troughs

19a and 19b are also arranged on the front and rear sides respectively of these tanks for catching treatment liquid escaping from the particular tank. The tanks 5, 6 and 8 arranged in front of and following the electrolyte tank 7 contain guide rollers 2G for supporting and guiding the tubes 1.

The bath tank 5 is filled with a degreasing liquid 21, whereas the tank 6 in front of the tank 7 contains a flushing liquid 22. The last bath tank 8 also contains a flushing liquid 23. In addition a pump is also coordinated to each of the tanks 5, 6 and 8 arranged in front of and following the electrolyte tank 7 for pumping back the treatment liquid caught in the collecting

troughs

19a and 19b, and also a circulating pump for continuously circulating the treatment liquid. The pumps are also in this case not shown in the drawings for the sake of clearness. The level of the treatment liquids contained in the bath tanks 5, 6 and 8 is also slightly higher than the tube inlet and

outlet apertures

18a and 18b of these tanks.

Another roller bed 24 with transportrollers 25 is connected up behind the galvanizing plant, the transport rollers 25 of this bed arranged transversely to the runthrough direction being all freely rotatable or in part capable of being mechanically driven.

The method of operation is as follows:

After the current contact-

makers

12a and 12b have been set at a distance apart which is slightly greater than the length of the tubes to be treated, the tubes 1 are slipped one after the other on to the anode 2 in the direction of the arrow x. As the tubes are slipped on,

the anode 2 receives current via the contact-maker 12b, whereas the contact-maker 12a is broken. When the rear end of a tube releases the contact-maker 12a, this closes the circuit whereas at the same time the second contact-maker 12b in the run-through direction indicated by the arrow x opens or breaks. The tube 1 can then be transported without hindrance in the run-through direction and is moved on by the transport rollers 14 in the direction of the arrow x. During this movement, the tube is pushed over the stoppers 9a arranged in front of the bath tank 5 and its front end subsequently enters the tube inlet aperture 18a in the tank 5. Seeing that the front tube opening is surrounded by the degreasing liquid 21 in the tank 5, a suction effect is caused by the front stopper 9a as the tube moves forward, so that the inner surface of the tube 1 is now flushed by the degreasing liquid 21 and degreased. This suction effect is maintained until the front end of the tube reaches the stopper 9b following the tank 5, by which stopper the degreasing liquid sucked into the tube and located between the two

stoppers

9a and 9b coordinated to the bath tank 5, is forced through the tube until the rear end of the tube is free of the front stopper 9a, wherebath tanks.

upon the degreasing liquid is pumped back through the ear end of the tube into the bath tank S by the stop- Subsequently the front opening of the tube is pushed over the-frontstopper 9a of the next-followingflushing tank 6, if necessary with the "aid of 'an' intermediary driving roller set. Inside this tankthe manner of operation is the same as that in the tank 5, that is the flush ing liquid 22 in the tank 6 is sucked into the interior of the tube until the front end of the tube reaches" the stopper 9b behind the tank 6,'when, on the rear end of the tube becoming free, the flushing liquid is pumped back into the bath tank 6 by the stopper 9b.

The tube pretreated in this manner is now' gripped by the driving rolls 15a, 15b of the roll stand 15. Thereby, after the tube has been slippedover'the stop- :per 9a arranged in front of the electrolyte tank 7 and introduced through the tube'inlet aperture 18a into' the yelectrolyte liquid, the circuit is closed so that the galvanization of the inner surface of the tube can start up. Hereby the tube'is fed through the plant at'a runthrough speed which is dependent on the one hand upon :thethickness of the metal coating it is desired to ob tain and on the other hand upon the concentration of the electrolyte and the density ofthe current employed.

' v The tube travels during its run-through movernent through the electrolyte tank 7 over thecentering cones of the anode 2 so that a uniform coating of the metal deposit is obtained on the inner surface of the tube. The electrolyte liquid sucked into'the tube by the stopper 19a is drawn in through the passages 10:; inthe centering H cones 10 until the front end of the tube'reaches the stopper 9b at the outlet aperture 18b of the electrolyte tank 7, by which stopper the electrolyte liquid is pressed towards the rear through the passages 10a in the centering cones 10 and, when the rear end of the tube becomes free, out of the tube; The tube is subsequently gripped by the driving rolls 16a and 16b of the roll'stand 16,

which rolls keep the tube connected up in the current circuit. In the meantime the 'next fol'owing tube is simultaneously connected u'pin the circuit by the roll stand arranged in front of the electrolyte tank 7 and sub jected to electrolytic treatment. The driving r'ollslGa and 16b of the roll stand 16 in the meantime guide the preceding tube to the flushing tank 8 in which the flush- "ing, liquid 23 is first sucked into the interior ofthe tube and subsequently pumped out of the tubesagain by the stoppers 9a and9b. i

When the galvanizing plant is no longer in use, bottom valves on the individual bath tanks are opened and the treatment liquids flowing out therefrom are cau ht in the collecting troughs coordinated to the individual The invention may be embodied in other specific forms without departing from the'spirit or essential characthe bath tanks a tube is free, pumping 8 the liquid back into the respective bath tank. '1

2, Method as .setforth--in claim- 1, wherein several rowsof tubes are fed simultaneously on a corresponding'nurnber o f anodes arranged in a horizontal plane preferably side by side and at a distance apart through '3; Apparatus for electroplating the inner surface of tubes having internal diameters down to 3 mm. and impermeable walls in a continuous operation, comprising a plurality of bath tanks connected up in series and adapted to be filled respectively with treatment liquids for the pre-treatment, electroplating and subsequent treatment of the tubes, each of said tanks having a tube inlet aperture and a tube outlet aperture at least -one anode connected up with contact-makers and extending throughsaid aperture of said tanks, a plurality of v piston-like stoppers mounted on said anode one in front ofdthe tube inlet'apertureand one following the outlet aperture of each of said tanks, and of a diameter corresponding approximately to the internal diameter of the n tubes to betreated, said stoppers'being'arranged at a -distance apart exceeding the actual'length of its assoelated tanks, and a plurality of rolls serving for transporting and guiding the tubes distributed in the'longitudinal directionof the anode.

4. Apparatus as set forth in claim 3, wherein centering elements for guiding the tubes are arranged on the v anode preferably only in the'run-through regionof that trolytetank, and loosely mounted guide rollers are arranged preferably inside'the tanks for supporting the tubes on the remaining portion of the length of the galvanizing plant.

I 6. Apparatusasset forth in claim 3, wherein the anode is provided with an electric insulating coating on a considerable portion of its length. 7 1

7; Apparatus as set forth in claim 3, wherein the-anode is provided with an electric insulating coating on a considerable p ortionof'its length, said insulating coating being interrupted by electric conducting surfacesections in the runthrough region of the electrolyte tank. v

s8.;Ap-paratus asset forth in claim 3, wherein the anode H is in'the form of a wire and is coated with alternating teristics thereof. The present embodiment is therefore 7 to be considered in all respects as illustrative and'not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come Within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

, Iclairn:

'1. Method of electroplating in continuous operation the inner surface of tubes having impermeable walls and internal diameters down to 3 mm., comprising the steps tubular sections composed respectively of electric insulating material and electric conductive material.

9. Apparatus as set'forth'in claim 8, wherein centering cones for the tubes are'arranged on the wire anode between the tubular sections preferably at uniform distances apart. 1 I

10." Apparatus as set forth in claim 3,wherein the pistonlike stoppers and centering elements for the tubes are made 'of electric insulating material of the group consisting "of plastics. I '11. Apparatus'asset forth in claim 10, wherein the '1 stoppers'andthe centering elements taper in conical shape awa'y"frorri the'run through direction, the centering elements having a plurality of apertures forming "flowof passing cathode-connected tubes continuously one after ranged stationary anode which they surround, supply- ;ing uninterrupted current to the anode during the movement of the tubes through the plant in longitudinal di'- I rection, automatically sucking the treatment liquids of 1 1 the individual bath tanks into the interior of the tubes, pressing it therethrough and, as soon as the rear end of I another through bath tanks filled with treatment liquids and at the same time feeding them along an axially ar- 5-1.

through passages distributed around its peripheryand extendingparallelfto the axis of the anode.

12:? Apparatus as set forth in claim 3', wherein.at ileast -oneof the contact rnakers is adjustable in the run-through clire ctioriof the tubes. 4

1 3. Apparat s a s set fo rthclaim '3, whereincollecting troughs are arranged under the tube outlet and tube inlet aperturesof each tankfor catchin g treatment liquids escaping through the inlet and outlet apertures.

one pump is coordinated to each bath tank tor pumping the treatment liquid out of a collecting trough back into its tank.

15. Apparatus as set forth in claim 3, wherein several anodes arranged approximately parallel to each other and side by side at a distance apart are coordinated to each of the bath tanks arranged one behind the other in a substantially horizontal plane.

16. Apparatus for electroplating the inner surface of metal tubes having impermeable walls in a continuous operation comprising, in combination, a tank having a pair of opposite walls being each formed with an aperture therethrough aligned with each other and having a preselected diameter substantially equal to the diameter of the tubes to be electroplated, said tank being adapted to be filled with electrolyte; combined anode and pumping means extending through said apertures for sucking electrolyte from said tank into the interior of a tube moving through one of said apertures into said tank and for pushing the electrolyte out of the interior of the tube as the tube leaves said tank through the other of said apertures and for connecting the electrolyte in the tube to one pole of an electric current supply during the movement of the tube through the tank; and combined moving and cathode means for moving a plurality of tubes successively through said apertures of said tank and for connecting the tubes during their movement thereof through said tank to the other pole of the current supply, whereby the interior of said tubes will be electroplated as the tubes move through said tank.

17. Apparatus for electroplating the inner surface of metal tubes having impermeable walls in a continuous operation comprising, in combination, a tank having a pair of opposite walls being each formed with an aperi 14. Apparatus as set forth in claim 3, wherein at least" ture therethrough aligned with each other and having a preselected diameter substantially equal to the diameter of the tubes to be electroplated, said tank being adapted to be filled with electrolyte; combined anode and pumping means extending through said apertures for sucking electrolyte from said tank into the interior of a tube moving through one of said apertures into said tank and for pushing the electrolyte out of the interior of the tube as the tube leaves said tank through the other of said apertures and for connecting the electrolyte in the tube to one pole of an electric current supply during the movement of the tube through the tank; means in said tank for supporting the tubes during their movement therethrough aligned with said apertures; means mounted on said combined pumping and anode means for supporting the same in the interior of the tubes moving through the tank coaxial with the tubes; and combined moving and cathode means for moving a plurality of tubes successively through said apertures of said tank and for connecting the tubes during the movement thereof through said tank to the other pole of the current supply, whereby the interior of said tubes will be electroplated as the tubes move through said tank.

References Cited in the file of this patent UNITED STATES PATENTS 938,489 James Nov. 2, 1909 947,440 Greenfield Jan. 25, 1910 1,733,404 Fahrenwald Oct. 29, 1929 1,927,162 Fiedler et al Sept. 19, 1933 1,956,722 Kennedy May 1, 1934 1,997,013 Potthofi Apr. 9, 1935 2,019,709 Kennedy Nov. 5, 1935 2,100,587 Chalker Nov. 30, 1937 2,408,358 Curtis et a1 Aug. 30, 1949 2,859,157 Curtiss Nov. 4, 1958

Claims

1. METHOD OF ELECTROPLATING IN CONTINUOUS OPERATION THE INNER SURFACR OF TUBES HAVING IMPERMEABLE WALLS AND INTERNAL DIAMETERS DOWN TO 3 MM., COMPRISING THE STEPS OF PASSING CATHODE-CONNECTED TUBES CONTINUOUSLY ONLY AFTER ANOTHER THROUGH BATH TANKS FILLED WITH TREATMENT LIQUIDS AND AT THE SAME TIME FEEDING THEM ALONG AN AXIALLY ARRANGED STATIONARY ANODE WHICH THEY SURROUND, SUPPLYING UNINTERRUPTED CURRENT TO THE ANODE DURING THE MOVEMENT OF THE TUBES THROUGH THE PLANT IN LOGITUDINAL DIRECTION, AUTOMATICALLY SUCKING THE TREATMENT LIQUIDS OF THE INDIVIDUAL BATH TANKS INTO THE INTERIOR OF THE TUBES, PRESSING IT THERETHROUGH AND, AS SOON AS THE REAR END OF A TUBE IS FREE, PUMPING THE LIQUID BACK INTO THE RESPECTIVE BATH TANK.