EP1761661B1 - Electrochemical surface treatment device and method - Google Patents

Abstract

The invention relates to a device for the electrochemical surface treatment of metal parts in an electrolyte bath (B). The device comprises a drum (12) which is rotatable about an axis (X) and provided with a shell (14) and sidewalls (16, 18). The sidewalls (16, 18) of the drum (12) are used as the anode in an electric circuit of the process and delimit, together with the shell (14), a gap-type working chamber (20) having a gap width (W) that is defined by the distance between the sidewalls (16, 18). The gap width (W) is chosen depending on the size and/or the geometry of the metal parts to be treated in the working chamber (20) in such a manner that all metal parts present in the working chamber (20) during the electrochemical surface treatment of the metal parts are subjected to substantially the same extent with current.

Description

The invention relates to a device for the electrochemical surface treatment of metal parts in an electrolyte bath according to the preamble of patent claim 1 and to a method for the electrochemical surface treatment of metal parts in an electrolyte bath.

Electrochemical pickling and polishing is a well-known process for the electrochemical surface treatment of metal objects. The metal object to be processed is electrically contacted, immersed in a suitable electrolyte and energized as an anode in a DC circuit. In this case, metal is removed from the surface of the object and a surface with certain desired properties is obtained. Larger metal objects are usually clamped for mounting and contacting on so-called contact racks or processed in a suspended arrangement.

For processing many small metal parts, however, the procedure just described is unsuitable, because a single shot of the small parts to be processed would be uneconomical. Bulk small parts are therefore loosely processed as bulk material in drums or bells. For this purpose, in each case a certain amount of metal small parts to be processed, a so-called batch, are introduced into a drum and the drum is then immersed in the electrolyte bath. The jacket of the drum is made of a mostly perforated conductive metal, usually titanium. During the machining process, it is connected as an anode in the process circuit and forwards the current to the parts to be treated by means of touch contact. The cathodes necessary for closing the process circuit are arranged both outside the drum and in its center (see FIG. 1 ).

Due to the Faraday effect, however, the electrochemical surface treatment process acts only on the surface of the bed and hardly penetrates into the bed, which is why only the respective metal parts located on the surface of the bed are processed. A uniform processing of all metal parts in the drum therefore requires a uniform circulation of the bed. For this purpose, the drum or bell is rotated about its axis during the processing time. Gradually, all parts arrive periodically the surface and are processed there. The adjustment of the current required to process a batch must be carried out in such a way that current is supplied to the parts in each case in the area of the surface of the bulk volume. Consequently, since the number of these parts is only a fraction X of the total batch, treatment time must be extended X times that of a single part treatment to treat this entire batch. From the phenomenon described also follows that larger batches do not allow a significant increase in the current, but that extends only the treatment time accordingly.

In the described process, the anodic contact of the charge in the drum (charge) of metal parts is through those parts which touch the inside of the drum shell. These parts pass the current through the entire bed to the parts located on the surface of the bed. These in turn are only contacted by their own weight. If the weight of a single metal part is very low, for example due to a small wall thickness of the part, then there may be insufficient intense contact to properly feed the current into the part. The consequence of this is either unevenly machined parts or local burns on the parts surfaces due to overheating of the contact points. Therefore, parts of very low weight in proportion to size are poorly suited for machining in conventional electrochemical surface treatment devices.

Parts that may interfere with each other during processing or impose and form a coherent ball (also referred to as "gel") are also not suitable for processing in conventional electrochemical surface treatment devices, since the individual parts cover each other during processing partially and thus a uniform machining of the parts is prevented.

The invention is therefore based on the object to provide an apparatus and a method for electrochemical surface treatment of metal parts in an electrolyte bath with or with which all parts of a batch can be processed largely simultaneously, regardless of the batch size, so that for larger batches only the However, the amount of electricity needed to be increased accordingly, the treatment time of the entire batch still corresponds to the time required to process an item. Furthermore, the surfaces of such parts should also be machinable with high uniformity and accuracy, which can fit into one another, tend to Vergeleln or have a very low weight.

Based on an initially described, known device for electrochemical surface treatment of metal parts in an electrolyte bath, this object is achieved in that the side walls of the drum serve as an anode, that the side walls define a gap-shaped working space with a gap width, which through the Distance between the side walls is defined, and that the gap width is selected depending on the size and / or the geometry of the metal parts to be treated so that during the electrochemical surface treatment of the metal parts all located in the working space metal parts are applied substantially equally with electricity.

In contrast to conventional devices, therefore, not the drum shell is used, but the sidewalls of the drum serve as an anode and the working space is slit-shaped, ie. its height (extension in the axial direction of the drum) is much smaller than its width. In this way, i. by the large contact surface in relation to the bulk volume of the two side walls of the drum and by the low, avoiding the Faraday effect height of the working space, the entire located in the working space bed of metal parts is fully and continuously energized, i. There are no areas inside the bed which are not processed as well. The time required to treat the entire batch thus largely corresponds to the time required to treat a single item. The weight of the bed pushes the metal parts in the working space against the side walls and thus ensures reliable contact with the anode. If the working space is almost completely filled with parts, very light parts can be processed with the device according to the invention.

A movement of the parts during the treatment is required only to a small extent in the device according to the invention, so that change over the treatment time, the contact points and is avoided so that they are visible after the treatment process. For example, it is enough to turn the drum slowly during the treatment. Because in the device according to the invention even a small movement of the parts during their treatment is sufficient to contact points to form again and again and the movement must not be so pronounced as in the prior art that more and more new parts reach the surface of the bed, can also be treated with the device according to the invention parts that tend to gel and clumping.

The drum used in the device according to the invention may for example have the shape of a circular cylinder. Instead of a circular cross-section, however, the drum may also have a rectangular, square, triangular or even polygonal cross section. In general, the device according to the invention is freer in terms of the choice of the cross-sectional shape of the drum than in the prior art, since it is not important to constantly carry new parts to the surface of the bed located in the drum.

In the device according to the invention, the side walls of the drum serve as the anode. This requires an embodiment of the side walls made of metal, for example of a titanium alloy. Preferably, the side walls of the drum are perforated to ensure the unhindered access of the electrolyte bath to the gap-shaped working space in the drum. Another advantage of perforated sidewalls is the fact that compared to conventional, known from the prior art devices in which the drum serves as an anode and is usually perforated, in terms of material selection and structural design of the drum wall is free. This aspect will be discussed in more detail later in connection with preferred embodiments of the device according to the invention.

Preferably, in the device according to the invention the gap width of the working space is adjustable. In this way, the working space of the geometry and the dimensions of each part to be machined can be adjusted. In a preferred embodiment, the gap width of the working space is adjustable in a range corresponding to the simple to 10 times the diameter of the metal parts to be treated.

In preferred embodiments of the device according to the invention, the working space on internals to its subdivision and / or for guiding the metal parts during rotation of the drum. By such internals can be better prevented that parts stuck together. The internals can subdivide the work space, for example, into several chambers. The internals Kings be designed so that they restrict the freedom of movement of the individual parts, so that the parts can not get caught together.

In order to rotate the drum of the device according to the invention, according to one embodiment, a shaft is attached to each side wall of the drum on the outside. The two outer shafts attached to the drum side walls aligned with each other and determine the axis of rotation of the drum. If the two shafts do not extend into the working space of the drum, the latter remains undisturbed. The device according to the invention may comprise a plurality of drums. Each drum may have its own two shafts or a plurality of drums may be interconnected by mutually aligned shaft sections.

According to another embodiment, the drum is accommodated in a rotatable holder and it is externally attached to two opposite sides of the holder depending on a shaft. These two waves are aligned with each other and set the axis of rotation of the drum. The device according to the invention can have a plurality of rotatable holders.

According to yet another embodiment, a plurality of drums are received in a rotatable support, wherein the support has a shaft defining the axis of rotation, on both sides of which at least two drum receiving racks are mounted for rotation with the shaft. In each case two Trommelaufnahmegestelle can be arranged with respect to the shaft in a common plane. In the axial direction of the shaft, a plurality of such each two drum receiving racks may be arranged planes, so that the capacity of the device according to the invention can be set as needed. Instead of the pairs in a common plane for rotation with the shaft attached Trommelaufnahmegestelle the individual Trommelaufnahmegestelle but also with respect to the shaft can be axially offset from one another. In an advantageous embodiment, the drum receiving racks are open on one side and designed for insertion and removal of the drums. A loading and unloading of the drums is in this way quickly and therefore economically possible because the holder does not have to be taken out of the electrolyte bath, but only the individual drums from the holder.

An embodiment of the device according to the invention has a closable opening in the drum shell for easy filling and emptying of the working space on. To empty the working space, the drum is positioned so that the closable opening comes to rest below. When opening the gravity then ensures an automatic emptying of the drum. To refill the drum then only needs to be rotated by 180 °, so that the opening comes to rest on top.

A somewhat modified embodiment has in the drum shell a first closable opening for filling and an opposite second closable opening for emptying the working space. In this way, the drum must not be rotated by 180 ° after refilling the working space for refilling.

In another embodiment of the device according to the invention for filling and emptying of the working space at least one side wall of the drum is formed so that it is open or is removable. Such an embodiment is particularly suitable for drums, which are received as described above in a rotatable holder and / or which are provided with internals.

In some preferred embodiments of the device according to the invention, the drum shell is formed by a frame designed as a separate component. This frame prevents the metal parts located in the working space from falling out and can also have the function of fixing the drum side walls. Suitable materials for the frame are all plastics and metals that are resistant to the conditions occurring in the respective treatment process. The frame may for example be arranged between the two drum side walls. In such an embodiment can be adjusted by different widths wide frame simply different gap widths of the working space.

However, according to another embodiment, the frame may also overlap the two drum side walls. On the inside of the frame then several grooves can be provided, in which the drum side walls are inserted. By selecting the appropriate grooves, the desired gap width of the working space is determined.

According to yet another embodiment of a device according to the invention, the drum shell is formed by mating folds of the side walls. In such an embodiment, the gap width of the working space simply by moving towards or away from each other the drum side walls are adjusted.

In all embodiments of the device according to the invention, at least one cathode is preferably arranged on each side of the drum at a distance from the corresponding side wall and parallel to the side wall in the electrolyte bath. Such a cathode arrangement is structurally simpler to implement than the arrangement chosen in the prior art with a cathode in the center of the drum.

The object mentioned at the outset is also achieved by a method for the electrochemical surface treatment of metal parts in an electrolyte bath, which comprises the steps of providing a drum for receiving metal parts to be treated, the drum having a jacket and side walls, being rotatable about an axis and wherein Coat and the side walls define a gap-shaped working space with a gap width, the pretending the gap width such that during the electrochemical surface treatment of the metal parts substantially all located in the working space metal parts are equally energized, the approximately complete filling of the working space to be treated metal parts of the Immersing the metal-filled drum in the electrolyte bath, switching the sidewalls of the drum as the anode, providing at least one cathode on each side of the drum spaced from the corresponding sidewall and parallel to it in the electrolyte bath, and to energize the anode and the cathodes with direct current and slowly rotating the drum about its axis of rotation during a predetermined treatment time.

Figur 1

das Funktionsprinzip einer herkömmlichen Vorrichtung zur elektroche- mischen Oberflächenbehandlung,

Figur 2

eine erste Ausführungsform einer erfindungsgemäßen Vorrichtung zur elektrochemischen Oberflächenbehandlung im Schnitt,

Figur 3

eine Trommel einer abgewandelten erfindungsgemäßen Vorrichtung im Schnitt,

Figur 4

eine weitere Abwandlung der Trommel einer erfindungsgemäßen Vor- richtung im Schnitt,

Figur 5

eine noch weitere Abwandlung der Trommel einer erfindungsgemäßen Vorrichtung im Schnitt,

Figur 6

eine grundsätzlich andere Ausführungsform der Trommel einer erfin- dungsgemäßen Vorrichtung im Schnitt,

Figur 7

eine Schnittansicht einer Ausführungsform einer erfindungsgemäßen Vorrichtung, bei der die Trommel in einer drehbaren Halterung aufge- nommen ist,

Figur 8

die Ausführungsform aus Figur 7 in Draufsicht,

Figur 9

eine mit Einbauten versehene Trommel einer erfindungsgemäßen Vor- richtung in auseinandergezogener und räumlicher Darstellung, und

Figur 10

eine räumliche Ansicht einer weiteren Ausführungsform einer erfin- dungsgemäßen Vorrichtung, bei der Trommeln in einer drehbaren Hal- terung aufgenommen sind.

The invention will be explained in more detail below with reference to the attached, schematic figures. It shows:

FIG. 1

the functional principle of a conventional device for electrochemical surface treatment,

FIG. 2

a first embodiment of an inventive device for electrochemical surface treatment in section,

FIG. 3

a drum of a modified device according to the invention in section,

FIG. 4

a further modification of the drum of a device according to the invention in section,

FIG. 5

a still further modification of the drum of a device according to the invention in section,

FIG. 6

a fundamentally different embodiment of the drum of an inventive device in section,

FIG. 7

FIG. 2 a sectional view of an embodiment of a device according to the invention, in which the drum is accommodated in a rotatable holder, FIG.

FIG. 8

the embodiment of FIG. 7 in plan view,

FIG. 9

an internally provided drum of a device according to the invention in exploded and spatial representation, and

FIG. 10

a spatial view of another embodiment of an inventive device in which drums are received in a rotatable holder sion.

For a better understanding of the present invention is first based on FIG. 1 explains the functional principle of the electrochemical surface treatment of metal parts. FIG. 1 shows schematically a known from the prior art device for the electrochemical surface treatment of metal parts in an electrolyte bath. The device has a drum T with a drum shell M and two side walls E, of which in FIG. 1 the viewer facing side wall E is not shown to allow insight into the interior of the drum T.

In the drum T is a bed of S to be processed metal parts. The drum T is almost completely submerged in an electrolyte bath B. As anode A for electrochemical surface treatment is made of a conductive metal drum shell M. A cathode K ₁ surrounds the drum T in the electrolyte bath, while another cathode K _{2 is arranged} in the center of the drum T.

For electrochemical machining, the anode A and the two cathodes K ₁ and K _{2 are} supplied with direct current and the drum T is rotated in the direction of the arrow R about an axis of rotation X. Due to the Faraday effect, which shields the metal parts located inside the bed S, the latter are not processed. By taking place due to the rotation of the drum T circulation of the individual metal parts in the bed S but always other metal parts reach the surface of the bed S and are processed there.

FIG. 2 shows in section a first embodiment of a device 10 according to the invention for the electrochemical surface treatment of metal parts. The device 10 has a drum 12 rotatable about an axis X with a jacket 14 and side walls 16, 18. The side walls 16, 18, which are made of a conductive metal and perforated in the embodiment shown, limit together with the jacket 14 a gap-shaped working space 20 for receiving the metal parts to be treated. The jacket 14 here consists of a plastic which is stable under process conditions, but it can consist of any material which withstands the process conditions. For filling and emptying of the working space 20, one or more openings, not shown, may be provided. For example, in the drum shell 14, a single opening may be present. To fill the drum 12 is rotated so that this opening is at the top. To empty the drum 12 is then rotated so that the opening is located below. Alternatively, two opposing openings may be present in the drum shell 14, so that the drum 12 at a corresponding position (an opening below and an opening above) initially emptied and can be refilled from above after closing the lower opening without rotation of the drum 12 is necessary. According to yet another alternative, one or more openings may be provided in the side wall or walls 16, 18 or the side wall may be designed to be removable as a whole. Such an embodiment will be related later FIG. 9 described in more detail.

The working space 20 has a dimension, referred to as a gap width W, in the axial direction, which is significantly smaller than a dimension L directed normal thereto. If the drum 12 has a circular cylindrical shape, then the dimension L corresponds to the diameter of the working space 20. If the drum 12 has a square cross section, then the dimension L corresponds to the side length of the working space 20. However, the drum 12 can also be a triangular, polygonal or different kind Have cross-section, it is only crucial that the gap width W is small compared to the extension of the working space 20 in the direction of the dimension L.

On each side wall 16, 18, a shaft 22, 24 is attached outside. The two shafts 22, 24, which are rotatably received in bearings, not shown, are aligned with each other and set the axis of rotation X of the drum 12.

During operation of the device 10, the working space 20 is almost completely filled with a bed S of metal parts to be processed. The drum 12 with the metal parts therein is immersed in an electrolyte bath B or submerged. The conductive side walls 16, 18 of the drum 12 serve as the anode of a process circuit, which further includes two cathodes 26, 28, one of which is on each side of the drum 12 with some distance and parallel to the corresponding side wall 16, 18 in the electrolyte B extends. The power supply to the anode walls serving as side walls 16, 18 can be done for example via the shafts 22, 24.

The metal parts forming the bed S are in contact with the insides of the side walls 16, 18, so that the current reaching the anode is forwarded by contact with the metal parts to be treated. Due to the small gap width W of the working space 20 in relation to the extension L, the Faraday effect does not occur in a disturbing manner, ie the metal parts located in the interior of the bed S are also energized and consequently surface-treated electrochemically. Because the Faraday effect is virtually nonexistent, the current flowing through the process circuit can be chosen to be so high that the treatment time is very short and substantially equal to the time required to treat a single piece of metal. During the treatment period, the drum 12 is slowly rotated, symbolized by the arrow R in FIG. 2 in order to repeatedly create contact points between the individual metal parts or between the metal parts and an adjacent side wall 16 or 18.

With reference to the FIGS. 3 to 6 Various types of drum 12 will now be described. According to FIG. 3 the jacket 14 of the drum 12 is formed by a frame 30 which engages over the two side walls 16, 18 and fixes them. According to FIG. 4 a frame 30a is disposed between the two side walls 16, 18 of the drum 12. In both embodiments, the gap width W of the working space 20 in a simple manner by using a frame 30, 30 a be set with the appropriate width. Especially in the execution of FIG. 4 For example, the frame 30a may be formed as a so-called removable frame, ie the frame 30a is connected to the two side walls 16, 18 by means of easily releasable connection mechanisms. Even with the frame 30 off FIG. 3 Such an embodiment is possible, for example, this frame 30 can be designed hinged, so that let him simply held the side walls 16, 18 can be removed.

FIG. 5 shows a drum 12 with a modified frame 30b, which is provided on its inside with here evenly in the axial direction X spaced grooves 32, which serve to receive the side walls 16, 18. By selecting the corresponding grooves 32 for the side walls 16, 18, the desired gap width W of the working space 20 is set.

According to FIG. 6 the jacket 14 of the drum 12 is formed by folds 34, 36 of the side walls 16, 18. In this case, the folded edges 36 of the side wall 18 can be inserted into the bounded by the folded edges 34 of the side wall 16 space. In this way, the gap width W of the working space 20 can also be within the limits set by the dimensions of the folded edges 34, 36 in the axial direction X set. It is understood that in this embodiment, the folded edges 34, 36 usually consist of the same material as the side walls 16, 18. The folded edges 34, 36 need not be perforated.

The FIGS. 7 and 8 show a modified embodiment of the device 10. In contrast to the first embodiment, no shafts 22, 24 are attached to the drum 12 itself, but the drum 12 is accommodated in a rotatable holder 38. On the rotatable support 38, a shaft 40, 42 is attached to the outside on two opposite sides. The two shafts 40, 42 are aligned with each other and set the axis of rotation X for the drum 12. The rotatable support 38 may be of any shape and design suitable for receiving the drum 12. According to FIG. 8 the rotatable support 38 is a substantially open frame 43, in which the drum 12 is prevented from falling out by two securing clips 44. Although the drum 12 and the rotatable support 38 in the embodiment shown have a cuboid shape, of course, many other forms can be used. For example, the drum 12 may be circular cylindrical or a polygonal one Have cross-section. The rotatable support 38 does not necessarily have to have a shape corresponding to the drum 12 as long as it is only suitable for holding the drum 12 securely.

FIG. 9 shows a drum 12, in which the side wall 16 is designed to be removable. Filling and emptying the working space 20 is so easy and completely possible. On the side wall 16, the shaft 22 is fixed, analogous to the side wall 18, the shaft 24 is fixed (not shown). If these two waves 22, 24 are omitted, the in FIG. 9 reproduced drum 12 also for use in a device 10 according to the FIGS. 7 and 8 ,

In FIG. 9 furthermore installations 46 are shown in the working space 20. The internals 46 have here the shape of partitions that divide the working space 20 into four equal chambers 48. The baffles 20 limit the mobility of the metal parts to be treated in the working space 20 and are particularly advantageous if the metal parts tend to get stuck or hooked. Other installations, for example in the form of a spiral wall in the working space 20, can also be used. The internals are tuned for optimal effectiveness on the geometry and dimensions of the metal parts to be treated.

In FIG. 10 a yet further modified embodiment of a device 10 is shown in a spatial view, in accordance with the in the FIGS. 7 and 8 shown embodiment, a holder 38a, in which a plurality of drums 12 (in the example shown six pieces) are added. The holder 38 a has a shaft 50 which defines the axis of rotation X of the entire device 10. On the shaft 50 on both sides of the same six here U-shaped drum receiving racks 52 are attached, each of which can accommodate a drum 12. Each two drum receiving racks 52 are arranged with respect to the shaft 50 in a common plane. In the exemplary embodiment shown, three such planes are preferably arranged on the shaft 50 so as to be equally spaced from each other axially.

Each drum support frame 52 is open on one side, so that an associated drum 12 can be easily inserted into the drum support frame 52 and pulled out again without having to remove the holder 38a from the electrolyte bath, not shown here. The loading and unloading of the drums 12 is thus possible quickly and economically.

Such an embodiment, in which the drum receiving racks 52 are connected for rotation with the shaft 50, readily allows the capacity of the apparatus 10 to be adjusted to predetermined needs by providing more or less drum receiving racks 52. In deviation from the illustrated embodiment, the drum receiving racks 52 may of course have a different shape and need not be arranged in pairs in a plane. The cathodes, which are arranged in the operating state between the drums 12 and outside of the axially first and last drum 12, preferably parallel to the drum side walls have, for reasons of clarity in FIG. 10 omitted.

Although not shown, the apparatus 10 may readily include a plurality of drums 12 in an electrolyte bath B, optionally in a corresponding number of rotatable supports 38. For example, a plurality of drums may be sequentially arrayed and interconnected by shaft portions which together define the axis of rotation X. Alternatively, a plurality of drums 12 each having its own axis of rotation X can be arranged in the electrolyte bath B.

Claims (19)

1. Device for electrochemical surface treatment of a plurality of metal parts in form of bulk material in an electrolyte bath (B), said device comprising an anode and a cathode as well as a drum (12) for receiving the metal parts to be treated, which drum comprises a jacket (14) and side walls (16, 18) and is rotatable about an axis (X),
   characterized in that

   - the side walls (16, 18) of the drum (12) serve as an anode,

   - the side walls (16, 18), together with the jacket (14), delimit a gap-shaped working space (20) having a gap width (W) which is defined by the distance between the side walls (16, 18) and is small compared to a dimension (L) of the working space (20) arranged normal thereto, and in that

   - the gap width (W) is chosen as a function of the size and/or geometry of the metal parts to be treated such that the contact surface of the two side walls (16, 18) of the drum (12) is large in relation to the packing volume so that all metal parts located in the working space (20) are charged with current in a substantially equal measure during the electrochemical surface treatment of the metal parts.
2. Device according to claim 1,
   characterized in that the side walls (16, 18) are perforated.
3. Device according to claim 1 or 2,
   characterized in that the gap width (W) is adjustable.
4. Device according to claim 3,
   characterized in that the gap width (W) is adjustable from the onefold to tenfold amount of the diameter of the metal parts to be treated.
5. Device according to any one of the preceding claims,
   characterized in that the working space (20) comprises built-in components (46) for separation thereof and/or for guiding the metal parts during rotation of the drum (12).
6. Device according to any one of the preceding claims,
   characterized in that a shaft (22, 24) is mounted on the outside of each side wall (16, 18), wherein the two shafts (22, 24) are aligned with each other and define the axis of rotation (X).
7. Device according to any one of claims 1 to 5,
   characterized in that the drum (12) is received in a rotatable support means (38), on the outside of which one shaft (40, 42) each is mounded on two opposite sides, wherein the two shafts (40, 42) are aligned with each other and define the axis of rotation (X).
8. Device according to any one of claims 1 to 5,
   characterized in that a number of drums (12) are received in a rotatable support means (38a), wherein the support means (38a) comprises a shaft (50) defining the axis of rotation (X), on both sides of which at least two drum receiving frames (52) are mounted for rotation with the shaft (50).
9. Device according to claim 8,
   characterized in that the drum receiving frames (52) are open on one side and are adapted for inserting and withdrawing the drums (12).
10. Device according to any one of the preceding claims,
    characterized in that the jacket (14) comprises a closable opening for charging and discharging the working space (20).
11. Device according to any one of claims 1 to 9,
    characterized in that the jacket (14) comprises a first closable opening for charging and an opposite second closable opening for discharging the working space (20).
12. Device according to any one of claims 1 to 9,
    characterized in that at least one side wall (16, 18) of the drum (12) can be opened or is removable for charging and discharging the working space (20).
13. Device according to any one of the preceding claims,
    characterized in that the jacket (14) of the drum (12) is formed by a frame (30; 30a; 30b) which is designed as a separate component.
14. Device according to claim 13,
    characterized in that the frame (30a) is arranged between the two side walls (16, 18).
15. Device according to claim 13,
    characterized in that the frame (30) straddles the two side walls (16, 18).
16. Device according to any one of claims 1 to 12,
    characterized in that the jacket (14) of the drum (12) is formed by overturned portions (34, 36) of the side walls (16, 18) which fit into each other.
17. Device according to any one of the preceding claims,
    characterized in that at least one cathode (26, 28) is arranged on each side of the drum (12) spaced from and parallel to the respective side wall (16, 18) in the electrolyte bath (B).
18. Device according to any one of the preceding claims,
    characterized in that a number of drums (12) are located simultaneously in the electrolyte bath (B).
19. Method for electrochemical surface treatment of a plurality of metal parts in form of bulk material in an electrolyte bath, comprising the steps of:

    - providing a drum for receiving the metal parts to be treated, which drum comprises a jacket and side walls and is rotatable about an axis, wherein the jacket and the side walls delimit a gap-shaped working space having a gap width (W) which is defined by the distance between the side walls and is small compared to a dimension (L) of the working space arranged normal thereto,

    - defining the gap width (W) such that the contact surface of the two side walls of the drum is large in relation to the packing volume so that substantially all metal parts located in the working space are charged with current in equal measure during the electrochemical surface treatment of the metal parts,

    - filling the working space essentially fully with the metal parts to be treated,

    - immersing the drum filled with metal parts into the electrolyte bath,

    - switching the side walls of the drum as an anode,

    - providing, on each side of the drum, at least one cathode spaced from and parallel to the corresponding side wall in the electrolyte bath, and

    - supplying direct current to the anode and the cathodes and slowly rotating the drum about its axis of rotation during a predetermined treatment period.

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