DE19722983C2 - Process for the electrochemical treatment of rod-shaped material to be treated and device for carrying out the process - Google Patents

Description

The invention relates to a method for partial electroplating or electrochemical etching of rod-shaped items to be treated in immersion baths gen. It also relates to an apparatus for performing the method.

The method and the device are preferably used for etching and galva nize elongated cylinders, especially round rods. The Bars can be tapered in diameter on one or both sides at the ends and / or be threaded. An example of this are cylinders for Vehicle shock absorbers. However, the invention is not limited to Treatment of round bars. It is also suitable for other cross sections. In In the following description, the material to be treated is briefly used as a rod draws.

The electrochemical treatment of the rods is used, for example, for shock absorbers cylinders to improve wear and corrosion properties. For this purpose, the rods are only used on surfaces subject to operational stress electrolytically coated with hard chrome. The other positions of the bars are supposed to remain uncoated or almost uncoated. To improve detention strength of the chrome layer, the surface is previously electrochemically etched. Insoluble electrodes are preferably used for both process steps turns. The treatment takes place in immersion baths with appropriate  Rinsing steps. A transport device takes care of the transport of the bars from Bath to bath.

For the partial treatment of the bars in the middle of the bar, the ends must be masked, d. H. be shielded in such a way that they are dimensionally accurate metal is not deposited in certain areas. The boundaries between the deposition and the areas not to be coated are usually closely tolerated. The transition must be within, for example, ± 3 millimeters for example with shock absorber cylinders. The layer to be deposited must be uniformly thick up to these limits. Edge effects, d. H. Layer Thickness increase or decrease in layer thickness at the layer boundaries must be avoided. The aim of the precise coating is to make a subsequent one To be able to avoid smoothing them.

In the known immersion bath systems, the electrochemical treatment of the Bars on frames that are attached to transportable goods carriers. The Frames are provided with individual masks so that both rod ends in the not be coated. For all occurring sta blanks, rod diameter and coating areas in the middle of the rod A sufficient number of masks and frames must be attached to an electroplating system be stocked. The loading of the frames with the bars is manual. The large range of products found in practice is for an automat difficult to access. Another disadvantage of rack technology is that double-sided masks including the power supply. Prevent the racks the use of tubular electrodes to enclose the Rod in the electrolytic cell. A rod attached to the frame on both sides cannot be inserted into such an electrode. The electrodes are divided. They only face the bars on two sides. As a result, the No layers of equal thickness were deposited on the circumference. The uneven The rod must subsequently be ground round. At Hartchrom this is one essential cost factor.  

Racks in immersion bath systems lead to carryover of electrolytes and Rinse water. Thanks to the masks and holders attached to the frames Procrastination particularly large. A corresponding number of rinsing steps must be added. The hard chrome baths work u. a. with chromic acid. Because of the aggressiveness are very good corrosion properties of all wetted materials required. Plastics are best suited for this. Because frames They also have to be metallic to supply the bath current to the rods be. The metal must be covered with plastic coatings that are prone to defects. to be protected. Rinsing after the active baths must be done very carefully happen. Especially when the carry-over is large depending on the mask is.

In the document DE 25 24 315 A1, an electroplating frame for receiving a plurality of rod-shaped, preferably cylindrical items to be treated, such as piston rods, is described. The cylindrical rods, which are accommodated in the form of a sleeve, are to be galvanized on the circumference with the same layer thickness. The anodes on both sides opposite the rods cause an elliptical layer thickness distribution. It is therefore proposed according to the invention to galvanize the rods so that they rotate about their longitudinal axis. Longitudinally adjustable protective sleeves ( 52 ) individually matched to the material to be treated limit the electroplating layer in the longitudinal direction of the rod at the rod ends. The electroplating frame adapts to the bar length by means of vertically adjustable side parts. The disadvantage of the proposed solution is the enormous technical effort that is required to set each individual rod in rotation in the aggressive electrolytic bath. The rotation also requires a transition of the usually very high electroplating current by means of brushes ( 40 ) to the rod, which is also only possible with great technical effort.

The document DE-AS 11 03 103 describes a device for partial Electroplating elongated cylindrical bodies. These bodies will arranged centrally in tubular anodes and at the top in one stepped metal core attached. The cathodic one takes place over the metal core Power connection. The metal core is separated from the elec trolytic cell separated. Metal core and insulating body limit the electroplating layer at the upper end of the material to be treated. The bottom end will protected from undesired galvanization by means of a protective lacquer.

The disadvantage of this design is the individual attachment of each one individual to be galvanized body and the moderately accurate application of the Protective varnish on one end of the body. Also the removal of the protection varnish after electroplating.

The object of the invention is to provide a method that the partial elec trochemical treatment, especially the electrochemical treatment of Bars of different dimensions while avoiding the described Disadvantages in immersion bath systems allowed.

The task is solved by electrolytic single cells per rod adjustable masks with sealants in the form of end sleeves two rod ends to limit the areas to be treated. In the Be The delivery station grabs several electrically conductive items attached to the goods carrier One side of the gripper. The rods are used to avoid large carry-over, preferably in a vertical position to the treatment transport stations. When entering the treatment station each rod into a single cell, each consisting of a stationary tubular elec trode is formed. The tubular electrodes are as long as it is for the longest rod to be electroplated is required. The upper and lower elec trolytically active electrode end is ver ver by a tubular axial adjustable mask. The mask ends are each with a cuff  completed. The rod travels centrally at least through the upper sleeve into the electrode until the product carrier is put down. Through each other independent adjustment of the upper and lower masks in the axial direction the two coating limits or the surface to be coated on Rod set uniformly for each product carrier or each product carrier row. These settings can only be readjusted when changing the dimensions of the goods to be treated by a subsequent goods carrier or a goods carrier series hey necessary. The bath flow is via the product carrier and the gripper Rods fed. The individual electrodes are individually or together on the Opposite pole of the bath power source or bath power sources connected.

The method avoids the disadvantages of the known rack technology. Individual le Masks for each rod dimension in the form of caps or holders are not required. The frames are completely eliminated. A product change is from one product carrier to the next product carrier without time-consuming retrofitting of masks and holders possible. The loading is limited to that one-sided insertion of the rod into the gripper and its closing. This process is also easy for bars with different dimensions to automate.

When the bars are lifted out of the bath, they drain quickly because the lower rod ends are free of holders and masks. Located at the top only the gripper with a small surface area. So overall is also the Procrastination minimal.

The method allows the rod to be positioned in the center of a pipe elec- trode trode. The distance of all surface areas of the rod to the opposite The electrode surface is always the same size. This is a requirement for an even layer to be deposited on the circumference of the rods. One after there is no longer any need for grinding the coating.

When treating rods with very different diameters and if a gripper with a fixed and a movable leg  is used, the position of the bar axis to the gripper axis changes.

Through different positioning of the gripper when lowering the rod this can be compensated for in the individual cell. All that is needed is the usual rod diameters are two different Countersink positions around all occurring rod diameters with one accordingly uniform coating.

Due to the stationary masks, only the material to be treated and the metallic pliers with electrolyte wetted brought from station to station. All other bathroom fittings apart from the metallic pliers with the counter electrode have no current-carrying function. They can be made from durable plastic getting produced.

Referring to Figs. 1 to 5, the method and the device are be described.

Fig. 1 shows an article carrier for transport of the treatment material through the dip bath.

Fig. 2a shows a treatment station schematically in side view and partially in section.

FIG. 2b shows the treatment station in plan view.

Fig. 3 shows an electrolytic single cell in cross section.

Fig. 4 shows a sleeve for very different diameter areas of the material to be treated.

Fig. 5 shows an electrolytic single cell in cross section, with an additionally arranged in the lower mask metallic body.

The product carrier shown in Fig. 1 consists of a multi-part frame 1 with the frame supports 2. Pliers-shaped grippers 3 are attached to the frame. The grippers consist of a fixed leg 4 and a movable leg 5 .

This is rotatably mounted with an axis 6 . A strong compression spring 7 closes the jaws on the gripper. The clamping jaw 8 on the fixed leg is prism-shaped. The jaw 9 on the movable leg 5 has the spherical profile shown. Rods 10 with different shaft diameters can thus be gripped. When gripping, they are aligned exactly in the longitudinal direction of the gripper in the prism-shaped jaw. In the illustration in FIG. 1, the alignment is vertical.

The bars 10 are gripped and released by exerting force on the movable leg 5 . A force, for example exerted by a pressure cylinder in the direction of arrow 11 , opens the gripper 3 . All grippers 3 on the goods carrier are opened and closed using known methods and means of mechanical engineering. They are therefore not shown. For example, a product carrier can hold 32 bars in the loading station. This process as well as the emptying process is easy to automate, even when changing the dimensions of the bars. The bar dimensions for each product carrier are at least the same size in each row. The carrying arms 12 serve to transport the goods carrier by means of a trolley from bath to bath. The frame 1 and the frame supports 2 as well as all gripper parts are electrically conductive. Via the frame supports 2 , the bath flow is supplied to the goods carrier and thus to the goods to be treated, ie the bars 10 . In the case of large currents, the support points for safe power lines are clamped. In this case, the frames are expediently made of copper with a titanium sheath for protection against corrosion. When metallizing, it can happen that the lower area of the metallic gripper 3 immersed in the bath is minimally metallized. For this reason, at least this area of the grippers is provided with an insulating layer except for the clamping jaws. If necessary, the clamping jaws are metallized chemically or electrolytically in a corresponding bath.

In the treatment station shown in FIGS. 2a and 2b, the goods carrier is placed on the goods carrier receivers 15 . The frame supports 2 and the goods carrier 15 position the goods carrier exactly in the treatment bath 16 . In this treatment bath 16 with the bath container 14 are installed:

• - Adjustable lower panel support 17 :
  It is a plastic plate provided with openings 18 for electrolyte exchange with side supports 19 . The carriers are supported on both sides on height adjustment devices 20 , which are moved in a defined manner by drives 21 shown symbolically. A tubular electrically non-conductive mask 23 is located on the panel support 17 for each individual cell 22 . This is completed with an elastic cuff 24 , which has a central hole. The lower part of the rod, which is not to be treated electrochemically, protrudes through this hole.
• - Adjustable top panel support 25 :
  Here, too, it is a plastic plate 13 which carries all of the upper tubular masks 26 . At the same time, the plate covers the usual hot bath. The escape of aggressive vapors is greatly reduced. The masks 26 are closed at the bottom with an elastic sleeve 27 . The rod to be treated protrudes into the single cell 22 through a central hole in the sleeve. The upper panel support is supported on both sides on height adjustment devices 28 , which are moved in a defined manner by drives 29 shown symbolically.
• Electrodes 30 for forming the individual cells 22 :
  In the treatment bath 16 , a tubular electrode 30 is installed stationary for each individual cell 22 . The electrodes 30 are attached in an electrically conductive manner to an electrode insert 31 . The electrode insert 31 rests on the container edge 32 . The insert is oriented so that the rods to be treated are positioned centrally in the tubular electrode 30 when the product carrier is put down.

The rods 10 to be treated are brought into the individual cells 22 by means of the plant transport device and the goods carrier and are positioned there exactly in the X, Y and Z axes. The area of the rod to be electrochemically treated is delimited at the top and bottom by the masks 23 , 26 and by the sleeves 24 , 27 in each individual cell 22 . This limitation is specific for each item to be treated, for a row on the goods carrier or for the entire goods carrier. By means of the height adjustment devices 20 , 28 , the limitation is automatically set individually for each product carrier. If rods of different lengths are to be treated per row on the goods carrier, the limits for each row are adjusted individually. The setpoints for the adjustments are communicated to the control system of the immersion bath system when the goods carrier is loaded. The smooth adjustment devices 20 , 28 perform the height adjustment of the upper and lower panel supports on the basis of these target values. The actual values are reported back to the control system from the system. This device enables the precise, partial treatment of the rods of various dimensions in a bath container without having to change this or the goods carrier. The polarity of the bath current feeds are entered in FIGS . 2a and 2b for the galvanizing. The polarity in brackets applies to electrochemical etching.

Without the goods carrier, the treatment station is shown in plan view in FIG. 2b. Only the bars 10 and the jaws 8 , 9 of the gripper 3 are drawn from the goods carrier. The upper panel holder 25 is not shown in the right part in order to expose the view of the electrodes 30 , the electrode insert 31 and the lower mask 23 and the lower sleeve 24 . The individual drives M1 and M2 shown in the drawing for the height adjustments can also be realized by one drive for all support points of a panel support. Drive elements such as shafts and gears then take care of the parallel height adjustment. The position of the aperture carrier is reported back to the control system by position sensors, not shown. This is thus able to move to any predetermined position of the aperture carrier.

Approaching the correct position of the panel supports 17 , 25 can take place before or after the product rack is placed in the bath container 14 .

Details of the individual cell 22 are shown in FIG. 3. The rod 10 to be treated generally has several turned-on shoulders 33 , some with threads. The jaws 8 and 9 grip the rod on the heel 33 . The jaw 9 , a half cylinder, touches the rod at one point and presses it into the prism-shaped jaw 8 for exact alignment. Both jaws are made of a wear-resistant, corrosion-resistant and electrically highly conductive material. The jaws are expediently attached to the legs of the grippers in an exchangeable manner. The tubular masks 23 , 26 can be adjusted in height in the electrode 30 . They are centered on the electrode 30 . The mask tubes are provided with an extension 35 at the top in the direction of the treatment room 34 and with an extension 36 at the bottom. These extensions wrangle the end of the rod surfaces to be treated in such a way that there is no increase or decrease in current density towards the limiting point 37 , which are formed by the sleeves 24 , 27 . Without these extensions, for example, an increase in layer thickness occurs during electroplating, the so-called bone effect. The extensions are not limited to a cylindrical tube extension. They can also have other shapes to adapt to the single cell. For example, funnel-shaped mask finishes in both directions are suitable. That is, funnels drawn in or opening. Furthermore, the extensions can also be provided with openings. The effect of a funnel-shaped mask closure is already given by the sleeves 24 and 27 when the rod to be treated is inserted into it (see FIG. 3). Here, an up and down the same, namely towards the treatment section of the rod 10 - or away from this shape can be achieved by moving either the lower or the upper mask a bit in the penetration direction of the rod after the insertion of the rod.

FIG. 5 shows how, by moving the mask 26 downward, after inserting the rod 10 , the sleeve 27 is “turned inside out” and thus the same conditions are achieved as on the lower sleeve 24 .

Outside the treatment room 34 , the field-free room 38 is at the top and the field-free room 39 is at the bottom. As intended, there is no electrochemical treatment here. The cuffs 24 , 27 enclose the rod 10 . They consist of an elastic material that is wear-resistant and corrosion-resistant. Plastic foils such as Viton are suitable. The cuffs have a round opening that is no larger than the smallest rod diameter at the limiting point 37 . They are fastened in the tube so that the opening lies in the mask center. To compensate for tolerances, the sleeves can also be attached in a floating manner in the tubular masks. The cuff then lies close to the rod even when the axes of rod 10 and mask 23 , 26 are not aligned.

In a special embodiment, the cuff has a multilayer pinnate structure. This allows the treatment of bars with large diameters differentiated at the delimitation point 37 . This means that very large differences in rod diameters can be produced in a system with a long service life of the sleeves. Fig. 4 shows this cuff. The layers are offset so that the incisions 42 of one film are covered by the other film. The same applies to other locations. It is also advantageous if the layers have stepped diameters of the central opening 40 . In this case, the limiting point 37 is particularly precise with minimal wear on the cuff. The layers are gripped by a cuff holder 41 . The holder is fixed or floating in the mask.

Instead of the feathered shape of the sleeves 24 and 27 , they can also be designed such that their thickness decreases in the radial direction from the outside to the center, as shown in FIG. 5. This has the advantage that the sleeve - although very dimensionally stable in the area of the outer diameter - is very flexible in the area of penetration of the rod 10 . There is little resistance to the penetrating rod, but the seal to the field-free spaces 38 and 39 is very reliable. This means that a sleeve is sufficient for many types of items to be treated to ensure a secure seal.

In a further embodiment, the cuff does not consist of electrical conductive brushes. The brushes are fastened in the cuff holder and point radial to the cuff center. In the case of dense bristles, this also becomes a reliable masking and a long service life.

Although the requirements for field-free spaces 38 and 39 are essentially met by the measures described above, z. B. when using feathered cuffs or too large tolerances between the center of the rod 10 and the center of the masks 23 and 26 , field lines from the treatment room 34 penetrate into the "field-free spaces". If the proportion of the field lines is so small that this results in a current density at the end regions of the rod 10 where no coating is to take place, which is below the threshold value for a deposition, this is irrelevant. If the proportion of the penetrating field lines is larger, a coating takes place at the end regions of the rod 10 . Although this is much thinner than the coating deposited in the loading area of the treatment room 34 . However, an additional step is required to remove them.

While now in the upper, "field-free space 38 ", the threshold value of the current density, from which deposition takes place, is not achieved because the additional metal surfaces of the clamping jaws 9 and 10 contribute to limiting the current density at the end of the rod, the threshold value in lower "field-free space 39 " are exceeded. In order to prevent this, in a further embodiment of the invention, an enlargement of the metal surfaces located in this "field-free space 39 " is provided.

For this purpose, as shown in FIG. 5, a metallic body 44 is arranged in the center of the "field-free space 39 ". This is freely movable in the direction of the penetrating rod 10 . For this purpose, it is attached to a holding element 45 made of non-conducting material that is guided in the mask 23 . The holding element 45 is either designed as a floating body, whereby it is pressed upwards in the liquid, or this effect is achieved by a spring 46 arranged between the holding element 45 and the lower diaphragm support 17 . In both measures, the metallic body 44 rests on the lower sleeve 24 when there is no rod 10 in the single cell 22 . When a rod 10 is lowered into the single cell 22 and thus into the "field-free space 39 ", the rod 10 contacts the metallic body 44 and thus brings it to the same electrical potential.

The electrode 30 is preferably designed as an insoluble electrode. The tube is provided with openings so that a good electrolyte exchange can take place in the treatment room 34 . An expanded metal grid is suitable, for example. A further electrolyte exchange takes place through the gap 43 , drawn in FIG. 3. If the masks 23 , 26 have the same diameter as the inside diameter of the electrodes and are firmly connected to the electrodes, the gap 43 is omitted. In this case, the electrodes are telescopically adjustable together with the mask adjustment. The electrolyte exchange in the treatment room 34 takes place solely through the electrode openings. The upper surface of the electrode 30 must be chemically and electrochemically resistant. Surface coatings made of platinum or mixed oxides are so durable that the electrodes have a long service life. The electrodes are connected to the electrode insert in an electrically conductive manner. The electrical connection of the bath current source to all electrodes 30 takes place together via this insert. An individual bath current source can be assigned to each electrode 30 for particularly precise or individual treatment. In this case, the electrodes 30 are fastened to the electrode insert 31 in an electrically insulated manner and are connected to the respective power source with an insulated cable. In special cases, the electrode 30 can be soluble.

Reference list

1

frame

2nd

Frame supports

3rd

Gripper

4th

fixed leg

5

movable leg

6

axis

7

Compression spring

8th

prismatic jaw

9

crowned jaw

10th

Rod (material to be treated)

11

Arrow for direction of force

12th

Beam

13

Plastic plate

14

Bath container

15

Product carrier

16

Treatment bath

17th

lower panel support

18th

Breakthroughs

19th

carrier

20th

Height adjustment device below

21

M2 drive

22

Single cell

23

tubular mask below

24th

Cuff below

25th

upper panel support

26

tubular mask on top

27

Cuff top

28

Height adjustment device above

29

M1 drive

30th

electrode

31

Electrode insert

32

Container rim

33

paragraph

34

Treatment room

35

Extension above

36

Extension below

37

Limiting point

38

field-free space above

39

field-free space below

40

central opening

41

Cuff holder

42

incision

43

gap

44

Metallic body

45

Holding element

46

feather

47

Bathroom mirror

Claims (20)

1. Process for the partial electrochemical treatment of rod-shaped material to be treated in immersion bath systems with the following process steps:

• - Loading a goods carrier by one-sided gripping of preferably rod-shaped items to be treated by means of electrically conductive grippers attached to the goods carrier in the loading station.
• - Transport of the goods carrier with material to be treated in the individual treatment stations, preferably in a vertical position with the grippers located at the top.
• - Sinking the items to be treated attached to the goods carrier in stationary, elongated, tubular electrodes of the treatment station.
• - Sinking the material to be treated in an upper mask, which is closed at its lower end with a sealant.
• - Further immersion in the elongated electrodes and then in the lower masks with appropriate sealants.
• - Storage of the product carrier in the treatment station such that the material to be treated is positioned centrally in the respective electrodes.
• - Axial adjustment of the upper and lower masks to readjust the upper and lower coating limits on the material to be treated if readjustment is required.
• - Feeding the bath flow to the material to be treated via the goods carrier and the grippers.
• - Supply of the bath current of the other pole of the bath current source to the stationary tube electrodes.

2. The method according to claim 1, characterized in that multilayer, feathered cuffs enclose the material to be treated and the Determine the surface to be treated. 3. Process according to claims 1 and 2, characterized in that the Limitation of the surface to be treated with different diameters knives by stepped diameter of the inner holes one more layered cuff. 4. The method according to claim 1, characterized in that the man cuffs that enclose the material to be treated, one from the outside knife have decreasing thickness towards the center and thus the The elasticity becomes so great that the feathering of the cuff is eliminated can.   5. The method according to claims 1 to 4, characterized in that in cuffs floatingly attached to the masks the tolerance between Compensate items to be treated and bathroom fittings. 6. The method according to at least one of claims 1 to 5, characterized records that by means of electrically non-conductive brushes attached to the masks are fixed, the surface to be treated is limited. 7. The method according to claim 1 to 5, characterized in that additional metal bodies are present in the "field-free spaces" in the area of the masks, which are in electrical contact with the rods ( 10 ) during the galvanic coating process and thus have the same potential as the rods have. 8. The method according to at least one of claims 1 to 7, characterized records that the flow through the treatment room through perfo electrodes is promoted. 9. The method according to at least one of claims 1 to 8, characterized records that the insoluble electrodes by a resistant, electrical conductive surface coating are protected. 10. The method according to at least one of claims 1 to 9, characterized records that all individual cells of a bath container by a bath current source are fed. 11. The method according to at least one of claims 1 to 10, characterized ge indicates that each individual cell is powered by a bath power source becomes.   12. The method according to at least one of claims 1 to 11, characterized in that the upper panel support ( 25 ) also covers the treatment bath. 13. The method according to at least one of claims 1 to 12, characterized characterized in that the upper coating limit on the material to be treated is determined by the setting of the bath level. 14. Device for the partial electrochemical treatment of rod-shaped material to be treated in immersion bath systems for carrying out the method according to claims 1 to 13, characterized by a treatment bath ( 16 ) with at least one single cell ( 22 ) consisting of electrodes ( 30 ) into which from both electrode ends masks ( 23 ), ( 26 ) protrude, which are each provided with a sleeve ( 24 ), ( 27 ) with a central hole and are equipped with mutually independent height adjustment devices ( 20 ), ( 28 ) for axial mask adjustment are. 15. The apparatus according to claim 14, characterized by grippers ( 3 ), which are formed from a fixed leg ( 4 ) and a movable leg ( 5 ), wherein at the lower end of each fixed leg ( 4 ) a prismatic jaw ( 8 ) and on movable leg ( 5 ) a crowned jaw ( 9 ) are exchangeably attached and with a spring ( 7 ) which closes the jaws. 16. The apparatus of claim 14 and 15, characterized by a force introduction ( 11 ) on the movable leg ( 5 ) for opening the gripper ( 3 ) in the loading station and in the emptying station. 17. The device according to claims 14 to 16, characterized by Mas ken with sleeves ( 24 ), ( 27 ), consisting of at least two layers of elastic, electrically non-conductive films, each with an opening ( 40 ) and radial on all sides to the opening Incisions ( 42 ) which are arranged one above the other in each layer and are fastened in the mask ( 41 ). 18. Device according to claims 14 to 17, characterized by masks (23, ( 26 ) which on the side facing the treatment room ( 34 ) an extension ( 35 ), ( 36 ) over which the cuffs ( 24 ), ( 27 ). 19. The apparatus according to claim 18, characterized in that which the Extension is funnel-shaped. 20. Device according to claims 18 and 19, characterized by openings in the extensions ( 35 ), ( 36 ).