EP2524071B1 - Tool for galvanically coating sliding bearings - Google Patents

Description

Technical area

The invention relates to a tool for the galvanic coating of plain bearings.

The typical structure of a plain bearing from the material group of the plain bearing to be plated consists of a steel backing with a lead-containing or lead-free composite layer. The galvanic sliding layer applied in the running surface of the sliding bearing is a multifunctional material and performs various tasks. This coating takes place in a box-shaped tool, which is also referred to as recording. When coating it is further to be noted that those surfaces on which the bearing shells are divided (partial surface), preferably not coated. Furthermore, no coating is desired for the bearing back, ie the cylindrical outer surface of the bearing shells. For this purpose, so-called robber cathodes or elements are provided in the area of the bearing back, which are switched in a suitable manner such that the bearing back remains largely free of a coating.

State of the art

So far, one or more "towers" or columns of bearing shells are constructed one above the other in such a way that the axial directions of the individual bearing shells coincide. In this axial direction, the bearing shells are clamped by means of a spring pressure. However, this structure is relatively unstable, so that the bearing shell columns often collapse, are heavily coated on the faces and results in a significant proportion of rejects. At the beginning and at the end of the respective column so-called dummy shells made of steel are used. The blind shell at the beginning of the bearing shell pillar to be coated covers the transition region between the air and the electrolyte. The lower dummy shell serves to stabilize the column and to limit the tolerance of the deposited layer within the bearing shell column. The above-mentioned robber cathode is fixed in the tool.

Such a tool is from the publication GB 1 239 222 known.

Presentation of the invention

The invention has for its object to provide a tool with the help of plain bearing shells can be galvanically coated efficiently.

The solution to this problem is achieved by the tool described in claim 1.

Consequently, the tool according to the invention has at least one cover on which a robber cathode is mounted. In other words, the robber cathode is integrated in the lid, which leads to the particular advantages that it can be removed during the process. This differs from the previous fixed in the tool cathodes. The possibility of removing the raid cathode during the coating process offers the following advantage. The tread will usually be after the "main" coating provided with a binary or ternary lead-free sliding layer. The steel back must then be provided with a so-called flash. This flash, for example, based on tin has the function of corrosion protection and is primarily applied to the bearing back of steel to protect the reactive steel from oxidation with the air (rust). This corrosion protection is thus primarily applied to the bearing back. However, this area is not coated in the presence of the robber cathode. Consequently, while in the context of the main coating, the current, before it is conducted to the bearing shells to be coated, is passed over a resistance of, for example, 0.001 ohms to 0.02 ohms, in particular 0.003 ohms to 0.0095 ohms, by a potential difference between the robber cathode and make the cups to prevent the coating to the back, this potential difference is removed by removing the burglar cathode, and the bearing backs can be provided in an advantageous manner with the desired corrosion protection.

Preferred developments of the tool according to the invention are described in the further claims.

Preferably, the tool according to the invention further comprises at least one holder, which is characterized in that it has at least one strip which is suitable for mechanically fixing and / or electrically contacting a plurality of bearing shells. The mechanical fixation, optionally in cooperation with a portion, for example a wall of the tool, prevents the bearing cup column from collapsing. The holder presses namely with the at least one bar the bearing shell column, for example, against a wall of the tool, so that there is a much lower risk of collapse of the bearing shell column, eliminating the collapse of the bearing shell column and the coating of the Part surface is avoided. This significantly reduces the reject rate. In particular, it was found in initial tests that the scrap can be reduced to zero due to collapsed bearing shells. Furthermore, the undesired coating of the partial surfaces can be prevented by pressing against the tool wall.

By contacting a plurality of bearing shells at their respective back several, preferably all to be coated cups are contacted by the holder according to the invention. This reduces the resistance within the bearing shell column, and the sliding surface of the bearing shell can be coated with a significantly reduced dispersion of the coating thickness. In particular, it was found that the dispersion within a bearing shell column with the holder according to the invention is only about 2 .mu.m to 3 .mu.m and the coating of the partial surface is avoided, whereas in the previous procedure, in which only the end faces of the bearing shell pillar were contacted, a scatter of 6 Up to 7 microns occurred and the partial surface was coated with up to 20 microns. As a result, the scrap could be significantly reduced as a result of considerable scattering of the coating density. Due to its function, the holder described can also be referred to as back contact. This constitutes an independent aspect of the present application, which, although independent of the features described above or below, has its advantages, but can be combined with them.

In particular, for the stability with regard to the mechanical fixation, several, in particular an even number of substantially parallel bars have proved to be advantageous. Together with the pressing against a wall of the tool, for example, by two parallel bars a statically determined fixation can be created. Furthermore, it is favorable for the efficiency in the coating of several, in particular relatively small bearing shells when two or more bearing shell pillars are constructed side by side, which means an even number largely parallel strips for a mechanically favorable fixation. It is understood that only two or three such strips may be present to electrically contact and mechanically fix a single bearing shell column. This can be provided, for example, with comparatively large bearing shells. Furthermore, it is conceivable in principle to provide such a holder for more than two bearing shell columns. A holder for two bearing shell columns has been proven, for example, for bearing shells with a diameter of 28 mm to 70 mm, while for larger bearings a holder for a single bearing shells can be provided.

The specific requirements for the respective components can be particularly well done when the holder, as is preferred, even made of plastic, and the contact strips or rails are made of metal.

In this case, it is favorable for the fulfillment of the tasks set for the holder if this can be fixed in the tool and preferably braced. In particular, the bracing can take place in such a way that the bearing backs contact particularly well and / or the partial surfaces of the bearing shells are pressed particularly firmly against a wall of the tool, so that a coating is advantageously prevented here.

Preferably, the tool according to the invention further comprises at least one plastic block, which is arranged above the bearing shell pillar, in particular to ensure at the upper end of the bearing shell pillar that all bearing shells are below the surface of the electrolyte bath and coated reliably. The dummy shell at the lower end is eliminated, resulting in an increase in productivity.

Brief description of the drawings

Fig. 1

eine perspektivische Ansicht eines Halters;

Fig. 2

eine Rückansicht eines erfindungsgemäßen Werkzeugs mit der Darstellung der Verspannung des zugehörigen Halters;

Fig. 3

einen Abschnitt des in Fig. 1 dargestellten Halters mit weiteren Elementen eines Werkzeugs; und

Fig. 4

einen Werkzeugdeckel.

Hereinafter, an embodiment shown in the drawings will be explained in more detail. Show it:

Fig. 1

a perspective view of a holder;

Fig. 2

a rear view of a tool according to the invention with the representation of the tension of the associated holder;

Fig. 3

a section of in Fig. 1 illustrated holder with other elements of a tool; and

Fig. 4

a tool lid.

Detailed description of an embodiment of the invention

The in Fig. 1 shown holder 10, which may also be referred to as Rückenkontaktierung has, in the illustrated embodiment, four substantially parallel rails or strips 12, which are made of metal, to contact in pairs (not shown) bearing shells. The metallic strips are embedded in the embodiment shown in slightly wider plastic strips, which are connected via numerous cross braces 14 with each other and with a central plastic strip 16. Overall, for the embodiment shown, the holder 10 is made of plastic with the exception of the metal rails 12. This also applies in particular to those bolts 18 which are present in triplicate in the embodiment shown and in the embodiment shown in each case have a radially continuous slot which extends approximately in the direction of the strips 12, 16.

The holder shown is used in such a way that the bearing shells to be coated are built up in a columnar structure. In the embodiment shown, two columns are constructed in parallel and each contacted by the two lying on one side or the other of the central strip 16 metal strips 12. This contacting takes place particularly reliably and securely, including a mechanical fixation on the tool, when the three bolts 18 have been inserted through a wall of the tool, and respective, preferably wedge-shaped strips or pins have been inserted and clamped in the described slots of the bolt in such a way that the holder 10 is pressed against the tool wall, so that the bearing shells arranged therebetween are mechanically fixed as well as electrically contacted by the metal strips 12.

This tension of the holder in a tool is in Fig. 2 shown. The wedges 22 to be inserted into the slots of the bolts 18 may be provided on a plate 20 having a recess 24 surrounding each of the wedges on three sides. In this way, the plate, for example, by inserting the bolt 18 in the recess 24 below each wedge 22 and subsequent displacement of the plate 20 such that each of the wedges 22 enters the respective slot, are braced. In this case, the plate 20 moves with respect to the bolt, in the Fig. 2 shown embodiment, wherein the bolts are received in the laterally arranged by the wedges 22 portions of the recesses 24.

In Fig. 3 It is shown that the metal rails 12 are brought together in a particular upper area by a transverse connection 26 and connected to a power connection 28. In this area, the metal rails 12 are no longer embedded in the plastic of the receptacle 10. Furthermore, in Fig. 3 a plastic block 30 is shown, which on the one hand has recesses for the upper end regions of the rails 12 and on the other serves to axially clamp the constructed bearing shells 32. Furthermore, the distance to the air above the electrolyte bath is compensated by the plastic block 30, so that in other words it is ensured that all the bearing shells 32 are reliably below the surface of the electrolyte bath.

In Fig. 4 Finally, a tool cover 34 is shown, in which the so-called robber cathode 36 is integrated in an advantageous manner. These are in the embodiment shown a few interconnected rods, in the range of (in Fig. 3 directed to the viewer) bearing back to make a potential difference to the bearing back, which ensures that they are not coated. In the upper region of the lid 34, a power connection 38 is provided for the Räuberkathode 36 to produce the described potential difference.

Claims (4)

1. Tool for galvanic coating of sliding bearings having at least one cover (34), to which a robber cathode (36) is attached, and at least one support (10) for several bearing shells (32) arranged like columns and to be coated galvanically, having an even number of parallel strips (12) which are suitable to mechanically fix and/or to electrically contact several bearing shells (32), and bolts which can be inserted through a wall of the tool and have slots into which strips or pins can be introduced and braced such that the support (10) is pressed against a tool wall, and the bearing shells (32) are arranged between the support (10) and the tool wall.
2. Tool according to claim 1, characterised in that the support (10) is made from plastic and at least one strip (12) is made from metal.
3. Tool according to one of claims 1 or 2, characterised in that the support (10) can be fixed and preferably braced in the tool.
4. Tool according to one of the preceding claims, further having at least one plastic block (30).

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